A study on oral microbiome characteristics and differences in epilepsy adults with depressive symptoms based on 16S...

Depression is a common comorbidity in epilepsy, but its underlying mechanisms are poorly understood. Although the "oral-brain axis" has gained increasing attention in neuropsychiatric disorders, oral microbial characteristics in epileptic patients with depressive symptoms remain largely unexplored. This study aimed to compare the oral microbial composition between epileptic patients with and without depressive symptoms and to identify bacterial genera and functional pathways that may be associated with depressive symptoms.

The study included 59 adult patients with epilepsy. Based on the Neuropsychiatric Depression Scale for Epilepsy (NDDI-E) scores, the participants were divided into two groups: patients with epilepsy with depressive symptoms (EDS, NDDI-E > 12, n = 28) and patients with epilepsy alone (EP, NDDI-E ≤ 12, n = 31). Tongue swab samples were collected and analyzed by 16S rRNA MiSeq sequencing. Firth-corrected logistic regression analysis was performed to identify potential factors associated with depressive symptoms in epilepsy.

No significant differences were found between the two groups in terms of general clinical data or oral microbial diversity (α- and β-diversity). Using an uncorrected p value < 0.05 as the screening criterion, microbial composition analysis revealed that Dialister and Olsenella were enriched in EDS, while Bacillus, Fusicatibacter, and [Eubacterium]_coprostanoligenes_group were enriched in EP. LEfSe analysis further suggested that Dialister and Bacillus were key differential genera with discriminatory capability. Based on PICRUSt2's functional prediction results, the predicted functional abundance annotated to the RIG-I-like receptor signaling pathway was higher in the EDS group than in the EP group. Multivariate Firth-corrected logistic regression analysis showed that the abundance of Dialister remained associated with EDS (OR = 1.646, 95% CI: 1.007-2.896, p = 0.047), after adjusting for potential confounding factors.

This study utilizing 16S rRNA sequencing elucidates alterations in the oral microbiome associated with epilepsy and concurrent depressive symptoms. Significantly, the enrichment of Dialister is independently correlated with depressive symptoms following adjustment for confounding variables, indicating its potential as a microbial biomarker. Functional prediction analysis further indicated that the associated oral microbial alterations may involve innate immune-related functional characteristics, particularly the RIG-I-like receptor signaling pathway. These findings provide new clues for further investigating the potential association between oral microbiota and epilepsy with depressive symptoms.