A Comparison of Meal‐derived Indices for Predicting Glucose Tolerance

Abstract

This investigation evaluated indices of insulin sensitivity and secretion from the liquid meal tolerance test (LMTT) as determinants of 2‐h glucose (G) values from an oral glucose tolerance test (OGTT). Subjects were 38 men and 31 women, 42% with pre‐diabetes, mean±SEM age 35.1±1.0 y and BMI 32.5±0.5 kg/m2. On separate days subjects completed a 75 g OGTT, a LMTT (Carnation Instant Breakfast®+ whole milk; 7 kcal/kg; 24% fat, 59% carbohydrate, and 17% protein) and an insulin‐modified intravenous glucose tolerance test (IVGTT). Multivariate linear regression was used to assess the variance in log‐transformed 2‐hour OGTT G values explained by indices of insulin (I) sensitivity ‐ Matsuda LMTT (MISI), Cobelli LMTT (CoSI) and IVGTT (Minmod SI) and I secretion ‐ LMTT 30 min ΔI/ΔG, 120 min AUC I/AUC G, Phi S and the acute insulin response to IV glucose (AIRG). The R2 value for the reference method (IVGTT SI and AIRG) was 0.199. R2 values for combinations of LMTT variables (all models P<0.001) were: 0.178 (CoSI and ΔI/ΔG), 0.154 (MISI and ΔI/ΔG), 0.127 (CoSI and Phi S), 0.112 (CoSI and 120 min AUC I/AUC G) and 0.086 (MISI and AUC I/AUC G). These results suggest that CoSI and ΔI/ΔG performs well compared to the IVGTT reference method, and that use of MISI and ΔI/ΔG (from I and G at 0, 30, 60, 90, 120 min vs. 23 timepoints for CoSI) results in only minor loss of explanatory power.