MicroRNAs in skeletal muscle biology and exercise adaptation

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

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

Changes in Circulating MicroRNA Levels as Potential Indicators of Training Adaptation in Professional Volleyball Players

The increasing demand placed on professional athletes to enhance their fitness and performance has prompted the search for new, more sensitive biomarkers of physiological ability. One such potential biomarker includes microRNA (miRNA) small regulatory RNA sequences. The study investigated the levels of the selected circulating miRNAs before and after a 10-week training cycle in 12 professional female volleyball players, as well as their association with cortisol, creatine kinase (CK), and interleukin 6 (IL-6), using the qPCR technique. Significant decreases in the miR-22 (0.40 ± 0.1 vs. 0.28 ± 0.12, p = 0.009), miR-17 (0.35 ± 0.13 vs. 0.23 ± 0.08; p = 0.039), miR-24 (0.09 ± 0.04 vs. 0.05 ± 0.02; p = 0.001), and miR-26a (0.11 ± 0.06 vs. 0.06 ± 0.04; p = 0.003) levels were observed after training, alongside reduced levels of cortisol and IL-6. The correlation analysis revealed associations between the miRNAs' relative quantity and the CK concentrations, highlighting their potential role in the muscle repair processes. The linear regression analysis indicated that miR-24 and miR-26a had the greatest impact on the CK levels. The study provides insights into the dynamic changes in the miRNA levels during training, suggesting their potential as biomarkers for monitoring the adaptive responses to exercise. Overall, the findings contribute to a better understanding of the physiological effects of exercise and the potential use of miRNAs, especially miR-24 and miR-26a, as biomarkers in sports science and medicine.

Discordant skeletal muscle gene and protein responses to exercise

The ability of skeletal muscle to adapt to repeated contractile stimuli is one of the most intriguing aspects of physiology. The molecular bases underpinning these adaptations involve increased protein activity and/or expression, mediated by an array of pre- and post-transcriptional processes, as well as translational and post-translational control. A longstanding dogma assumes a direct relationship between exercise-induced increases in mRNA levels and subsequent changes in the abundance of the proteins they encode. Drawing on the results of recent studies, we dissect and question the common assumption of a direct relationship between changes in the skeletal muscle transcriptome and proteome induced by repeated muscle contractions (e.g., exercise).

Modulation of the Circulating Extracellular Vesicles in Response to Different Exercise Regimens and Study of Their Inflammatory Effects

Exercise-released extracellular vesicles (EVs) are emerging as a novel class of exerkines that promotes systemic beneficial effects. However, slight differences in the applied exercise protocols in terms of mode, intensity and duration, as well as the need for standardized protocols for EV isolation, make the comparison of the studies in the literature extremely difficult. This work aims to investigate the EV amount and EV-associated miRNAs released in circulation in response to different physical exercise regimens. Healthy individuals were subjected to different exercise protocols: acute aerobic exercise (AAE) and training (AT), acute maximal aerobic exercise (AMAE) and altitude aerobic training (AAT). We found a tendency for total EVs to increase in the sedentary condition compared to trained participants following AAE. Moreover, the cytofluorimetric analysis showed an increase in CD81⁺/SGCA⁺/CD45^- EVs in response to AAE. Although a single bout of moderate/maximal exercise did not impact the total EV number, EV-miRNA levels were affected as a result. In detail, EV-associated miR-206, miR-133b and miR-146a were upregulated following AAE, and this trend appeared intensity-dependent. Finally, THP-1 macrophage treatment with exercise-derived EVs induced an increase of the mRNAs encoding for IL-1β, IL-6 and CD163 using baseline and immediately post-exercise EVs. Still, 1 h post-exercise EVs failed to stimulate a pro-inflammatory program. In conclusion, the reported data provide a better understanding of the release of circulating EVs and their role as mediators of the inflammatory processes associated with exercise.

MiRNA-based “fitness score” to assess the individual response to diet, metabolism, and exercise

Background

Regular, especially sustained exercise plays an important role in the prevention and treatment of multiple chronic diseases. Some of the underlying molecular and cellular mechanisms behind the adaptive response to physical activity are still unclear, but recent findings suggest a possible role of epigenetic mechanisms, especially miRNAs, in the progression and management of exercise-related changes. Due to the combination of the analysis of epigenetic biomarkers (miRNAs), the intake of food and supplements, and genetic dispositions, a “fitness score” was evaluated to assess the individual response to nutrition, exercise, and metabolic influence.

Methods

In response to a 12-week sports intervention, we analyzed genetic and epigenetic biomarkers in capillary blood from 61 sedentary, healthy participants (66.1% females, 33.9% males, mean age 33 years), including Line-1 methylation, three SNPs, and ten miRNAs using HRM and qPCR analysis. These biomarkers were also analyzed in a healthy, age- and sex-matched control group (n, 20) without intervention. Food frequency intake, including dietary supplement intake, and general health questionnaires were surveyed under the supervision of trained staff.

Results

Exercise training decreased the expression of miR-20a-5p, −22-5p, and −505-3p (p < 0.02) and improved the “fitness score,” which estimates eight different lifestyle factors to assess, nutrition, inflammation, cardiovascular fitness, injury risk, regeneration, muscle and hydration status, as well as stress level. In addition, we were able to determine correlations between individual miRNAs, miR-20a-5p, −22-5p, and −101-3p (p < 0.04), and the genetic predisposition for endurance and/or strength and obesity risk (ACE, ACTN3, and FTO), as well as between miRNAs and the body composition (p < 0.05). MiR-19b-3p and −101-3p correlated with the intake of B vitamins. Further, miR-19b-3p correlated with magnesium and miR-378a-3p with iron intake (p < 0.05).

Conclusions

In summary, our results indicate that a combined analysis of several biomarkers (miRNAs) can provide information about an individual’s training adaptions/fitness, body composition, nutritional needs, and possible recovery. In contrast to most studies using muscle biopsies, we were able to show that these biomarkers can also be measured using a minimally invasive method.

Epigenetic Alterations in Sports-Related Injuries

It is a well-known fact that physical activity benefits people of all age groups. However, highly intensive training, maladaptation, improper equipment, and lack of sufficient rest lead to contusions and sports-related injuries. From the perspectives of sports professionals and those performing regular–amateur sports activities, it is important to maintain proper levels of training, without encountering frequent injuries. The bodily responses to physical stress and intensive physical activity are detected on many levels. Epigenetic modifications, including DNA methylation, histone protein methylation, acetylation, and miRNA expression occur in response to environmental changes and play fundamental roles in the regulation of cellular activities. In the current review, we summarise the available knowledge on epigenetic alterations present in tissues and organs (e.g., muscles, the brain, tendons, and bones) as a consequence of sports-related injuries. Epigenetic mechanism observations have the potential to become useful tools in sports medicine, as predictors of approaching pathophysiological alterations and injury biomarkers that have already taken place.

High-Intensity Interval Training Improves Cardiac Function by miR-206 Dependent HSP60 Induction in Diabetic Rats

Objective

A role for microRNAs is implicated in several biological and pathological processes. We investigated the effects of high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on molecular markers of diabetic cardiomyopathy in rats.

Methods

Eighteen male Wistar rats (260 ± 10 g; aged 8 weeks) with streptozotocin (STZ)-induced type 1 diabetes mellitus (55 mg/kg, IP) were randomly allocated to three groups: control, MICT, and HIIT. The two different training protocols were performed 5 days each week for 5 weeks. Cardiac performance (end-systolic and end-diastolic dimensions, ejection fraction), the expression of miR-206, HSP60, and markers of apoptosis (cleaved PARP and cytochrome C) were determined at the end of the exercise interventions.

Results

Both exercise interventions (HIIT and MICT) decreased blood glucose levels and improved cardiac performance, with greater changes in the HIIT group (p < 0.001, η²: 0.909). While the expressions of miR-206 and apoptotic markers decreased in both training protocols (p < 0.001, η²: 0.967), HIIT caused greater reductions in apoptotic markers and produced a 20% greater reduction in miR-206 compared with the MICT protocol (p < 0.001). Furthermore, both training protocols enhanced the expression of HSP60 (p < 0.001, η²: 0.976), with a nearly 50% greater increase in the HIIT group compared with MICT.

Conclusions

Our results indicate that both exercise protocols, HIIT and MICT, have the potential to reduce diabetic cardiomyopathy by modifying the expression of miR-206 and its downstream targets of apoptosis. It seems however that HIIT is even more effective than MICT to modulate these molecular markers.

Resistance Exercise Differentially Alters Extracellular Vesicle Size and Subpopulation Characteristics in Healthy Men and Women: An Observational Cohort Study

Extracellular vesicles (EV) are established mediators of adaptation to exercise. Currently, there are no published data comparing changes in EVs between men and women after resistance exercise.

PURPOSE

We tested the hypothesis that EV profiles would demonstrate a sex-specific signature following resistance exercise.

METHODS

Ten men and 10 women completed an acute heavy resistance exercise test for back squats using 75% of their one-repetition maximum. Blood was drawn before and immediately after exercise. EVs were isolated from plasma using size exclusion chromatography and stained with antibodies associated with exosomes (CD63), microvesicles (VAMP3), apoptotic bodies (THSD1), and a marker for skeletal muscle EVs (SGCA).

RESULTS

CD63+ EV concentration and proportion of total EVs increased 23% (p=0.006) and 113% (p=0.005) in both sexes. EV mean size declined in men (p=0.020), but not women, suggesting a relative increase in small EVs in men. VAMP3+ EV concentration and proportion of total EVs increased by 93% (p=0.025) and 61% (p=0.030) in men and women, respectively. SGCA+ EV concentration was 69% higher in women compared to men independent of time (p=0.007). Differences were also observed for CD63, VAMP3, and SGCA median fluorescence intensity, suggesting altered surface protein density according to sex and time. There were no significant effects of time or sex on THSD1+ EVs or fluorescence intensity.

CONCLUSION

EV profiles, particularly among exosome-associated and muscle-derived EVs, exhibit sex-specific differences in response to resistance exercise which should be further studied to understand their relationship to training adaptations.

Physical exercise and the functions of microRNAs

MicroRNAs (miRNAs) control RNA translation and are a class of small, tissue-specific, non-protein-coding RNAs that maintain cellular homeostasis through negative gene regulation. Maintenance of the physiological environment depends on the proper control of miRNA expression, as these molecules influence almost all genetic pathways, from the cell cycle checkpoint to cell proliferation and apoptosis, with a wide range of target genes. Dysregulation of the expression of miRNAs is correlated with several types of diseases, acting as regulators of cardiovascular functions, myogenesis, adipogenesis, osteogenesis, hepatic lipogenesis, and important brain functions. miRNAs can be modulated by environmental factors or external stimuli, such as physical exercise, and can eventually induce specific and adjusted changes in the transcriptional response. Physical exercise is used as a preventive and non-pharmacological treatment for many diseases. It is well established that physical exercise promotes various benefits in the human body such as muscle hypertrophy, mental health improvement, cellular apoptosis, weight loss, and inhibition of cell proliferation. This review highlights the current knowledge on the main miRNAs altered by exercise in the skeletal muscle, cardiac muscle, bone, adipose tissue, liver, brain, and body fluids. In addition, knowing the modifications induced by miRNAs and relating them to the results of prescribed physical exercise with different protocols and intensities can serve as markers of physical adaptation to training and responses to the effects of physical exercise for some types of chronic diseases. This narrative review consists of randomized exercise training experiments with humans and/or animals, combined with analyses of miRNA modulation.

PGC-1α Methylation, miR-23a, and miR-30e Expression as Biomarkers for Exercise- and Diet-Induced Mitochondrial Biogenesis in Capillary Blood from Healthy Individuals: A Single-Arm Intervention

Healthy mitochondria and their epigenetic control are essential to maintaining health, extending life expectancy, and improving cardiovascular performance. Strategies to maintain functional mitochondria during aging include training; cardiovascular exercise has been suggested as the best method, but strength training has also been identified as essential to health and healthy aging. We therefore investigated the effects of concurrent exercise training and dietary habits on epigenetic mechanisms involved in mitochondrial (mt) functions and biogenesis. We analyzed epigenetic biomarkers that directly target the key regulator of mitochondrial biogenesis, PGC-1α, and mtDNA content. Thirty-six healthy, sedentary participants completed a 12-week concurrent training program. Before and after the intervention, dried blood spot samples and data on eating habits, lifestyle, and body composition were collected. MiR-23a, miR-30e expression, and mtDNA content were analyzed using real-time quantitative polymerase chain reaction (qPCR) analysis. PGC-1α methylation was analyzed using bisulfite pyrosequencing. MiR-23a, miR-30e expression, and PGC-1α methylation decreased after the intervention (p < 0.05). PGC-1α methylation increased with the consumption of red and processed meat, and mtDNA content increased with the ingestion of cruciferous vegetables (p < 0.05). Our results indicate that concurrent training could improve mitochondrial biogenesis and functions by altering the epigenetic regulation. These alterations can also be detected outside of the skeletal muscle and could potentially affect athletic performance.

An Investigation of the Mechanisms of Radiation-Induced Muscle Injury in a Tree Shrew (Tupaia belangeri) Model

Background

Animal models suitable for investigating mechanisms behind radiation-induced muscle injury are lacking. We developed a tree shrew model of such injury and investigated pathological changes and mechanisms.

Methods

Animals were divided into control (n = 5), radiation-induced acute injury (n = 5), and radiation-induced chronic injury (n = 5) groups. Tensor veli palatini (TVP) muscles of acute injury and chronic injury groups were dissected under a microscope at 1 and 24 weeks after radiation therapy, respectively. TVP muscles were stained with HE and Masson to visualize pathological changes. ELISA was performed to measure oxidative injury. RT-qPCR and immunohistochemical staining was performed to measure expression levels of miR-206 and histone deacetylase 4 (HDAC4).

Results

Compared to the control group, acute injury group showed a significant decrease in miR-206 expression (.061 ± .38, P < .05) and a significant increase in HDAC4 expression (37.05 ± 20.68, P < .05). Chronic injury group showed a significant decrease in miR-206 expression (.23 ± .19, P < .05) and a significant increase in HDAC4 expression (9.66 ± 6.12, P < .05).

Discussion

A tree shrew model of radiation-induced muscle injury was established by exposing TVP muscle region to radiation of 20-Gy. Experimental results indicated that injury caused by radiation persisted despite gradual healing of the TVP muscle and miR-206 regulatory pathway plays a key role in regulating radiation-induced muscle injury.

The Effects of Dietary Protein Supplementation on Acute Changes in Muscle Protein Synthesis and Longer-Term Changes in Muscle Mass, Strength, and Aerobic Capacity in Response to Concurrent Resistance and Endurance Exercise in Healthy Adults: A Systematic Review

BACKGROUND

Engaging in both resistance and endurance exercise within the same training program, termed 'concurrent exercise training,' is common practice in many athletic disciplines that require a combination of strength and endurance and is recommended by a number of organizations to improve muscular and cardiovascular health and reduce the risk of chronic metabolic disease. Dietary protein ingestion supports skeletal muscle remodeling after exercise by stimulating the synthesis of muscle proteins and can optimize resistance exercise-training mediated increases in skeletal muscle size and strength; however, the effects of protein supplementation on acute and longer-term adaptive responses to concurrent resistance and endurance exercise are unclear.

OBJECTIVES

The purpose of this systematic review is to evaluate the effects of dietary protein supplementation on acute changes in muscle protein synthesis and longer-term changes in muscle mass, strength, and aerobic capacity in responses to concurrent resistance and endurance exercise in healthy adults.

METHODS

A systematic search was conducted in five databases: Scopus, Embase, Medline, PubMed, and Web of Science. Acute and longer-term controlled trials involving concurrent exercise and protein supplementation in healthy adults (ages 18-65 years) were included in this systematic review. Main outcomes of interest were changes in skeletal muscle protein synthesis rates, muscle mass, muscle strength, and whole-body aerobic capacity (i.e., maximal/peak aerobic capacity [VO_2max/peak]). The quality of studies was assessed using the National Institute of Health Quality Assessment for Controlled Intervention Studies.

RESULTS

Four acute studies including 84 trained young males and ten longer-term studies including 167 trained and 391 untrained participants fulfilled the eligibility criteria. All included acute studies demonstrated that protein ingestion enhanced myofibrillar protein synthesis rates, but not mitochondrial protein synthesis rates during post-exercise recovery after an acute bout of concurrent exercise. Of the included longer-term training studies, five out of nine reported that protein supplementation enhanced concurrent training-mediated increases in muscle mass, while five out of nine studies reported that protein supplementation enhanced concurrent training-mediated increases in muscle strength and/or power. In terms of aerobic adaptations, all six included studies reported no effect of protein supplementation on concurrent training-mediated increases in VO_2max/peak.

CONCLUSION

Protein ingestion after an acute bout of concurrent exercise further increases myofibrillar, but not mitochondrial, protein synthesis rates during post-exercise recovery. There is some evidence that protein supplementation during longer-term training further enhances concurrent training-mediated increases in skeletal muscle mass and strength/power, but not whole-body aerobic capacity (i.e., VO_2max/peak).

MicroRNAs as Potential Biomarkers for Exercise-Based Cancer Rehabilitation in Cancer Survivors

Expression and functions of microRNAs (miRNAs) have been widely investigated in cancer treatment-induced complications and as a response to physical activity, respectively, but few studies focus on the application of miRNAs as biomarkers in exercise-based cancer rehabilitation. Research has shown that certain miRNA expression is altered substantially due to tissue damage caused by cancer treatment and chronic inflammation. MiRNAs are released from the damaged tissue and can be easily detected in blood plasma. Levels of the miRNA present in peripheral circulation can therefore be used to measure the extent of tissue damage. Moreover, damage to tissues such as cardiac and skeletal muscle significantly affects the individual's health-related fitness, which can be determined using physiologic functional assessments. These physiologic parameters are a measure of tissue health and function and can therefore be correlated with the levels of circulating miRNAs. In this paper, we reviewed miRNAs whose expression is altered during cancer treatment and may correlate to physiological, physical, and psychological changes that significantly impact the quality of life of cancer survivors and their role in response to physical activity. We aim to identify potential miRNAs that can not only be used for monitoring changes that occur in health-related fitness during cancer treatment but can also be used to evaluate response to exercise-based rehabilitation and monitor individual progress through the rehabilitation programme.

MicroRNAs associated with signaling pathways and exercise adaptation in sarcopenia

Considering the expansion of human life-span over the past few decades; sarcopenia, a physiological consequence of aging process characterized with a diminution in mass and strength of skeletal muscle, has become more frequent. Thus, there is a growing need for expanding our knowledge on the molecular mechanisms of muscle atrophy in sarcopenia which are complex and involve many signaling pathways associated with protein degradation and synthesis. MicroRNAs (miRNAs) as evolutionary conserved small RNAs, could complementarily bind to their target mRNAs and post-transcriptionally inhibit their translation. Aberrant expression of miRNAs contributes to the development of sarcopenia by regulating the expression of critical genes involved in age-related skeletal muscle mass loss. Here we have a review on the signaling pathways along with the miRNAs controlling their components expression and subsequently we provide a brief overview on the effects of exercise on expression pattern of miRNAs in sarcopenia.

SMA-miRs (miR-181a-5p, -324-5p, and -451a) are overexpressed in spinal muscular atrophy skeletal muscle and serum samples

Background:

Spinal muscular atrophy (SMA) is a neuromuscular disorder characterized by the degeneration of the second motor neuron. The phenotype ranges from very severe to very mild forms. All patients have the homozygous loss of the SMN1 gene and a variable number of SMN2 (generally 2–4 copies), inversely related to the severity. The amazing results of the available treatments have made compelling the need of prognostic biomarkers to predict the progression trajectories of patients. Besides the SMN2 products, few other biomarkers have been evaluated so far, including some miRs.

Methods:

We performed whole miRNome analysis of muscle samples of patients and controls (14 biopsies and 9 cultures). The levels of muscle differentially expressed miRs were evaluated in serum samples (51 patients and 37 controls) and integrated with SMN2 copies, SMN2 full-length transcript levels in blood and age (SMA-score).

Results:

Over 100 miRs were differentially expressed in SMA muscle; 3 of them (hsa-miR-181a-5p, -324-5p, -451a; SMA-miRs) were significantly upregulated in the serum of patients. The severity predicted by the SMA-score was related to that of the clinical classification at a correlation coefficient of 0.87 (p<10^-5).

Conclusions:

miRNome analyses suggest the primary involvement of skeletal muscle in SMA pathogenesis. The SMA-miRs are likely actively released in the blood flow; their function and target cells require to be elucidated. The accuracy of the SMA-score needs to be verified in replicative studies: if confirmed, its use could be crucial for the routine prognostic assessment, also in presymptomatic patients.

Funding:

Telethon Italia (grant #GGP12116).

Liquid Biopsy for Cancer Cachexia: Focus on Muscle-Derived microRNAs

Cancer cachexia displays a complex nature in which systemic inflammation, impaired energy metabolism, loss of muscle and adipose tissues result in unintentional body weight loss. Cachectic patients have a poor prognosis and the presence of cachexia reduces the tolerability of chemo/radio-therapy treatments and it is frequently the primary cause of death in advanced cancer patients. Early detection of this condition could make treatments more effective. However, early diagnostic biomarkers of cachexia are currently lacking. In recent years, although solid biopsy still remains the "gold standard" for diagnosis of cancer, liquid biopsy is gaining increasing interest as a source of easily accessible potential biomarkers. Moreover, the growing interest in circulating microRNAs (miRNAs), has made these molecules attractive for the diagnosis of several diseases, including cancer. Some muscle-derived circulating miRNA might play a pivotal role in the onset/progression of cancer cachexia. This topic is of great interest since circulating miRNAs might be easily detectable by means of liquid biopsies and might allow an early diagnosis of this syndrome. We here summarize the current knowledge on circulating muscular miRNAs involved in muscle atrophy, since they might represent easily accessible and promising biomarkers of cachexia.

Modulations of obesity-related microRNAs after exercise intervention: a systematic review and bioinformatics analysis

Obesity is one of the prevalent health-threatening conditions; however, it is preventable by lifestyle interventions such as exercise. The molecular mechanisms underlying physiological adaptation to physical activity are not fully understood. It has been documented that both intracellular and extracellular (circulating) microRNAs (miRNAs) are involved in both obesogenic and exercise adaptation mechanisms. We aimed to conduct a systematic review of publications that examined the effect of exercise on the expression of miRNAs in individuals with obesity. In addition, bioinformatics analysis was performed on most repetitive miRNAs. PubMed, Scopus, and Google Scholar were searched with relevant keywords. We only included studies that utilized exercise as a modality for the health management of human subjects with obesity to evaluate the changes in expression of obesity-related miRNAs. Through checking of 211 retrieved articles, we reached 12 eligible studies. Some studies reported a statistically significant correlation between the change of miRNAs and clinical parameters such as body mass index and fasting glucose. In silico analysis of most repetitive miRNAs i.e. miR-126, miR-21, miR-146a, miR-221, and miR-223 resulted in the molecular signaling pathways that potentially involve in cellular adaption to exercise in people with obesity. miRNAs partake in health-related benefits of physical activity on obesity-associated cellular and molecular phenomena. However, our understanding of the exact mechanism is still in its infancy. Consistently, the clinicians waiting for the result of more integrated experiments to develop a miRNAs panel as a predictive biomarker of exercise in patients with obesity.

Effects of physical activity on cell-to-cell communication during type 2 diabetes: A focus on miRNA signaling

Type 2 diabetes (TD2) is a progressive disease characterized by hyperglycemia that results from alteration in insulin secretion, insulin resistance, or both. A number of alterations involving different tissues and organs have been reported to the development and the progression of T2D, and more relevantly, through cell-to-cell communication pathways. Recent studies demonstrated that miRNAs are considerably implicated to cell-to-cell communication during T2D. Physical activity (PA) is associated with decreasing risks of developing T2D and acts as insulin-like factor. Cumulative evidence suggests that this effect could be mediated in part through improving insulin sensitivity in T2D and obese patients and modulating miRNAs synthesis and release in healthy patients. Therefore, the practice of PA should ideally be established before the initiation of T2D. This review describes cell-to-cell communications involved in the pathophysiology of T2D during PA.

Non-Coding RNAs in the Transcriptional Network That Differentiates Skeletal Muscles of Sedentary from Long-Term Endurance- and Resistance-Trained Elderly

In a previous study, the whole transcriptome of the vastus lateralis muscle from sedentary elderly and from age-matched athletes with an exceptional record of high-intensity, life-long exercise training was compared-the two groups representing the two extremes on a physical activity scale. Exercise training enabled the skeletal muscle to counteract age-related sarcopenia by inducing a wide range of adaptations, sustained by the expression of protein-coding genes involved in energy handling, proteostasis, cytoskeletal organization, inflammation control, and cellular senescence. Building on the previous study, we examined here the network of non-coding RNAs participating in the orchestration of gene expression and identified differentially expressed micro- and long-non-coding RNAs and some of their possible targets and roles. Unsupervised hierarchical clustering analyses of all non-coding RNAs were able to discriminate between sedentary and trained individuals, regardless of the exercise typology. Validated targets of differentially expressed miRNA were grouped by KEGG analysis, which pointed to functional areas involved in cell cycle, cytoskeletal control, longevity, and many signaling pathways, including AMP-activated protein kinase (AMPK) and mammalian target of rapamycin (mTOR), which had been shown to be pivotal in the modulation of the effects of high-intensity, life-long exercise training. The analysis of differentially expressed long-non-coding RNAs identified transcriptional networks, involving lncRNAs, miRNAs and mRNAs, affecting processes in line with the beneficial role of exercise training.

Circulating MicroRNA-486 and MicroRNA-146a serve as potential biomarkers of sarcopenia in the older adults

Background

Age-related sarcopenia meaningfully increases the risks of functional limitations and mortality in the older adults. Although circulating microRNAs (c-miRNAs) are associated with aging-related cellular senescence and inflammation, the relationships between c-miRNAs and sarcopenia in the older adults remain unclear. This study investigates whether circulating myo-miRNAs and inflammation-related miRNAs are associated with sarcopenia in the older adults.

Methods

This investigation recruited 77 eligible subjects (41 males and 36 females) from 597 community-dwelling older adults, and then divided them into normal (n = 24), dynapenic (loss of muscular function without mass, n = 35), and sarcopenic groups (loss of muscular function with mass, n = 18). Moreover, myo- (c-miRNA-133a and c-miRNA-486) and inflammation- (c-miRNA-21 and c-miRNA-146a) related miRNAs, as well as, inflammatory-related cytokine and peroxide levels in plasma were determined using quantitative polymerase chain reaction and ELISA, respectively.

Results

Sarcopenic group exhibited lesser skeletal muscle mass index (SMI), handgrip strength, and gait speed, as well as, lower c-miR-486 and c-miR-146a levels, compared to those of normal and dynapenic groups. Moreover, c-miR-486 level was positively related to SMI (r = 0.334, P = 0.003), whereas c-miR-146a level was positively associated with SMI (r = 0.240, P = 0.035) and handgrip strength (r = 0.253, P = 0.027). In the receiver operating characteristic analysis for predicting sarcopenia, the area under the curve in c-miR-486 was 0.708 (95% confidence interval: 0.561–0.855, P = 0.008) and c-miR-146a was 0.676 (95% CI: 0.551–0.801, P = 0.024). However, no significant relationships were observed between SMI/handgrip strength/gait speed and plasma myeloperoxidase/interleukin-1훽/interleukin-6 levels.

Conclusions

Myo-miRNA (c-miR-486) and inflammation-related miRNA (c-miR-146a) are superior to inflammatory peroxide/cytokines in plasma for serving as critical biomarkers of age-related sarcopenia.

How N-Acetylcysteine Supplementation Affects Redox Regulation, Especially at Mitohormesis and Sarcohormesis Level: Current Perspective

Exercise frequently alters the metabolic processes of oxidative metabolism in athletes, including exposure to extreme reactive oxygen species impairing exercise performance. Therefore, both researchers and athletes have been consistently investigating the possible strategies to improve metabolic adaptations to exercise-induced oxidative stress. N-acetylcysteine (NAC) has been applied as a therapeutic agent in treating many diseases in humans due to its precursory role in the production of hepatic glutathione, a natural antioxidant. Several studies have investigated NAC’s possible therapeutic role in oxidative metabolism and adaptive response to exercise in the athletic population. However, still conflicting questions regarding NAC supplementation need to be clarified. This narrative review aims to re-evaluate the metabolic effects of NAC on exercise-induced oxidative stress and adaptive response developed by athletes against the exercise, especially mitohormetic and sarcohormetic response.

The GALNTL6 Gene rs558129 Polymorphism Is Associated With Power Performance

Díaz, J, Álvarez Herms, J, Castañeda, A, Larruskain, J, Ramírez de la Piscina, X, Borisov, OV, Semenova, EA, Kostryukova, ES, Kulemin, NA, Andryushchenko, ON, Larin, AK, Andryushchenko, LB, Generozov, EV, Ahmetov, II, and Odriozola, A. The GALNTL6 gene rs558129 polymorphism is associated with power performance. J Strength Cond Res 34(11): 3031-3036, 2020-The largest genome-wide association study to date in sports genomics showed that endurance athletes were 1.23 times more likely to possess the C allele of the single nucleotide polymorphism rs558129 of N-acetylgalactosaminyltransferase-like 6 gene (GALNTL6), compared with controls. Nevertheless, no further study has investigated GALNTL6 gene in relation to physical performance. Considering that previous research has shown that the same polymorphism can be associated with both endurance and power phenotypes (ACTN3, ACE, and PPARA), we investigated the association between GALNTL6 rs558129 polymorphism and power performance. According to this objective we conducted 2 global studies regarding 2 different communities of athletes in Spain and Russia. The first study involved 85 Caucasian physically active men from the north of Spain to perform a Wingate anaerobic test (WAnT). In the second study we compared allelic frequencies between 173 Russian power athletes (49 strength and 124 speed-strength athletes), 169 endurance athletes, and 201 controls. We found that physically active men with the T allele of GALNTL6 rs558129 had 5.03-6.97% higher power values compared with those with the CC genotype (p < 0.05). Consistent with these findings, we have shown that the T allele was over-represented in power athletes (37.0%) compared with endurance athletes (29.3%; OR = 1.4, p = 0.032) and controls (28.6%; OR = 1.5, p = 0.015). Furthermore, the highest frequency of the T allele was observed in strength athletes (43.9%; odds ratio [OR] = 1.9, p = 0.0067 compared with endurance athletes; OR = 2.0, p = 0.0036 compared with controls). In conclusion, our data suggest that the GALNTL6 rs558129 T allele can be favorable for anaerobic performance and strength athletes. In addition, we propose a new possible functional role of GALNTL6 rs558129, gut microbiome regarding short-chain fatty acid regulation and their anti-inflammatory and resynthesis functions. Nevertheless, further studies are required to understand the mechanisms involved.

Skeletal muscle effects of two different 10-week exercise regimens, voluntary wheel running, and forced treadmill running, in mice: A pilot study

Physical activity and exercise induce a complex pattern of adaptation reactions in a broad variety of tissues and organs, particularly the cardiovascular and the musculoskeletal systems. The underlying mechanisms, however, specifically the molecular changes that occur in response to training, are still incompletely understood. Animal models help to systematically elucidate the mechanisms of exercise adaptation. With regard to endurance-based running exercise in mice, two basic regimens have been established: forced treadmill running (FTR), usually consisting of several sessions per week, and voluntary wheel running (VWR). However, the effects of these two programs on skeletal muscle molecular adaptation patterns have never been directly compared. To address this issue, in a pilot study, we analyzed the effects of two ten-week training regimens in juvenile, male, C57BL/6 mice: moderate-intensity forced treadmill running three-times-a-week, employing a protocol that has been widely used in similar studies before, and voluntary wheel running. Our data suggest that there are similarities, but also characteristic differences in the molecular responses of different skeletal muscle species to the two training regimens. In particular, we found that VWR induces a significant fiber type shift toward more type IIX fibers in the slow, oxidative soleus muscle (p = .0053), but not in the other three muscles analyzed. In addition, while training-induced expression patterns of the two metabolic markers Ppargc1a, encoding Pgc-1α (peroxisome proliferator-activated receptor gamma coactivator 1-alpha) and Nr4a3 (nuclear receptor subfamily 4 group A member 3) were roughly similar, downregulation of the Mstn (myostatin) gene and the "atrogene" Fbox32 could only be observed in response to VWR in specific muscles, such as in the gastrocnemius (p = .0015 for Mstn) and in the tibialis anterior (p = .0053 for Fbox32) muscles, suggesting that molecular adaptation reactions to the two training regimens show distinct characteristics.

The roles of microRNA in redox metabolism and exercise-mediated adaptation

MicroRNAs (miRs) are small regulatory RNA transcripts capable of post-transcriptional silencing of mRNA messages by entering a cellular bimolecular apparatus called RNA-induced silencing complex. miRs are involved in the regulation of cellular processes producing, eliminating or repairing the damage caused by reactive oxygen species, and they are active players in redox homeostasis. Increased mitochondrial biogenesis, function and hypertrophy of skeletal muscle are important adaptive responses to regular exercise. In the present review, we highlight some of the redox-sensitive regulatory roles of miRs.

Sedentary and Trained Older Men Have Distinct Circulating Exosomal microRNA Profiles at Baseline and in Response to Acute Exercise

Exercise has multi-systemic benefits and attenuates the physiological impairments associated with aging. Emerging evidence suggests that circulating exosomes mediate some of the beneficial effects of exercise via the transfer of microRNAs between tissues. However, the impact of regular exercise and acute exercise on circulating exosomal microRNAs (exomiRs) in older populations remains unknown. In the present study, we analyzed circulating exomiR expression in endurance-trained elderly men (n = 5) and age-matched sedentary males (n = 5) at baseline (Pre), immediately after a forty minute bout of aerobic exercise on a cycle ergometer (Post), and three hours after this acute exercise (3hPost). Following the isolation and enrichment of exosomes from plasma, exosome-enriched preparations were characterized and exomiR levels were determined by sequencing. The effect of regular exercise on circulating exomiRs was assessed by comparing the baseline expression levels in the trained and sedentary groups. The effect of acute exercise was determined by comparing baseline and post-training expression levels in each group. Regular exercise resulted in significantly increased baseline expression of three exomiRs (miR-486-5p, miR-215-5p, miR-941) and decreased expression of one exomiR (miR-151b). Acute exercise altered circulating exomiR expression in both groups. However, exomiRs regulated by acute exercise in the trained group (7 miRNAs at Post and 8 at 3hPost) were distinct from those in the sedentary group (9 at Post and 4 at 3hPost). Pathway analysis prediction and reported target validation experiments revealed that the majority of exercise-regulated exomiRs are targeting genes that are related to IGF-1 signaling, a pathway involved in exercise-induced muscle and cardiac hypertrophy. The immediately post-acute exercise exomiR signature in the trained group correlates with activation of IGF-1 signaling, whereas in the sedentary group it is associated with inhibition of IGF-1 signaling. While further validation is needed, including measurements of IGF-1/IGF-1 signaling in blood or skeletal muscle, our results suggest that training status may counteract age-related anabolic resistance by modulating circulating exomiR profiles both at baseline and in response to acute exercise.

Regulation of Circulatory Muscle-specific MicroRNA during 8 km Run

Acute prolonged endurance running has been shown to alter muscle-specific circulating microRNA (miRNA) levels. Here, eighteen participants completed an 8 km run. We assessed the levels of hsa-miR-1-3p, -133a-3p, -133b, and -206 and their correlation with conventional biomarkers following exercise. Compared to before exercise (Pre), 8 km run significantly increased the lactate level immediately after exercise (0 h). Myoglobin (Mb) level increased at 0 h while creatine kinase (CK) level increased 24 h after exercise (24 h). The levels of creatine kinase MB isoenzyme (CK-MB) and cardiac troponin I (cTnI) were all elevated at 24 h and within the normal physiological range; The levels of hsa-miR-1-3p, -133a-3p, -133b significantly increased at 0 h but only hsa-miR-133a-3p still elevated at 24 h. Only hsa-miR-206 level decreased at 24 h; Additionally, the changes of hsa-miR-1-3p and hsa-miR-133a-3p were correlated with Mb at 24 h. These findings suggest that muscle-specific miRNA elevation in plasma is likely physiological and that these miRNA may be used as potential biomarkers for load monitoring in individuals.

Non-coding RNAs as Putative Biomarkers of Cancer-Associated Cachexia

Cachexia is a complex metabolic syndrome that determines a severe body weight loss characterized by a marked reduction in muscle mass. About 80% of patients with advanced cancer develop cachexia due to both the tumor itself and cancer treatment (radiotherapy and/or chemotherapy), which is associated to a worse prognosis. Despite its clinical relevance, this syndrome is still under-diagnosed and it lacks effective treatments. Radio-chemotherapy treatment is essential in patients with advanced head and neck cancers (HNSCC). Although this treatment has improved patients' life expectancy, it has also dramatically increased their need for assistance and support. The management of adverse symptoms, including cachexia, is of great importance in order to avoid delays in therapy, reduction of dosages and hospitalizations. MicroRNAs (miRNAs) are small non-coding RNA molecules, which have emerged as powerful biomarkers in stratifying human cancers. Due to their high stability in body fluids, miRNAs might be excellent non-invasive biomarkers for the early detection and follow-up of cancer patients. Here, we will summarize the current knowledge and debate the strong need to identify circulating biomarkers for the early diagnosis of cachexia. We will propose circulating non-coding RNAs as biomarkers for detecting early cachexia and implementing specific treatment. We will also discuss the potential use of circulating miRNAs as biomarkers of cachexia in HNSCC patients' blood samples collected before and after radio-chemotherapy treatment. Our intent is to pave the way to the identification of specific circulating miRNAs associated to cachexia occurrence and to the design of specific interventions aimed at improving the quality of life of cancer patients.

Effects of Physical Exercise on the Expression of MicroRNAs: A Systematic Review

Silva, FCd, Iop, RdR, Andrade, A, Costa, VP, Gutierres Filho, PJB, and Silva, Rd. Effects of physical exercise on the expression of microRNAs: A systematic review 34(1): 270-280, 2020-Studies have detected changes in the expression of miRNAs after physical exercise, which brings new insight into the molecular control of adaptation to exercise. Therefore, the objective of the current systematic review of experimental and quasiexperimental studies published in the past 10 years was to assess evidence related to acute effects, chronic effects, and both acute and chronic effects of physical exercise on miRNA expression in humans, as well as its functions, evaluated in serum, plasma, whole blood, saliva, or muscle biopsy. For this purpose, the following electronic databases were selected: MEDLINE by Pubmed, SCOPUS, Web of Science, and also a manual search in references of the selected articles to April 2017. Experimental and quasiexperimental studies were included. Results indicate that, of the 345 studies retrieved, 40 studies met the inclusion criteria and two articles were included as a result of the manual search. The 42 studies were analyzed, and it can be observed acute and chronic effects of physical exercises (aerobic and resistance) on the expression of several miRNAs in healthy subjects, athletes, young, elderly and in patients with congestive heart failure, chronic kidney disease, diabetes mellitus type 2 associated with morbid obesity, prediabetic, and patients with intermittent claudication. It is safe to assume that miRNA changes, both in muscle tissues and bodily fluids, are presumably associated with the benefits induced by acute and chronic physical exercise. Thus, a better understanding of changes in miRNAs as a response to physical exercise might contribute to the development of miRNAs as therapeutic targets for the improvement of exercise capacity in individuals with any given disease. However, additional studies are necessary to draw accurate conclusions.

Circulating MicroRNAs in Duchenne Muscular Dystrophy

OBJECTIVE

The diagnosis of Duchenne Muscular Dystrophy (DMD) currently depends on non-specific measures such as Creatine kinase (CK) levels. MicroRNAs (miRNAs) are a class of small, endogenous RNAs of 21-25 nucleotides, that are important regulators for numerous physiological and pathological processes. The aim of the current study is to assess the potential of miRNAs as non-invasive biomarker for the diagnosis of DMD and for identifying carriers.

PATIENTS AND METHODS

Thirty healthy subjects and 29 families with one member diagnosed with DMD were enrolled in the study. Peripheral blood samples were collected from all subjects where microRNAs were extracted from plasma followed by the quantification of miR-499, miR-103a-3p, miR-103a-5p, miR-206, miR-208a, miR-223 and miR-191-5p. MLPA and NGS were carried out as a gold standard technique to identify the mutations in the participants.

RESULTS

Our data revealed that miR-499 was significantly upregulated in all DMD patients, and true carriers (mothers), while 78 % of potential carriers (sisters) exhibited high levels of this miRNA. Similarly, miR-103a-3p showed an increase in the patients' families although to a lesser extent. On the other hand, miR-206 and miR-191-5p were significantly downregulated in the majority of the DMD patients and the tested female family members. MicroRNA miR-103a-5p and miR-208a followed a comparable trend in patients and mothers.

CONCLUSIONS

Ourresults suggest that the plasma levels of miRNAs have the capability to diagnose DMD patients and more importantly, miRNAs can be used to identify female carriers.

Time-Course Responses of Muscle-Specific MicroRNAs Following Acute Uphill or Downhill Exercise in Sprague-Dawley Rats

Objective: The physiological characteristics and acute responses underpinning uphill running differ from those of downhill running and remain less understood. This study aimed to evaluate time-course changes of muscle-specific microRNA (miRNA) responses in striated muscle or circulation in response to uphill and downhill running. Methods: Male Sprague-Dawley rats (n = 84) were randomly assigned to a sedentary group (n = 12) and an exercise group (n = 72). The exercise group performed 90 min of uphill or downhill running. The striated muscle (quadriceps, gastrocnemius, soleus, and cardiac muscle) or circulation (plasma, exosome, exosome-free) levels of six muscle-specific miRNAs (miR-1, miR-133a, miR-133b, miR-206, miR-208a, and miR-499) were assessed at rest, immediately following exercise, and during recovery (1 h and 48 h). Results: Our results show that miR-1 and miR-133a levels are both decreased in quadriceps following downhill running (p < 0.05) while there is no change after uphill running (p > 0.05). In gastrocnemius, both uphill and downhill running decreased miR-1 level immediately after exercise and returned to baseline during recovery (p < 0.05): interestingly, only miR-499 significantly increased following uphill running (p > 0.05). Of the cell-free miRNAs in circulation, only the miR-133b levels in plasma were not affected following uphill running (p > 0.05); the other miRNA levels significantly increased immediately after exercise (p < 0.05), decreased at 1 h and significantly increased at 48 h after exercise (p < 0.05). All selected miRNA levels in exosomes were not affected following uphill running (p > 0.05), while all selected miRNA levels significantly increased during early recovery after downhill running (p > 0.05). In addition, only the miR-133a level in the exosome-free condition showed significant changes following uphill running (p < 0.05), while miR-1, miR-133a, and miR-499 levels showed significant changes after downhill running (p < 0.05). Conclusion: The results indicate that miRNA undergoes dynamic changes in tissue may play an important role in regulating different stress/adaptation following uphill and downhill running. It is likely that changed miRNA levels in plasma may act as a new biomarker for monitoring whole muscular stress during recovery.

Muscle and Systemic Molecular Responses to a Single Flywheel Based Iso-Inertial Training Session in Resistance-Trained Men

Growing evidence points to the effectiveness of flywheel (FW) based iso-inertial resistance training in improving physical performance capacities. However, molecular adaptations induced by FW exercises are largely unknown. Eight resistance-trained men performed 5 sets of 10 maximal squats on a FW device. Muscle biopsies (fine needle aspiration technique) and blood samples were collected before (t0), and 2 h (t1) after FW exercise. Blood samples were additionally drawn after 24 h (t2) and 48 h (t3). Paired samples t-tests revealed significant increases, at t1, of mRNA expression of the genes involved in inflammation, in both muscle (MCP-1, TNF-α, IL-6) and peripheral blood mononuclear cells (IkB-α, MCP-1). Circulating extracellular vesicles (EVs) and EV-encapsulated miRNA levels (miR-206, miR-146a) significantly increased at t1 as well. Conversely, muscle mRNA level of genes associated with muscle growth/remodeling (IGF-1Ea, cyclin D1, myogenin) decreased at t1. One-way repeated measure ANOVAs, with Bonferroni corrected post-hoc pairwise comparisons, revealed significant increases in plasma concentrations of IL-6 (t1; t2; t3) and muscle creatine kinase (t1; t2), while IGF-1 significantly increased at t2 only. Our findings show that, even in experienced resistance trained individuals, a single FW training session modifies local and systemic markers involved in late structural remodeling and functional adaptation of skeletal muscle.

Small non-coding RNAs are altered by short-term sprint interval training in men

Small non-coding RNAs (ncRNAs) are emerging as important molecules for normal biological processes and are deregulated in disease. Exercise training is a powerful therapeutic strategy that prevents cardiometabolic disease and improves cardiorespiratory fitness and performance. Despite the known systemic health benefits of exercise training, the underlying molecular mechanisms are incompletely understood. Recent evidence suggests a role for epigenetic mechanisms, such as microRNAs, but whether other small ncRNAs are modulated by chronic exercise training is unknown. Here, we used small RNA sequencing to explore whether sprint interval training (SIT) controls the abundance of circulating small ncRNAs in human whole blood samples. Ten healthy men performed SIT three times a week for 6 weeks. After training, subjects showed marked improvements in maximal oxygen consumption and cycling performance with concurrent changes to the abundance of diverse species of circulating small ncRNAs (n = 1266 small ncRNAs, n = 13 microRNAs, q < 0.05). Twelve microRNAs altered by 6 weeks of SIT were ubiquitously expressed microRNAs and two regulated important signaling pathways, including p53, thyroid hormone and cell cycle signaling. MicroRNAs altered by 6 weeks of SIT were unchanged after a single session of SIT (n = 24, all P > 0.05). Relative to older individuals, younger subjects exhibited an increased acute SIT-induced fold change in miR-1301-3p (P = 0.02) - a microRNA predicted to target mRNAs involved in alternative splicing, phosphoprotein and chromosomal rearrangement processes (all P < 0.001). Our findings indicate many species of circulating small ncRNAs are modulated by exercise training and that they could control signaling pathways responsible for health benefits achieved from exercise.

Genetic and epigenetic sex-specific adaptations to endurance exercise

In recent years, the interest in personalised interventions such as medicine, nutrition, and exercise is rapidly rising to maximize health outcomes and ensure the most appropriate treatments. Exercising regularly is recommended for both healthy and diseased populations to improve health. However, there are sex-specific adaptations to exercise that often are not taken into consideration. While endurance exercise training alters the human skeletal muscle epigenome and subsequent gene expression, it is still unknown whether it does so differently in men and women, potentially leading to sex-specific physiological adaptations. Elucidating sex differences in genetics, epigenetics, gene regulation and expression in response to exercise will have great health implications, as it may enable gene targets in future clinical interventions and may better individualised interventions. This review will cover this topic and highlight the recent findings of sex-specific genetic, epigenetic, and gene expression studies, address the gaps in the field, and offer recommendations for future research.

Neuromuscular electrical stimulation improves muscle atrophy induced by chronic hypoxia-hypercapnia through the MicroRNA-486/PTEN/FoxO1 pathway

Previous work has confirmed that the chronic hypoxia-hypercapnia (CHH) associated with chronic obstructive pulmonary disease contributes to the development of skeletal muscle atrophy. Neuromuscular Electrical Stimulation (NMES) has shown some efficacy when used as a treatment to reduce skeletal muscle atrophy. The present study focuses on the MicroRNA-486/PTEN/FoxO1 pathway with the goal of identifying its physiological role in skeletal muscle atrophy induced by CHH as well as its role during NMES treatment. To test this, 32 male Sprague Dawley rats were randomly divided into four groups. After completion of the disease modeling, gastrocnemius muscles were collected from all animals and cross-sectional areas of muscular fiber were observed and analyzed via H&E staining. MiR-486 expression was further assessed by qRT-PCR, and protein levels of TNF-α, PTEN, p-Akt, Akt, FoxO1, atrogin-1 and MuRF1 were measured by immunohistochemistry and western blotting. CSA, miR-486, and the ratio p-Akt/Akt were significantly reduced in the CHH group, while the levels of TNF-α, PTEN, FoxO1, atrogin-1, and MuRF1 were markedly increased. Importantly, these findings were reversed as a result of NMES. Thus, the MicroRNA-486/PTEN/FoxO1 pathway functions in muscle protein synthesis and degradation. NEW & NOTEWORTHY: Our research provides a theoretical basis for the application of NMES as a means of improving muscle atrophy. Moreover, these therapeutic targets provide possible clues relevant to the treatment of amyotrophic diseases.

MicroRNA and Long Non-coding RNA Regulation in Skeletal Muscle From Growth to Old Age Shows Striking Dysregulation of the Callipyge Locus

MicroRNAs (miRNAs) undergo high levels of regulation in skeletal muscle development and control skeletal muscle mass, function and metabolism over the lifespan. More recently, the role of long non-coding RNAs (lncRNAs) in skeletal muscle regulation has started to emerge. Following up on our recent study describing the expression pattern and putative roles of 768 miRNAs in the quadriceps muscle of mice at early life stages, we used a high-throughput miRNA qPCR-based array to assess the expression of the same miRNAs in 28-month old male mouse quadriceps muscle. In addition, we report the expression patterns of lncRNAs playing a putative role in muscle development and adaptation from growth to old age. Twelve miRNAs were significantly downregulated in 28-month old muscle when compared with 12-week old muscle. Ten of them clustered at the Dlk1-Dio3 locus, known as ‘Callipyge,’ which is associated with muscle development and hypertrophy. This collective downregulation was paralleled by decreases in the expression levels of the maternally expressed imprinted LncRNA coding genes Meg3 and Rian stemming from the same chromosomal region. In contrast, the paternally expressed imprinted Dlk1-Dio3 locus members Rtl1, Dio3, and Dlk1 and the muscle related lncRNAs lncMyoD1, Neat_v1, Neat_v2, and Malat1 underwent significant changes during growth, but their expression levels were not altered past the age of 12 weeks, suggesting roles limited to hyperplasia and early hypertrophy. In conclusion, collective muscle miRNA expression gradually decreases over the lifespan and a cluster of miRNAs and maternally expressed lncRNAs stemming from the Callipyge locus is significantly dysregulated in aging muscle. The Dlk1-Dio3 locus therefore represents a potential new mechanism for age-related muscle decline.

Non-coding RNAs and exercise: pathophysiological role and clinical application in the cardiovascular system

There is overwhelming evidence that regular exercise training is protective against cardiovascular disease (CVD), the main cause of death worldwide. Despite the benefits of exercise, the intricacies of their underlying molecular mechanisms remain largely unknown. Non-coding RNAs (ncRNAs) have been recognized as a major regulatory network governing gene expression in several physiological processes and appeared as pivotal modulators in a myriad of cardiovascular processes under physiological and pathological conditions. However, little is known about ncRNA expression and role in response to exercise. Revealing the molecular components and mechanisms of the link between exercise and health outcomes will catalyse discoveries of new biomarkers and therapeutic targets. Here we review the current understanding of the ncRNA role in exercise-induced adaptations focused on the cardiovascular system and address their potential role in clinical applications for CVD. Finally, considerations and perspectives for future studies will be proposed.

Circulating miRNAs as Putative Biomarkers of Exercise Adaptation in Endurance Horses

Endurance exercise induces metabolic adaptations and has recently been reported associated with the modulation of a particular class of small noncoding RNAs, microRNAs, that act as post-transcriptional regulators of gene expression. Released into body fluids, they termed circulating miRNAs, and they have been recognized as more effective and accurate biomarkers than classical serum markers. This study examined serum profile of miRNAs through massive parallel sequencing in response to prolonged endurance exercise in samples obtained from four competitive Arabian horses before and 2 h after the end of competition. MicroRNA identification, differential gene expression (DGE) analysis and a protein-protein interaction (PPI) network showing significantly enriched pathways of target gene clusters, were assessed and explored. Our results show modulation of more than 100 miRNAs probably arising from tissues involved in exercise responses and indicating the modulation of correlated processes as muscle remodeling, immune and inflammatory responses. Circulating miRNA high-throughput sequencing is a promising approach for sports medicine for the discovery of putative biomarkers for predicting risks related to prolonged activity and monitoring metabolic adaptations.

Influence of physical exercise on microRNAs in skeletal muscle regeneration, aging and diseases

Skeletal muscle is a dynamic tissue with remarkable plasticity and its growth and regeneration are highly organized, with the activation of specific transcription factors, proliferative pathways and cytokines. The decline of skeletal muscle tissue with age, is one of the most important causes of functional loss of independence in older adults. Maintaining skeletal muscle function throughout the lifespan is a prerequisite for good health and independent living.

Physical activity represents one of the most effective preventive agents for muscle decay in aging.

Several studies have underlined the importance of microRNAs (miRNAs) in the control of myogenesis and of skeletal muscle regeneration and function.

In this review, we reported an overview and recent advances about the role of miRNAs expressed in the skeletal muscle, miRNAs regulation by exercise in skeletal muscle, the consequences of different physical exercise training modalities in the skeletal muscle miRNA profile, their regulation under pathological conditions and the role of miRNAs in age-related muscle wasting.

Specific miRNAs appear to be involved in response to different types of exercise and therefore to play an important role in muscle fiber identity and myofiber gene expression in adults and elder population.

Understanding the roles and regulation of skeletal muscle miRNAs during muscle regeneration may result in new therapeutic approaches in aging or diseases with impaired muscle function or re-growth.

MicroRNA-133b inhibits cell proliferation and promotes apoptosis by targeting cullin 4B in esophageal squamous cell carcinoma

microRNAs (miRs) serve a role as modulators during carcinogenesis. It has been demonstrated that the expression of miR-133b is decreased in a variety of tumor tissues and cell lines and serves a suppressive role in the proliferation and apoptosis of different types of tumor cells. However, its effect on esophageal squamous cell carcinoma (ESCC) cells remains unclear. In the current study, the expression of mature miR-133b was measured using reverse transcription-quantitative polymerase chain reaction and the results indicated that miR-133b was significantly downregulated in ESCC tissues and various ESCC cell lines. The overexpression of miR-133b significantly inhibited the proliferation and promoted the apoptosis of KYSE150 and Eca-109 cells. Furthermore, it was demonstrated that cullin 4B (CUL4B) promotes ESCC cell proliferation and inhibits apoptosis by activating the protein kinase B/glycogen synthase kinase 3β/β-catenin pathway. Taken together, these results demonstrate that miR-133b/CUL4B serves a tumor suppressive role during ESCC progression and may therefore be used as a potential target to treat patients with ESCC.

Regulatory Role of MicroRNAs in Muscle Atrophy during Exercise Intervention

Skeletal muscle comprising approximately 40% of body weight is highly important for locomotion and metabolic homeostasis. The growth and regeneration of skeletal muscle are highly organized processes; thus, it is not surprising to reveal certain complexity during these regulatory processes. Recently, a large number of evidence indicate that microRNAs can result in obvious impacts on growth, regeneration and metabolism of skeletal muscle. In this review, recent research achievements of microRNAs in regulating myogenesis, atrophy and aging during exercise intervention are discussed, which will provide the guidance for developing potential applications of microRNAs in health promotion and rehabilitation of sports injuries.

Elevated and Correlated Expressions of miR-24, miR-30d, miR-146a, and SFRP-4 in Human Abdominal Adipose Tissue Play a Role in Adiposity and Insulin Resistance

OBJECTIVE

We explored the relationships among microRNAs (miRNAs) and SFRP4, as they relate to adipose tissue functions including lipolysis, glucose and glycerol turnover, and insulin sensitivity.

METHODS

Abdominal adipose tissue (AbdAT) levels of thirteen microRNAs (miRNAs), SFRP4, and VEGF in lean nondiabetic subjects (n = 7), subjects with obesity (n = 5), and subjects with obesity and type 2 diabetes (T2DM) (n = 5) were measured by qPCR. Insulin sensitivity was measured by the euglycemic-hyperinsulinemic clamp. Osmium fixation and Coulter counting were used for adipocyte sizing. Data were analyzed using generalized linear models that adjusted for age, gender, and ethnicity.

RESULTS

AbdAT miR-24, miR-30d, and miR-146a were elevated in subjects with obesity (P < 0.05) and T2DM (P < 0.1) and positively correlated with measures of percent body fat by DXA (r_miR.24 = 0.894, r_miR.146a = 0.883, P < 0.05), and AbdAT SFRP4 (r_miR.30 = 0.93, r_miR.146a = 0.88, P < 0.05). These three miRNAs additionally correlated among themselves (r_{miR.24~miR.146a} = 0.90, r_{miR.30~miR.146a} = 0.85, P < 0.01).

CONCLUSIONS

This study suggests a novel association between the elevated levels of miRNAs miR-24, miR-30d, and miR-146a (apparently coregulated) and the level of SFRP4 transcript in AbdAT of subjects with obesity and T2DM. These molecules might be part of a regulatory loop involved in AbdAT remodeling/adiposity and systemic insulin resistance. This trial is registered with NCT00704197.

Circulating MiRNAs as biomarkers of gait speed responses to aerobic exercise training in obese older adults

Gait speed is a useful predictor of adverse outcomes, including incident mobility disability and mortality in older adults. While aerobic exercise training (AEX) is generally an effective therapy to improve gait speed, individual responses are highly variable. Circulating microRNAs (miRNAs) may contribute to inter-individual changes in gait speed with AEX. We examined whether plasma miRNAs are associated with gait speed changes (dGaitSp) in 33 obese older adults (age: 69.3±3.6 years, BMI: 34.0±3.1 kg/m², 85% white, 73% women) who performed treadmill walking, 4 days/week for 5 months. Gait speed (baseline: 1.02±0.19 m/s; range of response: −0.2 to 0.35 m/s) was assessed using a 400 meter-fast-paced walk test. Using Nanostring technology, 120 out of 800 miRNAs were found to be abundantly expressed in plasma and 4 of these were significantly changed after AEX: miR-376a-5p increased, while miR-16-5p, miR-27a-3p, and miR-28-3p all decreased. In addition, baseline miR-181a-5p levels (r=-0.40, p=0.02) and percent changes in miR-92a-3p (r=-0.44, p=0.009) associated negatively with dGaitSp. Linear regression combined baseline miR-181a-5p and miR-92a-3p levels showed even stronger associations with dGaitSp (r=-0.48, p=0.005). These results suggest that circulating miR-181a-5p and miR-92a-3p may predict and/or regulate AEX-induced gait speed changes in obese older adults.

Role of microRNAs in obesity and obesity-related diseases

In recent years, the link between regulatory microRNAs (miRNAs) and diseases has been the object of intensive research. miRNAs have emerged as key mediators of metabolic processes, playing crucial roles in maintaining/altering physiological processes, including energy balance and metabolic homeostasis. Altered miRNAs expression has been reported in association with obesity, both in animal and human studies. Dysregulation of miRNAs may affect the status and functions of different tissues and organs, including the adipose tissue, pancreas, liver, and muscle, possibly contributing to metabolic abnormalities associated with obesity and obesity-related diseases. More recently, the discovery of circulating miRNAs easily detectable in plasma and other body fluids has emphasized their potential as both endocrine signaling molecules and disease indicators. In this review, the status of current research on the role of miRNAs in obesity and related metabolic abnormalities is summarized and discussed.

Mechanosensitive miRNAs and Bone Formation

Mechanical stimuli are required for the maintenance of skeletal integrity and bone mass. An increasing amount of evidence indicates that multiple regulators (e.g., hormone, cytoskeleton proteins and signaling pathways) are involved in the mechanical stimuli modulating the activities of osteogenic cells and the process of bone formation. Significantly, recent studies have showed that several microRNAs (miRNAs) were sensitive to various mechanical stimuli and played a crucial role in osteogenic differentiation and bone formation. However, the functional roles and further mechanisms of mechanosensitive miRNAs in bone formation are not yet completely understood. This review highlights the roles of mechanosensitive miRNAs in osteogenic differentiation and bone formation and underlines their potential therapeutic application for bone loss induced by the altering of mechanical stimuli.

Cross-sectional relations of whole-blood miRNA expression levels and hand grip strength in a community sample

MicroRNAs (miRNAs) regulate gene expression with emerging data suggesting miRNAs play a role in skeletal muscle biology. We sought to examine the association of miRNAs with grip strength in a community-based sample. Framingham Heart Study Offspring and Generation 3 participants (n = 5668 54% women, mean age 55 years, range 24, 90 years) underwent grip strength measurement and miRNA profiling using whole blood from fasting morning samples. Linear mixed-effects regression modeling of grip strength (kg) versus continuous miRNA 'Cq' values and versus binary miRNA expression was performed. We conducted an integrative miRNA-mRNA coexpression analysis and examined the enrichment of biologic pathways for the top miRNAs associated with grip strength. Grip strength was lower in women than in men and declined with age with a mean 44.7 (10.0) kg in men and 26.5 (6.3) kg in women. Among 299 miRNAs interrogated for association with grip strength, 93 (31%) had FDR q value < 0.05, 54 (18%) had an FDR q value < 0.01, and 15 (5%) had FDR q value < 0.001. For almost all miRNA-grip strength associations, increasing miRNA concentration is associated with increasing grip strength. miR-20a-5p (FDR q 1.8 × 10-6 ) had the most significant association and several among the top 15 miRNAs had links to skeletal muscle including miR-126-3p, miR-30a-5p, and miR-30d-5p. The top associated biologic pathways included metabolism, chemokine signaling, and ubiquitin-mediated proteolysis. Our comprehensive assessment in a community-based sample of miRNAs in blood associated with grip strength provides a framework to further our understanding of the biology of muscle strength.

Altered levels of circulating cytokines and microRNAs in lean and obese individuals with prediabetes and type 2 diabetes

Today obesity and type 2 diabetes (T2D) have both reached epidemic proportions. However, our current understanding of the primary mechanisms leading to these diseases is still limited due to the complex multifactorial nature of the underlying phenomena. We hypothesize that the levels of specific cytokines and miRNAs vary across the diabetes spectrum and unique signatures associated with them may serve as early biomarkers of the disease and provide insights into respective pathogenetic mechanisms. In this study, we measured the circulating levels of cytokines and microRNAs (miRNAs) in lean and obese humans with prediabetes (n = 21), T2D (n = 17), and healthy controls (n = 20) (ORIGINS trial, NCT02226640). Data were analyzed by fitting linear models adjusted for confounding variables (BMI, age, and gender in the diabetes context and age, gender, and diabetes status in the obesity context) and implementing nonparametric randomization-based tests for statistical inference. Group differences and correlations (r > 0.3) between variables with P < 0.05 were considered significant. False discovery rates (FDR) correcting for multiple testing were calculated using the Benjamini-Hochberg correction. We found a number of circulating cytokines and miRNAs deregulated in subjects with obesity, prediabetes, and T2D. Specifically, cytokines IL-6, IL-8, IL-10, IL-12, and SFRP4, as well as miRNAs miR-21, miR-24.1, miR-27a, miR-28-3p, miR-29b, miR-30d, miR-34a, miR-93, miR-126, miR-146a, miR-148, miR-150, miR-155, and miR-223, significantly changed across the diabetes spectrum, and were associated with measures of pancreatic islet β cell function and glycemic control, among others. Notably, SFRP4 was the only studied cytokine that was significantly associated with obesity, prediabetes, and T2D, which underscores the important role of this molecule during disease development and progression. Our data suggest that changes in circulating miRNAs and cytokines may have clinical utility as biomarkers of prediabetes.

Intensity- and Duration-Based Options to Regulate Endurance Training

The regulation of endurance training is usually based on the prescription of exercise intensity. Exercise duration, another important variable of training load, is rarely prescribed by individual measures and mostly set from experience. As the specific exercise duration for any intensity plays a substantial role regarding the different kind of cellular stressors, degree, and kind of fatigue as well as training effects, concepts integrating the prescription of both intensity and duration within one model are needed. An according recent approach was the critical power concept which seems to have a physiological basis; however, the mathematical approach of this concept does not allow applying the three zones/two threshold model of metabolism and its different physiological consequences. Here we show the combination of exercise intensity and duration prescription on an individual basis applying the power/speed to distance/time relationship. The concept is based on both the differentiation of intensities by two lactate or gas exchange variables derived turn points, and on the relationship between power (or velocity) and duration (or distance). The turn points define three zones of intensities with distinct acute metabolic, hormonal, and cardio-respiratory responses for endurance exercise. A maximal duration exists for any single power or velocity such as described in the power-duration relationship. Using percentages of the maximal duration allows regulating fatigue, recovery time, and adaptation for any single endurance training session. Four domains of duration with respect to induced fatigue can be derived from maximal duration obtained by the power-duration curve. For any micro-cycle, target intensities and durations may be chosen on an individual basis. The model described here is the first conceptual framework of integrating physiologically defined intensities and fatigue related durations to optimize high-performance exercise training.