A238 ALTERED GUT MICROBIOME COMPOSITION AND FUNCTION ARE ASSOCIATED WITH GUT BARRIER DYSFUNCTION IN HEALTHY RELATIVES OF CROHN’S DISEASE PATIENTS

Abstract Background The gut microbiome may play a role in gut barrier homeostasis including epithelial barrier function, but data are scarce and limited to animal studies Aims To assess if alterations in gut microbiome are associated with gut barrier function Methods We utilized the Genetic Environmental Microbial (CCC GEM) cohort of healthy first-degree relatives (FDRs) of Crohn’s disease (CD) patients. Gut barrier function was assessed using the ratio of urinary fractional excretion of lactulose to mannitol (LMR). Stool bacterial DNA was extracted and sequenced for the V4 hypervariable region of the 16S rRNA gene using MiSeq and processed using QIIME2. Microbial functions were imputed using PICRUSt2. The cohort was divided into a North American discovery cohort (n=2,472) and non-North American external validation cohort (n=655). LMR>0.025 was defined as abnormal. LMR-microbiome associations were assessed using multivariable regression model and Random Forest (RF) classifier algorithm. q<0.05 was considered significant when multiple tests were performed Results The median age of the entire cohort was 17.0 years [IQR 12.0; 24.0], 52.6% were females and 25.4% had LMR>0.025. In the discovery cohort, subjects with LMR>0.025 had markedly reduced alpha diversity (Chao1 index, estimate= -0.0037, p=4.0e-04) and altered beta diversity (Bray-Curtis dissimilarity index, PERMANOVA: pseudo-F statistic = 2.99, p=1.0e-03). We identified eight bacterial genera and 52 microbial pathways associated with LMR>0.025 (q<0.05). Four genera (decreased Adlercreutzia [odds ratio(OR)=0.74, 95% confidence interval (CI) 0.6–0.91], Clostridia-UCG-014 [OR=0.71, 95%CI 0.59–0.86], and Clostridium-sensu-stricto-1 [OR=0.75, 95%CI 0.61–0.92] and increased Colidextribacter [OR=1.65, 95%CI 1.2–2.26]) and eight pathways (including decreased biosynthesis of glutamate [OR=0.4, 95%CI 0.21–0.74], tryptophan [OR=0.06, 95%CI 0.01–0.27] and threonine [OR=0.038, 95%CI 0.003–0.41]) were replicated. Bacterial community composition was associated with gut barrier homeostasis as defined by the RF analysis (p= 1.4e-6) Conclusions Gut microbiome community and pathways are associated with gut barrier function. These findings may identify potential microbial targets to modulate barrier function Submitted on behalf of the CCC-GEM Consortium Funding Agencies CCC, CIHRCrohn’s and Colitis Canada Genetics Environment Microbial (CCC-GEM) III; The Leona M. and Harry B. Helmsley Charitable Trust; Kenneth Croitoru is the recipient of the Canada Research Chair in Inflammatory Bowel Disease

P701 Compositional and functional alterations of the gut microbiome are associated with impaired intestinal permeability in healthy relatives of patients with Crohn’s disease

Abstract Background The gut microbiome may play a role in gut barrier homeostasis including epithelial barrier integrity and function. However, data are scarce and limited to animal studies. We aimed to assess if alterations in the gut microbiome are associated with altered intestinal permeability. Methods We utilized the Genetic Environmental Microbial (CCC GEM) cohort of healthy first-degree relatives of patients with Crohn’s disease. Gut barrier function was assessed using the ratio of urinary fractional excretion of lactulose to mannitol (LMR). Stool bacterial DNA was extracted and sequenced for the V4 hypervariable region of the 16S rDNA gene using MiSeq and processed using QIIME2. PICRUSt2 was used to impute Microbial functions. In order to identify robust associations, the overall cohort was divided based on geographic region into a North American discovery cohort (n=2,472) and non-North American external validation cohort (n=655). LMR>0.025 was defined as abnormal. LMR-microbiome associations were assessed using generalized estimating equation multivariable regression model and Random Forest (RF) classifier algorithm. q<0.05 was considered significant when multiple tests were performed. Results The median age of the entire cohort was 17.0 years [IQR 12.0; 24.0], 52.6% were females and 25.4% had LMR>0.025. In the discovery cohort, subjects with LMR>0.025 had markedly reduced alpha diversity (Chao1 index, estimate= -0.0037, p=4.0e-04) and altered beta diversity (Bray-Curtis dissimilarity index, PERMANOVA: pseudo-F statistic = 2.99, p=1.0e-03). Eight bacterial genera and 52 microbial pathways were identified to be associated with LMR>0.025 (q<0.05). The compositional associations were replicated in four genera (Adlercreutzia [odds ratio(OR)=0.74, 95% confidence interval (CI) 0.6–0.91], Clostridia-UCG-014 [OR=0.71, 95%CI 0.59–0.86], Clostridium-sensu-stricto-1 [OR=0.75, 95%CI 0.61–0.92] and Colidextribacter [OR=1.65, 95%CI 1.2–2.26]). The pathway associations were replicated in eight pathways (biosynthesis of glutamate [OR=0.4, 95%CI 0.21–0.74], tryptophan [OR=0.06, 95%CI 0.01–0.27] and threonine [OR=0.038, 95%CI 0.003–0.41], among others). Bacterial community composition was associated with gut barrier homeostasis as defined by the RF analysis (p= 1.4e-6). Conclusion Gut microbiome community composition and microbial pathways are associated with gut barrier function. These findings may identify microbial targets that enhance barrier function

OP29 Peri-natal exposure to parental Crohn’s disease is associated with impaired gut barrier, microbiome composition differences and increased risk of Crohn’s disease

Abstract Background Previous studies have shown that offspring of Crohn’s disease (CD) patients have a 6-8 fold risk of incident CD than the general population. Also, newborns of women with CD (vs healthy women) have altered stool microbiome composition and elevated fecal calprotectin (FCP). The "peri-natal period" (pregnancy and first year postpartum) is critical for the development and maturation of the gut microbiome as well as immune responses. However, it is unclear if exposure to parental CD diagnosis during the peri-natal period is associated with increased risk of CD. We aimed to investigate whether peri-natal exposure to parental CD (compared to exposure later in life) has an impact on offspring’s gut barrier function, microbiome composition, and the offspring’s risk of incident CD. Methods We assessed 1252 healthy offspring (6-35 years of age) of patients with CD who were recruited in the CCC-GEM Project, a large prospective cohort study following healthy FDRs of CD patients. We classified offspring into "peri-natally exposed" or "exposed later in life" to parental CD diagnosis. We measured baseline FCP and urinary fractional excretion ratio of lactulose to mannitol (marker of intestinal permeability, LMR). Fecal microbiome composition was determined by 16S rRNA gene sequencing. General estimating equation regression and Cox-proportional hazard modeling was used to assess if peri-natal exposure to parental CD is associated with LMR, FCP, altered microbial composition, and future CD onset. Offspring’s age and sex and family clusters were accounted for in the models. Results Offspring exposed to a CD parent peri-natally have a 4.73 fold higher risk (aHR 95%CI 1.28-17.46) of developing CD compared to those exposed to a parent who developed CD later in life (11/586 vs 3/666). Baseline LMR was significantly higher in the offspring exposed to parental CD peri-natally (p=0.003) while no significant difference was observed for FCP at recruitment (p=0.94). We identified five bacterial taxa that were significantly increased in the peri-natally exposed group (FDR-adjusted p<0.05). In a subgroup of offspring of mothers with CD, a dose effect between exposure age and risk was seen; the earlier the offspring was exposed to mother’s CD diagnosis peri-natally, the higher the offspring’s risk of CD development; this trend was not seen in offspring of fathers with CD. Conclusion Offspring exposed to parental CD peri-natally had a higher risk of developing CD than those exposed to parental CD later in life. Early life exposure to parental CD was associated with higher baseline LMR and altered bacterial taxa. These results suggest that environmental exposure during the critical peri-natal period may determine the offspring’s future risk of developing CD