Generation of 1,25-dihydroxyvitamin D3 in Cyp27b1 knockout mice by treatment with 25-hydroxyvitamin D3 rescued their rachitic phenotypes

Publication date: Available online 18 July 2018Source: The Journal of Steroid Biochemistry and Molecular BiologyAuthor(s): Miyu Nishikawa, Kaori Yasuda, Masashi Takamatsu, Keisuke Abe, Kimie Nakagawa, Naoko Tsugawa, Yoshihisa Hirota, Kazuma Tanaka, Shigeaki Yamashita, Shinichi Ikushiro, Tatsuo Suda, Toshio Okano, Toshiyuki SakakiAbstractWe have reported that 25-hydroxyvitamin D3 [25(OH)D3] binds to vitamin D receptor and exhibits several biological functions directly in vitro. To evaluate the direct effect of 25(OH)D3 in vivo, we used Cyp27b1 knockout (KO) mice, which had no detectable plasma 1α,25-dihydroxyvitamin D3 [1,25(OH)2D3] when fed a diet containing normal Ca and vitamin D. Daily treatment with 25(OH)D3 at 250 μg kg-1 day-1 rescued rachitic phenotypes in the Cyp27b1 KO mice. Bone mineral density, female sexual cycles, and plasma levels of Ca, P, and PTH were all normalized following 25(OH)D3 administration. An elevated Cyp24a1 mRNA expression was observed in the kidneys, and plasma concentrations of Cyp24a1-dependent metabolites of 25(OH)D3 were increased. To our surprise, 1,25(OH)2D3 was detected at a normal level in the plasma of Cyp27b1 KO mice. The F1 to F4 generations of Cyp27b1 KO mice fed 25(OH)D3 showed normal growth, normal plasma levels of Ca, P, and parathyroid hormone, and normal bone mineral density. The curative effect of 25(OH)D3 was considered to depend on the de novo synthesis of 1,25(OH)2D3 in the Cyp27b1 KO mice. This suggests that another en...
Source: The Journal of Steroid Biochemistry and Molecular Biology - Category: Biochemistry Source Type: research