Muscle-enriched microRNA miR-486 decreases in circulation in response to exercise in young men

Background: MicroRNAs (miRNAs) are small non coding RNAs involved in post-transcriptional gene regulation. miRNAs are taken in by intracellular exosomes, secreted into circulation, and taken up by other cells, where they regulate cellular functions. We hypothesized that muscle-enriched miRNAs existing in circulation mediate beneficial metabolic responses induced by exercise. To test this hypothesis, we measured changes in muscle-enriched circulating miRNAs (c-miRNAs) in response to acute and chronic aerobic exercise. Methods: Eleven healthy young men (age, 21.5 +/- 4.5 y; height, 168.6 +/- 5.3 cm; and body weight, 62.5 +/- 9.0 kg) performed a single bout of steady-state cycling exercise at 70% VO(2)max for 60 min (acute exercise) and cycling training 3 days per week for 4 weeks (chronic exercise). Blood samples were collected from the antecubital vein before and after acute and chronic exercise. RNA was extracted from serum, and the levels of muscle enriched miRNAs (miR-1, miR-133a, miR-133b, miR-206, m R-208b, miR-486, and miR-499) were measured. Results: All of these miRNAs, except for miR-486, were found at too low copy numbers at baseline to be compared. miR-486 was significantly decreased by both acute (P = 0.013) and chronic exercise (P = 0.014). In addition, the change ratio of miR-486 due to acute exercise showed a significant negative correlation with VO(2)max for each subject (R = 0.58, P = 0.038). Conclusion: The reduction in circulating miR-486 may be associated with metabolic changes during exercise and adaptation induced by training.