Gram-negative Bacteria In Gut Research Articles

Intestinal permeability is associated with aggravated inflammation and myofibroblast accumulation in Graves' orbitopathy: the MicroGO study.

Graves' disease (GD) and Graves' orbitopathy (GO) result from ongoing stimulation of the TSH receptor due to autoantibodies acting as persistent agonists. Orbital pre-adipocytes and fibroblasts also express the TSH receptor, resulting in expanded retro-orbital tissue and causing exophthalmos and limited eye movement. Recent studies have shown that GD/GO patients have a disturbed gut microbiome composition, which has been associated with increased intestinal permeability. This study hypothesizes that enhanced intestinal permeability may aggravate orbital inflammation and, thus, increase myofibroblast differentiation and the degree of fibrosis. Two distinct cohorts of GO patients were studied, one of which was a unique cohort consisting of blood, fecal, and retro-orbital tissue samples. Intestinal permeability was assessed by measuring serum lipopolysaccharide-binding protein (LBP), zonulin, TLR5, and TLR9 ligands. The influx of macrophages and accumulation of T-cells and myofibroblast were quantified in orbital connective tissue. The NanoString immune-oncology RNA targets panel was used to determine the transcriptional profile of active fibrotic areas within orbital sections. GO patients displayed significantly higher LBP serum concentrations than healthy controls. Within the MicroGO cohort, patients with high serum LBP levels also showed higher levels of zonulin and TLR5 and TLR9 ligands in their circulation. The increased intestinal permeability was accompanied by augmented expression of genes marking immune cell infiltration and encoding key proteins for immune cell adhesion, antigen presentation, and cytokine signaling in the orbital tissue. Macrophage influx was positively linked to the extent of T cell influx and fibroblast activation within GO-affected orbital tissues. Moreover, serum LBP levels significantly correlated with the abundance of specific Gram-negative gut bacteria, linking the gut to local orbital inflammation. These results indicate that GO patients have enhanced intestinal permeability. The subsequent translocation of bacterial compounds to the systemic circulation may aggravate inflammatory processes within the orbital tissue and, as a consequence, augment the proportion of activated myofibroblasts, which actively secrete extracellular matrix leading to retro-orbital tissue expansion. These findings warrant further exploration to assess the correlation between specific inflammatory pathways in the orbital tissue and the gut microbiota composition and may pave the way for new microbiota-targeting therapies.

Priorities and Progress in Gram-negative Bacterial Infection Research by the Antibacterial Resistance Leadership Group.

Addressing the treatment and prevention of antibacterial-resistant gram-negative bacterial infections is a priority area of the Antibacterial Resistance Leadership Group (ARLG). The ARLG has conducted a series of observational studies to define the clinical and molecular global epidemiology of carbapenem-resistant and ceftriaxone-resistant Enterobacterales, carbapenem-resistant Pseudomonas aeruginosa, and carbapenem-resistant Acinetobacter baumannii, with the goal of optimizing the design and execution of interventional studies. One ongoing ARLG study aims to better understand the impact of fluoroquinolone-resistant gram-negative gut bacteria in neutropenic patients, which threatens to undermine the effectiveness of fluoroquinolone prophylaxis in these vulnerable patients. The ARLG has conducted pharmacokinetic studies to inform the optimal dosing of antibiotics that are important in the treatment of drug-resistant gram-negative bacteria, including oral fosfomycin, intravenous minocycline, and a combination of intravenous ceftazidime-avibactam and aztreonam. In addition, randomized clinical trials have assessed the safety and efficacy of step-down oral fosfomycin for complicated urinary tract infections and single-dose intravenous phage therapy for adult patients with cystic fibrosis who are chronically colonized with P. aeruginosa in their respiratory tract. Thus, the focus of investigation in the ARLG has evolved from improving understanding of drug-resistant gram-negative bacterial infections to positively affecting clinical care for affected patients through a combination of interventional pharmacokinetic and clinical studies, a focus that will be maintained moving forward.

Insights into early evolutionary adaptations of the Akkermansia genus to the vertebrate gut.

Akkermansia, a relevant mucin degrader from the vertebrate gut microbiota, is a member of the deeply branched Verrucomicrobiota, as well as the only known member of this phylum to be described as inhabitants of the gut. Only a few Akkermansia species have been officially described so far, although there is genomic evidence addressing the existence of more species-level variants for this genus. This niche specialization makes Akkermansia an interesting model for studying the evolution of microorganisms to their adaptation to the gastrointestinal tract environment, including which kind of functions were gained when the Akkermansia genus originated or how the evolutionary pressure functions over those genes. In order to gain more insight into Akkermansia adaptations to the gastrointestinal tract niche, we performed a phylogenomic analysis of 367 high-quality Akkermansia isolates and metagenome-assembled genomes, in addition to other members of Verrucomicrobiota. This work was focused on three aspects: the definition of Akkermansia genomic species clusters and the calculation and functional characterization of the pangenome for the most represented species; the evolutionary relationship between Akkermansia and their closest relatives from Verrucomicrobiota, defining the gene families which were gained or lost during the emergence of the last Akkermansia common ancestor (LAkkCA) and; the evaluation of the evolutionary pressure metrics for each relevant gene family of main Akkermansia species. This analysis found 25 Akkermansia genomic species clusters distributed in two main clades, divergent from their non-Akkermansia relatives. Pangenome analyses suggest that Akkermansia species have open pangenomes, and the gene gain/loss model indicates that genes associated with mucin degradation (both glycoside hydrolases and peptidases), (micro)aerobic metabolism, surface interaction, and adhesion were part of LAkkCA. Specifically, mucin degradation is a very ancestral innovation involved in the origin of Akkermansia. Horizontal gene transfer detection suggests that Akkermansia could receive genes mostly from unknown sources or from other Gram-negative gut bacteria. Evolutionary metrics suggest that Akkemansia species evolved differently, and even some conserved genes suffered different evolutionary pressures among clades. These results suggest a complex evolutionary landscape of the genus and indicate that mucin degradation could be an essential feature in Akkermansia evolution as a symbiotic species.

Gut-derived bacterial LPS attenuates incubation of methamphetamine craving via modulating microglia

BackgroundThe microbiota-gut-brain axis plays a critical role in the pathophysiology of neuropsychiatric disorders, and the compositions of gut microbiota are altered by addictive drugs. However, the role of gut microbiota in the incubation of methamphetamine (METH) craving remains poorly understood. Methods16S rRNA gene sequencing was performed to assess the richness and diversity of gut microbiota in METH self-administration model. Hematoxylin and eosin staining was performed to evaluate the integrity of intestinal barrier. Immunofluorescence and three-dimensional reconstruction were performed to assess the morphologic changes of microglia. Serum levels of lipopolysaccharide (LPS) were determined using the rat enzyme-linked immunosorbent assay kits. Quantitative real-time PCR was performed to assess transcript levels of dopamine receptor, glutamate ionotropic AMPA receptor 3 and brain-derived neurotrophic factor. ResultsMETH self-administration induced gut microbiota dysbiosis, intestinal barrier damage and microglia activation in the nucleus accumbens core (NAcc), which was partially recovered after prolonged withdrawal. Microbiota depletion via antibiotic treatment increased LPS levels and induced a marked change in the microglial morphology in the NAcc, as indicated by the decreases in the lengths and numbers of microglial branches. Depleting the gut microbiota also prevented the incubation of METH craving and increased the population of Klebsiella oxytoca. Furthermore, Klebsiella oxytoca treatment or exogenous administration of the gram-negative bacterial cell wall component LPS increased serum and central LPS levels, induced microglial morphological changes and reduced the dopamine receptor transcription in the NAcc. Both treatments and NAcc microinjections of gut-derived bacterial LPS significantly decreased METH craving after prolonged withdrawal. ConclusionsThese data suggest that LPS from gut gram-negative bacteria may enter circulating blood, activate microglia in the brain and consequently decrease METH craving after withdrawal, which may have important implications for novel strategies to prevent METH addiction and relapse.

Asphyxia-Induced Bacterial Translocation in an Animal Experimental Model in Neonatal Piglets.

The term "bacterial translocation" (BT) refers to the migration of bacteria or their products from the gastrointestinal tract to tissues located outside it, and may occur after intestinal ischemia-reperfusion injury. The term "endotoxin" is synonymous, and is used interchangeably with the term lipopolysaccharide (LPS). LPS, a component of Gram-negative gut bacteria, is a potent microbial virulence factor, that can trigger production of pro-inflammatory mediators, causing localized and systemic inflammation. The aim of this study is to investigate if neonatal asphyxia provokes BT and an increased concentration of LPS in an animal model of asphyxia in piglets. Twenty-one (21) newborn male Landrace/Large White piglets, 1-4 days old, were randomly allocated into three groups, Control (A), Asphyxia (B) and Asphyxia-Cardiopulmonary Resuscitation (CPR) (C). All animals were instrumented, anesthetized and underwent hemodynamic monitoring. In Group A, the animals were euthanized. In Group B, the endotracheal tube was occluded to cause asphyxia leading to cardiopulmonary arrest. In Group C, the animals were resuscitated after asphyxia and further monitored for 30'. Bacterial translocation was assessed by the measurement of endotoxin in blood from the portal vein and the aorta, and also by the measurement of endotoxin in mesenteric lymph nodes (MLNs) at euthanasia. The results are given as median (IQR) with LPS concentration in EU/mL. BT was observed in all groups with minimum LPS concentration in the MLN and maximum concentration in the portal vein. LPS levels in the MLNs were higher in the Group B: 6.38 EU/mL (2.69-9.34) compared to the other groups (Group A: 2.1 EU/mL (1.08-2.52), Group C: 1.66 EU/mL (1.51-2.48), p = 0.012). The aorta to MLNs LPS difference (%) was lower in Group B: 0.13% (0.04-1.17), compared to Group A: 5.08% (2.2-10.7), and Group C: 3.42% (1.5-5.1)) (p = 0.042). The same was detected for portal to MLNs LPS difference (%) which was lower in Group B: 0.94% (0.5-3) compared to Group A: 4.9% (4-15), and Group C: 3.85% (1.5-5.1)) (p = 0.044). Neonatal asphyxia can provoke ΒΤ and increased LPS concentration in blood and tissue located outside the gastrointestinal system.

Proanthocyanidins in grape seeds and their role in gut microbiota-white adipose tissue axis

Several factors can impact the gut microbiota, affecting host metabolism and immunity. It implies intestinal barrier disruption and translocation of gut microbiota metabolites to the bloodstream, such as lipopolysaccharides (LPS). LPS is an endotoxin from gram-negative gut bacteria that trigger the activation of the Toll-like receptor-4 (TLR-4) inflammatory pathway and can modulate white adipose tissue (WAT) metabolism. Dietary components, including diets rich in fiber and polyphenols, contribute to intestinal environment homeostasis. Grape seed proanthocyanidins extract (GSPE) may improve intestinal permeability and microbial diversity and increase short-chain fatty acids production. Furthermore, GSPE has been involved in LPS reduction, down-regulating the TLR-4 pathway, decreasing the WAT metainflammatory profile, and preventing adipocyte hypertrophy. Studies have pointed out strategies to promote health and control obesity by modulating the gut microbiota environment. Therefore, this review aims to summarize the potential effects of GSPE on the gut microbiota-white adipose tissue axis against obesity.

Interactions of semiconductor Cd-based quantum dots and Cd2+ with gut bacteria isolated from wild Salmo trutta fry.

BackgroundWith the rapid development of nanotechnology, more and more nanoproducts are being released into the environment where they may both pose ecological risks and be toxic to living organisms. The ecotoxicological impact of quantum dots (QDs), a class of nanoparticles (NPs), on aquatic organisms is becoming an emerging issue, this due to their nano-specific properties, to the physico-chemical transformation in the environment and to the possible release of toxic metals from their structure such as Cd.MethodsIn this work, (i) spectroscopic measurements of commercially available Cd-based QDs (CdSe/ZnS-COOH) were made at various pH values (5.0 and 7.0) to study their interactions (at a concentration of 4 nm) with various strains of Gram-positive and Gram-negative gut bacteria after short-term exposure and (ii) the antibacterial efficacy of QDs and Cd2+ (at a concentration 0.09–3.56 mM) against gut bacteria isolated from wild freshwater Salmo trutta fry was studied at different temperatures (15 °C and 25 °C) and pH values (5.0 and 7.0) by applying a well-established disc diffusion assay.ResultsTwenty-six gut bacterial isolates from wild Salmo trutta fry were identified as Aeromonas spp., A. popoffii, A. salmonicida, A. sobria, Carnobacterium maltaromaticum, Buttiauxella sp., Listeria sp., Microbacterium sp., Shewanella putrefaciens and Serratia sp. Cd-based (CdSe/ZnS-COOH) QDs at a concentration of 4 nm were found to be stable in aqueous media (with pH 7.0) or starting to form aggregates (at pH 5.0), thus, apparently, did not release heavy metals (HMs) into the media over 48 h in conditions of light or dark and did not show antibacterial efficacy on the gut bacteria isolated from wild Salmo trutta fry after short-term (9 h and 48 h) incubations. Cd2+ was found to produce significant dose-dependent toxic effects on bacterial growth, and the size of the inhibition zones on some of the tested strains significantly correlated with temperature. The most sensitive and the most resistant to Cd2+ were the Gram-positive bacteria, for which the minimum inhibitory concentration (MIC) values of Cd2+ were 0.09–0.27 mM and 3.11–3.29 mM respectively and varied significantly between the tested temperatures (15 °C and 25 °C). The MIC values of Cd2+ for the Gram-negative bacteria (18 out of 22 strains) ranged from 0.44 to 0.71 mM and did not differ significantly between the tested temperatures. Among the selected Gram-positive and Gram-negative strains, those with the higher sensitivity towards Cd2+ also revealed relatively stronger signals of QDs photoluminescence (PL) when transferred after incubation into fresh medium without QDs. In addition, the formation of endogenous metalloporphyrins observed spectroscopically in some bacterial strains indicates certain differences in metabolic activity that may play a protective role against potential oxidative damage.

High-fat meals do not affect thrombin formation and fibrin clot lysis in individuals with obesity during intentional weight loss

Repeated weight loss cycles are associated with increased cardiovascular morbidity. Meal-induced thrombin formation, measured as prothrombin fragment 1+2 (F1+2), is observed in individuals with overweight after weight loss, and postprandial effects can be one of the mechanisms underlying harmful effects during intentional weight loss. We hypothesize that consumption of high-fat meals during intentional weight loss triggers a prothrombotic state by increasing postprandial F1+2 or decreasing fibrin clot lysis in individuals with obesity, and that the response associates with the gut bacteria composition. A cross-over meal study was conducted in patients admitted to bariatric surgery during dietary weight loss (N = 20) and surgical weight loss (N = 16) (weight loss groups). High-fat (67 E%) and low-fat (16 E%) meals were served at 08:15 and 10:00 on 2 study days. Blood samples collected at 08:00 (fasting), 12:00, and 14:00 were analyzed for triglycerides, activated factor VII (FVIIa), F1+2, D-dimer, fibrinogen, tissue factor , and fibrin clot lysis. The proportion of Gram-negative bacteria and bacterial diversity were analyzed in fecal samples obtained less than 24 hours before the meal test. Triglyceride and FVIIa increased after high-fat meals in both weight loss groups, whereas D-dimer (dietary group) and F1+2 decreased and tissue factor and fibrin clot lysis did not change. There was a negative association between the proportion of Gram-negative bacteria and changes in FVIIa in the surgery group. Postprandial FVII activation after high-fat meals is not accompanied by increased F1+2, irrespective of the weight loss intervention, but might be associated with the proportion of Gram-negative gut bacteria.

Production of p-cresol by Decarboxylation of p-HPA by All Five Lineages of Clostridioides difficile Provides a Growth Advantage

Clostridioides difficile is the leading cause of antibiotic-associated diarrhea and is capable of causing severe symptoms, such as pseudomembranous colitis and toxic megacolon. An unusual feature of C. difficile is the distinctive production of high levels of the antimicrobial compound para-cresol. p-Cresol production provides C. difficile with a competitive colonization advantage over gut commensal species, in particular, Gram-negative species. p-Cresol is produced by the conversion of para-hydroxyphenylacetic acid (p-HPA) via the actions of HpdBCA decarboxylase coded by the hpdBCA operon. Host cells and certain bacterial species produce p-HPA; however, the effects of p-HPA on the viability of C. difficile and other gut microbiota are unknown. Here we show that representative strains from all five C. difficile clades are able to produce p-cresol by two distinct mechanisms: (i) via fermentation of p-tyrosine and (ii) via uptake and turnover of exogenous p-HPA. We observed strain-specific differences in p-cresol production, resulting from differential efficiency of p-tyrosine fermentation; representatives of clade 3 (CD305) and clade 5 (M120) produced the highest levels of p-cresol via tyrosine metabolism, whereas the toxin A-/B+ isolate from clade 4 (M68) produced the lowest level of p-cresol. All five lineages share at least 97.3% homology across the hpdBCA operon, responsible for decarboxylation of p-HPA to p-cresol, suggesting that the limiting step in p-cresol production may result from tyrosine to p-HPA conversion. We identified that elevated intracellular p-HPA, modulated indirectly via CodY, controls p-cresol production via inducing the expression of HpdBCA decarboxylase ubiquitously in C. difficile populations. Efficient turnover of p-HPA is advantageous to C. difficile as p-HPA has a deleterious effect on the growth of C. difficile and other representative Gram-negative gut bacteria, transduced potentially by the disruption of membrane permeability and release of intracellular phosphate. This study provides insights into the importance of HpdBCA decarboxylase in C. difficile pathogenesis, both in terms of p-cresol production and detoxification of p-HPA, highlighting its importance to cell survival and as a highly specific therapeutic target for the inhibition of p-cresol production across C. difficile species.

Carbapenem Resistant Gram Negative Bacteria in Gut and Correlation with Bacteraemia in a Paediatric Stem Cell Transplant Unit in India.

Carbapenem Resistant Gram Negative Bacteria in Gut and Correlation with Bacteraemia in a Paediatric Stem Cell Transplant Unit in India.

Low-Grade Inflammation in Hemophilia

We previously showed that impaired clotting in hemophilia leads to a deficit in macrophage differentiation, which negatively affects critical regenerative macrophage functions such as clot infiltration and red blood cell phagocytosis. These data provide a functional basis for the delayed wound healing as well as protracted joint inflammation commonly observed in hemophiliacs and suggest that altered macrophage function is linked to the activation of the innate immune system. We, therefore, hypothesize that hemophiliacs suffer from chronic low-grade inflammation, which in turn can affect joint health, tissue regeneration and age-related ailments such as cardiovascular disease. For this study, we collected citrated blood from 48 adult male patients with hemophilia A or B with an average age of 36 years and a body mass index (BMI) of 27.7 kg/m2. The majority of patients had a residual FVIII/FIX activity < 1% (77%) and received prophylactic treatment (60%) with a recombinant or plasmatic coagulation factor concentrate. Approximately one-half of the patients had target joints or other bleeding events in the last 3 months and one-third of the patients had contracted HBV, HCV or HIV. For controls, we randomly recruited male blood donors (n = 60; age, 35.8 years; BMI, 27.0) from our blood donation center. To assess inflammation in hemophiliacs, we analyzed platelet-poor plasma from our main collective and a BMI-adjusted cohort using commercially available ELISA kits. The results showed a significant increase of two acute-phase proteins, C-reactive protein and leptin in hemophilia patients compared to healthy controls. Further analysis demonstrated that C-reactive protein and leptin expression inversely correlated with the residual clotting activity as both parameters were high in patients with severe Hemophilia A or B and comparatively low in patients with moderate to mild hemophilia. Of note, there was neither an increase of C-reactive protein or leptin in hemophilia patients with recent bleeding (< 3 month), arthropathy, chronic viral infection nor a decrease in patients with coagulation factor activity > 10% due to prophylactic treatment or recent replacement. Therefore, these data suggest a basic link between clotting deficiencies and chronic low-grade inflammation. Low-grade inflammation is maintained by adipokines, which originate from the adipose tissue and are modulated by a process known as adipose tissue inflammation. In addition to the upregulation of the pro-inflammatory leptin, we detected a significant down-regulation of the anti-inflammatory adiponectin in the plasma of hemophilia patients resulting in a markedly decreased adiponectin/leptin ratio. To enquire if the adipose tissue inflammation in hemophilia originates from gram-negative gut bacteria that translocate into the blood circulation, we also detected elevated plasma levels of lipopolysaccharide-binding protein and hepcidin in hemophilia patients. Together, these data support the concept that low-grade inflammation in hemophilia originates from lipopolysaccharide, which in turn causes adipose tissue inflammation. To test the hypothesis that low-grade inflammation in hemophilia is caused by decreased clotting activity, we collected blood from hemophilia B patients before and after transition from a conventional standard-half-life factor IX concentrate to a prophylactic therapy with an elongated half-life (EHL) FIX (Albutrepennonacog alfa, Idelvion®). Following up on the enhanced factor replacement after > 6 months, we observed a return of hepcidin plasma levels back to baseline values in healthy controls. The decreased hepcidin values from EHL FXI therapy correlated with healing of target joints suggesting that EHL FIX not only controls bleeding but also inflammation. Together, our data demonstrate a specific link between hemophilia and low-grade inflammation that appears to involve increased lipopolysaccharide levels in the blood circulation and subsequent adipose tissue inflammation. In addition, we present evidence that low-grade inflammation is the result of the underlying clotting deficit and that sustained normalization of the clotting deficit with EHL factors ameliorates inflammation. Disclosures Eichler: Novo Nordisk: Membership on an entity's Board of Directors or advisory committees. Pilch:CSL Behring: Other: Grants (investigator initiated), Speakers Bureau; ASPIRE Award/Pfizer: Other: Grants (investigator initiated); Bayer: Consultancy, Speakers Bureau; Roche: Consultancy.

Ghrelin abates bacterial translocation following burn injury by improving gastric emptying.

In severe burns, increased intestinal permeability facilitates bacterial translocation, resulting in systemic endotoxemia and multi- organ failure. We investigated the role of burn-induced gastrointestinal dysmotility (BIGD) in promoting bacterial translocation following burn injury, and the protective effect of ghrelin in this process. We assessed gastric emptying (GE%) and intestinal transit (IT by geometric center "GC") in a 60% total body surface area scald burn rat model and measured bacterial counts in mesenteric lymph nodes (MLN) and distal small intestine by colony-forming unit per gram of tissue (CFU/g). A group of animals was treated with ghrelin or saline after burn. Scald burn was associated with a significant delay in GE (62%±4% vs 74%±4%; P=.02) and a trend of delay in intestinal transit (GC: 5.5±0.1 vs 5.8±0.2; P=.09). Concurrently, there was a marginal increase in small intestinal bacterial overgrowth (6×105 vs 2×105 CFU/g; P=.05) and significant translocation to MLN (2×102 vs 4×101 ; P=.03). We observed a negative correlation between GE and intestinal bacterial overgrowth (rs =-0.61; P=.002) and between IT and translocation (rs =-0.63; P=.004). Ghrelin administration significantly accelerated GE following burn injury (91%±3% vs 62%±4; P=.03), reduced small intestinal bacterial overgrowth, and completely inhibited translocation to MLN (0.0 vs 5×102 ; P=.01). Burn-induced gastrointestinal dysmotility is correlated with the systemic translocation of gram-negative gut bacteria that are implicated in multiple organ failure in burn patients. Therapeutic interventions to restore BIGD are warranted (Neurogastroenterol Motil, 2012, 24, 78).

Thiol-producing microbiota of the intestine modulate oxidative stress and inflammation in Chronic Kidney Disease

Background: Inflammation and oxidative stress are among the key contributing risk factors for cardiovascular disease (CVD) in chronic kidney disease (CKD). The human gut is the home for microbiota, of which some of the gram-negative gut bacteria are known to produce low-molecular-weight thiols including glutathione (GSH). GSH is used by mammals and eukaryotic cells as a substrate of glutathione peroxidase to eliminate reactive oxygen species. This study aims to investigate whether the presence of thiol-producing gut microbiota in CKD affects the level of oxidative stress and inflammation markers. Methods: This study examined the stool sample of 41 CKD patients at three hospitals in Surabaya, Indonesia to identify the gram-negative bacteria producing thiols. Based on Ellman's assay result, the study participants were grouped into patients with thiol-producing and non-thiol-producing gram-negative gut microbiota. The markers of inflammation, high sensitivity C-reactive protein (hs-CRP), total antioxidant capacity (TAC), and urinary oxidative stress marker 8-hydroxy-2' -deoxyguanosine (8-OHdG) were compared between the two groups. Results: The group with thiol-producing gut microbiota exhibited lower levels of plasma hs-CRP and urinary 8-OHdG compared to the group with non-thiol-producing gram-negative gut microbiota. In contrast, the group with thiol-producing gut microbiota has higher TAC compared to the group with non-thiol-producing gram-negative gut microbiota. Conclusion: This study emphasized that the phenotypical diversity regarding the ability to produce low-molecular-weight thiols might modulate inflammation and oxidative stress as CVD risk factors in CKD.

Rapid LPS transport during lipid absorption in rat small intestine

Lipopolysaccharide (LPS; endotoxin) is a lipophilic pathogenic factor derived from gut Gram-negative bacteria. Increased serum LPS concentrations are associated with the metabolic syndrome, termed metabolic endotoxemia. Since the origin of circulating LPS is the gut lumen, we studied the mechanisms of LPS transport across the gut mucosa, hypothesizing that transport occurs via known lipid uptake pathways. Since glucagon-like peptide-2 (GLP-2) reduces intestinal solute permeability but enhances fat absorption, we also hypothesized that GLP-2 affects LPS transport during fat absorption. We thus examined LPS transport mechanisms and the effect of exogenous GLP-2 on LPS transport in intact intestinal tissues in vitro and in vivo.

Metformin exerts glucose-lowering action in high-fat fed mice via attenuating endotoxemia and enhancing insulin signaling.

Accumulating evidence shows that lipopolysaccharides (LPS) derived from gut gram-negative bacteria can be absorbed, leading to endotoxemia that triggers systemic inflammation and insulin resistance. In this study we examined whether metformin attenuated endotoxemia, thus improving insulin signaling in high-fat diet fed mice. Mice were fed a high-fat diet for 18 weeks to induce insulin resistance. One group of the mice was treated with oral metformin (100 mg·kg(-1)·d(-1)) for 4 weeks. Another group was treated with LPS (50 μg·kg(-1)·d(-1), sc) for 5 days followed by the oral metformin for 10 d. Other two groups received a combination of antibiotics for 7 d or a combination of antibiotics for 7 d followed by the oral metformin for 4 weeks, respectively. Glucose metabolism and insulin signaling in liver and muscle were evaluated, the abundance of gut bacteria, gut permeability and serum LPS levels were measured. In high-fat fed mice, metformin restored the tight junction protein occludin-1 levels in gut, reversed the elevated gut permeability and serum LPS levels, and increased the abundance of beneficial bacteria Lactobacillus and Akkermansia muciniphila. Metformin also increased PKB Ser473 and AMPK T172 phosphorylation, decreased MDA contents and redox-sensitive PTEN protein levels, activated the anti-oxidative Nrf2 system, and increased IκBα in liver and muscle of the mice. Treatment with exogenous LPS abolished the beneficial effects of metformin on glucose metabolism, insulin signaling and oxidative stress in liver and muscle of the mice. Treatment with antibiotics alone produced similar effects as metformin did. Furthermore, the beneficial effects of antibiotics were addictive to those of metformin. Metformin administration attenuates endotoxemia and enhances insulin signaling in high-fat fed mice, which contributes to its anti-diabetic effects.

Infecciones bacterianas en la cirrosis

Introduction and pathophysiologyCirrhotic patients present more severe and frequent bacterial infections than general population. The immune dysfunction and the intestinal barrier changes developed over the course of the cirrhosis are related to this fact. EpidemiologySpontaneous bacterial peritonitis and urinary tract infections are the most common, followed by pneumonia, cellulitis and bacteremia. Gram-negative gut bacteria are the most frequently involved, although in recent years the isolation of multidrug resistant bacteria has increased. Profilaxis, outcomes and treatmentPrevention, early identification and appropriate antibiotic treatment are essential to reduce the negative impact on survival for cirrhotic patients.

Sublethal Pb exposure produces season-dependent effects on immune response, oxidative balance and investment in carotenoid-based coloration in red-legged partridges.

Ingestion of lead (Pb) shot pellets constitutes the main cause of Pb poisoning in avifauna. We studied the effects of sublethal Pb exposure on immunity, carotenoid-based coloration, oxidative stress and trade-offs among these types of responses during spring and autumn in red-legged partridges (Alectoris rufa). We evaluated constitutive immunity testing lysozyme and natural antibody levels, and blood bactericidal and phagocytic activities. We studied induced immunity by testing PHA and humoral responses. We analyzed fecal parasite and bacterial abundance and oxidative stress biomarkers. Pb exposure in spring reduced natural antibody levels, whereas in autumn, it reduced lysozyme levels and increased phagocytic activity. Pb exposure increased PHA response in both seasons, and decreased T-independent humoral response in autumn. Pb exposure also increased noncoliform and decreased coliform Gram-negative gut bacteria. In spring, Pb exposure decreased antioxidant levels and increased coloration in males, whereas in autumn, it increased retinol levels but reduced coloration in both genders. Our results suggest that in spring, Pb-exposed females used antioxidants to cope with oxidative stress at the expense of coloration, whereas Pb-exposed males increased coloration, which may reflect an increased breeding investment. In autumn, both genders prioritized oxidative balance maintenance at the expense of coloration.

Selective decontamination of the digestive tract ameliorates severe burn-induced insulin resistance in rats

BackgroundSevere burns often initiate the prevalence of hyperglycemia and insulin resistance, significantly contributing to adverse clinical outcomes. However, there are limited treatment options. This study was designed to investigate the role and the underlying mechanisms of oral antibiotics to selectively decontaminate the digestive tract (SDD) on burn-induced insulin resistance. Materials and methodsRats were subjected to 40% of total body surface area full-thickness burn or sham operation with or without SDD treatment. Translocation of FITC-labeled LPS was measured at 4h after burn. Furthermore, the effect of SDD on post-burn quantity of gram-negative bacteria in gut was investigated. Serum or muscle LPS and proinflammatory cytokines were measured. Intraperitoneal glucose tolerance test and insulin tolerance test were used to determine the status of systemic insulin resistance. Furthermore, intracellular insulin signaling (IRS-1 and Akt) and proinflammatory related kinases (JNK and IKKβ) were assessed by western blot. ResultsBurn increased the translocation of LPS from gut 4h after injury. SDD treatment effectively inhibited post-burn overgrowth of gram-negative enteric bacilli in gut. In addition, severe burns caused significant increases in the LPS and proinflammatory cytokines levels, activation of proinflammatory related kinases, and systemic insulin resistance as well. But SDD treatment could significantly attenuate burn-induced insulin resistance and improve the whole-body responsiveness to insulin, which was associated with the inhibition of gut-derived LPS, cytokines, proinflammatory related kinases JNK and IKKβ, as well as activation of IRS-1 and Akt. ConclusionsSDD appeared to have an effect on proinflammatory signaling cascades and further reduced severe burn-induced insulin resistance.

Fecal Colonization with ESBL-Producing

Gram-negative gut bacteria — Escherichia coli — constitute the reservoir from which urinary tract infections (UTIs) originate. The prevalence of

Toll-like receptor 4 polymorphisms and ankylosing spondylitis

Ankylosing spondylitis (AS) is a chronic systemic rheumatic disorder, which is characterised by sacroiliitis, enthesopathy, and a variety of extra-articular manifestations. Despite having the strongest association ever described with a tissue antigen, HLA B27, the pathogenesis of AS remains poorly understood. Immunoregulatory genes and Gram-negative gut bacteria are thought to be important in disease expression. It is now known that mammalian immune response to Gram-negative bacteria is mediated by Toll-like receptor 4 (TLR4), a pattern recognition receptor. Two cosegregating missense mutations have recently been described in TLR4 that lead to a diminished host response to Gram-negative bacteria. We hypothesise that TLR4 mutations occur with an increased frequency in HLA B27-positive individuals who develop AS than in healthy HLA B27-positive controls, and allow increased survival and the systemic distribution of Gram-negative gut bacteria to the joints. This study aims to compare the frequency of two common TLR4 mutations (Asp299Gly, and Thr399Ile) between AS patients and HLA B27 healthy controls.