Evaluation of a Reduced Sampling Schedule for Assessment of Pancreatic Beta‐Cell Function with the Intravenous Glucose Tolerance Test During a Dietary Intervention

Abstract

Pancreatic beta‐cell function is a key determinant of glucose tolerance. The intravenous glucose tolerance test (IVGTT) can be used to assess both the insulin sensitivity index (Si) and the acute insulin response to glucose (AIRg). The disposition index (DI = Si × AIRg) reflects the adequacy of pancreatic beta‐cell response for the level of insulin sensitivity. The aim of this analysis was to compare the AIRg and DI values calculated using a reduced early test sampling schedule (t = 0, 5, 10 min), to those from the full sampling schedule (t = 0, 3, 5, 7, and 10 min). Participants included men (n = 8) and women (n = 16) with mean (SD) age 48.9 (9.9) y and body mass index 30.8 (4.9) kg/m2. Subjects consumed 0, 15, and 30 g/d high‐amylose resistant starch (RS) for 4 weeks each, in a double‐blind, randomized, crossover trial, and underwent a 180‐min IVGTT at the end of each treatment period. The Minmod Millenium program was used to derive Si. AIRg was calculated as the mean increment in plasma insulin during the first 10 min of the test for the full and reduced sampling schedules. The median (interquartile range) full schedule AIRg values during the control, 15, and 30 g/d RS conditions were 43 (29, 103), 47 (23, 67) and 44 (30, 94) mU/L, respectively. Mean (95% confidence interval) percentages of the full schedule values for the reduced schedule values were 82 (79–86), 87 (76–98) and 83 (80–85) for the control, 15 and 30 g/d RS conditions, respectively, all p < 0.05 vs. the full schedule. Correlations between the AIRg and DI values from the two schedules during each RS condition were high (Pearson r values all ≥0.98, p < 0.001). Thus, although AIRg and DI values cannot be directly compared between sampling schedules, the reduced sampling schedule accurately reflects relative AIRg and DI values, and may thus be a time and cost‐effective option when conducting the IVGTT in clinical and epidemiological studies.Support or Funding InformationIngredion Inc., Westchester, IL