Hyperinsulinemia alters myoinositol to d-chiroinositol ratio in the follicular fluid of patients with PCOS

Myoinositol (MI) and d-chiroinositol (DCI) are 2 stereoisomers and insulin sensitizers. Their physiological ratio differs from tissue to tissue, and they are regulated by an insulin-dependent epimerase whose activity is drastically reduced in conditions of insulin resistance. Based on literature data and on the fact that MI phospholipids are follicle-stimulating hormone (FSH) second messengers, we speculated that patients with polycystic ovary syndrome (PCOS) having hyperinsulinemia, present an enhanced MI to DCI epimerization in the ovary, leading to MI deficiency that impairs FSH signaling, resulting in reduced oocyte quality. In the present study, 20 patients with PCOS and 20 healthy women were enrolled for measurement of MI and DCI levels in their follicular fluid. Follicular fluid samples were taken using a vaginal probe and both MI and DCI were quantified analytically. Results showed that the ratio of MI-DCI dropped from 100:1 in healthy participants to 0.2:1 in patients with PCOS who additionally displayed significantly higher levels of insulin resistance, hyperinsulinemia, and luteinizing hormone. This study is the first one to analyze the misbalance in the MI-DCI ratio in the ovary of patients with PCOS, supporting the concept that maintaining the physiological levels of the 2 stereoisomers is crucial, in restoring the ovarian functionality.