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Title: Intestinal calcium transporter genes are upregulated by estrogens and the reproductive cycle through vitamin D receptor-independent mechanisms
Authors: Van Cromphaut, Sophie ×
Rummens, K
Stockmans, Ingrid
Van Herck, Erik
Dijcks, F A
Ederveen, A G H
Carmeliet, Peter
Verhaeghe, Johan
Bouillon, Roger
Carmeliet, Geert #
Issue Date: Oct-2003
Publisher: Blackwell Science, Inc.
Series Title: Journal of Bone and Mineral Research vol:18 issue:10 pages:1725-36
Abstract: 1alpha,25(OH)2-vitamin D strongly regulates the expression of the epithelial calcium channel CaT1. CaT1 expression is reduced in ERKOalpha mice and induced by estrogen treatment, pregnancy, or lactation in VDR WT and KO mice. Estrogens and vitamin D are thus independent potent regulators of the expression of this calcium influx mechanism, which is involved in active intestinal calcium absorption. INTRODUCTION: Active duodenal calcium absorption consists of three major steps: calcium influx into, transfer through, and extrusion out of the enterocyte. These steps are carried out by the calcium transport protein 1 (CaT1), calbindin-D9K, and the plasma membrane calcium ATPase (PMCA1b), respectively. We investigated whether estrogens or hormonal changes during the female reproductive cycle influence the expression of these genes, and if so, whether these effects are vitamin D-vitamin D receptor (VDR) dependent. MATERIALS AND METHODS: We evaluated duodenal expression patterns in estrogen receptor (ER)alpha and -beta knockout (KO) mice, as well as in ovariectomized, estrogen-treated, pregnant, and lactating VDR wild-type (WT) and VDR KO mice. RESULTS: Expression of calcium transporter genes was not altered in ERKObeta mice. CaT1 mRNA expression was reduced by 55% in ERKOalpha mice, while the two other calcium transporter genes were not affected. Ovariectomy caused no change in duodenal expression pattern of VDR WT and KO mice, whereas treatment with a pharmacologic dose of estrogens induced CaT1 mRNA expression in VDR WT (4-fold) and KO (8-fold) mice. Pregnancy enhanced CaTI expression equally in VDR WT and KO mice (12-fold). Calbindin-D9K and PMCA1b expression increased to a lesser extent and solely in pregnant VDR WT animals. In lactating VDR WT and KO mice, CaT1 mRNA expression increased 13 times, which was associated with a smaller increase in calbindin-D9K protein content and PMCA1b mRNA expression. CONCLUSIONS: Estrogens or hormonal changes during pregnancy or lactation have distinct, vitamin D-independent effects at the genomic level on active duodenal calcium absorption mechanisms, mainly through a major upregulation of the calcium influx channel CaT1. The estrogen effects seem to be mediated solely by ERalpha.
ISSN: 0884-0431
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Clinical and Experimental Endocrinology
Molecular and Vascular Biology
Pathophysiology of Pregnancy Section (-)
Laboratory of Intensive Care Medicine
Laboratory of Angiogenesis and Vascular Metabolism (VIB-KU Leuven Centre for Cancer Biology) (+)
× corresponding author
# (joint) last author

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