ReviewOral intake of 7-dehydrocholesterol increases vitamin D3 concentrations in the liver and kidney

- The effect of dietary 7-dehydrocholesterol on vitamin D metabolism was investigated.
- Oral intake of 7-dehydrocholesterol induced a dose-responsive accumulation of vitamin D3 in the liver and kidney.
- 25-hydroxyvitamin D3 in the serum, liver and kidney was not affected by dietary 7-dehydrocholesterol.

IntroductionDue to the high prevalence of vitamin D deficiency, strategies are needed to improve vitamin D status. Food components can affect vitamin D metabolism and have to be considered when estimating the efficacy of vitamin D supplements. 7-dehydrocholesterol (7-DHC) occurs naturally in food, but its impact on vitamin D metabolism has not yet been examined.MethodsThree groups of male C57BL/6 mice (n = 12 per group) were placed on a diet that contained 0, 2.5 or 5 mg 7-DHC per kg diet over a period of 6 weeks. Vitamin D and other sterols in the serum, skin, liver and kidney were quantified by LC-MS/MS. The relative mRNA abundance of hepatic genes encoding vitamin D hydroxylation enzymes and transporters was analyzed by real-time RT-PCR.ResultsWe found a substantial dose-dependent increase of non-hydroxylated vitamin D3 in the liver and kidney of mice fed a diet containing 7-DHC. The vitamin D3 content in the liver was 2.80 ± 0.61 pmol/g, 7.34 ± 4.28 pmol/g and 12.9 ± 3.58 pmol/g in groups that received 0, 2.5 and 5 mg/kg 7-DHC, respectively. In the kidney, the vitamin D3 content of these groups was 1.78 ± 1.17 pmol/g, 3.55 ± 1.06 and 6.36 ± 2.29 pmol/g, respectively. The serum and tissue concentrations of 25-hydroxyvitamin D3 (25(OH)D3) remained unaffected by 7-DHC. The relative mRNA data provided no plausible mechanism for the observed effects of 7-DHC on vitamin D3. All groups of mice had similar concentrations of cholesterol, desmosterol and 7-DHC in their serum and tissues.ConclusionThe current findings provide the first evidence that dietary 7-DHC seems to affect vitamin D metabolism. The underlying mechanism remains elusive and needs further investigation.