Novel Insulin Modified Oral Glucose Tolerance Test Improves the Estimation of Insulin Sensitivity and Glucose Effectiveness

Estimating insulin resistance from the oral glucose tolerance test (OGTT) has long been a challenge in diabetes research and practice. Because the time courses of glucose and insulin during the OGTT are similar in shape, the estimates of insulin sensitivity per se may be corrupted by other metabolic responses such as insulin release or glucose absorption. We have previously shown insulin injection during the intravenous test yields accurate values of insulin sensitivity (SI) and glucose effectiveness (SG) . Here we examine an analogous approach during the OGTT - in which exogenous insulin is administered during the test. Methods: For 100 simulated subjects (NGT: n=25, IGT: n=25, T2D: n=25, T1D: n=25) , glucose and insulin data were calculated using Dalla Man Mixed Meal Simulator. For each simulated subject, several protocols were examined by varying the time of insulin bolus (30, 60, or 90 min) and the dose of the bolus (0, 0.01, 0.02, or 0.03 IU/kg) . The resulting 3600 simulated datasets were analyzed with Dalla Man’s OGTT model to estimate SI. Results: When adjusted for the dose of insulin, the time of the dose did not significantly impact the estimation of SI. The 0.IU/kg insulin dose resulted in significantly (P<0.001) better estimates of SI when compared to the three other doses. Unique estimates of SG were obtained only without and with insulin dose of 0.IU/kg. There was no difference (P=NS) between the quality of SG estimates with these two doses. Conclusions: An intravenous insulin bolus of 0.IU/kg given at 60 min during the OGTT will enable accurate and precise estimations of both SI and SG. Disclosure D.Stefanovski: None. F.Piccinini: Employee; Medtronic. M.Ader: None. M.Kabir: None. R.N.Bergman: Consultant; Fractyl Health, Inc., Novo Nordisk, Research Support; AstraZeneca, Janssen Research & Development, LLC.