title: Vitamin D receptor activation down-regulates the small heterodimer partner and increases CYP7A1 to lower cholesterol.
abstract: OBJECTIVE
  Little is known about the effects of the vitamin D receptor (VDR) on hepatic activity of human cholesterol 7α-hydroxylase (CYP7A1) and cholesterol metabolism. We studied these processes in mice in vivo and mouse and human hepatocytes.
  
  
  METHODS
  Farnesoid X receptor (Fxr)(-/-), small heterodimer partner (Shp)(-/-), and C57BL/6 (wild-type control) mice were fed normal or Western diets for 3 weeks and were then given intraperitoneal injections of vehicle (corn oil) or 1α,25-dihydroxyvitamin D3 (1,25[OH]2D3; 4 doses, 2.5 μg/kg, every other day). Plasma and tissue samples were collected and levels of Vdr, Shp, Cyp7a1, Cyp24a1, and rodent fibroblast growth factor (Fgf) 15 expression, as well as levels of cholesterol, were measured. We studied the regulation of Shp by Vdr using reporter and mobility shift assays in transfected human embryonic kidney 293 cells, quantitative polymerase chain reaction with mouse tissues and mouse and human hepatocytes, and chromatin immunoprecipitation assays with mouse liver.
  
  
  RESULTS
  We first confirmed the presence of Vdr mRNA and protein expression in livers of mice. In mice fed normal diets and given injections of 1,25(OH)2D3, liver and plasma concentrations of 1,25(OH)2D3 increased and decreased in unison. Changes in hepatic Cyp7a1 messenger RNA (mRNA) correlated with those of Cyp24a1 (a Vdr target gene) and inversely with Shp mRNA, but not ileal Fgf15 mRNA. Similarly, incubation with 1,25(OH)2D3 increased levels of Cyp24a1/CYP24A1 and Cyp7a1/CYP7A1 mRNA in mouse and human hepatocytes, and reduced levels of Shp mRNA in mouse hepatocytes. In Fxr(-/-) and wild-type mice with hypercholesterolemia, injection of 1,25(OH)2D3 consistently reduced levels of plasma and liver cholesterol and Shp mRNA, and increased hepatic Cyp7a1 mRNA and protein; these changes were not observed in Shp(-/-) mice given 1,25(OH)2D3 and fed Western diets. Truncation of the human small heterodimer partner (SHP) promoter and deletion analyses revealed VDR-dependent inhibition of SHP, and mobility shift assays showed direct binding of VDR to enhancer regions of SHP. In addition, chromatin immunoprecipitation analysis of livers from mice showed that injection of 1,25(OH)2D3 increased recruitment of Vdr and rodent retinoid X receptor to the Shp promoter.
  
  
  CONCLUSIONS
  Activation of the VDR represses hepatic SHP to increase levels of mouse and human CYP7A1 and reduce cholesterol.
authors.affiliation: Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Edwin C Y
authors.initials: EC
authors.lastname: Chow
authors.affiliation: Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Lilia
authors.initials: L
authors.lastname: Magomedova
authors.affiliation: Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Holly P
authors.initials: HP
authors.lastname: Quach
authors.affiliation: Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Rucha
authors.initials: R
authors.lastname: Patel
authors.affiliation: Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Durk
authors.affiliation: Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Jianghong
authors.initials: J
authors.lastname: Fan
authors.affiliation: Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Han-Joo
authors.initials: HJ
authors.lastname: Maeng
authors.affiliation: Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Kamdi
authors.initials: K
authors.lastname: Irondi
authors.affiliation: Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas.
authors.forename: Sayeepriyadarshini
authors.initials: S
authors.lastname: Anakk
authors.affiliation: Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas.
authors.forename: David D
authors.initials: DD
authors.lastname: Moore
authors.affiliation: Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Carolyn L
authors.initials: CL
authors.lastname: Cummins
authors.affiliation: Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, Canada. Electronic address: ks.pang@utoronto.ca.
authors.forename: K Sandy
authors.initials: KS
authors.lastname: Pang
mesh_terms: D000818:Animals; D001665:Binding Sites; D002117:Calcitriol / Q000494:pharmacology*; D002784:Cholesterol / Q000378:metabolism*; D002790:Cholesterol 7-alpha-Hydroxylase / Q000378:metabolism*; D004195:Disease Models, Animal; D005346:Fibroblast Growth Factors / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D057809:HEK293 Cells; D022781:Hepatocytes / Q000187:drug effects* / Q000201:enzymology; D006801:Humans; D006937:Hypercholesterolemia / Q000188:drug therapy / Q000201:enzymology / Q000235:genetics; D007082:Ileum / Q000187:drug effects / Q000201:enzymology; D008099:Liver / Q000187:drug effects* / Q000201:enzymology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D018167:Receptors, Calcitriol / Q000819:agonists* / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D013250:Steroid Hydroxylases / Q000378:metabolism; D013997:Time Factors; D014162:Transfection; D065668:Vitamin D3 24-Hydroxylase; D000099150:Receptor, Farnesoid X-Activated
chemical_list: D002117:Calcitriol; D002784:Cholesterol; D002790:Cholesterol 7-alpha-Hydroxylase; D005346:Fibroblast Growth Factors; D012333:RNA, Messenger; D018167:Receptors, Calcitriol; D018160:Receptors, Cytoplasmic and Nuclear; D013250:Steroid Hydroxylases; D065668:Vitamin D3 24-Hydroxylase; D000099150:Receptor, Farnesoid X-Activated; C579457:VDR protein, human; C108526:fibroblast growth factor 15, mouse; C099713:nuclear receptor subfamily 0, group B, member 2; C553219:CYP7A1 protein, human; C502772:Cyp7a1 protein, mouse; C585549:CYP24A1 protein, human; C585550:Cyp24a1 protein, mouse
keywords: Bile Acid; Farnesoid X Receptor; Liver; Transcriptional Regulation