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Vitamin D metabolism in the enterocyte
Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
2010 (English)Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

Vitamin D3, also known as cholecalciferol, can be produced by UV light from 7-dehydrocholesterol in the skin. However, as this synthesis is often insufficient, it should also be provided by the diet through fat fish, beef liver, miIk and egg yolk. Two successive hydroxylations occur to produce 1α,25(OH)2-D3, the biologically active form of vitamin D, which primarily functions to maintain the calcium and phosphorous homeostasis. Vitamin D is first hydroxylated in the liver by  D3-25-hydroxylase to 25(OH)D3. There have been several candidates suggested as the D3-25-hydroxylase such as the mitochondrial CYP27A enzyme. This enzyme is expressed in the liver, but it is also expressed in the intestinal cells of both rodents and humans. The aim of this project was to investigate whether a metabolization of the vitamin D3 could occur directly in the intestinal cell. Both an extraction method and two analytical HPLC methods were developed and used for comparing the putative vitamin D3 metabolization in HepG2 cell line (control) and the Caco-2 TC7 line. We first observed no spontaneous degradation when vitamin D3 was incubated in culture medium in similar conditions without cells. Then, a decrease of vitamin D3 joined with an increase in 25(OH)D3 were observed in both cell experiments in the apical medium. A small amount of 25(OH)D3 was detected in HepG2 cell compartment but not in the Caco-2 cells. This suggests that vitamin D3 can be incorporated into the HepG2 and Caco-2 cells, then metabolized and immediately re-secreted. Further research still needs to be done and we suggest conducting cell inhibitor experiments, evaluating the possible metabolization in mouse intestine by conducting ex vivo experiments, and finally validate these observations in humans with a postprandial experiment after a meal supplemented in vitamin D, which would definitely ensure the possible metabolization under dietary conditions.

Place, publisher, year, edition, pages
2010. , p. 32
Keywords [en]
Vitamin D, metabolization
National Category
Other Basic Medicine
Identifiers
URN: urn:nbn:se:lnu:diva-9193OAI: oai:DiVA.org:lnu-9193DiVA, id: diva2:359632
Uppsok
Physics, Chemistry, Mathematics
Supervisors
Examiners
Available from: 2010-11-01 Created: 2010-10-28 Last updated: 2018-01-12Bibliographically approved

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CiteExportLink to record
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Citation style
  • apa
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