title: Muscle-enriched microRNA miR-486 decreases in circulation in response to exercise in young men.
abstract: 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% VO2max 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, miR-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 VO2max for each subject (R = 0.58, P = 0.038).
  
  
  CONCLUSIONS
  The reduction in circulating miR-486 may be associated with metabolic changes during exercise and adaptation induced by training.
authors.affiliation: Laboratory of Health Science, Kyoto Prefectural University Kyoto, Japan.
authors.forename: Wataru
authors.initials: W
authors.lastname: Aoi
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Ichikawa
authors.forename: Keitaro
authors.initials: K
authors.lastname: Mune
authors.forename: Yuko
authors.initials: Y
authors.lastname: Tanimura
authors.forename: Katsura
authors.initials: K
authors.lastname: Mizushima
authors.forename: Yuji
authors.initials: Y
authors.lastname: Naito
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Yoshikawa
keywords: exercise; maximum oxygen uptake; metabolism; microRNA; skeletal muscle