Microbial-derived mediators of the gut-brain axis: Implications for neurological disorders

Gut-brain communication is mediated by metabolic and signaling pathways that play important roles in brain development and cognitive function. Recently, the bidirectional role of the gut microbiota in the gut-brain axis has drawn greater scientific attention. The gut microbiota, a group of bacteria that naturally colonize the gastrointestinal tract of mammals, may play a role in healthcare burden neurodegeneration, which affects many of the body's activities. Lately, it has been reported that some mediators produced by changes in the gut microbiota are associated with neurodegenerative diseases. Additionally, the host immune system plays a role in gut-brain communication, as gut microbiota are potent modulators of immune cells that reside in the central nervous system. Unfortunately, the majority of current strategies are based on pre-clinical studies, with little known about the causes and molecular mechanisms. Herein, we summarize the evidence supporting an integrated hypothesis of mediators in neurodegenerative diseases and gut-brain communication, which result from biologically conserved interactions and factors related to the distinct composition of the gut microbiota. We also mention the need for establishing a standardized approach for particular focal parts of the microbiota-gut-brain axis, thorough biological sample analyses, dietary strategies, and recognition of a new therapeutic paradigm. A stronger emphasis on omics technologies and on advanced in vitro and in vivo models is also urgently needed. This will enable research on the microbiota-gut-brain axis to proceed to the next stage, allowing us to identify practical opportunities to modify the microbiota for enhanced brain health.