Absence of the Vitamin D Receptor Inhibits Atherosclerotic Plaque Calcification in Female Hypercholesterolemic Mice

Epidemiological and clinical data suggest adverse cardiovascular outcomes with respect to vitamin D deficiency. Here, we explored the effects of vitamin D in atherosclerotic plaque calcification in vivo by utilizing vitamin D receptor (Vdr)-deficient mice in an Apoe−/− background. Animals were fed a high-fat diet (HFD) for either 12 or 18 weeks and then examined for atherosclerotic plaque development. In order to prevent calcium deficiency, Vdr−/− and Apoe−/−;Vdr−/− animals were fed a high-calcium rescue diet prior to initiation of the HFD feeding and supplemented with high-calcium water during HFD feeding. Although calcium supplementation improved bone mass in Vdr−/− and Apoe−/−;Vdr−/− mice, neither strain was fully rescued. Systemic inflammatory responses observed in the absence of VDR were exaggerated in Apoe−/− mice. Whereas, hyperlipidemic profiles seen in Apoe−/− mice were ameliorated in the absence of VDR. Micro-computed tomography (µCT) analysis revealed that six out of eight Apoe−/− animals developed atherosclerotic plaque calcification following 12 weeks of HFD feeding and 100% of the mice developed plaque calcification after 18 weeks. In contrast, although atherosclerotic lesions were evident in Apoe−/−;Vdr−/− mice at 12 and 18 weeks of HFD challenge, none of these animals developed plaque calcification at either time point. The active vitamin D hormone, 1,25(OH)2D3 likely increased calcification in aortic smooth muscle cells perhaps by directly modulating expression of Alpl, Rankl, and Opg. Our data suggest that the absence of VDR inhibits atherosclerotic plaque calcification in hypercholesterolemic Apoe−/− mice, providing additional insight into the role of vitamin D in atherosclerotic plaque calcification. J. Cell. Biochem. 118: 1050–1064, 2017. © 2016 Wiley Periodicals, Inc.