Prebiotic Modulation of Gut-Microbe Interactions as Therapeutic Strategy for Inflammatory Bowel Disease

Bourgonje, A.R. (Arno) (2017) Prebiotic Modulation of Gut-Microbe Interactions as Therapeutic Strategy for Inflammatory Bowel Disease. thesis, Medicine.

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Abstract

Background: Inflammatory bowel disease (IBD) consists of two main forms – Crohn’s disease (CD) and ulcerative colitis (UC) – and is characterized by a chronic inflammation, driven by an inappropriate immune response triggered by commensal microbiota. A disturbed balance of the gut microbiota – a phenomenon referred to as ‘’dysbiosis’’ - is a hallmark of IBD. Dysbiosis manifests itself by an increase in pathogenic bacteria and a decrease in commensal (‘beneficial’) bacteria. An important observation is the marked reduction in the abundance of the strict anaerobic gut bacteria Faecalibacterium prausnitzii in CD patients. This is a commensal bacterium that contributes to the protection of the gut mucosa and has proven to possess fiber-degrading, butyrate-producing and anti-inflammatory properties. Inulin-type fructans form a group of prebiotics that have the capacity to selectively affect the gut microbiota composition, including F. prausnitzii growth and metabolism. The aim of this study is to investigate whether the addition of selected prebiotics (such as inulin-type fructans) can stimulate growth of F. prausnitzii and at the same time promote viability and vitality of intestinal epithelial cells in the recently developed ‘Human oxygen-Bacteria anaerobic’ (HoxBan) co-culturing system. Methods: F. prausnitzii and Caco-2 gut epithelial cells were co-cultured for 18-36 h at 37ºC and 5% CO2 in the HoxBan system, providing the bacterial compartment with different carbon sources (glucose, inulin, pectin or resistant starch corn [RSC]) and the human gut epithelial compartment with or without glucose. F. prausnitzii colony formation was visualized by photography and Caco-2 cells were analyzed for their gene expressions of iNOS, IL-1β and HO-1 using qPCR. Caco-2 viability was evaluated using Trypan Blue staining. The ability of Caco-2 cells to grow on the different carbon sources, as well as potential metabolites of F. prausnitzii (butyrate, fructose) was monitored in a Real Time Cell Analyzer (RTCA, xCelligence). Results: Prebiotic fibers (inulin, pectin and RSC) induced F. prausnitzii colony formation in the standard HoxBan system and bacterial growth was further enhanced by Caco-2 cells. Concomitantly, expressions of iNOS (inflammatory marker) and HO-1 (oxidative stress marker) were reduced in Caco-2 cells. However, these effects were also observed in the complete absence of fibers and glucose in the bacterial compartment and are likely due to diffusion of glucose from the ‘ʻhuman’’ to the ‘ʻbacterial’’ compartment in the standard HoxBan system. Still, in a fully glucose-free HoxBan system, inulin promoted growth of F. prausnitzii, which in turn significantly improved Caco-2 cell viability and induced subtle (non-significant) anti-inflammatory and anti-oxidative effects in Caco-2 cells. Finally, Caco-2 cells were unable to grow on fibers, but grew well on fructose. Butyrate, in contrast, only provides short-term growth benefits to Caco-2 cells and turned into a toxic compound 2 days after exposure. Conclusion: These data suggest that inulin can be used as prebiotic to promote growth of the beneficial bacterium F. prausnitzii, from which it produces metabolites that improve gut epithelial regeneration. This may explain in part the therapeutic effects of inulin observed in patients with IBD.

Item Type:	Thesis (Thesis)
Supervisor name:	Supervisors and Dijkstra, Prof. dr. G. and Faber, Prof. dr. K.N. and Martels, Drs. J.Z.H. von and Institute and University of Groningen / University Medical Center Groninge and Department of Gastroenterology & Hepatology
Faculty:	Medical Sciences
Date Deposited:	25 Jun 2020 11:04
Last Modified:	25 Jun 2020 11:04
URI:	https://umcg.studenttheses.ub.rug.nl/id/eprint/2438

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