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Sample records for insulin secretory dysfunction

  1. Yeast secretory expression of insulin precursors.

    PubMed

    Kjeldsen, T

    2000-09-01

    Since the 1980s, recombinant human insulin for the treatment of diabetes mellitus has been produced using either the yeast Saccharomyces cerevisiae or the prokaryote Escherichia coli. Here, development of the insulin secretory expression system in S. cerevisiae and its subsequent optimisation is described. Expression of proinsulin in S. cerevisiae does not result in efficient secretion of proinsulin or insulin. However, expression of a cDNA encoding a proinsulin-like molecule with deletion of threonine(B30) as a fusion protein with the S. cerevisiae alpha-factor prepro-peptide (leader), followed either by replacement of the human proinsulin C-peptide with a small C-peptide (e.g. AAK), or by direct fusion of lysine(B29) to glycine(A1), results in the efficient secretion of folded single-chain proinsulin-like molecules to the culture supernatant. The secreted single-chain insulin precursor can then be purified and subsequently converted to human insulin by tryptic transpeptidation in organic aqueous medium in the presence of a threonine ester. The leader confers secretory competence to the insulin precursor, and constructed (synthetic) leaders have been developed for efficient secretory expression of the insulin precursor in the yeasts S. cerevisiae and Pichia pastories. The Kex2 endoprotease, specific for dibasic sites, cleaves the leader-insulin precursor fusion protein in the late secretory pathway and the folded insulin precursor is secreted to the culture supernatant. However, the Kex2 endoprotease processing of the pro-peptide-insulin precursor fusion protein is incomplete and a significant part of the pro-peptide-insulin precursor fusion protein is secreted to the culture supernatant in a hyperglycosylated form. A spacer peptide localised between the leader and the insulin precursor has been developed to optimise Kex2 endoprotease processing and insulin precursor fermentation yield. PMID:11030562

  2. Insulin dysfunction and Tau pathology

    PubMed Central

    El Khoury, Noura B.; Gratuze, Maud; Papon, Marie-Amélie; Bretteville, Alexis; Planel, Emmanuel

    2013-01-01

    The neuropathological hallmarks of Alzheimer's disease (AD) include senile plaques of β-amyloid (Aβ) peptides (a cleavage product of the Amyloid Precursor Protein, or APP) and neurofibrillary tangles (NFT) of hyperphosphorylated Tau protein assembled in paired helical filaments (PHF). NFT pathology is important since it correlates with the degree of cognitive impairment in AD. Only a small proportion of AD is due to genetic variants, whereas the large majority of cases (~99%) is late onset and sporadic in origin. The cause of sporadic AD is likely to be multifactorial, with external factors interacting with biological or genetic susceptibilities to accelerate the manifestation of the disease. Insulin dysfunction, manifested by diabetes mellitus (DM) might be such factor, as there is extensive data from epidemiological studies suggesting that DM is associated with an increased relative risk for AD. Type 1 diabetes (T1DM) and type 2 diabetes (T2DM) are known to affect multiple cognitive functions in patients. In this context, understanding the effects of diabetes on Tau pathogenesis is important since Tau pathology show a strong relationship to dementia in AD, and to memory loss in normal aging and mild cognitive impairment. Here, we reviewed preclinical studies that link insulin dysfunction to Tau protein pathogenesis, one of the major pathological hallmarks of AD. We found more than 30 studies reporting Tau phosphorylation in a mouse or rat model of insulin dysfunction. We also payed attention to potential sources of artifacts, such as hypothermia and anesthesia, that were demonstrated to results in Tau hyperphosphorylation and could major confounding experimental factors. We found that very few studies reported the temperature of the animals, and only a handful did not use anesthesia. Overall, most published studies showed that insulin dysfunction can promote Tau hyperphosphorylation and pathology, both directly and indirectly, through hypothermia. PMID:24574966

  3. SORCS1 is necessary for normal insulin secretory granule biogenesis in metabolically stressed β cells

    PubMed Central

    Kebede, Melkam A.; Oler, Angie T.; Gregg, Trillian; Balloon, Allison J.; Johnson, Adam; Mitok, Kelly; Rabaglia, Mary; Schueler, Kathryn; Stapleton, Donald; Thorstenson, Candice; Wrighton, Lindsay; Floyd, Brendan J.; Richards, Oliver; Raines, Summer; Eliceiri, Kevin; Seidah, Nabil G.; Rhodes, Christopher; Keller, Mark P.; Coon, Joshua L.; Audhya, Anjon; Attie, Alan D.

    2014-01-01

    We previously positionally cloned Sorcs1 as a diabetes quantitative trait locus. Sorcs1 belongs to the Vacuolar protein sorting-10 (Vps10) gene family. In yeast, Vps10 transports enzymes from the trans-Golgi network (TGN) to the vacuole. Whole-body Sorcs1 KO mice, when made obese with the leptinob mutation (ob/ob), developed diabetes. β Cells from these mice had a severe deficiency of secretory granules (SGs) and insulin. Interestingly, a single secretagogue challenge failed to consistently elicit an insulin secretory dysfunction. However, multiple challenges of the Sorcs1 KO ob/ob islets consistently revealed an insulin secretion defect. The luminal domain of SORCS1 (Lum-Sorcs1), when expressed in a β cell line, acted as a dominant-negative, leading to SG and insulin deficiency. Using syncollin-dsRed5TIMER adenovirus, we found that the loss of Sorcs1 function greatly impairs the rapid replenishment of SGs following secretagogue challenge. Chronic exposure of islets from lean Sorcs1 KO mice to high glucose and palmitate depleted insulin content and evoked an insulin secretion defect. Thus, in metabolically stressed mice, Sorcs1 is important for SG replenishment, and under chronic challenge by insulin secretagogues, loss of Sorcs1 leads to diabetes. Overexpression of full-length SORCS1 led to a 2-fold increase in SG content, suggesting that SORCS1 is sufficient to promote SG biogenesis. PMID:25157818

  4. Age-Dependent Labeling and Imaging of Insulin Secretory Granules

    PubMed Central

    Ivanova, Anna; Kalaidzidis, Yannis; Dirkx, Ronald; Sarov, Mihail; Gerlach, Michael; Schroth-Diez, Britta; Müller, Andreas; Liu, Yanmei; Andree, Cordula; Mulligan, Bernard; Münster, Carla; Kurth, Thomas; Bickle, Marc; Speier, Stephan; Anastassiadis, Konstantinos; Solimena, Michele

    2013-01-01

    Insulin is stored within the secretory granules of pancreatic β-cells, and impairment of its release is the hallmark of type 2 diabetes. Preferential exocytosis of newly synthesized insulin suggests that granule aging is a key factor influencing insulin secretion. Here, we illustrate a technology that enables the study of granule aging in insulinoma cells and β-cells of knock-in mice through the conditional and unequivocal labeling of insulin fused to the SNAP tag. This approach, which overcomes the limits encountered with previous strategies based on radiolabeling or fluorescence timer proteins, allowed us to formally demonstrate the preferential release of newly synthesized insulin and reveal that the motility of cortical granules significantly changes over time. Exploitation of this approach may enable the identification of molecular signatures associated with granule aging and unravel possible alterations of granule turnover in diabetic β-cells. Furthermore, the method is of general interest for the study of membrane traffic and aging. PMID:23929935

  5. Age-dependent labeling and imaging of insulin secretory granules.

    PubMed

    Ivanova, Anna; Kalaidzidis, Yannis; Dirkx, Ronald; Sarov, Mihail; Gerlach, Michael; Schroth-Diez, Britta; Müller, Andreas; Liu, Yanmei; Andree, Cordula; Mulligan, Bernard; Münster, Carla; Kurth, Thomas; Bickle, Marc; Speier, Stephan; Anastassiadis, Konstantinos; Solimena, Michele

    2013-11-01

    Insulin is stored within the secretory granules of pancreatic β-cells, and impairment of its release is the hallmark of type 2 diabetes. Preferential exocytosis of newly synthesized insulin suggests that granule aging is a key factor influencing insulin secretion. Here, we illustrate a technology that enables the study of granule aging in insulinoma cells and β-cells of knock-in mice through the conditional and unequivocal labeling of insulin fused to the SNAP tag. This approach, which overcomes the limits encountered with previous strategies based on radiolabeling or fluorescence timer proteins, allowed us to formally demonstrate the preferential release of newly synthesized insulin and reveal that the motility of cortical granules significantly changes over time. Exploitation of this approach may enable the identification of molecular signatures associated with granule aging and unravel possible alterations of granule turnover in diabetic β-cells. Furthermore, the method is of general interest for the study of membrane traffic and aging. PMID:23929935

  6. Pancreatic β-Cell Adaptive Plasticity in Obesity Increases Insulin Production but Adversely Affects Secretory Function.

    PubMed

    Alarcon, Cristina; Boland, Brandon B; Uchizono, Yuji; Moore, Patrick C; Peterson, Bryan; Rajan, Suryalekha; Rhodes, Olivia S; Noske, Andrew B; Haataja, Leena; Arvan, Peter; Marsh, Bradly J; Austin, Jotham; Rhodes, Christopher J

    2016-02-01

    Pancreatic β-cells normally produce adequate insulin to control glucose homeostasis, but in obesity-related diabetes, there is a presumed deficit in insulin production and secretory capacity. In this study, insulin production was assessed directly in obese diabetic mouse models, and proinsulin biosynthesis was found to be contrastingly increased, coupled with a significant expansion of the rough endoplasmic reticulum (without endoplasmic reticulum stress) and Golgi apparatus, increased vesicular trafficking, and a depletion of mature β-granules. As such, β-cells have a remarkable capacity to produce substantial quantities of insulin in obesity, which are then made available for immediate secretion to meet increased metabolic demand, but this comes at the price of insulin secretory dysfunction. Notwithstanding, it can be restored. Upon exposing isolated pancreatic islets of obese mice to normal glucose concentrations, β-cells revert back to their typical morphology with restoration of regulated insulin secretion. These data demonstrate an unrealized dynamic adaptive plasticity of pancreatic β-cells and underscore the rationale for transient β-cell rest as a treatment strategy for obesity-linked diabetes. PMID:26307586

  7. Mitochondrial dysfunction and insulin resistance: an update

    PubMed Central

    Montgomery, Magdalene K; Turner, Nigel

    2014-01-01

    Mitochondrial dysfunction has been implicated in the development of insulin resistance (IR); however, a large variety of association and intervention studies as well as genetic manipulations in rodents have reported contrasting results. Indeed, even 39 years after the first publication describing a relationship between IR and diminished mitochondrial function, it is still unclear whether a direct relationship exists, and more importantly if changes in mitochondrial capacity are a cause or consequence of IR. This review will take a journey through the past and summarise the debate about the occurrence of mitochondrial dysfunction and its possible role in causing decreased insulin action in obesity and type 2 diabetes. Evidence is presented from studies in various human populations, as well as rodents with genetic manipulations of pathways known to affect mitochondrial function and insulin action. Finally, we have discussed whether mitochondria are a potential target for the treatment of IR. PMID:25385852

  8. Insulin Secretory Defect and Insulin Resistance in Isolated Impaired Fasting Glucose and Isolated Impaired Glucose Tolerance

    PubMed Central

    Aoyama-Sasabe, Sae; Fukushima, Mitsuo; Xin, Xin; Taniguchi, Ataru; Nakai, Yoshikatsu; Mitsui, Rie; Takahashi, Yoshitaka; Tsuji, Hideaki; Yabe, Daisuke; Yasuda, Koichiro; Kurose, Takeshi; Inagaki, Nobuya; Seino, Yutaka

    2016-01-01

    Objective. To investigate the characteristics of isolated impaired glucose tolerance (IGT) and isolated impaired fasting glucose (IFG), we analyzed the factors responsible for elevation of 2-hour postchallenge plasma glucose (2 h PG) and fasting plasma glucose (FPG) levels. Methods. We investigated the relationship between 2 h PG and FPG levels who underwent 75 g OGTT in 5620 Japanese subjects at initial examination for medical check-up. We compared clinical characteristics between isolated IGT and isolated IFG and analyzed the relationships of 2 h PG and FPG with clinical characteristics, the indices of insulin secretory capacity, and insulin sensitivity. Results. In a comparison between isolated IGT and isolated IFG, insulinogenic index was lower in isolated IGT than that of isolated IFG (0.43 ± 0.34 versus 0.50 ± 0.47, resp.; p < 0.01). ISI composite was lower in isolated IFG than that of isolated IGT (6.87 ± 3.38 versus 7.98 ± 4.03, resp.; p < 0.0001). In isolated IGT group, insulinogenic index showed a significant correlation with 2 h PG (r = −0.245, p < 0.0001) and had the strongest correlation with 2 h PG (β = −0.290). In isolated IFG group, ISI composite showed a significant correlation with FPG (r = −0.162, p < 0.0001) and had the strongest correlation with FPG (β = −0.214). Conclusions. We have elucidated that decreased early-phase insulin secretion is the most important factor responsible for elevation of 2 h PG levels in isolated IGT subjects, and decreased insulin sensitivity is the most important factor responsible for elevation of FPG levels in isolated IFG subjects. PMID:26788515

  9. An Integrated View of Insulin Resistance and Endothelial Dysfunction

    PubMed Central

    Muniyappa, Ranganath; Iantorno, Micaela; Quon, Michael J.

    2008-01-01

    Synopsis Endothelial dysfunction and insulin resistance are frequently co-morbid states. Vasodilator actions of insulin are mediated by phosphatidylinositol 3-kinase (PI3K)-dependent signaling pathways that stimulate production of nitric oxide from vascular endothelium. This helps to couple metabolic and hemodynamic homeostasis under healthy conditions. In pathological states, shared causal factors including glucotoxicity, lipotoxicity, and inflammation selectively impair PI3K-dependent insulin signaling pathways that contribute to reciprocal relationships between insulin resistance and endothelial dysfunction. We discuss implications of pathway-selective insulin resistance in vascular endothelium, interactions between endothelial dysfunction and insulin resistance, and therapeutic interventions that may simultaneously improve both metabolic and cardiovascular physiology in insulin-resistant conditions. PMID:18775359

  10. Isocitrate-to-SENP1 signaling amplifies insulin secretion and rescues dysfunctional β cells

    PubMed Central

    Ferdaoussi, Mourad; Dai, Xiaoqing; Jensen, Mette V.; Wang, Runsheng; Peterson, Brett S.; Huang, Chao; Ilkayeva, Olga; Smith, Nancy; Miller, Nathanael; Hajmrle, Catherine; Spigelman, Aliya F.; Wright, Robert C.; Plummer, Gregory; Suzuki, Kunimasa; Mackay, James P.; van de Bunt, Martijn; Gloyn, Anna L.; Ryan, Terence E.; Norquay, Lisa D.; Brosnan, M. Julia; Trimmer, Jeff K.; Rolph, Timothy P.; Kibbey, Richard G.; Manning Fox, Jocelyn E.; Colmers, William F.; Shirihai, Orian S.; Neufer, P. Darrell; Yeh, Edward T.H.; Newgard, Christopher B.; MacDonald, Patrick E.

    2015-01-01

    Insulin secretion from β cells of the pancreatic islets of Langerhans controls metabolic homeostasis and is impaired in individuals with type 2 diabetes (T2D). Increases in blood glucose trigger insulin release by closing ATP-sensitive K+ channels, depolarizing β cells, and opening voltage-dependent Ca2+ channels to elicit insulin exocytosis. However, one or more additional pathway(s) amplify the secretory response, likely at the distal exocytotic site. The mitochondrial export of isocitrate and engagement with cytosolic isocitrate dehydrogenase (ICDc) may be one key pathway, but the mechanism linking this to insulin secretion and its role in T2D have not been defined. Here, we show that the ICDc-dependent generation of NADPH and subsequent glutathione (GSH) reduction contribute to the amplification of insulin exocytosis via sentrin/SUMO-specific protease-1 (SENP1). In human T2D and an in vitro model of human islet dysfunction, the glucose-dependent amplification of exocytosis was impaired and could be rescued by introduction of signaling intermediates from this pathway. Moreover, islet-specific Senp1 deletion in mice caused impaired glucose tolerance by reducing the amplification of insulin exocytosis. Together, our results identify a pathway that links glucose metabolism to the amplification of insulin secretion and demonstrate that restoration of this axis rescues β cell function in T2D. PMID:26389676

  11. Human islet preparations distributed for research exhibit a variety of insulin-secretory profiles

    PubMed Central

    Kayton, Nora S.; Poffenberger, Gregory; Henske, Joseph; Dai, Chunhua; Thompson, Courtney; Aramandla, Radhika; Shostak, Alena; Nicholson, Wendell; Brissova, Marcela; Bush, William S.

    2015-01-01

    Human islet research is providing new insights into human islet biology and diabetes, using islets isolated at multiple US centers from donors with varying characteristics. This creates challenges for understanding, interpreting, and integrating research findings from the many laboratories that use these islets. In what is, to our knowledge, the first standardized assessment of human islet preparations from multiple isolation centers, we measured insulin secretion from 202 preparations isolated at 15 centers over 11 years and noted five distinct patterns of insulin secretion. Approximately three quarters were appropriately responsive to stimuli, but one quarter were dysfunctional, with unstable basal insulin secretion and/or an impairment in stimulated insulin secretion. Importantly, the patterns of insulin secretion by responsive human islet preparations (stable Baseline and Fold stimulation of insulin secretion) isolated at different centers were similar and improved slightly over the years studied. When all preparations studied were considered, basal and stimulated insulin secretion did not correlate with isolation center, biological differences of the islet donor, or differences in isolation, such as Cold Ischemia Time. Dysfunctional islet preparations could not be predicted from the information provided by the isolation center and had altered expression of genes encoding components of the glucose-sensing pathway, but not of insulin production or cell death. These results indicate that insulin secretion by most preparations from multiple centers is similar but that in vitro responsiveness of human islets cannot be predicted, necessitating preexperimental human islet assessment. These results should be considered when one is designing, interpreting, and integrating experiments using human islets. PMID:25648831

  12. Human islet preparations distributed for research exhibit a variety of insulin-secretory profiles.

    PubMed

    Kayton, Nora S; Poffenberger, Gregory; Henske, Joseph; Dai, Chunhua; Thompson, Courtney; Aramandla, Radhika; Shostak, Alena; Nicholson, Wendell; Brissova, Marcela; Bush, William S; Powers, Alvin C

    2015-04-01

    Human islet research is providing new insights into human islet biology and diabetes, using islets isolated at multiple US centers from donors with varying characteristics. This creates challenges for understanding, interpreting, and integrating research findings from the many laboratories that use these islets. In what is, to our knowledge, the first standardized assessment of human islet preparations from multiple isolation centers, we measured insulin secretion from 202 preparations isolated at 15 centers over 11 years and noted five distinct patterns of insulin secretion. Approximately three quarters were appropriately responsive to stimuli, but one quarter were dysfunctional, with unstable basal insulin secretion and/or an impairment in stimulated insulin secretion. Importantly, the patterns of insulin secretion by responsive human islet preparations (stable Baseline and Fold stimulation of insulin secretion) isolated at different centers were similar and improved slightly over the years studied. When all preparations studied were considered, basal and stimulated insulin secretion did not correlate with isolation center, biological differences of the islet donor, or differences in isolation, such as Cold Ischemia Time. Dysfunctional islet preparations could not be predicted from the information provided by the isolation center and had altered expression of genes encoding components of the glucose-sensing pathway, but not of insulin production or cell death. These results indicate that insulin secretion by most preparations from multiple centers is similar but that in vitro responsiveness of human islets cannot be predicted, necessitating preexperimental human islet assessment. These results should be considered when one is designing, interpreting, and integrating experiments using human islets. PMID:25648831

  13. Insulin secretory defects in polycystic ovary syndrome. Relationship to insulin sensitivity and family history of non-insulin-dependent diabetes mellitus.

    PubMed Central

    Ehrmann, D A; Sturis, J; Byrne, M M; Karrison, T; Rosenfield, R L; Polonsky, K S

    1995-01-01

    The increased prevalence of non-insulin-dependent diabetes mellitus (NIDDM) among women with polycystic ovary syndrome (PCOS) has been ascribed to the insulin resistance characteristic of PCOS. This study was undertaken to determine the role of defects in insulin secretion as well as familial factors to the predisposition to NIDDM seen in PCOS. We studied three groups of women: PCOS with a family history of NIDDM (PCOS FHx POS; n = 11), PCOS without a family history of NIDDM (PCOS FHx NEG; n = 13), and women without PCOS who have a family history of NIDDM (NON-PCOS FHx POS; n = 8). Beta cell function was evaluated during a frequently sampled intravenous glucose tolerance test, by a low dose graded glucose infusion, and by the ability of the beta cell to be entrained by an oscillatory glucose infusion. PCOS FHx POS women were significantly less likely to demonstrate appropriate beta cell compensation for the degree of insulin resistance. The ability of the beta cell to entrain, as judged by the spectral power for insulin secretion rate, was significantly reduced in PCOS FHx POS subjects. In conclusion, a history of NIDDM in a first-degree relative appears to define a subset of PCOS subjects with a greater prevalence of insulin secretory defects. The risk of developing NIDDM imparted by insulin resistance in PCOS may be enhanced by these defects in insulin secretion. PMID:7615824

  14. Effect of low temperature cultivation on insulin secretory of human pancreatic islets.

    PubMed

    Nikolic, D M; Djordjevic, P B; Lackovic, V B; Stojiljkovic, V; Stanojevic, B

    2013-01-01

    The experiment compared the physiological function (insulin secretory capacity) and membrane integrity of human adult pancreatic islets incubated in culture at 37°C and 24°C. Pancreatic tissue was digested with Collagenase XI, using a non-automated method. Cultures were incubated at 37°C and 24°C. Secretory capacity of the islets is determined by measuring of the stimulation index (SI) on the 1st, 3rd and 7th day of cultivation. Membrane integrity of the islets was determined by dithizone staining. Both groups of examined cultures show a slight increase in SI during the incubation. However islets incubated at 24°C show higher SI values than those incubated at 37°C on the 1st, 3rd and 7th day of incubation. And on the first day of incubation, this difference was statistically significant (p <0.05). Islets incubated at 37°C showed preservation of membrane integrity, the islets are regular spherical shape, while those incubated at 24°C lose such an organization. During the seven-day cultivation, islets incubated at a standard temperature of 37°C show less preserve physiological functions in relation to cultures incubated at 24°C, but islets incubated at 37°C show more regular morphological forms. PMID:23489685

  15. Group X Secretory Phospholipase A2 Regulates Insulin Secretion through a Cyclooxygenase-2-dependent Mechanism*

    PubMed Central

    Shridas, Preetha; Zahoor, Lubna; Forrest, Kathy J.; Layne, Joseph D.; Webb, Nancy R.

    2014-01-01

    Group X secretory phospholipase A2 (GX sPLA2) potently hydrolyzes membrane phospholipids to release arachidonic acid (AA). While AA is an activator of glucose-stimulated insulin secretion (GSIS), its metabolite prostaglandin E2 (PGE2) is a known inhibitor. In this study, we determined that GX sPLA2 is expressed in insulin-producing cells of mouse pancreatic islets and investigated its role in beta cell function. GSIS was measured in vivo in wild-type (WT) and GX sPLA2-deficient (GX KO) mice and ex vivo using pancreatic islets isolated from WT and GX KO mice. GSIS was also assessed in vitro using mouse MIN6 pancreatic beta cells with or without GX sPLA2 overexpression or exogenous addition. GSIS was significantly higher in islets isolated from GX KO mice compared with islets from WT mice. Conversely, GSIS was lower in MIN6 cells overexpressing GX sPLA2 (MIN6-GX) compared with control (MIN6-C) cells. PGE2 production was significantly higher in MIN6-GX cells compared with MIN6-C cells and this was associated with significantly reduced cellular cAMP. The effect of GX sPLA2 on GSIS was abolished when cells were treated with NS398 (a COX-2 inhibitor) or L-798,106 (a PGE2-EP3 receptor antagonist). Consistent with enhanced beta cell function, GX KO mice showed significantly increased plasma insulin levels following glucose challenge and were protected from age-related reductions in GSIS and glucose tolerance compared with WT mice. We conclude that GX sPLA2 plays a previously unrecognized role in negatively regulating pancreatic insulin secretion by augmenting COX-2-dependent PGE2 production. PMID:25122761

  16. In utero origins of adult insulin resistance and vascular dysfunction.

    PubMed

    Thompson, Jennifer A; Regnault, Timothy R H

    2011-05-01

    The metabolic syndrome (or syndrome X) is a constellation of risk factors including insulin resistance, hypertension, dyslipidemia, and central obesity that predispose to the development of cardiovascular disease and type 2 diabetes in adult life. Insulin resistance is believed to be a critical pathophysiological event early in the disease process, impacting both skeletal muscle metabolic function and vascular responses. Adverse changes in insulin sensitivity have been found to originate in utero; for instance, prenatal events such as placental insufficiency/oxidative stress leading to altered fetal growth trajectories are associated with increased rates of metabolic syndrome in adult life. Such intrauterine insults result in reduced skeletal muscle mass in conjunction with altered insulin signaling, decreased oxidative fibers, and impaired mitochondrial function. These developmental disturbances set the stage for development of muscle triglyceride accumulation and depressed insulin sensitivity in childhood. Abnormalities of vascular structure and function arising from deprived intrauterine conditions that are exacerbated by insulin resistance account for the progression of hypertension from childhood to adulthood. Arterial changes initiated in utero include reduced endothelial nitric oxide (NO) bioavailability, vascular smooth muscle cell proliferation and inflammation, events leading to endothelial dysfunction, and atherosclerosis that are present in those destined for metabolic syndrome. In addition, the hypertensive phenotype that is a hallmark of metabolic syndrome may also be traced to blunted kidney development and renin-angiotensin system activation in growth-restricted offspring. The summative impact of these intrauterine programmed changes in terms of influencing adult health and disease encompasses dietary and lifestyle factors introduced postnatally. Establishing novel therapeutic interventions aimed at preventing and/or reducing in utero

  17. Protein Carbonylation, Mitochondrial Dysfunction, and Insulin Resistance123

    PubMed Central

    Frohnert, Brigitte I.; Bernlohr, David A.

    2013-01-01

    Oxidative stress has been identified as a common mechanism for cellular damage and dysfunction in a wide variety of disease states. Current understanding of the metabolic changes associated with obesity and the development of insulin resistance has focused on the role of oxidative stress and its interaction with inflammatory processes at both the tissue and organismal level. Obesity-related oxidative stress is an important contributing factor in the development of insulin resistance in the adipocyte as well as the myocyte. Moreover, oxidative stress has been linked to mitochondrial dysfunction, and this is thought to play a role in the metabolic defects associated with oxidative stress. Of the various effects of oxidative stress, protein carbonylation has been identified as a potential mechanism underlying mitochondrial dysfunction. As such, this review focuses on the relationship between protein carbonylation and mitochondrial biology and addresses those features that point to either the causal or casual relationship of lipid peroxidation–induced protein carbonylation as a determining factor in mitochondrial dysfunction. PMID:23493532

  18. The role of secretory granules in radiation-induced dysfunction of rat salivary glands

    SciTech Connect

    Peter, B.; Van Waarde, M.A.W.H.; Konings, A.W.T.; Vissink, A. |; `s-Gravenmade, E.J.

    1995-02-01

    To investigate the possible role of secretory granules in radiation-induced salivary gland dysfunction, rats were pretreated with isoproterenol (5 mg/kg intraperitoneally) to degranulate salivary gland acini. At maximal depletion, salivary glands were locally irradiated with a single dose of 15 Gy of X rays. Parotid and submandibular/sublingual saliva samples were collected before and 1-10 days after irradiation. The lag phase, flow rate, concentrations of potassium and sodium, and amylase secretion were determined. Sham-treated, isoproterenol-treated and irradiated animals provided reference data. In the parotid gland, but not in the submandibular gland, protection against radiation-induced changes in flow rate and composition of saliva occurred after pretreatment with isoproterenol. Combining morphological data from a previous study with data from the current study, it is suggested that improvement of parotid gland function is attributed predominantly to a proliferative stimulus on acinar cells by isoproterenol and not to its degranulation effect. After pretreatment with isoproterenol, an earlier expression of radiation-induced acinar cell damage leading to death was observed, followed by a faster tissue recovery. Thus the proliferative stimulus on acinar cells may accelerate the unmasking of latent lethal damage, resulting in the earlier replacement of dead cells by new, functionally intact cells. 33 refs., 2 figs.

  19. Impaired Insulin Signaling Accelerates Cardiac Mitochondrial Dysfunction After Myocardial Infarction

    PubMed Central

    Sena, Sandra; Hu, Ping; Zhang, Dongfang; Wang, Xiaohui; Wayment, Benjamin; Olsen, Curtis; Avelar, Erick; Abel, E. Dale; Litwin, Sheldon E

    2009-01-01

    Diabetes increases mortality and accelerates left ventricular (LV) dysfunction following myocardial infarction (MI). This study sought to determine the impact of impaired myocardial insulin signaling, in the absence of diabetes, on the development of LV dysfunction following MI. Mice with cardiomyocyte-restricted knock out of the insulin receptor (CIRKO) and wild type (WT) mice were subjected to proximal left coronary artery ligation (MI) and followed for 14 days. Despite equivalent infarct size, mortality was increased in CIRKO-MI vs. WT-MI mice (68 % vs. 40 %, respectively). In surviving mice, LV ejection fraction and dP/dt were reduced by > 40% in CIRKO-MI vs. WT-MI. Relative to shams, isometric developed tension in LV papillary muscles increased in WT-MI but not in CIRKO-MI. Time to peak tension and relaxation times were prolonged in CIRKO-MI vs. WT-MI suggesting impaired, load-independent myocardial contractile function. To elucidate mechanisms for impaired LV contractility, mitochondrial function was examined in permeabilized cardiac fibers. Whereas maximal ADP-stimulated mitochondrial O2 consumption rates (VADP) with palmitoyl carnitine were unchanged in WT-MI mice relative to sham-operated animals, VADP was significantly reduced in CIRKO-MI (13.17 ± 0.94 vs. 9.14 ± 0.88 nmol O2/min/mgdw, p<0.05). Relative to WT-MI, expression levels of GLUT4, PPAR-α, SERCA2, and the FA-Oxidation genes MCAD, LCAD, CPT2 and the electron transfer flavoprotein ETFDH were repressed in CIRKO-MI. Thus reduced insulin action in cardiac myocytes accelerates post-MI LV dysfunction, due in part to a rapid decline in mitochondrial FA oxidative capacity, which combined with limited glucose transport capacity may reduce substrate utilization and availability. PMID:19249310

  20. Roles of mitochondrial fragmentation and reactive oxygen species in mitochondrial dysfunction and myocardial insulin resistance

    SciTech Connect

    Watanabe, Tomoyuki; Saotome, Masao; Nobuhara, Mamoru; Sakamoto, Atsushi; Urushida, Tsuyoshi; Katoh, Hideki; Satoh, Hiroshi; Funaki, Makoto; Hayashi, Hideharu

    2014-05-01

    Purpose: Evidence suggests an association between aberrant mitochondrial dynamics and cardiac diseases. Because myocardial metabolic deficiency caused by insulin resistance plays a crucial role in heart disease, we investigated the role of dynamin-related protein-1 (DRP1; a mitochondrial fission protein) in the pathogenesis of myocardial insulin resistance. Methods and Results: DRP1-expressing H9c2 myocytes, which had fragmented mitochondria with mitochondrial membrane potential (ΔΨ{sub m}) depolarization, exhibited attenuated insulin signaling and 2-deoxy-D-glucose (2-DG) uptake, indicating insulin resistance. Treatment of the DRP1-expressing myocytes with Mn(III)tetrakis(1-methyl-4-pyridyl)porphyrin pentachloride (TMPyP) significantly improved insulin resistance and mitochondrial dysfunction. When myocytes were exposed to hydrogen peroxide (H{sub 2}O{sub 2}), they increased DRP1 expression and mitochondrial fragmentation, resulting in ΔΨ{sub m} depolarization and insulin resistance. When DRP1 was suppressed by siRNA, H{sub 2}O{sub 2}-induced mitochondrial dysfunction and insulin resistance were restored. Our results suggest that a mutual enhancement between DRP1 and reactive oxygen species could induce mitochondrial dysfunction and myocardial insulin resistance. In palmitate-induced insulin-resistant myocytes, neither DRP1-suppression nor TMPyP restored the ΔΨ{sub m} depolarization and impaired 2-DG uptake, however they improved insulin signaling. Conclusions: A mutual enhancement between DRP1 and ROS could promote mitochondrial dysfunction and inhibition of insulin signal transduction. However, other mechanisms, including lipid metabolite-induced mitochondrial dysfunction, may be involved in palmitate-induced insulin resistance. - Highlights: • DRP1 promotes mitochondrial fragmentation and insulin-resistance. • A mutual enhancement between DRP1 and ROS ipromotes insulin-resistance. • Palmitate increases DRP1 expression and induces insulin

  1. Complex mechanisms linking neurocognitive dysfunction to insulin resistance and other metabolic dysfunction

    PubMed Central

    Stoeckel, Luke E.; Arvanitakis, Zoe; Gandy, Sam; Small, Dana; Kahn, C. Ronald; Pascual-Leone, Alvaro; Pawlyk, Aaron; Sherwin, Robert; Smith, Philip

    2016-01-01

    Scientific evidence has established several links between metabolic and neurocognitive dysfunction, and epidemiologic evidence has revealed an increased risk of Alzheimer’s disease and vascular dementia in patients with diabetes. In July 2015, the National Institute of Diabetes, Digestive, and Kidney Diseases gathered experts from multiple clinical and scientific disciplines, in a workshop entitled “The Intersection of Metabolic and Neurocognitive Dysfunction”, to clarify the state-of-the-science on the mechanisms linking metabolic dysfunction, and insulin resistance and diabetes in particular, to neurocognitive impairment and dementia. This perspective is intended to serve as a summary of the opinions expressed at this meeting, which focused on identifying gaps and opportunities to advance research in this emerging area with important public health relevance. PMID:27303627

  2. Low-molecular-weight constituents of isolated insulin-secretory granules. Bivalent cations, adenine nucleotides and inorganic phosphate.

    PubMed Central

    Hutton, J C; Penn, E J; Peshavaria, M

    1983-01-01

    The concentrations of Zn2+, Ca2+, Mg2+, Pi and adenine nucleotides were determined in insulin-secretory granules prepared from a transplantable rat insulinoma. Differential and density-gradient centrifugation analyses revealed that Zn2+ in this tissue was principally localized in the secretory granule, a second major fraction being found in association with cytosolic proteins. Pi was principally recovered in the latter fraction, whereas Ca2+ and Mg2+ were more widely distributed. Intragranular ion-distribution experiments suggested that Zn2+ was complexed mainly to insulin and its precursor forms and remained in the granule in an insoluble state. The Zn2+/insulin ratio (0.54) was greater than that expected for insulin molecules having two centrally co-ordinated Zn2+ atoms/hexamer, but less than the maximal Zn2+-binding capacity of the molecule. Most of the granular Ca2+, Mg2+ and Pi was released in a soluble form when granules were disrupted by sonication. Simulation in vitro of the ionic composition of the granule suggested that up to 90% of its Ca2+ was complexed to Pi and adenine nucleotides. Granular macromolecules also bound Ca2+, as shown by equilibrium-dialysis studies of granule lysates. However, such binding was displaced by Mg2+. Examination of the efflux of Ca2+ from granules incubated in iso-osmotic suspensions at 37 degrees C suggested that the passive permeability of the granule membrane to Ca2+ was very low. Nevertheless, more than 50% of the granular Ca2+ was rapidly released in an ionized form on hypo-osmotic or detergent-induced disruption of the granule membrane. This may represent a potentially mobilizable pool of Ca2+ in vivo. PMID:6344863

  3. Characterization of Phospholipids in Insulin Secretory Granules and Mitochondria in Pancreatic Beta Cells and Their Changes with Glucose Stimulation*

    PubMed Central

    MacDonald, Michael J.; Ade, Lacmbouh; Ntambi, James M.; Ansari, Israr-Ul H.; Stoker, Scott W.

    2015-01-01

    The lipid composition of insulin secretory granules (ISG) has never previously been thoroughly characterized. We characterized the phospholipid composition of ISG and mitochondria in pancreatic beta cells without and with glucose stimulation. The phospholipid/protein ratios of most phospholipids containing unsaturated fatty acids were higher in ISG than in whole cells and in mitochondria. The concentrations of negatively charged phospholipids, phosphatidylserine, and phosphatidylinositol in ISG were 5-fold higher than in the whole cell. In ISG phosphatidylserine, phosphatidylinositol, phosphatidylethanolamine, and sphingomyelin, fatty acids 12:0 and 14:0 were high, as were phosphatidylserine and phosphatidylinositol containing 18-carbon unsaturated FA. With glucose stimulation, the concentration of many ISG phosphatidylserines and phosphatidylinositols increased; unsaturated fatty acids in phosphatidylserine increased; and most phosphatidylethanolamines, phosphatidylcholines, sphingomyelins, and lysophosphatidylcholines were unchanged. Unsaturation and shorter fatty acid length in phospholipids facilitate curvature and fluidity of membranes, which favors fusion of membranes. Recent evidence suggests that negatively charged phospholipids, such as phosphatidylserine, act as coupling factors enhancing the interaction of positively charged regions in SNARE proteins in synaptic or secretory vesicle membrane lipid bilayers with positively charged regions in SNARE proteins in the plasma membrane lipid bilayer to facilitate docking of vesicles to the plasma membrane during exocytosis. The results indicate that ISG phospholipids are in a dynamic state and are consistent with the idea that changes in ISG phospholipids facilitate fusion of ISG with the plasma membrane-enhancing glucose-stimulated insulin exocytosis. PMID:25762724

  4. Application of simple fed-batch technique to high-level secretory production of insulin precursor using Pichia pastoris with subsequent purification and conversion to human insulin

    PubMed Central

    2010-01-01

    Background The prevalence of diabetes is predicted to rise significantly in the coming decades. A recent analysis projects that by the year 2030 there will be ~366 million diabetics around the world, leading to an increased demand for inexpensive insulin to make this life-saving drug also affordable for resource poor countries. Results A synthetic insulin precursor (IP)-encoding gene, codon-optimized for expression in P. pastoris, was cloned in frame with the Saccharomyces cerevisiae α-factor secretory signal and integrated into the genome of P. pastoris strain X-33. The strain was grown to high-cell density in a batch procedure using a defined medium with low salt and high glycerol concentrations. Following batch growth, production of IP was carried out at methanol concentrations of 2 g L-1, which were kept constant throughout the remaining production phase. This robust feeding strategy led to the secretion of ~3 gram IP per liter of culture broth (corresponding to almost 4 gram IP per liter of cell-free culture supernatant). Using immobilized metal ion affinity chromatography (IMAC) as a novel approach for IP purification, 95% of the secreted product was recovered with a purity of 96% from the clarified culture supernatant. Finally, the purified IP was trypsin digested, transpeptidated, deprotected and further purified leading to ~1.5 g of 99% pure recombinant human insulin per liter of culture broth. Conclusions A simple two-phase cultivation process composed of a glycerol batch and a constant methanol fed-batch phase recently developed for the intracellular production of the Hepatitis B surface antigen was adapted to secretory IP production. Compared to the highest previously reported value, this approach resulted in an ~2 fold enhancement of IP production using Pichia based expression systems, thus significantly increasing the efficiency of insulin manufacture. PMID:20462406

  5. The Rab-binding protein Noc2 is associated with insulin-containing secretory granules and is essential for pancreatic beta-cell exocytosis.

    PubMed

    Cheviet, Séverine; Coppola, Thierry; Haynes, Lee P; Burgoyne, Robert D; Regazzi, Romano

    2004-01-01

    The small GTPases Rab3 and Rab27 are associated with secretory granules of pancreatic beta-cells and regulate insulin exocytosis. In this study, we investigated the role of Noc2, a potential partner of these two GTPases, in insulin secretion. In the beta-cell line INS-1E wild-type Noc2, Noc265E, and Noc258A, a mutant capable of interacting with Rab27 but not Rab3, colocalized with insulin-containing vesicles. In contrast, two mutants (Noc2138S,141S and Noc2154A,155A,156A) that bind neither Rab3 nor Rab27 did not associate with secretory granules and were uniformly distributed throughout the cell cytoplasm. Overexpression of wild-type Noc2, Noc265E, or Noc258A inhibited hormone secretion elicited by insulin secretagogues. In contrast, overexpression of the mutants not targeted to secretory granules was without effect. Silencing of the Noc2 gene by RNA interference led to a strong impairment in the capacity of INS-1E cells to respond to insulin secretagogues, indicating that appropriate levels of Noc2 are essential for pancreatic beta-cell exocytosis. The defect was already detectable in the early secretory phase (0-10 min) but was particularly evident during the sustained release phase (10-45 min). Protein-protein binding studies revealed that Noc2 is a potential partner of Munc13, a component of the machinery that controls vesicle priming and insulin exocytosis. These data suggest that Noc2 is involved in the recruitment of secretory granules at the plasma membrane possibly via the interaction with Munc13. PMID:14593078

  6. Insulin Resistance and Endothelial Dysfunction Constitute a Common Therapeutic Target in Cardiometabolic Disorders

    PubMed Central

    Mazur, G.

    2016-01-01

    Insulin resistance and other risk factors for atherosclerosis, such as hypertension and hypercholesterolemia, promote endothelial dysfunction and lead to development of metabolic syndrome which constitutes an introduction to cardiovascular disease. The insulin resistance and endothelial dysfunction cross talk between each other by numerous metabolic pathways. Hence, targeting one of these pathologies with pleiotropic treatment exerts beneficial effect on another one. Combined and expletive treatment of hypertension, lipid disorders, and insulin resistance with nonpharmacological interventions and conventional pharmacotherapy may inhibit the transformation of metabolic disturbances to fully developed cardiovascular disease. This paper summarises the common therapeutic targets for insulin resistance, endothelial dysfunction, and vascular inflammatory reaction at molecular level and analyses the potential pleiotropic effects of drugs used currently in management of cardiovascular disease, metabolic syndrome, and diabetes. PMID:27413253

  7. Genipin ameliorates age-related insulin resistance through inhibiting hepatic oxidative stress and mitochondrial dysfunction.

    PubMed

    Guan, Lili; Feng, Haiyan; Gong, Dezheng; Zhao, Xu; Cai, Li; Wu, Qiong; Yuan, Bo; Yang, Mei; Zhao, Jie; Zou, Yuan

    2013-12-01

    Insulin resistance (IR) increases with age and plays a key role in the pathogenesis of type 2 diabetes mellitus. Oxidative stress and mitochondrial dysfunction are supposed to be major factors leading to age-related IR. Genipin, an extract from Gardenia jasminoides Ellis fruit, has been reported to stimulate insulin secretion in pancreatic islet cells by regulating mitochondrial function. In this study, we first investigated the effects of genipin on insulin sensitivity and the potential mitochondrial mechanisms in the liver of aging rats. The rats were randomly assigned to receive intraperitoneal injections of either 25mg/kg genipin or vehicle once daily for 12days. The aging rats showed hyperinsulinemia and hyperlipidemia, and insulin resistance as examined by the decreased glucose decay constant rate during insulin tolerance test (kITT). The hepatic tissues showed steatosis and reduced glycogen content. Hepatic malondialdehyde level and mitochondrial reactive oxygen species (ROS) were higher, and levels of mitochondrial membrane potential (MMP) and ATP were lower as compared with the normal control rats. Administration of genipin ameliorated systemic and hepatic insulin resistance, alleviated hyperinsulinemia, hyperglyceridemia and hepatic steatosis, relieved hepatic oxidative stress and mitochondrial dysfunction in aging rats. Furthermore, genipin not only improved insulin sensitivity by promoting insulin-stimulated glucose consumption and glycogen synthesis, inhibited cellular ROS overproduction and alleviated the reduction of levels of MMP and ATP, but also reversed oxidative stress-associated JNK hyperactivation and reduced Akt phosphorylation in palmitate-treated L02 hepatocytes. In conclusion, genipin ameliorates age-related insulin resistance through inhibiting hepatic oxidative stress and mitochondrial dysfunction. PMID:24041487

  8. Prolonged Fasting Identifies Skeletal Muscle Mitochondrial Dysfunction as Consequence Rather Than Cause of Human Insulin Resistance

    PubMed Central

    Hoeks, Joris; van Herpen, Noud A.; Mensink, Marco; Moonen-Kornips, Esther; van Beurden, Denis; Hesselink, Matthijs K.C.; Schrauwen, Patrick

    2010-01-01

    OBJECTIVE Type 2 diabetes and insulin resistance have been associated with mitochondrial dysfunction, but it is debated whether this is a primary factor in the pathogenesis of the disease. To test the concept that mitochondrial dysfunction is secondary to the development of insulin resistance, we employed the unique model of prolonged fasting in humans. Prolonged fasting is a physiologic condition in which muscular insulin resistance develops in the presence of increased free fatty acid (FFA) levels, increased fat oxidation and low glucose and insulin levels. It is therefore anticipated that skeletal muscle mitochondrial function is maintained to accommodate increased fat oxidation unless factors secondary to insulin resistance exert negative effects on mitochondrial function. RESEARCH DESIGN AND METHODS While in a respiration chamber, twelve healthy males were subjected to a 60 h fast and a 60 h normal fed condition in a randomized crossover design. Afterward, insulin sensitivity was assessed using a hyperinsulinemic-euglycemic clamp, and mitochondrial function was quantified ex vivo in permeabilized muscle fibers using high-resolution respirometry. RESULTS Indeed, FFA levels were increased approximately ninefold after 60 h of fasting in healthy male subjects, leading to elevated intramuscular lipid levels and decreased muscular insulin sensitivity. Despite an increase in whole-body fat oxidation, we observed an overall reduction in both coupled state 3 respiration and maximally uncoupled respiration in permeabilized skeletal muscle fibers, which could not be explained by changes in mitochondrial density. CONCLUSIONS These findings confirm that the insulin-resistant state has secondary negative effects on mitochondrial function. Given the low insulin and glucose levels after prolonged fasting, hyperglycemia and insulin action per se can be excluded as underlying mechanisms, pointing toward elevated plasma FFA and/or intramuscular fat accumulation as possible

  9. Vitamin D receptor (VDR) mRNA and VDR protein levels in relation to vitamin D status, insulin secretory capacity, and VDR genotype in Bangladeshi Asians.

    PubMed

    Ogunkolade, Babatunji-William; Boucher, Barbara J; Prahl, Jean M; Bustin, Stephen A; Burrin, Jacky M; Noonan, Kate; North, Bernard V; Mannan, Nassima; McDermott, Michael F; DeLuca, Hector F; Hitman, Graham A

    2002-07-01

    Associations have been reported between vitamin D receptor (VDR) gene polymorphisms, type 1 diabetes, insulin secretion, and the insulin resistance syndrome. As VDR polymorphisms have no known functional significance, these findings may implicate a variant of the VDR gene or a locus in linkage disequilibrium with the VDR. We have examined VDR mRNA and VDR protein levels in relation to VDR polymorphisms (41 Bangladeshi subjects) and analyzed insulin secretory capacity (143 Bangladeshi subjects), allowing for other known determinants. Peripheral blood mononuclear cells (PBMCs) from subjects who had been genotyped for BsmI, ApaI, TaqI, and FokI VDR restriction fragment length polymorphisms were used for both total VDR mRNA quantitation (using TaqMan) and measurement of VDR protein levels (using a specific micro-immunoassay). Stepwise multiple regression analyses were used (to P < 0.05) to analyze the data. For the insulin secretion index, the best-fit model (n = 143, P < 0.0001) gave age (P = 0.002), TaqI (P < 0.0001), and BMI (P = 0.001) as independent determinants; with the inclusion of VDR mRNA and VDR protein levels, VDR mRNA was the sole independent determinant (n = 41, P = 0.024). However, the best-fit model for VDR mRNA (P = 0.004) gave FokI (P = 0.044) and TaqI (P = 0.04) genotypes and insulin secretory capacity (P = 0.042) as independent determinants. For VDR protein levels, the best-fit model (P = 0.006) gave TaqI genotype (P = 0.005) and circulating 1,25-dihydroxyvitamin-D levels (P = 0.03) as independent determinants. In conclusion, these studies confirm an association between VDR polymorphisms and insulin secretory capacity and demonstrate the VDR genotype to be a significant determinant of VDR mRNA and VDR protein levels in PBMCs, providing functional support to previously described genetic associations with the VDR gene. Furthermore, VDR expression has been shown to be a determinant of insulin secretory capacity. PMID:12086963

  10. Insulin-like growth factor 1 (IGF-1) therapy: Mitochondrial dysfunction and diseases.

    PubMed

    Sádaba, M C; Martín-Estal, I; Puche, J E; Castilla-Cortázar, I

    2016-07-01

    This review resumes the association between mitochondrial function and diseases, especially neurodegenerative diseases. Additionally, it summarizes the major role of IGF-1 as a mitochondrial protector, as studied in several experimental models (cirrhosis, aging …). The contribution of mitochondrial dysfunction to impairments in insulin metabolic signaling is also suggested by gene array analysis showing that reductions in gene expression, that regulates mitochondrial ATP production, are associated with insulin resistance and type 2 diabetes mellitus. Moreover, reductions in oxidative capacity of mitochondrial electron transport chain are manifested in obese, insulin-resistant and diabetic patients. Genetic and environmental factors, oxidative stress, and alterations in mitochondrial biogenesis can adversely affect mitochondrial function, leading to insulin resistance and several pathological conditions, such as type 2 diabetes. Finally, it remains essential to know the exact mechanisms involved in mitochondrial generation and metabolism, mitophagy, apoptosis, and oxidative stress to establish new targets in order to develop potentially effective therapies. One of the newest targets to recover mitochondrial dysfunction could be the administration of IGF-1 at low doses. In the last years, it has been observed that IGF-1 therapy has several beneficial effects: restores physiological IGF-1 levels; improves insulin resistance and lipid metabolism; exerts mitochondrial protection; and has hepatoprotective, neuroprotective, antioxidant and antifibrogenic effects. In consequence, treatment of mitochondrial dysfunctions with low doses of IGF-1 could be a powerful and useful effective therapy to restore normal mitochondrial functions. PMID:27020404

  11. Mitochondrial dysfunction leads to impairment of insulin sensitivity and adiponectin secretion in adipocytes.

    PubMed

    Wang, Chih-Hao; Wang, Ching-Chu; Huang, Hsin-Chang; Wei, Yau-Huei

    2013-02-01

    Adipocytes play an integrative role in the regulation of energy metabolism and glucose homeostasis in the human body. Functional defects in adipocytes may cause systemic disturbance of glucose homeostasis. Recent studies revealed mitochondrial abnormalities in the adipose tissue of patients with type 2 diabetes. In addition, patients with mitochondrial diseases usually manifest systemic metabolic disorder. However, it is unclear how mitochondrial dysfunction in adipocytes affects the regulation of glucose homeostasis. In this study, we induced mitochondrial dysfunction and overproduction of reactive oxygen species (ROS) by addition of respiratory inhibitors oligomycin A and antimycin A and by knockdown of mitochondrial transcription factor A (mtTFA), respectively. We found an attenuation of the insulin response as indicated by lower glucose uptake and decreased phosphorylation of Akt upon insulin stimulation of adipocytes with mitochondrial dysfunction. Furthermore, the expression of glucose transporter 4 (Glut4) and secretion of adiponectin were decreased in adipocytes with increased ROS generated by defective mitochondria. Moreover, the severity of insulin insensitivity was correlated with the extent of mitochondrial dysfunction. These results suggest that higher intracellular ROS levels elicited by mitochondrial dysfunction resulted in impairment of the function of adipocytes in the maintenance of glucose homeostasis through attenuation of insulin signaling, downregulation of Glut4 expression, and decrease in adiponectin secretion. Our findings substantiate the important role of mitochondria in the regulation of glucose homeostasis in adipocytes and also provide a molecular basis for the explanation of the manifestation of diabetes mellitus or insulin insensitivity in a portion of patients with mitochondrial diseases such as MELAS or MERRF syndrome. PMID:23253816

  12. Sirtuin3 Dysfunction Is the Key Determinant of Skeletal Muscle Insulin Resistance by Angiotensin II

    PubMed Central

    Macconi, Daniela; Perico, Luca; Longaretti, Lorena; Morigi, Marina; Cassis, Paola; Buelli, Simona; Perico, Norberto; Remuzzi, Giuseppe; Benigni, Ariela

    2015-01-01

    Background Angiotensin II promotes insulin resistance. The mechanism underlying this abnormality, however, is still poorly defined. In a different setting, skeletal muscle metabolism and insulin signaling are regulated by Sirtuin3. Objective Here, we investigate whether angiotensin II-induced insulin resistance in skeletal muscle is associated with Sirtuin3 dysregulation and whether pharmacological manipulation of Sirtuin3 confers protection. Study Design Parental and GLUT4-myc L6 rat skeletal muscle cells exposed to angiotensin II are used as in vitro models of insulin resistance. GLUT4 translocation, glucose uptake, intracellular molecular signals such as mitochondrial reactive oxygen species, Sirtuin3 protein expression and activity, along with its downstream targets and upstream regulators, are analyzed both in the absence and presence of acetyl-L-carnitine. The role of Sirtuin3 in GLUT4 translocation and intracellular molecular signaling is also studied in Sirtuin3-silenced as well as over-expressing cells. Results Angiotensin II promotes insulin resistance in skeletal muscle cells via mitochondrial oxidative stress, resulting in a two-fold increase in superoxide generation. In this context, reactive oxygen species open the mitochondrial permeability transition pore and significantly lower Sirtuin3 levels and activity impairing the cell antioxidant defense. Angiotensin II-induced Sirtuin3 dysfunction leads to the impairment of AMP-activated protein kinase/nicotinamide phosphoribosyltransferase signaling. Acetyl-L-carnitine, by lowering angiotensin II-induced mitochondrial superoxide formation, prevents Sirtuin3 dysfunction. This phenomenon implies the restoration of manganese superoxide dismutase antioxidant activity and AMP-activated protein kinase activation. Acetyl-L-carnitine protection is abrogated by specific Sirtuin3 siRNA. Conclusions Our data demonstrate that angiotensin II-induced insulin resistance fosters mitochondrial superoxide generation, in

  13. Type II PKAs are anchored to mature insulin secretory granules in INS-1 β-cells and required for cAMP-dependent potentiation of exocytosis.

    PubMed

    Villalpando, Sabrina; Cazevieille, Chantal; Fernandez, Anne; Lamb, Ned J; Hani, El-Habib

    2016-06-01

    Specificity of the cAMP-dependent protein kinase (PKA) pathway relies on an extremely sophisticated compartmentalization mechanism of the kinase within a given cell, based on high-affinity binding of PKA tetramer pools to different A-Kinase Anchoring Proteins (AKAPs). We and others have previously shown that AKAPs-dependent PKA subcellular targeting is a requisite for optimal cAMP-dependent potentiation of insulin exocytosis. We thus hypothesized that a PKA pool may directly anchor to the secretory compartment to potentiate insulin exocytosis. Here, using immunofluorescence analyses combined to subcellular fractionations and purification of insulin secretory granules (ISGs), we identified discrete subpools of type II PKAs, RIIα and RIIβ PKAs, along with the catalytic subunit, physically associated with ISGs within pancreatic insulin-secreting β-cells. Ultrastructural analysis of native rodent β-cells confirmed in vivo the occurrence of PKA on dense-core ISGs. Isoform-selective disruption of binding of PKAs to AKAPs reinforced the requirement of type II PKA isoforms for cAMP potentiation of insulin exocytosis. This granular localization of PKA was of critical importance since siRNA-mediated depletion of either RIIα or RIIβ PKAs resulted in a significant reduction of cAMP-dependent potentiation of insulin release. The present work provides evidence for a previously unrecognized pool of type II PKAs physically anchored to the β-cell ISGs compartment and supports a non-redundant function for type II PKAs during cAMP potentiation of exocytosis. PMID:26898328

  14. SIRT1 attenuates high glucose-induced insulin resistance via reducing mitochondrial dysfunction in skeletal muscle cells.

    PubMed

    Zhang, Hao-Hao; Ma, Xiao-Jun; Wu, Li-Na; Zhao, Yan-Yan; Zhang, Peng-Yu; Zhang, Ying-Hui; Shao, Ming-Wei; Liu, Fei; Li, Fei; Qin, Gui-Jun

    2015-05-01

    Insulin resistance is often characterized as the most critical factor contributing to the development of type 2 diabetes mellitus (T2DM). Sustained high glucose is an important extracellular environment that induces insulin resistance. Acquired insulin resistance is associated with reduced insulin-stimulated mitochondrial activity as a result of increased mitochondrial dysfunction. Silent information regulator 1 (SIRT1) is one member of the SIRT2 (Sir2)-like family of proteins involved in glucose homeostasis and insulin secretion in mammals. Although SIRT1 has a therapeutic effect on metabolic deterioration in insulin resistance, it is still not clear how SIRT1 is involved in the development of insulin resistance. Here, we demonstrate that pcDNA3.1 vector-mediated overexpression of SIRT1 attenuates insulin resistance in the high glucose-induced insulin-resistant skeleton muscle cells. These beneficial effects were associated with ameliorated mitochondrial dysfunction. Further studies have demonstrated that SIRT1 restores mitochondrial complex I activity leading to decreased oxidative stress and mitochondrial dysfunction. Furthermore, SIRT1 significantly elevated the level of another SIRT which is named SIRT3, and SIRT3 siRNA-suppressed SIRT1-induced mitochondria complex activity increments. Taken together, these results showed that SIRT1 improves insulin sensitivity via the amelioration of mitochondrial dysfunction, and this is achieved through the SIRT1-SIRT3-mitochondrial complex I pathway. PMID:25710929

  15. Reduced melanocortin production causes sexual dysfunction in male mice with POMC neuronal insulin and leptin insensitivity.

    PubMed

    Faulkner, Latrice D; Dowling, Abigail R; Stuart, Ronald C; Nillni, Eduardo A; Hill, Jennifer W

    2015-04-01

    Proopiomelanocortin (POMC)-derived peptides like α-melanocyte-stimulating hormone (MSH) substantially improve hepatic insulin sensitivity and regulate energy expenditure. Melanocortinergic agents are also powerful inducers of sexual arousal that are being investigated for a possible therapeutic role in erectile dysfunction. It is currently unclear whether reduced melanocortin (MC) activity may contribute to the sexual dysfunction accompanying obesity and type 2 diabetes. Male rodents with leptin and insulin resistance targeted to POMC neurons (leptin receptor [LepR]/insulin receptor [IR]POMC mice) exhibit obesity, hyperinsulinemia, hyperglycemia, and systemic insulin resistance. In this study, we demonstrate that LepR/IRPOMC males are also subfertile due to dramatic alterations in sexual behavior. Remarkably, these reproductive changes are accompanied by decreased α-MSH production not present when a single receptor type is deleted. Unexpectedly, behavioral sensitivity to α-MSH and MC receptor expression are also reduced in LepR/IRPOMC males, a potential adaptation of the MC system to altered α-MSH production. Together, these results suggest that concurrent insulin and leptin resistance in POMC neurons in individuals with obesity or type 2 diabetes can reduce endogenous α-MSH levels and impair sexual function. PMID:25590244

  16. Reduced Melanocortin Production Causes Sexual Dysfunction in Male Mice With POMC Neuronal Insulin and Leptin Insensitivity

    PubMed Central

    Faulkner, Latrice D.; Dowling, Abigail R.; Stuart, Ronald C.; Nillni, Eduardo A.

    2015-01-01

    Proopiomelanocortin (POMC)-derived peptides like α-melanocyte-stimulating hormone (MSH) substantially improve hepatic insulin sensitivity and regulate energy expenditure. Melanocortinergic agents are also powerful inducers of sexual arousal that are being investigated for a possible therapeutic role in erectile dysfunction. It is currently unclear whether reduced melanocortin (MC) activity may contribute to the sexual dysfunction accompanying obesity and type 2 diabetes. Male rodents with leptin and insulin resistance targeted to POMC neurons (leptin receptor [LepR]/insulin receptor [IR]POMC mice) exhibit obesity, hyperinsulinemia, hyperglycemia, and systemic insulin resistance. In this study, we demonstrate that LepR/IRPOMC males are also subfertile due to dramatic alterations in sexual behavior. Remarkably, these reproductive changes are accompanied by decreased α-MSH production not present when a single receptor type is deleted. Unexpectedly, behavioral sensitivity to α-MSH and MC receptor expression are also reduced in LepR/IRPOMC males, a potential adaptation of the MC system to altered α-MSH production. Together, these results suggest that concurrent insulin and leptin resistance in POMC neurons in individuals with obesity or type 2 diabetes can reduce endogenous α-MSH levels and impair sexual function. PMID:25590244

  17. Role of mitochondrial dysfunction and dysregulation of Ca(2+) homeostasis in insulin insensitivity of mammalian cells.

    PubMed

    Wang, Chih-Hao; Tsai, Ting-Fen; Wei, Yau-Huei

    2015-09-01

    Mitochondria and endoplasmic reticulum (ER) play an important role in the maintenance of intracellular Ca(2+) homeostasis, and their defects may be etiological factors contributing to insulin resistance and type 2 diabetes (T2D). Recent studies indicate that alterations of Ca(2+) levels and Ca(2+) -dependent signaling pathways can impede the insulin signaling cascade, resulting in insulin resistance of β cells and insulin-responsive cells. Mitochondria-associated ER membranes (MAMs) are essential for efficient communication between the ER and mitochondria. Thus, abnormalities in the structure and function of MAMs in affected tissue cells in T2D are an important area of study. Recently, we demonstrated that a deficiency of Cisd2, an iron-sulfur protein localized on MAMs, could lead to mitochondrial dysfunction and disturbance of intracellular Ca(2+) homeostasis. Moreover, we first elucidated that defects in the function of MAMs in Ca(2+) uptake resulted in insulin insensitivity of adipocytes, which plays an important role in the pathogenesis of diabetes in Cisd2 knockout mice. On the basis of these observations, we suggest improving the bioenergetic function of mitochondria and the function of MAMs in maintaining Ca(2+) homeostasis as a novel strategy for the development of new therapeutics aimed at preventing and treating insulin resistance and T2D. PMID:26214798

  18. Proteasome Dysfunction Associated to Oxidative Stress and Proteotoxicity in Adipocytes Compromises Insulin Sensitivity in Human Obesity

    PubMed Central

    Díaz-Ruiz, Alberto; Guzmán-Ruiz, Rocío; Moreno, Natalia R.; García-Rios, Antonio; Delgado-Casado, Nieves; Membrives, Antonio; Túnez, Isaac; El Bekay, Rajaa; Fernández-Real, José M.; Tovar, Sulay; Diéguez, Carlos; Tinahones, Francisco J.; Vázquez-Martínez, Rafael; López-Miranda, José

    2015-01-01

    Abstract Aims: Obesity is characterized by a low-grade systemic inflammatory state and adipose tissue (AT) dysfunction, which predispose individuals to the development of insulin resistance (IR) and metabolic disease. However, a subset of obese individuals, referred to as metabolically healthy obese (MHO) individuals, are protected from obesity-associated metabolic abnormalities. Here, we aim at identifying molecular factors and pathways in adipocytes that are responsible for the progression from the insulin-sensitive to the insulin-resistant, metabolically unhealthy obese (MUHO) phenotype. Results: Proteomic analysis of paired samples of adipocytes from subcutaneous (SC) and omental (OM) human AT revealed that both types of cells are altered in the MUHO state. Specifically, the glutathione redox cycle and other antioxidant defense systems as well as the protein-folding machinery were dysregulated and endoplasmic reticulum stress was increased in adipocytes from IR subjects. Moreover, proteasome activity was also compromised in adipocytes of MUHO individuals, which was associated with enhanced accumulation of oxidized and ubiquitinated proteins in these cells. Proteasome activity was also impaired in adipocytes of diet-induced obese mice and in 3T3-L1 adipocytes exposed to palmitate. In line with these data, proteasome inhibition significantly impaired insulin signaling in 3T3-L1 adipocytes. Innovation: This study provides the first evidence of the occurrence of protein homeostasis deregulation in adipocytes in human obesity, which, together with oxidative damage, interferes with insulin signaling in these cells. Conclusion: Our results suggest that proteasomal dysfunction and impaired proteostasis in adipocytes, resulting from protein oxidation and/or misfolding, constitute major pathogenic mechanisms in the development of IR in obesity. Antioxid. Redox Signal. 23, 597–612. PMID:25714483

  19. PROGRAMMING OF GROWTH, INSULIN RESISTANCE AND VASCULAR DYSFUNCTION IN OFFSPRING OF LATE GESTATION DIABETIC RATS

    PubMed Central

    Segar, Emily M.; Norris, Andrew W.; Yao, Jian-Rong; Hu, Shanming; Koppenhafer, Stacia L.; Roghair, Robert D.; Segar, Jeffrey L.; Scholz, Thomas D.

    2010-01-01

    The offspring of diabetic mothers (ODM) have an increased risk of developing metabolic and cardiovascular dysfunction. However, few studies have focused on susceptibility to disease in offspring of mothers developing diabetes during pregnancy. We developed an animal model of late-gestation diabetic pregnancy and characterized metabolic and vascular function in the offspring. Diabetes was induced by streptozotocin (50 mg/kg, i.p.) in pregnant rats on gestational day 13 and partially controlled by twice-daily injections of insulin. At 2 months of age, ODM had slightly better glucose tolerance than controls (p < 0.05), however, by 6 months of age this trend reversed. Hyperinsulinemic-euglycemic clamp revealed insulin resistance in male ODM (p < 0.05). In 6-8 mo old female ODM, aortas showed significantly enhanced contractility to potassium chloride (KCl), endothelin-1 (ET-1) and noradrenaline (NA). No differences in responses to endothelin-1 and noradrenaline were apparent with co-administration of NG-nitro-L-arginine (L-NNA). Relaxation to acetylcholine but not nitroprusside was significantly impaired in female ODM. In contrast, males displayed no between group differences in response to vasoconstrictors while relaxation to nitroprusside and acetylcholine was greater in ODM compared to control animals. Thus, development of diabetes during pregnancy programs gender specific insulin resistance and vascular dysfunction in adult offspring. PMID:19203348

  20. Mitochondrial dysfunction precedes depression of AMPK/AKT signaling in insulin resistance induced by high glucose in primary cortical neurons.

    PubMed

    Peng, Yunhua; Liu, Jing; Shi, Le; Tang, Ying; Gao, Dan; Long, Jiangang; Liu, Jiankang

    2016-06-01

    Recent studies have demonstrated brain insulin signaling impairment and mitochondrial dysfunction in diabetes. Hyperinsulinemia and hyperlipidemia arising from diabetes have been linked to neuronal insulin resistance, and hyperglycemia induces peripheral sensory neuronal impairment and mitochondrial dysfunction. However, how brain glucose at diabetic conditions elicits cortical neuronal insulin signaling impairment and mitochondrial dysfunction remains unknown. In the present study, we cultured primary cortical neurons with high glucose levels and investigated the neuronal mitochondrial function and insulin response. We found that mitochondrial function was declined in presence of 10 mmol/L glucose, prior to the depression of AKT signaling in primary cortical neurons. We further demonstrated that the cerebral cortex of db/db mice exhibited both insulin resistance and loss of mitochondrial complex components. Moreover, we found that adenosine monophosphate-activated protein kinase (AMPK) inactivation is involved in high glucose-induced mitochondrial dysfunction and insulin resistance in primary cortical neurons and neuroblastoma cells, as well as in cerebral cortex of db/db mice, and all these impairments can be rescued by mitochondrial activator, resveratrol. Taken together, our results extend the finding that high glucose (≥10 mmol/L) comparable to diabetic brain extracellular glucose level leads to neuronal mitochondrial dysfunction and resultant insulin resistance, and targeting mitochondria-AMPK signaling might be a promising strategy to protect against diabetes-related neuronal impairment in central nerves system. We found that high glucose (≥10 mmol/L), comparable to diabetic brain extracellular glucose level, leads to neuronal mitochondrial dysfunction and resultant insulin resistance in an AMPK-dependent manner, and targeting mitochondria-AMPK signaling might be a promising strategy to protect against diabetes-related neuronal impairment in central

  1. Levocetirizine ameliorates high fructose diet-induced insulin resistance, vascular dysfunction and hepatic steatosis in rats.

    PubMed

    Shawky, Noha M; Shehatou, George S G; Abdel Rahim, Mona; Suddek, Ghada M; Gameil, Nariman M

    2014-10-01

    This study investigates the possible protective effects of levocetirizine against fructose-induced insulin resistance, hepatic steatosis and vascular dysfunction, in comparison to pioglitazone, a standard insulin sensitizer. Male Sprague Dawley rats (150-200 g) were divided into 4 groups. Three groups were fed on high fructose diets (HFD) containing 60% w/w fructose, while the fourth control group was fed on standard laboratory food for 8 weeks. AUCOGTT, AUCITT, fasting glucose, HOMA-IR, hepatic glutathione (GSH) and malondialdehyde (MDA) levels, serum total cholesterol, LDL-C, C-reactive protein (CRP) level and lactate dehydrogenase (LDH) activity and liver steatosis scores were significantly higher in HFD group compared to control group. Moreover, body weight gain, food intake, feeding efficiency, HOMA-β, Emax and pEC50 of acetylcholine-induced relaxations of aortic rings and hepatic superoxide dismutase (SOD) activity were significantly lower in HFD group than in control group. Treatment with levocetirizine caused significant decreases in AUCOGTT, AUCITT, HOMA-IR, hepatic GSH and MDA levels and serum CRP level and LDH activity and significant increases in hepatic SOD activity and HOMA-β when compared with the HFD group. Although levocetirizine failed to alter TC and LDL-C levels, it produced a significant increase in HDL-C level relative to control group. Levocetirizine was also able to improve acetylcholine-induced relaxations of aortic rings, indicating a protective effect against insulin resistance-induced endothelial damage comparable to that offered by pioglitazone. Moreover, levocetirizine substantially attenuated insulin resistance-associated liver macrovesicular steatosis. These findings demonstrate that levocetirizine ameliorates insulin resistance, improves glucose tolerance and attenuates insulin resistance-linked hepatic steatosis and vascular damage. PMID:25064340

  2. CB1 receptor blockade counters age-induced insulin resistance and metabolic dysfunction.

    PubMed

    Lipina, Christopher; Vaanholt, Lobke M; Davidova, Anastasija; Mitchell, Sharon E; Storey-Gordon, Emma; Hambly, Catherine; Irving, Andrew J; Speakman, John R; Hundal, Harinder S

    2016-04-01

    The endocannabinoid system can modulate energy homeostasis by regulating feeding behaviour as well as peripheral energy storage and utilization. Importantly, many of its metabolic actions are mediated through the cannabinoid type 1 receptor (CB1R), whose hyperactivation is associated with obesity and impaired metabolic function. Herein, we explored the effects of administering rimonabant, a selective CB1R inverse agonist, upon key metabolic parameters in young (4 month old) and aged (17 month old) adult male C57BL/6 mice. Daily treatment with rimonabant for 14 days transiently reduced food intake in young and aged mice; however, the anorectic response was more profound in aged animals, coinciding with a substantive loss in body fat mass. Notably, reduced insulin sensitivity in aged skeletal muscle and liver concurred with increased CB1R mRNA abundance. Strikingly, rimonabant was shown to improve glucose tolerance and enhance skeletal muscle and liver insulin sensitivity in aged, but not young, adult mice. Moreover, rimonabant-mediated insulin sensitization in aged adipose tissue coincided with amelioration of low-grade inflammation and repressed lipogenic gene expression. Collectively, our findings indicate a key role for CB1R in aging-related insulin resistance and metabolic dysfunction and highlight CB1R blockade as a potential strategy for combating metabolic disorders associated with aging. PMID:26757949

  3. Secretory function of adipose tissue.

    PubMed

    Kuryszko, J; Sławuta, P; Sapikowski, G

    2016-01-01

    There are two kinds of adipose tissue in mammals: white adipose tissue - WAT and brown adipose tissue - BAT. The main function of WAT is accumulation of triacylglycerols whereas the function of BAT is heat generation. At present, WAT is also considered to be an endocrine gland that produces bioactive adipokines, which take part in glucose and lipid metabolism. Considering its endocrine function, the adipose tissue is not a homogeneous gland but a group of a few glands which act differently. Studies on the secretory function of WAT began in 1994 after discovery of leptin known as the satiation hormone, which regulates body energy homeostasis and maintainence of body mass. Apart from leptin, the following belong to adipokines: adiponectin, resistin, apelin, visfatin and cytokines: TNF and IL 6. Adiponectin is a polypeptide hormone of antidiabetic, anti-inflammatory and anti-atherogenic activity. It plays a key role in carbohydrate and fat metabolism. Resistin exerts a counter effect compared to adiponectin and its physiological role is to maintain fasting glycaemia. Visfatin stimulates insulin secretion and increases insulin sensitivity and glucose uptake by muscle cells and adipocytes. Apelin probably increases the insulin sensitivity of tissues. TNF evokes insulin resistance by blocking insulin receptors and inhibits insulin secretion. Approximately 30% of circulating IL 6 comes from adipose tissue. It causes insulin resistance by decreasing the expression of insulin receptors, decreases adipogenesis and adiponectin and visfatin secretion, and stimulates hepatic gluconeogenesis. In 2004, Bays introduced the notion of adiposopathy, defined as dysfunction of the adipose tissue, whose main feature is insulin and leptin resistance as well as the production of inflammatory cytokines: TNF and IL 6 and monocyte chemoattractant protein. This means that excess of adipose tissue, especially visceral adipose tissue, leads to the development of a chronic subclinical

  4. Withaferin A protects against palmitic acid-induced endothelial insulin resistance and dysfunction through suppression of oxidative stress and inflammation

    PubMed Central

    Batumalaie, Kalaivani; Amin, Muhammad Arif; Murugan, Dharmani Devi; Sattar, Munavvar Zubaid Abdul; Abdullah, Nor Azizan

    2016-01-01

    Activation of inflammatory pathways via reactive oxygen species (ROS) by free fatty acids (FFA) in obesity gives rise to insulin resistance and endothelial dysfunction. Withaferin A (WA), possesses both antioxidant and anti-inflammatory properties and therefore would be a good strategy to suppress palmitic acid (PA)-induced oxidative stress and inflammation and hence, insulin resistance and dysfunction in the endothelium. Effect of WA on PA-induced insulin resistance in human umbilical vein endothelial cells (HUVECs) was determined by evaluating insulin signaling mechanisms whilst effect of this drug on PA-induced endothelial dysfunction was determined in acetylcholine-mediated relaxation in isolated rat aortic preparations. WA significantly inhibited ROS production and inflammation induced by PA. Furthermore, WA significantly decreased TNF-α and IL-6 production in endothelial cells by specifically suppressing IKKβ/NF-κβ phosphorylation. WA inhibited inflammation-stimulated IRS-1 serine phosphorylation and improved the impaired insulin PI3-K signaling, and restored the decreased nitric oxide (NO) production triggered by PA. WA also decreased endothelin-1 and plasminogen activator inhibitor type-1 levels, and restored the impaired endothelium-mediated vasodilation in isolated aortic preparations. These findings suggest that WA inhibited both ROS production and inflammation to restore impaired insulin resistance in cultured endothelial cells and improve endothelial dysfunction in rat aortic rings. PMID:27250532

  5. Withaferin A protects against palmitic acid-induced endothelial insulin resistance and dysfunction through suppression of oxidative stress and inflammation.

    PubMed

    Batumalaie, Kalaivani; Amin, Muhammad Arif; Murugan, Dharmani Devi; Sattar, Munavvar Zubaid Abdul; Abdullah, Nor Azizan

    2016-01-01

    Activation of inflammatory pathways via reactive oxygen species (ROS) by free fatty acids (FFA) in obesity gives rise to insulin resistance and endothelial dysfunction. Withaferin A (WA), possesses both antioxidant and anti-inflammatory properties and therefore would be a good strategy to suppress palmitic acid (PA)-induced oxidative stress and inflammation and hence, insulin resistance and dysfunction in the endothelium. Effect of WA on PA-induced insulin resistance in human umbilical vein endothelial cells (HUVECs) was determined by evaluating insulin signaling mechanisms whilst effect of this drug on PA-induced endothelial dysfunction was determined in acetylcholine-mediated relaxation in isolated rat aortic preparations. WA significantly inhibited ROS production and inflammation induced by PA. Furthermore, WA significantly decreased TNF-α and IL-6 production in endothelial cells by specifically suppressing IKKβ/NF-κβ phosphorylation. WA inhibited inflammation-stimulated IRS-1 serine phosphorylation and improved the impaired insulin PI3-K signaling, and restored the decreased nitric oxide (NO) production triggered by PA. WA also decreased endothelin-1 and plasminogen activator inhibitor type-1 levels, and restored the impaired endothelium-mediated vasodilation in isolated aortic preparations. These findings suggest that WA inhibited both ROS production and inflammation to restore impaired insulin resistance in cultured endothelial cells and improve endothelial dysfunction in rat aortic rings. PMID:27250532

  6. Resveratrol prevents high-fructose corn syrup-induced vascular insulin resistance and dysfunction in rats.

    PubMed

    Babacanoglu, C; Yildirim, N; Sadi, G; Pektas, M B; Akar, F

    2013-10-01

    Dietary intake of fructose and sucrose can cause development of metabolic and cardiovascular disorders. The consequences of high-fructose corn syrup (HFCS), a commonly consumed form of fructose and glucose, have poorly been examined. Therefore, in this study, we investigated whether HFCS intake (10% and 20% beverages for 12 weeks) impacts vascular reactivity to insulin and endothelin-1 in conjunction with insulin receptor substrate-1(IRS-1), endothelial nitric oxide synthase (eNOS) and inducible NOS (iNOS) mRNA/proteins levels in aorta of rats. At challenge, we tested the effectiveness of resveratrol (28-30 mg/kg body weight/day) on outcomes of HFCS feeding. HFCS (20%) diet feeding increased plasma triglyceride, VLDL, cholesterol, insulin and glucose levels, but not body weights of rats. Impaired nitric oxide-mediated relaxation to insulin (10⁻⁹ to 3×10⁻⁶ M), and enhanced contraction to endothelin-1 (10⁻¹¹ to 10⁻⁸ M) were associated with decreased expression of IRS-1 and eNOS mRNA and protein, but increased expression of iNOS, in aortas of rats fed with HFCS. Resveratrol supplementation restored many features of HFCS-induced disturbances, probably by regulating eNOS and iNOS production. In conclusion, dietary HFCS causes vascular insulin resistance and endothelial dysfunction through attenuating IRS-1 and eNOS expressions as well as increasing iNOS in rats. Resveratrol has capability to recover HFCS-induced disturbances. PMID:23872130

  7. Palmitate-induced impairment of glucose-stimulated insulin secretion precedes mitochondrial dysfunction in mouse pancreatic islets.

    PubMed

    Barlow, Jonathan; Jensen, Verena Hirschberg; Jastroch, Martin; Affourtit, Charles

    2016-02-15

    It has been well established that excessive levels of glucose and palmitate lower glucose-stimulated insulin secretion (GSIS) by pancreatic β-cells. This β-cell 'glucolipotoxicity' is possibly mediated by mitochondrial dysfunction, but involvement of bioenergetic failure in the pathological mechanism is the subject of ongoing debate. We show in the present study that increased palmitate levels impair GSIS before altering mitochondrial function. We demonstrate that GSIS defects arise from increased insulin release under basal conditions in addition to decreased insulin secretion under glucose-stimulatory conditions. Real-time respiratory analysis of intact mouse pancreatic islets reveals that mitochondrial ATP synthesis is not involved in the mechanism by which basal insulin is elevated. Equally, mitochondrial lipid oxidation and production of reactive oxygen species (ROS) do not contribute to increased basal insulin secretion. Palmitate does not affect KCl-induced insulin release at a basal or stimulatory glucose level, but elevated basal insulin release is attenuated by palmitoleate and associates with increased intracellular calcium. These findings deepen our understanding of β-cell glucolipotoxicity and reveal that palmitate-induced GSIS impairment is disconnected from mitochondrial dysfunction, a notion that is important when targeting β-cells for the treatment of diabetes and when assessing islet function in human transplants. PMID:26621874

  8. Secretory products of guinea pig epicardial fat induce insulin resistance and impair primary adult rat cardiomyocyte function

    PubMed Central

    Greulich, Sabrina; de Wiza, Daniella Herzfeld; Preilowski, Sebastian; Ding, Zhaoping; Mueller, Heidi; Langin, Dominique; Jaquet, Kornelia; Ouwens, D Margriet; Eckel, Juergen

    2011-01-01

    Abstract Epicardial adipose tissue (EAT) has been implicated in the development of heart disease. Nonetheless, the crosstalk between factors secreted from EAT and cardiomyocytes has not been studied. Here, we examined the effect of factors secreted from EAT on contractile function and insulin signalling in primary rat cardiomocytes. EAT and subcutaneous adipose tissue (SAT) were isolated from guinea pigs fed a high-fat (HFD) or standard diet. HFD feeding for 6 months induced glucose intolerance, and decreased fractional shortening and ejection fraction (all P < 0.05). Conditioned media (CM) generated from EAT and SAT explants were subjected to cytokine profiling using antibody arrays, or incubated with cardiomyocytes to assess the effects on insulin action and contractile function. Eleven factors were differentially secreted by EAT when compared to SAT. Furthermore, secretion of 30 factors by EAT was affected by HFD feeding. Most prominently, activin A-immunoreactivity was 6.4-fold higher in CM from HFD versus standard diet-fed animals and, 2-fold higher in EAT versus SAT. In cardiomyocytes, CM from EAT of HFD-fed animals increased SMAD2-phosphorylation, a marker for activin A-signalling, decreased sarcoplasmic-endoplasmic reticulum calcium ATPase 2a expression, and reduced insulin-mediated phosphorylation of Akt-Ser473 versus CM from SAT and standard diet-fed animals. Finally, CM from EAT of HFD-fed animals as compared to CM from the other groups markedly reduced sarcomere shortening and cytosolic Ca2+ fluxes in cardiomyocytes. These data provide evidence for an interaction between factors secreted from EAT and cardiomyocyte function. PMID:21143387

  9. Secretory autophagy.

    PubMed

    Ponpuak, Marisa; Mandell, Michael A; Kimura, Tomonori; Chauhan, Santosh; Cleyrat, Cédric; Deretic, Vojo

    2015-08-01

    Autophagy, once viewed exclusively as a cytoplasmic auto-digestive process, has its less intuitive but biologically distinct non-degradative roles. One manifestation of these functions of the autophagic machinery is the process termed secretory autophagy. Secretory autophagy facilitates unconventional secretion of the cytosolic cargo such as leaderless cytosolic proteins, which unlike proteins endowed with the leader (N-terminal signal) peptides cannot enter the conventional secretory pathway normally operating via the endoplasmic reticulum and the Golgi apparatus. Secretory autophagy may also export more complex cytoplasmic cargo and help excrete particulate substrates. Autophagic machinery and autophagy as a process also affect conventional secretory pathways, including the constitutive and regulated secretion, as well as promote alternative routes for trafficking of integral membrane proteins to the plasma membrane. Thus, autophagy and autophagic factors are intimately intertwined at many levels with secretion and polarized sorting in eukaryotic cells. PMID:25988755

  10. Obesity is associated with insulin resistance but not skeletal muscle dysfunction or all-cause mortality.

    PubMed

    Loenneke, Jeremy P; Loprinzi, Paul D

    2016-02-01

    Recent work has found that older adults with obesity and systemic inflammation have associated metabolic dysfunction but do not have associated lower lean mass or strength. However, this lean mass estimate may be inflated with obesity, given that 15 % of adipose tissue is composed of fat-free tissue. The primary purpose of this study was to investigate, in a nationally representative sample of adults, whether obese adults with chronic systemic inflammation (unhealthy) have differences in lean mass, muscle strength, and insulin resistance when compared to normal weight individuals without elevated levels of systemic inflammation (healthy). A secondary objective was to determine whether these potential differences were moderated by physical activity and to determine if these groups had a differential risk for all-cause mortality. Our findings suggests that the unhealthy group was associated with higher upper body lean mass (β = 823; 95 % confidence interval (CI) 637-1010; P < 0.001), lower body lean mass (β = 2724; 95 % CI 2291-3158; P < 0.001), and strength (β = 34.6; 95 % CI 13.5-55.7; P = 0.003) compared to the healthy group despite having systemic inflammation and correcting for fat-free adipose tissue. However, the unhealthy group was associated with insulin resistance (odds ratio (OR) = 16.1; 95 % CI 2.7-96.1; P = 0.005) although this finding was attenuated in those physically active (OR = 8.5; 95 % CI 2.43-30.15; P = 0.003). Despite this metabolic dysfunction, there was no difference in all-cause mortality risk between groups (hazard ratio (HR) = 1.16 (95 % CI 0.69-1.96; P = 0.54)) suggesting that higher amounts of lean mass and strength may be protective of premature mortality. PMID:26698153

  11. Insulin resistance in SHR/NDmc-cp rats correlates with enlarged perivascular adipocytes and endothelial cell dysfunction in skeletal muscle.

    PubMed

    Hariya, Natsuyo; Mochizuki, Kazuki; Inoue, Seiya; Morioka, Kosuke; Shimada, Masaya; Okuda, Tohru; Goda, Toshinao

    2014-01-01

    Ectopic adipose tissue in skeletal muscle is implicated in the development of insulin resistance, which is frequently induced by abnormal dietary habits such as excessive eating and a high-fat diet. However, the characteristics of ectopic adipocytes are unknown. In this study, we investigated the characteristics of ectopic adipocytes in the skeletal muscle of spontaneously hypertensive corpulent congenic (SHR/NDmc-cp) rats as a model of insulin resistance from excessive eating. SHR/NDmc-cp rats displayed overt insulin resistance with high plasma glucose, insulin, and triacylglycerol concentrations relative to control Wistar-Kyoto (WKY) rats. In contrast, streptozotocin (STZ)-treated WKY rats had high glucose but low insulin concentrations. Ectopic adipocytes were found around blood vessels in the gastrocnemius in SHR/NDmc-cp rats. Areas of perivascular adipocytes and protein expression of resistin were greater in SHR/NDmc-cp rats than in control and STZ-treated WKY rats. The level of the phosphorylated (active) form of endothelial nitric oxide synthase in the gastrocnemius was lower in SHR/NDmc-cp rats than in the other groups. Insulin-resistant SHR/NDmc-cp rats showed enlarged perivascular adipocytes and greater endothelial cell dysfunction in the gastrocnemius. PMID:24759260

  12. α-Cell Dysfunctions and Molecular Alterations in Male Insulinopenic Diabetic Mice Are Not Completely Corrected by Insulin.

    PubMed

    Dusaulcy, Rodolphe; Handgraaf, Sandra; Heddad-Masson, Mounia; Visentin, Florian; Vesin, Christian; Reimann, Franck; Gribble, Fiona; Philippe, Jacques; Gosmain, Yvan

    2016-02-01

    Glucagon and α-cell dysfunction are critical in the development of hyperglycemia during diabetes both in humans and rodents. We hypothesized that α-cell dysfunction leading to dysregulated glucagon secretion in diabetes is due to both a lack of insulin and intrinsic defects. To characterize α-cell dysfunction in diabetes, we used glucagon-Venus transgenic male mice and induced insulinopenic hyperglycemia by streptozotocin administration leading to alterations of glucagon secretion. We investigated the in vivo impact of insulinopenic hyperglycemia on glucagon-producing cells using FACS-sorted α-cells from control and diabetic mice. We demonstrate that increased glucagonemia in diabetic mice is mainly due to increases of glucagon release and biosynthesis per cell compared with controls without changes in α-cell mass. We identified genes coding for proteins involved in glucagon biosynthesis and secretion, α-cell differentiation, and potential stress markers such as the glucagon, Arx, MafB, cMaf, Brain4, Foxa1, Foxa3, HNF4α, TCF7L2, Glut1, Sglt2, Cav2.1, Cav2.2, Nav1.7, Kir6.2/Sur1, Pten, IR, NeuroD1, GPR40, and Sumo1 genes, which were abnormally regulated in diabetic mice. Importantly, insulin treatment partially corrected α-cell function and expression of genes coding for proglucagon, or involved in glucagon secretion, glucose transport and insulin signaling but not those coding for cMAF, FOXA1, and α-cell differentiation markers as well as GPR40, NEUROD1, CAV2.1, and SUMO1. Our results indicate that insulinopenic diabetes induce marked α-cell dysfunction and molecular alteration, which are only partially corrected by in vivo insulin treatment. PMID:26696123

  13. Short communication: The relationship between mitochondrial dysfunction and insulin resistance in HIV-infected children receiving antiretroviral therapy.

    PubMed

    Sharma, Tanvi S; Jacobson, Denise L; Anderson, Lynn; Gerschenson, Mariana; Van Dyke, Russell B; McFarland, Elizabeth J; Miller, Tracie L

    2013-09-01

    Mitochondrial abnormalities may lead to metabolic complications in HIV-infected children who have been receiving long-term antiretroviral treatment. We conducted a matched, case-control study comparing 21 HIV-infected children with insulin resistance (cases) to 21 HIV-infected children without insulin resistance (controls) to assess differences in mitochondrial DNA (mtDNA) copies/cell and oxidative phosphorylation NADH dehydrogenase (C1) and cytochrome c oxidase (C4) enzyme activities in peripheral blood mononuclear cells. MtDNA copies/cell tended to be lower in cases, and fasting serum glucose levels were inversely and significantly correlated with C1 enzyme activity, more so in cases. Larger pediatric studies should evaluate mitochondrial etiologies of insulin resistance and determine the role of antiretroviral therapies or HIV infection on mitochondrial dysfunction. PMID:23742635

  14. Stimulation by ATP of proinsulin to insulin conversion in isolated rat pancreatic islet secretory granules. Association with the ATP-dependent proton pump

    SciTech Connect

    Rhodes, C.J.; Lucas, C.A.; Mutkoski, R.L.; Orci, L.; Halban, P.A.

    1987-08-05

    Isolated rat pancreatic islets were pulse-labeled for 5 min with (/sup 3/H)leucine then chased for 25 min, during which time endogenously labeled (/sup 3/H)proinsulin becomes predominantly compartmented in immature secretory granules. The islets were then homogenized in isotonic sucrose (pH 7.4) and a beta-granule preparation obtained by differential centrifugation and discontinuous sucrose gradient ultracentrifugation. This preparation was enriched 8-fold in beta-granules. Aside from contamination with mitochondria and a limited number of lysosomes, the beta-granule preparation was essentially free of any other organelles involved in proinsulin synthesis and packaging (i.e. microsomal elements and, more particularly, Golgi complex). Conversion of endogenously labeled (/sup 3/H)proinsulin was followed in this beta-granule fraction for up to 2 h at 37 degrees C in a buffer (pH 7.3) that mimicked the cationic constituents of B-cell cytosol, during which time 92% of the beta-granules remained intact. Proinsulin conversion was analyzed by high performance liquid chromatography. The rate of proinsulin conversion to insulin was stimulated by 2.2 +/- 0.1-fold (n = 6) (at a 60-min incubation) in the presence of ATP (2 mM) and an ATP regenerating system compared to beta-granule preparations incubated without ATP. This ATP stimulation was abolished in the presence of beta-granule proton pump ATPase inhibitors (tributyltin, 2.5 microM, or 1,3-dicyclohexylcarbodiimide, 50 microM). Inhibitors of mitochondrial proton pump ATPases had no effect on the ATP stimulation of proinsulin conversion. When granules were incubated in a more acidic buffer, proinsulin conversion was increased relative to that at pH 7.3. At pH 5.5, ATP no longer stimulated conversion, and tributyltin and 1,3-dicyclohexylcarbodiimide had no effect.

  15. The Potential Protective Action of Vitamin D in Hepatic Insulin Resistance and Pancreatic Islet Dysfunction in Type 2 Diabetes Mellitus

    PubMed Central

    Leung, Po Sing

    2016-01-01

    Vitamin D deficiency (i.e., hypovitaminosis D) is associated with increased insulin resistance, impaired insulin secretion, and poorly controlled glucose homeostasis, and thus is correlated with the risk of metabolic diseases, including type 2 diabetes mellitus (T2DM). The liver plays key roles in glucose and lipid metabolism, and its dysregulation leads to abnormalities in hepatic glucose output and triglyceride accumulation. Meanwhile, the pancreatic islets are constituted in large part by insulin-secreting β cells. Consequently, islet dysfunction, such as occurs in T2DM, produces hyperglycemia. In this review, we provide a critical appraisal of the modulatory actions of vitamin D in hepatic insulin sensitivity and islet insulin secretion, and we discuss the potential roles of a local vitamin D signaling in regulating hepatic and pancreatic islet functions. This information provides a scientific basis for establishing the benefits of the maintenance, or dietary manipulation, of adequate vitamin D status in the prevention and management of obesity-induced T2DM and non-alcoholic fatty liver disease. PMID:26959059

  16. The Potential Protective Action of Vitamin D in Hepatic Insulin Resistance and Pancreatic Islet Dysfunction in Type 2 Diabetes Mellitus.

    PubMed

    Leung, Po Sing

    2016-03-01

    Vitamin D deficiency (i.e., hypovitaminosis D) is associated with increased insulin resistance, impaired insulin secretion, and poorly controlled glucose homeostasis, and thus is correlated with the risk of metabolic diseases, including type 2 diabetes mellitus (T2DM). The liver plays key roles in glucose and lipid metabolism, and its dysregulation leads to abnormalities in hepatic glucose output and triglyceride accumulation. Meanwhile, the pancreatic islets are constituted in large part by insulin-secreting β cells. Consequently, islet dysfunction, such as occurs in T2DM, produces hyperglycemia. In this review, we provide a critical appraisal of the modulatory actions of vitamin D in hepatic insulin sensitivity and islet insulin secretion, and we discuss the potential roles of a local vitamin D signaling in regulating hepatic and pancreatic islet functions. This information provides a scientific basis for establishing the benefits of the maintenance, or dietary manipulation, of adequate vitamin D status in the prevention and management of obesity-induced T2DM and non-alcoholic fatty liver disease. PMID:26959059

  17. Renal scintigraphy in insulin-dependent diabetes mellitus: Early glomerular and urologic dysfunction

    SciTech Connect

    Poirier, J.Y.; Moisan, A.; Le Cloirec, J.; Siemen, C.; Yaouanq, J.; Edan, G.; Herry, J.Y. )

    1990-07-01

    Glomerular filtration rate (GFR) and renal plasma flow (RPF) were measured by intravenous injection of 99mTc-diethylenetriaminepentaacetic acid (DTPA) and 131I-Hippuran in 115 insulin-dependent diabetic patients with albumin excretion rates (AER) less than 200 micrograms/min, and in 45 normal subjects. Separate kidney function and urinary elimination were estimated by renography. GFR was increased in the diabetic patients (152 +/- 24 ml/min/1.73 m2 vs. 128 +/- 15) and correlated significantly with RPF (r = 0.5; p less than 10(-9)). No relationship was found between GFR and the duration of diabetes, blood glucose, HbA1c, or AER. Fifty patients were hyperfiltering with RPF and filtration fraction higher than those in the normofiltering group. Slow intrarenal or pyeloureteral elimination, either unilateral or bilateral, was observed in 3 controls and 60 diabetic subjects (24 hyperfiltering; 36 normofiltering) and did not disappear with the patient in the standing position. In these 60 patients, mean age, duration of diabetes, blood glucose, HbA1c, 24 h albumin excretion rate, and frequency of peripheral or autonomic neuropathy did not differ from patients with normal scintigraphy; GFR was lower in the group with slow elimination, but not significantly so. 99mTc-DTPA renal uptake was symmetric in all the controls; asymmetric renal uptake with asymmetric GFR was observed in 13 patients (7 hyperfiltering; 6 normofiltering) and often associated with slower elimination. No evidence for renal stenotic atheroma or parenchymatous disease was found on the angiopyleoureterography. The results suggest that incipient uropathy is a very common phenomenon that occurs irrespective of glomerular dysfunction.

  18. Decrease of the insulin-like growth factor-1 bioavailability in spontaneously hypertensive rats with erectile dysfunction.

    PubMed

    Zhou, Z-Y; Cheng, S-P; Huang, H; Sun, Y-L; Xiao, S; Liu, R-H; Mao, F-J; Zhong, G-J; Huang, J-B; Pan, H

    2016-09-01

    We investigated the role of insulin-like growth factor-1 (IGF-1) in spontaneously hypertensive rats with erectile dysfunction. Firstly, we evaluated intracavernous pressure. The bioavailability of IGF-1 at both mRNA and protein levels were measured by quantitative real-time PCR and Western blot respectively. Then, cavernous cyclic guanosine monophosphate concentrations were detected by enzyme-linked immunosorbent assay. The cavernosal pressure was significantly decreased in the hypertensive and the propranolol treatment groups compared to the normal control group (P < 0.01). Cavernous IGF-1 bioavailability and the concentrations of cavernous cyclic guanosine monophosphate were both significantly decreased in the hypertensive and the propranolol treatment groups compared to the normal control group (P < 0.01). This study suggests that an obvious decrease in cavernous IGF-1 levels might play an important role in spontaneously hypertensive rats with erectile dysfunction. PMID:26762757

  19. Leptin, Insulin, and Cinnamon Polyphenols Attenuate Glial Swelling and Mitochondrial Dysfunction in Ischemic Injury

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Obesity is a major risk factor for stroke, and tissue injury following a stroke may be more severe in the obese. A key feature of obesity is increased serum levels of obesity-related hormones including leptin and insulin, indicating a state of resistance to these hormones. Insulin resistance is gen...

  20. Insulin

    MedlinePlus

    ... pump is connected to your body by a flexible tube that has a tip that sticks under your skin. A cartridge of insulin is put in the pump. The insulin flows through the tube into your body. The pump controls how much insulin goes into your body. The ...

  1. Protection from palmitate-induced mitochondrial DNA damage prevents from mitochondrial oxidative stress, mitochondrial dysfunction, apoptosis, and impaired insulin signaling in rat L6 skeletal muscle cells.

    PubMed

    Yuzefovych, Larysa V; Solodushko, Viktoriya A; Wilson, Glenn L; Rachek, Lyudmila I

    2012-01-01

    Saturated free fatty acids have been implicated in the increase of oxidative stress, mitochondrial dysfunction, apoptosis, and insulin resistance seen in type 2 diabetes. The purpose of this study was to determine whether palmitate-induced mitochondrial DNA (mtDNA) damage contributed to increased oxidative stress, mitochondrial dysfunction, apoptosis, impaired insulin signaling, and reduced glucose uptake in skeletal muscle cells. Adenoviral vectors were used to deliver the DNA repair enzyme human 8-oxoguanine DNA glycosylase/(apurinic/apyrimidinic) lyase (hOGG1) to mitochondria in L6 myotubes. After palmitate exposure, we evaluated mtDNA damage, mitochondrial function, production of mitochondrial reactive oxygen species, apoptosis, insulin signaling pathways, and glucose uptake. Protection of mtDNA from palmitate-induced damage by overexpression of hOGG1 targeted to mitochondria significantly diminished palmitate-induced mitochondrial superoxide production, restored the decline in ATP levels, reduced activation of c-Jun N-terminal kinase (JNK) kinase, prevented cells from entering apoptosis, increased insulin-stimulated phosphorylation of serine-threonine kinase (Akt) (Ser473) and tyrosine phosphorylation of insulin receptor substrate-1, and thereby enhanced glucose transporter 4 translocation to plasma membrane, and restored insulin signaling. Addition of a specific inhibitor of JNK mimicked the effect of mitochondrial overexpression of hOGG1 and partially restored insulin sensitivity, thus confirming the involvement of mtDNA damage and subsequent increase of oxidative stress and JNK activation in insulin signaling in L6 myotubes. Our results are the first to report that mtDNA damage is the proximal cause in palmitate-induced mitochondrial dysfunction and impaired insulin signaling and provide strong evidence that targeting DNA repair enzymes into mitochondria in skeletal muscles could be a potential therapeutic treatment for insulin resistance. PMID:22128025

  2. Why can insulin resistance be a natural consequence of thyroid dysfunction?

    PubMed

    Brenta, Gabriela

    2011-01-01

    Evidence for a relationship between T4 and T3 and glucose metabolism appeared over 100 years ago when the influence of thyroid hormone excess in the deterioration of glucose metabolism was first noticed. Since then, it has been known that hyperthyroidism is associated with insulin resistance. More recently, hypothyroidism has also been linked to decreased insulin sensitivity. The explanation to this apparent paradox may lie in the differential effects of thyroid hormones at the liver and peripheral tissues level. The purpose of this paper is to explore the effects of thyroid hormones in glucose metabolism and analyze the mechanisms whereby alterations of thyroid hormones lead to insulin resistance. PMID:21941681

  3. Why Can Insulin Resistance Be a Natural Consequence of Thyroid Dysfunction?

    PubMed Central

    Brenta, Gabriela

    2011-01-01

    Evidence for a relationship between T4 and T3 and glucose metabolism appeared over 100 years ago when the influence of thyroid hormone excess in the deterioration of glucose metabolism was first noticed. Since then, it has been known that hyperthyroidism is associated with insulin resistance. More recently, hypothyroidism has also been linked to decreased insulin sensitivity. The explanation to this apparent paradox may lie in the differential effects of thyroid hormones at the liver and peripheral tissues level. The purpose of this paper is to explore the effects of thyroid hormones in glucose metabolism and analyze the mechanisms whereby alterations of thyroid hormones lead to insulin resistance. PMID:21941681

  4. Sympathetic nervous dysregulation in the absence of systolic left ventricular dysfunction in a rat model of insulin resistance with hyperglycemia

    PubMed Central

    2011-01-01

    Background Diabetes mellitus is strongly associated with cardiovascular dysfunction, derived in part from impairment of sympathetic nervous system signaling. Glucose, insulin, and non-esterified fatty acids are potent stimulants of sympathetic activity and norepinephrine (NE) release. We hypothesized that sustained hyperglycemia in the high fat diet-fed streptozotocin (STZ) rat model of sustained hyperglycemia with insulin resistance would exhibit progressive sympathetic nervous dysfunction in parallel with deteriorating myocardial systolic and/or diastolic function. Methods Cardiac sympathetic nervous integrity was investigated in vivo via biodistribution of the positron emission tomography radiotracer and NE analogue [11C]meta-hydroxyephedrine ([11C]HED). Cardiac systolic and diastolic function was evaluated by echocardiography. Plasma and cardiac NE levels and NE reuptake transporter (NET) expression were evaluated as correlative measurements. Results The animal model displays insulin resistance, sustained hyperglycemia, and progressive hypoinsulinemia. After 8 weeks of persistent hyperglycemia, there was a significant 13-25% reduction in [11C]HED retention in myocardium of STZ-treated hyperglycemic but not euglycemic rats as compared to controls. There was a parallel 17% reduction in immunoblot density for NE reuptake transporter, a 1.2 fold and 2.5 fold elevation of cardiac and plasma NE respectively, and no change in sympathetic nerve density. No change in ejection fraction or fractional area change was detected by echocardiography. Reduced heart rate, prolonged mitral valve deceleration time, and elevated transmitral early to atrial flow velocity ratio measured by pulse-wave Doppler in hyperglycemic rats suggest diastolic impairment of the left ventricle. Conclusions Taken together, these data suggest that sustained hyperglycemia is associated with elevated myocardial NE content and dysregulation of sympathetic nervous system signaling in the absence of

  5. Amelioration of Mitochondrial Dysfunction-Induced Insulin Resistance in Differentiated 3T3-L1 Adipocytes via Inhibition of NF-κB Pathways

    PubMed Central

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

    2014-01-01

    A growing body of evidence suggests that activation of nuclear factor kappa B (NF-κB) signaling pathways is among the inflammatory mechanism involved in the development of insulin resistance and chronic low-grade inflammation in adipose tissues derived from obese animal and human subjects. Nevertheless, little is known about the roles of NF-κB pathways in regulating mitochondrial function of the adipose tissues. In the present study, we sought to investigate the direct effects of celastrol (potent NF-κB inhibitor) upon mitochondrial dysfunction-induced insulin resistance in 3T3-L1 adipocytes. Celastrol ameliorates mitochondrial dysfunction by altering mitochondrial fusion and fission in adipocytes. The levels of oxidative DNA damage, protein carbonylation and lipid peroxidation were down-regulated. Further, the morphology and quantification of intracellular lipid droplets revealed the decrease of intracellular lipid accumulation with reduced lipolysis. Moreover, massive production of the pro-inflammatory mediators tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) were markedly depleted. Insulin-stimulated glucose uptake activity was restored with the enhancement of insulin signaling pathways. This study signified that the treatments modulated towards knockdown of NF-κB transcription factor may counteract these metabolic insults exacerbated in our model of synergy between mitochondrial dysfunction and inflammation. These results demonstrate for the first time that NF-κB inhibition modulates mitochondrial dysfunction induced insulin resistance in 3T3-L1 adipocytes. PMID:25474091

  6. Insulin-dependent (type I) diabetes mellitus.

    PubMed Central

    Rodger, W

    1991-01-01

    Insulin-dependent (type I) diabetes mellitus is a chronic disease characterized by hyperglycemia, impaired metabolism and storage of important nutrients, evidence of autoimmunity, and long-term vascular and neurologic complications. Insulin secretory function is limited. Cell membrane binding is not primarily involved. The goal of treatment is to relieve symptoms and to achieve blood glucose levels as close to normal as possible without severe hypoglycemia. However, even with education and self-monitoring of the blood glucose level, attaining recommended target values (plasma glucose level less than 8.0 mmol/L before main meals for adults) remains difficult. Human insulin offers no advantage in glycemic control but is important in the management and prevention of immune-related clinical problems (e.g., injection-site lipoatrophy, insulin resistance and allergy) associated with the use of beef or pork insulin. Therapy with one or two injections per day of mixed short-acting or intermediate-acting insulin preparations is a compromise between convenience and the potential for achieving target plasma glucose levels. Intensive insulin therapy with multiple daily injections or continuous infusion with an insulin pump improves mean glycated hemoglobin levels; however, it increases rates of severe hypoglycemia and has not been shown to decrease the incidence of clinically significant renal, retinal or neurologic dysfunction. Future prospects include automated techniques of insulin delivery, immunosuppression to preserve endogenous insulin secretion and islet transplantation. PMID:1933705

  7. Vagus Nerve Stimulation Improves Cardiac Function by Preventing Mitochondrial Dysfunction in Obese-Insulin Resistant Rats

    PubMed Central

    Samniang, Bencharunan; Shinlapawittayatorn, Krekwit; Chunchai, Titikorn; Pongkan, Wanpitak; Kumfu, Sirinart; Chattipakorn, Siriporn C.; KenKnight, Bruce H.; Chattipakorn, Nipon

    2016-01-01

    Long-term high-fat diet (HFD) consumption leads to not only obese-insulin resistance, but also impaired left ventricular (LV) function. Vagus nerve stimulation (VNS) has been shown to exert cardioprotection. However, its effects on the heart and metabolic parameters under obese-insulin resistant condition is not known. We determined the effects of VNS on metabolic parameters, heart rate variability (HRV) and LV function in obese-insulin resistant rats. Male Wistar rats were fed with HFD for 12 weeks, and were randomly divided into sham and VNS groups. VNS was applied for the next 12 weeks. Echocardiography, blood pressure and HRV were examined. Blood samples were collected for metabolic parameters. At the end, the heart was removed for determination of apoptosis, inflammation, oxidative stress, and cardiac mitochondrial function. VNS for 12 weeks significantly decreased plasma insulin, HOMA index, total cholesterol, triglyceride, LDL and visceral fat. Serum adiponectin was significantly increased in the VNS group. VNS also significantly decreased blood pressure, improved HRV and LV function, decreased cardiac MDA, TNF-α and Bax levels, and improved cardiac mitochondrial function. VNS improves metabolic and hemodynamic parameters, and the LV function via its ability against apoptosis, inflammation and oxidative stress, and preserved cardiac mitochondrial function in obese-insulin resistant rats. PMID:26830020

  8. Association of Bactericidal Dysfunction of Paneth Cells in Streptozocin-Induced Diabetic Mice with Insulin Deficiency.

    PubMed

    Yu, Tao; Yang, Hong-Sheng; Lu, Xi-Ji; Xia, Zhong-Sheng; Ouyang, Hui; Shan, Ti-Dong; Huang, Can-Ze; Chen, Qi-Kui

    2016-01-01

    BACKGROUND Type 1 diabetes mellitus (T1DM) is associated with increased risks of enteric infection. Paneth cells constitute the first line of the gut defense. Little is known about the impact of T1DM on the bactericidal function of intestinal Paneth cells. MATERIAL AND METHODS A T1DM mouse model was induced by intraperitoneal injection of streptozocin. The analysis of intestinal microbiota and the mucosal bactericidal assay were conducted to evaluate intestinal innate defense. Numbers of Paneth cells and their expression of related antimicrobial peptides were analyzed. Expression of total insulin receptor (IR) mRNA and relative levels of IR-A/IR-B were analyzed. The primary mouse small intestinal crypt culture was used to analyze the effect of insulin and glucose on the expression of related antimicrobial peptides of Paneth cells. RESULTS In T1DM mice, bacterial loads were increased and there was an alteration in the composition of the intestinal microflora. Exogenous bacteria had better survival in the small bowel of the T1DM mice. The expression of Paneth cell-derived antimicrobial peptides was significantly decreased in the T1DM mice, although the number of Paneth cells was increased. Relative levels of IR-A/IR-B in Paneth cells of diabetic mice were elevated, but the total IR mRNA did not change. Insulin treatment restored the expression of antimicrobial peptides and normalized the microbiota in the gut of T1DM mice. Subsequently, in vitro culture assay demonstrated that insulin rather than glucose was essential for the optimal expression of Paneth cell-derived antimicrobial peptides. CONCLUSIONS The bactericidal function of intestinal Paneth cells was impaired in STZ-induced diabetic mice, resulting in the altered intestinal flora, and insulin was essential for the optimal expression of Paneth cell-derived antimicrobial peptides. PMID:27572949

  9. Insulin resistance is associated with altered amino acid metabolism and adipose tissue dysfunction in normoglycemic women

    PubMed Central

    Wiklund, Petri; Zhang, Xiaobo; Pekkala, Satu; Autio, Reija; Kong, Lingjia; Yang, Yifan; Keinänen-Kiukaanniemi, Sirkka; Alen, Markku; Cheng, Sulin

    2016-01-01

    Insulin resistance is associated adiposity, but the mechanisms are not fully understood. In this study, we aimed to identify early metabolic alterations associated with insulin resistance in normoglycemic women with varying degree of adiposity. One-hundred and ten young and middle-aged women were divided into low and high IR groups based on their median HOMA-IR (0.9 ± 0.4 vs. 2.8 ± 1.2). Body composition was assessed using DXA, skeletal muscle and liver fat by proton magnetic resonance spectroscopy, serum metabolites by nuclear magnetic resonance spectroscopy and adipose tissue and skeletal muscle gene expression by microarrays. High HOMA-IR subjects had higher serum branched-chain amino acid concentrations (BCAA) (p < 0.05 for both). Gene expression analysis of subcutaneous adipose tissue revealed significant down-regulation of genes related to BCAA catabolism and mitochondrial energy metabolism and up-regulation of several inflammation-related pathways in high HOMA-IR subjects (p < 0.05 for all), but no differentially expressed genes in skeletal muscle were found. In conclusion, in normoglycemic women insulin resistance was associated with increased serum BCAA concentrations, down-regulation of mitochondrial energy metabolism and increased expression of inflammation-related genes in the adipose tissue. PMID:27080554

  10. Insulin

    NASA Technical Reports Server (NTRS)

    2004-01-01

    The manipulation of organic materials--cells, tissues, and even living organisms--offers many exciting possibilities for the future from organic computers to improved aquaculture. Commercial researchers are using the microgravity environment to produce large near perfect protein crystals Research on insulin has yielded crystals that far surpass the quality of insulin crystals grown on the ground. Using these crystals industry partners are working to develop new and improved treatments for diabetes. Other researchers are exploring the possibility of producing antibiotics using plant cell cultures which could lead to both orbital production and the improvement of ground-based antibiotic production.

  11. Urinary cholinesterase activity is increased in insulin-dependent diabetics: further evidence of diabetic tubular dysfunction.

    PubMed

    Matteucci, E; Pellegrini, L; Uncini-Manganelli, C; Cecere, M; Saviozzi, M; Giampietro, O

    1992-01-01

    We measured the cholinesterase activity in morning urines from 63 insulin-dependent diabetics and 27 controls. The total esterase (TotE) activity (Ellman's method) has been divided into aliesterase (AliE), pseudocholinesterase and acetylcholinesterase by means of two inhibitors, eserine and quinidine. Diabetics were divided in 2 groups according to the urinary albumin/creatinine ratio (mg/mmol, < 2 in group 1, > 2 in group 2). The urinary cholinesterase behavior was correlated with that of a known tubular lysosomal hydrolase, N-acetyl-beta-D-glucosaminidase (NAG). Compared to normals, in addition to a significant increase in urinary NAG in diabetes (in group 2 more than in group 1), TotE and AliE were also significantly raised (+36% and 109% of the controls, in group 1 as much as in group 2). PMID:1308857

  12. Chronic Insulin Exposure Induces ER Stress and Lipid Body Accumulation in Mast Cells at the Expense of Their Secretory Degranulation Response.

    PubMed

    Greineisen, William E; Maaetoft-Udsen, Kristina; Speck, Mark; Balajadia, Januaria; Shimoda, Lori M N; Sung, Carl; Turner, Helen

    2015-01-01

    Lipid bodies (LB) are reservoirs of precursors to inflammatory lipid mediators in immunocytes, including mast cells. LB numbers are dynamic, increasing dramatically under conditions of immunological challenge. We have previously shown in vitro that insulin-influenced lipogenic pathways induce LB biogenesis in mast cells, with their numbers attaining steatosis-like levels. Here, we demonstrate that in vivo hyperinsulinemia resulting from high fat diet is associated with LB accumulation in murine mast cells and basophils. We characterize the lipidome of purified insulin-induced LB, and the shifts in the whole cell lipid landscape in LB that are associated with their accumulation, in both model (RBL2H3) and primary mast cells. Lipidomic analysis suggests a gain of function associated with LB accumulation, in terms of elevated levels of eicosanoid precursors that translate to enhanced antigen-induced LTC4 release. Loss-of-function in terms of a suppressed degranulation response was also associated with LB accumulation, as were ER reprogramming and ER stress, analogous to observations in the obese hepatocyte and adipocyte. Taken together, these data suggest that chronic insulin elevation drives mast cell LB enrichment in vitro and in vivo, with associated effects on the cellular lipidome, ER status and pro-inflammatory responses. PMID:26263026

  13. Chronic Insulin Exposure Induces ER Stress and Lipid Body Accumulation in Mast Cells at the Expense of Their Secretory Degranulation Response

    PubMed Central

    Balajadia, Januaria; Shimoda, Lori M. N.; Sung, Carl; Turner, Helen

    2015-01-01

    Lipid bodies (LB) are reservoirs of precursors to inflammatory lipid mediators in immunocytes, including mast cells. LB numbers are dynamic, increasing dramatically under conditions of immunological challenge. We have previously shown in vitro that insulin-influenced lipogenic pathways induce LB biogenesis in mast cells, with their numbers attaining steatosis-like levels. Here, we demonstrate that in vivo hyperinsulinemia resulting from high fat diet is associated with LB accumulation in murine mast cells and basophils. We characterize the lipidome of purified insulin-induced LB, and the shifts in the whole cell lipid landscape in LB that are associated with their accumulation, in both model (RBL2H3) and primary mast cells. Lipidomic analysis suggests a gain of function associated with LB accumulation, in terms of elevated levels of eicosanoid precursors that translate to enhanced antigen-induced LTC4 release. Loss-of-function in terms of a suppressed degranulation response was also associated with LB accumulation, as were ER reprogramming and ER stress, analogous to observations in the obese hepatocyte and adipocyte. Taken together, these data suggest that chronic insulin elevation drives mast cell LB enrichment in vitro and in vivo, with associated effects on the cellular lipidome, ER status and pro-inflammatory responses. PMID:26263026

  14. Preserved Insulin Secretory Capacity and Weight Loss Are the Predominant Predictors of Glycemic Control in Patients With Type 2 Diabetes Randomized to Roux-en-Y Gastric Bypass.

    PubMed

    Nguyen, Kim T; Billington, Charles J; Vella, Adrian; Wang, Qi; Ahmed, Leaque; Bantle, John P; Bessler, Marc; Connett, John E; Inabnet, William B; Thomas, Avis; Ikramuddin, Sayeed; Korner, Judith

    2015-09-01

    Improvement in type 2 diabetes after Roux-en-Y gastric bypass (RYGB) has been attributed partly to weight loss, but mechanisms beyond weight loss remain unclear. We performed an ancillary study to the Diabetes Surgery Study to assess changes in incretins, insulin sensitivity, and secretion 1 year after randomization to lifestyle modification and intensive medical management (LS/IMM) alone (n = 34) or in conjunction with RYGB (n = 34). The RYGB group lost more weight and had greater improvement in HbA1c. Fasting glucose was lower after RYGB than after LS/IMM, although the glucose area under the curve decreased comparably for both groups. Insulin sensitivity increased in both groups. Insulin secretion was unchanged after LS/IMM but decreased after RYGB, except for a rapid increase during the first 30 min after meal ingestion. Glucagon-like peptide 1 (GLP-1) was substantially increased after RYGB, while gastric inhibitory polypeptide and glucagon decreased. Lower HbA1c was most strongly correlated with the percentage of weight loss for both groups. At baseline, a greater C-peptide index and 90-min postprandial C-peptide level were predictive of lower HbA1c at 1 year after RYGB. β-Cell glucose sensitivity, which improved only after RYGB, and improved disposition index were associated with lower HbA1c in both groups, independent of weight loss. Weight loss and preserved β-cell function both predominantly determine the greatest glycemic benefit after RYGB. PMID:25901097

  15. Hypermethylation of Cox5a Promoter Is Associated with Mitochondrial Dysfunction in Skeletal Muscle of High Fat Diet-Induced Insulin Resistant Rats

    PubMed Central

    Li, Jin; Su, Lei; Yu, Shuang; Zhu, Xiao-nan; Cao, Xiao-pei; Xiao, Hai-peng

    2014-01-01

    High-fat diet (HFD) is an environmental factor that contributes to the pathogenesis of obesity and type 2 diabetes. A number of genes influencing oxidative phosphorylation (OXPHOS) were found to be downregulated in skeletal muscle of humans and rats treated with HFD and have been implicated in mitochondrial dysfunction, insulin resistance, and consequent type 2 diabetes. In this study, we hypothesized that DNA methylation plays a crucial role in the regulation of OXPHOS genes in skeletal muscle of rats exposed to HFD. Using whole genome promoter methylation analysis of skeletal muscle followed by qPCR and bisulfite sequencing analysis, we identified hypermethylation of Cox5a in HFD rats. Furthermore, we found that Cox5a hypermethylation was associated with downregulation of Cox5a expression at the mRNA and protein level, and a reduction in mitochondrial complex IV activity and ATP content in HFD-induced insulin resistant rats compared to controls. Moreover, we found that while exposure to palmitate resulted in hypermethylation of the Cox5a promoter in rat myotubes, demethylation with 5-aza-2′-deoxycytidine was associated with preserved Cox5a expression, as well as restoration of complex IV activity and cellular ATP content. These novel observations indicate that Cox5a hypermethylation is associated with mitochondrial dysfunction in skeletal muscle of HFD-induced insulin resistant rats. PMID:25436770

  16. Soluble and Cell-Associated Insulin Receptor Dysfunction Correlates with Severity of HAND in HIV-Infected Women

    PubMed Central

    Gerena, Yamil; Skolasky, Richard L.; Velez, Joyce M.; Toro-Nieves, Dianedis; Mayo, Raul; Nath, Avindra; Wojna, Valerie

    2012-01-01

    Background Blood sugar metabolism abnormalities have been identified in HIV-infected individuals and associated with HIV-associated neurocognitive disorders (HAND). These abnormalities may occur as a result of chronic HIV infection, long-term use of combined antiretroviral treatment (CART), aging, genetic predisposition, or a combination of these factors, and may increase morbidity and mortality in this population. Objective To determine if changes in soluble and cell-associated insulin receptor (IR) levels, IR substrate-1 (IRS-1) levels, and IRS-1 tyrosine phosphorylation are associated with the presence and severity of HAND in a cohort of HIV-seropositive women. Methods and Results This is a retrospective cross-sectional study using patient database information and stored samples from 34 HIV-seropositive women and 10 controls without history of diabetes from the Hispanic-Latino Longitudinal Cohort of Women. Soluble IR subunits [sIR, ectodomain (α) and full-length or intact (αβ)] were assayed in plasma and CSF samples by ELISA. Membrane IR levels, IRS-1 levels, and IRS-1 tyrosine phosphorylation were analyzed in CSF white cell pellets (WCP) using flow cytometry. HIV-seropositive women had significantly increased levels of intact or full-length sIR in plasma (p<0.001) and CSF (p<0.005) relative to controls. Stratified by HAND, increased levels of full-length sIR in plasma were associated with the presence (p<0.001) and severity (p<0.005) of HAND. A significant decrease in IRS-1 tyrosine-phosphorylation in the WCP was also associated with the presence (p<0.02) and severity (p<0.02) of HAND. Conclusions This study provides evidence that IR secretion is increased in HIV-seropositive women, and increased IR secretion is associated with cognitive impairment in these women. Thus, IR dysfunction may have a role in the progression of HAND and could represent a biomarker for the presence and severity of HAND. PMID:22629383

  17. Role of Neural NO Synthase (nNOS) Uncoupling in the Dysfunctional Nitrergic Vasorelaxation of Penile Arteries from Insulin-Resistant Obese Zucker Rats

    PubMed Central

    Sánchez, Ana; Contreras, Cristina; Martínez, María Pilar; Climent, Belén; Benedito, Sara; García-Sacristán, Albino; Hernández, Medardo; Prieto, Dolores

    2012-01-01

    Objective Erectile dysfunction (ED) is considered as an early sign of vascular disease due to its high prevalence in patients with cardiovascular risk factors. Endothelial and neural dysfunction involving nitric oxide (NO) are usually implicated in the pathophysiology of the diabetic ED, but the underlying mechanisms are unclear. The present study assessed the role of oxidative stress in the dysfunctional neural vasodilator responses of penile arteries in the obese Zucker rat (OZR), an experimental model of metabolic syndrome/prediabetes. Methods and Results Electrical field stimulation (EFS) under non-adrenergic non-cholinergic (NANC) conditions evoked relaxations that were significantly reduced in penile arteries of OZR compared with those of lean Zucker rats (LZR). Blockade of NO synthase (NOS) inhibited neural relaxations in both LZR and OZR, while saturating concentrations of the NOS substrate L-arginine reversed the inhibition and restored relaxations in OZR to levels in arteries from LZR. nNOS expression was unchanged in arteries from OZR compared to LZR and nNOS selective inhibition decreased the EFS relaxations in LZR but not in OZR, while endothelium removal did not alter these responses in either strain. Superoxide anion production and nitro-tyrosine immunostaining were elevated in the erectile tissue from OZR. Treatment with the NADPH oxidase inhibitor apocynin or acute incubation with the NOS cofactor tetrahydrobiopterin (BH4) restored neural relaxations in OZR to levels in control arteries, while inhibition of the enzyme of BH4 synthesis GTP-cyclohydrolase (GCH) reduced neural relaxations in arteries from LZR but not OZR. The NO donor SNAP induced decreases in intracellular calcium that were impaired in arteries from OZR compared to controls. Conclusions The present study demonstrates nitrergic dysfunction and impaired neural NO signalling due to oxidative stress and nNOS uncoupling in penile arteries under conditions of insulin resistance. This

  18. The Roles of Adipokines, Proinflammatory Cytokines, and Adipose Tissue Macrophages in Obesity-Associated Insulin Resistance in Modest Obesity and Early Metabolic Dysfunction

    PubMed Central

    Kim, Ji Min; Joung, Kyong Hye; Lee, Ju Hee; You, Bo Ram; Choi, Min Jeong; Ryu, Min Jeong; Ko, Young Bok; Lee, Min A.; Lee, Junguee; Ku, Bon Jeong; Shong, Minho; Lee, Ki Hwan; Kim, Hyun Jin

    2016-01-01

    The roles of adipokines, proinflammatory cytokines, and adipose tissue macrophages in obesity-associated insulin resistance have been explored in both animal and human studies. However, our current understanding of obesity-associated insulin resistance relies on studies of artificial metabolic extremes. The purpose of this study was to explore the roles of adipokines, proinflammatory cytokines, and adipose tissue macrophages in human patients with modest obesity and early metabolic dysfunction. We obtained omental adipose tissue and fasting blood samples from 51 females undergoing gynecologic surgery. We investigated serum concentrations of proinflammatory cytokines and adipokines as well as the mRNA expression of proinflammatory and macrophage phenotype markers in visceral adipose tissue using ELISA and quantitative RT-PCR. We measured adipose tissue inflammation and macrophage infiltration using immunohistochemical analysis. Serum levels of adiponectin and leptin were significantly correlated with HOMA-IR and body mass index. The levels of expression of MCP-1 and TNF-α in visceral adipose tissue were also higher in the obese group (body mass index ≥ 25). The expression of mRNA MCP-1 in visceral adipose tissue was positively correlated with body mass index (r = 0.428, p = 0.037) but not with HOMA-IR, whereas TNF-α in visceral adipose tissue was correlated with HOMA-IR (r = 0.462, p = 0.035) but not with body mass index. There was no obvious change in macrophage phenotype or macrophage infiltration in patients with modest obesity or early metabolic dysfunction. Expression of mRNA CD163/CD68 was significantly related to mitochondrial-associated genes and serum inflammatory cytokine levels of resistin and leptin. These results suggest that changes in the production of inflammatory biomolecules precede increased immune cell infiltration and induction of a macrophage phenotype switch in visceral adipose tissue. Furthermore, serum resistin and leptin have specific

  19. Insulin resistance predicts endothelial dysfunction and cardiovascular risk in HIV-infected persons on long-term highly active antiretroviral therapy

    PubMed Central

    Mondy, Kristin E.; de las Fuentes, Lisa; Waggoner, Alan; Önen, Nur F.; Bopp, Coco S.; Lassa-Claxton, Sherry; Powderly, William G.; Dávila-Román, Victor; Yarasheski, Kevin E.

    2011-01-01

    Objective Cardiovascular disease risk among persons with HIV is likely multifactorial, thus testing a variety of available noninvasive vascular ultrasound and other surrogate tests may yield differing results. To address this issue, we assessed multiple metabolic and clinical predictors of endothelial function and carotid intima–media thickness in HIV-infected subjects and compared results with HIV-negative controls. Design Prospective, cross-sectional study of 50 HIV-infected, healthy adults on stable highly active antiretroviral therapy matched to 50 HIV-negative controls by age, sex, race, and body mass index. Methods Flow-mediated vasodilation of the brachial artery, carotid intima–media thickness, dual energy X-ray absorptiometry (HIV-infected subjects), and fasting insulin, lipids, and oral glucose tolerance tests were performed. Results were compared between HIV-infected and control groups. Results Fifty percent of subjects were African–American with 34% women. Among HIV-infected, mean CD4 cell count was 547 cells/ µl; 90% had HIV RNA less than 50 copies/ml. There were no significant differences between HIV-infected and control subjects with regard to brachial artery flow-mediated vasodilation or carotid intima–media thickness. In multivariate analyses of the HIV cohort, independent predictors of endothelial dysfunction (lower flow-mediated vasodilation) were increasing insulin resistance, greater alcohol consumption, and higher baseline brachial artery diameter (P < 0.05); predictors of increased carotid intima–media thickness were hypertension, higher trunk/limb fat ratio, and insulin resistance (P < 0.05). Conclusion In this HIV cohort on modern highly active antiretroviral therapy with well controlled HIV, there were no significant differences with regard to preclinical markers of cardiovascular disease. Insulin resistance was a strong predictor of impaired brachial artery flow-mediated vasodilation and increased carotid intima

  20. Associations of visceral adiposity and exercise participation with C-reactive protein, insulin resistance, and endothelial dysfunction in Korean healthy adults.

    PubMed

    Kim, Kijin; Valentine, Rudy J; Shin, Yoonjung; Gong, Kyungmin

    2008-09-01

    The aim of the current study was to examine the associations of visceral adiposity and exercise participation with C-reactive protein (CRP), insulin resistance, and endothelial dysfunction in Korean adults selected from the general population. We studied 160 Korean adults (aged 41.3 +/- 13.0 years; n = 38 men and n = 122 women) who volunteered in a health promotion program. Subjects were divided into 2 groups based upon spontaneous exercise participation for using a cross-sectional approach. We measured anthropometric factors (body mass index [BMI], percentage body fat, waist-hip ratio [WHR], and abdominal fat area by computed tomographic scanning), blood pressure (BP), blood levels of glucose, lipids, fibrinogen, CRP, leptin, hemoglobin A(1c), homeostasis model assessment (HOMA), and carotid intima media thickness (IMT; via ultrasonography). Associations among the variables were assessed by Pearson partial correlation and linear regression, controlling for age and sex. Independent t tests were used to assess differences between exercise participants and nonparticipants. Significance was accepted at P < .05. As expected, the measures of adiposity (BMI, percentage body fat, WHR, abdominal fat area) were highly correlated with each other (r = .49-.86, P < .01). Blood levels of high-sensitivity CRP (hsCRP), leptin, and HOMA were modestly correlated with all measures of adiposity. Visceral fat area was the most important predictor of hsCRP, explaining 19.6% of the variance using stepwise linear regression analysis (P < .01). As visceral fat area tertiles increased from low to high, a significant stepwise increment in blood levels of CRP (P < .001), HOMA (P = .005), and left carotid IMT (P = .035) was observed. However, hsCRP and HOMA were not significantly different when compared across whole-body fat tertiles. Systolic BP, diastolic BP, and left carotid IMT were modestly correlated with WHR and visceral fat area (P < .05); but systolic BP and diastolic BP were also

  1. Adaptation of β-Cell and Endothelial Function to Carbohydrate Loading: Influence of Insulin Resistance.

    PubMed

    Hurwitz, Barry E; Schneiderman, Neil; Marks, Jennifer B; Mendez, Armando J; Gonzalez, Alex; Llabre, Maria M; Smith, Steven R; Bizzotto, Roberto; Santini, Eleonora; Manca, Maria Laura; Skyler, Jay S; Mari, Andrea; Ferrannini, Ele

    2015-07-01

    High-carbohydrate diets have been associated with β-cell strain, dyslipidemia, and endothelial dysfunction. We examined how β-cell and endothelial function adapt to carbohydrate overloading and the influence of insulin resistance. On sequential days in randomized order, nondiabetic subjects (classified as insulin-sensitive [IS] [n = 64] or insulin-resistant [IR] [n = 79] by euglycemic clamp) received four mixed meals over 14 h with either standard (300 kcal) or double carbohydrate content. β-Cell function was reconstructed by mathematical modeling; brachial artery flow-mediated dilation (FMD) was measured before and after each meal. Compared with IS, IR subjects showed higher glycemia and insulin hypersecretion due to greater β-cell glucose and rate sensitivity; potentiation of insulin secretion, however, was impaired. Circulating free fatty acids (FFAs) were less suppressed in IR than IS subjects. Baseline FMD was reduced in IR, and postprandial FMD attenuation occurred after each meal, particularly with high carbohydrate, similarly in IR and IS. Throughout the two study days, higher FFA levels were significantly associated with lower (incretin-induced) potentiation and impaired FMD. In nondiabetic individuals, enhanced glucose sensitivity and potentiation upregulate the insulin secretory response to carbohydrate overloading. With insulin resistance, this adaptation is impaired. Defective suppression of endogenous FFA is one common link between impaired potentiation and vascular endothelial dysfunction. PMID:25754957

  2. Adaptation of β-Cell and Endothelial Function to Carbohydrate Loading: Influence of Insulin Resistance

    PubMed Central

    Hurwitz, Barry E.; Schneiderman, Neil; Marks, Jennifer B.; Mendez, Armando J.; Gonzalez, Alex; Llabre, Maria M.; Smith, Steven R.; Bizzotto, Roberto; Santini, Eleonora; Manca, Maria Laura; Skyler, Jay S.; Mari, Andrea

    2015-01-01

    High-carbohydrate diets have been associated with β-cell strain, dyslipidemia, and endothelial dysfunction. We examined how β-cell and endothelial function adapt to carbohydrate overloading and the influence of insulin resistance. On sequential days in randomized order, nondiabetic subjects (classified as insulin-sensitive [IS] [n = 64] or insulin-resistant [IR] [n = 79] by euglycemic clamp) received four mixed meals over 14 h with either standard (300 kcal) or double carbohydrate content. β-Cell function was reconstructed by mathematical modeling; brachial artery flow-mediated dilation (FMD) was measured before and after each meal. Compared with IS, IR subjects showed higher glycemia and insulin hypersecretion due to greater β-cell glucose and rate sensitivity; potentiation of insulin secretion, however, was impaired. Circulating free fatty acids (FFAs) were less suppressed in IR than IS subjects. Baseline FMD was reduced in IR, and postprandial FMD attenuation occurred after each meal, particularly with high carbohydrate, similarly in IR and IS. Throughout the two study days, higher FFA levels were significantly associated with lower (incretin-induced) potentiation and impaired FMD. In nondiabetic individuals, enhanced glucose sensitivity and potentiation upregulate the insulin secretory response to carbohydrate overloading. With insulin resistance, this adaptation is impaired. Defective suppression of endogenous FFA is one common link between impaired potentiation and vascular endothelial dysfunction. PMID:25754957

  3. Insulin Granule Biogenesis, Trafficking and Exocytosis

    PubMed Central

    Hou, June Chunqiu; Min, Le; Pessin, Jeffrey E.

    2015-01-01

    It is becoming increasingly apparent that beta cell dysfunction resulting in abnormal insulin secretion is the essential element in the progression of patients from a state of impaired glucose tolerance to frank type 2 diabetes (Del Prato, 2003; Del Prato and Tiengo, 2001). Although extensive studies have examined the molecular, cellular and physiologic mechanisms of insulin granule biogenesis, sorting, and exocytosis the precise mechanisms controlling these processes and their dysregulation in the developed of diabetes remains an area of important investigation. We now know that insulin biogenesis initiates with the synthesis of preproinsulin in rough endoplastic reticulum and conversion of preproinsulin to proinsulin. Proinsulin begins to be packaged in the Trans-Golgi Network and is sorting into immature secretory granules. These immature granules become acidic via ATP-dependent proton pump and proinsulin undergoes proteolytic cleavage resulting the formation of insulin and C-peptide. During the granule maturation process, insulin is crystallized with zinc and calcium in the form of dense-core granules and unwanted cargo and membrane proteins undergo selective retrograde trafficking to either the constitutive trafficking pathway for secretion or to degradative pathways. The newly formed mature dense-core insulin granules populate two different intracellular pools, the readily releasable pools (RRP) and the reserved pool. These two distinct populations are thought to be responsible for the biphasic nature of insulin release in which the RRP granules are associated with the plasma membrane and undergo an acute calcium-dependent release accounting for first phase insulin secretion. In contrast, second phase insulin secretion requires the trafficking of the reserved granule pool to the plasma membrane. The initial trigger for insulin granule fusion with the plasma membrane is a rise in intracellular calcium and in the case of glucose stimulation results from

  4. Increased androgen levels in rats impair glucose-stimulated insulin secretion through disruption of pancreatic beta cell mitochondrial function.

    PubMed

    Wang, Hongdong; Wang, Xiaping; Zhu, Yunxia; Chen, Fang; Sun, Yujie; Han, Xiao

    2015-11-01

    Although insulin resistance is recognized to contribute to the reproductive and metabolic phenotypes of polycystic ovary syndrome (PCOS), pancreatic beta cell dysfunction plays an essential role in the progression from PCOS to the development of type 2 diabetes. However, the role of insulin secretory abnormalities in PCOS has received little attention. In addition, the precise changes in beta cells and the underlying mechanisms remain unclear. In this study, we therefore attempted to elucidate potential mechanisms involved in beta cell alterations in a rat model of PCOS. Glucose-induced insulin secretion was measured in islets isolated from DHT-treated and control rats. Oxygen consumption rate (OCR), ATP production, and mitochondrial copy number were assayed to evaluate mitochondrial function. Glucose-stimulated insulin secretion is significantly decreased in islets from DHT-treated rats. On the other hand, significant reductions are observed in the expression levels of several key genes involved in mitochondrial biogenesis and in mitochondrial OCR and ATP production in DHT-treated rat islets. Meanwhile, we found that androgens can directly impair beta cell function by inducing mitochondrial dysfunction in vitro in an androgen receptor dependent manner. For the first time, our study demonstrates that increased androgens in female rats can impair glucose-stimulated insulin secretion partly through disruption of pancreatic beta cell mitochondrial function. This work has significance for hyperandrogenic women with PCOS: excess activation of the androgen receptor by androgens may provoke beta cell dysfunction via mitochondrial dysfunction. PMID:26348137

  5. Dynamin 2 regulates biphasic insulin secretion and plasma glucose homeostasis

    PubMed Central

    Fan, Fan; Ji, Chen; Wu, Yumei; Ferguson, Shawn M.; Tamarina, Natalia; Philipson, Louis H.; Lou, Xuelin

    2015-01-01

    Alterations in insulin granule exocytosis and endocytosis are paramount to pancreatic β cell dysfunction in diabetes mellitus. Here, using temporally controlled gene ablation specifically in β cells in mice, we identified an essential role of dynamin 2 GTPase in preserving normal biphasic insulin secretion and blood glucose homeostasis. Dynamin 2 deletion in β cells caused glucose intolerance and substantial reduction of the second phase of glucose-stimulated insulin secretion (GSIS); however, mutant β cells still maintained abundant insulin granules, with no signs of cell surface expansion. Compared with control β cells, real-time capacitance measurements demonstrated that exocytosis-endocytosis coupling was less efficient but not abolished; clathrin-mediated endocytosis (CME) was severely impaired at the step of membrane fission, which resulted in accumulation of clathrin-coated endocytic intermediates on the plasma membrane. Moreover, dynamin 2 ablation in β cells led to striking reorganization and enhancement of actin filaments, and insulin granule recruitment and mobilization were impaired at the later stage of GSIS. Together, our results demonstrate that dynamin 2 regulates insulin secretory capacity and dynamics in vivo through a mechanism depending on CME and F-actin remodeling. Moreover, this study indicates a potential pathophysiological link between endocytosis and diabetes mellitus. PMID:26413867

  6. Proteomics analysis of cytokine-induced dysfunction and death in insulin-producing INS-1E cells: new insights into the pathways involved.

    PubMed

    D'Hertog, Wannes; Overbergh, Lut; Lage, Kasper; Ferreira, Gabriela Bonfim; Maris, Michael; Gysemans, Conny; Flamez, Daisy; Cardozo, Alessandra Kupper; Van den Bergh, Gert; Schoofs, Liliane; Arckens, Lut; Moreau, Yves; Hansen, Daniel Aaen; Eizirik, Decio Laks; Waelkens, Ettienne; Mathieu, Chantal

    2007-12-01

    Cytokines released by islet-infiltrating immune cells play a crucial role in beta-cell dysfunction and apoptotic cell death in the pathogenesis of type 1 diabetes and after islet transplantation. RNA studies revealed complex pathways of genes being activated or suppressed during this beta-cell attack. The aim of the present study was to analyze protein changes in insulin-producing INS-1E cells exposed to inflammatory cytokines in vitro using two-dimensional DIGE. Within two different pH ranges we observed 2214 +/- 164 (pH 4-7) and 1641 +/- 73 (pH 6-9) spots. Analysis at three different time points (1, 4, and 24 h of cytokine exposure) revealed that the major changes were taking place only after 24 h. At this time point 158 proteins were altered in expression (4.1%, n = 4, p < or = 0.01) by a combination of interleukin-1beta and interferon-gamma, whereas only 42 and 23 proteins were altered by either of the cytokines alone, giving rise to 199 distinct differentially expressed spots. Identification of 141 of these by MALDI-TOF/TOF revealed proteins playing a role in insulin secretion, cytoskeleton organization, and protein and RNA metabolism as well as proteins associated with endoplasmic reticulum and oxidative stress/defense. We investigated the interactions of these proteins and discovered a significant interaction network (p < 1.27e-05) containing 42 of the identified proteins. This network analysis suggests that proteins of different pathways act coordinately in a beta-cell dysfunction/apoptotic beta-cell death interactome. In addition the data suggest a central role for chaperones and proteins playing a role in RNA metabolism. As many of these identified proteins are regulated at the protein level or undergo post-translational modifications, a proteomics approach, as performed in this study, is required to provide adequate insight into the mechanisms leading to beta-cell dysfunction and apoptosis. The present findings may open new avenues for the understanding

  7. Microcystin-LR induces dysfunction of insulin secretion in rat insulinoma (INS-1) cells: Implications for diabetes mellitus.

    PubMed

    Zhao, Yanyan; Shi, Kun; Su, Xiaomei; Xie, Liqiang; Yan, Yunjun

    2016-08-15

    Microcystins (MCs) are the most frequent cyanobacterial toxins observed in freshwater systems. Accumulating evidence suggests that MCs pose a serious threat to public health. However, the contributions of the exposure of MCs to the occurrence of human diseases remain largely unknown. This study provides the evidence of the effects of MC-LR on pancreatic β-cell function through the exposure of rat insulinoma (INS-1) cells to 0, 10, 20, or 40μM MC-LR for 72h and explores the underlying molecular mechanisms. Our results demonstrate that exposure to MC-LR for 72h suppresses cell viability, disturbs glucose-stimulated insulin secretion (GSIS), and decreases the expression of insulin protein. Moreover, MC-LR disrupts the cell cycle distribution and increases cell apoptosis at 20 or 40μM for 72h, respectively, indicating that the β-cell mass would be decreased by MC-LR exposure. A transcriptomic analysis revealed several key genes (e.g., Pdx-1, Neurod1, and Abcc8) involved in insulin secretion are significantly differentially expressed in INS-1 cells in response to MC-LR exposure. In addition, several signal transduction pathways associated with diabetes (e.g., type 1 and 2 diabetes) were also identified compared with the control cells. We recommend that MC be considered as a new environmental factor that promotes diabetes development. The identified key genes or pathways may potentially contribute to the future therapies in the environmental contaminants induced β-cell damage. PMID:27107231

  8. Intestinal secretory mechanisms in irritable bowel syndrome-diarrhea.

    PubMed

    Camilleri, Michael

    2015-06-01

    Although diarrhea is the predominant bowel dysfunction in as many as one-third of patients with irritable bowel syndrome (IBS), it is unclear whether there is a specific disorder of intestinal fluid or electrolyte secretion in IBS. Diarrhea is generally considered a result of accelerated colonic transit in patients with IBS. Although a primary secretory diathesis has not been well-documented in patients with IBS with diarrhea (IBS-D), several mechanisms that could potentially contribute to intestinal secretion have been reported. Some of these mechanisms also influence motor and secretory dysfunctions that contribute to the pathophysiology of IBS-D. We review the evidence supporting secretion in IBS-D caused by peptides and amines produced by enteroendocrine cells or submucosal neurons, enterocyte secretory processes, and intraluminal factors (bile acids and short-chain fatty acids). Understanding these mechanisms and developing clinical methods for their identification could improve management of patients with IBS-D. PMID:25041862

  9. Episodic hormone secretion during sleep in Kleine-Levin syndrome: evidence for hypothalamic dysfunction.

    PubMed

    Gadoth, N; Dickerman, Z; Bechar, M; Laron, Z; Lavie, P

    1987-01-01

    "Acute" hypothalamic-pituitary function tests including insulin tolerance test, LRH, ACTH and TRH stimulation tests and nocturnal secretory pattern of human growth hormone, 11-OHCS, prolactin, FSH, LH and TSH were studied in a 23-year-old male with Kleine-Levin syndrome during the course of a typical hypersomnic attack. The "acute" tests revealed paradoxical growth-hormone response to TRH stimulation, borderline high basal plasma prolactin levels with normal response to TRH. The hormonal secretory pattern during sleep revealed abnormalities in LH, 11-OHCS and prolactin secretion. These together with the results of the "acute" tests are indicative of an abnormality in the hypothalamic regulation of various pituitary hormones. This observation may indeed be the first laboratory demonstration confirming a long-standing hypothesis that Kleine-Levin syndrome is related to hypothalamic dysfunction. PMID:3477962

  10. Metformin increases APP expression and processing via oxidative stress, mitochondrial dysfunction and NF-κB activation: Use of insulin to attenuate metformin's effect.

    PubMed

    Picone, Pasquale; Nuzzo, Domenico; Caruana, Luca; Messina, Elisa; Barera, Annalisa; Vasto, Sonya; Di Carlo, Marta

    2015-05-01

    Clinical and experimental biomedical studies have shown Type 2 diabetes mellitus (T2DM) to be a risk factor for the development of Alzheimer's disease (AD). This study demonstrates the effect of metformin, a therapeutic biguanide administered for T2DM therapy, on β-amyloid precursor protein (APP) metabolism in in vitro, ex vivo and in vivo models. Furthermore, the protective role of insulin against metformin is also demonstrated. In LAN5 neuroblastoma cells, metformin increases APP and presenilin levels, proteins involved in AD. Overexpression of APP and presenilin 1 (Pres 1) increases APP cleavage and intracellular accumulation of β-amyloid peptide (Aβ), which, in turn, promotes aggregation of Aβ. In the experimental conditions utilized the drug causes oxidative stress, mitochondrial damage, decrease of Hexokinase-II levels and cytochrome C release, all of which lead to cell death. Several changes in oxidative stress-related genes following metformin treatment were detected by PCR arrays specific for the oxidative stress pathway. These effects of metformin were found to be antagonized by the addition of insulin, which reduced Aβ levels, oxidative stress, mitochondrial dysfunction and cell death. Similarly, antioxidant molecules, such as ferulic acid and curcumin, are able to revert metformin's effect. Comparable results were obtained using peripheral blood mononuclear cells. Finally, the involvement of NF-κB transcription factor in regulating APP and Pres 1 expression was investigated. Upon metformin treatment, NF-κB is activated and translocates from the cytoplasm to the nucleus, where it induces increased APP and Pres 1 transcription. The use of Bay11-7085 inhibitor suppressed the effect of metformin on APP and Pres 1 expression. PMID:25667085

  11. Toll-like receptor 4-induced endoplasmic reticulum stress contributes to endothelial dysfunction

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Impairment of vasodilator action of insulin is associated with endothelial dysfunction and insulin resistance. Endoplasmic reticulum (ER) stress is implicated as one of the mechanisms for pathophysiology of various cardiometabolic syndromes, including insulin resistance and endothelial dysfunction. ...

  12. Oral Metformin Treatment Prevents Enhanced Insulin Demand and Placental Dysfunction in the Pregnant Rat Fed a Fructose-Rich Diet

    PubMed Central

    Alzamendi, Ana; Del Zotto, Hector; Castrogiovanni, Daniel; Romero, Jose; Giovambattista, Andres; Spinedi, Eduardo

    2012-01-01

    The intake of a fructose-rich diet (FRD) in the normal female rat induces features similar to those observed in the human metabolic syndrome phenotype. We studied the impact of FRD administration to mothers on pregnancy outcome. On gestational day (Gd) zero rats were assigned to either group: ad libitum drinking tap water alone (normal diet, ND) or containing fructose (10% w/vol; FRD) through pregnancy; all rats were fed a Purina chow diet ad libitum ND and FRD rats were daily cotreated or not with metformin (60 mg/Kg/day oral; ND + MF and FRD + MF) and submitted to a high glucose load test on Gd 14. Additionally, placentas from different groups were studied on Gd 20. Data indicated that: (1) although FRD rats well tolerated glucose overload, their circulating levels of insulin were significantly higher than in ND rats; (2) the mesometrial triangle blood vessel area was significantly lower in placentas from FRD than ND dams; (3) the detrimental effects of FRD administration to mothers were ameliorated by metformin cotreatment. Our study suggests that excessive intake of fructose during pregnancy enhanced the risk for developing gestational diabetes and subsequent preeclampsia, and that metformin prevented the poor pregnancy outcome induced by FRD. PMID:22957268

  13. A psychometric evaluation of adult patients with type 1 (insulin-dependent) diabetes mellitus: prevalence of psychological dysfunction and relationship to demographic variables, metabolic control and complications.

    PubMed

    Winocour, P H; Main, C J; Medlicott, G; Anderson, D C

    1990-08-01

    The relationship between psychosocial traits and glycaemic control and complications was examined in 130 adults (83 men, 47 women) with insulin-dependent diabetes mellitus. Abnormal depression ratings were observed in more women (19.1%) than men (12.0%), p less than 0.01, whilst obsessive symptoms were recorded more frequently in men (41.0 v 21.3%, p less than 0.01). Abnormal anxiety ratings were present in roughly 8-13% of men and women, although a notably low feeling of insecurity rating was observed more frequently in men (56.5%) than in women (38.3% of cases), p less than 0.05. Psychological scores were related to age, employment status and social class, but not to duration of diabetes or glycaemic control. The anxiety, depression and obsessive ratings correlated with one another (rs range 0.24-0.62, all p less than 0.001). Higher anxiety and depression ratings or overt psychological dysfunction was recorded in patients with neuropathic symptoms and signs, impotence, macrovascular disease or proliferative retinopathy. It is concluded that the presence of diabetic complications and adverse social circumstances are more relevant to psychological status than glycaemic control. PMID:2132190

  14. Clinical utility of insulin and insulin analogs

    PubMed Central

    Sanlioglu, Ahter D.; Altunbas, Hasan Ali; Balci, Mustafa Kemal; Griffith, Thomas S.; Sanlioglu, Salih

    2013-01-01

    Diabetes is a pandemic disease characterized by autoimmune, genetic and metabolic abnormalities. While insulin deficiency manifested as hyperglycemia is a common sequel of both Type-1 and Type-2 diabetes (T1DM and T2DM), it does not result from a single genetic defect—rather insulin deficiency results from the functional loss of pancreatic β cells due to multifactorial mechanisms. Since pancreatic β cells of patients with T1DM are destroyed by autoimmune reaction, these patients require daily insulin injections. Insulin resistance followed by β cell dysfunction and β cell loss is the characteristics of T2DM. Therefore, most patients with T2DM will require insulin treatment due to eventual loss of insulin secretion. Despite the evidence of early insulin treatment lowering macrovascular (coronary artery disease, peripheral arterial disease and stroke) and microvascular (diabetic nephropathy, neuropathy and retinopathy) complications of T2DM, controversy exists among physicians on how to initiate and intensify insulin therapy. The slow acting nature of regular human insulin makes its use ineffective in counteracting postprandial hyperglycemia. Instead, recombinant insulin analogs have been generated with a variable degree of specificity and action. Due to the metabolic variability among individuals, optimum blood glucose management is a formidable task to accomplish despite the presence of novel insulin analogs. In this article, we present a recent update on insulin analog structure and function with an overview of the evidence on the various insulin regimens clinically used to treat diabetes. PMID:23584214

  15. Adipocyte lipolysis and insulin resistance.

    PubMed

    Morigny, Pauline; Houssier, Marianne; Mouisel, Etienne; Langin, Dominique

    2016-06-01

    Obesity-induced insulin resistance is a major risk factor for the development of type 2 diabetes. Basal fat cell lipolysis (i.e., fat cell triacylglycerol breakdown into fatty acids and glycerol in the absence of stimulatory factors) is elevated during obesity and is closely associated with insulin resistance. Inhibition of adipocyte lipolysis may therefore be a promising therapeutic strategy for treating insulin resistance and preventing obesity-associated type 2 diabetes. In this review, we explore the relationship between adipose lipolysis and insulin sensitivity. After providing an overview of the components of fat cell lipolytic machinery, we describe the hypotheses that may support the causality between lipolysis and insulin resistance. Excessive circulating fatty acids may ectopically accumulate in insulin-sensitive tissues and impair insulin action. Increased basal lipolysis may also modify the secretory profile of adipose tissue, influencing whole body insulin sensitivity. Finally, excessive fatty acid release may also worsen adipose tissue inflammation, a well-known parameter contributing to insulin resistance. Partial genetic or pharmacologic inhibition of fat cell lipases in mice as well as short term clinical trials using antilipolytic drugs in humans support the benefit of fat cell lipolysis inhibition on systemic insulin sensitivity and glucose metabolism, which occurs without an increase of fat mass. Modulation of fatty acid fluxes and, putatively, of fat cell secretory pattern may explain the amelioration of insulin sensitivity whereas changes in adipose tissue immune response do not seem involved. PMID:26542285

  16. SPARC is over-expressed in adipose tissues of diet-induced obese rats and causes insulin resistance in 3T3-L1 adipocytes.

    PubMed

    Shen, Yang; Zhao, Yuyan; Yuan, Lizhi; Yi, Wei; Zhao, Rui; Yi, Qianru; Yong, Tongwu

    2014-01-01

    Secreted protein acidic and rich in cysteine (SPARC) is a secretory multifunctional matricellular glycoprotein. High circulating levels of SPARC have been reported to be associated with obesity and insulin resistance. The aim of the present study was to investigate whether SPARC induces insulin resistance and mitochondrial dysfunction in adipocytes. Our results showed that feeding high fat diet to rats for 12 weeks significantly increased SPARC expression in adipose tissues at both mRNA and protein levels. Moreover, SPARC overexpression in stably transfected 3T3-L1 cells induced insulin resistance and mitochondrial dysfunction, as evidenced by inhibition of insulin-stimulated glucose transport, lower ATP synthesis and mitochondrial membrane potential, reduced expression of glucose transporter 4 (GLUT4), and increased levels of reactive oxygen species (ROS) in mature adipocytes. Finally, overexpression of SPARC also modulated the expression levels of several inflammatory cytokines, which play important roles in insulin resistance, glucose and lipid metabolism during adipogenesis. In conclusion, our data suggest that SPARC is involved in obesity-induced adipose insulin resistance and may serve as a potential target in the treatment of obesity and obesity-related insulin resistance. PMID:23910024

  17. Growth Hormone-Releaser Diet Attenuates Cognitive Dysfunction in Klotho Mutant Mice via Insulin-Like Growth Factor-1 Receptor Activation in a Genetic Aging Model

    PubMed Central

    Park, Seok Joo; Chung, Yoon Hee; Lee, Jeong Hyun; Dang, Duy-Khanh; Nam, Yunsung; Jeong, Ji Hoon; Kim, Yong Sun; Nabeshima, Toshitaka

    2014-01-01

    Background It has been recognized that a defect in klotho gene expression accelerates the degeneration of multiple age-sensitive traits. Accumulating evidence indicates that aging is associated with declines in cognitive function and the activity of growth hormone (GH)/insulin-like growth factor-1 (IGF-1). Methods In this study, we examined whether a GH-releaser diet could be effective in protecting against cognitive impairment in klotho mutant mice. Results The GH-releaser diet significantly induced the expression of IGF-1 and IGF-1 receptors in the hippocampus of klotho mutant mice. Klotho mutant mice showed significant memory impairments as compared with wild-type mice. In addition, the klotho mutation significantly decreased the expression of cell survival/antiapoptotic factors, including phospho-Akt (p-Akt)/phospho-glycogen synthase kinase3β (p-GSK3β), phospho-extracellular signal-related kinase (p-ERK), and Bcl-2, but significantly increased those of cell death/proapoptotic factors, such as phospho-c-jun N-terminal kinase (p-JNK), Bax, and cleaved caspase-3 in the hippocampus. Treatment with GH-releaser diet significantly attenuated both decreases in the expression of cell survival/antiapoptotic factors and increases in the expression of cell death/proapoptotic factors in the hippocampus of klotho mutant mice. In addition, klotho mutation-induced oxidative stress was significantly attenuated by the GH-releaser diet. Consequently, a GH-releaser diet significantly improved memory function in the klotho mutant mice. GH-releaser diet-mediated actions were significantly reversed by JB-1, an IGF-1 receptor antagonist. Conclusion The results suggest that a GH-releaser diet attenuates oxidative stress, proapoptotic changes and consequent dysfunction in klotho mutant mice by promoting IGF-1 expression and IGF-1 receptor activation. PMID:25309793

  18. Endocrine dysfunction in hereditary hemochromatosis.

    PubMed

    Pelusi, C; Gasparini, D I; Bianchi, N; Pasquali, R

    2016-08-01

    Hereditary hemochromatosis (HH) is a genetic disorder of iron overload and subsequent organ damage. Five types of HH are known, classified by age of onset, genetic cause, clinical manifestations and mode of inheritance. Except for the rare form of juvenile haemochromatosis, symptoms do not usually appear until after decades of progressive iron loading and may be triggered by environmental and lifestyle factors. Despite the last decades discovery of genetic and phenotype diversity of HH, early studies showed a frequent involvement of the endocrine glands where diabetes and hypogonadism are the most common encountered endocrinopathies. The pathogenesis of diabetes is still relatively unclear, but the main mechanisms include the loss of insulin secretory capacity and insulin resistance secondary to liver damage. The presence of obesity and/or genetic predisposition may represent addictive risk factor for the development of this metabolic disease. Although old cases of primary gonad involvement are described, hypogonadism is mainly secondary to selective deposition of iron on the gonadotropin-producing cells of the pituitary gland, leading to hormonal impaired secretion. Cases of hypopituitarism or selected tropin defects, and abnormalities of adrenal, thyroid and parathyroid glands, even if rare, are reported. The prevalence of individual gland dysfunction varies enormously within studies for several bias due to small numbers of and selected cases analyzed, mixed genotypes and missing data on medical history. Moreover, in the last few years early screening and awareness of the disease among physicians have allowed hemochromatosis to be diagnosed in most cases at early stages when patients have no symptoms. Therefore, the clinical presentation of this disease has changed significantly and the recognized common complications are encountered less frequently. This review summarizes the current knowledge on HH-associated endocrinopathies. PMID:26951056

  19. Changing Clinical Characteristics according to Insulin Resistance and Insulin Secretion in Newly Diagnosed Type 2 Diabetic Patients in Korea

    PubMed Central

    Son, Jang Won; Park, Cheol-Young; Lee, Han-Kyu; Lee, Yil-Seob

    2015-01-01

    Background The role of increased insulin resistance in the pathogenesis of type 2 diabetes has been emphasized in Asian populations. Thus, we evaluated the proportion of insulin resistance and the insulin secretory capacity in patients with early phase type 2 diabetes in Korea. Methods We performed a cross-sectional analysis of 1,314 drug-naive patients with newly diagnosed diabetes from primary care clinics nationwide. The homeostasis model assessment of insulin resistance (HOMA-IR) was used as an index to measure insulin resistance, which was defined as a HOMA-IR ≥2.5. Insulin secretory defects were classified based on fasting plasma C-peptide levels: severe (<1.1 ng/mL), moderate (1.1 to 1.7 ng/mL) and mild to non-insulin secretory defect (≥1.7 ng/mL). Results The mean body mass index (BMI) was 25.2 kg/m2; 77% of patients had BMIs >23.0 kg/m2. Up to 50% of patients had central obesity based on their waist circumference (≥90 cm in men and 85 cm in women), and 70.6% had metabolic syndrome. Overall, 59.5% of subjects had insulin resistance, and 20.2% demonstrated a moderate to severe insulin secretory defect. Among those with insulin resistance, a high proportion of subjects (79.0%) had a mild or no insulin secretory defect. Only 2.6% of the men and 1.9% of the women had both insulin resistance and a moderate to severe insulin secretory defect. Conclusion In this study, patients with early phase type 2 diabetes demonstrated increased insulin resistance, but preserved insulin secretion, with a high prevalence of obesity and metabolic syndrome. PMID:26566496

  20. Cell oxidant stress delivery and cell dysfunction onset in type 2 diabetes.

    PubMed

    Kassab, Asma; Piwowar, Agnieszka

    2012-09-01

    Most known pathways of diabetic complications involve oxidative stress. The mitochondria electron transport chain is a significant source of reactive oxygen species (ROS) in insulin secretory cells, insulin peripheral sensitive cells and endothelial cells. Elevated intracellular glucose level induces tricarboxylic acid cycle electron donor overproduction and mitochondrial proton gradient increase leading to an increase in electron transporter lifetime. Subsequently, the electrons leaked combine with respiratory oxygen (O(2)) resulting in superoxide anion ((•)O(2)(-)) production. Advanced glycation end products derive ROS via interaction with their receptors. Elevated diacylglycerol and ROS activate the protein kinase C pathway which, in turn, activates NADPH oxidases. A vicious circle of pathway derived ROS installs. Pathologic pathways induced ROS are activated and persistent though glycemia returns to normal due to hyperglycemia memory. Endothelial nitric oxide synthase may produce both superoxide anion ((•)O(2)(-)) and nitric oxide (NO) leading to peroxynitrite ((•)ONOO(-)) generation. Homocysteine is also implicated in oxidative stress pathogenesis. In this paper we have highlighted the pathologic mechanisms of ROS on atherosclerosis, renal dysfunction, retina dysfunction and nerve dysfunction in type 2 diabetes. Cell oxidant stress delivery have pivotal role in cell dysfunction onset and progression of angiopathies but an early introduction of good glycemic control may protect cells more efficiently than antioxidants. PMID:22333037

  1. Increased Insulin following an Oral Glucose Load, Genetic Variation near the Melatonin Receptor MTNR1B, but No Biochemical Evidence of Endothelial Dysfunction in Young Asian Men and Women

    PubMed Central

    Matuszek, Maria A.; Anton, Angelyn; Thillainathan, Sobana; Armstrong, Nicola J.

    2015-01-01

    Aim To identify biochemical and genetic variation relating to increased risk of developing type 2 diabetes mellitus and cardiovascular disease in young, lean male and female adults of different ethnicities. Method Fasting blood and urine and non-fasting blood following oral glucose intake were analysed in 90 Caucasians, South Asians and South East/East Asians. Results There were no differences in age, birthweight, blood pressure, body mass index, percent body fat, total energy, percentage of macronutrient intake, microalbumin, leptin, cortisol, adrenocorticotropic hormone, nitric oxide metabolites, C-reactive protein, homocysteine, tumor necrosis factor-α, interleukin-6, von Willebrand factor, vascular cell adhesion molecule-1, plasminogen activator inhibitor-1, and tissue plasminogen activator. Fasting total cholesterol (P = .000), triglycerides (P = .050), low density lipoprotein (P = .009) and non-fasting blood glucose (15 min) (P = .024) were elevated in South Asians compared with Caucasians, but there was no significant difference in glucose area under curve (AUC). Non-fasting insulin in South Asians (15–120 min), in South East/East Asians (60–120 min), and insulin AUC in South Asians and South East/East Asians, were elevated compared with Caucasians (P≤0.006). The molar ratio of C-peptide AUC/Insulin AUC (P = .045) and adiponectin (P = .037) were lower in South Asians compared with Caucasians. A significant difference in allele frequency distributions in Caucasians and South Asians was found for rs2166706 (P = 0.022) and rs10830963 (P = 0.009), which are both near the melatonin receptor MTNR1B. Conclusions Elevated non-fasting insulin exists in young South Asians of normal fasting glucose and insulin. Hepatic clearance of insulin may be reduced in South Asians. No current biochemical evidence exists of endothelial dysfunction at this stage of development. MTNR1B signalling may be a useful therapeutic target in Asian populations in the prevention of

  2. Epigenetics: The missing link to understanding β-cell dysfunction in the pathogenesis of type 2 diabetes

    PubMed Central

    Gilbert, Elizabeth R.; Liu, Dongmin

    2012-01-01

    Type 2 diabetes (T2D) is a growing health problem worldwide. While peripheral insulin resistance is common during obesity and aging in both animals and people, progression to T2D is largely due to insulin secretory dysfunction and significant apoptosis of functional β-cells, leading to an inability to compensate for insulin resistance. It is recognized that environmental factors and nutrition play an important role in the pathogenesis of diabetes. However, our knowledge surrounding molecular mechanisms by which these factors trigger β-cell dysfunction and diabetes is still limited. Recent discoveries raise the possibility that epigenetic changes in response to environmental stimuli may play an important role in the development of diabetes. In this paper, we review emerging knowledge regarding epigenetic mechanisms that may be involved in β-cell dysfunction and pathogenesis of diabetes, including the role of nutrition, oxidative stress and inflammation. We will mainly focus on the role of DNA methylation and histone modifications but will also briefly review data on miRNA effects on the pancreatic islets. Further studies aimed at better understanding how epigenetic regulation of gene expression controls β-cell function may reveal potential therapeutic targets for prevention and treatment of diabetes. PMID:22810088

  3. Long-Term Exposure of Pancreatic β-Cells to Palmitate Results in SREBP-1C-Dependent Decreases in GLP-1 Receptor Signaling via CREB and AKT and Insulin Secretory Response.

    PubMed

    Natalicchio, Annalisa; Biondi, Giuseppina; Marrano, Nicola; Labarbuta, Rossella; Tortosa, Federica; Spagnuolo, Rosaria; D'Oria, Rossella; Carchia, Emanuele; Leonardini, Anna; Cignarelli, Angelo; Perrini, Sebastio; Laviola, Luigi; Giorgino, Francesco

    2016-06-01

    The effects of prolonged exposure of pancreatic β-cells to high saturated fatty acids on glucagon-like peptide-1 (GLP-1) action were investigated. Murine islets, human pancreatic 1.1B4 cells, and rat INS-1E cells were exposed to palmitate for 24 hours. mRNA and protein expression/phosphorylation were measured by real-time RT-PCR and immunoblotting, respectively. Specific short interfering RNAs were used to knockdown expression of the GLP-1 receptor (Glp1r) and Srebf1. Insulin release was assessed with a specific ELISA. Exposure of murine islets, as well as of human and INS-1E β-cells, to palmitate reduced the ability of exendin-4 to augment insulin mRNA levels, protein content, and release. In addition, palmitate blocked exendin-4-stimulated cAMP-response element-binding protein and v-akt murine thymoma viral oncogene homolog phosphorylation, whereas phosphorylation of MAPK-ERK kinase-1/2 and ERK-1/2 was not altered. Similarly, RNA interference-mediated suppression of Glp1r expression prevented exendin-4-induced cAMP-response element-binding protein and v-akt murine thymoma viral oncogene homolog phosphorylation, but did not impair exendin-4 stimulation of MAPK-ERK kinase-1/2 and ERK-1/2. Both islets from mice fed a high fat diet and human and INS-1E β-cells exposed to palmitate showed reduced GLP-1 receptor and pancreatic duodenal homeobox-1 (PDX-1) and increased sterol regulatory element-binding protein (SREBP-1C) mRNA and protein levels. Furthermore, suppression of SREBP-1C protein expression prevented the reduction of PDX-1 and GLP-1 receptor levels and restored exendin-4 signaling and action. Finally, treatment of INS-1E cells with metformin for 24 h resulted in inhibition of SREBP-1C expression, increased PDX-1 and GLP-1 receptor levels, consequently, enhancement of exendin-4-induced insulin release. Palmitate impairs exendin-4 effects on β-cells by reducing PDX-1 and GLP-1 receptor expression and signaling in a SREBP-1C-dependent manner. Metformin

  4. Dietary Salba (Salvia hispanica L) seed rich in α-linolenic acid improves adipose tissue dysfunction and the altered skeletal muscle glucose and lipid metabolism in dyslipidemic insulin-resistant rats.

    PubMed

    Oliva, M E; Ferreira, M R; Chicco, A; Lombardo, Y B

    2013-10-01

    This work reports the effect of dietary Salba (chia) seed rich in n-3 α-linolenic acid on the morphological and metabolic aspects involved in adipose tissue dysfunction and the mechanisms underlying the impaired glucose and lipid metabolism in the skeletal muscle of rats fed a sucrose-rich diet (SRD). Rats were fed a SRD for 3 months. Thereafter, half the rats continued with SRD while in the other half, corn oil (CO) was replaced by chia seed for 3 months (SRD+chia). In control group, corn starch replaced sucrose. The replacement of CO by chia seed in the SRD reduced adipocyte hypertrophy, cell volume and size distribution, improved lipogenic enzyme activities, lipolysis and the anti-lipolytic action of insulin. In the skeletal muscle lipid storage, glucose phosphorylation and oxidation were normalized. Chia seed reversed the impaired insulin stimulated glycogen synthase activity, glycogen, glucose-6-phosphate and GLUT-4 protein levels as well as insulin resistance and dyslipidemia. PMID:24120122

  5. Urinary Dysfunction

    MedlinePlus

    ... PCF Spotlight Glossary African American Men Living with Prostate Cancer Urinary Dysfunction Side Effects Urinary Dysfunction Bowel Dysfunction ... dysfunction is normal following initial therapy for localized prostate cancer. But it’s important to realize that not all ...

  6. Neuroendocrine secretory protein 7B2: structure, expression and functions.

    PubMed Central

    Mbikay, M; Seidah, N G; Chrétien, M

    2001-01-01

    7B2 is an acidic protein residing in the secretory granules of neuroendocrine cells. Its sequence has been elucidated in many phyla and species. It shows high similarity among mammals. A Pro-Pro-Asn-Pro-Cys-Pro polyproline motif is its most conserved feature, being carried by both vertebrate and invertebrate sequences. It is biosynthesized as a precursor protein that is cleaved into an N-terminal fragment and a C-terminal peptide. In neuroendocrine cells, 7B2 functions as a specific chaperone for the proprotein convertase (PC) 2. Through the sequence around its Pro-Pro-Asn-Pro-Cys-Pro motif, it binds to an inactive proPC2 and facilitates its transport from the endoplasmic reticulum to later compartments of the secretory pathway where the zymogen is proteolytically matured and activated. Its C-terminal peptide can inhibit PC2 in vitro and may contribute to keep the enzyme transiently inactive in vivo. The PC2-7B2 model defines a new neuroendocrine paradigm whereby proteolytic activation of prohormones and proneuropeptides in the secretory pathway is spatially and temporally regulated by the dynamics of interactions between converting enzymes and their binding proteins. Interestingly, unlike PC2-null mice, which are viable, 7B2-null mutants die early in life from Cushing's disease due to corticotropin ('ACTH') hypersecretion by the neurointermediate lobe, suggesting a possible involvement of 7B2 in secretory granule formation and in secretion regulation. The mechanism of this regulation is yet to be elucidated. 7B2 has been shown to be a good marker of several neuroendocrine cell dysfunctions in humans. The possibility that anomalies in its structure and expression could be aetiological causes of some of these dysfunctions warrants investigation. PMID:11439082

  7. Proteolysis in the secretory pathway

    SciTech Connect

    Guzowski, D.E.; Bienkowski, R.S.

    1987-05-01

    Many secretory proteins are degraded intracellularly rather than secreted, however the location of this catabolic process is not known. The authors have tested the hypothesis that the degradation occurs in the organelles of the secretory pathway. Slices of rat liver were incubated with (/sup 14/C)leucine for 3 h and then incubated under chase conditions for 30 min. The tissue was homogenized and the Golgi apparatus, smooth endoplasmic reticulum (sER) and rough endoplasmic reticulum (rER) were isolated by ultracentrifugation on a discontinuous sucrose gradient. The organelles were incubated in 0.3M sucrose-50 mM citrate (pH 4) for 8-12 h at 37 C; control samples were incubated at 4 C. Percent degradation was calculated as the amount of acid soluble radioactivity released relative to total radioactivity in the sample. Proteolysis in the organelles incubated at 37 C was as follows: Golgi: 15-25%; sER: 10-20%; rER: 10-20%. Proteolysis at 4 C was negligible in all cases. These results support the hypothesis that the compartments of the secretory pathway are capable of degrading newly synthesized secretory proteins.

  8. Secretory Pathway of Trypanosomatid Parasites

    PubMed Central

    McConville, Malcolm J.; Mullin, Kylie A.; Ilgoutz, Steven C.; Teasdale, Rohan D.

    2002-01-01

    The Trypanosomatidae comprise a large group of parasitic protozoa, some of which cause important diseases in humans. These include Trypanosoma brucei (the causative agent of African sleeping sickness and nagana in cattle), Trypanosoma cruzi (the causative agent of Chagas' disease in Central and South America), and Leishmania spp. (the causative agent of visceral and [muco]cutaneous leishmaniasis throughout the tropics and subtropics). The cell surfaces of these parasites are covered in complex protein- or carbohydrate-rich coats that are required for parasite survival and infectivity in their respective insect vectors and mammalian hosts. These molecules are assembled in the secretory pathway. Recent advances in the genetic manipulation of these parasites as well as progress with the parasite genome projects has greatly advanced our understanding of processes that underlie secretory transport in trypanosomatids. This article provides an overview of the organization of the trypanosomatid secretory pathway and connections that exist with endocytic organelles and multiple lytic and storage vacuoles. A number of the molecular components that are required for vesicular transport have been identified, as have some of the sorting signals that direct proteins to the cell surface or organelles in the endosome-vacuole system. Finally, the subcellular organization of the major glycosylation pathways in these parasites is reviewed. Studies on these highly divergent eukaryotes provide important insights into the molecular processes underlying secretory transport that arose very early in eukaryotic evolution. They also reveal unusual or novel aspects of secretory transport and protein glycosylation that may be exploited in developing new antiparasite drugs. PMID:11875130

  9. REGULATION OF ADRENAL CHROMAFFIN CELL DEVELOPMENT BY THE CENTRAL MONOAMINERGIC SYSTEM: DIFFERENTIAL CONTROL OF NOREPINEPHRINE AND EPINEPHRINE LEVELS AND SECRETORY RESPONSES (JOURNAL VERSION)

    EPA Science Inventory

    In the mature rat, reflex sympathetic stimulation by insulin-induced hypoglycemia resulted in profound depletion of adrenal epinephrine, and to a lesser extent, Norepinephrine. In the developing rat, insulin evoked little or no secretory response from the adrenals prior to 1 week...

  10. Bowel Dysfunction

    MedlinePlus

    ... PCF Spotlight Glossary African American Men Living with Prostate Cancer Bowel Dysfunction Side Effects Urinary Dysfunction Bowel Dysfunction ... rectal worse. Back to Side Effects Print | Understanding Prostate Cancer Research Faces of Prostate Cancer About PCF Take ...

  11. Insulin Resistance in Alzheimer's Disease

    PubMed Central

    Dineley, Kelly T; Jahrling, Jordan B; Denner, Larry

    2014-01-01

    Insulin is a key hormone regulating metabolism. Insulin binding to cell surface insulin receptors engages many signaling intermediates operating in parallel and in series to control glucose, energy, and lipids while also regulating mitogenesis and development. Perturbations in the function of any of these intermediates, which occur in a variety of diseases, cause reduced sensitivity to insulin and insulin resistance with consequent metabolic dysfunction. Chronic inflammation ensues which exacerbates compromised metabolic homeostasis. Since insulin has a key role in learning and memory as well as directly regulating ERK, a kinase required for the type of learning and memory compromised in early Alzheimer's disease (AD), insulin resistance has been identified as a major risk factor for the onset of AD. Animal models of AD or insulin resistance or both demonstrate that AD pathology and impaired insulin signaling form a reciprocal relationship. Of note are human and animal model studies geared toward improving insulin resistance that have led to the identification of the nuclear receptor and transcription factor, peroxisome proliferator-activated receptor gamma (PPARγ) as an intervention tool for early AD. Strategic targeting of alternate nodes within the insulin signaling network has revealed disease-stage therapeutic windows in animal models that coalesce with previous and ongoing clinical trial approaches. Thus, exploiting the connection between insulin resistance and AD provides powerful opportunities to delineate therapeutic interventions that slow or block the pathogenesis of AD. PMID:25237037

  12. Salivary Secretory Disorders, Inducing Drugs, and Clinical Management

    PubMed Central

    Miranda-Rius, Jaume; Brunet-Llobet, Lluís; Lahor-Soler, Eduard; Farré, Magí

    2015-01-01

    Background: Salivary secretory disorders can be the result of a wide range of factors. Their prevalence and negative effects on the patient's quality of life oblige the clinician to confront the issue. Aim: To review the salivary secretory disorders, inducing drugs and their clinical management. Methods: In this article, a literature search of these dysfunctions was conducted with the assistance of a research librarian in the MEDLINE/PubMed Database. Results: Xerostomia, or dry mouth syndrome, can be caused by medication, systemic diseases such as Sjögren's Syndrome, glandular pathologies, and radiotherapy of the head and neck. Treatment of dry mouth is aimed at both minimizing its symptoms and preventing oral complications with the employment of sialogogues and topical acting substances. Sialorrhea and drooling, are mainly due to medication or neurological systemic disease. There are various therapeutic, pharmacologic, and surgical alternatives for its management. The pharmacology of most of the substances employed for the treatment of salivary disorders is well-known. Nevertheless, in some cases a significant improvement in salivary function has not been observed after their administration. Conclusion: At present, there are numerous frequently prescribed drugs whose unwanted effects include some kind of salivary disorder. In addition, the differing pathologic mechanisms, and the great variety of existing treatments hinder the clinical management of these patients. The authors have designed an algorithm to facilitate the decision making process when physicians, oral surgeons, or dentists face these salivary dysfunctions. PMID:26516310

  13. Hydrogen sulfide alleviates cardiac contractile dysfunction in an Akt2-knockout murine model of insulin resistance: role of mitochondrial injury and apoptosis

    PubMed Central

    Hu, Nan; Dong, Maolong

    2014-01-01

    Hydrogen sulfide (H2S) is a toxic gas now being recognized as an endogenous signaling molecule in multiple organ systems, in particular, the cardiovascular system. H2S is known to regulate cardiac function and protect against ischemic injury. However, little information is available regarding the effect of H2S on cardiac function in insulin resistance. This study was designed to examine the impact of H2S supplementation on cardiac function using an Akt2 knockout model of insulin resistance. Wild-type and Akt2 knockout mice were treated with NaHS (50 μM·kg−1·day−1 ip for 10 days) prior to evaluation of echocardiographic, cardiomyocyte contractile, and intracellular Ca2+ properties, apoptosis, and mitochondrial damage. Our results revealed that Akt2 ablation led to overtly enlarged ventricular end-systolic diameter, reduced myocardial and cardiomyocyte contractile function, and disrupted intracellular Ca2+ homeostasis and apoptosis, the effects of which were ameliorated by H2S. Furthermore, Akt2 knockout displayed upregulated apoptotic protein markers (Bax, caspase-3, caspase-9, and caspace-12) and mitochondrial damage (reduced aconitase activity and NAD+, elevated cytochrome-c release from mitochondria) along with reduced phosphorylation of PTEN, Akt, and GSK3β in the absence of changes in pan protein expression, the effects of which were abolished or significantly ameliorated by H2S treatment. In vitro data revealed that H2S-induced beneficial effect against Akt2 ablation was obliterated by mitochondrial uncoupling. Taken together, our findings suggest the H2S may reconcile Akt2 knockout-induced myocardial contractile defect and intracellular Ca2+ mishandling, possibly via attenuation of mitochondrial injury and apoptosis. PMID:24622975

  14. Favorable outcomes of hydroxychloroquine in insulin resistance may be accomplished by adjustment of the endothelial dysfunction as well as the skewed balance of adipokines.

    PubMed

    Abdel-Hamid, Ahmed A M; Firgany, Alaa El-Din L

    2016-07-01

    Hydroxychloroquine (HCQ) has been demonstrated to reduce the risk to develop diabetes mellitus (DM). However no previous experimental study had investigated its effect on the structure of the endocrine pancreas, islets of Langerhans (IOL), in insulin resistance (IR). In addition, the mechanism by which HCQ can prevent DM is not well understood. In this study, we hypothesized that the possible favorable outcome of HCQ may be partly achieved by its molecular effect on the endothelial stress markers as well as on the imparied balance of the adipokines that usually accompanies IR. A total of 54 rats were divided equally into; control, high fat diet (HFD) and HFD+HCQ groups (received standard chow, HFD and HFD+HCQ respectively). After 12 weeks, samples from pancreas as well as visceral adipose tissue (VAT) were histologically studied for the consequent changes. In the HFD group, there were mild degenerative changes and expansion of the IOL accompanied with a significantly increased (p<0.05) β-cell area%, mass, proliferation and neogenesis as well as a significantly decreased (p<0.05) α-cell area% compared with the other groups. On combining HCQ with HFD, reversal of these changes along with correction of the impaired adipokines levels (leptin, adiponectin, resistin, visfatin and lipocalin-2) and significant decrease (p<0.05) of the vascular endothelial stress markers (sE-selectin, sICAM and sVICAM) were manifested compared with the HFD group. Therefore, HCQ favorable effects in IR may be attributed to relieving of the endothelial stress as well as normalization of the skewed balance of adipokines. PMID:27320898

  15. Insulin Signaling and Heart Failure.

    PubMed

    Riehle, Christian; Abel, E Dale

    2016-04-01

    Heart failure is associated with generalized insulin resistance. Moreover, insulin-resistant states such as type 2 diabetes mellitus and obesity increases the risk of heart failure even after adjusting for traditional risk factors. Insulin resistance or type 2 diabetes mellitus alters the systemic and neurohumoral milieu, leading to changes in metabolism and signaling pathways in the heart that may contribute to myocardial dysfunction. In addition, changes in insulin signaling within cardiomyocytes develop in the failing heart. The changes range from activation of proximal insulin signaling pathways that may contribute to adverse left ventricular remodeling and mitochondrial dysfunction to repression of distal elements of insulin signaling pathways such as forkhead box O transcriptional signaling or glucose transport, which may also impair cardiac metabolism, structure, and function. This article will review the complexities of insulin signaling within the myocardium and ways in which these pathways are altered in heart failure or in conditions associated with generalized insulin resistance. The implications of these changes for therapeutic approaches to treating or preventing heart failure will be discussed. PMID:27034277

  16. Potent Insulin Secretagogue from Scoparia dulcis Linn of Nepalese Origin.

    PubMed

    Sharma, Khaga Raj; Adhikari, Achyut; Hafizur, Rahman M; Hameed, Abdul; Raza, Sayed Ali; Kalauni, Surya Kant; Miyazaki, Jun-Ichi; Choudhary, M Iqbal

    2015-10-01

    Ethno-botanical inspired isolation from plant Scoparia dulcis Linn. (Sweet Broomweed) yielded six compounds, coixol (1), glutinol (2), glutinone (3), friedelin (4), betulinic acid (5), and tetratriacontan-1-ol (6). There structures were identified using mass and 1D- and 2D-NMR spectroscopy techniques. Compounds 1-6 were evaluated for their insulin secretory activity on isolated mice islets and MIN-6 pancreatic β-cell line, and compounds 1 and 2 were found to be potent and mildly active, respectively. Compound 1 was further evaluated for insulin secretory activity on MIN-6 cells. Compound 1 was subjected to in vitro cytotoxicity assay against MIN-6, 3T3 cell lines, and islet cells, and in vivo acute toxicity test in mice that was found to be non-toxic. The insulin secretory activity of compounds 1 and 2 supported the ethno-botanic uses of S. dulcis as an anti-diabetic agent. PMID:26178652

  17. Rac1 Regulates Endometrial Secretory Function to Control Placental Development.

    PubMed

    Davila, Juanmahel; Laws, Mary J; Kannan, Athilakshmi; Li, Quanxi; Taylor, Robert N; Bagchi, Milan K; Bagchi, Indrani C

    2015-08-01

    During placenta development, a succession of complex molecular and cellular interactions between the maternal endometrium and the developing embryo ensures reproductive success. The precise mechanisms regulating this maternal-fetal crosstalk remain unknown. Our study revealed that the expression of Rac1, a member of the Rho family of GTPases, is markedly elevated in mouse decidua on days 7 and 8 of gestation. To investigate its function in the uterus, we created mice bearing a conditional deletion of the Rac1 gene in uterine stromal cells. Ablation of Rac1 did not affect the formation of the decidua but led to fetal loss in mid gestation accompanied by extensive hemorrhage. To gain insights into the molecular pathways affected by the loss of Rac1, we performed gene expression profiling which revealed that Rac1 signaling regulates the expression of Rab27b, another GTPase that plays a key role in targeting vesicular trafficking. Consequently, the Rac1-null decidual cells failed to secrete vascular endothelial growth factor A, which is a critical regulator of decidual angiogenesis, and insulin-like growth factor binding protein 4, which regulates the bioavailability of insulin-like growth factors that promote proliferation and differentiation of trophoblast cell lineages in the ectoplacental cone. The lack of secretion of these key factors by Rac1-null decidua gave rise to impaired angiogenesis and dysregulated proliferation of trophoblast cells, which in turn results in overexpansion of the trophoblast giant cell lineage and disorganized placenta development. Further experiments revealed that RAC1, the human ortholog of Rac1, regulates the secretory activity of human endometrial stromal cells during decidualization, supporting the concept that this signaling G protein plays a central and conserved role in controlling endometrial secretory function. This study provides unique insights into the molecular mechanisms regulating endometrial secretions that mediate stromal

  18. Rac1 Regulates Endometrial Secretory Function to Control Placental Development

    PubMed Central

    Davila, Juanmahel; Laws, Mary J.; Kannan, Athilakshmi; Li, Quanxi; Taylor, Robert N.; Bagchi, Milan K.; Bagchi, Indrani C.

    2015-01-01

    During placenta development, a succession of complex molecular and cellular interactions between the maternal endometrium and the developing embryo ensures reproductive success. The precise mechanisms regulating this maternal-fetal crosstalk remain unknown. Our study revealed that the expression of Rac1, a member of the Rho family of GTPases, is markedly elevated in mouse decidua on days 7 and 8 of gestation. To investigate its function in the uterus, we created mice bearing a conditional deletion of the Rac1 gene in uterine stromal cells. Ablation of Rac1 did not affect the formation of the decidua but led to fetal loss in mid gestation accompanied by extensive hemorrhage. To gain insights into the molecular pathways affected by the loss of Rac1, we performed gene expression profiling which revealed that Rac1 signaling regulates the expression of Rab27b, another GTPase that plays a key role in targeting vesicular trafficking. Consequently, the Rac1-null decidual cells failed to secrete vascular endothelial growth factor A, which is a critical regulator of decidual angiogenesis, and insulin-like growth factor binding protein 4, which regulates the bioavailability of insulin-like growth factors that promote proliferation and differentiation of trophoblast cell lineages in the ectoplacental cone. The lack of secretion of these key factors by Rac1-null decidua gave rise to impaired angiogenesis and dysregulated proliferation of trophoblast cells, which in turn results in overexpansion of the trophoblast giant cell lineage and disorganized placenta development. Further experiments revealed that RAC1, the human ortholog of Rac1, regulates the secretory activity of human endometrial stromal cells during decidualization, supporting the concept that this signaling G protein plays a central and conserved role in controlling endometrial secretory function. This study provides unique insights into the molecular mechanisms regulating endometrial secretions that mediate stromal

  19. Secretory diarrhoea: mechanisms and emerging therapies

    PubMed Central

    Thiagarajah, Jay R.; Donowitz, Mark; Verkman, Alan S.

    2016-01-01

    Diarrhoeal disease remains a major health burden worldwide. Secretory diarrhoeas are caused by certain bacterial and viral infections, inflammatory processes, drugs and genetic disorders. Fluid secretion across the intestinal epithelium in secretory diarrhoeas involves multiple ion and solute transporters, as well as activation of cyclic nucleotide and Ca2+ signalling pathways. In many secretory diarrhoeas, activation of Cl− channels in the apical membrane of enterocytes, including the cystic fibrosis transmembrane conductance regulator and Ca2+-activated Cl− channels, increases fluid secretion, while inhibition of Na+ transport reduces fluid absorption. Current treatment of diarrhoea includes replacement of fluid and electrolyte losses using oral rehydration solutions, and drugs targeting intestinal motility or fluid secretion. Therapeutics in the development pipeline target intestinal ion channels and transporters, regulatory proteins and cell surface receptors. This Review describes pathogenic mechanisms of secretory diarrhoea, current and emerging therapeutics, and the challenges in developing antidiarrhoeal therapeutics. PMID:26122478

  20. Vesicular Nucleotide Transporter-Mediated ATP Release Regulates Insulin Secretion

    PubMed Central

    Geisler, Jessica C.; Corbin, Kathryn L.; Li, Qin; Feranchak, Andrew P.; Nunemaker, Craig S.

    2013-01-01

    Extracellular ATP plays a critical role in regulating insulin secretion in pancreatic β cells. The ATP released from insulin secretory vesicles has been proposed to be a major source of extracellular ATP. Currently, the mechanism by which ATP accumulates into insulin secretory granules remains elusive. In this study, the authors identified the expression of a vesicular nucleotide transporter (VNUT) in mouse pancreas, isolated mouse islets, and MIN6 cells, a mouse β cell line. Immunohistochemistry and immunofluorescence revealed that VNUT colocalized extensively with insulin secretory granules. Functional studies showed that suppressing endogenous VNUT expression in β cells by small hairpin RNA knockdown greatly reduced basal- and glucose-induced ATP release. Importantly, knocking down VNUT expression by VNUT small hairpin RNA in MIN6 cells and isolated mouse islets dramatically suppressed basal insulin release and glucose-stimulated insulin secretion (GSIS). Moreover, acute pharmacologic blockade of VNUT with Evans blue, a VNUT antagonist, greatly attenuated GSIS in a dose-dependent manner. Exogenous ATP treatment effectively reversed the insulin secretion defect induced by both VNUT knockdown and functional inhibition, indicating that VNUT-mediated ATP release is essential for maintaining normal insulin secretion. In contrast to VNUT knockdown, overexpression of VNUT in β cells resulted in excessive ATP release and enhanced basal insulin secretion and GSIS. Elevated insulin secretion induced by VNUT overexpression was reversed by pharmacologic inhibition of P2X but not P2Y purinergic receptors. This study reveals VNUT is expressed in pancreatic β cells and plays an essential and novel role in regulating insulin secretion through vesicular ATP release and extracellular purinergic signaling. PMID:23254199

  1. Porosome: The Universal Secretory Portal in Cells

    NASA Astrophysics Data System (ADS)

    Jena, Bhanu

    2012-10-01

    In the past 50 years it was believed that during cell secretion, membrane-bound secretory vesicles completely merge at the cell plasma membrane resulting in the diffusion of intra-vesicular contents to the cell exterior and the compensatory retrieval of the excess membrane by endocytosis. This explanation made no sense or logic, since following cell secretion partially empty vesicles accumulate as demonstrated in electron micrographs. Furthermore, with the ``all or none'' mechanism of cell secretion by complete merger of secretory vesicle membrane at the cell plasma membrane, the cell is left with little regulation and control of the amount of content release. Moreover, it makes no sense for mammalian cells to possess such `all or none' mechanism of cell secretion, when even single-cell organisms have developed specialized and sophisticated secretory machinery, such as the secretion apparatus of Toxoplasma gondii, the contractile vacuoles in paramecium, or the various types of secretory structures in bacteria. Therefore, in 1993 in a News and Views article in Nature, E. Neher wrote ``It seems terribly wasteful that, during the release of hormones and neurotransmitters from a cell, the membrane of a vesicle should merge with the plasma membrane to be retrieved for recycling only seconds or minutes later.'' This conundrum in the molecular mechanism of cell secretion was finally resolved in 1997 following discovery of the ``Porosome,'' the universal secretory machinery in cells. Porosomes are supramolecular lipoprotein structures at the cell plasma membrane, where membrane-bound secretory vesicles transiently dock and fuse to release inravesicular contents to the outside during cell secretion. In the past decade, the composition of the porosome, its structure and dynamics at nm resolution and in real time, and its functional reconstitution into artificial lipid membrane, have all been elucidated. Since porosomes in exocrine and neuroendocrine cells measure 100-180 nm

  2. Oral Insulin

    PubMed Central

    2010-01-01

    Oral insulin is an exciting area of research and development in the field of diabetology. This brief review covers the various approaches used in the development of oral insulin, and highlights some of the recent data related to novel oral insulin preparation. PMID:21059246

  3. Diastolic Dysfunction

    PubMed Central

    Jeong, Euy-Myoung; Dudley, Samuel C.

    2016-01-01

    Despite the growing number of patients affected, the understanding of diastolic dysfunction and heart failure with preserved ejection fraction (HFpEF) is still poor. Clinical trials, largely based on successful treatments for systolic heart failure, have been disappointing, suggesting that HFpEF has a different pathology to that of systolic dysfunction. In this review, general concepts, epidemiology, diagnosis, and treatment of diastolic dysfunction are summarized, with an emphasis on new experiments suggesting that oxidative stress plays a crucial role in the pathogenesis of at least some forms of the disease. This observation has lead to potential new diagnostics and therapeutics for diastolic dysfunction and heart failure caused by diastolic dysfunction. PMID:25746522

  4. Protein mobility within secretory granules.

    PubMed

    Weiss, Annita Ngatchou; Bittner, Mary A; Holz, Ronald W; Axelrod, Daniel

    2014-07-01

    We investigated the basis for previous observations that fluorescent-labeled neuropeptide Y (NPY) is usually released within 200 ms after fusion, whereas labeled tissue plasminogen activator (tPA) is often discharged over many seconds. We found that tPA and NPY are endogenously expressed in small and different subpopulations of bovine chromaffin cells in culture. We measured the mobility of these proteins (tagged with fluorophore) within the lumen of individual secretory granules in living chromaffin cells, and related their mobilities to postfusion release kinetics. A method was developed that is not limited by standard optical resolution, in which a bright flash of strongly decaying evanescent field (∼64 nm exponential decay constant) produced by total internal reflection (TIR) selectively bleaches cerulean-labeled protein proximal to the glass coverslip within individual granules. Fluorescence recovery occurred as unbleached protein from distal regions within the 300 nm granule diffused into the bleached proximal regions. The fractional bleaching of tPA-cerulean (tPA-cer) was greater when subsequently probed with TIR excitation than with epifluorescence, indicating that tPA-cer mobility was low. The almost equal NPY-cer bleaching when probed with TIR and epifluorescence indicated that NPY-cer equilibrated within the 300 ms bleach pulse, and therefore had a greater mobility than tPA-cer. TIR-fluorescence recovery after photobleaching revealed a significant recovery of tPA-cer (but not NPY-cer) fluorescence within several hundred milliseconds after bleaching. Numerical simulations, which take into account bleach duration, granule diameter, and the limited number of fluorophores in a granule, are consistent with tPA-cer being 100% mobile, with a diffusion coefficient of 2 × 10(-10) cm(2)/s (∼1/3000 of that for a protein of similar size in aqueous solution). However, the low diffusive mobility of tPA cannot alone explain its slow postfusion release. In the

  5. Selective screening of secretory vesicle-associated proteins for autoantigens in type 1 diabetes: VAMP2 and NPY are new minor autoantigens.

    PubMed

    Hirai, Hiroki; Miura, Junnosuke; Hu, Yafang; Larsson, Helena; Larsson, Karin; Lernmark, Ake; Ivarsson, Sten-A; Wu, Tianxia; Kingman, Albert; Tzioufas, Athanasios G; Notkins, Abner L

    2008-06-01

    The four major autoantigens (IA-2, IA-2 beta, GAD65 and insulin) of type 1 diabetes are all associated with dense core or synaptic vesicles. This raised the possibility that other secretory vesicle-associated proteins might be targets of the autoimmune response in type 1 diabetes. To test this hypothesis 56 proteins, two-thirds of which are associated with secretory vesicles, were prepared by in vitro transcription/translation and screened for autoantibodies by liquid phase radioimmunoprecipitation. Two secretory vesicle-associated proteins, VAMP2 and NPY, were identified as new minor autoantigens with 21% and 9%, respectively, of 200 type 1 diabetes sera reacting positively. These findings add support to the hypothesis that secretory vesicle-associated proteins are particularly important, but not the exclusive, targets of the autoimmune response in type 1 diabetes. Selective screening of the human proteome offers a useful approach for identifying new autoantigens in autoimmune diseases. PMID:18359275

  6. Biosimilar Insulins

    PubMed Central

    Hompesch, Marcus

    2014-01-01

    Until now most of the insulin used in developed countries has been manufactured and distributed by a small number of multinational companies. Beyond the established insulin manufacturers, a number of new players have developed insulin manufacturing capacities based on modern biotechnological methods. Because the patents for many of the approved insulin formulations have expired or are going to expire soon, these not yet established companies are increasingly interested in seeking market approval for their insulin products as biosimilar insulins (BI) in highly regulated markets like the EU and the United States. Differences in the manufacturing process (none of the insulin manufacturing procedures are 100% identical) can lead to insulins that to some extent may differ from the originator insulin. The key questions are if subtle differences in the structure of the insulins, purity, and so on are clinically relevant and may result in different biological effects. The aim of this article is to introduce and discuss basic aspects that may be of relevance with regard to BI. PMID:24876530

  7. Biosimilar insulins.

    PubMed

    Heinemann, Lutz

    2012-08-01

    Until now most insulin used in developed countries is manufactured and distributed by a small number of multinational companies. Other pharmaceutical companies - many of these are located in countries such as India or China - are also able to manufacture insulin with modern biotechnological methods. Additionally, the patents for many insulin formulations have expired or are going to expire soon. This enables such companies to produce insulins and to apply for market approval of these as biosimilar insulins (BIs) in highly regulated markets such as the EU or the US. To understand the complexity of BIs' approval and usage, scientific and regulatory aspects have to be discussed. Differences in the manufacturing process (none of the insulin-manufacturing procedures are identical) result in the fact that all insulin that might become BIs differ from the originator insulin to some extent. The question is, have such differences in the structure of the insulin molecule and or the purity and so on clinically relevant consequences for the biological effects induced or not. The guidelines already in place in the EU for market approval require that the manufacturer demonstrates that his insulin has a safety and efficacy profile that is similar to that of the 'original' insulin formulation. Recently guidelines for biosimilars were issued in the US; however, these do not cover insulin. Although a challenging approval process for insulins to become BI might be regarded as a hurdle to keep companies out of certain markets, it is fair to say that the potential safety and efficacy issues surrounding BI are substantial and relevant, and do warrant a careful and evidence-driven approval process. Nevertheless, it is very likely that in the next years, BIs will come to the market also in highly regulated markets. PMID:22583127

  8. Globular adiponectin ameliorates metabolic insulin resistance via AMPK-mediated restoration of microvascular insulin responses.

    PubMed

    Zhao, Lina; Fu, Zhuo; Wu, Jing; Aylor, Kevin W; Barrett, Eugene J; Cao, Wenhong; Liu, Zhenqi

    2015-09-01

    Adiponectin is an adipokine with anti-inflammatory and anti-diabetic properties. Hypoadiponectinaemia is closely associated with endothelial dysfunction and insulin resistance in obesity and diabetes. Insulin resistance is present in muscle microvasculature and this may contribute to decreased insulin delivery to, and action in, muscle. In this study we examined whether adiponectin ameliorates metabolic insulin resistance by affecting muscle microvascular recruitment. We demonstrated that a high-fat diet induces vascular adiponectin and insulin resistance but globular adiponectin administration can restore vascular insulin responses and improve insulin's metabolic action via an AMPK- and nitric oxide-dependent mechanism. This suggests that globular adiponectin might have a therapeutic potential for improving insulin resistance and preventing cardiovascular complications in patients with diabetes via modulation of microvascular insulin responses. Hypoadiponectinaemia is closely associated with endothelial dysfunction and insulin resistance, and microvasculature plays a critical role in the regulation of insulin action in muscle. Here we tested whether adiponectin replenishment could improve metabolic insulin sensitivity in male rats fed a high-fat diet (HFD) via the modulation of microvascular insulin responses. Male Sprague-Dawley rats were fed either a HFD or low-fat diet (LFD) for 4 weeks. Small resistance artery myograph changes in tension, muscle microvascular recruitment and metabolic response to insulin were determined. Compared with rats fed a LFD, HFD feeding abolished the vasodilatory actions of globular adiponectin (gAd) and insulin on pre-constricted distal saphenous arteries. Pretreatment with gAd improved insulin responses in arterioles isolated from HFD rats, which was blocked by AMP-activated protein kinase (AMPK) inhibition. Similarly, HFD abolished microvascular responses to either gAd or insulin and decreased insulin-stimulated glucose disposal by

  9. Exogenous Insulin Enhances Glucose-Stimulated Insulin Response in Healthy Humans Independent of Changes in Free Fatty Acids

    PubMed Central

    Lopez, Ximena; Cypess, Aaron; Manning, Raquel; O'Shea, Sheila; Kulkarni, Rohit N.

    2011-01-01

    Context: Islet β-cells express both insulin receptors and insulin signaling proteins. Recent studies suggest insulin signaling is physiologically important for glucose sensing. Objective: Preexposure to insulin enhances glucose-stimulated insulin secretion (GSIS) in healthy humans. We evaluated whether the effect of insulin to potentiate GSIS is modulated through regulation of free fatty acids (FFA). Design and Setting: Subjects were studied on three occasions in this single-site study at an academic institution clinical research center. Patients: Subjects included nine healthy volunteers. Interventions: Glucose-induced insulin response was assessed on three occasions after 4 h saline (low insulin/sham) or isoglycemic-hyperinsulinemic (high insulin) clamps with or without intralipid and heparin infusion, using B28 Asp-insulin that could be distinguished from endogenous insulin immunologically. During the last 80 min of all three clamps, additional glucose was administered to stimulate insulin secretion (GSIS) with glucose concentrations maintained at similar concentrations during all studies. Main Outcome Measure: β-Cell response to glucose stimulation was assessed. Results: Preexposure to exogenous insulin increased the endogenous insulin-secretory response to glucose by 32% compared with sham clamp (P = 0.001). This was accompanied by a drop in FFA during hyperinsulinemic clamp compared with the sham clamp (0.06 ± 0.02 vs. 0.60 ± 0.09 mEq/liter, respectively), which was prevented during the hyperinsulinemic clamp with intralipid/heparin infusion (1.27 ± 0.17 mEq/liter). After preexposure to insulin with intralipid/heparin infusion to maintain FFA concentration, GSIS was 21% higher compared with sham clamp (P < 0.04) and similar to preexposure to insulin without intralipid/heparin (P = 0.2). Conclusions: Insulin potentiates glucose-stimulated insulin response independent of FFA concentrations in healthy humans. PMID:21956413

  10. Myosin Va Transports Dense Core Secretory Vesicles in Pancreatic MIN6 β-CellsV⃞

    PubMed Central

    Varadi, Aniko; Tsuboi, Takashi; Rutter, Guy A.

    2005-01-01

    The role of unconventional myosins in neuroendocrine cells is not fully understood, with involvement suggested in the movement of both secretory vesicles and mitochondria. Here, we demonstrate colocalization of myosin Va (MyoVa) with insulin in pancreatic β-cells and show that MyoVa copurifies with insulin in density gradients and with the vesicle marker phogrin-enhanced green fluorescent protein upon fluorescence-activated sorting of vesicles. By contrast, MyoVa immunoreactivity was poorly colocalized with mitochondrial or other markers. Demonstrating an important role for MyoVa in the recruitment of secretory vesicles to the cell surface, a reduction of MyoVa protein levels achieved by RNA interference caused a significant decrease in glucose- or depolarization-stimulated insulin secretion. Similarly, expression of the dominant-negative–acting globular tail domain of MyoVa decreased by ∼50% the number of vesicles docked at the plasma membrane and by 87% the number of depolarization-stimulated exocytotic events detected by total internal reflection fluorescence microscopy. We conclude that MyoVa-driven movements of vesicles along the cortical actin network are essential for the terminal stages of regulated exocytosis in β-cells. PMID:15788565

  11. Toxoplasma secretory granules: one population or more?

    PubMed

    Mercier, Corinne; Cesbron-Delauw, Marie-France

    2015-02-01

    In Toxoplasma gondii, dense granules are known as the storage secretory organelles of the so-called GRA proteins (for dense granule proteins), which are destined to the parasitophorous vacuole (PV) and the PV-derived cyst wall. Recently, newly annotated GRA proteins targeted to the host cell nucleus have enlarged this view. Here we provide an update on the latest developments on the Toxoplasma secreted proteins, which to date have been mainly studied at both the tachyzoite and bradyzoite stages, and we point out that recent discoveries could open the issue of a possible, yet uncharacterized, distinct secretory pathway in Toxoplasma. PMID:25599584

  12. Quality control in the secretory assembly line.

    PubMed Central

    Helenius, A

    2001-01-01

    As a rule, only proteins that have reached a native, folded and assembled structure are transported to their target organelles and compartments within the cell. In the secretory pathway of eukaryotic cells, this type of sorting is particularly important. A variety of molecular mechanisms are involved that distinguish between folded and unfolded proteins, modulate their intracellular transport, and induce degradation if they fail to fold. This phenomenon, called quality control, occurs at several levels and involves different types of folding sensors. The quality control system provides a stringent and versatile molecular sorting system that guaranties fidelity of protein expression in the secretory pathway. PMID:11260794

  13. Erectile dysfunction.

    PubMed

    Yafi, Faysal A; Jenkins, Lawrence; Albersen, Maarten; Corona, Giovanni; Isidori, Andrea M; Goldfarb, Shari; Maggi, Mario; Nelson, Christian J; Parish, Sharon; Salonia, Andrea; Tan, Ronny; Mulhall, John P; Hellstrom, Wayne J G

    2016-01-01

    Erectile dysfunction is a multidimensional but common male sexual dysfunction that involves an alteration in any of the components of the erectile response, including organic, relational and psychological. Roles for nonendocrine (neurogenic, vasculogenic and iatrogenic) and endocrine pathways have been proposed. Owing to its strong association with metabolic syndrome and cardiovascular disease, cardiac assessment may be warranted in men with symptoms of erectile dysfunction. Minimally invasive interventions to relieve the symptoms of erectile dysfunction include lifestyle modifications, oral drugs, injected vasodilator agents and vacuum erection devices. Surgical therapies are reserved for the subset of patients who have contraindications to these nonsurgical interventions, those who experience adverse effects from (or are refractory to) medical therapy and those who also have penile fibrosis or penile vascular insufficiency. Erectile dysfunction can have deleterious effects on a man's quality of life; most patients have symptoms of depression and anxiety related to sexual performance. These symptoms, in turn, affect his partner's sexual experience and the couple's quality of life. This Primer highlights numerous aspects of erectile dysfunction, summarizes new treatment targets and ongoing preclinical studies that evaluate new pharmacotherapies, and covers the topic of regenerative medicine, which represents the future of sexual medicine. PMID:27188339

  14. Extracellular CADM1 interactions influence insulin secretion by rat and human islet β-cells and promote clustering of syntaxin-1.

    PubMed

    Zhang, Charles; Caldwell, Thomas A; Mirbolooki, M Reza; Duong, Diana; Park, Eun Jee; Chi, Nai-Wen; Chessler, Steven D

    2016-06-01

    Contact between β-cells is necessary for their normal function. Identification of the proteins mediating the effects of β-cell-to-β-cell contact is a necessary step toward gaining a full understanding of the determinants of β-cell function and insulin secretion. The secretory machinery of the β-cells is nearly identical to that of central nervous system (CNS) synapses, and we hypothesize that the transcellular protein interactions that drive maturation of the two secretory machineries upon contact of one cell (or neural process) with another are also highly similar. Two such transcellular interactions, important for both synaptic and β-cell function, have been identified: EphA/ephrin-A and neuroligin/neurexin. Here, we tested the role of another synaptic cleft protein, CADM1, in insulinoma cells and in rat and human islet β-cells. We found that CADM1 is a predominant CADM isoform in β-cells. In INS-1 cells and primary β-cells, CADM1 constrains insulin secretion, and its expression decreases after prolonged glucose stimulation. Using a coculture model, we found that CADM1 also influences insulin secretion in a transcellular manner. We asked whether extracellular CADM1 interactions exert their influence via the same mechanisms by which they influence neurotransmitter exocytosis. Our results suggest that, as in the CNS, CADM1 interactions drive exocytic site assembly and promote actin network formation. These results support the broader hypothesis that the effects of cell-cell contact on β-cell maturation and function are mediated by the same extracellular protein interactions that drive the formation of the presynaptic exocytic machinery. These interactions may be therapeutic targets for reversing β-cell dysfunction in diabetes. PMID:27072493

  15. INSULIN BIOSYNTHESIS IN THE RAT: DEMONSTRATION OF TWO PROINSULINS*

    PubMed Central

    Clark, Jeffrey L.; Steiner, Donald F.

    1969-01-01

    Proinsulin, a single-chain precursor of insulin, has been detected in biosynthetic studies in vitro,1-4 and in crystalline preparations of insulin from several species.1, 5-7 It appears that proinsulin normally serves neither as a major storage nor secretory form of the hormone.8 Its primary functions seems to be to facilitate the efficient formation of the disulfide bonds of insulin.9 Although several species of fish have two insulins differing slightly in primary structure,10-12 the rat is the only mammal where this is known to be the case.13, 14 As the two rat insulins are nonallelic14 and presumably coded by two distinct genes, a separate proinsulin would be expected to precede each insulin. We have demonstrated the biosynthesis of both insulins15 and of a proinsulin corresponding to each in isolated islets of Langerhans, and have detected probable intermediates in the conversion of these proinsulins to insulin. Labeled peptide material corresponding to the free connecting segment of proinsulin (C-peptide) was detected in insulin-containing fractions isolated from incubated rat islets. It was noted that islets incubated in vitro secreted small amounts of newly synthesized proinsulin as well as the two insulins and essentially equivalent amounts of C-peptide. Increasing the glucose content of the medium selectively enhanced the incorporation of radioactivity into proinsulin and insulin and also seemed to increase the relative proportion of labeled proinsulin appearing in the medium. Images PMID:4890253

  16. Insulin resistance and insulin sensitizers.

    PubMed

    Stumvoll, M; Häring, H

    2001-01-01

    Insulin resistance is a key factor in the pathogenesis of type 2 diabetes mellitus and a co-factor in the development of dyslipidaemia, hypertension and atherosclerosis. The causes of insulin resistance include factors such as obesity and physical inactivity, and there may also be genetic factors. The mechanism of obesity-related insulin resistance involves the release of factors from adipocytes which exert a negative effect on glucose metabolism: free fatty acids, tumour necrosis factor-alpha and the recently discovered hormone, resistin. The two resulting abnormalities observed consistently in glucose-intolerant states are impaired suppression of endogenous glucose production, and impaired stimulation of glucose uptake. Among the genetic factors, a polymorphism (Pro12Ala) in the peroxisome proliferator-activated receptor (PPAR) gamma is associated with a reduced risk of type 2 diabetes mellitus and increased insulin sensitivity, primarily that of lipolysis. On the other hand, the association with insulin resistance of a common polymorphism (Gly972Arg) in the insulin receptor substrate 1, long believed to be a plausible candidate gene, is weak at best. This polymorphism may instead be associated with reduced insulin secretion, which, in view of the recent recognition of the insulin signalling system in beta-cells, results in the development of a novel pathogenic concept. Finally, fine-mapping and positional cloning of the susceptibility locus on chromosome 2 resulted in the identification of a polymorphism (UCSNP-43 G/A) in the calpain-10 gene. In non-diabetic Pima Indians, this polymorphism was associated with insulin resistance of glucose disposal. The pharmacological treatment of insulin resistance has recently acquired a novel class of agents: the thiazolidinediones. They act through regulation of PPARgamma-dependent genes and probably interfere favourably with factors released from adipocytes which mediate obesity-associated insulin resistance. PMID:11684868

  17. Gustatory dysfunction

    PubMed Central

    Maheswaran, T.; Abikshyeet, P.; Sitra, G.; Gokulanathan, S.; Vaithiyanadane, V.; Jeelani, S.

    2014-01-01

    Tastes in humans provide a vital tool for screening soluble chemicals for food evaluation, selection, and avoidance of potentially toxic substances. Taste or gustatory dysfunctions are implicated in loss of appetite, unintended weight loss, malnutrition, and reduced quality of life. Dental practitioners are often the first clinicians to be presented with complaints about taste dysfunction. This brief review provides a summary of the common causes of taste disorders, problems associated with assessing taste function in a clinical setting and management options available to the dental practitioner. PMID:25210380

  18. Insulin Protects against Hepatic Damage Postburn

    PubMed Central

    Jeschke, Marc G; Kraft, Robert; Song, Juquan; Gauglitz, Gerd G; Cox, Robert A; Brooks, Natasha C; Finnerty, Celeste C; Kulp, Gabriela A; Herndon, David N; Boehning, Darren

    2011-01-01

    Burn injury causes hepatic dysfunction associated with endoplasmic reticulum (ER) stress and induction of the unfolded protein response (UPR). ER stress/UPR leads to hepatic apoptosis and activation of the Jun-N-terminal kinase (JNK) signaling pathway, leading to vast metabolic alterations. Insulin has been shown to attenuate hepatic damage and to improve liver function. We therefore hypothesized that insulin administration exerts its effects by attenuating postburn hepatic ER stress and subsequent apoptosis. Male Sprague Dawley rats received a 60% total body surface area (TBSA) burn injury. Animals were randomized to receive saline (controls) or insulin (2.5 IU/kg q. 24 h) and euthanized at 24 and 48 h postburn. Burn injury induced dramatic changes in liver structure and function, including induction of the ER stress response, mitochondrial dysfunction, hepatocyte apoptosis, and up-regulation of inflammatory mediators. Insulin decreased hepatocyte caspase-3 activation and apoptosis significantly at 24 and 48 h postburn. Furthermore, insulin administration decreased ER stress significantly and reversed structural and functional changes in hepatocyte mitochondria. Finally, insulin attenuated the expression of inflammatory mediators IL-6, MCP-1, and CINC-1. Insulin alleviates burn-induced ER stress, hepatocyte apoptosis, mitochondrial abnormalities, and inflammation leading to improved hepatic structure and function significantly. These results support the use of insulin therapy after traumatic injury to improve patient outcomes. PMID:21267509

  19. Insulin Resistance and Heart Failure: Molecular Mechanisms

    PubMed Central

    Aroor, Annayya R.; Mandavia, Chirag H.; Sowers, James R.

    2012-01-01

    Insulin resistance and associated reductions in cardiac insulin metabolic signaling is emerging as a major factor for the development of heart failure and assumes more importance because of an epidemic increase in obesity and the cardiorenal metabolic syndrome and our aging population. Major factors contributing to the development of cardiac insulin resistance are oxidative stress, hyperglycemia, hyperlipidemia, dysregulated secretion of adipokines/cytokines and inappropriate activation of renin-angiotensin II-aldosterone system (RAAS) and the sympathetic nervous system. The effects of cardiac insulin resistance are exacerbated by metabolic, endocrine and cytokine alterations associated with systemic insulin resistance. The aggregate of these various alterations leads to an insulin resistant phenotype with metabolic inflexibility, impaired calcium handling, mitochondrial dysfunction and oxidative stress, dysregulated myocardial-endothelial interactions resulting in energy deficiency, impaired diastolic dysfunction, myocardial cell death and cardiac fibrosis. Therefore, understanding the molecular mechanisms linking insulin resistance and heart failure may help to design new and more effective mechanism-based drugs to improve myocardial and systemic insulin resistance. PMID:22999243

  20. Insulin requirements in patients with diabetes and declining kidney function: differences between insulin analogues and human insulin?

    PubMed Central

    Kulozik, Felix

    2013-01-01

    Objectives: In diabetic nephropathy the decline of renal function causes modifications of the insulin and carbohydrate metabolism resulting in changed insulin requirements. The aim of the present study was to identify potential differences in the requirements of human insulin and various insulin analogues in patients with type 1 diabetes mellitus and renal dysfunction. Methods: The insulin requirements of 346 patients with type 1 diabetes mellitus under everyday life circumstances were assessed in an observational study. Simultaneously, laboratory parameters were measured and the estimated glomerular filtration rate (eGFR) was calculated using the formula by Cockcroft–Gault. Medical history and concomitant medication were recorded. The insulin requirements of long- and short-acting insulin were tested for a relationship with the eGFR and laboratory parameters. Results: The dosage of long-acting human insulin did not show any relation to eGFR. In contrast, a strong positive relation between dosage and renal function was found for insulin glargine and insulin detemir. After classification according to renal function, the insulin dosage at eGFR less than 60 ml/min was 29.7% lower in glargine-treated and 27.3% lower in detemir-treated patients compared with eGFR greater than 90 ml/min. Considering the whole range of eGFR, short-acting human insulin did not show a relation with renal function. Only after classification according to renal function was a dose reduction found for human insulin at eGFR less than 60 ml/min. In contrast, requirements of insulin lispro were significantly related to eGFR over the whole range of eGFR. At eGFR less than 60 ml/min the insulin dosage was 32.6% lower than at eGFR greater than 90 ml/min. The requirements of insulin aspart did not show any association with the eGFR. Conclusions: Patients with type 1 diabetes mellitus show different insulin requirements according to the renal function depending on the applied insulin. This finding is

  1. Ejaculatory dysfunction.

    PubMed

    Phillips, Elizabeth; Carpenter, Christina; Oates, Robert D

    2014-02-01

    Ejaculatory dysfunction may occur after many different disorders ranging from traumatic spinal cord injury to diabetes mellitus. With an understanding of the many facets and nuances of the ejaculatory apparatus, both anatomic and neurologic, the well-versed clinician can proceed along a safe, efficient, and appropriate treatment algorithm to help affected men and their partners achieve parenthood. PMID:24286771

  2. Erectile Dysfunction

    MedlinePlus

    ... or vascular problems, will have a more difficult time returning to pre-treatment function. Management of Erectile Dysfunction When a man is sexually aroused, the erectile nerves running alongside the penis stimulate the ... blood to rush in. At the same time, tiny valves at the base of the penis ...

  3. Memory dysfunction.

    PubMed

    Amici, Serena

    2012-01-01

    Memory is the cognitive ability that allows to acquire, store and recall information; its dysfunction is called amnesia and can be a presentation of unilateral ischemic stroke in the territory of the posterior cerebral and anterior choroidal artery as well as subarachnoid hemorrhage. PMID:22377863

  4. Sensory Dysfunction

    MedlinePlus

    ... to Web version Sensory Dysfunction Overview Why are smell and taste important? Your senses of smell and taste let you fully enjoy the scents ... bitter and sour. Flavor involves both taste and smell. For example, because a person is able to ...

  5. [Usefulness and limitations of basal insulin replacement in type 2 diabetes].

    PubMed

    Hirata, Erina; Ohmori, Kazuno; Nagai, Sou

    2015-03-01

    In the earlier stage of type 2 diabetes, the disease can be managed by life-style modification with or without oral antidiabetic agents. However, as the disease progress, most patients eventually require insulin treatment to maintain good glycemic/control. Optimal insulin therapy should mimic the normal physiologic secretory pattern. As for ideal basal insulin, to maintain desirable pre-prandial glucose levels, duration of action should be long enough, profiles such as flat time-action and less day-to-day variation would be mandatory. This article discusses the usefulness and limitations of basal insulin therapy in type 2 diabetes comparing NPH insulin, insulin detemir, insulin glargin and insulin degludec. PMID:25812373

  6. H2O2 Signalling Pathway: A Possible Bridge between Insulin Receptor and Mitochondria

    PubMed Central

    Pomytkin, Igor A

    2012-01-01

    This review is focused on the mechanistic aspects of the insulin-induced H2O2 signalling pathway in neurons and the molecules affecting it, which act as risk factors for developing central insulin resistance. Insulin-induced H2O2 promotes insulin receptor activation and the mitochondria act as the insulin-sensitive H2O2 source, providing a direct molecular link between mitochondrial dysfunction and irregular insulin receptor activation. In this view, the accumulation of dysfunctional mitochondria during chronological ageing and Alzheimer’s disease (AD) is a risk factor that may contribute to the development of dysfunctional cerebral insulin receptor signalling and insulin resistance. Due to the high significance of insulin-induced H2O2 for insulin receptor activation, oxidative stress-induced upregulation of antioxidant enzymes, e.g., in AD brains, may represent another risk factor contributing to the development of insulin resistance. As insulin-induced H2O2 signalling requires fully functional mitochondria, pharmacological strategies based on activating mitochondria biogenesis in the brain are central to the treatment of diseases associated with dysfunctional insulin receptor signalling in this organ. PMID:23730255

  7. Mast cell secretory granules: armed for battle.

    PubMed

    Wernersson, Sara; Pejler, Gunnar

    2014-07-01

    Mast cells are important effector cells of the immune system and recent studies show that they have immunomodulatory roles in diverse processes in both health and disease. Mast cells are distinguished by their high content of electron-dense secretory granules, which are filled with large amounts of preformed and pre-activated immunomodulatory compounds. When appropriately activated, mast cells undergo degranulation, a process by which these preformed granule compounds are rapidly released into the surroundings. In many cases, the effects that mast cells have on an immune response are closely associated with the biological actions of the granule compounds that they release, as exemplified by the recent studies showing that mast cell granule proteases account for many of the protective and detrimental effects of mast cells in various inflammatory settings. In this Review, we discuss the current knowledge of mast cell secretory granules. PMID:24903914

  8. Docking of Secretory Vesicles Is Syntaxin Dependent

    PubMed Central

    de Wit, Heidi; Cornelisse, L. Niels; Toonen, Ruud F.G.; Verhage, Matthijs

    2006-01-01

    Secretory vesicles dock at the plasma membrane before they undergo fusion. Molecular docking mechanisms are poorly defined but believed to be independent of SNARE proteins. Here, we challenged this hypothesis by acute deletion of the target SNARE, syntaxin, in vertebrate neurons and neuroendocrine cells. Deletion resulted in fusion arrest in both systems. No docking defects were observed in synapses, in line with previous observations. However, a drastic reduction in morphologically docked secretory vesicles was observed in chromaffin cells. Syntaxin-deficient chromaffin cells showed a small reduction in total and plasma membrane staining for the docking factor Munc18-1, which appears insufficient to explain the drastic reduction in docking. The sub-membrane cortical actin network was unaffected by syntaxin deletion. These observations expose a docking role for syntaxin in the neuroendocrine system. Additional layers of regulation may have evolved to make syntaxin redundant for docking in highly specialized systems like synaptic active zones. PMID:17205130

  9. Insulin Test

    MedlinePlus

    ... people with type 2 diabetes , polycystic ovarian syndrome (PCOS) , prediabetes or heart disease , or metabolic syndrome . A ... resistance), especially in obese individuals and those with PCOS . This test involves an IV-infusion of insulin, ...

  10. RFP tags for labeling secretory pathway proteins

    SciTech Connect

    Han, Liyang; Zhao, Yanhua; Xu, Pingyong; Huan, Shuangyan

    2014-05-09

    Highlights: • Membrane protein Orai1 can be used to report the fusion properties of RFPs. • Artificial puncta are affected by dissociation constant as well as pKa of RFPs. • Among tested RFPs mOrange2 is the best choice for secretory protein labeling. - Abstract: Red fluorescent proteins (RFPs) are useful tools for live cell and multi-color imaging in biological studies. However, when labeling proteins in secretory pathway, many RFPs are prone to form artificial puncta, which may severely impede their further uses. Here we report a fast and easy method to evaluate RFPs fusion properties by attaching RFPs to an environment sensitive membrane protein Orai1. In addition, we revealed that intracellular artificial puncta are actually colocalized with lysosome, thus besides monomeric properties, pKa value of RFPs is also a key factor for forming intracellular artificial puncta. In summary, our current study provides a useful guide for choosing appropriate RFP for labeling secretory membrane proteins. Among RFPs tested, mOrange2 is highly recommended based on excellent monomeric property, appropriate pKa and high brightness.

  11. Hypertension Management and Microvascular Insulin Resistance in Diabetes

    PubMed Central

    Ko, Seung-Hyun; Cao, Wenhong; Liu, Zhenqi

    2011-01-01

    Type 2 diabetes is in essence a vascular disease and is frequently associated with hypertension, macrovascular events, and microvascular complications. Microvascular dysfunction, including impaired recruitment and capillary rarefaction, has been implicated in the pathogenesis of diabetic complications. Microvascular insulin resistance and renin-angiotensin system upregulation are present in diabetes, and each contributes to the development of hypertension and microvascular dysfunction. In the insulin-sensitive state, insulin increases microvascular perfusion by increasing endothelial nitric oxide production, but this effect is abolished by insulin resistance. Angiotensin II, acting via the type 1 receptors, induces inflammation and oxidative stress, leading to impaired insulin signaling, reduced nitric oxide availability, and vasoconstriction. Conversely, it acts on the type 2 receptors to cause vasodilatation. Because substrate and hormonal exchanges occur in the microvasculature, antihypertensive agents targeted to improve microvascular insulin sensitivity and function may have beneficial effects beyond their capacity to lower blood pressure in patients with diabetes. PMID:20582734

  12. Ionic and secretory response of pancreatic islet cells to minoxidil sulfate

    SciTech Connect

    Antoine, M.H.; Hermann, M.; Herchuelz, A.; Lebrun, P. )

    1991-07-01

    Minoxidil sulfate is an antihypertensive agent belonging to the new class of vasodilators, the K+ channel openers. The present study was undertaken to characterize the effects of minoxidil sulfate on ionic and secretory events in rat pancreatic islets. The drug unexpectedly provoked a concentration-dependent decrease in 86Rb outflow. This inhibitory effect was reduced in a concentration-dependent manner by glucose and tolbutamide. Minoxidil sulfate did not affect 45Ca outflow from islets perfused in the presence of extracellular Ca++ and absence or presence of glucose. However, in islets exposed to a medium deprived of extracellular Ca++, the drug provoked a rise in 45Ca outflow. Whether in the absence or presence of extracellular Ca++, minoxidil sulfate increased the cytosolic free Ca++ concentration of islet cells. Lastly, minoxidil sulfate increased the release of insulin from glucose-stimulated pancreatic islets. These results suggest that minoxidil sulfate reduces the activity of the ATP-sensitive K+ channels and promotes an intracellular translocation of Ca++. The latter change might account for the effect of the drug on the insulin-releasing process. However, the secretory response to minoxidil sulfate could also be mediated, at least in part, by a modest Ca++ entry.

  13. Mitochondrial efficiency and insulin resistance.

    PubMed

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

    2014-01-01

    Insulin resistance, "a relative impairment in the ability of insulin to exert its effects on glucose, protein and lipid metabolism in target tissues," has many detrimental effects on metabolism and is strongly correlated to deposition of lipids in non-adipose tissues. Mitochondria are the main cellular sites devoted to ATP production and fatty acid oxidation. Therefore, a role for mitochondrial dysfunction in the onset of skeletal muscle insulin resistance has been proposed and many studies have dealt with possible alteration in mitochondrial function in obesity and diabetes, both in humans and animal models. Data reporting evidence of mitochondrial dysfunction in type two diabetes mellitus are numerous, even though the issue that this reduced mitochondrial function is causal in the development of the disease is not yet solved, also because a variety of parameters have been used in the studies carried out on this subject. By assessing the alterations in mitochondrial efficiency as well as the impact of this parameter on metabolic homeostasis of skeletal muscle cells, we have obtained results that allow us to suggest that an increase in mitochondrial efficiency precedes and therefore can contribute to the development of high-fat-induced insulin resistance in skeletal muscle. PMID:25601841

  14. Long-term adaptation of Saccharomyces cerevisiae to the burden of recombinant insulin production.

    PubMed

    Kazemi Seresht, Ali; Cruz, Ana Luisa; de Hulster, Erik; Hebly, Marit; Palmqvist, Eva Akke; van Gulik, Walter; Daran, Jean-Marc; Pronk, Jack; Olsson, Lisbeth

    2013-10-01

    High-level production of heterologous proteins is likely to impose a metabolic burden on the host cell and can thus affect various aspects of cellular physiology. A data-driven approach was applied to study the secretory production of a human insulin analog precursor (IAP) in Saccharomyces cerevisiae during prolonged cultivation (80 generations) in glucose-limited aerobic chemostat cultures. Physiological characterization of the recombinant cells involved a comparison with cultures of a congenic reference strain that did not produce IAP, and time-course analysis of both strains aimed at identifying the metabolic adaptation of the cells towards the burden of IAP production. All cultures were examined at high cell density conditions (30 g/L dry weight) to increase the industrial relevance of the results. The burden of heterologous protein production in the recombinant strain was explored by global transcriptome analysis and targeted metabolome analysis, including the analysis of intracellular amino acid pools, glycolytic metabolites, and TCA intermediates. The cellular re-arrangements towards IAP production were categorized in direct responses, for example, enhanced metabolism of amino acids as precursors for the formation of IAP, as well as indirect responses, for example, changes in the central carbon metabolism. As part of the long-term adaptation, a metabolic re-modeling of the IAP-expressing strain was observed, indicating an augmented negative selection pressure on glycolytic overcapacity, and the emergence of mitochondrial dysfunction. The evoked metabolic re-modeling of the cells led to less optimal conditions with respect to the expression and processing of the target protein and thus decreased the cellular expression capacity for the secretory production of IAP during prolonged cultivation. PMID:23568816

  15. [Insulin receptor defect as a cause of Rabson-Mendenhall syndrome and other rare genetic insulin resistance syndromes].

    PubMed

    Rojek, Aleksandra; Niedziela, Marek

    2010-01-01

    Insulin plays a very important role in maintaining homeostasis of the whole organism. It regulates glucose metabolism, glycogen synthesis, lipid and protein metabolism. Insulin receptors are present in virtually all cells, which is reflected by the diversity of regulatory processes in which this hormone is involved. Any dysfunction of insulin signalling pathway as a result of insulin receptor gene mutations is linked with various forms of insulin resistance, including insulin resistance type A, Donohue or Rabson-Mendenhall syndrome, which differ in the level of severity. Molecular analysis of insulin receptor gene may lead to a better understanding of molecular mechanisms underlying various types of insulin resistance and help to develop a more efficient treatment. They may also be used as a powerful tool in prenatal diagnostics as well as in pregnancy planning. PMID:21092701

  16. Insulin receptor mutation results in insulin resistance and hyperinsulinemia but does not exacerbate Alzheimer's-like phenotypes in mice.

    PubMed

    Murakami, Kazuma; Yokoyama, Shin-ichi; Murata, Nakaba; Ozawa, Yusuke; Irie, Kazuhiro; Shirasawa, Takuji; Shimizu, Takahiko

    2011-05-27

    Obesity is a risk factor for Alzheimer's disease (AD), which is characterized by amyloid β depositions and cognitive dysfunction. Although insulin resistance is one of the phenotypes of obesity, its deleterious effects on AD progression remain to be fully elucidated. We previously reported that the suppression of insulin signaling in a mouse with a heterozygous mutation (P1195L) in the gene for the insulin receptor showed insulin resistance and hyperinsulinemia but did not develop diabetes mellitus [15]. Here, we generated a novel AD mouse model carrying the same insulin receptor mutation and showed that the combination of insulin resistance and hyperinsulinemia did not accelerate plaque formation or memory abnormalities in these mice. Interestingly, the insulin receptor mutation reduced oxidative damage in the brains of the AD mice. These findings suggest that insulin resistance is not always involved in the pathogenesis of AD. PMID:21549686

  17. Insulin and Insulin-Sensitizing Drugs in Neurodegeneration: Mitochondria as Therapeutic Targets

    PubMed Central

    Cardoso, Susana; Santos, Renato; Correia, Sonia; Carvalho, Cristina; Zhu, Xiongwei; Lee, Hyoung-Gon; Casadesus, Gemma; Smith, Mark A.; Perry, George; Moreira, Paula I.

    2009-01-01

    Insulin, besides its glucose lowering effects, is involved in the modulation of lifespan, aging and memory and learning processes. As the population ages, neurodegenerative disorders become epidemic and a connection between insulin signaling dysregulation, cognitive decline and dementia has been established. Mitochondria are intracellular organelles that despite playing a critical role in cellular metabolism are also one of the major sources of reactive oxygen species. Mitochondrial dysfunction, oxidative stress and neuroinflammation, hallmarks of neurodegeneration, can result from impaired insulin signaling. Insulin-sensitizing drugs such as the thiazolidinediones are a new class of synthetic compounds that potentiate insulin action in the target tissues and act as specific agonists of the peroxisome proliferator-activated receptor gamma (PPAR-γ). Recently, several PPAR agonists have been proposed as novel and possible therapeutic agents for neurodegenerative disorders. Indeed, the literature shows that these agents are able to protect against mitochondrial dysfunction, oxidative damage, inflammation and apoptosis. This review discusses the role of mitochondria and insulin signaling in normal brain function and in neurodegeneration. Furthermore, the potential protective role of insulin and insulin sensitizers in Alzheimer´s, Parkinson´s and Huntington´s diseases and amyotrophic lateral sclerosis will be also discussed.

  18. Diabetes and Insulin

    MedlinePlus

    ... years, but may eventually need insulin to maintain glucose control. What are the different types of insulin? Different ... glulisine • Short-acting: regular human insulin Basal insulin. Controls blood glucose levels between meals and throughout the night. This ...

  19. Differences in insulin biosynthesis pathway between small and large islets do not correspond to insulin secretion

    PubMed Central

    Huang, Han-Hung; Stehno-Bittel, Lisa

    2015-01-01

    In a variety of mammalian species, small islets secrete more insulin per volume than large islets. This difference may be due to diffusional limitations of large islets, or inherent differences in the insulin production pathways. The purpose of this study was to identify possible differences in the early phase of glucose-stimulated insulin biosynthesis between large and small islets. Isolated small and large rat islets were challenged with 30 minutes of high glucose. The expression of insulin gene transcription factors (MafA, NeuroD/ Beta2, and PDX-1), preproinsulin mRNA, proinsulin and insulin were compared between large and small islets. Under basal (low glucose) conditions, MafA and NeuroD had higher mRNA levels and greater protein amounts in large islets compared to small when normalized to GAPDH levels. 30 minutes of high glucose stimulation failed to alter the mRNA or subsequent protein levels of either gene. However, 30 minutes of high glucose suppressed activated PDX-1 protein levels in both small and large islets. High glucose stimulation did not statistically alter the preproinsulin mRNA (insulin 1 and insulin 2) levels. At the translational level, high glucose increased the proinsulin levels, and large islets showed a higher proinsulin content per cell than small islets. Insulin content per cell was not significantly different between small and large islets under basal or high glucose levels. The results fail to explain the higher level of insulin secretion noted in small versus large islets and may suggest that possible differences lie downstream in the secretory pathway rather than insulin biosynthesis. PMID:26752360

  20. Influence of experimental hypokinesia on gastric secretory function

    NASA Technical Reports Server (NTRS)

    Markova, O. O.; Vavryshchuk, V. I.; Rozvodovskyy, V. I.; Proshcheruk, V. A.

    1980-01-01

    The gastric secretory function of rats was studied in 4, 8, 16 and 30 day hypokinesia. Inhibition of both the gastric juice secretory and acid producing functions was found. The greatest inhibition was observed on day 8 of limited mobility. By days 16 and 30 of the experiment, a tendency of the gastric secretory activity to return to normal was observed, although it remained reduced.

  1. Dysfunctional voiding.

    PubMed

    Chiozza, M L

    2002-01-01

    Wetting may be considered the Cinderella of paediatric medicine. Before discussing dysfunctional voiding, the milestones of the normal development of continence in the child and the definitions used to describe this topic are presented. Bladder storage requires (1): accommodation of increasing volumes of urine at low intravesical pressure and with appropriate sensation; (2): a bladder outlet that is closed and not modified during increase in intra-abdominal pressure; (3): absence of involuntary bladder contractions. Development of continence in the child involves three independent factors maturing concomitantly: (1) development of normal bladder capacity; (2) maturation of urethral sphincter function; (3) development of neural control over bladder-sphincter function. All these processes are discussed. Abnormalities of any of these maturational sequences, which run parallel and overlapping, may result in clinically evident abnormalities of bladder sphincter control. Although dysfunctional voiding (DV) in children is very common its prevalence has not been well studied and, to date, and its origin is not well known. In a correct evaluation of functional voiding we must take into account different elements: the bladder capacity (that increases during the first 8 years of life roughly 30 ml per year), the micturition frequency, post-void residual volumes, bladder dynamics, urinary flow rates. Thus the correct assessment of children with lower urinary tract dysfunction should include a detailed history. Signs of DV range from urge syndrome to complex incontinence patterns during the day and the night. In addition to incontinence problems, children may have frequency, urgency, straining to void, weak or interrupted urinary stream, urinary tract infections (UTIs) and chronic constipation with or without encopresis. DV are also referred in enuretic children who wet the bed more than one time per night and have a functional bladder capacity lower than attended for age

  2. Psychological distress and salivary secretory immunity.

    PubMed

    Engeland, C G; Hugo, F N; Hilgert, J B; Nascimento, G G; Junges, R; Lim, H-J; Marucha, P T; Bosch, J A

    2016-02-01

    Stress-induced impairments of mucosal immunity may increase susceptibility to infectious diseases. The present study investigated the association of perceived stress, depressive symptoms, and loneliness with salivary levels of secretory immunoglobulin A (S-IgA), the subclasses S-IgA1, S-IgA2, and their transporter molecule Secretory Component (SC). S-IgA/SC, IgA1/SC and IgA2/SC ratios were calculated to assess the differential effects of stress on immunoglobulin transport versus availability. This study involved 113 university students, in part selected on high scores on the UCLA Loneliness Scale and/or the Beck Depression Inventory. Stress levels were assessed using the Perceived Stress Scale. Unstimulated saliva was collected and analysed for total S-IgA and its subclasses, as well as SC and total salivary protein. Multiple linear regression analyses, adjusted for gender, age, health behaviours, and concentration effects (total protein) revealed that higher perceived stress was associated with lower levels of IgA1 but not IgA2. Perceived stress, loneliness and depressive symptoms were all associated with lower IgA1/SC ratios. Surprisingly, higher SC levels were associated with loneliness and depressive symptoms, indicative of enhanced transport activity, which explained a lower IgA1/SC ratio (loneliness and depression) and IgA2/SC ratio (depression). This is the first study to investigate the effects of protracted psychological stress across S-IgA subclasses and its transporter SC. Psychological stress was negatively associated with secretory immunity, specifically IgA1. The lower immunoglobulin/transporter ratio that was associated with higher loneliness and depression suggested a relative immunoglobulin depletion, whereby availability was not keeping up with enhanced transport demand. PMID:26318411

  3. Isotonic water transport in secretory epithelia.

    PubMed

    Swanson, C H

    1977-01-01

    The model proposed by Diamond and Bossert [1] for isotonic water transport has received wide acceptance in recent years. It assumes that the local driving force for water transport is a standing osmotic gradient produced in the lateral intercellular spaces of the epithelial cell layer by active solute transport. While this model is based on work done in absorptive epithelia where the closed to open direction of the lateral space and the direction of net transport are the same, it has been proposed that the lateral spaces could also serve as the site of the local osmotic gradients for water transport in secretory epithelia, where the closed to open direction of the lateral space and net transport are opposed, by actively transporting solute out of the space rather than into it. Operation in the backward direction, however, requires a lower than ambient hydrostatic pressure within the lateral space which would seem more likely to cause the space to collapse with loss of function. On the other hand, most secretory epithelia are characterized by transport into a restricted ductal system which is similar to the lateral intercellular space in the absorptive epithelia in that its closed to open direction is the same as that of net transport. In vitro micropuncture studies on the exocrine pancreas of the rabbit indicate the presence of a small but statistically significant increase in juice osmolality, 6 mOsm/kg H(2)O, at the site of electrolyte and water secretion in the smallest extralobular ducts with secretin stimulation which suggests that the ductal system in the secretory epithelia rather than the lateral intercellular space is the site of the local osmotic gradients responsible for isotonic water transport. PMID:331693

  4. "Secretory" Carcinoma of the Skin Mimicking Secretory Carcinoma of the Breast: Case Report and Literature Review.

    PubMed

    Huang, Sixia; Liu, Yan; Su, Jing; Liu, Jianying; Guo, Xiaoning; Mei, Fang; Zheng, Jie; Liao, Songlin

    2016-09-01

    Secretory carcinoma is a unique kind of adenocarcinoma. It has distinct histological features and a special genetic change, that is, t (12; 15) (p13; q25) translocation which leads to the expression of the ETV6-NTRK3 fusion gene. Secretory carcinoma has been found to occur both in the breast and salivary gland. Here the authors present a case of 22-year-old woman with a unique cutaneous neoplasm located at the axilla. The tumor was characterized histologically with the formation of round to ovoid microcysts and papillary structure, which was similar to the secretory carcinoma of the breast and salivary gland. Furthermore, the gene sequence analysis of reverse-transcription polymerase chain reaction products demonstrated the expression of the ETV6-NTRK3 fusion gene. To the authors' knowledge, this is the first case of secretory carcinoma from the skin which has the same genetic change as those from the breast and salivary gland. Local excision was performed on this patient. She had been followed up for nearly 1 year. No recurrence or metastasis was found yet. PMID:26981741

  5. Cocoa, glucose tolerance, and insulin signaling: cardiometabolic protection.

    PubMed

    Grassi, Davide; Desideri, Giovambattista; Mai, Francesca; Martella, Letizia; De Feo, Martina; Soddu, Daniele; Fellini, Emanuela; Veneri, Mariangela; Stamerra, Cosimo A; Ferri, Claudio

    2015-11-18

    Experimental and clinical evidence reported that some polyphenol-rich natural products may offer opportunities for the prevention and treatment of type 2 diabetes, due to their biological properties. Natural products have been suggested to modulate carbohydrate metabolism by various mechanisms, such as restoring β-cell integrity and physiology and enhancing insulin-releasing activity and glucose uptake. Endothelium is fundamental in regulating arterial function, whereas insulin resistance plays a pivotal role in pathophysiological mechanisms of prediabetic and diabetic states. Glucose and insulin actions in the skeletal muscle are improved by insulin-dependent production of nitric oxide, favoring capillary recruitment, vasodilatation, and increased blood flow. Endothelial dysfunction, with decreased nitric oxide bioavailability, is a critical step in the development of atherosclerosis. Furthermore, insulin resistance has been described, at least in part, to negatively affect endothelial function. Consistent with this, conditions of insulin resistance are usually linked to endothelial dysfunction, and the exposure of the endothelial cells to cardiovascular risk factors such as hypertension, dyslipidemia, and hyperglycemia is associated with reduced nitric oxide bioavailability, resulting in impaired endothelial-dependent vasodilatation. Moreover, endothelial dysfunction has been described as an independent predictor of cardiovascular risk and events. Cocoa and cocoa flavonoids may positively affect the pathophysiological mechanisms involved in insulin resistance and endothelial dysfunction with possible benefits in the prevention of cardiometabolic diseases. PMID:26126077

  6. Proteomic analysis of conditioned media from glucose responsive and glucose non-responsive phenotypes reveals a panel of secreted proteins associated with beta cell dysfunction.

    PubMed

    Dowling, Paul; Shields, William; Rani, Sweta; Meleady, Paula; Henry, Michael; Jeppesen, Per; O'Driscoll, Lorraine; Clynes, Martin

    2008-11-01

    Media conditioned by dysfunctioning pancreatic beta cells offer an excellent source of potential protein markers associated with this phenotype. Proteins identified from cell culture model systems are often found to be of importance clinically. Previous work by us and others have shown that low-passage MIN-6 cells (MIN-6(L)) respond to changes in glucose concentrations, producing an approximately 5.5-fold glucose-stimulated insulin secretion (GSIS) in response to 26.7 mmol/L, compared with 3.3 mmol/L, glucose. After continuous culture or high-passage (MIN-(H)), this GSIS was no longer present and thus represents an excellent model system for investigating beta cell dysfunction. Employing 2-D difference gel electrophoresis and mass spectrometry a panel of protein markers were identified in conditioned media (CM) from MIN-6(L) and MIN-6(H) beta cells. These proteins, including secretogranin II, secretogranin III and transthyretin, are associated with secretory granule biogenesis and were found to have substantially increased levels in the CM from the non-responsive high-passage MIN-6 beta cells. A panel of protein markers found to have increased abundance levels in CM from MIN-6(H) compared with MIN-6(L) beta cells may have the potential to be used clinically for assessing beta cell function and to monitor the effects of specific therapeutics. PMID:18924105

  7. Endothelial Dysfunction in Type 2 Diabetes Mellitus.

    PubMed

    Dhananjayan, R; Koundinya, K S Srivani; Malati, T; Kutala, Vijay Kumar

    2016-10-01

    Endothelial dysfunction is an imbalance in the production of vasodilator factors and when this balance is disrupted, it predisposes the vasculature towards pro-thrombotic and pro-atherogenic effects. This results in vasoconstriction, leukocyte adherence, platelet activation, mitogenesis, pro-oxidation, impaired coagulation and nitric oxide production, vascular inflammation, atherosclerosis and thrombosis. Endothelial dysfunction is focussed as it is a potential contributor to the pathogenesis of vascular disease in diabetes mellitus. Under physiological conditions, there is a balanced release of endothelial-derived relaxing and contracting factors, but this delicate balance is altered in diabetes mellitus and atherosclerosis, thereby contributing to further progression of vascular and end-organ damage. This review focuses on endothelial dysfunction in atherosclerosis, insulin resistance, metabolic syndrome, oxidative stress associated with diabetes mellitus, markers and genetics that are implicated in endothelial dysfunction. PMID:27605734

  8. Maladaptive immune and inflammatory pathways lead to cardiovascular insulin resistance.

    PubMed

    Aroor, Annayya R; McKarns, Susan; Demarco, Vincent G; Jia, Guanghong; Sowers, James R

    2013-11-01

    Insulin resistance is a hallmark of obesity, the cardiorenal metabolic syndrome and type 2 diabetes mellitus (T2DM). The progression of insulin resistance increases the risk for cardiovascular disease (CVD). The significance of insulin resistance is underscored by the alarming rise in the prevalence of obesity and its associated comorbidities in the Unites States and worldwide over the last 40-50 years. The incidence of obesity is also on the rise in adolescents. Furthermore, premenopausal women have lower CVD risk compared to men, but this protection is lost in the setting of obesity and insulin resistance. Although systemic and cardiovascular insulin resistance is associated with impaired insulin metabolic signaling and cardiovascular dysfunction, the mechanisms underlying insulin resistance and cardiovascular dysfunction remain poorly understood. Recent studies show that insulin resistance in obesity and diabetes is linked to a metabolic inflammatory response, a state of systemic and tissue specific chronic low grade inflammation. Evidence is also emerging that there is polarization of macrophages and lymphocytes towards a pro-inflammatory phenotype that contributes to progression of insulin resistance in obesity, cardiorenal metabolic syndrome and diabetes. In this review, we provide new insights into factors, such as, the renin-angiotensin-aldosterone system, sympathetic activation and incretin modulators (e.g., DPP-4) and immune responses that mediate this inflammatory state in obesity and other conditions characterized by insulin resistance. PMID:23932846

  9. Impaired insulin signaling and mechanisms of memory loss.

    PubMed

    Bloemer, Jenna; Bhattacharya, Subhrajit; Amin, Rajesh; Suppiramaniam, Vishnu

    2014-01-01

    Insulin is secreted from the β-cells of the pancreas and helps maintain glucose homeostasis. Although secreted peripherally, insulin also plays a profound role in cognitive function. Increasing evidence suggests that insulin signaling in the brain is necessary to maintain health of neuronal cells, promote learning and memory, decrease oxidative stress, and ultimately increase neuronal survival. This chapter summarizes the different facets of insulin signaling necessary for learning and memory and additionally explores the association between cognitive impairment and central insulin resistance. The role of impaired insulin signaling in the advancement of cognitive dysfunction is relevant to the current debate of whether the shared pathophysiological mechanisms between diabetes and cognitive impairment implicate a direct relationship. Here, we summarize a vast amount of literature that suggests a strong association between impaired brain insulin signaling and cognitive impairment. PMID:24373245

  10. Characterization of proinsulin- and proglucagon-converting activities in isolated islet secretory granules.

    PubMed

    Fletcher, D J; Quigley, J P; Bauer, G E; Noe, B D

    1981-08-01

    The conversion of proglucagon and proinsulin by secretory granules isolated from both prelabeled and unlabeled anglerfish islets was investigated. Either granules isolated from tissue labeled with [3H]tryptophan and [14C]isoleucine or [35S]cysteine, or lysed granules from unlabeled tissue to which exogenously labeled prohormones had been added were incubated under various conditions. Acetic acid extracts of these granule preparations were analyzed for prohormone and hormone content by gel filtration. Both prelabeled and lysed, unlabeled secretory granules converted radiolabeled precursor peptides (Mr 8,000-15,000) to labeled insulin and glucagon. The accuracy of the cleavage process was established by demonstrating comigration of products obtained from in vitro cleavage with insulin and glucagon extracted from intact islets using electrophoresis and high-pressure liquid chromatography (HPLC). The pH optimum for granule-mediated conversion was found to be in the range of pH 4.5-5.5. Conversion of both proglucagon and proinsulin by secretory granules was significantly inhibited in the presence of antipain, leupeptin, p-chloromercuribenzoate (PCMB) or dithiodipyridine (DDP) but not chloroquine, diisopropyl fluorophosphate, EDTA, p-nitrophenyl guanidinobenzoate, soybean trypsin inhibitor, or N-p-tosyl-L-lysine chloromethyl ketone HCl. The inhibitory action of PCMB and DDP was reversed in the presence of dithiothreitol. Both membranous and soluble components of the secretory granules possessed significant converting activity. HPLC and electrophoretic analysis of cleavage products demonstrated that the converting activities of the membranous and soluble components were indistinguishable. The amount of inhibition of proinsulin and proglucagon conversion caused by 600 micrograms/ml porcine proinsulin was significantly lower than that caused by the same concentration of unlabeled anglerfish precursor peptides. These results indicate that the proinsulin and proglucagon

  11. ATP: The crucial component of secretory vesicles.

    PubMed

    Estévez-Herrera, Judith; Domínguez, Natalia; Pardo, Marta R; González-Santana, Ayoze; Westhead, Edward W; Borges, Ricardo; Machado, José David

    2016-07-12

    The colligative properties of ATP and catecholamines demonstrated in vitro are thought to be responsible for the extraordinary accumulation of solutes inside chromaffin cell secretory vesicles, although this has yet to be demonstrated in living cells. Because functional cells cannot be deprived of ATP, we have knocked down the expression of the vesicular nucleotide carrier, the VNUT, to show that a reduction in vesicular ATP is accompanied by a drastic fall in the quantal release of catecholamines. This phenomenon is particularly evident in newly synthesized vesicles, which we show are the first to be released. Surprisingly, we find that inhibiting VNUT expression also reduces the frequency of exocytosis, whereas the overexpression of VNUT drastically increases the quantal size of exocytotic events. To our knowledge, our data provide the first demonstration that ATP, in addition to serving as an energy source and purinergic transmitter, is an essential element in the concentration of catecholamines in secretory vesicles. In this way, cells can use ATP to accumulate neurotransmitters and other secreted substances at high concentrations, supporting quantal transmission. PMID:27342860

  12. Secretory pattern of canine growth hormone

    SciTech Connect

    French, M.B.; Vaitkus, P.; Cukerman, E.; Sirek, A.; Sirek, O.V.

    1987-02-01

    The aim of this paper was to define the secretory pattern of growth hormone (GH) under basal conditions in fasted, conscious, male dogs accustomed to handling. Blood samples were withdrawn from a cephalic vein at 15-min intervals. In this way, any ultradian rhythms, if present, could be detected within the frequency range of 0.042-2 cycles/h. In addition, samples were drawn at either 1- or 2.5-min intervals for 2.5 or 5 h to determine whether frequency components greater than 2 cycles/h were present. GH was measured by radioimmunoassay and the raw data were submitted to time series analysis employing power spectral estimation by means of fast Fourier transformation techniques. Peak plasma levels were up to 12 times higher than the baseline concentration of approx. 1 ng/ml. Spectral analysis revealed an endogenous frequency of 0.22 cycles/h, i.e., a periodicity of 4.5 h/cycle. The results indicate that under basal conditions the secretory bursts of canine GH are limited to one peak every 4.5 h.

  13. Role of mitochondrial function in insulin resistance.

    PubMed

    Brands, Myrte; Verhoeven, Arthur J; Serlie, Mireille J

    2012-01-01

    The obesity pandemic increases the prevalence of type 2 diabetes (DM2).DM2 develops when pancreatic β-cells fail and cannot compensate for the decrease in insulin sensitivity. How excessive caloric intake and weight gain cause insulin resistance has not completely been elucidated.Skeletal muscle is responsible for a major part of insulin stimulated whole-body glucose disposal and, hence, plays an important role in the pathogenesis of insulin resistance.It has been hypothesized that skeletal muscle mitochondrial dysfunction is involved in the accumulation of intramyocellular lipid metabolites leading to lipotoxicity and insulin resistance. However, findings on skeletal muscle mitochondrial function in relation to insulin resistance in human subjects are inconclusive. Differences in mitochondrial activity can be the result of several factors, including a reduced mitochondrial density, differences in insulin stimulated mitochondrial respiration, lower energy demand or reduced skeletal muscle perfusion, besides an intrinsic mitochondrial defect. The inconclusive results may be explained by the use of different techniques and study populations. Also, mitochondrial capacity is in far excess to meet energy requirements and therefore it may be questioned whether a reduced mitochondrial capacity limits mitochondrial fatty acid oxidation. Whether reduced mitochondrial function is causally related to insulin resistance or rather a consequence of the sedentary lifestyle remains to be elucidated. PMID:22399424

  14. Ameloblast transcriptome changes from secretory to maturation stages

    PubMed Central

    Simmer, James P.; Richardson, Amelia S.; Wang, Shih-Kai; Reid, Bryan M.; Bai, Yongsheng; Hu, Yuanyuan; Hu, Jan C.-C.

    2014-01-01

    The purpose of this study was to identify the major molecular components in the secretory and maturation stages of amelogenesis through transcriptome analyses. Ameloblasts (40 sections per age group) were laser micro-dissected from Day 5 (secretory stage) and Days 11–12 (maturation stage) first molars. PolyA+ RNA was isolated from the lysed cells, converted to cDNA, and amplified to generate a cDNA library. DNA sequences were obtained using next generation sequencing and analyzed to identify genes whose expression had increased or decreased at least 1.5-fold in maturation stage relative to secretory stage ameloblasts. Among the 9198 genes that surpassed the quality threshold, 373 showed higher expression in secretory stage, while 614 genes increased in maturation stage ameloblasts. The results were crosschecked against a previously published transcriptome generated from tissues overlying secretory and maturation stage mouse incisor enamel and 34 increasing and 26 decreasing expressers common to the two studies were identified. Expression of F2r, which encodes protease activated receptor 1 (PAR1) that showed 10-fold higher expression during the secretory stage in our transcriptome analysis, was characterized in mouse incisors by immunohistochemistry. PAR1 was detected in secretory, but not maturation stage ameloblasts. We conclude that transcriptome analyses are a good starting point for identifying genes/proteins that are critical for proper dental enamel formation and that PAR1 is specifically expressed by secretory stage ameloblasts. PMID:25158176

  15. 21 CFR 866.5380 - Free secretory component immuno-logical test system.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... immunochemical techniques free secretory component (normally a portion of the secretory IgA antibody molecule) in... repetitive lung infections and other hypogammaglobulinemic conditions (low antibody levels)....

  16. Technosphere insulin: an inhaled prandial insulin product.

    PubMed

    Neumiller, Joshua J; Campbell, R Keith

    2010-06-01

    Given the important role of insulin in the treatment of diabetes mellitus and in light of common barriers to insulin use, new strategies for insulin delivery by routes other than intravenous and subcutaneous injection have been investigated since the discovery of insulin in the 1920s. Most companies researching and developing pulmonary administration systems for the use of insulin announced the termination of product development following the failure of the first US FDA-approved inhaled insulin product, Exubera. One company in particular continued their pursuit of a useful inhaled insulin product. MannKind Corporation has developed a powder formulation of insulin that allows for a high percentage of the administered insulin to be absorbed via the lung. Their product, AFREZZA (Technosphere insulin), is currently under review by the FDA for use in patients with diabetes. Technosphere insulin appears to overcome some of the barriers that contributed to the market withdrawal of Exubera by the manufacturer. Studies with Technosphere insulin have shown it to be a unique insulin formulation in that it is very rapid acting, has a relatively short duration of action, and is efficacious in terms of improved glycemic control without contributing to increased weight gain or the incidence of hypoglycemia when compared with other prandial insulin products. Additionally, Technosphere insulin has demonstrated a favorable safety and tolerability profile in clinical studies to date. PMID:20462282

  17. Insulin-secreting non-islet cells are resistant to autoimmune destruction.

    PubMed Central

    Lipes, M A; Cooper, E M; Skelly, R; Rhodes, C J; Boschetti, E; Weir, G C; Davalli, A M

    1996-01-01

    Transgenic nonobese diabetic mice were created in which insulin expression was targeted to proopiomelanocortin-expressing pituitary cells. Proopiomelanocortin-expressing intermediate lobe pituitary cells efficiently secrete fully processed, mature insulin via a regulated secretory pathway, similar to islet beta cells. However, in contrast to the insulin-producing islet beta cells, the insulin-producing intermediate lobe pituitaries are not targeted or destroyed by cells of the immune system. Transplantation of the transgenic intermediate lobe tissues into diabetic nonobese diabetic mice resulted in the restoration of near-normoglycemia and the reversal of diabetic symptoms. The absence of autoimmunity in intermediate lobe pituitary cells engineered to secrete bona fide insulin raises the potential of these cell types for beta-cell replacement therapy for the treatment of insulin-dependent diabetes mellitus. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 PMID:8710916

  18. Dietary Sodium Restriction Decreases Insulin Secretion Without Affecting Insulin Sensitivity in Humans

    PubMed Central

    Byrne, Loretta M.; Yu, Chang; Wang, Thomas J.; Brown, Nancy J.

    2014-01-01

    Context: Interruption of the renin-angiotensin-aldosterone system prevents incident diabetes in high-risk individuals, although the mechanism remains unclear. Objective: To test the hypothesis that activation of the endogenous renin-angiotensin-aldosterone system or exogenous aldosterone impairs insulin secretion in humans. Design: We conducted a randomized, blinded crossover study of aldosterone vs vehicle and compared the effects of a low-sodium versus a high-sodium diet. Setting: Academic clinical research center. Participants: Healthy, nondiabetic, normotensive volunteers. Interventions: Infusion of exogenous aldosterone (0.7 μg/kg/h for 12.5 h) or vehicle during low or high sodium intake. Low sodium (20 mmol/d; n = 12) vs high sodium (160 mmol/d; n = 17) intake for 5–7 days. Main Outcome Measures: Change in acute insulin secretory response assessed during hyperglycemic clamps while in sodium balance during a low-sodium vs high-sodium diet during aldosterone vs vehicle. Results: A low-sodium diet increased endogenous aldosterone and plasma renin activity, and acute glucose-stimulated insulin (−16.0 ± 5.6%; P = .007) and C-peptide responses (−21.8 ± 8.4%; P = .014) were decreased, whereas the insulin sensitivity index was unchanged (−1.0 ± 10.7%; P = .98). Aldosterone infusion did not affect the acute insulin response (+1.8 ± 4.8%; P = .72) or insulin sensitivity index (+2.0 ± 8.8%; P = .78). Systolic blood pressure and serum potassium were similar during low and high sodium intake and during aldosterone infusion. Conclusions: Low dietary sodium intake reduces insulin secretion in humans, independent of insulin sensitivity. PMID:25029426

  19. BACE2 is stored in secretory granules of mouse and rat pancreatic beta cells.

    PubMed

    Finzi, Giovanna; Franzi, Francesca; Placidi, Claudia; Acquati, Francesco; Palumbo, Elisa; Russo, Antonella; Taramelli, Roberto; Sessa, Fausto; La Rosa, Stefano

    2008-01-01

    BACE2 is a protease homologous to BACE1 protein, an enzyme involved in the amyloid formation of Alzheimer disease (AD). However, despite the high homology between these two proteins, the biological role of BACE2 is still controversial, even though a few studies have suggested a pathogenetic role in sporadic inclusion-body myositis and hereditary inclusion-body myopathy, which are characterized by vacuolization of muscular fibers with intracellular deposits of proteins similar to those found in the brain of AD patients. Although BACE2 has also been identified in the pancreas, its function remains unknown and its specific localization in different pancreatic cell types has not been definitively ascertained. For these reasons, the authors have investigated the cellular and subcellular localization of BACE2 in normal rodent pancreases. BACE2 immunoreactivity was found in secretory granules of beta cells, co-stored with insulin and IAPP, while it was lacking in the other endocrine and exocrine cell types. The presence of BACE2 in secretory granules of beta cells suggests that it may play a role in diabetes-associated amyloidogenesis. PMID:19117266

  20. p24 family proteins: key players in the regulation of trafficking along the secretory pathway.

    PubMed

    Pastor-Cantizano, Noelia; Montesinos, Juan Carlos; Bernat-Silvestre, César; Marcote, María Jesús; Aniento, Fernando

    2016-07-01

    p24 family proteins have been known for a long time, but their functions have remained elusive. However, they are emerging as essential regulators of protein trafficking along the secretory pathway, influencing the composition, structure, and function of different organelles in the pathway, especially the ER and the Golgi apparatus. In addition, they appear to modulate the transport of specific cargos, including GPI-anchored proteins, G-protein-coupled receptors, or K/HDEL ligands. As a consequence, they have been shown to play specific roles in signaling, development, insulin secretion, and the pathogenesis of Alzheimer's disease. The search of new putative ligands may open the way to discover new functions for this fascinating family of proteins. PMID:26224213

  1. Estrogens prevent metabolic dysfunctions induced by circadian disruptions in female mice

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Circadian disruption has become a significant factor contributing to the epidemics of obesity and insulin resistance. However, interventions to treat metabolic dysfunctions induced by circadian disruptions are limited. The ovarian hormone, estrogen, produces important antiobesity and antidiabetic ef...

  2. Proinsulin C-peptide interferes with insulin fibril formation

    SciTech Connect

    Landreh, Michael; Stukenborg, Jan-Bernd; Willander, Hanna; Soeder, Olle; Johansson, Jan; Joernvall, Hans

    2012-02-17

    Highlights: Black-Right-Pointing-Pointer Insulin and C-peptide can interact under insulin fibril forming conditions. Black-Right-Pointing-Pointer C-peptide is incorporated into insulin aggregates and alters aggregation lag time. Black-Right-Pointing-Pointer C-peptide changes insulin fibril morphology and affects backbone accessibility. Black-Right-Pointing-Pointer C-peptide may be a regulator of fibril formation by {beta}-cell granule proteins. -- Abstract: Insulin aggregation can prevent rapid insulin uptake and cause localized amyloidosis in the treatment of type-1 diabetes. In this study, we investigated the effect of C-peptide, the 31-residue peptide cleaved from proinsulin, on insulin fibrillation at optimal conditions for fibrillation. This is at low pH and high concentration, when the fibrils formed are regular and extended. We report that C-peptide then modulates the insulin aggregation lag time and profoundly changes the fibril appearance, to rounded clumps of short fibrils, which, however, still are Thioflavine T-positive. Electrospray ionization mass spectrometry also indicates that C-peptide interacts with aggregating insulin and is incorporated into the aggregates. Hydrogen/deuterium exchange mass spectrometry further reveals reduced backbone accessibility in insulin aggregates formed in the presence of C-peptide. Combined, these effects are similar to those of C-peptide on islet amyloid polypeptide fibrillation and suggest that C-peptide has a general ability to interact with amyloidogenic proteins from pancreatic {beta}-cell granules. Considering the concentrations, these peptide interactions should be relevant also during physiological secretion, and even so at special sites post-secretory or under insulin treatment conditions in vivo.

  3. Mitochondrial involvement in skeletal muscle insulin resistance: A case of imbalanced bioenergetics.

    PubMed

    Affourtit, Charles

    2016-10-01

    Skeletal muscle insulin resistance in obesity associates with mitochondrial dysfunction, but the causality of this association is controversial. This review evaluates mitochondrial models of nutrient-induced muscle insulin resistance. It transpires that all models predict that insulin resistance arises as a result of imbalanced cellular bioenergetics. The nature and precise origin of the proposed insulin-numbing molecules differ between models but all species only accumulate when metabolic fuel supply outweighs energy demand. This observation suggests that mitochondrial deficiency in muscle insulin resistance is not merely owing to intrinsic functional defects, but could instead be an adaptation to nutrient-induced changes in energy expenditure. Such adaptive effects are likely because muscle ATP supply is fully driven by energy demand. This market-economic control of myocellular bioenergetics offers a mechanism by which insulin-signalling deficiency can cause apparent mitochondrial dysfunction, as insulin resistance lowers skeletal muscle anabolism and thus dampens ATP demand and, consequently, oxidative ATP synthesis. PMID:27473535

  4. Divergent role of sphingosine 1-phosphate on insulin resistance.

    PubMed

    Fayyaz, Susann; Japtok, Lukasz; Kleuser, Burkhard

    2014-01-01

    Insulin resistance is a complex metabolic disorder in which insulin-sensitive tissues fail to respond to the physiological action of insulin. There is a strong correlation of insulin resistance and the development of type 2 diabetes both reaching epidemic proportions. Dysfunctional lipid metabolism is a hallmark of insulin resistance and a risk factor for several cardiovascular and metabolic disorders. Numerous studies in humans and rodents have shown that insulin resistance is associated with elevations of non-esterified fatty acids (NEFA) in the plasma. Moreover, bioactive lipid intermediates such as diacylglycerol (DAG) and ceramides appear to accumulate in response to NEFA, which may interact with insulin signaling. However, recent work has also indicated that sphingosine 1-phosphate (S1P), a breakdown product of ceramide, modulate insulin signaling in different cell types. In this review, we summarize the current state of knowledge about S1P and insulin signaling in insulin sensitive cells. A specific focus is put on the action of S1P on hepatocytes, pancreatic β-cells and skeletal muscle cells. In particular, modulation of S1P-signaling can be considered as a potential therapeutic target for the treatment of insulin resistance and type 2 diabetes. PMID:24977487

  5. Giving an insulin injection

    MedlinePlus

    ... One Type of Insulin Wash your hands with soap and water. Dry them well. Check the insulin ... syringe before injecting it. Wash your hands with soap and water. Dry them well. Check the insulin ...

  6. Insulin Human Inhalation

    MedlinePlus

    Insulin inhalation is used in combination with a long-acting insulin to treat type 1 diabetes (condition in which the body does not produce insulin and therefore cannot control the amount of sugar ...

  7. Insulin Lispro Injection

    MedlinePlus

    ... is a short-acting, man-made version of human insulin. Insulin lispro works by replacing the insulin ... niacin (Niacor, Niaspan, in Advicor); certain medications for human immunodeficiency virus (HIV) or acquired immunodeficiency syndrome (AIDS) ...

  8. Presence of secretory IgA in human periapical lesions.

    PubMed

    Torres, J O; Torabinejad, M; Matiz, R A; Mantilla, E G

    1994-02-01

    The concentration of secretory IgA in fluids present in the canals of 33 teeth was determined by the rocket immunoelectrophoresis technique. Except for the presence or absence of communication between the oral cavity and the root canals of the affected teeth, no other clinical finding showed significant statistical correlation with the presence of secretory IgA. The canals which were open to the oral flora had significantly higher concentrations of secretory IgA. Leaving canals open to the oral cavity may result in formation of periapical cysts. PMID:8006572

  9. Atorvastatin ameliorates endothelium-specific insulin resistance induced by high glucose combined with high insulin.

    PubMed

    Yang, Ou; Li, Jinliang; Chen, Haiyan; Li, Jie; Kong, Jian

    2016-09-01

    The aim of the present study was to establish an endothelial cell model of endothelium-specific insulin resistance to evaluate the effect of atorvastatin on insulin resistance-associated endothelial dysfunction and to identify the potential pathway responsible for its action. Cultured human umbilical vein endothelial cells (HUVECs) were pretreated with different concentrations of glucose with, or without, 10‑5 M insulin for 24 h, following which the cells were treated with atorvastatin. The tyrosine phosphorylation of insulin receptor (IR) and insulin receptor substrate-1 (IRS‑1), the production of nitric oxide (NO), the activity and phosphorylation level of endothelial NO synthase (eNOS) on serine1177, and the mRNA levels of endothelin‑1 (ET‑1) were assessed during the experimental procedure. Treatment of the HUVECs with 30 mM glucose and 10‑5 M insulin for 24 h impaired insulin signaling, with reductions in the tyrosine phosphorylation of IR and protein expression of IRS‑1 by almost 75 and 65%, respectively. This, in turn, decreased the activity and phosphorylation of eNOS on serine1177, and reduced the production of NO by almost 80%. By contrast, the mRNA levels of ET‑1 were upregulated. All these changes were ameliorated by atorvastatin. Taken together, these results demonstrated that high concentrations of glucose and insulin impaired insulin signaling leading to endothelial dysfunction, and that atorvastatin ameliorated these changes, acting primarily through the phosphatidylinositol 3-kinase/Akt/eNOS signaling pathway. PMID:27484094

  10. Beta cells transfer vesicles containing insulin to phagocytes for presentation to T cells

    PubMed Central

    Vomund, Anthony N.; Zinselmeyer, Bernd H.; Hughes, Jing; Calderon, Boris; Valderrama, Carolina; Ferris, Stephen T.; Wan, Xiaoxiao; Kanekura, Kohsuke; Carrero, Javier A.; Urano, Fumihiko; Unanue, Emil R.

    2015-01-01

    Beta cells from nondiabetic mice transfer secretory vesicles to phagocytic cells. The passage was shown in culture studies where the transfer was probed with CD4 T cells reactive to insulin peptides. Two sets of vesicles were transferred, one containing insulin and another containing catabolites of insulin. The passage required live beta cells in a close cell contact interaction with the phagocytes. It was increased by high glucose concentration and required mobilization of intracellular Ca2+. Live images of beta cell–phagocyte interactions documented the intimacy of the membrane contact and the passage of the granules. The passage was found in beta cells isolated from islets of young nonobese diabetic (NOD) mice and nondiabetic mice as well as from nondiabetic humans. Ultrastructural analysis showed intraislet phagocytes containing vesicles having the distinct morphology of dense-core granules. These findings document a process whereby the contents of secretory granules become available to the immune system. PMID:26324934

  11. Beta cells transfer vesicles containing insulin to phagocytes for presentation to T cells.

    PubMed

    Vomund, Anthony N; Zinselmeyer, Bernd H; Hughes, Jing; Calderon, Boris; Valderrama, Carolina; Ferris, Stephen T; Wan, Xiaoxiao; Kanekura, Kohsuke; Carrero, Javier A; Urano, Fumihiko; Unanue, Emil R

    2015-10-01

    Beta cells from nondiabetic mice transfer secretory vesicles to phagocytic cells. The passage was shown in culture studies where the transfer was probed with CD4 T cells reactive to insulin peptides. Two sets of vesicles were transferred, one containing insulin and another containing catabolites of insulin. The passage required live beta cells in a close cell contact interaction with the phagocytes. It was increased by high glucose concentration and required mobilization of intracellular Ca2+. Live images of beta cell-phagocyte interactions documented the intimacy of the membrane contact and the passage of the granules. The passage was found in beta cells isolated from islets of young nonobese diabetic (NOD) mice and nondiabetic mice as well as from nondiabetic humans. Ultrastructural analysis showed intraislet phagocytes containing vesicles having the distinct morphology of dense-core granules. These findings document a process whereby the contents of secretory granules become available to the immune system. PMID:26324934

  12. [Aspartame--the sweet-tasting dipeptide--does not affect the pancreatic insulin-secreting function].

    PubMed

    Sadovnikova, N V; Fedotov, V P; Aleshina, L V; Shvachkin, Iu P; Girin, S K

    1984-01-01

    The action of a synthetic dipeptide aspartam (150 to 180 times as sweet as glucose) on pancreatic insulin-secretory function of rats was studied in vivo and in vitro. The drug was given orally while drinking (300 mg/kg body weight) or was added to the incubation medium of cultivated pancreatic cells (20 mM). It was shown that insulin content in the rat blood serum remained unchanged 10 and 35 minutes after aspartam administration. The drug did not exert any stimulating effect upon insulin secretion following the addition to the pancreatic cell culture medium. It is concluded that aspartam exhibits no direct or mediated action on pancreatic insulin-secretory function. PMID:6382247

  13. Concentrated insulins: the new basal insulins

    PubMed Central

    Lamos, Elizabeth M; Younk, Lisa M; Davis, Stephen N

    2016-01-01

    Introduction Insulin therapy plays a critical role in the treatment of type 1 and type 2 diabetes mellitus. However, there is still a need to find basal insulins with 24-hour coverage and reduced risk of hypoglycemia. Additionally, with increasing obesity and insulin resistance, the ability to provide clinically necessary high doses of insulin at low volume is also needed. Areas covered This review highlights the published reports of the pharmacokinetic (PK) and glucodynamic properties of concentrated insulins: Humulin-R U500, insulin degludec U200, and insulin glargine U300, describes the clinical efficacy, risk of hypoglycemic, and metabolic changes observed, and finally, discusses observations about the complexity of introducing a new generation of concentrated insulins to the therapeutic market. Conclusion Humulin-R U500 has a similar onset but longer duration of action compared with U100 regular insulin. Insulin glargine U300 has differential PK/pharmacodynamic effects when compared with insulin glargine U100. In noninferiority studies, glycemic control with degludec U200 and glargine U300 is similar to insulin glargine U100 and nocturnal hypoglycemia is reduced. Concentrated formulations appear to behave as separate molecular entities when compared with earlier U100 insulin analog compounds. In the review of available published data, newer concentrated basal insulins may offer an advantage in terms of reduced intraindividual variability as well as reducing the injection burden in individuals requiring high-dose and large volume insulin therapy. Understanding the PK and pharmacodynamic properties of this new generation of insulins is critical to safe dosing, dispensing, and administration. PMID:27022271

  14. Alpha-synuclein Toxicity in the Early Secretory Pathway: How It Drives Neurodegeneration in Parkinsons Disease

    PubMed Central

    Wang, Ting; Hay, Jesse C.

    2015-01-01

    Alpha-synuclein is a predominant player in the pathogenesis of Parkinson's Disease. However, despite extensive study for two decades, its physiological and pathological mechanisms remain poorly understood. Alpha-synuclein forms a perplexing web of interactions with lipids, trafficking machinery, and other regulatory factors. One emerging consensus is that synaptic vesicles are likely the functional site for alpha-synuclein, where it appears to facilitate vesicle docking and fusion. On the other hand, the dysfunctions of alpha-synuclein are more dispersed and numerous; when mutated or over-expressed, alpha-synuclein affects several membrane trafficking and stress pathways, including exocytosis, ER-to-Golgi transport, ER stress, Golgi homeostasis, endocytosis, autophagy, oxidative stress, and others. Here we examine recent developments in alpha-synuclein's toxicity in the early secretory pathway placed in the context of emerging themes from other affected pathways to help illuminate its underlying pathogenic mechanisms in neurodegeneration. PMID:26617485

  15. A Novel Mutation of DAX-1 Associated with Secretory Azoospermia

    PubMed Central

    Yang, Lihua; Liu, Yuchen; Diao, Ruiying; Cai, Zhiming; Li, Honggang; Gui, Yaoting

    2015-01-01

    Secretory azoospermia is a severe form of male infertility caused by unknown factors. DAX-1 is predominantly expressed in mammalian reproductive tissues and plays an important role in spermatogenesis because Dax-1 knockout male mice show spermatogenesis defects. To examine whether DAX-1 is involved in the pathogenesis of secretory azoospermia in humans, we sequenced all of the exons of DAX-1 in 776 patients diagnosed with secretory azoospermia and 709 proven fertile men. A number of coding mutations unique to the patient group, including two synonymous mutations and six missense mutations, were identified. Of the missense mutations, our functional assay demonstrated that the V385L mutation caused the reduced functioning of DAX-1. This novel mutation (p. V385L) of DAX-1 is the first to be identified in association with secretory azoospermia, thereby highlighting the important role of DAX-1 in spermatogenesis. PMID:26207377

  16. Secretory protein trafficking in Giardia intestinalis.

    PubMed

    Hehl, Adrian B; Marti, Matthias

    2004-07-01

    Early diverged extant organisms, which may serve as convenient laboratory models to look for and study evolutionary ancient features of eukaryotic cell biology, are rare. The diplomonad Giardia intestinalis, a protozoan parasite known to cause diarrhoeal disease, has become an increasingly popular object of basic research in cell biology, not least because of a genome sequencing project nearing completion. Commensurate with its phylogenetic status, the Giardia trophozoite has a very basic secretory system and even lacks hallmark structures such as a morphologically identifiable Golgi apparatus. The cell's capacity for protein sorting is nevertheless unimpeded, exemplified by its ability to cope with massive amounts of newly synthesized cyst wall proteins and glycans, which are sorted to dedicated Golgi-like compartments termed encystation-specific vesicles (ESVs) generated from endoplasmic reticulum (ER)-derived transport intermediates. This soluble bulk cargo is kept strictly separate from constitutively transported variant surface proteins during export, a function that is dependent on the stage-specific recognition of trafficking signals. Encysting Giardia therefore provide a unique system for the study of unconventional, Golgi-independent protein trafficking mechanisms in the broader context of eukaryotic endomembrane organization and evolution. PMID:15225300

  17. Role of the Transcription Factor Sox4 in Insulin Secretion and Impaired Glucose Tolerance

    PubMed Central

    Goldsworthy, Michelle; Hugill, Alison; Freeman, Helen; Horner, Emma; Shimomura, Kenju; Bogani, Debora; Pieles, Guido; Mijat, Vesna; Arkell, Ruth; Bhattacharya, Shoumo; Ashcroft, Frances M.; Cox, Roger D.

    2008-01-01

    OBJECTIVES— To identify, map, clone, and functionally validate a novel mouse model for impaired glucose tolerance and insulin secretion. RESEARCH DESIGN AND METHODS— Haploinsufficiency of the insulin receptor and associated mild insulin resistance has been used to sensitize an N-ethyl-N-nitrosourea (ENU) screen to identify novel mutations resulting in impaired glucose tolerance and diabetes. The new impaired glucose tolerance 4 (IGT4) model was selected using an intraperitoneal glucose tolerance test and inheritance of the phenotype confirmed by generation of backcross progeny. Segregation of the phenotype was correlated with genotype information to map the location of the gene and candidates sequenced for mutations. The function of the SRY-related high mobility group (HMG)-box 4 (Sox4) gene in insulin secretion was tested using another ENU allele and by small interfering RNA silencing in insulinoma cells. RESULTS— We describe two allelic autosomal dominant mutations in the highly conserved HMG box of the transcription factor Sox4. Previously associated with pancreas development, Sox4 mutations in the adult mouse result in an insulin secretory defect, which exhibits impaired glucose tolerance in association with insulin receptor+/−–induced insulin resistance. Elimination of the Sox4 transcript in INS1 and Min6 cells resulted in the abolition of glucose-stimulated insulin release similar to that observed for silencing of the key metabolic enzyme glucokinase. Intracellular calcium measurements in treated cells indicate that this defect lies downstream of the ATP-sensitive K+ channel (KATP channel) and calcium influx. CONCLUSIONS— IGT4 represents a novel digenic model of insulin resistance coupled with an insulin secretory defect. The Sox4 gene has a role in insulin secretion in the adult β-cell downstream of the KATP channel. PMID:18477811

  18. Secretory pathway of cellulase: a mini-review

    PubMed Central

    2013-01-01

    Cellulase plays an important role in modern industry and holds great potential in biofuel production. Many different types of organisms produce cellulase, which go through secretory pathways to reach the extracellular space, where enzymatic reactions take place. Secretory pathways in various cells have been the focus of many research fields; however, there are few studies on secretory pathways of cellulases in the literature. It is therefore necessary and important to review the current knowledge on the secretory pathways of cellulases. In this mini-review, we address the subcellular locations of cellulases in different organisms, discuss the secretory pathways of cellulases in different organisms, and examine the secretory mechanisms of cellulases. These sections start with a description of general secreted proteins, advance to the situation of cellulases, and end with the knowledge of cellulases, as documented in UniProt Knowledgebase (UniProtKB). Finally, gaps in existing knowledge are highlighted, which may shed light on future studies for biofuel engineering. PMID:24295495

  19. COMPARABLE OUTCOMES IN NON-SECRETORY AND SECRETORY MULTIPLE MYELOMA AFTER AUTOLOGOUS STEM CELL TRANSPLANTATION

    PubMed Central

    Kumar, Shaji; Pérez, Waleska S.; Zhang, Mei-Jie; Ballen, Karen; Bashey, Asad; To, L. Bik; Bredeson, Christopher N.; Cairo, Mitchell S.; Elfenbein, Gerald J.; Freytes, César O.; Gale, Robert Peter; Gibson, John; Kyle, Robert A.; Lacy, Martha Q.; Lazarus, Hillard M.; McCarthy, Philip L.; Milone, Gustavo A.; Moreb, Jan S.; Pavlovsky, Santiago; Reece, Donna E.; Vesole, David H.; Wiernik, Peter H.; Hari, Parameswaran

    2008-01-01

    Non-secretory myeloma (NSM) accounts for <5% of cases of multiple myeloma (MM). The outcome of these patients following autologous stem cell transplantation (ASCT) has not been evaluated in clinical trials. We compared the outcomes after ASCT for patients with NSM reported to the CIBMTR between 1989 and 2003, to a matched group of 438 patients (4 controls for each patient) with secretory myeloma (SM). The patients were matched using propensity scores calculated using age, Durie-Salmon stage, sensitivity to pre-transplant therapy, time from diagnosis to transplant and year of transplant. Disease characteristics were similar in both groups at diagnosis and at transplant except higher risk of anemia, hypoalbuminemia and marrow plasmacytosis (in SM) and plasmacytoma (more in NSM). Cumulative incidence of TRM, relapse, PFS and OS were similar between the groups. In multivariate analysis, based on a Cox model stratified on matched pairs and adjusted for covariates not considered in the propensity score, we found no difference in outcome between the NSM and SM groups. In this large cohort of patients undergoing ASCT, we found no difference in outcomes of patients with NSM compared to those with SM. PMID:18804043

  20. Proteolysis sensitizes LDL particles to phospholipolysis by secretory phospholipase A2 group V and secretory sphingomyelinase

    PubMed Central

    Plihtari, Riia; Hurt-Camejo, Eva; Öörni, Katariina; Kovanen, Petri T.

    2010-01-01

    LDL particles that enter the arterial intima become exposed to proteolytic and lipolytic modifications. The extracellular hydrolases potentially involved in LDL modification include proteolytic enzymes, such as chymase, cathepsin S, and plasmin, and phospholipolytic enzymes, such as secretory phospholipases A2 (sPLA2-IIa and sPLA2-V) and secretory acid sphingomyelinase (sSMase). Here, LDL was first proteolyzed and then subjected to lipolysis, after which the effects of combined proteolysis and lipolysis on LDL fusion and on binding to human aortic proteoglycans (PG) were studied. Chymase and cathepsin S led to more extensive proteolysis and release of peptide fragments from LDL than did plasmin. sPLA2-IIa was not able to hydrolyze unmodified LDL, and even preproteolysis of LDL particles failed to enhance lipolysis by this enzyme. However, preproteolysis with chymase and cathepsin S accelerated lipolysis by sPLA2-V and sSMase, which resulted in enhanced fusion and proteoglycan binding of the preproteolyzed LDL particles. Taken together, the results revealed that proteolysis sensitizes the LDL particles to hydrolysis by sPLA2-V and sSMase. By promoting fusion and binding of LDL to human aortic proteoglycans, the combination of proteolysis and phospholipolysis of LDL particles potentially enhances extracellular accumulation of LDL-derived lipids during atherogenesis. PMID:20124257

  1. Progressive quality control of secretory proteins in the early secretory compartment by ERp44

    PubMed Central

    Sannino, Sara; Anelli, Tiziana; Cortini, Margherita; Masui, Shoji; Degano, Massimo; Fagioli, Claudio; Inaba, Kenji; Sitia, Roberto

    2014-01-01

    ERp44 is a pH-regulated chaperone of the secretory pathway. In the acidic milieu of the Golgi, its C-terminal tail changes conformation, simultaneously exposing the substrate-binding site for cargo capture and the RDEL motif for ER retrieval via interactions with cognate receptors. Protonation of cysteine 29 in the active site allows tail movements in vitro and in vivo. Here we show that also conserved histidines in the C-terminal tail regulate ERp44 in vivo. Mutants lacking these histidines are hyperactive in retaining substrates. Surprisingly, they are also O-glycosylated and partially secreted. Co-expression of client proteins prevents secretion of the histidine mutants, forcing tail opening and RDEL accessibility. Client-induced RDEL exposure allows retrieval of proteins from distinct stations along the secretory pathway, as indicated by the changes in O-glycosylation patterns upon over-expression of different partners. The ensuing gradients may help optimising folding and assembly of different cargoes. Endogenous ERp44 is O-glycosylated and secreted by human primary endometrial cells, suggesting possible pathophysiological roles of these processes. PMID:25097228

  2. Secretory sphingomyelinase in health and disease.

    PubMed

    Kornhuber, Johannes; Rhein, Cosima; Müller, Christian P; Mühle, Christiane

    2015-06-01

    Acid sphingomyelinase (ASM), a key enzyme in sphingolipid metabolism, hydrolyzes sphingomyelin to ceramide and phosphorylcholine. In mammals, the expression of a single gene, SMPD1, results in two forms of the enzyme that differ in several characteristics. Lysosomal ASM (L-ASM) is located within the lysosome, requires no additional Zn2+ ions for activation and is glycosylated mainly with high-mannose oligosaccharides. By contrast, the secretory ASM (S-ASM) is located extracellularly, requires Zn2+ ions for activation, has a complex glycosylation pattern and has a longer in vivo half-life. In this review, we summarize current knowledge regarding the physiology and pathophysiology of S-ASM, including its sources and distribution, molecular and cellular mechanisms of generation and regulation and relevant in vitro and in vivo studies. Polymorphisms or mutations of SMPD1 lead to decreased S-ASM activity, as detected in patients with Niemann-Pick disease B. Thus, lower serum/plasma activities of S-ASM are trait markers. No genetic causes of increased S-ASM activity have been identified. Instead, elevated activity is the result of enhanced release (e.g., induced by lipopolysaccharide and cytokine stimulation) or increased enzyme activation (e.g., induced by oxidative stress). Increased S-ASM activity in serum or plasma is a state marker of a wide range of diseases. In particular, high S-ASM activity occurs in inflammation of the endothelium and liver. Several studies have demonstrated a correlation between S-ASM activity and mortality induced by severe inflammatory diseases. Serial measurements of S-ASM reveal prolonged activation and, therefore, the measurement of this enzyme may also provide information on past inflammatory processes. Thus, S-ASM may be both a promising clinical chemistry marker and a therapeutic target. PMID:25803076

  3. Gluconeogenesis is not acutely regulated by either plasma glucose or plasma insulin concentration in parenterally fed ELBW infants

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Parenterally fed ELBW infants often exhibit erratic regulation of plasma glucose levels in response to changes in glucose infusion rate. This apparent dysregulation could be the result of an inappropriate insulin secretory response, incomplete suppression of glucose production, or an inadequate chan...

  4. Dopamine-mediated autocrine inhibitory circuit regulating human insulin secretion in vitro.

    PubMed

    Simpson, Norman; Maffei, Antonella; Freeby, Matthew; Burroughs, Steven; Freyberg, Zachary; Javitch, Jonathan; Leibel, Rudolph L; Harris, Paul E

    2012-10-01

    We describe a negative feedback autocrine regulatory circuit for glucose-stimulated insulin secretion in purified human islets in vitro. Using chronoamperometry and in vitro glucose-stimulated insulin secretion measurements, evidence is provided that dopamine (DA), which is loaded into insulin-containing secretory granules by vesicular monoamine transporter type 2 in human β-cells, is released in response to glucose stimulation. DA then acts as a negative regulator of insulin secretion via its action on D2R, which are also expressed on β-cells. We found that antagonism of receptors participating in islet DA signaling generally drive increased glucose-stimulated insulin secretion. These in vitro observations may represent correlates of the in vivo metabolic changes associated with the use of atypical antipsychotics, such as increased adiposity. PMID:22915827

  5. Dopamine-Mediated Autocrine Inhibitory Circuit Regulating Human Insulin Secretion in Vitro

    PubMed Central

    Simpson, Norman; Maffei, Antonella; Freeby, Matthew; Burroughs, Steven; Freyberg, Zachary; Javitch, Jonathan; Leibel, Rudolph L.

    2012-01-01

    We describe a negative feedback autocrine regulatory circuit for glucose-stimulated insulin secretion in purified human islets in vitro. Using chronoamperometry and in vitro glucose-stimulated insulin secretion measurements, evidence is provided that dopamine (DA), which is loaded into insulin-containing secretory granules by vesicular monoamine transporter type 2 in human β-cells, is released in response to glucose stimulation. DA then acts as a negative regulator of insulin secretion via its action on D2R, which are also expressed on β-cells. We found that antagonism of receptors participating in islet DA signaling generally drive increased glucose-stimulated insulin secretion. These in vitro observations may represent correlates of the in vivo metabolic changes associated with the use of atypical antipsychotics, such as increased adiposity. PMID:22915827

  6. Sexual Dysfunction and Infertility

    MedlinePlus

    ... American Society for Reproductive Medicine Sexual dysfunction and infertility What is sexual dysfunction and how common is ... and 40% of women. For couples dealing with infertility, it is even more common. Often, people ignore ...

  7. Intrinsic Frequency and the Single Wave Biopsy: Implications for Insulin Resistance.

    PubMed

    Petrasek, Danny; Pahlevan, Niema M; Tavallali, Peyman; Rinderknecht, Derek G; Gharib, Morteza

    2015-11-01

    Insulin resistance is the hallmark of classical type II diabetes. In addition, insulin resistance plays a central role in metabolic syndrome, which astonishingly affects 1 out of 3 adults in North America. The insulin resistance state can precede the manifestation of diabetes and hypertension by years. Insulin resistance is correlated with a low-grade inflammatory condition, thought to be induced by obesity as well as other conditions. Currently, the methods to measure and monitor insulin resistance, such as the homeostatic model assessment and the euglycemic insulin clamp, can be impractical, expensive, and invasive. Abundant evidence exists that relates increased pulse pressure, pulse wave velocity (PWV), and vascular dysfunction with insulin resistance. We introduce a potential method of assessing insulin resistance that relies on a novel signal-processing algorithm, the intrinsic frequency method (IFM). The method requires a single pulse pressure wave, thus the term " wave biopsy." PMID:26183600

  8. Insulin signaling controls neurotransmission via the 4eBP-dependent modification of the exocytotic machinery.

    PubMed

    Mahoney, Rebekah Elizabeth; Azpurua, Jorge; Eaton, Benjamin A

    2016-01-01

    Altered insulin signaling has been linked to widespread nervous system dysfunction including cognitive dysfunction, neuropathy and susceptibility to neurodegenerative disease. However, knowledge of the cellular mechanisms underlying the effects of insulin on neuronal function is incomplete. Here, we show that cell autonomous insulin signaling within the Drosophila CM9 motor neuron regulates the release of neurotransmitter via alteration of the synaptic vesicle fusion machinery. This effect of insulin utilizes the FOXO-dependent regulation of the thor gene, which encodes the Drosophila homologue of the eif-4e binding protein (4eBP). A critical target of this regulatory mechanism is Complexin, a synaptic protein known to regulate synaptic vesicle exocytosis. We find that the amounts of Complexin protein observed at the synapse is regulated by insulin and genetic manipulations of Complexin levels support the model that increased synaptic Complexin reduces neurotransmission in response to insulin signaling. PMID:27525480

  9. Insulin pumps.

    PubMed

    Pickup, J

    2011-02-01

    The last year has seen a continued uptake of insulin pump therapy in most countries. The USA is still a leader in pump use, with probably some 40% of type 1 diabetic patients on continuous subcutaneous insulin infusion (CSII), but the large variation in usage within Europe remains, with relatively high use (> 15%) in, for example, Norway, Austria, Germany and Sweden and low use (< 5%) in Spain, the UK, Finland and Portugal. There is much speculation on the factors responsible for this variation, and the possibilities include physician attitudes to CSII and knowledge about its benefits and indications for its use (and inappropriate beliefs about dangers), the availability of reimbursement from insurance companies or funding from national health services, the availability of sufficient diabetes nurse educators and dietitians trained in pump procedures, and clear referral pathways for the pump candidate from general practitioner or general hospital to specialist pump centre. There are now several comprehensive national guidelines on CSII use (see ATTD Yearbook 2009) but more work needs to be done in unifying uptake and ensuring all those who can benefit do so. Technology developments recently include increasing use of pumps with continuous glucose monitoring (CGM) connectivity (see elsewhere in this volume) and the emergence of numerous manufacturers developing so-called 'patch pumps', often for the type 2 diabetes market. Interestingly, the evidence base for CSII in this group is not well established, and for this reason the selected papers on CSII in this section include several in this area. The use of CSII in diabetic pregnancy is a long-established practice, in spite of the lack of evidence that it is superior to multiple daily injections (MDI), and few randomised controlled trials have been done in recent years. Several papers in this field this year continue the debate about the usefulness of CSII in diabetic pregnancy and are reviewed here. It is pleasing

  10. The Role of Mitochondria in the Pathophysiology of Skeletal Muscle Insulin Resistance

    PubMed Central

    Pagel-Langenickel, Ines; Bao, Jianjun; Pang, Liyan; Sack, Michael N.

    2010-01-01

    Multiple organs contribute to the development of peripheral insulin resistance, with the major contributors being skeletal muscle, liver, and adipose tissue. Because insulin resistance usually precedes the development of type 2 diabetes mellitus (T2DM) by many years, understanding the pathophysiology of insulin resistance should enable development of therapeutic strategies to prevent disease progression. Some subjects with mitochondrial genomic variants/defects and a subset of lean individuals with hereditary predisposition to T2DM exhibit skeletal muscle mitochondrial dysfunction early in the course of insulin resistance. In contrast, in the majority of subjects with T2DM the plurality of evidence implicates skeletal muscle mitochondrial dysfunction as a consequence of perturbations associated with T2DM, and these mitochondrial deficits then contribute to subsequent disease progression. We review the affirmative and contrarian data regarding skeletal muscle mitochondrial biology in the pathogenesis of insulin resistance and explore potential therapeutic options to intrinsically modulate mitochondria as a strategy to combat insulin resistance. Furthermore, an overview of restricted molecular manipulations of skeletal muscle metabolic and mitochondrial biology offers insight into the mitochondrial role in metabolic substrate partitioning and in promoting innate adaptive and maladaptive responses that collectively regulate peripheral insulin sensitivity. We conclude that skeletal muscle mitochondrial dysfunction is not generally a major initiator of the pathophysiology of insulin resistance, although its dysfunction is integral to this pathophysiology and it remains an intriguing target to reverse/delay the progressive perturbations synonymous with T2DM. PMID:19861693

  11. Insulin resistance causes human gallbladder dysmotility.

    PubMed

    Nakeeb, Attila; Comuzzie, Anthony G; Al-Azzawi, Hayder; Sonnenberg, Gabriele E; Kissebah, Ahmed H; Pitt, Henry A

    2006-01-01

    Obesity, diabetes, and hyperlipidemia are known risk factors for the development of gallstones. A growing body of animal and human data has correlated insulin resistance with organ dysfunction. The relationship among obesity, diabetes, hyperlipidemia, and abnormal gallbladder motility remains unclear. Therefore, we designed a study to investigate the association among obesity, insulin resistance, hyperlipidemia, and gallbladder dysmotility. One hundred ninety-two healthy adult nondiabetic volunteers were studied. Gallbladder ultrasounds were performed before and after a standardized fatty meal. A gallbladder ejection fraction (EF) was calculated, and an EF of < 25% was considered abnormal. Serum was analyzed for cholesterol, triglycerides, cholecystokinin, leptin, glucose, and insulin. The homeostasis assessment model (HOMA) was used to determine insulin resistance. The volunteers had a mean age of 38 years (range, 18-77), and 55% were female. Thirty subjects (15%) had gallstones and were excluded from the study. Thirty subjects (19%) had abnormal gallbladder motility (EF < 25%). In lean subjects (n = 96) fasting glucose was significantly increased in the 16 subjects with gallbladder EF < 25% versus the 80 subjects with gallbladder EF > 25% (109 +/- 20 mg/dl versus 78 +/- 2 mg/dl, P < 0.05). Similarly, the HOMA index was significantly greater in subjects with gallbladder EF < 25% versus gallbladder EF >25% (3.3 +/- 1.2 versus 2.0 +/- 0.2, P < 0.05). In obese subjects (n = 66), fasting glucose, insulin, and insulin resistance were not associated with a gallbladder EF < 25%. These data suggest that in lean, nondiabetic volunteers without gallstones, gallbladder dysmotility is associated with an elevated fasting glucose as well as a high index of insulin resistance. We conclude that insulin resistance alone may be responsible for gallbladder dysmotility that may result in acalculous cholecystitis or gallstone formation. PMID:16843864

  12. Opiate-prostaglandin interactions in the regulation of insulin secretion from rat islets of Langerhans in vitro

    SciTech Connect

    Green, I.C.; Tadayyon, M.

    1988-01-01

    The inadequate insulin secretory response to glucose stimulation in non-insulin dependent diabetes has been attributed to many factors including high PGE/sub 2/ levels blunting the secretory response, and to the existence of inhibitory opiate activity in vivo. The purpose of the present work was to see if there was a connection between these two independent theories. Radioimmunoassayable PGE/sub 2/ in islets of Langerhans was found to be proportional to islet number and protein content and was typically 4 to 5pg/..mu..g islet protein. Indomethacin sodium salicylate and chlorpropamide all lowered islet PGE/sub 2/ levels and stimulated insulin release in vitro. Dynorphin stimulated insulin release at a concentration of 6 x 10/sup -9/M, while lowering islet PGE/sub 2/. Conversely, at a higher concentration, dynorphin had no stimulatory effect on insulin secretion and did not lower PGE/sub 2/ levels in islets or in the incubation media. The stimulatory effects of dynorphin and sodium salicylate on insulin secretion were blocked by exogenous PGE/sub 2/. PGE/sub 2/ at a lower concentration did not exert any inhibitory effect on dynorphin- or sodium salicylate-induced insulin release. This concentration of exogenous PGE/sub 2/ stimulated insulin release in the presence of 6mM glucose.

  13. Synchronization of Ca(2+)-signals within insulin-secreting pseudoislets: effects of gap-junctional uncouplers.

    PubMed

    Squires, P E; Hauge-Evans, A C; Persaud, S J; Jones, P M

    2000-05-01

    The secretory response of the intact islet is greater than the response of individual beta-cells in isolation, and functional coupling between cells is critical in insulin release. The changes in intracellular Ca(2+)([Ca(2+)](i)) which initiate insulin secretory responses are synchronized between groups of cells within the islet, and gap-junctions are thought to play a central role in coordinating signalling events. We have used the MIN6 insulin-secreting cell line, to examine whether uncoupling gap-junctions alters the synchronicity of nutrient- and non-nutrient-evoked Ca(2+)oscillations, or affects insulin secretion. MIN6 cells express mRNA species that can be amplified using PCR primers for connexin 36. A commonly used gap-junctional inhibitor, heptanol, inhibited glucose- and tolbutamide-induced Ca(2+)-oscillations to basal levels in MIN6 cell clusters at concentrations of 0.5 mM and greater, and it had similar effects in pseudoislets when used at 2.5 mM. Lower heptanol concentrations altered the frequency of Ca(2+)transients without affecting their synchronicity, in both monolayers and pseudoislets. Heptanol also had effects on insulin secretion from MIN6 pseudoislets such that 1 mM enhanced secretion while 2.5 mM was inhibitory. These data suggest that heptanol has multiple effects in pancreatic beta-cells, none of which appears to be related to uncoupling of synchronicity of Ca(2+)signalling between cells. A second gap-junction uncoupler, 18 alpha-glycyrrhetinic acid, also failed to uncouple synchronized Ca(2+)-oscillations, and it had no effect on insulin secretion. These data provide evidence that Ca(2+)signalling events occur simultaneously across the bulk mass of the pseudoislet, and suggest that gap-junctions are not required to coordinate the synchronicity of these events, nor is communication via gap junctions essential for integrated insulin secretory responses. PMID:10859595

  14. Stress modulates intestinal secretory immunoglobulin A

    PubMed Central

    Campos-Rodríguez, Rafael; Godínez-Victoria, Marycarmen; Abarca-Rojano, Edgar; Pacheco-Yépez, Judith; Reyna-Garfias, Humberto; Barbosa-Cabrera, Reyna Elizabeth; Drago-Serrano, Maria Elisa

    2013-01-01

    Stress is a response of the central nervous system to environmental stimuli perceived as a threat to homeostasis. The stress response triggers the generation of neurotransmitters and hormones from the hypothalamus pituitary adrenal axis, sympathetic axis and brain gut axis, and in this way modulates the intestinal immune system. The effects of psychological stress on intestinal immunity have been investigated mostly with the restraint/immobilization rodent model, resulting in an up or down modulation of SIgA levels depending on the intensity and time of exposure to stress. SIgA is a protein complex formed by dimeric (dIgA) or polymeric IgA (pIgA) and the secretory component (SC), a peptide derived from the polymeric immunoglobulin receptor (pIgR). The latter receptor is a transmembrane protein expressed on the basolateral side of gut epithelial cells, where it uptakes dIgA or pIgA released by plasma cells in the lamina propria. As a result, the IgA-pIgR complex is formed and transported by vesicles to the apical side of epithelial cells. pIgR is then cleaved to release SIgA into the luminal secretions of gut. Down modulation of SIgA associated with stress can have negative repercussions on intestinal function and integrity. This can take the form of increased adhesion of pathogenic agents to the intestinal epithelium and/or an altered balance of inflammation leading to greater intestinal permeability. Most studies on the molecular and biochemical mechanisms involved in the stress response have focused on systemic immunity. The present review analyzes the impact of stress (mostly by restraint/immobilization, but also with mention of other models) on the generation of SIgA, pIgR and other humoral and cellular components involved in the intestinal immune response. Insights into these mechanisms could lead to better therapies for protecting against pathogenic agents and avoiding epithelial tissue damage by modulating intestinal inflammation. PMID:24348350

  15. Human insulin genome sequence map, biochemical structure of insulin for recombinant DNA insulin.

    PubMed

    Chakraborty, Chiranjib; Mungantiwar, Ashish A

    2003-08-01

    Insulin is a essential molecule for type I diabetes that is marketed by very few companies. It is the first molecule, which was made by recombinant technology; but the commercialization process is very difficult. Knowledge about biochemical structure of insulin and human insulin genome sequence map is pivotal to large scale manufacturing of recombinant DNA Insulin. This paper reviews human insulin genome sequence map, the amino acid sequence of porcine insulin, crystal structure of porcine insulin, insulin monomer, aggregation surfaces of insulin, conformational variation in the insulin monomer, insulin X-ray structures for recombinant DNA technology in the synthesis of human insulin in Escherichia coli. PMID:12769691

  16. Adventures with Insulin in the Islets of Langerhans

    PubMed Central

    Steiner, Donald F.

    2011-01-01

    Insulin is a small but beautifully organized protein with a unique two-chain structure, the first protein to be sequenced. The mechanism of its biosynthesis invited much initial speculation but was finally clarified by the discovery of proinsulin, its single-chain precursor. The rich present-day field of protein precursor processing via post-translational proteolysis within the secretory pathway arose in the early 1970s as an offshoot of studies on insulin biosynthesis, which provided a novel paradigm for the generation of many other small neuroendocrine peptides. Before long, this mechanism was also found to play a role in the production of a much wider spectrum of proteins traversing the secretory pathway (receptors, growth factors, blood-clotting components, and even many viral envelope proteins) occurring in almost all eukaryotic cells. Indeed, yeast provided a key clue in the search for the proprotein convertases, the endoproteases that work along with carboxypeptidases and other modifying enzymes, such as the amidating enzyme complex (PAM), in converting inactive or less active precursor proteins into their fully active peptide products. In this “Reflections” article, I have tried to recount the people and events in my life that led to my involvement first in basic biochemical research and then on to insulin, proinsulin, and many relevant related areas that continue to fascinate and challenge my colleagues and me, as well as many other biomedical scientists today, as diabetes mellitus increasingly threatens human health throughout our contemporary world. PMID:21454641

  17. A secretory kinase complex regulates extracellular protein phosphorylation.

    PubMed

    Cui, Jixin; Xiao, Junyu; Tagliabracci, Vincent S; Wen, Jianzhong; Rahdar, Meghdad; Dixon, Jack E

    2015-01-01

    Although numerous extracellular phosphoproteins have been identified, the protein kinases within the secretory pathway have only recently been discovered, and their regulation is virtually unexplored. Fam20C is the physiological Golgi casein kinase, which phosphorylates many secreted proteins and is critical for proper biomineralization. Fam20A, a Fam20C paralog, is essential for enamel formation, but the biochemical function of Fam20A is unknown. Here we show that Fam20A potentiates Fam20C kinase activity and promotes the phosphorylation of enamel matrix proteins in vitro and in cells. Mechanistically, Fam20A is a pseudokinase that forms a functional complex with Fam20C, and this complex enhances extracellular protein phosphorylation within the secretory pathway. Our findings shed light on the molecular mechanism by which Fam20C and Fam20A collaborate to control enamel formation, and provide the first insight into the regulation of secretory pathway phosphorylation. PMID:25789606

  18. Control systems and coordination protocols of the secretory pathway.

    PubMed

    Luini, Alberto; Mavelli, Gabriella; Jung, Juan; Cancino, Jorge

    2014-01-01

    Like other cellular modules, the secretory pathway and the Golgi complex are likely to be supervised by control systems that support homeostasis and optimal functionality under all conditions, including external and internal perturbations. Moreover, the secretory apparatus must be functionally connected with other cellular modules, such as energy metabolism and protein degradation, via specific rules of interaction, or "coordination protocols". These regulatory devices are of fundamental importance for optimal function; however, they are generally "hidden" at steady state. The molecular components and the architecture of the control systems and coordination protocols of the secretory pathway are beginning to emerge through studies based on the use of controlled transport-specific perturbations aimed specifically at the detection and analysis of these internal regulatory devices. PMID:25374666

  19. [Physiology of secretory cells in the mouse mammary gland].

    PubMed

    Tolkunov, Iu A; Markov, A G

    2000-08-01

    Secretory cells' membrane potential and transepithelial potential difference in the mouse mammary gland diminish within 2.5 hours following breast-feeding of the litter. The transepithelial resistance for up to 20 hours after the feeding did not drop below 40-70 k omega. The secret pressure in the mammary gland does not grow during this period. Therefore an increase of interval between litter feeding up to 20 hours does not entail any mechanical lesion of the secretory epithelium. The latter's cells seem to secrete organic and inorganic substances in concentrations which do not change significantly during their transfer along the outgoing ducts. PMID:11059022

  20. Ultrastructural features of goat oviductal secretory cells at follicular and luteal phases of the oestrous cycle

    PubMed Central

    ABE, HIROYUKI; ONODERA, MASAKAZU; SUGAWARA, SHICHIRO; SATOH, TAKESHI; HOSHI, HIROYOSHI

    1999-01-01

    The aim of the present study was to investigate the ultrastructure of secretory cells in the various regions of the goat oviduct during the follicular and luteal phases of the oestrous cycle. During the follicular phase in the fimbriae, the secretory cells contained small secretory granules with electron-dense matrices. In the luteal phase, the secretory granules disappeared and cytoplasmic protrusions, extending beyond the luminal border of the ciliated cells and often containing the nucleus, were predominant. During the follicular phase in ampullary secretory cells, numerous secretory granules with moderately electron-dense matrices were present in the supranuclear cytoplasm and exocytosis of secretory granules was observed. The number of secretory granules was dramatically reduced in the ampullary secretory cells at the luteal phase. Conspicuous cytoplasmic protrusions of secretory cells were observed similar to those of the fimbrial epithelium. Isthmic cells were almost free of secretory granules and lysosome-like bodies were found both at the follicular and luteal phases. In conclusion, our ultrastructural observations of goat oviduct revealed marked cyclic changes in the ultrastructural features of secretory cells and the ultrastructural features and the numbers of secretory granules were distinctive for each particular segment. PMID:10634690

  1. Insulin pump (image)

    MedlinePlus

    The catheter at the end of the insulin pump is inserted through a needle into the abdominal ... with diabetes. Dosage instructions are entered into the pump's small computer and the appropriate amount of insulin ...

  2. Inflammation and Insulin Resistance

    PubMed Central

    de Luca, Carl; Olefsky, Jerrold M.

    2008-01-01

    Obesity-induced chronic inflammation is a key component in the pathogenesis of insulin resistance and the Metabolic syndrome. In this review, we focus on the interconnection between obesity, inflammation and insulin resistance. Pro-inflammatory cytokines can cause insulin resistance in adipose tissue, skeletal muscle and liver by inhibiting insulin signal transduction. The sources of cytokines in insulin resistant states are the insulin target tissue themselves, primarily fat and liver, but to a larger extent the activated tissue resident macrophages. While the initiating factors of this inflammatory response remain to be fully determined, chronic inflammation in these tissues could cause localized insulin resistance via autocrine/paracrine cytokine signaling and systemic insulin resistance via endocrine cytokine signaling all of which contribute to the abnormal metabolic state. PMID:18053812

  3. High-mix insulins

    PubMed Central

    Kalra, Sanjay; Farooqi, Mohammad Hamed; El-Houni, Ali E.

    2015-01-01

    Premix insulins are commonly used insulin preparations, which are available in varying ratios of different molecules. These drugs contain one short- or rapid-acting, and one intermediate- or long-acting insulin. High-mix insulins are mixtures of insulins that contain 50% or more than 50% of short-acting insulin. This review describes the clinical pharmacology of high-mix insulins, including data from randomized controlled trials. It suggests various ways, in which high-mix insulin can be used, including once daily, twice daily, thrice daily, hetero-mix, and reverse regimes. The authors provide a rational framework to help diabetes care professionals, identify indications for pragmatic high-mix use. PMID:26425485

  4. Giving an insulin injection

    MedlinePlus

    ... room temperature for a month. Gather your supplies: insulin, needles, syringes, alcohol wipes, and a container for used needles ... the plunger to get the right dose of insulin into the syringe. Check the syringe for air bubbles. If there ...

  5. Inflammation-induced microvascular insulin resistance is an early event in diet-induced obesity

    PubMed Central

    Zhao, Lina; Fu, Zhuo; Wu, Jing; Aylor, Kevin W.; Barrett, Eugene J.; Cao, Wenhong

    2015-01-01

    Endothelial dysfunction and vascular insulin resistance usually coexist and chronic inflammation engenders both. In the present study, we investigate the temporal relationship between vascular insulin resistance and metabolic insulin resistance. We assessed insulin responses in all arterial segments, including aorta, distal saphenous artery and the microvasculature, as well as the metabolic insulin responses in muscle in rats fed on a high-fat diet (HFD) for various durations ranging from 3 days to 4 weeks with or without sodium salicylate treatment. Compared with controls, HFD feeding significantly blunted insulin-mediated Akt (protein kinase B) and eNOS [endothelial nitric oxide (NO) synthase] phosphorylation in aorta in 1 week, blunted vasodilatory response in small resistance vessel in 4 weeks and microvascular recruitment in as early as 3 days. Insulin-stimulated whole body glucose disposal did not begin to progressively decrease until after 1 week. Salicylate treatment fully inhibited vascular inflammation, prevented microvascular insulin resistance and significantly improved muscle metabolic responses to insulin. We conclude that microvascular insulin resistance is an early event in diet-induced obesity and insulin resistance and inflammation plays an essential role in this process. Our data suggest microvascular insulin resistance contributes to the development of metabolic insulin resistance in muscle and muscle microvasculature is a potential therapeutic target in the prevention and treatment of diabetes and its related complications. PMID:26265791

  6. PGC-1α Integrates Insulin Signaling, Mitochondrial Regulation, and Bioenergetic Function in Skeletal Muscle*S⃞

    PubMed Central

    Pagel-Langenickel, Ines; Bao, Jianjun; Joseph, Joshua J.; Schwartz, Daniel R.; Mantell, Benjamin S.; Xu, Xiuli; Raghavachari, Nalini; Sack, Michael N.

    2008-01-01

    The pathophysiology underlying mitochondrial dysfunction in insulin-resistant skeletal muscle is incompletely characterized. To further delineate this we investigated the interaction between insulin signaling, mitochondrial regulation, and function in C2C12 myotubes and in skeletal muscle. In myotubes elevated insulin and glucose disrupt insulin signaling, mitochondrial biogenesis, and mitochondrial bioenergetics. The insulin-sensitizing thiazolidinedione pioglitazone restores these perturbations in parallel with induction of the mitochondrial biogenesis regulator PGC-1α. Overexpression of PGC-1α rescues insulin signaling and mitochondrial bioenergetics, and its silencing concordantly disrupts insulin signaling and mitochondrial bioenergetics. In primary skeletal myoblasts pioglitazone also up-regulates PGC-1α expression and restores the insulin-resistant mitochondrial bioenergetic profile. In parallel, pioglitazone up-regulates PGC-1α in db/db mouse skeletal muscle. Interestingly, the small interfering RNA knockdown of the insulin receptor in C2C12 myotubes down-regulates PGC-1α and attenuates mitochondrial bioenergetics. Concordantly, mitochondrial bioenergetics are blunted in insulin receptor knock-out mouse-derived skeletal myoblasts. Taken together these data demonstrate that elevated glucose and insulin impairs and pioglitazone restores skeletal myotube insulin signaling, mitochondrial regulation, and bioenergetics. Pioglitazone functions in part via the induction of PGC-1α. Moreover, PGC-1α is identified as a bidirectional regulatory link integrating insulin-signaling and mitochondrial homeostasis in skeletal muscle. PMID:18579525

  7. Inflammation-induced microvascular insulin resistance is an early event in diet-induced obesity.

    PubMed

    Zhao, Lina; Fu, Zhuo; Wu, Jing; Aylor, Kevin W; Barrett, Eugene J; Cao, Wenhong; Liu, Zhenqi

    2015-12-01

    Endothelial dysfunction and vascular insulin resistance usually coexist and chronic inflammation engenders both. In the present study, we investigate the temporal relationship between vascular insulin resistance and metabolic insulin resistance. We assessed insulin responses in all arterial segments, including aorta, distal saphenous artery and the microvasculature, as well as the metabolic insulin responses in muscle in rats fed on a high-fat diet (HFD) for various durations ranging from 3 days to 4 weeks with or without sodium salicylate treatment. Compared with controls, HFD feeding significantly blunted insulin-mediated Akt (protein kinase B) and eNOS [endothelial nitric oxide (NO) synthase] phosphorylation in aorta in 1 week, blunted vasodilatory response in small resistance vessel in 4 weeks and microvascular recruitment in as early as 3 days. Insulin-stimulated whole body glucose disposal did not begin to progressively decrease until after 1 week. Salicylate treatment fully inhibited vascular inflammation, prevented microvascular insulin resistance and significantly improved muscle metabolic responses to insulin. We conclude that microvascular insulin resistance is an early event in diet-induced obesity and insulin resistance and inflammation plays an essential role in this process. Our data suggest microvascular insulin resistance contributes to the development of metabolic insulin resistance in muscle and muscle microvasculature is a potential therapeutic target in the prevention and treatment of diabetes and its related complications. PMID:26265791

  8. Physical analysis of ejaculate to evaluate the secretory activity of the seminal vesicles and prostate.

    PubMed

    Andrade-Rocha, Fernando Tadeu

    2005-01-01

    The purpose of this study was to ascertain whether analysis of the physical properties of ejaculate also has any diagnostic potential for evaluating the function of these accessory sex glands. Diverse normal and abnormal states of coagulation, liquefaction, volume, viscosity and pH were studied with regard to the levels of biochemical markers of the seminal vesicles (fructose and inorganic phosphorus) and prostate (calcium, zinc and acid phosphatase). Fructose and inorganic phosphorus were significantly decreased in samples with absent or poor coagulation (p<0.001), volume < 2.0 mL (p=0.009 and p<0.001, respectively), hypoviscosity (p=0.013 and p<0.001), hyperviscosity (p=0.006 and p<0.001) and pH < or = 7.1 (p=0.018 and p<0.001). Also, fructose and inorganic phosphorus were significantly decreased in samples with liquefaction > 120 min (p=0.003) and pH > 8.0 (p<0.001), respectively. Calcium, zinc and acid phosphatase activity were significantly increased in samples with absent or poor coagulation (p<0.001), and significantly decreased in samples with volume > 5.0 mL (p=0.007, p=0.034 and p=0.011) and pH > 8.0 (p<0.001). Also, calcium and zinc were significantly increased in hypoviscous samples (p=0.012 and p=0.003), whereas the zinc concentration was significantly lower in hyperviscous samples (p=0.026). Using receiver operating characteristic (ROC) curve analysis, pH showed the highest predictive power to identify prostate dysfunction (83.6%) and simultaneous prostate and seminal vesicle dysfunction (98.8%). Physical analysis of ejaculate was also found to be clinically useful for evaluating the secretory activity of the seminal vesicles and prostate. Abnormal coagulation, liquefaction, volume, viscosity and pH strongly suggest gland dysfunction. PMID:16232086

  9. Adherence to Insulin Therapy.

    PubMed

    Sarbacker, G Blair; Urteaga, Elizabeth M

    2016-08-01

    IN BRIEF Six million people with diabetes use insulin either alone or in combination with an oral medication. Many barriers exist that lead to poor adherence with insulin. However, there is an underwhelming amount of data on interventions to address these barriers and improve insulin adherence. Until pharmacological advancements create easier, more acceptable insulin regimens, it is imperative to involve patients in shared decision-making. PMID:27574371

  10. Insulin therapy in pregnancy.

    PubMed

    Kalra, Sanjay; Jawad, Fatema

    2016-09-01

    Insulin is the mainstay of pharmacotherapy in pregnancy complicated by diabetes. This review covers the various insulin regimes and preparations, explaining how to use them, and decide appropriate doses in pregnancy. It approaches insulin treatment from a patient - centred, as well as physician and obstetrician friendly viewpoint, providing pragmatic guidance for management of diabetes in pregnancy. PMID:27582152

  11. Diapause is associated with a change in the polarity of secretion of insulin-like peptides.

    PubMed

    Matsunaga, Yohei; Honda, Yoko; Honda, Shuji; Iwasaki, Takashi; Qadota, Hiroshi; Benian, Guy M; Kawano, Tsuyoshi

    2016-01-01

    The insulin/IGF-1 signalling (IIS) pathway plays an important role in the regulation of larval diapause, the long-lived growth arrest state called dauer arrest, in Caenorhabditis elegans. In this nematode, 40 insulin-like peptides (ILPs) have been identified as putative ligands of the IIS pathway; however, it remains unknown how ILPs modulate larval diapause. Here we show that the secretory polarity of INS-35 and INS-7, which suppress larval diapause, is changed in the intestinal epithelial cells at larval diapause. These ILPs are secreted from the intestine into the body cavity during larval stages. In contrast, they are secreted into the intestinal lumen and degraded during dauer arrest, only to be secreted into the body cavity again when the worms return to developmental growth. The process that determines the secretory polarity of INS-35 and INS-7, thus, has an important role in the modulation of larval diapause. PMID:26838180

  12. Diapause is associated with a change in the polarity of secretion of insulin-like peptides

    PubMed Central

    Matsunaga, Yohei; Honda, Yoko; Honda, Shuji; Iwasaki, Takashi; Qadota, Hiroshi; Benian, Guy M.; Kawano, Tsuyoshi

    2016-01-01

    The insulin/IGF-1 signalling (IIS) pathway plays an important role in the regulation of larval diapause, the long-lived growth arrest state called dauer arrest, in Caenorhabditis elegans. In this nematode, 40 insulin-like peptides (ILPs) have been identified as putative ligands of the IIS pathway; however, it remains unknown how ILPs modulate larval diapause. Here we show that the secretory polarity of INS-35 and INS-7, which suppress larval diapause, is changed in the intestinal epithelial cells at larval diapause. These ILPs are secreted from the intestine into the body cavity during larval stages. In contrast, they are secreted into the intestinal lumen and degraded during dauer arrest, only to be secreted into the body cavity again when the worms return to developmental growth. The process that determines the secretory polarity of INS-35 and INS-7, thus, has an important role in the modulation of larval diapause. PMID:26838180

  13. Low- and high-frequency insulin secretion pulses in normal subjects and pancreas transplant recipients: role of extrinsic innervation.

    PubMed Central

    Sonnenberg, G E; Hoffmann, R G; Johnson, C P; Kissebah, A H

    1992-01-01

    Low-frequency ultradian and high-frequency insulin secretion pulses were studied in normal subjects and in metabolically stable pancreas transplant recipients. Insulin secretion pulsatility was evaluated after deconvoluting the pulsatile plasma C peptide concentrations with its kinetic coefficients. In normal subjects, ultradian insulin secretion pulses with periodicities of 75-115 min were consistently observed during the 24-h secretory cycle. Pulse period and relative amplitude during the overnight rest (95 +/- 4 min and 27.6 +/- 2.4%) were similar to those during the steady state of continuous enteral feeding (93 +/- 5 min and 32.6 +/- 3.3%). Sampling at 2-min intervals revealed the presence of high-frequency insulin secretion pulses with periodicities of 14-20 min and an average amplitude of 46.6 +/- 5.4%. Pancreas transplant recipients had normal fasting and fed insulin secretion rates. Both low- and high-frequency insulin secretion pulses were present. The high-frequency pulse characteristics were identical to normal. Low-frequency ultradian pulse periodicity was normal but pulse amplitude was increased. Thus, ultradian insulin secretory pulsatility is a consistent feature in normal subjects. The low- and high-frequency secretion pulsatilities are generated independent of extrinsic innervation. Autonomic innervation might modulate low-frequency ultradian pulse amplitude exerting a dampening effect. PMID:1644923

  14. PICK1 and ICA69 control insulin granule trafficking and their deficiencies lead to impaired glucose tolerance.

    PubMed

    Cao, Mian; Mao, Zhuo; Kam, Chuen; Xiao, Nan; Cao, Xiaoxing; Shen, Chong; Cheng, Kenneth K Y; Xu, Aimin; Lee, Kwong-Man; Jiang, Liwen; Xia, Jun

    2013-01-01

    Diabetes is a metabolic disorder characterized by hyperglycemia. Insulin, which is secreted by pancreatic beta cells, is recognized as the critical regulator of blood glucose, but the molecular machinery responsible for insulin trafficking remains poorly defined. In particular, the roles of cytosolic factors that govern the formation and maturation of insulin granules are unclear. Here we report that PICK1 and ICA69, two cytosolic lipid-binding proteins, formed heteromeric BAR-domain complexes that associated with insulin granules at different stages of their maturation. PICK1-ICA69 heteromeric complexes associated with immature secretory granules near the trans-Golgi network (TGN). A brief treatment of Brefeldin A, which blocks vesicle budding from the Golgi, increased the amount of PICK1 and ICA69 at TGN. On the other hand, mature secretory granules were associated with PICK1 only, not ICA69. PICK1 deficiency in mice caused the complete loss of ICA69 and led to increased food and water intake but lower body weight. Glucose tolerance tests demonstrated that these mutant mice had high blood glucose, a consequence of insufficient insulin. Importantly, while the total insulin level was reduced in PICK1-deficient beta cells, proinsulin was increased. Lastly, ICA69 knockout mice also displayed similar phenotype as the mice deficient in PICK1. Together, our results indicate that PICK1 and ICA69 are key regulators of the formation and maturation of insulin granules. PMID:23630453

  15. Secretory signal peptide modification for optimized antibody-fragment expression-secretion in Leishmania tarentolae

    PubMed Central

    2012-01-01

    Background Secretory signal peptides (SPs) are well-known sequence motifs targeting proteins for translocation across the endoplasmic reticulum membrane. After passing through the secretory pathway, most proteins are secreted to the environment. Here, we describe the modification of an expression vector containing the SP from secreted acid phosphatase 1 (SAP1) of Leishmania mexicana for optimized protein expression-secretion in the eukaryotic parasite Leishmania tarentolae with regard to recombinant antibody fragments. For experimental design the online tool SignalP was used, which predicts the presence and location of SPs and their cleavage sites in polypeptides. To evaluate the signal peptide cleavage site as well as changes of expression, SPs were N-terminally linked to single-chain Fragment variables (scFv’s). The ability of L. tarentolae to express complex eukaryotic proteins with highly diverse post-translational modifications and its easy bacteria-like handling, makes the parasite a promising expression system for secretory proteins. Results We generated four vectors with different SP-sequence modifications based on in-silico analyses with SignalP in respect to cleavage probability and location, named pLTEX-2 to pLTEX-5. To evaluate their functionality, we cloned four individual scFv-fragments into the vectors and transfected all 16 constructs into L. tarentolae. Independently from the expressed scFv, pLTEX-5 derived constructs showed the highest expression rate, followed by pLTEX-4 and pLTEX-2, whereas only low amounts of protein could be obtained from pLTEX-3 clones, indicating dysfunction of the SP. Next, we analysed the SP cleavage sites by Edman degradation. For pLTEX-2, -4, and -5 derived scFv’s, the results corresponded to in-silico predictions, whereas pLTEX-3 derived scFv’s contained one additional amino-acid (AA). Conclusions The obtained results demonstrate the importance of SP-sequence optimization for efficient expression-secretion of sc

  16. The transcriptional corepressor MTGR1 regulates intestinal secretory lineage allocation.

    PubMed

    Parang, Bobak; Rosenblatt, Daniel; Williams, Amanda D; Washington, Mary K; Revetta, Frank; Short, Sarah P; Reddy, Vishruth K; Hunt, Aubrey; Shroyer, Noah F; Engel, Michael E; Hiebert, Scott W; Williams, Christopher S

    2015-03-01

    Notch signaling largely determines intestinal epithelial cell fate. High Notch activity drives progenitors toward absorptive enterocytes by repressing secretory differentiation programs, whereas low Notch permits secretory cell assignment. Myeloid translocation gene-related 1 (MTGR1) is a transcriptional corepressor in the myeloid translocation gene/Eight-Twenty-One family. Given that Mtgr1(-/-) mice have a dramatic reduction of intestinal epithelial secretory cells, we hypothesized that MTGR1 is a key repressor of Notch signaling. In support of this, transcriptome analysis of laser capture microdissected Mtgr1(-/-) intestinal crypts revealed Notch activation, and secretory markers Mucin2, Chromogranin A, and Growth factor-independent 1 (Gfi1) were down-regulated in Mtgr1(-/-) whole intestines and Mtgr1(-/-) enteroids. We demonstrate that MTGR1 is in a complex with Suppressor of Hairless Homolog, a key Notch effector, and represses Notch-induced Hairy/Enhancer of Split 1 activity. Moreover, pharmacologic Notch inhibition using a γ-secretase inhibitor (GSI) rescued the hyperproliferative baseline phenotype in the Mtgr1(-/-) intestine and increased production of goblet and enteroendocrine lineages in Mtgr1(-/-) mice. GSI increased Paneth cell production in wild-type mice but failed to do so in Mtgr1(-/-) mice. We determined that MTGR1 can interact with GFI1, a transcriptional corepressor required for Paneth cell differentiation, and repress GFI1 targets. Overall, the data suggest that MTGR1, a transcriptional corepressor well characterized in hematopoiesis, plays a critical role in intestinal lineage allocation. PMID:25398765

  17. Clinical applications of the radioimmunoassay of secretory tuberculoprotein.

    PubMed Central

    Straus, E; Wu, N; Quraishi, M A; Levine, S

    1981-01-01

    A radioimmunoassay that measures a specific secretory tuberculoprotein was used to detect Mycobacterium tuberculosis in 9 of 30 liquid cultures of sputum. The accumulation of immunoreactive material in liquid cultures containing isoniazid was shown to reflect in vitro susceptibility of mycobacteria to the antibiotic effects of the drug. PMID:6789332

  18. Insulin Degludec (rDNA Origin) Injection

    MedlinePlus

    ... man-made version of human insulin. Insulin degludec works by replacing the insulin that is normally produced ... insulin label to make sure you received the right type of insulin from the pharmacy.Insulin degludec ...

  19. Porosome: the secretory NanoMachine in cells.

    PubMed

    Jena, Bhanu P

    2013-01-01

    Cells synthesize and store within membranous sacs products such as hormones, growth factors, neurotransmitters, or digestive enzymes, for release on demand. As recently as just 15 years ago, it was believed that during cell secretion, membrane-bound secretory vesicles completely merge at the cell plasma membrane resulting in the diffusion of intravesicular contents to the cell exterior and the compensatory retrieval of the excess membrane by endocytosis. This explanation, however, failed to explain the generation of partially empty vesicles observed in electron micrographs following secretion. Logically therefore, in a 1993 News and Views article in the journal Nature, Prof. Erwin Neher wrote "It seems terribly wasteful that, during the release of hormones and neurotransmitters from a cell, the membrane of a vesicle should merge with the plasma membrane to be retrieved for recycling only seconds or minutes later." The discovery of permanent secretory portals or nanomachines at the cell plasma membrane called POROSOMES, where membrane-bound secretory vesicles transiently dock and fuse to release intravesicular contents to the cell exterior, has finally resolved this conundrum. Following this discovery, the composition of the porosome, its structure and dynamics visualized with high-resolution imaging techniques atomic force and electron microscopy, and its functional reconstitution into artificial lipid membrane have provided a molecular understanding of cell secretion. In agreement, it has been demonstrated that "secretory granules are recaptured largely intact after stimulated exocytosis in cultured endocrine cells" (Proc Natl Acad Sci U S A 100:2070-2075, 2003); that "single synaptic vesicles fuse transiently and successively without loss of identity" (Nature 423:643-647, 2003); and that "zymogen granule exocytosis is characterized by long fusion pore openings and preservation of vesicle lipid identity" (Proc Natl Acad Sci U S A 101:6774-6779, 2004). It made no

  20. Isolated rat hepatocyte couplets: a primary secretory unit for electrophysiologic studies of bile secretory function.

    PubMed

    Graf, J; Gautam, A; Boyer, J L

    1984-10-01

    Hepatocyte couplets were isolated by collagenase perfusion from rat liver. Between adjacent cells, the bile canaliculus forms a closed space into which secretion occurs. As in intact liver, Mg2+-ATPase is localized at the canalicular lumen, the organic anion fluorescein is excreted, and secretion is modified by osmotic gradients. By passing a microelectrode through one cell into the canalicular vacuole, a transepithelial potential profile was obtained. In 27 cell couplets the steady-state intracellular (-26.3 +/- 5.3 mV) and intracanalicular (-5.9 +/- 3.3 mV) potentials were recorded at 37 degrees C with reference to the external medium. Input resistances were determined within the cell (86 +/- 23 M omega) and in the bile canalicular lumen (32 +/- 17 M omega) by passing current pulses through the microelectrode. These data define electrical driving forces for ion transport across the sinusoidal, canalicular, and paracellular barriers and indicate ion permeation across a leaky paracellular junctional pathway. These findings indicate that the isolated hepatocyte couplet is an effective model for electrophysiologic studies of bile secretory function. PMID:6149546

  1. Stress Hyperglycemia, Insulin Treatment, and Innate Immune Cells

    PubMed Central

    Xiu, Fangming; Jeschke, Marc G.

    2014-01-01

    Hyperglycemia (HG) and insulin resistance are the hallmarks of a profoundly altered metabolism in critical illness resulting from the release of cortisol, catecholamines, and cytokines, as well as glucagon and growth hormone. Recent studies have proposed a fundamental role of the immune system towards the development of insulin resistance in traumatic patients. A comprehensive review of published literatures on the effects of hyperglycemia and insulin on innate immunity in critical illness was conducted. This review explored the interaction between the innate immune system and trauma-induced hypermetabolism, while providing greater insight into unraveling the relationship between innate immune cells and hyperglycemia. Critical illness substantially disturbs glucose metabolism resulting in a state of hyperglycemia. Alterations in glucose and insulin regulation affect the immune function of cellular components comprising the innate immunity system. Innate immune system dysfunction via hyperglycemia is associated with a higher morbidity and mortality in critical illness. Along with others, we hypothesize that reduction in morbidity and mortality observed in patients receiving insulin treatment is partially due to its effect on the attenuation of the immune response. However, there still remains substantial controversy regarding moderate versus intensive insulin treatment. Future studies need to determine the integrated effects of HG and insulin on the regulation of innate immunity in order to provide more effective insulin treatment regimen for these patients. PMID:24899891

  2. Role of reduced insulin-stimulated bone blood flow in the pathogenesis of metabolic insulin resistance and diabetic bone fragility.

    PubMed

    Hinton, Pamela S

    2016-08-01

    Worldwide, 387 million adults live with type 2 diabetes (T2D) and an additional 205 million cases are projected by 2035. Because T2D has numerous complications, there is significant morbidity and mortality associated with the disease. Identification of early events in the pathogenesis of insulin resistance and T2D might lead to more effective treatments that would mitigate health and monetary costs. Here, we present our hypothesis that impaired bone blood flow is an early event in the pathogenesis of whole-body metabolic insulin resistance that ultimately leads to T2D. Two recent developments in different fields form the basis for this hypothesis. First, reduced vascular function has been identified as an early event in the development of T2D. In particular, before the onset of tissue or whole body metabolic insulin resistance, insulin-stimulated, endothelium-mediated skeletal muscle blood flow is impaired. Insulin resistance of the vascular endothelium reduces delivery of insulin and glucose to skeletal muscle, which leads to tissue and whole-body metabolic insulin resistance. Second is the paradigm-shifting discovery that the skeleton has an endocrine function that is essential for maintenance of whole-body glucose homeostasis. Specifically, in response to insulin signaling, osteoblasts secret osteocalcin, which stimulates pancreatic insulin production and enhances insulin sensitivity in skeletal muscle, adipose, and liver. Furthermore, the skeleton is not metabolically inert, but contributes to whole-body glucose utilization, consuming 20% that of skeletal muscle and 50% that of white adipose tissue. Without insulin signaling or without osteocalcin activity, experimental animals become hyperglycemic and insulin resistant. Currently, it is not known if insulin-stimulated, endothelium-mediated blood flow to bone plays a role in the development of whole body metabolic insulin resistance. We hypothesize that it is a key, early event. Microvascular dysfunction is a

  3. The transcriptional corepressor MTGR1 regulates intestinal secretory lineage allocation

    PubMed Central

    Parang, Bobak; Rosenblatt, Daniel; Williams, Amanda D.; Washington, Mary K.; Revetta, Frank; Short, Sarah P.; Reddy, Vishruth K.; Hunt, Aubrey; Shroyer, Noah F.; Engel, Michael E.; Hiebert, Scott W.; Williams, Christopher S.

    2015-01-01

    Notch signaling largely determines intestinal epithelial cell fate. High Notch activity drives progenitors toward absorptive enterocytes by repressing secretory differentiation programs, whereas low Notch permits secretory cell assignment. Myeloid translocation gene-related 1 (MTGR1) is a transcriptional corepressor in the myeloid translocation gene/Eight-Twenty-One family. Given that Mtgr1−/− mice have a dramatic reduction of intestinal epithelial secretory cells, we hypothesized that MTGR1 is a key repressor of Notch signaling. In support of this, transcriptome analysis of laser capture microdissected Mtgr1−/− intestinal crypts revealed Notch activation, and secretory markers Mucin2, Chromogranin A, and Growth factor-independent 1 (Gfi1) were down-regulated in Mtgr1−/− whole intestines and Mtgr1−/− enteroids. We demonstrate that MTGR1 is in a complex with Suppressor of Hairless Homolog, a key Notch effector, and represses Notch-induced Hairy/Enhancer of Split 1 activity. Moreover, pharmacologic Notch inhibition using a γ-secretase inhibitor (GSI) rescued the hyperproliferative baseline phenotype in the Mtgr1−/− intestine and increased production of goblet and enteroendocrine lineages in Mtgr1−/− mice. GSI increased Paneth cell production in wild-type mice but failed to do so in Mtgr1−/− mice. We determined that MTGR1 can interact with GFI1, a transcriptional corepressor required for Paneth cell differentiation, and repress GFI1 targets. Overall, the data suggest that MTGR1, a transcriptional corepressor well characterized in hematopoiesis, plays a critical role in intestinal lineage allocation.—Parang, B., Rosenblatt, D., Williams, A. D., Washington, M. K., Revetta, F., Short, S. P., Reddy, V. K., Hunt, A., Shroyer, N. F., Engel, M. E., Hiebert, S. W., Williams, C. S. The transcriptional corepressors MTGR1 regulates intestinal secretory lineage allocation. PMID:25398765

  4. Oral Insulin Reloaded

    PubMed Central

    Heinemann, Lutz; Plum-Mörschel, Leona

    2014-01-01

    Optimal coverage of insulin needs is the paramount aim of insulin replacement therapy in patients with diabetes mellitus. To apply insulin without breaking the skin barrier by a needle and/or to allow a more physiological provision of insulin are the main reasons triggering the continuous search for alternative routes of insulin administration. Despite numerous attempts over the past 9 decades to develop an insulin pill, no insulin for oral dosing is commercially available. By way of a structured approach, we aim to provide a systematic update on the most recent developments toward an orally available insulin formulation with a clear focus on data from clinical-experimental and clinical studies. Thirteen companies that claim to be working on oral insulin formulations were identified. However, only 6 of these companies published new clinical trial results within the past 5 years. Interestingly, these clinical data reports make up a mere 4% of the considerably high total number of publications on the development of oral insulin formulations within this time period. While this picture clearly reflects the rising research interest in orally bioavailable insulin formulations, it also highlights the fact that the lion’s share of research efforts is still allocated to the preclinical stages. PMID:24876606

  5. [Zinc and insulin level in islet cells under various functional state of insular apparatus].

    PubMed

    Berehova, T V; Hryhorova, N V; Ieshchenko, Iu V; Bovt, V D; Ieshchenko, V A

    2007-01-01

    The work is devoted to the study of zinc role in pancreas incretory function. Golden hamster and human pancreatic beta cells were investigated under varions functional state of insular apparatus. An increase of zinc and insulin content in islet beta cells was observed during inhibition of its' secretory activity and decrease of both components content in the cells occurred after intensifying of its' activity. Under pancreatic diabetes zinc and insulin quantities in beta cells were significantly less the norm. The results of comparative investigations confirm the thesis concerning this metal and hormone connection in beta-insulocytes. PMID:17902378

  6. Metabolic Actions of Angiotensin II and Insulin: A Microvascular Endothelial Balancing Act

    PubMed Central

    Muniyappa, Ranganath; Yavuz, Shazene

    2012-01-01

    Metabolic actions of insulin to promote glucose disposal are augmented by nitric oxide (NO)-dependent increases in microvascular blood flow to skeletal muscle. The balance between NO-dependent vasodilator actions and endothelin-1-dependent vasoconstrictor actions of insulin is regulated by phosphatidylinositol 3-kinase-dependent (PI3K) - and mitogen-activated protein kinase (MAPK)-dependent signaling in vascular endothelium, respectively. Angiotensin II acting on AT2 receptor increases capillary blood flow to increase insulin-mediated glucose disposal. In contrast, AT1 receptor activation leads to reduced NO bioavailability, impaired insulin signaling, vasoconstriction, and insulin resistance. Insulin-resistant states are characterized by dysregulated local renin-angiotensin-aldosterone system (RAAS). Under insulin-resistant conditions, pathway-specific impairment in PI3K-dependent signaling may cause imbalance between production of NO and secretion of endothelin-1, leading to decreased blood flow, which worsens insulin resistance. Similarly, excess AT1 receptor activity in the microvasculature may selectively impair vasodilation while simultaneously potentiating the vasoconstrictor actions of insulin. Therapeutic interventions that target pathway-selective impairment in insulin signaling and the imbalance in AT1 and AT2 receptor signaling in microvascular endothelium may simultaneously ameliorate endothelial dysfunction and insulin resistance. In the present review, we discuss molecular mechanisms in the endothelium underlying microvascular and metabolic actions of insulin and Angiotensin II, the mechanistic basis for microvascular endothelial dysfunction and insulin resistance in RAAS dysregulated clinical states, and the rationale for therapeutic strategies that restore the balance in vasodilator and constrictor actions of insulin and Angiotensin II in the microvasculature. PMID:22684034

  7. Insulin resistance and hyperinsulinaemia in diabetic cardiomyopathy

    PubMed Central

    Jia, Guanghong; DeMarco, Vincent G.; Sowers, James R.

    2016-01-01

    Insulin resistance, type 2 diabetes mellitus and associated hyperinsulinaemia can promote the development of a specific form of cardiomyopathy that is independent of coronary artery disease and hypertension. Termed diabetic cardiomyopathy, this form of cardiomyopathy is a major cause of morbidity and mortality in developed nations, and the prevalence of this condition is rising in parallel with increases in the incidence of obesity and type 2 diabetes mellitus. Of note, female patients seem to be particularly susceptible to the development of this complication of metabolic disease. The diabetic cardiomyopathy observed in insulin-resistant or hyperinsulinaemic states is characterized by impaired myocardial insulin signalling, mitochondrial dysfunction, endoplasmic reticulum stress, impaired calcium homeostasis, abnormal coronary microcirculation, activation of the sympathetic nervous system, activation of the renin–angiotensin–aldosterone system and maladaptive immune responses. These pathophysiological changes result in oxidative stress, fibrosis, hypertrophy, cardiac diastolic dysfunction and eventually systolic heart failure. This Review highlights a surge in diabetic cardiomyopathy research, summarizes current understanding of the molecular mechanisms underpinning this condition and explores potential preventive and therapeutic strategies. PMID:26678809

  8. Insulin resistance and hyperinsulinaemia in diabetic cardiomyopathy.

    PubMed

    Jia, Guanghong; DeMarco, Vincent G; Sowers, James R

    2016-03-01

    Insulin resistance, type 2 diabetes mellitus and associated hyperinsulinaemia can promote the development of a specific form of cardiomyopathy that is independent of coronary artery disease and hypertension. Termed diabetic cardiomyopathy, this form of cardiomyopathy is a major cause of morbidity and mortality in developed nations, and the prevalence of this condition is rising in parallel with increases in the incidence of obesity and type 2 diabetes mellitus. Of note, female patients seem to be particularly susceptible to the development of this complication of metabolic disease. The diabetic cardiomyopathy observed in insulin- resistant or hyperinsulinaemic states is characterized by impaired myocardial insulin signalling, mitochondrial dysfunction, endoplasmic reticulum stress, impaired calcium homeostasis, abnormal coronary microcirculation, activation of the sympathetic nervous system, activation of the renin-angiotensin-aldosterone system and maladaptive immune responses. These pathophysiological changes result in oxidative stress, fibrosis, hypertrophy, cardiac diastolic dysfunction and eventually systolic heart failure. This Review highlights a surge in diabetic cardiomyopathy research, summarizes current understanding of the molecular mechanisms underpinning this condition and explores potential preventive and therapeutic strategies. PMID:26678809

  9. Formation of secretory vesicles in permeabilized cells: a salt extract from yeast membranes promotes budding of nascent secretory vesicles from the trans-Golgi network of endocrine cells.

    PubMed Central

    Ling, W L; Shields, D

    1996-01-01

    The mechanism of secretory-vesicle formation from the trans-Golgi network (TGN) of endocrine cells is poorly understood. To identify cytosolic activities that facilitate the formation and fission of nascent secretory vesicles, we treated permeabilized pituitary GH3 cells with high salt to remove endogenous budding factors. Using this cell preparation, secretory-vesicle budding from the TGN required addition of exogenous cytosol and energy. Mammalian cytosols (GH3 cells and bovine brain) promoted post-TGN vesicle formation. Most significantly, a salt extract of membranes from the yeast Saccharomyces cerevisiae, a cell lacking a regulated secretory pathway, stimulated secretory vesicle budding in the absence of mammalian cytosolic factors. These results demonstrate that the factors which promote secretory-vesicle release from the TGN are conserved between yeast and mammalian cells. PMID:8615761

  10. Myocardial Fat Accumulation Is Independent of Measures of Insulin Sensitivity

    PubMed Central

    Noureldin, Radwa; Ouwerkerk, Ronald; Liu, Elizabeth Y.; Madan, Ritu; Abel, Brent S.; Mullins, Katherine; Walter, Mary F.; Skarulis, Monica C.; Gharib, Ahmed M.

    2015-01-01

    Background: Myocardial steatosis, an independent predictor of diastolic dysfunction, is frequently present in type 2 diabetes mellitus. High free fatty acid flux, hyperglycemia, and hyperinsulinemia may play a role in myocardial steatosis. There are no prior studies examining the relationship between insulin sensitivity (antilipolytic and glucose disposal actions of insulin) and cardiac steatosis. Objective: Using a cross-sectional study design of individuals with and without metabolic syndrome (MetSyn), we examined the relationships between cardiac steatosis and the sensitivity of the antilipolytic and glucose disposal actions of insulin. Methods: Pericardial fat (PF) volume, intramyocardial and hepatic fat (MF and HF) content, visceral fat (VF) and sc fat content were assessed by magnetic resonance imaging in 77 subjects (49 without MetSyn and 28 with MetSyn). In a subset of the larger cohort (n = 52), peripheral insulin sensitivity index (SI) and adipocyte insulin sensitivity (Adipo-SI) were determined from an insulin-modified frequently sampled iv glucose tolerance test. The Quantitative Insulin Sensitivity Check Index was used as a surrogate for hepatic insulin sensitivity. Results: Individuals with the MetSyn had significantly higher body mass index, total body fat, and MF, PF, HF, and VF content. HF and VF, but not MF, were negatively correlated with the Quantitative Insulin Sensitivity Check Index, Adipo-SI, and SI. Stepwise regression revealed that waist circumference and serum triglyceride levels independently predicted MF and PF, respectively. Adipo-SI and serum triglyceride levels independently predict HF. Conclusion: Myocardial steatosis is unrelated to hepatic, adipocyte, or peripheral insulin sensitivity. Although it is frequently observed in insulin-resistant subjects, further studies are necessary to identify and delineate pathogenic mechanisms that differentially affect cardiac and hepatic steatosis. PMID:26020762