Altering the redox state of skeletal muscle by glutathione depletion increases the exercise-activation of PGC-1α.
ABSTRACT: We investigated the relationship between markers of mitochondrial biogenesis, cell signaling, and antioxidant enzymes by depleting skeletal muscle glutathione with diethyl maleate (DEM) which resulted in a demonstrable increase in oxidative stress during exercise. Animals were divided into six groups: (1) sedentary control rats; (2) sedentary rats + DEM; (3) exercise control rats euthanized immediately after exercise; (4) exercise rats + DEM; (5) exercise control rats euthanized 4 h after exercise; and (6) exercise rats + DEM euthanized 4 h after exercise. Exercising animals ran on the treadmill at a 10% gradient at 20 m/min for the first 30 min. The speed was then increased every 10 min by 1.6 m/min until exhaustion. There was a reduction in total glutathione in the skeletal muscle of DEM treated animals compared to the control animals (P < 0.05). Within the control group, total glutathione was higher in the sedentary group compared to after exercise (P < 0.05). DEM treatment also significantly increased oxidative stress, as measured by increased plasma F2-isoprostanes (P < 0.05). Exercising animals given DEM showed a significantly greater increase in peroxisome proliferator activated receptor γ coactivator-1α (PGC-1α) mRNA compared to the control animals that were exercised (P < 0.05). This study provides novel evidence that by lowering the endogenous antioxidant glutathione in skeletal muscle and inducing oxidative stress through exercise, PGC-1α gene expression was augmented. These findings further highlight the important role of exercise induced oxidative stress in the regulation of mitochondrial biogenesis.
Project description:A frequently used end point of clinical outcomes in patients with pulmonary arterial hypertension (PAH) is the 6-minute walk distance. Furthermore, some data suggest that mild to moderate exercise as an intervention in stable PAH is beneficial. Some of these questions have been recapitulated in the monocrotaline and hypoxia animal models of pulmonary hypertension. However, mild exercise and walk distance as end points have not been rigorously examined in the severe progressive Sugen 5416/hypoxia/normoxia (Su/Hx/Nx) animal model of PAH at each stage of worsening disease. Our hypothesis was that animals that were preselected as runners would have increased walk times and improved right ventricle/left ventricle plus septum (RV/LV+S) ratios, echocardiography, and histology compared with nonexercised Su/Hx/Nx animals. We examined four groups of rats: Su/Hx/Nx sedentary, Su/Hx/Nx exercised, control sedentary, and control exercised. Echocardiography was performed at 5, 8, and 13 weeks to assess right ventricular inner diameter in diastole and left ventricular eccentricity index. We found no difference between exercised and sedentary Su/Hx/Nx rats, and both were worsened compared with controls. Rats were euthanized at 13 weeks, and we found that neither RV/LV+S nor the occurrence of occlusive lesions were influenced by exercise. Most interesting, however, was that despite progressive PAH development, exercised Su/Hx/Nx rats showed no decrease in time or distance for treadmill exercise. In all, our data suggest that, despite severe PAH development, Su/Hx/Nx rats retain the same treadmill exercise capacity as control animals.
Project description:Circulating oxidative stress and pro-inflammatory markers change after regular physical exercise; however, how a short session of acute physical activity affects the inflammatory status and redox balance in sedentary individuals is still unclear. Aim of this study is to assess antioxidant and inflammatory parameters, both at rest and after acute exercise, in sedentary young men with or without obesity. Thirty sedentary male volunteers, aged 20-45 (mean age 32 ± 7 years), were recruited, divided into 3 groups (normal weight: BMI < 25 kg/m2; overweight to moderate obesity: 25-35 kg/m2; severe obesity: 35-40 kg/m2), and their blood samples collected before and after a 20-min run at ~ 70% of their VO2max for the measurement of Glutathione Reductase, Glutathione Peroxidase, Superoxide Dismutase, Total Antioxidant Status (TAS) and cytokines (IL-2, IL-4, IL-6, IL-8, IL-10, IL-1?, IL-1?, TNF?, MCP-1, VEGF, IFN?, EGF). Inter-group comparisons demonstrated significantly higher Glutathione Reductase activity in severely obese subjects in the post-exercise period (P = 0.036), and higher EGF levels in normal weight individuals, either before (P = 0.003) and after exercise (P = 0.05). Intra-group comparisons showed that the acute exercise stress induced a significant increase in Glutathione Reductase activity in severely obese subjects only (P = 0.007), a significant decrease in MCP-1 in the normal weight group (P = 0.02), and a decrease in EGF levels in all groups (normal weight: P = 0.025, overweight/moderate obesity: P = 0.04, severe obesity: P = 0.018). Altogether, these findings suggest that in sedentary individuals with different ranges of BMI, Glutathione Reductase and distinct cytokines are differentially involved into the adaptive metabolic changes and redox responses induced by physical exercise. Therefore, these biomarkers may have the potential to identify individuals at higher risk for developing diseases pathophysiologically linked to oxidative stress.
Project description:Introduction: Lipopolysaccharide (LPS) is a systemic response-triggering endotoxin, which has the kidney as one of its first targets, thus causing acute injuries to this organ. Physical exercise is capable of promoting physiological alterations and modulating inflammatory responses in the infectious process through multiple parameters, including the toll-like receptor (TLR)-4 pathway, which is the main LPS signaling in sepsis. Additionally, previous studies have shown that physical exercise can be both a protector factor and an aggravating factor for some kidney diseases. This study aims at analyzing whether physical exercise before the induction of LPS endotoxemia can protect kidneys from acute kidney injury. Methods: C57BL/6J male mice, 12 weeks old, were distributed into four groups: (1) sedentary (control, N = 7); (2) sedentary + LPS (N = 7); (3) trained (N = 7); and (4) trained + LPS (N = 7). In the training groups, the animals exercised 5×/week in a treadmill, 60 min/day, for 4 weeks (60% of max. velocity). Sepsis was induced in the training group by the application of a single dose of LPS (5 mg/kg i.p.). Sedentary animals received LPS on the same day, and the non-LPS groups received a saline solution instead. All animals were euthanized 24 h after the administration of LPS or saline. Results: The groups receiving LPS presented a significant increase in serum urea (p < 0.0001) and creatinine (p < 0.001) concentration and renal gene expression of inflammatory markers, such as tumor necrosis factor alpha and interleukin-6, as well as TLRs. In addition, LPS promoted a decrease in reduced glutathione. Compared to the sedentary + LPS group, trained + LPS showed overexpression of a gene related to kidney injury (NGAL, p < 0.01) and the protein levels of LPS receptor TLR-4 (p < 0.01). Trained + LPS animals showed an expansion of the tubulointerstitial space in the kidney (p < 0.05) and a decrease in the gene expression of hepatic AOAH (p < 0.01), an enzyme involved in LPS clearance. Conclusion: In contrast to our hypothesis, training was unable to mitigate the renal inflammatory response caused by LPS. On the contrary, it seems to enhance injury by accentuating endotoxin-induced TLR-4 signaling. This effect could be partly due to the modulation of a hepatic enzyme that detoxifies LPS.
Project description:Endurance exercise is known to promote a substantial effect on the energy balance in rats and humans. However, little is known about the exact mechanisms for the appetite-suppressive effects of endurance exercise. We hypothesized that endurance training might activate signaling cascades in the hypothalamus known to be involved in leptin signaling.16 male Wistar rats were randomly assigned to two groups: sedentary (n = 8) and exercise groups (n = 8). Animals in the exercise group started treadmill running at 30 m/min, 0% grade, for 1 min/bout. Running time was gradually increased by 2 min/bout every day. The training plan was one bout per day during initial two weeks, and two bouts per day during 3rd-9th week. At the end of nine-week experiment, blood was analyzed for low-density lipoprotein cholesterol (LDL-C), triglyceride (TG), total cholesterol (TC), free fatty acid (FFA), interleukin (IL)-6, and leptin in both groups. Activations of janus kinase 2-signaling transducer and activator of transcription 3 (JAK2-STAT3), protein kinase B (Akt), extracellular regulated kninase (ERKs), and suppressor of cytokine signaling 3 (SOCS3) in hypothalamus were measured in the end of nine weeks of exercise protocol.Nine-week endurance exercise induced lower concentrations of LDL-C, TG, TC, FFA, and leptin in rats (P < 0.05 or P < 0.01). Nine-week endurance exercise significantly increased the circulating IL-6 concentration compared with sedentary group (239.6 ± 37.2 pg/ml vs. 151.8 ± 31.5 pg/ml, P < 0.01). Exercise rats showed significant increases in JAK2, STAT3, Akt, ERKs, and SOCS3 phosphorylations compared with sedentary rats (P < 0.01).The data suggest that endurance exercise is a leptin signaling mimetic in hypothalamus of Wistar rats.
Project description:Recent evidence suggests that exercise stimulates the degradation of cellular components in skeletal muscle through activation of autophagy, but the time course of the autophagy response during recovery from exercise has not been determined. Furthermore, the regulatory mechanisms behind exercise-induced autophagy remain unclear, although the muscle oxidative phenotype has been linked with basal autophagy levels. Therefore, the aim of this study was to investigate the role of the key regulator of muscle oxidative capacity, PGC-1α, in exercise-induced autophagy at several time points during recovery. Mice with transgenic muscle-specific overexpression (TG) or knockout (MKO) of PGC-1α and their respective littermate controls were subjected to a single 1 h bout of treadmill running and euthanized immediately (0 h), 2, 6, and 10 h after exercise. In the PGC-1α MKO strain, quadriceps protein content of the autophagy marker LC3II was increased from 2 h into recovery in lox/lox control, but not in MKO mice. In the PGC-1α TG strain, quadriceps protein content of LC3II was increased from 2 h after exercise in TG, but not in WT. Although AMPK and ACC phosphorylation was increased immediately following exercise, the observed exercise-induced autophagy response was not associated with phosphorylation of the AMPK-target ULK1. However, lower protein carbonyl content was observed in lox/lox and TG mice after exercise coinciding with the increased LC3 lipidation. In conclusion, the present results suggest a role of skeletal muscle PGC-1α in coordinating several exercise-induced adaptive responses including autophagic removal of damaged cellular components.
Project description:Gene expression data at rest and immediately post 30 min submaximal exercise in 3 month and 16 month old male rats, some of which were sedentary (SED), had access to a physical activity box twice weekly (PA) and some of which had daily access to a running wheel (EX). We used microarrays to detail global gene expression underlying select health-related phenotypes and identified differentially expressed genes among the three groups. Young (3 month) and old (16 month) male rats were separated into three different groups: Sedentary (SED), twice-weekly physical activity (PA), and regular exercise (EX). Animals were sacrificed either at rest or after 30 min of sub maximal exercise. Then, a portion of cardiac tissue was collected for RNA extraction and hybridization on Affymetrix microarrays.
Project description:We compared the influence of aerobic and resistance exercise on cardiac remodelling, physical capacity and skeletal muscle oxidative stress in rats with MI-induced heart failure. Three months after MI induction, Wistar rats were divided into four groups: Sham; sedentary MI (S-MI); aerobic exercised MI (A-MI); and resistance exercised MI (R-MI). Exercised rats trained three times a week for 12 weeks on a treadmill or ladder. Statistical analysis was performed by ANOVA or Kruskal-Wallis test. Functional aerobic capacity was greater in A-MI and strength gain higher in R-MI. Echocardiographic parameters did not differ between infarct groups. Reactive oxygen species production, evaluated by fluorescence, was higher in S-MI than Sham, and lipid hydroperoxide concentration was lower in A-MI than the other groups. Glutathione peroxidase activity was higher in A-MI than S-MI and R-MI. Superoxide dismutase was lower in S-MI than Sham and R-MI. Gastrocnemius cross-sectional area, satellite cell activation and expression of the ubiquitin-proteasome system proteins did not differ between groups. In conclusion, aerobic exercise and resistance exercise improve functional capacity and maximum load carrying, respectively, without changing cardiac remodelling in infarcted rats. In the gastrocnemius, infarction increases oxidative stress and changes antioxidant enzyme activities. Aerobic exercise reduces oxidative stress and attenuates superoxide dismutase and glutathione peroxidase changes.
Project description:1. The effects of hypothyroidism (caused by surgical thyroidectomy followed by treatment for 1 month with propylthiouracil) and of hyperthyroidism [induced by subcutaneous administration of L-tri-iodothyronine (T3)] on glucose tolerance and skeletal-muscle sensitivity to insulin were examined in rats. Glucose tolerance was estimated during 2 h after subcutaneous glucose injection (1 g/kg body wt.). The sensitivity of the soleus muscle to insulin was studied in vitro in sedentary and acutely exercised animals. 2. Glucose tolerance was impaired in both hypothyroid and hyperthyroid rats in comparison with euthyroid controls. 3. In the soleus muscle, responsiveness of the rate of lactate formation to insulin was abolished in hypothyroid rats, whereas the sensitivity of the rate of glycogen synthesis to insulin was unchanged. In hyperthyroid animals, opposite changes were found, i.e. responsiveness of the rate of glycogen synthesis was inhibited and the sensitivity of the rate of lactate production did not differ from that in control sedentary rats. 4. A single bout of exercise for 30 min potentiated the stimulatory effect of insulin on lactate formation in hyperthyroid rats and on glycogen synthesis in hypothyroid animals. 5. The data suggest that thyroid hormones exert an interactive effect with insulin in skeletal muscle. This is likely to be at the post-receptor level, inhibiting the effect of insulin on glycogen synthesis and stimulating oxidative glucose utilization.
Project description:PURPOSE:Doxorubicin (DOX) is a highly effective chemotherapeutic agent used in the treatment of a broad spectrum of cancers. However, clinical use of DOX is limited by irreversible and dose-dependent hepatotoxicity. The liver is the primary organ responsible for the clearance of antineoplastic agents, and evidence indicates that hepatotoxicity occurs as a result of impaired mitochondrial efficiency during DOX metabolism. In this regard, exercise training is sufficient to improve mitochondrial function and protect against DOX-induced cytotoxicity. Therefore, the purpose of this study was to determine whether short-term exercise preconditioning is sufficient to protect against DOX-induced liver mitochondrionopathy. METHODS:Female Sprague-Dawley rats (4-6 months old) were randomly assigned to one of four groups: 1) sedentary, treated with saline; 2) sedentary, treated with DOX; 3) exercise trained, treated with saline; and 4) exercise trained, treated with DOX. Exercise-trained animals underwent 5 d of treadmill running habituation followed by 10 d of running for 60 min·d (30 m·min; 0% grade). After the last training bout, exercise-trained and sedentary animals were injected with either DOX (20 mg·kg i.p.) or saline. Two days after drug treatment, the liver was removed and mitochondria were isolated. RESULTS:DOX treatment induced mitochondrial dysfunction of the liver in sedentary animals because of alterations in mitochondrial oxidative capacity, biogenesis, degradation, and protein acetylation. Furthermore, exercise preconditioning protected against DOX-mediated liver mitochondrionopathy, which was associated with the maintenance of mitochondrial oxidative capacity and protein acetylation. CONCLUSION:These findings demonstrate that endurance exercise training protects against DOX-induced liver mitochondrial dysfunction, which was attributed to modifications in organelle oxidative capacity and mitochondrial protein acetylation.
Project description:Physical activity exerts positive effects on glycemic control in type 2 diabetes (T2D), which is mediated in part by extensive metabolic and molecular remodeling of skeletal muscle in response to exercise, while many regulators of skeletal muscle remain unclear. In the present study, we investigated the effects of acute exercise on skeletal muscle transcriptomic responses in the Goto-Kakizaki (GK) rats which can spontaneously develop T2D. The transcriptomes of skeletal muscle from both 8-week-old GK and Wistar rats that underwent a single exercise session (60 min running using an animal treadmill at 15 m/min) or remained sedentary were analyzed by next-generation RNA sequencing. We identified 819 differentially expressed genes in the sedentary GK rats compared with those of the sedentary Wistar rats. After a single bout of running, we found 291 and 598 genes that were differentially expressed in the exercise GK and exercise Wistar rats when compared with the corresponding sedentary rats. By integrating our data and previous studies including RNA or protein expression patterns and transgenic experiments, the downregulated expression of Fasn and upregulated expression of Tbc1d1, Hk2, Lpin1, Ppargc1a, Sorbs1, and Hmox1 might enhance glucose uptake or improve insulin sensitivity to ameliorate hyperglycemia in the exercise GK rats. Our results provide mechanistic insight into the beneficial effects of exercise on hyperglycemia and insulin action in skeletal muscle of diabetic GK rats.