Effect of Transient Elevation of Plasma Insulin Within Physiologic Levels (Simulated Early Insulin Response) on Blood Glucose

To elucidate the quantitative effect of transient hyperinsulinemia at physiologic levels on blood glucose, the early insulin response (ER) to an acute stimulus was simulated by iv infusion of insulin (ERex). At 3 different doses (12, 25–30 and 40–60 μU/kg body wt) the peak plasma insulin values reached 44 ± 10, 111 ± 23 and 260 ± 20 μU/ml, respectively. These simulated responses induced dose related depression of blood glucose with 10 ± 2, 23 ± 4 and 35 ± 8 mg/100 ml, respectively. When the same insulin responses were simulated during moderate hyperglycaemia, the effect on blood glucose was slightly more pronounced. The effect of insulin infusion varied markedly between the individuals, but was inversely related to the endogenous early insulin response to 25 g glucose of each subject (ERend). An expression for the insulin response which had a constant dose related effect on blood glucose in all the persons tested was provided, when the magnitude of the simulated insulin response was expressed in relation to the endogenous insulin response of each individual (ERex/ERend). The influence of elevation of ER on the glucose assimilation rate (KG) during the iv glucose tolerance test (GTT) was studied by infusion of exogenous insulin (GITT) during the first 2½ min of the GTT, at a rate that raised the peak plasma insulin value to about 4 times as high as that induced by the GTT only. KG was significantly higher during the GITT (KG = 3.1 ± 0.3) than during the GTT (KG = 2.1 ± 0.2). The results show that a simulated early insulin response quantitatively influences the blood glucose level and the glucose assimilation rate. They also indicate that the magnitude of ERend reflects the insulin sensitivity of the individual.