Fusobacterium nucleatum promotes colon cancer progression by changing the mucosal microbiota and colon transcriptome in a mouse model

BACKGROUND Fusobacterium nucleatum(F.nucleatum)has long been known to cause opportunistic infections and has recently been implicated in colorectal cancer(CRC),which has attracted broad attention.However,the mechanism by which it is involved in CRC development is not fully understood.AIM To explore its potential causative role in CRC development,we evaluated the colon pathology,mucosa barrier,colon microbiota and host transcriptome profile after F.nucleatum infection in an azoxymethane/dextran sulfate sodium salt(AOM/DSS)mouse model.METHODS Three groups of mice were compared to reveal the differences,i.e.,the control,AOM/DSS-induced CRC and AOM/DSS-FUSO infection groups.RESULTS Both the AOM/DSS and AOM/DSS-FUSO groups exhibited a significantly reduced body weight and increased tumor numbers than the control group,and AOM/DSS mice with F.nucleatum infection showed the highest tumor formation ratio among the three groups.Moreover,the colon pathology was the most serious in the AOM/DSS-FUSO group.We found that the structure of the colon microbiota changed considerably after F.nucleatum infection;striking differences in mucosal microbial population patterns were observed between the AOM/DSS-FUSO and AOM/DSS groups,and inflammation-inducing bacteria were enriched in the mucosal microbiota in the AOM/DSS-FUSO group.By comparing intestinal transcriptomics data from AOM vs AOM/DSSFUSO mice,we showed that transcriptional activity was strongly affected by dysbiosis of the gut microbiota.The most microbiota-sensitive genes were oncogenes in the intestine,and the cyclic adenosine monophosphate signaling pathway,neuroactive ligand–receptor interaction,PPAR signaling pathway,retinol metabolism,mineral absorption and drug metabolism were highly enriched in the AOM/DSS-FUSO group.Additionally,we showed that microbial dysbiosis driven by F.nucleatum infection enriched eight taxa belonging to Proteobacteria,which correlates with increased expression of oncogenic genes.CONCLUSION Our study demonstrated that F.nucleatum infection altered the colon mucosal microbiota by enriching pathogens related to the development of CRC,providing new insights into the role of F.nucleatum in the oncogenic microbial environment of the colon.

Antidiabetic Effects of Gegen Qinlian Decoction via the Gut Microbiota Are Attributable to Its Key Ingredient Berberine

Gegen Qinlian Decoction(GQD),a traditional Chinese medicine(TCM)formula,has long been used for the treatment of common metabolic diseases,including type 2 diabetes mellitus.However,the main limitation of its wider application is ingredient complexity of this formula.Thus,it is critically important to identify the major active ingredients of GQD and to illustrate mechanisms underlying its action.Here,we compared the effects of GQD and berberine,a hypothetical key active pharmaceutical ingredient of GQD,on a diabetic rat model by comprehensive analyses of gut microbiota,short-chain fatty acids,proinflammatory cytokines,and ileum transcriptomics.Our results show that berberine and GQD had similar effects on lowering blood glucose levels,modulating gut microbiota,inducing ileal gene expression,as well as relieving systemic and local inflammation.As expected,both berberine and GQD treatment significantly altered the overall gut microbiota structure and enriched many butyrate-producing bacteria,including Faecalibacterium and Roseburia,thereby attenuating intestinal inflammation and lowering glucose.Levels of short-chain fatty acids in rat feces were also significantly elevated after treatment with berberine or GQD.Moreover,concentration of serum proinflammatory cytokines and expression of immune-related genes,including Nfkb1,Stat1,and Ifnrg1,in pancreatic islets were significantly reduced after treatment.Our study demonstrates that the main effects of GQD can be attributed to berberine via modulating gut microbiota.The strategy employed would facilitate further standardization and widespread application of TCM in many diseases.

Inulin Can Alleviate Metabolism Disorders in ob/ob Mice by Partially Restoring Leptinrelated Pathways Mediated by Gut Microbiota

Inulin has been used as a prebiotic to alleviate glucose and lipid metabolism disorders in mice and humans by modulating the gut microbiota. However, the mechanism underlying the alleviation of metabolic disorders by inulin through interactions between the gut microbiota and host cells is unclear. We use ob/ob mice as a model to study the effect of inulin on the cecal microbiota by16 S rRNA gene amplicon sequencing and its interaction with host cells by transcriptomics. The inulin-supplemented diet improved glucose and lipid metabolism disorder parameters in ob/ob mice,alleviating fat accumulation and glucose intolerance. The a diversity of gut microbial community of ob/ob mice was reduced after inulin treatment, while the b diversity tended to return to the level of wild type mice. Interestingly, Prevotellaceae UCG 001(family Prevotellaceae) was obviously enriched after inulin treatment. A comparative analysis of the gene expression profile showed that the cecal transcriptome was changed in leptin gene deficiency mice, whereas the inulin-supplemented diet partially reversed the changes in leptin gene-related signaling pathways, especially AMPK signaling pathway, where the levels of gene expression became comparable to those in wild type mice.Further analysis indicated that Prevotellaceae UCG 001 was positively correlated with the AMPK signaling pathway, which was negatively correlated with markers of glycolipid metabolism disorders. Our results suggest that the inulin-supplemented diet alleviates glucose and lipid metabolism disorders by partially restoring leptin related pathways mediated by gut microbiota.

Detection of Plasmid-Mediated Tigecycline Resistance Gene tet(X4) in a Salmonella enterica Serovar Llandoff Isolate

The emergence and spread of plasmid-mediated tigecycline resistance genes have attracted extensive attention worldwide.We investigated the distribution of mobile tigecycline resistance genes in Salmonella genomes generated by both our laboratory and public bacterial genomes downloaded from the NCBI GenBank.The tet(X4)-positive strains were subjected to susceptibility testing and conjugation assays.The genetic features of the tet(X4)-bearing plasmid sequence were analyzed.Here,we report the identification of the plasmid-mediated tigecycline resistance gene tet(X4)in a conjugative plasmid of the Salmonella enterica serovar Llandoff strain SH16G3606,isolated from a man in China in 2016,the first reported serovar Llandoff in China as a novel sequence type ST8300.The tet(X4)-mediated resistance phenotype was successfully transferred from the Salmonella Llandoff strain into Escherichia coli J53,resulting in a 32-fold increase in the minimal inhibitory concentration of tigecycline.The tet(X4)gene was located between two copies of ISCR2 in the plasmid pSal21GXH-tetX4.To our knowledge,this is the first report of the plasmid-mediated tigecycline resistance gene tet(X4)in a Salmonella Llandoff strain isolated from a human stool sample in China.In addition,our findings demonstrated that a total of 171 isolates are carrying tet(X)-like genes distributed in 21 countries or areas across 6 continents,posing a serious threat to humans and public health.Overall,our timely discovery of the recent emergence of the tet(X4)gene in Salmonella isolates and other Enterobacteriaceae bacteria species supports the need for rapid surveillance to prevent the tet(X)-like gene from spreading.