Dietary indole-3-carbinol activates AhR in the gut, alters Th17-microbe interactions, and exacerbates insulitis in NOD mice

Title: Dietary indole-3-carbinol activates AhR in the gut, alters Th17-microbe interactions, and exacerbates insulitis in NOD mice Abstract: Interventions to prevent the development of type 1 diabetes (T1D) in genetically susceptible individuals could negate the need for life-long insulin replacement. Previously, we found that treating prediabetic NOD mice by oral gavage with the high affinity AhR ligand, 11-Cl-BBQ, halts the progression toward clinical disease. In the current study, we tested the hypothesis that a dietary intervention using an AhR ligand, indole-3-carbinol (I3C), found in cruciferous vegetables, could mimic 11-Cl-BBQ treatment and prevent T1D development. Unlike 11-Cl-BBQ which activates AhR systemically, AhR activation by dietary I3C was confined to the intestine. Despite strong AhR activation in the intestine, NOD mice fed a diet supplemented with 2000ppm I3C had more severe insulitis. Dietary I3C did not alter Th1, Th17, Foxp3+ Treg, nor Th17 cell populations in the spleen or pancreatic draining lymph nodes. However, CD4+ROR?t+Foxp3- (Th17 cells), were increased in the lamina propria, intrapethelial layer, and Peyer's patches of the small intestine. AhR activation by I3C altered the intestinal microbiome. Consistent with increased insulitis, dietary I3C increased the ratio of Bacteriodetes to Firmicutes. A transkingdom network was generated to predict host-microbe interactions that were influenced by dietary I3C. Within the phylum Firmicutes, two genera (Intestinimonas and Ruminoclostridum 9) and one family (unclassified Lachnospiraceae) belonging to the phylum Firmicutes were negatively regulated by I3C. Intestinimonas and Lachnospiraceae were reduced within 1 week of dietary intervention followed by a reduction in Ruminoclostridium 9. Using AhR knockout mice, we validated that Intestinimonas is negatively regulated by AhR. Collectively, these data demonstrate that the route of administration, ligand selection, and site of AhR activation are important considerations in developing AhR-targeted therapies for T1D. Summary: Alterations in the intestinal microbiome following dietary I3C in NOD mice. The intestinal microbiome was analyzed in two independent experiments (Experiment 1: 9 mice per group, Experiment 2: 7-8 mice per group). Three timepoints were included in Experiment 1 (7, 8, and 12 weeks of age) and two timepoints in Experiment 2 (7 and 12 weeks of age). In addition, the intestinal microbiome was analyzed at 12 weeks of age for the NOD AhR WT, NOD AhR Het, and NOD AhR KO mice. Sequencing: Intestinal microbiome was analyzed by 16S sdequencing. Contact persons: Allison Ehrlich: [e-mail] Nolan Newman: [e-mail] Contact: Allison Ehrlich ([e-mail]). This submission was powered by METAGENOTE (https://metagenote.niaid.nih.gov).