Comparison of insulin-mediated and glucose-mediated glucose disposal in patients with insulin-dependent diabetes mellitus and in nondiabetic subjects

To determine whether glucose-mediated as well as insulin-mediated regulation of glucose utilization and glucose production is impaired in patients with insulin-dependent diabetes mellitus (DDM), six nonobese, diabetic patients and seven age-, sex-, and weight-matched nondiabetic subjects were studied. Despite slightly higher free insulin concentrations in the diabetic patients than in the nondiabetic subjects during 0.2 mU/kg · min (22 ± 3 versus 15 ± 2 μU/ml) and 1.0 mU/kg · min (98 ± 10 versus 75 μU/ml) insulin infusions, glucose utilization at plasma glucose concentrations of 95, 135, and 175 mg/dl was lower in the diabetic patients than in the nondiabetic subjects. The increment in glucose utilization per increment in plasma glucose (i.e., slope) in the diabetic and nondiabetic subjects, respectively, did not differ significantly during either the 0.2 (1.7 ± 1.3 versus 1.4 ± 0.5 dl/kg · min) or 1.0 (4.4 ± 1.1 versus 6.2 ± 1.0 dl/kg · min) mU/kg · min insulin infusions, although they tended to be higher in the nondiabetic subjects during the latter infusion. Thus, although stimulation of glucose utilization by insulin is impaired in patients with IDDM, the ability of an increase in glucose concentration to increase glucose utilization does not appear to differ from that present in nondiabetic subjects, at insulin concentrations in the low physiologic range. Whether differences exist in the high physiologic range remains to be determined.