Preferential redistribution of lipoprotein-unassociated apoA-IV to an HDL subpopulation with a high degree of LCAT modification

The relationship between LCAT mediated HDL modification and the redistribution of lipoprotein-unassociated apoA-IV to HDL was investigatedin vitro. Immunoaffinity-isolated rat lipoprotein-unassociated apoA-IV was added to apoB-, apoE-, apoA-IV depleted, [³H]cholesterol labelled rat plasma and incubated at 37°C. The addition of lipoprotein-unassociated apoA-IV resulted in a modest (10%) but significant reduction in the rate of cholesterol esterification. Incubations conducted in the presence of active LCAT led to a time-dependent increase in the amount of the³H label retained by an anti-apoA-IV immunoaffinity column. Lipoproteins retained by the anti-apoA-IV immunoaffinity column had experienced a greater conversion of [³H]cholesterol to [³H]cholesteryl esters (48% esterification at 30 min) than the unretained lipoproteins (19% esterification at 30 min). These data suggest that during the course of LACT-induced cholesterol esterification, lipoprotein-unassociated apoA-IV transfers to a subpopulation of HDL which has been modified by LCAT to a greater extent than the remaining HDL. Further analysis of the data demonstrates that 48% cholesterol esterification is sufficient to allow apoA-IV to be accommodated on the surface of an HDL particle.