Effect Of Epigallocatechin-Gallate Supplementation On Antioxidation Capacity And Insulin-resistance In Goto-kakizaki Rat

Part Ⅰ Effect of Epigallocatechin-Gallate supplementation on antioxidation capacity in Goto-kakizaki ratObjective To investigate the effect of epigalloca-techin-3-gallate(EGCG) on antioxidation capacity of Goto-kakizaki rats and the relative mechanisms.Methods Goto-kakizaki diabetic rats(GK, n=40) were observed and Wistar (n=10) as control. Rats were randomly divided into five groups:normal control group, TIIDM model group, diabetic model plus EGCG of50mg/kg,100mg/kg and300mg/kg therapy group.Two-hour postprandial plasma glucose and six-hour postprandial plasma glucose were detected once a week. Antioxidation indexes(SOD, GSH-Px, MDA, NO, NOS, iNOS, T-AOC), hepatic function(AST,ALT),renal function(BUN, CRE),blood lipid(TG,T-CHO,HDL-C,LDL-C) in serum were detected after6weeks treatment.Results The six-hour postprandial plasma glucose was significantly improved in the moderate and high dosage treatment groups(P<0.05). In antioxidation capacity, moderate and high dosage EGCG could increase the activity of SOD and decrease the activity of iNOS and the content of radical(MDA,NO) in serum (P<0.05).Thus, moderate and high dosage EGCG could increase T-AOC in serum(P<0.05).In addition, high dosage EGCG could increase the activity of GSH-Px in serum(P<0.05). In hepatic function, every dosage EGCG could decrease the level of AST in serum (P<0.05) and moderate dosage EGCG could decrease the level of ALT in serum(P<0.05).In renal function, moderate and high dosage EGCG could decrease the level of BUN in serum(P<0.05).In blood lipid, every dosage EGCG could decrease the level of TG in serum (P<0.05) and T-CHO in serum decreasing in high dosage EGCG (P<0.05).Then,moderate-high dosage EGCG could decrease the level of HDL-C and high dosage EGCG could decrease the level of LDL-C in serum(P<0.05).Conclusion Postprandial plasma glucose,antioxidation capacity,hepatic function,renal function and blood lipid of GK rat were improved by EGCG in dose-dependent manner.EGCG could improved the antioxidation capacity of GK rat through increasing the activity of antioxidant enzymes in vivo and improving Postprandial plasma glucose and blood lipid level of GK rat.High dosage EGCG might be toxic in liver. Part Ⅱ Effect of Epigallocatechin-Gallate supplementation on insulin-resistance in Goto-kakizaki ratObjective To investigate the effect of epigalloca-techin-3-gallate(EGCG) on insulin-resistance of Goto-kakizaki rats and the relative mechanisms.Methods Goto-kakizaki diabetic rats(GK, n=40) were observed and Wistar (n=10) as control. Rats were randomly divided into five groups:normal control group, TIIDM model group, diabetic model plus EGCG of50mg/kg,100mg/kg and300mg/kg therapy group. OGTT,ITT,the mRNA expression level of GcK,G6P,PEPCK and the GLUT4content of skeletal muscle plasma membrane were detected after6weeks treatment.Results The OGTT was improved in all three treatment groups(P<0.05). There was statistical difference on ITT between diabetic control group and low-to-moderate dosage groups at240min(P<0.05). In comparison with the diabetic control group, the mRNA expression of hepatic GcK gene were significantly increased(P<0.05),and the level of mRNA of G6P and PEPCK genes in liver were significantly decreased in low-to-moderate dosage treatment groups(P<0.05),but there was no statistical difference on the expression of three kinds of mRNA in liver between high-dose treatment group and diabetic control group;the GLUT4content of skeletal muscle membrane in three treatment groups was significantly higher than diabetic control group(P<0.05).Conclusion Every dosage EGCG can improve insulin-resistance in type Ⅱ diabetic rats, and its mechanisms might be closely related to the restriction of liver gluconeogenesis and the elevation of the level of GLUT4in the skeletal muscle tissues of rats.EGCG can make up for the dysfunction of insulin.