Abstract
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% VO2peak. 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.
Highlights
Skeletal muscle is a dynamic tissue that rapidly adapts to molecular and environment stimuli, such as the metabolic stress associated with endurance exercise (Frontera & Ochala, 2015)
The aim of this study was to describe extracellular vesicle (EV) miRNA expression following an acute bout of endurance cycling and to compare it to skeletal muscle miRNA expression
We observed no correlation between EV and skeletal muscle miRNA expression, suggesting that EV miRNA expression is not a proxy for skeletal muscle miRNA expression
Summary
Skeletal muscle is a dynamic tissue that rapidly adapts to molecular and environment stimuli, such as the metabolic stress associated with endurance exercise (Frontera & Ochala, 2015). Endurance exercise upregulates mitochondrial biogenesis and increases the capacity of contracting muscle to oxidise carbohydrate and lipid substrates (Holloszy & Coyle, 1984; Little, Safdar, Benton, & Wright, 2011). The intracellular transcriptional networks governing endurance exercise adaptations are well-established; for example, PGC-1α, an important regulator of skeletal muscle mitochondrial biogenesis, is transiently upregulated in response to acute endurance exercise (Puigserver et al, 1998). The mechanisms by which these skeletal muscle adaptations translate to systemic adaptations in other metabolic tissues (i.e., kidney, liver, cardiac muscle) are less clear (Little et al, 2011). The role and regulation of EVs and their content in response to exercise is only starting to be investigated (D'Souza et al, 2018; Whitham et al, 2018)
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