METABOLIC HETEROGENEITY IN IMPAIRED GLUCOSE-TOLERANCE

Type II (non-insulin-dependent) diabetes mellitus is a metabolically h eterogeneous condition, and is invariably preceded by impaired glucose tolerance (IGT). We examined whether metabolic heterogeneity is a fea ture of IGT. Three subject groups were studied: IGT subjects with two or more living non-insulin-dependent diabetic relatives (IGT(WF), n = 17), and IGT subjects (IGT(WOF), n = 17) and subjects with normal gluc ose tolerance (NGT, n = 25) without a family history of diabetes. Gluc ose tolerance, glucose (K-ITTG) and nonesterified fatty acid (K-ITTNEF ) insulin sensitivity, and first-phase insulin secretion (FPIS) were a ssessed by oral glucose tolerance (OGTT), insulin tolerance (ITT), and intravenous glucose tolerance (IVGTT) tests, respectively. Comparison of groups was made by ANOVA and t test. The three groups were matched for age, gender, body mass index (BMI), and waist to hip ratio (WHR). IGT(WOF) and IGT(WF) subjects had comparable 2-hour plasma glucose le vels on OGTT, and insulin secretion and K-ITTG were decreased to compa rable degrees. However, in comparison to IGT(WF) subjects, IGT(WOF) su bjects had increased fasting serum triglyceride (geometric mean, 1.8 [ range, 0.8 to 4.5] v 1.1 [0.4 to 2.5] mmol . L-1, P = .02) and 2-hour plasma nonesterified fatty acid ( (iNEFA) mean +/- SD, 0.12 +/- 0.07 v 0.08 +/- 0.03 mmol . L-1, P < .02) levels and decreased K-ITTNEF valu es (4.0 [1.7 to 8.9] v 6.2 [2.8. to 12.1] % . min(-1), P < .02). Thus, the two IGT groups had comparable changes in glucose metabolism, but IGT(WOF) subjects had additional abnormalities of lipid metabolism. In conclusion, metabolic heterogeneity is a feature of IGT, and this may reflect underlying etiological heterogeneity. Copyright (C) 1997 by W .B. Saunders Company.