Twenty-four hours of insulin infusion does not lower plasma lipoprotein(a) in healthy men

The effect of 24-h exogenous hyperinsulinaemia on the plasma level of the atherogenic lipoprotein(a) (Lp(a)) is unknown. We evaluated the responses of plasma cholesterol, triglycerides, apolipoprotein (apo) B and Lp(a) during 24-h insulin infusion (180 pmol/kg/h) in 6 healthy men. Plasma total cholesterol (p <0.01) and triglycerides (p <0.05) decreased after 24 h of hyperinsulinaemia. Apo B was unchanged after 8 h (-2.4 +/- 3.0%, n.s.) and decreased by 10.9 +/- 4.8% (p <0.025) after 24 h of insulin. In contrast, Lp(a) did not decrease (+28.4 +/- 18.4%, n.s., and +49.1 +/- 22.0%, n.s., after 8 and 24 h of insulin, respectively). This experiment supports the hypothesis that moderate hyperinsulinaemia has a different effect on the plasma level of triglyceride-rich lipoproteins compared to Lp(a).