Anti-hyperglycemic Efficacy Of Four Types Of Tea

Tea has long history as a wide beverage that ranks second only to water.Animal experiments indicate that tea has many biological health care efficacy,it can reduce body weight,blood glucose and insulin.Numerous convincing studies support that the supplementation of tea can reduce blood glucose,cholesterol,obesity.In addition,tea resists oxidation.Recently,animal experiments have shown other biological health care efficacy about tea: lowering the risk of cancer,nervous system and metabolic syndrome.The biological activity of tea is highly related to its doses level,high-dose levels is commonly used to investigate biological effects in animal experiments.Now there are reports that tea has significant effective on high blood glucose,while about yellow tea and dark tea are still not clear.The majority of studies is just for one kind of tea,such as green tea.But the research of black tea fully fermented is rarely,when compared with green tea,while study of various tea at the same time even less.There is still no systematic report about yellow tea,black tea,green tea and dark tea for their intervention hyperglycemia.Due to using high-dosage of tea or extract to intervene metabolic disease,which usually last for a long time,and assess biological efficacy is limited to the terminal time so it is difficult to monitor its biological efficacy in early period or not.Based on this,we studied yellow tea,black tea,green tea and dark tea for hypoglycemic effect in ICR mice.The present study found that mice were allowed free access to tea infusion(1:30,w/v)once daily for seven days,and yellow tea did not suppress animal growth,black tea and green tea suppressed animal growth,dark tea did not suppress animal growth either,but the efficacy of yellow tea is better than dark tea,compared to the control group.The rare yellow tea has a good adaptability when compared with other treatment groups.Mice were allowed free access to high-fat diet and tea infusion(1:30,w/v)once daily for 25 days,only yellow tea significantly reduced blood glucose and the efficacy of black tea and green tea for their intervention hyperglycemia has no statistical significantly when compared to the control group.This phenomenon repeated again in high-fat diet experiment which lasted for 36 days.qPCR analysis showed “adaptive” response appeared not only in 25 days but in 36 days experiments.However,qPCR results show that the “adaptive” response did not presented in 9 days of high-fat diet.Most importantly,high-fat diet caused a rapid hepatic TXNIP protein elevation,which was significantly reversed by yellow tea.In conclusion,yellow tea not only has a good tolerance but has the best efficacy of anti-hyperglycemic when compared to other groups.Yellow tea suppressed effectively high-fat diet-induced early elevation of hepatic thioredoxin-interacting protein,which is markedly involved in increasing fasting blood glucose.