Trained men display increased basal heat shock protein content of skeletal muscle

Unlocking peak performance: The role of Nrf2 in enhancing exercise outcomes and training adaptation in humans

Since the discovery of the nuclear factor erythroid-derived 2-like 2 (Nrf2) transcription factor thirty years ago, it has been shown that it regulates more than 250 genes involved in a multitude of biological processes, including redox balance, mitochondrial biogenesis, metabolism, detoxification, cytoprotection, inflammation, immunity, autophagy, cell differentiation, and xenobiotic metabolism. In skeletal muscle, Nrf2 signalling is primarily activated in response to perturbation of redox balance by reactive oxygen species or electrophiles. Initial investigations into human skeletal muscle Nrf2 responses to exercise, dating back roughly a decade, have consistently indicated that exercise-induced ROS production stimulates Nrf2 signalling. Notably, recent studies employing Nrf2 knockout mice have revealed impaired skeletal muscle contractile function characterised by reduced force output and increased fatigue susceptibility compared to wild-type counterparts. These deficiencies partially stem from diminished basal mitochondrial respiratory capacity and an impaired capacity to upregulate specific mitochondrial proteins in response to training, findings corroborated by inducible muscle-specific Nrf2 knockout models. In humans, baseline Nrf2 expression in skeletal muscle correlates with maximal oxygen uptake and high-intensity exercise performance. This manuscript delves into the mechanisms underpinning Nrf2 signalling in response to acute exercise in human skeletal muscle, highlighting the involvement of ROS, antioxidants and Keap1/Nrf2 signalling in exercise performance. Furthermore, it explores Nrf2's role in mediating adaptations to chronic exercise and its impact on overall exercise performance. Additionally, the influence of diet and certain supplements on basal Nrf2 expression and its role in modulating acute and chronic exercise responses are briefly addressed.

Underlying Mechanisms of the Protective Effects of Lifestyle Factors On Age-Related Diseases

The rise in life expectancy has significantly increased the occurrence of age-related chronic diseases, leading to escalating expenses for both society and individuals. Among the main factors influencing health and lifespan, lifestyle takes a forefront position. Specifically, nutrition, mental activity, and physical exercise influence the molecular and functional mechanisms that contribute to the prevention of major age-related diseases. Gaining deeper insights into the mechanisms that drive the positive effects of healthy lifestyles is valuable for creating interventions to prevent or postpone the development of chronic degenerative diseases. This review summarizes the main mechanisms that underlie the positive effect of lifestyle factors in counteracting the major age-related diseases involving brain health, musculoskeletal function, cancer, frailty, and cardiovascular diseases, among others. This knowledge will help to identify high-risk populations for targeted intervention trials and discover new biomarkers associated with healthy aging.

Exercise training and changes in skeletal muscle mitochondrial proteins: from blots to "omics"

Mitochondria are essential, membrane-enclosed organelles that consist of ∼1100 different proteins, which allow for many diverse functions critical to maintaining metabolism. Highly metabolic tissues, such as skeletal muscle, have a high mitochondrial content that increases with exercise training. The classic western blot technique has revealed training-induced increases in the relatively small number of individual mitochondrial proteins studied (∼5% of the >1100 proteins in MitoCarta), with some of these changes dependent on the training stimulus. Proteomic approaches have identified hundreds of additional mitochondrial proteins that respond to exercise training. There is, however, surprisingly little crossover in the mitochondrial proteins identified in the published human training studies. This suggests that to better understand the link between training-induced changes in mitochondrial proteins and metabolism, future studies need to move beyond maximizing protein detection to adopting methods that will increase the reliability of the changes in protein abundance observed.

The Genetic Selection of HSPD1 and HSPE1 Reduce Inflammation of Liver and Spleen While Restraining the Growth and Development of Skeletal Muscle in Wuzhishan Pigs

Wuzhishan (WZS) pigs, which are minipigs native to Hainan Province in China, are characterized by strong resistance to extreme hot temperatures and humidity. The relationship between their immune response and growth still needs to be clarified. In this study, we used whole genome sequencing (WGS) to detect variations within 37 WZS pigs, 32 Large White (LW) pigs, and 22 Xiangxi black (XXB) pigs, and ~2.49 GB of SNPs were obtained. These data were combined with those of two other pig breeds, and it was found that most of the genes detected (354) were located within the distinct genetic regions between WZS pigs and LW pigs. The network that was constructed using these genes represented a center including 12 hub genes, five of which had structural variations (SVs) within their regulatory regions. Furthermore, RNA-seq and RT-qPCR data for 12 genes were primarily consistent in liver, spleen, and LDM tissues. Notably, the expression of HSPs (HSPD1 and HSPE1) was higher while that of most genes involved in the JAK3-STAT pathway were lower in liver tissue of WZS pigs, compared with LW pigs. This likely not only reduced inflammation-related immune response but also impaired their growth. Our findings demonstrated the role of HSPs in the connection between inflammation and growth rate, while also providing the fundamental genetic selection of the adaptability of WZS pigs.

Effect of heat stress on heat shock protein expression and hypertrophy-related signaling in the skeletal muscle of trained individuals

Muscle mass is balanced between hypertrophy and atrophy by cellular processes, including activation of the protein kinase B-mechanistic target of rapamycin (Akt-mTOR) signaling cascade. Stressors apart from exercise and nutrition, such as heat stress, can stimulate the heat shock protein A (HSPA) and C (HSPC) families alongside hypertrophic signaling factors and muscle growth. The effects of heat stress on HSP expression and Akt-mTOR activation in human skeletal muscle and their magnitude of activation compared with known hypertrophic stimuli are unclear. Here, we show a single session of whole body heat stress following resistance exercise increases the expression of HSPA and activation of the Akt-mTOR cascade in skeletal muscle compared with resistance exercise in a healthy, resistance-trained population. Heat stress alone may also exert similar effects, though the responses are notably variable and require further investigation. In addition, acute heat stress in C2C12 muscle cells enhanced myotube growth and myogenic fusion, albeit to a lesser degree than growth factor-mediated hypertrophy. Though the mechanisms by which heat stress stimulates hypertrophy-related signaling and the potential mechanistic role of HSPs remain unclear, these findings provide additional evidence implicating heat stress as a novel growth stimulus when combined with resistance exercise in human skeletal muscle and alone in isolated murine muscle cells. We believe these findings will help drive further applied and mechanistic investigation into how heat stress influences muscular hypertrophy and atrophy.NEW & NOTEWORTHY We show that acute resistance exercise followed by whole body heat stress increases the expression of HSPA and increases activation of the Akt-mTOR cascade in a physically active and resistance-trained population.

Antioxidant enzymes and Nrf2/Keap1 in human skeletal muscle: Influence of age, sex, adiposity and aerobic fitness

Ageing, a sedentary lifestyle, and obesity are associated with increased oxidative stress, while regular exercise is associated with an increased antioxidant capacity in trained skeletal muscles. Whether a higher aerobic fitness is associated with increased expression of antioxidant enzymes and their regulatory factors in skeletal muscle remains unknown. Although oestrogens could promote a higher antioxidant capacity in females, it remains unknown whether a sex dimorphism exists in humans regarding the antioxidant capacity of skeletal muscle. Thus, the aim was to determine the protein expression levels of the antioxidant enzymes SOD1, SOD2, catalase and glutathione reductase (GR) and their regulatory factors Nrf2 and Keap1 in 189 volunteers (120 males and 69 females) to establish whether sex differences exist and how age, VO2max and adiposity influence these. For this purpose, vastus lateralis muscle biopsies were obtained in all participants under resting and unstressed conditions. No significant sex differences in Nrf2, Keap1, SOD1, SOD2, catalase and GR protein expression levels were observed after accounting for VO2max, age and adiposity differences. Multiple regression analysis indicates that the VO2max in mL.kg LLM-1.min-1can be predicted from the levels of SOD2, Total Nrf2 and Keap1 (R = 0.58, P < 0.001), with SOD2 being the main predictor explaining 28 % of variance in VO2max, while Nrf2 and Keap1 explained each around 3 % of the variance. SOD1 protein expression increased with ageing in the whole group after accounting for differences in VO2max and body fat percentage. Overweight and obesity were associated with increased pSer40-Nrf2, pSer40-Nrf2/Total Nrf2 ratio and SOD1 protein expression levels after accounting for differences in age and VO2max. Overall, at the population level, higher aerobic fitness is associated with increased basal expression of muscle antioxidant enzymes, which may explain some of the benefits of regular exercise.

Muscle-derived exosomes and exercise in cancer prevention

There are a lot of evidences on the beneficial effects mediated by exercise on the prevention of not communicable diseases (NCDs) including different type of cancer. The production of circulating exerkines transported in exosomes represents a novel pathway activated by exercise. However, the biological mechanisms that could explain the role of exosomes in cancer prevention have been not fully elucidated. The aim of this mini-review is to provide an update on the biological mechanisms bringing the release of muscle-derived exosomes during exercise and cancer prevention.

Physiological relationship between cardiorespiratory fitness and fitness for surgery: a narrative review

Epidemiological evidence has highlighted a strong relationship between cardiorespiratory fitness and surgical outcomes; specifically, fitter patients possess heightened resilience to withstand the surgical stress response. This narrative review draws on exercise and surgical physiology research to discuss and hypothesise the potential mechanisms by which higher fitness affords perioperative benefit. A higher fitness, as indicated by higher peak rate of oxygen consumption and ability to sustain metabolic homeostasis (i.e. higher anaerobic threshold) is beneficial postoperatively when metabolic demands are increased. However, the associated adaptations with higher fitness, and the related participation in regular exercise or physical activity, might also underpin the observed perioperative benefit through a process of hormesis, a protective adaptive response to the moderate and intermittent stress of exercise. Potential mediators discussed include greater antioxidant capacity, metabolic flexibility, glycaemic control, lean body mass, and improved mood.

Skeletal muscle angiogenic, regulatory, and heat shock protein responses to prolonged passive hyperthermia of the human lower limb

Passive hyperthermia induces a range of physiological responses including augmenting skeletal muscle mRNA expression. This experiment aimed to examine gene and protein responses to prolonged passive leg hyperthermia. Seven young participants underwent 3 h of resting unilateral leg heating (HEAT) followed by a further 3 h of rest, with the contralateral leg serving as an unheated control (CONT). Muscle biopsies were taken at baseline (0 h), and at 1.5, 3, 4, and 6 h in HEAT and 0 and 6 h in CONT to assess changes in selected mRNA expression via qRT-PCR, and HSP72 and VEGFα concentration via ELISA. Muscle temperature (T_m) increased in HEAT plateauing from 1.5 to 3 h (+3.5 ± 1.5°C from 34.2 ± 1.2°C baseline value; P < 0.001), returning to baseline at 6 h. No change occurred in CONT. Endothelial nitric oxide synthase (eNOS), Forkhead box O1 (FOXO-1), Hsp72, and VEGFα mRNA increased in HEAT (P < 0.05); however, post hoc analysis identified that only Hsp72 mRNA statistically increased (at 4 h vs. baseline). When peak change during HEAT was calculated angiopoietin 2 (ANGPT-2) decreased (-0.4 ± 0.2-fold), and C-C motif chemokine ligand 2 (CCL2) (+2.9 ± 1.6-fold), FOXO-1 (+6.2 ± 4.4-fold), Hsp27 (+2.9 ± 1.7-fold), Hsp72 (+8.5 ± 3.5-fold), Hsp90α (+4.6 ± 3.7-fold), and VEGFα (+5.9 ± 3.1-fold) increased from baseline (all P < 0.05). At 6 h T_m were not different between limbs (P = 0.582; CONT = 32.5 ± 1.6°C, HEAT = 34.3 ± 1.2°C), and only ANGPT-2 (P = 0.031; -1.3 ± 1.4-fold) and VEGFα (P = 0.030; 1.1 ± 1.2-fold) differed between HEAT and CONT. No change in VEGFα or HSP72 protein concentration were observed over time; however, peak change in VEGFα did increase (P < 0.05) in HEAT (+140 ± 184 pg·mL^-1) versus CONT (+7 ± 86 pg·mL^-1). Passive hyperthermia transiently augmented ANGPT-2, CCL2, eNOS, FOXO-1, Hsp27, Hsp72, Hsp90α and VEGFα mRNA, and VEGFα protein.

Resistance Training Modulates Reticulum Endoplasmic Stress, Independent of Oxidative and Inflammatory Responses, in Elderly People

Aging is related to changes in the redox status, low-grade inflammation, and decreased endoplasmic reticulum unfolded protein response (UPR). Exercise has been shown to regulate the inflammatory response, balance redox homeostasis, and ameliorate the UPR. This work aimed to investigate the effects of resistance training on changes in the UPR, oxidative status, and inflammatory responses in peripheral blood mononuclear cells of elderly subjects. Thirty elderly subjects volunteered to participate in an 8-week resistance training program, and 11 youth subjects were included for basal assessments. Klotho, heat shock protein 60 (HSP60), oxidative marker expression (catalase, glutathione, lipid peroxidation, nuclear factor erythroid 2-related factor 2, protein carbonyls, reactive oxygen species, and superoxide dismutase 1 and 2), the IRE1 arm of UPR, and TLR4/TRAF6/pIRAK1 pathway activation were evaluated before and following training. No changes in the HSP60 and Klotho protein content, oxidative status markers, and TLR4/TRAF6/pIRAK1 pathway activation were found with exercise. However, an attenuation of the reduced pIRE1/IRE1 ratio was observed following training. Systems biology analysis showed that a low number of proteins (RPS27A, SYVN1, HSPA5, and XBP1) are associated with IRE1, where XBP1 and RPS27A are essential nodes according to the centrality analysis. Additionally, a gene ontology analysis confirms that endoplasmic reticulum stress is a key mechanism modulated by IRE1. These findings might partially support the modulatory effect of resistance training on the endoplasmic reticulum in the elderly.

Heat shock proteins in adaptation to physical activity

The review article presents the author’s model of one of the blocks of the integrated adaptation mechanism to physical activity and the accompanying moderate heat effects. The participation of heat shock proteins in the stabilization of the tertiary structure and in the restoration of the function of proteins damaged by temperature and physical stressors but performing catalytic, transport, reception or protective role and being involved in the processes of contraction- relaxation and muscle and bone tissue remodeling is discussed.

Muscular heat shock protein response and muscle damage after semi-professional football match

PURPOSE

A typical football match leads to neuromuscular fatigue and physical performance impairments up to 72-96 h post-match. While muscle damage is thought to be a major factor, damage on the ultrastructural level has never been documented. The purpose of this study was to investigate post-match cellular muscle damage by quantifying the heat shock protein (HSP) response as a proxy for protein damage.

METHODS

Muscle biopsies, blood samples, countermovement jumps, and perception of muscle soreness were obtained from twelve semi-professional football players 1, 24, 48, and 72 h after a 90-min football match. Muscle biopsies were analyzed for αB-crystallin and HSP70 in the cytosolic and cytoskeletal sub-cellular fractions by Western blotting. Fiber type-specific αB-crystallin and HSP70 staining intensity, and tenascin-C immunoreactivity were analyzed with immunohistochemistry. Blood samples were analyzed for creatine kinase and myoglobin.

RESULTS

Within 24 h post-match, a 2.7- and 9.9-fold increase in creatine kinase and myoglobin were observed, countermovement jump performance decreased by -9.7% and muscle soreness increased by 0.68 units. αB-crystallin and HSP70 accumulated in cytoskeletal structures evident by a 3.6- and 1.8-fold increase in the cytoskeletal fraction and a parallel decrease in the cytosolic fraction. In type I and II fibers, αB-crystallin staining intensity increased by 15%-41% and remained elevated at 72 h post-match. Lastly, the percentage of fibers with granular staining of αB-crystallin increased 2.2-fold.

CONCLUSIONS

Football match play induced a muscular HSP stress response 1-72 h post-match. Specifically, the accumulation of HSPs in cytoskeletal structures and the granular staining of αB-crystallin suggests occurrence of ultrastructural damage. The damage, indicated by the HSP response, might be one reason for the typically 72 h decrease in force-generating capacity after football matches.

The expression of HSP70 in skeletal muscle is not associated with glycogen availability during recovery following prolonged exercise in elite endurance athletes

The 70-kDa heat shock protein (HSP70) is a ubiquitous molecular chaperone which is highly inducible by cellular stress such as exercise. To investigate the role of muscle glycogen content on the HSP70 expression, muscle glycogen was manipulated by consumption of either water (H₂O) or a carbohydrate-enriched diet (CHO) during recovery from 4 h of glycogen-depleting cycling exercise in fourteen elite endurance athletes. Muscle biopsies were obtained pre- and post-exercise, and after 4 and 24 h of recovery, and analyzed for HSP70 mRNA expression, as well as HSP70 protein expression and muscle glycogen within the same skeletal muscle fibers using immunohistochemistry. Exercise reduced glycogen by 59 ± 10% (P < 0.0001). After 4 h of recovery, glycogen approached resting levels in the CHO group (86% of pre, P = 0.28) but remained suppressed in the H₂O group (41% of pre, P < 0.001) (group × time interaction: P = 0.002). Importantly, both the HSP70 mRNA (+ 1.6-fold (+ 0.28/- 0.24), P = 0.02) and protein expression (+ 147 ± 99%, P < 0.0001) was substantially increased after exercise and remained elevated in both groups after 4 h of recovery, despite clear differences in muscle glycogen content. Thus, muscle glycogen content was not related to the variation in single fiber HSP70 expression at the 4-h time-point (r² = 0.004). In conclusion, muscle HSP70 expression remained elevated during recovery from prolonged exercise in highly trained skeletal muscle, irrespective of muscle glycogen availability.

Physiactisome: A New Nanovesicle Drug Containing Heat Shock Protein 60 for Treating Muscle Wasting and Cachexia

Currently, no commercially available drugs have the ability to reverse cachexia or counteract muscle wasting and the loss of lean mass. Here, we report the methodology used to develop Physiactisome—a conditioned medium released by heat shock protein 60 (Hsp60)—overexpressing C2C12 cell lines enriched with small and large extracellular vesicles. We also present evidence supporting its use in the treatment of cachexia. Briefly, we obtain a nanovesicle-based secretion by genetically modifying C2C12 cell lines with an Hsp60-overexpressing plasmid. The secretion is used to treat naïve C2C12 cell lines. Physiactisome activates the expression of PGC-1α isoform 1, which is directly involved in mitochondrial biogenesis and muscle atrophy suppression, in naïve C2C12 cell lines. Proteomic analyses show Hsp60 localisation inside isolated nanovesicles and the localisation of several apocrine and merocrine molecules, with potential benefits for severe forms of muscle atrophy. Considering that Physiactisome can be easily obtained following tissue biopsy and can be applied to autologous muscle stem cells, we propose a potential nanovesicle-based anti-cachexia drug that could mimic the beneficial effects of exercise. Thus, Physiactisome may improve patient survival and quality of life. Furthermore, the method used to add Hsp60 into nanovesicles can be used to deliver other drugs or active proteins to vesicles.

Alpha B-Crystallin in Muscle Disease Prevention: The Role of Physical Activity

HSPB5 or alpha B-crystallin (CRYAB), originally identified as lens protein, is one of the most widespread and represented of the human small heat shock proteins (sHSPs). It is greatly expressed in tissue with high rates of oxidative metabolism, such as skeletal and cardiac muscles, where HSPB5 dysfunction is associated with a plethora of human diseases. Since HSPB5 has a major role in protecting muscle tissues from the alterations of protein stability (i.e., microfilaments, microtubules, and intermediate filament components), it is not surprising that this sHSP is specifically modulated by exercise. Considering the robust content and the protective function of HSPB5 in striated muscle tissues, as well as its specific response to muscle contraction, it is then realistic to predict a specific role for exercise-induced modulation of HSPB5 in the prevention of muscle diseases caused by protein misfolding. After offering an overview of the current knowledge on HSPB5 structure and function in muscle, this review aims to introduce the reader to the capacity that different exercise modalities have to induce and/or activate HSPB5 to levels sufficient to confer protection, with the potential to prevent or delay skeletal and cardiac muscle disorders.

Effect of whole-body resistance training at different load intensities on circulating inflammatory biomarkers, body fat, muscular strength, and physical performance in postmenopausal women

The primary purpose of this study was to identify the impact of whole-body resistance training (RT) at different load intensities on adipokines, adhesion molecules, and extracellular heat shock proteins in postmenopausal women. As secondary purpose, we analyzed the impact of RT at different load intensities on body fat, muscular strength, and physical performance. Forty participants were randomized into lower-load intensity RT (LIRT, n = 20, 30-35 repetition maximum in the first set of each exercise) or higher-load intensity RT (HIRT, n = 20, 8-12 repetition maximum in the first set of each exercise). Adipokines (adiponectin and leptin), adhesion molecules (MCP-1 and ICAM-1), extracellular heat shock proteins (HO-1 and eHSP60), body fat, muscular strength (1RM), and physical performance [400-meter walking test (400-M) and 6-minute walking test (6MWT)] were analyzed at baseline and after 12-weeks RT. There was a significant time-by-group interaction for eHSP60 (P = 0.049) and 400-M (P = 0.003), indicating superiority of HIRT (d = 0.47 and 0.55). However, both groups similarly improved adiponectin, ICAM-1, HO-1, body fat, 1RM, and 6MWT (P < 0.05). Our study suggests that load intensity does not seem to determine the RT effect on several obesity-related pro-inflammatory and chemotactic compounds, body fat, 1RM, and 6MWT in postmenopausal women, although a greater improvement has been revealed for eHSP60 and 400-M in HIRT. Novelty: Higher-load intensity resistance training improves eHSP60 and 400-M in postmenopausal women. Resistance training improves the inflammatory profile, body fat, muscle strength, and 6MWT, regardless of load intensity.

Function and Fiber-Type Specific Distribution of Hsp60 and αB-Crystallin in Skeletal Muscles: Role of Physical Exercise

Simple Summary

Skeletal muscle represents about 40% of the body mass in humans and it is a copious and plastic tissue, rich in proteins that are subject to continuous rearrangements. Physical exercise is considered a physiological stressor for different organs, in particular for skeletal muscle, and it is a factor able to stimulate the cellular remodeling processes related to the phenomenon of adaptation. All cells respond to various stress conditions by up-regulating the expression and/or activation of a group of proteins called heat shock proteins (HSPs). Although their expression is induced by several stimuli, they are commonly recognized as HSPs due to the first experiments showing their increased transcription after application of heat shock. These proteins are molecular chaperones mainly involved in assisting protein transport and folding, assembling multimolecular complexes, and triggering protein degradation by proteasome. Among the HSPs, a special attention needs to be devoted to Hsp60 and αB-crystallin, proteins constitutively expressed in the skeletal muscle, where they are known to be important in muscle physiopathology. Therefore, here we provide a critical update on their role in skeletal muscle fibers after physical exercise, highlighting the control of their expression, their biological function, and their specific distribution within skeletal muscle fiber-types.

Abstract

Skeletal muscle is a plastic and complex tissue, rich in proteins that are subject to continuous rearrangements. Skeletal muscle homeostasis can be affected by different types of stresses, including physical activity, a physiological stressor able to stimulate a robust increase in different heat shock proteins (HSPs). The modulation of these proteins appears to be fundamental in facilitating the cellular remodeling processes related to the phenomenon of training adaptations such as hypertrophy, increased oxidative capacity, and mitochondrial activity. Among the HSPs, a special attention needs to be devoted to Hsp60 and αB-crystallin (CRYAB), proteins constitutively expressed in the skeletal muscle, where their specific features could be highly relevant in understanding the impact of different volumes of training regimes on myofiber types and in explaining the complex picture of exercise-induced mechanical strain and damaging conditions on fiber population. This knowledge could lead to a better personalization of training protocols with an optimal non-harmful workload in populations of individuals with different needs and healthy status. Here, we introduce for the first time to the reader these peculiar HSPs from the perspective of exercise response, highlighting the control of their expression, biological function, and specific distribution within skeletal muscle fiber-types.

Associations Among Physical Activity Level and Skeletal Muscle Antioxidants in Older Adults

BACKGROUND

Endogenous antioxidants are critical to limiting cellular oxidative damage.

METHODS

The authors determined if habitual physical activity (PA) and cardiorespiratory fitness were associated with skeletal muscle expression of endogenous antioxidants (superoxide dismutase, catalase, and glutathione peroxidase) and circulating oxidative stress markers (serum 8-hydroxy-2'-deoxyguanosine [8-OHdG]; oxidized low-density lipoprotein [LDL]) in older adults. Moderate to vigorous PA (MVPA) was estimated using a validated PA questionnaire in 26 older adults (mean [SD]; M/F = 9/17, age = 68 [4] y, body mass index = 26 [3] kg·m-2). Maximal oxygen consumption was estimated using the YMCA submaximal cycle test. Skeletal muscle endogenous antioxidants and serum 8-OHdG and oxidized LDL were measured. Bivariate and partial correlations (controlling for body mass index) were utilized to determine associations among variables.

RESULTS

MVPA (1640 [1176] kcal·wk-1) was correlated with superoxide dismutase 2 (r = .55), catalase (r = .55), glutathione peroxidase 1 (r = .48), and 8-OHdG (r = -.41) (all Ps < .05), but not oxidized LDL. MVPA and 8-OHdG were not significantly correlated when controlling for body mass index (r = -.29). Estimated maximal oxygen consumption was correlated with glutathione peroxidase 1 (r = .48; P < .05).

CONCLUSIONS

These data show that skeletal muscle endogenous antioxidant expression and circulating oxidative damage are associated with habitual MVPA in older adults. Thus, MVPA in older adults may be protective against reactive oxygen species damage due to higher expression of endogenous antioxidants.

Coordinated alpha-crystallin B phosphorylation and desmin expression indicate adaptation and deadaptation to resistance exercise-induced loading in human skeletal muscle

Skeletal muscle is a target of contraction-induced loading (CiL), leading to protein unfolding or cellular perturbations, respectively. While cytoskeletal desmin is responsible for ongoing structural stabilization, in the immediate response to CiL, alpha-crystallin B (CRYAB) is phosphorylated at serine 59 (_pCRYAB^S59) by P38, acutely protecting the cytoskeleton. To reveal adaptation and deadaptation of these myofibrillar subsystems to CiL, we examined CRYAB, P38, and desmin regulation following resistance exercise at diverse time points of a chronic training period. Mechanosensitive JNK phosphorylation (_pJNK^T183/Y185) was determined to indicate the presence of mechanical components in CiL. Within 6 wk, subjects performed 13 resistance exercise bouts at the 8-12 repetition maximum, followed by 10 days detraining and a final 14th bout. Biopsies were taken at baseline and after the 1st, 3rd, 7th, 10th, 13th, and 14th bout. To assess whether potential desensitization to CiL can be mitigated, one group trained with progressive and a second with constant loading. As no group differences were found, all subjects were combined for statistics. Total and phosphorylated P38 was not regulated over the time course. _pCRYAB^S59 and _pJNK^T183/Y185 strongly increased following the unaccustomed first bout. This exercise-induced _pCRYAB^S59/_pJNK^T183/Y185 increase disappeared with the 10th until 13th bout. As response to the detraining period, the 14th bout led to a renewed increase in _pCRYAB^S59. Desmin content followed _pCRYAB^S59 inversely, i.e., was up- when _pCRYAB^S59 was downregulated and vice versa. In conclusion, the _pCRYAB^S59 response indicates increase and decrease in resistance to CiL, in which a reinforced desmin network could play an essential role by structurally stabilizing the cells.

Hsp60 in Skeletal Muscle Fiber Biogenesis and Homeostasis: From Physical Exercise to Skeletal Muscle Pathology

Hsp60 is a molecular chaperone classically described as a mitochondrial protein with multiple roles in health and disease, participating to the maintenance of protein homeostasis. It is well known that skeletal muscle is a complex tissue, rich in proteins, that is, subjected to continuous rearrangements, and this homeostasis is affected by many different types of stimuli and stresses. The regular exercise induces specific histological and biochemical adaptations in skeletal muscle fibers, such as hypertrophy and an increase of mitochondria activity and oxidative capacity. The current literature is lacking in information regarding Hsp60 involvement in skeletal muscle fiber biogenesis and regeneration during exercise, and in disease conditions. Here, we briefly discuss the functions of Hsp60 in skeletal muscle fibers during exercise, inflammation, and ageing. Moreover, the potential usage of Hsp60 as a marker for disease and the evaluation of novel treatment options is also discussed. However, some questions remain open, and further studies are needed to better understand Hsp60 involvement in skeletal muscle homeostasis during exercise and in pathological condition.

Exercise, heat shock proteins and insulin resistance

Best known as chaperones, heat shock proteins (HSPs) also have roles in cell signalling and regulation of metabolism. Rodent studies demonstrate that heat treatment, transgenic overexpression and pharmacological induction of HSP72 prevent high-fat diet-induced glucose intolerance and skeletal muscle insulin resistance. Overexpression of skeletal muscle HSP72 in mice has been shown to increase endurance running capacity nearly twofold and increase mitochondrial content by 50%. A positive correlation between HSP72 mRNA expression and mitochondrial enzyme activity has been observed in human skeletal muscle, and HSP72 expression is markedly decreased in skeletal muscle of insulin resistant and type 2 diabetic patients. In addition, decreased levels of HSP72 correlate with insulin resistance and non-alcoholic fatty liver disease progression in livers from obese patients. These data suggest the targeted induction of HSPs could be a therapeutic approach for preventing metabolic disease by maintaining the body's natural stress response. Exercise elicits a number of metabolic adaptations and is a powerful tool in the prevention and treatment of insulin resistance. Exercise training is also a stimulus for increased HSP expression. Although the underlying mechanism(s) for exercise-induced HSP expression are currently unknown, the HSP response may be critical for the beneficial metabolic effects of exercise. Exercise-induced extracellular HSP release may also contribute to metabolic homeostasis by actively restoring HSP72 content in insulin resistant tissues containing low endogenous levels of HSPs.This article is part of the theme issue 'Heat shock proteins as modulators and therapeutic targets of chronic disease: an integrated perspective'.

Redox Aspects of Chaperones in Cardiac Function

Molecular chaperones are stress proteins that allow the correct folding or unfolding as well as the assembly or disassembly of macromolecular cellular components. Changes in expression and post-translational modifications of chaperones have been linked to a number of age- and stress-related diseases including cancer, neurodegeneration, and cardiovascular diseases. Redox sensible post-translational modifications, such as S-nitrosylation, glutathionylation and phosphorylation of chaperone proteins have been reported. Redox-dependent regulation of chaperones is likely to be a phenomenon involved in metabolic processes and may represent an adaptive response to several stress conditions, especially within mitochondria, where it impacts cellular bioenergetics. These post-translational modifications might underlie the mechanisms leading to cardioprotection by conditioning maneuvers as well as to ischemia/reperfusion injury. In this review, we discuss this topic and focus on two important aspects of redox-regulated chaperones, namely redox regulation of mitochondrial chaperone function and cardiac protection against ischemia/reperfusion injury.

Effects of age and exercise on inflammatory cytokines, HSP70 and HSP90 gene expression and protein content in Standardbred horses

We hypothesised that the cortisol response to acute exercise, markers of oxidative stress, expression of inflammatory cytokines, heat shock protein (HSP)70 and HSP90 expression in whole blood and skeletal muscle, and HSP70 and HSP90 protein concentrations in skeletal muscle are altered by age and in response to acute submaximal exercise in horses. Young (n=6; 5.5±2.8 year) and aged (n=6; 22.6±2.25 year) unconditioned Standardbred mares underwent an acute submaximal exercise test. Blood samples were collected and analysed for plasma cortisol and malondialdehyde (MDA) concentrations, and for cytokine and HSP gene expression pre- and post-exercise. Gluteus medius biopsies were obtained for analysis of cytokine and HSP gene expression pre- and at 0, 4, 24 and 48 h post-exercise. Data were analysed for main effects using a two-way ANOVA for repeated measures. Post-hoc comparisons of means were conducted using Student-Neuman-Keuls for pair-wise multiple comparisons where appropriate. Acute submaximal exercise increased plasma cortisol concentration in both young and aged mares, and the duration of the post-exercise rise in cortisol was altered in aged horses. Plasma MDA concentration and expression of tumour necrosis factor-α (TNF-α) and interleukin (IL)-6 were unchanged in blood and muscle. Exercise increased IL-1β expression in whole blood of young and aged mares, with young mares having greater exercise-induced expression at 2 (P<0.001) and 4 (P=0.019) h post-exercise. Both young and aged horses had increased HSP70 expression in whole blood following acute exercise, with young horses exhibiting 3-fold greater HSP70 expression than aged mares at 2 h post-exercise. HSP90 expression in whole blood following exercise was increased only in young horses. Both young and aged horses had increased HSP90 expression in skeletal muscle following exercise, but there was no difference due to age. However, the timing of HSP70 expression was different between young and aged horses. The age-related changes in cortisol and IL-1β expression following acute submaximal exercise can have implications for energy homeostasis and the adaption to such disturbances at a cellular and whole animal level. Quantification of HSP expression in whole blood may be a useful biomarker, with implications for cellular adaptation and survival in aged horses.

Hypoxic Air Inhalation and Ischemia Interventions Both Elicit Preconditioning Which Attenuate Subsequent Cellular Stress In vivo Following Blood Flow Occlusion and Reperfusion

Ischemic preconditioning (IPC) is valid technique which elicits reductions in femoral blood flow occlusion mediated reperfusion stress (oxidative stress, Hsp gene transcripts) within the systemic blood circulation and/or skeletal muscle. It is unknown whether systemic hypoxia, evoked by hypoxic preconditioning (HPC) has efficacy in priming the heat shock protein (Hsp) system thus reducing reperfusion stress following blood flow occlusion, in the same manner as IPC. The comparison between IPC and HPC being relevant as a preconditioning strategy prior to orthopedic surgery. In an independent group design, 18 healthy men were exposed to 40 min of (1) passive whole-body HPC (FiO₂ = 0.143; no ischemia. N = 6), (2) IPC (FiO₂ = 0.209; four bouts of 5 min ischemia and 5 min reperfusion. n = 6), or (3) rest (FiO₂ = 0.209; no ischemia. n = 6). The interventions were administered 1 h prior to 30 min of tourniquet derived femoral blood flow occlusion and were followed by 2 h subsequent reperfusion. Systemic blood samples were taken pre- and post-intervention. Systemic blood and gastrocnemius skeletal muscle samples were obtained pre-, 15 min post- (15PoT) and 120 min (120PoT) post-tourniquet deflation. To determine the cellular stress response gastrocnemius and leukocyte Hsp72 mRNA and Hsp32 mRNA gene transcripts were determined by RT-qPCR. The plasma oxidative stress response (protein carbonyl, reduced glutathione/oxidized glutathione ratio) was measured utilizing commercially available kits. In comparison to control, at 15PoT a significant difference in gastrocnemius Hsp72 mRNA was seen in HPC (−1.93-fold; p = 0.007) and IPC (−1.97-fold; p = 0.006). No significant differences were observed in gastrocnemius Hsp32 and Hsp72 mRNA, leukocyte Hsp72 and Hsp32 mRNA, or oxidative stress markers (p > 0.05) between HPC and IPC. HPC provided near identical amelioration of blood flow occlusion mediated gastrocnemius stress response (Hsp72 mRNA), compared to an established IPC protocol. This was seen independent of changes in systemic oxidative stress, which likely explains the absence of change in Hsp32 mRNA transcripts within leukocytes and the gastrocnemius. Both the established IPC and novel HPC interventions facilitate a priming of the skeletal muscle, but not leukocyte, Hsp system prior to femoral blood flow occlusion. This response demonstrates a localized tissue specific adaptation which may ameliorate reperfusion stress.

The Hsp72 and Hsp90α mRNA Responses to Hot Downhill Running Are Reduced Following a Prior Bout of Hot Downhill Running, and Occur Concurrently within Leukocytes and the Vastus Lateralis

The leukocyte heat shock response (HSR) is used to determine individual's thermotolerance. The HSR and thermotolerance are enhanced following interventions such as preconditioning and/or acclimation/acclimatization. However, it is unclear whether the leukocyte HSR is an appropriate surrogate for the HSR in other tissues implicated within the pathophysiology of exertional heat illnesses (e.g., skeletal muscle), and whether an acute preconditioning strategy (e.g., downhill running) can improve subsequent thermotolerance. Physically active, non-heat acclimated participants were split into two groups to investigate the benefits of hot downhill running as preconditioning strategy. A hot preconditioning group (HPC; n = 6) completed two trials (HPC1_HOTDOWN and HPC2_HOTDOWN) of 30 min running at lactate threshold (LT) on -10% gradient in 30°C and 50% relative humidity (RH) separated by 7 d. A temperate preconditioning group (TPC; n = 5) completed 30 min running at LT on a -1% gradient in 20°C and 50% (TPC1_TEMPFLAT) and 7 d later completed 30 min running at LT on -10% gradient in 30°C and 50% RH (TPC2_HOTDOWN). Venous blood samples and muscle biopsies (vastus lateralis; VL) were obtained before, immediately after, 3, 24, and 48 h after each trial. Leukocyte and VL Hsp72, Hsp90α, and Grp78 mRNA relative expression was determined via RT-QPCR. Attenuated leukocyte and VL Hsp72 (2.8 to 1.8 fold and 5.9 to 2.4 fold; p < 0.05) and Hsp90α mRNA (2.9 to 2.4 fold and 5.2 to 2.4 fold; p < 0.05) responses accompanied reductions (p < 0.05) in physiological strain [exercising rectal temperature (-0.3°C) and perceived muscle soreness (~ -14%)] during HPC2_HOTDOWN compared to HPC1_HOTDOWN (i.e., a preconditioning effect). Both VL and leukocyte Hsp72 and Hsp90α mRNA increased (p < 0.05) simultaneously following downhill runs and demonstrated a strong relationship (p < 0.01) of similar magnitudes with one another. Hot downhill running is an effective preconditioning strategy which ameliorates physiological strain, soreness and Hsp72 and Hsp90α mRNA responses to a subsequent bout. Leukocyte and VL analyses are appropriate tissues to infer the extent to which the HSR has been augmented.

Exercise-induced ROS in heat shock proteins response

Cells have evolved multiple and sophisticated stress response mechanisms aiming to prevent macromolecular (including proteins, lipids, and nucleic acids) damage and to maintain or re-establish cellular homeostasis. Heat shock proteins (HSPs) are among the most highly conserved, ubiquitous, and abundant proteins in all organisms. Originally discovered more than 50 years ago through heat shock stress, they display multiple, remarkable roles inside and outside cells under a variety of stresses, including also oxidative stress and radiation, recognizing unfolded or misfolded proteins and facilitating their restructuring. Exercise consists in a combination of physiological stresses, such as metabolic disturbances, changes in circulating levels of hormones, increased temperature, induction of mild to severe inflammatory state, increased production of reactive oxygen and nitrogen species (ROS and RNS). As a consequence, exercise is one of the main stimuli associated with a robust increase in different HSPs in several tissues, which appears to be also fundamental in facilitating the cellular remodeling processes related to the training regime. Among all factors involved in the exercise-related modulation of HSPs level, the ROS production in the contracting muscle or in other tissues represents one of the most attracting, but still under discussion, mechanism. Following exhaustive or damaging muscle exercise, major oxidative damage to proteins and lipids is likely involved in HSP expression, together with mechanically induced damage to muscle proteins and the inflammatory response occurring several days into the recovery period. Instead, the transient and reversible oxidation of proteins by physiological concentrations of ROS seems to be involved in the activation of stress response following non-damaging muscle exercise. This review aims to provide a critical update on the role of HSPs response in exercise-induced adaptation or damage in humans, focusing on experimental results where the link between redox homeostasis and HSPs expression by exercise has been addressed. Further, with the support of in vivo and in vitro studies, we discuss the putative molecular mechanisms underlying the ROS-mediated modulation of HSP expression and/or activity during exercise.

Skeletal muscle Heat shock protein 60 increases after endurance training and induces peroxisome proliferator-activated receptor gamma coactivator 1 α1 expression

Heat shock protein 60 (Hsp60) is a chaperone localizing in skeletal muscle mitochondria, whose role is poorly understood. In the present study, the levels of Hsp60 in fibres of the entire posterior group of hindlimb muscles (gastrocnemius, soleus, and plantaris) were evaluated in mice after completing a 6-week endurance training program. The correlation between Hsp60 levels and the expression of four isoforms of peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC1α) were investigated only in soleus. Short-term overexpression of hsp60, achieved by in vitro plasmid transfection, was then performed to determine whether this chaperone could have a role in the activation of the expression levels of PGC1α isoforms. The levels of Hsp60 protein were fibre-type specific in the posterior muscles and endurance training increased its content in type I muscle fibers. Concomitantly with the increased levels of Hsp60 released in the blood stream of trained mice, mitochondrial copy number and the expression of three isoforms of PGC1α increased. Overexpressing hsp60 in cultured myoblasts induced only the expression of PGC1 1α, suggesting a correlation between Hsp60 overexpression and PGC1 1 α activation.

Downhill running and exercise in hot environments increase leukocyte Hsp72 (HSPA1A) and Hsp90α (HSPC1) gene transcripts

Stressors within humans and other species activate Hsp72 and Hsp90α mRNA transcription, although it is unclear which environmental temperature or treadmill gradient induces the largest increase. To determine the optimal stressor for priming the Hsp system, physically active but not heat-acclimated participants (19.8 ± 1.9 and 20.9 ± 3.6 yr) exercised at lactate threshold in either temperate (20°C, 50% relative humidity; RH) or hot (30°C, 50% RH) environmental conditions. Within each condition, participants completed a flat running (temperate flat or hot flat) and a downhill running (temperate downhill or hot downhill) experimental trial in a randomized counterbalanced order separated by at least 7 days. Venous blood samples were taken immediately before (basal), immediately after exercise, and 3 and 24 h postexercise. RNA was extracted from leukocytes and RT-quantitative PCR conducted to determine Hsp72 and Hsp90α mRNA relative expression. Leukocyte Hsp72 mRNA was increased immediately after exercise following downhill running (1.9 ± 0.9-fold) compared with flat running (1.3 ± 0.4-fold; P = 0.001) and in hot (1.9 ± 0.6-fold) compared with temperate conditions (1.1 ± 0.5-fold; P = 0.003). Leukocyte Hsp90α mRNA increased immediately after exercise following downhill running (1.4 ± 0.8-fold) compared with flat running (0.9 ± 0.6-fold; P = 0.002) and in hot (1.6 ± 1.0-fold) compared with temperate conditions (0.9 ± 0.6-fold; P = 0.003). Downhill running and exercise in hot conditions induced the largest stimuli for leukocyte Hsp72 and Hsp90α mRNA increases.

Manganese superoxide dismutase and oxidative stress modulation

Oxidative stress is characterized by imbalanced reactive oxygen species (ROS) production and antioxidant defenses. Two main antioxidant systems exist. The nonenzymatic system relies on molecules to directly quench ROS and the enzymatic system is composed of specific enzymes that detoxify ROS. Among the latter, the superoxide dismutase (SOD) family is important in oxidative stress modulation. Of these, manganese-dependent SOD (MnSOD) plays a major role due to its mitochondrial location, i.e., the main site of superoxide (O(2)(·-)) production. As such, extensive research has focused on its capacity to modulate oxidative stress. Early data demonstrated the relevance of MnSOD as an O(2)(·-) scavenger. More recent research has, however, identified a prominent role for MnSOD in carcinogenesis. In addition, SOD downregulation appears associated with health risk in heart and brain. A single nucleotide polymorphism which alters the mitochondria signaling sequence for the cytosolic MnSOD form has been identified. Transport into the mitochondria was differentially affected by allelic presence and a new chapter in MnSOD research thus begun. As a result, an ever-increasing number of diseases appear associated with this allelic variation including metabolic and cardiovascular disease. Although diet and exercise upregulate MnSOD, the relationship between environmental and genetic factors remains unclear.

Effects of vitamin C and E supplementation on endogenous antioxidant systems and heat shock proteins in response to endurance training

Reactive oxygen and nitrogen species are important signal molecules for adaptations to training. Due to the antioxidant properties of vitamin C and E, supplementation has been shown to blunt adaptations to endurance training. In this study, we investigated the effects of vitamin C and E supplementation and endurance training on adaptations in endogenous antioxidants and heat shock proteins (HSP). Thirty seven males and females were randomly assigned to receive Vitamin C and E (C + E; C: 1000 mg, E: 235 mg daily) or placebo (PLA), and underwent endurance training for 11 weeks. After 5 weeks, a subgroup conducted a high intensity interval session to investigate acute stress responses. Muscle and blood samples were obtained to investigate changes in proteins and mRNA related to the antioxidant and HSP system. The acute response to the interval session revealed no effects of C + E supplementation on NFκB activation. However, higher stress responses to exercise in C + E group was indicated by larger translocation of HSPs and a more pronounced gene expression compared to PLA. Eleven weeks of endurance training decreased muscle GPx1, HSP27 and αB‐crystallin, while mnSOD, HSP70 and GSH remained unchanged, with no influence of supplementation. Plasma GSH increased in both groups, while uric acid decreased in the C + E group only. Our results showed that C + E did not affect long‐term training adaptations in the antioxidant‐ and HSP systems. However, the greater stress responses to exercise in the C + E group might indicate that long‐term adaptations occurs through different mechanisms in the two groups.

Reactive oxygen species are important signal molecules for adaptations to training. Previously vitamin C and E supplements has been shown to blunt adaptations to endurance training. In this study, we investigated the effects of vitamin C and E supplementation and endurance training on adaptations in endogenous antioxidants and heat shock proteins.

Two weeks of one-leg immobilization decreases skeletal muscle respiratory capacity equally in young and elderly men

Physical inactivity affects human skeletal muscle mitochondrial oxidative capacity but the influence of aging combined with physical inactivity is not known. This study investigates the effect of two weeks of immobilization followed by six weeks of supervised cycle training on muscle oxidative capacity in 17 young (23±1years) and 15 elderly (68±1years) healthy men. We applied high-resolution respirometry in permeabilized fibers from muscle biopsies at inclusion after immobilization and training. Furthermore, protein content of mitochondrial complexes I-V, mitochondrial heat shock protein 70 (mtHSP70) and voltage dependent anion channel (VDAC) were measured in skeletal muscle by Western blotting. The elderly men had lower content of complexes I-V and mtHSP70 but similar respiratory capacity and content of VDAC compared to the young. In both groups the respiratory capacity and protein content of VDAC, mtHSP70 and complexes I, II, IV and V decreased with immobilization and increased with retraining. Moreover, there was no overall difference in the response between the groups. When the intrinsic mitochondrial capacity was evaluated by normalizing respiration to citrate synthase activity, the respiratory differences with immobilization and training disappeared. In conclusion, aging is not associated with a decrease in muscle respiratory capacity in spite of lower complexes I-V and mtHSP70 protein content. Furthermore, immobilization decreased and aerobic training increased the respiratory capacity and protein contents of complexes I-V, mtHSP70 and VDAC similarly in the two groups. This suggests that inactivity and training alter mitochondrial biogenesis equally in young and elderly men.

Heat acclimation and cross tolerance to hypoxia: Bridging the gap between cellular and systemic responses

Recent research has suggested a potential for some of the physiological and cellular responses to heat acclimation to carry over to improved tolerance of the novel stresses of another environment. This cross-tolerance is evident in heat-acclimated animals that exhibit enhanced tolerance to either hypoxic or ischemic stress, and is primarily attributed to shared cellular stress response pathways. These pathways include Hypoxia-Inducible Factor-1 (HIF-1) and Heat Shock Proteins (HSP). Whether these shared cellular stress response pathways translate to systemic cross-tolerance (improved exercise tolerance, reduced risk of environment-associated illness) has not been clearly shown, particularly in humans. This review highlights the HIF-1 and HSP pathways and their relationship with systemic acclimation responses, and further examines the potential cellular and systemic adaptations that may result in cross-tolerance between hot and hypoxic environments.

The expression of heat shock protein in human skeletal muscle: effects of muscle fibre phenotype and training background

AIM

Exercise-induced adaptations of skeletal muscle are related to training mode and can be muscle fibre type specific. This study aimed to investigate heat shock protein expression in type I and type II muscle fibres in resting skeletal muscle of subjects with different training backgrounds.

METHODS

Three groups of subjects were included: healthy active not engaged in any training programme (ACT, n = 12), resistance trained (RES, n = 6) and endurance trained (END, n = 8). Biopsies were obtained from vastus lateralis, and immunohistochemistry was performed using monoclonal antibodies against myosin heavy chain I and IIA, αB-crystallin, HSP27, HSP60 and HSP70.

RESULTS

In ACT and RES, but not in END, a fibre type-specific expression with higher staining intensity in type I than type II fibres was seen for αB-crystallin. The opposite (II > I) was found for HSP27 in subjects from ACT (6 of 12 subjects) and RES (3 of 6), whereas all subjects from END displayed uniform staining. HSP60 showed no fibre-specific expression. HSP70 displayed a fibre-specific expression pattern (I > II) in ACT (4 of 12), but not in END or RES.

CONCLUSION

This study shows that the level of expression of the different HSPs in human skeletal muscle is influenced by muscle fibre phenotype. The fibre type-specific expression of HSP70 is influenced by resistance and endurance training, whereas those of αB-crystallin and HSP27 is influenced only by endurance training, suggesting the existence of a training-modality-specific action on the adaptive processes including heat shock proteins in human skeletal muscle.

Hypoxia-mediated prior induction of monocyte-expressed HSP72 and HSP32 provides protection to the disturbances to redox balance associated with human sub-maximal aerobic exercise

HSP72 is rapidly expressed in response to a variety of stressors in vitro and in vivo (including hypoxia). This project sought a hypoxic stimulus to elicit increases in HSP72 and HSP32 in attempts to confer protection to the sub-maximal aerobic exercise-induced disturbances to redox balance. Eight healthy recreationally active male subjects were exposed to five consecutive days of once-daily hypoxia (2,980 m, 75 min). Seven days prior to the hypoxic acclimation period, subjects performed 60 min of cycling on a cycle ergometer (exercise bout 1-EXB1), and this exercise bout was repeated 1 day post-cessation of the hypoxic period (exercise bout 2-EXB2). Blood samples were taken immediately pre- and post-exercise and 1, 4 and 8 h post-exercise for HSP72 and immediately pre, post and 1 h post-exercise for HSP32, TBARS and glutathione [reduced (GSH), oxidised (GSSG) and total (TGSH)], with additional blood samples obtained immediately pre-day 1 and post-day 5 of the hypoxic acclimation period for the same indices. Monocyte-expressed HSP32 and HSP72 were analysed by flow cytometry, with measures of oxidative stress accessed by commercially available kits. There were significant increases in HSP72 (P < 0.001), HSP32 (P = 0.03), GSSG (t = 9.5, P < 0.001) and TBARS (t = 5.6, P = 0.001) in response to the 5-day hypoxic intervention, whereas no significant changes were observed for GSH (P = 0.22) and TGSH (P = 0.25). Exercise-induced significant increases in HSP72 (P < 0.001) and HSP32 (P = 0.003) post-exercise in EXB1; this response was absent for HSP72 (P ≥ 0.79) and HSP32 (P ≥ 0.99) post-EXB2. The hypoxia-mediated increased bio-available HSP32 and HSP72 and favourable alterations in glutathione redox, prior to exercise commencing in EXB2 compared to EXB1, may acquiesce the disturbances to redox balance encountered during the second physiologically identical exercise bout.

Creatine-kinase- and exercise-related muscle damage implications for muscle performance and recovery

The appearance of creatine kinase (CK) in blood has been generally considered to be an indirect marker of muscle damage, particularly for diagnosis of medical conditions such as myocardial infarction, muscular dystrophy, and cerebral diseases. However, there is controversy in the literature concerning its validity in reflecting muscle damage as a consequence of level and intensity of physical exercise. Nonmodifiable factors, for example, ethnicity, age, and gender, can also affect enzyme tissue activity and subsequent CK serum levels. The extent of effect suggests that acceptable upper limits of normal CK levels may need to be reset to recognise the impact of these factors. There is a need for standardisation of protocols and stronger guidelines which would facilitate greater scientific integrity. The purpose of this paper is to examine current evidence and opinion relating to the release of CK from skeletal muscle in response to physical activity and examine if elevated concentrations are a health concern.

The intersection of inflammation, insulin resistance and ageing: implications for the study of molecular signalling pathways in horses

Inflammation-associated insulin resistance contributes to chronic disease in humans and other long-lived species, such as horses. Insulin resistance arises due to an imbalance among molecular signalling mediators in response to pro-inflammatory cytokines in the aged and obese. The mammalian heat shock protein response has received much attention as an avenue for attenuating inflammatory mediator signalling and for contributing to preservation and restoration of insulin signalling in metabolically important tissues. Data on heat shock proteins and inflammatory signalling mediators in untrained and aged horses are lacking, and horses represent an untapped resource for studying the mediator imbalance contributing to insulin resistance in a comparative model.

Strength training elevates HSP27, HSP70 and αB-crystallin levels in musculi vastus lateralis and trapezius

A single bout of high-force exercise has been shown to increase the muscle levels of heat shock proteins (HSPs). Here, changes in the levels of HSPs after 2 and 11 weeks of strength training with either one or three sets per exercise were examined. Fifteen young men (27 ± 6 years, 182 ± 8 cm and 82 ± 13 kg) were randomized to train either one set in lower-body exercises and three sets in upper-body exercises (1L-3UB), or three sets in lower-body exercises and one set in upper-body exercises (3L-1UB). Biopsies from vastus lateralis and trapezius were obtained before, during (2 weeks) and after 11 weeks of strength training (3 bouts per week). The biopsies were analysed for HSP27 (cytosolic and cytoskeletal fractions) and HSP70 and αB-crystallin (cytosolic fraction). No evidence for an effect of training volume (1 vs. 3 sets) on the HSP response was found. For all subjects combined, HSP27 [186 ± 69% (mean ± SD)], HSP70 (146 ± 51%) and αB-crystallin (184 ± 82%) increased in the cytosolic fraction of vastus lateralis after 11 weeks of training. In the trapezius, the only observed increase was for HSP27 in the cytosolic fraction after 2 weeks of training (149 ± 59%). However, the trapezius contained somewhat higher levels of HSP70 and αB-crystallin than vastus lateralis at baseline. The HSP27 levels in the cytoskeletal compartment did not increase significantly in either muscle. In conclusion, strength training resulted-independent of training volume-in elevated levels of HSP27, HSP70 and αB-crystallin in the cytosolic compartment of the vastus lateralis. In the trapezius, only the cytosolic HSP27 levels were increased with training.

Molecular adaptations to aerobic exercise training in skeletal muscle of older women

BACKGROUND

We have recently shown that 12 weeks of progressive aerobic exercise training improves whole-muscle size and function in older women. The purpose of this investigation was to evaluate molecular markers that may be associated with muscle hypertrophy after aerobic training in aging skeletal muscle.

METHODS

Muscle biopsies were obtained before and after 12 weeks of aerobic exercise training on a cycle ergometer in nine older women (70 ± 2 years) to determine basal levels of messenger RNA and protein content of select myogenic, proteolytic, and mitochondrial factors.

RESULTS

The training program increased (p < .05) aerobic capacity 30 ± 9%, whole-muscle cross-sectional area 11 ± 2%, and whole-muscle force production 29 ± 8%. Basal messenger RNA levels of FOXO3A, myostatin, HSP70, and MRF4 were lower (p < .05) after aerobic training. FOXO3A, FOXO3A phosphorylation, and HSP70 protein content were unaltered after training. Mitochondrial protein COX IV was elevated (p < .05) 33 ± 7% after aerobic training, whereas PGC-1α protein content was 20 ± 5% lower (p < .05).

CONCLUSIONS

These data suggest that reductions in FOXO3A and myostatin messenger RNA are potentially associated with exercise-induced muscle hypertrophy. Additionally, it appears that mitochondrial biogenesis can occur with aerobic training in older women independent of increased PGC-1α protein. Aerobic exercise training alters molecular factors related to the regulation of skeletal muscle, which supports the beneficial role of aerobic training for improving muscle health in older women.

High-intensity interval training attenuates the exercise-induced increase in plasma IL-6 in response to acute exercise

This aims of this study were to investigate the effects of carbohydrate availability during endurance training on the plasma interleukin (IL)-6, IL-8, and tumor necrosis factor (TNF)-alpha response to a subsequent acute bout of high-intensity interval exercise. Three groups of recreationally active males performed 6 weeks of high-intensity interval running. Groups 1 (LOW+GLU) and 2 (LOW+PLA) trained twice per day, 2 days per week, and consumed a 6.4% glucose or placebo solution, respectively, before every second training session and at regular intervals throughout exercise. Group 3 (NORM) trained once per day, 4 days per week, and consumed no beverage during training. Each group performed 50 min of high-intensity interval running at the same absolute workloads before and after training. Muscle glycogen utilization in the gastrocnemius muscle during acute exercise was reduced (p < 0.05) in all groups following training, although this was not affected by training condition. Plasma IL-6 concentration increased (p < 0.05) after acute exercise in all groups before and after training. Furthermore, the magnitude of increase was reduced (p < 0.05) following training. This training-induced attenuation in plasma IL-6 increase was similar among groups. Plasma IL-8 concentration increased (p < 0.05) after acute exercise in all groups, although the magnitude of increase was not affected (p > 0.05) by training. Acute exercise did not increase (p > 0.05) plasma TNF-alpha when undertaken before or after training. Data demonstrate that the exercise-induced increase in plasma IL-6 concentration in response to customary exercise is attenuated by previous exercise training, and that this attenuation appears to occur independent of carbohydrate availability during training.

Exercise training-induced gender-specific heat shock protein adaptations in human skeletal muscle

This study investigates the effects of short-term endurance training on heat shock protein (HSP) adaptations of male and female human skeletal muscle. The data demonstrate that females did not respond to continuous or interval training in terms of increasing HSP content of the vastus lateralis muscle. In contrast, males displayed HSP adaptations to both training interventions. These data provide a platform for future human studies to examine a potential gender-specific stress response to exercise.

Reduced carbohydrate availability does not modulate training-induced heat shock protein adaptations but does upregulate oxidative enzyme activity in human skeletal muscle

The primary aim of the present study was to test the hypothesis that training with reduced carbohydrate availability from both endogenous and exogenous sources provides an enhanced stimulus for training-induced heat shock protein (HSP) adaptations of skeletal muscle. A secondary aim was to investigate the influence of reduced carbohydrate availability on oxidative adaptations and exercise performance. Three groups of recreationally active men performed 6 wk of high-intensity intermittent running occurring four times per week. Group 1 (n = 8; Low + Glu) and 2 (n = 7; Low + Pla) trained twice per day, 2 days/wk, and consumed a 6.4% glucose or placebo solution, respectively, immediately before every second training session and at regular intervals throughout exercise. Group 3 (n = 8; Norm) trained once per day, 4 days/wk, and consumed no beverage throughout training. Training induced significant improvements in maximal oxygen uptake (Vo(2max)) (P = 0.001) and distance covered on Yo-Yo Intermittent Recovery Test 2 (P = 0.001) in all groups, with no difference between conditions. Similarly, training resulted in significant increases in HSP70, HSP60, and alphaB-crystallin in the gastrocnemius (P = 0.03, 0.02, and 0.01, respectively) and vastus lateralis (P = 0.01, 0.02, and 0.003, respectively) muscles in all groups, with no difference between conditions. In contrast, training resulted in significant increases in succinate dehydrogenase (SDH) activity of the gastrocnemeius (Low + Glu, Low + Pla, and Norm: 27, 76, and 53% increases, respectively; P = 0.001) and vastus lateralis muscles (Low + Glu, Low + Pla, and Norm: 17, 70, and 19% increases, respectively; P = 0.001) where the magnitude of increase in SDH activity was significantly larger for both muscles (P = 0.03 and 0.04 for gastrocnemius and vastus lateralis, respectively) for subjects training in the Low + Pla condition. Data provide the first evidence that in whole body exercise conditions, carbohydrate availability appears to have no modulating effect on training-induced increases of the HSP content of skeletal muscle. In contrast, training under conditions of reduced carbohydrate availability from both endogenous and exogenous sources provides an enhanced stimulus for inducing oxidative enzyme adaptations of skeletal muscle although this does not translate to improved performance during high-intensity exercise.

Reviewing scientific manuscripts: how much statistical knowledge should a reviewer really know?

In the sequel to their guidelines for reporting statistics in American Physiological Society journals, Curran-Everett and Benos highlighted that the initial guidelines of 2004 have had little effect on the statistical reporting practices of authors. In the present article, I suggest that the guidelines have also had little impact on both journal reviewers and editors. I present three cases of statistical reporting practices in which there appears to be considerable discrepancies between the author and reviewer and, moreover, inconsistencies between reviewers. I argue that for authors to comply with these guidelines, the initial challenge is to have a team of reviewers who are also willing to accept the unfamiliar. Indeed, the opinions of reviewers who are ill informed about relatively novel statistical methods and recommended reporting practices may have implications for the final editorial decision on the suitability of submitted manuscripts for publication.