Association of human gut microbiota with Alzheimer’s disease pathogenesis: An exploratory clinical study

The relationship between Alzheimer’s disease (AD) onset and the brain–gut axis has garnered increasing attention. This study aimed to investigate the potential role of the brain–gut axis in AD pathogenesis, with a specific focus on microbiota composition. This exploratory study enrolled 10 patients with AD and 13 healthy adults, grouped by age (≤30 years, 31–40 years, and ≥41 years). Fecal samples were collected, and 16S rRNA gene sequencing was employed to analyze differences in fecal microbiota composition at the bacterial species level. Certain bacterial species appeared more abundant in the AD group (e.g., Ruminococcus inulinivorans and Ruminococcus torques ), while others were relatively more abundant in healthy adults (e.g., Prevotella vulgatus 1 , Bacteroides wexlerae , Clostridium butyricum , and Alistipes rectalis ). However, these differences were not statistically significant, likely because of the limited sample size. These findings suggest that fecal microbiota composition may differ between patients with AD and healthy individuals, with a potential intermediate group at risk of AD development. Larger-scale clinical studies are necessary to further elucidate the bacterial species associated with AD pathogenesis, potentially enabling the use of microbiota composition as a screening tool to distinguish between healthy individuals, patients with AD, and those with preclinical AD.