A45 MANAGING THE IBDO’S AND IBDON’TS OF DIETARY FIBER CONSUMPTION IN INFLAMMATORY BOWEL DISEASE

Inflammatory bowel diseases (IBD), including Crohn disease and ulcerative colitis, are chronic and severely debilitating gastrointestinal disorders, with rising prevalence, especially in children. While the etiology of IBD remains poorly understood, gut microorganisms and diet have been implicated in IBD pathogenesis. Interestingly, dietary fibers pass through the small bowel undigested and are fermented within the large intestine by specific gut microbes, promoting gut health by altering the gut microenvironment, modulation of the immune system, and altered energy metabolism. Our previous work indicates an altered balance between commensal and pathobiont microbes in IBD, suggesting one opportunity for the misregulation of fiber fermentation within the IBD gut. Interestingly, specific carbohydrate receptors on the surface of immune cells interact with fibers, such as those expressed by certain species of fungi, driving an inflammatory response. Here we hypothesize that the altered microbiota in IBD causes significant changes in fiber fermentation, ultimately driving intestinal inflammation. Bacterial growth rates in response to specific fibers were examined by OD600 growth curves. Bacterial fiber fermentation patterns were evaluated by mass spectrometry of SCFAs. The effects of specific fibers on bacterial pathogenicity when co-cultured with human HT29 epithelial cells was measured by gentamicin protection assays and visualized by microscopy. Immunohistochemistry of biopsy tissues collected from pediatric IBD (n=14) and control patients (n=7) was utilised to examine expression levels of fiber receptors expressed on human cells. We have demonstrated that commensal microorganism, isolated live from IBD patients, display a different pattern of fiber fermentation compared to pathobiont species. Specific fibers also increase the invasive potential of these pathobionts. Preliminary immunohistochemistry suggests that there is increased expression of specific carbohydrate receptors in IBD, suggesting an increased sensitivity to unfermented dietary fibers in these patients. These results suggest that some patients may display a sensitivity to specific dietary fibers due to a lack of appropriate fiber fermenting microbes in their gut. Profiling the patient specific microbiota of IBD patients may allow us to make more specific dietary recommendations to assist in reducing intestinal inflammation in IBD. Comparing in vitro findings to our readily available patient food frequency questionnaires (FFQs) and detailed patient history will allow us to define key disease features of IBD and also identify new and improved treatment options, such as microbe-altering treatments, and tailored nutritional recommendations. CCCCCFC

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