Exercise metabolism and the molecular regulation of skeletal muscle adaptation

Crosstalk between Exercise-Derived Endocannabinoidome and Kynurenines: Potential Target Therapies for Obesity and Depression Symptoms

The kynurenine pathway (KP) and the endocannabinoid system (ECS) are known to be deregulated in depression and obesity; however, it has been recognized that acute physical exercise has an important modulating role inducing changes in the mobilization of their respective metabolites-endocannabinoids (eCBs) and kynurenines (KYNs)-which overlap at some points, acting as important antidepressant, anti-nociceptive, anti-inflammatory, and antioxidant biomarkers. Therefore, the aim of this review is to analyze and discuss some recently performed studies to investigate the potential interactions between both systems, particularly those related to exercise-derived endocannabinoidome and kynurenine mechanisms, and to elucidate how prescription of physical exercise could represent a new approach for the clinical management of these two conditions.

Moderate intensity continuous versus high intensity interval training: Metabolic responses of slow and fast skeletal muscles in rat

The healthy benefits of regular physical exercise are mainly mediated by the stimulation of oxidative and antioxidant capacities in skeletal muscle. Our understanding of the cellular and molecular responses involved in these processes remain often uncomplete particularly regarding muscle typology. The main aim of the present study was to compare the effects of two types of exercise training protocol: a moderate-intensity continuous training (MICT) and a high-intensity interval training (HIIT) on metabolic processes in two muscles with different typologies: soleus and extensor digitorum longus (EDL). Training effects in male Wistar rats were studied from whole organism level (maximal aerobic speed, morphometric and systemic parameters) to muscle level (transcripts, protein contents and enzymatic activities involved in antioxidant defences, aerobic and anaerobic metabolisms). Wistar rats were randomly divided into three groups: untrained (UNTR), n = 7; MICT, n = 8; and HIIT, n = 8. Rats of the MICT and HIIT groups ran five times a week for six weeks at moderate and high intensity, respectively. HIIT improved more than MICT the endurance performance (a trend to increased maximal aerobic speed, p = 0.07) and oxidative capacities in both muscles, as determined through protein and transcript assays (AMPK-PGC-1α signalling pathway, antioxidant defences, mitochondrial functioning and dynamics). Whatever the training protocol, the genes involved in these processes were largely more significantly upregulated in soleus (slow-twitch fibres) than in EDL (fast-twitch fibres). Solely on the basis of the transcript changes, we conclude that the training protocols tested here lead to specific muscular responses.

Physiology of sedentary behavior

Sedentary behaviors (SB) are characterized by low energy expenditure while in a sitting or reclining posture. Evidence relevant to understanding the physiology of SB can be derived from studies employing several experimental models: bed rest, immobilization, reduced step count, and reducing/interrupting prolonged SB. We examine the relevant physiological evidence relating to body weight and energy balance, intermediary metabolism, cardiovascular and respiratory systems, the musculoskeletal system, the central nervous system, and immunity and inflammatory responses. Excessive and prolonged SB can lead to insulin resistance, vascular dysfunction, shift in substrate use toward carbohydrate oxidation, shift in muscle fiber from oxidative to glycolytic type, reduced cardiorespiratory fitness, loss of muscle mass and strength and bone mass, and increased total body fat mass and visceral fat depot, blood lipid concentrations, and inflammation. Despite marked differences across individual studies, longer term interventions aimed at reducing/interrupting SB have resulted in small, albeit marginally clinically meaningful, benefits on body weight, waist circumference, percent body fat, fasting glucose, insulin, HbA1c and HDL concentrations, systolic blood pressure, and vascular function in adults and older adults. There is more limited evidence for other health-related outcomes and physiological systems and for children and adolescents. Future research should focus on the investigation of molecular and cellular mechanisms underpinning adaptations to increasing and reducing/interrupting SB and the necessary changes in SB and physical activity to impact physiological systems and overall health in diverse population groups.

Effects of exercise timing on metabolic health

The increasing prevalence of metabolic syndrome is associated with major health and socioeconomic consequences. Currently, physical exercise, together with dietary interventions, is the mainstay of the treatment of obesity and related metabolic complications. Although exercise training includes different modalities, with variable intensity, duration, volume, or frequency, which may have a distinct impact on several characteristics related to metabolic syndrome, the potential effects of exercise timing on metabolic health are yet to be fully elucidated. Remarkably, promising results with regard to this topic have been reported in the last few years. Similar to other time-based interventions, including nutritional therapy or drug administration, time-of-day-based exercise may become a useful approach for the management of metabolic disorders. In this article, we review the role of exercise timing in metabolic health and discuss the potential mechanisms that could drive the metabolic-related benefits of physical exercise performed in a time-dependent manner.

Chronic high-intensity interval training and moderate-intensity continuous training are both effective in increasing maximum fat oxidation during exercise in overweight and obese adults: A meta-analysis

Objective

to (1) systematically review the chronic effect of high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on maximal fat oxidation (MFO) in overweight and obese adults, and (2) explore MFO influencing factors and its dose-response relationships with HIIT and MICT.

Methods

Studies using a between-group design involving overweight and obese adults and assessing the effect of HIIT and MICT on MFO were included. A meta-analysis on MFO indices was conducted, and the observed heterogeneities were explored through subgroup, regression, and sensitivity analyses.

Results

Thirteen studies of moderate to high quality with a total of 519 overweight and obese subjects were included in this meta-analysis (HIIT, n = 136; MICT, n = 235; Control, n = 148). HIIT displayed a statistically significant favorable effect on MFO compared to no-training (MD = 0.07; 95%CI [0.03 to 0.11]; I2 = 0%). Likewise, MICT displayed a statistically significant favorable effect on MFO compared to no-training (MD = 0.10; 95%CI [0.06 to 0.15]; I2 = 95%). Subgroup and regression analyses revealed that exercise intensity (Fatmax vs. non-Fatmax; %VO2peak), exercise mode, BMI, and VO2peak all significantly moderated MICT on MFO. When analyzing studies that have directly compared HIIT and MCIT in obese people, it seems there is no difference in the MFO change (MD = 0.01; 95%CI [-0.02 to 0.04]; I2 = 64%). No publication bias was found in any of the above meta-analyses (Egger's test p > 0.05 for all).

Conclusion

Both HIIT and MICT are effective in improving MFO in overweight and obese adults, and they have similar effects. MCIT with an intensity of 65-70% VO2peak, performed 3 times per week for 60 min per session, will optimize MFO increases in overweight and obese adults. Given the lack of studies examining the effect of HIIT on MFO in overweight and obese adults and the great diversity in the training protocols in the existing studies, we were unable to make sound recommendations for training.

Protein Turnover in Skeletal Muscle: Looking at Molecular Regulation towards an Active Lifestyle

Skeletal muscle is a highly plastic tissue, able to change its mass and functional properties in response to several stimuli. Skeletal muscle mass is influenced by the balance between protein synthesis and breakdown, which is regulated by several signaling pathways. The relative contribution of Akt/mTOR signaling, ubiquitin-proteasome pathway, autophagy among other signaling pathways to protein turnover and, therefore, to skeletal muscle mass, differs depending on the wasting or loading condition and muscle type. By modulating mitochondria biogenesis, PGC-1α has a major role in the cell's bioenergetic status and, thus, on protein turnover. In fact, rates of protein turnover regulate differently the levels of distinct protein classes in response to atrophic or hypertrophic stimuli. Mitochondrial protein turnover rates may be enhanced in wasting conditions, whereas the increased turnover of myofibrillar proteins triggers muscle mass gain. The present review aims to update the knowledge on the molecular pathways implicated in the regulation of protein turnover in skeletal muscle, focusing on how distinct muscle proteins may be modulated by lifestyle interventions with emphasis on exercise training. The comprehensive analysis of the anabolic effects of exercise programs will pave the way to the tailored management of muscle wasting conditions.

Effects of Moderate Exercise Training on Cancer-Induced Muscle Wasting

BACKGROUND

Muscle wasting is a common phenomenon in oncology and seems to be attenuated by exercise training. The aim of this study is to determine the degree of aggressiveness of cancer-induced muscle wasting in two different phenotypic muscles. It will also determine whether exercise training can attenuate this muscle dysfunction.

METHODS

Fifty Sprague Dawley rats were randomly assigned to four experimental groups: two breast cancer model groups (sedentary and exercise) and two control groups (sedentary and exercise). Breast cancer was induced by 1-methyl-1-nitrosoureia (MNU). After 35 weeks of endurance training, animals were sacrificed, and gastrocnemius and soleus muscles harvested for morphometric analysis.

RESULTS

In sedentary tumor-bearing animals, a significant reduction in cross-sectional area was found in both muscles (p < 0.05). Interstitial fibrosis was significantly higher in the gastrocnemius muscle of the sedentary tumor-bearing animals (p < 0.05), but not in the soleus muscle. In the gastrocnemius of sedentary tumor-bearing animals, a shift from large to small fibers was observed. This cancer-related muscle dysfunction was prevented by long-term exercise training.

CONCLUSIONS

In sedentary animals with tumors, the gastrocnemius muscle showed a very pronounced reduction in cross-sectional area and a marked degree of interstitial fibrosis. There was no difference in collagen deposition between tumor groups, and the soleus muscle showed a less pronounced but significant reduction in cross-sectional area. These contrasting results confirm that cancer-induced muscle wasting can affect specific types of fibers and specific muscles, namely fast glycolytic muscles, and that exercise training can be used to improve it.

Arsenic disrupts extracellular vesicle-mediated signaling in regenerating myofibers

Chronic exposure to environmental arsenic is a public health crisis affecting hundreds of millions of individuals worldwide. Though arsenic is known to contribute to many pathologies and diseases, including cancers, cardiovascular and pulmonary diseases, and neurological impairment, the mechanisms for arsenic-promoted disease remain unresolved. This is especially true for arsenic impacts on skeletal muscle function and metabolism, despite the crucial role that skeletal muscle health plays in maintaining cardiovascular health, systemic homeostasis, and cognition. A barrier to researching this area is the challenge of interrogating muscle cell-specific effects in biologically relevant models. Ex vivo studies investigating mechanisms for muscle-specific responses to arsenic or other environmental contaminants primarily utilize traditional 2-dimensional culture models that cannot elucidate effects on muscle physiology or function. Therefore, we developed a contractile 3-dimensional muscle construct model-composed of primary mouse muscle progenitor cells differentiated in a hydrogel matrix-to study arsenic exposure impacts on skeletal muscle regeneration. Muscle constructs exposed to low-dose (50 nM) arsenic exhibited reduced strength and myofiber diameter following recovery from muscle injury. These effects were attributable to dysfunctional paracrine signaling mediated by extracellular vesicles (EVs) released from muscle cells. Specifically, we found that EVs collected from arsenic-exposed muscle constructs recapitulated the inhibitory effects of direct arsenic exposure on myofiber regeneration. In addition, muscle constructs treated with EVs isolated from muscles of arsenic-exposed mice displayed significantly decreased strength. Our findings highlight a novel model for muscle toxicity research and uncover a mechanism of arsenic-induced muscle dysfunction by the disruption of EV-mediated intercellular communication.

Metabolic elasticity: A new measure of age

Promoting healthy aging is contingent on understanding the underlying mechanisms for the age-associated decline in metabolic physiology. Through developing a novel concept of "metabolic elasticity" to evaluate metabolic adaptability in response to cyclical changes in energy balance, Zhou et al. present an impactful gauge of metabolic health that is particularly relevant to aging.

Efficacy of combined strategies of physical activity, diet and sleep disorders as treatment in patients with chronic shoulder pain. A systematic review

Introduction: The objective of this systematic review was to analyze the existing scientific evidence on the influence of dietary strategies, exercise, and sleep disorders on the symptomatology of patients with chronic shoulder pain, as well as to assess the methodological quality of the literature collected. Methods: The selection criteria were as follows: we included randomized controlled clinical trials written in English that investigated the effects of such interventions in patients with chronic shoulder pain and excluded studies where pre-operative rehabilitation or rehabilitation combined with corticosteroid injections was performed. We searched six databases Pubmed, Cochrane Library, Web of Science, CINAHL, Sportdiscus and Scopus, using the keywords "shoulder pain," "fasting," "physical therapy modalities," "rehabilitation," "exercise," "circadian clocks," and "chronic pain" to select randomized controlled clinical trials conducted in humans and written in English. The last search was conducted on 24/01/2023. (PROSPERO:CRD42023379925). Results: We used the tool proposed by the Cochrane Handbook to assess the risk of bias in the included studies of the 17 studies included, nine had a high risk of bias, two studies had an unclear risk of bias, and the remaining six studies had a low risk of bias. A total of 17 articles were selected, including 10 studies that showed a positive influences of exercise on chronic shoulder pain and five studies that showed a negative influence of sleep disorders on this patient profile. The remaining two articles analyzed the influence of nutritional strategies and metabolic problems in patients with chronic shoulder pain. The total sample size of the 17 included articles amounted to 9,991 individuals. Discussion: Studies confirm that exercise generates a hypoalgesic effect that improves chronic shoulder pain, functionality, and quality of life. Although dietary strategies and sleep disorders are known to influence chronic shoulder pain, there is a lack of studies that conduct interventions on these problems to assess how chronic shoulder pain varies.

Mitochondrial dysfunction and skeletal muscle atrophy: Causes, mechanisms, and treatment strategies

Skeletal muscle, which accounts for approximately 40% of total body weight, is one of the most dynamic and plastic tissues in the human body and plays a vital role in movement, posture and force production. More than just a component of the locomotor system, skeletal muscle functions as an endocrine organ capable of producing and secreting hundreds of bioactive molecules. Therefore, maintaining healthy skeletal muscles is crucial for supporting overall body health. Various pathological conditions, such as prolonged immobilization, cachexia, aging, drug-induced toxicity, and cardiovascular diseases (CVDs), can disrupt the balance between muscle protein synthesis and degradation, leading to skeletal muscle atrophy. Mitochondrial dysfunction is a major contributing mechanism to skeletal muscle atrophy, as it plays crucial roles in various biological processes, including energy production, metabolic flexibility, maintenance of redox homeostasis, and regulation of apoptosis. In this review, we critically examine recent knowledge regarding the causes of muscle atrophy (disuse, cachexia, aging, etc.) and its contribution to CVDs. Additionally, we highlight the mitochondrial signaling pathways involvement to skeletal muscle atrophy, such as the ubiquitin-proteasome system, autophagy and mitophagy, mitochondrial fission-fusion, and mitochondrial biogenesis. Furthermore, we discuss current strategies, including exercise, mitochondria-targeted antioxidants, in vivo transfection of PGC-1α, and the potential use of mitochondrial transplantation as a possible therapeutic approach.

Impact of short-term, pharmacological CARM1 inhibition on skeletal muscle mass, function, and atrophy in mice

Coactivator-associated arginine methyltransferase 1 (CARM1) catalyzes the methylation of arginine residues on target proteins critical for health and disease. The purpose of this study was to characterize the effects of short-term, pharmacological CARM1 inhibition on skeletal muscle size, function, and atrophy. Adult mice (n = 10 or 11/sex) were treated with either a CARM1 inhibitor (150 mg/kg EZM2302; EZM) or vehicle (Veh) via oral gavage for 11-13 days and muscle mass, function, and exercise capacity were assessed. In addition, we investigated the effect of CARM1 suppression on unilateral hindlimb denervation (DEN)-induced muscle atrophy (n = 8/sex). We report that CARM1 inhibition caused significant reductions in the asymmetric dimethylation of known CARM1 substrates but no change in CARM1 protein or mRNA content in skeletal muscle. Reduced CARM1 activity did not affect body or muscle mass, however, we observed a decrease in exercise capacity and muscular endurance in male mice. CARM1 methyltransferase activity increased in the muscle of Veh-treated mice following 7 days of DEN, and this response was blunted in EZM-dosed mice. Skeletal muscle mass and myofiber cross-sectional area were significantly reduced in DEN compared with contralateral, non-DEN limbs to a similar degree in both treatment groups. Furthermore, skeletal muscle atrophy and autophagy gene expression programs were elevated in response to DEN independent of CARM1 suppression. Collectively, these results suggest that short-term, pharmacological CARM1 inhibition in adult animals affects muscle performance in a sex-specific manner but does not impact the maintenance and remodeling of skeletal muscle mass during conditions of neurogenic muscle atrophy.NEW & NOTEWORTHY Short-term pharmacological inhibition of coactivator-associated arginine methyltransferase 1 (CARM1) was effective at significantly reducing CARM1 methyltransferase function in skeletal muscle. CARM1 inhibition did not impact muscle mass, but exercise capacity was impaired, particularly in male mice, whereas morphological and molecular signatures of denervation-induced muscle atrophy were largely maintained in animals administered the inhibitor. Altogether, the role of CARM1 in neuromuscular biology remains complex and requires further investigation of its therapeutic potential in muscle-wasting conditions.

Farnesol prevents aging-related muscle weakness in mice through enhanced farnesylation of Parkin-interacting substrate

Peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) is a master regulator of mitochondrial biogenesis. Reduced PGC-1α abundance is linked to skeletal muscle weakness in aging or pathological conditions, such as neurodegenerative diseases and diabetes; thus, elevating PGC-1α abundance might be a promising strategy to treat muscle aging. Here, we performed high-throughput screening and identified a natural compound, farnesol, as a potent inducer of PGC-1α. Farnesol administration enhanced oxidative muscle capacity and muscle strength, leading to metabolic rejuvenation in aged mice. Moreover, farnesol treatment accelerated the recovery of muscle injury associated with enhanced muscle stem cell function. The protein expression of Parkin-interacting substrate (PARIS/Zfp746), a transcriptional repressor of PGC-1α, was elevated in aged muscles, likely contributing to PGC-1α reduction. The beneficial effect of farnesol on aged muscle was mediated through enhanced PARIS farnesylation, thereby relieving PARIS-mediated PGC-1α suppression. Furthermore, short-term exercise increased PARIS farnesylation in the muscles of young and aged mice, whereas long-term exercise decreased PARIS expression in the muscles of aged mice, leading to the elevation of PGC-1α. Collectively, the current study demonstrated that the PARIS-PGC-1α pathway is linked to muscle aging and that farnesol treatment can restore muscle functionality in aged mice through increased farnesylation of PARIS.

Metformin Protects Rat Skeletal Muscle from Physical Exercise-Induced Injury

Metformin (Met) is a drug commonly prescribed in type 2 diabetes mellitus. Its efficacy is due to the suppression of hepatic gluconeogenesis, enhancement of peripheral glucose uptake and lower glucose absorption by the intestine. Recent studies have reported Met efficacy in other clinical applications, such as age-related diseases. Despite the wide clinical use of Met, its mechanism of action on muscle and its effect on muscle performance are unclear. We investigated the effects of Met combined with training on physical performance (PP) in healthy rats receiving Met for 8 weeks while undergoing daily moderate exercise. We evaluated the following: PP through graded endurance exercise test performed before the beginning of the training protocol and 48 h before the end of the training period; blood ALT, AST, LDH and CK-MB levels in order to address muscle damage; and several blood and muscle myokines and the expression of factors believed to be involved in muscle adaptation to exercise. Our data demonstrate that Met does not improve the positive effects of exercise on performance, although it protects myocytes from exercise-induced damage. Moreover, given that Met positively affects exercise-induced muscle adaptation, our data support the idea of the therapeutic application of Met when muscle function and structure are compromised.

Myonectin protects against skeletal muscle dysfunction in male mice through activation of AMPK/PGC1α pathway

To maintain and restore skeletal muscle mass and function is essential for healthy aging. We have found that myonectin acts as a cardioprotective myokine. Here, we investigate the effect of myonectin on skeletal muscle atrophy in various male mouse models of muscle dysfunction. Disruption of myonectin exacerbates skeletal muscle atrophy in age-associated, sciatic denervation-induced or dexamethasone (DEX)-induced muscle atrophy models. Myonectin deficiency also contributes to exacerbated mitochondrial dysfunction and reduces expression of mitochondrial biogenesis-associated genes including PGC1α in denervated muscle. Myonectin supplementation attenuates denervation-induced muscle atrophy via activation of AMPK. Myonectin also reverses DEX-induced atrophy of cultured myotubes through the AMPK/PGC1α signaling. Furthermore, myonectin treatment suppresses muscle atrophy in senescence-accelerated mouse prone (SAMP) 8 mouse model of accelerated aging or mdx mouse model of Duchenne muscular dystrophy. These data indicate that myonectin can ameliorate skeletal muscle dysfunction through AMPK/PGC1α-dependent mechanisms, suggesting that myonectin could represent a therapeutic target of muscle atrophy.

An integrative profiling of metabolome and transcriptome in the plasma and skeletal muscle following an exercise intervention in diet-induced obese mice

Exercise intervention at the early stage of type 2 diabetes mellitus (T2DM) can aid in the maintenance of blood glucose homeostasis and prevent the development of macrovascular and microvascular complications. However, the exercise-regulated pathways that prevent the development of T2DM remain largely unclear. In this study, two forms of exercise intervention, treadmill training and voluntary wheel running, were conducted for high-fat diet (HFD)-induced obese mice. We observed that both forms of exercise intervention alleviated HFD-induced insulin resistance and glucose intolerance. Skeletal muscle is recognized as the primary site for postprandial glucose uptake and for responsive alteration beyond exercise training. Metabolomic profiling of the plasma and skeletal muscle in Chow, HFD, and HFD-exercise groups revealed robust alterations in metabolic pathways by exercise intervention in both cases. Overlapping analysis identified nine metabolites, including beta-alanine, leucine, valine, and tryptophan, which were reversed by exercise treatment in both the plasma and skeletal muscle. Transcriptomic analysis of gene expression profiles in the skeletal muscle revealed several key pathways involved in the beneficial effects of exercise on metabolic homeostasis. In addition, integrative transcriptomic and metabolomic analyses uncovered strong correlations between the concentrations of bioactive metabolites and the expression levels of genes involved in energy metabolism, insulin sensitivity, and immune response in the skeletal muscle. This work established two models of exercise intervention in obese mice and provided mechanistic insights into the beneficial effects of exercise intervention on systemic energy homeostasis.

Multitissue responses to exercise: a MoTrPAC feasibility study

We assessed the feasibility of the Molecular Transducers of Physical Activity Consortium (MoTrPAC) human adult clinical exercise protocols, while also documenting select cardiovascular, metabolic, and molecular responses to these protocols. After phenotyping and familiarization sessions, 20 subjects (25 ± 2 yr, 12 M, 8 W) completed an endurance exercise bout (n = 8, 40 min cycling at 70% V̇o2max), a resistance exercise bout (n = 6, ∼45 min, 3 sets of ∼10 repetition maximum, 8 exercises), or a resting control period (n = 6, 40 min rest). Blood samples were taken before, during, and after (10 min, 2 h, and 3.5 h) exercise or rest for levels of catecholamines, cortisol, glucagon, insulin, glucose, free fatty acids, and lactate. Heart rate was recorded throughout exercise (or rest). Skeletal muscle (vastus lateralis) and adipose (periumbilical) biopsies were taken before and ∼4 h following exercise or rest for mRNA levels of genes related to energy metabolism, growth, angiogenesis, and circadian processes. Coordination of the timing of procedural components (e.g., local anesthetic delivery, biopsy incisions, tumescent delivery, intravenous line flushes, sample collection and processing, exercise transitions, and team dynamics) was reasonable to orchestrate while considering subject burden and scientific objectives. The cardiovascular and metabolic alterations reflected a dynamic and unique response to endurance and resistance exercise, whereas skeletal muscle was transcriptionally more responsive than adipose 4 h postexercise. In summary, the current report provides the first evidence of protocol execution and feasibility of key components of the MoTrPAC human adult clinical exercise protocols. Scientists should consider designing exercise studies in various populations to interface with the MoTrPAC protocols and DataHub.NEW & NOTEWORTHY This study highlights the feasibility of key aspects of the MoTrPAC adult human clinical protocols. This initial preview of what can be expected from acute exercise trial data from MoTrPAC provides an impetus for scientists to design exercise studies to interlace with the rich phenotypic and -omics data that will populate the MoTrPAC DataHub at the completion of the parent protocol.

Aerobic Exercise Training Improves Calcium Handling and Cardiac Function in Rats with Heart Failure Resulting from Aortic Stenosis

Aerobic exercise training (AET) has been used to manage heart disease. AET may totally or partially restore the activity and/or expression of proteins that regulate calcium (Ca2+) handling, optimize intracellular Ca2+ flow, and attenuate cardiac functional impairment in failing hearts. However, the literature presents conflicting data regarding the effects of AET on Ca2+ transit and cardiac function in rats with heart failure resulting from aortic stenosis (AoS). This study aimed to evaluate the impact of AET on Ca2+ handling and cardiac function in rats with heart failure due to AoS. Wistar rats were distributed into two groups: control (Sham; n = 61) and aortic stenosis (AoS; n = 44). After 18 weeks, the groups were redistributed into: non-exposed to exercise training (Sham, n = 28 and AoS, n = 22) and trained (Sham-ET, n = 33 and AoS-ET, n = 22) for 10 weeks. Treadmill exercise training was performed with a velocity equivalent to the lactate threshold. The cardiac function was analyzed by echocardiogram, isolated papillary muscles, and isolated cardiomyocytes. During assays of isolated papillary muscles and isolated cardiomyocytes, the Ca2+ concentrations were evaluated. The expression of regulatory proteins for diastolic Ca2+ was assessed via Western Blot. AET attenuated the diastolic dysfunction and improved the systolic function. AoS-ET animals presented an enhanced response to post-rest contraction and SERCA2a and L-type Ca2+ channel blockage compared to the AoS. Furthermore, AET was able to improve aspects of the mechanical function and the responsiveness of the myofilaments to the Ca2+ of the AoS-ET animals. AoS animals presented an alteration in the protein expression of SERCA2a and NCX, and AET restored SERCA2a and NCX levels near normal values. Therefore, AET increased SERCA2a activity and myofilament responsiveness to Ca2+ and improved the cellular Ca2+ influx mechanism, attenuating cardiac dysfunction at cellular, tissue, and chamber levels in animals with AoS and heart failure.

Aerobic adaptations following two iso-effort training programs: an intense continuous and a high-intensity interval

The intensity of the training stimulus and the effort exerted (regarded as an index of internal load) to complete an exercise session are driving forces for physiological processes and long-term training adaptations. This study compared the aerobic adaptations following two iso-effort, ratings of perceived exertion (RPE)-based training programs, an intense continuous (CON) and a high-intensity interval (INT). Young adults were assigned to a CON (n = 11) or an INT (n = 13) training group to perform 14 training sessions within 6 weeks. The INT group performed running bouts (9.3 ± 4.4 repetitions) at 90% of peak treadmill velocity (PTV) with bout duration equal to 1/4 of time to exhaustion at this speed (134.2 ± 27.9 s). The CONT group ran (1185.0 ± 487.6 s) at a speed corresponding to -2.5% of critical velocity (CV; 80.1% ± 3.0% of PTV). Training-sessions were executed until RPE attained 17 on the Borg scale. VO2max, PTV, CV, lactate threshold velocity (vLT), and running economy were assessed pre-, mid-, and post-training. Both CONT and INT methods increased (p < 0.05) VO2max (INT: 57.7 ± 8.1-61.41 ± 9.2; CONT: 58.1 ± 7.5-61.1 ± 6.3 mL kg-1 min-1), PTV (INT: 14.6 ± 1.8-15.7 ± 2.1; CONT: 15.0 ± 1.7-15.7 ± 1.8 km h-1), CV (INT: 11.8 ± 1.4-12.8 ± 1.8; CONT: 12.2 ± 1.6-12.9 ± 1.7 km h-1), and vLT (INT: 9.77 ± 1.1-10.8 ± 1.4; CONT: 10.4 ± 1.4-11.0 ± 1.8 km h-1) with no differences (p > 0.05) between them; running economy remained unchanged. The continuous training method, when matched for effort and executed at relatively high intensity at the upper boundaries of the heavy-intensity domain (∼80% of PTV), confers comparable aerobic adaptations to those attained after a high-intensity interval protocol following a short-term training period.

Plasma Proteomic Kinetics in Response to Acute Exercise

Regular exercise has many favorable effects on human health, which may be mediated in part by the release of circulating bioactive factors during each bout of exercise. Limited data exist regarding the kinetic responses of plasma proteins during and after acute exercise. Proteomic profiling of 4163 proteins was performed using a large-scale, affinity-based platform in 75 middle-aged adults who were referred for treadmill exercise stress testing. Plasma proteins were quantified at baseline, peak exercise, and 1-h postexercise, and those with significant changes at both exercise timepoints were further examined for their associations with cardiometabolic traits and change with aerobic exercise training in the Health, Risk Factors, Exercise Training and Genetics Family Study, a 20-week exercise intervention study. A total of 765 proteins changed (false discovery rate < 0.05) at peak exercise compared to baseline, and 128 proteins changed (false discovery rate < 0.05) at 1-h postexercise. The 56 proteins that changed at both timepoints included midkine, brain-derived neurotrophic factor, metalloproteinase inhibitor 4, and coiled-coil domain-containing protein 126 and were enriched for secreted proteins. The majority had concordant direction of change at both timepoints. Across all proteins assayed, gene set enrichment analysis showed increased abundance of coagulation-related proteins at 1-h postexercise. Forty-five proteins were associated with at least one measure of adiposity, lipids, glucose homeostasis, or cardiorespiratory fitness in Health, Risk Factors, Exercise Training and Genetics Family Study, and 20 proteins changed with aerobic exercise training. We identified hundreds of novel proteins that change during acute exercise, most of which resolved by 1 h into recovery. Proteins with sustained changes during exercise and recovery may be of particular interest as circulating biomarkers and pathways for further investigation in cardiometabolic diseases. These data will contribute to a biochemical roadmap of acute exercise that will be publicly available for the entire scientific community.

Novel whole blood transcriptome signatures of changes in maximal aerobic capacity in response to endurance exercise training in healthy women

Maximal aerobic exercise capacity [maximal oxygen consumption (V̇o2max)] is one of the strongest predictors of morbidity and mortality. Aerobic exercise training can increase V̇o2max, but inter-individual variability is marked and unexplained physiologically. The mechanisms underlying this variability have major clinical implications for extending human healthspan. Here, we report a novel transcriptome signature related to ΔV̇o2max with exercise training detected in whole blood RNA. We used RNA-Seq to characterize transcriptomic signatures of ΔV̇o2max in healthy women who completed a 16-wk randomized controlled trial comparing supervised, higher versus lower aerobic exercise training volume and intensity (4 training groups, fully crossed). We found significant baseline gene expression differences in subjects who responded to aerobic exercise training with robust versus little/no ΔV̇o2max, and differentially expressed genes/transcripts were mostly related to inflammatory signaling and mitochondrial function/protein translation. Baseline gene expression signatures associated with robust versus little/no ΔV̇o2max were also modulated by exercise training in a dose-dependent manner, and they predicted ΔV̇o2max in this and a separate dataset. Collectively, our data demonstrate the potential utility of using whole blood transcriptomics to study the biology of inter-individual variability in responsiveness to the same exercise training stimulus.

Association of the ACTN3 Gene's Single-Nucleotide Variant Rs1815739 (R577X) with Sports Qualification and Competitive Distance in Caucasian Athletes of the Southern Urals

An elite athlete's status is associated with a multifactorial phenotype depending on many environmental and genetic factors. Of course, the peculiarities of the structure and function of skeletal muscles are among the most important characteristics in the context of athletic performance.

PURPOSE

To study the associations of SNV rs1815739 (C577T or R577X) allelic variants and genotypes of the ACTN3 gene with qualification and competitive distance in Caucasian athletes of the Southern Urals.

METHODS

A total of 126 people of European origin who lived in the Southern Urals region took part in this study. The first group included 76 cyclical sports athletes (speed skating, running disciplines in track-and-field): SD (short distances) subgroup-40 sprinters (mean 22.1 ± 2.4 y.o.); LD (long distances) subgroup-36 stayer athletes (mean 22.6 ± 2.7 y.o.). The control group consisted of 50 healthy nonathletes (mean 21.4 ± 2.7 y.o.). We used the Step One Real-Time PCR System (Applied Biosystems, USA) device for real-time polymerase chain reaction.

RESULTS

The frequency of the major allele R was significantly higher in the SD subgroup compared to the control subgroup (80% vs. 64%; p-value = 0.04). However, we did not find any significant differences in the frequency of the R allele between the athletes of the SD subgroup and the LD subgroup (80% vs. 59.7%, respectively; p-value > 0.05). The frequency of the X allele was lower in the SD subgroup compared to the LD subgroup (20% vs. 40.3%; p-value = 0.03). The frequency of homozygous genotype RR was higher in the SD subgroup compared to the control group (60.0% vs. 34%; p-value = 0.04). The R allele was associated with competitive distance in the SD group athletes compared to those of the control group (OR = 2.45 (95% CI: 1.02-5.87)). The X allele was associated with competitive distance in the LD subgroup compared to the SD subgroup (OR = 2.7 (95% CI: 1.09-6.68)).

CONCLUSIONS

Multiplicative and additive inheritance models demonstrated that high athletic performance for sprinters was associated with the homozygous dominant genotype 577RR in cyclical sports athletes of Caucasian origin in the Southern Urals.

Baf155 regulates skeletal muscle metabolism via HIF-1a signaling

During exercise, skeletal muscle is exposed to a low oxygen condition, hypoxia. Under hypoxia, the transcription factor hypoxia-inducible factor-1α (HIF-1α) is stabilized and induces expressions of its target genes regulating glycolytic metabolism. Here, using a skeletal muscle-specific gene ablation mouse model, we show that Brg1/Brm-associated factor 155 (Baf155), a core subunit of the switch/sucrose non-fermentable (SWI/SNF) complex, is essential for HIF-1α signaling in skeletal muscle. Muscle-specific ablation of Baf155 increases oxidative metabolism by reducing HIF-1α function, which accompanies the decreased lactate production during exercise. Furthermore, the augmented oxidation leads to high intramuscular adenosine triphosphate (ATP) level and results in the enhancement of endurance exercise capacity. Mechanistically, our chromatin immunoprecipitation (ChIP) analysis reveals that Baf155 modulates DNA-binding activity of HIF-1α to the promoters of its target genes. In addition, for this regulatory function, Baf155 requires a phospho-signal transducer and activator of transcription 3 (pSTAT3), which forms a coactivator complex with HIF-1α, to activate HIF-1α signaling. Our findings reveal the crucial role of Baf155 in energy metabolism of skeletal muscle and the interaction between Baf155 and hypoxia signaling.

Operational Modal Analysis of Near-Infrared Spectroscopy Measure of 2-Month Exercise Intervention Effects in Sedentary Older Adults with Diabetes and Cognitive Impairment

The Global Burden of Disease Study (GBD 2019 Diseases and Injuries Collaborators) found that diabetes significantly increases the overall burden of disease, leading to a 24.4% increase in disability-adjusted life years. Persistently high glucose levels in diabetes can cause structural and functional changes in proteins throughout the body, and the accumulation of protein aggregates in the brain that can be associated with the progression of Alzheimer's Disease (AD). To address this burden in type 2 diabetes mellitus (T2DM), a combined aerobic and resistance exercise program was developed based on the recommendations of the American College of Sports Medicine. The prospectively registered clinical trials (NCT04626453, NCT04812288) involved two groups: an Intervention group of older sedentary adults with T2DM and a Control group of healthy older adults who could be either active or sedentary. The completion rate for the 2-month exercise program was high, with participants completing on an average of 89.14% of the exercise sessions. This indicated that the program was practical, feasible, and well tolerated, even during the COVID-19 pandemic. It was also safe, requiring minimal equipment and no supervision. Our paper presents portable near-infrared spectroscopy (NIRS) based measures that showed muscle oxygen saturation (SmO2), i.e., the balance between oxygen delivery and oxygen consumption in muscle, drop during bilateral heel rise task (BHR) and the 6 min walk task (6MWT) significantly (p < 0.05) changed at the post-intervention follow-up from the pre-intervention baseline in the T2DM Intervention group participants. Moreover, post-intervention changes from pre-intervention baseline for the prefrontal activation (both oxyhemoglobin and deoxyhemoglobin) showed statistically significant (p < 0.05, q < 0.05) effect at the right superior frontal gyrus, dorsolateral, during the Mini-Cog task. Here, operational modal analysis provided further insights into the 2-month exercise intervention effects on the very-low-frequency oscillations (<0.05 Hz) during the Mini-Cog task that improved post-intervention in the sedentary T2DM Intervention group from their pre-intervention baseline when compared to active healthy Control group. Then, the 6MWT distance significantly (p < 0.01) improved in the T2DM Intervention group at post-intervention follow-up from pre-intervention baseline that showed improved aerobic capacity and endurance. Our portable NIRS based measures have practical implications at the point of care for the therapists as they can monitor muscle and brain oxygenation changes during physical and cognitive tests to prescribe personalized physical exercise doses without triggering individual stress response, thereby, enhancing vascular health in T2DM.

Transient changes to metabolic homeostasis initiate mitochondrial adaptation to endurance exercise

Endurance exercise is well established to increase mitochondrial content and function in skeletal muscle, a process termed mitochondrial biogenesis. Current understanding is that exercise initiates skeletal muscle mitochondrial remodeling via modulation of cellular nutrient, energetic and contractile stress pathways. These subtle changes in the cellular milieu are sensed by numerous transduction pathways that serve to initiate and coordinate an increase in mitochondrial gene transcription and translation. The result of these acute signaling events is the promotion of growth and assembly of mitochondria, coupled to a greater capacity for aerobic ATP provision in skeletal muscle. The aim of this review is to highlight the acute metabolic events induced by endurance exercise and the subsequent molecular pathways that sense this transient change in cellular homeostasis to drive mitochondrial adaptation and remodeling.

Impacts of altered exercise volume, intensity, and duration on the activation of AMPK and CaMKII and increases in PGC-1α mRNA

The purpose of this review is to explore and discuss the impacts of augmented training volume, intensity, and duration on the phosphorylation/activation of key signaling protein - AMPK, CaMKII and PGC-1α - involved in the initiation of mitochondrial biogenesis. Specifically, we explore the impacts of augmented exercise protocols on AMP/ADP and Ca²⁺ signaling and changes in post exercise PGC - 1α gene expression. Although AMP/ADP concentrations appear to increase with increasing intensity and during extended durations of higher intensity exercise AMPK activation results are varied with some results supporting and intensity/duration effect and others not. Similarly, CaMKII activation and signaling results following exercise of different intensities and durations are inconsistent. The PGC-1α literature is equally inconsistent with only some studies demonstrating an effect of intensity on post exercise mRNA expression. We present a novel meta-analysis that suggests that the inconsistency in the PGC-1α literature may be due to sample size and statistical power limitations owing to the effect of intensity on PGC-1α expression being small. There is little data available regarding the impact of exercise duration on PGC-1α expression. We highlight the need for future well designed, adequately statistically powered, studies to clarify our understanding of the effects of volume, intensity, and duration on the induction of mitochondrial biogenesis by exercise.

Targeted Metabolomics in High Performance Sports: Differences between the Resting Metabolic Profile of Endurance- and Strength-Trained Athletes in Comparison with Sedentary Subjects over the Course of a Training Year

Little is known about the metabolic differences between endurance and strength athletes in comparison with sedentary subjects under controlled conditions and about variation of the metabolome throughout one year. We hypothesized that (1) the resting metabolic profile differs between sedentary subjects and athletes and between perennially endurance- and strength-trained athletes and (2) varies throughout one year of training. We performed quantitative, targeted metabolomics (Biocrates MxP^® Quant 500, Biocrates Life Sciences AG, Innsbruck, Austria) in plasma samples at rest in three groups of male adults, 12 strength-trained (weightlifters, 20 ± 3 years), 10 endurance-trained athletes (runners, 24 ± 3 years), and 12 sedentary subjects (25 ± 4 years) at the end of three training phases (regeneration, preparation, and competition) within one training year. Performance and anthropometric data showed significant (p < 0.05) differences between the groups. Metabolomic analysis revealed different resting metabolic profiles between the groups with acetylcarnitines, di- and triacylglycerols, and glycerophospho- and sphingolipids, as well as several amino acids as the most robust metabolites. Furthermore, we observed changes in free carnitine and 3-methylhistidine in strength-trained athletes throughout the training year. Regular endurance or strength training induces changes in the concentration of several metabolites associated with adaptations of the mitochondrial energy and glycolytic metabolism with concomitant changes in amino acid metabolism and cell signaling.

Numerous Trigger-like Interactions of Kinases/Protein Phosphatases in Human Skeletal Muscles Can Underlie Transient Processes in Activation of Signaling Pathways during Exercise

Optimizing physical training regimens to increase muscle aerobic capacity requires an understanding of the internal processes that occur during exercise that initiate subsequent adaptation. During exercise, muscle cells undergo a series of metabolic events that trigger downstream signaling pathways and induce the expression of many genes in working muscle fibers. There are a number of studies that show the dependence of changes in the activity of AMP-activated protein kinase (AMPK), one of the mediators of cellular signaling pathways, on the duration and intensity of single exercises. The activity of various AMPK isoforms can change in different directions, increasing for some isoforms and decreasing for others, depending on the intensity and duration of the load. This review summarizes research data on changes in the activity of AMPK, Ca²⁺/calmodulin-dependent protein kinase II (CaMKII), and other components of the signaling pathways in skeletal muscles during exercise. Based on these data, we hypothesize that the observed changes in AMPK activity may be largely related to metabolic and signaling transients rather than exercise intensity per se. Probably, the main events associated with these transients occur at the beginning of the exercise in a time window of about 1-10 min. We hypothesize that these transients may be partly due to putative trigger-like kinase/protein phosphatase interactions regulated by feedback loops. In addition, numerous dynamically changing factors, such as [Ca²⁺], metabolite concentration, and reactive oxygen and nitrogen species (RONS), can shift the switching thresholds and change the states of these triggers, thereby affecting the activity of kinases (in particular, AMPK and CaMKII) and phosphatases. The review considers the putative molecular mechanisms underlying trigger-like interactions. The proposed hypothesis allows for a reinterpretation of the experimental data available in the literature as well as the generation of ideas to optimize future training regimens.

Estrogen-related Receptor Signaling in Skeletal Muscle Fitness

Skeletal muscle is a highly plastic tissue that can alter its metabolic and contractile features, as well as regenerative potential in response to exercise and other conditions. Multiple signaling factors including metabolites, kinases, receptors, and transcriptional factors have been studied in the regulation of skeletal muscle plasticity. Recently, estrogen-related receptors (ERRs) have emerged as a critical transcriptional hub in control of skeletal muscle homeostasis. ERRα and ERRγ - the two highly expressed ERR sub-types in the muscle respond to various extracellular cues such as exercise, hypoxia, fasting and dietary factors, in turn regulating gene expression in the skeletal muscle. On the other hand, conditions such as diabetes and muscular dystrophy suppress expression of ERRs in the skeletal muscle, likely contributing to disease progression. We highlight key functions of ERRs in the skeletal muscle including the regulation of fiber type, mitochondrial metabolism, vascularization, and regeneration. We also describe how ERRs are regulated in the skeletal muscle, and their interaction with important muscle regulators (e. g. AMPK and PGCs). Finally, we identify critical gaps in our understanding of ERR signaling in the skeletal muscle, and suggest future areas of investigation to advance ERRs as potential targets for function promoting therapeutics in muscle diseases.

High-intensity interval training in the form of isometric contraction improves fatigue resistance in dystrophin-deficient muscle

Duchenne muscular dystrophy is a genetic muscle-wasting disorder characterized by progressive muscle weakness and easy fatigability. Here we examined whether high-intensity interval training (HIIT) in the form of isometric contraction improves fatigue resistance in skeletal muscle from dystrophin-deficient mdx52 mice. Isometric HIIT was performed on plantar flexor muscles in vivo with supramaximal electrical stimulation every other day for 4 weeks (a total of 15 sessions). In the non-trained contralateral gastrocnemius muscle from mdx52 mice, the decreased fatigue resistance was associated with a reduction in the amount of peroxisome proliferator-activated receptor γ coactivator 1-α, citrate synthase activity, mitochondrial respiratory complex II, LC3B-II/I ratio, and mitophagy-related gene expression (i.e. Pink1, parkin, Bnip3 and Bcl2l13) as well as an increase in the phosphorylation levels of Src Tyr416 and Akt Ser473, the amount of p62, and the percentage of Evans Blue dye-positive area. Isometric HIIT restored all these alterations and markedly improved fatigue resistance in mdx52 muscles. Moreover, an acute bout of HIIT increased the phosphorylation levels of AMP-activated protein kinase (AMPK) Thr172, acetyl CoA carboxylase Ser79, unc-51-like autophagy activating kinase 1 (Ulk1) Ser555, and dynamin-related protein 1 (Drp1) Ser616 in mdx52 muscles. Thus, our data show that HIIT with isometric contractions significantly mitigates histological signs of pathology and improves fatigue resistance in dystrophin-deficient muscles. These beneficial effects can be explained by the restoration of mitochondrial function via AMPK-dependent induction of the mitophagy programme and de novo mitochondrial biogenesis. KEY POINTS: Skeletal muscle fatigue is often associated with Duchenne muscular dystrophy (DMD) and leads to an inability to perform daily tasks, profoundly decreasing quality of life. We examined the effect of high-intensity interval training (HIIT) in the form of isometric contraction on fatigue resistance in skeletal muscle from the mdx52 mouse model of DMD. Isometric HIIT counteracted the reduced fatigue resistance as well as dystrophic changes in skeletal muscle of mdx52 mice. This beneficial effect could be explained by the restoration of mitochondrial function via AMP-activated protein kinase-dependent mitochondrial biogenesis and the induction of the mitophagy programme in the dystrophic muscles.

Estimation of maximal lactate steady state using the sweat lactate sensor

A simple, non-invasive algorithm for maximal lactate steady state (MLSS) assessment has not been developed. We examined whether MLSS can be estimated from the sweat lactate threshold (sLT) using a novel sweat lactate sensor for healthy adults, with consideration of their exercise habits. Fifteen adults representing diverse fitness levels were recruited. Participants with/without exercise habits were defined as trained/untrained, respectively. Constant-load testing for 30 min at 110%, 115%, 120%, and 125% of sLT intensity was performed to determine MLSS. The tissue oxygenation index (TOI) of the thigh was also monitored. MLSS was not fully estimated from sLT, with 110%, 115%, 120%, and 125% of sLT in one, four, three, and seven participants, respectively. The MLSS based on sLT was higher in the trained group as compared to the untrained group. A total of 80% of trained participants had an MLSS of 120% or higher, while 75% of untrained participants had an MLSS of 115% or lower based on sLT. Furthermore, compared to untrained participants, trained participants continued constant-load exercise even if their TOI decreased below the resting baseline (P < 0.01). MLSS was successfully estimated using sLT, with 120% or more in trained participants and 115% or less in untrained participants. This suggests that trained individuals can continue exercising despite decreases in oxygen saturation in lower extremity skeletal muscles.

Exercise ameliorates chronic inflammatory response induced by high-fat diet via Sestrin2 in an Nrf2-dependent manner

Chronic inflammation is a major contributor to the development of metabolic disorders and is commonly seen in studies of diet-induced obesity in humans and rodents. Exercise has been shown to have anti-inflammatory properties, though the exact mechanisms are still not fully understood. Sestrins and Nrf2 are of interest to researchers as they are known to protect against inflammation and oxidative stress. In this study, we aim to explore the interconnection between Sestrin2 (SESN2) and Nrf2 and their roles in exercise benefits on chronic inflammation. Our data showed that SESN2 knockout aggravated the abnormalities of body weight, fat mass, and serum lipid that were induced by a high-fat diet (HFD), and a concomitant increase of TNF-α, IL-1β and IL-6 in both serum and skeletal muscle. Notably, exercise was found to reverse these changes, and SESN2 was found to be necessary for exercise to reduce the inflammatory response in skeletal muscles, though not in serum. Immunoprecipitation and bioinformatics prediction experiments further revealed that SESN2 directly binds to Nrf2, indicating a protein-protein interaction between the two. Furthermore, our data demonstrated that SESN2 protein is necessary for exercise-induced effects on Nrf2 pathway in HFD-fed mice, and Nrf2 protein is necessary to enable SESN2 to reduce the inflammation caused by palmitic acid (PA)+ oleic acid (OA) treatment in vitro. Our findings indicate that exercise mitigates chronic inflammation induced by HFD through SESN2 in an Nrf2-dependent manner. Our study reveals a novel molecular mechanism whereby the SESN2/Nrf2 pathway mediates the positive impact of exercise on chronic inflammation.

Effects of Maternal Exercise Modes on Glucose and Lipid Metabolism in Offspring Stem Cells

CONTEXT

Maternal exercise positively influences pregnancy outcomes and metabolic health in progeny; however, data regarding the effects of different modes of prenatal exercise on offspring metabolic phenotype is lacking.

OBJECTIVE

To elucidate the effects of different modes of maternal exercise on offspring umbilical cord derived mesenchymal stem cell (MSC) metabolism.

DESIGN

Randomized controlled trial.

SETTING

Clinical research facility.

PATIENTS

Healthy females between 18 and 35 years of age and <16 weeks' gestation.

INTERVENTION

Women were randomized to either 150 minutes of moderate intensity aerobic, resistance (RE), or combination exercise per week or to a non-exercising control.

MAIN OUTCOME MEASURES

At delivery, MSCs were isolated from the umbilical cords. MSC glucose and fatty acid(s) metabolism was assessed using radiolabeled substrates.

RESULTS

MSCs from offspring of all the exercising women demonstrated greater partitioning of oleate (P ≤ 0.05) and palmitate (P ≤ 0.05) toward complete oxidation relative to non-exercisers. MSCs from offspring of all exercising mothers also had lower rates of incomplete fatty acid oxidation (P ≤ 0.05), which was related to infant adiposity at 1 month of age. MSCs from all exercising groups exhibited higher insulin-stimulated glycogen synthesis rates (P ≤ 0.05), with RE having the largest effect (P ≤ 0.05). RE also had the greatest effect on MSC glucose oxidation rates (P ≤ 0.05) and partitioning toward complete oxidation (P ≤ 0.05).

CONCLUSION

Our data demonstrates that maternal exercise enhances glucose and lipid metabolism of offspring MSCs. Improvements in MSC glucose metabolism seem to be the greatest with maternal RE. Clinical Trial: ClinicalTrials.gov Identifier: NCT03838146.

Combined exercise and nutrition intervention for older women with spinal sarcopenia: an open-label single-arm trial

PURPOSE

Spinal sarcopenia is a multifactorial disorder associated with atrophy and fatty changes in paraspinal muscles. Interventional studies for spinal sarcopenia are limited. We aimed to evaluate the effectiveness of a combined exercise and nutrition intervention for the treatment of spinal sarcopenia.

METHODS

35 community-dwelling older women diagnosed with spinal sarcopenia in a previous cohort study were included. The 12-week combined intervention consisted of back extensor strengthening exercises and protein supplementation. The following outcomes were measured at baseline (week 0), after the intervention (week 12), and follow-up (week 24): conventional variables of sarcopenia (appendicular skeletal muscle mass, handgrip strength, 6-meter gait speed, and short physical performance battery); lumbar extensor muscle mass; lumbar extensor muscle volume and signal intensity; back extensor isokinetic strength; and back performance scale. We used the intention-to-treat analysis method, and repeated measures analysis of variance was used to analyze the data.

RESULTS

Of the total 35 potential participants, 26 older women participated in the study (mean age 72.5 ± 4.0 years old). After 12 weeks of combined exercise and nutrition intervention, there were no changes in the appendicular skeletal muscle mass, lumbar extensor muscle mass, volume, or signal intensity. Handgrip strength and back extensor isokinetic strength did not change significantly. Short physical performance battery significantly increased (P = 0.042) from 11.46 ± 0.86 to 11.77 ± 0.53 at week 12 and 11.82 ± 0.40 at week 24. The back performance scale sum score also significantly improved (P = 0.034) from 2.68 ± 1.81 to 1.95 ± 1.21 at week 12 and 2.09 ± 1.34 at week 24.

CONCLUSION

The combined exercise and nutrition intervention for community-dwelling older women with spinal sarcopenia could be feasible and helpful in improving the physical performance as well as back performance.

Resistance exercise: a mighty tool that adapts, destroys, rebuilds and modulates the molecular and structural environment of skeletal muscle

PURPOSE

Skeletal muscle regulates health and performance by maintaining or increasing strength and muscle mass. Although the molecular mechanisms in response to resistance exercise (RE) significantly target the activation of protein synthesis, a plethora of other mechanisms and structures must be involved in orchestrating the communication, repair, and restoration of homeostasis after RE stimulation. In practice, RE can be modulated by variations in intensity, continuity and volume, which affect molecular responses and skeletal muscle adaptation. Knowledge of these aspects is important with respect to planning of training programs and assessing the impact of RE training on skeletal muscle.

METHODS

In this narrative review, we introduce general aspects of skeletal muscle substructures that adapt in response to RE. We further highlighted the molecular mechanisms that control human skeletal muscle anabolism, degradation, repair and memory in response to acute and repeated RE and linked these aspects to major training variables.

RESULTS

Although RE is a key stimulus for the activation of skeletal muscle anabolism, it also induces myofibrillar damage. Nevertheless, to increase muscle mass accompanied by a corresponding adaptation of the essential substructures of the sarcomeric environment, RE must be continuously repeated. This requires the permanent engagement of molecular mechanisms that re-establish skeletal muscle integrity after each RE-induced muscle damage.

CONCLUSION

Various molecular regulators coordinately control the adaptation of skeletal muscle after acute and repeated RE and expand their actions far beyond muscle growth. Variations of key resistance training variables likely affect these mechanisms without affecting muscle growth.

Exercise and ageing impact the kynurenine/tryptophan pathway and acylcarnitine metabolite pools in skeletal muscle of older adults

Exercise-induced perturbation of skeletal muscle metabolites is a probable mediator of long-term health benefits in older adults. Although specific metabolites have been identified to be impacted by age, physical activity and exercise, the depth of coverage of the muscle metabolome is still limited. Here, we investigated resting and exercise-induced metabolite distribution in muscle from well-phenotyped older adults who were active or sedentary, and a group of active young adults. Percutaneous biopsies of the vastus lateralis were obtained before, immediately after and 3 h following a bout of endurance cycling. Metabolite profile in muscle biopsies was determined by tandem mass spectrometry. Mitochondrial energetics in permeabilized fibre bundles was assessed by high resolution respirometry and fibre type proportion was assessed by immunohistology. We found that metabolites of the kynurenine/tryptophan pathway were impacted by age and activity. Specifically, kynurenine was elevated in muscle from older adults, whereas downstream metabolites of kynurenine (kynurenic acid and NAD+ ) were elevated in muscle from active adults and associated with cardiorespiratory fitness and muscle oxidative capacity. Acylcarnitines, a potential marker of impaired metabolic health, were elevated in muscle from physically active participants. Surprisingly, despite baseline group difference, acute exercise-induced alterations in whole-body substrate utilization, as well as muscle acylcarnitines and ketone bodies, were remarkably similar between groups. Our data identified novel muscle metabolite signatures that associate with the healthy ageing phenotype provoked by physical activity and reveal that the metabolic responsiveness of muscle to acute endurance exercise is retained [NB]:AUTHOR: Please ensure that the appropriate material has been provide for Table S2, as well as for Figures S1 to S7, as also cited in the text with age regardless of activity levels. KEY POINTS: Kynurenine/tryptophan pathway metabolites were impacted by age and physical activity in human muscle, with kynurenine elevated in older muscle, whereas downstream products kynurenic acid and NAD+ were elevated in exercise-trained muscle regardless of age. Acylcarnitines, a marker of impaired metabolic health when heightened in circulation, were elevated in exercise-trained muscle of young and older adults, suggesting that muscle act as a metabolic sink to reduce the circulating acylcarnitines observed with unhealthy ageing. Despite the phenotypic differences, the exercise-induced response of various muscle metabolite pools, including acylcarnitine and ketone bodies, was similar amongst the groups, suggesting that older adults can achieve the metabolic benefits of exercise seen in young counterparts.

Exercise, exerkines, and cardiometabolic health: from individual players to a team sport

Exercise confers numerous salutary effects that extend beyond individual organ systems to provide systemic health benefits. Here, we discuss the role of exercise in cardiovascular health. We summarize major findings from human exercise studies in cardiometabolic disease. We next describe our current understanding of cardiac-specific substrate metabolism that occurs with acute exercise and in response to exercise training. We subsequently focus on exercise-stimulated circulating biochemicals ("exerkines") as a paradigm for understanding the global health circuitry of exercise, and discuss important concepts in this emerging field before highlighting exerkines relevant in cardiovascular health and disease. Finally, this Review identifies gaps that remain in the field of exercise science and opportunities that exist to translate biologic insights into human health improvement.

The effects of physical exercise therapy on weight control: its regulation of adipocyte physiology and metabolic capacity

Factors associated with increased body mass, including dyslipidemia, hypertension, insulin resistance, vascular endothelial dysfunction and sleep disorders, may contribute to the exacerbation of cardiovascular disease. These health problems associated with obesity are caused by accumulated metabolism and physical and emotional stress. Lifestyle, especially exercise, is a major therapeutic strategy for the treatment and management of obesity-induced metabolic problems. Metabolic disease often co-occurs with abdominal obesity. Exercise is necessary for the treatment of obesity, diabetes and cardiovascular disease. A potential benefit of exercise is to promote fat burning and energy use increases both during exercise itself and in the post-exercise period. Exercise suppresses basal metabolic rate and also has many health benefits. Why should we exercise to lose weight? Does physical activity help lower blood pressure, blood cholesterol, and blood sugar? In this article, we review the positive effects of physical exercise on weight maintenance and weight loss, and the effectiveness of physical exercise on the treatment and prevention of metabolic syndrome.

Single-cell RNA sequencing in skeletal muscle developmental biology

Skeletal muscle is the most extensive tissue in mammals, and they perform several functions; it is derived from paraxial mesodermal somites and undergoes hyperplasia and hypertrophy to form multinucleated, contractile, and functional muscle fibers. Skeletal muscle is a complex heterogeneous tissue composed of various cell types that establish communication strategies to exchange biological information; therefore, characterizing the cellular heterogeneity and transcriptional signatures of skeletal muscle is central to understanding its ontogeny's details. Studies of skeletal myogenesis have focused primarily on myogenic cells' proliferation, differentiation, migration, and fusion and ignored the intricate network of cells with specific biological functions. The rapid development of single-cell sequencing technology has recently enabled the exploration of skeletal muscle cell types and molecular events during development. This review summarizes the progress in single-cell RNA sequencing and its applications in skeletal myogenesis, which will provide insights into skeletal muscle pathophysiology.

Conserved multi-tissue transcriptomic adaptations to exercise training in humans and mice

Physical activity is associated with beneficial adaptations in human and rodent metabolism. We studied over 50 complex traits before and after exercise intervention in middle-aged men and a panel of 100 diverse strains of female mice. Candidate gene analyses in three brain regions, muscle, liver, heart, and adipose tissue of mice indicate genetic drivers of clinically relevant traits, including volitional exercise volume, muscle metabolism, adiposity, and hepatic lipids. Although ∼33% of genes differentially expressed in skeletal muscle following the exercise intervention are similar in mice and humans independent of BMI, responsiveness of adipose tissue to exercise-stimulated weight loss appears controlled by species and underlying genotype. We leveraged genetic diversity to generate prediction models of metabolic trait responsiveness to volitional activity offering a framework for advancing personalized exercise prescription. The human and mouse data are publicly available via a user-friendly Web-based application to enhance data mining and hypothesis development.

Pre-exercise meal on oxidation of energy substrates during maximal exercise test in non-trained individuals

Objective

This study aimed to compare the influence of a high carbohydrate meal versus high-fat meal on the oxidation of substrates during an exercise incremental test.

Materials and methods

Ten untrained male subjects underwent two days of the protocol. Randomly, they received a high carbohydrate meal or a high-fat meal, receiving the other one in the next protocol. On both days, they performed an incremental treadmill test, with heart rate and maximal oxygen consumption to estimate the oxidation of substrates.

Results

The high-fat meal showed an increase in the absolute amount of oxidized fat along with the incremental test (P < 0.05; effect size = 0.9528), and a reduction in the respiratory exchange ratio at low intensities (P < 0.05; effect size = 0.7765).

Conclusion

The meals presented no difference when compared to maximum oxidation point of substrates, the oxidation rate of substrates over time, and heart rate. A pre-test high-fat meal in untrained individuals was shown to be a modulating factor of total oxidized fats throughout the exercise, although it did not exert a significant effect on the rate of this oxidation over time.

Skeletal Muscle MicroRNA Patterns in Response to a Single Bout of Exercise in Females: Biomarkers for Subsequent Training Adaptation?

microRNAs (miRs) have been proposed as a promising new class of biomarkers in the context of training adaptation. Using microarray analysis, we studied skeletal muscle miR patterns in sedentary young healthy females (n = 6) before and after a single submaximal bout of endurance exercise ('reference training'). Subsequently, participants were subjected to a structured training program, consisting of six weeks of moderate-intensity continuous endurance training (MICT) and six weeks of high-intensity interval training (HIIT) in randomized order. In vastus lateralis muscle, we found significant downregulation of myomiRs, specifically miR-1, 133a-3p, and -5p, -133b, and -499a-5p. Similarly, exercise-associated miRs-23a-3p, -378a-5p, -128-3p, -21-5p, -107, -27a-3p, -126-3p, and -152-3p were significantly downregulated, whereas miR-23a-5p was upregulated. Furthermore, in an untargeted approach for differential expression in response to acute exercise, we identified n = 35 miRs that were downregulated and n = 20 miRs that were upregulated by factor 4.5 or more. Remarkably, KEGG pathway analysis indicated central involvement of this set of miRs in fatty acid metabolism. To reproduce these data in a larger cohort of all-female subjects (n = 29), qPCR analysis was carried out on n = 15 miRs selected from the microarray, which confirmed their differential expression. Furthermore, the acute response, i.e., the difference between miR concentrations before and after the reference training, was correlated with changes in maximum oxygen uptake (V̇O₂max) in response to the training program. Here, we found that miRs-199a-3p and -19b-3p might be suitable acute-response candidates that correlate with individual degrees of training adaptation in females.

Skeletal muscle overexpression of sAnk1.5 in transgenic mice does not predispose to type 2 diabetes

Genome-wide association studies (GWAS) and cis-expression quantitative trait locus (cis-eQTL) analyses indicated an association of the rs508419 single nucleotide polymorphism (SNP) with type 2 diabetes (T2D). rs508419 is localized in the muscle-specific internal promoter (P2) of the ANK1 gene, which drives the expression of the sAnk1.5 isoform. Functional studies showed that the rs508419 C/C variant results in increased transcriptional activity of the P2 promoter, leading to higher levels of sAnk1.5 mRNA and protein in skeletal muscle biopsies of individuals carrying the C/C genotype. To investigate whether sAnk1.5 overexpression in skeletal muscle might predispose to T2D development, we generated transgenic mice (TgsAnk1.5/+) in which the sAnk1.5 coding sequence was selectively overexpressed in skeletal muscle tissue. TgsAnk1.5/+ mice expressed up to 50% as much sAnk1.5 protein as wild-type (WT) muscles, mirroring the difference reported between individuals with the C/C or T/T genotype at rs508419. However, fasting glucose levels, glucose tolerance, insulin levels and insulin response in TgsAnk1.5/+ mice did not differ from those of age-matched WT mice monitored over a 12-month period. Even when fed a high-fat diet, TgsAnk1.5/+ mice only presented increased caloric intake, but glucose disposal, insulin tolerance and weight gain were comparable to those of WT mice fed a similar diet. Altogether, these data indicate that sAnk1.5 overexpression in skeletal muscle does not predispose mice to T2D susceptibility.

The metabolic recovery of marathon runners: an untargeted 1H-NMR metabolomics perspective

Introduction: Extreme endurance events may result in numerous adverse metabolic, immunologic, and physiological perturbations that may diminish athletic performance and adversely affect the overall health status of an athlete, especially in the absence of sufficient recovery. A comprehensive understanding of the post-marathon recovering metabolome, may aid in the identification of new biomarkers associated with marathon-induced stress, recovery, and adaptation, which can facilitate the development of improved training and recovery programs and personalized monitoring of athletic health/recovery/performance. Nevertheless, an untargeted, multi-disciplinary elucidation of the complex underlying biochemical mechanisms involved in recovery after such an endurance event is yet to be demonstrated. Methods: This investigation employed an untargeted proton nuclear magnetic resonance metabolomics approach to characterize the post-marathon recovering metabolome by systematically comparing the pre-, immediately post, 24, and 48 h post-marathon serum metabolite profiles of 15 athletes. Results and Discussion: A total of 26 metabolites were identified to fluctuate significantly among post-marathon and recovery time points and were mainly attributed to the recovery of adenosine triphosphate, redox balance and glycogen stores, amino acid oxidation, changes to gut microbiota, and energy drink consumption during the post-marathon recovery phase. Additionally, metabolites associated with delayed-onset muscle soreness were observed; however, the mechanisms underlying this commonly reported phenomenon remain to be elucidated. Although complete metabolic recovery of the energy-producing pathways and fuel substrate stores was attained within the 48 h recovery period, several metabolites remained perturbed throughout the 48 h recovery period and/or fluctuated again following their initial recovery to pre-marathon-related levels.

DNA repair byproduct 8-oxoguanine base promotes myoblast differentiation

Muscle contraction increases the level of reactive oxygen species (ROS), which has been acknowledged as key signaling entities in muscle remodeling and to underlie the healthy adaptation of skeletal muscle. ROS inevitably endows damage to various cellular molecules including DNA. DNA damage ought to be repaired to ensure genome integrity; yet, how DNA repair byproducts affect muscle adaptation remains elusive. Here, we showed that exercise elicited the generation of 8-oxo-7,8-dihydroguanine (8-oxoG), that was primarily found in mitochondrial genome of myofibers. Upon exercise, TA muscle's 8-oxoG excision capacity markedly enhanced, and in the interstitial fluid of TA muscle from the post-exercise mice, the level of free 8-oxoG base was significantly increased. Addition of 8-oxoG to myoblasts triggered myogenic differentiation via activating Ras-MEK-MyoD signal axis. 8-Oxoguanine DNA glycosylase1 (OGG1) silencing from cells or Ogg1 KO from mice decreased Ras activation, ERK phosphorylation, MyoD transcriptional activation, myogenic regulatory factors gene (MRFs) expression. In reconstruction experiments, exogenously added 8-oxoG base enhanced the expression of MRFs and accelerated the recovery of the injured skeletal muscle. Collectively, these data not only suggest that DNA repair metabolite 8-oxoG function as a signal entity for muscle remodeling and contribute to exercise-induced adaptation of skeletal muscle, but also raised the potential for utilizing 8-oxoG in clinical treatment to skeletal muscle damage-related disorders.

Effects of luseogliflozin treatment on hyperglycemia-induced muscle atrophy in rats

Diabetes mellitus is recognized as a risk factor for sarcopenia. Luseogliflozin, a selective sodium-glucose cotransporter 2 (SGLT2) inhibitor, reduces inflammation and oxidative stress by improving hyperglycemia, subsequently improving hepatosteatosis or kidney dysfunction. However, the effects of SGLT2 inhibitor on the regulation of skeletal muscle mass or function in hyperglycemia are still unknown. In this study, we investigated the effects of luseogliflozin-mediated attenuation of hyperglycemia on the prevention of muscle atrophy. Twenty-four male Sprague-Dawley rats were randomly divided into four groups: control, control with SGLT2 inhibitor treatment, hyperglycemia, and hyperglycemia with SGLT2 inhibitor treatment. The hyperglycemic rodent model was established using a single injection of streptozotocin, a compound with preferential toxicity toward pancreatic beta cells. Muscle atrophy in streptozotocin-induced hyperglycemic model rats was inhibited by the suppression of hyperglycemia using luseogliflozin, which consequently suppressed hyperglycemia-mediated increase in the levels of advanced glycation end products (AGEs) and activated the protein degradation pathway in muscle cells. Treatment with luseogliflozin can restore the hyperglycemia-induced loss in the muscle mass to some degree partly through the inhibition of AGEs-induced or homeostatic disruption of mitochondria-induced activation of muscle degradation.