Abstract

Objectives: To assess chemerin levels in sera and adipose tissue (AT) from PCOS women and matched controls and its regulation.

Research Design and Methods: Real-time RT-PCR and western blotting were used to assess mRNA and protein expression of chemerin. Serum chemerin was measured by ELISA. We investigated the in vivo effects of insulin on serum chemerin levels via a prolonged insulin-glucose infusion. The ex vivo effect of insulin, metformin and steroid hormones on AT chemerin protein production and secretion into conditioned media were assessed by western blotting and ELISA, respectively.

Results: Serum chemerin, subcutaneous and omental AT chemerin were significantly higher in PCOS women (n = 14; P < 0.05, P < 0.01). Hyperinsulinemic induction in human subjects significantly increased serum chemerin levels (n = 6; P < 0.05, P < 0.01). In AT explants, insulin significantly increased (n = 6; P < 0.05, P < 0.01) whereas metformin significantly decreased (n = 6; P < 0.05, P < 0.01) chemerin protein production and secretion into conditioned media, respectively. After 6 months of metformin treatment, there was a significant decrease in serum chemerin (n = 21; P < 0.01). Importantly, changes in HOMA-IR were predictive of changes in serum chemerin (P = 0.046).

Conclusions: Serum and AT chemerin levels are increased in PCOS women and are up-regulated by insulin. Metformin treatment decreases serum chemerin in these women.