Study On Mechanism Of Hypoglycemic Effect Of Epigallocatechin-3-gallate

Objective:To investigate the activity of a-glucosidase inhibitory and the mechanism of hypoglycemic effect of epigallocatechin-3-gallate. Methods :①Respectively,by substrate of maltose and P-Nitrophenyl-α-D- Glucopyr- anoside, to establish a-glucosidase inhibitory activity evaluation system in vitro, the inhibitory effect for a-glucosidase of the epigallocatechin- 3-gallate were detected based on the concentration of glucose in the reaction system by glucose oxidase method and PNPG assays, and half inhibiting concentration(IC₅₀) values are calculated. By substrate of maltose, to establish a-glucosidase inhibitory activity evaluation system of the small intestine of wistar rats in vivo, the inhibitory activities for a-glucosidase of the epigallocatechin- 3-gallate were detected based on the concentration of glucose in the reaction system by glucose oxidase method, and half inhibiting concentration(IC₅₀) values are calculated. The positive control group is acarbose group, to analysis and compare with the effect of different substrates and enzymes to a-glucosidase inhibitory activity of epigallocatechin-3-gallate,and compared with epigallo- catechin-3-gallate and the inhibitory effect of 15 kinds of Chinese herbs onα-glucosidase by enzyme reaction system in vitro.②The model was established by high-fat-sucrose diet on ten weeks , to establish impaired glucose regulation of wistar rats. carrying out oral glucose maltose tolerance test. Fasting plasma glucose,postprandial blood glucose,fasting serum insuline level,total choleserol,and triglyceride were measured to observe the effect of impaired glucose regulation of wistar rats in vivo. Homeo stasis model assessment ratio were calculated. The positive control group is acarbose group, three doses (0.2,0.7,1.0g/kg.d) of epigallo catechin-3-gallate are applied by intragastric administration on three days, carrying out oral maltose tolerance test on fourth day. Fasting plasma glucose,postprandial blood glucose were measured to observe the effect of impaired glucose regulation of wistar rats. Three doses (20,50,200mg/kg.d) of epigallocatechin- 3-gallate are applied by intragastric administration on six weeks, carrying out oral maltose tolerance test on second and fourth weeks; On sixth weeks,executing all impaired glucose regulation of wistar rats. To obtain liver,kidney,heart and fat of rats ,and calculating organ index. Fasting plasma glucose, total cholesterol, triglyceride, high density lipoprotein cholesterol, low density lipoprotein cholesterol, glycogen in Liver and muscle and creatinine were measured to observe the effect of impaired glucose regulation of wistar rats in vivo. Results:①To establish definite enzyme and maltose concentration are 0.5mg/ml and 0.06mol/L in a-glucosidase inhibitory activity evaluation system in vitro and the small intestine of wistar rats in vivo.the IC₅₀ value of a-glucosidase inhibitory of epigallocatechin-3- gallate are 0.150 and 2.594mg/ml by measured with produced from substrate of maltose and P-Nitrophenyl-α-D- Glucopyranoside. the IC₅₀ value of the small intestine of wistar rats in vivo is 0.837mg/ml. Epigallocatechin-3- gallate is non-competitive inhibitor for a-glucosidase from the bakets yeast; Km=0.1518mol/L,Ki=0.4003mg/ml; the inhibitory effect of epigallocatechin- 3-gallate onα-glucosidase by enzyme reaction system in vitro is better than 15 kinds of Chinese herbs.②the hypoglycemic effect of epigallocatechin- 3-gallate for impaired glucose regulation of wistar rats in vivo is not clear by intragastric administration on three days. Epigallocatechin-3-gallate can remarkably reduce postprandial blood glucose after irrigating the maltose for 120 min on intragastric administration on second week. Two doses (50, 200mg/kg.d) of epigallocatechin-3-gallate can remarkably reduce fasting plasma glucose, total cholesterol, triglyceride, low density lipoprotein choleserol, creatinine,glycogen in liver and the weight of liver and kidney, and increase high density lipoprotein cholesterol. Conclusion:This study can be performed to the activity of a-glucosidase inhibitor and the hypoglycemic activity epigallocatechin- 3-gallate in vitro and vivo. the hypoglycemic mechanism of epigallocatechin-3-gallate possibly concern with portion of its effect of a-glucosidase inhibitor.