Skeletal muscle energy metabolism during exercise

Unveiling the link: exploring muscle oxygen saturation in fibromyalgia and its implications for symptomatology and therapeutic strategies

Fibromyalgia, characterized as a complex chronic pain syndrome, presents with symptoms of pervasive musculoskeletal pain, significant fatigue, and pronounced sensitivity at specific anatomical sites. Despite extensive research efforts, the origins of fibromyalgia remain enigmatic. This narrative review explores the intricate relationship between muscle oxygen saturation and fibromyalgia, positing that disruptions in the oxygenation processes within muscle tissues markedly influence the symptom profile of this disorder. Muscle oxygen saturation, crucial for muscle function, has been meticulously investigated in fibromyalgia patients through non-invasive techniques such as near-infrared spectroscopy and magnetic resonance imaging. The body of evidence consistently indicates substantial alterations in oxygen utilization within muscle fibers, manifesting as reduced efficiency in oxygen uptake during both rest and physical activity. These anomalies play a significant role in fibromyalgia's symptomatology, especially in terms of chronic pain and severe fatigue, potentially creating conditions that heighten pain sensitivity and accumulate metabolic byproducts. Hypothesized mechanisms for these findings encompass dysfunctions in microcirculation, mitochondrial irregularities, and autonomic nervous system disturbances, all meriting further research. Understanding the dynamics of muscle oxygen saturation in fibromyalgia is of paramount clinical importance, offering the potential for tailored therapeutic approaches to alleviate symptoms and improve the quality of life for sufferers. This investigation not only opens new avenues for innovative research but also fosters hope for more effective treatment strategies and improved outcomes for individuals with fibromyalgia.

Can incidental physical activity offset the deleterious associations of sedentary behaviour with major adverse cardiovascular events?

AIMS

Incidental physical activity as part of daily living may offer feasibility advantages over traditional exercise. We examined the joint associations of incidental physical activity and sedentary behaviour with major adverse cardiovascular events (MACE) risk.

METHODS AND RESULTS

Analyses included 22 368 non-exercising adults from the UK Biobank accelerometry sub-study (median age [IQR]: 62.9 [11.6] years; 41.8% male). Physical activity and sedentary behaviour exposures were derived using a machine learning-based intensity and posture classification schema. We assessed the tertile-based joint associations of sedentary behaviour and the following: a) incidental vigorous (VPA), b) incidental moderate to vigorous (MVPA), c) vigorous intermittent lifestyle physical activity (VILPA; bouts lasting up to 1 min), and d) moderate to vigorous intermittent lifestyle physical activity (MV-ILPA; bouts lasting up to 3 min) with MACE risk. Over an 8.0-year median follow-up, 819 MACE events occurred. Compared to the highest physical activity and lowest sedentary time, high sedentary behaviour (>11.4 h/day) with low incidental VPA (<2.1 min/day) had an HR of 1.34 (95% CI: 0.98, 1.84) and low incidental MVPA (<21.8 min/day) had a 1.89 HR (95% CI: 1.42, 2.52) for MACE. Sedentary behaviour was not associated with MACE at medium and high levels of VPA or VILPA. Completing 4.1 min/day of VPA or VILPA may offset the MACE risk associated with high sedentary behaviour. Conversely, 31-65 min of incidental MVPA or 26-52 min of MV-ILPA per day largely attenuated the associations with MACE.

CONCLUSION

Brief intermittent bursts of vigorous incidental physical activity may offset cardiovascular risks from high sedentary behaviour.

LAY SUMMARY

Literature to date has examined the role of total or leisure time physical activity in mitigating the health risks associated with high sedentary behaviour. However, the vast majority of adults achieve their daily physical activity incidentally through day-to-day activities. In this study of 22 368 adults from the UK Biobank accelerometry sub-study, we provide the first investigation into whether a) incidental vigorous (VPA), b) incidental moderate to vigorous (MVPA), c) vigorous intermittent lifestyle physical activity (VILPA; bouts lasting up to 1 min), and d) moderate to vigorous intermittent lifestyle physical activity (MV-ILPA; bouts lasting up to 3 min) completed through normal daily living can offset the risk of major adverse cardiovascular events (MACE) associated with high sedentary behaviour (>11.4 h per day). We demonstrate that incidental VPA and MVPA may offset the MACE risk associated with high-sedentary behaviour even if accrued in brief bursts lasting <3 min. Completing 4.1 min/day of VPA or VILPA may offset the MACE risk associated with high sedentary behaviour.A daily duration of 31-65 min of incidental MVPA or 26-52 min of MV-ILPA per day largely attenuated the associations with MACE.

Exercise-driven cellular autophagy: A bridge to systematic wellness

BACKGROUND

Exercise enhances health by supporting homeostasis, bolstering defenses, and aiding disease recovery. It activates autophagy, a conserved cellular process essential for maintaining balance, while dysregulated autophagy contributes to disease progression. Despite extensive research on exercise and autophagy independently, their interplay remains insufficiently understood.

AIM OF REVIEW

This review explores the molecular mechanisms of exercise-induced autophagy in various tissues, focusing on key transduction pathways. It examines how different types of exercise trigger specific autophagic responses, supporting cellular balance and addressing systemic dysfunctions. The review also highlights the signaling pathways involved, their roles in protecting organ function, reducing disease risk, and promoting longevity, offering a clear understanding of the link between exercise and autophagy.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Exercise-induced autophagy is governed by highly coordinated and dynamic pathways integrating direct and indirect mechanical forces and biochemical signals, linking physical activity to cellular and systemic health across multiple organ systems. Its activation is influenced by exercise modality, intensity, duration, and individual biological characteristics, including age, sex, and muscle fiber composition. Aerobic exercises primarily engage AMPK and mTOR pathways, supporting mitochondrial quality and cellular homeostasis. Anaerobic training activates PI3K/Akt signaling, modulating molecules like FOXO3a and Beclin1 to drive muscle autophagy and repair. In pathological contexts, exercise-induced autophagy enhances mitochondrial function, proteostasis, and tissue regeneration, benefiting conditions like sarcopenia, neurodegeneration, myocardial ischemia, metabolic disorders, and cancer. However, excessive exercise may lead to autophagic overactivation, leading to muscle atrophy or pathological cardiac remodeling. This underscores the critical need for balanced exercise regimens to maximize therapeutic efficacy while minimizing risks. Future research should prioritize identifying reliable biomarkers, optimizing exercise protocols, and integrating exercise with pharmacological strategies to enhance therapeutic outcomes.

Soft, Modular Power for Composing Robots with Embodied Energy

The adaptable, modular structure of muscles, combined with their confluent energy storage allows for numerous architectures found in nature: trunks, tongues, and tentacles to name some more complex ones. To provide an artificial analog to this biological soft muscle, a self-powered, soft hydrostat actuator is presented. As an example of how to use these modules, a worm robot is assembled where the near totality of the body stores electrochemical potential. The robot exhibits an extremely high system energy density (51.3 J g-1), using a redox flow battery motif, with a long theoretical operational range of more than 100 m on a single charge. The innovation lies in the battery pouch, fabricated with a dry-adhesion method, automatically bonding Nafion separators to a silicone-urethane copolymer body. These pouches contain anolyte within a hydrostat pod filled with catholyte, increasing current density per pod. Each pod has a motor and tendon actuator for radial compression and expansion. By linking these self-contained pods in series, the robot worm is created that automatically navigates an enclosed, curved path. This high-capacity soft worm also climbs up and down a vertical pipe, using a two-anchor crawling gait, with an extra payload equivalent to 1.5 times its body weight.

Cellular Feimin enhances exercise performance by suppressing muscle thermogenesis

Exercise can rapidly increase core body temperature, and research has indicated that elevated internal body temperature can independently contribute to fatigue during physical activity. However, the precise mechanisms responsible for regulating thermogenesis in muscles during exercise have remained unclear. Here, we demonstrate that cellular Feimin (cFeimin) enhances exercise performance by inhibiting muscle thermogenesis during physical activity. Mechanistically, we found that AMP-activated protein kinase (AMPK) phosphorylates cFeimin and facilitates its translocation into the cell nucleus during exercise. Within the nucleus, cFeimin binds to the forkhead transcription factor FOXC2, leading to the suppressed expression of sarcolipin (Sln), which is a key regulator of muscle thermogenesis. In addition, our results further reveal that short-term AMPK agonist treatments can enhance exercise performance through the activation of the AMPK-cFeimin signalling pathway. In summary, these results underscore the crucial role of cFeimin in enhancing exercise performance by modulating SLN-mediated thermogenesis.

Effects of seven days' fasting on physical performance and metabolic adaptation during exercise in humans

Humans have, throughout history, faced periods of starvation necessitating increased physical effort to gather food. To explore adaptations in muscle function, 13 participants (7 males and 6 females) fasted for seven days. They lost 4.6 ± 0.3 kg lean and 1.4 ± 0.1 kg fat mass. Maximal isometric and isokinetic strength remained unchanged, while peak oxygen uptake decreased by 13%. Muscle glycogen was halved, while expression of electron transport chain proteins was unchanged. Pyruvate dehydrogenase kinase 4 (PDK4) expression increased 13-fold, accompanied by inhibitory pyruvate dehydrogenase phosphorylation, reduced carbohydrate oxidation and decreased exercise endurance capacity. Fasting had no impact on 5' AMP-activated protein kinase (AMPK) activity, challenging its proposed role in muscle protein degradation. The participants maintained muscle strength and oxidative enzymes in skeletal muscle during fasting but carbohydrate oxidation and high-intensity endurance capacity were reduced.

Raman Spectroscopic Analysis of Urinary Creatine and Phosphate in Athletes: Pre- and Post-Training Assessment

The aim of this study was to detect biochemical components in the urine of bodybuilders who ingested creatine pretraining compared to individuals who did not ingest creatine after physical exercise using Raman spectroscopy. Twenty volunteers practicing bodybuilding were selected to collect pre- and post-training urine samples, where 10 volunteers ingested creatine 30 min before pretraining urine collection (creatine group), and 10 did not (control group). The samples were subjected to Raman spectroscopy, and the spectra of both creatine and control groups and the difference (post-pre) for both groups were analyzed. Principal component analysis (PCA) technique was applied to the samples. The results showed peaks of creatine and phosphate in urine after training (creatine post-training group), suggesting that part of the creatine was absorbed and metabolized, and part was excreted. Raman spectroscopy could be applied to detect biocompounds in urine, such as unmetabolized creatine and phosphate.

Age-related changes of skeletal muscle metabolic response to contraction are also sex-dependent

Mitochondria adapt to increased energy demands during muscle contraction by acutely altering metabolite fluxes and substrate oxidation. With age, an impaired mitochondrial metabolic response may contribute to reduced exercise tolerance and decreased skeletal muscle mass, specific force, increased overall fatty depositions in the skeletal muscle, frailty and depressed energy maintenance. We hypothesized that elevated energy stress in mitochondria with age alters the capacity of mitochondria to utilize different substrates following muscle contraction. To test this hypothesis, we used in vivo electrical stimulation to simulate high-intensity intervals (HII) or low intensity steady-state (LISS) exercise in young (5-7 months) and aged (27-29 months) male and female mice to characterize effects of age and sex on mitochondrial substrate utilization in skeletal muscle following contraction. Mitochondrial respiration using glutamate decreased in aged males following HII and glutamate oxidation was inhibited following HII in both the contracted and non-stimulated muscle of aged female muscle. Analyses of the muscle metabolome of female mice indicated that changes in metabolic pathways induced by HII and LISS contractions in young muscle are absent in aged muscle. To test improved mitochondrial function on substrate utilization following HII, we treated aged females with elamipretide (ELAM), a mitochondrially-targeted peptide shown to improve mitochondrial bioenergetics and restore redox status in aged muscle. ELAM removed inhibition of glutamate oxidation and showed increased metabolic pathway changes following HII, suggesting rescuing redox status and improving bioenergetic function in mitochondria from aged muscle increases glutamate utilization and enhances the metabolic response to muscle contraction in aged muscle. KEY POINTS: Acute local contraction of gastrocnemius can systemically alter mitochondrial respiration in non-stimulated muscle. Age-related changes in mitochondrial respiration using glutamate or palmitoyl carnitine following contraction are sex-dependent. Respiration using glutamate after high-intensity contraction is inhibited in aged female muscle. Metabolite level and pathway changes following muscle contraction decrease with age in female mice. Treatment with the mitochondrially-targeted peptide elamipretide can partially rescue metabolite response to muscle contraction.

Sex- and endurance training-mediated cardiovascular protection through lipids during exercise

Premenopausal women and endurance-trained individuals of either sex have reduced cardiovascular disease (CVD) risk. Endurance training shifts fuel selection towards fats to spare carbohydrates; interestingly, women prioritize fats as an energy resource more than men do during exercise. Relying on fats during exercise drives whole-body lipolysis and promotes lipid uptake and oxidation capacity in skeletal muscles. These metabolic adaptations during exercise result in protection against diet-induced obesity, a healthy body fat distribution, and reduced plasma triacylglycerol (TG) concentrations. Here, we analyze how sex differences and endurance training mediate changes in skeletal muscles, including exercise-induced lipolysis, lipid uptake and β-oxidation, intramuscular TG storage, and postexercise lipid metabolism, and discuss how regulating this processes affects CVD risk.

Modelling energy metabolism dysregulations in neuromuscular diseases: A case study of calpainopathy

Biological modelling helps understanding complex processes, like energy metabolism, by predicting pathway compensations and equilibrium under given conditions. When deciphering metabolic adaptations, traditional experiments face challenges due to numerous enzymatic activities, needing modelling to anticipate pathway behaviours and orientate research. This paper aims to implement a constraint-based modelling method of muscular energy metabolism, adaptable to individual situations, energy demands, and complex disease-specific metabolic alterations like muscular dystrophy calpainopathy. Our calpainopathy-like model not only confirms the ATP production defect under increasing energy demands, but suggests compensatory mechanisms through anaerobic glycolysis. However, excessive glycolysis indicates a need to enhance mitochondrial respiration, preventing excess lactate production common in several diseases. Our model suggests that moderate-intensity physiotherapy, known to improve aerobic performance and anaerobic buffering, combined with increased carbohydrate and amino acid sources, could be a potent therapeutic approach for calpainopathy.

Global consensus on optimal exercise recommendations for enhancing healthy longevity in older adults (ICFSR)

Aging, a universal and inevitable process, is characterized by a progressive accumulation of physiological alterations and functional decline over time, leading to increased vulnerability to diseases and ultimately mortality as age advances. Lifestyle factors, notably physical activity (PA) and exercise, significantly modulate aging phenotypes. Physical activity and exercise can prevent or ameliorate lifestyle-related diseases, extend health span, enhance physical function, and reduce the burden of non-communicable chronic diseases including cardiometabolic disease, cancer, musculoskeletal and neurological conditions, and chronic respiratory diseases as well as premature mortality. Physical activity influences the cellular and molecular drivers of biological aging, slowing aging rates-a foundational aspect of geroscience. Thus, PA serves both as preventive medicine and therapeutic agent in pathological states. Sub-optimal PA levels correlate with increased disease prevalence in aging populations. Structured exercise prescriptions should therefore be customized and monitored like any other medical treatment, considering the dose-response relationships and specific adaptations necessary for intended outcomes. Current guidelines recommend a multifaceted exercise regimen that includes aerobic, resistance, balance, and flexibility training through structured and incidental (integrated lifestyle) activities. Tailored exercise programs have proven effective in helping older adults maintain their functional capacities, extending their health span, and enhancing their quality of life. Particularly important are anabolic exercises, such as Progressive resistance training (PRT), which are indispensable for maintaining or improving functional capacity in older adults, particularly those with frailty, sarcopenia or osteoporosis, or those hospitalized or in residential aged care. Multicomponent exercise interventions that include cognitive tasks significantly enhance the hallmarks of frailty (low body mass, strength, mobility, PA level, and energy) and cognitive function, thus preventing falls and optimizing functional capacity during aging. Importantly, PA/exercise displays dose-response characteristics and varies between individuals, necessitating personalized modalities tailored to specific medical conditions. Precision in exercise prescriptions remains a significant area of further research, given the global impact of aging and broad effects of PA. Economic analyses underscore the cost benefits of exercise programs, justifying broader integration into health care for older adults. However, despite these benefits, exercise is far from fully integrated into medical practice for older people. Many healthcare professionals, including geriatricians, need more training to incorporate exercise directly into patient care, whether in settings including hospitals, outpatient clinics, or residential care. Education about the use of exercise as isolated or adjunctive treatment for geriatric syndromes and chronic diseases would do much to ease the problems of polypharmacy and widespread prescription of potentially inappropriate medications. This intersection of prescriptive practices and PA/exercise offers a promising approach to enhance the well-being of older adults. An integrated strategy that combines exercise prescriptions with pharmacotherapy would optimize the vitality and functional independence of older people whilst minimizing adverse drug reactions. This consensus provides the rationale for the integration of PA into health promotion, disease prevention, and management strategies for older adults. Guidelines are included for specific modalities and dosages of exercise with proven efficacy in randomized controlled trials. Descriptions of the beneficial physiological changes, attenuation of aging phenotypes, and role of exercise in chronic disease and disability management in older adults are provided. The use of exercise in cardiometabolic disease, cancer, musculoskeletal conditions, frailty, sarcopenia, and neuropsychological health is emphasized. Recommendations to bridge existing knowledge and implementation gaps and fully integrate PA into the mainstream of geriatric care are provided. Particular attention is paid to the need for personalized medicine as it applies to exercise and geroscience, given the inter-individual variability in adaptation to exercise demonstrated in older adult cohorts. Overall, this consensus provides a foundation for applying and extending the current knowledge base of exercise as medicine for an aging population to optimize health span and quality of life.

In vivo imaging of glycogen in human muscle

Probing regional glycogen metabolism in humans non-invasively has been challenging due to a lack of sensitive approaches. Here we studied human muscle glycogen dynamics post-exercise with a spatial resolution of millimeters and temporal resolution of minutes, using relayed nuclear Overhauser effect (glycoNOE) MRI. Data at 5T showed a homogeneous distribution of glycogen in resting muscle, with an average concentration of 99 ± 13 mM. After plantar flexion exercise following fasting with recovery under fasting conditions, the calf muscle showed spatially heterogeneous glycogen depletion and repletion kinetics that correlated with the severity of this depletion. Three types of regional glycogen kinetics were observed: (i) single exponential repletion (type a); (ii) biphasic recovery of rapid repletion followed by additional depletion (type b); (iii) biphasic recovery where continued depletion is followed by an exponential recovery (type c). The study of the complex patterns of glycogen kinetics suggests that glycogen breakdown may be quantitatively important during the initial recovery.

Flexible Fiber Sensors for Real-Time Monitoring of Redox Signaling Molecules in Exercise-Mimicking Engineered Skeletal Muscle

Real-time monitoring of reactive oxygen and nitrogen species (RONS) in skeletal muscle provides crucial insights into the cause-and-effect relationships between physical activity and health benefits. However, the dynamic production of exercise-induced RONS remains poorly explored, due to the lack of sensing tools that can conform to soft skeletal muscle while monitor RONS release during exercise. Here we introduce dual flexible sensors via twisting carbon nanotubes into helical bundles of fibers and subsequent assembling electrochemical sensing components. These flexible sensors exhibit low bending stiffness, excellent H2O2 and NO sensing abilities, outstanding biocompatibility and compliance with engineered skeletal muscle tissue. This allows real-time and simultaneous monitoring of H2O2 and NO release from engineered skeletal muscle in response to different exercise-mimicking stretches, which reveals that warm-up activities before high-intensity exercise may enhance adaptive responses by down-regulating H2O2 and up-regulating NO production. The proposed sensing strategy demonstrates great versatility in monitoring multiple biomarkers of soft tissue and organs.

Carbohydrate ingestion during prolonged exercise blunts the reduction in power output at the moderate-to-heavy intensity transition

PURPOSE

To determine the effect of carbohydrate ingestion during prolonged exercise on durability of the moderate-to-heavy-intensity transition and severe-intensity performance.

METHODS

Twelve trained cyclists and triathletes (10 males, 2 females;V ˙ O 2 peak, 59 ± 5 mL kg-1 min-1; training volume, 14 ± 5 h week-1) performed an incremental test and 5-min time trial (TT) without prior exercise (PRE), and after 150 min of moderate-intensity cycling, with (POSTCHO) and without (POSTCON) carbohydrate ingestion.

RESULTS

Power output at the first ventilatory threshold (VT1) was lower in POSTCHO (225 ± 36 W, ∆ -3 ± 2%, P = 0.027, n = 11) and POSTCON (216 ± 35 W, ∆ -6 ± 4%, P = 0.001, n = 12) than PRE (229 ± 37 W, n = 12), and lower in POSTCON than POSTCHO (∆ -7 ± 9 W, ∆ -3 ± 4%, P = 0.019). Mean power output in the 5-min TT was lower in POSTCHO (351 ± 53 W, ∆ -4 ± 3%, P = 0.025) and POSTCON (328 ± 63 W, ∆ -10 ± 10%, P = 0.027) than PRE (363 ± 55 W), but POSTCHO and POSTCON were not significantly different (∆ 25 ± 37 W, ∆ 9 ± 13%, P = 0.186). Blood glucose concentration was maintained in POSTCHO, and was significantly lower at the 120 and 150-min timepoint in POSTCON (P < 0.05).

CONCLUSION

These data suggest that durability of the moderate-to-heavy-intensity transition is improved with carbohydrate ingestion. This has implications for training programming and load monitoring.

The Dlk1-Dio3 noncoding RNA cluster coordinately regulates mitochondrial respiration and chromatin structure to establish proper cell state for muscle differentiation

The coordinate regulation of metabolism and epigenetics to establish cell state-specific gene expression patterns during lineage progression is a central aspect of cell differentiation, but the factors that regulate this elaborate interplay are not well-defined. The imprinted Dlk1-Dio3 noncoding RNA (ncRNA) cluster has been associated with metabolism in various progenitor cells, suggesting it functions as a regulator of metabolism and cell state. Here, we directly demonstrate that the Dlk1-Dio3 ncRNA cluster coordinates mitochondrial respiration and chromatin structure to maintain proper cell state. Stable mouse muscle cell lines were generated harboring two distinct deletions in the proximal promoter region, resulting in either greatly upregulated or downregulated expression of the entire Dlk1-Dio3 ncRNA cluster. Both mutant lines displayed impaired muscle differentiation along with dysregulated structural gene expression and abnormalities in mitochondrial respiration. Genome-wide chromatin accessibility and histone methylation patterns were also severely affected in these mutants. Our results strongly suggest that muscle cells are sensitive to Dlk1-Dio3 ncRNA dosage, and that the cluster coordinately regulates metabolic activity and the epigenome to maintain proper cell state in the myogenic lineage.

Acute effects of intra-training carbohydrate ingestion in CrossFit® trained adults: a randomized, triple-blind, placebo-controlled crossover trial

Carbohydrate (CHO) intake during exercise could decrease the subjective perceived exertion and promote recovery; however, the effects of intra-training CHO ingestion remain uncertain in CrossFit® (CF) sessions. Therefore, the aim of this randomized, triple-blind, placebo-controlled crossover trial was to investigate the effect of acute CHO intake during a CF session on the delayed onset muscle soreness (DOMS), the perceived exertion (RPE), performance, recovery, and metabolic markers (capillary lactate and glucose) in CF athletes. Twenty-three male athletes trained in CF ingested CHO (60 g of maltodextrin + fructose) or a placebo (PLA) during a CF session. DOMS was assessed 24 and 48 h after the CF session. The Counter Movement Jump (CMJ) test and the Deep Squat test at 70% of the athlete's body weight (AST70) were performed before, immediately after, and 24 h after the session. Perceived exertion, Feeling Scale (FS), Gastrointestinal Distress Score (GDS), heart rate, capillary lactate, and glucose were assessed across the session. CHO supplementation did not improve DOMS (all P ≥ 0.127), CMJ, or AST70 parameters (all P ≥ 0.053) compared to PLA. There were no differences between CHO and PLA in RPE, FS, GDS, heart rate (all P ≥ 0.088), performance (e.g., nº of repetitions; all P ≥ 0.556), or lactate levels (P = 0.810). However, glucose levels increased from the back squat to the WOD and remained stable after the AMRAP (P < 0.001). In conclusion, acute CHO intake during a CF session did not improve DOMS, perceived exertion, performance, recovery, or metabolic markers in CF athletes. TRN: NCT06440343. Date: 2024-05-10.

A study of long-term GABA and high-energy phosphate alterations in the primary motor cortex using anodal tDCS and 1H/31P MR spectroscopy

Introduction

Anodal transcranial direct current stimulation (tDCS) has been reported to modulate gamma-aminobutyric acid levels and cerebral energy consumption in the brain. This study aims to investigate long-term GABA and cerebral energy modulation following anodal tDCS over the primary motor cortex.

Method

To assess GABA and energy level changes, proton and phosphorus magnetic resonance spectroscopy data were acquired before and after anodal or sham tDCS. In anodal stimulation, a 1 mA current was applied for 20 min, and the duration of ramping the current up/down at the start and end of the intervention was 10 s. In the sham-stimulation condition, the current was first ramped up over a period of 10 s, then immediately ramped down, and the condition was maintained for the next 20 min.

Results

The GABA concentration increased significantly following anodal stimulation in the first and second post-stimulation measurements. Likewise, both ATP/Pi and PCr/Pi ratios increased after anodal stimulation in the first and second post-stimulation measurements.

Conclusion

The approach employed in this study shows the feasibility of measuring long-term modulation of GABA and high-energy phosphates following anodal tDCS targeting the left M1, offering valuable insights into the mechanisms of neuroplasticity and energy metabolism, which may have implications for applications of this intervention in clinical populations.

Exercise-induced methylation of the Serhl2 promoter and implication for lipid metabolism in rat skeletal muscle

OBJECTIVES

Environmental factors such as physical activity induce epigenetic modifications, with exercise-responsive DNA methylation changes occurring in skeletal muscle. To determine the skeletal muscle DNA methylation signature of endurance swim training, we used whole-genome methylated DNA immunoprecipitation (MeDIP) sequencing.

METHODS

We utilized endurance-trained rats, cultured L6 myotubes, and human skeletal muscle cells, employing MeDIP sequencing, gene silencing, and palmitate oxidation assays. Additional methods included promoter luciferase assays, fluorescence microscopy, and RNA/DNA analysis to investigate exercise-induced molecular changes.

RESULTS

Gene set enrichment analysis (GSEA) of differentially methylated promoter regions identified an enrichment of four gene sets, including those linked to lipid metabolic processes, with hypermethylated or hypomethylated promoter regions in skeletal muscle of exercise-trained rats. Bisulfite sequencing confirmed hypomethylation of CpGs in the Serhl2 (Serine Hydrolase Like 2) transcription start site in exercise-trained rats. Serhl2 gene expression was upregulated in both exercise-trained rats and an "exercise-in-a-dish" model of L6 myotubes subjected to electrical pulse stimulation (EPS). Serhl2 promoter activity was regulated by methylation and EPS. A Nr4a binding motif in the Serhl2 promoter, when deleted, reduced promoter activity and sensitivity to methylation in L6 myotubes. Silencing Serhl2 in L6 myotubes reduced intracellular lipid oxidation and triacylglycerol synthesis in response to EPS.

CONCLUSIONS

Exercise-training enhances intracellular lipid metabolism and phenotypic changes in skeletal muscle through epigenomic modifications on Serhl2. Hypomethylation of the Serhl2 promoter influences Nr4a transcription factor binding, promoter activity, and gene expression, linking exercise-induced epigenomic regulation of Serhl2 to lipid oxidation and triacylglycerol synthesis.

Quantification of nutrient fluxes during acute exercise in mice

Despite the known metabolic benefits of exercise, an integrated metabolic understanding of exercise is lacking. Here, we use in vivo steady-state isotope-labeled infusions to quantify fuel flux and oxidation during exercise in fasted, fed, and exhausted female mice, revealing several novel findings. Exercise strongly promoted glucose fluxes from liver glycogen, lactate, and glycerol, distinct from humans. Several organs spared glucose, a process that broke down in exhausted mice despite concomitant hypoglycemia. Proteolysis increased markedly, also divergent from humans. Fatty acid oxidation dominated during fasted exercise. Ketone production and oxidation rose rapidly, seemingly driven by a hepatic bottleneck caused by gluconeogenesis-induced cataplerotic stress. Altered fuel consumption was observed in organs not directly involved in muscle contraction, including the pancreas and brown fat. Several futile cycles surprisingly persisted during exercise, despite their energy cost. In sum, we provide a comprehensive, integrated, holistic, and quantitative accounting of metabolism during exercise in an intact organism.

Skeletal muscle cystathionine γ-lyase deficiency promotes obesity and insulin resistance and results in hyperglycemia and skeletal muscle injury upon HFD in mice

OBJECTIVES

The objective of this study was to investigate whether skeletal muscle cystathionine γ-lyase (CTH) contributes to high-fat diet (HFD)-induced metabolic disorders using skeletal muscle Cth knockout (CthΔskm) mice.

METHODS

The CthΔskm mice and littermate Cth-floxed (Cthf/f) mice were fed with either HFD or chow diet for 13 weeks. Metabolomics and transcriptome analysis were used to assess the impact of CTH deficiency in skeletal muscle.

RESULTS

Metabolomics coupled with transcriptome showed that CthΔskm mice displayed impaired energy metabolism and some signaling pathways linked to insulin resistance (IR) in skeletal muscle although the mice had normal insulin sensitivity. HFD led to reduced CTH expression and impaired energy metabolism in skeletal muscle in Cthf/f mice. CTH deficiency and HFD had some common pathways enriched in the aspects of amino acid metabolism, carbon metabolism, and fatty acid metabolism. CthΔskm+HFD mice exhibited increased body weight gain, fasting blood glucose, plasma insulin, and IR, and reduced glucose transporter 4 and CD36 expression in skeletal muscle compared to Cthf/f+HFD mice. Impaired mitochondria and irregular arrangement in myofilament occurred in CthΔskm+HFD mice. Omics analysis showed differential pathways enriched between CthΔskm mice and Cthf/f mice upon HFD. More severity in impaired energy metabolism, reduced AMPK signaling, and increased oxidative stress and ferroptosis occurred in CthΔskm+HFD mice compared to Cthf/f+HFD mice.

DISCUSSION

Our results indicate that skeletal muscle CTH expression dysregulation contributes to metabolism disorders upon HFD.

Post-exercise metabolic response to kettlebell complexes vs. high intensity functional training

PURPOSE

This study compared the magnitude of excess post-exercise oxygen consumption (EPOC) between kettlebell complexes (KC) and high-intensity functional training (HIFT) and identified predictors of the EPOC response.

METHODS

Active men (n = 11) and women (n = 10) (age 25 ± 6 yr) initially completed testing of resting energy expenditure and maximal oxygen uptake (VO2max), followed by lower and upper-body muscle endurance testing. On two subsequent days separated by ≥ 48 h, participants completed KC requiring 6 sets of kettlebell exercises (pushups, deadlifts, goblet squats, rows, and swings) with 60 s recovery between sets, and HIFT requiring 6 sets of bodyweight exercises (mountain climbers, jump squats, pushups, and air squats) with 60 s recovery. During exercise, gas exchange data and blood lactate concentration (BLa) were acquired and post-exercise, EPOC was assessed for 60 min.

RESULTS

Results showed no difference in EPOC (10.7 ± 4.5 vs. 11.6 ± 2.7 L, p = 0.37), and VO2 and ventilation (VE) were significantly elevated for 30 and 60 min post-exercise in response to KC and HIFT. For KC and HIFT, HRmean and post-exercise BLa (R2 = 0.37) and post-exercise BLa and VE (R2 = 0.52) explained the greatest shared variance of EPOC.

CONCLUSION

KC and HIFT elicit similar EPOC and elevation in VO2 which is sustained for 30-60 min post-exercise, leading to 55 extra calories expended. Results show no association between aerobic fitness and EPOC, although significant associations were revealed for mean HR as well as post-exercise VE and BLa.

Carbohydrate storage in cells: a laboratory activity for the assessment of glycogen stores in biological tissues

Carbohydrates and fats constitute our primary energy sources. The importance of each of these energy substrates varies across cell types and physiological conditions. For example, the brain normally relies almost exclusively on glucose oxidation, whereas skeletal muscle shifts from lipids toward higher carbohydrate oxidation rates as exercise intensity increases. Understanding how carbohydrates are stored in our cells and which tissues contain significant carbohydrate stores is crucial for health professionals, especially given the role of carbohydrate metabolism in various pathophysiological conditions. This laboratory activity uses a simple and low-cost iodine binding method to quantify glycogen in mouse skeletal muscle and liver samples. By integrating the results of this activity with literature data, students can determine overall glycogen storage in the human body. The primary goal of the activity is to enhance students' understanding of the importance and limitations of glycogen stores in energy metabolism.NEW & NOTEWORTHY Carbohydrates are one of the primary energy sources utilized by our cells. Liver and skeletal muscle glycogen, which are the main carbohydrate reserves in the body, play a central role in energy metabolism, especially during periods of fasting and exercise. In this laboratory activity, students measure glycogen levels in tissues to gain insights into how carbohydrates are stored in our cells and understand the role and limitations of liver and muscle carbohydrate stores.

Multi-omics reveals the molecular mechanism of muscle quality changes in common carp (Cyprinus carpio) under two aquaculture systems

Preliminary experiments in our laboratory have demonstrated that common carp (Cyprinus carpio) cultivated for two months in land-based container recirculating aquaculture systems (C-RAS) exhibit superior muscle quality compared to those raised in traditional pond systems (TP). To elucidate the molecular mechanisms underlying muscle quality variations in common carp cultured under two aquaculture systems, transcriptomic and metabolomic analyses were performed on muscle tissues of specimens aged 11 to 23 months. Comparison of muscle histological sections between the two groups indicated a significantly lower long diameter of muscle fibers in the C-RAS group compared to the TP group (P < 0.01). Conversely, the muscle fiber density was significantly higher in the C-RAS group than in the TP group (P < 0.05). Transcriptomic and metabolomic analyses identified 3390 differentially expressed genes (DEGs)-1558 upregulated and 1832 downregulated-and 181 differentially expressed metabolites (DEMs)-124 upregulated and 57 downregulated-between the groups. Based on integrated transcriptomic and metabolomic analyses, the significant differences focus on metabolic pathways involving glycolysis/gluconeogenesis, arginine and proline metabolism, arginine biosynthesis, and purine metabolism. The study revealed that the muscle quality of common carp in two aquaculture systems is primarily regulated through improvements in energy metabolism, amino acid metabolism, fatty acid metabolism, and purine metabolism. These metabolic processes play significant roles in promoting muscle fiber hyperplasia and hypertrophy, enhancing muscle flavor, and increasing muscle antioxidant capacity. This study provides new insights into the molecular and metabolic pathways that control muscle quality in common carp under different environmental factors.

Mitochondrial quality control measures, systemic inflammation, and lower-limb muscle power in older adults: a PROMPT secondary analysis

OBJECTIVES

The study was conducted to explore associations between markers of mitochondrial quality control (MQC) from vastus lateralis muscle biopsies, serum inflammatory markers, and measures of muscle power assessed by two different tools in a sample of older adults.

DESIGN

Secondary analysis of data collected in the PeppeR develOpMental ProjecT (PROMPT) at the University of Florida (Gainesville, FL, USA).

METHODS

Forty-three older adults (n = 20 women) were included in the study. Muscle volume of the calf and thigh was quantified by three-dimensional magnetic resonance imaging. Lower-limb muscle power was estimated using 5-time sit-to-stand (5STS) muscle power equations and isokinetic test. Protein markers of MQC were measured in muscle samples by Western immoblotting (n = 12-23), while type I and II fiber cross-sectional area (CSA) and their proportion were quantified using immunohistochemistry (n = 12). Cytochrome C oxidase enzyme activity was measured spectrophotometrically. Finally, inflammatory markers were quantified in the serum using a multiplex immunoassay (n = 39).

RESULTS

Mean age of participants was 78.1 ± 5.5 years, and the average body mass index was 26.2 ± 4.5 kg/m2. Markers of mitochondrial biogenesis (i.e., PGC-1α), mitochondrial import proteins (i.e., cHsp70 and mtHsp70), and type I fiber CSA were significantly associated with muscle power estimated via both 5STS muscle power equations and isokinetic test (p < 0.05). Specific associations were also found according to the muscle power assessment method. 5STS muscle power measures were negatively correlated with ClvCasp3, P-AMPK, T-AMPK, P-p38, GM-CSF, INF-γ, IL1b, IL6, IL8, and TNF-α, whereas positive associations were found with BAX (p < 0.05). In contrast, isokinetic measures were significantly and positively correlated with RIP140, Hsp60, and type II muscle fiber CSA (p < 0.05).

CONCLUSIONS

Markers of mitochondrial biogenesis (PGC-1α), mitochondrial import proteins (cHsp70 and mtHsp70), and type I muscle fiber CSA were significantly linked to lower-limb muscle power in older adults. These results suggest that muscle power is influenced by mitochondrial signaling. We also found that the relationship between mitochondrial mediators, inflammatory markers, and muscle power varied according to the assessment tool used.

Antifatigue effect of okara protein hydrolysate supplementation during cycling exercise in men: a pre-post uncontrolled pilot study

BACKGROUND

Prolonged exercise usually leads to exercise fatigue, which has a negative short-term impact on exercise performance and metabolic rate; thus, fatigue needs to be resolved. Okara is a protein-rich residue of soy processing. Enzyme hydrolysis is known to increase the content of branched-chain amino acids (BCAAs), which have been reported to confer benefits for exercise. The purpose of this study was to investigate the antifatigue effect of okara protein hydrolysate (OPH) on cycling exercise.

METHODS

A total of 16 male participants who habitually exercised (2 times or more per week and without participation in athletic contests) were instructed to receive 11.74 g of OPH once a day. They then completed two intense cycling exercise challenges before and after four weeks of supplementation. Exercise time and blood markers related to fatigue and energy metabolism were measured.

RESULTS

The results showed that the time to exhaustion significantly increased after the treatment. The levels of lactate during exercise and at the end of exercise were significantly lower after treatment than before. Additionally, postexercise insulin sensitivity was increased after treatment.

CONCLUSIONS

This study showed that OPH supplementation can promote endurance in exercise by decreasing the accumulation of fatigue-related metabolites during exercise and can promote energy recovery by increasing insulin function. These findings suggest that OPH has an antifatigue property.

Time to Elicit Physiological and Exertional Vigorous Responses from Daily Living Activities: Setting Foundations of an Empirical Definition of VILPA

PURPOSE

Vigorous intermittent lifestyle physical activity (VILPA) are bursts of incidental vigorous activity that occur during day-to-day activities outside of the exercise-domain. Vigorous intermittent lifestyle physical activity has shown promise in lowering risk of mortality and chronic disease. However, there is an absence of an empirically derived definition. Using physiological and effort-based metrics commonly used to define vigorous intensity, we investigated the minimum time needed to elicit physiological and perceived exertion responses to standardized activities of daily living.

METHODS

Seventy adults (age = 58.0 ± 9.6 yr; 35 female) completed 9 VILPA activities of daily living in a randomized order, which included fast walking, fast incline walking, stair climbing, stationary cycling, and carrying external weight equal to 5% and 10% of body weight. Metabolic rate (by continuous indirect calorimetry), heart rate (telemetry) and perceived effort (Borg Scale) were measured during exercise. Time to reach VILPA was assessed using %V̇O 2max , %HRmax, and rating of perceived exertion thresholds.

RESULTS

The mean time to elicit VILPA ranged from 65 to 95 s (mean ± sd = 76.7 ± 3.8 s) for %V̇O 2max , 68 to 105 s (mean ± sd = 82.8 ± 6.8 s) for %HRmax, and 20 to 60 s (mean ± sd = 44.6 ± 6.7 s) for rating of perceived exertion. For each of the three indices, there was no difference in the time to elicit VILPA responses by sex or age ( P > 0.08), and times were also consistent between activities of daily living tasks. For example, for females and males, the average time to elicit vigorous responses while walking on a flat surface was 85.8 s (±16.9 s) and 80 s (±13.9 s), respectively, and for stair climbing while carrying 10% of body weight the duration was 78.4 s (±17.6 s) and 76.9 (±17.7 s).

CONCLUSIONS

When participants undertook activities of daily living, VILPA elicited a physiological response at an average of 77 to 83 s for %V̇O 2max and %HRmax, and 45 s for perceived exertion. The absence of a difference in the time to reach VILPA between sex and age suggests that a consistent behavioral VILPA translation can be used in interventions and population-based studies designed to assess the health effects of incidental physical activity.

Sinapine suppresses ROS-induced C2C12 myoblast cell death through MAPK and autophagy pathways

Oxidative stress in skeletal muscle can lead to muscle atrophy through reactive oxygen species (ROS)-induced damage and cell death. tert-Butyl hydroperoxide (TBHP), an exogenous ROS generator, induces oxidative stress and cell death in various cells. Sinapine from cruciferous plants possesses beneficial effects, but its role in protecting skeletal muscle cells against ROS-induced cell death remains unclear. This study demonstrates that sinapine pretreatment significantly reduced TBHP-induced cell death and ROS accumulation in a dose-dependent manner. TBHP activated mitogen-activated protein kinase (MAPK) pathways including Akt, p38, and JNK, and triggered autophagy. Sinapine suppressed the phosphorylation of Akt, MEK3/6, p38, MEK4, and JNK, and modulated key autophagy markers. Notably, the co-treatment of MAPK inhibitors attenuated TBHP-induced cell death and LC3B-II accumulation. These findings suggest that sinapine is a promising phytochemical for mitigating oxidative stress-mediated muscle injury, offering potential therapeutic strategies for maintaining skeletal muscle homeostasis and addressing muscle-related pathologies.

Durable Muscle Extracellular Matrix Engineered with Adhesive Phenolic Moieties for Effective Skeletal Muscle Regeneration in Muscle Atrophy

Muscle atrophy detrimentally impacts health and exacerbates physical disability, leading to increased mortality. In particular, sarcopenia, aging-related degenerative muscle loss, necessitates urgent remedies. Current approaches for treating muscle atrophy include exercise and nutrition, while drug exploration remains in its early stages. Cell therapy, focusing on satellite cells, faces significant challenge due to poor engraftment, safety issue, and high cost. Cell-free approach using extracellular matrix (ECM) shows a regenerative potential, but a lack of mechanical and adhesive properties hinders prolonged efficacy of ECM therapy. Here, durable muscle ECM (MEM) hydrogels for muscle atrophy by fortifying MEM with adhesive phenolic moieties including catechol and pyrogallol are demonstrated. The resultant phenolic MEM hydrogels exhibit enhanced mechanical and adhesive properties and provide sustained muscle-like microenvironments to address muscle atrophy. No local and systemic toxicities are observed after phenolic MEM injection into tibialis anterior muscle. Notably, these engineered MEM hydrogels, devoid of cells or drugs, induce tissue rejuvenation by promoting muscle protein synthesis and facilitating functional muscle recovery in mouse models of disuse- and age-induced atrophy. This study introduces cell-free, ECM-based therapeutics with translational potential for muscle atrophy by reversing muscle loss and restoring function.

d-Amphetamine and Feeding States Cohesively Affect Locomotion and Motor Neuron Response in Zebrafish Larvae

PURPOSE

Amphetamine (AMPH) increases locomotor activities in animals, and the locomotor response to AMPH is further modulated by caloric deficits such as food deprivation and restriction. The increment in locomotor activity regulated by AMPH-caloric deficit concomitance can be further modulated by varying feeding schedules (e.g., acute and chronic food deprivation and acute feeding after chronic food deprivation). However, the effects of different feeding schedules on AMPH-induced locomotor activity are yet to be explicated. Here, we have explored the stimulatory responses of acutely administered D-amphetamine in locomotion under systematically varying feeding states (fed/sated and food deprivation) and schedules (chronic and acute) in zebrafish larvae.

METHOD

We exposed wild-type and transgenic [Tg(mnx1:GCaMP5)] zebrafish larvae to 0.7 µM concentration of AMPH and measured swimming activity and spinal motor neuron activity in vivo in real time. The analysis involved time-elapsed and cumulative manner pre- and post-AMPH treatment in four different caloric states including acute and chronic schedules of feeding and hunger. Both locomotor and motor neuron activities were compared in all four states in both fish lines.

FINDINGS

Our results show that locomotion and motor neuron activity increased in both chronic and acute food deprivation post-AMPH treatment cumulatively. A steady increase in locomotion was observed in acute food deprivation compared to an immediate abrupt increase in chronic food-deprivation state. The ad libitum-fed larvae exhibited a moderate increase both in locomotion and motor neuron activity. Conversely to all other caloric states, food-sated (acute feeding after chronic food deprivation) larvae moved moderately less and exhibited a mild decrease in motor neuron activity after AMPH treatment.

CONCLUSION

These results reveal the importance of cohesive effects of feeding schedule and AMPH treatment by revealing the changes in stimulatory characteristics of AMPH on locomotion and motor neuron activity in acute and chronic feeding states.

The Warburg Effect: Is it Always an Enemy?

The Warburg effect, also known as 'aerobic' glycolysis, describes the preference of cancer cells to favor glycolysis over oxidative phosphorylation for energy (adenosine triphosphate-ATP) production, despite having high amounts of oxygen and fully active mitochondria, a phenomenon first identified by Otto Warburg. This metabolic pathway is traditionally viewed as a hallmark of cancer, supporting rapid growth and proliferation by supplying energy and biosynthetic precursors. However, emerging research indicates that the Warburg effect is not just a strategy for cancer cells to proliferate at higher rates compared to normal cells; thus, it should not be considered an 'enemy' since it also plays complex roles in normal cellular functions and/or under stress conditions, prompting a reconsideration of its purely detrimental characterization. Moreover, this review highlights that distinguishing glycolysis as 'aerobic' and 'anaerobic' should not exist, as lactate is likely the final product of glycolysis, regardless of the presence of oxygen. Finally, this review explores the nuanced contributions of the Warburg effect beyond oncology, including its regulatory roles in various cellular environments and the potential effects on systemic physiological processes. By expanding our understanding of these mechanisms, we can uncover novel therapeutic strategies that target metabolic reprogramming, offering new avenues for treating cancer and other diseases characterized by metabolic dysregulation. This comprehensive reevaluation not only challenges traditional views but also enhances our understanding of cellular metabolism's adaptability and its implications in health and disease.

Research on the champion physical fitness model of freestyle skiing aerials athletes in preparation for the Beijing Winter olympics

The objective of this study is to establish a champion physical fitness model of freestyle skiing aerials athletes, thereby enhancing athletes' competitive ability and providing a reference for scientific training and monitoring in the 2026 Milan Winter Olympics. Initiated with a literature review, the study proceeded through expert interviews and questionnaire surveys to determine the physical fitness measurement items. A total of 29 elite athletes voluntarily participated in the test. Using statistical analysis, this study developed a physical fitness model based on three key aspects: indicator, weight, and quantitative models. The results indicate that the indicator model encompasses primary indicators of body morphology, physiological function, and athletic quality, along with 11 related secondary and tertiary indicators. The tertiary indicators include lean body mass, waist/height×100, lower limb length/height×100, relative maximum anaerobic power, relative maximum oxygen uptake, blood urea, 1RM barbell squat, overhead barbell squat on balance pads, side throw ball, 30-meter sprint, and 12-minute run. The weight model assigned different weight values to these indicators based on their importance in physical fitness assessments. The quantitative model, developed through factor analysis and stepwise multiple linear regression, includes the champion physical fitness characteristics model and the performance prediction model. The champion physical fitness characteristics model uses box plots to visually present the physical fitness differences between champions and other athletes, highlighting the superior physical characteristics of the champions. The performance prediction model identified training experience, relative maximum anaerobic power, 1RM barbell squat, and overhead barbell squat on balance pads as key predictive variables. This model provides forward-looking training guidance and competitive strategy recommendations for coaches and athletes.

Mitochondrial calcium uptake declines during aging and is directly activated by oleuropein to boost energy metabolism and skeletal muscle performance

Mitochondrial calcium (mtCa2+) uptake via the mitochondrial calcium uniporter (MCU) couples calcium homeostasis and energy metabolism. mtCa2+ uptake via MCU is rate-limiting for mitochondrial activation during muscle contraction, but its pathophysiological role and therapeutic application remain largely uncharacterized. By profiling human muscle biopsies, patient-derived myotubes, and preclinical models, we discovered a conserved downregulation of mitochondrial calcium uniporter regulator 1 (MCUR1) during skeletal muscle aging that associates with human sarcopenia and impairs mtCa2+ uptake and mitochondrial respiration. Through a screen of 5,000 bioactive molecules, we identify the natural polyphenol oleuropein as a specific MCU activator that stimulates mitochondrial respiration via mitochondrial calcium uptake 1 (MICU1) binding. Oleuropein activates mtCa2+ uptake and energy metabolism to enhance endurance and reduce fatigue in young and aged mice but not in muscle-specific MCU knockout (KO) mice. Our work demonstrates that impaired mtCa2+ uptake contributes to mitochondrial dysfunction during aging and establishes oleuropein as a novel food-derived molecule that specifically targets MCU to stimulate mitochondrial bioenergetics and muscle performance.

The Role of Ion-Transporting Proteins on Crosstalk Between the Skeletal Muscle and Central Nervous Systems Elicited by Physical Exercise

A paradigm shift in the understanding of bidirectional interactions between peripheral and central nervous systems is essential for development of rehabilitation and preventive interventions based on physical exercise. Although a causal relationship has not been completely established, modulation of voltage-dependent ion channels (Ca2+, Cl-, K+, Na+, lactate-, H+) in skeletal and neuronal cells provides opportunities to maintain force production during exercise and reduce the risk of disease. However, there are caveats to consider when interpreting the effects of physical exercise on this bidirectional axis, since exercise protocol details (e.g., duration and intensity) have variable effects on this crosstalk. Therefore, an integrative perspective of the skeletal muscle and brain's communication pathway is discussed, and the role of physical exercise on such communication highway is explained in this review.

Impact of Physical Activity on Cellular Metabolism Across Both Neurodegenerative and General Neurological Conditions: A Narrative Review

BACKGROUND

Regular physical activity plays a crucial role in modulating cellular metabolism and mitigating the progression of neurodegenerative diseases such as Alzheimer's, Parkinson's, and Multiple Sclerosis.

OBJECTIVE

The objective of this review is to evaluate the molecular mechanisms by which exercise influences cellular metabolism, with a focus on its potential as a therapeutic intervention for neurological disorders.

METHODS

A comprehensive literature review was conducted using peer-reviewed scientific articles, with a focus on the period between 2015 and 2024, to analyze the effects of exercise on mitochondrial function, oxidative stress, and metabolic health.

RESULTS

The findings indicate that exercise promotes mitochondrial biogenesis, enhances oxidative phosphorylation, and reduces reactive oxygen species, contributing to improved energy production and cellular resilience. These metabolic adaptations are associated with delayed disease progression and reduced symptoms in patients with neurodegenerative conditions. Additionally, integrating exercise with nutritional strategies may further enhance therapeutic outcomes by addressing metabolic disturbances comprehensively.

CONCLUSIONS

This review concludes that personalized exercise protocols should be developed to optimize metabolic benefits for patients with neurological diseases, while future research should focus on biomarker development for individualized treatment approaches. These findings highlight the importance of non-pharmacological interventions in managing neurodegenerative diseases.

High- and Low-carb Diet and Fasting State Modify Alternative Maximal Accumulated Oxygen Deficit

This investigation aimed to assess whether the alternative method of estimating the maximal accumulated oxygen deficit (MAODalt) can detect changes in energy system contribution in different substrate availabilities. Following a graded exercise test to determine maximal oxygen uptake intensity (iVO2max), 26 recreational runners performed a time to exhaustion effort (TTE) as baseline at 110% iVO2max. The same TTE was performed in fasting state, then, a muscle glycogen depletion protocol was executed. Subsequently, participants received a low-carbohydrate diet and beverages containing high (H-CHO, 10.8±2.1 g·kg- 1), moderate (M-CHO, 5.6±1.1 g·kg- 1), or zero (Z-CHO, 0.24±0.05 g·kg- 1) carbohydrates. Another TTE was performed 24 h later. Each energy system contribution was assessed. Generalized linear mixed models were used for statistical analysis (p<0.05). H-CHO increased relative anaerobic capacity (slope effect [baseline -intervention]x[H-CHO - M-CHO]) due to the relative lactic contribution maintenance (slope effect [baseline - intervention]x[H-CHO - Z-CHO] or [H-CHO - M-CHO]) and increase in relative alactic contribution (6.3±3.5 kJ·min- 1). The aerobic contribution was lower (- 8.7±4.0 kJ·min- 1), decreasing performance (- 34±16 s) for H-CHO. M-CHO and Z-CHO maintained anaerobic capacity due to increase in alactic contribution (slope effect [fasting - intervention]x[M-CHO - H-CHO]; and Z-CHO was 7.3±3.4 kJ·min- 1 higher than baseline). Fasting increased relative alactic (2.9±1.7 kJ·min- 1) but decreased aerobic contribution (- 3.3±2.3 kJ·min- 1), impairing performance (- 17±12 s). In conclusion, MAODalt can detect changes in energy system supply in different nutritional states. Therefore, participant's nutritional state must be considered prior to conducting the test.

Metabolic flexibility to lipid during exercise is not associated with metabolic health outcomes in individuals without obesity

A low metabolic flexibility to lipid (MetF-lip) in skeletal muscle may promote ectopic lipid accumulation, thus inducing metabolic disturbances. We aimed to determine the association between MetF-lip in skeletal muscle and metabolic health outcomes in individuals without obesity. We also explored the association between MetF-lip and the inflammatory signaling pathway in skeletal muscle. This was a cross-sectional study in 17 individuals aged (median [IQR]) 55.4 [48.6, 58.5] years, with a BMI of 24.4 [22.6, 26.0] kg/m2. MetF-lip was assessed as the increase in relative lipid oxidation during a single exercise session (~ 50% VO2max, 2 hours), quantified as the drop in whole-body respiratory exchange ratio (ΔRER = RER at 2 hours - maximum RER attained). HOMA-IR, metabolic syndrome z-score, fat percentage, trunk-to-appendicular fat, and VO2max were included as metabolic health outcomes. The abundance of proteins of the inflammatory pathway was analyzed in resting muscle. Acute exercise progressively increased relative lipid oxidation (ΔRER = -0.04 [-0.08, -0.02]). MetF-lip was not associated with any metabolic health outcome but correlated inversely with p-p38Thr180/Tyr182 in muscle. A low MetF-lip in skeletal muscle does not seem a major determinant of metabolic disturbances but associates with a partial activation of the inflammatory signaling in individuals without obesity.

Review: Feed efficiency and metabolic flexibility in livestock

Improving the conversion of feed into product has been a key focus of genetic improvement in all livestock species. Livestock feed efficiency is the amount of product produced per unit of feed intake. Feed efficiency also depends on processes that are not directly related to economically important phenotypes, which can be considered 'waste' from a production point of view but are vital maintenance-related functions that are closely associated with environmental flexibility and adaptation. Resource allocation theory suggests that an animal's resource budget is narrowed when production efficiency is improved through an increase in productive output, along with a decrease in feed intake (capacity) and body reserves (improved leanness). The resulting trade-offs between productivity and vital functions may render the animal less capable of responding to unexpected challenges, potentially leading to negative side effects that are not directly related to economically important phenotypes. However, selection for feed efficiency may not narrow the metabolic space and result in trade-offs if the increase in feed efficiency is the result of increased metabolic flexibility in fuel substrate choice (carbohydrates, lipids, and/or proteins) and other energy-saving strategies. This review evaluates the relationship between metabolic flexibility and feed efficiency during anabolism (growth), fasting, immune activation, general stress, and heat stress, with a focus on pig production. We start with a brief overview of energy processes and substrate metabolism of carbohydrates, lipids, and protein. During muscle metabolism, the type of fuel used depends on fibre type characteristics of the muscle. Selection for improved meat production has resulted in pigs with a greater abundance of fast-twitch fibres with lower energy expenditure and higher metabolic efficiency. Metabolic flexibility for adaptation to disease, and response to regular stress implies that a more reactive immune response and reduced fear response results in higher feed efficiency. The examples presented in this review show that selection for improved feed efficiency does not necessarily narrow the metabolic space and result in trade-offs between productivity and vital functions because of energy-sparing mechanisms.

Multi-tissue metabolomic profiling reveals the crucial metabolites and pathways associated with scallop growth

BACKGROUND

Bivalves represent a vital economic resource in aquaculture for their high productivity and extensive market demand. Growth is one of the most important and desired aquaculture traits for bivalves, regulated by multiple levels, notably intricate metabolic processes. However, the understanding of the metabolic profiles that influence bivalve growth is limited, particularly from a multi-tissue perspective.

RESULTS

In this study, metabolic profiles of multiple tissues of Chlamys farreri with different growth performance were systematically investigated by ultraperformance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS). Through comparing the metabolic variation between fast-growing (FG) scallops and slow-growing (SG) scallops, 613, 509, 105, and 192 significantly different metabolites (SDMs) were identified in the mantle, gill, adductor muscle, and digestive gland, respectively. Growth-related metabolic pathways including sphingolipid metabolism, fatty acid biosynthesis, and ABC transporter pathway, along with 11 SDMs associated with growth traits were identified in all four tissues, implying they were involved in the growth of multiple tissues in scallops. Tissue-specific metabolic profiling indicated that sulfur-containing amino acid metabolism in the mantle potentially contributed to shell growth, while the gill synergistically participated with the mantle through various metabolic processes, such as tyrosine metabolism, glycine, serine, and threonine metabolism and melanogenesis; energy metabolism was crucial for adductor muscle growth; and nutrients digestion and absorption in the digestive gland were linked to scallop growth.

CONCLUSIONS

Our results represent the first comprehensive analysis of the crucial pathways and metabolites associated with the growth of C. farreri, offering valuable insights for future bivalve aquaculture production.

Associations between biomarkers and skeletal muscle function in individuals with osteoarthritis: a systematic review and meta-analysis

OBJECTIVES

Skeletal muscle dysfunction is the primary cause of functional limitations in osteoarthritis, associated biomarkers have the potential as targets for early disease identification, diagnosis, and prevention of osteoarthritis disability. This review aimed to identify associations between biomarkers and lower limb skeletal muscle function in individuals with osteoarthritis.

METHODS

A systematic literature review and meta-analysis conducted in PubMed, MEDLINE, CINAHL, EMBASE, Scopus, SPORTDiscus and Web of Science databases from inception to 8th August 2023. Two independent reviewers performed the title, abstract, full-text screening, data extraction and methodological quality assessment. A meta-analysis was undertaken based on the available data.

RESULTS

Twenty-four studies with 4101 participants with osteoarthritis were included (females: 78%; age range; 49 to 71 years). One study reported muscle-specific biomarkers (n = 3), whilst six studies reported osteoarthritis-specific markers (n = 5). Overall, 93 biomarkers were reported, predominately characterised as inflammatory (n = 35), metabolic (n = 15), and hormones (n = 10). Muscle strength and vitamin D reported a significant association (Hedge's g: 0.58 (Standard Error (SE): 0.27; P = 0.03), k = 3 studies). Walking speed and high-sensitivity C-reactive protein reported no significant associations (Hedge's g: -0.02 (SE: 0.05; P = 0.73), k = 3 studies).

CONCLUSION

Associations between biomarkers and lower limb skeletal muscle function in individuals with osteoarthritis was limited, the few studies exploring lower limb muscle measures were mainly secondary outcomes. Furthermore, biomarkers were largely related to overall health, with a lack of muscle specific biomarkers. As such, the mechanistic pathways through which these associations occur are less evident, and difficult to draw clear conclusions on these relationships.

TRIAL REGISTRATION

Registered on PROSPERO (CRD42022359405).

Lack of sex-specific differences in the associations between the dimensions of great vessels and exercise performance in amateur cyclists

BACKGROUND

Endurance training enhances exercise capacity and triggers cardiovascular adaptations in both males and females. We investigated the relationship between the dimensions of great vessels and exercise capacity in amateur cyclists while considering sex differences.

METHODS

Using resting transthoracic echocardiography, we measured the dimensions of the main pulmonary artery (PA), aorta, and inferior vena cava (IVC) in 190 participants, who subsequently underwent a cardiopulmonary exercise test (CPET) until exhaustion.

RESULTS

The mean age of study participants was 30 years. Males (71%) exhibited a larger aortic annulus (approximately 3.5 mm, p<0.0001) and PA diameter (2.4 mm, p<0.0001) than females. No significant sex differences were found in expiratory or inspiratory IVC diameters. Males achieved greater peak exercise capacity, including workload, O2 consumption (VO2), and O2 pulse. Aortic and PA dimensions showed strong correlations with energy expenditure, workload, VO2, and O2 pulse. However, these correlations weakened when analyzed separately by sex. Multivariate linear regression revealed associations between CPET results, vessels size, and sex, with sex differences observed only in the intercepts-not in interactions between sex and vessels size. Despite males having better CPET results and larger vessels, the relationships between peak exercise capacity parameters and vessel dimensions were similar in both sexes.

CONCLUSION

Larger vessel dimensions (of the aorta, PA, and IVC) were associated with greater peak exercise capacity in amateur cyclists, with no significant sex differences in these associations.

Evidence-based sports supplements: A redox analysis

Despite the overwhelming number of sports supplements on the market, only seven are currently recognized as effective. Biological functions are largely regulated through redox reactions, yet no comprehensive analysis of the redox properties of these supplements has been compiled. Here, we analyze the redox characteristics of these seven supplements: bicarbonates, beta-alanine, caffeine, creatine, nitrates, carbohydrates, and proteins. Our findings suggest that all sports supplements exhibit some degree of redox activity. However, the precise physiological implications of these redox properties remain unclear. Future research, employing unconventional perspectives and methodologies, will reveal new redox pixels of the exercise physiology and sports nutrition picture.

Transcriptomic signatures of human single skeletal muscle fibers in response to high-intensity interval exercise

The heterogeneous fiber type composition of skeletal muscle makes it challenging to decipher the molecular signaling events driving the health- and performance benefits of exercise. We developed an optimized workflow for transcriptional profiling of individual human muscle fibers before, immediately after, and after 3 h of recovery from high-intensity interval cycling exercise. From a transcriptional point-of-view, we observe that there is no dichotomy in fiber activation, which could refer to a fiber being recruited or nonrecruited. Rather, the activation pattern displays a continuum with a more uniform response within fast versus slow fibers during the recovery from exercise. The transcriptome-wide response immediately after exercise is characterized by some distinct signatures for slow versus fast fibers, although the most exercise-responsive genes are common between the two fiber types. The temporal transcriptional waves further converge the gene signatures of both fiber types toward a more similar profile during the recovery from exercise. Furthermore, a large heterogeneity among all resting and exercised fibers was observed, with the principal drivers being independent of a slow/fast typology. This profound heterogeneity extends to distinct exercise responses of fibers beyond a classification based on myosin heavy chains. Collectively, our single-fiber methodological approach points to a substantial between-fiber diversity in muscle fiber responses to high-intensity interval exercise.NEW & NOTEWORTHY By development of a single-fiber transcriptomics technology, we assessed the transcriptional events in individual human skeletal muscle fibers upon high-intensity exercise. We demonstrate a large variability in transcriptional activation of fibers, with shared and distinct gene signatures for slow and fast fibers. The heterogeneous fiber-specific exercise response extends beyond this traditional slow/fast categorization. These findings expand on our understanding of exercise responses and uncover a profound between-fiber diversity in muscle fiber activation and transcriptional perturbations.

Comparative study on muscle function in two different streptozotocin-induced diabetic models

AIMS

Streptozotocin (STZ) is widely used to study diabetic complications. Owing to the nonspecific cytotoxicity of high-dose STZ, alternative models using moderate-dose or a combination of low-dose STZ and a high-fat diet have been established. This study aimed to investigate the effects of these models on muscle function.

METHODS

The muscle function of two STZ models using moderate-dose STZ (100 mg/kg, twice) and a combination of low-dose STZ and high-fat diet (50 mg/kg for 5 consecutive days + 45% high-fat diet) were examined using in vivo electrical stimulation. Biochemical and gene expression analysis were conducted on the skeletal muscles of the models immediately after the stimulation.

RESULTS

The contractile force did not differ significantly between the models compared to respective controls. However, the moderate-dose STZ model showed more severe fatigue and blunted exercise-induced glycogen degradation possibly thorough a downregulation of oxidative phosphorylation- and vasculature development-related genes expression.

CONCLUSIONS

Moderate-dose STZ model is suitable for fatigability assessment in diabetes and careful understanding on the molecular signatures of each model is necessary to guide the selection of suitable models to study diabetic myopathy.

Exercise intensity measurement using fractal analysis of heart rate variability: Reliability, agreement and influence of sex and cardiorespiratory fitness

The study aimed to establish the test-retest reliability of detrended fluctuation analysis of heart rate variability (DFA-α1) based exercise intensity thresholds, assess its agreement with ventilatory- and lactate-derived thresholds and the moderating effect of sex and cardiorespiratory fitness (CRF) on the agreement. Intensity thresholds for thirty-seven participants (17 females) based on blood lactate (LT1/LT2), gas-exchange (VT1/VT2) and DFA-α1 (αTh1/αTh2) were assessed. Heart rate (HR) at αTh1 and αTh2 showed good test-retest reliability (coefficient of variation [CV] < 6%), and moderate to high agreement with LTs (r = 0.40 - 0.57) and VTs (r = 0.61 - 0.66) respectively. Mixed effects models indicated bias magnitude depended on CRF, with DFA-α1 overestimating thresholds versus VTs for lower fitness levels (speed at VT1 <8.5 km⋅hr-1), while underestimating for higher fitness levels (speed at VT2 >15 km⋅hr-1; VO2max >55 mL·kg-1·min-1). Controlling for CRF, sex significantly affected bias magnitude only at first threshold, with males having higher mean bias (+2.41 bpm) than females (-1.26 bpm). DFA-α1 thresholds are practical and reliable intensity measures, however it is unclear if they accurately represent LTs/VTs from the observed limits of agreement and unexplained variance. To optimise DFA-α1 threshold estimation across different populations, bias should be corrected based on sex and CRF.

Exercise performance and health: Role of GLUT4

The glucose transporter GLUT4 is integral for optimal skeletal muscle performance during exercise, as well as for metabolic health. Physiological regulation of GLUT4 translocation during exercise and increased GLUT4 expression following exercise involves multiple, redundant signalling pathways. These include effects of reactive oxygen species (ROS). ROS contribute to GLUT4 translocation that increases skeletal muscle glucose uptake during exercise and stimulate signalling pathways that increase GLUT4 expression. Conversely, ROS can also inhibit GLUT4 translocation and expression in metabolic disease states. The opposing roles of ROS in GLUT4 regulation are ultimately linked to the metabolic state of skeletal muscle and the intricate mechanisms involved give insights into pathways critical for exercise performance and implicated in metabolic health and disease.

DNA methylation of Ad4BP/SF-1 suppresses Cyp11a1 and StAR transcripts in C2C12 myoblasts

Steroidogenesis occurs locally in peripheral tissues and via adrenal and gonadal glands' biosynthesis. The C2C12 mouse myoblast cell line and rat skeletal muscles harbor a local steroidogenesis pathway for glucocorticoids, and corticosterone is biosynthesized from skeletal muscle cells. However, Cyp11a1 and StAR protein expressions are not observed in C2C12 cells or rat muscular tissues. In this context, this study investigated the relationship between DNA methylation and key steroidogenic genes. Bioinformatics analysis of methylated DNA immune precipitation showed that C2C12 myoblasts and myotubes did not have remarkable DNA methylated regions in the gene-body of Cyp11a1. However, a highly methylated region in the CpG island was detected in the intronic enhancer of Ad4BP/SF-1, known as the transcriptional factor for steroidogenic genes. After C2C12 myoblasts treatment with 5-aza-2-deoxycytidine, the gene expressions of Ad4BP/SF-1, Cyp11a1, and StAR were significantly time- and concentration-dependent upregulated. To clarify the contribution of Ad4BP/SF-1 on Cyp11a1 and StAR transcripts, we silenced Ad4BP/SF-1 during the 5-aza-2-deoxycytidine treatment in C2C12 myoblasts, resulting in significant suppression of both Cyp11a1 and StAR. Additionally, pregnenolone levels in the supernatants of C2C12 cells were enhanced by 5-aza-2-deoxycytidine treatment, whereas pregnenolone production by C2C12 myoblasts was significantly suppressed by Ad4BP/SF-1 knockdown. These results indicate that DNA methylation of Ad4BP/SF-1 might be involved in the downregulation of steroidogenic genes, such as Cyp11a1 and StAR in C2C12 myoblasts.

Vampire bats rapidly fuel running with essential or non-essential amino acids from a blood meal

In most mammals, running is fuelled by oxidization of endogenous carbohydrates and lipids while amino acids contribute little (< 5-10%). Common vampire bats (Desmodus rotundus), however, specialize on a unique, protein-rich blood diet. Therefore, we hypothesized that (i) vampire bats would rapidly begin utilizing dietary amino acids to support running metabolism, and (ii) that relative reliance on essential and non-essential amino acids would be similar. We fed bats cow's blood enriched either with isotopically labelled glycine (non-essential amino acid) or leucine (essential amino acid). Bats were exercised at speeds of 10, 20 and 30 m min-1 on a respirometry treadmill, allowing us to assess metabolic rate (i.e. O2 consumption and CO2 production) and track the oxidation of labelled amino acids in exhaled CO2. Vampire bats oxidized amino acids as their primary fuel as indicated by a respiratory exchange ratio (RER = ratio of CO2 production to O2 consumption rates) of approximately 0.8-0.9 at all speeds, with the labelled meal accounting for as much as 60% of oxidized fuels at peak usage. Similar oxidation rates indicated bats did not discriminate between essential and non-essential amino acid use. These findings reiterate how strongly metabolism can be shaped by a specialized diet.

Exploring the impact of estrogen-related receptor gamma on metabolism and disease

Estrogen-related receptor gamma (ERRγ) is a member of the ERR orphan nuclear receptor family which possesses three subtypes, α, β, and γ. ERRγ is reportedly predominantly expressed in metabolically active tissues and cells, which promotes positive and negative effects in different tissues. ERRγ overexpression in the liver, pancreas, and thyroid cells is related to liver cancer, oxidative stress, reactive oxygen species (ROS) regulation, and carcinoma. Reduced ERRγ expression in the brain, immune cells, tumor cells, and energy metabolism causes neurological dysfunction, gastric cancer, and obesity. ERRγ is a constitutive receptor; however, its transcriptional activity also depends on co-regulators, agonists, and antagonists, which, when after forming a complex, can play a role in targeting and treating diseases. Moreover, ERRγ has proven crucial in regulating cellular and metabolic activity. However, many functions mediated via ERRγ remain unknown and require further exploration. Hence, considering the importance of ERRγ, this review focuses on the critical findings and interactions between ERRγ and co-regulators, agonists, and antagonists alongside its relationship with downstream and upstream signaling pathways and diseases. This review highlights new findings and provides a path to understanding the current ideas and future studies on ERRγ-mediated cellular activity.

Effects of low energy availability on performance in male athletes: A scoping review

OBJECTIVES

The primary aim of this study was to investigate the effects of low energy availability on different performance outcomes in male athletes. Secondary aims were to examine an assumed dose-response relationship and identify knowledge gaps.

DESIGN

Scoping review.

METHODS

The electronic database PubMed was searched until the end of June 2023. Additionally, we used reference tracking and hand-searching for related articles. Six studies with a total of 103 male athletes met the inclusion criteria.

RESULTS

Four of the included studies had an interventional study design, including one case study, and the remaining two were cross-sectional studies. Different performance outcomes (i.e., strength, endurance, speed) were either positively, negatively, or unaffected by low energy availability. The length and magnitude of the low energy availability, as well as the baseline status of the athletes could have influenced the results. Additionally, there are methodological considerations that might limit the validity of the results.

CONCLUSIONS

Current evidence shows heterogeneous results, as some studies suggested improvements in certain performance parameters, whilst other studies showed neutral or detrimental effects of low energy availability. Due to the limitations mentioned; additional research is warranted for a more comprehensive understanding.