THE OREXIN SYSTEM IN INSULIN RESISTANCE RAT MODEL INDUCED BY HIGH-FRUCTOSE DIET.

To evaluate the effects of high-fructose diet on expression of orexin and its receptors, orexin 1 receptor (OX[sub1]R) and orexin 2 receptor (OX[sub2]R) in rat hypothalamus tissue, and to analysis the interaction of related factors involved in regulating orexin and its receptors. Insulin resistance rat model induced by high fructose confirmed by the gold standard euglycaemic clamping was employed and mRNA expression of orexin and its receptors OX[sub1]R and OX[sub2]R in hypothalamus, mRNA expression of leptin in adipose tissue were measured by reverse transcription polymerase chain reaction. Serum insulin and triglyceride levels were measured by chemiluminescence immunoassay and biochemical enzyme techniques. Expression of orexin mRNA decreased about 40% in high fructose diet rats compared to control group (P<0.01), whereas expression of orexin 1 receptor and orexin 2 receptor mRNA increased up to 4.4 and 5.1 fold (P<0.01). Leptin mRNA expression in adipose tissue increased about 30% in comparison with control group (P<0.01). Blood glucose, serum insulin and triglyceride have shown sigfinicant higher levels than those in control group (P<0.01). Glucose infusion rate (GIR[sub60-120]) was much lower in comparison with control group. High- fructose diet induces insulin resistance in rats with impact on orexin and leptin regulations. Blood glucose, serum insulin, lipid metabolism and leptin play an interactive role on orexin and its receptors regulations in rats. Keywords: orexin, dietary fructose, insulin resistance [ABSTRACT FROM AUTHOR]