Salivary glutathione peroxidase-1 levels in periodontitis

BACKGROUND Periodontitis consists of a chronic inflammatory disease of the periodontal tissue. In addition to inflammation, oxidation is also involved in periodontitis. Glutathione peroxidase (GPx) is an antioxidant enzyme. There are 8 forms of GPx (GPx 1-8) and GPx-1 is the most abundant. The comparison of salivary GPx-1 levels in patients with periodontitis and periodontally healthy subjects has been explored in small sample size studies (the largest including 101 subjects) and the results are contradictory. AIM To compare salivary GPx-1 concentrations in subjects with and without periodontitis in a study with a larger sample size. In addition, novel aims were exploring the possible association of salivary GPx-1 concentrations with periodontitis by a regression analysis and determining the capability of salivary GPx-1 concentrations to predict the diagnosis of periodontitis by a receiver operating characteristic (ROC) analysis. METHODS Observational and prospective study including subjects with and without periodontitis. Salivary samples were taken to determine GPx-1 concentrations. A multivariate logistic regression analysis was performed to determine whether salivary GPx-1 levels were independently associated with periodontitis. A ROC analysis was carried out to determine the capability for the diagnosis of periodontitis by salivary GPx-1 concentrations. RESULTS We found lower salivary GPx-1 concentrations in 57 subjects with periodontitis than in 86 without periodontitis. We found that salivary GPx-1 concentrations showed an area under the curve for periodontitis diagnosis of 76% (95%CI: 68%-83%; P < 0.001) in ROC analysis, and that salivary GPx-1 levels < 1214 pg/mL showed an independent association with periodontitis (odds ratio: 6.25; 95%CI: 2.844-13.717; P < 0.001) in regression analysis. CONCLUSION To our knowledge, our series has the largest sample size on salivary GPx-1 concentrations in periodontitis. Novel findings of our study were that salivary GPx-1 levels were able to diagnose periodontitis and were independently associated with periodontitis. However, our preliminary study has some limitations as there were significant differences in age between subjects with and without periodontitis, other antioxidant enzymes or total antioxidant capacity were not assessed, other biological samples were not analyzed, and GPx-1 genetic variations were not studied. Nevertheless, we think that the results of our study could encourage further research on the role of salivary biomarkers concentrations (as GPx-1) in the management of periodontitis.