Oral Intake of Lumisterol Affects the Metabolism of Vitamin D

Abstract

Scope: The treatment of food with ultraviolet-B (UV-B) light to increase the vitamin D content is accompanied by the formation of photoisomers, such as lumisterol₂ . The physiological impact of photoisomers is largely unknown.

Methods and results: Three groups of C57Bl/6 mice are fed diets containing 50 µg kg^-1 deuterated vitamin D₃ with 0, 50 (moderate-dose) or 2000 µg kg^-1 (high-dose) lumisterol₂ for four weeks. Considerable quantities of lumisterol₂ and vitamin D₂ are found in the plasma and tissues of mice fed with 2000 µg kg^-1 lumisterol₂ but not in those fed 0 or 50 µg kg^-1 lumisterol₂ . Mice fed with 2000 µg kg^-1 lumisterol₂ showed strongly reduced deuterated 25-hydroxyvitamin D₃ (-50%) and calcitriol (-80%) levels in plasma, accompanied by downregulated mRNA abundance of cytochrom P450 (Cyp)27b1 and upregulated Cyp24a1 in the kidneys. Increased tissue levels of vitamin D₂ were also seen in mice in a second study that are kept on a diet with 0.2% UV-B exposed yeast versus those fed 0.2% untreated yeast containing iso-amounts of vitamin D₂ .

Conclusion: High doses of lumisterol₂ can enter the body, induce the formation of vitamin D₂ , reduce the levels of 25(OH)D₃ and calcitriol and strongly impact the expression of genes involved in the degradation and synthesis of bioactive vitamin D.

Keywords: 25-hydroxyvitamin D; UV-B irradiated yeast; calcitriol; lumisterol2; mice; vitamin D.