Trade-Off between Bile Resistance and Nutritional Competence Drives Escherichia coli Diversification in the Mouse Gut

Bacterial diversification is often observed, but underlying mechanisms are difficult to disentangle and remain generally unknown. Moreover, controlled diversification experiments in ecologically relevant environments are lacking. We studied bacterial diversification in the mammalian gut, one of the most complex bacterial environments, where usually hundreds of species and thousands of bacterial strains stably coexist. Herein we show rapid genetic diversification of an Escherichia coli strain upon colonisation of previously germ-free mice. In addition to the previously described mutations in the EnvZ/OmpR operon, we describe the rapid and systematic selection of mutations in the flagellar flhDC operon and in malT, the transcriptional activator of the maltose regulon. Moreover, within each mouse, the three mutant types coexisted at different levels after one month of colonisation. By combining in vivo studies and determination of the fitness advantages of the selected mutations in controlled in vitro experiments, we provide evidence that the selective forces that drive E. coli diversification in the mouse gut are the presence of bile salts and competition for nutrients. Altogether our results indicate that a trade-off between stress resistance and nutritional competence generates sympatric diversification of the gut microbiota. These results illustrate how experimental evolution in natural environments enables identification of both the selective pressures that organisms face in their natural environment and the diversification mechanisms

230: Heightened risk of coronary atheroma conferred by a decrease in the plasma concentrations of lithocholic acid

ContextThe bile acids receptors Farsenoid X and TGR5 protect against the formation of atheroma in mice, though no evidence have linked coronary atheroma and bile acid in human. Bile acids links these receptors with more or less efficient activation, depending on the species.ObjectiveTo test the hypothesis that changes in concentrations of circulating bile acid species influence the risk of developing coronary atheromas in humans.MethodsPilot, prospective, observational study conducted between June and September 2010. The serum concentrations of cholic, chenodeoxycholic, deoxycholic, and lithocholic acids were measured in a fasting blood sample. Consecutive hospitalized or ambulatory patients undergoing emergency or elective coronary angiograms were eligible for inclusion. Post-cardiac arrest and non-fasting states, hepatic disease, and treatment with antimicrobials, corticosteroids, statins or fibrates were exclusion criteria. Of 393 screened patients, 44 met the study entry criteria, and were divided between 27 patients with (Group A) and 17 without (Group B) angiographically visible coronary atheromas. The pool of circulating bile acids was analyzed to measure the plasmatic concentrations of 28 different bile acid species. The variables associated with the presence of angiographically visible coronary atheromas were examined by single and multiple variable logistic regression analysis.ResultsThe serum lithocholic acid concentration was significantly lower in group A than in group B. By multiple variable analysis, lithocholic acid was the only predictor of coronary atheroma independently of patient gender (odds ratio 2.41 per 0.05 decrease; 95% confidence interval 1.11 to 5.25, P=0.027ConclusionA low serum concentration of lithocholic acid was an independent predictor of coronary atheroma in human

Protective potential of the gallbladder in primary sclerosing cholangitis

Background & Aims: Gallbladder enlargement is common in patients with primary sclerosing cholangitis (PSC). The gallbladder may confer hepatoprotection against bile acid overload, through the sequestration and cholecystohepatic shunt of bile acids. The aim of this study was to assess the potential impact of the gallbladder on disease features and bile acid homeostasis in PSC.Methods: Patients with PSC from a single tertiary center who underwent liver MRI with three-dimensional cholangiography and concomitant analyses of serum bile acids were included. Gallbladder volume was measured by MRI and a cut-off of 50 ml was used to define gallbladder enlargement. Bile acid profiles and PSC severity, as assessed by blood tests and MRI features, were compared among patients according to gallbladder size (enlarged vs. normal-sized) or presence (removed vs. conserved). The impact of cholecystectomy was also assessed in the Abcb4 knockout mouse model of PSC.Results: Sixty-one patients with PSC, all treated with ursodeoxycholic acid (UDCA), were included. The gallbladder was enlarged in 30 patients, whereas 11 patients had been previously cholecystectomized. Patients with enlarged gallbladders had significantly lower alkaline phosphatase, a lower tauro-vs. glycoconjugate ratio and a higher UDCA vs. total bile acid ratio compared to those with normal-sized gallbladders. In addition, gallbladder volume negatively correlated with the hydrophobicity index of bile acids. Cholecystectomized patients displayed significantly higher aspartate aminotransferase and more severe bile duct strictures and dilatations compared to those with conserved gallbladder. In the Abcb4 knockout mice, cholecystectomy caused an increase in hepatic bile acid content and in circulating secondary bile acids, and an aggravation in cholangitis, inflammation and liver fibrosis.Conclusion: Altogether, our findings indicate that the gallbladder fulfills protective functions in PSC.Impact and implications: In patients with primary sclerosing cholangitis (PSC), gallbladder status impacts on bile acid homeostasis and disease features. We found evidence of lessened bile acid toxicity in patients with PSC and enlarged gall-bladders and of increased disease severity in those who were previously cholecystectomized. In the Abcb4 knockout mouse model of PSC, cholecystectomy causes an aggravation of cholangitis and liver fibrosis. Overall, our results suggest that the gallbladder plays a protective role in PSC.& COPY; 2022 The Authors. Published by Elsevier B.V. on behalf of European Association for the Study of the Liver (EASL). This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)

Saccharomyces boulardii CNCM I-745 Modulates the Fecal Bile Acids Metabolism During Antimicrobial Therapy in Healthy Volunteers

Saccharomyces boulardii CNCM I-745 (SB) is a probiotic yeast used to lower the incidence of antibiotic-associated Clostridium difficile (C. difficile) infection, though its mechanism of action remains unclear. Cholic acid is a primary bile acid, which triggers the germination and promotes the growth of C. difficile. The intestinal microbiota transforms primary into secondary bile acids. This study examined (1) the antimicrobial-induced alteration of fecal bile acid content, and (2) whether the concomitant administration of SB influences this transformation. This is an ancillary work from a randomized study, which revealed that SB modulates fecal microbiota dysbiosis during antibiotic treatment. Healthy subjects were randomly assigned to (1) SB only, (2) amoxicillin-clavulanate (AC), (3) SB plus AC, or (4) no treatment. We analyzed fecal concentrations of BA by high performance liquid chromatography/tandem mass spectrometry. Compared to the untreated or the SB-treated groups, AC decreased the percentage of fecal secondary BA significantly (days 3 and 7). When SB and AC were administered concomitantly, this decrease in secondary BA was no longer significant. Following treatment with AC, a significant peak of fecal CA was measured on days 3 and 7, which was prevented by the concomitant administration of SB. AC administered to healthy volunteers altered the microbial transformation of primary BA, decreased secondary BA, and increased CA. The latter was prevented by the concomitant administration of SB and AC, suggesting a potent mechanism protection conferred by SB against post-antimicrobial C. difficile infection.Clinical Trial Registration:www.ClinicalTrials.gov, identifier NCT01473368

Inhibitory Effect of Ursodeoxycholic Acid on Clostridium difficile Germination Is Insufficient to Prevent Colitis: A Study in Hamsters and Humans

Introduction: Bile acids (BA) influence germination and growth of Clostridium difficile. Ursodeoxycholic acid (UDCA), a BA minor in human, used for cholestatic liver diseases, inhibits germination and growth of C. difficile in vitro, but was never tested in vivo with an infectious challenge versus control. We hypothesized that UDCA could prevent CDI. We evaluated the effects of UDCA on C. difficile in vitro and in hamsters, with pharmacokinetics study and with an infectious challenge. Then, we studied CDI incidence in UDCA–treated patients.Methods: We evaluated germination and growth of C. difficile, with 0.01, 0.05, and 0.1% UDCA. We analyzed fecal BA of hamsters receiving antibiotics and UDCA (50 mg/kg/day), antibiotics, or UDCA alone. Then, we challenged with spores of C. difficile at D6 hamsters treated with UDCA (50 mg/kg/day) from D1 to D13, versus control. In human, we analyzed the database of a cohort on CDI in acute flares of inflammatory bowel disease (IBD). As PSC-IBD patients were under UDCA treatment, we compared PSC-IBD patients to IBD patients without PSC.Results:In vitro, UDCA inhibited germination and growth of C. difficile at 0.05 and 0.1%, competing with 0.1% TCA (with 0.1%: 0.05% ± 0.05% colony forming unit versus 100% ± 0%, P < 0.0001). In hamsters, UDCA reached high levels only when administered with antibiotics (43.5% UDCA at D5). Without antibiotics, UDCA was in small amount in feces (max. 4.28%), probably because of UDCA transformation into LCA by gut microbiota. During infectious challenge, mortality was similar in animals treated or not with UDCA (62.5%, n = 5/8, P = 0.78). UDCA percentage was high, similar and with the same kinetics in dead and surviving hamsters. However, dead hamsters had a higher ratio of primary over secondary BA compared to surviving hamsters. 9% (n = 41/404) of IBD patients without PSC had a CDI, versus 25% (n = 4/12) of PSC-IBD patients treated with UDCA.Conclusion: We confirmed the inhibitory effect of UDCA on growth and germination of C. difficile in vitro, with 0.05 or 0.1% UDCA. However, in our hamster model, UDCA was inefficient to prevent CDI, despite high levels of UDCA in feces. Patients with PSC-IBD treated with UDCA did not have less CDI than IBD patients

Expression de la calmoduline et des annexines au cours du developpement

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : TD 20305 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Analyse des mécanismes d'inhibition de l'intégrase du virus de l'immunodéficience humaine de type 1

L'intégrase (IN) rétrovirale catalyse l'intégration de l'ADN du VIH-1 dans l'ADN des cellules infectées en deux étapes: la maturation en 3 (3 P) et le transfert de brin (ST). Le ST est inhibé par les dicétoacidesou leurs isostèrestels que le raltégravir (RAL)approuvé par la FDA en tant que médicament anti-SIDA et le TB11 qui agit aussi sur 3 P. L étude comparative de ces deux composés montre que TB11 et RAL interagissent avec les extrémités LTR processée et non-processée, bien que l affinité de TB11 soit beaucoup plus faible. Les Kd de liaison à l'ADN processésont proches des IC50 rapportés pour le ST suggérant l existence d une corrélation fonctionnelle entre l'affinité pour l ADN processé et l'inhibition de ST. TB11 contrairement à RAL interagit avec IN prise isolément et s'intercale à forte concentration dans les paires de bases de l'ADN ce qui expliqueraitsa forte toxicité. La compréhension du mécanisme d inhibition de INs est poursuivi par l étude de deux anticorps monoclonaux anti-K159 (peptide 147-175 de IN), 4C6 et 4F4 dont les épitopes se situent respectivement dans les portions N- et C-terminalesde K159. Les résultats montrent que 1) les anticorps sont capables de reconnaître leurs épitopes dans IN; 2) IN se sert des mêmes résidus pour interagir avec les anticorps et l ADN viral ; 3) les anticorps reconnaissent leurs épitopes avec une forte affinité. Nos résultats sur les inhibiteurs de ST serviront au développementd une nouvelle génération d'inhibiteurs interagissant préférentiellement avec l ADN viral et induisant moins de mutations de résistance dans IN; ceux sur les anticorps aideront à progresser dans la recherche d'inhibiteurs actifs sur le 3 P.Retroviral Integrase (IN) catalyzes integration of viral cDNA into the infected cell chromosome in a two-step reaction: the 3 processing (3 P) and the strand transfer (ST). The ST reaction is inhibited by diketoacids or isosteres as raltegravir (RAL) approved by FDA for use in anti-AIDS therapy or TB11 that acts also on the 3 P reaction. The comparative study of the two compoundsdemonstrate that TB11 similarly to RAL interacts with the free LTR ends, either processed or unprocessed, although with a much lower affinity compared with RAL. For each compound, we found a good agreement between the affinity values for processed LTR and the in vitro IC50 values reported for ST inhibition, suggesting a functional relationship between drug binding to DNA and ST inhibition.TB11, unlike RAL, binds to free IN and intercalates into DNA base pairs upon increase of drug concentration which could be at the basis of its high toxicity.The understanding of the inhibition mechanism of INwas pursued by the study of two monoclonal antibodies anti-K159 (147-175 peptide of HIV-1 IN), 4C6 and 4F4. The antibodies recognize epitopes lying in the N-terminal portion and in the C-terminal portion of K159. Results show that 1) both antibodies are able to recognize their epitopes in the entire IN; 2) IN uses common residues to interact with the viral DNA and the antibody and 3) antibodies recognize epitopes with very high affinity. Our results on ST inhibitors can be used for developmentof a new family of inhibitors interacting preferentially with viral DNA, thereby inducing less resistance mutations in IN, those on antibodies should help us in the search of inhibitors acting preferentially on 3 P.PARIS-BIUSJ-Biologie recherche (751052107) / SudocSudocFranceF

Variations in gastrointestinal lipases, pH and bile acid levels with food intake, age and diseases: Possible impact on oral lipid-based drug delivery systems

International audienceThe lipids and some surfactants present in oral lipid-based drug delivery systems are potential substrates for the various lipases involved in gastrointestinal (GI) lipolysis. The levels of these enzymes, together with pH and biliairy secretion, are important parameters that condition the fate of lipid-based formulations (LBF) and the dispersion, solubilization and absorption of lipophilic drugs in the GI tract. Since in vitro methods of digestion are now combined with dissolution assays for a better assessment of LBF performance, it is essential to have a basic knowledge on lipase, pH and bile acid (BA) levels in vivo to develop relevant in vitro models. While these parameters and their variations in healthy subjects are today well documented, in vivo data on specific populations (age groups, patients with various diseases, patients with treatment affecting GI tract parameters, …) are scarce and obtaining them from clinical studies is sometimes difficult due to ethical limitations. Here we collected some in vivo data already available on the levels of digestive lipases, gastric and intestinal pH, and BAs at various ages and in patients with exocrine pancreatic insufficiency, a pathological situation that leads to drastic changes in GI tract parameters and impacts pharmacological treatments

Lipid-depleted diet perturbs membrane composition and intracellular transport in lactating mammary cells

International audienc