Society: AGA

Background The gut microbiome is central to Crohn’s disease (CD) pathogenesis but the relative contribution of different environmental factors to disease compositional variation is unknown. We determined the impact of environmental factors and diet on microbiome variation in this international study.
Methods 480 stool samples from 240 CD patients and 240 healthy controls from regions of different epidemiologic stages: Australia (Compounding prevalence; AUS: 97 CD; 77 controls), Hong Kong (Acceleration in incidence; HK: 90 CD; 63 controls) and Mainland China (Emergence in incidence; MC: 53 CD;100 controls) were studied. Demographic, clinical and 3 food intake questionnaires (processed food intake in early life, recent (last 12 months) and current (last 3-days)) were obtained from all subjects. Fecal microbiota was assessed by shotgun metagenomic sequencing. Dysbiosis score was defined as the median Bray-Curtis dissimilarity to the reference control group. Adonis was performed to rank the effect of disease-associated parameters, clinical metadata, dietary intake and geography on overall microbial composition.
Results Microbiota diversity was significantly reduced in CD compared with controls in all three geographical cohorts (all p<0.05). Beta diversity analysis showed a significant disease-associated shift along principal components for active CD followed by inactive CD away from controls (p<0.001). Gut microbiome structure of HK subjects were intermediate between that of AUS and MC. CD patients in MC had the highest dysbiosis score compared with AUS and HK, but dissimilarity scores were no different between controls in AUS, HK and MC (Fig 1A). Geography had the greatest impact on microbiota variance followed by disease diagnosis and bowel resection history. Additionally, disease complications, feeding pattern and processed food exposure at early age were significantly correlated with microbiota variance. CD patients who consumed more processed food at early age had a higher dysbiosis score than those who did not (p<0.05). Amongst all diet types consumed, current fiber intake was the most dominant in contributing to microbiome variance. Other major dietary factors that correlated with microbiome variance belonged to fat (polyunsatuated fat, saturated fat, monounsaturated fat and cholesterol) and vitamins (Fig 1B). The proportion of dietary factor-associated species in CD was lower than that of controls, suggesting that gut microbiota in controls were more susceptible to the effects of diet.
Conclusion Geography especially regions transiting through different epidemiologic stages of disease is a dominant driver of gut microbiome variation, followed by Crohn’s disease diagnosis. The Crohn’s disease microbiota is also shaped and influenced by current dietary pattern and early life food additive intake.

This work is supported by Helmsley Charitable Trust

<b>Fig1. (A)</b> Distribution of stool dysbiosis scores in relation to presence of Crohn’s disease (median Bray-Curtis dissimilarity between a sample and healthy control samples). <b>(B) </b>Current dietary factors impact on microbiota variance. Adjusted permutational multivariate analysis was performed to rank the variances. *<i>p</i><0.05; **<i>p</i><0.01; ***<i>p</i><0.001.

Fig1. (A) Distribution of stool dysbiosis scores in relation to presence of Crohn’s disease (median Bray-Curtis dissimilarity between a sample and healthy control samples). (B) Current dietary factors impact on microbiota variance. Adjusted permutational multivariate analysis was performed to rank the variances. *p<0.05; **p<0.01; ***p<0.001.

Background
It is widely accepted that high-fat diet (HFD) has been considered as one of the risk factors of inflammatory bowel disease(IBD), while the mechanism is little known. We aimed to examined whether dietary high fat promotes colonic inflammation through modulating gut microbial tryptophan metabolites.
Methods
The C57BL/6 female mice were fed with chow diet (12kcal% fat) or HFD (60kcal% fat) for 2 weeks. Fresh fecal samples were collected before administration of 2% DSS. LC-MS/MS analysis was performed to detect fecal microbial tryptophan metabolites. Next, 8-week-old mice were administrated 3-indoleacetic acid (IAA) for 7 days prior to 2.5% DSS treatment. The severity of colitis was assessed and the colonic sections were collected. RNA sequencing was performed to analyze the differential genes in intestinal tissue of mice fed with IAA or not. Real-time PCR and Western blotting were performed to detect the transcription and protein expression of mucin sulfation-related genes. High iron diamine-alcian blue (HID-AB) staining of colon tissues and LS174T cells was used to detect the abundance of sulfated mucin. Additionally, the Chromatin immunoprecipitation (ChIP) sequencing is performed to confirm the binding of aryl hydrocarbon receptor(AHR) to 3’-phosphoadenosine 5’-phosphosulfate (PAPS) synthase 2 (PAPSS2).
Results
Short-term HFD increased the susceptibility to colitis of mice. Mice fed with HFD have impaired tryptophan metabolism with remarkable lower level of IAA. IAA supplementation resulted in ameliorative colitis symptoms. Mechanistically, the transcriptome sequencing detected that IAA supplementation enriched the the cytosolic sulfonation pathway and significantly increased the expression of PAPSS2 of colon tissue, a rate-limiting enzyme on the mucin sulfation pathway. Next, in vivo and in vitro experiments verified IAA increased the expression of PAPSS2 and its downstream genes and promoted the mucin sulfation in golgi apparatus of colon through AHR. ChIP sequencing and ChIP-PCR verified IAA can enhance the binding of AHR to the promoter region of PAPSS2 , which further promoted the expression of PAPS transporter 2 (PAPST2 or Slc35b3) and ultimately promotes the mucin sulfation.
Conclusion
HFD altered the gut microbial tryptophan metabolites and disrupt the protective effect of IAA on the intestinal barrier. IAA could relief colitis through AHR-PAPSS2-PAPST2-mucin sulfation axis, which may present a potential approach for precise prevention and treatment of IBD.

Dietary fat exacerbated DSS–induced colitis and reduced gut microbial tryptophan metabolites especially IAA

Dietary fat exacerbated DSS–induced colitis and reduced gut microbial tryptophan metabolites especially IAA

IAA ameliorated the severity of DSS-induced colitis and strengthened the mucosal barrier function through promoting mucin sulfation

IAA ameliorated the severity of DSS-induced colitis and strengthened the mucosal barrier function through promoting mucin sulfation

Background: The etiology of Crohn’s disease (CD) is unknown but may arise from complex interactions between genetic susceptibility and abnormal host immune responses related to environmental exposures, including the diet. Dietary intake is known to influence the gut microbiome along with multiple host cellular pathways, together resulting in perturbation of the host metabolic profile. We recently identified serum-derived metabolites associated with CD onset. We hypothesized that nutrients could impact these specific serum-derived metabolites.

Methods: Healthy first-degree relatives of CD patients were recruited as part of the Crohn’s Colitis Canada- Genetic, Environmental, Microbial (GEM) Project. We focused on a subset of 389 subjects (n=78 who developed CD and n=311 healthy controls), matched for age, sex, postal code, and time in the study with available dietary and serum metabolomics data. A total of 150 dietary constituents were derived from baseline food frequency questionnaires using the 2015 release of the StatsCan Nutrient database. Serum metabolites were measured using the combination of four ultrahigh Performance Liquid Chromatography-Tandem Mass Spectroscopy. In total, we identified 63 metabolites associated with CD onset, these metabolites were utilized for this exploratory analysis.
We used general estimating equation models to identify associations between dietary constituents and these CD-associated metabolites. Benjamini-Hochberg corrected p values, q<0.05, defined significance.

Results:
In total, 52 nutrients were associated with 53 of the 63 CD-associated metabolites (2.04^-11<q<0.045). Of all significant associations, three dietary constituents, docosenoic acid (a monounsaturated fatty acid found in rapeseed oil), alcohol, and aspartame had the highest number of associations with CD-associated metabolites (17, 13, and 12, respectively). For example, increased consumption of docosenoic acid, alcohol, and aspartame were associated with increases in sphingomyelin-related metabolites (2.33^-10<q<0.046), (2, 2, and 4 respectively). Furthermore, increased docosenoic acid and alcohol consumption was also associated with increases in a lactosylceramide-related metabolite, q = 0.004, and q = 0.038, respectively. Finally, vitamin D related nutrients were also associated with bile acids related metabolites (2.10^-11<q<0.044).

Conclusions: The association of dietary constituents with specific CD-associated metabolites may suggest a link between dietary constituents and CD pathogenesis. Identifying these associations may help in defining strategic dietary interventions in treating or preventing CD.

Funding
The Leona M. and Harry B. Helmsley Charitable Trust
Kenneth Croitoru is the recipient of the Canada Research Chair in Inflammatory Bowel Diseases

Batia Weiss

Appearances