Rice bran oil ameliorates hepatic insulin resistance by improving insulin signaling in fructose fed-rats.

Abstract

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). 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 2months (HFD2). Group 4, rats fed HFD containing RBO for 1 month (HFD1 + RBO), while rats in group 5 fed HFD for 30days then RBO was added to the diet for another 30days (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. 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. HFD impaired the insulin sensitivity of the hepatocytes by down-regulating the insulin receptor genes. Addition of RBO alleviated all the hazardous effects.