Physical exercise induces rapid release of small extracellular vesicles into the circulation

Extracellular vesicular miRNA expression is not a proxy for skeletal muscle miRNA expression in males and females following acute, moderate intensity exercise

Skeletal muscle and extracellular vesicle (EV) miRNA expression increases following acute endurance exercise. However, research to date has only been performed in males. The aim of this study was to describe the expression levels of a subset of miRNAs in EVs following acute exercise and compare it to skeletal muscle miRNA expression. Twelve males (age 22.9 ± 2.6 years, mean ± SD) and eight females (age 23.0 ± 3.4 years) cycled for 60 min at 70% VO2 peak. Muscle biopsies and blood samples were collected at rest, immediately after and 3 hr after exercise. Acute exercise did not significantly alter the expression of miR-1, miR-16, miR-23b and miR-133a/b in EVs in males and females combined. There were no correlations between EV and skeletal muscle miRNA expression in any of the measured species at any time point. Exploratory analysis revealed differential miRNA responses to exercise between males and females. In males, a weak negative correlation was observed between skeletal muscle and EV miR-16 expression immediately following exercise; however, the physiological relevance of this correlation is unknown. Additionally, when compared with values at rest, male skeletal muscle miR-16 expression significantly increased immediately following exercise, whereas miR-133a expression significantly decreased 3 hr post exercise. Our findings suggest that miRNAs isolated from EVs are not a proxy for skeletal muscle miRNA content. Our exploratory data is the first known evidence of sex-specific differences in the miRNA response to an acute bout of endurance exercise, particularly for miRNA species implicated in mitochondrial metabolism and angiogenesis.

Advance in Drug Delivery for Ageing Skeletal Muscle

The age-related loss of skeletal muscle, sarcopenia, is characterized by progressive loss of muscle mass, reduction in muscle strength, and dysfunction of physical performance. It has become a global health problem leading to several adverse outcomes in the ageing population. Research on skeletal muscle loss prevention and treatment is developing quickly. However, the current clinical approaches to sarcopenia are limited. Recently, novel drug delivery systems offer new possibilities for treating aged muscle loss. Herein, we briefly recapitulate the potential therapeutic targets of aged skeletal muscle and provide a concise advance in the drug delivery systems, mainly focus on the use of nano-carriers. Furthermore, we elaborately discuss the prospect of aged skeletal muscle treatment by nanotechnology approaches.

Effects of endurance racing on horse plasma extracellular particle miRNA

BACKGROUND

Physical exercise is an essential factor in preventing and treating metabolic diseases by promoting systemic benefits throughout the body. The molecular factors involved in this process are poorly understood. Micro RNAs (miRNAs) are small non-coding RNAs that inhibit mRNA transcription. MiRNAs, which can participate in the benefits of exercise to health, circulate in plasma in extracellular particles (EP). Horses that undergo endurance racing are an excellent model to study the impact of long-duration/low intensity exercise in plasma EP miRNAs.

OBJECTIVES

To evaluate the effects of 160 km endurance racing on horse plasma extracellular particles and their miRNA population.

STUDY DESIGN

Cohort study.

METHODS

We collected plasma from five Arabian horses during five time-points of an endurance ride. Extracellular particles were purified from plasma and characterised by electron microscopy, resistive pulse sensing (qNano) and western blotting. Small RNAs were purified from horse plasma EP, and sequencing was performed.

RESULTS

Endurance racing increased EP concentration and average diameter compared to before the race. Western blotting showed a high concentration of extracellular vesicles proteins 2 hours after the race, which returned to baseline 15 hours after the race. MicroRNA differential expression analysis revealed increasing levels of eca-miR-486-5p during and after the race, and decreasing levels of eca-miR-9083 after the end.

CONCLUSIONS

This study adds new data about the variation in plasma EP concentrations after long-distance exercise and brings new insights about the roles of exercise-derived EP miRNAs during low-intensity endurance exercise.

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.

Molecular Cardioprotection and the Role of Exosomes: The Future Is Not Far Away

Heart disease is the leading cause of death in men and women in the United States. During the past several decades, research into the role of specific intracellular mediators, called exosomes, has advanced the understanding of molecular cardioprotection. Exosomes and the micro-RNAs within them may be potential targets for the development of genetically engineered or biosimilar medications for patients in heart failure or with ischemic cardiac disease. This review discusses anesthetic implications of exosome production and the future micro-RNA applications for cardioprotection.

Extracellular vesicles as signaling mediators in type 2 diabetes mellitus

Diabetes mellitus type 2, a chronic metabolic disease, has globally increased in incidence and prevalence throughout the lifespan due to the rise in obesity and sedentary lifestyle. The end-organ cardiovascular and cerebrovascular effects of diabetes mellitus result in significant morbidity and mortality that increases with age. Thus, it is crucial to fully understand how molecular mechanisms are influenced by diabetes mellitus and may influence the development of end-organ complications. Circulating factors are known to play important physiological and pathological roles in diabetes. Recent data have implicated extracellular vesicles (EVs) as being circulating mediators in type 2 diabetes. These small lipid-bound vesicles are released by cells into the circulation and can carry functional cargo, including lipids, proteins, and nucleic acids, to neighboring cells or between tissues. In this review, we will summarize the current evidence for EVs as promising diagnostic and prognostic factors in diabetes, the mechanisms that drive EV alterations with diabetes, and the role EVs play in the pathology associated with diabetes.

Redox Signaling in Widespread Health Benefits of Exercise

Significance: Exercise-induced reactive oxygen species (ROS) production activates multiple intracellular signaling pathways through genomic and nongenomic mechanisms that are responsible for the beneficial effects of exercise in muscle. Beyond the positive effect of exercise on skeletal muscle cells, other tissues such as white and brown adipose, liver, central nervous system, endothelial, heart, and endocrine organ tissues are also responsive to exercise. Recent Advances: Crosstalk between different cells is essential to achieve homeostasis and to promote the benefits of exercise through paracrine or endocrine signaling. This crosstalk can be mediated by different effectors that include the secretion of metabolites of muscle contraction, myokines, and exosomes. During the past 20 years, it has been demonstrated that contracting muscle cells produce and secrete different classes of myokines, which functionally link muscle with nearly all other cell types. Critical Issues: The redox signaling behind this exercise-induced crosstalk is now being decoded. Many of these widespread beneficial effects of exercise require not only a complex ROS-dependent intramuscular signaling cascade but simultaneously, an integrated network with many remote tissues. Future Directions: Strong evidence suggests that the powerful beneficial effect of regular physical activity for preventing (or treating) a large range of disorders might also rely on ROS-mediated signaling. Within a contracting muscle, ROS signaling may control exosomes and myokines secretion. In remote tissues, exercise generates regular and synchronized ROS waves, creating a transient pro-oxidative environment in many cells. These new concepts integrate exercise, ROS-mediated signaling, and the widespread health benefits of exercise.

Blood flow-restricted resistance exercise alters the surface profile, miRNA cargo and functional impact of circulating extracellular vesicles

Ischemic exercise conducted as low-load blood flow restricted resistance exercise (BFRE) can lead to muscle remodelling and promote muscle growth, possibly through activation of muscle precursor cells. Cell activation can be triggered by blood borne extracellular vesicles (EVs) as these nano-sized particles are involved in long distance signalling. In this study, EVs isolated from plasma of healthy human subjects performing a single bout of BFRE were investigated for their change in EV surface profiles and miRNA cargos as well as their impact on skeletal muscle precursor cell proliferation. We found that after BFRE, five EV surface markers and 12 miRNAs were significantly altered. Furthermore, target prediction and functional enrichment analysis of the miRNAs revealed several target genes that are associated to biological pathways involved in skeletal muscle protein turnover. Interestingly, EVs from BFRE plasma increased the proliferation of muscle precursor cells. In addition, alterations in surface markers and miRNAs indicated that the combination of exercise and ischemic conditioning during BFRE can stimulate blood cells to release EVs. These results support that BFRE promotes EV release to engage in muscle remodelling and/or growth processes.

The mechanisms and treatments for sarcopenia: could exosomes be a perspective research strategy in the future?

The age-related loss of muscle mass and muscle function known as sarcopenia is a primary contributor to the problems faced by the old people. Sarcopenia has been a major public health problem with high prevalence in many countries. The related underlying molecular mechanisms of sarcopenia are not completely understood. This review is focused on the potential mechanisms and current research strategies for sarcopenia with the aim of facilitating the recognition and treatment of age-related sarcopenia. Previous studies suggested that protein synthesis and degradation, autophagy, impaired satellite cell activation, mitochondria dysfunction, and other factors associated with muscle weakness and muscle degeneration may be potential molecular pathophysiology of sarcopenia. Importantly, we also prospectively highlight that exosomes (small vesicles) as carriers can regulate muscle regeneration and protein synthesis according to recent researches. Dietary strategies and exercise represent the interventions that can also alleviate the progression of sarcopenia. At last, building on recent studies pointing to exosomes with the roles in increasing muscle regeneration, mediating the beneficial effects of exercise, and serving as messengers of intercellular communication and as carriers for research strategies of many diseases, we propose that exosomes could be a potential research direction or strategies of sarcopenia in the future.

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 role of extracellular vesicles in skeletal muscle and systematic adaptation to exercise

Regular exercise has a central role in human health by reducing the risk of type 2 diabetes, obesity, stroke and cancer. How exercise is able to promote such systemic benefits has remained somewhat of a mystery but has been thought to be in part mediated by the release of myokines, skeletal muscle-specific cytokines, in response to exercise. Recent studies have revealed skeletal muscle can also release extracellular vesicles (EVs) into circulation following a bout of exercise. EVs are small membrane-bound vesicles capable of delivering biomolecules to recipient cells and subsequently altering their metabolism. The notion that EVs may have a role in both skeletal muscle and systemic adaptation to exercise has generated a great deal of excitement within a number of different fields including exercise physiology, neuroscience and metabolism. The purpose of this review is to provide an introduction to EV biology and what is currently known about skeletal muscle EVs and their potential role in the response of muscle and other tissues to exercise.

Multivesicular body and exosome pathway responses to acute exercise

NEW FINDINGS

What is the central question of this study? What is the impact of acute aerobic and aerobic + resistance (concurrent) exercise on the regulation of multivesicular body formation in human skeletal muscle? What is the main finding and its importance? Gene expression for proteins associated with multivesicular body biogenesis was increased in response to concurrent exercise, and gene expression of microRNA processing (genetic information) was increased in response to aerobic and concurrent exercise. A greater understanding of the processing of multivesicular bodies in response to acute exercise may lead to novel treatments focused on intercellular communication pathways.

ABSTRACT

Regular aerobic exercise (AEx) and resistance exercise (REx) promote many beneficial adaptations. Skeletal muscle participates in intercellular communication in part through the release of myokines and extracellular vesicles including exosomes (EXOs), the latter containing mRNA, microRNA (miRNA), lipids and proteins. Exercise-induced regulation of skeletal muscle multivesicular body (MVB) biogenesis leading to EXO formation and release is poorly understood. We hypothesized that acute exercise would increase skeletal muscle MVB biogenesis and EXO release pathways with a greater response to aerobic + resistance exercise (A+REx) than to AEx alone. Twelve sedentary, healthy male subjects exercised on a cycle ergometer for 45 min (AEx) followed by single leg, knee extensor, resistance exercise (A+REx). Vastus lateralis biopsies were obtained at rest and 1 h post-exercise. Key components of the MVB biogenesis, EXO biogenesis and release, and miRNA processing pathways were analysed. Clathrin and Alix mRNA (MVB biogenesis) were increased by A+REx, while DICER and exportin mRNA (miRNA processing) were increased by AEx and A+REx. There were positive relationships between MVBs and miRNA processing genes following both AEx and A+REx consistent with coordinated regulation of these interrelated processes (Alix mRNA increased with Drosha, exportin and Dicer mRNA). Acute exercise increases the regulation of components of MVB and EXO pathways as well as miRNA processing components. A greater understanding of the production and packaging of skeletal muscle MVBs, EXOs and mature miRNA could lead to novel treatments focused on intercellular communication.

Clinical Potential of Extracellular Vesicles in Type 2 Diabetes

Type 2 diabetes (T2D) is a major public health disease which is increased in incidence and prevalence throughout the whole world. Insulin resistance (IR) in peripheral tissues and insufficient pancreatic β-cell mass and function have been recognized as primary mechanisms in the pathogenesis of T2D, while recently, systemic chronic inflammation resulting from obesity and a sedentary lifestyle has also gained considerable attention in T2D progression. Nowadays, accumulating evidence has revealed extracellular vesicles (EVs) as critical mediators promoting the pathogenesis of T2D. They can also be used in the diagnosis and treatment of T2D and its complications. In this review, we briefly introduce the basic concepts of EVs and their potential roles in the pathogenesis of T2D. Then, we discuss their diagnostic and therapeutic potentials in T2D and its complications, hoping to open new prospects for the management of T2D.

Exosomes and Extracellular RNA in Muscle and Bone Aging and Crosstalk

PURPOSE OF REVIEW

Extracellular vesicles (EV), which include exosomes and microvesicles, are membrane-bound particles shed by most cell types and are important mediators of cell-cell communication by delivering their cargo of proteins, miRNA, and mRNA to target cells and altering their function. Here, we provide an overview of what is currently known about EV composition and function in bone and muscle cells and discuss their role in mediating crosstalk between these two tissues as well as their role in musculoskeletal aging.

RECENT FINDINGS

Recent studies have shown that muscle and bone cells produce EV, whose protein, mRNA, and miRNA cargo reflects the differentiated state of the parental cells. These EV have functional effects within their respective tissues, but evidence is accumulating that they are also shed into the circulation and can have effects on distant tissues. Bone- and muscle-derived EV can alter the differentiation and function of bone and muscle cells. Many of these effects are mediated via small microRNAs that regulate target genes in recipient cells. EV-mediated signaling in muscle and bone is an exciting and emerging field. While considerable progress has been made, much is still to be discovered about the mechanisms regulating EV composition, release, uptake, and function in muscle and bone. A key challenge is to understand more precisely how exosomes function in truly physiological settings.

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.

Acute Exercise Increases Plasma Levels of Muscle-Derived Microvesicles Carrying Fatty Acid Transport Proteins

CONTEXT

Microvesicles (MVs) are a class of membrane particles shed by any cell in the body in physiological and pathological conditions. They are considered to be key players in intercellular communication, and with a molecular content reflecting the composition of the cell of origin, they have recently emerged as a promising source of biomarkers in a number of diseases.

OBJECTIVE

The effects of acute exercise on the plasma concentration of skeletal muscle-derived MVs (SkMVs) carrying metabolically important membrane proteins were examined.

PARTICIPANTS

Thirteen men with obesity and type 2 diabetes mellitus (T2DM) and 14 healthy male controls with obesity exercised on a cycle ergometer for 60 minutes.

INTERVENTIONS

Muscle biopsies and blood samples-obtained before exercise, immediately after exercise, and 3 hours into recovery-were collected for the analysis of long-chain fatty acid (LCFA) transport proteins CD36 (a scavenger receptor class B protein) and fatty acid transport protein 4 (FATP4) mRNA content in muscle and for flow cytometric studies on circulating SkMVs carrying either LCFA transport protein.

RESULTS

Besides establishing a flow cytometric approach for the detection of circulating SkMVs and subpopulations carrying either CD36 or FATP4 and thereby adding proof to their existence, we demonstrated an overall exercise-induced change of SkMVs carrying these LCFA transport proteins. A positive correlation between exercise-induced changes in skeletal muscle CD36 mRNA expression and concentrations of SkMVs carrying CD36 was found in T2DM only.

CONCLUSIONS

This approach could add important real-time information about the abundance of LCFA transport proteins present on activated muscle cells in subjects with impaired glucose metabolism.

Exosomes are the novel players involved in the beneficial effects of exercise on type 2 diabetes

Exosomes contain regulatory signals such as lipids, proteins, and nucleic acids which can be transferred to adjacent or remote cells to mediate cell-to-cell communication. Exercise is a positive lifestyle for metabolic health and a nonpharmacological treatment of insulin resistance and metabolic diseases. Moreover, exercise is a stressor that induces cellular responses including gene expression and exosome release in various types of cells. Exosomes can carry the characters of parent cells by their modified cargoes, representing novel mechanisms for the effects of exercise. Here, we present a review of exosomes as the perspective players in mediating exercise's beneficial impacts on type 2 diabetes (T2D).

Skeletal Muscle-Released Extracellular Vesicles: State of the Art

All cells export part of their intracellular content into the extracellular space through the release of various types of extracellular vesicles (EVs). They are synthetized either from the budding of the plasma membrane [i.e., microparticles (MPs, 150–300 nm size)] or from the late endosomes in which intraluminal vesicles progressively (ILVs) accumulate during their maturation into multivesicular bodies (MVBs). ILVs are then released into the extracellular space through MVB fusion with the plasma membrane [i.e., exosomes (50–100 nm size)]. In the context of metabolic diseases, recent data have highlighted the role of EVs in inflammation associated with pancreas dysfunction, adipose tissue homeostasis, liver steatosis, inflammation, and skeletal muscle (SkM) insulin resistance (IR). Among these insulin-sensitive tissues, SkM is the largest organ in human and is responsible for whole-body glucose disposal and locomotion. Therefore, understanding the contribution of SkM-EVs in the development of diabetes/obesity/dystrophy/,-related diseases is a hot topic. In this review, we have summarized the role of SkM-EVs in muscle physiology and in the development of metabolic diseases and identify important gaps that have to be filled in order to have more precise information on SkM-EVs biological actions and to understand the functions of the different subpopulations of SkM-EVs on the whole-body homeostasis.

Contribution of Extracellular Vesicles in Rebuilding Injured Muscles

Skeletal myofibers are injured due to mechanical stresses experienced during physical activity, or due to myofiber fragility caused by genetic diseases. The injured myofiber needs to be repaired or regenerated to restore the loss in muscle tissue function. Myofiber repair and regeneration requires coordinated action of various intercellular signaling factors-including proteins, inflammatory cytokines, miRNAs, and membrane lipids. It is increasingly being recognized release and transmission of these signaling factors involves extracellular vesicle (EV) released by myofibers and other cells in the injured muscle. Intercellular signaling by these EVs alters the phenotype of their target cells either by directly delivering the functional proteins and lipids or by modifying longer-term gene expression. These changes in the target cells activate downstream pathways involved in tissue homeostasis and repair. The EVs are heterogeneous with regards to their size, composition, cargo, location, as well as time-course of genesis and release. These differences impact on the subsequent repair and regeneration of injured skeletal muscles. This review focuses on how intracellular vesicle production, cargo packaging, and secretion by injured muscle, modulates specific reparative, and regenerative processes. Insights into the formation of these vesicles and their signaling properties offer new understandings of the orchestrated response necessary for optimal muscle repair and regeneration.

Skeletal muscle-derived exosomes regulate endothelial cell functions via reactive oxygen species-activated nuclear factor-κB signalling

NEW FINDINGS

What is the central question of this study? Capillary rarefaction is found in diabetic and aged muscle, whereas exercise increases skeletal muscle angiogenesis. The association implies a crosstalk between muscle cells and endothelial cells. The underlying mechanisms mediating the crosstalk between these cells remains to be elucidated fully. What is the main finding and its importance? Endothelial cell functions are regulated by skeletal muscle cell-derived exosomes via a vascular endothelial growth factor-independent pathway. This study reveals a new mechanism mediating the crosstalk between skeletal muscle cells and endothelial cells.

ABSTRACT

Loss of skeletal muscle capillarization, known as capillary rarefaction, is found in type 2 diabetes, chronic heart failure and healthy ageing and is associated with impaired delivery of substrates to the muscle. However, the interaction and communication of skeletal muscle with endothelial cells in the regulation of capillaries surrounding the muscle remains elusive. Exosomes are a type of secreted extracellular vesicle containing mRNAs, proteins and, especially, microRNAs that exert paracrine and endocrine effects. In this study, we investigated whether skeletal muscle-derived exosomes (SkM-Exo) regulate the endothelial cell functions of angiogenesis. We demonstrated that C2C12 myotube-derived exosomes improved endothelial cell functions, assessed by the proliferation, migration and tube formation of human umbilical vein endothelial cells (HUVECs), which were increased by 20, 23 and 40%, respectively, after SkM-Exo exposure. The SkM-Exo failed to activate HUVEC vascular endothelial growth factor (VEGF) signalling. The SkM-Exo increased HUVEC reactive oxygen species and activated the nuclear factor-κB pathway, suggesting that SkM-Exo-induced angiogenesis was mediated by a VEGF-independent pathway. In addition, several angiogenic microRNAs were packaged in SkM-Exo, with miR-130a being particularly enriched and successfully transferred from SkM-Exo to HUVECs. Delivery of miRNAs into endothelial cells might explain the enhancement of reactive oxygen species production and angiogenesis by SkM-Exo. The potential angiogenic effect of SkM-Exo could provide an effective therapy for promoting skeletal muscle angiogenesis in diseases characterized by capillary rarefaction or inadequate angiogenesis.

Platelets, endothelial cells and leukocytes contribute to the exercise-triggered release of extracellular vesicles into the circulation

Physical activity initiates a wide range of multi-systemic adaptations that promote mental and physical health. Recent work demonstrated that exercise triggers the release of extracellular vesicles (EVs) into the circulation, possibly contributing to exercise-associated adaptive systemic signalling. Circulating EVs comprise a heterogeneous collection of different EV-subclasses released from various cell types. So far, a comprehensive picture of the parental and target cell types, EV-subpopulation diversity and functional properties of EVs released during exercise (ExerVs) is lacking. Here, we performed a detailed EV-phenotyping analysis to explore the cellular origin and potential subtypes of ExerVs. Healthy male athletes were subjected to an incremental cycling test until exhaustion and blood was drawn before, during, and immediately after the test. Analysis of total blood plasma by EV Array suggested endothelial and leukocyte characteristics of ExerVs. We further purified ExerVs from plasma by size exclusion chromatography as well as CD9-, CD63- or CD81-immunobead isolation to examine ExerV-subclass dynamics. EV-marker analysis demonstrated increasing EV-levels during cycling exercise, with highest levels at peak exercise in all EV-subclasses analysed. Phenotyping of ExerVs using a multiplexed flow-cytometry platform revealed a pattern of cell surface markers associated with ExerVs and identified lymphocytes (CD4, CD8), monocytes (CD14), platelets (CD41, CD42, CD62P), endothelial cells (CD105, CD146) and antigen presenting cells (MHC-II) as ExerV-parental cells. We conclude that multiple cell types associated with the circulatory system contribute to a pool of heterogeneous ExerVs, which may be involved in exercise-related signalling mechanisms and tissue crosstalk.

Extracellular Vesicles: Delivery Vehicles of Myokines

Movement and regular physical activity are two important factors that help the human body prevent, reduce and treat different chronic diseases such as obesity, type 2 diabetes, heart diseases, hypertension, sarcopenia, cachexia and cancer. During exercise, several tissues release molecules into the blood stream, and are able to mediate beneficial effects throughout the whole body. In particular, contracting skeletal muscle cells have the capacity to communicate with other organs through the release of humoral factors that play an important role in the mechanisms of adaptation to physical exercise. These muscle-derived factors, today recognized as myokines, act as endocrine and paracrine hormones. Moreover, exercise may stimulate the release of small membranous vesicles into circulation, whose composition is influenced by the same exercise. Combining the two hypotheses, these molecules related to exercise, named exer-kines, might be secreted from muscle cells inside small vesicles (nanovesicles). These could act as messengers in tissue cross talk during physical exercise. Thanks to their ability to deliver useful molecules (such as proteins and miRNA) in both physiological and pathological conditions, extracellular vesicles can be thought of as promising candidates for potential therapeutic and diagnostic applications for several diseases.

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.

Extracellular vesicles in lung health, disease, and therapy

Both physiological homeostasis and pathological disease processes in the lung typically result from complex, yet coordinated multicellular responses that are synchronized via paracrine and endocrine intercellular communication pathways. Of late, extracellular vesicles have emerged as important information shuttles that can coordinate and disseminate homeostatic and disease signals. In parallel, extracellular vesicles in biological fluids such as sputum, mucus, epithelial lining fluid, edema fluid, the pulmonary circulation, pleural fluid, and lymphatics have emerged as promising candidate biomarkers for diagnosis and prognosis in lung disease. Extracellular vesicles are small, subcellular, membrane-bound vesicles containing cargos from parent cells such as lipids, proteins, genetic information, or entire organelles. These cargos endow extracellular vesicles with biologically active information or functions by which they can reprogram their respective target cells. Recent studies show that extracellular vesicles found in lung-associated biological fluids play key roles as biomarkers and effectors of disease. Conversely, administration of naïve or engineered extracellular vesicles with homeostatic or reparative effects may provide a promising novel protective and regenerative strategy to treat lung disease. To highlight this rapidly developing field, the American Journal of Physiology-Lung Cellular and Molecular Physiology is now launching a special Call for Papers on extracellular vesicles in lung health, disease, and therapy. This review aims to set the stage for this call by introducing extracellular vesicles and their emerging roles in lung physiology and pathobiology.

The potential diagnostic and prognostic role of extracellular vesicles in glioma: current status and future perspectives

Lack of appropriate diagnostic/prognostic tools for glioblastoma (GB) is considered one of the major setbacks in the early diagnosis and treatment of this deadly brain tumor. The current gold standard for its diagnosis and staging still relies on invasive biopsy followed by histological examination as well as molecular profiling. Nevertheless, noninvasive approaches are being explored and one example is through the investigation of extracellular vesicles (EVs) in the biofluids of GB patients. EVs are known to carry molecular cargoes such as DNA, mRNA, miRNA, proteins and lipids in almost every type of body fluids. Thus, molecular signature of GB may be present in the EVs derived from these patients. This review focuses on the diagnostic/prognostic potential of EVs in GB, through presenting recent studies on (i) molecular components of EVs, (ii) links between EVs and GB tumor microenvironment, and (iii) clinical potential of EV biomarkers, together with the technical shortcomings researchers need to consider for future studies.

Children's Cortisol and Cell-Free DNA Trajectories in Relation to Sedentary Behavior and Physical Activity in School: A Pilot Study

The worldwide prevalence of mental disorders in children and adolescents increased constantly. Additionally, the recommended amount of physical activity (PA) is not achieved by this age group. These circumstances are associated with negative impacts on their health status in later life and can lead to public health issues. The exposure to natural green environments (NGE) seems to be beneficial for human health. The compulsory school system offers great opportunities to reach every child with suitable health-related contents and interventions at an early stage. The concept of Education Outside the Classroom (EOtC) uses NGE and sets focus on PA. Therefore, EOtC might be a beneficial educational intervention to promote students health. The association between biological stress markers and sedentary behavior (SB) plus PA is insufficiently evaluated in school settings. This exploratory study aims to evaluate the association between students' cortisol, plus circulating cell-free deoxyribonucleic acid (cfDNA) levels, and their SB, light PA (LPA), and moderate-to-vigorous PA (MVPA). We assessed data from an EOtC program (intervention group [IG], n = 37; control group [CG], n = 11) in three seasons (fall/spring/summer) in outdoor lessons (IG) in a NGE and normal indoor lessons (CG). SB and PA were evaluated by accelerometry, and cortisol and cfDNA levels by saliva samples. Fitted Bayesian hierarchical linear models evaluated the association between cortisol and cfDNA, and compositional SB/LPA/MVPA. A steady decline of cortisol in the IG is associated with relatively high levels of LPA (posterior mean = −0.728; credible interval [CRI 95%]: −1.268; −0.190). SB and MVPA tended to exhibit a similar effect in the CG. A high amount of cfDNA is positively associated with a relatively high amount of SB in the IG (posterior mean, 1.285; CRI: 0.390; 2.191), the same association is likely for LPA and MVPA in both groups. To conclude, LPA seems to support a healthy cortisol decrease in children during outdoor lessons in NGEs. Associations between cfDNA and SB/PA need to be evaluated in further research. This study facilitates the formulation of straightforward and directed hypotheses for further research with a focus on the potential health promotion of EOtC.

Aberrant redox signalling and stress response in age-related muscle decline: Role in inter- and intra-cellular signalling

Age-associated frailty is predominantly due to loss of muscle mass and function. The loss of muscle mass is also associated with a greater loss of muscle strength, suggesting that the remaining muscle fibres are weaker than those of adults. The mechanisms by which muscle is lost with age are unclear, but in this review we aim to pull together various strands of evidence to explain how muscle contractions support proteostasis in non-muscle tissues, particularly focussed on the production and potential transfer of Heat Shock Proteins (HSPs) and how this may fail during ageing, Furthermore we will identify logical approaches, based on this hypothesis, by which muscle loss in ageing may be reduced. Skeletal muscle generates superoxide and nitric oxide at rest and this generation is increased by contractile activity. In adults, this increased generation of reactive oxygen and nitrogen species (RONS) activate redox-sensitive transcription factors such as nuclear factor κB (NFκB), activator protein-1 (AP1) and heat shock factor 1 (HSF1), resulting in increases in cytoprotective proteins such as the superoxide dismutases, catalase and heat shock proteins that prevent oxidative damage to tissues and facilitate remodelling and proteostasis in both an intra- and inter-cellular manner. During ageing, the ability of skeletal muscle from aged organisms to respond to an increase in ROS generation by increased expression of cytoprotective proteins through activation of redox-sensitive transcription factors is severely attenuated. This age-related lack of physiological adaptations to the ROS induced by contractile activity appears to contribute to a loss of ROS homeostasis, increased oxidative damage and age-related dysfunction in skeletal muscle and potentially other tissues.

Forms of extracellular mitochondria and their impact in health

Mitochondria play an important role as an intracellular energy plant and signaling organelle. However, mitochondria also exist outside cells where they could mediate cell-to-cell communication, repair and serve as an activator of the immune response. Their effects depend on the mitochondrial state or the form in which it is present, either as a whole functional structure as fragments or only as mitochondrial DNA. Herein, we provide evidence of why extracellular mitochondria and their varying forms are considered regenerative factors or pro-inflammatory activators. Understanding these aspects will provide the base of their use in therapy or as a biomarker of disease severity and prognosis.

The Bottom-Up Rise Strength Transfer in Elderly After Endurance and Resistance Training: The BURST

The phenomenon of strength gain is highly relevant for sarcopenia and clinical aspect linked to aging. Recent advancements drive the interest toward the exercise-related cross-talk between distant tissues. We demonstrated the cross-talk between lower and upper limbs, we named the Bottom-Up Rise Strength Transfer (BURST), mainly linked to endurance training. In our opinion, this effect can be mainly related to systemic factors, likely circulating myokines and extracellular vesicles (recently defined in terms of “exerkines” and “exersomes”) whit an eventual concomitant reduction of a sub-clinical chronic inflammation. The neuronal mechanisms, even if to our sight less likely involved in this adaptation, need to be deeply investigated. Further studies are needed to better characterize the exercise-related BURST, concerning the specificity of different protocols and the underlying physiological mechanisms.

Retrograde transport of masseter muscle-derived neprilysin to hippocampus

Although the effects of neprilysin (NEP), also called CD10, on the clearance of Alzheimer's disease (AD)-associated amyloid-β (Aβ) have been reported, NEP is not made in the brain, and the mechanism for the transport of NEP to the brain has not been investigated. Our hypothesis is that muscle packages NEP in exosomes in response to a neuromuscular signal and sends it to the brain via retrograde axonal transport. The masseter muscle (MM) and the trigeminal nerve (TGN) are good candidates for this mechanism by virtue of their proximity to the brain. The aim of this study was to trace the NEP protein from the MM, through the TGN, and to the hippocampus (HPC) in muscle contraction models in vitro and in vivo. NEP expression in mouse tissue lysates was analyzed by RT-PCR and Western blot. Four-week-old mice were perfused to remove blood NEP contamination. The MM expressed substantial levels of NEP protein and mRNA. On the other hand, a remarkably high level of NEP protein was measured in the TGN in the absence of mRNA. NEP protein, without the corresponding mRNA, was also detected in the HPC. These results suggested that the MM derived NEP was taken up by the TGN, which in turn permitted NEP access to the central nervous system and within it the HPC. When the MM was induced to contract by electric stimulation in freshly euthanized mice, NEP protein decreased in the MM in a stimulus time-dependent manner, while that in the TGN and the HPC increased sequentially. Furthermore, NIR-labeled exosomes tracked along the same route. Finally, carbachol induced secretion of exosomal NEP in C2C12-derived myotube cells. These results support our hypothesis that MM-derived NEP is transported along the TGN to reach the HPC following electrical or cholinergic stimulation.

Extracellular vesicles for personalized medicine: The input of physically triggered production, loading and theranostic properties

Emerging advances in extracellular vesicle (EV) research brings along new promises for tailoring clinical treatments in order to meet specific disease features of each patient in a personalized medicine concept. EVs may act as regenerative effectors conveying endogenous therapeutic factors from parent cells or constitute a bio-camouflaged delivery system for exogenous therapeutic agents. Physical stimulation may be an important tool in the field of EVs for personalized therapy by powering EV production, loading and therapeutic properties. Physically-triggered EV production is inspired by naturally occurring EV release by shear stress in blood vessels. Bioinspired physically-triggered EV production technologies may bring along high yield advantages combined to scalability assets. Physical stimulation may also provide new prospects for high-efficient EV loading. Additionally, physically-triggered EV theranostic properties brings new hopes for spatio-temporal controlled therapy combined to tracking. Technological considerations related to EV-based personalized medicine and the input of physical stimulation on EV production, loading and theranostic properties will be overviewed herein.

Bone-Derived Extracellular Vesicles: Novel Players of Interorgan Crosstalk

An increasing number of studies have shown that bone plays an active role in regulating glucose metabolism, affects renal, and cardiovascular diseases and even influences the development of offspring. These novel findings have indicated that bone plays a much more important role in the human body than only providing physical support. However, further investigations of the mechanisms underlying the effects of bone are needed. Recently, extracellular vesicles (EVs) have received increased attention because they can transfer functional proteins, mRNAs, and miRNAs between cells/organs. After reviewing the existing evidence, we hypothesized that bone may be involved in interorgan communication via EVs. Further research exploring bone-derived EVs may facilitate the understanding of bone as a multifunctional organ.

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.

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.

Circulating extracellular vesicles are associated with lipid and insulin metabolism

We have reported that hypertrophic adipocytes release extracellular vesicles (EVs) and the number of circulating adipocyte-derived EVs correlated with insulin and homeostasis model assessment-insulin resistance (HOMA-IR) in a pilot study using obese patients. Here, we explored the association between circulating EV level and various metabolic parameters, including obesity and lipid and glucose metabolisms, among 203 subjects (76 men and 127 women; median age, 54 yr) with or without risk factor for metabolic diseases, who received a 75-g oral glucose tolerance test (OGTT). Circulating EV number was significantly higher in men than in women ( P < 0.001). Circulating EV number in individuals with impaired OGTT pattern was significantly higher compared with those with normal OGTT patterns ( P < 0.05). Multiple regression analysis revealed that circulating EV number correlated most strongly and significantly with elevated triglyceride (TG; t = 8.55, P < 0.001). Additionally, circulating EV number correlated significantly with homeostasis model assessment-β-cell function (HOMA-β; t = 2.38, P < 0.05). Receiver operating characteristic curve revealed that the cutoff value of EV numbers in individuals with elevated serum TG levels (≧150 mg/dl) was identified (136,738 EVs/μl of plasma, P < 0.001, sensitivity 0.842, false-positive rate of 0.257). Perilipin and asialoglycoprotein receptor 1 were detected on a part of isolated circulating EVs, indicating EV release from adipocytes and hepatocytes, which were related to lipid and glucose metabolism. Circulating EVs represent a promising metabolic biomarker for lipid and glucose metabolism and have potential for monitoring metabolic status in humans, including individuals without metabolic risk factors.

Exercise during hemodialysis does not affect the phenotype or prothrombotic nature of microparticles but alters their proinflammatory function

Hemodialysis patients have dysfunctional immune systems, chronic inflammation and comorbidity-associated risks of cardiovascular disease (CVD) and infection. Microparticles are biologically active nanovesicles shed from activated endothelial cells, immune cells, and platelets; they are elevated in hemodialysis patients and are associated with chronic inflammation and predictive of CVD mortality in this group. Exercise is advocated in hemodialysis to improve cardiovascular health yet acute exercise induces an increase in circulating microparticles in healthy populations. Therefore, this study aimed to assess acute effect of intradialytic exercise (IDE) on microparticle number and phenotype, and their ability to induce endothelial cell reactive oxygen species (ROS) in vitro. Eleven patients were studied during a routine hemodialysis session and one where they exercised in a randomized cross-over design. Microparticle number increased during hemodialysis (2064-7071 microparticles/μL, P < 0.001) as did phosphatidylserine+ (P < 0.05), platelet-derived (P < 0.01) and percentage procoagulant neutrophil-derived microparticles (P < 0.05), but this was not affected by IDE. However, microparticles collected immediately and 60 min after IDE (but not later) induced greater ROS generation from cultured endothelial cells (P < 0.05), suggesting a transient proinflammatory event. In summary IDE does not further increase prothrombotic microparticle numbers that occurs during hemodialysis. However, given acute proinflammatory responses to exercise stimulate an adaptation toward a circulating anti-inflammatory environment, microparticle-induced transient increases of endothelial cell ROS in vitro with IDE may indicate the potential for a longer-term anti-inflammatory adaptive effect. These findings provide a crucial evidence base for future studies of microparticles responses to IDE in view of the exceptionally high risk of CVD in these patients.

Novel approaches to restore beta cell function in prediabetes and type 2 diabetes

The World Health Organization estimates that diabetes prevalence has risen from 108 million in 1980 to 422 million in 2014, with type 2 diabetes accounting for more than 90% of these cases. Furthermore, the prevalence of prediabetes (impaired fasting glucose and/or impaired glucose tolerance) is more than 40% in some countries and is associated with a global rise in obesity. Therefore it is imperative that we develop new approaches to reduce the development of prediabetes and progression to type 2 diabetes. In this review, we explore the gains made over the past decade by focused efforts to improve insulin secretion by the beta cell or insulin sensitivity of target tissues. We also describe multitasking candidates, which could improve both beta cell dysfunction and peripheral insulin sensitivity. Moreover, we highlight provocative findings indicating that additional glucose regulatory tissues, such as the brain, may be key therapeutic targets. Taken together, the promise of these new multi-faceted approaches reinforces the importance of understanding and tackling type 2 diabetes pathogenesis from a multi-tissue perspective.

Investigation of Circulating Extracellular Vesicle MicroRNA Following Two Consecutive Bouts of Muscle-Damaging Exercise

Background: Extracellular vesicles (EVs) are nano-sized vesicles that are known to be powerful mediators of intercellular communication via their microRNA (miR) content. A paucity of information on EV-mediated communication arising from skeletal muscle (SkM) in response to exercise-induced muscle damage is present in the published literature. Lack of such information inhibits our understanding of muscle injury and repair processes. Aims: To assess circulating EV levels and selected miR content within them, in response to two consecutive bouts of muscle-damaging exercise. Methods: Serum creatine kinase activity (CK) and EVs were analyzed from the blood of 9 healthy, untrained males at baseline, and at 2 and 24 h post-exercise. The exercise regimen consisted of a combination of plyometric jumping and downhill running. Perceived muscle pain (PMP) was assessed on a scale from 1 to 10. Plasma EVs were isolated using size exclusion columns and visualized with transmission electron microscopy (TEM). EV size and number were quantified using nanoparticle tracking analysis (NTA). miR expression was quantified using qPCR, with normalization to an exogenous control (cel-miR-39). Results: PMP and CK were significantly elevated post-exercise compared to baseline levels, providing indirect evidence for muscle damage. EV visualization using TEM revealed an abundant and heterogeneously sized pool of intact particles within the exosome size range (30-150 nm). No significant change in mean EV size or number was seen over time. The SkM-specific miR-206 in EVs was found to be variable among participants and no significant change occurred in SkM-important miRs; 1, 133a, 133b, 486, and 499a. However, EV miR-31 decreased from baseline to 24 h post-exercise (p = 0.027). Conclusion: Mild to moderate exercise-induced muscle damage altered the miR-31 profile of circulating EVs within the first 24 h post-exercise, but not that of myomiRs in EVs. These data demonstrate that EVs carry selectively packaged cargo which can be affected by exercise. Future research into the total miR content of EVs in response to exercise-induced muscle damage may reveal other miRs responsive to this relatively mild perturbation. More time points post-muscle-damaging exercise would provide a better understanding of the temporal EV myomiR response.

Extracellular vesicles and their nucleic acids for biomarker discovery

Extracellular vesicles (EVs) are a heterogenous population of vesicles originate from cells. EVs are found in different biofluids and carry different macromolecules, including proteins, lipids, and nucleic acids, providing a snap shot of the parental cells at the time of release. EVs have the ability to transfer molecular cargoes to other cells and can initiate different physiological and pathological processes. Mounting lines of evidence demonstrated that EVs' cargo and machinery is affected in disease states, positioning EVs as potential sources for the discovery of novel biomarkers. In this review, we demonstrate a conceptual overview of the EV field with particular focus on their nucleic acid cargoes. Current knowledge of EV subtypes, nucleic acid cargo and pathophysiological roles are outlined, with emphasis placed on advantages against competing analytes. We review the utility of EVs and their nucleic acid cargoes as biomarkers and critically assess the newly available advances in the field of EV biomarkers and high throughput technologies. Challenges to achieving the diagnostic potential of EVs, including sample handling, EV isolation, methodological considerations, and bioassay reproducibility are discussed. Future implementation of 'omics-based technologies and integration of systems biology approaches for the development of EV-based biomarkers and personalized medicine are also considered.

Extracellular Vesicles: A Novel Target for Exercise-Mediated Reductions in Type 2 Diabetes and Cardiovascular Disease Risk

Regular exercise is important for reducing type 2 diabetes (T2D) and/or cardiovascular disease (CVD) risk. However, only about 40-50% of this CVD risk reduction is accounted for by adiposity, hyperglycemia, hypertension, and dyslipidemia. Herein, we present the novel hypothesis that extracellular vesicles (EVs) are candidate biomarkers that may relate to impaired endothelial function and insulin resistance independent of obesity risk factors. EVs are small membrane-bound particles that are generated by cells following stimulation, stress, or activation. They carry markers of their parent cell and are thought to be potent bioactivators and communicators. We discuss the underlying physiology of specific cell type EVs, as well as examine how acute and chronic exercise interventions impact EV count and phenotype. We also propose that current gaps in the field are in part related to use of different detection techniques and the lack of standardized measurements of EV affecting the pre- and postanalytical phase. Ultimately, improving the understanding of how EVs impact cardiometabolic health and their function will lead to improved approaches for enhancing diagnostic options as well as designing exercise interventions that treat and/or prevent T2D and CVD.

Extracellular vesicles as circulating cancer biomarkers: opportunities and challenges

Extracellular vesicles (EVs) are small, lipid-bound particles containing nucleic acid and protein cargo which are excreted from cells under a variety of normal and pathological conditions. EVs have garnered substantial research interest in recent years, due to their potential utility as circulating biomarkers for a variety of diseases, including numerous types of cancer. The following review will discuss the current understanding of the form and function of EVs, their specific role in cancer pathogenesis and their potential for non-invasive disease diagnosis and/or monitoring. This review will also highlight several key issues for this field, including the importance of implementing robust and reproducible sample handling protocols, and the challenge of extracting an EV-specific biomarker signal from a complex biological background.

Effects of Acute Aerobic Exercise on Rats Serum Extracellular Vesicles Diameter, Concentration and Small RNAs Content

Physical exercise stimulates organs, mainly the skeletal muscle, to release a broad range of molecules, recently dubbed exerkines. Among them, RNAs, such as miRNAs, piRNAs, and tRNAs loaded in extracellular vesicles (EVs) have the potential to play a significant role in the way muscle and other organs communicate to translate exercise into health. Low, moderate and high intensity treadmill protocols were applied to rat groups, aiming to investigate the impact of exercise on serum EVs and their associated small RNA molecules. Transmission electron microscopy, resistive pulse sensing, and western blotting were used to investigate EVs morphology, size distribution, concentration and EVs marker proteins. Small RNA libraries from EVs RNA were sequenced. Exercise did not change EVs size, while increased EVs concentration. Twelve miRNAs were found differentially expressed after exercise: rno-miR-128-3p, 103-3p, 330-5p, 148a-3p, 191a-5p, 10b-5p, 93-5p, 25-3p, 142-5p, 3068-3p, 142-3p, and 410-3p. No piRNA was found differentially expressed, and one tRNA, trna8336, was found down-regulated after exercise. The differentially expressed miRNAs were predicted to target genes involved in the MAPK pathway. A single bout of exercise impacts EVs and their small RNA load, reinforcing the need for a more detailed investigation into EVs and their load as mediators of health-promoting exercise.

Do skeletal muscle-secreted factors influence the function of pancreatic β-cells?

Skeletal muscle is an endocrine organ that secretes a variety of compounds including proteins (myokines), metabolites, microRNAs (miRNAs), and exosomes, many of which are regulated by exercise and play important roles in endocrine signaling. Interorgan communication via muscle-secreted factors therefore provides a novel area for investigation and implicates the importance of skeletal muscle in the pathophysiology of metabolic diseases such as type 2 diabetes (T2D). Given that underlying molecular mechanisms of T2D are subject of ongoing research, in light of new evidence it is probable that interorgan cross-talk between skeletal muscle and pancreatic β-cells plays an important part. To date, the number of studies published in this field provide the basis of this review. Specifically, we discuss current experimental evidence in support for a role of skeletal muscle to β-cell cross-talk, paying particular attention to muscle-secreted factors including myokines, metabolites, miRNAs, and factors contained within exosomes that influence the function and/or the survival of β-cells in health and disease. In reviewing this evidence, we provide an update on the list of known muscle-secreted factors that have potential to influence the function and/or survival of β-cells under normal and diabetic conditions. We also report limitations of current cross-talk methods and discuss future directions in this growing field.

Exosomes as Mediators of the Systemic Adaptations to Endurance Exercise

Habitual endurance exercise training is associated with multisystemic metabolic adaptations that lower the risk of inactivity-associated disorders such as obesity and type 2 diabetes mellitus (T2DM). Identification of complex systemic signaling networks responsible for these benefits are of great interest because of their therapeutic potential in metabolic diseases; however, specific signals that modulate the multisystemic benefits of exercise in multiple tissues and organs are only recently being discovered. Accumulated evidence suggests that muscle and other tissues have an endocrine function and release peptides and nucleic acids into the circulation in response to acute endurance exercise to mediate the multisystemic adaptations. Factors released from skeletal muscle have been termed myokines and we propose that the total of all factors released in response to endurance exercise (including peptides, nucleic acids, and metabolites) be termed, "exerkines." We propose that many of the exerkines are released within extracellular vesicles called exosomes, which regulate peripheral organ cross talk. Exosomes (30-140 nm) and larger microvesicles [MVs] (100-1000 nm) are subcategories of extracellular vesicles that are released into the circulation. Exosomes contain peptides and several nucleic acids (microRNA [miRNA], messenger RNA [mRNA], mitochondrial DNA [mtDNA]) and are involved in intercellular/tissue exchange of their contents. An acute bout of endurance exercise increases circulating exosomes that are hypothesized to mediate organ cross talk to promote systemic adaptation to endurance exercise. Further support for the role of exosomes (and possibly MVs) in mediating the systemic benefits of exercise comes from the fact that the majority of the previously reported myokines/exerkines are found in extracellular vesicles databases (Vesiclepedia and ExoCarta). We propose that exosomes isolated from athletes following exercise or exosomes bioengineered to incorporate one or many of known exerkines will be therapeutically useful in the treatment of obesity, T2DM, and other aging-associated metabolic disorders.

Extracellular Vesicles Provide a Means for Tissue Crosstalk during Exercise

Exercise stimulates the release of molecules into the circulation, supporting the concept that inter-tissue signaling proteins are important mediators of adaptations to exercise. Recognizing that many circulating proteins are packaged in extracellular vesicles (EVs), we employed quantitative proteomic techniques to characterize the exercise-induced secretion of EV-contained proteins. Following a 1-hr bout of cycling exercise in healthy humans, we observed an increase in the circulation of over 300 proteins, with a notable enrichment of several classes of proteins that compose exosomes and small vesicles. Pulse-chase and intravital imaging experiments suggested EVs liberated by exercise have a propensity to localize in the liver and can transfer their protein cargo. Moreover, by employing arteriovenous balance studies across the contracting human limb, we identified several novel candidate myokines, released into circulation independently of classical secretion. These data identify a new paradigm by which tissue crosstalk during exercise can exert systemic biological effects.

Denervation-related alterations and biological activity of miRNAs contained in exosomes released by skeletal muscle fibers

Exosomes are vesicles released by many eukaryotic cells; their cargo includes proteins, mRNA and microRNA (miR) that can be transferred to recipient cells and regulate cellular processes in an autocrine or paracrine manner. While cells of the myoblast lineage secrete exosomes, it is not known whether skeletal muscle fibers (myofibers) release exosomes. In this study, we found that cultured myofibers release nanovesicles that have bilamellar membranes and an average size of 60-130 nm, contain typical exosomal proteins and miRNAs and are taken up by C2C12 cells. miR-133a was found to be the most abundant myomiR in these vesicles while miR-720 was most enriched in exosomes compared to parent myofibers. Treatment of NIH 3T3 cells with myofiber-derived exosomes downregulated the miR-133a targets proteins Smarcd1 and Runx2, confirming that these exosomes have biologically relevant effects on recipient cells. Denervation resulted in a marked increase in miR-206 and reduced expression of miRs 1, 133a, and 133b in myofiber-derived exosomes. These findings demonstrate that skeletal muscle fibers release exosomes which can exert biologically significant effects on recipient cells, and that pathological muscle conditions such as denervation induce alterations in exosomal miR profile which could influence responses to disease states through autocrine or paracrine mechanisms.

Circulating extracellular vesicles in the aging process: impact of aerobic exercise

Our aim was to investigate transitory and delayed exercise effects on serum extracellular vesicles (EVs) in aging process. Male Wistar rats of 3-, 21-, and 26-month old were allocated into exercised and sedentary groups. The exercise protocol consisted in a daily moderate treadmill exercise (20 min daily during 2 weeks). Trunk blood was collected 1 and 18 h after the last exercise session, and circulating EVs were obtained. CD63 levels and acetylcholinesterase (AChE) activity were used as markers of exosome, a subtype of EVs. In addition, the quantification of amyloid-β (Aβ) levels and the oxidative status parameters, specifically reactive species content, superoxide dismutase (SOD) activity, and SOD1 content were evaluated. Aged rats showed reduced CD63 levels and increased AChE activity in circulating exosomes compared to young ones. Moreover, higher reactive species levels were found in circulating EVs of aged rats. Delayed exercise effects were observed on peripheral EVs, since CD63, reactive species content, and AChE activity were altered 18 h after the last exercise session. Our results suggest that the healthy aging process can modify circulating EVs profile, and exercise-induced beneficial effects may be related to its modulation on EVs.

Exercise-induced circulating extracellular vesicles protect against cardiac ischemia-reperfusion injury

Extracellular vesicles (EVs) serve an important function as mediators of intercellular communication. Exercise is protective for the heart, although the signaling mechanisms that mediate this cardioprotection have not been fully elucidated. Here using nano-flow cytometry, we found a rapid increase in plasma EVs in human subjects undergoing exercise stress testing. We subsequently identified that serum EVs were increased by ~1.85-fold in mice after 3-week swimming. Intramyocardial injection of equivalent quantities of EVs from exercised mice and non-exercised controls provided similar protective effects against acute ischemia/reperfusion (I/R) injury in mice. However, injection of exercise-induced EVs in a quantity equivalent to the increase seen with exercise (1.85 swim group) significantly enhanced the protective effect. Similarly, treatment with exercise-induced increased EVs provided additional anti-apoptotic effect in H₂O₂-treated H9C2 cardiomyocytes mediated by the activation of ERK1/2 and HSP27 signaling. Finally, by treating H9C2 cells with insulin-like growth factor-1 to mimic exercise stimulus in vitro, we found an increased release of EVs from cardiomyocytes associated with ALIX and RAB35 activation. Collectively, our results show that exercise-induced increase in circulating EVs enhances the protective effects of endogenous EVs against cardiac I/R injury. Exercise-derived EVs might serve as a potent therapy for myocardial injury in the future.