Expression of vitamin D receptor and 1α-hydroxylase in epicardial fat: association to plasma 25-hydroxyvitamin D level in coronary artery disease patients

25-hydroxyvitamin D (25OHD) is the main circulating vitamin D form and 1α-hydroxylase (CYP27B1) is the key enzyme which activates 25OHD in tissues. In adipose tissue, reduced vitamin D and increased vitamin D receptor (VDR) levels have been associated to fat accumulation and inflammation. Alterations in epicardial fat (EAT) biology (i.e. increased fat thickness and inflammation) have been described in patients with coronary artery disease (CAD) but it is unknown whether low plasma level of 25OHD and/or inadequate levels of VDR and CYP27B1 at EAT level may contribute to these EAT functional alterations. Our aim was to evaluate in CAD patients the relationship between plasma 25OHD level and gene expression of VDR and CYP27B1 at EAT level. Plasma 25OHD was quantified by an immunoluminometric assay. Gene expression was performed by microarray. CAD patients had low 25OHD level. After patient stratification according to 25OHD level, we observed increased expression of VDR and reduced expression of CYP27B1 at EAT level only in patients with 25OHD deficiency (< 20 ng/mL) and insufficiency (20-30 ng/mL). We may conclude that in CAD patients, EAT tries to compensate reduced plasma 25OHD level by increasing VDR expression. Anyway, due to the impairment in 25OHD activation, the local vitamin availability seems to be reduced. How this may contribute to EAT functional alterations observed in CAD needs further investigation.