Defects in insulin receptor signaling in vivo in the polycystic ovary syndrome (PCOS)

Abstract

Women with polycystic ovary syndrome (PCOS) are insulin resistant secondary to a postbinding defect in insulin signaling. Sequential euglycemic glucose clamp studies at 40 and 400 mU · m−2 · min−1 insulin doses with serial skeletal muscle biopsies were performed in PCOS and age-, weight-, and ethnicity-matched control women. Steady-state insulin levels did not differ, but insulin-mediated glucose disposal was significantly decreased in PCOS women ( P < 0.05). Insulin receptor substrate (IRS)-1-associated phosphatidylinositol 3-kinase (PI 3K) activity was significantly decreased in PCOS ( n = 12) compared with control skeletal muscle ( n = 8; P < 0.05). There was no significant difference in the abundance of IR, IRS-1, or the p85 regulatory subunit of PI 3K in PCOS ( n = 14) compared with control ( n = 12) muscle. The abundance of IRS-2 was significantly increased ( P < 0.05) in PCOS skeletal muscle, suggesting a compensatory change. We conclude that there is a physiologically relevant defect in insulin receptor signaling in PCOS that is independent of obesity and type 2 diabetes mellitus.