Composition of Plasma ApoA-I-Containing Lipoprotein Particles in Children and Adults

003 1-3998191/2903-03 15$03.00/0 PEDIATRIC RESEARCH Copyright O 1991 International Pediatric Research Foundation. Inc. Vol. 29. No. 3, 1991 Prinred in U.S. A . Composition of Plasma ApoA-I-Containing Lipoprotein Particles in Children and Adults E. D. BEKAERT,' P. ALAUPOVIC, C. KNIGHT-GIBSON, P. BLACKETT, AND M. AYRAULT-JARRIER Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104 [E.D.B.. P.A.. C.K.-G.];Departmcnf ojPediafrics. University of Oklahoma Health Science Center, Oklahoma Cify.Oklahoma 73104 [P.B.];and INSERM U32, Hopital Henri MGndor, 94010 Creteil, France 1M.A.-J.] ABSTRACT. The purpose of this study was to examine sex- and age-related differences in the concentration and composition of lipoprotein particles containing apoA-I (LPA-I) and those containing apoA-I and apoA-I1 (LP-1:A-11), 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 "panw-MAb to apoA-I and apoA-11. Although there was no difference between children and adults in the concentration of LP-A-1:A-11, 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-1:A-11. The IipidJapolipoprotein ratios of LP-A-I and LP-A-1:A-I1 were significantly higher in children and women than in men. The LP-A-I and LP-A-I:A-I1 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-1:A-11. The nonmolar ratios of minor apolipoproteins in LP-A-I and LP-A-1:A-I1 and the sex- and age-related differences in apoA-IJapoA-I1 ratios of LP-A-1:A-I1 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-1:A-I1 relate primarily to changes in the protein moieties of these particles. (Pediatr Res 29: 315-321, 1991) Previous evidence clearly supports heterogeneity of operationally defined plasma lipoprotein classes with respect to their chemical composition and metabolic properties ( 1-3). For example, by utilizing apolipoproteins as specific markers for identifying and classifying discrete lipoprotein particles in plasma, it has been shown that apoB- and apoA (apoA-I and apoA-11)containing lipoproteins form two major groups of plasma lipoproteins (1, 2). The apoB-containing lipoproteins are located in the very low and low density ranges, whereas the apoA-containing lipoproteins are present in the high and very high density ranges of the lipoprotein density spectrum. The latter group consists of two major lipoprotein families referred to on the basis of their characteristic apolipoprotein composition as LP-A-1:AI1 and LP-A-I. The isolation and partial characterization of these two lipoprotein families have been described in reports from several laboratories (4- 1 1). So far, the LP-A-1:A-I1 and LP-A-I particles have been isolated mainly from plasma of normolipidemic adults. However, because the human lipid transport system has been shown to undergo several changes from its fetal to adult form (2, 12- 15), the purpose of this study was to provide information on the concentration and composition of these two major HDL families in plasma of normal, prepubertal children of both sexes and to compare them with those of adults. SUBJECTS A group of 16 nomolipidemic children (10 males and six females), aged 4 to 9 y, were randomly selected from patients admitted to the outpatient surgical facility of the Oklahoma Children's Memorial Hospital for minor surgical procedures. All children were healthy, asymptomatic, and without family history of hyperlipoproteinemia or diabetes; they had normal weight and height for their age groups. The conditions under which the s drawn were unstressful. There was minimal blood s a m ~ l e were anticipation of the event; it took place soon after the parents, waiting with their children in a playroom, had given their written consent. Blood samples were collected into vacutainer tubes containing disodium EDTA (1.5 mg/mL) and the plasma was promptly separated by low centrifugation (1000 x g) at 4°C. The adult population consisted of seven male and eight female volunteers randomly selected from a pool of normolipidemic employees of the Oklahoma Medical Research Foundation according to some predetermined selection criteria (2). All subjects were healthv. asvm~tomaticCaucasians with no history of familial hyp&lip~proteinemiaor diabetes. Their weighi/height index was between 0.9 and 1. They were all nonsmokers except for one of the male subjects who consumed 10 cigarettes/d. Only two male subjects were regular alcohol drinkers, but their alcohol consumption did not exceed 50 g/wk. All women were premenopausal and none was using contraceptive agents. With the exception of one male subject, age 64 y, the mean age of men Abbreviations LP-A-I, lipoprotein particle containing apoA-I LP-A-1:A-11, lipoprotein particle containing apoA-I and apoA-I1 HDL-C, HDGcholesterol TG, triglyceride PL, phospholipid CE, cholesterol ester FC, free cholesterol Received June 4, 1990; accepted October 3 1, 1990. Correspondence and reprint requests: P. Alaupovic, Ph.D., Lipoprotein and Atherosclerosis Research Program, Oklahoma Medical Research Foundation, 825 N.E. 13th Street, Oklahoma City, OK 73104. Supported in part by funding from NIH Grant HL-2318 1 and the resources of the Oklahoma Medical Research Foundation. E.D. was sponsored by the Comite des Aides a la Recherche Fournier, Dijon, France. I Present address: Inserm U32, H6pital Henri Mondor, 94010 Creteil, France. 5 316 BEKAERT ET AL. + (34.8 + 6.7 y) was very similar to that of women (35.6 8.5 y). Informed consent was obtained from each adult volunteer. After an overnight fast, blood samples were drawn and plasma samples were prepared as already described for children. MATERIALS A N D METHODS Production and characterization of MA^ to a p o ~ - and I apoAII, MAb F59 4A12 2F4 (anti-apoA-I) and CdBs (anti-apoA-11) were produced, purified, and characterized as previously described (16, 17). These antibodies were selected on the basis of their specificity and binding capacity to the major circulating forms of corresponding apolipoproteins. Preparation of anti-apoA-I and anti-apoA-II immunosorbers. MAb to apoA-I and apoA-I1 were coupled to the cross-linked agarose activated with N-hydroxysuccinimide (Afi-Gel 10) purchased from Bio-Rad Laboratories (Richmond, CA). After exhausti (...truncated)