Exploratory insights into salivary E-cadherin as a non-invasive biomarker in a rat model of diabetes.

E-cadherin, an adhesion molecule critical for epithelial integrity, may be downregulated by oxidative stress (OS) in diabetes. While serum E-cadherin has been investigated in various conditions, its presence in saliva and potential as a non-invasive biomarker for diabetes remain poorly understood. This study aimed to evaluate salivary E-cadherin levels in streptozotocin (STZ)-induced diabetic rats and examine their relationship with OS markers, assessing the potential of E-cadherin as a non-invasive early diagnostic biomarker for diabetes. Twenty male Wistar rats were randomly assigned to control and diabetic groups. The diabetic model was established by administering a single intraperitoneal injection of 65 mg/kg STZ. Saliva was collected via pilocarpine stimulation, and blood samples were obtained for serum analysis. Salivary and serum E-cadherin levels, alongside serum OS markers including malondialdehyde (MDA), glutathione (GSH), superoxide dismutase (SOD), and catalase (CAT) were measured. Pearson's correlation assessed relationships between E-cadherin and OS markers. Diabetic rats exhibited significantly lower salivary E-cadherin levels (0.60 ± 0.15 ng/ml) compared to controls (1.21 ± 0.45 ng/ml; p < 0.05). Serum E-cadherin levels were higher than salivary levels in both groups (Control: 18.17 ± 2.23 vs. 1.21 ± 0.45 ng/ml, p < 0.001; Diabetic: 15.64 ± 3.62 vs. 0.60 ± 0.15 ng/ml, p < 0.001), but serum E-cadherin was also reduced in diabetic rats (15.64 ± 3.62 ng/ml) compared to controls (18.17 ± 2.23 ng/ml; p < 0.05). Diabetic rats showed elevated MDA (1.32 ± 0.03 nmol/ml vs. 0.50 ± 0.04 nmol/ml in controls; p < 0.001) and decreased antioxidant markers: GSH (0.76 ± 0.06 vs. 2.55 ± 0.04 µg/ml; p < 0.001), SOD (0.11 ± 0.02 vs. 0.18 ± 0.02 inhibition rate; p < 0.001), and CAT (2.02 ± 0.17 vs. 4.84 ± 0.56 mU/ml; p < 0.001). Furthermore, significant negative correlations were observed between E-cadherin and MDA levels (p < 0.05), while salivary E-cadherin positively correlated with GSH (p < 0.01) and SOD (p < 0.05). This preclinical investigation is the first to show that salivary E-cadherin levels are reduced in diabetic rats and correlate with serum levels, indicating that saliva may reflect systemic changes. Associations with oxidative stress markers suggest that oxidative imbalance contributes to E-cadherin downregulation. These findings provide preliminary evidence for salivary E-cadherin as a promising non-invasive biomarker for early detection and monitoring of diabetes-related epithelial dysfunction. Its translational potential lies in enabling simple, stress-free, and accessible screening approaches that could aid in early diagnosis and disease management in clinical settings.