How Probiotics Affect the Microbiota

Abstract

Probiotics have been used to treat a variety of diseases for decades; however, what is the rationale for their application? Such a treatment was first proposed in the early nineteenth century based on observations of decreased bifidobacterial populations in children suffering from diarrhea, suggesting that oral intake of bifidobacteria could replete this subpopulation of the microbiota and improve health. Since then, studies have shown modifications in the gut or skin microbiota in the course of a variety of diseases and suggested positive effects of certain probiotics. Most studies failed to report any impact on the microbiota. The impact of probiotics as well as of bacteria colonizing food does not reside in their ability to graft in the microbiota but rather in sharing genes and metabolites, supporting challenged microbiota, and directly influencing epithelial and immune cells. Such observations argue that probiotics could be associated with conventional drugs for insulin resistance, infectious diseases, inflammatory diseases, and psychiatric disorders and could also interfere with drug metabolism. Nevertheless, in the context of a plethora of probiotic strains and associations produced in conditions that do not allow direct comparisons, it remains difficult to know whether a patient would benefit from taking a particular probiotic. In other words, although several mechanisms are observed when studying a single probiotic strain, not all individual strains are expected to share the same effects. To clarify the role of probiotics in the clinic, we explored the relation between probiotics and the gut and skin microbiota.

Keywords: clinics; drug interaction; metabolism; microbiota; probiotic; psychiatry; skin.

Figure 1

How probiotic influence the microbiota and the course of diseases. Probiotics and next-generation beneficial bacteria influence eukaryotic cells by different mechanisms. For instance, Short Chain Fatty Acids (SCFAs) are able to activate specific G-protein coupled receptors (e.g., GPR41/43) expressed on enteroendocrine L-cells, thereby triggering the secretion of different gut peptides (i.e., GLP-1, GLP-2) involved in the regulation of energy metabolism and gut barrier function. SCFAs can also modulate gene transcription through the inhibition of histone deacetylase activity. Besides SCFAs, some gut microbes dialogue with the host cells through the production of other specific metabolites or cell components. Therefore, such interactions result in a variety of effects on the host ranging from the improvement of behavior in psychopathological conditions (e.g., alcoholism, autism), but also impacts on skin health and host metabolism by the mean of immune interaction and Gut—Brain—Skin axis. Also, bacteria colonizing the normal microbiota as Barnesiella have been associated with a reduced susceptibility to gut colonization with Vancomycin resistant Enterococcus, whereas, Lactobacillus treatment reduced the carriage of multi-drug resistant potential pathogens.