The Modulation Of Metabolic Syndrome And Gut Microbiota By Fuzhuan Brick Tea And Its Polysaccharides

Tea(Camellia sinensis),one of the most popular drinks in the world,has a long history of over 5,000 years in dietary and medicinal applications especially in Asian countries including China,Japan,India and Thailand.Thereinto,Fuzhaun brick tea(FBT),mainly produced in Hunan Province,is one of the dark tea,which has the most complex and unique processing technology.The FBT is mainly produced with the help of fermentation with Eurotium cristatum as the dominant fungi,which produces the golden yellow spots commonly known as "golden flowers".FBT has various health-promoting activities such as antioxidant,antibacterial,and modulating effect on lipid metabolism,which is considered as an essential drink for Tibetans,Uygurs and Mongolians in the southwest frontier region of China.The extensive and in-depth studies have been carried out to investigate the active ingredients in FBT and the modulating effect of FBT on lipid metabolism.However,the bioactive components contributing to the various health-promoting activities and the potential mechanisms responsible for regulating lipid metabolism remain unclear.An increasing number of works has shown that gut microbiota is closely related to human health,especially the lipid and energy metabolism.Thus,the modulation of the gut microbiota is important to regulate host metabolism and maintain human health.The recent studies show that dietary polysaccharides could pass through the digestive system without being broken down and reach the large intestine safely,where it could be degraded and utilized by gut microbiota.Thus,modulation of gut microbiota by dietary polysaccharides has been put forward as a new target in the treatment of diet-induced metabolic syndrome(MS).In this study,FBT,loved by people in the frontier region of China,was chosen as raw material to investigate its alleviating effect on high fat diet(HFD)induced MS and modulating effect on gut microbiota.The polysaccharides from FBT(FBTPS)was separated and purified,and then the in vitro digestion of FBTPS in simulated saliva,gastric and small intestinal conditions and the effect of FBTPS on gut microbiota were also studied.Based on result of digestion and fermentation in vitro,HFD fed mice model were used to evaluate the effect of FBTPS on MS and gut microbiota.The work has important significance in identification of bioactive components contributing to health-promoting activities and demonstrating the function mechanisms of FBT.The main research contents and results in this work are as follows:1.FBT and Kudingcha attenuate the MS in HFD miceThe effect of FBT on the MS and gut microbiota in HFD fed C57BL/6J mice was evaluated in this chapter.The result showed that FBT intervention could attenuate the HFD-induced body weight gain,fat accumulation,liver weight as well as content of TG in liver.After administration of FBT,plasma lipids levels,including triglyceride(TG)and low-density lipoprotein cholesterol(LDL-C)were also significantly reduced.FBT had suppressive effect on the HFD-induced oxidative injure,decreased the levels of LPS,TNF-?,IL-6 and CRP in serum and significantly reduced the hepatic expression levels of PPARy,SREBP-lc and FAS,which may result in the lipogenesis and accumulation of fat.FBT could enhance the microbial diversity and modulate the composition of gut microbiota.Thereinto,FBT intervention could significantly decrease the relative abundance of Firmicutes and increase the relative abundance of Bacteroidetes,which led to the significant decrease in the ratio of Firmicutes to Bacteroidetes.At family level,FBT could enhance the relative abundance of Bifidobacteriaceae.At OTUs level,FBT treatments reversed 58 OTUs,which were significantly changed by HFD intervention.In general,FBT treatment was an effective way for modulating the HFD induced gut microbiota.However,the potential mechanism should be further investigated.2.Evaluation of chemical property,cytotoxicity and antioxidant activity of FBTPSThe nine kinds of crude FBTPS were prepared from different kinds of FBT,and the chemical properties,cytotoxicities and antioxidant activities in vitro and in vivo were evaluated in this chapter.The results showed that FBTPS from different FBT exhibited similar chemical properties.The natural carbohydrate contents of FBTPS were ranged from 45.2 ± 3.3 to 59.4 ± 2.3%.The contents of protein in FBTPS were less than 5%.The contents of total polyphenols were ranged from 4.2 ± 0.1 to 10.3 ± 0.3 mg GAE/100 mg.Furthermore,FBTPS had high uronic acid contents,which belonged to typical acidic polysaccharides.The nine kinds of FBTPS were mainly composed of Man,Rha,GalA,Glc,Gal and Ara with little molar contents of Rib and GlcA,which were all typical heteropolysaccharides.FBTPS exhibited significant little cytotoxicity at concentrations ranging from 25 to 400 ?g/mL.Compared with ascorbic acid,FBTPS exhibited limited DPPH free radical scavenging activity(ranged from 54.3± 1.9 to 67.8 ± 2.5%),noticeable scavenging activity on superoxide radicals(over 85%),superior ABTS radical scavenging activity(near 100%)and protective effect on H2O2-induced oxidative injury in PC 12 cells.In general,FBTPS could be used as a natural safe antioxidant.3.Digestion of FBTPS under simulated digestive conditions in vitroThe digestion of FBTPS under simulated saliva,gastric and small intestinal conditions was carried out to examine digestion properties of FBTPS.After saliva,gastric and small intestinal digestion,there was no change for molecular weight of FBTPS in both retention time and response value.Furthermore,the reducing sugar(Cr)values of FBTPS solutions before and after digestion did not significantly changed,suggested that simulated saliva,gastric and small intestinal conditions could not break down FBTPS.Moreover,the monosaccharide composition of digestive solutions did not significantly changed suggested that no free monosaccharide was released after digestion.In general,FBTPS could pass through the digestive system without being hydrolyzed and reach the large intestine safely.The results in this study may provide some useful information on the digestion of FBTPS and other dietary polysaccharides in vitro.4.The fermentation of FBTPS and the effect of FBTPS on gut microbiota in vitroIn this work,the anaerobic fermentation model in vitro and high throughput sequencing technology were used to evaluate the effect of gut microbiota on FBTPS metabolism as well as the effect of FBTPS on gut microbiota.It was obvious that the response of FBTPS in HPLC significantly decreased with the increase of fermentation time.The contents of CR and polysaccharides in fermentation solution also significantly reduced with the increase of fermentation time.Furthermore,about 75.9%FBTPS was broken down after 24 h of fermentation.The results showed that indigestible FBTPS could be broken down and utilized by gut microbiota.At the same time,the results of principal component analysis(PCA)and clustering analysis showed FBTPS could significantly modulate the composition and structure of gut microbiota.FBTPS could significantly reduce the ratio of Firmicutes to Bacteroidetes.Thereinto,Prevotella and Bacteroides in genus level were significantly increased.The pH values for FBTPS fermentation solution continued to decrease with the increase of fermentation time,and the concentrations of total SCFAs increased from 3.46±0.17 to 48.22 ± 3.56 rnM for FBTPS group.Thereinto,the concentrations of acetic,lactic and propionic acid significantly increased.Unfortunately,there was no significant increase in concentrations of n-butyric,i-butyric,n-valeric and i-valeric acids.In general,FBTPS has the potential to modulate the gut microecology.5.FBTPS attenuated MS and gut microbiota dysbiosis in HFD induced miceHFD-fed C57BL/6J mice as MS model were treated daily either with water or FBTPS(200,400 or 800 mg/kg/day,respectively)through oral administration for 8 weeks to evaluate the effects of FBTPS on MS and gut microbiota.The results showed FBTPS could significantly suppress the HFD-induced body weight gain,accumulation of adipose tissue,adipocyte size,liver weight,hepatic lipid deposition as well as the levels of TC and LDL-C in serum,suggested that FBTPS could significantly prevent MS in a dose-dependent manner.Based on the result of qPCR analysis,FBTPS could significantly down-regulate the expression levels of LXRa,FAS,SREBP-lc and PPAR?,related to lipogenesis and accumulation of fat,and up-regulate the expression level of CPT-1,which is related to lipid catabolism.Based on result of sequencing,FBTPS treatment could increase the HFD-induced microbiota phylogenetic diversity and lead to profound alteration in gut microbiota structure and composition.Nevertheless,an obvious amelioration of HFD-induced gut microbiota back to health status was observed for medium and high dosages of FBTPS intervention.FBTPS intervention could significantly reverse the HFD-induced increases in the relative abundances of Erysipelotrichaceae,Coriobacteriaceae and Streptococcaceae in a dose-dependent manner.At OTUs level,33,31 and 36 of the 95 OTUs that altered by HFD treatment were reversed in HFD-L,HFD-M and HFD-H groups,respectively,resulting in significant reversion of 55 OTUs in total.The result of spearman's correlation analysis showed that 50 key OTUs were negatively or positively associated with MS.Notably,23 of the 50 OTUs which were negatively correlated with parameters of MS were significantly enhanced by FBTPS treatment.On the contrary,27 of the 50 OTUs which were positively correlated with parameters of MS were significantly reduced by FBTPS treatment.Although it is difficult to arrive at the cause-effect relationships among these associations in this work,our data suggested that FBTPS-induced modulation in the gut microbiota was highly associated with MS in obese mice and these changes in gut microbiota might be an important mechanism for FBTPS mediating its beneficial metabolic effects.In general,the possible mechanism of MS prevention by FBTPS is that indigestible FBTPS reach the large intestine and then modulate the gut microbiota and lipid metabolism.However,the accurate mechanism should be further investigated in the future.