Exercise/Resistance Training and Muscle Stem Cells

Control of muscle satellite cell function by specific exercise-induced cytokines and their applications in muscle maintenance

Exercise is recognized to play an observable role in improving human health, especially in promoting muscle hypertrophy and intervening in muscle mass loss-related diseases, including sarcopenia. Recent rapid advances have demonstrated that exercise induces the release of abundant cytokines from several tissues (e.g., liver, muscle, and adipose tissue), and multiple cytokines improve the functions or expand the numbers of adult stem cells, providing candidate cytokines for alleviating a wide range of diseases. Muscle satellite cells (SCs) are a population of muscle stem cells that are mitotically quiescent but exit from the dormancy state to become activated in response to physical stimuli, after which SCs undergo asymmetric divisions to generate new SCs (stem cell pool maintenance) and commit to later differentiation into myocytes (skeletal muscle replenishment). SCs are essential for the postnatal growth, maintenance, and regeneration of skeletal muscle. Emerging evidence reveals that exercise regulates muscle function largely via the exercise-induced cytokines that govern SC potential, but this phenomenon is complicated and confusing. This review provides a comprehensive integrative overview of the identified exercise-induced cytokines and the roles of these cytokines in SC function, providing a more complete picture regarding the mechanism of SC homeostasis and rejuvenation therapies for skeletal muscle.

Resistance exercise preconditioning prevents disuse muscle atrophy by inhibiting apoptosis and protein degradation via SESN2 in C57BL/6J mice

AIM

To compare the effects of different exercise preconditioning in the context of skeletal muscle atrophy and to investigate the potential involvement of Sestrin2 (SESN2), a stress-inducible protein that can be regulated by exercise, in exercise preconditioning on preventing disuse muscle atrophy.

METHODS

Eight-week-old male C57BL/6J mice were randomly assigned to sedentary groups (SD), aerobic exercise groups (AE), resistance exercise groups (RE), and combined exercise groups (CE) with or without 7 days of immobilization. The duration of the exercise intervention was 10 weeks. The effects of different exercise preconditioning to prevent muscle atrophy were analyzed by evaluating skeletal muscle function and mass. Additionally, to investigate the potential underlying mechanism of exercise-induced protection of skeletal muscle, wild-type and SESN2--/-- mice were randomly divided into sedentary group and resistance exercise preconditioning group. C2C12 cells were treated with SESN2 adenoviruses and MK2206 (an AKT inhibitor) for 48 h to elucidate the underlined mechanism.

RESULTS

RE was more effective in preserving skeletal muscle function, muscle mass and maintaining skeletal muscle protein homeostasis than AE and CE under immobilized condition. Importantly, exercise performance, muscle mass to body weight ratio, and the cross-sectional area of muscle fibers were significantly lower in SESN2-/- mice than wild-type mice after resistance exercise preconditioning. Mechanistically, the absence of SESN2 led to activation of the ubiquitin-proteasome system and induction of apoptosis. In vitro experiments showed that MK2206 treatment mitigated the regulatory effects of overexpression-SESN2 on protein hydrolysis and apoptosis.

CONCLUSION

RE was more effective than AE or CE in preventing disuse muscle atrophy. SESN2 mediated the protective effects of resistance exercise preconditioning on skeletal muscle atrophy.

The muscle stem cell niche at a glance

Skeletal muscle stem cells (MuSCs, also called satellite cells) are the source of the robust regenerative capability of this tissue. The hallmark property of MuSCs at homeostasis is quiescence, a reversible state of cell cycle arrest required for long-term preservation of the stem cell population. MuSCs reside between an individual myofiber and an enwrapping basal lamina, defining the immediate MuSC niche. Additional cell types outside the basal lamina, in the interstitial space, also contribute to niche function. Quiescence is actively maintained by multiple niche-derived signals, including adhesion molecules presented from the myofiber surface and basal lamina, as well as soluble signaling factors produced by myofibers and interstitial cell types. In this Cell Science at a Glance article and accompanying poster, we present the most recent information on how niche signals promote MuSC quiescence and provide perspectives for further research.

Anthropometric, muscle and serum myokine levels effects of physical exercise with an online platform in female patients with obesity

INTRODUCTION

Under physical exercise conditions, muscles can synthetise and release myokines and these molecules can exert paracrine and endocrine actions. Females with obesity have a sedentary lifestyle with alterations in myokine levels.

OBJECTIVE

The aim of our study was to evaluate the effect of physical exercise on myokine levels, anthropometric parameters, clinical data, impedance parameters, and muscle ultrasound data in sedentary females with obesity.

MATERIAL AND METHODS

Anthropometric data, muscle mass by ultrasound at the quadriceps level, myokine determination, and blood pressure were collected at baseline and after 12 weeks in 25 females with obesity. For 12 weeks, the physical exercise programme was prescribed through an online platform.

RESULTS

After the physical exercise programme, there was a significant improvement in body mass index (-1.49±0.1kg/m2; p=0.02), weight (-3.9±0.7kg; p=0.01), waist circumference (-7.2±0.2cm; p=0.01), skeletal muscle mass (5.4±1.2kg; p=0.01), appendicular skeletal muscle mass index (0.5±0.1kg; p=0.02) and appendicular skeletal muscle mass (1.4±0.1kg; p=0.03), and a decrease in fat mass (-4.1±0.2kg; p=0.01) and blood pressure. The ultrasound parameters of the anterior rectus quadriceps muscle improved significantly. The following biochemical parameters decreased; insulin levels (-66.3±10.2pg/ml; p=0.04), HOMA-IR (-0.4±0.1 units; p=0.03), apelin (-3.5±0.2IU/l; p=0.04), FABP3 (-143.6±38.1pg/ml; p=0.03), IL6 (-4.1±0.02pg/ml; p=0.02), myostatin (-81.6±18.1pg/ml; p=0.04), and FGF21 (-9.5±1.1pg/ml; p=0.03).

CONCLUSION

The prescription of physical exercise with an online platform for females with obesity decreases weight, body fat mass and increases muscle mass, producing a decrease in insulin resistance and some myokine levels.

Molecular mechanisms of exercise contributing to tissue regeneration

Physical activity has been known as an essential element to promote human health for centuries. Thus, exercise intervention is encouraged to battle against sedentary lifestyle. Recent rapid advances in molecular biotechnology have demonstrated that both endurance and resistance exercise training, two traditional types of exercise, trigger a series of physiological responses, unraveling the mechanisms of exercise regulating on the human body. Therefore, exercise has been expected as a candidate approach of alleviating a wide range of diseases, such as metabolic diseases, neurodegenerative disorders, tumors, and cardiovascular diseases. In particular, the capacity of exercise to promote tissue regeneration has attracted the attention of many researchers in recent decades. Since most adult human organs have a weak regenerative capacity, it is currently a key challenge in regenerative medicine to improve the efficiency of tissue regeneration. As research progresses, exercise-induced tissue regeneration seems to provide a novel approach for fighting against injury or senescence, establishing strong theoretical basis for more and more "exercise mimetics." These drugs are acting as the pharmaceutical alternatives of those individuals who cannot experience the benefits of exercise. Here, we comprehensively provide a description of the benefits of exercise on tissue regeneration in diverse organs, mainly focusing on musculoskeletal system, cardiovascular system, and nervous system. We also discuss the underlying molecular mechanisms associated with the regenerative effects of exercise and emerging therapeutic exercise mimetics for regeneration, as well as the associated opportunities and challenges. We aim to describe an integrated perspective on the current advances of distinct physiological mechanisms associated with exercise-induced tissue regeneration on various organs and facilitate the development of drugs that mimics the benefits of exercise.

Exercise Therapy for People With Sarcopenic Obesity: Myokines and Adipokines as Effective Actors

Sarcopenic obesity is defined as a multifactorial disease in aging with decreased body muscle, decreased muscle strength, decreased independence, increased fat mass, due to decreased physical activity, changes in adipokines and myokines, and decreased satellite cells. People with sarcopenic obesity cause harmful changes in myokines and adipokines. These changes are due to a decrease interleukin-10 (IL-10), interleukin-15 (IL-15), insulin-like growth factor hormone (IGF-1), irisin, leukemia inhibitory factor (LIF), fibroblast growth factor-21 (FGF-21), adiponectin, and apelin. While factors such as myostatin, leptin, interleukin-6 (IL-6), interleukin-8 (IL-8), and resistin increase. The consequences of these changes are an increase in inflammatory factors, increased degradation of muscle proteins, increased fat mass, and decreased muscle tissue, which exacerbates sarcopenia obesity. In contrast, exercise, especially strength training, reverses this process, which includes increasing muscle protein synthesis, increasing myogenesis, increasing mitochondrial biogenesis, increasing brown fat, reducing white fat, reducing inflammatory factors, and reducing muscle atrophy. Since some people with chronic diseases are not able to do high-intensity strength training, exercises with blood flow restriction (BFR) are newly recommended. Numerous studies have shown that low-intensity BFR training produces the same increase in hypertrophy and muscle strength such as high-intensity strength training. Therefore, it seems that exercise interventions with BFR can be an effective way to prevent the exacerbation of sarcopenia obesity. However, due to limited studies on adipokines and exercises with BFR in people with sarcopenic obesity, more research is needed.