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.

Background Mitochondria have an essential role in regulating metabolism and integrate environmental and physiological signals to affect processes such as cellular bioenergetics and response to stress. In the metabolically active skeletal muscle, mitochondrial biogenesis is one important component contributing to a broad set of mitochondrial adaptations occurring in response to signals, which converge on the biogenesis transcriptional regulator peroxisome proliferator-activated receptor coactivator 1-alpha (PGC-1α), and is central to the beneficial effects of exercise in skeletal muscle. We investigated the role of long non-coding RNA (lncRNA) taurine-upregulated gene 1 (TUG1), which interacts with PGC-1α in regulating transcriptional responses to exercise in skeletal muscle. Results In human skeletal muscle, TUG1 gene expression was upregulated post-exercise and was also positively correlated with the increase in PGC-1α gene expression (PPARGC1A). Tug1 knockdown (KD) in differentiating mouse myotubes led to decreased Ppargc1a gene expression, impaired mitochondrial respiration and morphology, and enhanced myosin heavy chain slow isoform protein expression. In response to a Ca2+-mediated stimulus, Tug1 KD prevented an increase in Ppargc1a expression. RNA sequencing revealed that Tug1 KD impacted mitochondrial Ca2+ transport genes and several downstream PGC-1α targets. Finally, Tug1 KD modulated the expression of ~300 genes that were upregulated in response to an in vitro model of exercise in myotubes, including genes involved in regulating myogenesis. Conclusions We found that TUG1 is upregulated in human skeletal muscle after a single session of exercise, and mechanistically, Tug1 regulates transcriptional networks associated with mitochondrial calcium handling, muscle differentiation and myogenesis. These data demonstrate that lncRNA Tug1 exerts regulation over fundamental aspects of skeletal muscle biology and response to exercise stimuli.

Skeletal muscle is a highly metabolic tissue characterized by high mitochondrial abundance. As such, skeletal muscle homeostasis relies on the tight control of mitochondrial gene expression to ensure efficient mitochondrial function. Mitochondria retain a conserved genome from prokaryotic ancestors, and mitochondrial gene regulation relies on communication between mitochondrial- and nuclear-encoded transcripts. Small and long non-coding RNAs (ncRNAs) have regulatory roles in the modulation of gene expression. Emerging evidence demonstrates that regulatory ncRNAs, particularly microRNAs (miRNAs) and long ncRNAs (lncRNAs), localize within the mitochondria in diverse physiological and pathological states. These molecules present intriguing possibilities for the regulation of mitochondrial gene expression. Current research suggests that all known miRNAs are encoded by the nuclear genome but can target mitochondrial genes. Initial investigations demonstrate direct interactions between the muscle-enriched miR-1 and miR-181c and mitochondrial transcripts, suggesting advanced roles of miRNAs in mitochondrial gene regulation. This review draws evidence from the current literature to discuss the hypothesis that a level of ncRNA-mediated gene regulation, in particular miRNA-mediated gene regulation, takes place in the mitochondria. Although ncRNA-mediated regulation of the mitochondrial genome is a relatively unexplored field, it presents exciting possibilities to further our understanding of mitochondrial metabolism and human muscle physiology.

Mitochondria are central to cellular function, particularly in metabolically active tissues such as skeletal muscle. Non-coding RNAs (ncRNAs) typically localise within the nucleus and cytosol but may also translocate to subcellular compartments such as mitochondria. We aimed to investigate the nuclear-encoded ncRNAs that localise within the mitochondria of skeletal muscle cells and tissue. Intact mitochondria were isolated via immunoprecipitation and an enzymatic digestion approach was optimised to remove transcripts located exterior to mitochondria, making it amenable for high-throughput transcriptomic sequencing. Small-RNA sequencing libraries were successfully constructed from as little as 1.8ng mitochondrial RNA input. Small-RNA and whole transcriptome sequencing of mitochondria reveals the enrichment of over 200 miRNAs and 200 lncRNAs that have not previously been observed within skeletal muscle mitochondria. In summary, we describe a novel, powerful sequencing approach applicable to animal and human tissues and cells that reveals the unexpected diversity of nuclear-encoded ncRNA transcripts localised within skeletal muscle mitochondria.

Background Non-steroidal anti-inflammatory drugs (NSAIDs) and analgesics are used frequently by athletes either prophylactically for the prevention of pain, or to accelerate recovery following an injury. However, these types of pain management strategies have been shown to inhibit signalling pathways (e.g., cyclooxygenase-2) that may hinder muscular adaptations such as hypertrophy and strength. Nutraceuticals such as palmitoylethanolamide (PEA) have analgesic properties that act via different mechanisms to NSAIDS/analgesics. Furthermore, PEA has been shown to have a positive effect on sleep and may contribute positively to muscle hypertrophy via PKB activation. Although PEA has not been widely studied in the athletic or recreationally active population, it may provide an alternative solution for pain management if it is found not to interfere with, or enhance training adaptations. Therefore, the study aim is to investigate the effects of daily PEA supplementation (Levagen + ®) with resistance training on lean body mass, strength, power and physical performance and outcomes of recovery (e.g., sleep) compared to placebo. Methods This double-blind, randomised controlled study will take place over an 11-week period (including 8-weeks of progressive resistance training). Participants for this study will be 18–35 years old, healthy active adults that are not resistance trained. Participants will attend a familiarisation (week 0), pre-testing (week 1) and final-testing (week 11). At the pre-testing and final-testing weeks, total lean body mass (dual-energy X-ray absorptiometry; DXA), total mid-thigh cross sectional area (pQCT), maximal muscular strength (1 repetition maximum bench press, isometric mid-thigh pull) and power (countermovement jump and bench throw) will be assessed. Additionally, circulating inflammatory cytokines and anabolic hormones, sleep quality and quantity (ActiGraph), pain and subjective wellbeing (questionnaires) will also be examined. Discussion This study is designed to investigate the effects that PEA may have on pre-to post intervention changes in total body and regional lean muscle mass, strength, power, sleep, subjective wellbeing, and pain associated with resistance training and menstruation compared with the placebo condition. Unlike other NSAIDs and analgesics, which may inhibit muscle protein synthesis and training adaptations, PEA which provides analgesia via alternative mechanisms may provide an alternative pain management solution. It is therefore important to determine if this analgesic compound interferes with or enhances training adaptations so that athletes and active individuals can make an informed decision on their pain management strategies. Trial registration Australian New Zealand Clinical Trials Registry (ANZCTR: ACTRN12621001726842p).