title: LXR driven induction of HDL-cholesterol is independent of intestinal cholesterol absorption and ABCA1 protein expression.
abstract: We investigated whether: (1) liver X receptor (LXR)-driven induction of high-density lipoprotein cholesterol (HDL-C) and other LXR-mediated effects on cholesterol metabolism depend on intestinal cholesterol absorption; and (2) combined treatment with the LXR agonist GW3965 and the cholesterol absorption inhibitor ezetimibe results in synergistic effects on cholesterol metabolism that could be beneficial for treatment of atherosclerosis. Mice were fed 0.2 % cholesterol and treated with GW3965+ezetimibe, GW3965 or ezetimibe. GW3965+ezetimibe treatment elevated serum HDL-C and Apolipoprotein (Apo) AI, effectively reduced the intestinal cholesterol absorption and increased the excretion of faecal neutral sterols. No changes in intestinal ATP-binding cassette (ABC) A1 or ABCG5 protein expression were observed, despite increased mRNA expression, while hepatic ABCA1 was slightly reduced. The combined treatment caused a pronounced down-regulation of intestinal Niemann-Pick C1-like 1 (NPC1L1) and reduced hepatic and intestinal cholesterol levels. GW3965 did not affect the intestinal cholesterol absorption, but increased serum HDL-C and ApoAI levels. GW3965 also increased Apoa1 mRNA levels in primary mouse hepatocytes and HEPA1-6 cells. Ezetimibe reduced the intestinal cholesterol absorption, ABCA1 and ABCG5, but did not affect the serum HDL-C or ApoAI levels. Thus, the LXR-driven induction of HDL-C and ApoAI was independent of the intestinal cholesterol absorption and increased expression of intestinal or hepatic ABCA1 was not required. Inhibited influx of cholesterol via NPC1L1 and/or low levels of intracellular cholesterol prevented post-transcriptional expression of intestinal ABCA1 and ABCG5, despite increased mRNA levels. Combined LXR activation and blocked intestinal cholesterol absorption induced effective faecal elimination of cholesterol.
authors.affiliation: Division of Clinical Chemistry, Department of Laboratory Medicine, Karolinska Institutet, Karolinska University Hospital, Huddinge, 141 86, Stockholm, Sweden.
authors.forename: Kristina
authors.initials: K
authors.lastname: Kannisto
authors.forename: Mats
authors.initials: M
authors.lastname: Gåfvels
authors.forename: Zhao-Yan
authors.initials: ZY
authors.lastname: Jiang
authors.forename: Katharina
authors.initials: K
authors.lastname: Slätis
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Hu
authors.forename: Carl
authors.initials: C
authors.lastname: Jorns
authors.forename: Knut R
authors.initials: KR
authors.lastname: Steffensen
authors.forename: Gösta
authors.initials: G
authors.lastname: Eggertsen
mesh_terms: D064286:ATP Binding Cassette Transporter 1 / Q000235:genetics / Q000378:metabolism*; D000071018:ATP Binding Cassette Transporter, Subfamily G, Member 5; D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism; D000818:Animals; D000924:Anticholesteremic Agents / Q000494:pharmacology; D016632:Apolipoprotein A-I / Q000097:blood / Q000378:metabolism; D001384:Azetidines / Q000494:pharmacology; D001565:Benzoates / Q000494:pharmacology; D001596:Benzylamines / Q000494:pharmacology; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D002784:Cholesterol / Q000097:blood / Q000378:metabolism*; D008076:Cholesterol, HDL / Q000097:blood / Q000378:metabolism*; D000069438:Ezetimibe; D005243:Feces / Q000737:chemistry; D015870:Gene Expression / Q000187:drug effects; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism; D007408:Intestinal Absorption / Q000187:drug effects; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000187:drug effects; D008074:Lipoproteins / Q000235:genetics / Q000378:metabolism; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D000071518:Liver X Receptors; D008297:Male; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D057093:Orphan Nuclear Receptors / Q000819:agonists / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: C462600:ABCG5 protein, mouse; D064286:ATP Binding Cassette Transporter 1; D000071018:ATP Binding Cassette Transporter, Subfamily G, Member 5; D018528:ATP-Binding Cassette Transporters; D000924:Anticholesteremic Agents; D016632:Apolipoprotein A-I; D001384:Azetidines; D001565:Benzoates; D001596:Benzylamines; D008076:Cholesterol, HDL; C473027:GW 3965; D008074:Lipoproteins; D000071518:Liver X Receptors; D026901:Membrane Transport Proteins; C482445:Npc1l1 protein, mouse; D057093:Orphan Nuclear Receptors; D002784:Cholesterol; D000069438:Ezetimibe