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

Abstract 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.