Irisin, a newly discovered myokine, is a novel biomarker associated with physical activity in patients with chronic obstructive pulmonary disease

Background and objectiveIrisin is a recently identified hormone secreted by skeletal myocytes, which has been proposed to mediate the beneficial effects of exercise. Physical activity has been emphasized as one of the principal targets of the treatment for chronic obstructive pulmonary disease (COPD). This study was designed to evaluate the possibility of using serum irisin level as a novel biomarker associated with physical activity in patients with COPD. MethodsWe measured the serum irisin level in 72 COPD patients and 27 control subjects, and investigated its correlation to pulmonary function parameters, exercise capacity and physical activity level. In addition, we analysed the effects of acute and chronic exercise on serum irisin level. ResultsFat-free mass index was not significantly different between the two study groups. However, lower serum irisin level was observed in COPD patients than in the control subjects (COPD patients: median (interquartile range) 31.6 (22.7-40.4) ng/mL; control subjects: 50.7 (39.3-65.8) ng/mL; P<0.001). The serum irisin level did not significantly correlate with any pulmonary function parameters and 6-min walk distance. However, serum irisin level was associated with the physical activity level in all subjects. In COPD patients, acute exercise did not affect serum irisin level, but an 8-week exercise training was linked to the significant increase in its level. ConclusionsCirculating irisin could be used to evaluate physical activity in COPD patients and increased after an 8-week exercise training. Serum irisin level may prove to be a valuable biomarker in clinical follow up of COPD. Serum levels of irisin increased in COPD patients following an 8-week training programme. Serum irisin level could be used as a novel biomarker associated with physical activity in patients with COPD and may prove to be a valuable tool in clinical follow up of COPD.