Control of Blood Glucose in Normal and in Diabetic Subjects: Studies by Compartmental Analysis and Digital Computer Technics

A model with two compartments (glucose and insulin) by and a negative feedback has been used to fit the values of blood glucose obtained experimentally by infusing intravenously glucose (0.5 gm. min⁻¹) or insulin (0.055 U. min⁻¹) for about 250 minutes. Glucose was infused to normal ambulatory or hospitalized subjects and to diabetic patients; insulin was infused to normal subjects. The model employed fits the data of all the groups. The SAAM program and a digital computer (IBM 7094) were used. The model cannot be solved completely due to the number of degrees of freedom of the system but values related to the transfer constants of the model can be computed, as the damping constant a, the natural frequency w, the natural period T and the free frequency b of the system, which shows damped oscillations in normal subjects; in diabetic patients the system passes through states of overdamping until no oscillations can be seen in the more severe cases. The effect of ten days of treatment with prednisone (25 mg. m per day, per os) has been evaluated in a group of normal subjects. Discriminant analysis between normal and diabetic subjects and between glucose and insulin infusion has been carried out by using a BMD program and a digital computer.