Vitamin D Status of Mice Deficient in Scavenger Receptor Class B Type 1, Cluster Determinant 36 and ATP-Binding Cassette Proteins G5/G8.

Classical lipid transporters are suggested to modulate cellular vitamin D uptake. This study investigated the vitamin D levels in serum and tissues of mice deficient in SR-B1 (Srb1), CD36 (Cd36) and ABC-G5/G8 (Abcg5/g8) and compared them with corresponding wild-type (WT) mice. All mice received triple-deuterated vitamin D (vitamin D-d) for six weeks. All knockout mice vs. WT mice showed specific alterations in their vitamin D concentrations. Srb1 mice had higher levels of vitamin D-d in the serum, adipose tissue, kidney and heart, whereas liver levels of vitamin D-d remained unaffected. Additionally, Srb1 mice had lower levels of deuterated 25-hydroxyvitamin D (25(OH)D-d) in the serum, liver and kidney compared to WT mice. In contrast, Cd36 and WT mice did not differ in the serum and tissue levels of vitamin D-d, but Cd36 vs. WT mice were characterized by lower levels of 25(OH)D-d in the serum, liver and kidney. Finally, Abcg5/g8 mice tended to have higher levels of vitamin D-d in the serum and liver. Major alterations in Abcg5/g8 mice were notably higher levels of 25(OH)D-d in the serum and kidney, accompanied by a higher hepatic mRNA abundance of hydroxylase. To conclude, the current data emphasize the significant role of lipid transporters in the uptake, tissue distribution and activation of vitamin D.