The Gut Microbiome's Influence on Extra- Intestinal Diseases: A Cross-Sectional Analysis of Neurological and Autoimmune Disorders

The human gut microbiome, composed of trillions of microorganisms, plays a pivotal role in maintaining
health and influencing disease processes far beyond the gastrointestinal tract. Disruptions in microbial
balance, known as dysbiosis, have been increasingly associated with neurological and autoimmune
conditions through complex interactions involving microbial metabolites, immune modulation, and
neural pathways. This study investigated gut microbiome alterations in Alzheimer’s disease, Parkinson’s
disease, rheumatoid arthritis, and systemic lupus erythematosus using a cross-sectional design
involving 160 participants, including 120 patients and 40 matched healthy controls. Stool samples were
analyzed by 16S rRNA gene sequencing on the Illumina MiSeq platform, with bioinformatic assessment
conducted using the QIIME2 pipeline. Results showed pronounced dysbiosis in all patient groups, with
significant reductions in beneficial taxa such as Faecalibacterium prausnitzii and Bifidobacterium
species, alongside increased pro-inflammatory taxa, particularly Proteobacteria. Distinct microbial
patterns were observed between neurological and autoimmune disorders, including enrichment of
Enterobacteriaceae in neurological groups and Prevotella copri in autoimmune groups. These findings
suggest that gut microbial imbalances may contribute to extra-intestinal disease mechanisms and
provide a rationale for microbiome-based therapeutic interventions.