Integrative biology of exercise

Glucose metabolism in the perfused liver did not improve with resistance training in male Swiss mice under caloric restriction

CONTEXT

Energy homeostasis is a primary factor for the survival of mammals. Many tissues and organs, among which is the liver, keep this homeostasis in varied circumstances, including caloric restriction (CR) and physical activity.

OBJECTIVE

This study investigated glucose metabolism using the following groups of eight-week-old male Swiss mice: CS, sedentary and fed freely; RS, sedentary and RT, trained, both under 30% CR (n = 20-23 per group).

RESULTS

Organs and fat depots of groups RS and RT were similar to CS, although body weight was lower. CR did not impair training performance nor affected systemic or hepatic glucose metabolism. Training combined with CR (group RT) improved in vivo glucose tolerance and did not affect liver gluconeogenesis.

CONCLUSIONS

The mice tolerated the prolonged moderate CR without impairment of their well-being, glucose homeostasis, and resistance training performance. But the higher liver gluconeogenic efficiency previously demonstrated using this training protocol in mice was not evidenced under CR.

Investigating the Causal Effects of Exercise-Induced Genes on Sarcopenia

Exercise is increasingly recognized as an effective strategy to counteract skeletal muscle aging and conditions such as sarcopenia. However, the specific exercise-induced genes responsible for these protective effects remain unclear. To address this, we conducted an eight-week aerobic exercise regimen on late-middle-aged mice and developed an integrated approach that combines mouse exercise-induced genes with human GWAS datasets to identify causal genes for sarcopenia. This approach led to significant improvements in the skeletal muscle phenotype of the mice and the identification of exercise-induced genes and miRNAs. By constructing a miRNA regulatory network enriched with transcription factors and GWAS signals related to muscle function and traits, we focused on 896 exercise-induced genes. Using human skeletal muscle cis-eQTLs as instrumental variables, 250 of these exercise-induced genes underwent two-sample Mendelian randomization analysis, identifying 40, 68, and 62 causal genes associated with sarcopenia and its clinical indicators-appendicular lean mass (ALM) and hand grip strength (HGS), respectively. Sensitivity analyses and cross-phenotype validation confirmed the robustness of our findings. Consistently across the three outcomes, RXRA, MDM1, RBL2, KCNJ2, and ADHFE1 were identified as risk factors, while NMB, TECPR2, MGAT3, ECHDC2, and GINM1 were identified as protective factors, all with potential as biomarkers for sarcopenia progression. Biological activity and disease association analyses suggested that exercise exerts its anti-sarcopenia effects primarily through the regulation of fatty acid oxidation. Based on available drug-gene interaction data, 21 of the causal genes are druggable, offering potential therapeutic targets. Our findings highlight key genes and molecular pathways potentially responsible for the anti-sarcopenia benefits of exercise, offering insights into future therapeutic strategies that could mimic the safe and mild protective effects of exercise on age-related skeletal muscle degeneration.

The biphasic activity of autophagy and heat shock protein response in peripheral blood mononuclear cells following acute resistance exercise in resistance-trained males

PURPOSE

Autophagy and heat shock protein (HSP) response are proteostatic systems involved in the acute and adaptive responses to exercise. These systems may upregulate sequentially following cellular stress including acute exercise, however, currently few data exist in humans. This study investigated the autophagic and HSP responses to acute intense lower body resistance exercise in peripheral blood mononuclear cells (PBMCs) with and without branched-chain amino acids (BCAA) supplementation.

METHODS

Twenty resistance-trained males (22.3 ± 1.5 yr; 175.4 ± .7 cm; 86.4 ± 15.6 kg) performed a bout of intense lower body resistance exercise and markers of autophagy and HSP70 were measured immediately post- (IPE) and 2, 4, 24, 48, and 72 h post-exercise. Prior to resistance exercise, 10 subjects were randomly assigned to BCAA supplementation of 0.22 g/kg/d for 5 days pre-exercise and up to 72 h following exercise while the other 10 subjects consumed a placebo (PLCB).

RESULTS

There were no difference in autophagy markers or HSP70 expression between BCAA and PLCB groups. LC3II protein expression was significantly lower 2 and 4 h post-exercise compared to pre-exercise. LC3II: I ratio was not different at any time point compared to pre-exercise. Protein expression of p62 was lower IPE, 2, and 4 h post-exercise and elevated 24 h post-exercise. HSP70 expression was elevated 48 and 72 h post-exercise.

CONCLUSIONS

Autophagy and HSP70 are upregulated in PBMCs following intense resistance exercise with autophagy increasing initially post-exercise and HSP response in the latter period. Moreover, BCAA supplementation did not affect this response.

Integrative effects of resistance training and endurance training on mitochondrial remodeling in skeletal muscle

Resistance training activates mammalian target of rapamycin (mTOR) pathway of hypertrophy for strength gain, while endurance training increases peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) pathway of mitochondrial biogenesis benefiting oxidative phosphorylation. The conventional view suggests that resistance training-induced hypertrophy signaling interferes with endurance training-induced mitochondrial remodeling. However, this idea has been challenged because acute leg press and knee extension in humans enhance both muscle hypertrophy and mitochondrial remodeling signals. Thus, we first examined the muscle mitochondrial remodeling and hypertrophy signals with endurance training and resistance training, respectively. In addition, we discussed the influence of resistance training on muscle mitochondria, demonstrating that the PGC-1α-mediated muscle mitochondrial adaptation and hypertrophy occur simultaneously. The second aim was to discuss the integrative effects of concurrent training, which consists of endurance and resistance training sessions on mitochondrial remodeling. The study found that the resistance training component does not reduce muscle mitochondrial remodeling signals in concurrent training. On the contrary, concurrent training has the potential to amplify skeletal muscle mitochondrial biogenesis compared to a single exercise model. Concurrent training involving differential sequences of resistance and endurance training may result in varied mitochondrial biogenesis signals, which should be linked to the pre-activation of mTOR or PGC-1α signaling. Our review proposed a mechanism for mTOR signaling that promotes PGC-1α signaling through unidentified pathways. This mechanism may be account for the superior muscle mitochondrial remodeling change following the concurrent training. Our review suggested an interaction between resistance training and endurance training in skeletal muscle mitochondrial adaptation.

Systemic and tissue-specific spexin response to acute treadmill exercise in rats

Spexin (SPX) is a 14-amino-acid peptide that plays an important role in the regulation of metabolism and energy homeostasis. It is well known that a variety of bioactive molecules released into the circulation by organs and tissues in response to acute and chronic exercise, known as exerkines, mediate the benefits of exercise by improving metabolic health. However, it is unclear whether acute exercise affects SPX levels in the circulation and peripheral tissues. This study aimed to determine whether acute treadmill exercise induces plasma SPX levels, as well as mRNA expression and immunostaining of SPX in skeletal muscle, adipose tissue, and liver. Male Sprague Dawley rats were divided into sedentary and acute exercise groups. Plasma, soleus (SOL), extensor digitorum longus (EDL), adipose tissue, and liver samples were collected at six time points (0, 1, 3, 6, 12, and 24 h) following 60 min of acute treadmill exercise at a speed of 25 m/min and 0 % grade. Acute exercise increased plasma SPX levels and induced mRNA expression of Spx in the SOL, EDL, and liver. Immunohistochemical analysis demonstrated that acute exercise led to a decrease in SPX immunostaining in the liver. Taken together, these findings suggest that SPX increases in response to acute exercise as a potential exerkine candidate, and the liver may be one of the sources of acute exercise-induced plasma SPX levels in rats. However, a comprehensive analysis is needed to fully elucidate the systemic response of SPX to acute exercise, as well as the tissue from which SPX is secreted.

Tai Chi-Induced Exosomal LRP1 is Associated With Memory Function and Hippocampus Plasticity in aMCI Patients

OBJECTIVES

The study was designed to identify the potential peripheral processes of circulating exosome in response to Tai Chi (TC) exercise and the possibility of its loaded cargos in mediating the effects of TC training on cognitive function among older adults with amnestic mild cognitive impairment (aMCI).

DESIGN, SETTING, AND PARTICIPANTS

This was a multicenter randomized controlled trial. One hundred community-dwelling old adults with aMCI were randomly assigned (1:1) to experimental (n = 50) and control groups (n = 50).

INTERVENTION

The experimental group participated in TC exercise 5 times/week, with each session lasting 60 minutes for 12 weeks. Both experimental and control groups received health education every 4 weeks.

MEASUREMENTS

The primary outcome was global cognitive function. Neurocognitive assessments, MRI examination, and large-scale proteomics analysis of peripheric exosome were conducted at baseline and after 12-week training. Outcome assessors and statisticians were blinded to group allocation.

RESULTS

A total of 96 participants (96%) completed all outcome measurements. TC training improved global cognitive function (adjusted mean difference [MD] = 1.9, 95%CI 0.93-2.87, p <0.001) and memory (adjusted MD = 6.42, 95%CI 2.09-10.74, p = 0.004), increased right hippocampus volume (adjusted MD = 88.52, 95%CI 13.63-163.4, p = 0.021), and enhanced rest state functional connectivity (rsFC) between hippocampus and cuneus, which mediated the group effect on global cognitive function (bootstrapping CIs: [0.0208, 1.2826], [0.0689, 1.2211]) and verbal delay recall (bootstrapping CI: [0.0002, 0.6277]). Simultaneously, 24 differentially expressed exosomal proteins were detected in tandem mass tag-labelling proteomic analysis. Of which, the candidate protein low-density lipoprotein receptor-related protein 1 (LRP1) was further confirmed by parallel reaction monitoring and ELISA. Moreover, the up-regulated LRP1 was both positively associated with verbal delay recall and rsFC (left hippocampus-right cuneus).

CONCLUSION

TC promotes LRP1 release via exosome, which was associated with enhanced memory function and hippocampus plasticity in aMCI patients. Our findings provided an insight into potential therapeutic neurobiological targets focusing on peripheric exosome in respond to TC exercise.

Molecular aspects of the exercise response and training adaptation in skeletal muscle

Skeletal muscle plasticity enables an enormous potential to adapt to various internal and external stimuli and perturbations. Most notably, changes in contractile activity evoke a massive remodeling of biochemical, metabolic and force-generating properties. In recent years, a large number of signals, sensors, regulators and effectors have been implicated in these adaptive processes. Nevertheless, our understanding of the molecular underpinnings of training adaptation remains rudimentary. Specifically, the mechanisms that underlie signal integration, output coordination, functional redundancy and other complex traits of muscle adaptation are unknown. In fact, it is even unclear how stimulus-dependent specification is brought about in endurance or resistance exercise. In this review, we will provide an overview on the events that describe the acute perturbations in single endurance and resistance exercise bouts. Furthermore, we will provide insights into the molecular principles of long-term training adaptation. Finally, current gaps in knowledge will be identified, and strategies for a multi-omic and -cellular analyses of the molecular mechanisms of skeletal muscle plasticity that are engaged in individual, acute exercise bouts and chronic training adaptation discussed.

Exercise, Neuroprotective Exerkines, and Parkinson's Disease: A Narrative Review

Parkinson's disease (PD) is a prevalent neurodegenerative disease in which treatment often includes an exercise regimen. Exercise is neuroprotective in animal models of PD, and, more recently, human clinical studies have verified exercise's disease-modifying effect. Aerobic exercise and resistance training improve many of PD's motor and non-motor symptoms, while neuromotor therapy and stretching/flexibility exercises positively contribute to the quality of life in people with PD. Therefore, understanding the role of exercise in managing this complex disorder is crucial. Exerkines are bioactive substances that are synthesized and released during exercise and have been implicated in several positive health outcomes, including neuroprotection. Exerkines protect neuronal cells in vitro and rodent PD models in vivo. Aerobic exercise and resistance training both increase exerkine levels in the blood, suggesting a role for exerkines in the neuroprotective theory. Many exerkines demonstrate the potential for protecting the brain against pathological missteps caused by PD. Every person (people) with Parkinson's (PwP) needs a comprehensive exercise plan tailored to their unique needs and abilities. Here, we provide an exercise template to help PwP understand the importance of exercise for treating PD, describe barriers confronting many PwP in their attempt to exercise, provide suggestions for overcoming these barriers, and explore the role of exerkines in managing PD. In conclusion, exercise and exerkines together create a powerful neuroprotective system that should contribute to slowing the chronic progression of PD.

The repeated bout effect evokes the training-induced skeletal muscle cellular memory

Physical exercise is well-established as beneficial for health. With the 20th-century epidemiological transition, promoting healthy habits like exercise has become crucial for preventing chronic diseases. Stress can yield adaptive long-term benefits, potentially transmitted trans-generationally. Physical training exposes individuals to metabolic, thermal, mechanical, and oxidative stressors, activating cell signaling pathways that regulate gene expression and adaptive responses, thereby enhancing stress tolerance - a phenomenon known as hormesis. Muscle memory is the capacity of skeletal muscle to respond differently to environmental stimuli in an adaptive (positive) or maladaptive (negative) manner if the stimuli have been encountered previously. The Repeated Bout Effect encompasses our skeletal muscle capacity to activate an intrinsic protective mechanism that reacts to eccentric exercise-induced damage by activating an adaptive response that resists subsequent damage stimuli. Deciphering the molecular mechanism of this phenomenon would allow the incorporation of muscle memory in training programs for professional athletes, active individuals looking for the health benefits of exercise training, and patients with "exercise intolerance." Moreover, enhancing the adaptive response of muscle memory could promote healing in individuals who traditionally do not recover after immobilization. The improvement could be part of an exercise program but could also be targeted pharmacologically. This review explores Repeated Bout Effect mechanisms: neural adaptations, tendon and muscle fiber property changes, extracellular matrix remodeling, and improved inflammatory responses.

Exercise-based cardiac rehabilitation for adults with atrial fibrillation

BACKGROUND

Atrial fibrillation (AF), the most prevalent cardiac arrhythmia, disrupts the heart's rhythm through numerous small re-entry circuits in the atrial tissue, leading to irregular atrial contractions. The condition poses significant health risks, including increased stroke risk, heart failure, and reduced quality of life. Given the complexity of AF and its growing incidence globally, exercise-based cardiac rehabilitation (ExCR) may provide additional benefits for people with AF or those undergoing routine treatment for the condition.

OBJECTIVES

To assess the benefits and harms of ExCR compared with non-exercise controls for people who currently have AF or who have been treated for AF.

SEARCH METHODS

We searched the following electronic databases: CENTRAL in the Cochrane Library, MEDLINE Ovid, Embase Ovid, PsycINFO Ovid, Web of Science Core Collection Thomson Reuters, CINAHL EBSCO, LILACS BIREME, and two clinical trial registers on 24 March 2024. We imposed no language restrictions.

SELECTION CRITERIA

We included randomised clinical trials (RCTs) that investigated ExCR interventions compared with any type of non-exercise control. We included adults 18 years of age or older with any subtype of AF or those who had received treatment for AF.

DATA COLLECTION AND ANALYSIS

Five review authors independently screened and extracted data in duplicate. We assessed risk of bias using Cochrane's RoB 1 tool as outlined in the Cochrane Handbook for Systematic Reviews of Interventions. We assessed clinical and statistical heterogeneity by visual inspection of the forest plots and by using standard Chi² and I² statistics. We performed meta-analyses using random-effects models for continuous and dichotomised outcomes. We calculated standardised mean differences where different scales were used for the same outcome. We used the GRADE approach to assess the certainty of the evidence.

MAIN RESULTS

We included 20 RCTs involving a total of 2039 participants with AF. All trials were conducted between 2006 and 2024, with a follow-up period ranging from eight weeks to five years. We assessed the certainty of evidence as moderate to very low. Five trials assessed comprehensive ExCR programmes, which included educational or psychological interventions, or both; the remaining 15 trials compared exercise-only cardiac rehabilitation with controls. The overall risk of bias in the included studies was mixed. Details on random sequence generation, allocation concealment, and use of intention-to-treat analysis were typically poorly reported. Evidence from nine trials (n = 1173) suggested little to no difference in mortality between ExCR and non-exercise controls (risk ratio (RR) 1.06, 95% confidence interval (CI) 0.76 to 1.49; I² = 0%; 101 deaths; low-certainty evidence). Based on evidence from 10 trials (n = 825), ExCR may have little to no effect on SAEs (RR 1.30, 95% CI 0.63 to 2.67; I² = 0%; 28 events; low-certainty evidence). Evidence from four trials (n = 378) showed that ExCR likely reduced AF recurrence (measured via Holter monitoring) compared to controls (RR 0.70, 95% CI 0.56 to 0.88; I² = 2%; moderate-certainty evidence). ExCR may reduce AF symptom severity (mean difference (MD) -1.59, 95% CI -2.98 to -0.20; I² = 61%; n = 600; low-certainty evidence); likely reduces AF symptom burden (MD -1.61, 95% CI -2.76 to -0.45; I² = 0%; n = 317; moderate-certainty evidence); may reduce AF episode frequency (MD -1.29, 95% CI -2.50 to -0.07; I² = 75%; n = 368; low-certainty evidence); and likely reduces AF episode duration (MD -0.58, 95% CI -1.14 to -0.03; I² = 0%; n = 317; moderate-certainty evidence), measured via the AF Severity Scale (AFSS) questionnaire. Moderate-certainty evidence from six trials (n = 504) showed that ExCR likely improved the mental component summary measure in health-related quality of life (HRQoL) of the 36-item Short Form Health Survey (SF-36) (MD 2.66, 95% CI 1.22 to 4.11; I² = 2%), but the effect of ExCR on the physical component summary measure was very uncertain (MD 1.75, 95% CI -0.31 to 3.81; I² = 52%; very low-certainty evidence). ExCR also may improve individual components of HRQoL (general health, vitality, emotional role functioning, and mental health) and exercise capacity (peak oxygen uptake (VO2peak) and 6-minute walk test) following ExCR. The effects of ExCR on serious adverse events and exercise capacity were consistent across different models of ExCR delivery: centre compared to home-based, exercise dose, exercise only compared to comprehensive programmes, and aerobic training alone compared to aerobic plus resistance programmes. Using univariate meta-regression, there was evidence of significant association between location of trial and length of longest follow-up on exercise capacity.

AUTHORS' CONCLUSIONS

Due to few randomised participants and typically short-term follow-up, the impact of ExCR on all-cause mortality or serious adverse events for people with AF is uncertain. ExCR likely improves AF-specific measures including reduced AF recurrence, symptom burden, and episode duration, as well as the mental components of HRQoL. ExCR may improve AF symptom severity, episode frequency, and VO2peak. Future high-quality RCTs are needed to assess the benefits of ExCR for people with AF on patient-relevant outcomes including AF symptom severity and burden, AF recurrence, AF-specific quality of life, and clinical events such as mortality, readmissions, and serious adverse events. High-quality trials are needed to investigate how AF subtype and clinical setting (i.e. primary and secondary care) may influence ExCR effectiveness.

Vgll2 as an integrative regulator of mitochondrial function and contractility specific to skeletal muscle

During skeletal muscle adaptation to physiological or pathophysiological signals, contractile apparatus and mitochondrial function are coordinated to alter muscle fiber type. Although recent studies have identified various factors involved in modifying contractile proteins and mitochondrial function, the molecular mechanisms coordinating contractile and metabolic functions during muscle fiber transition are not fully understood. Using a gene-deficient mouse approach, our previous studies uncovered that vestigial-like family member 2 (Vgll2), a skeletal muscle-specific transcription cofactor activated by exercise, is essential for fast-to-slow adaptation of skeletal muscle. The current study provides evidence that Vgll2 plays a role in increasing muscle mitochondrial mass and oxidative capacity. Transgenic Vgll2 overexpression in mice altered muscle fiber composition toward the slow type and enhanced exercise endurance, which contradicted the outcomes observed with Vgll2 deficiency. Vgll2 expression was positively correlated with the expression of genes related to mitochondrial function in skeletal muscle, mitochondrial DNA content, and protein abundance of oxidative phosphorylation complexes. Additionally, Vgll2 overexpression significantly increased the maximal respiration of isolated muscle fibers and enhanced the suppressive effects of endurance training on weight gain. Notably, no additional alteration in expression of myosin heavy chain genes was observed after exercise, suggesting that Vgll2 plays a direct role in regulating mitochondrial function, independent of its effect on contractile components. The observed increase in exercise endurance and metabolic efficiency may be attributed to the acute upregulation of genes promoting fatty acid utilization as a direct consequence of Vgll2 activation facilitated by endurance exercise. Thus, the current study establishes that Vgll2 is an integrative regulator of mitochondrial function and contractility in skeletal muscle.

Exploring the Impact of Exercise-Derived Extracellular Vesicles in Cancer Biology

Cancer remains a major challenge in medicine, prompting exploration of innovative therapies. Recent studies suggest that exercise-derived extracellular vesicles (EVs) may offer potential anti-cancer benefits. These small, membrane-bound particles, including exosomes, carry bioactive molecules such as proteins and RNA that mediate intercellular communication. Exercise has been shown to increase EV secretion, influencing physiological processes like tissue repair, inflammation, and metabolism. Notably, preclinical studies have demonstrated that exercise-derived EVs can inhibit tumor growth, reduce metastasis, and enhance treatment response. For instance, in a study using animal models, exercise-derived EVs were shown to suppress tumor proliferation in breast and colon cancers. Another study reported that these EVs reduced metastatic potential by decreasing the migration and invasion of cancer cells. Additionally, exercise-induced EVs have been found to enhance the effectiveness of chemotherapy by sensitizing tumor cells to treatment. This review highlights the emerging role of exercise-derived circulating biomolecules, particularly EVs, in cancer biology. It discusses the mechanisms through which EVs impact cancer progression, the challenges in translating preclinical findings to clinical practice, and future research directions. Although research in this area is still limited, current findings suggest that EVs could play a crucial role in spreading molecules that promote better health in cancer patients. Understanding these EV profiles could lead to future therapies, such as exercise mimetics or targeted drugs, to treat cancer.

Fibre-specific mitochondrial protein abundance is linked to resting and post-training mitochondrial content in the muscle of men

Analyses of mitochondrial adaptations in human skeletal muscle have mostly used whole-muscle samples, where results may be confounded by the presence of a mixture of type I and II muscle fibres. Using our adapted mass spectrometry-based proteomics workflow, we provide insights into fibre-specific mitochondrial differences in the human skeletal muscle of men before and after training. Our findings challenge previous conclusions regarding the extent of fibre-type-specific remodelling of the mitochondrial proteome and suggest that most baseline differences in mitochondrial protein abundances between fibre types reported by us, and others, might be due to differences in total mitochondrial content or a consequence of adaptations to habitual physical activity (or inactivity). Most training-induced changes in different mitochondrial functional groups, in both fibre types, were no longer significant in our study when normalised to changes in markers of mitochondrial content.

A 2-hydroxybutyrate-mediated feedback loop regulates muscular fatigue

Several metabolites have been shown to have independent and at times unexpected biological effects outside of their metabolic pathways. These include succinate, lactate, fumarate, and 2-hydroxyglutarate. 2-Hydroxybutyrate (2HB) is a byproduct of endogenous cysteine synthesis, produced during periods of cellular stress. 2HB rises acutely after exercise; it also rises during infection and is also chronically increased in a number of metabolic disorders. We show here that 2HB inhibits branched-chain aminotransferase enzymes, which in turn triggers a SIRT4-dependent shift in the compartmental abundance of protein ADP-ribosylation. The 2HB-induced decrease in nuclear protein ADP-ribosylation leads to a C/EBPβ-mediated transcriptional response in the branched-chain amino acid degradation pathway. This response to 2HB exposure leads to an improved oxidative capacity in vitro. We found that repeated injection with 2HB can replicate the improvement to oxidative capacity that occurs following exercise training. Together, we show that 2-HB regulates fundamental aspects of skeletal muscle metabolism.

Exercise as a tool to mitigate metabolic disease

Metabolic diseases, notably obesity and type 2 diabetes (T2D), have reached alarming proportions and constitute a significant global health challenge, emphasizing the urgent need for effective preventive and therapeutic strategies. In contrast, exercise training emerges as a potent intervention, exerting numerous positive effects on metabolic health through adaptations to the metabolic tissues. Here, we reviewed the major features of our current understanding with respect to the intricate interplay between metabolic diseases and key metabolic tissues, including adipose tissue, skeletal muscle, and liver, describing some of the main underlying mechanisms driving pathogenesis, as well as the role of exercise to combat and treat obesity and metabolic disease.

Exercise-induced response of proteinogenic and non-proteinogenic plasma free amino acids is sport-specific: A comparison of sprint and endurance athletes

Circulating blood is an important plasma free amino acids (PFAAs) reservoir and a pivotal link between metabolic pathways. No comparisons are available between athletes with opposite training adaptations that include a broader spectrum of both proteinogenic and non-proteinogenic amino acids, and that take into account skeletal muscle mass. We hypothesized that the levels of the exercise-induced PFAAs concentration are related to the type of training-related metabolic adaptation. We compared highly trained endurance athletes (n = 11) and sprinters (n = 10) aged 20‒35 years who performed incremental exercise until exhaustion. Venous blood was collected before and during the test and 30-min recovery (12 samples). Forty-two PFAAs were assayed using LC-ESI-MS/MS technique. Skeletal muscle mass was estimated using dual X-ray absorptiometry method. Glutamine and alanine were dominant PFAAs throughout the whole exercise and recovery period (~350‒650 μmol∙L-1). Total, combined proteinogenic, non-essential, and non-proteinogenic PFAAs levels were significantly higher in endurance athletes than sprinters (ANOVA group effects: p = 0.007, η2 = 0.321; p = 0.011, η2 = 0.294; p = 0.003, η2 = 0.376; p = 0.001, η2 = 0.471, respectively). The exercise response was more pronounced in endurance athletes, especially for non-proteinogenic PFAAs (ANOVA interaction effect: p = 0.038, η2 = 0.123). Significant between-group differences were observed for 19 of 33 PFAAs detected, including 4 essential, 7 non-essential, and 8 non-proteinogenic ones. We demonstrated that the PFAAs response to incremental aerobic exercise is associated with the type of training-related metabolic adaptation. A greater turnover and availability of circulating PFAAs for skeletal muscles and other body tissues is observed in endurance- than in sprint-trained individuals. Non-proteinogenic PFAAs, despite low concentrations, also respond to exercise loads, indicating their important, though less understood role in exercise metabolism. Our study provides additional insight into the exercise-induced physiological response of PFAAs, and may also provide a rationale in discussions regarding dietary amino acid requirements in high-performance athletes with respect to sports specialization.

GDF15 is dispensable for the insulin-sensitizing effects of chronic exercise

Growth and differentiation factor 15 (GDF15) has recently emerged as a weight loss and insulin-sensitizing factor. Growing evidence also supports a role for GDF15 as a physiological, exercise-induced stress signal. Here, we tested whether GDF15 is required for the insulin-sensitizing effects of exercise in mice and humans. At baseline, both under a standard nutritional state and high-fat feeding, GDF15 knockout (KO) mice display normal glucose tolerance, systemic insulin sensitivity, maximal speed, and endurance running capacity when compared to wild-type littermates independent of sex. When submitted to a 4-week exercise training program, both lean and obese wild-type and GDF15 KO mice similarly improve their endurance running capacity, glucose tolerance, systemic insulin sensitivity, and peripheral glucose uptake. Insulin-sensitizing effects of exercise training were also unrelated to changes in plasma GDF15 in humans. In summary, we here show that GDF15 is dispensable for the insulin-sensitizing effects of chronic exercise.

Physical exercise in amyotrophic lateral sclerosis: a potential co-adjuvant therapeutic option to counteract disease progression

Amyotrophic lateral sclerosis (ALS) is a fatal disorder characterized by the selective degeneration of upper and lower motor neurons, leading to progressive muscle weakness and atrophy. The mean survival time is two to five years. Although the hunt for drugs has greatly advanced over the past decade, no cure is available for ALS yet. The role of intense physical activity in the etiology of ALS has been debated for several decades without reaching a clear conclusion. The benefits of organized physical activity on fitness and mental health have been widely described. Indeed, by acting on specific mechanisms, physical activity can influence the physiology of several chronic conditions. It was shown to improve skeletal muscle metabolism and regeneration, neurogenesis, mitochondrial biogenesis, and antioxidant defense. Interestingly, all these pathways are involved in ALS pathology. This review will provide a broad overview of the effect of different exercise protocols on the onset and progression of ALS, both in humans and in animal models. Furthermore, we will discuss challenges and opportunities to exploit physiological responses of imposed exercise training for therapeutic purposes.

Comparison of Polarized Versus Other Types of Endurance Training Intensity Distribution on Athletes' Endurance Performance: A Systematic Review with Meta-analysis

BACKGROUND

Polarized training intensity distribution (POL) was recently suggested to be superior to other training intensity distribution (TID) regimens for endurance performance improvement.

OBJECTIVE

We aimed to systematically review and meta-analyze evidence comparing POL to other TIDs on endurance performance.

METHODS

PRISMA guidelines were followed. The protocol was registered at PROSPERO (CRD42022365117). PubMed, Scopus, and Web of Science were searched up to 20 October 2022 for studies in adults and young adults for ≥ 4 weeks comparing POL with other TID interventions regarding VO2peak, time-trial (TT), time to exhaustion (TTE) or speed or power at the second ventilatory or lactate threshold (V/P at VT2/LT2). Risk of bias was assessed with RoB-2 and ROBINS-I. Certainty of evidence was assessed with GRADE. Results were analyzed by random effects meta-analysis using standardized mean differences.

RESULTS

Seventeen studies met the inclusion criteria (n = 437 subjects). Pooled effect estimates suggest POL superiority for improving VO2peak (SMD = 0.24 [95% CI 0.01, 0.48]; z = 2.02 (p = 0.040); 11 studies, n = 284; I2 = 0%; high certainty of evidence). Superiority, however, only occurred in shorter interventions (< 12 weeks) (SMD = 0.40 [95% CI 0.08, 0.71; z = 2.49 (p = 0.01); n = 163; I2 = 0%) and for highly trained athletes (SMD = 0.46 [95% CI 0.10, 0.82]; z = 2.51 (p = 0.01); n = 125; I2 = 0%). The remaining endurance performance surrogates were similarly affected by POL and other TIDs: TT (SMD = - 0.01 [95% CI -0.28, 0.25]; z =  - 0.10 (p = 0.92); n = 221; I2 = 0%), TTE (SMD = 0.30 [95% CI - 0.20, 0.79]; z = 1.18 (p = 0.24); n = 66; I2 = 0%) and V/P VT2/LT2 (SMD = 0.04 [95% CI -0.21, 0.29]; z = 0.32 (p = 0.75); n = 253; I2 = 0%). Risk of bias for randomized controlled trials was rated as of some concern and for non-randomized controlled trials as low risk of bias (two studies) and some concerns (one study).

CONCLUSIONS

POL is superior to other TIDs for improving VO2peak, particularly in shorter duration interventions and highly trained athletes. However, the effect of POL was similar to that of other TIDs on the remaining surrogates of endurance performance. The results suggest that POL more effectively improves aerobic power but is similar to other TIDs for improving aerobic capacity.

The delta concept does not effectively normalise exercise responses to exhaustive interval training

OBJECTIVES

This study was designed to quantify inter- and intra-individual variability in performance, physiological, and perceptual responses to high-intensity interval training prescribed using the percentage of delta (%Δ) method, in which the gas exchange threshold and maximal oxygen uptake (V̇O2max) are taken into account to normalise relative exercise intensity.

DESIGN

Repeated-measures, within-subjects design with mixed-effects modelling.

METHODS

Eighteen male and four female cyclists (age: 36 ± 12 years, height: 178 ± 10 cm, body mass: 75.2 ± 13.7 kg, V̇O2max: 51.6 ± 5.3 ml·kg-1·min-1) undertook an incremental test to exhaustion to determine the gas exchange threshold and V̇O2max as prescription benchmarks. On separate occasions, participants then completed four high-intensity interval training sessions of identical intensity (70 %Δ) and format (4-min on, 2-min off); all performed to exhaustion. Acute high-intensity interval training responses were modelled with participant as a random effect to provide estimates of inter- and intra-individual variability.

RESULTS

Greater variability was generally observed at the between- compared with the within-individual level, ranging from 50 % to 89 % and from 11 % to 50 % of the total variability, respectively. For the group mean time to exhaustion of 20.3 min, inter- and intra-individual standard deviations reached 9.3 min (coefficient of variation = 46 %) and 4.5 min (coefficient of variation = 22 %), respectively.

CONCLUSIONS

Due to the high variability observed, the %Δ method does not effectively normalise the relative intensity of exhaustive high-intensity interval training across individuals. The generally larger inter- versus intra-individual variability suggests that day-to-day biological fluctuations and/or measurement errors cannot explain the identified shortcoming of the method.

Physiological Adaptations to Progressive Endurance Exercise Training in Adult and Aged Rats: Insights from the Molecular Transducers of Physical Activity Consortium (MoTrPAC)

While regular physical activity is a cornerstone of health, wellness, and vitality, the impact of endurance exercise training on molecular signaling within and across tissues remains to be delineated. The Molecular Transducers of Physical Activity Consortium (MoTrPAC) was established to characterize molecular networks underlying the adaptive response to exercise. Here, we describe the endurance exercise training studies undertaken by the Preclinical Animal Sites Studies component of MoTrPAC, in which we sought to develop and implement a standardized endurance exercise protocol in a large cohort of rats. To this end, Adult (6-mo) and Aged (18-mo) female (n = 151) and male (n = 143) Fischer 344 rats were subjected to progressive treadmill training (5 d/wk, ∼70%-75% VO2max) for 1, 2, 4, or 8 wk; sedentary rats were studied as the control group. A total of 18 solid tissues, as well as blood, plasma, and feces, were collected to establish a publicly accessible biorepository and for extensive omics-based analyses by MoTrPAC. Treadmill training was highly effective, with robust improvements in skeletal muscle citrate synthase activity in as little as 1-2 wk and improvements in maximum run speed and maximal oxygen uptake by 4-8 wk. For body mass and composition, notable age- and sex-dependent responses were observed. This work in mature, treadmill-trained rats represents the most comprehensive and publicly accessible tissue biorepository, to date, and provides an unprecedented resource for studying temporal-, sex-, and age-specific responses to endurance exercise training in a preclinical rat model.

Reduced-exertion high-intensity interval training (REHIT): a feasible approach for improving health and fitness?

In recent years, research investigating the dose-response to sprint interval training (SIT) has provided evidence that the number and duration of repetitions in a SIT session can be reduced whilst preserving the beneficial health-related adaptations. Together this research has led to the development of protocols involving minimal doses of SIT: regularly performing just two or three 20-30 s all-out sprints in a 10 min training session has been shown to elicit beneficial metabolic and cardiovascular adaptations. These SIT protocols, which we originally termed "reduced-exertion high-intensity interval training" (or REHIT), have the potential to remove many of the common barriers associated with other SIT protocols, as well as with HIT and aerobic exercise. Here, we critically review the evidence on the efficacy, feasibility and acceptability, and effectiveness of REHIT for improving health and fitness.

The effects of exercise on epigenetic modifications: focus on DNA methylation, histone modifications and non-coding RNAs

Physical activity on a regular basis has been shown to bolster the overall wellness of an individual; research is now revealing that these changes are accompanied by epigenetic modifications. Regular exercise has been proven to make intervention plans more successful and prolong adherence to them. When it comes to epigenetic changes, there are four primary components. This includes changes to the DNA, histones, expression of particular non-coding RNAs and DNA methylation. External triggers, such as physical activity, can lead to modifications in the epigenetic components, resulting in changes in the transcription process. This report pays attention to the current knowledge that pertains to the epigenetic alterations that occur after exercise, the genes affected and the resulting characteristics.

Heavy-, Severe-, and Extreme-, but Not Moderate-Intensity Exercise Increase V̇o 2max and Thresholds after 6 wk of Training

INTRODUCTION

This study assessed the effect of individualized, domain-based exercise intensity prescription on changes in maximal oxygen uptake (V̇O 2max ) and submaximal thresholds.

METHODS

Eighty-four young healthy participants (42 females, 42 males) were randomly assigned to six age, sex, and V̇O 2max -matched groups (14 participants each). Groups performed continuous cycling in the 1) moderate (MOD), 2) lower heavy (HVY1), and 3) upper heavy-intensity (HVY2) domain; interval cycling in the form of 4) high-intensity interval training (HIIT) in the severe-intensity domain, or 5) sprint-interval training (SIT) in the extreme-intensity domain; or no exercise for 6) control (CON). All training groups, except SIT, were work-matched. Training participants completed three sessions per week for 6 wk with physiological evaluations performed at PRE, MID, and POST intervention.

RESULTS

Compared with the change in V̇O 2max (∆V̇O 2max ) in CON (0.1 ± 1.2 mL·kg -1 ·min -1 ), all training groups, except MOD (1.8 ± 2.7 mL·kg -1 ·min -1 ), demonstrated a significant increase ( P < 0.05). HIIT produced the highest increase (6.2 ± 2.8 mL·kg -1 ·min -1 ) followed by HVY2 (5.4 ± 2.3 mL·kg -1 ·min -1 ), SIT (4.7 ± 2.3 mL·kg -1 ·min -1 ), and HVY1 (3.3 ± 2.4 mL·kg -1 ·min -1 ), respectively. The ΔPO at the estimated lactate threshold ( θLT ) was similar across HVY1, HVY2, HIIT, and SIT, which were all greater than CON ( P < 0.05). The ΔV̇O 2 and ΔPO at θLT for MOD was not different from CON ( P > 0.05). HIIT produced the highest ΔPO at maximal metabolic steady state, which was greater than CON, MOD, and SIT ( P < 0.05).

CONCLUSIONS

This study demonstrated that i) exercise intensity is a key component determining changes in V̇O 2max and submaximal thresholds and ii) exercise intensity domain-based prescription allows for a homogenous metabolic stimulus across individuals.

Changes in Plasma Free Amino Acid Profile in Endurance Athletes over a 9-Month Training Cycle

We aimed to evaluate long-term changes in proteinogenic and non-proteinogenic plasma free amino acids (PFAA). Eleven male endurance triathletes participated in a 9-month study. Blood was collected at rest, immediately after exhaustive exercise, and during 30-min recovery, in four consecutive training phases: transition, general, specific, and competition. Twenty proteinogenic and 22 non-proteinogenic PFAAs were assayed using the LC-ESI-MS/MS technique. The structured training modified the patterns of exercise-induced PFAA response, with the competition phase being the most distinct from the others. Branched-chain amino acids (p = 0.002; η2 = 0.216), phenylalanine (p = 0.015; η2 = 0.153), methionine (p = 0.002; η2 = 0.206), and lysine (p = 0.006; η2 = 0.196) declined more rapidly between rest and exhaustion in the competition phase. Glutamine (p = 0.008; η2 = 0.255), glutamate (p = 0.006; η2 = 0.265), tyrosine (p = 0.001; η2 = 0.195), cystine (p = 0.042; η2 = 0.183), and serine (p < 0.001; η2 = 0.346) levels were reduced in the competition phase. Arginine (p = 0.046; η2 = 0.138) and aspartate (p = 0.011; η2 = 0.171) levels were highest during exercise in the transition phase. During the competition phase, α-aminoadipic acid (p = 0.023; η2 = 0.145), β-aminoisobutyric acid (p = 0.007; η2 = 0.167), β-alanine (p < 0.001; η2 = 0.473), and sarcosine (p = 0.017; η2 = 0.150) levels increased, whereas phosphoethanolamine (p = 0.037; η2 = 0.189) and taurine (p = 0.008; η2 = 0.251) concentrations decreased. Overtraining indicators were not elevated. The altered PFAA profile suggests adaptations within energy metabolic pathways such as the tricarboxylic acid cycle, oxidative phosphorylation, ammonia neutralization, the purine nucleotide cycle, and buffering of intracellular H+ ions. The changes seem to reflect normal adaptations.

Eicosapentaenoic acid increases proportion of type 1 muscle fibers through PPARδ and AMPK pathways in rats

Muscle fiber type composition (% slow-twitch and % fast-twitch fibers) is associated with metabolism, with increased slow-twitch fibers alleviating metabolic disorders. Previously, we reported that dietary fish oil intake induced a muscle fiber-type transition in a slower direction in rats. The aim of this study was to determine the functionality of eicosapentaenoic acid (EPA), a unique fatty acid in fish oil, to skeletal muscle fiber type and metabolism in rats. Here, we showed that dietary EPA promotes whole-body oxidative metabolism and improves muscle function by increasing proportion of slow-twitch type 1 fibers in rats. Transcriptomic and metabolomic analyses revealed that EPA supplementation activated the peroxisome proliferator-activated receptor δ (PPARδ) and AMP-activated protein kinase (AMPK) pathways in L6 myotube cultures, which potentially increasing slow-twitch fiber share. This highlights the role of EPA as an exercise-mimetic dietary component that improves metabolism and muscle function, with potential benefits for health and athletic performance.

Joint association of genetic risk and accelerometer-measured physical activity with incident coronary artery disease in the UK biobank cohort

Previous research demonstrates the joint association of self-reported physical activity and genotype with coronary artery disease. However, an existing research gap is whether accelerometer-measured overall physical activity or physical activity intensity can offset genetic predisposition to coronary artery disease. This study explores the independent and joint associations of accelerometer-measured physical activity and genetic predisposition with incident coronary artery disease. Incident coronary artery disease based on hospital inpatient records and death register data serves as the outcome of this study. Polygenic risk score and overall physical activity, measured as Euclidean Norm Minus One, and intensity, measured as minutes per day of moderate-to-vigorous intensity physical activity (MVPA), are examined both linearly and by decile. The UK Biobank population-based cohort recruited over 500,000 individuals aged 40 to 69 between 2006 and 2010, with 103,712 volunteers participating in a weeklong wrist-worn accelerometer study from 2013 to 2015. Individuals of White British ancestry (n = 65,079) meeting the genotyping and accelerometer-based inclusion criteria and with no missing covariates were included in the analytic sample. In the sample of 65,079 individuals, the mean (SD) age was 62.51 (7.76) and 61% were female. During a median follow-up of 6.8 years, 1,382 cases of coronary artery disease developed. At the same genetic risk, physical activity intensity had a hazard ratio (HR) of 0.41 (95% CI: 0.29-0.60) at the 90th compared to 10th percentile, equivalent to 31.68 and 120.96 minutes of moderate-to-vigorous physical activity per day, respectively, versus an HR of 0.61 (95% CI: 0.52-0.72) for overall physical activity. The combination of high genetic risk and low physical activity intensity showed the greatest risk, with an individual at the 10th percentile of genetic risk and 90th percentile of intensity facing an HR of 0.14 (95% CI: 0.09-0.21) compared to an individual at the 90th percentile of genetic risk and 10th percentile of intensity. Physical activity, especially physical activity intensity, is associated with an attenuation of some of the risk of coronary artery disease but this pattern does not vary by genetic risk. This accelerometer-based study provides the clearest evidence to date regarding the joint influence of genetics, overall physical activity, and physical activity intensity on coronary artery disease.

A Combination of Exercise and Yogurt Intake Protects Mice against Obesity by Synergistic Promotion of Adipose Browning

Exercise exerts many beneficial effects on obesity, but the mechanism remains elusive. Here, we report a previously unidentified role of the lactate receptor GPR81 in exercise. We observed that GPR81 was significantly up-regulated in white adipose tissues (WAT) upon exercise training in both lean and obese mice. Exercise could induce thermogenesis and beige adipocyte development, whereas such an effect was markedly impaired by the deficiency of GPR81. Furthermore, the activation of GPR81 by exercise and lactate supplementation (250 or 500 mg/kg) yielded a synergistic enhancement of WAT browning and thermogenesis. Yogurt is a dairy product enriched with lactate. A combination of exercise and yogurt intake (20 g/kg) synergistically protected mice against high-fat-diet-induced obesity, as evidenced by decreased body weight, ameliorative dyslipidemia, improved glucose tolerance, and reduced hepatic steatosis. Mechanistically, lactate-GPR81 axis might aid in the norepinephrine-stimulated beige adipocyte biogenesis cascade via the Ca2+/CaMK pathway. Together, these findings reveal the critical role of lactate-GPR81 signaling in exercise-induced WAT browning and provide a new strategy for personalized diet and lifestyle interventions for obesity management.

Effect of an endothelial regulatory module on plasma proteomics in exercising horses

Elite performing exercise requires an intricate modulation of the blood pressure to support the working muscles with oxygen. We have previously identified a genomic regulatory module that associates with differences in blood pressures of importance for elite performance in racehorses. This study aimed to determine the effect of the regulatory module on the protein repertoire. We sampled plasma from 12 Coldblooded trotters divided into two endothelial regulatory module haplotype groups, a sub-elite performing haplotype (SPH) and an elite performing haplotype (EPH), each at rest and exercise. The haplotype groups and their interaction were interrogated in two analyses, i) individual paired ratio analysis for identifying differentially abundant proteins of exercise (DAPE) and interaction (DAPI) between haplotype and exercise, and ii) unpaired ratio analysis for identifying differentially abundant protein of haplotype (DAPH). The proteomics analyses revealed a widespread change in plasma protein content during exercise, with a decreased tendency in protein abundance that is mainly related to lung function, tissue fluids, metabolism, calcium ion pathway and cellular energy metabolism. Furthermore, we provide the first investigation of the proteome variation due to the interaction between exercise and related blood pressure haplotypes, which this difference was related to a faster switch to the lipoprotein and lipid metabolism during exercise for EPH. The molecular signatures identified in the present study contribute to an improved understanding of exercise-related blood pressure regulation.

Next-generation sequencing reveals that miR-16-5p, miR-19a-3p, miR-451a, and miR-25-3p cargo in plasma extracellular vesicles differentiates sedentary young males from athletes

A sedentary lifestyle and Olympic participation are contrary risk factors for global mortality and incidence of cancer and cardiovascular disease. Extracellular vesicle miRNAs have been described to respond to exercise. No molecular characterization of young male sedentary people versus athletes is available; so, our aim was to identify the extracellular vesicle miRNA profile of chronically trained young endurance and resistance male athletes compared to their sedentary counterparts. A descriptive case-control design was used with 16 sedentary young men, 16 Olympic male endurance athletes, and 16 Olympic male resistance athletes. Next-generation sequencing and RT-qPCR and external and internal validation were performed in order to analyze extracellular vesicle miRNA profiles. Endurance and resistance athletes had significant lower levels of miR-16-5p, miR-19a-3p, and miR-451a compared to sedentary people. Taking all together, exercise-trained miRNA profile in extracellular vesicles provides a differential signature of athletes irrespective of the type of exercise compared to sedentary people. Besides, miR-25-3p levels were specifically lower in endurance athletes which defines its role as a specific responder in this type of athletes. In silico analysis of this profile suggests a role in adaptive energy metabolism in this context that needs to be experimentally validated. Therefore, this study provides for the first time basal levels of circulating miRNA in extracellular vesicles emerge as relevant players in intertissue communication in response to chronic exercise exposure in young elite male athletes.

Readjustment of circadian clocks by exercise intervention is a potential therapeutic target for sleep disorders: a narrative review

PURPOSE

Circadian clocks are evolved endogenous biological systems that communicate with environmental cues to optimize physiological processes, such as the sleep-wake cycle, which is nearly related to quality of life. Sleep disorders can be treated using pharmacological strategies targeting melatonin, orexin, or core clock genes. Exercise has been widely explored as a behavioral treatment because it challenges homeostasis in the human body and affects the regulation of core clock genes. Exercise intervention at the appropriate time of the day can induce a phase shift in internal clocks. Although exercise is a strong external time cue for resetting the circadian clock, exercise therapy for sleep disorders remains poorly understood.

METHODS

This review focused on exercise as a potential treatment for sleep disorders by tuning the internal circadian clock. We used scientific paper depositories, including Google Scholar, PubMed, and the Cochrane Library, to identify previous studies that investigated the effects of exercise on circadian clocks and sleep disorders.

RESULTS

The exercise-induced adjustment of the circadian clock phase depended on exercise timing and individual chronotypes. Adjustment of circadian clocks through scheduled morning exercises can be appropriately prescribed for individuals with delayed sleep phase disorders. Individuals with advanced sleep phase disorders can synchronize their internal clocks with their living environment by performing evening exercises. Exercise-induced physiological responses are affected by age, sex, and current fitness conditions.

CONCLUSION

Personalized approaches are necessary when implementing exercise interventions for sleep disorders.

Metabolic plasticity and obesity-associated changes in diurnal postexercise metabolism in mice

BACKGROUND

Circadian disruption is widespread and increases the risk of obesity. Timing of therapeutic interventions may promote coherent and efficient gating of metabolic processes and restore energy homeostasis.

AIM

To characterize the diurnal postexercise metabolic state in mice and to identify the influence of diet-induced obesity on identified outcomes.

METHODS

C57BL6/NTac male mice (6 wks of age) were fed a standard chow or high-fat diet for 5 weeks. At week 5, mice were subjected to a 60-min (16 m/min, 5 % incline) running bout (or sham) during the early rest (day) or early active (night) phase. Tissue and serum samples were collected immediately post-exercise (n = 6/group). In vivo glucose oxidation was measured after oral administration of 13C-glucose via 13CO2 exhalation analysis in metabolic cages. Basal and isoproterenol-stimulated adipose tissue lipolysis was assessed ex vivo for 1 h following exercise.

RESULTS

Lean mice displayed exercise-timing-specific plasticity in metabolic outcomes, including phase-specificity in systemic glucose metabolism and adipose-tissue-autonomous lipolytic activity depending on time of day. Conversely, obesity impaired temporal postexercise differences in whole-body glucose oxidation, as well as the phase- and exercise-mediated induction of lipolysis in isolated adipose tissue. This obesity-induced alteration in diurnal metabolism, as well as the indistinct response to exercise, was observed concomitant with disruption of core clock gene expression in peripheral tissues.

CONCLUSIONS

Overall, high-fat fed obese mice exhibit metabolic inflexibility, which is also evident in the diurnal exercise response. Our study provides physiological insight into exercise timing-dependent aspects in the dynamic regulation of metabolism and the influence of obesity on this biology.

Time-course and muscle-specific gene expression of matrix metalloproteinases and inflammatory cytokines in response to acute treadmill exercise in rats

BACKGROUND

The extracellular matrix (ECM) of skeletal muscle plays a pivotal role in tissue repair and growth, and its remodeling tightly regulated by matrix metalloproteinases (MMPs), tissue inhibitors of metalloproteinases (TIMPs), and inflammatory cytokines. This study aimed to investigate changes in the mRNA expression of MMPs (Mmp-2 and Mmp-14), TIMPs (Timp-1 and Timp-2), and inflammatory cytokines (Il-1β, Tnf-α, and Tgfβ1) in the soleus (SOL) and extensor digitorum longus (EDL) muscles of rats following acute treadmill exercise. Additionally, muscle morphology was examined using hematoxylin and eosin (H&E) staining.

METHODS AND RESULTS

Male rats were subjected to acute treadmill exercise at 25 m/min for 60 min with a %0 slope. The mRNA expression of ECM components and muscle morphology in the SOL and EDL were assessed in both sedentary and exercise groups at various time points (immediately (0) and 1, 3, 6, 12, and 24 h post-exercise). Our results revealed a muscle-specific response, with early upregulation of the mRNA expression of Mmp-2, Mmp-14, Timp-1, Timp-2, Il-1β, and Tnf-α observed in the SOL compared to the EDL. A decrease in Tgfβ1 mRNA expression was evident in the SOL at all post-exercise time points. Conversely, Tgfβ1 mRNA expression increased at 0 and 3 h post-exercise in the EDL. Histological analysis also revealed earlier cell infiltration in the SOL than in the EDL following acute exercise.

CONCLUSIONS

Our results highlight how acute exercise modulates ECM components and muscle structure differently in the SOL and EDL muscles, leading to distinct muscle-specific responses.

BCAA-nitrogen flux in brown fat controls metabolic health independent of thermogenesis

Brown adipose tissue (BAT) is best known for thermogenesis. Rodent studies demonstrated that enhanced BAT thermogenesis is tightly associated with increased energy expenditure, reduced body weight, and improved glucose homeostasis. However, human BAT is protective against type 2 diabetes, independent of body weight. The mechanism underlying this dissociation remains unclear. Here, we report that impaired mitochondrial catabolism of branched-chain amino acids (BCAAs) in BAT, by deleting mitochondrial BCAA carriers (MBCs), caused systemic insulin resistance without affecting energy expenditure and body weight. Brown adipocytes catabolized BCAA in the mitochondria as nitrogen donors for the biosynthesis of non-essential amino acids and glutathione. Impaired mitochondrial BCAA-nitrogen flux in BAT resulted in increased oxidative stress, decreased hepatic insulin signaling, and decreased circulating BCAA-derived metabolites. A high-fat diet attenuated BCAA-nitrogen flux and metabolite synthesis in BAT, whereas cold-activated BAT enhanced the synthesis. This work uncovers a metabolite-mediated pathway through which BAT controls metabolic health beyond thermogenesis.

Mechanisms and benefits of cardiac rehabilitation in individuals with stroke: emerging role of its impact on improving cardiovascular and neurovascular health

Human and animal studies have demonstrated the mechanisms and benefits of aerobic exercise for both cardiovascular and neurovascular health. Aerobic exercise induces neuroplasticity and neurophysiologic reorganization of brain networks, improves cerebral blood flow, and increases whole-body VO2peak (peak oxygen consumption). The effectiveness of a structured cardiac rehabilitation (CR) program is well established and a vital part of the continuum of care for people with cardiovascular disease. Individuals post stroke exhibit decreased cardiovascular capacity which impacts their neurologic recovery and extends disability. Stroke survivors share the same risk factors as patients with cardiac disease and can therefore benefit significantly from a comprehensive CR program in addition to neurorehabilitation to address their cardiovascular health. The inclusion of individuals with stroke into a CR program, with appropriate adaptations, can significantly improve their cardiovascular health, promote functional recovery, and reduce future cardiovascular and cerebrovascular events thereby reducing the economic burden of stroke.

Evaluation of the "Step-Ramp-Step" Protocol: Accurate Aerobic Exercise Prescription with Different Steps and Ramp Slopes

PURPOSE

To assess whether: i) a lower amplitude constant-load MOD is appropriate to determine the mean response time (MRT); ii) the method accurately corrects the dissociation in the V̇O 2 -PO relationship during ramp compared with constant-load exercise when using different ramp slopes.

METHODS

Eighteen participants (7 females) performed three SRS tests including: i) step-transitions into MOD from 20 to 50 W (MOD 50 ) and 80 W (MOD 80 ); and ii) slopes of 15, 30, and 45 W·min -1 . The V̇O 2 and PO at the gas exchange threshold (GET) and the corrected respiratory compensation point (RCP CORR ) were determined. Two to three 30-min constant-load trials evaluated the V̇O 2 and PO at the maximal metabolic steady state (MMSS).

RESULTS

There were no differences in V̇O 2 at GET (1.97 ± 0.36, 1.99 ± 0.36, 1.95 ± 0.30 L·min -1 ), and RCP (2.81 ± 0.57, 2.86 ± 0.59, 2.84 ± 0.59) between 15, 30, and 45 W·min -1 ramps, respectively ( P > 0.05). The MRT in seconds was not affected by the amplitude of the MOD or the slope of the ramp (range 19 ± 10 s to 23 ± 20 s; P > 0.05). The mean PO at GET was not significantly affected by the amplitude of the MOD or the slope of the ramp (range 130 ± 30 W to 137 ± 30 W; P > 0.05). The PO at RCP CORR was similar for all conditions ((range 186 ± 43 W to 193 ± 47 W; P > 0.05).

CONCLUSIONS

The SRS protocol accounts for the V̇O 2 MRT when using smaller amplitude steps, and for the V̇O 2 slow component when using different ramp slopes, allowing for accurate partitioning of the exercise intensity domains in a single test.

Exercise-Induced Cell-Free DNA Correlates with Energy Expenditure in Multiple Exercise Protocols

PURPOSE

Exercise-induced cell-free DNA (ei-cfDNA) has been studied in response to various types of exercise. Its correlation with exercise intensity and duration has been observed consistently. However, comprehensive measurements and exploration of the tissue of origin are lacking. The aim of this study is to establish precise connections between exercise variables and the distribution of tissue of origin, aiming to provide further evidence supporting its use as a biomarker for exercise.

METHODS

Twelve self-identified active adults (six men and six women) performed a crossover study starting with either endurance testing or resistance testing under different intensities and protocols. We obtained blood before and after each exercise session and measured the levels of cfDNA and determined its tissue of origin utilizing cell type-specific DNA methylation patterns in plasma.

RESULTS

We found that when duration and intensity are fixed, ei-cfDNA fold change correlates with energy expenditure ( P = 0.001) in endurance testing and years trained ( P = 0.001) in resistance testing. Most of the ei-cfDNA comes from increases in white blood cells (~95%) where neutrophils make up the majority (~74%) and the distribution is different between exercise modalities and protocols.

CONCLUSIONS

This study highlights the potential of exercise-induced cfDNA as a biomarker for exercise, showing correlations with energy expenditure and a consistent pattern of tissue origin. Additional research is needed to investigate potential sex differences in the response of cfDNA to exercise, further exploring its clinical implications.

Exercise-Regulated Mitochondrial and Nuclear Signalling Networks in Skeletal Muscle

Exercise perturbs energy homeostasis in skeletal muscle and engages integrated cellular signalling networks to help meet the contraction-induced increases in skeletal muscle energy and oxygen demand. Investigating exercise-associated perturbations in skeletal muscle signalling networks has uncovered novel mechanisms by which exercise stimulates skeletal muscle mitochondrial biogenesis and promotes whole-body health and fitness. While acute exercise regulates a complex network of protein post-translational modifications (e.g. phosphorylation) in skeletal muscle, previous investigations of exercise signalling in human and rodent skeletal muscle have primarily focused on a select group of exercise-regulated protein kinases [i.e. 5' adenosine monophosphate-activated protein kinase (AMPK), protein kinase A (PKA), Ca2+/calmodulin-dependent protein kinase (CaMK) and mitogen-activated protein kinase (MAPK)] and only a small subset of their respective protein substrates. Recently, global mass spectrometry-based phosphoproteomic approaches have helped unravel the extensive complexity and interconnection of exercise signalling pathways and kinases beyond this select group and phosphorylation and/or translocation of exercise-regulated mitochondrial and nuclear protein substrates. This review provides an overview of recent advances in our understanding of the molecular events associated with acute endurance exercise-regulated signalling pathways and kinases in skeletal muscle with a focus on phosphorylation. We critically appraise recent evidence highlighting the involvement of mitochondrial and nuclear protein phosphorylation and/or translocation in skeletal muscle adaptive responses to an acute bout of endurance exercise that ultimately stimulate mitochondrial biogenesis and contribute to exercise's wider health and fitness benefits.

High-intensity exercise training using a rotarod instrument (RotaHIIT) significantly improves exercise capacity in mice

Voluntary or forced exercise training in mice is used to assess functional capacity as well as potential disease-modifying effects of exercise over a range of cardiovascular disease phenotypes. Compared to voluntary wheel running, forced exercise training enables precise control of exercise workload and volume, and results in superior changes in cardiovascular performance. However, the use of a shock grid with treadmill-based training is associated with stress and risk of injury, and declining compliance with longer periods of training time for many mouse strains. With these limitations in mind, we designed a novel, high-intensity interval training modality (HIIT) for mice that is carried out on a rotarod. Abbreviated as RotaHIIT, this protocol establishes interval workload intensities that are not time or resource intensive, maintains excellent training compliance over time, and results in improved exercise capacity independent of sex when measured by treadmill graded exercise testing (GXT) and rotarod specific acceleration and endurance testing. This protocol may therefore be useful and easily implemented for a broad range of research investigations. As RotaHIIT training was not associated cardiac structural or functional changes, or changes in oxidative capacity in cardiac or skeletal muscle tissue, further studies will be needed to define the physiological adaptations and molecular transducers that are driving the training effect of this exercise modality.

Exercise therapy for chronic symptomatic peripheral artery disease

All guidelines worldwide strongly recommend exercise as a pillar of the management of patients affected by lower extremity peripheral artery disease (PAD). Exercise therapy in this setting presents different modalities, and a structured programme provides optimal results. This clinical consensus paper is intended for clinicians to promote and assist for the set-up of comprehensive exercise programmes to best advice in patients with symptomatic chronic PAD. Different exercise training protocols specific for patients with PAD are presented. Data on patient assessment and outcome measures are narratively described based on the current best evidence. The document ends by highlighting disparities in access to supervised exercise programmes across Europe and the series of gaps for evidence requiring further research.

Ergothioneine boosts mitochondrial respiration and exercise performance via direct activation of MPST

Ergothioneine (EGT) is a diet-derived, atypical amino acid that accumulates to high levels in human tissues. Reduced EGT levels have been linked to age-related disorders, including neurodegenerative and cardiovascular diseases, while EGT supplementation is protective in a broad range of disease and aging models in mice. Despite these promising data, the direct and physiologically relevant molecular target of EGT has remained elusive. Here we use a systematic approach to identify how mitochondria remodel their metabolome in response to exercise training. From this data, we find that EGT accumulates in muscle mitochondria upon exercise training. Proteome-wide thermal stability studies identify 3-mercaptopyruvate sulfurtransferase (MPST) as a direct molecular target of EGT; EGT binds to and activates MPST, thereby boosting mitochondrial respiration and exercise training performance in mice. Together, these data identify the first physiologically relevant EGT target and establish the EGT-MPST axis as a molecular mechanism for regulating mitochondrial function and exercise performance.

Effects of a 10-Week Exercise and Nutritional Intervention with Variable Dietary Carbohydrates and Glycaemic Indices on Substrate Metabolism, Glycogen Storage, and Endurance Performance in Men: A Randomized Controlled Trial

BACKGROUND

Daily nutrition plays an important role in supporting training adaptions and endurance performance. The objective of this 10-week study was to investigate the consequences of varying carbohydrate consumption and the glycaemic index (GI) together with an endurance training regimen on substrate oxidation, muscle energy storage and endurance performance under free-living conditions. Sixty-five moderately trained healthy men (29 ± 4 years; VO2 peak 55 ± 8 mL min-1 kg-1) were randomized to one of three different nutritional regimes (LOW-GI: 50-60% CHO with ≥ 65% of these CHO with GI < 50 per day, n = 24; HIGH-GI: 50-60% CHO with ≥ 65% CHO with GI > 70 per day, n = 20; LCHF: ≤ 50 g CHO daily, n = 21). Metabolic alterations and performance were assessed at baseline (T0) and after 10 weeks (T10) during a graded exercise treadmill test. Additionally, a 5 km time trial on a 400-m outdoor track was performed and muscle glycogen was measured by magnet resonance spectroscopy.

RESULTS

Total fat oxidation expressed as area under the curve (AUC) during the graded exercise test increased in LCHF (1.3 ± 2.4 g min-1 × km h-1, p < 0.001), remained unchanged in LOW-GI (p > 0.05) and decreased in HIGH-GI (- 1.7 ± 1.5 g min-1 × km h-1, p < 0.001). After the intervention, LOW-GI (- 0.4 ± 0.5 mmol L-1 × km h-1, p < 0.001) and LCHF (- 0.8 ± 0.7 mmol L-1 × km h-1, p < 0.001) showed significantly lower AUC of blood lactate concentrations. Peak running speed increased in LOW-GI (T0: 4.3 ± 0.4 vs. T10: 4.5 ± 0.3 m s-1, p < 0.001) and HIGH-GI (T0: 4.4 ± 0.5 vs. T10: 4.6 ± 0.4 m s-1), while no improvement was observed in LCHF. Yet, time trial performance improved significantly in all groups. Muscle glycogen content increased for participants in HIGH-GI (T0: 97.3 ± 18.5 vs. T10: 144.5 ± 39.8 mmol L wet-tissue-1, p = 0.027) and remained unchanged in the LOW-GI and the LCHF group. At the last examination, muscle glycogen concentration was significantly higher in LOW-GI compared to LCHF (p = 0.014).

CONCLUSION

Changes in fat oxidation were only present in LCHF, however, lower lactate concentrations in LOW-GI resulted in changes indicating an improved substrate metabolism. Compared to a LCHF diet, changes in peak running speed, and muscle glycogen stores were superior in LOW- and HIGH-GI diets. The low GI diet seems to have an influence on substrate metabolism without compromising performance at higher intensities, suggesting that a high-carbohydrate diet with a low GI is a viable alternative to a LCHF or a high GI diet.

TRIAL REGISTRATION

Clinical Trials, NCT05241730. https://clinicaltrials.gov/study/NCT05241730 . Registered 25 January 2021.

Exercise therapy for chronic symptomatic peripheral artery disease

All guidelines worldwide strongly recommend exercise as a pillar in the management of patients affected by lower extremity peripheral artery disease (PAD). Exercise therapy in this setting presents different modalities, and a structured programme provides optimal results. This clinical consensus paper is intended to promote and assist the set up of comprehensive exercise programmes and best advice for patients with symptomatic chronic PAD. Different exercise training protocols specific for patients with PAD are presented. Data on patient assessment and outcome measures are described based on the current best evidence. The document ends by highlighting supervised exercise programme access disparities across Europe and the evidence gaps requiring further research.

The microarchitecture and chemical composition of the femur neck of senescent female rats after different physical training protocols

A sedentary lifestyle, coupled with a decrease in estrogen, impairs bone homeostasis, favoring to the development of osteopenia and osteoporosis, both recognized as risk factors for fractures. Here, we investigated the quality of the femur, particularly the femur neck region, and the ambulation performance of senescent rats subjected to three different physical training protocols during the periestropause period. Forty-eight female rats, 18 months of age, were subjected to a 120-day training period, three times a week. The rats were distributed into four groups: aerobic training (AT), strength training (ST), concurrent training (CT), or no training (NT). After the experimental period, at 21 months of age, ambulation performance and femur were analyzed using microtomography, Raman stereology, densitometry, and mechanical strength tests. The results demonstrated greater remodeling activity and improvement in resistance and bone microarchitecture in the femur neck of senescent female rats after undergoing physical training. Our verified higher intensities of bands related to collagen, phosphate, amide III, and amide I. Furthermore, the analysis of the secondary collagen structures indicated alterations in the collagen network due to the exercise, resulting in increased bone strength. Both AT and strength-based training proved beneficial, with AT showing greater adaptations in bone density and stiffness in the femur, while strength-based training greater adaptations in trabecular and cortical structure. These insights contribute to the understanding of the potential interventions for preventing osteopenia and osteoporosis, which are critical risk factors for fractures.

Winners do what they fear: exercise and peripheral arterial disease-an umbrella review

AIMS

This systematic review aims to evaluate and summarize findings from published meta-analyses on the effects of regular exercise in patients with peripheral arterial disease (PAD). The review will assess the impact of exercise on functional parameters, health-related quality of life, haemodynamic parameters, physical activity levels, adverse events, and mortality.

METHODS AND RESULTS

A systematic search was performed in PubMed, Web of Science, Scopus, and Cochrane Library databases (up to May 2023) to identify meta-analyses including randomized controlled trials that examined the effects of regular exercise in patients with PAD. Sixteen studies, with a total of 198 meta-analyses, were identified. Results revealed with strong evidence that patients with PAD who exercised improved functional and health-related quality of life parameters. Specifically, supervised aerobic exercise (i.e. walking to moderate-maximum claudication pain) improves maximum walking distance [mean difference (MD): 177.94 m, 95% confidence interval (CI) 142.29-213.60; P < 0.00001; I2: 65%], pain-free walking distance (fixed MD: 68.78 m, 95% CI 54.35-83.21; P < 0.00001; I2: 67%), self-reported walking ability [i.e. distance score (MD: 9.22 points, 95% CI 5.74-12.70; P < 0.00001; I2: 0%), speed score (MD: 8.71 points, 95% CI 5.64-11.77; P < 0.00001, I2: 0%), stair-climbing score (MD: 8.02 points, 95% CI 4.84-11.21; P < 0.00001, I2: 0%), and combined score (MD: 8.76 points, 95% CI 2.78-14.74; P < 0.0001, I2: 0%)], aerobic capacity (fixed MD: 0.62 mL/kg/min, 95% CI 0.47-0.77, P < 0.00001, I2: 64%), and pain score (MD: 7.65, 95% CI 3.15-12.15; P = 0.0009; I2: 0%), while resistance exercise improves lower limb strength (standardized mean difference: 0.71, 95% CI 0.29-1.13, P = 0.0009; I2: 0%]. Regarding other outcomes, such as haemodynamic parameters, no significant evidence was found, while physical activity levels, adverse events, and mortality require further investigation.

CONCLUSION

Synthesis of the currently available meta-analyses suggests that regular exercise may be beneficial for a broad range of functional tasks improving health-related quality of life in patients with PAD. Supervised aerobic exercise is the best type of exercise to improve walking-related outcomes and pain, while resistance exercise is more effective to improve lower limb strength.

Carnosine regulation of intracellular pH homeostasis promotes lysosome-dependent tumor immunoevasion

Tumor cells and surrounding immune cells undergo metabolic reprogramming, leading to an acidic tumor microenvironment. However, it is unclear how tumor cells adapt to this acidic stress during tumor progression. Here we show that carnosine, a mobile buffering metabolite that accumulates under hypoxia in tumor cells, regulates intracellular pH homeostasis and drives lysosome-dependent tumor immune evasion. A previously unrecognized isoform of carnosine synthase, CARNS2, promotes carnosine synthesis under hypoxia. Carnosine maintains intracellular pH (pHi) homeostasis by functioning as a mobile proton carrier to accelerate cytosolic H+ mobility and release, which in turn controls lysosomal subcellular distribution, acidification and activity. Furthermore, by maintaining lysosomal activity, carnosine facilitates nuclear transcription factor X-box binding 1 (NFX1) degradation, triggering galectin-9 and T-cell-mediated immune escape and tumorigenesis. These findings indicate an unconventional mechanism for pHi regulation in cancer cells and demonstrate how lysosome contributes to immune evasion, thus providing a basis for development of combined therapeutic strategies against hepatocellular carcinoma that exploit disrupted pHi homeostasis with immune checkpoint blockade.

A Hierarchical Mechanotransduction System: From Macro to Micro

Mechanotransduction is a strictly regulated process whereby mechanical stimuli, including mechanical forces and properties, are sensed and translated into biochemical signals. Increasing data demonstrate that mechanotransduction is crucial for regulating macroscopic and microscopic dynamics and functionalities. However, the actions and mechanisms of mechanotransduction across multiple hierarchies, from molecules, subcellular structures, cells, tissues/organs, to the whole-body level, have not been yet comprehensively documented. Herein, the biological roles and operational mechanisms of mechanotransduction from macro to micro are revisited, with a focus on the orchestrations across diverse hierarchies. The implications, applications, and challenges of mechanotransduction in human diseases are also summarized and discussed. Together, this knowledge from a hierarchical perspective has the potential to refresh insights into mechanotransduction regulation and disease pathogenesis and therapy, and ultimately revolutionize the prevention, diagnosis, and treatment of human diseases.

Acute exercise-induced release of innate immune proteins via small extracellular vesicles changes with aerobic fitness and age

AIM

Physical exercise triggers the secretion of small extracellular vesicles (sEVs) into the circulation in humans, enabling signalling crosstalk between tissues. Exercise-derived EVs and their cargo have been proposed to mediate adaptations to exercise; however, our understanding of how exercise-derived EV protein cargo is modulated by factors such as aerobic fitness and age of an individual is currently unknown. Here, we examined the circulating sEV proteome following aerobic exercise in healthy males of different ages and aerobic fitness to understand exercise-induced EV response during the aging process.

METHODS

Twenty-eight healthy men completed a bout of 20-min cycling exercise at 70% estimated VO2peak . Small EVs were isolated from blood samples collected before and immediately after exercise, and then quantified using particle analysis and Western blotting. Small EV proteome was examined using quantitative proteomic analysis.

RESULTS

We identified a significant increase in 13 proteins in small plasma EVs following moderate-to-vigorous intensity exercise. We observed distinct changes in sEV proteome after exercise in young, mature, unfit, and fit individuals, highlighting the impact of aerobic fitness and age on sEV protein secretion. Functional enrichment and pathway analysis identified that the majority of the significantly altered sEV proteins are associated with the innate immune system, including proteins known to be damage-associated molecular patterns (DAMPs).

CONCLUSION

Together, our findings suggest that exercise-evoked acute stress can positively challenge the innate immune system through the release of signalling molecules such as DAMPs in sEVs, proposing a novel EV-based mechanism for moderate-to-vigorous intensity exercise in immune surveillance pathways.

Global scientific trends in research of epigenetic response to exercise: A bibliometric analysis

The purpose of this work is to comprehensively understand the adaptive response of multiple epigenetic modifications on gene expression changes driven by exercise. Here, we retrieved literatures from publications in the PubMed and Web of Science Core Collection databases up to and including October 15, 2023. After screening with the exclusion criteria, 1910 publications were selected in total, comprising 1399 articles and 511 reviews. Specifically, a total of 512, 224, and 772 publications is involved in DNA methylation, histone modification, and noncoding RNAs, respectively. The correlations between publication number, authors, institutions, countries, references, and the characteristics of hotspots were explored by CiteSpace. Here, the USA (621 publications) ranked the world's most-influential countries, the University of California System (68 publications) was the most productive, and Tiago Fernandes (14 publications) had the most-published publications. A comprehensive keyword analysis revealed that cardiovascular disease, cancer, skeletal muscle development, and metabolic syndrome, and are the research hotspots. The detailed impact of exercise was further discussed in different aspects of these three categories of epigenetic modifications. Detailed analysis of epigenetic modifications in response to exercise, including DNA methylation, histone modification, and changes in noncoding RNAs, will offer valuable information to help researchers understand hotspots and emerging trends.