Induction of bacterial antigen-specific colitis by a simplified human microbiota consortium in gnotobiotic interleukin-10-/- mice.

We evaluated whether a simplified human microbiota consortium (SIHUMI) induces colitis in germfree (GF) 129S6/SvEv (129) and C57BL/6 (B6) interleukin-10-deficient (IL-10(-/-)) mice, determined mouse strain effects on colitis and the microbiota, examined the effects of inflammation on relative bacterial composition, and identified immunodominant bacterial species in "humanized" IL-10(-/-) mice. GF wild-type (WT) and IL-10(-/-) 129 and B6 mice were colonized with 7 human-derived inflammatory bowel disease (IBD)-related intestinal bacteria and maintained under gnotobiotic conditions. Quantification of bacteria in feces, ileal and colonic contents, and tissues was performed using 16S rRNA gene selective quantitative PCR. Colonic segments were scored histologically, and gamma interferon (IFN-γ), IL-12p40, and IL-17 levels were measured in supernatants of unstimulated colonic tissue explants and of mesenteric lymph node (MLN) cells stimulated by lysates of individual or aggregate bacterial strains. Relative bacterial species abundances changed over time and differed between 129 and B6 mice, WT and IL-10(-/-) mice, luminal and mucosal samples, and ileal and colonic or fecal samples. SIHUMI induced colitis in all IL-10(-/-) mice, with more aggressive colitis and MLN cell activation in 129 mice. Escherichia coli LF82 and Ruminococcus gnavus lysates induced dominant effector ex vivo MLN TH1 and TH17 responses, although the bacterial mucosal concentrations were low. In summary, this study shows that a simplified human bacterial consortium induces colitis in ex-GF 129 and B6 IL-10(-/-) mice. Relative concentrations of individual SIHUMI species are determined by host genotype, the presence of inflammation, and anatomical location. A subset of IBD-relevant human enteric bacterial species preferentially stimulates bacterial antigen-specific TH1 and TH17 immune responses in this model, independent of luminal and mucosal bacterial concentrations.

Dietary crystalline common-, micro-, nanoscale and emulsified nanoscale sitosterol reduce equally the cholesterol pool in guinea pigs, but varying nanosystems result in different sterol concentrations in serosal jejunum.

Due to hypocholesterolemic effects, sitosterol is used in functional foods and nanoscale dispersions. To investigate the influence of dietary sitosterol on sterol concentrations in Dunkin Hartley guinea pigs, seven groups consisting of eight animals each were fed either a basal diet (BD), a high-cholesterol diet (HC) or a high-cholesterol diet supplemented with crystalline commonscale (CCS), microscale (CMS, low-dosed: CMLS), nanoscale (CNS) or emulsified nanoscale (ENS) sitosterol. When compared to HC group, all sitosterol formulations decreased liver cholesterol concentrations. No differences in cholesterol or sitosterol concentration were found in plasma and liver between CCS, CMS, CNS, and ENS groups. Apparent cholesterol digestibility decreased by increasing crystalline microscale sitosterol doses. Despite a lower sitosterol intake, ENS group had higher serosal sitosterol concentrations in jejunum than CNS group. To elucidate an impact of the sitosterol nanosystem on gut tissues further studies are necessary. FROM THE CLINICAL EDITOR: In this study, the use of sitosterols in a rat model led to contradicting conclusions regarding their ability to reduce cholesterol levels efficiently in guinea pigs, suggesting that more preclinical data is needed before this method could become applicable to human studies.

Recent developments and perspectives in the investigation of probiotic effects.

The quest for a better understanding of how probiotics work has boosted an enormous interest in the molecular processes underlying host-microbe interactions. This review covers recent developments and perspectives in the study of probiotic mechanisms.

Reduced microbial diversity and high numbers of one single Escherichia coli strain in the intestine of colitic mice.

Commensal bacteria play a role in the aetiology of inflammatory bowel diseases (IBD). High intestinal numbers of Escherichia coli in IBD patients suggest a role of this organism in the initiation or progression of chronic gut inflammation. In addition, some E. coli genotypes are more frequently detected in IBD patients than others. We aimed to find out whether gut inflammation in an IBD mouse model is associated with a particular E. coli strain. Intestinal contents and tissue material were taken from 1-, 8-, 16- and 24-week-old interleukin 10-deficient (IL-10(-/-)) mice and the respective wild-type animals. Caecal and colonic inflammation was observed in IL-10(-/-) animals from the 8 weeks of life on accompanied by a lower intestinal microbial diversity than in the respective wild-type animals. Culture- based and molecular approaches revealed that animals with gut inflammation harboured significantly higher numbers of E. coli than healthy controls. Phylogenetic grouping according to the E. coli Reference Collection (ECOR) system and strain typing by random-amplified polymorphic DNA and pulsed-field gel electrophoresis revealed that all mice were colonized by one single E. coli strain. The strain was shown to have the O7:H7:K1 serotype and to belong to the virulence-associated phylogenetic group B2. In a co-association experiment with gnotobiotic mice, the strain outnumbered E. coli ECOR strains belonging to the phylogenetic group A and B2 respectively. A high number of virulence- and fitness-associated genes were detected in the strain's genome possibly involved in the bacterial adaptation to the murine intestine.

Intestinal steroid profiles and microbiota composition in colitic mice.

Reduced gut microbiota diversity in conjunction with a bloom of few bacterial species is a common feature in inflammatory bowel disease (IBD) patients. However, the environmental changes caused by inflammation and their possible impact on the microbiota are largely unknown. Since IBD is associated with an impaired intestinal steroid metabolism, we hypothesized that changes in intestinal steroid and particularly bile acid (BA) concentrations affect microbial communities. We used Interleukin-10 deficient (IL-10-/-) mice as a model for chronic gut inflammation. Healthy wild-type mice served as controls. In these animals, intestinal steroid concentrations and gut microbial diversity were analyzed at 24 weeks of age. The IL 10-/- mice developed moderate inflammation in cecum and colon and colorectal tumor formation was observed in 55 % of the animals. Compared to the healthy conditions, gut inflammation was associated with higher intestinal cholesterol and cholic acid concentrations and a reduced microbial diversity. The latter was accompanied by a proliferation of Robinsoniella peoriensis, Clostridium innocuum, Escherichia coli, and Enterococcus gallinarum. All these species proved to be highly bile acid resistant. We concluded that chronic colitis in IL-10-/- mice is associated with changes in intestinal steroid profiles. These changes may be due to alterations in gut microbiota composition or vice versa. Whether the bacterial sterol and bile acid metabolism is implicated in colitis and colorectal carcinoma etiology remains to be clarified.