Gallic Acid and Vitamin C Mitigate Histopathological Changes in the Retina by Attenuating Dyslipidemia and Mitigating Oxidative Stress, Inflammation, and Apoptosis in the Eyes of Type 2 Diabetic Rats Induced With Fructose/Streptozotocin

The result of combined supplementation of gallic acid and vitamin C on histopathological changes in the retina of type 2 diabetic rats induced with fructose and streptozotocin (STZ) was studied. Albino male rats (numbering 25) were assigned into five groups of five rats each as follows: Normal control and diabetic control (non-diabetic and diabetic rats given rat feeds and water); diabetic + gallic acid (diabetic rats given gallic acid, 20 mg/kg, orally), diabetic + vitamin C (diabetic rats given vitamin C, 25 mg/kg, orally), diabetic + gallic acid + vitamin C (diabetic rats given gallic acid, 20 mg/kg and vitamin C, 25 mg/kg, orally). The study lasted for 10 weeks. The diabetic rats had a marked increase (p < 0.05) in fasting blood glucose, glycated hemoglobin (HbA1C), insulin resistance (IR), lipase, dyslipidemia, vascular endothelial growth factor (VEGF), pro-apoptotic marker level, oxidative stress and inflammatory mediators, and a significant decline (p < 0.05) in pancreatic beta cell function index (HOMA-β), serum levels of amylase and vitamin C, body weights, anti-apoptotic marker level as well as histopathological changes in their retina. These changes were improved after supplementing with gallic acid, vitamin C, and their combination. The HOMA-β levels of the diabetic rats that received vitamin C (1.39 ± 0.59) and the combination of gallic acid and vitamin C (0.86 ± 0.77) were significantly higher (p < 0.05) than the diabetic rats that received gallic acid (−0.01 ± 0.62) while their HbA1C and VEGF levels were lower (p < 0.05) than the diabetic rats that received gallic acid. Vitamin C treatment was better than gallic acid, and its combination with gallic acid enhanced the therapeutic effect of gallic acid.