O31 Dysregulated gut microbiota-host metabolism underpins immune activation in a microbiota-dependent model of ulcerative colitis

Abstract

<h3>Introduction</h3> TRUC (<i>Tbx21</i>^-/-<i> Rag2</i>^-/- ulcerative colitis) mice spontaneously develop chronic colitis characterized by excessive TNF production by mononuclear phagocytes, and induction of pathogenic, mucosal innate lymphoid cell responses, which closely resembles aspects of human ulcerative colitis. TRUC disease is dependent on the composition of the intestinal microbiota and mechanistic insights are now needed to understand how microbially-derived metabolites drive dysregulated mucosal immune responses. <h3>Methods</h3> We performed an integrated analysis of the microbiota-associated metabolome (nuclear magnetic resonance) and host response (next-generation mRNA-sequencing). Metabolites were extracted from faecal samples TRUC and control <i>Rag2</i>^-/- mice. Distal colon was collected for RNA sequencing. For metabonomic analysis, Principal Component Analysis was performed to display the metabolic profiles and Orthogonal Projections to Latent Structures Discriminant Analysis was utilized to determine changed metabolites. Metabolite set enrichment analysis was done with MetaboAnalyst. Differential gene expression was calculated by DESeq2. Gene set enrichment analysis was carried out with clusterProfiler. Pathway mapping with both gene and metabolites was achieved with Pathview. <h3>Results</h3> The faecal metabolome of TRUC mice was distinct from <i>Rag2</i>^-/- mice, including significantly increased dimethylamine, lysine, alanine, hypoxanthine, glycerol, pyruvate, 4-aminobutyrate, galactose, aspartate and butyrate, while tyramine was decreased. Metabolite set enrichment analysis showed that amino acids metabolism (lysine, alanine, aspartate, glutamate, arginine, proline) and energy-related metabolism (glycolysis, gluconeogenesis, citric cycle) were the most enriched pathways. Integration of gene and metabolic pathway analyses demonstrated increased expression of transcripts involved pyruvate biosynthesis, and modulation of glucose and amino acid metabolism (figure 1A). Gene set enrichment analysis identified cytokine/chemokine signalling, pathogen phagocytosis and complement activation among the 5 most significantly enriched biological pathways (figure 1B). <h3>Conclusions</h3> In TRUC colitis there is marked dysregulation of the microbiota-associated metabolome and disruption of key host metabolic pathways, including energy and amino acids metabolism, which is associated with perturbed mucosal immune function. Integrated analysis of the microbiome-metabolome-immune response axis is warranted to determine whether therapeutic targeting of key metabolic pathways can be harnessed as novel therapies.