title: ABCA1 overexpression in the liver of LDLr-KO mice leads to accumulation of pro-atherogenic lipoproteins and enhanced atherosclerosis.
abstract: The identification of ABCA1 as a key transporter responsible for cellular lipid efflux has led to considerable interest in defining its role in cholesterol metabolism and atherosclerosis. In this study, the effect of overexpressing ABCA1 in the liver of LDLr-KO mice was investigated. Compared with LDLr-KO mice, ABCA1-Tg x LDLr-KO (ABCA1-Tg) mice had significantly increased plasma cholesterol levels, mostly because of a 2.8-fold increase in cholesterol associated with a large pool of apoB-lipoproteins. ApoB synthesis was unchanged but the catabolism of (125)I-apoB-VLDL and -LDL were significantly delayed, accounting for the 1.35-fold increase in plasma apoB levels in ABCA1-Tg mice. We also found rapid in vivo transfer of free cholesterol from HDL to apoB-lipoproteins in ABCA1-Tg mice, associated with a significant 2.7-fold increase in the LCAT-derived cholesteryl linoleate content found primarily in apoB-lipoproteins. ABCA1-Tg mice had 1.4-fold increased hepatic cholesterol concentrations, leading to a compensatory 71% decrease in de novo hepatic cholesterol synthesis, as well as enhanced biliary cholesterol, and bile acid secretion. CAV-1, CYP2b10, and ABCG1 were significantly induced in ABCA1-overexpressing livers; however, no differences were observed in the hepatic expression of CYP7alpha1, CYP27alpha1, or ABCG5/G8 between ABCA1-Tg and control mice. As expected from the pro-atherogenic plasma lipid profile, aortic atherosclerosis was increased 10-fold in ABCA1-Tg mice. In summary, hepatic overexpression of ABCA1 in LDLr-KO mice leads to: 1) expansion of the pro-atherogenic apoB-lipoprotein cholesterol pool size via enhanced transfer of HDL-cholesterol to apoB-lipoproteins and delayed catabolism of cholesterol-enriched apoB-lipoproteins; 2) increased cholesterol concentration in the liver, resulting in up-regulated hepatobiliary sterol secretion; and 3) significantly enhanced aortic atherosclerotic lesions.
authors.affiliation: Molecular Disease Section, NHLBI, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Charles W
authors.initials: CW
authors.lastname: Joyce
authors.forename: Elke M
authors.initials: EM
authors.lastname: Wagner
authors.forename: Federica
authors.initials: F
authors.lastname: Basso
authors.forename: Marcelo J
authors.initials: MJ
authors.lastname: Amar
authors.forename: Lita A
authors.initials: LA
authors.lastname: Freeman
authors.forename: Robert D
authors.initials: RD
authors.lastname: Shamburek
authors.forename: Catherine L
authors.initials: CL
authors.lastname: Knapper
authors.forename: Jafri
authors.initials: J
authors.lastname: Syed
authors.forename: Justina
authors.initials: J
authors.lastname: Wu
authors.forename: Boris L
authors.initials: BL
authors.lastname: Vaisman
authors.forename: Jamila
authors.initials: J
authors.lastname: Fruchart-Najib
authors.forename: Eric M
authors.initials: EM
authors.lastname: Billings
authors.forename: Beverly
authors.initials: B
authors.lastname: Paigen
authors.forename: Alan T
authors.initials: AT
authors.lastname: Remaley
authors.forename: Silvia
authors.initials: S
authors.lastname: Santamarina-Fojo
authors.forename: H Bryan
authors.initials: HB
authors.lastname: Brewer
mesh_terms: D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001011:Aorta / Q000378:metabolism / Q000473:pathology; D050197:Atherosclerosis / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D001659:Biliary Tract / Q000378:metabolism; D002784:Cholesterol / Q000097:blood; D018450:Disease Progression; D005243:Feces; D005260:Female; D005786:Gene Expression Regulation; D006487:Hemostasis; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism; D050356:Lipid Metabolism; D008074:Lipoproteins / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D020411:Oligonucleotide Array Sequence Analysis; D009928:Organ Specificity; D011973:Receptors, LDL / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism*; D013261:Sterols / Q000378:metabolism
chemical_list: C577836:ABCA1 protein, human; D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters; D008074:Lipoproteins; D011973:Receptors, LDL; D013261:Sterols; D002784:Cholesterol