# Shotgun metagenomic analysis of the tongue-coating microbiome reveals oral microbes and their functions in older adults with dementia

## TL;DR

This study uses metagenomic sequencing to find oral microbiome differences in older adults with dementia and healthy controls, identifying potential biomarkers for cognitive decline.

## Contribution

The study identifies specific oral microbes and metabolic pathways associated with dementia severity in older adults.

## Key findings

- Veillonella parvula is enriched in dementia patients, while Lautropia dentalis is more abundant in healthy controls.
- Dementia group shows increased histidine degradation and biotin biosynthesis, while ubiquinol biosynthesis is higher in healthy controls.
- Microbial taxa and pathways like Prevotella pleuritidis and glutamine/glutamate biosynthesis correlate with cognitive performance.

## Abstract

Dementia poses a growing burden in the aging population, prompting the search for noninvasive biomarkers for early detection.

We performed shotgun metagenomic sequencing of tongue-coating samples from older adults with dementia (n = 30) and cognitively healthy controls (n = 28) to identify oral microbiome signatures.

The analysis revealed distinct microbial compositions associated with dementia, including an enrichment of Veillonella parvula in dementia patients, whereas Lautropia dentalis was more abundant in healthy controls. We also identified functional alterations in the microbiome in the dementia group, including increased abundance of the histidine degradation and biotin biosynthesis pathways, whereas ubiquinol biosynthesis was more abundant in the healthy control group. The abundance of several microbial taxa and metabolic pathways were correlated with scores on the Korean Mini-Mental State Examination 2nd edition (K-MMSE), a clinical assessment of dementia severity. Prevotella pleuritidis, Actinomyces sp., Leptotrichia buccalis, and Leptotrichia sp. were positively correlated, whereas Oribacterium parvum was negatively associated with K-MMSE scores. Among the metabolic pathways, glutamine/glutamate biosynthesis was positively correlated with cognitive performance.

These results suggest that specific oral taxa and their metabolic functions are associated with cognitive status and may reflect underlying neurodegenerative processes.