Relationships of insulin sensitivity to abdominal fat accumulation, sex hormones, and sex hormone-binding globulin in male subjects with impaired glucose tolerance

Insulin sensitivity (glucose infusion rate; GIR) evaluated by hyperinsulinemic euglycemic clamp method, abdominal fat accumulation by computed tomography, sex steroid hormones (free testosterone; Free T, estradiol; E2, and dehydroepiandrosterone sulfate; DHEA-S) and sex hormone binding globulin (SHBG) were measured in 30 male subjects with impaired glucose tolerance aged from 3175 yrs. The participants in this study included both lean and obese subjects. The value of GIR (mg/kg/min) ranged from 3.3 to 13.4 mg/kg/min. Among these subjects, about 50% were within normal range. Both Free T and DHEA-S were significantly and negatively correlated with age, while SHBG was positively correlated with age. Visceral fat area (VFA) was negatively associated with SHBG, and positively with DHEA-S. Subcutaneous fat area (SFA) was negatively associated with SHBG and age (p<0.05). In a stepwise multiple regression analysis, SHBG and age were selected as significant independent variables of VFA and SFA, respectively. No significant correlation was observed between GIR and fasting glucose or glucose response to 75g oral glucose tolerance test (OGTT). On the other hand, significant negative correlation was found between GIR and insulin concentration at 120' after oral glucose load (IRI120'; r=-0.613) and area under the curve of IRI (AUCIRI; r=-0.705). In a simple correlation analysis, GIR showed a significant positive association with age (r=0.497) and SHBG (r=0.392), and negative association with obesity indices, especially with SFA (r=-0.701), and DHEA-S. The IRII20' and AUCIRI were significantly and positively associated with obesity indices, especially with SFA, and negatively with SHBG. A stepwise multiple regression analysis indicated that SFA is significant independent variable of GIR, IRI120', and AUCIRI. From these results, it is suggested that SFA is one of the determinants of insulin sensitivity and insulin response to oral glucose load in male subjects with impaired glucose tolerance.