Evaluation of an Insulin Sensitivity Index from the Short Intravenous Glucose Tolerance Test

Abstract

The aim of this analysis was to compare insulin sensitivity indices calculated from a short (50 min), insulin‐modified intravenous glucose tolerance test (IVGTT; Tura SI) to that from a full 180 min IVGTT using minimal model analysis (MM SI), as well as the Matsuda Index (M‐SI) from a 120 min liquid meal tolerance test (Maki et al. Diabetes Tech Ther 2011;13:661–6). The IVGTT included glucose (0.3 g/kg, t = 0 min) and regular human insulin (0.03 U/kg; t = 20 min) injection with samples collected at frequent intervals over 180 min. Tura SI was calculated as the fractional glucose disappearance rate/average increment in plasma insulin, both from 10–50 min. The MINMOD MILLENNIUM program (v6.02) was used to calculate MM SI. Subjects were overweight or obese men (n = 8) and women (n = 16) without diabetes who agreed to participate in a substudy after completing a dietary intervention trial. Mean ± SEM MM SI was 3.94 ± 3.38 × 10−4 L*min−1*mU−1, age was 48.9 ± 2.0 y and body mass index was 30.8 ± 0.6 kg/m2. Pearson correlation coefficients were: Tura SI with MM SI r = 0.963, Tura SI with M‐SI r = 0.803, and MM SI with M‐SI r = 0.776, all p < 0.001. Thus, Tura SI from the first 50 min of an insulin‐modified IVGTT correlates very strongly with 180 min MM SI (reference method), and the relationship between Tura SI with M‐SI was similar in magnitude to that between MM SI and M‐SI. These results suggest that the short IVGTT may be used as a less costly and time‐consuming alternative to the 180 min IVGTT for assessment of whole‐body insulin sensitivity.Support or Funding InformationIngredion, Westchester, IL