Gut Microflora Modulates Th17/Treg Cell Differentiation in Experimental Autoimmune Prostatitis via the Short-Chain Fatty Acid Propionate

Gut Microbial-Derived Metabolites as Immune Modulators of T Helper 17 and Regulatory T Cells

The gut microbiota and its derived metabolites greatly impact the host immune system, both innate and adaptive responses. Gut dysbiosis and altered levels of microbiota-derived metabolites have been described in several immune-related and immune-mediated diseases such as intestinal bowel disease, multiple sclerosis, or colorectal cancer. Gut microbial-derived metabolites are synthesized from dietary compounds ingested by the host or host-produced metabolites, and additionally, some bacterial products can be synthesized de novo. In this review, we focus on the two first metabolites families including short-chain fatty acids, indole metabolites, polyamines, choline-derived compounds, and secondary bile acids. They all have been described as immunoregulatory molecules that specifically affect the adaptive immune system and T helper 17 and regulatory T cells. We discuss the mechanisms of action and the consequences in health and diseases related to these gut microbial-derived metabolites. Finally, we propose that the exogenous administration of these molecules or other compounds that bind to their immunoregulatory receptors in a homologous manner could be considered therapeutic approaches.

The Role of the Human Microbiome in the Pathogenesis of Pain

Understanding of the gut microbiome's role in human physiology developed rapidly in recent years. Moreover, any alteration of this microenvironment could lead to a pathophysiological reaction of numerous organs. It results from the bidirectional communication of the gastrointestinal tract with the central nervous system, called the gut-brain axis. The signals in the gut-brain axis are mediated by immunological, hormonal, and neural pathways. However, it is also influenced by microorganisms in the gut. The disturbances in the gut-brain axis are associated with gastrointestinal syndromes, but recently their role in the development of different types of pain was reported. The gut microbiome could be the factor in the central sensitization of chronic pain by regulating microglia, astrocytes, and immune cells. Dysbiosis could lead to incorrect immune responses, resulting in the development of inflammatory pain such as endometriosis. Furthermore, chronic visceral pain, associated with functional gastrointestinal disorders, could result from a disruption in the gut microenvironment. Any alteration in the gut-brain axis could also trigger migraine attacks by affecting cytokine expression. Understanding the gut microbiome's role in pain pathophysiology leads to the development of analgetic therapies targeting microorganisms. Probiotics, FODMAP diet, and fecal microbiota transplantation are reported to be beneficial in treating visceral pain.