Comparison Of Hypoglycemic Activity Of Three Kinds Of Selenium-enriched Tea And Ordinary Tea And Preliminary Exploration Of Its Mechanism

Based on the previous research,this project was conducted to compare the chemical components and in vitro glucose and lipid metabolism,oxidative stress and hypoglycaemic activity of different teas(including selenium-rich steamed green,common steamed green,selenium-rich black tea,common black tea(Gong Gong black tea),selenium-rich black tea and common black tea(Fu brick tea)),as well as to compare the hypoglycaemic ability of six tea extracts on hyperglycaemic mice in vivo and related mechanisms,in order to explore The study was carried out to investigate the possible mechanisms of different teas to alleviate hyperglycemia and reverse target organ damage,so as to provide some scientific basis for the prevention and treatment of diabetes and provide reference for the development of functional foods from tea.As a traditional health drink,tea has a variety of health benefits.Green tea,black tea and dark tea,among the six major tea groups,have a variety of biological activities,with active substances derived from theanine,polysaccharides and polyphenols.The hypoglycaemic effect is one of its most notable activities,but little is known about its evaluation and its potential role in the mechanism of hypoglycaemia.At the same time,as selenium is an essential trace element for improving human immunity,improving human selenium nutrition through selenium-enriched foods and investigating the health benefits of selenium-enriched tea has gradually become one of the important hot spots in the field of tea research today.Through the comparison of the hypoglycaemic activity of three kinds of selenium-rich tea and ordinary tea and the preliminary investigation of the mechanism,the results of the study showed that.Firstly,the results of in vitro chemical fraction analysis showed that the highest total content of tea polyphenols and catechins was in selenium-rich steamed green(43.16%,23.31%),the highest total content of tea polysaccharides,flavonoids and alkaloids was in normal steamed green(18.73%,5.94%,10.86%),the highest total nitrogen content was in normal black tea(22.77%),the highest total content of theanine and minerals was in selenium-rich(8.77%,73.83 mg/g)and the highest total phenolic acid content was found in regular black tea(4.84%).The inhibitory activity of ?-glucosidase activity of all six tea extracts was proportional to their concentration and was concentration dependent.The most effective selenium-rich black tea(98.2%)at the highest concentration(1000 mg/L),with an IC50 around 0.4%,had good glucosidase inhibitory activity,elucidating that there were significant differences in the chemical fractions of the different tea types due to their different qualities,processing methods and storage conditions of the finished products.Secondly,the results of selenium-rich tea and normal tea extracts in regulating blood glucose in mice on a high-fat diet showed that the degree of intervention of different tea extracts on blood glucose and body weight in mice at the same concentration(400 mg/kg-d)was significantly different.Compared with the model group,selenium-rich black tea had the best effect on blood glucose control(blood glucose decreased by 2.7 mmol/L)and mice body weight decreased by 1.5 g.The ITT-AUC of selenium-rich steamed green and regular black tea was lower than that of regular black tea and selenium-rich black tea,which significantly enhanced the glucose tolerance and insulin sensitivity of hyperglycaemic mice.The results of serum parameters analysis showed that ordinary black tea significantly increased the SOD activity and decreased the ALT and GSP concentrations in mice serum,showing the best modulating effect.Selenium-rich black tea significantly reduced TG,HDL and MDA concentrations in mice serum,showing the best regulatory effect.Selenium-rich steamed green could significantly reduce the serum levels of ASL and TC in mice,showing the best regulatory effect.It indicates that the pathways of action of different teas to alleviate the elevated blood glucose caused by glucolipid metabolism and oxidative stress are not exactly the same.Meanwhile,the histological analysis of mice on high-fat diet under the intervention of tea extracts showed that different tea extract groups were able to alleviate to a certain extent the symptoms of target organ damage caused by elevated blood glucose,such as liver cell degeneration,tissue disorganization,cell deformation and vacuolation,and inflammatory factor infiltration in mice.It can also effectively improve the cell volume expansion status of white adipose tissue.This indicates that the intervention of selenium-rich black tea and normal black tea had a certain degree of reversal on organ damage such as liver and white adipose.In addition,RT-PCR analysis showed that common black tea could significantly up-regulate GLUT-2 and IRS-1 m RNA expression and down-regulate PTEN and GSK-3? m RNA expression,while selenium-rich black tea could significantly up-regulate PI3 K,AKT and PDX-1 m RNA expression.It showed that selenium-rich black tea and common black tea tea aqueous extracts could promote glucolipid metabolism and improve glucose homeostasis and insulin sensitivity by regulating the PI3K/AKT/GSK-3? proliferation-activated receptor cascade signaling pathway in the liver and increasing the expression levels of GLUT-2,PDX-1 and other genes.Finally,the analysis of the diversity of intestinal microorganisms in the faeces of mice showed that the intake of both the aqueous extract of regular black tea(OBT)and the aqueous extract of selenium-rich black tea(SBT)affected the distribution of intestinal flora in hyperglycaemic mice.The results of the Shannon and Simpson indices showed that the higher index of SBT increased the diversity of intestinal microflora in mice.The number of OTUs in SBT increased by 49 compared to the model group,demonstrating that it enhanced the diversity and abundance of microorganisms in the mouse intestinal flora.At the phylum level,Firmicutes/Bacteroidetes values were reduced after OBT and SBT interventions,and the effect was more pronounced in the SBT group.Reversal of gut microbiota dysbiosis by inhibition of Firmicutes/Bacteroidetes.Genus-level compositional analysis revealed significant differences in the abundance of Allobaculum,Unspecified S24-7,Bacteroides,Ruminococcus?1,Ruminococcus,and Lachnospiraceae in the intestinal microbiota of the four groups of mice.Further aggregation analysis revealed that SBT was the most effective in enriching the diversity of the species,mainly enriching the species making Actinobacteria,Paraprevotellaceae,Bifidobacteriales,Bifidobacteriaceae,f?Paraprevotellaceae,Enteroccaceae,Enterococcus,etc.,resulting in a significant increase in their abundance,while OBT resulted in a significant increase in the abundance of Erysipelotrichi,Allobaculum,Clostridium,etc.These genera have been reported to play an important role in the homeostasis of the intestinal environment and in the metabolic processes of the body,participating in glycolipid metabolism and altering the intestinal environment.In addition the effect of black tea aqueous extract group on intestinal flora also involved metabolic pathways including nucleotide metabolism,cell growth and death,energy metabolism,lipid metabolism and glycan biometabolism.The results of this thesis show that all six tea extracts differed significantly in their chemical composition due to their quality and processing methods,and all of them could improve glucolipid metabolism and oxidative stress levels in mice,and the main ways in which different types of tea exerted their hyperglycaemic activity were not identical.In comparison,the selenium-rich black tea group was more effective,with the highest total theanine and mineral content and the best inhibition rate of ?-glucosidase activity;the best effect on the regulation of blood glucose and body weight in mice on a high-fat diet after 7 weeks;inhibition of excessive weight gain in the model group and higher area under the OGTT curve,enhancement of glucose tolerance in mice,and the ability to regulate the hepatic insulin resistance pathway in the liver.It could significantly up-regulate the expression of PI3 K,AKT and PDX-1 m RNA,promote glucolipid metabolism and reduce liver injury.In addition,the diversity index of the intestinal flora in the selenium-rich black tea group was higher,and the proportion of Firmicutes/Bacteroidetes could be significantly reduced,and the aqueous extract of this tea had the most obvious enrichment effect on the flora closely related to the change of blood glucose,so it was speculated that it might,to a certain extent,reverse the disrupted intestinal microbiological environment due to high blood glucose and bring it closer to the normal flora pattern.The results of this thesis suggest that selenium-rich black tea has great potential and application value for further development as an active ingredient of functional health food for hyperglycaemia.