Short summary

The gut microbiota is essential to the function of the immune system, and the composition and activity of the gut microbiota plays a central role in development of inflammation in the gut, colorectal cancer, diabetes and other diseases associated with Western lifestyle. The incidence of these diseases is rapidly rising, and diet plays a role in the composition and function of the gut microbiota. Thus, identification of modifiable factors is essential. With this project we seek to identify components in the gut microbiota with therapeutic and pathogenic effects on inflammation in the gut.

The overall aim of this project is to identify gut microbiota effector strains in Inflammatory Bowel Disease (IBD) patients which impact the development and course of IBD.  It is hypothesized that: differences in microbiota account for differences in disease expression in genetically identical twins and therefore the phenotype of these twin can be transferred to a murine IBD model. 

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Rationale

We will perform microbial and metabolomic characterization of feces from identical twin pairs with one suffering from IBD while the other being healthy and, next, we will transfer the microbiomes from three twin pairs to pregnant mice and induce colitis in the offspring by the use of dextran sodium sulphate (DSS) in order to perform microbial and metabolomic characterization of the fecal and luminal content of the mice. According to the hypothesis we expect that transfer of gut microbiome from the human twins to germ free mice subsequently induced with DSS will cause severe colitis (high inflammatory response) in mice receiving IBD microbiome and mild colitis (low inflammatory response) in mice receiving microbiome from the healthy twin. Thereby, we hope to find differences between the twins, which we are able to replicate in the mouse model indicating that those differences observed may be causal. We will apply combined analyses of microbiome and metabolomic datasets in this murine transfer model to define gut microbes which impact disease activity and thereby form a basis for development of new prevention and treatment strategies for IBD.

Inflammatory Bowel Disease (IBD), including Crohns Disease (CD) and ulcerative colitis (UC), are life-long diseases, affecting the life quality of the affected persons and their families, and also affecting society due to e.g. absence from work. The prevalence of IBD has almost reached 1 % of the population in some countries and is increasing rapidly in developing countries as their lifestyle approaches a Western lifestyle. Research strongly indicates that IBD are caused by a complex interplay between host immune factors and gut microbiota. 

A human contains in its gut bacteria in a number ten times the number of cells in its body, and these contribute significantly to a variety of human functions. Commensal bacteria provide the host with valuable energy, essential vitamins and amino acids, pro- and anti-inflammatory molecules. Also, the gut bacteria are important for the development of a functioning immune system. Thus, an intricate homeostasis exists between gut bacteria and the host immune system. Indeed, specific members of the gut microbiome have been found to modulate the immune system in a way relevant for IBD as well as for a number of other autoimmune and inflammatory diseases. For such diseases associated with Western living, low bacterial diversity, as well as other alterations of the gut bacterial compositions of have been found, and attempts to identify an IBD-associated microbiome have been performed. For instance, segmented filamentous bacteria (SFB) have been found to induce the IL17-IL23 pathway, a core pathway involved in IBD, type 1 diabetes and other inflammatory diseases. The phosphate reducing bacteria Desulfovibrio spp. have been associated with UC, and Faecalibacterium prausnitzii is known to reduce inflammation in IBD in both man and mouse. Thus, interactions between the gut microbiota and the immune system play a critical role in IBD development and disease progression in humans.

Fecal samples have been collected from monozygotic (MZ) twin pairs discordant for IBD. Gut microbiome co-variation between twin pair is lower than between unrelated persons. Thus, disease-associated modifications may be identified with high power. The question is how much of the IBD-related inter-twin differences can be allocated to microbiota differences. Utilizing a mouse model enables us to evaluate the results found in the twin pairs and thereby evaluate potential causality. Using the feces from the identical twin pairs with and without IBD, we want to transfer the two phenotypes to the mice, which should enable us to analyze gut microbiome composition and activity of the mice with severe colitis versus those with mild.

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Description of the cohort

The cohort consists of 54 monozygotic twin pairs discordant (44) or concordant (10) for inflammatory bowel disease (IBD). It is comprised of both genders and persons of 27-79 years of age.

Data and biological material

A biobank has previously been established. Samples consisting of feces, blood, urine, saliva and nose mucus are stored at the Danish twin registry's biobank.

The present project is part of a larger study and uses only the fecal samples.

As part of the study, questionnaire data on diet has been collected but data entry remains. The OPEN database will contain pseudo anonymized ID as well as the data from the inter99 food frequency questionnaire and 48 hour dietary recall developed for the metahit consortium.

Information has also been collected from the Danish Twin Registry and the Danish National Patient Register.

Collaborating researchers and departments

Department of Epidemiology Research, Statens Serum Institut

• PhD-student Frederik Trier Møller

Molecular Diagnostic and Clinical Research Unit, Hospital of Southern Jutland, Aabenraa

• Professor and Chief Physician Vibeke Andersen

Department of Experimental Animal Models, Institute for Veterinary Disease Biology, University of Copenhagen

• Professor Axel Kornerup Hansen, DVM

Department of Cancer and Inflammation, Institute of Molecular Medicine, University of Southern Denmark

• Professor Uffe Holmskov

Institute of Clinical Molecular Biology, Kiel University, University Hospital Schleswig-Holstein

• Professor Andre Franke

Laboratory of Medical Mass Spectrometry, Department of Health Science and Technology, Aalborg University

• Associate Professor Allan Stensballe