Vitamin D might be generated in the eye by UVB – May 2012

Enhancement of Vitamin D Metabolites in the Eye Following Vitamin D3 Supplementation and UV-B Irradiation.

Curr Eye Res. 2012 May 25.
Lin Y, Ubels JL, Schotanus MP, Yin Z, Pintea V, Hammock BD, Watsky MA. mwatsky at uthsc.edu
Department of Entomology & Cancer Center, University of California , Davis, CA , USA.

Purpose: This study was designed to measure vitamin D metabolites in the aqueous and vitreous humor and in tear fluid, and to determine if dietary vitamin D3 supplementation affects these levels. We also determined if the corneal epithelium can synthesize vitamin D following UV-B exposure.

Methods: Rabbits were fed a control or vitamin D3 supplemented diet. Pilocarpine-stimulated tear fluid was collected and aqueous and vitreous humor were drawn from enucleated eyes. Plasma vitamin D was also measured. To test for epithelial vitamin D synthesis, a human corneal limbal epithelial cell line was irradiated with two doses of UV-B (10 and 20 mJ/cm(2)/day for 3 days) and vitamin D was measured in control or 7-dehydrocholesterol treated culture medium. Measurements were made using mass spectroscopy.

Results: 25(OH)-vitamin D3 and 24,25(OH)(2)-vitamin D3 increased significantly following D3 supplementation in all samples except vitreous humor.

Tear fluid and aqueous humor had small but detectable 1,25(OH)(2)-vitamin D3 levels.
Vitamin D2 metabolites were observed in all samples.
Vitamin D3 levels were below the detection limit for all samples.
Minimal vitamin D3 metabolites were observed in control and UV-B-irradiated epithelial culture medium except following 7-dehydrocholesterol treatment, which resulted in a UV-B-dose dependent increase in vitamin D3, 25(OH)-vitamin D3 and 24,25(OH)(2)-vitamin D3.

Conclusions: There are measurable concentrations of vitamin D metabolites in tear fluid and aqueous and vitreous humor, and oral vitamin D supplementation affects vitamin D metabolite concentrations in the anterior segment of the eye. In addition, the UV exposure results lead us to conclude that corneal epithelial cells are likely capable of synthesizing vitamin D3 metabolites in the presence of 7-dehydrocholesterol following UV-B exposure.

PMID: 22632164

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21 articles cited the above study as of Sept 2017

• Characterization of Vitamin D Production by Human Ocular Barrier Cells April 2014
  the eye activates Vitamin D, similar to the Kidney and epithelial cells of skin, lung, intestine, prostate, endometrium, and breast, etc.

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