Objective: To compare tumour necrosis factor-alpha (TNF) and interleukin (IL)-6 levels in saliva between different stages of diabetic retinopathy (DR).
Methods: This comparative cross-sectional study was conducted between January 2018 and November 2020. This study included diabetes mellitus (DM) patients with no DR, non-proliferative DR (NPDR), and proliferative DR (PDR). None of the patients with DM were included in the control group. Unstimulated saliva samples were then collected. TNF-α and IL-6 levels were measured.
Results: Altogether, 120 patients were included in the study (DM without DR, 33 patients; DM with NPDR, 30 patients; DM with PDR, 32 patients; non-DM, 25 patients). The mean IL-6 level in saliva was significantly higher in the DM group (0.033 ± 0.005 pg/ml) than in the non-DM group (0.027 ± 0.001 pg/ml) (p < 0.001 after adjusting for covariates). There was no significant difference in the mean salivary TNF-α between patients with DM and those without DM after adjusting for covariates. The mean IL-6 in saliva was significantly higher in the NPDR (0.036 ± 0.003 pg/ml) and PDR (0.093 ± 0.023 pg/ml) groups than in the no DR group (0.027 ± 0.001 pg/ml) (p < 0.001 and p < 0.001, respectively). Mean TNF-α in saliva was significantly higher in the NPDR (0.086 ± 0.022 pg/ml) and PDR (0.093 ± 0.023 pg/ml) groups than in the no DR group (0.049 ± 0.011 pg/ml) (p = 0.015 and p = 0.003, respectively).
Conclusion: There is an association between inflammatory biomarkers in saliva (IL-6 and TNF-α) and severity of DR among patients with DM, suggesting that these salivary biomarkers are potential biomarkers for screening, monitoring, and predicting the progression of DR.
Keywords: IL-6; TNF-α; diabetes mellitus; diabetic retinopathy; saliva.
© 2022 John Wiley & Sons Ltd.