Patterns of Insulin Concentration During the OGTT Predict the Risk of Type 2 Diabetes in Japanese Americans

OBJECTIVEdTo examine whether the patterns of insulin concentration during the oral glu-cose tolerance test (OGTT) predict type 2 diabetes. RESEARCHDESIGNANDMETHODSdWe followed 400 nondiabetic Japanese Amer-icans for 10–11 years. Insulin concentrations at 30, 60, and 120 min during a 2-h 75-g OGTT at baseline were used to derive the following possible patterns of insulin: pattern 1 (30-min peak, higher insulin level at 60 than at 120 min), pattern 2 (30-min peak, lower or equal level at 60 vs. 120 min), pattern 3 (60-min peak); pattern 4 (120-min peak, lower level at 30 than at 60 min), and pattern 5 (120-min peak, equal or higher level at 30 vs. 60 min). Insulin sensitivity was estimated by homeostasis model assessment of insulin resistance (HOMA-IR) and Matsuda in-dex. Insulin secretion was estimated by the insulinogenic index (IGI) [Dinsulin/Dglucose (30– 0 min)] and disposition index (IGI/HOMA-IR). RESULTSdThere were 86 incident cases of type 2 diabetes. The cumulative incidence was 3.2, 9.8, 15.4, 47.8, and 37.5 % for patterns 1, 2, 3, 4, and 5, respectively. Compared with pattern 1, patterns 4 and 5, characterized by a lasting late insulin response, were associated with signifi-cantly less insulin sensitivity as measured by the Matsuda index and lower early insulin respons