Two-Hour Seven-Sample Oral Glucose Tolerance Test and Meal Protocol

Abstract

Highly informative yet simple protocols to assess insulin secretion and action would considerably enhance the quality of epidemiological and large-scale clinical trials. In an effort to develop such protocols, a 5-h, 11-sample oral glucose tolerance test (OGTT) was performed in 100 individuals and a 7-h, 21-sample meal in another 100. Plasma glucose, insulin, and C-peptide concentrations were measured. We show that virtually the same minimal model assessment of β-cell responsivity (dynamic [Φ_d] and static [Φ_s]), insulin sensitivity (S_i), and disposition index (DI) can be obtained with a reduced seven-sample 2-h protocol: Φ_d, reduced versus full: 871.50 vs. 873.32, r = 0.98 in OGTT and 494.88 vs. 477.99 10⁻⁹, r = 0.91 in meal; Φ_s: 42.36 vs. 44.35, r = 0.88 in OGTT and 35.31 vs. 35.37 10⁻⁹ min⁻¹, r = 0.90 in meal; S_i: 24.33 vs. 22.77 10⁻⁵ dl · kg⁻¹ · min⁻¹ per pmol/l, r = 0.89 in OGTT and 19.03 vs. 19.77 10⁻⁵ dl · kg⁻¹ · min⁻¹ per pmol/l, r = 0.85 in meal; and DI: 1,282.26 vs. 1,273.23, r = 0.84 in OGTT and 726.92 vs. 776.97 10⁻¹⁴ dl · kg⁻¹ · min⁻² per pmol/l, r = 0.84 in meal. This reduced protocol will facilitate the study of insulin secretion and action under physiological conditions in nondiabetic humans.