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Vitamin D-enhanced duodenal calcium transport
Kannikar Wongdee1, Narattaphol Charoenphandhu2
1Office of Academic Management, Faculty of Allied Health Sciences, Burapha University, Chonburi, Thailand; Center of Calcium and Bone Research (COCAB), Faculty of Science, Mahidol University, Bangkok, Thailand.
Vitamins and Hormones
|March 31, 2015
Summary
The duodenum absorbs calcium through vitamin D-dependent and independent pathways, crucial for maintaining calcium homeostasis. Vitamin D regulates key calcium transporters and tight junctions, influencing absorption efficiency.
Area of Science:
- Physiology
- Molecular Biology
- Nutritional Science
Background:
- The duodenum is a primary site for dietary calcium absorption in humans and rodents.
- Calcium absorption occurs via transcellular and paracellular routes, significantly influenced by vitamin D.
Purpose of the Study:
- To elucidate the mechanisms of vitamin D-mediated calcium transport in the duodenum.
- To explore the regulation of duodenal calcium absorption by hormonal axes and feedback mechanisms.
- To investigate the role of vitamin D-independent calcium absorption in specific physiological states.
Main Methods:
- Analysis of vitamin D receptor (VDR) binding and its effect on calcium transporter gene expression (e.g., TRPV5/6, calbindin-D9k).
- Investigation of the influence of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] on tight junction proteins and water transport.
- Review of regulatory roles of parathyroid-kidney-intestinal and bone-kidney-intestinal axes, including feedback regulators like fibroblast growth factor-23.
Main Results:
- 1,25(OH)2D3 upregulates essential calcium transporter genes, enhancing transcellular calcium uptake.
- Vitamin D modulates tight junction gene expression and water flow, potentially increasing paracellular calcium transport.
- Negative feedback regulation by plasma calcium and FGF-23 influences vitamin D's action.
Conclusions:
- Vitamin D plays a central role in regulating duodenal calcium absorption through both transcellular and paracellular pathways.
- Hormonal axes and feedback mechanisms fine-tune calcium homeostasis.
- Vitamin D-independent absorption is significant in specific conditions like neonatal development and lactation.
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