Altered Steroid Metabolism and Insulin Signaling in PCOS Endometria: Impact in Tissue Function

Background: Polycystic Ovary Syndrome (PCOS) is a prevalent endocrine/ metabolic disorder characterized by hyperandrogenemia and in most cases, by hyperinsulinemia in addition to obesity. Besides ovarian dysfunction, endometrial physiology is also disrupted since this tissue is highly dependent on the action of steroids; in case of conception cycles, high percentage of abortion is observed. Because of the endocrine/metabolic alterations, PCOS-women present high probability to develop hyperplasia and endometrial cancer, where an imbalance of cell proliferation/apoptosis processes is detected. Additionally, insulin pathway and the endometrial energetic homeostasis are also compromised. Methods: The aim of this review was to report molecular alterations related to insulinresistance and/or obesity in PCOS-women endometria that could drive to infertility. For this, several methods were employed: immunohistocytochemistry, qPCR, western-blot, glucoseuptake, cell cultures, among others. Results: Diminished levels and activity of several insulin signaling pathway molecules, like IRS-1/AS160/PKCζ, were detected. Concomitantly, a defect in the synthesis and GLUT4 translocation to cell surface is induced. Oral administration of metformin (insulin sensitizer) to PCOS-patients increases GLUT4 endometrial levels, improving fertility of those patients. Another relevant feature is the high percentage of obesity in PCOS-women; adiponectin is an obesity marker and elicits an insulin-sensitizer action, being diminished in plasma of obese PCOSwomen similar to its endometrial level, adiponectin-receptors and APPL1, an adapter molecule of adiponectin pathway. Moreover, obesity and PCOS can induce a pro-inflammatory environment, exaggerating the alterations in insulin pathway. Conclusion: The evidences obtained in PCOS-endometria clearly indicate that these molecular defects could partially explain the reproductive failures of these patients.