COMPOSITION OF PLASMA APOA-I-CONTAINING LIPOPROTEIN PARTICLES IN CHILDREN AND ADULTS

The purpose of this study was to examine sex- and age-related differences in the concentration and composition of lipoprotein particles containing apoA-I (LP-A-I) and those containing apoA-I and apoA-II (LP-I:A-II), the main HDL as defined by their apolipoprotein composition. Lipoproteins were isolated by immunoaffinity chromatography of whole plasma from 16 normal prepubertal children and 15 normal male and female adults using "pan"-MAb to apoA-I and apoA-II. Although there was no difference between children and adults in the concentration of LP-A-I:A-II, adult females had significantly higher levels of LP-A-I than either children or adult males. Main differences between children and adults as well as between adult males and females were in the apolipoprotein composition of the lipoprotein particles; children had the highest content of minor apolipoproteins (apoC and apoE) in LP-A-I but the lowest in LP-A-I:A-II. The lipid/apolipoprotein ratios of LP-A-I and LP-A-I:A-II were significantly higher in children and women than in men. The LP-A-I and LP-A-I:A-II contained 75% of the total plasma apoC and apoE in women and children but only 50% in men. However, in all three groups, 70-90% of the minor HDL apolipoproteins were associated with LP-A-I:A-II. The nonmolar ratios of minor apolipoproteins in LP-A-I and LP-A-I:A-II and the sex- and age-related differences in apoA-I/apoA-II ratios of LP-A-I:A-II suggest that both lipoproteins may consist of a spectrum of lipoprotein subfamilies differing in their apolipoprotein composition. Results of this study indicate that the age- and sex-related differences in the levels and composition of LP-A-I and LP-A-I:A-II relate primarily to changes in the protein moieties of these particles.