title: Apolipoprotein A-II production rate is a major factor regulating the distribution of apolipoprotein A-I among HDL subclasses LpA-I and LpA-I:A-II in normolipidemic humans.
abstract: HDLs are heterogeneous in their apolipoprotein composition. Apolipoprotein (apo) A-I and apoA-II are the major proteins found in HDL and form the two major HDL subclasses: those that contain only apoA-I (LpA-I) and those that contain both apoA-I and apoA-II (LpA-I:A-II). Substantial evidence indicates that these two subclasses differ in their in vivo metabolism and effect on atherosclerosis, with LpA-I the more specifically protective subfraction against atherosclerosis. The purpose of this study was to investigate the effect of apoA-I and apoA-II production and catabolism on plasma LpA-I and LpA-I:A-II levels. Fifty normolipidemic subjects (those with HDL cholesterol levels in the top and bottom tenth percentiles were excluded) underwent kinetic studies with radiolabeled apoA-I and apoA-II, and the kinetic parameters of apoA-I and apoA-II were correlated with LpA-I and LpA-I:A-II levels. ApoA-I levels were strongly correlated with apoA-I residence times and less strongly correlated with apoA-I production rates. In contrast, apoA-II levels were correlated only with apoA-II production rates and not with apoA-II residence times. Levels of apoA-I in LpA-I were correlated with apoA-I residence times, whereas levels of apoA-I in LpA-I:A-II were correlated primarily with apoA-II production rates. The fraction of apoA-I in LpA-I was highly inversely correlated with apoA-II production rate (r = -.67, P < .001). In multiple regression analysis, apoA-II production rate was the most significant independent variable determining percent apoA-I in LpA-I among all the kinetic parameters.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Molecular Disease Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA.
authors.forename: K
authors.initials: K
authors.lastname: Ikewaki
authors.forename: L A
authors.initials: LA
authors.lastname: Zech
authors.forename: M
authors.initials: M
authors.lastname: Kindt
authors.forename: H B
authors.initials: HB
authors.lastname: Brewer
authors.forename: D J
authors.initials: DJ
authors.lastname: Rader
mesh_terms: D000328:Adult; D016632:Apolipoprotein A-I / Q000145:classification / Q000378:metabolism*; D016633:Apolipoprotein A-II / Q000096:biosynthesis* / Q000145:classification; D005260:Female; D006801:Humans; D007700:Kinetics; D008055:Lipids / Q000097:blood*; D008075:Lipoproteins, HDL / Q000097:blood* / Q000145:classification; D008297:Male; D012016:Reference Values; D012044:Regression Analysis
chemical_list: D016632:Apolipoprotein A-I; D016633:Apolipoprotein A-II; D008055:Lipids; D008075:Lipoproteins, HDL