Effect of vitamin K on the calcium channel (TRPV6) and calbindin-D9k genes in the gastrointestinal tract of rats and Caco-2 cells.

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Recently, a novel mechanism of vitamin K functions via transcriptional regulation as a ligand for steroid and xenobiotic receptor (SXR) in osteoblastic cells was reported. Three genes, TRPV6, calbindin-D9k and PMCA1b were determined to be involved in the process of calcium absorption in the mucosal cells of intestine and induced gene expression by vitamin D.SXR is also expressed at high level in intestine and SXR-binding site contains binding motifs for vitamin D receptor (VDR). Therefore we expected that vitamin K bound to VDR binding motif and regulated the expression of genes that were involved in calcium absorption in intestine. Colon cancer cell line SW-480 revealed the increase of the TRPV6 mRNA expression by the addition of vitamin K2. In this study, we fed rats vitamin K supplemented diet and analyzed the change of expression of TRPV6 and calbindin-D9k mRNA. The vitamin K diet increased expression of TRPV6 and calbindin-D9k.