title: Diosgenin-induced biliary cholesterol secretion in mice requires Abcg8.
abstract: The plant sterol diosgenin has been shown to stimulate biliary cholesterol secretion in mice without affecting the expression of the adenosine triphosphate-binding cassette transporter heterodimer Abcg5/g8. The aim of this study was to investigate the mechanism of diosgenin-induced cholesterol hypersecretion and to identify the genes involved. Surprisingly, despite its lack of effect on Abcg5/g8 expression in wild-type mice, diosgenin did not stimulate biliary cholesterol secretion in mice deficient for Abcg8. Analysis of the kinetics of cholesterol secretion suggested that diosgenin probably activates a step before Abcg5/g8. To identify potential diosgenin targets, gene expression profiling was performed in mice fed a diosgenin-supplemented diet. Diosgenin feeding increased hepatic expression of genes involved in cholesterol synthesis as well as genes encoding for several cytochrome P450s. No significant change in expression of known cholesterol transporters was found. Comparison with published expression-profiling data for Srebp2-overexpressing mice, another mouse model in which biliary cholesterol secretion is elevated, revealed a number of genes with unknown function that were upregulated in both diosgenin-fed mice and mice overexpressing Srebp2. In conclusion, we found that although Abcg8 is essential for most diosgenin-induced biliary cholesterol hypersecretion, diosgenin probably does not interact directly with Abcg5/Abcg8, but rather increases cholesterol delivery to the heterodimer. Supplementary material for this article can be found on the HEPATOLOGY website (http://interscience.wiley.com/jpages/0270-9139/suppmat/index.html).
authors.affiliation: AMC Liver Center Academic Medical Center, Amsterdam, The Netherlands. astridkosters@yahoo.com
authors.forename: Astrid
authors.initials: A
authors.lastname: Kosters
authors.forename: Raoul J J M
authors.initials: RJ
authors.lastname: Frijters
authors.forename: Cindy
authors.initials: C
authors.lastname: Kunne
authors.forename: Edwin
authors.initials: E
authors.lastname: Vink
authors.forename: Marit S
authors.initials: MS
authors.lastname: Schneiders
authors.forename: Frank G
authors.initials: FG
authors.lastname: Schaap
authors.forename: Catherina P
authors.initials: CP
authors.lastname: Nibbering
authors.forename: Shailendra B
authors.initials: SB
authors.lastname: Patel
authors.forename: Albert K
authors.initials: AK
authors.lastname: Groen
mesh_terms: D000071018:ATP Binding Cassette Transporter, Subfamily G, Member 5; D000071019:ATP Binding Cassette Transporter, Subfamily G, Member 8; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism*; D000818:Animals; D001659:Biliary Tract / Q000187:drug effects* / Q000378:metabolism*; D002784:Cholesterol / Q000378:metabolism*; D004144:Diosgenin / Q000494:pharmacology*; D005260:Female; D007700:Kinetics; D008074:Lipoproteins / Q000378:metabolism*; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D018345:Mice, Knockout
chemical_list: C462600:ABCG5 protein, mouse; C462601:ABCG8 protein, mouse; D000071018:ATP Binding Cassette Transporter, Subfamily G, Member 5; D000071019:ATP Binding Cassette Transporter, Subfamily G, Member 8; D018528:ATP-Binding Cassette Transporters; D008074:Lipoproteins; D002784:Cholesterol; D004144:Diosgenin