Protective Effects of Quercetin on Hyperglycemia and Stress Proteins Expression in Rats with Streptozocin-Induced Diabetes

Abstract

Background: Hyperglycemia-mediated oxidative stress has been participated in complications of diabetes. Although the beneficial effects of flavonoid quercetin in diabetes is known, target of this flavonoid in molecular level is unclear. This study aimed to investigate expression level of glucokinase and glucose-6-phosphatase as key enzyme in glucose metabolism in diabetes model rats treated with Methods: 24 adult male Wistar rats were used in this study. Healthy control group (n = 8) and two streptozotocin-induced diabetic rats (60 mg/kg) as diabetic control group (n = 8) and quercetin treated group (15 mg/kg, intraperitoneally) (n = 8). At the end of treatment period (21 days), fasting blood sugar, malondialdehyde, and total antioxidant capacity in three groups of rats were measured, and the expression of stress proteins such as HSF-1, HSP27, and HSP70 as well as the enzymes glucokinase and glucose-6-phosphatase were assayed by real time PCR. Results: Quercetin significantly decreased fasting blood sugar and malondialdehyde levels compared with diabetic control group (P ≤ 0.05). In contrast total antioxidant capacity increased in quercetin treated group. The mRNA levels of HSP27, HSP70, HSF-1, and glucose-6-phosphatase decreased while the expression of glucokinase significantly increased in response to quercetin (P ≤ 0.05). Conclusions: These findings indicate that therapeutic effects of quercetin could be through increase in transcript level of glucokinase simultaneously decreasing expression level of glucose-6-phosphatase and stress proteins. This is useful especially for Health-care practitioners to set up clinical use of quercetin for nutritional management of diabetes.