The Effects Of Two Akkermansia Muciniphila Strains On Murine Colitis And Gut Microbiota

Inflammatory bowel diseases(IBD)is a kind of chronic intestinal inflammation,and the colon is one of the main tissues affected by it.Its generation and development are closely related with the host gut microbiota.During studying of this relationship,scientists concerned the abundance of Akkermansia muciniphila was significantly reduced in the patients with IBD,suggesting that it might affect the development of IBD.However,a number of studies have found that the abundance of A.muciniphila increased significantly in mice with acute colitis,suggesting that the role of A.muciniphila in acute and chronic colitis may be different,and the A.muciniphila strains from different sources may have different roles.So far,most researches on Akkermansia muciniphila were focused on its type strain BAA-835 BAA-835(contracted into BAA-835),this strain was regarded as a potential probiotic in that it has beneficial effects upon obesity and diabetes.However,the effects of strain BAA-835 and other A.muciniphila strains on the IBD or acute colitis,are unknown.In this study,we isolated and idenfited a murine A.muciniphila strain(designated 139),compared its genome with strain BAA-835,then investigated and compared the anti-inflammatory properties of the two strains in cell models,in dextran sulfate sodium(DSS)-induced chronic and acute colitis of mice.First,we identified the isolated murine strain 139 as a novel A.muciniphila strain based on the neighbor-joining tree using its 16S rRNA full sequence.Then we observed the appearance of strain 139 under electron microscopy,determined the growth curve of the two strains,and compared the whole genomes of them.We found that the two strains did share great similarity in terms of their appearance and their whole genome sequence was 91%similarity.Also,they shared many functional genes.However,we also found that the two strains had some different characteristics.The concentration of strain BAA-835 in the synthetic medium was more than strain 139 when cultured to the plateau stage.Also,to their genomes,strain BAA-835 and strain 139 had 41 and 59 specific coding sequences(CDSs)respectively,which suggested that the two strains may show some different physiological proeprties in mice with colitis.Next,to investigate the effects of two A.muciniphila strains on chronic colitis,we firstly used human colon cancer cell line HT-29 cells to test the anti-inflammatory potentials of strain BAA-835 and strain 139 at first,then investigated their effects on mice with 3%DSS-induced chornic colitis.In vitro,the two strains exerted notably anti-inflammatory properties.In vivo,both strains ameliorated the chronic colitis as they improved clinical parameters including spleen weight,colon inflammation index,and colon histological score.They also down-regulated the expression of some pro-inflammatory cytokines in the colon of mice.However,the anti-inflammatory effects of strain BAA-835 were stronger than strain 139.Dysbiosis of the gut microbiota was observed in mice with chronic colitis.Both A.muciniphila strains facilitated the normalization of the gut microbiota.The specific capacity of strain BAA-835 to modulate the differentiation of Tregs as well as increase production of short chain fatty acids in mice,demonstrated strain-specific characteristics for these two A.muciniphila strains.This part of study demonstrated that both strain BAA-835 and strain 139 ameliorate the intestinal inflammation and dysbiosis of gut microbiota in mice with chronic colitis,but the effect of strain BAA-835 was stronger than strain 139 and it showed specific physiological properties.Finally,to investigate the effects of two A.muciniphila strains on acute colitis,we used 3%DSS to induce acute colitis of mice and gavaged the mice with two strains respectively.It was found that the mice gavaged strain BAA-835 had significantly lower body weight and colon length than the mice in DSS control group at the later stage of the experiment,and had higher DAI index and colon histological score,while the mice gavaged strain 139 did not.In terms of gut microbiota,both strains significantly changed the gut microbiota structure of mice.24 operational taxonomic units(OTUs)responded to strain BAA-835 and 19 OTUs responded to strain 139,but only 6 OTUs were responded to both strains.This part of the study showed that strain BAA-835 may inhibit the recovery of acute colitis in mice,while strain 139 did not,which may be related to their different effects on gut microbiota of mice.In conclusion,our study found that two A.muciniphila strains,human-derived strain BAA-835 and murine strain 139,both could ameliorate the chronic colitis and the dysbiosis of gut microbiota in mice,suggesting that these two strains have the potential to treat IBD.However,the effect of A.muciniphila on acute colitis in mice was not obvious,suggesting if the A.muciniphila strains were applied to the treatment of colitis,attention should be given to the type of the colitis.And because strain BAA-835 showed tendency to slow the recovery of inflammation and gut microbiota dysbiosis in acute colitis,if it was hard to make sure the types of colitis,the strain 139 could be a safer choice.Moreover,our study found both strains have strain-specificities in their genomes and physiological properties,highlighting the importance of studying the impact of gut microbiota on host disease and identifying the probiotics at strain level.