Quercetin Enhances VDR Activity, Leading to Stimulation of Its Target Gene Expression in Caco-2 Cells

Vitamin D receptor (VDR) is a nuclear receptor that regulates the expression of genes involved in calcium homeostasis. Activation of VDR is thought to be a promising drug target for osteoporosis. Using a VDR-driven luciferase expression assay for screening a naturally occurring food component, we identified quercetin as a VDR activator. Quercetin also activated the GAL4 DNA-binding domain fused to the VDR ligand-binding domain. Moreover. it was confirmed that quercetin increases the mRNA level of TRPV6, which is a VDR target gene, in Caco-2 cells. These results indicate that quercetin enhances VDR activity through the alteration of cofactor recruitment, thereby stimulating its target genes while providing a new function for quercetin as the VDR activator.