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Thyroid Hormones Decrease Plasma 1α,25-Dihydroxyvitamin D Levels Through Transcriptional Repression of the Renal 25-Hydroxyvitamin D3 1α-Hydroxylase Gene (CYP27B1).
MedLine Citation:
PMID:  23307792     Owner:  NLM     Status:  Publisher    
The primary determinant of circulating 1α,25-dihydroxyvitamin D (1,25[OH](2)D) levels is the activity of 25-hydroxyvitamin D-1α-hydroxylase (cytochrome P450 27B1 [CYP27B1]) in the kidney. Hyperthyroid patients have been reported to have low levels of plasma 1,25(OH)(2)D. However, the detailed mechanism of thyroid hormone action on vitamin D metabolism is still poorly understood. The present study determined whether renal CYP27B1 gene expression was negatively regulated by thyroid hormones. T(3)-induced hyperthyroid mice showed marked decreases in plasma 1,25(OH)(2)D levels and in renal expression of CYP27B1 mRNA but no changes in plasma concentrations of calcium, PTH, or fibroblast growth factor-23. In addition, we observed that T(3) administration significantly decreased plasma 1,25(OH)(2)D and renal CYP27B1 mRNA levels that were increased by low-calcium or low-phosphorus diets and induced hypocalcemia in mice fed a low-calcium diet. Promoter analysis revealed that T(3) decreases the basal transcriptional activity of the CYP27B1 gene through thyroid hormone receptors (TRα and TRβ1) and the retinoid X receptor α (RXRα) in renal proximal tubular cells. Interestingly, we identified an everted repeat negative thyroid hormone response element (1α-nTRE) overlapping the sterol regulatory element (1α-SRE) and the TATA-box -50 to -20 base pairs from the human CYP27B1 gene transcription start site. Finally, we established that CYP27B1 gene transcription is positively regulated by SRE-binding proteins and that a T(3)-bound TRβ1/RXRα heterodimer inhibits SRE-binding protein-1c-induced transcriptional activity through the 1α-nTRE. These results suggest that transcriptional repression of the CYP27B1 gene by T(3)-bound TRs/RXRα, acting through the 1α-nTRE, results in decreased renal CYP27B1 expression and plasma 1,25(OH)(2)D levels.
Mina Kozai; Hironori Yamamoto; Mariko Ishiguro; Nagakatsu Harada; Masashi Masuda; Tomohiro Kagawa; Yuichiro Takei; Ayako Otani; Otoki Nakahashi; Shoko Ikeda; Yutaka Taketani; Ken-Ichi Takeyama; Shigeaki Kato; Eiji Takeda
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2013-1-10
Journal Detail:
Title:  Endocrinology     Volume:  -     ISSN:  1945-7170     ISO Abbreviation:  Endocrinology     Publication Date:  2013 Jan 
Date Detail:
Created Date:  2013-1-11     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0375040     Medline TA:  Endocrinology     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Departments of Clinical Nutrition (M.K., H.Y., M.I., M.M., T.K, Y.Takei., A.O., O.N., S.I., Y.Taket., E.T.) and Nutrition and Metabolism (N.H.), Institute of Health Biosciences, University of Tokushima Graduate School, Tokushima 770-8503 Japan; and Institute of Molecular and Cellular Biosciences (K.T., S.K.), the University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan.
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