Characteristics of insulin resistance and insulin secretory capacity in Korean subjects with IFG and IGT.

Both IFG and IGT are prediabetic conditions that can progress to type 2 DM. However, previous studies have shown that these are not identical. This study was conducted on 307 drug naïve prediabetic adults who did not meet the diagnostic criteria for diabetes based on the OGTT. According to the OGTT, the subjects were divided into isolated IFG (i-IFG), isolated IGT (i-IGT), and combined glucose intolerance (CGI) group. We also measured insulin resistance indices (HOMA-IR, WBISI), an insulin secretion indices (insulinogenic index [IGI], AUC I/G(0-120), disposition index [DI]), and compared each of the three groups. The OGTT measurements showed that 87 subjects were diagnosed with i-IFG, 75 subjects had i-IGT, and 145 subjects had CGI. With respect to the insulin resistance indices, HOMA-IR and WBISI were not significantly different. However, insulin secretory capacity, the IGI and DI were significantly higher for the i-IFG group. Moreover, after confounders were adjusted, HOMA-IR, IGI, AUC I/G(0-120), and the DI were significantly higher for the i-IFG group and WBISI was significantly higher for the i-IGT group. These results demonstrate that the pathogenesis of IFG is more closely associated with insulin resistance, and the pathogenesis of IGT is more closely associated with impaired insulin secretion.