| Objective: To observe the effects of cellulose on intestinal flora composition,intestinal barrier function,inflammation related indexes and to investigate the inhibitory effect on the occurrence and development of colorectal cancer and its possible mechanism in AOM/DSS-treated C57BL/6 Mice.Methods: 100 male C57BL/6 mice were randomly divided into control group(CG,standard AIN-93M),model group(MG,without cellulose)and low dose cellulose group(LCEG,2.5% cellulose),medium dose cellulose group(MCEG,5% cellulose),high dose cellulose group(HCEG,10% cellulose)according weight.After one week of adaptive feeding,AIN-93 M feeds with different dose cellulose were given.Two weeks after preventive diet intervention,AOM(10 mg/kg)with 1 mg/m L concentration was injected intraperitoneally,and 2% DSS was given 7 days later,and then stopped giving DSS,to return to normal drinking water for 14 days.After 3 cycles of this process,the establishment of colorectal inflammatory tumor model was completed,and the experiment lasted for 13 weeks.During the experiment,each group of mice were treated with AIN-93 M diet with different cellulose content.At the end of the experiment,the mice were sacrificed,tumor formation rate and tumor inhibition rate were calculated,and the pathological changes of colon and rectum were observed by HE staining.The intestinal flora of mice were analyzed and compared by 16 s r DNA sequencing.The expression levels of inflammatory factors IL-6,IL-1β,IL-12 and TNF-α in mouse serum were detected by enzyme linked immunosorbent assay(ELISA).Detection of Claudin-1,Occludin,ZO-1 m RNA level by real-time quantitative PCR(RT-PCR).Western blot detection of Claudin-1,Occludin,ZO-1 protein expression in mouse colorectal tumors.Results: The survival rates of MG,LCEG,MCEG and HCEG were 55%,75%,85% and90%.The tumor inhibition rates of LCEG,MCEG and HCEG were 47.06%,61.34% and73.95%,respectively.Compared with MG,the colorectal length was elongated in MCEG and HCEG(p< 0.05),the number of colorectal tumors was decreased in LCEG,MCEG and HCEG(p<0.05).The analysis of intestinal flora in mice showed that compared with MG,the abundance of Firmicutes in mice treated with different doses of cellulose was lower than that in MG(p<0.05).In the different doses of cellulose-treated mice,the relative abundance of some beneficial bacteria increased(e.g,Candidatus-saccharimonas[p<0.05]).However,the abundance of some pro-inflammatory bacteria decreased(e.g,Streptococcus [p<0.05],Eubacteriaceae [p<0.05] and Clostridioides-difficiles [p<0.05]).Compared with MG,the expression levels of IL-6,IL-1β and TNF-α in serum of mice treated with cellulose were significantly decreased(p< 0.05),while the expression level of IL-12 was significantly increased(p<0.05).Spearman correlation analysis shows that the abundance of Candidatus-saccharimonas was negatively correlated with the expression of IL-6,IL-1β and TNF-α in serum(p<0.01),and positively correlated with IL-12(p<0.01).There was no significant correlation between the abundance of Streptococcus and the expression of IL-6,IL-1β and IL-12,TNF-α in serum of mice(p﹥0.05).The abundance of Eubacteriaceae was positively correlated with the expression of IL-6,IL-1β and TNF-α in serum(p<0.01),and negatively correlated with IL-12(p<0.01).The abundance of Clostridioide-difficiles was positively correlated with the expression of IL-1β in serum(p<0.05),and negatively correlated with IL-12(p<0.05).In addition,compared with MG,the expression levels of Claudin-1 m RNA and protein in colorectal tumors of mice in LCEG,MCEG,HCEG decreased,while the levels of Occludin and ZO-1 m RNA increased(p<0.01).Conclusion: Cellulose intervention can reduce intestinal inflammatory response in AOM/DSS colorectal cancer in mice,and its possible mechanism is to change the structure of intestinal flora,increase the abundance of intestinal beneficial bacteria,reduce the abundance of Pro-inflammatory pathogenic bacteria in the intestine,improve intestinal barrier function and reduce intestinal inflammation. |
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