Circulating microRNAs after a 24-h ultramarathon run in relation to muscle damage markers in elite athletes.

Ultra-endurance sports are growing in popularity but can be associated with adverse health effects; such as exercise-induced muscle damage (EIMD), which can lead to exertional rhabdomyolysis. Circulating microRNAs (miRNAs) may be useful to approach the degree of EIMD. We aimed to: 1) investigate the relevance of circulating miRNAs as biomarkers of muscle damage and 2) examine the acute response of skeletal/cardiac muscle and kidney biomarkers to a 24-h run in elite athletes. Eleven elite athletes participated in the 24-h Run World Championships. Counter-movement jump (CMJ), creatine kinase (CK), myoglobin (Mb), creatinine (Cr), high-sensitive cardiac troponin T (hs-cTnT) and muscle-specific miRNA (myomiR) levels were measured before, immediately after, and 24 and 48h after the race. CMJ height was reduced immediately after the race (-84.0±25.2%, p<0.001) and remained low at 24h (-43.6±20.4%, p=0.002). We observed high CK activity (53,239±63,608 U/L, p<0.001) immediately after the race and it remained elevated 24h after (p<0.01). Circulating myomiRs levels (miR-1-3p, miR-133a-3p, miR-133b, miR-208a-3p, miR-208b-3p, and miR-499a-5p) were elevated immediately after the 24-h run (fold changes: 18-124,723, p<0.001) and significantly (p<0.05) correlated or tended to significantly (p<0.07) correlate with the reduction in CMJ height at 24h. We found no significant correlation between CMJ height loss at 24h and CK (p=0.23) or Mb (p=0.41) values. All elite ultramarathon runners included in our study were diagnosed with exertional rhabdomyolysis after the 24-h ultramarathon race. MyomiR levels may be useful to approach the degree of muscle damage.