A meta-study of the microbiome and related dysfunction of the brain reveals distinct microbial signatures in the microbiota-gut-brain axis

The gut microbiome has emerged as a potential contributor to neurological disorders, with growing evidence linking microbial alterations to conditions such as Alzheimer's disease (AD), Parkinson's disease (PD), and autism spectrum disorder (ASD). However, a comprehensive understanding of shared and distinct microbial signatures across these disorders remains elusive. In this meta-analysis, we re-analyzed 31 16S rRNA gene amplicon sequencing datasets to investigate gut microbiome alterations in AD, PD, and ASD. Using a unified bioinformatic pipeline and robust statistical approaches, we identified both common and disorder-specific microbial signatures. While alpha diversity was significantly altered only in PD, beta diversity analysis revealed consistent compositional changes across all disorders. The genera Blautia and Bacteroides emerged as shared markers, showing differential abundance in AD, PD, and ASD, albeit with varying directions of change. PD exhibited the most distinct microbial profile, with 19 genera showing PD-specific alterations, including enrichment of Akkermansia and depletion of Faecalibacterium . Network analysis revealed complex, disorder-specific patterns of microbial interactions, with PD showing the highest number of altered microbial associations. These findings provide a nuanced picture of gut microbiome alterations across neurological disorders, highlighting potential common mechanisms and disease-specific signatures that may contribute to pathogenesis or serve as diagnostic biomarkers.