Gut microbiome dysbiosis as a convergent contributor of neurodegenerative disease: unifying mechanistic pathways and emerging precision microbiome-directed therapies

Neurodegenerative diseases (NDDs) are increasingly recognized as systemic disorders shaped by the microbiota-gut-brain axis. Within this framework, gut microbiome dysbiosis is better defined by reproducible modules of functional imbalance than by isolated taxonomic shifts. These aberrant microbial networks transmit peripheral signals to the central nervous system through three interconnected routes: immune-inflammatory activation, metabolic reprogramming, and aberrant vagal and humoral neural transmission. Because peripheral inputs may converge on shared downstream pathways within the brain, they can drive mitochondrial decompensation, oxidative stress, and pathological protein aggregation. This review integrates current evidence into a conceptual framework describing how host-microbiome interactions may contribute to neurodegeneration and then critically appraises microbiome-targeted interventions, including dietary modulation, next-generation probiotics, and fecal microbiota transplantation. Moving from correlation-based reasoning toward a causal, mechanism-driven account, we argue for patient stratification and outline a path toward precision microecological therapies against NDDs.