Quercetin, a Plant Flavonol Attenuates Diabetic Complications, Renal Tissue Damage, Renal Oxidative Stress and Inflammation in Streptozotocin-Induced Diabetic Rats

Diabetes mellitus is a metabolic syndrome characterized by increased glucose levels, oxidative stress, hyperlipidemia, and frequently decreased insulin levels. The current research was carried out for eight consecutive weeks to evaluate the possible reno-protective effects of quercetin (50 mg/kg b.w.) on streptozotocin (STZ) (55 mg/kg b.w.) induced diabetes rat models. Various physiological, biochemical, and histopathological parameters were determined in control, diabetic control, and quercetin-treated diabetic rats. The current findings demonstrated that diabetes control rats showed significantly decreased body weights (198 +/- 10 vs. 214 +/- 13 g) and insulin levels (0.28 +/- 0.04 vs. 1.15 +/- 0.05 ng/mL) in comparison to normal control. Besides this, the other parameters showed increased values, such as fasting blood glucose, triglyceride (TG), and total cholesterol levels (99 +/- 5 vs. 230 +/- 7 mg/dL, 122.9 +/- 8.7 vs. 230.7 +/- 7.2 mg/dL, 97.34 +/- 5.7 vs. 146.3 +/- 8 mg/dL) (p < 0.05). In addition, the urea and creatinine levels (39.9 +/- 1.8 mg/dL and 102.7 +/- 7.8 mu mol/L) were also high in diabetes control rats. After 8 weeks of quercetin treatment in STZ-treated animals, body weight, insulin, and fasting blood sugar levels were significantly restored (p < 0.05). The inflammatory markers (TNF-alpha, IL-6, and IL-1 beta) were significantly increased (52.64 +/- 2, 95.64 +/- 3, 23.3 +/- 1.2 pg/mL) and antioxidant enzymes levels (SOD, GST, CAT, and GSH) were significantly decreased (40.3 +/- 3 U/mg, 81.9 +/- 10 mU/mg, 14.2 +/- 2 U/mg, 19.9 +/- 2 mu mol/g) in diabetic rats. All the parameters in diabetic animals treated with quercetin were restored towards their normal values. Histopathological findings revealed that the quercetin-treated group showed kidney architecture maintenance, reduction of fibrosis, and decreased expression of COX-2 protein. These results determined that quercetin has reno-protective effects, and conclude that quercetin possesses a strong antidiabetic potential and might act as a therapeutic agent in the prevention or delay of diabetes-associated kidney dysfunction.