The Role of an Altered Gut Microbiome in Parkinson’s Disease: A Narrative Review

Abstract

Parkinson’s disease is a debilitating multisystemic disorder affecting both the central and peripheral nervous systems. Accumulating evidence suggests a potential interaction between gut microbiota and the pathophysiology of the disease. As a result of the degradation of dopaminergic neurons, PD patients develop motor impairments such as tremors, rigidity, and slowness of movement. These motor features are preceded by gastrointestinal issues, including constipation. Given these gastrointestinal issues, the gut has emerged as a potential modulator of the neurodegenerative cascade of PD. Several studies have been carried out to broaden our understanding of the gut–microbiota–brain axis in PD. As a result, a decrease in short-chain fatty acid synthesizing bacteria has been observed in multiple studies. Some studies, on the other hand, have shown an enrichment of mucin- and levodopa-degrading microbes. In this review, we compiled the available evidence from the literature on the bidirectional communication between the gut microbiome system and the brain in PD. We also addressed the association between dysbiosis and the clinical symptoms of PD and host–drug metabolism. Finally, we touched on some of the therapeutic interventions that may restore eubiosis and modulate the gut structure to restrain disease progression.

Keywords

• Parkinson’s disease
• gut–brain axis
• dysbiosis
• metabolomics
• levodopa metabolism
• therapeutics