Vitamin D C3-epimer levels are proportionally higher with oral vitamin D supplementation compared to ultraviolet irradiation of skin in mice but not humans

[Display omitted] •In mice, oral vitamin D compared to UV irradiation leads to a greater proportion of 25-hydroxy vitamin D3 as epimers.•Exposure of mice to UV radiation alters liver CYP2R1 and GC protein gene expression and kidney CYP24A1 gene expression.•Using samples from two human clinical trial...

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Published in:The Journal of steroid biochemistry and molecular biology 2019-02, Vol.186, p.110-116
Main Authors: Ghaly, Simon, Bliuc, Dana, Center, Jacqueline R., Clarke, Michael W., Jones, Anderson P., Trend, Stephanie, Kermode, Allan G., Neale, Rachel E., Hart, Prue H.
Format: Article
Language:English
Subjects:
Calcitriol
Clinical trials
Dietary supplements
Epimer
Light therapy
Metabolites
Nutrient deficiency
Phototherapy
Skin
Ultraviolet radiation
Vitamin D
Vitamin D3
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Summary:[Display omitted] •In mice, oral vitamin D compared to UV irradiation leads to a greater proportion of 25-hydroxy vitamin D3 as epimers.•Exposure of mice to UV radiation alters liver CYP2R1 and GC protein gene expression and kidney CYP24A1 gene expression.•Using samples from two human clinical trials, the proportion of 25(OH)D3 as epimers is significantly less compared to mice.•The proportion of 25(OH)D3 as epimers is not different with UV-irradiation compared to oral vitamin D in humans. A proportion of circulating 25-hydroxy vitamin D3 (25(OH)D3)) undergoes epimerization to form C3-epi 25(OH)D3 and C3-epi 1,25(OH)2D3. These epimers have less calcaemic activity than non-epimerized metabolites and are not differentiated by many immunoassays when reporting total 25(OH)D3 levels. This study aimed to compare the effect of exposure to ultraviolet radiation (UVR) and oral vitamin D3 supplementation on vitamin D C3-epimer levels. C57Bl/6 female mice were fed either vitamin D-sufficient (vitamin D3 2000 IU/kg) or -deficient diets (no vitamin D3) for 4 weeks. Among the vitamin D-deficient group, the shaved backs of half were irradiated daily for 4 days with 1 kJ/m2 UVR, followed by twice weekly irradiation for 4 weeks. Despite similar 25(OH)D3 levels, the UV-irradiated group had a lower proportion of C3-epi 25(OH)D3 at week 7 (p 
ISSN:0960-0760
1879-1220
DOI:10.1016/j.jsbmb.2018.10.002