Hypoglycemic Effect And Molecular Mechanism Of Black Tea And Its Black Brick Tea With Fungus Growing On Hyperglycemic Model Mice

Diabetes is a chronic non-infectious,metabolic disease characterized by hyperglycemia.It is mainly caused by the deficiency of insulin or the decrease of insulin utilization rate due to the destruction of islet ? cell function mediated by T cells.Although hypoglycemic drugs such as insulin-stimulating secretors and metformin have good hypoglycemic effect,they are mostly synthesized chemically and are difficult to prevent complications effectively.Developing and utilizing natural,safe and effective hypoglycemic drugs or auxiliary hypoglycemic functional foods will be the development trend of preventing and treating diabetes,and also an important development direction of dietary nutrition intervention.Studies have shown that green tea,black tea,dark tea,oolong tea,yellow tea and other tea products have hypoglycemic effects,However,related researches are mainly limited to whether a certain kind of tea or tea component has hypoglycemic effects,while the hypoglycemic effect of the same tea with different characteristics processed by the same tea fresh leaves remains unknown.Black brick tea with fungus growing,a new black tea product,is processed by steaming,pressing,blooming and drying on the basis of black tea.However,whether it has better hypoglycemic effect than black tea and how the molecular mechanism remains to be explored.In this study,three different doses of water extract of black tea and black tea with fungus growing(low(300 mg·(kg·d)-1),medium(500 mg·(kg·d)-1),and high(1000 mg·(kg·d)-1))were used to intervene SPF KM male hyperglycemic model mice for 28 days,employing enzyme-linked immunosorbent assay(Elisa),qRT-PCR,and Western blot,aimed to study the hypoglycemic effect and molecular mechanism of black tea and its black brick tea with fungus growing on hyperglycemia model mice via the aspects of body weight,food intake,drinking water,pancreas morphological structure,organ index,biochemical indexes of blood and liver,and the key enzymes,genes,protein expression and signal pathway in glucose synthesis,decomposition,transformation.So as to provide scientific basis for the production and consumption of black tea and black brick tea with fungus growing.The main findings and conclusions are as follows:(1)Hypoglycemic effect.The hyperglycemia model was determined by continuous injection of streptozotocin at a dose of 50 mg.(kg·d)-1 for five days,once a day,and the blood sugar was determined after fasting for 16 hours.Compared with th normal group,the body weight,drinking water and diet of mice in model group reach significant difference(P < 0.01),and blood sugar reached the standard of hyperglycemia,which indicated that the model was successful.Compared with the model group,the blood glucose level decreased and the insulin level and oral glucose tolerance increased(P <0.05),the high-dose group increased the pancreatic index and the high-dose of black brick tea with fungus growing group decreased(P <0.05).The levels of total cholesterol in medium and high-dose group and triglyceride and malondialdehyde in each dose group decreased(P <0.05).The activities of catalase and superoxide dismutase in medium and high dose groups andthe activity of glutathione peroxidase in each dose group increased(P <0.05),and the activity of malondialdehyde and superoxide dismutase in the high-dose group of black brick tea with fungus growing reached extremely significant level(P <0.01).The content of hepatic glycogen in different dosage groups of black brick tea with fungus growing and middle and high dosage groups of black tea increased(P <0.05).Compared with the black tea group,the high-dose group of black brick tea with fungus growing was significantly better than the high-dose black tea group in improving insulin,blood sugar,malondialdehyde,hepatic glycogen and oral glucose tolerance(P <0.05).The activities of superoxide dismutase,catalase and glutathione peroxidase in middle and high dose groups of black brick tea with fungus growing were significantly higher than those in middle and high dose groups of black tea(P <0.05).(2)The molecular mechanism of hypoglycemia.On the mRNA level,compared with the model group,PDK1 and PFKFB2 mRNA were up-regulated in the lowdose group ofblack brick tea with fungus growing(P <0.05).AKT,PDK1,GLUT2 mRNA was up-regulated in the middle dose group of black tea(P <0.05),PIP5 K,PFKFB2,HKII mRNA was up-regulated butdidin't reached significant level,while GSK3? mRNA was down-regulated(P <0.01).IRS1,AKT,PI3 K,PDK1,PFKFB2,HK II,GS,GLUT2,AS160,PIP5 K were up-regulated and GSK3? mRNA was down-regulated in high-dose black tea group and middle-dose and high-dose black brick tea with fungus growing group(P <0.01).Compared with the black tea group,the high-dose group of black brick tea with fungus growing was superior to the black tea group in regulating PI3 K,PDK1,GSK3 beta and GS mRNA(P <0.05),and the high-dose group of black tea was superior to the black brick tea with fungus growing group in regulating PFKFB2 and HKII mRNA(P <0.05).On the protein level,the GSK3? protein was down-regulated in the low-dose black tea group compared with the model group(P <0.05);The p-AKT and PI3 K proteins were up-regulated in the low-dose group(P <0.01)and the p-GSK3? protein was down-regulated(P <0.01)in the low dose group of black brick tea.with fungus growing.The PFKFB2 protein was up-regulated in the middle dose of black tea group(P <0.05),the p-AKT protein was up-regulated in the middle and high dose of black tea groups,the GSK3? and p-GSK3? proteins were down-regulated(P <0.01),and the PDK1 and INSR proteins were up-regulated in the high-dose of black tea group(P <0.05)and PFKFB2 protein up-regulated(P <0.01);The p-AKT,p-IRS1,GLUT2,PDK1,PI3 K,GSK3?,p-GSK3?,INSR and PFKFB2 protein were up-regulated in the high-dose group,and except for the middle dose group,the level of p-IRS1 protein wasup-regulated extremely significant(P <0.01)Compared with the black tea group,the black brick tea with fungus growing group was better in regulating p-AKT and PI3 K protein(P <0.01)and medium and high dose groups were better in regulating GLUT2 and PDK1 protein(P <0.05).In summary,black tea and itsblack brick tea with fungus growing can lower blood sugar in hyperglycemic mice.And black brick tea with fungus growing is better than black tea in improving the levels of insulin,blood sugar,malondialdehyde,hepatic glycogen and oral glucose tolerance,and increasing superoxide dismutase,catalase and glutathione peroxidase activity;The mechanism is that black tea and its black brick tea can repair damaged islets and liver tissue.And can lower blood sugar level in hyperglycemic organisms via glucogen synthesis pathway INSR/ISR-1/PI3K/PDK1/GSK3?/GS,glucose absorption and transport pathway INSR/ISR-1/PI3K/PDK1/PIP5K/AS160/GLUT2 and glycolysis pathway INSR/ISR-1/PI3K/PDK1/PFKFB2/HKII.Moreover,theblack brick tea with fungus growing has better regulation effect on PI3 K,PDK1,GSK3?,GS mRNA and p-AKT,PI3 K,GLUT2,PDK1 proteins than black tea.