Green Tea Polyphenols Ameliorate Dysmetabolism

Objective: Metabolic syndrome (MS), with such characteristics as insulin resistance, iscaused by carbohydrates, lipids, and other metabolic disorders, including a variety ofmetabolic disorders related diseases, such as obesity, diabetes, hypertension, lipidmetabolism disorders, etc. MS is one of the main cause of morbidity and mortalityworldwide. Liver, the main organ in regulating the body glucose and lipid metabolism,plays key role in the occurence and development of MS. Evidences have shownthat teapolyphenols have preventive and improving effects on metabolic syndrome. The aimsof the present study are to observe the effects of green tea polyphenols (GTPs) onmetabolism of the high-fat diet induced metabolic syndrome rats, to analyze the vitalgenes of hepatic carbohydrates and lipid metabolism, and to investigate the underlyingmechanisms.Method: Fifty male wistar rats were randomly divided into five groups: normal control(Control), high fat fed control (HF), low dose (0.8g/L) GTPs treated groups (GL),medium dose (1.6g/L) GTPs treated groups (GM), high dose (3.2g/L) GTPs treatedgroups (GH). The rats was fed with normal diet or high fat diet, GTPs wereadministered via drinking water. The food intake ande the body weight of the rats wasrecorded every other day and every week, respectively. The experiment lasted for26weeks. At the end of experiment, all rats were sacrificed. The peripheral fat mass oftestis, perirenal adipose tissue and liver were separated rapidly and weighed. Frozensections of hepatic tissue were made by frost slice techniques and stained with OilRed-O. Total cholesterol (TC), triglyceride (TG), high-density lipoprotein (HDL), lowdensity lipoprotein (LDL) and glucose in the serum were measured with commercialkits. Serum adiponectin was measured by ELISA. The protein level of PPARγ wasdetermined by western blot. The mRNA expressions of PPARγ and adiponectin in visceral adipose tissue (VAT),3-hydroxy-3-methylglutaryl-CoA (HMG CoA reductase),FAS, Sterol regulatory element binding protein (SREBP-lc), peroxisomeproliferator–activated receptorα (PPARα), PEPCK, and GLUT2were quantified byReal-time PCR.Results:1. No significant difference was found in energy intakes among groups. The bodyweight in HF group was significant higher than that of control rats (P <0.05), andobviously lower in the GL, GM, GH groups in compare with the HF group (P <0.05).The fat coefficient of HF group was significantly higher than the control group (P <0.05), GTPs treatment decreased the fat coefficient (P <0.05). Compared to the controlgroup, the serum glucose, TC, TG, HDL and LDL in HF group were significantlyincreased (P <0.05) and decreased in GL, GM, GH groups in compare with HF group(P <0.05).2. Liver coefficient in HF group was significantly higher in compare with thecontrol group (P <0.05) and lower in GL, GM, GH groups compared to the HF group(P <0.05). The levels of FAS, SREBP-1c, HMG-CoAR and PEPCK mRNA weresignificantly lower in GL,GM,GH groups than HF group, while the levels of PPARα,GLUT2were higher than HF group (P <0.05).3. The levels of serum adiponectin, adiponectin and PPARγ mRNA, proteinexpressions of PPARγ in HF group were decreased in compared with control group (P<0.05) and GTPs treatment alleviated these effects induced by HF (P <0.05).Conclusion: Green tea polyphenols can prevent the metabolism disorder, weight gainand liver glucolipid metabolism dysregulation caused by high-fat diet. GTPs alsoup-regulated the expression of adiponectin via PPARγ, amelioratedhypoadiponectinemia in HF-fed rats. It is one of the mechanisms explaining theregulation roles of GTPs on high fat fed rats.