A microbiota derived metabolite and pediatric celiac disease pathogenesis

Celiac Disease (CD) is an autoimmune condition triggered by gluten ingestion and defined by small intestine inflammation leading to villous atrophy in genetically predisposed individuals. 20-40% of the general population possess the predisposing HLA-DQ2 or HLA-DQ8 alleles, however only 1-2% of the population develops CD, indicating that there are additional environmental factors at play in the pathogenesis of the disease.

In a prospective cohort study using fecal and plasma samples from children at ages 2.5 and 5 years, before the onset of celiac disease (CD progressors), we found that CD progressors have an altered gut microbiome, plasma metabolome and cytokine profile years before diagnosis. IgA sequencing revealed an increased IgA response and unique microbial targets of IgA. One metabolite increased in CD progressors is taurodeoxycholic acid (TDCA), a secondary bile acid produced by gut microbes. Treating C57BL/B6 mice with TDCA caused villous atrophy as well as upregulated CD4+T-cells in intraepithelial lymphocytes and natural killer cells in the lamina propria (LP). TDCA increased the expression of Qa-1 and NKG2D on T-cells.

The DQ8-Dd-villin-IL-15tg mouse model of CD possesses the predisposing HLA-DQ8 molecule and overexpresses IL-15 in the LP. Treating these mice with TDCA caused the villi/crypt ratio to decrease in the treatment group of pooled villi. Our results indicate that TDCA and TDCA-producing bacteria could potentially contribute to the pathogenesis of CD.