title: Irisin, a newly discovered myokine, is a novel biomarker associated with physical activity in patients with chronic obstructive pulmonary disease.
abstract: OBJECTIVE
  Irisin 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.
  
  
  METHODS
  We 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.
  
  
  RESULTS
  Fat-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.
  
  
  CONCLUSIONS
  Circulating 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.
authors: Department of Respiratory Medicine, Graduate School of Medicine, Osaka City University, Osaka, Japan.
authors: Naoki
authors: N
authors: Ijiri
authors: Hiroshi
authors: H
authors: Kanazawa
authors: Kazuhisa
authors: K
authors: Asai
authors: Tetsuya
authors: T
authors: Watanabe
authors: Kazuto
authors: K
authors: Hirata
mesh_terms: D000368:Aged; D015415:Biomarkers / Q000097:blood; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005353:Fibronectins / Q000097:blood*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D018485:Muscle Fibers, Skeletal / Q000378:metabolism; D029424:Pulmonary Disease, Chronic Obstructive / Q000097:blood* / Q000503:physiopathology
chemical_list: D015415:Biomarkers; C577593:FNDC5 protein, human; D005353:Fibronectins
keywords: 6-min walk distance; exercise; fibronectin type III domain-containing protein 5; irisin; physical activity