OBJECTIVES: Cytokines are critical role in the pathogenesis of periodontal diseases. Meteorin-like (Metrnl), a protein released in the oral mucosa, is a novel cytokine associated with various inflammatory diseases. This study aimed to evaluate levels of salivary and gingival crevicular fluid (GCF), interleukin - 1 beta (IL-1β), interleukin - 10 (IL-10), and Metrnl in periodontal disease. MATERIALS AND METHODS: It was formed three groups of 20 individuals each: the healthy, gingivitis, and periodontitis (Stage III, Grades A and B) groups. The enzyme-linked immunosorbent assay method measured IL-1β, IL-10, and Metrnl levels in salivary and GCF samples. Clinical periodontal measurement including probing pocket depth (PD), clinical attachment loss (CAL), plaque index (PI), gingival index (GI) and percentage of bleeding on probing (%BOP)
and biochemical parameters were evaluated using statistical analysis. RESULTS: Salivary concentrations and GCF total amount of IL-1β were significantly higher in the periodontal disease groups (p <
0.001). There was no significant difference among the groups in either salivary concentrations or GCF total amount of IL-10 (p >
0.05). Salivary Metrnl concentrations were significantly lower in the periodontitis group (p = 0.002). Salivary Metrnl concentrations had significant negative correlations with %BOP, PD, and CAL (p <
0.05). GCF total amount of Metrnl had significant negative correlations with GCF total amount of IL-1β (p = 0.03). The receiver operating characteristics curve showed: area under the curve (AUC) = 0.731 for salivary Metrnl concentrations to discriminate periodontitis from periodontal health and gingivitis. CONCLUSION: Based on the findings of this study, Metrnl, as an immunoregulatory cytokine, may have an important relationship with periodontitis. Additional studies are needed to fully elucidate the functional effect of Metrnl in periodontal disease. CLINICAL RELEVANCE: Background In knock-out experimental studies, it has been reported that Metrnl acts as an inflammation-related immunoregulatory cytokine. The findings relating it to inflammatory diseases support the idea that Metrnl may play a role in the pathogenesis of a variety of inflammatory diseases. ADDED VALUE OF THIS STUDY: Although Metrnl is a protein abundantly secreted in the oral mucosa, to the authors' knowledge there has been no study evaluating it in gingivitis and periodontitis, inflammatory diseases. In this study, the levels of Metrnl in oral fluids, such as GCF and saliva, were examined in the presence of different periodontal diseases. CLINICAL IMPLICATIONS: Metrnl can be useful in distinguishing periodontal destruction from periodontal health.