Do All Roads Lead to Rome? - Rethinking Parkinson’s Disease Through the Gut-Brain Axis

Parkinson’s disease (PD) is a chronic, progressive, and disabling neurodegenerative disorder that affects the middle-aged and elderly population. It has been ranked second neurodegenerative disorders worldwide just after Alzheimer’s disease (AD), with a prevalence and incidence that was observed in 1–2% of the population with age over 60 years. Emerging research suggests that the gut–brain axis plays a critical role in the pathogenesis of Parkinson’s disease (PD), with the gut microbiota increasingly implicated as a key player. The hypothesis that PD may begin in the gastrointestinal tract—supported by early non-motor symptoms such as constipation and the presence of alpha-synuclein pathology in enteric neurons—has led to a paradigm shift in how the disease is understood. This review explores current evidence linking gut dysbiosis to neuroinflammation, alpha-synuclein aggregation, and disease progression in PD.