The Interplay of the Gut Microbiome, Bile Acids, and Volatile Organic Compounds

Figure 1

Proposed schema of interplay between gut dysbiosis, modified BA pool, and disease. In health, secondary BAs are modified by microbial BSH and HSDH enzymes through deconjugation, oxidation, and epimerization as well as dehydroxylation via 7α-dehydroxylation activity. The BA metabolites as a result of microbial transformations act as signaling molecules via the TGR5 and FXR receptors to regulate intestinal homeostasis. In disease, it is unclear how gut dysbiosis causes a modified BA pool, which then results in disease, which is possibly secondary to impaired BA signaling. (BSH: bile salt hydrolases; HSDH: hydroxysteroid dehydrogenases; TGR5: G protein coupled BA receptor; FXR: farnesoid x receptor).