Factors associated with circulating concentrations of irisin in the general population cohort of the ABCD study.

OBJECTIVE: Animal studies have shown that irisin is a myokine secreted following physical exercise, and that it induces the remodeling of white adipose tissue toward brown adipose tissue. Therefore, a protective role of irisin against obesity, diabetes, and other metabolic and cardiovascular conditions has been hypothesized. However, data in humans are contradictory and few data are available concerning the general population. DESIGN: We aimed to evaluate the association between serum irisin concentrations and habitual physical activity, as well as other metabolic and cardiovascular factors in a general population in a Mediterranean area. METHODS: We considered 858 consecutive individuals included in the ABCD (Alimentazione, Benessere Cardiovascolare e Diabete) study (ISRCTN15840340), a longitudinal observational single-center study of a cohort representative of the general population of Palermo, Sicily. Irisin serum concentrations (Phoenix Europe, Germany), habitual physical activity (HPA) level, and other blood and clinical variables were measured. RESULTS: The irisin serum concentrations were not normally distributed in the cohort (Shapiro-Wilk test=0.94; P<0.001). A significant association between irisin concentrations and HPA was observed (P<0.001). Irisin concentrations were higher in women than in men (P<0.01), and significantly correlated with serum concentrations of HDL-cholesterol (P<0.05) and hs-C-reactive protein (hs-CRP; P<0.05). Binary logistic regression analysis demonstrated that high (⩾ median value) irisin serum concentrations were significantly associated with female gender (OR=1.63; 95% CI=1.16-2.28), high serum hs-CRP concentrations (OR=1.61; 95% CI=1.02-2.54) and the HPA level (OR=1.42; 95% CI=1.02-1.96). CONCLUSIONS: Our study confirms, in a cohort of a general population, that irisin concentrations gradually increase with the usual level of habitual physical activity.