Decreased hypoglycemic effect of insulin at night in insulin-dependent diabetes mellitus and healthy subjects.

Abstract

Diurnal variations in insulin-induced hypoglycemia and in plasma counterregulatory hormone concentrations were explored in eight insulin-dependent diabetic and six healthy subjects during a 100-min iv insulin infusion performed at 0300 h and 1500 h. In healthy subjects, plasma glucose concentrations (mean +/- SD) fell by 35 +/- 2% during the daytime test and by 26.5 +/- 2% during the nocturnal test (P less than 0.01). Plasma cortisol, GH, and epinephrine concentrations increased more during the daytime than during the nocturnal test. In contrast, plasma glucagon concentrations rose more during the nocturnal tests. In insulin-dependent diabetes mellitus patients, insulin infusion had to be interrupted in three subjects because plasma glucose fell below 1.9 mmol/L 80 min after the beginning of the test. In the other five patients plasma glucose fell by 34 +/- 5% during the daytime test while no significant decrease in plasma glucose was observed in any of the eight patients during the nighttime test. Counterregulatory hormone concentrations were consistent with the results of plasma glucose, with no change during the nocturnal test and significant increases in cortisol, GH, and epinephrine during the daytime test. These results show that insulin sensitivity is decreased at night in comparison to midafternoon in healthy subjects and that in insulin-dependent diabetes mellitus patients this phenomenon is exaggerated, even in patients with defective counterregulation to hypoglycemia.