Superoxide dismutase gene expression in skeletal muscle: fiber-specific adaptation to endurance training

Study of nitrogen heterocycles as DNA/HSA binder, topoisomerase inhibitors and toxicological safety

Four new nitrogen-containing heterocyclic derivatives (acridine, quinoline, indole, pyridine) were synthesized and their biological properties were evaluated. The compounds showed affinity for DNA and HSA, with CAIC and CAAC displaying higher binding constants (Kb) of 9.54 × 104 and 1.06 × 106, respectively. The fluorescence quenching assay (Ksv) revealed suppression values ranging from 0.34 to 0.64 × 103 M-1 for ethidium bromide (EB) and 0.1 to 0.34 × 103 M-1 for acridine orange (AO). Molecular docking confirmed the competition of the derivatives with intercalation probes at the same binding site. At 10 μM concentrations, the derivatives inhibited topoisomerase IIα activity. In the antiproliferative assays, the compounds demonstrated activity against MCF-7 and T47-D tumor cells and nonhemolytic profile. Regarding toxicity, no acute effects were observed in the embryos. However, some compounds caused enzymatic and cardiac changes, particularly the CAIC, which increased SOD activity and altered heart rate compared to the control. These findings suggest potential antitumor action of the derivatives and indicate that substituting the acridine core with different cores does not interfere with their interaction and topoisomerase inhibition. Further investigations are required to assess possible toxicological effects, including reactive oxygen species generation.

Redox Profile of Skeletal Muscles: Implications for Research Design and Interpretation

Mammalian skeletal muscles contain varying proportions of Type I and II fibers, which feature different structural, metabolic and functional properties. According to these properties, skeletal muscles are labeled as 'red' or 'white', 'oxidative' or 'glycolytic', 'slow-twitch' or 'fast-twitch', respectively. Redox processes (i.e., redox signaling and oxidative stress) are increasingly recognized as a fundamental part of skeletal muscle metabolism at rest, during and after exercise. The aim of the present review was to investigate the potential redox differences between slow- (composed mainly of Type I fibers) and fast-twitch (composed mainly of Type IIa and IIb fibers) muscles at rest and after a training protocol. Slow-twitch muscles were almost exclusively represented in the literature by the soleus muscle, whereas a wide variety of fast-twitch muscles were used. Based on our analysis, we argue that slow-twitch muscles exhibit higher antioxidant enzyme activity compared to fast-twitch muscles in both pre- and post-exercise training. This is also the case between heads or regions of fast-twitch muscles that belong to different subcategories, namely Type IIa (oxidative) versus Type IIb (glycolytic), in favor of the former. No safe conclusion could be drawn regarding the mRNA levels of antioxidant enzymes either pre- or post-training. Moreover, slow-twitch skeletal muscles presented higher glutathione and thiol content as well as higher lipid peroxidation levels compared to fast-twitch. Finally, mitochondrial hydrogen peroxide production was higher in fast-twitch muscles compared to slow-twitch muscles at rest. This redox heterogeneity between different muscle types may have ramifications in the analysis of muscle function and health and should be taken into account when designing exercise studies using specific muscle groups (e.g., on an isokinetic dynamometer) or isolated muscle fibers (e.g., electrical stimulation) and may deliver a plausible explanation for the conflicting results about the ergogenic potential of antioxidant supplements.

Effect of exercise training on nitric oxide and nitrate/nitrite (NOx) production: A systematic review and meta-analysis

Background: Exercise and physical activity can improve circulation through various mechanisms, such as the increment of nitric oxide (NO) production, by affecting vascular endothelial nitric oxide synthase, and reducing reactive oxygen species (ROS). Although, theoretically, this mechanism is well known, studies in living subjects have made controversial findings regarding the association of NO production and its metabolites [nitrate/nitrite (NOx)] with physical activity. Hence, this systematic review and meta-analysis was designed to gather all these studies and evaluate the effects of exercise training, and physical activity duration and length on the mean change of serum/plasma NO and NOx.

Method: We searched all available bibliographic electronic databases from inception through to May 2022 to include all randomized controlled trials (RCT) and quasi-experimental trials which assessed the effect of exercise and training on NO and NOx levels. Random-effects meta-analysis was used to pool the standardized mean difference (SMD) and 95% confidence interval (CI) of included RCT studies which assessed the effect of training. Stratified meta-analysis was performed according to the type of exercise (high-intensity interval training (HIIT), aerobic training (AT), the duration of exercise (≤8 and > 8 weeks), and length of exercise in each session ≥40 and 40 < minutes).

Results: Overall, 15 and 10 studies were included in the systematic review and meta-analysis, respectively. According to the random-effects meta-analysis, exercise significantly increased the mean change of NO and NOx compared to control (SMD: 1.82, 95%CI: 1.14 to 2.49. In the stratified meta-analysis, the mean change of NO and NOx in the intervention group was significantly higher than in the control group in the AT (SMD: 1.36, 95%CI: 0.55–2.18), HIIT (SMD: 2.55, 95%CI: 1.14–3.96), duration of ≤8 (SMD: 2.29, 95%CI: 1.24–3.35) and > 8 weeks (SMD: 1.19, 95%CI: 0.52–1.86), length of ≥40 (SMD: 1.61, 95%CI: 1.04–2.18), and 40 < minutes in each session (SMD: 2.07, 95%CI: 0.79–3.35).

Conclusion: The findings of this study indicate that, regardless of exercise duration, length, and type (AT or HIIT), exercise can significantly increase serum NO and NOx levels.

Effects of exercise-induced metabolic and mechanical loading on skeletal muscle mitochondrial function in male rats

Over the last decades, a growing interest in eccentric (ECC) exercise has emerged, but mitochondrial adaptations to ECC training remain poorly documented. Using an approach for manipulating mechanical and metabolic exercise power, we positioned that for same metabolic power, training using concentric (CON) or ECC contractions would induce similar skeletal muscle mitochondrial adaptations. Sixty adult rats were randomly assigned to a control (CTRL) or three treadmill training groups running at 15m·min^-1 for 45min, 5days weekly for 8 weeks at targeted upward or downward slopes. Animals from the CON (+15%) and ECC30 (-30%) groups trained at iso-metabolic power while CON and ECC15 (-15%) exercised at iso-mechanical power. Assessments were made of Vastus Intermedius mitochondrial respiration (oxygraphy), enzymatic activities (spectrophotometry) and real-time qPCR for mRNA transcripts. Maximal rates of mitochondrial respiration was 14-15% higher in CON and ECC30 compared to CTRL and ECC15. Apparent K_m for ADP for trained groups was 40-66% higher than CTRL, with statistical significance reached for CON and ECC30. Complex I and citrate synthase activities were 1.6 (ECC15) to 1.8 (ECC30 and CON) times values of CTRL. Complex IV activity was higher than CTRL (p<0.05) only for CON and ECC30. mRNA transcripts analyses showed higher TFAM, SLC25A4, CKMT2 and PPID in the ECC30 compared to CTRL. Findings confirm that training-induced skeletal muscle mitochondrial function adaptations are governed by the extent of metabolic overload irrespective of exercise modality. The distinctive ECC30 mRNA transcript pattern may reflect a cytoskeleton damage-repair or ECC adaptive cycle that differs from that of biogenesis.

Physical activity level (PAL) and risk factors of cardiovascular disease in the MASHAD study cohort

BACKGROUND AND AIM

The relationship between physical activity levels (PAL) and the presence of cardiovascular disease (CVD) risk factors such as anthropometric and biochemical indices and heat shock proteins 27 antibody (anti-HSP-27) concentration, and serum inflammatory markers, was investigated in the MASHAD cohort study.

METHODS

The overall study population consisted of 9,684 subjects (3,858 men, 5,826 women) with a mean age of 47.73 ± 8.08 to 48.87 ± 9.26 years respectively. They were divided into four categories based on their PAL. Biochemical parameters were determined for all participants. Also, serum anti-HSP-27 levels were measured using an in-house enzyme-linked immune sorbent assay method. Multiple regression analysis was used to explore the association between the anti-HSP antibody titers and physical activity after adjusting for confounding factors. The level of statistical significance was set at p < 0.05.

RESULTS

Several CVD risk factors were associated with the level of PAL including: body mass index, waist hip ratio, systolic and diastolic blood pressure, serum HDL-C and TG (p < 0.001) and also fasting blood glucose (0.004). Also, serum anti-HSP-27 titers were significantly higher in inactive subjects (P > 0.05).

CONCLUSION

We found that PAL was significantly associated with several established CVD risk factors. Also, the level of anti-HSP-27 was lower in individuals with moderate and high PAL.

Beneficial Role of Exercise in the Modulation of mdx Muscle Plastic Remodeling and Oxidative Stress

Duchenne muscular dystrophy (DMD) is an X-linked recessive progressive lethal disorder caused by the lack of dystrophin, which determines myofibers mechanical instability, oxidative stress, inflammation, and susceptibility to contraction-induced injuries. Unfortunately, at present, there is no efficient therapy for DMD. Beyond several promising gene- and stem cells-based strategies under investigation, physical activity may represent a valid noninvasive therapeutic approach to slow down the progression of the pathology. However, ethical issues, the limited number of studies in humans and the lack of consistency of the investigated training interventions generate loss of consensus regarding their efficacy, leaving exercise prescription still questionable. By an accurate analysis of data about the effects of different protocol of exercise on muscles of mdx mice, the most widely-used pre-clinical model for DMD research, we found that low intensity exercise, especially in the form of low speed treadmill running, likely represents the most suitable exercise modality associated to beneficial effects on mdx muscle. This protocol of training reduces muscle oxidative stress, inflammation, and fibrosis process, and enhances muscle functionality, muscle regeneration, and hypertrophy. These conclusions can guide the design of appropriate studies on human, thereby providing new insights to translational therapeutic application of exercise to DMD patients.

Exercise-Stimulated ROS Sensitive Signaling Pathways in Skeletal Muscle

Physical exercise represents a major challenge to whole-body homeostasis, provoking acute and adaptative responses at the cellular and systemic levels. Different sources of reactive oxygen species (ROS) have been described in skeletal muscle (e.g., NADPH oxidases, xanthine oxidase, and mitochondria) and are closely related to the physiological changes induced by physical exercise through the modulation of several signaling pathways. Many signaling pathways that are regulated by exercise-induced ROS generation, such as adenosine monophosphate-activated protein kinase (AMPK), mitogen activated protein kinase (MAPK), nuclear respiratory factor2 (NRF2), and PGC-1α are involved in skeletal muscle responses to physical exercise, such as increased glucose uptake, mitochondriogenesis, and hypertrophy, among others. Most of these adaptations are blunted by antioxidants, revealing the crucial role played by ROS during and after physical exercise. When ROS generation is either insufficient or exacerbated, ROS-mediated signaling is disrupted, as well as physical exercise adaptations. Thus, an understanding the limit between "ROS that can promote beneficial effects" and "ROS that can promote harmful effects" is a challenging question in exercise biology. The identification of new mediators that cause reductive stress and thereby disrupt exercise-stimulated ROS signaling is a trending on this topic and are covered in this current review.

The Role of Natural Antioxidants in the Prevention of Dementia-Where Do We Stand and Future Perspectives

Dementia, and especially Alzheimer's disease (AD), puts significant burden on global healthcare expenditure through its increasing prevalence. Research has convincingly demonstrated the implication of oxidative stress in the pathogenesis of dementia as well as of the conditions which increase the risk of developing dementia. However, drugs which target single pathways have so far failed in providing significant neuroprotection. Natural antioxidants, due to their effects in multiple pathways through which oxidative stress leads to neurodegeneration and triggers neuroinflammation, could prove valuable weapons in our fight against dementia. Although efficient in vitro and in animal models of AD, natural antioxidants in human trials have many drawbacks related to the limited bioavailability, unknown optimal dose, or proper timing of the treatment. Nonetheless, trials evaluating several of these natural compounds are ongoing, as are attempts to modify these compounds to achieve improved bioavailability.

Aerobic exercise training attenuates detrimental effects of cigarette smoke exposure on peripheral muscle through stimulation of the Nrf2 pathway and cytokines: a time-course study in mice

Cigarette smoke (CS) exposure reduces skeletal muscle function; however, the mechanisms involved have been poorly investigated. The current study evaluated the temporal effects of aerobic exercise training on oxidant and antioxidant systems as well as inflammatory markers in skeletal muscle of mice exposed to CS. Mice were randomly allocated to control, exercise, smoke, and smoke+exercise groups and 3 time points (4, 8, and 12 weeks; n = 12 per group). Exercise training and CS exposure were performed for 30 min/day, twice a day, 5 days/week for 4, 8, and 12 weeks. Aerobic exercise improved functional capacity and attenuated the increase in the cachexia index induced by CS exposure after 12 weeks. Concomitantly, exercise training downregulated tumor necrosis factor α concentration, glutathione oxidation, and messenger RNA (mRNA) expression of Keap1 (P < 0.01) and upregulated interleukin 10 concentration, total antioxidant capacity, and mRNA expression of Nrf2, Gsr, and Txn1 (P < 0.01) in muscle. Exercise increased mRNA expression of Hmox1 compared with the control after 12 weeks (P < 0.05). There were no significant differences between smoke groups for superoxide dismutase activity and Hmox1 mRNA expression. Exercise training improved the ability of skeletal muscle to adequately upregulate key antioxidant and anti-inflammatory defenses to detoxify electrophilic compounds induced by CS exposure, and these effects were more pronounced after 12 weeks. Novelty Exercise attenuates oxidative stress in skeletal muscle from animals exposed to CS via Nrf2 and glutathione pathways. Exercise is a helpful tool to control the inflammatory balance in skeletal muscle from animals exposed to CS. These beneficial effects were evident after 12 weeks.

Redox basis of exercise physiology

Redox reactions control fundamental processes of human biology. Therefore, it is safe to assume that the responses and adaptations to exercise are, at least in part, mediated by redox reactions. In this review, we are trying to show that redox reactions are the basis of exercise physiology by outlining the redox signaling pathways that regulate four characteristic acute exercise-induced responses (muscle contractile function, glucose uptake, blood flow and bioenergetics) and four chronic exercise-induced adaptations (mitochondrial biogenesis, muscle hypertrophy, angiogenesis and redox homeostasis). Based on our analysis, we argue that redox regulation should be acknowledged as central to exercise physiology.

Strenuous Acute Exercise Induces Slow and Fast Twitch-Dependent NADPH Oxidase Expression in Rat Skeletal Muscle

The enzymatic complex Nicotinamide Adenine Dinucleotide Phosphate (NADPH) oxidase (NOx) may be the principal source of reactive oxygen species (ROS). The NOX2 and NOX4 isoforms are tissue-dependent and are differentially expressed in slow-twitch fibers (type I fibers) and fast-twitch fibers (type II fibers) of skeletal muscle, making them different markers of ROS metabolism induced by physical exercise. The aim of this study was to investigate NOx signaling, as a non-adaptive and non-cumulative response, in the predominant fiber types of rat skeletal muscles 24 h after one strenuous treadmill exercise session. The levels of mRNA, reduced glycogen, thiol content, NOx, superoxide dismutase, catalase, glutathione peroxidase activity, and PPARGC1α and SLC2A4 gene expression were measured in the white gastrocnemius (WG) portion, the red gastrocnemius (RG) portion, and the soleus muscle (SOL). NOx activity showed higher values in the SOL muscle compared to the RG and WG portions. The same was true of the NOX2 and NOX4 mRNA levels, antioxidant enzymatic activities, glycogen content. Twenty-four hours after the strenuous exercise session, NOx expression increased in slow-twitch oxidative fibers. The acute strenuous exercise condition showed an attenuation of oxidative stress and an upregulation of antioxidant activity through PPARGC1α gene activity, antioxidant defense adaptations, and differential gene expression according to the predominant fiber type. The most prominent location of detoxification (indicated by NOX4 activation) in the slow-twitch oxidative SOL muscle was the mitochondria, while the fast-twitch oxidative RG portion showed a more cytosolic location. Glycolytic metabolism in the WG portion suggested possible NOX2/NOX4 non-regulation, indicating other possible ROS regulation pathways.

Mediators of Physical Activity Protection against ROS-Linked Skeletal Muscle Damage

Unaccustomed and/or exhaustive exercise generates excessive free radicals and reactive oxygen and nitrogen species leading to muscle oxidative stress-related damage and impaired contractility. Conversely, a moderate level of free radicals induces the body’s adaptive responses. Thus, a low oxidant level in resting muscle is essential for normal force production, and the production of oxidants during each session of physical training increases the body’s antioxidant defenses. Mitochondria, NADPH oxidases and xanthine oxidases have been identified as sources of free radicals during muscle contraction, but the exact mechanisms underlying exercise-induced harmful or beneficial effects yet remain elusive. However, it is clear that redox signaling influences numerous transcriptional activators, which regulate the expression of genes involved in changes in muscle phenotype. The mitogen-activated protein kinase family is one of the main links between cellular oxidant levels and skeletal muscle adaptation. The family components phosphorylate and modulate the activities of hundreds of substrates, including transcription factors involved in cell response to oxidative stress elicited by exercise in skeletal muscle. To elucidate the complex role of ROS in exercise, here we reviewed the literature dealing on sources of ROS production and concerning the most important redox signaling pathways, including MAPKs that are involved in the responses to acute and chronic exercise in the muscle, particularly those involved in the induction of antioxidant enzymes.

The early response of αB-crystallin to a single bout of aerobic exercise in mouse skeletal muscles depends upon fiber oxidative features

Besides its substantial role in eye lens, αB-crystallin (HSPB5) retains fundamental function in striated muscle during physiological or pathological modifications. In this study, we aimed to analyse the cellular and molecular factors driving the functional response of HSPB5 protein in different muscles from mice subjected to an acute bout of non-damaging endurance exercise or in C2C12 myocytes upon exposure to pro-oxidant environment, chosen as “in vivo” and “in vitro” models of a physiological stressing conditions, respectively.

To this end, red (GR) and white gastrocnemius (GW), as sources of slow-oxidative and fast-glycolytic/oxidative fibers, as well as the soleus (SOL), mainly composed of slow-oxidative type fibers, were obtained from BALB/c mice, before (CTRL) and at different times (0′, 15′, 30′ 120′) following 1-h of running. Although the total level of HSPB5 protein was not affected by exercise, we found a significantly increase of phosphorylated HSPB5 (p-HSPB5) only in GR and SOL skeletal muscle with a higher amount of type I and IIA/X myofibers. The fiber-specific activation of HSPB5 was correlated to its interaction with the actin filaments, as well as to an increased level of lipid peroxidation and carbonylated proteins. The role of the pro-oxidant environment in HSPB5 response was investigated in terminally differentiated C2C12 myotubes, where most of HSPB5/pHSPB5 pool was present in the cytosolic compartment in standard culture conditions. As a result of exposure to pro-oxidizing, but not cytotoxic, H₂O₂ concentration, the p-38MAPK-mediated phosphorylation of HSPB5 resulted functional to promote its interaction with the myofibrillar components, such as β-actin, desmin and filamin 1.

This study provides novel information on the molecular pathway underlying the HSPB5 physiological function in skeletal muscle, confirming the contribution of the pro-oxidant environment in HSPB5 activation and interaction with substrate/client myofibrillar proteins, offering new insights for the study of myofibrillar myopathies and cardiomyopathies.

Effects of flight activity and age on oxidative damage in the honey bee, Apis mellifera

Frequent and highly aerobic behaviors likely contribute to naturally occurring stress, accelerate senescence and limit lifespan. To understand how the physiological and cellular mechanisms that determine the onset and duration of senescence are shaped by behavioral development and behavioral duration, we exploited the tractability of the honey bee (Apis mellifera) model system. First, we determined whether a cause-effect relationship exists between honey bee flight and oxidative stress by comparing oxidative damage accrued from intense flight bouts to damage accrued from d-galactose ingestion, which induces oxidative stress and limits lifespan in other insects. Second, we experimentally manipulated the duration of honey bee flight across a range of ages to determine the effects on reactive oxygen species (ROS) accumulation and associated enzymatic antioxidant protective mechanisms. In bees fed d-galactose, lipid peroxidation (assessed by measuring malondialdehyde levels) was higher than in bees fed sucrose and age-matched bees with a high and low number of flight experiences collected from a colony. Bees with high amounts of flight experience exhibited elevated 8-hydroxy-2'-deoxyguanosine, a marker of oxidative DNA damage, relative to bees with less flight experience. Bees with high amounts of flight experience also showed increased levels of pro-oxidants (superoxide and hydrogen peroxide) and decreased or unchanged levels of antioxidants (superoxide dismutase and catalase). These data implicate an imbalance of pro- to anti-oxidants in flight-associated oxidative stress, and reveal how behavior can damage a cell and consequently limit lifespan.

C60 Fullerenes Diminish Muscle Fatigue in Rats Comparable to N-acetylcysteine or β-Alanine

The aim of this study is to detect the effects of C60 fullerenes, which possess pronounced antioxidant properties, in comparison with the actions of the known exogenous antioxidants N-acetylcysteine (NAC) and β-Alanine in terms of exercise tolerance and contractile property changes of the m. triceps surae (TS) during development of the muscle fatigue in rats. The electrical stimulation of the TS muscle during four 30 min series in control rats led to total reduction of the muscle contraction force. Furthermore, the effects of prior intraperitoneal (i.p.) or oral C60FAS application and preliminary i.p. injection of NAC or β-Alanine on muscle contraction force under fatigue development conditions is studied. In contrast to control rats, animals with C60FAS, NAC, or β-Alanine administration could maintain a constant level of muscle effort over five stimulation series. The accumulation of secondary products and changes in antioxidant levels in the muscle tissues were also determined after the fatigue tests. The increased levels of lactic acid, thiobarbituric acid reactive substances and H2O2 after stimulation were statistically significant with respect to intact muscles. In the working muscle, there was a significant (p < 0.05) increase in the activity of endogenous antioxidants: reduced glutathione, catalase, glutathione peroxidase, and superoxide dismutase. Treated animal groups showed a decrease in endogenous antioxidant activity relative to the fatigue-induced animals (P < 0.05). Oral C60FAS administration clearly demonstrated an action on skeletal muscle fatigue development similar to the effects of i.p. injections of the exogenous antioxidants NAC or β-Alanine. This creates opportunities to oral use of C60FAS as a potential therapeutic agent. Due to the membranotropic activity of C60 fullerenes, non-toxic C60FAS has a more pronounced effect on the prooxidant-antioxidant homeostasis of muscle tissues in rats.

Role of Redox Signaling and Inflammation in Skeletal Muscle Adaptations to Training

The inflammatory response to exercise-induced muscle damage has been extensively described. Exercise has important modulatory effects on immune function. These effects are mediated by diverse factors including pro-inflammatory cytokines, classical stress hormones, and hemodynamic effects leading to cell redistribution. As has been reported regarding oxidative stress, inflammation can have both detrimental and beneficial effects in skeletal muscle. In this review we will address the role of inflammation on protein metabolism in skeletal muscle. Specifically, we will review studies showing that treatment with cyclooxygenase-inhibiting drugs modulate the protein synthesis response to one bout of resistance exercise and to training. Understanding how these drugs work is important for the millions of individuals worldwide that consume them regularly. We will also discuss the importance of reactive oxygen species and inflammatory cytokines in muscle adaptations to exercise and the Janus faced of the use of antioxidant and anti-inflammatory drugs by athletes for optimizing their performance, especially during the periods in which muscle hypertrophy is expected.

Mitochondria in the middle: exercise preconditioning protection of striated muscle

Cellular and physiological adaptations to an atmosphere which became enriched in molecular oxygen spurred the development of a layered system of stress protection, including antioxidant and stress response proteins. At physiological levels reactive oxygen and nitrogen species regulate cell signalling as well as intracellular and intercellular communication. Exercise and physical activity confer a variety of stressors on skeletal muscle and the cardiovascular system: mechanical, metabolic, oxidative. Transient increases of stressors during acute bouts of exercise or exercise training stimulate enhancement of cellular stress protection against future insults of oxidative, metabolic and mechanical stressors that could induce injury or disease. This phenomenon has been termed both hormesis and exercise preconditioning (EPC). EPC stimulates transcription factors such as Nrf-1 and heat shock factor-1 and up-regulates gene expression of a cadre of cytosolic (e.g. glutathione peroxidase and heat shock proteins) and mitochondrial adaptive or stress proteins (e.g. manganese superoxide dismutase, mitochondrial KATP channels and peroxisome proliferator activated receptor γ coactivator-1 (PGC-1)). Stress response and antioxidant enzyme inducibility with exercise lead to protection against striated muscle damage, oxidative stress and injury. EPC may indeed provide significant clinical protection against ischaemia-reperfusion injury, Type II diabetes and ageing. New molecular mechanisms of protection, such as δ-opioid receptor regulation and mitophagy, reinforce the notion that mitochondrial adaptations (e.g. heat shock proteins, antioxidant enzymes and sirtuin-1/PGC-1 signalling) are central to the protective effects of exercise preconditioning.

Role of ROS and RNS Sources in Physiological and Pathological Conditions

There is significant evidence that, in living systems, free radicals and other reactive oxygen and nitrogen species play a double role, because they can cause oxidative damage and tissue dysfunction and serve as molecular signals activating stress responses that are beneficial to the organism. Mitochondria have been thought to both play a major role in tissue oxidative damage and dysfunction and provide protection against excessive tissue dysfunction through several mechanisms, including stimulation of opening of permeability transition pores. Until recently, the functional significance of ROS sources different from mitochondria has received lesser attention. However, the most recent data, besides confirming the mitochondrial role in tissue oxidative stress and protection, show interplay between mitochondria and other ROS cellular sources, so that activation of one can lead to activation of other sources. Thus, it is currently accepted that in various conditions all cellular sources of ROS provide significant contribution to processes that oxidatively damage tissues and assure their survival, through mechanisms such as autophagy and apoptosis.

Dietary Antioxidants as Modifiers of Physiologic Adaptations to Exercise

INTRODUCTION

Adaptive responses to exercise training (ET) are crucial in maintaining physiologic homeostasis and health span. Exercise-induced aerobic bioenergetic reactions in the mitochondria and cytosol increase production of reactive oxygen species, where excess of reactive oxygen species can be scavenged by enzymatic and nonenzymatic antioxidants (AO) to protect against deleterious oxidative stress. Free radicals, however, have recently been recognized as crucial signaling agents that promote adaptive mechanisms to ET, such as mitochondrial biogenesis, AO enzyme activity defense system upregulation, insulin sensitivity, and glucose uptake in the skeletal muscle. Commonly used nonenzymatic AO supplements, such as vitamins C and E, α-lipoic acid, and polyphenols, in combination with ET, have been proposed as ways to prevent exercise-induced oxidative stress and hence improve adaptation responses to endurance training.

METHODS

During the PubMed search, we selected studies that examined and compared ET effects with and without administration of commonly used AO supplements.

RESULTS

Preclinical and clinical studies to date have shown inconsistent results indicating either positive or negative effects of endurance training combined with different blends of AO supplements (mostly vitamins C and E and α-lipoic acid) on redox status, mitochondrial biogenesis pathways, and insulin sensitivity. Preclinical reports on ET combined with resveratrol, however, have shown consistent positive effects on exercise performance, mitochondrial biogenesis, and insulin sensitivity, with clinical trials reporting mixed effects. Relevant clinical studies have been few and have used inconsistent results and methodology (types of compounds, combinations, and supplementation time).

CONCLUSIONS

The future studies should investigate the effects of specific AO and other popular supplements, such as α-lipoic acid and resveratrol, on training effects in humans. Of particular importance are older adults who may be at higher risk of age-related increased oxidative stress, an impaired AO enzyme defense system, and comorbidities such as hypertension, insulin resistance, and diabetes.

Physiological and pathophysiological reactive oxygen species as probed by EPR spectroscopy: the underutilized research window on muscle ageing

Reactive oxygen and nitrogen species (ROS and RNS) play crucial roles in triggering, mediating and regulating physiological and pathophysiological signal transduction pathways within the cell. Within the cell, ROS efflux is firmly controlled both spatially and temporally, making the study of ROS dynamics a challenging task. Different approaches have been developed for ROS assessment; however, many of these assays are not capable of direct identification or determination of subcellular localization of different ROS. Here we highlight electron paramagnetic resonance (EPR) spectroscopy as a powerful technique that is uniquely capable of addressing questions on ROS dynamics in different biological specimens and cellular compartments. Due to their critical importance in muscle functions and dysfunction, we discuss in some detail spin trapping of various ROS and focus on EPR detection of nitric oxide before highlighting how EPR can be utilized to probe biophysical characteristics of the environment surrounding a given stable radical. Despite the demonstrated ability of EPR spectroscopy to provide unique information on the identity, quantity, dynamics and environment of radical species, its applications in the field of muscle physiology, fatiguing and ageing are disproportionately infrequent. While reviewing the limited examples of successful EPR applications in muscle biology we conclude that the field would greatly benefit from more studies exploring ROS sources and kinetics by spin trapping, protein dynamics by site-directed spin labelling, and membrane dynamics and global redox changes by spin probing EPR approaches.

Role of reactive oxygen species in regulation of glucose transport in skeletal muscle during exercise

Glucose derived from extracellular sources serves as an energy source in virtually all eukaryotic cells, including skeletal muscle. Its contribution to energy turnover increases with exercise intensity up to moderately heavy workloads. However, at very high workloads, the contribution of extracellular glucose to energy turnover is negligible, despite the high rate of glucose transport. Reactive oxygen species (ROS) are involved in the stimulation of glucose transport in isolated skeletal muscle preparations during intense repeated contractions. Consistent with this observation, heavy exercise is associated with significant production of ROS. However, during more mild to moderate stimulation or exercise conditions (in vitro, in situ and in vivo) antioxidants do not affect glucose transport. It is noteworthy that the production of ROS is limited or not observed under these conditions and that the concentration of the antioxidant used was extremely low. The results to date suggest that ROS involvement in activation of glucose transport occurs primarily during intense short-term exercise and that other mechanisms are involved during mild to moderate exercise. What remains puzzling is why ROS-mediated activation of glucose transport would occur under conditions where glucose transport is highest and utilization (i.e. phosphorylation of glucose by hexokinase) is low. Possibly ROS production is involved in priming glucose transport during heavy exercise to accelerate glycogen biogenesis during the initial recovery period after exercise, as well as altering other aspects of intracellular metabolism.

Exercise Modulates Oxidative Stress and Inflammation in Aging and Cardiovascular Diseases

Despite the wealth of epidemiological and experimental studies indicating the protective role of regular physical activity/exercise training against the sequels of aging and cardiovascular diseases, the molecular transducers of exercise/physical activity benefits are not fully identified but should be further investigated in more integrative and innovative approaches, as they bear the potential for transformative discoveries of novel therapeutic targets. As aging and cardiovascular diseases are associated with a chronic state of oxidative stress and inflammation mediated via complex and interconnected pathways, we will focus in this review on the antioxidant and anti-inflammatory actions of exercise, mainly exerted on adipose tissue, skeletal muscles, immune system, and cardiovascular system by modulating anti-inflammatory/proinflammatory cytokines profile, redox-sensitive transcription factors such as nuclear factor kappa B, activator protein-1, and peroxisome proliferator-activated receptor gamma coactivator 1-alpha, antioxidant and prooxidant enzymes, and repair proteins such as heat shock proteins, proteasome complex, oxoguanine DNA glycosylase, uracil DNA glycosylase, and telomerase. It is important to note that the effects of exercise vary depending on the type, intensity, frequency, and duration of exercise as well as on the individual's characteristics; therefore, the development of personalized exercise programs is essential.

Reduction in mdx mouse muscle degeneration by low-intensity endurance exercise: a proteomic analysis in quadriceps muscle of exercised compared with sedentary mdx mice

By proteomic analysis we found an up-regulation of four carbonic anhydrase-3 (CA3) isoforms and a down-regulation of superoxide dismutase [Cu-Zn] (SODC) in quadriceps of sedentary X-linked muscular dystrophy (mdx) mice as compared with wild–type (WT) mice and the levels were significantly restored to WT values following low-intensity endurance exercise.

In our recent study was shown a significant recovery of damaged skeletal muscle of mice with X-linked muscular dystrophy (mdx) following low-intensity endurance exercise, probably by reducing the degeneration of dystrophic muscle. Consequently, in the present work, we aimed to identify proteins involved in the observed reduction in degenerating fibres. To this end, we used proteomic analysis to evaluate changes in the protein profile of quadriceps dystrophic muscles of exercised compared with sedentary mdx mice. Four protein spots were found to be significantly changed and were identified as three isoforms of carbonic anhydrase 3 (CA3) and superoxide dismutase [Cu-Zn] (SODC). Protein levels of CA3 isoforms were significantly up-regulated in quadriceps of sedentary mdx mice and were completely restored to wild–type (WT) mice values, both sedentary and exercised, in quadriceps of exercised mdx mice. Protein levels of SODC were down-regulated in quadriceps of sedentary mdx mice and were significantly restored to WT mice values, both sedentary and exercised, in quadriceps of exercised mdx mice. Western blot data were in agreement with those obtained using proteomic analysis and revealed the presence of one more CA3 isoform that was significantly changed. Based on data found in the present study, it seems that low-intensity endurance exercise may in part contribute to reduce cell degeneration process in mdx muscles, by counteracting oxidative stress.

Impact of oxidative stress on exercising skeletal muscle

It is well established that muscle contractions during exercise lead to elevated levels of reactive oxygen species (ROS) in skeletal muscle. These highly reactive molecules have many deleterious effects, such as a reduction of force generation and increased muscle atrophy. Since the discovery of exercise-induced oxidative stress several decades ago, evidence has accumulated that ROS produced during exercise also have positive effects by influencing cellular processes that lead to increased expression of antioxidants. These molecules are particularly elevated in regularly exercising muscle to prevent the negative effects of ROS by neutralizing the free radicals. In addition, ROS also seem to be involved in the exercise-induced adaptation of the muscle phenotype. This review provides an overview of the evidences to date on the effects of ROS in exercising muscle. These aspects include the sources of ROS, their positive and negative cellular effects, the role of antioxidants, and the present evidence on ROS-dependent adaptations of muscle cells in response to physical exercise.

Exercise is the real polypill

The concept of a "polypill" is receiving growing attention to prevent cardiovascular disease. Yet similar if not overall higher benefits are achievable with regular exercise, a drug-free intervention for which our genome has been haped over evolution. Compared with drugs, exercise is available at low cost and relatively free of adverse effects. We summarize epidemiological evidence on the preventive/therapeutic benefits of exercise and on the main biological mediators involved.

Skeletal muscle reactive oxygen species: a target of good cop/bad cop for exercise and disease

Metabolic stresses associated with disease, ageing, and exercise increase the levels of reactive oxygen species (ROS) in skeletal muscle. These ROS have been linked mechanistically to adaptations in skeletal muscle that can be favourable (i.e. in response to exercise) or detrimental (i.e. in response to disease). The magnitude, duration (acute versus chronic), and cellular origin of the ROS are important underlying factors in determining the metabolic perturbations associated with the ROS produced in skeletal muscle. In particular, insulin resistance has been linked to excess ROS production in skeletal muscle mitochondria. A chronic excess of mitochondrial ROS can impair normal insulin signalling pathways and glucose disposal in skeletal muscle. In contrast, ROS produced in skeletal muscle in response to exercise has been linked to beneficial metabolic adaptations including mitochondrial biogenesis and muscle hypertrophy. Moreover, unlike insulin resistance, exercise-induced ROS appears to be primarily of non-mitochondrial origin. The present review summarizes the diverse ROS-targeted metabolic outcomes associated with insulin resistance versus exercise in skeletal muscle, thus, presenting two contrasting perspectives of pathologically harmful versus physiologically beneficial ROS. Here, we discuss the key sites of ROS production during exercise and the effect of ROS in skeletal muscle of people with type 2 diabetes.

Cordyceps sinensis increases hypoxia tolerance by inducing heme oxygenase-1 and metallothionein via Nrf2 activation in human lung epithelial cells

Cordyceps sinensis, an edible mushroom growing in Himalayan regions, is widely recognized in traditional system of medicine. In the present study, we report the efficacy of Cordyceps sinensis in facilitating tolerance to hypoxia using A549 cell line as a model system. Treatment with aqueous extract of Cordyceps sinensis appreciably attenuated hypoxia induced ROS generation, oxidation of lipids and proteins and maintained antioxidant status similar to that of controls via induction of antioxidant gene HO1 (heme oxygenase-1), MT (metallothionein) and Nrf2 (nuclear factor erythroid-derived 2-like 2). In contrast, lower level of NF κ B (nuclear factor kappaB) and tumor necrosis factor- α observed which might be due to higher levels of HO1, MT and transforming growth factor- β . Further, increase in HIF1 (hypoxia inducible factor-1) and its regulated genes; erythropoietin, vascular endothelial growth factor, and glucose transporter-1 was observed. Interestingly, Cordyceps sinensis treatment under normoxia did not regulate the expression HIF1, NF κ B and their regulated genes evidencing that Cordyceps sinensis per se did not have an effect on these transcription factors. Overall, Cordyceps sinensis treatment inhibited hypoxia induced oxidative stress by maintaining higher cellular Nrf2, HIF1 and lowering NF κ B levels. These findings provide a basis for possible use of Cordyceps sinensis in tolerating hypoxia.

Potential mechanisms of exercise in gestational diabetes

Gestational diabetes mellitus (GDM) is defined as glucose intolerance first diagnosed during pregnancy. This condition shares same array of underlying abnormalities as occurs in diabetes outside of pregnancy, for example, genetic and environmental causes. However, the role of a sedentary lifestyle and/or excess energy intake is more prominent in GDM. Physically active women are less likely to develop GDM and other pregnancy-related diseases. Weight gain in pregnancy causes increased release of adipokines from adipose tissue; many adipokines increase oxidative stress and insulin resistance. Increased intramyocellular lipids also increase cellular oxidative stress with subsequent generation of reactive oxygen species. A well-planned program of exercise is an important component of a healthy lifestyle and, in spite of old myths, is also recommended during pregnancy. This paper briefly reviews the role of adipokines in gestational diabetes and attempts to shed some light on the mechanisms by which exercise can be beneficial as an adjuvant therapy in GDM. In this regard, we discuss the mechanisms by which exercise increases insulin sensitivity, changes adipokine profile levels, and boosts antioxidant mechanisms.

Swimming training induces liver mitochondrial adaptations to oxidative stress in rats submitted to repeated exhaustive swimming bouts

BACKGROUND AND AIMS

Although acute exhaustive exercise is known to increase liver reactive oxygen species (ROS) production and aerobic training has shown to improve the antioxidant status in the liver, little is known about mitochondria adaptations to aerobic training. The main objective of this study was to investigate the effects of the aerobic training on oxidative stress markers and antioxidant defense in liver mitochondria both after training and in response to three repeated exhaustive swimming bouts.

METHODS

Wistar rats were divided into training (n = 14) and control (n = 14) groups. Training group performed a 6-week swimming training protocol. Subsets of training (n = 7) and control (n = 7) rats performed 3 repeated exhaustive swimming bouts with 72 h rest in between. Oxidative stress biomarkers, antioxidant activity, and mitochondria functionality were assessed.

RESULTS

Trained group showed increased reduced glutathione (GSH) content and reduced/oxidized (GSH/GSSG) ratio, higher superoxide dismutase (MnSOD) activity, and decreased lipid peroxidation in liver mitochondria. Aerobic training protected against exhaustive swimming ROS production herein characterized by decreased oxidative stress markers, higher antioxidant defenses, and increases in methyl-tetrazolium reduction and membrane potential. Trained group also presented higher time to exhaustion compared to control group.

CONCLUSIONS

Swimming training induced positive adaptations in liver mitochondria of rats. Increased antioxidant defense after training coped well with exercise-produced ROS and liver mitochondria were less affected by exhaustive exercise. Therefore, liver mitochondria also adapt to exercise-induced ROS and may play an important role in exercise performance.

Anti-oxidized low-density lipoprotein antibodies in chronic heart failure

Oxidative stress may play a significant role in the pathogenesis of heart failure (HF). Antibodies to oxidized low-density lipoprotein (oxLDL Abs) reflect an immune response to LDL over a prolonged period and may represent long-term oxidative stress in HF. The oxLDL plasma level is a useful predictor of mortality in HF patients, and measurement of the oxLDL Abs level may allow better management of those patients. Antibodies to oxLDL also significantly correlate with the New York Heart Association score. Hypercholesterolemia, smoking, hypertension, and obesity are risk factors for atherosclerotic coronary heart disease (CHD) leading to HF, but these factors account for only one-half of all cases, and understanding of the pathologic process underlying HF remains incomplete. Nutrients with antioxidant properties can reduce the susceptibility of LDL to oxidation. Antioxidant therapy may be an adjunct to lipid-lowering, angiotensin converting enzyme inhibition and metformin (in diabetes) therapy for the greatest impact on CHD and HF. Observational data suggest a protective effect of antioxidant supplementation on the incidence of HD. This review summarizes the data on oxLDL Abs as a predictor of morbidity and mortality in HF patients.

Adaptive response, evidence of cross-resistance and its potential clinical use

Organisms and their cells are constantly exposed to environmental fluctuations. Among them are stressors, which can induce macromolecular damage that exceeds a set threshold, independent of the underlying cause. Stress responses are mechanisms used by organisms to adapt to and overcome stress stimuli. Different stressors or different intensities of stress trigger different cellular responses, namely induce cell repair mechanisms, induce cell responses that result in temporary adaptation to some stressors, induce autophagy or trigger cell death. Studies have reported life-prolonging effects of a wide variety of so-called stressors, such as oxidants, heat shock, some phytochemicals, ischemia, exercise and dietary energy restriction, hypergravity, etc. These stress responses, which result in enhanced defense and repair and even cross-resistance against multiple stressors, may have clinical use and will be discussed, while the emphasis will be on the effects/cross-effects of oxidants.

Regular physical exercise as a strategy to improve antioxidant and anti-inflammatory status: benefits in type 2 diabetes mellitus

Over the last 30 years the combination of both a sedentary lifestyle and excessive food availability has led to a significant increase in the prevalence of obesity and aggravation of rates of metabolic syndrome and type 2 diabetes mellitus (T2DM). Several lines of scientific evidence have been demonstrating that a low level of physical activity and decreased daily energy expenditure leads to the accumulation of visceral fat and, consequently, the activation of the oxidative stress/inflammation cascade, which underlies the development of insulin resistant T2DM and evolution of micro, and macrovascular complications. This paper focuses on the pathophysiological pathways associated with the involvement of oxidative stress and inflammation in the development of T2DM and the impact of regular physical exercise (training) as a natural antioxidant and anti-inflammatory strategy to prevent evolution of T2DM and its serious complications.

Interaction between overtraining and the interindividual variability may (not) trigger muscle oxidative stress and cardiomyocyte apoptosis in rats

Severe endurance training (overtraining) may cause underperformance related to muscle oxidative stress and cardiomyocyte alterations. Currently, such relationship has not been empirically established. In this study, Wistar rats (n = 19) underwent eight weeks of daily exercise sessions followed by three overtraining weeks in which the daily frequency of exercise sessions increased. After the 11th training week, eight rats exhibited a reduction of 38% in performance (nonfunctional overreaching group (NFOR)), whereas eleven rats exhibited an increase of 18% in performance (functional overreaching group (FOR)). The red gastrocnemius of NFOR presented significantly lower citrate synthase activity compared to FOR, but similar to that of the control. The activity of mitochondrial complex IV in NFOR was lower than that of the control and FOR. This impaired mitochondrial adaptation in NFOR was associated with increased antioxidant enzyme activities and increased lipid peroxidation (in muscle and plasma) relative to FOR and control. Cardiomyocyte apoptosis was higher in NFOR. Plasma creatine kinase levels were unchanged. We observed that some rats that presented evidence of muscle oxidative stress are also subject to cardiomyocyte apoptosis under endurance overtraining. Blood lipid peroxides may be a suitable biomarker for muscle oxidative stress that is unrelated to severe muscle damage.

Strategies for reducing or preventing the generation of oxidative stress

The reduction of oxidative stress could be achieved in three levels: by lowering exposure to environmental pollutants with oxidizing properties, by increasing levels of endogenous and exogenous antioxidants, or by lowering the generation of oxidative stress by stabilizing mitochondrial energy production and efficiency. Endogenous oxidative stress could be influenced in two ways: by prevention of ROS formation or by quenching of ROS with antioxidants. However, the results of epidemiological studies where people were treated with synthetic antioxidants are inconclusive and contradictory. Recent evidence suggests that antioxidant supplements (although highly recommended by the pharmaceutical industry and taken by many individuals) do not offer sufficient protection against oxidative stress, oxidative damage or increase the lifespan. The key to the future success of decreasing oxidative-stress-induced damage should thus be the suppression of oxidative damage without disrupting the wellintegrated antioxidant defense network. Approach to neutralize free radicals with antioxidants should be changed into prevention of free radical formation. Thus, this paper addresses oxidative stress and strategies to reduce it with the focus on nutritional and psychosocial interventions of oxidative stress prevention, that is, methods to stabilize mitochondria structure and energy efficiency, or approaches which would increase endogenous antioxidative protection and repair systems.

Antioxidant and anti-inflammatory effects of exercise in diabetic patients

Diabetes is a chronic metabolic disease which is characterized by absolute or relative deficiencies in insulin secretion and/or insulin action. The key roles of oxidative stress and inflammation in the progression of vascular complications of this disease are well recognized. Accumulating epidemiologic evidence confirms that physical inactivity is an independent risk factor for insulin resistance and type II diabetes. This paper briefly reviews the pathophysiological pathways associated with oxidative stress and inflammation in diabetes mellitus and then discusses the impact of exercise on these systems. In this regard, we discuss exercise induced activation of cellular antioxidant systems through “nuclear factor erythroid 2-related factor.” We also discuss anti-inflammatory myokines, which are produced and released by contracting muscle fibers. Antiapoptotic, anti-inflammatory and chaperon effects of exercise-induced heat shock proteins are also reviewed.

Cordyceps sinensis promotes exercise endurance capacity of rats by activating skeletal muscle metabolic regulators

ETHNOPHARMACOLOGICAL RELEVANCE

Cordyceps sinensis is a traditional Chinese medicine used for promotion of health, longevity and athletic power. However, the molecular mechanism for anti-fatigue activity and physical fitness has not yet been reported.

AIM OF THE STUDY

The present study was conducted to evaluate the exercise endurance promoting activities of fungal traditional Chinese medicine (FTCM) Cordyceps sinensis cultured whole mycelium (CS) and the underlying mechanisms.

MATERIALS AND METHODS

CS was orally supplemented (200mg/kg body weight/day) to rats for 15days with or without swimming exercise along with exercise and placebo groups.

RESULTS

Both CS supplementation and supplementation concurrent with exercise improved exercise endurance by 1.79- (P<0.05) and 2.9-fold (P<0.01) respectively as compared to placebo rats. CS supplementation concurrent with exercise also increased the swimming endurance by 1.32-fold (P<0.05) over the exercise group. To study the molecular mechanism of the observed effect, we measured the expression levels of endurance responsive skeletal muscle metabolic regulators AMPK, PGC-1α and PPAR-δ as well as endurance promoting and antioxidant genes like MCT1, MCT4, GLUT4, VEGF, NRF-2, SOD1 and TRX in red gastrocnemius muscle. Our results indicate that CS supplementation significantly upregulates the skeletal muscle metabolic regulators, angiogenesis, better glucose and lactate uptake both in exercised and non-exercised rats. We have also observed increased expression of oxidative stress responsive transcription factor NRF-2 and its downstream targets SOD1 and TRX by CS supplementation.

CONCLUSION

CS supplementation with or without exercise improves exercise endurance capacity by activating the skeletal muscle metabolic regulators and a coordinated antioxidant response. Consequently, CS can be used as a potent natural exercise mimetic.

17β-estradiol attenuates exercise-induced neutrophil infiltration in men

17β-estradiol (E2) attenuates exercise-induced muscle damage and inflammation in some models. Eighteen men completed 150 eccentric contractions after random assignment to placebo (Control group) or E2 supplementation (Experimental group). Muscle biopsies and blood samples were collected at baseline, following 8-day supplementation and 3 h and 48 h after exercise. Blood samples were analyzed for sex hormone concentration, creatine kinase (CK) activity and total antioxidant capacity. The mRNA content of genes involved in lipid and cholesterol homeostasis [forkhead box O1 (FOXO1), caveolin 1, and sterol regulatory element binding protein-2 (SREBP2)] and antioxidant defense (SOD1 and -2) were measured by RT-PCR. Immunohistochemistry was used to quantify muscle neutrophil (myeloperoxidase) and macrophage (CD68) content. Serum E2 concentration increased 2.5-fold with supplementation ( P < 0.001), attenuating neutrophil infiltration at 3 h ( P < 0.05) and 48 h ( P < 0.001), and the induction of SOD1 at 48 h ( P = 0.02). Macrophage density at 48 h ( P < 0.05) and SOD2 mRNA at 3 h ( P = 0.01) increased but were not affected by E2. Serum CK activity was higher at 48 h for both groups ( P < 0.05). FOXO1, caveolin 1 and SREBP2 expression were 2.8-fold ( P < 0.05), 1.4-fold ( P < 0.05), and 1.5-fold ( P < 0.001) and higher at 3 h after exercise with no effect of E2. This suggests that E2 attenuates neutrophil infiltration; however, the mechanism does not appear to be lesser oxidative stress or membrane damage and may indicate lesser neutrophil/endothelial interaction.

Free Radical Formation after Intensive Exercise in Thoroughbred Skeletal Muscles

Although high oxygen consumption in skeletal muscle may result in severe oxidative stress, there are no direct studies that have documented free radical production in horse muscles after intensive exercise. To find a new parameter indicating the muscle adaptation state for the training of Thoroughbred horses, we examined free radical formation in the muscle by using electron paramagnetic resonance (EPR). Ten male Thoroughbred horses received conventional training for 18 weeks. Before and after the training period, all horses performed an exhaustive incremental load exercise on a 6% incline treadmill. Muscle samples of the middle gluteal muscle were taken pre-exercise and 1 min, 1 hr, and 1 day after exercise. Muscle fiber type composition was also determined in the pre-exercise samples by immunohistochemical staining with monoclonal antibody to myosin heavy chain. We measured the free radical in the muscle homogenate using EPR at room temperature, and the amount was expressed as relative EPR signal intensity. There was a significant increase in Type IIA muscle fiber composition and a decrease in Type IIX fiber composition after the training period. Before the training period, the mean value of the relative EPR signal intensity showed a significant increase over the pre-exercise value at 1 min after the exercise and an incomplete recovery at 24 hr after the exercise. While no significant changes were found in the relative EPR signal intensity after the training period. There was a significant relationship between percentages of Type IIA fiber and change rates in EPR signal intensity at 1 min after exercise. The measurement of free radicals may be useful for determining the muscle adaptation state in the training of Thoroughbred horses.

Effects of age and glutathione levels on oxidative stress in rats after chronic exposure to stretch-shortening contractions

We investigated effects of age and glutathione synthesis inhibition on the oxidative stress status of tibialis anterior muscles from young and old Fisher 344 x Brown Norway male rats after chronic administration of stretch-shortening contractions. Oral supplementation of L: -buthionine-(S,R)-sulfoximine (BSO) inhibited glutathione synthesis. Dorsiflexor muscles in the hindlimb were exposed to 80 maximal stretch-shortening contractions (SSCs) three times per week for 4.5 weeks. We measured malondialdehyde, hydrogen peroxide (H(2)O(2)), and free isoprostanes to determine oxidative stress. Glutathione peroxidase activity was measured as an indicator of H(2)O(2) scavenging. Glutathione measurements confirmed the effectiveness of BSO treatment. In young rats, the SSC exposure protocol prevented oxidative stress and enhanced H(2)O(2) scavenging. In old rats, malondialdehyde was increased in the exposed muscle and a BSO-induced increase in H(2)O(2) was not alleviated with SSC exposure as seen in young rats. In addition, glutathione peroxidase activity and total glutathione were increased in old rats relative to their young counterparts. All comparisons were significant at the 0.05 level. Overall, BSO administration was effective in decreasing total glutathione levels and increasing H(2)O(2) levels in old and young rats exposed to SSCs. In addition, effects of chronic exposure to high-force resistive loading SSCs in active muscle from old animals are: (1) antioxidant capacity is enhanced similar to what is seen with endurance training and (2) oxidative stress is increased, probably as a consequence of the enhanced vulnerability due to aging.

Exercise-training in young Drosophila melanogaster reduces age-related decline in mobility and cardiac performance

Declining mobility is a major concern, as well as a major source of health care costs, among the elderly population. Lack of mobility is a primary cause of entry into managed care facilities, and a contributing factor to the frequency of damaging falls. Exercise-based therapies have shown great promise in sustaining mobility in elderly patients, as well as in rodent models. However, the genetic basis of the changing physiological responses to exercise during aging is not well understood. Here, we describe the first exercise-training paradigm in an invertebrate genetic model system. Flies are exercised by a mechanized platform, known as the Power Tower, that rapidly, repeatedly, induces their innate instinct for negative geotaxis. When young flies are subjected to a carefully controlled, ramped paradigm of exercise-training, they display significant reduction in age-related decline in mobility and cardiac performance. Fly lines with improved mitochondrial efficiency display some of the phenotypes observed in wild-type exercised flies. The exercise response in flies is influenced by the amount of protein and lipid, but not carbohydrate, in the diet. The development of an exercise-training model in Drosophila melanogaster opens the way to direct testing of single-gene based genetic therapies for improved mobility in aged animals, as well as unbiased genetic screens for loci involved in the changing response to exercise during aging.

Exercise restores endothelial function independently of weight loss or hyperglycaemic status in db/db mice

AIMS/HYPOTHESIS

Exercise ameliorates oxidative stress-mediated diabetic vascular endothelial dysfunction through poorly defined mechanisms. We hypothesised that, in addition to improving metabolic parameters, upregulation of antioxidants such as superoxide dismutase (SOD) mediates exercise-induced reductions of oxidative stress and increased nitric oxide (NO) bioavailability, and also restores vasodilatation.

METHODS

Type 2 diabetic db/db and normoglycaemic wild-type mice were exercised at moderate intensity for 1 h a day for 7 weeks, leading to a 10% body weight loss. Sedentary animals or those undergoing a low-intensity exercise regimen causing non-significant weight loss were also used. We examined aortic endothelial cell function, NO bioavailability and various biomarkers of oxidative stress.

RESULTS

Moderate-intensity exercise lowered body weight, increased mitochondrial manganese SOD (MnSOD) and both total and phosphorylated (Ser1177) endothelial nitric oxide synthase (eNOS) protein production; it also reduced whole-body (plasma 8-isoprostane) and tissue oxidative stress (nitrotyrosine immunostaining or protein carbonyl levels in the aorta). Low-intensity exercise did not alter body weight; however, it upregulated cytosolic Cu/Zn-SOD instead of MnSOD, and still demonstrated all the above benefits in the db/db aorta. Importantly, both exercise protocols improved endothelial-dependent vasodilatation and NO bioavailability without altering hyperglycaemic status in db/db mice.

CONCLUSIONS/INTERPRETATION

Exercise reverses diabetic vascular endothelial dysfunction independently of improvements in body weight or hyperglycaemia. Our data suggest that upregulation of eNOS and specific SOD isoforms could play important roles in improving NO bioavailability, as well as in reversing endothelial dysfunction in type 2 diabetes patients through lifestyle modifications in the management of diabetes.

Kinase-specific responsiveness to incremental contractile activity in skeletal muscle with low and high mitochondrial content

Muscle contractions activate protein kinases, leading to signal transduction. We hypothesized that kinase activation would be influenced by mitochondrial content, as well as by contractile activity-induced increases in muscle O(2) consumption (Vo(2)). Kinase phosphorylation in high-oxidative red and low-oxidative white tibialis anterior (TA) muscle (RTA and WTA, respectively) with 2.5-fold differences in mitochondrial content were compared. Stimulation of the TA muscle elicited large increases in Vo(2) (3- to 6-fold and 4- to 60-fold above resting levels in WTA and RTA, respectively). At rest, AMP-activated protein kinase (AMPK), p38, p42, and p44 activation were nearly twofold greater in WTA than in RTA, suggesting an inverse relationship between mitochondrial content and kinase activation in resting muscle. During contractions, similar degrees of phosphorylation in RTA and WTA were evident as a function of Vo(2) for p38 and p42. During increases in Vo(2) up to sixfold above rest, greater responses were observed in RTA than in WTA for AMPK and p44, whereas Akt activation was greater in WTA. In RTA, elevations in Vo(2) elicited increases in AMPK and p44 activation, whereas Akt, p38, and p42 were less sensitive to increments in Vo(2). Reactive oxygen species (ROS) production was greater in mitochondria from white muscle, but when it was calculated in the context of the whole muscle, ROS production was twofold greater in red than in white myofibers. Thus mitochondrial content influences ROS production and is inversely related to kinase activation in resting muscle. During contractions, kinases are differentially sensitive to contraction-induced increments in Vo(2), suggesting that muscle mitochondrial content is important, but it is not the sole determinant of kinase activation during exercise of different intensities.

Repeated bouts of aerobic exercise lead to reductions in skeletal muscle free radical generation and nuclear factor kappaB activation

Chronic exercise improves endurance and skeletal muscle oxidative capacity. Despite the potential importance of reactive oxygen species (ROS) generated during exercise as regulators of these adaptations, the effect of repeated bouts of aerobic exercise on ROS generation by skeletal muscles during contractions has not been examined. Our aim was to establish the impact of repeated treadmill running exercise on muscle ROS generation and activation of redox-sensitive transcription factors. Following 8 weeks of treadmill running, mice displayed an improvement in running speed that was associated with an enhanced ability of gastrocnemius (GTN) muscles to maintain force during a protocol of isometric contractions. In contrast to GTN muscles of cage-sedentary (Sed) mice, muscles from exercised (Exer) mice did not release superoxide or nitric oxide during the isometric contractions. For male mice, basal levels of nuclear factor kappaB (NFkappaB) and activator protein-1 (AP-1) DNA binding were increased by treadmill running, and the contraction-induced activation of NFkappaB and AP-1 observed in muscles of Sed mice was absent in Exer muscles. Also in contrast to Sed muscles, Exer muscles displayed no reductions in glutathione or protein thiol levels in response to contraction. Our observations of decreases for Exer compared with Sed muscles in contraction-induced (i) ROS generation, (ii) activation of redox-sensitive signalling pathways, and (iii) ROS stress suggest that exercise conditioning enhances the ability of skeletal muscle to readily and rapidly detoxify ROS and/or reduces ROS generation, providing protection from ROS-induced damage and reducing signals that might act to mediate further unnecessary adaptations.

Fiber type-specific nitric oxide protects oxidative myofibers against cachectic stimuli

Oxidative skeletal muscles are more resistant than glycolytic muscles to cachexia caused by chronic heart failure and other chronic diseases. The molecular mechanism for the protection associated with oxidative phenotype remains elusive. We hypothesized that differences in reactive oxygen species (ROS) and nitric oxide (NO) determine the fiber type susceptibility. Here, we show that intraperitoneal injection of endotoxin (lipopolysaccharide, LPS) in mice resulted in higher level of ROS and greater expression of muscle-specific E3 ubiqitin ligases, muscle atrophy F-box (MAFbx)/atrogin-1 and muscle RING finger-1 (MuRF1), in glycolytic white vastus lateralis muscle than in oxidative soleus muscle. By contrast, NO production, inducible NO synthase (iNos) and antioxidant gene expression were greatly enhanced in oxidative, but not in glycolytic muscles, suggesting that NO mediates protection against muscle wasting. NO donors enhanced iNos and antioxidant gene expression and blocked cytokine/endotoxin-induced MAFbx/atrogin-1 expression in cultured myoblasts and in skeletal muscle in vivo. Our studies reveal a novel protective mechanism in oxidative myofibers mediated by enhanced iNos and antioxidant gene expression and suggest a significant value of enhanced NO signaling as a new therapeutic strategy for cachexia.

Activation of aconitase in mouse fast-twitch skeletal muscle during contraction-mediated oxidative stress

Aconitase is a mitochondrial enzyme that converts citrate to isocitrate in the tricarboxylic acid cycle and is inactivated by reactive oxygen species (ROS). We investigated the effect of exercise/contraction, which is associated with elevated ROS production, on aconitase activity in skeletal muscle. Humans cycled at 75% of maximal workload, followed by six 60-s bouts at 125% of maximum workload. Biopsies were taken from the thigh muscle at rest and after the submaximal and supramaximal workloads. Isolated mouse extensor digitorum longus (EDL; fast twitch) and soleus (slow twitch) muscles were stimulated to perform repeated contractions for 10 min. Muscles were analyzed for enzyme activities and glutathione status. Exercise did not affect aconitase activity in human muscle despite increased oxidative stress, as judged by elevated levels of oxidized glutathione. Similarly, repeated contractions did not alter aconitase activity in soleus muscle. In contrast, repeated contractions significantly increased aconitase activity in EDL muscle by ∼50%, despite increased ROS production. This increase was not associated with a change in the amount of immunoreactive aconitase (Western blot) but was markedly inhibited by cyclosporin A, an inhibitor of the protein phosphatase calcineurin. Immunoprecipitation experiments demonstrated that aconitase was phosphorylated on serine residues. Aconitase in cell-free extracts was inactivated by the addition of the ROS hydrogen peroxide. In conclusion, the results suggest that aconitase activity can be regulated by at least two mechanisms: oxidation/reduction and phosphorylation/dephosphorylation. During contraction, a ROS-mediated inactivation of aconitase can be overcome, possibly by dephosphorylation of the enzyme. The dual-control system may be important in maintaining aerobic ATP production during muscle contraction.

Obesity-related derangements in metabolic regulation

An epidemic surge in the incidence of obesity has occurred worldwide over the past two decades. This alarming trend has been triggered by lifestyle habits that encourage overconsumption of energy-rich foods while also discouraging regular physical activity. These environmental influences create a chronic energy imbalance that leads to persistent weight gain in the form of body fat and a host of other abnormalities in metabolic homeostasis. As adiposity increases, so does the risk of developing comorbidities such as diabetes, hypertension, and cardiovascular disease. The intimate association between obesity and systemic metabolic dysregulation has inspired a new area of biochemistry research in which scientists are seeking to understand the molecular mechanisms that link chronic lipid oversupply to tissue dysfunction and disease development. The purpose of this chapter is to review recent findings in this area, placing emphasis on lipid-induced functional impairments in the major peripheral organs that control energy flux: adipose tissue, the liver, skeletal muscle, and the pancreas.

Oxidative stress : relationship with exercise and training

Free radicals are reactive compounds that are naturally produced in the human body. They can exert positive effects (e.g. on the immune system) or negative effects (e.g. lipids, proteins or DNA oxidation). To limit these harmful effects, an organism requires complex protection - the antioxidant system. This system consists of antioxidant enzymes (catalase, glutathione peroxidase, superoxide dismutase) and non-enzymatic antioxidants (e.g. vitamin E [tocopherol], vitamin A [retinol], vitamin C [ascorbic acid], glutathione and uric acid). An imbalance between free radical production and antioxidant defence leads to an oxidative stress state, which may be involved in aging processes and even in some pathology (e.g. cancer and Parkinson's disease). Physical exercise also increases oxidative stress and causes disruptions of the homeostasis. Training can have positive or negative effects on oxidative stress depending on training load, training specificity and the basal level of training. Moreover, oxidative stress seems to be involved in muscular fatigue and may lead to overtraining.

Respiratory loading intensity and diaphragm oxidative stress:N-acetyl-cysteine effects

We hypothesized that resistive breathing of moderate to high intensity might increase diaphragm oxidative stress, which could be partially attenuated by antioxidants. Our objective was to assess the levels of oxidative stress in the dog diaphragm after respiratory muscle training of a wide range of intensities and whether N-acetyl-cysteine (NAC) might act as an antioxidant. Twelve Beagle dogs were anesthetized with 1% propophol, tracheostomized, and subjected to continuous inspiratory resistive breathing (IRB) (2 h/day for 2 wk). They were further divided into two groups ( n = 6): NAC group (oral NAC administration/24 h for 14 days) and control group (placebo). Diaphragm biopsies were obtained before (baseline biopsy) and after (contralateral hemidiaphragm) IRB and NAC vs. placebo treatment. Oxidative stress was evaluated in all diaphragm biopsies through determination of 3-nitrotyrosine immunoreactivity, protein carbonylation, hydroxynoneal protein adducts, Mn-SOD, and catalase, using immunoblotting and immunohistochemistry. Both protein tyrosine nitration and protein carbonylation were directly related to the amount of the respiratory loads, and NAC treatment abrogated this proportional rise in these two indexes of oxidative stress in response to increasing inspiratory loads. A post hoc analysis revealed that only the diaphragms of dogs subjected to high-intensity loads showed a significant increase in both protein tyrosine nitration and carbonylation, which were also significantly reduced by NAC treatment. These results suggest that high-intensity respiratory loading-induced oxidative stress may be neutralized by NAC treatment during IRB in the canine diaphragm.