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Altered Gut Microbiota in Adults with Subjective Cognitive Decline: The SILCODE Study
1Department of Neurology, Xuanwu Hospital of Capital Medical University, Beijing, China.
Background:
Subjective cognitive decline (SCD) is the earliest symptomatic manifestation of preclinical Alzheimer's disease (AD). Gut microbiota may serve as a susceptibility factor for AD. Altered gut microbiota has been reported in patients with mild cognitive impairment (MCI) and AD dementia. However, whether gut microbial compositions changed in SCD remains largely unknown.
Objective:
To characterize the gut microbiota in SCD.
Methods:
In this study, a total of 105 participants including 38 normal controls (NC), 53 individuals with SCD, and 14 patients with cognitive impairment (CI) were recruited. Gut microbiota of all participants isolated from fecal samples were investigated using 16S ribosomal RNA (rRNA) Illumina Miseq sequencing technique. The gut microbial compositions were compared among the three groups, and the association between altered gut microbiota and cognitive performance was analyzed. To validate the alteration of gut microbiota in SCD, we conducted amyloid positron emission tomography (PET) in selected participants and further compared the gut microbiota among subgroups.
Results:
The abundance of phylum Firmicutes, class Clostridia, order Clostridiales, family Ruminococcaceae, and genus Faecalibacterium showed a trend toward a progressive decline from NC to SCD and CI. Specifically, the abundance of the anti-inflammatory genus Faecalibacterium was significantly decreased in SCD compared with NC. In addition, altered bacterial taxa among the three groups were associated with cognitive performance. The findings were validated in SCD participants with positive amyloid evidence.
Conclusion:
The composition of gut microbiota is altered in individuals with SCD. This preliminary study will provide novel insights into the pathophysiological mechanism of AD.
Insights
Gut microbiota composition changes in individuals with subjective cognitive decline (SCD), a preclinical stage of Alzheimer's disease (AD). The anti-inflammatory genus Faecalibacterium was significantly decreased in SCD, suggesting a link between gut health and early AD.
Area of Science:
- Microbiome research
- Neuroscience
- Gastroenterology
Background:
- Subjective cognitive decline (SCD) is the earliest indicator of preclinical Alzheimer's disease (AD).
- Gut microbiota alterations are implicated in mild cognitive impairment (MCI) and AD dementia.
- The specific changes in gut microbial composition in individuals with SCD are not well understood.
Purpose of the Study:
- To characterize the gut microbiota in individuals experiencing subjective cognitive decline.
- To investigate the relationship between gut microbial composition and cognitive performance in early AD stages.
Main Methods:
- 16S rRNA Illumina Miseq sequencing of fecal samples from 105 participants (38 normal controls, 53 SCD, 14 cognitive impairment).
- Comparative analysis of gut microbial compositions across the three groups.
- Association analysis between altered gut microbiota and cognitive performance, with amyloid PET validation in selected SCD individuals.
Main Results:
- A progressive decline in the abundance of Firmicutes, Clostridia, Clostridiales, Ruminococcaceae, and Faecalibacterium was observed from normal controls to SCD and cognitive impairment groups.
- The anti-inflammatory genus Faecalibacterium was significantly reduced in individuals with SCD compared to normal controls.
- Altered bacterial taxa were associated with cognitive performance, and findings were consistent in SCD participants with positive amyloid evidence.
Conclusions:
- Gut microbiota composition is altered in individuals with subjective cognitive decline.
- These alterations may offer novel insights into the pathophysiological mechanisms of Alzheimer's disease.
- This study highlights the potential role of the gut microbiome in the early stages of AD.
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