Characterization of the intestinal microbial profile in mild cognitive impairment and Alzheimer's disease.

UNLABELLED: Alzheimer's disease (AD) and mild cognitive impairment (MCI) are major contributors to dementia, with growing prevalence in Latin America. Evidence suggests that gut microbiota alterations may influence neurodegeneration, but data on Hispanic population are lacking.

OBJECTIVE

Characterize gut microbiota in individuals with AD, MCI, and controls in the Dominican Republic, exploring clinical, demographic, and dietary associations.

METHODS

Prospective-translational study including 88 participants aged ≥60 years. Performed clinical, cognitive, and functional assessments. Stool samples analyzed using 16S rRNA gene sequencing. Bioinformatic processing using Quantitative Insights into Microbial Ecology Version 2 (QIIME2) and R. Alpha and beta diversity, taxonomy, and differential abundance were evaluated. Dietary influences were assessed using PERMANOVA.

RESULTS

No significant differences in alpha diversity (Shannon index 4-5, Simpson index 0.94-0.99, p>0.05) or beta diversity (p>0.05) were observed between groups. Firmicutes (51.9%) and Bacteroidota (34.1%) dominated the microbiota. Higher Desulfobacterota abundance in MCI and AD (0.54 and 0.61%, respectively, vs. 0.34% in controls; p<0.05). The Firmicutes/Bacteroidota ratio was lower in men with MCI (1.09) compared to controls and AD (1.70). MCI and AD were associated with increased levels of the genera Bilophila, Odoribacter, and Parabacteroides (p<0.05) and reduced levels of Mitsuokella and Eubacterium ruminantium. Dietary interactions, e.g., mango, lettuce, and carrot, influenced specific taxa (p<0.05).

CONCLUSION

This study pioneers gut microbiota characterization in AD and MCI in the Dominican Republic, identifying microbial alterations in cognitive impairment and highlighting regional dietary and ethnic factors. Longitudinal and multi-omics studies are warranted to clarify causality and therapeutic potential.