维生素D3代谢产物的C-3差向异构化及C-3差向异构体的进一步代谢：25-羟基维生素D3代谢为3-表-25-羟基维生素D3，随后通过C-1α或C-24羟基化进行代谢。

C-3 epimerization of vitamin D3 metabolites and further metabolism of C-3 epimers: 25-hydroxyvitamin D3 is metabolized to 3-epi-25-hydroxyvitamin D3 and subsequently metabolized through C-1alpha or C-24 hydroxylation.

作者信息

Kamao Maya, Tatematsu Syuichiro, Hatakeyama Susumi, Sakaki Toshiyuki, Sawada Natsumi, Inouye Kuniyo, Ozono Keiichi, Kubodera Noboru, Reddy G Satyanarayana, Okano Toshio

机构信息

Department of Hygienic Sciences, Kobe Pharmaceutical University, Kobe 658-8558, Japan.

出版信息

J Biol Chem. 2004 Apr 16;279(16):15897-907. doi: 10.1074/jbc.M311473200. Epub 2004 Feb 2.

DOI:10.1074/jbc.M311473200

PMID:14757768

Abstract

Recently, it was revealed that 1alpha,25-dihydroxyvitamin D3 (1alpha,25(OH)2D3) and 24R,25-dihydroxyvitamin D3 (24,25(OH)2D3) were metabolized to their respective epimers of the hydroxyl group at C-3 of the A-ring. We now report the isolation and structural assignment of 3-epi-25-hydroxyvitamin D3 (3-epi-25(OH)D3 as a major metabolite of 25-hydroxyvitamin D3 (25(OH)D3) and the further metabolism of C-3 epimers of vitamin D3 metabolites. When 25(OH)D3 was incubated with various cultured cells including osteosarcoma, colon adenocarcinoma, and hepatoblastoma cell lines, 3-epi-25(OH)D3 and 24,25 (OH)2D3 were commonly observed as a major and minor metabolite of 25(OH)D3, respectively. 25(OH)D3 was at least as sensitive to C-3 epimerization as 1alpha, 25(OH)2D3 which has been reported as a substrate for the C-3 epimerization reaction. Unlike these cultured cells, LLC-PK1 cells, a porcine kidney cell line, preferentially produced 24,25(OH)2D3 rather than 3-epi-25(OH)D3. We also confirmed the existence of 3-epi-25(OH)D3 in the serum of rats intravenously given pharmacological doses of 25(OH)D3. The cultured cells metabolized 3-epi-25OHD3 and 3-epi-1alpha,25(OH)2D3 to 3-epi-24,25(OH)2D3 and 3-epi-1alpha,24,25(OH)3D3, respectively. In addition, we demonstrated that 3-epi-25(OH)D3 was metabolized to 3-epi-1alpha,25(OH)2D3 by CYP27B1 and to 3-epi-24,25(OH)2D3 by CYP24 using recombinant Escherichia coli cell systems. 3-Epi-25(OH)D3, 3-epi-1alpha,25(OH)2D3, and 3-epi-24,25(OH)2D3 were biologically less active than 25(OH)D3, 1alpha,25(OH)2D3, and 24,25(OH)2D3, but 3-epi-1alpha,25(OH)2D3 showed to some extent transcriptional activity toward target genes and anti-proliferative/differentiation-inducing activity against human myeloid leukemia cells (HL-60). These results indicate that C-3 epimerization may be a common metabolic pathway for the major metabolites of vitamin D3.

摘要

最近有研究表明，1α,25 - 二羟基维生素D3（1α,25(OH)2D3）和24R,25 - 二羟基维生素D3（24,25(OH)2D3）会代谢为其在A环C - 3位羟基的各自差向异构体。我们现在报告3 - 表 - 25 - 羟基维生素D3（3 - epi - 25(OH)D3）作为25 - 羟基维生素D3（25(OH)D3）的主要代谢产物的分离及结构鉴定，以及维生素D3代谢产物C - 3差向异构体的进一步代谢情况。当将25(OH)D3与包括骨肉瘤、结肠腺癌和肝母细胞瘤细胞系在内的多种培养细胞共同孵育时，3 - epi - 25(OH)D3和24,25(OH)2D3分别被普遍观察到是25(OH)D3的主要和次要代谢产物。25(OH)D3对C - 3差向异构化的敏感性至少与已被报道为C - 3差向异构化反应底物的1α,25(OH)2D3相同。与这些培养细胞不同，猪肾细胞系LLC - PK1细胞优先产生24,25(OH)2D3而非3 - epi - 25(OH)D3。我们还证实，在静脉注射药理剂量25(OH)D3的大鼠血清中存在3 - epi - 25(OH)D3。培养细胞将3 - epi - 25OHD3和3 - epi - 1α,25(OH)2D3分别代谢为3 - epi - 24,25(OH)2D3和3 - epi - 1α,24,25(OH)3D3。此外，我们利用重组大肠杆菌细胞系统证明，3 - epi - 25(OH)D3可被CYP27B1代谢为3 - epi - 1α,25(OH)2D3，被CYP24代谢为3 - epi - 24,25(OH)2D3。3 - epi - 25(OH)D3、3 - epi - 1α,25(OH)2D3和3 - epi - 24,25(OH)2D3的生物活性低于25(OH)D3、1α,25(OH)2D3和24,25(OH)2D3，但3 - epi - 1α,25(OH)2D3对靶基因表现出一定程度的转录活性，以及对人髓系白血病细胞（HL - 60）的抗增殖/诱导分化活性。这些结果表明，C - 3差向异构化可能是维生素D3主要代谢产物的常见代谢途径。