Gut microbiota analysis in diabetic mice with periodontitis

This study aimed to investigate the composition and alterations of gut microbiota in mice with comorbid diabetes and periodontitis.

A total of 40 six-week-old male db/db and db/m mice were divided into four groups (n = 10 per group): healthy control group, periodontitis group, diabetes group, and diabetes with periodontitis group. Fasting blood glucose (FBG) and oral glucose tolerance test (OGTT) were measured in all four groups to confirm the reliability of the diabetes model. Periodontitis was induced by silk thread ligation, and alveolar bone resorption was assessed using micro-computed tomography (Micro-CT) scanning. Fecal samples were collected from the four groups of mice, and the composition and structure of the gut microbiota were analyzed using 16S ribosomal DNA (16S rDNA) sequencing. Simultaneously, blood samples were collected and centrifuged to obtain serum for the measurement of blood biochemical parameters and inflammatory cytokines.

Compared with the db/m group, the db/m + PD group showed no significant differences in fasting blood glucose and the area under the oral glucose tolerance test curve (AUC). In contrast, compared with the db/db group, the db/db + PD group exhibited significantly elevated fasting blood glucose and the area under the oral glucose tolerance test curve. Relative to the db/m group, the db/m + PD group demonstrated a significant increase in C-reactive protein (CRP). Compared with the db/db group, the db/db + PD group showed high density lipoprotein cholesterol (HDL-C) significantly reduced and Interleukin-10 (IL-10) significantly increased. Pancreatic histology revealed marked islet morphological alterations in both db/db and db/db + PD groups. Significant alveolar bone loss was observed in db/m + PD and db/db + PD groups, with pronounced inflammatory infiltration on periodontal histology, most severe in db/db + PD group. Alpha and beta diversity analyses indicated notable changes in microbial richness and community structure across the four groups. The gut microbiota dysbiosis index was significantly higher in the three experimental groups than in the db/m group. Intergroup comparisons revealed extensive compositional differences at both phylum and genus levels.

Our results showed that the degree of alveolar bone resorption and the microbial dysbiosis index (MDI) in the db/db + PD group were significantly higher than those in the db/m, db/m + PD, and db/db groups. Meanwhile, the destruction of pancreatic β cells and periodontal tissues was most severe in the db/db + PD group, and the structure and richness of the gut microbiota in this group were also markedly different from those in the other three groups. Diabetes and periodontitis exerted synergistic effects, inducing and exacerbating gut microbiota dysbiosis in mice, which was closely associated with abnormal blood glucose levels, periodontal inflammation, and alveolar bone resorption. These findings suggest that the gut microbiota may serve as a critical target mediating the bidirectional interaction between diabetes and periodontitis.