Insulin secretion and kinetics in mice assessed by mathematical modeling

Insulin secretion and kinetics were assessed in a group of six mice (weighing 20-25 g) by a mathematical model applied to data from IVGTT (Intravenous Glucose Tolerance Test). The model, originally developed for assessing B-cell secretion during OGTT (Oral Glucose Tolerance Test) in men, describes insulin dynamics with two compartments, one for C-peptide and one for insulin. In this study, important modifications were introduced in the numerical strategy for the estimation of insulin secretion rate. This was necessary mainly because the data in mice (glucose, C-peptide and insulin) were collected over a 50 min interval and were made of 7 samples only, instead of the 180 min interval and as many as 20 samples typical of studies in man. On the other hand, mice IVGTT data are characterized by lower dynamics with respect to IVGTT data in humans, and hence a model developed only for low dynamic OGTT studies can be applied to IVGTT data in this case. Parameters estimated on the 6 mice were the total amount of insulin secretion, the post-hepatic insulin delivery, and the insulin fractional clearance rate.