Dietary Calcium and 1,25-Dihydroxyvitamin D3 Regulate Transcription of Calcium Transporter Genes in Calbindin-D9k Knockout Mice

Abstract

Abstract. The effect(s) of oral calcium and vitamin D3 were examined on the expression of duodenal and renal active calcium transport genes, i.e., calbindin-D9k (CaBP-9k) and calbindin-D28k (CaBP-28k), transient receptor potential cation channels (TRPV5 and TRPV6), Na + /Ca 2+ exchanger 1 (NCX1) and plasma membrane calcium ATPase 1b (PMCA1b), in CaBP-9k KO mice. Wild-type (WT) and KO mice were provided with calcium and vitamin D3-deficient diets for 10 weeks. The deficient diet significantly decreased body weights compared with the normal diet groups. The serum calcium concentration of the WT mice was decreased by the deficient diet but was unchanged in the KO mice. The deficient diet significantly increased duodenal transcription of CaBP-9k and TRPV6 in the WT mice, but no alteration was observed in the KO mice. In the kidney, the deficient diet significantly increased renal transcripts of TRPV6, PMCA1b, and TRPV5 in the WT mice but did not alter calcium-relating genes in the KO mice. Two potential mediators of calcium-processing genes, vitamin D receptor (VDR) and parathyroid hormone receptor (PTHR), have been suggested to be useful for elucidating these differential regulations in the calcium-related genes of the KO mice. Expression of VDR was not significantly affected by diet or the KO mutation. Renal PTHR mRNA levels were reduced by the diet, and reduced expression was also seen in the KO mice given the normal diet. Taken together, these results suggest that the active calcium transporting genes in KO mice may have resistance to the deficiency diet of calcium and vitamin D3. Key words: Calbindin-D9k (CaBP-9k), Calbindin-D28k (CaBP-28k), Knokout mouse, Na + /Ca 2+ exchanger 1 (NCX1), Plasma membrane calcium ATPase 1b (PMCA1b), TRPV5, TRPV6 (J. Reprod. Dev. 55: [137][138][139][140][141][142] 2009) alcium is the most abundant ion in the body and is present in all tissues and organs, where it participates in vital processes such as cardiac and skeletal muscle contraction, neurotransmission, tissue differentiation and cell metabolism [1]. Therefore, calcium homeostasis is of crucial importance for many physiological functions, including neuronal excitation, muscle contraction, blood clotting and bone mineralization [2]. The calcium balance is tightly controlled through constant regulation of three processes: intestinal calcium absorption, renal calcium reabsorption, and bone calcium exchange [3].The intestinal and renal calcium absorption response to 1, 25-hydroxyvitamin D3 (1,25-(OH)2D3) involves the following three steps [4]: 1) calcium influx through two epithelial calcium channels belonging to the transient receptor potential channel vaniloid subfamily (TRPV5 and 6) [5], 2) intracellular calcium transfer by calbindin-D9k (CaBP-9k) and calbindin-D28k (CaBP-28k) [6,7], and 3) calcium extrusion against an electrochemical gradient mediated by plasma membrane calcium ATPase 1b (PMCA1b) and Na + / Ca 2+ exchanger 1 (NCX1) [8,9]. Calcium ion influx occurs through two highly Ca 2+ -selective members of the tran...

Calcium and phosphate concentrations and future development of type 2 diabetes: the Insulin Resistance Atherosclerosis Study

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Association of vitamin D deficiency with incidence of type 2 diabetes in high-risk Asian subjects

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Mutations in the vitamin D receptor and hereditary vitamin D-resistant rickets

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