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(3) (vitamin D(3)-d(3)) 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(3)-d(3) in the serum, adipose tissue, kidney and heart, whereas liver levels of vitamin D(3)-d(3) remained unaffected. Additionally, Srb1(-/-) mice had lower levels of deuterated 25-hydroxyvitamin D(3) (25(OH)D(3)-d(3)) 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(3)-d(3), but Cd36(-/-) vs. WT mice were characterized by lower levels of 25(OH)D(3)-d(3) in the serum, liver and kidney. Finally, Abcg5/g8(-/-) mice tended to have higher levels of vitamin D(3)-d(3) in the serum and liver. Major alterations in Abcg5/g8(-/-) mice were notably higher levels of 25(OH)D(3)-d(3) in the serum and kidney, accompanied by a higher hepatic mRNA abundance of Cyp27a1 hydroxylase. To conclude, the current data emphasize the significant role of lipid transporters in the uptake, tissue distribution and activation of vitamin D.