The role of the gut microbiome in the progression of Parkinson's disease: a systematic review of patient cohorts.

introductionParkinson's disease (PD) is the second most common neurodegenerative disease. The etiology of PD is not yet fully understood. In recent years, the role of the gut microbiome in the progression of the disease came to attention. A deeper understanding of the relationship between the gut microbiome and the development and progression of PD may innovate therapeutic approaches.

aimThe aim of the present literature analysis is to systematically evaluate alterations in gut microbiome in PD and its correlation with clinical symptoms. MATERIALS AND

methodsA search for publications via PubMed using the search terms "Parkinson's disease" AND "gut microbiome" AND "human" was performed. The main inclusion criteria were a subject number ≥ 30 per group, patients with clinically confirmed PD, an analysis of the gut microbiome in a case-control, cross-sectional or longitudinal study design.

resultsThe evaluation of the results showed that gut microbiome of PD patients is altered both in early stages of the disease and throughout its progression compared to healthy controls. These alterations correlate with clinical symptoms. In general, the diversity of micro-organisms in the gut is reduced in PD patients, and the composition of the gut microbiome differs significantly from healthy persons. Particularly a reduction in short-chain fatty acid (SCFA) producing genera such as Faecalibacterium and Roseburia and the increase in pro-inflammatory taxa such as Collinsella and Akkermansia is described. CONCLUSIONS AND DISCUSSION: According to current evidence, the relationship between alterations in the gut microbiome and the pathogenesis of PD is not yet fully understood. Recent findings suggests that intestinal dysbiosis may contribute to the progression of PD.