Association of circulating irisin and cardiopulmonary exercise capacity in healthy volunteers: results of the Study of Health in Pomerania.

BACKGROUND: Irisin, a recently discovered myokine, is assumed to be secreted by muscle cells in response to exercise and is involved in the regulation of energy metabolism by browning white adipose tissue cells. However, due to the fact that previous studies revealed conflicting results concerning the association between irisin and exercise, the aim of the present study was to investigate the potential relationship between irisin and exercise capacity in a population-based setting. METHODS: From the population-based Study of Health in Pomerania (SHIP-TREND) 334 men and 406 women with irisin measurements were selected and a standardised symptom limited cardiopulmonary exercise test was used. Exercise capacity was quantified by oxygen uptake at anaerobic threshold (VO2@AT), peak exercise (peakVO2) and maximum power output at peak exertion. In addition, the oxygen pulse was assessed. ANOVA and multivariable linear regression analyses were performed stratified by sex and adjusted for age, weight, height and smoking. RESULTS: In men, we observed inverse associations between irisin serum concentration and exercise capacity assessed by peakVO2 and maximum power output. In contrast, in women a trend towards a positive relationship between irisin and peakVO2 was detected, whereas none of the other parameters showed significant associations with irisin. CONCLUSION: Based on a large population sample, our results did not confirm the previous reported positive linkage between exercise and irisin. Thus the relationship needs further investigation in particular with respect to sex differences.