The Preventive Effect Of Auricularia Auricular-judae(Bull.) Polysaccharide Against IBD And Its Modification

With the change of the lifestyle,the prevalence of inflammatory bowel disease(IBD)has increased year by year.IBD can be separated to ulcerative colitis(UC)and Crohn disease(CD)by different symptoms,among which UC has the highest incidence in China.IBD is difficult to cure,so finding an effective preventive agent has become an effective method for the prevention and treatment of IBD.This article selects a polysaccharide extracted from fungus,Auricularia auricular-judae(Bull.),named as Aap,as the research object,aiming to explore the effect of Aap in preventing IBD and its mechanism.Our purpose is to provide theoretical support for the deep processing of Auricularia auricular and develop its application.In this study,dextran sodium sulfate(DSS)solution was used to induce acute UC in BALB/c mice and the preventive effect of Aap on acute UC was evaluated.Through high-throughput sequencing,we found that Aap would change the gut microbiota.Then,the fecal bacteria ingested from Aap mice were transplanted to normal mice to explore the preventive effect of recipient mice on acute UC.At the same time,Aap was modified by carboxymethylation to improve the solubility of Aap.Main conclusions are as followed:1.7-day-3.5%DSS as drinking water could significantly lower the body weight of BALB/c mice and make their stool loose and bleed,which showed that the above conditions could effectively construct an acute UC model in mice.2.The preventive effect of Aap on acute UC was tested.Firstly,high dose of Aap could prevent weight lost,lower their disease activity index(DAI)and increase their colon length.Then,compared with disease mice,intaking Aap in 40mg/kg body weight could significantly lower white blood cell count(WBC)and serum interleukin(IL)-6 content and tumor necrosis factor(TNF)-? content,which showed that Aap could prevent the inflammation induced by UC.At the same time,after taking 40 mg/kg body weight Aap,the plasma D-lactic acid(D-LA)and the diamine peroxidase(DAO)content was significantly decreased.And the H&E staining pictures showed that Aap mice had a complete colon construction.Results showed that Aap could significantly prevent intestinal mucosal barrier dysfunction.Finally,the results of high-throughput sequencing showed that the composition of the intestinal flora of the mice after ingesting Aap was significantly different from that of the diseased mice.The sample abundance heat map showed that compared with diseased mice,the Aap group had higher levels of beneficial bacteria including Bacteroides.The content of harmful bacteria was reduced,including Deferrobacteria,Actinobacteria and Ruminococcus.The above results showed that:Aap had a significant preventive effect on acute UC in mice and could positively regulate the intestinal flora of mice.3.A fecal bacteria transplantation was conducted.We found that receiving Aap fecal bacteria transplantation could significantly increase the colon length,lower the WBC count and lower the serum IL-6 and TNF-? content and could prevent micropathological damage.Such results indicated that the recipient mice who received Aap fecal bacteria transplantation showed a significant preventive effect towards UC.Aap prevented DSS-induced acute UC by regulating the intestinal flora.4.Carboxymethylated Aap(CM-Aap)was prepared by solvent method.The fourier transform infrared spectrogram showed that CM-Aap had new strong absorption peaks at 1596 cm-1,1415 cm-1 and 1322 cm-1,indicating that the carboxymethyl substitution was successful.Compared with Aap,the solubility of CM-Aap was increased by 71%.However,after carboxymethylation,the results of the Congo red experiment showed that the triple helix structure in Aap disappeared.Compared with Aap,the free radical scavenging rate of CM-Aap dropped.The decreased antioxidant activity of CM-Aap in vitro may be related to the destruction of the triple helix structure in Aap during the carboxymethylation process.The results showed that carboxymethylation modification could improve the solubility of Aap,but the structural changes caused by the modification process would affect the antioxidant properties of CM-Aap in vitro.