Science Update

Recent Review Investigates Relationship Between Gut Microbiome and Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is classified as two main types: ulcerative colitis (UC) and Crohn’s disease (CD). The complete etiology of IBD is not fully understood yet, however, it is believed to be the result of a combination of environmental factors, gut microbiome dysbiosis, genetic susceptibility, and autoimmune or unhealthy immune responses. Conditions involving chronic gastrointestinal (GI) inflammation, such as IBD, have been shown to involve an imbalance in GI microbiota and a reduction in bacterial diversity. This can cause downstream effects due to changes in the number of metabolites from microbes. For instance, species in certain Bacteroides, Lactobacillus, and Clostridium genera have been shown to produce bile acids, tryptophan metabolites, and short-chain fatty acids (SCFAs). These metabolites have been shown to influence intestinal permeability, epithelial repair, cellular differentiation, and barrier integrity. 

A recently published review article by Hu and colleagues explored the relationship between the gut microbiome and IBD. Research indicates that disturbances in bile acid and tryptophan metabolism may occur in the presence of IBD. Tryptophan can be metabolized in a pathway involving GI microbes into indole derivatives, which can help modulate pro-inflammatory cytokines and help protect the intestinal barrier. 

The authors describe the potential impact of probiotic supplementation in the presence of IBD. Probiotics may support GI health and the inflammatory response by helping to increase metabolites derived from microbiota, such as SCFAs. In an animal study, Lactobacillus lactis ML2018 was reported to help suppress fibrosis, improve intestinal barrier integrity, and help increase SCFA levels. 

Microbial-derived aryl hydrocarbon (AhR) receptor agonists have been shown to significantly decrease in individuals with IBD. Significant improvements in intestinal barrier integrity and IBD symptoms have been observed in the presence of supplementation with AhR agonists. In an animal study, Bifidobacterium bifidum was shown to help increase AhR activity and help support a healthy inflammatory response. Another animal study involving the administration of L. casei reported an improvement in UC-related symptoms, circulating bile acid profiles, and gut microbial composition.

The administration of L. plantarum in preclinical studies was shown to help increase Treg cells, stimulate interleukin-10 production, and help support a normal response to inflammation. In an animal model, a mixed probiotic product helped maintain tight junction protein expression and helped to prevent apoptosis. More research is needed before conclusions can be made, especially at the clinical level. 

Research indicates that certain probiotics may help support a healthy inflammatory response. They may also help support gut microbial composition and intestinal barrier integrity. 

By Colleen Ambrose, ND, MAT