Sample records for factor-1 modulate skeletal

  1. Vascular Endothelial Growth Factor Modulates Skeletal Myoblast Function

    PubMed Central

    Germani, Antonia; Di Carlo, Anna; Mangoni, Antonella; Straino, Stefania; Giacinti, Cristina; Turrini, Paolo; Biglioli, Paolo; Capogrossi, Maurizio C.

    2003-01-01

    Vascular endothelial growth factor (VEGF) expression is enhanced in ischemic skeletal muscle and is thought to play a key role in the angiogenic response to ischemia. However, it is still unknown whether, in addition to new blood vessel growth, VEGF modulates skeletal muscle cell function. In the present study immunohistochemical analysis showed that, in normoperfused mouse hindlimb, VEGF and its receptors Flk-1 and Flt-1 were expressed mostly in quiescent satellite cells. Unilateral hindlimb ischemia was induced by left femoral artery ligation. At day 3 and day 7 after the induction of ischemia, Flk-1 and Flt-1 were expressed in regenerating muscle fibers and VEGF expression by these fibers was markedly enhanced. Additional in vitro experiments showed that in growing medium both cultured satellite cells and myoblast cell line C2C12 expressed VEGF and its receptors. Under these conditions, Flk-1 receptor exhibited constitutive tyrosine phosphorylation that was increased by VEGF treatment. During myogenic differentiation Flk-1 and Flt-1 were down-regulated. In a modified Boyden Chamber assay, VEGF enhanced C2C12 myoblasts migration approximately fivefold. Moreover, VEGF administration to differentiating C2C12 myoblasts prevented apoptosis, while inhibition of VEGF signaling either with selective VEGF receptor inhibitors (SU1498 and CB676475) or a neutralizing Flk-1 antibody, enhanced cell death approximately 3.5-fold. Finally, adenovirus-mediated VEGF165 gene transfer inhibited ischemia-induced apoptosis in skeletal muscle. These results support a role for VEGF in myoblast migration and survival, and suggest a novel autocrine role of VEGF in skeletal muscle repair during ischemia. PMID:14507649

  2. Health Occupations Module. The Skeletal System--I.

    ERIC Educational Resources Information Center

    Temple Univ., Philadelphia, PA. Div. of Vocational Education.

    This module on the skeletal system is one of eight modules designed for individualized instruction in health occupations education programs at both the secondary and postsecondary levels. This module contains an introduction to the module topic, three objectives (e.g., define the skeletal system and list its functions), and three learning…

  3. Collagen and Stretch Modulate Autocrine Secretion of Insulin-like Growth Factor-1 and Insulin-like Growth Factor Binding Proteins from Differentiated Skeletal Muscle Cells

    NASA Technical Reports Server (NTRS)

    Perrone, Carmen E.; Fenwick-Smith, Daniela; Vandenburgh, Herman H.

    1995-01-01

    Stretch-induced skeletal muscle growth may involve increased autocrine secretion of insulin-like growth factor-1 (IGF-1) since IGF-1 is a potent growth factor for skeletal muscle hypertrophy, and stretch elevates IGF-1 mRNA levels in vivo. In tissue cultures of differentiated avian pectoralis skeletal muscle cells, nanomolar concentrations of exogenous IGF-1 stimulated growth in mechanically stretched but not static cultures. These cultures released up to 100 pg of endogenously produced IGF-1/micro-g of protein/day, as well as three major IGF binding proteins of 31, 36, and 43 kilodaltons (kDa). IGF-1 was secreted from both myofibers and fibroblasts coexisting in the muscle cultures. Repetitive stretch/relaxation of the differentiated skeletal muscle cells stimulated the acute release of IGF-1 during the first 4 h after initiating mechanical activity, but caused no increase in the long-term secretion over 24-72 h of IGF-1, or its binding proteins. Varying the intensity and frequency of stretch had no effect on the long-term efflux of IGF-1. In contrast to stretch, embedding the differentiated muscle cells in a three-dimensional collagen (Type I) matrix resulted in a 2-5-fold increase in long-term IGF-1 efflux over 24-72 h. Collagen also caused a 2-5-fold increase in the release of the IGF binding proteins. Thus, both the extracellular matrix protein type I collagen and stretch stimulate the autocrine secretion of IGF-1, but with different time kinetics. This endogenously produced growth factor may be important for the growth response of skeletal myofibers to both types of external stimuli.

  4. Growth Factors and Tension-Induced Skeletal Muscle Growth

    NASA Technical Reports Server (NTRS)

    Vandenburgh, Herman H.

    1994-01-01

    The project investigated biochemical mechanisms to enhance skeletal muscle growth, and developed a computer based mechanical cell stimulator system. The biochemicals investigated in this study were insulin/(Insulin like Growth Factor) IGF-1 and Steroids. In order to analyze which growth factors are essential for stretch-induced muscle growth in vitro, we developed a defined, serum-free medium in which the differentiated, cultured avian muscle fibers could be maintained for extended periods of time. The defined medium (muscle maintenance medium, MM medium) maintains the nitrogen balance of the myofibers for 3 to 7 days, based on myofiber diameter measurements and myosin heavy chain content. Insulin and IGF-1, but not IGF-2, induced pronounced myofiber hypertrophy when added to this medium. In 5 to 7 days, muscle fiber diameters increase by 71 % to 98% compared to untreated controls. Mechanical stimulation of the avian muscle fibers in MM medium increased the sensitivity of the cells to insulin and IGF-1, based on a leftward shift of the insulin dose/response curve for protein synthesis rates. (54). We developed a ligand binding assay for IGF-1 binding proteins and found that the avian skeletal muscle cultures produced three major species of 31, 36 and 43 kD molecular weight (54) Stretch of the myofibers was found to have no significant effect on the efflux of IGF-1 binding proteins, but addition of exogenous collagen stimulated IGF-1 binding protein production 1.5 to 5 fold. Steroid hormones have a profound effect on muscle protein turnover rates in vivo, with the stress-related glucocorticoids inducing rapid skeletal muscle atrophy while androgenic steroids induce skeletal muscle growth. Exercise in humans and animals reduces the catabolic effects of glucocorticoids and may enhance the anabolic effects of androgenic steroids on skeletal muscle. In our continuing work on the involvement of exogenrus growth factors in stretch-induced avian skeletal muscle growth, we

  5. Developmental Patterning as a Quantitative Trait: Genetic Modulation of the Hoxb6 Mutant Skeletal Phenotype

    PubMed Central

    Kappen, Claudia

    2016-01-01

    The process of patterning along the anterior-posterior axis in vertebrates is highly conserved. The function of Hox genes in the axis patterning process is particularly well documented for bone development in the vertebral column and the limbs. We here show that Hoxb6, in skeletal elements at the cervico-thoracic junction, controls multiple independent aspects of skeletal pattern, implicating discrete developmental pathways as substrates for this transcription factor. In addition, we demonstrate that Hoxb6 function is subject to modulation by genetic factors. These results establish Hox-controlled skeletal pattern as a quantitative trait modulated by gene-gene interactions, and provide evidence that distinct modifiers influence the function of conserved developmental genes in fundamental patterning processes. PMID:26800342

  6. Health Occupations Module. The Skeletal System--II.

    ERIC Educational Resources Information Center

    Temple Univ., Philadelphia, PA. Div. of Vocational Education.

    This module on the skeletal system is one of eight modules designed for individualized instruction in health occupations education programs at both the secondary and postsecondary levels. This module contains an introduction to the module topic, two objectives (e.g., list the types of joints and movements, and give examples), and two learning…

  7. Autocrine and/or paracrine insulin-like growth factor-I activity in skeletal muscle

    NASA Technical Reports Server (NTRS)

    Adams, Gregory R.

    2002-01-01

    Similar to bone, skeletal muscle responds and adapts to changes in loading state via mechanisms that appear to be intrinsic to the muscle. One of the mechanisms modulating skeletal muscle adaptation it thought to involve the autocrine and/or paracrine production of insulinlike growth factor-I. This brief review outlines components of the insulinlike growth factor-I system as it relates to skeletal muscle and provides the rationale for the theory that insulinlike growth factor-I is involved with muscle adaptation.

  8. Insulin-like growth factor-1 receptor is regulated by microRNA-133 during skeletal myogenesis.

    PubMed

    Huang, Mian-Bo; Xu, Hui; Xie, Shu-Juan; Zhou, Hui; Qu, Liang-Hu

    2011-01-01

    The insulin-like growth factor (IGF) signaling pathway has long been established as playing critical roles in skeletal muscle development. However, the underlying regulatory mechanism is poorly understood. Recently, a large family of small RNAs, named microRNAs (miRNAs), has been identified as key regulators for many developmental processes. Because miRNAs participate in the regulation of various signaling pathways, we hypothesized that miRNAs may be involved in the regulation of IGF signaling in skeletal myogenesis. In the present study, we determined that the cell-surface receptor IGF-1R is directly regulated by a muscle-specific miRNA, microRNA-133 (miR-133). A conserved and functional binding site for miR-133 was identified in the 3'untranslated region (3'UTR) of IGF-1R. During differentiation of C2C12 myoblasts, IGF-1R protein, but not messenger RNA (mRNA) expression, was gradually reduced, concurrent with the upregulation of miR-133. Overexpression of miR-133 in C2C12 cells significantly suppressed IGF-1R expression at the posttranscriptional level. We also demonstrated that both overexpression of miR-133 and knockdown of IGF-1R downregulated the phosphorylation of Akt, the central mediator of the PI3K/Akt signaling pathway. Furthermore, upregulation of miR-133 during C2C12 differentiation was significantly accelerated by the addition of IGF-1. Mechanistically, we found that the expression of myogenin, a myogenic transcription factor reported to transactivate miR-133, was increased by IGF-1 stimulation. Our results elucidate a negative feedback circuit in which IGF-1-stimulated miR-133 in turn represses IGF-1R expression to modulate the IGF-1R signaling pathway during skeletal myogenesis. These findings also suggest that miR-133 may be a potential therapeutic target in muscle diseases.

  9. Insulin-Like Growth Factor-1 Receptor Is Regulated by microRNA-133 during Skeletal Myogenesis

    PubMed Central

    Huang, Mian-Bo; Xu, Hui; Xie, Shu-Juan; Zhou, Hui; Qu, Liang-Hu

    2011-01-01

    Background The insulin-like growth factor (IGF) signaling pathway has long been established as playing critical roles in skeletal muscle development. However, the underlying regulatory mechanism is poorly understood. Recently, a large family of small RNAs, named microRNAs (miRNAs), has been identified as key regulators for many developmental processes. Because miRNAs participate in the regulation of various signaling pathways, we hypothesized that miRNAs may be involved in the regulation of IGF signaling in skeletal myogenesis. Methodology/Principal Findings In the present study, we determined that the cell-surface receptor IGF-1R is directly regulated by a muscle-specific miRNA, microRNA-133 (miR-133). A conserved and functional binding site for miR-133 was identified in the 3′untranslated region (3′UTR) of IGF-1R. During differentiation of C2C12 myoblasts, IGF-1R protein, but not messenger RNA (mRNA) expression, was gradually reduced, concurrent with the upregulation of miR-133. Overexpression of miR-133 in C2C12 cells significantly suppressed IGF-1R expression at the posttranscriptional level. We also demonstrated that both overexpression of miR-133 and knockdown of IGF-1R downregulated the phosphorylation of Akt, the central mediator of the PI3K/Akt signaling pathway. Furthermore, upregulation of miR-133 during C2C12 differentiation was significantly accelerated by the addition of IGF-1. Mechanistically, we found that the expression of myogenin, a myogenic transcription factor reported to transactivate miR-133, was increased by IGF-1 stimulation. Conclusion/Significance Our results elucidate a negative feedback circuit in which IGF-1-stimulated miR-133 in turn represses IGF-1R expression to modulate the IGF-1R signaling pathway during skeletal myogenesis. These findings also suggest that miR-133 may be a potential therapeutic target in muscle diseases. PMID:22195016

  10. Module-based multiscale simulation of angiogenesis in skeletal muscle

    PubMed Central

    2011-01-01

    Background Mathematical modeling of angiogenesis has been gaining momentum as a means to shed new light on the biological complexity underlying blood vessel growth. A variety of computational models have been developed, each focusing on different aspects of the angiogenesis process and occurring at different biological scales, ranging from the molecular to the tissue levels. Integration of models at different scales is a challenging and currently unsolved problem. Results We present an object-oriented module-based computational integration strategy to build a multiscale model of angiogenesis that links currently available models. As an example case, we use this approach to integrate modules representing microvascular blood flow, oxygen transport, vascular endothelial growth factor transport and endothelial cell behavior (sensing, migration and proliferation). Modeling methodologies in these modules include algebraic equations, partial differential equations and agent-based models with complex logical rules. We apply this integrated model to simulate exercise-induced angiogenesis in skeletal muscle. The simulation results compare capillary growth patterns between different exercise conditions for a single bout of exercise. Results demonstrate how the computational infrastructure can effectively integrate multiple modules by coordinating their connectivity and data exchange. Model parameterization offers simulation flexibility and a platform for performing sensitivity analysis. Conclusions This systems biology strategy can be applied to larger scale integration of computational models of angiogenesis in skeletal muscle, or other complex processes in other tissues under physiological and pathological conditions. PMID:21463529

  11. Six Month Report on Tissue Cultured Avian Skeletal Myofibers in the STL/A Module Aboard STS-77

    NASA Technical Reports Server (NTRS)

    Vandenburgh, Herman H.

    1997-01-01

    Space travel is know to effect skeletal muscle, causing rapid and pronounced atrophy in humans and animals, even when strenuous exercise is used as a countermeasure. The cellular and molecular bases of this atrophy are unknown. Space travel may cause muscle atrophy by a direct effect on the muscle fibers and/or indirectly by reducing circulating levels of growth factors such as growth hormone. The recent development of a tissue culture incubator system for Shuttle Middeck basic science experiments [Space Tissue Loss (STL) Module] by the Walter Reed Army Institute of Research (WRAIR) allows the study of the effects of space travel directly on isolated skeletal myofibers. Avian bioartificial skeletal muscle 'organoids' containing differentiated skeletal myofibers and connective tissue fibroblasts were flown aboard the Space Shuttle (Space Transportation System, STS) on Flight STS-77, a repeat of a similar experiment flown on STS-66. The results from these two flight experiments show for the first time that space travel has a direct effect on skeletal muscle cells separate from any systemic effects resulting from altered circulating growth factors.

  12. Modulation of visceral fat adipokine secretion by dietary fatty acids and ensuing changes in skeletal muscle inflammation.

    PubMed

    Tishinsky, Justine M; De Boer, Anna A; Dyck, David J; Robinson, Lindsay E

    2014-01-01

    Given the link between obesity and insulin resistance, the role of adipose-derived factors in communicating with skeletal muscle to affect its function is important. We sought to determine if high fat diets modulate visceral adipose tissue (VAT) adipokines with subsequent effects on skeletal muscle inflammation and insulin sensitivity. Rats were fed (i) low fat (LF), (ii) high saturated fatty acid (SFA), or (iii) high SFA with n-3 polyunsaturated fatty acid (SFA/n-3 PUFA) diets for 4 weeks. VAT-derived adipokines were measured in adipose conditioned medium (ACM) after 72 h. Next, skeletal muscles from LF-fed rats were incubated for 8 h in (i) control buffer (CON), (ii) CON with 2 mmol·L(-1) palmitate (PALM, positive control), (iii) ACM from LF, (iv) ACM from SFA, or (v) ACM from SFA/n-3 PUFA. ACM from rats fed SFA and SFA/n-3 PUFA had increased (P ≤ 0.05) interleukin-6 (IL-6) (+31%) and monocyte chemoattractant protein-1 (MCP-1) (+30%). Adiponectin was decreased (-29%, P ≤ 0.05) in ACM from SFA, and this was prevented in SFA/n-3 PUFA ACM. Toll-like receptor 4 (TLR4) gene expression was increased (P ≤ 0.05) in PALM soleus muscle (+356%) and all ACM groups (+175%-191%). MCP-1 gene expression was elevated (P ≤ 0.05) in PALM soleus muscle (+163%) and soleus muscle incubated in ACM from animals fed SFA (+159%) and SFA/n-3 PUFA (+151%). Glucose transport was impaired (P ≤ 0.05) in PALM muscles but preserved in ACM groups. Acute exposure of muscle to fatty acid modulated adipokines affects skeletal muscle inflammatory gene expression but not insulin sensitivity.

  13. Bilingual Skills Training Program. Barbering/Cosmetology. Module 4.0: Skeletal System.

    ERIC Educational Resources Information Center

    Northern New Mexico Community Coll., El Rito.

    This module on the skeletal system is the fourth of ten (CE 028 308-318) in the barbering/cosmetology course of a bilingual skill training program. (A Vocabulary Development Workbook for modules 6-10 is available as CE 028 313.) The course is designed to furnish theoretical and laboratory experience. Module objectives are for students to develop…

  14. TAK1 modulates satellite stem cell homeostasis and skeletal muscle repair

    PubMed Central

    Ogura, Yuji; Hindi, Sajedah M.; Sato, Shuichi; Xiong, Guangyan; Akira, Shizuo; Kumar, Ashok

    2015-01-01

    Satellite cells are resident adult stem cells that are required for regeneration of skeletal muscle. However, signalling mechanisms that regulate satellite cell function are less understood. Here we demonstrate that transforming growth factor-β-activated kinase 1 (TAK1) is important in satellite stem cell homeostasis and function. Inactivation of TAK1 in satellite cells inhibits muscle regeneration in adult mice. TAK1 is essential for satellite cell proliferation and its inactivation causes precocious differentiation. Moreover, TAK1-deficient satellite cells exhibit increased oxidative stress and undergo spontaneous cell death, primarily through necroptosis. TAK1 is required for the activation of NF-κB and JNK in satellite cells. Forced activation of NF-κB improves survival and proliferation of TAK1-deficient satellite cells. Furthermore, TAK1-mediated activation of JNK is essential to prevent oxidative stress and precocious differentiation of satellite cells. Collectively, our study suggests that TAK1 is required for maintaining the pool of satellite stem cells and for regenerative myogenesis. PMID:26648529

  15. Expression of Pannexin 1 and Pannexin 3 during skeletal muscle development, regeneration, and Duchenne muscular dystrophy.

    PubMed

    Pham, Tammy L; St-Pierre, Marie-Eve; Ravel-Chapuis, Aymeric; Parks, Tara E C; Langlois, Stéphanie; Penuela, Silvia; Jasmin, Bernard J; Cowan, Kyle N

    2018-05-10

    Pannexin 1 (Panx1) and Pannexin 3 (Panx3) are single membrane channels recently implicated in myogenic commitment, as well as myoblast proliferation and differentiation in vitro. However, their expression patterns during skeletal muscle development and regeneration had yet to be investigated. Here, we show that Panx1 levels increase during skeletal muscle development becoming highly expressed together with Panx3 in adult skeletal muscle. In adult mice, Panx1 and Panx3 were differentially expressed in fast- and slow-twitch muscles. We also report that Panx1/PANX1 and Panx3/PANX3 are co-expressed in mouse and human satellite cells, which play crucial roles in skeletal muscle regeneration. Interestingly, Panx1 and Panx3 levels were modulated in muscle degeneration/regeneration, similar to the pattern seen during skeletal muscle development. As Duchenne muscular dystrophy is characterized by skeletal muscle degeneration and impaired regeneration, we next used mild and severe mouse models of this disease and found a significant dysregulation of Panx1 and Panx3 levels in dystrophic skeletal muscles. Together, our results are the first demonstration that Panx1 and Panx3 are differentially expressed amongst skeletal muscle types with their levels being highly modulated during skeletal muscle development, regeneration, and dystrophy. These findings suggest that Panx1 and Panx3 channels may play important and distinct roles in healthy and diseased skeletal muscles. © 2018 Wiley Periodicals, Inc.

  16. WNK1 regulates skeletal muscle cell hypertrophy by modulating the nuclear localization and transcriptional activity of FOXO4.

    PubMed

    Mandai, Shintaro; Mori, Takayasu; Nomura, Naohiro; Furusho, Taisuke; Arai, Yohei; Kikuchi, Hiroaki; Sasaki, Emi; Sohara, Eisei; Rai, Tatemitsu; Uchida, Shinichi

    2018-06-14

    With-no-lysine (K) (WNK) kinases, which are mutated in the inherited form of hypertension pseudohypoaldosteronism type II, are essential regulators of membrane ion transporters. Here, we report that WNK1 positively regulates skeletal muscle cell hypertrophy via mediating the function of the pro-longevity transcription factor forkhead box protein O4 (FOXO4) independent of the conventional WNK signaling pathway linking SPS/STE20-related proline-alanine-rich kinase (SPAK)/oxidative stress response kinase 1 (OSR1) to downstream effector ion transporters. Small interfering RNA (siRNA)-mediated silencing of WNK1, but not SPAK/OSR1 kinases, induced myotube atrophy and remarkable increases in the mRNA expression of the muscle atrophy ubiquitin ligases MAFbx and MuRF1 in C2C12 mouse skeletal muscle cells. WNK1 silencing also increased FOXO4 nuclear localization, and co-transfection of Foxo4-targeted siRNA completely reversed the myotube atrophy and upregulation of atrogene transcription induced by WNK1 silencing. We further illustrated that WNK1 protein abundance in skeletal muscle was increased by chronic voluntary wheel running exercise (hypertrophic stimulus) and markedly decreased by adenine-induced chronic kidney disease (atrophic stimulus) in mice. These findings suggest that WNK1 is involved in the physiological regulation of mammalian skeletal muscle hypertrophy and atrophy via interactions with FOXO4. The WNK1-FOXO4 axis may be a potential therapeutic target in human diseases causing sarcopenia.

  17. Modulation of the Neuregulin 1/ErbB system after skeletal muscle denervation and reinnervation.

    PubMed

    Morano, Michela; Ronchi, Giulia; Nicolò, Valentina; Fornasari, Benedetta Elena; Crosio, Alessandro; Perroteau, Isabelle; Geuna, Stefano; Gambarotta, Giovanna; Raimondo, Stefania

    2018-03-22

    Neuregulin 1 (NRG1) is a growth factor produced by both peripheral nerves and skeletal muscle. In muscle, it regulates neuromuscular junction gene expression, acetylcholine receptor number, muscle homeostasis and satellite cell survival. NRG1 signalling is mediated by the tyrosine kinase receptors ErbB3 and ErbB4 and their co-receptors ErbB1 and ErbB2. The NRG1/ErbB system is well studied in nerve tissue after injury, but little is known about this system in skeletal muscle after denervation/reinnervation processes. Here, we performed a detailed time-course expression analysis of several NRG1 isoforms and ErbB receptors in the rat superficial digitorum flexor muscle after three types of median nerve injuries of different severities. We found that ErbB receptor expression was correlated with the innervated state of the muscle, with upregulation of ErbB2 clearly associated with the denervation state. Interestingly, the NRG1 isoforms were differently regulated depending on the nerve injury type, leading to the hypothesis that both the NRG1α and NRG1β isoforms play a key role in the muscle reaction to injury. Indeed, in vitro experiments with C2C12 atrophic myotubes revealed that both NRG1α and NRG1β treatment influences the best-known atrophic pathways, suggesting that NRG1 might play an anti-atrophic role.

  18. skNAC, a Smyd1-interacting transcription factor, is involved in cardiac development and skeletal muscle growth and regeneration.

    PubMed

    Park, Chong Yon; Pierce, Stephanie A; von Drehle, Morgan; Ivey, Kathryn N; Morgan, Jayson A; Blau, Helen M; Srivastava, Deepak

    2010-11-30

    Cardiac and skeletal muscle development and maintenance require complex interactions between DNA-binding proteins and chromatin remodeling factors. We previously reported that Smyd1, a muscle-restricted histone methyltransferase, is essential for cardiogenesis and functions with a network of cardiac regulatory proteins. Here we show that the muscle-specific transcription factor skNAC is the major binding partner for Smyd1 in the developing heart. Targeted deletion of skNAC in mice resulted in partial embryonic lethality by embryonic day 12.5, with ventricular hypoplasia and decreased cardiomyocyte proliferation that were similar but less severe than in Smyd1 mutants. Expression of Irx4, a ventricle-specific transcription factor down-regulated in hearts lacking Smyd1, also depended on the presence of skNAC. Viable skNAC(-/-) adult mice had reduced postnatal skeletal muscle growth and impaired regenerative capacity after cardiotoxin-induced injury. Satellite cells isolated from skNAC(-/-) mice had impaired survival compared with wild-type littermate satellite cells. Our results indicate that skNAC plays a critical role in ventricular cardiomyocyte expansion and regulates postnatal skeletal muscle growth and regeneration in mice.

  19. Selected Contribution: Skeletal muscle focal adhesion kinase, paxillin, and serum response factor are loading dependent

    NASA Technical Reports Server (NTRS)

    Gordon, S. E.; Fluck, M.; Booth, F. W.

    2001-01-01

    This investigation examined the effect of mechanical loading state on focal adhesion kinase (FAK), paxillin, and serum response factor (SRF) in rat skeletal muscle. We found that FAK concentration and tyrosine phosphorylation, paxillin concentration, and SRF concentration are all lower in the lesser load-bearing fast-twitch plantaris and gastrocnemius muscles compared with the greater load-bearing slow-twitch soleus muscle. Of these three muscles, 7 days of mechanical unloading via tail suspension elicited a decrease in FAK tyrosine phosphorylation only in the soleus muscle and decreases in FAK and paxillin concentrations only in the plantaris and gastrocnemius muscles. Unloading decreased SRF concentration in all three muscles. Mechanical overloading (via bilateral gastrocnemius ablation) for 1 or 8 days increased FAK and paxillin concentrations in the soleus and plantaris muscles. Additionally, whereas FAK tyrosine phosphorylation and SRF concentration were increased by < or =1 day of overloading in the soleus muscle, these increases did not occur until somewhere between 1 and 8 days of overloading in the plantaris muscle. These data indicate that, in the skeletal muscles of rats, the focal adhesion complex proteins FAK and paxillin and the transcription factor SRF are generally modulated in association with the mechanical loading state of the muscle. However, the somewhat different patterns of adaptation of these proteins to altered loading in slow- vs. fast-twitch skeletal muscles indicate that the mechanisms and time course of adaptation may partly depend on the prior loading state of the muscle.

  20. IGF-1 induces skeletal myocyte hypertrophy through calcineurin in association with GATA-2 and NF-ATc1

    NASA Technical Reports Server (NTRS)

    Musaro, A.; McCullagh, K. J.; Naya, F. J.; Olson, E. N.; Rosenthal, N.

    1999-01-01

    Localized synthesis of insulin-like growth factors (IGFs) has been broadly implicated in skeletal muscle growth, hypertrophy and regeneration. Virally delivered IGF-1 genes induce local skeletal muscle hypertrophy and attenuate age-related skeletal muscle atrophy, restoring and improving muscle mass and strength in mice. Here we show that the molecular pathways underlying the hypertrophic action of IGF-1 in skeletal muscle are similar to those responsible for cardiac hypertrophy. Transfected IGF-1 gene expression in postmitotic skeletal myocytes activates calcineurin-mediated calcium signalling by inducing calcineurin transcripts and nuclear localization of calcineurin protein. Expression of activated calcineurin mimics the effects of IGF-1, whereas expression of a dominant-negative calcineurin mutant or addition of cyclosporin, a calcineurin inhibitor, represses myocyte differentiation and hypertrophy. Either IGF-1 or activated calcineurin induces expression of the transcription factor GATA-2, which accumulates in a subset of myocyte nuclei, where it associates with calcineurin and a specific dephosphorylated isoform of the transcription factor NF-ATc1. Thus, IGF-1 induces calcineurin-mediated signalling and activation of GATA-2, a marker of skeletal muscle hypertrophy, which cooperates with selected NF-ATc isoforms to activate gene expression programs.

  1. FOXL2 modulates cartilage, skeletal development and IGF1-dependent growth in mice.

    PubMed

    Marongiu, Mara; Marcia, Loredana; Pelosi, Emanuele; Lovicu, Mario; Deiana, Manila; Zhang, Yonqing; Puddu, Alessandro; Loi, Angela; Uda, Manuela; Forabosco, Antonino; Schlessinger, David; Crisponi, Laura

    2015-07-02

    Haploinsufficiency of the FOXL2 transcription factor in humans causes Blepharophimosis/Ptosis/Epicanthus Inversus syndrome (BPES), characterized by eyelid anomalies and premature ovarian failure. Mice lacking Foxl2 recapitulate human eyelid/forehead defects and undergo female gonadal dysgenesis. We report here that mice lacking Foxl2 also show defects in postnatal growth and embryonic bone and cartilage formation. Foxl2 (-/-) male mice at different stages of development have been characterized and compared to wild type. Body length and weight were measured and growth curves were created. Skeletons were stained with alcian blue and/or alizarin red. Bone and cartilage formation was analyzed by Von Kossa staining and immunofluorescence using anti-FOXL2 and anti-SOX9 antibodies followed by confocal microscopy. Genes differentially expressed in skull vaults were evaluated by microarray analysis. Analysis of the GH/IGF1 pathway was done evaluating the expression of several hypothalamic-pituitary-bone axis markers by RT-qPCR. Compared to wild-type, Foxl2 null mice are smaller and show skeletal abnormalities and defects in cartilage and bone mineralization, with down-regulation of the GH/IGF1 axis. Consistent with these effects, we find FOXL2 expressed in embryos at 9.5 dpc in neural tube epithelium, in head mesenchyme near the neural tube, and within the first branchial arch; then, starting at 12.5 dpc, expressed in cartilaginous tissue; and at PO and P7, in hypothalamus. Our results support FOXL2 as a master transcription factor in a spectrum of developmental processes, including growth, cartilage and bone formation. Its action overlaps that of SOX9, though they are antagonistic in female vs male gonadal sex determination but conjoint in cartilage and skeletal development.

  2. MEF2 Transcription Factors Regulate Distinct Gene Programs in Mammalian Skeletal Muscle Differentiation*

    PubMed Central

    Estrella, Nelsa L.; Desjardins, Cody A.; Nocco, Sarah E.; Clark, Amanda L.; Maksimenko, Yevgeniy; Naya, Francisco J.

    2015-01-01

    Skeletal muscle differentiation requires precisely coordinated transcriptional regulation of diverse gene programs that ultimately give rise to the specialized properties of this cell type. In Drosophila, this process is controlled, in part, by MEF2, the sole member of an evolutionarily conserved transcription factor family. By contrast, vertebrate MEF2 is encoded by four distinct genes, Mef2a, -b, -c, and -d, making it far more challenging to link this transcription factor to the regulation of specific muscle gene programs. Here, we have taken the first step in molecularly dissecting vertebrate MEF2 transcriptional function in skeletal muscle differentiation by depleting individual MEF2 proteins in myoblasts. Whereas MEF2A is absolutely required for proper myoblast differentiation, MEF2B, -C, and -D were found to be dispensable for this process. Furthermore, despite the extensive redundancy, we show that mammalian MEF2 proteins regulate a significant subset of nonoverlapping gene programs. These results suggest that individual MEF2 family members are able to recognize specific targets among the entire cohort of MEF2-regulated genes in the muscle genome. These findings provide opportunities to modulate the activity of MEF2 isoforms and their respective gene programs in skeletal muscle homeostasis and disease. PMID:25416778

  3. Overexpression of insulin-like growth factor-1 attenuates skeletal muscle damage and accelerates muscle regeneration and functional recovery after disuse.

    PubMed

    Ye, Fan; Mathur, Sunita; Liu, Min; Borst, Stephen E; Walter, Glenn A; Sweeney, H Lee; Vandenborne, Krista

    2013-05-01

    Skeletal muscle is a highly dynamic tissue that responds to endogenous and external stimuli, including alterations in mechanical loading and growth factors. In particular, the antigravity soleus muscle experiences significant muscle atrophy during disuse and extensive muscle damage upon reloading. Given that insulin-like growth factor-1 (IGF-1) has been implicated as a central regulator of muscle repair and modulation of muscle size, we examined the effect of virally mediated overexpression of IGF-1 on the soleus muscle following hindlimb cast immobilization and upon reloading. Recombinant IGF-1 cDNA virus was injected into one of the posterior hindlimbs of the mice, while the contralateral limb was injected with saline (control). At 20 weeks of age, both hindlimbs were immobilized for 2 weeks to induce muscle atrophy in the soleus and ankle plantarflexor muscle group. Subsequently, the mice were allowed to reambulate, and muscle damage and recovery were monitored over a period of 2-21 days. The primary finding of this study was that IGF-1 overexpression attenuated reloading-induced muscle damage in the soleus muscle, and accelerated muscle regeneration and force recovery. Muscle T2 assessed by magnetic resonance imaging, a non-specific marker of muscle damage, was significantly lower in IGF-1-injected compared with contralateral soleus muscles at 2 and 5 days reambulation (P<0.05). The reduced prevalence of muscle damage in IGF-1-injected soleus muscles was confirmed on histology, with a lower fractional area of abnormal muscle tissue in IGF-1-injected muscles at 2 days reambulation (33.2±3.3 versus 54.1±3.6%, P<0.05). Evidence of the effect of IGF-1 on muscle regeneration included timely increases in the number of central nuclei (21% at 5 days reambulation), paired-box transcription factor 7 (36% at 5 days), embryonic myosin (37% at 10 days) and elevated MyoD mRNA (7-fold at 2 days) in IGF-1-injected limbs (P<0.05). These findings demonstrate a potential role

  4. Skeletal muscle wasting: new role of nonclassical renin-angiotensin system.

    PubMed

    Cabello-Verrugio, Claudio; Rivera, Juan C; Garcia, Dominga

    2017-05-01

    Skeletal muscle can be affected by many physiological and pathological conditions that contribute to the development of muscle weakness, including skeletal muscle loss, inflammatory processes, or fibrosis. Therefore, research into therapeutic treatment alternatives or alleviation of these effects on skeletal muscle is of great importance. Recent studies have shown that angiotensin (1-7) [Ang-(1-7)] - a vasoactive peptide of the nonclassical axis in the renin-angiotensin system (RAS) - and its Mas receptor are expressed in skeletal muscle. Ang-(1-7), through its Mas receptor, prevents or diminishes deleterious effects induced by skeletal muscle disease or injury. Specifically, the Ang-(1-7)-Mas receptor axis modulates molecular mechanisms involved in muscle mass regulation, such as the ubiquitin proteasome pathway, the insulin-like growth factor type 1/Akt (protein kinase B) pathway, or myonuclear apoptosis, and also inflammation and fibrosis pathways. Although further research into this topic and the possible side effects of Ang-(1-7) is necessary, these findings are promising, and suggest that the Ang-(1-7)-Mas axis can be considered a possible therapeutic target for treating patients with muscular disorders.

  5. New prognostic factors and scoring system for patients with skeletal metastasis.

    PubMed

    Katagiri, Hirohisa; Okada, Rieko; Takagi, Tatsuya; Takahashi, Mitsuru; Murata, Hideki; Harada, Hideyuki; Nishimura, Tetsuo; Asakura, Hirofumi; Ogawa, Hirofumi

    2014-10-01

    The aim of this study was to update a previous scoring system for patients with skeletal metastases, that was proposed by Katagiri et al. in 2005, by introducing a new factor (laboratory data) and analyzing a new patient cohort. Between January 2005 and January 2008, we treated 808 patients with symptomatic skeletal metastases. They were prospectively registered regardless of their treatments, and the last follow-up evaluation was performed in 2012. There were 441 male and 367 female patients with a median age of 64 years. Of these patients, 749 were treated nonsurgically while the remaining 59 underwent surgery for skeletal metastasis. A multivariate analysis was conducted using the Cox proportional hazards model. We identified six significant prognostic factors for survival, namely, the primary lesion, visceral or cerebral metastases, abnormal laboratory data, poor performance status, previous chemotherapy, and multiple skeletal metastases. The first three factors had a larger impact than the remaining three. The prognostic score was calculated by adding together all the scores for individual factors. With a prognostic score of ≥7, the survival rate was 27% at 6 months, and only 6% at 1 year. In contrast, patients with a prognostic score of ≤3 had a survival rate of 91% at 1 year, and 78% at 2 years. Comparing the revised system with the previous one, there was a significantly lower number of wrongly predicted patients using the revised system. This revised scoring system was able to predict the survival rates of patients with skeletal metastases more accurately than the previous system and may be useful for selecting an optimal treatment. © 2014 The Authors. Cancer Medicine published by John Wiley & Sons Ltd.

  6. Green tea component EGCG, insulin and IGF-1 promote nuclear efflux of atrophy-associated transcription factor Foxo1 in skeletal muscle fibers.

    PubMed

    Wimmer, Robert J; Russell, Sarah J; Schneider, Martin F

    2015-12-01

    Prevention and slowing of skeletal muscle atrophy with nutritional approaches offers the potential to provide far-reaching improvements in the quality of life for our increasingly aging population. Here we show that polyphenol flavonoid epigallocatechin 3-gallate (EGCG), found in the popular beverage green tea (Camellia sinensis), demonstrates similar effects to the endogenous hormones insulin-like growth factor 1 (IGF-1) and insulin in the ability to suppress action of the atrophy-promoting transcription factor Foxo1 through a net translocation of Foxo1 out of the nucleus as monitored by nucleo-cytoplasmic movement of Foxo1-green fluorescent protein (GFP) in live skeletal muscle fibers. Foxo1-GFP nuclear efflux is rapid in IGF-1 or insulin, but delayed by an additional 30 min for EGCG. Once activated, kinetic analysis with a simple mathematical model shows EGCG, IGF-1 and insulin all produce similar apparent rate constants for Foxo1-GFP unidirectional nuclear influx and efflux. Interestingly, EGCG appears to have its effect at least partially via parallel signaling pathways that are independent of IGF-1's (and insulin's) downstream PI3K/Akt/Foxo1 signaling axis. Using the live fiber model system, we also determine the dose-response curve for both IGF-1 and insulin on Foxo1 nucleo-cytoplasmic distribution. The continued understanding of the activation mechanisms of EGCG could allow for nutritional promotion of green tea's antiatrophy skeletal muscle benefits and have implications in the development of a clinically significant parallel pathway for new drugs to target muscle wasting and the reduced insulin receptor sensitivity which causes type II diabetes mellitus. Copyright © 2015 Elsevier Inc. All rights reserved.

  7. Dietary vitamin B6 modulates the gene expression of myokines, Nrf2-related factors, myogenin and HSP60 in the skeletal muscle of rats.

    PubMed

    Suidasari, Sofya; Uragami, Shinji; Yanaka, Noriyuki; Kato, Norihisa

    2017-10-01

    Previous studies have suggested that vitamin B6 is an ergogenic factor. However, the role of dietary vitamin B6 in skeletal muscle has not been widely researched. The aim of the present study was to investigate the effects of dietary vitamin B6 on the gene expression of 19 myokines, 14 nuclear factor erythroid 2-related factor 2 (Nrf2)-regulated factors, 8 myogenesis-related factors and 4 heat shock proteins (HSPs), which may serve important roles in skeletal muscles. Rats were fed a diet containing 1 (marginal vitamin B6 deficiency), 7 (recommended dietary level) or 35 mg/kg of pyridoxine (PN) HCl/ for 6 weeks. Gene expressions were subsequently analysed using reverse transcription-quantitative polymerase chain reaction. Food intake and growth were unaffected by this dietary treatment. The rats in the 7 and 35 mg/kg PN HCl groups exhibited a significant increase in the concentration of pyridoxal 5'-phosphate in the gastrocnemius muscle compared with the 1 mg/kg PN HCl diet (P<0.01). The expressions of myokines, such as IL-7, IL-8, secreted protein acidic and rich in cysteine, IL-6, growth differentiation factor 11, myonectin, leukaemia inhibitory factor, apelin and retinoic acid receptor responder (tazarotene induced) 1, the expression of Nrf2 and its regulated factors, such as heme oxygenase 1, superoxide dismutase 2, glutathione peroxidase 1 and glutathione S-transferase, and the expression of myogenin and HSP60 were significantly elevated in the 7 mg/kg PN HCl group compared with the 1 mg/kg PN HCl diet (P<0.05). No significant differences in levels of these genes were observed between the 35 and 1 mg/kg PN HCl, with the exception of GDF11 and myonectin, whose expressions were significantly increased in the 35 mg/kg PN HCl (P<0.05). Notably, the majority of gene expressions that were affected responded to dietary supplemental vitamin B6 in a similar manner. The results suggest that compared with the marginal vitamin B6 deficiency, the recommended dietary intake

  8. β-Agonists Selectively Modulate Proinflammatory Gene Expression in Skeletal Muscle Cells via Non-Canonical Nuclear Crosstalk Mechanisms

    PubMed Central

    Kolmus, Krzysztof; Van Troys, Marleen; Van Wesemael, Karlien; Ampe, Christophe; Haegeman, Guy; Tavernier, Jan; Gerlo, Sarah

    2014-01-01

    The proinflammatory cytokine Tumour Necrosis Factor (TNF)-α is implicated in a variety of skeletal muscle pathologies. Here, we have investigated how in vitro cotreatment of skeletal muscle C2C12 cells with β-agonists modulates the TNF-α-induced inflammatory program. We observed that C2C12 myotubes express functional TNF receptor 1 (TNF-R1) and β2-adrenoreceptors (β2-ARs). TNF-α activated the canonical Nuclear Factor-κB (NF-κB) pathway and Mitogen-Activated Protein Kinases (MAPKs), culminating in potent induction of NF-κB-dependent proinflammatory genes. Cotreatment with the β-agonist isoproterenol potentiated the expression of inflammatory mediators, including Interleukin-6 (IL-6) and several chemokines. The enhanced production of chemotactic factors upon TNF-α/isoproterenol cotreatment was also suggested by the results from migrational analysis. Whereas we could not explain our observations by cytoplasmic crosstalk, we found that TNF-R1-and β2-AR-induced signalling cascades cooperate in the nucleus. Using the IL-6 promoter as a model, we demonstrated that TNF-α/isoproterenol cotreatment provoked phosphorylation of histone H3 at serine 10, concomitant with enhanced promoter accessibility and recruitment of the NF-κB p65 subunit, cAMP-response element-binding protein (CREB), CREB-binding protein (CBP) and RNA polymerase II. In summary, we show that β-agonists potentiate TNF-α action, via nuclear crosstalk, that promotes chromatin relaxation at selected gene promoters. Our data warrant further study into the mode of action of β-agonists and urge for caution in their use as therapeutic agents for muscular disorders. PMID:24603712

  9. Cytokine Response of Cultured Skeletal Muscle Cells Stimulated with Proinflammatory Factors Depends on Differentiation Stage

    PubMed Central

    Podbregar, Matej; Lainscak, Mitja; Prelovsek, Oja; Mars, Tomaz

    2013-01-01

    Myoblast proliferation and myotube formation are critical early events in skeletal muscle regeneration. The attending inflammation and cytokine signaling are involved in regulation of skeletal muscle cell proliferation and differentiation. Secretion of muscle-derived cytokines upon exposure to inflammatory factors may depend on the differentiation stage of regenerating muscle cells. Cultured human myoblasts and myotubes were exposed to 24-hour treatment with tumor necrosis factor (TNF)-α or lipopolysaccharide (LPS). Secretion of interleukin 6 (IL-6), a major muscle-derived cytokine, and interleukin 1 (IL-1), an important regulator of inflammatory response, was measured 24 hours after termination of TNF-α or LPS treatment. Myoblasts pretreated with TNF-α or LPS displayed robustly increased IL-6 secretion during the 24-hour period after removal of treatments, while IL-1 secretion remained unaltered. IL-6 secretion was also increased in myotubes, but the response was less pronounced compared with myoblasts. In contrast to myoblasts, IL-1 secretion was markedly stimulated in LPS-pretreated myotubes. We demonstrate that preceding exposure to inflammatory factors stimulates a prolonged upregulation of muscle-derived IL-6 and/or IL-1 in cultured skeletal muscle cells. Our findings also indicate that cytokine response to inflammatory factors in regenerating skeletal muscle partially depends on the differentiation stage of myogenic cells. PMID:23509435

  10. Endothelium-dependent vasodilatory signalling modulates α1 -adrenergic vasoconstriction in contracting skeletal muscle of humans.

    PubMed

    Hearon, Christopher M; Kirby, Brett S; Luckasen, Gary J; Larson, Dennis G; Dinenno, Frank A

    2016-12-15

    'Functional sympatholysis' describes the ability of contracting skeletal muscle to attenuate sympathetic vasoconstriction, and is critical to ensure proper blood flow and oxygen delivery to metabolically active skeletal muscle. The signalling mechanism responsible for sympatholysis in healthy humans is unknown. Evidence from animal models has identified endothelium-derived hyperpolarization (EDH) as a potential mechanism capable of attenuating sympathetic vasoconstriction. In this study, increasing endothelium-dependent signalling during exercise significantly enhanced the ability of contracting skeletal muscle to attenuate sympathetic vasoconstriction in humans. This is the first study in humans to identify endothelium-dependent regulation of sympathetic vasoconstriction in contracting skeletal muscle, and specifically supports a role for EDH-like vasodilatory signalling. Impaired functional sympatholysis is a common feature of cardiovascular ageing, hypertension and heart failure, and thus identifying fundamental mechanisms responsible for sympatholysis is clinically relevant. Stimulation of α-adrenoceptors elicits vasoconstriction in resting skeletal muscle that is blunted during exercise in an intensity-dependent manner. In humans, the underlying mechanisms remain unclear. We tested the hypothesis that stimulating endothelium-dependent vasodilatory signalling will enhance the ability of contracting skeletal muscle to blunt α 1 -adrenergic vasoconstriction. Changes in forearm vascular conductance (FVC; Doppler ultrasound, brachial intra-arterial pressure via catheter) to local intra-arterial infusion of phenylephrine (PE; α 1 -adrenoceptor agonist) were calculated during (1) infusion of the endothelium-dependent vasodilators acetylcholine (ACh) and adenosine triphosphate (ATP), the endothelium-independent vasodilator (sodium nitroprusside, SNP), or potassium chloride (KCl) at rest; (2) mild or moderate intensity handgrip exercise; and (3) combined mild

  11. Insulin-like growth factors in embryonic and fetal growth and skeletal development (Review).

    PubMed

    Agrogiannis, Georgios D; Sifakis, Stavros; Patsouris, Efstratios S; Konstantinidou, Anastasia E

    2014-08-01

    The insulin-like growth factors (IGF)-I and -II have a predominant role in fetal growth and development. IGFs are involved in the proliferation, differentiation and apoptosis of fetal cells in vitro and the IGF serum concentration has been shown to be closely correlated with fetal growth and length. IGF transcripts and peptides have been detected in almost every fetal tissue from as early in development as pre‑implantation to the final maturation stage. Furthermore, IGFs have been demonstrated to be involved in limb morphogenesis. However, although ablation of Igf genes in mice resulted in growth retardation and delay in skeletal maturation, no impact on outgrowth and patterning of embryonic limbs was observed. Additionally, various molecular defects in the Igf1 and Igf1r genes in humans have been associated with severe intrauterine growth retardation and impaired skeletal maturation, but not with truncated limbs or severe skeletal dysplasia. The conflicting data between in vitro and in vivo observations with regard to bone morphogenesis suggests that IGFs may not be the sole trophic factors involved in fetal skeletal growth and that redundant mechanisms may exist in chondro- and osteogenesis. Further investigation is required in order to elucidate the functions of IGFs in skeletal development.

  12. Imaging of Skeletal Disorders Caused by Fibroblast Growth Factor Receptor Gene Mutations.

    PubMed

    Sargar, Kiran M; Singh, Achint K; Kao, Simon C

    2017-10-01

    Fibroblast growth factors and fibroblast growth factor receptors (FGFRs) play important roles in human axial and craniofacial skeletal development. FGFR1, FGFR2, and FGFR3 are crucial for both chondrogenesis and osteogenesis. Mutations in the genes encoding FGFRs, types 1-3, are responsible for various skeletal dysplasias and craniosynostosis syndromes. Many of these disorders are relatively common in the pediatric population, and diagnosis is often challenging. These skeletal disorders can be classified based on which FGFR is affected. Skeletal disorders caused by type 1 mutations include Pfeiffer syndrome (PS) and osteoglophonic dysplasia, and disorders caused by type 2 mutations include Crouzon syndrome (CS), Apert syndrome (AS), and PS. Disorders caused by type 3 mutations include achondroplasia, hypochondroplasia, thanatophoric dysplasia (TD), severe achondroplasia with developmental delay and acanthosis nigricans, Crouzonodermoskeletal syndrome, and Muenke syndrome. Most of these mutations are inherited in an autosomal dominant fashion and are gain-of-function-type mutations. Imaging plays a key role in the evaluation of these skeletal disorders. Knowledge of the characteristic imaging and clinical findings can help confirm the correct diagnosis and guide the appropriate molecular genetic tests. Some characteristics and clinical findings include premature fusion of cranial sutures and deviated broad thumbs and toes in PS; premature fusion of cranial sutures and syndactyly of the hands and feet in AS; craniosynostosis, ocular proptosis, and absence of hand and foot abnormalities in CS; rhizomelic limb shortening, caudal narrowing of the lumbar interpediculate distance, small and square iliac wings, and trident hands in achondroplasia; and micromelia, bowing of the femora, and platyspondyly in TD. © RSNA, 2017.

  13. The cAMP Response Element Binding protein (CREB) is activated by Insulin-like Growth Factor-1 (IGF-1) and regulates myostatin gene expression in skeletal myoblast

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zuloaga, R.; Fuentes, E.N.; Molina, A.

    2013-10-18

    Highlights: •IGF-1 induces the activation of CREB via IGF-1R/PI3K/PLC signaling pathway. •Calcium dependent signaling pathways regulate myostatin gene expression. •IGF-1 regulates myostatin gene expression via CREB transcription in skeletal myoblast. -- Abstract: Myostatin, a member of the Transforming Growth Factor beta (TGF-β) superfamily, plays an important role as a negative regulator of skeletal muscle growth and differentiation. We have previously reported that IGF-1 induces a transient myostatin mRNA expression, through the activation of the Nuclear Factor of Activated T cells (NFAT) in an IP{sub 3}/calcium-dependent manner. Here we examined the activation of CREB transcription factor as downstream targets of IGF-1more » during myoblast differentiation and its role as a regulator of myostatin gene expression. In cultured skeletal myoblast, IGF-1 induced the phosphorylation and transcriptional activation of CREB via IGF-1 Receptor/Phosphatidylinositol 3-Kinase (PI3K)/Phospholipase C gamma (PLC γ), signaling pathways. Also, IGF-1 induced calcium-dependent molecules such as Calmodulin Kinase II (CaMK II), Extracellular signal-regulated Kinases (ERK), Protein Kinase C (PKC). Additionally, we examined myostatin mRNA levels and myostatin promoter activity in differentiated myoblasts stimulated with IGF-1. We found a significant increase in mRNA contents of myostatin and its reporter activity after treatment with IGF-1. The expression of myostatin in differentiated myoblast was downregulated by the transfection of siRNA–CREB and by pharmacological inhibitors of the signaling pathways involved in CREB activation. By using pharmacological and genetic approaches together these data demonstrate that IGF-1 regulates the myostatin gene expression via CREB transcription factor during muscle cell differentiation.« less

  14. O-GlcNAcylation is a key modulator of skeletal muscle sarcomeric morphometry associated to modulation of protein-protein interactions.

    PubMed

    Lambert, Matthias; Richard, Elodie; Duban-Deweer, Sophie; Krzewinski, Frederic; Deracinois, Barbara; Dupont, Erwan; Bastide, Bruno; Cieniewski-Bernard, Caroline

    2016-09-01

    The sarcomere structure of skeletal muscle is determined through multiple protein-protein interactions within an intricate sarcomeric cytoskeleton network. The molecular mechanisms involved in the regulation of this sarcomeric organization, essential to muscle function, remain unclear. O-GlcNAcylation, a post-translational modification modifying several key structural proteins and previously described as a modulator of the contractile activity, was never considered to date in the sarcomeric organization. C2C12 skeletal myotubes were treated with Thiamet-G (OGA inhibitor) in order to increase the global O-GlcNAcylation level. Our data clearly showed a modulation of the O-GlcNAc level more sensitive and dynamic in the myofilament-enriched fraction than total proteome. This fine O-GlcNAc level modulation was closely related to changes of the sarcomeric morphometry. Indeed, the dark-band and M-line widths increased, while the I-band width and the sarcomere length decreased according to the myofilament O-GlcNAc level. Some structural proteins of the sarcomere such as desmin, αB-crystallin, α-actinin, moesin and filamin-C have been identified within modulated protein complexes through O-GlcNAc level variations. Their interactions seemed to be changed, especially for desmin and αB-crystallin. For the first time, our findings clearly demonstrate that O-GlcNAcylation, through dynamic regulations of the structural interactome, could be an important modulator of the sarcomeric structure and may provide new insights in the understanding of molecular mechanisms of neuromuscular diseases characterized by a disorganization of the sarcomeric structure. In the present study, we demonstrated a role of O-GlcNAcylation in the sarcomeric structure modulation. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. Macrophage depletion impairs skeletal muscle regeneration: The roles of regulatory factors for muscle regeneration.

    PubMed

    Liu, Xiaoguang; Liu, Yu; Zhao, Linlin; Zeng, Zhigang; Xiao, Weihua; Chen, Peijie

    2017-03-01

    Though macrophages are essential for skeletal muscle regeneration, which is a complex process, the roles and mechanisms of the macrophages in the process of muscle regeneration are still not fully understood. The objective of this study is to explore the roles of macrophages and the mechanisms involved in the regeneration of injured skeletal muscle. One hundred and twelve C57BL/6 mice were randomly divided into muscle contusion and macrophages depleted groups. Their gastrocnemius muscles were harvested at the time points of 12 h, 1, 3, 5, 7, 14 d post-injury. The changes in skeletal muscle morphology were assessed by hematoxylin and eosin (HE) stain. The gene expression was analyzed by real-time polymerase chain reaction. The data showed that CL-liposomes treatment did affect the expression of myogenic regulatory factors (MyoD, myogenin) after injury. In addition, CL-liposomes treatment decreased the expression of regulatory factors of muscle regeneration (HGF, uPA, COX-2, IGF-1, MGF, FGF6) and increased the expression of inflammatory cytokines (TGF-β1, TNF-α, IL-1β, RANTES) in the late stage of regeneration. Moreover, there were significant correlations between macrophages and some regulatory factors (such as HGF, uPA) for muscle regeneration. These results suggested that macrophages depletion impairs skeletal muscle regeneration and that the regulatory factors for muscle regeneration may play important roles in this process. © 2017 International Federation for Cell Biology.

  16. Alterations in the mitochondrial regulatory pathways constituted by the nuclear co-factors PGC-1alpha or PGC-1beta and mitofusin 2 in skeletal muscle in type 2 diabetes.

    PubMed

    Zorzano, Antonio; Hernández-Alvarez, María Isabel; Palacín, Manuel; Mingrone, Geltrude

    2010-01-01

    Muscle mitochondrial metabolism is regulated by a number of factors, many of which are responsible for the transcription of nuclear genes encoding mitochondrial proteins such as PPARdelta, PGC-1alpha or PGC-1beta. Recent evidence indicates that proteins participating in mitochondrial dynamics also regulate mitochondrial metabolism. Thus, in cultured cells the mitochondrial fusion protein mitofusin 2 (Mfn2) stimulates respiration, substrate oxidation and the expression of subunits involved in respiratory complexes. Mitochondrial dysfunction has been reported in skeletal muscle of type 2 diabetic patients. Reduced mitochondrial mass and defective activity has been proposed to explain this dysfunction. Alterations in mitochondrial metabolism may be crucial to account for some of the pathophysiological traits that characterize type 2 diabetes. Skeletal muscle of type 2 diabetic patients shows reduced expression of PGC-1alpha, PGC-1beta, and Mfn2. In addition, a differential response to bilio-pancreatic diversion-induced weight loss in non-diabetic and type 2 diabetic patients has been reported. While non-diabetic morbidly obese subjects showed an increased expression of genes encoding Mfn2, PGC-1alpha, PGC-1beta, PPARdelta or SIRT1 in response to bariatric surgery-induced weight loss, no effect was detected in type 2 diabetic patients. These observations suggest the existence of a heritable component responsible for the abnormal control of the expression of genes encoding for modulators of mitochondrial biogenesis/metabolism, and which may participate in the development of the disease. Copyright © 2010 Elsevier B.V. All rights reserved.

  17. MST1, a key player, in enhancing fast skeletal muscle atrophy

    PubMed Central

    2013-01-01

    Background Skeletal muscle undergoes rapid atrophy upon denervation and the underlying mechanisms are complicated. FOXO3a has been implicated as a major mediator of muscle atrophy, but how its subcellular location and activity is controlled during the pathogenesis of muscle atrophy remains largely unknown. MST1 (Mammalian Sterile 20-like kinase 1) is identified as a central component of the Hippo signaling pathway. MST1 has been shown to mediate phosphorylation of FOXO3a at Ser207. Whether this MST1-FOXO signaling cascade exerts any functional consequence on cellular homeostasis remains to be investigated. Result We identified that MST1 kinase was expressed widely in skeletal muscles and was dramatically up-regulated in fast- but not slow-dominant skeletal muscles immediately following denervation. The results of our histological and biochemical studies demonstrated that deletion of MST1 significantly attenuated denervation-induced skeletal muscle wasting and decreased expression of Atrogin-1 and LC3 genes in fast-dominant skeletal muscles from three- to five-month-old adult mice. Further studies indicated that MST1, but not MST2, remarkably increased FOXO3a phosphorylation level at Ser207 and promoted its nuclear translocation in atrophic fast-dominant muscles. Conclusions We have established that MST1 kinase plays an important role in regulating denervation-induced skeletal muscle atrophy. During the early stage of muscle atrophy, the up-regulated MST1 kinase promoted progression of neurogenic atrophy in fast-dominant skeletal muscles through activation of FOXO3a transcription factors. PMID:23374633

  18. FGFR1 inhibits skeletal muscle atrophy associated with hindlimb suspension

    PubMed Central

    Eash, John; Olsen, Aaron; Breur, Gert; Gerrard, Dave; Hannon, Kevin

    2007-01-01

    Background Skeletal muscle atrophy can occur under many different conditions, including prolonged disuse or immobilization, cachexia, cushingoid conditions, secondary to surgery, or with advanced age. The mechanisms by which unloading of muscle is sensed and translated into signals controlling tissue reduction remains a major question in the field of musculoskeletal research. While the fibroblast growth factors (FGFs) and their receptors are synthesized by, and intimately involved in, embryonic skeletal muscle growth and repair, their role maintaining adult muscle status has not been examined. Methods We examined the effects of ectopic expression of FGFR1 during disuse-mediated skeletal muscle atrophy, utilizing hindlimb suspension and DNA electroporation in mice. Results We found skeletal muscle FGF4 and FGFR1 mRNA expression to be modified by hind limb suspension,. In addition, we found FGFR1 protein localized in muscle fibers within atrophying mouse muscle which appeared to be resistant to atrophy. Electroporation and ectopic expression of FGFR1 significantly inhibited the decrease in muscle fiber area within skeletal muscles of mice undergoing suspension induced muscle atrophy. Ectopic FGFR1 expression in muscle also significantly stimulated protein synthesis in muscle fibers, and increased protein degradation in weight bearing muscle fibers. Conclusion These results support the theory that FGF signaling can play a role in regulation of postnatal skeletal muscle maintenance, and could offer potentially novel and efficient therapeutic options for attenuating muscle atrophy during aging, illness and spaceflight. PMID:17425786

  19. L-Citrulline Supplementation-Increased Skeletal Muscle PGC-1α Expression is Associated With Exercise Performance and Increased Skeletal Muscle Weight.

    PubMed

    Villareal, Myra O; Matsukawa, Toshiya; Isoda, Hiroko

    2018-05-24

    L-citrulline has recently been reported as a more effective supplement for promoting intracellular NO production compared to L-arginine. Here, the effect of L-citrulline on skeletal muscle and its influence on exercise performance were investigated. The underlying mechanism of its effect, specifically on the expression of skeletal muscle peroxisome proliferator-activated receptor-gamma coactivator-1α (PGC-1α), was also elucidated. Six-week-old ICR mice were orally supplemented with L-citrulline (250 mg kg -1 ) daily, and their performance in weight-loaded swimming exercise every other day for 15 days, was evaluated. In addition, mice muscles were weighed and evaluated for the expression of PGC-1α and PGC-1α-regulated genes. Mice orally supplemented with L-citrulline had significantly higher gastrocnemius and biceps femoris muscle mass. Although not statistically significant, L-citrulline prolonged the swimming time to exhaustion. PGC-1α upregulation was associated with vascular endothelial growth factor α (VEGFα) and insulin-like growth factor 1 (IGF1) upregulation. VEGFα and IGF1 are important for angiogenesis and muscle growth, respectively, and are regulated by PGC-1α. Treatment with L-NAME, a nitric oxide synthesis inhibitor, suppressed the L-citrulline-induced PGC-1α upregulation in-vitro. Supplementation with L-citrulline upregulates skeletal muscle PGC-1α levels resulting to higher skeletal muscle weight that improves time to exhaustion during exercise. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  20. Human Milk and Donkey Milk, Compared to Cow Milk, Reduce Inflammatory Mediators and Modulate Glucose and Lipid Metabolism, Acting on Mitochondrial Function and Oleylethanolamide Levels in Rat Skeletal Muscle.

    PubMed

    Trinchese, Giovanna; Cavaliere, Gina; De Filippo, Chiara; Aceto, Serena; Prisco, Marina; Chun, Jong Tai; Penna, Eduardo; Negri, Rossella; Muredda, Laura; Demurtas, Andrea; Banni, Sebastiano; Berni-Canani, Roberto; Mattace Raso, Giuseppina; Calignano, Antonio; Meli, Rosaria; Greco, Luigi; Crispino, Marianna; Mollica, Maria P

    2018-01-01

    Scope: Milk from various species differs in nutrient composition. In particular, human milk (HM) and donkey milk (DM) are characterized by a relative high level of triacylglycerol enriched in palmitic acid in sn-2 position. These dietary fats seem to exert beneficial nutritional properties through N-acylethanolamine tissue modulation. The aim of this study is to compare the effects of cow milk (CM), DM, and HM on inflammation and glucose and lipid metabolism, focusing on mitochondrial function, efficiency, and dynamics in skeletal muscle, which is the major determinant of resting metabolic rate. Moreover, we also evaluated the levels of endocannabinoids and N-acylethanolamines in liver and skeletal muscle, since tissue fatty acid profiles can be modulated by nutrient intervention. Procedures: To this aim, rats were fed with CM, DM, or HM for 4 weeks. Then, glucose tolerance and insulin resistance were analyzed. Pro-inflammatory and anti-inflammatory cytokines were evaluated in serum and skeletal muscle. Skeletal muscle was also processed to estimate mitochondrial function, efficiency, and dynamics, oxidative stress, and antioxidant/detoxifying enzyme activities. Fatty acid profiles, endocannabinoids, and N-acylethanolamine congeners were determined in liver and skeletal muscle tissue. Results: We demonstrated that DM or HM administration reducing inflammation status, improves glucose disposal and insulin resistance and reduces lipid accumulation in skeletal muscle. Moreover, HM or DM administration increases redox status, and mitochondrial uncoupling, affecting mitochondrial dynamics in the skeletal muscle. Interestingly, HM and DM supplementation increase liver and muscle levels of the N-oleoylethanolamine (OEA), a key regulator of lipid metabolism and inflammation. Conclusions: HM and DM have a healthy nutritional effect, acting on inflammatory factors and glucose and lipid metabolism. This beneficial effect is associated to a modulation of mitochondrial function

  1. Human Milk and Donkey Milk, Compared to Cow Milk, Reduce Inflammatory Mediators and Modulate Glucose and Lipid Metabolism, Acting on Mitochondrial Function and Oleylethanolamide Levels in Rat Skeletal Muscle

    PubMed Central

    Trinchese, Giovanna; Cavaliere, Gina; De Filippo, Chiara; Aceto, Serena; Prisco, Marina; Chun, Jong Tai; Penna, Eduardo; Negri, Rossella; Muredda, Laura; Demurtas, Andrea; Banni, Sebastiano; Berni-Canani, Roberto; Mattace Raso, Giuseppina; Calignano, Antonio; Meli, Rosaria; Greco, Luigi; Crispino, Marianna; Mollica, Maria P.

    2018-01-01

    Scope: Milk from various species differs in nutrient composition. In particular, human milk (HM) and donkey milk (DM) are characterized by a relative high level of triacylglycerol enriched in palmitic acid in sn-2 position. These dietary fats seem to exert beneficial nutritional properties through N-acylethanolamine tissue modulation. The aim of this study is to compare the effects of cow milk (CM), DM, and HM on inflammation and glucose and lipid metabolism, focusing on mitochondrial function, efficiency, and dynamics in skeletal muscle, which is the major determinant of resting metabolic rate. Moreover, we also evaluated the levels of endocannabinoids and N-acylethanolamines in liver and skeletal muscle, since tissue fatty acid profiles can be modulated by nutrient intervention. Procedures: To this aim, rats were fed with CM, DM, or HM for 4 weeks. Then, glucose tolerance and insulin resistance were analyzed. Pro-inflammatory and anti-inflammatory cytokines were evaluated in serum and skeletal muscle. Skeletal muscle was also processed to estimate mitochondrial function, efficiency, and dynamics, oxidative stress, and antioxidant/detoxifying enzyme activities. Fatty acid profiles, endocannabinoids, and N-acylethanolamine congeners were determined in liver and skeletal muscle tissue. Results: We demonstrated that DM or HM administration reducing inflammation status, improves glucose disposal and insulin resistance and reduces lipid accumulation in skeletal muscle. Moreover, HM or DM administration increases redox status, and mitochondrial uncoupling, affecting mitochondrial dynamics in the skeletal muscle. Interestingly, HM and DM supplementation increase liver and muscle levels of the N-oleoylethanolamine (OEA), a key regulator of lipid metabolism and inflammation. Conclusions: HM and DM have a healthy nutritional effect, acting on inflammatory factors and glucose and lipid metabolism. This beneficial effect is associated to a modulation of mitochondrial function

  2. Fibroblast growth factor signaling in skeletal development and disease

    PubMed Central

    Ornitz, David M.; Marie, Pierre J.

    2015-01-01

    Fibroblast growth factor (FGF) signaling pathways are essential regulators of vertebrate skeletal development. FGF signaling regulates development of the limb bud and formation of the mesenchymal condensation and has key roles in regulating chondrogenesis, osteogenesis, and bone and mineral homeostasis. This review updates our review on FGFs in skeletal development published in Genes & Development in 2002, examines progress made on understanding the functions of the FGF signaling pathway during critical stages of skeletogenesis, and explores the mechanisms by which mutations in FGF signaling molecules cause skeletal malformations in humans. Links between FGF signaling pathways and other interacting pathways that are critical for skeletal development and could be exploited to treat genetic diseases and repair bone are also explored. PMID:26220993

  3. Fibroblast growth factor signaling in skeletal development and disease.

    PubMed

    Ornitz, David M; Marie, Pierre J

    2015-07-15

    Fibroblast growth factor (FGF) signaling pathways are essential regulators of vertebrate skeletal development. FGF signaling regulates development of the limb bud and formation of the mesenchymal condensation and has key roles in regulating chondrogenesis, osteogenesis, and bone and mineral homeostasis. This review updates our review on FGFs in skeletal development published in Genes & Development in 2002, examines progress made on understanding the functions of the FGF signaling pathway during critical stages of skeletogenesis, and explores the mechanisms by which mutations in FGF signaling molecules cause skeletal malformations in humans. Links between FGF signaling pathways and other interacting pathways that are critical for skeletal development and could be exploited to treat genetic diseases and repair bone are also explored. © 2015 Ornitz and Marie; Published by Cold Spring Harbor Laboratory Press.

  4. Nitric oxide-dependent modulation of sympathetic neural control of oxygenation in exercising human skeletal muscle

    PubMed Central

    Chavoshan, Bahman; Sander, Mikael; Sybert, Troy E; Hansen, Jim; Victor, Ronald G; Thomas, Gail D

    2002-01-01

    Nitric oxide (NO) attenuates α-adrenergic vasoconstriction in contracting rodent skeletal muscle, but it is unclear if NO plays a similar role in human muscle. We therefore hypothesized that in humans, NO produced in exercising skeletal muscle blunts the vasoconstrictor response to sympathetic activation. We assessed vasoconstrictor responses in the microcirculation of human forearm muscle using near-infrared spectroscopy to measure decreases in muscle oxygenation during reflex sympathetic activation evoked by lower body negative pressure (LBNP). Experiments were performed before and after NO synthase inhibition produced by systemic infusion of NG-nitro-l-arginine methyl ester (l-NAME). Before l-NAME, LBNP at −20 mmHg decreased muscle oxygenation by 20 ± 2 % in resting forearm and by 2 ± 3 % in exercising forearm (n = 20), demonstrating metabolic modulation of sympathetic vasoconstriction. As expected, l-NAME increased mean arterial pressure by 17 ± 3 mmHg, leading to baroreflex-mediated supression of baseline muscle sympathetic nerve activity (SNA). The increment in muscle SNA in response to LBNP at −20 mmHg also was attenuated after l-NAME (before, +14 ± 2; after, +8 ± 1 bursts min−1; n = 6), but this effect of l-NAME was counteracted by increasing LBNP to −40 mmHg (+19 ± 2 bursts min−1). After l-NAME, LBNP at −20 mmHg decreased muscle oxygenation similarly in resting (−11 ± 3 %) and exercising (−10 ± 2 %) forearm (n = 12). Likewise, LBNP at −40 mmHg decreased muscle oxygenation both in resting (−19 ± 4 %) and exercising (−21 ± 5 %) forearm (n = 8). These data advance the hypothesis that NO plays an important role in modulating sympathetic vasoconstriction in the microcirculation of exercising muscle, because such modulation is abrogated by NO synthase inhibition with l-NAME. PMID:11927694

  5. SIRT1 may play a crucial role in overload‐induced hypertrophy of skeletal muscle

    PubMed Central

    Koltai, Erika; Bori, Zoltán; Chabert, Clovis; Dubouchaud, Hervé; Naito, Hisashi; Machida, Shuichi; Davies, Kelvin JA; Murlasits, Zsolt; Fry, Andrew C; Boldogh, Istvan

    2017-01-01

    Key points Silent mating type information regulation 2 homologue 1 (SIRT1) activity and content increased significantly in overload‐induced hypertrophy.SIRT1‐mediated signalling through Akt, the endothelial nitric oxide synthase mediated pathway, regulates anabolic process in the hypertrophy of skeletal muscle.The regulation of catabolic signalling via forkhead box O 1 and protein ubiquitination is SIRT1 dependent.Overload‐induced changes in microRNA levels regulate SIRT1 and insulin‐like growth factor 1 signalling. Abstract Significant skeletal muscle mass guarantees functional wellbeing and is important for high level performance in many sports. Although the molecular mechanism for skeletal muscle hypertrophy has been well studied, it still is not completely understood. In the present study, we used a functional overload model to induce plantaris muscle hypertrophy by surgically removing the soleus and gastrocnemius muscles in rats. Two weeks of muscle ablation resulted in a 40% increase in muscle mass, which was associated with a significant increase in silent mating type information regulation 2 homologue 1 (SIRT1) content and activity (P < 0.001). SIRT1‐regulated Akt, endothelial nitric oxide synthase and GLUT4 levels were also induced in hypertrophied muscles, and SIRT1 levels correlated with muscle mass, paired box protein 7 (Pax7), proliferating cell nuclear antigen (PCNA) and nicotinamide phosphoribosyltransferase (Nampt) levels. Alternatively, decreased forkhead box O 1 (FOXO1) and increased K48 polyubiquitination also suggest that SIRT1 could be involved in the catabolic process of hypertrophy. Furthermore, increased levels of K63 and muscle RING finger 2 (MuRF2) protein could also be important enhancers of muscle mass. We report here that the levels of miR1 and miR133a decrease in hypertrophy and negatively correlate with muscle mass, SIRT1 and Nampt levels. Our results reveal a strong correlation between SIRT1 levels and activity, SIRT1

  6. Skeletal unloading induces resistance to insulin-like growth factor I

    NASA Technical Reports Server (NTRS)

    Bikle, D. D.; Harris, J.; Halloran, B. P.; Morey-Holton, E. R.

    1994-01-01

    In previous studies with a hindlimb elevation model, we demonstrated that skeletal unloading transiently inhibits bone formation. This effect is limited to the unloaded bones (the normally loaded humerus does not cease growing), suggesting that local factors are of prime importance. IGF-I is one such factor; it is produced in bone and stimulates bone formation. To determine the impact of skeletal unloading on IGF-I production and function, we assessed the mRNA levels of IGF-I and its receptor (IGF-IR) in the proximal tibia and distal femur of growing rats during 2 weeks of hindlimb elevation. The mRNA levels for IGF-I and IGF-IR rose during hindlimb elevation, returning toward control values during recovery. This was accompanied by a 77% increase in IGF-I levels in the bone, peaking at day 10 of unloading. Changes in IGF binding protein levels were not observed. Infusion of IGF-I (200 micrograms/day) during 1 week of hindlimb elevation doubled the increase in bone mass of the control animals but failed to reverse the cessation of bone growth in the hindlimb-elevated animals. We conclude that skeletal unloading induces resistance to IGF-I, which may result secondarily in increased local production of IGF-I.

  7. Endothelium‐dependent vasodilatory signalling modulates α1‐adrenergic vasoconstriction in contracting skeletal muscle of humans

    PubMed Central

    Hearon, Christopher M.; Kirby, Brett S.; Luckasen, Gary J.; Larson, Dennis G.

    2016-01-01

    Key points ‘Functional sympatholysis’ describes the ability of contracting skeletal muscle to attenuate sympathetic vasoconstriction, and is critical to ensure proper blood flow and oxygen delivery to metabolically active skeletal muscle. The signalling mechanism responsible for sympatholysis in healthy humans is unknown.Evidence from animal models has identified endothelium‐derived hyperpolarization (EDH) as a potential mechanism capable of attenuating sympathetic vasoconstriction.In this study, increasing endothelium‐dependent signalling during exercise significantly enhanced the ability of contracting skeletal muscle to attenuate sympathetic vasoconstriction in humans.This is the first study in humans to identify endothelium‐dependent regulation of sympathetic vasoconstriction in contracting skeletal muscle, and specifically supports a role for EDH‐like vasodilatory signalling.Impaired functional sympatholysis is a common feature of cardiovascular ageing, hypertension and heart failure, and thus identifying fundamental mechanisms responsible for sympatholysis is clinically relevant. Abstract Stimulation of α‐adrenoceptors elicits vasoconstriction in resting skeletal muscle that is blunted during exercise in an intensity‐dependent manner. In humans, the underlying mechanisms remain unclear. We tested the hypothesis that stimulating endothelium‐dependent vasodilatory signalling will enhance the ability of contracting skeletal muscle to blunt α1‐adrenergic vasoconstriction. Changes in forearm vascular conductance (FVC; Doppler ultrasound, brachial intra‐arterial pressure via catheter) to local intra‐arterial infusion of phenylephrine (PE; α1‐adrenoceptor agonist) were calculated during (1) infusion of the endothelium‐dependent vasodilators acetylcholine (ACh) and adenosine triphosphate (ATP), the endothelium‐independent vasodilator (sodium nitroprusside, SNP), or potassium chloride (KCl) at rest; (2) mild or moderate intensity

  8. PGC-1α-mediated branched-chain amino acid metabolism in the skeletal muscle.

    PubMed

    Hatazawa, Yukino; Tadaishi, Miki; Nagaike, Yuta; Morita, Akihito; Ogawa, Yoshihiro; Ezaki, Osamu; Takai-Igarashi, Takako; Kitaura, Yasuyuki; Shimomura, Yoshiharu; Kamei, Yasutomi; Miura, Shinji

    2014-01-01

    Peroxisome proliferator-activated receptor (PPAR) γ coactivator 1α (PGC-1α) is a coactivator of various nuclear receptors and other transcription factors, which is involved in the regulation of energy metabolism, thermogenesis, and other biological processes that control phenotypic characteristics of various organ systems including skeletal muscle. PGC-1α in skeletal muscle is considered to be involved in contractile protein function, mitochondrial function, metabolic regulation, intracellular signaling, and transcriptional responses. Branched-chain amino acid (BCAA) metabolism mainly occurs in skeletal muscle mitochondria, and enzymes related to BCAA metabolism are increased by exercise. Using murine skeletal muscle overexpressing PGC-1α and cultured cells, we investigated whether PGC-1α stimulates BCAA metabolism by increasing the expression of enzymes involved in BCAA metabolism. Transgenic mice overexpressing PGC-1α specifically in the skeletal muscle had increased the expression of branched-chain aminotransferase (BCAT) 2, branched-chain α-keto acid dehydrogenase (BCKDH), which catabolize BCAA. The expression of BCKDH kinase (BCKDK), which phosphorylates BCKDH and suppresses its enzymatic activity, was unchanged. The amount of BCAA in the skeletal muscle was significantly decreased in the transgenic mice compared with that in the wild-type mice. The amount of glutamic acid, a metabolite of BCAA catabolism, was increased in the transgenic mice, suggesting the activation of muscle BCAA metabolism by PGC-1α. In C2C12 cells, the overexpression of PGC-1α significantly increased the expression of BCAT2 and BCKDH but not BCKDK. Thus, PGC-1α in the skeletal muscle is considered to significantly contribute to BCAA metabolism.

  9. PGC-1α-Mediated Branched-Chain Amino Acid Metabolism in the Skeletal Muscle

    PubMed Central

    Nagaike, Yuta; Morita, Akihito; Ogawa, Yoshihiro; Ezaki, Osamu; Takai-Igarashi, Takako; Kitaura, Yasuyuki; Shimomura, Yoshiharu; Kamei, Yasutomi; Miura, Shinji

    2014-01-01

    Peroxisome proliferator-activated receptor (PPAR) γ coactivator 1α (PGC-1α) is a coactivator of various nuclear receptors and other transcription factors, which is involved in the regulation of energy metabolism, thermogenesis, and other biological processes that control phenotypic characteristics of various organ systems including skeletal muscle. PGC-1α in skeletal muscle is considered to be involved in contractile protein function, mitochondrial function, metabolic regulation, intracellular signaling, and transcriptional responses. Branched-chain amino acid (BCAA) metabolism mainly occurs in skeletal muscle mitochondria, and enzymes related to BCAA metabolism are increased by exercise. Using murine skeletal muscle overexpressing PGC-1α and cultured cells, we investigated whether PGC-1α stimulates BCAA metabolism by increasing the expression of enzymes involved in BCAA metabolism. Transgenic mice overexpressing PGC-1α specifically in the skeletal muscle had increased the expression of branched-chain aminotransferase (BCAT) 2, branched-chain α-keto acid dehydrogenase (BCKDH), which catabolize BCAA. The expression of BCKDH kinase (BCKDK), which phosphorylates BCKDH and suppresses its enzymatic activity, was unchanged. The amount of BCAA in the skeletal muscle was significantly decreased in the transgenic mice compared with that in the wild-type mice. The amount of glutamic acid, a metabolite of BCAA catabolism, was increased in the transgenic mice, suggesting the activation of muscle BCAA metabolism by PGC-1α. In C2C12 cells, the overexpression of PGC-1α significantly increased the expression of BCAT2 and BCKDH but not BCKDK. Thus, PGC-1α in the skeletal muscle is considered to significantly contribute to BCAA metabolism. PMID:24638054

  10. Specification of skeletal muscle differentiation by repressor element-1 silencing transcription factor (REST)-regulated Kv7.4 potassium channels

    PubMed Central

    Iannotti, Fabio Arturo; Barrese, Vincenzo; Formisano, Luigi; Miceli, Francesco; Taglialatela, Maurizio

    2013-01-01

    Changes in the expression of potassium (K+) channels is a pivotal event during skeletal muscle differentiation. In mouse C2C12 cells, similarly to human skeletal muscle cells, myotube formation increased the expression of Kv7.1, Kv7.3, and Kv7.4, the last showing the highest degree of regulation. In C2C12 cells, Kv7.4 silencing by RNA interference reduced the expression levels of differentiation markers (myogenin, myosin heavy chain, troponinT-1, and Pax3) and impaired myotube formation and multinucleation. In Kv7.4-silenced cells, the differentiation-promoting effect of the Kv7 activator N-(2-amino-4-(4-fluorobenzylamino)-phenyl)-carbamic acid ethyl ester (retigabine) was abrogated. Expression levels for the repressor element-1 silencing transcription factor (REST) declined during myotube formation. Transcript levels for Kv7.4, as well as for myogenin, troponinT-1, and Pax3, were reduced by REST overexpression and enhanced upon REST suppression by RNA interference. Four regions containing potential REST-binding sites in the 5′ untranslated region and in the first intron of the Kv7.4 gene were identified by bioinformatic analysis. Chromatin immunoprecipitation assays showed that REST binds to these regions, exhibiting a higher efficiency in myoblasts than in myotubes. These data suggest that Kv7.4 plays a permissive role in skeletal muscle differentiation and highlight REST as a crucial transcriptional regulator for this K+ channel subunit. PMID:23242999

  11. Undernutrition regulates the expression of a novel splice variant of myostatin and insulin-like growth factor 1 in ovine skeletal muscle.

    PubMed

    Jeanplong, F; Osepchook, C C; Falconer, S J; Smith, H K; Bass, J J; McMahon, C D; Oldham, J M

    2015-07-01

    Undernutrition suppresses the growth of skeletal muscles and alters the expression of insulin-like growth factor 1 (IGF1), a key mitogen, and myostatin, a potent inhibitor of myogenesis. These changes can explain, at least in part, the reduced growth of skeletal muscles in underfed lambs. We have recently identified a myostatin splice variant (MSV) that binds to and antagonizes the canonical signaling of myostatin. In the present study, we hypothesized that the expression of MSV would be reduced in conjunction with myostatin and IGF1 in response to underfeeding in skeletal muscles of sheep. Young growing ewes were fed either ad libitum or an energy-restricted diet (30% of maintenance requirements) for 28 d. This regime of underfeeding resulted in a 24% reduction in body mass (P < 0.001) and a 36% reduction in the mass of the semitendinosus muscles relative to controls (P < 0.001) by day 28. The concentrations of MSV and IGF1 messenger RNA (mRNA) were reduced (both P < 0.001), but myostatin mRNA was not altered in semitendinosus muscles. Unlike the reduced expression of mRNA, the abundance of MSV protein was increased (P < 0.05) and there was no change in the abundance of myostatin protein. Our results suggest that undernutrition for 28 d decreases the signaling of myostatin by increasing the abundance of MSV protein. Although this action may reduce the growth inhibitory activity of myostatin, it cannot prevent the loss of growth of skeletal muscles during undernutrition. Copyright © 2015 Elsevier Inc. All rights reserved.

  12. Myogenic Growth Factor Present in Skeletal Muscle is Purified by Heparin-Affinity Chromatography

    NASA Astrophysics Data System (ADS)

    Kardami, Elissavet; Spector, Dennis; Strohman, Richard C.

    1985-12-01

    A myogenic growth factor has been purified from a skeletal muscle, the anterior latissimus dorsi, of adult chickens. In the range of 1-10 ng, this factor stimulates DNA synthesis as well as protein and muscle-specific myosin accumulation in myogenic cell cultures. Purification is achieved through binding of the factor to heparin. The factor is distinct from transferrin and works synergistically with transferrin in stimulating myogenesis in vitro.

  13. SIRT1 may play a crucial role in overload-induced hypertrophy of skeletal muscle.

    PubMed

    Koltai, Erika; Bori, Zoltán; Chabert, Clovis; Dubouchaud, Hervé; Naito, Hisashi; Machida, Shuichi; Davies, Kelvin Ja; Murlasits, Zsolt; Fry, Andrew C; Boldogh, Istvan; Radak, Zsolt

    2017-06-01

    Silent mating type information regulation 2 homologue 1 (SIRT1) activity and content increased significantly in overload-induced hypertrophy. SIRT1-mediated signalling through Akt, the endothelial nitric oxide synthase mediated pathway, regulates anabolic process in the hypertrophy of skeletal muscle. The regulation of catabolic signalling via forkhead box O 1 and protein ubiquitination is SIRT1 dependent. Overload-induced changes in microRNA levels regulate SIRT1 and insulin-like growth factor 1 signalling. Significant skeletal muscle mass guarantees functional wellbeing and is important for high level performance in many sports. Although the molecular mechanism for skeletal muscle hypertrophy has been well studied, it still is not completely understood. In the present study, we used a functional overload model to induce plantaris muscle hypertrophy by surgically removing the soleus and gastrocnemius muscles in rats. Two weeks of muscle ablation resulted in a 40% increase in muscle mass, which was associated with a significant increase in silent mating type information regulation 2 homologue 1 (SIRT1) content and activity (P < 0.001). SIRT1-regulated Akt, endothelial nitric oxide synthase and GLUT4 levels were also induced in hypertrophied muscles, and SIRT1 levels correlated with muscle mass, paired box protein 7 (Pax7), proliferating cell nuclear antigen (PCNA) and nicotinamide phosphoribosyltransferase (Nampt) levels. Alternatively, decreased forkhead box O 1 (FOXO1) and increased K48 polyubiquitination also suggest that SIRT1 could be involved in the catabolic process of hypertrophy. Furthermore, increased levels of K63 and muscle RING finger 2 (MuRF2) protein could also be important enhancers of muscle mass. We report here that the levels of miR1 and miR133a decrease in hypertrophy and negatively correlate with muscle mass, SIRT1 and Nampt levels. Our results reveal a strong correlation between SIRT1 levels and activity, SIRT1-regulated pathways and

  14. Growth factor involvement in tension-induced skeletal muscle growth

    NASA Technical Reports Server (NTRS)

    Vandenburgh, H. H.

    1987-01-01

    Muscle tissue culture techniques were developed to grow skeletal myofibers which differentiate into more adult-like myofibers. Mechanical simulation studies of these muscle cells in a newly developed mechanical cell simulator can now be performed to study growth processes in skeletal muscle. Conditions in the mechanical cell simulator were defined where mechanical activity can either prevent muscle wasting or stimulate muscle growth. The role of endogenous and exogenous growth factors in tension-induced muscle growth is being investigated under the defined conditions of tissue culture.

  15. Monocyte/Macrophage-derived IGF-1 Orchestrates Murine Skeletal Muscle Regeneration and Modulates Autocrine Polarization

    PubMed Central

    Tonkin, Joanne; Temmerman, Lieve; Sampson, Robert D; Gallego-Colon, Enrique; Barberi, Laura; Bilbao, Daniel; Schneider, Michael D; Musarò, Antonio; Rosenthal, Nadia

    2015-01-01

    Insulin-like growth factor 1 (IGF-1) is a potent enhancer of tissue regeneration, and its overexpression in muscle injury leads to hastened resolution of the inflammatory phase. Here, we show that monocytes/macrophages constitute an important initial source of IGF-1 in muscle injury, as conditional deletion of the IGF-1 gene specifically in mouse myeloid cells (ϕIGF-1 CKO) blocked the normal surge of local IGF-1 in damaged muscle and significantly compromised regeneration. In injured muscle, Ly6C+ monocytes/macrophages and CD206+ macrophages expressed equivalent IGF-1 levels, which were transiently upregulated during transition from the inflammation to repair. In injured ϕIGF-1 CKO mouse muscle, accumulation of CD206+ macrophages was impaired, while an increase in Ly6C+ monocytes/macrophages was favored. Transcriptional profiling uncovered inflammatory skewing in ϕIGF-1 CKO macrophages, which failed to fully induce a reparative gene program in vitro or in vivo, revealing a novel autocrine role for IGF-1 in modulating murine macrophage phenotypes. These data establish local macrophage-derived IGF-1 as a key factor in inflammation resolution and macrophage polarization during muscle regeneration. PMID:25896247

  16. Insulin-like growth factor-1 enhances rat skeletal muscle charge movement and L-type Ca2+ channel gene expression

    PubMed Central

    Wang, Zhong-Min; Laura Messi, María; Renganathan, Muthukrishnan; Delbono, Osvaldo

    1999-01-01

    We investigated whether insulin-like growth factor-1 (IGF-1), an endogenous potent activator of skeletal muscle proliferation and differentiation, enhances L-type Ca2+ channel gene expression resulting in increased functional voltage sensors in single skeletal muscle cells. Charge movement and inward Ca2+ current were recorded in primary cultured rat myoballs using the whole-cell configuration of the patch-clamp technique. Ca2+ current and maximum charge movement (Qmax) were potentiated in cells treated with IGF-1 without significant changes in their voltage dependence. Peak Ca2+ current in control and IGF-1-treated cells was -7·8 ± 0·44 and -10·5 ± 0·37 pA pF−1, respectively (P < 0·01), whilst Qmax was 12·9 ± 0·4 and 22·0 ± 0·3 nC μF−1, respectively (P < 0·01). The number of L-type Ca2+ channels was found to increase in the same preparation. The maximum binding capacity (Bmax) of the high-affinity radioligand [3H]PN200-110 in control and IGF-1-treated cells was 1·21 ± 0·25 and 3·15 ± 0·5 pmol (mg protein)−1, respectively (P < 0·01). No significant change in the dissociation constant for [3H]PN200-110 was found. Antisense RNA amplification showed a significant increase in the level of mRNA encoding the L-type Ca2+ channel α1-subunit in IGF-1-treated cells. This study demonstrates that IGF-1 regulates charge movement and the level of L-type Ca2+ channel α1-subunits through activation of gene expression in skeletal muscle cells. PMID:10087334

  17. Growth factor involvement in tension-induced skeletal muscle growth

    NASA Technical Reports Server (NTRS)

    Vandenburgh, Herman H.

    1993-01-01

    Long-term manned space travel will require a better understanding of skeletal muscle atrophy which results from microgravity. Astronaut strength and dexterity must be maintained for normal mission operations and for emergency situations. Although exercise in space slows the rate of muscle loss, it does not prevent it. A biochemical understanding of how gravity/tension/exercise help to maintain muscle size by altering protein synthesis and/or degradation rate should ultimately allow pharmacological intervention to prevent muscle atrophy in microgravity. The overall objective is to examine some of the basic biochemical processes involved in tension-induced muscle growth. With an experimental in vitro system, the role of exogenous and endogenous muscle growth factors in mechanically stimulated muscle growth are examined. Differentiated avian skeletal myofibers can be 'exercised' in tissue culture using a newly developed dynamic mechanical cell stimulator device which simulates different muscle activity patterns. Patterns of mechanical activity which significantly affect muscle growth and metabolic characteristics were found. Both exogenous and endogenous growth factors are essential for tension-induced muscle growth. Exogenous growth factors found in serum, such as insulin, insulin-like growth factors, and steroids, are important regulators of muscle protein turnover rates and mechanically-induced muscle growth. Endogenous growth factors are synthesized and released into the culture medium when muscle cells are mechanically stimulated. At least one family of mechanically induced endogenous factors, the prostaglandins, help to regulate the rates of protein turnover in muscle cells. Endogenously synthesized IGF-1 is another. The interaction of muscle mechanical activity and these growth factors in the regulation of muscle protein turnover rates with our in vitro model system is studied.

  18. NF-κB Regulation of YY1 Inhibits Skeletal Myogenesis through Transcriptional Silencing of Myofibrillar Genes▿ †

    PubMed Central

    Wang, Huating; Hertlein, Erin; Bakkar, Nadine; Sun, Hao; Acharyya, Swarnali; Wang, Jingxin; Carathers, Micheal; Davuluri, Ramana; Guttridge, Denis C.

    2007-01-01

    NF-κB signaling is implicated as an important regulator of skeletal muscle homeostasis, but the mechanisms by which this transcription factor contributes to muscle maturation and turnover remain unclear. To gain insight into these mechanisms, gene expression profiling was examined in C2C12 myoblasts devoid of NF-κB activity. Interestingly, even in proliferating myoblasts, the absence of NF-κB caused the pronounced induction of several myofibrillar genes, suggesting that NF-κB functions as a negative regulator of late-stage muscle differentiation. Although several myofibrillar promoters contain predicted NF-κB binding sites, functional analysis using the troponin-I2 gene as a model revealed that NF-κB-mediated repression does not occur through direct DNA binding. In the search for an indirect mediator, the transcriptional repressor YinYang1 (YY1) was identified. While inducers of NF-κB stimulated YY1 expression in multiple cell types, genetic ablation of the RelA/p65 subunit of NF-κB in both cultured cells and adult skeletal muscle correlated with reduced YY1 transcripts and protein. NF-κB regulation of YY1 occurred at the transcriptional level, mediated by direct binding of the p50/p65 heterodimer complex to the YY1 promoter. Furthermore, YY1 was found associated with multiple myofibrillar promoters in C2C12 myoblasts containing NF-κB activity. Based on these results, we propose that NF-κB regulation of YY1 and transcriptional silencing of myofibrillar genes represent a new mechanism by which NF-κB functions in myoblasts to modulate skeletal muscle differentiation. PMID:17438126

  19. Body composition and skeletal health: too heavy? Too thin?

    PubMed

    Faje, Alexander; Klibanski, Anne

    2012-09-01

    The relationship between body composition and skeletal metabolism has received growing recognition. Low body weight is an established risk factor for fracture. The effect of obesity on skeletal health is less well defined. Extensive studies in patients with anorexia nervosa and obesity have illuminated many of the underlying biologic mechanisms by which body composition modulates bone mass. This review examines the relationship between body composition and bone mass through data from recent research studies throughout the weight spectrum ranging from anorexia nervosa to obesity.

  20. Insulin and insulin-like growth factor-1 induce pronounced hypertrophy of skeletal myofibers in tissue culture

    NASA Technical Reports Server (NTRS)

    Vandenburgh, Herman H.; Karlisch, Patricia; Shansky, Janet

    1990-01-01

    Skeletal myofibers differentiated from primary avian myoblasts in tissue culture can be maintained in positive nitrogen balance in a serum-free medium for at least 6 to 7 days when embedded in a three dimensional collagen gel matrix. The myofibers are metabolically sensitive to physiological concentrations of insulin but these concentrations do not stimulate cell growth. Higher insulin concentrations stimulate both cell hyperplasia and myofiber hypertrophy. Cell growth results from a long term 42 percent increase in total protein synthesis and a 38 percent increase in protein degradation. Myofiber diameters increase by 71 to 98 percent after 6 to 7 days in insulin-containing medium. Insulin-like growth factor-1 but not insulin-like growth factor-2, at 250 ng/ml, is as effective as insulin in stimulating cell hyperplasia and myofiber hypertrophy. This model system provides a new method for studying the long-term anabolic effects of insulin and insulin-like growth factors on myofiber hypertrophy under defined tissue culture conditions.

  1. TAK1 regulates skeletal muscle mass and mitochondrial function

    PubMed Central

    Hindi, Sajedah M.; Sato, Shuichi; Xiong, Guangyan; Bohnert, Kyle R.; Gibb, Andrew A.; Gallot, Yann S.; McMillan, Joseph D.; Hill, Bradford G.

    2018-01-01

    Skeletal muscle mass is regulated by a complex array of signaling pathways. TGF-β–activated kinase 1 (TAK1) is an important signaling protein, which regulates context-dependent activation of multiple intracellular pathways. However, the role of TAK1 in the regulation of skeletal muscle mass remains unknown. Here, we report that inducible inactivation of TAK1 causes severe muscle wasting, leading to kyphosis, in both young and adult mice.. Inactivation of TAK1 inhibits protein synthesis and induces proteolysis, potentially through upregulating the activity of the ubiquitin-proteasome system and autophagy. Phosphorylation and enzymatic activity of AMPK are increased, whereas levels of phosphorylated mTOR and p38 MAPK are diminished upon inducible inactivation of TAK1 in skeletal muscle. In addition, targeted inactivation of TAK1 leads to the accumulation of dysfunctional mitochondria and oxidative stress in skeletal muscle of adult mice. Inhibition of TAK1 does not attenuate denervation-induced muscle wasting in adult mice. Finally, TAK1 activity is highly upregulated during overload-induced skeletal muscle growth, and inactivation of TAK1 prevents myofiber hypertrophy in response to functional overload. Overall, our study demonstrates that TAK1 is a key regulator of skeletal muscle mass and oxidative metabolism. PMID:29415881

  2. Insulin-like growth factor-1 (IGF-1) promotes myoblast proliferation and skeletal muscle growth of embryonic chickens via the PI3K/Akt signalling pathway.

    PubMed

    Yu, Minli; Wang, Huan; Xu, Yali; Yu, Debing; Li, Dongfeng; Liu, Xiuhong; Du, Wenxing

    2015-08-01

    During embryonic development, IGF-1 fulfils crucial roles in skeletal myogenesis. However, the involvement of IGF-1-induced myoblast proliferation in muscle growth is still unclear. In the present study, we have characterised the role of IGF-1 in myoblast proliferation both in vitro and in vivo and have revealed novel details of how exogenous IGF-1 influences myogenic genes in chicken embryos. The results show that IGF-1 significantly induces the proliferation of cultured myoblasts in a dose-dependent manner. Additionally, the IGF-1 treatment significantly promoted myoblasts entering a new cell cycle and increasing the mRNA expression levels of cell cycle-dependent genes. However, these effects were inhibited by the PI3K inhibitor LY294002 and the Akt inhibitor KP372-1. These data indicated that the pro-proliferative effect of IGF-1 was mediated in response to the PI3K/Akt signalling pathway. Moreover, we also showed that exogenous IGF-1 stimulated myoblast proliferation in vivo. IGF-1 administration obviously promoted the incorporation of BrdU and remarkably increased the number of PAX7-positive cells in the skeletal muscle of chicken embryos. Administration of IGF-1 also significantly induced the upregulation of myogenic factors gene, the enhancement of c-Myc and the inhibition of myostatin (Mstn) expression. These findings demonstrate that IGF-1 has strong activity as a promoter of myoblast expansion and muscle fiber formation during early myogenesis. Therefore, this study offers insight into the mechanisms responsible for IGF-1-mediated stimulation of embryonic skeletal muscle development, which could have important implications for the improvement of chicken meat production. © 2015 International Federation for Cell Biology.

  3. Role of IGF1 and EFN-EPH signaling in skeletal metabolism.

    PubMed

    Lindsey, Richard C; Rundle, Charles H; Mohan, Subburaman

    2018-07-01

    Insulin-like growth factor 1(IGF1) and ephrin ligand (EFN)-receptor (EPH) signaling are both crucial for bone cell function and skeletal development and maintenance. IGF1 signaling is the major mediator of growth hormone-induced bone growth, but a host of different signals and factors regulate IGF1 signaling at the systemic and local levels. Disruption of the Igf1 gene results in reduced peak bone mass in both experimental animal models and humans. Additionally, EFN-EPH signaling is a complex system which, particularly through cell-cell interactions, contributes to the development and differentiation of many bone cell types. Recent evidence has demonstrated several ways in which the IGF1 and EFN-EPH signaling pathways interact with and depend upon each other to regulate bone cell function. While much remains to be elucidated, the interaction between these two signaling pathways opens a vast array of new opportunities for investigation into the mechanisms of and potential therapies for skeletal conditions such as osteoporosis and fracture repair. © 2018 Society for Endocrinology.

  4. Impact of skeletal unloading on bone formation: Role of systemic and local factors

    NASA Astrophysics Data System (ADS)

    Bikle, Daniel D.; Halloran, Bernard P.; Morey-Holton, Emily

    We have developed a model of skeletal unloading using growing rats whose hindlimbs are unweighted by tail suspension. The bones in the hindlimbs undergo a transient cessation of bone growth; when reloaded bone formation is accelerated until bone mass is restored. These changes do not occur in the normally loaded bones of the forelimbs. Associated with the fall in bone formation is a fall in 1,25(OH) 2D 3 production and osteocalcin levels. In contrast, no changes in parathyroid hormone, calcium, or corticosterone levels are seen. To examine the role of locally produced growth factors, we have measured the mRNA and protein levels of insulin like growth factor-1 (IGF-1) in bone during tail suspension. Surprisingly, both the mRNA and protein levels of IGF-1 increase during tail suspension as bone formation is reduced. Furthermore, the bones in the hindlimbs of the suspended animals develop a resistance to the growth promoting effects of both growth hormone and IGF-1 when given parenterally. Thus, the cessation of bone growth with skeletal unloading is apparently associated with a resistance to rather than failure to produce local growth factors. The cause of this resistance remains under active investigation.

  5. HIF-1-driven skeletal muscle adaptations to chronic hypoxia: molecular insights into muscle physiology.

    PubMed

    Favier, F B; Britto, F A; Freyssenet, D G; Bigard, X A; Benoit, H

    2015-12-01

    Skeletal muscle is a metabolically active tissue and the major body protein reservoir. Drop in ambient oxygen pressure likely results in a decrease in muscle cells oxygenation, reactive oxygen species (ROS) overproduction and stabilization of the oxygen-sensitive hypoxia-inducible factor (HIF)-1α. However, skeletal muscle seems to be quite resistant to hypoxia compared to other organs, probably because it is accustomed to hypoxic episodes during physical exercise. Few studies have observed HIF-1α accumulation in skeletal muscle during ambient hypoxia probably because of its transient stabilization. Nevertheless, skeletal muscle presents adaptations to hypoxia that fit with HIF-1 activation, although the exact contribution of HIF-2, I kappa B kinase and activating transcription factors, all potentially activated by hypoxia, needs to be determined. Metabolic alterations result in the inhibition of fatty acid oxidation, while activation of anaerobic glycolysis is less evident. Hypoxia causes mitochondrial remodeling and enhanced mitophagy that ultimately lead to a decrease in ROS production, and this acclimatization in turn contributes to HIF-1α destabilization. Likewise, hypoxia has structural consequences with muscle fiber atrophy due to mTOR-dependent inhibition of protein synthesis and transient activation of proteolysis. The decrease in muscle fiber area improves oxygen diffusion into muscle cells, while inhibition of protein synthesis, an ATP-consuming process, and reduction in muscle mass decreases energy demand. Amino acids released from muscle cells may also have protective and metabolic effects. Collectively, these results demonstrate that skeletal muscle copes with the energetic challenge imposed by O2 rarefaction via metabolic optimization.

  6. Leucine modulation of mitochondrial mass and oxygen consumption in skeletal muscle cells and adipocytes

    PubMed Central

    Sun, Xiaocun; Zemel, Michael B

    2009-01-01

    Background The effects of dairy on energy metabolism appear to be mediated, in part, by leucine and calcium which regulate both adipocyte and skeletal muscle energy metabolism. We recently demonstrated that leucine and calcitriol regulate fatty acid oxidation in skeletal muscle cells in vitro, with leucine promoting and calcitriol suppressing fatty acid oxidation. Moreover, leucine coordinately regulated adipocyte lipid metabolism to promote flux of lipid to skeletal muscle and regulate metabolic flexibility. We have now investigated the role of mitochondrial biogenesis in mediating these effects. Methods We tested the effect of leucine, calcitriol and calcium in regulation of mitochondrial mass using a fluorescence method and tested mitochondrial biogenesis regulatory genes as well mitochondrial component genes using real-time PCR. We also evaluated the effect of leucine on oxygen consumption with a modified perfusion system. Results Leucine (0.5 mM) increased mitochondrial mass by 30% and 53% in C2C12 myocytes and 3T3-L1 adipocytes, respectively, while calcitriol (10 nM) decreased mitochondrial abundance by 37% and 27% (p < 0.02). Leucine also stimulated mitochondrial biogenesis genes SIRT-1, PGC-1α and NRF-1 as well as mitochondrial component genes UCP3, COX, and NADH expression by 3–5 fold in C2C12 cells (p < 0.003). Adipocyte-conditioned medium reduced mitochondrial abundance (p < 0.001) and decreased UCP3 but increased PGC-1α expression in myocytes, suggesting a feedback stimulation of mitochondrial biogenesis. Similar data were observed in C2C12 myocytes co-cultured with adipocytes, with co-culture markedly suppressing mitochondrial abundance (p < 0.02). Leucine stimulated oxygen consumption in both C2C12 cells and adipocytes compared with either control or valine-treated cells. Transfection of C2C12 myocytes with SIRT-1 siRNA resulted in parallel suppression of SIRT-1 expression and leucine-induced stimulation of PGC-1α and NRF-1, indicating that SIRT

  7. Mesenchymal Stromal Cell Secreted Sphingosine 1-Phosphate (S1P) Exerts a Stimulatory Effect on Skeletal Myoblast Proliferation

    PubMed Central

    Tani, Alessia; Anderloni, Giulia; Pierucci, Federica; Matteini, Francesca; Chellini, Flaminia; Zecchi Orlandini, Sandra; Meacci, Elisabetta

    2014-01-01

    Bone-marrow-derived mesenchymal stromal cells (MSCs) have the potential to significantly contribute to skeletal muscle healing through the secretion of paracrine factors that support proliferation and enhance participation of the endogenous muscle stem cells in the process of repair/regeneration. However, MSC-derived trophic molecules have been poorly characterized. The aim of this study was to investigate paracrine signaling effects of MSCs on skeletal myoblasts. It was found, using a biochemical and morphological approach that sphingosine 1-phosphate (S1P), a natural bioactive lipid exerting a broad range of muscle cell responses, is secreted by MSCs and represents an important factor by which these cells exert their stimulatory effects on C2C12 myoblast and satellite cell proliferation. Indeed, exposure to conditioned medium obtained from MSCs cultured in the presence of the selective sphingosine kinase inhibitor (iSK), blocked increased cell proliferation caused by the conditioned medium from untreated MSCs, and the addition of exogenous S1P in the conditioned medium from MSCs pre-treated with iSK further increased myoblast proliferation. Finally, we also demonstrated that the myoblast response to MSC-secreted vascular endothelial growth factor (VEGF) involves the release of S1P from C2C12 cells. Our data may have important implications in the optimization of cell-based strategies to promote skeletal muscle regeneration. PMID:25264785

  8. The role of nNOS and PGC-1α in skeletal muscle cells.

    PubMed

    Baldelli, Sara; Lettieri Barbato, Daniele; Tatulli, Giuseppe; Aquilano, Katia; Ciriolo, Maria Rosa

    2014-11-15

    Neuronal nitric oxide synthase (nNOS) and peroxisome proliferator activated receptor γ co-activator 1α (PGC-1α) are two fundamental factors involved in the regulation of skeletal muscle cell metabolism. nNOS exists as several alternatively spliced variants, each having a specific pattern of subcellular localisation. Nitric oxide (NO) functions as a second messenger in signal transduction pathways that lead to the expression of metabolic genes involved in oxidative metabolism, vasodilatation and skeletal muscle contraction. PGC-1α is a transcriptional coactivator and represents a master regulator of mitochondrial biogenesis by promoting the transcription of mitochondrial genes. PGC-1α can be induced during physical exercise, and it plays a key role in coordinating the oxidation of intracellular fatty acids with mitochondrial remodelling. Several lines of evidence demonstrate that NO could act as a key regulator of PGC-1α expression; however, the link between nNOS and PGC-1α in skeletal muscle remains only poorly understood. In this Commentary, we review important metabolic pathways that are governed by nNOS and PGC-1α, and aim to highlight how they might intersect and cooperatively regulate skeletal muscle mitochondrial and lipid energetic metabolism and contraction. © 2014. Published by The Company of Biologists Ltd.

  9. Splicing Factor 1 Modulates Dietary Restriction and TORC1 Pathway Longevity in C. elegans

    PubMed Central

    Heintz, Caroline; Escoubas, Caroline; Zhang, Yue; Weir, Heather J.; Dutta, Sneha; Silva-García, Carlos Giovanni; Bruun, Gitte Hoffmann; Morantte, Ianessa; Hoxhaj, Gerta; Manning, Brendan D.; Andresen, Brage S.; Mair, William B.

    2016-01-01

    Ageing is driven by a loss of transcriptional and protein homeostasis1–3 and is the key risk factor for multiple chronic diseases. Interventions that attenuate or reverse systemic dysfunction seen with age therefore have potential to reduce overall disease risk in the elderly. Pre-mRNA splicing is a fundamental link between gene expression and the proteome, and deregulation of the splicing machinery is linked to multiple age-related chronic diseases4,5. However, the role of splicing homeostasis in healthy ageing remains unclear. Here we demonstrate that pre-mRNA splicing homeostasis is a biomarker and predictor of life expectancy in Caenorhabditis elegans. Using transcriptomics and in-depth splicing analysis in young and old animals fed ad libitum or on dietary restriction (DR), we find defects in global pre-mRNA splicing with age that are reduced by DR via the branch point binding protein (BBP)/splicing factor 1 (SFA-1). We show that SFA-1 is specifically required for lifespan extension both by DR, and modulation of TORC1 pathway components AMPK, RAGA-1 and RSKS-1/S6 Kinase. Lastly, we demonstrate that overexpression of SFA-1 is sufficient to extend lifespan. Together, these data demonstrate a role for RNA splicing homeostasis in DR longevity and suggest modulation of specific spliceosome components can prolong healthy ageing. PMID:27919065

  10. Connective tissue growth factor is required for skeletal development and postnatal skeletal homeostasis in male mice.

    PubMed

    Canalis, Ernesto; Zanotti, Stefano; Beamer, Wesley G; Economides, Aris N; Smerdel-Ramoya, Anna

    2010-08-01

    Connective tissue growth factor (CTGF), a member of the cysteine-rich 61 (Cyr 61), CTGF, nephroblastoma overexpressed (NOV) (CCN) family of proteins, is synthesized by osteoblasts, and its overexpression inhibits osteoblastogenesis and causes osteopenia. The global inactivation of Ctgf leads to defective endochondral bone formation and perinatal lethality; therefore, the consequences of Ctgf inactivation on the postnatal skeleton are not known. To study the function of CTGF, we generated Ctgf(+/LacZ) heterozygous null mice and tissue-specific null Ctgf mice by mating Ctgf conditional mice, where Ctgf is flanked by lox sequences with mice expressing the Cre recombinase under the control of the paired-related homeobox gene 1 (Prx1) enhancer (Prx1-Cre) or the osteocalcin promoter (Oc-Cre). Ctgf(+/LacZ) heterozygous mice exhibited transient osteopenia at 1 month of age secondary to decreased trabecular number. A similar osteopenic phenotype was observed in 1-month-old Ctgf conditional null male mice generated with Prx1-Cre, suggesting that the decreased trabecular number was secondary to impaired endochondral bone formation. In contrast, when the conditional deletion of Ctgf was achieved by Oc-Cre, an osteopenic phenotype was observed only in 6-month-old male mice. Osteoblast and osteoclast number, bone formation, and eroded surface were not affected in Ctgf heterozygous or conditional null mice. In conclusion, CTGF is necessary for normal skeletal development but to a lesser extent for postnatal skeletal homeostasis.

  11. Core-binding factor beta interacts with Runx2 and is required for skeletal development.

    PubMed

    Yoshida, Carolina A; Furuichi, Tatsuya; Fujita, Takashi; Fukuyama, Ryo; Kanatani, Naoko; Kobayashi, Shinji; Satake, Masanobu; Takada, Kenji; Komori, Toshihisa

    2002-12-01

    Core-binding factor beta (CBFbeta, also called polyomavirus enhancer binding protein 2beta (PEBP2B)) is associated with an inversion of chromosome 16 and is associated with acute myeloid leukemia in humans. CBFbeta forms a heterodimer with RUNX1 (runt-related transcription factor 1), which has a DNA binding domain homologous to the pair-rule protein runt in Drosophila melanogaster. Both RUNX1 and CBFbeta are essential for hematopoiesis. Haploinsufficiency of another runt-related protein, RUNX2 (also called CBFA1), causes cleidocranial dysplasia in humans and is essential in skeletal development by regulating osteoblast differentiation and chondrocyte maturation. Mice deficient in Cbfb (Cbfb(-/-)) die at midgestation, so the function of Cbfbeta in skeletal development has yet to be ascertained. To investigate this issue, we rescued hematopoiesis of Cbfb(-/-) mice by introducing Cbfb using the Gata1 promoter. The rescued Cbfb(-/-) mice recapitulated fetal liver hematopoiesis in erythroid and megakaryocytic lineages and survived until birth, but showed severely delayed bone formation. Although mesenchymal cells differentiated into immature osteoblasts, intramembranous bones were poorly formed. The maturation of chondrocytes into hypertrophic cells was markedly delayed, and no endochondral bones were formed. Electrophoretic mobility shift assays and reporter assays showed that Cbfbeta was necessary for the efficient DNA binding of Runx2 and for Runx2-dependent transcriptional activation. These findings indicate that Cbfbeta is required for the function of Runx2 in skeletal development.

  12. Determining skeletal maturation using insulin-like growth factor I (IGF-I) test.

    PubMed

    Gupta, Shreya; Jain, Sandhya; Gupta, Puneet; Deoskar, Anuradha

    2012-11-01

    To investigate the validity of Insulin like Growth Factor -1(IGF-1) as a skeletal maturity indicator by comparing serum IGF-1 levels with the stages in cervical vertebral maturation (CVM) and in the middle phalanx of the third finger (MP3). The study population was selected by using simple random sampling technique and consisted of 30 female subjects in the age range of 8-23 years who had blood sample, cephalometric and MP3 radiographs taken on the same day. Serum IGF-I estimation was carried out on the blood samples using chemiluminescence immunoassay (CLIA) method. CVM was evaluated using method by Baccetti et al and MP3 staging was done using Rajagopal & Kansal method. Mean IGF-1 level between the stages was compared by Kruskal-Wallis and Mann Whitney test. Serum IGF-1 levels in females correlate well with skeletal maturity determined by CVM and MP3 stages and increase sharply during early pubertal stages followed by a decrease in late puberty. In addition we hypothesis that serum IGF-1 testing can be undertaken as a preliminary screening test in patients in whom the orthodontist predicts the possibility of using myofunctional appliance but in whom the chronologic age is not suggestive for a growth modification therapy. The finding of the study highlights the fact that the serum IGF-1 estimation can be a valuable tool in assessing skeletal maturation. Copyright © 2012 Società Italiana di Ortodonzia SIDO. Published by Elsevier Srl. All rights reserved.

  13. Differential epigenetic and transcriptional response of the skeletal muscle carnitine palmitoyltransferase 1B (CPT1B) gene to lipid exposure with obesity

    PubMed Central

    Maples, Jill M.; Brault, Jeffrey J.; Witczak, Carol A.; Park, Sanghee; Hubal, Monica J.; Weber, Todd M.; Houmard, Joseph A.

    2015-01-01

    The ability to increase fatty acid oxidation (FAO) in response to dietary lipid is impaired in the skeletal muscle of obese individuals, which is associated with a failure to coordinately upregulate genes involved with FAO. While the molecular mechanisms contributing to this metabolic inflexibility are not evident, a possible candidate is carnitine palmitoyltransferase-1B (CPT1B), which is a rate-limiting step in FAO. The present study was undertaken to determine if the differential response of skeletal muscle CPT1B gene transcription to lipid between lean and severely obese subjects is linked to epigenetic modifications (DNA methylation and histone acetylation) that impact transcriptional activation. In primary human skeletal muscle cultures the expression of CPT1B was blunted in severely obese women compared with their lean counterparts in response to lipid, which was accompanied by changes in CpG methylation, H3/H4 histone acetylation, and peroxisome proliferator-activated receptor-δ and hepatocyte nuclear factor 4α transcription factor occupancy at the CPT1B promoter. Methylation of specific CpG sites in the CPT1B promoter that correlated with CPT1B transcript level blocked the binding of the transcription factor upstream stimulatory factor, suggesting a potential causal mechanism. These findings indicate that epigenetic modifications may play important roles in the regulation of CPT1B in response to a physiologically relevant lipid mixture in human skeletal muscle, a major site of fatty acid catabolism, and that differential DNA methylation may underlie the depressed expression of CPT1B in response to lipid, contributing to the metabolic inflexibility associated with severe obesity. PMID:26058865

  14. NEU3 sialidase strictly modulates GM3 levels in skeletal myoblasts C2C12 thus favoring their differentiation and protecting them from apoptosis.

    PubMed

    Anastasia, Luigi; Papini, Nadia; Colazzo, Francesca; Palazzolo, Giacomo; Tringali, Cristina; Dileo, Loredana; Piccoli, Marco; Conforti, Erika; Sitzia, Clementina; Monti, Eugenio; Sampaolesi, Maurilio; Tettamanti, Guido; Venerando, Bruno

    2008-12-26

    Membrane-bound sialidase NEU3, often referred to as the "ganglioside sialidase," has a critical regulatory function on the sialoglycosphingolipid pattern of the cell membrane, with an anti-apoptotic function, especially in cancer cells. Although other sialidases have been shown to be involved in skeletal muscle differentiation, the role of NEU3 had yet to be disclosed. Herein we report that NEU3 plays a key role in skeletal muscle differentiation by strictly modulating the ganglioside content of adjacent cells, with special regard to GM3. Induced down-regulation of NEU3 in murine C2C12 myoblasts, even when partial, totally inhibits their capability to differentiate by increasing the GM3 level above a critical point, which causes epidermal growth factor receptor inhibition (and ultimately its down-regulation) and an higher responsiveness of myoblasts to the apoptotic stimuli.

  15. High-Density Lipoprotein Maintains Skeletal Muscle Function by Modulating Cellular Respiration in Mice

    PubMed Central

    Lehti, Maarit; Donelan, Elizabeth; Abplanalp, William; Al-Massadi, Omar; Habegger, Kirk; Weber, Jon; Ress, Chandler; Mansfeld, Johannes; Somvanshi, Sonal; Trivedi, Chitrang; Keuper, Michaela; Ograjsek, Teja; Striese, Cynthia; Cucuruz, Sebastian; Pfluger, Paul T.; Krishna, Radhakrishna; Gordon, Scott M.; Silva, R. A. Gangani D.; Luquet, Serge; Castel, Julien; Martinez, Sarah; D'Alessio, David; Davidson, W. Sean; Hofmann, Susanna M.

    2014-01-01

    Background Abnormal glucose metabolism is a central feature of disorders with increased rates of cardio-vascular disease (CVD). Low levels of high density lipoprotein (HDL) are a key predictor for CVD. We used genetic mouse models with increased HDL levels (apoA-I tg) and reduced HDL levels (apoA-I ko) to investigate whether HDL modulates mitochondrial bioenergetics in skeletal muscle. Methods and Results ApoA-I ko mice exhibited fasting hyperglycemia and impaired glucose tolerance test (GTT) compared to wild type (wt) mice. Mitochondria isolated from gastrocnemius muscle of apoA-I ko mice displayed markedly blunted ATP synthesis. Endurance capacity (EC) during exercise exhaustion test was impaired in apoA-I ko mice. HDL directly enhanced glucose oxidation by increasing glycolysis and mitochondrial respiration rate (OCR) in C2C12 muscle cells. ApoA-I tg mice exhibited lower fasting glucose levels, improved GTT, increased lactate levels, reduced fat mass, associated with protection against age-induced decline of EC compared to wt mice. Circulating levels of fibroblast growth factor 21 (FGF21), a novel biomarker for mitochondrial respiratory chain deficiencies and inhibitor of white adipose lipolysis, were significantly reduced in apoA-I tg mice. Consistent with an increase in glucose utilization of skeletal muscle, genetically increased HDL and apoA-I levels in mice prevented high fat diet-induced impairment of glucose homeostasis. Conclusions In view of impaired mitochondrial function and decreased HDL levels in T2D, our findings indicate that HDL-raising therapies may preserve muscle mitochondrial function and address key aspects of T2D beyond CVD. PMID:24170386

  16. Dihydrotestosterone activates the MAPK pathway and modulates maximum isometric force through the EGF receptor in isolated intact mouse skeletal muscle fibres.

    PubMed

    Hamdi, M M; Mutungi, G

    2010-02-01

    It is generally believed that steroid hormones have both genomic and non-genomic (rapid) actions. Although the latter form an important component of the physiological response of these hormones, little is known about the cellular signalling pathway(s) mediating these effects and their physiological functions in adult mammalian skeletal muscle fibres. Therefore, the primary aim of this study was to investigate the non-genomic actions of dihydrotestosterone (DHT) and their physiological role in isolated intact mammalian skeletal muscle fibre bundles. Our results show that treating the fibre bundles with physiological concentrations of DHT increases both twitch and tetanic contractions in fast twitch fibres. However, it decreases them in slow twitch fibres. These changes in force are accompanied by an increase in the phosphorylation of MAPK/ERK1/2 in both fibre types and that of regulatory myosin light chains in fast twitch fibres. Both effects were insensitive to inhibitors of Src kinase, androgen receptor, insulin-like growth factor 1 receptor and platelet-derived growth factor receptor. However, they were abolished by the MAPK/ERK1/2 kinase inhibitor PD98059 and the epidermal growth factor (EGF) receptor inhibitor tyrphostin AG 1478. In contrast, testosterone had no effect on force and increased the phosphorylation of ERK1/2 in slow twitch fibres only. From these results we conclude that sex steroids have non-genomic actions in isolated intact mammalian skeletal muscle fibres. These are mediated through the EGF receptor and one of their main physiological functions is the enhancement of force production in fast twitch skeletal muscle fibres.

  17. Controlled delivery of SDF-1α and IGF-1: CXCR4(+) cell recruitment and functional skeletal muscle recovery.

    PubMed

    Rybalko, Viktoriya Y; Pham, Chantal B; Hsieh, Pei-Ling; Hammers, David W; Merscham-Banda, Melissa; Suggs, Laura J; Farrar, Roger P

    2015-11-01

    Therapeutic delivery of regeneration-promoting biological factors directly to the site of injury has demonstrated its efficacy in various injury models. Several reports describe improved tissue regeneration following local injection of tissue specific growth factors, cytokines and chemokines. Evidence exists that combined cytokine/growth factor treatment is superior for optimizing tissue repair by targeting different aspects of the regeneration response. The purpose of this study was to evaluate the therapeutic potential of the controlled delivery of stromal cell-derived factor-1alpha (SDF-1α) alone or in combination with insulin-like growth factor-I (SDF-1α/IGF-I) for the treatment of tourniquet-induced ischemia/reperfusion injury (TK-I/R) of skeletal muscle. We hypothesized that SDF-1α will promote sustained stem cell recruitment to the site of muscle injury, while IGF-I will induce progenitor cell differentiation to effectively restore muscle contractile function after TK-I/R injury while concurrently reducing apoptosis. Utilizing a novel poly-ethylene glycol PEGylated fibrin gel matrix (PEG-Fib), we incorporated SDF-1α alone (PEG-Fib/SDF-1α) or in combination with IGF-I (PEG-Fib/SDF-1α/IGF-I) for controlled release at the site of acute muscle injury. Despite enhanced cell recruitment and revascularization of the regenerating muscle after SDF-1α treatment, functional analysis showed no benefit from PEG-Fib/SDF-1α therapy, while dual delivery of PEG-Fib/SDF-1α/IGF-I resulted in IGF-I-mediated improvement of maximal force recovery and SDF-1α-driven in vivo neovasculogenesis. Histological data supported functional data, as well as highlighted the important differences in the regeneration process among treatment groups. This study provides evidence that while revascularization may be necessary for maximizing muscle force recovery, without modulation of other effects of inflammation it is insufficient.

  18. Controlled delivery of SDF-1α and IGF-1: CXCR4+ cell recruitment and functional skeletal muscle recovery

    PubMed Central

    Rybalko, Viktoriya Y.; Pham, Chantal B.; Hsieh, Pei-Ling; Hammers, David W.; Merscham-Banda, Melissa; Suggs, Laura J.; Farrar, Roger P.

    2017-01-01

    Therapeutic delivery of regeneration-promoting biological factors directly to the site of injury has demonstrated its efficacy in various injury models. Several reports describe improved tissue regeneration following local injection of tissue specific growth factors, cytokines and chemokines. Evidence exists that combined cytokine/growth factor treatment is superior for optimizing tissue repair by targeting different aspects of the regeneration response. The purpose of this study was to evaluate the therapeutic potential of the controlled delivery of stromal cell-derived factor-1alpha (SDF-1α) alone or in combination with insulin-like growth factor-I (SDF-1α/IGF-I) for the treatment of tourniquet-induced ischemia/reperfusion injury (TK-I/R) of skeletal muscle. We hypothesized that SDF-1α will promote sustained stem cell recruitment to the site of muscle injury, while IGF-I will induce progenitor cell differentiation to effectively restore muscle contractile function after TK-I/R injury while concurrently reducing apoptosis. Utilizing a novel poly-ethylene glycol PEGylated fibrin gel matrix (PEG-Fib), we incorporated SDF-1α alone (PEG-Fib/SDF-1α) or in combination with IGF-I (PEG-Fib/SDF-1α/IGF-I) for controlled release at the site of acute muscle injury. Despite enhanced cell recruitment and revascularization of the regenerating muscle after SDF-1α treatment, functional analysis showed no benefit from PEG-Fib/SDF-1α therapy, while dual delivery of PEG-Fib/SDF-1α/IGF-I resulted in IGF-I-mediated improvement of maximal force recovery and SDF-1α-driven in vivo neovasculogenesis. Histological data supported functional data, as well as highlighted the important differences in the regeneration process among treatment groups. This study provides evidence that while revascularization may be necessary for maximizing muscle force recovery, without modulation of other effects of inflammation it is insufficient. PMID:26247892

  19. The Skeletal Site-Specific Role of Connective Tissue Growth Factor in Prenatal Osteogenesis

    PubMed Central

    Lambi, Alex G.; Pankratz, Talia L.; Mundy, Christina; Gannon, Maureen; Barbe, Mary F.; Richtsmeier, Joan T.; Popoff, Steven N.

    2013-01-01

    Background Connective tissue growth factor (CTGF/CCN2) is a matricellular protein that is highly expressed during bone development. Mice with global CTGF ablation (knockout, KO) have multiple skeletal dysmorphisms and perinatal lethality. A quantitative analysis of the bone phenotype has not been conducted. Results We demonstrated skeletal site-specific changes in growth plate organization, bone microarchitecture, and shape and gene expression levels in CTGF KO compared with wild-type mice. Growth plate malformations included reduced proliferation zone and increased hypertrophic zone lengths. Appendicular skeletal sites demonstrated decreased metaphyseal trabecular bone, while having increased mid-diaphyseal bone and osteogenic expression markers. Axial skeletal analysis showed decreased bone in caudal vertebral bodies, mandibles, and parietal bones in CTGF KO mice, with decreased expression of osteogenic markers. Analysis of skull phenotypes demonstrated global and regional differences in CTGF KO skull shape resulting from allometric (size-based) and nonallometric shape changes. Localized differences in skull morphology included increased skull width and decreased skull length. Dysregulation of the transforming growth factor-β-CTGF axis coupled with unique morphologic traits provides a potential mechanistic explanation for the skull phenotype. Conclusions We present novel data on a skeletal phenotype in CTGF KO mice, in which ablation of CTGF causes site-specific aberrations in bone formation. PMID:23073844

  20. IGF-1 signaling mediated cell-specific skeletal mechano-transduction.

    PubMed

    Tian, Faming; Wang, Yongmei; Bikle, Daniel D

    2018-02-01

    Mechanical loading preserves bone mass and stimulates bone formation, whereas skeletal unloading leads to bone loss. In addition to osteocytes, which are considered the primary sensor of mechanical load, osteoblasts, and bone specific mesenchymal stem cells also are involved. The skeletal response to mechanical signals is a complex process regulated by multiple signaling pathways including that of insulin-like growth factor-1 (IGF-1). Conditional osteocyte deletion of IGF-1 ablates the osteogenic response to mechanical loading. Similarly, osteocyte IGF-1 receptor (IGF-1R) expression is necessary for reloading-induced periosteal bone formation. Transgenic overexpression of IGF-1 in osteoblasts results in enhanced responsiveness to in vivo mechanical loading in mice, a response which is eliminated by osteoblastic conditional disruption of IGF-1 in vivo. Bone marrow derived stem cells (BMSC) from unloaded bone fail to respond to IGF-1 in vitro. IGF-1R is required for the transduction of a mechanical stimulus to downstream effectors, transduction which is lost when the IGF-1R is deleted. Although the molecular mechanisms are not yet fully elucidated, the IGF signaling pathway and its interactions with potentially interlinked signaling cascades involving integrins, the estrogen receptor, and wnt/β-catenin play an important role in regulating adaptive response of cancer bone cells to mechanical stimuli. In this review, we discuss recent advances investigating how IGF-1 and other interlinked molecules and signaling pathways regulate skeletal mechano-transduction involving different bone cells, providing an overview of the IGF-1 signaling mediated cell-specific response to mechanical stimuli. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:576-583, 2018. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

  1. Skeletal and cardiac muscle pericytes: Functions and therapeutic potential

    PubMed Central

    Murray, Iain R.; Baily, James E.; Chen, William C.W.; Dar, Ayelet; Gonzalez, Zaniah N.; Jensen, Andrew R.; Petrigliano, Frank A.; Deb, Arjun; Henderson, Neil C.

    2017-01-01

    Pericytes are periendothelial mesenchymal cells residing within the microvasculature. Skeletal muscle and cardiac pericytes are now recognized to fulfill an increasing number of functions in normal tissue homeostasis, including contributing to microvascular function by maintaining vessel stability and regulating capillary flow. In the setting of muscle injury, pericytes contribute to a regenerative microenvironment through release of trophic factors and by modulating local immune responses. In skeletal muscle, pericytes also directly enhance tissue healing by differentiating into myofibers. Conversely, pericytes have also been implicated in the development of disease states, including fibrosis, heterotopic ossication and calcification, atherosclerosis, and tumor angiogenesis. Despite increased recognition of pericyte heterogeneity, it is not yet clear whether specific subsets of pericytes are responsible for individual functions in skeletal and cardiac muscle homeostasis and disease. PMID:27595928

  2. Betaglycan expression is transcriptionally up-regulated during skeletal muscle differentiation. Cloning of murine betaglycan gene promoter and its modulation by MyoD, retinoic acid, and transforming growth factor-beta.

    PubMed

    Lopez-Casillas, Fernando; Riquelme, Cecilia; Perez-Kato, Yoshiaki; Ponce-Castaneda, M Veronica; Osses, Nelson; Esparza-Lopez, Jose; Gonzalez-Nunez, Gerardo; Cabello-Verrugio, Claudio; Mendoza, Valentin; Troncoso, Victor; Brandan, Enrique

    2003-01-03

    Betaglycan is a membrane-anchored proteoglycan co-receptor that binds transforming growth factor beta (TGF-beta) via its core protein and basic fibroblast growth factor through its glycosaminoglycan chains. In this study we evaluated the expression of betaglycan during the C(2)C(12) skeletal muscle differentiation. Betaglycan expression, as determined by Northern and Western blot, was up-regulated during the conversion of myoblasts to myotubes. The mouse betaglycan gene promoter was cloned, and its sequence showed putative binding sites for SP1, Smad3, Smad4, muscle regulatory factor elements such as MyoD and MEF2, and retinoic acid receptor. Transcriptional activity of the mouse betaglycan promoter reporter was also up-regulated in differentiating C(2)C(12) cells. We found that MyoD, but not myogenin, stimulated this transcriptional activity even in the presence of high serum. Betaglycan promoter activity was increased by RA and inhibited by the three isoforms of TGF-beta. On the other hand, basic fibroblast growth factor, BMP-2, and hepatocyte growth factor/scatter factor, which are inhibitors of myogenesis, had little effect. In myotubes, up-regulated betaglycan was also detectable by TGF-beta affinity labeling and immunofluorescence microscopy studies. The latter indicated that betaglycan was localized both on the cell surface and in the ECM. Forced expression of betaglycan in C(2)C(12) myoblasts increases their responsiveness to TGF-beta2, suggesting that it performs a TGF-beta presentation function in this cell lineage. These results indicate that betaglycan expression is up-regulated during myogenesis and that MyoD and RA modulate its expression by a mechanism that is independent of myogenin.

  3. Factors which modulate the rates of skeletal muscle mass loss in non-small cell lung cancer patients: a pilot study.

    PubMed

    Atlan, Philippe; Bayar, Mohamed Amine; Lanoy, Emilie; Besse, Benjamin; Planchard, David; Ramon, Jordy; Raynard, Bruno; Antoun, Sami

    2017-11-01

    Advanced non-small cell lung cancer (NSCLC) is associated with weight loss which may reflect skeletal muscle mass (SMM) and/or total adipose tissue (TAT) depletion. This study aimed to describe changes in body composition (BC) parameters and to identify the factors unrelated to the tumor which modulate them. SMM, TAT, and the proportion of SMM to SMM + TAT were assessed with computed tomography. Estimates of each BC parameter at follow-up initiation and across time were derived from a mixed linear model of repeated measurements with a random intercept and a random slope. The same models were used to assess the independent effect of gender, age, body mass index (BMI), and initial values on changes in each BC parameter. Sixty-four patients with stage III or IV NSCLC were reviewed. The mean ± SD decreases in body weight and SMM were respectively 59 ± 3 g/week (P < 0.03) and 7 mm 2 /m 2 /week (P = 0.0003). During follow-up, no changes were identified in TAT nor in muscle density or in the proportion of SMM to SMM + TAT, estimated at 37 ± 2% at baseline. SMM loss was influenced by initial BMI (P < 0.0001) and SMM values (P = 0.0002): the higher the initial BMI or SMM values, the greater the loss observed. Weight loss was greater when the initial weight was heavier (P < 0.0001). Our results demonstrate that SMM wasting in NSCLC is lower when initial SMM and BMI values are low. These exploratory findings after our attempt to better understand the intrinsic factors associated with muscle mass depletion need to be confirmed in larger studies.

  4. Tumor Necrosis Factor Alpha and Insulin-Like Growth Factor 1 Induced Modifications of the Gene Expression Kinetics of Differentiating Skeletal Muscle Cells

    PubMed Central

    Meyer, Swanhild U.; Krebs, Stefan; Thirion, Christian; Blum, Helmut; Krause, Sabine; Pfaffl, Michael W.

    2015-01-01

    Introduction TNF-α levels are increased during muscle wasting and chronic muscle degeneration and regeneration processes, which are characteristic for primary muscle disorders. Pathologically increased TNF-α levels have a negative effect on muscle cell differentiation efficiency, while IGF1 can have a positive effect; therefore, we intended to elucidate the impact of TNF-α and IGF1 on gene expression during the early stages of skeletal muscle cell differentiation. Methodology/Principal Findings This study presents gene expression data of the murine skeletal muscle cells PMI28 during myogenic differentiation or differentiation with TNF-α or IGF1 exposure at 0 h, 4 h, 12 h, 24 h, and 72 h after induction. Our study detected significant coregulation of gene sets involved in myoblast differentiation or in the response to TNF-α. Gene expression data revealed a time- and treatment-dependent regulation of signaling pathways, which are prominent in myogenic differentiation. We identified enrichment of pathways, which have not been specifically linked to myoblast differentiation such as doublecortin-like kinase pathway associations as well as enrichment of specific semaphorin isoforms. Moreover to the best of our knowledge, this is the first description of a specific inverse regulation of the following genes in myoblast differentiation and response to TNF-α: Aknad1, Cmbl, Sepp1, Ndst4, Tecrl, Unc13c, Spats2l, Lix1, Csdc2, Cpa1, Parm1, Serpinb2, Aspn, Fibin, Slc40a1, Nrk, and Mybpc1. We identified a gene subset (Nfkbia, Nfkb2, Mmp9, Mef2c, Gpx, and Pgam2), which is robustly regulated by TNF-α across independent myogenic differentiation studies. Conclusions This is the largest dataset revealing the impact of TNF-α or IGF1 treatment on gene expression kinetics of early in vitro skeletal myoblast differentiation. We identified novel mRNAs, which have not yet been associated with skeletal muscle differentiation or response to TNF-α. Results of this study may facilitate

  5. Skeletal muscle and nuclear hormone receptors: implications for cardiovascular and metabolic disease.

    PubMed

    Smith, Aaron G; Muscat, George E O

    2005-10-01

    Skeletal muscle is a major mass peripheral tissue that accounts for approximately 40% of the total body mass and a major player in energy balance. It accounts for >30% of energy expenditure, is the primary tissue of insulin stimulated glucose uptake, disposal, and storage. Furthermore, it influences metabolism via modulation of circulating and stored lipid (and cholesterol) flux. Lipid catabolism supplies up to 70% of the energy requirements for resting muscle. However, initial aerobic exercise utilizes stored muscle glycogen but as exercise continues, glucose and stored muscle triglycerides become important energy substrates. Endurance exercise increasingly depends on fatty acid oxidation (and lipid mobilization from other tissues). This underscores the importance of lipid and glucose utilization as an energy source in muscle. Consequently skeletal muscle has a significant role in insulin sensitivity, the blood lipid profile, and obesity. Moreover, caloric excess, obesity and physical inactivity lead to skeletal muscle insulin resistance, a risk factor for the development of type II diabetes. In this context skeletal muscle is an important therapeutic target in the battle against cardiovascular disease, the worlds most serious public health threat. Major risk factors for cardiovascular disease include dyslipidemia, hypertension, obesity, sedentary lifestyle, and diabetes. These risk factors are directly influenced by diet, metabolism and physical activity. Metabolism is largely regulated by nuclear hormone receptors which function as hormone regulated transcription factors that bind DNA and mediate the patho-physiological regulation of gene expression. Metabolism and activity, which directly influence cardiovascular disease risk factors, are primarily driven by skeletal muscle. Recently, many nuclear receptors expressed in skeletal muscle have been shown to improve glucose tolerance, insulin resistance, and dyslipidemia. Skeletal muscle and nuclear receptors are

  6. Non-pathogenic protein aggregates in skeletal muscle in MLF1 transgenic mice.

    PubMed

    Li, Zhi-Fang; Wu, Xiaohua; Jiang, Yun; Liu, Jianxiang; Wu, Chun; Inagaki, Masaki; Izawa, Ichiro; Mizisin, Andrew P; Engvall, Eva; Shelton, G Diane

    2008-01-15

    Protein aggregate formation in muscle is thought to be pathogenic and associated with clinical weakness. Over-expression of either wild type or a mutant form of myeloid leukemia factor 1 (MLF1) in transgenic mouse skeletal muscle and in cultured cells resulted in aggregate formation. Aggregates were detected in MLF1 transgenic mice at 6 weeks of age, and increased in size with age. However, histological examination of skeletal muscles of MLF1 transgenic mice revealed no pathological changes other than the aggregates, and RotaRod testing did not detect functional deficits. MLF1 has recently been identified as a protein that could neutralize the toxicity of intracellular protein aggregates in a Drosophila model of Huntington's disease (HD). We also demonstrate that MLF1 interacts with MRJ, a heat shock protein, which can independently neutralize the toxicity of intracellular protein aggregates in the Drosophila HD model. Our data suggest that over-expression of MLF1 has no significant impact on skeletal muscle function in mice; that progressive formation of protein aggregates in muscle are not necessarily pathogenic; and that MLF1 and MRJ may function together to ameliorate the toxic effects of polyglutamine or mutant proteins in myodegenerative diseases such as inclusion body myositis and oculopharyngeal muscular dystrophy, as well as neurodegenerative disease.

  7. Deletion of Pofut1 in Mouse Skeletal Myofibers Induces Muscle Aging-Related Phenotypes in cis and in trans

    PubMed Central

    Zygmunt, Deborah A.; Singhal, Neha; Kim, Mi-Lyang; Cramer, Megan L.; Crowe, Kelly E.; Xu, Rui; Jia, Ying; Adair, Jessica; Martinez-Pena y Valenzuela, Isabel; Akaaboune, Mohammed; White, Peter; Janssen, Paulus M.

    2017-01-01

    ABSTRACT Sarcopenia, the loss of muscle mass and strength during normal aging, involves coordinate changes in skeletal myofibers and the cells that contact them, including satellite cells and motor neurons. Here we show that the protein O-fucosyltransferase 1 gene (Pofut1), which encodes a glycosyltransferase required for NotchR-mediated cell-cell signaling, has reduced expression in aging skeletal muscle. Moreover, premature postnatal deletion of Pofut1 in skeletal myofibers can induce aging-related phenotypes in cis within skeletal myofibers and in trans within satellite cells and within motor neurons via the neuromuscular junction. Changed phenotypes include reduced skeletal muscle size and strength, decreased myofiber size, increased slow fiber (type 1) density, increased muscle degeneration and regeneration in aged muscles, decreased satellite cell self-renewal and regenerative potential, and increased neuromuscular fragmentation and occasional denervation. Pofut1 deletion in skeletal myofibers reduced NotchR signaling in young adult muscles, but this effect was lost with age. Increasing muscle NotchR signaling also reduced muscle size. Gene expression studies point to regulation of cell cycle genes, muscle myosins, NotchR and Wnt pathway genes, and connective tissue growth factor by Pofut1 in skeletal muscle, with additional effects on α dystroglycan glycosylation. PMID:28265002

  8. Wushenziye Formula Improves Skeletal Muscle Insulin Resistance in Type 2 Diabetes Mellitus via PTP1B-IRS1-Akt-GLUT4 Signaling Pathway.

    PubMed

    Tian, Chunyu; Chang, Hong; La, Xiaojin; Li, Ji-An

    2017-01-01

    Background. Wushenziye formula (WSZYF) is an effective traditional Chinese medicine in the treatment of type 2 diabetes mellitus (T2DM). Aim. This study aimed to identify the effects and underlying mechanisms of WSZYF on improving skeletal muscle insulin resistance in T2DM. Methods. An animal model of T2DM was induced by Goto-Kakizaki diabetes prone rats fed with high fat and sugar for 4 weeks. Insulin resistance model was induced in skeletal muscle cell. Results. In vivo , WSZYF improved general conditions and decreased significantly fasting blood glucose, glycosylated serum protein, glycosylated hemoglobin, insulin concentration, and insulin resistance index of T2DM rats. In vitro , WSZYF enhanced glucose consumption in insulin resistance model of skeletal muscle cell. Furthermore, WSZYF affected the expressions of molecules in regulating T2DM, including increasing the expressions of p-IRS1, p-Akt, and GLUT4, reducing PTP1B expression. Conclusion . These findings displayed the potential of WSZYF as a new drug candidate in the treatment of T2DM and the antidiabetic mechanism of WSZYF is probably mediated through modulating the PTP1B-IRS1-Akt-GLUT4 signaling pathway.

  9. Wushenziye Formula Improves Skeletal Muscle Insulin Resistance in Type 2 Diabetes Mellitus via PTP1B-IRS1-Akt-GLUT4 Signaling Pathway

    PubMed Central

    La, Xiaojin; Li, Ji-an

    2017-01-01

    Background. Wushenziye formula (WSZYF) is an effective traditional Chinese medicine in the treatment of type 2 diabetes mellitus (T2DM). Aim. This study aimed to identify the effects and underlying mechanisms of WSZYF on improving skeletal muscle insulin resistance in T2DM. Methods. An animal model of T2DM was induced by Goto-Kakizaki diabetes prone rats fed with high fat and sugar for 4 weeks. Insulin resistance model was induced in skeletal muscle cell. Results. In vivo, WSZYF improved general conditions and decreased significantly fasting blood glucose, glycosylated serum protein, glycosylated hemoglobin, insulin concentration, and insulin resistance index of T2DM rats. In vitro, WSZYF enhanced glucose consumption in insulin resistance model of skeletal muscle cell. Furthermore, WSZYF affected the expressions of molecules in regulating T2DM, including increasing the expressions of p-IRS1, p-Akt, and GLUT4, reducing PTP1B expression. Conclusion. These findings displayed the potential of WSZYF as a new drug candidate in the treatment of T2DM and the antidiabetic mechanism of WSZYF is probably mediated through modulating the PTP1B-IRS1-Akt-GLUT4 signaling pathway. PMID:29479370

  10. [Molecular mechanisms of skeletal muscle hypertrophy].

    PubMed

    Astratenkova, I V; Rogozkin, V A

    2014-06-01

    Enzymes Akt, AMPK, mTOR, S6K and PGC-1a coactivator take part in skeletal muscles in the regulation of synthesis of proteins. The expression of these proteins is regulated by growth factors, hormones, nutrients, mechanical loading and leads to an increase in muscle mass and skeletal muscle hypertrophy. The review presents the results of studies published in the past four years, which expand knowledge on the effects of various factors on protein synthesis in skeletal muscle. The attention is focused on the achievements that reveal and clarify the signaling pathways involved in the regulation of protein synthesis in skeletal muscle. The central place is taken by mTOR enzyme which controls and regulates the main stages of the cascade of reactions of muscle proteins providing synthesis in the conditions of human life. coactivator PGC-1a.

  11. Skeletal Metabolism, Fracture Risk, and Fracture Outcomes in Type 1 and Type 2 Diabetes

    PubMed Central

    Civitelli, Roberto; Hofbauer, Lorenz C.; Khosla, Sundeep; Lecka-Czernik, Beata; Schwartz, Ann V.

    2016-01-01

    Fracture risk is significantly increased in both type 1 and type 2 diabetes, and individuals with diabetes experience worse fracture outcomes than normoglycemic individuals. Factors that increase fracture risk include lower bone mass in type 1 diabetes and compromised skeletal quality and strength despite preserved bone density in type 2 diabetes, as well as the effects of comorbidities such as diabetic macro- and microvascular complications. In this Perspective, we assess the developing scientific knowledge regarding the epidemiology and pathophysiology of skeletal fragility in patients with diabetes and the emerging data on the prediction, treatment, and outcomes of fractures in individuals with type 1 and type 2 diabetes. PMID:27329951

  12. Deep Proteomics of Mouse Skeletal Muscle Enables Quantitation of Protein Isoforms, Metabolic Pathways, and Transcription Factors*

    PubMed Central

    Deshmukh, Atul S.; Murgia, Marta; Nagaraj, Nagarjuna; Treebak, Jonas T.; Cox, Jürgen; Mann, Matthias

    2015-01-01

    Skeletal muscle constitutes 40% of individual body mass and plays vital roles in locomotion and whole-body metabolism. Proteomics of skeletal muscle is challenging because of highly abundant contractile proteins that interfere with detection of regulatory proteins. Using a state-of-the art MS workflow and a strategy to map identifications from the C2C12 cell line model to tissues, we identified a total of 10,218 proteins, including skeletal muscle specific transcription factors like myod1 and myogenin and circadian clock proteins. We obtain absolute abundances for proteins expressed in a muscle cell line and skeletal muscle, which should serve as a valuable resource. Quantitation of protein isoforms of glucose uptake signaling pathways and in glucose and lipid metabolic pathways provides a detailed metabolic map of the cell line compared with tissue. This revealed unexpectedly complex regulation of AMP-activated protein kinase and insulin signaling in muscle tissue at the level of enzyme isoforms. PMID:25616865

  13. Intercellular adhesion molecule-1 expression by skeletal muscle cells augments myogenesis

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Goh, Qingnian; Dearth, Christopher L.; Corbett, Jacob T.

    We previously demonstrated that the expression of intercellular adhesion molecule-1 (ICAM-1) by skeletal muscle cells after muscle overload contributes to ensuing regenerative and hypertrophic processes in skeletal muscle. The objective of the present study is to reveal mechanisms through which skeletal muscle cell expression of ICAM-1 augments regenerative and hypertrophic processes of myogenesis. This was accomplished by genetically engineering C2C12 myoblasts to stably express ICAM-1, and by inhibiting the adhesive and signaling functions of ICAM-1 through the use of a neutralizing antibody or cell penetrating peptide, respectively. Expression of ICAM-1 by cultured skeletal muscle cells augmented myoblast–myoblast adhesion, myotube formation,more » myonuclear number, myotube alignment, myotube–myotube fusion, and myotube size without influencing the ability of myoblasts to proliferate or differentiate. ICAM-1 augmented myotube formation, myonuclear accretion, and myotube alignment through a mechanism involving adhesion-induced activation of ICAM-1 signaling, as these dependent measures were reduced via antibody and peptide inhibition of ICAM-1. The adhesive and signaling functions of ICAM-1 also facilitated myotube hypertrophy through a mechanism involving myotube–myotube fusion, protein synthesis, and Akt/p70s6k signaling. Our findings demonstrate that ICAM-1 expression by skeletal muscle cells augments myogenesis, and establish a novel mechanism through which the inflammatory response facilitates growth processes in skeletal muscle. - Highlights: • We examined mechanisms through which skeletal muscle cell expression of ICAM-1 facilitates events of in vitro myogenesis. • Expression of ICAM-1 by cultured myoblasts did not influence their ability to proliferate or differentiate. • Skeletal muscle cell expression of ICAM-1 augmented myoblast fusion, myotube alignment, myotube–myotube fusion, and myotube size. • ICAM-1 augmented myogenic processes

  14. The regulation of skeletal muscle fiber-type composition by betaine is associated with NFATc1/MyoD.

    PubMed

    Du, Jingjing; Shen, Linyuan; Zhang, Peiwen; Tan, Zhendong; Cheng, Xiao; Luo, Jia; Zhao, Xue; Yang, Qiong; Gu, Hao; Jiang, An'an; Ma, Jideng; Tang, Qianzi; Jin, Long; Shuai, Surong; Li, Mingzhou; Jiang, Yanzhi; Tang, Guoqing; Bai, Lin; Li, Xuewei; Wang, Jinyong; Zhang, Shunhua; Zhu, Li

    2018-06-06

    Increasing evidence indicates that muscular dysfunction or alterations in skeletal muscle fiber-type composition not only are involved in muscle metabolism and function but also can limit functional capacity. Therefore, understanding the mechanisms regulating key events during skeletal myogenesis is necessary. Betaine is a naturally occurring component of commonly eaten foods. Here, we showed that 10 mM betaine supplementation in vitro significantly repressed myoblast proliferation and enhanced myoblast differentiation. This effect can be mediated by regulation of miR-29b-3p. Further analysis showed that betaine supplementation in vitro regulated skeletal muscle fiber-type composition through the induction of NFATc1 and the negative regulation of MyoD expression. Furthermore, mice fed with 10 mM betaine in water for 133 days showed no impairment in overall health. Consistently, betaine supplementation increased muscle mass, promoted muscle formation, and modulated the ratio of fiber types in skeletal muscle in vivo. These findings shed light on the diverse biological functions of betaine and indicate that betaine supplementation may lead to new therapies for diseases such as muscular dystrophy or other diseases related to muscle dysfunction. Betaine supplementation inhibits proliferation and promotes differentiation of C2C12 myoblasts. Betaine supplementation regulates fast to slow muscle fiber-type conversion and is associated with NFATc1/MyoD. Betaine supplementation enhances skeletal myogenesis in vivo. Betaine supplementation does not impair health of mice.

  15. Anti-inflammatory drugs for Duchenne muscular dystrophy: focus on skeletal muscle-releasing factors.

    PubMed

    Miyatake, Shouta; Shimizu-Motohashi, Yuko; Takeda, Shin'ichi; Aoki, Yoshitsugu

    2016-01-01

    Duchenne muscular dystrophy (DMD), an incurable and a progressive muscle wasting disease, is caused by the absence of dystrophin protein, leading to recurrent muscle fiber damage during contraction. The inflammatory response to fiber damage is a compelling candidate mechanism for disease exacerbation. The only established pharmacological treatment for DMD is corticosteroids to suppress muscle inflammation, however this treatment is limited by its insufficient therapeutic efficacy and considerable side effects. Recent reports show the therapeutic potential of inhibiting or enhancing pro- or anti-inflammatory factors released from DMD skeletal muscles, resulting in significant recovery from muscle atrophy and dysfunction. We discuss and review the recent findings of DMD inflammation and opportunities for drug development targeting specific releasing factors from skeletal muscles. It has been speculated that nonsteroidal anti-inflammatory drugs targeting specific inflammatory factors are more effective and have less side effects for DMD compared with steroidal drugs. For example, calcium channels, reactive oxygen species, and nuclear factor-κB signaling factors are the most promising targets as master regulators of inflammatory response in DMD skeletal muscles. If they are combined with an oligonucleotide-based exon skipping therapy to restore dystrophin expression, the anti-inflammatory drug therapies may address the present therapeutic limitation of low efficiency for DMD.

  16. Anti-inflammatory drugs for Duchenne muscular dystrophy: focus on skeletal muscle-releasing factors

    PubMed Central

    Miyatake, Shouta; Shimizu-Motohashi, Yuko; Takeda, Shin’ichi; Aoki, Yoshitsugu

    2016-01-01

    Duchenne muscular dystrophy (DMD), an incurable and a progressive muscle wasting disease, is caused by the absence of dystrophin protein, leading to recurrent muscle fiber damage during contraction. The inflammatory response to fiber damage is a compelling candidate mechanism for disease exacerbation. The only established pharmacological treatment for DMD is corticosteroids to suppress muscle inflammation, however this treatment is limited by its insufficient therapeutic efficacy and considerable side effects. Recent reports show the therapeutic potential of inhibiting or enhancing pro- or anti-inflammatory factors released from DMD skeletal muscles, resulting in significant recovery from muscle atrophy and dysfunction. We discuss and review the recent findings of DMD inflammation and opportunities for drug development targeting specific releasing factors from skeletal muscles. It has been speculated that nonsteroidal anti-inflammatory drugs targeting specific inflammatory factors are more effective and have less side effects for DMD compared with steroidal drugs. For example, calcium channels, reactive oxygen species, and nuclear factor-κB signaling factors are the most promising targets as master regulators of inflammatory response in DMD skeletal muscles. If they are combined with an oligonucleotide-based exon skipping therapy to restore dystrophin expression, the anti-inflammatory drug therapies may address the present therapeutic limitation of low efficiency for DMD. PMID:27621596

  17. The excitation-contraction coupling on C2C12 skeletal muscle myotubes was modulated by NO-donor ester of gemfibrozil.

    PubMed

    Maccallini, Cristina; Pietrangelo, Tiziana; Mancinelli, Rosa; Amoroso, Rosa; Bettoni, Giancarlo; Fulle, Stefania

    2008-05-01

    The excitation-contraction coupling in skeletal muscle is modulated by nitric oxide via redox status modification of ryanodine receptor on sarcoplasmic reticulum during events that lead to muscle contraction. We have synthesized a derivative of antilipidemic drug, gemfibrozil, in which a NO-donor furoxan moiety is joined to the fibrate by an ester linkage. Aim of the present study was to determine if the NO released from the above compound is capable of influencing the NO-sensible E-C coupling steps in skeletal muscle and if this effect could be potentially utilised for physiopathological studies and pharmaceutical applications. To obtain this goal we decided to study some of the excitation-contraction mechanisms in the presence of NO-releasing derivative of gemfibrozil in skeletal muscle C2C12 cell line.

  18. Defining the role of mesenchymal stromal cells on the regulation of matrix metalloproteinases in skeletal muscle cells

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sassoli, Chiara; Nosi, Daniele; Tani, Alessia

    Recent studies indicate that mesenchymal stromal cell (MSC) transplantation improves healing of injured and diseased skeletal muscle, although the mechanisms of benefit are poorly understood. In the present study, we investigated whether MSCs and/or their trophic factors were able to regulate matrix metalloproteinase (MMP) expression and activity in different cells of the muscle tissue. MSCs in co-culture with C2C12 cells or their conditioned medium (MSC-CM) up-regulated MMP-2 and MMP-9 expression and function in the myoblastic cells; these effects were concomitant with the down-regulation of the tissue inhibitor of metalloproteinases (TIMP)-1 and -2 and with increased cell motility. In the singlemore » muscle fiber experiments, MSC-CM administration increased MMP-2/9 expression in Pax-7{sup +} satellite cells and stimulated their mobilization, differentiation and fusion. The anti-fibrotic properties of MSC-CM involved also the regulation of MMPs by skeletal fibroblasts and the inhibition of their differentiation into myofibroblasts. The treatment with SB-3CT, a potent MMP inhibitor, prevented in these cells, the decrease of α-smooth actin and type-I collagen expression induced by MSC-CM, suggesting that MSC-CM could attenuate the fibrogenic response through mechanisms mediated by MMPs. Our results indicate that growth factors and cytokines released by these cells may modulate the fibrotic response and improve the endogenous mechanisms of muscle repair/regeneration. - Highlights: • MSC-CM contains paracrine factors that up-regulate MMP expression and function in different skeletal muscle cells. • MSC-CM promotes myoblast and satellite cell migration, proliferation and differentiation. • MSC-CM negatively interferes with fibroblast-myoblast transition in primary skeletal fibroblasts. • Paracrine factors from MSCs modulate the fibrotic response and improve the endogenous mechanisms of muscle regeneration.« less

  19. Disruption of both nesprin 1 and desmin results in nuclear anchorage defects and fibrosis in skeletal muscle

    PubMed Central

    Chapman, Mark A.; Zhang, Jianlin; Banerjee, Indroneal; Guo, Ling T.; Zhang, Zhiwei; Shelton, G. Diane; Ouyang, Kunfu; Lieber, Richard L.; Chen, Ju

    2014-01-01

    Proper localization and anchorage of nuclei within skeletal muscle is critical for cellular function. Alterations in nuclear anchoring proteins modify a number of cellular functions including mechanotransduction, nuclear localization, chromatin positioning/compaction and overall organ function. In skeletal muscle, nesprin 1 and desmin are thought to link the nucleus to the cytoskeletal network. Thus, we hypothesize that both of these factors play a key role in skeletal muscle function. To examine this question, we utilized global ablation murine models of nesprin 1, desmin or both nesprin 1 and desmin. Herein, we have created the nesprin-desmin double-knockout (DKO) mouse, eliminating a major fraction of nuclear-cytoskeletal connections and enabling understanding of the importance of nuclear anchorage in skeletal muscle. Globally, DKO mice are marked by decreased lifespan, body weight and muscle strength. With regard to skeletal muscle, DKO myonuclear anchorage was dramatically decreased compared with wild-type, nesprin 1−/− and desmin−/− mice. Additionally, nuclear-cytoskeletal strain transmission was decreased in DKO skeletal muscle. Finally, loss of nuclear anchorage in DKO mice coincided with a fibrotic response as indicated by increased collagen and extracellular matrix deposition and increased passive mechanical properties of muscle bundles. Overall, our data demonstrate that nesprin 1 and desmin serve redundant roles in nuclear anchorage and that the loss of nuclear anchorage in skeletal muscle results in a pathological response characterized by increased tissue fibrosis and mechanical stiffness. PMID:24943590

  20. Loss of Prox1 in striated muscle causes slow to fast skeletal muscle fiber conversion and dilated cardiomyopathy.

    PubMed

    Petchey, Louisa K; Risebro, Catherine A; Vieira, Joaquim M; Roberts, Tom; Bryson, John B; Greensmith, Linda; Lythgoe, Mark F; Riley, Paul R

    2014-07-01

    Correct regulation of troponin and myosin contractile protein gene isoforms is a critical determinant of cardiac and skeletal striated muscle development and function, with misexpression frequently associated with impaired contractility or disease. Here we reveal a novel requirement for Prospero-related homeobox factor 1 (Prox1) during mouse heart development in the direct transcriptional repression of the fast-twitch skeletal muscle genes troponin T3, troponin I2, and myosin light chain 1. A proportion of cardiac-specific Prox1 knockout mice survive beyond birth with hearts characterized by marked overexpression of fast-twitch genes and postnatal development of a fatal dilated cardiomyopathy. Through conditional knockout of Prox1 from skeletal muscle, we demonstrate a conserved requirement for Prox1 in the repression of troponin T3, troponin I2, and myosin light chain 1 between cardiac and slow-twitch skeletal muscle and establish Prox1 ablation as sufficient to cause a switch from a slow- to fast-twitch muscle phenotype. Our study identifies conserved roles for Prox1 between cardiac and skeletal muscle, specifically implicated in slow-twitch fiber-type specification, function, and cardiomyopathic disease.

  1. Loss of Prox1 in striated muscle causes slow to fast skeletal muscle fiber conversion and dilated cardiomyopathy

    PubMed Central

    Petchey, Louisa K.; Risebro, Catherine A.; Vieira, Joaquim M.; Roberts, Tom; Bryson, John B.; Greensmith, Linda; Lythgoe, Mark F.; Riley, Paul R.

    2014-01-01

    Correct regulation of troponin and myosin contractile protein gene isoforms is a critical determinant of cardiac and skeletal striated muscle development and function, with misexpression frequently associated with impaired contractility or disease. Here we reveal a novel requirement for Prospero-related homeobox factor 1 (Prox1) during mouse heart development in the direct transcriptional repression of the fast-twitch skeletal muscle genes troponin T3, troponin I2, and myosin light chain 1. A proportion of cardiac-specific Prox1 knockout mice survive beyond birth with hearts characterized by marked overexpression of fast-twitch genes and postnatal development of a fatal dilated cardiomyopathy. Through conditional knockout of Prox1 from skeletal muscle, we demonstrate a conserved requirement for Prox1 in the repression of troponin T3, troponin I2, and myosin light chain 1 between cardiac and slow-twitch skeletal muscle and establish Prox1 ablation as sufficient to cause a switch from a slow- to fast-twitch muscle phenotype. Our study identifies conserved roles for Prox1 between cardiac and skeletal muscle, specifically implicated in slow-twitch fiber-type specification, function, and cardiomyopathic disease. PMID:24938781

  2. Myostatin-deficiency in mice increases global gene expression at the Dlk1-Dio3 locus in the skeletal muscle

    PubMed Central

    Hitachi, Keisuke; Tsuchida, Kunihiro

    2017-01-01

    Myostatin, a member of the transforming growth factor-beta superfamily, is a negative regulator of skeletal muscle growth and development. Myostatin inhibition leads to increased skeletal muscle mass in mammals; hence, myostatin is considered a potential therapeutic target for skeletal muscle wasting. However, downstream molecules of myostatin in the skeletal muscle have not been fully elucidated. Here, we identified the Dlk1-Dio3 locus at the mouse chromosome 12qF1, also called as the callipyge locus in sheep, as a novel downstream target of myostatin. In skeletal muscle of myostatin knockout mice, the expression of mature miRNAs at the Dlk1-Dio3 locus was significantly increased. The increased miRNA levels are caused by the transcriptional activation of the Dlk1-Dio3 locus, because a significant increase in the primary miRNA transcript was observed in myostatin knockout mice. In addition, we found increased expression of coding and non-coding genes (Dlk1, Gtl2, Rtl1/Rtl1as, and Rian) at the Dlk1-Dio3 locus in myostatin-deficient skeletal muscle. Moreover, epigenetic changes, associated with the regulation of the Dlk1-Dio3 locus, were observed in myostatin knockout mice. Taken together, this is the first report demonstrating the role of myostatin in regulating the Dlk1-Dio3 (the callipyge) locus in the skeletal muscle. PMID:27992376

  3. Myostatin-deficiency in mice increases global gene expression at the Dlk1-Dio3 locus in the skeletal muscle.

    PubMed

    Hitachi, Keisuke; Tsuchida, Kunihiro

    2017-01-24

    Myostatin, a member of the transforming growth factor-beta superfamily, is a negative regulator of skeletal muscle growth and development. Myostatin inhibition leads to increased skeletal muscle mass in mammals; hence, myostatin is considered a potential therapeutic target for skeletal muscle wasting. However, downstream molecules of myostatin in the skeletal muscle have not been fully elucidated. Here, we identified the Dlk1-Dio3 locus at the mouse chromosome 12qF1, also called as the callipyge locus in sheep, as a novel downstream target of myostatin. In skeletal muscle of myostatin knockout mice, the expression of mature miRNAs at the Dlk1-Dio3 locus was significantly increased. The increased miRNA levels are caused by the transcriptional activation of the Dlk1-Dio3 locus, because a significant increase in the primary miRNA transcript was observed in myostatin knockout mice. In addition, we found increased expression of coding and non-coding genes (Dlk1, Gtl2, Rtl1/Rtl1as, and Rian) at the Dlk1-Dio3 locus in myostatin-deficient skeletal muscle. Moreover, epigenetic changes, associated with the regulation of the Dlk1-Dio3 locus, were observed in myostatin knockout mice. Taken together, this is the first report demonstrating the role of myostatin in regulating the Dlk1-Dio3 (the callipyge) locus in the skeletal muscle.

  4. The effect of SIRT1 protein knock down on PGC-1α acetylation during skeletal muscle contraction.

    PubMed

    Park, Dae Ryoung; Kim, Jeong Seok; Kim, Chang Keun

    2014-03-01

    The purpose of this study was to investigate the effect of Sirtuin 1 (SIRT1) and General control nonderepressible 5 (GCN5) knock down on peroxisome proliferator- activated receptor gamma coactivator 1-alpha (PGC-1α) deacetylation during electrical stimulated skeletal muscle contraction. Skeletal muscle primary cell were isolated from C57BL/6 mice gastrocnemius and transfected lentiviral SIRT1 and GCN5 shRNA. Knock downed muscle cell were stimulated by electrical stimulation (1Hz, 3min) and collected for PGC-1α deceatylation assays. Immunoprecipitation performed for PGC-1α deacetylation, acetyl-lysine level was measured. Our resulted showed SIRT1 knock down not influenced to PGC-1α deacetylation during electrical stimulation induced muscle contraction while GCN5 knock down decreased PGC-1α deacetylation significantly (p<0.05). This study can be concluded that GCN5 is a critical factor for muscle contraction induced PGC-1α deacetylation.

  5. Intercellular adhesion molecule-1 expression by skeletal muscle cells augments myogenesis.

    PubMed

    Goh, Qingnian; Dearth, Christopher L; Corbett, Jacob T; Pierre, Philippe; Chadee, Deborah N; Pizza, Francis X

    2015-02-15

    We previously demonstrated that the expression of intercellular adhesion molecule-1 (ICAM-1) by skeletal muscle cells after muscle overload contributes to ensuing regenerative and hypertrophic processes in skeletal muscle. The objective of the present study is to reveal mechanisms through which skeletal muscle cell expression of ICAM-1 augments regenerative and hypertrophic processes of myogenesis. This was accomplished by genetically engineering C2C12 myoblasts to stably express ICAM-1, and by inhibiting the adhesive and signaling functions of ICAM-1 through the use of a neutralizing antibody or cell penetrating peptide, respectively. Expression of ICAM-1 by cultured skeletal muscle cells augmented myoblast-myoblast adhesion, myotube formation, myonuclear number, myotube alignment, myotube-myotube fusion, and myotube size without influencing the ability of myoblasts to proliferate or differentiate. ICAM-1 augmented myotube formation, myonuclear accretion, and myotube alignment through a mechanism involving adhesion-induced activation of ICAM-1 signaling, as these dependent measures were reduced via antibody and peptide inhibition of ICAM-1. The adhesive and signaling functions of ICAM-1 also facilitated myotube hypertrophy through a mechanism involving myotube-myotube fusion, protein synthesis, and Akt/p70s6k signaling. Our findings demonstrate that ICAM-1 expression by skeletal muscle cells augments myogenesis, and establish a novel mechanism through which the inflammatory response facilitates growth processes in skeletal muscle. Copyright © 2014 Elsevier Inc. All rights reserved.

  6. Intercellular Adhesion Molecule-1 Expression by Skeletal Muscle Cells Augments Myogenesis

    PubMed Central

    Goh, Qingnian; Dearth, Christopher L.; Corbett, Jacob T.; Pierre, Philippe; Chadee, Deborah N.; Pizza, Francis X.

    2014-01-01

    We previously demonstrated that the expression of intercellular adhesion molecule-1 (ICAM-1) by skeletal muscle cells after muscle overload contributes to ensuing regenerative and hypertrophic processes in skeletal muscle. The objective of the present study is to reveal mechanisms through which skeletal muscle cell expression of ICAM-1 augments regenerative and hypertrophic processes of myogenesis. This was accomplished by genetically engineering C2C12 myoblasts to stably express ICAM-1, and by inhibiting the adhesive and signaling functions of ICAM-1 through the use of a neutralizing antibody or cell penetrating peptide, respectively. Expression of ICAM-1 by cultured skeletal muscle cells augmented myoblast-myoblast adhesion, myotube formation, myonuclear number, myotube alignment, myotube-myotube fusion, and myotube size without influencing the ability of myoblasts to proliferate or differentiate. ICAM-1 augmented myotube formation, myonuclear accretion, and myotube alignment through a mechanism involving adhesion-induced activation of ICAM-1 signaling, as these dependent measures were reduced via antibody and peptide inhibition of ICAM-1. The adhesive and signaling functions of ICAM-1 also facilitated myotube hypertrophy through a mechanism involving myotube-myotube fusion, protein synthesis, and Akt/p70s6k signaling. Our findings demonstrate that ICAM-1 expression by skeletal muscle cells augments myogenesis, and establish a novel mechanism through which the inflammatory response facilitates growth processes in skeletal muscle. PMID:25281303

  7. Skeletal Complications in Neurofibromatosis Type 1: The Role of Neurofibromin Haploinsufficiency in Defective Skeletal Remodeling and Bone Healing in NF1

    DTIC Science & Technology

    2007-01-01

    including scoliosis and pseudoarthrosis, which are compounded by osteoporosis and poor bone healing. Corrective orthopaedic intervention often fails...3 - Introduction: A large proportion of patients with Neurofibromatosis Type 1 display skeletal abnormalities including scoliosis and...abnormalities including alterations in bone size and shape, the presence of scoliosis , and a tendency to develop pseudoarthrosis. These skeletal

  8. Fnip1 regulates skeletal muscle fiber type specification, fatigue resistance, and susceptibility to muscular dystrophy

    PubMed Central

    Reyes, Nicholas L.; Banks, Glen B.; Tsang, Mark; Margineantu, Daciana; Gu, Haiwei; Djukovic, Danijel; Chan, Jacky; Torres, Michelle; Liggitt, H. Denny; Hirenallur-S, Dinesh K.; Hockenbery, David M.; Raftery, Daniel; Iritani, Brian M.

    2015-01-01

    Mammalian skeletal muscle is broadly characterized by the presence of two distinct categories of muscle fibers called type I “red” slow twitch and type II “white” fast twitch, which display marked differences in contraction strength, metabolic strategies, and susceptibility to fatigue. The relative representation of each fiber type can have major influences on susceptibility to obesity, diabetes, and muscular dystrophies. However, the molecular factors controlling fiber type specification remain incompletely defined. In this study, we describe the control of fiber type specification and susceptibility to metabolic disease by folliculin interacting protein-1 (Fnip1). Using Fnip1 null mice, we found that loss of Fnip1 increased the representation of type I fibers characterized by increased myoglobin, slow twitch markers [myosin heavy chain 7 (MyH7), succinate dehydrogenase, troponin I 1, troponin C1, troponin T1], capillary density, and mitochondria number. Cultured Fnip1-null muscle fibers had higher oxidative capacity, and isolated Fnip1-null skeletal muscles were more resistant to postcontraction fatigue relative to WT skeletal muscles. Biochemical analyses revealed increased activation of the metabolic sensor AMP kinase (AMPK), and increased expression of the AMPK-target and transcriptional coactivator PGC1α in Fnip1 null skeletal muscle. Genetic disruption of PGC1α rescued normal levels of type I fiber markers MyH7 and myoglobin in Fnip1-null mice. Remarkably, loss of Fnip1 profoundly mitigated muscle damage in a murine model of Duchenne muscular dystrophy. These results indicate that Fnip1 controls skeletal muscle fiber type specification and warrant further study to determine whether inhibition of Fnip1 has therapeutic potential in muscular dystrophy diseases. PMID:25548157

  9. GSNOR Deficiency Enhances In Situ Skeletal Muscle Strength, Fatigue Resistance, and RyR1 S-Nitrosylation Without Impacting Mitochondrial Content and Activity

    PubMed Central

    Moon, Younghye; Cao, Yenong; Zhu, Jingjing; Xu, Yuanyuan; Balkan, Wayne; Buys, Emmanuel S.; Diaz, Francisca; Kerrick, W. Glenn; Hare, Joshua M.

    2017-01-01

    Abstract Aim: Nitric oxide (NO) plays important, but incompletely defined roles in skeletal muscle. NO exerts its regulatory effects partly though S-nitrosylation, which is balanced by denitrosylation by enzymes such as S-nitrosoglutathione reductase (GSNOR), whose functions in skeletal muscle remain to be fully deciphered. Results: GSNOR null (GSNOR−/−) tibialis anterior (TA) muscles showed normal growth and were stronger and more fatigue resistant than controls in situ. However, GSNOR−/− lumbrical muscles showed normal contractility and Ca2+ handling in vitro, suggesting important differences in GSNOR function between muscles or between in vitro and in situ environments. GSNOR−/− TA muscles exhibited normal mitochondrial content, and capillary densities, but reduced type IIA fiber content. GSNOR inhibition did not impact mitochondrial respiratory complex I, III, or IV activities. These findings argue that enhanced GSNOR−/− TA contractility is not driven by changes in mitochondrial content or activity, fiber type, or blood vessel density. However, loss of GSNOR led to RyR1 hypernitrosylation, which is believed to increase muscle force output under physiological conditions. cGMP synthesis by soluble guanylate cyclase (sGC) was decreased in resting GSNOR−/− muscle and was more responsive to agonist (DETANO, BAY 41, and BAY 58) stimulation, suggesting that GSNOR modulates cGMP production in skeletal muscle. Innovation: GSNOR may act as a “brake” on skeletal muscle contractile performance under physiological conditions by modulating nitrosylation/denitrosylation balance. Conclusions: GSNOR may play important roles in skeletal muscle contractility, RyR1 S-nitrosylation, fiber type specification, and sGC activity. Antioxid. Redox Signal. 26, 165–181. PMID:27412893

  10. Deep proteomics of mouse skeletal muscle enables quantitation of protein isoforms, metabolic pathways, and transcription factors.

    PubMed

    Deshmukh, Atul S; Murgia, Marta; Nagaraj, Nagarjuna; Treebak, Jonas T; Cox, Jürgen; Mann, Matthias

    2015-04-01

    Skeletal muscle constitutes 40% of individual body mass and plays vital roles in locomotion and whole-body metabolism. Proteomics of skeletal muscle is challenging because of highly abundant contractile proteins that interfere with detection of regulatory proteins. Using a state-of-the art MS workflow and a strategy to map identifications from the C2C12 cell line model to tissues, we identified a total of 10,218 proteins, including skeletal muscle specific transcription factors like myod1 and myogenin and circadian clock proteins. We obtain absolute abundances for proteins expressed in a muscle cell line and skeletal muscle, which should serve as a valuable resource. Quantitation of protein isoforms of glucose uptake signaling pathways and in glucose and lipid metabolic pathways provides a detailed metabolic map of the cell line compared with tissue. This revealed unexpectedly complex regulation of AMP-activated protein kinase and insulin signaling in muscle tissue at the level of enzyme isoforms. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

  11. Disruption of both nesprin 1 and desmin results in nuclear anchorage defects and fibrosis in skeletal muscle.

    PubMed

    Chapman, Mark A; Zhang, Jianlin; Banerjee, Indroneal; Guo, Ling T; Zhang, Zhiwei; Shelton, G Diane; Ouyang, Kunfu; Lieber, Richard L; Chen, Ju

    2014-11-15

    Proper localization and anchorage of nuclei within skeletal muscle is critical for cellular function. Alterations in nuclear anchoring proteins modify a number of cellular functions including mechanotransduction, nuclear localization, chromatin positioning/compaction and overall organ function. In skeletal muscle, nesprin 1 and desmin are thought to link the nucleus to the cytoskeletal network. Thus, we hypothesize that both of these factors play a key role in skeletal muscle function. To examine this question, we utilized global ablation murine models of nesprin 1, desmin or both nesprin 1 and desmin. Herein, we have created the nesprin-desmin double-knockout (DKO) mouse, eliminating a major fraction of nuclear-cytoskeletal connections and enabling understanding of the importance of nuclear anchorage in skeletal muscle. Globally, DKO mice are marked by decreased lifespan, body weight and muscle strength. With regard to skeletal muscle, DKO myonuclear anchorage was dramatically decreased compared with wild-type, nesprin 1(-/-) and desmin(-/-) mice. Additionally, nuclear-cytoskeletal strain transmission was decreased in DKO skeletal muscle. Finally, loss of nuclear anchorage in DKO mice coincided with a fibrotic response as indicated by increased collagen and extracellular matrix deposition and increased passive mechanical properties of muscle bundles. Overall, our data demonstrate that nesprin 1 and desmin serve redundant roles in nuclear anchorage and that the loss of nuclear anchorage in skeletal muscle results in a pathological response characterized by increased tissue fibrosis and mechanical stiffness. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  12. Prolyl hydroxylase domain 2 deficiency promotes skeletal muscle fiber-type transition via a calcineurin/NFATc1-dependent pathway.

    PubMed

    Shin, Junchul; Nunomiya, Aki; Kitajima, Yasuo; Dan, Takashi; Miyata, Toshio; Nagatomi, Ryoichi

    2016-01-01

    Hypoxia exposure is known to induce an alteration in skeletal muscle fiber-type distribution mediated by hypoxia-inducible factor (HIF)-α. The downstream pathway of HIF-α leading to fiber-type shift, however, has not been elucidated. The calcineurin pathway is one of the pathways responsible for slow muscle fiber transition. Because calcineurin pathway is activated by vascular endothelial growth factor (VEGF), one of the factors induced by HIF-1α, we hypothesized that the stabilization of HIF-1α may lead to slow muscle fiber transition via the activation of calcineurin pathway in skeletal muscles. To induce HIF-1α stabilization, we used a loss of function strategy to abrogate Prolyl hydroxylase domain protein (PHD) 2 responsible for HIF-1α hydroxylation making HIF-1α susceptible to ubiquitin dependent degradation by proteasome. The purpose of this study was therefore to examine the effect of HIF-1α stabilization in PHD2 conditional knockout mouse on skeletal muscle fiber-type transition and to elucidate the involvement of calcineurin pathway on muscle fiber-type transition. PHD2 deficiency resulted in an increased capillary density in skeletal muscles due to the induction of vascular endothelial growth factor. It also elicited an alteration of skeletal muscle phenotype toward the type I fibers in both of the soleus (35.8 % in the control mice vs. 46.7 % in the PHD2-deficient mice, p < 0.01) and the gastrocnemius muscle (0.94 vs. 1.89 %, p < 0.01), and the increased proportion of type I fibers appeared to correspond to the area of increased capillary density. In addition, calcineurin and nuclear factor of activated T cell (NFATc1) protein levels were increased in both the gastrocnemius and soleus muscles, suggesting that the calcineurin/NFATc1 pathway was responsible for the type I fiber transition regardless of PGC-1α, which responded minimally to PHD2 deficiency. Indeed, we found that tacrolimus (FK-506), a calcineurin inhibitor, successfully

  13. A Rhodiola rosea root extract protects skeletal muscle cells against chemically induced oxidative stress by modulating heat shock protein 70 (HSP70) expression.

    PubMed

    Hernández-Santana, Aaron; Pérez-López, Verónica; Zubeldia, Jose María; Jiménez-del-Rio, Miguel

    2014-04-01

    Rhodiola rosea is a perennial plant in the Crassulaceae family, recently postulated to exert its adaptogenic functions partially by modulating the expression of molecular factors such as heat shock proteins (HSP). The aim of this study was to analyze the efficacy of a Rhodiola rosea extract (Rhodiolife) in protecting murine skeletal muscle cells (C2 C12 myotubes) from chemically induced oxidative stress and to establish whether modulation of HSP70 expression is observed. C2 C12 cells treated with Rhodiolife did not experience any loss of viability (p > 0.05) at concentrations of 1-100 µg/mL for up to 24 h. In control cultures, viability decreased 25% following exposure to 2 mM H2 O2 (1 h). However, no significant decrease in viability in cells pre-treated with extract at concentrations as low as 1 µg/mL was observed. HSP70 mRNA levels were up-regulated two-fold in cell cultures treated with Rhodiolife (10 µg/mL), and expression was further enhanced by exposure to H2 O2 (six-fold, p < 0.05). HSP70 protein levels were maintained in pre-treated cell cultures compared to controls but was significantly lower (-50%) in cells lacking treatment exposed to H2 O2 . The present results indicate that Rhodiolife protects C2 C12 myotubes against peroxide-induced oxidative stress through the modulation of the molecular chaperone HSP70. Copyright © 2013 John Wiley & Sons, Ltd.

  14. Overexpression of IGF-1 attenuates skeletal muscle damage and accelerates muscle regeneration and functional recovery after disuse

    PubMed Central

    Ye, Fan; Mathur, Sunita; Liu, Min; Borst, Stephen E.; Walter, Glenn A.; Sweeney, H. Lee; Vandenborne, Krista

    2014-01-01

    Skeletal muscle is a highly dynamic tissue that responds to endogenous and external stimuli, including alterations in mechanical loading and growth factors. In particular, the antigravity soleus muscle experiences significant muscle atrophy during disuse and extensive muscle damage upon reloading. Since insulin-like growth factor-1 (IGF-1) has been implicated as a central regulator of muscle repair and modulation of muscle size, we examined the effect of viral mediated overexpression of IGF-1 on the soleus muscle following hindlimb cast immobilization and upon reloading. Recombinant IGF-1 cDNA virus was injected into one of the posterior hindlimbs of the mice, while the contralateral limb was injected with saline (control). At 20 weeks of age, both hindlimbs were immobilized for two weeks to induce muscle atrophy in the soleus and ankle plantar flexor muscle group. Subsequently, the mice were allowed to reambulate and muscle damage and recovery was monitored over a period of 2 to 21 days. The primary finding of this study was that IGF-1 overexpression attenuated reloading-induced muscle damage in the soleus muscle, and accelerated muscle regeneration and force recovery. Muscle T2 assessed by MRI, a nonspecific marker of muscle damage, was significantly lower in IGF-1 injected, compared to contralateral soleus muscles at 2 and 5 days reambulation (P<0.05). The reduced prevalence of muscle damage in IGF-1 injected soleus muscles was confirmed on histology, with a lower fraction area of abnormal muscle tissue in IGF-I injected muscles at 2 days reambulation (33.2±3.3%vs 54.1±3.6%, P<0.05). Evidence of the effect of IGF-1 on muscle regeneration included timely increases in the number of central nuclei (21% at 5 days reambulation), paired-box transcription factor 7 (36% at 5 days), embryonic myosin (37% at 10 days), and elevated MyoD mRNA (7-fold at 2 days) in IGF-1 injected limbs (P<0.05). These findings demonstrate a potential role of IGF-1 in protecting unloaded

  15. A unified anatomy ontology of the vertebrate skeletal system.

    PubMed

    Dahdul, Wasila M; Balhoff, James P; Blackburn, David C; Diehl, Alexander D; Haendel, Melissa A; Hall, Brian K; Lapp, Hilmar; Lundberg, John G; Mungall, Christopher J; Ringwald, Martin; Segerdell, Erik; Van Slyke, Ceri E; Vickaryous, Matthew K; Westerfield, Monte; Mabee, Paula M

    2012-01-01

    The skeleton is of fundamental importance in research in comparative vertebrate morphology, paleontology, biomechanics, developmental biology, and systematics. Motivated by research questions that require computational access to and comparative reasoning across the diverse skeletal phenotypes of vertebrates, we developed a module of anatomical concepts for the skeletal system, the Vertebrate Skeletal Anatomy Ontology (VSAO), to accommodate and unify the existing skeletal terminologies for the species-specific (mouse, the frog Xenopus, zebrafish) and multispecies (teleost, amphibian) vertebrate anatomy ontologies. Previous differences between these terminologies prevented even simple queries across databases pertaining to vertebrate morphology. This module of upper-level and specific skeletal terms currently includes 223 defined terms and 179 synonyms that integrate skeletal cells, tissues, biological processes, organs (skeletal elements such as bones and cartilages), and subdivisions of the skeletal system. The VSAO is designed to integrate with other ontologies, including the Common Anatomy Reference Ontology (CARO), Gene Ontology (GO), Uberon, and Cell Ontology (CL), and it is freely available to the community to be updated with additional terms required for research. Its structure accommodates anatomical variation among vertebrate species in development, structure, and composition. Annotation of diverse vertebrate phenotypes with this ontology will enable novel inquiries across the full spectrum of phenotypic diversity.

  16. A Unified Anatomy Ontology of the Vertebrate Skeletal System

    PubMed Central

    Dahdul, Wasila M.; Balhoff, James P.; Blackburn, David C.; Diehl, Alexander D.; Haendel, Melissa A.; Hall, Brian K.; Lapp, Hilmar; Lundberg, John G.; Mungall, Christopher J.; Ringwald, Martin; Segerdell, Erik; Van Slyke, Ceri E.; Vickaryous, Matthew K.; Westerfield, Monte; Mabee, Paula M.

    2012-01-01

    The skeleton is of fundamental importance in research in comparative vertebrate morphology, paleontology, biomechanics, developmental biology, and systematics. Motivated by research questions that require computational access to and comparative reasoning across the diverse skeletal phenotypes of vertebrates, we developed a module of anatomical concepts for the skeletal system, the Vertebrate Skeletal Anatomy Ontology (VSAO), to accommodate and unify the existing skeletal terminologies for the species-specific (mouse, the frog Xenopus, zebrafish) and multispecies (teleost, amphibian) vertebrate anatomy ontologies. Previous differences between these terminologies prevented even simple queries across databases pertaining to vertebrate morphology. This module of upper-level and specific skeletal terms currently includes 223 defined terms and 179 synonyms that integrate skeletal cells, tissues, biological processes, organs (skeletal elements such as bones and cartilages), and subdivisions of the skeletal system. The VSAO is designed to integrate with other ontologies, including the Common Anatomy Reference Ontology (CARO), Gene Ontology (GO), Uberon, and Cell Ontology (CL), and it is freely available to the community to be updated with additional terms required for research. Its structure accommodates anatomical variation among vertebrate species in development, structure, and composition. Annotation of diverse vertebrate phenotypes with this ontology will enable novel inquiries across the full spectrum of phenotypic diversity. PMID:23251424

  17. pH-modulation of chloride channels from the sarcoplasmic reticulum of skeletal muscle.

    PubMed

    Kourie, J I

    1999-01-01

    The understanding of the role of cytoplasmic pH in modulating sarcoplasmic reticulum (SR) ion channels involved in Ca2+ regulation is important for the understanding of the function of normal and adversely affected muscles. The dependency of the SR small chloride (SCl) channel from rabbit skeletal muscle on cytoplasmic pH (pHcis) and luminal pH (pHtrans) was investigated using the lipid bilayer-vesicle fusion technique. Low pHcis 6.75-4.28 modifies the operational mode of this multiconductance channel (conductance levels between 5 and 75 pS). At pHcis 7.26-7.37 the channel mode is dominated by the conductance and kinetics of the main conductance state (65-75 pS) whereas at low pHcis 6.75-4.28 the channel mode is dominated by the conductance and kinetics of subconductance states (5-40 pS). Similarly, low pHtrans 4.07, but not pHtrans 6.28, modified the activity of SCl channels. The effects of low pHcis are pronounced at 10(-3) and 10(-4) M [Ca2+]cis but are not apparent at 10(-5) M [Ca2+]cis, where the subconductances of the channel are already prominent. Low pHcis-induced mode shift in the SCl channel activity is due to modification of the channel proteins that cause the uncoupling of the subconductance states. The results in this study suggest that low pHcis can modify the functional properties of the skeletal SR ion channels and hence contribute, at least partly, to the malfunction in the contraction-relaxation mechanism in skeletal muscle under low cytoplasmic pH levels.

  18. Effects of long-term resveratrol-induced SIRT1 activation on insulin and apoptotic signalling in aged skeletal muscle.

    PubMed

    Sin, Thomas K; Yu, Angus P; Yung, Benjamin Y; Yip, Shea P; Chan, Lawrence W; Wong, Cesar S; Rudd, John A; Siu, Parco M

    2015-12-01

    Activation of Foxo1 is known to promote apoptosis and disturbances to insulin signalling. However, their modulating roles in aged skeletal muscle are not clear. The present study tested the hypothesis that long-term (i.e. 8 month) resveratrol supplementation would improve physical traits including exercise capacity and basal voluntary activity of aged mice and modulate insulin/apoptotic signalling in aged skeletal muscle. This study also examined whether these resveratrol-associated alterations would involve orchestration of the SIRT1-Foxo1 signalling axis. Two-month-old SAMP8 mice were randomly assigned to young, aged and aged with resveratrol treatment (AR) groups. The AR mice were supplemented with 4.9 mg(-1) kg(-1) day(-1) resveratrol for 8 months. All animals were subject to endurance capacity test and voluntary motor behaviour assessment. The lateral gastrocnemius muscle tissues were harvested for further analyses. Long-term resveratrol treatment significantly alleviated the age-associated reductions in exercise capacity and voluntary motor behaviour. The protein content, but not the deacetylase activity of SIRT1 was increased with concomitant elevations of p300 acetylase and acetylation of Foxo1 in aged muscle. The aged muscle also manifested signs of impaired insulin signalling including attenuated phosphorylation of Akt, activity of pyruvate dehydrogenase and membrane trafficking of GLUT4 and elevated levels of phosphorylated IRS1 and iNOS and apoptotic activation measured as Bim, p53 and apoptotic DNA fragmentation. Intriguingly, all these age-related adverse changes were mitigated with the activation of SIRT1 deacetylase activity after long-term resveratrol treatment. These data suggest that modulation of the SIRT1-Foxo1 axis by long-term resveratrol treatment enhances physical traits and alleviates the unfavourable changes in insulin and apoptotic signalling in aged muscle.

  19. Regulation of skeletal growth and mineral acquisition by the GH/IGF-1 axis: Lessons from mouse models.

    PubMed

    Yakar, Shoshana; Isaksson, Olle

    2016-06-01

    The growth hormone (GH) and its downstream mediator, the insulin-like growth factor-1 (IGF-1), construct a pleotropic axis affecting growth, metabolism, and organ function. Serum levels of GH/IGF-1 rise during pubertal growth and associate with peak bone acquisition, while during aging their levels decline and associate with bone loss. The GH/IGF-1 axis was extensively studied in numerous biological systems including rodent models and cell cultures. Both hormones act in an endocrine and autocrine/paracrine fashion and understanding their distinct and overlapping contributions to skeletal acquisition is still a matter of debate. GH and IGF-1 exert their effects on osteogenic cells via binding to their cognate receptor, leading to activation of an array of genes that mediate cellular differentiation and function. Both hormones interact with other skeletal regulators, such as sex-steroids, thyroid hormone, and parathyroid hormone, to facilitate skeletal growth and metabolism. In this review we summarized several rodent models of the GH/IGF-1 axis and described key experiments that shed new light on the regulation of skeletal growth by the GH/IGF-1 axis. Copyright © 2015 Elsevier Ltd. All rights reserved.

  20. Regulation of skeletal growth and mineral acquisition by the GH/IGF-1 axis: Lessons from mouse models

    PubMed Central

    Yakar, Shoshana; Isaksson, Olle

    2015-01-01

    The growth hormone (GH) and its downstream mediator, the insulin-like growth factor-1 (IGF-1), construct a pleotropic axis affecting growth, metabolism, and organ function. Serum levels of GH/IGF-1 rise during pubertal growth and associate with peak bone acquisition, while during aging their levels decline and associate with bone loss. The GH/IGF-1 axis was extensively studied in numerous biological systems including rodent models and cell cultures. Both hormones act in an endocrine and autocrine/paracrine fashion and understanding their distinct and overlapping contributions to skeletal acquisition is still a matter of debate. GH and IGF-1 exert their effects on osteogenic cells via binding to their cognate receptor, leading to activation of an array of genes that mediate cellular differentiation and function. Both hormones interact with other skeletal regulators, such as sex-steroids, thyroid hormone, and parathyroid hormone, to facilitate skeletal growth and metabolism. In this review we summarized several rodent models of the GH/IGF-1 axis and described key experiments that shed new light on the regulation of skeletal growth by the GH/IGF-1 axis. PMID:26432542

  1. Kruppel-like factor 15 regulates skeletal muscle lipid flux and exercise adaptation

    PubMed Central

    Haldar, Saptarsi M.; Jeyaraj, Darwin; Anand, Priti; Zhu, Han; Lu, Yuan; Prosdocimo, Domenick A.; Eapen, Betty; Kawanami, Daiji; Okutsu, Mitsuharu; Brotto, Leticia; Fujioka, Hisashi; Kerner, Janos; Rosca, Mariana G.; McGuinness, Owen P.; Snow, Rod J.; Russell, Aaron P.; Gerber, Anthony N.; Bai, Xiaodong; Yan, Zhen; Nosek, Thomas M.; Brotto, Marco; Hoppel, Charles L.; Jain, Mukesh K.

    2012-01-01

    The ability of skeletal muscle to enhance lipid utilization during exercise is a form of metabolic plasticity essential for survival. Conversely, metabolic inflexibility in muscle can cause organ dysfunction and disease. Although the transcription factor Kruppel-like factor 15 (KLF15) is an important regulator of glucose and amino acid metabolism, its endogenous role in lipid homeostasis and muscle physiology is unknown. Here we demonstrate that KLF15 is essential for skeletal muscle lipid utilization and physiologic performance. KLF15 directly regulates a broad transcriptional program spanning all major segments of the lipid-flux pathway in muscle. Consequently, Klf15-deficient mice have abnormal lipid and energy flux, excessive reliance on carbohydrate fuels, exaggerated muscle fatigue, and impaired endurance exercise capacity. Elucidation of this heretofore unrecognized role for KLF15 now implicates this factor as a central component of the transcriptional circuitry that coordinates physiologic flux of all three basic cellular nutrients: glucose, amino acids, and lipids. PMID:22493257

  2. The role of E3 ubiquitin-ligases MuRF-1 and MAFbx in loss of skeletal muscle mass.

    PubMed

    Rom, Oren; Reznick, Abraham Z

    2016-09-01

    The ubiquitin-proteasome system (UPS) is the main regulatory mechanism of protein degradation in skeletal muscle. The ubiquitin-ligase enzymes (E3s) have a central role in determining the selectivity and specificity of the UPS. Since their identification in 2001, the muscle specific E3s, muscle RING finger-1 (MuRF-1) and muscle atrophy F-box (MAFbx), have been shown to be implicated in the regulation of skeletal muscle atrophy in various pathological and physiological conditions. This review aims to explore the involvement of MuRF-1 and MAFbx in catabolism of skeletal muscle during various pathologies, such as cancer cachexia, sarcopenia of aging, chronic kidney disease (CKD), diabetes, and chronic obstructive pulmonary disease (COPD). In addition, the effects of various lifestyle and modifiable factors (e.g. nutrition, exercise, cigarette smoking, and alcohol) on MuRF-1 and MAFbx regulation will be discussed. Finally, evidence of potential strategies to protect against skeletal muscle wasting through inhibition of MuRF-1 and MAFbx expression will be explored. Copyright © 2015 Elsevier Inc. All rights reserved.

  3. PGC-1α and fasting-induced PDH regulation in mouse skeletal muscle.

    PubMed

    Gudiksen, Anders; Pilegaard, Henriette

    2017-04-01

    The purpose of the present study was to examine whether lack of skeletal muscle peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1 α ) affects the switch in substrate utilization from a fed to fasted state and the fasting-induced pyruvate dehydrogenase (PDH) regulation in skeletal muscle. Skeletal muscle-specific PGC-1 α knockout (MKO) mice and floxed littermate controls were fed or fasted for 24 h. Fasting reduced PDHa activity, increased phosphorylation of all four known sites on PDH-E1 α and increased pyruvate dehydrogenase kinase (PDK4) and sirtuin 3 (SIRT3) protein levels, but did not alter total acetylation of PDH-E1 α Lack of muscle PGC-1 α did not affect the switch from glucose to fat oxidation in the transition from the fed to fasted state, but was associated with lower and higher respiratory exchange ratio (RER) in the fed and fasted state, respectively. PGC-1 α MKO mice had lower skeletal muscle PDH-E1 α , PDK1, 2, 4, and pyruvate dehydrogenase phosphatase (PDP1) protein content than controls, but this did not prevent the fasting-induced increase in PDH-E1 α phosphorylation in PGC-1 α MKO mice. However, lack of skeletal muscle PGC-1 α reduced SIRT3 protein content, increased total lysine PDH-E1 α acetylation in the fed state, and prevented a fasting-induced increase in SIRT3 protein. In conclusion, skeletal muscle PGC-1 α is required for fasting-induced upregulation of skeletal muscle SIRT3 and maintaining high fat oxidation in the fasted state, but is dispensable for preserving the capability to switch substrate during the transition from the fed to the fasted state and for fasting-induced PDH regulation in skeletal muscle. © 2017 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.

  4. Biological properties of human skeletal myoblasts genetically modified to simultaneously overexpress the pro-angiogenic factors vascular endothelial growth factor-A and fibroblast growth factor-4.

    PubMed

    Zimna, A; Janeczek, A; Rozwadowska, N; Fraczek, M; Kucharzewska, P; Rucinski, M; Mietkiewski, T; Kurpisz, M

    2014-04-01

    Myocardial infarction results in cardiomyocyte loss and may eventually lead to cardiac failure. Skeletal myoblast transplantation into the scar area may compensate for this observed cell loss by strengthening the weakened myocardium and inducing myogenesis. Moreover, skeletal myoblasts may serve as potential transgene carriers for the myocardium (i.e., delivering pro-angiogenic factors, which may potentially improve blood perfusion in infarcted heart). We examined the influence of the simultaneous overexpression of two potent pro-angiogenic factors, fibroblast growth factor-4 (FGF-4) and vascular endothelial growth factor (VEGF), on human primary myoblast proliferation, cell cycle, resistance to hypoxic stress conditions and myogenic gene expression, as well as the induction of pro-angiogenic activities. We used a bicistronic plasmid vector encoding two factors introduced via an efficient myoblast electroporation method. The levels of overexpressed proteins were assessed, and their functionality at capillary formation was evaluated. This combined approach led to a high level of non-viral transient overexpression of both pro-angiogenic proteins, which proved to be potent regulators of blood vessel development assayed in capillary formation tests. We demonstrated in in vitro conditions that the transfection of human skeletal myoblasts with both FGF-4 and VEGF did not affect their basic biological properties such as the cell cycle, proliferation or expression of myogenic lineage-specific genes, and the modified cells adapted to oxidative stress conditions. Overall, the results obtained suggest that the applied combined approach with the use of two pro-angiogenic genes overexpressed in skeletal muscle stem cells may be an interesting alternative for the effective therapy of myocardial infarction in animal models and/or prospective clinical trials.

  5. ATXN1L, CIC, and ETS Transcription Factors Modulate Sensitivity to MAPK Pathway Inhibition

    PubMed Central

    Wang, Belinda; Krall, Elsa Beyer; Aguirre, Andrew James; Kim, Miju; Widlund, Hans Ragnar; Doshi, Mihir Bhavik; Sicinska, Ewa; Sulahian, Rita; Goodale, Amy; Cowley, Glenn Spencer; Piccioni, Federica; Doench, John Gerard; Root, David Edward; Hahn, William Chun

    2017-01-01

    SUMMARY Intrinsic resistance and RTK-RAS-MAPK pathway reactivation has limited the effectiveness of MEK and RAF inhibitors (MAPKi) in RAS- and RAF-mutant cancers. To identify genes that modulate sensitivity to MAPKi, we performed genome scale CRISPR-Cas9 loss-of-function screens in two KRAS-mutant pancreatic cancer cell lines treated with the MEK1/2 inhibitor trametinib. Loss of CIC, a transcriptional repressor of ETV1, 4, and 5, promoted survival in the setting of MAPKi in cancer cells derived from several lineages. ATXN1L deletion, which reduces CIC protein, or ectopic expression of ETV1, 4, or 5 also modulated sensitivity to trametinib. ATXN1L expression inversely correlates with response to MAPKi inhibition in clinical studies. These observations identify the ATXN1L-CIC-ETS transcription factor axis as a mediator of resistance to MAPKi. PMID:28178529

  6. Akt1 deficiency diminishes skeletal muscle hypertrophy by reducing satellite cell proliferation.

    PubMed

    Moriya, Nobuki; Miyazaki, Mitsunori

    2018-05-01

    Skeletal muscle mass is determined by the net dynamic balance between protein synthesis and degradation. Although the Akt/mechanistic target of rapamycin (mTOR)-dependent pathway plays an important role in promoting protein synthesis and subsequent skeletal muscle hypertrophy, the precise molecular regulation of mTOR activity by the upstream protein kinase Akt is largely unknown. In addition, the activation of satellite cells has been indicated as a key regulator of muscle mass. However, the requirement of satellite cells for load-induced skeletal muscle hypertrophy is still under intense debate. In this study, female germline Akt1 knockout (KO) mice were used to examine whether Akt1 deficiency attenuates load-induced skeletal muscle hypertrophy through suppressing mTOR-dependent signaling and satellite cell proliferation. Akt1 KO mice showed a blunted hypertrophic response of skeletal muscle, with a diminished rate of satellite cell proliferation following mechanical overload. In contrast, Akt1 deficiency did not affect the load-induced activation of mTOR signaling and the subsequent enhanced rate of protein synthesis in skeletal muscle. These observations suggest that the load-induced activation of mTOR signaling occurs independently of Akt1 regulation and that Akt1 plays a critical role in regulating satellite cell proliferation during load-induced muscle hypertrophy.

  7. Relationship between serum IGF-1 and skeletal muscle IGF-1 mRNA expression to phosphocreatine recovery after exercise in obese men with reduced GH.

    PubMed

    Hamarneh, Sulaiman R; Murphy, Caitlin A; Shih, Cynthia W; Frontera, Walter; Torriani, Martin; Irazoqui, Javier E; Makimura, Hideo

    2015-02-01

    GH and IGF-1 are believed to be physiological regulators of skeletal muscle mitochondria. The objective of this study was to examine the relationship between GH/IGF-1 and skeletal muscle mitochondria in obese subjects with reduced GH secretion in more detail. Fifteen abdominally obese men with reduced GH secretion were treated for 12 weeks with recombinant human GH. Subjects underwent (31)P-magnetic resonance spectroscopy to assess phosphocreatine (PCr) recovery as an in vivo measure of skeletal muscle mitochondrial function and percutaneous muscle biopsies to assess mRNA expression of IGF-1 and mitochondrial-related genes at baseline and 12 weeks. At baseline, skeletal muscle IGF-1 mRNA expression was significantly associated with PCr recovery (r = 0.79; P = .01) and nuclear respiratory factor-1 (r = 0.87; P = .001), mitochondrial transcription factor A (r = 0.86; P = .001), peroxisome proliferator-activated receptor (PPAR)γ (r = 0.72; P = .02), and PPARα (r = 0.75; P = .01) mRNA expression, and trended to an association with PPARγ coactivator 1-α (r = 0.59; P = .07) mRNA expression. However, serum IGF-1 concentration was not associated with PCr recovery or any mitochondrial gene expression (all P > .10). Administration of recombinant human GH increased both serum IGF-1 (change, 218 ± 29 μg/L; P < .0001) and IGF-1 mRNA in muscle (fold change, 2.1 ± 0.3; P = .002). Increases in serum IGF-1 were associated with improvements in total body fat (r = -0.53; P = .04), trunk fat (r = -0.55; P = .03), and lean mass (r = 0.58; P = .02), but not with PCr recovery (P > .10). Conversely, increase in muscle IGF-1 mRNA was associated with improvements in PCr recovery (r = 0.74; P = .02), but not with body composition parameters (P > .10). These data demonstrate a novel association of skeletal muscle mitochondria with muscle IGF-1 mRNA expression, but independent of serum IGF-1 concentrations.

  8. Relationship Between Serum IGF-1 and Skeletal Muscle IGF-1 mRNA Expression to Phosphocreatine Recovery After Exercise in Obese Men With Reduced GH

    PubMed Central

    Hamarneh, Sulaiman R.; Murphy, Caitlin A.; Shih, Cynthia W.; Frontera, Walter; Torriani, Martin; Irazoqui, Javier E.

    2015-01-01

    Context: GH and IGF-1 are believed to be physiological regulators of skeletal muscle mitochondria. Objective: The objective of this study was to examine the relationship between GH/IGF-1 and skeletal muscle mitochondria in obese subjects with reduced GH secretion in more detail. Design: Fifteen abdominally obese men with reduced GH secretion were treated for 12 weeks with recombinant human GH. Subjects underwent 31P-magnetic resonance spectroscopy to assess phosphocreatine (PCr) recovery as an in vivo measure of skeletal muscle mitochondrial function and percutaneous muscle biopsies to assess mRNA expression of IGF-1 and mitochondrial-related genes at baseline and 12 weeks. Results: At baseline, skeletal muscle IGF-1 mRNA expression was significantly associated with PCr recovery (r = 0.79; P = .01) and nuclear respiratory factor-1 (r = 0.87; P = .001), mitochondrial transcription factor A (r = 0.86; P = .001), peroxisome proliferator-activated receptor (PPAR)γ (r = 0.72; P = .02), and PPARα (r = 0.75; P = .01) mRNA expression, and trended to an association with PPARγ coactivator 1-α (r = 0.59; P = .07) mRNA expression. However, serum IGF-1 concentration was not associated with PCr recovery or any mitochondrial gene expression (all P > .10). Administration of recombinant human GH increased both serum IGF-1 (change, 218 ± 29 μg/L; P < .0001) and IGF-1 mRNA in muscle (fold change, 2.1 ± 0.3; P = .002). Increases in serum IGF-1 were associated with improvements in total body fat (r = −0.53; P = .04), trunk fat (r = −0.55; P = .03), and lean mass (r = 0.58; P = .02), but not with PCr recovery (P > .10). Conversely, increase in muscle IGF-1 mRNA was associated with improvements in PCr recovery (r = 0.74; P = .02), but not with body composition parameters (P > .10). Conclusion: These data demonstrate a novel association of skeletal muscle mitochondria with muscle IGF-1 mRNA expression, but independent of serum IGF-1 concentrations. PMID:25375982

  9. Insulin-like growth factor-1 suppresses the Myostatin signaling pathway during myogenic differentiation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Retamales, A.; Zuloaga, R.; Valenzuela, C.A.

    Myogenic differentiation is a complex and well-coordinated process for generating mature skeletal muscle fibers. This event is autocrine/paracrine regulated by growth factors, principally Myostatin (MSTN) and Insulin-like Growth Factor-1 (IGF-1). Myostatin, a member of the transforming growth factor-β superfamily, is a negative regulator of skeletal muscle growth in vertebrates that exerts its inhibitory function by activating Smad transcription factors. In contrast, IGF-1 promotes the differentiation of skeletal myoblasts by activating the PI3K/Akt signaling pathway. This study reports on a novel functional crosstalk between the IGF-1 and MSTN signaling pathways, as mediated through interaction between PI3K/Akt and Smad3. Stimulation of skeletalmore » myoblasts with MSTN resulted in a transient increase in the pSmad3:Smad3 ratio and Smad-dependent transcription. Moreover, MSTN inhibited myod gene expression and myoblast fusion in an Activin receptor-like kinase/Smad3-dependent manner. Preincubation of skeletal myoblasts with IGF-1 blocked MSTN-induced Smad3 activation, promoting myod expression and myoblast differentiation. This inhibitory effect of IGF-1 on the MSTN signaling pathway was dependent on IGF-1 receptor, PI3K, and Akt activities. Finally, immunoprecipitation assay analysis determined that IGF-1 pretreatment increased Akt and Smad3 interaction. These results demonstrate that the IGF-1/PI3K/Akt pathway may inhibit MSTN signaling during myoblast differentiation, providing new insight to existing knowledge on the complex crosstalk between both growth factors. - Highlights: • IGF-1 inhibits Myostatin canonical signaling pathway through IGF-1R/PI3K/Akt pathway. • IGF-1 promotes myoblast differentiation through a direct blocking of Myostatin signaling pathway. • IGF-1 induces the interaction of Akt with Smad3 in skeletal myoblast.« less

  10. Association of the CPT1B Gene with Skeletal Muscle Fat Infiltration in Afro-Caribbean Men

    PubMed Central

    Miljkovic, Iva; Yerges, Laura M.; Li, Hu; Gordon, Christopher L.; Goodpaster, Bret H.; Kuller, Lewis H.; Nestlerode, Cara S.; Bunker, Clareann H.; Patrick, Alan L.; Wheeler, Victor W.; Zmuda, Joseph M.

    2010-01-01

    Skeletal muscle fat is greater in African ancestry individuals compared with whites, is associated with diabetes, and is a heritable polygenic trait. However, specific genetic factors contributing to skeletal muscle fat in humans remain to be defined. Muscle carnitine palmitoyltransferase-1B (CPT1B) is a key enzyme in the regulation of skeletal muscle mitochondrial β-oxidation of long-chain fatty acids, and as such is a reasonable biological candidate gene for skeletal muscle fat accumulation. Therefore, we examined the association of three nonsynonymous coding variants in CPT1B (G531L, I66V, and S427C; a fourth, A320G, could not be genotyped) and quantitative computed tomography measured tibia skeletal muscle composition and BMI among 1,774 Afro-Caribbean men aged ≥40, participants of the population-based Tobago Health Study. For all variants, no significant differences were observed for BMI or total adipose tissue. Among individuals who were homozygous for the minor allele at G531L or I66V, intermuscular adipose tissue (IMAT) was 87% (P = 0.03) and 54% lower (P = 0.03), respectively. In contrast, subcutaneous adipose tissue (SAT) was 11% (P = 0.017) and 7% (P = 0.049) higher, respectively, than among individuals without these genotypes. These associations were independent of age, body size, and muscle area. Finally, no individuals with type 2 diabetes were found among those who were homozygous for the minor allele of either at G531L and I66V whereas 14–18% of men with the major alleles had type 2 diabetes (P = 0.03 and 0.007, respectively). Our results suggest a novel association between common nonsynonymous coding variants in CPT1B and ectopic skeletal muscle fat among middle-aged and older African ancestry men. PMID:19553926

  11. Myostatin and the skeletal muscle atrophy and hypertrophy signaling pathways.

    PubMed

    Rodriguez, J; Vernus, B; Chelh, I; Cassar-Malek, I; Gabillard, J C; Hadj Sassi, A; Seiliez, I; Picard, B; Bonnieu, A

    2014-11-01

    Myostatin, a member of the transforming growth factor-β superfamily, is a potent negative regulator of skeletal muscle growth and is conserved in many species, from rodents to humans. Myostatin inactivation can induce skeletal muscle hypertrophy, while its overexpression or systemic administration causes muscle atrophy. As it represents a potential target for stimulating muscle growth and/or preventing muscle wasting, myostatin regulation and functions in the control of muscle mass have been extensively studied. A wealth of data strongly suggests that alterations in skeletal muscle mass are associated with dysregulation in myostatin expression. Moreover, myostatin plays a central role in integrating/mediating anabolic and catabolic responses. Myostatin negatively regulates the activity of the Akt pathway, which promotes protein synthesis, and increases the activity of the ubiquitin-proteasome system to induce atrophy. Several new studies have brought new information on how myostatin may affect both ribosomal biogenesis and translation efficiency of specific mRNA subclasses. In addition, although myostatin has been identified as a modulator of the major catabolic pathways, including the ubiquitin-proteasome and the autophagy-lysosome systems, the underlying mechanisms are only partially understood. The goal of this review is to highlight outstanding questions about myostatin-mediated regulation of the anabolic and catabolic signaling pathways in skeletal muscle. Particular emphasis has been placed on (1) the cross-regulation between myostatin, the growth-promoting pathways and the proteolytic systems; (2) how myostatin inhibition leads to muscle hypertrophy; and (3) the regulation of translation by myostatin.

  12. A Novel YY1-miR-1 Regulatory Circuit in Skeletal Myogenesis Revealed by Genome-Wide Prediction of YY1-miRNA Network

    PubMed Central

    Lu, Leina; Zhou, Liang; Chen, Eric Z.; Sun, Kun; Jiang, Peiyong; Wang, Lijun; Su, Xiaoxi; Sun, Hao; Wang, Huating

    2012-01-01

    microRNAs (miRNAs) are non-coding RNAs that regulate gene expression post-transcriptionally, and mounting evidence supports the prevalence and functional significance of their interplay with transcription factors (TFs). Here we describe the identification of a regulatory circuit between muscle miRNAs (miR-1, miR-133 and miR-206) and Yin Yang 1 (YY1), an epigenetic repressor of skeletal myogenesis in mouse. Genome-wide identification of potential down-stream targets of YY1 by combining computational prediction with expression profiling data reveals a large number of putative miRNA targets of YY1 during skeletal myoblasts differentiation into myotubes with muscle miRs ranking on top of the list. The subsequent experimental results demonstrate that YY1 indeed represses muscle miRs expression in myoblasts and the repression is mediated through multiple enhancers and recruitment of Polycomb complex to several YY1 binding sites. YY1 regulating miR-1 is functionally important for both C2C12 myogenic differentiation and injury-induced muscle regeneration. Furthermore, we demonstrate that miR-1 in turn targets YY1, thus forming a negative feedback loop. Together, these results identify a novel regulatory circuit required for skeletal myogenesis and reinforce the idea that regulatory circuitries involving miRNAs and TFs are prevalent mechanisms. PMID:22319554

  13. The impact of skeletal unloading on bone formation

    NASA Technical Reports Server (NTRS)

    Bikle, Daniel D.; Sakata, Takeshi; Halloran, Bernard P.

    2003-01-01

    Skeletal unloading leads to decreased bone formation and decreased bone mass. Bone resorption is uncoupled from bone formation, contributing to the bone loss. During space flight bone is lost principally from the bones most loaded in the 1 g environment. Determining the mechanism(s) by which loading of bone is sensed and translated into a signal(s) controlling bone formation remains the holy grail in this field. It seems likely that matrix/cell interactions will underlie much of the mechanocoupling. Integrins are a prime mediator of such interactions. The role for systemic hormones such as PTH, GH and 1,25(OH)2D compared to locally produced factors such as IGF-I, PTHrP, BMPs and TGF beta in modulating the cellular response to load remains unclear. Our studies demonstrate that skeletal unloading leads to resistance to the anabolic actions of IGF-I on bone as a result of failure of IGF-I to activate its own signaling pathways. This is associated with a reduction in integrin expression, suggesting crosstalk between these two pathways. As the mechanism(s) by which bone responds to changes in mechanical load with changes in bone formation is further elucidated, applications of this knowledge to other etiologies of osteoporosis are likely to develop. Skeletal unloading provides a perturbation in bone mineral homeostasis that can be used to understand the mechanisms by which bone mineral homeostasis is maintained, and that such understanding will lead to effective treatment for disuse osteoporosis in addition to preventive measures for the bone loss that accompanies space travel.

  14. mTORC1 Plays an Important Role in Skeletal Development by Controlling Preosteoblast Differentiation

    PubMed Central

    Matthews, Mary P.; Martin, Sally K.; Xie, Jianling; Ooi, Soo Siang; Walkley, Carl R.; Codrington, John D.; Ruegg, Markus A.; Hall, Michael N.; Proud, Christopher G.; Gronthos, Stan; Zannettino, Andrew C. W.

    2017-01-01

    ABSTRACT The mammalian target of rapamycin complex 1 (mTORC1) is activated by extracellular factors that control bone accrual. However, the direct role of this complex in osteoblast biology remains to be determined. To investigate this question, we disrupted mTORC1 function in preosteoblasts by targeted deletion of Raptor (Rptor) in Osterix-expressing cells. Deletion of Rptor resulted in reduced limb length that was associated with smaller epiphyseal growth plates in the postnatal skeleton. Rptor deletion caused a marked reduction in pre- and postnatal bone accrual, which was evident in skeletal elements derived from both intramembranous and endochondrial ossification. The decrease in bone accrual, as well as the associated increase in skeletal fragility, was due to a reduction in osteoblast function. In vitro, osteoblasts derived from knockout mice display a reduced osteogenic potential, and an assessment of bone-developmental markers in Rptor knockout osteoblasts revealed a transcriptional profile consistent with an immature osteoblast phenotype suggesting that osteoblast differentiation was stalled early in osteogenesis. Metabolic labeling and an assessment of cell size of Rptor knockout osteoblasts revealed a significant decrease in protein synthesis, a major driver of cell growth. These findings demonstrate that mTORC1 plays an important role in skeletal development by regulating mRNA translation during preosteoblast differentiation. PMID:28069737

  15. Contrasting roles for MyoD in organizing myogenic promoter structures during embryonic skeletal muscle development.

    PubMed

    Cho, Ok Hyun; Mallappa, Chandrashekara; Hernández-Hernández, J Manuel; Rivera-Pérez, Jaime A; Imbalzano, Anthony N

    2015-01-01

    Among the complexities of skeletal muscle differentiation is a temporal distinction in the onset of expression of different lineage-specific genes. The lineage-determining factor MyoD is bound to myogenic genes at the onset of differentiation whether gene activation is immediate or delayed. How temporal regulation of differentiation-specific genes is established remains unclear. Using embryonic tissue, we addressed the molecular differences in the organization of the myogenin and muscle creatine kinase (MCK) gene promoters by examining regulatory factor binding as a function of both time and spatial organization during somitogenesis. At the myogenin promoter, binding of the homeodomain factor Pbx1 coincided with H3 hyperacetylation and was followed by binding of co-activators that modulate chromatin structure. MyoD and myogenin binding occurred subsequently, demonstrating that Pbx1 facilitates chromatin remodeling and modification before myogenic regulatory factor binding. At the same time, the MCK promoter was bound by HDAC2 and MyoD, and activating histone marks were largely absent. The association of HDAC2 and MyoD was confirmed by co-immunoprecipitation, proximity ligation assay (PLA), and sequential ChIP. MyoD differentially promotes activated and repressed chromatin structures at myogenic genes early after the onset of skeletal muscle differentiation in the developing mouse embryo. © 2014 Wiley Periodicals, Inc.

  16. Functional conservation between rodents and chicken of regulatory sequences driving skeletal muscle gene expression in transgenic chickens

    PubMed Central

    2010-01-01

    Background Regulatory elements that control expression of specific genes during development have been shown in many cases to contain functionally-conserved modules that can be transferred between species and direct gene expression in a comparable developmental pattern. An example of such a module has been identified at the rat myosin light chain (MLC) 1/3 locus, which has been well characterised in transgenic mouse studies. This locus contains two promoters encoding two alternatively spliced isoforms of alkali myosin light chain. These promoters are differentially regulated during development through the activity of two enhancer elements. The MLC3 promoter alone has been shown to confer expression of a reporter gene in skeletal and cardiac muscle in transgenic mice and the addition of the downstream MLC enhancer increased expression levels in skeletal muscle. We asked whether this regulatory module, sufficient for striated muscle gene expression in the mouse, would drive expression in similar domains in the chicken. Results We have observed that a conserved downstream MLC enhancer is present in the chicken MLC locus. We found that the rat MLC1/3 regulatory elements were transcriptionally active in chick skeletal muscle primary cultures. We observed that a single copy lentiviral insert containing this regulatory cassette was able to drive expression of a lacZ reporter gene in the fast-fibres of skeletal muscle in chicken in three independent transgenic chicken lines in a pattern similar to the endogenous MLC locus. Reporter gene expression in cardiac muscle tissues was not observed for any of these lines. Conclusions From these results we conclude that skeletal expression from this regulatory module is conserved in a genomic context between rodents and chickens. This transgenic module will be useful in future investigations of muscle development in avian species. PMID:20184756

  17. ATXN1L, CIC, and ETS Transcription Factors Modulate Sensitivity to MAPK Pathway Inhibition.

    PubMed

    Wang, Belinda; Krall, Elsa Beyer; Aguirre, Andrew James; Kim, Miju; Widlund, Hans Ragnar; Doshi, Mihir Bhavik; Sicinska, Ewa; Sulahian, Rita; Goodale, Amy; Cowley, Glenn Spencer; Piccioni, Federica; Doench, John Gerard; Root, David Edward; Hahn, William Chun

    2017-02-07

    Intrinsic resistance and RTK-RAS-MAPK pathway reactivation has limited the effectiveness of MEK and RAF inhibitors (MAPKi) in RAS- and RAF-mutant cancers. To identify genes that modulate sensitivity to MAPKi, we performed genome-scale CRISPR-Cas9 loss-of-function screens in two KRAS mutant pancreatic cancer cell lines treated with the MEK1/2 inhibitor trametinib. Loss of CIC, a transcriptional repressor of ETV1, ETV4, and ETV5, promoted survival in the setting of MAPKi in cancer cells derived from several lineages. ATXN1L deletion, which reduces CIC protein, or ectopic expression of ETV1, ETV4, or ETV5 also modulated sensitivity to trametinib. ATXN1L expression inversely correlates with response to MAPKi inhibition in clinical studies. These observations identify the ATXN1L-CIC-ETS transcription factor axis as a mediator of resistance to MAPKi. Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.

  18. Ventromedial hypothalamic melanocortin receptor activation: regulation of activity energy expenditure and skeletal muscle thermogenesis.

    PubMed

    Gavini, Chaitanya K; Jones, William C; Novak, Colleen M

    2016-09-15

    The ventromedial hypothalamus (VMH) and the central melanocortin system both play vital roles in regulating energy balance by modulating energy intake and utilization. Recent evidence suggests that activation of the VMH alters skeletal muscle metabolism. We show that intra-VMH melanocortin receptor activation increases energy expenditure and physical activity, switches fuel utilization to fats, and lowers work efficiency such that excess calories are dissipated by skeletal muscle as heat. We also show that intra-VMH melanocortin receptor activation increases sympathetic nervous system outflow to skeletal muscle. Intra-VMH melanocortin receptor activation also induced significant changes in the expression of mediators of energy expenditure in muscle. These results support the role of melanocortin receptors in the VMH in the modulation of skeletal muscle metabolism. The ventromedial hypothalamus (VMH) and the brain melanocortin system both play vital roles in increasing energy expenditure (EE) and physical activity, decreasing appetite and modulating sympathetic nervous system (SNS) outflow. Because of recent evidence showing that VMH activation modulates skeletal muscle metabolism, we propose the existence of an axis between the VMH and skeletal muscle, modulated by brain melanocortins, modelled on the brain control of brown adipose tissue. Activation of melanocortin receptors in the VMH of rats using a non-specific agonist melanotan II (MTII), compared to vehicle, increased oxygen consumption and EE and decreased the respiratory exchange ratio. Intra-VMH MTII enhanced activity-related EE even when activity levels were held constant. MTII treatment increased gastrocnemius muscle heat dissipation during controlled activity, as well as in the home cage. Compared to vehicle-treated rats, rats with intra-VMH melanocortin receptor activation had higher skeletal muscle norepinephrine turnover, indicating an increased SNS drive to muscle. Lastly, intra-VMH MTII induced m

  19. Macrophage Depletion Impairs Skeletal Muscle Regeneration: the Roles of Pro-fibrotic Factors, Inflammation, and Oxidative Stress.

    PubMed

    Xiao, Weihua; Liu, Yu; Chen, Peijie

    2016-12-01

    Muscle contusion is one of the most common muscle injuries in sports medicine. Macrophages play complex roles in the regeneration of skeletal muscle. However, the roles of macrophages, especially the mechanisms involved, in the regeneration of muscle contusion are still not fully understood. We hypothesize that the depletion of macrophages impairs skeletal muscle regeneration and that pro-fibrotic factors, inflammation, and oxidative stress may be involved in the process. To test these hypotheses, we constructed a muscle contusion injury and a macrophage depletion model and followed it up with morphological and gene expression analyses. The data showed that fibrotic scars were formed in the muscle of contusion injury, and they deteriorated in the mice of macrophage depletion. Furthermore, the sizes of regenerating myofibers were significantly reduced by macrophage depletion. Pro-fibrotic factors, inflammatory cytokines, chemokines, and oxidative stress-related enzymes increased significantly after muscle injury. Moreover, the expression of these factors was delayed by macrophage depletion. Most of them were still significantly higher in the later stage of regeneration. These results suggest that macrophage depletion impairs skeletal muscle regeneration and that pro-fibrotic factors, inflammation, and oxidative stress may play important roles in the process.

  20. Effect of acute and chronic eccentric exercise on FOXO1 mRNA expression as fiber type transition factor in rat skeletal muscles.

    PubMed

    Azad, Milad; Khaledi, Neda; Hedayati, Mehdi

    2016-06-15

    Skeletal muscle is a highly elastic tissue which can respond to various functional demands by altering fiber-type composition. Exercise affects muscle fiber phenotype. One of the transcription factors that induce fiber-type transition is forkhead box O1 (FOXO1). Since eccentric contraction considered an essential part of exercise, so we are interested to see the effects of eccentric exercise (acute/chronic) on FOXO1 as an important factor of fiber-type transition in rat skeletal muscles. Twenty-four Sprague-Dawley rats (190-235g) were divided to 3 groups of 8 rats: 1) chronic eccentric exercise (CEE), 2) acute eccentric exercise (AEE), and 3) control (C). The exercise groups underwent downhill running protocol. CEE was running on treadmill in 3 days of week for 9 weeks, that slope and duration gradually managed from -4° to -16° and 15 to 90 min, respectively. AEE group was running with 16 m/min on -16° slope for 3 consecutive days that included 18 sets of 5 min with rest interval of 2 min in between. Soleus and super vastus lateralis (SVL) muscles mRNA were analyzed by real-time RT-PCR. SVL FOXO1 mRNA levels increased by 3.92-fold in the AEE and decreased 0.56-fold in the CEE group and were not significant in soleus muscle. In soleus muscle, myosin heavy chain (MHC) IIa, IIx, and IIb decreased in the AEE group and MHC IIa and IIx decreased in the CEE group. In SVL muscle, MHC I, IIa, and IIx increased in the AEE group and MHC IIa and IIX increased in the CEE group. In summary, both acute and chronic eccentric exercise could lead to change in FOXO1 mRNA only in fast SVL muscle of rat and so could induce fiber-type transition in both muscles regardless of changes in expression of FOXO1. So, oxidative stress can play important role in change of FOXO1. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. IGF-1 prevents ANG II-induced skeletal muscle atrophy via Akt- and Foxo-dependent inhibition of the ubiquitin ligase atrogin-1 expression

    PubMed Central

    Yoshida, Tadashi; Semprun-Prieto, Laura; Sukhanov, Sergiy

    2010-01-01

    Congestive heart failure is associated with activation of the renin-angiotensin system and skeletal muscle wasting. Angiotensin II (ANG II) has been shown to increase muscle proteolysis and decrease circulating and skeletal muscle IGF-1. We have shown previously that skeletal muscle-specific overexpression of IGF-1 prevents proteolysis and apoptosis induced by ANG II. These findings indicated that downregulation of IGF-1 signaling in skeletal muscle played an important role in the wasting effect of ANG II. However, the signaling pathways and mechanisms whereby IGF-1 prevents ANG II-induced skeletal muscle atrophy are unknown. Here we show ANG II-induced transcriptional regulation of two ubiquitin ligases atrogin-1 and muscle ring finger-1 (MuRF-1) that precedes the reduction of skeletal muscle IGF-1 expression, suggesting that activation of atrogin-1 and MuRF-1 is an initial mechanism leading to skeletal muscle atrophy in response to ANG II. IGF-1 overexpression in skeletal muscle prevented ANG II-induced skeletal muscle wasting and the expression of atrogin-1, but not MuRF-1. Dominant-negative Akt and constitutively active Foxo-1 blocked the ability of IGF-1 to prevent ANG II-mediated upregulation of atrogin-1 and skeletal muscle wasting. Our findings demonstrate that the ability of IGF-1 to prevent ANG II-induced skeletal muscle wasting is mediated via an Akt- and Foxo-1-dependent signaling pathway that results in inhibition of atrogin-1 but not MuRF-1 expression. These data suggest strongly that atrogin-1 plays a critical role in mechanisms of ANG II-induced wasting in vivo. PMID:20228261

  2. Phthalimide neovascular factor 1 (PNF1) modulates MT1-MMP activity in human microvascular endothelial cells

    PubMed Central

    Wieghaus, Kristen A.; Gianchandani, Erwin P.; Neal, Rebekah A.; Paige, Mikell A.; Brown, Milton L.; Papin, Jason A.; Botchwey, Edward A.

    2009-01-01

    We are creating synthetic pharmaceuticals with angiogenic activity and potential to promote vascular invasion. We previously demonstrated that one of these molecules, phthalimide neovascular factor 1 (PNF1), significantly expands microvascular networks in vivo following sustained release from poly(lactic-co-glycolic acid) (PLAGA) films. In addition, to probe PNF1 mode-of-action, we recently applied a novel pathway-based compendium analysis to a multi-timepoint, controlled microarray dataset of PNF1-treated (versus control) human microvascular endothelial cells (HMVECs), and we identified induction of tumor necrosis factor-alpha (TNF-α) and, subsequently, transforming growth factor-beta (TGF-β) signaling networks by PNF1. Here we validate this microarray data-set with quantitative real-time polymerase chain reaction (RT-PCR) analysis. Subsequently, we probe this dataset and identify three specific TGF-β-induced genes with regulation by PNF1 conserved over multiple timepoints—amyloid beta (A4) precursor protein (APP), early growth response 1 (EGR-1), and matrix metalloproteinase 14 (MMP14 or MT1-MMP)—that are also implicated in angiogenesis. We further focus on MMP14 given its unique role in angiogenesis, and we validate MT1-MMP modulation by PNF1 with an in vitro fluorescence assay that demonstrates the direct effects that PNF1 exerts on functional metalloproteinase activity. We also utilize endothelial cord formation in collagen gels to show that PNF1-induced stimulation of endothelial cord network formation in vitro is in some way MT1-MMP-dependent. Ultimately, this new network analysis of our transcriptional footprint characterizing PNF1 activity 1–48 h post-supplementation in HMVECs coupled with corresponding validating experiments suggests a key set of a few specific targets that are involved in PNF1 mode-of-action and important for successful promotion of the neovascularization that we have observed by the drug in vivo. PMID:19326468

  3. Phthalimide neovascular factor 1 (PNF1) modulates MT1-MMP activity in human microvascular endothelial cells.

    PubMed

    Wieghaus, Kristen A; Gianchandani, Erwin P; Neal, Rebekah A; Paige, Mikell A; Brown, Milton L; Papin, Jason A; Botchwey, Edward A

    2009-07-01

    We are creating synthetic pharmaceuticals with angiogenic activity and potential to promote vascular invasion. We previously demonstrated that one of these molecules, phthalimide neovascular factor 1 (PNF1), significantly expands microvascular networks in vivo following sustained release from poly(lactic-co-glycolic acid) (PLAGA) films. In addition, to probe PNF1 mode of action, we recently applied a novel pathway-based compendium analysis to a multi-timepoint, controlled microarray data set of PNF1-treated (vs. control) human microvascular endothelial cells (HMVECs), and we identified induction of tumor necrosis factor-alpha (TNF-alpha) and, subsequently, transforming growth factor-beta (TGF-beta) signaling networks by PNF1. Here we validate this microarray data set with quantitative real-time polymerase chain reaction (RT-PCR) analysis. Subsequently, we probe this data set and identify three specific TGF-beta-induced genes with regulation by PNF1 conserved over multiple timepoints-amyloid beta (A4) precursor protein (APP), early growth response 1 (EGR-1), and matrix metalloproteinase 14 (MMP14 or MT1-MMP)-that are also implicated in angiogenesis. We further focus on MMP14 given its unique role in angiogenesis, and we validate MT1-MMP modulation by PNF1 with an in vitro fluorescence assay that demonstrates the direct effects that PNF1 exerts on functional metalloproteinase activity. We also utilize endothelial cord formation in collagen gels to show that PNF1-induced stimulation of endothelial cord network formation in vitro is in some way MT1-MMP-dependent. Ultimately, this new network analysis of our transcriptional footprint characterizing PNF1 activity 1-48 h post-supplementation in HMVECs coupled with corresponding validating experiments suggests a key set of a few specific targets that are involved in PNF1 mode of action and important for successful promotion of the neovascularization that we have observed by the drug in vivo.

  4. Regenerating skeletal muscle in the face of aging and disease.

    PubMed

    Jasuja, Ravi; LeBrasseur, Nathan K

    2014-11-01

    Skeletal muscle is a fundamental organ in the generation of force and movement, the regulation of whole-body metabolism, and the provision of resiliency. Indeed, physical medicine and rehabilitation is recognized for optimizing skeletal muscle health in the context of aging (sarcopenia) and disease (cachexia). Exercise is, and will remain, the cornerstone of therapies to improve skeletal muscle health. However, there are now a number of promising biologic and small molecule interventions currently under development to rejuvenate skeletal muscle, including myostatin inhibitors, selective androgen receptor modulators, and an activator of the fast skeletal muscle troponin complex. The opportunities for skeletal muscle-based regenerative therapies and a selection of emerging pharmacologic interventions are discussed in this review.

  5. Exercise increases TBC1D1 phosphorylation in human skeletal muscle

    PubMed Central

    Jessen, Niels; An, Ding; Lihn, Aina S.; Nygren, Jonas; Hirshman, Michael F.; Thorell, Anders

    2011-01-01

    Exercise and weight loss are cornerstones in the treatment and prevention of type 2 diabetes, and both interventions function to increase insulin sensitivity and glucose uptake into skeletal muscle. Studies in rodents demonstrate that the underlying mechanism for glucose uptake in muscle involves site-specific phosphorylation of the Rab-GTPase-activating proteins AS160 (TBC1D4) and TBC1D1. Multiple kinases, including Akt and AMPK, phosphorylate TBC1D1 and AS160 on distinct residues, regulating their activity and allowing for GLUT4 translocation. In contrast to extensive rodent-based studies, the regulation of AS160 and TBC1D1 in human skeletal muscle is not well understood. In this study, we determined the effects of dietary intervention and a single bout of exercise on TBC1D1 and AS160 site-specific phosphorylation in human skeletal muscle. Ten obese (BMI 33.4 ± 2.4, M-value 4.3 ± 0.5) subjects were studied at baseline and after a 2-wk dietary intervention. Muscle biopsies were obtained from the subjects in the resting (basal) state and immediately following a 30-min exercise bout (70% V̇o2 max). Muscle lysates were analyzed for AMPK activity and Akt phosphorylation and for TBC1D1 and AS160 phosphorylation on known or putative AMPK and Akt sites as follows: AS160 Ser711 (AMPK), TBC1D1 Ser231 (AMPK), TBC1D1 Ser660 (AMPK), TBC1D1 Ser700 (AMPK), and TBC1D1 Thr590 (Akt). The diet intervention that consisted of a major shift in the macronutrient composition resulted in a 4.2 ± 0.4 kg weight loss (P < 0.001) and a significant increase in insulin sensitivity (M value 5.6 ± 0.6), but surprisingly, there was no effect on expression or phosphorylation of any of the muscle-signaling proteins. Exercise increased muscle AMPKα2 activity but did not increase Akt phosphorylation. Exercise increased phosphorylation on AS160 Ser711, TBC1D1 Ser231, and TBC1D1 Ser660 but had no effect on TBC1D1 Ser700. Exercise did not increase TBC1D1 Thr590 phosphorylation or TBC1D1/AS160 PAS

  6. Skeletal muscle performance and ageing

    PubMed Central

    Trouwborst, Inez; Clark, Brian C.

    2017-01-01

    Abstract The world population is ageing rapidly. As society ages, the incidence of physical limitations is dramatically increasing, which reduces the quality of life and increases healthcare expenditures. In western society, ~30% of the population over 55 years is confronted with moderate or severe physical limitations. These physical limitations increase the risk of falls, institutionalization, co‐morbidity, and premature death. An important cause of physical limitations is the age‐related loss of skeletal muscle mass, also referred to as sarcopenia. Emerging evidence, however, clearly shows that the decline in skeletal muscle mass is not the sole contributor to the decline in physical performance. For instance, the loss of muscle strength is also a strong contributor to reduced physical performance in the elderly. In addition, there is ample data to suggest that motor coordination, excitation–contraction coupling, skeletal integrity, and other factors related to the nervous, muscular, and skeletal systems are critically important for physical performance in the elderly. To better understand the loss of skeletal muscle performance with ageing, we aim to provide a broad overview on the underlying mechanisms associated with elderly skeletal muscle performance. We start with a system level discussion and continue with a discussion on the influence of lifestyle, biological, and psychosocial factors on elderly skeletal muscle performance. Developing a broad understanding of the many factors affecting elderly skeletal muscle performance has major implications for scientists, clinicians, and health professionals who are developing therapeutic interventions aiming to enhance muscle function and/or prevent mobility and physical limitations and, as such, support healthy ageing. PMID:29151281

  7. MicroRNA-761 regulates mitochondrial biogenesis in mouse skeletal muscle in response to exercise

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Xu, Yanli; Zhao, Chaoxian; Sun, Xuewen

    MicroRNAs (miRNAs) have been suggested to play critical roles in skeletal muscle in response to exercise. Previous study has shown that miR-761 was involved in a novel model regulating the mitochondrial network. However, its role in mitochondrial biogenesis remains poorly understood. Therefore, the current study was aimed to examine the effect of miR-761 on mitochondrial biogenesis in skeletal muscle. Real-time quantitative PCR analysis demonstrated that aberrantly expressed miR-761 is involved in exercise activity and miR-761 is decreased by exercise training compared with the sedentary control mice. miR-761 suppresses mitochondrial biogenesis of C{sub 2}C{sub 12} myocytes by targeting the 3′-UTR ofmore » peroxisome proliferator-activated receptor gamma (PPARγ) coactivator-1 (PGC-1α). Overexpression of miR-761 was capable of inhibiting the protein expression levels of PGC-1α. Moreover, miR-761 overexpression suppressed the p38 MAPK signaling pathway and down-regulated the expression of phosphorylated MAPK-activated protein kinase-2 (P-MK2), a downstream kinase of p38 MAPK. The phosphorylation of activating transcription factors 2 (ATF2) that plays a functional role in linking the activation of the p38 MAPK pathway to enhanced transcription of the PGC-1α was also inhibited by the overexpression of miR-761. These findings revealed a novel regulation mechanism for miR-761 in skeletal myocytes, and contributed to a better understanding of the modulation of skeletal muscle in response to exercise. - Highlights: • Endurance exercise decreases miR-761 expression in skeletal muscle. • MiR-761 suppresses mitochondrial biogenesis in C{sub 2}C{sub 12} myocytes. • MiR-761 directly targeted PGC-1α expression. • MiR-761 suppresses p38 MAPK signaling pathways in C{sub 2}C{sub 12} myocytes. • A novel mechanism for miR-761 in skeletal myocytes is demonstrated.« less

  8. Nanosecond electric pulses modulate skeletal muscle calcium dynamics and contraction

    NASA Astrophysics Data System (ADS)

    Valdez, Chris; Jirjis, Michael B.; Roth, Caleb C.; Barnes, Ronald A.; Ibey, Bennett L.

    2017-02-01

    Irreversible electroporation therapy is utilized to remove cancerous tissues thru the delivery of rapid (250Hz) and high voltage (V) (1,500V/cm) electric pulses across microsecond durations. Clinical research demonstrated that bipolar (BP) high voltage microsecond pulses opposed to monophasic waveforms relieve muscle contraction during electroporation treatment. Our group along with others discovered that nanosecond electric pulses (nsEP) can activate second messenger cascades, induce cytoskeletal rearrangement, and depending on the nsEP duration and frequency, initiate apoptotic pathways. Of high interest across in vivo and in vitro applications, is how nsEP affects muscle physiology, and if nuances exist in comparison to longer duration electroporation applications. To this end, we exposed mature skeletal muscle cells to monopolar (MP) and BP nsEP stimulation across a wide range of electric field amplitudes (1-20 kV/cm). From live confocal microscopy, we simultaneously monitored intracellular calcium dynamics along with nsEP-induced muscle movement on a single cell level. In addition, we also evaluated membrane permeability with Yo-PRO-1 and Propidium Iodide (PI) across various nsEP parameters. The results from our findings suggest that skeletal muscle calcium dynamics, and nsEP-induced contraction exhibit exclusive responses to both MP and BP nsEP exposure. Overall the results suggest in vivo nsEP application may elicit unique physiology and field applications compared to longer pulse duration electroporation.

  9. Opposite effects of statins on mitochondria of cardiac and skeletal muscles: a ‘mitohormesis’ mechanism involving reactive oxygen species and PGC-1

    PubMed Central

    Bouitbir, Jamal; Charles, Anne-Laure; Echaniz-Laguna, Andoni; Kindo, Michel; Daussin, Frédéric; Auwerx, Johan; Piquard, François; Geny, Bernard; Zoll, Joffrey

    2012-01-01

    Aims Statins protect against cardiovascular-related mortality but induce skeletal muscle toxicity. To investigate mechanisms of statins, we tested the hypothesis that statins optimized cardiac mitochondrial function but impaired vulnerable skeletal muscle by inducing different level of reactive oxygen species (ROS). Methods and results In atrium of patients treated with statins, ROS production was decreased and oxidative capacities were enhanced together with an extensive augmentation of mRNAs expression of peroxisome proliferator-activated receptor gamma co-activator (PGC-1) family. However, in deltoid biopsies from patients with statin-induced muscular myopathy, oxidative capacities were decreased together with ROS increase and a collapse of PGC-1 mRNA expression. Several animal and cell culture experiments were conducted and showed by using ROS scavengers that ROS production was the triggering factor responsible of atorvastatin-induced activation of mitochondrial biogenesis pathway and improvement of antioxidant capacities in heart. Conversely, in skeletal muscle, the large augmentation of ROS production following treatment induced mitochondrial impairments, and reduced mitochondrial biogenesis mechanisms. Quercetin, an antioxidant molecule, was able to counteract skeletal muscle deleterious effects of atorvastatin in rat. Conclusion Our findings identify statins as a new activating factor of cardiac mitochondrial biogenesis and antioxidant capacities, and suggest the importance of ROS/PGC-1 signalling pathway as a key element in regulation of mitochondrial function in cardiac as well as skeletal muscles. PMID:21775390

  10. pH Modulates the Binding of EGR1 Transcription Factor to DNA

    PubMed Central

    Mikles, David C.; Bhat, Vikas; Schuchardt, Brett J.; Deegan, Brian J.; Seldeen, Kenneth L.; McDonald, Caleb B.; Farooq, Amjad

    2013-01-01

    EGR1 transcription factor orchestrates a plethora of signaling cascades involved in cellular homeostasis and its down-regulation has been implicated in the development of prostate cancer. Herein, using a battery of biophysical tools, we show that the binding of EGR1 to DNA is tightly regulated by solution pH. Importantly, the binding affinity undergoes an enhancement of more than an order of magnitude with increasing pH from 5 to 8, implying that the deprotonation of an ionizable residue accounts for such behavior. This ionizable residue is identified as H382 by virtue of the fact that its substitution to non-ionizable residues abolishes pH-dependence of the binding of EGR1 to DNA. Notably, H382 inserts into the major groove of DNA and stabilizes the EGR1-DNA interaction via both hydrogen bonding and van der Waals contacts. Remarkably, H382 is predominantly conserved across other members of EGR1 family, implying that histidine protonation-deprotonation may serve as a molecular switch for modulating protein-DNA interactions central to this family of transcription factors. Collectively, our findings uncover an unexpected but a key step in the molecular recognition of EGR1 family of transcription factors and suggest that they may act as sensors of pH within the intracellular environment. PMID:23718776

  11. Quercetin Reduces Tumor Necrosis Factor Alpha-Induced Muscle Atrophy by Upregulation of Heme Oxygenase-1.

    PubMed

    Kim, Yeji; Kim, Chu-Sook; Joe, Yeonsoo; Chung, Hun Taeg; Ha, Tae Youl; Yu, Rina

    2018-06-01

    The inflammatory cytokine tumor necrosis factor α (TNFα), upregulated in the obese condition, promotes protein degradation and is implicated in obesity-related skeletal muscle atrophy and age-related sarcopenia. Quercetin, a flavonoid, elicits antioxidative and anti-inflammatory activities. In this study, we investigated the effect of quercetin on TNFα-induced skeletal muscle atrophy as well as its potential mechanism of action. In this study, we observed that quercetin suppressed expression of TNFα-induced atrophic factors such as MAFbx/atrogin-1 and MuRF1 in myotubes, and it enhanced heme oxygenase-1 (HO-1) protein level accompanied by increased nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2) in myotubes. The HO-1 inhibitor ZnPP suppressed the inhibitory actions of quercetin on TNFα-induced atrophic responses and degradation of IκB-α in myotubes. Moreover, quercetin supplementation to high-fat diet-fed obese mice inhibited obesity-induced atrophic responses in skeletal muscle, accompanied by upregulation of HO-1 and inactivation of nuclear factor-kappa B (NF-κB), and the quercetin actions were attenuated in Nrf2-deficient mice. These findings suggest that quercetin protects against TNFα-induced muscle atrophy under obese conditions through Nrf2-mediated HO-1 induction accompanied by inactivation of NF-κB. Quercetin may be used as a dietary supplement to protect against obesity-induced skeletal muscle atrophy.

  12. Eukaryotic initiation factor 2B epsilon induces cap-dependent translation and skeletal muscle hypertrophy

    PubMed Central

    Mayhew, David L; Hornberger, Troy A; Lincoln, Hannah C; Bamman, Marcas M

    2011-01-01

    Abstract The purpose of this study was to identify signalling components known to control mRNA translation initiation in skeletal muscle that are responsive to mechanical load and may be partly responsible for myofibre hypertrophy. To accomplish this, we first utilized a human cluster model in which skeletal muscle samples from subjects with widely divergent hypertrophic responses to resistance training were used for the identification of signalling proteins associated with the degree myofibre hypertrophy. We found that of 11 translational signalling molecules examined, the response of p(T421/S424)-p70S6K phosphorylation and total eukaryotic initiation factor 2Bɛ (eIF2Bɛ) protein abundance after a single bout of unaccustomed resistance exercise was associated with myofibre hypertrophy following 16 weeks of training. Follow up studies revealed that overexpression of eIF2Bɛ alone was sufficient to induce an 87% increase in cap-dependent translation in L6 myoblasts in vitro and 21% hypertrophy of myofibres in mouse skeletal muscle in vivo (P < 0.05). However, genetically altering p70S6K activity had no impact on eIF2Bɛ protein abundance in mouse skeletal muscle in vivo or multiple cell lines in vitro (P > 0.05), suggesting that the two phenomena were not directly related. These are the first data that mechanistically link eIF2Bɛ abundance to skeletal myofibre hypertrophy, and indicate that eIF2Bɛ abundance may at least partially underlie the widely divergent hypertrophic phenotypes in human skeletal muscle exposed to mechanical stimuli. PMID:21486778

  13. Harnessing Sphingosine-1-Phosphate Signaling and Nanotopographical Cues To Regulate Skeletal Muscle Maturation and Vascularization.

    PubMed

    Tsui, Jonathan H; Janebodin, Kajohnkiart; Ieronimakis, Nicholas; Yama, David M P; Yang, Hee Seok; Chavanachat, Rakchanok; Hays, Aislinn L; Lee, Haeshin; Reyes, Morayma; Kim, Deok-Ho

    2017-12-26

    Despite possessing substantial regenerative capacity, skeletal muscle can suffer from loss of function due to catastrophic traumatic injury or degenerative disease. In such cases, engineered tissue grafts hold the potential to restore function and improve patient quality of life. Requirements for successful integration of engineered tissue grafts with the host musculature include cell alignment that mimics host tissue architecture and directional functionality, as well as vascularization to ensure tissue survival. Here, we have developed biomimetic nanopatterned poly(lactic-co-glycolic acid) substrates conjugated with sphingosine-1-phosphate (S1P), a potent angiogenic and myogenic factor, to enhance myoblast and endothelial maturation. Primary muscle cells cultured on these functionalized S1P nanopatterned substrates developed a highly aligned and elongated morphology and exhibited higher expression levels of myosin heavy chain, in addition to genes characteristic of mature skeletal muscle. We also found that S1P enhanced angiogenic potential in these cultures, as evidenced by elevated expression of endothelial-related genes. Computational analyses of live-cell videos showed a significantly improved functionality of tissues cultured on S1P-functionalized nanopatterns as indicated by greater myotube contraction displacements and velocities. In summary, our study demonstrates that biomimetic nanotopography and S1P can be combined to synergistically regulate the maturation and vascularization of engineered skeletal muscles.

  14. Factor IX expression in skeletal muscle of a severe hemophilia B patient 10 years after AAV-mediated gene transfer.

    PubMed

    Buchlis, George; Podsakoff, Gregory M; Radu, Antonetta; Hawk, Sarah M; Flake, Alan W; Mingozzi, Federico; High, Katherine A

    2012-03-29

    In previous work we transferred a human factor IX-encoding adeno-associated viral vector (AAV) into skeletal muscle of men with severe hemophilia B. Biopsy of injected muscle up to 1 year after vector injection showed evidence of gene transfer by Southern blot and of protein expression by IHC and immunofluorescent staining. Although the procedure appeared safe, circulating F.IX levels remained subtherapeutic (< 1%). Recently, we obtained muscle tissue from a subject injected 10 years earlier who died of causes unrelated to gene transfer. Using Western blot, IHC, and immunofluorescent staining, we show persistent factor IX expression in injected muscle tissue. F.IX transcripts were detected in injected skeletal muscle using RT-PCR, and isolated whole genomic DNA tested positive for the presence of the transferred AAV vector sequence. This is the longest reported transgene expression to date from a parenterally administered AAV vector, with broad implications for the future of muscle-directed gene transfer.

  15. Factor IX expression in skeletal muscle of a severe hemophilia B patient 10 years after AAV-mediated gene transfer

    PubMed Central

    Buchlis, George; Podsakoff, Gregory M.; Radu, Antonetta; Hawk, Sarah M.; Flake, Alan W.; Mingozzi, Federico

    2012-01-01

    In previous work we transferred a human factor IX–encoding adeno-associated viral vector (AAV) into skeletal muscle of men with severe hemophilia B. Biopsy of injected muscle up to 1 year after vector injection showed evidence of gene transfer by Southern blot and of protein expression by IHC and immunofluorescent staining. Although the procedure appeared safe, circulating F.IX levels remained subtherapeutic (< 1%). Recently, we obtained muscle tissue from a subject injected 10 years earlier who died of causes unrelated to gene transfer. Using Western blot, IHC, and immunofluorescent staining, we show persistent factor IX expression in injected muscle tissue. F.IX transcripts were detected in injected skeletal muscle using RT-PCR, and isolated whole genomic DNA tested positive for the presence of the transferred AAV vector sequence. This is the longest reported transgene expression to date from a parenterally administered AAV vector, with broad implications for the future of muscle-directed gene transfer. PMID:22271447

  16. Aberrant and alternative splicing in skeletal system disease.

    PubMed

    Fan, Xin; Tang, Liling

    2013-10-01

    The main function of skeletal system is to support the body and help movement. A variety of factors can lead to skeletal system disease, including age, exercise, and of course genetic makeup and expression. Pre-mRNA splicing plays a crucial role in gene expression, by creating multiple protein variants with different biological functions. The recent studies show that several skeletal system diseases are related to pre-mRNA splicing. This review focuses on the relationship between pre-mRNA splicing and skeletal system disease. On the one hand, splice site mutation that leads to aberrant splicing often causes genetic skeletal system disease, like COL1A1, SEDL and LRP5. On the other hand, alternative splicing without genomic mutation may generate some marker protein isoforms, for example, FN, VEGF and CD44. Therefore, understanding the relationship between pre-mRNA splicing and skeletal system disease will aid in uncovering the mechanism of disease and contribute to the future development of gene therapy. © 2013 Elsevier B.V. All rights reserved.

  17. Induction of Sirt1 by Mechanical Stretch of Skeletal Muscle through the Early Response Factor EGR1 Triggers an Antioxidative Response*

    PubMed Central

    Pardo, Patricia S.; Mohamed, Junaith S.; Lopez, Michael A.; Boriek, Aladin M.

    2011-01-01

    Mechanical loading of muscles by intrinsic muscle activity or passive stretch leads to an increase in the production of reactive oxygen species (1, 2). The NAD-dependent protein deacetylase SIRT1 is involved in the protection against oxidative stress by enhancing FOXO-driven Sod2 transcription (3–5). In this report, we unravel a mechanism triggered by mechanical stretch of skeletal muscle cells that leads to an EGR1-dependent transcriptional activation of the Sirt1 gene. The resulting transient increase in SIRT1 expression generates an antioxidative response that contributes to reactive oxygen species scavenging. PMID:20971845

  18. Low levels of lipopolysaccharide modulate mitochondrial oxygen consumption in skeletal muscle

    PubMed Central

    Frisard, Madlyn I.; Wu, Yaru; McMillan, Ryan P.; Voelker, Kevin A.; Wahlberg, Kristin A.; Anderson, Angela S.; Boutagy, Nabil; Resendes, Kyle; Ravussin, Eric; Hulver, Matthew W.

    2014-01-01

    Objective We have previously demonstrated that activation of toll-like receptor 4 (TLR4) in skeletal muscle results in an increased reliance on glucose as an energy source and a concomitant decrease in fatty acid oxidation under basal conditions. Herein, we examined the effects of lipopolysaccharide (LPS), the primary ligand for TLR4, on mitochondrial oxygen consumption in skeletal muscle cell culture and isolated mitochondria. Materials/ methods Skeletal muscle cell cultures were exposed to LPS and oxygen consumption was assessed using a Seahorse Bioscience extracellular flux analyzer. Mice were also exposed to LPS and oxygen consumption was assessed in mitochondria isolated from skeletal muscle. Results Acute LPS exposure resulted in significant reductions in cyanide 4-(trifluoromethoxy) phenylhydrazone (FCCP)-stimulated maximal respiration (state 3u) and increased oligomycin induced state 4 (state 4O) respiration in C2C12 and human primary myotubes. These findings were observed in conjunction with increased mRNA of uncoupling protein 3 (UCP3), superoxide dismutase 2 (SOD2), and pyruvate dehydrogenase activity. The LPS-mediated changes in substrate oxidation and maximal mitochondrial respiration were prevented in the presence of the antioxidants N-acetylcysteine and catalase, suggesting a potential role of reactive oxygen species in mediating these effects. Mitochondria isolated from red gastrocnemius and quadriceps femoris muscle from mice injected with LPS also demonstrated reduced respiratory control ratio (RCR), and ADP- and FCCP-stimulated respiration. Conclusion LPS exposure in skeletal muscle alters mitochondrial oxygen consumption and substrate preference, which is absent when antioxidants are present. PMID:25528444

  19. Growth hormone mediates pubertal skeletal development independent of hepatic IGF-1 production.

    PubMed

    Courtland, Hayden-William; Sun, Hui; Beth-On, Mordechay; Wu, Yingjie; Elis, Sebastien; Rosen, Clifford J; Yakar, Shoshana

    2011-04-01

    Deficiencies in either growth hormone (GH) or insulin-like growth factor 1 (IGF-1) are associated with reductions in bone size during growth in humans and animal models. Liver-specific IGF-1-deficient (LID) mice, which have 75% reductions in serum IGF-1, were created previously to separate the effects of endocrine (serum) IGF-1 from autocrine/paracrine IGF-1. However, LID mice also have two- to threefold increases in GH, and this may contribute to the observed pubertal skeletal phenotype. To clarify the role of GH in skeletal development under conditions of significantly reduced serum IGF-1 levels (but normal tissue IGF-1 levels), we studied the skeletal response of male LID and control mice to GH inhibition by pegvisomant from 4 to 8 weeks of age. Treatment of LID mice with pegvisomant resulted in significant reductions in body weight, femur length (Le), and femur total area (Tt.Ar), as well as further reductions in serum IGF-1 levels by 8 weeks of age, compared with the mean values of vehicle-treated LID mice. Reductions in both Tt.Ar and Le were proportional after treatment with pegvisomant. On the other hand, the relative amount of cortical tissue formed (RCA) in LID mice treated with pegvisomant was significantly less than that in both vehicle-treated LID and control mice, indicating that antagonizing GH action, either directly (through GH receptor signaling inhibition) or indirectly (through further reductions in serum/tissue IGF-1 levels), results in disproportionate reductions in the amount of cortical bone formed. This resulted in bones with significantly reduced mechanical properties (femoral whole-bone stiffness and work to failure were markedly decreased), suggesting that compensatory increases of GH in states of IGF-1 deficiency (LID mice) act to protect against a severe inhibition of bone modeling during growth, which otherwise would result in bones that are too weak for normal and/or extreme loading conditions. Copyright © 2011 American Society for

  20. Insulin-like growth factor-I extends in vitro replicative life span of skeletal muscle satellite cells by enhancing G1/S cell cycle progression via the activation of phosphatidylinositol 3'-kinase/Akt signaling pathway

    NASA Technical Reports Server (NTRS)

    Chakravarthy, M. V.; Abraha, T. W.; Schwartz, R. J.; Fiorotto, M. L.; Booth, F. W.

    2000-01-01

    Interest is growing in methods to extend replicative life span of non-immortalized stem cells. Using the insulin-like growth factor I (IGF-I) transgenic mouse in which the IGF-I transgene is expressed during skeletal muscle development and maturation prior to isolation and during culture of satellite cells (the myogenic stem cells of mature skeletal muscle fibers) as a model system, we elucidated the underlying molecular mechanisms of IGF-I-mediated enhancement of proliferative potential of these cells. Satellite cells from IGF-I transgenic muscles achieved at least five additional population doublings above the maximum that was attained by wild type satellite cells. This IGF-I-induced increase in proliferative potential was mediated via activation of the phosphatidylinositol 3'-kinase/Akt pathway, independent of mitogen-activated protein kinase activity, facilitating G(1)/S cell cycle progression via a down-regulation of p27(Kip1). Adenovirally mediated ectopic overexpression of p27(Kip1) in exponentially growing IGF-I transgenic satellite cells reversed the increase in cyclin E-cdk2 kinase activity, pRb phosphorylation, and cyclin A protein abundance, thereby implicating an important role for p27(Kip1) in promoting satellite cell senescence. These observations provide a more complete dissection of molecular events by which increased local expression of a growth factor in mature skeletal muscle fibers extends replicative life span of primary stem cells than previously known.

  1. Gravity and Skeletal Growth

    NASA Technical Reports Server (NTRS)

    Morey-Holton, Emily; Turner, Russell T.

    1999-01-01

    Two simultaneous experiments were performed using 5-week-old male Sprague Dawley rats; in one study, the rats were flown in low earth orbit; in the other study, the hindlimbs of the growing rats were elevated to prevent weight bearing. Following 9 d of unloading, weight bearing was restored for 4, 28, and 76 hrs. Afterwards, additional hindlimb unloading experiments were performed to evaluate the skeletal response to 0, 2, 4, 6, 8, 10, 12, 16, and 24 hrs of restored weight bearing following 7 d of unloading. Cancellous and cortical bone histomorphometry were evaluated in the left tibia at the proximal metaphysis and in the left femur at mid-diaphysis, respectively. Steady-state mRNA levels for bone matrix proteins and skeletal signaling peptides were determined in total cellular RNA extracted from trabeculae from the right proximal tibiametaphysis and periosteum from the right femur. Spaceflight and hindlimb unloading each resulted in cancellous osteopenia, as well as a tendency towards decreased periosteal bone formation. Both models for skeletal unloading resulted in site specific reductions in mRNA levels for transforming growth factor-beta (sub 1) (TGF-beta) osteocalcin (OC), and prepro-alpha (I) subunit of type 1 collagen (collagen) and little or no changes in mRNA levels for glyceraldehyde-3-phosphate dehydrogenase (GAP) and insulin-like growth factor I (IGF-I). Restoration of normal weight bearing resulted in transient increases in mRNA levels for the bone matrix proteins and TGF-beta in the proximal metaphysis and periosteum and no changes in either GAP or IGF-I mRNA levels. The timecourse for the response differed between the two skeletal compartments; the tibial metaphysis responded much more quickly to reloading. These results suggest that the skeletal adaptation to acute physiological changes in mechanical usage are mediated, in part, by changes in mRNA levels for bone matrix proteins and TGF-beta.

  2. Insulinlike Growth Factor-1 and Its Binding Protein-3 Polymorphisms Predict Circulating IGF-1 Level and Appendicular Skeletal Muscle Mass in Chinese Elderly.

    PubMed

    Yang, Chuan-Wei; Li, Tsai-Chung; Li, Chia-Ing; Liu, Chiu-Shong; Lin, Chih-Hsueh; Lin, Wen-Yuan; Lin, Cheng-Chieh

    2015-05-01

    Previous studies have demonstrated the polymorphisms of insulinlike growth factor-1 (IGF-1) and its binding protein-3 (IGFBP3) genes could affect the circulating IGF-1 level. Moreover, the serum IGF-1 level was correlated with muscle size. This study aimed to explore the effect of polymorphisms of IGF1, IGFBP3, and IGFBP5 genes on appendicular skeletal muscle mass in Taiwanese older adults in a metropolitan area. A community-based cross-sectional study. A random sample of 472 elders with complete information of dual energy X-ray absorptiometry examination, genotyping analysis, and serum IGF-1 level from Taichung Community Health Study for Elders (TCHS-E) was included. Low appendicular skeletal muscle mass index (ASMI) was defined as 2 SDs below the mean of young adults from our TCHS study (n = 471). Seven polymorphisms of IGF1, IGFBP3, and IGFBP5 were analyzed by using Illumina GoldenGate Genotyping Assay. The χ(2) test, Student t test, and multiple logistic regression were applied for statistical analysis. The prevalence of low ASMI was 7.1%, 8.8%, and 23.0% in those aged 70 or younger, 71 to 75, and older than 75 years, respectively. We found that serum IGF-1 level (natural logarithmic transformation) was significantly lower in the low ASMI group compared with the normal ASMI group and the SNP rs2854744 near IGFBP3 gene was significantly associated with low ASMI. Moreover, we discovered the SNP rs6214 on the IGF1 gene would significantly affect the serum IGF-1 level. Therefore, the joint effect of rs6214 and rs2854744 was analyzed. Elders with GG genotype of rs6214 and AC or CC genotypes of rs2854744 had a 3.18-fold (95% CI 1.02-9.89) risk of having low ASMI compared with those with the AA and AA genotype, after adjusting for age, gender, smoking, exercise, hyperlipidemia, and albumin level. Our results suggest that rs6214 on the IGF1 gene and rs2854744 near the IGFBP3 gene potentially play an important role with ASMI in Taiwanese older adults in a metropolitan

  3. miR-24 and miR-122 Negatively Regulate the Transforming Growth Factor-β/Smad Signaling Pathway in Skeletal Muscle Fibrosis.

    PubMed

    Sun, Yaying; Wang, Hui; Li, Yan; Liu, Shaohua; Chen, Jiwu; Ying, Hao

    2018-06-01

    Fibrosis is common after skeletal muscle injury, undermining tissue regeneration and function. The mechanism underlying skeletal muscle fibrosis remains unveiled. Transforming growth factor-β/Smad signaling pathway is supposed to play a pivotal role. However, how microRNAs interact with transforming growth factor-β/Smad-related muscle fibrosis remains unclear. We showed that microRNA (miR)-24-3p and miR-122-5p declined in skeletal muscle fibrosis, which was a consequence of transforming growth factor-β. Upregulating Smad4 suppressed two microRNAs, whereas inhibiting Smad4 elevated microRNAs. Luciferase reporter assay and chromatin immunoprecipitation confirmed that Smad4 directly inhibited two microRNAs. On the other hand, overexpression of these two miRs retarded fibrotic process. We further identified that Smad2 was a direct target of miR-24-3p, whereas miR-122-5p targeted transforming growth factor-β receptor-II. Both targets were important participants in transforming growth factor-β/Smad signaling. Taken together, a positive feedback loop in transforming growth factor-β/Smad4 signaling pathway in skeletal muscle fibrosis was identified. Transforming growth factor-β/Smad axis could be downregulated by microRNAs. This effect, however, was suppressed by Smad4, the downstream of transforming growth factor-β. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

  4. AHNAK1 and AHNAK2 are costameric proteins: AHNAK1 affects transverse skeletal muscle fiber stiffness

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Marg, Andreas, E-mail: andreas.marg@mdc-berlin.de; Haase, Hannelore; Neumann, Tanja

    2010-10-08

    Research highlights: {yields} AHNAK1 and AHNAK2 are costameric proteins. {yields} Intact membrane repair in AHNAK1-deficient mice. {yields} AHNAK1{sup -/-} single fibers have a higher transverse stiffness. -- Abstract: The AHNAK scaffold PDZ-protein family is implicated in various cellular processes including membrane repair; however, AHNAK function and subcellular localization in skeletal muscle are unclear. We used specific AHNAK1 and AHNAK2 antibodies to analyzed the detailed localization of both proteins in mouse skeletal muscle. Co-localization of AHNAK1 and AHNAK2 with vinculin clearly demonstrates that both proteins are components of the costameric network. In contrast, no AHNAK expression was detected in the T-tubulemore » system. A laser wounding assay with AHNAK1-deficient fibers suggests that AHNAK1 is not involved in membrane repair. Using atomic force microscopy (AFM), we observed a significantly higher transverse stiffness of AHNAK1{sup -/-} fibers. These findings suggest novel functions of AHNAK proteins in skeletal muscle.« less

  5. Skeletal muscle performance and ageing.

    PubMed

    Tieland, Michael; Trouwborst, Inez; Clark, Brian C

    2018-02-01

    The world population is ageing rapidly. As society ages, the incidence of physical limitations is dramatically increasing, which reduces the quality of life and increases healthcare expenditures. In western society, ~30% of the population over 55 years is confronted with moderate or severe physical limitations. These physical limitations increase the risk of falls, institutionalization, co-morbidity, and premature death. An important cause of physical limitations is the age-related loss of skeletal muscle mass, also referred to as sarcopenia. Emerging evidence, however, clearly shows that the decline in skeletal muscle mass is not the sole contributor to the decline in physical performance. For instance, the loss of muscle strength is also a strong contributor to reduced physical performance in the elderly. In addition, there is ample data to suggest that motor coordination, excitation-contraction coupling, skeletal integrity, and other factors related to the nervous, muscular, and skeletal systems are critically important for physical performance in the elderly. To better understand the loss of skeletal muscle performance with ageing, we aim to provide a broad overview on the underlying mechanisms associated with elderly skeletal muscle performance. We start with a system level discussion and continue with a discussion on the influence of lifestyle, biological, and psychosocial factors on elderly skeletal muscle performance. Developing a broad understanding of the many factors affecting elderly skeletal muscle performance has major implications for scientists, clinicians, and health professionals who are developing therapeutic interventions aiming to enhance muscle function and/or prevent mobility and physical limitations and, as such, support healthy ageing. © 2017 The Authors. Journal of Cachexia, Sarcopenia and Muscle published by John Wiley & Sons Ltd on behalf of the Society on Sarcopenia, Cachexia and Wasting Disorders.

  6. Circadian Rhythms, the Molecular Clock, and Skeletal Muscle

    PubMed Central

    Lefta, Mellani; Wolff, Gretchen; Esser, Karyn A.

    2015-01-01

    Almost all organisms ranging from single cell bacteria to humans exhibit a variety of behavioral, physiological, and biochemical rhythms. In mammals, circadian rhythms control the timing of many physiological processes over a 24-h period, including sleep-wake cycles, body temperature, feeding, and hormone production. This body of research has led to defined characteristics of circadian rhythms based on period length, phase, and amplitude. Underlying circadian behaviors is a molecular clock mechanism found in most, if not all, cell types including skeletal muscle. The mammalian molecular clock is a complex of multiple oscillating networks that are regulated through transcriptional mechanisms, timed protein turnover, and input from small molecules. At this time, very little is known about circadian aspects of skeletal muscle function/metabolism but some progress has been made on understanding the molecular clock in skeletal muscle. The goal of this chapter is to provide the basic terminology and concepts of circadian rhythms with a more detailed review of the current state of knowledge of the molecular clock, with reference to what is known in skeletal muscle. Research has demonstrated that the molecular clock is active in skeletal muscles and that the muscle-specific transcription factor, MyoD, is a direct target of the molecular clock. Skeletal muscle of clock-compromised mice, Bmal1−/− and ClockΔ19 mice, are weak and exhibit significant disruptions in expression of many genes required for adult muscle structure and metabolism. We suggest that the interaction between the molecular clock, MyoD, and metabolic factors, such as PGC-1, provide a potential system of feedback loops that may be critical for both maintenance and adaptation of skeletal muscle. PMID:21621073

  7. Uric acid and transforming growth factor in fructose-induced production of reactive oxygen species in skeletal muscle

    PubMed Central

    Maarman, Gerald J.; Ojuka, Edward

    2016-01-01

    The consumption of fructose, a major constituent of the modern diet, has raised increasing concern about the effects of fructose on health. Research suggests that excessive intake of fructose (>50 g/d) causes hyperuricemia, insulin resistance, mitochondrial dysfunction, de novo lipogenesis by the liver, and increased production of reactive oxygen species (ROS) in muscle. In a number of tissues, uric acid has been shown to stimulate the production of ROS via activation of transforming growth factor β1 and NADPH (nicotinamide adenine dinucleotide phosphate) oxidase 4. The role of uric acid in fructose-induced production of ROS in skeletal muscle, however, has not been investigated. This review examines the evidence for fructose-induced production of ROS in skeletal muscle, highlights proposed mechanisms, and identifies gaps in current knowledge. PMID:26946251

  8. Type 2 iodothyronine deiodinase in skeletal muscle: effects of hypothyroidism and fasting.

    PubMed

    Heemstra, Karen A; Soeters, Maarten R; Fliers, Eric; Serlie, Mireille J; Burggraaf, Jacobus; van Doorn, Martijn B; van der Klaauw, Agatha A; Romijn, Johannes A; Smit, Johannes W; Corssmit, Eleonora P; Visser, Theo J

    2009-06-01

    The iodothyronine deiodinases D1, D2, and D3 enable tissue-specific adaptation of thyroid hormone levels in response to various conditions, such as hypothyroidism or fasting. The possible expression of D2 mRNA in skeletal muscle is intriguing because this enzyme could play a role in systemic as well as local T3 production. We determined D2 activity and D2 mRNA expression in human skeletal muscle biopsies under control conditions and during hypothyroidism, fasting, and hyperinsulinemia. This was a prospective study. The study was conducted at a university hospital. We studied 11 thyroidectomized patients with differentiated thyroid carcinoma (DTC) on and after 4 wk off T4( replacement and six healthy lean subjects in the fasting state and during hyperinsulinemia after both 14 and 62 h of fasting. D2 activity and D2 mRNA levels were measured in skeletal muscle samples. No differences were observed in muscle D2 mRNA levels in DTC patients on and off T4 replacement therapy. In healthy subjects, muscle D2 mRNA levels were lower after 62 h compared to 14 h of fasting. Insulin increased mRNA expression after 62 h, but not after 14 h of fasting. Skeletal muscle D2 activities were very low and not influenced by hypothyroidism and fasting. Human skeletal muscle D2 mRNA expression is modulated by fasting and insulin, but not by hypothyroidism. The lack of a clear effect of D2 mRNA modulation on the observed low D2 activities questions the physiological relevance of D2 activity in human skeletal muscle.

  9. Human skeletal muscle drug transporters determine local exposure and toxicity of statins.

    PubMed

    Knauer, Michael J; Urquhart, Bradley L; Meyer zu Schwabedissen, Henriette E; Schwarz, Ute I; Lemke, Christopher J; Leake, Brenda F; Kim, Richard B; Tirona, Rommel G

    2010-02-05

    The 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors, or statins, are important drugs used in the treatment and prevention of cardiovascular disease. Although statins are well tolerated, many patients develop myopathy manifesting as muscle aches and pain. Rhabdomyolysis is a rare but severe toxicity of statins. Interindividual differences in the activities of hepatic membrane drug transporters and metabolic enzymes are known to influence statin plasma pharmacokinetics and risk for myopathy. Interestingly, little is known regarding the molecular determinants of statin distribution into skeletal muscle and its relevance to toxicity. We sought to identify statin transporters in human skeletal muscle and determine their impact on statin toxicity in vitro. We demonstrate that the uptake transporter OATP2B1 (human organic anion transporting polypeptide 2B1) and the efflux transporters, multidrug resistance-associated protein (MRP)1, MRP4, and MRP5 are expressed on the sarcolemmal membrane of human skeletal muscle fibers and that atorvastatin and rosuvastatin are substrates of these transporters when assessed using a heterologous expression system. In an in vitro model of differentiated, primary human skeletal muscle myoblast cells, we demonstrate basal membrane expression and drug efflux activity of MRP1, which contributes to reducing intracellular statin accumulation. Furthermore, we show that expression of human OATP2B1 in human skeletal muscle myoblast cells by adenoviral vectors increases intracellular accumulation and toxicity of statins and such effects were abrogated when cells overexpressed MRP1. These results identify key membrane transporters as modulators of skeletal muscle statin exposure and toxicity.

  10. Fibroblast growth factor (FGF) signaling in development and skeletal diseases.

    PubMed

    Teven, Chad M; Farina, Evan M; Rivas, Jane; Reid, Russell R

    2014-12-01

    Fibroblast growth factors (FGF) and their receptors serve many functions in both the developing and adult organism. Humans contain 18 FGF ligands and four FGF receptors (FGFR). FGF ligands are polypeptide growth factors that regulate several developmental processes including cellular proliferation, differentiation, and migration, morphogenesis, and patterning. FGF-FGFR signaling is also critical to the developing axial and craniofacial skeleton. In particular, the signaling cascade has been implicated in intramembranous ossification of cranial bones as well as cranial suture homeostasis. In the adult, FGFs and FGFRs are crucial for tissue repair. FGF signaling generally follows one of three transduction pathways: RAS/MAP kinase, PI3/AKT, or PLCγ. Each pathway likely regulates specific cellular behaviors. Inappropriate expression of FGF and improper activation of FGFRs are associated with various pathologic conditions, unregulated cell growth, and tumorigenesis. Additionally, aberrant signaling has been implicated in many skeletal abnormalities including achondroplasia and craniosynostosis. The biology and mechanisms of the FGF family have been the subject of significant research over the past 30 years. Recently, work has focused on the therapeutic targeting and potential of FGF ligands and their associated receptors. The majority of FGF-related therapy is aimed at age-related disorders. Increased understanding of FGF signaling and biology may reveal additional therapeutic roles, both in utero and postnatally. This review discusses the role of FGF signaling in general physiologic and pathologic embryogenesis and further explores it within the context of skeletal development.

  11. Fibroblast growth factor (FGF) signaling in development and skeletal diseases

    PubMed Central

    Teven, Chad M.; Farina, Evan M.; Rivas, Jane; Reid, Russell R.

    2014-01-01

    Fibroblast growth factors (FGF) and their receptors serve many functions in both the developing and adult organism. Humans contain 18 FGF ligands and four FGF receptors (FGFR). FGF ligands are polypeptide growth factors that regulate several developmental processes including cellular proliferation, differentiation, and migration, morphogenesis, and patterning. FGF-FGFR signaling is also critical to the developing axial and craniofacial skeleton. In particular, the signaling cascade has been implicated in intramembranous ossification of cranial bones as well as cranial suture homeostasis. In the adult, FGFs and FGFRs are crucial for tissue repair. FGF signaling generally follows one of three transduction pathways: RAS/MAP kinase, PI3/AKT, or PLCγ. Each pathway likely regulates specific cellular behaviors. Inappropriate expression of FGF and improper activation of FGFRs are associated with various pathologic conditions, unregulated cell growth, and tumorigenesis. Additionally, aberrant signaling has been implicated in many skeletal abnormalities including achondroplasia and craniosynostosis. The biology and mechanisms of the FGF family have been the subject of significant research over the past 30 years. Recently, work has focused on the therapeutic targeting and potential of FGF ligands and their associated receptors. The majority of FGF-related therapy is aimed at age-related disorders. Increased understanding of FGF signaling and biology may reveal additional therapeutic roles, both in utero and postnatally. This review discusses the role of FGF signaling in general physiologic and pathologic embryogenesis and further explores it within the context of skeletal development. PMID:25679016

  12. Factors related to stability following the surgical correction of skeletal open bite.

    PubMed

    Ito, Goshi; Koh, Myongsun; Fujita, Tadashi; Shirakura, Maya; Ueda, Hiroshi; Tanne, Kazuo

    2014-05-01

    If a skeletal anterior open bite malocclusion is treated by orthognathic surgery directed only at the mandible, the lower jaw is repositioned upward in a counter-clockwise rotation. However, this procedure has a high risk of relapse. In the present study, the key factors associated with post-surgical stability of corrected skeletal anterior open bite malocclusions were investigated. Eighteen orthognathic patients were subjected to cephalometric analysis to assess the dental and skeletal changes following mandibular surgery for the correction of an anterior open bite. The patients were divided into two groups, determined by an increase or decrease in nasion-menton (N-Me) distance as a consequence of surgery. Changes in overbite, the displacements of molars and positional changes in Menton were evaluated immediately before and after surgery and after a minimum of one year post-operatively. The group with a decreased N-Me distance exhibited a significantly greater backward positioning of the mandible. The group with an increased N-Me distance experienced significantly greater dentoalveolar extrusion of the lower molars. A sufficient mandibular backward repositioning is an effective technique in the prevention of open bite relapse. In addition, it is important not to induce molar extrusion during post-surgical orthodontic treatment to preserve stability of the surgical open bite correction.

  13. Early growth response-1 negative feedback regulates skeletal muscle postprandial insulin sensitivity via activating Ptp1b transcription.

    PubMed

    Wu, Jing; Tao, Wei-Wei; Chong, Dan-Yang; Lai, Shan-Shan; Wang, Chuang; Liu, Qi; Zhang, Tong-Yu; Xue, Bin; Li, Chao-Jun

    2018-03-15

    Postprandial insulin desensitization plays a critical role in maintaining whole-body glucose homeostasis by avoiding the excessive absorption of blood glucose; however, the detailed mechanisms that underlie how the major player, skeletal muscle, desensitizes insulin action remain to be elucidated. Herein, we report that early growth response gene-1 ( Egr-1) is activated by insulin in skeletal muscle and provides feedback inhibition that regulates insulin sensitivity after a meal. The inhibition of the transcriptional activity of Egr-1 enhanced the phosphorylation of the insulin receptor (InsR) and Akt, thus increasing glucose uptake in L6 myotubes after insulin stimulation, whereas overexpression of Egr-1 decreased insulin sensitivity. Furthermore, deletion of Egr-1 in the skeletal muscle improved systemic insulin sensitivity and glucose tolerance, which resulted in lower blood glucose levels after refeeding. Mechanistic analysis demonstrated that EGR-1 inhibited InsR phosphorylation and glucose uptake in skeletal muscle by binding to the proximal promoter region of protein tyrosine phosphatase-1B (PTP1B) and directly activating transcription. PTP1B knockdown largely restored insulin sensitivity and enhanced glucose uptake, even under conditions of EGR-1 overexpression. Our results indicate that EGR-1/PTP1B signaling negatively regulates postprandial insulin sensitivity and suggest a potential therapeutic target for the prevention and treatment of excessive glucose absorption.-Wu, J., Tao, W.-W., Chong, D.-Y., Lai, S.-S., Wang, C., Liu, Q., Zhang, T.-Y., Xue, B., Li, C.-J. Early growth response-1 negative feedback regulates skeletal muscle postprandial insulin sensitivity via activating Ptp1b transcription.

  14. Matrix factorization reveals aging-specific co-expression gene modules in the fat and muscle tissues in nonhuman primates

    NASA Astrophysics Data System (ADS)

    Wang, Yongcui; Zhao, Weiling; Zhou, Xiaobo

    2016-10-01

    Accurate identification of coherent transcriptional modules (subnetworks) in adipose and muscle tissues is important for revealing the related mechanisms and co-regulated pathways involved in the development of aging-related diseases. Here, we proposed a systematically computational approach, called ICEGM, to Identify the Co-Expression Gene Modules through a novel mathematical framework of Higher-Order Generalized Singular Value Decomposition (HO-GSVD). ICEGM was applied on the adipose, and heart and skeletal muscle tissues in old and young female African green vervet monkeys. The genes associated with the development of inflammation, cardiovascular and skeletal disorder diseases, and cancer were revealed by the ICEGM. Meanwhile, genes in the ICEGM modules were also enriched in the adipocytes, smooth muscle cells, cardiac myocytes, and immune cells. Comprehensive disease annotation and canonical pathway analysis indicated that immune cells, adipocytes, cardiomyocytes, and smooth muscle cells played a synergistic role in cardiac and physical functions in the aged monkeys by regulation of the biological processes associated with metabolism, inflammation, and atherosclerosis. In conclusion, the ICEGM provides an efficiently systematic framework for decoding the co-expression gene modules in multiple tissues. Analysis of genes in the ICEGM module yielded important insights on the cooperative role of multiple tissues in the development of diseases.

  15. IGFBP-4 regulates adult skeletal growth in a sex-specific manner.

    PubMed

    Maridas, David E; DeMambro, Victoria E; Le, Phuong T; Nagano, Kenichi; Baron, Roland; Mohan, Subburaman; Rosen, Clifford J

    2017-04-01

    Insulin-like growth factor-1 (IGF-1) and its binding proteins are critical mediators of skeletal growth. Insulin-like growth factor-binding protein 4 (IGFBP-4) is highly expressed in osteoblasts and inhibits IGF-1 actions in vitro Yet, in vivo studies suggest that it could potentiate IGF-1 and IGF-2 actions. In this study, we hypothesized that IGFBP-4 might potentiate the actions of IGF-1 on the skeleton. To test this, we comprehensively studied 8- and 16-week-old Igfbp4 -/- mice. Both male and female adult Igfbp4 -/- mice had marked growth retardation with reductions in body weight, body and femur lengths, fat proportion and lean mass at 8 and 16 weeks. Marked reductions in aBMD and aBMC were observed in 16-week-old Igfbp4 -/- females, but not in males. Femoral trabecular BV/TV and thickness, cortical fraction and thickness in 16-week-old Igfbp4 -/- females were significantly reduced. However, surprisingly, males had significantly more trabeculae with higher connectivity density than controls. Concordantly, histomorphometry revealed higher bone resorption and lower bone formation in Igfbp4 -/- females. In contrast, Igfbp4 -/- males had lower mineralized surface/bone surface. Femoral expression of Sost and circulating levels of sclerostin were reduced but only in Igfbp4 -/- males. Bone marrow stromal cultures from mutants showed increased osteogenesis, whereas osteoclastogenesis was markedly increased in cells from Igfbp4 -/- females but decreased in males. In sum, our results indicate that loss of Igfbp4 affects mesenchymal stromal cell differentiation, regulates osteoclastogenesis and influences both skeletal development and adult bone maintenance. Thus, IGFBP-4 modulates the skeleton in a gender-specific manner, acting as both a cell autonomous and cell non-autonomous factor. © 2017 The authors.

  16. IGFBP-4 regulates adult skeletal growth in a sex-specific manner

    PubMed Central

    DeMambro, Victoria E; Le, Phuong T; Nagano, Kenichi; Baron, Roland; Mohan, Subburaman; Rosen, Clifford J

    2017-01-01

    Insulin-like growth factor-1 (IGF-1) and its binding proteins are critical mediators of skeletal growth. Insulin-like growth factor-binding protein 4 (IGFBP-4) is highly expressed in osteoblasts and inhibits IGF-1 actions in vitro. Yet, in vivo studies suggest that it could potentiate IGF-1 and IGF-2 actions. In this study, we hypothesized that IGFBP-4 might potentiate the actions of IGF-1 on the skeleton. To test this, we comprehensively studied 8- and 16-week-old Igfbp4−/− mice. Both male and female adult Igfbp4−/− mice had marked growth retardation with reductions in body weight, body and femur lengths, fat proportion and lean mass at 8 and 16 weeks. Marked reductions in aBMD and aBMC were observed in 16-week-old Igfbp4−/− females, but not in males. Femoral trabecular BV/TV and thickness, cortical fraction and thickness in 16-week-old Igfbp4−/− females were significantly reduced. However, surprisingly, males had significantly more trabeculae with higher connectivity density than controls. Concordantly, histomorphometry revealed higher bone resorption and lower bone formation in Igfbp4−/− females. In contrast, Igfbp4−/− males had lower mineralized surface/bone surface. Femoral expression of Sost and circulating levels of sclerostin were reduced but only in Igfbp4−/− males. Bone marrow stromal cultures from mutants showed increased osteogenesis, whereas osteoclastogenesis was markedly increased in cells from Igfbp4−/− females but decreased in males. In sum, our results indicate that loss of Igfbp4 affects mesenchymal stromal cell differentiation, regulates osteoclastogenesis and influences both skeletal development and adult bone maintenance. Thus, IGFBP-4 modulates the skeleton in a gender-specific manner, acting as both a cell autonomous and cell non-autonomous factor. PMID:28184001

  17. [Molecular mechanism for ET-1-induced insulin resistance in skeletal muscle cells].

    PubMed

    Horinouchi, Takahiro; Mazaki, Yuichi; Terada, Koji; Miwa, Soichi

    2018-01-01

    Insulin resistance is a condition where the sensitivity to insulin of the tissues expressing insulin receptor (InsR) is decreased due to a functional disturbance of InsR-mediated intracellular signaling. Insulin promotes the entry of glucose into the tissues and skeletal muscle is the most important tissue responsible for the insulin's action of decreasing blood glucose levels. Endothelin-1 (ET-1), a potent vasoconstrictor and pro-inflammatory peptide, induces insulin resistance through a direct action on skeletal muscle. However, the signaling pathways of ET-1-induced insulin resistance in skeletal muscle remain unclear. Here we show molecular mechanism underlying the inhibitory effect of ET-1 on insulin-stimulated Akt phosphorylation and glucose uptake in myotubes of rat L6 skeletal muscle cell line. mRNA expression levels of differentiation marker genes, MyoD and myogenin, were increased during L6 myoblasts differentiation into myotubes. Some of myotubes possessed the ability to spontaneously contract. In myotubes, insulin promoted Akt phosphorylation at Thr 308 and Ser 473 , and [ 3 H]-labelled 2-deoxy-D-glucose ([ 3 H]2-DG) uptake. The insulin-facilitated Akt phosphorylation and [ 3 H]2-DG uptake were inhibited by ET-1. The inhibitory effect of ET-1 was counteracted by blockade of ET type A receptor (ET A R), inhibition of G q/11 protein, and siRNA knockdown of G protein-coupled receptor kinase 2 (GRK2). The exogenously overexpressed GRK2 directly bound to endogenous Akt and their association was facilitated by ET-1. In summary, activation of ET A R with ET-1 inhibits insulin-induced Akt phosphorylation and [ 3 H]2-DG uptake in a G q/11 protein- and GRK2-dependent manner in skeletal muscle. These findings indicate that ET A R and GRK2 are potential targets for insulin resistance.

  18. Tumor Necrosis Factor-α Regulates Distinct Molecular Pathways and Gene Networks in Cultured Skeletal Muscle Cells

    PubMed Central

    Gupta, Sanjay K.; Dahiya, Saurabh; Lundy, Robert F.; Kumar, Ashok

    2010-01-01

    Background Skeletal muscle wasting is a debilitating consequence of large number of disease states and conditions. Tumor necrosis factor-α (TNF-α) is one of the most important muscle-wasting cytokine, elevated levels of which cause significant muscular abnormalities. However, the underpinning molecular mechanisms by which TNF-α causes skeletal muscle wasting are less well-understood. Methodology/Principal Findings We have used microarray, quantitative real-time PCR (QRT-PCR), Western blot, and bioinformatics tools to study the effects of TNF-α on various molecular pathways and gene networks in C2C12 cells (a mouse myoblastic cell line). Microarray analyses of C2C12 myotubes treated with TNF-α (10 ng/ml) for 18h showed differential expression of a number of genes involved in distinct molecular pathways. The genes involved in nuclear factor-kappa B (NF-kappaB) signaling, 26s proteasome pathway, Notch1 signaling, and chemokine networks are the most important ones affected by TNF-α. The expression of some of the genes in microarray dataset showed good correlation in independent QRT-PCR and Western blot assays. Analysis of TNF-treated myotubes showed that TNF-α augments the activity of both canonical and alternative NF-κB signaling pathways in myotubes. Bioinformatics analyses of microarray dataset revealed that TNF-α affects the activity of several important pathways including those involved in oxidative stress, hepatic fibrosis, mitochondrial dysfunction, cholesterol biosynthesis, and TGF-β signaling. Furthermore, TNF-α was found to affect the gene networks related to drug metabolism, cell cycle, cancer, neurological disease, organismal injury, and abnormalities in myotubes. Conclusions TNF-α regulates the expression of multiple genes involved in various toxic pathways which may be responsible for TNF-induced muscle loss in catabolic conditions. Our study suggests that TNF-α activates both canonical and alternative NF-κB signaling pathways in a time

  19. The expression of NFATc1 in adult rat skeletal muscle fibres.

    PubMed

    Mutungi, Gabriel

    2008-03-01

    Although numerous studies have recently implicated the calcineurin-nuclear factor of activated T-cells (Cn-NFAT) signalling pathway in the regulation of activity-dependent fibre type switching in adult mammalian skeletal muscles, little is known about the endogenous expression of NFAT proteins in the various fibre types present in these muscles. In this study, the immunolocalization of NFATc1 (also known as NFATc or NFAT2) in the extensor digitorum longus (EDL; a mainly fast-twitch muscle) and the soleus (a predominantly slow-twitch muscle) muscles of adult ( approximately 90-day-old) Wistar rats was investigated. The results show that NFATc1 is expressed only in oxidative fibres (i.e. type I and type IIA fibres) that stain intensely for succinate dehydrogenase activity irrespective of whether they are from the fast- or slow-twitch muscle. Thus, 99 +/- 4% (n = 7 rats) of the muscle fibres in the soleus and 42 +/- 2% (n = 7 rats) of those in the EDL expressed NFATc1. In the soleus muscle fibres, NFATc1 was localized mainly in the fibre nuclei, whereas in the EDL fibres it was localized in both the cytoplasm and the nuclei. However, no difference in its localization was observed between type I and type IIA fibres in both muscles. Western blot experiments showed that the soleus expressed more NFATc1 proteins than the EDL. From these results, we suggest that NFATc1 controls the number and distribution of both type I and type IIA fibres, as well as the oxidative capacity of adult mammalian skeletal muscles.

  20. Tissue Engineered Skeletal Myofibers can Directly "Sense" Gravitational Force Changes

    NASA Technical Reports Server (NTRS)

    Vandenburgh, Herman H.; Shansky, J.; DelTatto, M.; Lee, Peter; Meir, J.

    1999-01-01

    Long-term manned space flight requires a better understanding of skeletal muscle atrophy resulting from microgravity. Atrophy most likely results from changes at both the systemic level (e.g. decreased circulating growth hormone, increased circulating glucocorticoids) and locally (e.g. decreased myofiber resting tension). Differentiated skeletal myofibers in tissue culture have provided a model system over the last decade for gaining a better understanding of the interactions of exogenous growth factors, endogenous growth factors, and muscle fiber tension in regulating protein turnover rates and muscle cell growth. Tissue engineering these cells into three dimensional bioartificial muscle (BAM) constructs has allowed us to extend their use to Space flight studies for the potential future development of countermeasures. Embryonic avian muscle cells were isolated and BAMs tissue engineered as described previously. The myoblasts proliferate and fuse into aligned postmitotic myofibers after ten to fourteen days in vitro. A cylindrical muscle-like structure containing several thousand myofibers is formed which is approximately 30 mm in length, 2-3 mm in diameter, and attached at each end. For the Space Shuttle experiments, the BAMs were transferred to 55 mL bioreactor cartridges (6 BAMs/cartridge). At Kennedy Space Center, the cartridges were mounted in two Space Tissue Loss (STL) Modules (three to four cartridges per Module) and either maintained as ground controls or loaded in a Mid-Deck locker of the Space Shuttle. The BAM cartridges were continuously perfused during the experiment at 1.5 mL/ min with tissue culture medium. Eighteen BAMs were flown for nine days on Mission STS66 while eighteen BAMs served as ground controls. The complete experiment was repeated on Mission STS77 with twenty four BAMs in each group. BAMs could be maintained in a healthy state for at least 30 days in the perfusion bioreactor cartridges. The BAM muscle fibers directly detected both the

  1. Histone Deacetylase 6 Is a FoxO Transcription Factor-dependent Effector in Skeletal Muscle Atrophy*

    PubMed Central

    Ratti, Francesca; Ramond, Francis; Moncollin, Vincent; Simonet, Thomas; Milan, Giulia; Méjat, Alexandre; Thomas, Jean-Luc; Streichenberger, Nathalie; Gilquin, Benoit; Matthias, Patrick; Khochbin, Saadi; Sandri, Marco; Schaeffer, Laurent

    2015-01-01

    Skeletal muscle atrophy is a severe condition of muscle mass loss. Muscle atrophy is caused by a down-regulation of protein synthesis and by an increase of protein breakdown due to the ubiquitin-proteasome system and autophagy activation. Up-regulation of specific genes, such as the muscle-specific E3 ubiquitin ligase MAFbx, by FoxO transcription factors is essential to initiate muscle protein ubiquitination and degradation during atrophy. HDAC6 is a particular HDAC, which is functionally related to the ubiquitin proteasome system via its ubiquitin binding domain. We show that HDAC6 is up-regulated during muscle atrophy. HDAC6 activation is dependent on the transcription factor FoxO3a, and the inactivation of HDAC6 in mice protects against muscle wasting. HDAC6 is able to interact with MAFbx, a key ubiquitin ligase involved in muscle atrophy. Our findings demonstrate the implication of HDAC6 in skeletal muscle wasting and identify HDAC6 as a new downstream target of FoxO3a in stress response. This work provides new insights in skeletal muscle atrophy development and opens interesting perspectives on HDAC6 as a valuable marker of muscle atrophy and a potential target for pharmacological treatments. PMID:25516595

  2. Overload-mediated skeletal muscle hypertrophy is not impaired by loss of myofiber STAT3.

    PubMed

    Pérez-Schindler, Joaquín; Esparza, Mary C; McKendry, James; Breen, Leigh; Philp, Andrew; Schenk, Simon

    2017-09-01

    Although the signal pathways mediating muscle protein synthesis and degradation are well characterized, the transcriptional processes modulating skeletal muscle mass and adaptive growth are poorly understood. Recently, studies in mouse models of muscle wasting or acutely exercised human muscle have suggested a potential role for the transcription factor signal transducer and activator of transcription 3 (STAT3), in adaptive growth. Hence, in the present study we sought to define the contribution of STAT3 to skeletal muscle adaptive growth. In contrast to previous work, two different resistance exercise protocols did not change STAT3 phosphorylation in human skeletal muscle. To directly address the role of STAT3 in load-induced (i.e., adaptive) growth, we studied the anabolic effects of 14 days of synergist ablation (SA) in skeletal muscle-specific STAT3 knockout (mKO) mice and their floxed, wild-type (WT) littermates. Plantaris muscle weight and fiber area in the nonoperated leg (control; CON) was comparable between genotypes. As expected, SA significantly increased plantaris weight, muscle fiber cross-sectional area, and anabolic signaling in WT mice, although interestingly, this induction was not impaired in STAT3 mKO mice. Collectively, these data demonstrate that STAT3 is not required for overload-mediated hypertrophy in mouse skeletal muscle. Copyright © 2017 the American Physiological Society.

  3. The HO-1/CO system regulates mitochondrial-capillary density relationships in human skeletal muscle.

    PubMed

    Pecorella, Shelly R H; Potter, Jennifer V F; Cherry, Anne D; Peacher, Dionne F; Welty-Wolf, Karen E; Moon, Richard E; Piantadosi, Claude A; Suliman, Hagir B

    2015-10-15

    The heme oxygenase-1 (HO-1)/carbon monoxide (CO) system induces mitochondrial biogenesis, but its biological impact in human skeletal muscle is uncertain. The enzyme system generates CO, which stimulates mitochondrial proliferation in normal muscle. Here we examined whether CO breathing can be used to produce a coordinated metabolic and vascular response in human skeletal muscle. In 19 healthy subjects, we performed vastus lateralis muscle biopsies and tested one-legged maximal O2 uptake (V̇o2max) before and after breathing air or CO (200 ppm) for 1 h daily for 5 days. In response to CO, there was robust HO-1 induction along with increased mRNA levels for nuclear-encoded mitochondrial transcription factor A (Tfam), cytochrome c, cytochrome oxidase subunit IV (COX IV), and mitochondrial-encoded COX I and NADH dehydrogenase subunit 1 (NDI). CO breathing did not increase V̇o2max (1.96 ± 0.51 pre-CO, 1.87 ± 0.50 post-CO l/min; P = not significant) but did increase muscle citrate synthase, mitochondrial density (139.0 ± 34.9 pre-CO, 219.0 ± 36.2 post-CO; no. of mitochondrial profiles/field), myoglobin content and glucose transporter (GLUT4) protein level and led to GLUT4 localization to the myocyte membrane, all consistent with expansion of the tissue O2 transport system. These responses were attended by increased cluster of differentiation 31 (CD31)-positive muscle capillaries (1.78 ± 0.16 pre-CO, 2.37 ± 0.59 post-CO; capillaries/muscle fiber), implying the enrichment of microvascular O2 reserve. The findings support that induction of the HO-1/CO system by CO not only improves muscle mitochondrial density, but regulates myoglobin content, GLUT4 localization, and capillarity in accordance with current concepts of skeletal muscle plasticity. Copyright © 2015 the American Physiological Society.

  4. Interdependence of skeletal sclerosis and elevated circulating levels of 1,25-dihydroxyvitamin D in osteopetrotic (op and tl) rats.

    PubMed

    Popoff, S N; Osier, L K; Zerwekh, J E; Marks, S C

    1994-01-01

    Osteopetrosis describes a heterogeneous group of inherited, metabolic bone disorders characterized by reduced bone resorption which coexists with elevated circulating levels of 1,25-dihydroxyvitamin D [1,25(OH)2D]. To determine whether or not skeletal sclerosis and high concentrations of 1,25(OH)2D are interdependent, this study used two distinct, nonallelic osteopetrotic mutations in the rat, osteopetrosis (op) and toothless (tl). The op rat is a mutation in which skeletal sclerosis can be cured (mutant) or induced (normal) following the transfer of normal or mutant osteoclast progenitors, respectively. Although these procedures are ineffective in rats of tl stock, infusions of pharmacological doses of macrophage colony-stimulating factor (CSF-1) can stimulate bone resorption and eliminate most of the excess skeletal matrix in tl mutants. This study examined the effects of cure/induction in neonatal mutant/normal rats of op stock and CSF-1 infusions in mutant rats of tl stock on skeletal (bone resorption) and serum [1,25(OH)2D] parameters as a function of time after treatment. Osteopetrotic mutants transplanted (cured) with normal spleen cells demonstrated cellular changes in osteoclast phenotype within 2-3 days followed by histologic and radiographic evidence for increased bone resorption that culminated in a normal appearance of the skeleton by 4 weeks. The markedly elevated serum levels of 1,25(OH)2D observed in untreated mutants fell significantly in transplanted mutants by the end of the first week and were similar to those in normal littermates at 3 and 4 weeks. Normal littermates transplanted (induced) with mutant spleen cells showed a progressive increase in skeletal sclerosis paralleled by significant increases in circulating levels of 1,25(OH)2D.(ABSTRACT TRUNCATED AT 250 WORDS)

  5. Tissue engineering skeletal muscle for orthopaedic applications

    NASA Technical Reports Server (NTRS)

    Payumo, Francis C.; Kim, Hyun D.; Sherling, Michael A.; Smith, Lee P.; Powell, Courtney; Wang, Xiao; Keeping, Hugh S.; Valentini, Robert F.; Vandenburgh, Herman H.

    2002-01-01

    With current technology, tissue-engineered skeletal muscle analogues (bioartificial muscles) generate too little active force to be clinically useful in orthopaedic applications. They have been engineered genetically with numerous transgenes (growth hormone, insulinlike growth factor-1, erythropoietin, vascular endothelial growth factor), and have been shown to deliver these therapeutic proteins either locally or systemically for months in vivo. Bone morphogenetic proteins belonging to the transforming growth factor-beta superfamily are osteoinductive molecules that drive the differentiation pathway of mesenchymal cells toward the chondroblastic or osteoblastic lineage, and stimulate bone formation in vivo. To determine whether skeletal muscle cells endogenously expressing bone morphogenetic proteins might serve as a vehicle for systemic bone morphogenetic protein delivery in vivo, proliferating skeletal myoblasts (C2C12) were transduced with a replication defective retrovirus containing the gene for recombinant human bone morphogenetic protein-6 (C2BMP-6). The C2BMP-6 cells constitutively expressed recombinant human bone morphogenetic protein-6 and synthesized bioactive recombinant human bone morphogenetic protein-6, based on increased alkaline phosphatase activity in coincubated mesenchymal cells. C2BMP-6 cells did not secrete soluble, bioactive recombinant human bone morphogenetic protein-6, but retained the bioactivity in the cell layer. Therefore, genetically-engineered skeletal muscle cells might serve as a platform for long-term delivery of osteoinductive bone morphogenetic proteins locally.

  6. Expression and functional characterization of Smyd1a in myofibril organization of skeletal muscles.

    PubMed

    Gao, Jie; Li, Junling; Li, Bao-Jun; Yagil, Ezra; Zhang, Jianshe; Du, Shao Jun

    2014-01-01

    Smyd1, the founding member of the Smyd family including Smyd-1, 2, 3, 4 and 5, is a SET and MYND domain containing protein that plays a key role in myofibril assembly in skeletal and cardiac muscles. Bioinformatic analysis revealed that zebrafish genome contains two highly related smyd1 genes, smyd1a and smyd1b. Although Smyd1b function is well characterized in skeletal and cardiac muscles, the function of Smyd1a is, however, unknown. To investigate the function of Smyd1a in muscle development, we isolated smyd1a from zebrafish, and characterized its expression and function during muscle development via gene knockdown and transgenic expression approaches. The results showed that smyd1a was strongly expressed in skeletal muscles of zebrafish embryos. Functional analysis revealed that knockdown of smyd1a alone had no significant effect on myofibril assembly in zebrafish skeletal muscles. However, knockdown of smyd1a and smyd1b together resulted in a complete disruption of myofibril organization in skeletal muscles, a phenotype stronger than knockdown of smyd1a or smyd1b alone. Moreover, ectopic expression of zebrafish smyd1a or mouse Smyd1 transgene could rescue the myofibril defects from the smyd1b knockdown in zebrafish embryos. Collectively, these data indicate that Smyd1a and Smyd1b share similar biological activity in myofibril assembly in zebrafish embryos. However, Smyd1b appears to play a major role in this process.

  7. Lsd1 regulates skeletal muscle regeneration and directs the fate of satellite cells.

    PubMed

    Tosic, Milica; Allen, Anita; Willmann, Dominica; Lepper, Christoph; Kim, Johnny; Duteil, Delphine; Schüle, Roland

    2018-01-25

    Satellite cells are muscle stem cells required for muscle regeneration upon damage. Of note, satellite cells are bipotent and have the capacity to differentiate not only into skeletal myocytes, but also into brown adipocytes. Epigenetic mechanisms regulating fate decision and differentiation of satellite cells during muscle regeneration are not yet fully understood. Here, we show that elevated levels of lysine-specific demethylase 1 (Kdm1a, also known as Lsd1) have a beneficial effect on muscle regeneration and recovery after injury, since Lsd1 directly regulates key myogenic transcription factor genes. Importantly, selective Lsd1 ablation or inhibition in Pax7-positive satellite cells, not only delays muscle regeneration, but changes cell fate towards brown adipocytes. Lsd1 prevents brown adipocyte differentiation of satellite cells by repressing expression of the novel pro-adipogenic transcription factor Glis1. Together, downregulation of Glis1 and upregulation of the muscle-specific transcription program ensure physiological muscle regeneration.

  8. Nerve-dependent factors regulating transcript levels of glycogen phosphorylase in skeletal muscle.

    PubMed

    Matthews, C C; Carlsen, R C; Froman, B; Tait, R; Gorin, F

    1998-06-01

    1. Muscle glycogen phosphorylase (MGP), the rate-limiting enzyme for glycogen metabolism in skeletal muscle, is neurally regulated. Steady-state transcript levels of the skeletal muscle isozyme of MGP decrease significantly following muscle denervation and after prolonged muscle inactivity with an intact motor nerve. These data suggest that muscle activity has an important influence on MGP gene expression. The evidence to this point, however, does not preclude the possibility that MGP is also regulated by motor neuron-derived trophic factors. This study attempts to distinguish between regulation provided by nerve-evoked muscle contractile activity and that provided by the delivery of neurotrophic factors. 2. Steady-state MGP transcript levels were determined in rat tibialis anterior (TA) muscles following controlled interventions aimed at separating the contributions of contractile activity from axonally transported trophic factors. The innervated TA was rendered inactive by daily epineural injections of tetrodotoxin (TTX) into the sciatic nerve. Sustained inhibition of axonal transport was accomplished by applying one of three different concentrations of the antimicrotubule agent, vinblastine (VIN), to the proximal sciatic nerve for 1 hr. The axonal transport of acetylcholinesterase (AChE) was assessed 7, 14, and 28 days after the single application of VIN. 3. MGP transcript levels normalized to total RNA were reduced by 67% in rat TA, 7 days after nerve section. Daily injection of 2 microg TTX into the sciatic nerve for 7 days eliminated muscle contractile activity and reduced MGP transcript levels by 60%. 4. A single, 1-hr application of 0.10% (w/v) VIN to the sciatic nerve reduced axonal transport but did not alter MGP transcript levels in the associated TA, 7 days after treatment. Application of 0.10% VIN to the sciatic nerve also did not affect IA sensory or motor nerve conduction velocities or TA contractile function. 5. Treatment of the sciatic nerve with 0

  9. The methyltransferase SMYD3 mediates the recruitment of transcriptional cofactors at the myostatin and c-Met genes and regulates skeletal muscle atrophy

    PubMed Central

    Proserpio, Valentina; Fittipaldi, Raffaella; Ryall, James G.; Sartorelli, Vittorio; Caretti, Giuseppina

    2013-01-01

    Elucidating the epigenetic mechanisms underlying muscle mass determination and skeletal muscle wasting holds the potential of identifying molecular pathways that constitute possible drug targets. Here, we report that the methyltransferase SMYD3 modulates myostatin and c-Met transcription in primary skeletal muscle cells and C2C12 myogenic cells. SMYD3 targets the myostatin and c-Met genes and participates in the recruitment of the bromodomain protein BRD4 to their regulatory regions through protein–protein interaction. By recruiting BRD4, SMYD3 favors chromatin engagement of the pause–release factor p-TEFb (positive transcription elongation factor) and elongation of Ser2-phosphorylated RNA polymerase II (PolIISer2P). Reducing SMYD3 decreases myostatin and c-Met transcription, thus protecting from glucocorticoid-induced myotube atrophy. Supporting functional relevance of the SMYD3/BRD4 interaction, BRD4 pharmacological blockade by the small molecule JQ1 prevents dexamethasone-induced myostatin and atrogene up-regulation and spares myotube atrophy. Importantly, in a mouse model of dexamethasone-induced skeletal muscle atrophy, SMYD3 depletion prevents muscle loss and fiber size decrease. These findings reveal a mechanistic link between SMYD3/BRD4-dependent transcriptional regulation, muscle mass determination, and skeletal muscle atrophy and further encourage testing of small molecules targeting specific epigenetic regulators in animal models of muscle wasting. PMID:23752591

  10. Assessing skeletal maturity by using blood spot insulin-like growth factor I (IGF-I) testing.

    PubMed

    Masoud, Mohamed; Masoud, Ibrahim; Kent, Ralph L; Gowharji, Nour; Cohen, Laurie E

    2008-08-01

    Accurate determination of skeletal maturity and remaining growth is crucial to many orthodontic, orthognathic, and dental-implant timing decisions. Cervical vertebral stages and hand-wrist radiographs are currently used to identify peak mandibular bone growth. These are highly subjective techniques that not only involve radiographic exposure but also lack the ability to determine the intensity of the growth spurt and the end of growth. Insulin-like growth factor I (IGF-I) is a circulating growth hormone-dependent factor whose level correlates with sexual maturity; it is used to diagnose growth hormone deficiency and excess. We hypothesized that IGF-I levels would also correlate with cervical skeletal maturity and would be highest at the cervical stages that correspond to the greatest amount of facial growth. We measured mean blood spot IGF-I levels in a cross-sectional study of 83 patients (44 female, 39 male) on recall to begin orthodontic treatment, in active treatment, or in posttreatment follow-up. Mean blood spot IGF-I levels were significantly higher in the late pubertal stages than in the prepubertal, early pubertal, and postpubertal stages. Linear correlation showed that IGF-I levels had a significant positive correlation with cervical skeletal maturity from the prepubertal to the late pubertal stages, and a significant negative correlation from the late pubertal to the postpubertal stages. In the postpubertal stage, IGF-I levels had a negative linear correlation with increasing time since the onset of puberty and with chronological age. Blood spot IGF-I could be used as a skeletal maturity indicator and might be useful in detecting residual mandibular growth in young adults.

  11. Muscle-specific deletion of Prkaa1 enhances skeletal muscle lipid accumulation in mice fed a high-fat diet.

    PubMed

    Wu, Weiche; Xu, Ziye; Zhang, Ling; Liu, Jiaqi; Feng, Jie; Wang, Xinxia; Shan, Tizhong; Wang, Yizhen

    2018-05-01

    Excessive intramyocellular triacylglycerols (IMTGs, muscle lipids) are associated with the abnormal energy metabolism and insulin resistance of skeletal muscle. AMP-activated protein kinase (AMPK), a crucial cellular energy sensor, consists of α, β and γ subunits. Researchers have not clearly determined whether Prkaa1 (also known as AMPKα1) affects IMTG accumulation in skeletal muscle. Here, we show an important role of Prkaa1 in skeletal muscle lipid metabolism. Deletion of muscle Prkaa1 leads to the delayed development of skeletal muscles but does not affect glucose tolerance or insulin sensitivity in animals fed a normal diet. Notably, when animals are fed a high-fat diet, the skeletal muscle of muscle-specific Prkaa1 knockout mice accumulates more lipids than the skeletal muscle of wild-type (WT) mice, with concomitant upregulation of adipogenic gene expressions and downregulation of the expression of genes associated with mitochondrial oxidation. Muscle-specific Prkaa1 ablation also results in hyperlipidemia, which may contribute to the increased IMTG levels. Furthermore, Prkaa1 deletion activates skeletal muscle mTOR signalling, which has a central role in lipid metabolism and mitochondrial oxidation. Collectively, our study provides new insights into the role of Prkaa1 in skeletal muscle. This knowledge may contribute to the treatment of related metabolic diseases.

  12. Type 1 Inositol (1,4,5)-Trisphosphate Receptor Activates Ryanodine Receptor 1 to Mediate Calcium Spark Signaling in Adult Mammalian Skeletal Muscle*♦

    PubMed Central

    Tjondrokoesoemo, Andoria; Li, Na; Lin, Pei-Hui; Pan, Zui; Ferrante, Christopher J.; Shirokova, Natalia; Brotto, Marco; Weisleder, Noah; Ma, Jianjie

    2013-01-01

    Functional coupling between inositol (1,4,5)-trisphosphate receptor (IP3R) and ryanodine receptor (RyR) represents a critical component of intracellular Ca2+ signaling in many excitable cells; however, the role of this mechanism in skeletal muscle remains elusive. In skeletal muscle, RyR-mediated Ca2+ sparks are suppressed in resting conditions, whereas application of transient osmotic stress can trigger activation of Ca2+ sparks that are restricted to the periphery of the fiber. Here we show that onset of these spatially confined Ca2+ sparks involves interaction between activation of IP3R and RyR near the sarcolemmal membrane. Pharmacological prevention of IP3 production or inhibition of IP3R channel activity abolishes stress-induced Ca2+ sparks in skeletal muscle. Although genetic ablation of the type 2 IP3R does not appear to affect Ca2+ sparks in skeletal muscle, specific silencing of the type 1 IP3R leads to ablation of stress-induced Ca2+ sparks. Our data indicate that membrane-delimited signaling involving cross-talk between IP3R1 and RyR1 contributes to Ca2+ spark activation in skeletal muscle. PMID:23223241

  13. Severity of Asynchronous Slipped Capital Femoral Epiphyses in Skeletally Immature Versus More Skeletally Mature Patients.

    PubMed

    Nowicki, Philip D; Silva, Selina; Toelle, Lisa; Strohmeyer, Greg; Wahlquist, Trevor; Li, Ying; Farley, Frances A; Caird, Michelle S

    2017-01-01

    Routine prophylactic screw fixation for skeletally immature patients with slipped capital femoral epiphysis (SCFE) continues to be debated. The purpose of this study was to assess the slip severity of a second SCFE in skeletally immature versus more mature patients and determine necessity of contralateral hip prophylactic screw fixation. All patients treated for SCFE at 3 pediatric hospitals over a 10-year time period (January 1, 2002 to December 31, 2011) were evaluated. Patients were included if they had a unilateral SCFE and a contralateral asynchronous SCFE, and were divided into immature (Oxford triradiate score 1) versus more mature (Oxford triradiate score 2 and 3) groups. Data evaluation included age, time between slips, body mass index, Southwick angles of first then second SCFEs, and follow-up duration. There were a total of 45 patients: 16 patients in the skeletally immature and 29 patients in the more mature group. Average age at first SCFE in immature patients was 10.9 years and in more mature patients 12.1 years (P=0.70). Age at second SCFE in immature patients was 11.5 years and in more mature patients 13.0 years (P=0.023). Average time between SCFEs was 6.6 months for immature and 11.4 months for more mature patients (P=0.093). Southwick angles for immature patient first and second SCFEs were 25 and 12.9 degrees, respectively, and for more mature patient first and second SCFEs were 31 and 21 degrees, respectively. Southwick angles were higher at first and second slips in the more mature group, significant only at the second slip (P=0.032). SCFE severity at initial event was predictive of severity of second SCFE regardless of maturity (P=0.043). Regression analysis of slip severity against multiple patient factors demonstrated triradiate score was not a factor assessing subsequent SCFE magnitude (P=0.099). There was no significant difference between first and second SCFEs regardless of skeletal maturity but severity of initial SCFE did correlate with

  14. STIM1 as a key regulator for Ca2+ homeostasis in skeletal-muscle development and function

    PubMed Central

    2011-01-01

    Stromal interaction molecules (STIM) were identified as the endoplasmic-reticulum (ER) Ca2+ sensor controlling store-operated Ca2+ entry (SOCE) and Ca2+-release-activated Ca2+ (CRAC) channels in non-excitable cells. STIM proteins target Orai1-3, tetrameric Ca2+-permeable channels in the plasma membrane. Structure-function analysis revealed the molecular determinants and the key steps in the activation process of Orai by STIM. Recently, STIM1 was found to be expressed at high levels in skeletal muscle controlling muscle function and properties. Novel STIM targets besides Orai channels are emerging. Here, we will focus on the role of STIM1 in skeletal-muscle structure, development and function. The molecular mechanism underpinning skeletal-muscle physiology points toward an essential role for STIM1-controlled SOCE to drive Ca2+/calcineurin/nuclear factor of activated T cells (NFAT)-dependent morphogenetic remodeling programs and to support adequate sarcoplasmic-reticulum (SR) Ca2+-store filling. Also in our hands, STIM1 is transiently up-regulated during the initial phase of in vitro myogenesis of C2C12 cells. The molecular targets of STIM1 in these cells likely involve Orai channels and canonical transient receptor potential (TRPC) channels TRPC1 and TRPC3. The fast kinetics of SOCE activation in skeletal muscle seem to depend on the triad-junction formation, favoring a pre-localization and/or pre-formation of STIM1-protein complexes with the plasma-membrane Ca2+-influx channels. Moreover, Orai1-mediated Ca2+ influx seems to be essential for controlling the resting Ca2+ concentration and for proper SR Ca2+ filling. Hence, Ca2+ influx through STIM1-dependent activation of SOCE from the T-tubule system may recycle extracellular Ca2+ losses during muscle stimulation, thereby maintaining proper filling of the SR Ca2+ stores and muscle function. Importantly, mouse models for dystrophic pathologies, like Duchenne muscular dystrophy, point towards an enhanced Ca2+ influx

  15. JunB transcription factor maintains skeletal muscle mass and promotes hypertrophy

    PubMed Central

    Raffaello, Anna; Milan, Giulia; Masiero, Eva; Carnio, Silvia; Lee, Donghoon

    2010-01-01

    The size of skeletal muscle cells is precisely regulated by intracellular signaling networks that determine the balance between overall rates of protein synthesis and degradation. Myofiber growth and protein synthesis are stimulated by the IGF-1/Akt/mammalian target of rapamycin (mTOR) pathway. In this study, we show that the transcription factor JunB is also a major determinant of whether adult muscles grow or atrophy. We found that in atrophying myotubes, JunB is excluded from the nucleus and that decreasing JunB expression by RNA interference in adult muscles causes atrophy. Furthermore, JunB overexpression induces hypertrophy without affecting satellite cell proliferation and stimulated protein synthesis independently of the Akt/mTOR pathway. When JunB is transfected into denervated muscles, fiber atrophy is prevented. JunB blocks FoxO3 binding to atrogin-1 and MuRF-1 promoters and thus reduces protein breakdown. Therefore, JunB is important not only in dividing populations but also in adult muscle, where it is required for the maintenance of muscle size and can induce rapid hypertrophy and block atrophy. PMID:20921137

  16. [Skeletal Mass Depletion Is a Negative Prognostic Factor in Gastrointestinal Cancer Patients in the Terminal Stage].

    PubMed

    Takahashi, Goro; Yamada, Takeshi; Kan, Hayato; Koizumi, Michihiro; Shinji, Seiichi; Yokoyama, Yasuyuki; Iwai, Takuma; Uchida, Eiji

    2015-10-01

    Skeletal mass depletion has been reported to be a prognostic factor for cancer patients. However, special and expensive devices are required to measure skeletal mass, and this is a major reason why skeletal mass is not used extensively for prognostic marker in clinical settings. We developed a new method to measure skeletal mass for use as a prognostic marker using CT images without special and expensive devices. In this study, we evaluated the usefulness of skeletal mass as measured by this new method as a prognostic marker for gastrointestinal cancer patients. Patients who died from gastrointestinal cancer between March 2010 and October 2013 were included. We measured the right-sided maximum psoas muscle cross sectional area (MPCA) by using CT images before surgery and after the patients developed a terminal condition. The maximum psoas muscle cross sectional area ratio (MPCA-R) was defined as follows: MPCA-R=MPCA before surgery/MPCA after developing a terminal condition. We evaluated the correlation between MPCA-R and survival. Fifty-nine patients were included. The median survival was 44 days, and MPCA-R was significantly correlated with survival (p=0.001). On receiver operating characteristic (ROC) analysis, the area under the curve (AUC) to predict 30-day and 90-day survival was 0.710 and 0.748, respectively. MPCA-R is a new and novel prognostic marker for gastrointestinal cancer patients in terminal condition.

  17. Adipocyte-myocyte crosstalk in skeletal muscle insulin resistance; is there a role for thyroid hormone?

    PubMed

    Havekes, Bas; Sauerwein, Hans P

    2010-11-01

    To review original research studies and reviews that present data on adipocyte-myocyte crosstalk in the development of skeletal muscle insulin resistance with a specific focus on thyroid hormone. Adipose tissue communicates with skeletal muscle not only through free fatty acids but also through secretion of various products called adipokines. Adipokines came out as governors of insulin sensitivity and are deregulated in obesity. In addition to well known leptin, adiponectin, interleukin-6 and tumor necrosis factor-alpha, newer adipokines like retinol-binding protein 4 have been associated with insulin resistance. There is mounting evidence that not only adipose tissue but also skeletal muscle produces and secretes biologically active proteins or 'myokines' that facilitate metabolic crosstalk between organ systems. In recent years, increased expression of myostatin, a secreted anabolic inhibitor of muscle growth and development, has been associated with obesity and insulin resistance. Both hypothyroidism and hyperthyroidism affect insulin sensitivity in multiple ways that might overlap adipocyte-myocyte crosstalk. Recent studies have provided new insights in effects of processing of the parent hormone T4 to the active T3 at the level of the skeletal muscle. Adipocyte-myocyte crosstalk is an important modulator in the development of skeletal muscle insulin resistance. Thyroid disorders are very common and may have detrimental effects on skeletal muscle insulin resistance, potentially by interacting with adipocyte-myocyte crosstalk.

  18. The Ubiquitin Ligase Nedd4-1 Participates in Denervation-Induced Skeletal Muscle Atrophy in Mice

    PubMed Central

    Nagpal, Preena; Plant, Pamela J.; Correa, Judy; Bain, Alexandra; Takeda, Michiko; Kawabe, Hiroshi; Rotin, Daniela; Bain, James R.; Batt, Jane A. E.

    2012-01-01

    Skeletal muscle atrophy is a consequence of muscle inactivity resulting from denervation, unloading and immobility. It accompanies many chronic disease states and also occurs as a pathophysiologic consequence of normal aging. In all these conditions, ubiquitin-dependent proteolysis is a key regulator of the loss of muscle mass, and ubiquitin ligases confer specificity to this process by interacting with, and linking ubiquitin moieties to target substrates through protein∶protein interaction domains. Our previous work suggested that the ubiquitin-protein ligase Nedd4-1 is a potential mediator of skeletal muscle atrophy associated with inactivity (denervation, unloading and immobility). Here we generated a novel tool, the Nedd4-1 skeletal muscle-specific knockout mouse (myoCre;Nedd4-1flox/flox) and subjected it to a well validated model of denervation induced skeletal muscle atrophy. The absence of Nedd4-1 resulted in increased weights and cross-sectional area of type II fast twitch fibres of denervated gastrocnemius muscle compared with wild type littermates controls, at seven and fourteen days following tibial nerve transection. These effects are not mediated by the Nedd4-1 substrates MTMR4, FGFR1 and Notch-1. These results demonstrate that Nedd4-1 plays an important role in mediating denervation-induced skeletal muscle atrophy in vivo. PMID:23110050

  19. Matrix Metalloproteinases and Tissue Inhibitor of Metalloproteinases in Inflammation and Fibrosis of Skeletal Muscles

    PubMed Central

    Alameddine, Hala S.; Morgan, Jennifer E.

    2016-01-01

    In skeletal muscles, levels and activity of Matrix MetalloProteinases (MMPs) and Tissue Inhibitors of MetalloProteinases (TIMPs) have been involved in myoblast migration, fusion and various physiological and pathological remodeling situations including neuromuscular diseases. This has opened perspectives for the use of MMPs’ overexpression to improve the efficiency of cell therapy in muscular dystrophies and resolve fibrosis. Alternatively, inhibition of individual MMPs in animal models of muscular dystrophies has provided evidence of beneficial, dual or adverse effects on muscle morphology or function. We review here the role played by MMPs/TIMPs in skeletal muscle inflammation and fibrosis, two major hurdles that limit the success of cell and gene therapy. We report and analyze the consequences of genetic or pharmacological modulation of MMP levels on the inflammation of skeletal muscles and their repair in light of experimental findings. We further discuss how the interplay between MMPs/TIMPs levels, cytokines/chemokines, growth factors and permanent low-grade inflammation favor cellular and molecular modifications resulting in fibrosis. PMID:27911334

  20. Identification of the functional domain in the transcription factor RTEF-1 that mediates alpha 1-adrenergic signaling in hypertrophied cardiac myocytes.

    PubMed

    Ueyama, T; Zhu, C; Valenzuela, Y M; Suzow, J G; Stewart, A F

    2000-06-09

    Cardiac myocytes respond to alpha(1)-adrenergic receptor stimulation by a progressive hypertrophy accompanied by the activation of many fetal genes, including skeletal muscle alpha-actin. The skeletal muscle alpha-actin gene is activated by signaling through an MCAT element, the binding site of the transcription enhancer factor-1 (TEF-1) family of transcription factors. Previously, we showed that overexpression of the TEF-1-related factor (RTEF-1) increased the alpha(1)-adrenergic response of the skeletal muscle alpha-actin promoter, whereas TEF-1 overexpression did not. Here, we identified the functional domains and specific sequences in RTEF-1 that mediate the alpha(1)-adrenergic response. Chimeric TEF-1 and RTEF-1 expression constructs localized the region responsible for the alpha(1)-adrenergic response to the carboxyl-terminal domain of RTEF-1. Site-directed mutagenesis was used to inactivate eight serine residues of RTEF-1, not present in TEF-1, that are putative targets of alpha(1)-adrenergic-dependent kinases. Mutation of a single serine residue, Ser-322, reduced the alpha(1)-adrenergic activation of RTEF-1 by 70% without affecting protein stability, suggesting that phosphorylation at this serine residue accounts for most of the alpha(1)-adrenergic response. Thus, these results demonstrate that RTEF-1 is a direct target of alpha(1)-adrenergic signaling in hypertrophied cardiac myocytes.

  1. Modulation of GH/IGF-1 axis: potential strategies to counteract sarcopenia in older adults.

    PubMed

    Giovannini, Silvia; Marzetti, Emanuele; Borst, Stephen E; Leeuwenburgh, Christiaan

    2008-10-01

    Aging is associated with progressive decline of skeletal muscle mass and function. This condition, termed sarcopenia, is associated with several adverse outcomes, including loss of autonomy and mortality. Due to the high prevalence of sarcopenia, a deeper understanding of its pathophysiology and possible remedies represents a high public health priority. Evidence suggests the existence of a relationship between declining growth hormone (GH) and insulin-like growth factor-1 (IGF-1) levels and age-related changes in body composition and physical function. Therefore, the age-dependent decline of GH and IGF-1 serum levels may promote frailty by contributing to the loss of muscle mass and strength. Preclinical studies showed that infusion of angiotensin II produced a marked reduction in body weight, accompanied by decreased serum and muscle levels of IGF-1. Conversely, overexpression of muscle-specific isoform of IGF-1 mitigates angiotensin II-induced muscle loss. Moreover, IGF-1 serum levels have been shown to increase following angiotensin converting enzyme inhibitors (ACEIs) treatment. Here we will review the most recent evidence regarding age-related changes of the GH/IGF-1 axis and its modulation by several interventions, including ACEIs which might represent a potential novel strategy to delay the onset and impede the progression of sarcopenia.

  2. BAIBA Does Not Regulate UCP-3 Expression in Human Skeletal Muscle as a Response to Aerobic Exercise.

    PubMed

    Morales, Flor E; Forsse, Jeffrey S; Andre, Thomas L; McKinley-Barnard, Sarah K; Hwang, Paul S; Anthony, Ian G; Tinsley, Grant M; Spillane, Mike; Grandjean, Peter W; Ramirez, Alejandro; Willoughby, Darryn S

    2017-01-01

    β-Aminoisobutyric acid (BAIBA) has shown to modulate uncoupling protein (UCP)-1 expression, which is mainly expressed in white adipose tissue; however, no studies to date have analyzed its potential effect on the main uncoupling protein of skeletal muscle, UCP-3. The main goal of this study was to assess the potential effect of acute aerobic exercise on serum BAIBA and skeletal muscle UCP-3. The secondary goal was to assess the potential involvement of the transcription factors proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) and peroxisome proliferator-activated receptor alpha (PPARα), as well as free fatty acids (FFAs) in UCP-3 expression. A tertiary goal of the study was to evaluate the potential effect of consuming a preexercise meal on the outcome of the first 2 objectives. In a randomized crossover design, untrained participants performed 2 acute cycling sessions (350 kcal at 70% of their VO 2peak ) after 2 experimental conditions: (1) consumption of a multi-macronutrient shake and (2) a fasting period of 8 hours. Blood samples were taken at baseline, preexercise, postexercise, 1 hour, and 4 hours postexercise, and muscle biopsies were taken at the last 4 time points. UCP-3 protein concentration and expression, as well as the mRNA expression of PGC-1α and PPARα, were measured in muscle, and BAIBA, glucose, and FFA were measured in serum. Aerobic exercise failed to induce a significant effect on serum BAIBA, PGC-1α, and PPARα regardless on the feeding condition. Despite the lack of effect of exercise on the previous variables, UCP-3 expression and protein concentration significantly increased in the shake condition. The expression of human skeletal muscle UCP-3 as a result of exercise might be controlled by factors other than BAIBA.

  3. Regulatory circuitry of TWEAK-Fn14 system and PGC-1α in skeletal muscle atrophy program

    PubMed Central

    Hindi, Sajedah M.; Mishra, Vivek; Bhatnagar, Shephali; Tajrishi, Marjan M.; Ogura, Yuji; Yan, Zhen; Burkly, Linda C.; Zheng, Timothy S.; Kumar, Ashok

    2014-01-01

    Skeletal muscle wasting attributed to inactivity has significant adverse functional consequences. Accumulating evidence suggests that peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) and TNF-like weak inducer of apoptosis (TWEAK)-Fn14 system are key regulators of skeletal muscle mass in various catabolic states. While the activation of TWEAK-Fn14 signaling causes muscle wasting, PGC-1α preserves muscle mass in several conditions, including functional denervation and aging. However, it remains unknown whether there is any regulatory interaction between PGC-1α and TWEAK-Fn14 system during muscle atrophy. Here we demonstrate that TWEAK significantly reduces the levels of PGC-1α and mitochondrial content (∼50%) in skeletal muscle. Levels of PGC-1α are significantly increased in skeletal muscle of TWEAK-knockout (KO) and Fn14-KO mice compared to wild-type mice on denervation. Transgenic (Tg) overexpression of PGC-1α inhibited progressive muscle wasting in TWEAK-Tg mice. PGC-1α inhibited the TWEAK-induced activation of NF-κB (∼50%) and dramatically reduced (∼90%) the expression of atrogenes such as MAFbx and MuRF1. Intriguingly, muscle-specific overexpression of PGC-1α also prevented the inducible expression of Fn14 in denervated skeletal muscle. Collectively, our study demonstrates that TWEAK induces muscle atrophy through repressing the levels of PGC-1α. Overexpression of PGC-1α not only blocks the TWEAK-induced atrophy program but also diminishes the expression of Fn14 in denervated skeletal muscle.—Hindi, S. M., Mishra, V., Bhatnagar, S., Tajrishi, M. M., Ogura, Y., Yan, Z., Burkly, L. C., Zheng, T. S., Kumar, A. Regulatory circuitry of TWEAK-Fn14 system and PGC-1α in skeletal muscle atrophy program. PMID:24327607

  4. Glucagon-like peptide-1 binding to rat skeletal muscle.

    PubMed

    Delgado, E; Luque, M A; Alcántara, A; Trapote, M A; Clemente, F; Galera, C; Valverde, I; Villanueva-Peñacarrillo, M L

    1995-01-01

    We have found [125I]glucagon-like peptide-1(7-36)-amide-specific binding activity in rat skeletal muscle plasma membranes, with an estimated M(r) of 63,000 by cross-linking and SDS-PAGE. The specific binding was time and membrane protein concentration dependent, and displaceable by unlabeled GLP-1(7-36)-amide with an ID50 of 3 x 10(-9) M of the peptide; GLP-1(1-36)-amide also competed, whereas glucagon and insulin did not. GLP-1(7-36)-amide did not modify the basal adenylate cyclase activity in skeletal muscle plasma membranes. These data, together with our previous finding of a potent glycogenic effect of GLP-1(7-36)-amide in rat soleus muscle, and also in isolated hepatocytes, which was not accompanied by a rise in the cell cyclic AMP content, lead use to believe that the insulin-like effects of this peptide on glucose metabolism in the muscle could be mediated by a type of receptor somehow different to that described for GLP-1 in pancreatic B cells, where GLP-1 action is mediated by the cyclic AMP-adenylate cyclase system.

  5. O-GlcNAcase deficiency suppresses skeletal myogenesis and insulin sensitivity in mice through the modulation of mitochondrial homeostasis.

    PubMed

    Wang, Xun; Feng, Zhihui; Wang, Xueqiang; Yang, Liang; Han, Shujun; Cao, Ke; Xu, Jie; Zhao, Lin; Zhang, Yong; Liu, Jiankang

    2016-06-01

    O-GlcNAcylation is implicated in modulating mitochondrial function, which is closely involved in regulating muscle metabolism. The presence of O-GlcNAcase (OGA), the enzyme involved in the removal of O-GlcNAc, in mitochondria was recently confirmed in rats. In the present study, we investigated the regulation of myogenesis and muscle insulin sensitivity to OGA in mice, with a focus on mitochondria. C57BL/6J mice fed a high-fat diet for 4 months were used to observe mitochondrial density, activity and O-GlcNAcylation in muscle. Small interfering RNA and overexpression vectors were used to modulate protein content in vitro. High-fat feeding decreased the OGA level and largely increased mitochondrial O-GlcNAcylation in mouse skeletal muscle that was accompanied by decreased levels of peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), decreased mitochondrial density and disrupted mitochondrial complex activities. Knockdown of OGA in C2C12 myoblasts promoted PGC-1α degradation, resulting in the suppression of mitochondrial biogenesis and myogenesis, whereas neither knockdown of O-GlcNAc transferase nor overexpression of OGA had significant effects on myogenesis. Mitochondrial dysfunction as evidenced by decreased ATP content and increased reactive oxygen species production, and increased lipid and protein oxidation was observed in both myoblasts and myotubes after OGA knockdown. Meanwhile, elevated O-GlcNAcylation through either OGA knockdown or treatment with the OGA inhibitor PUGNAc and the O-GlcNAc transferase substrate D-GlcNAc suppressed myotube insulin signalling transduction and glucose uptake. OGA overexpression had no significant effect on insulin sensitivity but sufficiently improved the insulin resistance induced by D-GlcNAc treatment. These data suggest that OGA can modulate mitochondrial density via PGC-1α and mitochondrial function via protein O-GlcNAcylation. In this manner, OGA appears to play a key role in myogenesis and the

  6. Regulation of skeletal muscle capillary growth in exercise and disease.

    PubMed

    Haas, Tara L; Nwadozi, Emmanuel

    2015-12-01

    Capillaries, which are the smallest and most abundant type of blood vessel, form the primary site of gas, nutrient, and waste transfer between the vascular and tissue compartments. Skeletal muscle exhibits the capacity to generate new capillaries (angiogenesis) as an adaptation to exercise training, thus ensuring that the heightened metabolic demand of the active muscle is matched by an improved capacity for distribution of gases, nutrients, and waste products. This review summarizes the current understanding of the regulation of skeletal muscle capillary growth. The multi-step process of angiogenesis is coordinated through the integration of a diverse array of signals associated with hypoxic, metabolic, hemodynamic, and mechanical stresses within the active muscle. The contributions of metabolic and mechanical factors to the modulation of key pro- and anti-angiogenic molecules are discussed within the context of responses to a single aerobic exercise bout and short-term and long-term training. Finally, the paradoxical lack of angiogenesis in peripheral artery disease and diabetes and the implications for disease progression and muscle health are discussed. Future studies that emphasize an integrated analysis of the mechanisms that control skeletal muscle capillary growth will enable development of targeted exercise programs that effectively promote angiogenesis in healthy individuals and in patient populations.

  7. Modulation of transcription factors by curcumin.

    PubMed

    Shishodia, Shishir; Singh, Tulika; Chaturvedi, Madan M

    2007-01-01

    Curcumin is the active ingredient of turmeric that has been consumed as a dietary spice for ages. Turmeric is widely used in traditional Indian medicine to cure biliary disorders, anorexia, cough, diabetic wounds, hepatic disorders, rheumatism, and sinusitis. Extensive investigation over the last five decades has indicated that curcumin reduces blood cholesterol, prevents low-density lipoprotein oxidation, inhibits platelet aggregation, suppresses thrombosis and myocardial infarction, suppresses symptoms associated with type II diabetes, rheumatoid arthritis, multiple sclerosis, and Alzheimer's disease, inhibits HIV replication, enhances wound healing, protects from liver injury, increases bile secretion, protects from cataract formation, and protects from pulmonary toxicity and fibrosis. Evidence indicates that the divergent effects of curcumin are dependent on its pleiotropic molecular effects. These include the regulation of signal transduction pathways and direct modulation of several enzymatic activities. Most of these signaling cascades lead to the activation of transcription factors. Curcumin has been found to modulate the activity of several key transcription factors and, in turn, the cellular expression profiles. Curcumin has been shown to elicit vital cellular responses such as cell cycle arrest, apoptosis, and differentiation by activating a cascade of molecular events. In this chapter, we briefly review the effects of curcumin on transcription factors NF-KB, AP-1, Egr-1, STATs, PPAR-gamma, beta-catenin, nrf2, EpRE, p53, CBP, and androgen receptor (AR) and AR-related cofactors giving major emphasis to the molecular mechanisms of its action.

  8. Inhibition of platelet-derived growth factor signaling prevents muscle fiber growth during skeletal muscle hypertrophy.

    PubMed

    Sugg, Kristoffer B; Korn, Michael A; Sarver, Dylan C; Markworth, James F; Mendias, Christopher L

    2017-03-01

    The platelet-derived growth factor receptors alpha and beta (PDGFRα and PDGFRβ) mark fibroadipogenic progenitor cells/fibroblasts and pericytes in skeletal muscle, respectively. While the role that these cells play in muscle growth and development has been evaluated, it was not known whether the PDGF receptors activate signaling pathways that control transcriptional and functional changes during skeletal muscle hypertrophy. To evaluate this, we inhibited PDGFR signaling in mice subjected to a synergist ablation muscle growth procedure, and performed analyses 3 and 10 days after induction of hypertrophy. The results from this study indicate that PDGF signaling is required for fiber hypertrophy, extracellular matrix production, and angiogenesis that occur during muscle growth. © 2017 Federation of European Biochemical Societies.

  9. 1α,25 dihydroxi-vitamin D{sub 3} modulates CDK4 and CDK6 expression and localization

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Irazoqui, Ana P.; Heim, Nadia B.; Boland, Ricardo L.

    We recently reported that the vitamin D receptor (VDR) and p38 MAPK participate in pro-differentiation events triggered by 1α,25(OH){sub 2}-vitamin D{sub 3} [1,25D] in skeletal muscle cells. Specifically, our studies demonstrated that 1,25D promotes G0/G1 arrest of cells inducing cyclin D3 and cyclin dependent kinases inhibitors (CKIs) p21{sup Waf1/Cip1} and p27{sup Kip1} expression in a VDR and p38 MAPK dependent manner. In this work we present data indicating that cyclin-dependent kinases (CDKs) 4 and 6 also play a role in the mechanism by which 1,25D stimulates myogenesis. To investigate VDR involvement in hormone regulation of CDKs 4 and 6, wemore » significantly reduced its expression by the use of a shRNA against mouse VDR, generating the skeletal muscle cell line C2C12-VDR. Investigation of changes in cellular cycle regulating proteins by immunoblotting showed that the VDR is involved in the 1,25D –induced CDKs 4 and 6 protein levels at 6 h of hormone treatment. CDK4 levels remains high during S phase peak and G0/G1 arrest while CDK6 expression decreases at 12 h and increases again al 24 h. The up-regulation of CDKs 4 and 6 by 1,25D (6 h) was abolished in C2C12 cells pre-treated with the ERK1/2 inhibitor, UO126. Moreover, CDKs 4 and 6 expression induced by the hormone nor was detected when α and β isoforms of p38 MAPK were inhibited by compound SB203580. Confocal images show that there is not co-localization between VDR and CDKs at 6 h of hormone treatment, however CDK4 and VDR co-localizates in nucleus after 12 h of 1,25D exposure. Of relevance, at this time 1,25D promotes CDK6 localization in a peri-nuclear ring. Our data demonstrate that the VDR, ERK1/2 and p38 MAPK are involved in the control of CDKs 4 and 6 by 1,25D in skeletal muscle cells sustaining the operation of a VDR and MAPKs –dependent mechanism in hormone modulation of myogenesis. - Highlights: • 1,25D modulates CDKs 4 and 6 expression in skeletal muscle cells. • CDK4 co

  10. Regulatory circuitry of TWEAK-Fn14 system and PGC-1α in skeletal muscle atrophy program.

    PubMed

    Hindi, Sajedah M; Mishra, Vivek; Bhatnagar, Shephali; Tajrishi, Marjan M; Ogura, Yuji; Yan, Zhen; Burkly, Linda C; Zheng, Timothy S; Kumar, Ashok

    2014-03-01

    Skeletal muscle wasting attributed to inactivity has significant adverse functional consequences. Accumulating evidence suggests that peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) and TNF-like weak inducer of apoptosis (TWEAK)-Fn14 system are key regulators of skeletal muscle mass in various catabolic states. While the activation of TWEAK-Fn14 signaling causes muscle wasting, PGC-1α preserves muscle mass in several conditions, including functional denervation and aging. However, it remains unknown whether there is any regulatory interaction between PGC-1α and TWEAK-Fn14 system during muscle atrophy. Here we demonstrate that TWEAK significantly reduces the levels of PGC-1α and mitochondrial content (∼50%) in skeletal muscle. Levels of PGC-1α are significantly increased in skeletal muscle of TWEAK-knockout (KO) and Fn14-KO mice compared to wild-type mice on denervation. Transgenic (Tg) overexpression of PGC-1α inhibited progressive muscle wasting in TWEAK-Tg mice. PGC-1α inhibited the TWEAK-induced activation of NF-κB (∼50%) and dramatically reduced (∼90%) the expression of atrogenes such as MAFbx and MuRF1. Intriguingly, muscle-specific overexpression of PGC-1α also prevented the inducible expression of Fn14 in denervated skeletal muscle. Collectively, our study demonstrates that TWEAK induces muscle atrophy through repressing the levels of PGC-1α. Overexpression of PGC-1α not only blocks the TWEAK-induced atrophy program but also diminishes the expression of Fn14 in denervated skeletal muscle.

  11. Role of TRPC1 channel in skeletal muscle function

    PubMed Central

    Zanou, Nadège; Shapovalov, Georges; Louis, Magali; Tajeddine, Nicolas; Gallo, Chiara; Van Schoor, Monique; Anguish, Isabelle; Cao, My Linh; Schakman, Olivier; Dietrich, Alexander; Lebacq, Jean; Ruegg, Urs; Roulet, Emmanuelle; Birnbaumer, Lutz

    2010-01-01

    Skeletal muscle contraction is reputed not to depend on extracellular Ca2+. Indeed, stricto sensu, excitation-contraction coupling does not necessitate entry of Ca2+. However, we previously observed that, during sustained activity (repeated contractions), entry of Ca2+ is needed to maintain force production. In the present study, we evaluated the possible involvement of the canonical transient receptor potential (TRPC)1 ion channel in this entry of Ca2+ and investigated its possible role in muscle function. Patch-clamp experiments reveal the presence of a small-conductance channel (13 pS) that is completely lost in adult fibers from TRPC1−/− mice. The influx of Ca2+ through TRPC1 channels represents a minor part of the entry of Ca2+ into muscle fibers at rest, and the activity of the channel is not store dependent. The lack of TRPC1 does not affect intracellular Ca2+ concentration ([Ca2+]i) transients reached during a single isometric contraction. However, the involvement of TRPC1-related Ca2+ entry is clearly emphasized in muscle fatigue. Indeed, muscles from TRPC1−/− mice stimulated repeatedly progressively display lower [Ca2+]i transients than those observed in TRPC1+/+ fibers, and they also present an accentuated progressive loss of force. Interestingly, muscles from TRPC1−/− mice display a smaller fiber cross-sectional area, generate less force per cross-sectional area, and contain less myofibrillar proteins than their controls. They do not present other signs of myopathy. In agreement with in vitro experiments, TRPC1−/− mice present an important decrease of endurance of physical activity. We conclude that TRPC1 ion channels modulate the entry of Ca2+ during repeated contractions and help muscles to maintain their force during sustained repeated contractions. PMID:19846750

  12. Serum IGF-1 is insufficient to restore skeletal size in the total absence of the growth hormone receptor

    PubMed Central

    Wu, Yingjie; Sun, Hui; Basta-Pljakic, Jelena; Cardoso, Luis; Kennedy, Oran D; Jasper, Hector; Domené, Horacio; Karabatas, Liliana; Guida, Clara; Schaffler, Mitchell B; Rosen, Clifford J; Yakar, Shoshana

    2013-01-01

    States of growth hormone (GH) resistance, such those observed in Laron’s dwarf patients, are characterized by mutations in the GH receptor (GHR), decreased serum and tissue IGF-1 levels, impaired glucose tolerance, and impaired skeletal acquisition. IGF-1 replacement therapy in such patients increases growth velocity but does not normalize growth. Herein we combined the GH-resistant (GHR knockout, GHRKO) mouse model with mice expressing the hepatic Igf-1 transgene (HIT) to generate the GHRKO-HIT mouse model. In GHRKOHIT mice, serum IGF-1 levels were restored via transgenic expression of Igf-1 allowing us to study how endocrine IGF-1 affects growth, metabolic homeostasis, and skeletal integrity. We show that in a GH-resistant state, normalization of serum IGF-1 improved body adiposity and restored glucose tolerance but was insufficient to support normal skeletal growth, resulting in an osteopenic skeletal phenotype. The inability of serum IGF-1 to restore skeletal integrity in the total absence of GHR likely resulted from reduced skeletal Igf-1 gene expression, blunted GH-mediated effects on the skeleton that are independent of serum or tissue IGF-1, and from poor delivery of IGF-1 to the tissues. These findings are consistent with clinical data showing that IGF-I replacement therapy in patients with Laron’s syndrome does not achieve full skeletal growth. PMID:23456957

  13. ATF4 mediation of NF1 functions in osteoblast reveals a nutritional basis for congenital skeletal dysplasiae.

    PubMed

    Elefteriou, Florent; Benson, M Douglas; Sowa, Hideaki; Starbuck, Michael; Liu, Xiuyun; Ron, David; Parada, Luis F; Karsenty, Gerard

    2006-12-01

    The transcription factor ATF4 enhances bone formation by favoring amino acid import and collagen synthesis in osteoblasts, a function requiring its phosphorylation by RSK2, the kinase inactivated in Coffin-Lowry Syndrome. Here, we show that in contrast, RSK2 activity, ATF4-dependent collagen synthesis, and bone formation are increased in mice lacking neurofibromin in osteoblasts (Nf1(ob)(-/-) mice). Independently of RSK2, ATF4 phosphorylation by PKA is enhanced in Nf1(ob)(-/-) mice, thereby increasing Rankl expression, osteoclast differentiation, and bone resorption. In agreement with ATF4 function in amino acid transport, a low-protein diet decreased bone protein synthesis and normalized bone formation and bone mass in Nf1(ob)(-/-) mice without affecting other organ weight, while a high-protein diet overcame Atf4(-/-) and Rsk2(-/-) mice developmental defects, perinatal lethality, and low bone mass. By showing that ATF4-dependent skeletal dysplasiae are treatable by dietary manipulations, this study reveals a molecular connection between nutrition and skeletal development.

  14. The β1a Subunit of the Skeletal DHPR Binds to Skeletal RyR1 and Activates the Channel via Its 35-Residue C-Terminal Tail

    PubMed Central

    Rebbeck, Robyn T.; Karunasekara, Yamuna; Gallant, Esther M.; Board, Philip G.; Beard, Nicole A.; Casarotto, Marco G.; Dulhunty, Angela F.

    2011-01-01

    Although it has been suggested that the C-terminal tail of the β1a subunit of the skeletal dihyropyridine receptor (DHPR) may contribute to voltage-activated Ca2+ release in skeletal muscle by interacting with the skeletal ryanodine receptor (RyR1), a direct functional interaction between the two proteins has not been demonstrated previously. Such an interaction is reported here. A peptide with the sequence of the C-terminal 35 residues of β1a bound to RyR1 in affinity chromatography. The full-length β1a subunit and the C-terminal peptide increased [3H]ryanodine binding and RyR1 channel activity with an AC50 of 450–600 pM under optimal conditions. The effect of the peptide was dependent on cytoplasmic Ca2+, ATP, and Mg2+ concentrations. There was no effect of the peptide when channel activity was very low as a result of Mg2+ inhibition or addition of 100 nM Ca2+ (without ATP). Maximum increases were seen with 1–10 μM Ca2+, in the absence of Mg2+ inhibition. A control peptide with the C-terminal 35 residues in a scrambled sequence did not bind to RyR1 or alter [3H]ryanodine binding or channel activity. This high-affinity in vitro functional interaction between the C-terminal 35 residues of the DHPR β1a subunit and RyR1 may support an in vivo function of β1a during voltage-activated Ca2+ release. PMID:21320436

  15. Combination of small RNAs for skeletal muscle regeneration.

    PubMed

    Kim, NaJung; Yoo, James J; Atala, Anthony; Lee, Sang Jin

    2016-03-01

    Selectively controlling the expression of the target genes through RNA interference (RNAi) has significant therapeutic potential for injuries or diseases of tissues. We used this strategy to accelerate and enhance skeletal muscle regeneration for the treatment of muscular atrophy. In this study, we used myostatin small interfering (si)RNA (siGDF-8), a major inhibitory factor in the development and postnatal regeneration of skeletal muscle and muscle-specific microRNAs (miR-1 and -206) to further accelerate muscle regeneration. This combination of 3 small RNAs significantly improved the gene expression of myogenic regulatory factors in vitro, suggesting myogenic activation. Moreover, cell proliferation and myotube formation improved without compromising each other, which indicates the myogenic potential of this combination of small RNAs. The recovery of chemically injured tibialis anterior muscles in rats was significantly accelerated, both functionally and structurally. This novel combination of siRNA and miRNAs has promising therapeutic potential to improve in situ skeletal muscle regeneration. © FASEB.

  16. Uric acid and transforming growth factor in fructose-induced production of reactive oxygen species in skeletal muscle.

    PubMed

    Madlala, Hlengiwe P; Maarman, Gerald J; Ojuka, Edward

    2016-04-01

    The consumption of fructose, a major constituent of the modern diet, has raised increasing concern about the effects of fructose on health. Research suggests that excessive intake of fructose (>50 g/d) causes hyperuricemia, insulin resistance, mitochondrial dysfunction, de novo lipogenesis by the liver, and increased production of reactive oxygen species (ROS) in muscle. In a number of tissues, uric acid has been shown to stimulate the production of ROS via activation of transforming growth factor β1 and NADPH (nicotinamide adenine dinucleotide phosphate) oxidase 4. The role of uric acid in fructose-induced production of ROS in skeletal muscle, however, has not been investigated. This review examines the evidence for fructose-induced production of ROS in skeletal muscle, highlights proposed mechanisms, and identifies gaps in current knowledge. © The Author(s) 2016. Published by Oxford University Press on behalf of the International Life Sciences Institute. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  17. Fatigue mechanisms in patients with cancer: effects of tumor necrosis factor and exercise on skeletal muscle

    NASA Technical Reports Server (NTRS)

    St Pierre, B. A.; Kasper, C. E.; Lindsey, A. M.

    1992-01-01

    Fatigue is a common adverse effect of cancer and its therapy. However, the specific mechanisms underlying cancer fatigue are unclear. One physiologic mechanism may involve changes in skeletal muscle protein stores or metabolite concentration. A reduction in skeletal muscle protein stores may result from endogenous tumor necrosis factor (TNF) or from TNF administered as antineoplastic therapy. This muscle wasting would require patients to exert an unusually high amount of effort to generate adequate contractile force during exercise performance or during extended periods of sitting or standing. This additional effort could result in the onset of fatigue. Additionally, cancer fatigue may develop or become exacerbated during exercise as a consequence of changes in the concentration of skeletal muscle metabolites. These biochemical alterations may interfere with force that is produced by the muscle contractile proteins. These physiologic changes may play a role in the decision to include exercise in the rehabilitation plans of patients with cancer. They also may affect ideas about fatigue.

  18. Mesenchymal stem cells and myoblast differentiation under HGF and IGF-1 stimulation for 3D skeletal muscle tissue engineering.

    PubMed

    Witt, R; Weigand, A; Boos, A M; Cai, A; Dippold, D; Boccaccini, A R; Schubert, D W; Hardt, M; Lange, C; Arkudas, A; Horch, R E; Beier, J P

    2017-02-28

    Volumetric muscle loss caused by trauma or after tumour surgery exceeds the natural regeneration capacity of skeletal muscle. Hence, the future goal of tissue engineering (TE) is the replacement and repair of lost muscle tissue by newly generating skeletal muscle combining different cell sources, such as myoblasts and mesenchymal stem cells (MSCs), within a three-dimensional matrix. Latest research showed that seeding skeletal muscle cells on aligned constructs enhance the formation of myotubes as well as cell alignment and may provide a further step towards the clinical application of engineered skeletal muscle. In this study the myogenic differentiation potential of MSCs upon co-cultivation with myoblasts and under stimulation with hepatocyte growth factor (HGF) and insulin-like growth factor-1 (IGF-1) was evaluated. We further analysed the behaviour of MSC-myoblast co-cultures in different 3D matrices. Primary rat myoblasts and rat MSCs were mono- and co-cultivated for 2, 7 or 14 days. The effect of different concentrations of HGF and IGF-1 alone, as well as in combination, on myogenic differentiation was analysed using microscopy, multicolour flow cytometry and real-time PCR. Furthermore, the influence of different three-dimensional culture models, such as fibrin, fibrin-collagen-I gels and parallel aligned electrospun poly-ε-caprolacton collagen-I nanofibers, on myogenic differentiation was analysed. MSCs could be successfully differentiated into the myogenic lineage both in mono- and in co-cultures independent of HGF and IGF-1 stimulation by expressing desmin, myocyte enhancer factor 2, myosin heavy chain 2 and alpha-sarcomeric actinin. An increased expression of different myogenic key markers could be observed under HGF and IGF-1 stimulation. Even though, stimulation with HGF/IGF-1 does not seem essential for sufficient myogenic differentiation. Three-dimensional cultivation in fibrin-collagen-I gels induced higher levels of myogenic differentiation

  19. Mitochondrial and performance adaptations to exercise training in mice lacking skeletal muscle LKB1

    PubMed Central

    Tanner, Colby B.; Madsen, Steven R.; Hallowell, David M.; Goring, Darren M. J.; Moore, Timothy M.; Hardman, Shalene E.; Heninger, Megan R.; Atwood, Daniel R.

    2013-01-01

    LKB1 and its downstream targets of the AMP-activated protein kinase family are important regulators of many aspects of skeletal muscle cell function, including control of mitochondrial content and capillarity. LKB1 deficiency in skeletal and cardiac muscle (mLKB1-KO) greatly impairs exercise capacity. However, cardiac dysfunction in that genetic model prevents a clear assessment of the role of skeletal muscle LKB1 in the observed effects. Our purposes here were to determine whether skeletal muscle-specific knockout of LKB1 (skmLKB1-KO) decreases exercise capacity and mitochondrial protein content, impairs accretion of mitochondrial proteins after exercise training, and attenuates improvement in running performance after exercise training. We found that treadmill and voluntary wheel running capacity was reduced in skmLKB1-KO vs. control (CON) mice. Citrate synthase activity, succinate dehydrogenase activity, and pyruvate dehydrogenase kinase content were lower in KO vs. CON muscles. Three weeks of treadmill training resulted in significantly increased treadmill running performance in both CON and skmLKB1-KO mice. Citrate synthase activity increased significantly with training in both genotypes, but protein content and activity for components of the mitochondrial electron transport chain increased only in CON mice. Capillarity and VEGF protein was lower in skmLKB1-KO vs. CON muscles, but VEGF increased with training only in skmLKB1-KO. Three hours after an acute bout of muscle contractions, PGC-1α, cytochrome c, and VEGF gene expression all increased in CON but not skmLKB1-KO muscles. Our findings indicate that skeletal muscle LKB1 is required for accretion of some mitochondrial proteins but not for early exercise capacity improvements with exercise training. PMID:23982155

  20. Skeletal effects of carcinoma of the breast and prostate.

    PubMed Central

    Percival, R. C.

    1986-01-01

    Recent research has led to improved understanding of the pathology of skeletal metastases in carcinoma of the breast and prostate. Several humoral mechanisms have been identified which have both primary and secondary consequences on skeletal metabolism and probably depend on the complex interplay of a number of factors derived from tumour tissues. An improved understanding of these interactions may lead to new approaches in the management of these common disorders. Images Fig. 1 PMID:3789624

  1. Creatine Supplementation and Skeletal Muscle Metabolism for Building Muscle Mass- Review of the Potential Mechanisms of Action.

    PubMed

    Farshidfar, Farnaz; Pinder, Mark A; Myrie, Semone B

    2017-01-01

    Creatine, a very popular supplement among athletic populations, is of growing interest for clinical applications. Since over 90% of creatine is stored in skeletal muscle, the effect of creatine supplementation on muscle metabolism is a widely studied area. While numerous studies over the past few decades have shown that creatine supplementation has many favorable effects on skeletal muscle physiology and metabolism, including enhancing muscle mass (growth/hypertrophy); the underlying mechanisms are poorly understood. This report reviews studies addressing the mechanisms of action of creatine supplementation on skeletal muscle growth/hypertrophy. Early research proposed that the osmotic effect of creatine supplementation serves as a cellular stressor (osmosensing) that acts as an anabolic stimulus for protein synthesis signal pathways. Other reports indicated that creatine directly affects muscle protein synthesis via modulations of components in the mammalian target of rapamycin (mTOR) pathway. Creatine may also directly affect the myogenic process (formation of muscle tissue), by altering secretions of myokines, such as myostatin and insulin-like growth factor-1, and expressions of myogenic regulatory factors, resulting in enhanced satellite cells mitotic activities and differentiation into myofiber. Overall, there is still no clear understanding of the mechanisms of action regarding how creatine affects muscle mass/growth, but current evidence suggests it may exert its effects through multiple approaches, with converging impacts on protein synthesis and myogenesis. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

  2. Skeletal Muscle Function during Exercise—Fine-Tuning of Diverse Subsystems by Nitric Oxide

    PubMed Central

    Suhr, Frank; Gehlert, Sebastian; Grau, Marijke; Bloch, Wilhelm

    2013-01-01

    Skeletal muscle is responsible for altered acute and chronic workload as induced by exercise. Skeletal muscle adaptations range from immediate change of contractility to structural adaptation to adjust the demanded performance capacities. These processes are regulated by mechanically and metabolically induced signaling pathways, which are more or less involved in all of these regulations. Nitric oxide is one of the central signaling molecules involved in functional and structural adaption in different cell types. It is mainly produced by nitric oxide synthases (NOS) and by non-enzymatic pathways also in skeletal muscle. The relevance of a NOS-dependent NO signaling in skeletal muscle is underlined by the differential subcellular expression of NOS1, NOS2, and NOS3, and the alteration of NO production provoked by changes of workload. In skeletal muscle, a variety of highly relevant tasks to maintain skeletal muscle integrity and proper signaling mechanisms during adaptation processes towards mechanical and metabolic stimulations are taken over by NO signaling. The NO signaling can be mediated by cGMP-dependent and -independent signaling, such as S-nitrosylation-dependent modulation of effector molecules involved in contractile and metabolic adaptation to exercise. In this review, we describe the most recent findings of NO signaling in skeletal muscle with a special emphasis on exercise conditions. However, to gain a more detailed understanding of the complex role of NO signaling for functional adaptation of skeletal muscle (during exercise), additional sophisticated studies are needed to provide deeper insights into NO-mediated signaling and the role of non-enzymatic-derived NO in skeletal muscle physiology. PMID:23538841

  3. DMP-1-mediated Ghr gene recombination compromises skeletal development and impairs skeletal response to intermittent PTH.

    PubMed

    Liu, Zhongbo; Kennedy, Oran D; Cardoso, Luis; Basta-Pljakic, Jelena; Partridge, Nicola C; Schaffler, Mitchell B; Rosen, Clifford J; Yakar, Shoshana

    2016-02-01

    Bone minerals are acquired during growth and are key determinants of adult skeletal health. During puberty, the serum levels of growth hormone (GH) and its downstream effector IGF-1 increase and play critical roles in bone acquisition. The goal of the current study was to determine how bone cells integrate signals from the GH/IGF-1 to enhance skeletal mineralization and strength during pubertal growth. Osteocytes, the most abundant bone cells, were shown to orchestrate bone modeling during growth. We used dentin matrix protein (Dmp)-1-mediated Ghr knockout (DMP-GHRKO) mice to address the role of the GH/IGF axis in osteocytes. We found that DMP-GHRKO did not affect linear growth but compromised overall bone accrual. DMP-GHRKO mice exhibited reduced serum inorganic phosphate and parathyroid hormone (PTH) levels and decreased bone formation indices and were associated with an impaired response to intermittent PTH treatment. Using an osteocyte-like cell line along with in vivo studies, we found that PTH sensitized the response of bone to GH by increasing Janus kinase-2 and IGF-1R protein levels. We concluded that endogenously secreted PTH and GHR signaling in bone are necessary to establish radial bone growth and optimize mineral acquisition during growth. © FASEB.

  4. Pigment epithelium-derived factor stimulates skeletal muscle glycolytic activity through NADPH oxidase-dependent reactive oxygen species production.

    PubMed

    Carnagarin, Revathy; Carlessi, Rodrigo; Newsholme, Philip; Dharmarajan, Arun M; Dass, Crispin R

    2016-09-01

    Pigment epithelium-derived factor is a multifunctional serpin implicated in insulin resistance in metabolic disorders. Recent evidence suggests that exposure of peripheral tissues such as skeletal muscle to PEDF has profound metabolic consequences with predisposition towards chronic conditions such as obesity, type 2 diabetes, metabolic syndrome and polycystic ovarian syndrome. Chronic inflammation shifts muscle metabolism towards increased glycolysis and decreased oxidative metabolism. In the present study, we demonstrate a novel effect of PEDF on cellular metabolism in mouse cell line (C2C12) and human primary skeletal muscle cells. PEDF addition to skeletal muscle cells induced enhanced phospholipase A2 activity. This was accompanied with increased production of reactive oxygen species in a nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-dependent manner that triggered a shift towards a more glycolytic phenotype. Extracellular flux analysis and glucose consumption assays demonstrated that PEDF treatment resulted in enhanced glycolysis but did not change mitochondrial respiration. Our results demonstrate that skeletal muscle cells express a PEDF-inducible oxidant generating system that enhances glycolysis but is sensitive to antioxidants and NADPH oxidase inhibition. Copyright © 2016 Elsevier Ltd. All rights reserved.

  5. PGC-1α and exercise intensity dependent adaptations in mouse skeletal muscle

    PubMed Central

    Dethlefsen, Maja Munk; Bangsbo, Jens; Pilegaard, Henriette

    2017-01-01

    The aim of the present study was to examine the role of PGC-1α in intensity dependent exercise and exercise training-induced metabolic adaptations in mouse skeletal muscle. Whole body PGC-1α knockout (KO) and littermate wildtype (WT) mice performed a single treadmill running bout at either low intensity (LI) for 40 min or moderate intensity (MI) for 20 min. Blood and quadriceps muscles were removed either immediately after exercise or at 3h or 6h into recovery from exercise and from resting controls. In addition PGC-1α KO and littermate WT mice were exercise trained at either low intensity (LIT) for 40 min or at moderate intensity (MIT) for 20 min 2 times pr. day for 5 weeks. In the first and the last week of the intervention period, mice performed a graded running endurance test. Quadriceps muscles were removed before and after the training period for analyses. The acute exercise bout elicited intensity dependent increases in LC3I and LC3II protein and intensity independent decrease in p62 protein in skeletal muscle late in recovery and increased LC3II with exercise training independent of exercise intensity and volume in WT mice. Furthermore, acute exercise and exercise training did not increase LC3I and LC3II protein in PGC-1α KO. In addition, exercise-induced mRNA responses of PGC-1α isoforms were intensity dependent. In conclusion, these findings indicate that exercise intensity affected autophagy markers differently in skeletal muscle and suggest that PGC-1α regulates both acute and exercise training-induced autophagy in skeletal muscle potentially in a PGC-1α isoform specific manner. PMID:29049322

  6. Cerium oxide nanozyme modulate the ‘exercise’ redox biology of skeletal muscle

    NASA Astrophysics Data System (ADS)

    Arya, Aditya; Sethy, Niroj Kumar; Gangwar, Anamika; Bhargava, Neelima; Dubey, Amarish; Roy, Manas; Srivastava, Gaurav; Singh, Sushil Kumar; Das, Mainak; Bhargava, Kalpana

    2017-05-01

    ‘Exercise’ is a double-edged sword for the skeletal muscle. Small amount of ROS generated during mild exercise, is essential for normal force generation; whereas large quantity of ROS generated during intense exercise, may cause contractile dysfunction, resulting in muscle weakness and fatigue. One of the key question in skeletal muscle physiology is ‘could antioxidant therapy improve the skeletal muscle endurance? A question, which has resulted in contradictory experimental findings till this date. This work has addressed this ‘very question’ using a synthetic, inorganic, antioxidant nano-material viz., ‘cerium oxide nanozyme’ (CON). It has been introduced in the rat by intramuscular injection, and the skeletal muscle endurance has been evaluated. Intramuscular injections of CON, concurrent with exercise, enhanced muscle mass, glycogen and ATP content, type I fiber ratio, thus resulting in significantly higher muscle endurance. Electron microscope studies confirmed the presence of CON in the vicinity of muscle mitochondria. There was an increase in the number and size of the muscle mitochondria in the CON treated muscle, following exercise, as compared to the untreated group with only exercised muscle. Quantitative proteomics data and subsequent biological network analysis studies, identified higher levels of oxidative phosphorylation, TCA cycle output and glycolysis in CON supplemented exercised muscle over only exercised muscle. This was further associated with significant increase in the mitochondrial respiratory capacity and muscle contraction, primarily due to higher levels of electron transport chain proteins like NDUFA9, SDHA, ATP5B and ATP5D, which were validated by real-time PCR and western blotting. Along with this, persistence of CON in muscle was evaluated with ICP-MS analysis, which revealed clearance of the particles after 90 d, without exhibiting any inflammation or adverse affects on the health of the experimental animals. Thus a

  7. 11β-Hydroxysteroid Dehydrogenase Type 1 Regulates Glucocorticoid-Induced Insulin Resistance in Skeletal Muscle

    PubMed Central

    Morgan, Stuart A.; Sherlock, Mark; Gathercole, Laura L.; Lavery, Gareth G.; Lenaghan, Carol; Bujalska, Iwona J.; Laber, David; Yu, Alice; Convey, Gemma; Mayers, Rachel; Hegyi, Krisztina; Sethi, Jaswinder K.; Stewart, Paul M.; Smith, David M.; Tomlinson, Jeremy W.

    2009-01-01

    OBJECTIVE Glucocorticoid excess is characterized by increased adiposity, skeletal myopathy, and insulin resistance, but the precise molecular mechanisms are unknown. Within skeletal muscle, 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) converts cortisone (11-dehydrocorticosterone in rodents) to active cortisol (corticosterone in rodents). We aimed to determine the mechanisms underpinning glucocorticoid-induced insulin resistance in skeletal muscle and indentify how 11β-HSD1 inhibitors improve insulin sensitivity. RESEARCH DESIGN AND METHODS Rodent and human cell cultures, whole-tissue explants, and animal models were used to determine the impact of glucocorticoids and selective 11β-HSD1 inhibition upon insulin signaling and action. RESULTS Dexamethasone decreased insulin-stimulated glucose uptake, decreased IRS1 mRNA and protein expression, and increased inactivating pSer307 insulin receptor substrate (IRS)-1. 11β-HSD1 activity and expression were observed in human and rodent myotubes and muscle explants. Activity was predominantly oxo-reductase, generating active glucocorticoid. A1 (selective 11β-HSD1 inhibitor) abolished enzyme activity and blocked the increase in pSer307 IRS1 and reduction in total IRS1 protein after treatment with 11DHC but not corticosterone. In C57Bl6/J mice, the selective 11β-HSD1 inhibitor, A2, decreased fasting blood glucose levels and improved insulin sensitivity. In KK mice treated with A2, skeletal muscle pSer307 IRS1 decreased and pThr308 Akt/PKB increased. In addition, A2 decreased both lipogenic and lipolytic gene expression. CONCLUSIONS Prereceptor facilitation of glucocorticoid action via 11β-HSD1 increases pSer307 IRS1 and may be crucial in mediating insulin resistance in skeletal muscle. Selective 11β-HSD1 inhibition decreases pSer307 IRS1, increases pThr308 Akt/PKB, and decreases lipogenic and lipolytic gene expression that may represent an important mechanism underpinning their insulin-sensitizing action. PMID

  8. TERATOGENIC RESPONSES ARE MODULATED IN MICE LACKING EXPRESSION OF EPIDERMAL GROWTH FACTOR (EGF) AND TRANSFORMING GROWTH FACTOR-ALPHA (TGF)

    EPA Science Inventory

    TITLE:
    TERATOGENIC RESPONSES ARE MODULATED IN MICE LACKING EXPRESSION OF EPIDERMAL GROWTH FACTOR (EGF) AND TRANSFORMING GROWTH FACTOR-ALPHA (TGF). AUTHORS (ALL): Abbott, Barbara D.1; Best, Deborah S.1; Narotsky, Michael G.1. SPONSOR NAME: None INSTITUTIONS (ALL): 1. Repro Tox ...

  9. Muscle RANK is a key regulator of Ca2+ storage, SERCA activity, and function of fast-twitch skeletal muscles.

    PubMed

    Dufresne, Sébastien S; Dumont, Nicolas A; Boulanger-Piette, Antoine; Fajardo, Val A; Gamu, Daniel; Kake-Guena, Sandrine-Aurélie; David, Rares Ovidiu; Bouchard, Patrice; Lavergne, Éliane; Penninger, Josef M; Pape, Paul C; Tupling, A Russell; Frenette, Jérôme

    2016-04-15

    Receptor-activator of nuclear factor-κB (RANK), its ligand RANKL, and the soluble decoy receptor osteoprotegerin are the key regulators of osteoclast differentiation and bone remodeling. Here we show that RANK is also expressed in fully differentiated myotubes and skeletal muscle. Muscle RANK deletion has inotropic effects in denervated, but not in sham, extensor digitorum longus (EDL) muscles preventing the loss of maximum specific force while promoting muscle atrophy, fatigability, and increased proportion of fast-twitch fibers. In denervated EDL muscles, RANK deletion markedly increased stromal interaction molecule 1 content, a Ca(2+)sensor, and altered activity of the sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA) modulating Ca(2+)storage. Muscle RANK deletion had no significant effects on the sham or denervated slow-twitch soleus muscles. These data identify a novel role for RANK as a key regulator of Ca(2+)storage and SERCA activity, ultimately affecting denervated skeletal muscle function. Copyright © 2016 the American Physiological Society.

  10. Muscle RANK is a key regulator of Ca2+ storage, SERCA activity, and function of fast-twitch skeletal muscles

    PubMed Central

    Dufresne, Sébastien S.; Dumont, Nicolas A.; Boulanger-Piette, Antoine; Fajardo, Val A.; Gamu, Daniel; Kake-Guena, Sandrine-Aurélie; David, Rares Ovidiu; Bouchard, Patrice; Lavergne, Éliane; Penninger, Josef M.; Pape, Paul C.; Tupling, A. Russell

    2016-01-01

    Receptor-activator of nuclear factor-κB (RANK), its ligand RANKL, and the soluble decoy receptor osteoprotegerin are the key regulators of osteoclast differentiation and bone remodeling. Here we show that RANK is also expressed in fully differentiated myotubes and skeletal muscle. Muscle RANK deletion has inotropic effects in denervated, but not in sham, extensor digitorum longus (EDL) muscles preventing the loss of maximum specific force while promoting muscle atrophy, fatigability, and increased proportion of fast-twitch fibers. In denervated EDL muscles, RANK deletion markedly increased stromal interaction molecule 1 content, a Ca2+ sensor, and altered activity of the sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) modulating Ca2+ storage. Muscle RANK deletion had no significant effects on the sham or denervated slow-twitch soleus muscles. These data identify a novel role for RANK as a key regulator of Ca2+ storage and SERCA activity, ultimately affecting denervated skeletal muscle function. PMID:26825123

  11. Sumoylated α-skeletal muscle actin in the skeletal muscle of adult rats.

    PubMed

    Uda, Munehiro; Kawasaki, Hiroaki; Iizumi, Kyoichi; Shigenaga, Ayako; Baba, Takeshi; Naito, Hisashi; Yoshioka, Toshitada; Yamakura, Fumiyuki

    2015-11-01

    Skeletal muscles are composed of two major muscle fiber types: slow-twitch oxidative fibers and fast-twitch glycolytic fibers. The proteins in these muscle fibers are known to differ in their expression, relative abundance, and post-translational modifications. In this study, we report a previously unreported post-translational modification of α-skeletal muscle actin in the skeletal muscles of adult male F344 rats in vivo. Using two-dimensional electrophoresis (2D-PAGE), we first examined the differences in the protein expression profiles between the soleus and plantaris muscles. We found higher intensity protein spots at approximately 60 kDa and pH 9 on 2D-PAGE for the soleus muscle compared with the plantaris muscle. These spots were identified as α-skeletal muscle actin by liquid chromatography-nanoelectrospray ionization-tandem mass spectrometry and western blot analyses. In addition, we found that the 60 kDa α-skeletal muscle actin is modified by small ubiquitin-like modifier (SUMO) 1, using 2D-PAGE and western blot analyses. Furthermore, we found that α-skeletal muscle actin with larger molecular weight was localized in the nuclear and cytosol of the skeletal muscle, but not in the myofibrillar fraction by the combination of subcellular fractionation and western blot analyses. These results suggest that α-skeletal muscle actin is modified by SUMO-1 in the skeletal muscles, localized in nuclear and cytosolic fractions, and the extent of this modification is much higher in the slow muscles than in the fast muscles. This is the first study to show the presence of SUMOylated actin in animal tissues.

  12. Stretch-stimulated glucose transport in skeletal muscle is regulated by Rac1

    PubMed Central

    Sylow, Lykke; Møller, Lisbeth L V; Kleinert, Maximilian; Richter, Erik A; Jensen, Thomas E

    2015-01-01

    An alternative to the canonical insulin signalling pathway for glucose transport is muscle contraction/exercise. Mechanical stress is an integrated part of the muscle contraction/relaxation cycle, and passive stretch stimulates muscle glucose transport. However, the signalling mechanism regulating stretch-stimulated glucose transport is not well understood. We recently reported that the actin cytoskeleton regulating GTPase, Rac1, was activated in mouse muscle in response to stretching. Rac1 is a regulator of contraction- and insulin-stimulated glucose transport, however, its role in stretch-stimulated glucose transport and signalling is unknown. We therefore investigated whether stretch-induced glucose transport in skeletal muscle required Rac1 and the actin cytoskeleton. We used muscle-specific inducible Rac1 knockout mice as well as pharmacological inhibitors of Rac1 and the actin cytoskeleton in isolated soleus and extensor digitorum longus muscles. In addition, the role of Rac1 in contraction-stimulated glucose transport during conditions without mechanical load on the muscles was evaluated in loosely hanging muscles and muscles in which cross-bridge formation was blocked by the myosin ATPase inhibitors BTS and Blebbistatin. Knockout as well as pharmacological inhibition of Rac1 reduced stretch-stimulated glucose transport by 30–50% in soleus and extensor digitorum longus muscle. The actin depolymerizing agent latrunculin B similarly decreased glucose transport in response to stretching by 40–50%. Rac1 inhibition reduced contraction-stimulated glucose transport by 30–40% in tension developing muscle but did not affect contraction-stimulated glucose transport in muscles in which force development was prevented. Our findings suggest that Rac1 and the actin cytoskeleton regulate stretch-stimulated glucose transport and that Rac1 is a required part of the mechanical stress-component of the contraction-stimulus to glucose transport in skeletal muscle. Key

  13. Zinc stimulates glucose oxidation and glycemic control by modulating the insulin signaling pathway in human and mouse skeletal muscle cell lines.

    PubMed

    Norouzi, Shaghayegh; Adulcikas, John; Sohal, Sukhwinder Singh; Myers, Stephen

    2018-01-01

    Zinc is a metal ion that is an essential cell signaling molecule. Highlighting this, zinc is an insulin mimetic, activating cellular pathways that regulate cellular homeostasis and physiological responses. Previous studies have linked dysfunctional zinc signaling with several disease states including cancer, obesity, cardiovascular disease and type 2 diabetes. The present study evaluated the insulin-like effects of zinc on cell signaling molecules including tyrosine, PRSA40, Akt, ERK1/2, SHP-2, GSK-3β and p38, and glucose oxidation in human and mouse skeletal muscle cells. Insulin and zinc independently led to the phosphorylation of these proteins over a 60-minute time course in both mouse and human skeletal muscle cells. Similarly, utilizing a protein array we identified that zinc could active the phosphorylation of p38, ERK1/2 and GSK-3B in human and ERK1/2 and GSK-3B in mouse skeletal muscle cells. Glucose oxidation assays were performed on skeletal muscle cells treated with insulin, zinc, or a combination of both and resulted in a significant induction of glucose consumption in mouse (p<0.01) and human (p<0.05) skeletal muscle cells when treated with zinc alone. Insulin, as expected, increased glucose oxidation in mouse (p<0.001) and human (0.001) skeletal muscle cells, however the combination of zinc and insulin did not augment glucose consumption in these cells. Zinc acts as an insulin mimetic, activating key molecules implicated in cell signaling to maintain glucose homeostasis in mouse and human skeletal muscle cells. Zinc is an important metal ion implicated in several biological processes. The role of zinc as an insulin memetic in activating key signaling molecules involved in glucose homeostasis could provide opportunities to utilize this ion therapeutically in treating disorders associated with dysfunctional zinc signaling.

  14. Increased IGF-1 in muscle modulates the phenotype of severe SMA mice

    PubMed Central

    Bosch-Marcé, Marta; Wee, Claribel D.; Martinez, Tara L.; Lipkes, Celeste E.; Choe, Dong W.; Kong, Lingling; Van Meerbeke, James P.; Musarò, Antonio; Sumner, Charlotte J.

    2011-01-01

    Spinal muscular atrophy (SMA) is an inherited motor neuron disease caused by the mutation of the survival motor neuron 1 (SMN1) gene and deficiency of the SMN protein. Severe SMA mice have abnormal motor function and small, immature myofibers early in development suggesting that SMN protein deficiency results in retarded muscle growth. Insulin-like growth factor 1 (IGF-1) stimulates myoblast proliferation, induces myogenic differentiation and generates myocyte hypertrophy in vitro and in vivo. We hypothesized that increased expression of IGF-1 specifically in skeletal muscle would attenuate disease features of SMAΔ7 mice. SMAΔ7 mice overexpressing a local isoform of IGF-1 (mIGF-1) in muscle showed enlarged myofibers and a 40% increase in median survival compared with mIGF-1-negative SMA littermates (median survival = 14 versus 10 days, respectively, log-rank P = 0.025). Surprisingly, this was not associated with a significant improvement in motor behavior. Treatment of both mIGF-1NEG and mIGF-1POS SMA mice with the histone deacetylase inhibitor, trichostatin A (TSA), resulted in a further extension of survival and improved motor behavior, but the combination of mIGF-1 and TSA treatment was not synergistic. These results show that increased mIGF-1 expression restricted to muscle can modulate the phenotype of SMA mice indicating that therapeutics targeted to muscle alone should not be discounted as potential disease-modifying therapies in SMA. IGF-1 may warrant further investigation in mild SMA animal models and perhaps SMA patients. PMID:21325354

  15. Distinct transcriptomic changes in E14.5 mouse skeletal muscle lacking RYR1 or Cav1.1 converge at E18.5

    PubMed Central

    Henry, Margit; Rotshteyn, Tamara; Brunn, Anna; Carstov, Mariana; Deckert, Martina; Hescheler, Jürgen; Sachinidis, Agapios; Pfitzer, Gabriele

    2018-01-01

    In skeletal muscle the coordinated actions of two mechanically coupled Ca2+ channels—the 1,4-dihydropyridine receptor (Cav1.1) and the type 1 ryanodine receptor (RYR1)–underlie the molecular mechanism of rapid cytosolic [Ca2+] increase leading to contraction. While both [Ca2+]i and contractile activity have been implicated in the regulation of myogenesis, less is known about potential specific roles of Cav1.1 and RYR1 in skeletal muscle development. In this study, we analyzed the histology and the transcriptomic changes occurring at E14.5 –the end of primary myogenesis and around the onset of intrauterine limb movement, and at E18.5 –the end of secondary myogenesis, in WT, RYR1-/-, and Cav1.1-/- murine limb skeletal muscle. At E14.5 the muscle histology of both mutants exhibited initial alterations, which became much more severe at E18.5. Immunohistological analysis also revealed higher levels of activated caspase-3 in the Cav1.1-/- muscles at E14.5, indicating an increase in apoptosis. With WT littermates as controls, microarray analyses identified 61 and 97 differentially regulated genes (DEGs) at E14.5, and 493 and 1047 DEGs at E18.5, in RYR1-/- and Cav1.1-/- samples, respectively. Gene enrichment analysis detected no overlap in the affected biological processes and pathways in the two mutants at E14.5, whereas at E18.5 there was a significant overlap of DEGs in both mutants, affecting predominantly processes linked to muscle contraction. Moreover, the E18.5 vs. E14.5 comparison revealed multiple genotype-specific DEGs involved in contraction, cell cycle and miRNA-mediated signaling in WT, neuronal and bone development in RYR1-/-, and lipid metabolism in Cav1.1-/- samples. Taken together, our study reveals discrete changes in the global transcriptome occurring in limb skeletal muscle from E14.5 to E18.5 in WT, RYR1-/- and Cav1.1-/- mice. Our results suggest distinct functional roles for RYR1 and Cav1.1 in skeletal primary and secondary myogenesis. PMID

  16. The relationship between salivary insulin-like growth factor I and quantitative cervical maturational stages of skeletal maturity.

    PubMed

    Nayak, Subash; Bhad Patil, Wasundhara A; Doshi, Umal Hiralal

    2014-09-01

    Insulin-like growth factor (IGF-I) has been used as an indicator of growth hormone levels and hence can also be used as a marker of growth. The main objective of the study was to quantify salivary IGF-I levels and its secretion rate at different quantitative cervical maturation (QCVM) stages and evaluate a possible role for salivary IGF-I in evaluating skeletal growth. Forty-five subjects (24 female, 21 male) between the ages of 7 and 23 years were included in the study. Each subject had personal information, a lateral cephalogram, and a parotid saliva sample collected on the same day. Salivary IGF-I levels and salivary secretion rates were lowest at QCVM skeletal stages previously associated with the acceleration phase of mandibular growth. Highest levels were found at the high velocity stage. After this there was gradual drop in salivary IGF-I levels and secretion rate at deceleration and completing velocity stages. Relatively high levels in the decelerating velocity stage may be an indication of residual skeletal growth. There was a negative correlation between patient age and levels of IGF-I and its secretion rate, once growth velocity decreased. Salivary IGF-I levels or its secretion rate can be used as an indicator of skeletal growth but longitudinal data are necessary to confirm salivary IGF-I as a marker for skeletal growth prediction and residual mandibular growth. © 2014 British Orthodontic Society.

  17. Impact of angiotensin II on skeletal muscle metabolism and function in mice: contribution of IGF-1, Sirtuin-1 and PGC-1α.

    PubMed

    Kackstein, Katharina; Teren, Andrej; Matsumoto, Yasuharu; Mangner, Norman; Möbius-Winkler, Sven; Linke, Axel; Schuler, Gerhard; Punkt, Karla; Adams, Volker

    2013-05-01

    Activation of the renin-angiotensin-aldosterone system and increased levels of angiotensin II (Ang-II) occurs in numerous cardiovascular diseases such as chronic heart failure (CHF). Another hallmark in CHF is a reduced exercise tolerance with impaired skeletal muscle function. The aim of this study was to investigate in an animal model the impact of Ang-II on skeletal muscle function and concomitant molecular alterations. Mice were infused with Ang-II for 4 weeks. Subsequently, skeletal muscle function of the soleus muscle was assessed. Expression of selected proteins was quantified by qRT-PCR and Western blot. Infusion of Ang-II resulted in a 33% reduction of contractile force, despite a lack of changes in muscle weight. At the molecular level an increased expression of NAD(P)H oxidase and a reduced expression of Sirt1, PGC-1α and IGF-1 were noticed. No change was evident for the ubiquitin E3-ligases MuRF1 and MafBx and α-sarcomeric actin expression. Cytophotometrical analysis of the soleus muscle revealed a metabolic shift toward a glycolytic profile. This study provides direct evidence of Ang-II-mediated, metabolic deterioration of skeletal muscle function despite preserved muscle mass. One may speculate that the Ang-II-mediated loss of muscle force is due to an activation of NAD(P)H oxidase expression and a subsequent ROS-induced down regulation of IGF-1, PGC-1α and Sirt1. Copyright © 2012 Elsevier GmbH. All rights reserved.

  18. Role of nitric oxide in skeletal muscle glucose uptake during exercise.

    PubMed

    Hong, Yet Hoi; Betik, Andrew C; McConell, Glenn K

    2014-12-01

    Nitric oxide is produced within skeletal muscle fibres and has various functions in skeletal muscle. There is evidence that NO may be essential for normal increases in skeletal muscle glucose uptake during contraction/exercise. Although there have been some discrepant results, it has been consistently demonstrated that inhibition of NO synthase (NOS) attenuates the increase in skeletal muscle glucose uptake during contraction in mouse and rat muscle ex vivo, during in situ contraction in rats and during exercise in humans. The NO-mediated increase in skeletal muscle glucose uptake during contraction/exercise is probably due to the modulation of intramuscular signalling that ultimately increases glucose transporter 4 (GLUT4) translocation and is, surprisingly, independent of blood flow. In this review, we discuss the evidence for and against a role of NO in regulating skeletal muscle glucose uptake during contraction/exercise and outline the possible mechanism(s) involved. Emerging findings regarding the role of neuronal NOS mu (nNOSμ) in this process are also discussed. © 2014 The Authors. Experimental Physiology © 2014 The Physiological Society.

  19. Effects of microgravity on myogenic factor expressions during postnatal development of rat skeletal muscle

    NASA Technical Reports Server (NTRS)

    Inobe, Manabu; Inobe, Ikuko; Adams, Gregory R.; Baldwin, Kenneth M.; Takeda, Shin'Ichi

    2002-01-01

    To clarify the role of gravity in the postnatal development of skeletal muscle, we exposed neonatal rats at 7 days of age to microgravity. After 16 days of spaceflight, tibialis anterior, plantaris, medial gastrocnemius, and soleus muscles were removed from the hindlimb musculature and examined for the expression of MyoD-family transcription factors such as MyoD, myogenin, and MRF4. For this purpose, we established a unique semiquantitative method, based on RT-PCR, using specific primers tagged with infrared fluorescence. The relative expression of MyoD in the tibialis anterior and plantaris muscles and that of myogenin in the plantaris and soleus muscles were significantly reduced (P < 0.001) in the flight animals. In contrast, MRF4 expression was not changed in any muscle. These results suggest that MyoD and myogenin, but not MRF4, are sensitive to gravity-related stimuli in some skeletal muscles during postnatal development.

  20. Ubiquitous overexpression of Hey1 transcription factor leads to osteopenia and chondrocyte hypertrophy in bone.

    PubMed

    Salie, Rishard; Kneissel, Michaela; Vukevic, Mirko; Zamurovic, Natasa; Kramer, Ina; Evans, Glenda; Gerwin, Nicole; Mueller, Matthias; Kinzel, Bernd; Susa, Mira

    2010-03-01

    The transcription factor Hey1, a known Notch target gene of the HES family, has recently been described as a target gene of bone morphogenetic protein-2 (BMP-2) during osteoblastic differentiation in vitro. As the role of Hey1 in skeletal physiology is unknown, we analyzed bones of mice ubiquitously lacking or overexpressing Hey1. This strategy enabled us to evaluate whether Hey1 modulation in the whole organism could serve as a drug or antibody target for therapy of diseases associated with bone loss. Hey1 deficiency resulted in modest osteopenia in vivo and increased number and activity of osteoclasts generated ex vivo. Hey1 overexpression resulted in distinct progressive osteopenia and inhibition of osteoblasts ex vivo, an effect apparently dominant to a mild inhibition of osteoclasts. In both Hey1 deficient and overexpressing mice, males were less affected than females and skeleton was not affected during development. Bone histomorphometry did not reveal major changes in animals at 20 weeks, suggesting that modulation had occurred before. Adult Hey1 transgenics also displayed increased type X collagen expression and an enlarged hypertrophic zone in the growth plate. Taken together, our data suggest that ubiquitous in vivo Hey1 regulation affects osteoblasts, osteoclasts and chondrocytes. Due to the complex role of Hey1 in bone, inhibition of Hey1 does not appear to be a straightforward therapeutic strategy to increase the bone mass.

  1. Perm1 enhances mitochondrial biogenesis, oxidative capacity, and fatigue resistance in adult skeletal muscle

    PubMed Central

    Cho, Yoshitake; Hazen, Bethany C.; Gandra, Paulo G.; Ward, Samuel R.; Schenk, Simon; Russell, Aaron P.; Kralli, Anastasia

    2016-01-01

    Skeletal muscle mitochondrial content and oxidative capacity are important determinants of muscle function and whole-body health. Mitochondrial content and function are enhanced by endurance exercise and impaired in states or diseases where muscle function is compromised, such as myopathies, muscular dystrophies, neuromuscular diseases, and age-related muscle atrophy. Hence, elucidating the mechanisms that control muscle mitochondrial content and oxidative function can provide new insights into states and diseases that affect muscle health. In past studies, we identified Perm1 (PPARGC1- and ESRR-induced regulator, muscle 1) as a gene induced by endurance exercise in skeletal muscle, and regulating mitochondrial oxidative function in cultured myotubes. The capacity of Perm1 to regulate muscle mitochondrial content and function in vivo is not yet known. In this study, we use adeno-associated viral (AAV) vectors to increase Perm1 expression in skeletal muscles of 4-wk-old mice. Compared to control vector, AAV1-Perm1 leads to significant increases in mitochondrial content and oxidative capacity (by 40–80%). Moreover, AAV1-Perm1–transduced muscles show increased capillary density and resistance to fatigue (by 33 and 31%, respectively), without prominent changes in fiber-type composition. These findings suggest that Perm1 selectively regulates mitochondrial biogenesis and oxidative function, and implicate Perm1 in muscle adaptations that also occur in response to endurance exercise.—Cho, Y., Hazen, B. C., Gandra, P. G., Ward, S. R., Schenk, S., Russell, A. P., Kralli, A. Perm1 enhances mitochondrial biogenesis, oxidative capacity, and fatigue resistance in adult skeletal muscle. PMID:26481306

  2. ATF4 mediation of NF1 functions in osteoblast reveals a nutritional basis for congenital skeletal dysplasiae

    PubMed Central

    Elefteriou, Florent; Benson, M. Douglas; Sowa, Hideaki; Starbuck, Michael; Liu, Xiuyun; Ron, David; Parada, Luis F.; Karsenty, Gerard

    2009-01-01

    Summary The transcription factor ATF4 enhances bone formation by favoring amino acid import and collagen synthesis in osteoblasts, a function requiring its phosphorylation by RSK2, the kinase inactivated in Coffin-Lowry Syndrome. Here, we show that in contrast, RSK2 activity, ATF4-dependent collagen synthesis, and bone formation are increased in mice lacking neurofibromin in osteoblasts (Nf1ob−/− mice). Independently of RSK2, ATF4 phosphorylation by PKA is enhanced in Nf1ob−/− mice, thereby increasing Rankl expression, osteoclast differentiation, and bone resorption. In agreement with ATF4 function in amino acid transport, a low-protein diet decreased bone protein synthesis and normalized bone formation and bone mass in Nf1ob−/− mice without affecting other organ weight, while a high-protein diet overcame Atf4−/− and Rsk2−/− mice developmental defects, perinatal lethality, and low bone mass. By showing that ATF4-dependent skeletal dysplasiae are treatable by dietary manipulations, this study reveals a molecular connection between nutrition and skeletal development. PMID:17141628

  3. Deletion of the transcriptional coactivator PGC1α in skeletal muscles is associated with reduced expression of genes related to oxidative muscle function

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hatazawa, Yukino; Research Fellow of Japan Society for the Promotion of Science, Tokyo; Minami, Kimiko

    The expression of the transcriptional coactivator PGC1α is increased in skeletal muscles during exercise. Previously, we showed that increased PGC1α leads to prolonged exercise performance (the duration for which running can be continued) and, at the same time, increases the expression of branched-chain amino acid (BCAA) metabolism-related enzymes and genes that are involved in supplying substrates for the TCA cycle. We recently created mice with PGC1α knockout specifically in the skeletal muscles (PGC1α KO mice), which show decreased mitochondrial content. In this study, global gene expression (microarray) analysis was performed in the skeletal muscles of PGC1α KO mice compared withmore » that of wild-type control mice. As a result, decreased expression of genes involved in the TCA cycle, oxidative phosphorylation, and BCAA metabolism were observed. Compared with previously obtained microarray data on PGC1α-overexpressing transgenic mice, each gene showed the completely opposite direction of expression change. Bioinformatic analysis of the promoter region of genes with decreased expression in PGC1α KO mice predicted the involvement of several transcription factors, including a nuclear receptor, ERR, in their regulation. As PGC1α KO microarray data in this study show opposing findings to the PGC1α transgenic data, a loss-of-function experiment, as well as a gain-of-function experiment, revealed PGC1α’s function in the oxidative energy metabolism of skeletal muscles. - Highlights: • Microarray analysis was performed in the skeletal muscle of PGC1α KO mice. • Expression of genes in the oxidative energy metabolism was decreased. • Bioinformatic analysis of promoter region of the genes predicted involvement of ERR. • PGC1α KO microarray data in this study show the mirror image of transgenic data.« less

  4. Osthole improves glucose and lipid metabolism via modulation of PPARα/γ-mediated target gene expression in liver, adipose tissue, and skeletal muscle in fatty liver rats.

    PubMed

    Qi, Zhi-Gang; Zhao, Xi; Zhong, Wen; Xie, Mei-Lin

    2016-01-01

    Osthole may be a dual agonist of peroxisome proliferator-activated receptors (PPAR) α/γ and ameliorate the insulin resistance (IR), but its mechanisms are not yet understood completely. We investigated the effects of osthole on PPARα/γ-mediated target genes involved in glucose and lipid metabolism in liver, adipose tissue, and skeletal muscle in fatty liver and IR rats. The rat model was established by orally feeding high-fat and high-sucrose emulsion for 9 weeks. The experimental rats were treated with osthole 5-10 mg/kg by gavage after feeding the emulsion for 6 weeks, and were sacrificed 4 weeks after administration. After treatment with osthole 5-10 mg/kg for 4 weeks, the lipid levels in serum and liver were decreased by 37.9-67.2% and 31.4-38.5% for triglyceride, 33.1-47.5% and 28.5-31.2% for free fatty acid, respectively, the fasting blood glucose, fasting serum insulin, and homeostasis model assessment of IR were also decreased by 17.2-22.7%, 25.9-26.7%, and 37.5-42.8%, respectively. Osthole treatment might simultaneously decrease the sterol regulatory element binding protein-1c, diacylglycerol acyltransferase, and fatty acid synthase mRNA expressions in liver and adipose tissue, and increase the carnitine palmitoyltransferase-1A mRNA expression in liver and glucose transporter-4 mRNA expression in skeletal muscle, especially in the osthole 10 mg/kg group (p < 0.01). Osthole can improve glucose and lipid metabolism in fatty liver and IR rats, and its mechanisms may be associated with synergic modulation of PPARα/γ-mediated target genes involved in glucose and lipid metabolism in liver, adipose tissue, and skeletal muscle.

  5. Effects of different dietary intake on mRNA levels of MSTN, IGF-I, and IGF-II in the skeletal muscle of Dorper and Hu sheep hybrid F1 rams.

    PubMed

    Xing, H J; Wang, Z Y; Zhong, B S; Ying, S J; Nie, H T; Zhou, Z R; Fan, Y X; Wang, F

    2014-07-24

    MSTN, IGF-І(insulin-like growth factor-І) and IGF-II (insulin-like growth factor-II) regulate skeletal muscle growth. This study investigated the effects of different dietary intake levels on skeletal muscles. Sheep was randomly assigned to 3 feeding groups: 1) the maintenance diet (M), 2) 1.4 x the maintenance diet (1.4M), and 3) 2.15 x the maintenance diet (2.15M). Before slaughtering the animals, blood samples were collected to measure plasma urea, growth hormone, and insulin concentrations. After slaughtering, the longissimus dorsi, semitendinosus, semimembranosus, gastrocnemius, soleus, and chest muscle were removed to record various parameters, including the mRNA expression levels of MSTN and IGFs, in addition to skeletal muscle fiber diameter and cross-sectional area. The result showed that as dietary intake improved, the mRNA expression levels of MSTN and IGF-II decreased, whereas IGF-Іexpression increased. The mRNA expression levels of MSTN and IGFs were significantly different in the same skeletal muscle under different dietary intake. The skeletal muscle fiber diameter and cross-sectional area increased with greater dietary intake, as observed for the mRNA expression of IGF-І; however, it contrasted to that observed for the mRNA expression of MSTN and IGF-II. In conclusion, dietary intake levels have a certain influence on MSTN and IGFs mRNA expression levels, in addition to skeletal muscle fiber diameter and cross-sectional area. This study contributes valuable information for enhancing the molecular-based breeding of sheep.

  6. Exercise training increases protein O-GlcNAcylation in rat skeletal muscle.

    PubMed

    Hortemo, Kristin Halvorsen; Lunde, Per Kristian; Anonsen, Jan Haug; Kvaløy, Heidi; Munkvik, Morten; Rehn, Tommy Aune; Sjaastad, Ivar; Lunde, Ida Gjervold; Aronsen, Jan Magnus; Sejersted, Ole M

    2016-09-01

    Protein O-GlcNAcylation has emerged as an important intracellular signaling system with both physiological and pathophysiological functions, but the role of protein O-GlcNAcylation in skeletal muscle remains elusive. In this study, we tested the hypothesis that protein O-GlcNAcylation is a dynamic signaling system in skeletal muscle in exercise and disease. Immunoblotting showed different protein O-GlcNAcylation pattern in the prototypical slow twitch soleus muscle compared to fast twitch EDL from rats, with greater O-GlcNAcylation level in soleus associated with higher expression of the modulating enzymes O-GlcNAc transferase (OGT), O-GlcNAcase (OGA), and glutamine fructose-6-phosphate amidotransferase isoforms 1 and 2 (GFAT1, GFAT2). Six weeks of exercise training by treadmill running, but not an acute exercise bout, increased protein O-GlcNAcylation in rat soleus and EDL There was a striking increase in O-GlcNAcylation of cytoplasmic proteins ~50 kDa in size that judged from mass spectrometry analysis could represent O-GlcNAcylation of one or more key metabolic enzymes. This suggests that cytoplasmic O-GlcNAc signaling is part of the training response. In contrast to exercise training, postinfarction heart failure (HF) in rats and humans did not affect skeletal muscle O-GlcNAcylation level, indicating that aberrant O-GlcNAcylation cannot explain the skeletal muscle dysfunction in HF Human skeletal muscle displayed extensive protein O-GlcNAcylation that by large mirrored the fiber-type-related O-GlcNAcylation pattern in rats, suggesting O-GlcNAcylation as an important signaling system also in human skeletal muscle. © 2016 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society.

  7. The effects of 1α, 25-dihydroxyvitamin D3 and transforming growth factor-β3 on bone development in an ex vivo organotypic culture system of embryonic chick femora.

    PubMed

    Smith, Emma L; Rashidi, Hassan; Kanczler, Janos M; Shakesheff, Kevin M; Oreffo, Richard O C

    2015-01-01

    Transforming growth factor-beta3 (TGF-β3) and 1α,25-dihydroxyvitamin D3 (1α,25 (OH) 2D3) are essential factors in chondrogenesis and osteogenesis respectively. These factors also play a fundamental role in the developmental processes and the maintenance of skeletal integrity, but their respective direct effects on these processes are not fully understood. Using an organotypic bone rudiment culture system the current study has examined the direct roles the osteotropic factors 1α,25 (OH)2D3 and TGF-β3 exert on the development and modulation of the three dimensional structure of the embryonic femur. Isolated embryonic chick femurs (E11) were organotypically cultured for 10 days in basal media, or basal media supplemented with either 1α,25 (OH) 2D3 (25 nM) or TGF-β3 (5 ng/mL & 15 ng/mL). Analyses of the femurs were undertaken using micro-computed tomography (μCT), histology and immunohistochemistry. 1α,25 (OH)2D3 supplemented cultures enhanced osteogenesis directly in the developing femurs with elevated levels of osteogenic markers such as type 1 collagen. In marked contrast organotypic femur cultures supplemented with TGF-β3 (5 ng/mL & 15 ng/mL) demonstrated enhanced chondrogenesis with a reduction in osteogenesis. These studies demonstrate the efficacy of the ex vivo organotypic embryonic femur culture employed to elucidate the direct roles of these molecules, 1α,25 (OH) 2D3 and TGF-β3 on the structural development of embryonic bone within a three dimensional framework. We conclude that 1α,25(OH)2D and TGF-β3 modify directly the various cell populations in bone rudiment organotypic cultures effecting tissue metabolism resulting in significant changes in embryonic bone growth and modulation. Understanding the roles of osteotropic agents in the process of skeletal development is integral to developing new strategies for the recapitulation of bone tissue in later life.

  8. Liver kinase B1 inhibits the expression of inflammation-related genes postcontraction in skeletal muscle

    PubMed Central

    Chen, Ting; Moore, Timothy M.; Ebbert, Mark T. W.; McVey, Natalie L.; Madsen, Steven R.; Hallowell, David M.; Harris, Alexander M.; Char, Robin E.; Mackay, Ryan P.; Hancock, Chad R.; Hansen, Jason M.; Kauwe, John S.

    2016-01-01

    Skeletal muscle-specific liver kinase B1 (LKB1) knockout mice (skmLKB1-KO) exhibit elevated mitogen-activated protein kinase (MAPK) signaling after treadmill running. MAPK activation is also associated with inflammation-related signaling in skeletal muscle. Since exercise can induce muscle damage, and inflammation is a response triggered by damaged tissue, we therefore hypothesized that LKB1 plays an important role in dampening the inflammatory response to muscle contraction, and that this may be due in part to increased susceptibility to muscle damage with contractions in LKB1-deficient muscle. Here we studied the inflammatory response and muscle damage with in situ muscle contraction or downhill running. After in situ muscle contractions, the phosphorylation of both NF-κB and STAT3 was increased more in skmLKB1-KO vs. wild-type (WT) muscles. Analysis of gene expression via microarray and RT-PCR shows that expression of many inflammation-related genes increased after contraction only in skmLKB1-KO muscles. This was associated with mild skeletal muscle fiber membrane damage in skmLKB1-KO muscles. Gene markers of oxidative stress were also elevated in skmLKB1-KO muscles after contraction. Using the downhill running model, we observed significantly more muscle damage after running in skmLKB1-KO mice, and this was associated with greater phosphorylation of both Jnk and STAT3 and increased expression of SOCS3 and Fos. In conclusion, we have shown that the lack of LKB1 in skeletal muscle leads to an increased inflammatory state in skeletal muscle that is exacerbated by muscle contraction. Increased susceptibility of the muscle to damage may underlie part of this response. PMID:26796753

  9. Does the GH/IGF-1 axis contribute to skeletal sexual dimorphism? Evidence from mouse studies.

    PubMed

    Liu, Zhongbo; Mohan, Subburaman; Yakar, Shoshana

    2016-04-01

    The contribution of the gonadotropic axis to skeletal sexual dimorphism (SSD) was clarified in recent years. Studies with animal models of estrogen receptor (ER) or androgen receptor (AR) null mice, as well as mice with bone cell-specific ablation of ER or AR, revealed that both hormones play major roles in skeletal acquisition, and that estrogen regulates skeletal accrual in both sexes. The growth hormone (GH) and its downstream effector, the insulin-like growth factor-1 (IGF-1) are also major determinants of peak bone mass during puberty and young adulthood, and play important roles in maintaining bone integrity during aging. A few studies in both humans and animal models suggest that in addition to the differences in sex steroid actions on bone, sex-specific effects of GH and IGF-1 play essential roles in SSD. However, the contributions of the somatotropic (GH/IGF-1) axis to SSD are controversial and data is difficult to interpret. GH/IGF-1 are pleotropic hormones that act in an endocrine and autocrine/paracrine fashion on multiple tissues, affecting body composition as well as metabolism. Thus, understanding the contribution of the somatotropic axis to SSD requires the use of mouse models that will differentiate between these two modes of action. Elucidation of the relative contribution of GH/IGF-1 axis to SSD is significant because GH is approved for the treatment of normal children with short stature and children with congenital growth disorders. Thus, if the GH/IGF-1 axis determines SSD, treatment with GH may be tailored according to sex. In the following review, we give an overview of the roles of sex steroids in determining SSD and how they may interact with the GH/IGF-1 axis in bone. We summarize several mouse models with impaired somatotropic axis and speculate on the possible contribution of that axis to SSD. Copyright © 2015 Elsevier Ltd. All rights reserved.

  10. Thyroid Hormone Transporters MCT8 and OATP1C1 Control Skeletal Muscle Regeneration.

    PubMed

    Mayerl, Steffen; Schmidt, Manuel; Doycheva, Denica; Darras, Veerle M; Hüttner, Sören S; Boelen, Anita; Visser, Theo J; Kaether, Christoph; Heuer, Heike; von Maltzahn, Julia

    2018-06-05

    Thyroid hormone (TH) transporters are required for the transmembrane passage of TH in target cells. In humans, inactivating mutations in the TH transporter MCT8 cause the Allan-Herndon-Dudley syndrome, characterized by severe neuromuscular symptoms and an abnormal TH serum profile, which is fully replicated in Mct8 knockout mice and Mct8/Oatp1c1 double-knockout (M/O DKO) mice. Analysis of tissue TH content and expression of TH-regulated genes indicate a thyrotoxic state in Mct8-deficient skeletal muscles. Both TH transporters are upregulated in activated satellite cells (SCs). In M/O DKO mice, we observed a strongly reduced number of differentiated SCs, suggesting an impaired stem cell function. Moreover, M/O DKO mice and mice lacking both transporters exclusively in SCs showed impaired skeletal muscle regeneration. Our data provide solid evidence for a unique gate-keeper function of MCT8 and OATP1C1 in SC activation, underscoring the importance of a finely tuned TH signaling during myogenesis. Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.

  11. Disrupted Membrane Structure and Intracellular Ca2+ Signaling in Adult Skeletal Muscle with Acute Knockdown of Bin1

    PubMed Central

    Tjondrokoesoemo, Andoria; Park, Ki Ho; Ferrante, Christopher; Komazaki, Shinji; Lesniak, Sebastian; Brotto, Marco; Ko, Jae-Kyun; Zhou, Jingsong; Weisleder, Noah; Ma, Jianjie

    2011-01-01

    Efficient intracellular Ca2+ ([Ca2+]i) homeostasis in skeletal muscle requires intact triad junctional complexes comprised of t-tubule invaginations of plasma membrane and terminal cisternae of sarcoplasmic reticulum. Bin1 consists of a specialized BAR domain that is associated with t-tubule development in skeletal muscle and involved in tethering the dihydropyridine receptors (DHPR) to the t-tubule. Here, we show that Bin1 is important for Ca2+ homeostasis in adult skeletal muscle. Since systemic ablation of Bin1 in mice results in postnatal lethality, in vivo electroporation mediated transfection method was used to deliver RFP-tagged plasmid that produced short –hairpin (sh)RNA targeting Bin1 (shRNA-Bin1) to study the effect of Bin1 knockdown in adult mouse FDB skeletal muscle. Upon confirming the reduction of endogenous Bin1 expression, we showed that shRNA-Bin1 muscle displayed swollen t-tubule structures, indicating that Bin1 is required for the maintenance of intact membrane structure in adult skeletal muscle. Reduced Bin1 expression led to disruption of t-tubule structure that was linked with alterations to intracellular Ca2+ release. Voltage-induced Ca2+ released in isolated single muscle fibers of shRNA-Bin1 showed that both the mean amplitude of Ca2+ current and SR Ca2+ transient were reduced when compared to the shRNA-control, indicating compromised coupling between DHPR and ryanodine receptor 1. The mean frequency of osmotic stress induced Ca2+ sparks was reduced in shRNA-Bin1, indicating compromised DHPR activation. ShRNA-Bin1 fibers also displayed reduced Ca2+ sparks' amplitude that was attributed to decreased total Ca2+ stores in the shRNA-Bin1 fibers. Human mutation of Bin1 is associated with centronuclear myopathy and SH3 domain of Bin1 is important for sarcomeric protein organization in skeletal muscle. Our study showing the importance of Bin1 in the maintenance of intact t-tubule structure and ([Ca2+]i) homeostasis in adult skeletal muscle

  12. Nicorandil improves post-fatigue tension in slow skeletal muscle fibers by modulating glutathione redox state.

    PubMed

    Sánchez-Duarte, E; Trujillo, X; Cortés-Rojo, C; Saavedra-Molina, A; Camargo, G; Hernández, L; Huerta, M; Montoya-Pérez, R

    2017-04-01

    Fatigue is a phenomenon in which force reduction has been linked to impairment of several biochemical processes. In skeletal muscle, the ATP-sensitive potassium channels (K ATP ) are actively involved in myoprotection against metabolic stress. They are present in sarcolemma and mitochondria (mitoK ATP channels). K + channel openers like nicorandil has been recognized for their ability to protect skeletal muscle from ischemia-reperfusion injury, however, the effects of nicorandil on fatigue in slow skeletal muscle fibers has not been explored, being the aim of this study. Nicorandil (10 μM), improved the muscle function reversing fatigue as increased post-fatigue tension in the peak and total tension significantly with respect to the fatigued condition. However, this beneficial effect was prevented by the mitoK ATP channel blocker 5-hydroxydecanoate (5-HD, 500 μM) and by the free radical scavenger N-2-mercaptopropionyl glycine (MPG, 1 mM), but not by the nitric oxide (NO) synthase inhibitor Nω-nitro-L-arginine methyl ester (L-NAME, 100 μM). Nicorandil also decreased lipid peroxidation and maintained both reduced glutathione (GSH) levels and an elevated GSH/GSSG ratio, whereas total glutathione (TGSH) remained unaltered during post-fatigue tension. In addition, NO production, measured through nitrite concentrations was significantly increased with nicorandil during post-fatigue tension; this increase remained unaltered in the presence of nicorandil plus L-NAME, nonetheless, this effect was reversed with nicorandil plus MPG. Hence, these results suggest that nicorandil improves the muscle function reversing fatigue in slow skeletal muscle fibers of chicken through its effects not only as a mitoK ATP channel opener but also as NO donor and as an antioxidant.

  13. Advances in Skeletal Dysplasia Genetics

    PubMed Central

    Geister, Krista A.; Camper, Sally A.

    2017-01-01

    Skeletal dysplasias result from disruptions in normal skeletal growth and development and are a major contributor to severe short stature. They occur in approximately 1/5,000 births, and some are lethal. Since the most recent publication of the Nosology and Classification of Genetic Skeletal Disorders, genetic causes of 56 skeletal disorders have been uncovered. This remarkable rate of discovery is largely due to the expanded use of high-throughput genomic technologies. In this review, we discuss these recent discoveries and our understanding of the molecular mechanisms behind these skeletal dysplasia phenotypes. We also cover potential therapies, unusual genetic mechanisms, and novel skeletal syndromes both with and without known genetic causes. The acceleration of skeletal dysplasia genetics is truly spectacular, and these advances hold great promise for diagnostics, risk prediction, and therapeutic design. PMID:25939055

  14. Ex Vivo Assessment of Contractility, Fatigability and Alternans in Isolated Skeletal Muscles

    PubMed Central

    Park, Ki Ho; Brotto, Leticia; Lehoang, Oanh; Brotto, Marco; Ma, Jianjie; Zhao, Xiaoli

    2012-01-01

    Described here is a method to measure contractility of isolated skeletal muscles. Parameters such as muscle force, muscle power, contractile kinetics, fatigability, and recovery after fatigue can be obtained to assess specific aspects of the excitation-contraction coupling (ECC) process such as excitability, contractile machinery and Ca2+ handling ability. This method removes the nerve and blood supply and focuses on the isolated skeletal muscle itself. We routinely use this method to identify genetic components that alter the contractile property of skeletal muscle though modulating Ca2+ signaling pathways. Here, we describe a newly identified skeletal muscle phenotype, i.e., mechanic alternans, as an example of the various and rich information that can be obtained using the in vitro muscle contractility assay. Combination of this assay with single cell assays, genetic approaches and biochemistry assays can provide important insights into the mechanisms of ECC in skeletal muscle. PMID:23149471

  15. Skeletal Maturation, Body Size, and Motor Coordination in Youth 11-14 Years.

    PubMed

    Freitas, Duarte Luís; Lausen, Berthold; Maia, José Antonio Ribeiro; Gouveia, Élvio Rúbio; Thomis, Martine; Lefevre, Johan; Silva, Ricardo Dinis; Malina, Robert M

    2016-06-01

    The objective of this study is to estimate the relative contribution of biological maturation to variance in the motor coordination (MC) among youth and to explore gender differences in the associations. Skeletal maturation (Tanner-Whitehouse 3), stature, body mass, and MC (Körperkoordinationstest für Kinder) were assessed in 613 youths, 284 boys and 329 girls 11-14 yr of age. Standardized residuals of skeletal age on chronological age were used as the estimate of skeletal maturity status independent of chronological age. Hierarchical multiple regression analyses were used to analyse associations between skeletal maturity status and MC. Skeletal maturity status by itself, i.e., standardized residuals of skeletal age on chronological age (step 3) explained a maximum of 8.1% of the variance in MC in boys (ΔR3 in the range of 0.0%-8.1%) and 2.8% of the variance in girls (ΔR3 in the range of 0.0%-2.8%), after controlling for stature, body mass and interactions of the standardized residuals of skeletal age on chronological age with stature and body mass. Corresponding percentages for the interactions of the standardized residuals of skeletal age and stature and body mass, after adjusting for stature and body mass (step 2) were 8.7% in boys (ΔR2 in the range of 0.3%-8.7%) and 7.1% in girls (ΔR2 in the range of 0.1%-7.1%). Chow tests suggested structural changes in β-coefficients in the four MC tests among boys and girls, 12-13 yr. The percentage of variance in the four MC tests explained by skeletal maturation was relatively small, but the relationships differed between boys and girls. By inference, other factors, e.g., neuromuscular maturation, specific instruction and practice, sport participation, and others may influence MC at these ages.

  16. Differences in the skeletal muscle transcriptome profile associated with extreme values of fatty acids content.

    PubMed

    Cesar, Aline S M; Regitano, Luciana C A; Poleti, Mirele D; Andrade, Sónia C S; Tizioto, Polyana C; Oliveira, Priscila S N; Felício, Andrezza M; do Nascimento, Michele L; Chaves, Amália S; Lanna, Dante P D; Tullio, Rymer R; Nassu, Renata T; Koltes, James E; Fritz-Waters, Eric; Mourão, Gerson B; Zerlotini-Neto, Adhemar; Reecy, James M; Coutinho, Luiz L

    2016-11-22

    Lipids are a class of molecules that play an important role in cellular structure and metabolism in all cell types. In the last few decades, it has been reported that long-chain fatty acids (FAs) are involved in several biological functions from transcriptional regulation to physiological processes. Several fatty acids have been both positively and negatively implicated in different biological processes in skeletal muscle and other tissues. To gain insight into biological processes associated with fatty acid content in skeletal muscle, the aim of the present study was to identify differentially expressed genes (DEGs) and functional pathways related to gene expression regulation associated with FA content in cattle. Skeletal muscle transcriptome analysis of 164 Nellore steers revealed no differentially expressed genes (DEGs, FDR 10%) for samples with extreme values for linoleic acid (LA) or stearic acid (SA), and only a few DEGs for eicosapentaenoic acid (EPA, 5 DEGs), docosahexaenoic acid (DHA, 4 DEGs) and palmitic acid (PA, 123 DEGs), while large numbers of DEGs were associated with oleic acid (OA, 1134 DEGs) and conjugated linoleic acid cis9 trans11 (CLA-c9t11, 872 DEGs). Functional annotation and functional enrichment from OA DEGs identified important genes, canonical pathways and upstream regulators such as SCD, PLIN5, UCP3, CPT1, CPT1B, oxidative phosphorylation mitochondrial dysfunction, PPARGC1A, and FOXO1. Two important genes associated with lipid metabolism, gene expression and cancer were identified as DEGs between animals with high and low CLA-c9t11, specifically, epidermal growth factor receptor (EGFR) and RNPS. Only two out of seven classes of molecules of FA studied were associated with large changes in the expression profile of skeletal muscle. OA and CLA-c9t11 content had significant effects on the expression level of genes related to important biological processes associated with oxidative phosphorylation, and cell growth, survival, and migration

  17. [Effect of Jinlida on DGAT1 in Skeletal Muscle in Fat-Induced Insulin Resistance ApoE -/- Mice].

    PubMed

    Jin, Xin; Zhang, Hui-xin; Cui, Wen-wen

    2015-06-01

    To investigate the effect of Jinlida on DGAT1 in skeletal muscle in fat-induced insulin resistance ApoE-/- mice. Eight male C57BL/6J mice were used as normal group. 40 male ApoE -/- mice were fed high-fat diet for 16 weeks and divided into five groups: control group, rosiglitazone group, and Jinlida low, middle and high dose groups. Then corresponding drugs were administrated intragastrically for eight weeks. TG content in skeletal muscle was measured by enzymic enzymatic, Glucose tolerance test (OGTT) was used to evaluate the degree of insulin resistance in mice. The mRNA and protein expression of insulin receptor substrate (IRS-1) and diacylglycerol acyltransferase 1 (DGAT1) in skeletal muscle were measured by real-time quantitative reverse transcription PCR (RT-PCR)and Western blot. Jinlida particles reduced fasting blood glucose (FBG) cholesterol (TC), triglyceride (TG), free fatty acid (FFA)and fasting insulin (FIns) levels, raised insulin sensitive index (ISI), improved glucose tolerance, and reduced skeletal muscle lipid deposition in ApoE -/- mice significantly. Jinlida particles increased the expression of IRS-1 mRNA and protein, and reduced DGAT1. Jinlida can alleviate the expression of DGAT in skeletal muscle in fat-induced insulin resistance ApoE-/- mice.

  18. Deletion of Skeletal Muscle SOCS3 Prevents Insulin Resistance in Obesity

    PubMed Central

    Jorgensen, Sebastian Beck; O’Neill, Hayley M.; Sylow, Lykke; Honeyman, Jane; Hewitt, Kimberly A.; Palanivel, Rengasamy; Fullerton, Morgan D.; Öberg, Lisa; Balendran, Anudharan; Galic, Sandra; van der Poel, Chris; Trounce, Ian A.; Lynch, Gordon S.; Schertzer, Jonathan D.; Steinberg, Gregory R.

    2013-01-01

    Obesity is associated with chronic low-grade inflammation that contributes to defects in energy metabolism and insulin resistance. Suppressor of cytokine signaling (SOCS)-3 expression is increased in skeletal muscle of obese humans. SOCS3 inhibits leptin signaling in the hypothalamus and insulin signal transduction in adipose tissue and the liver. Skeletal muscle is an important tissue for controlling energy expenditure and whole-body insulin sensitivity; however, the physiological importance of SOCS3 in this tissue has not been examined. Therefore, we generated mice that had SOCS3 specifically deleted in skeletal muscle (SOCS MKO). The SOCS3 MKO mice had normal muscle development, body mass, adiposity, appetite, and energy expenditure compared with wild-type (WT) littermates. Despite similar degrees of obesity when fed a high-fat diet, SOCS3 MKO mice were protected against the development of hyperinsulinemia and insulin resistance because of enhanced skeletal muscle insulin receptor substrate 1 (IRS1) and Akt phosphorylation that resulted in increased skeletal muscle glucose uptake. These data indicate that skeletal muscle SOCS3 does not play a critical role in regulating muscle development or energy expenditure, but it is an important contributing factor for inhibiting insulin sensitivity in obesity. Therapies aimed at inhibiting SOCS3 in skeletal muscle may be effective in reversing obesity-related glucose intolerance and insulin resistance. PMID:22961088

  19. Control of skeletal muscle perfusion at the onset of dynamic exercise

    NASA Technical Reports Server (NTRS)

    Delp, M. D.

    1999-01-01

    At the onset of exercise there is a rapid increase in skeletal muscle vascular conductance and blood flow. Several mechanisms involved in the regulation of muscle perfusion have been proposed to initiate this hyperemic response, including neural, metabolic, endothelial, myogenic, and muscle pump mechanisms. Investigators utilizing pharmacological blockade of cholinergic muscarinic receptors and sympathectomy have concluded that neither sympathetic cholinergic nor adrenergic neural mechanisms are involved in the initial hyperemia. Studies have also shown that the time course for vasoactive metabolite release, diffusion, accumulation, and action is too long to account for the rapid increase in vascular conductance at the initiation of exercise. Furthermore, there is little or no evidence to support an endothelium or myogenic mechanism as the initiating factor in the muscle hyperemia. Thus, the rise in muscle blood flow does not appear to be explained by known neural, metabolic, endothelial, or myogenic influences. However, the initial hyperemia is consistent with the mechanical effects of the muscle pump to increase the arteriovenous pressure gradient across muscle. Because skeletal muscle blood flow is regulated by multiple and redundant mechanisms, it is likely that neural, metabolic, and possibly endothelial factors become important modulators of mechanically induced exercise hyperemia following the first 5-10 s of exercise.

  20. Early energy metabolism-related molecular events in skeletal muscle of diabetic rats: The effects of l-arginine and SOD mimic.

    PubMed

    Stancic, Ana; Filipovic, Milos; Ivanovic-Burmazovic, Ivana; Masovic, Sava; Jankovic, Aleksandra; Otasevic, Vesna; Korac, Aleksandra; Buzadzic, Biljana; Korac, Bato

    2017-06-25

    Considering the vital role of skeletal muscle in control of whole-body metabolism and the severity of long-term diabetic complications, we aimed to reveal the molecular pattern of early diabetes-related skeletal muscle phenotype in terms of energy metabolism, focusing on regulatory mechanisms, and the possibility to improve it using two redox modulators, l-arginine and superoxide dismutase (SOD) mimic. Alloxan-induced diabetic rats (120 mg/kg) were treated with l-arginine or the highly specific SOD mimic, M40403, for 7 days. As appropriate controls, non-diabetic rats received the same treatments. We found that l-arginine and M40403 restored diabetes-induced impairment of phospho-5'-AMP-activated protein kinase α (AMPKα) signaling by upregulating AMPKα protein itself and its downstream effectors, peroxisome proliferator-activated receptor-γ coactivator-1α and nuclear respiratory factor 1. Also, there was a restitution of the protein levels of oxidative phosphorylation components (complex I, complex II and complex IV) and mitofusin 2. Furthermore, l-arginine and M40403 induced translocation of glucose transporter 4 to the membrane and upregulation of protein of phosphofructokinase and acyl coenzyme A dehydrogenase, diminishing negative diabetic effects on limiting factors of glucose and lipid metabolism. Both treatments abolished diabetes-induced downregulation of sarcoplasmic reticulum calcium-ATPase proteins (SERCA 1 and 2). Similar effects of l-arginine and SOD mimic treatments suggest that disturbances in the superoxide/nitric oxide ratio may be responsible for skeletal muscle mitochondrial and metabolic impairment in early diabetes. Our results provide evidence that l-arginine and SOD mimics have potential in preventing and treating metabolic disturbances accompanying this widespread metabolic disease. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Wnt antagonist, secreted frizzled-related protein 1, is involved in prenatal skeletal muscle development and is a target of miRNA-1/206 in pigs.

    PubMed

    Yang, Yalan; Sun, Wei; Wang, Ruiqi; Lei, Chuzhao; Zhou, Rong; Tang, Zhonglin; Li, Kui

    2015-03-08

    The Wnt signaling pathway is involved in the control of cell proliferation and differentiation during skeletal muscle development. Secreted frizzled-related proteins (SFRPs), such as SFRP1, function as inhibitors of Wnt signaling. MicroRNA-1/206(miRNA-1/206) is specifically expressed in skeletal muscle and play a critical role in myogenesis. The miRNA-mRNA profiles and bioinformatics study suggested that the SFRP1 gene was potentially regulated by miRNA-1/206 during porcine skeletal muscle development. To understand the function of SFRP1 and miRNA-1/206 in swine myogenesis, we first predicted the targets of miRNA-1/206 with the TargetScan and PicTar programs, and analyzed the molecular characterization of the porcine SFRP1 gene. We performed a temporal-spatial expression analysis of SFRP1 mRNA and miRNA-206 in Tongcheng pigs (a Chinese indigenous breed) by quantitative real-time polymerase chain reaction, and conducted the co-expression analyses of SFRP1 and miRNA-1/206. Subsequently, the interaction between SFRP1 and miRNA-1/206 was validated via dual luciferase and Western blot assays. The bioinformatics analysis predicted SFRP1 to be a target of miRNA-1/206. The expression level of the SFRP1 was highly varied across numerous pig tissues and it was down-regulated during porcine skeletal muscle development. The expression level of the SFRP1 was significantly higher in the embryonic skeletal compared with postnatal skeletal muscle, whereas miR-206 showed the inverse pattern of expression. A significant negative correlation was observed between the expression of miR-1/206 and SFRP1 during porcine skeletal muscle development (p <0.05). Dual luciferase assay and Western-blot results demonstrated that SFRP1 was a target of miR-1/206 in porcine iliac endothelial cells. Our results indicate that the SFRP1 gene is regulated by miR-1/206 and potentially affects skeletal muscle development. These findings increase understanding of the biological functions and the regulation

  2. Potential role of TBC1D4 in enhanced post-exercise insulin action in human skeletal muscle.

    PubMed

    Treebak, J T; Frøsig, C; Pehmøller, C; Chen, S; Maarbjerg, S J; Brandt, N; MacKintosh, C; Zierath, J R; Hardie, D G; Kiens, B; Richter, E A; Pilegaard, H; Wojtaszewski, J F P

    2009-05-01

    TBC1 domain family, member 4 (TBC1D4; also known as AS160) is a cellular signalling intermediate to glucose transport regulated by insulin-dependent and -independent mechanisms. Skeletal muscle insulin sensitivity is increased after acute exercise by an unknown mechanism that does not involve modulation at proximal insulin signalling intermediates. We hypothesised that signalling through TBC1D4 is involved in this effect of exercise as it is a common signalling element for insulin and exercise. Insulin-regulated glucose metabolism was evaluated in 12 healthy moderately trained young men 4 h after one-legged exercise at basal and during a euglycaemic-hyperinsulinaemic clamp. Vastus lateralis biopsies were taken before and immediately after the clamp. Insulin stimulation increased glucose uptake in both legs, with greater effects (approximately 80%, p < 0.01) in the previously exercised leg. TBC1D4 phosphorylation, assessed using the phospho-AKT (protein kinase B)substrate antibody and phospho- and site-specific antibodies targeting six phosphorylation sites on TBC1D4, increased at similar degrees to insulin stimulation in the previously exercised and rested legs (p < 0.01). However, TBC1D4 phosphorylation on Ser-318, Ser-341, Ser-588 and Ser-751 was higher in the previously exercised leg, both in the absence and in the presence of insulin (p < 0.01; Ser-588, p = 0.09; observed power = 0.39). 14-3-3 binding capacity for TBC1D4 increased equally (p < 0.01) in both legs during insulin stimulation. We provide evidence for site-specific phosphorylation of TBC1D4 in human skeletal muscle in response to physiological hyperinsulinaemia. The data support the idea that TBC1D4 is a nexus for insulin- and exercise-responsive signals that may mediate increased insulin action after exercise.

  3. pH modulates the binding of early growth response protein 1 transcription factor to DNA.

    PubMed

    Mikles, David C; Bhat, Vikas; Schuchardt, Brett J; Deegan, Brian J; Seldeen, Kenneth L; McDonald, Caleb B; Farooq, Amjad

    2013-08-01

    The transcription factor early growth response protein (EGR)1 orchestrates a plethora of signaling cascades involved in cellular homeostasis, and its downregulation has been implicated in the development of prostate cancer. Herein, using a battery of biophysical tools, we show that the binding of EGR1 to DNA is tightly regulated by solution pH. Importantly, the binding affinity undergoes an enhancement of more than an order of magnitude with an increase in pH from 5 to 8, implying that the deprotonation of an ionizable residue accounts for such behavior. This ionizable residue is identified as His382 by virtue of the fact that its replacement by nonionizable residues abolishes the pH dependence of the binding of EGR1 to DNA. Notably, His382 inserts into the major groove of DNA, and stabilizes the EGR1-DNA interaction via both hydrogen bonding and van der Waals contacts. Remarkably, His382 is mainly conserved across other members of the EGR family, implying that histidine protonation-deprotonation may serve as a molecular switch for modulating the protein-DNA interactions that are central to this family of transcription factors. Collectively, our findings reveal an unexpected but a key step in the molecular recognition of the EGR family of transcription factors, and suggest that they may act as sensors of pH within the intracellular environment. © 2013 FEBS.

  4. Stretch-stimulated glucose transport in skeletal muscle is regulated by Rac1.

    PubMed

    Sylow, Lykke; Møller, Lisbeth L V; Kleinert, Maximilian; Richter, Erik A; Jensen, Thomas E

    2015-02-01

    Rac1 regulates stretch-stimulated (i.e. mechanical stress) glucose transport in muscle. Actin depolymerization decreases stretch-induced glucose transport in skeletal muscle. Rac1 is a required part of the mechanical stress-component of the contraction-stimulus to glucose transport in skeletal muscle. An alternative to the canonical insulin signalling pathway for glucose transport is muscle contraction/exercise. Mechanical stress is an integrated part of the muscle contraction/relaxation cycle, and passive stretch stimulates muscle glucose transport. However, the signalling mechanism regulating stretch-stimulated glucose transport is not well understood. We recently reported that the actin cytoskeleton regulating GTPase, Rac1, was activated in mouse muscle in response to stretching. Rac1 is a regulator of contraction- and insulin-stimulated glucose transport, however, its role in stretch-stimulated glucose transport and signalling is unknown. We therefore investigated whether stretch-induced glucose transport in skeletal muscle required Rac1 and the actin cytoskeleton. We used muscle-specific inducible Rac1 knockout mice as well as pharmacological inhibitors of Rac1 and the actin cytoskeleton in isolated soleus and extensor digitorum longus muscles. In addition, the role of Rac1 in contraction-stimulated glucose transport during conditions without mechanical load on the muscles was evaluated in loosely hanging muscles and muscles in which cross-bridge formation was blocked by the myosin ATPase inhibitors BTS and Blebbistatin. Knockout as well as pharmacological inhibition of Rac1 reduced stretch-stimulated glucose transport by 30-50% in soleus and extensor digitorum longus muscle. The actin depolymerizing agent latrunculin B similarly decreased glucose transport in response to stretching by 40-50%. Rac1 inhibition reduced contraction-stimulated glucose transport by 30-40% in tension developing muscle but did not affect contraction-stimulated glucose transport in

  5. Leucine stimulates protein synthesis in skeletal muscle of neonatal pigs by enhancing mTORC1 activation.

    PubMed

    Suryawan, Agus; Jeyapalan, Asumthia S; Orellana, Renan A; Wilson, Fiona A; Nguyen, Hanh V; Davis, Teresa A

    2008-10-01

    Skeletal muscle in the neonate grows at a rapid rate due in part to an enhanced sensitivity to the postprandial rise in amino acids, particularly leucine. To elucidate the molecular mechanism by which leucine stimulates protein synthesis in neonatal muscle, overnight-fasted 7-day-old piglets were treated with rapamycin [an inhibitor of mammalian target of rapamycin (mTOR) complex (mTORC)1] for 1 h and then infused with leucine for 1 h. Fractional rates of protein synthesis and activation of signaling components that lead to mRNA translation were determined in skeletal muscle. Rapamycin completely blocked leucine-induced muscle protein synthesis. Rapamycin markedly reduced raptor-mTOR association, an indicator of mTORC1 activation. Rapamycin blocked the leucine-induced phosphorylation of mTOR, S6 kinase 1 (S6K1), and eukaryotic initiation factor (eIF)4E-binding protein-1 (4E-BP1) and formation of the eIF4E.eIF4G complex and increased eIF4E.4E-BP1 complex abundance. Rapamycin had no effect on the association of mTOR with rictor, a crucial component for mTORC2 activation, or G protein beta-subunit-like protein (GbetaL), a component of mTORC1 and mTORC2. Neither leucine nor rapamycin affected the phosphorylation of AMP-activated protein kinase (AMPK), PKB, or tuberous sclerosis complex (TSC)2, signaling components that reside upstream of mTOR. Eukaryotic elongation factor (eEF)2 phosphorylation was not affected by leucine or rapamycin, although current dogma indicates that eEF2 phosphorylation is mTOR dependent. Together, these in vivo data suggest that leucine stimulates muscle protein synthesis in neonates by enhancing mTORC1 activation and its downstream effectors.

  6. Leucine stimulates protein synthesis in skeletal muscle of neonatal pigs by enhancing mTORC1 activation

    PubMed Central

    Suryawan, Agus; Jeyapalan, Asumthia S.; Orellana, Renan A.; Wilson, Fiona A.; Nguyen, Hanh V.; Davis, Teresa A.

    2008-01-01

    Skeletal muscle in the neonate grows at a rapid rate due in part to an enhanced sensitivity to the postprandial rise in amino acids, particularly leucine. To elucidate the molecular mechanism by which leucine stimulates protein synthesis in neonatal muscle, overnight-fasted 7-day-old piglets were treated with rapamycin [an inhibitor of mammalian target of rapamycin (mTOR) complex (mTORC)1] for 1 h and then infused with leucine for 1 h. Fractional rates of protein synthesis and activation of signaling components that lead to mRNA translation were determined in skeletal muscle. Rapamycin completely blocked leucine-induced muscle protein synthesis. Rapamycin markedly reduced raptor-mTOR association, an indicator of mTORC1 activation. Rapamycin blocked the leucine-induced phosphorylation of mTOR, S6 kinase 1 (S6K1), and eukaryotic initiation factor (eIF)4E-binding protein-1 (4E-BP1) and formation of the eIF4E·eIF4G complex and increased eIF4E·4E-BP1 complex abundance. Rapamycin had no effect on the association of mTOR with rictor, a crucial component for mTORC2 activation, or G protein β-subunit-like protein (GβL), a component of mTORC1 and mTORC2. Neither leucine nor rapamycin affected the phosphorylation of AMP-activated protein kinase (AMPK), PKB, or tuberous sclerosis complex (TSC)2, signaling components that reside upstream of mTOR. Eukaryotic elongation factor (eEF)2 phosphorylation was not affected by leucine or rapamycin, although current dogma indicates that eEF2 phosphorylation is mTOR dependent. Together, these in vivo data suggest that leucine stimulates muscle protein synthesis in neonates by enhancing mTORC1 activation and its downstream effectors. PMID:18682538

  7. Store-operated Ca(2+) entry (SOCE) contributes to normal skeletal muscle contractility in young but not in aged skeletal muscle.

    PubMed

    Thornton, Angela M; Zhao, Xiaoli; Weisleder, Noah; Brotto, Leticia S; Bougoin, Sylvain; Nosek, Thomas M; Reid, Michael; Hardin, Brian; Pan, Zui; Ma, Jianjie; Parness, Jerome; Brotto, Marco

    2011-06-01

    Muscle atrophy alone is insufficient to explain the significant decline in contractile force of skeletal muscle during normal aging. One contributing factor to decreased contractile force in aging skeletal muscle could be compromised excitation-contraction (E-C) coupling, without sufficient available Ca(2+) to allow for repetitive muscle contractility, skeletal muscles naturally become weaker. Using biophysical approaches, we previously showed that store-operated Ca(2+) entry (SOCE) is compromised in aged skeletal muscle but not in young ones. While important, a missing component from previous studies is whether or not SOCE function correlates with contractile function during aging. Here we test the contribution of extracellular Ca(2+) to contractile function of skeletal muscle during aging. First, we demonstrate graded coupling between SR Ca(2+) release channel-mediated Ca(2+) release and activation of SOCE. Inhibition of SOCE produced significant reduction of contractile force in young skeletal muscle, particularly at high frequency stimulation, and such effects were completely absent in aged skeletal muscle. Our data indicate that SOCE contributes to the normal physiological contractile response of young healthy skeletal muscle and that defective extracellular Ca(2+) entry through SOCE contributes to the reduced contractile force characteristic of aged skeletal muscle.

  8. Increased Resting Intracellular Calcium Modulates NF-κB-dependent Inducible Nitric-oxide Synthase Gene Expression in Dystrophic mdx Skeletal Myotubes*

    PubMed Central

    Altamirano, Francisco; López, Jose R.; Henríquez, Carlos; Molinski, Tadeusz; Allen, Paul D.; Jaimovich, Enrique

    2012-01-01

    Duchenne muscular dystrophy (DMD) is a genetic disorder caused by dystrophin mutations, characterized by chronic inflammation and severe muscle wasting. Dystrophic muscles exhibit activated immune cell infiltrates, up-regulated inflammatory gene expression, and increased NF-κB activity, but the contribution of the skeletal muscle cell to this process has been unclear. The aim of this work was to study the pathways that contribute to the increased resting calcium ([Ca2+]rest) observed in mdx myotubes and its possible link with up-regulation of NF-κB and pro-inflammatory gene expression in dystrophic muscle cells. [Ca2+]rest was higher in mdx than in WT myotubes (308 ± 6 versus 113 ± 2 nm, p < 0.001). In mdx myotubes, both the inhibition of Ca2+ entry (low Ca2+ solution, Ca2+-free solution, and Gd3+) and blockade of either ryanodine receptors or inositol 1,4,5-trisphosphate receptors reduced [Ca2+]rest. Basal activity of NF-κB was significantly up-regulated in mdx versus WT myotubes. There was an increased transcriptional activity and p65 nuclear localization, which could be reversed when [Ca2+]rest was reduced. Levels of mRNA for TNFα, IL-1β, and IL-6 were similar in WT and mdx myotubes, whereas inducible nitric-oxide synthase (iNOS) expression was increased 5-fold. Reducing [Ca2+]rest using different strategies reduced iNOS gene expression presumably as a result of decreased activation of NF-κB. We propose that NF-κB, modulated by increased [Ca2+]rest, is constitutively active in mdx myotubes, and this mechanism can account for iNOS overexpression and the increase in reactive nitrogen species that promote damage in dystrophic skeletal muscle cells. PMID:22549782

  9. Growth Modulation in Achondroplasia.

    PubMed

    McClure, Philip K; Kilinc, Eray; Birch, John G

    2017-09-01

    Achondroplasia is the most common skeletal dysplasia with a rate of nearly 1/10,000. The development of lower extremity deformity is well documented, and various modes of correction have been reported. There are no reports on the use of growth modulation to correct angular deformity in achondroplasia. Medical Records from 1985 to 2015 were reviewed for the diagnosis of achondroplasia and growth modulation procedures. Patients who had been treated for angular deformity of the legs by growth modulation were identified. A detailed analysis of their medical record and preoperative and final lower extremity radiographs was completed. Four patients underwent growth modulation procedures, all to correct existing varus deformity of the legs. Three of the 4 patients underwent bilateral distal femoral and proximal tibial growth modulation. The remaining patient underwent tibial correction only. Two of the 4 patients had a combined proximal fibular epiphysiodesis. All limbs had some improvement of alignment; however, 1 patient went on to bilateral osteotomies. Only 1 limb corrected to a neutral axis with growth modulation alone at last follow-up, initial implantation was done before 5 years of age. Growth modulation is an effective means for deformity correction in the setting of achondroplasia. However implantation may need to be done earlier than would be typical for patients without achondroplasia. Osteotomy may still be required after growth modulation for incomplete correction.

  10. Rap1b Is an Effector of Axin2 Regulating Crosstalk of Signaling Pathways During Skeletal Development.

    PubMed

    Maruyama, Takamitsu; Jiang, Ming; Abbott, Alycia; Yu, H-M Ivy; Huang, Qirong; Chrzanowska-Wodnicka, Magdalena; Chen, Emily I; Hsu, Wei

    2017-09-01

    Recent identification and isolation of suture stem cells capable of long-term self-renewal, clonal expanding, and differentiating demonstrate their essential role in calvarial bone development, homeostasis, and injury repair. These bona fide stem cells express a high level of Axin2 and are able to mediate bone regeneration and repair in a cell autonomous fashion. The importance of Axin2 is further demonstrated by its genetic inactivation in mice causing skeletal deformities resembling craniosynostosis in humans. The fate determination and subsequent differentiation of Axin2+ stem cells are highly orchestrated by a variety of evolutionary conserved signaling pathways including Wnt, FGF, and BMP. These signals are often antagonistic of each other and possess differential effects on osteogenic and chondrogenic cell types. However, the mechanisms underlying the interplay of these signaling transductions remain largely elusive. Here we identify Rap1b acting downstream of Axin2 as a signaling interrogator for FGF and BMP. Genetic analysis reveals that Rap1b is essential for development of craniofacial and body skeletons. Axin2 regulates Rap1b through modulation of canonical BMP signaling. The BMP-mediated activation of Rap1b promotes chondrogenic fate and chondrogenesis. Furthermore, by inhibiting MAPK signaling, Rap1b mediates the antagonizing effect of BMP on FGF to repress osteoblast differentiation. Disruption of Rap1b in mice not only enhances osteoblast differentiation but also impairs chondrocyte differentiation during intramembranous and endochondral ossifications, respectively, leading to severe defects in craniofacial and body skeletons. Our findings reveal a dual role of Rap1b in development of the skeletogenic cell types. Rap1b is critical for balancing the signaling effects of BMP and FGF during skeletal development and disease. © 2017 American Society for Bone and Mineral Research. © 2017 American Society for Bone and Mineral Research.

  11. The p27 Pathway Modulates the Regulation of Skeletal Growth and Osteoblastic Bone Formation by Parathyroid Hormone-Related Peptide.

    PubMed

    Zhu, Min; Zhang, Jing; Dong, Zhan; Zhang, Ying; Wang, Rong; Karaplis, Andrew; Goltzman, David; Miao, Dengshun

    2015-11-01

    Parathyroid hormone-related peptide (PTHrP) 1-84 knock-in mice (Pthrp KI) develop skeletal growth retardation and defective osteoblastic bone formation. To further examine the mechanisms underlying this phenotype, microarray analyses of differential gene expression profiles were performed in long bone extracts from Pthrp KI mice and their wild-type (WT) littermates. We found that the expression levels of p27, p16, and p53 were significantly upregulated in Pthrp KI mice relative to WT littermates. To determine whether p27 was involved in the regulation by PTHrP of skeletal growth and development in vivo, we generated compound mutant mice, which were homozygous for both p27 deletion and the Pthrp KI mutation (p27(-/-) Pthrp KI). We then compared p27(-/-) Pthrp KI mice with p27(-/-), Pthrp KI, and WT littermates. Deletion of p27 in Pthrp KI mice resulted in a longer lifespan, increased body weight, and improvement in skeletal growth. At 2 weeks of age, skeletal parameters, including length of long bones, size of epiphyses, numbers of proliferating cell nuclear antigen (PCNA)-positive chondrocytes, bone mineral density, trabecular bone volume, osteoblast numbers, and alkaline phosphatase (ALP)-, type I collagen-, and osteocalcin-positive bone areas were increased in p27(-/-) mice and reduced in both Pthrp KI and p27(-/-) Pthrp KI mice compared with WT mice; however, these parameters were increased in p27(-/-) Pthrp KI mice compared with Pthrp KI mice. As well, protein expression levels of PTHR, IGF-1, and Bmi-1, and the numbers of total colony-forming unit fibroblastic (CFU-f) and ALP-positive CFU-f were similarly increased in p27(-/-) Pthrp KI mice compared with Pthrp KI mice. Our results demonstrate that deletion of p27 in Pthrp KI mice can partially rescue defects in skeletal growth and osteoblastic bone formation by enhancing endochondral bone formation and osteogenesis. These studies, therefore, indicate that the p27 pathway may function downstream in the action

  12. Deletion of the transcriptional coactivator PGC1α in skeletal muscles is associated with reduced expression of genes related to oxidative muscle function.

    PubMed

    Hatazawa, Yukino; Minami, Kimiko; Yoshimura, Ryoji; Onishi, Takumi; Manio, Mark Christian; Inoue, Kazuo; Sawada, Naoki; Suzuki, Osamu; Miura, Shinji; Kamei, Yasutomi

    2016-12-09

    The expression of the transcriptional coactivator PGC1α is increased in skeletal muscles during exercise. Previously, we showed that increased PGC1α leads to prolonged exercise performance (the duration for which running can be continued) and, at the same time, increases the expression of branched-chain amino acid (BCAA) metabolism-related enzymes and genes that are involved in supplying substrates for the TCA cycle. We recently created mice with PGC1α knockout specifically in the skeletal muscles (PGC1α KO mice), which show decreased mitochondrial content. In this study, global gene expression (microarray) analysis was performed in the skeletal muscles of PGC1α KO mice compared with that of wild-type control mice. As a result, decreased expression of genes involved in the TCA cycle, oxidative phosphorylation, and BCAA metabolism were observed. Compared with previously obtained microarray data on PGC1α-overexpressing transgenic mice, each gene showed the completely opposite direction of expression change. Bioinformatic analysis of the promoter region of genes with decreased expression in PGC1α KO mice predicted the involvement of several transcription factors, including a nuclear receptor, ERR, in their regulation. As PGC1α KO microarray data in this study show opposing findings to the PGC1α transgenic data, a loss-of-function experiment, as well as a gain-of-function experiment, revealed PGC1α's function in the oxidative energy metabolism of skeletal muscles. Copyright © 2016 Elsevier Inc. All rights reserved.

  13. Molecular characterization of a patient with an interstitial 1q deletion [del(1)(q24.1q25.3)] and distinctive skeletal abnormalities.

    PubMed

    Descartes, Maria; Hain, Julie Zenger; Conklin, Michael; Franklin, Judy; Mikhail, Fady M; Lachman, Ralph S; Nolet, Serge; Messiaen, Ludwine M

    2008-11-15

    Here we report on a patient with an interstitial deletion on the long(q) arm of chromosome 1 who presents with a unique constellation of anomalies including brachydactyly type E, Müllerian agenesis, growth hormone deficiency, as well as other abnormalities. We present the clinical details of this patient's presentation, the skeletal findings, and provide characterization of the deletion at the molecular level. We postulate that these skeletal anomalies are distinctive to 1q deletions involving the 1q24q25 region. (c) 2008 Wiley-Liss, Inc.

  14. Ginsenoside Rb1 improves energy metabolism in the skeletal muscle of an animal model of postoperative fatigue syndrome.

    PubMed

    Tan, Shan-Jun; Li, Ning; Zhou, Feng; Dong, Qian-Tong; Zhang, Xiao-Dong; Chen, Bi-Cheng; Yu, Zhen

    2014-10-01

    Postoperative fatigue syndrome (POFS) is a common clinical complication followed by almost every major abdominal surgery. Ginsenoside Rb1 (GRb1), a principle ginsenoside in ginseng, could exert a potent anti-fatigue effect on POFS. However, the mechanism is still unknown. Previous studies revealed that alterations in the energy metabolism in the skeletal muscle may play a vital role in the development and progression of fatigue. In the present study, we investigate the effect of GRb1 on energy metabolism in the skeletal muscle of a rat model of POFS induced by major small intestinal resection. GRb1 (10 mg/kg) was intraperitoneally administrated once daily for 1, 3, 7, and 10 d from the operation day, respectively. The locomotor activity was recorded every day, and total food intake was calculated starting from 24 h after surgery. After GRb1 treatment was completed, blood and skeletal muscle were sampled. The level of blood glucose was determined by an automatic biochemical analyzer. The content of adenosine triphosphate (ATP) in skeletal muscle was determined by high-performance liquid chromatography. The activity of energy metabolic enzymes Na(+)-K(+)-ATPase, pyruvate kinase, and succinate dehydrogenase (SDH) was assessed by commercially available kits. The results revealed that GRb1 could increase locomotor activity of POFS rats and significantly increase their total food intake postoperatively (P < 0.05). Furthermore, GRb1 also significantly increased ATP content in the skeletal muscle of POFS rats (P < 0.05). Meanwhile, the activity of Na(+)-K(+)-ATPase and SDH in the skeletal muscle of POFS rats was enhanced by GRb1 (P < 0.05). However, no significant differences in blood glucose and pyruvate kinase were found between the POFS and GRb1 treatment rats (P > 0.05). These results suggest that GRb1 may improve skeletal muscle energy metabolism in POFS, and the underlying mechanism may be associated with an increase in the content of ATP and an enhancement in the

  15. Diclofenac pretreatment modulates exercise-induced inflammation in skeletal muscle of rats through the TLR4/NF-κB pathway.

    PubMed

    Barcelos, Rômulo Pillon; Bresciani, Guilherme; Cuevas, Maria José; Martínez-Flórez, Susana; Soares, Félix Alexandre Antunes; González-Gallego, Javier

    2017-07-01

    Nonsteroidal anti-inflammatory drugs, such as diclofenac, are widely used to treat inflammation and pain in several conditions, including sports injuries. This study analyzes the influence of diclofenac on the toll-like receptor-nuclear factor kappa B (TLR-NF-κB) pathway in skeletal muscle of rats submitted to acute eccentric exercise. Twenty male Wistar rats were divided into 4 groups: control-saline, control-diclofenac, exercise-saline, and exercise-diclofenac. Diclofenac or saline were administered for 7 days prior to an acute eccentric exercise bout. The inflammatory status was evaluated through mRNA levels of cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), interleukin-6 (IL-6), IL-1β, and tumor necrosis factor alpha (TNF-α), and protein content of COX-2, IL-6, and TNF-α in vastus lateralis muscle. Data obtained showed that a single bout of eccentric exercise significantly increased COX-2 gene expression. Similarly, mRNA expression and protein content of other inflammation-related genes also increased after the acute exercise. However, these effects were attenuated in the exercise + diclofenac group. TLR4, myeloid differentiation primary response gene 88 (MyD88), and p65 were also upregulated after the acute eccentric bout and the effect was blunted by the anti-inflammatory drug. These findings suggest that pretreatment with diclofenac may represent an effective tool to ameliorate the pro-inflammatory status induced by acute exercise in rat skeletal muscle possibly through an attenuation of the TLR4-NF-κB signaling pathway.

  16. NEU3 Sialidase Is Activated under Hypoxia and Protects Skeletal Muscle Cells from Apoptosis through the Activation of the Epidermal Growth Factor Receptor Signaling Pathway and the Hypoxia-inducible Factor (HIF)-1α

    PubMed Central

    Scaringi, Raffaella; Piccoli, Marco; Papini, Nadia; Cirillo, Federica; Conforti, Erika; Bergante, Sonia; Tringali, Cristina; Garatti, Andrea; Gelfi, Cecilia; Venerando, Bruno; Menicanti, Lorenzo; Tettamanti, Guido; Anastasia, Luigi

    2013-01-01

    NEU3 sialidase, a key enzyme in ganglioside metabolism, is activated under hypoxic conditions in cultured skeletal muscle cells (C2C12). NEU3 up-regulation stimulates the EGF receptor signaling pathway, which in turn activates the hypoxia-inducible factor (HIF-1α), resulting in a final increase of cell survival and proliferation. In the same cells, stable overexpression of sialidase NEU3 significantly enhances cell resistance to hypoxia, whereas stable silencing of the enzyme renders cells more susceptible to apoptosis. These data support the working hypothesis of a physiological role played by NEU3 sialidase in protecting cells from hypoxic stress and may suggest new directions in the development of therapeutic strategies against ischemic diseases, particularly of the cerebro-cardiovascular system. PMID:23209287

  17. NEU3 sialidase is activated under hypoxia and protects skeletal muscle cells from apoptosis through the activation of the epidermal growth factor receptor signaling pathway and the hypoxia-inducible factor (HIF)-1α.

    PubMed

    Scaringi, Raffaella; Piccoli, Marco; Papini, Nadia; Cirillo, Federica; Conforti, Erika; Bergante, Sonia; Tringali, Cristina; Garatti, Andrea; Gelfi, Cecilia; Venerando, Bruno; Menicanti, Lorenzo; Tettamanti, Guido; Anastasia, Luigi

    2013-02-01

    NEU3 sialidase, a key enzyme in ganglioside metabolism, is activated under hypoxic conditions in cultured skeletal muscle cells (C2C12). NEU3 up-regulation stimulates the EGF receptor signaling pathway, which in turn activates the hypoxia-inducible factor (HIF-1α), resulting in a final increase of cell survival and proliferation. In the same cells, stable overexpression of sialidase NEU3 significantly enhances cell resistance to hypoxia, whereas stable silencing of the enzyme renders cells more susceptible to apoptosis. These data support the working hypothesis of a physiological role played by NEU3 sialidase in protecting cells from hypoxic stress and may suggest new directions in the development of therapeutic strategies against ischemic diseases, particularly of the cerebro-cardiovascular system.

  18. Forward Genetics Defines Xylt1 as a Key, Conserved Regulator of Early Chondrocyte Maturation and Skeletal Length

    PubMed Central

    Mis, Emily K.; Liem, Karel F.; Kong, Yong; Schwartz, Nancy B.; Domowicz, Miriam; Weatherbee, Scott D.

    2014-01-01

    The long bones of the vertebrate body are built by the initial formation of a cartilage template that is later replaced by mineralized bone. The proliferation and maturation of the skeletal precursor cells (chondrocytes) within the cartilage template and their replacement by bone is a highly coordinated process which, if misregulated, can lead to a number of defects including dwarfism and other skeletal deformities. This is exemplified by the fact that abnormal bone development is one of the most common types of human birth defects. Yet, many of the factors that initiate and regulate chondrocyte maturation are not known. We identified a recessive dwarf mouse mutant (pug) from an N-ethyl-N-nitrosourea (ENU) mutagenesis screen. pug mutant skeletal elements are patterned normally during development, but display a ~20% length reduction compared to wild-type embryos. We show that the pug mutation does not lead to changes in chondrocyte proliferation but instead promotes premature maturation and early ossification, which ultimately leads to disproportionate dwarfism. Using sequence capture and high-throughput sequencing, we identified a missense mutation in the Xylosyltransferase 1 (Xylt1) gene in pug mutants. Xylosyltransferases catalyze the initial step in glycosaminoglycan (GAG) chain addition to proteoglycan core proteins, and these modifications are essential for normal proteoglycan function. We show that the pug mutation disrupts Xylt1 activity and subcellular localization, leading to a reduction in GAG chains in pug mutants. The pug mutant serves as a novel model for mammalian dwarfism and identifies a key role for proteoglycan modification in the initiation of chondrocyte maturation. PMID:24161523

  19. Forward genetics defines Xylt1 as a key, conserved regulator of early chondrocyte maturation and skeletal length.

    PubMed

    Mis, Emily K; Liem, Karel F; Kong, Yong; Schwartz, Nancy B; Domowicz, Miriam; Weatherbee, Scott D

    2014-01-01

    The long bones of the vertebrate body are built by the initial formation of a cartilage template that is later replaced by mineralized bone. The proliferation and maturation of the skeletal precursor cells (chondrocytes) within the cartilage template and their replacement by bone is a highly coordinated process which, if misregulated, can lead to a number of defects including dwarfism and other skeletal deformities. This is exemplified by the fact that abnormal bone development is one of the most common types of human birth defects. Yet, many of the factors that initiate and regulate chondrocyte maturation are not known. We identified a recessive dwarf mouse mutant (pug) from an N-ethyl-N-nitrosourea (ENU) mutagenesis screen. pug mutant skeletal elements are patterned normally during development, but display a ~20% length reduction compared to wild-type embryos. We show that the pug mutation does not lead to changes in chondrocyte proliferation but instead promotes premature maturation and early ossification, which ultimately leads to disproportionate dwarfism. Using sequence capture and high-throughput sequencing, we identified a missense mutation in the Xylosyltransferase 1 (Xylt1) gene in pug mutants. Xylosyltransferases catalyze the initial step in glycosaminoglycan (GAG) chain addition to proteoglycan core proteins, and these modifications are essential for normal proteoglycan function. We show that the pug mutation disrupts Xylt1 activity and subcellular localization, leading to a reduction in GAG chains in pug mutants. The pug mutant serves as a novel model for mammalian dwarfism and identifies a key role for proteoglycan modification in the initiation of chondrocyte maturation. © 2013 Published by Elsevier Inc.

  20. Curcumin attenuates skeletal muscle mitochondrial impairment in COPD rats: PGC-1α/SIRT3 pathway involved.

    PubMed

    Zhang, Ming; Tang, Jingjing; Li, Yali; Xie, Yingying; Shan, Hu; Chen, Mingxia; Zhang, Jie; Yang, Xia; Zhang, Qiuhong; Yang, Xudong

    2017-11-01

    Curcumin has been widely used to treat numerous diseases due to its antioxidant property. The aim of the present study is to investigate the effect of curcumin on skeletal muscle mitochondria in chronic obstructive pulmonary disease (COPD) and its underlying mechanism. The rat model of COPD was established by cigarette smoke exposure combined with intratracheal administration of lipopolysaccharide. Airway inflammation and emphysema were notably ameliorated by the treatment with curcumin. Oral administration of curcumin significantly improved muscle fiber atrophy, myofibril disorganization, interstitial fibrosis and mitochondrial structure damage in the skeletal muscle of COPD rats. Mitochondrial enzyme activities of cytochrome c oxidase, succinate dehydrogenase, Na + /K + -ATPase and Ca 2+ -ATPase in skeletal muscle mitochondria from COPD rats were significantly increased after treatment with curcumin. Moreover, curcumin significantly decreased oxidative stress and inflammation by determining the levels of malondialdehyde, manganese superoxide dismutase, glutathione peroxidase, catalase, IL-6 and TNF-α in skeletal muscle of COPD rats. Furthermore, curcumin significantly increased the mRNA and protein expression of PGC-1α and SIRT3 in the skeletal muscle tissues of COPD rats. These results suggested that curcumin can attenuate skeletal muscle mitochondrial impairment in COPD rats possibly by the up-regulation of PGC-1α/SIRT3 signaling pathway. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Crystallin-αB Regulates Skeletal Muscle Homeostasis via Modulation of Argonaute2 Activity*

    PubMed Central

    Neppl, Ronald L.; Kataoka, Masaharu; Wang, Da-Zhi

    2014-01-01

    The core functional machinery of the RNAi pathway is the RNA-induced silencing complex (RISC), wherein Argonaute2 (Ago2) is essential for siRNA-directed endonuclease activity and RNAi/microRNA-mediated gene silencing. Crystallin-αB (CryAB) is a small heat shock protein involved in preventing protein aggregation. We demonstrate that CryAB interacts with the N and C termini of Ago2, not the catalytic site defined by the convergence of the PAZ, MID, and PIWI domains. We further demonstrate significantly reduced Ago2 activity in the absence of CryAB, highlighting a novel role of CryAB in the mammalian RNAi/microRNA pathway. In skeletal muscle of CryAB null mice, we observe a shift in the hypertrophy-atrophy signaling axis toward atrophy under basal conditions. Moreover, loss of CryAB altered the capability of satellite cells to regenerate skeletal muscle. These studies establish that CryAB is necessary for normal Ago2/RISC activity and cellular homeostasis in skeletal muscle. PMID:24782307

  2. Skeletal muscle plasticity induced by seasonal acclimatization involves IGF1 signaling: implications in ribosomal biogenesis and protein synthesis.

    PubMed

    Fuentes, Eduardo N; Zuloaga, Rodrigo; Valdes, Juan Antonio; Molina, Alfredo; Alvarez, Marco

    2014-10-01

    One of the most fundamental biological processes in living organisms that are affected by environmental fluctuations is growth. In fish, skeletal muscle accounts for the largest proportion of body mass, and the growth of this tissue is mainly controlled by the insulin-like growth factor (IGF) system. By using the carp (Cyprinus carpio), a fish that inhabits extreme conditions during winter and summer, we assessed the skeletal muscle plasticity induced by seasonal acclimatization and the relation of IGF signaling with protein synthesis and ribosomal biogenesis. The expression of igf1 in muscle decreased during winter in comparison with summer, whereas the expression for both paralogues of igf2 did not change significantly between seasons. The expression of igf1 receptor a (igf1ra), but not of igf1rb, was down-regulated in muscle during the winter as compared to the summer. A decrease in protein contents and protein phosphorylation for IGF signaling molecules in muscle was observed in winter-acclimatized carp. This was related with a decreased expression in muscle for markers of myogenesis (myoblast determination factor (myod), myogenic factor 5 (myf5), and myogenin (myog)); protein synthesis (myosin heavy chain (mhc) and myosin light chain (mlc3 and mlc1b)); and ribosomal biogenesis (pre-rRNA and ribosomal proteins). IGF signaling, and key markers of ribosomal biogenesis, protein synthesis, and myogenesis were affected by seasonal acclimatization, with differential regulation in gene expression and signaling pathway activation observed in muscle between both seasons. This suggests that these molecules are responsible for the muscle plasticity induced by seasonal acclimatization in carp. Copyright © 2014 Elsevier Inc. All rights reserved.

  3. Venlafaxine treatment after endothelin-1-induced cortical stroke modulates growth factor expression and reduces tissue damage in rats.

    PubMed

    Zepeda, Rodrigo; Contreras, Valentina; Pissani, Claudia; Stack, Katherine; Vargas, Macarena; Owen, Gareth I; Lazo, Oscar M; Bronfman, Francisca C

    2016-08-01

    Neuromodulators, such as antidepressants, may contribute to neuroprotection by modulating growth factor expression to exert anti-inflammatory effects and to support neuronal plasticity after stroke. Our objective was to study whether early treatment with venlafaxine, a serotonin-norepinephrine reuptake inhibitor, modulates growth factor expression and positively contributes to reducing the volume of infarcted brain tissue resulting in increased functional recovery. We studied the expression of BDNF, FGF2 and TGF-β1 by examining their mRNA and protein levels and cellular distribution using quantitative confocal microscopy at 5 days after venlafaxine treatment in control and infarcted brains. Venlafaxine treatment did not change the expression of these growth factors in sham rats. In infarcted rats, BDNF mRNA and protein levels were reduced, while the mRNA and protein levels of FGF2 and TGF-β1 were increased. Venlafaxine treatment potentiated all of the changes that were induced by cortical stroke alone. In particular, increased levels of FGF2 and TGF-β1 were observed in astrocytes at 5 days after stroke induction, and these increases were correlated with decreased astrogliosis (measured by GFAP) and increased synaptophysin immunostaining at twenty-one days after stroke in venlafaxine-treated rats. Finally, we show that venlafaxine reduced infarct volume after stroke resulting in increased functional recovery, which was measured using ladder rung motor tests, at 21 days after stroke. Our results indicate that the early oral administration of venlafaxine positively contributes to neuroprotection during the acute and late events that follow stroke. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Peroxisome proliferator-activated receptor-δ activates endothelial progenitor cells to induce angio-myogenesis through matrix metallo-proteinase-9-mediated insulin-like growth factor-1 paracrine networks.

    PubMed

    Han, Jung-Kyu; Kim, Hack-Lyoung; Jeon, Ki-Hyun; Choi, Young-Eun; Lee, Hyun-Sook; Kwon, Yoo-Wook; Jang, Ja-June; Cho, Hyun-Jai; Kang, Hyun-Jae; Oh, Byung-Hee; Park, Young-Bae; Kim, Hyo-Soo

    2013-06-01

    The roles of peroxisome proliferator-activated receptor (PPAR)-δ in vascular biology are mainly unknown. We investigated the effects of PPAR-δ activation on the paracrine networks between endothelial progenitor cells (EPCs) and endothelial cells (ECs)/skeletal muscle. Treatment of EPCs with GW501516, a PPAR-δ agonist, induced specifically matrix metallo-proteinase (MMP)-9 by direct transcriptional activation. Subsequently, this increased-MMP-9 broke down insulin-like growth factor-binding protein (IGFBP)-3, resulting in IGF-1 receptor (IGF-1R) activation in surrounding target cells. Treatment of conditioned medium from GW501516-stimulated EPCs enhanced the number and functions of human umbilical vein ECs and C2C12 myoblasts via MMP-9-mediated IGF-1R activation. Systemic administration of GW501516 in mice increased MMP-9 expression in EPCs, and augmented IGFBP-3 degradation in serum. In a mouse hindlimb ischaemia model, systemic treatment of GW501516 or local transplantation of GW501516-treated EPCs induced IGF-1R phosphorylation in ECs and skeletal muscle in the ischaemic limbs, leading to augmented angiogenesis and skeletal muscle regeneration. It also enhanced wound healing with increased angiogenesis in a mouse skin punch wound model. These pro-angiogenic and muscle-regenerating effects were abolished by MMP-9 knock-out. Our results suggest that PPAR-δ is a crucial modulator of angio-myogenesis via the paracrine effects of EPCs, and its agonist is a good candidate as a therapeutic drug for patients with peripheral vascular diseases.

  5. Effects of dietary protein restriction on muscle fiber characteristics and mTORC1 pathway in the skeletal muscle of growing-finishing pigs.

    PubMed

    Li, Yinghui; Li, Fengna; Wu, Li; Wei, Hongkui; Liu, Yingying; Li, Tiejun; Tan, Bie; Kong, Xiangfeng; Yao, Kang; Chen, Shuai; Wu, Fei; Duan, Yehui; Yin, Yulong

    2016-01-01

    To investigate the effects of dietary crude protein (CP) restriction on muscle fiber characteristics and key regulators related to protein deposition in skeletal muscle, a total of 18 growing-finishing pigs (62.30 ± 0.88 kg) were allotted to 3 groups and fed with the recommended adequate protein (AP, 16 % CP) diet, moderately restricted protein (MP, 13 % CP) diet and low protein (LP, 10 % CP) diet, respectively. The skeletal muscle of different locations in pigs, including longissimus dorsi muscle (LDM), psoas major muscle (PMM) and biceps femoris muscle (BFM) were collected and analyzed. Results showed that growing-finishing pigs fed the MP or AP diet improved (P < 0.01) the average daily gain and feed: gain ratio compared with those fed the LP diet, and the MP diet tended to increase (P = 0.09) the weight of LDM. Moreover, the ATP content and energy charge value were varied among muscle samples from different locations of pigs fed the reduced protein diets. We also observed that pigs fed the MP diet up-regulated (P < 0.05) muscular mRNA expression of all the selected key genes, except that myosin heavy chain (MyHC) IIb, MyHC IIx, while mRNA expression of ubiquitin ligases genes was not affected by dietary CP level. Additionally, the activation of mammalian target of rapamycin complex 1 (mTORC1) pathway was stimulated (P < 0.05) in skeletal muscle of the pigs fed the MP or AP diet compared with those fed the LP diet. The results suggest that the pigs fed the MP diet could catch up to the growth performance and the LDM weight of the pigs fed the AP diet, and the underlying mechanism may be partly due to the alteration in energy status, modulation of muscle fiber characteristics and mTORC1 activation as well as its downstream effectors in skeletal muscle of different locations in growing-finishing pigs.

  6. O-GlcNAc Transferase/Host Cell Factor C1 Complex Regulates Gluconeogenesis by Modulating PGC-1α Stability

    PubMed Central

    Ruan, Hai-Bin; Han, Xuemei; Li, Min-Dian; Singh, Jay Prakash; Qian, Kevin; Azarhoush, Sascha; Zhao, Lin; Bennett, Anton M.; Samuel, Varman T.; Wu, Jing; Yates, John R.; Yang, Xiaoyong

    2012-01-01

    SUMMARY A major cause of hyperglycemia in diabetic patients is inappropriate hepatic gluconeogenesis. PGC-1α is a master regulator of gluconeogenesis, and its activity is controlled by various post-translational modifications. A small portion of glucose metabolizes through the hexosamine biosynthetic pathway, which leads to O-linked β-N-acetylglucosamine (O-GlcNAc) modification of cytoplasmic and nuclear proteins. Using a proteomic approach, we identified a broad variety of proteins associated with O-GlcNAc transferase (OGT), among which host cell factor C1 (HCF-1) is highly abundant. HCF-1 recruits OGT to O-GlcNAcylate PGC-1α and O-GlcNAcylation facilitates the binding of the deubiquitinase BAP1, thus protecting PGC-1α from degradation and promoting gluconeogenesis. Glucose availability modulates gluconeogenesis through the regulation of PGC-1α O-GlcNAcylation and stability by the OGT/HCF1 complex. Hepatic knockdown of OGT and HCF-1 improves glucose homeostasis in diabetic mice. These findings define the OGT/HCF-1 complex as a glucose sensor and key regulator of gluconeogenesis, shedding light on new strategies for treating diabetes. PMID:22883232

  7. Inhalation of Carbon Monoxide Reduces Skeletal Muscle Injury Following Hind Limb Ischemia Reperfusion Injury in Mice

    PubMed Central

    Patel, Rajendra; Albadawi, Hassan; Steudel, Wolfgang; Hashmi, Faraz F.; Kang, Jeanwan; Yoo, Hyung-Jin; Watkins, Michael T.

    2011-01-01

    Introduction The purpose of this study was to determine if inhaled carbon monoxide (CO) can ameliorate skeletal muscle injury, modulate endogenous heme oxygenase-1 (HO) expression, improve indices of tissue integrity and inflammation following hind limb ischemia reperfusion(IR). Methods C57BL6 mice inhaling CO (250ppm) or room air were subjected to 1.5 hrs of ischemia followed by limb reperfusion for either 3 or 6 hours (total treatment time of 4.5 or 7.5 hrs). After the initial period of reperfusion, all mice breathed only room air until 24 hours after the onset of ischemia. Mice were sacrificed at either the end of CO treatment or at 24 hours reperfusion. Skeletal muscle was subjected to histologic and biochemical analysis. Results CO treatment for 7.5 hours protected skeletal muscle from histologic and structural evidence of skeletal muscle injury. Serum and tissue cytokines were significantly reduced (p<0.05) in mice treated with CO for 7.5 hours. Tubulin, Heme Oxygenase, and ATP levels were higher in CO treated mice. Conclusions Inhaled CO protected muscle from structural injury and energy depletion following IR. PMID:22450026

  8. Skeletal Muscle-specific G Protein-coupled Receptor Kinase 2 Ablation Alters Isolated Skeletal Muscle Mechanics and Enhances Clenbuterol-stimulated Hypertrophy*

    PubMed Central

    Woodall, Benjamin P.; Woodall, Meryl C.; Luongo, Timothy S.; Grisanti, Laurel A.; Tilley, Douglas G.; Elrod, John W.; Koch, Walter J.

    2016-01-01

    GRK2, a G protein-coupled receptor kinase, plays a critical role in cardiac physiology. Adrenergic receptors are the primary target for GRK2 activity in the heart; phosphorylation by GRK2 leads to desensitization of these receptors. As such, levels of GRK2 activity in the heart directly correlate with cardiac contractile function. Furthermore, increased expression of GRK2 after cardiac insult exacerbates injury and speeds progression to heart failure. Despite the importance of this kinase in both the physiology and pathophysiology of the heart, relatively little is known about the role of GRK2 in skeletal muscle function and disease. In this study we generated a novel skeletal muscle-specific GRK2 knock-out (KO) mouse (MLC-Cre:GRK2fl/fl) to gain a better understanding of the role of GRK2 in skeletal muscle physiology. In isolated muscle mechanics testing, GRK2 ablation caused a significant decrease in the specific force of contraction of the fast-twitch extensor digitorum longus muscle yet had no effect on the slow-twitch soleus muscle. Despite these effects in isolated muscle, exercise capacity was not altered in MLC-Cre:GRK2fl/fl mice compared with wild-type controls. Skeletal muscle hypertrophy stimulated by clenbuterol, a β2-adrenergic receptor (β2AR) agonist, was significantly enhanced in MLC-Cre:GRK2fl/fl mice; mechanistically, this seems to be due to increased clenbuterol-stimulated pro-hypertrophic Akt signaling in the GRK2 KO skeletal muscle. In summary, our study provides the first insights into the role of GRK2 in skeletal muscle physiology and points to a role for GRK2 as a modulator of contractile properties in skeletal muscle as well as β2AR-induced hypertrophy. PMID:27566547

  9. Skeletal Muscle-specific G Protein-coupled Receptor Kinase 2 Ablation Alters Isolated Skeletal Muscle Mechanics and Enhances Clenbuterol-stimulated Hypertrophy.

    PubMed

    Woodall, Benjamin P; Woodall, Meryl C; Luongo, Timothy S; Grisanti, Laurel A; Tilley, Douglas G; Elrod, John W; Koch, Walter J

    2016-10-14

    GRK2, a G protein-coupled receptor kinase, plays a critical role in cardiac physiology. Adrenergic receptors are the primary target for GRK2 activity in the heart; phosphorylation by GRK2 leads to desensitization of these receptors. As such, levels of GRK2 activity in the heart directly correlate with cardiac contractile function. Furthermore, increased expression of GRK2 after cardiac insult exacerbates injury and speeds progression to heart failure. Despite the importance of this kinase in both the physiology and pathophysiology of the heart, relatively little is known about the role of GRK2 in skeletal muscle function and disease. In this study we generated a novel skeletal muscle-specific GRK2 knock-out (KO) mouse (MLC-Cre:GRK2 fl/fl ) to gain a better understanding of the role of GRK2 in skeletal muscle physiology. In isolated muscle mechanics testing, GRK2 ablation caused a significant decrease in the specific force of contraction of the fast-twitch extensor digitorum longus muscle yet had no effect on the slow-twitch soleus muscle. Despite these effects in isolated muscle, exercise capacity was not altered in MLC-Cre:GRK2 fl/fl mice compared with wild-type controls. Skeletal muscle hypertrophy stimulated by clenbuterol, a β 2 -adrenergic receptor (β 2 AR) agonist, was significantly enhanced in MLC-Cre:GRK2 fl/fl mice; mechanistically, this seems to be due to increased clenbuterol-stimulated pro-hypertrophic Akt signaling in the GRK2 KO skeletal muscle. In summary, our study provides the first insights into the role of GRK2 in skeletal muscle physiology and points to a role for GRK2 as a modulator of contractile properties in skeletal muscle as well as β 2 AR-induced hypertrophy. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

  10. Store-Operated Ca2+ Entry (SOCE) Contributes to Normal Skeletal Muscle Contractility in young but not in aged skeletal muscle

    PubMed Central

    Brotto, Leticia S.; Bougoin, Sylvain; Nosek, Thomas M.; Reid, Michael; Hardin, Brian; Pan, Zui; Ma, Jianjie; Parness, Jerome

    2011-01-01

    Muscle atrophy alone is insufficient to explain the significant decline in contractile force of skeletal muscle during normal aging. One contributing factor to decreased contractile force in aging skeletal muscle could be compromised excitation-contraction (E-C) coupling, without sufficient available Ca2+ to allow for repetitive muscle contractility, skeletal muscles naturally become weaker. Using biophysical approaches, we previously showed that store-operated Ca2+ entry (SOCE) is compromised in aged skeletal muscle but not in young ones. While important, a missing component from previous studies is whether or not SOCE function correlates with contractile function during aging. Here we test the contribution of extracellular Ca2+ to contractile function of skeletal muscle during aging. First, we demonstrate graded coupling between SR Ca2+ release channel-mediated Ca2+ release and activation of SOCE. Inhibition of SOCE produced significant reduction of contractile force in young skeletal muscle, particularly at high frequency stimulation, and such effects were completely absent in aged skeletal muscle. Our data indicate that SOCE contributes to the normal physiological contractile response of young healthy skeletal muscle and that defective extracellular Ca2+ entry through SOCE contributes to the reduced contractile force characteristic of aged skeletal muscle. PMID:21666285

  11. Stage of perinatal development regulates skeletal muscle mitochondrial biogenesis and myogenic regulatory factor genes with little impact of growth restriction or cross-fostering.

    PubMed

    Laker, R C; Wadley, G D; McConell, G K; Wlodek, M E

    2012-02-01

    Foetal growth restriction impairs skeletal muscle development and adult muscle mitochondrial biogenesis. We hypothesized that key genes involved in muscle development and mitochondrial biogenesis would be altered following uteroplacental insufficiency in rat pups, and improving postnatal nutrition by cross-fostering would ameliorate these deficits. Bilateral uterine vessel ligation (Restricted) or sham (Control) surgery was performed on day 18 of gestation. Males and females were investigated at day 20 of gestation (E20), 1 (PN1), 7 (PN7) and 35 (PN35) days postnatally. A separate cohort of Control and Restricted pups were cross-fostered onto a different Control or Restricted mother and examined at PN7. In both sexes, peroxisome proliferator-activated receptor (PPAR)-γ coactivator-1α (PGC-1α), cytochrome c oxidase subunits 3 and 4 (COX III and IV) and myogenic regulatory factor 4 expression increased from late gestation to postnatal life, whereas mitochondrial transcription factor A, myogenic differentiation 1 (MyoD), myogenin and insulin-like growth factor I (IGF-I) decreased. Foetal growth restriction increased MyoD mRNA in females at PN7, whereas in males IGF-I mRNA was higher at E20 and PN1. Cross-fostering Restricted pups onto a Control mother significantly increased COX III mRNA in males and COX IV mRNA in both sexes above controls with little effect on other genes. Developmental age appears to be a major factor regulating skeletal muscle mitochondrial and developmental genes, with growth restriction and cross-fostering having only subtle effects. It therefore appears that reductions in adult mitochondrial biogenesis markers likely develop after weaning.

  12. Amino Acid Sensing in Skeletal Muscle

    PubMed Central

    Moro, Tatiana; Ebert, Scott M.; Adams, Christopher M.; Rasmussen, Blake B.

    2016-01-01

    Aging impairs skeletal muscle protein synthesis, leading to muscle weakness and atrophy. However, the underlying molecular mechanisms remain poorly understood. Here, we review evidence that mTORC1- and ATF4-mediated amino acid sensing pathways, triggered by impaired amino acid delivery to aged skeletal muscle, may play important roles in skeletal muscle aging. Interventions that alleviate age-related impairments in muscle protein synthesis, strength and/or muscle mass appear to do so by reversing age-related changes in skeletal muscle amino acid delivery, mTORC1 activity and/or ATF4 activity. An improved understanding of the mechanisms and roles of amino acid sensing pathways in skeletal muscle may lead to evidence-based strategies to attenuate sarcopenia. PMID:27444066

  13. Interaction between vestibulosympathetic and skeletal muscle reflexes on sympathetic activity in humans

    NASA Technical Reports Server (NTRS)

    Ray, C. A.

    2001-01-01

    Evidence from animals indicates that skeletal muscle afferents activate the vestibular nuclei and that both vestibular and skeletal muscle afferents have inputs to the ventrolateral medulla. The purpose of the present study was to investigate the interaction between the vestibulosympathetic and skeletal muscle reflexes on muscle sympathetic nerve activity (MSNA) and arterial pressure in humans. MSNA, arterial pressure, and heart rate were measured in 17 healthy subjects in the prone position during three experimental trials. The three trials were 2 min of 1) head-down rotation (HDR) to engage the vestibulosympathetic reflex, 2) isometric handgrip (IHG) at 30% maximal voluntary contraction to activate skeletal muscle afferents, and 3) HDR and IHG performed simultaneously. The order of the three trials was randomized. HDR and IHG performed alone increased total MSNA by 46 +/- 16 and 77 +/- 24 units, respectively (P < 0.01). During the HDR plus IHG trial, MSNA increased 142 +/- 38 units (P < 0.01). This increase was not significantly different from the sum of the individual trials (130 +/- 41 units). This finding was also observed with mean arterial pressure (sum = 21 +/- 2 mmHg and HDR + IHG = 22 +/- 2 mmHg). These findings suggest that there is an additive interaction for MSNA and arterial pressure when the vestibulosympathetic and skeletal muscle reflexes are engaged simultaneously in humans. Therefore, no central modulation exists between these two reflexes with regard to MSNA output in humans.

  14. Exercise, Hormones, and Skeletal Adaptations During Childhood and Adolescence

    PubMed Central

    Farr, Joshua N.; Laddu, Deepika R.; Going, Scott B.

    2015-01-01

    Although primarily considered a disorder of the elderly, emerging evidence suggests the antecedents of osteoporosis are established during childhood and adolescence. A complex interplay of genetic, environmental, hormonal and behavioral factors determines skeletal development, and a greater effort is needed to identify the most critical factors that establish peak bone strength. Indeed, knowledge of modifiable factors that determine skeletal development may permit optimization of skeletal health during growth and could potentially offset reductions in bone strength with aging. The peripubertal years represent a unique period when the skeleton is particularly responsive to loading exercises, and there is now overwhelming evidence that exercise can optimize skeletal development. While this is not controversial, the most effective exercise prescription and how much investment in this prescription is needed to significantly impact bone health continues to be debated. Despite considerable progress, these issues are not easy to address, and important questions remain unresolved. This review focuses on the key determinants of skeletal development, whether exercise during childhood and adolescence should be advocated as a safe and effective strategy for optimizing peak bone strength, and whether investment in exercise early in life protects against the development of osteoporosis and fractures later in life. PMID:25372373

  15. Ulk1-mediated autophagy plays an essential role in mitochondrial remodeling and functional regeneration of skeletal muscle

    PubMed Central

    Call, Jarrod A.; Wilson, Rebecca J.; Laker, Rhianna C.; Zhang, Mei; Kundu, Mondira

    2017-01-01

    Autophagy is a conserved cellular process for degrading aggregate proteins and dysfunctional organelle. It is still debatable if autophagy and mitophagy (a specific process of autophagy of mitochondria) play important roles in myogenic differentiation and functional regeneration of skeletal muscle. We tested the hypothesis that autophagy is critical for functional regeneration of skeletal muscle. We first observed time-dependent increases (3- to 6-fold) of autophagy-related proteins (Atgs), including Ulk1, Beclin1, and LC3, along with reduced p62 expression during C2C12 differentiation, suggesting increased autophagy capacity and flux during myogenic differentiation. We then used cardiotoxin (Ctx) or ischemia-reperfusion (I/R) to induce muscle injury and regeneration and observed increases in Atgs between days 2 and 7 in adult skeletal muscle followed by increased autophagy flux after day 7. Since Ulk1 has been shown to be essential for mitophagy, we asked if Ulk1 is critical for functional regeneration in skeletal muscle. We subjected skeletal muscle-specific Ulk1 knockout mice (MKO) to Ctx or I/R. MKO mice had significantly impaired recovery of muscle strength and mitochondrial protein content post-Ctx or I/R. Imaging analysis showed that MKO mice have significantly attenuated recovery of mitochondrial network at 7 and 14 days post-Ctx. These findings suggest that increased autophagy protein and flux occur during muscle regeneration and Ulk1-mediated mitophagy is critical for recovery for the mitochondrial network and hence functional regeneration. PMID:28356270

  16. Determinants of relative skeletal maturity in South African children.

    PubMed

    Hawley, Nicola L; Rousham, Emily K; Johnson, William; Norris, Shane A; Pettifor, John M; Cameron, Noël

    2012-01-01

    The variation of skeletal maturity about chronological age is a sensitive indicator of population health. Age appropriate or advanced skeletal maturity is a reflection of adequate environmental and social conditions, whereas delayed maturation suggests inadequate conditions for optimal development. There remains a paucity of data, however, to indicate which specific biological and environmental factors are associated with advancement or delay in skeletal maturity. The present study utilises longitudinal data from the South African Birth to Twenty (Bt20) study to indentify predictors of relative skeletal maturity (RSM) in early adolescence. A total of 244 black South African children (n=131 male) were included in this analysis. Skeletal maturity at age 9/10 years was assessed using the Tanner and Whitehouse III RUS technique. Longitudinal data on growth, socio-economic position and pubertal development were entered into sex-specific multivariable general linear regression models with relative skeletal maturity (skeletal age-chronological age) as the outcome. At 9/10 years of age males showed an average of 0.66 years delay in skeletal maturation relative to chronological age. Females showed an average of 1.00 year delay relative to chronological age. In males, being taller at 2 years (p<0.01) and heavier at 2 years (p<0.01) predicted less delay in RSM at age 9/10 years, independent of current size and body composition. In females, both height at 2 years and conditional weight at 2 years predicted less delay in RSM at 9/10 years (p<0.05) but this effect was mediated by current body composition. Having greater lean mass at 9/10 years was associated with less delayed RSM in females (p<0.01) as was pubertal status at the time of skeletal maturity assessment (p<0.01). This study identifies several predictors of skeletal maturation at 9/10 years, indicating a role for early life exposures in determining the rate of skeletal maturation during childhood independently of

  17. Effect of transforming growth factor-beta1 on decorin expression and muscle morphology during chicken embryonic and posthatch growth and development.

    PubMed

    Li, X; Velleman, S G

    2009-02-01

    During skeletal muscle development, transforming growth factor-beta1 (TGF-beta1) is a potent inhibitor of muscle cell proliferation and differentiation, as well as a regulator of extracellular matrix (ECM) production. Decorin, a member of the small leucine-rich ECM proteoglycans, binds to TGF-beta1 and modulates TGF-beta1-dependent cell growth stimulation or inhibition. The expression of decorin can be regulated by TGF-beta1 during muscle proliferation and differentiation. How TGF-beta1 affects decorin and muscle growth, however, has not been well documented in vivo. The present study investigated the effect of TGF-beta1 on decorin expression and intracellular connective tissue development during skeletal muscle growth. Exogenous TGF-beta1 significantly decreased the number of myofibers in a given area at both 1 d and 6 wk posthatch. The TGF-beta1-treated muscle had a significant decrease in decorin mRNA expression at embryonic day (ED) 10, whereas protein amounts decreased at 17 ED and 1 d posthatch compared to the control muscle. Decorin was localized in both the endomysium and perimysium in the control pectoralis major muscle. Transforming growth factor-beta1 reduced decorin in both the endomysium and perimysium from 17 ED to 6 wk posthatch. Compared to the control muscle, the perimysium space in the pectoralis major muscle was dramatically decreased by TGF-beta1 during embryonic development through posthatch growth. Because decorin regulates collagen fibrillogenesis, a major component of the ECM, the reduction of decorin by TGF-beta1 treatment may cause the irregular formation of collagen fibrils, leading to the decrease in endomysium and perimysium space. The results from the current study suggest that the effect of TGF-beta1 on decorin expression and localization was likely associated with altered development of the perimysium and the regulation of muscle fiber development.

  18. Modulation of DNA binding by gene-specific transcription factors.

    PubMed

    Schleif, Robert F

    2013-10-01

    The transcription of many genes, particularly in prokaryotes, is controlled by transcription factors whose activity can be modulated by controlling their DNA binding affinity. Understanding the molecular mechanisms by which DNA binding affinity is regulated is important, but because forming definitive conclusions usually requires detailed structural information in combination with data from extensive biophysical, biochemical, and sometimes genetic experiments, little is truly understood about this topic. This review describes the biological requirements placed upon DNA binding transcription factors and their consequent properties, particularly the ways that DNA binding affinity can be modulated and methods for its study. What is known and not known about the mechanisms modulating the DNA binding affinity of a number of prokaryotic transcription factors, including CAP and lac repressor, is provided.

  19. A kidney-specific genetic control module in mice governs endocrine regulation of the cytochrome P450 gene Cyp27b1 essential for vitamin D3 activation.

    PubMed

    Meyer, Mark B; Benkusky, Nancy A; Kaufmann, Martin; Lee, Seong Min; Onal, Melda; Jones, Glenville; Pike, J Wesley

    2017-10-20

    The vitamin D endocrine system regulates mineral homeostasis through its activities in the intestine, kidney, and bone. Terminal activation of vitamin D 3 to its hormonal form, 1α,25-dihydroxyvitamin D 3 (1,25(OH) 2 D 3 ), occurs in the kidney via the cytochrome P450 enzyme CYP27B1. Despite its importance in vitamin D metabolism, the molecular mechanisms underlying the regulation of the gene for this enzyme, Cyp27b1 , are unknown. Here, we identified a kidney-specific control module governed by a renal cell-specific chromatin structure located distal to Cyp27b1 that mediates unique basal and parathyroid hormone (PTH)-, fibroblast growth factor 23 (FGF23)-, and 1,25(OH) 2 D 3 -mediated regulation of Cyp27b1 expression. Selective genomic deletion of key components within this module in mice resulted in loss of either PTH induction or FGF23 and 1,25(OH) 2 D 3 suppression of Cyp27b1 gene expression; the former loss caused a debilitating skeletal phenotype, whereas the latter conferred a quasi-normal bone mineral phenotype through compensatory homeostatic mechanisms involving Cyp24a1 We found that Cyp27b1 is also expressed at low levels in non-renal cells, in which transcription was modulated exclusively by inflammatory factors via a process that was unaffected by deletion of the kidney-specific module. These results reveal that differential regulation of Cyp27b1 expression represents a mechanism whereby 1,25(OH) 2 D 3 can fulfill separate functional roles, first in the kidney to control mineral homeostasis and second in extra-renal cells to regulate target genes linked to specific biological responses. Furthermore, we conclude that these mouse models open new avenues for the study of vitamin D metabolism and its involvement in therapeutic strategies for human health and disease. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

  20. A kidney-specific genetic control module in mice governs endocrine regulation of the cytochrome P450 gene Cyp27b1 essential for vitamin D3 activation

    PubMed Central

    Meyer, Mark B.; Benkusky, Nancy A.; Kaufmann, Martin; Lee, Seong Min; Onal, Melda; Jones, Glenville; Pike, J. Wesley

    2017-01-01

    The vitamin D endocrine system regulates mineral homeostasis through its activities in the intestine, kidney, and bone. Terminal activation of vitamin D3 to its hormonal form, 1α,25-dihydroxyvitamin D3 (1,25(OH)2D3), occurs in the kidney via the cytochrome P450 enzyme CYP27B1. Despite its importance in vitamin D metabolism, the molecular mechanisms underlying the regulation of the gene for this enzyme, Cyp27b1, are unknown. Here, we identified a kidney-specific control module governed by a renal cell-specific chromatin structure located distal to Cyp27b1 that mediates unique basal and parathyroid hormone (PTH)-, fibroblast growth factor 23 (FGF23)-, and 1,25(OH)2D3-mediated regulation of Cyp27b1 expression. Selective genomic deletion of key components within this module in mice resulted in loss of either PTH induction or FGF23 and 1,25(OH)2D3 suppression of Cyp27b1 gene expression; the former loss caused a debilitating skeletal phenotype, whereas the latter conferred a quasi-normal bone mineral phenotype through compensatory homeostatic mechanisms involving Cyp24a1. We found that Cyp27b1 is also expressed at low levels in non-renal cells, in which transcription was modulated exclusively by inflammatory factors via a process that was unaffected by deletion of the kidney-specific module. These results reveal that differential regulation of Cyp27b1 expression represents a mechanism whereby 1,25(OH)2D3 can fulfill separate functional roles, first in the kidney to control mineral homeostasis and second in extra-renal cells to regulate target genes linked to specific biological responses. Furthermore, we conclude that these mouse models open new avenues for the study of vitamin D metabolism and its involvement in therapeutic strategies for human health and disease. PMID:28808057

  1. Irisin is a pro-myogenic factor that induces skeletal muscle hypertrophy and rescues denervation-induced atrophy.

    PubMed

    Reza, Musarrat Maisha; Subramaniyam, Nathiya; Sim, Chu Ming; Ge, Xiaojia; Sathiakumar, Durgalakshmi; McFarlane, Craig; Sharma, Mridula; Kambadur, Ravi

    2017-10-24

    Exercise induces expression of the myokine irisin, which is known to promote browning of white adipose tissue and has been shown to mediate beneficial effects following exercise. Here we show that irisin induces expression of a number of pro-myogenic and exercise response genes in myotubes. Irisin increases myogenic differentiation and myoblast fusion via activation of IL6 signaling. Injection of irisin in mice induces significant hypertrophy and enhances grip strength of uninjured muscle. Following skeletal muscle injury, irisin injection improves regeneration and induces hypertrophy. The effects of irisin on hypertrophy are due to activation of satellite cells and enhanced protein synthesis. In addition, irisin injection rescues loss of skeletal muscle mass following denervation by enhancing satellite cell activation and reducing protein degradation. These data suggest that irisin functions as a pro-myogenic factor in mice.

  2. Regulation of skeletal muscle blood flow during exercise in ageing humans

    PubMed Central

    Hearon, Christopher M.

    2015-01-01

    Abstract The regulation of skeletal muscle blood flow and oxygen delivery to contracting skeletal muscle is complex and involves the mechanical effects of muscle contraction; local metabolic, red blood cell and endothelium‐derived substances; and the sympathetic nervous system (SNS). With advancing age in humans, skeletal muscle blood flow is typically reduced during dynamic exercise and this is due to a lower vascular conductance, which could ultimately contribute to age‐associated reductions in aerobic exercise capacity, a primary predictor of mortality in both healthy and diseased ageing populations. Recent findings have highlighted the contribution of endothelium‐derived substances to blood flow control in contracting muscle of older adults. With advancing age, impaired nitric oxide availability due to scavenging by reactive oxygen species, in conjunction with elevated vasoconstrictor signalling via endothelin‐1, reduces the local vasodilatory response to muscle contraction. Additionally, ageing impairs the ability of contracting skeletal muscle to blunt sympathetic vasoconstriction (i.e. ‘functional sympatholysis’), which is critical for the proper regulation of tissue blood flow distribution and oxygen delivery, and could further reduce skeletal muscle perfusion during high intensity and/or large muscle mass exercise in older adults. We propose that initiation of endothelium‐dependent hyperpolarization is the underlying signalling event necessary to properly modulate sympathetic vasoconstriction in contracting muscle, and that age‐associated impairments in red blood cell adenosine triphosphate release and stimulation of endothelium‐dependent vasodilatation may explain impairments in both local vasodilatation and functional sympatholysis with advancing age in humans. PMID:26332887

  3. In Vivo Rodent Models of Skeletal Muscle Adaptation to Decreased Use.

    PubMed

    Cho, Su Han; Kim, Jang Hoe; Song, Wook

    2016-03-01

    Skeletal muscle possesses plasticity and adaptability to external and internal physiological changes. Due to these characteristics, skeletal muscle shows dramatic changes depending on its response to stimuli such as physical activity, nutritional changes, disease status, and environmental changes. Modulation of the rate of protein synthesis/degradation plays an important role in atrophic responses. The purpose of this review is to describe different features of skeletal muscle adaptation with various models of deceased use. In this review, four models were addressed: immobilization, spinal cord transection, hindlimb unloading, and aging. Immobilization is a form of decreased use in which skeletal muscle shows electrical activity, tension development, and motion. These results differ by muscle group. Spinal cord transection was selected to simulate spinal cord injury. Similar to the immobilization model, dramatic atrophy occurs in addition to fiber type conversion in this model. Despite the fact that electromyography shows unremarkable changes in muscle after hindlimb unloading, decreased muscle mass and contractile force are observed. Lastly, aging significantly decreases the numbers of muscle fibers and motor units. Skeletal muscle responses to decreased use include decreased strength, decreased fiber numbers, and fiber type transformation. These four models demonstrated different changes in the skeletal muscle. This review elucidates the different skeletal muscle adaptations in these four decreased use animal models and encourages further studies.

  4. The TWEAK–Fn14 dyad is involved in age-associated pathological changes in skeletal muscle

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Tajrishi, Marjan M.; Sato, Shuichi; Shin, Jonghyun

    Highlights: • The levels of TWEAK receptor Fn14 are increased in skeletal muscle during aging. • Deletion of Fn14 attenuates age-associated skeletal muscle fiber atrophy. • Deletion of Fn14 inhibits proteolysis in skeletal muscle during aging. • TWEAK–Fn14 signaling activates transcription factor NF-κB in aging skeletal muscle. • TWEAK–Fn14 dyad is involved in age-associated fibrosis in skeletal muscle. - Abstract: Progressive loss of skeletal muscle mass and strength (sarcopenia) is a major clinical problem in the elderly. Recently, proinflammatory cytokine TWEAK and its receptor Fn14 were identified as key mediators of muscle wasting in various catabolic states. However, the rolemore » of the TWEAK–Fn14 pathway in pathological changes in skeletal muscle during aging remains unknown. In this study, we demonstrate that the levels of Fn14 are increased in skeletal muscle of 18-month old (aged) mice compared with adult mice. Genetic ablation of Fn14 significantly increased the levels of specific muscle proteins and blunted the age-associated fiber atrophy in mice. While gene expression of two prominent muscle-specific E3 ubiquitin ligases MAFBx and MuRF1 remained comparable, levels of ubiquitinated proteins and the expression of autophagy-related molecule Atg12 were significantly reduced in Fn14-knockout (KO) mice compared with wild-type mice during aging. Ablation of Fn14 significantly diminished the DNA-binding activity of transcription factor nuclear factor-kappa B (NF-κB), gene expression of various inflammatory molecules, and interstitial fibrosis in skeletal muscle of aged mice. Collectively, our study suggests that the TWEAK–Fn14 signaling axis contributes to age-associated muscle atrophy and fibrosis potentially through its local activation of proteolytic systems and inflammatory pathways.« less

  5. Tuning the Fano factor of graphene via Fermi velocity modulation

    NASA Astrophysics Data System (ADS)

    Lima, Jonas R. F.; Barbosa, Anderson L. R.; Bezerra, C. G.; Pereira, Luiz Felipe C.

    2018-03-01

    In this work we investigate the influence of a Fermi velocity modulation on the Fano factor of periodic and quasi-periodic graphene superlattices. We consider the continuum model and use the transfer matrix method to solve the Dirac-like equation for graphene where the electrostatic potential, energy gap and Fermi velocity are piecewise constant functions of the position x. We found that in the presence of an energy gap, it is possible to tune the energy of the Fano factor peak and consequently the location of the Dirac point, by a modulation in the Fermi velocity. Hence, the peak of the Fano factor can be used experimentally to identify the Dirac point. We show that for higher values of the Fermi velocity the Fano factor goes below 1/3 at the Dirac point. Furthermore, we show that in periodic superlattices the location of Fano factor peaks is symmetric when the Fermi velocity vA and vB is exchanged, however by introducing quasi-periodicity the symmetry is lost. The Fano factor usually holds a universal value for a specific transport regime, which reveals that the possibility of controlling it in graphene is a notable result.

  6. ANKRD1 modulates inflammatory responses in C2C12 myoblasts through feedback inhibition of NF-κB signaling activity

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Liu, Xin-Hua; Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029; Bauman, William A.

    2015-08-14

    Transcription factors of the nuclear factor-kappa B (NF-κB) family play a pivotal role in inflammation, immunity and cell survival responses. Recent studies revealed that NF-κB also regulates the processes of muscle atrophy. NF-κB activity is regulated by various factors, including ankyrin repeat domain 2 (AnkrD2), which belongs to the muscle ankyrin repeat protein family. Another member of this family, AnkrD1 is also a transcriptional effector. The expression levels of AnkrD1 are highly upregulated in denervated skeletal muscle, suggesting an involvement of AnkrD1 in NF-κB mediated cellular responses to paralysis. However, the molecular mechanism underlying the interactive role of AnkrD1 inmore » NF-κB mediated cellular responses is not well understood. In the current study, we examined the effect of AnkrD1 on NF-κB activity and determined the interactions between AnkrD1 expression and NF-κB signaling induced by TNFα in differentiating C2C12 myoblasts. TNFα upregulated AnkrD1 mRNA and protein levels. AnkrD1-siRNA significantly increased TNFα-induced transcriptional activation of NF-κB, whereas overexpression of AnkrD1 inhibited TNFα-induced NF-κB activity. Co-immunoprecipitation studies demonstrated that AnkrD1 was able to bind p50 subunit of NF-κB and vice versa. Finally, CHIP assays revealed that AnkrD1 bound chromatin at a NF-κB binding site in the AnrkD2 promoter and required NF-κB to do so. These results provide evidence of signaling integration between AnkrD1 and NF-κB pathways, and suggest a novel anti-inflammatory role of AnkrD1 through feedback inhibition of NF-κB transcriptional activity by which AnkrD1 modulates the balance between physiological and pathological inflammatory responses in skeletal muscle. - Highlights: • AnkrD1 is upregulated by TNFα and represses NF-κB-induced transcriptional activity. • AnkrD1 binds to p50 subunit of NF-κB and is recruited to NF-κB bound to chromatin. • AnkrD1 mediates a feed

  7. Local injections of adipose-derived mesenchymal stem cells modulate inflammation and increase angiogenesis ameliorating the dystrophic phenotype in dystrophin-deficient skeletal muscle.

    PubMed

    Pinheiro, Carlos Hermano da Justa; de Queiroz, Jean César Farias; Guimarães-Ferreira, Lucas; Vitzel, Kaio Fernando; Nachbar, Renato Tadeu; de Sousa, Luís Gustavo Oliveira; de Souza, Alcione Lescano; Nunes, Maria Tereza; Curi, Rui

    2012-06-01

    The effects of adipose-derived mesenchymal stem cells (ADMSC) transplantation on degeneration, regeneration and skeletal muscle function were investigated in dystrophin-deficient mice (24-week-old). ADMSC transplantation improved muscle strength and, resistance to fatigue. An increase in fiber cross-sectional area and in the number of fibers with centralized nuclei and augment of myogenin content were observed. In ADMSC-treated muscles a decrease in muscle content of TNF-α, IL-6 and oxidative stress measured by Amplex(®) reagent were observed. The level of TGF-β1 was lowered whereas that of VEGF, IL-10 and IL-4 were increased by ADMSC treatment. An increase in markers of macrophage M1 (CD11 and F4-80) and a decrease in T lymphocyte marker (CD3) and arginase-1 were also observed in ADMSCs-treated dystrophic muscle. No change was observed in iNOS expression. Increased phosphorylation of Akt, p70S6k and 4E-BP1 was found in dystrophic muscles treated with ADMSC. These results suggest that ADMSC transplantation modulates inflammation and improves muscle tissue regeneration, ameliorating the dystrophic phenotype in dystrophin-deficient mice.

  8. Elevated extracellular glucose and uncontrolled type 1 diabetes enhance NFAT5 signaling and disrupt the transverse tubular network in mouse skeletal muscle

    PubMed Central

    Hernández-Ochoa, Erick O; Robison, Patrick; Contreras, Minerva; Shen, Tiansheng; Zhao, Zhiyong; Schneider, Martin F

    2012-01-01

    The transcription factor nuclear factor of activated T-cells 5 (NFAT5) is a key protector from hypertonic stress in the kidney, but its role in skeletal muscle is unexamined. Here, we evaluate the effects of glucose hypertonicity and hyperglycemia on endogenous NFAT5 activity, transverse tubular system morphology and Ca2+ signaling in adult murine skeletal muscle fibers. We found that exposure to elevated glucose (25–50 mmol/L) increased NFAT5 expression and nuclear translocation, and NFAT-driven transcriptional activity. These effects were insensitive to the inhibition of calcineurin A, but sensitive to both p38a mitogen-activated protein kinases and phosphoinositide 3-kinase-related kinase inhibition. Fibers exposed to elevated glucose exhibited disrupted transverse tubular morphology, characterized by swollen transverse tubules and an increase in longitudinal connections between adjacent transverse tubules. Ca2+ transients elicited by a single, brief electric field stimuli were increased in amplitude in fibers challenged by elevated glucose. Muscle fibers from type 1 diabetic mice exhibited increased NFAT5 expression and transverse tubule disruptions, but no differences in electrically evoked Ca2+ transients. Our results suggest the hypothesis that these changes in skeletal muscle could play a role in the pathophysiology of acute and severe hyperglycemic episodes commonly observed in uncontrolled diabetes. PMID:22966145

  9. Gestalt factors modulate basic spatial vision.

    PubMed

    Sayim, B; Westheimer, G; Herzog, M H

    2010-05-01

    Human perception of a stimulus varies depending on the context in which the stimulus is presented. Such contextual modulation has often been explained by two basic neural mechanisms: lateral inhibition and spatial pooling. In the present study, we presented observers with a vernier stimulus flanked by single lines; observers' ability to discriminate the offset direction of the vernier stimulus deteriorated in accordance with both explanations. However, when the flanking lines were part of a geometric shape (i.e., a good Gestalt), this deterioration strongly diminished. These findings cannot be explained by lateral inhibition or spatial pooling. It seems that Gestalt factors play an important role in contextual modulation. We propose that contextual modulation can be used as a quantitative measure to investigate the rules governing the grouping of elements into meaningful wholes.

  10. Altered mitochondrial bioenergetics and ultrastructure in the skeletal muscle of young adults with type 1 diabetes.

    PubMed

    Monaco, Cynthia M F; Hughes, Meghan C; Ramos, Sofhia V; Varah, Nina E; Lamberz, Christian; Rahman, Fasih A; McGlory, Chris; Tarnopolsky, Mark A; Krause, Matthew P; Laham, Robert; Hawke, Thomas J; Perry, Christopher G R

    2018-06-01

    A comprehensive assessment of skeletal muscle ultrastructure and mitochondrial bioenergetics has not been undertaken in individuals with type 1 diabetes. This study aimed to systematically assess skeletal muscle mitochondrial phenotype in young adults with type 1 diabetes. Physically active, young adults (men and women) with type 1 diabetes (HbA 1c 63.0 ± 16.0 mmol/mol [7.9% ± 1.5%]) and without type 1 diabetes (control), matched for sex, age, BMI and level of physical activity, were recruited (n = 12/group) to undergo vastus lateralis muscle microbiopsies. Mitochondrial respiration (high-resolution respirometry), site-specific mitochondrial H 2 O 2 emission and Ca 2+ retention capacity (CRC) (spectrofluorometry) were assessed using permeabilised myofibre bundles. Electron microscopy and tomography were used to quantify mitochondrial content and investigate muscle ultrastructure. Skeletal muscle microvasculature was assessed by immunofluorescence. Mitochondrial oxidative capacity was significantly lower in participants with type 1 diabetes vs the control group, specifically at Complex II of the electron transport chain, without differences in mitochondrial content between groups. Muscles of those with type 1 diabetes also exhibited increased mitochondrial H 2 O 2 emission at Complex III and decreased CRC relative to control individuals. Electron tomography revealed an increase in the size and number of autophagic remnants in the muscles of participants with type 1 diabetes. Despite this, levels of the autophagic regulatory protein, phosphorylated AMP-activated protein kinase (p-AMPKα Thr172 ), and its downstream targets, phosphorylated Unc-51 like autophagy activating kinase 1 (p-ULK1 Ser555 ) and p62, was similar between groups. In addition, no differences in muscle capillary density or platelet aggregation were observed between the groups. Alterations in mitochondrial ultrastructure and bioenergetics are evident within the skeletal muscle of

  11. 14-3-3 Proteins Modulate the ETS Transcription Factor ETV1 in Prostate Cancer

    PubMed Central

    Oh, Sangphil; Shin, Sook; Lightfoot, Stan A.; Janknecht, Ralf

    2013-01-01

    Overexpression of the ETS-related transcription factor ETV1 can initiate neoplastic transformation of the prostate. ETV1 activity is highly regulated by phosphorylation, but the underlying mechanisms are unknown. Here we report that all 14-3-3 proteins, with the exception of the tumor suppressor 14-3-3σ, can bind to ETV1 in a condition manner dictated by its prominent phosphorylation site S216. All non-σ 14-3-3 proteins synergized with ETV1 to activate transcription of its target genes MMP-1 and MMP-7, which regulate extracellular matrix in the prostate tumor microenvironment. S216 mutation or 14-3-3τ downregulation was sufficient to reduce ETV1 protein levels in prostate cancer cells, indicating that non-σ 14-3-3 proteins protect ETV1 from degradation. Notably, S216 mutation also decreased ETV1-dependent migration and invasion in benign prostate cells. Downregulation of 14-3-3τ reduced prostate cancer cell invasion and growth in the same manner as ETV1 attenuation. Lastly, we showed that 14-3-3τ and 14-3-3ε were overexpressed in human prostate tumors. Taken together, our results demonstrated that non-σ 14-3-3 proteins are important modulators of ETV1 function that promote prostate tumorigenesis. PMID:23774214

  12. Skeletal Effects of Growth Hormone and Insulin-like Growth Factor-I Therapy

    PubMed Central

    Lindsey, Richard C.; Mohan, Subburaman

    2015-01-01

    The growth hormone/insulin-like growth factor (GH/IGF) axis is critically important for the regulation of bone formation, and deficiencies in this system have been shown to contribute to the development of osteoporosis and other diseases of low bone mass. The GH/IGF axis is regulated by a complex set of hormonal and local factors which can act to regulate this system at the level of the ligands, receptors, IGF binding proteins (IGFBPs), or IGFBP proteases. A combination of in vitro studies, transgenic animal models, and clinical human investigations has provided ample evidence of the importance of the endocrine and local actions of both GH and IGF-I, the two major components of the GH/IGF axis, in skeletal growth and maintenance. GH- and IGF-based therapies provide a useful avenue of approach for the prevention and treatment of diseases such as osteoporosis. PMID:26408965

  13. Insulin-like growth factor-1 receptor in mature osteoblasts is required for periosteal bone formation induced by reloading

    NASA Astrophysics Data System (ADS)

    Kubota, Takuo; Elalieh, Hashem Z.; Saless, Neema; Fong, Chak; Wang, Yongmei; Babey, Muriel; Cheng, Zhiqiang; Bikle, Daniel D.

    2013-11-01

    Skeletal loading and unloading has a pronounced impact on bone remodeling, a process also regulated by insulin-like growth factor-1 (IGF-1) signaling. Skeletal unloading leads to resistance to the anabolic effect of IGF-1, while reloading after unloading restores responsiveness to IGF-1. However, a direct study of the importance of IGF-1 signaling in the skeletal response to mechanical loading remains to be tested. In this study, we assessed the skeletal response of osteoblast-specific Igf-1 receptor deficient (Igf-1r-/-) mice to unloading and reloading. The mice were hindlimb unloaded for 14 days and then reloaded for 16 days. Igf-1r-/- mice displayed smaller cortical bone and diminished periosteal and endosteal bone formation at baseline. Periosteal and endosteal bone formation decreased with unloading in Igf-1r+/+ mice. However, the recovery of periosteal bone formation with reloading was completely inhibited in Igf-1r-/- mice, although reloading-induced endosteal bone formation was not hampered. These changes in bone formation resulted in the abolishment of the expected increase in total cross-sectional area with reloading in Igf-1r-/- mice compared to the control mice. These results suggest that the Igf-1r in mature osteoblasts has a critical role in periosteal bone formation in the skeletal response to mechanical loading.

  14. Ulk1-mediated autophagy plays an essential role in mitochondrial remodeling and functional regeneration of skeletal muscle.

    PubMed

    Call, Jarrod A; Wilson, Rebecca J; Laker, Rhianna C; Zhang, Mei; Kundu, Mondira; Yan, Zhen

    2017-06-01

    Autophagy is a conserved cellular process for degrading aggregate proteins and dysfunctional organelle. It is still debatable if autophagy and mitophagy (a specific process of autophagy of mitochondria) play important roles in myogenic differentiation and functional regeneration of skeletal muscle. We tested the hypothesis that autophagy is critical for functional regeneration of skeletal muscle. We first observed time-dependent increases (3- to 6-fold) of autophagy-related proteins (Atgs), including Ulk1, Beclin1, and LC3, along with reduced p62 expression during C2C12 differentiation, suggesting increased autophagy capacity and flux during myogenic differentiation. We then used cardiotoxin (Ctx) or ischemia-reperfusion (I/R) to induce muscle injury and regeneration and observed increases in Atgs between days 2 and 7 in adult skeletal muscle followed by increased autophagy flux after day 7 Since Ulk1 has been shown to be essential for mitophagy, we asked if Ulk1 is critical for functional regeneration in skeletal muscle. We subjected skeletal muscle-specific Ulk1 knockout mice (MKO) to Ctx or I/R. MKO mice had significantly impaired recovery of muscle strength and mitochondrial protein content post-Ctx or I/R. Imaging analysis showed that MKO mice have significantly attenuated recovery of mitochondrial network at 7 and 14 days post-Ctx. These findings suggest that increased autophagy protein and flux occur during muscle regeneration and Ulk1-mediated mitophagy is critical for recovery for the mitochondrial network and hence functional regeneration. Copyright © 2017 the American Physiological Society.

  15. Skeletal muscle Ca(2+)-independent kinase activity increases during either hypertrophy or running

    NASA Technical Reports Server (NTRS)

    Fluck, M.; Waxham, M. N.; Hamilton, M. T.; Booth, F. W.

    2000-01-01

    Spikes in free Ca(2+) initiate contractions in skeletal muscle cells, but whether and how they might signal to transcription factors in skeletal muscles of living animals is unknown. Since previous studies in non-muscle cells have shown that serum response factor (SRF) protein, a transcription factor, is phosphorylated rapidly by Ca(2+)/calmodulin (CaM)-dependent protein kinase after rises in intracellular Ca(2+), we measured enzymatic activity that phosphorylates SRF (designated SRF kinase activity). Homogenates from 7-day-hypertrophied anterior latissimus dorsi muscles of roosters had more Ca(2+)-independent SRF kinase activity than their respective control muscles. However, no differences were noted in Ca(2+)/CaM-dependent SRF kinase activity between control and trained muscles. To determine whether the Ca(2+)-independent and Ca(2+)/CaM-dependent forms of Ca(2+)/CaM-dependent protein kinase II (CaMKII) might contribute to some of the SRF kinase activity, autocamtide-3, a synthetic substrate that is specific for CaMKII, was employed. While the Ca(2+)-independent form of CaMKII was increased, like the Ca(2+)-independent form of SRF kinase, no alteration in CaMKII occurred at 7 days of stretch overload. These observations suggest that some of SRF phosphorylation by skeletal muscle extracts could be due to CaMKII. To determine whether this adaptation was specific to the exercise type (i.e., hypertrophy), similar measurements were made in the white vastus lateralis muscle of rats that had completed 2 wk of voluntary running. Although Ca(2+)-independent SRF kinase was increased, no alteration occurred in Ca(2+)/CaM-dependent SRF kinase activity. Thus any role of Ca(2+)-independent SRF kinase signaling has downstream modulators specific to the exercise phenotype.

  16. Interleukin-2 therapy reverses some immunosuppressive effects of skeletal unloading

    NASA Technical Reports Server (NTRS)

    Armstrong, Jason W.; Balch, Signe; Chapes, Stephen K.

    1994-01-01

    Using antiorthostatic suspension, we characterized hematopoietic changes that may be responsible for the detrimental effect of skeletal unloading on macrophage development. Skeletally unloaded mice had suppressed macrophage development in unloaded and loaded bones, which indicated a systemic effect. Bone marrow cells from unloaded mice secreted less macrophage colony-stimulating factor and interleukin-6 than control mice. Additionally, T-lymphocyte proliferation was reduced after skeletal unloading. We show that polyethylene glycol-interleukin-2 therapy reversed the effects of skeletal unloading on macrophage development and cell proliferation.

  17. STIM1 signaling controls store operated calcium entry required for development and contractile function in skeletal muscle

    PubMed Central

    Stiber, Jonathan; Hawkins, April; Zhang, Zhu-Shan; Wang, Sunny; Burch, Jarrett; Graham, Victoria; Ward, Cary C.; Seth, Malini; Finch, Elizabeth; Malouf, Nadia; Williams, R. Sanders; Eu, Jerry P.; Rosenberg, Paul

    2009-01-01

    It is now well established that stromal interaction molecule 1 (STIM1) is the calcium sensor of endoplasmic reticulum (ER) stores required to activate store-operated calcium entry (SOC) channels at the surface of non-excitable cells. Yet little is known about STIM1 in excitable cells such as striated muscle where the complement of calcium regulatory molecules is rather disparate from that of non-excitable cells. Here, we show that STIM1 is expressed in both myotubes and adult skeletal muscle. Myotubes lacking functional STIM1 fail to exhibit SOC and fatigue rapidly. Moreover, mice lacking functional STIM1 die perinatally from a skeletal myopathy. In addition, STIM1 haploinsufficiency confers a contractile defect only under conditions where rapid refilling of stores would be needed. These findings provide novel insight to the role of STIM1 in skeletal muscle and suggest that STIM1 has a universal role as an ER/SR calcium sensor in both excitable and non-excitable cells. PMID:18488020

  18. Contrasting skeletal phenotypes in mice with an identical mutation targeted to thyroid hormone receptor alpha1 or beta.

    PubMed

    O'Shea, Patrick J; Bassett, J H Duncan; Sriskantharajah, Srividya; Ying, Hao; Cheng, Sheue-yann; Williams, Graham R

    2005-12-01

    Thyroid hormone (T(3)) regulates bone turnover and mineralization in adults and is essential for skeletal development. Surprisingly, we identified a phenotype of skeletal thyrotoxicosis in T(3) receptor beta(PV) (TRbeta(PV)) mice in which a targeted frameshift mutation in TRbeta results in resistance to thyroid hormone. To characterize mechanisms underlying thyroid hormone action in bone, we analyzed skeletal development in TRalpha1(PV) mice in which the same PV mutation was targeted to TRalpha1. In contrast to TRbeta(PV) mice, TRalpha1(PV) mutants exhibited skeletal hypothyroidism with delayed endochondral and intramembranous ossification, severe postnatal growth retardation, diminished trabecular bone mineralization, reduced cortical bone deposition, and delayed closure of the skull sutures. Skeletal hypothyroidism in TRalpha1(PV) mutants was accompanied by impaired GH receptor and IGF-I receptor expression and signaling in the growth plate, whereas GH receptor and IGF-I receptor expression and signaling were increased in TRbeta(PV) mice. These data indicate that GH receptor and IGF-I receptor are physiological targets for T(3) action in bone in vivo. The divergent phenotypes observed in TRalpha1(PV) and TRbeta(PV) mice arise because the pituitary gland is a TRbeta-responsive tissue, whereas bone is TRalpha responsive. These studies provide a new understanding of the complex relationship between central and peripheral thyroid status.

  19. Heat shock transcription factor 1-deficiency attenuates overloading-associated hypertrophy of mouse soleus muscle.

    PubMed

    Koya, Tomoyuki; Nishizawa, Sono; Ohno, Yoshitaka; Goto, Ayumi; Ikuta, Akihiro; Suzuki, Miho; Ohira, Tomotaka; Egawa, Tatsuro; Nakai, Akira; Sugiura, Takao; Ohira, Yoshinobu; Yoshioka, Toshitada; Beppu, Moroe; Goto, Katsumasa

    2013-01-01

    Hypertrophic stimuli, such as mechanical stress and overloading, induce stress response, which is mediated by heat shock transcription factor 1 (HSF1), and up-regulate heat shock proteins (HSPs) in mammalian skeletal muscles. Therefore, HSF1-associated stress response may play a key role in loading-associated skeletal muscle hypertrophy. The purpose of this study was to investigate the effects of HSF1-deficiency on skeletal muscle hypertrophy caused by overloading. Functional overloading on the left soleus was performed by cutting the distal tendons of gastrocnemius and plantaris muscles for 4 weeks. The right muscle served as the control. Soleus muscles from both hindlimbs were dissected 2 and 4 weeks after the operation. Hypertrophy of soleus muscle in HSF1-null mice was partially inhibited, compared with that in wild-type (C57BL/6J) mice. Absence of HSF1 partially attenuated the increase of muscle wet weight and fiber cross-sectional area of overloaded soleus muscle. Population of Pax7-positive muscle satellite cells in HSF1-null mice was significantly less than that in wild-type mice following 2 weeks of overloading (p<0.05). Significant up-regulations of interleukin (IL)-1β and tumor necrosis factor mRNAs were observed in HSF1-null, but not in wild-type, mice following 2 weeks of overloading. Overloading-related increases of IL-6 and AFT3 mRNA expressions seen after 2 weeks of overloading tended to decrease after 4 weeks in both types of mice. In HSF1-null mice, however, the significant overloading-related increase in the expression of IL-6, not ATF3, mRNA was noted even at 4th week. Inhibition of muscle hypertrophy might be attributed to the greater and prolonged enhancement of IL-6 expression. HSF1 and/or HSF1-mediated stress response may, in part, play a key role in loading-induced skeletal muscle hypertrophy.

  20. Heat Shock Transcription Factor 1-Deficiency Attenuates Overloading-Associated Hypertrophy of Mouse Soleus Muscle

    PubMed Central

    Koya, Tomoyuki; Nishizawa, Sono; Ohno, Yoshitaka; Goto, Ayumi; Ikuta, Akihiro; Suzuki, Miho; Ohira, Tomotaka; Egawa, Tatsuro; Nakai, Akira; Sugiura, Takao; Ohira, Yoshinobu; Yoshioka, Toshitada; Beppu, Moroe; Goto, Katsumasa

    2013-01-01

    Hypertrophic stimuli, such as mechanical stress and overloading, induce stress response, which is mediated by heat shock transcription factor 1 (HSF1), and up-regulate heat shock proteins (HSPs) in mammalian skeletal muscles. Therefore, HSF1-associated stress response may play a key role in loading-associated skeletal muscle hypertrophy. The purpose of this study was to investigate the effects of HSF1-deficiency on skeletal muscle hypertrophy caused by overloading. Functional overloading on the left soleus was performed by cutting the distal tendons of gastrocnemius and plantaris muscles for 4 weeks. The right muscle served as the control. Soleus muscles from both hindlimbs were dissected 2 and 4 weeks after the operation. Hypertrophy of soleus muscle in HSF1-null mice was partially inhibited, compared with that in wild-type (C57BL/6J) mice. Absence of HSF1 partially attenuated the increase of muscle wet weight and fiber cross-sectional area of overloaded soleus muscle. Population of Pax7-positive muscle satellite cells in HSF1-null mice was significantly less than that in wild-type mice following 2 weeks of overloading (p<0.05). Significant up-regulations of interleukin (IL)-1β and tumor necrosis factor mRNAs were observed in HSF1-null, but not in wild-type, mice following 2 weeks of overloading. Overloading-related increases of IL-6 and AFT3 mRNA expressions seen after 2 weeks of overloading tended to decrease after 4 weeks in both types of mice. In HSF1-null mice, however, the significant overloading-related increase in the expression of IL-6, not ATF3, mRNA was noted even at 4th week. Inhibition of muscle hypertrophy might be attributed to the greater and prolonged enhancement of IL-6 expression. HSF1 and/or HSF1-mediated stress response may, in part, play a key role in loading-induced skeletal muscle hypertrophy. PMID:24167582

  1. Muscle-targeted hydrodynamic gene introduction of insulin-like growth factor-1 using polyplex nanomicelle to treat peripheral nerve injury.

    PubMed

    Nagata, Kazuya; Itaka, Keiji; Baba, Miyuki; Uchida, Satoshi; Ishii, Takehiko; Kataoka, Kazunori

    2014-06-10

    The recovery of neurologic function after peripheral nerve injury often remains incomplete because of the prolonged reinnervation process, which leads to skeletal muscle atrophy and articular contracture from disuse over time. To rescue the skeletal muscle and promote functional recovery, insulin-like growth factor-1 (IGF-1), a potent myogenic factor, was introduced into the muscle by hydrodynamic injection of IGF-1-expressing plasmid DNA using a biocompatible nonviral gene carrier, a polyplex nanomicelle. In a mouse model of sciatic nerve injury, the introduction of IGF-1 into the skeletal muscle of the paralyzed limb effectively alleviated a decrease in muscle weight compared with that in untreated control mice. Histologic analysis of the muscle revealed the IGF-1-expressing plasmid DNA (pDNA) to have a myogenic effect, inducing muscle hypertrophy with the upregulation of the myogenic regulatory factors, myogenin and MyoD. The evaluation of motor function by walking track analysis revealed that the group that received the hydrodynamic injection of IGF-1-expressing pDNA using the polyplex nanomicelle had significantly early recovery of motor function compared with groups receiving negative control pDNA and untreated controls. Early recovery of sensation in the distal area of sciatic nerve injury was also induced by the introduction of IGF-1-expressing pDNA, presumably because of the effect of secreted IGF-1 protein in the vicinity of the injured sciatic nerve exerting a synergistic effect with muscle hypertrophy, inducing a more favorable prognosis. This approach of introducing IGF-1 into skeletal muscle is promising for the treatment of peripheral nerve injury by promoting early motor function recovery. Copyright © 2014 Elsevier B.V. All rights reserved.

  2. Effect of nandrolone decanoate on skeletal muscle repair.

    PubMed

    Piovesan, R F; Fernandes, K P S; Alves, A N; Teixeira, V P; Silva Junior, J A; Martins, M D; Bussadori, S K; Albertini, R; Mesquita-Ferrari, R A

    2013-01-01

    This study analyzed the effect of nandrolone decanoate (ND) on muscle repair and the expression of myogenic regulatory factors following cryoinjury in rat skeletal muscle. Adult male Wistar rats were randomly divided into 4 groups: control group, sham group, cryoinjured group treated with ND and non-injured group treated with ND. Treatment consisted of subcutaneous injections of ND (5 mg/kg) twice a week. After sacrifice, the tibialis anterior muscle was removed for the isolation of total RNA and analysis of myogenic regulatory factors using real-time PCR as well as morphological analysis using the hematoxylin-eosin assay. There was a significant increase in MyoD mRNA after 7 days and in myogenin mRNA after 21 days in the cryoinjured ND group in comparison to other groups in the same period. The morphological analysis revealed no edema or myonecrosis after 7 days as well as no edema or inflammatory infiltrate after 14 days in the cryoinjured ND group. In conclusion the anabolic steroid nandrolone decanoate can modulate the muscle repair process in rats following cryoinjury by influencing the expression of regulatory myogenic factors and phases of muscle repair. © Georg Thieme Verlag KG Stuttgart · New York.

  3. Coupled gating of skeletal muscle ryanodine receptors is modulated by Ca2+, Mg2+, and ATP

    PubMed Central

    Porta, Maura; Diaz-Sylvester, Paula L.; Neumann, Jake T.; Escobar, Ariel L.; Fleischer, Sidney

    2012-01-01

    Coupled gating (synchronous openings and closures) of groups of skeletal muscle ryanodine receptors (RyR1), which mimics RyR1-mediated Ca2+ release underlying Ca2+ sparks, was first described by Marx et al. (Marx SO, Ondrias K, Marks AR. Science 281: 818–821, 1998). The nature of the RyR1-RyR1 interactions for coupled gating still needs to be characterized. Consequently, we defined planar lipid bilayer conditions where ∼25% of multichannel reconstitutions contain mixtures of coupled and independently gating RyR1. In ∼10% of the cases, all RyRs (2–10 channels; most frequently 3–4) gated in coupled fashion, allowing for quantification. Our results indicated that coupling required cytosolic solutions containing ATP/Mg2+ and high (50 mM) luminal Ca2+ (Calum) or Sr2+ solutions. Bursts of coupled activity (events) started and ended abruptly, with all channels activating/deactivating within ∼300 μs. Coupled RyR1 were heterogeneous, where highly active RyR1 (“drivers”) seemed open during the entire coupled event (Po = 1), while other RyR1s (“followers”) displayed abundant flickering and smaller amplitude. Drivers mean open time increased with cytosolic Ca2+ (Cacyt) or caffeine, whereas followers flicker frequency was Cacyt independent and more sensitive to inhibition by cytosolic Mg2+. Coupled events were insensitive to varying lumen-to-cytosol Ca2+ fluxes from ∼1 to 8 pA, which does not corroborate coupling of neighboring RyR1 by local Ca2+-induced Ca2+ release. However, coupling requires specific Calum sites, as it was lost when Calum was replaced by luminal Ba2+ or Mg2+. In summary, coupled events reveal complex interactions among heterogeneous RyR1, differentially modulated by cytosolic ATP/Mg2+, Cacyt, and Calum, which under cell-like ionic conditions may parallel synchronous RyR1 gating during Ca2+ sparks. PMID:22785120

  4. The relative expression levels of insulin-like growth factor 1 and myostatin mRNA in the asynchronous development of skeletal muscle in ducks during early development.

    PubMed

    Hu, Yan; Liu, Hongxiang; Shan, Yanju; Ji, Gaige; Xu, Wenjuan; Shu, Jingting; Li, Huifang

    2015-08-10

    Genetic selection is a powerful tool for modifying poultry muscle yield. Insulin-like growth factor I (IGF-I) and myostatin (MSTN) are important regulators of muscle growth, especially in the myogenesis stage. This study compared the developmental pattern of the pectoralis major (PM) and lateral gastrocnemius (LM) muscles, mRNA expression characterization of IGF-I and MSTN-A and their correlation between 14 days in ovo and 1 week post-hatch in two Chinese local duck breeds. During early development, the growth of duck PM and LM followed an asynchronous pattern. Variations in PM growth rate observed with development followed the relative variations of MSTN and IGF-I expression; however, the same behavior was not observed in LM. Moreover, the profile of IGF-I expression in duck skeletal muscles indicated that genetic selection for high meat-yield poultry has altered the temporal expression of IGF-I and affected cellular characteristics and mass by hatch in a PM-specific manner. The MSTN-A expression profile showed synchronization with the growth of skeletal muscle and peaks of myofiber proliferation. The expression patterns of IGF-I and MSTN suggest that duck pectoralis fibers are prioritized for proliferation in embryogenesis. The IGF-1/MSTN-A mRNA ratios in PM and LM presented very similar trends in the changes of myofiber characteristics, and differences in the IGF-1/MSTN-A mRNA ratio in PM between the two breeds corresponded to the timing of differences in PM mass between the varieties. Our results support the hypothesis that relative levels of IGF-I and MSTN mRNA may participate in ordering muscle growth rates with selected development. Copyright © 2015 Elsevier B.V. All rights reserved.

  5. Contractile activity of human skeletal muscle cells prevents insulin resistance by inhibiting pro-inflammatory signalling pathways.

    PubMed

    Lambernd, S; Taube, A; Schober, A; Platzbecker, B; Görgens, S W; Schlich, R; Jeruschke, K; Weiss, J; Eckardt, K; Eckel, J

    2012-04-01

    Obesity is closely associated with muscle insulin resistance and is a major risk factor for the pathogenesis of type 2 diabetes. Regular physical activity not only prevents obesity, but also considerably improves insulin sensitivity and skeletal muscle metabolism. We sought to establish and characterise an in vitro model of human skeletal muscle contraction, with a view to directly studying the signalling pathways and mechanisms that are involved in the beneficial effects of muscle activity. Contracting human skeletal muscle cell cultures were established by applying electrical pulse stimulation. To induce insulin resistance, skeletal muscle cells were incubated with human adipocyte-derived conditioned medium, monocyte chemotactic protein (MCP)-1 and chemerin. Similarly to in exercising skeletal muscle in vivo, electrical pulse stimulation induced contractile activity in human skeletal muscle cells, combined with the formation of sarcomeres, activation of AMP-activated protein kinase (AMPK) and increased IL-6 secretion. Insulin-stimulated glucose uptake was substantially elevated in contracting cells compared with control. The incubation of skeletal muscle cells with adipocyte-conditioned media, chemerin and MCP-1 significantly reduced the insulin-stimulated phosphorylation of Akt. This effect was abrogated by concomitant pulse stimulation of the cells. Additionally, pro-inflammatory signalling by adipocyte-derived factors was completely prevented by electrical pulse stimulation of the myotubes. We showed that the effects of electrical pulse stimulation on skeletal muscle cells were similar to the effect of exercise on skeletal muscle in vivo in terms of enhanced AMPK activation and IL-6 secretion. In our model, muscle contractile activity eliminates insulin resistance by blocking pro-inflammatory signalling pathways. This novel model therefore provides a unique tool for investigating the molecular mechanisms that mediate the beneficial effects of muscle

  6. Astaxanthin supplementation attenuates immobilization-induced skeletal muscle fibrosis via suppression of oxidative stress.

    PubMed

    Maezawa, Toshiyuki; Tanaka, Masayuki; Kanazashi, Miho; Maeshige, Noriaki; Kondo, Hiroyo; Ishihara, Akihiko; Fujino, Hidemi

    2017-09-01

    Immobilization induces skeletal muscle fibrosis characterized by increasing collagen synthesis in the perimysium and endomysium. Transforming growth factor1 (TGF-β1) is associated with this lesion via promoting differentiation of fibroblasts into myofibroblasts. In addition, reactive oxygen species (ROS) are shown to mediate TGF-β1-induced fibrosis in tissues. These reports suggest the importance of ROS reduction for attenuating skeletal muscle fibrosis. Astaxanthin, a powerful antioxidant, has been shown to reduce ROS production in disused muscle. Therefore, we investigated the effects of astaxanthin supplementation on muscle fibrosis under immobilization. In the present study, immobilization increased the collagen fiber area, the expression levels of TGF-β1, α-smooth muscle actin, and superoxide dismutase-1 protein and ROS production. However, these changes induced by immobilization were attenuated by astaxanthin supplementation. These results indicate the effectiveness of astaxanthin supplementation on skeletal muscle fibrosis induced by ankle joint immobilization.

  7. Activation of peroxisome proliferator-activated receptor-{delta} by GW501516 prevents fatty acid-induced nuclear factor-{kappa}B activation and insulin resistance in skeletal muscle cells.

    PubMed

    Coll, Teresa; Alvarez-Guardia, David; Barroso, Emma; Gómez-Foix, Anna Maria; Palomer, Xavier; Laguna, Juan C; Vázquez-Carrera, Manuel

    2010-04-01

    Elevated plasma free fatty acids cause insulin resistance in skeletal muscle through the activation of a chronic inflammatory process. This process involves nuclear factor (NF)-kappaB activation as a result of diacylglycerol (DAG) accumulation and subsequent protein kinase Ctheta (PKCtheta) phosphorylation. At present, it is unknown whether peroxisome proliferator-activated receptor-delta (PPARdelta) activation prevents fatty acid-induced inflammation and insulin resistance in skeletal muscle cells. In C2C12 skeletal muscle cells, the PPARdelta agonist GW501516 prevented phosphorylation of insulin receptor substrate-1 at Ser(307) and the inhibition of insulin-stimulated Akt phosphorylation caused by exposure to the saturated fatty acid palmitate. This latter effect was reversed by the PPARdelta antagonist GSK0660. Treatment with the PPARdelta agonist enhanced the expression of two well known PPARdelta target genes involved in fatty acid oxidation, carnitine palmitoyltransferase-1 and pyruvate dehydrogenase kinase 4 and increased the phosphorylation of AMP-activated protein kinase, preventing the reduction in fatty acid oxidation caused by palmitate exposure. In agreement with these changes, GW501516 treatment reversed the increase in DAG and PKCtheta activation caused by palmitate. These effects were abolished in the presence of the carnitine palmitoyltransferase-1 inhibitor etomoxir, thereby indicating that increased fatty acid oxidation was involved in the changes observed. Consistent with these findings, PPARdelta activation by GW501516 blocked palmitate-induced NF-kappaB DNA-binding activity. Likewise, drug treatment inhibited the increase in IL-6 expression caused by palmitate in C2C12 and human skeletal muscle cells as well as the protein secretion of this cytokine. These findings indicate that PPARdelta attenuates fatty acid-induced NF-kappaB activation and the subsequent development of insulin resistance in skeletal muscle cells by reducing DAG accumulation

  8. Development and external validation of nomograms to predict the risk of skeletal metastasis at the time of diagnosis and skeletal metastasis-free survival in nasopharyngeal carcinoma.

    PubMed

    Yang, Lin; Xia, Liangping; Wang, Yan; He, Shasha; Chen, Haiyang; Liang, Shaobo; Peng, Peijian; Hong, Shaodong; Chen, Yong

    2017-09-06

    The skeletal system is the most common site of distant metastasis in nasopharyngeal carcinoma (NPC); various prognostic factors have been reported for skeletal metastasis, though most studies have focused on a single factor. We aimed to establish nomograms to effectively predict skeletal metastasis at initial diagnosis (SMAD) and skeletal metastasis-free survival (SMFS) in NPC. A total of 2685 patients with NPC who received bone scintigraphy (BS) and/or 18F-deoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) and 2496 patients without skeletal metastasis were retrospectively assessed to develop individual nomograms for SMAD and SMFS. The models were validated externally using separate cohorts of 1329 and 1231 patients treated at two other institutions. Five independent prognostic factors were included in each nomogram. The SMAD nomogram had a significantly higher c-index than the TNM staging system (training cohort, P = 0.005; validation cohort, P < 0.001). The SMFS nomogram had significantly higher c-index values in the training and validation sets than the TNM staging system (P < 0.001 and P = 0.005, respectively). Three proposed risk stratification groups were created using the nomograms, and enabled significant discrimination of SMFS for each risk group. The prognostic nomograms established in this study enable accurate stratification of distinct risk groups for skeletal metastasis, which may improve counseling and facilitate individualized management of patients with NPC.

  9. Modulation of sarcoplasmic reticulum Ca2+ release in skeletal muscle expressing ryanodine receptor impaired in regulation by calmodulin and S100A1

    PubMed Central

    Yamaguchi, Naohiro; Prosser, Benjamin L.; Ghassemi, Farshid; Xu, Le; Pasek, Daniel A.; Eu, Jerry P.; Hernández-Ochoa, Erick O.; Cannon, Brian R.; Wilder, Paul T.; Lovering, Richard M.; Weber, David; Melzer, Werner; Schneider, Martin F.

    2011-01-01

    In vitro, calmodulin (CaM) and S100A1 activate the skeletal muscle ryanodine receptor ion channel (RyR1) at submicromolar Ca2+ concentrations, whereas at micromolar Ca2+ concentrations, CaM inhibits RyR1. One amino acid substitution (RyR1-L3625D) has previously been demonstrated to impair CaM binding and regulation of RyR1. Here we show that the RyR1-L3625D substitution also abolishes S100A1 binding. To determine the physiological relevance of these findings, mutant mice were generated with the RyR1-L3625D substitution in exon 74, which encodes the CaM and S100A1 binding domain of RyR1. Homozygous mutant mice (Ryr1D/D) were viable and appeared normal. However, single RyR1 channel recordings from Ryr1D/D mice exhibited impaired activation by CaM and S100A1 and impaired CaCaM inhibition. Isolated flexor digitorum brevis muscle fibers from Ryr1D/D mice had depressed Ca2+ transients when stimulated by a single action potential. However, during repetitive stimulation, the mutant fibers demonstrated greater relative summation of the Ca2+ transients. Consistently, in vivo stimulation of tibialis anterior muscles in Ryr1D/D mice demonstrated reduced twitch force in response to a single action potential, but greater summation of force during high-frequency stimulation. During repetitive stimulation, Ryr1D/D fibers exhibited slowed inactivation of sarcoplasmic reticulum Ca2+ release flux, consistent with increased summation of the Ca2+ transient and contractile force. Peak Ca2+ release flux was suppressed at all voltages in voltage-clamped Ryr1D/D fibers. The results suggest that the RyR1-L3625D mutation removes both an early activating effect of S100A1 and CaM and delayed suppressing effect of CaCaM on RyR1 Ca2+ release, providing new insights into CaM and S100A1 regulation of skeletal muscle excitation-contraction coupling. PMID:21289290

  10. Exercise Promotes Healthy Aging of Skeletal Muscle

    PubMed Central

    Cartee, Gregory D.; Hepple, Russell T.; Bamman, Marcas M.; Zierath, Juleen R.

    2016-01-01

    Primary aging is the progressive and inevitable process of bodily deterioration during adulthood. In skeletal muscle, primary aging causes defective mitochondrial energetics, and reduced muscle mass. Secondary aging refers to additional deleterious structural and functional age-related changes caused by diseases and lifestyle factors. Secondary aging can exacerbate deficits in mitochondrial function and muscle mass, concomitant with the development of skeletal muscle insulin resistance. Exercise opposes deleterious effects of secondary aging by preventing the decline in mitochondrial respiration, mitigating aging-related loss of muscle mass and enhancing insulin sensitivity. This review focuses on mechanisms by which exercise promotes “healthy aging” by inducing modifications in skeletal muscle. PMID:27304505

  11. Root resorption of maxillary incisors retracted with and without skeletal anchorage.

    PubMed

    Barros, Sérgio Estelita; Janson, Guilherme; Chiqueto, Kelly; Baldo, Vitor Oliveira; Baldo, Taiana Oliveira

    2017-02-01

    Our objective was to compare root resorption degree of the maxillary central incisors retracted with and without skeletal anchorage. This nonrandomized historical control study included 37 patients requiring maximum anterior retraction and treated with extraction of 2 maxillary premolars. Group 1 consisted of 22 patients (11 male, 11 female) in whom anterior retraction was performed without skeletal anchorage, and group 2 included 15 patients (3 male, 12 female) treated with skeletally anchored anterior retraction. Periapical radiographs were used to evaluate root resorption degree by a scoring system. The groups were compared regarding the resorption score and resorption degree distribution with the Mann-Whitney U test, chi-square test, and Z test on proportions. There was no statistically significant intergroup difference regarding root resorption, but the number of patients with severe and extreme root resorption degrees was significantly greater in group 2. Although the root resorption degree of the skeletal anchorage group was not significantly different from the group without skeletal anchorage, the number of patients with severe to extreme resorption in the first group was significantly greater. Therefore, careful clinical monitoring of skeletally anchored anterior retraction is needed, especially when there are known root resorption predisposing factors. Copyright © 2017 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.

  12. The skeletal vascular system - Breathing life into bone tissue.

    PubMed

    Stegen, Steve; Carmeliet, Geert

    2017-08-26

    During bone development, homeostasis and repair, a dense vascular system provides oxygen and nutrients to highly anabolic skeletal cells. Characteristic for the vascular system in bone is the serial organization of two capillary systems, each typified by specific morphological and physiological features. Especially the arterial capillaries mediate the growth of the bone vascular system, serve as a niche for skeletal and hematopoietic progenitors and couple angiogenesis to osteogenesis. Endothelial cells and osteoprogenitor cells interact not only physically, but also communicate to each other by secretion of growth factors. A vital angiogenic growth factor is vascular endothelial growth factor and its expression in skeletal cells is controlled by osteogenic transcription factors and hypoxia signaling, whereas the secretion of angiocrine factors by endothelial cells is regulated by Notch signaling, blood flow and possibly hypoxia. Bone loss and impaired fracture repair are often associated with reduced and disorganized blood vessel network and therapeutic targeting of the angiogenic response may contribute to enhanced bone regeneration. Copyright © 2017 Elsevier Inc. All rights reserved.

  13. Translating golden retriever muscular dystrophy microarray findings to novel biomarkers for cardiac/skeletal muscle function in Duchenne muscular dystrophy.

    PubMed

    Galindo, Cristi L; Soslow, Jonathan H; Brinkmeyer-Langford, Candice L; Gupte, Manisha; Smith, Holly M; Sengsayadeth, Seng; Sawyer, Douglas B; Benson, D Woodrow; Kornegay, Joe N; Markham, Larry W

    2016-04-01

    In Duchenne muscular dystrophy (DMD), abnormal cardiac function is typically preceded by a decade of skeletal muscle disease. Molecular reasons for differences in onset and progression of these muscle groups are unknown. Human biomarkers are lacking. We analyzed cardiac and skeletal muscle microarrays from normal and golden retriever muscular dystrophy (GRMD) dogs (ages 6, 12, or 47+ mo) to gain insight into muscle dysfunction and to identify putative DMD biomarkers. These biomarkers were then measured using human DMD blood samples. We identified GRMD candidate genes that might contribute to the disparity between cardiac and skeletal muscle disease, focusing on brain-derived neurotropic factor (BDNF) and osteopontin (OPN/SPP1, hereafter indicated as SPP1). BDNF was elevated in cardiac muscle of younger GRMD but was unaltered in skeletal muscle, while SPP1 was increased only in GRMD skeletal muscle. In human DMD, circulating levels of BDNF were inversely correlated with ventricular function and fibrosis, while SPP1 levels correlated with skeletal muscle function. These results highlight gene expression patterns that could account for differences in cardiac and skeletal disease in GRMD. Most notably, animal model-derived data were translated to DMD and support use of BDNF and SPP1 as biomarkers for cardiac and skeletal muscle involvement, respectively.

  14. Pregnancy and Smoothelin-like Protein 1 (SMTNL1) Deletion Promote the Switching of Skeletal Muscle to a Glycolytic Phenotype in Human and Mice.

    PubMed

    Lontay, Beata; Bodoor, Khaldon; Sipos, Adrienn; Weitzel, Douglas H; Loiselle, David; Safi, Rachid; Zheng, Donghai; Devente, James; Hickner, Robert C; McDonnell, Donald P; Ribar, Thomas; Haystead, Timothy A

    2015-07-17

    Pregnancy promotes physiological adaptations throughout the body, mediated by the female sex hormones progesterone and estrogen. Changes in the metabolic properties of skeletal muscle enable the female body to cope with the physiological challenges of pregnancy and may also be linked to the development of insulin resistance. We conducted global microarray, proteomic, and metabolic analyses to study the role of the progesterone receptor and its transcriptional regulator, smoothelin-like protein 1 (SMTNL1) in the adaptation of skeletal muscle to pregnancy. We demonstrate that pregnancy promotes fiber-type changes from an oxidative to glycolytic isoform in skeletal muscle. This phenomenon is regulated through an interaction between SMTNL1 and progesterone receptor, which alters the expression of contractile and metabolic proteins. smtnl1(-/-) mice are metabolically less efficient and show impaired glucose tolerance. Pregnancy antagonizes these effects by inducing metabolic activity and increasing glucose tolerance. Our results suggest that SMTNL1 has a role in mediating the actions of steroid hormones to promote fiber switching in skeletal muscle during pregnancy. Our findings also bear on the management of gestational diabetes that develops as a complication of pregnancy in ~4% of women. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

  15. A novel approach for treatment of skeletal Class II malocclusion: Miniplates-based skeletal anchorage.

    PubMed

    Al-Dumaini, Abdullsalam Abdulqawi; Halboub, Esam; Alhammadi, Maged Sultan; Ishaq, Ramy Abdul Rahman; Youssef, Mohamed

    2018-02-01

    The objective of this study was to evaluate the effect of a new approach-bimaxillary miniplates-based skeletal anchorage-in the treatment of skeletal Class II malocclusion compared with untreated subjects. The study (miniplates) group comprised 28 patients (14 boys, 14 girls) with skeletal Class II malocclusion due to mandibular retrusion, with a mean age of 11.83 years. After 0.017 × 0.025-in stainless steel archwires were placed in both arches, 4 miniplates were fixed bilaterally, 2 in the maxillary anterior areas and 2 in the mandibular posterior areas, and used for skeletal treatment with elastics. Twenty-four Class II untreated subjects (11 boys, 13 girls), with a mean age of 11.75 years, were included as controls. Skeletal and dental changes were evaluated using pretreatment and posttreatment or observational lateral cephalometric radiographs. The treatment changes were compared with the growth changes observed in the control group using independent t tests. Compared with the minimal changes induced by growth in the control group, the skeletal changes induced by miniplates were more obvious. The mandibular length increased significantly (3 mm), and the mandible moved forward, with a significant restraint in the sagittal position of the maxilla (P <0.001). The overjet correction (-4.26 mm) was found to be a net result of skeletal changes (A-Y-axis = -1.18 mm and B-Y-axis = 3.83 mm). The mandibular plane was significantly decreased by 2.75° (P <0.001). This new technique, bimaxillary miniplates-based skeletal anchorage, is an effective method for treating patients with skeletal Class II malocclusions through obvious skeletal, but minimal dentoalveolar, changes. Copyright © 2017 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.

  16. RNA helicase, DDX27 regulates skeletal muscle growth and regeneration by modulation of translational processes

    PubMed Central

    Gundry, Stacey R.; Chan, Aye T.; Widrick, Jeffrey; Draper, Isabelle; Chakraborty, Anirban; Zhou, Yi; Zon, Leonard I.; Gleizes, Pierre-Emmanuel

    2018-01-01

    Gene expression in a tissue-specific context depends on the combined efforts of epigenetic, transcriptional and post-transcriptional processes that lead to the production of specific proteins that are important determinants of cellular identity. Ribosomes are a central component of the protein biosynthesis machinery in cells; however, their regulatory roles in the translational control of gene expression in skeletal muscle remain to be defined. In a genetic screen to identify critical regulators of myogenesis, we identified a DEAD-Box RNA helicase, DDX27, that is required for skeletal muscle growth and regeneration. We demonstrate that DDX27 regulates ribosomal RNA (rRNA) maturation, and thereby the ribosome biogenesis and the translation of specific transcripts during myogenesis. These findings provide insight into the translational regulation of gene expression in myogenesis and suggest novel functions for ribosomes in regulating gene expression in skeletal muscles. PMID:29518074

  17. Smad4 deficiency impairs chondrocyte hypertrophy via the Runx2 transcription factor in mouse skeletal development.

    PubMed

    Yan, Jianyun; Li, Jun; Hu, Jun; Zhang, Lu; Wei, Chengguo; Sultana, Nishat; Cai, Xiaoqiang; Zhang, Weijia; Cai, Chen-Leng

    2018-06-15

    Chondrocyte hypertrophy is the terminal step in chondrocyte differentiation and is crucial for endochondral bone formation. How signaling pathways regulate chondrocyte hypertrophic differentiation remains incompletely understood. In this study, using a Tbx18:Cre ( Tbx18 Cre /+ ) gene-deletion approach, we selectively deleted the gene for the signaling protein SMAD family member 4 ( Smad4 f/f ) in the limbs of mice. We found that the Smad4 -deficient mice develop a prominent shortened limb, with decreased expression of chondrocyte differentiation markers, including Col2a1 and Acan , in the humerus at mid-to-late gestation. The most striking defects in these mice were the absence of stylopod elements and failure of chondrocyte hypertrophy in the humerus. Moreover, expression levels of the chondrocyte hypertrophy-related markers Col10a1 and Panx3 were significantly decreased. Of note, we also observed that the expression of runt-related transcription factor 2 ( Runx2 ), a critical mediator of chondrocyte hypertrophy, was also down-regulated in Smad4 -deficient limbs. To determine how the skeletal defects arose in the mouse mutants, we performed RNA-Seq with ChIP-Seq analyses and found that Smad4 directly binds to regulatory elements in the Runx2 promoter. Our results suggest a new mechanism whereby Smad4 controls chondrocyte hypertrophy by up-regulating Runx2 expression during skeletal development. The regulatory mechanism involving Smad4-mediated Runx2 activation uncovered here provides critical insights into bone development and pathogenesis of chondrodysplasia. © 2018 Yan et al.

  18. Cytoskeletal tropomyosin Tm5NM1 is required for normal excitation-contraction coupling in skeletal muscle.

    PubMed

    Vlahovich, Nicole; Kee, Anthony J; Van der Poel, Chris; Kettle, Emma; Hernandez-Deviez, Delia; Lucas, Christine; Lynch, Gordon S; Parton, Robert G; Gunning, Peter W; Hardeman, Edna C

    2009-01-01

    The functional diversity of the actin microfilaments relies in part on the actin binding protein tropomyosin (Tm). The muscle-specific Tms regulate actin-myosin interactions and hence contraction. However, there is less known about the roles of the numerous cytoskeletal isoforms. We have shown previously that a cytoskeletal Tm, Tm5NM1, defines a Z-line adjacent cytoskeleton in skeletal muscle. Recently, we identified a second cytoskeletal Tm in this region, Tm4. Here we show that Tm4 and Tm5NM1 define separate actin filaments; the former associated with the terminal sarcoplasmic reticulum (SR) and other tubulovesicular structures. In skeletal muscles of Tm5NM1 knockout (KO) mice, Tm4 localization was unchanged, demonstrating the specificity of the membrane association. Tm5NM1 KO muscles exhibit potentiation of T-system depolarization and decreased force rundown with repeated T-tubule depolarizations consistent with altered T-tubule function. These results indicate that a Tm5NM1-defined actin cytoskeleton is required for the normal excitation-contraction coupling in skeletal muscle.

  19. Cytoskeletal Tropomyosin Tm5NM1 Is Required for Normal Excitation–Contraction Coupling in Skeletal Muscle

    PubMed Central

    Vlahovich, Nicole; Kee, Anthony J.; Van der Poel, Chris; Kettle, Emma; Hernandez-Deviez, Delia; Lucas, Christine; Lynch, Gordon S.; Parton, Robert G.; Gunning, Peter W.

    2009-01-01

    The functional diversity of the actin microfilaments relies in part on the actin binding protein tropomyosin (Tm). The muscle-specific Tms regulate actin-myosin interactions and hence contraction. However, there is less known about the roles of the numerous cytoskeletal isoforms. We have shown previously that a cytoskeletal Tm, Tm5NM1, defines a Z-line adjacent cytoskeleton in skeletal muscle. Recently, we identified a second cytoskeletal Tm in this region, Tm4. Here we show that Tm4 and Tm5NM1 define separate actin filaments; the former associated with the terminal sarcoplasmic reticulum (SR) and other tubulovesicular structures. In skeletal muscles of Tm5NM1 knockout (KO) mice, Tm4 localization was unchanged, demonstrating the specificity of the membrane association. Tm5NM1 KO muscles exhibit potentiation of T-system depolarization and decreased force rundown with repeated T-tubule depolarizations consistent with altered T-tubule function. These results indicate that a Tm5NM1-defined actin cytoskeleton is required for the normal excitation–contraction coupling in skeletal muscle. PMID:19005216

  20. Blockade of Metallothioneins 1 and 2 Increases Skeletal Muscle Mass and Strength

    PubMed Central

    Summermatter, Serge; Bouzan, Anais; Pierrel, Eliane; Melly, Stefan; Stauffer, Daniela; Gutzwiller, Sabine; Nolin, Erin; Dornelas, Christina; Fryer, Christy; Leighton-Davies, Juliet; Glass, David J.

    2016-01-01

    ABSTRACT Metallothioneins are proteins that are involved in intracellular zinc storage and transport. Their expression levels have been reported to be elevated in several settings of skeletal muscle atrophy. We therefore investigated the effect of metallothionein blockade on skeletal muscle anabolism in vitro and in vivo. We found that concomitant abrogation of metallothioneins 1 and 2 results in activation of the Akt pathway and increases in myotube size, in type IIb fiber hypertrophy, and ultimately in muscle strength. Importantly, the beneficial effects of metallothionein blockade on muscle mass and function was also observed in the setting of glucocorticoid addition, which is a strong atrophy-inducing stimulus. Given the blockade of atrophy and the preservation of strength in atrophy-inducing settings, these results suggest that blockade of metallothioneins 1 and 2 constitutes a promising approach for the treatment of conditions which result in muscle atrophy. PMID:27956698

  1. Prevalence of skeletal deformity due to nutritional rickets in children between 1 and 18 years in tea garden community.

    PubMed

    Chabra, Tarun; Tahbildar, Pranjal; Sharma, Ayush; Boruah, Sushanta; Mahajan, Rajat; Raje, Amrut

    2016-01-01

    The present study was undertaken to find out the prevalence of skeletal deformity due to nutritional rickets in children aged 1-18 years in tea garden community in Dibrugarh District of Assam. It was a cross-sectional study and two-stage cluster sampling was used. In the selected tea gardens, all the children aged 1-18 years were screened for skeletal deformity by house-to-house visit. The overall prevalence of skeletal deformity was 2.7 per thousand. Majority of children with deformities (57.27%) were between 7 and 12 years of age. Widening of wrists and ankle was the most frequent symptom (53.8%). Most of the children with deformity had moderate malnutrition (77.27%). Most of the children with skeletal deformity belong to lower (v) (45.45%) grade of Kuppuswamy's grading scale. Bilateral genu valgus deformity (54.54%) and bilateral genu varum (25.92%) deformity were the most common deformities. Widening of wrists and ankle was the most frequent symptom (61.66%). Of the 16,274 tea garden children included in our study (male and female) in the age group 1-18 years, 44 had skeletal deformity due to nutritional rickets. The prevalence of skeletal deformity due to nutritional rickets was found to be 2.7 per thousand children, which are significantly higher when compared with the only other such study, which was on general population in Bangladesh.

  2. [Actual conditions of occupational health administration of small-scale enterprises in Japan: (II). Occupational health controls for hazardous and musculo-skeletally stressful working factors].

    PubMed

    Kumagai, S; Hirata, M; Tabuchi, T; Tainaka, H; Andoh, K; Oda, H

    2000-09-01

    In order to clarify the actual condition of occupational health management for hazardous and musculo-skeletally stressful work factors in small-scale enterprises (SSEs) in Japan, a questionnaire survey was conducted in an area near Osaka city. The hazardous work factors examined were dust, organic solvents, lead, specified chemical substances, anoxia, noise, hand-arm vibration, ionizing radiation, high and low temperatures, and high air pressure. The musculo-skeletally stressful work factors examined were VDT work, prolonged standing, unnatural postures, handling of heavy weights, and stress on neck, shoulders and arms. The number of SSEs that replied to the questionnaire was 765 (recovery rate: 69.3%). Enterprises with noise, dust, hand-arm vibration and organic solvents numbered 14.0%, 10.7%, 6.9% and 6.4%, respectively, and those with other hazardous factors numbered less than 3%. Special medical examinations and working environment measurements for hazardous factors were conducted in 0.0% to 26.7% and 0.0% to 13.3%, respectively, of the enterprises. Working environment controls were conducted in 0.0% to 40.2%. Enterprises with prolonged standing and VDT work, were 42.0% and 35.8%, whereas those with other stressful factors were approximately 30%. Special medical examinations for musculo-skeletally stressful factors were conducted in 3.0% to 5.1% of the enterprises, and work controls were conducted in 20.4% to 25.3%. Non execution of the special medical examinations and working environment measurements were mainly due to "lack of knowledge of the law (19.7% and 30.2%)" and "lack of time to perform (16.0% and 23.3%)". Non execution of the controls for the hazardous work factors was due to "lack of knowledge as to how to control (9.0%)", "high costs (7.4%)", "lack of time to perform (6.4%)" and "absence of a suitable adviser (5.9%)". Non execution of the controls for stressful work factors was due to "lack of knowledge as to how to control (15.6%)" and "lack of

  3. The postcranial skeletal maturation of Australopithecus sediba.

    PubMed

    Cameron, Noel; Bogin, Barry; Bolter, Debra; Berger, Lee R

    2017-07-01

    In 2008, an immature hominin defined as the holotype of the new species Australopithecus sediba was discovered at the 1.9 million year old Malapa site in South Africa. The specimen (MH1) includes substantial post-cranial skeletal material, and provides a unique opportunity to assess its skeletal maturation. Skeletal maturity indicators observed on the proximal and distal humerus, proximal ulna, distal radius, third metacarpal, ilium and ischium, proximal femur and calcaneus were used to assess the maturity of each bone in comparison to references for modern humans and for wild chimpanzees (Pan troglodytes). In comparison to humans the skeletal maturational ages for Au. sediba correspond to between 12.0 years and 15.0 years with a mean (SD) age of 13.1 (1.1) years. In comparison to the maturational pattern of chimpanzees the Au. sediba indicators suggest a skeletal maturational age of 9-11 years. Based on either of these skeletal maturity estimates and the body length at death of MH1, an adult height of 150-156 cm is predicted. We conclude that the skeletal remains of MH1 are consistent with an ape-like pattern of maturity when dental age estimates are also taken into consideration. This maturity schedule in australopiths is consistent with ape-like estimates of age at death for the Nariokotome Homo erectus remains (KMN-WT 15000), which are of similar postcranial immaturity to MH1. The findings suggest that humans may have distinctive and delayed post-cranial schedules from australopiths and H. erectus, implicating a recent evolution of somatic and possibly life history strategies in human evolution. © 2017 Wiley Periodicals, Inc.

  4. Bibliometric study of articles on skeletal Class II malocclusions published in four high impact factor journals.

    PubMed

    Ousehal, Lahcen; El Aouame, Amal; Fatene, Nassiba; Lazrak, Laila; Traiba, Loubna; N'Gom, Papa Ibrahima

    2018-04-11

    Perform a bibliometric analysis of the orthodontic literature on skeletal Class II malocclusions during the first decade of the 21st century. A retrospective, observational, and comprehensive study ranging from January the first 2001 to December 31 2010, based on the articles published in four high impact factor orthodontic journals: Angle Orthod, OCR, EJO, and AJODO (Quotation Report Newspaper of the Scientific Information Institute). In the 4565 reviewed articles, only 338 were published on Class II malocclusions. Brazil, the United States, Turkey, and Germany are the nationalities, which have published the most. The cross-sectional descriptive studies represent 33%, randomized clinical trials (RCTs) 10.5%, meta-analyses 0.3%. Kanavakis et al. (2006) reported 72.34% of original articles, 2.83% of synthetic reviews, 8.89% of case reports, and 15.75% of unclassifiable articles. In conclusion, searchers in Orthodontics are invited to publish more clinical trials on skeletal Class II malocclusions. Copyright © 2018. Published by Elsevier Masson SAS.

  5. Long-term insulin-like growth factor-I expression in skeletal muscles attenuates the enhanced in vitro proliferation ability of the resident satellite cells in transgenic mice

    NASA Technical Reports Server (NTRS)

    Chakravarthy, M. V.; Fiorotto, M. L.; Schwartz, R. J.; Booth, F. W.

    2001-01-01

    Insulin-like growth factor-I (IGF-I) overexpression for 1-month in mouse skeletal muscle increases satellite cell proliferation potential. However, it is unknown whether this beneficial enhancement by IGF-I expression would persist over a longer-term duration in aged mice. This is an important issue to address if a prolonged course of IGF-I is to be used clinically in muscle-wasting conditions where satellite cells may become limiting. Using the IGF-I transgenic (IGF-I Tg) mouse that selectively expresses the IGF-I transgene in striated muscles, we found that 18-months of continuous IGF-I overexpression led to a loss in the enhanced in vitro proliferative capacity of satellite cells from Tg skeletal muscles. Also 18-month-old IGF-I Tg satellite cells lost the enhanced BrdU incorporation, greater pRb and Akt phosphorylations, and decreased p27(Kip1) levels initially observed in cells from 1-month-old IGF-I Tg mice. The levels of those biochemical markers reverted to similar values seen in the 18-months WT littermates. These findings, therefore, suggest that there is no further beneficial effect on enhancing satellite cell proliferation ability with persistent long-term expression of IGF-I in skeletal muscles of these transgenic mice.

  6. Renin-angiotensin system: an old player with novel functions in skeletal muscle.

    PubMed

    Cabello-Verrugio, Claudio; Morales, María Gabriela; Rivera, Juan Carlos; Cabrera, Daniel; Simon, Felipe

    2015-05-01

    Skeletal muscle is a tissue that shows the most plasticity in the body; it can change in response to physiological and pathological stimuli. Among the diseases that affect skeletal muscle are myopathy-associated fibrosis, insulin resistance, and muscle atrophy. A common factor in these pathologies is the participation of the renin-angiotensin system (RAS). This system can be functionally separated into the classical and nonclassical RAS axis. The main components of the classical RAS pathway are angiotensin-converting enzyme (ACE), angiotensin II (Ang-II), and Ang-II receptors (AT receptors), whereas the nonclassical axis is composed of ACE2, angiotensin 1-7 [Ang (1-7)], and the Mas receptor. Hyperactivity of the classical axis in skeletal muscle has been associated with insulin resistance, atrophy, and fibrosis. In contrast, current evidence supports the action of the nonclassical RAS as a counter-regulator axis of the classical RAS pathway in skeletal muscle. In this review, we describe the mechanisms involved in the pathological effects of the classical RAS, advances in the use of pharmacological molecules to inhibit this axis, and the beneficial effects of stimulation of the nonclassical RAS pathway on insulin resistance, atrophy, and fibrosis in skeletal muscle. © 2015 Wiley Periodicals, Inc.

  7. Bmp signaling regulates a dose-dependent transcriptional program to control facial skeletal development.

    PubMed

    Bonilla-Claudio, Margarita; Wang, Jun; Bai, Yan; Klysik, Elzbieta; Selever, Jennifer; Martin, James F

    2012-02-01

    We performed an in depth analysis of Bmp4, a critical regulator of development, disease, and evolution, in cranial neural crest (CNC). Conditional Bmp4 overexpression, using a tetracycline-regulated Bmp4 gain-of-function allele, resulted in facial skeletal changes that were most dramatic after an E10.5 Bmp4 induction. Expression profiling uncovered a signature of Bmp4-induced genes (BIG) composed predominantly of transcriptional regulators that control self-renewal, osteoblast differentiation and negative Bmp autoregulation. The complimentary experiment, CNC inactivation of Bmp2, Bmp4 and Bmp7, resulted in complete or partial loss of multiple CNC-derived skeletal elements, revealing a crucial requirement for Bmp signaling in membranous bone and cartilage development. Importantly, the BIG signature was reduced in Bmp loss-of-function mutants, indicating Bmp-regulated target genes are modulated by Bmp dose. Chromatin immunoprecipitation (ChIP) revealed a subset of the BIG signature, including Satb2, Smad6, Hand1, Gadd45γ and Gata3, that was bound by Smad1/5 in the developing mandible, revealing direct Smad-mediated regulation. These data support the hypothesis that Bmp signaling regulates craniofacial skeletal development by balancing self-renewal and differentiation pathways in CNC progenitors.

  8. Factors Modulating Estrogen Receptor Activity

    DTIC Science & Technology

    1997-07-01

    public release; distribution unlimited The views, opinions and/or findings contained in this report are those of the author( s ) and should not be...TITLE AND SUBTITLE Activity Factors Modulating Estrogen Receptor 6. AUTHOR( S ) Michael J. Garabedian, Ph.D. 7. PERFORMING ORGANIZATION NAME( S ) AND...ADDRESS(ES) New York University Medical Center New York, New York 10016 9. SPONSORING/MONITORING AGENCY NAME( S ) AND ADDRESS(ES) Commander U.S

  9. Role of FGFs/FGFRs in skeletal development and bone regeneration.

    PubMed

    Du, Xiaolan; Xie, Yangli; Xian, Cory J; Chen, Lin

    2012-12-01

    Fibroblast growth factor (FGF)/FGF (FGFR) signaling is an important pathway involved in skeletal development. Missense mutations in FGFs and FGFRs were found clinically to cause multiple congenital skeleton diseases including chondrodysplasia, craniosynostosis, syndromes with dysregulated phosphate metabolism. FGFs/FGFRs also have crucial roles in bone fracture repair and bone regeneration. Understanding the molecular mechanisms for the role of FGFs/FGFRs in the regulation of skeletal development, genetic skeletal diseases, and fracture healing will ultimately lead to better treatment of skeleton diseases caused by mutations of FGFs/FGFRs and fracture. This review summarizes the major findings on the role of FGF signaling in skeletal development, genetic skeletal diseases and bone healing, and discusses issues that remain to be resolved in applying FGF signaling-related measures to promote bone healing. This review has also provided a perspective view on future work for exploring the roles and action mechanisms of FGF signaling in skeletal development, genetic skeletal diseases, and fracture healing. Copyright © 2012 Wiley Periodicals, Inc.

  10. Molecular Factors Underlying the Deposition of Intramuscular Fat and Collagen in Skeletal Muscle of Nellore and Angus Cattle.

    PubMed

    Martins, Taiane S; Sanglard, Letícia M P; Silva, Walmir; Chizzotti, Mário L; Rennó, Luciana N; Serão, Nick V L; Silva, Fabyano F; Guimarães, Simone E F; Ladeira, Márcio M; Dodson, Michael V; Du, Min; Duarte, Marcio S

    2015-01-01

    Studies have shown that intramuscular adipogenesis and fibrogenesis may concomitantly occur in skeletal muscle of beef cattle. Thus, we hypothesized that the discrepancy of intramuscular fat content in beef from Nellore and Angus was associated with differences in intramuscular adipogenesis and fibrogenesis during the finishing phase. To test our hypothesis, longissimus muscle samples of Nellore (n = 6; BW = 372.5 ± 37.3 kg) and Angus (n = 6; BW = 382.8 ± 23.9 kg) cattle were collected for analysis of gene and protein expression, and quantification of intramuscular fat and collagen. Least-squares means were estimated for the effect of Breed and differences were considered at P ≤ 0.05. A greater intramuscular fat content was observed in skeletal muscle of Angus compared to Nellore cattle (P≤0.05). No differences were observed for mRNA expression of lipogenic and lipolytic markers ACC, FAS, FABP4, SERBP-1, CPT-2, LPL, and ACOX (P > 0.05) in skeletal muscle of Nellore and Angus cattle. Similarly, no differences were observed in mRNA expression of adipogenic markers Zfp423, PPARγ, and C/EBPα (P>0.05) However, a greater PPARγ protein content was observed in skeletal muscle of Angus compared to Nellore cattle (P≤0.05). A greater abundance of adipo/fibrogenic cells, evaluated by the PDGFRα content, was observed in skeletal muscle of Angus than Nellore cattle (P≤0.05). No differences in fibrogenesis were observed in skeletal muscle of Angus and Nellore cattle, which is in accordance with the lack of differences in intramuscular collagen content in beef from both breeds (P>0.05). These findings demonstrate that difference in intramuscular fat content is associated with a slightly enhanced adipogenesis in skeletal muscle of Angus compared to Nellore cattle, while no difference in fibrogenesis.

  11. Molecular Factors Underlying the Deposition of Intramuscular Fat and Collagen in Skeletal Muscle of Nellore and Angus Cattle

    PubMed Central

    Martins, Taiane S.; Sanglard, Letícia M. P.; Silva, Walmir; Chizzotti, Mário L.; Rennó, Luciana N.; Serão, Nick V. L.; Silva, Fabyano F.; Guimarães, Simone E. F.; Ladeira, Márcio M.; Dodson, Michael V.; Du, Min; Duarte, Marcio S.

    2015-01-01

    Studies have shown that intramuscular adipogenesis and fibrogenesis may concomitantly occur in skeletal muscle of beef cattle. Thus, we hypothesized that the discrepancy of intramuscular fat content in beef from Nellore and Angus was associated with differences in intramuscular adipogenesis and fibrogenesis during the finishing phase. To test our hypothesis, longissimus muscle samples of Nellore (n = 6; BW = 372.5 ± 37.3 kg) and Angus (n = 6; BW = 382.8 ± 23.9 kg) cattle were collected for analysis of gene and protein expression, and quantification of intramuscular fat and collagen. Least-squares means were estimated for the effect of Breed and differences were considered at P ≤ 0.05. A greater intramuscular fat content was observed in skeletal muscle of Angus compared to Nellore cattle (P≤0.05). No differences were observed for mRNA expression of lipogenic and lipolytic markers ACC, FAS, FABP4, SERBP–1, CPT–2, LPL, and ACOX (P > 0.05) in skeletal muscle of Nellore and Angus cattle. Similarly, no differences were observed in mRNA expression of adipogenic markers Zfp423, PPARγ, and C/EBPα (P>0.05) However, a greater PPARγ protein content was observed in skeletal muscle of Angus compared to Nellore cattle (P≤0.05). A greater abundance of adipo/fibrogenic cells, evaluated by the PDGFRα content, was observed in skeletal muscle of Angus than Nellore cattle (P≤0.05). No differences in fibrogenesis were observed in skeletal muscle of Angus and Nellore cattle, which is in accordance with the lack of differences in intramuscular collagen content in beef from both breeds (P>0.05). These findings demonstrate that difference in intramuscular fat content is associated with a slightly enhanced adipogenesis in skeletal muscle of Angus compared to Nellore cattle, while no difference in fibrogenesis. PMID:26436893

  12. Superoxide dismutase 1 expression is modulated by the core pluripotency transcription factors Oct4, Sox2 and Nanog in embryonic stem cells.

    PubMed

    Solari, Claudia; Petrone, María Victoria; Echegaray, Camila Vázquez; Cosentino, María Soledad; Waisman, Ariel; Francia, Marcos; Barañao, Lino; Miriuka, Santiago; Guberman, Alejandra

    2018-06-19

    Redox homeostasis is vital for cellular functions and to prevent the detrimental consequences of oxidative stress. Pluripotent stem cells (PSCs) have an enhanced antioxidant system which supports the preservation of their genome. Besides, reactive oxygen species (ROS) are proposed to be involved in both self-renewal maintenance and in differentiation in embryonic stem cells (ESCs). Increasing evidence shows that cellular systems related to the oxidative stress defense decline along differentiation of PSCs. Although redox homeostasis has been extensively studied for many years, the knowledge about the transcriptional regulation of the genes involved in these systems is still limited. In this work, we studied Sod1 gene modulation by the PSCs fundamental transcription factors Oct4, Sox2 and Nanog. We found that this gene, which is expressed in mouse ESCs (mESCs), was repressed when they were induced to differentiate. Accordingly, these factors induced Sod1 promoter activity in a trans-activation assay. Finally, Sod1 mRNA levels were reduced when Oct4, Sox2 and Nanog were down-regulated by a shRNA approach in mESCs. Taken together, we found that PSCs' key transcription factors are involved in the modulation of Sod1 gene, suggesting a relationship between the pluripotency core and redox homeostasis in these cells. Copyright © 2018. Published by Elsevier B.V.

  13. Lifelong exercise and locally produced insulin-like growth factor-1 (IGF-1) have a modest influence on reducing age-related muscle wasting in mice.

    PubMed

    McMahon, C D; Chai, R; Radley-Crabb, H G; Watson, T; Matthews, K G; Sheard, P W; Soffe, Z; Grounds, M D; Shavlakadze, T

    2014-12-01

    The age-related loss of skeletal muscle mass and function is termed sarcopenia and has been attributed to a decline in concentrations of insulin-like growth factor-1 (IGF-1). We hypothesized that constitutively expressed IGF-1 within skeletal muscles with or without exercise would prevent sarcopenia. Male transgenic mice that overexpress IGF-1 Ea in skeletal muscles were compared with wild-type littermates. Four-month-old mice were assigned to be sedentary, or had access to free-running wheels, until 18 or 28 months of age. In wild-type mice, the mass of the quadriceps muscles was reduced at 28 months and exercise prevented such loss, without affecting the diameter of myofibers. Conversely, increased IGF-1 alone was ineffective, whereas the combination of exercise and IGF-1 was additive in maintaining the diameter of myofibers in the quadriceps muscles. For other muscles, the combination of IGF-1 and exercise was variable and either increased or decreased the mass at 18 months of age, but was ineffective thereafter. Despite an increase in the diameter of myofibers, grip strength was not improved. In conclusion, our data show that exercise and IGF-1 have a modest effect on reducing aged-related wasting of skeletal muscle, but that there is no improvement in muscle function when assessed by grip strength. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  14. [Skeletal muscles, physical activity and health].

    PubMed

    Saltin, B; Helge, J W

    2000-11-01

    The metabolic capacity of skeletal muscle plays a significant role for insulin sensitivity and the blood lipid profile. The metabolic capacity of the muscle is a function of the individual's physical activity level. This is also true for the content of type IIa muscle fibres, which is reduced, and the number of capillaries, which is elevated with muscle usage. Several of these skeletal muscle features are risk factors for or linked with life-style induced diseases such as type II diabetes, hypertension, hyperlipemia and obesity. The central role of the skeletal muscle and its functional metabolic capacity for life style diseases highlights the importance of people maintaining daily physical activity. This article focuses on the link between the metabolic capacity of skeletal muscle and the metabolic syndrome and briefly discusses the explanations for this relationship. As one important aspect if skeletal muscle has a high capacity for lipid oxidation, then more saturated fatty acids are oxidised and more unsaturated fatty acids are built in the phospholipid fraction of the plasma membrane, giving it more fluidity and improved insulin sensitivity. Moreover, the article points at the role of these fatty acids in activating genes via the PPAR-receptor system essential for enzyme and transport proteins in the lipid metabolism.

  15. Acute exercise and physiological insulin induce distinct phosphorylation signatures on TBC1D1 and TBC1D4 proteins in human skeletal muscle

    PubMed Central

    Treebak, Jonas T; Pehmøller, Christian; Kristensen, Jonas M; Kjøbsted, Rasmus; Birk, Jesper B; Schjerling, Peter; Richter, Erik A; Goodyear, Laurie J; Wojtaszewski, Jørgen F P

    2014-01-01

    We investigated the phosphorylation signatures of two Rab-GTPase activating proteins TBC1D1 and TBC1D4 in human skeletal muscle in response to physical exercise and physiological insulin levels induced by a carbohydrate rich meal using a paired experimental design. Eight healthy male volunteers exercised in the fasted or fed state and muscle biopsies were taken before and immediately after exercise. We identified TBC1D1/4 phospho-sites that (1) did not respond to exercise or postprandial increase in insulin (TBC1D4: S666), (2) responded to insulin only (TBC1D4: S318), (3) responded to exercise only (TBC1D1: S237, S660, S700; TBC1D4: S588, S751), and (4) responded to both insulin and exercise (TBC1D1: T596; TBC1D4: S341, T642, S704). In the insulin-stimulated leg, Akt phosphorylation of both T308 and S473 correlated significantly with multiple sites on both TBC1D1 (T596) and TBC1D4 (S318, S341, S704). Interestingly, in the exercised leg in the fasted state TBC1D1 phosphorylation (S237, T596) correlated significantly with the activity of the α2/β2/γ3 AMPK trimer, whereas TBC1D4 phosphorylation (S341, S704) correlated with the activity of the α2/β2/γ1 AMPK trimer. Our data show differential phosphorylation of TBC1D1 and TBC1D4 in response to physiological stimuli in human skeletal muscle and support the idea that Akt and AMPK are upstream kinases. TBC1D1 phosphorylation signatures were comparable between in vitro contracted mouse skeletal muscle and exercised human muscle, and we show that AMPK regulated phosphorylation of these sites in mouse muscle. Contraction and exercise elicited a different phosphorylation pattern of TBC1D4 in mouse compared with human muscle, and although different circumstances in our experimental setup may contribute to this difference, the observation exemplifies that transferring findings between species is problematic. Key points Phosphorylation signature patterns on TBC1D1 and TBC1D4 proteins in the insulin–glucose pathway were

  16. ATP Released by Electrical Stimuli Elicits Calcium Transients and Gene Expression in Skeletal Muscle*

    PubMed Central

    Buvinic, Sonja; Almarza, Gonzalo; Bustamante, Mario; Casas, Mariana; López, Javiera; Riquelme, Manuel; Sáez, Juan Carlos; Huidobro-Toro, Juan Pablo; Jaimovich, Enrique

    2009-01-01

    ATP released from cells is known to activate plasma membrane P2X (ionotropic) or P2Y (metabotropic) receptors. In skeletal muscle cells, depolarizing stimuli induce both a fast calcium signal associated with contraction and a slow signal that regulates gene expression. Here we show that nucleotides released to the extracellular medium by electrical stimulation are partly involved in the fast component and are largely responsible for the slow signals. In rat skeletal myotubes, a tetanic stimulus (45 Hz, 400 1-ms pulses) rapidly increased extracellular levels of ATP, ADP, and AMP after 15 s to 3 min. Exogenous ATP induced an increase in intracellular free Ca2+ concentration, with an EC50 value of 7.8 ± 3.1 μm. Exogenous ADP, UTP, and UDP also promoted calcium transients. Both fast and slow calcium signals evoked by tetanic stimulation were inhibited by either 100 μm suramin or 2 units/ml apyrase. Apyrase also reduced fast and slow calcium signals evoked by tetanus (45 Hz, 400 0.3-ms pulses) in isolated mouse adult skeletal fibers. A likely candidate for the ATP release pathway is the pannexin-1 hemichannel; its blockers inhibited both calcium transients and ATP release. The dihydropyridine receptor co-precipitated with both the P2Y2 receptor and pannexin-1. As reported previously for electrical stimulation, 500 μm ATP significantly increased mRNA expression for both c-fos and interleukin 6. Our results suggest that nucleotides released during skeletal muscle activity through pannexin-1 hemichannels act through P2X and P2Y receptors to modulate both Ca2+ homeostasis and muscle physiology. PMID:19822518

  17. Exercise Promotes Healthy Aging of Skeletal Muscle.

    PubMed

    Cartee, Gregory D; Hepple, Russell T; Bamman, Marcas M; Zierath, Juleen R

    2016-06-14

    Primary aging is the progressive and inevitable process of bodily deterioration during adulthood. In skeletal muscle, primary aging causes defective mitochondrial energetics and reduced muscle mass. Secondary aging refers to additional deleterious structural and functional age-related changes caused by diseases and lifestyle factors. Secondary aging can exacerbate deficits in mitochondrial function and muscle mass, concomitant with the development of skeletal muscle insulin resistance. Exercise opposes deleterious effects of secondary aging by preventing the decline in mitochondrial respiration, mitigating aging-related loss of muscle mass and enhancing insulin sensitivity. This review focuses on mechanisms by which exercise promotes "healthy aging" by inducing modifications in skeletal muscle. Copyright © 2016 Elsevier Inc. All rights reserved.

  18. Exercise training and return to a well-balanced diet activate the neuregulin 1/ErbB pathway in skeletal muscle of obese rats.

    PubMed

    Ennequin, Gaël; Boisseau, Nathalie; Caillaud, Kevin; Chavanelle, Vivien; Gerbaix, Maude; Metz, Lore; Etienne, Monique; Walrand, Stéphane; Masgrau, Aurélie; Guillet, Christelle; Courteix, Daniel; Niu, Airu; Li, Yi-Ping; Capel, Fréderic; Sirvent, Pascal

    2015-06-15

    Some studies suggest that neuregulin 1 (NRG1) could be involved in the regulation of skeletal muscle energy metabolism in rodents. Here we assessed whether unbalanced diet is associated with alterations of the NRG1 signalling pathway and whether exercise and diet might restore NRG1 signalling in skeletal muscle of obese rats. We show that diet-induced obesity does not impair NRG1 signalling in rat skeletal muscle. We also report that endurance training and a well-balanced diet activate the NRG1 signalling in skeletal muscle of obese rats, possibly via a new mechanism mediated by the protease ADAM17. These results suggest that some beneficial effects of physical activity and diet in obese rats could be partly explained by stimulation of the NRG1 signalling pathway. Some studies suggest that the signalling pathway of neuregulin 1 (NRG1), a protein involved in the regulation of skeletal muscle metabolism, could be altered by nutritional and exercise interventions. We hypothesized that diet-induced obesity could lead to alterations of the NRG1 signalling pathway and that chronic exercise could improve NRG1 signalling in rat skeletal muscle. To test this hypothesis, male Wistar rats received a high fat/high sucrose (HF/HS) diet for 16 weeks. At the end of this period, NRG1 and ErbB expression/activity in skeletal muscle was assessed. The obese rats then continued the HF/HS diet or were switched to a well-balanced diet. Moreover, in both groups, half of the animals also performed low intensity treadmill exercise training. After another 8 weeks, NRG1 and ErbB expression/activity in skeletal muscle were tested again. The 16 week HF/HS diet induced obesity, but did not significantly affect the NRG1/ErbB signalling pathway in rat skeletal muscle. Conversely, after the switch to a well-balanced diet, NRG1 cleavage ratio and ErbB4 amount were increased. Chronic exercise training also promoted NRG1 cleavage, resulting in increased ErbB4 phosphorylation. This result was

  19. Identification and Small Molecule Inhibition of an Activating Transcription Factor 4 (ATF4)-dependent Pathway to Age-related Skeletal Muscle Weakness and Atrophy*

    PubMed Central

    Ebert, Scott M.; Dyle, Michael C.; Bullard, Steven A.; Dierdorff, Jason M.; Murry, Daryl J.; Fox, Daniel K.; Bongers, Kale S.; Lira, Vitor A.; Meyerholz, David K.; Talley, John J.; Adams, Christopher M.

    2015-01-01

    Aging reduces skeletal muscle mass and strength, but the underlying molecular mechanisms remain elusive. Here, we used mouse models to investigate molecular mechanisms of age-related skeletal muscle weakness and atrophy as well as new potential interventions for these conditions. We identified two small molecules that significantly reduce age-related deficits in skeletal muscle strength, quality, and mass: ursolic acid (a pentacyclic triterpenoid found in apples) and tomatidine (a steroidal alkaloid derived from green tomatoes). Because small molecule inhibitors can sometimes provide mechanistic insight into disease processes, we used ursolic acid and tomatidine to investigate the pathogenesis of age-related muscle weakness and atrophy. We found that ursolic acid and tomatidine generate hundreds of small positive and negative changes in mRNA levels in aged skeletal muscle, and the mRNA expression signatures of the two compounds are remarkably similar. Interestingly, a subset of the mRNAs repressed by ursolic acid and tomatidine in aged muscle are positively regulated by activating transcription factor 4 (ATF4). Based on this finding, we investigated ATF4 as a potential mediator of age-related muscle weakness and atrophy. We found that a targeted reduction in skeletal muscle ATF4 expression reduces age-related deficits in skeletal muscle strength, quality, and mass, similar to ursolic acid and tomatidine. These results elucidate ATF4 as a critical mediator of age-related muscle weakness and atrophy. In addition, these results identify ursolic acid and tomatidine as potential agents and/or lead compounds for reducing ATF4 activity, weakness, and atrophy in aged skeletal muscle. PMID:26338703

  20. Repression of myoblast proliferation and fibroblast growth factor receptor 1 promoter activity by KLF10 protein.

    PubMed

    Parakati, Rajini; DiMario, Joseph X

    2013-05-10

    FGFR1 gene expression regulates myoblast proliferation and differentiation, and its expression is controlled by Krüppel-like transcription factors. KLF10 interacts with the FGFR1 promoter, repressing its activity and cell proliferation. KLF10 represses FGFR1 promoter activity and thereby myoblast proliferation. A model of transcriptional control of chicken FGFR1 gene regulation during myogenesis is presented. Skeletal muscle development is controlled by regulation of myoblast proliferation and differentiation into muscle fibers. Growth factors such as fibroblast growth factors (FGFs) and their receptors (FGFRs) regulate cell proliferation and differentiation in numerous tissues, including skeletal muscle. Transcriptional regulation of FGFR1 gene expression is developmentally regulated by the Sp1 transcription factor, a member of the Krüppel-like factor (KLF) family of transcriptional regulators. Here, we show that another KLF transcription factor, KLF10, also regulates myoblast proliferation and FGFR1 promoter activity. Expression of KLF10 reduced myoblast proliferation by 86%. KLF10 expression also significantly reduced FGFR1 promoter activity in myoblasts and Sp1-mediated FGFR1 promoter activity in Drosophila SL2 cells. Southwestern blot, electromobility shift, and chromatin immunoprecipitation assays demonstrated that KLF10 bound to the proximal Sp factor binding site of the FGFR1 promoter and reduced Sp1 complex formation with the FGFR1 promoter at that site. These results indicate that KLF10 is an effective repressor of myoblast proliferation and represses FGFR1 promoter activity in these cells via an Sp1 binding site.

  1. Myocyte enhancer factor 2A promotes proliferation and its inhibition attenuates myogenic differentiation via myozenin 2 in bovine skeletal muscle myoblast

    PubMed Central

    Wang, Ya-Ning; Yang, Wu-Cai; Li, Pei-Wei; Wang, Hong-Bao; Zhang, Ying-Ying

    2018-01-01

    Myocyte enhancer factor 2A (MEF2A) is widely distributed in various tissues or organs and plays crucial roles in multiple biological processes. To examine the potential effects of MEF2A on skeletal muscle myoblast, the functional role of MFE2A in myoblast proliferation and differentiation was investigated. In this study, we found that the mRNA expression level of Mef2a was dramatically increased during the myogenesis of bovine skeletal muscle primary myoblast. Overexpression of MEF2A significantly promoted myoblast proliferation, while knockdown of MEF2A inhibited the proliferation and differentiation of myoblast. RT-PCR and western blot analysis revealed that this positive effect of MEF2A on the proliferation of myoblast was carried out by triggering cell cycle progression by activating CDK2 protein expression. Besides, MEF2A was found to be an important transcription factor that bound to the myozenin 2 (MyoZ2) proximal promoter and performed upstream of MyoZ2 during myoblast differentiation. This study provides the first experimental evidence that MEF2A is a positive regulator in skeletal muscle myoblast proliferation and suggests that MEF2A regulates myoblast differentiation via regulating MyoZ2. PMID:29698438

  2. Factors affecting the structure and maturation of human tissue engineered skeletal muscle.

    PubMed

    Martin, Neil R W; Passey, Samantha L; Player, Darren J; Khodabukus, Alastair; Ferguson, Richard A; Sharples, Adam P; Mudera, Vivek; Baar, Keith; Lewis, Mark P

    2013-07-01

    Tissue engineered skeletal muscle has great utility in experimental studies of physiology, clinical testing and its potential for transplantation to replace damaged tissue. Despite recent work in rodent tissue or cell lines, there is a paucity of literature concerned with the culture of human muscle derived cells (MDCs) in engineered constructs. Here we aimed to tissue engineer for the first time in the literature human skeletal muscle in self-assembling fibrin hydrogels and determine the effect of MDC seeding density and myogenic proportion on the structure and maturation of the constructs. Constructs seeded with 4 × 10(5) MDCs assembled to a greater extent than those at 1 × 10(5) or 2 × 10(5), and immunostaining revealed a higher fusion index and a higher density of myotubes within the constructs, showing greater structural semblance to in vivo tissue. These constructs primarily expressed perinatal and slow type I myosin heavy chain mRNA after 21 days in culture. In subsequent experiments MACS(®) technology was used to separate myogenic and non-myogenic cells from their heterogeneous parent population and these cells were seeded at varying myogenic (desmin +) proportions in fibrin based constructs. Only in the constructs seeded with 75% desmin + cells was there evidence of striations when immunostained for slow myosin heavy chain compared with constructs seeded with 10 or 50% desmin + cells. Overall, this work reveals the importance of cell number and myogenic proportions in tissue engineering human skeletal muscle with structural resemblance to in vivo tissue. Copyright © 2013 Elsevier Ltd. All rights reserved.

  3. Role of MCT1 and CAII in skeletal muscle pH homeostasis, energetics, and function: in vivo insights from MCT1 haploinsufficient mice.

    PubMed

    Chatel, Benjamin; Bendahan, David; Hourdé, Christophe; Pellerin, Luc; Lengacher, Sylvain; Magistretti, Pierre; Le Fur, Yann; Vilmen, Christophe; Bernard, Monique; Messonnier, Laurent A

    2017-06-01

    The purpose of this study was to investigate the effects of a partial suppression of monocarboxylate transporter (MCT)-1 on skeletal muscle pH, energetics, and function (MCT1 +/- mice). Twenty-four MCT1 +/- and 13 wild-type (WT) mice were subjected to a rest-exercise-recovery protocol, allowing assessment of muscle energetics (by magnetic resonance spectroscopy) and function. The study included analysis of enzyme activities and content of protein involved in pH regulation. Skeletal muscle of MCT1 +/- mice had lower MCT1 (-61%; P < 0.05) and carbonic anhydrase (CA)-II (-54%; P < 0.05) contents. Although intramuscular pH was higher in MCT1 +/- mice at rest ( P < 0.001), the mice showed higher acidosis during the first minute of exercise ( P < 0.01). Then, the pH time course was similar among groups until exercise completion. MCT1 +/- mice had higher specific peak ( P < 0.05) and maximum tetanic ( P < 0.01) forces and lower fatigability ( P < 0.001) when compared to WT mice. We conclude that both MCT1 and CAII are involved in the homeostatic control of pH in skeletal muscle, both at rest and at the onset of exercise. The improved muscle function and resistance to fatigue in MCT1 +/- mice remain unexplained.-Chatel, B., Bendahan, D., Hourdé, C., Pellerin, L., Lengacher, S., Magistretti, P., Fur, Y. L., Vilmen, C., Bernard, M., Messonnier, L. A. Role of MCT1 and CAII in skeletal muscle pH homeostasis, energetics, and function: in vivo insights from MCT1 haploinsufficient mice. © FASEB.

  4. GPER1-mediated IGFBP-1 induction modulates IGF-1-dependent signaling in tamoxifen-treated breast cancer cells.

    PubMed

    Vaziri-Gohar, Ali; Houston, Kevin D

    2016-02-15

    Tamoxifen, a selective estrogen receptor modulator, is a commonly prescribed adjuvant therapy for estrogen receptor-α (ERα)-positive breast cancer patients. To determine if extracellular factors contribute to the modulation of IGF-1 signaling after tamoxifen treatment, MCF-7 cells were treated with IGF-1 in conditioned medium (CM) obtained from 4-OHT-treated MCF-7 cells and the accumulation of phospho-Akt (S473) was measured. CM inhibited IGF-1-dependent cell signaling and suggesting the involvement of extracellular factors (ie. IGFBPs). A significant increase in IGFBP-1 mRNA and extracellular IGFBP-1 protein was observed in 4-OHT-treated MCF-7 cells. Knockdown experiments demonstrated that both GPER1 and CREB mediate IGFBP-1 induction. Furthermore, experiments showed that 4-OHT-dependent IGFBP-1 transcription is downstream of GPER1-activation in breast cancer cells. Additionally, neutralization and knockdown experiments demonstrated a role for IGFBP-1 in the observed inhibition of IGF-1 signaling. These results suggested that 4-OHT inhibits IGF-1 signaling via GPER1 and CREB mediated extracellular IGFBP-1 accumulation in breast cancer cells. Copyright © 2015 The Authors. Published by Elsevier Ireland Ltd.. All rights reserved.

  5. The Mas receptor mediates modulation of insulin signaling by angiotensin-(1-7).

    PubMed

    Muñoz, Marina C; Giani, Jorge F; Burghi, Valeria; Mayer, Marcos A; Carranza, Andrea; Taira, Carlos A; Dominici, Fernando P

    2012-08-20

    Angiotensin (Ang)-(1-7) stimulates proteins belonging to the insulin signaling pathway and ameliorates the Ang II negative effects at this level. However, up to date, receptors involved and mechanisms behind these observations remain unknown. Accordingly, in the present study, we explored the in vivo effects of antagonism of the Ang-(1-7) specific Mas receptor on insulin signal transduction in rat insulin-target tissues. We evaluated the acute modulation of insulin-stimulated phosphorylation of Akt, GSK-3β (Glycogen synthase kinase-3β) and AS160 (Akt substrate of 160kDa) by Ang-(1-7) and/or Ang II in the presence and absence of the selective Mas receptor antagonist A-779 in insulin-target tissues of normal rats. Also using A-779, we determined whether the Mas receptor mediates the improvement of insulin sensitivity exerted by chronic Ang-(1-7) treatment in fructose-fed rats (FFR), a model of insulin resistance, dyslipidemia and mild hypertension. The two major findings of the present work are as follows; 1) Ang-(1-7) attenuates acute Ang II-mediated inhibition of insulin signaling components in normal rats via a Mas receptor-dependent mechanism; and 2). The Mas receptor appears to be involved in beneficial effects of Ang-(1-7) on the phosphorylation of crucial insulin signaling mediators (Akt, GSK-3β and AS160), in liver, skeletal muscle and adipose tissue of FFR. These results shed light into the mechanism by which Ang-(1-7) exerts its positive physiological modulation of insulin actions in classical metabolic tissues and reinforces the central role of Akt in these effects. Copyright © 2012 Elsevier B.V. All rights reserved.

  6. MCAT elements and the TEF-1 family of transcription factors in muscle development and disease.

    PubMed

    Yoshida, Tadashi

    2008-01-01

    MCAT elements are located in the promoter-enhancer regions of cardiac, smooth, and skeletal muscle-specific genes including cardiac troponin T, beta-myosin heavy chain, smooth muscle alpha-actin, and skeletal alpha-actin, and play a key role in the regulation of these genes during muscle development and disease. The binding factors of MCAT elements are members of the transcriptional enhancer factor-1 (TEF-1) family. However, it has not been fully understood how these transcription factors confer cell-specific expression in muscle, because their expression patterns are relatively broad. Results of recent studies revealed multiple mechanisms whereby TEF-1 family members control MCAT element-dependent muscle-specific gene expression, including posttranslational modifications of TEF-1 family members, the presence of muscle-selective TEF-1 cofactors, and cell-selective control of TEF-1 accessibility to MCAT elements. In addition, of particular interest, recent studies regarding MCAT element-dependent transcription of the myocardin gene and the smooth muscle alpha-actin gene in muscle provide evidence for the transcriptional diversity among distinct cell types and subtypes. This article summarizes the role of MCAT elements and the TEF-1 family of transcription factors in muscle development and disease, and reviews recent progress in our understanding of the transcriptional regulatory mechanisms involved in MCAT element-dependent muscle-specific gene expression.

  7. The Nell-1 Growth Factor Stimulates Bone Formation by Purified Human Perivascular Cells

    PubMed Central

    Zhang, Xinli; Péault, Bruno; Chen, Weiwei; Li, Weiming; Corselli, Mirko; James, Aaron W.; Lee, Min; Siu, Ronald K.; Shen, Pang; Zheng, Zhong; Shen, Jia; Kwak, Jinny; Zara, Janette N.; Chen, Feng; Zhang, Hong; Yin, Zack; Wu, Ben; Ting, Kang

    2011-01-01

    The search for novel sources of stem cells other than bone marrow mesenchymal stem cells (MSCs) for bone regeneration and repair has been a critical endeavor. We previously established an effective protocol to homogeneously purify human pericytes from multiple fetal and adult tissues, including adipose, bone marrow, skeletal muscle, and pancreas, and identified pericytes as a primitive origin of human MSCs. In the present study, we further characterized the osteogenic potential of purified human pericytes combined with a novel osteoinductive growth factor, Nell-1. Purified pericytes grown on either standard culture ware or human cancellous bone chip (hCBC) scaffolds exhibited robust osteogenic differentiation in vitro. Using a nude mouse muscle pouch model, pericytes formed significant new bone in vivo as compared to scaffold alone (hCBC). Moreover, Nell-1 significantly increased pericyte osteogenic differentiation, both in vitro and in vivo. Interestingly, Nell-1 significantly induced pericyte proliferation and was observed to have pro-angiogenic effects, both in vitro and in vivo. These studies suggest that pericytes are a potential new cell source for future efforts in skeletal regenerative medicine, and that Nell-1 is a candidate growth factor able to induce pericyte osteogenic differentiation. PMID:21615216

  8. Dissociation between PGC-1alpha and GLUT-4 expression in skeletal muscle of rats fed a high-fat diet.

    PubMed

    Higashida, Kazuhiko; Higuchi, Mitsuru; Terada, Shin

    2009-12-01

    It has recently been reported that a 4-wk high-fat diet gradually increases skeletal muscle peroxisome proliferator activated receptor (PPAR) gamma coactivator-1alpha (PGC-1alpha) protein content, which has been suggested to regulate GLUT-4 gene transcription. However, it has not been reported that a high-fat diet enhances GLUT-4 mRNA expression and protein content in skeletal muscle, suggesting that an increase in PGC-1alpha protein content is not sufficient to induce muscle GLUT-4 biogenesis in a high-fat fed animal. Therefore, we first evaluated the relationship between PGC-1alpha and GLUT-4 expression in skeletal muscle of rats fed a high-fat diet for 4 wk. The PGC-1alpha protein content in rat epitrochlearis muscle significantly increased by twofold after the 4-wk high-fat diet feeding. However, the high-fat diet had no effect on GLUT-4 protein content and induced a 30% decrease in GLUT-4 mRNA expression in rat skeletal muscle (p<0.05). To clarify the mechanism by which a high-fat diet downregulates GLUT-4 mRNA expression, we next examined the effect of PPARdelta activation, which is known to occur in response to a high-fat diet, on GLUT-4 mRNA expression in L6 myotubes. Incubation with 500 nM GW501516 (PPARdelta activator) for 24 h significantly decreased GLUT-4 mRNA in L6 myotubes. Taken together, these findings suggest that a high-fat diet downregulates GLUT-4 mRNA, possibly through the activation of PPARdelta, despite an increase in PGC-1alpha protein content in rat skeletal muscle, and that a posttranscriptional regulatory mechanism maintains GLUT-4 protein content in skeletal muscle of rats fed a high-fat diet.

  9. Loss of transcription factor early growth response gene 1 results in impaired endochondral bone repair

    PubMed Central

    Reumann, Marie K.; Strachna, Olga; Yagerman, Sarah; Torrecilla, Daniel; Kim, Jihye; Doty, Steven B.; Lukashova, Lyudmila; Boskey, Adele L.; Mayer-Kuckuk, Philipp

    2011-01-01

    Transcription factors that play a role in ossification during development are expected to participate in postnatal fracture repair since the endochondral bone formation that occurs in embryos is recapitulated during fracture repair. However, inherent differences exist between bone development and fracture repair, including a sudden disruption of tissue integrity followed by an inflammatory response. This raises the possibility that repair-specific transcription factors participate in bone healing. Here, we assessed the consequence of loss of early growth response gene 1 (EGR-1) on endochondral bone healing because this transcription factor has been shown to modulate repair in vascularized tissues. Model fractures were created in ribs of wild type (wt) and EGR-1−/− mice. Differences in tissue morphology and composition between these two animal groups were followed over 28 post fracture days (PFDs). In wt mice, bone healing occurred in healing phases characteristic of endochondral bone repair. A similar healing sequence was observed in EGR-1−/− mice but was impaired by alterations. A persistent accumulation of fibrin between the disconnected bones was observed on PFD7 and remained pronounced in the callus on PFD14. Additionally, the PFD14 callus was abnormally enlarged and showed increased deposition of mineralized tissue. Cartilage ossification in the callus was associated with hyper-vascularity and -proliferation. Moreover, cell deposits located in proximity to the callus within skeletal muscle were detected on PFD14. Despite these impairments, repair in EGR-1−/− callus advanced on PFD28, suggesting EGR-1 is not essential for healing. Together, this study provides genetic evidence that EGR-1 is a pleiotropic regulator of endochondral fracture repair. PMID:21726677

  10. Loss of transcription factor early growth response gene 1 results in impaired endochondral bone repair.

    PubMed

    Reumann, Marie K; Strachna, Olga; Yagerman, Sarah; Torrecilla, Daniel; Kim, Jihye; Doty, Stephen B; Lukashova, Lyudmila; Boskey, Adele L; Mayer-Kuckuk, Philipp

    2011-10-01

    Transcription factors that play a role in ossification during development are expected to participate in postnatal fracture repair since the endochondral bone formation that occurs in embryos is recapitulated during fracture repair. However, inherent differences exist between bone development and fracture repair, including a sudden disruption of tissue integrity followed by an inflammatory response. This raises the possibility that repair-specific transcription factors participate in bone healing. Here, we assessed the consequence of loss of early growth response gene 1 (EGR-1) on endochondral bone healing because this transcription factor has been shown to modulate repair in vascularized tissues. Model fractures were created in ribs of wild type (wt) and EGR-1(-/-) mice. Differences in tissue morphology and composition between these two animal groups were followed over 28 post fracture days (PFDs). In wt mice, bone healing occurred in healing phases characteristic of endochondral bone repair. A similar healing sequence was observed in EGR-1(-/-) mice but was impaired by alterations. A persistent accumulation of fibrin between the disconnected bones was observed on PFD7 and remained pronounced in the callus on PFD14. Additionally, the PFD14 callus was abnormally enlarged and showed increased deposition of mineralized tissue. Cartilage ossification in the callus was associated with hyper-vascularity and -proliferation. Moreover, cell deposits located in proximity to the callus within skeletal muscle were detected on PFD14. Despite these impairments, repair in EGR-1(-/-) callus advanced on PFD28, suggesting EGR-1 is not essential for healing. Together, this study provides genetic evidence that EGR-1 is a pleiotropic regulator of endochondral fracture repair. Copyright © 2011 Elsevier Inc. All rights reserved.

  11. REDD1 induction regulates the skeletal muscle gene expression signature following acute aerobic exercise.

    PubMed

    Gordon, Bradley S; Steiner, Jennifer L; Rossetti, Michael L; Qiao, Shuxi; Ellisen, Leif W; Govindarajan, Subramaniam S; Eroshkin, Alexey M; Williamson, David L; Coen, Paul M

    2017-12-01

    The metabolic stress placed on skeletal muscle by aerobic exercise promotes acute and long-term health benefits in part through changes in gene expression. However, the transducers that mediate altered gene expression signatures have not been completely elucidated. Regulated in development and DNA damage 1 (REDD1) is a stress-induced protein whose expression is transiently increased in skeletal muscle following acute aerobic exercise. However, the role of this induction remains unclear. Because REDD1 altered gene expression in other model systems, we sought to determine whether REDD1 induction following acute exercise altered the gene expression signature in muscle. To do this, wild-type and REDD1-null mice were randomized to remain sedentary or undergo a bout of acute treadmill exercise. Exercised mice recovered for 1, 3, or 6 h before euthanization. Acute exercise induced a transient increase in REDD1 protein expression within the plantaris only at 1 h postexercise, and the induction occurred in both cytosolic and nuclear fractions. At this time point, global changes in gene expression were surveyed using microarray. REDD1 induction was required for the exercise-induced change in expression of 24 genes. Validation by RT-PCR confirmed that the exercise-mediated changes in genes related to exercise capacity, muscle protein metabolism, neuromuscular junction remodeling, and Metformin action were negated in REDD1-null mice. Finally, the exercise-mediated induction of REDD1 was partially dependent upon glucocorticoid receptor activation. In all, these data show that REDD1 induction regulates the exercise-mediated change in a distinct set of genes within skeletal muscle. Copyright © 2017 the American Physiological Society.

  12. Improved muscle-derived expression of human coagulation factor IX from a skeletal actin/CMV hybrid enhancer/promoter.

    PubMed

    Hagstrom, J N; Couto, L B; Scallan, C; Burton, M; McCleland, M L; Fields, P A; Arruda, V R; Herzog, R W; High, K A

    2000-04-15

    Hemophilia B is caused by the absence of functional coagulation factor IX (F.IX) and represents an important model for treatment of genetic diseases by gene therapy. Recent studies have shown that intramuscular injection of an adeno-associated viral (AAV) vector into mice and hemophilia B dogs results in vector dose-dependent, long-term expression of biologically active F.IX at therapeutic levels. In this study, we demonstrate that levels of expression of approximately 300 ng/mL (6% of normal human F.IX levels) can be reached by intramuscular injection of mice using a 2- to 4-fold lower vector dose (1 x 10(11) vector genomes/mouse, injected into 4 intramuscular sites) than previously described. This was accomplished through the use of an improved expression cassette that uses the cytomegalovirus (CMV) immediate early enhancer/promoter in combination with a 1.2-kilobase portion of human skeletal actin promoter. These results correlated with enhanced levels of F.IX transcript and secreted F.IX protein in transduced murine C2C12 myotubes. Systemic F.IX expression from constructs containing the CMV enhancer/promoter alone was 120 to 200 ng/mL in mice injected with 1 x 10(11) vector genomes. Muscle-specific promoters performed poorly for F.IX transgene expression in vitro and in vivo. However, the incorporation of a sequence from the alpha-skeletal actin promoter containing at least 1 muscle-specific enhancer and 1 enhancer-like element further improved muscle-derived expression of F.IX from a CMV enhancer/promoter-driven expression cassette over previously published results. These findings will allow the design of a clinical protocol for therapeutic levels of F.IX expression with lower vector doses, thus enhancing efficacy and safety of the protocol. (Blood. 2000;95:2536-2542)

  13. Losartan Restores Skeletal Muscle Remodeling and Protects Against Disuse Atrophy in Sarcopenia

    PubMed Central

    Burks, Tyesha N.; Andres-Mateos, Eva; Marx, Ruth; Mejias, Rebeca; Van Erp, Christel; Simmers, Jessica L.; Walston, Jeremy D.; Ward, Christopher W.; Cohn, Ronald D.

    2011-01-01

    Sarcopenia, a critical loss of muscle mass and function because of the physiological process of aging, contributes to disability and mortality in older adults. It increases the incidence of pathologic fractures, causing prolonged periods of hospitalization and rehabilitation. The molecular mechanisms underlying sarcopenia are poorly understood, but recent evidence suggests that increased transforming growth factor–β (TGF-β) signaling contributes to impaired satellite cell function and muscle repair in aged skeletal muscle. We therefore evaluated whether antagonism of TGF-β signaling via losartan, an angiotensin II receptor antagonist commonly used to treat high blood pressure, had a beneficial impact on the muscle remodeling process of sarcopenic mice. We demonstrated that mice treated with losartan developed significantly less fibrosis and exhibited improved in vivo muscle function after cardiotoxin-induced injury. We found that losartan not only blunted the canonical TGF-β signaling cascade but also modulated the noncanonical TGF-β mitogen-activated protein kinase pathway. We next assessed whether losartan was able to combat disuse atrophy in aged mice that were subjected to hindlimb immobilization. We showed that immobilized mice treated with losartan were protected against loss of muscle mass. Unexpectedly, this protective mechanism was not mediated by TGF-β signaling but was due to an increased activation of the insulin-like growth factor 1 (IGF-1)/Akt/mammalian target of rapamycin (mTOR) pathway. Thus, blockade of the AT1 (angiotensin II type I) receptor improved muscle remodeling and protected against disuse atrophy by differentially regulating the TGF-β and IGF-1/Akt/mTOR signaling cascades, two pathways critical for skeletal muscle homeostasis. Thus, losartan, a Food and Drug Administration–approved drug, may prove to have clinical benefits to combat injury-related muscle remodeling and provide protection against disuse atrophy in humans with

  14. Investigation of the Comparative Effects of Red and Infrared Laser Therapy on Skeletal Muscle Repair in Diabetic Rats.

    PubMed

    Assis, Lívia; Manis, Camila; Fernandes, Kelly Rossetti; Cabral, Daniel; Magri, Angela; Veronez, Suellen; Renno, Ana Claudia Muniz

    2016-07-01

    The aim of this study was to evaluate the in vivo response of 2 different laser wavelengths (red and infrared) on skeletal muscle repair process in diabetic rats. Forty Wistar rats were randomly divided into 4 experimental groups: basal control-nondiabetic and muscle-injured animals without treatment (BC); diabetic muscle-injured without treatment (DC); diabetic muscle-injured, treated with red laser (DCR) and infrared laser (DCIR). The injured region was irradiated daily for 7 consecutive days, starting immediately after the injury using a red (660 nm) and an infrared (808 nm) laser. The histological results demonstrated in both treated groups (red and infrared wavelengths) a modulation of the inflammatory process and a better tissue organization located in the site of the injury. However, only infrared light significantly reduced the injured area and increased MyoD and myogenin protein expression. Moreover, both red and infrared light increased the expression of the proangiogenic vascular endothelial growth factor and reduced the cyclooxygenase 2 protein expression. These results suggest that low-level laser therapy was efficient in promoting skeletal muscle repair in diabetic rats. However, the effect of infrared wavelength was more pronounced by reducing the area of the injury and modulating the expression proteins related to the repair.

  15. In vivo stimulation of oestrogen receptor α increases insulin-stimulated skeletal muscle glucose uptake

    PubMed Central

    Gorres, Brittany K; Bomhoff, Gregory L; Morris, Jill K; Geiger, Paige C

    2011-01-01

    Abstract Previous studies suggest oestrogen receptor α (ERα) is involved in oestrogen-mediated regulation of glucose metabolism and is critical for maintenance of whole body insulin action. Despite this, the effect of direct ERα modulation in insulin-responsive tissues is unknown. The purpose of the current study was to determine the impact of ERα activation, using the ER subtype-selective ligand propylpyrazoletriyl (PPT), on skeletal muscle glucose uptake. Two-month-old female Sprague–Dawley rats, ovariectomized for 1 week, were given subcutaneous injections of PPT (10 mg kg−1), oestradiol benzoate (EB; 20 μg kg−1), the ERβ agonist diarylpropionitrile (DPN, 10 mg kg−1) or vehicle every 24 h for 3 days. On the fourth day, insulin-stimulated skeletal muscle glucose uptake was measured in vitro and insulin signalling intermediates were assessed via Western blotting. Activation of ERα with PPT resulted in increased insulin-stimulated glucose uptake into the slow-twitch soleus and fast-twitch extensor digitorum longus (EDL) muscles, activation of insulin signalling intermediates (as measured by phospho-Akt (pAkt) and pAkt substrate (PAS)) and phosphorylation of AMP-activated protein kinase (AMPK). GLUT4 protein was increased only in the EDL muscle. Rats treated with EB or DPN for 3 days did not show an increase in insulin-stimulated skeletal muscle glucose uptake compared to vehicle-treated animals. These new findings reveal that direct activation of ERα positively mediates glucose uptake and insulin action in skeletal muscle. Evidence that oestrogens and ERα stimulate glucose uptake has important implications for understanding mechanisms of glucose homeostasis, particularly in postmenopausal women. PMID:21486807

  16. Effects of prior exercise on the action of insulin-like growth factor I in skeletal muscle

    NASA Technical Reports Server (NTRS)

    Henriksen, E. J.; Louters, L. L.; Stump, C. S.; Tipton, C. M.

    1992-01-01

    Prior exercise increases insulin sensitivity for glucose and system A neutral amino acid transport activities in skeletal muscle. Insulin-like growth factor I (IGF-I) also activates these transport processes in resting muscle. It is not known, however, whether prior exercise increases IGF-I action in muscle. Therefore we determined the effect of a single exhausting bout of swim exercise on IGF-I-stimulated glucose transport activity [assessed by 2-deoxy-D-glucose (2-DG) uptake] and system A activity [assessed by alpha-(methylamino)isobutyric acid (MeAIB) uptake] in the isolated rat epitrochlearis muscle. When measured 3.5 h after exercise, the responses to a submaximal concentration (0.2 nM), but not a maximal concentration (13.3 nM), of insulin for activation of 2-DG uptake and MeAIB uptake were enhanced. In contrast, prior exercise increased markedly both the submaximal (5 nM) and maximal (20 nM) responses to IGF-I for activation of 2-DG uptake, whereas only the submaximal response to IGF-I (3 nM) for MeAIB uptake was enhanced after exercise. We conclude that 1) prior exercise significantly enhances the response to a submaximal concentration of IGF-I for activation of the glucose transport and system A neutral amino acid transport systems in skeletal muscle and 2) the enhanced maximal response for IGF-I action after exercise is restricted to the signaling pathway for activation of the glucose transport system.

  17. Smad4 restricts differentiation to promote expansion of satellite cell derived progenitors during skeletal muscle regeneration.

    PubMed

    Paris, Nicole D; Soroka, Andrew; Klose, Alanna; Liu, Wenxuan; Chakkalakal, Joe V

    2016-11-18

    Skeletal muscle regenerative potential declines with age, in part due to deficiencies in resident stem cells (satellite cells, SCs) and derived myogenic progenitors (MPs); however, the factors responsible for this decline remain obscure. TGFβ superfamily signaling is an inhibitor of myogenic differentiation, with elevated activity in aged skeletal muscle. Surprisingly, we find reduced expression of Smad4 , the downstream cofactor for canonical TGFβ superfamily signaling, and the target Id1 in aged SCs and MPs during regeneration. Specific deletion of Smad4 in adult mouse SCs led to increased propensity for terminal myogenic commitment connected to impaired proliferative potential. Furthermore, SC-specific Smad4 disruption compromised adult skeletal muscle regeneration. Finally, loss of Smad4 in aged SCs did not promote aged skeletal muscle regeneration. Therefore, SC-specific reduction of Smad4 is a feature of aged regenerating skeletal muscle and Smad4 is a critical regulator of SC and MP amplification during skeletal muscle regeneration.

  18. 100-Gb/s InP DP-IQ modulator for small-form-factor pluggable coherent transceivers

    NASA Astrophysics Data System (ADS)

    Kikuchi, Nobuhiro; Ogiso, Yoshihiro; Yamada, Eiichi

    2016-02-01

    We developed a compact InP-based DP-IQ modulator for small-form-factor pluggable coherent transceivers. The modulator achieves 112-Gb/s DP-QPSK modulation with a driving voltage of 6 Vppd. In addition, it provides 86-Gb/s DP-16 QAM signal generation and 240-km transmission with negligible degradation of BER performance. The halfwavelength voltage of our recent device is 1.9 V, and a high median extinction ratio of over 32 dB was achieved for more than 1,400 child MZ modulators. We have also proposed an athermal InP-based twin IQ modulator that enables us to use a modulator in a TEC-free operation. It contributes to lowering the power consumption of transceivers. Under a constant driving condition, there is little change in 56-Gb/s x 2 QPSK modulation characteristics in the range of 20 to 80°C.

  19. Multi-omic integrated networks connect DNA methylation and miRNA with skeletal muscle plasticity to chronic exercise in Type 2 diabetic obesity.

    PubMed

    Rowlands, David S; Page, Rachel A; Sukala, William R; Giri, Mamta; Ghimbovschi, Svetlana D; Hayat, Irum; Cheema, Birinder S; Lys, Isabelle; Leikis, Murray; Sheard, Phillip W; Wakefield, St John; Breier, Bernhard; Hathout, Yetrib; Brown, Kristy; Marathi, Ramya; Orkunoglu-Suer, Funda E; Devaney, Joseph M; Leiken, Benjamin; Many, Gina; Krebs, Jeremy; Hopkins, Will G; Hoffman, Eric P

    2014-10-15

    Epigenomic regulation of the transcriptome by DNA methylation and posttranscriptional gene silencing by miRNAs are potential environmental modulators of skeletal muscle plasticity to chronic exercise in healthy and diseased populations. We utilized transcriptome networks to connect exercise-induced differential methylation and miRNA with functional skeletal muscle plasticity. Biopsies of the vastus lateralis were collected from middle-aged Polynesian men and women with morbid obesity (44 kg/m(2) ± 10) and Type 2 diabetes before and following 16 wk of resistance (n = 9) or endurance training (n = 8). Longitudinal transcriptome, methylome, and microRNA (miRNA) responses were obtained via microarray, filtered by novel effect-size based false discovery rate probe selection preceding bioinformatic interrogation. Metabolic and microvascular transcriptome topology dominated the network landscape following endurance exercise. Lipid and glucose metabolism modules were connected to: microRNA (miR)-29a; promoter region hypomethylation of nuclear receptor factor (NRF1) and fatty acid transporter (SLC27A4), and hypermethylation of fatty acid synthase, and to exon hypomethylation of 6-phosphofructo-2-kinase and Ser/Thr protein kinase. Directional change in the endurance networks was validated by lower intramyocellular lipid, increased capillarity, GLUT4, hexokinase, and mitochondrial enzyme activity and proteome. Resistance training also lowered lipid and increased enzyme activity and caused GLUT4 promoter hypomethylation; however, training was inconsequential to GLUT4, capillarity, and metabolic transcriptome. miR-195 connected to negative regulation of vascular development. To conclude, integrated molecular network modelling revealed differential DNA methylation and miRNA expression changes occur in skeletal muscle in response to chronic exercise training that are most pronounced with endurance training and topographically associated with functional metabolic and

  20. Multi-omic integrated networks connect DNA methylation and miRNA with skeletal muscle plasticity to chronic exercise in Type 2 diabetic obesity

    PubMed Central

    Page, Rachel A.; Sukala, William R.; Giri, Mamta; Ghimbovschi, Svetlana D.; Hayat, Irum; Cheema, Birinder S.; Lys, Isabelle; Leikis, Murray; Sheard, Phillip W.; Wakefield, St. John; Breier, Bernhard; Hathout, Yetrib; Brown, Kristy; Marathi, Ramya; Orkunoglu-Suer, Funda E.; Devaney, Joseph M.; Leiken, Benjamin; Many, Gina; Krebs, Jeremy; Hopkins, Will G.; Hoffman, Eric P.

    2014-01-01

    Epigenomic regulation of the transcriptome by DNA methylation and posttranscriptional gene silencing by miRNAs are potential environmental modulators of skeletal muscle plasticity to chronic exercise in healthy and diseased populations. We utilized transcriptome networks to connect exercise-induced differential methylation and miRNA with functional skeletal muscle plasticity. Biopsies of the vastus lateralis were collected from middle-aged Polynesian men and women with morbid obesity (44 kg/m2 ± 10) and Type 2 diabetes before and following 16 wk of resistance (n = 9) or endurance training (n = 8). Longitudinal transcriptome, methylome, and microRNA (miRNA) responses were obtained via microarray, filtered by novel effect-size based false discovery rate probe selection preceding bioinformatic interrogation. Metabolic and microvascular transcriptome topology dominated the network landscape following endurance exercise. Lipid and glucose metabolism modules were connected to: microRNA (miR)-29a; promoter region hypomethylation of nuclear receptor factor (NRF1) and fatty acid transporter (SLC27A4), and hypermethylation of fatty acid synthase, and to exon hypomethylation of 6-phosphofructo-2-kinase and Ser/Thr protein kinase. Directional change in the endurance networks was validated by lower intramyocellular lipid, increased capillarity, GLUT4, hexokinase, and mitochondrial enzyme activity and proteome. Resistance training also lowered lipid and increased enzyme activity and caused GLUT4 promoter hypomethylation; however, training was inconsequential to GLUT4, capillarity, and metabolic transcriptome. miR-195 connected to negative regulation of vascular development. To conclude, integrated molecular network modelling revealed differential DNA methylation and miRNA expression changes occur in skeletal muscle in response to chronic exercise training that are most pronounced with endurance training and topographically associated with functional metabolic and microvascular

  1. Mechanisms Behind Pyrroloquinoline Quinone Supplementation on Skeletal Muscle Mitochondrial Biogenesis: Possible Synergistic Effects with Exercise.

    PubMed

    Hwang, Paul; Willoughby, Darryn S

    2018-05-01

    There is clear evidence that endurance exercise training elicits intramuscular adaptations that can lead to elevations in mitochondrial biogenesis, oxidative capacity, mitochondrial density, and mitochondrial function. Mitochondrial biogenesis is regulated by the activation of the transcriptional coactivator peroxisome proliferator-activated receptor gamma coactivator 1-alpha. This master regulator of mitochondrial biogenesis activates nuclear respiratory factors (NRF-1, NRF-2) and mitochondrial transcription factor A, which enables the expansion of mitochondrial size and transcription of mitochondrial DNA. Pyrroloquinoline quinone (PQQ) has been identified as a novel supplement that is involved in various physiological processes such as redox modulation, cellular energy metabolism, and mitochondrial biogenesis and is a potent antioxidant. Since both exercise and supplemental PQQ have mechanisms associated with mitochondrial biogenesis, it is plausible that a differential additive ergogenic benefit with PQQ can ensue. However, there is a major paucity of research exploring the role of PQQ in conjunction with exercise. In this respect, the purpose of the critical literature review will be to present a comprehensive overview of PQQ and the proposed mechanisms underlying mitochondrial biogenesis. Because exercise can instigate the molecular responses indicative of mitochondrial biogenesis, it is plausible that PQQ and exercise may instigate a synergistic response. Key teaching points • Endurance exercise training enables skeletal muscle adaptations that can induce increases in mitochondrial biogenesis, improve oxidative capacity, mitochondrial density, and mitochondrial function. • Pyrroloquinoline quinone (PQQ) has been identified as a novel supplement that is involved in physiological processes including redox modulation, cellular energy metabolism, mitochondrial biogenesis, and antioxidant potential. • There is emerging evidence to support that PQQ

  2. Physical activity opposes the age-related increase in skeletal muscle and plasma endothelin-1 levels and normalizes plasma endothelin-1 levels in individuals with essential hypertension.

    PubMed

    Nyberg, M; Mortensen, S P; Hellsten, Y

    2013-03-01

    Endothelin-1 has potent constrictor and proliferative activity in vascular smooth muscle, and essential hypertension and aging are associated with increased endothelin-1-mediated vasoconstrictor tone. The aim of this study was to investigate the effect of physical activity, hypertension and age on endothelin-1 levels in plasma and skeletal muscle and endothelin receptors in skeletal muscle in human subjects. In study 1, normotensive (46 ± 1 years, n = 11) and hypertensive (47 ± 1 years, n = 10) subjects were studied before and after 8 weeks of aerobic exercise training. In study 2, young (23 ± 1 years, n = 8), older lifelong sedentary (66 ± 2 years, n = 8) and older lifelong endurance-trained (62 ± 2 years, n = 8) subjects were studied in a cross-sectional design. Skeletal muscle and plasma endothelin-1 levels were increased with age and plasma endothelin-1 levels were higher in hypertensive than normotensive individuals. Eight weeks of exercise training normalized plasma endothelin-1 levels in the hypertensive subjects and increased the protein expression of the ET(A) receptor in skeletal muscle of normotensive subjects. Similarly, individuals that had performed lifelong physical activity had similar plasma and muscle endothelin-1 levels as the young controls and had higher ET(A) receptor levels. Our findings suggest that aerobic exercise training opposes the age-related increase in skeletal muscle and plasma endothelin-1 levels and normalizes plasma endothelin-1 levels in individuals with essential hypertension. This effect may explain some of the beneficial effects of training on the cardiovascular system in older and hypertensive subjects. © 2012 The Authors Acta Physiologica © 2012 Scandinavian Physiological Society.

  3. Factors Associated with the Serum Myostatin Level in Patients Undergoing Peritoneal Dialysis: Potential Effects of Skeletal Muscle Mass and Vitamin D Receptor Activator Use.

    PubMed

    Yamada, Shunsuke; Tsuruya, Kazuhiko; Yoshida, Hisako; Tokumoto, Masanori; Ueki, Kenji; Ooboshi, Hiroaki; Kitazono, Takanari

    2016-07-01

    Myostatin is a member of the transforming growth factor-β family, which regulates synthesis and degradation of skeletal muscle proteins and is associated with the development of sarcopenia. It is up-regulated in the skeletal muscle of chronic kidney disease patients and is considered to be involved in the development of uremic sarcopenia. However, serum myostatin levels have rarely been determined, and the relationship between serum myostatin levels with clinical and metabolic factors remains unknown. This cross-sectional study investigated the association between serum myostatin level and clinical factors in 69 outpatients undergoing peritoneal dialysis. Serum myostatin level was determined by commercially available enzyme-linked immunosorbent assay (ELISA). Univariable and multivariable analysis were conducted to determine factors associated with serum myostatin levels. The factors included age, sex, diabetes mellitus, dialysis history, body mass index, residual kidney function, peritoneal dialysate volume, serum biochemistries, and the use of vitamin D receptor activators (VDRAs). Mean serum myostatin level was 7.59 ± 3.37 ng/mL. There was no association between serum myostatin level and residual kidney function. Serum myostatin levels were significantly and positively associated with lean body mass measured by the creatinine kinetic method and negatively associated with the use of VDRAs after adjustment for potential confounding factors. Our study indicated that serum myostatin levels are associated with skeletal muscle mass and are lower in patients treated with VDRAs. Further studies are necessary to determine the significance of measuring serum myostatin level in patients undergoing peritoneal dialysis.

  4. Pregnane and Xenobiotic Receptor gene expression in liver cells is modulated by Ets-1 in synchrony with transcription factors Pax5, LEF-1 and c-jun

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kumari, Sangeeta; Saradhi, Mallampati; Rana, Manjul

    2015-01-15

    Nuclear receptor PXR is predominantly expressed in liver and intestine. Expression of PXR is observed to be dysregulated in various metabolic disorders indicating its involvement in disease development. However, information available on mechanisms of PXR self-regulation is fragmentary. The present investigation identifies some of the regulatory elements responsible for its tight regulation and low cellular expression. Here, we report that the PXR-promoter is a target for some key transcription factors like PU.1/Ets-1, Pax5, LEF-1 and c-Jun. Interestingly, we observed that PXR-promoter responsiveness to Pax5, LEF-1 and c-Jun, is considerably enhanced by Ets transcription factors (PU.1 and Ets-1). Co-transfection of cellsmore » with Ets-1, LEF-1 and c-Jun increased PXR-promoter activity by 5-fold and also induced expression of endogenous human PXR. Site-directed mutagenesis and transfection studies revealed that two Ets binding sites and two of the three LEF binding sites in the PXR-promoter are functional and have a positive effect on PXR transcription. Results suggest that expression of Ets family members, in conjunction with Pax5, LEF-1 and c-Jun, lead to coordinated up-regulation of PXR gene transcription. Insights obtained on the regulation of PXR gene have relevance in offering important cues towards normal functioning as well as development of several metabolic disorders via PXR signaling. - Highlights: • The study identified cis-regulatory elements in the nuclear receptor PXR promoter. • Several trans-acting factors modulating the PXR-promoter have been identified. • PU.1/Ets-1, Pax5, LEF-1, c-Jun, LyF-VI and NF-1 act as modulators of the PXR-promoter. • Ets-1 in conjunction with LEF-1 and c-Jun exhibit 5-fold activation of the PXR-promoter. • Insights into PXR-regulation have relevance in normal and pathological conditions.« less

  5. Identification and Small Molecule Inhibition of an Activating Transcription Factor 4 (ATF4)-dependent Pathway to Age-related Skeletal Muscle Weakness and Atrophy.

    PubMed

    Ebert, Scott M; Dyle, Michael C; Bullard, Steven A; Dierdorff, Jason M; Murry, Daryl J; Fox, Daniel K; Bongers, Kale S; Lira, Vitor A; Meyerholz, David K; Talley, John J; Adams, Christopher M

    2015-10-16

    Aging reduces skeletal muscle mass and strength, but the underlying molecular mechanisms remain elusive. Here, we used mouse models to investigate molecular mechanisms of age-related skeletal muscle weakness and atrophy as well as new potential interventions for these conditions. We identified two small molecules that significantly reduce age-related deficits in skeletal muscle strength, quality, and mass: ursolic acid (a pentacyclic triterpenoid found in apples) and tomatidine (a steroidal alkaloid derived from green tomatoes). Because small molecule inhibitors can sometimes provide mechanistic insight into disease processes, we used ursolic acid and tomatidine to investigate the pathogenesis of age-related muscle weakness and atrophy. We found that ursolic acid and tomatidine generate hundreds of small positive and negative changes in mRNA levels in aged skeletal muscle, and the mRNA expression signatures of the two compounds are remarkably similar. Interestingly, a subset of the mRNAs repressed by ursolic acid and tomatidine in aged muscle are positively regulated by activating transcription factor 4 (ATF4). Based on this finding, we investigated ATF4 as a potential mediator of age-related muscle weakness and atrophy. We found that a targeted reduction in skeletal muscle ATF4 expression reduces age-related deficits in skeletal muscle strength, quality, and mass, similar to ursolic acid and tomatidine. These results elucidate ATF4 as a critical mediator of age-related muscle weakness and atrophy. In addition, these results identify ursolic acid and tomatidine as potential agents and/or lead compounds for reducing ATF4 activity, weakness, and atrophy in aged skeletal muscle. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

  6. Localisation of the high-affinity choline transporter-1 in the rat skeletal motor unit.

    PubMed

    Lips, Katrin S; Pfeil, Uwe; Haberberger, Rainer V; Kummer, Wolfgang

    2002-03-01

    The rate-limiting step in neuronal acetylcholine (ACh) synthesis is the uptake of choline via a high-affinity transporter. We have generated antisera against the recently identified transporter CHT1 to investigate its distribution in rat motor neurons and skeletal muscle and have used these antisera in combination with (1) antisera against the vesicular acetylcholine transporter (VAChT) to identify cholinergic synapses and (2) Alexa-488-labelled alpha-bungarotoxin to identify motor endplates. In the motor unit, immunohistochemistry and RT-PCR have demonstrated that CHT1 is restricted to motoneurons and absent from the non-neuronal ACh-synthesizing elements, e.g. skeletal muscle fibres. In addition, CHT1 is also present in parasympathetic neurons of the tongue, as evidenced by immunohistochemistry and RT-PCR. CHT1 immunoreativity is principally found at all segments (perikaryon, dendrites, axon) of the motoneuron but is enriched at neuro-neuronal and neuro-muscular synapses. This preferential localisation matches well with its anticipated pivotal role in synaptic transmitter recycling and synthesis.

  7. Structural modulation of factor VIIa by full-length tissue factor (TF1-263): implication of novel interactions between EGF2 domain and TF.

    PubMed

    Prasad, Ramesh; Sen, Prosenjit

    2018-02-01

    Tissue factor (TF)-mediated factor VII (FVII) activation and a subsequent proteolytic TF-FVIIa binary complex formation is the key step initiating the coagulation cascade, with implications in various homeostatic and pathologic scenarios. TF binding allosterically modifies zymogen-like free FVIIa to its highly catalytically active form. As a result of unresolved crystal structure of the full-length TF 1-263 -FVIIa binary complex and free FVIIa, allosteric alterations in FVIIa following its binding to full-length TF and the consequences of these on function are not entirely clear. The present study aims to map and identify structural alterations in FVIIa and TF resulting from full-length TF binding to FVIIa and the key events responsible for enhanced FVIIa activity in coagulation. We constructed the full-length TF 1-263 -FVIIa membrane bound complex using computational modeling and subjected it to molecular dynamics (MD) simulations. MD simulations showed that TF alters the structure of each domain of FVIIa and these combined alterations contribute to enhanced TF-FVIIa activity. Detailed, domain-wise investigation revealed several new non-covalent interactions between TF and FVIIa that were not found in the truncated soluble TF-FVIIa crystal structure. The structural modulation of each FVIIa domain imparted by TF indicated that both inter and intra-domain communication is crucial for allosteric modulation of FVIIa. Our results suggest that these newly formed interactions can provide additional stability to the protease domain and regulate its activity profile by governing catalytic triad (CT) orientation and localization. The unexplored newly formed interactions between EGF2 and TF provides a possible explanation for TF-induced allosteric activation of FVIIa.

  8. Colostrum supplementation protects against exercise - induced oxidative stress in skeletal muscle in mice

    PubMed Central

    2012-01-01

    Background This study examined the effects of bovine colostrum on exercise –induced modulation of antioxidant parameters in skeletal muscle in mice. Adult male BALB/c mice were randomly divided into four groups (control, colostrum alone, exercise and exercise with colostrum) and each group had three subgroups (day 0, 21 and 42). Colostrum groups of mice were given a daily oral supplement of 50 mg/kg body weight of bovine colostrum and the exercise group of mice were made to exercise on the treadmill for 30 minutes per day. Total antioxidants, lipid hydroperoxides, xanthine oxidase and super oxide dismutase level was assayed from the homogenate of hind limb skeletal muscle. Results Exercise—induced a significant oxidative stress in skeletal muscles as evidenced by the elevated lipid hydroperoxides and xanthine oxidase levels. There was a significant decrease in skeletal muscle total antioxidants and superoxide dismutase levels. Daily colostrum supplement significantly reduced the lipid hydroperoxides and xanthine oxidase enzyme level and increased the total antioxidant levels in the leg muscle. Conclusion Thus, the findings of this study showed that daily bovine colostrum supplementation was beneficial to skeletal muscle to reduce the oxidant-induced damage during muscular exercise. PMID:23173926

  9. The coactivator PGC-1α regulates skeletal muscle oxidative metabolism independently of the nuclear receptor PPARβ/δ in sedentary mice fed a regular chow diet.

    PubMed

    Pérez-Schindler, Joaquín; Svensson, Kristoffer; Vargas-Fernández, Elyzabeth; Santos, Gesa; Wahli, Walter; Handschin, Christoph

    2014-11-01

    Physical activity improves oxidative capacity and exerts therapeutic beneficial effects, particularly in the context of metabolic diseases. The peroxisome proliferator-activated receptor (PPAR) γ coactivator-1α (PGC-1α) and the nuclear receptor PPARβ/δ have both been independently discovered to play a pivotal role in the regulation of oxidative metabolism in skeletal muscle, though their interdependence remains unclear. Hence, our aim was to determine the functional interaction between these two factors in mouse skeletal muscle in vivo. Adult male control mice, PGC-1α muscle-specific transgenic (mTg) mice, PPARβ/δ muscle-specific knockout (mKO) mice and the combination PPARβ/δ mKO + PGC-1α mTg mice were studied under basal conditions and following PPARβ/δ agonist administration and acute exercise. Whole-body metabolism was assessed by indirect calorimetry and blood analysis, while magnetic resonance was used to measure body composition. Quantitative PCR and western blot were used to determine gene expression and intracellular signalling. The proportion of oxidative muscle fibre was determined by NADH staining. Agonist-induced PPARβ/δ activation was only disrupted by PPARβ/δ knockout. We also found that the disruption of the PGC-1α-PPARβ/δ axis did not affect whole-body metabolism under basal conditions. As expected, PGC-1α mTg mice exhibited higher exercise performance, peak oxygen consumption and lower blood lactate levels following exercise, though PPARβ/δ mKO + PGC-1α mTg mice showed a similar phenotype. Similarly, we found that PPARβ/δ was dispensable for PGC-1α-mediated enhancement of an oxidative phenotype in skeletal muscle. Collectively, these results indicate that PPARβ/δ is not an essential partner of PGC-1α in the control of skeletal muscle energy metabolism.

  10. Functional nonequality of the cardiac and skeletal ryanodine receptors.

    PubMed

    Nakai, J; Ogura, T; Protasi, F; Franzini-Armstrong, C; Allen, P D; Beam, K G

    1997-02-04

    Dihydropyridine receptors (DHPRs), which are voltage-gated Ca2+ channels, and ryanodine receptors (RyRs), which are intracellular Ca2+ release channels, are expressed in diverse cell types, including skeletal and cardiac muscle. In skeletal muscle, there appears to be reciprocal signaling between the skeletal isoforms of both the DHPR and the RyR (RyR-1), such that Ca2+ release activity of RyR-1 is controlled by the DHPR and Ca2+ channel activity of the DHPR is controlled by RyR-1. Dyspedic skeletal muscle cells, which do not express RyR-1, lack excitation-contraction coupling and have an approximately 30-fold reduction in L-type Ca2+ current density. Here we have examined the ability of the predominant cardiac and brain RyR isoform, RyR-2, to substitute for RyR-1 in interacting with the skeletal DHPR. When RyR-2 is expressed in dyspedic muscle cells, it gives rise to spontaneous intracellular Ca2+ oscillations and supports Ca2+ entry-induced Ca2+ release. However, unlike RyR-1, the expressed RyR-2 does not increase the Ca2+ channel activity of the DHPR, nor is the gating of RyR-2 controlled by the skeletal DHPR. Thus, the ability to participate in skeletal-type reciprocal signaling appears to be a unique feature of RyR-1.

  11. Growth factor involvement in tension-induced skeletal muscle growth

    NASA Technical Reports Server (NTRS)

    Vandenburgh, Herman W.

    1987-01-01

    New muscle tissue culture techniques were developed to grow embryonic skeletal myofibers which are able to differentiate into more adultlike myofibers. Studies on mechanical simulation of cultured muscle cell growth will now be more directly applicable to mechanically-induced growth in adult muscle, and lead to better models for understanding muscle tissue atrophy caused by disuse in the microgravity of space.

  12. MG53-IRS-1 (Mitsugumin 53-Insulin Receptor Substrate-1) Interaction Disruptor Sensitizes Insulin Signaling in Skeletal Muscle.

    PubMed

    Lee, Hyun; Park, Jung-Jin; Nguyen, Nga; Park, Jun Sub; Hong, Jin; Kim, Seung-Hyeob; Song, Woon Young; Kim, Hak Joong; Choi, Kwangman; Cho, Sungchan; Lee, Jae-Seon; Kim, Bong-Woo; Ko, Young-Gyu

    2016-12-23

    Mitsugumin 53 (MG53) is an E3 ligase that interacts with and ubiquitinates insulin receptor substrate-1 (IRS-1) in skeletal muscle; thus, an MG53-IRS-1 interaction disruptor (MID), which potentially sensitizes insulin signaling with an elevated level of IRS-1 in skeletal muscle, is an excellent candidate for treating insulin resistance. To screen for an MID, we developed a bimolecular luminescence complementation system using an N-terminal luciferase fragment fused with IRS-1 and a C-terminal luciferase fragment fused with an MG53 C14A mutant that binds to IRS-1 but does not have E3 ligase activity. An MID, which was discovered using the bimolecular luminescence complementation system, disrupted the molecular association of MG53 with IRS-1, thus abolishing MG53-mediated IRS-1 ubiquitination and degradation. Thus, the MID sensitized insulin signaling and increased insulin-elicited glucose uptake with an elevated level of IRS-1 in C2C12 myotubes. These data indicate that this MID holds promise as a drug candidate for treating insulin resistance. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

  13. PKCε as a novel promoter of skeletal muscle differentiation and regeneration.

    PubMed

    Di Marcantonio, D; Galli, D; Carubbi, C; Gobbi, G; Queirolo, V; Martini, S; Merighi, S; Vaccarezza, M; Maffulli, N; Sykes, S M; Vitale, M; Mirandola, P

    2015-11-15

    Satellite cells are muscle resident stem cells and are responsible for muscle regeneration. In this study we investigate the involvement of PKCε during muscle stem cell differentiation in vitro and in vivo. Here, we describe the identification of a previously unrecognized role for the PKCε-HMGA1 signaling axis in myoblast differentiation and regeneration processes. PKCε expression was modulated in the C2C12 cell line and primary murine satellite cells in vitro, as well as in an in vivo model of muscle regeneration. Immunohistochemistry and immunofluorescence, RT-PCR and shRNA silencing techniques were used to determine the role of PKCε and HMGA1 in myogenic differentiation. PKCε expression increases and subsequently re-localizes to the nucleus during skeletal muscle cell differentiation. In the nucleus, PKCε blocks Hmga1 expression to promote Myogenin and Mrf4 accumulation and myoblast formation. Following in vivo muscle injury, PKCε accumulates in regenerating, centrally-nucleated myofibers. Pharmacological inhibition of PKCε impairs the expression of two crucial markers of muscle differentiation, namely MyoD and Myogenin, during injury induced muscle regeneration. This work identifies the PKCε-HMGA1 signaling axis as a positive regulator of skeletal muscle differentiation. Copyright © 2015 Elsevier Inc. All rights reserved.

  14. Calcium influx through L-type channels attenuates skeletal muscle contraction via inhibition of adenylyl cyclases.

    PubMed

    Menezes-Rodrigues, Francisco Sandro; Pires-Oliveira, Marcelo; Duarte, Thiago; Paredes-Gamero, Edgar Julian; Chiavegatti, Tiago; Godinho, Rosely Oliveira

    2013-11-15

    Skeletal muscle contraction is triggered by acetylcholine induced release of Ca(2+) from sarcoplasmic reticulum. Although this signaling pathway is independent of extracellular Ca(2+), L-type voltage-gated calcium channel (Cav) blockers have inotropic effects on frog skeletal muscles which occur by an unknown mechanism. Taking into account that skeletal muscle fiber expresses Ca(+2)-sensitive adenylyl cyclase (AC) isoforms and that cAMP is able to increase skeletal muscle contraction force, we investigated the role of Ca(2+) influx on mouse skeletal muscle contraction and the putative crosstalk between extracellular Ca(2+) and intracellular cAMP signaling pathways. The effects of Cav blockers (verapamil and nifedipine) and extracellular Ca(2+) chelator EGTA were evaluated on isometric contractility of mouse diaphragm muscle under direct electrical stimulus (supramaximal voltage, 2 ms, 0.1 Hz). Production of cAMP was evaluated by radiometric assay while Ca(2+) transients were assessed by confocal microscopy using L6 cells loaded with fluo-4/AM. Ca(2+) channel blockers verapamil and nifedipine had positive inotropic effect, which was mimicked by removal of extracellular Ca(+2) with EGTA or Ca(2+)-free Tyrode. While phosphodiesterase inhibitor IBMX potentiates verapamil positive inotropic effect, it was abolished by AC inhibitors SQ22536 and NYK80. Finally, the inotropic effect of verapamil was associated with increased intracellular cAMP content and mobilization of intracellular Ca(2+), indicating that positive inotropic effects of Ca(2+) blockers depend on cAMP formation. Together, our results show that extracellular Ca(2+) modulates skeletal muscle contraction, through inhibition of Ca(2+)-sensitive AC. The cross-talk between extracellular calcium and cAMP-dependent signaling pathways appears to regulate the extent of skeletal muscle contraction responses. © 2013 Published by Elsevier B.V.

  15. Factors modulating expression of Renilla luciferase from control plasmids used in luciferase reporter gene assays1

    PubMed Central

    Shifera, Amde Selassie; Hardin, John A.

    2009-01-01

    The Renilla luciferase gene is commonly used as an internal control in luciferase-based reporter gene assays to normalize the values of the experimental reporter gene for variations that could be caused by transfection efficiency and sample handling. Various plasmids encoding Renilla luciferase under different promoter constructs are commercially available. The validity of the use of Renilla luciferase as an internal control is based on the assumption that it is constitutively expressed in transfected cells and that its constitutive expression is not modulated by experimental factors that could result in either the upregulation or the downregulation of the amounts of the enzyme produced. During the past ten years, a number of reports have appeared that identified a variety of conditions that could alter the basal constitutive expression of Renilla luciferase. The use of Renilla luciferase in those circumstances would not be valid and an alternative way of normalization would be necessary. This review covers the factors that have been reported thus far as modulating the expression of Renilla luciferase from plasmid constructs. PMID:19788887

  16. The complex pericentriolar material 1 protein allows differentiation between myonuclei and nuclei of satellite cells of the skeletal muscle.

    PubMed

    Brunn, Anna

    2018-05-27

    The original article by Winje et al., entitled "Specific labelling of myonuclei by an antibody against pericentriolar material 1 (PCM1) on skeletal muscle tissue sections" 1 , sheds new light on the issue of heterogeneity of skeletal muscle and, thus, the problem to reliably distinguish between myonuclei versus nuclei of satellite cells of the skeletal muscle which are intimately associated. At the light microscopical level this differentiation is particularly difficult since only nuclei inside the muscle fiber are defined as true myonuclei. This is a major problem in analyses that use tissue homogenates, while in situ immunohistochemical studies using appropriate antibodies usually allow differentiation of cell populations. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  17. Insulin alleviates degradation of skeletal muscle protein by inhibiting the ubiquitin-proteasome system in septic rats.

    PubMed

    Chen, Qiyi; Li, Ning; Zhu, Weiming; Li, Weiqin; Tang, Shaoqiu; Yu, Wenkui; Gao, Tao; Zhang, Juanjuan; Li, Jieshou

    2011-06-03

    Hypercatabolism is common under septic conditions. Skeletal muscle is the main target organ for hypercatabolism, and this phenomenon is a vital factor in the deterioration of recovery in septic patients. In skeletal muscle, activation of the ubiquitin-proteasome system plays an important role in hypercatabolism under septic status. Insulin is a vital anticatabolic hormone and previous evidence suggests that insulin administration inhibits various steps in the ubiquitin-proteasome system. However, whether insulin can alleviate the degradation of skeletal muscle protein by inhibiting the ubiquitin-proteasome system under septic condition is unclear. This paper confirmed that mRNA and protein levels of the ubiquitin-proteasome system were upregulated and molecular markers of skeletal muscle proteolysis (tyrosine and 3-methylhistidine) simultaneously increased in the skeletal muscle of septic rats. Septic rats were infused with insulin at a constant rate of 2.4 mU.kg-1.min-1 for 8 hours. Concentrations of mRNA and proteins of the ubiquitin-proteasome system and molecular markers of skeletal muscle proteolysis were mildly affected. When the insulin infusion dose increased to 4.8 mU.kg-1.min-1, mRNA for ubiquitin, E2-14 KDa, and the C2 subunit were all sharply downregulated. At the same time, the levels of ubiquitinated proteins, E2-14KDa, and the C2 subunit protein were significantly reduced. Tyrosine and 3-methylhistidine decreased significantly. We concluded that the ubiquitin-proteasome system is important skeletal muscle hypercatabolism in septic rats. Infusion of insulin can reverse the detrimental metabolism of skeletal muscle by inhibiting the ubiquitin-proteasome system, and the effect is proportional to the insulin infusion dose.

  18. Role of ATF4 in skeletal muscle atrophy.

    PubMed

    Adams, Christopher M; Ebert, Scott M; Dyle, Michael C

    2017-05-01

    Here, we discuss recent work focused on the role of activating transcription factor 4 (ATF4) in skeletal muscle atrophy. Muscle atrophy involves and requires widespread changes in skeletal muscle gene expression; however, the transcriptional regulatory proteins responsible for those changes are not yet well defined. Recent work indicates that some forms of muscle atrophy require ATF4, a stress-inducible bZIP transcription factor subunit that helps to mediate a broad range of stress responses in mammalian cells. ATF4 expression in skeletal muscle fibers is sufficient to induce muscle fiber atrophy and required for muscle atrophy during several stress conditions, including aging, fasting, and limb immobilization. By helping to activate specific genes in muscle fibers, ATF4 contributes to the expression of numerous mRNAs, including at least two mRNAs (Gadd45a and p21) that encode mediators of muscle fiber atrophy. Gadd45a promotes muscle fiber atrophy by activating the protein kinase MEKK4. p21 promotes atrophy by reducing expression of spermine oxidase, a metabolic enzyme that helps to maintain muscle fiber size under nonstressed conditions. In skeletal muscle fibers, ATF4 is critical component of a complex and incompletely understood molecular signaling network that causes muscle atrophy during aging, fasting, and immobilization.

  19. Angiotensin II Evokes Angiogenic Signals within Skeletal Muscle through Co-ordinated Effects on Skeletal Myocytes and Endothelial Cells

    PubMed Central

    Gorman, Jennifer L.; Liu, Sammy T. K.; Slopack, Dara; Shariati, Khashayar; Hasanee, Adam; Olenich, Sara; Olfert, I. Mark; Haas, Tara L.

    2014-01-01

    Skeletal muscle overload induces the expression of angiogenic factors such as vascular endothelial growth factor (VEGF) and matrix metalloproteinase (MMP)-2, leading to new capillary growth. We found that the overload-induced increase in angiogenesis, as well as increases in VEGF, MMP-2 and MT1-MMP transcripts were abrogated in muscle VEGF KO mice, highlighting the critical role of myocyte-derived VEGF in controlling this process. The upstream mediators that contribute to overload-induced expression of VEGF have yet to be ascertained. We found that muscle overload increased angiotensinogen expression, a precursor of angiotensin (Ang) II, and that Ang II signaling played an important role in basal VEGF production in C2C12 cells. Furthermore, matrix-bound VEGF released from myoblasts induced the activation of endothelial cells, as evidenced by elevated endothelial cell phospho-p38 levels. We also found that exogenous Ang II elevates VEGF expression, as well as MMP-2 transcript levels in C2C12 myotubes. Interestingly, these responses also were observed in skeletal muscle endothelial cells in response to Ang II treatment, indicating that these cells also can respond directly to the stimulus. The involvement of Ang II in muscle overload-induced angiogenesis was assessed. We found that blockade of AT1R-dependent Ang II signaling using losartan did not attenuate capillary growth. Surprisingly, increased levels of VEGF protein were detected in overloaded muscle from losartan-treated rats. Similarly, we observed elevated VEGF production in cultured endothelial cells treated with losartan alone or in combination with Ang II. These studies conclusively establish the requirement for muscle derived VEGF in overload-induced angiogenesis and highlight a role for Ang II in basal VEGF production in skeletal muscle. However, while Ang II signaling is activated following overload and plays a role in muscle VEGF production, inhibition of this pathway is not sufficient to halt overload

  20. Skeletal muscle deiodinase type 2 regulation during illness in mice.

    PubMed

    Kwakkel, J; van Beeren, H C; Ackermans, M T; Platvoet-Ter Schiphorst, M C; Fliers, E; Wiersinga, W M; Boelen, A

    2009-11-01

    We have previously shown that skeletal muscle deiodinase type 2 (D2) mRNA (listed as Dio2 in MGI Database) is upregulated in an animal model of acute illness. However, human studies on the expression of muscle D2 during illness report conflicting data. Therefore, we evaluated the expression of skeletal muscle D2 and D2-regulating factors in two mouse models of illness that differ in timing and severity of illness: 1) turpentine-induced inflammation, and 2) Streptococcus pneumoniae infection. During turpentine-induced inflammation, D2 mRNA and activity increased compared to pair-fed controls, most prominently at day 1 and 2, whereas after S. pneumoniae infection D2 mRNA decreased. We evaluated the association of D2 expression with serum thyroid hormones, (de-)ubiquitinating enzymes ubiquitin-specific peptidase 33 and WD repeat and SOCS box-containing 1 (Wsb1), cytokine expression and activation of inflammatory pathways and cAMP pathway. During chronic inflammation the increased muscle D2 expression is associated with the activation of the cAMP pathway. The normalization of D2 5 days after turpentine injection coincides with increased Wsb1 and tumor necrosis factor alpha expression. Muscle interleukin-1beta (Il1b) expression correlated with decreased D2 mRNA expression after S. pneumoniae infection. In conclusion, muscle D2 expression is differentially regulated during illness, probably related to differences in the inflammatory response and type of pathology. D2 mRNA and activity increases in skeletal muscle during the acute phase of chronic inflammation compared to pair-fed controls probably due to activation of the cAMP pathway. In contrast, muscle D2 mRNA decreases 48 h after a severe bacterial infection, which is associated with local Il1b mRNA expression and might also be due to diminished food-intake.

  1. FGFR3-related condition: a skeletal dysplasia with similarities to thanatophoric dysplasia and SADDAN due to Lys650Met.

    PubMed

    Farmakis, Shannon G; Shinawi, Marwan; Miller-Thomas, Michelle; Radmanesh, Alireza; Herman, Thomas E

    2015-03-01

    Mutations in the fibroblast growth factor receptor 3 (FGFR3) gene account for six related skeletal dysplasia conditions: achondroplasia, hypochondroplasia, thanatophoric dysplasia types 1 and 2, SADDAN (severe achondroplasia with developmental delay and acanthosis nigricans), and platyspondylic lethal skeletal dysplasia, San Diego type. This group of disorders has very characteristic clinical and radiologic features, which distinguish them from other skeletal dysplasias. They display a spectrum of severity in the skeletal findings, ranging from relatively mild hypochondroplasia to lethal thanatophoric dysplasia. We report a patient who has the missense FGFR3 mutation, Lys650Met, previously reported in association only with SADDAN, who exhibits some findings similar to both thanatophoric dysplasia (types 1 and 2) in addition to those findings characteristic of SADDAN.

  2. Advances on microRNA in regulating mammalian skeletal muscle development.

    PubMed

    Li, Xin-Yun; Fu, Liang-Liang; Cheng, Hui-Jun; Zhao, Shu-Hong

    2017-11-20

    MicroRNA (miRNA) is a class of short non-coding RNA, which is about 22 bp in length. In mammals, miRNA exerts its funtion through binding with the 3°-UTR region of target genes and inhibiting their translation. Skeletal muscle development is a complex event, including: proliferation, migration and differentiation of skeletal muscle stem cells; proliferation, differentiation and fusion of myocytes; as well as hypertrophy, energy metabolism and conversion of muscle fiber types. The miRNA plays important roles in all processes of skeletal muscle development through targeting the key factors of different stages. Herein we summarize the miRNA related to muscle development, providing a better understanding of the skeletal muscle development.

  3. Effect of insulin-like factors on glucose transport activity in unweighted rat skeletal muscle

    NASA Technical Reports Server (NTRS)

    Henriksen, Erik J.; Ritter, Leslie S.

    1993-01-01

    The effect of 3 or 6 days of unweighting on glucose transport activity, as assessed by 2-deoxyglucose uptake, in soleus strips stimulated by maximally effective concentrations of insulin, IGF-I, vanadate, or phospholipase C (PLC) is examined. Progressively increased responses to maximally effective doses of insulin or insulin-like growth factor were observed after 3 and 6 days of unweighting compared with weight matched control strips. Enhanced maximal responses to vanadate (6 days only) and PLC (3 and 6 days) were also observed. The data provide support for the existance of postreceptor binding mechanisms for the increased action of insulin on the glucose transport system in unweighted rat skeletal muscle.

  4. Skeletal muscle regeneration and impact of aging and nutrition.

    PubMed

    Domingues-Faria, Carla; Vasson, Marie-Paule; Goncalves-Mendes, Nicolas; Boirie, Yves; Walrand, Stephane

    2016-03-01

    After skeletal muscle injury a regeneration process takes place to repair muscle. Skeletal muscle recovery is a highly coordinated process involving cross-talk between immune and muscle cells. It is well known that the physiological activities of both immune cells and muscle stem cells decline with advancing age, thereby blunting the capacity of skeletal muscle to regenerate. The age-related reduction in muscle repair efficiency contributes to the development of sarcopenia, one of the most important factors of disability in elderly people. Preserving muscle regeneration capacity may slow the development of this syndrome. In this context, nutrition has drawn much attention: studies have demonstrated that nutrients such as amino acids, n-3 polyunsaturated fatty acids, polyphenols and vitamin D can improve skeletal muscle regeneration by targeting key functions of immune cells, muscle cells or both. Here we review the process of skeletal muscle regeneration with a special focus on the cross-talk between immune and muscle cells. We address the effect of aging on immune and skeletal muscle cells involved in muscle regeneration. Finally, the mechanisms of nutrient action on muscle regeneration are described, showing that quality of nutrition may help to preserve the capacity for skeletal muscle regeneration with age. Copyright © 2015 Elsevier B.V. All rights reserved.

  5. Structure-function relationship of skeletal muscle provides inspiration for design of new artificial muscle

    NASA Astrophysics Data System (ADS)

    Gao, Yingxin; Zhang, Chi

    2015-03-01

    A variety of actuator technologies have been developed to mimic biological skeletal muscle that generates force in a controlled manner. Force generation process of skeletal muscle involves complicated biophysical and biochemical mechanisms; therefore, it is impossible to replace biological muscle. In biological skeletal muscle tissue, the force generation of a muscle depends not only on the force generation capacity of the muscle fiber, but also on many other important factors, including muscle fiber type, motor unit recruitment, architecture, structure and morphology of skeletal muscle, all of which have significant impact on the force generation of the whole muscle or force transmission from muscle fibers to the tendon. Such factors have often been overlooked, but can be incorporated in artificial muscle design, especially with the discovery of new smart materials and the development of innovative fabrication and manufacturing technologies. A better understanding of the physiology and structure-function relationship of skeletal muscle will therefore benefit the artificial muscle design. In this paper, factors that affect muscle force generation are reviewed. Mathematical models used to model the structure-function relationship of skeletal muscle are reviewed and discussed. We hope the review will provide inspiration for the design of a new generation of artificial muscle by incorporating the structure-function relationship of skeletal muscle into the design of artificial muscle.

  6. Distribution of skeletal malignancies in beagles injected with 239Pu citrate.

    PubMed

    Lloyd, R D; Taylor, G N; Angus, W; Miller, S C; Bruenger, F W; Jee, W S

    1994-04-01

    The distribution of skeletal malignancies among our beagles injected with 239Pu as young adults roughly seems to follow the distribution of skeletal mass and skeletal 239Pu. These findings are similar to those we reported previously for a group of dogs given 26Ra. Although there were differences in tumor distribution between the animals given 226Ra and those given 239Pu, most of them were not statistically significant; however, the radium dogs seemed to show a greater sensitivity to bone tumor origin in the tibia, while there may have been a tendency among the plutonium dogs toward increased relative sensitivity in the scapula, lumbar vertebrae, sacrum, and ribs. In contrast, the most common site for the formation of naturally-occurring bone malignancy in the dog is the distal radius. Perhaps there were too few tumors and too few dogs to establish statistical significance. A correlation between tumor location and at least two anatomical-physiological factors in the skeleton indicated that these two factors (site-specific bone turnover rate and percent of red marrow at the site, which is correlated with vascularity) may influence the appearance of malignancies both individually and in combination. Except for the femur, there appeared to be no difference between the relative distribution of skeletal malignancies of low-level (30 Bq-2 Bq kg-1 injected) and high-level (3-122 kBq kg-1) dogs. Distribution of bone tumors between the axial and appendicular skeleton was 50% vs. 50% for 239Pu (42 and 42), but it was 39% axial vs. 61% appendicular (22 and 35, respectively) for dogs given 226Ra. This difference was not significant (p > 0.2).

  7. Advanced age-related denervation and fiber-type grouping in skeletal muscle of SOD1 knockout mice.

    PubMed

    Kostrominova, Tatiana Y

    2010-11-30

    In this study skeletal muscles from 1.5- and 10-month-old Cu/Zn superoxide dismutase (SOD1) homozygous knockout (JLSod1(-/-)) mice obtained from The Jackson Laboratory (C57Bl6/129SvEv background) were compared with muscles from age- and sex-matched heterozygous (JLSod1(+/-)) littermates. The results of this study were compared with previously published data on two different strains of Sod1(-/-) mice: one from Dr. Epstein's laboratory (ELSod1(-/-); C57Bl6 background) and the other from Cephalon, Inc. (CSod1(-/-); 129/CD-1 background). Grouping of succinate dehydrogenase-positive fibers characterized muscles of Sod1(-/-) mice from all three strains. The 10-month-old Sod1(-/-)C and JL mice displayed pronounced denervation of the gastrocnemius muscle, whereas the ELSod1(-/-) mice displayed a small degree of denervation at this age, but developed accelerated age-related denervation later on. Denervation markers were up-regulated in skeletal muscle of 10-month-old JLSod1(-/-) mice. This study is the first to show that metallothionein mRNA and protein expression was up-regulated in the skeletal muscle of 10-month-old JLSod1(-/-) mice and was mostly localized to the small atrophic muscle fibers. In conclusion, all three strains of Sod1(-/-) mice develop accelerated age-related muscle denervation, but the genetic background has significant influence on the progress of denervation. Copyright © 2010 Elsevier Inc. All rights reserved.

  8. Atomoxetine Prevents Dexamethasone-Induced Skeletal Muscle Atrophy in Mice

    PubMed Central

    Jesinkey, Sean R.; Korrapati, Midhun C.; Rasbach, Kyle A.; Beeson, Craig C.

    2014-01-01

    Skeletal muscle atrophy remains a clinical problem in numerous pathologic conditions. β2-Adrenergic receptor agonists, such as formoterol, can induce mitochondrial biogenesis (MB) to prevent such atrophy. Additionally, atomoxetine, an FDA-approved norepinephrine reuptake inhibitor, was positive in a cellular assay for MB. We used a mouse model of dexamethasone-induced skeletal muscle atrophy to investigate the potential role of atomoxetine and formoterol to prevent muscle mass loss. Mice were administered dexamethasone once daily in the presence or absence of formoterol (0.3 mg/kg), atomoxetine (0.1 mg/kg), or sterile saline. Animals were euthanized at 8, 16, and 24 hours or 8 days later. Gastrocnemius muscle weights, changes in mRNA and protein expression of peroxisome proliferator–activated receptor-γ coactivator-1 α (PGC-1α) isoforms, ATP synthase β, cytochrome c oxidase subunit I, NADH dehydrogenase (ubiquinone) 1 β subcomplex, 8, ND1, insulin-like growth factor 1 (IGF-1), myostatin, muscle Ring-finger protein-1 (muscle atrophy), phosphorylated forkhead box protein O 3a (p-FoxO3a), Akt, mammalian target of rapamycin (mTOR), and ribosomal protein S6 (rp-S6; muscle hypertrophy) in naive and muscle-atrophied mice were measured. Atomoxetine increased p-mTOR 24 hours after treatment in naïve mice, but did not change any other biomarkers. Formoterol robustly activated the PGC-1α-4-IGF1–Akt-mTOR-rp-S6 pathway and increased p-FoxO3a as early as 8 hours and repressed myostatin at 16 hours. In contrast to what was observed with acute treatment, chronic treatment (7 days) with atomoxetine increased p-Akt and p-FoxO3a, and sustained PGC-1α expression and skeletal muscle mass in dexamethasone-treated mice, in a manner comparable to formoterol. In conclusion, chronic treatment with a low dose of atomoxetine prevented dexamethasone-induced skeletal muscle wasting and supports a potential role in preventing muscle atrophy. PMID:25292181

  9. Study of the relationship between the lifestyle of residents residing in fluorosis endemic areas and adult skeletal fluorosis.

    PubMed

    Liu, GuoJie; Ye, QingFang; Chen, Wei; Zhao, ZhenJuan; Li, Ling; Lin, Ping

    2015-07-01

    The relationship between fluorosis and the lifestyle of adult residents of areas in which fluorosis is endemic was evaluated. A cross-sectional and case-control analysis was performed to study 289 villagers living in fluorosis endemic areas who drank the local water. Subjects were divided into skeletal fluorosis and non-skeletal fluorosis groups according to whether they were afflicted with skeletal fluorosis. A semi-quantitative food frequency questionnaire, homemade lifestyle questionnaires, and general characteristics were analyzed. The factors that affected the occurrence of skeletal fluorosis were determined by generalized estimating equations. Our results showed that protective factors against skeletal fluorosis included drinking boiled water, storing water in a ceramic tank, and ingesting fruits, vitamin A, thiamine, and folic acid. Risk factors for skeletal fluorosis were overweight status and obesity, drinking tea, drinking water without storage, and ingestion of oils, fats, and phosphorus. Our results demonstrate that skeletal fluorosis has a close relationship with lifestyle. Copyright © 2015 Elsevier B.V. All rights reserved.

  10. Differential response of skeletal muscles to mTORC1 signaling during atrophy and hypertrophy

    PubMed Central

    2013-01-01

    Background Skeletal muscle mass is determined by the balance between protein synthesis and degradation. Mammalian target of rapamycin complex 1 (mTORC1) is a master regulator of protein translation and has been implicated in the control of muscle mass. Inactivation of mTORC1 by skeletal muscle-specific deletion of its obligatory component raptor results in smaller muscles and a lethal dystrophy. Moreover, raptor-deficient muscles are less oxidative through changes in the expression PGC-1α, a critical determinant of mitochondrial biogenesis. These results suggest that activation of mTORC1 might be beneficial to skeletal muscle by providing resistance to muscle atrophy and increasing oxidative function. Here, we tested this hypothesis by deletion of the mTORC1 inhibitor tuberous sclerosis complex (TSC) in muscle fibers. Method Skeletal muscles of mice with an acute or a permanent deletion of raptor or TSC1 were examined using histological, biochemical and molecular biological methods. Response of the muscles to changes in mechanical load and nerve input was investigated by ablation of synergistic muscles or by denervation . Results Genetic deletion or knockdown of raptor, causing inactivation of mTORC1, was sufficient to prevent muscle growth and enhance muscle atrophy. Conversely, short-term activation of mTORC1 by knockdown of TSC induced muscle fiber hypertrophy and atrophy-resistance upon denervation, in both fast tibialis anterior (TA) and slow soleus muscles. Surprisingly, however, sustained activation of mTORC1 by genetic deletion of Tsc1 caused muscle atrophy in all but soleus muscles. In contrast, oxidative capacity was increased in all muscles examined. Consistently, TSC1-deficient soleus muscle was atrophy-resistant whereas TA underwent normal atrophy upon denervation. Moreover, upon overloading, plantaris muscle did not display enhanced hypertrophy compared to controls. Biochemical analysis indicated that the atrophy response of muscles was based on the

  11. SMAD3 Negatively Regulates Serum Irisin and Skeletal Muscle FNDC5 and Peroxisome Proliferator-activated Receptor γ Coactivator 1-α (PGC-1α) during Exercise*

    PubMed Central

    Tiano, Joseph P.; Springer, Danielle A.; Rane, Sushil G.

    2015-01-01

    Beige adipose cells are a distinct and inducible type of thermogenic fat cell that express the mitochondrial uncoupling protein-1 and thus represent a powerful target for treating obesity. Mice lacking the TGF-β effector protein SMAD3 are protected against diet-induced obesity because of browning of their white adipose tissue (WAT), leading to increased whole body energy expenditure. However, the role SMAD3 plays in WAT browning is not clearly understood. Irisin is an exercise-induced skeletal muscle hormone that induces WAT browning similar to that observed in SMAD3-deficient mice. Together, these observations suggested that SMAD3 may negatively regulate irisin production and/or secretion from skeletal muscle. To address this question, we used wild-type and SMAD3 knock-out (Smad3−/−) mice subjected to an exercise regime and C2C12 myotubes treated with TGF-β, a TGF-β receptor 1 pharmacological inhibitor, adenovirus expressing constitutively active SMAD3, or siRNA against SMAD3. We find that in Smad3−/− mice, exercise increases serum irisin and skeletal muscle FNDC5 (irisin precursor) and its upstream activator peroxisome proliferator-activated receptor γ coactivator 1-α (PGC-1α) to a greater extent than in wild-type mice. In C2C12 myotubes, TGF-β suppresses FNDC5 and PGC-1α mRNA and protein levels via SMAD3 and promotes SMAD3 binding to the FNDC5 and PGC-1α promoters. These data establish that SMAD3 suppresses FNDC5 and PGC-1α in skeletal muscle cells. These findings shed light on the poorly understood regulation of irisin/FNDC5 by demonstrating a novel association between irisin and SMAD3 signaling in skeletal muscle. PMID:25648888

  12. DNA damage checkpoint pathway modulates the regulation of skeletal growth and osteoblastic bone formation by parathyroid hormone-related peptide.

    PubMed

    Zhang, Ying; Chen, Guangpei; Gu, Zhen; Sun, Haijian; Karaplis, Andrew; Goltzman, David; Miao, Dengshun

    2018-01-01

    We previously demonstrated that parathyroid hormone-related peptide (PTHrP) 1-84 knockin ( Pthrp KI) mice, which lacked a PTHrP nuclear localization sequence (NLS) and C-terminus, displayed early senescence, defective osteoblastic bone formation, and skeletal growth retardation. However, the mechanism of action of the PTHrP NLS and C-terminus in regulating development of skeleton is still unclear. In this study, we examined alterations of oxidative stress and DNA damage response-related molecules in Pthrp KI skeletal tissue. We found that ROS levels, protein expression levels of γ-H2AX, a DNA damage marker, and the DNA damage response markers p-Chk2 and p53 were up-regulated, whereas gene expression levels of anti-oxidative enzymes were down-regulated significantly. We therefore further disrupted the DNA damage response pathway by deleting the Chk2 in Pthrp KI (Chk2 -/- KI) mice and did comparison with WT, Chk2 -/- and Pthrp KI littermates. The Pthrp KI mice with Chk2 deletion exhibited a longer lifespan, improvement in osteoblastic bone formation and skeletal growth including width of growth plates and length of long bones, trabecular and epiphyseal bone volume, BMD, osteoblast numbers, type I collagen and ALP positive bone areas, the numbers of total colony-forming unit fibroblasts (CFU-f), ALP + CFU-f and the expression levels of osteogenic genes. In addition, the genes associated with anti-oxidative enzymes were up-regulated significantly, whereas the tumor suppressor genes related to senescence were down-regulated in Chk2 -/- KI mice compared to Pthrp KI mice. Our results suggest that Chk2 deletion in Pthrp KI mice can somewhat rescue defects in osteoblastic bone formation and skeletal growth by enhancing endochondral bone formation and osteogenesis. These studies therefore indicate that the DNA damage checkpoint pathway may be a target for the nuclear action of PTHrP to regulate skeletal development and growth.

  13. Modulation of sphingosine-1-phosphate in inflammatory bowel disease.

    PubMed

    Peyrin-Biroulet, Laurent; Christopher, Ronald; Behan, Dominic; Lassen, Cheryl

    2017-05-01

    Inflammatory bowel diseases (IBD), including ulcerative colitis and Crohn's disease, involve an inappropriate immune reaction in the digestive tract, causing a variety of disabling symptoms. The advent of monoclonal antibodies (anti-tumor necrosis factor, anti-integrin, anti-interleukin -23) has revolutionized IBD management. Nevertheless, these agents, with potential for immunogenicity, are associated with high rates of response loss and disease relapse over time. They are also associated with high production costs. Sphingosine-1-phosphate (S1P), a membrane-derived lysophospholipid signaling molecule, is implicated in a vast array of physiological and pathophysiological processes, primarily via extracellular activation of S1P1-S1P5 receptors. S1P1, S1P4 and S1P5 are involved in regulation of the immune system, while S1P2 and S1P3 may be associated with cardiovascular, pulmonary, and theoretical cancer-related risks. Targeting S1P receptors for inflammatory conditions has been successful in clinical trials leading to approval of the non-selective S1P modulator, fingolimod, for relapsing forms of multiple sclerosis. However, the association of this non-selective S1P modulator with serious adverse events provides the rationale for developing more selective S1P receptor modulators. Until recently, three S1P modulators with differing selectivity for S1P receptors were in clinical development for IBD: ozanimod (RPC1063), etrasimod (APD334) and amiselimod (MT-1303). The development of amiselimod has been stopped as Biogen are currently focusing on other drugs in its portfolio. Following encouraging results from the Phase 2 TOUCHSTONE trial, a Phase 3 trial of the S1P modulator ozanimod in patients with moderate-to-severe ulcerative colitis is ongoing. Etrasimod is also being tested in a phase 2 trial in ulcerative colitis. These pipeline medications can be administered orally and may avoid the formation of anti-drug antibodies that can lead to treatment failure with

  14. Role of inhibition of osteogenesis function by Sema4D/Plexin-B1 signaling pathway in skeletal fluorosis in vitro.

    PubMed

    Liu, Xiao-li; Song, Jing; Liu, Ke-jian; Wang, Wen-peng; Xu, Chang; Zhang, Yu-zeng; Liu, Yun

    2015-10-01

    Skeletal fluorosis is a chronically metabolic bone disease with extensive hyperostosis osteosclerosis caused by long time exposure to fluoride. Skeletal fluorosis brings about a series of abnormal changes of the extremity, such as joint pain, joint stiffness, bone deformity, etc. Differentiation and maturation of osteoblasts were regulated by osteoclasts via Sema4D/Plexin-B1 signaling pathway. Furthermore, the differentiation and maturation of osteoclasts are conducted by osteoblasts via RANKL/RANK/OPG pathway. Both of these processes form a feedback circuit which is a key link in skeletal fluorosis. In this study, an osteoblast-osteoclast co-culture model in vitro was developed to illustrate the mechanism of skeletal fluorosis. With the increase of fluoride concentration, the expression level of Sema4D was decreased and TGF-β1 was increased continuously. OPG/RANKL mRNA level, however, increased gradually. On the basis of that, the inhibition of Sema4D/Plexin-B1/RhoA/ROCK signaling pathway caused by fluoride promoted the level of TGF-β1 and activated the proliferation of osteoblasts. In addition, osteroprotegerin (OPG) secreted by osteoblasts was up-regulated by fluoride. The competitive combination of OPG and RANKL was strengthened and the combination of RANKL and RANK was hindered. And then the differentiation and maturation of osteoclasts were inhibited, and bone absorption was weakened, leading to skeletal fluorosis.

  15. Space travel directly induces skeletal muscle atrophy

    NASA Technical Reports Server (NTRS)

    Vandenburgh, H.; Chromiak, J.; Shansky, J.; Del Tatto, M.; Lemaire, J.

    1999-01-01

    Space travel causes rapid and pronounced skeletal muscle wasting in humans that reduces their long-term flight capabilities. To develop effective countermeasures, the basis of this atrophy needs to be better understood. Space travel may cause muscle atrophy indirectly by altering circulating levels of factors such as growth hormone, glucocorticoids, and anabolic steroids and/or by a direct effect on the muscle fibers themselves. To determine whether skeletal muscle cells are directly affected by space travel, tissue-cultured avian skeletal muscle cells were tissue engineered into bioartificial muscles and flown in perfusion bioreactors for 9 to 10 days aboard the Space Transportation System (STS, i.e., Space Shuttle). Significant muscle fiber atrophy occurred due to a decrease in protein synthesis rates without alterations in protein degradation. Return of the muscle cells to Earth stimulated protein synthesis rates of both muscle-specific and extracellular matrix proteins relative to ground controls. These results show for the first time that skeletal muscle fibers are directly responsive to space travel and should be a target for countermeasure development.

  16. Elevated stearoyl-CoA desaturase-1 expression in skeletal muscle contributes to abnormal fatty acid partitioning in obese humans

    PubMed Central

    Hulver, Matthew W.; Berggren, Jason R.; Carper, Michael J.; Miyazaki, Makoto; Ntambi, James M.; Hoffman, Eric P.; Thyfault, John P.; Stevens, Robert; Dohm, G. Lynis; Houmard, Joseph A.; Muoio, Deborah M.

    2014-01-01

    Summary Obesity and type 2 diabetes are strongly associated with abnormal lipid metabolism and accumulation of intramyocellular triacylglycerol, but the underlying cause of these perturbations are yet unknown. Herein, we show that the lipogenic gene, stearoyl-CoA desaturase 1 (SCD1), is robustly up-regulated in skeletal muscle from extremely obese humans. High expression and activity of SCD1, an enzyme that catalyzes the synthesis of monounsaturated fatty acids, corresponded with low rates of fatty acid oxidation, increased triacylglycerol synthesis and increased monounsaturation of muscle lipids. Elevated SCD1 expression and abnormal lipid partitioning were retained in primary skeletal myocytes derived from obese compared to lean donors, implying that these traits might be driven by epigenetic and/or heritable mechanisms. Overexpression of human SCD1 in myotubes from lean subjects was sufficient to mimic the obese phenotype. These results suggest that elevated expression of SCD1 in skeletal muscle contributes to abnormal lipid metabolism and progression of obesity. PMID:16213227

  17. Elevated stearoyl-CoA desaturase-1 expression in skeletal muscle contributes to abnormal fatty acid partitioning in obese humans.

    PubMed

    Hulver, Matthew W; Berggren, Jason R; Carper, Michael J; Miyazaki, Makoto; Ntambi, James M; Hoffman, Eric P; Thyfault, John P; Stevens, Robert; Dohm, G Lynis; Houmard, Joseph A; Muoio, Deborah M

    2005-10-01

    Obesity and type 2 diabetes are strongly associated with abnormal lipid metabolism and accumulation of intramyocellular triacylglycerol, but the underlying cause of these perturbations are yet unknown. Herein, we show that the lipogenic gene, stearoyl-CoA desaturase 1 (SCD1), is robustly up-regulated in skeletal muscle from extremely obese humans. High expression and activity of SCD1, an enzyme that catalyzes the synthesis of monounsaturated fatty acids, corresponded with low rates of fatty acid oxidation, increased triacylglycerol synthesis and increased monounsaturation of muscle lipids. Elevated SCD1 expression and abnormal lipid partitioning were retained in primary skeletal myocytes derived from obese compared to lean donors, implying that these traits might be driven by epigenetic and/or heritable mechanisms. Overexpression of human SCD1 in myotubes from lean subjects was sufficient to mimic the obese phenotype. These results suggest that elevated expression of SCD1 in skeletal muscle contributes to abnormal lipid metabolism and progression of obesity.

  18. The coactivator PGC-1α regulates mouse skeletal muscle oxidative metabolism independently of the nuclear receptor PPARβ/δ in sedentary mice fed a regular chow diet

    PubMed Central

    Pérez-Schindler, Joaquín; Svensson, Kristoffer; Vargas-Fernández, Elyzabeth; Santos, Gesa; Wahli, Walter; Handschin, Christoph

    2015-01-01

    Aims/hypothesis Physical activity improves oxidative capacity and exerts therapeutic beneficial effects, particularly in the context of metabolic diseases. The peroxisome proliferator-activated receptor γ (PPARγ) coactivator-1α (PGC-1α) and the nuclear receptor PPARβ/δ have both been independently discovered to play a pivotal role in the regulation of oxidative metabolism in skeletal muscle, though their interdependence remain unclear. Hence, our aim was to determine the functional interaction between these two factors in mouse skeletal muscle in vivo. Methods Adult male control mice, PGC-1α muscle-specific transgenic (mTg) mice, PPARβ/δ muscle-specific knockout (mKO) mice and the combination PPARβ/δ mKO + PGC-1α mTg were studied under basal conditions and following PPARβ/δ agonist administration and acute exercise. Whole body metabolism was assessed by indirect calorimetry and blood analysis, while magnetic resonance was used to measure body composition. Quantitative PCR and western blot were used to determine gene expression and intracellular signaling. Proportion of oxidative muscle fiber was determined by NADH staining. Results Agonist-induced PPARβ/δ activation was only disrupted by PPARβ/δ knockout. We also found that the disruption of the PGC-1α-PPARβ/δ axis does not affect whole body metabolism under basal conditions. As expected, PGC-1α mTg mice exhibited higher exercise performance, peak oxygen consumption and lower blood lactate levels following exercise, though PPARβ/δ mKO+PGC-1α mTg mice showed a similar phenotype. Similarly, we found that PPARβ/δ was dispensable for PGC-1α-mediated enhancement of an oxidative phenotype in skeletal muscle. Conclusions/interpretation Collectively, these results indicate that PPARβ/δ is not an essential partner of PGC-1α in the control of skeletal muscle energy metabolism. PMID:25116175

  19. A novel approach for studying the temporal modulation of embryonic skeletal development using organotypic bone cultures and microcomputed tomography.

    PubMed

    Kanczler, Janos M; Smith, Emma L; Roberts, Carol A; Oreffo, Richard O C

    2012-10-01

    , structural developmental paradigms and modulation of bone tissue formation to underpin innovative skeletal regenerative technology for clinical therapeutic strategies in musculoskeletal trauma and diseases.

  20. A Novel Approach for Studying the Temporal Modulation of Embryonic Skeletal Development Using Organotypic Bone Cultures and Microcomputed Tomography

    PubMed Central

    Smith, Emma L.; Roberts, Carol A.

    2012-01-01

    , structural developmental paradigms and modulation of bone tissue formation to underpin innovative skeletal regenerative technology for clinical therapeutic strategies in musculoskeletal trauma and diseases. PMID:22472170

  1. Disruption of ATP-sensitive potassium channel function in skeletal muscles promotes production and secretion of musclin

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sierra, Ana, E-mail: ana-sierra@uiowa.edu; Subbotina, Ekaterina, E-mail: ekaterina-subbotina@uiowa.edu; Zhu, Zhiyong, E-mail: zhiyong-zhu@uiowa.edu

    Sarcolemmal ATP-sensitive potassium (K{sub ATP}) channels control skeletal muscle energy use through their ability to adjust membrane excitability and related cell functions in accordance with cellular metabolic status. Mice with disrupted skeletal muscle K{sub ATP} channels exhibit reduced adipocyte size and increased fatty acid release into the circulation. As yet, the molecular mechanisms underlying this link between skeletal muscle K{sub ATP} channel function and adipose mobilization have not been established. Here, we demonstrate that skeletal muscle-specific disruption of K{sub ATP} channel function in transgenic (TG) mice promotes production and secretion of musclin. Musclin is a myokine with high homology tomore » atrial natriuretic peptide (ANP) that enhances ANP signaling by competing for elimination. Augmented musclin production in TG mice is driven by a molecular cascade resulting in enhanced acetylation and nuclear exclusion of the transcription factor forkhead box O1 (FOXO1) – an inhibitor of transcription of the musclin encoding gene. Musclin production/secretion in TG is paired with increased mobilization of fatty acids and a clear trend toward increased circulating ANP, an activator of lipolysis. These data establish K{sub ATP} channel-dependent musclin production as a potential mechanistic link coupling “local” skeletal muscle energy consumption with mobilization of bodily resources from fat. Understanding such mechanisms is an important step toward designing interventions to manage metabolic disorders including those related to excess body fat and associated co-morbidities. - Highlights: • ATP-sensitive K{sup +} channels regulate musclin production by skeletal muscles. • Lipolytic ANP signaling is promoted by augmented skeletal muscle musclin production. • Skeletal muscle musclin transcription is promoted by a CaMKII/HDAC/FOXO1 pathway. • Musclin links adipose mobilization to energy use in K{sub ATP} channel deficient skeletal

  2. Smad4 restricts differentiation to promote expansion of satellite cell derived progenitors during skeletal muscle regeneration

    PubMed Central

    Paris, Nicole D; Soroka, Andrew; Klose, Alanna; Liu, Wenxuan; Chakkalakal, Joe V

    2016-01-01

    Skeletal muscle regenerative potential declines with age, in part due to deficiencies in resident stem cells (satellite cells, SCs) and derived myogenic progenitors (MPs); however, the factors responsible for this decline remain obscure. TGFβ superfamily signaling is an inhibitor of myogenic differentiation, with elevated activity in aged skeletal muscle. Surprisingly, we find reduced expression of Smad4, the downstream cofactor for canonical TGFβ superfamily signaling, and the target Id1 in aged SCs and MPs during regeneration. Specific deletion of Smad4 in adult mouse SCs led to increased propensity for terminal myogenic commitment connected to impaired proliferative potential. Furthermore, SC-specific Smad4 disruption compromised adult skeletal muscle regeneration. Finally, loss of Smad4 in aged SCs did not promote aged skeletal muscle regeneration. Therefore, SC-specific reduction of Smad4 is a feature of aged regenerating skeletal muscle and Smad4 is a critical regulator of SC and MP amplification during skeletal muscle regeneration. DOI: http://dx.doi.org/10.7554/eLife.19484.001 PMID:27855784

  3. Protein Availability and Satellite Cell Dynamics in Skeletal Muscle.

    PubMed

    Shamim, Baubak; Hawley, John A; Camera, Donny M

    2018-06-01

    Human skeletal muscle satellite cells are activated in response to both resistance and endurance exercise. It was initially proposed that satellite cell proliferation and differentiation were only required to support resistance exercise-induced hypertrophy. However, satellite cells may also play a role in muscle fibre remodelling after endurance-based exercise and extracellular matrix regulation. Given the importance of dietary protein, particularly branched chain amino acids, in supporting myofibrillar and mitochondrial adaptations to both resistance and endurance-based training, a greater understanding of how protein intake impacts satellite cell activity would provide further insight into the mechanisms governing skeletal muscle remodelling with exercise. While many studies have investigated the capacity for protein ingestion to increase post-exercise rates of muscle protein synthesis, few investigations have examined the role for protein ingestion to modulate satellite cell activity. Here we review the molecular mechanisms controlling the activation of satellite cells in response to mechanical stress and protein intake in both in vitro and in vivo models. We provide a mechanistic framework that describes how protein ingestion may enhance satellite activity and promote exercise adaptations in human skeletal muscle.

  4. EZH1 and EZH2 promote skeletal growth by repressing inhibitors of chondrocyte proliferation and hypertrophy

    PubMed Central

    Lui, Julian C.; Garrison, Presley; Nguyen, Quang; Ad, Michal; Keembiyehetty, Chithra; Chen, Weiping; Jee, Youn Hee; Landman, Ellie; Nilsson, Ola; Barnes, Kevin M.; Baron, Jeffrey

    2016-01-01

    Histone methyltransferases EZH1 and EZH2 catalyse the trimethylation of histone H3 at lysine 27 (H3K27), which serves as an epigenetic signal for chromatin condensation and transcriptional repression. Genome-wide associated studies have implicated EZH2 in the control of height and mutations in EZH2 cause Weaver syndrome, which includes skeletal overgrowth. Here we show that the combined loss of Ezh1 and Ezh2 in chondrocytes severely impairs skeletal growth in mice. Both of the principal processes underlying growth plate chondrogenesis, chondrocyte proliferation and hypertrophy, are compromised. The decrease in chondrocyte proliferation is due in part to derepression of cyclin-dependent kinase inhibitors Ink4a/b, while ineffective chondrocyte hypertrophy is due to the suppression of IGF signalling by the increased expression of IGF-binding proteins. Collectively, our findings reveal a critical role for H3K27 methylation in the regulation of chondrocyte proliferation and hypertrophy in the growth plate, which are the central determinants of skeletal growth. PMID:27897169

  5. Active shortening protects against stretch-induced force deficits in human skeletal muscle

    PubMed Central

    Saripalli, Anjali L.; Sugg, Kristoffer B.; Brooks, Susan V.

    2017-01-01

    Skeletal muscle contraction results from molecular interactions of myosin “crossbridges” with adjacent actin filament binding sites. The binding of myosin to actin can be “weak” or “strong,” and only strong binding states contribute to force production. During active shortening, the number of strongly bound crossbridges declines with increasing shortening velocity. Forcibly stretching a muscle that is actively shortening at high velocity results in no apparent negative consequences, whereas stretch of an isometrically (fixed-length) contracting muscle causes ultrastructural damage and a decline in force-generating capability. Our working hypothesis is that stretch-induced damage is uniquely attributable to the population of crossbridges that are strongly bound. We tested the hypothesis that stretch-induced force deficits decline as the prevailing shortening velocity is increased. Experiments were performed on permeabilized segments of individual skeletal muscle fibers obtained from human subjects. Fibers were maximally activated and allowed either to generate maximum isometric force (Fo), or to shorten at velocities that resulted in force maintenance of ≈50% Fo or ≈2% Fo. For each test condition, a rapid stretch equivalent to 0.1 × optimal fiber length was applied. Relative to prestretch Fo, force deficits resulting from stretches applied during force maintenance of 100, ≈50, and ≈2% Fo were 23.2 ± 8.6, 7.8 ± 4.2, and 0.3 ± 3.3%, respectively (means ± SD, n = 20). We conclude that stretch-induced damage declines with increasing shortening velocity, consistent with the working hypothesis that the fraction of strongly bound crossbridges is a causative factor in the susceptibility of skeletal muscle to stretch-induced damage. NEW & NOTEWORTHY Force deficits caused by stretch of contracting muscle are most severe when the stretch is applied during an isometric contraction, but prevented if the muscle is shortening at high velocity when the

  6. Genetic engineering for skeletal regenerative medicine.

    PubMed

    Gersbach, Charles A; Phillips, Jennifer E; García, Andrés J

    2007-01-01

    The clinical challenges of skeletal regenerative medicine have motivated significant advances in cellular and tissue engineering in recent years. In particular, advances in molecular biology have provided the tools necessary for the design of gene-based strategies for skeletal tissue repair. Consequently, genetic engineering has emerged as a promising method to address the need for sustained and robust cellular differentiation and extracellular matrix production. As a result, gene therapy has been established as a conventional approach to enhance cellular activities for skeletal tissue repair. Recent literature clearly demonstrates that genetic engineering is a principal factor in constructing effective methods for tissue engineering approaches to bone, cartilage, and connective tissue regeneration. This review highlights this literature, including advances in the development of efficacious gene carriers, novel cell sources, successful delivery strategies, and optimal target genes. The current status of the field and the challenges impeding the clinical realization of these approaches are also discussed.

  7. Transforming growth factor β-activated kinase 1 negatively regulates interleukin-1α-induced stromal-derived factor-1 expression in vascular smooth muscle cells

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yang, Bin; Li, Wei; Zheng, Qichang

    Stromal-derived Factor-1 (SDF-1) derived from vascular smooth muscle cells (VSMCs) contributes to vascular repair and remodeling in various vascular diseases. In this study, the mechanism underlying regulation of SDF-1 expression by interleukin-1α (IL-1α) was investigated in primary rat VSMCs. We found IL-1α promotes SDF-1 expression by up-regulating CCAAT-enhancer-binding protein β (C/EBPβ) in an IκB kinase β (IKKβ) signaling-dependent manner. Moreover, IL-1α-induced expression of C/EBPβ and SDF-1 was significantly potentiated by knockdown of transforming growth factor β-activated kinase 1 (TAK1), an upstream activator of IKKβ signaling. In addition, we also demonstrated that TAK1/p38 mitogen-activated protein kinase (p38 MAPK) signaling exerted negativemore » effect on IL-1α-induced expression of C/EBPβ and SDF-1 through counteracting ROS-dependent up-regulation of nuclear factor erythroid 2-related factor 2 (NRF2). In conclusion, TAK1 acts as an important regulator of IL-1α-induced SDF-1 expression in VSMCs, and modulating activity of TAK1 may serve as a potential strategy for modulating vascular repair and remodeling. - Highlights: • IL-1α induces IKKβ signaling-dependent SDF-1 expression by up-regulating C/EBPβ. • Activation of TAK1 by IL-1α negatively regulates C/EBPβ-dependent SDF-1 expression. • IL-1α-induced TAK1/p38 MAPK signaling counteracts ROS-dependent SDF-1 expression. • TAK1 counteracts IL-1α-induced SDF-1 expression by attenuating NRF2 up-regulation.« less

  8. The skeletal endocannabinoid system: clinical and experimental insights.

    PubMed

    Raphael, Bitya; Gabet, Yankel

    2016-05-01

    Recently, there has been a rapidly growing interest in the role of cannabinoids in the regulation of skeletal remodeling and bone mass, addressed in basic, translational and clinical research. Since the first publications in 2005, there are more than 1000 publications addressing the skeletal endocannabinoid system. This review focuses on the roles of the endocannabinoid system in skeletal biology via the cannabinoid receptors CB1, CB2 and others. Endocannabinoids play important roles in bone formation, bone resorption and skeletal growth, and are sometimes age, gender, species and strain dependent. Controversies in the literature and potential therapeutic approaches targeting the endocannabinoid system in skeletal disorders are also discussed.

  9. Exercise training and return to a well-balanced diet activate the neuregulin 1/ErbB pathway in skeletal muscle of obese rats

    PubMed Central

    Ennequin, Gaël; Boisseau, Nathalie; Caillaud, Kevin; Chavanelle, Vivien; Gerbaix, Maude; Metz, Lore; Etienne, Monique; Walrand, Stéphane; Masgrau, Aurélie; Guillet, Christelle; Courteix, Daniel; Niu, Airu; Li, Yi-Ping; Capel, Fréderic; Sirvent, Pascal

    2015-01-01

    Some studies suggest that the signalling pathway of neuregulin 1 (NRG1), a protein involved in the regulation of skeletal muscle metabolism, could be altered by nutritional and exercise interventions. We hypothesized that diet-induced obesity could lead to alterations of the NRG1 signalling pathway and that chronic exercise could improve NRG1 signalling in rat skeletal muscle. To test this hypothesis, male Wistar rats received a high fat/high sucrose (HF/HS) diet for 16 weeks. At the end of this period, NRG1 and ErbB expression/activity in skeletal muscle was assessed. The obese rats then continued the HF/HS diet or were switched to a well-balanced diet. Moreover, in both groups, half of the animals also performed low intensity treadmill exercise training. After another 8 weeks, NRG1 and ErbB expression/activity in skeletal muscle were tested again. The 16 week HF/HS diet induced obesity, but did not significantly affect the NRG1/ErbB signalling pathway in rat skeletal muscle. Conversely, after the switch to a well-balanced diet, NRG1 cleavage ratio and ErbB4 amount were increased. Chronic exercise training also promoted NRG1 cleavage, resulting in increased ErbB4 phosphorylation. This result was associated with increased protein expression and phosphorylation ratio of the metalloprotease ADAM17, which is involved in NRG1 shedding. Similarly, in vitro stretch-induced activation of ADAM17 in rat myoblasts induced NRG1 cleavage and ErbB4 activation. These results show that low intensity endurance training and well-balanced diet activate the NRG1-ErbB4 pathway, possibly via the metalloprotease ADAM17, in skeletal muscle of diet-induced obese rats. PMID:25820551

  10. Expression of the genes for insulin-like growth factors and their receptors in bone during skeletal growth

    NASA Technical Reports Server (NTRS)

    Bikle, D. D.; Harris, J.; Halloran, B. P.; Roberts, C. T.; Leroith, D.; Morey-Holton, E.

    1994-01-01

    Insulin-like growth factors (IGF) are important regulators of skeletal growth. To determine whether the capacity to produce and respond to these growth factors changes during skeletal development, we measured the protein and mRNA levels for IGF-I, IGF-II, and their receptors (IGF-IR and IGF-IIR, respectively) in the tibia and femur of rats before and up to 28 mo after birth. The mRNA levels remained high during fetal development but fell after birth, reaching a nadir by 3-6 wk. This fall was most pronounced for IGF-II and IGF-IIR mRNA and least pronounced for IGF-I mRNA. However, after 6 wk, both IGF-I and IGF-IR mRNA levels recovered toward the levels observed at birth. In the prenatal bones, the signals for the mRNAs of IGF-II and IGF-IIR were stronger than the signals for the mRNAs of IGF-I and IGF-IR, although the content of IGF-I was three- to fivefold greater than that of IGF-II. IGF-II levels fell postnatally, whereas the IGF-I content rose after birth such that the ratio IGF-I/IGF-II continued to increase with age. We conclude that, during development, rat bone changes its capacity to produce and respond to IGFs with a progressive trend toward the dominance of IGF-I.

  11. Non-synaptic ion channels in insects--basic properties of currents and their modulation in neurons and skeletal muscles.

    PubMed

    Wicher, D; Walther, C; Wicher, C

    2001-08-01

    Insects are favoured objects for studying information processing in restricted neuronal networks, e.g. motor pattern generation or sensory perception. The analysis of the underlying processes requires knowledge of the electrical properties of the cells involved. These properties are determined by the expression pattern of ionic channels and by the regulation of their function, e.g. by neuromodulators. We here review the presently available knowledge on insect non-synaptic ion channels and ionic currents in neurons and skeletal muscles. The first part of this article covers genetic and structural informations, the localization of channels, their electrophysiological and pharmacological properties, and known effects of second messengers and modulators such as neuropeptides or biogenic amines. In a second part we describe in detail modulation of ionic currents in three particularly well investigated preparations, i.e. Drosophila photoreceptor, cockroach DUM (dorsal unpaired median) neuron and locust jumping muscle. Ion channel structures are almost exclusively known for the fruitfly Drosophila, and most of the information on their function has also been obtained in this animal, mainly based on mutational analysis and investigation of heterologously expressed channels. Now the entire genome of Drosophila has been sequenced, it seems almost completely known which types of channel genes--and how many of them--exist in this animal. There is much knowledge of the various types of channels formed by 6-transmembrane--spanning segments (6TM channels) including those where four 6TM domains are joined within one large protein (e.g. classical Na+ channel). In comparison, two TM channels and 4TM (or tandem) channels so far have hardly been explored. There are, however, various well characterized ionic conductances, e.g. for Ca2+, Cl- or K+, in other insect preparations for which the channels are not yet known. In some of the larger insects, i.e. bee, cockroach, locust and moth

  12. NDR1 modulates the UV-induced DNA-damage checkpoint and nucleotide excision repair

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Park, Jeong-Min; Choi, Ji Ye; Yi, Joo Mi

    2015-06-05

    Nucleotide excision repair (NER) is the sole mechanism of UV-induced DNA lesion repair in mammals. A single round of NER requires multiple components including seven core NER factors, xeroderma pigmentosum A–G (XPA–XPG), and many auxiliary effector proteins including ATR serine/threonine kinase. The XPA protein helps to verify DNA damage and thus plays a rate-limiting role in NER. Hence, the regulation of XPA is important for the entire NER kinetic. We found that NDR1, a novel XPA-interacting protein, modulates NER by modulating the UV-induced DNA-damage checkpoint. In quiescent cells, NDR1 localized mainly in the cytoplasm. After UV irradiation, NDR1 accumulated inmore » the nucleus. The siRNA knockdown of NDR1 delayed the repair of UV-induced cyclobutane pyrimidine dimers in both normal cells and cancer cells. It did not, however, alter the expression levels or the chromatin association levels of the core NER factors following UV irradiation. Instead, the NDR1-depleted cells displayed reduced activity of ATR for some set of its substrates including CHK1 and p53, suggesting that NDR1 modulates NER indirectly via the ATR pathway. - Highlights: • NDR1 is a novel XPA-interacting protein. • NDR1 accumulates in the nucleus in response to UV irradiation. • NDR1 modulates NER (nucleotide excision repair) by modulating the UV-induced DNA-damage checkpoint response.« less

  13. The actin-related p41ARC subunit contributes to p21-activated kinase-1 (PAK1)-mediated glucose uptake into skeletal muscle cells.

    PubMed

    Tunduguru, Ragadeepthi; Zhang, Jing; Aslamy, Arianne; Salunkhe, Vishal A; Brozinick, Joseph T; Elmendorf, Jeffrey S; Thurmond, Debbie C

    2017-11-17

    Defects in translocation of the glucose transporter GLUT4 are associated with peripheral insulin resistance, preclinical diabetes, and progression to type 2 diabetes. GLUT4 recruitment to the plasma membrane of skeletal muscle cells requires F-actin remodeling. Insulin signaling in muscle requires p21-activated kinase-1 (PAK1), whose downstream signaling triggers actin remodeling, which promotes GLUT4 vesicle translocation and glucose uptake into skeletal muscle cells. Actin remodeling is a cyclic process, and although PAK1 is known to initiate changes to the cortical actin-binding protein cofilin to stimulate the depolymerizing arm of the cycle, how PAK1 might trigger the polymerizing arm of the cycle remains unresolved. Toward this, we investigated whether PAK1 contributes to the mechanisms involving the actin-binding and -polymerizing proteins neural Wiskott-Aldrich syndrome protein (N-WASP), cortactin, and ARP2/3 subunits. We found that the actin-polymerizing ARP2/3 subunit p41ARC is a PAK1 substrate in skeletal muscle cells. Moreover, co-immunoprecipitation experiments revealed that insulin stimulates p41ARC phosphorylation and increases its association with N-WASP coordinately with the associations of N-WASP with cortactin and actin. Importantly, all of these associations were ablated by the PAK inhibitor IPA3, suggesting that PAK1 activation lies upstream of these actin-polymerizing complexes. Using the N-WASP inhibitor wiskostatin, we further demonstrated that N-WASP is required for localized F-actin polymerization, GLUT4 vesicle translocation, and glucose uptake. These results expand the model of insulin-stimulated glucose uptake in skeletal muscle cells by implicating p41ARC as a new component of the insulin-signaling cascade and connecting PAK1 signaling to N-WASP-cortactin-mediated actin polymerization and GLUT4 vesicle translocation. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

  14. Bioreactor perfusion system for the long-term maintenance of tissue-engineered skeletal muscle organoids

    NASA Technical Reports Server (NTRS)

    Chromiak, J. A.; Shansky, J.; Perrone, C.; Vandenburgh, H. H.

    1998-01-01

    Three-dimensional skeletal muscle organ-like structures (organoids) formed in tissue culture by fusion of proliferating myoblasts into parallel networks of long, unbranched myofibers provide an in vivo-like model for examining the effects of growth factors, tension, and space flight on muscle cell growth and metabolism. To determine the feasibility of maintaining either avian or mammalian muscle organoids in a commercial perfusion bioreactor system, we measured metabolism, protein turnover. and autocrine/paracrine growth factor release rates. Medium glucose was metabolized at a constant rate in both low-serum- and serum-free media for up to 30 d. Total organoid noncollagenous protein and DNA content decreased approximately 22-28% (P < 0.05) over a 13-d period. Total protein synthesis rates could be determined accurately in the bioreactors for up to 30 h and total protein degradation rates could be measured for up to 3 wk. Special fixation and storage conditions necessary for space flight studies were validated as part of the studies. For example, the anabolic autocrine/paracrine skeletal muscle growth factors prostaglandin F2alpha (PGF2alpha) and insulin-like growth factor-1 (IGF-1) could be measured accurately in collected media fractions, even after storage at 37 degrees C for up to 10 d. In contrast, creatine kinase activity (a marker of cell damage) in collected media fractions was unreliable. These results provide initial benchmarks for long-term ex vivo studies of tissue-engineered skeletal muscle.

  15. Skeletal and chronological ages in American adolescents: current findings in skeletal maturation.

    PubMed

    Calfee, Ryan P; Sutter, Melanie; Steffen, Jennifer A; Goldfarb, Charles A

    2010-10-01

    This study was designed to assess the relationship between skeletal and chronological ages among current American adolescents using the Greulich and Pyle atlas for skeletal age determination. We used the Greulich and Pyle atlas to prospectively determine skeletal age in a group of 138 otherwise healthy American adolescents from 12 to 18 years of age. 62 males and 76 females were enrolled in this cohort. Paired Student t-tests were used to statistically compare the skeletal and chronological ages in this population. Subgroup analysis examined the effect of gender on differences between chronologic age and skeletal age. For the entire cohort, mean skeletal age was significantly greater than chronological age (mean 0.80 years, P < 0.01). In 29 cases (21%) the skeletal age was at least 2 years greater than the chronologic age. Among females, such cases with marked discrepancy occurred exclusively in those chronologically between 12 and 15 years of age (P < 0.01). Males demonstrated a 2-year or greater discrepancy more commonly than females (26 vs. 17%). In males, 2-year discrepancies were equally likely across chronologic ages (P = 0.82). Current American adolescents are significantly more mature by skeletal age, as determined by the Greulich and Pyle method, than their chronological age would suggest. The skeletal ages of females are most likely to markedly exceed chronologic age between the ages of 12-15 years.

  16. Satellite-like cells contribute to pax7-dependent skeletal muscle repair in adult zebrafish

    PubMed Central

    Berberoglu, Michael A.; Gallagher, Thomas L.; Morrow, Zachary T.; Talbot, Jared C.; Hromowyk, Kimberly J.; Tenente, Inês M.; Langenau, David M.; Amacher, Sharon L.

    2017-01-01

    Satellite cells, also known as muscle stem cells, are responsible for skeletal muscle growth and repair in mammals. Pax7 and Pax3 transcription factors are established satellite cell markers required for muscle development and regeneration, and there is great interest in identifying additional factors that regulate satellite cell proliferation, differentiation, and/or skeletal muscle regeneration. Due to the powerful regenerative capacity of many zebrafish tissues, even in adults, we are exploring the regenerative potential of adult zebrafish skeletal muscle. Here, we show that adult zebrafish skeletal muscle contains cells similar to mammalian satellite cells. Adult zebrafish satellite-like cells have dense heterochromatin, express Pax7 and Pax3, proliferate in response to injury, and show peak myogenic responses 4–5 days post-injury (dpi). Furthermore, using a pax7a-driven GFP reporter, we present evidence implicating satellite-like cells as a possible source of new muscle. In lieu of central nucleation, which distinguishes regenerating myofibers in mammals, we describe several characteristics that robustly identify newly-forming myofibers from surrounding fibers in injured adult zebrafish muscle. These characteristics include partially overlapping expression in satellite cells and regenerating myofibers of two RNA-binding proteins Rbfox2 and Rbfoxl1, known to regulate embryonic muscle development and function. Finally, by analyzing pax7a; pax7b double mutant zebrafish, we show that Pax7 is required for adult skeletal muscle repair, as it is in the mouse. PMID:28279710

  17. Chicken ovalbumin upstream promoter-transcription factor II regulates nuclear receptor, myogenic, and metabolic gene expression in skeletal muscle cells.

    PubMed

    Crowther, Lisa M; Wang, Shu-Ching Mary; Eriksson, Natalie A; Myers, Stephen A; Murray, Lauren A; Muscat, George E O

    2011-02-24

    We demonstrate that chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII) mRNA is more abundantly expressed (than COUP-TFI mRNA) in skeletal muscle C2C12 cells and in (type I and II) skeletal muscle tissue from C57BL/10 mice. Consequently, we have utilized the ABI TaqMan Low Density Array (TLDA) platform to analyze gene expression changes specifically attributable to ectopic COUP-TFII (relative to vector only) expression in muscle cells. Utilizing a TLDA-based platform and 5 internal controls, we analyze the entire NR superfamily, 96 critical metabolic genes, and 48 important myogenic regulatory genes on the TLDA platform utilizing 5 internal controls. The low density arrays were analyzed by rigorous statistical analysis (with Genorm normalization, Bioconductor R, and the Empirical Bayes statistic) using the (integromics) statminer software. In addition, we validated the differentially expressed patho-physiologically relevant gene (identified on the TLDA platform) glucose transporter type 4 (Glut4). We demonstrated that COUP-TFII expression increased the steady state levels of Glut4 mRNA and protein, while ectopic expression of truncated COUP-TFII lacking helix 12 (COUP-TFΔH12) reduced Glut4 mRNA expression in C2C12 cells. Moreover, COUP-TFII expression trans-activated the Glut4 promoter (-997/+3), and ChIP analysis identified selective recruitment of COUP-TFII to a region encompassing a highly conserved SP1 binding site (in mouse, rat, and human) at nt positions -131/-118. Mutation of the SpI site ablated COUP-TFII mediated trans-activation of the Glut4 promoter. In conclusion, this study demonstrates that in skeletal muscle cells, COUP-TFII regulates several nuclear hormone receptors, and critical metabolic and muscle specific genes.

  18. Fibroblast growth factor receptor signaling crosstalk in skeletogenesis.

    PubMed

    Miraoui, Hichem; Marie, Pierre J

    2010-11-02

    Fibroblast growth factors (FGFs) play important roles in the control of embryonic and postnatal skeletal development by activating signaling through FGF receptors (FGFRs). Germline gain-of-function mutations in FGFR constitutively activate FGFR signaling, causing chondrocyte and osteoblast dysfunctions that result in skeletal dysplasias. Crosstalk between the FGFR pathway and other signaling cascades controls skeletal precursor cell differentiation. Genetic analyses revealed that the interplay of WNT and FGFR1 determines the fate and differentiation of mesenchymal stem cells during mouse craniofacial skeletogenesis. Additionally, interactions between FGFR signaling and other receptor tyrosine kinase networks, such as those mediated by the epidermal growth factor receptor and platelet-derived growth factor receptor α, were associated with excessive osteoblast differentiation and bone formation in the human skeletal dysplasia called craniosynostosis, which is a disorder of skull development. We review the roles of FGFR signaling and its crosstalk with other pathways in controlling skeletal cell fate and discuss how this crosstalk could be pharmacologically targeted to correct the abnormal cell phenotype in skeletal dysplasias caused by aberrant FGFR signaling.

  19. Sodium butyrate epigenetically modulates high-fat diet-induced skeletal muscle mitochondrial adaptation, obesity and insulin resistance through nucleosome positioning

    PubMed Central

    Henagan, Tara M; Stefanska, Barbara; Fang, Zhide; Navard, Alexandra M; Ye, Jianping; Lenard, Natalie R; Devarshi, Prasad P

    2015-01-01

    Background and Purpose Sodium butyrate (NaB), an epigenetic modifier, is effective in promoting insulin sensitivity. The specific genomic loci and mechanisms underlying epigenetically induced obesity and insulin resistance and the targets of NaB are not fully understood. Experimental Approach The anti-diabetic and anti-obesity effects of NaB treatment were measured by comparing phenotypes and physiologies of C57BL/6J mice fed a low-fat diet (LF), high-fat diet (HF) or high-fat diet plus NaB (HF + NaB) for 10 weeks. We determined a possible mechanism of NaB action through induction of beneficial skeletal muscle mitochondrial adaptations and applied microccocal nuclease digestion with sequencing (MNase-seq) to assess whole genome differences in nucleosome occupancy or positioning and to identify associated epigenetic targets of NaB. Key Results NaB prevented HF diet-induced increases in body weight and adiposity without altering food intake or energy expenditure, improved insulin sensitivity as measured by glucose and insulin tolerance tests, and decreased respiratory exchange ratio. In skeletal muscle, NaB increased the percentage of type 1 fibres, improved acylcarnitine profiles as measured by metabolomics and produced a chromatin structure, determined by MNase-seq, similar to that seen in LF. Targeted analysis of representative nuclear-encoded mitochondrial genes showed specific repositioning of the −1 nucleosome in association with altered gene expression. Conclusions and Implications NaB treatment may be an effective pharmacological approach for type 2 diabetes and obesity by inducing −1 nucleosome repositioning within nuclear-encoded mitochondrial genes, causing skeletal muscle mitochondrial adaptations that result in more complete β-oxidation and a lean, insulin sensitive phenotype. PMID:25559882

  20. Discovery of Aminopiperidine Indoles That Activate the Guanine Nucleotide Exchange Factor SOS1 and Modulate RAS Signaling.

    PubMed

    Abbott, Jason R; Hodges, Timothy R; Daniels, R Nathan; Patel, Pratiq A; Kennedy, Jack Phillip; Howes, Jennifer E; Akan, Denis T; Burns, Michael C; Sai, Jiqing; Sobolik, Tammy; Beesetty, Yugandhar; Lee, Taekyu; Rossanese, Olivia W; Phan, Jason; Waterson, Alex G; Fesik, Stephen W

    2018-06-01

    Deregulated RAS activity, often the result of mutation, is implicated in approximately 30% of all human cancers. Despite this statistic, no clinically successful treatment for RAS-driven tumors has yet been developed. One approach for modulating RAS activity is to target and affect the activity of proteins that interact with RAS, such as the guanine nucleotide exchange factor (GEF) son of sevenless homologue 1 (SOS1). Here, we report on structure-activity relationships (SAR) in an indole series of compounds. Using structure-based design, we systematically explored substitution patterns on the indole nucleus, the pendant amino acid moiety, and the linker unit that connects these two fragments. Best-in-class compounds activate the nucleotide exchange process at sub-micromolar concentrations in vitro, increase levels of active RAS-GTP in HeLa cells, and elicit signaling changes in the mitogen-activated protein kinase/extracellular regulated kinase (MAPK/ERK) pathway, resulting in a decrease in pERK1/2 T202/Y204 protein levels at higher compound concentrations.

  1. Transcription factor specificity protein 1 modulates TGFβ1/Smad signaling to negatively regulate SIGIRR expression by human M1 macrophages stimulated with substance P.

    PubMed

    Yamaguchi, Rui; Sakamoto, Arisa; Yamaguchi, Reona; Haraguchi, Misa; Narahara, Shinji; Sugiuchi, Hiroyuki; Yamaguchi, Yasuo

    2018-08-01

    The stimuli inducing expression of single immunoglobulin IL-1-related receptor (SIGIRR) and the relevant regulatory mechanisms are not well defined. Transforming growth factor β1 (TGFβ1) delays internalization of neurokinin-1 receptor (NK1R) and subsequently enhances cellular signaling. This study investigated the effect of TGFβ1 on SIGIRR protein production by human M1 macrophages in response to stimulation with substance P (SP). SP caused upregulation of SIGIRR expression in a concentration-dependent manner, whereas aprepitant (an NK1R inhibitor) blunted this response. Silencing p38γMAPK or TAK-1 partially attenuated the response to SP stimulation, while TGFβ1/2/3 siRNA dramatically diminished it. SP induced much greater SIGIRR protein production than either lipopolysaccharide (a TLR4 agonist) or resiquimod (a TLR7/8 agonist). Unexpectedly, silencing of transcription factor specificity protein 1 (Sp1) led to significant upregulation of SIGIRR expression after SP stimulation, while KLF2 siRNA only partially enhanced it and Fli-1 siRNA reduced it. SP also upregulated TGFβ1 expression, along with a corresponding increase of SIGIRR protein, whereas silencing TGFβ1/2/3 blunted these responses. Sp1 siRNA or mithramycin (a gene-selective Sp1 inhibitor) significantly enhanced the expression of TGFβ1 and SIGIRR by macrophages after SP stimulation. Importantly, this effect of Sp1 siRNA on TGFβ1 and SIGIRR was blunted by siRNA for Smad2, Smad3, or Smad4, but not by TAK-1 siRNA. Next, we investigated the influence of transcription factor cross-talk on SIGIRR expression in response to SP. Co-transfection of macrophages with Sp1 siRNA and C/EBPβ or TIF1β siRNA attenuated the upregulation of SIGIRR by SP, while a combination of Sp1 siRNA and Fli-1 siRNA dramatically diminished it. In conclusion, TGFβ1 may be an intermediary between SP/NK1R activation and SIGIRR expression in Sp1 siRNA-transfected macrophages. In addition, Sp1 modulates TGFβ1/Smad signaling and

  2. β1- and β2-adrenergic receptor stimulation differ in their effects on PGC-1α and atrogin-1/MAFbx gene expression in chick skeletal muscle.

    PubMed

    Shimamoto, Saki; Ijiri, Daichi; Kawaguchi, Mana; Nakashima, Kazuki; Tada, Osamu; Inoue, Hiroki; Ohtsuka, Akira

    2017-09-01

    Adrenaline changes expression of the genes encoding peroxisome proliferator-activated receptor-gamma coactivator-1 alpha (PGC-1α), which is known as a regulator of muscle size, and atrogin-1/muscle atrophy F-box (MAFbx), which is a muscle-specific ubiquitin ligase. However, the subtype of β-adrenergic receptor (β-AR) involved in regulating these genes in skeletal muscle is not yet well defined. In this study, the effects of intraperitoneal injection of adrenaline and three β 1-3 -AR selective agonists on chick skeletal muscle metabolism were examined, to evaluate the functions of β-AR subtypes. Adrenaline decreased atrogin-1/MAFbx mRNA levels accompanied by an increase in PGC-1α mRNA and protein levels. However, among the three selective agonists, only the β 1 -AR agonist, dobutamine, increased PGC-1α mRNA and protein levels, while the β 2 -AR agonist, clenbuterol, suppressed atrogin-1/MAFbx mRNA levels. In addition, preinjection of the β 1 -AR antagonist, acebutolol, and the β 2 -AR antagonist, butoxamine, inhibited the adrenaline-induced increase in PGC-1α mRNA levels and the decrease in atrogin-1/MAFbx mRNA levels, respectively. Compared with adrenaline administration, the β 3 -AR agonist, BRL37344, decreased PGC-1α mRNA levels and increased atrogin-1/MAFbx mRNA levels. These results suggest that, in chick skeletal muscle, PGC-1α is induced via the β 1 -AR, while atrogin-1/MAFbx is suppressed via the β 2 -AR. Copyright © 2017. Published by Elsevier Inc.

  3. Skeletal fluorosis in relation to drinking water in rural areas of West Azerbaijan, Iran.

    PubMed

    Mohammadi, Ali Akbar; Yousefi, Mahmood; Yaseri, Mehdi; Jalilzadeh, Mohsen; Mahvi, Amir Hossein

    2017-12-11

    Skeletal fluorosis resulting from high fluoride level in drinking water is a major public health problem. The present study evaluated the association between exposures to drinking water fluoride and skeletal fluorosis in 5 villages of Poldasht County, Iran. All the data and information on the prevalence of bone diseases were obtained from the Health Record Department, Poldasht Health Centre. To obtain the odds ratio of bone disease problem in different risk factors, when considering the cluster effect of rural area, logistic regression in a multilevel model was used. Results showed that skeletal fluorosis of people who live in areas with high fluoride concentration is 18.1% higher than that of individuals who live in areas with low fluoride concentration. Skeletal fluorosis (54.5%) was observed in the age group of 71 years and above, and was more commonly found in females than males. According to Unadjusted, individuals who consume ≤3 unit milk and dairy products per week have almost the same level of bone diseases as compared to those that consume more than 3 units. This study indicated that, skeletal fluorosis is a general health problem in these rural areas because the results revealed that high percentage of the studied population had symptoms of skeletal fluorosis.

  4. Acetylcholine Modulates the Hormones of the Growth Hormone/Insulinlike Growth Factor-1 Axis During Development in Mice.

    PubMed

    Lecomte, Marie-José; Bertolus, Chloé; Ramanantsoa, Nélina; Saurini, Françoise; Callebert, Jacques; Sénamaud-Beaufort, Catherine; Ringot, Maud; Bourgeois, Thomas; Matrot, Boris; Collet, Corinne; Nardelli, Jeannette; Mallet, Jacques; Vodjdani, Guilan; Gallego, Jorge; Launay, Jean-Marie; Berrard, Sylvie

    2018-04-01

    Pituitary growth hormone (GH) and insulinlike growth factor (IGF)-1 are anabolic hormones whose physiological roles are particularly important during development. The activity of the GH/IGF-1 axis is controlled by complex neuroendocrine systems including two hypothalamic neuropeptides, GH-releasing hormone (GHRH) and somatostatin (SRIF), and a gastrointestinal hormone, ghrelin. The neurotransmitter acetylcholine (ACh) is involved in tuning GH secretion, and its GH-stimulatory action has mainly been shown in adults but is not clearly documented during development. ACh, together with these hormones and their receptors, is expressed before birth, and somatotroph cells are already responsive to GHRH, SRIF, and ghrelin. We thus hypothesized that ACh could contribute to the modulation of the main components of the somatotropic axis during development. In this study, we generated a choline acetyltransferase knockout mouse line and showed that heterozygous mice display a transient deficit in ACh from embryonic day 18.5 to postnatal day 10, and they recover normal ACh levels from the second postnatal week. This developmental ACh deficiency had no major impact on weight gain and cardiorespiratory status of newborn mice. Using this mouse model, we found that endogenous ACh levels determined the concentrations of circulating GH and IGF-1 at embryonic and postnatal stages. In particular, serum GH level was correlated with brain ACh content. ACh also modulated the levels of GHRH and SRIF in the hypothalamus and ghrelin in the stomach, and it affected the levels of these hormones in the circulation. This study identifies ACh as a potential regulator of the somatotropic axis during the developmental period.

  5. Effects of exercise training on brain-derived neurotrophic factor in skeletal muscle and heart of rats post myocardial infarction.

    PubMed

    Lee, Heow Won; Ahmad, Monir; Wang, Hong-Wei; Leenen, Frans H H

    2017-03-01

    What is the central question of this study? Exercise training increases brain-derived neurotrophic factor (BDNF) in the hippocampus, which depends on a myokine, fibronectin type III domain-containing protein 5 (FNDC5). Whether exercise training after myocardial infarction induces parallel increases in FNDC5 and BDNF expression in skeletal muscle and the heart has not yet been studied. What is the main finding and its importance? Exercise training after myocardial infarction increases BDNF protein in skeletal muscle and the non-infarct area of the LV without changes in FNDC5 protein, suggesting that BDNF is not regulated by FNDC5 in skeletal muscle and heart. An increase in cardiac BDNF may contribute to the improvement of cardiac function by exercise training. Exercise training after myocardial infarction (MI) attenuates progressive left ventricular (LV) remodelling and dysfunction, but the peripheral stimuli induced by exercise that trigger these beneficial effects are still unclear. We investigated as possible mediators fibronectin type III domain-containing protein 5 (FNDC5) and brain-derived neurotrophic factor (BDNF) in the skeletal muscle and heart. Male Wistar rats underwent either sham surgery or ligation of the left descending coronary artery, and surviving MI rats were allocated to either a sedentary (Sed-MI) or an exercise group (ExT-MI). Exercise training was done for 4 weeks on a motor-driven treadmill. At the end, LV function was evaluated, and FNDC5 and BDNF mRNA and protein were assessed in soleus muscle, quadriceps and non-, peri- and infarct areas of the LV. At 5 weeks post MI, FNDC5 mRNA was decreased in soleus muscle and all areas of the LV, but FNDC5 protein was increased in the soleus muscle and the infarct area. Mature BDNF (mBDNF) protein was decreased in the infarct area without a change in mRNA. Exercise training attenuated the decrease in ejection fraction and the increase in LV end-diastolic pressure post MI. Exercise training had no

  6. Skeletal muscle growth and fiber composition in mice are regulated through the transcription factors STAT5a/b: linking growth hormone to the androgen receptor.

    PubMed

    Klover, Peter; Chen, Weiping; Zhu, Bing-Mei; Hennighausen, Lothar

    2009-09-01

    In skeletal muscle, STAT5a/b transcription factors are critical for normal postnatal growth, whole-animal glucose homeostasis, and local IGF-1 production. These observations have led us to hypothesize that STAT5a/b are critical for maintenance of normal muscle mass and function. To investigate this, mice with a skeletal muscle-specific deletion of the Stat5a/b genes (Stat5MKO) were used. Stat5MKO mice displayed reduced muscle mass, altered fiber-type distribution and reduced activity. On a molecular level, gene expression in skeletal muscle of Stat5MKO and control mice was analyzed by microarrays and real-time PCR, both in the presence and absence of growth hormone (GH) stimulation. Expression of several genes involved in muscle growth and fiber type were significantly changed. Specifically, in the quadriceps, a muscle almost exclusively composed of type II fibers, the absence of STAT5a/b led to increased expression of several genes associated with type I fibers and the de novo appearance of type I fibers. In addition, it is shown here that expression of the androgen receptor gene (Ar) is controlled by GH through STAT5a/b. The link between STAT5a/b and Ar gene is likely through direct transcriptional regulation, as chromatin immunoprecipitaion of the Ar promoter region in C2C12 myoblasts was accomplished by antibodies against STAT5a. These experiments demonstrate an important role for STAT5a/b in skeletal muscle physiology, and they provide a direct link to androgen signaling.

  7. Imbalance in SOD/CAT activities in rat skeletal muscles submitted to treadmill training exercise.

    PubMed

    Pinho, Ricardo A; Andrades, Michael E; Oliveira, Marcos R; Pirola, Aline C; Zago, Morgana S; Silveira, Paulo C L; Dal-Pizzol, Felipe; Moreira, José Cláudio F

    2006-10-01

    The association between physical exercise and oxidative damage in the skeletal musculature has been the focus of many studies in literature, but the balance between superoxide dismutase and catalase activities and its relation to oxidative damage is not well established. Thus, the aim of the present study was to investigate the association between regular treadmill physical exercise, oxidative damage and antioxidant defenses in skeletal muscle of rats. Fifteen male Wistar rats (8-12 months) were randomly separated into two groups (trained n=9 and untrained n=6). Trained rats were treadmill-trained for 12 weeks in progressive exercise (velocity, time, and inclination). Training program consisted in a progressive exercise (10 m/min without inclination for 10 min/day). After 1 week the speed, time and inclination were gradually increased until 17 m/min at 10% for 50 min/day. After the training period animals were killed, and gastrocnemius and quadriceps were surgically removed to the determination of biochemical parameters. Lipid peroxidation, protein oxidative damage, catalase, superoxide dismutase and citrate synthase activities, and muscular glycogen content were measured in the isolated muscles. We demonstrated that there is a different modulation of CAT and SOD in skeletal muscle in trained rats when compared to untrained rats (increased SOD/CAT ratio). TBARS levels were significantly decreased and, in contrast, a significant increase in protein carbonylation was observed. These results suggest a non-described adaptation of skeletal muscle against exercise-induced oxidative stress.

  8. Insulin modulates energy and substrate sensing and protein catabolism induced by chronic peritonitis in skeletal muscle of neonatal pigs

    USDA-ARS?s Scientific Manuscript database

    Acute infection promotes skeletal muscle wasting and insulin resistance, but the effect of insulin on energy and substrate sensing in skeletal muscle of chronically infected neonates has not been studied. Eighteen 2-d-old pigs underwent cecal ligation and puncture (CLP) or sham surgery (CON) to ind...

  9. The relationships among IGF-1, DNA content, and protein accumulation during skeletal muscle hypertrophy

    NASA Technical Reports Server (NTRS)

    Adams, G. R.; Haddad, F.

    1996-01-01

    Insulin-like growth factor-1 (IGF-1) is known to have anabolic effects on skeletal muscle cells. This study examined the time course of muscle hypertrophy and associated IGF-1 peptide and mRNA expression. Data were collected at 3, 7, 14, and 28 days after surgical removal of synergistic muscles of both normal and hypophysectomized (HX) animals. Overloading increased the plantaris (Plant) mass, myofiber size, and protein-to-body weight ratio in both groups (normal and HX; P < 0.05). Muscle IGF-1 peptide levels peaked at 3 (normal) and 7 (HX) days of overloading with maximum 4.1-fold (normal) and 6.2-fold (HX) increases. Increases in muscle IGF-1 preceded the hypertrophic response. Total DNA content of the overloaded Plant increased in both groups. There was a strong positive relationship between IGF-1 peptide and DNA content in the overloaded Plant from both groups. These results indicate that 1) the muscles from rats with both normal and severely depressed systemic levels of IGF-1 respond to functional overload with an increase in local IGF-1 expression and 2) this elevated IGF-1 may be contributing to the hypertrophy response, possibly via the mobilization of satellite cells to provide increases in muscle DNA.

  10. RACK1 binds to Smad3 to modulate transforming growth factor-beta1-stimulated alpha2(I) collagen transcription in renal tubular epithelial cells.

    PubMed

    Okano, Kazuhiro; Schnaper, H William; Bomsztyk, Karol; Hayashida, Tomoko

    2006-09-08

    Although it is clear that transforming growth factor-beta1 (TGF-beta1) is critical for renal fibrogenesis, the complexity of the involved mechanisms is increasingly apparent. TGF-beta1 stimulates phosphorylation of Smad2/3 and activates other signaling molecules as well. The molecular link between these other kinases and Smads is not known. We sought new binding partners for Smad3 in renal cells and identified receptor for activated protein kinase C 1 (RACK1) as a novel binding partner of Smad3. The linker region of Smad3 and the tryptophan-aspartic acid repeat 6 and 7 of RACK1 are sufficient for the association. RACK1 also interacts with Smad3 in the human kidney epithelial cell line, HKC. Silencing RACK1 increases transcriptional activity of TGF-beta1-responsive promoter sequences of the Smad binding element (SBE), p3TP-Lux, and alpha2(I) collagen. Conversely, overexpressed RACK1 negatively modulates alpha2(I) collagen transcriptional activity in TGF-beta1-stimulated cells. RACK1 did not affect phosphorylation of Smad3 at the C terminus or in the linker region. However, RACK1 reduced direct binding of Smad3 to the SBE motif. Mutating a RACK1 tyrosine at residue 246, but not at 228, decreased the inhibitory effect of RACK1 on both alpha2(I) collagen promoter activity and Smad binding to SBE induced by TGF-beta1. These results suggest that RACK1 modulates transcription of alpha2(I) collagen by TGF-beta1 through interference with Smad3 binding to the gene promoter.

  11. Expression of interleukin-15 and inflammatory cytokines in skeletal muscles of STZ-induced diabetic rats: effect of resistance exercise training.

    PubMed

    Molanouri Shamsi, M; Hassan, Z H; Gharakhanlou, R; Quinn, L S; Azadmanesh, K; Baghersad, L; Isanejad, A; Mahdavi, M

    2014-05-01

    Skeletal muscle atrophy is associated with type-1 diabetes. Skeletal muscle is the source of pro- and anti-inflammatory cytokines that can mediate muscle hypertrophy and atrophy, while resistance exercise can modulate both muscle mass and muscle cytokine expression. This study determined the effects of a 5-week resistance exercise training regimen on the expression of muscle cytokines in healthy and streptozotocin-induced diabetic rats, with special emphasis on interleukin-15 (IL-15), a muscle-derived cytokine proposed to be involved in muscle hypertrophy or responses to stress. Induction of diabetes reduced muscle weight in both the fast flexor hallucis longus (FHL) and slow soleus muscles, while resistance training preserved FHL muscle weight in diabetic rats. IL-15 protein content was increased by training in both FHL and soleus muscles, as well as serum, in normal and diabetic rats. With regard to proinflammatory cytokines, muscle IL-6 levels were increased in diabetic rats, while training decreased muscle IL-6 levels in diabetic rats; training had no effect on FHL muscle IL-6 levels in healthy rats. Also, tumor necrosis factor-alpha (TNF-α) and IL-1β levels were increased by diabetes, but not changed by training. In conclusion, we found that in diabetic rats, resistance training increased muscle and serum IL-15 levels, decreased muscle IL-6 levels, and preserved FHL muscle mass.

  12. Detection of eQTL modules mediated by activity levels of transcription factors.

    PubMed

    Sun, Wei; Yu, Tianwei; Li, Ker-Chau

    2007-09-01

    Studies of gene expression quantitative trait loci (eQTL) in different organisms have shown the existence of eQTL hot spots: each being a small segment of DNA sequence that harbors the eQTL of a large number of genes. Two questions of great interest about eQTL hot spots arise: (1) which gene within the hot spot is responsible for the linkages, i.e. which gene is the quantitative trait gene (QTG)? (2) How does a QTG affect the expression levels of many genes linked to it? Answers to the first question can be offered by available biological evidence or by statistical methods. The second question is harder to address. One simple situation is that the QTG encodes a transcription factor (TF), which regulates the expression of genes linked to it. However, previous results have shown that TFs are not overrepresented in the eQTL hot spots. In this article, we consider the scenario that the propagation of genetic perturbation from a QTG to other linked genes is mediated by the TF activity. We develop a procedure to detect the eQTL modules (eQTL hot spots together with linked genes) that are compatible with this scenario. We first detect 27 eQTL modules from a yeast eQTL data, and estimate TF activity profiles using the method of Yu and Li (2005). Then likelihood ratio tests (LRTs) are conducted to find 760 relationships supporting the scenario of TF activity mediation: (DNA polymorphism --> cis-linked gene --> TF activity --> downstream linked gene). They are organized into 4 eQTL modules: an amino acid synthesis module featuring a cis-linked gene LEU2 and the mediating TF Leu3; a pheromone response module featuring a cis-linked gene GPA1 and the mediating TF Ste12; an energy-source control module featuring two cis-linked genes, GSY2 and HAP1, and the mediating TF Hap1; a mitotic exit module featuring four cis-linked genes, AMN1, CSH1, DEM1 and TOS1, and the mediating TF complex Ace2/Swi5. Gene Ontology is utilized to reveal interesting functional groups of the downstream

  13. Skeletal Muscle Tissue Engineering: Methods to Form Skeletal Myotubes and Their Applications

    PubMed Central

    Ostrovidov, Serge; Hosseini, Vahid; Ahadian, Samad; Fujie, Toshinori; Parthiban, Selvakumar Prakash; Ramalingam, Murugan; Bae, Hojae; Kaji, Hirokazu

    2014-01-01

    Skeletal muscle tissue engineering (SMTE) aims to repair or regenerate defective skeletal muscle tissue lost by traumatic injury, tumor ablation, or muscular disease. However, two decades after the introduction of SMTE, the engineering of functional skeletal muscle in the laboratory still remains a great challenge, and numerous techniques for growing functional muscle tissues are constantly being developed. This article reviews the recent findings regarding the methodology and various technical aspects of SMTE, including cell alignment and differentiation. We describe the structure and organization of muscle and discuss the methods for myoblast alignment cultured in vitro. To better understand muscle formation and to enhance the engineering of skeletal muscle, we also address the molecular basics of myogenesis and discuss different methods to induce myoblast differentiation into myotubes. We then provide an overview of different coculture systems involving skeletal muscle cells, and highlight major applications of engineered skeletal muscle tissues. Finally, potential challenges and future research directions for SMTE are outlined. PMID:24320971

  14. Skeletal muscle hypertrophy and regeneration: interplay between the myogenic regulatory factors (MRFs) and insulin-like growth factors (IGFs) pathways.

    PubMed

    Zanou, Nadège; Gailly, Philippe

    2013-11-01

    Adult skeletal muscle can regenerate in response to muscle damage. This ability is conferred by the presence of myogenic stem cells called satellite cells. In response to stimuli such as injury or exercise, these cells become activated and express myogenic regulatory factors (MRFs), i.e., transcription factors of the myogenic lineage including Myf5, MyoD, myogenin, and Mrf4 to proliferate and differentiate into myofibers. The MRF family of proteins controls the transcription of important muscle-specific proteins such as myosin heavy chain and muscle creatine kinase. Different growth factors are secreted during muscle repair among which insulin-like growth factors (IGFs) are the only ones that promote both muscle cell proliferation and differentiation and that play a key role in muscle regeneration and hypertrophy. Different isoforms of IGFs are expressed during muscle repair: IGF-IEa, IGF-IEb, or IGF-IEc (also known as mechano growth factor, MGF) and IGF-II. MGF is expressed first and is observed in satellite cells and in proliferating myoblasts whereas IGF-Ia and IGF-II expression occurs at the state of muscle fiber formation. Interestingly, several studies report the induction of MRFs in response to IGFs stimulation. Inversely, IGFs expression may also be regulated by MRFs. Various mechanisms are proposed to support these interactions. In this review, we describe the general process of muscle hypertrophy and regeneration and decipher the interactions between the two groups of factors involved in the process.

  15. The IGF-1/Akt/S6 pathway and expressions of glycolytic myosin heavy chain isoforms are upregulated in chicken skeletal muscle during the first week after hatching.

    PubMed

    Saneyasu, Takaoki; Tsuchihashi, Tatsuya; Kitashiro, Ayana; Tsuchii, Nami; Kimura, Sayaka; Honda, Kazuhisa; Kamisoyama, Hiroshi

    2017-11-01

    Skeletal muscle mass is an important trait in the animal industry. We previously reported an age-dependent downregulation of the insulin-like growth factor 1 (IGF-1)/Akt/S6 pathway, major protein synthesis pathway, in chicken breast muscle after 1 week of age, despite a continuous increase of breast muscle weight. Myosin heavy chain (HC), a major protein in muscle fiber, has several isoforms depending on chicken skeletal muscle types. HC I (fast-twitch glycolytic type) is known to be expressed in adult chicken breast muscle. However, little is known about the changes in the expression levels of protein synthesis-related factors and HC isoforms in perihatching chicken muscle. In the present study, protein synthesis-related factors, such as IGF-1 messenger RNA (mRNA) levels, phosphorylation of Akt, and phosphorylated S6 content, increased in an age-dependent manner after post-hatch day (D) 0. The mRNA levels of HC I, III and V (fast-twitch glycolytic type) dramatically increased after D0. The increase ratio of breast muscle weight was approximately 1100% from D0 to D7. To our knowledge, these findings provide the first evidence that upregulation of protein synthesis pathway and transcription of fast twitch glycolytic HC isoforms play critical roles in the increase of chicken breast muscle weight during the first week after hatching. © 2017 Japanese Society of Animal Science.

  16. Functional modules of sigma factor regulons guarantee adaptability and evolvability

    PubMed Central

    Binder, Sebastian C.; Eckweiler, Denitsa; Schulz, Sebastian; Bielecka, Agata; Nicolai, Tanja; Franke, Raimo; Häussler, Susanne; Meyer-Hermann, Michael

    2016-01-01

    The focus of modern molecular biology turns from assigning functions to individual genes towards understanding the expression and regulation of complex sets of molecules. Here, we provide evidence that alternative sigma factor regulons in the pathogen Pseudomonas aeruginosa largely represent insulated functional modules which provide a critical level of biological organization involved in general adaptation and survival processes. Analysis of the operational state of the sigma factor network revealed that transcription factors functionally couple the sigma factor regulons and significantly modulate the transcription levels in the face of challenging environments. The threshold quality of newly evolved transcription factors was reached faster and more robustly in in silico testing when the structural organization of sigma factor networks was taken into account. These results indicate that the modular structures of alternative sigma factor regulons provide P. aeruginosa with a robust framework to function adequately in its environment and at the same time facilitate evolutionary change. Our data support the view that widespread modularity guarantees robustness of biological networks and is a key driver of evolvability. PMID:26915971

  17. Exercise-induced TBC1D1 Ser237 phosphorylation and 14-3-3 protein binding capacity in human skeletal muscle.

    PubMed

    Frøsig, Christian; Pehmøller, Christian; Birk, Jesper B; Richter, Erik A; Wojtaszewski, Jørgen F P

    2010-11-15

    TBC1D1 is a Rab-GTPase activating protein involved in regulation of GLUT4 translocation in skeletal muscle. We here evaluated exercise-induced regulation of TBC1D1 Ser237 phosphorylation and 14-3-3 protein binding capacity in human skeletal muscle. In separate experiments healthy men performed all-out cycle exercise lasting either 30 s, 2  min or 20  min. After all exercise protocols, TBC1D1 Ser237 phosphorylation increased (∼70-230%, P < 0.005), with the greatest response observed after 20  min of cycling. Interestingly, capacity of TBC1D1 to bind 14-3-3 protein showed a similar pattern of regulation, increasing 60-250% (P < 0.001). Furthermore, recombinant 5AMP-activated protein kinase (AMPK) induced both Ser237 phosphorylation and 14-3-3 binding properties on human TBC1D1 when evaluated in vitro. To further characterize the role of AMPK as an upstream kinase regulating TBC1D1, extensor digitorum longus muscle (EDL) from whole body α1 or α2 AMPK knock-out and wild-type mice were stimulated to contract in vitro. In wild-type and α1 knock-out mice, contractions resulted in a similar ∼100% increase (P < 0.001) in Ser237 phosphorylation. Interestingly, muscle of α2 knock-out mice were characterized by reduced protein content of TBC1D1 (∼50%, P < 0.001) as well as in basal and contraction-stimulated (∼60%, P < 0.001) Ser237 phosphorylation, even after correction for the reduced TBC1D1 protein content. This study shows that TBC1D1 is Ser237 phosphorylated and 14-3-3 protein binding capacity is increased in response to exercise in human skeletal muscle. Furthermore, we show that the catalytic α2 AMPK subunit is the main (but probably not the only) donor of AMPK activity regulating TBC1D1 Ser237 phosphorylation in mouse EDL muscle.

  18. Thyroid hormones regulate skeletal muscle regeneration after acute injury.

    PubMed

    Leal, Anna Lúcia R C; Albuquerque, João Paulo C; Matos, Marina S; Fortunato, Rodrigo S; Carvalho, Denise P; Rosenthal, Doris; da Costa, Vânia Maria Corrêa

    2015-02-01

    We evaluated the effects of hypo- and hyperthyroid statuses during the initial phase of skeletal muscle regeneration in rats. To induce hypo- or hyperthyroidism, adult male Wistar rats were treated with methimazole (0.03%) or T4 (10 μg/100 g), respectively, for 10 days. Three days before sacrifice, a crush injury was produced in the solear muscles of one half of the animals, while the other half remained intact. T3, T4, TSH, and leptin serum levels were not affected by the injury. Serum T3 and T4 levels were significantly increased in hyperthyroid and hyper-injury animals. Hypothyroidism was confirmed by the significant increase in serum TSH levels in hypothyroid and hypo-injury animals. Injury increased cell infiltration and macrophage accumulation especially in hyperthyroid animals. Both type 2 and type 3 deiodinases were induced by lesion, and the opposite occurred with the type 1 isoform, at least in the control and hyperthyroid groups. Injury increased both MyoD and myogenin expression in all the studied groups, but only MyoD expression was increased by thyroidal status only at the protein level. We conclude that thyroid hormones modulate skeletal muscle regeneration possibly by regulating the inflammatory process, as well as MyoD and myogenin expression in the injured tissue.

  19. Ablation of Lgr4 enhances energy adaptation in skeletal muscle via activation of Ampk/Sirt1/Pgc1α pathway.

    PubMed

    Sun, Yingkai; Hong, Jie; Chen, Maopei; Ke, Yingying; Zhao, Shaoqian; Liu, Wen; Ma, Qinyun; Shi, Juan; Zou, Yaoyu; Ning, Tinglu; Zhang, Zhiguo; Liu, Ruixin; Wang, Jiqiu; Ning, Guang

    2015-08-21

    Leucine-rich repeat-containing G protein-coupled receptor 4 (Lgr4) is a newfound obese-associated gene. Previous study reveals that heterozygous mutation of Lgr4 correlates with decreased body weight in human. In our recent study, we demonstrate that Lgr4 ablation promotes browning of white adipose tissue and improves whole-body metabolic status. However little is known about its role in other metabolic tissues. Herein, we show that Lgr4 homozygous mutant (Lgr4(m/m)) mice show increased respiratory exchange ratio (RER, closer to 1.0) than wild-type mice at 12:00 AM (food-intake time for mice) while decreased RER (closer to 0.75) at 12:00 PM (fasting for mice), indicating a glucose-prone versus fatty acid-prone metabolic pattern, respectively. Furthermore, Lgr4 ablation increases lipid oxidation-related gene expression while suppresses glucose transporter type 4 (Glut4) levels in skeletal muscle under fasting condition. These data suggest that Lgr4 ablation enhances the flexibility of skeletal muscle to switch energy provider from glucose to fatty acid in response to glucose depletion. We further reveal the activation of Ampk/Sirt1/Pgc1α pathway during this adaptive fuel shift due to Lgr4 ablation. This study suggests that Lgr4 might serve as an adaptive regulator between glucose and lipid metabolism in skeletal muscle and reveals a potentially new regulator for a well-established adaptive network. Copyright © 2015 Elsevier Inc. All rights reserved.

  20. The Arabidopsis SR45 Splicing Factor, a Negative Regulator of Sugar Signaling, Modulates SNF1-Related Protein Kinase 1 Stability

    PubMed Central

    Barbosa, Inês C.R.

    2016-01-01

    The ability to sense and respond to sugar signals allows plants to cope with environmental and metabolic changes by adjusting growth and development accordingly. We previously reported that the SR45 splicing factor negatively regulates glucose signaling during early seedling development in Arabidopsis thaliana. Here, we show that under glucose-fed conditions, the Arabidopsis sr45-1 loss-of-function mutant contains higher amounts of the energy-sensing SNF1-Related Protein Kinase 1 (SnRK1) despite unaffected SnRK1 transcript levels. In agreement, marker genes for SnRK1 activity are upregulated in sr45-1 plants, and the glucose hypersensitivity of sr45-1 is attenuated by disruption of the SnRK1 gene. Using a high-resolution RT-PCR panel, we found that the sr45-1 mutation broadly targets alternative splicing in vivo, including that of the SR45 pre-mRNA itself. Importantly, the enhanced SnRK1 levels in sr45-1 are suppressed by a proteasome inhibitor, indicating that SR45 promotes targeting of the SnRK1 protein for proteasomal destruction. Finally, we demonstrate that SR45 regulates alternative splicing of the Arabidopsis 5PTase13 gene, which encodes an inositol polyphosphate 5-phosphatase previously shown to interact with and regulate the stability of SnRK1 in vitro, thus providing a mechanistic link between SR45 function and the modulation of degradation of the SnRK1 energy sensor in response to sugars. PMID:27436712

  1. The Effect of Conditional Inactivation of Beta 1 Integrins using Twist 2 Cre, Osterix Cre and Osteocalcin Cre Lines on Skeletal Phenotype

    PubMed Central

    Shekaran, Asha; Shoemaker, James T.; Kavanaugh, Taylor E.; Lin, Angela S.; LaPlaca, Michelle C.; Fan, Yuhong; Guldberg, Robert E.; García, Andrés J.

    2014-01-01

    Skeletal development and growth are complex processes regulated by multiple microenvironmental cues, including integrin-ECM interactions. The β1 sub-family of integrins is the largest integrin sub-family and constitutes the main integrin binding partners of collagen I, the major ECM component of bone. As complete β1 integrin integrin knockout results in embryonic lethality, studies of β1 integrin function in vivo rely on tissue-specific gene deletions. While multiple in vitro studies indicate that β1 integrins are crucial regulators of osteogenesis and mineralization, in vivo osteoblast-specific perturbations of β1 integrins have resulted in mild and sometimes contradictory skeletal phenotypes. To further investigate the role of β1 integrins on skeletal phenotype, we used the Twist2-Cre, Osterix-Cre and Osteocalcin-Cre lines to generate conditional β1 integrin deletions, where cre is expressed primarily in mesenchymal condensation, pre-osteoblast, and mature osteoblast lineage cells respectively within these lines. Mice with Twist2-specific β1 integrin disruption were smaller, had impaired skeletal development, especially in the craniofacial and vertebral tissues at E19.5, and did not survive beyond birth. Osterix-specific β1 integrin deficiency resulted in viable mice which were normal at birth but displayed early defects in calvarial ossification, incisor eruption and growth as well as femoral bone mineral density, structure, and mechanical properties. Although these defects persisted into adulthood, they became milder with age. Finally, a lack of β1 integrins in mature osteoblasts and osteocytes resulted in minor alterations to femur structure but had no effect on mineral density, biomechanics or fracture healing. Taken together, our data indicate that β1 integrin expression in early mesenchymal condensations play an important role in skeletal ossification, while β1 integrin-ECM interactions in pre-osteoblast, odontoblast- and hypertrophic

  2. Sarcopenia Impairs Prognosis of Patients with Hepatocellular Carcinoma: The Role of Liver Functional Reserve and Tumor-Related Factors in Loss of Skeletal Muscle Volume.

    PubMed

    Imai, Kenji; Takai, Koji; Watanabe, Satoshi; Hanai, Tatsunori; Suetsugu, Atsushi; Shiraki, Makoto; Shimizu, Masahito

    2017-09-22

    Sarcopenia impairs survival in patients with hepatocellular carcinoma (HCC). This study aimed to clarify the factors that contribute to decreased skeletal muscle volume in patients with HCC. The third lumbar vertebra skeletal muscle index (L3 SMI) in 351 consecutive patients with HCC was calculated to identify sarcopenia. Sarcopenia was defined as an L3 SMI value ≤ 29.0 cm²/m² for women and ≤ 36.0 cm²/m² for men. The factors affecting L3 SMI were analyzed by multiple linear regression analysis and tree-based models. Of the 351 HCC patients, 33 were diagnosed as having sarcopenia and showed poor prognosis compared with non-sarcopenia patients ( p = 0.007). However, this significant difference disappeared after the adjustments for age, sex, Child-Pugh score, maximum tumor size, tumor number, and the degree of portal vein invasion by propensity score matching analysis. Multiple linear regression analysis showed that age ( p = 0.015) and sex ( p < 0.0001) were significantly correlated with a decrease in L3 SMI. Tree-based models revealed that sex (female) is the most significant factor that affects L3 SMI. In male patients, L3 SMI was decreased by aging, increased Child-Pugh score (≥56 years), and enlarged tumor size (<56 years). Maintaining liver functional reserve and early diagnosis and therapy for HCC are vital to prevent skeletal muscle depletion and improve the prognosis of patients with HCC.

  3. Conditional deletion of Pkd1 in osteocytes disrupts skeletal mechanosensing in mice

    PubMed Central

    Xiao, Zhousheng; Dallas, Mark; Qiu, Ni; Nicolella, Daniel; Cao, Li; Johnson, Mark; Bonewald, Lynda; Quarles, L. Darryl

    2011-01-01

    We investigated whether polycystin-1 is a bone mechanosensor. We conditionally deleted Pkd1 in mature osteoblasts/osteocytes by crossing Dmp1-Cre with Pkd1flox/m1Bei mice, in which the m1Bei allele is nonfunctional. We assessed in wild-type and Pkd1-deficient mice the response to mechanical loading in vivo by ulna loading and ex vivo by measuring the response of isolated osteoblasts to fluid shear stress. We found that conditional Pkd1 heterozygotes (Dmp1-Cre;Pkd1flox/+) and null mice (Pkd1Dmp1-cKO) exhibited a ∼40 and ∼90% decrease, respectively, in functional Pkd1 transcripts in bone. Femoral bone mineral density (12 vs. 27%), trabecular bone volume (32 vs. 48%), and cortical thickness (6 vs. 17%) were reduced proportionate to the reduction of Pkd1 gene dose, as were mineral apposition rate (MAR) and expression of Runx2-II, Osteocalcin, Dmp1, and Phex. Anabolic load-induced periosteal lamellar MAR (0.58±0.14; Pkd1Dmp1-cKO vs. 1.68±0.34 μm/d; control) and increases in Cox-2, c-Jun, Wnt10b, Axin2, and Runx2-II gene expression were significantly attenuated in Pkd1Dmp1-cKO mice compared with controls. Application of fluid shear stress to immortalized osteoblasts from Pkd1null/null and Pkd1m1Bei/m1Bei-derived osteoblasts failed to elicit the increments in cytosolic calcium observed in wild-type controls. These data indicate that polycystin-1 is essential for the anabolic response to skeletal loading in osteoblasts/osteocytes.—Xiao, Z., Dallas, M., Qiu, N., Nicolella, D., Cao, L., Johnson, M., Bonewald, L., Quarles, L. D. Conditional deletion of Pkd1 in osteocytes disrupts skeletal mechanosensing in mice. PMID:21454365

  4. Crucial yet divergent roles of mitochondrial redox state in skeletal muscle vs. brown adipose tissue energetics.

    PubMed

    Mailloux, Ryan J; Adjeitey, Cyril Nii-Klu; Xuan, Jian Ying; Harper, Mary-Ellen

    2012-01-01

    Reduced glutathione (GSH) is the major determinant of redox balance in mitochondria and as such is fundamental in the control of cellular bioenergetics. GSH is also the most important nonprotein antioxidant molecule in cells. Surprisingly, the effect of redox environment has never been examined in skeletal muscle and brown adipose tissue (BAT), two tissues that have exceptional dynamic range and that are relevant to the development of obesity and related diseases. Here, we show that the redox environment plays crucial, yet divergent, roles in modulating mitochondrial bioenergetics in skeletal muscle and BAT. Skeletal muscle mitochondria were found to naturally have a highly reduced environment (GSH/GSSG≈46), and this was associated with fairly high (∼40%) rates of state 4 (nonphosphorylating) respiration and decreased reactive oxygen species (ROS) emission. The deglutathionylation of uncoupling protein 3 (UCP3) following an increase in the reductive potential of mitochondria results in a further increase in nonphosphorylating respiration (∼20% in situ). BAT mitochondria were found to have a much more oxidized status (GSH/GSSG≈13) and had basal reactive oxygen species emission that was higher (∼250% increase in ROS generation) than that in skeletal muscle mitochondria. When redox status was subsequently increased (i.e., more reduced), UCP1-mediated uncoupling was more sensitive to GDP inhibition. Surprisingly, BAT was found to be devoid of glutaredoxin-2 (Grx2) expression, while there was abundant expression in skeletal muscle. Taken together, these findings reveal the importance of redox environment in controlling bioenergetic functions in both tissues, and the highly unique characteristics of BAT in this regard.

  5. Skeletal injuries in small mammals: a multispecies assessment of prevalence and location

    USGS Publications Warehouse

    Stephens, Ryan B.; Burke, Christopher B.; Woodman, Neal; Poland, Lily B.; Rowe, Rebecca J.

    2018-01-01

    Wild mammals are known to survive injuries that result in skeletal abnormalities. Quantifying and comparing skeletal injuries among species can provide insight into the factors that cause skeletal injuries and enable survival following an injury. We documented the prevalence and location of structural bone abnormalities in a community of 7 small mammal species inhabiting the White Mountains of New Hampshire. These species differ in locomotion type and levels of intraspecific aggression. Overall, the majority of injuries were to the ribs or caudal vertebrae. Incidence of skeletal injuries was highest in older animals, indicating that injuries accumulate over a lifetime. Compared to species with ambulatory locomotion, those with more specialized (semi-fossorial, saltatorial, and scansorial) locomotion exhibited fewer skeletal abnormalities in the arms and legs, which we hypothesize is a result of a lesser ability to survive limb injuries. Patterns of skeletal injuries in shrews (Soricidae) were consistent with intraspecific aggression, particularly in males, whereas skeletal injuries in rodents (Rodentia) were more likely accidental or resulting from interactions with predators. Our results demonstrate that both the incidence and pattern of skeletal injuries vary by species and suggest that the ability of an individual to survive a specific skeletal injury depends on its severity and location as well as the locomotor mode of the species involved.

  6. Protein Phosphatase 1-α Regulates AS160 Ser588 and Thr642 Dephosphorylation in Skeletal Muscle.

    PubMed

    Sharma, Pragya; Arias, Edward B; Cartee, Gregory D

    2016-09-01

    Akt substrate of 160 kDa (AS160) phosphorylation on Thr(642) and Ser(588) by Akt is essential for insulin's full effect on glucose transport. However, protein phosphorylation is determined by the balance of actions by kinases and phosphatases, and the specific phosphatase(s) controlling AS160 dephosphorylation is (are) unknown. Accordingly, we assessed roles of highly expressed skeletal muscle serine/threonine phosphatases (PP1, PP2A, PP2B, and PP2C) on AS160 dephosphorylation. Preliminary screening of candidate phosphatases used an AS160 dephosphorylation assay. Lysates from insulin-stimulated skeletal muscle were treated with pharmacological phosphatase inhibitors and assessed for AS160 Ser(588) and Thr(642) dephosphorylation. AS160 dephosphorylation on both phosphorylation sites was unaltered by PP2B or PP2C inhibitors. Okadaic acid (low dose inhibits PP2A; high dose inhibits PP1) delayed AS160 Ser(588) (both doses) and Thr(642) (high dose only) dephosphorylation concomitant with greater Akt phosphorylation (both doses). AS160 was coimmunoprecipitated with PP1-α but not with PP1-β, PP11, or PP2A. Recombinant inhibitor-2 protein (a selective PP1 inhibitor) delayed AS160 dephosphorylation on both phosphorylation sites without altering Akt phosphorylation. Furthermore, knockdown of PP1-α but not PP1-β or PP11 by small interfering RNA caused greater AS160 Ser(588) and Thr(642) phosphorylation concomitant with unaltered Akt phosphorylation. Together, these results identified PP1-α as a regulator of AS160 Thr(642) and Ser(588) dephosphorylation in skeletal muscle. © 2016 by the American Diabetes Association.

  7. Geometric morphometric evaluation of cervical vertebrae shape and its relationship to skeletal maturation.

    PubMed

    Chatzigianni, Athina; Halazonetis, Demetrios J

    2009-10-01

    Cervical vertebrae shape has been proposed as a diagnostic factor for assessing skeletal maturation in orthodontic patients. However, evaluation of vertebral shape is mainly based on qualitative criteria. Comprehensive quantitative measurements of shape and assessments of its predictive power have not been reported. Our aims were to measure vertebral shape by using the tools of geometric morphometrics and to evaluate the correlation and predictive power of vertebral shape on skeletal maturation. Pretreatment lateral cephalograms and corresponding hand-wrist radiographs of 98 patients (40 boys, 58 girls; ages, 8.1-17.7 years) were used. Skeletal age was estimated from the hand-wrist radiographs. The first 4 vertebrae were traced, and 187 landmarks (34 fixed and 153 sliding semilandmarks) were used. Sliding semilandmarks were adjusted to minimize bending energy against the average of the sample. Principal components analysis in shape and form spaces was used for evaluating shape patterns. Shape measures, alone and combined with centroid size and age, were assessed as predictors of skeletal maturation. Shape alone could not predict skeletal maturation better than chronologic age. The best prediction was achieved with the combination of form space principal components and age, giving 90% prediction intervals of approximately 200 maturation units in the girls and 300 units in the boys. Similar predictive power could be obtained by using centroid size and age. Vertebrae C2, C3, and C4 gave similar results when examined individually or combined. C1 showed lower correlations, signifying lower integration with hand-wrist maturation. Vertebral shape is strongly correlated to skeletal age but does not offer better predictive value than chronologic age.

  8. CB1 cannabinoid receptors mediate endochondral skeletal growth attenuation by Δ9-tetrahydrocannabinol.

    PubMed

    Wasserman, Elad; Tam, Joseph; Mechoulam, Raphael; Zimmer, Andreas; Maor, Gila; Bab, Itai

    2015-01-01

    The endocannabinoid (EC) system regulates bone mass. Because cannabis use during pregnancy results in stature shorter than normal, we examined the role of the EC system in skeletal elongation. We show that CB1 and CB2 cannabinoid receptors are expressed specifically in hypertrophic chondrocytes of the epiphyseal growth cartilage (EGC), which drives vertebrate growth. These cells also express diacylglycerol lipases, critical biosynthetic enzymes of the main EC, and 2-arachidonoylglycerol (2-AG), which is present at significant levels in the EGC. Femora of CB1- and/or CB2-deficient mice at the end of the rapid growth phase are longer compared to wild-type (WT) animals. We find that Δ(9) -tetrahydrocannabinol (THC) slows skeletal elongation of female WT and CB2-, but not CB1-, deficient mice, which is reflected in femoral and lumbar vertebral body length. This in turn results in lower body weight, but unaltered fat content. THC inhibits EGC chondrocyte hypertrophy in ex vivo cultures and reduces the hypertrophic cell zone thickness of CB1-, but not CB2-, deficient mice. These results demonstrate a local growth-restraining EC system in the EGC. The relevance of the present findings to humans remains to be studied. © 2015 New York Academy of Sciences.

  9. Transcription factors CEP-1/p53 and CEH-23 collaborate with AAK-2/AMPK to modulate longevity in Caenorhabditis elegans.

    PubMed

    Chang, Hsin-Wen; Pisano, Steve; Chaturbedi, Amaresh; Chen, Jennifer; Gordon, Sarah; Baruah, Aiswarya; Lee, Siu Sylvia

    2017-08-01

    A decline in mitochondrial electron transport chain (ETC) function has long been implicated in aging and various diseases. Recently, moderate mitochondrial ETC dysfunction has been found to prolong lifespan in diverse organisms, suggesting a conserved and complex role of mitochondria in longevity determination. Several nuclear transcription factors have been demonstrated to mediate the lifespan extension effect associated with partial impairment of the ETC, suggesting that compensatory transcriptional response to be crucial. In this study, we showed that the transcription factors CEP-1/p53 and CEH-23 act through a similar mechanism to modulate longevity in response to defective ETC in Caenorhabditis elegans. Genomewide gene expression profiling comparison revealed a new link between these two transcription factors and AAK-2/AMP kinase (AMPK) signaling. Further functional analyses suggested that CEP-1/p53 and CEH-23 act downstream of AAK-2/AMPK signaling and CRTC-1 transcriptional coactivator to promote stress resistance and lifespan. As AAK-2, CEP-1, and CEH-23 are all highly conserved, our findings likely provide important insights for understanding the organismal adaptive response to mitochondrial dysfunction in diverse organisms and will be relevant to aging and pathologies with a mitochondrial etiology in human. © 2017 The Authors. Aging Cell published by the Anatomical Society and John Wiley & Sons Ltd.

  10. Functional electrical stimulation exercise increases GLUT-1 and GLUT-4 in paralyzed skeletal muscle.

    PubMed

    Chilibeck, P D; Bell, G; Jeon, J; Weiss, C B; Murdoch, G; MacLean, I; Ryan, E; Burnham, R

    1999-11-01

    The study purpose was to determine the effect of functional electrical stimulation (FES)-leg cycle ergometer training (30 minutes on 3 d/wk for 8 weeks) on the GLUT-1 and GLUT-4 content of paralyzed skeletal muscle. Biopsy samples of vastus lateralis muscle were obtained pre- and post-training from five individuals with motor-complete spinal cord injury ([SCI] four men and one woman aged 31 to 50 years, 3 to 25 years postinjury involving C5-T8). Western blot analysis indicated that GLUT-1 increased by 52% and GLUT-4 increased by 72% with training (P < .05). This coincided with an increase in the muscle oxidative capacity as indicated by a 56% increase in citrate synthase (CS) activity (P < .05) and an improvement in the insulin sensitivity index as determined from oral glucose tolerance tests (P < .05). It is concluded that FES endurance training is effective to increase glucose transporter protein levels in paralyzed skeletal muscle of individuals with SCI.

  11. Modulation of Nrf2/Keap1 system by Wasabi 6-methylthiohexyl isothiocyanate in ARE-mediated NQO1 expression.

    PubMed

    Korenori, Yoshimi; Tanigawa, Shunsuke; Kumamoto, Takuma; Qin, Si; Daikoku, Yosuke; Miyamori, Koji; Nagai, Masashi; Hou, De-Xing

    2013-05-01

    6-Methylthiohexyl isothiocyanate (6-MTITC), one of the major bioactive ingredients in Japanese Wasabi, has revealed cytoprotective and cancer chemopreventive effects. This study aims to clarify the molecular mechanisms how 6-MTITC modulates nuclear factor E2-related factor 2 (Nrf2)/Kelchlike ECH-associating protein 1 (Keap1) system in antioxidant-responsive element (ARE)-mediated nicotinamide adenine dinucleotide phosphate (NADP): quinone oxidoreductase 1 (NQO1) expression. HepG2 cells were treated with 6-MTITC with varying time and dose. NQO1, Nrf2, and Keap1 proteins were detected by Western blotting. ARE transactivation was detected by electrophilic mobility shift assay and reporter gene assay. Nuclear localization of Nrf2 was determined by immunocytochemistry assay. Ubiquitination of Nrf2 and Keap1 was detected using immunoprecipitation after treatment with MG132. Small interfering RNA was used to knockdown Nrf2 or Keap1. The results revealed that 6-MTITC modulated Nrf2/ARE pathway by stimulating Keap1 modification, and inhibiting Nrf2 ubiquitination and protein turnover. These actions finally increased nuclear Nrf2 accumulation and ARE-binding activity. Moreover, silencing Nrf2 markedly reduced ARE-driven activity induced by 6-MTITC. 6-MTITC modulated ARE-driven NQO1 expression by stabilizing Nrf2 with enhanced Keap1 modification and decreased Nrf2 degradation. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Effect of Exercise Training on Skeletal Muscle SIRT1 and PGC-1α Expression Levels in Rats of Different Age

    PubMed Central

    Huang, Chi-Chang; Wang, Ting; Tung, Yu-Tang; Lin, Wan-Teng

    2016-01-01

    The protein deacetylase sirtuin 1 (SIRT1) and activate peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) pathway drives the muscular fiber-type switching, and can directly regulate the biophysiological functions of skeletal muscle. To investigate whether 12-week swimming exercise training modulates the SIRT1/PGC-1α pathway associated proteins expression in rats of different age. Male 3-month-old (3M), 12-month-old (12M) and 18-month-old (18M) Sprague-Dawley rats were used and assigned to sedentary control (C) or 12-week swimming exercise training (E) and divided into six groups: 3MC (n = 8), 12MC (n = 6), 18MC (n = 8), 3ME (n = 8), 12ME (n = 5) and 18ME (n = 6). Body weight, muscle weight, epididymal fat mass and muscle morphology were performed at the end of the experiment. The protein levels of SIRT1, PGC-1α, AMPK and FOXO3a in the gastrocnemius and soleus muscles were examined. The SIRT1, PGC-1α and AMPK levels in the gastrocnemius and soleus muscles were up-regulated in the three exercise training groups than three control groups. The FOXO3a level in the 12ME group significantly increased in the gastrocnemius muscles than 12MC group, but significantly decreased in the soleus muscles. In 3-, 12- and 18-month-old rats with and without exercise, there was a significant main effect of exercise on PGC-1α, AMPK and FOXO3a in the gastrocnemius muscles, and SIRT1, PGC-1α and AMPK in the soleus muscles. Our result suggests that swimming training can regulate the SIRT1/PGC-1α, AMPK and FOXO3a proteins expression of the soleus muscles in aged rats. PMID:27076782

  13. Effect of experimental hyperthyroidism on protein turnover in skeletal and cardiac muscle.

    PubMed

    Carter, W J; Van Der Weijden Benjamin, W S; Faas, F H

    1980-10-01

    Since experimental hyperthyroidism reduces skeletal muscle mass while simultaneously increasing cardiac muscle mass, the effect of hyperthyroidism on muscle protein degradation was compared in skeletal and cardiac muscle. Pulse-labeling studies using (3H) leucine and (14C) carboxyl labeled aspartate and glutamate were carried out. Hyperthyroidism caused a 25%-29% increase in protein breakdown in both sarcoplasmic and myofibrillar fractions of skeletal muscle. Increased muscle protein degradation may be a major factor in the development of skeletal muscle wasting and weakness in hyperthyroidism. In contrast, protein breakdown appeared to be reduced 22% in the sarcoplasmic fraction of hyperthyroid heart muscle and was unchanged in the myofibrillar fraction. Possible reasons for the contrasting effects of hyperthyroidism on skeletal and cardiac muscle include increased sensitivity of the hyperthyroid heart to catecholamines, increased cardiac work caused by the hemodynamic effects of hyperthyroidism, and a different direct effect of thyroid hormone at the nuclear level in cardiac as opposed to skeletal muscle.

  14. Myosin Light Chain Kinase and the Role of Myosin Light Chain Phosphorylation in Skeletal Muscle

    PubMed Central

    Stull, James T.; Kamm, Kristine E.; Vandenboom, Rene

    2011-01-01

    Skeletal muscle myosin light chain kinase (skMLCK) is a dedicated Ca2+/calmodulin-dependent serine-threonine protein kinase that phosphorylates the regulatory light chain (RLC) of sarcomeric myosin. It is expressed from the MYLK2 gene specifically in skeletal muscle fibers with most abundance in fast contracting muscles. Biochemically, activation occurs with Ca2+ binding to calmodulin forming a (Ca2+)4•calmodulin complex sufficient for activation with a diffusion limited, stoichiometic binding and displacement of a regulatory segment from skMLCK catalytic core. The N-terminal sequence of RLC then extends through the exposed catalytic cleft for Ser15 phosphorylation. Removal of Ca2+ results in the slow dissociation of calmodulin and inactivation of skMLCK. Combined biochemical properties provide unique features for the physiological responsiveness of RLC phosphorylation, including (1) rapid activation of MLCK by Ca2+/calmodulin, (2) limiting kinase activity so phosphorylation is slower than contraction, (3) slow MLCK inactivation after relaxation and (4) much greater kinase activity relative to myosin light chain phosphatase (MLCP). SkMLCK phosphorylation of myosin RLC modulates mechanical aspects of vertebrate skeletal muscle function. In permeabilized skeletal muscle fibers, phosphorylation-mediated alterations in myosin structure increase the rate of force-generation by myosin cross bridges to increase Ca2+-sensitivity of the contractile apparatus. Stimulation-induced increases in RLC phosphorylation in intact muscle produces isometric and concentric force potentiation to enhance dynamic aspects of muscle work and power in unfatigued or fatigued muscle. Moreover, RLC phosphorylation-mediated enhancements may interact with neural strategies for human skeletal muscle activation to ameliorate either central or peripheral aspects of fatigue. PMID:21284933

  15. PAX3/7 EXPRESSION COINCIDES WITH MYOD DURING CHRONIC SKELETAL MUSCLE OVERLOAD

    PubMed Central

    Hyatt, Jon-Philippe K.; McCall, Gary E.; Kander, Elizabeth M.; Zhong, Hui; Roy, Roland R.; Huey, Kimberly A.

    2009-01-01

    Paired box (Pax) proteins 3 and 7 are key determinants for embryonic skeletal muscle development by initiating myogenic regulatory factor (MRF) gene expression. We show that Pax3 and 7 participate in adult skeletal muscle plasticity during the initial responses to chronic overload (≤7 days) and appear to coordinate MyoD expression, a member of the MRF family of genes. Pax3 and 7 mRNA were higher than control within 12 h after initiation of overload, preceded the increase in MyoD mRNA on day 1, and peaked on day 2. On days 3 and 7, Pax7 mRNA remained higher than control, suggesting that satellite cell self-renewal was occurring. Pax3 and 7 and MyoD protein levels were higher than control on days 2 and 3. These data indicate that Pax3 and 7 coordinate the recapitulation of developmental-like regulatory mechanisms in response to growth-inducing stimuli in adult skeletal muscle, presumably through activation of satellite cells. PMID:18508329

  16. Skeletal muscle cells express ICAM-1 after muscle overload and ICAM-1 contributes to the ensuing hypertrophic response.

    PubMed

    Dearth, Christopher L; Goh, Qingnian; Marino, Joseph S; Cicinelli, Peter A; Torres-Palsa, Maria J; Pierre, Philippe; Worth, Randall G; Pizza, Francis X

    2013-01-01

    We previously reported that leukocyte specific β2 integrins contribute to hypertrophy after muscle overload in mice. Because intercellular adhesion molecule-1 (ICAM-1) is an important ligand for β2 integrins, we examined ICAM-1 expression by murine skeletal muscle cells after muscle overload and its contribution to the ensuing hypertrophic response. Myofibers in control muscles of wild type mice and cultures of skeletal muscle cells (primary and C2C12) did not express ICAM-1. Overload of wild type plantaris muscles caused myofibers and satellite cells/myoblasts to express ICAM-1. Increased expression of ICAM-1 after muscle overload occurred via a β2 integrin independent mechanism as indicated by similar gene and protein expression of ICAM-1 between wild type and β2 integrin deficient (CD18-/-) mice. ICAM-1 contributed to muscle hypertrophy as demonstrated by greater (p<0.05) overload-induced elevations in muscle protein synthesis, mass, total protein, and myofiber size in wild type compared to ICAM-1-/- mice. Furthermore, expression of ICAM-1 altered (p<0.05) the temporal pattern of Pax7 expression, a marker of satellite cells/myoblasts, and regenerating myofiber formation in overloaded muscles. In conclusion, ICAM-1 expression by myofibers and satellite cells/myoblasts after muscle overload could serve as a mechanism by which ICAM-1 promotes hypertrophy by providing a means for cell-to-cell communication with β2 integrin expressing myeloid cells.

  17. Skeletal Muscle Cells Express ICAM-1 after Muscle Overload and ICAM-1 Contributes to the Ensuing Hypertrophic Response

    PubMed Central

    Dearth, Christopher L.; Goh, Qingnian; Marino, Joseph S.; Cicinelli, Peter A.; Torres-Palsa, Maria J.; Pierre, Philippe; Worth, Randall G.; Pizza, Francis X.

    2013-01-01

    We previously reported that leukocyte specific β2 integrins contribute to hypertrophy after muscle overload in mice. Because intercellular adhesion molecule-1 (ICAM-1) is an important ligand for β2 integrins, we examined ICAM-1 expression by murine skeletal muscle cells after muscle overload and its contribution to the ensuing hypertrophic response. Myofibers in control muscles of wild type mice and cultures of skeletal muscle cells (primary and C2C12) did not express ICAM-1. Overload of wild type plantaris muscles caused myofibers and satellite cells/myoblasts to express ICAM-1. Increased expression of ICAM-1 after muscle overload occurred via a β2 integrin independent mechanism as indicated by similar gene and protein expression of ICAM-1 between wild type and β2 integrin deficient (CD18-/-) mice. ICAM-1 contributed to muscle hypertrophy as demonstrated by greater (p<0.05) overload-induced elevations in muscle protein synthesis, mass, total protein, and myofiber size in wild type compared to ICAM-1-/- mice. Furthermore, expression of ICAM-1 altered (p<0.05) the temporal pattern of Pax7 expression, a marker of satellite cells/myoblasts, and regenerating myofiber formation in overloaded muscles. In conclusion, ICAM-1 expression by myofibers and satellite cells/myoblasts after muscle overload could serve as a mechanism by which ICAM-1 promotes hypertrophy by providing a means for cell-to-cell communication with β2 integrin expressing myeloid cells. PMID:23505517

  18. Peroxisome Proliferator-Activated Receptor γ Decouples Fatty Acid Uptake from Lipid Inhibition of Insulin Signaling in Skeletal Muscle

    PubMed Central

    Hu, Shanming; Yao, Jianrong; Howe, Alexander A.; Menke, Brandon M.; Sivitz, William I.; Spector, Arthur A.

    2012-01-01

    Peroxisome proliferator-activated receptor γ (PPARγ) is expressed at low levels in skeletal muscle, where it protects against adiposity and insulin resistance via unclear mechanisms. To test the hypothesis that PPARγ directly modulates skeletal muscle metabolism, we created two models that isolate direct PPARγ actions on skeletal myocytes. PPARγ was overexpressed in murine myotubes by adenotransfection and in mouse skeletal muscle by plasmid electroporation. In cultured myotubes, PPARγ action increased fatty acid uptake and incorporation into myocellular lipids, dependent upon a 154 ± 20-fold up-regulation of CD36 expression. PPARγ overexpression more than doubled insulin-stimulated thymoma viral proto-oncogene (AKT) phosphorylation during low lipid availability. Furthermore, in myotubes exposed to palmitate levels that inhibit insulin signaling, PPARγ overexpression increased insulin-stimulated AKT phosphorylation and glycogen synthesis over 3-fold despite simultaneously increasing myocellular palmitate uptake. The insulin signaling enhancement was associated with an increase in activating phosphorylation of phosphoinositide-dependent protein kinase 1 and a normalized expression of palmitate-induced genes that antagonize AKT phosphorylation. In vivo, PPARγ overexpression more than doubled insulin-dependent AKT phosphorylation in lipid-treated mice but did not augment insulin-stimulated glucose uptake. We conclude that direct PPARγ action promotes myocellular storage of energy by increasing fatty acid uptake and esterification while simultaneously enhancing insulin signaling and glycogen formation. However, direct PPARγ action in skeletal muscle is not sufficient to account for the hypoglycemic actions of PPARγ agonists during lipotoxicity. PMID:22474127

  19. Genome-wide survey by ChIP-seq reveals YY1 regulation of lincRNAs in skeletal myogenesis

    PubMed Central

    Lu, Leina; Sun, Kun; Chen, Xiaona; Zhao, Yu; Wang, Lijun; Zhou, Liang; Sun, Hao; Wang, Huating

    2013-01-01

    Skeletal muscle differentiation is orchestrated by a network of transcription factors, epigenetic regulators, and non-coding RNAs. The transcription factor Yin Yang 1 (YY1) silences multiple target genes in myoblasts (MBs) by recruiting Ezh2 (Enhancer of Zeste Homologue2). To elucidate genome-wide YY1 binding in MBs, we performed chromatin immunoprecipitation (ChIP)-seq and found 1820 specific binding sites in MBs with a large portion residing in intergenic regions. Detailed analysis demonstrated that YY1 acts as an activator for many loci in addition to its known repressor function. No significant co-occupancy was found between YY1 and Ezh2, suggesting an additional Ezh2-independent function for YY1 in MBs. Further analysis of intergenic binding sites showed that YY1 potentially regulates dozens of large intergenic non-coding RNAs (lincRNAs), whose function in myogenesis is underexplored. We characterized a novel muscle-associated lincRNA (Yam-1) that is positively regulated by YY1. Yam-1 is downregulated upon differentiation and acts as an inhibitor of myogenesis. We demonstrated that Yam-1 functions through in cis regulation of miR-715, which in turn targets Wnt7b. Our findings not only provide the first genome-wide picture of YY1 association in muscle cells, but also uncover the functional role of lincRNA Yam-1. PMID:23942234

  20. Application of skeletal age based on x-ray in selecting sports talents

    NASA Astrophysics Data System (ADS)

    Mao, Zongzhen; Xu, Guodong; Song, Tao

    2012-01-01

    Skeletal age has been studied and proved that for most elite athletes, it was coincident with the chronological ages when they were young. In order to explore the application of skeletal age in selecting sports talent, 32 athletes (female, chronological age 5-12 y) were chosen from the Gymnastics Training Base in this study. Their left hand-wrists were photographed with X-rays, and then the skeletal ages were estimated by Chinese version of the Tanner-Whitehouse Skeletal Maturity Assessment System. At the same time, their body shapes, functions, and sports ability were also measured. Results showed that 71.88% of the skeletal age was proportional to their chronological age (+/- 1 y); while 18.75% of the skeletal maturity was retarded by 1- 2 year, 9.37% of those was advanced more than 1 year. On the other hand, the body shape, functions and sports ability of the athletes were positively related with their skeletal maturity. This study proved that the determination of skeletal maturity is a reliable evaluation for selecting sports talent. A further study on the influence of gymnastics on the skeletal age is of great significance.

  1. Toward a mechanism-based understanding of skeletal formation: Toolbox for biomineralization past, present, and future

    NASA Astrophysics Data System (ADS)

    Dove, P. M.; Wallace, A. F.; Stephenson, A. E.; Wang, D. E.; Hamm, L.; de Yoreo, J. J.

    2008-05-01

    water structure in confined biomineralization environments may have important, yet-unrecognized roles in biomolecule-solute- mineral interactions. With the realization that biogenic minerals often form by nonclassical processes from amorphous precursors, new studies are focused on establishing factors that drive the transformation of intermediate phases to final biomineral products. By developing model systems to probe how biological substrates can modulate the onset of mineral formation, we are working to establish 1) Principles of mineral formation by nonclassical processes and influences on resultant signatures; 2) Thermodynamic and kinetic role(s) of the organic matrix as a trigger/inhibitor to the timing and location of mineral formation; and 3) Interplay of solvation and organic matrix in polymorph selection. The next 10 years promise to be an exciting time of uncovering how skeletal formation is modulated by a rich biochemical machinery at sites of mineralization while also providing insights to phylogenetic relations.

  2. Microvascular Permeability of Skeletal Muscle After Eccentric Contraction-Induced Muscle Injury: In Vivo Imaging Using Two-Photon Laser Scanning Microscopy.

    PubMed

    Hotta, Kazuki; Behnke, Bradley Jon; Masamoto, Kazuto; Shimotsu, Rie; Onodera, Naoya; Yamaguchi, Akihiko; Poole, David C; Kano, Yutaka

    2018-05-03

    Via modulation of endothelial integrity and vascular permeability in response to damage skeletal muscle microvessels play a crucial permissive role in tissue leukocyte invasion. However, direct visual evidence of altered microvascular permeability of skeletal muscle has not been technically feasible impairing mechanistic understanding of these responses. Two-photon laser scanning microscopy (TPLSM) allows three-dimensional in vivo imaging of skeletal muscle microcirculation. We hypothesized that the regulation of microvessels permeability in vivo is temporally related to acute inflammatory and regenerative processes following muscle injury. To test our hypothesis, tibialis anterior muscle of anesthetized male Wistar rats were subjected to eccentric contractions (ECC) via electrical stimulation. The skeletal muscle microcirculation was imaged by an intravenously infused fluorescent dye (rhodamine b isothiocyanate dextran) to assess microvascular permeability via TPLSM 1, 3 and 7 days after ECC. Immunohistochemistry on muscle sections was performed to determine the proportion of VEGF-A positive fibers in the damaged muscle. Compared with control rats, the volumetrically-determined interstitial leakage of fluorescent dye (5.1 {plus minus} 1.4, 5.3 {plus minus} 1.2 vs. 0.51 {plus minus} 0.14 μm 3 x 10 6 , P < 0.05 respectively days 1 and 3 vs. control) and percentage of VEGF-A positive fibers in the damaged muscle (10 {plus minus} 0.4, 22 {plus minus} 1.1 vs. 0%; days 1 and 3 vs. control) were significantly higher on days 1 and 3 after ECC. The interstitial leakage volume returned to control by day 7. These results suggest that microvascular hyperpermeability assessed by in vivo TPLSM imaging is associated with ECC-induced muscle damage and increased VEGF expression.

  3. Modulation of skeletal muscle fiber type by mitogen-activated protein kinase signaling.

    PubMed

    Shi, Hao; Scheffler, Jason M; Pleitner, Jonathan M; Zeng, Caiyun; Park, Sungkwon; Hannon, Kevin M; Grant, Alan L; Gerrard, David E

    2008-08-01

    Skeletal muscle is composed of diverse fiber types, yet the underlying molecular mechanisms responsible for this diversification remain unclear. Herein, we report that the extracellular signal-regulated kinase (ERK) 1/2 pathway, but not p38 or c-Jun NH(2)-terminal kinase (JNK), is preferentially activated in fast-twitch muscles. Pharmacological blocking of ERK1/2 pathway increased slow-twitch fiber type-specific reporter activity and repressed those associated with the fast-twitch fiber phenotype in vitro. Overexpression of a constitutively active ERK2 had an opposite effect. Inhibition of ERK signaling in cultured myotubes increased slow-twitch fiber-specific protein accumulation while repressing those characteristic of fast-twitch fibers. Overexpression of MAP kinase phosphatase-1 (MKP1) in mouse and rat muscle fibers containing almost exclusively type IIb or IIx fast myosin heavy chain (MyHC) isoforms induced de novo synthesis of the slower, more oxidative type IIa and I MyHCs in a time-dependent manner. Conversion to the slower phenotype was confirmed by up-regulation of slow reporter gene activity and down-regulation of fast reporter activities in response to forced MKP1 expression in vivo. In addition, activation of ERK2 signaling induced up-regulation of fast-twitch fiber program in soleus. These data suggest that the MAPK signaling, most likely the ERK1/2 pathway, is necessary to preserve the fast-twitch fiber phenotype with a concomitant repression of slow-twitch fiber program.

  4. Mitochondrial uncoupling in skeletal muscle by UCP1 augments energy expenditure and glutathione content while mitigating ROS production.

    PubMed

    Adjeitey, Cyril Nii-Klu; Mailloux, Ryan J; Dekemp, Robert A; Harper, Mary-Ellen

    2013-08-01

    Enhancement of proton leaks in muscle tissue represents a potential target for obesity treatment. In this study, we examined the bioenergetic and physiological implications of increased proton leak in skeletal muscle. To induce muscle-specific increases in proton leak, we used mice that selectively express uncoupling protein-1 (UCP1) in skeletal muscle tissue. UCP1 expression in muscle mitochondria was ∼13% of levels in brown adipose tissue (BAT) mitochondria and caused increased GDP-sensitive proton leak. This was associated with an increase in whole body energy expenditure and a decrease in white adipose tissue content. Muscle UCP1 activity had divergent effects on mitochondrial ROS emission and glutathione levels compared with BAT. UCP1 in muscle increased total mitochondrial glutathione levels ∼7.6 fold. Intriguingly, unlike in BAT mitochondria, leak through UCP1 in muscle controlled mitochondrial ROS emission. Inhibition of UCP1 with GDP in muscle mitochondria increased ROS emission ∼2.8-fold relative to WT muscle mitochondria. GDP had no impact on ROS emission from BAT mitochondria from either genotype. Collectively, these findings indicate that selective induction of UCP1-mediated proton leak in muscle can increase whole body energy expenditure and decrease adiposity. Moreover, ectopic UCP1 expression in skeletal muscle can control mitochondrial ROS emission, while it apparently plays no such role in its endogenous tissue, brown fat.

  5. Mitochondrial uncoupling in skeletal muscle by UCP1 augments energy expenditure and glutathione content while mitigating ROS production

    PubMed Central

    Adjeitey, Cyril Nii-Klu; Mailloux, Ryan J.; deKemp, Robert A.

    2013-01-01

    Enhancement of proton leaks in muscle tissue represents a potential target for obesity treatment. In this study, we examined the bioenergetic and physiological implications of increased proton leak in skeletal muscle. To induce muscle-specific increases in proton leak, we used mice that selectively express uncoupling protein-1 (UCP1) in skeletal muscle tissue. UCP1 expression in muscle mitochondria was ∼13% of levels in brown adipose tissue (BAT) mitochondria and caused increased GDP-sensitive proton leak. This was associated with an increase in whole body energy expenditure and a decrease in white adipose tissue content. Muscle UCP1 activity had divergent effects on mitochondrial ROS emission and glutathione levels compared with BAT. UCP1 in muscle increased total mitochondrial glutathione levels ∼7.6 fold. Intriguingly, unlike in BAT mitochondria, leak through UCP1 in muscle controlled mitochondrial ROS emission. Inhibition of UCP1 with GDP in muscle mitochondria increased ROS emission ∼2.8-fold relative to WT muscle mitochondria. GDP had no impact on ROS emission from BAT mitochondria from either genotype. Collectively, these findings indicate that selective induction of UCP1-mediated proton leak in muscle can increase whole body energy expenditure and decrease adiposity. Moreover, ectopic UCP1 expression in skeletal muscle can control mitochondrial ROS emission, while it apparently plays no such role in its endogenous tissue, brown fat. PMID:23757405

  6. Skeletal muscle proteomic signature and metabolic impairment in pulmonary hypertension.

    PubMed

    Malenfant, Simon; Potus, François; Fournier, Frédéric; Breuils-Bonnet, Sandra; Pflieger, Aude; Bourassa, Sylvie; Tremblay, Ève; Nehmé, Benjamin; Droit, Arnaud; Bonnet, Sébastien; Provencher, Steeve

    2015-05-01

    Exercise limitation comes from a close interaction between cardiovascular and skeletal muscle impairments. To better understand the implication of possible peripheral oxidative metabolism dysfunction, we studied the proteomic signature of skeletal muscle in pulmonary arterial hypertension (PAH). Eight idiopathic PAH patients and eight matched healthy sedentary subjects were evaluated for exercise capacity, skeletal muscle proteomic profile, metabolism, and mitochondrial function. Skeletal muscle proteins were extracted, and fractioned peptides were tagged using an iTRAQ protocol. Proteomic analyses have documented a total of 9 downregulated proteins in PAH skeletal muscles and 10 upregulated proteins compared to healthy subjects. Most of the downregulated proteins were related to mitochondrial structure and function. Focusing on skeletal muscle metabolism and mitochondrial health, PAH patients presented a decreased expression of oxidative enzymes (pyruvate dehydrogenase, p < 0.01) and an increased expression of glycolytic enzymes (lactate dehydrogenase activity, p < 0.05). These findings were supported by abnormal mitochondrial morphology on electronic microscopy, lower citrate synthase activity (p < 0.01) and lower expression of the transcription factor A of the mitochondria (p < 0.05), confirming a more glycolytic metabolism in PAH skeletal muscles. We provide evidences that impaired mitochondrial and metabolic functions found in the lungs and the right ventricle are also present in skeletal muscles of patients. • Proteomic and metabolic analysis show abnormal oxidative metabolism in PAH skeletal muscle. • EM of PAH patients reveals abnormal mitochondrial structure and distribution. • Abnormal mitochondrial health and function contribute to exercise impairments of PAH. • PAH may be considered a vascular affliction of heart and lungs with major impact on peripheral muscles.

  7. Long-chain acyl-CoA synthetase 6 regulates lipid synthesis and mitochondrial oxidative capacity in human and rat skeletal muscle.

    PubMed

    Teodoro, Bruno G; Sampaio, Igor H; Bomfim, Lucas H M; Queiroz, André L; Silveira, Leonardo R; Souza, Anderson O; Fernandes, Anna M A P; Eberlin, Marcos N; Huang, Tai-Yu; Zheng, Donghai; Neufer, P Darrell; Cortright, Ronald N; Alberici, Luciane C

    2017-02-01

    Long-chain acyl-CoA synthetase 6 (ACSL6) mRNA is present in human and rat skeletal muscle, and is modulated by nutritional status: exercise and fasting decrease ACSL6 mRNA, whereas acute lipid ingestion increase its expression. ACSL6 genic inhibition in rat primary myotubes decreased lipid accumulation, as well as activated the higher mitochondrial oxidative capacity programme and fatty acid oxidation through the AMPK/PGC1-α pathway. ACSL6 overexpression in human primary myotubes increased phospholipid species and decreased oxidative metabolism. Long-chain acyl-CoA synthetases (ACSL 1 to 6) are key enzymes regulating the partitioning of acyl-CoA species toward different metabolic fates such as lipid synthesis or β-oxidation. Despite our understanding of ecotopic lipid accumulation in skeletal muscle being associated with metabolic diseases such as obesity and type II diabetes, the role of specific ACSL isoforms in lipid synthesis remains unclear. In the present study, we describe for the first time the presence of ACSL6 mRNA in human skeletal muscle and the role that ACSL6 plays in lipid synthesis in both rodent and human skeletal muscle. ACSL6 mRNA was observed to be up-regulated by acute high-fat meal ingestion in both rodents and humans. In rats, we also demonstrated that fasting and chronic aerobic training negatively modulated the ACSL6 mRNA and other genes of lipid synthesis. Similar results were obtained following ACSL6 knockdown in rat myotubes, which was associated with a decreased accumulation of TAGs and lipid droplets. Under the same knockdown condition, we further demonstrate an increase in fatty acid content, p-AMPK, mitochondrial content, mitochondrial respiratory rates and palmitate oxidation. These results were associated with increased PGC-1α, UCP2 and UCP3 mRNA and decreased reactive oxygen species production. In human myotubes, ACSL6 overexpression reduced palmitate oxidation and PGC-1α mRNA. In conclusion, ACSL6 drives acyl-CoA toward lipid

  8. Nitric oxide augments voltage-activated calcium currents of crustacea (Idotea baltica) skeletal muscle.

    PubMed

    Erxleben, C; Hermann, A

    2001-03-16

    Invertebrate skeletal muscle contraction is regulated by calcium influx through voltage-dependent calcium channels in the sarcolemmal membrane. In present study we investigated the effects of nitric oxide (NO) donors on calcium currents of single skeletal muscle fibres from the marine isopod, Idotea baltica, using two-electrode voltage clamp recording techniques. The NO donors, S-nitrosocysteine, S-nitroso-N-acetyl-penicillamine or hydroxylamine reversibly increased calcium inward currents in a time dependent manner. The increase of the current was prevented by methylene blue. Our experiments suggest that NO increases calcium inward currents. NO, by acting on calcium ion channels in the sarcolemmal membrane, therefore, may directly be involved in the modulation of muscle contraction.

  9. Mandibular dimensional changes and skeletal maturity.

    PubMed

    Subramaniam, Priya; Naidu, Premila

    2010-10-01

    Growth and development of the human face provides a fascinating interplay of form and function. Among the various facial bones, the mandible plays a very important role during various growth-modification therapies. These treatment modalities will yield a better result in less time if properly correlated with skeletal maturity. It is very essential to know where the site of growth occurs and also the time when it occurs or ceases to occur. This study was conducted to assess the mandibular dimensions at various stages of skeletal maturation. The subjects included 6 to 18-year-old children who were grouped according to their middle phalanx of the third finger stages of skeletal maturity. Lateral cephalographs were taken and, from their cephalometric tracings, linear and angular measurements of the mandible were made. The values obtained were subjected to statistical analysis. Results showed that the mandibular height, length and symphysis thickness increased with skeletal maturity. An increase in angles SNB (Sella, Nasion, Supramentale) and L1-MP (Long axis lower incisors- Mandibular plane) and a decrease in the gonial angle and ANB (Subspinale, Nasion, Supramentale) angle were observed. The study showed a significant correlation between mandibular growth and skeletal maturity.

  10. Ca2+ sensitizers: An emerging class of agents for counterbalancing weakness in skeletal muscle diseases?

    PubMed

    Ochala, Julien

    2010-02-01

    Ca(2+) ions are key regulators of skeletal muscle contraction. By binding to contractile proteins, they initiate a cascade of molecular events leading to cross-bridge formation and ultimately, muscle shortening and force production. The ability of contractile proteins to respond to Ca(2+) attachment, also known as Ca(2+) sensitivity, is often compromised in acquired and congenital skeletal muscle disorders. It constitutes, undoubtedly, a major physiological cause of weakness for patients. In this review, we discuss recent studies giving strong molecular and cellular evidence that pharmacological modulators of some of the contractile proteins, also termed Ca(2+) sensitizers, are efficient agents to improve Ca(2+) sensitivity and function in diseased skeletal muscle cells. In fact, they compensate for the impaired contractile proteins response to Ca(2+) binding. Currently, such Ca(2+) sensitizing compounds are successfully used for reducing problems in cardiac disorders. Therefore, in the future, under certain conditions, these agents may represent an emerging class of agents to enhance the quality of life of patients suffering from skeletal muscle weakness. Copyright 2009 Elsevier B.V. All rights reserved.

  11. Loss of ephrinB1 in osteogenic progenitor cells impedes endochondral ossification and compromises bone strength integrity during skeletal development.

    PubMed

    Nguyen, Thao M; Arthur, Agnieszka; Paton, Sharon; Hemming, Sarah; Panagopoulos, Romana; Codrington, John; Walkley, Carl R; Zannettino, Andrew C W; Gronthos, Stan

    2016-12-01

    The EphB receptor tyrosine kinase family and their ephrinB ligands have been implicated as mediators of skeletal development and bone homeostasis in humans, where mutations in ephrinB1 contribute to frontonasal dysplasia and coronal craniosynostosis. In mouse models, ephrinB1 has been shown to be a critical factor mediating osteoblast function. The present study examined the functional importance of ephrinB1 during endochondral ossification using the Cre recombination system with targeted deletion of ephrinB1 (EfnB1 fl/fl ) in osteogenic progenitor cells, under the control of the osterix (Osx:Cre) promoter. The Osx:EfnB1 -/- mice displayed aberrant bone growth during embryonic and postnatal skeletal development up to 4weeks of age, when compared to the Osx:Cre controls. Furthermore, compared to the Osx:Cre control mice, the Osx:EfnB1 -/- mice exhibited significantly weaker and less rigid bones, with a reduction in trabecular/ cortical bone formation, reduced trabecular architecture and a reduction in the size of the growth plates at the distal end of the femora from newborn through to 4weeks of age. The aberrant bone formation correlated with increased numbers of tartrate resistant acid phosphatase positive osteoclasts and decreased numbers of bone lining osteoblasts in 4week old Osx:EfnB1 -/- mice, compared to Osx:Cre control mice. Taken together, these observations demonstrate the importance of ephrinB1 signalling between cells of the skeleton required for endochondral ossification. Copyright © 2016 Elsevier Inc. All rights reserved.

  12. Modulation of telomerase activity in fish muscle by biological and environmental factors.

    PubMed

    Peterson, Drew Ryan; Mok, Helen Oi Lam; Au, Doris Wai Ting

    2015-12-01

    Telomerase expression has long been linked to promotion of tumor growth and cell proliferation in mammals. Interestingly, telomerase activity (TA) has been detected in skeletal muscle for a variety of fish species. Despite this being a unique feature in fish, very few studies have investigated the potential role of TA in muscle. The present study was set to prove the concepts that muscle telomerase in fish is related to body growth, and more specifically, to muscle cell proliferation and apoptosis in vivo. Moreover, muscle TA can be influenced by biotic factors and modulated by environmental stress. Using three fish species, mangrove red snapper (Lutjanus argentimaculatus), orange-spotted grouper (Epinephelus coioides), and marine medaka (Oryzias melastigma), the present work reports for the first time that fish muscle TA was sensitive to the environmental stresses of starvation, foodborne exposure to benzo[a]pyrene, and hypoxia. In marine medaka, muscle TA was coupled with fish growth during early life stages. Upon sexual maturation, muscle TA was confounded by sex (female>male). Muscle TA was significantly correlated with telomerase reverse transcriptase (TERT) protein expression (Pearson correlation r=0.892; p≤0.05), which was coupled with proliferating cell nuclear antigen (PCNA) cell proliferation, but not associated with apoptosis (omBax/omBcl2 ratio) in muscle tissue. The results reported here have bridged the knowledge gap between the existence and function of telomerase in fish muscle. The underlying regulatory mechanisms of muscle TA in fish warrant further exploration for comparison with telomerase regulation in mammals. Copyright © 2015 Elsevier Inc. All rights reserved.

  13. p53 improves aerobic exercise capacity and augments skeletal muscle mitochondrial DNA content.

    PubMed

    Park, Joon-Young; Wang, Ping-Yuan; Matsumoto, Takumi; Sung, Ho Joong; Ma, Wenzhe; Choi, Jeong W; Anderson, Stasia A; Leary, Scot C; Balaban, Robert S; Kang, Ju-Gyeong; Hwang, Paul M

    2009-09-25

    Exercise capacity is a physiological characteristic associated with protection from both cardiovascular and all-cause mortality. p53 regulates mitochondrial function and its deletion markedly diminishes exercise capacity, but the underlying genetic mechanism orchestrating this is unclear. Understanding the biology of how p53 improves exercise capacity may provide useful insights for improving both cardiovascular as well as general health. The purpose of this study was to understand the genetic mechanism by which p53 regulates aerobic exercise capacity. Using a variety of physiological, metabolic, and molecular techniques, we further characterized maximum exercise capacity and the effects of training, measured various nonmitochondrial and mitochondrial determinants of exercise capacity, and examined putative regulators of mitochondrial biogenesis. As p53 did not affect baseline cardiac function or inotropic reserve, we focused on the involvement of skeletal muscle and now report a wider role for p53 in modulating skeletal muscle mitochondrial function. p53 interacts with Mitochondrial Transcription Factor A (TFAM), a nuclear-encoded gene important for mitochondrial DNA (mtDNA) transcription and maintenance, and regulates mtDNA content. The increased mtDNA in p53(+/+) compared to p53(-/-) mice was more marked in aerobic versus glycolytic skeletal muscle groups with no significant changes in cardiac tissue. These in vivo observations were further supported by in vitro studies showing overexpression of p53 in mouse myoblasts increases both TFAM and mtDNA levels whereas depletion of TFAM by shRNA decreases mtDNA content. Our current findings indicate that p53 promotes aerobic metabolism and exercise capacity by using different mitochondrial genes and mechanisms in a tissue-specific manner.

  14. Rosiglitazone increases fatty acid Δ9-desaturation and decreases elongase activity index in human skeletal muscle in vivo.

    PubMed

    Mai, Knut; Andres, Janin; Bobbert, Thomas; Assmann, Anke; Biedasek, Katrin; Diederich, Sven; Graham, Ian; Larson, Tony R; Pfeiffer, Andreas F H; Spranger, Joachim

    2012-01-01

    The ratio of unsaturated to saturated long-chain fatty acids (LC-FAs) in skeletal muscle has been associated with insulin resistance. Some animal data suggest a modulatory effect of peroxisome proliferator receptor γ (PPARγ) stimulation on stearoyl-CoA desaturase 1 (SCD1) and LC-FA composition in skeletal muscle, but human data are rare. We here investigate whether treatment with a PPARγ agonist affects myocellular SCD1 expression and modulates the intramyocellular fatty acid profile in individuals with impaired glucose tolerance. Muscle biopsies and hyperinsulinemic-euglycemic clamps were performed in 7 men before and after 8 weeks of rosiglitazone treatment. Intramyocellular saturated, monounsaturated, and polyunsaturated intramuscular fatty acid profiles were measured by gas chromatography. Effects on SCD1 messenger RNA expression were analyzed in C2C12 cells and in human biopsies before and after rosiglitazone treatment. As expected, treatment with the PPARγ activator rosiglitazone improved insulin sensitivity in humans. Myocellular SCD1 messenger RNA expression was increased in human biopsies and C2C12 cells. Although the total content of myocellular LC-FA was unchanged, a relative shift from saturated LC-FAs to unsaturated LC-FAs was observed in human biopsies. Particularly, the amount of stearate was reduced, whereas the amounts of palmitoleate as well as oleate and vaccenate were increased, after rosiglitazone therapy. These changes resulted in an increased fatty acid Δ9-desaturation index (16:1/16:0 and 18:1/18:0) in skeletal muscle and a decreased elongase activity index (18:0/16:0). The PPARγ associated phenotypes may be partially explained by an increased Δ9-desaturation and a decreased elongase activity of skeletal muscle. Copyright © 2012 Elsevier Inc. All rights reserved.

  15. The association between skeletal maturation and adrenal androgen levels in obese children and adolescents.

    PubMed

    Kim, Sung Eun; Jang, Joon Weon; Ahn, Moon Bae; Kim, Shin-Hee; Cho, Won Kyoung; Cho, Kyoung Soon; Park, So Hyun; Jung, Min Ho; Suh, Byoung Kyu

    2017-06-01

    This study aimed to investigate the association between skeletal maturation and adrenal androgen levels in obese children and adolescents. Fifty-three children and adolescents (aged 7-15 years) diagnosed as obese or overweight were investigated. Anthropometric measurements, bone age (BA) determination, serum biochemical analyses, and hormonal measurements were performed. The difference between BA and chronological age (BA-CA, dBACA) was calculated and used to represent the degree of advanced skeletal maturation. Thirty-one subjects were classified into the obese group and 22 subjects into the overweight group. Insulin resistance as calculated by the homeostasis model assessment of insulin resistance (HOMA-IR) was significantly higher in the obese group than in the overweight group (4.03±2.20 vs. 2.86±1.11, P =0.026). The skeletal maturation of the obese group was advanced, but the dBACA did not differ between the obese and overweight groups statistically (1.43±1.35 vs. 0.91±1.15, P =0.141). Serum dehydroepiandrosterone sulfate (DHEA-S) levels were significantly higher in subjects with dBACA>1 compared to those with dBACA≤1 (104.3±62.2 vs. 59.6±61.0, P =0.014). Correlation analyses demonstrated that dBACA was positively correlated with body mass index standard deviation scores ( r =0.35, P =0.010), fasting insulin ( r =0.36, P =0.009), HOMA-IR ( r =0.30, P =0.031), and insulin-like growth factor-binding protein-3 ( r =0.331, P =0.028). In multivariate linear regression analysis, HOMA-IR ( P =0.026) and serum DHEA-S ( P =0.032) were positively correlated with the degree of advanced skeletal maturation. Advanced skeletal maturation is associated with increased insulin resistance and elevated DHEA-S levels in obese children and adolescents.

  16. The association between skeletal maturation and adrenal androgen levels in obese children and adolescents

    PubMed Central

    Kim, Sung Eun; Jang, Joon Weon; Ahn, Moon Bae; Kim, Shin-Hee; Cho, Won Kyoung; Cho, Kyoung Soon; Park, So Hyun; Suh, Byoung Kyu

    2017-01-01

    Purpose This study aimed to investigate the association between skeletal maturation and adrenal androgen levels in obese children and adolescents. Methods Fifty-three children and adolescents (aged 7–15 years) diagnosed as obese or overweight were investigated. Anthropometric measurements, bone age (BA) determination, serum biochemical analyses, and hormonal measurements were performed. The difference between BA and chronological age (BA–CA, dBACA) was calculated and used to represent the degree of advanced skeletal maturation. Results Thirty-one subjects were classified into the obese group and 22 subjects into the overweight group. Insulin resistance as calculated by the homeostasis model assessment of insulin resistance (HOMA-IR) was significantly higher in the obese group than in the overweight group (4.03±2.20 vs. 2.86±1.11, P=0.026). The skeletal maturation of the obese group was advanced, but the dBACA did not differ between the obese and overweight groups statistically (1.43±1.35 vs. 0.91±1.15, P=0.141). Serum dehydroepiandrosterone sulfate (DHEA-S) levels were significantly higher in subjects with dBACA>1 compared to those with dBACA≤1 (104.3±62.2 vs. 59.6±61.0, P=0.014). Correlation analyses demonstrated that dBACA was positively correlated with body mass index standard deviation scores (r=0.35, P=0.010), fasting insulin (r=0.36, P=0.009), HOMA-IR (r=0.30, P=0.031), and insulin-like growth factor-binding protein-3 (r=0.331, P=0.028). In multivariate linear regression analysis, HOMA-IR (P=0.026) and serum DHEA-S (P=0.032) were positively correlated with the degree of advanced skeletal maturation. Conclusion Advanced skeletal maturation is associated with increased insulin resistance and elevated DHEA-S levels in obese children and adolescents. PMID:28690989

  17. Effects of spaceflight and Insulin-like Growth Factor-1 on rat bone properties

    NASA Astrophysics Data System (ADS)

    Bateman, Ted A.; Ayers, Reed A.; Spetzler, Michael L.; Simske, Steven J.; Zimmerman, Robert J.

    1997-01-01

    Spaceflight induces bone degradation which is analogous to an accelerated onset of osteoporosis in humans (Tilton et al., 1980). In rats, decreased bone formation is indicative of reduced osteoblast activity (Morey and Baylink, 1978). Chiron Corporation (Emeryville, CA) is interested in using the microgravity environment of low-Earth-orbit to test its therapeutic drug, Insulin-like Growth Factor-1 (IGF-1). This pharmaceutic is known to promote osteoblast activity (Schmid et al., 1984) and therefore may encourage bone growth in rats. Chiron sponsored the Immune.3 payload on STS-73 (May 19-29, 1996) through its Center for Space Commercialization (CSC) partner BioServe Space Technologies (University of Colorado and Kansas State University) to investigate the effects of IGF-1 on mitigating the skeletal degradation that affects rats and humans during spaceflight. Twelve rats were flown for 10 days using two Animal Enclosure Modules (AEMs) provided by NASA Ames Research Center. Of the twelve, six received 1.4 mg/day of IGF-1; the other six saline. Sixteen vivarium ground controls received the same treatment on a one day delay. Rat femora and tibiae were examined for bone mineral density via DXA scan. Femora and humeri were measured for physical and compositional properties, as well as mechanically tested in three point flexure. Quantitative histomorphometric examination of tibiae, humeri, fibulae, ribs and cranial bone; and microhardness testing on tibiae and humeri are currently in progress. Flight humeri and vivarium femora were significantly larger than their counterparts; however, significant differences in mechanical properties and mineral density were not concurrent to these mass changes.

  18. Divergent biophysical properties, gating mechanisms, and possible functions of the two skeletal muscle Ca(V)1.1 calcium channel splice variants.

    PubMed

    Tuluc, Petronel; Flucher, Bernhard E

    2011-12-01

    Voltage-gated calcium channels are multi-subunit protein complexes that specifically allow calcium ions to enter the cell in response to membrane depolarization. But, for many years it seemed that the skeletal muscle calcium channel Ca(V)1.1 is the exception. The classical splice variant Ca(V)1.1a activates slowly, has a very small current amplitude and poor voltage sensitivity. In fact adult muscle fibers work perfectly well even in the absence of calcium influx. Recently a new splice variant of the skeletal muscle calcium channel Ca(V)1.1e has been characterized. The lack of the 19 amino acid exon 29 in this splice variant results in a rapidly activating calcium channel with high current amplitude and good voltage sensitivity. Ca(V)1.1e is the dominant channel in embryonic muscle, where the expression of this high calcium-conducting Ca(V)1.1 isoform readily explains developmental processes depending on L-type calcium currents. Moreover, the availability of these two structurally similar but functionally distinct channel variants facilitates the analysis of the molecular mechanisms underlying the unique current properties of the classical Ca(V)1.1a channel.

  19. Comprehensive Analysis of Tropomyosin Isoforms in Skeletal Muscles by Top-down Proteomics

    PubMed Central

    Jin, Yutong; Peng, Ying; Lin, Ziqing; Chen, Yi-Chen; Wei, Liming; Hacker, Timothy A.; Larsson, Lars; Ge, Ying

    2016-01-01

    Mammalian skeletal muscles are heterogeneous in nature and are capable of performing various functions. Tropomyosin (Tpm) is a major component of the thin filament in skeletal muscles and plays an important role in controlling muscle contraction and relaxation. Tpm is known to consist of multiple isoforms resulting from different encoding genes and alternative splicing, along with post-translational modifications. However, a systematic characterization of Tpm isoforms in skeletal muscles is still lacking. Therefore, we employed top-down mass spectrometry (MS) to identify and characterize Tpm isoforms present in different skeletal muscles from multiple species, including swine, rat, and human. Our study revealed that Tpm1.1 and Tpm2.2 are the two major Tpm isoforms in swine and rat skeletal muscles, whereas Tpm1.1, Tpm2.2, and Tpm3.12 are present in human skeletal muscles. Tandem MS was utilized to identify the sequences of the major Tpm isoforms. Furthermore, quantitative analysis revealed muscle-type specific differences in the abundance of un-modified and modified Tpm isoforms in rat and human skeletal muscles. This study represents the first systematic investigation of Tpm isoforms in skeletal muscles, which not only demonstrates the capabilities of top-down MS for the comprehensive characterization of skeletal myofilament proteins but also provides the basis for further studies on these Tpm isoforms in muscle-related diseases. PMID:27090236

  20. Activity of LKB1 and AMPK-related kinases in skeletal muscle: effects of contraction, phenformin, and AICAR.

    PubMed

    Sakamoto, Kei; Göransson, Olga; Hardie, D Grahame; Alessi, Dario R

    2004-08-01

    Activation of AMP-activated protein kinase (AMPK) by exercise and metformin is beneficial for the treatment of type 2 diabetes. We recently found that, in cultured cells, the LKB1 tumor suppressor protein kinase activates AMPK in response to the metformin analog phenformin and the AMP mimetic drug 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR). We have also reported that LKB1 activates 11 other AMPK-related kinases. The activity of LKB1 or the AMPK-related kinases has not previously been studied in a tissue with physiological relevance to diabetes. In this study, we have investigated whether contraction, phenformin, and AICAR influence LKB1 and AMPK-related kinase activity in rat skeletal muscle. Contraction in situ, induced via sciatic nerve stimulation, significantly increased AMPKalpha2 activity and phosphorylation in multiple muscle fiber types without affecting LKB1 activity. Treatment of isolated skeletal muscle with phenformin or AICAR stimulated the phosphorylation and activation of AMPKalpha1 and AMPKalpha2 without altering LKB1 activity. Contraction, phenformin, or AICAR did not significantly increase activities or expression of the AMPK-related kinases QSK, QIK, MARK2/3, and MARK4 in skeletal muscle. The results of this study suggest that muscle contraction, phenformin, or AICAR activates AMPK by a mechanism that does not involve direct activation of LKB1. They also suggest that the effects of excercise, phenformin, and AICAR on metabolic processes in muscle may be mediated through activation of AMPK rather than activation of LKB1 or the AMPK-related kinases.