Role of the gut microbiota in the development of various neurological diseases

Introduction: In recent years, the scientific evidence supporting a relationship between the microbiota and various diseases has increased significantly; this trend has also been observed for neurological diseases. This has given rise to the concept of the gut-brain axis and the idea of a relationship between the gut microbiota and several neurological diseases whose aetiopathogenesis is yet to be clearly defined. Development: We review the role of the gut microbiota in the gut-brain axis and analyse those neurological diseases in which alterations in the gut microbiota have been described as a result of human studies: specifically, Parkinson's disease, Alzheimer disease, amyotrophic lateral sclerosis, neuromyelitis optica, and multiple sclerosis. Conclusions: The body of evidence linking the gut microbiota to various neurological diseases has grown considerably. Several interesting studies show a relationship between the gut micro-biota and Parkinson's disease, Alzheimer disease, neuromyelitis optica, and multiple sclerosis, whereas other controversial studies implicate it in amyotrophic lateral sclerosis. Many of these studies place considerable emphasis on modulation of inflammation, particularly by bacteria capable of producing short-chain fatty acids. Despite these encouraging results, many questions remain, and there is a need to demonstrate causality, determine the role of fungi or viruses, and research possible treatment through diet, probiotics, or faecal microbiota transplantation. (c) 2019 Sociedad Espanola de Neurologia. Published by Elsevier Espana, S.L.U. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

Automated summary

In recent years, there has been increasing scientific evidence supporting a relationship between the gut microbiota and neurological diseases. This has led to the concept of the gut-brain axis and the idea that alterations in the gut microbiota may be involved in the pathogenesis of various neurological diseases. This review highlights the role of the gut microbiota in the gut-brain axis and analyzes the relationship between the gut microbiota and neurological diseases such as Parkinson's disease, Alzheimer's disease, amyotrophic lateral sclerosis, neuromyelitis optica, and multiple sclerosis. While several studies show a strong association between the gut microbiota and Parkinson's disease, Alzheimer's disease, neuromyelitis optica, and multiple sclerosis, there are conflicting results regarding amyotrophic lateral sclerosis. Many of these studies focus on the modulation of inflammation, particularly through the production of short-chain fatty acids by bacteria. However, further research is needed to establish causality, understand the role of fungi or viruses, and investigate potential treatments such as diet, probiotics, or fecal microbiota transplantation.