Circulating serum irisin levels in obesity and type 2 diabetes mellitus.

Irisin is an exercise-regulated myokine inducing browning of white adipose tissue and has gained interest as a potential new strategy to combat obesity and its associated disorders, such as type 2 diabetes mellitus (T2DM). The aim of this study is to evaluate the circulating serum irisin levels in obesity and T2DM and also to elucidate possible relationships between serum irisin levels with anthropometric and metabolic parameters of obesity and T2DM. One hundred fifty newly diagnosed T2DM patients as well as 150 nondiabetic control subjects were enrolled in this study. Nondiabetic controls were then stratified according to their body mass index (BMI) into three subgroups; lean, overweight, and obese. Serum irisin levels were evaluated by enzyme-linked immunosorbent assay. Serum irisin levels were significantly decreased in T2DM patients compared with nondiabetic controls. Obese nondiabetic controls had significantly higher serum irisin levels compared with lean nondiabetic controls. In both nondiabetic controls and T2DM patients, serum irisin was significantly positively correlated with BMI (r = 0.985, P < 0.001 and r = 0.218, P = 0.007, respectively), fat mass (r = 0.959, P < 0.001 and r = 0.202, P = 0.013, respectively), fat-free mass (r = 0.606, P < 0.001 and r = 0.194, P = 0.017, respectively), fat-free mass index (r = 0.820, P < 0.001 and r = 0.179, P = 0.028, respectively), waist-to-hip ratio (r = 0.880, P < 0.001 and r = 0.194, P = 0.017, respectively), fasting insulin (r = 0.989, P < 0.001 and r = 0.207, P = 0.011, respectively), and HOMA-IR (r = 0.989, P < 0.001 and r = 0.185, P = 0.023, respectively), whereas; significantly negatively correlated with insulin sensitivity (r = -0.992, P < 0.001 and r = -0.187, P = 0.022, respectively). In this study, we demonstrated that circulating serum irisin levels were increased in obese nondiabetic subjects, while decreased in T2DM patients. Moreover, serum irisin levels were correlated with anthropometric and metabolic markers of obesity and T2DM.