RESUMEN
PURPOSE: 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. METHODS: 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 D3 per day or a placebo, respectively. RESULTS: 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. CONCLUSIONS: Current data from studies with model animals and humans provide no indication for a vitamin D effect on intestinal uptake and status of folate.