The Oral-Gut Microbiome-Brain Axis in Cognition

Area of Science:

• Neuroscience
• Microbiology
• Immunology

Background:

• Alzheimer's disease (AD) is a progressive neurodegenerative disorder impacting millions globally.
• The oral microbiome, a complex ecosystem, is increasingly recognized for its role in cognitive health.
• Oral microbiome dysbiosis is linked to systemic inflammation, blood-brain barrier disruption, and neuroinflammation, key factors in AD pathogenesis.

Purpose of the Study:

• To review the mechanisms connecting oral microbiome dysbiosis to cognitive decline via the oral-brain and oral-gut-brain axes.
• To explore the role of oral pathogens, virulence factors, and metabolic byproducts in neuroinflammation.
• To examine the influence of lifestyle and environmental factors on oral microbial diversity and cognitive outcomes.

Main Methods:

• Literature review of studies investigating the oral-brain and oral-gut-brain axes.
• Analysis of mechanisms involving oral pathogens (e.g., *Porphyromonas gingivalis*), virulence factors (LPS, gingipains), and microbial metabolites (SCFAs, peptidoglycans).
• Exploration of external factors (diet, hygiene, smoking, alcohol) affecting oral microbiome and cognition.

Main Results:

• Bidirectional communication between the oral cavity, gut, and brain occurs via neural, immune, and endocrine signaling.
• Oral pathogens and their products exacerbate neuroinflammation and systemic immune activation.
• Factors like diet, hygiene, and lifestyle significantly influence oral microbial composition and cognitive health.

Conclusions:

• The oral microbiome plays a critical role in maintaining systemic and neurological health.
• Interventions targeting the oral microbiome, such as probiotics, prebiotics, and dietary changes, show promise for supporting cognitive function and reducing AD risk.
• Further longitudinal research is necessary to fully understand the long-term impact of oral microbiome dysbiosis on cognition.