Alteration of ghrelin-neuropeptide Y network in obese patients with polycystic ovary syndrome: role of hyperinsulinism

Objective Insulin, ghrelin, neuropeptide Y (NPY) and leptin interact in the regulation of energy homeostasis. Most of these signals are altered in polycystic ovary syndrome (PCOS), which is characterized by a high prevalence of obesity. The present study was conducted to evaluate ghrelin–NPY and ghrelin–leptin interplays in relation to insulin secretion in obese PCOS subjects. Design Pilot prospective study. Patients Seven obese PCOS women and seven age–weight matched controls. Measurements Hormonal measurements, oral glucose tolerance test (OGTT) and a ghrelin test (1 µg/kg i.v. bolus). PCOS patients repeated the clinical work‐up after 4 months of metformin treatment (1500 mg/day orally). Results At baseline, PCOS women showed a significantly higher insulinaemic response to the OGTT compared to controls (P < 0·05). In basal conditions, PCOS women exhibited lower NPY levels than controls (P < 0·01). Ghrelin injection markedly increased NPY in controls (P < 0·01), whereas PCOS women showed a deeply blunted NPY response to the stimulus (area under the curve – AUC–NPY: P < 0·01 vs. controls.). Metformin treatment induced a significant decrease in insulin levels (P < 0·01) and the concomitant recovery of NPY secretory capacity in response to ghrelin (AUC–NPY: P < 0·05 vs. baseline) in PCOS women. Leptin levels, which were similar in the two groups, were not modified by ghrelin injection; metformin did not affect this pattern. Conclusion Hyperinsulinaemia seems to play a pivotal role in the alteration of NPY response to ghrelin in obese PCOS women. This derangement could be implicated in the physiopatology of obesity in these patients.