Find in Library

The activation of the vitamin D receptor (VDR) in the ileum has been shown to regulate Paneth cell-specific defensins, a large family of antimicrobial peptides; hence, this may serve as a potential mechanism to maintain intestinal homeostasis. Previously, we have demonstrated that a combination of vitamin D₃ (VD) and fructooligosaccharides (FOSs) upregulates colonic <i>Vdr</i> in mice. Here, we aim to examine the effect of VD, alone or in combination with FOSs, on intestinal barrier integrity and the secretion of antimicrobial peptides, as well as the gut microbial community. Male and female C57BL/6J mice at 6 weeks old were randomized into three groups to receive the following dietary regimens (n = 10/sex/group) for 8 weeks: (1) standard AIN-93G control diet (CTR), (2) CTR + 5000 IU vitamin D₃ (VD), and (3) VD + 5% fructooligosaccharides (VF). VD and VF differentially regulated the mRNA expressions of tight junction proteins in the colon and ileum. VF suppressed the upregulation of colonic <i>ZO-1</i> and <i>occludin</i>, which was induced by VD supplementation alone. In the ileum, <i>occludin</i> but not <i>ZO-1</i> was upregulated 20-fold in the VF-treated mice. While VD did not alter the mRNA expressions of <i>Vdr</i> and defensins in the ileum, these targets were downregulated by VF. Microbial analysis further reveals a shift of microbial beta diversity and a reduction in <i>Romboutsia ilealis</i>, a pathobiont, in VF-treated mice. Though the implications of these phenotypical and microbial changes remain to be determined, the administration of FOSs in the presence of VD may serve as an effective dietary intervention for maintaining intestinal homeostasis.