Metabolic effects of low-dose incremental insulin infusion in diabetic man

An incremental insulin infusion technique to assess insulin action at physiological circulating levels in diabetic man is described. Insulin was infused during sequential one hour periods at rates of 0.01, 0.05 and 0.10 u/kg/h. Serum free insulin concentrations had reached a plateau by the second 30 minutes of each infusion period. Blood glucose concentrations fell at a similar rate during the two lower rates of insulin infusion, but the fall was significantly greater with the highest insulin infusion. Glucose production and utilisation were measured isotopically using a 3-3H glucose infusion technique. Glucose production was inhibited with the lowest insulin infusion rate and a marked increase in glucose metabolic clearance rate occurred with the highest insulin infusion. Key intermediary metabolites were measured and blood glycerol, total ketone bodies, and plasma non-esterified fatty acids fell with the lowest insulin infusion rate. It is concluded that this technique allows identification of the effect of insulin upon different metabolic processes.