It was previously believed that inflammatory bowel disease was caused by several, separate root causes. Both genetics and the gut microbiome were considered, but they were considered to be separate causes. A recent study has found that the two have a synergism in the pathogenesis of IBD.

The microbiota of an individual evolves with them from their birth and contributes to both the immune system and their metabolism. A microbiome must maintain its diversity in order to maintain intestinal homeostasis. However, as a result of genetics, dysbiosis can cause a loss of the necessary pathways for bacteria to create certain metabolites. It was revealed that certain genes promote tolerant immune responses to natural bacteria, as opposed to pathogens. A flaw in this could cause depletion of certain bacteria species. In specific, patients with inflammatory bowel disease were found to have lower levels of tryptophan and SCFAs, both of which are metabolites normally created by bacteria in the GI tract. Further work is being done to determine if these are biomarkers of IBD, but supplementation of the missing bacteria may prove to be a potential therapy for IBD. By supplementing the missing bacteria, the appropriate pathways can be restored and the metabolites can be sufficiently produced again.

Chu, H. (2017). Host gene–microbiome interactions: molecular mechanisms in inflammatory bowel disease. Genome Medicine, 9, 69. https://genomemedicine.biomedcentral.com/articles/10.1186/s13073-017-0459-4