Effects of oleuropein on serum paraoxonase and arylesterase activities and some biochemi̇cal parameters in rats with high fructose-induced metabolic syndrome

2. ABSTRACT EFFECTS OF OLEUROPEIN ON SERUM PARAOXONASE AND ARYLESTERASE ACTIVITIES AND SOME BIOCHEMİCAL PARAMETERS IN RATS WITH HIGH FRUCTOSE-INDUCED METABOLIC SYNDROME Metabolic syndrome (MS) is a pathophysiologic entity which is characterised by insulin resistance, hyperinsulinemia, dyslipidemia, hypertension and obesity. This sydrome, considered to occur as a result of sedentary lifestyle, changes in dietary habits, genetic and environmental factors, is seen more and more in the world and in our country. Oleuropein, contained in oliveleaves, is a polyphenolic compound which is thought to have antioxidant, antimicrobial, antiviral, anti-inflammatory, hypoglycemic effects. It could decrease blood pressure, also, its antioxidant activitiy prevents LDL cholesterol from oxidation, reduces total cholesterol and triglycerid leves and regulates blood glucose in diabetes. In this study, it is aimed to investigate the effects of oleuropein on serum glucose, insulin, lipid profile and paraoxonase activity in rats, on high-fructosediet in which insulin resistance in pathogenesis and oxidative stres play an important role and possible changes which may occur in the process of metabolic syndrome formation. In the study, 32 male adults (8 weekaged) Spraque-Dawley rats were randomly divided into four groups (n=8); control (K), metabolic syndrome (MS), oleuropein (OLE) and metabolic syndrome plus oleuropein (MS+OLE). Metabolic syndrome was induced by fructose solution 20% in tap water, and oleuropein was administered at the dose of 10 mg/kg dailyby oral gavage. Body weights and water consuptions were measured weekly. Systolic blood pressures (SBP) were measured by Tail- Cuff method at the beginning of the study, at the end of 4th and 8th weeks. After the experimental period of 8 weeks, rats were decapitated and blood samples were collected. Serum glucose, HDL cholesterol, LDL cholesterol, VLDL cholesterol, triglycerides, uricacid, insulin, HOMA and the activities of PON and ARE were measured. At the end of the experiment, the rats' weight gain and water consumptions were found higher in metabolic syndrome ve metabolic syndrome plus oleuropein groups compared to the control and oleuropein groups. Systolic blood pressure increased in metabolic syndrome group compared to the control group and reduction was found in metabolic syndrome plus oleuropein group compared to metabolic syndrome group. It was found that serum glucose, LDL cholesterol, VLDL cholesterol, triglycerides, uricacid, insulin, HOMA levels increased, PON and ARE activities reduced in metabolic syndrome group compared to the control group. As for metabolic syndrome plus oleuropein groups, it was found that serum parameters reduced showing improvement than metabolic sydrome group, also PON and ARE activities increased in this group when compared to metabolic syndrome group. Consequently, it was observed that, in addition to high-fructose diet causing metabolic syndrome formation, oleuropein application provided positive contribution to serum parameters, and increased the levels of PON and ARE activities, known as antioxidant enzymes. These findings show that oleuropein application can have protective effects against oxidative stress in the process of metabolic syndrome formation. However, by making more detailed studies, it may be suggested the clinicaluse of treatment approaches depend on oleuropein usage. Keywords: metabolic syndrome, oleuropein, paraoxonase, arylesterase, serum.