Insulin secretion and action show differences in impaired fasting glucose and in impaired glucose tolerance in Asian Indians

BACKGROUND: The aim of the study was to compare the abnormalities in insulin secretion and insulin sensitivity in impaired fasting glucose (IFG) and in impaired glucose tolerance (IGT). METHODS: Glucose tolerance was determined by oral glucose tolerance test in 289 non-diabetic subjects selected for this study (M : F, 160 : 129, mean age 42.2 +/- 11.0 (SD) years, mean body mass index (BMI) 24.9 +/- 4.2 kg/m(2)). Diabetic subjects were excluded from the study. The association of insulin resistance and beta-cell function (calculated by HOMA model) with IFG and IGT was studied using linear and multiple logistic regression analyses. Subjects with normoglycaemia (NGT) were used as controls. RESULTS: Insulin resistance was significantly more in IFG and in IGT than in NGT. beta-cell dysfunction was significantly higher in IFG than in IGT. IFG was associated with both insulin resistance (OR = 9.11, p < 0.001) and beta-cell dysfunction (inverse correlation, OR = 0.103, p < 0.001), while only insulin resistance was significantly associated with IGT (OR = 1.24, p = 0.005). CONCLUSIONS: In urban South Asian Indians, IFG differed from IGT in having combined insulin resistance and beta-cell dysfunction, while IGT was associated only with insulin resistance.