Plasma omentin-1 levels are reduced in non-obese women with normal glucose tolerance and polycystic ovary syndrome

OBJECTIVE: Omentin-1 is a novel adipokine that increases insulin sensitivity and is expressed in visceral adipose tissue. The aim of this study was to determine the metabolic parameters that influence plasma omentin-1 levels in women with polycystic ovary syndrome (PCOS). DESIGN AND METHODS: A cross-sectional study was performed in 87 women with PCOS and 53 body mass index (BMI)-matched healthy controls including 39 non-obese, normal-weight (NW) PCOS women with normal glucose tolerance (NGT) and 44 BMI- and homeostasis model assessment (HOMA)-matched controls. Indices of insulin sensitivity, metabolic variables, circulating androgen levels, serum adiponectin, and omentin-1 levels were measured. A 75 g oral glucose tolerance test was performed in all participants. RESULTS: Plasma omentin-1 levels were significantly lower in women with PCOS compared with those in BMI-matched controls (P<0.001). A significantly lower level of plasma omentin-1 was observed in non-obese women with PCOS and NGT compared with that in BMI- and HOMA-matched controls (P<0.001). Omentin-1 level was negatively correlated with BMI, indices of insulin sensitivity, and circulating androgens and was associated with greater 2 h postprandial glucose, C-peptide, and insulin levels compared with fasting values. Within the NW and NGT groups, omentin-1 levels remained negatively correlated with BMI, 2 h postprandial C-peptide, and circulating androgens and demonstrated a negative linear trend according to quartile of free testosterone (P=0.028). CONCLUSIONS: Plasma levels of omentin-1 were reduced in non-obese women with PCOS and NGT. Postprandial hyperinsulinemia and hyperglycemia contributed more to lower omentin-1 levels than did fasting values in the setting of PCOS. Increased androgen levels contributed to decreased omentin-1 levels in women with PCOS.