title: 1,25-dihydroxyvitamin D3 influences cellular homocysteine levels in murine preosteoblastic MC3T3-E1 cells by direct regulation of cystathionine β-synthase.
abstract: High homocysteine (HCY) levels are a risk factor for osteoporotic fracture. Furthermore, bone quality and strength are compromised by elevated HCY owing to its negative impact on collagen maturation. HCY is cleared by cystathionine β-synthase (CBS), the first enzyme in the transsulfuration pathway. CBS converts HCY to cystathionine, thereby committing it to cysteine synthesis. A microarray experiment on MC3T3-E1 murine preosteoblasts treated with 1,25-dihydroxyvitamin D(3) [1,25(OH)(2) D(3) ] revealed a cluster of genes including the cbs gene, of which the transcription was rapidly and strongly induced by 1,25(OH)(2) D(3) . Quantitative real-time PCR and Western blot analysis confirmed higher levels of cbs mRNA and protein after 1,25(OH)(2) D(3) treatment in murine and human cells. Moreover, measurement of CBS enzyme activity and quantitative measurements of HCY, cystathionine, and cysteine concentrations were consistent with elevated transsulfuration activity in 1,25(OH)(2) D(3) -treated cells. The importance of a functional vitamin D receptor (VDR) for transcriptional regulation of cbs was shown in primary murine VDR knockout osteoblasts, in which upregulation of cbs in response to 1,25(OH)(2) D(3) was abolished. Chromatin immunoprecipitation on chip and transfection studies revealed a functional vitamin D response element in the second intron of cbs. To further explore the potential clinical relevance of our ex vivo findings, human data from the Longitudinal Aging Study Amsterdam suggested a correlation between vitamin D status [25(OH)D(3) levels] and HCY levels. In conclusion, this study showed that cbs is a primary 1,25(OH)(2) D(3) target gene which renders HCY metabolism responsive to 1,25(OH)(2) D(3).
authors: Laboratory for Experimental Medicine and Endocrinology (LEGENDO), Catholic University of Leuven, Leuven, Belgium.
authors: Carsten
authors: C
authors: Kriebitzsch
authors: Lieve
authors: L
authors: Verlinden
authors: Guy
authors: G
authors: Eelen
authors: Natasja M
authors: NM
authors: van Schoor
authors: Karin
authors: K
authors: Swart
authors: Paul
authors: P
authors: Lips
authors: Mark B
authors: MB
authors: Meyer
authors: J Wesley
authors: JW
authors: Pike
authors: Steven
authors: S
authors: Boonen
authors: Carsten
authors: C
authors: Carlberg
authors: Victor
authors: V
authors: Vitvitsky
authors: Roger
authors: R
authors: Bouillon
authors: Ruma
authors: R
authors: Banerjee
authors: Annemieke
authors: A
authors: Verstuyf
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D003541:Cystathionine beta-Synthase / Q000235:genetics* / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D006710:Homocysteine / Q000378:metabolism*; D006801:Humans; D053858:Metabolic Networks and Pathways / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D008875:Middle Aged; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology*; D011485:Protein Binding / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018167:Receptors, Calcitriol / Q000378:metabolism; D020218:Response Elements / Q000235:genetics; D015533:Transcriptional Activation / Q000187:drug effects / Q000235:genetics; D015854:Up-Regulation / Q000187:drug effects; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood / Q000494:pharmacology
chemical_list: D000596:Amino Acids; D012333:RNA, Messenger; D018167:Receptors, Calcitriol; D006710:Homocysteine; D014807:Vitamin D; C097949:1,25-dihydroxyvitamin D; D003541:Cystathionine beta-Synthase