Abstract

BACKGROUND
Type 2 diabetes mellitus(DM) is characterized by impaired insulin secretion and decreased insulin sensitivity, and often preceded by impaired glucose tolerance (IGT). To determine the relative importance of impaired insulin secretion and insulin resistance in development of type 2 DM, we evaluated body fat distribution patterns, insulin secretion and sensitivity in patients with IGT. METHODS: Thirty-six patients with IGT and age and weight matched twenty-four control subjects, were recruited from urban diabetes incidence cohort. Fasting serum glucose and insulin were measured. Body fat distribution pattern was assessed by waist to hip ratio (WHR), percent body fat and fat mass measured by bioelectrical impedence analyzer, and visceral to subcutaneous fat ratio (VSR) at the level of umbilicus using the computed tomography. Using insulin modified intravenous glucose tolerance test, insulin sensitivity was measured as minimal model derived sensitivity index (S(I)), and insulin secretion was measured as acute insulin response to glucose (AIR(g)) and beta-cell disposition index (AlR(g) X Sr). RESULT: l) In the patients with IGT, AIR(g)X S(I)(p<0.01) and area under the curve of insulin (AUC(I))(p<0.01) were significantly decreased compared with control subjects and age was greater than control subjects without statistical significance (p=0.17). 2) In the patients with IGT, body fat distribution patterns, indices of insulin secretion and sensitivity were not different according to the presence of family history of DM. AIR, and S(I) were negatively correlated in control subjects (r=-0.38, p=0.08) and the patients with IGT without family history of DM (r=-0.37, p=0.10), but not in the patients with IGT with family history of DM. 3) In the patients with IGT, indices of insulin secretion and sensitivity were not different according to body mass index (BMI). In both obese (BMI>=25 kg/m ) and non-obese (BMI<25 kg/m) patients with IGT, AIR(g)(p<0.05) and AIR(g) X S(I) were significantly decreased compared with control subjects (p<0.01). 4) In control subjects, age (p<0.05) and body fat mass (p<0.05) were significantly associated with AIR(g) X S(I) by multiple regression analysis. In the patients with IGT, body fat mass was significantly associated with AIR(g)(p<0.01) and AUC(I)(p<0.01), and BMI(p<0.01) was significantly associated with S(I). CONCLUSION: In patients with IGT, impaired insulin secretion was more prominent than decreased insulin sensitivity as compared with control subjects regardless of obesity and the presence of family history.

• Keywords: Impaired glucose tolerance;Insulin secretion;Insulin sensitivity