Study of gut microbiota alterations in Alzheimer’s dementia patients from Kazakhstan Original paper

What was studied?

This original research article investigated gut microbiota alterations in Alzheimer’s disease (AD), focusing on how microbial signatures differ between patients with AD and healthy seniors. The authors used 16S rRNA sequencing to characterize microbial communities and identify disease-associated taxa. This microbiome signatures comparison provides insight into how gut microbial shifts—particularly those involving Acidobacteriota, Verrucomicrobiota, Prevotella, Akkermansia, and Bifidobacterium—may contribute to AD-related metabolic and inflammatory processes. The study also explored correlations between microbial taxa, serum biomarkers such as adiponectin and CRP, and AD severity.

Who was studied?

The study included 41 AD patients and 43 cognitively healthy seniors aged 55 years or older from Nur-Sultan, Kazakhstan. All AD diagnoses followed DSM-IV and NINCDS-ADRDA criteria, confirmed by neurologists. Cognitive status was quantified using MMSE and CDT testing. Participants had similar demographic and clinical backgrounds, and major comorbidities were evenly distributed, ensuring that microbiome differences reflected disease status rather than underlying health disparities. Fecal samples were self-collected, stored at –20°C, and sequenced; blood samples were also analyzed for metabolic and inflammatory biomarkers.

Most important findings

The study revealed distinct microbial shifts in AD patients. At the phylum level, AD microbiomes displayed higher abundance of Acidobacteriota, Verrucomicrobiota, Synergistota, Planctomycota, and Latescibacterota, while core phyla such as Firmicutes and Bacteroidota remained dominant in both groups. Genus-level analysis showed depletion of Bifidobacterium, Roseburia, Faecalibacterium, Lactobacillaceae genera, Monoglobus, Tyzzerella, and Erysipelotrichaceae UCG-003, all known producers of short-chain fatty acids (SCFAs) and anti-inflammatory metabolites. Conversely, Akkermansia, Prevotella, Alloprevotella, Ruminococcus, and Flavobacterium were enriched in AD patients. Microbiome–host metabolic interactions were prominent. Elevated adiponectin in AD correlated positively with Actinobacteria, Oscillospiraceae, Prevotella, Christensenellaceae R-7, and negatively with Faecalibacterium, suggesting altered SCFA metabolism. CRP correlated with Firmicutes, Acidobacteriales bacterium, Castellaniella, Lachnospiraceae, and Klebsiella pneumoniae, indicating links between dysbiosis and chronic inflammation. Several taxa, including Bacteroides, Proteobacteria, Clostridia, and Collinsella, were associated with AD severity, showing progressive shifts in microbial signatures with worsening clinical status.

Key implications

The findings highlight a distinct regional microbiome signature of AD within the Kazakh population, differing in several aspects from Chinese and U.S. cohorts. Loss of SCFA-producing bacteria and enrichment of taxa linked to mucin degradation, pro-inflammatory pathways, and metabolic dysregulation suggest that gut microbiota may influence AD pathology through immune activation and altered lipid and glucose metabolism. Elevated adiponectin and its strong microbial correlations further underscore microbiota–metabolic interplay. These insights support the growing concept of a microbiome-driven component in neurodegeneration and encourage the development of microbiome-based biomarkers and interventions, particularly those tailored to regional and ethnic differences.

Citation

Kaiyrlykyzy A, Kozhakhmetov S, Babenko D, et al. Study of gut microbiota alterations in Alzheimer’s dementia patients from Kazakhstan. Scientific Reports. 2022;12:15115. doi:10.1038/s41598-022-19393-0