Muscle Insulin Research Articles

Network pharmacology integrated molecular dynamics reveals the bioactive compounds and potential targets of Tinospora crispa Linn. as insulin sensitizer.

Insulin resistance is a metabolic disorder characterized by the decreased response to insulin in muscle, liver, and adipose cells. This condition remains a complex phenomenon that involves several genetic defects and environmental stresses. In the present study, we investigated the mechanism of known phytochemical constituents of Tinospora crispa and its interaction with insulin-resistant target proteins by using network pharmacology, molecular docking, and molecular dynamics (MD) simulation. Tinoscorside A, Makisterone C, Borapetoside A and B, and β sitosterol consider the main phytoconstituents of Tinospora crispa by its binding with active sites of main protein targets of insulin resistance potential therapy. Moreover, Tinoscorside A was revealed from the docking analysis as the ligand that binds most strongly to the target protein, PI3K. This finding was strengthened by the results of MD simulation, which stated that the conformational stability of the ligand-protein complex was achieved at 15 ns and the formation of hydrogen bonds at the active site. In conclusion, Tinospora crispa is one of the promising therapeutic agent in type 2 diabetes mellitus management. Regulation in glucose homeostasis, adipolysis, cell proliferation, and antiapoptosis are predicted to be the critical mechanism of Tinospora crispa as an insulin sensitizer.

1368-P: Skeletal Muscle Mitochondrial Dysfunction Contributes to Increased GDF15 Levels in Aged Mice with Insulin Resistance and Sarcopenia

Growth differentiation factor 15 (GDF15) is a secreted protein whose cellular expression increases in response to a variety of stimuli, including mitochondrial dysfunction. Plasma GDF15 levels increase with advanced age and positively associate with sarcopenia. The prevalence of type 2 diabetes (T2D) increases with age and the incidence of sarcopenia is elevated in patients with T2D. Despite these established associations, the relationship between skeletal muscle mitochondrial function and changes in GDF15 expression, as well as how they may contribute to sarcopenia and T2D in the context of aging, remain poorly defined. We hypothesized that mitochondrial dysfunction in skeletal muscle would be positively associated with increased GDF15 expression and plasma levels in aged mice, and that muscle function and insulin sensitivity would be impaired also. Lean mass as a percentage of body weight was significantly reduced in aged (52 months) male C57BL6 compared with young (4 months) mice. Skeletal muscle function and mobility, assessed as peak and max sustained speeds achieved during voluntary wheel running, were significantly impaired in aged mice. Hyperinsulinemic euglycemic clamps demonstrated impaired insulin sensitivity in skeletal muscle, adipose and liver of aged mice. High-resolution respirometry studies using permeabilized muscle fibers detected significant reductions in the respiratory control ratio (RCR) in aged mice that was due to increased state 4 or leak respiration. Muscle GDF15 gene expression was significantly elevated in old mice, as were plasma levels of circulating GDF15. Our data suggests that skeletal muscle is a significant contributor to increased plasma GDF15 levels seen during aging, and that changes in mitochondrial function may contribute to increased skeletal muscle GDF15 expression. Elevated GDF15 may therefore serve as a strong predictor of mitochondrial pathology and subsequent risk of T2D in aging. Disclosure J.Chen: None. F.Bello: None. J.Kastroll: None. A.Vandevender: None. M.Pangburn: None. A.A.Gil silva: None. I.J.Sipula: None. J.Alder: None. M.J.Jurczak: None.

Excess glutamine does not alter myotube metabolism or insulin sensitivity.

Glutamine is an amino acid previously linked with improved skeletal muscle metabolism and insulin signaling, however, past observations often use cell culture models with only supraphysiological concentrations. Additionally, past reports have yet to simultaneously investigate both metabolic outcomes and insulin signaling. The present report utilized cell culture experiments and measured the effects of both physiological and supraphysiological levels of glutamine on myotube metabolism and insulin signaling/resistance. It was hypothesized the addition of glutamine at any level would increase cell metabolism and related gene expression, as well as improve insulin signaling versus respective control cells. C2C12 myotubes were treated with glutamine ranging from 0.25mM-4mM (or media control) for 24h to capture a range of physiological and supraphysiological concentrations. qRT-PCR was used to measure metabolic gene expression. Mitochondrial and glycolytic metabolism were measured via oxygen consumption and extracellular acidification rate, respectively. Insulin sensitivity (indicated by pAkt:Akt) and metabolism following glucose/insulin infusion were also assessed. Glutamine treatment consistently increased mitochondrial and glycolytic metabolism versus true controls (cells treated with mediavoid of glutamine), however, supraphysiological glutamine did not enhance metabolism beyond that of cells with physiological levels of glutamine. Neither physiological nor supraphysiological levels of glutamine altered insulin signaling regardless of insulin stimulation or insulin resistance when compared with respective controls. These data demonstrate excess glutamine does not appear to alter myotube metabolism or glucose disposal when base levels of glutamine are present. Moreover, glutamine does not appear to alter insulin sensitivity regardless of level of insulin resistance or presence of insulin stimulation.

A Review on Metformin: Clinical Significance and Side Effects

Metformin is a biguanide that has been used extensively worldwide for the treatment of type II diabetes mellitus. It improves glycaemic control by enhancing insulin sensitivity in liver and muscle. An advantage of metformin treatment is the tendency of weight reduction and the absence of significant hypoglycaemia; blood glucose levels are reduced only to normal as it does not stimulate insulin secretion. Metformin also has a beneficial effect on several cardiovascular risk factors including dyslipidemia, elevated plasminogen activator inhibitor 1 levels, other fibrinolytic abnormalities, hyperinsulinemia, and insulin resistance. Metformin enhances muscle and adipocyte insulin receptor number and/or affinity, increases insulin receptor tyrosine kinase activity, stimulates glucose transport and glycogen synthesis, and reduces both hepatic gluconeogenesis and glycogenolysis. The disadvantages are confined to the gastro-intestinal side effects and the potential risk of vitamin B 12 and folic acid deficiency during long-term use. These side effects can be minimized by slow titration and consumption with meals. The under lying mechanism for gastrointestinal intolerance are proposed to be stimulation of intestinal secretion of serotonin, alteration in incretin and metabolism of glucose, and malabsorption of bile salts. Lactic acidosis is rare contraindication associated with metformin. Most reported cases of lactic acidosis occur in patients with contraindications, particularly impaired renal function. Metformin has a good safety profile, efficacy and comparatively reduced cost. Its ability to improve insulin sensitivity and the cardiovascular risk profile of type II diabetic patients has enhanced its clinical use as first-line therapy.

338-OR: Reversal of Insulin Resistance by Resveratrol and Hesperetin Combination in Overweight and Obese Subjects Correlates with Decrease in Expression of Thioredoxin Interacting Protein

Trans-Resveratrol and hesperetin combination (tRES-HESP) in randomized, double-blind, placebo-controlled crossover study in overweight and obese subjects corrected insulin resistance; healthy aging through functional food study (HATFF, Clinicaltrials.gov identifier NCT02095873). tRES-HESP is an optimized supplement for induction of expression of glyoxalase 1 (Glo1) via activation of transcription factor Nrf2. Increased Glo1 expression decreases reactive metabolite, methylglyoxal (MG), contributing to insulin resistance through glycation-linked unfolded protein formation and activation of the unfolded protein response (UPR). Herein, we report further analysis of study variables and follow-up reverse translational studies. With tRES-HESP treatment, plasma MG correlated negatively with peripheral blood mononuclear cell (PBMC) quinone reductase activity - a marker of Nrf2 activation (r = - 0.68, P<0.01). For change from baseline of PBMC gene expression with tRES-HESP treatment (assessed by the Nanostring method), change in area-under-the-curve plasma glucose (ΔAUGg) during oral glucose tolerance tests correlated negatively with change in Glo1 expression (r = - 0.56, P<0.05) and correlated positively with change in expression of thioredoxin interacting protein (TXNIP) (r = 0.59, P<0.05). In reverse translational studies, we found tRES-HESP decreased TXNIP expression by 39 ± 1% (P<0.001) in human hepatocyte-like HepG2 cells and 14 ± 3% in BJ fibroblasts in vitro (P<0.01). tRES-HESP may decrease TXNIP expression by decreasing the MG-driven UPR and by direct Nrf2-driven down regulation. TXNIP is a mediator of insulin resistance in liver and skeletal muscle and impaired pancreatic beta-cell insulin secretion. tRES-HESP is suitable for further evaluation for prevention and treatment of type 2 diabetes where decreased TXNIP may contribute to the therapeutic response. Disclosure M. Xue: None. M. Weickert: None. N. Rabbani: None. P. Thornalley: None. Funding Qatar Foundation; Qatar University

Serum IRAP, a Novel Direct Biomarker of Prediabetes and Type 2 Diabetes?

Insulin resistance (IR), currently called prediabetes (PD), affects more than half of the adult population worldwide. Type 2 diabetes (T2D), which often follows in the absence of treatment, affects more than 475 million people and represents 10–20% of the health budget in industrialized countries. A preventive public health policy is urgently needed in order to stop this constantly progressing epidemic. Indeed, early management of prediabetes does not only strongly reduce its evolution toward T2D but also strongly reduces the appearance of cardiovascular comorbidity as well as that of associated cancers. There is however currently no simple and reliable test available for the diagnosis or screening of prediabetes and it is generally estimated that 20–60% of diabetics are not diagnosed. We therefore developed an ELISA for the quantitative determination of serum Insulin-Regulated AminoPeptidase (IRAP). IRAP is associated with and translocated in a stoechiometric fashion to the plasma membrane together with GLUT4 in response to insulin in skeletal muscle and adipose tissue which are the two major glucose storage sites. Its extracellular domain (IRAPs) is subsequently cleaved and secreted in the blood stream. In T2D, IRAP translocation in response to insulin is strongly decreased. Our patented sandwich ELISA is highly sensitive (≥10.000-fold “normal” fasting concentrations) and specific, robust and very cost-effective. Dispersion of fasting plasma concentration values in a healthy population is very low (101.4 ± 15.9 μg/ml) as compared to those of insulin (21–181 pmol/l) and C-peptide (0.4–1.7 nmol/l). Results of pilot studies indicate a clear correlation between IRAPs levels and insulin sensitivity. We therefore think that plasma IRAPs may be a direct marker of insulin sensitivity and that the quantitative determination of its plasma levels should allow large-scale screening of populations at risk for PD and T2D, thereby allow the enforcement of a preventive health policy aiming at efficiently reducing this epidemic.

Effect of 8-Week Interval Training on Protein Tyrosine Phosphatase 1B Expression in Gastrocnemius Muscle and Insulin Resistance in Rats with Type 2 Diabetes

Background: Insulin resistance induced by genetic and metabolic disorders is the main cause of the prevalence or severity of type 2 diabetes (T2D). Protein tyrosine phosphatase 1B (PTP1B) plays a key role in regulating glucose homeostasis as a negative regulator of insulin signaling pathway. Objectives: This study aimed to assess the effect of interval training on PTP1B expression in gastrocnemius muscle and insulin resistance in male rats with T2D. Methods: T2D was induced by high fat diet (HFD) and intraperitoneal injection of STZ in 14 male Wistar rats and then they were divided randomly into exercise (n=7) or control (n=7) groups. Exercise rats completed an 8 weeks interval training (5 days/week) and control rats remained without training. Fasting glucose, serum insulin, and PTP1B expression in gastrocnemius muscle were measured 48 hours after the last exercise session. Insulin resistance was assessed using homeostasis model assessment of insulin resistance (HOMA-IR) formula based on fasting insulin and glucose levels. An independent t test was used to compare each parameter between 2 groups. A P value less than 0.05 was considered statistically significant. Results: Interval training resulted in a significant decrease in fasting glucose level (P<0.0001) and insulin resistance (P=0.018) as well as an increase in serum insulin level (P<0.0001). PTP1B expression in gastrocnemius muscle decreased significantly compared with control rats (P=0.003) Conclusion: Interval training can improve insulin resistance in T2D rats. This improvement may be attributed to the decrease in PTP1B expression in gastrocnemius muscle by interval training.

Effects of metformin treatment on expression and activity of AMP-activated protein kinase α in skeletal muscle in type 2 diabetes

Objective To investigate the effects of metformin treatment on fatty acid metabolism and expression and activity of AMP-activated protein kinase (AMPK)α in skeletal muscle in type 2 diabetes. Methods A total of 30 cases with or without type 2 diabetes mellitus (T2DM) who received selective surgery were enrolled from department of orthopaedics. These patients were divided into three groups: DM group, DM+ MET group and NC group. Blood samples were drawn from an antecubial vein for measurement of plasma glucose, insulin, lipid and free fatty acid (FFA). Insulin sensitivity index (ISI) was calculated. Skeletal muscle was freezed in liquid nitrogen during orthopaedics surgery and was kept at -70 ℃ until assay. Skeletal muscle tissue was analysed en bloc for triglyceride, long chain fatty acyl-CoA (LCACoAs), AMPKα1 and AMPKα2 mRNA expression [quantitative real-time polymerase chain reaction (qRT-PCR)], as well as protein expression of AMPKα1, AMPKα2 and phosphorylated AMPKα (p-AMPKα) (Western blot). Results ⑴ Compared with NC group, HbA1c, fasting blood glucose (FBG), fasting insulin (FINS), FFA and triglyceride(TG) were increased in DM group, while metformin treatment decreased FFA and TG; ISI was reduced in DM group than that in NC group, but ISI was higher in DM+ MET group compared with DM group (P 0.05). Compared with NC group, AMPKα2 mRNA expression and protein levels of AMPKα2 and p-AMPKα in skeletal muscle were decreased in DM group, while metformin treatment increased protein level of p-AMPKα (P<0.05). Conclusions Compared with NC group, muscle lipid accumulation and insulin resistance always exist in T2DM patients. Metformin treatment may increase activity of AMPKα, resulting in a decrease in lipid accumulation in skeletal muscle and increase insulin sensitivity in T2DM patients. Key words: Metformin; Diabetes mellitus, type 2; Muscle, skeletal; AMP-activated protein kinases; Insulin resistance

Inhibition of mitochondrial complex 1 by the S6K1 inhibitor PF-4708671 partly contributes to its glucose metabolic effects in muscle and liver cells

mTOR complex 1 (mTORC1) and p70 S6 kinase (S6K1) are both involved in the development of obesity-linked insulin resistance. Recently, we showed that the S6K1 inhibitor PF-4708671 (PF) increases insulin sensitivity. However, we also reported that PF can increase glucose metabolism even in the absence of insulin in muscle and hepatic cells. Here we further explored the potential mechanisms by which PF increases glucose metabolism in muscle and liver cells independent of insulin. Time course experiments revealed that PF induces AMP-activated protein kinase (AMPK) activation before inhibiting S6K1. However, PF-induced glucose uptake was not prevented in primary muscle cells from AMPK α1/2 double KO (dKO) mice. Moreover, PF-mediated suppression of hepatic glucose production was maintained in hepatocytes derived from AMPK α1/2-dKO mice. Remarkably, PF could still reduce glucose production and activate AMPK in hepatocytes from S6K1/2 dKO mice. Mechanistically, bioenergetics experiments revealed that PF reduces mitochondrial complex I activity in both muscle and hepatic cells. The stimulatory effect of PF on glucose uptake was partially reduced by expression of the Saccharomyces cerevisiae NADH:ubiquinone oxidoreductase in L6 cells. These results indicate that PF-mediated S6K1 inhibition is not required for its effect on insulin-independent glucose metabolism and AMPK activation. We conclude that, although PF rapidly activates AMPK, its ability to acutely increase glucose uptake and suppress glucose production does not require AMPK activation. Unexpectedly, PF rapidly inhibits mitochondrial complex I activity, a mechanism that partially underlies PF's effect on glucose metabolism.

1967-P: Mild Physiologic Hyperglycemia Impairs Insulin-Mediated Suppression of Plasma Glucagon in Healthy Normal Glucose Tolerant Subjects

Hyperglycemia adversely affects skeletal muscle and hepatic insulin sensitivity (glucotoxicity). However, the effect of prolonged hyperglycemia on glucose and insulin-mediated suppression of glucagon is not known. The aim of the present study was to evaluate effect of a chronic (72 hours) physiologic increase (+45 mg/dl) in plasma glucose concentration on the suppression of plasma glucagon concentration in healthy NGT individuals: 12 without family history of T2DM (FH-) (9M/3F, age = 50± 4 years, BMI = 27 ± 1 kg/m2) and 8 with FH of T2DM (FH+) (4M/4F, age = 48±2, BMI = 26±1 kg/m2). Subjects received an OGTT and 2-step hyperglycemic (+125 and +300 mg/dl) clamp (duration of each step = 80 minutes) before and after 72-hour glucose infusion. Plasma insulin and C-peptide concentrations were obtained every 2-5 minutes during each hyperglycemic clamp step and plasma glucagon concentrations were measured every 10 minutes. The ratio of insulin/glucagon was measured and used as an index of insulin-medicated suppression of plasma glucagon. FPG concentration increased from 97±4 to 140±4 mg/dl during the 72-hour glucose infusion. Following chronic glucose infusion, plasma insulin levels were significantly higher during the basal state and during each hyperglycemic clamp step (by 59% and 78%) during the 0-80 and 80-160 min time periods, respectively. There was no difference in plasma glucagon levels following chronic glucose infusion. However, the plasma insulin/glucagon ratio was significantly higher during the fasting state (by 76%) and during the first (by 128%) and second (by 178%) hyperglycemic clamp steps. There was no difference in the effect of chronic glucose infusion on glucagon secretion between FH+ and FH-subjects. These results demonstrate that sustained physiologic hyperglycemia for 72 hours (i.e., glucotoxicity) impairs insulin-mediated suppression of glucagon, and could contribute to fasting and post-prandial hyperglycemia in T2DM patients. Disclosure A. Merovci: None. X. Chen: None. R.A. DeFronzo: Advisory Panel; Self; AstraZeneca, Boehringer Ingelheim Pharmaceuticals, Inc., Elcelyx Therapeutics, Inc., Intarcia Therapeutics, Inc., Janssen Pharmaceuticals, Inc., Novo Nordisk Inc. Research Support; Self; AstraZeneca, Boehringer Ingelheim Pharmaceuticals, Inc., Janssen Pharmaceuticals, Inc., Merck &amp; Co., Inc. Speaker's Bureau; Self; AstraZeneca, Novo Nordisk Inc. D. Tripathy: None. Funding National Institutes of Health

1939-P: Intermuscular Adipose Tissue Has a Metabolically Adverse Secretome Compared with Visceral and Subcutaneous Depots

Adipose tissue is a dynamic secretory organ that has differing effects on metabolic disease depending upon location and composition. Resting beneath the fascia, and bordering muscle fibers, intermuscular adipose tissue (IMAT) secretes proteins and lipid signaling molecules that are uniquely positioned to directly impact insulin sensitivity and inflammation in skeletal muscle. Individuals with Obesity and type 2 diabetes have increased IMAT volume, and while IMAT is inversely correlated with muscle strength, function, and insulin sensitivity, the mechanisms by which it exerts these effects are unknown. We quantified the secretome of IMAT, subcutaneous adipose tissue (SAT), and visceral adipose tissue (VAT) to determine if there are differences between depots in the secretion of cytokines, eicosanoids, FFAs and proteins that influence metabolic function. SAT and VAT biopsies from bariatric surgery patients and IMAT from the vastus lateralis biopsies of individuals with Obesity were cultured for 48 hours in DMEM, and the conditioned media was analyzed using nanoflow HPLC-MS, multiplex ELISAs and LC/MS/MS for proteins, cytokines and eicosanoids/FFA, respectively. IMAT secretion of various extracellular matrix proteins was significantly different than VAT and SAT. Pro-inflammatory cytokine secretion of IFNγ, TNFα, IL-8 and IL-13 from IMAT was higher than VAT and significantly higher than SAT (p &amp;lt; 0.05). IMAT secretes significantly more pro-inflammatory eicosanoids TXB2 and PGE2 than VAT (p = 0.02, 0.05) and SAT (p = 0.01, 0.04). IMAT and VAT have significantly greater basal lipolysis assessed by FFA release rates compared to SAT (p = 0.01, 0.04). These data begin to characterize the disparate secretory properties of SAT, VAT and IMAT that may impact tissue function, and suggest that the metabolically adverse secretome of IMAT, with such proximity to skeletal muscle may play an important functional role in the pathogenesis of insulin resistance and type 2 diabetes. Disclosure D.E. Kahn: None. E. Macias: None. S. Zarini: None. K.A. Harrison: None. M. Cree-Green: None. B.C. Bergman: Advisory Panel; Spouse/Partner; AstraZeneca, Merck &amp; Co., Inc., Novo Nordisk Inc. Funding National Institutes of Health (R01DK118149, RR-00036); Colorado Nutrition Obesity Research Center (P30DK048520)

1979-P: GLP-1 Recruits Skeletal Muscle Microvasculature without Impacting Glucose Uptake or Protein Metabolism in Older Men during Postabsorptive Insulin Clamps

Introduction: Ageing muscle is associated with impaired blood flow, “anabolic resistance” to dietary protein, and impaired glucose uptake - culminating in muscle atrophy and insulin resistance. Since GLP-1 has been shown to recruit muscle microvasculature, and due to the presence of its receptors in local tissue(s) (e.g., endothelium, myocytes) we hypothesized that GLP-1 infusions in older people, would positively impact muscle microcirculation, protein and/or glucose metabolism - in an insulin-independent fashion. Methods: We studied seven older men (∼70±1 y, mean±SEM) in a cross-over design. Baseline measures were taken (first 3 h) prior to insulin and glucose clamps where participants received co-infusions of octreotide, Vamin 14-EF (containing essential amino acids and dextrose) - with or without GLP-1, over the next 3 h. Four muscle biopsies were taken over 90-120 minute intervals. Muscle protein turnover was quantified via A-V balance, and direct incorporation of 13C6 phenylalanine via mass spectrometric techniques. Plasma GLP-1 and insulin were quantified via Milliplex Map, ELISA. Muscle microvascular flow was assessed via contrast enhanced ultrasound. Leg glucose uptake was determined via A-V balance. Results: GLP-1 increased microvascular flow in +GLP-1 vs. -GLP-1 conditions (increase vs. without GLP-1 infusion: 7.2±4.7 vs. 0.40±0.26-fold, p=0.009) while leg glucose uptake was unchanged. Muscle proteolysis (nb. no effects on synthesis) was equally suppressed vs. basal with GLP-1 (32.1±5.3 vs. 67.4±3.2 nmol.100 g leg-1.min-1, p&amp;lt;0.05) and without GLP-1 (32.77±6.1 vs. 57.9±5.1 nmol.100 g leg-1.min-1 p&amp;lt;0.05, respectively). Conclusion: GLP-1 recruits muscle microcirculation independent of insulin. A lack of impact of GLP-1 on muscle glucose uptake or protein metabolism, could reflect a requirement for fed-state insulin levels. GLP-1 may hold therapeutic value for muscle microvascular health. Disclosure H. Abdulla: None. B.E. Phillips: None. M.C. Limb: None. D.J. Wilkinson: None. T. Jandova: None. J. Cegielski: None. J.J. Bass: None. D. Rankin: None. J.S. Lewis: None. J. Williams: None. K. Smith: None. P.J. Atherton: None. I.R. Idris: None. Funding Medical Research Council UK; Arthritis Research UK

New insights for statistical analysis of blood pressure response to exercise in elderly hypertensive women

It is possible to identity responders, low responders and adverse responders to exercise by looking for the variability of scores around the mean. Thus, it is important to identify these groups of subjects to amplify the understanding of the initial alternative hypothesis. In addition, the use of complementary statistics, as control of regression to the mean, standard error of measurement and smallest real difference presents new insights for a better understanding of the practical implications of data interpretation in exercise research. This article discusses the use of complementary statistical procedures that allow for critical interpretation of data while avoiding bias in studies with exercise and blood pressure. We present real data from an experimental 10-week RT program and its effect on SBP in hypertensive elderly women. We demonstrate that not every difference in systolic blood pressure carries a clinical meaning, but are characterized as a measurement error. In addition, responsiveness to exercise will, in the great majority of cases, be misinterpretation of regression to the mean and random variation. The complementary statistics presented in this review should be considered in future studies, and are also useful for other variables such as muscle strength, cytokines, triglycerides, and insulin.

The Effect of resistance training on GLUT4 expression in muscle tissue, glucose and insulin resistance in rats

The Effect of resistance training on GLUT4 expression in muscle tissue, glucose and insulin resistance in rats

Branched chain α-ketoacids: Novel Regulator of Insulin and mTOR Signalling in Skeletal and Cardiac Muscle

Branched chain α-ketoacids: Novel Regulator of Insulin and mTOR Signalling in Skeletal and Cardiac Muscle

Beta-Cell Function and Survival Are Modulated Differentially by Type I or Type II Muscle through Specific Myokines

Type 2 diabetes has a complex pathophysiology implicating several organs as the adipose tissue the liver, the skeletal muscle and the pancreas. Tissue crosstalk is emerging as a determinant way to coordinate the different organs implicated in glucose homeostasis. Among the inter-organ communication factors, muscle-secreted myokines can modulate the function and survival of pancreatic beta-cells. We establish human primary in vitro models of cells isolated from soleus (type I), triceps brachii (type II) and vastus lateralis (mixte) muscles to study the myokines profile secretion using and antibody-based array, the transcriptome using RNA-sequencing, and their sensitivity to TNF-alpha-induced insulin resistance, by assessing the glucose uptake rate. We then investigate how the muscle type and insulin resistance status impact on beta-cell function (glucose stimulated insulin secretion), survival (proliferation and apoptose) in order to identify new myokines in fiber type specific muscle pancreas crosstalk. We show that type I and type II primary myotubes present specific mRNA and myokine signatures as well as different sensitivity to TNF-alpha induced insulin resistance (TNF-alpha failed to induce insulin resistance in type II muscle). We also report here that the impact of myokines on beta-cells proliferation, apoptosis and insulin secretion, depends on fiber types and their metabolic status. Finally, that angiogenin and osteoprotegerin are triceps specific myokines with beta-cell protective actions against proinflammatory cytokines. These results suggest that type I and II muscles could impact insulin secretion and beta-cell mass differentially in type 2 diabetes through specific myokines secretion. Disclosure M.L. Mizgier: None. S. Rutti: None. M. Pinget: None. K. Bouzakri: None.

Comparison of Low and High-dose Growth Hormone Administration on Muscle Ceramide Contents and Insulin Resistance in Rats

Comparison of Low and High-dose Growth Hormone Administration on Muscle Ceramide Contents and Insulin Resistance in Rats

The role of PLIN protein in healthy lipid storage and lipid droplet expansion.

In skeletal muscle, fatty acids are stored in vesicle-like organelles known as lipid droplets (LDs). The importance of how lipids are stored in skeletal muscle has emerged from studies demonstrating a strong association between muscle lipids and insulin sensitivity. This article is protected by copyright. All rights reserved

Development of microdialysis methodology for interstitial insulin measurement in rodents

IntroductionAccurate assessment of muscle insulin sensitivity requires measurement of insulin concentration in interstitial fluid (ISF), but has proved difficult. We aimed to optimise measurement of ISF insulin concentrations in rat muscles in vivo using microdialysis. MethodsFactorial experimental design experiments were performed in vitro to determine optimal conditions for insulin recovery with microdialysis probes. These conditions were tested in vivo, adjusted appropriately and used in lean and obese Zucker rats to compare ISF insulin concentrations basally and during hyperinsulinaemic-euglycaemic (HE) clamp. ResultsOptimal conditions in vivo were: a 100kDa microdialysis probe inserted in muscle, perfused with 1% BSA, 1.5mM glucose in 0.9% sodium chloride at 1μl/min. Samples were collected into siliconised glass microvials. As a reference for insulin, we established a protocol of inulin infusion, beginning at −80min and reaching equilibrium within 60min. HE clamp, beginning at 0min, increased ISF insulin concentration from 122±56 basally to 429±180pmol/l (P<0.05) in lean rats and from 643±165 to 1087±243pmol/l (P=0.07) in obese rats; ISF insulin concentrations were significantly higher throughout in obese rats. The difference between ISF and plasma insulin concentration (ISF:plasma ratio) was substantially higher in obese rats, but fell to similar values in obese and lean rats during HE clamp. DiscussionOptimising insulin recovery with microdialysis allowed accurate measurement of basal ISF insulin in muscle of lean and obese Zucker rats and indicates insulin transport across capillaries is impaired in obese rats, basally and during hyperinsulinaemia.

Innovative biomarkers for predicting type 2 diabetes mellitus: relevance to dietary management of frailty in older adults.

Type 2 diabetes mellitus (T2DM) increases in prevalence in the elderly. There is evidence for significant muscle loss and accelerated cognitive impairment in older adults with T2DM; these comorbidities are critical features of frailty. In the early stages of T2DM, insulin sensitivity can be improved by a "healthy" diet. Management of insulin resistance by diet in people over 65years of age should be carefully re-evaluated because of the risk for falling due to hypoglycaemia. To date, an optimal dietary programme for older adults with insulin resistance and T2DM has not been described. The use of biomarkers to identify those at risk for T2DM will enable clinicians to offer early dietary advice that will delay onset of disease and of frailty. Here we have used an in silico literature search for putative novel biomarkers of T2DM risk and frailty. We suggest that plasma bilirubin, plasma, urinary DPP4-positive microparticles and plasma pigment epithelium-derived factor merit further investigation as predictive biomarkers for T2DM and frailty risk in older adults. Bilirubin is screened routinely in clinical practice. Measurement of specific microparticle frequency in urine is less invasive than a blood sample so is a good choice for biomonitoring. Future studies should investigate whether early dietary changes, such as increased intake of whey protein and micronutrients that improve muscle function and insulin sensitivity, affect biomarkers and can reduce the longer term complication of frailty in people at risk for T2DM.