Elevated Circulating Levels of Irisin and the Effect of Metformin Treatment in Women With Polycystic Ovary Syndrome

Context: Polycystic ovary syndrome (PCOS) is an insulin resistance (IR) state, like obesity and type 2 diabetes mellitus (T2DM). Although previous studies have suggested a correlation between irisin and the metabolic parameters associated with obesity and T2DM, the results have been inconsistent. Objective: Our objective was to (1) determine circulating irisin levels in women with PCOS and control subjects, (2) examine the relationship of irisin and conventional markers of insulin resistance, and (3) examine irisin changes with interventions modulating IR in PCOS women. Patients and Design: This study was comprised of a series of cross-sectional and interventional studies of 178 PCOS and 123 healthy women from the general population and outpatients of the Internal Medicine Department at the Second Affiliated Hospital, Chongqing Medical University, China. Forty seven women with PCOS were randomly assigned to 6 months of oral metformin (850 mg bid). The oral glucose tolerance test (OGTT) and the euglycemic-hyperinsulinemic clamp (EHC) were performed to assess glucose tolerance and insulin sensitivity. Outcome measures were IR (AUC(Insulin) and M values) on an OGTT and EHC, irisin levels, and metabolic markers. Results: Circulating irisin was significantly higher in both overweight/obese (body mass index [BMI] >= 25 kg/m2) and PCOS women (P < .01). Circulating irisin levels correlated with BMI, WHR, FAT%, total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), AUC(Insulin), homeostasis model assessment of insulin resistance (HOMA2-IR), M values, and free androgen index (FAI). During EHC, short-term hyperinsulinemia exhibited an inhibitory effect on irisin levels. After 6 months of metformin treatment, there was a significant decrease in circulating irisin in PCOS women following improved IR. Conclusions: These data suggest that irisin may be a useful marker of IR in PCOS women.