Post-prandial hyperinsulinemia does not affect the intravascular synthesis of HDL-apoproteins in humans

This study was performed to establish whether post-prandial hyperinsulinemia affects HDL production rate in humans. For this reason, the intravascular fractional synthetic rates (IFSR)) of HDL₂ and HDL₃ were measured in 8 healthy volunteers, randomized in a control (CTRL) and a meal (MEAL) group matched for age (CTRL 26 ± 6, MEAL 24 ± 2 yr) and BMI (CTRL 22 ± 3, MEAL 23 ± 2 kg/m²). All subjects were studied for a period of 8 hr (0-480 min); the first study period (0-240) was used to measure HDL kinetics in the overnight post-absorptive state, the second study period (240-480 min) differed between the two groups. The subjects of the MEAL, group received an intragastric infusion of a glucose-lipid meal (~ 632 kcal) whereas those of the CTRL group only water. Plasma lipoproteins IFSR were measured after sequential ultracentrifugation and acid hydrolysis using plasma KIC specific activity (SA) as a precursor pool SA, during the continuous infusion of [1-¹⁴C] leucine. Plasma HDL-cholesterol decreased by 11% after meal ingestion (p < 0.05). In the post-absorptive state (180-240 min) the IFSR (%·h^-1) of HDL₂ and HDL₃ apoproteins did not differ between the CTRL and the MEAL, groups (HDL₂: 1.2 ± 0.4, 1.1 ± 0.2; HDL₃: 0.9 ± 0.2, 1.0 ± 0.1). Meal ingestion (absorptive state, 420-480 min) increased plasma insulin but did not affect the IFSR of the HDL₂ (CTRL: 1.1 ± 0.2 vs MEAL: 1.0 ± 0.3) and HDL₃ apoproteins (CTRL: 0.8 ± 0.2 vs MEAL: 1.1 ± 0.2). Thus, we conclude that: 1) post-prandial hyperinsulinemia does not affect HDL production; 2) the post-prandial decrement of plasma HDL concentrations is due to increased HDL cholesterol catabolism.