Insulin Resistance and Metabolic Syndrome Contribute Significantly to the Transition of Borderline Glucose Tolerance to Type 2 Diabetes Mellitus

Abstract

We followed up 47 subjects with borderline glucose tolerance (BGT) for 3 years, and compared differences between subjects who subsequently developed type 2 diabetes (T2DM) and those who did not, focusing on the role of insulin resistance (IR) and metabolic syndrome (MS) in the transition of BGT to T2DM. Insulin sensitivity was measured directly using the insulin tolerance test K index (Kitt). Patients who subsequently developed T2DM (n=16) within 3 years of follow-up had a significantly greater waist circumference (89±14 vs. 82±9 cm, p<0.05), higher fasting glucose concentration (111±17 vs. 101±10 mg/dl, p<0.05), a significantly lower Kitt (3.31±1.11 vs. 4.23±1.13%/min, p<0.05), and were more likely to be diagnosed with MS (68.8% vs. 32.3%, p<0.05) at baseline, compared to the other group (n=31). A significantly larger proportion of subjects diagnosed with MS at baseline developed T2DM than non-MS subjects (52.4% vs. 19.2%, p<0.05 ; odds ratio 4.6, 95% CI ; 1.3-16.9). Multiple logistic regression analysis showed that both IR and MS were significant independent contributors to the transition from BGT to T2DM. Reduced insulin secretion did not correlate, however, with the development of T2DM. Thus, individuals with BGT who have IR and/or MS have a higher relative risk for developing T2DM. The 75 g oral glucose tolerance test and the measurement of waist circumference, blood pressure, and serum lipids are thus important for identifying those at relatively high risk for T2DM among individuals with BGT.