Potential role of gut microbiota and tissue barriers in Parkinson's disease and amyotrophic lateral sclerosis

Parkinson's disease (PD) and amyotrophic lateral sclerosis (ALS) are neurodegenerative diseases with pathophysiology that may be related to the gastrointestinal tract. It is well established that tissue barriers maintain homeostasis and health. Furthermore, gut microbiota may have an impact on brain activity through the gutmicrobiota-brain axis under both physiological and pathological conditions. In this review, we highlight the current knowledge regarding the role of gut microbiota and tissue barriers in PD and ALS. To our knowledge, this is the first review of the key issues involving both the altered gut microbiota and impaired tissue barriers in the pathophysiology of PD and ALS.