Glucose Dynamics in Plasma and Interstitial Fluid after Intravenous Glucose Injection

Recent experimental evidence suggests that estimates of glucose effectiveness (SG) from the minimal model of unlabeled glucose disappearance (Cold-MM) are in error. The single-compartment glucose distribution assumption embedded in the model has been indicated as a possible source of error. In this study, in order to directly examine the single-compartment assumption, plasma and interstitial glucose concentrations were measured after intravenous glucose injection. Additionally, the accuracy of the estimates of glucose effectiveness from the Cold-MM and the single-compartment tracer minimal model (Hot-MM) was compared. Furthermore, compartmental modeling was used to characterize on the basis of insulin and tracer glucose data the temporal relationship between changes in plasma insulin and the action of the hormone on glucose disposal. Paired labeled intravenous glucose tolerance tests (IVGTT) were performed in six C-peptide-negative insulin-dependent diabetic subjects. Two different insulin infusion protocols were used: an infusion at constant basal rates, and an infusion at variable rates in order to mimic a normal insulin response. During the labeled IVGTT with basal insulin infusion, the microperfusion technique was employed to sample adipose tissue interstitial fluid. Marked differences between the plasma and interstitial dynamics of (cold) glucose were observed during the first 22 min after glucose injection. T..