Differences in the Pattern of Insulin Secretion and Insulin Resistance Based on the OGTT in Subjects with IFG and IGT.

Impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) are pre-diabetes states that can progress to type 2 diabetes mellitus. However, it has been shown that only 29 - 76% of pre-diabetic subjects diagnosed satisfy the definition of IFG and IGT simultaneously, and it appears that a significant difference between them is also present. We performed an oral glucose tolerance test (OGTT) on 528 subjects who had no history of the medication that affect on glucose tolerance, and the patients were classified into four groups: the normal glucose tolerance, the isolated IFG, the isolated IGT, and the combined glucose intolerance (CGI) group satisfying IFG and IGT conditions simultaneously. The characteristics of each group were compared. In addition, for all subjects, the insulin resistance indices HOMA-IR, WBISI, and the insulin secretion indices insulinogenic index (IGI), and AUC insulin[sub 0-120]/AUC glucose[sub 0-120] (AUC I/G 120) were determined. The OGTT measurements showed that 87 subjects were diagnosed as having isolated IFG, 75 subjects as having isolated IGT, and 145 subjects as having CGI, and 43.2% of the pre-diabetes subjects were placed in the CGI group. Comparing the isolated IFG and the isolated IGT group, the isolated IFG group was relatively young (49.9±11.3 years vs. 51.4±14.4 years, p=0.038), the percentage of male was higher (56.3% vs. 40%, p=0.028), and the isolated IFG group subjects showed a trend to be leaner. In addition, the HOMA-IR of the isolated IFG group was significantly higher (2.30±0.12 vs. 1.89±0.13, p=0.028), the WBISI between two groups was not different (10.8±0.67 vs. 12.4±0.78, p=0.123), and these findings suggest that the difference in insulin resistance between two groups was mainly caused by hepatic resistance. For the insulin secretory indices, the IGI (140.3±10.6 vs. 91.0±11.5, p=0.002) and the AUC I/G 120 (65.2±3.4 vs. 54.0±4.0, p=0.037) were significantly higher for the isolated IFG group. This significance of the insulin secretory capacity between each group did not change after an adjustment for insulin resistance (IGI/WBISI) or the disposition index (IGI X WBISI). In conclusion, following the use of the OGTT, it was found that significant metabolic differences in insulin sensitivity and insulin the secretory capacity between the isolated IFG group and the isolated IGT group exist. [ABSTRACT FROM AUTHOR]