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Sample records for cultured skeletal muscle

  1. Mechanically induced alterations in cultured skeletal muscle growth

    NASA Technical Reports Server (NTRS)

    Vandenburgh, H. H.; Hatfaludy, S.; Karlisch, P.; Shansky, J.

    1991-01-01

    Model systems are available for mechanically stimulating cultured skeletal muscle cells by passive tensile forces which simulate those found in vivo. When applied to embryonic muscle cells in vitro these forces induce tissue organogenesis, metabolic adaptations, and muscle cell growth. The mechanical stimulation of muscle cell growth correlates with stretch-induced increases in the efflux of prostaglandins PGE2 and PGF2(alpha) in a time and frequency dependent manner. These prostaglandins act as mechanical 'second messengers' regulating skeletal muscle protein turnover rates. Since they also effect bone remodelling in response to tissue loading and unloading, secreted prostaglandins may serve as paracrine growth factors, coordinating the growth rates of muscle and bone in response to external mechanical forces. Cell culture model systems will supplement other models in understanding mechanical transduction processes at the molecular level.

  2. Improved Cell Culture Method for Growing Contracting Skeletal Muscle Models

    NASA Technical Reports Server (NTRS)

    Marquette, Michele L.; Sognier, Marguerite A.

    2013-01-01

    An improved method for culturing immature muscle cells (myoblasts) into a mature skeletal muscle overcomes some of the notable limitations of prior culture methods. The development of the method is a major advance in tissue engineering in that, for the first time, a cell-based model spontaneously fuses and differentiates into masses of highly aligned, contracting myotubes. This method enables (1) the construction of improved two-dimensional (monolayer) skeletal muscle test beds; (2) development of contracting three-dimensional tissue models; and (3) improved transplantable tissues for biomedical and regenerative medicine applications. With adaptation, this method also offers potential application for production of other tissue types (i.e., bone and cardiac) from corresponding precursor cells.

  3. Skeletal muscle satellite cells cultured in simulated microgravity

    NASA Technical Reports Server (NTRS)

    Molnar, Greg; Hartzell, Charles R.; Schroedl, Nancy A.; Gonda, Steve R.

    1993-01-01

    Satellite cells are postnatal myoblasts responsible for providing additional nuclei to growing or regenerating muscle cells. Satellite cells retain the capacity to proliferate and differentiate in vitro and therefore provide a useful model to study postnatal muscle development. Most culture systems used to study postnatal muscle development are limited by the two-dimensional (2-D) confines of the culture dish. Limiting proliferation and differentiation of satellite cells in 2-D could potentially limit cell-cell contacts important for developing the level of organization in skeletal muscle obtained in vivo. Culturing satellite cells on microcarrier beads suspended in the High-Aspect-Ratio-Vessel (HARV) designed by NASA provides a low shear, three-dimensional (3-D) environment to study muscle development. Primary cultures established from anterior tibialis muscles of growing rats (approximately 200 gm) were used for all studies and were composed of greater than 75 % satellite cells. Different inoculation densities did not affect the proliferative potential of satellite cells in the HARV. Plating efficiency, proliferation, and glucose utilization were compared between 2-D flat culture and 3-D HARV culture. Plating efficiency (cells attached - cells plated x 100) was similar between the two culture systems. Proliferation was reduced in HARV cultures and this reduction was apparent for both satellite cells and non-satellite cells. Furthermore, reduction in proliferation within the HARV could not be attributed to reduced substrate availability since glucose levels in media from HARV and 2-D cell culture were similar. Morphologically, microcarrier beads within the HARVS were joined together by cells into three-dimensional aggregates composed of greater than 10 beads/aggregate. Aggregation of beads did not occur in the absence of cells. Myotubes were often seen on individual beads or spanning the surface of two beads. In summary, proliferation and differentiation of

  4. Methods for the Organogenesis of Skeletal Muscle in Tissue Culture

    NASA Technical Reports Server (NTRS)

    Vandenburgh, Herman; Shansky, Janet; DelTatto, Michael; Chromiak, Joseph

    1997-01-01

    Skeletal muscle structure is regulated by many factors, including nutrition, hormones, electrical activity, and tension. The muscle cells are subjected to both passive and active mechanical forces at all stages of development and these forces play important but poorly understood roles in regulating muscle organogenesis and growth. For example, during embryogenesis, the rapidly growing skeleton places large passive mechanical forces on the attached muscle tissue. These forces not only help to organize the proliferating mononucleated myoblasts into the oriented, multinucleated myofibers of a functional muscle but also tightly couple the growth rate of muscle to that of bone. Postnatally, the actively contracting, innervated muscle fibers are subjected to different patterns of active and passive tensions which regulate longitudinal and cross sectional myofiber growth. These mechanically-induced organogenic processes have been difficult to study under normal tissue culture conditions, resulting in the development of numerous methods and specialized equipment to simulate the in vivo mechanical environment.These techniques have led to the "engineering" of bioartificial muscles (organoids) which display many of the characteristics of in vivo muscle including parallel arrays of postmitotic fibers organized into fascicle-like structures with tendon-like ends. They are contractile, express adult isoforms of contractile proteins, perform directed work, and can be maintained in culture for long periods. The in vivo-like characteristics and durability of these muscle organoids make them useful for long term in vitro studies on mechanotransduction mechanisms and on muscle atrophy induced by decreased tension. In this report, we described a simple method for generating muscle organoids from either primary embrionic avain or neonatal rodent myoblasts.

  5. Skeletal muscle

    Technology Transfer Automated Retrieval System (TEKTRAN)

    There are approximately 650-850 muscles in the human body these include skeletal (striated), smooth and cardiac muscle. The approximation is based on what some anatomists consider separate muscle or muscle systems. Muscles are classified based on their anatomy (striated vs. smooth) and if they are v...

  6. Primary skeletal muscle cells cultured on gelatin bead microcarriers develop structural and biochemical features characteristic of adult skeletal muscle.

    PubMed

    Kubis, Hans-Peter; Scheibe, Renate J; Decker, Brigitte; Hufendiek, Karsten; Hanke, Nina; Gros, Gerolf; Meissner, Joachim D

    2016-04-01

    A primary skeletal muscle cell culture, in which myoblasts derived from newborn rabbit hindlimb muscles grow on gelatin bead microcarriers in suspension and differentiate into myotubes, has been established previously. In the course of differentiation and beginning spontaneous contractions, these multinucleated myotubes do not detach from their support. Here, we describe the development of the primary myotubes with respect to their ultrastructural differentiation. Scanning electron microscopy reveals that myotubes not only grow around the surface of one carrier bead but also attach themselves to neighboring carriers, forming bridges between carriers. Transmission electron microscopy demonstrates highly ordered myofibrils, T-tubules, and sarcoplasmic reticulum. The functionality of the contractile apparatus is evidenced by contractile activity that occurs spontaneously or can be elicited by electrostimulation. Creatine kinase activity increases steadily until day 20 of culture. Regarding the expression of isoforms of myosin heavy chains (MHC), we could demonstrate that from day 16 on, no non-adult MHC isoform mRNAs are present. Instead, on day 28 the myotubes express predominantly adult fast MHCIId/x mRNA and protein. This MHC pattern resembles that of fast muscles of adult rabbits. In contrast, primary myotubes grown on matrigel-covered culture dishes express substantial amounts of non-adult MHC protein even on day 21. To conclude, primary myotubes grown on microcarriers in their later stages exhibit many features of adult skeletal muscle and characteristics of fast type II fibers. Thus, the culture represents an excellent model of adult fast skeletal muscle, for example, when investigating molecular mechanisms of fast-to-slow fiber-type transformation. PMID:26610066

  7. Mechanism of glycogen supercompensation in rat skeletal muscle cultures.

    PubMed

    Mamedova, Liaman K; Shneyvays, Vladimir; Katz, Abram; Shainberg, Asher

    2003-08-01

    A model to study glycogen supercompensation (the significant increase in glycogen content above basal level) in primary rat skeletal muscle culture was established. Glycogen was completely depleted in differentiated myotubes by 2 h of electrical stimulation or exposure to hypoxia during incubation in medium devoid of glucose. Thereafter, cells were incubated in medium containing glucose, and glycogen supercompensation was clearly observed in treated myotubes after 72 h. Peak glycogen levels were obtained after 120 h, averaging 2.5 and 4 fold above control values in the stimulated- and hypoxia-treated cells, respectively. Glycogen synthase activity increased and phosphorylase activity decreased continuously during 120 h of recovery in the treated cells. Rates of 2-deoxyglucose uptake were significantly elevated in the treated cells at 96 and 120 h, averaging 1.4-2 fold above control values. Glycogenin content increased slightly in the treated cells after 48 h (1.2 fold vs. control) and then increased considerably, achieving peak values after 120 h (2 fold vs. control). The results demonstrate two phases of glycogen supercompensation: the first phase depends primarily on activation of glycogen synthase and inactivation of phosphorylase; the second phase includes increases in glucose uptake and glycogenin level. PMID:12962138

  8. Isolation, Culture and Identification of Porcine Skeletal Muscle Satellite Cells

    PubMed Central

    Li, Bo-jiang; Li, Ping-hua; Huang, Rui-hua; Sun, Wen-xing; Wang, Han; Li, Qi-fa; Chen, Jie; Wu, Wang-jun; Liu, Hong-lin

    2015-01-01

    The objective of this study was to establish the optimum protocol for the isolation and culture of porcine muscle satellite cells. Mononuclear muscle satellite cells are a kind of adult stem cell, which is located between the basal lamina and sarcolemma of muscle fibers and is the primary source of myogenic precursor cells in postnatal muscle. Muscle satellite cells are a useful model to investigate the mechanisms of muscle growth and development. Although the isolation and culture protocols of muscle satellite cells in some species (e.g. mouse) have been established successfully, the culture system for porcine muscle satellite cells is very limited. In this study, we optimized the isolation procedure of porcine muscle satellite cells and elaborated the isolation and culture process in detail. Furthermore, we characterized the porcine muscle satellite cells using the immunofluorecence. Our study provides a reference for the isolation of porcine muscle satellite cells and will be useful for studying the molecular mechanisms in these cells. PMID:26104526

  9. Neural control of skeletal muscle cholinesterase: a study using organ-cultured rat muscle.

    PubMed Central

    Davey, B; Younkin, L H; Younkin, S G

    1979-01-01

    1. It has been proposed that the influence of innervation on the cholinesterase activity (ChE) of skeletal muscle and on end-plate ChE in particular is mediated by trophic substance(s) moved by axonal transport and released from nerve. We have tested this hypothesis using rat extensor digitorum longus (e.d.l.) and diaphragm muscles denervated in vitro for several days and then maintained in organ culture to assay putative trophic substance(s). 2. The cholinesterase activity (ChE) of rat extensor digitorum longus (e.d.l.) muscles decreased dramatically after 5 days of denervation in vivo as previously reported. The ChE of rat e.d.l. muscles denervated in vivo for 3 days and then maintained in organ culture for 2 days was essentially identical to that of muscles denervated 5 days in vivo. 3. The ChE OF E.D.L. MUSCLES DENERVATED IN VIVO FOR 3 DAYS AND THEN MAINTAINED FOR 2 DAYS IN CULTURE MEDIUM SUPPLEMENTED WITH SCIATIC NERVE OR INNERVATED MUSCLE EXTRACT WAS SIGNIFICANTLY HIGHER THAN THAT OF MUSCLES DENERVATED IN VIVO FOR 5 DAYS OR DENERVATED IN VIVO FOR 3 DAYS AND THEN CULTURED FOR 2 DAYS IN CULTURE MEDIUM ALONE. Supplementing the culture medium with brain or spinal cord extract also significantly increased the ChE of organ-cultured e.d.l. muscles. 4. Supplementing the culture medium with liver or spleen extract or with the extract of muscle denervated for 3--7 days in vivo before extraction did not increase the ChE or organ-cultured e.d.l. muscles. 5. The effect of muscle extract on the ChE of organ-cultured e.d.l. muscles was dose dependent and occurred gradually reaching a maximum after approximately 24 h of culture. 6. Substance(s) which increased the ChE of organ-cultured e.d.l. muscles were found to accumulate in transected sciatic nerve in the region just proximal to the site of transection where substances moved by axonal transport are known to accumulate. 7. Media conditioned with neurally stimulated e.d.l. or diaphragm muscles caused a substantial and

  10. Receptor Expression in Rat Skeletal Muscle Cell Cultures

    NASA Technical Reports Server (NTRS)

    Young, Ronald B.

    1996-01-01

    One on the most persistent problems with long-term space flight is atrophy of skeletal muscles. Skeletal muscle is unique as a tissue in the body in that its ability to undergo atrophy or hypertrophy is controlled exclusively by cues from the extracellular environment. The mechanism of communication between muscle cells and their environment is through a group of membrane-bound and soluble receptors, each of which carries out unique, but often interrelated, functions. The primary receptors include acetyl choline receptors, beta-adrenergic receptors, glucocorticoid receptors, insulin receptors, growth hormone (i.e., somatotropin) receptors, insulin-like growth factor receptors, and steroid receptors. This project has been initiated to develop an integrated approach toward muscle atrophy and hypertrophy that takes into account information on the populations of the entire group of receptors (and their respective hormone concentrations), and it is hypothesized that this information can form the basis for a predictive computer model for muscle atrophy and hypertrophy. The conceptual basis for this project is illustrated in the figure below. The individual receptors are shown as membrane-bound, with the exception of the glucocorticoid receptor which is a soluble intracellular receptor. Each of these receptors has an extracellular signalling component (e.g., innervation, glucocorticoids, epinephrine, etc.), and following the interaction of the extracellular component with the receptor itself, an intracellular signal is generated. Each of these intracellular signals is unique in its own way; however, they are often interrelated.

  11. Stretch-induced prostaglandins and protein turnover in cultured skeletal muscle

    NASA Technical Reports Server (NTRS)

    Vandenburgh, Herman H.; Hatfaludy, Sophia; Sohar, Istvan; Shansky, Janet

    1990-01-01

    The purpose of the study is to determine whether mechanical stimulation of cultured muscle cells influences prostaglandin efflux rates and whether they are related to stretch-induced alterations in protein turnover rates. The materials and methods of the experiment, including cell cultures, mechanical stimulation, protein synthesis, and degradation assays are outlined, and emphasis is placed on the effect of short-term mechanical stimulation in basal medium prostaglandin efflux from cultured skeletal muscle and stretch-induced alterations in prostaglandins efflux in complete medium. The major finding of the study is that mechanical stimulation of tissue-cultured skeletal-muscle cells under conditions inducing skeletal-muscle hypertropy increases the efflux of PGE(2) and PGE(2-alpha) but not 6-keto-PGF(1-alpha), the prostacyclin product.

  12. Differentiation of mammalian skeletal muscle cells cultured on microcarrier beads in a rotating cell culture system

    NASA Technical Reports Server (NTRS)

    Torgan, C. E.; Burge, S. S.; Collinsworth, A. M.; Truskey, G. A.; Kraus, W. E.

    2000-01-01

    The growth and repair of adult skeletal muscle are due in part to activation of muscle precursor cells, commonly known as satellite cells or myoblasts. These cells are responsive to a variety of environmental cues, including mechanical stimuli. The overall goal of the research is to examine the role of mechanical signalling mechanisms in muscle growth and plasticity through utilisation of cell culture systems where other potential signalling pathways (i.e. chemical and electrical stimuli) are controlled. To explore the effects of decreased mechanical loading on muscle differentiation, mammalian myoblasts are cultured in a bioreactor (rotating cell culture system), a model that has been utilised to simulate microgravity. C2C12 murine myoblasts are cultured on microcarrier beads in a bioreactor and followed throughout differentiation as they form a network of multinucleated myotubes. In comparison with three-dimensional control cultures that consist of myoblasts cultured on microcarrier beads in teflon bags, myoblasts cultured in the bioreactor exhibit an attenuation in differentiation. This is demonstrated by reduced immunohistochemical staining for myogenin and alpha-actinin. Western analysis shows a decrease, in bioreactor cultures compared with control cultures, in levels of the contractile proteins myosin (47% decrease, p < 0.01) and tropomyosin (63% decrease, p < 0.01). Hydrodynamic measurements indicate that the decrease in differentiation may be due, at least in part, to fluid stresses acting on the myotubes. In addition, constraints on aggregate size imposed by the action of fluid forces in the bioreactor affect differentiation. These results may have implications for muscle growth and repair during spaceflight.

  13. Skeletal Muscle Satellite Cells: Background and Methods for Isolation and Analysis in a Primary Culture System

    PubMed Central

    Danoviz, Maria Elena; Yablonka-Reuveni, Zipora

    2012-01-01

    Summary Repair of adult skeletal muscle depends on satellite cells, myogenic stem cells located between the basal lamina and the plasmalemma of the myofiber. Standardized protocols for the isolation and culture of satellite cells are key tools for understanding cell autonomous and extrinsic factors that regulate their performance. Knowledge gained from such studies can contribute important insights to developing strategies for the improvement of muscle repair following trauma and in muscle wasting disorders. This chapter provides an introduction to satellite cell biology and further describes the basic protocol used in our laboratory to isolate and culture satellite cells from adult skeletal muscle. The cell culture conditions detailed herein support proliferation and differentiation of satellite cell progeny and the development of reserve cells, which are thought to reflect the in vivo self-renewal ability of satellite cells. Additionally, this chapter describes our standard immunostaining protocol that allows the characterization of satellite cell progeny by the temporal expression of characteristic transcription factors and structural proteins associated with different stages of myogenic progression. While emphasis is given here to the isolation and characterization of satellite cells from mouse hindlimb muscles, the protocols are suitable for other muscle types (such as diaphragm and extraocular muscles) and for muscles from other species, including chicken and rat. Altogether, the basic protocols described are straightforward and facilitate the study of diverse aspects of skeletal muscle stem cells. PMID:22130829

  14. Cell culture as a tool for the study of poultry skeletal muscle development.

    PubMed

    McFarland, D C

    1992-03-01

    Postnatal development of skeletal muscle is the responsibility of the myogenic satellite cells. Satellite cells, isolated from the pectoralis major muscle of young growing tom turkeys, have been cultured in vitro to provide a system for studying cellular and hormonal aspects of poultry skeletal muscle development. Satellite cell clones derived from primary cultures have been developed so that in vitro observations would not be confounded by the presence of nonmyogenic cells. Likewise, a serum-free medium that promotes proliferation of the turkey satellite cell has been developed to provide a hormonally controlled environment for in vitro developmental studies. These two techniques have enabled us to examine the following: 1) factors that influence satellite cell proliferation and differentiation, 2) the interaction of hormones with cellular receptors, 3) secretion of biologically important proteins from cells and 4) the expression of genes important to muscle development. PMID:1371806

  15. Mechanical load induces sarcoplasmic wounding and FGF release in differentiated human skeletal muscle cultures

    NASA Technical Reports Server (NTRS)

    Clarke, M. S.; Feeback, D. L.

    1996-01-01

    The transduction mechanism (or mechanisms) responsible for converting a mechanical load into a skeletal muscle growth response are unclear. In this study we have used a mechanically active tissue culture model of differentiated human skeletal muscle cells to investigate the relationship between mechanical load, sarcolemma wounding, fibroblast growth factor release, and skeletal muscle cell growth. Using the Flexcell Strain Unit we demonstrate that as mechanical load increases, so too does the amount of sarcolemma wounding. A similar relationship was also observed between the level of mechanical load inflicted on the cells and the amount of bFGF (FGF2) released into the surrounding medium. In addition, we demonstrate that the muscle cell growth response induced by chronic mechanical loading in culture can be inhibited by the presence of an antibody capable of neutralizing the biological activity of FGF. This study provides direct evidence that mechanically induced, sarcolemma wound-mediated FGF release is an important autocrine mechanism for transducing the stimulus of mechanical load into a skeletal muscle growth response.

  16. Human skeletal muscle-derived stem cells retain stem cell properties after expansion in myosphere culture

    SciTech Connect

    Wei, Yan; Li, Yuan; Chen, Chao; Stoelzel, Katharina; Kaufmann, Andreas M.

    2011-04-15

    Human skeletal muscle contains an accessible adult stem-cell compartment in which differentiated myofibers are maintained and replaced by a self-renewing stem cell pool. Previously, studies using mouse models have established a critical role for resident stem cells in skeletal muscle, but little is known about this paradigm in human muscle. Here, we report the reproducible isolation of a population of cells from human skeletal muscle that is able to proliferate for extended periods of time as floating clusters of rounded cells, termed 'myospheres' or myosphere-derived progenitor cells (MDPCs). The phenotypic characteristics and functional properties of these cells were determined using reverse transcription-polymerase chain reaction (RT-PCR), flow cytometry and immunocytochemistry. Our results showed that these cells are clonogenic, express skeletal progenitor cell markers Pax7, ALDH1, Myod, and Desmin and the stem cell markers Nanog, Sox2, and Oct3/4 significantly elevated over controls. They could be maintained proliferatively active in vitro for more than 20 weeks and passaged at least 18 times, despite an average donor-age of 63 years. Individual clones (4.2%) derived from single cells were successfully expanded showing clonogenic potential and sustained proliferation of a subpopulation in the myospheres. Myosphere-derived cells were capable of spontaneous differentiation into myotubes in differentiation media and into other mesodermal cell lineages in induction media. We demonstrate here that direct culture and expansion of stem cells from human skeletal muscle is straightforward and reproducible with the appropriate technique. These cells may provide a viable resource of adult stem cells for future therapies of disease affecting skeletal muscle or mesenchymal lineage derived cell types.

  17. Interactions between Skeletal Muscle Myoblasts and their Extracellular Matrix Revealed by a Serum Free Culture System

    PubMed Central

    Chaturvedi, Vishal; Dye, Danielle E.; Kinnear, Beverley F.; van Kuppevelt, Toin H.; Grounds, Miranda D.; Coombe, Deirdre R.

    2015-01-01

    Decellularisation of skeletal muscle provides a system to study the interactions of myoblasts with muscle extracellular matrix (ECM). This study describes the efficient decellularisation of quadriceps muscle with the retention of matrix components and the use of this matrix for myoblast proliferation and differentiation under serum free culture conditions. Three decellularisation approaches were examined; the most effective was phospholipase A2 treatment, which removed cellular material while maximizing the retention of ECM components. Decellularised muscle matrices were then solubilized and used as substrates for C2C12 mouse myoblast serum free cultures. The muscle matrix supported myoblast proliferation and differentiation equally as well as collagen and fibronectin. Immunofluorescence analyses revealed that myoblasts seeded on muscle matrix and fibronectin differentiated to form long, well-aligned myotubes, while myoblasts seeded on collagen were less organized. qPCR analyses showed a time dependent increase in genes involved in skeletal muscle differentiation and suggested that muscle-derived matrix may stimulate an increased rate of differentiation compared to collagen and fibronectin. Decellularized whole muscle three-dimensional scaffolds also supported cell adhesion and spreading, with myoblasts aligning along specific tracts of matrix proteins within the scaffolds. Thus, under serum free conditions, intact acellular muscle matrices provided cues to direct myoblast adhesion and migration. In addition, myoblasts were shown to rapidly secrete and organise their own matrix glycoproteins to create a localized ECM microenvironment. This serum free culture system has revealed that the correct muscle ECM facilitates more rapid cell organisation and differentiation than single matrix glycoprotein substrates. PMID:26030912

  18. Isolation and Culture of Skeletal Muscle Myofibers as a Means to Analyze Satellite Cells

    PubMed Central

    Shefer, Gabi; Yablonka-Reuveni, Zipora

    2012-01-01

    Summary Myofibers are the functional contractile units of skeletal muscle. Mononuclear satellite cells located between the basal lamina and the plasmalemma of the myofiber are the primary source of myogenic precursor cells in postnatal muscle. This chapter describes protocols used in our laboratory for isolation, culturing and immunostaining of single myofibers from mouse skeletal muscle. The isolated myofibers are intact and retain their associated satellite cells underneath the basal lamina. The first protocol discusses myofiber isolation from the flexor digitorum brevis (FDB) muscle. Myofibers are cultured in dishes coated with Vitrogen collagen and satellite cells remain associated with the myofibers undergoing proliferation and differentiation on the myofiber surface. The second protocol discusses the isolation of longer myofibers from the extensor digitorum longus (EDL). Different from the FDB myofibers, the longer EDL myofibers tend to tangle and break if cultured together; therefore, EDL myofibers are cultured individually. These myofibers are cultured in dishes coated with Matrigel. The satellite cells initially remain associated with the myofiber and later migrate away to its vicinity, resulting in extensive cell proliferation and differentiation. These culture protocols allow studies on the interplay between the myofiber and its associated satellite cells. PMID:15361669

  19. Isolation and Culture of Skeletal Muscle Myofibers as a Means to Analyze Satellite Cells

    PubMed Central

    Keire, Paul; Shearer, Andrew; Shefer, Gabi; Yablonka-Reuveni, Zipora

    2012-01-01

    Multinucleated myofibers are the functional contractile units of skeletal muscle. In adult muscle, mononuclear satellite cells, located between the basal lamina and the plasmalemma of the myofiber, are the primary myogenic stem cells. This chapter describes protocols for isolation, culturing and immunostaining of myofibers from mouse skeletal muscle. Myofibers are isolated intact and retain their associated satellite cells. The first protocol discusses myofiber isolation from the flexor digitorum brevis (FDB) muscle. These short myofibers are cultured in dishes coated with PureCol collagen (formerly known as Vitrogen) using a serum replacement medium. Employing such culture conditions, satellite cells remain associated with the myofibers, undergoing proliferation and differentiation on the myofiber surface. The second protocol discusses the isolation of longer myofibers from the extensor digitorum longus (EDL) muscle. Different from the FDB preparation, where multiple myofibers are processed together, the longer EDL myofibers are typically processed and cultured individually in dishes coated with Matrigel using a growth factor rich medium. Under these conditions, satellite cells initially remain associated with the parent myofiber and later migrate away, giving rise to proliferating and differentiating progeny. Myofibers from other types of muscles, such as diaphragm, masseter, and extraocular muscles can also be isolated and analyzed using protocols described herein. Overall, cultures of isolated myofibers provide essential tools for studying the interplay between the parent myofiber and its associated satellite cells. The current chapter provides background, procedural, and reagent updates, and step-by-step images of FDB and EDL muscle isolations, not included in our 2005 publication in this series. PMID:23179849

  20. Metabolic alterations induced in cultured skeletal muscle by stretch-relaxation activity

    NASA Technical Reports Server (NTRS)

    Hatfaludy, Sophia; Shansky, Janet; Vandenburgh, Herman H.

    1989-01-01

    Muscle cells differentiated in vitro are repetitively stretched and relaxed in order to determine the presence of short- and long-term alterations occurring in glucose uptake and lactate efflux that are similar to the metabolic alterations occurring in stimulated organ-cultured muscle and in vivo skeletal muscle during the active state. It is observed that whereas mechanical stimulation increases these metabolic parameters within 4-6 h of starting activity, unstimulated basal rates in control cultures also increase during this period of time, and by 8 h, their rates have reached or exceeded the rates in continuously stimulated cells. Measurements of these parameters in media of different compositions show that activity-induced long-term alterations in the parameters occur independently of growth factors in serium and embryo extracts.

  1. Abnormalities of AMPK Activation and Glucose Uptake in Cultured Skeletal Muscle Cells from Individuals with Chronic Fatigue Syndrome

    PubMed Central

    Brown, Audrey E.; Jones, David E.; Walker, Mark; Newton, Julia L.

    2015-01-01

    Background Post exertional muscle fatigue is a key feature in Chronic Fatigue Syndrome (CFS). Abnormalities of skeletal muscle function have been identified in some but not all patients with CFS. To try to limit potential confounders that might contribute to this clinical heterogeneity, we developed a novel in vitro system that allows comparison of AMP kinase (AMPK) activation and metabolic responses to exercise in cultured skeletal muscle cells from CFS patients and control subjects. Methods Skeletal muscle cell cultures were established from 10 subjects with CFS and 7 age-matched controls, subjected to electrical pulse stimulation (EPS) for up to 24h and examined for changes associated with exercise. Results In the basal state, CFS cultures showed increased myogenin expression but decreased IL6 secretion during differentiation compared with control cultures. Control cultures subjected to 16h EPS showed a significant increase in both AMPK phosphorylation and glucose uptake compared with unstimulated cells. In contrast, CFS cultures showed no increase in AMPK phosphorylation or glucose uptake after 16h EPS. However, glucose uptake remained responsive to insulin in the CFS cells pointing to an exercise-related defect. IL6 secretion in response to EPS was significantly reduced in CFS compared with control cultures at all time points measured. Conclusion EPS is an effective model for eliciting muscle contraction and the metabolic changes associated with exercise in cultured skeletal muscle cells. We found four main differences in cultured skeletal muscle cells from subjects with CFS; increased myogenin expression in the basal state, impaired activation of AMPK, impaired stimulation of glucose uptake and diminished release of IL6. The retention of these differences in cultured muscle cells from CFS subjects points to a genetic/epigenetic mechanism, and provides a system to identify novel therapeutic targets. PMID:25836975

  2. Cultured embryonic chick skeletal muscle cells contain specific receptors for a myotrophic factor identified as neutrotransferrin

    SciTech Connect

    Stamotos, C.G.

    1985-01-01

    Cultured embryonic chick myotubes require iron during proliferation and differentiation. Ovotransferrin (OvoTF), the iron-binding protein of egg white, produced a concentration-dependent stimulation of myogenesis, as evaluated by a sensitive quantitative bioassay for acetylcholine receptors. Neurotransferrin, a myotrophic protein isolated from adult chicken sciatic nerve, is immunologically and physiologically very similar, if not identical, to OvoTf. Cultured embryonic chick spinal cord neurons were metabolically labeled with /sup 35/S-methionine, homogenized and subjected to immunoprecipitation with antibody against neurotransferrin. The authors demonstrated that neuronal cell enriched cultures synthesize and secrete neurotransferrin. The binding of OvoTf to cultured myotubes is specific, saturated at a concentration of 80 nM OvoTf and reversible. Binding of OvoTf to cultured myotubes occurs at 4/sup 0/C and at 37/sup 0/C. Internalization studies using /sup 125/I-ovotransferrin or /sup 55/Fe-OvoTf suggested that OvoTf is internalized, depleted of iron and then recycled intact to the extracellular milieu. Autoradiography of muscle cell cultures incubated with /sup 125/I-OvoTf revealed clusters of OvoTf receptors along the surface of the myotubes. Electron microscopy autoradiography of myotubes incubated with /sup 55/Fe-OvoTf showed that iron delivered by OvoTf is rapidly distributed throughout the cell. The results of the studies suggest that neurotransferrin may play a critical role during in vivo embryonic chick skeletal muscle development.

  3. Structure of Skeletal Muscle

    MedlinePlus

    ... Cells, Tissues, & Membranes Cell Structure & Function Cell Structure Cell Function Body Tissues Epithelial Tissue Connective Tissue Muscle Tissue ... nerves. This is directly related to the primary function of skeletal muscle, ... an impulse from a nerve cell. Generally, an artery and at least one vein ...

  4. Glucocorticoids and Skeletal Muscle.

    PubMed

    Bodine, Sue C; Furlow, J David

    2015-01-01

    Glucocorticoids are known to regulate protein metabolism in skeletal muscle, producing a catabolic effect that is opposite that of insulin. In many catabolic diseases, such as sepsis, starvation, and cancer cachexia, endogenous glucocorticoids are elevated contributing to the loss of muscle mass and function. Further, exogenous glucocorticoids are often given acutely and chronically to treat inflammatory conditions such as asthma, chronic obstructive pulmonary disease, and rheumatoid arthritis, resulting in muscle atrophy. This chapter will detail the nature of glucocorticoid-induced muscle atrophy and discuss the mechanisms thought to be responsible for the catabolic effects of glucocorticoids on muscle. PMID:26215994

  5. Engineering skeletal muscle repair.

    PubMed

    Juhas, Mark; Bursac, Nenad

    2013-10-01

    Healthy skeletal muscle has a remarkable capacity for regeneration. Even at a mature age, muscle tissue can undergo a robust rebuilding process that involves the formation of new muscle cells and extracellular matrix and the re-establishment of vascular and neural networks. Understanding and reverse-engineering components of this process is essential for our ability to restore loss of muscle mass and function in cases where the natural ability of muscle for self-repair is exhausted or impaired. In this article, we will describe current approaches to restore the function of diseased or injured muscle through combined use of myogenic stem cells, biomaterials, and functional tissue-engineered muscle. Furthermore, we will discuss possibilities for expanding the future use of human cell sources toward the development of cell-based clinical therapies and in vitro models of human muscle disease. PMID:23711735

  6. [Muscle-skeletal pain].

    PubMed

    Vygonskaya, M V; Filatova, E G

    2016-01-01

    The paper is devoted to the most complicated aspects of low back pain. The differences between specific and nonspecific low back pain using the "red flags" system is highlighted. The authors consider the causes of pain chronification (the "yellow flags" system) and the necessity of using a biopsychosocial model. Main pathogenetic mechanisms of chronic muscle/skeletal pain are considered and the possible involvement of several mechanism in the pathogenesis of chronic pain as well as the use of complex therapy is discussed. The high efficacy and safety of ketorolac in treatment of nonspecific muscle/skeletal pain is demonstrated. PMID:27042717

  7. Growth of bone marrow and skeletal muscle side population stem cells in suspension culture.

    PubMed

    Pacak, Christina A; Cowan, Douglas B

    2014-01-01

    The ability to efficiently isolate and expand various stem cell populations in vitro is crucial for successful translation of cell-based therapies to the clinical setting. One such heterogeneous population that possesses a remarkable potential for the development of cell-based treatments for a variety of degenerative diseases and disorders is called the Side Population (SP). For many years, investigators have isolated these primitive cells based upon their ability to efflux the fluorophore Hoechst 33342. This attribute enabled separation of SP cells derived from multiple tissue sources from other endogenous cell populations using fluorescence-activated cell sorting (FACS). While all tissue-specific SP fractions appear to contain cells with multi-potent stem cell activity, the therapeutic utility of these cells has yet to be fully realized because of the scarcity of this fraction in vivo. In view of that, we developed a method to expand adult murine bone marrow and skeletal muscle-derived SP cells in vitro. Here, we describe a spinner-flask culture system that supports the growth of SP cells in suspension when they are combined with feeder cells cultured on spherical microcarriers. In this way, their distinguishing biological characteristics can be maintained, attachment-stimulated differentiation is avoided, and therapeutically relevant quantities of SP cells are generated. Modification of the described procedure may permit expansion of the SP from other relevant tissue sources and our method is amenable to establishing compliance with current good manufacturing practices. PMID:25173160

  8. Effect of beta-ADrenergic Agonist on Cyclic AMP Synthesis in Chicken Skeletal Muscle Cells in Culture

    NASA Technical Reports Server (NTRS)

    Young, R. B.; Bridge, K. Y.; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    Several beta-adrenergic receptor (bAR) agonists are known to cause hypertrophy of skeletal muscle tissue. Because it seems logical that these agonists exert their action on muscle through stimulation of cAMP synthesis, five bAR agonists encompassing a range in activity from strong to weak were evaluated for their ability to stimulate cAMP accumulation in embryonic chicken skeletal muscle cells in culture. Two strong agonists (epinephrine and isoproterenol), one moderate agonist (albuterol), and two weak agonists known to cause hypertrophy in animals (clenbuterol and cimaterol) were studied. Dose response curves were determined over six orders of magnitude in concentration for each agonist, and values were determined for their maximum stimulation of cAMP synthesis rate (Bmax) and the agonist concentration at which 50% stimulation of cAMP synthesis (EC50) occurred. Bmax values decreased in the following order: isoproterenol, epinephrine, albuterol, cimaterol, clenbuterol. Cimaterol and clenbuterol at their Bmax levels were approximately 15-fold weaker than isoproterenol in stimulating the rate of cAMP synthesis. In addition, the EC50 values for isoproterenol, cimaterol, clenbuterol, epinephrine, and albuterol were 360 nM, 630 nM, 900 nM, 2,470 nM, and 3,650 nM, respectively. Finally, dose response curves show that the concentrations of cimaterol and clenbuterol in culture media at concentrations known to cause significant muscle hypertrophy in animals had no detectable effect on stimulation of CAMP accumulation in chicken skeletal muscle cells.

  9. Expression and function of heterotypic adhesion molecules during differentiation of human skeletal muscle in culture.

    PubMed Central

    Beauchamp, J. R.; Abraham, D. J.; Bou-Gharios, G.; Partridge, T. A.; Olsen, I.

    1992-01-01

    The infiltration of skeletal muscle by leukocytes occurs in a variety of myopathies and frequently accompanies muscle degeneration and regeneration. The latter involves development of new myofibers from precursor myoblasts, and so infiltrating cells may interact with muscle at all stages of differentiation. The authors have investigated the surface expression of ligands for T-cell adhesion during the differentiation of human skeletal muscle in vitro. Myoblasts expressed low levels of ICAM-1 (CD54), which remained constant during muscle cell differentiation and could be induced by cytokines such as gamma-interferon. It is therefore likely that ICAM-1 is involved in the invasive accumulation of lymphocytes during skeletal muscle inflammation. In contrast, LFA-3 (CD58) was expressed at higher levels than ICAM-1 on myoblasts, decreased significantly during myogenesis, and was unaffected by immune mediators. Both ICAM-1 and LFA-3 were able to mediate T cell binding to myoblasts, whereas adhesion to myotubes was independent of the LFA-3 ligand. Although expressed throughout myogenesis, human leukocyte antigen class I and CD44 did not appear to mediate T cell binding. The expression of ligands that facilitate interaction of myogenic cells with lymphocytes may have important implications for myoblast transplantation. Images Figure 1 Figure 3 Figure 4 PMID:1739132

  10. Developmental Changes is Expression of Beta-Adrenergic Receptors in Cultures of C2C12 Skeletal Muscle Cells

    NASA Technical Reports Server (NTRS)

    Young, Ronald B.; Bridge, K. Y.; Vaughn, J. R.

    2000-01-01

    beta-Adrenergic receptor (bAR) agonists have been reported to modulate growth in several mammalian and avian species, and bAR agonists presumably exert their physiological action on skeletal muscle cells through this receptor. Because of the importance of bAR regulation on muscle protein metabolism in muscle cells, the objectives of this study were to determine the developmental expression pattern of the bAR population in C2C12 skeletal muscle cells, and to analyze changes in both the quantity and isoform expression of the major muscle protein, myosin. The number of bAR in mononucleated C2C12 cells was approximately 8,000 bAR per cell, which is comparable with the population reported in several other nonmuscle cell types. However, the bar population increased after myoblast fusion to greater than 50,000 bAR per muscle cell equivalent. The reasons for this apparent over-expression of bAR in C2C12 cells is not known. The quantity of myosin also increased after C2C12 myoblast fusion, but the quantity of myosin was less than that reported in primary muscle cell cultures. Finally, at least five different isoforms of myosin heavy chain could be resolved in C2C12 cells, and three of these exhibited either increased or decreased developmental regulation relative to the others. Thus, C2C12 myoblasts undergo developmental regulation of bAR population and myosin heavy chain isoform expression.

  11. Substrate elasticity regulates skeletal muscle stem cell self-renewal in culture

    PubMed Central

    Gilbert, PM; Havenstrite, KL; Magnusson, KEG; Sacco, A; Leonardi, NA; Kraft, P; Nguyen, NK; Thrun, S; Lutolf, MP; Blau, HM

    2010-01-01

    Freshly isolated muscle stem cells (MuSCs) exhibit robust regenerative capacity in vivo that is rapidly lost in culture. Using a bioengineered substrate to recapitulate key biophysical and biochemical niche features in conjunction with a novel highly automated single cell tracking algorithm, we show that substrate elasticity is a potent regulator of MuSC fate in culture. Unlike MuSCs on rigid plastic dishes (~106kPa), MuSCs cultured on soft hydrogel substrates that mimic the elasticity of muscle (12kPa) self-renew in vitro and contribute extensively to muscle regeneration when subsequently transplanted into mice and assayed histologically and quantitatively by non-invasive bioluminescence imaging. Our studies provide novel evidence that by recapitulating physiological tissue rigidity, propagation of adult muscle stem cells is possible, enabling future cell-based therapies for muscle wasting diseases. PMID:20647425

  12. Effects in skeletal muscle.

    PubMed

    Young, Andrew

    2005-01-01

    The first biological action of amylin to be described was the inhibition of insulin-stimulated incorporation of radiolabeled glucose into glycogen in the isolated soleus muscle of the rat. This antagonism of insulin action in muscle was non-competitive, occurring with equal potency and efficacy at all insulin concentrations. Amylin inhibited activation of glycogen synthase, partially accounting for the inhibition of radiolabeled glucose incorporation. However, this did not account for a low rate of labeling at higher amylin concentrations, wherein the radioglycogen accumulation was even less than in incubations where insulin was absent. The principal action of amylin accounting for reduction of insulin-stimulated accumulation of glycogen was activation of glycogen phosphorylase via a cyclic AMP-, protein kinase C-dependent signaling pathway to cause glycogenolysis (glycogen breakdown). At physiological concentrations, amylin activated glycogen phosphorylase at its ED50, but because glycogen phosphorylase is present in such high activity, the resulting flux out of glycogen was estimated to be similar to insulin-mediated flux of glucosyl moieties into glycogen. Thus, in the rat, endogenous amylin secreted in response to meals appeared to mobilize carbon from skeletal muscle. Amylin-induced glycogenolysis resulted in intramuscular accumulation of glucose-6-phosphate and release of lactate from tissue beds that included muscle. When muscle glycogen was pre-labeled with tritium in the three position, amylin could be shown to evoke the release of free glucose. This is made possible by glucosyl moieties cleaved at the branch points in glycogen being released as free glucose, rather than being phosphorylated, as occurs with the bulk of the glycogen glucosyls. Free glucose is free to exit cells via facilitated transport, down a concentration gradient that might exist under such circumstances. When measured by a sensitive technique utilizing efflux of labeled glucose, amylin

  13. Mechanotransduction in skeletal muscle

    PubMed Central

    Burkholder, Thomas J.

    2007-01-01

    Mechanical signals are critical to the development and maintenance of skeletal muscle, but the mechanisms that convert these shape changes to biochemical signals is not known. When a deformation is imposed on a muscle, changes in cellular and molecular conformations link the mechanical forces with biochemical signals, and the close integration of mechanical signals with electrical, metabolic, and hormonal signaling may disguise the aspect of the response that is specific to the mechanical forces. The mechanically induced conformational change may directly activate downstream signaling and may trigger messenger systems to activate signaling indirectly. Major effectors of mechanotransduction include the ubiquitous mitogen activated protein kinase (MAP) and phosphatidylinositol-3’ kinase (PI-3K), which have well described receptor dependent cascades, but the chain of events leading from mechanical stimulation to biochemical cascade is not clear. This review will discuss the mechanics of biological deformation, loading of cellular and molecular structures, and some of the principal signaling mechanisms associated with mechanotransduction. PMID:17127292

  14. Triadin Deletion Induces Impaired Skeletal Muscle Function*

    PubMed Central

    Oddoux, Sarah; Brocard, Julie; Schweitzer, Annie; Szentesi, Peter; Giannesini, Benoit; Brocard, Jacques; Fauré, Julien; Pernet-Gallay, Karine; Bendahan, David; Lunardi, Joël; Csernoch, Laszlo; Marty, Isabelle

    2009-01-01

    Triadin is a multiple proteins family, some isoforms being involved in muscle excitation-contraction coupling, and some having still unknown functions. To obtain clues on triadin functions, we engineered a triadin knock-out mouse line and characterized the physiological effect of triadin ablation on skeletal muscle function. These mice presented a reduced muscle strength, which seemed not to alter their survival and has been characterized in the present work. We first checked in these mice the expression level of the different proteins involved in calcium homeostasis and observed in fast muscles an increase in expression of dihydropyridine receptor, with a large reduction in calsequestrin expression. Electron microscopy analysis of KO muscles morphology demonstrated the presence of triads in abnormal orientation and a reduction in the sarcoplasmic reticulum terminal cisternae volume. Using calcium imaging on cultured myotubes, we observed a reduction in the total amount of calcium stored in the sarcoplasmic reticulum. Physiological studies have been performed to evaluate the influence of triadin deletion on skeletal muscle function. Muscle strength has been measured both on the whole animal model, using hang test or electrical stimulation combined with NMR analysis and strength measurement, or on isolated muscle using electrical stimulation. All the results obtained demonstrate an important reduction in muscle strength, indicating that triadin plays an essential role in skeletal muscle function and in skeletal muscle structure. These results indicate that triadin alteration leads to the development of a myopathy, which could be studied using this new animal model. PMID:19843516

  15. Effect of Electrical Stimulation on Beta-Adrenergic Receptor Population and Cyclic AMP Production in Chicken and Rat Skeletal Muscle Cell Cultures

    NASA Technical Reports Server (NTRS)

    Young, Ronald B.; Bridge, Kristin Y.; Strietzel, Catherine J.

    2000-01-01

    Expression of the beta-adrenergic receptor (PAR) and its coupling to Adenosine 3'5' Cyclic Monophosphate (cAMP) synthesis are important components of the signaling system that controls muscle atrophy and hypertrophy and the goal of this study was to determine if electrical stimulation in a pattern simulating slow muscle contraction would alter the PAR response in primary cultures of avian and mammalian skeletal muscle cells. Specifically chicken skeletal muscle cells and rat skeletal muscle cells that had been grown for 7 d in culture, were subjected to electrical stimulation for an additional 2 d at a pulse frequency of 0.5 pulses/sec and a pulse duration of 200 msec. In chicken skeletal muscle cells, the PAR population was not significantly affected by electrical stimulation; however, the ability, of these cells to synthesize cyclic AMP was reduced by approximately one-half. In contrast, the PAR population in rat muscle cells was increased slightly but not significantly by electrical stimulation, and the ability of these cells to synthesize cyclic AMP was increased by almost twofold. The basal levels of intracellular cyclic AMP in neither rat muscle cells nor chicken muscle cells were affected by electrical stimulation.

  16. Effect of electrical stimulation on beta-adrenergic receptor population and cyclic amp production in chicken and rat skeletal muscle cell cultures

    NASA Technical Reports Server (NTRS)

    Young, R. B.; Bridge, K. Y.; Strietzel, C. J.

    2000-01-01

    Expression of the beta-adrenergic receptor (betaAR) and its coupling to cyclic AMP (cAMP) synthesis are important components of the signaling system that controls muscle atrophy and hypertrophy, and the goal of this study was to determine if electrical stimulation in a pattern simulating slow muscle contraction would alter the betaAR response in primary cultures of avian and mammalian skeletal muscle cells. Specifically, chicken skeletal muscle cells and rat skeletal muscle cells that had been grown for 7 d in culture were subjected to electrical stimulation for an additional 2 d at a pulse frequency of 0.5 pulses/sec and a pulse duration of 200 msec. In chicken skeletal muscle cells, the betaAR population was not significantly affected by electrical stimulation; however, the ability of these cells to synthesize cyclic AMP was reduced by approximately one-half. In contrast, the betaAR population in rat muscle cells was increased slightly but not significantly by electrical stimulation, and the ability of these cells to synthesize cyclic AMP was increased by almost twofold. The basal levels of intracellular cyclic AMP in neither rat muscle cells nor chicken muscle cells were affected by electrical stimulation.

  17. 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.

  18. Skeletal muscle regeneration via engineered tissue culture over electrospun nanofibrous chitosan/PVA scaffold.

    PubMed

    Kheradmandi, Mahsa; Vasheghani-Farahani, Ebrahim; Ghiaseddin, Ali; Ganji, Fariba

    2016-07-01

    Skeletal muscle tissue shows a remarkable potential in regeneration of injured tissue. However, in some of chronic and volumetric muscle damages, the native tissue is incapable to repair and remodeling the trauma. In the same condition, stem-cell therapy increased regeneration in situations of deficient muscle repair, but the major problem seems to be the lack of ability to attachment and survive of injected cells on the exact location. In this study, chitosan/poly(vinyl alcohol) nanofibrous scaffold was studied to promote cell attachment and provide mechanical support during regeneration. Scaffold was characterized using scanning electron microscope, X-ray diffraction, and tensile test. Degradation and swelling behavior of scaffold were studied for 20 days. The cell-scaffold interaction was characterized by MTT assay for 10 days and in vivo biocompatibility of scaffold in a rabbit model was evaluated. Results showed that cells had a good viability, adhesion, growth, and spread on the scaffold, which make this mat a desirable engineered muscular graft. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1720-1727, 2016. PMID:26945909

  19. 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

  20. Effect of Increased Cyclic AMP Concentration on Muscle Protein Synthesis and Beta-Adrenergic Receptor Expression in Chicken Skeletal Muscle Cells in Culture

    NASA Technical Reports Server (NTRS)

    Young, R. B.; Vaughn, J. R.; Bridge, K. Y.; Smith, C. K.

    1998-01-01

    Analogies of epinephrine are known to cause hypertrophy of skeletal muscle when fed to animals. These compounds presumably exert their physiological action through interaction with the P-adrenergic receptor. Since the intracellular signal generated by the Beta-adrenergic receptor is cyclic AMP (cAMP), experiments were initiated in cell culture to determine if artificial elevation of cAMP by treatment with forskolin would alter muscle protein metabolism and P-adrenergic receptor expression. Chicken skeletal muscle cells after 7 days in culture were treated with 0.2-30 micrometers forskolin for a total of three days. At the end of the treatment period, both the concentration of cAMP and the quantity of myosin heavy chain (MHC) were measured. Concentration of cAMP in forskolin-treated cells increased up to 10-fold in a dose dependent manner. In contrast, the quantity of MHC was increased approximately 50% above control cells at 0.2 micrometers forskolin, but exhibited a gradual decline at higher levels of forskolin so that the quantity of MHC in cells treated with 30 micrometers forskolin was not significantly different from controls. Curiously, the intracellular concentration of cAMP which elicited the maximum increase in the quantity of MHC was only 40% higher than cAMP concentration in control cells.

  1. The effect of Ca2+ ionophores upon the synthesis of proteins in cultured skeletal muscle.

    PubMed

    Roufa, D; Wu, F S; Martonosi, A N

    1981-05-01

    The influence of the Ca2+ ionophores, ionomycin and A23187 upon the incorporation of [35S]methionine into proteins of cultured chicken pectoralis muscle was studied during differentiation of myoblasts into multinucleated myotubes. Fusion was reversibly arrested by growing cells in low-calcium media from the time of plating. Exposure of normal and fusion blocked cultures to 10-6-10-5 M ionomycin or A23187 for 2-6 h on the second to fourth day of growth, resulted in a selective increase in the incorporation of [35S]methionine into two proteins of about 100 000 and 80 000 dalton. When 10-5 M ionomycin or A23187 were added to older cultures, all large myotubes contracted and detached from the plate. Only the adhering myoblasts and small myotubes incorporated [35s[methionine into the muscle proteins and showed increased incorporation of label into 100 000 and 80 000 proteins. After ionophore pulse, the adhering cells retained the ability to differentiate and accumulate myosin. The effect of Ca2+ ionophores upon the rate of protein synthesis is presumably related to increased influx of extracellular Ca2+ with a rise in the Ca2+ concentration of the cytoplasm. We conclude that Ca2+ sensitive mechanisms may regulate the synthesis of a select group of muscle proteins. PMID:6786362

  2. 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.

  3. Connexins in skeletal muscle development and disease.

    PubMed

    Merrifield, Peter A; Laird, Dale W

    2016-02-01

    Gap junctions consist of clusters of intercellular channels composed of connexins that connect adjacent cells and allow the exchange of small molecules. While the 21 member multi-gene family of connexins are ubiquitously found in humans, only Cx39, Cx40, Cx43 and Cx45 have been documented in developing myoblasts and injured adult skeletal muscle while healthy adult skeletal muscle is devoid of connexins. The use of gap junctional blockers and cultured myoblast cell lines have suggested that these connexins play a critical role in myotube formation and muscle regeneration. More recent genetically-modified mouse models where Cx43 function is greatly compromized or ablated have further supported a role for Cx43 in regulating skeletal muscle development. In the last decade, we have become aware of a cohort of patients that have a development disorder known as oculodentodigital dysplasia (ODDD). These patients harbor either gain or loss of Cx43 function gene mutations that result in many organ anomalies raising questions as to whether they suffer from defects in skeletal muscle formation or regeneration upon injury. Interesting, some ODDD patients report muscle weakness and loss of limb control but it is not clear if this is neurogenic or myogenic in origin. This review will focus on the role connexins play in muscle development and repair and discuss the impact of Cx43 mutants on muscle function. PMID:26688333

  4. Skeletal Muscle Hypertrophy after Aerobic Exercise Training

    PubMed Central

    Konopka, Adam R.; Harber, Matthew P.

    2014-01-01

    Current dogma suggests aerobic exercise training has minimal effect on skeletal muscle size. We and others have demonstrated that aerobic exercise acutely and chronically alters protein metabolism and induces skeletal muscle hypertrophy. These findings promote an antithesis to the status quo by providing novel perspective on skeletal muscle mass regulation and insight into exercise-countermeasures for populations prone to muscle loss. PMID:24508740

  5. Skeletal muscle involvement in cardiomyopathies.

    PubMed

    Limongelli, Giuseppe; D'Alessandro, Raffaella; Maddaloni, Valeria; Rea, Alessandra; Sarkozy, Anna; McKenna, William J

    2013-12-01

    The link between heart and skeletal muscle disorders is based on similar molecular, anatomical and clinical features, which are shared by the 'primary' cardiomyopathies and 'primary' neuromuscular disorders. There are, however, some peculiarities that are typical of cardiac and skeletal muscle disorders. Skeletal muscle weakness presenting at any age may indicate a primary neuromuscular disorder (associated with creatine kinase elevation as in dystrophinopathies), a mitochondrial disease (particularly if encephalopathy, ocular myopathy, retinitis, neurosensorineural deafness, lactic acidosis are present), a storage disorder (progressive exercise intolerance, cognitive impairment and retinitis pigmentosa, as in Danon disease), or metabolic disorders (hypoglycaemia, metabolic acidosis, hyperammonaemia or other specific biochemical abnormalities). In such patients, skeletal muscle weakness usually precedes the cardiomyopathy and dominates the clinical picture. Nevertheless, skeletal involvement may be subtle, and the first clinical manifestation of a neuromuscular disorder may be the occurrence of heart failure, conduction disorders or ventricular arrhythmias due to cardiomyopathy. ECG and echocardiogram, and eventually, a more detailed cardiovascular evaluation may be required to identify early cardiac involvement. Paediatric and adult cardiologists should be proactive in screening for neuromuscular and related disorders to enable diagnosis in probands and evaluation of families with a focus on the identification of those at risk of cardiac arrhythmia and emboli who may require specific prophylactic treatments, for example, pacemaker, implantable cardioverter-defibrillator and anticoagulation. PMID:24149064

  6. Glucose transport in human skeletal muscle cells in culture. Stimulation by insulin and metformin.

    PubMed Central

    Sarabia, V; Lam, L; Burdett, E; Leiter, L A; Klip, A

    1992-01-01

    Primary human muscle cell cultures were established and the regulation of glucose transport was investigated. Primary cultures were allowed to proceed to the stage of myotubes through fusion of myoblasts or were used for clonal selection based on fusion potential. In clonally selected cultures, hexose (2-deoxy-glucose) uptake into myotubes was linear within the time of study and inhibitable by cytochalasin B (IC50 = 400 nM). Cytochalasin B photolabeled a protein(s) of 45,000-50,000 D in a D-glucose-protectable manner, suggesting identity with the glucose transporters. In the myotube stage, the cells expressed both the GLUT1 and GLUT4 glucose transporter protein isoforms at an average molar ratio of 7:1. Preincubation in media of increasing glucose concentrations (range 5-25 mM) progressively decreased the rate of 2-deoxyglucose uptake. Insulin elevated 2-deoxyglucose uptake in a dose-dependent manner, with half maximal stimulation achieved at 3.5 nM. Insulin also stimulated the transport of the nonmetabolizable hexose 3-O-methylglucose, as well as the activity of glycogen synthase, responsible for nonoxidative glucose metabolism. The oral antihyperglycemic drug metformin stimulated the cytochalasin B-sensitive component of both 2-deoxyglucose and 3-O-methylglucose uptake. Maximal stimulation was observed at 8 h of exposure to 50 microM metformin, and this effect was not prevented by incubation with the protein-synthesis inhibitor cycloheximide. The relative effect of metformin was higher in cells incubated in 25 mM glucose than in 5 mM glucose, consistent with its selective action in hyperglycemic conditions in vivo. Metformin (50 microM for 24 h) was more effective than insulin (1 microM for 1 h) in stimulating hexose uptake and the hormone was effective on top of the stimulation caused by the biguanide, suggesting independent mechanisms of action. Images PMID:1401073

  7. 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.

  8. Choosing a skeletal muscle relaxant.

    PubMed

    See, Sharon; Ginzburg, Regina

    2008-08-01

    Skeletal muscle relaxants are widely used in treating musculoskeletal conditions. However, evidence of their effectiveness consists mainly of studies with poor methodologic design. In addition, these drugs have not been proven to be superior to acetaminophen or nonsteroidal anti-inflammatory drugs for low back pain. Systematic reviews and meta-analyses support using skeletal muscle relaxants for short-term relief of acute low back pain when nonsteroidal anti-inflammatory drugs or acetaminophen are not effective or tolerated. Comparison studies have not shown one skeletal muscle relaxant to be superior to another. Cyclobenzaprine is the most heavily studied and has been shown to be effective for various musculoskeletal conditions. The sedative properties of tizanidine and cyclobenzaprine may benefit patients with insomnia caused by severe muscle spasms. Methocarbamol and metaxalone are less sedating, although effectiveness evidence is limited. Adverse effects, particularly dizziness and drowsiness, are consistently reported with all skeletal muscle relaxants. The potential adverse effects should be communicated clearly to the patient. Because of limited comparable effectiveness data, choice of agent should be based on side-effect profile, patient preference, abuse potential, and possible drug interactions. PMID:18711953

  9. Microfluidic devices for construction of contractile skeletal muscle microtissues.

    PubMed

    Shimizu, Kazunori; Araki, Hiroyuki; Sakata, Kohei; Tonomura, Wataru; Hashida, Mitsuru; Konishi, Satoshi

    2015-02-01

    Cell-culture microchips mimicking tissue/organ-specific functions are required as alternatives to animal testing for drug discovery and disease models. Although three-dimensional (3D) cell culture microfluidic devices can create more biologically relevant cellular microenvironments and higher throughput analysis platforms of cell behavior than conventional techniques, devices for skeletal muscle cells have not been developed. In the present study, we aimed to develop microfluidic devices for 3D cultures of skeletal muscle cells. Skeletal muscle cells mixed with a collagen type-I solution was introduced into the microchannel for cells (MC-C) and was gelated. Then, the medium was introduced into the microchannel for medium (MC-M). During this process, connecting microchannels (Con-MCs) prevented leakage of the collagen solution mixed with cells from MC-C to MC-M and supplied the nutrients from the medium in MC-M to the cells in MC-C. Skeletal muscle microtissues cultured in the microchannel for a week consisted of myotubes were confirmed by histological analysis and immunofluorescence staining. The skeletal muscle microtissues in the microchannel contracted in response to externally applied electrical stimulation (1 and 50 Hz). These results indicate that the functional skeletal muscle microtissues were constructed in the microchannel. Thus, the microfluidic device for culturing 3D skeletal muscle microtissues presented in this study has a potential to be used for drug discovery and toxicological tests. PMID:25085533

  10. Stretch-activated single ion channel currents in tissue-cultured embryonic chick skeletal muscle.

    PubMed Central

    Guharay, F; Sachs, F

    1984-01-01

    The membrane of tissue-cultured chick pectoral muscle contains an ionic channel which is activated by membrane stretch. Nicotinic channels and Ca2+-activated K+ channels are not affected by stretch. In 150 mM-external K+ and 150 mM-internal Na+ the channel has a conductance of 70 pS, linear current-voltage relationship between -50 and -140 mV and a reversal potential of +30 mV. Kinetic analysis of single-channel records indicates that there are one open (O) and three closed (C) states. The data can be fitted by the reaction scheme: C1-C2-C3-O. Only the rate constant that governs the C1-C2 transition (k1,2) is stretch-sensitive. None of the rates are voltage-sensitive. The rate constant k1,2 varies with the square of the tension as k1, 2 = k0 X e alpha T2, where alpha is a constant describing the sensitivity to stretch and T is the tension. A typical value of alpha is 0.08 (dyn cm-1)-2. Following exposure to cytochalasin B the channel becomes more sensitive to stretch. The stretch-sensitivity constant, alpha, increases from 0.08 to 2.4 (dyn cm-1)-2. The probability of the channel being open is strongly dependent upon the extracellular K+ concentration. With a suction of 2 cmHg the probability increases from 0.004 in normal saline (5 mM-K+) to 0.26 in 150 mM-K+. The channel appears to gather force from a large area of membrane (greater than 3 X 10(5) A2), probably by a cytochalasin-resistant cytoskeletal network. PMID:6086918

  11. Altered expression of triadin 95 causes parallel changes in localized Ca2+ release events and global Ca2+ signals in skeletal muscle cells in culture

    PubMed Central

    Fodor, János; Gönczi, Monika; Sztretye, Monika; Dienes, Beatrix; Oláh, Tamás; Szabó, László; Csoma, Eszter; Szentesi, Péter; Szigeti, Gyula P; Marty, Isabelle; Csernoch, László

    2008-01-01

    The 95 kDa triadin (Trisk 95), an integral protein of the sarcoplasmic reticular membrane in skeletal muscle, interacts with both the ryanodine receptor (RyR) and calsequestrin. While its role in the regulation of calcium homeostasis has been extensively studied, data are not available on whether the overexpression or the interference with the expression of Trisk 95 would affect calcium sparks the localized events of calcium release (LCRE). In the present study LCRE and calcium transients were studied using laser scanning confocal microscopy on C2C12 cells and on primary cultures of skeletal muscle. Liposome- or adenovirus-mediated Trisk 95 overexpression and shRNA interference with triadin translation were used to modify the level of the protein. Stable overexpression in C2C12 cells significantly decreased the amplitude and frequency of calcium sparks, and the frequency of embers. In line with these observations, depolarization-evoked calcium transients were also suppressed. Similarly, adenoviral transfection of Trisk 95 into cultured mouse skeletal muscle cells significantly decreased both the frequency and amplitude of spontaneous global calcium transients. Inhibition of endogenous triadin expression by RNA interference caused opposite effects. Primary cultures of rat skeletal muscle cells expressing endogenous Trisk 95 readily generated spontaneous calcium transients but rarely produced calcium sparks. Their transfection with specific shRNA sequence significantly reduced the triadin-specific immunoreactivity. Functional experiments on these cells revealed that while caffeine-evoked calcium transients were reduced, LCRE appeared with higher frequency. These results suggest that Trisk 95 negatively regulates RyR function by suppressing localized calcium release events and global calcium signals in cultured muscle cells. PMID:18845610

  12. The effects of Securidaca longepedunculata root extract on ionic currents and contraction of cultured rat skeletal muscle cells.

    PubMed

    Mouzou, A P; Bulteau, L; Raymond, G

    1999-05-01

    The effects of the primary extract roots of Securidaca longepedunculata were tested on sodium, calcium and potassium currents in rat skeletal muscle cells developed in culture. In addition, they were tested on depolarisation-induced contraction and resting intracellular calcium levels. S. longepedunculata extract (10(-6) g/l) increases sodium current at all potentials. No clear effect was observed on calcium current except for a slight increase at negative potentials (-30, -10 mV) revealing a 5 mV shift towards negative potentials of the I(Ca)/V curve, as with potassium current. In contrast, at the same concentration, S. longepedunculata enhanced the contractile response elicited by durable depolarisation. This was not attributable to the slight increase in resting intracellular free calcium concentration which did not change during and following S. longepedunculata application. These results strongly suggest that S. longepedunculata root extract contains one or more components acting on the voltage-sensor of excitation-contraction coupling (dihydropyridine receptors), regardless of its implication as a calcium channel. PMID:10465656

  13. Skeletal muscle satellite cells

    NASA Technical Reports Server (NTRS)

    Schultz, E.; McCormick, K. M.

    1994-01-01

    Evidence now suggests that satellite cells constitute a class of myogenic cells that differ distinctly from other embryonic myoblasts. Satellite cells arise from somites and first appear as a distinct myoblast type well before birth. Satellite cells from different muscles cannot be functionally distinguished from one another and are able to provide nuclei to all fibers without regard to phenotype. Thus, it is difficult to ascribe any significant function to establishing or stabilizing fiber type, even during regeneration. Within a muscle, satellite cells exhibit marked heterogeneity with respect to their proliferative behavior. The satellite cell population on a fiber can be partitioned into those that function as stem cells and those which are readily available for fusion. Recent studies have shown that the cells are not simply spindle shaped, but are very diverse in their morphology and have multiple branches emanating from the poles of the cells. This finding is consistent with other studies indicating that the cells have the capacity for extensive migration within, and perhaps between, muscles. Complexity of cell shape usually reflects increased cytoplasmic volume and organelles including a well developed Golgi, and is usually associated with growing postnatal muscle or muscles undergoing some form of induced adaptive change or repair. The appearance of activated satellite cells suggests some function of the cells in the adaptive process through elaboration and secretion of a product. Significant advances have been made in determining the potential secretion products that satellite cells make. The manner in which satellite cell proliferative and fusion behavior is controlled has also been studied. There seems to be little doubt that cellcell coupling is not how satellite cells and myofibers communicate. Rather satellite cell regulation is through a number of potential growth factors that arise from a number of sources. Critical to the understanding of this form

  14. Physiology and metabolism of tissue-engineered skeletal muscle.

    PubMed

    Cheng, Cindy S; Davis, Brittany N J; Madden, Lauran; Bursac, Nenad; Truskey, George A

    2014-09-01

    Skeletal muscle is a major target for tissue engineering, given its relative size in the body, fraction of cardiac output that passes through muscle beds, as well as its key role in energy metabolism and diabetes, and the need for therapies for muscle diseases such as muscular dystrophy and sarcopenia. To date, most studies with tissue-engineered skeletal muscle have utilized murine and rat cell sources. On the other hand, successful engineering of functional human muscle would enable different applications including improved methods for preclinical testing of drugs and therapies. Some of the requirements for engineering functional skeletal muscle include expression of adult forms of muscle proteins, comparable contractile forces to those produced by native muscle, and physiological force-length and force-frequency relations. This review discusses the various strategies and challenges associated with these requirements, specific applications with cultured human myoblasts, and future directions. PMID:24912506

  15. Physiology and Metabolism of Tissue Engineered Skeletal Muscle

    PubMed Central

    Cheng, Cindy S.; Davis, Brittany N.J.; Madden, Lauran; Bursac, Nenad; Truskey, George A.

    2014-01-01

    Skeletal muscle is a major target for tissue engineering, given its relative size in the body, fraction of cardiac output that passes through muscle beds, as well as its key role in energy metabolism and diabetes, and the need for therapies for muscle diseases such as muscular dystrophy and sarcopenia. To date, most studies with tissue-engineered skeletal muscle have utilized murine and rat cell sources. On the other hand, successful engineering of functional human muscle would enable different applications including improved methods for preclinical testing of drugs and therapies. Some of the requirements for engineering functional skeletal muscle include expression of adult forms of muscle proteins, comparable contractile forces to those produced by native muscle, and physiological force-length and force-frequency relations. This review discusses the various strategies and challenges associated with these requirements, specific applications with cultured human myoblasts, and future directions. PMID:24912506

  16. 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. PMID:27304505

  17. Heat stress inhibits proliferation, promotes growth, and induces apoptosis in cultured Lantang swine skeletal muscle satellite cells.

    PubMed

    Gao, Chun-qi; Zhao, Yin-ling; Li, Hai-chang; Sui, Wei-guo; Yan, Hui-chao; Wang, Xiu-qi

    2015-06-01

    Proliferation suppression and apoptosis are the prominent characteristics induced by heat stress (HS) in cells, whereas the effects of HS on cell growth (mass accumulation) are unknown. In this study, Lantang swine (an indigenous breed of China) skeletal muscle satellite cells (SCs) were pre-cultured at 37 °C for 24 h. The HS group was subjected to HS at 41 °C, while the control group was maintained at 37 °C. Heat shock protein 70 (HSP70) expression and SC size are significantly increased (P<0.05) by HS, but cell proliferation is suppressed (P<0.05) and apoptosis is induced (P<0.05). HS led to a lower percentage of SCs in the G0/G1 phase (P<0.05) together with a higher percentage of SCs in the S phase (P<0.05). However, the percentage of SCs in the G2/M phase was decreased (P<0.05) at 48 h but then increased (P<0.05) at 72 h with HS. In addition, the phosphorylation ratios of protein kinase b (Akt), ribosomal protein S6 kinase (S6K), and ribosomal protein S6 were increased (P<0.05) by HS. Nevertheless, the phosphorylation ratios of the 4E binding protein 1 and the eukaryotic initiation factor-4E were indistinguishable (P>0.05) from those of the control group. The phosphorylation ratio of the mammalian target of rapamycin (mTOR) (Ser(2448)) increased (P<0.05) within 48 h, and apparent differences were abrogated at 72 h (P>0.05). Moreover, cleaved caspase-3 expression was increased at 72 h (P<0.05). These findings indicate that HS induces apoptosis and disrupts cell cycle distribution to decrease the number of cells. Additionally, HS can promote SC growth via an activated Akt/mTOR/S6K signaling pathway. PMID:26055917

  18. Mitochondrial isolation from skeletal muscle.

    PubMed

    Garcia-Cazarin, Mary L; Snider, Natalie N; Andrade, Francisco H

    2011-01-01

    Mitochondria are organelles controlling the life and death of the cell. They participate in key metabolic reactions, synthesize most of the ATP, and regulate a number of signaling cascades. Past and current researchers have isolated mitochondria from rat and mice tissues such as liver, brain and heart. In recent years, many researchers have focused on studying mitochondrial function from skeletal muscles. Here, we describe a method that we have used successfully for the isolation of mitochondria from skeletal muscles. Our procedure requires that all buffers and reagents are made fresh and need about 250-500 mg of skeletal muscle. We studied mitochondria isolated from rat and mouse gastrocnemius and diaphragm, and rat extraocular muscles. Mitochondrial protein concentration is measured with the Bradford assay. It is important that mitochondrial samples be kept ice-cold during preparation and that functional studies be performed within a relatively short time (~1 hr). Mitochondrial respiration is measured using polarography with a Clark-type electrode (Oxygraph system) at 37°C⁷. Calibration of the oxygen electrode is a key step in this protocol and it must be performed daily. Isolated mitochondria (150 μg) are added to 0.5 ml of experimental buffer (EB). State 2 respiration starts with addition of glutamate (5 mM) and malate (2.5 mM). Then, adenosine diphosphate (ADP) (150 μM) is added to start state 3. Oligomycin (1 μM), an ATPase synthase blocker, is used to estimate state. Lastly, carbonyl cyanide p-[trifluoromethoxy]-phenyl-hydrazone (FCCP, 0.2 μM) is added to measurestate, or uncoupled respiration. The respiratory control ratio (RCR), the ratio of state 3 to state 4, is calculated after each experiment. An RCR ≥ 4 is considered as evidence of a viable mitochondria preparation. In summary, we present a method for the isolation of viable mitochondria from skeletal muscles that can be used in biochemical (e.g., enzyme activity, immunodetection, proteomics

  19. Truncated CASK does not alter skeletal muscle or protein interactors.

    PubMed

    Sanford, Jamie L; Mays, Tessily A; Varian, Kenneth D; Wilson, Joanna B; Janssen, Paul M L; Rafael-Fortney, Jill A

    2008-09-01

    CASK (Ca2+, calmodulin-associated serine/threonine kinase) is an essential mammalian cell junction protein and is also crucial at Drosophila neuromuscular synapses. We have shown that CASK is present in mammalian skeletal muscle at the postsynaptic membrane of the neuromuscular junction. CASK interacts biochemically with channels at central synapses, and studies in cultured cells have led to proposed functions for CASK. However, in vivo functions of CASK in skeletal muscle remain unknown. To test hypotheses of CASK functions, we generated two lines of transgenic mice, which overexpress full-length and truncated CASK protein in skeletal muscle. Extensive analyses showed that overexpression of CASK protein did not affect the morphology or physiology of skeletal muscle, the morphology of the neuromuscular junction, or the levels or distribution of protein interactors. These results contrast with previous cell culture experiments and emphasize the importance of in vivo analysis of protein function. PMID:18642383

  20. Enhancement of skeletal muscle regeneration.

    PubMed

    Bischoff, R; Heintz, C

    1994-09-01

    We have studied the effect of adding extra satellite cells or soluble factors from crushed muscle on regeneration of minced fragments from rat tibialis muscle. The muscle mince was wrapped in an artificial epimysium to prevent adhesions and cell immigration from adjacent muscles. Regeneration was quantitatively assessed by electrophoretic determination of the muscle-specific form of creatine kinase. Control minces exhibited three periods of change in creatine kinase activity during a 7-week regeneration period. Activity fell rapidly during the first week, then rose gradually from 1-3 weeks and increased more rapidly from 3-7 weeks. To augment the original complement of myogenic cells, satellite cells were isolated from the contralateral muscle, purified by density gradient centrifugation, and expanded in culture for 3 days before adding to the muscle mince. The added cells resulted in a 3-fold enhancement of creatine kinase activity throughout the regeneration period. Soluble muscle extract incorporated into a collagen matrix also stimulated regeneration when added to muscle mince. The extract accelerated the rate of creatine kinase increase during the 1-3 week period beyond that observed in the control or cell augmented mince, suggesting that factors in the extract may facilitate revascularization or reinnervation. The specific activity of creatine kinase was increased in regenerates augmented with both cells and extract, indicating that the effects enhance primarily myogenic processes. PMID:7803846

  1. Systems-based discovery of tomatidine as a natural small molecule inhibitor of skeletal muscle atrophy.

    PubMed

    Dyle, Michael C; Ebert, Scott M; Cook, Daniel P; Kunkel, Steven D; Fox, Daniel K; Bongers, Kale S; Bullard, Steven A; Dierdorff, Jason M; Adams, Christopher M

    2014-05-23

    Skeletal muscle atrophy is a common and debilitating condition that lacks an effective therapy. To address this problem, we used a systems-based discovery strategy to search for a small molecule whose mRNA expression signature negatively correlates to mRNA expression signatures of human skeletal muscle atrophy. This strategy identified a natural small molecule from tomato plants, tomatidine. Using cultured skeletal myotubes from both humans and mice, we found that tomatidine stimulated mTORC1 signaling and anabolism, leading to accumulation of protein and mitochondria, and ultimately, cell growth. Furthermore, in mice, tomatidine increased skeletal muscle mTORC1 signaling, reduced skeletal muscle atrophy, enhanced recovery from skeletal muscle atrophy, stimulated skeletal muscle hypertrophy, and increased strength and exercise capacity. Collectively, these results identify tomatidine as a novel small molecule inhibitor of muscle atrophy. Tomatidine may have utility as a therapeutic agent or lead compound for skeletal muscle atrophy. PMID:24719321

  2. Proteomic profiling of skeletal muscle plasticity

    PubMed Central

    Ohlendieck, Kay

    2011-01-01

    Summary One of the most striking physiological features of skeletal muscle tissues are their enormous capacity to adapt to changed functional demands. Muscle plasticity has been extensively studied by histological, biochemical, physiological and genetic methods over the last few decades. With the recent emergence of high-throughput and large-scale proteomic techniques, mass spectrometry-based surveys have also been applied to the global analysis of the skeletal muscle protein complement during physiological modifications and pathophysiological alterations. This review outlines and discusses the impact of recent proteomic profiling studies of skeletal muscle transitions, including the effects of chronic electro-stimulation, physical exercise, denervation, disuse atrophy, hypoxia, myotonia, motor neuron disease and age-related fibre type shifting. This includes studies on the human skeletal muscle proteome, animal models of muscle plasticity and major neuromuscular pathologies. The biomedical importance of establishing reliable biomarker signatures for the various molecular and cellular transition phases involved in muscle transformation is critically examined. PMID:23738259

  3. Proteomic profiling of skeletal muscle plasticity.

    PubMed

    Ohlendieck, Kay

    2011-10-01

    One of the most striking physiological features of skeletal muscle tissues are their enormous capacity to adapt to changed functional demands. Muscle plasticity has been extensively studied by histological, biochemical, physiological and genetic methods over the last few decades. With the recent emergence of high-throughput and large-scale proteomic techniques, mass spectrometry-based surveys have also been applied to the global analysis of the skeletal muscle protein complement during physiological modifications and pathophysiological alterations. This review outlines and discusses the impact of recent proteomic profiling studies of skeletal muscle transitions, including the effects of chronic electro-stimulation, physical exercise, denervation, disuse atrophy, hypoxia, myotonia, motor neuron disease and age-related fibre type shifting. This includes studies on the human skeletal muscle proteome, animal models of muscle plasticity and major neuromuscular pathologies. The biomedical importance of establishing reliable biomarker signatures for the various molecular and cellular transition phases involved in muscle transformation is critically examined. PMID:23738259

  4. Regulation of NADPH oxidases in skeletal muscle.

    PubMed

    Ferreira, Leonardo F; Laitano, Orlando

    2016-09-01

    The only known function of NAD(P)H oxidases is to produce reactive oxygen species (ROS). Skeletal muscles express three isoforms of NAD(P)H oxidases (Nox1, Nox2, and Nox4) that have been identified as critical modulators of redox homeostasis. Nox2 acts as the main source of skeletal muscle ROS during contractions, participates in insulin signaling and glucose transport, and mediates the myocyte response to osmotic stress. Nox2 and Nox4 contribute to skeletal muscle abnormalities elicited by angiotensin II, muscular dystrophy, heart failure, and high fat diet. Our review addresses the expression and regulation of NAD(P)H oxidases with emphasis on aspects that are relevant to skeletal muscle. We also summarize: i) the most widely used NAD(P)H oxidases activity assays and inhibitors, and ii) studies that have defined Nox enzymes as protagonists of skeletal muscle redox homeostasis in a variety of health and disease conditions. PMID:27184955

  5. Redox control of skeletal muscle atrophy.

    PubMed

    Powers, Scott K; Morton, Aaron B; Ahn, Bumsoo; Smuder, Ashley J

    2016-09-01

    Skeletal muscles comprise the largest organ system in the body and play an essential role in body movement, breathing, and glucose homeostasis. Skeletal muscle is also an important endocrine organ that contributes to the health of numerous body organs. Therefore, maintaining healthy skeletal muscles is important to support overall health of the body. Prolonged periods of muscle inactivity (e.g., bed rest or limb immobilization) or chronic inflammatory diseases (i.e., cancer, kidney failure, etc.) result in skeletal muscle atrophy. An excessive loss of muscle mass is associated with a poor prognosis in several diseases and significant muscle weakness impairs the quality of life. The skeletal muscle atrophy that occurs in response to inflammatory diseases or prolonged inactivity is often associated with both oxidative and nitrosative stress. In this report, we critically review the experimental evidence that provides support for a causative link between oxidants and muscle atrophy. More specifically, this review will debate the sources of oxidant production in skeletal muscle undergoing atrophy as well as provide a detailed discussion on how reactive oxygen species and reactive nitrogen species modulate the signaling pathways that regulate both protein synthesis and protein breakdown. PMID:26912035

  6. Channelopathies of skeletal muscle excitability

    PubMed Central

    Cannon, Stephen C.

    2016-01-01

    Familial disorders of skeletal muscle excitability were initially described early in the last century and are now known to be caused by mutations of voltage-gated ion channels. The clinical manifestations are often striking, with an inability to relax after voluntary contraction (myotonia) or transient attacks of severe weakness (periodic paralysis). An essential feature of these disorders is fluctuation of symptoms that are strongly impacted by environmental triggers such as exercise, temperature, or serum K+ levels. These phenomena have intrigued physiologists for decades, and in the past 25 years the molecular lesions underlying these disorders have been identified and mechanistic studies are providing insights for therapeutic strategies of disease modification. These familial disorders of muscle fiber excitability are “channelopathies” caused by mutations of a chloride channel (ClC-1), sodium channel (NaV1.4), calcium channel (CaV1.1) and several potassium channels (Kir2.1, Kir2.6, Kir3.4). This review provides a synthesis of the mechanistic connections between functional defects of mutant ion channels, their impact on muscle excitability, how these changes cause clinical phenotypes, and approaches toward therapeutics. PMID:25880512

  7. MicroRNAs overexpressed in growth-restricted rat skeletal muscles regulate the glucose transport in cell culture targeting central TGF-β factor SMAD4.

    PubMed

    Raychaudhuri, Santanu

    2012-01-01

    The micro-array profiling of micro-RNA has been performed in rat skeletal muscle tissues, isolated from male adult offspring of intrauterine plus postnatal growth restricted model (IPGR). Apparently, the GLUT4 mRNA expression in male sk. muscle was found to be unaltered in contrast to females. The over-expression of miR-29a and miR-23a in the experimental group of SMSP (Starved Mother Starved Pups) have been found to regulate the glucose transport activity with respect to their control counterparts CMCP (Control Mother Control Pups) as confirmed in rat L6 myoblast-myocyte cell culture system. The ex-vivo experimentation demonstrates an aberration in insulin signaling pathway in male sk. muscle that leads to the localization of the membrane-bound Glut4 protein. We have identified through a series of experiments one important protein factor SMAD4, a co-SMAD critical to the TGF-beta signaling pathway. This factor is targeted by miR-29a, as identified in an in vitro reporter-assay system in cell-culture experiment. The other micro-RNA, miR-23a, targets SMAD4 indirectly that seems to be critical in regulating insulin-dependent glucose transport activity. MicroRNA mimics, inhibitors and siRNA studies indicate the role of SMAD4 as inhibitory for glucose transport activities in normal physiological condition. The data demonstrate for the first time a critical function of microRNAs in fine-tuning the regulation of glucose transport in skeletal muscle. Chronic starved conditions (IPGR) in sk. muscle up-regulates microRNA changing the target protein expression patterns, such as SMAD4, to alter the glucose transport pathways for the survival. The innovative outcome of this paper identifies a critical pathway (TGF-beta) that may act negatively for the mammalian glucose transport machinery. PMID:22506032

  8. Angiopoietin-1 enhances skeletal muscle regeneration in mice

    PubMed Central

    Mofarrahi, Mahroo; McClung, Joseph M.; Kontos, Christopher D.; Davis, Elaine C.; Tappuni, Bassman; Moroz, Nicolay; Pickett, Amy E.; Huck, Laurent; Harel, Sharon; Danialou, Gawiyou

    2015-01-01

    Activation of muscle progenitor cell myogenesis and endothelial cell angiogenesis is critical for the recovery of skeletal muscle from injury. Angiopoietin-1 (Ang-1), a ligand of Tie-2 receptors, enhances angiogenesis and skeletal muscle satellite cell survival; however, its role in skeletal muscle regeneration after injury is unknown. We assessed the effects of Ang-1 on fiber regeneration, myogenesis, and angiogenesis in injured skeletal muscle (tibialis anterior, TA) in mice. We also assessed endogenous Ang-1 levels and localization in intact and injured TA muscles. TA fiber injury was triggered by cardiotoxin injection. Endogenous Ang-1 mRNA levels immediately decreased in response to cardiotoxin then increased during the 2 wk. Ang-1 protein was expressed in satellite cells, both in noninjured and recovering TA muscles. Positive Ang-1 staining was present in blood vessels but not in nerve fibers. Four days after the initiation of injury, injection of adenoviral Ang-1 into injured muscles resulted in significant increases in in situ TA muscle contractility, muscle fiber regeneration, and capillary density. In cultured human skeletal myoblasts, recombinant Ang-1 protein increased survival, proliferation, migration, and differentiation into myotubes. The latter effect was associated with significant upregulation of the expression of the myogenic regulatory factors MyoD and Myogenin and certain genes involved in cell cycle regulation. We conclude that Ang-1 strongly enhances skeletal muscle regeneration in response to fiber injury and that this effect is mediated through induction of the myogenesis program in muscle progenitor cells and the angiogenesis program in endothelial cells. PMID:25608750

  9. Increased skeletal muscle capillarization enhances insulin sensitivity.

    PubMed

    Akerstrom, Thorbjorn; Laub, Lasse; Vedel, Kenneth; Brand, Christian Lehn; Pedersen, Bente Klarlund; Lindqvist, Anna Kaufmann; Wojtaszewski, Jørgen F P; Hellsten, Ylva

    2014-12-15

    Increased skeletal muscle capillarization is associated with improved glucose tolerance and insulin sensitivity. However, a possible causal relationship has not previously been identified. Therefore, we investigated whether increased skeletal muscle capillarization increases insulin sensitivity. Skeletal muscle-specific angiogenesis was induced by adding the α1-adrenergic receptor antagonist prazosin to the drinking water of Sprague-Dawley rats (n = 33), whereas 34 rats served as controls. Insulin sensitivity was measured ≥40 h after termination of the 3-wk prazosin treatment, which ensured that prazosin was cleared from the blood stream. Whole body insulin sensitivity was measured in conscious, unrestrained rats by hyperinsulinemic euglycemic clamp. Tissue-specific insulin sensitivity was assessed by administration of 2-deoxy-[(3)H]glucose during the plateau phase of the clamp. Whole body insulin sensitivity increased by ∼24%, and insulin-stimulated skeletal muscle 2-deoxy-[(3)H]glucose disposal increased by ∼30% concomitant with an ∼20% increase in skeletal muscle capillarization. Adipose tissue insulin sensitivity was not affected by the treatment. Insulin-stimulated muscle glucose uptake was enhanced independent of improvements in skeletal muscle insulin signaling to glucose uptake and glycogen synthesis, suggesting that the improvement in insulin-stimulated muscle glucose uptake could be due to improved diffusion conditions for glucose in the muscle. The prazosin treatment did not affect the rats on any other parameters measured. We conclude that an increase in skeletal muscle capillarization is associated with increased insulin sensitivity. These data point toward the importance of increasing skeletal muscle capillarization for prevention or treatment of type 2 diabetes. PMID:25352432

  10. Muscle-specific microRNAs in skeletal muscle development.

    PubMed

    Horak, Martin; Novak, Jan; Bienertova-Vasku, Julie

    2016-02-01

    Proper muscle function constitutes a precondition for good heath and an active lifestyle during an individual's lifespan and any deviations from normal skeletal muscle development and its functions may lead to numerous health conditions including e.g. myopathies and increased mortality. It is thus not surprising that there is an increasing need for understanding skeletal muscle developmental processes and the associated molecular pathways, especially as such information could find further uses in therapy. The understanding of complex skeletal muscle developmental networks was broadened with the discovery of microRNA (miRNA) molecules. MicroRNAs are evolutionary conserved small non-coding RNAs capable of negatively regulating gene expression on a post-transcriptional level by means of miRNA-mRNA interaction. Several miRNAs expressed exclusively in muscle have been labeled myomiRs. MyomiRs represent an integral part of skeletal muscle development, i.e. playing a significant role during skeletal muscle proliferation, differentiation and regeneration. The purpose of this review is to provide a summary of current knowledge regarding the involvement of myomiRs in the individual phases of myogenesis and other aspects of skeletal muscle biology, along with an up-to-date list of myomiR target genes and their functions in skeletal muscle and miRNA-related therapeutic approaches and future prospects. PMID:26708096

  11. Redox regulation of autophagy in skeletal muscle.

    PubMed

    Rodney, George G; Pal, Rituraj; Abo-Zahrah, Reem

    2016-09-01

    Autophagy is a cellular degradative pathway that involves the delivery of cytoplasmic components, including proteins and organelles, to the lysosome for degradation. Autophagy is implicated in the maintenance of skeletal muscle; increased autophagy leads to muscle atrophy while decreased autophagy leads to degeneration and weakness. A growing body of work suggests that reactive oxygen species (ROS) are important cellular signal transducers controlling autophagy. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidases and mitochondria are major sources of ROS generation in skeletal muscle that are likely regulating autophagy through different signaling cascades based on localization of the ROS signals. This review aims to provide insight into the redox control of autophagy in skeletal muscle. Understanding the mechanisms by which ROS regulate autophagy will provide novel therapeutic targets for skeletal muscle diseases. PMID:27184957

  12. Regulation of skeletal muscle perfusion during exercise

    NASA Technical Reports Server (NTRS)

    Delp, M. D.; Laughlin, M. H.

    1998-01-01

    For exercise to be sustained, it is essential that adequate blood flow be provided to skeletal muscle. The local vascular control mechanisms involved in regulating muscle perfusion during exercise include metabolic control, endothelium-mediated control, propagated responses, myogenic control, and the muscle pump. The primary determinant of muscle perfusion during sustained exercise is the metabolic rate of the muscle. Metabolites from contracting muscle diffuse to resistance arterioles and act directly to induce vasodilation, or indirectly to inhibit noradrenaline release from sympathetic nerve endings and oppose alpha-adrenoreceptor-mediated vasoconstriction. The vascular endothelium also releases vasodilator substances (e.g., prostacyclin and nitric oxide) that are prominent in establishing basal vascular tone, but these substances do not appear to contribute to the exercise hyperemia in muscle. Endothelial and smooth muscle cells may also be involved in propagating vasodilator signals along arterioles to parent and daughter vessels. Myogenic autoregulation does not appear to be involved in the exercise hyperemia in muscle, but the rhythmic propulsion of blood from skeletal muscle veins facilitates venous return to the heart and muscle perfusion. It appears that the primary determinants of sustained exercise hyperemia in skeletal muscle are metabolic vasodilation and increased vascular conductance via the muscle pump. Additionally, sympathetic neural control is important in regulating muscle blood flow during exercise.

  13. 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

  14. Skeletal Muscle Autophagy: A New Metabolic Regulator

    PubMed Central

    Neel, Brian A.; Lin, Yuxi; Pessin, Jeffrey E.

    2013-01-01

    Autophagy classically functions as a physiological process to degrade cytoplasmic components, protein aggregates, and/or organelles, as a mechanism for nutrient breakdown, and as a regulator of cellular architecture. Proper autophagic flux is vital for both functional skeletal muscle, which controls support and movement of the skeleton, and muscle metabolism. The role of autophagy as a metabolic regulator in muscle has been previously studied; however, the underlying molecular mechanisms that control autophagy in skeletal muscle have only just begun to emerge. Here, we review recent literature on the molecular pathways controlling skeletal muscle autophagy, and discuss how they connect autophagy to metabolic regulation. We also focus on the implications these studies hold for understanding metabolic and muscle wasting diseases. PMID:24182456

  15. Heterogeneous ageing of skeletal muscle microvascular function.

    PubMed

    Muller-Delp, Judy M

    2016-04-15

    The distribution of blood flow to skeletal muscle during exercise is altered with advancing age. Changes in arteriolar function that are muscle specific underlie age-induced changes in blood flow distribution. With advancing age, functional adaptations that occur in resistance arterioles from oxidative muscles differ from those that occur in glycolytic muscles. Age-related adaptations of morphology, as well as changes in both endothelial and vascular smooth muscle signalling, differ in muscle of diverse fibre type. Age-induced endothelial dysfunction has been reported in most skeletal muscle arterioles; however, unique alterations in signalling contribute to the dysfunction in arterioles from oxidative muscles as compared with those from glycolytic muscles. In resistance arterioles from oxidative muscle, loss of nitric oxide signalling contributes significantly to endothelial dysfunction, whereas in resistance arterioles from glycolytic muscle, alterations in both nitric oxide and prostanoid signalling underlie endothelial dysfunction. Similarly, adaptations of the vascular smooth muscle that occur with advancing age are heterogeneous between arterioles from oxidative and glycolytic muscles. In both oxidative and glycolytic muscle, late-life exercise training reverses age-related microvascular dysfunction, and exercise training appears to be particularly effective in reversing endothelial dysfunction. Patterns of microvascular ageing that develop among muscles of diverse fibre type and function may be attributable to changing patterns of physical activity with ageing. Importantly, aerobic exercise training, initiated even at an advanced age, restores muscle blood flow distribution patterns and vascular function in old animals to those seen in their young counterparts. PMID:26575597

  16. Cardiac assistance from skeletal muscle: a reappraisal.

    PubMed

    Salmons, Stanley

    2009-02-01

    Cardiac assistance from skeletal muscle offers an attractive surgical solution to the problem of end-stage heart failure, yet it is widely regarded as a failed approach. I argue here that this is an outdated assessment. Systematic progress has been made over the last 25 years in understanding the relevant basic science. In the light of these advances we should be reconsidering the place of skeletal muscle assist in the surgical armamentarium. PMID:18954996

  17. Beta-Adrenergic Receptor Population is Up-Regulated by Increased Cyclic Amp Concentration in Chicken Skeletal Muscle Cells in Culture

    NASA Technical Reports Server (NTRS)

    Young, Ronald B.; Bridge, Kristin Y.; Vaughn, Jeffrey R.

    1999-01-01

    Skeletal muscle hypertrophy is promoted in vivo by administration of beta-drenergic receptor (bAR) agonists. Chicken skeletal muscle cells were treated with 1 (mu)M isoproterenol, a strong bAR agonist, between days 7 and 10 in culture. bAR population increased by approximately 40% during this treatment; however, the ability of the cells to synthesize cyclic AMP (cAMP) was diminished by two-fold. The quantity of myosin heavy chain (MHC) was not affected. To understand further the relationship between intracellular cAMP levels, bAR population, and muscle protein accumulation, intracellular cAMP levels were artificially elevated by treatment with 0-10 uM forskolin for up to three days. The basal concentration of CAMP in forskolin-treated cells increased up to 7-fold in a dose dependent manner. Increasing concentrations of forskolin also led to an increase in bAR population, with a maximum increase of approximately 40-60% at 10 uM forskolin. A maximum increase of 40-50% in the quantity of MHC was observed at 0.2 uM forskolin, but higher concentrations of forskolin reduced the quantity of MHC back to control levels. At 0.2 uM forskolin, intracellular levels of cAMP were higher by approximately 35%, and the (beta)AR population was higher by approximately 30%. Neither the number of muscle nuclei fused into myotubes nor the percentage of nuclei in myotubes were affected by forskolin at any of the concentrations studied.

  18. Male ironman triathletes lose skeletal muscle mass.

    PubMed

    Knechtle, Beat; Baumann, Barbara; Wirth, Andrea; Knechtle, Patrizia; Rosemann, Thomas

    2010-01-01

    We investigated whether male triathletes in an Ironman triathlon lose body mass in the form of fat mass or skeletal muscle mass in a field study at the Ironman Switzerland in 27 male Caucasian non-professional Ironman triathletes. Pre- and post-race body mass, fat mass and skeletal muscle mass were determined. In addition, total body water, hematological and urinary parameters were measured in order to quantify hydration status. Body mass decreased by 1.8 kg (p< 0.05), skeletal muscle decreased by 1.0 kg (p< 0.05) whereas fat mass showed no changes. Urinary specific gravity, plasma urea and plasma volume increased (p< 0.05). Pre- to post-race change (Delta) in body mass was not associated with ? skeletal muscle mass. Additionally, there was no association between Delta plasma urea and Delta skeletal muscle mass; Delta plasma volume was not associated with Delta total body water (p< 0.05). We concluded that male triathletes in an Ironman triathlon lose 1.8 kg of body mass and 1 kg of skeletal muscle mass, presumably due to a depletion of intramyocellular stored glycogen and lipids. PMID:20199992

  19. Skeletal muscle functions around the clock.

    PubMed

    Mayeuf-Louchart, A; Staels, B; Duez, H

    2015-09-01

    In mammals, the central clock localized in the central nervous system imposes a circadian rhythmicity to all organs. This is achieved thanks to a well-conserved molecular clockwork, involving interactions between several transcription factors, whose pace is conveyed to peripheral tissues through neuronal and humoral signals. The molecular clock plays a key role in the control of numerous physiological processes and takes part in the regulation of metabolism and energy balance. Skeletal muscle is one of the peripheral organs whose function is under the control of the molecular clock. However, although skeletal muscle metabolism and performances display circadian rhythmicity, the role of the molecular clock in the skeletal muscle has remained unappreciated for years. Peripheral organs such as skeletal muscle, and the liver, among others, can be desynchronized from the central clock by external stimuli, such as feeding or exercise, which impose a new rhythm at the organism level. In this review, we discuss our current understanding of the clock in skeletal muscle circadian physiology, focusing on the control of myogenesis and skeletal muscle metabolism. PMID:26332967

  20. How sex hormones promote skeletal muscle regeneration.

    PubMed

    Velders, Martina; Diel, Patrick

    2013-11-01

    Skeletal muscle regeneration efficiency declines with age for both men and women. This decline impacts on functional capabilities in the elderly and limits their ability to engage in regular physical activity and to maintain independence. Aging is associated with a decline in sex hormone production. Therefore, elucidating the effects of sex hormone substitution on skeletal muscle homeostasis and regeneration after injury or disuse is highly relevant for the aging population, where sarcopenia affects more than 30 % of individuals over 60 years of age. While the anabolic effects of androgens are well known, the effects of estrogens on skeletal muscle anabolism have only been uncovered in recent times. Hence, the purpose of this review is to provide a mechanistic insight into the regulation of skeletal muscle regenerative processes by both androgens and estrogens. Animal studies using estrogen receptor (ER) antagonists and receptor subtype selective agonists have revealed that estrogens act through both genomic and non-genomic pathways to reduce leukocyte invasion and increase satellite cell numbers in regenerating skeletal muscle tissue. Although animal studies have been more conclusive than human studies in establishing a role for sex hormones in the attenuation of muscle damage, data from a number of recent well controlled human studies is presented to support the notion that hormonal therapies and exercise induce added positive effects on functional measures and lean tissue mass. Based on the fact that aging human skeletal muscle retains the ability to adapt to exercise with enhanced satellite cell activation, combining sex hormone therapies with exercise may induce additive effects on satellite cell accretion. There is evidence to suggest that there is a 'window of opportunity' after the onset of a hypogonadal state such as menopause, to initiate a hormonal therapy in order to achieve maximal benefits for skeletal muscle health. Novel receptor subtype selective

  1. Aspects of skeletal muscle modelling.

    PubMed Central

    Epstein, Marcelo; Herzog, Walter

    2003-01-01

    The modelling of skeletal muscle raises a number of philosophical questions, particularly in the realm of the relationship between different possible levels of representation and explanation. After a brief incursion into this area, a list of desiderata is proposed as a guiding principle for the construction of a viable model, including: comprehensiveness, soundness, experimental consistency, predictive ability and refinability. Each of these principles is illustrated by means of simple examples. The presence of internal constraints, such as incompressibility, may lead to counterintuitive results. A one-panel example is exploited to advocate the use of the principle of virtual work as the ideal tool to deal with these situations. The question of stability in the descending limb of the force-length relation is addressed and a purely mechanical analogue is suggested. New experimental results confirm the assumption that fibre stiffness is positive even in the descending limb. The indeterminacy of the force-sharing problem is traditionally resolved by optimizing a, presumably, physically meaningful target function. After presenting some new results in this area, based on a separation theorem, it is suggested that a more fundamental approach to the problem is the abandoning of optimization criteria in favour of an explicit implementation of activation criteria. PMID:14561335

  2. Heparan sulfate in skeletal muscle development

    SciTech Connect

    Noonan, D.M.

    1985-01-01

    In this study, chick breast skeletal muscle cells developing in vitro from myoblasts to myotubes were found to synthesize heparan sulfate (HS), chrondroitin-6-sulfate, chrondroitin-4-sulfate, dermatan sulfate, unsulfated chrondroitin and hyaluronic acid in both the substratum attached material (SAM) and the cellular fraction. SAM was found to contain predominantly chrondroitin-6-sulfate and relatively little HS whereas the cellular fraction contained relatively higher levels of HS and lower levels of chrondroitin-6-sulfate. Hyaluronic acid was also a major component in both fractions with the other glycosaminoglycan isomers present as minor components. Muscle derived fibroblast cultures had higher levels of dermatan sulfate in the cell layer and higher levels of HS in the SAM fraction than did muscle cultures. The structure of the proteoglycans were partially characterized in /sup 35/SO/sub 4//sup 2 -/ radio-labeled cultures which indicated an apparent increase in the hydrodynamic size of the cell fraction heparan sulfate proteoglycan (HS PG). Myotubes incorporated /sup 35/SO/sub 4//sup 2 -/ into HS PG at a rate 3 times higher than myoblasts. The turnover rate of HS in the cellular fraction was the same for myoblasts and myotubes, with a t/sub 1/2/ of approximately 5 hours. Fibroblasts in culture synthesized the smallest HS PG, and incorporated /sup 35/SO/sub 4//sup 2 -/ into HS PG at a rate lower than that of myotubes. Studies in which fusion was reversibly inhibited with decreased medium (Ca/sup + +/) closely linked the increased synthesis of cell fraction, but not SAM fraction, HS with myotube formation. However, decreasing medium calcium appeared to cause significant alterations in the metabolism of inorganic sulfate.

  3. Biomaterial-based delivery for skeletal muscle repair

    PubMed Central

    Cezar, Christine A.; Mooney, David J.

    2015-01-01

    Skeletal muscle possesses a remarkable capacity for regeneration in response to minor damage, but severe injury resulting in a volumetric muscle loss can lead to extensive and irreversible fibrosis, scarring, and loss of muscle function. In early clinical trials, the intramuscular injection of cultured myoblasts was proven to be a safe but ineffective cell therapy, likely due to rapid death, poor migration, and immune rejection of the injected cells. In recent years, appropriate therapeutic cell types and culturing techniques have improved progenitor cell engraftment upon transplantation. Importantly, the identification of several key biophysical and biochemical cues that synergistically regulate satellite cell fate has paved the way for the development of cell-instructive biomaterials that serve as delivery vehicles for cells to promote in vivo regeneration. Material carriers designed to spatially and temporally mimic the satellite cell niche may be of particular importance for the complete regeneration of severely damaged skeletal muscle. PMID:25271446

  4. Skeletal Muscle Loading Changes its Regenerative Capacity.

    PubMed

    Teixeira, Eduardo; Duarte, José Alberto

    2016-06-01

    Whenever skeletal muscle insults occur, both by functional impositions or other injury forms, skeletal muscle repair (SMR) follows. The SMR succeeds when proper skeletal muscle regeneration and limited fibrosis ensue. Muscle fiber replenishment by fibrosis negatively affects the tissue quality and functionality and, furthermore, represents the worst post-injury phenotypic adaptation. Acute muscle injury treatment commonly follows the RICE method-rest, ice, compression, and elevation. This immediate immobilization seems to be beneficial to preserving the tissue structure and avoiding further destruction; however, if these interventions are delayed, the risk of muscle atrophy and its deleterious-related effects increase, with resultant impaired SMR. Moreover, a growing body of evidence shows positive skeletal muscle loading (SML) effects during SMR since it seems to effectively increase satellite cells (SCs) in their activation, proliferation, self-renewal, and differentiation capacities. Additionally, recent data show that SML may also influence the functions of other participants in SMR, compelling SMR to achieve less fibrotic accretion and accelerated muscle mass recovery. Moreover, given the SML effects on SCs, it is plausible to consider that these can increase the myofibers' basal myogenic potential. Thus, it seems relevant to scrutinize the possible acute and chronic SML therapeutic and prophylactic effects regarding the SMR process. PMID:26838984

  5. Myoglobinuria and Skeletal Muscle Phosphorylase Deficiency

    PubMed Central

    Nixon, J. C.; Hobbs, W. K.; Greenblatt, J.

    1966-01-01

    Investigation of a patient complaining of exercise-induced dark urine, pain, stiffness and tenderness of skeletal muscle revealed findings characteristic of McArdle's disease. The dark urine was attributable to the excretion of myoglobin, and an ischemic exercise test failed to demonstrate the usual rise and fall in blood lactate and pyruvate. Enzyme assays of skeletal muscle showed an absence of phosphorylase, a slight increase in phosphorylase b kinase and a slight decrease in phosphoglucomutase. Chemical and histochemical analyses demonstrated an increase in the skeletal muscle glycogen content and an enlargement of the muscle cells. No abnormality of liver glycogen metabolism was found. In the absence of specific therapy, an effective and practical form of treatment is reduction of exercise below the threshold of symptoms. ImagesFig. 1Fig. 2Fig. 6Fig. 7Fig. 8 PMID:4952390

  6. 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.

  7. Coaxing stem cells for skeletal muscle repair

    PubMed Central

    McCullagh, Karl J.A.; Perlingeiro, Rita C. R.

    2014-01-01

    Skeletal muscle has a tremendous ability to regenerate, attributed to a well-defined population of muscle stem cells called satellite cells. However, this ability to regenerate diminishes with age and can also be dramatically affected by multiple types of muscle diseases, or injury. Extrinsic and/or intrinsic defects in the regulation of satellite cells are considered to be major determinants for the diminished regenerative capacity. Maintenance and replenishment of the satellite cell pool is one focus for muscle regenerative medicine, which will be discussed. There are other sources of progenitor cells with myogenic capacity, which may also support skeletal muscle repair. However, all of these myogenic cell populations have inherent difficulties and challenges in maintaining or coaxing their derivation for therapeutic purpose. This review will highlight recent reported attributes of these cells and new bioengineering approaches to creating a supply of myogenic stem cells or implants applicable for acute and/or chronic muscle disorders. PMID:25049085

  8. Epigenetic regulation of skeletal muscle metabolism.

    PubMed

    Howlett, Kirsten F; McGee, Sean L

    2016-07-01

    Normal skeletal muscle metabolism is essential for whole body metabolic homoeostasis and disruptions in muscle metabolism are associated with a number of chronic diseases. Transcriptional control of metabolic enzyme expression is a major regulatory mechanism for muscle metabolic processes. Substantial evidence is emerging that highlights the importance of epigenetic mechanisms in this process. This review will examine the importance of epigenetics in the regulation of muscle metabolism, with a particular emphasis on DNA methylation and histone acetylation as epigenetic control points. The emerging cross-talk between metabolism and epigenetics in the context of health and disease will also be examined. The concept of inheritance of skeletal muscle metabolic phenotypes will be discussed, in addition to emerging epigenetic therapies that could be used to alter muscle metabolism in chronic disease states. PMID:27215678

  9. Denervation and reinnervation of skeletal muscle

    NASA Technical Reports Server (NTRS)

    Mayer, R. F.; Max, S. R.

    1983-01-01

    A review is presented of the physiological and biochemical changes that occur in mammalian skeletal muscle after denervation and reinnervation. These changes are compared with those observed after altered motor function. Also considered is the nature of the trophic influence by which nerves control muscle properties. Topics examined include the membrane and contractile properties of denervated and reinnervated muscle; the cholinergic proteins, such as choline acetyltransferase, acetylcholinesterase, and the acetylcholine receptor; and glucose-6-phosphate dehydrogenase.

  10. Skeletal muscle pathology in Huntington's disease

    PubMed Central

    Zielonka, Daniel; Piotrowska, Izabela; Marcinkowski, Jerzy T.; Mielcarek, Michal

    2014-01-01

    Huntington's disease (HD) is a hereditary neurodegenerative disorder caused by the expansion of a polyglutamine stretch within the huntingtin protein (HTT). The neurological symptoms, that involve motor, cognitive and psychiatric disturbances, are caused by neurodegeneration that is particularly widespread in the basal ganglia and cereberal cortex. HTT is ubiquitously expressed and in recent years it has become apparent that HD patients experience a wide array of peripheral organ dysfunction including severe metabolic phenotype, weight loss, HD-related cardiomyopathy and skeletal muscle wasting. Although skeletal muscles pathology became a hallmark of HD, the mechanisms underlying muscular atrophy in this disorder are unknown. Skeletal muscles account for approximately 40% of body mass and are highly adaptive to physiological and pathological conditions that may result in muscle hypertrophy (due to increased mechanical load) or atrophy (inactivity, chronic disease states). The atrophy is caused by degeneration of myofibers and their replacement by fibrotic tissue is the major pathological feature in many genetic muscle disorders. Under normal physiological conditions the muscle function is orchestrated by a network of intrinsic hypertrophic and atrophic signals linked to the functional properties of the motor units that are likely to be imbalanced in HD. In this article, we highlight the emerging field of research with particular focus on the recent studies of the skeletal muscle pathology and the identification of new disease-modifying treatments. PMID:25339908

  11. Human Skeletal Muscle Health with Spaceflight

    NASA Astrophysics Data System (ADS)

    Trappe, Scott

    2012-07-01

    This lecture will overview the most recent aerobic and resistance exercise programs used by crewmembers while aboard the International Space Station (ISS) for six months and examine its effectiveness for protecting skeletal muscle health. Detailed information on the exercise prescription program, whole muscle size, whole muscle performance, and cellular data obtained from muscle biopsy samples will be presented. Historically, detailed information on the exercise program while in space has not been available. These most recent exercise and muscle physiology findings provide a critical foundation to guide the exercise countermeasure program forward for future long-duration space missions.

  12. Multiple Sclerosis Affects Skeletal Muscle Characteristics

    PubMed Central

    Wens, Inez; Dalgas, Ulrik; Vandenabeele, Frank; Krekels, Maartje; Grevendonk, Lotte; Eijnde, Bert O.

    2014-01-01

    Background The impact of multiple sclerosis (MS) on skeletal muscle characteristics, such as muscle fiber cross sectional area (CSA), fiber type proportion, muscle strength and whole muscle mass, remains conflicting. Methods In this cross sectional study, body composition and muscle strength of the quadriceps were assessed in 34 MS (EDSS: 2.5±0.19) patients and 18 matched healthy controls (HC). Hereafter a muscle biopsy (m.vastus lateralis) was taken. Results Compared to HC, mean muscle fiber CSA of all fibers, as well as CSA of type I, II and IIa fibers were smaller and muscle strength of the quadriceps was lower in MS patients. Whole body composition was comparable between groups. However, compared to HC, the biopsied leg tended to have a higher fat percentage (p = 0.1) and a lower lean mass (p = 0.06) in MS patients. Conclusion MS seems to negatively influence skeletal muscle fiber CSA, muscle strength and muscle mass of the lower limbs of mildly affected MS patients. This emphasises the need for rehabilitation programs focusing on muscle preservation of the lower limb. Trial Registration ClinicalTrials.gov NCT01845896 PMID:25264868

  13. Myoblast proliferation and syncytial fusion both depend on connexin43 function in transfected skeletal muscle primary cultures

    SciTech Connect

    Gorbe, Aniko; Krenacs, Tibor; Cook, Jeremy E.; Becker, David L. . E-mail: d.becker@ucl.ac.uk

    2007-04-01

    Muscles are formed by fusion of individual postmitotic myoblasts to form multinucleated syncytial myotubes. The process requires a well-coordinated transition from proliferation, through migratory alignment and cycle exit, to breakdown of apposed membranes. Connexin43 protein and cell-cycle inhibitor levels are correlated, and gap junction blockers can delay muscle regeneration, so a coordinating role for gap junctions has been proposed. Here, wild-type and dominant-negative connexin43 variants (wtCx43, dnCx43) were introduced into rat myoblasts in primary culture through pIRES-eGFP constructs that made transfected cells fluoresce. GFP-positive cells and vitally-stained nuclei were counted on successive days to reveal differences in proliferation, and myotubes were counted to reveal differences in fusion. Individual transfected cells were injected with Cascade Blue, which permeates gap junctions, mixed with FITC-dextran, which requires cytoplasmic continuity to enter neighbouring cells. Myoblasts transfected with wtCx43 showed more gap-junctional coupling than GFP-only controls, began fusion sooner as judged by the incidence of cytoplasmic coupling, and formed more myotubes. Myoblasts transfected with dnCx43 remained proliferative for longer than either GFP-only or wtCx43 myoblasts, showed less coupling, and underwent little fusion into myotubes. These results highlight the critical role of gap-junctional coupling in myotube formation.

  14. Skeletal muscle as an endogenous nitrate reservoir

    PubMed Central

    Piknova, Barbora; Park, Ji Won; Swanson, Kathryn M.; Dey, Soumyadeep; Noguchi, Constance Tom; Schechter, Alan N

    2015-01-01

    The nitric oxide synthase (NOS) family of enzymes form nitric oxide (NO) from arginine in the presence of oxygen. At reduced oxygen availability NO is also generated from nitrate in a two step process by bacterial and mammalian molybdopterin proteins, and also directly from nitrite by a variety of five-coordinated ferrous hemoproteins. The mammalian NO cycle also involves direct oxidation of NO to nitrite, and both NO and nitrite to nitrate by oxy-ferrous hemoproteins. The liver and blood are considered the sites of active mammalian NO metabolism and nitrite and nitrate concentrations in the liver and blood of several mammalian species, including human, have been determined. However, the large tissue mass of skeletal muscle had not been generally considered in the analysis of the NO cycle, in spite of its long-known presence of significant levels of active neuronal NOS (nNOS or NOS1). We hypothesized that skeletal muscle participates in the NO cycle and, due to its NO oxidizing heme protein, oxymyoglobin, has high concentrations of nitrate ions. We measured nitrite and nitrate concentrations in rat and mouse leg skeletal muscle and found unusually high concentrations of nitrate but similar levels of nitrite, when compared to the liver. The nitrate reservoir in muscle is easily accessible via the bloodstream and therefore nitrate is available for transport to internal organs where it can be reduced to nitrite and NO. Nitrate levels in skeletal muscle and blood in nNOS−/− mice were dramatically lower when compared with controls, which support further our hypothesis. Although the nitrate reductase activity of xanthine oxidoreductase in muscle is less than that of liver, the residual activity in muscle could be very important in view of its total mass and the high basal level of nitrate. We suggest that skeletal muscle participates in overall NO metabolism, serving as a nitrate reservoir, for direct formation of nitrite and NO, and for determining levels of nitrate

  15. Gene Regions Responding to Skeletal Muscle Atrophy

    NASA Technical Reports Server (NTRS)

    Booth, Frank W.

    1997-01-01

    Our stated specific aims for this project were: 1) Identify the region(s) of the mouse IIb myosin heavy chain (MHC) promoter necessary for in vivo expression in mouse fast-twitch muscle, and 2) Identify the region(s) of the mouse IIb MHC promoter responsive to immobilization in mouse slow-twitch muscle in vivo. We sought to address these specific aims by introducing various MHC IIb promoter/reporter gene constructs directly into the tibialis anterior and gastrocnemius muscles of living mice. Although the method of somatic gene transfer into skeletal muscle by direct injection has been successfully used in our laboratory to study the regulation of the skeletal alpha actin gene in chicken skeletal muscle, we had many difficulties utilizing this procedure in the mouse. Because of the small size of the mouse soleus and the difficulty in obtaining consistent results, we elected not to study this muscle as first proposed. Rather, our MHC IIb promoter deletion experiments were performed in the gastrocnemius. Further, we decided to use hindlimb unloading via tail suspension to induce an upregulation of the MHC IIb gene, rather than immobilization of the hindlimbs via plaster casts. This change was made because tail suspension more closely mimics spaceflight, and this procedure in our lab results in a smaller loss of overall body mass than the mouse hindlimb immobilization procedure. This suggests that the stress level during tail suspension is less than during immobilization. This research has provided an important beginning point towards understanding the molecular regulation of the MHC lIb gene in response to unweighting of skeletal muscle Future work will focus on the regulation of MHC IIb mRNA stability in response to altered loading of skeletal muscle

  16. Satellite cells in human skeletal muscle plasticity

    PubMed Central

    Snijders, Tim; Nederveen, Joshua P.; McKay, Bryon R.; Joanisse, Sophie; Verdijk, Lex B.; van Loon, Luc J. C.; Parise, Gianni

    2015-01-01

    Skeletal muscle satellite cells are considered to play a crucial role in muscle fiber maintenance, repair and remodeling. Our knowledge of the role of satellite cells in muscle fiber adaptation has traditionally relied on in vitro cell and in vivo animal models. Over the past decade, a genuine effort has been made to translate these results to humans under physiological conditions. Findings from in vivo human studies suggest that satellite cells play a key role in skeletal muscle fiber repair/remodeling in response to exercise. Mounting evidence indicates that aging has a profound impact on the regulation of satellite cells in human skeletal muscle. Yet, the precise role of satellite cells in the development of muscle fiber atrophy with age remains unresolved. This review seeks to integrate recent results from in vivo human studies on satellite cell function in muscle fiber repair/remodeling in the wider context of satellite cell biology whose literature is largely based on animal and cell models. PMID:26557092

  17. Prospective heterotopic ossification progenitors in adult human skeletal muscle.

    PubMed

    Downey, Jennifer; Lauzier, Dominique; Kloen, Peter; Klarskov, Klaus; Richter, Martin; Hamdy, Reggie; Faucheux, Nathalie; Scimè, Anthony; Balg, Frédéric; Grenier, Guillaume

    2015-02-01

    Skeletal muscle has strong regenerative capabilities. However, failed regeneration can lead to complications where aberrant tissue forms as is the case with heterotopic ossification (HO), in which chondrocytes, osteoblasts and white and brown adipocytes can arise following severe trauma. In humans, the various HO cell types likely originate from multipotent mesenchymal stromal cells (MSCs) in skeletal muscle, which have not been identified in humans until now. In the present study, adherent cells from freshly digested skeletal muscle tissue were expanded in defined culture medium and were FACS-enriched for the CD73(+)CD105(+)CD90(-) population, which displayed robust multilineage potential. Clonal differentiation assays confirmed that all three lineages originated from a single multipotent progenitor. In addition to differentiating into typical HO lineages, human muscle resident MSCs (hmrMSCs) also differentiated into brown adipocytes expressing uncoupling protein 1 (UCP1). Characterizing this novel multipotent hmrMSC population with a brown adipocyte differentiation capacity has enhanced our understanding of the contribution of non-myogenic progenitor cells to regeneration and aberrant tissue formation in human skeletal muscle. PMID:25445454

  18. Mechanotransduction pathways in skeletal muscle hypertrophy.

    PubMed

    Yamada, André Katayama; Verlengia, Rozangela; Bueno Junior, Carlos Roberto

    2012-02-01

    In the last decade, molecular biology has contributed to define some of the cellular events that trigger skeletal muscle hypertrophy. Recent evidence shows that insulin like growth factor 1/phosphatidyl inositol 3-kinase/protein kinase B (IGF-1/PI3K/Akt) signaling is not the main pathway towards load-induced skeletal muscle hypertrophy. During load-induced skeletal muscle hypertrophy process, activation of mTORC1 does not require classical growth factor signaling. One potential mechanism that would activate mTORC1 is increased synthesis of phosphatidic acid (PA). Despite the huge progress in this field, it is still early to affirm which molecular event induces hypertrophy in response to mechanical overload. Until now, it seems that mTORC1 is the key regulator of load-induced skeletal muscle hypertrophy. On the other hand, how mTORC1 is activated by PA is unclear, and therefore these mechanisms have to be determined in the following years. The understanding of these molecular events may result in promising therapies for the treatment of muscle-wasting diseases. For now, the best approach is a good regime of resistance exercise training. The objective of this point-of-view paper is to highlight mechanotransduction events, with focus on the mechanisms of mTORC1 and PA activation, and the role of IGF-1 on hypertrophy process. PMID:22171534

  19. Laminin-211 in skeletal muscle function

    PubMed Central

    Holmberg, Johan; Durbeej, Madeleine

    2013-01-01

    A chain is no stronger than its weakest link is an old idiom that holds true for muscle biology. As the name implies, skeletal muscle’s main function is to move the bones. However, for a muscle to transmit force and withstand the stress that contractions give rise to, it relies on a chain of proteins attaching the cytoskeleton of the muscle fiber to the surrounding extracellular matrix. The importance of this attachment is illustrated by a large number of muscular dystrophies caused by interruption of the cytoskeletal-extracellular matrix interaction. One of the major components of the extracellular matrix is laminin, a heterotrimeric glycoprotein and a major constituent of the basement membrane. It has become increasingly apparent that laminins are involved in a multitude of biological functions, including cell adhesion, differentiation, proliferation, migration and survival. This review will focus on the importance of laminin-211 for normal skeletal muscle function. PMID:23154401

  20. YAP-Mediated Mechanotransduction in Skeletal Muscle

    PubMed Central

    Fischer, Martina; Rikeit, Paul; Knaus, Petra; Coirault, Catherine

    2016-01-01

    Skeletal muscle is not only translating chemical energy into mechanical work, it is also a highly adaptive and regenerative tissue whose architecture and functionality is determined by its mechanical and physical environment. Processing intra- and extracellular mechanical signaling cues contributes to the regulation of cell growth, survival, migration and differentiation. Yes-associated Protein (YAP), a transcriptional coactivator downstream of the Hippo pathway and its paralog, the transcriptional co-activator with PDZ-binding motif (TAZ), were recently found to play a key role in mechanotransduction in various tissues including skeletal muscle. Furthermore, YAP/TAZ modulate myogenesis and muscle regeneration and abnormal YAP activity has been reported in muscular dystrophy and rhabdomyosarcoma. Here, we summarize the current knowledge of mechanosensing and -signaling in striated muscle. We highlight the role of YAP signaling and discuss the different routes and hypotheses of its regulation in the context of mechanotransduction. PMID:26909043

  1. Cytokine Signaling in Skeletal Muscle Wasting.

    PubMed

    Zhou, Jin; Liu, Bin; Liang, Chun; Li, Yangxin; Song, Yao-Hua

    2016-05-01

    Skeletal muscle wasting occurs in a variety of diseases including diabetes, cancer, Crohn's disease, chronic obstructive pulmonary disease (COPD), disuse, and denervation. Tumor necrosis factor α (TNF-α) is involved in mediating the wasting effect. To date, a causal relationship between TNF-α signaling and muscle wasting has been established in animal models. However, results from clinical trials are conflicting. This is partly due to the fact that other factors such as TNF-like weak inducer of apoptosis (TWEAK) and interleukin 6 (IL-6) are also involved in skeletal muscle wasting. Because muscle wasting is often associated with physical inactivity and reduced food intake, therapeutic interventions will be most effective when multiple approaches are used in conjunction with nutritional support and exercise. PMID:27025788

  2. Dynamics of the Skeletal Muscle Secretome during Myoblast Differentiation*

    PubMed Central

    Henningsen, Jeanette; Rigbolt, Kristoffer T. G.; Blagoev, Blagoy; Pedersen, Bente Klarlund; Kratchmarova, Irina

    2010-01-01

    During recent years, increased efforts have focused on elucidating the secretory function of skeletal muscle. Through secreted molecules, skeletal muscle affects local muscle biology in an auto/paracrine manner as well as having systemic effects on other tissues. Here we used a quantitative proteomics platform to investigate the factors secreted during the differentiation of murine C2C12 skeletal muscle cells. Using triple encoding stable isotope labeling by amino acids in cell culture, we compared the secretomes at three different time points of muscle differentiation and followed the dynamics of protein secretion. We identified and quantitatively analyzed 635 secreted proteins, including 35 growth factors, 40 cytokines, and 36 metallopeptidases. The extensive presence of these proteins that can act as potent signaling mediators to other cells and tissues strongly highlights the important role of the skeletal muscle as a prominent secretory organ. In addition to previously reported molecules, we identified many secreted proteins that have not previously been shown to be released from skeletal muscle cells nor shown to be differentially released during the process of myogenesis. We found 188 of these secreted proteins to be significantly regulated during the process of myogenesis. Comparative analyses of selected secreted proteins revealed little correlation between their mRNA and protein levels, indicating pronounced regulation by posttranscriptional mechanisms. Furthermore, analyses of the intracellular levels of members of the semaphorin family and their corresponding secretion dynamics demonstrated that the release of secreted proteins is tightly regulated by the secretory pathway, the stability of the protein, and/or the processing of secreted proteins. Finally, we provide 299 unique hydroxyproline sites mapping to 48 distinct secreted proteins and have discovered a novel hydroxyproline motif. PMID:20631206

  3. Redox Characterization of Functioning Skeletal Muscle

    PubMed Central

    Zuo, Li; Pannell, Benjamin K.

    2015-01-01

    Skeletal muscle physiology is influenced by the presence of chemically reactive molecules such as reactive oxygen species (ROS). These molecules regulate multiple redox-sensitive signaling pathways that play a critical role in cellular processes including gene expression and protein modification. While ROS have gained much attention for their harmful effects in muscle fatigue and dysfunction, research has also shown ROS to facilitate muscle adaptation after stressors such as physical exercise. This manuscript aims to provide a comprehensive review of the current understanding of redox signaling in skeletal muscle. ROS-induced oxidative stress and its role in the aging process are discussed. Mitochondria have been shown to generate large amounts of ROS during muscular contractions, and thus are susceptible to oxidative stress. ROS can modify proteins located in the mitochondrial membrane leading to cell death and osmotic swelling. ROS also contribute to the necrosis and inflammation of muscle fibers that is associated with muscular diseases including Duchenne muscular dystrophy. It is imperative that future research continues to investigate the exact role of ROS in normal skeletal muscle function as well as muscular dysfunction and disease. PMID:26635624

  4. Human skeletal muscle biochemical diversity.

    PubMed

    Tirrell, Timothy F; Cook, Mark S; Carr, J Austin; Lin, Evie; Ward, Samuel R; Lieber, Richard L

    2012-08-01

    The molecular components largely responsible for muscle attributes such as passive tension development (titin and collagen), active tension development (myosin heavy chain, MHC) and mechanosensitive signaling (titin) have been well studied in animals but less is known about their roles in humans. The purpose of this study was to perform a comprehensive analysis of titin, collagen and MHC isoform distributions in a large number of human muscles, to search for common themes and trends in the muscular organization of the human body. In this study, 599 biopsies were obtained from six human cadaveric donors (mean age 83 years). Three assays were performed on each biopsy - titin molecular mass determination, hydroxyproline content (a surrogate for collagen content) and MHC isoform distribution. Titin molecular mass was increased in more distal muscles of the upper and lower limbs. This trend was also observed for collagen. Percentage MHC-1 data followed a pattern similar to collagen in muscles of the upper extremity but this trend was reversed in the lower extremity. Titin molecular mass was the best predictor of anatomical region and muscle functional group. On average, human muscles had more slow myosin than other mammals. Also, larger titins were generally associated with faster muscles. These trends suggest that distal muscles should have higher passive tension than proximal ones, and that titin size variability may potentially act to 'tune' the protein's mechanotransduction capability. PMID:22786631

  5. Human skeletal muscle biochemical diversity

    PubMed Central

    Tirrell, Timothy F.; Cook, Mark S.; Carr, J. Austin; Lin, Evie; Ward, Samuel R.; Lieber, Richard L.

    2012-01-01

    SUMMARY The molecular components largely responsible for muscle attributes such as passive tension development (titin and collagen), active tension development (myosin heavy chain, MHC) and mechanosensitive signaling (titin) have been well studied in animals but less is known about their roles in humans. The purpose of this study was to perform a comprehensive analysis of titin, collagen and MHC isoform distributions in a large number of human muscles, to search for common themes and trends in the muscular organization of the human body. In this study, 599 biopsies were obtained from six human cadaveric donors (mean age 83 years). Three assays were performed on each biopsy – titin molecular mass determination, hydroxyproline content (a surrogate for collagen content) and MHC isoform distribution. Titin molecular mass was increased in more distal muscles of the upper and lower limbs. This trend was also observed for collagen. Percentage MHC-1 data followed a pattern similar to collagen in muscles of the upper extremity but this trend was reversed in the lower extremity. Titin molecular mass was the best predictor of anatomical region and muscle functional group. On average, human muscles had more slow myosin than other mammals. Also, larger titins were generally associated with faster muscles. These trends suggest that distal muscles should have higher passive tension than proximal ones, and that titin size variability may potentially act to ‘tune’ the protein's mechanotransduction capability. PMID:22786631

  6. Advances and challenges in skeletal muscle angiogenesis

    PubMed Central

    Baum, Oliver; Hellsten, Ylva; Egginton, Stuart

    2015-01-01

    The role of capillaries is to serve as the interface for delivery of oxygen and removal of metabolites to/from tissues. During the past decade there has been a proliferation of studies that have advanced our understanding of angiogenesis, demonstrating that tissue capillary supply is under strict control during health but poorly controlled in disease, resulting in either excessive capillary growth (pathological angiogenesis) or losses in capillarity (rarefaction). Given that skeletal muscle comprises nearly 40% of body mass in humans, skeletal muscle capillary density has a significant impact on metabolism, endocrine function, and locomotion and is tightly regulated at many different levels. Skeletal muscle is also high adaptable and thus one of the few organ systems that can be experimentally manipulated (e.g., by exercise) to study physiological regulation of angiogenesis. This review will focus on the methodological concerns that have arisen in determining skeletal muscle capillarity and highlight the concepts that are reshaping our understanding of the angio-adaptation process. We also summarize selected new findings (physical influences, molecular changes, and ultrastructural rearrangement of capillaries) that identify areas of future research with the greatest potential to expand our understanding of how angiogenesis is normally regulated, and that may also help to better understand conditions of uncontrolled (pathological) angiogenesis. PMID:26608338

  7. 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.

  8. Advances and challenges in skeletal muscle angiogenesis.

    PubMed

    Olfert, I Mark; Baum, Oliver; Hellsten, Ylva; Egginton, Stuart

    2016-02-01

    The role of capillaries is to serve as the interface for delivery of oxygen and removal of metabolites to/from tissues. During the past decade there has been a proliferation of studies that have advanced our understanding of angiogenesis, demonstrating that tissue capillary supply is under strict control during health but poorly controlled in disease, resulting in either excessive capillary growth (pathological angiogenesis) or losses in capillarity (rarefaction). Given that skeletal muscle comprises nearly 40% of body mass in humans, skeletal muscle capillary density has a significant impact on metabolism, endocrine function, and locomotion and is tightly regulated at many different levels. Skeletal muscle is also high adaptable and thus one of the few organ systems that can be experimentally manipulated (e.g., by exercise) to study physiological regulation of angiogenesis. This review will focus on the methodological concerns that have arisen in determining skeletal muscle capillarity and highlight the concepts that are reshaping our understanding of the angio-adaptation process. We also summarize selected new findings (physical influences, molecular changes, and ultrastructural rearrangement of capillaries) that identify areas of future research with the greatest potential to expand our understanding of how angiogenesis is normally regulated, and that may also help to better understand conditions of uncontrolled (pathological) angiogenesis. PMID:26608338

  9. Development of Sensory Receptors in Skeletal Muscle

    NASA Technical Reports Server (NTRS)

    DeSantis, Mark

    2000-01-01

    The two major goals for this project is to (1) examine the hindlimb walking pattern of offspring from the Flight dams as compared with offspring of the ground control groups from initiation of walking up to two months thereafter; and (2) examine skeletal muscle.

  10. Vitamin D Deficiency Promotes Skeletal Muscle Hypersensitivity and Sensory Hyperinnervation

    PubMed Central

    Tague, Sarah E.; Clarke, Gwenaëlle L.; Winter, Michelle K.; McCarson, Kenneth E.; Wright, Douglas E.; Smith, Peter G.

    2012-01-01

    Musculoskeletal pain affects nearly half of all adults, most of whom are vitamin D deficient. Previous findings demonstrated that putative nociceptors (“pain-sensing” nerves) express vitamin D receptors (VDRs), suggesting responsiveness to 1,25-dihydroxyvitamin D. In the present study, rats receiving vitamin D-deficient diets for 2– 4 weeks showed mechanical deep muscle hypersensitivity, but not cutaneous hypersensitivity. Muscle hypersensitivity was accompanied by balance deficits and occurred before onset of overt muscle or bone pathology. Hypersensitivity was not due to hypocalcemia and was actually accelerated by increased dietary calcium. Morphometry of skeletal muscle innervation showed increased numbers of presumptive nociceptor axons (peripherin-positive axons containing calcitonin gene-related peptide), without changes in sympathetic or skeletal muscle motor innervation. Similarly, there was no change in epidermal innervation. In culture, sensory neurons displayed enriched VDR expression in growth cones, and sprouting was regulated by VDR-mediated rapid response signaling pathways, while sympathetic outgrowth was not affected by different concentrations of 1,25-dihydroxyvitamin D. These findings indicate that vitamin D deficiency can lead to selective alterations in target innervation, resulting in presumptive nociceptor hyperinnervation of skeletal muscle, which in turn is likely to contribute to muscular hypersensitivity and pain. PMID:21957236

  11. Skeletal muscle adaptations and muscle genomics of performance horses.

    PubMed

    Rivero, José-Luis L; Hill, Emmeline W

    2016-03-01

    Skeletal muscles in horses are characterised by specific adaptations, which are the result of the natural evolution of the horse as a grazing animal, centuries of selective breeding and the adaptability of this tissue in response to training. These adaptations include an increased muscle mass relative to body weight, a great locomotor efficiency based upon an admirable muscle-tendon architectural design and an adaptable fibre-type composition with intrinsic shortening velocities greater than would be predicted from an animal of comparable body size. Furthermore, equine skeletal muscles have a high mitochondrial volume that permits a higher whole animal aerobic capacity, as well as large intramuscular stores of energy substrates (glycogen in particular). Finally, high buffer and lactate transport capacities preserve muscles against fatigue during anaerobic exercise. Many of these adaptations can improve with training. The publication of the equine genome sequence in 2009 has provided a major advance towards an improved understanding of equine muscle physiology. Equine muscle genomics studies have revealed a number of genes associated with elite physical performance and have also identified changes in structural and metabolic genes following exercise and training. Genes involved in muscle growth, muscle contraction and specific metabolic pathways have been found to be functionally relevant for the early performance evaluation of elite athletic horses. The candidate genes discussed in this review are important for a healthy individual to improve performance. However, muscle performance limiting conditions are widespread in horses and many of these conditions are also genetically influenced. PMID:26831154

  12. Cellular Players in Skeletal Muscle Regeneration

    PubMed Central

    Ceafalan, Laura Cristina; Popescu, Bogdan Ovidiu; Hinescu, Mihail Eugen

    2014-01-01

    Skeletal muscle, a tissue endowed with remarkable endogenous regeneration potential, is still under focused experimental investigation mainly due to treatment potential for muscle trauma and muscular dystrophies. Resident satellite cells with stem cell features were enthusiastically described quite a long time ago, but activation of these cells is not yet controlled by any medical interventions. However, after thorough reports of their existence, survival, activation, and differentiation there are still many questions to be answered regarding the intimate mechanism of tissue regeneration. This review delivers an up-to-date inventory of the main known key players in skeletal muscle repair, revealed by various models of tissue injuries in mechanical trauma, toxic lesions, and muscular dystrophy. A better understanding of the spatial and temporal relationships between various cell populations, with different physical or paracrine interactions and phenotype changes induced by local or systemic signalling, might lead to a more efficient approach for future therapies. PMID:24779022

  13. Pannexin 1 channels in skeletal muscles

    PubMed Central

    Cea, Luis A.; Riquelme, Manuel A.; Vargas, Anibal A.; Urrutia, Carolina; Sáez, Juan C.

    2014-01-01

    Normal myotubes and adult innervated skeletal myofibers express the glycoprotein pannexin1 (Panx1). Six of them form a “gap junction hemichannel-like” structure that connects the cytoplasm with the extracellular space; here they will be called Panx1 channels. These are poorly selective channels permeable to ions, small metabolic substrate, and signaling molecules. So far little is known about the role of Panx1 channels in muscles but skeletal muscles of Panx1−/− mice do not show an evident phenotype. Innervated adult fast and slow skeletal myofibers show Panx1 reactivity in close proximity to dihydropyridine receptors in the sarcolemma of T-tubules. These Panx1 channels are activated by electrical stimulation and extracellular ATP. Panx1 channels play a relevant role in potentiation of muscle contraction because they allow release of ATP and uptake of glucose, two molecules required for this response. In support of this notion, the absence of Panx1 abrogates the potentiation of muscle contraction elicited by repetitive electrical stimulation, which is reversed by exogenously applied ATP. Phosphorylation of Panx1 Thr and Ser residues might be involved in Panx1 channel activation since it is enhanced during potentiation of muscle contraction. Under denervation, Panx1 levels are upregulated and this partially explains the reduction in electrochemical gradient, however its absence does not prevent denervation-induced atrophy but prevents the higher oxidative state. Panx1 also forms functional channels at the cell surface of myotubes and their functional state has been associated with intracellular Ca2+ signals and regulation of myotube plasticity evoked by electrical stimulation. We proposed that Panx1 channels participate as ATP channels and help to keep a normal oxidative state in skeletal muscles. PMID:24782784

  14. Sexual dimorphism in skeletal muscle protein turnover.

    PubMed

    Smith, Gordon I; Mittendorfer, Bettina

    2016-03-15

    Skeletal muscle is the major constituent of lean body mass and essential for the body's locomotor function. Women have less muscle mass (and more body fat) than men and are therefore not able to exert the same absolute maximal force as men. The difference in body composition between the sexes is evident from infancy but becomes most marked after puberty (when boys experience an accelerated growth spurt) and persists into old age. During early adulthood until approximately the fourth decade of life, muscle mass is relatively stable, both in men and women, but then begins to decline, and the rate of loss is slower in women than in men. In this review we discuss the underlying mechanisms responsible for the age-associated sexual dimorphism in muscle mass (as far as they have been elucidated to date) and highlight areas that require more research to advance our understanding of the control of muscle mass throughout life. PMID:26702024

  15. Elevated nuclear Foxo1 suppresses excitability of skeletal muscle fibers.

    PubMed

    Hernández-Ochoa, Erick O; Schachter, Tova Neustadt; Schneider, Martin F

    2013-09-15

    Forkhead box O 1 (Foxo1) controls the expression of proteins that carry out processes leading to skeletal muscle atrophy, making Foxo1 of therapeutic interest in conditions of muscle wasting. The transcription of Foxo1-regulated proteins is dependent on the translocation of Foxo1 to the nucleus, which can be repressed by insulin-like growth factor-1 (IGF-1) treatment. The role of Foxo1 in muscle atrophy has been explored at length, but whether Foxo1 nuclear activity affects skeletal muscle excitation-contraction (EC) coupling has not yet been examined. Here, we use cultured adult mouse skeletal muscle fibers to investigate the effects of Foxo1 overexpression on EC coupling. Fibers expressing Foxo1-green fluorescent protein (GFP) exhibit an inability to contract, impaired propagation of action potentials, and ablation of calcium transients in response to electrical stimulation compared with fibers expressing GFP alone. Evaluation of the transverse (T)-tubule system morphology, the membranous system involved in the radial propagation of the action potential, revealed an intact T-tubule network in fibers overexpressing Foxo1-GFP. Interestingly, long-term IGF-1 treatment of Foxo1-GFP fibers, which maintains Foxo1-GFP outside the nucleus, prevented the loss of normal calcium transients, indicating that Foxo1 translocation and the atrogenes it regulates affect the expression of proteins involved in the generation and/or propagation of action potentials. A reduction in the sodium channel Nav1.4 expression in fibers overexpressing Foxo1-GFP was also observed in the absence of IGF-1. We conclude that increased nuclear activity of Foxo1 prevents the normal muscle responses to electrical stimulation and that this indicates a novel capability of Foxo1 to disable the functional activity of skeletal muscle. PMID:23804205

  16. Wave biomechanics of the skeletal muscle

    NASA Astrophysics Data System (ADS)

    Rudenko, O. V.; Sarvazyan, A. P.

    2006-12-01

    Results of acoustic measurements in skeletal muscle are generalized. It is shown that assessment of the pathologies and functional condition of the muscular system is possible with the use of shear waves. The velocity of these waves in muscles is much smaller than the velocity of sound; therefore, a higher symmetry type is formed for them. In the presence of a preferential direction (along muscle fibers), it is characterized by only two rather than five (as in usual media with the same anisotropy) moduli of elasticity. A covariant form of the corresponding wave equation is presented. It is shown that dissipation properties of skeletal muscles can be controlled by contracting them isometrically. Pulsed loads (shocks) and vibrations are damped differently, depending on their frequency spectrum. Characteristic frequencies on the order of tens and hundreds of hertz are attenuated due to actin-myosin bridges association/dissociation dynamics in the contracted muscle. At higher (kilohertz) frequencies, when the muscle is tensed, viscosity of the tissue increases by a factor of several tens because of the increase in friction experienced by fibrillar structures as they move relative to the surrounding liquid; the tension of the fibers changes the hydrodynamic conditions of the flow around them. Finally, at higher frequencies, the attenuation is associated with the rheological properties of biological molecules, in particular, with their conformational dynamics in the wave field. Models that describe the controlled shock dissipation mechanisms are proposed. Corresponding solutions are found, including those that allow for nonlinear effects.

  17. Generation of skeletal muscle from transplanted embryonic stem cells in dystrophic mice

    SciTech Connect

    Bhagavati, Satyakam . E-mail: satyakamb@hotmail.com; Xu Weimin

    2005-07-29

    Embryonic stem (ES) cells have great therapeutic potential because of their capacity to proliferate extensively and to form any fully differentiated cell of the body, including skeletal muscle cells. Successful generation of skeletal muscle in vivo, however, requires selective induction of the skeletal muscle lineage in cultures of ES cells and following transplantation, integration of appropriately differentiated skeletal muscle cells with recipient muscle. Duchenne muscular dystrophy (DMD), a severe progressive muscle wasting disease due to a mutation in the dystrophin gene and the mdx mouse, an animal model for DMD, are characterized by the absence of the muscle membrane associated protein, dystrophin. Here, we show that co-culturing mouse ES cells with a preparation from mouse muscle enriched for myogenic stem and precursor cells, followed by injection into mdx mice, results occasionally in the formation of normal, vascularized skeletal muscle derived from the transplanted ES cells. Study of this phenomenon should provide valuable insights into skeletal muscle development in vivo from transplanted ES cells.

  18. 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. PMID:26690801

  19. Skeletal Muscle Mitochondrial Energetic Efficiency and Aging

    PubMed Central

    Crescenzo, Raffaella; Bianco, Francesca; Mazzoli, Arianna; Giacco, Antonia; Liverini, Giovanna; Iossa, Susanna

    2015-01-01

    Aging is associated with a progressive loss of maximal cell functionality, and mitochondria are considered a key factor in aging process, since they determine the ATP availability in the cells. Mitochondrial performance during aging in skeletal muscle is reported to be either decreased or unchanged. This heterogeneity of results could partly be due to the method used to assess mitochondrial performance. In addition, in skeletal muscle the mitochondrial population is heterogeneous, composed of subsarcolemmal and intermyofibrillar mitochondria. Therefore, the purpose of the present review is to summarize the results obtained on the functionality of the above mitochondrial populations during aging, taking into account that the mitochondrial performance depends on organelle number, organelle activity, and energetic efficiency of the mitochondrial machinery in synthesizing ATP from the oxidation of fuels. PMID:25970752

  20. Tissue Engineered Strategies for Skeletal Muscle Injury

    PubMed Central

    Longo, Umile Giuseppe; Loppini, Mattia; Berton, Alessandra; Spiezia, Filippo; Maffulli, Nicola; Denaro, Vincenzo

    2012-01-01

    Skeletal muscle injuries are common in athletes, occurring with direct and indirect mechanisms and marked residual effects, such as severe long-term pain and physical disability. Current therapy consists of conservative management including RICE protocol (rest, ice, compression and elevation), nonsteroidal anti-inflammatory drugs, and intramuscular corticosteroids. However, current management of muscle injuries often does not provide optimal restoration to preinjury status. New biological therapies, such as injection of platelet-rich plasma and stem-cell-based therapy, are appealing. Although some studies support PRP application in muscle-injury management, reasons for concern persist, and further research is required for a standardized and safe use of PRP in clinical practice. The role of stem cells needs to be confirmed, as studies are still limited and inconsistent. Further research is needed to identify mechanisms involved in muscle regeneration and in survival, proliferation, and differentiation of stem cells. PMID:25098362

  1. Control of cell volume in skeletal muscle.

    PubMed

    Usher-Smith, Juliet A; Huang, Christopher L-H; Fraser, James A

    2009-02-01

    Regulation of cell volume is a fundamental property of all animal cells and is of particular importance in skeletal muscle where exercise is associated with a wide range of cellular changes that would be expected to influence cell volume. These complex electrical, metabolic and osmotic changes, however, make rigorous study of the consequences of individual factors on muscle volume difficult despite their likely importance during exercise. Recent charge-difference modelling of cell volume distinguishes three major aspects to processes underlying cell volume control: (i) determination by intracellular impermeant solute; (ii) maintenance by metabolically dependent processes directly balancing passive solute and water fluxes that would otherwise cause cell swelling under the influence of intracellular membrane-impermeant solutes; and (iii) volume regulation often involving reversible short-term transmembrane solute transport processes correcting cell volumes towards their normal baselines in response to imposed discrete perturbations. This review covers, in turn, the main predictions from such quantitative analysis and the experimental consequences of comparable alterations in extracellular pH, lactate concentration, membrane potential and extracellular tonicity. The effects of such alterations in the extracellular environment in resting amphibian muscles are then used to reproduce the intracellular changes that occur in each case in exercising muscle. The relative contributions of these various factors to the control of cell volume in resting and exercising skeletal muscle are thus described. PMID:19133959

  2. Development of Sensory Receptors in Skeletal Muscle

    NASA Technical Reports Server (NTRS)

    DeSantis, Mark

    2000-01-01

    There were two major goals for my project. One was to examine the hindlimb walking pattern of offspring from the Flight dams as compared with offspring of the ground control groups from initiation of walking up to two months thereafter. This initial goal was subsequently modified so that additional developmental measures were taken (e.g. body weight, eye opening) as the progeny developed, and the study period was lengthened to eighty days. Also videotapes taken shortly after the pregnant Flight dams returned to Earth were scored for locomotor activity and compared to those for the Synchronous control dams at the same stage of pregnancy. The second goal was to examine skeletal muscle. Selected hindlimb skeletal muscles were to be identified, weighed, and examined for the presence and integrity of muscle receptors, (both muscle spindles and tendon organs), at the level of the light and electron microscope. Muscles were examined from rats that were at fetal (G20), newborn (postnatal day 1 or P1, where P1 = day of birth), and young adult (approx. P100) stages. At the present time data from only the last group of rats (i.e. P100) has been completely examined.

  3. Effect of limb immobilization on skeletal muscle

    NASA Technical Reports Server (NTRS)

    Booth, F. W.

    1982-01-01

    Current knowledge and questions remaining concerning the effects of limb immobilization on skeletal muscle is reviewed. The most dramatic of these effects is muscle atrophy, which has been noted in cases of muscles fixed at or below their resting length. Immobilization is also accompanied by a substantial decrease in motoneuronal discharges, which results in the conversion of slow-twitch muscle to muscle with fast-twitch characteristics. Sarcolemma effects include no change or a decrease in resting membrane potential, the appearance of extrajunctional acetylcholine receptors, and no change in acetylcholinesterase activity. Evidence of changes in motoneuron after hyperpolarization characteristics suggests that the muscle inactivity is responsible for neuronal changes, rather than vice versa. The rate of protein loss from atrophying muscles is determined solely by the first-order rate constant for degradation. Various other biochemical and functional changes have been noted, including decreased insulin responsiveness and protein synthesis. The model of limb immobilization may also be useful for related studies of muscle adaptation.

  4. Regeneration of skeletal muscle fibers from autologous satellite cells multiplied in vitro. An experimental model for testing cultured cell myogenicity

    SciTech Connect

    Alameddine, H.S.; Dehaupas, M.; Fardeau, M. )

    1989-07-01

    An experimental model used to test in vivo myogenicity of autologous satellite cells multiplied in vitro is described. Free muscle autotransplantation served as the basis and was combined with x-irradiation. Administration of 1500, 2500, and 3500 rad doses 24 hours before or after ischemia showed that inhibition of spontaneous regeneration is dose dependent and more efficient when irradiation was applied before injury. A single dose of 2500 rad before injury resulted in the formation of a cystic structure ideal for cell implantation. FITC-latex beads and/or carbocyanine dyes were internalized by mononucleated satellite cells in vitro. Labeling did not affect survival or development of these cells. No sign of marker release or spreading from labeled to unlabeled cells was detectable unless by the fusion process. These labels were retained for several weeks. Grafting of labeled dense cellular suspensions into x-irradiated ischemic muscles indicated that satellite cells retain their myogenic characteristic and are able to reform fully differentiated muscle fibers. 55 references.

  5. Engineered skeletal muscle tissue networks with controllable architecture

    PubMed Central

    Bian, Weining; Bursac, Nenad

    2009-01-01

    The engineering of functional skeletal muscle tissue substitutes holds promise for the treatment of various muscular diseases and injuries. However, no tissue fabrication technology currently exists for the generation of a relatively large and thick bioartificial muscle made of densely packed, uniformly aligned, and differentiated myofibers. In this study, we describe a versatile cell/hydrogel micromolding approach where polydimethylsiloxane (PDMS) molds containing an array of elongated posts were used to fabricate relatively large neonatal rat skeletal muscle tissue networks with reproducible and controllable architecture. By combining cell-mediated fibrin gel compaction and precise microfabrication of mold dimensions including the length and height of the PDMS posts, we were able to simultaneously support high cell viability, guide cell alignment along the microfabricated tissue pores, and reproducibly control the overall tissue porosity, size, and thickness. The interconnected muscle bundles within the porous tissue networks were composed of densely packed, aligned, and highly differentiated myofibers. The formed myofibers expressed myogenin, developed abundant cross-striations, and generated spontaneous tissue contractions at the macroscopic spatial scale. The proliferation of non-muscle cells was significantly reduced compared to monolayer cultures. The more complex muscle tissue architectures were fabricated by controlling the spatial distribution and direction of the PDMS posts. PMID:19070360

  6. Trbp Is Required for Differentiation of Myoblasts and Normal Regeneration of Skeletal Muscle.

    PubMed

    Ding, Jian; Nie, Mao; Liu, Jianming; Hu, Xiaoyun; Ma, Lixin; Deng, Zhong-Liang; Wang, Da-Zhi

    2016-01-01

    Global inactivation of Trbp, a regulator of miRNA pathways, resulted in developmental defects and postnatal lethality in mice. Recently, we showed that cardiac-specific deletion of Trbp caused heart failure. However, its functional role(s) in skeletal muscle has not been characterized. Using a conditional knockout model, we generated mice lacking Trbp in the skeletal muscle. Unexpectedly, skeletal muscle specific Trbp mutant mice appear to be phenotypically normal under normal physiological conditions. However, these mice exhibited impaired muscle regeneration and increased fibrosis in response to cardiotoxin-induced muscle injury, suggesting that Trbp is required for muscle repair. Using cultured myoblast cells we further showed that inhibition of Trbp repressed myoblast differentiation in vitro. The impaired myogenesis is associated with reduced expression of muscle-specific miRNAs, miR-1a and miR-133a. Together, our study demonstrated that Trbp participates in the regulation of muscle differentiation and regeneration. PMID:27159388

  7. Trbp Is Required for Differentiation of Myoblasts and Normal Regeneration of Skeletal Muscle

    PubMed Central

    Ding, Jian; Nie, Mao; Liu, Jianming; Hu, Xiaoyun; Ma, Lixin; Deng, Zhong-Liang; Wang, Da-Zhi

    2016-01-01

    Global inactivation of Trbp, a regulator of miRNA pathways, resulted in developmental defects and postnatal lethality in mice. Recently, we showed that cardiac-specific deletion of Trbp caused heart failure. However, its functional role(s) in skeletal muscle has not been characterized. Using a conditional knockout model, we generated mice lacking Trbp in the skeletal muscle. Unexpectedly, skeletal muscle specific Trbp mutant mice appear to be phenotypically normal under normal physiological conditions. However, these mice exhibited impaired muscle regeneration and increased fibrosis in response to cardiotoxin-induced muscle injury, suggesting that Trbp is required for muscle repair. Using cultured myoblast cells we further showed that inhibition of Trbp repressed myoblast differentiation in vitro. The impaired myogenesis is associated with reduced expression of muscle-specific miRNAs, miR-1a and miR-133a. Together, our study demonstrated that Trbp participates in the regulation of muscle differentiation and regeneration. PMID:27159388

  8. Mineralocorticoid receptors are present in skeletal muscle and represent a potential therapeutic target.

    PubMed

    Chadwick, Jessica A; Hauck, J Spencer; Lowe, Jeovanna; Shaw, Jeremiah J; Guttridge, Denis C; Gomez-Sanchez, Celso E; Gomez-Sanchez, Elise P; Rafael-Fortney, Jill A

    2015-11-01

    Early treatment with heart failure drugs lisinopril and spironolactone improves skeletal muscle pathology in Duchenne muscular dystrophy (DMD) mouse models. The angiotensin converting enzyme inhibitor lisinopril and mineralocorticoid receptor (MR) antagonist spironolactone indirectly and directly target MR. The presence and function of MR in skeletal muscle have not been explored. MR mRNA and protein are present in all tested skeletal muscles from both wild-type mice and DMD mouse models. MR expression is cell autonomous in both undifferentiated myoblasts and differentiated myotubes from mouse and human skeletal muscle cultures. To test for MR function in skeletal muscle, global gene expression analysis was conducted on human myotubes treated with MR agonist (aldosterone; EC50 1.3 nM) or antagonist (spironolactone; IC50 1.6 nM), and 53 gene expression differences were identified. Five differences were conserved in quadriceps muscles from dystrophic mice treated with spironolactone plus lisinopril (IC50 0.1 nM) compared with untreated controls. Genes down-regulated more than 2-fold by MR antagonism included FOS, ANKRD1, and GADD45B, with known roles in skeletal muscle, in addition to NPR3 and SERPINA3, bona fide targets of MR in other tissues. MR is a novel drug target in skeletal muscle and use of clinically safe antagonists may be beneficial for muscle diseases. PMID:26178166

  9. Na,K-ATPase regulation in skeletal muscle.

    PubMed

    Pirkmajer, Sergej; Chibalin, Alexander V

    2016-07-01

    Skeletal muscle contains one of the largest and the most dynamic pools of Na,K-ATPase (NKA) in the body. Under resting conditions, NKA in skeletal muscle operates at only a fraction of maximal pumping capacity, but it can be markedly activated when demands for ion transport increase, such as during exercise or following food intake. Given the size, capacity, and dynamic range of the NKA pool in skeletal muscle, its tight regulation is essential to maintain whole body homeostasis as well as muscle function. To reconcile functional needs of systemic homeostasis with those of skeletal muscle, NKA is regulated in a coordinated manner by extrinsic stimuli, such as hormones and nerve-derived factors, as well as by local stimuli arising in skeletal muscle fibers, such as contractions and muscle energy status. These stimuli regulate NKA acutely by controlling its enzymatic activity and/or its distribution between the plasma membrane and the intracellular storage compartment. They also regulate NKA chronically by controlling NKA gene expression, thus determining total NKA content in skeletal muscle and its maximal pumping capacity. This review focuses on molecular mechanisms that underlie regulation of NKA in skeletal muscle by major extrinsic and local stimuli. Special emphasis is given to stimuli and mechanisms linking regulation of NKA and energy metabolism in skeletal muscle, such as insulin and the energy-sensing AMP-activated protein kinase. Finally, the recently uncovered roles for glutathionylation, nitric oxide, and extracellular K(+) in the regulation of NKA in skeletal muscle are highlighted. PMID:27166285

  10. GLUT-3 expression in human skeletal muscle

    NASA Technical Reports Server (NTRS)

    Stuart, C. A.; Wen, G.; Peng, B. H.; Popov, V. L.; Hudnall, S. D.; Campbell, G. A.

    2000-01-01

    Muscle biopsy homogenates contain GLUT-3 mRNA and protein. Before these studies, it was unclear where GLUT-3 was located in muscle tissue. In situ hybridization using a midmolecule probe demonstrated GLUT-3 within all muscle fibers. Fluorescent-tagged antibody reacting with affinity-purified antibody directed at the carboxy-terminus demonstrated GLUT-3 protein in all fibers. Slow-twitch muscle fibers, identified by NADH-tetrazolium reductase staining, possessed more GLUT-3 protein than fast-twitch fibers. Electron microscopy using affinity-purified primary antibody and gold particle-tagged second antibody showed that the majority of GLUT-3 was in association with triads and transverse tubules inside the fiber. Strong GLUT-3 signals were seen in association with the few nerves that traversed muscle sections. Electron microscopic evaluation of human peripheral nerve demonstrated GLUT-3 within the axon, with many of the particles related to mitochondria. GLUT-3 protein was found in myelin but not in Schwann cells. GLUT-1 protein was not present in nerve cells, axons, myelin, or Schwann cells but was seen at the surface of the peripheral nerve in the perineurium. These studies demonstrated that GLUT-3 mRNA and protein are expressed throughout normal human skeletal muscle, but the protein is predominantly found in the triads of slow-twitch muscle fibers.

  11. Phosphorylation of human skeletal muscle myosin

    SciTech Connect

    Houston, M.E.; Lingley, M.D.; Stuart, D.S.; Hoffman-Goetz, L.

    1986-03-01

    Phosphorylation of the P-light chains (phosphorylatable light chains) in human skeletal muscle myosin was studied in vitro and in vivo under resting an d contracted conditions. biopsy samples from rested vastus lateralis muscle of male and female subjects were incubated in oxygenated physiological solution at 30/sup 0/C. Samples frozen following a quiescent period showed the presence of only unphosphorylated P-light chains designated LC2f (light chain two of fast myosin) CL2s and LC2s'(light chains two of slow myosin). Treatment with caffeine (10 mM) or direct electrical stimulation resulted in the appearance of three additional bands which were identified as the phosphorylated forms of the P-light chains i.e. LC2f-P, LC2s-P and LC2s'-P. The presence of phosphate was confirmed by prior incubation with (/sup 30/P) orthophosphate. Muscle samples rapidly frozen from resting vastus lateralis muscle revealed the presence of unphosphorylated and phosphorylated P-light chains in approximately equal ratios. Muscle samples rapidly frozen following a maximal 10 second isometric contraction showed virtually only phosphorylated fast and slow P-light chains. These results reveal that the P-light chains in human fast and slow myosin may be rapidly phosphorylated, but the basal level of phosphorylation in rested human muscle considerably exceeds that observed in animal muscles studied in vitro or in situ.

  12. The sarcoglycan complex in skeletal muscle.

    PubMed

    Tarakci, Hakan; Berger, Joachim

    2016-01-01

    In skeletal muscle, the dystrophin-associated glycoprotein complex forms a link between the actin cytoskeleton and the extracellular matrix that is critical for muscle integrity. Within this complex resides the sarcoglycan subcomplex, which consists of four transmembrane glycoproteins (alpha-, beta-, gamma-, and delta-sarcoglycan). During assembly, beta-sarcoglycan tightly associates with delta-sarcoglycan to form a functional core that then recruits gamma- and alpha-sarcoglycan to form the sarcoglycan complex. Together with sarcospan, the sarcoglycan complex binds other components of the dystrophin-associated glycoprotein complex and integrates into the myofibre's membrane. Once integrated, the sarcoglycan complex plays a pivotal role in mechanically stabilising the sarcolemma as well as the dystrophin-associated glycoprotein complex. Additionally, the sarcoglycan complex undergoes chemical modifications in response to muscle contractions, thereby transducing mechanical information into a cellular signal. Mutations in the sarcoglycans induce limb girdle muscular dystrophy, and several animal models have been established to study the molecular biology and function of the sarcoglycan complex. This review discusses the role of the sarcoglycan complex in skeletal muscle and describes the functional deficiencies that lead to muscular dystrophies. PMID:26709803

  13. Immobilization depresses insulin signaling in skeletal muscle.

    PubMed

    Hirose, M; Kaneki, M; Sugita, H; Yasuhara, S; Martyn, J A

    2000-12-01

    Prolonged immobilization depresses insulin-induced glucose transport in skeletal muscle and leads to a catabolic state in the affected areas, with resultant muscle wasting. To elucidate the altered intracellular mechanisms involved in the insulin resistance, we examined insulin-stimulated tyrosine phosphorylation of the insulin receptor beta-subunit (IR-beta) and insulin receptor substrate (IRS)-1 and activation of its further downstream molecule, phosphatidylinositol 3-kinase (PI 3-K), after unilateral hindlimb immobilization in the rat. The contralateral hindlimb served as control. After 7 days of immobilization of the rat, insulin was injected into the portal vein, and tibialis anterior muscles on both sides were extracted. Immobilization reduced insulin-stimulated tyrosine phosphorylation of IR-beta and IRS-1. Insulin-stimulated binding of IRS-1 to p85, the regulatory subunit of PI 3-K, and IRS-1-associated PI 3-K activity were also decreased in the immobilized hindlimb. Although IR-beta and p85 protein levels were unchanged, IRS-1 protein expression was downregulated by immobilization. Thus prolonged immobilization may cause depression of insulin-stimulated glucose transport in skeletal muscle by altering insulin action at multiple points, including the tyrosine phosphorylation, protein expression, and activation of essential components of insulin signaling pathways. PMID:11093909

  14. 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

  15. Three-dimensional co-culture of C2C12/PC12 cells improves skeletal muscle tissue formation and function.

    PubMed

    Ostrovidov, Serge; Ahadian, Samad; Ramon-Azcon, Javier; Hosseini, Vahid; Fujie, Toshinori; Parthiban, S Prakash; Shiku, Hitoshi; Matsue, Tomokazu; Kaji, Hirokazu; Ramalingam, Murugan; Bae, Hojae; Khademhosseini, Ali

    2014-11-13

    Engineered muscle tissues demonstrate properties far from native muscle tissue. Therefore, fabrication of muscle tissues with enhanced functionalities is required to enable their use in various applications. To improve the formation of mature muscle tissues with higher functionalities, we co-cultured C2C12 myoblasts and PC12 neural cells. While alignment of the myoblasts was obtained by culturing the cells in micropatterned methacrylated gelatin (GelMA) hydrogels, we studied the effects of the neural cells (PC12) on the formation and maturation of muscle tissues. Myoblasts cultured in the presence of neural cells showed improved differentiation, with enhanced myotube formation. Myotube alignment, length and coverage area were increased. In addition, the mRNA expression of muscle differentiation markers (Myf-5, myogenin, Mefc2, MLP), muscle maturation markers (MHC-IId/x, MHC-IIa, MHC-IIb, MHC-pn, α-actinin, sarcomeric actinin) and the neuromuscular markers (AChE, AChR-ε) were also upregulated. All these observations were amplified after further muscle tissue maturation under electrical stimulation. Our data suggest a synergistic effect on the C2C12 differentiation induced by PC12 cells, which could be useful for creating improved muscle tissue. Copyright © 2014 John Wiley & Sons, Ltd. PMID:25393357

  16. 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. PMID:24879554

  17. Skeletal muscle gender dimorphism from proteomics.

    PubMed

    Dimova, Kalina; Metskas, Lauren Ann; Kulp, Mohini; Scordilis, Stylianos P

    2011-01-01

    Gross contraction in skeletal muscle is primarily determined by a relatively small number of contractile proteins, however this tissue is also remarkably adaptable to environmental factors such as hypertrophy by resistance exercise and atrophy by disuse. It thereby exhibits remodeling and adaptations to stressors (heat, ischemia, heavy metals, etc.). Damage can occur to muscle by a muscle exerting force while lengthening, the so-called eccentric contraction. The contractile proteins can be damaged in such exertions and need to be repaired, degraded and/or resynthesized; these functions are not part of the contractile proteins, but of other much less abundant proteins in the cell. To determine what subset of proteins is involved in the amelioration of this type of damage, a global proteome must be established prior to exercise and then followed subsequent to the exercise to determine the differential protein expression and thereby highlight candidate proteins in the adaptations to damage and its repair. Furthermore, most studies of skeletal muscle have been conducted on the male of the species and hence may not be representative of female muscle. In this article we present a method for extracting proteins reproducibly from male and female muscles, and separating them by two-dimensional gel electrophoresis followed by high resolution digital imaging. This provides a protocol for spots (and subsequently identified proteins) that show a statistically significant (p < 0.05) two-fold increase or decrease, appear or disappear from the control state. These are then excised, digested with trypsin and separated by high-pressure liquid chromatography coupled to a mass spectrometer (LC/MS) for protein identification (LC/MS/MS). This methodology (Figure 1) can be used on many tissues with little to no modification (liver, brain, heart etc.). PMID:22215112

  18. Primary sacrococcygeal chordoma with unusual skeletal muscle metastasis

    PubMed Central

    Vu, Lisa; Haygood, Tamara Miner

    2015-01-01

    Chordomas are rare neoplasms that do not often metastasize. Of the small percent that do metastasize, they very infrequently involve skeletal muscle. Only a few cases of skeletal muscle metastases have been reported in the literature. We report an unusual case of a patient with a primary sacrococcygeal chordoma who experienced a long period of remission but who subsequently developed recurrence and multiple metastatic lesions to skeletal muscles including the deltoid, triceps, and pectineus.

  19. Effects of regular exercise training on skeletal muscle contractile function

    NASA Technical Reports Server (NTRS)

    Fitts, Robert H.

    2003-01-01

    Skeletal muscle function is critical to movement and one's ability to perform daily tasks, such as eating and walking. One objective of this article is to review the contractile properties of fast and slow skeletal muscle and single fibers, with particular emphasis on the cellular events that control or rate limit the important mechanical properties. Another important goal of this article is to present the current understanding of how the contractile properties of limb skeletal muscle adapt to programs of regular exercise.

  20. REACTIVE OXYGEN SPECIES: IMPACT ON SKELETAL MUSCLE

    PubMed Central

    Powers, Scott K.; Ji, Li Li; Kavazis, Andreas N.; Jackson, Malcolm J.

    2014-01-01

    It is well established that contracting muscles produce both reactive oxygen and nitrogen species. Although the sources of oxidant production during exercise continue to be debated, growing evidence suggests that mitochondria are not the dominant source. Regardless of the sources of oxidants in contracting muscles, intense and prolonged exercise can result in oxidative damage to both proteins and lipids in the contracting myocytes. Further, oxidants regulate numerous cell signaling pathways and modulate the expression of many genes. This oxidant-mediated change in gene expression involves changes at transcriptional, mRNA stability, and signal transduction levels. Furthermore, numerous products associated with oxidant-modulated genes have been identified and include antioxidant enzymes, stress proteins, and mitochondrial electron transport proteins. Interestingly, low and physiological levels of reactive oxygen species are required for normal force production in skeletal muscle, but high levels of reactive oxygen species result in contractile dysfunction and fatigue. Ongoing research continues to explore the redox-sensitive targets in muscle that are responsible for both redox-regulation of muscle adaptation and oxidant-mediated muscle fatigue. PMID:23737208

  1. Circadian rhythms, the molecular clock, and skeletal muscle.

    PubMed

    Harfmann, Brianna D; Schroder, Elizabeth A; Esser, Karyn A

    2015-04-01

    Circadian rhythms are the approximate 24-h biological cycles that function to prepare an organism for daily environmental changes. They are driven by the molecular clock, a transcriptional:translational feedback mechanism that in mammals involves the core clock genes Bmal1, Clock, Per1/2, and Cry1/2. The molecular clock is present in virtually all cells of an organism. The central clock in the suprachiasmatic nucleus (SCN) has been well studied, but the clocks in the peripheral tissues, such as heart and skeletal muscle, have just begun to be investigated. Skeletal muscle is one of the largest organs in the body, comprising approximately 45% of total body mass. More than 2300 genes in skeletal muscle are expressed in a circadian pattern, and these genes participate in a wide range of functions, including myogenesis, transcription, and metabolism. The circadian rhythms of skeletal muscle can be entrained both indirectly through light input to the SCN and directly through time of feeding and activity. It is critical for the skeletal muscle molecular clock not only to be entrained to the environment but also to be in synchrony with rhythms of other tissues. When circadian rhythms are disrupted, the observed effects on skeletal muscle include fiber-type shifts, altered sarcomeric structure, reduced mitochondrial respiration, and impaired muscle function. Furthermore, there are detrimental effects on metabolic health, including impaired glucose tolerance and insulin sensitivity, which skeletal muscle likely contributes to considering it is a key metabolic tissue. These data indicate a critical role for skeletal muscle circadian rhythms for both muscle and systems health. Future research is needed to determine the mechanisms of molecular clock function in skeletal muscle, identify the means by which skeletal muscle entrainment occurs, and provide a stringent comparison of circadian gene expression across the diverse tissue system of skeletal muscle. PMID:25512305

  2. A Pilot Study of Ceramic Powder Far-Infrared Ray Irradiation (cFIR) on Physiology: Observation of Cell Cultures and Amphibian Skeletal Muscle.

    PubMed

    Leung, Ting-Kai; Lee, Chi-Ming; Tsai, Shih-Yin; Chen, Yi-Chien; Chao, Jo-Shui

    2011-08-31

    The purpose of this research was to assess the potential for far-infrared ray irradiation from ceramic powder to improve exercise performance at room temperature. We designed experiments with murine myoblast cells (C2C12) to study the effect of cFIR irradiation on cell viability and lactate dehydrogenase release under H2O2-mediated oxidative stress and evaluated intracellular levels of nitric oxide and calmodulin. We also used electro-stimulation of amphibian skeletal muscle. Our results show that cFIR strengthened C2C12 under oxidative stress and delayed onset of fatigue induced by muscle contractions. We discuss possible mechanisms including anti-oxidation and prevention of acid build-up in muscle tissue based, and expect to see more applications of cFIR in the future. PMID:22129823

  3. Looking Beyond Structure: Membrane Phospholipids of Skeletal Muscle Mitochondria.

    PubMed

    Heden, Timothy D; Neufer, P Darrell; Funai, Katsuhiko

    2016-08-01

    Skeletal muscle mitochondria are highly dynamic and are capable of tremendous expansion to meet cellular energetic demands. Such proliferation in mitochondrial mass requires a synchronized supply of enzymes and structural phospholipids. While transcriptional regulation of mitochondrial enzymes has been extensively studied, there is limited information on how mitochondrial membrane lipids are generated in skeletal muscle. Herein we describe how each class of phospholipids that constitute mitochondrial membranes are synthesized and/or imported, and summarize genetic evidence indicating that membrane phospholipid composition represents a significant modulator of skeletal muscle mitochondrial respiratory function. We also discuss how skeletal muscle mitochondrial phospholipids may mediate the effect of diet and exercise on oxidative metabolism. PMID:27370525

  4. Modeling of the Skeletal Muscle Microcirculation

    NASA Astrophysics Data System (ADS)

    Jacobitz, Frank; Beth, Christophe; Salado, Jerome

    2004-11-01

    Numerical simulations of blood flow in a microvascular network require extensive modeling. This contribution focuses on the reconstruction of a complete network topology from microscopic images of rat skeletal muscle and skeletal muscle fascia. The bifurcating network is composed of a feeding arterial network, a collecting venous network, and bundles of capillaries. Multiple topologies of each network component are recontructed and statistical properties of the network, such as distributions of vessel diameters, vessel lengths, and branching patters are determined. Particular attention has been paid to venous vessel loops that are observed only in the muscle fascia. The flow in the microvessel network is then computed. In the simulations, the microvessels are distensible by pressure, and the arterioles are actively contractile. The blood has non-Newtonian apparent viscosity. Models of each of these properties have previously been determined and are used in the computations. The method of indefinite admittances is used to compute the flow in the network. The apparent viscosity is computed from the local hematocrit, which is found using a combination of breadth first search and Dykstra's algorithms. The computations allow the determination of additional properties of the network, such as flow velocities, shear stresses, and hematocrit.

  5. Prolonged Culture of Aligned Skeletal Myotubes on Micromolded Gelatin Hydrogels

    PubMed Central

    Bettadapur, Archana; Suh, Gio C.; Geisse, Nicholas A.; Wang, Evelyn R.; Hua, Clara; Huber, Holly A.; Viscio, Alyssa A.; Kim, Joon Young; Strickland, Julie B.; McCain, Megan L.

    2016-01-01

    In vitro models of skeletal muscle are critically needed to elucidate disease mechanisms, identify therapeutic targets, and test drugs pre-clinically. However, culturing skeletal muscle has been challenging due to myotube delamination from synthetic culture substrates approximately one week after initiating differentiation from myoblasts. In this study, we successfully maintained aligned skeletal myotubes differentiated from C2C12 mouse skeletal myoblasts for three weeks by utilizing micromolded (μmolded) gelatin hydrogels as culture substrates, which we thoroughly characterized using atomic force microscopy (AFM). Compared to polydimethylsiloxane (PDMS) microcontact printed (μprinted) with fibronectin (FN), cell adhesion on gelatin hydrogel constructs was significantly higher one week and three weeks after initiating differentiation. Delamination from FN-μprinted PDMS precluded robust detection of myotubes. Compared to a softer blend of PDMS μprinted with FN, myogenic index, myotube width, and myotube length on μmolded gelatin hydrogels was similar one week after initiating differentiation. However, three weeks after initiating differentiation, these parameters were significantly higher on μmolded gelatin hydrogels compared to FN-μprinted soft PDMS constructs. Similar results were observed on isotropic versions of each substrate, suggesting that these findings are independent of substrate patterning. Our platform enables novel studies into skeletal muscle development and disease and chronic drug testing in vitro. PMID:27350122

  6. Prolonged Culture of Aligned Skeletal Myotubes on Micromolded Gelatin Hydrogels.

    PubMed

    Bettadapur, Archana; Suh, Gio C; Geisse, Nicholas A; Wang, Evelyn R; Hua, Clara; Huber, Holly A; Viscio, Alyssa A; Kim, Joon Young; Strickland, Julie B; McCain, Megan L

    2016-01-01

    In vitro models of skeletal muscle are critically needed to elucidate disease mechanisms, identify therapeutic targets, and test drugs pre-clinically. However, culturing skeletal muscle has been challenging due to myotube delamination from synthetic culture substrates approximately one week after initiating differentiation from myoblasts. In this study, we successfully maintained aligned skeletal myotubes differentiated from C2C12 mouse skeletal myoblasts for three weeks by utilizing micromolded (μmolded) gelatin hydrogels as culture substrates, which we thoroughly characterized using atomic force microscopy (AFM). Compared to polydimethylsiloxane (PDMS) microcontact printed (μprinted) with fibronectin (FN), cell adhesion on gelatin hydrogel constructs was significantly higher one week and three weeks after initiating differentiation. Delamination from FN-μprinted PDMS precluded robust detection of myotubes. Compared to a softer blend of PDMS μprinted with FN, myogenic index, myotube width, and myotube length on μmolded gelatin hydrogels was similar one week after initiating differentiation. However, three weeks after initiating differentiation, these parameters were significantly higher on μmolded gelatin hydrogels compared to FN-μprinted soft PDMS constructs. Similar results were observed on isotropic versions of each substrate, suggesting that these findings are independent of substrate patterning. Our platform enables novel studies into skeletal muscle development and disease and chronic drug testing in vitro. PMID:27350122

  7. Prolonged Culture of Aligned Skeletal Myotubes on Micromolded Gelatin Hydrogels

    NASA Astrophysics Data System (ADS)

    Bettadapur, Archana; Suh, Gio C.; Geisse, Nicholas A.; Wang, Evelyn R.; Hua, Clara; Huber, Holly A.; Viscio, Alyssa A.; Kim, Joon Young; Strickland, Julie B.; McCain, Megan L.

    2016-06-01

    In vitro models of skeletal muscle are critically needed to elucidate disease mechanisms, identify therapeutic targets, and test drugs pre-clinically. However, culturing skeletal muscle has been challenging due to myotube delamination from synthetic culture substrates approximately one week after initiating differentiation from myoblasts. In this study, we successfully maintained aligned skeletal myotubes differentiated from C2C12 mouse skeletal myoblasts for three weeks by utilizing micromolded (μmolded) gelatin hydrogels as culture substrates, which we thoroughly characterized using atomic force microscopy (AFM). Compared to polydimethylsiloxane (PDMS) microcontact printed (μprinted) with fibronectin (FN), cell adhesion on gelatin hydrogel constructs was significantly higher one week and three weeks after initiating differentiation. Delamination from FN-μprinted PDMS precluded robust detection of myotubes. Compared to a softer blend of PDMS μprinted with FN, myogenic index, myotube width, and myotube length on μmolded gelatin hydrogels was similar one week after initiating differentiation. However, three weeks after initiating differentiation, these parameters were significantly higher on μmolded gelatin hydrogels compared to FN-μprinted soft PDMS constructs. Similar results were observed on isotropic versions of each substrate, suggesting that these findings are independent of substrate patterning. Our platform enables novel studies into skeletal muscle development and disease and chronic drug testing in vitro.

  8. Effect of vitamin D on skeletal muscle.

    PubMed

    Walrand, Stéphane

    2016-06-01

    Beyond its traditional biological roles on bone health, extra-skeletal effects of vitamin D are currently under extensive research. The expression of the vitamin D receptor in most tissues has also strengthened the argument for its multiple functions. Among these, the effect of vitamin D on the mass and muscle performance has long been discussed. In ancient Greece, Herodotus recommended the sun as a cure for the "weak and soft muscles" and former Olympians exposed to sunlight to improve their physical performance. In 1952, Dr Spellerberg, a sports physiologist, has conducted an extensive study on the effects of UV irradiation on the performance of elite athletes. Following the significant results of this investigation, the scientist has informed the Olympic Committee that UV irradiation had a "persuasive" effect on physical performance and motor skills. These data are consistent with many subsequent studies reporting an improvement in physical activity, speed and endurance in young subjects treated with UV or with supplements containing vitamin D. Additional observation indicates a significant effect on muscle strength, particularly in the lower limbs. Concerning the mechanisms involved, some recent fundamental studies have shown that vitamin D exerts some molecular effects within the muscle cell. Specifically, a regulatory effect of vitamin D on calcium flux, mineral homeostasis and signaling pathways controlling protein anabolism has been reported in muscle tissue. Several epidemiological studies show that low vitamin D status is always associated with a decrease in muscle mass, strength and contractile capacity in older people. Vitamin D deficiency accelerates muscle loss with age (sarcopenia), and therefore leads to a reduction in physical capacity and to an increased risk of falls and fractures. In contrast, an additional intake of vitamin D in older people significantly improves muscle function and physical performance. PMID:27100224

  9. Molecular networks in skeletal muscle plasticity.

    PubMed

    Hoppeler, Hans

    2016-01-01

    The skeletal muscle phenotype is subject to considerable malleability depending on use as well as internal and external cues. In humans, low-load endurance-type exercise leads to qualitative changes of muscle tissue characterized by an increase in structures supporting oxygen delivery and consumption, such as capillaries and mitochondria. High-load strength-type exercise leads to growth of muscle fibers dominated by an increase in contractile proteins. In endurance exercise, stress-induced signaling leads to transcriptional upregulation of genes, with Ca(2+) signaling and the energy status of the muscle cells sensed through AMPK being major input determinants. Several interrelated signaling pathways converge on the transcriptional co-activator PGC-1α, perceived to be the coordinator of much of the transcriptional and post-transcriptional processes. Strength training is dominated by a translational upregulation controlled by mTORC1. mTORC1 is mainly regulated by an insulin- and/or growth-factor-dependent signaling cascade as well as mechanical and nutritional cues. Muscle growth is further supported by DNA recruitment through activation and incorporation of satellite cells. In addition, there are several negative regulators of muscle mass. We currently have a good descriptive understanding of the molecular mechanisms controlling the muscle phenotype. The topology of signaling networks seems highly conserved among species, with the signaling outcome being dependent on the particular way individual species make use of the options offered by the multi-nodal networks. As a consequence, muscle structural and functional modifications can be achieved by an almost unlimited combination of inputs and downstream signaling events. PMID:26792332

  10. Analysis of Aerobic Respiration in Intact Skeletal Muscle Tissue by Microplate-Based Respirometry.

    PubMed

    Shintaku, Jonathan; Guttridge, Denis C

    2016-01-01

    Mitochondrial function is a key component of skeletal muscle health, and its dysfunction has been associated with a wide variety of diseases. Microplate-based respirometry measures aerobic respiration of live cells through extracellular changes in oxygen concentration. Here, we describe a methodology to measure aerobic respiration of intact murine skeletal muscle tissue. The tissues are not cultured, permeabilized, or enzymatically dissociated to single fibers, so there is minimal experimental manipulation affecting the samples prior to acquiring measurements. PMID:27492183

  11. Osmoregulatory processes and skeletal muscle metabolism

    NASA Astrophysics Data System (ADS)

    Boschmann, Michael; Gottschalk, Simone; Adams, Frauke; Luft, Friedrich C.; Jordan, Jens

    Prolonged microgravity during space flight is associated with a decrease in blood and extracellular volume. These changes in water and electrolyte balance might activate catabolic processes which contribute finally to the loss of muscle and bone mass and strength. Recently, we found a prompt increase that energy expenditure by about 30% in both normal and overweight men and women after drinking 500 ml water. This effect is mediated by an increased sympathetic nervous system activity, obviously secondary to stimulation of osmosensitive afferent neurons in the liver, and skeletal muscle is possibly one effector organ. Therefore, we tested the hypothesis that this thermogenic response to water is accompanied by a stimulation of aerobic glucose metabolism in skeletal muscle. To this end, 16 young healthy volunteers (8 men) were studied. After an overnight fast (12h), a microdialysis probe was implanted into the right M. quadriceps femoris vastus lateralis and subsequently perfused with Ringer's solution (+50 mM ethanol). After 1h, volunteers were asked to drink 500 ml water (22° C) followed by continuing microdialysis for another 90 min. Dialysates (15 min fractions) were analyzed for [ethanol], [glucose], [lactate], [pyruvate], and [glycerol] in order to assess changes in muscle tissue perfusion (ethanol dilution technique), glycolysis and lipolysis. Blood samples were taken and heart rate (HR) and blood pressure (BP) were monitored. Neither HR and systolic and diastolic BP, nor plasma [glucose], [lactate], [insulin], and [C peptide] changed significantly after water drinking. Also, tissue perfusion and dialysate [glucose] did not change significantly. However, dialysate [lactate] increased by about 10 and 20% and dialysate [pyruvate] by about 100 and 200% in men and women, respectively. In contrast, dialysate [glycerol] decreased by about 30 and 20% in men and women, respectively. Therefore, drinking of 500 ml water stimulates aerobic glucose metabolism and inhibits

  12. Effect of Serum from Chickens Treated with Clenbuterol on Myosin Accumulation, Beta-Adrenergic Receptor Population, and Cyclic AM Synthesis in Embryonic Chicken Skeletal Muscle Cell Cultures

    NASA Technical Reports Server (NTRS)

    Young, R. B.; Bridge, K. Y.; Wuethrich, A. J.; Hancock, D. L.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    Broiler chickens at 35 days of age were fed 1 ppm clenbuterol for 14 days. This level of dietary clenbuterol led to 5-7% increases in weights of leg and breast muscle tissue. At the end of the 14-day period, serum was prepared from both control and clenbuterol-treated chickens and was then employed as a component of cell culture media at a final concentration of 20% (v/v). Muscle cell cultures were prepared from both the leg and breast muscle groups of twelve-day chick embryos. Treatment groups included control chicken serum to which 10 nM, 50 nM, and 1 micron clenbuterol had been added, as well as cells grown in media containing 10% horse serum. Cultures were subjected to each treatment for 3 days beginning on the seventh day in culture. Neither the percent fusion nor the number of nuclei in myotubes were significantly affected by any of the treatments. The quantity of MHC was not increased by serum from clenbuterol-treated chickens in either breast and leg muscle cultures; however, MHC quantity was 50- 100% higher in cultures grown in control chicken serum to which 10 nM and 50 nM clenbuterol had also been added. The Beta-AR population was 4,000-7,000 Beta-AR per cell in cultures grown in chicken serum, with leg muscle cultures having approximately 25-30% more receptors than breast muscle cultures. Receptor population was not significantly affected by the presence of clenbuterol or by the presence of serum from clenbuterol-treated chickens. In contrast, the Beta-AR population in leg and breast muscle cultures grown in the presence of 10% horse serum was 18,000-20,000 Beta-AR per cell. Basal concentration of cAMP was not significantly affected by any of the treatments. When cultures grown in chicken serum were stimulated for 10 min with 1 micron isoproterenol, limited increases of 12-20% in cAMP concentration above basal levels were observed. However, when cultures grown in the presence of horse serum were stimulated with 1 micron isoproterenol, increases of 600

  13. PGC-1α Induces Mitochondrial and Myokine Transcriptional Programs and Lipid Droplet and Glycogen Accumulation in Cultured Human Skeletal Muscle Cells

    PubMed Central

    Mormeneo, Emma; Jimenez-Mallebrera, Cecilia; Palomer, Xavier; De Nigris, Valeria; Vázquez-Carrera, Manuel; Orozco, Anna; Nascimento, Andrés; Colomer, Jaume; Lerín, Carles; Gómez-Foix, Anna M.

    2012-01-01

    The transcriptional coactivator peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PGC-1α) is a chief activator of mitochondrial and metabolic programs and protects against atrophy in skeletal muscle (skm). Here we tested whether PGC-1α overexpression could restructure the transcriptome and metabolism of primary cultured human skm cells, which display a phenotype that resembles the atrophic phenotype. An oligonucleotide microarray analysis was used to reveal the effects of PGC-1α on the whole transcriptome. Fifty-three different genes showed altered expression in response to PGC-1α: 42 upregulated and 11 downregulated. The main gene ontologies (GO) associated with the upregulated genes were mitochondrial components and processes and this was linked with an increase in COX activity, an indicator of mitochondrial content. Furthermore, PGC-1α enhanced mitochondrial oxidation of palmitate and lactate to CO2, but not glucose oxidation. The other most significantly associated GOs for the upregulated genes were chemotaxis and cytokine activity, and several cytokines, including IL-8/CXCL8, CXCL6, CCL5 and CCL8, were within the most highly induced genes. Indeed, PGC-1α highly increased IL-8 cell protein content. The most upregulated gene was PVALB, which is related to calcium signaling. Potential metabolic regulators of fatty acid and glucose storage were among mainly regulated genes. The mRNA and protein level of FITM1/FIT1, which enhances the formation of lipid droplets, was raised by PGC-1α, while in oleate-incubated cells PGC-1α increased the number of smaller lipid droplets and modestly triglyceride levels, compared to controls. CALM1, the calcium-modulated δ subunit of phosphorylase kinase, was downregulated by PGC-1α, while glycogen phosphorylase was inactivated and glycogen storage was increased by PGC-1α. In conclusion, of the metabolic transcriptome deficiencies of cultured skm cells, PGC-1α rescued the expression of genes encoding

  14. Fetal stem cells and skeletal muscle regeneration: a therapeutic approach.

    PubMed

    Pozzobon, Michela; Franzin, Chiara; Piccoli, Martina; De Coppi, Paolo

    2014-01-01

    More than 40% of the body mass is represented by muscle tissue, which possesses the innate ability to regenerate after damage through the activation of muscle-specific stem cells, namely satellite cells. Muscle diseases, in particular chronic degenerative states of skeletal muscle such as dystrophies, lead to a perturbation of the regenerative process, which causes the premature exhaustion of satellite cell reservoir due to continuous cycles of degeneration/regeneration. Nowadays, the research is focused on different therapeutic approaches, ranging from gene and cell to pharmacological therapy, but still there is no definitive cure in particular for genetic muscle disease. Keeping this in mind, in this article, we will give special consideration to muscle diseases and the use of fetal derived stem cells as a new approach for therapy. Cells of fetal origin, from cord blood to placenta and amniotic fluid, can be easily obtained without ethical concern, expanded and differentiated in culture, and possess immune-modulatory properties. The in vivo approach in animal models can be helpful to study the mechanism underneath the operating principle of the stem cell reservoir, namely the niche, which holds great potential to understand the onset of muscle pathologies. PMID:25221507

  15. Regulation of exercise-stimulated glucose uptake in skeletal muscle

    PubMed Central

    2016-01-01

    AMP-activated protein kinase (AMPK) is a Ser/Thr kinase that has been thought to be an important mediator for exercise-stimulated glucose uptake in skeletal muscle. Liver kinase B1 (LKB1) is an upstream kinase for AMPK and AMPK-related protein kinases, of which the function in skeletal muscle has not been well documented. Our group and others have generated mice lacking AMPK activity in skeletal muscle, as well as muscle-specific LKB1 knockout mice. In this review, we discuss the potential role of AMPK and LKB1 in regulating exercise-stimulated glucose uptake in skeletal muscle. We also discuss our recent study, demonstrating the molecular mechanism of obesity-induced development of skeletal muscle insulin resistance. PMID:27462580

  16. FOXO1 delays skeletal muscle regeneration and suppresses myoblast proliferation.

    PubMed

    Yamashita, Atsushi; Hatazawa, Yukino; Hirose, Yuma; Ono, Yusuke; Kamei, Yasutomi

    2016-08-01

    Unloading stress, such as bed rest, inhibits the regenerative potential of skeletal muscles; however, the underlying mechanisms remain largely unknown. FOXO1 expression, which induces the upregulated expression of the cell cycle inhibitors p57 and Gadd45α, is known to be increased in the skeletal muscle under unloading conditions. However, there is no report addressing FOXO1-induced inhibition of myoblast proliferation. Therefore, we induced muscle injury by cardiotoxin in transgenic mice overexpressing FOXO1 in the skeletal muscle (FOXO1-Tg mice) and observed regeneration delay in skeletal muscle mass and cross-sectional area in FOXO1-Tg mice. Increased p57 and Gadd45α mRNA levels, and decreased proliferation capacity were observed in C2C12 myoblasts expressing a tamoxifen-inducible active form of FOXO1. These results suggest that decreased proliferation capacity of myoblasts by FOXO1 disrupts skeletal muscle regeneration under FOXO1-increased conditions, such as unloading. PMID:27010781

  17. Skeletal muscle responses to unloading in humans

    NASA Technical Reports Server (NTRS)

    Dudley, G.; Tesch, P.; Hather, B.; Adams, G.; Buchanan, P.

    1992-01-01

    This study examined the effects of unloading on skeletal muscle structure. Method: Eight subjects walked on crutches for six weeks with a 110 cm elevated sole on the right shoe. This removed weight bearing by the left lower limb. Magnetic resonance imaging of both lower limbs and biopsies of the left m. vastus laterallis (VL) were used to study muscle structure. Results: Unloading decreased (P less than 0.05) muscle cross-sectional areas (CSA) of the knee extensors 16 percent. The knee flexors showed about 1/2 of this response (-7 percent, P less than 0.05). The three vasti muscles each showed decreases (P less than 0.05) of about 15 percent. M. rectus femoris did not change. Mean fiber CSA in VL decreased (P less than 0.05) 14 percent with type 2 and type 1 fibers showing reductions of 15 and 11 percent respectively. The ankle extensors showed a 20 percent decrease (P less than 0.05) in CSA. The reduction for the 'fast' m. gastrocnemius was 27 percent compared to the 18 percent decrease for the 'slow' soleus. Summary: The results suggest that decreases in muscle CSA are determined by the relative change in impact loading history because atrophy was (1) greater in extensor than flexor muscles, (2) at least as great in fast as compared to slow muscles or fibers, and (3) not dependent on single or multi-joint function. They also suggest that the atrophic responses to unloading reported for lower mammals are quantitatively but not qualitatively similar to those of humans.

  18. 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.

  19. Chemerin-induced mitochondrial dysfunction in skeletal muscle.

    PubMed

    Xie, Qihai; Deng, Yujie; Huang, Chenglin; Liu, Penghao; Yang, Ying; Shen, Weili; Gao, Pingjin

    2015-05-01

    Chemerin is a novel adipocyte-derived factor that induces insulin resistance in skeletal muscle. However, the effect of chemerin on skeletal muscle mitochondrial function has received little attention. In the present study, we investigated whether mitochondrial dysfunction is involved in the pathogenesis of chemerin-mediated insulin resistance. In this study, we used recombinant adenovirus to express murine chemerin in C57BL/6 mice. The mitochondrial function and structure were evaluated in isolated soleus muscles from mice. The oxidative mechanism of mitochondrial dysfunction in cultured C2C12 myotubes exposed to recombinant chemerin was analysed by western blotting, immunofluorescence and quantitative real-time polymerase chain reaction. The overexpression of chemerin in mice reduced the muscle mitochondrial content and increased mitochondrial autophagy, as determined by the increased conversion of LC3-I to LC3-II and higher expression levels of Beclin1 and autophagy-related protein-5 and 7. The chemerin treatment of C2C12 myotubes increased the generation of mitochondrial reactive oxygen species, concomitant with a reduced mitochondrial membrane potential and increased the occurrence of mitochondrial protein carbonyls and mitochondrial DNA deletions. Knockdown of the expression of chemokine-like receptor 1 or the use of mitochondria-targeting antioxidant Mito-TEMPO restored the mitochondrial dysfunction induced by chemerin. Furthermore, chemerin exposure in C2C12 myotubes not only reduced the insulin-stimulated phosphorylation of protein kinase B (AKT) but also dephosphorylated forkhead box O3α (FoxO3α). Chemerin-induced mitochondrial autophagy likely through an AKT-FoxO3α-dependent signalling pathway. These findings provide direct evidence that chemerin may play an important role in regulating mitochondrial remodelling and function in skeletal muscle. PMID:25754411

  20. A role of tensin in skeletal-muscle regeneration.

    PubMed Central

    Ishii, A; Lo, S H

    2001-01-01

    Regeneration of skeletal muscle requires the activation, proliferation, differentiation and fusion of satellite cells to generate new muscle fibres. This study was designed to determine the role of tensin in this process. Cardiotoxin was used to induce regeneration in the anterior tibial muscles of tensin-knockout and wild-type mice. From histological analysis, we found that the regeneration process lasted longer in knockout than in wild-type mice. To investigate the mechanism involved in this delay, we examined each regeneration step in animals and cultured primary cells. We found fewer proliferating myogenic cells identified by bromodeoxyuridine and desmin double labelling in knockout mice on the first 2 days after injury. Expression of myosin, paxillin, dystrophin and dystrophin-associated proteins were delayed in knockout mice. Withdrawal from the cell cycle was less efficient in isolated knockout myoblasts, and the fusion capacity was reduced in these cells as well. These defects in regeneration most likely contributed to the 9-fold increase of centrally nucleated fibres occurring in the non-injected knockout mice. Our results demonstrated clearly that tensin plays a role in skeletal-muscle regeneration. PMID:11389681

  1. Measurement of calcium release due to inositol trisphosphate receptors in skeletal muscle.

    PubMed

    Casas, Mariana; Altamirano, Francisco; Jaimovich, Enrique

    2012-01-01

    Calcium transients elicited by IP(3) receptors upon electrical stimulation of skeletal muscle cells (slow calcium signals) are often hard to visualize due to their relatively small amplitude compared to the large transient originated from ryanodine receptors associated to excitation-contraction coupling. The study of slow calcium transients, however, is relevant due to their function in regulation of muscle gene expression and in the process of excitation-transcription coupling. Discussed here are the procedures used to record slow calcium signals from both cultured mouse myotubes and from cultured adult skeletal muscle fibers. PMID:22130849

  2. MicroRNA transcriptome profiles during swine skeletal muscle development

    PubMed Central

    McDaneld, Tara G; Smith, Timothy PL; Doumit, Matthew E; Miles, Jeremy R; Coutinho, Luiz L; Sonstegard, Tad S; Matukumalli, Lakshmi K; Nonneman, Dan J; Wiedmann, Ralph T

    2009-01-01

    Background MicroRNA (miR) are a class of small RNAs that regulate gene expression by inhibiting translation of protein encoding transcripts. To evaluate the role of miR in skeletal muscle of swine, global microRNA abundance was measured at specific developmental stages including proliferating satellite cells, three stages of fetal growth, day-old neonate, and the adult. Results Twelve potential novel miR were detected that did not match previously reported sequences. In addition, a number of miR previously reported to be expressed in mammalian muscle were detected, having a variety of abundance patterns through muscle development. Muscle-specific miR-206 was nearly absent in proliferating satellite cells in culture, but was the highest abundant miR at other time points evaluated. In addition, miR-1 was moderately abundant throughout developmental stages with highest abundance in the adult. In contrast, miR-133 was moderately abundant in adult muscle and either not detectable or lowly abundant throughout fetal and neonate development. Changes in abundance of ubiquitously expressed miR were also observed. MiR-432 abundance was highest at the earliest stage of fetal development tested (60 day-old fetus) and decreased throughout development to the adult. Conversely, miR-24 and miR-27 exhibited greatest abundance in proliferating satellite cells and the adult, while abundance of miR-368, miR-376, and miR-423-5p was greatest in the neonate. Conclusion These data present a complete set of transcriptome profiles to evaluate miR abundance at specific stages of skeletal muscle growth in swine. Identification of these miR provides an initial group of miR that may play a vital role in muscle development and growth. PMID:19208255

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

    SciTech Connect

    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. - 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 through

  4. Myonase is localized in skeletal muscle myofibrils.

    PubMed

    Hori, Shinichiro; Yamada, Makoto; Ohtani, Sachiko; Hori, Chiyo; Yokomizo, Tadahiro; Webb, Timothy; Shimokawa, Teruhiko

    2002-09-01

    A novel chymotrypsin-like proteinase termed myonase was previously purified from MDX-mouse skeletal muscle [Hori et al. (1998) J. Biochem. 123, 650-658]. Western blots and immunohistochemical analyses showed that myonase was present within myocytes of both MDX-mouse and control mouse, and subcellular fractionation showed that it was associated with myofibrils. No significant difference was observed on Western blots between the amounts of myonase in myofibrils of MDX-mouse and control mouse, but the amount of myonase recoverable as a pure protein was 5-10-fold more when MDX-mouse was the source of the skeletal muscle. Myofibrils also possessed an endogenous inhibitor of myonase, whose inhibitory activity at physiological pH (pH 7.4) depended on salt concentration, stronger inhibition being observed at a low salt concentration. Inhibition at alkaline pH (pH 9) was weak and independent of salt concentration. Myonase in myofibrils was partially released at neutral pH by a high salt concentration (>0.6 M NaCl). However, even at 4 M NaCl, more than 80% of myonase remained within the myofibrils. Under alkaline conditions, release of myonase from myofibril was more extensive. At pH 12, myonase was almost completely present in the soluble fraction. Release of myonase under these conditions coincided with the solubilization of other myofibrillar proteins. PMID:12204111

  5. Satellite cell proliferation in adult skeletal muscle

    NASA Technical Reports Server (NTRS)

    Booth, Frank W. (Inventor); Thomason, Donald B. (Inventor); Morrison, Paul R. (Inventor); Stancel, George M. (Inventor)

    1995-01-01

    Novel methods of retroviral-mediated gene transfer for the in vivo corporation and stable expression of eukaryotic or prokaryotic foreign genes in tissues of living animals is described. More specifically, methods of incorporating foreign genes into mitotically active cells are disclosed. The constitutive and stable expression of E. coli .beta.-galactosidase gene under the promoter control of the Moloney murine leukemia virus long terminal repeat is employed as a particularly preferred embodiment, by way of example, establishes the model upon which the incorporation of a foreign gene into a mitotically-active living eukaryotic tissue is based. Use of the described methods in therapeutic treatments for genetic diseases, such as those muscular degenerative diseases, is also presented. In muscle tissue, the described processes result in genetically-altered satellite cells which proliferate daughter myoblasts which preferentially fuse to form a single undamaged muscle fiber replacing damaged muscle tissue in a treated animal. The retroviral vector, by way of example, includes a dystrophin gene construct for use in treating muscular dystrophy. The present invention also comprises an experimental model utilizable in the study of the physiological regulation of skeletal muscle gene expression in intact animals.

  6. Modelling skeletal muscle fibre orientation arrangement.

    PubMed

    Lu, Y T; Zhu, H X; Richmond, S; Middleton, J

    2011-12-01

    Skeletal muscle tissues have complex geometries. In addition, the complex fibre orientation arrangement makes it quite difficult to create an accurate finite element muscle model. There are many possible ways to specify the complex fibre orientations in a finite element model, for example defining a local element coordinate system. In this paper, an alternative method using ABAQUS, which is combination of the finite element method and the non-uniform rational B-spline solid representation, is proposed to calculate the initial fibre orientations. The initial direction of each muscle fibre is specified as the tangent direction of the NURBS curve which the fibre lies on, and the directions of the deformed fibres are calculated from the initial fibre directions, the deformation gradients and the fibre stretch ratios. Several examples are presented to demonstrate the ability of the proposed method. Results show that the proposed method is able to characterise both the muscle complex fibre orientation arrangement and its complex mechanical response. PMID:20924862

  7. Skeletal muscle stem cells from animals I. Basic cell biology

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Skeletal muscle stem cells from food-producing animals have been of interest to agricultural life scientists seeking to develop a better understanding of the molecular regulation of lean tissue (skeletal muscle protein hypertrophy) and intramuscular fat (marbling) development. Enhanced understanding...

  8. TWEAK promotes exercise intolerance by decreasing skeletal muscle oxidative phosphorylation capacity

    PubMed Central

    2013-01-01

    Background Proinflammatory cytokine tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) and its receptor Fn14 are the major regulators of skeletal muscle mass in many catabolic conditions. However, their role in muscle metabolism remains largely unknown. In the present study, we investigated the role of TWEAK on exercise capacity and skeletal muscle mitochondrial content and oxidative metabolism. Methods We employed wild-type and TWEAK-knockout (KO) mice and primary myotube cultures and performed biochemical, bioenergetics, and morphometric assays to evaluate the effects of TWEAK on exercise tolerance and muscle mitochondrial function and angiogenesis. Results TWEAK-KO mice showed improved exercise tolerance compared to wild-type mice. Electron microscopy analysis showed that the abundance of subsarcolemmal and intermyofibrillar mitochondria is significantly increased in skeletal muscle of TWEAK-KO mice compared to wild-type mice. Furthermore, age-related loss in skeletal muscle oxidative capacity was rescued in TWEAK-KO mice. Expression of a key transcriptional regulator peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) and several other molecules involved in oxidative metabolism were significantly higher in skeletal muscle of TWEAK-KO mice. Moreover, treatment of primary myotubes with soluble TWEAK inhibited the expression of PGC-1α and mitochondrial genes and decreased mitochondrial respiratory capacity. Deletion of TWEAK also improved angiogenesis and transcript levels of vascular endothelial growth factor in skeletal muscle of mice. Conclusions These results demonstrate that TWEAK decreases mitochondrial content and oxidative phosphorylation and inhibits angiogenesis in skeletal muscle. Neutralization of TWEAK is a potential approach for improving exercise capacity and oxidative metabolism in skeletal muscle. PMID:23835416

  9. Omega-3 Fatty Acids and Skeletal Muscle Health

    PubMed Central

    Jeromson, Stewart; Gallagher, Iain J.; Galloway, Stuart D. R.; Hamilton, D. Lee

    2015-01-01

    Skeletal muscle is a plastic tissue capable of adapting and mal-adapting to physical activity and diet. The response of skeletal muscle to adaptive stimuli, such as exercise, can be modified by the prior nutritional status of the muscle. The influence of nutrition on skeletal muscle has the potential to substantially impact physical function and whole body metabolism. Animal and cell based models show that omega-3 fatty acids, in particular those of marine origin, can influence skeletal muscle metabolism. Furthermore, recent human studies demonstrate that omega-3 fatty acids of marine origin can influence the exercise and nutritional response of skeletal muscle. These studies show that the prior omega-3 status influences not only the metabolic response of muscle to nutrition, but also the functional response to a period of exercise training. Omega-3 fatty acids of marine origin therefore have the potential to alter the trajectory of a number of human diseases including the physical decline associated with aging. We explore the potential molecular mechanisms by which omega-3 fatty acids may act in skeletal muscle, considering the n-3/n-6 ratio, inflammation and lipidomic remodelling as possible mechanisms of action. Finally, we suggest some avenues for further research to clarify how omega-3 fatty acids may be exerting their biological action in skeletal muscle. PMID:26610527

  10. Omega-3 Fatty Acids and Skeletal Muscle Health.

    PubMed

    Jeromson, Stewart; Gallagher, Iain J; Galloway, Stuart D R; Hamilton, D Lee

    2015-11-01

    Skeletal muscle is a plastic tissue capable of adapting and mal-adapting to physical activity and diet. The response of skeletal muscle to adaptive stimuli, such as exercise, can be modified by the prior nutritional status of the muscle. The influence of nutrition on skeletal muscle has the potential to substantially impact physical function and whole body metabolism. Animal and cell based models show that omega-3 fatty acids, in particular those of marine origin, can influence skeletal muscle metabolism. Furthermore, recent human studies demonstrate that omega-3 fatty acids of marine origin can influence the exercise and nutritional response of skeletal muscle. These studies show that the prior omega-3 status influences not only the metabolic response of muscle to nutrition, but also the functional response to a period of exercise training. Omega-3 fatty acids of marine origin therefore have the potential to alter the trajectory of a number of human diseases including the physical decline associated with aging. We explore the potential molecular mechanisms by which omega-3 fatty acids may act in skeletal muscle, considering the n-3/n-6 ratio, inflammation and lipidomic remodelling as possible mechanisms of action. Finally, we suggest some avenues for further research to clarify how omega-3 fatty acids may be exerting their biological action in skeletal muscle. PMID:26610527

  11. A Novel Glycerophosphodiester Phosphodiesterase, GDE5, Controls Skeletal Muscle Development via a Non-enzymatic Mechanism*

    PubMed Central

    Okazaki, Yuri; Ohshima, Noriyasu; Yoshizawa, Ikumi; Kamei, Yasutomi; Mariggiò, Stefania; Okamoto, Keiko; Maeda, Masahiro; Nogusa, Yoshihito; Fujioka, Yuichiro; Izumi, Takashi; Ogawa, Yoshihiro; Shiro, Yoshitsugu; Wada, Masanobu; Kato, Norihisa; Corda, Daniela; Yanaka, Noriyuki

    2010-01-01

    Mammalian glycerophosphodiester phosphodiesterases (GP-PDEs) have been identified recently and shown to be implicated in several physiological functions. This study isolated a novel GP-PDE, GDE5, and showed that GDE5 selectively hydrolyzes glycerophosphocholine (GroPCho) and controls skeletal muscle development. We show that GDE5 expression was reduced in atrophied skeletal muscles in mice and that decreasing GDE5 abundance promoted myoblastic differentiation, suggesting that decreased GDE5 expression has a counter-regulatory effect on the progression of skeletal muscle atrophy. Forced expression of full-length GDE5 in cultured myoblasts suppressed myogenic differentiation. Unexpectedly, a truncated GDE5 construct (GDE5ΔC471), which contained a GP-PDE sequence identified in other GP-PDEs but lacked GroPCho phosphodiesterase activity, showed a similar inhibitory effect. Furthermore, transgenic mice specifically expressing GDE5ΔC471 in skeletal muscle showed less skeletal muscle mass, especially type II fiber-rich muscle. These results indicate that GDE5 negatively regulates skeletal muscle development even without GroPCho phosphodiesterase activity, providing novel insight into the biological significance of mammalian GP-PDE function in a non-enzymatic mechanism. PMID:20576599

  12. Syndecans in skeletal muscle development, regeneration and homeostasis

    PubMed Central

    Pisconti, Addolorata; Bernet, Jennifer D.; Olwin, Bradley B.

    2012-01-01

    Summary Skeletal muscle is a highly dynamic tissue that can change in size in response to physiological demands and undergo successful regeneration even upon extensive injury. A population of resident stem cells, termed satellite cells, accounts for skeletal muscle plasticity, maintenance and regeneration. Mammalian satellite cells, generated from muscle precursor cells during development, are maintained quiescent in the musculature throughout a lifespan, but ready to activate, proliferate and differentiate into myocytes upon demand. Syndecans are transmembrane heparan sulfate proteoglycans expressed in muscle precursors during embryonic development and in satellite cells during postnatal life. In the last decades a number of crucial functions for syndecans in myogenesis and muscle disease have been described. Here we review the current knowledge of the multiple roles played by syndecans in the skeletal muscle of several animal models and explore future perspectives for human muscle health, with a focus on muscle aging and muscular dystrophy. PMID:23738267

  13. Inhibition of skeletal muscle development: less differentiation gives more muscle.

    PubMed

    Füchtbauer, Ernst-Martin

    2002-01-01

    The fact that stem cells have to be protected from premature differentiation is true for many organs in the developing embryo and the adult organism. However, there are several arguments that this is particularly important for (skeletal) muscle. There are some evolutionary arguments that muscle is a "default" pathway for mesodermal cells, which has to be actively prevented in order to allow cells to differentiate into other tissues. Myogenic cells originate from very small areas of the embryo where only a minor portion of these cells is supposed to differentiate. Differentiated muscle fibres are unconditionally post-mitotic, leaving undifferentiated stem cells as the only source of regeneration. The mechanical usage of muscle and its superficial location in the vertebrate body makes regeneration a frequently used mechanism. Looking at the different inhibitory mechanisms that have been found within the past 10 or so years, it appears as if evolution has taken this issue very serious. At all possible levels we find regulatory mechanisms that help to fine tune the differentiation of myogenic cells. Secreted molecules specifying different populations of somitic cells, diffusing or membrane-bound signals among fellow myoblasts, modulating molecules within the extracellular matrix and last, but not least, a changing set of activating and repressing cofactors. We have come a long way from the simple model of MyoD just to be turned on at the right time in the right cell. PMID:12132393

  14. Satellite Cell Heterogeneity in Skeletal Muscle Homeostasis.

    PubMed

    Tierney, Matthew T; Sacco, Alessandra

    2016-06-01

    The cellular turnover required for skeletal muscle maintenance and repair is mediated by resident stem cells, also termed satellite cells. Satellite cells normally reside in a quiescent state, intermittently entering the cell cycle to fuse with neighboring myofibers and replenish the stem cell pool. However, the mechanisms by which satellite cells maintain the precise balance between self-renewal and differentiation necessary for long-term homeostasis remain unclear. Recent work has supported a previously unappreciated heterogeneity in the satellite cell compartment that may underlie the observed variability in cell fate and function. In this review, we examine the work supporting this notion as well as the potential governing principles, developmental origins, and principal determinants of satellite cell heterogeneity. PMID:26948993

  15. Compartmentalized ATP synthesis in skeletal muscle triads.

    PubMed

    Han, J W; Thieleczek, R; Varsányi, M; Heilmeyer, L M

    1992-01-21

    Isolated skeletal muscle triads contain a compartmentalized glycolytic reaction sequence catalyzed by aldolase, triosephosphate isomerase, glyceraldehyde-3-phosphate dehydrogenase, and phosphoglycerate kinase. These enzymes express activity in the structure-associated state leading to synthesis of ATP in the triadic junction upon supply of glyceraldehyde 3-phosphate or fructose 1,6-bisphosphate. ATP formation occurs transiently and appears to be kinetically compartmentalized, i.e., the synthesized ATP is not in equilibrium with the bulk ATP. The apparent rate constants of the aldolase and the glyceraldehyde-3-phosphate dehydrogenase/phosphoglycerate kinase reaction are significantly increased when fructose 1,6-bisphosphate instead of glyceraldehyde 3-phosphate is employed as substrate. The observations suggest that fructose 1,6-bisphosphate is especially effectively channelled into the junctional gap. The amplitude of the ATP transient is decreasing with increasing free [Ca2+] in the range of 1 nM to 30 microM. In the presence of fluoride, the ATP transient is significantly enhanced and its declining phase is substantially retarded. This observation suggests utilization of endogenously synthesized ATP in part by structure associated protein kinases and phosphatases which is confirmed by the detection of phosphorylated triadic proteins after gel electrophoresis and autoradiography. Endogenous protein kinases phosphorylate proteins of apparent Mr 450,000, 180,000, 160,000, 145,000, 135,000, 90,000, 54,000, 51,000, and 20,000, respectively. Some of these phosphorylated polypeptides are in the Mr range of known phosphoproteins involved in excitation-contraction coupling of skeletal muscle, which might give a first hint at the functional importance of the sequential glycolytic reactions compartmentalized in triads. PMID:1731894

  16. Effect of Serum from Chickens Treated with Clenbuterol on Myosin Accumulation, Beta-Adrenergic Receptor Population, and Cyclic AMP Synthesis in Embryonic Chicken Skeletal Muscle Cell Cultures

    NASA Technical Reports Server (NTRS)

    Young, Ronald B.; Bridge, Kristin Y.; Wuethrich, Andrew J.; Hancock, Deana L.

    2002-01-01

    Broiler chickens at 35 d of age were fed 1 ppm clenbuterol for 14 d. This level of dietary clenbuterol led to 5-7% increases in the weights of leg and breast muscle tissue. At the end of the 14-d period, serum was prepared from both control and clenbuterol-treated chickens, and was then employed as a component of cell culture media at a final concentration of 20% (v/v). Muscle cell cultures were prepared from both the leg and the breast muscle groups of 12-d chick embryos. Treatment groups included control chicken serum to which 10 nM, 50 nM, and 1 uM clenbuterol had been added, as well as cells grown in media containing 10% horse serum. Cultures were subjected to each treatment for 3 d, beginning on the seventh d in culture. Neither the percent fusion nor the number of nuclei in myotubes was significantly affected by any of the treatments. The quantity of myosin heavy chains (MHCs) was not increased by serum from clenbuterol-treated chickens in either breast or leg muscle cultures; however, the MHC quantity was 50-150% higher in cultures grown in control chicken serum to which 10 and 50 nM clenbuterol had also been added. The B-adrenergic receptor (betaAR) population was 4000-7000 betaARs per cell in cultures grown in chicken serum with leg muscle cultures having approximately 25-30% more receptors than breast muscle Culture. Receptor population was not significantly affected by the presence of clenbuterol or by the presence of serum from clenbuterol-treated chickens. In contrast, the betaAR Population in leg and breast muscle cultures grown in the presence of 10% horse serum was 16,000-18,000 betaARs per cell. Basal concentration of cyclic adenosine 3':5'monophosphate (cAMP) was not significantly affected by the treatments. When cultures grown in chicken serum were stimulated for 10 min with 1 uM isoproterenol, limited increases of 12-20% in cAMP Concentration above the. basal levels were observed. However, when cultures grown in the presence of horse serum were

  17. Altered Skeletal Muscle Mitochondrial Proteome As the Basis of Disruption of Mitochondrial Function in Diabetic Mice.

    PubMed

    Zabielski, Piotr; Lanza, Ian R; Gopala, Srinivas; Heppelmann, Carrie J Holtz; Bergen, H Robert; Dasari, Surendra; Nair, K Sreekumaran

    2016-03-01

    Insulin plays pivotal role in cellular fuel metabolism in skeletal muscle. Despite being the primary site of energy metabolism, the underlying mechanism on how insulin deficiency deranges skeletal muscle mitochondrial physiology remains to be fully understood. Here we report an important link between altered skeletal muscle proteome homeostasis and mitochondrial physiology during insulin deficiency. Deprivation of insulin in streptozotocin-induced diabetic mice decreased mitochondrial ATP production, reduced coupling and phosphorylation efficiency, and increased oxidant emission in skeletal muscle. Proteomic survey revealed that the mitochondrial derangements during insulin deficiency were related to increased mitochondrial protein degradation and decreased protein synthesis, resulting in reduced abundance of proteins involved in mitochondrial respiration and β-oxidation. However, a paradoxical upregulation of proteins involved in cellular uptake of fatty acids triggered an accumulation of incomplete fatty acid oxidation products in skeletal muscle. These data implicate a mismatch of β-oxidation and fatty acid uptake as a mechanism leading to increased oxidative stress in diabetes. This notion was supported by elevated oxidative stress in cultured myotubes exposed to palmitate in the presence of a β-oxidation inhibitor. Together, these results indicate that insulin deficiency alters the balance of proteins involved in fatty acid transport and oxidation in skeletal muscle, leading to impaired mitochondrial function and increased oxidative stress. PMID:26718503

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

    PubMed

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

    2016-02-01

    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. PMID:26481306

  19. Arginylation of myosin heavy chain regulates skeletal muscle strength

    PubMed Central

    Cornachione, Anabelle S.; Leite, Felipe S.; Wang, Junling; Leu, Nicolae A.; Kalganov, Albert; Volgin, Denys; Han, Xuemei; Xu, Tao; Cheng, Yu-Shu; Yates, John R. R.; Rassier, Dilson E.; Kashina, Anna

    2014-01-01

    Protein arginylation is a post-translational modification with an emerging global role in the regulation of actin cytoskeleton. To test the role of arginylation in the skeletal muscle, we generated a mouse model with Ate1 knockout driven by skeletal muscle-specific creatine kinase (Ckmm) promoter. Such Ckmm-Ate1 mice were viable and outwardly normal, however their skeletal muscle strength was significantly reduced compared to the control. Mass spectrometry of the isolated skeletal myofibrils showed a limited set of proteins arginylated on specific sites, including myosin heavy chain. Atomic force microscopy measurements of the contractile strength in individual myofibrils and isolated myosin filaments from these mice showed a significant reduction of contractile forces, which, in the case of the myosin filaments could be fully rescued by re-arginylation with purified Ate1. Our results demonstrate that arginylation regulates force production in the muscle and exerts a direct effect on muscle strength through arginylation of myosin. PMID:25017061

  20. Circulating protein synthesis rates reveal skeletal muscle proteome dynamics.

    PubMed

    Shankaran, Mahalakshmi; King, Chelsea L; Angel, Thomas E; Holmes, William E; Li, Kelvin W; Colangelo, Marc; Price, John C; Turner, Scott M; Bell, Christopher; Hamilton, Karyn L; Miller, Benjamin F; Hellerstein, Marc K

    2016-01-01

    Here, we have described and validated a strategy for monitoring skeletal muscle protein synthesis rates in rodents and humans over days or weeks from blood samples. We based this approach on label incorporation into proteins that are synthesized specifically in skeletal muscle and escape into the circulation. Heavy water labeling combined with sensitive tandem mass spectrometric analysis allowed integrated synthesis rates of proteins in muscle tissue across the proteome to be measured over several weeks. Fractional synthesis rate (FSR) of plasma creatine kinase M-type (CK-M) and carbonic anhydrase 3 (CA-3) in the blood, more than 90% of which is derived from skeletal muscle, correlated closely with FSR of CK-M, CA-3, and other proteins of various ontologies in skeletal muscle tissue in both rodents and humans. Protein synthesis rates across the muscle proteome generally changed in a coordinate manner in response to a sprint interval exercise training regimen in humans and to denervation or clenbuterol treatment in rodents. FSR of plasma CK-M and CA-3 revealed changes and interindividual differences in muscle tissue proteome dynamics. In human subjects, sprint interval training primarily stimulated synthesis of structural and glycolytic proteins. Together, our results indicate that this approach provides a virtual biopsy, sensitively revealing individualized changes in proteome-wide synthesis rates in skeletal muscle without a muscle biopsy. Accordingly, this approach has potential applications for the diagnosis, management, and treatment of muscle disorders. PMID:26657858

  1. Circulating protein synthesis rates reveal skeletal muscle proteome dynamics

    PubMed Central

    Shankaran, Mahalakshmi; King, Chelsea L.; Angel, Thomas E.; Holmes, William E.; Li, Kelvin W.; Colangelo, Marc; Price, John C.; Turner, Scott M.; Bell, Christopher; Hamilton, Karyn L.; Miller, Benjamin F.; Hellerstein, Marc K.

    2015-01-01

    Here, we have described and validated a strategy for monitoring skeletal muscle protein synthesis rates in rodents and humans over days or weeks from blood samples. We based this approach on label incorporation into proteins that are synthesized specifically in skeletal muscle and escape into the circulation. Heavy water labeling combined with sensitive tandem mass spectrometric analysis allowed integrated synthesis rates of proteins in muscle tissue across the proteome to be measured over several weeks. Fractional synthesis rate (FSR) of plasma creatine kinase M-type (CK-M) and carbonic anhydrase 3 (CA-3) in the blood, more than 90% of which is derived from skeletal muscle, correlated closely with FSR of CK-M, CA-3, and other proteins of various ontologies in skeletal muscle tissue in both rodents and humans. Protein synthesis rates across the muscle proteome generally changed in a coordinate manner in response to a sprint interval exercise training regimen in humans and to denervation or clenbuterol treatment in rodents. FSR of plasma CK-M and CA-3 revealed changes and interindividual differences in muscle tissue proteome dynamics. In human subjects, sprint interval training primarily stimulated synthesis of structural and glycolytic proteins. Together, our results indicate that this approach provides a virtual biopsy, sensitively revealing individualized changes in proteome-wide synthesis rates in skeletal muscle without a muscle biopsy. Accordingly, this approach has potential applications for the diagnosis, management, and treatment of muscle disorders. PMID:26657858

  2. Human skeletal muscle xenograft as a new preclinical model for muscle disorders.

    PubMed

    Zhang, Yuanfan; King, Oliver D; Rahimov, Fedik; Jones, Takako I; Ward, Christopher W; Kerr, Jaclyn P; Liu, Naili; Emerson, Charles P; Kunkel, Louis M; Partridge, Terence A; Wagner, Kathryn R

    2014-06-15

    Development of novel therapeutics requires good animal models of disease. Disorders for which good animal models do not exist have very few drugs in development or clinical trial. Even where there are accepted, albeit imperfect models, the leap from promising preclinical drug results to positive clinical trials commonly fails, including in disorders of skeletal muscle. The main alternative model for early drug development, tissue culture, lacks both the architecture and, usually, the metabolic fidelity of the normal tissue in vivo. Herein, we demonstrate the feasibility and validity of human to mouse xenografts as a preclinical model of myopathy. Human skeletal muscle biopsies transplanted into the anterior tibial compartment of the hindlimbs of NOD-Rag1(null) IL2rγ(null) immunodeficient host mice regenerate new vascularized and innervated myofibers from human myogenic precursor cells. The grafts exhibit contractile and calcium release behavior, characteristic of functional muscle tissue. The validity of the human graft as a model of facioscapulohumeral muscular dystrophy is demonstrated in disease biomarker studies, showing that gene expression profiles of xenografts mirror those of the fresh donor biopsies. These findings illustrate the value of a new experimental model of muscle disease, the human muscle xenograft in mice, as a feasible and valid preclinical tool to better investigate the pathogenesis of human genetic myopathies and to more accurately predict their response to novel therapeutics. PMID:24452336

  3. Postnatal ontogeny of skeletal muscle protein synthesis in pigs

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The neonatal period is characterized by rapid growth and elevated rates of synthesis and accretion of skeletal muscle proteins. The fractional rate of muscle protein synthesis is very high at birth and declines rapidly with age. The elevated capacity for muscle protein synthesis in the neonatal pig ...

  4. Molecular events in skeletal muscle during disuse atrophy

    NASA Technical Reports Server (NTRS)

    Kandarian, Susan C.; Stevenson, Eric J.

    2002-01-01

    This review summarizes the current knowledge of the molecular processes underlying skeletal muscle atrophy due to disuse. Because the processes involved with muscle wasting due to illness are similar to disuse, this literature is used for comparison. Areas that are ripe for further study and that will advance our understanding of muscle atrophy are suggested.

  5. Glucose transporter expression in human skeletal muscle fibers.

    PubMed

    Gaster, M; Handberg, A; Beck-Nielsen, H; Schroder, H D

    2000-09-01

    The present study was initiated to investigate GLUT-1 through -5 expression in developing and mature human skeletal muscle. To bypass the problems inherent in techniques using tissue homogenates, we applied an immunocytochemical approach, employing the sensitive enhanced tyramide signal amplification (TSA) technique to detect the localization of glucose transporter expression in human skeletal muscle. We found expression of GLUT-1, GLUT-3, and GLUT-4 in developing human muscle fibers showing a distinct expression pattern. 1) GLUT-1 is expressed in human skeletal muscle cells during gestation, but its expression is markedly reduced around birth and is further reduced to undetectable levels within the first year of life; 2) GLUT-3 protein expression appears at 18 wk of gestation and disappears after birth; and 3) GLUT-4 protein is diffusely expressed in muscle cells throughout gestation, whereas after birth, the characteristic subcellular localization is as seen in adult muscle fibers. Our results show that GLUT-1, GLUT-3, and GLUT-4 seem to be of importance during muscle fiber growth and development. GLUT-5 protein was undetectable in fetal and adult skeletal muscle fibers. In adult muscle fibers, only GLUT-4 was expressed at significant levels. GLUT-1 immunoreactivity was below the detection limit in muscle fibers, indicating that this glucose transporter is of minor importance for muscle glucose supply. Thus we hypothesize that GLUT-4 also mediates basal glucose transport in muscle fibers, possibly through constant exposure to tonal contraction and basal insulin levels. PMID:10950819

  6. Postnatal ontogeny of skeletal muscle protein synthesis in pigs

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The neonatal period is characterized by rapid growth and elevated rates of synthesis and accretion of skeletal muscle proteins. The fractional rate of muscle protein synthesis is very high at birth and declines rapidly with development. The elevated capacity for muscle protein synthesis in the neo...

  7. A second MNGIE patient without typical mitochondrial skeletal muscle involvement.

    PubMed

    Cardaioli, Elena; Da Pozzo, Paola; Malfatti, Edoardo; Battisti, Carla; Gallus, Gian Nicola; Gaudiano, Carmen; Macucci, Marco; Malandrini, Alessandro; Margollicci, Maria; Rubegni, Anna; Dotti, Maria Teresa; Federico, Antonio

    2010-08-01

    Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is an autosomal recessive disease caused by mutations in the gene encoding thymidine phosphorylase (TYMP). Clinically, MNGIE is characterized by gastrointestinal dysmotility, cachexia, ptosis, ophthalmoparesis, peripheral neuropathy and leukoencephalopathy. Most MNGIE patients have signs of mitochondrial dysfunction in skeletal muscle at morphological and enzyme level, as well as mitochondrial DNA depletion, multiple deletions and point mutations. A case without mitochondrial skeletal muscle involvement and with a TYMP splice-acceptor site mutation (c. 215-1 G>C) has been reported. Here, we describe an Italian patient with the same mutation and without mitochondrial skeletal muscle involvement, suggesting a possible genotype-phenotype correlation. PMID:20232099

  8. Coordination of metabolic plasticity in skeletal muscle.

    PubMed

    Hood, David A; Irrcher, Isabella; Ljubicic, Vladimir; Joseph, Anna-Maria

    2006-06-01

    Skeletal muscle is a highly malleable tissue, capable of pronounced metabolic and morphological adaptations in response to contractile activity (i.e. exercise). Each bout of contractile activity results in a coordinated alteration in the expression of a variety of nuclear DNA and mitochondrial DNA (mtDNA) gene products, leading to phenotypic adaptations. This results in an increase in muscle mitochondrial volume and changes in organelle composition, referred to as mitochondrial biogenesis. The functional consequence of this biogenesis is an improved resistance to fatigue. Signals initiated by the exercise bout involve changes in intracellular Ca2+ as well as alterations in energy status (i.e. ATP/ADP ratio) and the consequent activation of downstream kinases such as AMP kinase and Ca2+-calmodulin-activated kinases. These kinases activate transcription factors that bind DNA to affect the transcription of genes, the most evident manifestation of which occurs during the post-exercise recovery period when energy metabolism is directed toward anabolism, rather than contractile activity. An important protein that is affected by exercise is the transcriptional coactivator PGC-1alpha, which cooperates with multiple transcription factors to induce the expression of nuclear genes encoding mitochondrial proteins. Once translated in the cytosol, these mitochondrially destined proteins are imported into the mitochondrial outer membrane, inner membrane or matrix space via specific import machinery transport components. Contractile activity affects the expression of the import machinery, as well as the kinetics of import, thus facilitating the entry of newly synthesized proteins into the expanding organelle. An important set of proteins that are imported are the mtDNA transcription factors, which influence the expression and replication of mtDNA. While mtDNA contributes only 13 proteins to the synthesis of the organelle, these proteins are vital for the proper assembly of multi

  9. Training-induced apoptosis in skeletal muscle.

    PubMed

    Boffi, F M; Cittar, J; Balskus, G; Muriel, M; Desmaras, E

    2002-09-01

    Apoptosis or programmed cell death is a genetically controlled response of cells to commit suicide and is associated with DNA fragmentation or laddering. The common inducers of apoptosis include Ca2+i and oxygen free radicals/oxidative stress, which are also implicated in the pathogenesis of exercise-induced myopathies. To examine training-induced apoptosis, Thoroughbred horses were subjected to 3 months training programme on a treadmill. At the end of the training programme venous blood samples were taken for a creatine kinase (CK) assay. In addition, muscle biopsy samples were obtained for a membrane lipid peroxidation measurement by malondialdehyde (MDA) assay and for apoptosis detection. Apoptosis was studied by visualising the apoptotic myocytes on the paraffin sections by the modified TUNEL method. DNA laddering was evaluated by subjecting the DNA obtained from the biopsies to 1.5% agarose gel electrophoresis. There was a significant increase (P<0.05) of protein-bound MDA, and a nonsignificant trend (P = 0.14) for the control group to have higher levels of CK compared to the trained group. Under light microscopy, percentage of the TUNEL positive cells was higher (P<0.001) in the training group. This result was corroborated with the findings of DNA fragmentation by gel electrophoresis, which showed higher ladders of DNA band at the same group. In conclusion, these results clearly demonstrate that there is training-induced apoptosis in skeletal muscle. It is probable that apoptosis allows the work/recovery/rebound/supercompensation cycle, when unaccustomed muscle cells activate programmed cell death and are replaced by new and stronger cells, which is the mechanism for training-induced increases in fitness. PMID:12405700

  10. Skeletal Muscle Phospholipid Metabolism Regulates Insulin Sensitivity and Contractile Function.

    PubMed

    Funai, Katsuhiko; Lodhi, Irfan J; Spears, Larry D; Yin, Li; Song, Haowei; Klein, Samuel; Semenkovich, Clay F

    2016-02-01

    Skeletal muscle insulin resistance is an early defect in the development of type 2 diabetes. Lipid overload induces insulin resistance in muscle and alters the composition of the sarcoplasmic reticulum (SR). To test the hypothesis that skeletal muscle phospholipid metabolism regulates systemic glucose metabolism, we perturbed choline/ethanolamine phosphotransferase 1 (CEPT1), the terminal enzyme in the Kennedy pathway of phospholipid synthesis. In C2C12 cells, CEPT1 knockdown altered SR phospholipid composition and calcium flux. In mice, diet-induced obesity, which decreases insulin sensitivity, increased muscle CEPT1 expression. In high-fat diet-fed mice with skeletal muscle-specific knockout of CEPT1, systemic and muscle-based approaches demonstrated increased muscle insulin sensitivity. In CEPT1-deficient muscles, an altered SR phospholipid milieu decreased sarco/endoplasmic reticulum Ca(2+) ATPase-dependent calcium uptake, activating calcium-signaling pathways known to improve insulin sensitivity. Altered muscle SR calcium handling also rendered these mice exercise intolerant. In obese humans, surgery-induced weight loss increased insulin sensitivity and decreased skeletal muscle CEPT1 protein. In obese humans spanning a spectrum of metabolic health, muscle CEPT1 mRNA was inversely correlated with insulin sensitivity. These results suggest that high-fat feeding and obesity induce CEPT1, which remodels the SR to preserve contractile function at the expense of insulin sensitivity. PMID:26512026

  11. Regulation of Skeletal Muscle by microRNAs.

    PubMed

    Diniz, Gabriela Placoná; Wang, Da-Zhi

    2016-01-01

    MicroRNAs (miRNAs) are a class of small noncoding RNAs highly conserved across species. miRNAs regulate gene expression posttranscriptionally by base pairing to complementary sequences mainly in the 3'-untranslated region of their target mRNAs to induce mRNA cleavage and translational repression. Thousands of miRNAs have been identified in human and their function has been linked to the regulation of both physiological and pathological processes. The skeletal muscle is the largest human organ responsible for locomotion, posture, and body metabolism. Several conditions such as aging, immobilization, exercise, and diet are associated with alterations in skeletal muscle structure and function. The genetic and molecular pathways that regulate muscle development, function, and regeneration as well as muscular disease have been well established in past decades. In recent years, numerous studies have underlined the importance of miRNAs in the control of skeletal muscle development and function, through its effects on several biological pathways critical for skeletal muscle homeostasis. Furthermore, it has become clear that alteration of the expression of many miRNAs or genetic mutations of miRNA genes is associated with changes on myogenesis and on progression of several skeletal muscle diseases. The present review provides an overview of the current studies and recent progress in elucidating the complex role exerted by miRNAs on skeletal muscle physiology and pathology. © 2016 American Physiological Society. Compr Physiol 6:1279-1294, 2016. PMID:27347893

  12. The extracellular compartments of frog skeletal muscle.

    PubMed Central

    Neville, M C; Mathias, R T

    1979-01-01

    1. Detailed studies of solute efflux from frog sartorius muscle and single muscle fibres were carried out in order to characterize a 'special region' (Harris, 1963) in the extracellular space of muscle and determine whether this 'special region' is the sarcoplasmic reticulum. 2. The efflux of radioactive Na, Cl, glusose, 3-O-methylglucose, xylose, glycine, leucine, cycloleucine, Rb, K, inulin (mol. wt. 5000) and dextran (mol. wt. 17,000) from previously loaded muscles was studied. In all cases except dextran the curve had three components, a rapid (A) component which could be equated with efflux from the extracellular space proper, a slow (C) component representing cellular solute and an intermediate (B) component. The distribution space for the B component was 8% of muscle volume in summer frogs and 12% in winter frogs and appeared to be equal for all compounds studied. We tested the hypothesis that the B component originated from the sarcoplasmic reticulum. 3. The C component was missing from the dextran curves. Both dextran and inulin entered the compartment of origin of the B component (compartment B) to the same extent as small molecules. 4. For all compounds studies, the efflux rate constant for the A component could be predicted from the diffusion coefficient. For the B component the efflux rate constant was 6--10 times slower than that for the A component but was still proportional to the diffusion coefficient for the solute in question. 5. When Na and sucrose efflux from single fibres was followed, a B component was usually observed. The average distribution space for this component was small, averaging 1.5% of fibre volume. There was no difference between the average efflux rate constants for Na and sucrose. 6. In an appendix, the constraints placed on the properties of a hypothetical channel between the sarcoplasmic reticulum and the T-system by the linear electrical parameters of frog skeletal muscle are derived. It is shown that the conductance of such

  13. Establishment and cryopreservation of a giant panda skeletal muscle-derived cell line.

    PubMed

    Yu, Fang-Jian; Zeng, Chang-Jun; Zhang, Yan; Wang, Cheng-Dong; Xiong, Tie-Yi; Fang, Sheng-Guo; Zhang, He-Min

    2015-06-01

    The giant panda Ailuropoda melanoleuca is an endangered species and is a symbol for wildlife conservation. Although efforts have been made to protect this rare and endangered species through breeding and conservative biology, the long-term preservation of giant panda genome resources (gametes, tissues, organs, genomic libraries, etc.) is still a practical option. In this study, the giant panda skeletal muscle-derived cell line was successfully established via primary explants culture and cryopreservation techniques. The population doubling time of giant panda skeletal cells was approximately 33.8 h, and this population maintained a high cell viability before and after cryopreservation (95.6% and 90.7%, respectively). The two skeletal muscle-specific genes SMYD1 and MYF6 were expressed and detected by RT-PCR in the giant panda skeletal muscle-derived cell line. Karyotyping analysis revealed that the frequencies of giant panda skeletal muscle cells showing a chromosome number of 2n=42 ranged from 90.6∼94.2%. Thus, the giant panda skeletal muscle-derived cell line provides a vital resource and material platform for further studies and is likely to be useful for the protection of this rare and endangered species. PMID:26035009

  14. Structure and Function of the Skeletal Muscle Extracellular Matrix

    PubMed Central

    Gillies, Allison R.; Lieber, Richard L.

    2011-01-01

    The skeletal muscle extracellular matrix (ECM) plays an important role in muscle fiber force transmission, maintenance, and repair. In both injured and diseased states, ECM adapts dramatically, a property thathas clinical manifestations and alters muscle function. Here, we review the structure, composition, and mechanical properties of skeletal muscle ECM, describe the cells that contribute to the maintenance of the ECM and, finally, overview changes that occur with pathology. New scanning electron micrographs of ECM structure are also presented with hypotheses about ECM structure-function relationships. Detailed structure-function relationships of the ECM have yet to be defined and, as a result, we propose areas for future studies. PMID:21949456

  15. The effects of obesity on skeletal muscle regeneration

    PubMed Central

    Akhmedov, Dmitry; Berdeaux, Rebecca

    2013-01-01

    Obesity and metabolic disorders such as type 2 diabetes mellitus are accompanied by increased lipid deposition in adipose and non-adipose tissues including liver, pancreas, heart and skeletal muscle. Recent publications report impaired regenerative capacity of skeletal muscle following injury in obese mice. Although muscle regeneration has not been thoroughly studied in obese and type 2 diabetic humans and mechanisms leading to decreased muscle regeneration in obesity remain elusive, the initial findings point to the possibility that muscle satellite cell function is compromised under conditions of lipid overload. Elevated toxic lipid metabolites and increased pro-inflammatory cytokines as well as insulin and leptin resistance that occur in obese animals may contribute to decreased regenerative capacity of skeletal muscle. In addition, obesity-associated alterations in the metabolic state of skeletal muscle fibers and satellite cells may directly impair the potential for satellite cell-mediated repair. Here we discuss recent studies that expand our understanding of how obesity negatively impacts skeletal muscle maintenance and regeneration. PMID:24381559

  16. Effect of extraluminal ATP application on vascular tone and blood flow in skeletal muscle: implications for exercise hyperemia

    PubMed Central

    Al-Khazraji, Baraa K.; Mortensen, Stefan P.; Jackson, Dwayne N.; Ellis, Christopher G.; Hellsten, Ylva

    2013-01-01

    During skeletal muscle contractions, the concentration of ATP increases in muscle interstitial fluid as measured by microdialysis probes. This increase is associated with the magnitude of blood flow, suggesting that interstitial ATP may be important for contraction-induced vasodilation. However, interstitial ATP has solely been described to induce vasoconstriction in skeletal muscle. To examine whether interstitial ATP induces vasodilation in skeletal muscle and to what extent this vasoactive effect is mediated by formation of nitric oxide (NO) and prostanoids, three different experimental models were studied. The rat gluteus maximus skeletal muscle model was used to study changes in local skeletal muscle hemodynamics. Superfused ATP at concentrations found during muscle contractions (1–10 μM) increased blood flow by up to 400%. In this model, the underlying mechanism was also examined by inhibition of NO and prostanoid formation. Inhibition of these systems abolished the vasodilator effect of ATP. Cell-culture experiments verified ATP-induced formation of NO and prostacyclin in rat skeletal muscle microvascular endothelial cells, and ATP-induced formation of NO in rat skeletal muscle cells. To confirm these findings in humans, ATP was infused into skeletal muscle interstitium of healthy subjects via microdialysis probes and found to increase muscle interstitial concentrations of NO and prostacyclin by ∼60% and ∼40%, respectively. Collectively, these data suggest that a physiologically relevant elevation in interstitial ATP concentrations increases muscle blood flow, indicating that the contraction-induced increase in skeletal muscle interstitial [ATP] is important for exercise hyperemia. The vasodilator effect of ATP application is mediated by NO and prostanoid formation. PMID:23761642

  17. Renal function alterations during skeletal muscle disuse in simulated microgravity

    NASA Technical Reports Server (NTRS)

    Tucker, Bryan J.

    1992-01-01

    This project was to examine the alterations in renal functions during skeletal muscle disuse in simulated microgravity. Although this area could cover a wide range of investigative efforts, the limited funding resulted in the selection of two projects. These projects would result in data contributing to an area of research deemed high priority by NASA and would address issues of the alterations in renal response to vasoactive stimuli during conditions of skeletal muscle disuse as well as investigate the contribution of skeletal muscle disuse, conditions normally found in long term human exposure to microgravity, to the balance of fluid and macromolecules within the vasculature versus the interstitium. These two projects selected are as follows: investigate the role of angiotensin 2 on renal function during periods of simulated microgravity and skeletal muscle disuse to determine if the renal response is altered to changes in circulating concentrations of angiotensin 2 compared to appropriate controls; and determine if the shift of fluid balance from vasculature to the interstitium, the two components of extracellular fluid volume, that occur during prolonged exposure to microgravity and skeletal muscle disuse is a result, in part, to alterations in the fluid and macromolecular balance in the peripheral capillary beds, of which the skeletal muscle contains the majority of recruitment capillaries. A recruitment capillary bed would be most sensitive to alterations in Starling forces and fluid and macromolecular permeability.

  18. Systems analysis of biological networks in skeletal muscle function

    PubMed Central

    Smith, Lucas R.; Meyer, Gretchen; Lieber, Richard L.

    2014-01-01

    Skeletal muscle function depends on the efficient coordination among subcellular systems. These systems are composed of proteins encoded by a subset of genes, all of which are tightly regulated. In the cases where regulation is altered because of disease or injury, dysfunction occurs. To enable objective analysis of muscle gene expression profiles, we have defined nine biological networks whose coordination is critical to muscle function. We begin by describing the expression of proteins necessary for optimal neuromuscular junction function that results in the muscle cell action potential. That action potential is transmitted to proteins involved in excitation–contraction coupling enabling Ca2+ release. Ca2+ then activates contractile proteins supporting actin and myosin cross-bridge cycling. Force generated by cross-bridges is transmitted via cytoskeletal proteins through the sarcolemma and out to critical proteins that support the muscle extracellular matrix. Muscle contraction is fueled through many proteins that regulate energy metabolism. Inflammation is a common response to injury that can result in alteration of many pathways within muscle. Muscle also has multiple pathways that regulate size through atrophy or hypertrophy. Finally, the isoforms associated with fast muscle fibers and their corresponding isoforms in slow muscle fibers are delineated. These nine networks represent important biological systems that affect skeletal muscle function. Combining high-throughput systems analysis with advanced networking software will allow researchers to use these networks to objectively study skeletal muscle systems. PMID:23188744

  19. Systems analysis of biological networks in skeletal muscle function.

    PubMed

    Smith, Lucas R; Meyer, Gretchen; Lieber, Richard L

    2013-01-01

    Skeletal muscle function depends on the efficient coordination among subcellular systems. These systems are composed of proteins encoded by a subset of genes, all of which are tightly regulated. In the cases where regulation is altered because of disease or injury, dysfunction occurs. To enable objective analysis of muscle gene expression profiles, we have defined nine biological networks whose coordination is critical to muscle function. We begin by describing the expression of proteins necessary for optimal neuromuscular junction function that results in the muscle cell action potential. That action potential is transmitted to proteins involved in excitation-contraction coupling enabling Ca(2+) release. Ca(2+) then activates contractile proteins supporting actin and myosin cross-bridge cycling. Force generated by cross-bridges is transmitted via cytoskeletal proteins through the sarcolemma and out to critical proteins that support the muscle extracellular matrix. Muscle contraction is fueled through many proteins that regulate energy metabolism. Inflammation is a common response to injury that can result in alteration of many pathways within muscle. Muscle also has multiple pathways that regulate size through atrophy or hypertrophy. Finally, the isoforms associated with fast muscle fibers and their corresponding isoforms in slow muscle fibers are delineated. These nine networks represent important biological systems that affect skeletal muscle function. Combining high-throughput systems analysis with advanced networking software will allow researchers to use these networks to objectively study skeletal muscle systems. PMID:23188744

  20. 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

  1. Extracellular formation and uptake of adenosine during skeletal muscle contraction in the rat: role of adenosine transporters.

    PubMed

    Lynge, J; Juel, C; Hellsten, Y

    2001-12-01

    1. The existence of adenosine transporters in plasma membrane giant vesicles from rat skeletal muscles and in primary skeletal muscle cell cultures was investigated. In addition, the contribution of intracellularly or extracellularly formed adenosine to the overall extracellular adenosine concentration during muscle contraction was determined in primary skeletal muscle cell cultures. 2. In plasma membrane giant vesicles, the carrier-mediated adenosine transport demonstrated saturation kinetics with Km = 177 +/- 36 microM and Vmax = 1.9 +/- 0.2 nmol x ml(-1) x s(-1) (0.7 nmol (mg protein)(-1) x s(-1)). The existence of an adenosine transporter was further evidenced by the inhibition of the carrier-mediated adenosine transport in the presence of NBMPR (nitrobenzylthioinosine; 72% inhibition) or dipyridamol (64% inhibition; P < 0.05). 3. In primary skeletal muscle cells, the rate of extracellular adenosine accumulation was 5-fold greater (P < 0.05) with electrical stimulation than without electrical stimulation. Addition of the adenosine transporter inhibitor NBMPR led to a 57% larger (P < 0.05) rate of extracellular adenosine accumulation in the electro-stimulated muscle cells compared with control cells, demonstrating that adenosine is taken up by the skeletal muscle cells during contractions. 4. Inhibition of ecto-5'-nucleotidase with AOPCP in electro-stimulated cells resulted in a 70% lower (P < 0.05) rate of extracellular adenosine accumulation compared with control cells, indicating that adenosine to a large extent is formed in the extracellular space during contraction. 5. The present study provides evidence for the existence of an NBMPR-sensitive adenosine transporter in rat skeletal muscle. Our data furthermore demonstrate that the increase in extracellular adenosine observed during electro-stimulation of skeletal muscle is due to production of adenosine in the extracellular space of skeletal muscle and that adenosine is taken up rather than released by the

  2. Fetal skeletal muscle progenitors have regenerative capacity after intramuscular engraftment in dystrophin deficient mice.

    PubMed

    Sakai, Hiroshi; Sato, Takahiko; Sakurai, Hidetoshi; Yamamoto, Takuya; Hanaoka, Kazunori; Montarras, Didier; Sehara-Fujisawa, Atsuko

    2013-01-01

    Muscle satellite cells (SCs) are stem cells that reside in skeletal muscles and contribute to regeneration upon muscle injury. SCs arise from skeletal muscle progenitors expressing transcription factors Pax3 and/or Pax7 during embryogenesis in mice. However, it is unclear whether these fetal progenitors possess regenerative ability when transplanted in adult muscle. Here we address this question by investigating whether fetal skeletal muscle progenitors (FMPs) isolated from Pax3(GFP/+) embryos have the capacity to regenerate muscle after engraftment into Dystrophin-deficient mice, a model of Duchenne muscular dystrophy. The capacity of FMPs to engraft and enter the myogenic program in regenerating muscle was compared with that of SCs derived from adult Pax3(GFP/+) mice. Transplanted FMPs contributed to the reconstitution of damaged myofibers in Dystrophin-deficient mice. However, despite FMPs and SCs having similar myogenic ability in culture, the regenerative ability of FMPs was less than that of SCs in vivo. FMPs that had activated MyoD engrafted more efficiently to regenerate myofibers than MyoD-negative FMPs. Transcriptome and surface marker analyses of these cells suggest the importance of myogenic priming for the efficient myogenic engraftment. Our findings suggest the regenerative capability of FMPs in the context of muscle repair and cell therapy for degenerative muscle disease. PMID:23671652

  3. Fetal Skeletal Muscle Progenitors Have Regenerative Capacity after Intramuscular Engraftment in Dystrophin Deficient Mice

    PubMed Central

    Sakai, Hiroshi; Sato, Takahiko; Sakurai, Hidetoshi; Yamamoto, Takuya; Hanaoka, Kazunori; Montarras, Didier; Sehara-Fujisawa, Atsuko

    2013-01-01

    Muscle satellite cells (SCs) are stem cells that reside in skeletal muscles and contribute to regeneration upon muscle injury. SCs arise from skeletal muscle progenitors expressing transcription factors Pax3 and/or Pax7 during embryogenesis in mice. However, it is unclear whether these fetal progenitors possess regenerative ability when transplanted in adult muscle. Here we address this question by investigating whether fetal skeletal muscle progenitors (FMPs) isolated from Pax3GFP/+ embryos have the capacity to regenerate muscle after engraftment into Dystrophin-deficient mice, a model of Duchenne muscular dystrophy. The capacity of FMPs to engraft and enter the myogenic program in regenerating muscle was compared with that of SCs derived from adult Pax3GFP/+ mice. Transplanted FMPs contributed to the reconstitution of damaged myofibers in Dystrophin-deficient mice. However, despite FMPs and SCs having similar myogenic ability in culture, the regenerative ability of FMPs was less than that of SCs in vivo. FMPs that had activated MyoD engrafted more efficiently to regenerate myofibers than MyoD-negative FMPs. Transcriptome and surface marker analyses of these cells suggest the importance of myogenic priming for the efficient myogenic engraftment. Our findings suggest the regenerative capability of FMPs in the context of muscle repair and cell therapy for degenerative muscle disease. PMID:23671652

  4. More than a bystander: the contributions of intrinsic skeletal muscle defects in motor neuron diseases

    PubMed Central

    Boyer, Justin G.; Ferrier, Andrew; Kothary, Rashmi

    2013-01-01

    Spinal muscular atrophy (SMA), amyotrophic lateral sclerosis (ALS), and spinal-bulbar muscular atrophy (SBMA) are devastating diseases characterized by the degeneration of motor neurons. Although the molecular causes underlying these diseases differ, recent findings have highlighted the contribution of intrinsic skeletal muscle defects in motor neuron diseases. The use of cell culture and animal models has led to the important finding that muscle defects occur prior to and independently of motor neuron degeneration in motor neuron diseases. In SMA for instance, the muscle specific requirements of the SMA disease-causing gene have been demonstrated by a series of genetic rescue experiments in SMA models. Conditional ALS mouse models expressing a muscle specific mutant SOD1 gene develop atrophy and muscle degeneration in the absence of motor neuron pathology. Treating SBMA mice by over-expressing IGF-1 in a skeletal muscle-specific manner attenuates disease severity and improves motor neuron pathology. In the present review, we provide an in depth description of muscle intrinsic defects, and discuss how they impact muscle function in these diseases. Furthermore, we discuss muscle-specific therapeutic strategies used to treat animal models of SMA, ALS, and SBMA. The study of intrinsic skeletal muscle defects is crucial for the understanding of the pathophysiology of these diseases and will open new therapeutic options for the treatment of motor neuron diseases. PMID:24391590

  5. Macrophage Plasticity in Skeletal Muscle Repair

    PubMed Central

    Rigamonti, Elena; Sciorati, Clara; Rovere-Querini, Patrizia

    2014-01-01

    Macrophages are one of the first barriers of host defence against pathogens. Beyond their role in innate immunity, macrophages play increasingly defined roles in orchestrating the healing of various injured tissues. Perturbations of macrophage function and/or activation may result in impaired regeneration and fibrosis deposition as described in several chronic pathological diseases. Heterogeneity and plasticity have been demonstrated to be hallmarks of macrophages. In response to environmental cues they display a proinflammatory (M1) or an alternative anti-inflammatory (M2) phenotype. A lot of evidence demonstrated that after acute injury M1 macrophages infiltrate early to promote the clearance of necrotic debris, whereas M2 macrophages appear later to sustain tissue healing. Whether the sequential presence of two different macrophage populations results from a dynamic shift in macrophage polarization or from the recruitment of new circulating monocytes is a subject of ongoing debate. In this paper, we discuss the current available information about the role that different phenotypes of macrophages plays after injury and during the remodelling phase in different tissue types, with particular attention to the skeletal muscle. PMID:24860823

  6. Water uptake in stimulated cat skeletal muscle.

    PubMed

    Watson, P D; Garner, R P; Ward, D S

    1993-04-01

    Isolated vasodilated cat hindlimb skeletal muscles were perfused at constant flow and stimulated at 4 Hz for 2-4 min in three studies. Water uptake rates were measured gravimetrically or calculated from venous protein concentration changes. Venous plasma sodium, potassium, chloride, and osmolality were also measured. Maximum water uptake rates averaged 1.8 +/- 0.2 (SE) ml.min-1 x 100 g-1, reaching twice that in some experiments. Water uptake continued after stimulation had ceased. Constant-flow perfusion maintained a constant capillary pressure that was corroborated by measurements of arterial and venous perfusate pressures. Water uptake rate was not influenced by hematocrit but was highly correlated with plasma flow rate. The evidence strongly suggests that small-molecule osmotic pressure was the primary pressure causing the transcapillary water flux. Venous plasma sodium and chloride concentrations increased almost as much as protein (108 and 87% of the protein increase, respectively), as would be expected when water fluxes are driven by small-molecule osmotic pressure. Peak potassium efflux averaged 36 +/- 3 mu eq.min-1 x 100 g-1, but potassium did not contribute significantly to the osmotic gradient. PMID:8476122

  7. Bex1 knock out mice show altered skeletal muscle regeneration

    SciTech Connect

    Koo, Jae Hyung Smiley, Mark A.; Lovering, Richard M.; Margolis, Frank L.

    2007-11-16

    Bex1 and Calmodulin (CaM) are upregulated during skeletal muscle regeneration. We confirm this finding and demonstrate the novel finding that they interact in a calcium-dependent manner. To study the role of Bex1 and its interaction with CaM in skeletal muscle regeneration, we generated Bex1 knock out (Bex1-KO) mice. These mice appeared to develop normally and are fertile, but displayed a functional deficit in exercise performance compared to wild type (WT) mice. After intramuscular injection of cardiotoxin, which causes extensive and reproducible myotrauma followed by recovery, regenerating muscles of Bex1-KO mice exhibited elevated and prolonged cell proliferation, as well as delayed cell differentiation, compared to WT mice. Thus, our results provide the first evidence that Bex1-KO mice show altered muscle regeneration, and allow us to propose that the interaction of Bex1 with Ca{sup 2+}/CaM may be involved in skeletal muscle regeneration.

  8. Skeletal muscle hypertrophy and structure and function of skeletal muscle fibres in male body builders

    PubMed Central

    D'Antona, Giuseppe; Lanfranconi, Francesca; Pellegrino, Maria Antonietta; Brocca, Lorenza; Adami, Raffaella; Rossi, Rosetta; Moro, Giorgio; Miotti, Danilo; Canepari, Monica; Bottinelli, Roberto

    2006-01-01

    Needle biopsy samples were taken from vastus lateralis muscle (VL) of five male body builders (BB, age 27.4 ± 0.93 years; mean ±s.e.m.), who had being performing hypertrophic heavy resistance exercise (HHRE) for at least 2 years, and from five male active, but untrained control subjects (CTRL, age 29.9 ± 2.01 years). The following determinations were performed: anatomical cross-sectional area and volume of the quadriceps and VL muscles in vivo by magnetic resonance imaging (MRI); myosin heavy chain isoform (MHC) distribution of the whole biopsy samples by SDS-PAGE; cross-sectional area (CSA), force (Po), specific force (Po/CSA) and maximum shortening velocity (Vo) of a large population (n= 524) of single skinned muscle fibres classified on the basis of MHC isoform composition by SDS-PAGE; actin sliding velocity (Vf) on pure myosin isoforms by in vitro motility assays. In BB a preferential hypertrophy of fast and especially type 2X fibres was observed. The very large hypertrophy of VL in vivo could not be fully accounted for by single muscle fibre hypertrophy. CSA of VL in vivo was, in fact, 54% larger in BB than in CTRL, whereas mean fibre area was only 14% larger in BB than in CTRL. MHC isoform distribution was shifted towards 2X fibres in BB. Po/CSA was significantly lower in type 1 fibres from BB than in type 1 fibres from CTRL whereas both type 2A and type 2X fibres were significantly stronger in BB than in CTRL. Vo of type 1 fibres and Vf of myosin 1 were significantly lower in BB than in CTRL, whereas no difference was observed among fast fibres and myosin 2A. The findings indicate that skeletal muscle of BB was markedly adapted to HHRE through extreme hypertrophy, a shift towards the stronger and more powerful fibre types and an increase in specific force of muscle fibres. Such adaptations could not be fully accounted for by well known mechanisms of muscle plasticity, i.e. by the hypertrophy of single muscle fibre (quantitative mechanism) and by a

  9. Functional Skeletal Muscle Formation with a Biologic Scaffold

    PubMed Central

    Valentin, Jolene E.; Turner, Neill J.; Gilbert, Thomas W.; Badylak, Stephen F.

    2010-01-01

    Biologic scaffolds composed of extracellular matrix (ECM) have been used to reinforce or replace damaged or missing musculotendinous tissues in both preclinical studies and in human clinical applications. However, most studies have focused upon morphologic endpoints and few studies have assessed the in-situ functionality of newly formed tissue; especially new skeletal muscle tissue. The objective of the present study was to determine both the in-situ tetanic contractile response and histomorphologic characteristics of skeletal muscle tissue reconstructed using one of four test articles in a rodent abdominal wall model: 1) porcine small intestinal submucosa (SIS)-ECM; 2) carbodiimide-crosslinked porcine SIS-ECM; 3) autologous tissue; or 4) polypropylene mesh. Six months after surgery, the remodeled SIS-ECM showed almost complete replacement by islands and sheets of skeletal muscle, which generated a similar maximal contractile force to native tissue but with greater resistance to fatigue. The autologous tissue graft was replaced by a mixture of collagenous connective tissue, adipose tissue with fewer islands of skeletal muscle compared to SIS-ECM and a similar fatigue resistance to native muscle. Carbodiimide-crosslinked SIS-ECM and polypropylene mesh were characterized by a chronic inflammatory response and produced little or no measureable tetanic force. The findings of this study show that non-crosslinked xenogeneic SIS scaffolds and autologous tissue are associated with the restoration of functional skeletal muscle with histomorphologic characteristics that resemble native muscle. PMID:20638716

  10. Estimation of skeletal muscle mass from body creatine content

    NASA Technical Reports Server (NTRS)

    Pace, N.; Rahlmann, D. F.

    1982-01-01

    Procedures have been developed for studying the effect of changes in gravitational loading on skeletal muscle mass through measurements of the body creatine content. These procedures were developed for studies of gravitational scale effects in a four-species model, comprising the hamster, rat, guinea pig, and rabbit, which provides a sufficient range of body size for assessment of allometric parameters. Since intracellular muscle creatine concentration varies among species, and with age within a given species, the concentration values for metabolically mature individuals of these four species were established. The creatine content of the carcass, skin, viscera, smooth muscle, and skeletal muscle was determined for each species. In addition, the skeletal muscle mass of the major body components was determined, as well as the total and fat-free masses of the body and carcass, and the percent skeletal muscle in each. It is concluded that these procedures are particularly useful for studying the effect of gravitational loading on the skeletal muscle content of the animal carcass, which is the principal weight-bearing organ of the body.

  11. Nuclear Factor-kappa B Signaling in Skeletal Muscle Atrophy

    PubMed Central

    Li, Hong; Malhotra, Shweta; Kumar, Ashok

    2008-01-01

    Skeletal muscle atrophy/wasting is a serious complication of a wide range of diseases and conditions such as aging, disuse, AIDS, chronic obstructive pulmonary disease, space travel, muscular dystrophy, chronic heart failure, sepsis, and cancer. Emerging evidence suggests that nuclear factor-kappa B (NF-κB) is one of most important signaling pathways linked to the loss of skeletal muscle mass in various physiological and pathophysiological conditions. Activation of NF-κB in skeletal muscle leads to degradation of specific muscle proteins, induces inflammation and fibrosis, and blocks the regeneration of myofibers after injury/atrophy. Recent studies employing genetic mouse models have provided strong evidence that NF-κB can serve as an important molecular target for the prevention of skeletal muscle loss. In this article, we have outlined the current understanding regarding the role of NF-κB in skeletal muscle with particular reference to different models of muscle-wasting and the development of novel therapy. PMID:18574572

  12. Challenges to acellular biological scaffold mediated skeletal muscle tissue regeneration.

    PubMed

    Corona, Benjamin T; Greising, Sarah M

    2016-10-01

    Volumetric muscle loss (VML) injuries present a complex and heterogeneous clinical problem that results in a chronic loss of muscle tissue and strength. The primary limitation to muscle tissue regeneration after VML injury is the frank loss of all native muscle constituents in the defect, especially satellite cells and the basal lamina. Recent advancements in regenerative medicine have set forth encouraging and emerging translational and therapeutic options for these devastating injuries including the surgical implantation of acellular biological scaffolds. While these biomaterials can modulate the wound environment, the existing data do not support their capacity to promote appreciable muscle fiber regeneration that can contribute to skeletal muscle tissue functional improvements. An apparent restriction of endogenous satellite cell (i.e., pax7(+)) migration to acellular biological scaffolds likely underlies this deficiency. This work critically evaluates the role of an acellular biological scaffold in orchestrating skeletal muscle tissue regeneration, specifically when used as a regenerative medicine approach for VML injury. PMID:27472161

  13. No-dependent signaling pathways in unloaded skeletal muscle

    PubMed Central

    Shenkman, Boris S.; Nemirovskaya, Tatiana L.; Lomonosova, Yulia N.

    2015-01-01

    The main focus of the current review is the nitric oxide (NO)-mediated signaling mechanism in unloaded skeletal. Review of the published data describing muscles during physical activity and inactivity demonstrates that NO is an essential trigger of signaling processes, which leads to structural and metabolic changes of the muscle fibers. The experiments with modulation of NO-synthase (NOS) activity during muscle unloading demonstrate the ability of an activated enzyme to stabilize degradation processes and prevent development of muscle atrophy. Various forms of muscle mechanical activity, i.e., plantar afferent stimulation, resistive exercise and passive chronic stretch increase the content of neural NOS (nNOS) and thus may facilitate an increase in NO production. Recent studies demonstrate that NO-synthase participates in the regulation of protein and energy metabolism in skeletal muscle by fine-tuning and stabilizing complex signaling systems which regulate protein synthesis and degradation in the fibers of inactive muscle. PMID:26582991

  14. Action of Obestatin in Skeletal Muscle Repair: Stem Cell Expansion, Muscle Growth, and Microenvironment Remodeling

    PubMed Central

    Gurriarán-Rodríguez, Uxía; Santos-Zas, Icía; González-Sánchez, Jessica; Beiroa, Daniel; Moresi, Viviana; Mosteiro, Carlos S; Lin, Wei; Viñuela, Juan E; Señarís, José; García-Caballero, Tomás; Casanueva, Felipe F; Nogueiras, Rubén; Gallego, Rosalía; Renaud, Jean-Marc; Adamo, Sergio; Pazos, Yolanda; Camiña, Jesús P

    2015-01-01

    The development of therapeutic strategies for skeletal muscle diseases, such as physical injuries and myopathies, depends on the knowledge of regulatory signals that control the myogenic process. The obestatin/GPR39 system operates as an autocrine signal in the regulation of skeletal myogenesis. Using a mouse model of skeletal muscle regeneration after injury and several cellular strategies, we explored the potential use of obestatin as a therapeutic agent for the treatment of trauma-induced muscle injuries. Our results evidenced that the overexpression of the preproghrelin, and thus obestatin, and GPR39 in skeletal muscle increased regeneration after muscle injury. More importantly, the intramuscular injection of obestatin significantly enhanced muscle regeneration by simulating satellite stem cell expansion as well as myofiber hypertrophy through a kinase hierarchy. Added to the myogenic action, the obestatin administration resulted in an increased expression of vascular endothelial growth factor (VEGF)/vascular endothelial growth factor receptor 2 (VEGFR2) and the consequent microvascularization, with no effect on collagen deposition in skeletal muscle. Furthermore, the potential inhibition of myostatin during obestatin treatment might contribute to its myogenic action improving muscle growth and regeneration. Overall, our data demonstrate successful improvement of muscle regeneration, indicating obestatin is a potential therapeutic agent for skeletal muscle injury and would benefit other myopathies related to muscle regeneration. PMID:25762009

  15. Chemokine receptor CCR2 involvement in skeletal muscle regeneration.

    PubMed

    Warren, Gordon L; Hulderman, Tracy; Mishra, Dawn; Gao, Xin; Millecchia, Lyndell; O'Farrell, Laura; Kuziel, William A; Simeonova, Petia P

    2005-03-01

    Chemokines, signaling through the CCR2 receptor, are highly expressed in injured skeletal muscle. Their target specificity depends on the cellular expression of the specific receptors. Here we demonstrate that, in freeze-injured muscle, CCR2 co-localized with Mac-3, a marker of activated macrophages as well as with myogenin, a marker of activated muscle precursor cells. The degeneration/regeneration process in skeletal muscle of CCR2-/- and wild-type mice was not significantly different at day 3. However in contrast to the regenerated muscle of the wild-type mice, the muscle from CCR2-/- mice was characterized by impaired regeneration, inflammation, and fibrotic response at day 14, increased fat infiltration, fibrosis, and calcification at day 21, and impaired strength recovery until at least 28 days post-injury. Consistently, the increased expression of Mac-1 and TNF-alpha was prolonged in the injured muscle of CCR2-/- mice. The expression pattern of the myogenic factors MyoD and myogenin was similar for both types of mice, while NCAM, which is associated with the initiation of fusion of muscle precursor cells, was more increased in the injured muscle of CCR2-/- mice. In conclusion, the study delineates that signaling through CCR2 is involved in muscle precursor cell activities necessary for complete and rapid regeneration of injured skeletal muscle. PMID:15601671

  16. Piecing together the puzzle of perilipin proteins and skeletal muscle lipolysis.

    PubMed

    MacPherson, Rebecca E K; Peters, Sandra J

    2015-07-01

    The regulation of skeletal muscle lipolysis and fat oxidation is a complex process involving multiple proteins and enzymes. Emerging work indicates that skeletal muscle PLIN proteins likely play a role in the hydrolysis of triglycerides stored in lipid droplets and the passage of fatty acids to the mitochondria for oxidation. In adipocytes, PLIN1 regulates lipolysis by interacting with comparative gene identification-58 (CGI-58), an activator of adipose triglyceride lipase (ATGL). Upon lipolytic stimulation, PLIN1 is phosphorylated, releasing CGI-58 to activate ATGL and initiate triglyceride breakdown. The absence of PLIN1 in skeletal muscle leads us to believe that other PLIN family members undertake this role. The focus of this review is on the PLIN family proteins expressed in skeletal muscle: PLIN2, PLIN3, and PLIN5. To date, most studies involving these PLIN proteins have used nonmuscle tissues and cell cultures to determine their potential roles. Results from work in these models support a role for PLIN proteins in sequestering lipases during basal conditions and in potentially working together for lipase translocation and activity during lipolysis. In skeletal muscle, PLIN2 tends to mirror the lipid content and may play a role in lipid droplet growth and stability through lipase interactions on the lipid droplet surface, whereas the skeletal muscle roles of both PLIN3 and PLIN5 seem to be more complex because they are found not only on the lipid droplet, but also at the mitochondria. Clearly, further work is needed to fully understand the intricate mechanisms by which PLIN proteins contribute to skeletal muscle lipid metabolism. PMID:25971423

  17. Frizzled-9 impairs acetylcholine receptor clustering in skeletal muscle cells

    PubMed Central

    Avilés, Evelyn C.; Pinto, Cristina; Hanna, Patricia; Ojeda, Jorge; Pérez, Viviana; De Ferrari, Giancarlo V.; Zamorano, Pedro; Albistur, Miguel; Sandoval, Daniel; Henríquez, Juan P.

    2014-01-01

    Cumulative evidence indicates that Wnt pathways play crucial and diverse roles to assemble the neuromuscular junction (NMJ), a peripheral synapse characterized by the clustering of acetylcholine receptors (AChR) on postsynaptic densities. The molecular determinants of Wnt effects at the NMJ are still to be fully elucidated. We report here that the Wnt receptor Frizzled-9 (Fzd9) is expressed in developing skeletal muscles during NMJ synaptogenesis. In cultured myotubes, gain- and loss-of-function experiments revealed that Fzd9-mediated signaling impairs the AChR-clustering activity of agrin, an organizer of postsynaptic differentiation. Overexpression of Fzd9 induced the cytosolic accumulation of β-catenin, a key regulator of Wnt signaling. Consistently, Fzd9 and β-catenin localize in the postsynaptic domain of embryonic NMJs in vivo. Our findings represent the first evidence pointing to a crucial role of a Fzd-mediated, β-catenin-dependent signaling on the assembly of the vertebrate NMJ. PMID:24860427

  18. Skeletal muscle PGC-1α modulates systemic ketone body homeostasis and ameliorates diabetic hyperketonemia in mice.

    PubMed

    Svensson, Kristoffer; Albert, Verena; Cardel, Bettina; Salatino, Silvia; Handschin, Christoph

    2016-05-01

    Ketone bodies (KBs) are crucial energy substrates during states of low carbohydrate availability. However, an aberrant regulation of KB homeostasis can lead to complications such as diabetic ketoacidosis. Exercise and diabetes affect systemic KB homeostasis, but the regulation of KB metabolism is still enigmatic. In our study in mice with either knockout or overexpression of the peroxisome proliferator-activated receptor-γ coactivator (PGC)-1α in skeletal muscle, PGC-1α regulated ketolytic gene transcription in muscle. Furthermore, KB homeostasis of these mice was investigated during withholding of food, exercise, and ketogenic diet feeding, and after streptozotocin injection. In response to these ketogenic stimuli, modulation of PGC-1α levels in muscle affected systemic KB homeostasis. Moreover, the data demonstrate that skeletal muscle PGC-1α is necessary for the enhanced ketolytic capacity in response to exercise training and overexpression of PGC-1α in muscle enhances systemic ketolytic capacity and is sufficient to ameliorate diabetic hyperketonemia in mice. In cultured myotubes, the transcription factor estrogen-related receptor-α was a partner of PGC-1α in the regulation of ketolytic gene transcription. These results demonstrate a central role of skeletal muscle PGC-1α in the transcriptional regulation of systemic ketolytic capacity.-Svensson, K., Albert, V., Cardel, B., Salatino, S., Handschin, C. Skeletal muscle PGC-1α modulates systemic ketone body homeostasis and ameliorates diabetic hyperketonemia in mice. PMID:26849960

  19. Skeletal Muscle as a Peripheral Modifier of Behavior

    ERIC Educational Resources Information Center

    Jenkins, Robert R.

    1978-01-01

    Discusses how muscle can exert an influence on the behavioral potential of an organism and attempts to refute the "all or none law" by demonstrating that skeletal muscle is not merely a slave of the central nervous system. (Author/MA)

  20. The impact of vitamin D on skeletal muscle function

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This review discusses the clinical and laboratory studies that have examined a role of vitamin D in skeletal muscle. Many observational studies, mainly in older populations, indicate that vitamin D status is positively associated with muscle strength and physical performance and inversely associated...

  1. Physiologic and biochemical aspects of skeletal muscle denervation and reinnervation

    NASA Technical Reports Server (NTRS)

    Max, S. R.; Mayer, R. F.

    1984-01-01

    Some of the physiologic and biochemical changes that occur in mammalian skeletal muscle following denervation and reinnervation are considered and some comparisons are made with changes observed following altered motor function. The nature of the trophic influence by which nerves control muscle properties are discussed, including the effects of choline acetyltransferase and acetylcholinesterase and the role of the acetylcholine receptor.

  2. Acylcarnitines: potential implications for skeletal muscle insulin resistance

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Insulin resistance is linked to increased acylcarnitine species in a number of tissues including skeletal muscle, due to incomplete fatty acid oxidation (FAO). It is not known if acylcarnitines participate in muscle insulin resistance or simply reflect dysregulated metabolism. The aim of this stud...

  3. Molecular responses to moderate endurance exercise in skeletal muscle

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study examined alterations in skeletal-muscle growth and atrophy-related molecular events after a single bout of moderate-intensity endurance exercise. Muscle biopsies were obtained from 10 men (23 +/- 1 yr, body mass 80 +/- 2 kg, and VO(2peak) 45 +/- 1 ml x kg'¹ x min'¹) immediately (0 hr) and...

  4. 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.

  5. E-box sites and a proximal regulatory region of the muscle creatine kinase gene differentially regulate expression in diverse skeletal muscles and cardiac muscle of transgenic mice.

    PubMed Central

    Shield, M A; Haugen, H S; Clegg, C H; Hauschka, S D

    1996-01-01

    Previous analysis of the muscle creatine kinase (MCK) gene indicated that control elements required for transcription in adult mouse muscle differed from those required in cell culture, suggesting that distinct modes of muscle gene regulation occur in vivo. To examine this further, we measured the activity of MCK transgenes containing E-box and promoter deletions in a variety of striated muscles. Simultaneous mutation of three E boxes in the 1,256-bp MCK 5' region, which abolished transcription in muscle cultures, had strikingly different effects in mice. The mutations abolished transgene expression in cardiac and tongue muscle and caused a reduction in expression in the soleus muscle (a muscle with many slow fibers) but did not affect expression in predominantly fast muscles: quadriceps, abdominals, and extensor digitorum longus. Other regulatory sequences with muscle-type-specific activities were found within the 358-bp 5'-flanking region. This proximal region conferred relatively strong expression in limb and abdominal skeletal muscles but was inactive in cardiac and tongue muscles. However, when the 206-bp 5' enhancer was ligated to the 358-bp region, high levels of tissue-specific expression were restored in all muscle types. These results indicate that E boxes and a proximal regulatory region are differentially required for maximal MCK transgene expression in different striated muscles. The overall results also imply that within skeletal muscles, the steady-state expression of the MCK gene and possibly other muscle genes depends on transcriptional mechanisms that differ between fast and slow fibers as well as between the anatomical and physiological attributes of each specific muscle. PMID:8756664

  6. High skeletal muscle adenylate cyclase in malignant hyperthermia.

    PubMed Central

    Willner, J H; Cerri, C G; Wood, D S

    1981-01-01

    Malignant hyperthermia occurs in humans with several congenital myopathies, usually in response to general anesthesia. Commonly, individuals who develop this syndrome lack symptoms of muscle disease, and their muscle lacks specific pathological changes. A biochemical marker for this myopathy has not previously been available; we found activity of adenylate cyclase and content of cyclic AMP to be abnormally high in skeletal muscle. Secondary modification of protein phosphorylation could explain observed abnormalities of phosphorylase activation and sarcoplasmic reticulum function. PMID:6271806

  7. What governs skeletal muscle VO2max? New evidence.

    PubMed

    Richardson, R S

    2000-01-01

    Recent investigations into the determinants of skeletal muscle maximal oxygen consumption (VO2) have provided further evidence regarding the role of O2 supply and demand in governing exercise metabolism. Specifically, four studies utilizing both animal and human exercise models are highlighted here: 1) the role of the diffusive O2 component was examined in the exercising canine gastrocnemius muscle by a rightward shift in the O2 dissociation curve while maintaining O2 delivery constant; 2) the role of peripheral and central components was examined by studying the human quadriceps muscle, already recognized to have a very high mass specific O2 delivery, under conditions of increased (hyperoxia) and reduced O2 availability (hypoxia); 3) the role of intracellular PO2 in the progressive increase in lactate efflux from skeletal muscle from submaximal to maximal effort; and finally 4) the role of intracellular PO2 itself as a determinant of maximal mitochondrial O2 consumption. In summary, these investigations illustrate 1) the importance of the diffusion gradient from blood to muscle cell; 2) illustrate that even in functionally isolated trained skeletal muscle the highest recorded metabolic rates can be increased by increasing O2 supply; 3) that a constant intracellular PO2 during graded exercise is therefore unrelated to increasing lactate efflux; and 4) that only in hyperoxia does trained human skeletal muscle approaching very high mitochondrial metabolic limits, as shown by a disproportionate increase in intracellular PO2 for the recorded change in VO2max. PMID:10647536

  8. Decellularized Human Skeletal Muscle as Biologic Scaffold for Reconstructive Surgery.

    PubMed

    Porzionato, Andrea; Sfriso, Maria Martina; Pontini, Alex; Macchi, Veronica; Petrelli, Lucia; Pavan, Piero G; Natali, Arturo N; Bassetto, Franco; Vindigni, Vincenzo; De Caro, Raffaele

    2015-01-01

    Engineered skeletal muscle tissues have been proposed as potential solutions for volumetric muscle losses, and biologic scaffolds have been obtained by decellularization of animal skeletal muscles. The aim of the present work was to analyse the characteristics of a biologic scaffold obtained by decellularization of human skeletal muscles (also through comparison with rats and rabbits) and to evaluate its integration capability in a rabbit model with an abdominal wall defect. Rat, rabbit and human muscle samples were alternatively decellularized with two protocols: n.1, involving sodium deoxycholate and DNase I; n.2, trypsin-EDTA and Triton X-NH4OH. Protocol 2 proved more effective, removing all cellular material and maintaining the three-dimensional networks of collagen and elastic fibers. Ultrastructural analyses with transmission and scanning electron microscopy confirmed the preservation of collagen, elastic fibres, glycosaminoglycans and proteoglycans. Implantation of human scaffolds in rabbits gave good results in terms of integration, although recellularization by muscle cells was not completely achieved. In conclusion, human skeletal muscles may be effectively decellularized to obtain scaffolds preserving the architecture of the extracellular matrix and showing mechanical properties suitable for implantation/integration. Further analyses will be necessary to verify the suitability of these scaffolds for in vitro recolonization by autologous cells before in vivo implantation. PMID:26140375

  9. Decellularized Human Skeletal Muscle as Biologic Scaffold for Reconstructive Surgery

    PubMed Central

    Porzionato, Andrea; Sfriso, Maria Martina; Pontini, Alex; Macchi, Veronica; Petrelli, Lucia; Pavan, Piero G.; Natali, Arturo N.; Bassetto, Franco; Vindigni, Vincenzo; De Caro, Raffaele

    2015-01-01

    Engineered skeletal muscle tissues have been proposed as potential solutions for volumetric muscle losses, and biologic scaffolds have been obtained by decellularization of animal skeletal muscles. The aim of the present work was to analyse the characteristics of a biologic scaffold obtained by decellularization of human skeletal muscles (also through comparison with rats and rabbits) and to evaluate its integration capability in a rabbit model with an abdominal wall defect. Rat, rabbit and human muscle samples were alternatively decellularized with two protocols: n.1, involving sodium deoxycholate and DNase I; n.2, trypsin-EDTA and Triton X-NH4OH. Protocol 2 proved more effective, removing all cellular material and maintaining the three-dimensional networks of collagen and elastic fibers. Ultrastructural analyses with transmission and scanning electron microscopy confirmed the preservation of collagen, elastic fibres, glycosaminoglycans and proteoglycans. Implantation of human scaffolds in rabbits gave good results in terms of integration, although recellularization by muscle cells was not completely achieved. In conclusion, human skeletal muscles may be effectively decellularized to obtain scaffolds preserving the architecture of the extracellular matrix and showing mechanical properties suitable for implantation/integration. Further analyses will be necessary to verify the suitability of these scaffolds for in vitro recolonization by autologous cells before in vivo implantation. PMID:26140375

  10. Compensatory Hypertrophy of Skeletal Muscle: Contractile Characteristics

    ERIC Educational Resources Information Center

    Ianuzzo, C. D.; Chen, V.

    1977-01-01

    Describes an experiment using rats that demonstrates contractile characteristics of normal and hypertrophied muscle. Compensatory hypertrophy of the plantaris muscle is induced by surgical removal of the synergistic gastrocnemium muscle. Includes methods for determination of contractile properties of normal and hypertrophied muscle and…

  11. Hypodynamic and hypokinetic condition of skeletal muscles

    NASA Technical Reports Server (NTRS)

    Katinas, G. S.; Oganov, V. S.; Potapov, A. N.

    1980-01-01

    Data are presented in regard to the effect of unilateral brachial amputation on the physiological characteristics of two functionally different muscles, the brachial muscle (flexor of the brachium) and the medial head of the brachial triceps muscle (extensor of the brachium), which in rats represents a separate muscle. Hypokinesia and hypodynamia were studied.

  12. Lack of phosphatidylethanolamine N-methyltransferase in mice does not promote fatty acid oxidation in skeletal muscle.

    PubMed

    Tasseva, Guergana; van der Veen, Jelske N; Lingrell, Susanne; Jacobs, René L; Vance, Dennis E; Vance, Jean E

    2016-02-01

    Phosphatidylethanolamine N-methyltransferase (PEMT) converts phosphatidylethanolamine (PE) to phosphatidylcholine (PC) in the liver. Mice lacking PEMT are protected from high-fat diet-induced obesity and insulin resistance, and exhibit increased whole-body energy expenditure and oxygen consumption. Since skeletal muscle is a major site of fatty acid oxidation and energy utilization, we determined if rates of fatty acid oxidation/oxygen consumption in muscle are higher in Pemt(-/-) mice than in Pemt(+/+) mice. Although PEMT is abundant in the liver, PEMT protein and activity were undetectable in four types of skeletal muscle. Moreover, amounts of PC and PE in the skeletal muscle were not altered by PEMT deficiency. Thus, we concluded that any influence of PEMT deficiency on skeletal muscle would be an indirect consequence of lack of PEMT in liver. Neither the in vivo rate of fatty acid uptake by muscle nor the rate of fatty acid oxidation in muscle explants and cultured myocytes depended upon Pemt genotype. Nor did PEMT deficiency increase oxygen consumption or respiratory function in skeletal muscle mitochondria. Thus, the increased whole body oxygen consumption in Pemt(-/-) mice, and resistance of these mice to diet-induced weight gain, are not primarily due to increased capacity of skeletal muscle for utilization of fatty acids as an energy source. PMID:26603903

  13. Circadian clock regulation of skeletal muscle growth and repair.

    PubMed

    Chatterjee, Somik; Ma, Ke

    2016-01-01

    Accumulating evidence indicates that the circadian clock, a transcriptional/translational feedback circuit that generates ~24-hour oscillations in behavior and physiology, is a key temporal regulatory mechanism involved in many important aspects of muscle physiology. Given the clock as an evolutionarily-conserved time-keeping mechanism that synchronizes internal physiology to environmental cues, locomotor activities initiated by skeletal muscle enable entrainment to the light-dark cycles on earth, thus ensuring organismal survival and fitness. Despite the current understanding of the role of molecular clock in preventing age-related sarcopenia, investigations into the underlying molecular pathways that transmit clock signals to the maintenance of skeletal muscle growth and function are only emerging. In the current review, the importance of the muscle clock in maintaining muscle mass during development, repair and aging, together with its contribution to muscle metabolism, will be discussed. Based on our current understandings of how tissue-intrinsic muscle clock functions in the key aspects muscle physiology, interventions targeting the myogenic-modulatory activities of the clock circuit may offer new avenues for prevention and treatment of muscular diseases. Studies of mechanisms underlying circadian clock function and regulation in skeletal muscle warrant continued efforts. PMID:27540471

  14. Circadian clock regulation of skeletal muscle growth and repair

    PubMed Central

    Chatterjee, Somik; Ma, Ke

    2016-01-01

    Accumulating evidence indicates that the circadian clock, a transcriptional/translational feedback circuit that generates ~24-hour oscillations in behavior and physiology, is a key temporal regulatory mechanism involved in many important aspects of muscle physiology. Given the clock as an evolutionarily-conserved time-keeping mechanism that synchronizes internal physiology to environmental cues, locomotor activities initiated by skeletal muscle enable entrainment to the light-dark cycles on earth, thus ensuring organismal survival and fitness. Despite the current understanding of the role of molecular clock in preventing age-related sarcopenia, investigations into the underlying molecular pathways that transmit clock signals to the maintenance of skeletal muscle growth and function are only emerging. In the current review, the importance of the muscle clock in maintaining muscle mass during development, repair and aging, together with its contribution to muscle metabolism, will be discussed. Based on our current understandings of how tissue-intrinsic muscle clock functions in the key aspects muscle physiology, interventions targeting the myogenic-modulatory activities of the clock circuit may offer new avenues for prevention and treatment of muscular diseases. Studies of mechanisms underlying circadian clock function and regulation in skeletal muscle warrant continued efforts. PMID:27540471

  15. Regulation of insulin-like growth factor-I in skeletal muscle and muscle cells.

    PubMed

    Frost, R A; Lang, C H

    2003-03-01

    Growth hormone (GH) and insulin-like growth factor-I (IGF-I) are potent regulators of muscle mass. Transgenic mice that over-express these proteins exhibit dramatically enlarged skeletal muscles. In contrast, malnutrition, critical illness, sepsis, and aging are all associated with a dramatic reduction in muscle mass and function. The circulating concentration of IGF-I and the expression of IGF-I in skeletal muscle are also reduced during catabolic states. Consequently, GH has been used clinically to increase lean body mass in patients with muscle wasting. Likewise, delivery of IGF-I specifically into muscle has been proposed as a genetic therapy for muscle disorders. A better understanding of the regulation of IGF-I expression in skeletal muscle and muscle cells is therefore of importance. Yet, our knowledge in this area has been limited by a lack of GH responsive muscle cells. In addition the IGF-I gene spans over 90 kb of genomic DNA and it exhibits a very complex regulatory pattern. This review will summarize our knowledge of the control of muscle mass by GH, IGF-I, anabolic steroids, exercise and other growth enhancing hormones. We will also highlight recent advances in the regulation of IGF-I and signal transducers and activators of transcription (Stats) by GH. A special emphasis will be placed on the interaction of IGF-I and proinflammatory cytokines in skeletal muscle and muscle cells. PMID:12621363

  16. The adipokine leptin increases skeletal muscle mass and significantly alters skeletal muscle miRNA expression profile in aged mice

    SciTech Connect

    Hamrick, Mark W.; Herberg, Samuel; Arounleut, Phonepasong; He, Hong-Zhi; Shiver, Austin; Qi, Rui-Qun; Zhou, Li; Isales, Carlos M.; and others

    2010-09-24

    Research highlights: {yields} Aging is associated with muscle atrophy and loss of muscle mass, known as the sarcopenia of aging. {yields} We demonstrate that age-related muscle atrophy is associated with marked changes in miRNA expression in muscle. {yields} Treating aged mice with the adipokine leptin significantly increased muscle mass and the expression of miRNAs involved in muscle repair. {yields} Recombinant leptin therapy may therefore be a novel approach for treating age-related muscle atrophy. -- Abstract: Age-associated loss of muscle mass, or sarcopenia, contributes directly to frailty and an increased risk of falls and fractures among the elderly. Aged mice and elderly adults both show decreased muscle mass as well as relatively low levels of the fat-derived hormone leptin. Here we demonstrate that loss of muscle mass and myofiber size with aging in mice is associated with significant changes in the expression of specific miRNAs. Aging altered the expression of 57 miRNAs in mouse skeletal muscle, and many of these miRNAs are now reported to be associated specifically with age-related muscle atrophy. These include miR-221, previously identified in studies of myogenesis and muscle development as playing a role in the proliferation and terminal differentiation of myogenic precursors. We also treated aged mice with recombinant leptin, to determine whether leptin therapy could improve muscle mass and alter the miRNA expression profile of aging skeletal muscle. Leptin treatment significantly increased hindlimb muscle mass and extensor digitorum longus fiber size in aged mice. Furthermore, the expression of 37 miRNAs was altered in muscles of leptin-treated mice. In particular, leptin treatment increased the expression of miR-31 and miR-223, miRNAs known to be elevated during muscle regeneration and repair. These findings suggest that aging in skeletal muscle is associated with marked changes in the expression of specific miRNAs, and that nutrient

  17. Uncovering the exercise-related proteome signature in skeletal muscle.

    PubMed

    Padrão, Ana Isabel; Ferreira, Rita; Amado, Francisco; Vitorino, Rui; Duarte, José Alberto

    2016-03-01

    Exercise training has been recommended as a nonpharmacological strategy for the prevention and attenuation of skeletal muscle atrophy in distinct pathophysiological conditions. Despite the well-established phenotypic alterations, the molecular mechanisms underlying exercise-induced skeletal muscle remodeling are poorly characterized. Proteomics based on mass spectrometry have been successfully applied for the characterization of skeletal muscle proteome, representing a pivotal approach for the wide characterization of the molecular networks that lead to skeletal muscle remodeling. Nevertheless, few studies were performed to characterize the exercise-induced proteome remodeling of skeletal muscle, with only six research papers focused on the cross-talk between exercise and pathophysiological conditions. In order to add new insights on the impact of distinct exercise programs on skeletal muscle proteome, molecular network analysis was performed with bioinformatics tools. This analysis highlighted an exercise-related proteome signature characterized by the up-regulation of the capacity for ATP generation, oxygen delivery, antioxidant capacity and regulation of mitochondrial protein synthesis. Chronic endurance training up-regulates the tricarboxylic acid cycle and oxidative phosphorylation system, whereas the release of calcium ion into cytosol and amino acid metabolism are the biological processes up-regulated by a single bout of exercise. Other issues as exercise intensity, load, mode and regimen as well as muscle type also influence the exercise-induced proteome signature. The comprehensive analysis of the molecular networks modulated by exercise training in health and disease, taking in consideration all these variables, might not only support the therapeutic effect of exercise but also highlight novel targets for the development of enhanced pharmacological strategies. PMID:26632760

  18. Bone Marrow Mesenchymal Cells Improve Muscle Function in a Skeletal Muscle Re-Injury Model

    PubMed Central

    Ribeiro, Karla C.; Porto, Anderson; Peçanha, Ramon; Fortes, Fabio S. A.; Zapata-Sudo, Gisele; Campos-de-Carvalho, Antonio C.; Goldenberg, Regina C. S.; Werneck-de-Castro, João Pedro

    2015-01-01

    Skeletal muscle injury is the most common problem in orthopedic and sports medicine, and severe injury leads to fibrosis and muscle dysfunction. Conventional treatment for successive muscle injury is currently controversial, although new therapies, like cell therapy, seem to be promise. We developed a model of successive injuries in rat to evaluate the therapeutic potential of bone marrow mesenchymal cells (BMMC) injected directly into the injured muscle. Functional and histological assays were performed 14 and 28 days after the injury protocol by isometric tension recording and picrosirius/Hematoxilin & Eosin staining, respectively. We also evaluated the presence and the fate of BMMC on treated muscles; and muscle fiber regeneration. BMMC treatment increased maximal skeletal muscle contraction 14 and 28 days after muscle injury compared to non-treated group (4.5 ± 1.7 vs 2.5 ± 0.98 N/cm2, p<0.05 and 8.4 ± 2.3 vs. 5.7 ± 1.3 N/cm2, p<0.05 respectively). Furthermore, BMMC treatment increased muscle fiber cross-sectional area and the presence of mature muscle fiber 28 days after muscle injury. However, there was no difference in collagen deposition between groups. Immunoassays for cytoskeleton markers of skeletal and smooth muscle cells revealed an apparent integration of the BMMC within the muscle. These data suggest that BMMC transplantation accelerates and improves muscle function recovery in our extensive muscle re-injury model. PMID:26039243

  19. Regulation of skeletal muscle oxidative capacity and muscle mass by SIRT3

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We have previously reported that the expression of mitochondrial deacetylase SIRT3 is high in the slow oxidative muscle and that the expression of muscle SIRT3 level is increased by dietary restriction or exercise training. To explore the function of SIRT3 in skeletal muscle, we report here the esta...

  20. Kelch proteins: emerging roles in skeletal muscle development and diseases

    PubMed Central

    2014-01-01

    Our understanding of genes that cause skeletal muscle disease has increased tremendously over the past three decades. Advances in approaches to genetics and genomics have aided in the identification of new pathogenic mechanisms in rare genetic disorders and have opened up new avenues for therapeutic interventions by identification of new molecular pathways in muscle disease. Recent studies have identified mutations of several Kelch proteins in skeletal muscle disorders. The Kelch superfamily is one of the largest evolutionary conserved gene families. The 66 known family members all possess a Kelch-repeat containing domain and are implicated in diverse biological functions. In skeletal muscle development, several Kelch family members regulate the processes of proliferation and/or differentiation resulting in normal functioning of mature muscles. Importantly, many Kelch proteins function as substrate-specific adaptors for Cullin E3 ubiquitin ligase (Cul3), a core component of the ubiquitin-proteasome system to regulate the protein turnover. This review discusses the emerging roles of Kelch proteins in skeletal muscle function and disease. PMID:24959344

  1. Skeletal muscle as a regulator of the longevity protein, Klotho

    PubMed Central

    Avin, Keith G.; Coen, Paul M.; Huang, Wan; Stolz, Donna B.; Sowa, Gwendolyn A.; Dubé, John J.; Goodpaster, Bret H.; O'Doherty, Robert M.; Ambrosio, Fabrisia

    2014-01-01

    Klotho is a powerful longevity protein that has been linked to the prevention of muscle atrophy, osteopenia, and cardiovascular disease. Similar anti-aging effects have also been ascribed to exercise and physical activity. While an association between muscle function and Klotho expression has been previously suggested from longitudinal cohort studies, a direct relationship between circulating Klotho and skeletal muscle has not been investigated. In this paper, we present a review of the literature and preliminary evidence that, together, suggests Klotho expression may be modulated by skeletal muscle activity. Our pilot clinical findings performed in young and aged individuals suggest that circulating Klotho levels are upregulated in response to an acute exercise bout, but that the response may be dependent on fitness level. A similar upregulation of circulating Klotho is also observed in response to an acute exercise in young and old mice, suggesting that this may be a good model for mechanistically probing the role of physical activity on Klotho expression. Finally, we highlight overlapping signaling pathways that are modulated by both Klotho and skeletal muscle and propose potential mechanisms for cross-talk between the two. It is hoped that this review will stimulate further consideration of the relationship between skeletal muscle activity and Klotho expression, potentially leading to important insights into the well-documented systemic anti-aging effects of exercise. PMID:24987372

  2. Changes in skeletal muscle gene expression following clenbuterol administration

    PubMed Central

    Spurlock, Diane M; McDaneld, Tara G; McIntyre, Lauren M

    2006-01-01

    Background Beta-adrenergic receptor agonists (BA) induce skeletal muscle hypertrophy, yet specific mechanisms that lead to this effect are not well understood. The objective of this research was to identify novel genes and physiological pathways that potentially facilitate BA induced skeletal muscle growth. The Affymetrix platform was utilized to identify gene expression changes in mouse skeletal muscle 24 hours and 10 days after administration of the BA clenbuterol. Results Administration of clenbuterol stimulated anabolic activity, as indicated by decreased blood urea nitrogen (BUN; P < 0.01) and increased body weight gain (P < 0.05) 24 hours or 10 days, respectively, after initiation of clenbuterol treatment. A total of 22,605 probesets were evaluated with 52 probesets defined as differentially expressed based on a false discovery rate of 10%. Differential mRNA abundance of four of these genes was validated in an independent experiment by quantitative PCR. Functional characterization of differentially expressed genes revealed several categories that participate in biological processes important to skeletal muscle growth, including regulators of transcription and translation, mediators of cell-signalling pathways, and genes involved in polyamine metabolism. Conclusion Global evaluation of gene expression after administration of clenbuterol identified changes in gene expression and overrepresented functional categories of genes that may regulate BA-induced muscle hypertrophy. Changes in mRNA abundance of multiple genes associated with myogenic differentiation may indicate an important effect of BA on proliferation, differentiation, and/or recruitment of satellite cells into muscle fibers to promote muscle hypertrophy. Increased mRNA abundance of genes involved in the initiation of translation suggests that increased levels of protein synthesis often associated with BA administration may result from a general up-regulation of translational initiators. Additionally

  3. Skeletal muscle fatty acid handling in insulin resistant men.

    PubMed

    van Hees, Anneke M J; Jans, Anneke; Hul, Gabby B; Roche, Helen M; Saris, Wim H M; Blaak, Ellen E

    2011-07-01

    Disturbances in skeletal muscle lipid metabolism may precede or contribute to the development of whole body insulin resistance. In this study, we examined fasting and postprandial skeletal muscle fatty acid (FA) handling in insulin resistant (IR) men. Thirty men with the metabolic syndrome (MetS) (National Cholesterol Education Program-Adult Treatment Panel III) were included in this sub-study to the LIPGENE study, and divided in two groups (IR and control) based on the median of insulin sensitivity (S(I) = 2.06 (mU/l(-1))·min(-1)·10(-4)). Fasting and postprandial skeletal muscle FA handling were examined by combining the forearm balance technique with stable isotopes of palmitate. [(2)H(2)]-palmitate was infused intravenously to label endogenous triacylglycerol (TAG) and free FAs (FFAs) in the circulation and [U-(13)C]-palmitate was incorporated in a high-fat mixed meal (2.6 MJ, 61 E% fat) to label chylomicron-TAG. Muscle biopsies were taken to determine muscle TAG, diacylglycerol (DAG), FFA, and phospholipid (PL) content, their fractional synthetic rates (FSRs) and degree of saturation, as well as messenger RNA (mRNA) expression of genes involved in lipid metabolism. In the first 2 h after meal consumption, forearm muscle [(2)H(2)]-labeled TAG extraction was higher in IR vs. control (P = 0.05). Fasting percentage saturation of muscle DAG was higher in IR vs. control (P = 0.016). No differences were observed for intramuscular TAG, DAG, FFA, and PL content, FSR, and muscle mRNA expression. In conclusion, increased muscle (hepatically derived) TAG extraction during postprandial conditions and increased saturation of intramuscular DAG are associated with insulin resistance, suggesting that disturbances in skeletal muscle FA handling could play a role in the development of whole body insulin resistance and type 2 diabetes. PMID:21331063

  4. Bone and Skeletal Muscle: Neighbors With Close Ties

    PubMed Central

    DiGirolamo, Douglas J; Kiel, Douglas P; Esser, Karyn A

    2016-01-01

    The musculoskeletal system evolved in mammals to perform diverse functions that include locomotion, facilitating breathing, protecting internal organs, and coordinating global energy expenditure. Bone and skeletal muscles involved with locomotion are both derived from somitic mesoderm and accumulate peak tissue mass synchronously, according to genetic information and environmental stimuli. Aging results in the progressive and parallel loss of bone (osteopenia) and skeletal muscle (sarcopenia) with profound consequences for quality of life. Age-associated sarcopenia results in reduced endurance, poor balance, and reduced mobility that predispose elderly individuals to falls, which more frequently result in fracture because of concomitant osteoporosis. Thus, a better understanding of the mechanisms underlying the parallel development and involution of these tissues is critical to developing new and more effective means to combat osteoporosis and sarcopenia in our increasingly aged population. This perspective highlights recent advances in our understanding of mechanisms coupling bone and skeletal muscle mass, and identify critical areas where further work is needed. PMID:23630111

  5. 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

  6. Substrate kinetics in patients with disorders of skeletal muscle metabolism.

    PubMed

    Ørngreen, Mette Cathrine

    2016-07-01

    The main purpose of the following studies was to investigate pathophysiological mechanisms in fat and carbohydrate metabolism and effect of nutritional interventions in patients with metabolic myopathies and in patients with severe muscle wasting. Yet there is no cure for patients with skeletal muscle disorders. The group of patients is heterozygous and this thesis is focused on patients with metabolic myopathies and low muscle mass due to severe muscle wasting. Disorders of fatty acid oxidation (FAO) are, along with myophosphorylase deficiency (McArdle disease), the most common inborn errors of metabolism leading to recurrent episodes of rhabdomyolysis in adults. Prolonged exercise, fasting, and fever are the main triggering factors for rhabdomyolysis in these conditions, and can be complicated by acute renal failure. Patients with low muscle mass are in risk of loosing their functional skills and depend on a wheel chair and respiratory support. We used nutritional interventions and metabolic studies with stable isotope technique and indirect calorimetry in patients with metabolic myopathies and patients with low muscle mass to get information of the metabolism of the investigated diseases, and to gain knowledge of the biochemical pathways of intermediary metabolism in human skeletal muscle. We have shown that patients with fat metabolism disorders in skeletal muscle affecting the transporting enzyme of fat into the mitochondria (carnitine palmitoyltransferase II deficiency) and affecting the enzyme responsible for breakdown of the long-chain fatty acids (very long chain acyl-CoA dehydrogenase deficiency) have a normal fatty acid oxidation at rest, but enzyme activity is too low to increase fatty acid oxidation during exercise. Furthermore, these patients benefit from a carbohydrate rich diet. Oppositely is exercise capacity worsened by a fat-rich diet in these patients. The patients also benefit from IV glucose, however, when glucose is given orally just before

  7. Functional heterogeneity of side population cells in skeletal muscle

    SciTech Connect

    Uezumi, Akiyoshi; Ojima, Koichi; Fukada, So-ichiro; Ikemoto, Madoka; Masuda, Satoru; Miyagoe-Suzuki, Yuko; Takeda, Shin'ichi . E-mail: takeda@ncnp.go.jp

    2006-03-17

    Skeletal muscle regeneration has been exclusively attributed to myogenic precursors, satellite cells. A stem cell-rich fraction referred to as side population (SP) cells also resides in skeletal muscle, but its roles in muscle regeneration remain unclear. We found that muscle SP cells could be subdivided into three sub-fractions using CD31 and CD45 markers. The majority of SP cells in normal non-regenerating muscle expressed CD31 and had endothelial characteristics. However, CD31{sup -}CD45{sup -} SP cells, which are a minor subpopulation in normal muscle, actively proliferated upon muscle injury and expressed not only several regulatory genes for muscle regeneration but also some mesenchymal lineage markers. CD31{sup -}CD45{sup -} SP cells showed the greatest myogenic potential among three SP sub-fractions, but indeed revealed mesenchymal potentials in vitro. These SP cells preferentially differentiated into myofibers after intramuscular transplantation in vivo. Our results revealed the heterogeneity of muscle SP cells and suggest that CD31{sup -}CD45{sup -} SP cells participate in muscle regeneration.

  8. Fat cell invasion in long-term denervated skeletal muscle.

    PubMed

    de Castro Rodrigues, Antonio; Andreo, Jesus Carlos; Rosa, Geraldo Marco; dos Santos, Nícolas Bertolaccini; Moraes, Luis Henrique Rapucci; Lauris, José Roberto P

    2007-01-01

    There are several differences between red and white muscles submitted to different experimental conditions, especially following denervation: a) denervation atrophy is more pronounced in red than white muscles; b) the size of the fibers in the red muscles does not vary between different parts of the muscle before and after denervation, when compared to white muscles; c) the regional difference in the white muscles initially more pronounced after denervation than red muscle; d) red muscle fibers and fibers of the deep white muscle present degenerative changes such as disordered myofibrils and sarcolemmal folds after long-term denervation; e) myotube-like fibers with central nuclei occur in the red muscle more rapidly than white after denervation. Denervation of skeletal muscles causes, in addition to fibers atrophy, loss of fibers with subsequent regeneration, but the extent of fat cell percentage invasion is currently unknown. The present article describes a quantitative study on fat cell invasion percentage in red m. soleus and white m. extensor digitorum longus (EDL) rat muscles at 7 weeks for up to 32 weeks postdenervation. The results indicate that the percentage of fat cells increase after denervation and it is steeper than the age-related fat invasion in normal muscles. The fat percentage invasion is more pronounced in red compared with white muscle. All experimental groups present a statistically significant difference as regard fat cell percentage invasion. PMID:17941108

  9. Skeletal muscle metabolism in hypokinetic rats

    NASA Technical Reports Server (NTRS)

    Tischler, M. E.

    1984-01-01

    Muscle growth, protein metabolism, and amino acid metabolism were studied in various groups of rats. Certain groups were adrenaliectomized; some rats were suspended while others (the controls) were weight bearing. Results show that: (1) metabolic changes in the extensor digitorum longus muscle of suspended rats are due primarily to increased circulating glucocorticoids; (2) metabolic changes in the soleus muscle due to higher steroid levels are probably potentiated by greater numbers of steroid receptors; and (3) not all metabolic responses of the soleus muscle to unloading are due to the elevated levels of glucocorticoids or the increased sensitivity of this muscle to these hormones.

  10. The mechanistic and ergogenic effects of phosphatidic acid in skeletal muscle.

    PubMed

    Shad, Brandon James; Smeuninx, Benoit; Atherton, Philip James; Breen, Leigh

    2015-12-01

    Skeletal muscle mass plays a vital role in locomotion, whole-body metabolic health, and is a positive predictor of longevity. It is well established the mammalian target of rapamycin (mTOR) is a central regulator of skeletal muscle protein turnover. The pursuit to find novel nutrient compounds or functional food sources that possess the ability to activate mTOR and promote skeletal muscle protein accretion has been on going. Over the last decade, a key role has been proposed for the phospholipid phosphatidic acid (PA) in mTOR activation. Mechanical load-induced (i.e., resistance exercise) intramuscular PA can directly bind to and activate mTOR. In addition, PA provided exogenously in cell culture heightens mTOR activity, albeit indirectly. Thus, endogenously generated PA and exogenous provision of PA appear to act through distinct mechanisms that converge on mTOR and, potentially, may amplify muscle protein synthesis. In support of this notion, limited evidence from humans suggests that resistance exercise training combined with oral supplemental PA enhances strength gains and muscle hypertrophy. However, the precise mechanisms underpinning the augmented muscle remodelling response with supplemental PA remain elusive. In this review, we will critically examine available evidence from cell cultures and animal and human experimental models to provide an overview of the mechanisms through which endogenous and exogenous PA may act to promote muscle anabolism, and discuss the potential for PA as a therapeutic tool to maintain or restore skeletal muscle mass in the context of ageing and disease. PMID:26566242

  11. Assessment of the Contractile Properties of Permeabilized Skeletal Muscle Fibers.

    PubMed

    Claflin, Dennis R; Roche, Stuart M; Gumucio, Jonathan P; Mendias, Christopher L; Brooks, Susan V

    2016-01-01

    Permeabilized individual skeletal muscle fibers offer the opportunity to evaluate contractile behavior in a system that is greatly simplified, yet physiologically relevant. Here we describe the steps required to prepare, permeabilize and preserve small samples of skeletal muscle. We then detail the procedures used to isolate individual fiber segments and attach them to an experimental apparatus for the purpose of controlling activation and measuring force generation. We also describe our technique for estimating the cross-sectional area of fiber segments. The area measurement is necessary for normalizing the absolute force to obtain specific force, a measure of the intrinsic force-generating capability of the contractile system. PMID:27492182

  12. Skeletal Muscle Laminopathies: A Review of Clinical and Molecular Features.

    PubMed

    Maggi, Lorenzo; Carboni, Nicola; Bernasconi, Pia

    2016-01-01

    LMNA-related disorders are caused by mutations in the LMNA gene, which encodes for the nuclear envelope proteins, lamin A and C, via alternative splicing. Laminopathies are associated with a wide range of disease phenotypes, including neuromuscular, cardiac, metabolic disorders and premature aging syndromes. The most frequent diseases associated with mutations in the LMNA gene are characterized by skeletal and cardiac muscle involvement. This review will focus on genetics and clinical features of laminopathies affecting primarily skeletal muscle. Although only symptomatic treatment is available for these patients, many achievements have been made in clarifying the pathogenesis and improving the management of these diseases. PMID:27529282

  13. Altered Myokine Secretion Is an Intrinsic Property of Skeletal Muscle in Type 2 Diabetes

    PubMed Central

    Ciaraldi, Theodore P.; Ryan, Alexander J.; Mudaliar, Sunder R.; Henry, Robert R.

    2016-01-01

    Skeletal muscle secretes factors, termed myokines. We employed differentiated human skeletal muscle cells (hSMC) cultured from Type 2 diabetic (T2D) and non-diabetic (ND) subjects to investigate the impact of T2D on myokine secretion. Following 24 hours of culture concentrations of selected myokines were determined to range over 4 orders of magnitude. T2D hSMC released increased amounts of IL6, IL8, IL15, TNFa, Growth Related Oncogene (GRO)a, monocyte chemotactic protein (MCP)-1, and follistatin compared to ND myotubes. T2D and ND hSMC secreted similar levels of IL1ß and vascular endothelial growth factor (VEGF). Treatment with the inflammatory agents lipopolysaccharide (LPS) or palmitate augmented the secretion of many myokines including: GROa, IL6, IL8, IL15, and TNFa, but did not consistently alter the protein content and/or phosphorylation of IkBa, p44/42 MAPK, p38 MAPK, c-Jun N-terminal kinase (JNK) and NF-kB, nor lead to consistent changes in basal and insulin-stimulated glucose uptake or free fatty acid oxidation. Conversely, treatment with pioglitazone or oleate resulted in modest reductions in the secretion of several myokines. Our results demonstrate that altered secretion of a number of myokines is an intrinsic property of skeletal muscle in T2D, suggesting a putative role of myokines in the response of skeletal muscle to T2D. PMID:27453994

  14. Isolation of Nuclei from Skeletal Muscle Satellite Cells and Myofibers for Use in Chromatin lmmunoprecipitation Assays

    PubMed Central

    Ohkawa, Yasuyuki; Mallappa, Chandrashekara; Dacwag Vallaster, Caroline S.; lmbalzano, Anthony N.

    2014-01-01

    Studies investigating mechanisms controlling gene regulation frequently examine specific DNA sequences using chromatin immunoprecipitation (ChIP) assays to determine whether specific regulatory factors or modified histones are present. While use of primary cells or cell line models for differentiating or differentiated tissue is widespread, the ability to assess factor binding and histone modification in tissue defines the events that occur in vivo and provides corroboration for studies in cultured cells. Many tissues can be analyzed with minimal modification to existing ChIP protocols that are designed for cultured cells; however, some tissues, such as skeletal muscle, are problematic in that accessibility of the cross-linking agent is limited. We describe a method to isolate skeletal muscle tissue nuclei suitable for use in ChIP protocols. Furthermore, we utilize a simple fractionation of digested skeletal muscle tissue that can separate mature myofibers from satellite cells, which are responsible for postnatal skeletal muscle regeneration, thereby allowing simultaneous preparation of nuclei from both cell types. PMID:22130858

  15. 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. PMID:25080109

  16. Therapeutic Approaches to Skeletal Muscle Repair and Healing

    PubMed Central

    Danna, Natalie R.; Beutel, Bryan G.; Campbell, Kirk A.; Bosco, Joseph A.

    2014-01-01

    Context: Skeletal muscle is comprised of a highly organized network of cells, neurovascular structures, and connective tissue. Muscle injury is typically followed by a well-orchestrated healing response that consists of the following phases: inflammation, regeneration, and fibrosis. This review presents the mechanisms of action and evidence supporting the effectiveness of various traditional and novel therapies at each phase of the skeletal muscle healing process. Evidence Acquisition: Relevant published articles were identified using MEDLINE (1978-2013). Study Design: Clinical review. Level of Evidence: Level 3. Results: To facilitate muscle healing, surgical techniques involving direct suture repair, as well as the implantation of innovative biologic scaffolds, have been developed. Nonsteroidal anti-inflammatory drugs may be potentially supplanted by nitric oxide and curcumin in modulating the inflammatory pathway. Studies in muscle regeneration have identified stem cells, myogenic factors, and β-agonists capable of enhancing the regenerative capabilities of injured tissue. Furthermore, transforming growth factor-β1 (TGF-β1) and, more recently, myostatin and the rennin-angiotensin system have been implicated in fibrous tissue formation; several antifibrotic agents have demonstrated the ability to disrupt these systems. Conclusion: Effective repair of skeletal muscle after severe injury is unlikely to be achieved with a single intervention. For full functional recovery of muscle there is a need to control inflammation, stimulate regeneration, and limit fibrosis. Strength-of-Recommendation Taxonomy (SORT): B PMID:24982709

  17. Maternal nutrient restriction affects properties of skeletal muscle in offspring

    PubMed Central

    Zhu, Mei J; Ford, Stephen P; Means, Warrie J; Hess, Bret W; Nathanielsz, Peter W; Du, Min

    2006-01-01

    Maternal nutrient restriction (NR) affects fetal development with long-term consequences on postnatal health of offspring, including predisposition to obesity and diabetes. Most studies have been conducted in fetuses in late gestation, and little information is available on the persistent impact of NR from early to mid-gestation on properties of offspring skeletal muscle, which was the aim of this study. Pregnant ewes were subjected to 50% NR from day 28–78 of gestation and allowed to deliver. The longissimus dorsi muscle was sampled from 8-month-old offspring. Maternal NR during early to mid-gestation decreased the number of myofibres in the offspring and increased the ratio of myosin IIb to other isoforms by 17.6 ± 4.9% (P < 0.05) compared with offspring of ad libitum fed ewes. Activity of carnitine palmitoyltransferase-1, a key enzyme controlling fatty acid oxidation, was reduced by 24.7 ± 4.5% (P < 0.05) in skeletal muscle of offspring of NR ewes and would contribute to increased fat accumulation observed in offspring of NR ewes. Intramuscular triglyceride content (IMTG) was increased in skeletal muscle of NR lambs, a finding which may be linked to predisposition to diabetes in offspring of NR mothers, since enhanced IMTG predisposes to insulin resistance in skeletal muscle. Proteomic analysis by two-dimensional gel electrophoresis demonstrated downregulation of several catabolic enzymes in 8-month-old offspring of NR ewes. These data demonstrate that the early to mid-gestation period is important for skeletal muscle development. Impaired muscle development during this stage of gestation affects the number and composition of fibres in offspring which may lead to long-term physiological consequences, including predisposition to obesity and diabetes. PMID:16763001

  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. Road to Exercise Mimetics: Targeting Nuclear Receptors in Skeletal Muscle

    PubMed Central

    Fan, Weiwei; Atkins, Annette R; Yu, Ruth T.; Downes, Michael; Evans, Ronald M.

    2014-01-01

    Skeletal muscle comprises the largest organ in the human body and is the major site for energy expenditure. It exhibits remarkable plasticity in response to physiological stimuli such as exercise. Physical exercise remodels skeletal muscle and enhances its capability to burn calories, which has been shown to be beneficial for many clinical conditions including metabolic syndrome and cancer. Nuclear receptors (NRs) comprise a class of transcription factors found only in metazoans that regulate major biological processes such as reproduction, development, and metabolism. Recent studies have demonstrated crucial roles for NRs and their co-regulators in regulating skeletal muscle energy metabolism and exercise-induced muscle remodeling. While nothing can fully replace exercise, development of exercise mimetics that enhance or even substitute for the beneficial effects of physical exercise would be of great benefit. The unique property of NRs that allows modulation by endogenous or synthetic ligands makes them bona fide therapeutic targets. In this review, we present an overview of the current understanding of NRs and their co-regulators in skeletal muscle oxidative metabolism and summarize recent progress in the development of exercise mimetics that target NRs and their co-regulators. PMID:24280961

  20. Functional classification of skeletal muscle networks. II. Applications to pathophysiology

    PubMed Central

    Wang, Yu; Winters, Jack

    2012-01-01

    In our preceding companion paper (Wang Y, Winters J, Subramaniam S. J Appl Physiol. doi: 10.1152/japplphysiol.01514.2011), we used extensive expression profile data on normal human subjects, in combination with legacy knowledge to classify skeletal muscle function into four models, namely excitation-activation, mechanical, metabolic, and signaling-production model families. In this paper, we demonstrate how this classification can be applied to study two well-characterized myopathies: amyotrophic lateral sclerosis (ALS) and Duchenne muscular dystrophy (DMD). Using skeletal muscle profile data from ALS and DMD patients compared with that from normal subjects, normal young in the case of DMD, we delineate molecular mechanisms that are causative and consequential to skeletal muscle dysfunction. In ALS, our analysis establishes the metabolic role and specifically identifies the mechanisms of calcium dysregulation and defects in mitochondrial transport of materials as important for muscle dysfunction. In DMD, we illustrate how impaired mechanical function is strongly coordinated with other three functional networks, resulting in transformation of the skeletal muscle into hybrid forms as a compensatory mechanism. Our functional models also provide, in exquisite detail, the mechanistic role of myriad proteins in these four families in normal and disease function. PMID:23085957

  1. Human skeletal muscle responses to spaceflight and possible countermeasures

    NASA Technical Reports Server (NTRS)

    Gollnick, Philip D.; Edgerton, V. Reggie; Saltin, Bengt

    1990-01-01

    The current status of knowledge concerning the effects of unweighting skeletal muscle is summarized. The results of both ground-based and space-based animal studies are reviewed which show that there is rapid loss in muscle mass, primarily in slow-twitch muscle, of the rat during unweighting of muscle. There is also a shift in the myosin isoforms with muscles such that slow-twitch muscles take on many of the characteristics of fast-twitch muscles. Ground-based studies in human suggest that programs of electrical stimulation can be developed to simulate normal muscular contractions. Attempts to develop countermeasures to the adverse effects of space travel on muscular functions in humans have not been successful to date.

  2. Prostaglandin E2/cyclooxygenase pathway in human skeletal muscle: influence of muscle fiber type and age.

    PubMed

    Liu, Sophia Z; Jemiolo, Bozena; Lavin, Kaleen M; Lester, Bridget E; Trappe, Scott W; Trappe, Todd A

    2016-03-01

    Prostaglandin E2 (PGE2) produced by the cyclooxygenase (COX) pathway regulates skeletal muscle protein turnover and exercise training adaptations. The purpose of this study was twofold: 1) define the PGE2/COX pathway enzymes and receptors in human skeletal muscle, with a focus on type I and II muscle fibers; and 2) examine the influence of aging on this pathway. Muscle biopsies were obtained from the soleus (primarily type I fibers) and vastus lateralis (proportionally more type II fibers than soleus) of young men and women (n = 8; 26 ± 2 yr), and from the vastus lateralis of young (n = 8; 25 ± 1 yr) and old (n = 12; 79 ± 2 yr) men and women. PGE2/COX pathway proteins [COX enzymes (COX-1 and COX-2), PGE2 synthases (cPGES, mPGES-1, and mPGES-2), and PGE2 receptors (EP1, EP2, EP3, and EP4)] were quantified via Western blot. COX-1, cPGES, mPGES-2, and all four PGE2 receptors were detected in all skeletal muscle samples examined. COX-1 (P < 0.1) and mPGES-2 were ∼20% higher, while EP3 was 99% higher and EP4 57% lower in soleus compared with vastus lateralis (P < 0.05). Aging did not change the level of skeletal muscle COX-1, while cPGES increased 45% and EP1 (P < 0.1), EP3, and EP4 decreased ∼33% (P < 0.05). In summary, PGE2 production capacity and receptor levels are different in human skeletal muscles with markedly different type I and II muscle fiber composition. In aging skeletal muscle, PGE2 production capacity is elevated and receptor levels are downregulated. These findings have implications for understanding the regulation of skeletal muscle adaptations to exercise and aging by the PGE2/COX pathway and related inhibitors. PMID:26607246

  3. Glucocorticoid-induced skeletal muscle atrophy.

    PubMed

    Schakman, O; Kalista, S; Barbé, C; Loumaye, A; Thissen, J P

    2013-10-01

    Many pathological states characterized by muscle atrophy (e.g., sepsis, cachexia, starvation, metabolic acidosis and severe insulinopenia) are associated with an increase in circulating glucocorticoids (GC) levels, suggesting that GC could trigger the muscle atrophy observed in these conditions. GC-induced muscle atrophy is characterized by fast-twitch, glycolytic muscles atrophy illustrated by decreased fiber cross-sectional area and reduced myofibrillar protein content. GC-induced muscle atrophy results from increased protein breakdown and decreased protein synthesis. Increased muscle proteolysis, in particular through the activation of the ubiquitin proteasome and the lysosomal systems, is considered to play a major role in the catabolic action of GC. The stimulation by GC of these two proteolytic systems is mediated through the increased expression of several Atrogenes ("genes involved in atrophy"), such as FOXO, Atrogin-1, and MuRF-1. The inhibitory effect of GC on muscle protein synthesis is thought to result mainly from the inhibition of the mTOR/S6 kinase 1 pathway. These changes in muscle protein turnover could be explained by changes in the muscle production of two growth factors, namely Insulin-like Growth Factor (IGF)-I, a muscle anabolic growth factor and Myostatin, a muscle catabolic growth factor. This review will discuss the recent progress made in the understanding of the mechanisms involved in GC-induced muscle atrophy and consider the implications of these advancements in the development of new therapeutic approaches for treating GC-induced myopathy. This article is part of a Directed Issue entitled: Molecular basis of muscle wasting. PMID:23806868

  4. Changes in skeletal muscle with aging: effects of exercise training.

    PubMed

    Rogers, M A; Evans, W J

    1993-01-01

    There is an approximate 30% decline in muscle strength and a 40% reduction in muscle area between the second and seventh decades of life. Thus, the loss of muscle mass with aging appears to be the major factor in the age-related loss of muscle strength. The loss of muscle mass is partially due to a significant decline in the numbers of both Type I and Type II muscle fibers plus a decrease in the size of the muscle cells, with the Type II fibers showing a preferential atrophy. There appears to be no loss of glycolytic capacity in senescent skeletal muscle whereas muscle oxidative enzyme activity and muscle capillarization decrease by about 25%. Vigorous endurance exercise training in older people, where the stimulus is progressively increased, elicits a proliferation of muscle capillaries, an increase in oxidative enzyme activity, and a significant improvement in VO2max. Likewise, progressive resistive training in older individuals results in muscle hypertrophy and increased strength, if the training stimulus is of a sufficient intensity and duration. Since older individuals adapt to resistive and endurance exercise training in a similar fashion to young people, the decline in the muscle's metabolic and force-producing capacity can no longer be considered as an inevitable consequence of the aging process. Rather, the adaptations in aging skeletal muscle to exercise training may prevent sarcopenia, enhance the ease of carrying out the activities of daily living, and exert a beneficial effect on such age-associated diseases as Type II diabetes, coronary artery disease, hypertension, osteoporosis, and obesity. PMID:8504850

  5. Mathematically modeling the effects of electrically stimulating skeletal muscle.

    PubMed

    Davidson, J B; Kim, J; Cheng, L K; Röhrle, O; Shorten, P R; Soboleva, T K; Clarke, R D; Pullan, A J

    2006-01-01

    A framework for modeling the activation of skeletal muscle is presented for studying functional electrical stimulation. A mathematical model of the cellular responses of skeletal muscle, created at AgResearch (Ruakura, New Zealand www.agresearch.co.nz), has been integrated with an anatomical, finite element model of the semitendinosus muscle, which was constructed from CT scans of the hind limb of a sheep. The tibial nerve was also constructed from digitized CT scans, and has been modeled using the Hodgkin Huxley neural model. The relevant cellular equations have been solved over these geometries. The results obtained, i.e speed of action potential propagation through the nerve and muscle, and the duration of twitch force, agree with published values. PMID:17946255

  6. Transcriptional regulation of decreased protein synthesis during skeletal muscle unloading

    NASA Technical Reports Server (NTRS)

    Howard, G.; Steffen, J. M.; Geoghegan, T. E.

    1989-01-01

    The regulatory role of transcriptional alterations in unloaded skeletal muscles was investigated by determining levels of total muscle RNA and mRNA fractions in soleus, gastrocnemius, and extensor digitorum longus (EDL) of rats subjected to whole-body suspension for up to 7 days. After 7 days, total RNA and mRNA contents were lower in soleus and gastrocnemius, compared with controls, but the concentrations of both RNAs per g muscle were unaltered. Alpha-actin mRNA (assessed by dot hybridization) was significantly reduced in soleus after 1, 3, and 7 days of suspension and in gastrocnemius after 3 and 7 days, but was unchanged in EDL. Protein synthesis directed by RNA extracted from soleus and EDL indicated marked alteration in mRNAs coding for several small proteins. Results suggest that altered transcription and availability of specific mRNAs contribute significantly to the regulation of protein synthesis during skeletal muscle unloading.

  7. Leucine supplementation improves regeneration of skeletal muscles from old rats.

    PubMed

    Pereira, Marcelo G; Silva, Meiricris T; da Cunha, Fernanda M; Moriscot, Anselmo S; Aoki, Marcelo S; Miyabara, Elen H

    2015-12-01

    The decreased regenerative capacity of old skeletal muscles involves disrupted turnover of proteins. This study investigated whether leucine supplementation in old rats could improve muscle regenerative capacity. Young and old male Wistar rats were supplemented with leucine; then, the muscles were cryolesioned and examined after 3 and 10 days. Leucine supplementation attenuated the decrease in the expression of eukaryotic translation initiation factor 4E binding protein 1 (4E-BP1) and eukaryotic translation initiation factor 4E (eIF4E) in young and old muscles on day 3 post-injury and promoted an increase in the cross-sectional area of regenerating myofibers from both young and old soleus muscles on day 10 post-injury. This supplementation decreased the levels of ubiquitinated proteins and increased the proteasome activity in young regenerating muscles, but the opposite effect was observed in old regenerating muscles. Moreover, leucine decreased the inflammation area and induced an increase in the number of proliferating satellite cells in both young and old muscles. Our results suggest that leucine supplementation improves the regeneration of skeletal muscles from old rats, through the preservation of certain biological responses upon leucine supplementation. Such responses comprise the decrease in the inflammation area, increase in the number of proliferating satellite cells and size of regenerating myofibers, combined with the modulation of components of the phosphoinositide 3-kinase/Akt-protein kinase B/mammalian target of rapamycin (PI3K/Akt/mTOR) pathway and ubiquitin-proteasome system. PMID:26481769

  8. Inactivity amplifies the catabolic response of skeletal muscle to cortisol

    NASA Technical Reports Server (NTRS)

    Ferrando, A. A.; Stuart, C. A.; Sheffield-Moore, M.; Wolfe, R. R.

    1999-01-01

    Severe injury or trauma is accompanied by both hypercortisolemia and prolonged inactivity or bed rest (BR). Trauma and BR alone each result in a loss of muscle nitrogen, albeit through different metabolic alterations. Although BR alone can result in a 2-3% loss of lean body mass, the effects of severe trauma can be 2- to 3-fold greater. We investigated the combined effects of hypercortisolemia and prolonged inactivity on muscle protein metabolism in healthy volunteers. Six males were studied before and after 14 days of strict BR using a model based on arteriovenous sampling and muscle biopsy. Fractional synthesis and breakdown rates of skeletal muscle protein were also directly calculated. Each assessment of protein metabolism was conducted during a 12-h infusion of hydrocortisone sodium succinate (120 microg/kg x h), resulting in blood cortisol concentrations that mimic severe injury (approximately 31 microg/dL). After 14 days of strict BR, hypercortisolemia increased phenylalanine efflux from muscle by 3-fold (P < 0.05). The augmented negative amino acid balance was the result of an increased muscle protein breakdown (P < 0.05) without a concomitant change in muscle protein synthesis. Muscle efflux of glutamine and alanine increased significantly after bed rest due to a significant increase in de novo synthesis (P < 0.05). Thus, inactivity sensitizes skeletal muscle to the catabolic effects of hypercortisolemia. Furthermore, these effects on healthy volunteers are analogous to those seen after severe injury.

  9. Metformin Protects Skeletal Muscle from Cardiotoxin Induced Degeneration

    PubMed Central

    Langone, Francesca; Cannata, Stefano; Fuoco, Claudia; Lettieri Barbato, Daniele; Testa, Stefano; Nardozza, Aurelio Pio; Ciriolo, Maria Rosa; Castagnoli, Luisa; Gargioli, Cesare; Cesareni, Gianni

    2014-01-01

    The skeletal muscle tissue has a remarkable capacity to regenerate upon injury. Recent studies have suggested that this regenerative process is improved when AMPK is activated. In the muscle of young and old mice a low calorie diet, which activates AMPK, markedly enhances muscle regeneration. Remarkably, intraperitoneal injection of AICAR, an AMPK agonist, improves the structural integrity of muscles of dystrophin-deficient mdx mice. Building on these observations we asked whether metformin, a powerful anti-hyperglycemic drug, which indirectly activates AMPK, affects the response of skeletal muscle to damage. In our conditions, metformin treatment did not significantly influence muscle regeneration. On the other hand we observed that the muscles of metformin treated mice are more resilient to cardiotoxin injury displaying lesser muscle damage. Accordingly myotubes, originated in vitro from differentiated C2C12 myoblast cell line, become more resistant to cardiotoxin damage after pre-incubation with metformin. Our results indicate that metformin limits cardiotoxin damage by protecting myotubes from necrosis. Although the details of the molecular mechanisms underlying the protective effect remain to be elucidated, we report a correlation between the ability of metformin to promote resistance to damage and its capacity to counteract the increment of intracellular calcium levels induced by cardiotoxin treatment. Since increased cytoplasmic calcium concentrations characterize additional muscle pathological conditions, including dystrophies, metformin treatment could prove a valuable strategy to ameliorate the conditions of patients affected by dystrophies. PMID:25461598

  10. Potential of laryngeal muscle regeneration using induced pluripotent stem cell-derived skeletal muscle cells.

    PubMed

    Dirja, Bayu Tirta; Yoshie, Susumu; Ikeda, Masakazu; Imaizumi, Mitsuyoshi; Nakamura, Ryosuke; Otsuki, Koshi; Nomoto, Yukio; Wada, Ikuo; Hazama, Akihiro; Omori, Koichi

    2016-04-01

    Conclusion Induced pluripotent stem (iPS) cells may be a new potential cell source for laryngeal muscle regeneration in the treatment of vocal fold atrophy after recurrent laryngeal nerve paralysis. Objectives Unilateral vocal fold paralysis can lead to degeneration, atrophy, and loss of force of the thyroarytenoid muscle. At present, there are some treatments such as thyroplasty, arytenoid adduction, and vocal fold injection. However, such treatments cannot restore reduced mass of the thyroarytenoid muscle. iPS cells have been recognized as supplying a potential resource for cell transplantation. The aim of this study was to assess the effectiveness of the use of iPS cells for the regeneration of laryngeal muscle through the evaluation of both in vitro and in vivo experiments. Methods Skeletal muscle cells were generated from tdTomato-labeled iPS cells using embryoid body formation. Differentiation into skeletal muscle cells was analyzed by gene expression and immunocytochemistry. The tdTomato-labeled iPS cell-derived skeletal muscle cells were transplanted into the left atrophied thyroarytenoid muscle. To evaluate the engraftment of these cells after transplantation, immunohistochemistry was performed. Results The tdTomato-labeled iPS cells were successfully differentiated into skeletal muscle cells through an in vitro experiment. These cells survived in the atrophied thyroarytenoid muscle after transplantation. PMID:26824385

  11. Muscle-specific GSK-3β ablation accelerates regeneration of disuse-atrophied skeletal muscle.

    PubMed

    Pansters, Nicholas A M; Schols, Annemie M W J; Verhees, Koen J P; de Theije, Chiel C; Snepvangers, Frank J; Kelders, Marco C J M; Ubags, Niki D J; Haegens, Astrid; Langen, Ramon C J

    2015-03-01

    Muscle wasting impairs physical performance, increases mortality and reduces medical intervention efficacy in chronic diseases and cancer. Developing proficient intervention strategies requires improved understanding of the molecular mechanisms governing muscle mass wasting and recovery. Involvement of muscle protein- and myonuclear turnover during recovery from muscle atrophy has received limited attention. The insulin-like growth factor (IGF)-I signaling pathway has been implicated in muscle mass regulation. As glycogen synthase kinase 3 (GSK-3) is inhibited by IGF-I signaling, we hypothesized that muscle-specific GSK-3β deletion facilitates the recovery of disuse-atrophied skeletal muscle. Wild-type mice and mice lacking muscle GSK-3β (MGSK-3β KO) were subjected to a hindlimb suspension model of reversible disuse-induced muscle atrophy and followed during recovery. Indices of muscle mass, protein synthesis and proteolysis, and post-natal myogenesis which contribute to myonuclear accretion, were monitored during the reloading of atrophied muscle. Early muscle mass recovery occurred more rapidly in MGSK-3β KO muscle. Reloading-associated changes in muscle protein turnover were not affected by GSK-3β ablation. However, coherent effects were observed in the extent and kinetics of satellite cell activation, proliferation and myogenic differentiation observed during reloading, suggestive of increased myonuclear accretion in regenerating skeletal muscle lacking GSK-3β. This study demonstrates that muscle mass recovery and post-natal myogenesis from disuse-atrophy are accelerated in the absence of GSK-3β. PMID:25496993

  12. Ultrastructural alterations in skeletal muscle fibers of rats after exercise

    NASA Technical Reports Server (NTRS)

    Akuzawa, M.; Hataya, M.

    1982-01-01

    Ultrastructural alterations in skeletal muscle fibers were electron microscopically studied in rats forced to run on the treadmill until all-out. When they were mild and limited to relatively small areas, the reconstruction of filaments ensued within 10 days without infiltration of cells. When they were severe and extensive, phagocytes infiltrated in the lesions and removed degenerative sacroplasmic debris from muscle fibers. A little later, myoblasts appeared and regeneration was accomplished in 30 days in much the same manner as in myogenesis.

  13. Statin Therapy Alters Lipid Storage in Diabetic Skeletal Muscle

    PubMed Central

    Rebalka, Irena A.; Raleigh, Matthew J.; Snook, Laelie A.; Rebalka, Alexandra N.; MacPherson, Rebecca E. K.; Wright, David C.; Schertzer, Jonathan D.; Hawke, Thomas J.

    2016-01-01

    While statins significantly reduce cholesterol levels and thereby reduce the risk of cardiovascular disease, the development of myopathy with statin use is a significant clinical side effect. Recent guidelines recommend increasing inclusion criteria for statin treatment in diabetic individuals; however, the impact of statins on skeletal muscle health in those with diabetes (who already suffer from impairments in muscle health) is ill defined. Here, we investigate the effects of fluvastatin treatment on muscle health in wild type (WT) and streptozotocin (STZ)-induced diabetic mice. WT and STZ-diabetic mice received diet enriched with 600 mg/kg fluvastatin or control chow for 24 days. Muscle morphology, intra and extracellular lipid levels, and lipid transporter content were investigated. Our findings indicate that short-term fluvastatin administration induced a myopathy that was not exacerbated by the presence of STZ-induced diabetes. Fluvastatin significantly increased ectopic lipid deposition within the muscle of STZ-diabetic animals, findings that were not seen with diabetes or statin treatment alone. Consistent with this observation, only fluvastatin-treated diabetic mice downregulated protein expression of lipid transporters FAT/CD36 and FABPpm in their skeletal muscle. No differences in FAT/CD36 or FABPpm mRNA content were observed. Altered lipid compartmentalization resultant of a downregulation in lipid transporter content in STZ-induced diabetic skeletal muscle was apparent in the current investigation. Given the association between ectopic lipid deposition in skeletal muscle and the development of insulin-resistance, our findings highlight the necessity for more thorough investigations into the impact of statins in humans with diabetes. PMID:27486434

  14. Statin Therapy Alters Lipid Storage in Diabetic Skeletal Muscle.

    PubMed

    Rebalka, Irena A; Raleigh, Matthew J; Snook, Laelie A; Rebalka, Alexandra N; MacPherson, Rebecca E K; Wright, David C; Schertzer, Jonathan D; Hawke, Thomas J

    2016-01-01

    While statins significantly reduce cholesterol levels and thereby reduce the risk of cardiovascular disease, the development of myopathy with statin use is a significant clinical side effect. Recent guidelines recommend increasing inclusion criteria for statin treatment in diabetic individuals; however, the impact of statins on skeletal muscle health in those with diabetes (who already suffer from impairments in muscle health) is ill defined. Here, we investigate the effects of fluvastatin treatment on muscle health in wild type (WT) and streptozotocin (STZ)-induced diabetic mice. WT and STZ-diabetic mice received diet enriched with 600 mg/kg fluvastatin or control chow for 24 days. Muscle morphology, intra and extracellular lipid levels, and lipid transporter content were investigated. Our findings indicate that short-term fluvastatin administration induced a myopathy that was not exacerbated by the presence of STZ-induced diabetes. Fluvastatin significantly increased ectopic lipid deposition within the muscle of STZ-diabetic animals, findings that were not seen with diabetes or statin treatment alone. Consistent with this observation, only fluvastatin-treated diabetic mice downregulated protein expression of lipid transporters FAT/CD36 and FABPpm in their skeletal muscle. No differences in FAT/CD36 or FABPpm mRNA content were observed. Altered lipid compartmentalization resultant of a downregulation in lipid transporter content in STZ-induced diabetic skeletal muscle was apparent in the current investigation. Given the association between ectopic lipid deposition in skeletal muscle and the development of insulin-resistance, our findings highlight the necessity for more thorough investigations into the impact of statins in humans with diabetes. PMID:27486434

  15. Voluntary Movement Controlled by the Surface EMG Signal for Tissue-Engineered Skeletal Muscle on a Gripping Tool

    PubMed Central

    Kabumoto, Ken-ichiro; Hoshino, Takayuki; Akiyama, Yoshitake

    2013-01-01

    We have developed a living prosthesis consisting of a living muscle-powered device, which is controlled by neuronal signals to recover some of the functions of a lost extremity. A tissue-engineered skeletal muscle was fabricated with two anchorage points from a primary rat myoblast cultured in a collagen Matrigel mixed gel. Differentiation to the skeletal muscle was confirmed in the tissue-engineered skeletal muscle, and the contraction force increased with increasing frequency of electric stimulation. Then, the tissue-engineered skeletal muscle was assembled into a gripper-type microhand. The tissue-engineered skeletal muscle of the microhand was stimulated electrically, which was then followed by the voluntary movement of the subject's hand. The signal of the surface electromyogram from a subject was processed to mimic the firing spikes of a neuromuscular junction to control the contraction of the tissue-engineered skeletal muscle. The tele-operation of the microhand was demonstrated by optical microscope observations. PMID:23444880

  16. Calsequestrins in skeletal and cardiac muscle from adult Danio rerio.

    PubMed

    Furlan, Sandra; Mosole, Simone; Murgia, Marta; Nagaraj, Nagarjuna; Argenton, Francesco; Volpe, Pompeo; Nori, Alessandra

    2016-04-01

    Calsequestrin (Casq) is a high capacity, low affinity Ca(2+)-binding protein, critical for Ca(2+)-buffering in cardiac and skeletal muscle sarcoplasmic reticulum. All vertebrates have multiple genes encoding for different Casq isoforms. Increasing interest has been focused on mammalian and human Casq genes since mutations of both cardiac (Casq2) and skeletal muscle (Casq1) isoforms cause different, and sometime severe, human pathologies. Danio rerio (zebrafish) is a powerful model for studying function and mutations of human proteins. In this work, expression, biochemical properties cellular and sub-cellular localization of D. rerio native Casq isoforms are investigated. By quantitative PCR, three mRNAs were detected in skeletal muscle and heart with different abundances. Three zebrafish Casqs: Casq1a, Casq1b and Casq2 were identified by mass spectrometry (Data are available via ProteomeXchange with identifier PXD002455). Skeletal and cardiac zebrafish calsequestrins share properties with mammalian Casq1 and Casq2. Skeletal Casqs were found primarily, but not exclusively, at the sarcomere Z-line level where terminal cisternae of sarcoplasmic reticulum are located. PMID:26585961

  17. Myopathic changes in murine skeletal muscle lacking synemin

    PubMed Central

    García-Pelagio, Karla P.; Muriel, Joaquin; O'Neill, Andrea; Desmond, Patrick F.; Lovering, Richard M.; Lund, Linda; Bond, Meredith

    2015-01-01

    Diseases of striated muscle linked to intermediate filament (IF) proteins are associated with defects in the organization of the contractile apparatus and its links to costameres, which connect the sarcomeres to the cell membrane. Here we study the role in skeletal muscle of synemin, a type IV IF protein, by examining mice null for synemin (synm-null). Synm-null mice have a mild skeletal muscle phenotype. Tibialis anterior (TA) muscles show a significant decrease in mean fiber diameter, a decrease in twitch and tetanic force, and an increase in susceptibility to injury caused by lengthening contractions. Organization of proteins associated with the contractile apparatus and costameres is not significantly altered in the synm-null. Elastimetry of the sarcolemma and associated contractile apparatus in extensor digitorum longus myofibers reveals a reduction in tension consistent with an increase in sarcolemmal deformability. Although fatigue after repeated isometric contractions is more marked in TA muscles of synm-null mice, the ability of the mice to run uphill on a treadmill is similar to controls. Our results suggest that synemin contributes to linkage between costameres and the contractile apparatus and that the absence of synemin results in decreased fiber size and increased sarcolemmal deformability and susceptibility to injury. Thus synemin plays a moderate but distinct role in fast twitch skeletal muscle. PMID:25567810

  18. Skeletal muscle disorders associated with selenium deficiency in humans.

    PubMed

    Chariot, Patrick; Bignani, Olivier

    2003-06-01

    Skeletal muscle disorders manifested by muscle pain, fatigue, proximal weakness, and serum creatine kinase (CK) elevation have been reported in patients with selenium deficiency. The object of this report was to review the conditions in which selenium deficiency is associated with human skeletal muscle disorders and to evaluate the importance of mitochondrial alterations in these disorders. A systematic literature review using the Medline database and Cochrane Library provided 38 relevant articles. The main conditions associated with selenium deficiency fell into three categories: (1) insufficient selenium intake in low soil-selenium areas; (2) parenteral or enteral nutrition, or malabsorption; and (3) chronic conditions associated with oxidative stress, such as chronic alcohol abuse and human immunodeficiency virus (HIV) infection. In low soil-selenium areas, reversibility of muscle symptoms was similar after selenium supplementation and placebo administration, suggesting a role for other factors in the development of disease. In parenteral or enteral nutrition, or malabsorption, muscle symptoms improved after selenium supplementation in 18 of 19 patients (median delay: 4 weeks). The reason that only a minority of selenium-deficient patients present with skeletal muscle disorders is unclear and is possibly related to cofactors, such as viral infections and drugs. Prospective studies of selenium-deficient myopathies would be useful in critically ill patients, alcohol abusers, and HIV-infected patients. PMID:12766976

  19. Novel inhibition of contractility by wortmannin in skeletal muscle

    PubMed Central

    Hong, S J; Chang, C C

    1998-01-01

    The effects of wortmannin and 2-(4-morpholinyl)-8-phenyl-1[4H]-benzopyran-4-one (LY294002), inhibitors of phosphatidylinositol 3-kinase, on the contractile responses of murine skeletal muscle were studied. Wortmannin (10–100 μM) suppressed twitch and tetanic contraction evoked by field stimulation of diaphragm without causing elevation of muscle tone. The inhibition was quasi-irreversible with IC50∼15 μM. In contrast, LY294002 increased twitch responses and elevated muscle tone.Wortmannin reversibly depressed the maximal slope of action potential upstroke by ∼40% and inhibited the membrane depolarization and spontaneous burst of action potential induced by crotamine, a polypeptide toxin that activates the Na+ channel of skeletal muscle.Wortmannin inhibited contractures evoked by high K+, ryanodine and caffeine, but potentiated the contracture induced by rapamycin, which binds to myoplasmic FK506 binding protein, an immunophilin closely associated with the ryanodine receptor. The contractures elicited by cardiotoxin, which disrupts the integrity of sarcolemma and thereby elevates `myoplasmic' Ca2+ level, were suppressed only slightly.In placed left atrium and ventricular strip, wortmannin and LY294002 produced a positive inotropic effect.The results suggest that, in addition to depressing the Ca2+ mobilization from sarcoplasmic reticulum, wortmannin exerts a novel inhibitory action on the excitation-contraction coupling in skeletal muscle but not in cardiac muscle. PMID:9692768

  20. 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. PMID:26554747

  1. Acylated and unacylated ghrelin impair skeletal muscle atrophy in mice

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cachexia is a wasting syndrome associated with cancer, AIDS, multiple sclerosis, and several other disease states. It is characterized by weight loss, fatigue, loss of appetite, and skeletal muscle atrophy and is associated with poor patient prognosis, making it an important treatment target. Ghreli...

  2. MicroRNA Transcriptome Profiles During Swine Skeletal Muscle Development

    Technology Transfer Automated Retrieval System (TEKTRAN)

    MicroRNA (miR) are a class of small RNAs that regulate gene expression by inhibiting translation of protein encoding transcripts. To evaluate the role of miR in skeletal muscle of swine, global microRNA abundance was measured at specific developmental stages including proliferating satellite cells,...

  3. In utero Undernutrition Programs Skeletal and Cardiac Muscle Metabolism

    PubMed Central

    Beauchamp, Brittany; Harper, Mary-Ellen

    2016-01-01

    In utero undernutrition is associated with increased risk for insulin resistance, obesity, and cardiovascular disease during adult life. A common phenotype associated with low birth weight is reduced skeletal muscle mass. Given the central role of skeletal muscle in whole body metabolism, alterations in its mass as well as its metabolic characteristics may contribute to disease risk. This review highlights the metabolic alterations in cardiac and skeletal muscle associated with in utero undernutrition and low birth weight. These tissues have high metabolic demands and are known to be sites of major metabolic dysfunction in obesity, type 2 diabetes, and cardiovascular disease. Recent research demonstrates that mitochondrial energetics are decreased in skeletal and cardiac muscles of adult offspring from undernourished mothers. These effects apparently lead to the development of a thrifty phenotype, which may represent overall a compensatory mechanism programmed in utero to handle times of limited nutrient availability. However, in an environment characterized by food abundance, the effects are maladaptive and increase adulthood risks of metabolic disease. PMID:26779032

  4. Functional Overload Enhances Satellite Cell Properties in Skeletal Muscle.

    PubMed

    Fujimaki, Shin; Machida, Masanao; Wakabayashi, Tamami; Asashima, Makoto; Takemasa, Tohru; Kuwabara, Tomoko

    2016-01-01

    Skeletal muscle represents a plentiful and accessible source of adult stem cells. Skeletal-muscle-derived stem cells, termed satellite cells, play essential roles in postnatal growth, maintenance, repair, and regeneration of skeletal muscle. Although it is well known that the number of satellite cells increases following physical exercise, functional alterations in satellite cells such as proliferative capacity and differentiation efficiency following exercise and their molecular mechanisms remain unclear. Here, we found that functional overload, which is widely used to model resistance exercise, causes skeletal muscle hypertrophy and converts satellite cells from quiescent state to activated state. Our analysis showed that functional overload induces the expression of MyoD in satellite cells and enhances the proliferative capacity and differentiation potential of these cells. The changes in satellite cell properties coincided with the inactivation of Notch signaling and the activation of Wnt signaling and likely involve modulation by transcription factors of the Sox family. These results indicate the effects of resistance exercise on the regulation of satellite cells and provide insight into the molecular mechanism of satellite cell activation following physical exercise. PMID:26779264

  5. Redox Signaling in Skeletal Muscle: Role of Aging and Exercise

    ERIC Educational Resources Information Center

    Ji, Li Li

    2015-01-01

    Skeletal muscle contraction is associated with the production of ROS due to altered O[subscript 2] distribution and flux in the cell. Despite a highly efficient antioxidant defense, a small surplus of ROS, such as hydrogen peroxide and nitric oxide, may serve as signaling molecules to stimulate cellular adaptation to reach new homeostasis largely…

  6. Adipose tissue and skeletal muscle blood flow during mental stress

    SciTech Connect

    Linde, B.; Hjemdahl, P.; Freyschuss, U.; Juhlin-Dannfelt, A.

    1989-01-01

    Mental stress (a modified Stroop color word conflict test (CWT)) increased adipose tissue blood flow (ATBF; 133Xe clearance) by 70% and reduced adipose tissue vascular resistance (ATR) by 25% in healthy male volunteers. The vasculatures of adipose tissue (abdomen as well as thigh), skeletal muscle of the calf (133Xe clearance), and the entire calf (venous occlusion plethysmography) responded similarly. Arterial epinephrine (Epi) and glycerol levels were approximately doubled by stress. Beta-Blockade by metoprolol (beta 1-selective) or propranolol (nonselective) attenuated CWT-induced tachycardia similarly. Metoprolol attenuated stress-induced vasodilation in the calf and tended to do so in adipose tissue. Propranolol abolished vasodilation in the calf and resulted in vasoconstriction during CWT in adipose tissue. Decreases in ATR, but not in skeletal muscle or calf vascular resistances, were correlated to increases in arterial plasma glycerol (r = -0.42, P less than 0.05), whereas decreases in skeletal muscle and calf vascular resistances, but not in ATR, were correlated to increases in arterial Epi levels (r = -0.69, P less than 0.01; and r = -0.43, P less than 0.05, respectively). The results suggest that mental stress increases nutritive blood flow in adipose tissue and skeletal muscle considerably, both through the elevation of perfusion pressure and via vasodilatation. Withdrawal of vasoconstrictor nerve activity, vascular beta 2-adrenoceptor stimulation by circulating Epi, and metabolic mechanisms (in adipose tissue) may contribute to the vasodilatation.

  7. Skeletal muscle PGC-1α modulates systemic ketone body homeostasis and ameliorates diabetic hyperketonemia in mice

    PubMed Central

    Svensson, Kristoffer; Albert, Verena; Cardel, Bettina; Salatino, Silvia; Handschin, Christoph

    2016-01-01

    Ketone bodies are crucial energy substrates during states of low carbohydrate availability. However, an aberrant regulation of ketone body homeostasis can lead to complications such as diabetic ketoacidosis. Exercise and diabetes affect systemic ketone body homeostasis, but the regulation of ketone body metabolism is still enigmatic. Using mice with either a knockout or overexpression of the peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) in skeletal muscle, we show that PGC-1α regulates ketolytic gene transcription in muscle. Furthermore, ketone body homeostasis of these mice was investigated during fasting, exercise, ketogenic diet feeding and after streptozotocin injection. In response to these ketogenic stimuli, we show that modulation of PGC-1α levels in muscle affects systemic ketone body homeostasis. Moreover, our data demonstrate that skeletal muscle PGC-1α is necessary for the enhanced ketolytic capacity in response to exercise training and overexpression of PGC-1α in muscle enhances systemic ketolytic capacity and is sufficient to ameliorate diabetic hyperketonemia in mice. Using cultured myotubes, we also show that the transcription factor estrogen related receptor α (ERRα) is a partner of PGC-1α in the regulation of ketolytic gene transcription. Collectively, these results demonstrate a central role of skeletal muscle PGC-1α in the transcriptional regulation of systemic ketolytic capacity. PMID:26849960

  8. Non-invasive measurement of glucose uptake of skeletal muscle tissue models using a glucose nanobiosensor.

    PubMed

    Obregón, Raquel; Ahadian, Samad; Ramón-Azcón, Javier; Chen, Luyang; Fujita, Takeshi; Shiku, Hitoshi; Chen, Mingwei; Matsue, Tomokazu

    2013-12-15

    Skeletal muscle tissues play a significant role to maintain the glucose level of whole body and any dysfunction of this tissue leads to the diabetes disease. A culture medium was created in which the muscle cells could survive for a long time and meanwhile it did not interfere with the glucose sensing. We fabricated a model of skeletal muscle tissues in vitro to monitor its glucose uptake. A nanoporous gold as a high sensitive nanobiosensor was then successfully developed and employed to detect the glucose uptake of the tissue models in this medium upon applying the electrical stimulation in a rapid, and non-invasive approach. The response of the glucose sensor was linear in a wide concentration range of 1-50 mM, with a detection limit of 3 μM at a signal-to-noise ratio of 3.0. The skeletal muscle tissue was electrically stimulated during 24 h and glucose uptake was monitored during this period. During the first 3 h of stimulation, electrically stimulated muscle tissue consumed almost twice the amount of glucose than counterpart non-stimulated sample. In total, the glucose consumption of muscle tissues was higher for the electrically stimulated tissues compared to those without applying the electrical field. PMID:23856563

  9. Lifelong physical exercise delays age-associated skeletal muscle decline.

    PubMed

    Zampieri, S; Pietrangelo, L; Loefler, S; Fruhmann, H; Vogelauer, M; Burggraf, S; Pond, A; Grim-Stieger, M; Cvecka, J; Sedliak, M; Tirpáková, V; Mayr, W; Sarabon, N; Rossini, K; Barberi, L; De Rossi, M; Romanello, V; Boncompagni, S; Musarò, A; Sandri, M; Protasi, F; Carraro, U; Kern, H

    2015-02-01

    Aging is usually accompanied by a significant reduction in muscle mass and force. To determine the relative contribution of inactivity and aging per se to this decay, we compared muscle function and structure in (a) male participants belonging to a group of well-trained seniors (average of 70 years) who exercised regularly in their previous 30 years and (b) age-matched healthy sedentary seniors with (c) active young men (average of 27 years). The results collected show that relative to their sedentary cohorts, muscle from senior sportsmen have: (a) greater maximal isometric force and function, (b) better preserved fiber morphology and ultrastructure of intracellular organelles involved in Ca(2+) handling and ATP production, (c) preserved muscle fibers size resulting from fiber rescue by reinnervation, and (d) lowered expression of genes related to autophagy and reactive oxygen species detoxification. All together, our results indicate that: (a) skeletal muscle of senior sportsmen is actually more similar to that of adults than to that of age-matched sedentaries and (b) signaling pathways controlling muscle mass and metabolism are differently modulated in senior sportsmen to guarantee maintenance of skeletal muscle structure, function, bioenergetic characteristics, and phenotype. Thus, regular physical activity is a good strategy to attenuate age-related general decay of muscle structure and function (ClinicalTrials.gov: NCT01679977). PMID:24550352

  10. Differential global gene expression in red and white skeletal muscle

    NASA Technical Reports Server (NTRS)

    Campbell, W. G.; Gordon, S. E.; Carlson, C. J.; Pattison, J. S.; Hamilton, M. T.; Booth, F. W.

    2001-01-01

    The differences in gene expression among the fiber types of skeletal muscle have long fascinated scientists, but for the most part, previous experiments have only reported differences of one or two genes at a time. The evolving technology of global mRNA expression analysis was employed to determine the potential differential expression of approximately 3,000 mRNAs between the white quad (white muscle) and the red soleus muscle (mixed red muscle) of female ICR mice (30-35 g). Microarray analysis identified 49 mRNA sequences that were differentially expressed between white and mixed red skeletal muscle, including newly identified differential expressions between muscle types. For example, the current findings increase the number of known, differentially expressed mRNAs for transcription factors/coregulators by nine and signaling proteins by three. The expanding knowledge of the diversity of mRNA expression between white and mixed red muscle suggests that there could be quite a complex regulation of phenotype between muscles of different fiber types.

  11. Androgens Regulate Gene Expression in Avian Skeletal Muscles

    PubMed Central

    Fuxjager, Matthew J.; Barske, Julia; Du, Sienmi; Day, Lainy B.; Schlinger, Barney A.

    2012-01-01

    Circulating androgens in adult reproductively active male vertebrates influence a diversity of organ systems and thus are considered costly. Recently, we obtained evidence that androgen receptors (AR) are expressed in several skeletal muscles of three passeriform birds, the golden-collared manakin (Manacus vitellinus), zebra finch (Taenopygia guttata), and ochre-bellied flycatcher (Mionectes oleagieus). Because skeletal muscles that control wing movement make up the bulk of a bird’s body mass, evidence for widespread effects of androgen action on these muscles would greatly expand the functional impact of androgens beyond their well-characterized effects on relatively discrete targets throughout the avian body. To investigate this issue, we use quantitative PCR (qPCR) to determine if androgens alter gene mRNA expression patterns in wing musculature of wild golden-collared manakins and captive zebra finches. In manakins, the androgen testosterone (T) up-regulated expression of parvalbumin (PV) and insulin-like growth factor I (IGF-I), two genes whose products enhance cellular Ca2+ cycling and hypertrophy of skeletal muscle fibers. In T-treated zebra finches, the anti-androgen flutamide blunted PV and IGF-I expression. These results suggest that certain transcriptional effects of androgen action via AR are conserved in passerine skeletal muscle tissue. When we examined wing muscles of manakins, zebra finches and ochre-bellied flycatchers, we found that expression of PV and IGF-I varied across species and in a manner consistent with a function for AR-dependent gene regulation. Together, these findings imply that androgens have the potential to act on avian muscle in a way that may enhance the physicality required for successful reproduction. PMID:23284699

  12. The effect of heat stress on skeletal muscle contractile properties.

    PubMed

    Locke, Marius; Celotti, Carlo

    2014-07-01

    An elevated heat-shock protein (HSP) content protects cells and tissues, including skeletal muscles, from certain stressors. We determined if heat stress and the elevated HSP content that results is correlated with protection of contractile characteristics of isolated fast and slow skeletal muscles when contracting at elevated temperatures. To elevate muscle HSP content, one hindlimb of Sprague-Dawley rats (21-28 days old, 70-90 g) was subjected to a 15 min 42 °C heat-stress. Twenty-four hours later, both extensor digitorum longus (EDL) and soleus muscles were removed, mounted in either 20 °C or 42 °C Krebs-Ringer solution, and electrically stimulated. Controls consisted of the same muscles from the contra-lateral (non-stressed) hindlimbs as well as muscles from other (unstressed) animals. Isolated muscles were twitched and brought to tetanus every 5 min for 30 min. As expected, HSP content was elevated in muscles from the heat-stressed limbs when compared with controls. Regardless of prior treatment, both EDL and soleus twitch tensions were lower at 42 °C when compared with 20 °C. In addition, when incubated at 42 °C, both muscles showed a drop in twitch tension between 5 and 30 min. For tetanic tension, both muscles also showed an increase in tension between 5 and 30 min when stimulated at 20 °C regardless of treatment but when stimulated at 42 °C no change was observed. No protective effect of an elevated HSP content was observed for either muscle. In conclusion, although heat stress caused an elevation in HSP content, no protective effects were conferred to isolated contracting muscles. PMID:24264930

  13. Celastrol Protects against Antimycin A-Induced Insulin Resistance in Human Skeletal Muscle Cells.

    PubMed

    Abu Bakar, Mohamad Hafizi; Cheng, Kian-Kai; Sarmidi, Mohamad Roji; Yaakob, Harisun; Huri, Hasniza Zaman

    2015-01-01

    Mitochondrial dysfunction and inflammation are widely accepted as key hallmarks of obesity-induced skeletal muscle insulin resistance. The aim of the present study was to evaluate the functional roles of an anti-inflammatory compound, celastrol, in mitochondrial dysfunction and insulin resistance induced by antimycin A (AMA) in human skeletal muscle cells. We found that celastrol treatment improved insulin-stimulated glucose uptake activity of AMA-treated cells, apparently via PI3K/Akt pathways, with significant enhancement of mitochondrial activities. Furthermore, celastrol prevented increased levels of cellular oxidative damage where the production of several pro-inflammatory cytokines in cultures cells was greatly reduced. Celastrol significantly increased protein phosphorylation of insulin signaling cascades with amplified expression of AMPK protein and attenuated NF-κB and PKC θ activation in human skeletal muscle treated with AMA. The improvement of insulin signaling pathways by celastrol was also accompanied by augmented GLUT4 protein expression. Taken together, these results suggest that celastrol may be advocated for use as a potential therapeutic molecule to protect against mitochondrial dysfunction-induced insulin resistance in human skeletal muscle cells. PMID:25961164

  14. Expression profiling and functional characterization of miR-192 throughout sheep skeletal muscle development.

    PubMed

    Zhao, Qian; Kang, Ye; Wang, Hong-Yang; Guan, Wei-Jun; Li, Xiang-Chen; Jiang, Lin; He, Xiao-Hong; Pu, Ya-Bin; Han, Jian-Lin; Ma, Yue-Hui; Zhao, Qian-Jun

    2016-01-01

    MicroRNAs (miRNAs) are evolutionarily conserved, small, non-coding RNAs that have emerged as key regulators of myogenesis. Here, we examined the miRNA expression profiles of developing sheep skeletal muscle using a deep sequencing approach. We detected 2,396 miRNAs in the sheep skeletal muscle tissues. Of these, miR-192 was found to be up-regulated in prenatal skeletal muscle, but was down-regulated postnatally. MiR-192 expression also decreased during the myogenic differentiation of sheep satellite cells (SCs). MiR-192 overexpression significantly attenuated SCs myogenic differentiation but promoted SCs proliferation, whereas miR-192 inhibition enhanced SCs differentiation but suppressed SCs proliferation. We found that miR-192 targeted retinoblastoma 1 (RB1), a known regulator of myogenesis. Furthermore, knockdown of RB1 in cultured cells significantly inhibited SCs myogenic differentiation but accelerated SCs proliferation, confirming the role of RB1 in myogenesis. Taken together, our findings enrich the ovine miRNA database, and outline the miRNA transcriptome of sheep during skeletal muscle development. Moreover, we show that miR-192 affects SCs proliferation and myogenic differentiation via down-regulation of RB1. PMID:27452271

  15. Expression profiling and functional characterization of miR-192 throughout sheep skeletal muscle development

    PubMed Central

    Zhao, Qian; Kang, Ye; Wang, Hong-Yang; Guan, Wei-Jun; Li, Xiang-Chen; Jiang, Lin; He, Xiao-Hong; Pu, Ya-Bin; Han, Jian-Lin; Ma, Yue-Hui; Zhao, Qian-Jun

    2016-01-01

    MicroRNAs (miRNAs) are evolutionarily conserved, small, non-coding RNAs that have emerged as key regulators of myogenesis. Here, we examined the miRNA expression profiles of developing sheep skeletal muscle using a deep sequencing approach. We detected 2,396 miRNAs in the sheep skeletal muscle tissues. Of these, miR-192 was found to be up-regulated in prenatal skeletal muscle, but was down-regulated postnatally. MiR-192 expression also decreased during the myogenic differentiation of sheep satellite cells (SCs). MiR-192 overexpression significantly attenuated SCs myogenic differentiation but promoted SCs proliferation, whereas miR-192 inhibition enhanced SCs differentiation but suppressed SCs proliferation. We found that miR-192 targeted retinoblastoma 1 (RB1), a known regulator of myogenesis. Furthermore, knockdown of RB1 in cultured cells significantly inhibited SCs myogenic differentiation but accelerated SCs proliferation, confirming the role of RB1 in myogenesis. Taken together, our findings enrich the ovine miRNA database, and outline the miRNA transcriptome of sheep during skeletal muscle development. Moreover, we show that miR-192 affects SCs proliferation and myogenic differentiation via down-regulation of RB1. PMID:27452271

  16. Tomographic elastography of contracting skeletal muscles from their natural vibrations

    NASA Astrophysics Data System (ADS)

    Sabra, Karim G.; Archer, Akibi

    2009-11-01

    Conventional elastography techniques require an external mechanical or radiation excitation to measure noninvasively the viscoelastic properties of skeletal muscles and thus monitor human motor functions. We developed instead a passive elastography technique using only an array of skin-mounted accelerometers to record the low-frequency vibrations of the biceps brachii muscle naturally generated during voluntary contractions and to determine their two-dimensional directionality. Cross-correlating these recordings provided travel-times measurements of these muscle vibrations between multiple sensor pairs. Travel-time tomographic inversions yielded spatial variations of their propagation velocity during isometric elbow flexions which indicated a nonuniform longitudinal stiffening of the biceps.

  17. Metabolic benefits of resistance training and fast glycolytic skeletal muscle

    PubMed Central

    Walsh, Kenneth; Arany, Zoltan

    2011-01-01

    Skeletal muscle exhibits remarkable plasticity with respect to its metabolic properties. Recent work has shown that interventions such as resistance training, genetic alterations and pharmacological strategies that increase muscle mass and glycolytic capacity, and not necessarily oxidative competence, can improve body composition and systemic metabolism. We review here recent advances in our understanding of the signaling and transcriptional regulatory pathways of this strategy and review new evidence obtained from mice and humans that supports the notion that increasing muscle mass and glycolytic capacity may effectively counter insulin resistance and type 2 diabetes mellitus. PMID:21045171

  18. Passive in vivo elastography from skeletal muscle noise

    SciTech Connect

    Sabra, Karim G.; Conti, Stephane; Roux, Philippe; Kuperman, W. A.

    2007-05-07

    Measuring the in vivo elastic properties of muscles (e.g., stiffness) provides a means for diagnosing and monitoring muscular activity. The authors demonstrated a passive in vivo elastography technique without an active external radiation source. This technique instead uses cross correlations of contracting skeletal muscle noise recorded with skin-mounted sensors. Each passive sensor becomes a virtual in vivo shear wave source. The results point to a low-cost, noninvasive technique for monitoring biomechanical in vivo muscle properties. The efficacy of the passive elastography technique originates from the high density of cross paths between all sensor pairs, potentially achieving the same sensitivity obtained from active elastography methods.

  19. Influence of spaceflight on rat skeletal muscle

    NASA Technical Reports Server (NTRS)

    Martin, Thomas P.; Edgerton, V. Reggie; Grindeland, Richard E.

    1988-01-01

    The effect of a 7-day spaceflight (aboard NASA's SL-3) on the size and the metabolism of single fibers from several rat muscles was investigated along with the specificity of these responses as related to the muscle type and the size of fibers. It was found that the loss of mass after flight was varied from 36 percent in the soleus to 15 percent in the extensor digitorum longus. Results of histochemical analyses showed that the succinate dehydrogenase (SDH) activity in muscles of flight-exposed rats was maintained at the control levels, whereas the alpha-glycerol phosphate dehydrogenase (GPD) activity was either maintained or increased. The analyses of the metabolic profiles of ATPase, SDH, and GPD indicated that, in some muscles, there was an increase in the poportion of fast oxidative-glycolytic fibers.

  20. The compliance of contracting skeletal muscle

    PubMed Central

    Bressler, B. H.; Clinch, N. F.

    1974-01-01

    1. The method of controlled releases was used to obtain tension—extension curves in toad (Bufo bufo) sartorii under a variety of conditions at 0° C. 2. The curves obtained were approximately linear over a considerable range of force (0·4P0 to P0) if the releases were given from the plateau of tetanic tension. The slope of this linear region was little affected by changes of release velocity in the range 10-120 mm/sec. 3. Such changes as did occur with alterations in release velocity could be quantitatively accounted for in terms of the internal shortening predicted by A. V. Hill's two-component model. 4. As the muscles were stretched above l0, we found that the maximum stiffness of the tetanized muscles fell in much the same way as the maximum developed force, P0. 5. In another series of experiments we found a rapid change in the overall shape of the tension—extension curve during the early phase of force development in an isometric tetanus. The stiffness of the muscle increased with increasing developed force during this period. 6. The force—velocity curve in these muscles was measured by two methods, both giving a similar result. Surprisingly, toad muscle appears to have about the same intrinsic speed as frog muscle at 0° C. The a.b product from our experiments is considerably greater than the reported values for the maintenance heat rate at 0° C in these muscles. 7. The probable site of the variable compliance in active muscle is discussed. It seems most likely that this is within the A-band, perhaps in the cross-bridges themselves. ImagesFig. 2Fig. 3 PMID:4207658

  1. Immunomodulatory effects of massage on nonperturbed skeletal muscle in rats

    PubMed Central

    Waters-Banker, Christine; Dupont-Versteegden, Esther E.

    2013-01-01

    Massage is an ancient manual therapy widely utilized by individuals seeking relief from various musculoskeletal maladies. Despite its popularity, the majority of evidence associated with massage benefits is anecdotal. Recent investigations have uncovered physiological evidence supporting its beneficial use following muscle injury; however, the effects of massage on healthy, unperturbed skeletal muscle are unknown. Utilizing a custom-fabricated massage mimetic device, the purpose of this investigation was to elucidate the effects of various loading magnitudes on healthy skeletal muscle with particular interest in the gene expression profile and modulation of key immune cells involved in the inflammatory response. Twenty-four male Wistar rats (200 g) were subjected to cyclic compressive loading (CCL) over the right tibialis anterior muscle for 30 min, once a day, for 4 consecutive days using four loading conditions: control (0N), low load (1.4N), moderate load (4.5N), and high load (11N). Microarray analysis showed that genes involved with the immune response were the most significantly affected by application of CCL. Load-dependent changes in cellular abundance were seen in the CCL limb for CD68+ cells, CD163+ cells, and CD43+cells. Surprisingly, load-independent changes were also discovered in the non-CCL contralateral limb, suggesting a systemic response. These results show that massage in the form of CCL exerts an immunomodulatory response to uninjured skeletal muscle, which is dependent upon the applied load. PMID:24201707

  2. Hedgehog-driven myogenic tumors recapitulate skeletal muscle cellular heterogeneity.

    PubMed

    Hettmer, Simone; Lin, Michael M; Tchessalova, Daria; Tortorici, Sara J; Castiglioni, Alessandra; Desai, Tushar; Mao, Junhao; McMahon, Andrew P; Wagers, Amy J

    2016-01-01

    Hedgehog (Hh) pathway activation in R26-SmoM2;CAGGS-CreER mice, which carry a tamoxifen-inducible activated Smoothened allele (SmoM2), results in numerous microscopic tumor foci in mouse skeletal muscle. These tumors exhibit a highly differentiated myogenic phenotype and resemble human fetal rhabdomyomas. This study sought to apply previously established strategies to isolate lineally distinct populations of normal mouse myofiber-associated cells in order to examine cellular heterogeneity in SmoM2 tumors. We demonstrate that established SmoM2 tumors are composed of cells expressing myogenic, adipocytic and hematopoietic lineage markers and differentiation capacity. SmoM2 tumors thus recapitulate the phenotypic and functional hetereogeneity observed in normal mouse skeletal muscle. SmoM2 tumors also contain an expanded population of PAX7+ and MyoD+ satellite-like cells with extremely low clonogenic activity. Selective activation of Hh signaling in freshly isolated muscle satellite cells enhanced terminal myogenic differentiation without stimulating proliferation. Our findings support the conclusion that SmoM2 tumors represent an aberrant skeletal muscle state and demonstrate that, similar to normal muscle, myogenic tumors contain functionally distinct cell subsets, including cells lacking myogenic differentiation potential. PMID:26460176

  3. Skeletal muscle responses to lower limb suspension in humans

    NASA Technical Reports Server (NTRS)

    Hather, Bruce M.; Adams, Gregory R.; Tesch, Per A.; Dudley, Gary A.

    1992-01-01

    The morphological responses of human skeletal muscle to unweighting were assessed by analyzing multiple transaxial magnetic resonance (MR) images of both lower limbs and skeletal muscle biopsies of the unweighted lower limb before and after six weeks of unilaterial (left) lower limb suspension (ULLS). Results indicated that, as a results of 6 weeks of unweighting (by the subjects walking on crutches using only one limb), the cross sectional area (CSA) of the thigh muscle of the unweighted left limb decreased 12 percent, while the CSA of the right thigh muscle did not change. The decrease was due to a twofold greater response of the knee extensors than the knee flexors. The pre- and post-ULLS biopsies of the left vastus lateralis showed a 14 percent decrease in average fiber CSA due to unweighting. The number of capillaries surrounding the different fiber types was unchanged after ULLS. Results showed that the adaptive responses of human skeletal muscle to unweighting are qualitatively, but not quantitatively, similar to those of lower mammals and not necessarily dependent on the fiber-type composition.

  4. Noncoding RNAs, Emerging Regulators of Skeletal Muscle Development and Diseases

    PubMed Central

    Nie, Mao; Deng, Zhong-Liang; Liu, Jianming; Wang, Da-Zhi

    2015-01-01

    A healthy and independent life requires skeletal muscles to maintain optimal function throughout the lifespan, which is in turn dependent on efficient activation of processes that regulate muscle development, homeostasis, and metabolism. Thus, identifying mechanisms that modulate these processes is of crucial priority. Noncoding RNAs (ncRNAs), including microRNAs (miRNAs) and long noncoding RNAs (lncRNAs), have emerged as a class of previously unrecognized transcripts whose importance in a wide range of biological processes and human disease is only starting to be appreciated. In this review, we summarize the roles of recently identified miRNAs and lncRNAs during skeletal muscle development and pathophysiology. We also discuss several molecular mechanisms of these noncoding RNAs. Undoubtedly, further systematic understanding of these noncoding RNAs' functions and mechanisms will not only greatly expand our knowledge of basic skeletal muscle biology, but also significantly facilitate the development of therapies for various muscle diseases, such as muscular dystrophies, cachexia, and sarcopenia. PMID:26258142

  5. Postmortem calpain changes in ostrich skeletal muscle.

    PubMed

    Chang, Ya-Shiou; Hsu, Dun-Hui; Stromer, Mavin H; Chou, Rong-Ghi R

    2016-07-01

    The objective of this study was to study the postmortem calpain change in ostrich muscle. Iliotibialis cranialis and Obturatorius medialis muscles were removed from the both sides of carcasses (n=8). The muscles from the left side were sampled after 0, 1, 2, 3, and 7days of storage at 5°C, while the right-side muscles were taken at 1-, 3-, and 7-day postmortem for shear force measurements. The results showed that the calpain-1 activity was not detected in ostrich muscle during the entire 7-day postmortem storage period, while the calpain-11 was. The unautolyzed calpain-11 activity decreased and the autolyzed calpain-11 activity increased with time postmortem. Desmin content and shear force did not change during postmortem storage although a minor degradation of desmin was observed. Therefore, our results suggest that limited postmortem proteolysis (as suggested by the limited degradation of desmin) and tenderization might be due to the lack of calpain-1 and/or insufficient calpain-11 activity present in ostrich muscle. PMID:26971307

  6. 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. PMID:26298291

  7. Molecular studies of exercise, skeletal muscle, and ageing

    PubMed Central

    Timmons, James A.; Gallagher, Iain J.

    2016-01-01

    The purpose of an F1000 review is to reflect on the bigger picture, exploring controversies and new concepts as well as providing opinion as to what is limiting progress in a particular field. We reviewed about 200 titles published in 2015 that included reference to ‘skeletal muscle, exercise, and ageing’ with the aim of identifying key articles that help progress our understanding or research capacity while identifying methodological issues which represent, in our opinion, major barriers to progress. Loss of neuromuscular function with chronological age impacts on both health and quality of life. We prioritised articles that studied human skeletal muscle within the context of age or exercise and identified new molecular observations that may explain how muscle responds to exercise or age. An important aspect of this short review is perspective: providing a view on the likely ‘size effect’ of a potential mechanism on physiological capacity or ageing. PMID:27303646

  8. Compartmentalization of NO signaling cascade in skeletal muscles

    SciTech Connect

    Buchwalow, Igor B. . E-mail: buchwalo@uni-muenster.de; Minin, Evgeny A.; Samoilova, Vera E.; Boecker, Werner; Wellner, Maren; Schmitz, Wilhelm; Neumann, Joachim

    2005-05-06

    Skeletal muscle functions regulated by NO are now firmly established. However, the literature on the compartmentalization of NO signaling in myocytes is highly controversial. To address this issue, we examined localization of enzymes engaged in L-arginine-NO-cGMP signaling in the rat quadriceps muscle. Employing immunocytochemical labeling complemented with tyramide signal amplification and electron microscopy, we found NO synthase expressed not only in the sarcolemma, but also along contractile fibers, in the sarcoplasmic reticulum and mitochondria. The expression pattern of NO synthase in myocytes showed striking parallels with the enzymes engaged in L-arginine-NO-cGMP signaling (arginase, phosphodiesterase, and soluble guanylyl cyclase). Our findings are indicative of an autocrine fashion of NO signaling in skeletal muscles at both cellular and subcellular levels, and challenge the notion that the NO generation is restricted to the sarcolemma.

  9. Molecular studies of exercise, skeletal muscle, and ageing.

    PubMed

    Timmons, James A; Gallagher, Iain J

    2016-01-01

    The purpose of an F1000 review is to reflect on the bigger picture, exploring controversies and new concepts as well as providing opinion as to what is limiting progress in a particular field. We reviewed about 200 titles published in 2015 that included reference to 'skeletal muscle, exercise, and ageing' with the aim of identifying key articles that help progress our understanding or research capacity while identifying methodological issues which represent, in our opinion, major barriers to progress. Loss of neuromuscular function with chronological age impacts on both health and quality of life. We prioritised articles that studied human skeletal muscle within the context of age or exercise and identified new molecular observations that may explain how muscle responds to exercise or age. An important aspect of this short review is perspective: providing a view on the likely 'size effect' of a potential mechanism on physiological capacity or ageing. PMID:27303646

  10. Attenuation of ultrasound in post rigor bovine skeletal muscle.

    PubMed

    Shore, D; Woods, M O; Miles, C A

    1986-03-01

    A pulse transmission method for measuring the attenuation of 1-7 MHz ultrasound in bovine skeletal muscle is described. Measurements of the attenuation coefficient at -20, 0, 20 and 40 degrees C conformed to the relation alpha = Afn, where A and n are temperature-dependent coefficients and f is the frequency. alpha/f varied slowly with frequency, and at 4 MHz and 20 degrees C mean values were 1.3 dB cm-1 MHz-1 along the fibres and 0.55 dB cm-1 MHz-1 across the fibres. These data are lower than most previous measurements of skeletal muscle, but comparable with recent measurements of canine heart muscle. PMID:3952886

  11. Engineered Skeletal Muscle Units for Repair of Volumetric Muscle Loss in the Tibialis Anterior Muscle of a Rat

    PubMed Central

    VanDusen, Keith W.; Syverud, Brian C.; Williams, Michael L.; Lee, Jonah D.

    2014-01-01

    Volumetric muscle loss (VML) is the traumatic, degenerative, or surgical loss of muscle tissue, which may result in function loss and physical deformity. To date, clinical treatments for VML—the reflected muscle flap or transferred muscle graft—are limited by tissue availability and donor site morbidity. To address the need for more innovative skeletal muscle repair options, our laboratory has developed scaffoldless tissue-engineered skeletal muscle units (SMUs), multiphasic tissue constructs composed of engineered skeletal muscle with engineered bone-tendon ends, myotendinous junctions, and entheses, which in vitro can produce force both spontaneously and in response to electrical stimulation. Though phenotypically immature in vitro, we have shown that following 1 week of implantation in an ectopic site, our muscle constructs develop vascularization and innervation, an epimysium-like outer layer of connective tissue, an increase in myosin protein content, formation of myofibers, and increased force production. These findings suggest that our engineered muscle tissue survives implantation and develops the interfaces necessary to advance the phenotype toward adult muscle. The purpose of this study was to evaluate the potential of our SMUs to restore muscle tissue to sites of acute VML. Our results indicate that our SMUs continue to mature in vivo with longer recovery times and have the potential to repair VML sites by providing additional muscle fibers to damaged muscles. We conclude from this study that our SMUs have the potential to restore lost tissue volume in cases of acute VML. PMID:24813922

  12. Exercise conditioning in old mice improves skeletal muscle regeneration.

    PubMed

    Joanisse, Sophie; Nederveen, Joshua P; Baker, Jeff M; Snijders, Tim; Iacono, Carlo; Parise, Gianni

    2016-09-01

    Skeletal muscle possesses the ability to regenerate after injury, but this ability is impaired or delayed with aging. Regardless of age, muscle retains the ability to positively respond to stimuli, such as exercise. We examined whether exercise is able to improve regenerative response in skeletal muscle of aged mice. Twenty-two-month-old male C57Bl/6J mice (n = 20) underwent an 8-wk progressive exercise training protocol [old exercised (O-Ex) group]. An old sedentary (O-Sed) and a sedentary young control (Y-Ctl) group were included. Animals were subjected to injections of cardiotoxin into the tibialis anterior muscle. The tibialis anterior were harvested before [O-Ex/O-Sed/Y-Ctl control (CTL); n = 6], 10 d (O-Ex/O-Sed/Y-Ctl d 10; n = 8), and 28 d (O-Ex/O-Sed/Y-Ctl d 28; n = 6) postinjection. Average fiber cross-sectional area was reduced in all groups at d 10 (CTL: O-Ex: 2499 ± 140; O-Sed: 2320 ± 165; Y-Ctl: 2474 ± 269; d 10: O-Ex: 1191 ± 100; O-Sed: 1125 ± 99; Y-Ctl: 1481 ± 167 µm(2); P < 0.05), but was restored to control values in O-Ex and Y-Ctl groups at d 28 (O-Ex: 2257 ± 181; Y-Ctl: 2398 ± 171 µm(2); P > 0.05). Satellite cell content was greater at CTL in O-Ex (2.6 ± 0.4 satellite cells/100 fibers) compared with O-Sed (1.0 ± 0.1% satellite cells/100 fibers; P < 0.05). Exercise conditioning appears to improve ability of skeletal muscle to regenerate after injury in aged mice.-Joanisse, S., Nederveen, J. P., Baker, J. M., Snijders, T., Iacono, C., Parise, G. Exercise conditioning in old mice improves skeletal muscle regeneration. PMID:27306336

  13. Dysregulation of skeletal muscle protein metabolism by alcohol.

    PubMed

    Steiner, Jennifer L; Lang, Charles H

    2015-05-01

    Alcohol abuse, either by acute intoxication or prolonged excessive consumption, leads to pathological changes in many organs and tissues including skeletal muscle. As muscle protein serves not only a contractile function but also as a metabolic reserve for amino acids, which are used to support the energy needs of other tissues, its content is tightly regulated and dynamic. This review focuses on the etiology by which alcohol perturbs skeletal muscle protein balance and thereby over time produces muscle wasting and weakness. The preponderance of data suggest that alcohol primarily impairs global protein synthesis, under basal conditions as well as in response to several anabolic stimuli including growth factors, nutrients, and muscle contraction. This inhibitory effect of alcohol is mediated, at least in part, by a reduction in mTOR kinase activity via a mechanism that remains poorly defined but likely involves altered protein-protein interactions within mTOR complex 1. Furthermore, alcohol can exacerbate the decrement in mTOR and/or muscle protein synthesis present in other catabolic states. In contrast, alcohol-induced changes in muscle protein degradation, either global or via specific modulation of the ubiquitin-proteasome or autophagy pathways, are relatively inconsistent and may be model dependent. Herein, changes produced by acute intoxication versus chronic ingestion are contrasted in relation to skeletal muscle metabolism, and limitations as well as opportunities for future research are discussed. As the proportion of more economically developed countries ages and chronic illness becomes more prevalent, a better understanding of the etiology of biomedical consequences of alcohol use disorders is warranted. PMID:25759394

  14. Dysregulation of skeletal muscle protein metabolism by alcohol

    PubMed Central

    Steiner, Jennifer L.

    2015-01-01

    Alcohol abuse, either by acute intoxication or prolonged excessive consumption, leads to pathological changes in many organs and tissues including skeletal muscle. As muscle protein serves not only a contractile function but also as a metabolic reserve for amino acids, which are used to support the energy needs of other tissues, its content is tightly regulated and dynamic. This review focuses on the etiology by which alcohol perturbs skeletal muscle protein balance and thereby over time produces muscle wasting and weakness. The preponderance of data suggest that alcohol primarily impairs global protein synthesis, under basal conditions as well as in response to several anabolic stimuli including growth factors, nutrients, and muscle contraction. This inhibitory effect of alcohol is mediated, at least in part, by a reduction in mTOR kinase activity via a mechanism that remains poorly defined but likely involves altered protein-protein interactions within mTOR complex 1. Furthermore, alcohol can exacerbate the decrement in mTOR and/or muscle protein synthesis present in other catabolic states. In contrast, alcohol-induced changes in muscle protein degradation, either global or via specific modulation of the ubiquitin-proteasome or autophagy pathways, are relatively inconsistent and may be model dependent. Herein, changes produced by acute intoxication versus chronic ingestion are contrasted in relation to skeletal muscle metabolism, and limitations as well as opportunities for future research are discussed. As the proportion of more economically developed countries ages and chronic illness becomes more prevalent, a better understanding of the etiology of biomedical consequences of alcohol use disorders is warranted. PMID:25759394

  15. Skeletal muscle tissue engineering: strategies for volumetric constructs

    PubMed Central

    Cittadella Vigodarzere, Giorgio; Mantero, Sara

    2014-01-01

    Skeletal muscle tissue is characterized by high metabolic requirements, defined structure and high regenerative potential. As such, it constitutes an appealing platform for tissue engineering to address volumetric defects, as proven by recent works in this field. Several issues common to all engineered constructs constrain the variety of tissues that can be realized in vitro, principal among them the lack of a vascular system and the absence of reliable cell sources; as it is, the only successful tissue engineering constructs are not characterized by active function, present limited cellular survival at implantation and possess low metabolic requirements. Recently, functionally competent constructs have been engineered, with vascular structures supporting their metabolic requirements. In addition to the use of biochemical cues, physical means, mechanical stimulation and the application of electric tension have proven effective in stimulating the differentiation of cells and the maturation of the constructs; while the use of co-cultures provided fine control of cellular developments through paracrine activity. This review will provide a brief analysis of some of the most promising improvements in the field, with particular attention to the techniques that could prove easily transferable to other branches of tissue engineering. PMID:25295011

  16. Dietary Nitrate and Skeletal Muscle Contractile Function in Heart Failure.

    PubMed

    Coggan, Andrew R; Peterson, Linda R

    2016-08-01

    Heart failure (HF) patients suffer from exercise intolerance that diminishes their ability to perform normal activities of daily living and hence compromises their quality of life. This is due largely to detrimental changes in skeletal muscle mass, structure, metabolism, and function. This includes an impairment of muscle contractile performance, i.e., a decline in the maximal force, speed, and power of muscle shortening. Although numerous mechanisms underlie this reduction in contractility, one contributing factor may be a decrease in nitric oxide (NO) bioavailability. Consistent with this, recent data demonstrate that acute ingestion of NO3 (-)-rich beetroot juice, a source of NO via the NO synthase-independent enterosalivary pathway, markedly increases maximal muscle speed and power in HF patients. This review discusses the role of muscle contractile dysfunction in the exercise intolerance characteristic of HF, and the evidence that dietary NO3 (-) supplementation may represent a novel and simple therapy for this currently underappreciated problem. PMID:27271563

  17. Rapidly aggravated skeletal muscle metastases from an intrahepatic cholangiocarcinoma

    PubMed Central

    Lee, Jiyoung; Lee, Sung Wook; Han, Sang Young; Baek, Yang Hyun; Kim, Su Young; Rhyou, Hyo In

    2015-01-01

    We present a rare case of intrahepatic cholangiocarcinoma (ICC) with multiple skeletal muscle metastases. The patient was a 55-year-old Asian woman presenting with abdominal pain; abdominal and pelvic computed tomography and magnetic resonance cholangiopancreatography revealed an unresectable ICC with hepatic metastasis and metastastatic lymphadenopathy in the porto-caval area. After 3 mo of treatment with palliative radiotherapy and chemotherapy, magnetic resonance imaging of the thoracolumbar spine detected right psoas muscle and paraspinous muscle metastases. We performed an ultrasound-guided percutaneous fine-needle biopsy that confirmed a similar pattern of poorly differentiated adenocarcinoma. The patient treated with palliative chemotherapy and achieved 10 mo of survival. Here we report the first case quickly spread to multiple sites of muscle even though the three-month treatment, compare to the other cases reported muscle metastases at diagnosis. PMID:25684968

  18. Isolation and Purification of Satellite Cells for Skeletal Muscle Tissue Engineering

    PubMed Central

    Syverud, Brian C; Lee, Jonah D; VanDusen, Keith W; Larkin, Lisa M

    2015-01-01

    Engineered skeletal muscle holds promise as a source of graft tissue for the repair of traumatic injuries such as volumetric muscle loss. The resident skeletal muscle stem cell, the satellite cell, has been identified as an ideal progenitor for tissue engineering due to its role as an essential player in the potent skeletal muscle regeneration mechanism. A significant challenge facing tissue engineers, however, is the isolation of sufficiently large satellite cell populations with high purity. The two common isolation techniques, single fiber explant culture and enzymatic dissociation, can yield either a highly pure satellite cell population or a suitably large number or cells but fail to do both simultaneously. As a result, it is often necessary to use a purification technique such as pre-plating or cell sorting to enrich the satellite cell population post-isolation. Furthermore, the absence of complex chemical and biophysical cues influencing the in vivo satellite cell “niche” complicates the culture of isolated satellite cells. Techniques under investigation to maximize myogenic proliferation and differentiation in vitro are described in this article, along with current methods for isolating and purifying satellite cells. PMID:26413555

  19. Skeletal muscle responses to unweighting in humans

    NASA Technical Reports Server (NTRS)

    Dudley, Gary A.

    1991-01-01

    An overview of earth-based studies is presented emphasizing the data on muscular strength and size derived from experiments under simulated microgravity. The studies involve the elimination of weight-bearing responsibility of lower-limb human musculature to simulate the unweighting effects of space travel in the absence of exercise. Reference is given to bedrest and unilateral lower-limb suspension, both of which provide data that demonstrate the decreased strength of the knee extensors of 20-25 percent. The response is related to the decrease in cross-sectional area of the knee extensors which is a direct indication of muscle-fiber atrophy. Most of the effects of unweighting are associated with extensor muscles in the lower limbs and not with postural muscles. Unweighting is concluded to cause significant adaptations in the human neuromuscular system that require further investigation.

  20. Neuromuscular Electrical Stimulation for Skeletal Muscle Function

    PubMed Central

    Doucet, Barbara M.; Lam, Amy; Griffin, Lisa

    2012-01-01

    Lack of neural innervation due to neurological damage renders muscle unable to produce force. Use of electrical stimulation is a medium in which investigators have tried to find a way to restore movement and the ability to perform activities of daily living. Different methods of applying electrical current to modify neuromuscular activity are electrical stimulation (ES), neuromuscular electrical stimulation (NMES), transcutaneous electrical nerve stimulation (TENS), and functional electrical stimulation (FES). This review covers the aspects of electrical stimulation used for rehabilitation and functional purposes. Discussed are the various parameters of electrical stimulation, including frequency, pulse width/duration, duty cycle, intensity/amplitude, ramp time, pulse pattern, program duration, program frequency, and muscle group activated, and how they affect fatigue in the stimulated muscle. PMID:22737049

  1. Enhanced Myogenesis in adult skeletal muscle by transgenic expression of Myostatin Propeptide

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Skeletal muscle growth and maintenance are essential for human health. One of the muscle regulatory genes, namely myostatin, a member of transforming growth factor-ß, plays a dominant role in the genetic control of muscle mass. Transgenic expression of myostatin propeptide in skeletal muscle showed ...

  2. Mechanical stimulation of skeletal muscle mitigates glucocorticoid induced decreases in prostaglandin synthesis

    NASA Technical Reports Server (NTRS)

    Chromiak, Joseph A.; Vandenburgh, Herman H.

    1993-01-01

    The glucocorticoid dexamethasone (Dex) induces a decline in protein synthesis and protein content of tissue cultured, avian skeletal muscle cells, and this atrophy is attenuated by repetitive mechanical stretch. Since the prostaglandin synthesis inhibitor indomethacin mitigated this stretch attenuation of muscle atrophy, the role of prostaglandins as growth modulators in these processes was examined. Dex at 10(exp -8) M reduced PGF(sub 2(alpha)) production 55 percent - 65 percent and PGE(sub 2) production 84 - 90 percent after 24 - 72 h of incubation in static cultures. Repetitive 10 percent stretch-relaxations of the non-Dex treated cultures increased PGF(sub 2(alpha)) efflux 41 percent at 24 h and 276 percent at 72 h and increased PGE(sub 2) production 51 percent at 24 h and 236 percent at 72 h. Mechanical stimulation of Dex treated cultures increased PGF(sub 2(alpha)) production 162 percent after 24 h, thus returning PGF(sub 2(alpha)) efflux to the level of non-Dex treated cultures. At 72 h, stretch increased PGF(sub 2(alpha)) efflux 65 percent in Dex treated cultures, but PGF(sub 2(alpha)) production was 45-84 percent less than non-Dex treated cultures. Mechanical stimulation of Dex treated cultures increased PGE(sub 2) production at 24 h, but not at 72 h. Dex reduced prostaglandin H synthase (PGHS) activity in the muscle cultures by 70 percent after 8 - 24 h of incubation, and mechanical stimulation increased PGHS activity of the Dex treated cultures by 98 percent. It is concluded that repetitive mechanical stimulation attenuates the catabolic effects of Dex on cultured skeletal muscle cells in part by reversing the Dex-induced declines in PGHS activity and prostaglandin production.

  3. 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.

  4. Mechanisms of protein balance in skeletal muscle.

    PubMed

    Anthony, T G

    2016-07-01

    Increased global demand for adequate protein nutrition against a backdrop of climate change and concern for animal agriculture sustainability necessitates new and more efficient approaches to livestock growth and production. Anabolic growth is achieved when rates of new synthesis exceed turnover, producing a positive net protein balance. Conversely, deterioration or atrophy of lean mass is a consequence of a net negative protein balance. During early life and periods of growth, muscle mass is driven by increases in protein synthesis at the level of mRNA translation. Throughout life, muscle mass is further influenced by degradative processes such as autophagy and the ubiquitin proteasome pathway. Multiple signal transduction networks guide and coordinate these processes alongside quality control mechanisms to maintain protein homeostasis (proteostasis). Genetics, hormones, and environmental stimuli each influence proteostasis control, altering capacity and/or efficiency of muscle growth. An overview of recent findings and current methods to assess muscle protein balance and proteostasis is presented. Current efforts to identify novel control points have the potential through selective breeding design or development of hormetic strategies to better promote growth and health span during environmental stress. PMID:27345321

  5. Activity Dependent Signal Transduction in Skeletal Muscle

    NASA Technical Reports Server (NTRS)

    Hamilton, Susan L.

    1999-01-01

    The overall goals of this project are: 1) to define the initial signal transduction events whereby the removal of gravitational load from antigravity muscles, such as the soleus, triggers muscle atrophy, and 2) to develop countermeasures to prevent this from happening. Our rationale for this approach is that, if countermeasures can be developed to regulate these early events, we could avoid having to deal with the multiple cascades of events that occur downstream from the initial event. One of our major findings is that hind limb suspension causes an early and sustained increase in intracellular Ca(2+) concentration ([Ca (2+)](sub i)). In most cells the consequences of changes in ([Ca (2+)](sub i))depend on the amplitude, frequency and duration of the Ca(2+) signal and on other factors in the intracellular environment. We propose that muscle remodeling in microgravity represents a change in the balance among several CA(2+) regulated signal transduction pathways, in particular those involving the transcription factors NFAT and NFkB and the pro-apoptotic protein BAD. Other Ca(2+) sensitive pathways involving PKC, ras, rac, and CaM kinase II may also contribute to muscle remodeling.

  6. Diaphragmatic lymphatic vessel behavior during local skeletal muscle contraction.

    PubMed

    Moriondo, Andrea; Solari, Eleonora; Marcozzi, Cristiana; Negrini, Daniela

    2015-02-01

    The mechanism through which the stresses developed in the diaphragmatic tissue during skeletal muscle contraction sustain local lymphatic function was studied in 10 deeply anesthetized, tracheotomized adult Wistar rats whose diaphragm was exposed after thoracotomy. To evaluate the direct effect of skeletal muscle contraction on the hydraulic intraluminal lymphatic pressures (Plymph) and lymphatic vessel geometry, the maximal contraction of diaphragmatic fibers adjacent to a lymphatic vessel was elicited by injection of 9.2 nl of 1 M KCl solution among diaphragmatic fibers while Plymph was recorded through micropuncture and vessel geometry via stereomicroscopy video recording. In lymphatics oriented perpendicularly to the longitudinal axis of muscle fibers and located at <300 μm from KCl injection, vessel diameter at maximal skeletal muscle contraction (Dmc) decreased to 61.3 ± 1.4% of the precontraction value [resting diameter (Drest)]; however, if injection was at >900 μm from the vessel, Dmc enlarged to 131.1 ± 2.3% of Drest. In vessels parallel to muscle fibers, Dmc increased to 122.8 ± 2.9% of Drest. During contraction, Plymph decreased as much as 22.5 ± 2.6 cmH2O in all submesothelial superficial vessels, whereas it increased by 10.7 ± 5.1 cmH2O in deeper vessels running perpendicular to contracting muscle fibers. Hence, the three-dimensional arrangement of the diaphragmatic lymphatic network seems to be finalized to efficiently exploit the stresses exerted by muscle fibers during the contracting inspiratory phase to promote lymph formation in superficial submesothelial lymphatics and its further propulsion in deeper intramuscular vessels. PMID:25485903

  7. Skeletal Muscle Oxidative Capacity in Patients with Cystic Fibrosis

    PubMed Central

    Erickson, Melissa L.; Seigler, Nichole; McKie, Kathleen T.; McCully, Kevin K.; Harris, Ryan A.

    2016-01-01

    Introduction Exercise intolerance predicts mortality in patients with cystic fibrosis (CF); however, the mechanisms have yet to be fully elucidated. Using near infrared spectroscopy (NIRS), this study compared skeletal muscle oxidative capacity in patients with CF to healthy controls. Methods Thirteen patients and 16 demographically-matched controls participated in this study. NIRS was utilized to measure the recovery rate of oxygen consumption (musVO2max) of the vastus lateralis muscle after 15 s of electrical stimulation (4 Hz) and subsequent repeated transient arterial occlusions. Results musVO2max was reduced in patients with CF (1.82 ± 0.4 min−1) compared to controls (2.13 ± 0.5 min−1, p = 0.04). A significant inverse relationship between age and musVO2max was observed in patients (r = −0.676, p = 0.011), but not controls (r = −0.291, p = 0.274). Discussion Patients with CF exhibit a reduction in skeletal muscle oxidative capacity compared to controls. It appears as the reduced skeletal muscle oxidative capacity is accelerated by age and could likely contribute to exercise intolerance in patients with CF. PMID:25758606

  8. Myostatin gene inactivation prevents skeletal muscle wasting in cancer.

    PubMed

    Gallot, Yann S; Durieux, Anne-Cécile; Castells, Josiane; Desgeorges, Marine M; Vernus, Barbara; Plantureux, Léa; Rémond, Didier; Jahnke, Vanessa E; Lefai, Etienne; Dardevet, Dominique; Nemoz, Georges; Schaeffer, Laurent; Bonnieu, Anne; Freyssenet, Damien G

    2014-12-15

    Cachexia is a muscle-wasting syndrome that contributes significantly to morbidity and mortality of many patients with advanced cancers. However, little is understood about how the severe loss of skeletal muscle characterizing this condition occurs. In the current study, we tested the hypothesis that the muscle protein myostatin is involved in mediating the pathogenesis of cachexia-induced muscle wasting in tumor-bearing mice. Myostatin gene inactivation prevented the severe loss of skeletal muscle mass induced in mice engrafted with Lewis lung carcinoma (LLC) cells or in Apc(Min) (/+) mice, an established model of colorectal cancer and cachexia. Mechanistically, myostatin loss attenuated the activation of muscle fiber proteolytic pathways by inhibiting the expression of atrophy-related genes, MuRF1 and MAFbx/Atrogin-1, along with autophagy-related genes. Notably, myostatin loss also impeded the growth of LLC tumors, the number and the size of intestinal polyps in Apc(Min) (/+) mice, thus strongly increasing survival in both models. Gene expression analysis in the LLC model showed this phenotype to be associated with reduced expression of genes involved in tumor metabolism, activin signaling, and apoptosis. Taken together, our results reveal an essential role for myostatin in the pathogenesis of cancer cachexia and link this condition to tumor growth, with implications for furthering understanding of cancer as a systemic disease. PMID:25336187

  9. Skeletal muscle gene expression in space-flown rats.

    PubMed

    Nikawa, Takeshi; Ishidoh, Kazumi; Hirasaka, Katsuya; Ishihara, Ibuki; Ikemoto, Madoka; Kano, Mihoko; Kominami, Eiki; Nonaka, Ikuya; Ogawa, Takayuki; Adams, Gregory R; Baldwin, Kenneth M; Yasui, Natsuo; Kishi, Kyoichi; Takeda, Shin'ichi

    2004-03-01

    Skeletal muscles are vulnerable to marked atrophy under microgravity. This phenomenon is due to the transcriptional alteration of skeletal muscle cells to weightlessness. To further investigate this issue at a subcellular level, we examined the expression of approximately 26,000 gastrocnemius muscle genes in space-flown rats by DNA microarray analysis. Comparison of the changes in gene expression among spaceflight, tail-suspended, and denervated rats revealed that such changes were unique after spaceflight and not just an extension of simulated weightlessness. The microarray data showed two spaceflight-specific gene expression patterns: 1) imbalanced expression of mitochondrial genes with disturbed expression of cytoskeletal molecules, including putative mitochondria-anchoring proteins, A-kinase anchoring protein, and cytoplasmic dynein, and 2) up-regulated expression of ubiquitin ligase genes, MuRF-1, Cbl-b, and Siah-1A, which are rate-limiting enzymes of muscle protein degradation. Distorted expression of cytoskeletal genes during spaceflight resulted in dislocation of the mitochondria in the cell. Several oxidative stress-inducible genes were highly expressed in the muscle of spaceflight rats. We postulate that mitochondrial dislocation during spaceflight has deleterious effects on muscle fibers, leading to atrophy in the form of insufficient energy provision for construction and leakage of reactive oxygen species from the mitochondria. PMID:14715702

  10. Adult stem cells: the therapeutic potential of skeletal muscle.

    PubMed

    Saini, Amarjit; Stewart, Claire E H

    2006-05-01

    Embryonic stem cells have revolutionised our understanding of normal and deregulated growth and development. The potential to produce cells and tissues as needed offers enormous therapeutic potential. The use of these cells, however, is accompanied by ongoing ethical, religious and biomedical issues. The expansion potential and plasticity of adult stem cells have therefore received much interest. Adult skeletal muscle is highly adaptable, responding to both the hypertrophic and degenerative stresses placed upon it. This extreme plasticity is in part regulated by resident stem cells. In addition to regenerating muscle, if exposed to osteogenic or adipogenic inducers, these cells spontaneously form osteoblasts or adipocytes. The potential for and heterogeneity of muscle stem cells is underscored by the observation that CD45+ muscle side population cells are capable of reconstituting bone marrow in lethally irradiated mice and of contributing to neo-vascularisation of regenerating muscle. Finally, first attempts to replace infarcted myocardium relied on injection of skeletal myoblasts into the heart. Cells successfully engrafted and cardiac function was improved. Harnessing their differentiation/trans-differentiation capacity provides enormous potential for adult stem cells. In this review, current understanding of the different stem cells within muscle will be discussed as will their potential utility for regenerative medicine. PMID:18220864

  11. Mitochondrial respiratory chain function in skeletal muscle of ALS patients.

    PubMed

    Echaniz-Laguna, Andoni; Zoll, Joffrey; Ribera, Florence; Tranchant, Christine; Warter, Jean-Marie; Lonsdorfer, Jean; Lampert, Eliane

    2002-11-01

    Evidence implicating mitochondrial dysfunction in the central nervous system of patients with sporadic amyotrophic lateral sclerosis (SALS) has recently been accumulating. In contrast, data on mitochondrial function in skeletal muscle in SALS are scarce and controversial. We investigated the in situ properties of muscle mitochondria in patients with early-stage SALS and sedentary (SED) controls using the skinned fiber technique to determine whether respiration of muscle tissue is altered in early-stage SALS in comparison with SED. Musculus vastus lateralis biopsies were obtained from 7 SED group members and 14 patients with early-stage SALS (mean disease duration, 9 months). Muscle fibers were permeabilized with saponine and then skinned and placed in an oxygraphic chamber to measure basal (V(0)) and maximal (V(max)) adenosine diphosphate-stimulated respiration rates and to assess mitochondrial regulation by adenosine diphosphate. Muscle oxidative capacity, evaluated with V(max), was identical in patients in the SALS and SED groups (V(0): SALS, 1.1 +/- 0.1; SED, 0.8 +/- 0.1, micromol 0(2). min(-1). gm(-1)dw and V(max): SALS, 3.1 +/- 0.3; SED, 2.5 +/- 0.3, micromol 0(2). min(-1). gm(-1)dw). This study shows an absence of large mitochondrial damage in skeletal muscle of patients with early-stage SALS, suggesting that mitochondrial dysfunction in the earlier stages of SALS is almost certainly not systemic. PMID:12402260

  12. Regeneration of injured skeletal muscle after the injury

    PubMed Central

    Järvinen, Tero AH; Järvinen, Markku; Kalimo, Hannu

    2013-01-01

    Summary Muscle injuries are one of the most common traumas occurring in sports. Despite their clinical importance, few clinical studies exist on the treatment of these traumas. Thus, the current treatment recommendations for muscle injuries have either been derived from experimental studies or been tested only empirically. Although non operative treatment should almost always be the 1st choice as it results in good functional outcomes in the majority of athletes with muscle injuries, the consequences of failed treatment can be very dramatic, possibly postponing an athlete’s return to sports for weeks or even months. Moreover, the recognition of some basic principles of skeletal muscle regeneration and healing processes can considerably help in both avoiding the imminent dangers and accelerating the return to competition. Accordingly, in this review, the authors have summarized the prevailing understanding on the biology of muscle regeneration in hopes of extending these findings to clinical practice in an attempt to propose an evidence-based approach for the diagnosis and optimal treatment of skeletal muscle injuries. PMID:24596699

  13. Eccentric exercise facilitates mesenchymal stem cell appearance in skeletal muscle.

    PubMed

    Valero, M Carmen; Huntsman, Heather D; Liu, Jianming; Zou, Kai; Boppart, Marni D

    2012-01-01

    Eccentric, or lengthening, contractions result in injury and subsequently stimulate the activation and proliferation of satellite stem cells which are important for skeletal muscle regeneration. The discovery of alternative myogenic progenitors in skeletal muscle raises the question as to whether stem cells other than satellite cells accumulate in muscle in response to exercise and contribute to post-exercise repair and/or growth. In this study, stem cell antigen-1 (Sca-1) positive, non-hematopoetic (CD45⁻) cells were evaluated in wild type (WT) and α7 integrin transgenic (α7Tg) mouse muscle, which is resistant to injury yet liable to strain, 24 hr following a single bout of eccentric exercise. Sca-1⁺CD45⁻ stem cells were increased 2-fold in WT muscle post-exercise. The α7 integrin regulated the presence of Sca-1⁺ cells, with expansion occurring in α7Tg muscle and minimal cells present in muscle lacking the α7 integrin. Sca-1⁺CD45⁻ cells isolated from α7Tg muscle following exercise were characterized as mesenchymal-like stem cells (mMSCs), predominantly pericytes. In vitro multiaxial strain upregulated mMSC stem cells markers in the presence of laminin, but not gelatin, identifying a potential mechanistic basis for the accumulation of these cells in muscle following exercise. Transplantation of DiI-labeled mMSCs into WT muscle increased Pax7⁺ cells and facilitated formation of eMHC⁺DiI⁻ fibers. This study provides the first demonstration that mMSCs rapidly appear in skeletal muscle in an α7 integrin dependent manner post-exercise, revealing an early event that may be necessary for effective repair and/or growth following exercise. The results from this study also support a role for the α7 integrin and/or mMSCs in molecular- and cellular-based therapeutic strategies that can effectively combat disuse muscle atrophy. PMID:22253772

  14. Skeletal muscle calcineurin: influence of phenotype adaptation and atrophy

    NASA Technical Reports Server (NTRS)

    Spangenburg, E. E.; Williams, J. H.; Roy, R. R.; Talmadge, R. J.; Spangenberg, E. E. (Principal Investigator)

    2001-01-01

    Calcineurin (CaN) has been implicated as a signaling molecule that can transduce physiological stimuli (e.g., contractile activity) into molecular signals that initiate slow-fiber phenotypic gene expression and muscle growth. To determine the influence of muscle phenotype and atrophy on CaN levels in muscle, the levels of soluble CaN in rat muscles of varying phenotype, as assessed by myosin heavy chain (MHC)-isoform proportions, were determined by Western blotting. CaN levels were significantly greater in the plantaris muscle containing predominantly fast (IIx and IIb) MHC isoforms, compared with the soleus (predominantly type I MHC) or vastus intermedius (VI, contains all 4 adult MHC isoforms). Three months after a complete spinal cord transection (ST), the CaN levels in the VI muscle were significantly reduced, despite a significant increase in fast MHC isoforms. Surprisingly, the levels of CaN in the VI were highly correlated with muscle mass but not MHC isoform proportions in ST and control rats. These data demonstrate that CaN levels in skeletal muscle are highly correlated to muscle mass and that the normal relationship with phenotype is lost after ST.

  15. PI3 kinase regulation of skeletal muscle hypertrophy and atrophy.

    PubMed

    Glass, David J

    2010-01-01

    Activation of the PI3 kinase pathway can induce skeletal muscle hypertrophy, defined as an increase in skeletal muscle mass. In mammals, skeletal muscle hypertrophy occurs as a result of an increase in the size, as opposed to the number, of pre-existing skeletal muscle fibers. This pathway's effects on skeletal muscle have been implicated most prominently downstream of Insulin-like growth factor 1 signaling. IGF-1's pro-hypertrophy activity comes predominantly through its ability to activate the Phosphoinositide 3-kinase (PI3K)/Akt signaling pathway. Akt is a serine-threonine protein kinase that can induce protein synthesis and block the transcriptional upregulation of key mediators of skeletal muscle atrophy, the E3 ubiquitin ligases MuRF1 and MAFbx (also called Atrogin-1), by phosphorylating and thereby inhibiting the nuclear translocation of the FOXO (also called "forkhead") family of transcription factors. Once phosphorylated by Akt, the FOXOs are excluded from the nucleus, and upregulation of MuRF1 and MAFbx is blocked. MuRF1 and MAFbx mediate atrophy by ubiquitinating particular protein substrates, causing them to undergo degradation by the proteasome. MuRF1's substrates include several components of the sarcomeric thick filament, including Myosin Heavy Chain (MyHC). Thus, by blocking MuRF1 activation, IGF-1 helps prevent the breakdown of the thick filament under atrophy conditions.IGF1/PI3K/Akt signaling also can dominantly inhibit the effects of a secreted protein called "myostatin," which is a member of the TGFβ family of proteins. Deletion or inhibition of myostatin causes an increase in skeletal muscle size, because myostatin acts both to inhibit myoblast differentiation and to block the Akt pathway. Thus by blocking myostatin, PI3K/Akt activation stimulates differentiation and protein synthesis by this distinct mechanism. Myostatin induces the phosphorylation and activation of the transcription factors of Smad2 and Smad3, downstream of the Act

  16. Human Skeletal Muscle Protein Metabolism Responses to Amino Acid Nutrition.

    PubMed

    Mitchell, W Kyle; Wilkinson, Daniel J; Phillips, Bethan E; Lund, Jonathan N; Smith, Kenneth; Atherton, Philip J

    2016-07-01

    Healthy individuals maintain remarkably constant skeletal muscle mass across much of adult life, suggesting the existence of robust homeostatic mechanisms. Muscle exists in dynamic equilibrium whereby the influx of amino acids (AAs) and the resulting increases in muscle protein synthesis (MPS) associated with the intake of dietary proteins cancel out the efflux of AAs from muscle protein breakdown that occurs between meals. Dysregulated proteostasis is evident with aging, especially beyond the sixth decade of life. Women and men aged 75 y lose muscle mass at a rate of ∼0.7% and 1%/y, respectively (sarcopenia), and lose strength 2- to 5-fold faster (dynapenia) as muscle "quality" decreases. Factors contributing to the disruption of an otherwise robust proteostatic system represent targets for potential therapies that promote healthy aging. Understanding age-related impairments in anabolic responses to AAs and identifying strategies to mitigate these factors constitute major areas of interest. Numerous studies have aimed to identify 1) the influence of distinct protein sources on absorption kinetics and muscle anabolism, 2) the latency and time course of MPS responses to protein/AAs, 3) the impacts of protein/AA intake on muscle microvascular recruitment, and 4) the role of certain AAs (e.g., leucine) as signaling molecules, which are able to trigger anabolic pathways in tissues. This review aims to discuss these 4 issues listed, to provide historical and modern perspectives of AAs as modulators of human skeletal muscle protein metabolism, to describe how advances in stable isotope/mass spectrometric approaches and instrumentation have underpinned these advances, and to highlight relevant differences between young adults and older individuals. Whenever possible, observations are based on human studies, with additional consideration of relevant nonhuman studies. PMID:27422520

  17. Abnormal skeletal muscle bioenergetics in familial hypertrophic cardiomyopathy.

    PubMed Central

    Thompson, C. H.; Kemp, G. J.; Taylor, D. J.; Conway, M.; Rajagopalan, B.; O'Donoghue, A.; Styles, P.; McKenna, W. J.; Radda, G. K.

    1997-01-01

    OBJECTIVE: To determine the skeletal muscle metabolic manifestations of familial hypertrophic cardiomyopathy. DESIGN: A case-control study. SETTING: 31P magnetic resonance spectroscopy of the calf muscle was performed on volunteers from a centre specialising in familial hypertrophic cardiomyopathy. PATIENTS: Five patients with abnormal beta myosin heavy chain protein in cardiac and skeletal muscle and five patients with a troponin T abnormality in cardiac muscle were compared with healthy controls. RESULTS: High energy phosphate metabolism in vivo was examined in a non-invasive manner. In resting muscle, the beta myosin heavy chain group had a higher ratio of phosphocreatine to ATP concentration (4.51 (SD 0.17)) than either the troponin T group (3.88 (0.42)) or controls (n = 16; 4.04 (0.40)). Exercise duration was reduced compared to controls, and during the fourth minute of exercise phosphocreatine depletion and muscle acidification were greater in both patient groups. After exercise, the recovery of phosphocreatine-an index of oxidative metabolic capacity of the muscle-was slower in the beta myosin heavy chain group (mean half time 0.65 (0.08) minutes) than in the troponin T group (0.60 (0.17) minutes) or controls (0.48 (0.14) minutes). CONCLUSIONS: Exercise metabolism was abnormal in both groups of subjects, and the affected contractile protein determined the metabolic changes in muscle at rest and during recovery. In patients with abnormal beta myosin heavy chain protein, there was a decrease in oxidative capacity consistent with the reduction in mitochondria reported in muscle biopsy studies of similar patients. PMID:9326994

  18. Sarcoglycans in human skeletal muscle and human cardiac muscle: a confocal laser scanning microscope study.

    PubMed

    Anastasi, G; Cutroneo, G; Trimarchi, F; Rizzo, G; Bramanti, P; Bruschetta, D; Fugazzotto, D; Cinelli, M P; Soscia, A; Santoro, G; Favaloro, A

    2003-01-01

    Sarcoglycans are a subcomplex of transmembrane proteins which are part of the dystrophin-glycoprotein complex. They are expressed in the skeletal, cardiac and smooth muscle. Although numerous studies have been conducted on the sarcoglycan subcomplex in skeletal and cardiac muscle, the manner of the distribution and localization of these proteins along the nonjunctional sarcolemma is not clear. We therefore carried out an indirect immunofluorescence study on surgical biopsies of normal human skeletal muscle and of healthy human atrial myocardium biopsies of patients affected by valvulopathy. Our results indicate that, in skeletal muscle, sarcoglycans have a costameric distribution and all colocalize with each other. Only in a few cases did the alpha-sarcoglycan not colocalize with other sarcoglycans. In addition, these glycoproteins can be localized in different fibers either in the regions of the sarcolemma over band I or band A. In cardiac muscle, our results show a costameric distribution of all proteins examined and, unlike in skeletal muscle, they show a constant colocalization of all sarcoglycans with each other, along with a consistent localization of these proteins in the region of the sarcolemma over band I. In our opinion, this situation seems to confirm the hypothesis of a correlation between the region of the sarcolemma occupied by costameric proteins and the metabolic type, fast or slow, of the muscular fibers. These data, besides opening a new line of research in understanding interactions between the sarcoglycans and other transmembrane proteins, could also be extended to skeletal and cardiac muscles affected by neuromuscular and cardiovascular pathologies to understand possible structural alterations. PMID:12566627

  19. Skeletal muscle fiber type: using insights from muscle developmental biology to dissect targets for susceptibility and resistance to muscle disease.

    PubMed

    Talbot, Jared; Maves, Lisa

    2016-07-01

    Skeletal muscle fibers are classified into fiber types, in particular, slow twitch versus fast twitch. Muscle fiber types are generally defined by the particular myosin heavy chain isoforms that they express, but many other components contribute to a fiber's physiological characteristics. Skeletal muscle fiber type can have a profound impact on muscle diseases, including certain muscular dystrophies and sarcopenia, the aging-induced loss of muscle mass and strength. These findings suggest that some muscle diseases may be treated by shifting fiber type characteristics either from slow to fast, or fast to slow phenotypes, depending on the disease. Recent studies have begun to address which components of muscle fiber types mediate their susceptibility or resistance to muscle disease. However, for many diseases it remains largely unclear why certain fiber types are affected. A substantial body of work has revealed molecular pathways that regulate muscle fiber type plasticity and early developmental muscle fiber identity. For instance, recent studies have revealed many factors that regulate muscle fiber type through modulating the activity of the muscle regulatory transcription factor MYOD1. Future studies of muscle fiber type development in animal models will continue to enhance our understanding of factors and pathways that may provide therapeutic targets to treat muscle diseases. WIREs Dev Biol 2016, 5:518-534. doi: 10.1002/wdev.230 For further resources related to this article, please visit the WIREs website. PMID:27199166

  20. Optical NIR monitoring of skeletal muscle contraction

    NASA Astrophysics Data System (ADS)

    Lago, Paolo; Gelmetti, Andrea; Pavesi, Roberta; Zambarbieri, Daniela

    1996-12-01

    NIR spectroscopy allows monitoring of muscle oxygenation and perfusion during contraction. The knowledge of modifications of blood characteristics in body tissues has relevant clinical interest. A compact and reliable device, which makes use of two laser diodes at 750 and 810 nm coupled with the skin surface through optical fibers, was tested. NIR and surface EMG signals during isometric contractions both in normal and ischaemic conditions were analyzed. A set of parameters from the 750/810 spectroscopic curve was analyzed. Two different categories depending on the recovery rate from maximal voluntary contraction to basal oxygenation conditions were found. This behavior can give information about metabolic modifications during muscle fatigue. Interesting results in testing isokinetic rehabilitation training were also obtained.

  1. Preliminary evidence for a postsynaptic action of beta-bungarotoxin in mammalian skeletal muscle

    NASA Technical Reports Server (NTRS)

    Storella, R. J.; Schouchoff, A. L.; Fujii, M.; Hill, J.; Fletcher, J. E.; Jiang, M. S.; Smith, L. A.

    1992-01-01

    Two hours after treatment with beta-bungarotoxin (0.34-0.4 microM), when there was complete neuromuscular block, the peak contracture response to 50 microM succinylcholine was significantly reduced by about 35% in the mouse phrenic nerve-diaphragm preparation. Additionally, significant phospholipase A2 activity was detected on primary cell cultures from skeletal muscle which were incubated for 2 hr with concentrations of beta-bungarotoxin greater than or equal to 0.1 microM. Thus, beta-bungarotoxin appears to have pharmacologically and biochemically detectable postsynaptic actions in mammalian muscle systems.

  2. Direct optical activation of skeletal muscle fibres efficiently controls muscle contraction and attenuates denervation atrophy

    PubMed Central

    Magown, Philippe; Shettar, Basavaraj; Zhang, Ying; Rafuse, Victor F.

    2015-01-01

    Neural prostheses can restore meaningful function to paralysed muscles by electrically stimulating innervating motor axons, but fail when muscles are completely denervated, as seen in amyotrophic lateral sclerosis, or after a peripheral nerve or spinal cord injury. Here we show that channelrhodopsin-2 is expressed within the sarcolemma and T-tubules of skeletal muscle fibres in transgenic mice. This expression pattern allows for optical control of muscle contraction with comparable forces to nerve stimulation. Force can be controlled by varying light pulse intensity, duration or frequency. Light-stimulated muscle fibres depolarize proportionally to light intensity and duration. Denervated triceps surae muscles transcutaneously stimulated optically on a daily basis for 10 days show a significant attenuation in atrophy resulting in significantly greater contractile forces compared with chronically denervated muscles. Together, this study shows that channelrhodopsin-2/H134R can be used to restore function to permanently denervated muscles and reduce pathophysiological changes associated with denervation pathologies. PMID:26460719

  3. Validation of Shear Wave Elastography in Skeletal Muscle

    PubMed Central

    Eby, Sarah F.; Song, Pengfei; Chen, Shigao; Chen, Qingshan; Greenleaf, James F.; An, Kai-Nan

    2013-01-01

    Skeletal muscle is a very dynamic tissue, thus accurate quantification of skeletal muscle stiffness throughout its functional range is crucial to improve the physical functioning and independence following pathology. Shear wave elastography (SWE) is an ultrasound-based technique that characterizes tissue mechanical properties based on the propagation of remotely induced shear waves. The objective of this study is to validate SWE throughout the functional range of motion of skeletal muscle for three ultrasound transducer orientations. We hypothesized that combining traditional materials testing (MTS) techniques with SWE measurements will show increased stiffness measures with increasing tensile load, and will correlate well with each other for trials in which the transducer is parallel to underlying muscle fibers. To evaluate this hypothesis, we monitored the deformation throughout tensile loading of four porcine brachialis whole-muscle tissue specimens, while simultaneously making SWE measurements of the same specimen. We used regression to examine the correlation between Young's modulus from MTS and shear modulus from SWE for each of the transducer orientations. We applied a generalized linear model to account for repeated testing. Model parameters were estimated via generalized estimating equations. The regression coefficient was 0.1944, with a 95% confidence interval of (0.1463 – 0.2425) for parallel transducer trials. Shear waves did not propagate well for both the 45° and perpendicular transducer orientations. Both parallel SWE and MTS showed increased stiffness with increasing tensile load. This study provides the necessary first step for additional studies that can evaluate the distribution of stiffness throughout muscle. PMID:23953670

  4. Effects of Dexamethasone on Satellite Cells and Tissue Engineered Skeletal Muscle Units.

    PubMed

    Syverud, Brian C; VanDusen, Keith W; Larkin, Lisa M

    2016-03-01

    Tissue engineered skeletal muscle has potential for application as a graft source for repairing soft tissue injuries, a model for testing pharmaceuticals, and a biomechanical actuator system for soft robots. However, engineered muscle to date has not produced forces comparable to native muscle, limiting its potential for repair and for use as an in vitro model for pharmaceutical testing. In this study, we examined the trophic effects of dexamethasone (DEX), a glucocorticoid that stimulates myoblast differentiation and fusion into myotubes, on our tissue engineered three-dimensional skeletal muscle units (SMUs). Using our established SMU fabrication protocol, muscle isolates were cultured with three experimental DEX concentrations (5, 10, and 25 nM) and compared to untreated controls. Following seeding onto a laminin-coated Sylgard substrate, the administration of DEX was initiated on day 0 or day 6 in growth medium or on day 9 after the switch to differentiation medium and was sustained until the completion of SMU fabrication. During this process, total cell proliferation was measured with a BrdU assay, and myogenesis and structural advancement of muscle cells were observed through immunostaining for MyoD, myogenin, desmin, and α-actinin. After SMU formation, isometric tetanic force production was measured to quantify function. The histological and functional assessment of the SMU showed that the administration of 10 nM DEX beginning on either day 0 or day 6 yielded optimal SMUs. These optimized SMUs exhibited formation of advanced sarcomeric structure and significant increases in myotube diameter and myotube fusion index, compared with untreated controls. Additionally, the optimized SMUs matured functionally, as indicated by a fivefold rise in force production. In conclusion, we have demonstrated that the addition of DEX to our process of engineering skeletal muscle tissue improves myogenesis, advances muscle structure, and increases force production in the

  5. Muscle metaboreflex activation during dynamic exercise vasoconstricts ischemic active skeletal muscle.

    PubMed

    Kaur, Jasdeep; Machado, Tiago M; Alvarez, Alberto; Krishnan, Abhinav C; Hanna, Hanna W; Altamimi, Yasir H; Senador, Danielle; Spranger, Marty D; O'Leary, Donal S

    2015-12-15

    Metabolite accumulation due to ischemia of active skeletal muscle stimulates group III/IV chemosensitive afferents eliciting reflex increases in arterial blood pressure and sympathetic activity, termed the muscle metaboreflex. We and others have previously demonstrated sympathetically mediated vasoconstriction of coronary, renal, and forelimb vasculatures with muscle metaboreflex activation (MMA). Whether MMA elicits vasoconstriction of the ischemic muscle from which it originates is unknown. We hypothesized that the vasodilation in active skeletal muscle with imposed ischemia becomes progressively restrained by the increasing sympathetic vasoconstriction during MMA. We activated the metaboreflex during mild dynamic exercise in chronically instrumented canines via graded reductions in hindlimb blood flow (HLBF) before and after α1-adrenergic blockade [prazosin (50 μg/kg)], β-adrenergic blockade [propranolol (2 mg/kg)], and α1 + β-blockade. Hindlimb resistance was calculated as femoral arterial pressure/HLBF. During mild exercise, HLBF must be reduced below a threshold level before the reflex is activated. With initial reductions in HLBF, vasodilation occurred with the imposed ischemia. Once the muscle metaboreflex was elicited, hindlimb resistance increased. This increase in hindlimb resistance was abolished by α1-adrenergic blockade and exacerbated after β-adrenergic blockade. We conclude that metaboreflex activation during submaximal dynamic exercise causes sympathetically mediated α-adrenergic vasoconstriction in ischemic skeletal muscle. This limits the ability of the reflex to improve blood flow to the muscle. PMID:26475591

  6. Targeted expression of IGF-1 transgene to skeletal muscle accelerates muscle and motor neuron regeneration.

    PubMed

    Rabinovsky, Eric D; Gelir, Ethem; Gelir, Seda; Lui, Hui; Kattash, Maan; DeMayo, Francesco J; Shenaq, Saleh M; Schwartz, Robert J

    2003-01-01

    Currently, there is no known medical treatment that hastens the repair of damaged nerve and muscle. Using IGF-1 transgenic mice that specifically express human recombinant IGF-1 in skeletal muscle, we test the hypotheses that targeted gene expression of IGF-1 in skeletal muscle enhances motor nerve regeneration after a nerve crush injury. The IGF-1 transgene affects the initiation of the muscle repair process after nerve injury as shown by increased activation of SCA-1positive myogenic stem cells. Increased satellite cell differentiation and proliferation are observed in IGF-1 transgenic mice, shown by increased expression of Cyclin D1, MyoD, and myogenin. Expression of myogenin and nicotinic acetylcholine receptor subunits, initially increased in both wild-type and IGF-1 transgenic mice, are restored to normal levels at a faster rate in IGF-1 transgenic mice, which indicates a rescue of nerve-evoked muscle activity. Expression of the IGF-1 transgene in skeletal muscle results in accelerated recovery of saltatory nerve conduction, increased innervation as detected by neurofilament expression, and faster recovery of muscle mass. These studies demonstrate that local expression of IGF-1 augments the repair of injured nerve and muscle. PMID:12424223

  7. ATP citrate lyase improves mitochondrial function in skeletal muscle.

    PubMed

    Das, Suman; Morvan, Frederic; Jourde, Benjamin; Meier, Viktor; Kahle, Peter; Brebbia, Pascale; Toussaint, Gauthier; Glass, David J; Fornaro, Mara

    2015-06-01

    Mitochondrial dysfunction is associated with skeletal muscle pathology, including cachexia, sarcopenia, and the muscular dystrophies. ATP citrate lyase (ACL) is a cytosolic enzyme that catalyzes mitochondria-derived citrate into oxaloacetate and acetyl-CoA. Here we report that activation of ACL in skeletal muscle results in improved mitochondrial function. IGF1 induces activation of ACL in an AKT-dependent fashion. This results in an increase in cardiolipin, thus increasing critical mitochondrial complexes and supercomplex activity, and a resultant increase in oxygen consumption and cellular ATP levels. Conversely, knockdown of ACL in myotubes not only reduces mitochondrial complex I, IV, and V activity but also blocks IGF1-induced increases in oxygen consumption. In vivo, ACL activity is associated with increased ATP. Activation of this IGF1/ACL/cardiolipin pathway combines anabolic signaling with induction of mechanisms needed to provide required ATP. PMID:26039450

  8. Mitochondrial function in skeletal muscle in type 2 diabetes.

    PubMed

    Rabøl, Rasmus

    2011-04-01

    Reduced skeletal muscle mitochondrial function has been proposed to lead to insulin resistance and type 2 diabetes. It has been known for several years that oxidative capacity of skeletal muscle is reduced in patients with type 2 diabetes compared to weight matched controls. The reduction in oxidative capacity supposedly leads to the accumulation of intramyocellular lipid which inhibits insulin signalling and causes insulin resistance. It is not known whether this reduction in mitochondrial capacity is the cause or the effect of type 2 diabetes. This PhD-thesis describes the effect of different pharmacological interventions on mitochondrial function in type 2 diabetes and describe whether mitochondrial function is uniformly distributed to both upper and lower extremities. Furthermore, a hypothesis on the molecular mechanism for weight gain observed with anthyperglycaemic treatment will be presented. PMID:21466770

  9. Detyrosinated microtubules modulate mechanotransduction in heart and skeletal muscle

    PubMed Central

    Kerr, Jaclyn P.; Robison, Patrick; Shi, Guoli; Bogush, Alexey I.; Kempema, Aaron M.; Hexum, Joseph K.; Becerra, Natalia; Harki, Daniel A.; Martin, Stuart S.; Raiteri, Roberto; Prosser, Benjamin L.; Ward, Christopher W.

    2015-01-01

    In striated muscle, X-ROS is the mechanotransduction pathway by which mechanical stress transduced by the microtubule network elicits reactive oxygen species. X-ROS tunes Ca2+ signalling in healthy muscle, but in diseases such as Duchenne muscular dystrophy (DMD), microtubule alterations drive elevated X-ROS, disrupting Ca2+ homeostasis and impairing function. Here we show that detyrosination, a post-translational modification of α-tubulin, influences X-ROS signalling, contraction speed and cytoskeletal mechanics. In the mdx mouse model of DMD, the pharmacological reduction of detyrosination in vitro ablates aberrant X-ROS and Ca2+ signalling, and in vivo it protects against hallmarks of DMD, including workload-induced arrhythmias and contraction-induced injury in skeletal muscle. We conclude that detyrosinated microtubules increase cytoskeletal stiffness and mechanotransduction in striated muscle and that targeting this post-translational modification may have broad therapeutic potential in muscular dystrophies. PMID:26446751

  10. Atrophy of rat skeletal muscles in simulated weightlessness

    NASA Technical Reports Server (NTRS)

    Feller, D. D.; Ginoza, H. S.; Morey, E. R.

    1982-01-01

    A hypokinetic rat model was used for elucidation of the mechanism of skeletal muscle wasting which occurs in weightlessness. Rats were suspended from a back-harness with the head tilted downward and the hind limbs totally unloaded. A progressive decrease in the size of the soleus muscle from suspended rats was observed as a function of time. The rate of protein degradation of the homogenates from the soleus muscles of suspended and control animals was not significantly different. The rate of cell-free protein synthesis was severely repressed in the atrophied muscle. An initial rise in the levels of plasma glucose and corticosterone was observed on the second day of suspension, but they subsequently returned to normal values.

  11. Effect of hindlimb immobilization on the fatigability of skeletal muscle

    NASA Technical Reports Server (NTRS)

    Witzmann, F. A.; Kim, D. H.; Fitts, R. H.

    1983-01-01

    The effect of 6 weeks of disuse atrophy produced by hindlimb immobilization was studied in situ (33.5 C) in the soleus and extensor digitorum longus muscles of rats. The results indicate that disuse causes preferential alterations in the isometric contractile properties of slow-twitch, as opposed to fast-twitch, skeletal muscles. During continuous contractile activity, atrophied muscles were found to have lower ATP levels and an apparent increase in their dependence on anaerobic metabolism, as reflected by the more extensive depletion of glycogen and enhanced lactate formation. Although the atrophied muscles were determined to have fewer cross bridges and thus generated lower tension, the pattern of decline in active cross-bridge formation and tetanic tension during contractile activity was found to proceed in a manner similar to controls.

  12. Turning terminally differentiated skeletal muscle cells into regenerative progenitors.

    PubMed

    Wang, Heng; Lööf, Sara; Borg, Paula; Nader, Gustavo A; Blau, Helen M; Simon, András

    2015-01-01

    The ability to repeatedly regenerate limbs during the entire lifespan of an animal is restricted to certain salamander species among vertebrates. This ability involves dedifferentiation of post-mitotic cells into progenitors that in turn form new structures. A long-term enigma has been how injury leads to dedifferentiation. Here we show that skeletal muscle dedifferentiation during newt limb regeneration depends on a programmed cell death response by myofibres. We find that programmed cell death-induced muscle fragmentation produces a population of 'undead' intermediate cells, which have the capacity to resume proliferation and contribute to muscle regeneration. We demonstrate the derivation of proliferating progeny from differentiated, multinucleated muscle cells by first inducing and subsequently intercepting a programmed cell death response. We conclude that cell survival may be manifested by the production of a dedifferentiated cell with broader potential and that the diversion of a programmed cell death response is an instrument to achieve dedifferentiation. PMID:26243583

  13. cap alpha. -skeletal and. cap alpha. -cardiac actin genes are coexpressed in adult human skeletal muscle and heart

    SciTech Connect

    Gunning, P.; Ponte, P.; Blau, H.; Kedes, L.

    1983-11-01

    The authors determined the actin isotypes encoded by 30 actin cDNA clones previously isolated from an adult human muscle cDNA library. Using 3' untranslated region probes, derived from ..cap alpha.. skeletal, ..beta..- and ..gamma..-actin cDNAs and from an ..cap alpha..-cardiac actin genomic clone, they showed that 28 of the cDNAs correspond to ..cap alpha..-skeletal actin transcripts. Unexpectedly, however, the remaining two cDNA clones proved to derive from ..cap alpha..-cardiac actin mRNA. Sequence analysis confirmed that the two skeletal muscle ..cap alpha..-cardiac actin cDNAs are derived from transcripts of the cloned ..cap alpha..-cardiac actin gene. Comparison of total actin mRNA levels in adult skeletal muscle and adult heart revealed that the steady-state levels in skeletal muscle are about twofold greater, per microgram of total cellular RNA, than those in heart. Thus, in skeletal muscle and in heart, both of the sarcomeric actin mRNA isotypes are quite abundant transcripts. They conclude that ..cap alpha..-skeletal and ..cap alpha..-cardiac actin genes are coexpressed as an actin pair in human adult striated muscles. Since the smooth-muscle actins (aortic and stomach) and the cytoplasmic actins (..beta.. and ..gamma..) are known to be coexpressed in smooth muscle and nonmuscle cells, respectively, they postulate that coexpression of actin pairs may be a common feature of mammalian actin gene expression in all tissues.

  14. Bone marrow-derived cell regulation of skeletal muscle regeneration.

    PubMed

    Sun, Dongxu; Martinez, Carlo O; Ochoa, Oscar; Ruiz-Willhite, Lourdes; Bonilla, Jose R; Centonze, Victoria E; Waite, Lindsay L; Michalek, Joel E; McManus, Linda M; Shireman, Paula K

    2009-02-01

    Limb regeneration requires the coordination of multiple stem cell populations to recapitulate the process of tissue formation. Therefore, bone marrow (BM) -derived cell regulation of skeletal muscle regeneration was examined in mice lacking the CC chemokine receptor 2 (CCR2). Myofiber size, numbers of myogenic progenitor cells (MPCs), and recruitment of BM-derived cells and macrophages were assessed after cardiotoxin-induced injury of chimeric mice produced by transplanting BM from wild-type (WT) or CCR2(-/-) mice into irradiated WT or CCR2(-/-) host mice. Regardless of the host genotype, muscle regeneration and recruitment of BM-derived cells and macrophages were similar in mice replenished with WT BM, whereas BM-derived cells and macrophage accumulation were decreased and muscle regeneration was impaired in all animals receiving CCR2(-/-) BM. Furthermore, numbers of MPCs (CD34(+)/Sca-1(-)/CD45(-) cells) were significantly increased in mice receiving CCR2(-/-) BM despite the decreased size of regenerated myofibers. Thus, the expression of CCR2 on BM-derived cells regulated macrophage recruitment into injured muscle, numbers of MPC, and the extent of regenerated myofiber size, all of which were independent of CCR2 expression on host-derived cells. Future studies in regenerative medicine must include consideration of the role of BM-derived cells, possibly macrophages, in CCR2-dependent events that regulate effective skeletal muscle regeneration. PMID:18827026

  15. Dysferlin overexpression in skeletal muscle produces a progressive myopathy

    PubMed Central

    Glover, Louise E.; Newton, Kimberly; Krishnan, Gomathi; Bronson, Roderick; Boyle, Alexandra; Krivickas, Lisa S.; Brown, Robert H.

    2013-01-01

    Objective The dose-response effects of dysferlin transgenesis were analyzed to determine if the dysferlin-deficient myopathies are good candidates for gene replacement therapy. Methods We have generated three lines of transgenic mice, expressing low, mid and high levels of full-length human dysferlin from a muscle-specific promoter. Transgenic skeletal muscle was analyzed and scored for morphological and functional deficits. Results Overexpression of dysferlin in mice resulted in a striking phenotype of kyphosis, irregular gait and reduced muscle mass and strength. Moreover, protein dosage correlated with phenotype severity. In contrast to dysferlin-null skeletal muscle, no evidence of sarcolemmal impairment was revealed. Rather, increased levels of Ca2+-regulated, dysferlin-binding proteins and ER stress chaperone proteins were observed in muscle lysates from transgenic mice as compared to controls. Interpretation Expression levels of dysferlin are important for appropriate function without deleterious or cytotoxic effects. As a corollary, we propose that future endeavors in gene replacement for correction of dysferlinopathy should be tailored to take account of this. PMID:20373350

  16. Mechanical stimulation improves tissue-engineered human skeletal muscle

    NASA Technical Reports Server (NTRS)

    Powell, Courtney A.; Smiley, Beth L.; Mills, John; Vandenburgh, Herman H.

    2002-01-01

    Human bioartificial muscles (HBAMs) are tissue engineered by suspending muscle cells in collagen/MATRIGEL, casting in a silicone mold containing end attachment sites, and allowing the cells to differentiate for 8 to 16 days. The resulting HBAMs are representative of skeletal muscle in that they contain parallel arrays of postmitotic myofibers; however, they differ in many other morphological characteristics. To engineer improved HBAMs, i.e., more in vivo-like, we developed Mechanical Cell Stimulator (MCS) hardware to apply in vivo-like forces directly to the engineered tissue. A sensitive force transducer attached to the HBAM measured real-time, internally generated, as well as externally applied, forces. The muscle cells generated increasing internal forces during formation which were inhibitable with a cytoskeleton depolymerizer. Repetitive stretch/relaxation for 8 days increased the HBAM elasticity two- to threefold, mean myofiber diameter 12%, and myofiber area percent 40%. This system allows engineering of improved skeletal muscle analogs as well as a nondestructive method to determine passive force and viscoelastic properties of the resulting tissue.

  17. The Role of Skeletal Muscle in Amyotrophic Lateral Sclerosis.

    PubMed

    Loeffler, Jean-Philippe; Picchiarelli, Gina; Dupuis, Luc; Gonzalez De Aguilar, Jose-Luis

    2016-03-01

    Amyotrophic lateral sclerosis (ALS) is a fatal adult-onset disease primarily characterized by upper and lower motor neuron degeneration, muscle wasting and paralysis. It is increasingly accepted that the pathological process leading to ALS is the result of multiple disease mechanisms that operate within motor neurons and other cell types both inside and outside the central nervous system. The implication of skeletal muscle has been the subject of a number of studies conducted on patients and related animal models. In this review, we describe the features of ALS muscle pathology and discuss on the contribution of muscle to the pathological process. We also give an overview of the therapeutic strategies proposed to alleviate muscle pathology or to deliver curative agents to motor neurons. ALS muscle mainly suffers from oxidative stress, mitochondrial dysfunction and bioenergetic disturbances. However, the way by which the disease affects different types of myofibers depends on their contractile and metabolic features. Although the implication of muscle in nourishing the degenerative process is still debated, there is compelling evidence suggesting that it may play a critical role. Detailed understanding of the muscle pathology in ALS could, therefore, lead to the identification of new therapeutic targets. PMID:26780251

  18. In vivo myosin step-size from zebrafish skeletal muscle

    PubMed Central

    Ajtai, Katalin; Sun, Xiaojing; Takubo, Naoko; Wang, Yihua

    2016-01-01

    Muscle myosins transduce ATP free energy into actin displacement to power contraction. In vivo, myosin side chains are modified post-translationally under native conditions, potentially impacting function. Single myosin detection provides the ‘bottom-up’ myosin characterization probing basic mechanisms without ambiguities inherent to ensemble observation. Macroscopic muscle physiological experimentation provides the definitive ‘top-down’ phenotype characterizations that are the concerns in translational medicine. In vivo single myosin detection in muscle from zebrafish embryo models for human muscle fulfils ambitions for both bottom-up and top-down experimentation. A photoactivatable green fluorescent protein (GFP)-tagged myosin light chain expressed in transgenic zebrafish skeletal muscle specifically modifies the myosin lever-arm. Strychnine induces the simultaneous contraction of the bilateral tail muscles in a live embryo, causing them to be isometric while active. Highly inclined thin illumination excites the GFP tag of single lever-arms and its super-resolution orientation is measured from an active isometric muscle over a time sequence covering many transduction cycles. Consecutive frame lever-arm angular displacement converts to step-size by its product with the estimated lever-arm length. About 17% of the active myosin steps that fall between 2 and 7 nm are implicated as powerstrokes because they are beyond displacements detected from either relaxed or ATP-depleted (rigor) muscle. PMID:27249818

  19. Compartment calcium model of frog skeletal muscle during activation.

    PubMed

    Liu, Weifan; Olson, Sarah D

    2015-01-01

    Skeletal muscle contraction is triggered by a rise in calcium (Ca(2+)) concentration in the myofibrillar space. The objective of this study was to develop a voltage dependent compartment model of Ca(2+) dynamics in frog skeletal muscle fibers. The compartment model corresponds to the myofibrillar space (MS) and a calcium store, the sarcoplasmic reticulum (SR). Ca(2+) is released from the SR to the MS based on the voltage and is able to bind to several proteins in the MS. We use a detailed model to account for voltage dependent Ca(2+) release and inactivation. With this model, we are able to match previous experimental data for Ca(2+) release and binding to proteins for an applied (fixed) voltage. We explore the sensitivity of parameters in the model and illustrate the importance of inactivation of the SR; during a long depolarization, the SR must be inactivated in order to achieve realistic Ca(2+) concentrations in the MS. A Hodgkin Huxley type model was also developed to describe voltage at the surface membrane using electrophysiological data from previous experiments. This voltage model was then used as the time dependent voltage to determine Ca(2+) release from the SR. With this fully coupled model, we were able to match previous experimental results for Ca(2+) concentrations for a given applied current. Additionally, we examined simulated Ca(2+) concentrations in the case of twitch and tetanus, corresponding to different applied currents. The developed model is robust and reproduces many aspects of voltage dependent calcium signaling in frog skeletal muscle fibers. This modeling framework provides a platform for future studies of excitation contraction coupling in skeletal muscle fibers. PMID:25234233

  20. Leukemia inhibitory factor increases glucose uptake in mouse skeletal muscle.

    PubMed

    Brandt, Nina; O'Neill, Hayley M; Kleinert, Maximilian; Schjerling, Peter; Vernet, Erik; Steinberg, Gregory R; Richter, Erik A; Jørgensen, Sebastian B

    2015-07-15

    Members of the IL-6 family, IL-6 and ciliary neurotrophic factor (CNTF), have been shown to increase glucose uptake and fatty acid oxidation in skeletal muscle. However, the metabolic effects of another family member, leukemia inhibitory factor (LIF), are not well characterized. Effects of LIF on skeletal muscle glucose uptake and palmitate oxidation and signaling were investigated in ex vivo incubated mouse soleus and EDL muscles from muscle-specific AMPKα2 kinase-dead, muscle-specific SOCS3 knockout, and lean and high-fat-fed mice. Inhibitors were used to investigate involvement of specific signaling pathways. LIF increased muscle glucose uptake in dose (50-5,000 pM/l) and time-dependent manners with maximal effects at the 30-min time point. LIF increased Akt Ser(473) phosphorylation (P) in soleus and EDL, whereas AMPK Thr(172) P was unaffected. Incubation with parthenolide abolished LIF-induced glucose uptake and STAT3 Tyr(705) P, whereas incubation with LY-294002 and wortmannin suppressed both basal and LIF-induced glucose uptake and Akt Ser(473) P, indicating that JAK and PI 3-kinase signaling is required for LIF-stimulated glucose uptake. Incubation with rapamycin and AZD8055 indicated that mammalian target of rapamycin complex (mTORC)2, but not mTORC1, also is required for LIF-stimulated glucose uptake. In contrast to CNTF, LIF stimulation did not alter palmitate oxidation. LIF-stimulated glucose uptake was maintained in EDL from obese insulin-resistant mice, whereas soleus developed LIF resistance. Lack of SOCS3 and AMPKα2 did not affect LIF-stimulated glucose uptake. In conclusion, LIF acutely increased muscle glucose uptake by a mechanism potentially involving the PI 3-kinase/mTORC2/Akt pathway and is not impaired in EDL muscle from obese insulin-resistant mice. PMID:25968579

  1. Cell death, clearance and immunity in the skeletal muscle.

    PubMed

    Sciorati, C; Rigamonti, E; Manfredi, A A; Rovere-Querini, P

    2016-06-01

    The skeletal muscle is an immunologically unique tissue. Leukocytes, virtually absent in physiological conditions, are quickly recruited into the tissue upon injury and persist during regeneration. Apoptosis, necrosis and autophagy coexist in the injured/regenerating muscles, including those of patients with neuromuscular disorders, such as inflammatory myopathies, dystrophies, metabolic and mitochondrial myopathies and drug-induced myopathies. Macrophages are able to alter their function in response to microenvironment conditions and as a consequence coordinate changes within the tissue from the early injury throughout regeneration and eventual healing, and regulate the activation and the function of stem cells. Early after injury, classically activated macrophages ('M1') dominate the picture. Alternatively activated M2 macrophages predominate during resolution phases and regulate the termination of the inflammatory responses. The dynamic M1/M2 transition is increasingly felt to be the key to the homeostasis of the muscle. Recognition and clearance of debris originating from damaged myofibers and from dying stem/progenitor cells, stromal cells and leukocytes are fundamental actions of macrophages. Clearance of apoptotic cells and M1/M2 transition are causally connected and represent limiting steps for muscle healing. The accumulation of apoptotic cells, which reflects their defective clearance, has been demonstrated in various tissues to prompt autoimmunity against intracellular autoantigens. In the muscle, in the presence of type I interferon, apoptotic myoblasts indeed cause the production of autoantibodies, lymphocyte infiltration and continuous cycles of muscle injury and regeneration, mimicking human inflammatory myopathies. The clearance of apoptotic cells thus modulates the homeostatic response of the skeletal muscle to injury. Conversely, defects in the process may have deleterious local effects, guiding maladaptive tissue remodeling with collagen and fat

  2. Prioritization of skeletal muscle growth for emergence from hibernation.

    PubMed

    Hindle, Allyson G; Otis, Jessica P; Epperson, L Elaine; Hornberger, Troy A; Goodman, Craig A; Carey, Hannah V; Martin, Sandra L

    2015-01-15

    Mammalian hibernators provide an extreme example of naturally occurring challenges to muscle homeostasis. The annual hibernation cycle is characterized by shifts between summer euthermy with tissue anabolism and accumulation of body fat reserves, and winter heterothermy with fasting and tissue catabolism. The circannual patterns of skeletal muscle remodelling must accommodate extended inactivity during winter torpor, the motor requirements of transient winter active periods, and sustained activity following spring emergence. Muscle volume in thirteen-lined ground squirrels (Ictidomys tridecemlineatus) calculated from MRI upper hindlimb images (n=6 squirrels, n=10 serial scans) declined from hibernation onset, reaching a nadir in early February. Paradoxically, mean muscle volume rose sharply after February despite ongoing hibernation, and continued total body mass decline until April. Correspondingly, the ratio of muscle volume to body mass was steady during winter atrophy (October-February) but increased (+70%) from February to May, which significantly outpaced changes in liver or kidney examined by the same method. Generally stable myocyte cross-sectional area and density indicated that muscle remodelling is well regulated in this hibernator, despite vastly altered seasonal fuel and activity levels. Body composition analysis by echo MRI showed lean tissue preservation throughout hibernation amid declining fat mass by the end of winter. Muscle protein synthesis was 66% depressed in early but not late winter compared with a summer fasted baseline, while no significant changes were observed in the heart, liver or intestine, providing evidence that could support a transition in skeletal muscle regulation between early and late winter, prior to spring emergence and re-feeding. PMID:25452506

  3. Prioritization of skeletal muscle growth for emergence from hibernation

    PubMed Central

    Hindle, Allyson G.; Otis, Jessica P.; Epperson, L. Elaine; Hornberger, Troy A.; Goodman, Craig A.; Carey, Hannah V.; Martin, Sandra L.

    2015-01-01

    Mammalian hibernators provide an extreme example of naturally occurring challenges to muscle homeostasis. The annual hibernation cycle is characterized by shifts between summer euthermy with tissue anabolism and accumulation of body fat reserves, and winter heterothermy with fasting and tissue catabolism. The circannual patterns of skeletal muscle remodelling must accommodate extended inactivity during winter torpor, the motor requirements of transient winter active periods, and sustained activity following spring emergence. Muscle volume in thirteen-lined ground squirrels (Ictidomys tridecemlineatus) calculated from MRI upper hindlimb images (n=6 squirrels, n=10 serial scans) declined from hibernation onset, reaching a nadir in early February. Paradoxically, mean muscle volume rose sharply after February despite ongoing hibernation, and continued total body mass decline until April. Correspondingly, the ratio of muscle volume to body mass was steady during winter atrophy (October–February) but increased (+70%) from February to May, which significantly outpaced changes in liver or kidney examined by the same method. Generally stable myocyte cross-sectional area and density indicated that muscle remodelling is well regulated in this hibernator, despite vastly altered seasonal fuel and activity levels. Body composition analysis by echo MRI showed lean tissue preservation throughout hibernation amid declining fat mass by the end of winter. Muscle protein synthesis was 66% depressed in early but not late winter compared with a summer fasted baseline, while no significant changes were observed in the heart, liver or intestine, providing evidence that could support a transition in skeletal muscle regulation between early and late winter, prior to spring emergence and re-feeding. PMID:25452506

  4. Skeletal muscle metabolism in hypokinetic rats

    NASA Technical Reports Server (NTRS)

    Tischler, Marc E.

    1993-01-01

    This grant focused on the mechanisms of metabolic changes associated with unweighting atrophy and reduced growth of hind limb muscles of juvenile rats. Metabolic studies included a number of different areas. Amino acid metabolic studies placed particular emphasis on glutamine and branched-chain amino acid metabolism. These studies were an outgrowth of understanding stress effects and the role of glucocorticoids in these animals. Investigations on protein metabolism were largely concerned with selective loss of myofibrillar proteins and the role of muscle proteolysis. These investigations lead to finding important differences from denervation and atrophy and to define the roles of cytosolic versus lysosomal proteolysis in these atrophy models. A major outgrowth of these studies was demonstrating an ability to prevent atrophy of the unweighted muscle for at least 24 hours. A large amount of work concentrated on carbohydrate metabolism and its regulation by insulin and catecholamines. Measurements focused on glucose transport, glycogen metabolism, and glucose oxidation. The grant was used to develop an important new in situ approach for studying protein metabolism, glucose transport, and hormonal effects which involves intramuscular injection of various agents for up to 24 hours. Another important consequence of this project was the development and flight of Physiological-Anatomical Rodent Experiment-1 (PARE-1), which was launched aboard Space Shuttle Discovery in September 1991. Detailed descriptions of these studies can be found in the 30 peer-reviewed publications, 15 non-reviewed publications, 4 reviews and 33 abstracts (total 82 publications) which were or are scheduled to be published as a result of this project. A listing of these publications grouped by area (i.e. amino acid metabolism, protein metabolism, carbohydrate metabolism, and space flight studies) are included.

  5. Toxicity of statins on rat skeletal muscle mitochondria.

    PubMed

    Kaufmann, P; Török, M; Zahno, A; Waldhauser, K M; Brecht, K; Krähenbühl, S

    2006-10-01

    We investigated mitochondrial toxicity of four lipophilic stains (cerivastatin, fluvastatin, atorvastatin, simvastatin) and one hydrophilic statin (pravastatin). In L6 cells (rat skeletal muscle cell line), the four lipophilic statins (100 micromol/l) induced death in 27-49% of the cells. Pravastatin was not toxic up to 1 mmol/l. Cerivastatin, fluvastatin and atorvastatin (100 micromol/l) decreased the mitochondrial membrane potential by 49-65%, whereas simvastatin and pravastatin were less toxic. In isolated rat skeletal muscle mitochondria, all statins, except pravastatin, decreased glutamate-driven state 3 respiration and respiratory control ratio. Beta-oxidation was decreased by 88-96% in the presence of 100 micromol/l of the lipophilic statins, but only at higher concentrations by pravastatin. Mitochondrial swelling, cytochrome c release and DNA fragmentation was induced in L6 cells by the four lipophilic statins, but not by pravastatin. Lipophilic statins impair the function of skeletal muscle mitochondria, whereas the hydrophilic pravastatin is significantly less toxic. PMID:17013560

  6. Low Intensity Exercise Training Improves Skeletal Muscle Regeneration Potential

    PubMed Central

    Pietrangelo, Tiziana; Di Filippo, Ester S.; Mancinelli, Rosa; Doria, Christian; Rotini, Alessio; Fanò-Illic, Giorgio; Fulle, Stefania

    2015-01-01

    Purpose: The aim of this study was to determine whether 12 days of low-to-moderate exercise training at low altitude (598 m a.s.l.) improves skeletal muscle regeneration in sedentary adult women. Methods: Satellite cells were obtained from the vastus lateralis skeletal muscle of seven women before and after this exercise training at low altitude. They were investigated for differentiation aspects, superoxide anion production, antioxidant enzymes, mitochondrial potential variation after a depolarizing insult, intracellular Ca2+ concentrations, and micro (mi)RNA expression (miR-1, miR-133, miR-206). Results: In these myogenic populations of adult stem cells, those obtained after exercise training, showed increased Fusion Index and intracellular Ca2+ concentrations. This exercise training also generally reduced superoxide anion production in cells (by 12–67%), although not in two women, where there was an increase of ~15% along with a reduced superoxide dismutase activity. miRNA expression showed an exercise-induced epigenetic transcription profile that was specific according to the reduced or increased superoxide anion production of the cells. Conclusions: The present study shows that low-to-moderate exercise training at low altitude improves the regenerative capacity of skeletal muscle in adult women. The differentiation of cells was favored by increased intracellular calcium concentration and increased the fusion index. This low-to-moderate training at low altitude also depicted the epigenetic signature of cells. PMID:26733888

  7. Signalling and the control of skeletal muscle size

    SciTech Connect

    Otto, Anthony; Patel, Ketan

    2010-11-01

    Skeletal muscle is highly adaptive to environmental stimuli and can alter its mass accordingly. This tissue is almost unique in that it can increase its size through two distinct mechanisms. It can grow through a cellular process mediated by cell fusion, or it can increase its size simply by increasing its protein content. Understanding how these processes are regulated is crucial for the development of potential therapies against debilitating skeletal muscle wasting diseases. Two key signalling molecules, Insulin like Growth Factor (IGF) and GDF-8/myostatin, have emerged in recent years to be potent regulators of skeletal muscle size. In this review we bring together recent data highlighting the important and novel aspects of both molecules and their signalling pathways, culminating in a discussion of the cellular and tissue phenotypic outcomes of their stimulation or antagonism. We emphasise the complex regulatory mechanisms and discuss the temporal and spatial differences that control their action, understanding of which is crucial to further their use as potential therapeutic targets.

  8. Syndecan-3 and syndecan-4 specifically mark skeletal muscle satellite cells and are implicated in satellite cell maintenance and muscle regeneration.

    PubMed

    Cornelison, D D; Filla, M S; Stanley, H M; Rapraeger, A C; Olwin, B B

    2001-11-01

    Myogenesis in the embryo and the adult mammal consists of a highly organized and regulated sequence of cellular processes to form or repair muscle tissue that include cell proliferation, migration, and differentiation. Data from cell culture and in vivo experiments implicate both FGFs and HGF as critical regulators of these processes. Both factors require heparan sulfate glycosaminoglycans for signaling from their respective receptors. Since syndecans, a family of cell-surface transmembrane heparan sulfate proteoglycans (HSPGs) are implicated in FGF signaling and skeletal muscle differentiation, we examined the expression of syndecans 1-4 in embryonic, fetal, postnatal, and adult muscle tissue, as well as on primary adult muscle fiber cultures. We show that syndecan-1, -3, and -4 are expressed in developing skeletal muscle tissue and that syndecan-3 and -4 expression is highly restricted in adult skeletal muscle to cells retaining myogenic capacity. These two HSPGs appear to be expressed exclusively and universally on quiescent adult satellite cells in adult skeletal muscle tissue, suggesting a role for HSPGs in satellite cell maintenance or activation. Once activated, all satellite cells maintain expression of syndecan-3 and syndecan-4 for at least 96 h, also implicating these HSPGs in muscle regeneration. Inhibition of HSPG sulfation by treatment of intact myofibers with chlorate results in delayed proliferation and altered MyoD expression, demonstrating that heparan sulfate is required for proper progression of the early satellite cell myogenic program. These data suggest that, in addition to providing potentially useful new markers for satellite cells, syndecan-3 and syndecan-4 may play important regulatory roles in satellite cell maintenance, activation, proliferation, and differentiation during skeletal muscle regeneration. PMID:11784020

  9. Data on skeletal muscle apoptosis, autophagy, and morphology in mice treated with doxorubicin.

    PubMed

    Campbell, Troy L; Quadrilatero, Joe

    2016-06-01

    Skeletal muscle apoptosis and autophagy are catabolic processes that contribute to muscle atrophy during aging, disease, and following muscle injury. In this article, we present data on skeletal muscle apoptosis, autophagy, and morphology in C57BL/6 mice following doxorubicin administration. More specifically, time-course data on caspase-3, caspase-8, caspase-9, calpain, and cathepsin activity are presented, along with data on ATG7, p62, LC3-I, and LC3-II protein expression. Data on skeletal muscle reactive oxygen species (ROS) production, muscle morphology, as well as body and muscle weights are also presented. PMID:27077080

  10. Production of arrays of cardiac and skeletal muscle myofibers by micropatterning techniques on a soft substrate.

    PubMed

    Cimetta, Elisa; Pizzato, Sara; Bollini, Sveva; Serena, Elena; De Coppi, Paolo; Elvassore, Nicola

    2009-04-01

    Micropatterning and microfabrication techniques have been widely used to pattern cells on surfaces and to have a deeper insight into many processes in cell biology such as cell adhesion and interactions with the surrounding environment. The aim of this study was the development of an easy and versatile technique for the in vitro production of arrays of functional cardiac and skeletal muscle myofibers using micropatterning techniques on soft substrates. Cardiomyocytes were used for the production of oriented cardiac myofibers whereas mouse muscle satellite cells for that of differentiated parallel myotubes. We performed micro-contact printing of extracellular matrix proteins on soft polyacrylamide-based hydrogels photopolymerized onto functionalized glass slides. Our methods proved to be simple, repeatable and effective in obtaining an extremely selective adhesion of both cardiomyocytes and satellite cells onto patterned soft hydrogel surfaces. Cardiomyocytes resulted in aligned cardiac myofibers able to exhibit a synchronous contractile activity after 2 days of culture. We demonstrated for the first time that murine satellite cells, cultured on a soft hydrogel substrate, fuse and form aligned myotubes after 7 days of culture. Immunofluorescence analyses confirmed correct expression of cell phenotype, differentiation markers and sarcomeric organization. These results were obtained in myotubes derived from satellite cells from both wild type and MDX mice which are research models for the study of muscle dystrophy. These arrays of both cardiac and skeletal muscle myofibers could be used as in vitro models for pharmacological screening tests or biological studies at the single fiber level. PMID:18987976

  11. MyoD-positive myoblasts are present in mature fetal organs lacking skeletal muscle

    PubMed Central

    Gerhart, Jacquelyn; Bast, Brian; Neely, Christine; Iem, Stephanie; Amegbe, Paula; Niewenhuis, Robert; Miklasz, Steven; Cheng, Pei Feng; George-Weinstein, Mindy

    2001-01-01

    The epiblast of the chick embryo gives rise to the ectoderm, mesoderm, and endoderm during gastrulation. Previous studies revealed that MyoD-positive cells were present throughout the epiblast, suggesting that skeletal muscle precursors would become incorporated into all three germ layers. The focus of the present study was to examine a variety of organs from the chicken fetus for the presence of myogenic cells. RT-PCR and in situ hybridizations demonstrated that MyoD-positive cells were present in the brain, lung, intestine, kidney, spleen, heart, and liver. When these organs were dissociated and placed in culture, a subpopulation of cells differentiated into skeletal muscle. The G8 antibody was used to label those cells that expressed MyoD in vivo and to follow their fate in vitro. Most, if not all, of the muscle that formed in culture arose from cells that expressed MyoD and G8 in vivo. Practically all of the G8-positive cells from the intestine differentiated after purification by FACS®. This population of ectopically located cells appears to be distinct from multipotential stem cells and myofibroblasts. They closely resemble quiescent, stably programmed skeletal myoblasts with the capacity to differentiate when placed in a permissive environment. PMID:11684706

  12. An allometric analysis of the number of muscle spindles in mammalian skeletal muscles.

    PubMed

    Banks, R W

    2006-06-01

    An allometric analysis of the number of muscle spindles in relation to muscle mass in mammalian (mouse, rat, guinea-pig, cat, human) skeletal muscles is presented. It is shown that the trend to increasing number as muscle mass increases follows an isometric (length) relationship between species, whereas within a species, at least for the only essentially complete sample (human), the number of spindles scales, on average, with the square root rather than the cube root of muscle mass. An attempt is made to reconcile these apparently discrepant relationships. Use of the widely accepted spindle density (number of spindles g(-1) of muscle) as a measure of relative abundance of spindles in different muscles is shown to be grossly misleading. It is replaced with the residuals of the linear regression of ln spindle number against ln muscle mass. Significant differences in relative spindle abundance as measured by residuals were found between regional groups of muscles: the greatest abundance is in axial muscles, including those concerned with head position, whereas the least is in muscles of the shoulder girdle. No differences were found between large and small muscles operating in parallel, or between antigravity and non-antigravity muscles. For proximal vs. distal muscles, spindles were significantly less abundant in the hand than the arm, but there was no difference between the foot and the leg. PMID:16761976

  13. Bioengineered human myobundles mimic clinical responses of skeletal muscle to drugs.

    PubMed

    Madden, Lauran; Juhas, Mark; Kraus, William E; Truskey, George A; Bursac, Nenad

    2015-01-01

    Existing in vitro models of human skeletal muscle cannot recapitulate the organization and function of native muscle, limiting their use in physiological and pharmacological studies. Here, we demonstrate engineering of electrically and chemically responsive, contractile human muscle tissues ('myobundles') using primary myogenic cells. These biomimetic constructs exhibit aligned architecture, multinucleated and striated myofibers, and a Pax7(+) cell pool. They contract spontaneously and respond to electrical stimuli with twitch and tetanic contractions. Positive correlation between contractile force and GCaMP6-reported calcium responses enables non-invasive tracking of myobundle function and drug response. During culture, myobundles maintain functional acetylcholine receptors and structurally and functionally mature, evidenced by increased myofiber diameter and improved calcium handling and contractile strength. In response to diversely acting drugs, myobundles undergo dose-dependent hypertrophy or toxic myopathy similar to clinical outcomes. Human myobundles provide an enabling platform for predictive drug and toxicology screening and development of novel therapeutics for muscle-related disorders. PMID:25575180

  14. Comprehensive analysis of tropomyosin isoforms in skeletal muscles by top-down proteomics.

    PubMed

    Jin, Yutong; Peng, Ying; Lin, Ziqing; Chen, Yi-Chen; Wei, Liming; Hacker, Timothy A; Larsson, Lars; Ge, Ying

    2016-04-01

    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

  15. Fast skeletal muscle troponin T increases the cooperativity of transgenic mouse cardiac muscle contraction

    PubMed Central

    Huang, Qi-Quan; Brozovich, Frank V; Jin, Jian-Ping

    1999-01-01

    To investigate the functional significance of different troponin T (TnT) isoforms in the Ca2+ activation of muscle contraction, transgenic mice have been constructed with a chicken fast skeletal muscle TnT transgene driven by a cardiac α-myosin heavy chain gene promoter. Cardiac muscle-specific expression of the fast skeletal muscle TnT has been obtained with significant myofibril incorporation. Expression of the endogenous cardiac muscle thin filament regulatory proteins, such as troponin I and tropomyosin, was not altered in the transgenic mouse heart, providing an authentic system for the functional characterization of TnT isoforms. Cardiac muscle contractility was analysed for the force vs. Ca2+ relationship in skinned ventricular trabeculae of transgenic mice in comparison with wild-type litter-mates. The results showed unchanged pCa50 values (5.1 ± 0.04 and 5.1 ± 0.1, respectively) but significantly steeper slopes (the Hill coefficient was 2.0 ± 0.2 vs. 1.0 ± 0.2, P < 0.05). The results demonstrate that the structural and functional variation of different TnT isoforms may contribute to the difference in responsiveness and overall cooperativity of the thin filament-based Ca2+ regulation between cardiac and skeletal muscles. PMID:10517814

  16. Optical reflectance in fibrous tissues and skeletal muscles

    NASA Astrophysics Data System (ADS)

    Ranasinghesagara, Janaka C.

    We studied two biological tissues with optically anisotropic structures: high moisture soy protein extrudates and skeletal muscles. High moisture extrusion has been used to produce vegetable meat analogs that resemble real animal meat and have significant health benefits. Since visual and textural properties are key factors for consumer acceptance, assessing fiber formation in the extruded soy protein product is important for quality control purpose. A non-destructive method based on photon migration was developed to measure fiber formation in extruded soy proteins. The measured fiber formation index in intact samples showed good agreement with that obtained from image analysis on peeled samples. By implementing this new method in a fast laser scanning system, we have acquired two dimensional mappings of fiber formation and orientation in the entire sample in real time. In addition to fibrous structures, skeletal muscles have a unique periodic sarcomere structure which produces strong light diffractions. However, inconsistent experimental results have been reported in single fiber diffraction studies. By applying the three-dimensional coupled wave theory in a physical sarcomere model, we found that a variety of experimental observations can be explained if inhomogeneous muscle morphological profiles are considered. We also discovered that the sarcomere structure produced a unique optical reflectance pattern in whole muscle. None of the existing light propagation theories are able to describe this pattern. We developed a Monte Carlo model incorporating the sarcomere diffraction effect. The simulated results quantitatively resemble the unique patterns observed in experiments. We used a set of parameters to quantify the optical reflectance profiles produced by a point incident light in whole muscle. Two parameters, q and B, were obtained by numerically fitting the equi-intensity contours of the reflectance pattern. Two spatial gradients were calculated along the

  17. Dietary nitrate reduces skeletal muscle oxygenation response to physical exercise: a quantitative muscle functional MRI study.

    PubMed

    Bentley, Rachel; Gray, Stuart R; Schwarzbauer, Christian; Dawson, Dana; Frenneaux, Michael; He, Jiabao

    2014-07-01

    Dietary inorganic nitrate supplementation (probably via conversion to nitrite) increases skeletal muscle metabolic efficiency. In addition, it may also cause hypoxia-dependent vasodilation and this has the potential to augment oxygen delivery to exercising skeletal muscle. However, direct evidence for the latter with spatial localization to exercising muscle groups does not exist. We employed quantitative functional MRI (fMRI) to characterize skeletal muscle oxygen utilization and replenishment by assessment of tissue oxygenation maximal change and recovery change, respectively. Eleven healthy subjects were enrolled, of whom 9 (age 33.3 ± 4.4 years, five males) completed the study. Each subject took part in three MRI visits, with dietary nitrate (7cl concentrated beetroot juice) consumed before the third visit. During each visit fMRIs were conducted concurrently with plantar flexion exercise at workloads of 15% and 25% maximum voluntary contraction (MVC). No significant changes were found between visits 1 and 2 in the fMRI measures. A decrease in maximal change was found at 15% MVC in soleus between visits 2 and 3 (5.12 ± 2.36 to 2.55 ± 1.42, P = 0.004) and between visits 1 and 3 (4.43 ± 2.12 to 2.55 ± 1.42, P = 0.043), but not at 25% MVC or within gastrocnemius. There was no difference in recovery change between visits. We found that dietary nitrate supplementation reduces tissue oxygenation alterations during physical exercise in skeletal muscle. This effect is more prominent in muscles with predominantly type 1 fibers and at lower workloads. This indicates that in healthy subjects dietary nitrate predominantly affects skeletal muscle energy efficiency with no change in oxygen delivery. PMID:25052493

  18. Dietary nitrate reduces skeletal muscle oxygenation response to physical exercise: a quantitative muscle functional MRI study

    PubMed Central

    Bentley, Rachel; Gray, Stuart R.; Schwarzbauer, Christian; Dawson, Dana; Frenneaux, Michael; He, Jiabao

    2014-01-01

    Abstract Dietary inorganic nitrate supplementation (probably via conversion to nitrite) increases skeletal muscle metabolic efficiency. In addition, it may also cause hypoxia‐dependent vasodilation and this has the potential to augment oxygen delivery to exercising skeletal muscle. However, direct evidence for the latter with spatial localization to exercising muscle groups does not exist. We employed quantitative functional MRI (fMRI) to characterize skeletal muscle oxygen utilization and replenishment by assessment of tissue oxygenation maximal change and recovery change, respectively. Eleven healthy subjects were enrolled, of whom 9 (age 33.3 ± 4.4 years, five males) completed the study. Each subject took part in three MRI visits, with dietary nitrate (7cl concentrated beetroot juice) consumed before the third visit. During each visit fMRIs were conducted concurrently with plantar flexion exercise at workloads of 15% and 25% maximum voluntary contraction (MVC). No significant changes were found between visits 1 and 2 in the fMRI measures. A decrease in maximal change was found at 15% MVC in soleus between visits 2 and 3 (5.12 ± 2.36 to 2.55 ± 1.42, P = 0.004) and between visits 1 and 3 (4.43 ± 2.12 to 2.55 ± 1.42, P = 0.043), but not at 25% MVC or within gastrocnemius. There was no difference in recovery change between visits. We found that dietary nitrate supplementation reduces tissue oxygenation alterations during physical exercise in skeletal muscle. This effect is more prominent in muscles with predominantly type 1 fibers and at lower workloads. This indicates that in healthy subjects dietary nitrate predominantly affects skeletal muscle energy efficiency with no change in oxygen delivery. PMID:25052493

  19. Laser-inflicted injury of zebrafish embryonic skeletal muscle.

    PubMed

    Otten, Cécile; Abdelilah-Seyfried, Salim

    2013-01-01

    Various experimental approaches have been used in mouse to induce muscle injury with the aim to study muscle regeneration, including myotoxin injections (bupivacaine, cardiotoxin or notexin), muscle transplantations (denervation-devascularization induced regeneration), intensive exercise, but also murine muscular dystrophy models such as the mdx mouse (for a review of these approaches see). In zebrafish, genetic approaches include mutants that exhibit muscular dystrophy phenotypes (such as runzel or sapje) and antisense oligonucleotide morpholinos that block the expression of dystrophy-associated genes. Besides, chemical approaches are also possible, e.g. with Galanthamine, a chemical compound inhibiting acetylcholinesterase, thereby resulting in hypercontraction, which eventually leads to muscular dystrophy. However, genetic and pharmacological approaches generally affect all muscles within an individual, whereas the extent of physically inflicted injuries are more easily controlled spatially and temporally. Localized physical injury allows the assessment of contralateral muscle as an internal control. Indeed, we recently used laser-mediated cell ablation to study skeletal muscle regeneration in the zebrafish embryo, while another group recently reported the use of a two-photon laser (822 nm) to damage very locally the plasma membrane of individual embryonic zebrafish muscle cells. Here, we report a method for using the micropoint laser (Andor Technology) for skeletal muscle cell injury in the zebrafish embryo. The micropoint laser is a high energy laser which is suitable for targeted cell ablation at a wavelength of 435 nm. The laser is connected to a microscope (in our setup, an optical microscope from Zeiss) in such a way that the microscope can be used at the same time for focusing the laser light onto the sample and for visualizing the effects of the wounding (brightfield or fluorescence). The parameters for controlling laser pulses include wavelength

  20. Acylcarnitines: potential implications for skeletal muscle insulin resistance

    PubMed Central

    Aguer, Céline; McCoin, Colin S.; Knotts, Trina A.; Thrush, A. Brianne; Ono-Moore, Kikumi; McPherson, Ruth; Dent, Robert; Hwang, Daniel H.; Adams, Sean H.; Harper, Mary-Ellen

    2015-01-01

    Insulin resistance may be linked to incomplete fatty acid β-oxidation and the subsequent increase in acylcarnitine species in different tissues including skeletal muscle. It is not known if acylcarnitines participate in muscle insulin resistance or simply reflect dysregulated metabolism. The aims of this study were to determine whether acylcarnitines can elicit muscle insulin resistance and to better understand the link between incomplete muscle fatty acid β-oxidation, oxidative stress, inflammation, and insulin-resistance development. Differentiated C2C12, primary mouse, and human myotubes were treated with acylcarnitines (C4:0, C14:0, C16:0) or with palmitate with or without carnitine acyltransferase inhibition by mildronate. Treatment with C4:0, C14:0, and C16:0 acylcarnitines resulted in 20–30% decrease in insulin response at the level of Akt phosphorylation and/or glucose uptake. Mildronate reversed palmitate-induced insulin resistance concomitant with an ∼25% decrease in short-chain acylcarnitine and acetylcarnitine secretion. Although proinflammatory cytokines were not affected under these conditions, oxidative stress was increased by 2–3 times by short- or long-chain acylcarnitines. Acylcarnitine-induced oxidative stress and insulin resistance were reversed by treatment with antioxidants. Results are consistent with the conclusion that incomplete muscle fatty acid β-oxidation causes acylcarnitine accumulation and associated oxidative stress, raising the possibility that these metabolites play a role in muscle insulin resistance.—Aguer, C., McCoin, C. S., Knotts, T. A., Thrush, A. B., Ono-Moore, K., McPherson, R., Dent, R., Hwang, D. H., Adams, S. H., Harper, M.-E. Acylcarnitines: potential implications for skeletal muscle insulin resistance. PMID:25342132

  1. Exercise influences circadian gene expression in equine skeletal muscle.

    PubMed

    Murphy, B A; Wagner, A L; McGlynn, O F; Kharazyan, F; Browne, J A; Elliott, J A

    2014-07-01

    Circadian rhythms are endogenously generated 24-h oscillations that coordinate numerous aspects of mammalian physiology, metabolism and behaviour. The existence of a molecular circadian clock in equine skeletal muscle has previously been demonstrated. This study investigates how the circadian 24-h expression of exercise-relevant genes in skeletal muscle is influenced by a regular exercise regime. Mid-gluteal, percutaneous muscle biopsies were obtained over a 24-h period from six Thoroughbred mares before and after an 8-week exercise programme. Real-time qPCR assays were used to assess the expression patterns of core clock genes ARNTL, PER2, NR1D1, clock-controlled gene DBP, and muscle genes MYF6, UCP3, VEGFA, FOXO1, MYOD1, PPARGC1A, PPARGC1B, FBXO32 and PDK4. Two-way repeated measures ANOVA revealed a significant interaction between circadian time and exercise for muscle genes MYF6, UCP3, MYOD1 and PDK4. A significant effect of time was observed for all genes with the exception of VEGFA, where a main effect of exercise was observed. By cosinor analysis, the core clock genes, ARNTL (P <0.01) and NR1D1 (P <0.05), showed 24-h rhythmicity both pre- and post-exercise, while PER2 expression was rhythmic post-exercise (P <0.05) but not pre-exercise. The expression profiles of muscle genes MYOD1 and MYF6 showed significant fits to a 24-h cosine waveform indicative of circadian rhythmicity post-exercise only (P <0.01). This study suggests that the metabolic capacity of muscle is influenced by scheduled exercise and that optimal athletic performance may be achieved when exercise times and competition times coincide. PMID:24888677

  2. Neural control of glutamine synthetase activity in rat skeletal muscles.

    PubMed

    Feng, B; Konagaya, M; Konagaya, Y; Thomas, J W; Banner, C; Mill, J; Max, S R

    1990-05-01

    The mechanism of glutamine synthetase induction in rat skeletal muscle after denervation or limb immobilization was investigated. Adult male rats were subjected to midthigh section of the sciatic nerve. At 1, 2, and 5 h and 1, 2, and 7 days after denervation, rats were killed and denervated, and contralateral control soleus and plantaris muscles were excised, weighted, homogenized, and assayed for glutamine synthetase. Glutamine synthetase activity increased approximately twofold 1 h after denervation in both muscles. By 7 days postdenervation enzyme activity had increased to three times the control level in plantaris muscle and to four times the control level in soleus muscle. Increased enzyme activity after nerve section was associated with increased maximum velocity with no change in apparent Michaelis constant. Immunotitration with an antiglutamine synthetase antibody suggested that denervation caused an increase in the number of glutamine synthetase molecules in muscle. However, Northern-blot analysis revealed no increase in the steady-state level of glutamine synthetase mRNA after denervation. A mixing experiment failed to yield evidence for the presence of a soluble factor involved in regulating the activity of glutamine synthetase in denervated muscle. A combination of denervation and dexamethasone injections resulted in additive increases in glutamine synthetase. Thus the mechanism underlying increased glutamine synthetase after denervation appears to be posttranscriptional and is distinct from that of the glucocorticoid-mediated glutamine synthetase induction previously described by us. PMID:1970709

  3. Impact of Oxidative Stress on Exercising Skeletal Muscle

    PubMed Central

    Steinbacher, Peter; Eckl, Peter

    2015-01-01

    It is well established that muscle contractions during exercise lead to elevated levels of reactive oxygen species (ROS) in skeletal muscle. These highly reactive molecules have many deleterious effects, such as a reduction of force generation and increased muscle atrophy. Since the discovery of exercise-induced oxidative stress several decades ago, evidence has accumulated that ROS produced during exercise also have positive effects by influencing cellular processes that lead to increased expression of antioxidants. These molecules are particularly elevated in regularly exercising muscle to prevent the negative effects of ROS by neutralizing the free radicals. In addition, ROS also seem to be involved in the exercise-induced adaptation of the muscle phenotype. This review provides an overview of the evidences to date on the effects of ROS in exercising muscle. These aspects include the sources of ROS, their positive and negative cellular effects, the role of antioxidants, and the present evidence on ROS-dependent adaptations of muscle cells in response to physical exercise. PMID:25866921

  4. Estrogens maintain skeletal muscle and satellite cell functions.

    PubMed

    Kitajima, Yuriko; Ono, Yusuke

    2016-06-01

    Estrogens have crucial roles in an extensive range of physiological functions regulating cellular proliferation and differentiation, development, homeostasis, and metabolism. Therefore, prolonged estrogen insufficiency influences various types of tissues expressing estrogen receptors (ERs). Although ERs are expressed in skeletal muscle and its stem cells, called satellite cells, how prolonged estrogen insufficiency affects their function remains unclear. In this study, we investigated the effect of estrogen reduction on muscle in young ovariectomized (OVX) female mice. We found that reduced estrogens resulted in muscle atrophy in a time-dependent manner. Muscle force generation was reduced in OVX mice. Interestingly, prolonged estrogen insufficiency shifted fiber types toward faster myosin heavy chain isoforms. The number of satellite cells per isolated myofiber was unchanged, while satellite cell expansion, differentiation, and self-renewal were all markedly impaired in OVX mice. Indeed, muscle regeneration was significantly compromised in OVX mice. Taken together, our results demonstrate that estrogens are essential for comprehensively maintaining muscle function with its insufficiency affecting muscle strength and regeneration in young female mice. PMID:27048232

  5. Potency of nondepolarizing muscle relaxants on muscle-type acetylcholine receptors in denervated mouse skeletal muscle

    PubMed Central

    Wang, Hong; Yang, Bin; Han, Guang-wei; Li, Shi-tong

    2010-01-01

    Aim: To investigate the changing resistance to nondepolarizing muscle relaxants (NDMRs) during the first month after denervation. Methods: The denervated and innervated skeletal muscle cells were examined on days 1, 4, 7, 14, 21, and 28 after denervation. Individual denervated and innervated cells were prepared from the flexor digitorum brevis of the surgically denervated and contralateral hind feet, respectively. Nicotinic acetylcholine receptors (nAChRs) in the cells were activated with 30 μmol/L acetylcholine, either alone or in combination with various concentrations of vecuronium. Currents were recorded using a whole-cell patch-clamp technique. Results: The concentrations of vecuronium resulting in half-maximal inhibitory responses (IC50) increased 1.2- (P>0.05), 1.7-, 3.7-, 2.5-, 1.9-, and 1.8-fold (P<0.05) at Days 1, 4, 7, 14, 21, and 28 after denervation, respectively, compared to the innervated control. Resistance to vecuronium appeared at Day 4, peaked at Day 7, and declined at Day 14 after denervation. Nevertheless, IC50 values at Day 28 remained significantly higher than those for the innervated control, suggesting that the resistance to vecuronium had not disappeared at Day 28. Conclusion: The NDMR doses required to achieve satisfactory clinical effects differ at different times after muscle denervation. PMID:21102480

  6. Identification of Histone Deacetylase 2 as a Functional Gene for Skeletal Muscle Development in Chickens

    PubMed Central

    Shahjahan, Md.; Liu, Ranran; Zhao, Guiping; Wang, Fangjie; Zheng, Maiqing; Zhang, Jingjing; Song, Jiao; Wen, Jie

    2016-01-01

    A previous genome-wide association study (GWAS) exposed histone deacetylase 2 (HDAC2) as a possible candidate gene for breast muscle weight in chickens. The present research has examined the possible role of HDAC2 in skeletal muscle development in chickens. Gene expression was measured by quantitative polymerase chain reaction in breast and thigh muscles during both embryonic (four ages) and post-hatch (five ages) development and in cultures of primary myoblasts during both proliferation and differentiation. The expression of HDAC2 increased significantly across embryonic days (ED) in breast (ED 14, 16, 18, and 21) and thigh (ED 14 and 18, and ED 14 and 21) muscles suggesting that it possibly plays a role in myoblast hyperplasia in both breast and thigh muscles. Transcript abundance of HDAC2 identified significantly higher in fast growing muscle than slow growing in chickens at d 90 of age. Expression of HDAC2 during myoblast proliferation in vitro declined between 24 h and 48 h when expression of the marker gene paired box 7 (PAX7) increased and cell numbers increased throughout 72 h of culture. During induced differentiation of myoblasts to myotubes, the abundance of HDAC2 and the marker gene myogenic differentiation 1 (MYOD1), both increased significantly. Taken together, it is suggested that HDAC2 is most likely involved in a suppressive fashion in myoblast proliferation and may play a positive role in myoblast differentiation. The present results confirm the suggestion that HDAC2 is a functional gene for pre-hatch and post-hatch (fast growing muscle) development of chicken skeletal muscle. PMID:26949948

  7. 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

  8. Customized Platelet-Rich Plasma for Skeletal Muscle Injuries

    PubMed Central

    Hicks, Justin James; Li, Hongshuai; Philippon, Marc J.; Hurwitz, Shepard R.; Huard, Johnny; Hogan, MaCalus Vinson

    2016-01-01

    Objectives: Skeletal muscle injuries are among the most common sports-related trauma. Current treatment strategies result in formation of fibrous tissue that hinders the healing process before complete recovery. Incomplete recovery impairs muscle function and predisposes to re-injury. Platelet-Rich-Plasma (PRP) contains a multitude of growth factors and is an autologous source of growth factors for various tissue repairs. It is well established that PRP contains beneficial growth factors for muscle repair; however, it also contains high concentrations of deleterious growth factors for optimal muscle healing, such as transforming growth factor-beta 1 (TGF-β1). TGF-β1 leads to increased fibrosis impeding muscle healing. We therefore hypothesized that neutralization of TGF-β1’s action within PRP could improve PRP’s beneficial effect on skeletal muscle repair. Methods: Sixteen week old in-bred Fisher rats were used. Three rats were used for PRP isolation. 10 ml of blood were extracted from abdominal aorta and mixed with citrate phosphate dextrose solution. PRP were isolated by twice centrifugation. 24 rats were randomly assigned to four groups. A small incision was made along the tibialis anterior (TA) muscle; 50 µl cardiotoxin (CTX) (0.15ug/ul) was injected intramuscularly to the TA. One day after CTX injection, the animals were treated with PBS (control), plain PRP (PRP group), customized PRP+Ab-1x, and PRP+Ab-5x. Animals were sacrificed, and TA muscles were dissected on week 1 and 2 for assessment of muscle regeneration, fibrosis, macrophage infiltration, and satellite cell activation. Results: We observed significantly more regenerative myofibers in the PRP and customized PRP groups compared to control (Fig 1A-C). Collagen deposition (fibrosis) was detected in all groups at week 1 and week 2 after injury; while customized PRP group showed significantly decreased collagen deposition at week 1 and week 2 when compare to control and PRP groups (Fig. 1D-F). PRP

  9. Defective Homocysteine Metabolism: Potential Implications for Skeletal Muscle Malfunction

    PubMed Central

    Veeranki, Sudhakar; Tyagi, Suresh C.

    2013-01-01

    Hyperhomocysteinemia (HHcy) is a systemic medical condition and has been attributed to multi-organ pathologies. Genetic, nutritional, hormonal, age and gender differences are involved in abnormal homocysteine (Hcy) metabolism that produces HHcy. Homocysteine is an intermediate for many key processes such as cellular methylation and cellular antioxidant potential and imbalances in Hcy production and/or catabolism impacts gene expression and cell signaling including GPCR signaling. Furthermore, HHcy might damage the vagus nerve and superior cervical ganglion and affects various GPCR functions; therefore it can impair both the parasympathetic and sympathetic regulation in the blood vessels of skeletal muscle and affect long-term muscle function. Understanding cellular targets of Hcy during HHcy in different contexts and its role either as a primary risk factor or as an aggravator of certain disease conditions would provide better interventions. In this review we have provided recent Hcy mediated mechanistic insights into different diseases and presented potential implications in the context of reduced muscle function and integrity. Overall, the impact of HHcy in various skeletal muscle malfunctions is underappreciated; future studies in this area will provide deeper insights and improve our understanding of the association between HHcy and diminished physical function. PMID:23873298

  10. Skeletal muscle mass and composition during mammalian hibernation.

    PubMed

    Cotton, Clark J

    2016-01-01

    Hibernation is characterized by prolonged periods of inactivity with concomitantly low nutrient intake, conditions that would typically result in muscle atrophy combined with a loss of oxidative fibers. Yet, hibernators consistently emerge from winter with very little atrophy, frequently accompanied by a slight shift in fiber ratios to more oxidative fiber types. Preservation of muscle morphology is combined with down-regulation of glycolytic pathways and increased reliance on lipid metabolism instead. Furthermore, while rates of protein synthesis are reduced during hibernation, balance is maintained by correspondingly low rates of protein degradation. Proposed mechanisms include a number of signaling pathways and transcription factors that lead to increased oxidative fiber expression, enhanced protein synthesis and reduced protein degradation, ultimately resulting in minimal loss of skeletal muscle protein and oxidative capacity. The functional significance of these outcomes is maintenance of skeletal muscle strength and fatigue resistance, which enables hibernating animals to resume active behaviors such as predator avoidance, foraging and mating immediately following terminal arousal in the spring. PMID:26792334

  11. Phosphatidylinositol 3-kinase inhibitors block differentiation of skeletal muscle cells.

    PubMed

    Kaliman, P; Viñals, F; Testar, X; Palacín, M; Zorzano, A

    1996-08-01

    Skeletal muscle differentiation involves myoblast alignment, elongation, and fusion into multinucleate myotubes, together with the induction of regulatory and structural muscle-specific genes. Here we show that two phosphatidylinositol 3-kinase inhibitors, LY294002 and wortmannin, blocked an essential step in the differentiation of two skeletal muscle cell models. Both inhibitors abolished the capacity of L6E9 myoblasts to form myotubes, without affecting myoblast proliferation, elongation, or alignment. Myogenic events like the induction of myogenin and of glucose carrier GLUT4 were also blocked and myoblasts could not exit the cell cycle, as measured by the lack of mRNA induction of p21 cyclin-dependent kinase inhibitor. Overexpresssion of MyoD in 10T1/2 cells was not sufficient to bypass the myogenic differentiation blockade by LY294002. Upon serum withdrawal, 10T1/2-MyoD cells formed myotubes and showed increased levels of myogenin and p21. In contrast, LY294002-treated cells exhibited none of these myogenic characteristics and maintained high levels of Id, a negative regulator of myogenesis. These data indicate that whereas phosphatidylinositol 3-kinase is not indispensable for cell proliferation or in the initial events of myoblast differentiation, i.e. elongation and alignment, it appears to be essential for terminal differentiation of muscle cells. PMID:8702591

  12. 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. PMID:7784253

  13. The Molecular Basis for Load-Induced Skeletal Muscle Hypertrophy

    PubMed Central

    Marcotte, George R.; West, Daniel W.D.; Baar, Keith

    2016-01-01

    In a mature (weight neutral) animal, an increase in muscle mass only occurs when the muscle is loaded sufficiently to cause an increase in myofibrillar protein balance. A tight relationship between muscle hypertrophy, acute increases in protein balance, and the activity of the mechanistic target of rapamycin complex 1 (mTORC1) was demonstrated 15 years ago. Since then, our understanding of the signals that regulate load-induced hypertrophy has evolved considerably. For example, we now know that mechanical load activates mTORC1 in the same way as growth factors, by moving TSC2 (a primary inhibitor of mTORC1) away from its target (the mTORC activator) Rheb. However, the kinase that phosphorylates and moves TSC2 is different in the two processes. Similarly, we have learned that a distinct pathway exists whereby amino acids activate mTORC1 by moving it to Rheb. While mTORC1 remains at the forefront of load-induced hypertrophy, the importance of other pathways that regulate muscle mass are becoming clearer. Myostatin, is best known for its control of developmental muscle size. However, new mechanisms to explain how loading regulates this process are suggesting that it could play an important role in hypertrophic muscle growth as well. Lastly, new mechanisms are highlighted for how β2 receptor agonists could be involved in load-induced muscle growth and why these agents are being developed as non-exercise-based therapies for muscle atrophy. Overall, the results highlight how studying the mechanism of load-induced skeletal muscle mass is leading the development of pharmaceutical interventions to promote muscle growth in those unwilling or unable to perform resistance exercise. PMID:25359125

  14. Free Radical Formation after Intensive Exercise in Thoroughbred Skeletal Muscles

    PubMed Central

    MINAMI, Yoshio; KAWAI, Minako; MIGITA, Taiko C.; HIRAGA, Atsushi; MIYATA, Hirofumi

    2011-01-01

    Although high oxygen consumption in skeletal muscle may result in severe oxidative stress, there are no direct studies that have documented free radical production in horse muscles after intensive exercise. To find a new parameter indicating the muscle adaptation state for the training of Thoroughbred horses, we examined free radical formation in the muscle by using electron paramagnetic resonance (EPR). Ten male Thoroughbred horses received conventional training for 18 weeks. Before and after the training period, all horses performed an exhaustive incremental load exercise on a 6% incline treadmill. Muscle samples of the middle gluteal muscle were taken pre-exercise and 1 min, 1 hr, and 1 day after exercise. Muscle fiber type composition was also determined in the pre-exercise samples by immunohistochemical staining with monoclonal antibody to myosin heavy chain. We measured the free radical in the muscle homogenate using EPR at room temperature, and the amount was expressed as relative EPR signal intensity. There was a significant increase in Type IIA muscle fiber composition and a decrease in Type IIX fiber composition after the training period. Before the training period, the mean value of the relative EPR signal intensity showed a significant increase over the pre-exercise value at 1 min after the exercise and an incomplete recovery at 24 hr after the exercise. While no significant changes were found in the relative EPR signal intensity after the training period. There was a significant relationship between percentages of Type IIA fiber and change rates in EPR signal intensity at 1 min after exercise. The measurement of free radicals may be useful for determining the muscle adaptation state in the training of Thoroughbred horses. PMID:24833984

  15. STAT3 Activation in Skeletal Muscle Links Muscle Wasting and the Acute Phase Response in Cancer Cachexia

    PubMed Central

    Kunzevitzky, Noelia; Guttridge, Denis C.; Khuri, Sawsan; Koniaris, Leonidas G.; Zimmers, Teresa A.

    2011-01-01

    Background Cachexia, or weight loss despite adequate nutrition, significantly impairs quality of life and response to therapy in cancer patients. In cancer patients, skeletal muscle wasting, weight loss and mortality are all positively associated with increased serum cytokines, particularly Interleukin-6 (IL-6), and the presence of the acute phase response. Acute phase proteins, including fibrinogen and serum amyloid A (SAA) are synthesized by hepatocytes in response to IL-6 as part of the innate immune response. To gain insight into the relationships among these observations, we studied mice with moderate and severe Colon-26 (C26)-carcinoma cachexia. Methodology/Principal Findings Moderate and severe C26 cachexia was associated with high serum IL-6 and IL-6 family cytokines and highly similar patterns of skeletal muscle gene expression. The top canonical pathways up-regulated in both were the complement/coagulation cascade, proteasome, MAPK signaling, and the IL-6 and STAT3 pathways. Cachexia was associated with increased muscle pY705-STAT3 and increased STAT3 localization in myonuclei. STAT3 target genes, including SOCS3 mRNA and acute phase response proteins, were highly induced in cachectic muscle. IL-6 treatment and STAT3 activation both also induced fibrinogen in cultured C2C12 myotubes. Quantitation of muscle versus liver fibrinogen and SAA protein levels indicates that muscle contributes a large fraction of serum acute phase proteins in cancer. Conclusions/Significance These results suggest that the STAT3 transcriptome is a major mechanism for wasting in cancer. Through IL-6/STAT3 activation, skeletal muscle is induced to synthesize acute phase proteins, thus establishing a molecular link between the observations of high IL-6, increased acute phase response proteins and muscle wasting in cancer. These results suggest a mechanism by which STAT3 might causally influence muscle wasting by altering the profile of genes expressed and translated in muscle such

  16. Smooth muscle and skeletal muscle myosins produce similar unitary forces and displacements in the laser trap.

    PubMed Central

    Guilford, W H; Dupuis, D E; Kennedy, G; Wu, J; Patlak, J B; Warshaw, D M

    1997-01-01

    Purified smooth muscle myosin in the in vitro motility assay propels actin filaments at 1/10 the velocity, yet produces 3-4 times more force than skeletal muscle myosin. At the level of a single myosin molecule, these differences in force and actin filament velocity may be reflected in the size and duration of single motion and force-generating events, or in the kinetics of the cross-bridge cycle. Specifically, an increase in either unitary force or duty cycle may explain the enhanced force-generating capacity of smooth muscle myosin. Similarly, an increase in attached time or decrease in unitary displacement may explain the reduced actin filament velocity of smooth muscle myosin. To discriminate between these possibilities, we used a laser trap to measure unitary forces and displacements from single smooth and skeletal muscle myosin molecules. We analyzed our data using mean-variance analysis, which does not rely on scoring individual events by eye, and emphasizes periods in the data with constant properties. Both myosins demonstrated multiple but similar event populations with discrete peaks at approximately +11 and -11 nm in displacement, and 1.5 and 3.5 pN in force. Mean attached times for smooth muscle myosin were longer than for skeletal-muscle myosin. These results explain much of the difference in actin filament velocity between these myosins, and suggest that an increased duty cycle is responsible for the enhanced force-generating capacity of smooth over skeletal-muscle myosin. Images FIGURE 3 FIGURE 4 FIGURE 5 FIGURE 6 FIGURE 7 FIGURE 8 PMID:9138552

  17. LEUCINE STIMULATION OF SKELETAL MUSCLE PROTEIN SYNTHESIS DURING PROLONGED LEUCINE INFUSION IS DEPENDENT ON AMINO ACID AVAILABILITY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Leucine stimulates protein synthesis in cultured cells, mature rats and neonatal pigs. We have reported that leucine infusion increases protein synthesis in skeletal muscle of neonatal pigs during a 60-min infusion. When leucine infusion was prolonged for 120 min, however, protein synthesis was no...

  18. Variability in training-induced skeletal muscle adaptation

    PubMed Central

    2011-01-01

    When human skeletal muscle is exposed to exercise training, the outcomes, in terms of physiological adaptation, are unpredictable. The significance of this fact has long been underappreciated, and only recently has progress been made in identifying some of the molecular bases for the heterogeneous response to exercise training. It is not only of great medical importance that some individuals do not substantially physiologically adapt to exercise training, but the study of the heterogeneity itself provides a powerful opportunity to dissect out the genetic and environmental factors that limit adaptation, directly in humans. In the following review I will discuss new developments linking genetic and transcript abundance variability to an individual's potential to improve their aerobic capacity or endurance performance or induce muscle hypertrophy. I will also comment on the idea that certain gene networks may be associated with muscle “adaptability” regardless the stimulus provided. PMID:21030666

  19. Effects of prostaglandins and COX-inhibiting drugs on skeletal muscle adaptations to exercise

    PubMed Central

    Liu, Sophia Z.

    2013-01-01

    It has been ∼40 yr since the discovery that PGs are produced by exercising skeletal muscle and since the discovery that inhibition of PG synthesis is the mechanism of action of what are now known as cyclooxygenase (COX)-inhibiting drugs. Since that time, it has been established that PGs are made during and after aerobic and resistance exercise and have a potent paracrine and autocrine effect on muscle metabolism. Consequently, it has also been determined that orally consumed doses of COX inhibitors can profoundly influence muscle PG synthesis, muscle protein metabolism, and numerous other cellular processes that regulate muscle adaptations to exercise loading. Although data from acute human exercise studies, as well as animal and cell-culture data, would predict that regular consumption of a COX inhibitor during exercise training would dampen the typical muscle adaptations, the chronic data do not support this conjecture. From the studies in young and older individuals, lasting from 1.5 to 4 mo, no interfering effects of COX inhibitors on muscle adaptations to resistance-exercise training have been noted. In fact, in older individuals, a substantial enhancement of muscle mass and strength has been observed. The collective findings of the PG/COX-pathway regulation of skeletal muscle responses and adaptations to exercise are compelling. Considering the discoveries in other areas of COX regulation of health and disease, there is certainly an interesting future of investigation in this re-emerging area, especially as it pertains to older individuals and the condition of sarcopenia, as well as exercise training and performance of individuals of all ages. PMID:23539318

  20. Human skeletal muscle protein breakdown during spaceflight

    NASA Technical Reports Server (NTRS)

    Stein, T. P.; Schluter, M. D.

    1997-01-01

    Human spaceflight is associated with a loss of body protein. Excretion of 3-methylhistidine (3-MH) in the urine is a useful measurement of myofibrillar protein breakdown. Bed rest, particularly with 6 degrees head-down tilt, is an accepted ground-based model for human spaceflight. The objectives of this report were to compare 3-MH excretion from two Life Sciences shuttle missions (duration 9.5 and 15 days, n = 9) and from 17 days of bed rest (n = 7) with 6 degrees head-down tilt. The bed rest study was designed to mimic an actual Life Sciences spaceflight and so incorporated an extensive battery of physiological tests focused on the musculoskeletal system. Results showed that nitrogen retention, based on excretion of nitrogen in the urine, was reduced during both bed rest [from 22 +/- 1 to 1 +/- 5 mg N x kg(-1) x day(-1) (n = 7; P < 0.05)] and spaceflight [from 57 +/- 9 to 19 +/- 3 mg N x kg(-1) x day(-1) (n = 9; P < 0.05)]. 3-MH excretion was unchanged with either bed rest [pre-bed rest 5.30 +/- 0.29 vs. bed rest 5.71 +/- 0.30 micromol 3-MH x kg(-1) x day(-1), n = 7; P = not significant (NS)] or spaceflight [preflight 4.98 +/- 0.37 vs. 4.59 +/- 0.39 micromol 3-MH x kg(-1) x day(-1) in-flight, n = 9; P = NS]. We conclude that 1) 3-MH excretion was unaffected by spaceflight on the shuttle or with bed rest plus exercise, and 2) because protein breakdown (elevated 3-MH) was increased on Skylab but not on the shuttle, it follows that muscle protein breakdown is not an inevitable consequence of spaceflight.

  1. Skeletal muscle vasodilation during systemic hypoxia in humans.

    PubMed

    Dinenno, Frank A

    2016-01-15

    In humans, the net effect of acute systemic hypoxia in quiescent skeletal muscle is vasodilation despite significant reflex increases in muscle sympathetic vasoconstrictor nerve activity. This vasodilation increases tissue perfusion and oxygen delivery to maintain tissue oxygen consumption. Although several mechanisms may be involved, we recently tested the roles of two endothelial-derived substances during conditions of sympathoadrenal blockade to isolate local vascular control mechanisms: nitric oxide (NO) and prostaglandins (PGs). Our findings indicate that 1) NO normally plays a role in regulating vascular tone during hypoxia independent of the PG pathway; 2) PGs do not normally contribute to vascular tone during hypoxia, however, they do affect vascular tone when NO is inhibited; 3) NO and PGs are not independently obligatory to observe hypoxic vasodilation when assessed as a response from rest to steady-state hypoxia; and 4) combined NO and PG inhibition abolishes hypoxic vasodilation in human skeletal muscle. When the stimulus is exacerbated via combined submaximal rhythmic exercise and systemic hypoxia to cause further red blood cell (RBC) deoxygenation, skeletal muscle blood flow is augmented compared with normoxic exercise via local dilator mechanisms to maintain oxygen delivery to active tissue. Data obtained in a follow-up study indicate that combined NO and PG inhibition during hypoxic exercise blunts augmented vasodilation and hyperemia compared with control (normoxic) conditions by ∼50%; however, in contrast to hypoxia alone, the response is not abolished, suggesting that other local substances are involved. Factors associated with greater RBC deoxygenation such as ATP release, or nitrite reduction to NO, or both likely play a role in regulating this response. PMID:26023228

  2. Role of hydrogen sulfide in skeletal muscle biology and metabolism

    PubMed Central

    Veeranki, Sudhakar; Tyagi, Suresh C.

    2014-01-01

    Hydrogen sulfide (H2S) is a novel endogenous gaseous signal transducer (gasotransmittor). Its emerging role in multiple facets of inter- and intra-cellular signaling as a metabolic, inflammatory, neuro and vascular modulator has been increasingly realized. Although H2S is known for its effects as an anti-hypertensive, anti-inflammatory and anti-oxidant molecule, the relevance of these effects in skeletal muscle biology during health and during metabolic syndromes is unclear. H2S has been implicated in vascular relaxation and vessel tone enhancement, which might lead to mitigation of vascular complications caused by the metabolic syndromes. Metabolic complications may also lead to mitochondrial remodeling by interfering with fusion and fission, therefore, leading to mitochondrial mitophagy and skeletal muscle myopathy. Mitochondrial protection by H2S enhancing treatments may mitigate deterioration of muscle function during metabolic syndromes. In addition, H2S might upregulate uncoupling proteins and might also cause browning of white fat, resulting in suppression of imbalanced cytokine signaling caused by abnormal fat accumulation. Likewise, as a source for H+ ions, it has the potential to augment anaerobic ATP synthesis. However, there is a need for studies to test these putative H2S benefits in different patho-physiological scenarios before its full-fledged usage as a therapeutic molecule. The present review highlights current knowledge with regard to exogenous and endogenous H2S roles in skeletal muscle biology, metabolism, exercise physiology and related metabolic disorders, such as diabetes and obesity, and also provides future directions. PMID:25461301

  3. MicroRNA expression profiles of porcine skeletal muscle.

    PubMed

    Zhou, B; Liu, H L; Shi, F X; Wang, J Y

    2010-10-01

    MicroRNAs (miRNAs) are endogenous non-coding RNAs of ∼22 nucleotides in length that play important roles in multiple biological processes by degrading targeted mRNAs or repressing mRNA translation. To evaluate the roles of miRNA in porcine skeletal muscle, miRNA expression profiles were investigated using longissimus muscle tissue from pigs at embryonic day 90 (E90) and postpartum day 120 (PD120). First, we used previously known miRNA sequences from humans and mice to perform blast searches against the porcine expressed sequence tag (EST) database; 98 new miRNA candidates were identified according to a range of filtering criteria. These miRNA candidates and 73 known miRNAs (miRBase 13.0) from pigs were chosen for porcine miRNA microarray analysis. A total of 16 newly identified miRNAs and 31 previously known miRNAs were detected in porcine skeletal muscle tissues. During later foetal development at E90, miR-1826, miR-26a, miR-199b and let-7 were highly expressed, whilst miR-1a, miR-133a, miR-26a and miR-1826 showed highest abundance during the fast growing stage at PD120. Using the 47 miRNAs detected by the microarray assay, we performed further investigations using the publicly available porcine mRNA database from NCBI and computed potential target hits using the software rnahybrid. This study identified 16 new miRNA candidates, computed potential target hits for 18 miRNA families and determined the miRNA expression profiles in porcine skeletal muscle tissues at different developmental stages. These results provide a valuable resource for investigators interested in post-transcriptional gene regulation in pigs and related animals. PMID:20331612

  4. Regulation of VEGF and bFGF mRNA expression and other proliferative compounds in skeletal muscle cells.

    PubMed

    Jensen, L; Schjerling, P; Hellsten, Y

    2004-01-01

    The role of muscle contraction, prostanoids, nitric oxide and adenosine in the regulation of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF) and endothelial cell proliferative compounds in skeletal muscle cell cultures was examined. VEGF and bFGF mRNA, protein release as well as the proliferative effect of extracellular medium was determined in non-stimulated and electro-stimulated rat and human skeletal muscle cells. In rat skeletal muscle cells these aspects were also determined after treatment with inhibitors and/or donors of nitric oxide (NO), prostanoids and adenosine. Electro-stimulation caused an elevation in the VEGF and bFGF mRNA levels of rat muscle cells by 33% and 43% (P < 0.05), respectively, and in human muscle cells VEGF mRNA was elevated by 24%. Medium from electro-stimulated human, but not rat muscle cells induced a 126% higher (P < 0.05) endothelial cell proliferation than medium from non-stimulated cells. Cyclooxygenase inhibition of rat muscle cells induced a 172% increase (P < 0.05) in VEGF mRNA and a 104% increase in the basal VEGF release. Treatment with the NO donor SNAP (0.5 microM) decreased (P < 0.05) VEGF and bFGF mRNA by 42 and 38%, respectively. Medium from SNAP treated muscle cells induced a 45% lower (P < 0.05) proliferation of endothelial cells than control medium. Adenosine enhanced the basal VEGF release from muscle cells by 75% compared to control. The present data demonstrate that contractile activity, NO, adenosine and products of cyclooxygenase regulate the expression of VEGF and bFGF mRNA in skeletal muscle cells and that contractile activity and NO regulate endothelial cell proliferative compounds in muscle extracellular fluid. PMID:15609080

  5. Murine Muscle Engineered from Dermal Precursors: An In Vitro Model for Skeletal Muscle Generation, Degeneration, and Fatty Infiltration

    PubMed Central

    García-Parra, Patricia; Naldaiz-Gastesi, Neia; Maroto, Marcos; Padín, Juan Fernando; Goicoechea, María; Aiastui, Ana; Fernández-Morales, José Carlos; García-Belda, Paula; Lacalle, Jaione; Álava, Jose Iñaki; García-Verdugo, José Manuel; García, Antonio G.

    2014-01-01

    Skeletal muscle can be engineered by converting dermal precursors into muscle progenitors and differentiated myocytes. However, the efficiency of muscle development remains relatively low and it is currently unclear if this is due to poor characterization of the myogenic precursors, the protocols used for cell differentiation, or a combination of both. In this study, we characterized myogenic precursors present in murine dermospheres, and evaluated mature myotubes grown in a novel three-dimensional culture system. After 5–7 days of differentiation, we observed isolated, twitching myotubes followed by spontaneous contractions of the entire tissue-engineered muscle construct on an extracellular matrix (ECM). In vitro engineered myofibers expressed canonical muscle markers and exhibited a skeletal (not cardiac) muscle ultrastructure, with numerous striations and the presence of aligned, enlarged mitochondria, intertwined with sarcoplasmic reticula (SR). Engineered myofibers exhibited Na+- and Ca2+-dependent inward currents upon acetylcholine (ACh) stimulation and tetrodotoxin-sensitive spontaneous action potentials. Moreover, ACh, nicotine, and caffeine elicited cytosolic Ca2+ transients; fiber contractions coupled to these Ca2+ transients suggest that Ca2+ entry is activating calcium-induced calcium release from the SR. Blockade by d-tubocurarine of ACh-elicited inward currents and Ca2+ transients suggests nicotinic receptor involvement. Interestingly, after 1 month, engineered muscle constructs showed progressive degradation of the myofibers concomitant with fatty infiltration, paralleling the natural course of muscular degeneration. We conclude that mature myofibers may be differentiated on the ECM from myogenic precursor cells present in murine dermospheres, in an in vitro system that mimics some characteristics found in aging and muscular degeneration. PMID:23631552

  6. Sex-Based Differences in Skeletal Muscle Kinetics and Fiber-Type Composition

    PubMed Central

    Haizlip, K. M.; Harrison, B. C.

    2015-01-01

    Previous studies have identified over 3,000 genes that are differentially expressed in male and female skeletal muscle. Here, we review the sex-based differences in skeletal muscle fiber composition, myosin heavy chain expression, contractile function, and the regulation of these physiological differences by thyroid hormone, estrogen, and testosterone. The findings presented lay the basis for the continued work needed to fully understand the skeletal muscle differences between males and females. PMID:25559153

  7. The effects of growth factors on skeletal muscle lesions

    PubMed Central

    GIGANTE, ANTONIO; CIANFORLINI, MARCO; MANZOTTI, SANDRA; ULISSE, SERENA

    2013-01-01

    Skeletal muscle injuries are common causes of severe long-term pain and physical disability, accounting for up to 55% of all sports injuries. The phases of the healing process after direct or indirect muscle injury are complex but clearly defined processes comprising well-coordinated steps: degeneration, inflammation, regeneration, and fibrosis. Despite this frequent occurrence and the presence of a body of data on the pathophysiology of muscle injuries, none of the treatment strategies adopted to date have been shown to be really effective in strictly controlled trials. Most current muscle injury treatments are based on limited experimental and clinical data and/or were only empirically tested. Platelet-rich plasma (PRP) is a promising alternative approach based on the ability of autologous growth factors (GFs) to accelerate tissue healing, improve muscular regeneration, increase neovascularization and reduce fibrosis, allowing rapid recovery after muscle lesions. Thus, further experimental studies that include the quantification of specific GFs released by PRP, as well as additional data on angiogenesis, myogenesis and functional recovery are needed to ultimately validate the hypothesis of PRP efficacy in the treatment of muscle lesions and open the way for its wide clinical application. PMID:25606531

  8. Mitochondrial Ca(2+) uptake in skeletal muscle health and disease.

    PubMed

    Zhou, Jingsong; Dhakal, Kamal; Yi, Jianxun

    2016-08-01

    Muscle uses Ca(2+) as a messenger to control contraction and relies on ATP to maintain the intracellular Ca(2+) homeostasis. Mitochondria are the major sub-cellular organelle of ATP production. With a negative inner membrane potential, mitochondria take up Ca(2+) from their surroundings, a process called mitochondrial Ca(2+) uptake. Under physiological conditions, Ca(2+) uptake into mitochondria promotes ATP production. Excessive uptake causes mitochondrial Ca(2+) overload, which activates downstream adverse responses leading to cell dysfunction. Moreover, mitochondrial Ca(2+) uptake could shape spatio-temporal patterns of intracellular Ca(2+) signaling. Malfunction of mitochondrial Ca(2+) uptake is implicated in muscle degeneration. Unlike non-excitable cells, mitochondria in muscle cells experience dramatic changes of intracellular Ca(2+) levels. Besides the sudden elevation of Ca(2+) level induced by action potentials, Ca(2+) transients in muscle cells can be as short as a few milliseconds during a single twitch or as long as minutes during tetanic contraction, which raises the question whether mitochondrial Ca(2+) uptake is fast and big enough to shape intracellular Ca(2+) signaling during excitation-contraction coupling and creates technical challenges for quantification of the dynamic changes of Ca(2+) inside mitochondria. This review focuses on characterization of mitochondrial Ca(2+) uptake in skeletal muscle and its role in muscle physiology and diseases. PMID:27430885

  9. Short-range mechanical properties of skeletal and cardiac muscles.

    PubMed

    Campbell, Kenneth S

    2010-01-01

    Striated muscles are disproportionately stiff for small movements. This facet of their behavior can be demonstrated by measuring the force produced when the muscle is stretched more than about 1% of its initial length. When this is done, it can be seen that force rises rapidly during the initial phases of the movement and much less rapidly during the latter stages of the stretch. Experiments performed using chemically permeabilized skeletal and cardiac muscles show that the initial stiffness of the preparations increases in proportion with isometric force as the free Ca²(+) concentration in the bathing solution is raised from a minimal to a saturating value. This is strong evidence that the short-range mechanical properties of activated muscle result from stretching myosin cross-bridges that are attached between the thick and thin filaments. Relaxed intact muscles also exhibit short-range mechanical properties but the molecular mechanisms underlying this behavior are less clear. This chapter summarizes some of the interesting features of short-range mechanical properties in different types of muscle preparation, describes some of the likely underlying mechanisms and discusses the potential physiological significance of the behavior. PMID:20824529

  10. Dexamethasone regulates glutamine synthetase expression in rat skeletal muscles

    NASA Technical Reports Server (NTRS)

    Max, Stephen R.; Konagaya, Masaaki; Konagaya, Yoko; Thomas, John W.; Banner, Carl; Vitkovic, Ljubisa

    1986-01-01

    The regulation of glutamine synthetase by glucocorticoids in rat skeletal muscles was studied. Administration of dexamethasone strikingly enhanced glutamine synthetase activity in plantaris and soleus muscles. The dexamethasone-mediated induction of glutamine synthetase activity was blocked to a significant extent by orally administered RU38486, a glucocorticoid antagonist, indicating the involvement of intracellular glucocorticoid receptors in the induction. Northern blot analysis revealed that dexamethasone-mediated enhancement of glutamine synthetase activity involves dramatically increased levels of glutamine synthetase mRNA. The induction of glutamine synthetase was selective in that glutaminase activity of soleus and plantaris muscles was not increased by dexamethasone. Furthermore, dexamethasone treatment resulted in only a small increase in glutamine synthetase activity in the heart. Accordingly, there was only a slight change in glutamine synthetase mRNA level in this tissue. Thus, glucocorticoids regulate glutamine synthetase gene expression in rat muscles at the transcriptional level via interaction with intracellular glutamine production by muscle and to mechanisms underlying glucocorticoid-induced muscle atrophy.

  11. Leucine incorporation into mixed skeletal muscle protein in humans

    SciTech Connect

    Nair, K.S.; Halliday, D.; Griggs, R.C. Clinical Research Centre, Harrow )

    1988-02-01

    Fractional mixed skeletal muscle protein synthesis (FMPS) was estimated in 10 postabsorptive healthy men by determining the increment in the abundance of ({sup 13}C)-leucine in quadriceps muscle protein during an intravenous infusion of L-(1-{sup 13}C)leucine. Whole-body muscle protein synthesis (MPS) was calculated based on the estimation of muscle mass from creatinine excretion and compared with whole-body protein synthesis (WBPS) calculated from the nonoxidative portion of leucine flux. A significant correlation was found between MPS. The contribution of MPS to WBPS was 27 {plus minus} 1%, which is comparable to the reports in other species. Morphometric analyses of adjacent muscle samples in eight subjects demonstrated that the biopsy specimens consisted of 86.5 {plus minus} 2% muscular as opposed to other tissues. Because fiber type composition varies between biopsies, the authors examined the relationship between proportions of each fiber type and FMPS. Variation in the composition of biopsies and in fiber-type proportion did not affect the estimation of muscle protein synthesis rate. They conclude that stable isotope techniques using serial needle biopsies permit the direct measurement of FMPS in humans and that this estimation is correlated with an indirect estimation of WBPS.

  12. Increased excitability of acidified skeletal muscle: role of chloride conductance.

    PubMed

    Pedersen, Thomas H; de Paoli, Frank; Nielsen, Ole B

    2005-02-01

    Generation of the action potentials (AP) necessary to activate skeletal muscle fibers requires that inward membrane currents exceed outward currents and thereby depolarize the fibers to the voltage threshold for AP generation. Excitability therefore depends on both excitatory Na+ currents and inhibitory K+ and Cl- currents. During intensive exercise, active muscle loses K+ and extracellular K+ ([K+]o) increases. Since high [K+]o leads to depolarization and ensuing inactivation of voltage-gated Na+ channels and loss of excitability in isolated muscles, exercise-induced loss of K+ is likely to reduce muscle excitability and thereby contribute to muscle fatigue in vivo. Intensive exercise, however, also leads to muscle acidification, which recently was shown to recover excitability in isolated K(+)-depressed muscles of the rat. Here we show that in rat soleus muscles at 11 mM K+, the almost complete recovery of compound action potentials and force with muscle acidification (CO2 changed from 5 to 24%) was associated with reduced chloride conductance (1731 +/- 151 to 938 +/- 64 microS/cm2, P < 0.01) but not with changes in potassium conductance (405 +/- 20 to 455 +/- 30 microS/cm2, P < 0.16). Furthermore, acidification reduced the rheobase current by 26% at 4 mM K+ and increased the number of excitable fibers at elevated [K+]o. At 11 mM K+ and normal pH, a recovery of excitability and force similar to the observations with muscle acidification could be induced by reducing extracellular Cl- or by blocking the major muscle Cl- channel, ClC-1, with 30 microM 9-AC. It is concluded that recovery of excitability in K(+)-depressed muscles induced by muscle acidification is related to reduction in the inhibitory Cl- currents, possibly through inhibition of ClC-1 channels, and acidosis thereby reduces the Na+ current needed to generate and propagate an AP. Thus short term regulation of Cl- channels is important for maintenance of excitability in working muscle. PMID:15684096

  13. Skeletal muscle regeneration in Xenopus tadpoles and zebrafish larvae

    PubMed Central

    2012-01-01

    Background Mammals are not able to restore lost appendages, while many amphibians are. One important question about epimorphic regeneration is related to the origin of the new tissues and whether they come from mature cells via dedifferentiation and/or from stem cells. Several studies in urodele amphibians (salamanders) indicate that, after limb or tail amputation, the multinucleated muscle fibres do dedifferentiate by fragmentation and proliferation, thereby contributing to the regenerate. In Xenopus laevis tadpoles, however, it was shown that muscle fibres do not contribute directly to the tail regenerate. We set out to study whether dedifferentiation was present during muscle regeneration of the tadpole limb and zebrafish larval tail, mainly by cell tracing and histological observations. Results Cell tracing and histological observations indicate that zebrafish tail muscle do not dedifferentiate during regeneration. Technical limitations did not allow us to trace tadpole limb cells, nevertheless we observed no signs of dedifferentiation histologically. However, ultrastructural and gene expression analysis of regenerating muscle in tadpole tail revealed an unexpected dedifferentiation phenotype. Further histological studies showed that dedifferentiating tail fibres did not enter the cell cycle and in vivo cell tracing revealed no evidences of muscle fibre fragmentation. In addition, our results indicate that this incomplete dedifferentiation was initiated by the retraction of muscle fibres. Conclusions Our results show that complete skeletal muscle dedifferentiation is less common than expected in lower vertebrates. In addition, the discovery of incomplete dedifferentiation in muscle fibres of the tadpole tail stresses the importance of coupling histological studies with in vivo cell tracing experiments to better understand the regenerative mechanisms. PMID:22369050

  14. Autophagy Signaling in Skeletal Muscle of Infarcted Rats

    PubMed Central

    Jannig, Paulo R.; Moreira, Jose B. N.; Bechara, Luiz R. G.; Bozi, Luiz H. M.; Bacurau, Aline V.; Monteiro, Alex W. A.; Dourado, Paulo M.; Wisløff, Ulrik; Brum, Patricia C.

    2014-01-01

    Background Heart failure (HF)-induced skeletal muscle atrophy is often associated to exercise intolerance and poor prognosis. Better understanding of the molecular mechanisms underlying HF-induced muscle atrophy may contribute to the development of pharmacological strategies to prevent or treat such condition. It has been shown that autophagy-lysosome system is an important mechanism for maintenance of muscle mass. However, its role in HF-induced myopathy has not been addressed yet. Therefore, the aim of the present study was to evaluate autophagy signaling in myocardial infarction (MI)-induced muscle atrophy in rats. Methods/Principal Findings Wistar rats underwent MI or Sham surgeries, and after 12 weeks were submitted to echocardiography, exercise tolerance and histology evaluations. Cathepsin L activity and expression of autophagy-related genes and proteins were assessed in soleus and plantaris muscles by fluorimetric assay, qRT-PCR and immunoblotting, respectively. MI rats displayed exercise intolerance, left ventricular dysfunction and dilation, thereby suggesting the presence of HF. The key findings of the present study were: a) upregulation of autophagy-related genes (GABARAPL1, ATG7, BNIP3, CTSL1 and LAMP2) was observed only in plantaris while muscle atrophy was observed in both soleus and plantaris muscles, and b) Cathepsin L activity, Bnip3 and Fis1 protein levels, and levels of lipid hydroperoxides were increased specifically in plantaris muscle of MI rats. Conclusions Altogether our results provide evidence for autophagy signaling regulation in HF-induced plantaris atrophy but not soleus atrophy. Therefore, autophagy-lysosome system is differentially regulated in atrophic muscles comprising different fiber-types and metabolic characteristics. PMID:24427319

  15. Gadd45a Protein Promotes Skeletal Muscle Atrophy by Forming a Complex with the Protein Kinase MEKK4.

    PubMed

    Bullard, Steven A; Seo, Seongjin; Schilling, Birgit; Dyle, Michael C; Dierdorff, Jason M; Ebert, Scott M; DeLau, Austin D; Gibson, Bradford W; Adams, Christopher M

    2016-08-19

    Skeletal muscle atrophy is a serious and highly prevalent condition that remains poorly understood at the molecular level. Previous work found that skeletal muscle atrophy involves an increase in skeletal muscle Gadd45a expression, which is necessary and sufficient for skeletal muscle fiber atrophy. However, the direct mechanism by which Gadd45a promotes skeletal muscle atrophy was unknown. To address this question, we biochemically isolated skeletal muscle proteins that associate with Gadd45a as it induces atrophy in mouse skeletal muscle fibers in vivo We found that Gadd45a interacts with multiple proteins in skeletal muscle fibers, including, most prominently, MEKK4, a mitogen-activated protein kinase kinase kinase that was not previously known to play a role in skeletal muscle atrophy. Furthermore, we found that, by forming a complex with MEKK4 in skeletal muscle fibers, Gadd45a increases MEKK4 protein kinase activity, which is both sufficient to induce skeletal muscle fiber atrophy and required for Gadd45a-mediated skeletal muscle fiber atrophy. Together, these results identify a direct biochemical mechanism by which Gadd45a induces skeletal muscle atrophy and provide new insight into the way that skeletal muscle atrophy occurs at the molecular level. PMID:27358404

  16. Muscle-specific Drp1 overexpression impairs skeletal muscle growth via translational attenuation

    PubMed Central

    Touvier, T; De Palma, C; Rigamonti, E; Scagliola, A; Incerti, E; Mazelin, L; Thomas, J-L; D'Antonio, M; Politi, L; Schaeffer, L; Clementi, E; Brunelli, S

    2015-01-01

    Mitochondrial fission and fusion are essential processes in the maintenance of the skeletal muscle function. The contribution of these processes to muscle development has not been properly investigated in vivo because of the early lethality of the models generated so far. To define the role of mitochondrial fission in muscle development and repair, we have generated a transgenic mouse line that overexpresses the fission-inducing protein Drp1 specifically in skeletal muscle. These mice displayed a drastic impairment in postnatal muscle growth, with reorganisation of the mitochondrial network and reduction of mtDNA quantity, without the deficiency of mitochondrial bioenergetics. Importantly we found that Drp1 overexpression activates the stress-induced PKR/eIF2α/Fgf21 pathway thus leading to an attenuated protein synthesis and downregulation of the growth hormone pathway. These results reveal for the first time how mitochondrial network dynamics influence muscle growth and shed light on aspects of muscle physiology relevant in human muscle pathologies. PMID:25719247

  17. Lower skeletal muscle capillarization in hypertensive elderly men.

    PubMed

    Gueugneau, Marine; Coudy-Gandilhon, Cécile; Meunier, Bruno; Combaret, Lydie; Taillandier, Daniel; Polge, Cécile; Attaix, Didier; Roche, Frédéric; Féasson, Léonard; Barthélémy, Jean-Claude; Béchet, Daniel

    2016-04-01

    Aging strongly affects the skeletal muscle and is associated with microvascular dysfunctions. Age is also a primary risk factor for the metabolic syndrome, which is a cluster of metabolic and cardiovascular symptoms. Among the metabolic syndrome components, hypertension is the most prevalent in elderly subjects and has a central role in vascular alterations. Despite critical clinical outcomes, the effects of hypertension and metabolic syndrome on skeletal muscle capillarization have poorly been investigated during aging. In the present study, muscle biopsies from normotensive young (YO) and elderly (ELc) men, and elderly men with hypertension (EL-HT) or metabolic syndrome (EL-MS) were assessed for the number of capillaries around a fiber (CAF), capillary-to-fiber perimeter exchange (CFPE), length of contact to perimeter of fiber ratio (LC/PF), capillary tortuosity, and for extracellular matrix (ECM) embedding capillaries. As capillarization and muscle mitochondrial oxidative capacity may be associated, we also investigated cytochrome c oxidase (COX) content. Our findings indicate that capillarization and COX did not change between normotensive adult and old individuals. They further reveal that hypertension in elderly men is associated with reduced CAF (ELc: 5.2±0.4, EL-HT: 4.1±0.2, P<0.02 for type I fibers; ELc: 4.1±0.2, EL-HT: 3.1±0.3, P<0.03 for type IIA fibers), CFPE (ELc: 7.9±0.7, EL-HT: 6.4±0.4 capillaries/1000μm, P<0.03 for type I fibers; ELc: 6.5±0.4, EL-HT: 5.2±0.4 capillaries/1000μm, P<0.03 for type IIA fibers), LC/PF (ELc: 23.3±1.2, EL-HT: 17.8±0.6%, P<0.01 for type I fibers; ELc: 19.8±1.1, EL-HT: 15.6±0.8%, P<0.01 for type IIA fibers) and capillary tortuosity, and with ECM endomysium fibrosis. Capillary rarefaction also correlated with lower COX content in the old hypertensive muscle. No further modification occurred with metabolic syndrome in elderly men. Collectively, our results suggest that hypertension plays a central role in muscle

  18. Ca2+-Dependent Regulations and Signaling in Skeletal Muscle: From Electro-Mechanical Coupling to Adaptation

    PubMed Central

    Gehlert, Sebastian; Bloch, Wilhelm; Suhr, Frank

    2015-01-01

    Calcium (Ca2+) plays a pivotal role in almost all cellular processes and ensures the functionality of an organism. In skeletal muscle fibers, Ca2+ is critically involved in the innervation of skeletal muscle fibers that results in the exertion of an action potential along the muscle fiber membrane, the prerequisite for skeletal muscle contraction. Furthermore and among others, Ca2+ regulates also intracellular processes, such as myosin-actin cross bridging, protein synthesis, protein degradation and fiber type shifting by the control of Ca2+-sensitive proteases and transcription factors, as well as mitochondrial adaptations, plasticity and respiration. These data highlight the overwhelming significance of Ca2+ ions for the integrity of skeletal muscle tissue. In this review, we address the major functions of Ca2+ ions in adult muscle but also highlight recent findings of critical Ca2+-dependent mechanisms essential for skeletal muscle-regulation and maintenance. PMID:25569087

  19. Noncoding RNAs in the regulation of skeletal muscle biology in health and disease.

    PubMed

    Simionescu-Bankston, Adriana; Kumar, Ashok

    2016-08-01

    Skeletal muscle is composed of multinucleated myofibers that arise from the fusion of myoblasts during development. Skeletal muscle is essential for various body functions such as maintaining posture, locomotion, breathing, and metabolism. Skeletal muscle undergoes remarkable adaptations in response to environmental stimuli leading to atrophy or hypertrophy. Moreover, degeneration of skeletal muscle is a common feature in a number of muscular disorders including muscular dystrophy. Emerging evidence suggests that noncoding RNAs, such as microRNAs (miRNAs) and long noncoding RNAs (lncRNAs), are critical for skeletal muscle physiology. Several miRNAs and lncRNAs have now been found to control skeletal muscle development and regeneration. Noncoding RNAs also play an important role in the regulation of skeletal muscle mass in adults. Furthermore, aberrant expression of miRNAs and lncRNAs has been observed in several muscular disorders. In this article, we discuss the mechanisms of action of miRNAs and lncRNAs in skeletal muscle formation, growth, regeneration, and disease. We further highlight potential therapeutic strategies for utilizing noncoding RNAs to improve skeletal muscle function. PMID:27377406

  20. Brain and muscle Arnt-like 1 promotes skeletal muscle regeneration through satellite cell expansion

    SciTech Connect

    Chatterjee, Somik; Yin, Hongshan; Nam, Deokhwa; Li, Yong; Ma, Ke

    2015-02-01

    Circadian clock is an evolutionarily conserved timing mechanism governing diverse biological processes and the skeletal muscle possesses intrinsic functional clocks. Interestingly, although the essential clock transcription activator, Brain and muscle Arnt-like 1 (Bmal1), participates in maintenance of muscle mass, little is known regarding its role in muscle growth and repair. In this report, we investigate the in vivo function of Bmal1 in skeletal muscle regeneration using two muscle injury models. Bmal1 is highly up-regulated by cardiotoxin injury, and its genetic ablation significantly impairs regeneration with markedly suppressed new myofiber formation and attenuated myogenic induction. A similarly defective regenerative response is observed in Bmal1-null mice as compared to wild-type controls upon freeze injury. Lack of satellite cell expansion accounts for the regeneration defect, as Bmal1{sup −/−} mice display significantly lower satellite cell number with nearly abolished induction of the satellite cell marker, Pax7. Furthermore, satellite cell-derived primary myoblasts devoid of Bmal1 display reduced growth and proliferation ex vivo. Collectively, our results demonstrate, for the first time, that Bmal1 is an integral component of the pro-myogenic response that is required for muscle repair. This mechanism may underlie its role in preserving adult muscle mass and could be targeted therapeutically to prevent muscle-wasting diseases. - Highlights: • Bmal1 is highly inducible by muscle injury and myogenic stimuli. • Genetic ablation of Bmal1 significantly impairs muscle regeneration. • Bmal1 promotes satellite cell expansion during muscle regeneration. • Bmal1-deficient primary myoblasts display attenuated growth and proliferation.

  1. A new mtDNA mutation showing accumulation with time and restriction to skeletal muscle

    SciTech Connect

    Weber, K.; Wilson, J.N.; Taylor, L.

    1997-02-01

    We have identified a new mutation in mtDNA, involving tRNA{sup Leu(CUN)} in a patient manifesting an isolated skeletal myopathy. This heteroplasmic A{r_arrow}G transition at position 12320 affects the T{Psi}C loop at a conserved site and was not found in 120 controls. Analysis of cultured fibroblasts, white blood cells/platelets, and skeletal muscle showed that only skeletal muscle contained the mutation and that only this tissue demonstrated a biochemical defect of respiratory-chain activity. In a series of four muscle-biopsy specimens taken over a 12-year period, there was a gradual increase, from 70% to 90%, in the overall level of mutation, as well as a marked clinical deterioration. Single-fiber PCR confirmed that the proportion of mutant mtDNA was highest in cytochrome c oxidase-negative fibers. This study, which reports a mutation involving tRNA{sup Leu(CUN)}, demonstrates clearly that mtDNA point mutations can accumulate over time and may be restricted in their tissue distribution. Furthermore, clinical deterioration seemed to follow the increase in the level of mutation, although, interestingly, the appearance of fibers deficient in respiratory-chain activity showed a lag period. 32 refs., 4 figs., 1 tab.

  2. Viral vector-mediated expression of K+ channels regulates electrical excitability in skeletal muscle.

    PubMed

    Falk, T; Kilani, R K; Yool, A J; Sherman, S J

    2001-09-01

    Modification of K+ currents by exogenous gene expression may lead to therapeutic interventions in skeletal muscle diseases characterized by alterations in electrical excitability. In order to study the specific effects of increasing outward K+ currents, we expressed a modified voltage-dependent K+ channel in primary cultured rat skeletal muscle cells. The rat Kv1.4 channel was expressed as an N-terminal fusion protein containing a bioluminescent marker (green fluorescent protein). Transgene expression was carried out using the helper-dependent herpes simplex 1 amplicon system. Transduced myoballs, identified using fluorescein optics and studied electrophysiologically with single-cell patch clamp, exhibited a greater than two-fold increase in K+ conductance by 20-30 h after infection. This increase in K+ current led to a decrease in membrane resistance and a 10-fold increase in the current threshold for action potential generation. Electrical hyperexcitability induced by the Na+ channel toxin anemone toxin II (1 microM) was effectively counteracted by overexpression of Kv1.4 at 30-32 h after transduction. Thus, virally induced overexpression of a voltage-gated K+ channel in skeletal muscle has a powerful effect in reducing electrical excitability. PMID:11571576

  3. Cardiac Meets Skeletal: What's New in Microfluidic Models for Muscle Tissue Engineering.

    PubMed

    Visone, Roberta; Gilardi, Mara; Marsano, Anna; Rasponi, Marco; Bersini, Simone; Moretti, Matteo

    2016-01-01

    In the last few years microfluidics and microfabrication technique principles have been extensively exploited for biomedical applications. In this framework, organs-on-a-chip represent promising tools to reproduce key features of functional tissue units within microscale culture chambers. These systems offer the possibility to investigate the effects of biochemical, mechanical, and electrical stimulations, which are usually applied to enhance the functionality of the engineered tissues. Since the functionality of muscle tissues relies on the 3D organization and on the perfect coupling between electrochemical stimulation and mechanical contraction, great efforts have been devoted to generate biomimetic skeletal and cardiac systems to allow high-throughput pathophysiological studies and drug screening. This review critically analyzes microfluidic platforms that were designed for skeletal and cardiac muscle tissue engineering. Our aim is to highlight which specific features of the engineered systems promoted a typical reorganization of the engineered construct and to discuss how promising design solutions exploited for skeletal muscle models could be applied to improve cardiac tissue models and vice versa. PMID:27571058

  4. 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. PMID:24798447

  5. Nrf2 Protects Against TWEAK-mediated Skeletal Muscle Wasting

    NASA Astrophysics Data System (ADS)

    Al-Sawaf, Othman; Fragoulis, Athanassios; Rosen, Christian; Kan, Yuet Wai; Sönmez, Tolga Taha; Pufe, Thomas; Wruck, Christoph Jan

    2014-01-01

    Skeletal muscle (SM) regeneration after injury is impaired by excessive inflammation. Particularly, the inflammatory cytokine tumour necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) is a potent inducer of skeletal muscle wasting and fibrosis. In this study we investigated the role of Nrf2, a major regulator of oxidative stress defence, in SM ischemia/reperfusion (I/R) injury and TWEAK induced atrophy. We explored the time-dependent expression of TWEAK after I/R in SM of Nrf2-wildtype (WT) and knockout (KO) mice. Nrf2-KO mice expressed significant higher levels of TWEAK as compared to WT mice. Consequently, Nrf2-KO mice present an insufficient regeneration as compared to Nrf2-WT mice. Moreover, TWEAK stimulation activates Nrf2 in the mouse myoblast cell line C2C12. This Nrf2 activation inhibits TWEAK induced atrophy in C2C12 differentiated myotubes. In summary, we show that Nrf2 protects SM from TWEAK-induced cell death in vitro and that Nrf2-deficient mice therefore have poorer muscle regeneration.

  6. Decreased phosphofructokinase activity in skeletal muscle of diabetic rats.

    PubMed

    Bauer, B A; Younathan, E S

    1984-01-01

    The activities of phosphofructokinase, aldolase and pyruvate kinase were diminished in extracts from skeletal muscle of streptozotocin diabetic rats, whereas the activities of glucose phosphate isomerase and phosphoglucomutase were not changed. Treatment of diabetic rats with insulin restored the activity of phosphofructokinase to normal. A kinetic study of the partially purified enzyme from normal and diabetic rats showed identical Michaelis constants for ATP and equal sensitivity to inhibition by excess of this substrate. Extracts of quick frozen muscle from diabetic rats had higher levels of citrate (an inhibitor of phosphofructokinase) and lower levels of D-fructose-1,6-bisphosphate and D-glucose-1,6-bisphosphate (activators of this enzyme). The levels of D-fructose-6-phosphate, D-glucose-6-phosphate, ATP, ADP and AMP were the same for the two groups. Our data suggest that the in vivo decrease of phosphofructokinase activity in skeletal muscle of diabetic rats is due to a decrease in the level of the enzymatically active protein as well as to an unfavorable change in the level of several of its allosteric modulators. PMID:6237837

  7. Time-dependent behavior of passive skeletal muscle

    NASA Astrophysics Data System (ADS)

    Ahamed, T.; Rubin, M. B.; Trimmer, B. A.; Dorfmann, L.

    2016-03-01

    An isotropic three-dimensional nonlinear viscoelastic model is developed to simulate the time-dependent behavior of passive skeletal muscle. The development of the model is stimulated by experimental data that characterize the response during simple uniaxial stress cyclic loading and unloading. Of particular interest is the rate-dependent response, the recovery of muscle properties from the preconditioned to the unconditioned state and stress relaxation at constant stretch during loading and unloading. The model considers the material to be a composite of a nonlinear hyperelastic component in parallel with a nonlinear dissipative component. The strain energy and the corresponding stress measures are separated additively into hyperelastic and dissipative parts. In contrast to standard nonlinear inelastic models, here the dissipative component is modeled using an evolution equation that combines rate-independent and rate-dependent responses smoothly with no finite elastic range. Large deformation evolution equations for the distortional deformations in the elastic and in the dissipative component are presented. A robust, strongly objective numerical integration algorithm is used to model rate-dependent and rate-independent inelastic responses. The constitutive formulation is specialized to simulate the experimental data. The nonlinear viscoelastic model accurately represents the time-dependent passive response of skeletal muscle.

  8. Skeletal alteration to improve beef longissimus muscle tenderness.

    PubMed

    Ludwig, C J; Claus, J R; Marriott, N G; Johnson, J; Wang, H

    1997-09-01

    A prerigor cut was made through the 12th thoracic vertebra of one side of the beef carcasses (Tendercut) studied (five unbranded), and the other sides served as the controls (C). After 48 h postmortem, the longissimus from each side was removed starting from the junction between the 5th and 6th lumbar vertebrae to the point between the 5th and 6th thoracic vertebrae. The longissimus muscle was cut into four equal boneless sections to determine the effectiveness of this treatment on improving tenderness at different locations along this muscle. The effects of Tendercut upon yield grade, sensory attributes, and tenderness of longissimus steaks were determined. This treatment did not affect (P > .05) yield grade, CIE L* a* b* values, chemical states of myoglobin, purge and cooking losses, and total collagen. Steaks located closer to the treatment site were more juicy than controls. Peak force values were not significantly different. Sarcomere length was longer (P < .05) and sensory panel ratings for myofibrillar tenderness, connective tissue, and overall tenderness were higher (P < .05), indicating that this skeletal alteration technique increased tenderness. Sensory data revealed that skeletal and connective tissue cuts at a single site (12th thoracic vertebrae) on the beef rib improved the tenderness along the entire length of the longissimus muscle. This study demonstrated that Tendercut, a simple process that does not require any new equipment or alterations to existing facilities to implement, is a viable tenderness enhancement technique. PMID:9303458

  9. Metabolic functions of glucocorticoid receptor in skeletal muscle

    PubMed Central

    Kuo, Taiyi; Harris, Charles A.; Wang, Jen-Chywan

    2016-01-01

    Glucocorticoids (GCs) exert key metabolic influences on skeletal muscle. GCs increase protein degradation and decrease protein synthesis. The released amino acids are mobilized from skeletal muscle to liver, where they serve as substrates for hepatic gluconeogenesis. This metabolic response is critical for mammals’ survival under stressful conditions, such as fasting and starvation. GCs suppress insulin-stimulated glucose uptake and utilization and glycogen synthesis, and play a permissive role for catecholamine-induced glycogenolysis, thus preserving the level of circulating glucose, the major energy source for the brain. However, chronic or excess exposure of GCs can induce muscle atrophy and insulin resistance. GCs convey their signal mainly through the intracellular glucocorticoid receptor (GR). While GR can act through different mechanisms, one of its major actions is to regulate the transcription of its primary target genes through genomic glucocorticoid response elements (GREs) by directly binding to DNA or tethering onto other DNA-binding transcription factors. These GR primary targets trigger physiological and pathological responses of GCs. Much progress has been made to understand how GCs regulate protein and glucose metabolism. In this review, we will discuss how GR primary target genes confer metabolic functions of GCs, and the mechanisms governing the transcriptional regulation of these targets. Comprehending these processes not only contributes to the fundamental understanding of mammalian physiology, but also will provide invaluable insight for improved GC therapeutics. PMID:23523565

  10. Targeting of gene expression to skeletal and cardiac muscle of trangenic animals.

    PubMed

    Sands, A T; DeMayo, F; Lei, X; Schwartz, R J

    1991-01-01

    The tissue restricted and developmental potentiation of transcription by chicken alpha-skeletal actin promoter regions fused to the reporter gene chloramphenicol acetyl transferase (CAT) were characterized in transgenic mice. Six of eight expressing transgenic mouse lines containing the chicken alpha-skeletal actin promoter fused to CAT resulted in preferential transgene transcription in skeletal muscle tissue, similar to the endogenous mouse alpha-skeletal actin gene. Two of the eight lines departed from the preferred pattern of skeletal muscle expression with primary expression of the transgene in the heart, a tissue containing primarily cardiac actin isoforms. Developmentally, a transition from embryonic heart to fetal and neonatal skeletal muscle expression was produced by the transgene promoter, a pattern of regulation similar to that of the endogenous alpha-skeletal actin gene. Instances of departure of transgene expression from the endogenous gene implied the existance of higher order muscle gene regulatory mechanisms. PMID:1367249

  11. Mutations in CAV3 cause mechanical hyperirritability of skeletal muscle in rippling muscle disease.

    PubMed

    Betz, R C; Schoser, B G; Kasper, D; Ricker, K; Ramírez, A; Stein, V; Torbergsen, T; Lee, Y A; Nöthen, M M; Wienker, T F; Malin, J P; Propping, P; Reis, A; Mortier, W; Jentsch, T J; Vorgerd, M; Kubisch, C

    2001-07-01

    Hereditary rippling muscle disease (RMD) is an autosomal dominant human disorder characterized by mechanically triggered contractions of skeletal muscle. Genome-wide linkage analysis has identified an RMD locus on chromosome 3p25. We found missense mutations in positional candidate CAV3 (encoding caveolin 3; ref. 5) in all five families analyzed. Mutations in CAV3 have also been described in limb-girdle muscular dystrophy type 1C (LGMD1C; refs. 6,7), demonstrating the allelism of dystrophic and non-dystrophic muscle diseases. PMID:11431690

  12. Altered macrophage phenotype transition impairs skeletal muscle regeneration.

    PubMed

    Wang, Hanzhou; Melton, David W; Porter, Laurel; Sarwar, Zaheer U; McManus, Linda M; Shireman, Paula K

    2014-04-01

    Monocyte/macrophage polarization in skeletal muscle regeneration is ill defined. We used CD11b-diphtheria toxin receptor transgenic mice to transiently deplete monocytes/macrophages at multiple stages before and after muscle injury induced by cardiotoxin. Fat accumulation within regenerated muscle was maximal when ablation occurred at the same time as cardiotoxin-induced injury. Early ablation (day 1 after cardiotoxin) resulted in the smallest regenerated myofiber size together with increased residual necrotic myofibers and fat accumulation. However, muscle regeneration after late (day 4) ablation was similar to controls. Levels of inflammatory cells in injured muscle following early ablation and associated with impaired muscle regeneration were determined by flow cytometry. Delayed, but exaggerated, monocyte [CD11b(+)(CD90/B220/CD49b/NK1.1/Ly6G)(-)(F4/80/I-Ab/CD11c)(-)Ly6C(+/-)] accumulation occurred; interestingly, Ly6C(+) and Ly6C(-) monocytes were present concurrently in ablated animals and control mice. In addition to monocytes, proinflammatory, Ly6C(+) macrophage accumulation following early ablation was delayed compared to controls. In both groups, CD11b(+)F4/80(+) cells exhibited minimal expression of the M2 markers CD206 and CD301. Nevertheless, early ablation delayed and decreased the transient accumulation of CD11b(+)F4/80(+)Ly6C(-)CD301(-) macrophages; in control animals, the later tissue accumulation of these cells appeared to correspond to that of anti-inflammatory macrophages, determined by cytokine production and arginase activity. In summary, impairments in muscle regeneration were associated with exaggerated monocyte recruitment and reduced Ly6C(-) macrophages; the switch of macrophage/monocyte subsets is critical to muscle regeneration. PMID:24525152

  13. Altered Macrophage Phenotype Transition Impairs Skeletal Muscle Regeneration

    PubMed Central

    Wang, Hanzhou; Melton, David W.; Porter, Laurel; Sarwar, Zaheer U.; McManus, Linda M.; Shireman, Paula K.

    2015-01-01

    Monocyte/macrophage polarization in skeletal muscle regeneration is ill defined. We used CD11b-diphtheria toxin receptor transgenic mice to transiently deplete monocytes/macrophages at multiple stages before and after muscle injury induced by cardiotoxin. Fat accumulation within regenerated muscle was maximal when ablation occurred at the same time as cardiotoxin-induced injury. Early ablation (day 1 after cardiotoxin) resulted in the smallest regenerated myofiber size together with increased residual necrotic myofibers and fat accumulation. However, muscle regeneration after late (day 4) ablation was similar to controls. Levels of inflammatory cells in injured muscle following early ablation and associated with impaired muscle regeneration were determined by flow cytometry. Delayed, but exaggerated, monocyte [CD11b+(CD90/B220/CD49b/NK1.1/Ly6G)−(F4/80/I-Ab/CD11c)−Ly6C+/−] accumulation occurred; interestingly, Ly6C+ and Ly6C− monocytes were present concurrently in ablated animals and control mice. In addition to monocytes, proinflammatory, Ly6C+ macrophage accumulation following early ablation was delayed compared to controls. In both groups, CD11b+F4/80+ cells exhibited minimal expression of the M2 markers CD206 and CD301. Nevertheless, early ablation delayed and decreased the transient accumulation of CD11b+F4/80+Ly6C−CD301− macrophages; in control animals, the later tissue accumulation of these cells appeared to correspond to that of anti-inflammatory macrophages, determined by cytokine production and arginase activity. In summary, impairments in muscle regeneration were associated with exaggerated monocyte recruitment and reduced Ly6C− macrophages; the switch of macrophage/monocyte subsets is critical to muscle regeneration. PMID:24525152

  14. The effect of radiation dose on mouse skeletal muscle remodeling

    PubMed Central

    Hardee, Justin P.; Puppa, Melissa J.; Fix, Dennis K.; Gao, Song; Hetzler, Kimbell L.; Bateman, Ted A.; Carson, James A.

    2014-01-01

    Background The purpose of this study was to determine the effect of two clinically relevant radiation doses on the susceptibility of mouse skeletal muscle to remodeling. Materials and methods. Alterations in muscle morphology and regulatory signaling were examined in tibialis anterior and gastrocnemius muscles after radiation doses that differed in total biological effective dose (BED). Female C57BL/6 (8-wk) mice were randomly assigned to non-irradiated control, four fractionated doses of 4 Gy (4x4 Gy; BED 37 Gy), or a single 16 Gy dose (16 Gy; BED 100 Gy). Mice were sacrificed 2 weeks after the initial radiation exposure. Results The 16 Gy, but not 4x4 Gy, decreased total muscle protein and RNA content. Related to muscle regeneration, both 16 Gy and 4x4 Gy increased the incidence of central nuclei containing myofibers, but only 16 Gy increased the extracellular matrix volume. However, only 4x4 Gy increased muscle 4-hydroxynonenal expression. While both 16 Gy and 4x4 Gy decreased IIB myofiber mean cross-sectional area (CSA), only 16 Gy decreased IIA myofiber CSA. 16 Gy increased the incidence of small diameter IIA and IIB myofibers, while 4x4 Gy only increased the incidence of small diameter IIB myofibers. Both treatments decreased the frequency and CSA of low succinate dehydrogenase activity (SDH) fibers. Only 16 Gy increased the incidence of small diameter myofibers having high SDH activity. Neither treatment altered muscle signaling related to protein turnover or oxidative metabolism. Conclusions Collectively, these results demonstrate that radiation dose differentially affects muscle remodeling, and these effects appear to be related to fiber type and oxidative metabolism. PMID:25177239

  15. Skeletal muscle signature of a champion sprint runner.

    PubMed

    Trappe, Scott; Luden, Nicholas; Minchev, Kiril; Raue, Ulrika; Jemiolo, Bozena; Trappe, Todd A

    2015-06-15

    We had the unique opportunity to study the skeletal muscle characteristics, at the single fiber level, of a world champion sprint runner who is the current indoor world record holder in the 60-m hurdles (7.30 s) and former world record holder in 110-m hurdles (12.91 s). Muscle biopsies were obtained from the vastus lateralis at rest and 4 h after a high-intensity exercise challenge (4 × 7 repetitions of resistance exercise). Single muscle fiber analyses were conducted for fiber type distribution (myosin heavy chain, MHC), fiber size, contractile function (strength, speed, and power) and mRNA expression (before and after the exercise bout). The world-class sprinter's leg muscle had a high abundance (24%) of the pure MHC IIx muscle fibers with a total fast-twitch fiber population of 71%. Power output of the MHC IIx fibers (35.1 ± 1.4 W/l) was 2-fold higher than MHC IIa fibers (17.1 ± 0.5 W/l) and 14-fold greater than MHC I fibers (2.5 ± 0.1 W/l). Additionally, the MHC IIx fibers were highly responsive to intense exercise at the transcriptional level for genes involved with muscle growth and remodeling (Fn14 and myostatin). To our knowledge, the abundance of pure MHC IIx muscle fibers is the highest observed in an elite sprinter. Further, the power output of the MHC IIa and MHC IIx muscle fibers was greater than any human values reported to date. These data provide a myocellular basis for the high level of sprinting success achieved by this individual. PMID:25749440

  16. TRIM32 regulates skeletal muscle stem cell differentiation and is necessary for normal adult muscle regeneration.

    PubMed

    Nicklas, Sarah; Otto, Anthony; Wu, Xiaoli; Miller, Pamela; Stelzer, Sandra; Wen, Yefei; Kuang, Shihuan; Wrogemann, Klaus; Patel, Ketan; Ding, Hao; Schwamborn, Jens C

    2012-01-01

    Limb girdle muscular dystrophy type 2H (LGMD2H) is an inherited autosomal recessive disease of skeletal muscle caused by a mutation in the TRIM32 gene. Currently its pathogenesis is entirely unclear. Typically the regeneration process of adult skeletal muscle during growth or following injury is controlled by a tissue specific stem cell population termed satellite cells. Given that TRIM32 regulates the fate of mammalian neural progenitor cells through controlling their differentiation, we asked whether TRIM32 could also be essential for the regulation of myogenic stem cells. Here we demonstrate for the first time that TRIM32 is expressed in the skeletal muscle stem cell lineage of adult mice, and that in the absence of TRIM32, myogenic differentiation is disrupted. Moreover, we show that the ubiquitin ligase TRIM32 controls this process through the regulation of c-Myc, a similar mechanism to that previously observed in neural progenitors. Importantly we show that loss of TRIM32 function induces a LGMD2H-like phenotype and strongly affects muscle regeneration in vivo. Our studies implicate that the loss of TRIM32 results in dysfunctional muscle stem cells which could contribute to the development of LGMD2H. PMID:22299041

  17. Osmosensation in TRPV2 dominant negative expressing skeletal muscle fibres.

    PubMed

    Zanou, Nadège; Mondin, Ludivine; Fuster, Clarisse; Seghers, François; Dufour, Inès; de Clippele, Marie; Schakman, Olivier; Tajeddine, Nicolas; Iwata, Yuko; Wakabayashi, Shigeo; Voets, Thomas; Allard, Bruno; Gailly, Philippe

    2015-09-01

    Increased plasma osmolarity induces intracellular water depletion and cell shrinkage (CS) followed by activation of a regulatory volume increase (RVI). In skeletal muscle, the hyperosmotic shock-induced CS is accompanied by a small membrane depolarization responsible for a release of Ca(2+) from intracellular pools. Hyperosmotic shock also induces phosphorylation of STE20/SPS1-related proline/alanine-rich kinase (SPAK). TRPV2 dominant negative expressing fibres challenged with hyperosmotic shock present a slower membrane depolarization, a diminished Ca(2+) response, a smaller RVI response, a decrease in SPAK phosphorylation and defective muscle function. We suggest that hyperosmotic shock induces TRPV2 activation, which accelerates muscle cell depolarization and allows the subsequent Ca(2+) release from the sarcoplasmic reticulum, activation of the Na(+) -K(+) -Cl(-) cotransporter by SPAK, and the RVI response. Increased plasma osmolarity induces intracellular water depletion and cell shrinkage followed by activation of a regulatory volume increase (RVI). In skeletal muscle, this is accompanied by transverse tubule (TT) dilatation and by a membrane depolarization responsible for a release of Ca(2+) from intracellular pools. We observed that both hyperosmotic shock-induced Ca(2+) transients and RVI were inhibited by Gd(3+) , ruthenium red and GsMTx4 toxin, three inhibitors of mechanosensitive ion channels. The response was also completely absent in muscle fibres overexpressing a non-permeant, dominant negative (DN) mutant of the transient receptor potential, V2 isoform (TRPV2) ion channel, suggesting the involvement of TRPV2 or of a TRP isoform susceptible to heterotetramerization with TRPV2. The release of Ca(2+) induced by hyperosmotic shock was increased by cannabidiol, an activator of TRPV2, and decreased by tranilast, an inhibitor of TRPV2, suggesting a role for the TRPV2 channel itself. Hyperosmotic shock-induced membrane depolarization was impaired in TRPV2

  18. Procedures for rat in situ skeletal muscle contractile properties.

    PubMed

    MacIntosh, Brian R; Esau, Shane P; Holash, R John; Fletcher, Jared R

    2011-01-01

    There are many circumstances where it is desirable to obtain the contractile response of skeletal muscle under physiological circumstances: normal circulation, intact whole muscle, at body temperature. This includes the study of contractile responses like posttetanic potentiation, staircase and fatigue. Furthermore, the consequences of disease, disuse, injury, training and drug treatment can be of interest. This video demonstrates appropriate procedures to set up and use this valuable muscle preparation. To set up this preparation, the animal must be anesthetized, and the medial gastrocnemius muscle is surgically isolated, with the origin intact. Care must be taken to maintain the blood and nerve supplies. A long section of the sciatic nerve is cleared of connective tissue, and severed proximally. All branches of the distal stump that do not innervate the medial gastrocnemius muscle are severed. The distal nerve stump is inserted into a cuff lined with stainless steel stimulating wires. The calcaneus is severed, leaving a small piece of bone still attached to the Achilles tendon. Sonometric crystals and/or electrodes for electromyography can be inserted. Immobilization by metal probes in the femur and tibia prevents movement of the muscle origin. The Achilles tendon is attached to the force transducer and the loosened skin is pulled up at the sides to form a container that is filled with warmed paraffin oil. The oil distributes heat evenly and minimizes evaporative heat loss. A heat lamp is directed on the muscle, and the muscle and rat are allowed to warm up to 37°C. While it is warming, maximal voltage and optimal length can be determined. These are important initial conditions for any experiment on intact whole muscle. The experiment may include determination of standard contractile properties, like the force-frequency relationship, force-length relationship, and force-velocity relationship. With care in surgical isolation, immobilization of the origin of the

  19. Interaction among Skeletal Muscle Metabolic Energy Systems during Intense Exercise

    PubMed Central

    Baker, Julien S.; McCormick, Marie Clare; Robergs, Robert A.

    2010-01-01

    High-intensity exercise can result in up to a 1,000-fold increase in the rate of ATP demand compared to that at rest (Newsholme et al., 1983). To sustain muscle contraction, ATP needs to be regenerated at a rate complementary to ATP demand. Three energy systems function to replenish ATP in muscle: (1) Phosphagen, (2) Glycolytic, and (3) Mitochondrial Respiration. The three systems differ in the substrates used, products, maximal rate of ATP regeneration, capacity of ATP regeneration, and their associated contributions to fatigue. In this exercise context, fatigue is best defined as a decreasing force production during muscle contraction despite constant or increasing effort. The replenishment of ATP during intense exercise is the result of a coordinated metabolic response in which all energy systems contribute to different degrees based on an interaction between the intensity and duration of the exercise, and consequently the proportional contribution of the different skeletal muscle motor units. Such relative contributions also determine to a large extent the involvement of specific metabolic and central nervous system events that contribute to fatigue. The purpose of this paper is to provide a contemporary explanation of the muscle metabolic response to different exercise intensities and durations, with emphasis given to recent improvements in understanding and research methodology. PMID:21188163

  20. Adaptations of human skeletal muscle fibers to spaceflight

    NASA Technical Reports Server (NTRS)

    Day, M. Kathleen; Allen, David L.; Mohajerani, Laleh; Greenisen, Michael C.; Roy, Roland R.; Edgerton, V. Reggie

    1995-01-01

    Human skeletal muscle fibers seem to share most of the same interrelationships among myosin ATPase activity, myosin heavy chain (MHC) phenotype, mitochondrial enzyme activities, glycolytic enzyme activities, and cross-sectional area (CSA) as found in rat, cat, and other species. One difference seems to be that fast fibers with high mitochrondrial content occur less frequently in humans than in the rat or cat. Recently, we have reported that the type of MHC expressed and the size of the muscle fibers in humans that have spent 11 days in space change significantly. Specifically, about 8% more fibers express fast MHCs and all phenotypes atrophy in the vastus lateralis (VL) post compared to preflight. In the present paper we examine the relationships among the population of myonuclei, MHC type, and CSA of single human muscle fibers before and after spaceflight. These are the first data that define the relationship among the types of MHC expressed, myonuclei number, and myonuclei domain of single fibers in human muscle. We then compare these data to similar measures in the cat. In addition, the maximal torque that can be generated by the knee extensors and their fatigability before and after spaceflight are examined. These data provide some indication of the potential physiologica consequences of the muscle adaptations that occur in humans in response to spaceflight.

  1. Prednisolone-induced changes in dystrophic skeletal muscle.

    PubMed

    Fisher, Ivan; Abraham, David; Bouri, Khaled; Hoffmann, Eric P; Hoffman, Eric P; Muntoni, Francesco; Morgan, Jennifer

    2005-05-01

    Although glucocorticoids delay the progression of Duchenne muscular dystrophy (DMD) their mechanism of action is unknown. Skeletal muscle gene expression profiles of mdx mice, an animal model of DMD, treated with prednisolone were compared with control mice at 1 and 6 wk. Of the 89 early differentially regulated genes and ESTs, delta-sarcoglycan, myosin Va, FK506-binding protein 51 (FKBP51), the potassium channel regulator potassium inwardly-rectifying channel Isk-like (IRK2) and ADAM 10 were overexpressed, whereas growth hormone-releasing hormone receptor (GHRHR) and Homer-2 were underexpressed. The 58 late differentially overexpressed genes included kallikreins (13, 16, and 26), FKBP51, PI3K alpha regulatory subunit, and IGFBP6, while underexpressed genes included NeuroD and nicotinic cholinergic receptor gamma. At both time points, overexpression of a cohort of genes relating to metabolism and proteolysis was apparent, alongside the differential expression of genes relating to calcium metabolism. Treatment did not increase muscle regeneration, reduce the number of infiltrating macrophages, or alter utrophin expression or localization. However, in the treated mdx soleus muscle, the percentage of slow fibers was significantly lower compared with untreated controls after 6 wk of treatment. These results show that glucocorticoids confer their benefit to dystrophic muscle in a complex fashion, culminating in a switch to a more normal muscle fiber type. PMID:15734791

  2. Effect of spaceflight on skeletal muscle: Mechanical properties and myosin isoform content of a slow muscle

    NASA Technical Reports Server (NTRS)

    Caiozzo, Vincent J.; Baker, Michael J.; Herrick, Robert E.; Tao, Ming; Baldwin, Kenneth M.

    1994-01-01

    This study examined changes in contractile, biochemical, and histochemical properties of slow antigravity skeletal muscle after a 6-day spaceflight mission. Twelve male Sprague-Dawley rats were randomly divided into two groups: flight and ground-based control. Approximately 3 h after the landing, in situ contractile measurements were made on the soleus muscles of the flight animals. The control animals were studied 24 h later. The contractile measurements included force-velocity relationship, force-frequency relationship, and fatigability. Biochemical measurements focused on the myosin heavy chain (MHC) and myosin light chain profiles. Adenosinetriphosphatase histochemistry was performed to identify cross-sectional area of slow and fast muscle fibers and to determine the percent fiber type distribution. The force-velocity relationships of the flight muscles were altered such that maximal isometric tension P(sub o) was decreased by 24% and maximal shortening velocity was increased by 14% (P less than 0.05). The force-frequency relationship of the flight muscles was shifted to the right of the control muscles. At the end of the 2-min fatigue test, the flight muscles generated only 34% of P(sub o), whereas the control muscles generated 64% of P(sub o). The flight muscles exhibited de novo expression of the type IIx MHC isoform as well as a slight decrease in the slow type I and fast type IIa MHC isoforms. Histochemical analyses of flight muscles demonstrated a small increase in the percentage of fast type II fibers and a greater atrophy of the slow type I fibers. The results demonstrate that contractile properties of slow antigravity skeletal muscle are sensitive to the microgravity environment and that changes begin to occur within the 1st wk. These changes were at least, in part, associated with changes in the amount and type of contractile protein expressed.

  3. Tissue-Engineered Skeletal Muscle Organoids for Reversible Gene Therapy

    NASA Technical Reports Server (NTRS)

    Vandenburgh, Herman; DelTatto, Michael; Shansky, Janet; Lemaire, Julie; Chang, Albert; Payumo, Francis; Lee, Peter; Goodyear, Amy; Raven, Latasha

    1996-01-01

    Genetically modified murine skeletal myoblasts were tissue engineered in vitro into organ-like structures (organoids) containing only postmitotic myoribers secreting pharmacological levels of recombinant human growth hormone (rhGH). Subcutaneous organoid implantation under tension led to the rapid and stable appearance of physiological sera levels of rhGH for up to 12 weeks, whereas surgical removal led to its rapid disappearance. Reversible delivery of bioactive compounds from postmitotic cells in tissue engineered organs has several advantages over other forms of muscle gene therapy.

  4. Tissue-Engineered Skeletal Muscle Organoids for Reversible Gene Therapy

    NASA Technical Reports Server (NTRS)

    Vandenburgh, Herman; DelTatto, Michael; Shansky, Janet; Lemaire, Julie; Chang, Albert; Payumo, Francis; Lee, Peter; Goodyear, Amy; Raven, Latasha

    1996-01-01

    Genetically modified murine skeletal myoblasts were tissue engineered in vitro into organ-like structures (organoids) containing only postmitotic myofibers secreting pharmacological levels of recombinant human growth hormone (rhGH). Subcutaneous organoid Implantation under tension led to the rapid and stable appearance of physiological sera levels of rhGH for up to 12 weeks, whereas surgical removal led to its rapid disappearance. Reversible delivery of bioactive compounds from postimtotic cells in tissue engineered organs has several advantages over other forms of muscle gene therapy.

  5. Statins and PPAR{alpha} agonists induce myotoxicity in differentiated rat skeletal muscle cultures but do not exhibit synergy with co-treatment

    SciTech Connect

    Johnson, Timothy E. . E-mail: Timothy_Johnson@merck.com; Zhang, Xiaohua; Shi, Shu; Umbenhauer, Diane R.

    2005-11-01

    Statins and fibrates (weak PPAR{alpha} agonists) are prescribed for the treatment of lipid disorders. Both drugs cause myopathy, but with a low incidence, 0.1-0.5%. However, combined statin and fibrate therapy can enhance myopathy risk. We tested the myotoxic potential of PPAR subtype selective agonists alone and in combination with statins in a differentiated rat myotube model. A pharmacologically potent experimental PPAR{alpha} agonist, Compound A, induced myotoxicity as assessed by TUNEL staining at a minimum concentration of 1 nM, while other weaker PPAR{alpha} compounds, for example, WY-14643, Gemfibrozil and Bezafibrate increased the percentage of TUNEL-positive nuclei at micromolar concentrations. In contrast, the PPAR{gamma} agonist Rosiglitazone caused little or no cell death at up to 10 {mu}M and the PPAR{delta} ligand GW-501516 exhibited comparatively less myotoxicity than that seen with Compound A. An experimental statin (Compound B) and Atorvastatin also increased the percentage of TUNEL-positive nuclei and co-treatment with WY-14643, Gemfibrozil or Bezafibrate had less than a full additive effect on statin-induced cell killing. The mechanism of PPAR{alpha} agonist-induced cell death was different from that of statins. Unlike statins, Compound A and WY-14643 did not activate caspase 3/7. In addition, mevalonate and geranylgeraniol reversed the toxicity caused by statins, but did not prevent the cell killing induced by WY-14643. Furthermore, unlike statins, Compound A did not inhibit the isoprenylation of rab4 or rap1a. Interestingly, Compound A and Compound B had differential effects on ATP levels. Taken together, these observations support the hypothesis that in rat myotube cultures, PPAR{alpha} agonism mediates in part the toxicity response to PPAR{alpha} compounds. Furthermore, PPAR{alpha} agonists and statins cause myotoxicity through distinct and independent pathways.

  6. Skeletal Muscle Lipid Deposition and Insulin Resistance: Impact of Dietary Fatty Acids and Exercise

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Evidence has mounted indicating that elevated intramuscular triacylglycerol levels are associated with diminished insulin sensitivity in skeletal muscle. This lipid accumulation is most likely due to enhanced fatty acid uptake into the muscle coupled with diminished mitochondrial lipid oxidation. Th...

  7. The STARS signaling pathway: a key regulator of skeletal muscle function.

    PubMed

    Lamon, Séverine; Wallace, Marita A; Russell, Aaron P

    2014-09-01

    During the last decade, the striated muscle activator of Rho signaling (STARS), a muscle-specific protein, has been proposed to play an increasingly important role in skeletal muscle growth, metabolism, regeneration and stress adaptation. STARS influences actin dynamics and, as a consequence, regulates the myocardin-related transcription factor A/serum response factor (MRTF-A/SRF) transcriptional program, a well-known pathway controlling skeletal muscle development and function. Muscle-specific stress conditions, such as exercise, positively regulates, while disuse and degenerative muscle diseases are associated with a downregulation of STARS and its downstream partners, suggesting a pivotal role for STARS in skeletal muscle health. This review provides a comprehensive overview of the known role and regulation of STARS and the members of its signaling pathway, RhoA, MRTF-A and SRF, in skeletal muscle. PMID:24557714

  8. In Vivo Rodent Models of Skeletal Muscle Adaptation to Decreased Use

    PubMed Central

    Cho, Su Han; Kim, Jang Hoe

    2016-01-01

    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. PMID:26996420

  9. 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. PMID:26996420

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