Importance of early postprandial insulin delivery in insulin-dependent diabetics

In nine insulin-dependent diabetics postprandial glucose control under closed loop insulin infusion by an artificial endocrine pancreas was compared with that obtained under open loop infusion employing identical infusion profiles which were advanced 20 min by time in the case of open loop infusion. The earlier increase of insulin infusion rates in the latter case resulted in lower postprandial glucose concentrations during the first 90 min after meal intake. Incremental areas under the blood glucose curves during this time were significantly lower when insulin infusion rates rose earlier (4.5 X 10(3) +/- 0.5 X 10(3) vs 2.1 X 10(3) +/- 0.6 X 10(3) mg/dl X min; p less than 0.02). Insulin was administered at maximum rates 45-50 min after the start of the meal during closed loop infusion (196 +/- 38 mU/min) and 25-30 min after the meal during open loop infusion (192 +/- 35 mU/min). Correspondingly, mean free insulin concentrations which are available from six patients rose to 135 +/- 47 (40 min) or 141 +/- 50 muU/ml (20 min). Glucagon levels did not differ between both parts of the study. It is concluded that increases of postprandial insulin infusion rates occurring earlier than increases of blood glucose levels are important for optimizing glucose profiles and possibly reflect physiologic conditions.