The role of glucuronidated 25-hydroxyvitamin D on colon gene expression in mice.

The role of glucuronidated 25-hydroxyvitamin D on colon gene expression in mice. Am J Physiol Gastrointest Liver Physiol. 2020 Jul 06;: Authors: Reynolds CJ, Koszewski NJ, Horst RL, Beitz DC, Goff JP Abstract 25-Hydroxyvitamin D3-3β-glucuronic acid (25OHD-Gluc) is produced in the liver and is a constituent of human blood and bile. Bacterial glucuronidases (GUS) in mammalian digestive microbiota cleave glucuronide conjugates, such as 25OHD-Gluc, and release the free aglycone (i.e. 25OHD) inside the intestinal lumen. We hypothesized that 25OHD-Gluc would elicit a VDR-dependent mRNA response in the colon after cleavage by gut microbiota. The activity of 25OHD-Gluc was investigated by measuring expression of cytochrome P450 24A1 (Cyp24) mRNA both in vitro and in vivo. In cell culture, Caco2 cells responded to 25OHD-Gluc, while HT29 cells did not. When co-incubated with GUS, both cell lines elicited a robust response as indicated by a 5 Ct (32-fold) increase in Cyp24 mRNA. In vitamin D-sufficient mice, we found that both oral and subcutaneous administration of 1 nmol 25OHD-Gluc induced expression of Cyp24 mRNA in the colon whereas 25OHD did not. In contrast, 25OHD, but not 25OHD-Gluc, was active in the duodenum. When the jejunum was surgically ligated to block flow of digesta to the colon, neither oral nor subcutaneous administration of 2 nmol 25OHD-Gluc was able to induce expression of Cyp24 in the colon. Our findings suggest that 25OHD...
Source: Am J Physiol Gastroi... - Category: Gastroenterology Authors: Tags: Am J Physiol Gastrointest Liver Physiol Source Type: research