Insulin secretory dysfunction and insulin resistance in the pathogenesis of korean type 2 diabetes mellitus

Although insulin resistance has been shown to be a primary defect causing type 2 (non insulin-dependent) diabetes mellitus in Pima Indians and Caucasians, insulin secretory defect has also been known to be an important factor in the development of type 2 diabetes. We undertook a study to investigate the initial abnormality of glucose intolerance in Koreans. A total of 370 Korean subjects were classified into 5 groups according to their degree of glucose intolerance (normal fasting glucose [NFG]/normal glucose tolerance [NGT], n = 95; impaired fasting glucose [IFG]/NGT, n = 29; NFG/impaired glucose tolerance [IGT], n = 60; IFG/IGT, n = 68; diabetes, n = 118). Insulinogenic index was used as an index of early-phase insulin secretion. Insulin resistance was assessed by the R value of the homeostasis model assessment [HOMA(R)]. Insulinogenic index significantly decreased in subjects with IFG/NGT and NFG/IGT compared with those with NFG/NGT. However, there was no significant difference in HOMA(R) between subjects with NFG/NGT and those with IFG/NGT or NFG/IGT. Insulinogenic index decreased significantly with the increase of plasma glucose 120-minute value at the earlier stage of glucose intolerance compared with HOMA(R). These results suggest that early-phase insulin secretory defect may be the initial abnormality in the development of type 2 diabetes in Korean subjects.