Differential Associations of Oral Glucose Tolerance Test–Derived Measures of Insulin Sensitivity and Pancreatic β-Cell Function With Coronary Artery Calcification and Microalbuminuria in Type 2 Diabetes

Abstract

OBJECTIVE We evaluated relationships of oral glucose tolerance testing (OGTT)–derived measures of insulin sensitivity and pancreatic β-cell function with indices of diabetes complications in a cross-sectional study of patients with type 2 diabetes who are free of overt cardiovascular or renal disease. RESEARCH DESIGN AND METHODS A subset of participants from the Penn Diabetes Heart Study (n = 672; mean age 59 ± 8 years; 67% male; 60% Caucasian) underwent a standard 2-h, 75-g OGTT. Insulin sensitivity was estimated using the Matsuda Insulin Sensitivity Index (ISI), and β-cell function was estimated using the Insulinogenic Index. Multivariable modeling was used to analyze associations between quartiles of each index with coronary artery calcification (CAC) and microalbuminuria. RESULTS The Insulinogenic Index and Matsuda ISI had distinct associations with cardiometabolic risk factors. The top quartile of the Matsuda ISI had a negative association with CAC that remained significant after adjusting for traditional cardiovascular risk factors (Tobit ratio −0.78 [95% CI −1.51 to −0.05]; P = 0.035), but the Insulinogenic Index was not associated with CAC. Conversely, the highest quartile of the Insulinogenic Index, but not the Matsuda ISI, was associated with lower odds of microalbuminuria (OR 0.52 [95% CI 0.30–0.91]; P = 0.022); however, this association was attenuated in models that included duration of diabetes. CONCLUSIONS Lower β-cell function is associated with microalbuminuria, a microvascular complication, while impaired insulin sensitivity is associated with higher CAC, a predictor of macrovascular complications. Despite these pathophysiological insights, the Matsuda ISI and Insulinogenic Index are unlikely to be translated into clinical use in type 2 diabetes beyond established clinical variables, such as obesity or duration of diabetes.