Mechanical overload-induced muscle-derived extracellular vesicles promote adipose tissue lipolysis

How regular physical activity is able to improve health remains poorly understood, but release of substances from skeletal muscle following exercise is one proposed mechanism. Here we describe a novel mechanism through which physical activity initiates extracellular vesicle (EV)-mediated communication between skeletal muscle and adipose tissue causing increased adipocyte lipolysis as a result of enhanced catecholamine sensitivity. In response to a hypertrophic stimulus induced by mechanical overload (MOV), skeletal muscle released EVs containing muscle-specific miR-1 which were preferentially taken up by epididymal white adipose tissue (eWAT) and were associated with elevated adrenergic signaling and lipolysis. Inhibiting EV release by GW4869 treatment prevented the MOV-induced increase in eWAT miR-1 abundance and expression of lipolytic factors. miR-1 was shown to induce adrenergic receptor beta β3 (Adrβ3) expression in adipocytes by targeting transcription factor AP-2, alpha (Tfap2α, a known repressor of Adrβ3 expression. Ex vivo experiments showed enhanced catecholamine sensitivity and elevated fatty acid oxidation in eWAT following MOV. Following a bout of resistance exercise in humans, skeletal muscle miR-1 expression was decreased with a concomitant increase in EV miR-1 abundance, suggesting that a skeletal muscle-adipose tissue axis is operative in humans. Altogether, our highly novel findings demonstrate that skeletal muscle promotes metabolic adaptations in adipose tissue in response to MOV via EV-mediated delivery of miR-1. 4 samples: 1 Veh-Sham, 1 Veh-SA, 1 GW-Sham, 1 GW-SA. Veh:Vehicle (DMSO), GW: GW4869 (EV inhibitor), SA (Mechanical Overload, synergist ablation)