Vitamin D Deficiency in Mice Impairs Colonic Antibacterial Activity and Predisposes to Colitis

Abstract

Vitamin D insufficiency is a global health issue. Although classically associated with rickets, low vitamin D levels have also been linked to aberrant immune function and associated health problems such as inflammatory bowel disease (IBD). To test the hypothesis that impaired vitamin D status predisposes to IBD, 8-wk-old C57BL/6 mice were raised from weaning on vitamin D-deficient or vitamin D-sufficient diets and then treated with dextran sodium sulphate (DSS) to induce colitis. Vitamin D-deficient mice showed decreased serum levels of precursor 25-hydroxyvitamin D(3) (2.5 +/- 0.1 vs. 24.4 +/- 1.8 ng/ml) and active 1,25-dihydroxyvitamin D(3) (28.8 +/- 3.1 vs. 45.6 +/- 4.2 pg/ml), greater DSS-induced weight loss (9 vs. 5%), increased colitis (4.71 +/- 0.85 vs. 1.57 +/- 0.18), and splenomegaly relative to mice on vitamin D-sufficient chow. DNA array analysis of colon tissue (n = 4 mice) identified 27 genes consistently (P < 0.05) up-regulated or down-regulated more than 2-fold in vitamin D-deficient vs. vitamin D-sufficient mice, in the absence of DSS-induced colitis. This included angiogenin-4, an antimicrobial protein involved in host containment of enteric bacteria. Immunohistochemistry confirmed that colonic angiogenin-4 protein was significantly decreased in vitamin D-deficient mice even in the absence of colitis. Moreover, the same animals showed elevated levels (50-fold) of bacteria in colonic tissue. These data show for the first time that simple vitamin D deficiency predisposes mice to colitis via dysregulated colonic antimicrobial activity and impaired homeostasis of enteric bacteria. This may be a pivotal mechanism linking vitamin D status with IBD in humans.

Vitamin D Regulates the Gut Microbiome and Protects Mice from Dextran Sodium Sulfate–Induced Colitis

“…In the colon, Cramp expression was not different in the Cyp KO mice compared with WT mice. Decreased expression of angiogenin-4 mRNA and protein has been reported in vitamin D-deficient mice (45). There were no differences in several of the antibacterial peptides, mucins, etc.…”

Vitamin D Deficiency Reduces the Immune Response, Phagocytosis Rate, and Intracellular Killing Rate of Microglial Cells

“…Once bacteria are engulfed, they are incorporated into phagolysosomes and exposed to reactive oxygen species and other bacteriotoxic compounds, which eventually results in bacterial lysis. The stimulation of microglia with TLR agonists is dose dependent (reference 28 and this study), and the efficacy of the phagocytic activity of reactive microglia depends not only on their ability to ingest bacteria but also on the pathogen's ability to modulate phagocyte signaling (49,50). This may be an additional reason why we found small differences in the phagocytosis rate between vitamin D-deficient and -sufficient microglia which failed to reach statistical significance at many individual concentrations tested.…”

“…Our experiments were performed with mouse microglial cells. Although the innate antibacterial activity of vitamin D has been thought to be restricted to primates that express the promoter vitamin D response element (VDRE) required for vitamin D-mediated transcriptional regulation of antibacterial proteins (44), some mouse antimicrobial molecules such as angiogenin-4 (Ang4) also appear to be influenced by vitamin D (49). Although the function of Ang4 appears to be restricted to specific areas of the gastrointestinal tract, this observation underlines the versatility of vitamin D as a promoter of antibacterial activity in different tissues and animal species (34).…”

Vitamin D and colon cancer

“…Several studies have shown that 1,25(OH) 2 D 3 and VDR play a role in the innate immunity against bacterial infections in the colon. It has been observed that bacterial infiltration of the colon is higher in vitamin D-deficient animals than in controls (Lagishetty et al 2010). Accordingly, in CRC cells 1,25(OH) 2 D 3 induces the expression of cathelicidin anti-microbial peptide in a VDRE-dependent mechanism (Gombart et al 2005) and VDR mediates the up-regulation of the anti-microbial peptide b-defensin-2 by dietary sulphoraphane (Schwab et al 2008).…”