Pharmacological Evaluation of Metformin, Dapagliflozin alone and in Combination, in a Wistar Rat Model of Diabetic Neuropathy: An Experimental Study

Introduction: Diabetic Neuropathy (DN) is a common and debilitating complication of Diabetes Mellitus (DM), involving the sensory, motor, and autonomic nervous systems, with limited disease-modifying treatment options. Emerging evidence suggests that commonly used antidiabetic agents may exert additional neuroprotective effects beyond glycaemic control. Aim: To evaluate the individual and combined effects of metformin and dapagliflozin on the Wistar rat model of DN. Materials and Methods: This experimental study was conducted in the Department of Pharmacology, KAHER’s Jawaharlal Nehru Medical College, Belagavi, Karnataka, India from January 2022 to December 2022. Thirty-two male Wistar rats were used, of which six served as normal controls. Diabetes was induced in the remaining animals by a single intraperitoneal injection of Streptozotocin (STZ) (60 mg/kg). After confirmation of diabetes (fasting blood glucose >250 mg/dL), rats were randomly allocated to Diabetic Control (DC), metformin (180 mg/kg), dapagliflozin (0.9 mg/kg), or combination treatment groups and treated orally for eight weeks. Sensory neuropathy was assessed by measuring the Paw Withdrawal Latency (PWL) using Eddy’s hot plate at 2, 4, 6, and 8 weeks. At the end of eight weeks, motor neuropathy was evaluated by measuring Motor Nerve Conduction Velocity (MNCV) of the sciatic nerve, and autonomic dysfunction was assessed by measuring gastrointestinal transit using the charcoal meal method. Histopathological changes in the sciatic nerve were examined for perineural inflammation using Haematoxylin and Eosin (H&E). The quantitative data were expressed as Mean±SEM and analysed using ANOVA followed by Tukey’s post-hoc test, and p-value <0.05 was considered significant. Results: A total of 32 rats were included (n=6 each in normal control and treatment groups; n=8 in DC). At eight weeks, DC rats exhibited significant neuropathic alterations compared with normal controls, including prolonged PWL (8.33±0.25 vs 3.58±0.33 s; p-value=0.0000011), reduced MNCV (11.48±1.24 vs 56.67±3.33 m/s; p-value=0.0001), and decreased intestinal transit (49.25±4.74% vs 85.69±0.97%; p-value=0.0000011). Metformin and dapagliflozin significantly improved thermal latency (5.42±0.24 s; p-value=0.000119 and 5.58±0.15 s; p-value=0.0000022), nerve conduction velocity (28.52±4.03 m/s; p-value=0.0004 and 27.67±2.49 m/s; p-value=0.0007), and intestinal transit (74.66±3.79%; p-value=0.000245 and 69.85±3.10%; p-value=0.01347) compared with DC. Combination therapy further improved PWL (5.17±0.21 s), MNCV (34.00±5.89 m/s), and intestinal transit (77.44±2.08%). Sciatic nerve inflammation score was significantly elevated in DC (2.50±0.22) and reduced with metformin (0.33±0.21), dapagliflozin (0.33±0.21), and combination therapy (0.00±0.00). Conclusion: Metformin and dapagliflozin, alone and more effectively in combination, significantly ameliorated sensory, motor, and autonomic neuropathy in STZ-induced diabetic rats, which highlights the potential of combination antidiabetic therapy for DN, warranting further mechanistic and translational studies.