Mechanism Research Of Regulation Of Green Tea On Intestinal Microbes

Tea is one of the three largest non-alcoholic beverages in the world.It is popular in the world for its various health benefits.Inhibition of obesity is one of the many health-care functions of drinking tea,and there is a close relationship between obesity and intestinal microbes.Therefore,research on drinking tea and regulating intestinal microbes has become a hot topic.However,the effect of different doses of green tea on intestinal flora regulation is not clear.The regulation mechanism and contribution rate of the three components of tea(tea polyphenols,caffeine and L-theanine)on gut microbiota regulation is not clear.It is not clear whether the tea infusion contaminated with the Colletotrichum gloeosporioides affects the original regulation of the intestinal flora of green tea infusion.Therefore,this research studied the dose-effect of green tea,the different contribution of three components of tea,and Colletotrichum gloeosporioides-contaminated tea infusion on the regulation of intestinal microbiota.It was clarified the dose-effect of green tea on improve the disorder of intestinal microbiota caused by high-fat diet.the intestinal flora disorder caused by high fat diet.The mechanism was clarified of three functional components of tea on the regulation of intestinal microbiota.The effect was evaluated of Colletotrichum gloeosporioides-contaminated tea infusion on the food safety of tea concentrate and products.This doctoral thesis is of great significance to clarify the mechanism of green tea on health-care effect.The main content of this research is as follows.1.C57BL/6J mice were fed with a high-fat diet and treated with 1%,2%,and 4%green tea for 8 weeks.The body weight,physiological and biochemical index,histological morphology,and composition of gut microbiota were measured.The results showed that these three concentrations of green tea can regulate lipid metabolism in high-fat diet mice,restore intestinal morphology,and exert varying degrees of weight loss.However,only the intestinal flora cluster of 2%and 4%green tea drinking groups completely separated from the high-fat group,and controlled the reduce of intestinal microbial diversity in high-fat diet mice.Drinking 4%of green tea also restored the ratio of Firmicutes/Bacteroidetes in the gut.At the same time,compared with the high-fat diet group,content of 14 genera including Allobaculum were significantly reduced in the tea drinking group,and content of 18 genera including Intestinimonas were significantly increased.In a word,within 1 to 4%concentration range,4%high-concentration green tea had the most significant effect on improving the intestinal microbiota disorder caused by high-fat diet.2.The comparative effects of three functional components of green tea,tea polyphenols,caffeine and L-theanine on intestinal flora were studied in C57BL/6J mice fed with high-fat diet.And the three components were fed to high-fat diet mice by the proportion of green tea.After 8 weeks of treatment,body weight,physiological and biochemical index,histological morphology and composition of intestinal flora were measured.The results showed that tea polyphenols and L-theanine treatment had a significant effect on body weight control,while tea polyphenols had the most obvious effect on improving the intestinal villus morphology of obese mice.L-theanine had the most significant effect on improving glucose tolerance in obese mice.In respect of intestinal flora regulation,tea polyphenols significantly reduced the richness and diversity of intestinal microflora and the relative content of Firmicutes.However,only the intestinal flora cluster of tea polyphenols drinking group completely separated from the high-fat group.Besides,Akkermansia Saccharofermentans,and Allobaculum was significantly altered by tea polyphenols,L-theanine,and caffeine intake.The intake of tea polyphenols in vivo positively regulated the growth of Akkermansia.At the same time,the intake of tea polyphenols was significantly positively correlated with the number of intestinal goblet cells,which was positively correlated with the amount of Akkermansia.However,in vitro anaerobic culture conditions,tea polyphenols inhibited the growth of Akkermansia.It is concluded that tea polyphenols do not directly promote the growth of Akkermansia but promote the growth of Akkermansia by promoting goblet-cells formation and increasing the secretion of the mucin secret,which is the food source of Akkermansia.In conclusion,tea polyphenols have the most significant effect on preventing obesity and improving intestinal microecological imbalance caused by obesity,while L-theanine and caffeine acted as auxiliary functions.3.We further validated and analyzed the effects of green tea and tea polyphenols on the regulation of intestinal microflora and the degradation in catechin composition by in vitro anaerobic culture.It was found that catechin components in green tea extract and tea polyphenols were degraded to varying degrees by intestinal bacteria.At the same time,green tea extract or tea polyphenols also significantly altered the intestinal microflora.The addition of green tea extract and tea polyphenols significantly reduced the proportion of Firmicutes/Bacteroidetes,but significantly increased the content of Fusobacteria.By the results of Lefse,green tea extract significantly increased the content of Fusobacterium,Bacteroides,and Phascolarctobacterium,but significantly decreased the content of Lachnoclostridium,Acidaminococcaceae and Veillonellaceae.Tea polyphenols significantly increased the content of Bacteroides and Fusobacterium,but significantly decreased the content of Lachnoclostridium,Acidaminococcus,and Megamonas.4.Liquid fermentation culture was carried out by adding fungal mycelium of C.gloeosporioides in tea extract to appreciate the effect of C.gloeosporioides on the functional composition of tea extraction and its effect on health.After 48 hours of culture,tea polyphenols,caffeine and L-theanine in the fermentation broth decreased by 31.0%,26.2%and 8.3%,respectively.The color of the fermentation liquor turned brown and produced a small amount of phthalate toxic substances.Animal studies showed that the fermentation blocked the original lipid-lowering function of tea extract to a certain extent,and induces kidney damage in mice.However,the uptake of contaminated tea increased the intestinal bacterial abundance and the relative content of some beneficial microorganisms such as Bifidobacteriaceae,Lactobacillus,Coriobacterineae and Faecalibacterium,but also reduced Firmicutes and some pathogenic intestinal bacteria such as Oscillibacter,Stomatobaculum and Anaerorotus.This phenomenon may be caused by the invasion of allogenic microorganisms,which stimulates the intestinal mucosal immunity of the host,and the mechanism deserves further study.In summary,this doctoral thesis clarified the dose-effect of green tea on regulation of intestinal flora.The synergistic and complementary effects of different functional components of green tea in regulating intestinal flora were clarified.Tea polyphenols among different components of green tea played the most significant role in preventing obesity and regulating intestinal flora.At the same time,it was found that the uptake of tea polyphenols significantly changed the emerging probiotics Akkermansia in the intestine,and the mechanism was explored.And the food safety of C.gloeosporioides-fermentation tea infusion was evaluated.In conclusion,this doctoral thesis discussed the regulation mechanism of green tea to the intestinal microbes,and it is of great significance to provide theoretical guidance for the better use of green tea health efficacy.