Study On The Anti-obesity Effect And Mechanism Of Dancong Tea With Different Storage Years

Tea contains many active ingredients such as tea polyphenols and theaflavin,and has unique medicinal and health functions.It is a kind of diet food with safety and effectiveness.In the process of the conversion of new tea to aged tea,the internal chemical components transformed,resulting in a certain change in its anti-obesity effect.In this study,the compositions of Dancong tea samples with the same variety and different storage years were detected and analyzed,and the inhibitory rate of these samples on the lipase activity in vitro was measured as well.Combined with animal experiments,the anti-obesity effect of Dancong tea has been systematically studied.By spectrophotometry and high-performance liquid chromatography,it was found that Dancong tea samples with different storage years had different chemical composition.The contents of tea polyphenol,catechins and free amino acid in Dancong tea stored for years were lower than that of the fresh tea,while the contents of aqueous extract,total soluble sugars,gallic acid and theaflavin in Dancong tea stored for years were higher than the fresh tea,and there was no significant difference in caffeine content among three tea samples.Moreover,the experiments in vitro indicated that the inhibition of Dancong tea in 1996 on lipase activity was the highest at 43.01 %,although the other two also showed inhibitory effect.At the same time,a high-fat diet was used to build a nutritional obese mouse model,and then the mice in the experimental group were treated respectively with 1000 mg/kg·BW three different tea extracts for 6 weeks.By comparing the body weight change and the final blood lipid,it was found that Dancong tea extract could significantly improve body weight,Lee’s index and the serum levels of TG,TC,LDL-C and HDL-C,although no marked differences were observed in Dancong tea extracts with different years.The organ index,combined with the organ section and hematoxylin-eosin staining technique,was used to evaluate the accumulation of fat in mice and observe the morphological changes of hepatocytes and adipocytes.Dancong tea showed inhibitory effects on organ indexes,hepatic steatosis and adipocyte enlargement.In addition,tea samples with different storage years can inhibit fat accumulation in varying degrees,and the effect of Dancong tea extract in 2006 was the best.With western blot and immunohistochemical staining techniques,the expression changes of energy metabolism-related proteins in the liver of mice were further studied to explore the mechanism of Dancong tea’s anti-obesity effect.It was found that Dancong tea extract could upregulate the expression of p-AMPK,p-ACC and CPT-1,which promoted the oxidation of fatty acids.At the same time,the tea extracts down-regulated the expression of FAS protein and inhibited the biosynthesis of fat.In addition,Dancong tea extract could inhibit the expression of inflammatory factors iNOS and TNF-α in nutritional obese mice.Dancong tea extract showed excellent performance in improving dyslipidemia and diet-induced obesity,and tea extract in 2006 had the best inhibitory effect on fat accumulation.This result provides new ideas for the prevention and treatment of obesity,and helps to develop the aged tea market as well.