The Effect Of Gut Microbiota On DSS Induced Acute Colitis In Mouse Model

Intestinal dysbiosis is one of the characteristics of inflammatory bowel disease(IBD)patients,and gut microbiota is necessary for the development of IBD.Calorie restriction can enrich probiotics(such as Lactobacilli group)and reduce the abundance of opportunistic pathogens,resulting in significantly attenuated antigenic burden which is emanated from gut microbiota and reduce inflammation.Thus,calorie restriction may be a potentially effective therapy to prevent or cure IBD.SPF C57 BL/6J male mice were employed in our research to observe the effect of calorie restriction on DSS induced acute colitis.After calorie restriction for four weeks,the mice were fed with 2.5% DSS(w/v)solution for 7 days,and then followed by a switch to sterile drinking water for 2 days.At the same time,the pathology of mice during DSS treatment and the followed recovery phase were observed and recorded.The Illumina highthroughput sequencing was used to sequence the V3-V4 regions in the16 sRNA gene of gut microbiota and the intestinal microbiota structure between the two groups were compared.After calorie restriction,the gut microbiota of CR group significantly varied from that of NC group,such as significantly enriched probiotic Lactobacillus spp.and decreased opportunistic pathogens(including bacteria from Akkermansia,Prevotella and Ocillibacter)which are associated with intestinal inflammation or permeability.After DSS treatment,CR showed lesser body weight loss and lower disease activity index(DAI)compared with NC group.In addition,the concentration of LCN-2 in feces which can sensitively indicate the intestinal inflammation level was significantly lower in CR group than NC group on Day 6 of feeding DSS.Evidences above indicated that the calorie restriction can modulate gut microbiota structure and plays a protective role in DSS induced acute colitis in mice.In order to confirm that it is the gut microbiota which connects calorie restriction and alleviated DSS induced acute colitis,we established gnotobiotic animal models by transplanting the intestinal flora of NC group or CR group mice to germ-free mice,followed by observing the variances between two kinds of GN mice responding to DSS treatment.The results showed that the DAI of GN-CR group mice was significantly lower than that of GN-NC group mice on Day 3 and Day 9 of feeding DSS.The results suggested that the gut microbiota may be the intermediary in which the calorie restriction protects the mice from DSS induced acute colitis.In this research,we also noticed that the DSS induced colitis mouse model was with poor reproducibility.Controversial results also have been obtained from experiments employing this model even by using the same mouse strain under the same conditions but by different researchers.As the gut microbiota play an important role in DSS-induced colitis,it is essential to evaluate the influence of the initial gut microbiota on this model.Therefore,we identified significant variations in the initial gut microbiota of different batches of mice and found that the initial intestinal microbiota had a profound influence on DSS-induced colitis.We performed three independent trials using the same C57BL/6J mouse model with DSS treatment and used high-throughput 16 S rRNA gene sequencing to analyze the gut microbiota.We found that the structure and composition of the gut microbiota in mice with severe colitis,as compared with mice with milder colon damage,had unique features,such as an increase in Akkermansia bacteria and a decrease in Barnesiella spp.Moreover,these varied gut bacteria in the different trials also showed different responses to DSS treatment.Taken together,our research revealed that gut microbiota modulated by calorie restriction plays a protective role in DSS induced acute colitis in mice,and that the variactions in initial gut microbiota affected the stability of DSS induced colitis mouse model.The results indicated that calorie restriction targeting gut microbiota might be a potential therapy to inflammatory bowel disease,and suggested that,in studies using mouse models,the gut microbiota must be evaluated when examining mechanisms of diseases to ensure that comparable results are obtained.