Comparative Analysis of Oral Microbiome in Indian Type 2 Diabetes Mellitus (T2DM) and Periodontitis Cohorts

Type 2 diabetes mellitus (T2DM) and periodontitis are highly prevalent immune-inflammatory diseases that interact bidirectionally. However, how early-onset T2DM, periodontitis, and adverse lifestyle behaviors collectively remodel the gingival plaque microbiome at the ecological network level remains poorly understood in Indian populations.

A cross-sectional 16S rRNA gene (V3-V4) sequencing study was conducted on supragingival and subgingival plaque from 60 adults (30-40 years) recruited in Mumbai. Participants were categorized as healthy (H, n = 10), periodontitis (P, n = 10), T2DM (n = 20), and T2DM with periodontitis (T2DM_P, n = 20). Comprehensive demographic, anthropometric, metabolic, periodontal, dietary, lifestyle, and oral hygiene data were collected. Sequence data were processed using QIIME2-DADA2, followed by diversity, differential abundance, and genus-level co-occurrence network analyses (Spearman |r| ≥ 0.6, FDR < 0.05; core prevalence ≥ 70%).

α-diversity showed no marked depletion across groups, whereas Bray-Curtis β-diversity revealed significant global separation, with maximal dissimilarity between H and T2DM_P. Healthy individuals with favorable lifestyle behaviors harbored scaffold-forming taxa such as Corynebacterium matruchotii, Lautropia mirabilis, and Capnocytophaga spp. In contrast, P and T2DM_P groups showed enrichment of proteolytic, inflammation-adapted genera including Porphyromonas, Tannerella, Treponema, Fretibacterium, Peptostreptococcus, and Selenomonas. Network analysis revealed a shift from commensal-rich modular networks to densely connected, keystone-centered disease modules.

Early-onset T2DM and periodontitis, particularly under adverse lifestyle behaviors, reorganize plaque microbial composition and interaction architecture rather than depleting diversity, highlighting plaque-based keystone taxa and networks as targets for microbiome-informed risk stratification and integrated medical-dental-lifestyle interventions.