Circulating and skeletal muscle microRNA profiles are more sensitive to sustained aerobic exercise than energy balance in males

MicroRNAs (miRNAs) regulate molecular processes governing muscle metabolism. Physical activity and energy balance influence both muscle anabolism and substrate metabolism, but whether circulating and skeletal muscle miRNAs mediate those effects remains unknown. This study assessed the impact of sustained physical activity with participants in energy balance (BAL) or deficit (DEF) on circulating and skeletal muscle miRNAs. Using a randomized cross-over design, 10 recreational active healthy males (mean +/- SD, 22 +/- 5 years, 87 +/- 11 kg) completed 72 h of high aerobic exercise-induced energy expenditures in BAL (689 +/- 852 kcal/day) or DEF (-2047 +/- 920 kcal/day). Blood and muscle samples were collected under rested/fasted conditions before (PRE) and immediately after 120 min load carriage exercise bout at the end (POST) of the 72 h. Trials were separated by 7 days. Circulating and skeletal muscle miRNAs were measured using microarray RT-qPCR. Independent of energy status, 36 circulating miRNAs decreased (P < 0.05), while 10 miRNAs increased and three miRNAs decreased in skeletal muscle (P < 0.05) at POST compared to PRE. Of these, miR-122-5p, miR-221-3p, miR-222-3p and miR-24-3p decreased in circulation and increased in skeletal muscle. Two circulating (miR-145-5p and miR-193a-5p) and four skeletal muscle (miR-21-5p, miR-372-3p, miR-34a-5p and miR-9-5p) miRNAs had time-by-treatment effects (P < 0.05). These data suggest that changes in miRNA profiles are more sensitive to increased physical activity compared to energy status, and that changes in circulating miRNAs in response to high levels of daily aerobic exercise are not reflective of changes in skeletal muscle miRNAs.