scholarly journals Myostatin propeptide mutation of the hypermuscular Compact mice decreases the formation of myostatin and improves insulin sensitivity

2017 ◽  
Vol 312 (3) ◽  
pp. E150-E160 ◽  
Author(s):  
Tamas Kocsis ◽  
Gyorgy Trencsenyi ◽  
Kitti Szabo ◽  
Julia Aliz Baan ◽  
Geza Muller ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Insulin Sensitivity ◽  
Genetic Background ◽  
Negative Regulator ◽  
Metabolic Effects ◽  
Muscle Size ◽  
Whole Body ◽  
Rab Gtpase ◽  
Wild Type ◽  
Absolute Size

The TGFβ family member myostatin (growth/differentiation factor-8) is a negative regulator of skeletal muscle growth. The hypermuscular Compact mice carry the 12-bp Mstn(Cmpt-dl1Abc) deletion in the sequence encoding the propeptide region of the precursor promyostatin, and additional modifier genes of the Compact genetic background contribute to determine the full expression of the phenotype. In this study, by using mice strains carrying mutant or wild-type myostatin alleles with the Compact genetic background and nonmutant myostatin with the wild-type background, we studied separately the effect of the Mstn(Cmpt-dl1Abc) mutation or the Compact genetic background on morphology, metabolism, and signaling. We show that both the Compact myostatin mutation and Compact genetic background account for determination of skeletal muscle size. Despite the increased musculature of Compacts, the absolute size of heart and kidney is not influenced by myostatin mutation; however, the Compact genetic background increases them. Both Compact myostatin and genetic background exhibit systemic metabolic effects. The Compact mutation decreases adiposity and improves whole body glucose uptake, insulin sensitivity, and 18FDG uptake of skeletal muscle and white adipose tissue, whereas the Compact genetic background has the opposite effect. Importantly, the mutation does not prevent the formation of mature myostatin; however, a decrease in myostatin level was observed, leading to altered activation of Smad2, Smad1/5/8, and Akt, and an increased level of p-AS160, a Rab-GTPase-activating protein responsible for GLUT4 translocation. Based on our analysis, the Compact genetic background strengthens the effect of myostatin mutation on muscle mass, but those can compensate for each other when systemic metabolic effects are compared.

Whole body metabolic effects of prolonged endurance training in combination with erythropoietin treatment in humans: a randomized placebo controlled trial

2013 ◽  
Vol 305 (7) ◽  
pp. E879-E889 ◽  
Author(s):  
Britt Christensen ◽  
Birgitte Nellemann ◽  
Mads S. Larsen ◽  
Line Thams ◽  
Peter Sieljacks ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Insulin Sensitivity ◽  
Endurance Training ◽  
Exercise Capacity ◽  
Uncoupling Protein ◽  
Metabolic Effects ◽  
Whole Body ◽  
Mrna Levels ◽  
Healthy Humans ◽  
Ucp2 Mrna

Erythropoietin (Epo) administration improves aerobic exercise capacity and insulin sensitivity in renal patients and also increases resting energy expenditure (REE). Similar effects are observed in response to endurance training. The aim was to compare the effects of endurance training with erythropoiesis-stimulating agent (ESA) treatment in healthy humans. Thirty-six healthy untrained men were randomized to 10 wk of either: 1) placebo ( n = 9), 2) ESA ( n = 9), 3) endurance training ( n = 10), or 4) ESA and endurance training ( n = 8). In a single-blinded design, ESA/placebo was injected one time weekly. Training consisted of biking for 1 h at 65% of wattmax three times per week. Measurements performed before and after the intervention were as follows: body composition, maximal oxygen uptake, insulin sensitivity, REE, and palmitate turnover. Uncoupling protein 2 (UCP2) mRNA levels were assessed in skeletal muscle. Fat mass decreased after training ( P = 0.003), whereas ESA induced a small but significant increase in intrahepatic fat ( P = 0.025). Serum free fatty acid (FFA) levels and palmitate turnover decreased significantly in response to training, whereas the opposite pattern was found after ESA. REE corrected for lean body mass increased in response to ESA and training, and muscle UCP2 mRNA levels increased after ESA ( P = 0.035). Insulin sensitivity increased only after training ( P = 0.011). In conclusion: 1) insulin sensitivity is not improved after ESA treatment despite improved exercise capacity, 2) the calorigenic effects of ESA may be related to increased UCP2 gene expression in skeletal muscle, and 3) training and ESA exert opposite effects on lipolysis under basal conditions, increased FFA levels and liver fat fraction was observed after ESA treatment.

scholarly journals Two weeks of early time-restricted feeding (eTRF) improves skeletal muscle insulin and anabolic sensitivity in healthy men

2020 ◽  
Vol 112 (4) ◽  
pp. 1015-1028
Author(s):  
Robert Jones ◽  
Pardeep Pabla ◽  
Joanne Mallinson ◽  
Aline Nixon ◽  
Tariq Taylor ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Weight Loss ◽  
Insulin Sensitivity ◽  
Temporal Distribution ◽  
Early Time ◽  
Metabolic Effects ◽  
Whole Body ◽  
Intermittent Fasting ◽  
Restricted Feeding ◽  
Branched Chain

ABSTRACT Background Altering the temporal distribution of energy intake (EI) and introducing periods of intermittent fasting (IF) exert important metabolic effects. Restricting EI to earlier in the day [early time-restricted feeding (eTRF)] is a novel type of IF. Objectives We assessed the chronic effects of eTRF compared with an energy-matched control on whole-body and skeletal muscle insulin and anabolic sensitivity. Methods Sixteen healthy males (aged 23 ± 1 y; BMI 24.0 ± 0.6 kg·m−2) were assigned to 2 groups that underwent either 2 wk of eTRF (n = 8) or control/caloric restriction (CON:CR; n = 8) diet. The eTRF diet was consumed ad libitum and the intervention was conducted before the CON:CR, in which the diet was provided to match the reduction in EI and body weight observed in eTRF. During eTRF, daily EI was restricted to between 08:00 and 16:00, which prolonged the overnight fast by ∼5 h. The metabolic responses to a carbohydrate/protein drink were assessed pre- and post-interventions following a 12-h overnight fast. Results When compared with CON:CR, eTRF improved whole-body insulin sensitivity [between-group difference (95% CI): 1.89 (0.18, 3.60); P = 0.03; η2p = 0.29] and skeletal muscle uptake of glucose [between-group difference (95% CI): 4266 (261, 8270) μmol·min−1·kg−1·180 min; P = 0.04; η2p = 0.31] and branched-chain amino acids (BCAAs) [between-group difference (95% CI): 266 (77, 455) nmol·min−1·kg−1·180 min; P = 0.01; η2p = 0.44]. eTRF caused a reduction in EI (∼400 kcal·d−1) and weight loss (−1.04 ± 0.25 kg; P = 0.01) that was matched in CON:CR (−1.24 ± 0.35 kg; P = 0.01). Conclusions Under free-living conditions, eTRF improves whole-body insulin sensitivity and increases skeletal muscle glucose and BCAA uptake. The metabolic benefits of eTRF are independent of its effects on weight loss and represent chronic adaptations rather than the effect of the last bout of overnight fast. This trial was registered at clinicaltrials.gov as NCT03969745.

Abstract P645: Chronic Angiotensin-(1-7) Improves Whole-Body Insulin Sensitivity in High-Fat Fed Mice by Enhancing Skeletal Muscle Glucose Uptake

Hypertension ◽  
2015 ◽  
Vol 66 (suppl_1) ◽  
Author(s):  
Ian M Williams ◽  
David H Wasserman ◽  
Italo Biaggioni ◽  
Amy C Arnold
Keyword(s):  
Blood Pressure ◽  
Skeletal Muscle ◽  
Body Weight ◽  
Insulin Sensitivity ◽  
Glucose Uptake ◽  
Hepatic Glucose Production ◽  
Metabolic Effects ◽  
Whole Body ◽  
High Fat ◽  
Sites Of Action

Angiotensin (Ang)-(1-7) is a vasodilatory peptide implicated in the pathophysiology of hypertension, in part by opposing deleterious Ang II cardiovascular actions. Recent studies show that Ang-(1-7) restoration lowers blood pressure and improves glycemic control in animal models of cardiometabolic syndrome. The tissue-specific sites of action and blood pressure dependence for these metabolic effects, however, remain unclear. We hypothesized that Ang-(1-7) improves insulin sensitivity by enhancing peripheral glucose delivery. To test this hypothesis, adult male C57BL/6 mice were placed on standard chow or 60% high-fat diet for 11 weeks, with Ang-(1-7) [400 ng/kg/min] or saline given during the last 3 weeks of diet by subcutaneous osmotic mini-pump. Hyperinsulinemic (4 mU/kg/min) euglycemic clamps were performed in conscious, unrestrained mice at the end of the treatment period. High-fat fed mice exhibited modest hypertension (systolic blood pressure: 137±3 high-fat vs. 123±5 mmHg chow; p=0.043), which was not altered by Ang-(1-7) infusion (141±4 mmHg; p=0.516). Body weight, body composition, and fasting plasma glucose and insulin levels were not significantly different following Ang-(1-7) treatment in chow or high-fat fed mice. Ang-(1-7) increased the glucose infusion rate (GIR) needed to maintain euglycemia in high-fat fed mice (steady-state GIR: 31±5 Ang-(1-7) vs. 16±1 mg/kg/min vehicle; p=0.017) indicating enhanced whole-body insulin sensitivity, with no significant effect in chow fed mice. The improvement in insulin sensitivity in high-fat fed mice was due to an enhanced rate of whole-body glucose disappearance (R d : 34±5 Ang-(1-7) vs. 20±2 mg/kg/min vehicle; p=0.049), with increased rates of glucose uptake in gastrocnemius, vastus, and soleus muscle. There was no effect of Ang-(1-7) on insulin-mediated suppression of hepatic glucose production. Our data shows that Ang-(1-7) has direct insulin-sensitizing effects on skeletal muscle, which are independent of changes in body weight or systemic blood pressure. These overall findings provide new insight into mechanisms by which Ang-(1-7) improves insulin action, and provide further support to targeting this peptide for treatment of cardiometabolic disease.

Effect of training on insulin binding to rat skeletal muscle sarcolemmal vesicles

1986 ◽  
Vol 250 (5) ◽  
pp. E570-E575
Author(s):  
G. K. Grimditch ◽  
R. J. Barnard ◽  
S. A. Kaplan ◽  
E. Sternlicht
Keyword(s):  
Skeletal Muscle ◽  
Insulin Sensitivity ◽  
Exercise Training ◽  
Insulin Binding ◽  
Whole Body ◽  
Rat Skeletal Muscle ◽  
Binding Studies ◽  
Muscle Enzyme ◽  
Intravenous Glucose ◽  
High Affinity

We examined the hypothesis that the exercise training-induced increase in skeletal muscle insulin sensitivity is mediated by adaptations in insulin binding to sarcolemmal (SL) insulin receptors. Insulin binding studies were performed on rat skeletal muscle SL isolated from control and trained rats. No significant differences were noted between groups in body weight or fat. An intravenous glucose tolerance test showed an increase in whole-body insulin sensitivity with training, and specific D-glucose transport studies on isolated SL vesicles indicated that this was due in part to adaptations in skeletal muscle. Enzyme marker analyses revealed no differences in yield, purity, or contamination of SL membranes between the two groups. Scatchard analyses indicated no significant differences in the number of insulin binding sites per milligram SL protein on the high-affinity (15.0 +/- 4.1 vs. 18.1 +/- 6.4 X 10(9)) or on the low-affinity portions (925 +/- 80 vs. 884 +/- 106 X 10(9)) of the curves. The association constants of the high-affinity (0.764 +/- 0.154 vs. 0.685 +/- 0.264 X 10(9) M-1) and of the low affinity sites (0.0096 +/- 0.0012 vs. 0.0102 +/- 0.0012 X 10(9) M-1) also were similar. These results do not support the hypothesis that the increased sensitivity to insulin after exercise training is due to changes in SL insulin receptor binding.

ALY688 elicits adiponectin-mimetic signaling and improves insulin action in skeletal muscle cells

2021 ◽  
Author(s):  
Hye Kyoung Sung ◽  
Patricia L. Mitchell ◽  
Sean Gross ◽  
Andre Marette ◽  
Gary Sweeney
Keyword(s):  
Skeletal Muscle ◽  
Insulin Sensitivity ◽  
Glucose Uptake ◽  
Glucose Transporter ◽  
Muscle Cells ◽  
Temporal Analysis ◽  
Skeletal Muscle Cells ◽  
Adiponectin Receptor ◽  
Metabolic Effects

Adiponectin is well established to mediate many beneficial metabolic effects, and this has stimulated great interest in development and validation of adiponectin receptor agonists as pharmaceutical tools. This study investigated the effects of ALY688, a peptide-based adiponectin receptor agonist, in rat L6 skeletal muscle cells. ALY688 significantly increased phosphorylation of several adiponectin downstream effectors, including AMPK, ACC and p38MAPK, assessed by immunoblotting and immunofluorescence microscopy. Temporal analysis using cells expressing an Akt biosensor demonstrated that ALY688 enhanced insulin sensitivity. This effect was associated with increased insulin-stimulated Akt and IRS-1 phosphorylation. The functional metabolic significance of these signaling effects was examined by measuring glucose uptake in myoblasts stably overexpressing the glucose transporter GLUT4. ALY688 treatment both increased glucose uptake itself and enhanced insulin-stimulated glucose uptake. In the model of high glucose/high insulin (HGHI)-induced insulin resistant cells, both temporal studies using the Akt biosensor as well as immunoblotting assessing Akt and IRS-1 phosphorylation indicated that ALY688 significantly reduced insulin resistance. Importantly, we observed that ALY688 administration to high-fat high sucrose fed mice also improve glucose handling, validating its efficacy in vivo. In summary, these data indicate that ALY688 activates adiponectin signaling pathways in skeletal muscle, leading to improved insulin sensitivity and beneficial metabolic effects.

scholarly journals Hepatokine ERAP1 impairs skeletal muscle insulin sensitivity via ADRB2/PKA pathway

2020 ◽  
Author(s):  
Feifan Guo ◽  
Yuguo Niu ◽  
Haizhou Jiang ◽  
Hanrui Yin ◽  
Fenfen Wang ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Skeletal Muscle ◽  
Insulin Sensitivity ◽  
Neutralizing Antibodies ◽  
Leptin Receptor ◽  
Whole Body ◽  
C2c12 Myotubes ◽  
Insulin Resistant ◽  
Skeletal Muscle Insulin Sensitivity ◽  
Pka Pathway

Abstract The current study aimed to investigate the role of endoplasmic reticulum aminopeptidase 1 (ERAP1), a novel hepatokine, in whole-body glucose metabolism. Here, we found that hepatic ERAP1 levels were increased in insulin-resistant leptin-receptor-mutated (db/db) and high-fat diet (HFD)-fed mice. Consistently, hepatic ERAP1 overexpression attenuated skeletal muscle (SM) insulin sensitivity, whereas knockdown ameliorated SM insulin resistance. Furthermore, serum and hepatic ERAP1 levels were positively correlated, and recombinant mouse ERAP1 or conditioned medium with high ERAP1 content (CM-ERAP1) attenuated insulin signaling in C2C12 myotubes, and CM-ERAP1 or HFD-induced insulin resistance was blocked by ERAP1 neutralizing antibodies. Mechanistically, ERAP1 reduced ADRB2 expression and interrupted ADRB2-dependent signaling in C2C12 myotubes. Finally, ERAP1 inhibition via global knockout or the inhibitor thimerosal improved insulin sensitivity. Together, ERAP1 is a hepatokine that impairs SM and whole-body insulin sensitivity, and its inhibition might provide a therapeutic strategy for diabetes, particularly for those with SM insulin resistance.

Dissociation of obesity and insulin resistance in transgenic mice with skeletal muscle expression of uncoupling protein 1

2008 ◽  
Vol 32 (3) ◽  
pp. 352-359 ◽  
Author(s):  
Yvonne Katterle ◽  
Susanne Keipert ◽  
Jana Hof ◽  
Susanne Klaus
Keyword(s):  
Insulin Resistance ◽  
Skeletal Muscle ◽  
Insulin Sensitivity ◽  
Uncoupling Protein ◽  
Wild Type ◽  
Uncoupling Protein 1 ◽  
Mitochondrial Uncoupling ◽  
High Fat Diets ◽  
Fat Diets ◽  
White Fat

We evaluated the effect of skeletal muscle mitochondrial uncoupling on energy and glucose metabolism under different diets. For 3 mo, transgenic HSA-mUCP1 mice with ectopic expression of uncoupling protein 1 in skeletal muscle and wild-type littermates were fed semisynthetic diets with varying macronutrient ratios (energy % carbohydrate-protein-fat): HCLF (41:42:17), HCHF (41:16:43); LCHF (11:45:44). Body composition, energy metabolism, and insulin resistance were assessed by NMR, indirect calorimetry, and insulin tolerance test, respectively. Gene expression in different organs was determined by real-time PCR. In wild type, both high-fat diets led to an increase in body weight and fat. HSA-mUCP1 mice considerably increased body fat on HCHF but stayed lean on the other diets. Irrespective of differences in body fat content, HSA-mUCP1 mice showed higher insulin sensitivity and decreased plasma insulin and liver triglycerides. Respiratory quotient and gene expression indicated overall increased carbohydrate oxidation of HSA-mUCP1 but a preferential channeling of fatty acids into muscle rather than liver with high-fat diets. Evidence for increased lipogenesis in white fat of HSA-mUCP1 mice suggests increased energy dissipating substrate cycling. Retinol binding protein 4 expression in white fat was increased in HSA-mUCP1 mice despite increased insulin sensitivity, excluding a causal role in the development of insulin resistance. We conclude that skeletal muscle mitochondrial uncoupling does not protect from the development of obesity in all circumstances. Rather it can lead to a “healthy” obese phenotype by preserving insulin sensitivity and a high metabolic flexibility, thus protecting from the development of obesity associated disturbances of glucose homeostasis.

scholarly journals Role of TRIB3 in regulation of insulin sensitivity and nutrient metabolism during short-term fasting and nutrient excess

2012 ◽  
Vol 303 (7) ◽  
pp. E908-E916 ◽  
Author(s):  
Jiarong Liu ◽  
Wei Zhang ◽  
Gin C. Chuang ◽  
Helliner S. Hill ◽  
Ling Tian ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Oxygen Consumption ◽  
Insulin Sensitivity ◽  
Glucose Uptake ◽  
Glucose Transport ◽  
Oxygen Consumption Rate ◽  
Glucose Oxidation ◽  
Consumption Rate ◽  
Negative Regulator ◽  
Short Term

We have suggested previously that Tribbles homolog 3 (TRIB3), a negative regulator of Akt activity in insulin-sensitive tissues, could mediate glucose-induced insulin resistance in muscle under conditions of chronic hyperglycemia (Liu J, Wu X, Franklin JL, Messina JL, Hill HS, Moellering DR, Walton RG, Martin M, Garvey WT. Am J Physiol Endocrinol Metab 298: E565–E576, 2010). In the current study, we have assessed short-term physiological regulation of TRIB3 in skeletal muscle and adipose tissues by nutrient excess and fasting as well as TRIB3's ability to modulate glucose transport and mitochondrial oxidation. In Sprague-Dawley rats, we found that short-term fasting enhanced insulin sensitivity concomitantly with decrements in TRIB3 mRNA (66%, P < 0.05) and protein (81%, P < 0.05) in muscle and increments in TRIB3 mRNA (96%, P < 0.05) and protein (∼10-fold, P < 0.05) in adipose tissue compared with nonfasted controls. On the other hand, rats fed a Western diet for 7 days became insulin resistant concomitantly with increments in TRIB3 mRNA (155%, P < 0.05) and protein (69%, P = 0.0567) in muscle and a decrease in the mRNA (76%, P < 0.05) and protein (70%, P < 0.05) in adipose. In glucose transport and mitochondria oxidation studies using skeletal muscle cells, we found that stable TRIB3 overexpression impaired insulin-stimulated glucose uptake without affecting basal glucose transport and increased both basal glucose oxidation and the maximal uncoupled oxygen consumption rate. With stable knockdown of TRIB3, basal and insulin-stimulated glucose transport rates were increased, whereas basal glucose oxidation and the maximal uncoupled oxygen consumption rate were decreased. In conclusion, TRIB3 impacts glucose uptake and oxidation oppositely in muscle and fat according to levels of nutrient availability. The above data for the first time implicate TRIB3 as a potent physiological regulator of insulin sensitivity and mitochondrial glucose oxidation under conditions of nutrient deprivation and excess.

Abstract 15445: The Sirtuin SIRT3 Blocks Doxorubicin-induced Cardiac Hypertrophic Response of Mice

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Vinodkumar Pillai ◽  
Sadhana Samant ◽  
Nagalingam Sundaresan ◽  
Gene Kim ◽  
Mahesh P Gupta
Keyword(s):  
Negative Regulator ◽  
Neonatal Rat ◽  
Whole Body ◽  
Wild Type ◽  
Electron Microscopic ◽  
Specific Expression ◽  
Rat Cardiomyocytes ◽  
Fluorescent Intensity ◽  
Hypertrophic Response

Background and objective: Doxorubicin is a chemotherapeutic drug widely used to treat variety of cancers. One of the serious side effects of doxorubicin is its toxicity to the heart. Previously, we have shown that overexpression of SIRT3 blocks the hypertrophic response of the heart to agonist treatments. This study was undertaken to investigate whether SIRT3 can also attenuate the doxorubicin-induced cardiac hypertrophic response in mice. Methods and results: Neonatal rat cardiomyocytes overexpressed with SIRT3 and treated with doxorubicin (10μM) showed 28% reduced mean fluorescent intensity for CM-H 2 DCFDA dye, compared to mock infected control cells treated with doxorubicin, thus suggesting that SIRT3 was capable of blocking doxorubicin-induced ROS synthesis in cardiomyocytes. To examine the cardioprotective effects of SIRT3 in doxorubicin-induced cardiotoxicity in vivo ; we used a cumulative dose of 15mg/kg of doxorubicin for two different time points. One group of mice was treated intraperitoneally with 5mg/kg doxorubicin or an equal volume of saline every two weeks for a total of three doses. Transgenic mice having cardiac specific expression of SIRT3 (SIRT3-Tg) showed 33% reduced HW/BW ratio compared to control mice. Echocardiographic evaluation of hearts showed significantly reduced fractional shortening in control mice, compared to SIRT3-Tg mice (24.6 vs 34.7 %, P<0.05). SIRT3-Tg mice also showed significantly reduced fetal gene expression for ANF, βMHC and collagen-1 as determined by RT-PCR. Masson’s trichrome staining showed significantly reduced fibrosis in doxorubicin treated SIRT3-Tg mice compared to its control. Furthermore, electron microscopic analysis showed preserved mitochondrial and sarcomeres structures in doxorubicin treated SIRT3-Tg hearts, whereas in wild-type hearts these structures were highly disorganized. Second group of mice that received 15mg/kg dose for two weeks also showed similar results. Contrary to this, whole body SIRT3 knockout mice showed exacerbated cardiac hypertrophic response compared to wild-type mice in response to doxorubicin treatment. Conclusion: These results demonstrated that SIRT3 is an endogenous negative regulator of doxorubicin-induced cardiac hypertrophic response.

scholarly journals LOW-INTENSITY EXERCISE ENHANCES MUSCULAR ANDROGEN/ANDROGEN RECEPTOR TO INHIBIT MYOSTATIN PATHWAY

2019 ◽  
Vol 3 (Supplement_1) ◽  
pp. S85-S86
Author(s):  
Bo-Kyung Son ◽  
Masato Eto ◽  
Miya Oura ◽  
Masahiro Akishita
Keyword(s):  
Skeletal Muscle ◽  
Androgen Receptor ◽  
Electric Pulse ◽  
Negative Regulator ◽  
Muscle Size ◽  
C2c12 Myotubes ◽  
Protein Levels ◽  
Low Intensity ◽  
Low Intensity Exercise ◽  
Response To Exercise

Abstract Background: Physical exercise is well documented to induce muscle size, strength, and energy metabolism. Although the contribution of systemic or local androgen in exercise-adapted muscle hypertrophy has been suggested, less is known about the molecular pathway of androgen in response to exercise. In the present study, we examined roles of androgen/androgen receptor (AR) after exercise, especially for the suppression of myostatin, a potent negative regulator of muscle mass. Methods and Results: To examine the effects of exercise, we employed low-intensity exercise in mice and electric pulse stimulation (EPS) in C2C12 myotubes. Both mRNA and protein levels of AR significantly increased in skeletal muscle of low-intensity exercised mice and C2C12 myotubes exposed to EPS. Production of testosterone and DHT from EPS-treated C2C12 myotubes was markedly increased. Of interest, we found that myostatin was clearly inhibited by EPS, and its inhibition was significantly abrogated by flutamide, a specific antagonist of AR. Furthermore, IL-6 and phospho-STAT3 (pSTAT3) expression, the downstream pathway of myostatin, were decreased by EPS and this was also reversed by flutamide. Similar downregulation of myostatin and IL-6 was seen in skeletal muscle of low-intensity exercised mice. Conclusion: Muscle AR expression and androgen production were increased by exercise and EPS treatment. As a mechanistical insight, it is suggested that AR inhibited myostatin expression transcriptionally, which downregulates IL-6/pSTAT3 pathway and thus contributes to the prevention of muscle degradation.

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