Pathophysiologic heterogeneity in the development of type 2 diabetes mellitus in Korean subjects

Objective: To investigate the clinical characteristics and predisposing metabolic abnormalities in the development of glucose intolerance and diabetes mellitus in obese and non-obese Korean subjects. Methods: Four hundred Korean subjects were classified into five groups according to degree of glucose tolerance by OGTT: NGT, IGT alone, IFG alone, IFG + IGT, and DM. The groups were also subdivided into obese and non-obese group according to body mass index. Insulin resistance was assessed by using homeostasis model assessment of insulin resistance (HOMA-R), and insulinogenic index was used as an index of early-phase insulin secretion. Results: Impaired early-phase insulin secretion was seen in non-obese IGT alone, IFG alone, and IFG + IGT, though more profound secretory defects were noted in IFG + IGT and DM. No significant difference were found in HOMA-R among non-obese IGT alone, IFG alone, or IFG + IGT, or in terms of early-phase insulin secretion in obese IGT alone, IFG alone, or IFG + IGT. However, the magnitude of insulin resistance differed in the obese group, IFG + IGT and DM being more insulin resistant than IGT alone or IFG alone. Conclusions: These results suggest that the predisposing metabolic abnormality in non-obese subjects with IGT alone or IFG alone and in progression to IFG + IGT might be deterioration of early phase insulin secretion, whereas insulin resistance might be the major contributory factor in obese subjects. The predisposing metabolic abnormality leading to diabetes in both obese and non-obese groups was deterioration of early-phase insulin secretion.