Objective: The aim of this study was to analyze coronary artery vitamin D receptor (VDR) expression, the plasma concentrations of 25-hydroxyvitamin D3 (25OHD3), and their relationship with coronary artery atherosclerosis.
Methods: Premenopausal cynomolgus monkeys were fed atherogenic diets containing the equivalent of 1,000 IU/day of vitamin D3. Protein was derived from casein-lactalbumin (C/L, n = 10), soy protein isolate (soy, n = 10), or a combination (n = 19). After 32 months of consuming the diets, each monkey underwent surgical menopause. After 32 postmenopausal months, coronary atherosclerosis was measured in the left circumflex (LCX) artery and left anterior descending (LAD) artery. VDR expression was determined for the LAD, and 25OHD3 concentrations were assessed.
Results: Both the cross-sectional area of atherosclerotic plaques (in square millimeters) and plaque thickness (in millimeters) in the LCX as well as the LAD arteries were analyzed in these monkeys. Those with higher plasma vitamin D3 concentrations and higher VDR were compared with those with higher plasma 25OHD3 concentrations and lower VDR. Significantly smaller plaque sizes were noted with higher plasma 25OHD3 concentrations and higher VDR. For the LCX artery, there was also a significantly lower plaque size (both plaque thickness and cross-sectional area) in those with higher quantities of VDR and lower 25OHD3 concentrations versus those with lower quantities of VDR and higher plasma concentrations of 25OHD3 (P = 0.009 and P = 0.040, respectively).
Conclusions: Cynomolgus monkeys with higher quantities of VDR have significantly less atherosclerosis than do those with lower quantities of VDR and higher plasma 25OHD3 concentrations. If these findings translate to human beings, it might explain why some individuals with higher plasma concentrations of 25OHD3 have more coronary artery atherosclerosis.