The prevalence of inflammatory bowel disease (IBD), such as Crohn’s disease and ulcerative colitis, is increasing in Veterans. Diet plays an important role in shaping the intestinal microbiota and has emerged as an important and actionable modifier of IBD. In addition, metabolites derived from nutrients by gut bacteria have been shown to modify IBD progression. For example, pomegranate ellagitannins (ET) are broken down to ellagic acid (EA) and further converted to urolithins by gut bacteria. Both EA and UA were demonstrated to improve symptoms of IBD in chemically induced mouse models of colitis. We have recently shown that dietary pomegranate extract (PomX) supplementation reduced colitis markers and downregulated colitis associated inflammatory pathways in IL-10-/- mice. We also found that PomX and UA reduced pathobionts in wildtype mice. In addition, inter- individual variations in urolithin production, so called metabotypes (A: only produce UA, B: forms urolithin B (UB), or isoUA; 0: do not form any urolithins) have been well documented and associated with individual’s metabolic health. It is our hypothesis that dietary PomX and/or UA suppress IBD pathogenesis by changing the gut microbiome, strengthening the gut barrier integrity and inhibiting the differentiation of Th1 and Th17 intestinal T cells and pro-inflammatory cytokine. Therefore, we propose to investigate whether dietary supplementation with PomX and/or UA will prevent or alleviate colitis and to identify the mechanisms involved in PomX/UA-induced suppression of colonic inflammatory pathways. The IL-10-/- mouse model, which mirrors the multifactorial nature of IBD, is ideal to investigate the effect of dietary supplementation on colitis. To accomplish this, in aim 1 we will investigate the effect of PomX in suppressing spontaneous colitis development in IL-10-/- mice, which either produce UA (metabotye A) naturally, or lack bacteria forming UA (metabotype 0). We will also evaluate whether UA will enhance PomX effects in metabotype 0 mice. Last, we will interrogate the potential mechanism of action of PomX and/or UA supplementation on gut microbiome and host immunity by performing fecal shotgun metagenomics sequencing, fecal and blood metabolomics, colonic tissue snRNAseq, cytokine RTqPCR, tissue tight junction analysis and immune cell phenotyping in IL-10-/- mice receiving dietary PomX and/or UA. In aim 2, we will investigate whether PomX and/or UA induced changes in the gut microbiome are responsible for their effect on colitis suppression in IL-10-/- mice. Gnotobiotic IL10-/-mice will be colonized with naïve, or PomX, and/or UA treated gut microbiome from human donors (metabotype A and B), and fed a high fat/high sucrose (HFHS) diet for 12 weeks. We will investigate the role of donor microbiome metabotype to PomX treatment could play in colitis susceptibility. In aim 3, we will evaluate the effects of PomX and/or UA on the intestinal T cell- mediated immune inflammatory pathways...