Title : Gut microbiome and metabolic signatures in early and prodromal Parkinson’s disease: A systematic review and meta-analysis of microbial diversity
Abstract:
Parkinson’s disease may begin years before motor diagnosis,and gastrointestinal symptoms are among the earliest clinical clues.This has made the gut microbiome an important focus in prodromal Parkinson’s disease research, particularly for understanding gut–brain axis changes and identifying non-invasive biomarkers.
This study summarizes gut microbiome and related metabolic signatures in early and prodromal Parkinson’s disease.We included studies comparing Parkinson’s disease,early Parkinson’s disease, or prodromal/REM sleep behavior disorder-related phenotypes with healthy controls.Extracted data included study design, diagnostic definitions, sequencing methods, diversity outcomes, differentially abundant taxa, and functional or metabolomic findings.Quantitative pooling of alpha-diversity indices is planned where sufficient numerical data are extractable or clarified by study authors; the current synthesis focuses on revised taxa-level and metabolic patterns.
Across 30 included publications, the findings showed recurrent dysbiosis rather than a single disease-specific organism.The most frequently reported increase involved Akkermansia/Akkermansia muciniphila, reported in 13 papers. Other repeated increases included Escherichia/Shigella-related taxa in 7 papers, Bacteroides and Desulfovibrio in 5 papers each, and Citrobacter in 4 papers. In contrast, reductions were most consistently reported for short-chain-fatty-acid-producing and fiber-fermenting taxa,including Faecalibacterium in 13 papers, Prevotella/Prevotella copri in 8 papers, Roseburia-related taxa in 7 papers, and Butyricicoccus in 3 papers. Findings for Lactobacillus, Lachnospiraceae-related taxa, and Clostridium-related groups were mixed and should be interpreted cautiously.Available functional findings also suggested disturbances in short-chain fatty acid,bile acid, and glutamate-related pathways.
Overall,early and prodromal Parkinson’s disease appear to be associated with a shift away from protective fiber-fermenting bacteria and toward mucin-degrading, inflammatory, and metabolically altered microbial profiles. These findings support further longitudinal work on the gut–brain axis and may help prioritize microbial candidates for early Parkinson’s disease biomarker development.
