Association between Gut Microbiota with Mild Cognitive Impairment and Alzheimer's Disease in a Thai Population
Pagakrong Wanapaisan1, Mallika Chuansangeam2, Saifon Nopnipa3
1Department of Microbiology, Faculty of Pharmacy, Mahidol University, Bangkok, Thailand.
Background:
Mild cognitive impairment (MCI) and Alzheimer's disease (AD) are common in older adults. Much recent work has implicated the connection between the gut and the brain via bidirectional communication of the gastrointestinal tract and the central nervous system through biochemical signaling. Altered gut microbiota composition has shown controversial results based on geographic location, age, diet, physical activity, psychological status, underlying diseases, medication, and drug use.
Objectives:
This study aimed to investigate the relationships of gut microbiota with MCI and AD.
Methods:
16S metagenome profiles from stool collection of participant groups (normal; n = 20, MCI; n = 12, AD; n = 20) were analyzed. The diagnosis of cognitive conditions was made by standard criteria consisting of clinical interviews, physical examinations, cognitive assessments, laboratory examinations, and neuroimaging by both structural neuroimaging and amyloid positron emission tomography scans. Correlations between medical factors with food frequency and the fecal microbiome were elucidated.
Results:
A significant difference at the operational taxonomic unit level was observed. The significantly higher abundance of bacteria in nondementia patients belonged to the Clostridiales order, including Clostridium sensu stricto 1 (p < 0.0001), Fusicatenibacter (p = 0.0007), Lachnospiraceae (p = 0.001), Agathobacter (p = 0.021), and Fecalibacterium (p < 0.0001). In contrast, Escherichia-Shigella (p = 0.0002), Bacteroides (p = 0.0014), Holdemanella (p < 0.0001), Romboutsia (p = 0.001), and Megamonas (p = 0.047) were the dominant genera in the AD group. Left and right hippocampus and right amygdala volumes were significantly decreased in the AD group (p < 0.001) and significantly correlated with the groups of bacteria that were significantly different between groups.
Conclusion:
There was a relationship between the composition of the gut microbiome and neurodegenerative disorders, including MCI and AD. Reduction of Clostridiaceae and increases in Enterobacteriaceae and Bacteroides were associated with persons with MCI and AD, consistent with previous studies. The altered gut microbiome could be potentially targeted for the early diagnosis of dementia and the reduction of AD risk.
Insights
Gut microbiome alterations are linked to mild cognitive impairment (MCI) and Alzheimer's disease (AD). Reduced beneficial bacteria and increased harmful bacteria correlate with cognitive decline, suggesting potential diagnostic and therapeutic targets.
Area of Science:
- Neuroscience
- Microbiology
- Gastroenterology
Background:
- Mild cognitive impairment (MCI) and Alzheimer's disease (AD) are prevalent neurodegenerative conditions in aging populations.
- Emerging research highlights the gut-brain axis, a bidirectional communication pathway between the gastrointestinal tract and the central nervous system.
- Gut microbiota dysbiosis has been inconsistently associated with various health conditions, influenced by numerous lifestyle and environmental factors.
Purpose of the Study:
- To investigate the specific relationships between gut microbiota composition and the presence of MCI and AD.
- To identify bacterial taxa that differ significantly between healthy individuals, MCI patients, and AD patients.
Main Methods:
- Analysis of 16S rRNA gene sequencing data from fecal samples of 20 normal, 12 MCI, and 20 AD participants.
- Standard diagnostic criteria including clinical interviews, cognitive assessments, and neuroimaging (structural MRI, amyloid PET) were used to classify participants.
- Correlations were examined between medical factors, dietary habits (food frequency questionnaires), and the fecal microbiome composition.
Main Results:
- Significant differences in bacterial abundance were observed at the operational taxonomic unit level between cognitive groups.
- Nondemented individuals showed higher levels of Clostridiales (e.g., Clostridium sensu stricto 1, Fecalibacterium), while AD patients had dominant genera including Escherichia-Shigella and Bacteroides.
- Reduced hippocampal and amygdala volumes in the AD group significantly correlated with specific bacterial groups identified as different between the study cohorts.
Conclusions:
- A distinct gut microbiome composition is associated with neurodegenerative disorders like MCI and AD.
- The observed reduction in Clostridiaceae and increase in Enterobacteriaceae and Bacteroides in MCI and AD patients align with previous findings.
- Targeting the gut microbiome may offer a novel strategy for early dementia diagnosis and reducing Alzheimer's disease risk.
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