Evaluation of salivary interleukin-17 and developmental endothelial locus-1 in patients with periodontitis with and without type 2 diabetes mellitus.

Background: Bidirectional positive relationship between periodontitis and type 2 diabetes mellitus (T2DM) has been recognized, interleukin 17 (IL-17) and developmental endothelial locus-1 (Del-1) are proposed to play roles in periodontitis and T2DM. This study aims to investigate the association of IL-17 and Del-1 in patients with periodontitis with and without T2DM by measuring their salivary levels.

Methods: A total of 80 participants were enrolled in a cross-sectional study and divided into healthy (H, n = 27), periodontitis (P, n = 29) and periodontitis with diabetes (PDM, n = 24) groups based on their periodontal and diabetic examination results. Periodontal parameters (plaque index [PI], bleeding on probing [BOP], probing depth [PD], and clinical attachment level [CAL]) as well as diabetic parameters (fasting plasma glucose [FG] and glycated hemoglobin [HbA1c]) were documented and unstimulated saliva was collected. Salivary IL-1β, active-matrix metalloproteinase-8 (aMMP-8), tumor necrosis factor-α (TNF-α), IL-6, IL-8, IL-17, and Del-1 were determined through enzyme-linked immunosorbent assay (ELISA) and their relationships with periodontal and diabetic parameters were examined.

Results: The periodontitis and periodontitis with diabetes groups showed significantly higher levels of IL-17 and lower levels of Del-1 compared with healthy group. The periodontitis with diabetes group exhibited higher levels of IL-17 and lower levels of Del-1 compared with the periodontitis group. After correlation analysis, there were significant correlations between salivary IL-17 and Del-1 and clinical parameters, IL-17 and Del-1 were correlated with PD (r = 0.36, -0.39, p < 0.01), CAL (r = 0.40, -0.42, p < 0.01) and BOP (r = 0.35, -0.37, p < 0.01), they were correlated with FG (r = 0.26, -0.25, p < 0.05) and HbA1c (r = 0.28, -0.40, p < 0.05). Positive relationships were observed between IL-17 and IL-1β and between IL-17 and aMMP-8 (r = 0.80, 0.77, p < 0.01), while Del-1 exhibited negative correlations with IL-1β and aMMP-8 (r = 0.59, 0.69 p < 0.01). Comparison between IL-17 and Del-1 confirmed an inverse relationship (r = -0.71, p < 0.01). Salivary Del-1 levels in the older group were lower compared with young group across the H, P and PDM groups, although these differences were not statistically significant (p > 0.05).

Conclusions: Salivary IL-17 and Del-1 levels in the periodontitis with diabetes group showed significant changes compared with the periodontitis group, they exhibited an inverse relationship and were both correlated with periodontal parameters (PD, CAL, and BOP) and diabetic parameters (FG and HbA1c).

Plain language summary: Periodontitis and type 2 diabetes mellitus (T2DM) are two common diseases all over the world, some inflammatory mediators (interleukin 17 [IL-17] and developmental endothelial locus-1 [Del-1]) regulate neutrophil production, recruitment and clearance when the body becomes infected and believed to be involved in the progress of diseases of periodontitis and diabetes. In this study, we enrolled healthy subjects, patients with periodontitis, patients with periodontitis and diabetes. We performed dental examinations and evaluated their blood glucose levels, collected their saliva, and detected IL-17 and Del-1 levels in their saliva. We found both patients with periodontitis and patients with periodontitis and diabetes showed higher IL-17 levels and lower Del-1 levels compared with healthy subjects. Patients with periodontitis and diabetes showed higher IL-17 levels and lower Del-1 levels compared with patients with periodontitis. Salivary IL-17 and Del-1 levels were both correlated with dental examination results and blood glucose levels, and salivary IL-17 and Del-1 displayed an inverse relationship.