Oral Microbial and Metabolic Alterations in Patients With Oral Lichen Planus Concomitant With Type 2 Diabetes Mellitus.

The present study aimed to comprehensively characterize the oral microbiome and metabolic profiles in patients with oral lichen planus (OLP) concomitant with type 2 diabetes mellitus (T2DM), and to explore the potential mechanisms driving the co-occurrence. This was a cross-sectional observational study. A total of 60 participants were enrolled, including 20 normal controls, 20 patients with OLP alone (OLP group), and 20 patients with both OLP and T2DM (OLP_DM group). Salivary samples were subjected to 16S rRNA sequencing and untargeted metabolomics to assess microbiological and metabolic differences across the groups. Spearman's correlation analysis was used to evaluate associations between clinical characteristics and microbial or metabolic features. Alpha diversity (Chao1 index) was significantly reduced in both disease groups compared to the controls, while beta diversity analysis revealed no remarkable separation among groups. At the genus level, the abundance of Pseudomonas was elevated in the OLP_DM group relative to both the OLP and control groups, and positively correlated with lesion severity. Metabolomic analysis revealed significantly lower levels of limonin and higher levels of thymine and epinephrine in the OLP_DM group compared to the OLP. Limonin was negatively correlated with lesion severity, whereas thymine and epinephrine showed positive correlations with both lesion severity and pain scores. The study provides comprehensive evidence of oral microbial dysbiosis and metabolic disturbances in patients with OLP concomitant with T2DM. The findings suggest an interplay between specific bacterial populations and metabolic alterations in the progression and severity of OLP concomitant with diabetes.