Role of Microbiota in Neurodegenerative Diseases

Abstract

Functional interaction of the gastrointestinal tract (GI) and the central nervous system (CNS) is due to various relationships, which includes autonomic and enteral nervous systems as well as the immune and neuroendocrine systems. The microbiota of the macroorganism plays the central role in this interaction. Microbiota produces hundreds of biologically active substances that have a neurochemical effects through neuroendocrine, immune, and metabolic pathways. The microbiota also synthesizes and releases products (neurotoxins, neurotransmitters, lipopolysaccharides, amyloids, etc.) that can negatively affect the neurochemistry of the CNS, stimulating the development of amyloidosis, synucleinopathies, and tauopathies, thereby promoting the development and/or progression of neurodegenerative diseases. Under the influence of external and internal factors, human microbiota can be changed and the symbionts/pathogens ratio is also changed. The permeability of intestinal and blood-brain barrier varies. Metabolites produced by the altered microflora are able to enter the bloodstream and possibly into the CNS, thereby disrupting its functioning. Infections can play a significant role and even act as a cofactor in the induction of neurodegenerative diseases. Disturbance of the functions of the GI can precede long before the neurodegenerative processes. Early diagnosis, detection, monitoring, and treatment of negative gastrointestinal symptoms, including normalization of the microbiota, can lead to a significant improvement in the quality of life of patients with neurodegenerative diseases.