Gastrointestinal dysfunction in Parkinson’s disease: molecular pathology and implications of gut microbiome, probiotics, and fecal microbiota transplantation

Gastrointestinal symptoms and gut dysbiosis may occur before the onset of motor symptoms in Parkinson’s disease (PD). Prediagnostic and prodromal features, such as constipation and α-synuclein pathology, can be detected several years before the clinical diagnosis of PD and have the potential to develop as early PD biomarkers. Environmental toxins and gut dysbiosis may trigger oxidative stress and mucosal inflammation, and initiate α-synuclein accumulation in the enteric nervous system, early in PD. Chronic gut inflammation can lead to a leaky gut and systemic inflammation, neuro inflammation, and neuro degeneration via gut–vagus–brain signaling or through blood–brain barrier permeability. Concepts regarding the gut–brain signaling in PD pathogenesis are changing rapidly and more investigation is required. The…