title: Analysis of HSD3B7 knockout mice reveals that a 3alpha-hydroxyl stereochemistry is required for bile acid function.
abstract: Primary bile acids are synthesized from cholesterol in the liver and thereafter are secreted into the bile and small intestine. Gut flora modify primary bile acids to produce secondary bile acids leading to a chemically diverse bile acid pool that is circulated between the small intestine and liver. A majority of primary and secondary bile acids in higher vertebrates have a 3alpha-hydroxyl group. Here, we characterize a line of knockout mice that cannot epimerize the 3beta-hydroxyl group of cholesterol and as a consequence synthesize a bile acid pool in which 3beta-hydroxylated bile acids predominate. This alteration causes death in 90% of newborn mice and decreases the absorption of dietary cholesterol in surviving adults. Negative feedback regulation of bile acid synthesis mediated by the farnesoid X receptor (FXR) is disrupted in the mutant mice. We conclude that the correct stereochemistry of a single hydroxyl group at carbon 3 in bile acids is required to maintain their physiologic and regulatory functions in mammals.
authors.affiliation: Department of Molecular Genetics, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA.
authors.forename: Heidi C
authors.initials: HC
authors.lastname: Shea
authors.forename: Daphne D
authors.initials: DD
authors.lastname: Head
authors.forename: Kenneth D R
authors.initials: KD
authors.lastname: Setchell
authors.forename: David W
authors.initials: DW
authors.lastname: Russell
mesh_terms: D015096:3-Hydroxysteroid Dehydrogenases / Q000737:chemistry / Q000172:deficiency* / Q000235:genetics* / Q000502:physiology; D000818:Animals; D001647:Bile Acids and Salts / Q000096:biosynthesis / Q000737:chemistry* / Q000502:physiology*; D002384:Catalysis; D002460:Cell Line; D002784:Cholesterol / Q000737:chemistry / Q000378:metabolism; D004764:Enterohepatic Circulation / Q000235:genetics; D025461:Feedback, Physiological / Q000235:genetics; D005260:Female; D008107:Liver Diseases / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008968:Molecular Conformation
chemical_list: D001647:Bile Acids and Salts; D002784:Cholesterol; D015096:3-Hydroxysteroid Dehydrogenases; C066485:3 beta-hydroxy-delta 5-C(27)-steroid dehydrogenase