Feedback Inhibition Of Insulin Secretion In Obese Female Subjects With Different Insulin-Resistant States

In order to examine the effect of exogenously induced hyperinsulinemia on insulin secretion during euglycemic conditions in insulin resistant subjects, 15 female obese subjects, five of whom with normal glucose tolerance (NGT), five with impaired glucose tolerance (IGT), five with polycystic ovarian syndrome (PCO) were studied, together with five nonobese healthy subjects as controls'. We examined the ''whole body'' insulin sensitivity and the insulin/insulin short-loop feedback and insulin resistance by percentage suppression of basal serum C-peptide during glucose clamp, M, MCR, M/I ratio values (as expression of insulin resistance) were significantly lower in NGT, IGT and PCO obese subjects vs controls, The basal serum C-peptide levels were significantly higher in NGT and IGT obese subjects vs controls and PCO subjects, The suppression of C-peptide at 120 min of glucose clamp was significantly lesser in IGT vs NGT, PCO and control subjects, In conclusion, the insulin/insulin negative short-loop feed-back is not an expression of a beta-cell insulin resistance, but may be considered as a marker of an independent dysfunction of insulin secretion. (C) 1997, Editrice Kurtis.