Altered gut microbiota has evidenced to be associated with colitis and colonic tumorigenesis, however bacteria-driven mechanism underlying inflammation-related colon pathologies remains undetermined. This study identifies a previously overlooked genus, Megasphaera , is highly abundant in inflammatory bowel diseases (IBD) and colorectal cancer (CRC) cohorts. A Megasphaera species, M. elsdenii reshapes colonic immunity by triggering dendritic cell (DC)-mediated Th1 and Th17 inflammation. Mechanistically, M. elsdenii and its lipopolysaccharide triggers DC activation via TLR4/NF-κB/IRF4 pathway. Accordingly, in Tlr4 −/− mice, M. elsdenii colonization cannot expand colonic infiltration of DCs and fails to induce Th1 and Th17 responses in. In a Shanghai CRC cohort with a 100% detective rate for Megasphaera , the species of Megasphaera significantly dominated in early onset CRC patients (<50 years old) rather than late-onset CRC (≥50 years old). M. elsdenii and M. elsdenii -enriched microbiota exacerbate colonic inflammation and tumorigenesis in azoxymethane (AOM)/dextran sodium sulfate (DSS)-induced murine colitis-associated cancer model. Taken together, this study uncovers a pathogenic role of Megasphaera in developing colonic tumorigenesis via activating DC-mediated inflammation.
Yuanyuan Zhao,Jinfeng Bi,Jianyong Yi,Xinye Wu,Youchuan Ma,Ruiping Li
The intestinal fermentability of pectic polysaccharides is largely determined by its molecular size. In this study, fermentation properties of enzymatic-modified apple pectin (AP) and homogalacturonans (HG) with high, medium and low molecular weight (Mw) were evaluated by in vitro fermentation model , and their structural changes were also investigated. Results showed that Mw, monosaccharide contents and molecular linearity of the AP hydrolysates were reduced after microbial degradation . On the other hand, culture media supplemented with low-Mw AP (60,300 g/mol) and low-Mw HG (861 g/mol) exhibited lower pH (5.1 and 5.7, respectively) and produced higher total short-chain fatty acid contents (SCFA, 230.40 mmol/L and 187.19 mmol/L, respectively). However, reduced trends in abundance of the pectinolytic microorganisms Faecalibacterium and Eubacterium were showed as Mw of the HG decreased, whereas growth of the SCFA-producer genera Bifidobaacterium , Megasphaera and Allisonella were improved. This work confirmed that low-Mw pectin and homogalacturonan generated more beneficial metabolites, developing structure-microbiota-gut health relationship.
危险品化学品经营许可证（带存储）