Control of insulin secretion during fasting hyperglycemia in adult diabetics and in nondiabetic subjects during infusion of glucose

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Abstract

In obese adult diabetics, the concentration of insulin in venous plasma was unrelated to the degree of hyperglycemia after an overnight fast. However, in these subjects, insulin rose and fell in proportion to the magnitude of change in plasma glucose induced by small intravenous infusions of glucose. The minimal dose of glucose to cause a significant rise in insulin above the fasting level was similar in normal subjects, obese nondiabetic subjects, and in obese, hyperglycemic adult diabetics. This dose lay between infusion of 60 and 100 mg of glucose per min for 30 min. These results suggested that the secretion of insulin was under regulation by changes in blood glucose but was not stimulated in proportion to the stable raised blood glucose concentration of the hyperglycemic diabetic. Artificial hyperglycemia was induced in fasting normal subjects by constant intravenous infusion of glucose at rates of 100-250 mg of glucose per min for periods up to 8 hr. Plasma glucose rose during the 1st hr of infusion and then remained constantly elevated for up to 8 hr. The concentration of plasma insulin paralleled that of plasma glucose. During the period of constant hyperglycemia and elevated insulin, superimposition of a brief additional glucose load resulted in a prompt rise in glucose and insulin, both returning to the previous elevated levels.

Authors

Charles J. Goodner, Martin J. Conway, Jon H. Werrbach