Effects of Pioglitazone on Insulin and Glucose Metabolism in Women With Polycystic Ovary Syndrome (PCOS)

Overview

Our hypothesis is that hyperinsulinemia increases the renal clearance of D-chiro-inositol (DCI) in women with polycystic ovary syndrome (PCOS) and that this leads to a reduction in circulating insulin-stimulated D-chiro-inositol-containing inositol phosphoglycan (DCI-IPG) release. To assess the effects of a chronic reduction in circulating insulin on DCI metabolism, we propose to reduce circulating insulin in obese women with PCOS by improving insulin sensitivity with the drug pioglitazone. Pioglitazone is a thiazolidinedione that improves peripheral insulin sensitivity, presumably by activation of the peroxisome proliferator-activated receptor gamma (PPARγ) receptor. Administration of pioglitazone to women with PCOS has been shown to improve insulin sensitivity, reduce insulin secretion, and decrease both fasting and post-prandial serum insulin concentrations.

This protocol focuses on the hypothesis that a deficiency in a putative inositolphosphoglycan (IPG) mediator of insulin action, namely a D-chiro-inositol-containing IPG (DCI-IPG), contributes to the insulin resistance of some women with PCOS. Our interest in this area stems directly from our previous studies, which demonstrated that administration of the precursor, D-chiro-inositol (DCI), to both obese and lean women with PCOS improved glucose intolerance while reducing circulating insulin, and simultaneously improved ovulatory function and decreased serum androgens. These findings were recently confirmed in a large-scale study by an independent group. The findings of these three studies suggested that administration of DCI improved insulin sensitivity in PCOS, which then resulted in an improved hormonal and metabolic milieu.