Objective To isolate Parkinson’s disease (PD)-specific gut dysbiosis from motility-related changes, this study compared the fecal microbiota of PD patients with constipation (PDC, n=20) against a functional constipation (FC, n=15) control group. Methods High-throughput 16S rRNA gene sequencing and functional prediction were performed on fecal samples. Diversity metrics and taxonomic compositions were analyzed to identify PD-specific signatures. Results The PDC group exhibited significantly higher microbial richness than the FC group (P = 0.01). Despite structural similarities driven by the shared constipation phenotype (ANOSIM R = 0.084), PDC was distinguished by specific compositional shifts, including the enrichment of Paraprevotella , Akkermansia , unclassified Ruminococcaceae , and Campylobacter . Functionally, the PDC microbiome showed significant deficits in tyrosine and glutathione metabolism pathways (P0.05), indicating compromised dopamine precursor synthesis and antioxidant defense. Conclusion By controlling for colonic transit time, this study identified specific microbial alterations and metabolic deficits in PD independent of constipation. These findings support a “gut-first” etiology linked to specific pathobionts and barrier compromise.
Yang et al. (2026) studied this question.