Could Salivary Kynurenine Pathway Metabolites Be A Biomarker Of Psychological Stress In Periodontitis?

Abstract

Background: In this study, we investigated the relationship between cortisol levels and kynurenine (KYN) metabolism changes in saliva samples of individuals with periodontitis (PD) and periodontal parameters.

Methods: Saliva samples were collected from 20 periodontitis patients and 20 periodontally healthy control individuals. Samples were analyzed for cortisol, interferon-gamma (IFN-γ), Tryptophan (TRP), KYN, kynurenic acid (KYNA), and quinolinic acid (QA) by were measured with an Elisa kit. Indoleamine-pyrrole 2,3-dioxygenase (IDO) activity was calculated using the KYN/TRP ratio. Clinical periodontal parameters (plaque index (PI), probing pocket depth (PPD), gingival recession (GR), clinical attachment loss (CAL), and bleeding on probing (BOP)) were recorded. 

Results: Clinical parameters were significantly higher in the periodontitis group (p<0.001). Salivary Cortisol, IFN-γ, TRP, KYN, KYNA, QA levels, and KYN/TRP ratio were significantly higher in the periodontitis group than in the control group (p<0.001). PPD, BOP, PI, and CAL significantly positively correlated with salivary cortisol levels. Also, salivary cortisol levels are significantly positively correlated with salivary KYN/TRP ratio.

Conclusion: Our findings suggest that the stress marker cortisol plays a role in the local and tryptophan-kynurenine metabolism of periodontal inflammation.

Keywords: Cortisol, Kynurenine, Periodontitis, Stress.