High density lipoproteins with differing apolipoproteins: relationships to postprandial lipemia, cholesteryl ester transfer protein, and activities of lipoprotein lipase, hepatic lipase, and lecithin: cholesterol acyltransferase.

Abstract

To gain insight into metabolic determinants of high density lipoproteins (HDL) containing apolipoproteins A-I and A-II (LpA-I/A-II) and those containing A-I, but devoid of A-II (LpA-I), the plasma concentration of LpA-I and LpA-I/A-II within the HDL2 and HDL3 density spectrum was measured in 14 normolipidemic male subjects on a standardized diet. Apolipoprotein plasma concentrations of HDL subspecies were compared with the magnitude of postprandial lipemia, activities of lipoprotein lipase and hepatic lipase in postheparin plasma, plasma lecithin:cholesterol acyltransferase (LCAT) activity, and cholesteryl ester transfer protein (CETP) mass. Plasma levels of LpA-I/A-II were 2.5 times higher than levels of LpA-I (123 +/- 20 vs. 48.3 +/- 22.1 mg protein/dl) and the partition of LpA-I and LpA-I/A-II between HDL2 and HDL3 differed in that the proportion of LpA-I associated with HDL2 was greater than that of LpA-I/A-II (23 +/- 19 vs. 6 +/- 6%, P < 0.002). With increasing levels of HDL2, the proportion of LpA-I in HDL2 increased (P < 0.002). Furthermore, levels of LpA-I and LpA-I/A-II were strongly correlated within the HDL2 but not within the HDL3 density region. Plasma levels of LpA-I, but not LpA-I/A-II, were inversely correlated with the magnitude of postprandial lipemia. However, activities of lipoprotein lipase and hepatic lipase tended to show stronger associations with the partition of LpA-I/A-II between HDL2 and HDL3 than with that of LpA-I. Within the HDL3, but not the HDL2 density spectrum, LpA-I/A-II exhibited a positive association with plasma LCAT activity, while LpA-I displayed an inverse association with plasma CETP mass. These results are consistent with differences in substrate properties of LpA-I and LpA-I/A-II for lipoprotein modifying enzymes and imply different, but overlapping metabolic pathways of LpA-I and LpA-I/A-II.