Vitamin D is not linked to folate status and mRNA expression of intestinal proton-coupled folate transporter

In vitro studies discovered intestinal proton-coupled folate transporter (PCFT) as a vitamin D hormone-responsive gene. In vivo effects of vitamin D on PCFT and folate status are currently not available. Three experiments were conducted. At first, vitamin D receptor knockout (VDR-/-) mice and corresponding wild-type (WT) mice were compared for their plasma and hepatic folate concentration and PCFT mRNA expression in intestinal mucosa. In a second experiment with rats, we analyzed the folate status of offspring in response to a maternal vitamin D-adequate (1,000 IU/kg) or vitamin D-deficient (0 IU/kg) diet that was fed for 11 weeks. Finally, the plasma folate concentration of healthy individuals was studied at baseline (in winter) and in response to an oral treatment for 8 weeks with 2,000 IU vitamin D-3 per day or a placebo, respectively. Here, we show that folate status and intestinal PCFT mRNA abundance did not differ between the VDR-/- and the WT mice. No effect of vitamin D on folate status was also found in rat dams and their offspring, and plasma folate levels of individuals did not change in response to vitamin D. Current data from studies with model animals and humans provide no indication for a vitamin D effect on intestinal uptake and status of folate.