Bacterial Metabolites: A Link between Gut Microbiota and Dermatological Diseases

Abstract

Dysbiosis has been identified in many dermatological conditions (e.g., psoriasis, atopic dermatitis, systemic lupus erythematosus). One of the ways by which the microbiota affect homeostasis is through microbiota-derived molecules (metabolites). There are three main groups of metabolites: short-chain fatty acids (SCFAs), tryptophan metabolites, and amine derivatives including trimethylamine N-oxide (TMAO). Each group has its own uptake and specific receptors through which these metabolites can exert their systemic function. This review provides up-to-date knowledge about the impact that these groups of gut microbiota metabolites may have in dermatological conditions. Special attention is paid to the effect of microbial metabolites on the immune system, including changes in the profile of the immune cells and cytokine disbalance, which are characteristic of several dermatological diseases, especially psoriasis and atopic dermatitis. Targeting the production of microbiota metabolites may serve as a novel therapeutic approach in several immune-mediated dermatological diseases.

Keywords: SCFA; TMAO; dysbiosis; fecal microbiota transplantation; gut–skin axis; immune-mediated inflammatory diseases; inflammation; intestinal microbial metabolites; microbiota; probiotics.

Figure 1

Three pathways of tryptophan metabolism. The indole pathway is mostly associated with intestinal microbiota metabolism. Various compounds produced in this pathway are considered beneficial to human health. I3A—indole-3-aldehyde, ILA—indole lactic acid, IPA—indole propionic acid, IPyr—indole pyruvate, IAA—indole acetic acid. Created with BioRender.com.

Figure 2

Production of microbiota metabolites and potential treatment options at various steps of this process. Ingested food is rich in compounds that can be utilized by intestinal microbiota. End products of microbiota metabolism are absorbed into the circulation. 1. Prebiotics, e.g., fructooligosaccharides and inulins, can be supplemented to achieve growth of beneficial microorganisms and an increase in production of eligible metabolites. 2. Probiotics. 3. Fecal microbiota transplantation is carried out with the aim to replace pathogenic bacteria with health-promoting ones. 4. Postbiotics consist of favorable metabolites of intestinal microbiota. Created with BioRender.com.