Effect of Anthocyanin Extract from black rice (Oryza sativa L.) on Hyperlipidemia and Insulin Resistance Induced in rats.

Abstract

Consumption of rice is very high in Saudi Arabia. Usually Saudis prefer white rice although other types of rice such as brown and black rice are reported to be healthier. It is well known that black rice is very rich in anthocyanin. Anthocyanin is very strong antioxidant and can neutralize free radicals. We assume that anthocyanin from black rice may protect against type 2 diabetes and hyperlipidemia associated with consumption of high fat diet (HFD). This study was designed to evaluate the protective effect of anthocyanin rich extract from black rice (Oryza sativa L.) on lipid disturbances and insulin resistance in diabetic rats and in rats fed HFD. In the present study, rats were divided into five groups; one group was fed on HFD to upset plasma lipid profile and induce lipid peroxidation and in another group diabetes was induced by Streptozocin (STZ). Diabetic rats and rats fed HFD were treated for four weeks with the anthocyanin extract (116 mg /100 g of diet). At the end of the experimental period rats were bled and sacrificed. Anthocyanin was found to reduce the body weight gain in rats fed HFD and increased the gain in body weight of diabetic rats suggesting a role of ACN in body weight control. High Fat Diet and diabetes induced hyperlipidemia as manifested by significant (P≤0.05) increases in the levels of cholesterol, triglycerides (TG) and low density lipoproteins (LDL) in serum of treated animals. In diabetic rats the levels of cholesterol, triglycerides and LDL also increased significantly. Cholesterol and triglyceride levels in liver homogenate were also significantly (p<0.05) elevated in rats fed HFD and in the diabetic group. Inclusion of anthocyanin rich extract in the diet of rats reduced significantly (p<0.05) serum level of cholesterol, triglycerides, LDL and cholesterol and triglycerides levels in liver homogenate. HDL level was reduced in HFD and diabetic groups but treatment with anthocyanin improved and significantly elevated the serum levels of HDL. There was a significant (p<0.05) increase in the activities of ALT and AST in diabetic and HFD group that was significantly (p<0.05) improved by anthocyanin. Serum urea concentration in the control group was 31.62+1.48 mg/dl and increased significantly (p<0.05) in the diabetic and HFD groups Anthocyanin administration reduced non- significantly the level of urea Indicators of lipid peroxidation (reduced glutathione, total antioxidant capacity and malondialdehyde) (GSH, TAC and MDA) were found to be affected by anthocyanin treatment. The levels of GSH and TAC decreased significantly (p<0.05) in diabetic rats and in rats fed HFD while the level of lipid peroxidation product (MDA) increased significantly in the two groups. Administration of anthocyanin increased significantly the levels of GSH and TAC and decreased significantly the level of MDA. Activities of the antioxidant enzymes – Glutathione peroxidase (GSH Px), Catalase (CAT) and Superoxide dismutase (SOD) in the liver homogenate decreased significantly in diabetic rats and in rats fed HFD indicating lipid peroxidation in the liver. However, when anthocyanin was incorporated in their diets, the activities of the three enzymes increased significantly to almost the activities of the normal control. The level of MDA in liver homogenate increased significantly in diabetic rats and in rats fed HFD due to peroxidation reactions but when these rats were offered anthocyanin in their diets, the level of MDA decreased significantly. The concentration of reduced glutathione (GSH) was found to decrease significantly by feeding on HFD or after induction of diabetes. However, administration of anthocyanin resulted in a significant (p<0.05) elevation of the level of indigenous GSH. Administration of anthocyanin resulted in higher degree of insulin sensitivity in rats receiving HFD since lower values indicate higher degree of insulin sensitivity when calculated from HOMA-IR index. (index of insulin resistance). On the other hand, anthocyanin when fed to diabetic rats did not improve insulin sensitivity. It can be concluded from this study that inclusion of Anthocyanin Rich Extract from black rice in diet of rats modulates lipid metabolism and enhances antioxidant status. The beneficial effect produced may enhance and encourage consumption of black rice. These results suggest that the anthocyanin rich extract from black rice improved certain metabolic abnormalities associated with diabetes and high fat diet