EFFECT OF RICE BRAN AND ITS OIL ON LIPID PEROXIDATION AND INSULIN RESISTANCE INDUCED BY HIGH FRUCTOSE DIET IN RATS

Abstract

Metabolic syndrome is a disorder of energy utilization and storage, diagnosed by a co-occurrence of three out of five of the following medical conditions: abdominal (central) obesity, elevated blood pressure, elevated fasting plasma glucose, high serum triglycerides, and low high density lipoprotein (HDL) levels. Metabolic syndrome increases the risk of developing cardiovascular disease and diabetes (Kaur, 2014). Feeding rats with high fructose diet affects both glucose and lipid metabolism which result in a cluster of metabolic abnormalities such as hyperinsulinemia and hyperlipidemia. Also, feeding high fructose diet facilitates oxidative damage and has deleterious effects both due to reduction in antioxidant defense and enhanced free radical production. This work aims to study the effects of daily intake of RB or RBO on lipid metabolism and hepatic IRS-1. To fulfill the goals of this target, 40 adult male rats were divided into 4 groups: Group (1): Rats fed on standard diet. Group (2): Rats fed on HFD (52.5%). Group (3): Rats fed on HFD (52.5%) + 5% RB replacing cellulose. Group (4): Rats fed on HFD (52.5%) + 10% RBO replacing corn oil. At the end of the experiment (5weeks) rats decapitated and plasma, serum and livers were subjected to the following analysis 1- Plasma fasting glucose level. 2- Serum insulin, HOMA-IR, lipid profile and total antioxidant capacity 3- Hepatic total cholesterol, triacylglycerol, malondialdehyde, IRS-1 and HMG-COA reductase mRNA levels. The results obtained from this study were: 1- Feeding rats on HFD for 5 weeks caused a significant increase (P˂0.05) in plasma glucose, serum insulin and HOMA-IR whereas a significant decrease (P˂0.05) in hepatic IRS-1 was observed compared with group fed standard diet. Treatment by RB or RBO showed a significant decrease (P˂0.05) in glucose, insulin and HOMA-IR while hepatic IRS-1 level was significantly elevated (P˂0.05) compared with group fed high fructose diet. 2- Moreover, HFD caused significant elevation (P˂0.05) in serum TC, TAG, LDL-C, VLDL-C and atherogenic index compared with group fed standard diet. Treatment by RB or RBO showed a significant decrease (P˂0.05) in TC, TAG, LDL-C, VLDL-C and atherogenic index as compared group fed high fructose diet. 3- Significant increase (P˂ 0.05) in hepatic TC, TAG and HMG-COA reductase mRNA was observed in HFD fed rats, compared with group fed standard diet. These disturbances were corrected by RB or RBO which caused significant decrease (P˂0.05) in all these parameter, compared with group fed high fructose diet. 4- Hepatic MDA concentration was significantly increased (P˂0.05) in rats fed HFD, while serum TAC was significantly decreased (P˂0.05) as compared with group fed standard diet. However, rats fed HFD contained RB or RBO showed a significant decrease (P˂0.05) in hepatic MDA and significant increase in serum TAC, compared with group fed high fructose diet.