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

Abstract

IntroductionDementia poses a growing burden in the aging population, prompting the search for noninvasive biomarkers for early detection.Materials and methodsWe 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.ResultsThe 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.ConclusionsThese results suggest that specific oral taxa and their metabolic functions are associated with cognitive status and may reflect underlying neurodegenerative processes.