Eeffects Of Dietary Tea On Ameliorating Intestinal Immune Function In Mice Fed A High Fat Diet

Obesity is the result of excess energy intake and metabolic abnomality,which has become a serious public health problem in the world.It is indicated that obesity is a state of chronic low-grade systemic inflammation,but the casual relationship between obesity and inflammation is unclear.Tea is a well-known heathy beverage,the effects of which on reducing fat accumulation and weight gain and on alleviating metabolic syndrome have been frequently reported.However,due to the low bioavailability and ambugious molecular targets of tea polyphenols(main bioactive components of tea),the underlying mechanisms of health benefits of tea were largely unknown.Based on our previous studies,C57BL/6J mice fed on a high-fat diet were selected to explore the alterations of intestinal barrier function by tea intervention using transcriptome sequencing technology in the present study,and the role of intestinal immune barrier in alleviating metabolic abnormalities was also preliminarily clarified.Specifically,a total of 74 male C57BL/6 mice(6-week-old)were randomly divided into four groups:low fat diet group(LF,n=14),high fat diet group(HF,n=20),high fat diet plus green tea supplementation group(GT,n=20)and high fat diet plus black tea supplementation group(BT,n=20).During the 14-week experiment period,the food and water intake of mice were monitored every two days,the body weight was monitored every week,and the fasting blood sugar level was monitored every four weeks.The main results are as follows:1.Compared with mice in HF group,the average weights of animals in GT and BT groups were decreased by 20.49%(p<0.001)and 17.67%(p<0.001)respectively,and the fat depositions of experimental mice were decreased(p<0.001).Also,the dispersion of fat vacuoles and fat accumulation in the liver of tea treated mice were significantly ameliorated.In addition,compared with HF group,the levels of aspartate aminotransferase(AST)and alanine aminotransferase(ALT)in GT treated mice were decreased by 24.42%and 81.32%,respectively,and these two enzymes in mice of BT group were decreased by 33.04%and 77.76%,respectively.Tea supplements also significanlty decreased the levels of serum total cholesterol(TC),triglyceride(TG),high density lipoprotein cholesterol(HDL-C)and low density lipoprotein cholesterol(LDL-C)(p<0.001).Moreover,the levels of blood glucose in GT and BT treated mice were lowered by 23.22%(p<0.01)and 22.35%(p<0.01).2.The levels of lipopolysaccharide(LPS),tumor necrosis factor-alpha(TNF-?),interleukin-6(IL-6)and monocyte chemoattractant protein-1(MCP-1)in mice treated with dietary tea powders were significantly decreased.Specifically,GT and BT treatments decreased the levels of LPS by 83.95%(p<0.01)and 69.14%(p<0.05),and lowered the concentrations of TNF-? by 80.54%and 68.11%(p<0.001),respectively.Furthermore,green and black tea treatments decreased the levels of serum SIgA by 35.70%(p<0.01)and 24.37%(p<0.05),respectively.In addition,the gene expressions of TNF-?,matrix metalloproteinase-3(MMP-3)and cyclooxygenase-2(COX-2)in the livers of mice treated with dietary tea powders were significantly decreased(p<0.01).Compared with HF group,the mRNA level of hepatic MMP-3 gene in mice from GT and BT groups were decreased by 66.13%(p<0.01)and 49.19%(p<0.05),respectively.3.The changes of intestinal gene expression profile in tea treated mice were further investigated using transcriptome sequencing technology.Based on the differentially expressed gene data,the results of GO classification showed that the top 10 GO Terms between HF-vs-LF,GT-vs-HF and BT-vs-HF groups were significantly related to intestinal immunity,such as immune response(32 genes of GT-vs-HF,50 genes of BT-vs-HF;74 genes of HF-vs-LF),immune system process(82 genes of BT-vs-HF),innate immune response(22 genes of GT-vs-HF).Furthermore,using the differential genes aforementioned,KEGG pathway analysis showed that IgA-related intestinal immune network,B-cell receptor signaling pathway and NF-?B signaling pathway were significantly enriched.Among the genes screened,classic MHC-? genes,F4/80,CD 40,CD 80,CD11c,CD163,BAFF,APRIL,LBP,TRAM,CD74,MyD88 and NF-?B were all significantly down-regulated in mice from GT and BT groups(p<0.01 or p<0.05)compared to those of HF animals.And it was worthy to mention that the changes of all the genes listed above maitained the same trend with those from LF group.Also,the alterations of these genes were further verified by q-PCR tests.In conclusion,tea supplementation in diet significantly improved metabolic abnormalities and low-grade systemic inflammation in mice fed a high-fat diet,and the key genes of intestinal mucosal antigen presentation,IgA production and inflammation in mice were significantly changed.However,the underlying mechanism of tea intervention on intestinal mucosal immune barrier function and the role of intestinal flora in this process need to be further explored.The results of this study provide novel perspectives to clarify the underlying mechanisms of tea consumption in alleviating metabolic syndrome.