Background

Evidence from animal studies suggests that myokine irisin could mediate some of the exercise benefits for metabolism and cognition. Aim of this work was to evaluate effects of (i) acute and regular exercise on serum irisin and that of (ii) acute exercise on skeletal muscle FNDC5 gene expression in association with adiposity, metabolic flexibility and cognitive functions.

Methods

Serum irisin was assessed (Biovendor) at baseline, immediately after and 60min after an acute bout of aerobic exercise (40-min at 70%VO2max), performed before & after 3-month supervised aerobic-strength exercise intervention (3x1h/week) in the 30 (7M/23F) seniors (65.8+/-4.7yrs.). Cognitive functions were assessed by computerized cognitive tests (MemTrax, Cogstate). Metabolic flexibility (∆RQ) was determined by euglycemic hyperinsulinemic clamp and indirect calorimetry. FNDC5 mRNA was measured in biopsy samples of m. vastus lateralis by qPCR. Body composition was assessed by DEXA.

Results

At baseline pre-exercise state, irisin did not correlated with metabolic flexibility (∆RQ) or cognitive functions. However, serum irisin levels detected immediately after acute aerobic exercise were positively associated with ∆RQ (r=0.532; p=0.002), learning/working memory (Cogstate, r=0.351; p=0.018), MemTrax score (r=0.304; p=0.03) and negatively with the abdominal adiposity (truncal/extremity fat ratio) (r=-0.389; p=0.012). Exercise-regulation of circulating irisin was not found. Expression of gene encoding irisin preprotein FNDC5 in skeletal muscle was not regulated by 3-month training. Metabolic flexibility was the best predictor of the post-exercise serum irisin levels, explaining more than 22% of its variability.

Conclusions

Subtle dynamic changes of circulating irisin levels induced by acute aerobic exercise are associated with metabolic flexibility and cognitive performance in the elderly.Grant support: APVV 15-0253, VEGA 2/0107/18, SAS-MOST JRP 2018/10