Brain-gut-microbiota axis in Parkinson's disease: A historical review and future perspective

Parkinson's disease (PD) is the second most common degenerative disease of the central nervous system (CNS) after Alzheimer's disease. In addition to the typical motor symptoms, the clinical manifestations of patients with PD include gastrointestinal symptoms, which even precede the motor symptoms. Recent research has found that the gut microbiota regulates the brain-gut axial interaction through immune, endocrine, and direct neural mechanisms, supporting the hypothesis that the pathological process of PD spreads from the gut to the brain. In this review article, we highlight the landmark findings in the field of PD, with particular attention to the brain-gut-microbiota axis. We summarize the changes and their clinical effects on the gut microbiota and metabolites observed in PD. The intestinal microbiota may contain appropriate targets for the prevention and treatment of PD. Clinical cohort studies suggest that certain intestinal microbes have protective or pathogenic effects on the progression of PD. A better understanding of the interaction between the gut-brain axis, the gut microbiota, and PD has the potential to lead to new diagnostic and therapeutic approaches. Animal experiments suggest that fecal microbiota transplantation (FMT) is helpful for treating PD, and FMT is expected to be an effective treatment for PD in the future.