Investigation of simple carbohydrates diet fed rats a high content of antioxidant effects of green tea

With secular increase of the products that are high in simple carbohydrates, total consumption of refined fructose has increased amazingly in the last 30 years. Many researchers investigate the effect of high fructose intake on weight loss, lipid profiles, and glucose metabolism in mice and humans. The results of those studies indicated that green tea is effective in reducing plasma and liver triglycerides (TG) and reducing fasting plasma glucose, insulin and free fatty acid levels in mice with hypertriglyceridemia resulting from being fed with high fructose. Additionally, green tea has been also shown to elevate the total plasma antioxidant activity. There are also studies suggesting that green tea consumption increases superoxide dismutase (SOD) activity and aortic catalase (CAT) expression, has effective against reactive oxygen species along with cellular defense enzymes while decreasing malondialdehyde (MDA)- an indicator of oxidative stress. The present study aimed to determine the antioxidant effect of green tea in rats fed with a diet that is high in simple carbohydrate. We included 32 adult male Sprague Dawley rats at 8-10 weeks of age (weighting between 164-224 g) in the study. The rats were randomly divided into 4 groups as Control group (CG), Fructose group (FG), Green Tea group (GTG), Fructose plus Green Tea group (FGTG). Control Group was given tap water; Fructose Group was given 20% fructose (20 g/100 mL); and Green Tea Group was given camellia sinensis (2 g/kg/day), while FGTG was given C. sinensis (2 g/kg/day) + 20% fructose (20 g/100 mL) 8 week time through oral route. Body weight and waist circumference of the rats were measured weekly on regular basis. Eight weeks later rats were decapitated, blood was collected, and the liver was removed. Serum glucose, total cholesterol (TC), high density lipoprotein (HDL), low density lipoprotein (LDL), very low density lipoprotein (VLDL), triglycerides (TG), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels were measured, and livers were examined histologically. Liver tissue was used for lipid peroxidation, glutathione (GSH), CAT, SOD protein analysis. The highest body weight was obtained in FG while the lowest was in GTG. Glucose level was significantly higher in CG and FG as compared to FGTG (p<0.05). However, there was no significant statistical difference between CG, FG, GTG and FGTG regarding TC, HDL, and LDL cholesterol levels. VLDL cholesterol and TG levels were observed to be higher in FG and FGTG groups in comparison to CG and GTG (p<0.05). On the other side, the MDA, SOD, CAT, and GSH levels did not show any significant difference between CG, FG, GTG and FGTG. The amount of green tea, temperature of brewing water, brewing time, and preparation method affect the composition of bioactive compounds in green tea. In conclusion, there is a need for new studies examining the dose and duration of fructose and green tea administration in order to identify the antioxidant effect of green tea on hepatic oxidative stress for using of fructose and green tea together. Key Words: Fructose, Green Tea, Antioxidant, Hepatic Oxidative Stress, Liver This doctorate thesis was approved by Başkent University Medical and Health Sciences Research Board with the Decision No. 2015/49 dated February 27, 2015.