title: Hepatobiliary cholesterol transport is not impaired in Abca1-null mice lacking HDL.
abstract: The ABC transporter ABCA1 regulates HDL levels and is considered to control the first step of reverse cholesterol transport from the periphery to the liver. To test this concept, we studied the effect of ABCA1 deficiency on hepatic metabolism and hepatobiliary flux of cholesterol in mice. Hepatic lipid contents and biliary secretion rates were determined in Abca1(-/-), Abca1(+/-), and Abca1(+/+) mice with a DBA background that were fed either standard chow or a high-fat, high-cholesterol diet. Hepatic cholesterol and phospholipid contents in Abca1(-/-) mice were indistinguishable from those in Abca1(+/-) and Abca1(+/+) mice on both diets. In spite of the absence of HDL, biliary secretion rates of cholesterol, bile salts, and phospholipid were unimpaired in Abca1(-/-) mice. Neither the hepatic expression levels of genes controlling key steps in cholesterol metabolism nor the contribution of de novo synthesis to biliary cholesterol and bile salts were affected by Abca genotype. Finally, fecal excretion of neutral and acidic sterols was similar in all groups. We conclude that plasma HDL levels and ABCA1 activity do not control net cholesterol transport from the periphery via the liver into the bile, indicating that the importance of HDL in reverse cholesterol transport requires re-evaluation.
authors.affiliation: Department of Gastroenterology, Academic Medical Center, Amsterdam, The Netherlands. a.k.groen@amc.uva.nl
authors.forename: A K
authors.initials: AK
authors.lastname: Groen
authors.forename: V W
authors.initials: VW
authors.lastname: Bloks
authors.forename: R H
authors.initials: RH
authors.lastname: Bandsma
authors.forename: R
authors.initials: R
authors.lastname: Ottenhoff
authors.forename: G
authors.initials: G
authors.lastname: Chimini
authors.forename: F
authors.initials: F
authors.lastname: Kuipers
mesh_terms: D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000502:physiology*; D000818:Animals; D001659:Biliary Tract / Q000378:metabolism*; D001693:Biological Transport, Active; D018955:CD36 Antigens / Q000235:genetics; D002352:Carrier Proteins; D002784:Cholesterol / Q000378:metabolism*; D006801:Humans; D006903:Hydroxymethylglutaryl CoA Reductases / Q000235:genetics; D008075:Lipoproteins, HDL / Q000172:deficiency* / Q000378:metabolism; D008099:Liver / Q000378:metabolism*; D008565:Membrane Proteins; D051379:Mice; D008811:Mice, Inbred DBA; D018345:Mice, Knockout; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins; D011971:Receptors, Immunologic; D011973:Receptors, LDL / Q000235:genetics; D018110:Receptors, Lipoprotein / Q000235:genetics; D051116:Receptors, Scavenger; D051122:Scavenger Receptors, Class B
chemical_list: C577836:ABCA1 protein, human; D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters; D018955:CD36 Antigens; D002352:Carrier Proteins; D008075:Lipoproteins, HDL; D008565:Membrane Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D011971:Receptors, Immunologic; D011973:Receptors, LDL; D018110:Receptors, Lipoprotein; D051116:Receptors, Scavenger; C454739:Scarb1 protein, mouse; D051122:Scavenger Receptors, Class B; C031616:high density lipoprotein receptors; C075197:high density lipoprotein binding protein; D002784:Cholesterol; D006903:Hydroxymethylglutaryl CoA Reductases