Oxidative Stress In Skeletal Muscle Research Articles

Ascorbic acid supplementation improves skeletal muscle oxidative stress and insulin sensitivity in people with type 2 diabetes: Findings of a randomized controlled study

Aim/hypothesisSkeletal muscle insulin resistance and oxidative stress are characteristic metabolic disturbances in people with type 2 diabetes. Studies in insulin resistant rodents show an improvement in skeletal muscle insulin sensitivity and oxidative stress following antioxidant supplementation. We therefore investigated the potential ameliorative effects of antioxidant ascorbic acid (AA) supplementation on skeletal muscle insulin sensitivity and oxidative stress in people with type 2 diabetes. MethodsParticipants with stable glucose control commenced a randomized cross-over study involving four months of AA (2×500mg/day) or placebo supplementation. Insulin sensitivity was assessed using a hyperinsulinaemic, euglycaemic clamp coupled with infusion of 6,6-D2 glucose. Muscle biopsies were measured for AA concentration and oxidative stress markers that included basal measures (2′,7′-dichlorofluorescin [DCFH] oxidation, ratio of reduced-to-oxidized glutathione [GSH/GSSG] and F2-Isoprostanes) and insulin-stimulated measures (DCFH oxidation). Antioxidant concentrations, citrate synthase activity and protein abundances of sodium-dependent vitamin C transporter 2 (SVCT2), total Akt and phosphorylated Akt (ser473) were also measured in muscle samples. ResultsAA supplementation significantly increased insulin-mediated glucose disposal (delta rate of glucose disappearance; ∆Rd) (p=0.009), peripheral insulin-sensitivity index (p=0.046), skeletal muscle AA concentration (p=0.017) and muscle SVCT2 protein expression (p=0.008); but significantly decreased skeletal muscle DCFH oxidation during hyperinsulinaemia (p=0.007) when compared with placebo. Total superoxide dismutase activity was also lower following AA supplementation when compared with placebo (p=0.006). Basal oxidative stress markers, citrate synthase activity, endogenous glucose production, HbA1C and muscle Akt expression were not significantly altered by AA supplementation. Conclusions/interpretationIn summary, oral AA supplementation ameliorates skeletal muscle oxidative stress during hyperinsulinaemia and improves insulin-mediated glucose disposal in people with type 2 diabetes. Findings implicate AA supplementation as a potentially inexpensive, convenient, and effective adjunct therapy in the treatment of insulin resistance in people with type 2 diabetes.

Statins Trigger Mitochondrial Reactive Oxygen Species-Induced Apoptosis in Glycolytic Skeletal Muscle.

Although statins are the most widely used cholesterol-lowering agents, they are associated with a variety of muscle complaints. The goal of this study was to characterize the effects of statins on the mitochondrial apoptosis pathway induced by mitochondrial oxidative stress in skeletal muscle using human muscle biopsies as well as in vivo and in vitro models. Statins increased mitochondrial H2O2 production, the Bax/Bcl-2 ratio, and TUNEL staining in deltoid biopsies of patients with statin-associated myopathy. Furthermore, atorvastatin treatment for 2 weeks at 10 mg/kg/day in rats increased H2O2 accumulation and mRNA levels and immunostaining of the Bax/Bcl-2 ratio, as well as TUNEL staining and caspase 3 cleavage in glycolytic (plantaris) skeletal muscle, but not in oxidative (soleus) skeletal muscle, which has a high antioxidative capacity. Atorvastatin also decreased the GSH/GSSG ratio, but only in glycolytic skeletal muscle. Cotreatment with the antioxidant, quercetin, at 25 mg/kg/day abolished these effects in plantaris. An in vitro study with L6 myoblasts directly demonstrated the link between mitochondrial oxidative stress following atorvastatin exposure and activation of the mitochondrial apoptosis signaling pathway. Treatment with atorvastatin is associated with mitochondrial oxidative stress, which activates apoptosis and contributes to myopathy. Glycolytic muscles are more sensitive to atorvastatin than oxidative muscles, which may be due to the higher antioxidative capacity in oxidative muscles. There is a link between statin-induced mitochondrial oxidative stress and activation of the mitochondrial apoptosis signaling pathway in glycolytic skeletal muscle, which may be associated with statin-associated myopathy.

Beneficial Effects of Physical Exercise on Functional Capacity and Skeletal Muscle Oxidative Stress in Rats with Aortic Stenosis-Induced Heart Failure.

Objective. We evaluated the influence of exercise on functional capacity, cardiac remodeling, and skeletal muscle oxidative stress, MAPK, and NF-κB pathway in rats with aortic stenosis- (AS-) induced heart failure (HF). Methods and Results. Eighteen weeks after AS induction, rats were assigned into sedentary control (C-Sed), exercised control (C-Ex), sedentary AS (AS-Sed), and exercised AS (AS-Ex) groups. Exercise was performed on treadmill for eight weeks. Statistical analyses were performed with Goodman and ANOVA or Mann-Whitney. HF features frequency and mortality did not differ between AS groups. Exercise improved functional capacity, assessed by maximal exercise test on treadmill, without changing echocardiographic parameters. Soleus cross-sectional areas did not differ between groups. Lipid hydroperoxide concentration was higher in AS-Sed than C-Sed and AS-Ex. Activity of antioxidant enzymes superoxide dismutase and glutathione peroxidase was changed in AS-Sed and restored in AS-Ex. NADPH oxidase activity and gene expression of its subunits did not differ between AS groups. Total ROS generation was lower in AS-Ex than C-Ex. Exercise modulated MAPK in AS-Ex and did not change NF-κB pathway proteins. Conclusion. Exercise improves functional capacity in rats with AS-induced HF regardless of echocardiographic parameter changes. In soleus, exercise reduces oxidative stress, preserves antioxidant enzyme activity, and modulates MAPK expression.

Poor maternal nutrition and accelerated postnatal growth induces an accelerated aging phenotype and oxidative stress in skeletal muscle of male rats.

ABSTRACT‘Developmental programming’, which occurs as a consequence of suboptimal in utero and early environments, can be associated with metabolic dysfunction in later life, including an increased incidence of cardiovascular disease and type 2 diabetes, and predisposition of older men to sarcopenia. However, the molecular mechanisms underpinning these associations are poorly understood. Many conditions associated with developmental programming are also known to be associated with the aging process. We therefore utilized our well-established rat model of low birth weight and accelerated postnatal catch-up growth (termed ‘recuperated’) in this study to establish the effects of suboptimal maternal nutrition on age-associated factors in skeletal muscle. We demonstrated accelerated telomere shortening (a robust marker of cellular aging) as evidenced by a reduced frequency of long telomeres (48.5-8.6 kb) and an increased frequency of short telomeres (4.2-1.3 kb) in vastus lateralis muscle from aged recuperated offspring compared to controls. This was associated with increased protein expression of the DNA-damage-repair marker 8-oxoguanine-glycosylase (OGG1) in recuperated offspring. Recuperated animals also demonstrated an oxidative stress phenotype, with decreased citrate synthase activity, increased electron-transport-complex activities of complex I, complex II-III and complex IV (all markers of functional mitochondria), and increased xanthine oxidase (XO), p67phox and nuclear-factor kappa-light-chain-enhancer of activated B-cells (NF-κB). Recuperated offspring also demonstrated increased antioxidant defense capacity, with increased protein expression of manganese superoxide dismutase (MnSOD), copper-zinc superoxide dismutase (CuZnSOD), catalase and heme oxygenase-1 (HO1), all of which are known targets of NF-κB and can be upregulated as a consequence of oxidative stress. Recuperated offspring also had a pro-inflammatory phenotype, as evidenced by increased tumor necrosis factor-α (TNFα) and interleukin-1β (IL1β) protein levels. Taken together, we demonstrate, for the first time to our knowledge, an accelerated aging phenotype in skeletal muscle in the context of developmental programming. These findings may pave the way for suitable interventions in at-risk populations.

Beneficial effects of exercise on age-related mitochondrial dysfunction and oxidative stress in skeletal muscle.

Mitochondria are negatively affected by ageing leading to their inability to adapt to higher levels of oxidative stress and this ultimately contributes to the systemic loss of muscle mass and function termed sarcopenia. Since mitochondria are central mediators of muscle health, they have become highly sought-after targets of physiological and pharmacological interventions. Exercise is the only known strategy to combat sarcopenia and this is largely mediated through improvements in mitochondrial plasticity. More recently a critical role for mitochondrial turnover in preserving muscle has been postulated. Specifically, cellular pathways responsible for the regulation of mitochondrial turnover including biogenesis, dynamics and autophagy may become dysregulated during ageing resulting in the reduced clearance and accumulation of damaged organelles within the cell. When mitochondrial quality is compromised and homeostasis is not re-established, myonuclear cell death is activated and muscle atrophy ensues. In contrast, acute and chronic exercise attenuates these deficits, restoring mitochondrial turnover and promoting a healthier mitochondrial pool that leads to the preservation of muscle. Additionally, the magnitude of these exercise-induced mitochondrial adaptations is currently debated with several studies reporting a lower adaptability of old muscle relative to young, but the processes responsible for this diminished training response are unclear. Based on these observations, understanding the molecular details of how advancing age and exercise influence mitochondria in older muscle will provide invaluable insight into the development of exercise protocols that will maximize beneficial adaptations in the elderly. This information will also be imperative for future research exploring pharmacological targets of mitochondrial plasticity.

Vitamin C and E supplementation prevents some of the cellular adaptations to endurance-training in humans

BackgroundIt is clear that reactive oxygen species (ROS) produced during skeletal muscle contraction have a regulatory role in skeletal muscle adaptation to endurance exercise. However, there is much controversy in the literature regarding whether attenuation of ROS by antioxidant supplementation can prevent these cellular adaptations. Therefore, the aim of this study was to determine whether vitamin C and E supplementation attenuates performance and cellular adaptations following acute endurance exercise and endurance training. MethodsA double-blinded, placebo-controlled randomized control trial was conducted in eleven healthy young males. Participants were matched for peak oxygen consumption (VO2peak) and randomly allocated to placebo or antioxidant (vitamin C (2×500mg/day) and E (400IU/day)) groups. Following a four-week supplement loading period, participants completed acute exercise (10×4min cycling at 90% VO2peak, 2min active recovery). Vastus lateralis muscle samples were collected pre-, immediately-post- and 3h-post-exercise. Participants then completed four weeks of training (3 days/week) using the aforementioned exercise protocol while continuing supplementation. Following exercise training, participants again completed an acute exercise bout with muscle biopsies. ResultsAcute exercise tended to increase skeletal muscle oxidative stress as measured by oxidized glutathione (GSSG) (P=0.058) and F2-isoprostanes (P=0.056), with no significant effect of supplementation. Acute exercise significantly increased mRNA levels of peroxisome proliferator-activated receptor gamma coactivator 1α (PGC-1α), mitochondrial transcription factor A (TFAM) and PGC related coactivator (PRC), with no effect of supplementation. Following endurance training, supplementation did not prevent significantly increased VO2peak, skeletal muscle levels of citrate synthase activity or mRNA or protein abundance of cytochrome oxidase subunit 4 (COX IV) (P<0.05). However, following training, vitamin C and E supplementation significantly attenuated increased skeletal muscle superoxide dismutase (SOD) activity and protein abundance of SOD2 and TFAM. ConclusionFollowing acute exercise, supplementation with vitamin C and E did not attenuate skeletal muscle oxidative stress or increased gene expression of mitochondrial biogenesis markers. However, supplementation attenuated some (SOD, TFAM) of the increased skeletal muscle adaptations following training in healthy young men.

High-intensity interval training beneficial effects on body mass, blood pressure, and oxidative stress in diet-induced obesity in ovariectomized mice.

To investigate the possible beneficial effect of high-intensity interval training (HIIT) on skeletal muscle oxidative stress, body mass (BM) and systolic blood pressure (SBP) in ovariectomized mice fed or not fed a high-fat diet. Three-month-old female C57BL/6 mice were bilaterally ovariectomized (OVX group) or submitted to surgical stress without ovariectomy (SHAM group) and separated into standard chow (SHAM-SC; OVX-SC) and high-fat diet (SHAM-HF; OVX-HF) groups. After 13 weeks, an HIIT program (swimming) was carried out for 8 weeks in non-trained (NT) and trained (T) groups. The significant reduction of uterine mass and the cytological examination of vaginal smears in the OVX group confirmed that ovariectomy was successful. Before the HIIT protocol, the ovariectomized groups showed a greater BM than the SHAM group, irrespective of the diet they received. The HIIT minimized BM gain in animals fed an HF diet and/or ovariectomized. SBP and total cholesterol were increased in the OVX and HF animals compared to their counterparts, and the HIIT efficiently reduced these factors. In the HF and OVX mice, the muscular superoxide dismutase and catalase levels were low while their glutathione peroxidase and glutathione reductase levels were high and the HIIT normalized these parameters. Diet-induced obesity maximizes the deleterious effects of an ovariectomy. The HIIT protocol significantly reduced BM, SBP and oxidative stress in the skeletal muscle indicating that HIIT diminishes the cardiovascular and metabolic risk that is inherent to obesity and menopause.

Grape polyphenols supplementation reduces muscle atrophy in a mouse model of chronic inflammation

ObjectivesPolyphenols (PP) have demonstrated beneficial effects on low-grade inflammation and oxidative stress; however, little is known about their effect on highly inflamed muscle. The purposes of this study were (i) to evaluate muscle alteration induced by high-grade inflammation, and (ii) to test the effects of red grape PP supplementation on these alterations. MethodsWe used a transgenic mice model (transforming growth factor [TGF] mice) to develop a high T cell–dependent inflammation and C57 BL/6 control (CTL) mice model. Skeletal muscles of TGF and CTL mice were investigated for inflammation, atrophy and oxidative stress markers. Isolated mitochondria from hindlimb muscles were used for respiration with pyruvate as substrate and oxidative damages were measured by Western blot. TGF mice were supplemented with a mixture of red grape polyphenols (50 mg/kg/d) for 4 wk. Data were analyzed by one-way analysis of variance (ANOVA) and post hoc Bonferroni's multiple comparison tests. ResultsTGF mice presented skeletal muscle inflammation, oxidative stress, mitochondrial alteration and muscle atrophy. Atrophy was associated with two distinct pathways: (i) one linked to inflammation, NF-κB activation and increased ubiquitin ligase expression, and (ii) one dependent on reactive oxygen species (ROS) production leading to damaged mitochondria accumulation and activation of caspase-9 and 3. Supplementation of TGF mice with a mixture of red grape polyphenols (50 mg/kg/d) for 4 wk improved mitochondrial function and highly decreased caspases activation, which allowed muscle atrophy mitigation. ConclusionsThese observations suggest that nutritional dosages of red grape polyphenols might be beneficial for reducing skeletal muscle atrophy, even in a high-grade inflammation environment.

Effects of Dark Chocolate on Exercise Capacity in Sedentary Older Subjects: Underlying Mechanisms

We previously shown in patients with heart failure and type II diabetes that treatment with dark chocolate (DC) improves mitochondrial structure, indicators of mitochondrial biogenesis and oxidative stress in skeletal muscle (SkM). For this study, 17 sedentary subjects (mean age 50 years old) were randomized to placebo (n=8) or DC groups (n=9). In a double blind manner, subjects consumed either 2 squares of Hersheys' Extra Dark chocolate or placebo (20 g) for 3 months. Subjects underwent bicycle ergometry to assess VO2 max and power, lipid profile and SkM biopsy to investigate underlying mechanisms. In the DC group, there was a trend for an increase in V02 max (p=0.056 before vs. after) with no changes with placebo. In the DC group post‐treatment there was an increase in maximum exercise related work (watts) achieved (p=0.03). The DC group showed significant increases in HDL levels (p=0.005) and a trend for decreases in triglycerides (p=0.07). SkM biochemistry showed significant increases in protein for metabolic and/or mitochondrial biogenesis control enzymes (PGC1‐alpha, AMPK and LKB1), in their phosphorylation levels and in citrate synthase activity with DC. In conclusion, treatment of sedentary, older subjects with DC improves HDL cholesterol in association with upstream regulators of SkM metabolic control. There were improvements in maximum work and in VO2 max, which may suggest that DC enhances SkM mitochondria efficiency.

Potential therapeutic role of L-carnitine in skeletal muscle oxidative stress and atrophy conditions.

The targeting of nutraceutical treatment to skeletal muscle damage is an emerging area of research, driven by the need for new therapies for a range of muscle-associated diseases. L-Carnitine (CARN) is an essential nutrient and plays a key role in mitochondrial β-oxidation and in the ubiquitin-proteasome system regulation. As a dietary supplement to improve athletic performance, CARN has been studied for its potential to enhance β-oxidation. However, CARN effects on myogenesis, mitochondrial activity, and hypertrophy process are not completely elucidated. This in vitro study aims to investigate CARN role on skeletal muscle remodeling, differentiation process, and myotubes formation. We analyzed muscle differentiation and morphological features in C2C12 myoblasts exposed to 5 mM CARN. Our results showed that CARN was able to accelerate C2C12 myotubes formation and induce morphological changes, characterizing the start of hypertrophy process. In addition, CARN improved AKT activation and downstream cellular signaling pathways involved in skeletal muscle atrophy process prevention. Also, CARN positively regulated the pathways involved in oxidative stress defense. In this work, we provide an interesting novel mechanism of the potential therapeutic use of CARN to treat pathological conditions characterized by skeletal muscle morphological and functional impairment, oxidative stress production, and atrophy process in aging.

Skeletal muscle dysfunction and oxidative stress in patients with chronic obstructive lung disease

Skeletal muscle dysfunction and oxidative stress in patients with chronic obstructive lung disease

Influence of N-Acetylcysteine on Oxidative Stress in Slow-Twitch Soleus Muscle of Heart Failure Rats

Background: Chronic heart failure is characterized by decreased exercise capacity with early exacerbation of fatigue and dyspnea. Intrinsic skeletal muscle abnormalities can play a role in exercise intolerance. Causal or contributing factors responsible for muscle alterations have not been completely defined. This study evaluated skeletal muscle oxidative stress and NADPH oxidase activity in rats with myocardial infarction (MI) induced heart failure. Methods and Results: Four months after MI, rats were assigned to Sham, MI-C (without treatment), and MI-NAC (treated with N-acetylcysteine) groups. Two months later, echocardiogram showed left ventricular dysfunction in MI-C; NAC attenuated diastolic dysfunction. In soleus muscle, glutathione peroxidase and superoxide dismutase activity was decreased in MI-C and unchanged by NAC. 3-nitrotyrosine was similar in MI-C and Sham, and lower in MI-NAC than MI-C. Total reactive oxygen species (ROS) production was assessed by HPLC analysis of dihydroethidium (DHE) oxidation fluorescent products. The 2-hydroxyethidium (EOH)/DHE ratio did not differ between Sham and MI-C and was higher in MI-NAC. The ethidium/DHE ratio was higher in MI-C than Sham and unchanged by NAC. NADPH oxidase activity was similar in Sham and MI-C and lower in MI-NAC. Gene expression of p47^phox was lower in MI-C than Sham. NAC decreased NOX4 and p22^phox expression. Conclusions: We corroborate the case that oxidative stress is increased in skeletal muscle of heart failure rats and show for the first time that oxidative stress is not related to increased NADPH oxidase activity.

Oxidative Stress and Nerve Function After Cardiopulmonary Bypass in Patients With Diabetes

Chronic hyperglycemia has been associated with increased oxidative stress in skeletal muscle and sympathetic nerve dysfunction. We investigated the effect of chronic hyperglycemia on the myocardium of patients with uncontrolled diabetes (UD) compared with patients with well-controlled diabetes (CD) and patients without diabetes (ND) after cardioplegic cardiopulmonary bypass (CP/CPB) with acute intraoperative glycemic control. Atrial tissue and serum were collected from 47 patients (ND=18 with glycated hemoglobin [HbA1c] of 5.8±0.2; CD=8 with HbA1c of 6.1±0.1; with UD=21 with HbA1c=9.6±0.5) before and after CP/CPB for immunoblotting, protein oxidation assays, immunohistochemical evaluation, and microarray analysis. The uncontrolled group had increased total protein oxidation (p<0.05) and decreased levels of antioxidative enzyme manganese superoxide dismutase (MnSOD) (p<0.05) after CP/CPB compared with the controlled group. Collagen staining revealed increased fibrosis in patients with UD (p<0.05) compared with patients with CD and patients without diabetes. The uncontrolled group also showed a decrease in the neurogenic and angiogenic markers nerve growth factor (NGF) (p<0.05), neurotrophin (NT)-3 (p<0.05), and platelet-derived growth factor (PDGF)-β (p<0.05) compared with the other groups after CP/CPB. Atrial and serum microarray analysis showed increased oxidative stress and sympathetic nerve damage, increased fibrosis, and a decrease in angiogenesis in patients with UD (p<0.03) compared with patients without diabetes. CP/CPB led to higher oxidative stress in patients with UD before surgical intervention, even after normal glucose levels were maintained intraoperatively. Thus, controlled HbA1C in addition to acute intraoperative glucose control may be a more suitable end point for patients with diabetes undergoing cardiac operations.

High-dose vitamin C supplementation increases skeletal muscle vitamin C concentration and SVCT2 transporter expression but does not alter redox status in healthy males

Antioxidant vitamin C (VC) supplementation is of potential clinical benefit to individuals with skeletal muscle oxidative stress. However, there is a paucity of data reporting on the bioavailability of high-dose oral VC in human skeletal muscle. We aimed to establish the time course of accumulation of VC in skeletal muscle and plasma during high-dose VC supplementation in healthy individuals. Concurrently we investigated the effects of VC supplementation on expression levels of the key skeletal muscle VC transporter sodium-dependent vitamin C transporter 2 (SVCT2) and intramuscular redox and mitochondrial measures. Eight healthy males completed a randomized placebo-controlled, crossover trial involving supplementation with ascorbic acid (2×500mg/day) over 42 days. Participants underwent muscle and blood sampling on days 0, 1, 7, and 42 during each treatment. VC supplementation significantly increased skeletal muscle VC concentration after 7 days, which was maintained at 42 days (VC 3.0±0.2 (mean±SEM) to 3.9±0.4mg/100g wet weight (ww) versus placebo 3.1±0.3 to 2.9±0.2mg/100g ww, p=0.001). Plasma VC increased after 1 day, which was maintained at 42 days (VC 61.0±6.1 to 111.5±10.4µmol/L versus placebo 60.7±5.3 to 59.2±4.8µmol/L, p<0.001). VC supplementation significantly increased skeletal muscle SVCT2 protein expression (main treatment effect p=0.006) but did not alter skeletal muscle redox measures or citrate synthase activity. A main finding of our study was that 7 days of high-dose VC supplementation was required to significantly increase skeletal muscle vitamin C concentration in healthy males. Our findings implicate regular high-dose vitamin C supplementation as a means to safely increase skeletal muscle vitamin C concentration without impairing intramuscular ascorbic acid transport, antioxidant concentrations, or citrate synthase activity.

Effects of chronic administration of arachidonic acid on lipid profiles and morphology in the skeletal muscles of aged rats

Arachidonic acid (20:4n−6, ARA) is a major component of the cell membrane, whereas ARA-derived eicosanoids are formed when cells are damaged. Aging is associated with an accretion of oxidative stress in skeletal muscles. In this study, we examined the effects of chronic administration (13 weeks) of ARA (240mg/kg/day) on fatty acid composition, antioxidative status, and morphology of slow (soleus muscles) and fast (extensor digitorum longus muscles; EDL)-twitch muscles in aged rats (21 months old). The level of reactive oxygen species was higher in the EDL of ARA-administered rats than in that of control rats. ARA administration decreased the muscle cell volumes and increased the number of slow myosin heavy chain (MHC)-positive cells in the EDL. The relative content of MHC2X was increased whereas the relative content of MHC2B was decreased in the EDL of ARA-administered rats. These results suggest that ARA deposition in the fast-twitch muscle of aged rats reduced cell volume with an increase in oxidative stress.

Ginsenoside Rb1 improves postoperative fatigue syndrome by reducing skeletal muscle oxidative stress through activation of the PI3K/Akt/Nrf2 pathway in aged rats

Ginsenoside Rb1 is reported to possess anti-fatigue activity, but the mechanisms remain unknown. The aim of this study was to investigate the molecular mechanisms responsible for the anti-fatigue effect of ginsenoside Rb1 on postoperative fatigue syndrome induced by major small intestinal resection (MSIR) in aged rat. Aged rats with MSIR were administrated with ginsenoside Rb1 (15mg/kg) once a day from 3 days before surgery to the day of sacrifice, or with saline as corresponding controls. Rats without MSIR but going through the same surgery procedure were administrated with saline as blank controls. Anti-fatigue effect was assessed by an open field test; superoxide dismutase, reactive oxygen species and malondialdehyde in skeletal muscle were determined. The mRNA levels of Akt2 and Nrf2 in skeletal muscle were measured by real-time quantitative PCR. The activation of Akt and Nrf2 was examined by western blot and immunohistofluorescence. Our results revealed that ginsenoside Rb1 significantly increased the journey and the rearing frequency, decreased the time of rest in aged rats with MSIR. In addition, ginsenoside Rb1 significantly reduced reactive oxygen species and malondialdehyde release and increased the superoxide dismutase activity of skeletal muscle in aged rats with MSIR. Ginsenoside Rb1 also increased the expression of Akt2 and Nrf2 mRNA, up-regulated Akt phosphorylation and Nrf2 nuclear translocation. These findings indicate that ginsenoside Rb1 has an anti-fatigue effect on postoperative fatigue syndrome in aged rat, and the mechanism possibly involves activation of the PI3K/Akt pathway with subsequent Nrf2 nuclear translocation and induction of antioxidant enzymes.

P6 Oxidative stress suppresses expression of cystathionine beta-synthase (CBS), cystathionine gamma-lyase (CSE), and 3-mercaptopyruvate sulfurtransferase (3-MST) in critical limb ischemia (CLI) patients

Introduction CBS, CSE and 3-MST are the enzymatic source of endogenous hydrogen sulfide (H 2 S), a gaseous signaling molecule implicated in a wide range of physiological processes. We investigated the status of CBS, CSE, and 3-MST as well as the extent of oxidative stress in skeletal muscle tissue obtained from patients suffering from critical limb ischemia (CLI) ± diabetes mellitus (Db). Methods/Results We found that both mRNA and protein levels of CSE, CBS, and 3-MST were significantly decreased in skeletal muscle of CLI (>2 fold, p p Nrf2 ), a factor responsible for the expression of antioxidant response element-regulated genes (2 fold, p P Conclusion The present study suggests that the induction of oxidative stress in skeletal muscle of both CLI and CLI + Db patients may directly down-regulate the expression of the endogenous H 2 S-generating enzymes: CSE, CBS, and 3-MST. Increased oxidative stress and reductions in H 2 S bioavailability may contribute to the pathogenesis of CLI.

Effect of Bisphenol A (BPA) on Skeletal Muscle Oxidative Stress.

Effect of Bisphenol A (BPA) on Skeletal Muscle Oxidative Stress.

0420: Acute exercise preconditioning induced mitochondrial protection against skeletal muscle ischemia–reperfusion injury

Ischemia-reperfusion (I-R) induces mitochondrial function impairments and oxidative stress in skeletal muscle. In cardiac muscle, one-to-several days of exercise attenuate I-R injury. The objective of the present study was to show that a single exercise (EXO) prior to the I-R period protects the hind limb mitochondrial function. Twenty mice were randomly divided into 2 groups: The control group (CTL I-R, n=10) underwent I-R without exercise and the exercise group (EXO I-R, n=10) ran before I-R. Mice underwent 2 hours of ischemia induced by a rubber band tourniquet applied on the right root of the hind limb (the left leg was used as control leg), followed by a reperfusion period of 2 h. The EXO was performed on a treadmill with 10% incline 1h before I-R. The mice ran at a speed of 30cm until 40cm/sec during 30min. Blood lactate obtained from the tip of the tail at the end of EXO was above 9 mmol/L. In skinned gastrocnemius fibers, I-R significantly decreased the maximal mitochondrial respiration (Vmax) of the ischemic leg in comparison to the control leg in the CTL group (23.6 vs 28.6 pmol/(sec*mg wet weight); p<0.05). EXO I-R mice increased Vmax in comparison to CTL I-R mice (39.5 vs 31.8 pmol/(sec*dw) in the ischemic leg and the control leg respectively; p<0.05)). After EXO, the impairment between ischemic leg and control leg was partially restored (p=0.22). Without preconditioning, I-R increased H202 production of the ischemic leg in comparison to the control leg (42.6 vs 37.8 umol/mg dw; p=0.23). EXO I-R mice significantly decreased the H202 production in comparison to CTL I-R mice (26.6 vs 42.6 umol/mg dw; p<0.01) in the ischemic leg. After EXO, the impairment between ischemic leg and control leg was completely abolished (p=0.8). These results show that a preconditioning exercise protect the maximal mitochondrial respiration in mice and reduce the mitochondrial production of ROS following a period of I-R.

Chronic binge alcohol consumption alters myogenic gene expression and reduces in vitro myogenic differentiation potential of myoblasts from rhesus macaques

Chronic alcohol abuse is associated with skeletal muscle myopathy. Previously, we demonstrated that chronic binge alcohol (CBA) consumption by rhesus macaques accentuates skeletal muscle wasting at end-stage of simian immunodeficiency virus (SIV) infection. A proinflammatory, prooxidative milieu and enhanced ubiquitin proteasome activity were identified as possible mechanisms leading to loss of skeletal muscle. The possibility that impaired regenerative capacity, as reflected by the ability of myoblasts derived from satellite cell (SCs) to differentiate into myotubes has not been examined. We hypothesized that the inflammation and oxidative stress in skeletal muscle from CBA animals impair the differentiation capacity of myoblasts to form new myofibers in in vitro assays. We isolated primary myoblasts from the quadriceps femoris of rhesus macaques that were administered CBA or isocaloric sucrose (SUC) for 19 mo. Proliferation and differentiation potential of cultured myoblasts were examined in vitro. Myoblasts from the CBA group had significantly reduced PAX7, MYOD1, MYOG, MYF5, and MEF2C expression. This was associated with decreased myotube formation as evidenced by Jenner-Giemsa staining and myonuclei fusion index. No significant difference in the proliferative ability, cell cycle distribution, or autophagy was detected between myoblasts isolated from CBA and SUC groups. Together, these results reflect marked dysregulation of myoblast myogenic gene expression and myotube formation, which we interpret as evidence of impaired skeletal muscle regenerative capacity in CBA-administered macaques. The contribution of this mechanism to alcoholic myopathy warrants further investigation.