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

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 Diseases

A236 ASSOCIATION OF STOOL METABOLOMIC PROFILE AND MICROBIOME COMPOSITION RISK SCORE WITH FUTURE ONSET OF CROHN’S DISEASE

Background

Microbial composition-based risk score (MRS) was recently developed and validated to predict future risk of developing Crohn’s disease (CD) among healthy first-degree relatives (FDR) of CD patients. We hypothesized that stool metabolomic profiles, some of which are linked to the gut microbiome, are associated with future risk of CD.

Aims

To assess the association of stool metabolomic profile with onset of CD and to determine the correlation between stool metabolites and the MRS

Methods

Healthy FDR of CD patients were recruited as part of the nested case-control cohort of the CCC-GEM Project. Healthy FDRs who later developed CD (n=56) were matched approximately 1:1 by age, sex, follow-up duration, and geographical location with control FDRs remaining healthy (n=66). Stool metabolomics were assessed using the Metabolon’s DiscoveryHD4™ platform, and the stool microbiome characterised by 16s rDNA amplicon sequencing. We fitted a multivariable conditional logistic regression model on the disease status as a function of individual stool metabolites. We additionally performed Spearman correlation between each stool metabolite and the MRS.

Results

Among 1,029 stool metabolites that were analyzed, 79 were associated with future risk of CD (p&lt;0.05); however, none remained significant after multiple testing correction (FDR correction). Considering the exploratory nature of this study with limited sample size, we focused on the top seven metabolites associated with CD onset (p&lt;0.01). Of these, two stool metabolites (dimethylglycine, methylmyristate) were associated with increased risk of CD onset while five (cytosine, guanine, cytidine, hydroxyglutarate, nervonate) were associated with decreased risk of developing CD. The two metabolites positively associated with CD onset were positively correlated with the MRS, while the five metabolites negatively associated with CD onset, were negatively correlated with the MRS. Meanwhile, 24 stool metabolites had significant correlation with MRS (FDR-corrected p&lt;0.2). Among those, a total of four stool metabolites (cytosine, guanine, methymyristate, cytidine) overlapped with the top seven stool metabolites associated with CD onset.

Conclusions

Stool metabolite profiles may predict future risk of CD. A subset of these metabolites have significant correlation with the MRS with consistent direction of effect. This may suggest that stool metabolites mediate the putative effect of the gut microbiome on CD risk. Further validation in the full GEM cohort is warranted.

Funding Agencies

CCC, CIHRThe Leona M. and Harry B. Helmsley Charitable Trust; Kenneth Croitoru is the recipient of the Canada Research Chair in Inflammatory Bowel Diseases; Sun-Ho Lee is a recipient of the Imagine/ CIHR/CAG Fellowship Award; Sun-Ho Lee, Juan Antonio Raygoza Garay, and Williams Turpin are recipients of fellowship awards from the Department of Medicine, Mount Sinai Hospital, Toronto, Canada.

A29 NOVEL FECAL BIOMARKERS THAT PRECEDE CLINICAL DIAGNOSIS OF ULCERATIVE COLITIS

Background

Altered gut microbiota composition and function has been associated with inflammatory bowel diseases (IBD) including ulcerative colitis (UC), but causality and mechanisms remain unknown. Most studies have examined patients with active or treated disease and little is known about microbial compositional or functional changes that occur before disease onset.

Aims

We studied a longitudinal cohort of subjects at risk for IBD to define the fecal microbial composition and function in subjects prior to UC onset (pre-UC) and at diagnosis (post-UC), and in matched at-risk subjects that remained healthy.

Methods

Fecal samples were collected from healthy individuals at-risk for IBD (pre-UC; n=13) and subjects were followed longitudinally until UC diagnosis (post-UC, n=9), at which point another fecal sample was collected. Fecal samples from a cohort of matched at-risk individuals that did not develop UC were used as healthy controls (n=48). We applied 16S rRNA gene sequencing, next generation shotgun sequencing, in vitro proteolytic assays and gnotobiotic colonizations to define the microbial composition and proteolytic function in fecal samples.

Results

The microbiota of post-UC subjects clustered separately from pre-UC and HC subjects, based on bray-curtis and unweighted UniFrac, had reduced alpha-diversity, and had reduced abundance of Aldercreutzia compared to pre-UC and HC. In vitro functional analysis revealed increased fecal proteolytic and elastase activity in pre-UC and post-UC samples compared to HC. Metagenomics identified pathways and gene families related to protein metabolism and proteases/peptides that were significantly different between HC and pre-UC samples, suggesting a bacterial component to the pre-UC proteolytic signature. Elastase activity inversely correlated with the relative abundance of Adlercreutzia, and other potentially beneficial taxa, and directly correlated with Bacteroides vulgatus, a known proteolytic taxon. High elastase activity was confirmed in Bacteroides isolates from fecal samples. Bacterial contribution and functional significance of the proteolytic signature was investigated in germ-free adults and litters born from dams colonized with HC, pre-UC or post-UC microbiota. Mice colonized with pre-UC microbiota at adulthood or neonatally developed higher fecal proteolytic activity and an inflammatory immune tone compared with HC colonized mice.

Conclusions

We have identified increased fecal proteolytic activity that precedes clinical diagnosis of UC and associates with gut microbiota changes. This may constitute a non-invasive biomarker of inflammation to monitor at-risk populations that can be targeted therapeutically with anti-proteases.

Funding Agencies

CAG, CCC, CIHR

A221 CROHN’S DISEASE POLYGENIC RISK SCORE IS ASSOCIATED WITH FECAL CALPROTECTIN CONCENTRATION IN ASYMPTOMATIC FIRST-DEGREE RELATIVES OF CROHN’S DISEASE PATIENTS

Background

Fecal calprotectin concentration (FC), a measure of gut inflammation is reported to be significantly higher in healthy first-degree relatives (FDR) of Crohn’s disease (CD) patients compared to healthy controls. In contrast, FC in spouses of CD patients was not significantly different from controls, suggesting that a genetic predisposition rather than a shared environmental factor affects FC.

Aims

We investigated the genetic association with FC in healthy FDRs of CD patients. Notably, these subjects are known to be enriched with CD risk alleles.

Methods

We investigated 1455 healthy Caucasian FDRs of CD patients from the GEM Project. Subjects were genotyped by HumanCoreEXOME chip and ImmunoChip platforms and then imputed by the Haplotype Reference Consortium v1.1 panel (Michigan Imputation Server). SNPs with a minor allele frequency&lt;5% were removed. FC was measured using BUHLMANN ELISA kit. Heritability was estimated using a pedigree based SOLAR program and a SNP-based GCTA software. Genome wide association of FC was tested using the GEE framework that accounts for family clusters, age, sex, first 3 genetic principal components and multiplex family status (≥2 FDRs diagnosed with CD). In addition, CD-polygenic risk scores were derived based on summary statistics and imputed SNPs from a recent GWAS by pruning and thresholding (P+T) and LDPred algorithm (PMID:31002795).

Results

Among 1455 subjects, 45.2% were male, median age was 19 years (IQR 13–26), 8.8% were from multiplex families, and median FC was 52 mg/kg (IQR 31–87; 20.8% had FC&gt;100). We estimated the heritability of FC to be 27% (27.1%, standard error=9%, p&lt;0.001 by pedigree approach; 27.9%, SE=12%, p&lt;0.001 by SNP approach). An untargeted GWAS failed to show any significant association with FC (i.e. p&lt;5x10-8). The lowest p value was obtained for rs224631 (p=5x10-7). Strikingly, an increase in CD polygenic risk scores was significantly associated with an increase of FC (p=5.2x10-5 with P+T method).

Conclusions

We demonstrate that FC concentration is a heritable trait in unaffected FDRs of CD patients. Although the association between genetic variants with FC did not reach GWAS significance, CD-polygenic risk score, which incorporates small effect size CD-associated SNPs, was significantly associated with FC concentrationin this cohort. Our results suggest that FC concentration is influenced genetically with contributions from CD-associated SNPs in unaffected FDRs of CD probands. It remains to be determined if the genetic influence to FC concentration is dependent/independent with the future development of CD.

Submitted on behalf of The CCC-GEM Project research team

Funding Agencies

CCCHelmsley Charitable Trust/ Mount Sinai Hospital Fellowship Award

A17 ASSOCIATION BETWEEN HOST INFLAMMATION-RELATED PROTEOMICS AND GUT MICROBIOME IN HEALTHY FIRST-DEGREE RELATIVES OF CROHN’S DISEASE PATIENTS

Background

Crohn’s disease (CD) is a chronic inflammatory condition of the gastrointestinal tract. It has been suggested that the cause of CD is due to microbial and environmental factors that induce an imbalance of the immune system in genetically susceptible individuals. The Genetic Environmental Microbial (GEM) Project is a prospective study of asymptomatic first-degree relatives (FDR) of CD patients, recruited to understand the biological and environmental determinants of disease development.

Aims

Here, we aim to define the relationships between the host inflammation-related proteomics and gut microbiome composition in a cohort of 320 healthy CD FDRs at the time of recruitment.

Methods

We measured 92 inflammation-related serum proteins using the Olink® ’Inflammation’ proteomics panel. Stool microbial composition was determined by sequencing the V4 region of the 16S rRNA. To assess the relationship between serum protein levels and the relative abundance of microbial taxa, we used a zero-inflated two-part regression model corrected for multiple-comparisons (significant association at p&lt; 2.75 × 10–4).

Results

We found fifteen serum proteins that were each significantly associated with the relative abundances of one to five genera or families, depending on the analyte. Of particular interest to CD, the relative abundance of both TNF-β and LIGHT (TNFSF14) were negatively associated with the relative abundance of bacteria in the Parabacteroides genus. Both TNF-β and LIGHT are members of the Tumor Necrosis Factor (TNF) family of cytokines with roles in mucosal healing, IgA production, and in control of innate lymphoid cells (ILCs). These processes have been hypothesized to have critical roles in CD pathology. Interestingly, prior work also demonstrates that Parabacteroides distasonis enhanced colitis in a mouse model and was isolated from a gut wall-cavitating microlesion in a patient with severe CD. Other inflammation-related proteins with significant taxa associations include IL-2, IL-33, OSM, 4E_BP1, IL-1α, ARTN, AXIN1, and CDCP1.

Conclusions

This study highlights the associations between inflammation associated proteomics and gut microbial taxa in asymptomatic FDRs of CD patients. The mechanisms explaining this association will require further analysis.

Funding Agencies

CCC The Leona M. and Harry B. Helmsley Charitable Trust

Understanding, compliance and psychological impact of the SARS quarantine experience

This study examines a cohort of persons quarantined during the 2003 SARS outbreak in Canada and describes their understanding of, difficulties and compliance with, and the psychological impact of the quarantine experience. A mailed questionnaire was administered to 1912 eligible adults and included the Impact of Events Scale - Revised (IES-R) to assess symptoms of post-traumatic stress disorder (PTSD). Self-reported compliance with all required quarantine measures was low (15.8+/-2.3%), although significantly higher when the rationale for quarantine was understood (P=0.018). Health-care workers (HCW) experienced greater psychological distress, including symptoms of PTSD (P<0.001). Increasing perceived difficulty with compliance, HCW, longer quarantine and compliance with quarantine requirements were significant contributors to higher IES-R scores. The low compliance with quarantine requirements introduces concerns about the effectiveness of quarantine as a public health measure. Improvements in compliance and reduced psychological distress may be possible by minimizing duration, revising requirements, and providing enhanced education and support.