Rapid upregulation and clearance of distinct circulating microRNAs after prolonged aerobic exercise

Moderate exercise has beneficial effects on mouse ischemic stroke by enhancing the functions of circulating endothelial progenitor cell-derived exosomes

Exosomes (EXs) are emerging as novel players in the beneficial effects induced by exercise on vascular diseases. We have recently revealed that moderate exercise enhances the function of circulating endothelial progenitor cell-derived EXs (cEPC-EXs) on protecting endothelial cells against hypoxia injury. However, the relationship between the changes of cEPC-EXs and the effects of exercise on ischemic stroke (IS) is unknown. Here, we investigated whether exercise-regulated EPC-EXs contribute to the beneficial effects of exercise on IS. C57BL/6 mice received moderate treadmill exercise (10 m/min) for 4-wks and then were subjected to middle cerebral artery occlusion (MCAO) stroke. The neurologic deficit score (NDS), infarct volume, microvessel density, cell apoptosis, angiogenesis/neurogenesis, sensorimotor functions were determined on day 2 (acute stage) and/or day 28 (chronic stage) post-stroke. The miR-126 and EPC-EX levels were analyzed by RT-PCR or nanoparticle tracking analysis combined with microbeads and used for correlation analyses. The function of EPC-EXs from exercised mice was detected in a hypoxia neuron model. Cell apoptosis, axon growth ability and gene expressions (cas-3 and Akt) were measured. Our data showed that: i) On day 2, exercised mice had decreased NDS and infarct volume, reduced cell apoptosis rate and cleaved cas-3 level, and a higher microvessel density than those in control (no-exercise) mice. The levels of EPC-EXs in plasma and brain tissue were raised and positively correlated in exercised mice. Meanwhile, the miR-126 level in cEPC-EXs and in ischemic tissue were upregulated in exercised mice. The EPC-EXs and their carried miR-126 levels negatively correlated with the infarct volume and cell apoptosis, whereas positively correlated with microvessel density. In addition, cEPC-EXs from exercised mice elicited protective effects on neurons against hypoxia-induced apoptosis and compromised axon growth ability which were blocked by miR-126 and PI3k inhibitors in vitro. ii) On day 28, exercised mice had less infarct volume, higher microvessel density, angiogenesis/neurogenesis and better sensorimotor functions. The levels of BDNF, p-TrkB/TrkB and p-Akt/Akt were upregulated in the brain of exercised mice. These recovery indexes correlated with the levels of cEPC-EXs and their miR-126. In conclusion, our data suggest that moderate exercise intervention has protective effects on the brain against MCAO-induced ischemic injury in both acute and chronic stages which might via the release of miR-126 enriched EPC-EXs.

Noncoding RNAs in Cardiovascular Disease: Current Knowledge, Tools and Technologies for Investigation, and Future Directions: A Scientific Statement From the American Heart Association

Background:

The discovery that much of the non–protein-coding genome is transcribed and plays a diverse functional role in fundamental cellular processes has led to an explosion in the development of tools and technologies to investigate the role of these noncoding RNAs in cardiovascular health. Furthermore, identifying noncoding RNAs for targeted therapeutics to treat cardiovascular disease is an emerging area of research. The purpose of this statement is to review existing literature, offer guidance on tools and technologies currently available to study noncoding RNAs, and identify areas of unmet need.

Methods:

The writing group used systematic literature reviews (including MEDLINE, Web of Science through 2018), expert opinion/statements, analyses of databases and computational tools/algorithms, and review of current clinical trials to provide a broad consensus on the current state of the art in noncoding RNA in cardiovascular disease.

Results:

Significant progress has been made since the initial studies focusing on the role of miRNAs (microRNAs) in cardiovascular development and disease. Notably, recent progress on understanding the role of novel types of noncoding small RNAs such as snoRNAs (small nucleolar RNAs), tRNA (transfer RNA) fragments, and Y-RNAs in cellular processes has revealed a noncanonical function for many of these molecules. Similarly, the identification of long noncoding RNAs that appear to play an important role in cardiovascular disease processes, coupled with the development of tools to characterize their interacting partners, has led to significant mechanistic insight. Finally, recent work has characterized the unique role of extracellular RNAs in mediating intercellular communication and their potential role as biomarkers.

Conclusions:

The rapid expansion of tools and pipelines for isolating, measuring, and annotating these entities suggests that caution in interpreting results is warranted until these methodologies are rigorously validated. Most investigators have focused on investigating the functional role of single RNA entities, but studies suggest complex interaction between different RNA molecules. The use of network approaches and advanced computational tools to understand the interaction of different noncoding RNA species to mediate a particular phenotype may be required to fully comprehend the function of noncoding RNAs in mediating disease phenotypes.

Modulation of MicroRNAs as a Potential Molecular Mechanism Involved in the Beneficial Actions of Physical Exercise in Alzheimer Disease

Alzheimer disease (AD) is one of the most common neurodegenerative diseases, affecting middle-aged and elderly individuals worldwide. AD pathophysiology involves the accumulation of beta-amyloid plaques and neurofibrillary tangles in the brain, along with chronic neuroinflammation and neurodegeneration. Physical exercise (PE) is a beneficial non-pharmacological strategy and has been described as an ally to combat cognitive decline in individuals with AD. However, the molecular mechanisms that govern the beneficial adaptations induced by PE in AD are not fully elucidated. MicroRNAs are small non-coding RNAs involved in the post-transcriptional regulation of gene expression, inhibiting or degrading their target mRNAs. MicroRNAs are involved in physiological processes that govern normal brain function and deregulated microRNA profiles are associated with the development and progression of AD. It is also known that PE changes microRNA expression profile in the circulation and in target tissues and organs. Thus, this review aimed to identify the role of deregulated microRNAs in the pathophysiology of AD and explore the possible role of the modulation of microRNAs as a molecular mechanism involved in the beneficial actions of PE in AD.

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.

Clinical utility of miRNA-1, miRNA-29g and miRNA-133s plasma levels in prostate cancer patients with high-intensity training after androgen-deprivation therapy

The randomized trials showed that the addition of training resistance program to androgen-deprivation therapy (ADT) had many beneficial effects for prostate cancer (PC) patients (significant protective effect on the volume of muscle mass) and the studies have revealed a panel of miRNAs, which are deregulate in PC and may serve as promising biomarkers of PC risk. The primary aim of our present study was to investigate the effect of exercise training to changes in body composition (muscle strength) and the secondary endpoint was to investigate the impact of an exercise training program on plasma levels of selected myogenic microRNAs (miRNAs) (miRNA-1, miRNA-29b, and miRNA-133) in PC patients undergoing the ADT. Effect of ADT and exercise intervention showed significant increase (experimental group vs. control group) the changes in body composition, free testosterone levels, IL-6 and plasma levels of myogenic miRNAs and significant reduced insulin serum levels. In conclusion, resistance training with ADT in the treatment of PC significantly changed the physical and metabolic function and the plasma levels of specific myogenic miRNAs. Our data support with the other publicized results.

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.

Serum Level of miR-1 and miR-155 as Potential Biomarkers of Stress-Resilience of NET-KO and SWR/J Mice

In the present study, we used three strains of mice with various susceptibility to stress: mice with knock-out of the gene encoding norepinephrine transporter (NET-KO), which are well characterized as displaying a stress-resistant phenotype, as well as two strains of mice displaying two different stress-coping strategies, i.e., C57BL/6J (WT in the present study) and SWR/J. The procedure of restraint stress (RS, 4 h) was applied, and the following behavioral experiments (the forced swim test and sucrose preference test) indicated that NET-KO and SWR/J mice were less sensitive to RS than WT mice. Then, we aimed to find the miRNAs which changed in similar ways in the serum of NET-KO and SWR/J mice subjected to RS, being at the same time different from the miRNAs found in the serum of WT mice. Using Custom TaqMan Array MicroRNA Cards, with primers for majority of miRNAs expressed in the serum (based on a preliminary experiment using the TaqMan Array Rodent MicroRNA A + B Cards Set v3.0, Thermo Fisher Scientific, Waltham, MA, USA) allowed the identification of 21 such miRNAs. Our further analysis focused on miR-1 and miR-155 and their targets—these two miRNAs are involved in the regulation of BDNF expression and can be regarded as biomarkers of stress-resilience.

Circulating microRNAs in Response to Exercise Training in Healthy Adults

Circulating microRNAs (miRNAs, miRs) have great potential as cardiac biomarkers and they are also being explored for their roles in intercellular communication and gene expression regulation. The analysis of circulating miRNAs in response to exercise would provide a deeper understanding of the molecular response to physical activity and valuable information for clinical practice. Here, eight male college students were recruited to participate in cardiopulmonary exercise testing (CPET) and 1 h acute exercise training (AET). Blood samples were collected and serum miRNAs involved in angiogenesis, inflammation and enriched in muscle and/or cardiac tissues were analyzed before and after cardiopulmonary exercise and acute exercise. The miRNAs we detected were miR-1, miR-20a, miR-21, miR-126, miR-133a, miR-133b, miR-146, miR155, miR-208a, miR-208b, miR-210, miR-221, miR-222, miR-328, miR-378, miR-499, and miR-940. We found that serum miR-20a was decreased significantly after CPET and serum miR-21 was increased after AET. In addition, no robust correlation was identified between the changes of these miRNAs and makers of cardiac function and exercise capacity, which indicates a distinct adaptation of these miRNAs to exercise. Future studies are highly needed to define the potential use of these circulating miRNAs as useful biomarkers of exercise training, and disclose the biological function of circulating miRNAs as physiological mediators of exercise-induced cardiovascular adaptation.

Novel Mechanisms of Exercise-Induced Cardioprotective Factors in Myocardial Infarction

Exercise training has been reported to ameliorate heart dysfunction in both humans and animals after myocardial infarction (MI). Exercise-induced cardioprotective factors have been implicated in mediating cardiac repair under pathological conditions. These protective factors secreted by or enriched in the heart could exert cardioprotective functions in an autocrine or paracrine manner. Extracellular vesicles, especially exosomes, contain key molecules and play an essential role in cell-to-cell communication via delivery of various factors, which may be a novel target to study the mechanism of exercise-induced benefits, besides traditional signaling pathways. This review is designed to demonstrate the function and underlying protective mechanism of exercise-induced cardioprotective factors in MI, with an aim to offer more potential therapeutic targets for MI.

The Association Between Atrial Fibrillation and Endurance Physical Activity: How Much is too Much?

Atrial fibrillation (AF) is the most common arrhythmia in middle-aged athletes. Physical exercise performed in a regular basis has been shown to be beneficial for cardiovascular health. Moderate physical exercise, aside from producing a nice, peaceful and well-being sensation, has been associated with a reduced risk of AF. However, more strenuous endurance exercise, like the one experiencing marathon runners, seems to increase the risk of AF in healthy athletes without organic heart disease. On the other hand, low physical activity was found to be a risk factor for the appearance of AF. Nevertheless, the relationship of exercise to AF is complex, influenced by the intensity and the duration of the physical activity, and seems to have a U-shaped relationship with the greatest levels of physical activity possibly increasing AF incidence. There is cumulative data associating moderate physical activity to reduced AF incidence, hence physicians should recommend moderate exercise training to patients with AF. This may not only reduce AF risk, but would also contribute to an overall cardiovascular benefit. However, since there is also important data suggesting significant increased incidence of AF in elite athletes with long-term endurance physical activity, it may be a serious concern to go to the extreme. In most things in life it is much better and wiser to be well balanced, always in equilibrium.

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.

Epigenetic Modifications as Outcomes of Exercise Interventions Related to Specific Metabolic Alterations: A Systematic Review

BACKGROUND

Chronic diseases arise as a consequence of an unhealthy lifestyle primarily characterized by physical inactivity and unbalanced diets. Regular physical activity can improve health, and there is consistent evidence that these improvements may be the result of epigenetic modifications.

OBJECTIVE

To identify epigenetic modificationsas outcomes of exercise interventions related to specific metabolic alterations.

METHODS

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocols (PRISMA-P) methodology for manuscript research and preparation was followed using PubMed and EBSCO databases for literature review. Out of 2,638 articles identified, only 34 articles met the inclusion criteria.

RESULTS

The sections of the review were organized by metabolic alterations in which studies were grouped according to healthy, diseased, and trained individuals. Resistance exercise in humans induced epigenetic changes in pathways associated with energy metabolism and insulin sensitivity, contributing to healthy skeletal muscle. Endurance exercise also caused modifications in biomarkers associated to metabolic alterations through changes in DNA methylation and the expression of specific miRNAs. However, both resistance and endurance exercise are necessary to obtain a better physiological adaptation and a combination of both seems to be needed to properly tackle the increasing prevalence of non-communicable pathologies.

CONCLUSION

Given the heterogeneity and complexity of the existing literature, it is currently not possible to propose a specific recommendation about the type, intensity, or duration of exercise that could be beneficial for different subsets of the population (healthy, diseased, and/or trained). Nevertheless, this review highlights the importance of exercise for health and shows the need to perform more research in this emerging area to identify epigenetic biomarkers that could serve as indicators of exercise adaptations.

The Development of a Personalised Training Framework: Implementation of Emerging Technologies for Performance

Over the last decade, there has been considerable interest in the individualisation of athlete training, including the use of genetic information, alongside more advanced data capture and analysis techniques. Here, we explore the evidence for, and practical use of, a number of these emerging technologies, including the measurement and quantification of epigenetic changes, microbiome analysis and the use of cell-free DNA, along with data mining and machine learning. In doing so, we develop a theoretical model for the use of these technologies in an elite sport setting, allowing the coach to better answer six key questions: (1) To what training will my athlete best respond? (2) How well is my athlete adapting to training? (3) When should I change the training stimulus (i.e., has the athlete reached their adaptive ceiling for this training modality)? (4) How long will it take for a certain adaptation to occur? (5) How well is my athlete tolerating the current training load? (6) What load can my athlete handle today? Special consideration is given to whether such an individualised training framework will outperform current methods as well as the challenges in implementing this approach.

Moderate Exercise Enhances Endothelial Progenitor Cell Exosomes Release and Function

PURPOSE

Exercise has cardiovascular benefits which might be related to endothelial progenitor cells (EPC). Meanwhile, there is evidence suggesting that EPC-derived exosomes (EPC-EX) promote vascular repair and angiogenesis through their carried microRNA (miR)-126. In this study, we investigated whether exercise could increase the levels of circulating EPC-EX and their miR-126 cargo, and by which promote the protective function of EPC-EX on endothelial cells (EC).

METHODS

Plasma EPC-EX from sedentary, low, or moderate exercise mice, respectively, denoted as EPC-EX, EPC-EX, and EPC-EX, were isolated using microbead-based sorting techniques and characterized by nanoparticle tracking analysis, Western blot, and quantitative real-time polymerase chain reaction assessments of biomarkers and miR-126. High glucose (25 mM) with hypoxia (1% O2) was used for inducing an EC injury model. The injured EC were treated by coculturing with vehicle, EPC-EX, EPC-EX, EPC-EX, or EPC-EX + anti-miR-126. After that, EC were used for flow cytometry analysis of apoptosis, assessments of tube formation and migration, and measurements of miR-126 level and its downstream sprouty-related protein-1 (SPRED1) and vascular endothelial growth factor (VEGF).

RESULTS

1) Isolated EPC-EX positively expressed exosomal markers (CD63 and Tsg101) and EPC markers (CD34 and VEGFR2). 2) Exercise intensity dependently elevated plasma level of EPC, EPC-EX/EPC ratio, and miR-126 expression in EPC and EPC-EX. 3) Injured EC displayed apoptosis increment, angiogenic dysfunction and miR-126 reduction. 4) EPC-EX had better effects than EPC-EX and EPC-EX on alleviating those changes of injured EC, accompanied with SPRED1 downregulation and VEGF upregulation. 5) The effects of EPC-EX were abolished by miR-126 knockdown.

CONCLUSIONS

Our data demonstrate that exercise can increase EPC-EX release and miR-126 level and enhance the effects of EPC-EX on protecting EC against injury through the SPRED1/VEGF pathway.

Distinct plasma gradients of microRNA-204 in the pulmonary circulation of patients suffering from WHO Groups I and II pulmonary hypertension

Pulmonary hypertension (PH), a heterogeneous vascular disease, consists of subtypes with overlapping clinical phenotypes. MicroRNAs, small non-coding RNAs that negatively regulate gene expression, have emerged as regulators of PH pathogenesis. The muscle-specific micro RNA (miR)-204 is known to be depleted in diseased pulmonary artery smooth muscle cells (PASMCs), furthering proliferation and promoting PH. Alterations of circulating plasma miR-204 across the trans-pulmonary vascular bed might provide mechanistic insights into the observed intracellular depletion and may help distinguish PH subtypes. MiR-204 levels were quantified at sequential pulmonary vasculature sites in 91 patients with World Health Organization (WHO) Group I pulmonary arterial hypertension (PAH) (n = 47), Group II PH (n = 22), or no PH (n = 22). Blood from the right atrium/superior vena cava, pulmonary artery, and pulmonary capillary wedge was collected. Peripheral blood mononuclear cells (PBMCs) were isolated (n = 5/group). Excretion of miR-204 by PAH-PASMCs was also quantified in vitro. In Group I patients only, miR-204 concentration increased sequentially along the pulmonary vasculature (log fold-change slope = 0.22 [95% CI = 0.06–0.37], P = 0.008). PBMCs revealed insignificant miR-204 variations among PH groups (P = 0.12). Cultured PAH-PAMSCs displayed a decrease of intracellular miR-204 (P = 0.0004), and a converse increase of extracellular miR-204 (P = 0.0018) versus control. The stepwise elevation of circulating miR-204 across the pulmonary vasculature in Group I, but not Group II, PH indicates differences in muscle-specific pathobiology between subtypes. Considering the known importance of miR-204 in PH, these findings may suggest pathologic excretion of miR-204 in Group I PAH by PASMCs, thereby accounting for decreased intracellular miR-204 concentration.

Normalization strategies differently affect circulating miRNA profile associated with the training status

MicroRNAs are fine regulators of the whole-body adaptive response but their use as biomarkers is limited by the lack of standardized pre- and post-analytical procedures. This work aimed to compare different normalization approaches for RT-qPCR data analyses, in order to identify the most reliable and reproducible method to analyze circulating miRNA expression profiles in sedentary and highly-trained subjects. As the physically active status is known to affect miRNA expression, they could be effective biomarkers of the homeostatic response. Following RNA extraction from plasma, a panel of 179 miRNAs was assayed by RT-qPCR and quantified by applying different normalization strategies based on endogenous miRNAs and exogenous oligonucleotides. hsa-miR-320d was found as the most appropriate reference miRNA in reducing the technical variability among the experimental replicates and, hence, in highlighting the inter-cohorts differences. Our data showed an association between the physically active status and specific skeletal muscle- and bone-associated circulating miRNAs profiles, revealing that established epigenetic modifications affect the baseline physiological status of these tissues. Since different normalization strategies led to different outputs, in order to avoid misleading interpretation of data, we remark the importance of the accurate choice of the most reliable normalization method in every experimental setting.

Exercise Training-Induced Changes in MicroRNAs: Beneficial Regulatory Effects in Hypertension, Type 2 Diabetes, and Obesity

MicroRNAs are small non-coding RNAs that regulate gene expression post-transcriptionally. They are involved in the regulation of physiological processes, such as adaptation to physical exercise, and also in disease settings, such as systemic arterial hypertension (SAH), type 2 diabetes mellitus (T2D), and obesity. In SAH, microRNAs play a significant role in the regulation of key signaling pathways that lead to the hyperactivation of the renin-angiotensin-aldosterone system, endothelial dysfunction, inflammation, proliferation, and phenotypic change in smooth muscle cells, and the hyperactivation of the sympathetic nervous system. MicroRNAs are also involved in the regulation of insulin signaling and blood glucose levels in T2D, and participate in lipid metabolism, adipogenesis, and adipocyte differentiation in obesity, with specific microRNA signatures involved in the pathogenesis of each disease. Many studies report the benefits promoted by exercise training in cardiovascular diseases by reducing blood pressure, glucose levels, and improving insulin signaling and lipid metabolism. The molecular mechanisms involved, however, remain poorly understood, especially regarding the participation of microRNAs in these processes. This review aimed to highlight microRNAs already known to be associated with SAH, T2D, and obesity, as well as their possible regulation by exercise training.

Circulating microRNA as Emerging Biomarkers of Exercise

An interest has recently emerged in the role of circulating microRNAs (c-miRNAs) as posttranscriptional regulators, intercellular communicators and, especially, as potential biomarkers of the systemic response to acute exercise and training. We propose that, with the limited, heterogeneous, and mainly descriptive information currently available, c-miRNAs do not provide a reliable biomarker of exercise in healthy or diseased individuals.

Understanding Key Mechanisms of Exercise-Induced Cardiac Protection to Mitigate Disease: Current Knowledge and Emerging Concepts

The benefits of exercise on the heart are well recognized, and clinical studies have demonstrated that exercise is an intervention that can improve cardiac function in heart failure patients. This has led to significant research into understanding the key mechanisms responsible for exercise-induced cardiac protection. Here, we summarize molecular mechanisms that regulate exercise-induced cardiac myocyte growth and proliferation. We discuss in detail the effects of exercise on other cardiac cells, organelles, and systems that have received less or little attention and require further investigation. This includes cardiac excitation and contraction, mitochondrial adaptations, cellular stress responses to promote survival (heat shock response, ubiquitin-proteasome system, autophagy-lysosomal system, endoplasmic reticulum unfolded protein response, DNA damage response), extracellular matrix, inflammatory response, and organ-to-organ crosstalk. We summarize therapeutic strategies targeting known regulators of exercise-induced protection and the challenges translating findings from bench to bedside. We conclude that technological advancements that allow for in-depth profiling of the genome, transcriptome, proteome and metabolome, combined with animal and human studies, provide new opportunities for comprehensively defining the signaling and regulatory aspects of cell/organelle functions that underpin the protective properties of exercise. This is likely to lead to the identification of novel biomarkers and therapeutic targets for heart disease.

MicroRNAs in heart and circulation during physical exercise

Exercise training is beneficial to the cardiovascular system. MicroRNAs (miRNAs, miRs) are a class of conserved non-coding RNAs and play a wide-ranging role in the regulation of eukaryotic gene expression. Exercise training alters the expression levels of large amounts of miRNAs in the heart. In addition, circulating miRNAs appear to be regulated by exercise training. In this review, we will summarize recent advances in the regulation of miRNAs during physical exercise intervention in various cardiovascular diseases, including pathologic cardiac hypertrophy, myocardial fibrosis, ischemia-reperfusion injury, myocardial infarction, and heart failure. The regulatory role of circulating miRNAs after exercise training was also reviewed. In conclusion, miRNAs might be a valuable target for treatment of cardiovascular diseases and have great potential as biomarkers for assessment of physical performance.

Circulatory exosomal miRNA following intense exercise is unrelated to muscle and plasma miRNA abundances

MicroRNAs (miRNAs) regulate gene expression via transcript degradation and translational inhibition, and they may also function as long distance signaling molecules. Circulatory miRNAs are either protein-bound or packaged within vesicles (exosomes). Ten young men (24.6 ± 4.0 yr) underwent a single bout of high-intensity interval cycling exercise. Vastus lateralis biopsies and plasma were collected immediately before and after exercise, as well as 4 h following the exercise bout. Twenty-nine miRNAs previously reported to be regulated by acute exercise were assessed within muscle, venous plasma, and enriched circulatory exosomes via qRT-PCR. Of the 29 targeted miRNAs, 11 were altered in muscle, 8 in plasma, and 9 in the exosome fraction. Although changes in muscle and plasma expression were bidirectional, all regulated exosomal miRNAs increased following exercise. Three miRNAs were altered in all three sample pools (miR-1-3p, -16-5p, and -222-3p), three in both muscle and plasma (miR-21-5p, -134-3p, and -107), three in both muscle and exosomes (miR-23a-3p, -208a-3p, and -150-5p), and three in both plasma and exosomes (miR-486-5p, -126-3p, and -378a-5p). There was a marked discrepancy between the observed alterations between sample pools. A subset of exosomal miRNAs increased in abundance following exercise, suggesting an exercise-induced release of exosomes enriched in specific miRNAs. The uniqueness of the exosomal miRNA response suggests its relevance as a sample pool that needs to be further explored in better understanding biological functions.

Evolving systems biology approaches to understanding non-coding RNAs in pulmonary hypertension

Our appreciation of the roles of non-coding RNAs, in particular microRNAs, in the manifestation of pulmonary hypertension (PH) has advanced considerably over the past decade. Comprised of small nucleotide sequences, microRNAs have demonstrated critical and broad regulatory roles in the pathogenesis of PH via the direct binding to messenger RNA transcripts for degradation or inhibition of translation, thereby exerting a profound influence on cellular activity. Yet, as inherently pleiotropic molecules, microRNAs have been difficult to study using traditional, reductionist approaches alone. With the advent of high-throughput -omics technologies and more advanced computational modelling, the study of microRNAs and their multi-faceted and complex functions in human disease serves as a fertile platform for the application of systems biology methodologies in combination with traditional experimental techniques. Here, we offer our viewpoint of past successes of systems biology in elucidating the otherwise hidden actions of microRNAs in PH, as well as areas for future development to integrate these strategies into the discovery of RNA pathobiology in this disease. We contend that such successful applications of systems biology in elucidating the functional architecture of microRNA regulation will further reveal the molecular mechanisms of disease, while simultaneously revealing potential diagnostic and therapeutic strategies in disease amelioration.

Children's screen time alters the expression of saliva extracellular miR-222 and miR-146a

An imbalance between energy uptake and energy expenditure is the most important reason for increasing trends in obesity starting from early in life. Extracellular miRNAs are expressed in all bodily fluids and their expression is influenced by a broad range of stimuli. We examined whether screen time, physical activity and BMI are associated with children’s salivary extracellular miR-222 and miR-146a expression. In 80 children the extracellular fraction of saliva was obtained by means of differential centrifugation and ultracentrifugation. Expression levels of miR-222 and miR-146a were profiled by qPCR. We studied the association between children’s salivary extracellular miRNA expression and screen time, physical activity and BMI using mixed models, while accounting for potential confounders. We found that higher screen time was positively associated with salivary extracellular miR-222 and miR-146a levels. On average, one hour more screen time use per week was associated with a 3.44% higher miR-222 (95% CI: 1.34 to 5.58; p = 0.002) and 1.84% higher miR-146a (95% CI: −0.04 to 3.75; p = 0.055) level in saliva. BMI and physical activity of the child were not significantly associated with either miR-222 or miR-146a. A sedentary behaviour, represented by screen time use in children, is associated with discernible changes in salivary expression of miR-146a and or miR-222. These miRNA targets may emerge attractive candidates to explore the role of these exposures in developmental processes of children’s health.

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.

MicroRNAs Mediate Beneficial Effects of Exercise in Heart

MicroRNAs (miRNAs, miRs), a group of small non-coding RNAs, repress gene expressions at posttranscriptional level in most cases and are involved in cardiovascular physiology and disease pathogenesis. Increasing evidence has proved that miRNAs are potential regulators of exercise induced cardiac growth and mediate the benefits of exercise in a variety of cardiovascular diseases. In this chapter, we will review the regulatory effects of miRNAs in cardiac adaptations to exercise, and summarize their cardioprotective effects against myocardial infarction, ischemia/reperfusion injury, heart failure, diabetic cardiomyopathy, atherosclerosis, hypertension, and pulmonary hypertension. Also, we will introduce circulating miRNAs in response to acute and chronic exercise. Therefore, miRNAs may serve as novel therapeutic targets and potential biomarkers for cardiovascular diseases.

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.

Cardiovascular disease-related miRNAs expression: potential role as biomarkers and effects of training exercise

Cardiovascular diseases (CVDs) are one of the most important causes of mortality worldwide, therefore the need of effective preventive strategies is imperative. Aging is associated with significant changes in both cardiovascular structure and function that lower the threshold for clinical signs and symptoms, making older people more susceptible to CVDs morbidity and mortality. microRNAs (miRNAs) modulate gene expression at post-transcriptional level and increasing evidence has shown that miRNAs are involved in cardiovascular physiology and in the pathogenesis of CVDs. Physical activity is recommended by the medical community and the cardiovascular benefits of exercise are multifactorial and include important systemic effects on skeletal muscle, the peripheral vasculature, metabolism, and neuroendocrine systems, as well as beneficial modifications within the myocardium itself. In this review we describe the role of miRNAs and their dysregulation in several types of CVDs. We provide an overview of miRNAs in CVDs and of the effects of physical activity on miRNA regulation involved in both cardiovascular pathologies and age-related cardiovascular changes and diseases. Circulating miRNAs in response to acute and chronic sport exercise appear to be modulated following training exercise, and may furthermore serve as potential biomarkers for CVDs and different age-related CVDs.

Specific circulating microRNAs display dose-dependent responses to variable intensity and duration of endurance exercise

Circulating microRNAs (c-miRNAs), plasma-based noncoding RNAs that control posttranscriptional gene expression, mediate processes that underlie phenotypical plasticity to exercise. The relationship and biological relevance between c-miRNA expression and variable dose exercise exposure remains uncertain. We hypothesized that certain c-miRNAs respond to changes in exercise intensity and/or duration in a dose-dependent fashion. Muscle release of such c-miRNAs may then deplete intracellular stores, thus facilitating gene reprogramming and exercise adaptation. To address these hypotheses, healthy men participated in variable intensity ( n = 12, 30 × 1 min at 6, 7, and 8 miles/h, order randomized) and variable duration ( n = 14, 7 × 1 mile/h for 30, 60, and 90 min, order randomized) treadmill-running protocols. Muscle-enriched c-miRNAs (i.e., miRNA-1 and miRNA-133a) and others with known relevance to exercise were measured before and after exercise. c-miRNA responses followed three profiles: 1) nonresponsive (miRNA-21 and miRNA-210), 2) responsive to exercise at some threshold but without dose dependence (miRNA-24 and miRNA-146a), and 3) responsive to exercise with dose dependence to increasing intensity (miRNA-1) or duration (miRNA-133a and miRNA-222). We also studied aerobic exercise-trained mice, comparing control, low-intensity (0.5 km/h), or high-intensity (1 km/h) treadmill-running protocols over 4 wk. In high- but not low-intensity-trained mice, we found increased plasma c-miR-133a along with decreased intracellular miRNA-133a and increased serum response factor, a known miR-133a target gene, in muscle. Characterization of c-miRNAs that are dose responsive to exercise in humans and mice supports the notion that they directly mediate physiological adaptation to exercise, potentially through depletion of intracellular stores of muscle-specific miRNAs. NEW & NOTEWORTHY In this study of humans and mice, we define circulating microRNAs in plasma that are dose responsive to exercise. Our data support the notion that these microRNAs mediate physiological adaptation to exercise potentially through depletion of intracellular stores of muscle-specific microRNAs and releasing their inhibitory effects on target gene expression.

Circulating myomiRs: a new class of biomarkers to monitor skeletal muscle in physiology and medicine

MicroRNAs (miRNA) are small non-coding RNAs that target mRNAs and are consequently involved in the post-transcriptional regulation of gene expression. Some miRNAs are ubiquitously expressed in tissue, while others are tissue-specific or tissue-enriched. miRNAs can be released by cells and are found in various biofluids, including serum and plasma. Thus, measuring miRNAs in the circulation may provide information on the originating tissue or cells. MyomiRs are described as striated muscle-specific or muscle-enriched miRNAs. Their circulating levels can be measured and have been proposed to be new biomarkers of physiological and pathological muscle processes. The aims of this review are to summarize the current knowledge of circulating myomiRs, to identify the types of information they can provide about skeletal muscle, and to determine how to apply that information in the fields of research and medicine.

Circulating miR-21, miR-378, and miR-940 increase in response to an acute exhaustive exercise in chronic heart failure patients

Congestive heart failure (CHF) is a major cause of hospitalizations, morbidity, and mortality in Western societies. In addition to optimal medical and device therapy, exercise training is an important adjunct treatment option for CHF patients. MicroRNAs (miRNAs, miRs) participate in a variety of physiological and pathological processes. Dynamic regulation of circulating miRNAs during exercise in healthy persons and athletes has recently been documented, however, the response of circulating miRNAs to exercise in CHF patients is undetermined. Twenty-eight CHF patients underwent a symptom-limited incremental cardiopulmonary exercise test on a bicycle ergometer using a standardized exercise protocol of revised Ramp10 programs at Shanghai Tongji Hospital. Blood samples were collected before and immediately after an acute exercise session. RNA was extracted from the serum and selected miRNAs were determined using quantitative polymerase chain reactions. Moreover, inflammatory and muscle damage markers were determined by enzyme linked immunosorbent assays. We found that serum miR-21, miR-378 and miR-940 levels were significantly up-regulated immediately following an acute exercise while the rest were not changed. In addition, no robust correlation was identified between changes of these miRNAs and exercise capacity, muscle damage or inflammation. In conclusion, serum miR-21, miR-378, and miR-940 increase in response to an acute exhaustive exercise in CHF patients. Further studies are needed to clarify the potential use of circulating miRNAs as biomarkers of exercise adaptation in CHF patients, and if they have any use as prognostic markers of cardiovascular outcomes.

Expression analysis of selected classes of circulating exosomal miRNAs in soccer players as an indicator of adaptation to physical activity

Recently studies have shown that, depending on the type of training and its duration, the expression levels of selected circulating myomiRNAs (c-miR-27a,b, c-miR-29a,b,c, c-miR-133a) differ and correlate with the physiological indicators of adaptation to physical activity. To analyse the expression of selected classes of miRNAs in soccer players during different periods of their training cycle. The study involved 22 soccer players aged 17-18 years. The multi-stage 20-m shuttle run test was used to estimate VO2 max among the soccer players. Samples serum were collected at baseline (time point I), after one week (time point II), and after 2 months of training (time point III). The analysis of the relative quantification (RQ) level of three exosomal myomiRNAs, c-miRNA-27b, c-miR-29a, and c-miR-133, was performed by quantitative polymerase chain reaction (qPCR) at three time points - before the training, after 1 week of training and after the completion of two months of competition season training. The expression analysis showed low expression levels (according to references) of all evaluated myomiRNAs before the training cycle. Analysis performed after a week of the training cycle and after completion of the entire training cycle showed elevated expression of all tested myomiRNAs. Statistical analysis revealed significant differences between the first and the second time point in soccer players for c-miR-27b and c-miR-29a; between the first and the third time point for c-miR-27b and c-miR-29a; and between the second and the third time point for c-miR-27b. Statistical analysis showed a positive correlation between the levels of c-miR-29a and VO2 max. Two months of training affected the expression of c-miR-27b and miR-29a in soccer players. The increased expression of c-miR-27b and c-miR-29 with training could indicate their probable role in the adaptation process that takes place in the muscular system. Possibly, the expression of c-miR-29a will be found to be involved in cardiorespiratory fitness in future research.

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.

Transition from physical activity to inactivity increases skeletal muscle miR-148b content and triggers insulin resistance

This study investigated miR‐148b as a potential physiological actor of physical inactivity‐induced effects in skeletal muscle. By using animal and human protocols, we demonstrated that the early phase of transition toward inactivity was associated with an increase in muscle miR‐148b content, which triggered the downregulation of NRAS and ROCK1 target genes. Using human myotubes, we demonstrated that overexpression of miR‐148b decreased NRAS and ROCK1 protein levels, and PKB phosphorylation and glucose uptake in response to insulin. Increase in muscle miR‐148b content might thus participate in the decrease in insulin sensitivity at the whole body level during the transition toward physical inactivity.

Epigenetic effects of physical activity in elderly patients with cardiovascular disease

Cardiovascular disease (CVD) is an important public health problem affecting especially the elderly. Over the past 20years, an increasing number of studies have examined its underlying pathophysiological mechanisms and new therapies are continually being discovered. However, despite considerable progress in CVD management, mortality and morbidity remain a major healthcare concern, and frequent hospital admissions compromise the daily life and social activities of these patients. Physical activity has emerged as an important non-pharmacological adjunctive therapy for CVD in older patients, especially for heart failure patients, exerting its beneficial effects on mortality, morbidity, and functional capacity. The mechanisms underlying the cardiovascular benefits of exercise are not wholly clear. Mounting evidence suggest that epigenetic modifications, such as DNA methylation, histone post-translational modifications (hPTMs) and non-coding RNA, especially microRNAs (miRNAs), may be induced by physical activity. Recently, a number of miRNAs have been identified as key players in gene expression modulation by exercise. MiRNAs are synthesized by living cells and actively released into the bloodstream through different shuttles. The epigenetic information, thus carried and delivered, is involved in the interplay between environmental factors, including physical activity, and individual genetic make-up. We review and discuss the effects of exercise on age-related CVDs, focusing on circulating miRNA (c-miRNAs) modulation. Epigenetic mechanisms may have clinical relevance in CVD prevention and management; since they can be modified, insights into the implications of lifestyle-related epigenetic changes in CVD etiology may help develop therapeutic protocols of exercise training that can be suitable and effective for elderly patients.

Circulating MicroRNA Are Predictive of Aging and Acute Adaptive Response to Resistance Exercise in Men

Circulating microRNA (c-miRNA) have the potential to function as novel noninvasive markers of the underlying physiological state of skeletal muscle. This investigation sought to determine the influence of aging on c-miRNA expression at rest and following resistance exercise in male volunteers (Young: n = 9; Older: n = 9). Primary findings were that fasting c-miRNA expression profiles were significantly predictive of aging, with miR-19b-3p, miR-206, and miR-486 distinguishing between age groups. Following resistance exercise, principal component analysis revealed a divergent response in expression of 10 c-miRNA, where expression profiles were upregulated in younger and downregulated in older participants. Using Ingenuity Pathway Analysis to test c-miRNA-to-mRNA interactions in skeletal muscle, it was found that response of c-miRNA to exercise was indicative of an anabolic response in younger but not older participants. These findings were corroborated with a positive association observed with the phosphorylation status of p-AktSer473 and p-S6K1Thr389 and expression of miR-19a-3p, miR-19b-3p, miR-20a-5p, miR-26b-5p, miR-143-3p, and miR-195-5p. These important findings provide compelling evidence that dysregulation of c-miRNA expression with aging may not only serve as a predictive marker, but also reflect underlying molecular mechanisms resulting in age-associated declines in skeletal muscle mass, increased fat mass, and "anabolic resistance."

Exercise and Competitive Sport: Physiology, Adaptations, and Uncertain Long-Term Risks

OPINION STATEMENT

The benefits of regular and moderate exercise training on cardiovascular outcomes have been well established. In addition, strenuous exercise training leads to corollary cardiac structural and functional adaptations that are sport-specific and facilitate athletic performance. In this review, the normal physiologic and hemodynamic changes that occur during exercise and the subsequent differential exercise-induced cardiac remodeling patterns that develop will be discussed. Paradoxically, recent data have raised concern about the long-term impact of higher doses of physical activity and exercise on mortality and cardiovascular health outcomes. We will discuss important aspects of these controversial data and review the supporting evidence as well as the limitations of prior research. Specifically, we will address the association between high levels of exercise and relative reductions in overall mortality, increased risk of atrial fibrillation, arrhythmogenic cardiac remodeling, and accelerated coronary artery calcifications. For the practitioner, this review aims to detail these contemporary sports cardiology controversies and highlights the critical need to incorporate shared decision making with the athlete in dealing with the uncertainties that exist. Finally, we will discuss key "athlete-specific" variables that should be considered in the design of future important research in this arena.

Exercise-Induced Cardioprotection and the Therapeutic Potential of RIPC

In the search for innovative solutions to treat ischemic heart disease, recent basic science and clinical approaches have focused on remote ischemic preconditioning (RIPC). Remote ischemic preconditioning involves short intervals of limb blood flow occlusion by the application of a blood pressure cuff inflated to a suprasystolic pressure. The promise of RIPC in the development of new cardioprotective therapies is founded on the premise that it is cost-effective, technically simple, and overcomes many logistical and biochemical hurdles associated with other ischemic preconditioning approaches. However, RIPC as a research subarea is still in its infancy and clinical applications for individuals at high risk of cardiovascular disease remain elusive. The thesis of the current review is that observational and mechanistic similarities between exercise-induced preconditioning and RIPC may reveal novel therapeutic links to cardioprotection. While reductionist understanding of the exercised heart is still in the formative stages, available mechanistic knowledge of exercise-induced cardioprotection is juxtaposed to RIPC and potential implications discussed. In total, additional research is needed in order to fully appreciate the mechanistic and translative connections between exercise and RIPC. Nonetheless, existing rationale are strong and suggest that RIPC approaches may be helpful in the development and application to pharmacologic interventions in those with ischemic heart disease.

Dose-Response of High-Intensity Training (HIT) on Atheroprotective miRNA-126 Levels

Aim: MicroRNA-126 (miR-126) exerts beneficial effects on vascular integrity, angiogenesis, and atherosclerotic plaque stability. The purpose of this investigation was to analyze the dose-response relationship of high-intensity interval training (HIIT) on miR-126-3p and -5p levels. Methods: Sixty-one moderately trained individuals (females = 31 [50.8%]; 22.0 ± 1.84 years) were consecutively recruited and allocated into three matched groups using exercise capacity. During a 4-week intervention a HIIT group performed three exercise sessions/week of 4 × 30 s at maximum speed (all-out), a progressive HIIT (proHIIT) group performed three exercise sessions/week of 4 × 30 s at maximum speed (all-out) with one extra session every week (up to 7 × 30 s) and a low-intensity training (LIT) control group performed three exercise sessions/week for 25 min <75% of maximum heart rate. Exercise miR-126-3p/-5p plasma levels were determined using capillary blood from earlobes. Results: No exercise-induced increase in miR-126 levels was detected at baseline, neither in the LIT (after 25 min low-intensity running) nor the HIIT groups (after 4 min of high-intensity running). After the intervention, the LIT group presented an increase in miR-126-3p, while in the HIIT group, miR-126-3p levels were still reduced (all p < 0.05). An increase for both, miR-126-3p and -5p levels (all p < 0.05, pre- vs. during and post-exercise) was detected in the proHIIT group. Between group analysis revealed that miR-126-3p levels after LIT and proHIIT increased by 2.12 ± 2.55 and 1.24 ± 2.46 units (all p < 0.01), respectively, compared to HIIT (-1.05 ± 2.6 units). Conclusions: LIT and proHIIT may be performed to increase individual miR-126 levels. HIIT without progression was less effective in increasing miR-126.

Time-course responses of circulating microRNAs to three resistance training protocols in healthy young men

Circulating microRNAs (c-miRNAs) in human plasma have been described as a potential marker of exercise. The present study investigated the effects of three acute resistance training (RT) protocols on the time-course changes of the c-miRNAs profiles in young males. The subjects (n = 45) were randomly divided into three groups: muscular strength endurance (SE), muscular hypertrophy (MH) and maximum strength (MS). Venous blood samples were obtained before exercise and immediately, 1 h and 24 h after each RT protocol to assess the following biological parameters: c-miRNAs, anabolic and catabolic hormones, inflammatory cytokines and muscle damage markers. The results revealed that the levels of two c-miRNAs (miR-208b and miR-532), six c-miRNAs (miR-133a, miR-133b, miR-206, miR-181a, miR-21 and miR-221) and two c-miRNAs (miR-133a and miR-133b) changed significantly in response to the SE, MH and MS protocols (p < 0.05), respectively. The nature and dynamic processes of the c-miRNAs response were likely influenced by the RT modality and intensity. Moreover, miR-532 was negatively correlated with insulin-like growth factor-1 and positively correlated with interleukin-10, whereas miR-133a was negatively correlated with cortisol and positively correlated with testosterone/cortisol. These findings suggest that these c-miRNAs may serve as markers for monitoring the RT responses.

Obesity Downregulates MicroRNA-126 Inducing Capillary Rarefaction in Skeletal Muscle: Effects of Aerobic Exercise Training

Background. We investigated the effects of exercise training (ET) on miR-126 levels and skeletal muscle angiogenesis in obese Zucker rats. Results. Zucker rats were randomly assigned to sedentary and swimming-trained groups: lean sedentary (LS) and trained (LTR); obese sedentary (OB) and trained (OBTR). The OB group displayed capillary rarefaction compared with the LS group. In contrast, ET increased the capillary/fiber ratio by 38% in the LTR group and normalized capillary rarefaction in the OBTR group. VEGF, PI3K, and eNOS levels were reduced in the skeletal muscle of the OB group. ET normalized VEGF, PI3K, and eNOS levels in OBTR, contributing to vascular network homeostasis. PI3KR2 inhibits PI3K, a key mediator of the VEGF signaling pathway. Obesity decreased miR-126 and increased PI3KR2 levels compared with the LS group. However, ET normalized miR-126 levels in the OBTR group versus the LS group and decreased expression of PI3KR2. Conclusion. Our findings show that obesity leads to skeletal muscle capillary rarefaction, which is regulated by decreased miR-126 levels and increased PI3KR2. Inversely, ET normalizes miR-126 levels and VEGF signaling and should be considered an important therapeutic strategy for vascular disorders.

Exosomes Mediate the Beneficial Effects of Exercise

It is known that moderate exercise can prevent the development of cardiovascular diseases, but the exact molecular mechanisms mediating cardioprotective effect of exercise remain unknown. Emerging evidence suggests that exercise has great impact on the biogenesis of exosomes, which have been found in both interstitial fluid and circulation, and play important roles in cellular communication. Exosomes carry functional molecules such as mRNAs, microRNA, and specific proteins, which can be used in the early diagnosis and targeted therapy of a variety of diseases. Our review focus on the current knowledge on exosome production, secretion, uptake and how exercise influence exosome content. We also highlight recent research development in exosome based approach for cardiac repair.