Depending on the author, Parkinson's disease is a disease characterized by ⍺-synuclein aggregation (Lewy bodies) or by dopaminergic neuronal loss in the substantia nigra pars compacta, which leads to motor and non-motor symptoms.
Over the past few decades of research, there has been a vague discourse on inflammation-induced oxidative stress, mitochondrial dysfunction, and cytokine-induced toxicity as the cause of neuronal damage and loss associated with Parkinson's disease. However, this type of discourse is also present in other neurodegenerative diseases and it is not clear how it would explain the characteristics of Parkinson's disease (or of other diseases).
Recently enteric and central nervous systems have been implicated in the pathogenesis of sporadic Parkinson disease, thus highlighting the crosstalk between the gut and brain. Indeed the staging in Parkinson's disease was described by Heiko Braak in 2003. Braak and colleagues state that Parkinson's disease begins when a foreign agent enters the body via the nose or gastrointestinal system and travels into the central nervous system (CNS). The presence of Lewy bodies in the enteric and peripheral nervous systems supports their claim.
In this review, the authors summarize how the alterations in the gut microbiome can affect Parkinson disease pathogenesis.
The scientists highlight various mechanisms increasing/decreasing the risk of Parkinson disease development. Based on the previous supporting evidence, they suggest how early interventions could protect against Parkinson disease development and how controlling specific factors, including patients' diet, could modify disease's mechanisms.
The scientists explain the strong relationship between the gut microbiota and the brain in Parkinson disease subjects, by delineating the multiple mechanisms involved in neuroinflammation and oxidative stress.
They conclude that the neurodetrimental effects of western diet and the neuroprotective effects of Mediterranean diets should be further explored in humans through clinical trials.