The vitamin D3-25-hydroxylase CYP27A is located predominantly in liver, but its expression is also detected in extrahepatic tissues. Our aim was to evaluate the regulation of CYP27A by vitamin D3 (D3) or its metabolites in rat duodena. Vitamin D-depleted rats were repleted with D3, 25-hydroxyvitamin D (25OHD), or 1,25-dihydroxyvitamin D3[1,25(OH)2D3] or acutely injected 1,25(OH)2D3 to investigate the mechanisms of action of the hormone. All D3 compounds led to a progressive decrease in CYP27A mRNA, with levels after D3 representing 20% of that observed in D depletion. 25OHD decreased CYP27A mRNA by 55%, whereas 1,25(OH)2D3 led to a 40% decrease, which was accompanied by a 31% decrease in CYP27A protein levels and an 89% decrease in enzyme activity. Peak circulating 1,25(OH)2D3 concentrations were, however, the highest in D3-repleted, followed by 25OHD- and 1,25(OH)2D3-repleted animals. 1,25(OH)2D3 resulted in a decrease in both CYP27A mRNA half-life and transcription rate. Our data illustrate that the intestine expresses the D3-25-hydroxylase and that the gene is highly regulated in vivo through a direct action of 1,25(OH)2D3 or through the local production of D3 metabolites.
Obesity Represses
CYP2R1
, the Vitamin D 25‐Hydroxylase, in the Liver and Extrahepatic Tissues