Gut Microbiome Changes in Preclinical Alzheimer's Disease

Area of Science:

• Neuroscience
• Microbiology
• Metabolism

Background:

• Alzheimer's disease (AD) is a progressive neurodegenerative disorder with poorly understood early biological changes.
• The preclinical stage of AD may involve gradual gut microbial and metabolic alterations.
• The gut microbiome is increasingly implicated in early AD pathogenesis via immune, metabolic, and gut-brain axis pathways.

Purpose of the Study:

• To review the evidence linking gut microbiota, short-chain fatty acids (SCFAs), microbial metabolism, and diet to early Alzheimer's disease pathology.
• To highlight knowledge gaps in understanding these relationships during the preclinical stage of AD.

Main Methods:

• Literature review of studies investigating the gut microbiome, SCFAs, metabolism, and diet in relation to early AD.
• Analysis of research on microbial composition changes (e.g., reduced SCFA-producers) in AD and mild cognitive impairment.
• Examination of dietary pattern influences (Mediterranean, DASH, Western) on gut microbiota and SCFA production.

Main Results:

• Reduced levels of SCFA-producing bacteria (e.g., Faecalibacterium, Roseburia) are observed in individuals with AD and mild cognitive impairment.
• Gut microbial alterations correlate with metabolic dysfunction, impaired gut barrier, and neuroinflammation.
• Dietary patterns significantly impact gut microbial profiles, with Western diets linked to lower diversity and increased inflammation, while Mediterranean/DASH diets promote beneficial microbes and SCFAs.

Conclusions:

• Gut microbiota, SCFAs, and associated metabolic activities represent potential early biomarkers and contributors to AD pathogenesis.
• Dietary interventions targeting the gut microbiome may offer a strategy for modulating early AD pathology.
• Further research is needed to elucidate the precise mechanisms and causal relationships between gut health and preclinical AD.