Association of Circulating Irisin Levels with Adiposity and Glucose Metabolic Profiles in a Middle-Aged Chinese Population: A Cross-Sectional Study

OBJECTIVE: The myokine irisin has been proposed to affect obesity and metabolism disorders. However, data about the association of irisin with obesity and glucose metabolic status in humans remains controversial, and limited data are available concerning the Chinese population. This study aimed to evaluate the association between serum irisin concentrations and obesity, as well as glucose metabolic and cardiovascular factors in the middle-aged physical activity-matched Chinese Han race population. METHODS: A total of 740 participants were included in this cross-sectional study, who were divided into a normal weight (NW) group, overweight/obese (OB) group, normal weight type 2 diabetes (DM-NW) group and overweight/obese diabetes (DM-OB) group, and physical activity was evaluated and matched for the four groups. Circulating irisin levels were analyzed and compared among the groups with different adiposity and glucose status. Linear regression analysis was performed to test the relationship between serum irisin and adiposity indices, glucose metabolic and other cardiovascular risk factors. RESULTS: Circulating irisin levels were significantly correlated with higher levels of direct and indirect adiposity markers, including BMI, waist circumference and fat mass, and other cardiovascular risk factors, such as plasma triglyceride and low-density lipoprotein cholesterol level (p < 0.01). Diabetes patients had lower irisin levels compared to non-diabetes participants, in either normal weight and obese group, resulting in a correlation of irisin with HbA1c, HOMA-IR and HOMA-IS (p < 0.01). Linear regression analysis demonstrated that irisin serum concentrations were independently associated with sex, BMI, HbA1c, HOMA-IR and HOMA-IS (R(2) = 0.465). CONCLUSION: These data indicated that circulating irisin was affected by adiposity and glucose metabolism condition in the middle-aged Chinese population. The increase of irisin under conditions of obesity may indicate its physiological function to improve glucose tolerance which is often impaired in obese subjects, but this compensatory secretion of irisin seems likely to be progressing to a secretion failure once diabetes developed.