Gut Microbes in Parkinson's Disease

Parkinson's disease is characterized by motor impairments due to the progressive degeneration of dopaminergic neurons in the substantia nigra of the midbrain, but converging evidence suggests that non-motor symptoms can predate the motor symptoms by many years. Gut dysfunction and gut dysbiosis are thought to be among these early changes and are also believed to contribute to the neurodegenerative process via the gut–brain axis. The interactions that form this communication pathway are numerous and complex. This chapter aims to present an overview of how gut function and gut microbiota composition are disturbed in Parkinson's disease. Additionally, the mechanisms by which the gut microbes might exert modulatory effects in Parkinson's disease are contextualized and discussed. Finally, recently performed clinical and preclinical studies that target the gut microbiota, such as dietary interventions and fecal microbial transplantation, are summarized. These microbial-based therapies can have an impact in the gastrointestinal symptoms associated with Parkinson's disease and might also influence disease pathological progression.