Project description:Germfree (GF) mice have been used as a model to study the contribution of the intestinal microbiota to metabolic energy balance of the host. Despite a wealth of knowledge accumulated since the 1940’s, the response of GF mice to a high fat diet is largely unknown. In the present study, we compared the metabolic consequences of a high fat (HF) diet on GF and conventional (Conv) C57BL/6J mice. As expected, Conv mice developed obesity and glucose intolerance with a HF diet. In contrast, GF mice remained lean and resisted the HF diet-induced insulin resistance. The anti-obesity phenotype of GF/HF mice was accompanied by reduced caloric intake, diminished food efficiency, and excessive fecal lipid excretion contributed to the reduced food efficiency. In addition, HF diet-induced hypercholesterolemia was ameliorated, which was partially due to an increase in fecal cholesterol excretion. However, hepatic cholesterols were increased in GF/HF mice. Elevated nuclear SREBP2 proteins and the up-regulation of cholesterol biosynthesis genes support the increased liver cholesterol biosynthesis in GF/HF mice. The resistance to HF diet-induced metabolic abnormalities in GF mice was also associated with a reduced immune response, indicated by low plasma pro-inflammatory and anti-inflammatory markers. These data suggest that the gut microbiota of Conv mice contributes to HF diet-induced obesity, insulin resistance, dyslipidemia and hepatic steatosis in mice. Thus, results of the present study describe the metabolic responses of GF mice to a HF diet and further our understandings of the relationship between the gut microbiota and the host. Germfree and conventional C57BL/6J mice were fed with a high fat diet for 11 weeks. Then, all mice were sacrified under 10-h food deprevation, and liver samples of germfree (n=14) and conventional (n=16) were examined.
Project description:We analyzed the effects of antibiotics using a popular model of gut microbiota depletion in mice by a cocktail of antibiotics. We combined intestinal transcriptome together with metagenomic analysis of the gut microbiota to develop a new bioinformatics approach that probes the links between microbial components and host functions. We found that most antibiotic-induced alterations can be explained by three factors: depletion of the microbiota; direct effects of antibiotics on host tissues; and the effects of remaining antibiotic-resistant microbes. While microbe depletion led to down-regulation of immunity, the two other factors primarily inhibited mitochondrial gene expression and amounts of active mitochondria, and induced cell death. By reconstructing and analyzing a transkingdom network, we discovered that these toxic effects were mediated by virulence/quorum sensing in antibiotic-resistant bacteria. This series includes gene expression in the ileum of control, antibiotics (ABx)-treated, germfree, germfree-ABx-treated and mice colonized with normal or Abx-resistant microbiota. common reference design with a pool of small intestine RNA labeled with Cy3
Project description:We analyzed the effects of antibiotics using a popular model of gut microbiota depletion in mice by a cocktail of antibiotics. We combined intestinal transcriptome together with metagenomic analysis of the gut microbiota to develop a new bioinformatics approach that probes the links between microbial components and host functions. We found that most antibiotic-induced alterations can be explained by three factors: depletion of the microbiota; direct effects of antibiotics on host tissues; and the effects of remaining antibiotic-resistant microbes. While microbe depletion led to down-regulation of immunity, the two other factors primarily inhibited mitochondrial gene expression and amounts of active mitochondria, and induced cell death. By reconstructing and analyzing a transkingdom network, we discovered that these toxic effects were mediated by virulence/quorum sensing in antibiotic-resistant bacteria. This series includes gene expression in the ileum of control, antibiotics (ABx)-treated, germfree, germfree-ABx-treated and mice colonized with normal or Abx-resistant microbiota.
Project description:Increased evidences demonstrated that gut microbiota targeted diet intervention can alleviate obesity and related metabolic disorders. The underlying mechanism of interactions among diet, microbiota and host still remains unclear. Enterobacter cloacae B29, an endotoxin-producing strain dominated in the gut of a morbidly obese volunteer (weight 174.8 kg, BMI 58.8 kg m-2) was isolated and transplanted to germfree mice. Using deep mRNA sequencing technology, we compared different gene expression profiles in the colon samples of the germfree mice before and after treated with B29 and/or high fat diet (HFD) and identified 279 differential expressed genes in total, including up-regulated genes Apoa4, Ido1, Cyp4a10, and down-regulated genes Cyp2e1, Cyp26b1, Akr1b7, Adipoq, Cyp1a1, Apoa1, Npc1l1, Tff2, Apoc1, Ctla2a, Mttp, Lpl. Fifty-nine GO biological processes and five KEGG pathways, particularly the Peroxisome proliferator-activated receptors (PPARs) signaling pathway, were significantly enriched in response to HFD+B29, which were mainly relevant to inflammation and the metabolism of lipid, lipoprotein and sterols. These functional changes were consistent with the developed obesity, insulin-resistance, and aggravated inflammatory conditions of the HFD+B29 mice. This work provides insight into the gene expression changes in response to HFD+B29, helping to understand the mechanism of the interactions among HFD, B29 and the germfree mice.
Project description:The human intestinal microbiota associated with rats produces in vivo a soluble(s) factor(s) that down-regulates the expression of genes encoding for the Shiga toxin II in E. coli O157:H7. The Shiga toxin II is one of the major virulence factors of E. coli enterohemorragic leading to the deadly hemolitic and uremic syndrome. Investigation of the effect of the human intestinal microbiota on the whole transcriptome of EHEC O157:H7 is of major importance to increase our understanding of the pathogen transcriptomic adaptation in response to the human microbiota. We analysed by microarray hybridization the gene expression pattern of EHEC O157:H7 grown in the caecal content of germ-free rats or rats associated with the human microbiota of a healthy human subject. By doing so, we increased our understanding of the regulatory activities of the human gut microbiota on E. coli O157:H7 A first group of twelve weeks old, male, germfree rats was colonized with the human fecal microbiota and a second group was kept germfree and condidered as a controle group. Rats were fed for two weeks with a sterile human type diet, and were sacrificed. E. coli O157:H7 was cultivated for 6 hours in the caecal content of germfree rats and rats associated with the human intestinal microbiota. RNAs were extracted and cDNAs were synthesized, fragmented and biotinylated before being hybridized on Affymetrix E. coli genome 2.0 arrays. The effect of the human intestinal microbiota was investigated by comparing the gene expression level in the caecal content of rats associated with the human microbiota with their expression level in the caecal content of the germfree rats.
Project description:Acetaminophen is a widely used antipyretic and analgesic drug, and its overdose is the leading cause of drug-induced acute liver failure. This study aimed to investigate the effect and mechanism of Lacticaseibacillus casei Shirota (LcS), an extensively used and highly studied probiotic, on acetaminophen-induced acute liver injury. C57BL/6 mice were gavaged with LcS suspension or saline once daily for 7 days before the acute liver injury was induced via intraperitoneal injection of 300 mg/kg acetaminophen. The results showed that LcS significantly decreased acetaminophen-induced liver and ileum injury, as demonstrated by reductions in the increases in aspartate aminotransferase, total bile acids, total bilirubin, indirect bilirubin and hepatic cell necrosis. Moreover, LcS alleviated the acetaminophen-induced intestinal mucosal permeability, elevation in serum IL-1α and lipopolysaccharide, and decreased levels of serum eosinophil chemokine (eotaxin) and hepatic glutathione levels. Furthermore, analysis of the gut microbiota and metabolome showed that LcS reduced the acetaminophen-enriched levels of Cyanobacteria, Oxyphotobacteria, long-chain fatty acids, cholesterol and sugars in the gut. Additionally, the transcriptome and proteomics showed that LcS mitigated the downregulation of metabolism and immune pathways as well as glutathione formation during acetaminophen-induced acute liver injury. This is the first study showing that pretreatment with LcS alleviates acetaminophen-enriched acute liver injury, and it provides a reference for the application of LcS.