SUMMARY
# Gut-Brain Axis Pathogenesis in Parkinson's Disease — Mechanism and Intervention
## Background and Rationale
Parkinson's disease (PD) affects over 10 million people worldwide, with mounting evidence supporting the gut-brain axis as a critical pathway in disease pathogenesis. Recent studies demonstrate that α-synuclein pathology begins in the enteric nervous system years before motor symptoms manifest, suggesting that gut microbiome dysbiosis may trigger the cascade leading to neurodegeneration.
METHODOLOGY NOTES
Phase 1 (Months 1-12): Recruit and characterize 400 participants (n=150 prodromal PD, n=150 early PD, n=100 controls). Collect baseline fecal samples for 16S rRNA and metagenomic sequencing using Illumina NovaSeq platform. Quantify α-synuclein levels in stool and plasma via Simoa ultrasensitive immunoassays. Perform structural and functional MRI including vagus nerve tractography and substantia nigra neuromelanin imaging. Conduct DaTscan SPECT imaging and comprehensive clinical assessment (MDS-UPDRS, Montreal Cognitive Assessment, constipation severity scales). Phase 2 (Months 13-18): Longitudinal monitoring with sample collection every 3 months to establish temporal relationships between microbiome changes and biomarker progression. Phase 3 (Months 19-36): Randomized, double-blind, placebo-controlled intervention trial. Stratify participants based on dysbiosis severity and randomize to receive either personalized probiotic therapy (containing Lactobacillus plantarum, Bifidobacterium l