Entamoeba muris mitigates metabolic consequences of high-fat diet in mice.

Metabolic syndrome (MetS) is a cluster of several human conditions including abdominal obesity, hypertension, dyslipidemia, and hyperglycemia, all of which are risk factors of type 2 diabetes, cardiovascular disease, and metabolic dysfunction-associated steatotic liver disease (MASLD). Dietary pattern is a well-recognized MetS risk factor, but additional changes related to the modern Western life-style may also contribute to MetS. Here we hypothesize that the disappearance of amoebas in the gut plays a role in the emergence of MetS in association with dietary changes. Four groups of C57B/6J mice fed with a high-fat diet (HFD) or a normal diet (ND) were colonized or not with Entamoeba muris, a commensal amoeba. Seventy days after inoculation, cecal microbiota, and bile acid compositions were analyzed by high-throughput sequencing of 16S rDNA and mass spectrometry, respectively. Cytokine concentrations were measured in the gut, liver, and mesenteric fat looking for low-grade inflammation. The impact of HFD on liver metabolic dysfunction was explored by Oil Red O staining, triglycerides, cholesterol concentrations, and the expression of genes involved in ß-oxidation and lipogenesis. Colonization with E. muris had a beneficial impact, with a reduction in dysbiosis, lower levels of fecal secondary bile acids, and an improvement in hepatic steatosis, arguing for a protective role of commensal amoebas in MetS and more specifically HFD-associated MASLD.

New insights into the regulation of bile acids synthesis during the early stages of liver regeneration: A human and experimental study.

BACKGROUND AND AIMS: Liver regeneration is essential for the preservation of homeostasis and survival. Bile acids (BAs)-mediated signaling is necessary for liver regeneration, but BAs levels need to be carefully controlled to avoid hepatotoxicity. We studied the early response of the BAs-fibroblast growth factor 19 (FGF19) axis in healthy individuals undergoing hepatectomy for living donor liver transplant. We also evaluated BAs synthesis in mice upon partial hepatectomy (PH) and acute inflammation, focusing on the regulation of cytochrome-7A1 (CYP7A1), a key enzyme in BAs synthesis from cholesterol. METHODS: Serum was obtained from twelve human liver donors. Mice underwent 2/3-PH or sham-operation. Acute inflammation was induced with bacterial lipopolysaccharide (LPS) in mice fed control or antoxidant-supplemented diets. BAs and 7α-hydroxy-4-cholesten-3-one (C4) levels were measured by HPLC-MS/MS; serum FGF19 by ELISA. Gene expression and protein levels were analyzed by RT-qPCR and western-blot. RESULTS: Serum BAs levels increased after PH. In patients with more pronounced hypercholanemia, FGF19 concentrations transiently rose, while C4 levels (a readout of CYP7A1 activity) dropped 2 h post-resection in all cases. Serum BAs and C4 followed the same pattern in mice 1 h after PH, but C4 levels also dropped in sham-operated and LPS-treated animals, without marked changes in CYP7A1 protein levels. LPS-induced serum C4 decline was attenuated in mice fed an antioxidant-supplemented diet. CONCLUSIONS: In human liver regeneration FGF19 upregulation may constitute a protective response from BAs excess during liver regeneration. Our findings suggest the existence of post-translational mechanisms regulating CYP7A1 activity, and therefore BAs synthesis, independent from CYP7A1/Cyp7a1 gene transcription.

Perturbation and resilience of the gut microbiome up to 3 months after ß-lactams exposure in healthy volunteers suggest an important role of microbial ß-lactamases.

BACKGROUND: Antibiotics notoriously perturb the gut microbiota. We treated healthy volunteers either with cefotaxime or ceftriaxone for 3 days, and collected in each subject 12 faecal samples up to day 90. Using untargeted and targeted phenotypic and genotypic approaches, we studied the changes in the bacterial, phage and fungal components of the microbiota as well as the metabolome and the ß-lactamase activity of the stools. This allowed assessing their degrees of perturbation and resilience. RESULTS: While only two subjects had detectable concentrations of antibiotics in their faeces, suggesting important antibiotic degradation in the gut, the intravenous treatment perturbed very significantly the bacterial and phage microbiota, as well as the composition of the metabolome. In contrast, treatment impact was relatively low on the fungal microbiota. At the end of the surveillance period, we found evidence of resilience across the gut system since most components returned to a state like the initial one, even if the structure of the bacterial microbiota changed and the dynamics of the different components over time were rarely correlated. The observed richness of the antibiotic resistance genes repertoire was significantly reduced up to day 30, while a significant increase in the relative abundance of ß-lactamase encoding genes was observed up to day 10, consistent with a concomitant increase in the ß-lactamase activity of the microbiota. The level of ß-lactamase activity at baseline was positively associated with the resilience of the metabolome content of the stools. CONCLUSIONS: In healthy adults, antibiotics perturb many components of the microbiota, which return close to the baseline state within 30 days. These data suggest an important role of endogenous ß-lactamase-producing anaerobes in protecting the functions of the microbiota by de-activating the antibiotics reaching the colon. Video Abstract.

Prospective comparison of diagnostic tests for bile acid diarrhoea.

BACKGROUND: Bile acid diarrhoea is often missed because gold standard nuclear medicine tauroselcholic [75-Se] acid (SeHCAT) testing has limited availability. Empirical treatment effect has unknown diagnostic performance, whereas plasma 7α-hydroxy-4-cholesten-3-one (C4) is inexpensive but lacks sensitivity. AIMS: To determine diagnostic characteristics of empirical treatment and explore improvements in diagnostics with potential better availability than SeHCAT. METHODS: This diagnostic accuracy study was part of a randomised, placebo-controlled trial of colesevelam. Consecutive patients with chronic diarrhoea attending SeHCAT had blood and stool sampled. Key thresholds were C4 > 46 ng/mL and SeHCAT retention ≤10%. A questionnaire recorded patient-reported empirical treatment effect. We analysed receiver operating characteristics and explored machine learning applied logistic regression and decision tree modelling with internal validation. RESULTS: Ninety-six (38%) of 251 patients had SeHCAT retention ≤10%. The effect of empirical treatment assessed with test results for bile acid studies blinded had 63% (95% confidence interval 44%-79%) sensitivity and 65% (47%-80%) specificity; C4 > 46 ng/mL had 47% (37%-57%) and 92% (87%-96%), respectively. A decision tree combining C4 ≥ 31 ng/mL with ≥1.1 daily watery stools (Bristol type 6 and 7) had 70% (51%-85%) sensitivity and 95% (83%-99%) specificity. The logistic regression model, including C4, the sum of measured stool bile acids and daily watery stools, had 77% (58%-90%) sensitivity and 93% (80%-98%) specificity. CONCLUSIONS: Diagnosis of bile acid diarrhoea using empirical treatment was inadequate. Exploration suggested considerable improvements in the sensitivity of C4-based testing, offering potential widely available diagnostics. Further validation is warranted. CLINICALTRIALS: gov: NCT03876717.

An obesogenic diet increases atherosclerosis through promoting microbiota dysbiosis-induced gut lymphocyte trafficking into the periphery.

Although high-fat diet (HFD)-induced gut microbiota dysbiosis is known to affect atherosclerosis, the underlying mechanisms remain to be fully explored. Here, we show that the progression of atherosclerosis depends on a gut microbiota shaped by an HFD but not a high-cholesterol (HC) diet and, more particularly, on low fiber (LF) intake. Mechanistically, gut lymphoid cells impacted by HFD- or LF-induced microbiota dysbiosis highly proliferate in mesenteric lymph nodes (MLNs) and migrate from MLNs to the periphery, which fuels T cell accumulation within atherosclerotic plaques. This is associated with the induction of mucosal addressin cell adhesion molecule 1 (MAdCAM-1) within plaques and the presence of enterotropic lymphocytes expressing ß7 integrin. MLN resection or lymphocyte deficiency abrogates the pro-atherogenic effects of a microbiota shaped by LF. Our study shows a pathological link between a diet-shaped microbiota, gut immune cells, and atherosclerosis, suggesting that a diet-modulated microbiome might be a suitable therapeutic target to prevent atherosclerosis.

Hepatic deletion of serine palmitoyl transferase 2 impairs ceramide/sphingomyelin balance, bile acids homeostasis and leads to liver damage in mice.

Ceramides (Cer) have been shown as lipotoxic inducers, which disturb numerous cell-signaling pathways, leading to metabolic disorders such as type 2 diabetes. In this study, we aimed to determine the role of de novo hepatic ceramide synthesis in energy and liver homeostasis in mice. We generated mice lacking serine palmitoyltransferase 2 (Sptlc2), the rate limiting enzyme of ceramide de novo synthesis, in liver under albumin promoter. Liver function, glucose homeostasis, bile acid (BA) metabolism and hepatic sphingolipids content were assessed using metabolic tests and LC-MS. Despite lower expression of hepatic Sptlc2, we observed an increased concentration of hepatic Cer, associated with a 10-fold increase in neutral sphingomyelinase 2 (nSMase2) expression, and a decreased sphingomyelin content in the liver. Sptlc2ΔLiv mice were protected against obesity induced by high fat diet and displayed a defect in lipid absorption. In addition, an important increase in tauro-muricholic acid was associated with a downregulation of the nuclear BA receptor FXR target genes. Sptlc2 deficiency also enhanced glucose tolerance and attenuated hepatic glucose production, while the latter effect was dampened in presence of nSMase2 inhibitor. Finally, Sptlc2 disruption promoted apoptosis, inflammation and progressive development of hepatic fibrosis, worsening with age. Our data suggest a compensatory mechanism to regulate hepatic ceramides content from sphingomyelin hydrolysis, with deleterious impact on liver homeostasis. In addition, our results show the involvement of hepatic sphingolipid modulation in BA metabolism and hepatic glucose production in an insulin-independent manner, which highlight the still under-researched role of ceramides in many metabolic functions.

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 gallbladders 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.

Efficacy and safety of colesevelam for the treatment of bile acid diarrhoea: a double-blind, randomised, placebo-controlled, phase 4 clinical trial.

BACKGROUND: Bile acid diarrhoea is a common but overlooked cause of chronic watery diarrhoea. Plasma 7α-hydroxy-4-cholesten-3-one (C4) is an alternative to the gold standard tauroselcholic [75Se] acid (SeHCAT) test. Low-certainty evidence supports sequestrant treatment, including colesevelam. We aimed to determine the efficacy and safety of colesevelam in bile acid diarrhoea. METHODS: In this randomised, double-blind, placebo-controlled, investigator-initiated phase 4 trial of the sequestrant colesevelam in bile acid diarrhoea (SINBAD), we enrolled consecutive patients aged 18-79 years without inflammatory bowel disease attending SeHCAT testing for suspected bile acid diarrhoea at four Danish secondary care centres. Participants were randomly allocated 1:1 to receive 12 days of treatment with colesevelam (overencapsulated tablets of 625 mg) or placebo, with the starting dose of two capsules twice daily and titrated to effect during the first 5 days of treatment. A pharmacist independent of the clinical investigators generated a randomisation list on the web page randomization.com using block randomisation (randomisation was not stratified). C4 and SeHCAT diagnostic results were blinded during treatment. We treated all patients with diarrhoea, with a daily mean of 3·0 or more bowel movements or 1·0 or more watery bowel movements (Bristol stool scale type 6 and 7). Remission was defined as the absence of both these criteria during treatment days 6-12. The primary outcome was the intention-to-treat remission rate in bile acid diarrhoea diagnosed by C4 concentration greater than 46 ng/mL. A secondary outcome was the intention-to-treat remission rate in bile acid diarrhoea diagnosed by SeHCAT retention of 10% or less. This trial is registered with ClinicalTrials.gov, NCT03876717. FINDINGS: Between Oct 25, 2018, and July 1, 2021, 168 patients were randomly assigned to receive colesevelam (n=84) or placebo (n=84). 41 patients had C4 concentration greater than 46 ng/mL (22 assigned to the colesevelam group and 19 to the placebo group). For the C4-defined primary outcome, 14 (64%) of 22 participants receiving colesevelam versus three (16%) of 19 participants receiving placebo achieved remission (adjusted odds ratio 9·1, 95% CI 1·9-62·8; p=0·011). For the SeHCAT-defined secondary outcome, 75 of the 168 participants had retention of less than 10% (37 assigned to the colesevelam group and 38 assigned to the placebo group); 22 (59%) of 37 participants receiving colesevelam achieved remission versus five (13%) of 38 participants receiving placebo (adjusted odds ratio 11·1, 95% CI 3·4-45·6; p=0·00020). There were no serious adverse events. Common adverse events were transient. For patients receiving colesevelam within the primary outcome population, five had abdominal pain, nine had bloating, and four had nausea. For patients receiving placebo, four had abdominal pain, four had bloating, and one had nausea. No participants with bile acid diarrhoea withdrew due to adverse events. INTERPRETATION: Colesevelam was superior to placebo at inducing remission of bile acid diarrhoea diagnosed with C4 concentration greater than 46 ng/mL. Secondary outcome data suggest similar efficacy treating SeHCAT-defined bile acid diarrhoea. Colesevelam was safe during the treatment. FUNDING: Fabrikant Vilhelm Pedersen og hustrus mindelegat; recommended by the Novo Nordisk Foundation.

Impact of IBD-Associated Dysbiosis on Bacterial Quorum Sensing Mediated by Acyl-Homoserine Lactone in Human Gut Microbiota.

Intestinal dysbiosis is a key feature in the pathogenesis of inflammatory bowel disease (IBD). Acyl-homoserine lactones (AHL) are bacterial quorum-sensing metabolites that may play a role in the changes in host cells-gut microbiota interaction observed during IBD. The objective of our study was to investigate the presence and expression of AHL synthases and receptor genes in the human gut ecosystem during IBD. We used an in silico approach, applied to the Inflammatory Bowel Disease Multi'omics Database comprising bacterial metagenomic and metatranscriptomic data from stools of patients with Crohn's disease (CD) (n = 50), ulcerative colitis (UC) (n = 27) and non-IBD controls (n = 26). No known putative AHL synthase gene was identified; however, several putative luxR receptors were observed. Regarding the expression of these receptor genes, the luxR gene from Bacteroides dorei was under-expressed in IBD patients (p = 0.02) compared to non-IBD patients, especially in CD patients (p = 0.02). In the dysbiosis situation, one luxR receptor gene from Bacteroides fragilis appeared to be over-expressed (p = 0.04) compared to that of non-dysbiotic patients. Targeting LuxR receptors of bacterial quorum sensing might represent a new approach to modulate the gut microbiota in IBD.

High performance liquid chromatography-tandem mass spectrometry quantification of tryptophan metabolites in human serum and stool - Application to clinical cohorts in Inflammatory Bowel Diseases.

Tryptophan, an essential amino acid, and its metabolites are involved in many physiological processes including neuronal functions, immune system, and gut homeostasis. Alterations to tryptophan metabolism are associated with various pathologies such as neurologic, psychiatric disorders, inflammatory bowel diseases (IBD), metabolic disorders, and cancer. It is consequently critical to develop a reliable, quantitative method for the analysis of tryptophan and its downstream metabolites from the kynurenine, serotonin, and indoles pathways. An LC-MS/MS method was designed for the analysis of tryptophan and 20 of its metabolites, without derivatization and performed in a single run. This method was validated for both serum and stool. The comparisons between serum and plasma, collected with several differing anticoagulants, showed significant differences only for serotonin. References values were established in sera and stools from healthy donors. For stool samples, as a proof of concept, the developed method was applied to a healthy control group and an IBD patient group. Results showed significant differences in the concentrations of tryptophan, xanthurenic acid, kynurenic acid, indole-3-lactic acid, and picolinic acid. This method allowed an extensive analysis of the three tryptophan metabolic pathways in two compartments. Beyond the application to IBD patients, the clinical use of this method is wide-ranging and may be applied to other pathological conditions involving tryptophan metabolism, such as neurological, psychiatric, or auto-inflammatory pathologies.

Diurnal Interplay between Epithelium Physiology and Gut Microbiota as a Metronome for Orchestrating Immune and Metabolic Homeostasis.

The behavior and physiology of most organisms are temporally coordinated and aligned with geophysical time by a complex interplay between the master and peripheral clocks. Disruption of such rhythmic physiological activities that are hierarchically organized has been linked to a greater risk of developing diseases ranging from cancer to metabolic syndrome. Herein, we summarize the molecular clockwork that is employed by intestinal epithelial cells to anticipate environmental changes such as rhythmic food intake and potentially dangerous environmental stress. We also discuss recent discoveries contributing to our understanding of how a proper rhythm of intestinal stem cells may achieve coherence for the maintenance of tissue integrity. Emerging evidence indicates that the circadian oscillations in the composition of the microbiota may operate as an important metronome for the proper preservation of intestinal physiology and more. Furthermore, in this review, we outline how epigenetic clocks that are based on DNA methylation levels may extensively rewire the clock-controlled functions of the intestinal epithelium that are believed to become arrhythmic during aging.

Fecal microbiota and bile acids in IBD patients undergoing screening for colorectal cancer.

Due to the potential role of the gut microbiota and bile acids in the pathogenesis of both inflammatory bowel disease (IBD) and sporadic colorectal cancer, we aimed to determine whether these factors were associated with colorectal cancer in IBD patients. 215 IBD patients and 51 non-IBD control subjects were enrolled from 10 French IBD centers between September 2011 and July 2018. Fecal samples were processed for bacterial 16S rRNA gene sequencing and bile acid profiling. Demographic, clinical, endoscopic, and histological outcomes were recorded. Characteristics of IBD patients included: median age: 41.6 (IQR 22); disease duration 13.2 (13.1); 47% female; 21.9% primary sclerosing cholangitis; 109 patients with Crohn's disease (CD); 106 patients with ulcerative colitis (UC). The prevalence of cancer was 2.8% (6/215: 1 CD; 5 UC), high-grade dysplasia 3.7% (8/215) and low-grade dysplasia 7.9% (17/215). Lachnospira was decreased in IBD patients with cancer, while Agathobacter was decreased and Escherichia-Shigella increased in UC patients with any neoplasia. Bile acids were not associated with cancer or neoplasia. Unsupervised clustering identified three gut microbiota clusters in IBD patients associated with bile acid composition and clinical features, including a higher risk of neoplasia in UC in two clusters when compared to the third (relative risk (RR) 4.07 (95% CI 1.6-10.3, P < .01) and 3.56 (95% CI 1.4-9.2, P < .01)). In this multicentre observational study, a limited number of taxa were associated with neoplasia and exploratory microbiota clusters co-associated with clinical features, including neoplasia risk in UC. Given the very small number of cancers, the robustness of these findings will require assessment and validation in future studies.

Evidence of Adult Features and Functions of Hepatocytes Differentiated from Human Induced Pluripotent Stem Cells and Self-Organized as Organoids.

BACKGROUND: Human-induced pluripotent stem cell-derived hepatocytes (iHeps) have been shown to have considerable potential in liver diseases, toxicity, and pharmacological studies. However, there is a growing need to obtain iHeps that are truly similar to primary adult hepatocytes in terms of morphological features and functions. We generated such human iHeps, self-assembled as organoids (iHep-Orgs). METHODS: iPSC-derived hepatoblasts were self-assembled into spheroids and differentiated into mature hepatocytes modulating final step of differentiation. RESULTS: In about four weeks of culture, the albumin secretion levels and the complete disappearance of α-fetoprotein from iHep-Orgs suggested the acquisition of a greater degree of maturation than those previously reported. The expression of apical transporters and bile acid secretion evidenced the acquisition of complex hepatocyte polarity as well as the development of a functional and well-defined bile canalicular network confirmed by computational analysis. Activities recorded for CYP450, UGT1A1, and alcohol dehydrogenase, response to hormonal stimulation, and glucose metabolism were also remarkable. Finally, iHep-Orgs displayed a considerable ability to detoxify pathological concentrations of lactate and ammonia. CONCLUSIONS: With features similar to those of primary adult hepatocytes, the iHep-Orgs thus produced could be considered as a valuable tool for the development and optimization of preclinical and clinical applications.

Circulating bile acids concentration is predictive of coronary artery disease in human.

Synthetized by the liver and metabolized by the gut microbiota, BA are involved in metabolic liver diseases that are associated with cardiovascular disorders. Animal models of atheroma documented a powerful anti-atherosclerotic effect of bile acids (BA). This prospective study examined whether variations in circulating BA are predictive of coronary artery disease (CAD) in human. Consecutive patients undergoing coronary angiography were enrolled. Circulating and fecal BA were measured by high pressure liquid chromatography and tandem mass spectrometry. Of 406 screened patients, 80 were prospectively included and divided in two groups with (n = 45) and without (n = 35) CAD. The mean serum concentration of total BA was twice lower in patients with, versus without CAD (P = 0.005). Adjusted for gender and age, this decrease was an independent predictor of CAD. In a subgroup of 17 patients, statin therapy doubled the serum BA concentration. Decreased serum concentrations of BA were predictors of CAD in humans. A subgroup analysis showed a possible correction by statins. With respect to the anti-atherosclerotic effect of BA in animal models, and their role in human lipid metabolism, this study describe a new metabolic disturbance associated to CAD in human.

Metformin treatment for 8 days impacts multiple intestinal parameters in high-fat high-sucrose fed mice.

Although the mechanism of action of the antidiabetic drug metformin is still a matter of discussions, it is well accepted that the gut plays an important role. To gain more insights into the mechanisms occurring in the different regions of the intestine, adult male mice were fed a high-fat-high sucrose (HFS) diet for 8 days and treated with metformin by gavage (300 mg/day/kg body weight) during the HFS diet. Metformin counteracted HFS diet-induced overexpression of a network of genes involved in the transport of glucose and fatty acids in the different regions of the small intestine. It also induced beneficial modification of secondary bile acid profile in the caecum, with a reduction of deoxycholic acid and lithocholic acid levels and increased abundance of ursodeoxycholic acid and tauroursodeoxycholic acid, potentially leading to FRX inhibition. In parallel, metformin treatment was associated with specific changes of the microbiota composition in the lumen of the different regions of the intestine. Metformin induced a marked increase in the abundance of Akkermansia muciniphila in the lumen all along the gut and counteracted the effects of HFS diet on the abundances of some bacterial groups generally associated with metabolic disturbances (f-Lachnospiraceae, f-Petostreptococcaceae, g-Clostidium). Therefore, the present work clearly emphasises the role of all the regions of the intestinal tract in the beneficial action of the antidiabetic drug metformin in a prediabetic mouse model.

SARS-CoV-2 infection in nonhuman primates alters the composition and functional activity of the gut microbiota.

The current pandemic of coronavirus disease (COVID) 2019 constitutes a global public health issue. Regarding the emerging importance of the gut-lung axis in viral respiratory infections, analysis of the gut microbiota's composition and functional activity during a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection might be instrumental in understanding and controling COVID 19. We used a nonhuman primate model (the macaque), that recapitulates mild COVID-19 symptoms, to analyze the effects of a SARS-CoV-2 infection on dynamic changes of the gut microbiota. 16S rRNA gene profiling and analysis of ß diversity indicated significant changes in the composition of the gut microbiota with a peak at 10-13 days post-infection (dpi). Analysis of bacterial abundance correlation networks confirmed disruption of the bacterial community at 10-13 dpi. Some alterations in microbiota persisted after the resolution of the infection until day 26. Some changes in the relative bacterial taxon abundance associated with infectious parameters. Interestingly, the relative abundance of Acinetobacter (Proteobacteria) and some genera of the Ruminococcaceae family (Firmicutes) was positively correlated with the presence of SARS-CoV-2 in the upper respiratory tract. Targeted quantitative metabolomics indicated a drop in short-chain fatty acids (SCFAs) and changes in several bile acids and tryptophan metabolites in infected animals. The relative abundance of several taxa known to be SCFA producers (mostly from the Ruminococcaceae family) was negatively correlated with systemic inflammatory markers while the opposite correlation was seen with several members of the genus Streptococcus. Collectively, SARS-CoV-2 infection in a nonhuman primate is associated with changes in the gut microbiota's composition and functional activity.

Impact of Rapeseed and Soy Lecithin on Postprandial Lipid Metabolism, Bile Acid Profile, and Gut Bacteria in Mice.

SCOPE: Synthetic emulsifiers have recently been shown to promote metabolic syndrome and considerably alter gut microbiota. Yet, data are lacking regarding the effects of natural emulsifiers, such as plant lecithins rich in essential α-linolenic acid (ALA), on gut and metabolic health. METHODS AND RESULTS: For 5 days, male Swiss mice are fed diets containing similar amounts of ALA and 0, 1, 3, or 10% rapeseed lecithin (RL) or 10% soy lecithin (SL). Following an overnight fast, they are force-fed the same oil mixture and euthanized after 90 minutes. The consumption of lecithin significantly increased fecal levels of the Clostridium leptum group (p = 0.0004), regardless of origin or dose, without altering hepatic or intestinal expression of genes of lipid metabolism. 10%-RL increased ALA abundance in plasma triacylglycerols at 90 minutes, reduced cecal bile acid hydrophobicity, and increased their sulfatation, as demonstrated by the increased hepatic RNA expression of Sult2a1 (p = 0.037) and cecal cholic acid-7 sulfate (CA-7S) concentration (p = 0.05) versus 0%-lecithin. CONCLUSION: After only 5 days, nutritional doses of RL and SL modified gut bacteria in mice, by specifically increasing C. leptum group. RL also increased postprandial ALA abundance and induced beneficial modifications of the bile acid profile. ALA-rich lecithins, especially RL, may then appear as promising natural emulsifiers.

Bile acid-receptor TGR5 deficiency worsens liver injury in alcohol-fed mice by inducing intestinal microbiota dysbiosis.

BACKGROUND & AIMS: Bile-acid metabolism and the intestinal microbiota are impaired in alcohol-related liver disease. Activation of the bile-acid receptor TGR5 (or GPBAR1) controls both biliary homeostasis and inflammatory processes. We examined the role of TGR5 in alcohol-induced liver injury in mice. METHODS: We used TGR5-deficient (TGR5-KO) and wild-type (WT) female mice, fed alcohol or not, to study the involvement of liver macrophages, the intestinal microbiota (16S sequencing), and bile-acid profiles (high-performance liquid chromatography coupled to tandem mass spectrometry). Hepatic triglyceride accumulation and inflammatory processes were assessed in parallel. RESULTS: TGR5 deficiency worsened liver injury, as shown by greater steatosis and inflammation than in WT mice. Isolation of liver macrophages from WT and TGR5-KO alcohol-fed mice showed that TGR5 deficiency did not increase the pro-inflammatory phenotype of liver macrophages but increased their recruitment to the liver. TGR5 deficiency induced dysbiosis, independently of alcohol intake, and transplantation of the TGR5-KO intestinal microbiota to WT mice was sufficient to worsen alcohol-induced liver inflammation. Secondary bile-acid levels were markedly lower in alcohol-fed TGR5-KO than normally fed WT and TGR5-KO mice. Consistent with these results, predictive analysis showed the abundance of bacterial genes involved in bile-acid transformation to be lower in alcohol-fed TGR5-KO than WT mice. This altered bile-acid profile may explain, in particular, why bile-acid synthesis was not repressed and inflammatory processes were exacerbated. CONCLUSIONS: A lack of TGR5 was associated with worsening of alcohol-induced liver injury, a phenotype mainly related to intestinal microbiota dysbiosis and an altered bile-acid profile, following the consumption of alcohol. LAY SUMMARY: Excessive chronic alcohol intake can induce liver disease. Bile acids are molecules produced by the liver and can modulate disease severity. We addressed the specific role of TGR5, a bile-acid receptor. We found that TGR5 deficiency worsened alcohol-induced liver injury and induced both intestinal microbiota dysbiosis and bile-acid pool remodelling. Our data suggest that both the intestinal microbiota and TGR5 may be targeted in the context of human alcohol-induced liver injury.

TGR5 controls bile acid composition and gallbladder function to protect the liver from bile acid overload.

BACKGROUND & AIMS: As the composition of the bile acid (BA) pool has a major impact on liver pathophysiology, we studied its regulation by the BA receptor Takeda G protein coupled receptor (TGR5), which promotes hepatoprotection against BA overload. METHODS: Wild-type, total and hepatocyte-specific TGR5-knockout, and TGR5-overexpressing mice were used in: partial (66%) and 89% extended hepatectomies (EHs) upon normal, ursodeoxycholic acid (UDCA)- or cholestyramine (CT)-enriched diet, bile duct ligation (BDL), cholic acid (CA)-enriched diet, and TGR5 agonist (RO) treatments. We thereby studied the impact of TGR5 on: BA composition, liver injury, regeneration and survival. We also performed analyses on the gut microbiota (GM) and gallbladder (GB). Liver BA composition was analysed in patients undergoing major hepatectomy. RESULTS: The TGR5-KO hyperhydrophobic BA composition was not directly related to altered BA synthesis, nor to TGR5-KO GM dysbiosis, as supported by hepatocyte-specific KO mice and co-housing experiments, respectively. The TGR5-dependent control of GB dilatation was crucial for BA composition, as determined by experiments including RO treatment and/or cholecystectomy. The poor TGR5-KO post-EH survival rate, related to exacerbated peribiliary necrosis and BA overload, was improved by shifting BAs toward a less toxic composition (CT treatment). After either BDL or a CA-enriched diet with or without cholecystectomy, we found that GB dilatation had strong TGR5-dependent hepatoprotective properties. In patients, a more hydrophobic liver BA composition was correlated with an unfavourable outcome after hepatectomy. CONCLUSIONS: BA composition is crucial for hepatoprotection in mice and humans. We indicate TGR5 as a key regulator of BA profile and thereby as a potential hepatoprotective target under BA overload conditions. LAY SUMMARY: Through multiple in vivo experimental approaches in mice, together with a patient study, this work brings some new light on the relationships between biliary homeostasis, gallbladder function, and liver protection. We showed that hepatic bile acid composition is crucial for optimal liver repair, not only in mice, but also in human patients undergoing major hepatectomy.

Anti-Inflammatory Effects of Analogues of N-Acyl Homoserine Lactones on Eukaryotic Cells.

BACKGROUND: Since acyl-homoserine lactone (AHL) profiling has been described in the gut of healthy subjects and patients with inflammatory bowel disease (IBD), the potential effects of these molecules on host cells have raised interest in the medical community. In particular, natural AHLs such as the 3-oxo-C12-HSL exhibit anti-inflammatory properties. Our study aimed at finding stable 3-oxo-C12-HSL-derived analogues with improved anti-inflammatory effects on epithelial and immune cells. METHODS: We first studied the stability and biological properties of the natural 3-oxo-C12-HSL on eukaryotic cells and a bacterial reporter strain. We then constructed and screened a library of 22 AHL-derived molecules. Anti-inflammatory effects were assessed by cytokine release in an epithelial cell model, Caco-2, and a murine macrophage cell line, RAW264.7, (respectively, IL-8 and IL-6) upon exposure to the molecule and after appropriate stimulation (respectively, TNF-α 50 ng/mL and IFN-γ 50 ng/mL, and LPS 10 ng/mL and IFN-γ 20 U/mL). RESULTS: We found two molecules of interest with amplified anti-inflammatory effects on mammalian cells without bacterial-activating properties in the reporter strain. The molecules furthermore showed improved stability in biological medium compared to the native 3-oxo-C12-HSL. CONCLUSIONS: We provide new bio-inspired AHL analogues with strong anti-inflammatory properties that will need further study from a therapeutic perspective.