Exercise and Regulation of Adipokine and Myokine Production

Influence of Amino Acids and Exercise on Muscle Protein Turnover, Particularly in Cancer Cachexia

Cancer cachexia is a multifaceted syndrome that impacts individuals with advanced cancer. It causes numerous pathological changes in cancer patients, such as inflammation and metabolic dysfunction, which further diminish their quality of life. Unfortunately, cancer cachexia also increases the risk of mortality in affected individuals, making it an important area of focus for cancer research and treatment. Several potential nutritional therapies are being tested in preclinical and clinical models for their efficacy in improving muscle metabolism in cancer patients. Despite promising results, no special nutritional therapies have yet been validated in clinical practice. Multiple studies provide evidence of the benefits of increasing muscle protein synthesis through an increased intake of amino acids or protein. There is also increasing evidence that exercise can reduce muscle atrophy by modulating protein synthesis. Therefore, the combination of protein intake and exercise may be more effective in improving cancer cachexia. This review provides an overview of the preclinical and clinical approaches for the use of amino acids with and without exercise therapy to improve muscle metabolism in cachexia.

The causal effect of sarcopenia-associated traits on brain cortical structure: A Mendelian randomization study

BACKGROUND

Previous observational studies have reported sarcopenia can affect the structure and function of brain cortical structure. However, the causality inferred from those studies was subjected to residual confounding and reverse causation. Herein, we use a two-sample Mendelian randomization (MR) analysis to illustrate the causal effect of sarcopenia-associated traits on brain cortical structure.

METHODS

We selected appendicular lean mass (ALM), hand grip strength (left and right) (HGSL and HGSR), and usual walking pace (UWP) to symbolize sarcopenia. The definition of brain cortical structure is human brain cortical surface area (SA) and cortical thickness (TH) globally and in 34 functional regions measured by magnetic resonance imaging. Instrumental variables at the genome-wide significance level were obtained from publicly available datasets, and inverse variance weighted as the primary method was used for MR analysis.

RESULT

At the global level, we found ALM (β=2604.68, 95 % confidence interval (CI): 1886.17 to 3323.19, P = 1.20 × 10-12) and HGSR (β=4733.05, 95 % CI: 2245.08 to 7221.01, P = 1.93 × 10-4) were associated with increased SA. At the region level, the SA of 25 functional gyrus without global weighted was influenced by ALM. The HGSR significantly increased SA of medial orbitofrontal and precentral gyrus without global weighted and ALM was associated with decrease of TH of lateral occipital gyrus with global weighted. No pleiotropy was detected.

CONCLUSION

This was the first MR study investigated the causal effect of sarcopenia-associated traits on brain cortical structure. In our study, we revealed genetically predicted sarcopenia-associated traits including ALM and HGSR could affect brain cortical structure.

Plasma irisin and the brain-derived neurotrophic factor levels in sedentary subjects: effect of 8-weeks lifestyle intervention

Objectives. Sedentary lifestyle increasingly observed in the population contributes to the incremental incidence of obesity, cardiovascular diseases, mental disorders, type 2 diabetes, hyper-tension, dyslipidemia, and others. Physical inactivity together with an imbalance in caloric intake and expenditure leads to a loss of muscle mass, reduced insulin sensitivity, and accumulation of the visceral fat. Organokines (adipokines, myokines, hepatokines, etc.) serve in the organism for inter-organ communication. However, human studies focused on the exercise-related changes in plasma levels of certain myokines have produced contradictory results. In the present study, we verified a hypothesis that myokine irisin, which is expected to increase in response to physical activity, induces brain-derived neurotrophic factor (BDNF) production and by this way mediates the beneficial effect of exercise on several brain functions. Subjects and Methods. Women (n=27) and men (n=10) aged 44.5±12.0 years, who were sedentary and overweight/obese (men ≥25%, women ≥28% body fat), participated in the study. The effect of an 8-week intensive lifestyle intervention (150 minutes of moderate physical activity per week, diet modification, and reduction of caloric intake) on the selected organokines (irisin, BDNF) in the context of an expected improvement in cardiometabolic status was examined. Results. The 8-week lifestyle intervention resulted in a significant (p<0.05) reduction in body mass index, body fat, blood pressure, insulin resistance, lipid and liver parameters, and irisin levels (p<0.001). However, BDNF increase in the whole group did not reach statistical significance. After the improvement of cardiometabolic parameters, a significant decrease in irisin and increase in BDNF levels were also observed in the subgroup with unsatisfactory (≤5%) body weight reduction. Neither relationship between irisin and BDNF levels, nor effect of age or sex on their levels was observed. Conclusions. We cannot confirm the hypothesis that exercise-induced irisin may increase the BDNF levels, whereas, the organokine levels in the periphery may not completely reflect the processes in the brain compartments. The observed decrease in irisin levels after 8-week intensive lifestyle intervention program, which was in contrary to its supposed mechanisms of action and dynamics, suggests the presence of several yet undiscovered impacts on the secretion of irisin.

Irisin/BDNF signaling in the muscle-brain axis and circadian system: A review

In mammals, the timing of physiological, biochemical and behavioral processes over a 24-h period is controlled by circadian rhythms. To entrain the master clock located in the suprachiasmatic nucleus of the hypothalamus to a precise 24-h rhythm, environmental zeitgebers are used by the circadian system. This is done primarily by signals from the retina via the retinohypothalamic tract, but other cues like exercise, feeding, temperature, anxiety, and social events have also been shown to act as non-photic zeitgebers. The recently identified myokine irisin is proposed to serve as an entraining non-photic signal of exercise. Irisin is a product of cleavage and modification from its precursor membrane fibronectin type Ⅲ domain-containing protein 5 (FNDC5) in response to exercise. Apart from well-known peripheral effects, such as inducing the "browning" of white adipocytes, irisin can penetrate the blood-brain barrier and display the effects on the brain. Experimental data suggest that FNDC5/irisin mediates the positive effects of physical activity on brain functions. In several brain areas, irisin induces the production of brain-derived neurotrophic factor (BDNF). In the master clock, a significant role in gating photic stimuli in the retinohypothalamic synapse for BDNF is suggested. However, the brain receptor for irisin remains unknown. In the current review, the interactions of physical activity and the irisin/BDNF axis with the circadian system are reconceptualized.

Regulatory effects and mechanisms of exercise on activation of brown adipose tissue (BAT) and browning of white adipose tissue (WAT)

Exercise is a universally acknowledged and healthy way to reducing body weight. However, the roles and mechanisms of exercise on metabolism of adipose tissue remain largely unclear. Adipose tissues include white adipose tissue (WAT), brown adipose tissue (BAT) and beige adipose tissue (BeAT). The main function of WAT is to store energy, while the BAT and BeAT can generate heat and consume energy. Therefore, promotion of BAT activation and WAT browning contributes to body weight loss. To date, many studies have suggested that exercise exerts the potential regulatory effects on BAT activation and WAT browning. In the present review, we compile the evidence for the regulatory effects of exercise on BAT activation and WAT browning and summarize the possible mechanisms whereby exercise modulates BAT activation and WAT browning, including activating sympathetic nervous system (SNS) and promoting the secretion of exerkines, with special focus on exerkines. These data might provide reference for prevention or treatment of obesity and the related metabolic disease through exercise.

Molecular investigation of the effect of weightlifting training on helper T cell subsets in female weightlifting athletes: an immune profiling panel

BACKGROUND

In this study, it was aimed to molecularly investigate the changes in the helper T (Th) cell subgroups of intense weightlifting training. For this purpose, transcription factor and cytokine expressions of Th1, Th2, Th17, and regulator T cell (Treg) cells were evaluated.

METHODS

Eight elite weightlifting athletes were included in the study. Within the scope of the study, transcription factor and cytokine expressions of Th cell subgroups were evaluated by real-time polymerase chain reaction (qPCR) method before training, after intense training with 90-100% capacity, and after 120 minutes of rest from training.

RESULTS

As a result of the study, when the pre-training and post-training expressions were compared, an increase in Th1 and Th2 cell factors and a decrease in Th17 and Treg cell-related expressions were detected. These changes were statistically significant (P<0.05). The changes in expressions after training and after 120 minutes of rest were not statistically significant (P>0.05).

CONCLUSIONS

Changes have been detected in Th cell subgroups due to intense weightlifting training, and these changes are the first study conducted with female weightlifters.

Tissue-specific mechanisms of fat metabolism that focus on insulin actions

BACKGROUND

The accumulation of ectopic fats is related to metabolic syndromes with insulin resistance, which is considered as the first hit in obesity-related diseases. However, systematic understanding of the occurrence of ectopic fats is limited, since organisms are capable of orchestrating complicated intracellular signaling pathways to ensure that the correct nutritional components reach the tissues where they are needed. Interestingly, tissue-specific mechanisms lead to different consequences of fat metabolism with different insulin sensitivities.

AIM OF REVIEW

To summarize the mechanisms of fat deposition in different tissues including adipose tissue, subcutis, liver, muscle and intestines, in an attempt to elucidate interactive mechanisms involving insulin actions and establish a potential reference for the rational uptake of fat.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Tissue-specific fat metabolism serves as a trigger for developing abnormal fat metabolism or as a compensatory agent for regulating normal fat metabolism. Outcomes of de novo lipogenesis and adipogenesis differ in the subcutaneous adipose tissue (SAT), liver and muscle, with the participation of insulin actions. Overload of lipid metabolic capability results in SAT fat expansion, and ectopic fat accumulation implicates impaired lipo-/adipogenesis in SAT. Regulating insulin actions may be a key measure on fat deposition and metabolism in individuals.

Fatiguing freestyle swimming modifies miRNA profiles of circulating extracellular vesicles in athletes

Extracellular vesicles (EVs) are secreted by various tissues and cells under normal physiological or pathological conditions. Exercise-induced EVs may be involved in the adaptation of exercise-induced fatigue. The 1500-m freestyle is the longest pool-based swimming event in the Olympic Games, and there is a paucity of information regarding changes in the miRNA profiles of circulating EVs after a single session of fatiguing swimming. In this study, 13 male freestyle swimmers conducted a fatiguing 1500-m freestyle swimming session at the speed of their best previously recorded swimming performance. Fasting venous blood was collected before and after the swimming session for analysis. 70 miRNAs from the circulating EVs were found to be differentially expressed after the fatiguing 1500-m freestyle swimming session, among which 45 and 25 miRNAs were up-regulated and down-regulated, respectively. As for the target genes of five miRNAs (miR-144-3p, miR-145-3p, miR-509-5p, miR-891b, and miR-890) with the largest expression-fold variation, their functional enrichment analysis demonstrated that the target genes were involved in the regulation of long-term potentiation (LTP), vascular endothelial growth factor (VEGF), glutathione metabolism pathway, dopaminergic synapse, signal transmission, and other biological processes. In summary, these findings reveal that a single session of fatiguing swimming modifies the miRNAs profiles of the circulating EVs, especially miR-144-3p, miR-145-3p, miR-509-5p, miR-891b, and miR-890, which clarifies new mechanisms for the adaptation to a single session of fatiguing exercise from the perspective of EV-miRNAs.

Myokines as mediators of exercise-induced cognitive changes in older adults: protocol for a comprehensive living systematic review and meta-analysis

Background

The world's population is aging, but life expectancy has risen more than healthy life expectancy (HALE). With respect to brain and cognition, the prevalence of neurodegenerative disorders increases with age, affecting health and quality of life, and imposing significant healthcare costs. Although the effects of physical exercise on cognition in advanced age have been widely explored, in-depth fundamental knowledge of the underlying mechanisms of the exercise-induced cognitive improvements is lacking. Recent research suggests that myokines, factors released into the blood circulation by contracting skeletal muscle, may play a role in mediating the beneficial effect of exercise on cognition. Our goal in this ongoing (living) review is to continuously map the rapidly accumulating knowledge on pathways between acute or chronic exercise-induced myokines and cognitive domains enhanced by exercise.

Method

Randomized controlled studies will be systematically collected at baseline and every 6 months for at least 5 years. Literature search will be performed online in PubMed, EMBASE, PsycINFO, Web of Science, SportDiscus, LILACS, IBECS, CINAHL, SCOPUS, ICTRP, and ClinicalTrials.gov. Risk of bias will be assessed using the Revised Cochrane Risk of Bias tool (ROB 2). A random effects meta-analysis with mediation analysis using meta-analytic structural equation modeling (MASEM) will be performed. The primary research question is to what extent exercise-induced myokines serve as mediators of cognitive function. Secondarily, the pooled effect size of specific exercise characteristics (e.g., mode of exercise) or specific older adults' populations (e.g., cognitively impaired) on the relationship between exercise, myokines, and cognition will be assessed. The review protocol was registered in PROSPERO (CRD42023416996).

Discussion

Understanding the triad relationship between exercise, myokines and cognition will expand the knowledge on multiple integrated network systems communicating between skeletal muscles and other organs such as the brain, thus mediating the beneficial effects of exercise on health and performance. It may also have practical implications, e.g., if a certain myokine is found to be a mediator between exercise and cognition, the optimal exercise characteristics for inducing this myokine can be prescribed. The living review is expected to improve our state of knowledge and refine exercise regimes for enhancing cognitive functioning in diverse older adults' populations.

Registration

Systematic review and meta-analysis protocol was registered with the International Prospective Register of Systematic Reviews (PROSPERO) on the 24th of April 2023 (registration number CRD42023416996).

Sclerostin decreases in regular swimmers after ice swimming and is associated with meteorin-like protein serum levels

Introduction: Cold and exercise are two important stimuli affecting the secretion of osteokines and adipomyokines, which often occur simultaneously. However, few studies have investigated the changes in osteokines and adipomyokines induced by exercise during severe cold and their corresponding associations. Therefore, this study aimed to investigate the changes in sclerostin and meteorin-like (metrnl) protein before and after cold exercise (ice swimming [IS]) and observe their correlation. Methods: For this, 56 daily ice swimmers' data were included in this study. Serum sclerostin and metrnl were measured 30 min before IS and 30 min after. The fat mass, visceral fat area, fat-free mass, skeletal muscle mass, lumbar spine, and femoral neck bone mineral density of the ice swimmers were measured. Results: After IS, sclerostin exhibited significant decreases, whereas metrnl showed no significant change. In addition, the baseline level of sclerostin and the decrease in sclerostin were positively correlated with serum metrnl after adjusting for age, gender, and body composition indicators. Discussion: IS caused a significant decrease in sclerostin but did not affect metrnl. Furthermore, the associations between sclerostin and metrnl suggested a correlation between osteokines and adipomyokines; this encourages future exploration of the interconnection between bone, muscle, and fat, which will be beneficial for identifying potential common therapeutic targets for diseases such as osteoporosis, sarcopenia, and obesity.

Changes in selected exerkines concentration post folk-dance training are accompanied by glucose homeostasis and physical performance improvement in older adults

The study aimed to evaluate the impact of selected exerkines concentration induced by folk-dance and balance training on physical performance, insulin resistance, and blood pressure in older adults. Participants (n = 41, age 71.3 ± 5.5 years) were randomly assigned to folk-dance (DG), balance training (BG), or control group (CG). The training was performed 3 times a week for 12 weeks. Physical performance tests-time up and go (TUG) and 6-min walk test (6MWT), blood pressure, insulin resistance, and selected proteins induced by exercise (exerkines) were assessed at baseline and post-exercise intervention. Significant improvement in TUG (p = 0.006 for BG and 0.039 for DG) and 6MWT tests (in BG and DG p = 0.001), reduction of systolic blood pressure (p = 0.001 for BG and 0.003 for DG), and diastolic blood pressure (for BG; p = 0.001) were registered post-intervention. These positive changes were accompanied by the drop in brain-derived neurotrophic factor (p = 0.002 for BG and 0.002 for DG), the increase of irisin concentration (p = 0.029 for BG and 0.022 for DG) in both groups, and DG the amelioration of insulin resistance indicators (HOMA-IR p = 0.023 and QUICKI p = 0.035). Folk-dance training significantly reduced the c-terminal agrin fragment (CAF; p = 0.024). Obtained data indicated that both training programs effectively improved physical performance and blood pressure, accompanied by changes in selected exerkines. Still, folk-dance had enhanced insulin sensitivity.

Effects of recreational SCUBA diving practiced once a week on neurohormonal response and myokines-mediated communication between muscles and the brain

Objective

During physical activity, activation of muscular, endocrine, and nervous systems, results in intensive crosstalk between muscles and other organs, which enables response to physiological stress. In SCUBA diving, extreme environmental conditions represent an additional challenge for homeostasis maintenance, but underlying mechanisms are largely unknown. We aimed to contribute to the understanding of neurohormonal response and muscle-brain crosstalk by measuring the concentrations of the selected hormones secreted by the pituitary-target organ axis and myokines involved in the muscle-brain endocrine loop in recreational SCUBA (rSCUBA) divers.

Methods

Fourteen male divers performed five open-water recreational dives (one per week, depth of 20–30 m, lasting 30 min, between 9 and 10 am), after a winter non-diving period of 5 months. Blood samples were collected immediately before and after the first, third, and fifth dives. Adrenocorticotropic hormone (ACTH), cortisol, thyroid-stimulating hormone (TSH), free thyroxine (fT4), prolactin, total testosterone, growth hormone (GH), insulin-like growth factor-1 (IGF-1), irisin, brain-derived neurotrophic factor (BDNF), S100B, glial fibrillary acidic protein (GFAP), and neuron-specific enolase (NSE) were measured using commercially available immunoassays.

Results

Cortisol and ACTH levels decreased after every dive, while total testosterone decreased only after the first dive. No significant changes in post-dive values, as well as the cumulative effect on any other measured hormone, were observed. Although irisin and BDNF levels decreased after the first and third dives, the fifth dive caused a significant increase in both myokines. Changes in IGF-1 levels were not observed. All three dives caused a significant increase in S100B levels. A statistically significant decrease in GFAP concentration was observed after every dive, while NSE pre-dive concentration declined over the studied period. The cumulative effect on myokine levels was reflected in a continuous decline in irisin and BDNF pre-dive levels throughout the studied period, but an increasing trend after the fifth dive was observed.

Conclusions

Observed changes in myokines and hormone levels point to a specific response to rSCUBA practiced once a week, most likely due to extreme environmental conditions. Further studies on communication between muscles and other organ systems, particularly on the muscle-brain endocrine loop, are required for a deeper understanding of the adaptation mechanisms to this kind of physiological stress.

Effects of weight-bearing vs. non-weight-bearing endurance exercise on reducing body fat and inflammatory markers in obese females

OBJECTIVES

Endurance exercise is an effective strategy for maintaining an anti-inflammatory environment and weight management. However, the effect of this type of exercise on decreasing body fat and TNF-α levels and increasing adiponectin levels is controversial. The aims of this study was to prove the effects of weight-bearing vs. non-weight-bearing endurance exercise on reducing body fat and inflammatory markers in obese females.

METHODS

24 obese adolescents were recruited from female students from the State University of Malang. The interventions given in this study were weight-bearing endurance exercise (WBEE), and non-weight-bearing endurance exercise (NWBEE). Serum TNF-α levels and serum adiponectin levels were evaluated using enzyme-linked immunosorbent assay (ELISA). Statistical analysis techniques use paired sample T-test with a significant level of 5%.

RESULTS

Results of the statistical analysis show that the average body fat (PBF, FM, FFM) and TNF-α levels before endurance exercise vs. after endurance exercise in both types of exercise experienced a significant decrease (p≤0.05), while average adiponectin levels in both types of exercise experienced a significant increase before endurance exercise vs. after endurance exercise (p≤0.001).

CONCLUSIONS

In general, it can be concluded that weight-bearing and non-weight-bearing endurance exercise with moderate-intensity for 40 min/exercise session reduce body fat and TNF-α levels and increase adiponectin levels as a marker of inflammation in obese female.

Interaction of Cardiovascular Nonmodifiable Risk Factors, Comorbidities and Comedications With Ischemia/Reperfusion Injury and Cardioprotection by Pharmacological Treatments and Ischemic Conditioning

Preconditioning, postconditioning, and remote conditioning of the myocardium enhance the ability of the heart to withstand a prolonged ischemia/reperfusion insult and the potential to provide novel therapeutic paradigms for cardioprotection. While many signaling pathways leading to endogenous cardioprotection have been elucidated in experimental studies over the past 30 years, no cardioprotective drug is on the market yet for that indication. One likely major reason for this failure to translate cardioprotection into patient benefit is the lack of rigorous and systematic preclinical evaluation of promising cardioprotective therapies prior to their clinical evaluation, since ischemic heart disease in humans is a complex disorder caused by or associated with cardiovascular risk factors and comorbidities. These risk factors and comorbidities induce fundamental alterations in cellular signaling cascades that affect the development of ischemia/reperfusion injury and responses to cardioprotective interventions. Moreover, some of the medications used to treat these comorbidities may impact on cardioprotection by again modifying cellular signaling pathways. The aim of this article is to review the recent evidence that cardiovascular risk factors as well as comorbidities and their medications may modify the response to cardioprotective interventions. We emphasize the critical need for taking into account the presence of cardiovascular risk factors as well as comorbidities and their concomitant medications when designing preclinical studies for the identification and validation of cardioprotective drug targets and clinical studies. This will hopefully maximize the success rate of developing rational approaches to effective cardioprotective therapies for the majority of patients with multiple comorbidities. SIGNIFICANCE STATEMENT: Ischemic heart disease is a major cause of mortality; however, there are still no cardioprotective drugs on the market. Most studies on cardioprotection have been undertaken in animal models of ischemia/reperfusion in the absence of comorbidities; however, ischemic heart disease develops with other systemic disorders (e.g., hypertension, hyperlipidemia, diabetes, atherosclerosis). Here we focus on the preclinical and clinical evidence showing how these comorbidities and their routine medications affect ischemia/reperfusion injury and interfere with cardioprotective strategies.

Exercise sustains the hallmarks of health

Exercise has long been known for its active role in improving physical fitness and sustaining health. Regular moderate-intensity exercise improves all aspects of human health and is widely accepted as a preventative and therapeutic strategy for various diseases. It is well-documented that exercise maintains and restores homeostasis at the organismal, tissue, cellular, and molecular levels to stimulate positive physiological adaptations that consequently protect against various pathological conditions. Here we mainly summarize how moderate-intensity exercise affects the major hallmarks of health, including the integrity of barriers, containment of local perturbations, recycling and turnover, integration of circuitries, rhythmic oscillations, homeostatic resilience, hormetic regulation, as well as repair and regeneration. Furthermore, we summarize the current understanding of the mechanisms responsible for beneficial adaptations in response to exercise. This review aimed at providing a comprehensive summary of the vital biological mechanisms through which moderate-intensity exercise maintains health and opens a window for its application in other health interventions. We hope that continuing investigation in this field will further increase our understanding of the processes involved in the positive role of moderate-intensity exercise and thus get us closer to the identification of new therapeutics that improve quality of life.

Sarcopenia in Chronic Liver Disease: A Metabolic Perspective

Sarcopenia, a condition of low muscle mass, quality, and strength, is commonly found in patients with chronic liver disease (CLD) and is associated with adverse clinical outcomes including reduction in quality of life, increased mortality, and complications. A major contributor to sarcopenia in CLD is the imbalance in muscle protein turnover wherein changes in various metabolic factors such as hyperammonemia, amino acid deprivation, hormonal imbalance, gut dysbiosis, insulin resistance, chronic inflammation, etc. have important roles. In particular, hyperammonemia is a key mediator of the liver-gut axis and is known to contribute to sarcopenia by various mechanisms including increased expression of myostatin, increased phosphorylation of eukaryotic initiation factor 2a, cataplerosis of α-ketoglutarate, mitochondrial dysfunction, increased reactive oxygen species that decrease protein synthesis and increased autophagy-mediated proteolysis. Skeletal muscle is a major organ of insulin-induced glucose metabolism, and sarcopenia is closely linked to insulin resistance and metabolic syndrome. Patients with liver cirrhosis are in a hypermetabolic state that is associated with catabolism and depletion of amino acids, particularly branched-chain amino acids. Sarcopenia can have significant implications for nonalcoholic fatty liver disease, the most common form of CLD worldwide, because of the close link between metabolic syndrome and sarcopenia. This review discusses the potential metabolic derangement as a cause or effect of sarcopenia in CLD, as well as interorgan crosstalk, which that might help identifying a novel therapeutic strategies.

Reactive Oxygen and Nitrogen Species (RONS) and Cytokines-Myokines Involved in Glucose Uptake and Insulin Resistance in Skeletal Muscle

Insulin resistance onset in skeletal muscle is characterized by the impairment of insulin signaling, which reduces the internalization of glucose, known as glucose uptake, into the cell. Therefore, there is a deficit of intracellular glucose, which is the main source for energy production in the cell. This may compromise cellular viability and functions, leading to pathological dysfunction. Skeletal muscle fibers continuously generate reactive oxygen and nitrogen species (RONS). An excess of RONS produces oxidative distress, which may evoke cellular damage and dysfunction. However, a moderate level of RONS, which is called oxidative eustress, is critical to maintain, modulate and regulate cellular functions through reversible interactions between RONS and the components of cellular signaling pathways that control those functions, such as the facilitation of glucose uptake. The skeletal muscle releases peptides called myokines that may have endocrine and paracrine effects. Some myokines bind to specific receptors in skeletal muscle fibers and might interact with cellular signaling pathways, such as PI3K/Akt and AMPK, and facilitate glucose uptake. In addition, there are cytokines, which are peptides produced by non-skeletal muscle cells, that bind to receptors at the plasma membrane of skeletal muscle cells and interact with the cellular signaling pathways, facilitating glucose uptake. RONS, myokines and cytokines might be acting on the same signaling pathways that facilitate glucose uptake in skeletal muscle. However, the experimental studies are limited and scarce. The aim of this review is to highlight the current knowledge regarding the role of RONS, myokines and cytokines as potential signals that facilitate glucose uptake in skeletal muscle. In addition, we encourage researchers in the field to lead and undertake investigations to uncover the fundamentals of glucose uptake evoked by RONS, myokines, and cytokines.

Fatigue and Recovery Time Course After Female Soccer Matches: A Systematic Review And Meta-analysis

Background

This study aimed to analyze the extent of fatigue responses after female soccer matches and the ensuing recovery time course of performance, physiological, and perceptual responses.

Methods

Three databases (PubMed, Web of Science, and SPORTDiscus) were searched in October 2020 and updated in November 2021. Studies were included when participants were female soccer players, regardless of their ability level. Further, the intervention was an official soccer match with performance, physiological, or perceptual parameters collected pre- and post-match (immediately, 12 h, 24 h, 48 h, or 72 h-post).

Results

A total of 26 studies (n = 465 players) were included for meta-analysis. Most performance parameters showed some immediate post-match reduction (effect size [ES] = − 0.72 to − 1.80), apart from countermovement jump (CMJ; ES = − 0.04). Reduced CMJ performance occurred at 12 h (ES = − 0.38) and 24 h (ES = − 0.42) and sprint at 48 h post-match (ES = − 0.75). Inflammatory and immunological parameters responded acutely with moderate-to-large increases (ES = 0.58–2.75) immediately post-match. Creatine kinase and lactate dehydrogenase alterations persisted at 72 h post-match (ES = 3.79 and 7.46, respectively). Small-to-moderate effects were observed for increased cortisol (ES = 0.75) and reduced testosterone/cortisol ratio (ES = -0.47) immediately post-match, while negligible to small effects existed for testosterone (ES = 0.14) and estradiol (ES = 0.34). Large effects were observed for perceptual variables, with increased fatigue (ES = 1.79) and reduced vigor (ES = − 0.97) at 12 h post-match, while muscle soreness was increased immediately post (ES = 1.63) and at 24 h post-match (ES = 1.00).

Conclusions

Acute fatigue exists following female soccer matches, and the performance, physiological, and perceptual parameters showed distinctive recovery timelines. Importantly, physical performance was recovered at 72 h post-match, whereas muscle damage markers were still increased at this time point. These timelines should be considered when planning training and match schedules. However, some caution should be advised given the small number of studies available on this population.

Registration

The protocol for this systematic review was pre-registered on the International Prospective Register of Systematic Reviews (PROSPERO, Registration Number: CRD42021237857).

Supplementary Information

The online version contains supplementary material available at 10.1186/s40798-022-00466-3.

The Potential of Exerkines in Women's COVID-19: A New Idea for a Better and More Accurate Understanding of the Mechanisms behind Physical Exercise

The benefits of physical exercise are well-known, but there are still many questions regarding COVID-19. Chow et al.'s 2022 study, titled Exerkines and Disease, showed that a special focus on exerkines can help to better understand the underlying mechanisms of physical exercise and disease. Exerkines are a group of promising molecules that may underlie the beneficial effects of physical exercise in diseases. The idea of exerkines is to understand the effects of physical exercise on diseases better. Exerkines have a high potential for the treatment of diseases and, considering that, there is still no study of the importance of exerkines on the most dangerous disease in the world in recent years, COVID-19. This raises the fundamental question of whether exerkines have the potential to manage COVID-19. Most of the studies focused on the general changes in physical exercise in patients with COVID-19, both during the illness and after discharge from the hospital, and did not investigate the basic differences. A unique look at the management of COVID-19 by exerkines, especially in obese and overweight women who experience high severity of COVID-19 and whose recovery period is long after discharge from the hospital, can help to understand the basic mechanisms. In this review, we explore the potential of exerkines in COVID-19 by practicing physical exercise to provide compelling practice recommendations with new insights.

Evaluation of the Anti-Obesity Effect of Zeaxanthin and Exercise in HFD-Induced Obese Rats

Obesity is a worldwide epidemic associated with many health problems. One of the new trends in health care is the emphasis on regular exercise and a healthy diet. Zeaxanthin (Zea) is a carotenoid with many beneficial effects on human health. The aim of this study was to investigate whether the combination of Zea and exercise had therapeutic effects on obesity induced by an HFD in rats. Sixty male Wistar rats were randomly divided into five groups of twelve: rats fed a standard diet; rats fed a high-fat diet (HFD); rats fed an HFD with Zea; rats fed an HFD with Exc; and rats fed an HFD with both Zea and Exc. To induce obesity, rats were fed an HFD for twelve weeks. Then, Zea and exercise were introduced with the HFD for five weeks. The results showed that the HFD significantly increased visceral adipose tissue, oxidative stress, and inflammation biomarkers and reduced insulin, high-density lipoprotein, and antioxidant parameters. Treatments with Zea, Exc, and Zea plus Exc reduced body weight gain, triacylglycerol, glucose, total cholesterol, and nitric oxide levels and significantly increased catalase and insulin compared with the HFD group. This study demonstrated that Zea administration and Exc performance appeared to effectively alleviate the metabolic alterations induced by an HFD. Furthermore, Zea and Exc together had a better effect than either intervention alone.

Exercise training rescues adipose tissue spexin expression and secretion in diet-induced obese mice

Exercise training improves obesity-induced metabolic diseases through regulation of adipokines. Previous studies have shown that adipocyte-spexin participates in metabolic diseases such as obesity and diabetes via the modulation of energy homeostasis and insulin resistance. The objective of this research was to investigate the effects of swimming exercise on the levels of adipocyte-spexin and the underlying mechanisms. The normal chow diet (NC)-fed and high-fat diet (HFD)-fed mice were divided into exercise or sedentary groups. The expression and secretion of spexin in adipose tissue were assessed by quantitative real-time PCR and ELISA. The present findings uncovered the effect of exercise-induced spexin expression in the adipose tissue of obese mice. Besides, chronic exercise-induced upregulation of adipose spexin may be mediated by COUP-TF2 and KLF9. In addition, constant-moderate intensity exercise increased the levels of GLUT4, SIRT1 and PGC-1α in the skeletal muscles of mice. These results suggest that spexin is a potential mediator for exercise to ameliorate obesity-induced insulin resistance, namely, the beneficial effect of exercise on insulin sensitivity is at least partly mediated by spexin. Thus, exercise restores spexin production and release, which increases insulin sensitivity and maintains metabolic balance in the adipose tissues of HFD-induced obese mice.

Association of Physical Activity with Retinal Thickness and Vascular Structure in Elderly Chinese Population

INTRODUCTION

We aimed to assess the association of physical activity (PA) with retinal thickness and vascular structure in an elderly Chinese population.

METHODS

This study enrolled 220 retirees aged 50 years and above from Tianjin University of Sport, China. PA data gathered through the International Physical Activity Questionnaires were computed for metabolic equivalent of task-minutes per week. All participants underwent full ophthalmic examination including optical coherence tomography angiography. Multiple linear regression analyses were used to evaluate the association of PA with retinal thickness and vascular structure.

RESULTS

A high amount of total PA was associated with smaller size of foveal avascular zone (FAZ) (high vs. low: area, β = -0.04; circumference β = -0.14) and greater central vessel density (VD) (β = 1.04) and perfusion density (PD) (β = 0.02). For domain-specific PA, participants with high and moderate recreational PA levels were found to have greater central VDs and PDs. Nonleisure activities demonstrated negative relationship with FAZ perimeter ratio (moderate vs. low: β = -0.08; high vs. low: β = -0.13) and, counter-intuitively, negative relation with VDs measured at the inner (high vs. low: β = -0.98) and outer retinal layers (high vs. low: β = -0.38). Additionally, higher levels of total PA were related to increased macular fovea thickness and average thickness of retinal nerve fiber layer.

CONCLUSIONS

High PA level, particularly recreational PA, was associated with smaller FAZ and greater VD and PD in senior adults. Nonleisure-time PA might not confer the same health benefits as leisure-time PA. Our data support a possible protective role of recreational PA in the retina against microvascular changes.

Aerobic exercise-induced circulating extracellular vesicle combined decellularized dermal matrix hydrogel facilitates diabetic wound healing by promoting angiogenesis

Background: Insufficient blood supply results in unsatisfactory wound healing, especially for challenging wound repair such as diabetic wound defects. Regular exercise training brings a lot of benefits to cardiovascular fitness and metabolic health including attenuation of T2DM progression. Circulating extracellular vesicles (EVs) are postulated to carry a variety of signals involved in tissue crosstalk by their modified cargoes, representing novel mechanisms for the effects of exercise. Prominently, both acute and chronic aerobic exercise training can promote the release of exercise-induced cytokines and enhance the angiogenic function of circulating angiogenic cell–derived EVs.

Methods: We investigated the possible angiogenesis potential of aerobic exercise-induced circulating EVs (EXE-EVs) on diabetic wound healing. Circulating EVs were isolated from the plasma of rats subjected to 4 weeks of moderate aerobic exercise or sedentariness 24 h after the last training session. The therapeutic effect of circulating EVs was evaluated in vitro by proliferation, migration, and tube formation assays of human umbilical vein endothelial cells (HUVECs), as well as in vivo by quantification of angiogenesis and cutaneous wound healing in diabetic rats.

Results: The number of circulating EVs did not change significantly in exercised rats 24 h post-exercise in comparison with the sedentary rats. Nevertheless, EXE-EVs showed remarkable pro-angiogenic effect by augmenting proliferation, migration, and tube formation of HUVECs. Furthermore, the findings of animal experiments revealed that the EXE-EVs delivered by decellularized dermal matrix hydrogel (DDMH) could significantly promote the repair of skin defects through stimulating the regeneration of vascularized skin.

Discussion: The present study is the first attempt to demonstrate that aerobic exercise-induced circulating EVs could be utilized as a cell-free therapy to activate angiogenesis and promote diabetic wound healing. Our findings suggest that EXE-EVs may stand for a potential strategy for diabetic soft tissue wound repair.

Exerkines and long-term synaptic potentiation: Mechanisms of exercise-induced neuroplasticity

Physical exercise may improve cognitive function by modulating molecular and cellular mechanisms within the brain. We propose that the facilitation of long-term synaptic potentiation (LTP)-related pathways, by products induced by physical exercise (i.e., exerkines), is a crucial aspect of the exercise-effect on the brain. This review summarizes synaptic pathways that are activated by exerkines and may potentiate LTP. For a total of 16 exerkines, we indicated how blood and brain exerkine levels are altered depending on the type of physical exercise (i.e., cardiovascular or resistance exercise) and how they respond to a single bout (i.e., acute exercise) or multiple bouts of physical exercise (i.e., chronic exercise). This information may be used for designing individualized physical exercise programs. Finally, this review may serve to direct future research towards fundamental gaps in our current knowledge regarding the biophysical interactions between muscle activity and the brain at both cellular and system levels.

BAIBA Involves in Hypoxic Training Induced Browning of White Adipose Tissue in Obese Rats

In recent years, obesity has become an important risk factor for human health; how to effectively prevent and reduce the occurrence of obesity is a hot research topic in recent years. Hypoxic training effectively improves abnormalities of lipid metabolism caused by obesity. The current study explored the effects of hypoxic training on BAIBA secretion and white fat browning in inguinal fat in obese rats. Analyses were performed by HPLC/MS/MS—MS/MS, RT-q PCR and western blot methods. The findings showed that 4 weeks of hypoxic training reduced body weight, Lee’s index, and regulated blood lipid profile in obese rats. Hypoxic training up-regulated BAIBA concentration in gastrocnemius muscle and circulation in obese rats. Hypoxic training significantly upregulated expression of PPARα and UCP-1 in inguinal fat of obese rats and increased white fat browning. The findings showed that BAIBA may involve in improveing blood lipid profile and white fat browning by modulating PPARα and UCP-1 expression.

Daily running enhances molecular and physiological circadian rhythms in skeletal muscle

Objective

Exercise is a critical component of a healthy lifestyle and a key strategy for the prevention and management of metabolic disease. Identifying molecular mechanisms underlying adaptation in response to chronic physical activity is of critical interest in metabolic physiology. Circadian rhythms broadly modulate metabolism, including muscle substrate utilization and exercise capacity. Here, we define the molecular and physiological changes induced across the daily cycle by voluntary low intensity daily exercise.

Methods

Wildtype C57BL6/J male and female mice were housed with or without access to a running wheel for six weeks. Maximum running speed was measured at four different zeitgeber times (ZTs, hours after lights on) using either electrical or manual stimulation to motivate continued running on a motorized treadmill. RNA isolated from plantaris muscles at six ZTs was sequenced to establish the impact of daily activity on genome-wide transcription. Patterns of gene expression were analyzed using Gene Set Enrichment Analysis (GSEA) and Detection of Differential Rhythmicity (DODR). Blood glucose, lactate, and ketones, and muscle and liver glycogen were measured before and after exercise.

Results

We demonstrate that the use of mild electrical shocks to motivate running negatively impacts maximum running speed in mice, and describe a manual method to motivate running in rodent exercise studies. Using this method, we show that time of day influences the increase in exercise capacity afforded by six weeks of voluntary wheel running: when maximum running speed is measured at the beginning of the nighttime active period in mice, there is no measurable benefit from a history of daily voluntary running, while maximum increase in performance occurs at the end of the night. We show that daily voluntary exercise dramatically remodels the murine muscle circadian transcriptome. Finally, we describe daily rhythms in carbohydrate metabolism associated with the time-dependent response to moderate daily exercise in mice.

Conclusions

Collectively, these data indicate that chronic nighttime physical activity dramatically remodels daily rhythms of murine muscle gene expression, which in turn support daily fluctuations in exercise performance.

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Daily voluntary running dramatically remodels the mouse muscle circadian transcriptome.

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Daily voluntary running maximally increases mouse running speed in the late active period.

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Muscle and liver glycogen content exhibit robust daily rhythms in laboratory mice.

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Use of mild electric shocks to motivate running in mice impairs maximum running speed.

Long-term GABA administration improves FNDC5, TFAM, and UCP3 mRNA expressions in the skeletal muscle and serum irisin levels in chronic type 2 diabetic rats

In this study, we aimed to investigate whether the anti-diabetic effects of γ-aminobutyric acid (GABA) and insulin can be mediated through the regulation of gene expression related to irisin production and mitochondrial biogenesis in type 2 diabetic mellitus (T2DM) rats. Four groups (n = 6) were used in this study: control, T2DM, T2DM + insulin, and T2DM + GABA groups. After T2DM induction for 3 months (high-fat diet + 35 mg/kg streptozotocin) and treatment with GABA or insulin for 3 months, circulating levels of FBG, triglyceride, LDL, Ox-LDL, and insulin as well as hepatic and serum irisin levels were measured. The mRNA expressions of fibronectin type III domain-containing protein 5 (FNDC5), mitochondrial transcription factor A (TFAM), and mitochondrial uncoupling protein 3 (UCP3) were also evaluated in the skeletal muscle of all groups. GABA therapy improved the FBG and insulin levels in diabetic rats. Insulin treatment significantly reduced FBG and failed to maintain glucose close to the control level. Insulin or GABA therapy significantly decreased the levels of LDL, Ox-LDL, and HOMA-IR index. Circulating irisin levels were markedly decreased in insulin-treated group, while irisin levels did not show significant changes in GABA-treated group compared with control group. GABA or insulin therapy increased mRNA expressions of TFAM and UCP3 in diabetic rats. GABA therapy also led to a significant increase in FNDC5 mRNA. Our findings suggest that the anti-diabetic effect of GABA may be mediated, in part, by a decrease in Ox-LDL levels and an increase in the levels of irisin as well as FNDC5, TFAM, and UCP3 gene expression in T2DM rats.

Healthy versus Unhealthy Adipose Tissue Expansion: the Role of Exercise

Although the hallmark of obesity is the expansion of adipose tissue, not all adipose tissue expansion is the same. Expansion of healthy adipose tissue is accompanied by adequate capillary angiogenesis and mitochondria-centered metabolic integrity, whereas expansion of unhealthy adipose tissue is associated with capillary and mitochondrial derangement, resulting in deposition of immune cells (M1-stage macrophages) and excess production of pro-inflammatory cytokines. Accumulation of these dysfunctional adipose tissues has been linked to the development of obesity comorbidities, such as type 2 diabetes, hypertension, dyslipidemia, and cardiovascular disease, which are leading causes of human mortality and morbidity in modern society. Mechanistically, vascular rarefaction and mitochondrial incompetency (for example, low mitochondrial content, fragmented mitochondria, defective mitochondrial respiratory function, and excess production of mitochondrial reactive oxygen species) are frequently observed in adipose tissue of obese patients. Recent studies have demonstrated that exercise is a potent behavioral intervention for preventing and reducing obesity and other metabolic diseases. However, our understanding of potential cellular mechanisms of exercise, which promote healthy adipose tissue expansion, is at the beginning stage. In this review, we hypothesize that exercise can induce unique physiological stimuli that can alter angiogenesis and mitochondrial remodeling in adipose tissues and ultimately promote the development and progression of healthy adipogenesis. We summarize recent reports on how regular exercise can impose differential processes that lead to the formation of either healthy or unhealthy adipose tissue and discuss key knowledge gaps that warrant future research.

Potential Mechanisms for How Long-Term Physical Activity May Reduce Insulin Resistance

Insulin became available for the treatment of patients with diabetes 100 years ago, and soon thereafter it became evident that the biological response to its actions differed markedly between individuals. This prompted extensive research into insulin action and resistance (IR), resulting in the universally agreed fact that IR is a core finding in patients with type 2 diabetes mellitus (T2DM). T2DM is the most prevalent form of diabetes, reaching epidemic proportions worldwide. Physical activity (PA) has the potential of improving IR and is, therefore, a cornerstone in the prevention and treatment of T2DM. Whereas most research has focused on the acute effects of PA, less is known about the effects of long-term PA on IR. Here, we describe a model of potential mechanisms behind reduced IR after long-term PA to guide further mechanistic investigations and to tailor PA interventions in the therapy of T2DM. The development of such interventions requires knowledge of normal glucose metabolism, and we briefly summarize an integrated physiological perspective on IR. We then describe the effects of long-term PA on signaling molecules involved in cellular responses to insulin, tissue-specific functions, and whole-body IR.

Single bout of exercise triggers the increase of vitamin D blood concentration in adolescent trained boys: a pilot study

Vitamin D is necessary for musculoskeletal health, however, the supplementation of vitamin D above the sufficiency level does not bring additional bone mass density (BMD), unlike physical exercise which enhances the bone formatting process. Regular physical activity has been shown to upregulate VDR expression in muscles and to increase circulating vitamin D. Here we investigate whether a single bout of exercise might change 25(OH)D₃ blood concentration and how it affects metabolic response to exercise. Twenty-six boys, 13.8 years old (SD ± 0.7) soccer players, participated in the study. The participants performed one of two types of exercise: the first group performed the VO₂max test until exhaustion, and the second performed three times the repeated 30 s Wingate Anaerobic Test (WAnT). Blood was collected before, 15 min and one hour after the exercise. The concentration of 25(OH)D₃, parathyroid hormone (PTH), interleukin-6 (IL-6), lactate, non-esterified fatty acids (NEFA) and glycerol were determined. 25(OH)D₃ concentration significantly increased after the exercise in all boys. The most prominent changes in 25(OH)D₃, observed after WAnT, were associated with the rise of PTH. The dimensions of response to the exercises observed through the changes in the concentration of 25(OH)D₃, PTH, NEFA and glycerol were associated with the significant increases of IL-6 level. A single bout of exercise may increase the serum’s 25(OH)D₃ concentration in young trained boys. The intensive interval exercise brings a more potent stimulus to vitamin D fluctuations in young organisms. Our results support the hypothesis that muscles may both store and release 25(OH)D₃.

A research update: Significance of cytokine storm and diaphragm in COVID-19

Emerging research on severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) shows that it is spreading to multiple organs in addition to the respiratory system. Though the SARS-CoV2 enters the human body by binding to ACE2 receptors on pulmonary alveolar cells, recent studies indicate that it is spreading to the central nervous system, cardiac and skeletal muscles leading to various pathological conditions in these organs. In particular, the effects of SARS-CoV-2 on triggering the cytokine storm and its consequential effects on skeletal muscles has generated a lot of discussion. The effects of this virus on muscular function especially in susceptible elderly populations is still being explored. However, its effects on diaphragm, a respiratory muscle which plays an important role in determining lung capacity are not completely explored. Currently, as new evidence on using lung ultrasounds to confirm COVID-19 diagnosis is gaining traction, it is necessary to explore the role of diaphragm in treating COVID-19 patients. This article will review the effects of cytokine storm triggered by the SARS-CoV-2 and its resultant effects on skeletal muscle with a specific focus on the diaphragm in order to identify knowledge gaps in effectively treating COVID-19 patients, especially those who are on a mechanical ventilator.

Muscle-brain communication in pain: The key role of myokines

Pain is the most common reason for a physician visit, which accounts for a considerable proportion of the global burden of disease and greatly affects patients' quality of life. Therefore, there is an urgent need to identify new therapeutic targets involved in pain. Exercise-induced hypoalgesia (EIH) is a well known phenomenon observed worldwide. However, the available evidence demonstrates that the mechanisms of EIH remain unclear. One of the most accepted hypotheses has been the activation of several endogenous systems in the brain. Recently, the concept that the muscle acts as a secretory organ has attracted increasing attention. Proteins secreted by the muscle are called myokines, playing a critical role in communicating with other organs, such as the brain. This review will focus on several myokines and discuss their roles in EIH.

Effect of vanillic acid and exercise training on fatty liver and insulin resistance in rats: Possible role of fibroblast growth factor 21 and autophagy

BACKGROUND AND AIMS

The prevalence of non-alcoholic fatty liver disease has been alarmingly increased with no lines of effective treatment. Vanillic acid is a naturally occurring polyphenol with promising therapeutic effects. Exercise is well known to be an effective tool against obesity and its consequences. Thus, we aim to study the effect of vanillic acid alone and along with exercise on fatty liver induced by a high-fat diet in a rat model and to investigate possible novel mechanisms involved in their action.

METHODS

In this study, 40 male rats were divided equally into five groups: control (standard chow diet), HFD (high-fat diet), HFD+VA (HFD+ vanillic acid (50 mg/kg/day orally), HFD+EX (HFD+ swimming exercise 5 days/week), HFD+VA+EX (HFD+ vanillic acid+ swimming exercise) for eight weeks.

RESULTS

Body mass, liver weight, liver enzymes, cholesterol, and triglycerides were significantly decreased in the combined VA+EX group, with marked improvement in hyperglycemia, hyperinsulinemia, and consequently HOMA-IR index compared to the HFD group. These improvements were also reflected in the pathological view. VA and swimming, either solely or in combination, markedly increased hepatic and circulating fibroblast growth factor 21. Additionally, VA and swimming increased the immunohistochemical expression of the autophagosomal marker LC3 and decreased the expression of P62, which is selectively degraded during autophagy.

CONCLUSIONS

These results suggest the hepatoprotective effect of VA and swimming exercise against fatty liver and the involvement of FGF21 and autophagy in their effect.

Soluble Interleukin-6 Receptor Regulates Interleukin-6-Dependent Vascular Remodeling in Long-Distance Runners

Little is known about the effects of training load on exercise-induced plasma increase of interleukin-6 (IL-6) and soluble IL-6 receptor (sIL-6R) and their relationship with vascular remodeling. We sought to evaluate the role of sIL 6R as a regulator of IL-6-induced vascular remodeling. Forty-four male marathon runners were recruited and allocated into two groups: low-training (LT, <100 km/week) and high-training (HT, ≥100 km/week), 22 athletes per group. Twenty-one sedentary participants were used as reference. IL-6, sIL-6R and sgp130 levels were measured in plasma samples obtained before and immediately after finishing a marathon (42.2-km). Aortic diameter was measured by echocardiography. The inhibitory effect of sIL-6R on IL-6-induced VSMC migration was assessed using cultured A7r5 VSMCs. Basal plasma IL-6 and sIL-6R levels were similar among sedentary and athlete groups. Plasma IL-6 and sIL-6R levels were elevated after the marathon, and HT athletes had higher post-race plasma sIL-6R, but not IL-6, level than LT athletes. No changes in sgp130 plasma levels were found in LT and HT groups before and after running the marathon. Athletes had a more dilated ascending aorta and aortic root than sedentary participants with no differences between HT and LT athletes. However, a positive correlation between ascending aorta diameter and plasma IL-6 levels corrected by training load and years of training was observed. IL-6 could be responsible for aorta dilation because IL-6 stimulated VSMC migration in vitro, an effect that is inhibited by sIL-6R. However, IL-6 did not modify cell proliferation, collagen type I and contractile protein of VSMC. Our results suggest that exercise induces vascular remodeling. A possible association with IL-6 is proposed. Because sIL-6R inhibits IL-6-induced VSMC migration, a possible mechanism to regulate IL-6-dependent VSMC migration is also proposed.

Variation in myokine and adipokine levels according to menstrual cycle following regular resistance exercise

BACKGROUND

The purpose of this study was to analyze the differences between myokine and adipokine factors under stable conditions according to the menstrual cycle (luteal and follicular phases), and investigate the effect of regular resistance exercise on the changes in myokine and adipokine factors according to menstrual cycle in obese female college students.

METHODS

The study participants were female college students with a body fat percentage of 30% or more (n = 20), divided into two groups: luteal phase (n = 12) and follicular phase (n = 8). They performed regular resistance exercise three times a week, 60 minutes daily, for 16 weeks. Parameters measured include body composition via impedance, visceral fat area using computed tomography and myokine and adipokine factors in blood.

RESULTS

Levels of BDNF (p < .05), NGF (p < .01), and adiponectin (p < .01) were significantly increased in the luteal phase group after 16 weeks relative to the baseline values. Leptin (p < .01) was significantly decreased in the luteal phase group after 16 weeks. Weight, body mass index, % fat, and visceral fat area were significantly decreased in both groups after 16 weeks. Muscle mass was significantly increased in both groups after 16 weeks.

CONCLUSIONS

Regular resistance exercise affected the reduction in visceral fat area and had a positive effect on body composition, which might be altered favorably by myokines and adipokines. Thus, the timing of blood collection is very important in obese female college students.

Exploring the Role of Skeletal Muscle in Insulin Resistance: Lessons from Cultured Cells to Animal Models

Skeletal muscle is essential to maintain vital functions such as movement, breathing, and thermogenesis, and it is now recognized as an endocrine organ. Muscles release factors named myokines, which can regulate several physiological processes. Moreover, skeletal muscle is particularly important in maintaining body homeostasis, since it is responsible for more than 75% of all insulin-mediated glucose disposal. Alterations of skeletal muscle differentiation and function, with subsequent dysfunctional expression and secretion of myokines, play a key role in the pathogenesis of obesity, type 2 diabetes, and other metabolic diseases, finally leading to cardiometabolic complications. Hence, a deeper understanding of the molecular mechanisms regulating skeletal muscle function related to energy metabolism is critical for novel strategies to treat and prevent insulin resistance and its cardiometabolic complications. This review will be focused on both cellular and animal models currently available for exploring skeletal muscle metabolism and endocrine function.

Epigenetic Regulation of Inflammatory Responses in the Context of Physical Activity

Epigenetic modifications occur in response to environmental changes and play a fundamental role in the regulation of gene expression. PA is found to elicit an inflammatory response, both from the innate and adaptive divisions of the immunological system. The inflammatory reaction is considered a vital trigger of epigenetic changes that in turn modulate inflammatory actions. The tissue responses to PA involve local and general changes. The epigenetic mechanisms involved include: DNA methylation, histone proteins modification and microRNA. All of them affect genetic expression in an inflammatory milieu in physical exercise depending on the magnitude of physiological stress experienced by the exerciser. PA may evoke acute or chronic biochemical and physiological responses and have a positive or negative immunomodulatory effect.

Exercise during Pregnancy: Developmental Programming Effects and Future Directions in Humans

Epidemiological studies show that low birth weight is associated with mortality from cardiovascular disease in adulthood, indicating that chronic diseases could be influenced by hormonal or metabolic insults encountered in utero. This concept, now known as the Developmental Origins of Health and Disease hypothesis, postulates that the intrauterine environment may alter the structure and function of the organs of the fetus as well as the expression of genes that impart an increased vulnerability to chronic diseases later in life. Lifestyle interventions initiated during the prenatal period are crucial as there is the potential to attenuate progression towards chronic diseases. However, how lifestyle interventions such as physical activity directly affect human offspring metabolism and the potential mechanisms involved in regulating metabolic balance at the cellular level are not known. The purpose of this review is to highlight the effects of exercise during pregnancy on offspring metabolic health and emphasize gaps in the current human literature and suggestions for future research.

Muscle multiorgan crosstalk with MG53 as a myokine for tissue repair and regeneration

Through stress and injury to tissues, the cell membrane is damaged and can lead to cell death and a cascade of inflammatory events. Soluble factors that mitigate and repair membrane injury are important to normal homeostasis and are a potential therapeutic intervention for regenerative medicine. A myokine is a type of naturally occurring factors that come from muscle and have impact on remote organs. MG53, a tripartite motif-containing family protein, is such a myokine which has protective effects on lungs, kidneys, liver, heart, eye, and brain. Three mechanisms of action for the beneficial regenerative medicine potential of MG53 have been identified and consist of 1) repair of acute injury to the cellular membrane, 2) anti-inflammatory effects associated with chronic injuries, and 3) rejuvenation of stem cells for tissue regeneration. As such, MG53 has the potential to be a novel and effective regeneration medicine therapeutic.

Progress and Challenges in the Biology of FNDC5 and Irisin

In 2002, a transmembrane protein-now known as FNDC5-was discovered and shown to be expressed in skeletal muscle, heart, and brain. It was virtually ignored for 10 years, until a study in 2012 proposed that, in response to exercise, the ectodomain of skeletal muscle FNDC5 was cleaved, traveled to white adipose tissue, and induced browning. The wasted energy of this browning raised the possibility that this myokine, named irisin, might mediate some beneficial effects of exercise. Since then, more than 1000 papers have been published exploring the roles of irisin. A major interest has been on adipose tissue and metabolism, following up the major proposal from 2012. Many studies correlating plasma irisin levels with physiological conditions have been questioned for using flawed assays for irisin concentration. However, experiments altering irisin levels by injecting recombinant irisin or by gene knockout are more promising. Recent discoveries have suggested potential roles of irisin in bone remodeling and in the brain, with effects potentially related to Alzheimer's disease. We discuss some discrepancies between research groups and the mechanisms that are yet to be determined. Some important questions raised in the initial discovery of irisin, such as the role of the mutant start codon of human FNDC5 and the mechanism of ectodomain cleavage, remain to be answered. Apart from these specific questions, a promising new tool has been developed-mice with a global or tissue-specific knockout of FNDC5. In this review, we critically examine the current knowledge and delineate potential solutions to resolve existing ambiguities.

Can conditions of skeletal muscle loss be improved by combining exercise with anabolic-androgenic steroids? A systematic review and meta-analysis of testosterone-based interventions

Sarcopenia, cachexia, and atrophy due to inactivity and disease states are characterized by a loss of skeletal muscle mass, often accompanied by reduced levels of anabolic hormones (e.g. testosterone). These conditions are associated with an increase in mortality, hospitalization and worsening in quality of life. Both physical exercise (EX) and anabolic-androgenic steroid (AAS) administration can improve the prognosis of patients as they increase physical functionality. However, there is a gap in the literature as to the impact of these therapies on the gains in strength and muscle mass and their implications for patient safety. Accordingly, we performed a random-effects meta-analysis to elucidate the effects of AAS and/or EX interventions on lean body mass (LBM) and muscle strength in conditions involving muscle loss. A systematic search for relevant clinical trials was conducted in MEDLINE, EMBASE, SCOPUS, Web of Science, and SPORTDiscus. Comparisons included AAS vs. Control, EX vs. Control, AAS vs. EX, AAS + EX vs. AAS and AAS + EX vs. EX. A total of 1114 individuals were analyzed. AAS increased LBM (effect size [ES]: 0.46; 95% CI: 0.25, 0.68, P = 0.00) and muscle strength (ES: 0.31; 95% CI: 0.08, 0.53, P = 0.01) when compared to a control group. EX promoted an increase in muscular strength (ES: 0.89; 95% CI: 0.53, 1.25, P = 0.00), with no effect on LBM when compared to the control group (ES: 0.15; 95% CI: -0.07, 0.38, P = 0.17). AAS did not demonstrate statistically significant differences when compared to EX for LBM and muscle strength. The combination of EX + AAS promoted a greater increase in LBM and muscular strength when compared to AAS or EX in isolation. Qualitatively, AAS administration had relatively few side effects. Significant heterogeneity was found in some analyses, which may be explained by the use of different AAS types and EX protocols. Our findings suggest that AAS administration in cachectic and sarcopenic conditions may be a viable interventional strategy to enhance muscle function when exercise is not a possible approach. Moreover, combining AAS with exercise may enhance positive outcomes in this population.

Histamine H3 Receptor Signaling Regulates the NLRP3 Inflammasome Activation in C2C12 Myocyte During Myogenic Differentiation

NLRP3 inflammasome has been implicated in impaired post-injury muscle healing and in muscle atrophy. Histamine receptors play an important role in inflammation, but the role of histamine H₃ receptor (H₃R) in myocyte regeneration and in the regulation of NLRP3 inflammasome is not known. We studied the effects of H₃R signaling on C2C12 myocyte viability, apoptosis, and tumor necrosis factor alpha (TNFα)-induced NLRP3 inflammasome activation during striated myogenic differentiation at three time points (days 0, 3, and 6). Expression of Nlrp3, interleukin-1β (IL-1β), and myogenesis markers were determined. TNFα reduced overall viability of C2C12 cells, and exposure to TNFα induced apoptosis of cells at D6. Activation of H₃R had no effect on viability or apoptosis, whereas inhibition of H₃R increased TNFα-induced apoptosis. Stimulation of C2C12 cells with TNFα increased Nlrp3 mRNA expression at D3 and D6. Moreover, TNFα reduced the expression of myogenesis markers MyoD1, Myogenin, and Myosin-2 at D3 and D6. H₃R attenuated TNFα-induced expression of Nlrp3 and further inhibited the myogenesis marker expression; while H₃R -blockage enhanced the proinflammatory effects of TNFα and increased the myogenesis marker expression. TNFα-induced secretion of mature IL-1β was dependent on the activation of the NLRP3 inflammasome, as shown by the reduced secretion of mature IL-1β upon treatment of the cells with the small molecule inhibitor of the NLRP3 inflammasome (MCC950). The activation of H₃R reduced TNFα-induced IL-1β secretion, while the H₃R blockage had an opposite effect. In conclusion, the modulation of H₃R activity regulates the effects of TNFα on C2C12 myocyte differentiation and TNFα-induced activation of NLRP3 inflammasome. Thus, H₃R signaling may represent a novel target for limiting postinjury muscle inflammation and muscle atrophy.

The Role of Exercise, Diet, and Cytokines in Preventing Obesity and Improving Adipose Tissue

The prevalence of obesity continues to rise worldwide despite evidence-based public health recommendations. The promise to adopt a healthy lifestyle is increasingly important for tackling this global epidemic. Calorie restriction or regular exercise or a combination of the two is accepted as an effective strategy in preventing or treating obesity. Furthermore, the benefits conferred by regular exercise to overcome obesity are attributed not only to reduced adiposity or reduced levels of circulating lipids but also to the proteins, peptides, enzymes, and metabolites that are released from contracting skeletal muscle or other organs. The secretion of these molecules called cytokines in response to exercise induces browning of white adipose tissue by increasing the expression of brown adipocyte-specific genes within the white adipose tissue, suggesting that exercise-induced cytokines may play a significant role in preventing obesity. In this review, we present research-based evidence supporting the effects of exercise and various diet interventions on preventing obesity and adipose tissue health. We also discuss the interplay between adipose tissue and the cytokines secreted from skeletal muscle and other organs that are known to affect adipose tissue and metabolism.

Interleukin-6 mediated exercise-induced alleviation of adiposity and hepatic steatosis in mice

INTRODUCTION

Exercise training has been shown to be the most effective strategy to combat obesity and non-alcoholic fatty liver disease. However, exercise promotes loss of adipose tissue mass and improves obesity-related hepatic steatosis through mechanisms that remain obscure.

RESEARCH DESIGN AND METHODS

To study the role of interleukin-6 (IL-6) in high-fat diet (HFD)-induced adiposity and hepatic steatosis during treadmill running, IL-6 knockout (IL-6 KO) mice and wild-type (WT) mice were randomly divided into lean, obese (fed a HFD) and trained obese groups (fed a HFD and exercise trained).

RESULTS

After 20 weeks of HFD feeding and 8 weeks of treadmill running, we found that exercise obviously reduced HFD-induced body weight gain, inhibited visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) expansion and almost completely reversed obesity-related intrahepatic fat accumulation in WT mice. However, IL-6 knockout (IL-6 KO) mice are refractory to the benefits of treadmill training on body weight, VAT and SAT mass elevation, and hepatic steatosis. Moreover, a panel of lipolytic-related and thermogenic-related genes, including ATGL, HSL and PGC-1α, was upregulated in the VAT and SAT of WT mice that received exercise training compared with untrained mice, which was not observed in IL-6 KO mice. In addition, exercise training resulted in a significant inhibition of hepatic peroxisome proliferator-activated receptor gamma (PPAR-γ) expression in WT mice, and these effects were not noted in IL-6 KO mice.

CONCLUSION

These results revealed that IL-6 is involved in the prevention of obesity and hepatic fat accumulation during exercise training. The mechanisms underlying these antiobesity effects may be associated with enhanced lipolysis and thermogenesis in white adipose tissue. The improvement in hepatic steatosis by exercise training may benefit from the marked inhibition of PPAR-γ expression by IL-6.

Transthyretin contributes to insulin resistance and diminishes exercise-induced insulin sensitivity in obese mice by inhibiting AMPK activity in skeletal muscle

Exercise improves obesity-induced insulin resistance and metabolic disorders via mechanisms that remain unclear. Here, we show that the levels of the hepatokine transthyretin (TTR) in circulation are elevated in insulin-resistant individuals including high-fat diet (HFD)-induced obese mice, db/db mice, and patients with metabolic syndrome. Liver Ttr mRNA and circulating TTR levels were reduced in mice by treadmill training, as was the TTR levels in quadriceps femoris muscle; however, AMP-activated protein kinase (AMPK) signaling activity was enhanced. Transgenic overexpression of TTR or injection of purified TTR triggered insulin resistance in mice fed on regular chow (RC). Furthermore, TTR overexpression reduced the beneficial effects of exercise on insulin sensitivity in HFD-fed mice. TTR was internalized by muscle cells via the membrane receptor Grp78 and the internalization into the quadriceps femoris was reduced by treadmill training. The TTR/Grp78 combination in C2C12 cells was increased, whereas the AMPK activity of C2C12 cells was decreased as the TTR concentration rose. In addition, Grp78 silencing prevented the TTR internalization and reversed its inhibitory effect on AMPK activity in C2C12 cells. Our study suggests that elevated circulating TTR may contribute to insulin resistance and counteract the exercise-induced insulin sensitivity improvement; the TTR suppression might be an adaptive response to exercise through enhancing AMPK activity in skeletal muscles.NEW & NOTEWORTHY Exercise improves obesity-induced insulin resistance via mechanisms that remain unclear. The novel findings of the study are that circulating TTR (a hepatokine) level is decreased by exercise, and the elevated circulating TTR, as was the elevated transthyretin internalization mediated by Grp78, counteracts the exercise-induced insulin sensitivity by downregulating AMPK activity in skeletal muscle of obese mice. These data suggest that TTR suppression might be an adaptive response to exercise through the crosstalk between liver and muscle.

Sarcopenia and Cognitive Function: Role of Myokines in Muscle Brain Cross-Talk

Sarcopenia is a geriatric syndrome characterized by the progressive degeneration of muscle mass and function, and it is associated with severe complications, which are falls, functional decline, frailty, and mortality. Sarcopenia is associated with cognitive impairment, defined as a decline in one or more cognitive domains as language, memory, reasoning, social cognition, planning, making decisions, and solving problems. Although the exact mechanism relating to sarcopenia and cognitive function has not yet been defined, several studies have shown that skeletal muscle produces and secrete molecules, called myokines, that regulate brain functions, including mood, learning, locomotor activity, and neuronal injury protection, showing the existence of muscle-brain cross-talk. Moreover, studies conducted on physical exercise supported the existence of muscle-brain cross-talk, showing how physical activity, changing myokines' circulating levels, exerts beneficial effects on the brain. The review mainly focuses on describing the role of myokines on brain function and their involvement in cognitive impairment in sarcopenia.

Another Weapon against Cancer and Metastasis: Physical-Activity-Dependent Effects on Adiposity and Adipokines

Physically active behavior has been associated with a reduced risk of developing certain types of cancer and improved psychological conditions for patients by reducing anxiety and depression, in turn improving the quality of life of cancer patients. On the other hand, the correlations between inactivity, sedentary behavior, and overweight and obesity with the risk of development and progression of various cancers are well studied, mainly in middle-aged and elderly subjects. In this article, we have revised the evidence on the effects of physical activity on the expression and release of the adipose-tissue-derived mediators of low-grade chronic inflammation, i.e., adipokines, as well as the adipokine-mediated impacts of physical activity on tumor development, growth, and metastasis. Importantly, exercise training may be effective in mitigating the side effects related to anti-cancer treatment, thereby underlining the importance of encouraging cancer patients to engage in moderate-intensity activities. However, the strong need to customize and adapt exercises to a patient’s abilities is apparent. Besides the preventive effects of physically active behavior against the adipokine-stimulated cancer risk, it remains poorly understood how physical activity, through its actions as an adipokine, can actually influence the onset and development of metastases.

Mitochondria Homeostasis and Oxidant/Antioxidant Balance in Skeletal Muscle-Do Myokines Play a Role?

Mitochondria are the cellular powerhouses that generate adenosine triphosphate (ATP) to substantiate various biochemical activities. Instead of being a static intracellular structure, they are dynamic organelles that perform constant structural and functional remodeling in response to different metabolic stresses. In situations that require a high ATP supply, new mitochondria are assembled (mitochondrial biogenesis) or formed by fusing the existing mitochondria (mitochondrial fusion) to maximize the oxidative capacity. On the other hand, nutrient overload may produce detrimental metabolites such as reactive oxidative species (ROS) that wreck the organelle, leading to the split of damaged mitochondria (mitofission) for clearance (mitophagy). These vital processes are tightly regulated by a sophisticated quality control system involving energy sensing, intracellular membrane interaction, autophagy, and proteasomal degradation to optimize the number of healthy mitochondria. The effective mitochondrial surveillance is particularly important to skeletal muscle fitness because of its large tissue mass as well as its high metabolic activities for supporting the intensive myofiber contractility. Indeed, the failure of the mitochondrial quality control system in skeletal muscle is associated with diseases such as insulin resistance, aging, and muscle wasting. While the mitochondrial dynamics in cells are believed to be intrinsically controlled by the energy content and nutrient availability, other upstream regulators such as hormonal signals from distal organs or factors generated by the muscle itself may also play a critical role. It is now clear that skeletal muscle actively participates in systemic energy homeostasis via producing hundreds of myokines. Acting either as autocrine/paracrine or circulating hormones to crosstalk with other organs, these secretory myokines regulate a large number of physiological activities including insulin sensitivity, fuel utilization, cell differentiation, and appetite behavior. In this article, we will review the mechanism of myokines in mitochondrial quality control and ROS balance, and discuss their translational potential.