In Vivo Stimulation of Low-Density Lipoprotein Degradation by Insulin

The effect of insulin on low-density lipoprotein (LDL) metabolism in vivo was evaluated using the euglycemic insulin clamp technique. In seven subjects, mononuclear cells isolated after a 4-h insulin infusion degraded more ¹²⁵I-Iabeled LDL than cells isolated after a saline infusion in six control subjects. In addition, insulin caused the accelerated disappearance of ¹²⁵I-labeled LDL from plasma in subjects previously injected with autologous ¹²⁵I-LDL. Infusion of saline had no such effect. These data suggest that insulin, in vivo, stimulates LDL catabolism and could thereby influence LDL cholesterol levels. Insulin-induced stimulation of LDL catabolism could account for the reduction of LDL-cholesterol levels observed in intensively treated type I diabetic patients.