Abstract
BACKGROUND: Insulin resistance is an inadequate metabolic response of the peripheral tissue to circulating insulin. It plays an important pathophysiological role in type 2 diabetes mellitus. The purpose of the study was to investigate the molecular effects of rice bran oil (RBO) on the gene expression of insulin receptor (IR), insulin receptor substrate-1 (IRS-1), glucose transporters-4 and 5 (GLUT-4 and 5) in insulin-resistant rats induced by high fructose diet (HFD). METHODS: Rats were divided into six groups (10 rats each) as follows: Groups 1 and 2: rats received a standard diet with corn oil or RBO (as the sole source of fat), respectively. Group 3: animals fed on HFD, which was furtherly divided into 2 sub-groups: rats fed HFD either for one (HFD1) or for 2 months (HFD2). Group 4, rats fed HFD containing RBO for 1 month (HFD1 + RBO), while rats in group 5 fed HFD for 30 days then RBO was added to the diet for another 30 days (HFD2 + RBO). Serum levels of glucose and insulin, as well as hepatic gene expression of insulin receptors and glucose transporters were determined. Livers were isolated for histopathological study. RESULTS: HFD induced insulin resistance with a reduction in the hepatic level of insulin receptor and glucose transporters at both protein and molecular levels. Addition of RBO improved the insulin sensitivity and up-regulated the expression of the tested genes. CONCLUSION: HFD impaired the insulin sensitivity of the hepatocytes by down-regulating the insulin receptor genes. Addition of RBO alleviated all the hazardous effects.