Salivary Apelin and Asprosin Levels in Periodontitis and Diabetes Mellitus and Their Relationship with Clinical Periodontal Parameters

Background/Objectives: Periodontitis and diabetes mellitus (DM) are chronic inflammatory conditions that share common biological mechanisms, including systemic inflammation and insulin resistance. Adipokines are considered key mediators in this interrelationship; however, the roles of many adipokines remain unclear. Apelin and asprosin are relatively novel adipokines that have not yet been sufficiently investigated in dentistry. Therefore, this study aimed to evaluate salivary apelin and asprosin levels in periodontally healthy individuals, patients with periodontitis, and patients with periodontitis + DM and to investigate their associations with clinical periodontal parameters. Methods: A total of 90 individuals were included in the study, comprising 30 periodontally healthy subjects, 30 with periodontitis, and 30 with periodontitis and DM. Clinical periodontal indices and body mass index (BMI) were measured for each participant. Unstimulated saliva was collected from each participant, and apelin and asprosin concentrations were analyzed using an enzyme-linked immunosorbent assay (ELISA). The normality of continuous variables was examined with the Shapiro–Wilk test. For non-normally distributed data, non-parametric procedures such as the Mann–Whitney U and Kruskal–Wallis tests were applied. Comparisons of categorical variables between groups were performed using Pearson’s chi-square or the Fisher–Freeman–Halton test. Associations between continuous parameters were assessed through Spearman’s rank correlation analysis. A significance threshold of 5% (p < 0.05) was adopted for all statistical evaluations. Results: No significant intergroup differences were detected for age, gender, or BMI. The healthy group exhibited significantly lower plaque index (PI), gingival index (GI), and probing depth (PD) scores compared with both periodontitis groups, and these differences reached statistical significance (p < 0.001).The median salivary apelin level in the periodontitis + DM group was significantly reduced relative to the healthy group (p = 0.009). However, salivary asprosin concentrations did not differ significantly among the groups (p = 0.053). Spearman’s correlation analysis revealed positive correlations between asprosin and PD and clinical attachment loss (CAL), whereas apelin showed negative correlations with these parameters. Conclusions: Salivary apelin may serve as a potential biomarker for distinguishing healthy individuals from those with diabetic periodontitis. The opposing correlation patterns indicate that apelin and asprosin may be differentially related to periodontal tissue breakdown. However, further longitudinal and mechanistic studies are required to clarify the biological significance of these associations.