Quantitative lipopolysaccharide analysis using HPLC/MS/MS and its combination with the limulus amebocyte lysate assay

Neuroretinal and Retinal Pigment Epithelium Changes and Susceptibility to Age-Related Macular Degeneration: Insights from the Longitudinal ALIENOR Study

PURPOSE

We assessed the associations of macular layer thicknesses, measured using spectral-domain (SD) OCT, with incident age-related macular degeneration (AMD) and AMD polygenic risk scores (PRSs).

DESIGN

Population-based cohort study.

PARTICIPANTS

A total of 653 participants from the ALIENOR study, with biennial eye imaging from 2009 through 2024.

METHODS

Macular layer thicknesses of 8 distinct layers were automatically segmented based on SD-OCT imaging. Total and pathway-specific PRSs were calculated from previous AMD genome-wide association studies summary statistics. Associations of macular layer thicknesses with incident intermediate and advanced AMD were analyzed using time-dependent Cox proportional hazards models. Associations of macular layer thicknesses with PRS were assessed using linear mixed models.

MAIN OUTCOME MEASURES

Incident intermediate and advanced AMD based on fundus color photographs and SD-OCT.

RESULTS

Mean age at first OCT examination of the 653 participants was 82.2 ± 4.2 years, 61.3% of which were women. In multivariable adjusted models, incident intermediate AMD was associated with thicker retinal pigment epithelium (RPE)-Bruch membrane (BM) complex in the 1-mm central circle (hazard ratio [HR], 1.13 for 1-μm increase; P = 8.08 × 10-4 with false discovery rate [FDR] correction). Incident advanced AMD was associated with thicker RPE-BM complex in both the central (HR, 1.09; PFDR = 0.005) and inner circle (1- to 3 mm; HR, 1.28; PFDR = 1.61 × 10-5). Over the study period, RPE-BM complex thickening in the inner circle was more pronounced in individuals with high total PRS (β = 0.06 μm/year for 1-standard deviation increase; PFDR = 1.61 × 10-10), high complement pathway PRS (β = 0.04 μm/year; PFDR = 3.23 × 10-5), high lipid pathway PRS (β = 0.03 μm/year; PFDR = 3.74 × 10-4), and ARMS2 (β = 0.03 μm/year, PFDR = 0.002). High total PRS and high complement-specific PRS were associated with thinner photoreceptor segment layer (PSL) at baseline and longitudinal thinning of the outer nuclear layer.

CONCLUSIONS

These findings highlight RPE-BM complex thickening in the pathophysiologic sequence of AMD. Further longitudinal studies are needed, in particular to determine the value of RPE-BM thickening and PSL thinning measured using SD-OCT for the clinical follow-up of patients with AMD.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Glucagon-like peptide 1 level and risk of death within 90 days after intensive care unit admission: A substudy of the IVOIRE cohort

BACKGROUND

Elevated plasma levels of glucagon-like peptide-1 (GLP-1) have been associated with poor clinical outcome in patients with sepsis. This study investigated the association between GLP-1 levels, and survival at 90 days in a large cohort of critically ill patients.

METHODS

All patients aged ≥ 18 years admitted to the intensive care unit (ICU) in a large university hospital, and receiving ≥1 life support therapy for organ failure were eligible for inclusion. Plasma samples were taken within 24h of ICU admission. We measured GLP-1 using a commercial ELISA kit. Cumulative probability of death at 90 days (D90) was plotted using the Kaplan-Meier method by quartiles of GLP-1. The effect of GLP-1 quartile on D90 survival was analyzed using a Cox proportional hazards model.

RESULTS

A total of 507 patients had GLP-1 dosage; mean age 64.5 ± 14.5 years; 179 (35.3%) women. GLP-1 levels ranged from 0.03 to 129.2 (median 7.3[IQR:3.3;19.1]). Higher mean age, SOFA, SAPS II, and LPS 3HM were found in patients with higher GLP-1 quartile by univariate analysis. Overall, 229 patients (45.2%) died within 90 days. The cumulative probability of death was significantly associated with GLP-1 quartile (p log rank<0.0001). After adjustment for age, SOFA, renal replacement therapy and vasopressor treatment, a significantly increased risk was observed only for patients with the highest quartile of GLP-1 (adjusted hazard ratio 1.65 [1.06; 2.56] for 4th vs 1st quartile of GLP-1).

CONCLUSION

After adjusting for demographic and clinical characteristics, only the highest quartile of GLP-1 remained independently associated with an increased risk of death at 90 days after admission to ICU.

Pneumococcal meningitis and endotoxemia: A cross-sectional clinical study

INTRODUCTION

Lipopolysaccharide (LPS) is a major virulence factor during both meningococcal and Haemophilus influenzae meningitis. Pneumococcus does not produce LPS but could be responsible for bacterial digestive translocation as a consequence of sepsis. We addressed this question in the context of pneumococcal meningitis.

METHODS

A cross-sectional study on 24 patients with pneumococcal meningitis (20 (83%) admitted in intensive care unit, 4 (17%) with septic shock) and 34 prospectively-enrolled healthy volunteers. Interleukin 6 and C-reactive proteins plasma concentrations were measured as markers of systemic inflammation. Endotoxemia was measured using mass spectrometry (LC-MS/MS) for detection of molecules bound to the lipid A, namely 3-OH fatty acids.

RESULTS

Meningitis patients had significantly higher levels of plasma C-reactive protein (237 (74-373) vs. 2 (2-2) mg/l, p < 0.001 and interleukin 6 (43 (13-128) vs. 4.6 (4.6-16.6) pg/ml; p < 0.001) than healthy volunteers. However, we observed no significant difference in plasma lipopolysaccharide concentrations between patients and healthy volunteers (674 (554-896) vs. 668 (623-777) pmol/ml; p = 0.546).

CONCLUSIONS

Our results suggest that LPS is not a key determinant of the excessive inflammation associated with severe forms of pneumococcal meningitis.

Progress in Characterization of Lipopolysaccharides and Lipid A by Mass Spectrometry

Lipopolysaccharides (LPS) are complex molecules embedded in the outer membrane of Gram-negative bacteria. LPS are highly heterogeneous across species and strains, posing a significant analytical challenge. This review article explores recent advances in the identification and characterization of LPS, with a particular focus on the role of mass spectrometry (MS) techniques. The review highlights how MS, in conjunction with various separation methods and spanning different ionization techniques and dissociation modes, has enabled more precise and sensitive determination of LPS composition, with a focus on lipid A structure. Finally, emerging trends in MS applications for LPS research are discussed and its potential to provide deeper insights into the development of antibiotic resistance among pathogenic bacteria.

Combining in vivo and in vitro approaches to investigate the effect of sainfoin on strongyle infection, immunity, and large intestine ecosystem of horses

Sainfoin (Onobrychis viciifolia), a polyphenol-rich plant, has shown promising anti-parasitic properties in ruminants, but results in horses are fewer and inconsistent. The mechanisms of action involved are not fully understood and different factors may influence its anti-parasitic properties. Recently, it has been shown that the effect of sainfoin depends on the horse's diet. Indeed, the inclusion of dehydrated sainfoin pellets in a high-starch diet limited the rate of increase in strongyle egg shedding over a short period of time (21 d). The objective of this study was to evaluate, in vivo, the effect of long-term inclusion of sainfoin in a high-starch diet on strongyle infection and intestinal health in horses and to compare in vitro anti-parasitic activity of 2 different dehydrated sainfoin pellets. Horses known to have a past history of strongyle egg excretion (n = 16) were allocated to 2 groups and fed with a high-starch diet containing either sainfoin (SF) pellets or control pellets (sunflower and hay) (CONT) for 84 d. In vitro tests including egg hatch test (EHT) and larval migration inhibition test (LMIT) were performed with different concentrations of aqueous extracts of the sainfoin pellets. No effect of the inclusion of sainfoin in the high-starch diet was observed on the number of strongyle eggs excreted in the feces (P = 0.671). At the different sampling dates, including sainfoin in a high-starch diet-induced some changes in the relative abundance of bacterial taxa (e.g., Oscillibacter, P < 0.05), but not on bacterial diversity (all P's > 0.05), function (P > 0.05) or activity (P > 0.05). Adding sainfoin to a high-starch diet increased plasma acetate concentration (P = 0.032) but no statistically significant differences were observed on other markers of intestinal integrity (plasma lipopolysaccharides) and health (complete blood count) (all P's > 0.05). Both sainfoin pellets showed anti-parasitic activity in the 2 in vitro tests (all P's < 0.05), and 1 sainfoin had a stronger anti-parasitic effect than the other (EHT, all P's < 0.05; LMIT, P = 0.008). Overall, these results suggest that the anti-parasitic effect of sainfoin may depend on its polyphenolic concentration. Thus, preliminary in vitro testing may help to identify sainfoin best suited for in vivo use.

Association of Lipopolysaccharide-Type Endotoxins with Retinal Neurodegeneration: The Alienor Study

Purpose

Lipopolysaccharide (LPS)-type endotoxins are naturally found in the gut microbiota and there is emerging evidence linking gut microbiota and neuroinflammation leading to retinal neurodegeneration. Thinning of the retinal nerve fiber layer (RNFL) is a biomarker of retinal neurodegeneration, and a hallmark of glaucoma, the second leading cause of blindness worldwide. We assessed the association of a blood biomarker of LPS with peripapillary RNFL thickness (RNFLT) and its longitudinal evolution up to 11 years.

Design

The Alienor study is a single center prospective population-based cohort study.

Subjects

The studied sample of this study includes 1062 eyes of 548 participants receiving ≥1 gradable RNFL measurement.

Methods

Plasma esterified 3-hydroxy fatty acids (3-OH FAs) were measured as a proxy of LPS burden. Retinal nerve fiber layer thickness was acquired using spectral-domain OCT imaging every 2 years from 2009 to 2020 (up to 5 visits).

Main Outcome Measures

Associations of plasma esterified 3-OH FAs with RNFLT were assessed using linear mixed models.

Results

Mean age of the included 548 participants was 82.4 ± 4.3 years and 62.6% were women. Higher plasma esterified 3-OH FAs was significantly associated with thinner RNFLT at baseline (coefficient beta = -1.42 microns for 1 standard deviation-increase in 3-OH FAs, 95% confidence interval [-2.56; -0.28], P = 0.02). This association remained stable after multivariate adjustment for potential confounders. No statistically significant association was found between 3-OH FAs and longitudinal RNFLT change.

Conclusions

Higher plasma esterified 3-OH FAs were associated with thinner RNFLT at baseline, indicating an involvement of LPS in the early processes of optic nerve neurodegeneration and highlighting the potential importance of the human microbiota in preserving retinal health.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Fast, Easy, and Reproducible Fingerprint Methods for Endotoxin Characterization in Nanocellulose and Alginate-Based Hydrogel Scaffolds

Nanocellulose- and alginate-based hydrogels have been suggested as potential wound-healing materials, but their utilization is limited by the Food and Drug Administration (FDA) requirements regarding endotoxin levels. Cytotoxicity and the presence of endotoxin were assessed after gel sterilization using an autoclave and UV treatment. A new fingerprinting method was developed to characterize the compounds detected in cellulose nanocrystal (CNC)- and cellulose-nanofiber (CNF)-based hydrogels using both positive- and negative-ion mode electrospray ionization Fourier transform ion cyclotron resonance mass spectroscopy (ESI FT-ICR MS). These biobased hydrogels were used as scaffolds for the cultivation and growth of human dermal fibroblasts to test their biocompatibility. A resazurin-based assay was preferred over all other biocompatibility methodologies since it allowed for the evaluation of viability over time in the same sample without causing cell lysis. The CNF dispersion of 6 EU mL-1 was slightly above the limits, and it did not affect the cell viability, whereas CNC hydrogels induced a reduction of metabolic activity by the fibroblasts. The chemical structure of the detected endotoxins did not contain phosphates, but it encompassed hydrophobic sulfonate groups, requiring the development of new high-pressure sterilization methods for the use of cellulose hydrogels in medicine.

Intestinal fatty acid binding protein is associated with infarct size and cardiac function in acute heart failure following myocardial infarction

BACKGROUND

In acute heart failure (HF), reduced cardiac output, vasoconstriction and congestion may damage the intestinal mucosa and disrupt its barrier function. This could facilitate the leakage of bacterial products into circulation and contribute to inflammation and adverse cardiac remodelling. We aimed to investigate gut leakage markers and their associations with inflammation, infarct size and cardiac function.

METHODS

We examined 61 ST-elevation myocardial infarction (STEMI) patients who developed acute HF within 48 hours of successful percutaneous coronary intervention (PCI). Serial blood samples were taken to measure lipopolysaccharide (LPS), LPS-binding protein (LBP), soluble cluster of differentiation 14 (sCD14) and intestinal fatty acid binding protein (I-FABP). Cumulative areas under the curve (AUCs) from baseline to day 5 were calculated. Serial echocardiography was performed to assess left ventricular ejection fraction (LVEF), global longitudinal strain (GLS) and wall motion score index (WMSI). Single-photon emission CT (SPECT) was performed at 6 weeks to determine infarct size and LVEF.

RESULTS

I-FABPAUC correlated positively with infarct size (rs=0.45, p=0.002), GLS (rs=0.32, p=0.035) and WMSI (rs=0.45, p=0.002) and negatively with LVEF measured by SPECT (rs=-0.40, p=0.007) and echocardiography (rs=-0.33, p=0.021) at 6 weeks. LPSAUC, LBPAUC and sCD14AUC did not correlate to any cardiac function marker or infarct size. Patients, who at 6 weeks had above median GLS and WMSI, and below-median LVEF measured by SPECT, were more likely to have above median I-FABPAUC during admission (adjusted OR (aOR) 5.22, 95% CI 1.21 to 22.44; aOR 5.05, 95% CI 1.25 to 20.43; aOR 5.67, 95% CI 1.42 to 22.59, respectively). The same was observed for patients in the lowest quartile of LVEF measured by echocardiography (aOR 9.99, 95% CI 1.79 to 55.83) and three upper quartiles of infarct size (aOR 20.34, 95% CI 1.56 to 264.65).

CONCLUSIONS

In primary PCI-treated STEMI patients with acute HF, I-FABP, a marker of intestinal epithelial damage, was associated with larger infarct size and worse cardiac function after 6 weeks.

Effects of Omega-3 Polyunsaturated Fatty Acids on the Formation of Adipokines, Cytokines, and Oxylipins in Retroperitoneal Adipose Tissue of Mice

Oxylipins and specialized pro-resolving lipid mediators (SPMs) derived from polyunsaturated fatty acids (PUFAs) are mediators that coordinate an active process of inflammation resolution. While these mediators have potential as circulating biomarkers for several disease states with inflammatory components, the source of plasma oxylipins/SPMs remains a matter of debate but may involve white adipose tissue (WAT). Here, we aimed to investigate to what extent high or low omega (n)-3 PUFA enrichment affects the production of cytokines and adipokines (RT-PCR), as well as oxylipins/SPMs (liquid chromatography-tandem mass spectrometry) in the WAT of mice during lipopolysaccharide (LPS)-induced systemic inflammation (intraperitoneal injection, 2.5 mg/kg, 24 h). For this purpose, n-3 PUFA genetically enriched mice (FAT-1), which endogenously synthesize n-3 PUFAs, were compared to wild-type mice (WT) and combined with n-3 PUFA-sufficient or deficient diets. LPS-induced systemic inflammation resulted in the decreased expression of most adipokines and interleukin-6 in WAT, whereas the n-3-sufficient diet increased them compared to the deficient diet. The n-6 PUFA arachidonic acid was decreased in WAT of FAT-1 mice, while n-3 derived PUFAs (eicosapentaenoic acid, docosahexaenoic acid) and their metabolites (oxylipins/SPMs) were increased in WAT by genetic and nutritional n-3 enrichment. Several oxylipins/SPMs were increased by LPS treatment in WAT compared to PBS-treated controls in genetically n-3 enriched FAT-1 mice. Overall, we show that WAT may significantly contribute to circulating oxylipin production. Moreover, n-3-sufficient or n-3-deficient diets alter adipokine production. The precise interplay between cytokines, adipokines, and oxylipins remains to be further investigated.

Protection against the H1N1 influenza virus using self-assembled nanoparticles formed by lumazine synthase and bearing the M2e peptide

There is an urgent need for influenza vaccines that offer broad cross-protection. The highly conserved ectodomain of the influenza matrix protein 2 (M2e) is a promising candidate; however, its low immunogenicity can be addressed. In this study, we developed influenza vaccines using the Lumazine synthase (LS) platform. The primary objective of this study was to determine the protective potential of M2e proteins expressed on Lumazine synthase (LS) nanoparticles. M2e-LS proteins, produced through the E. coli system, spontaneously assemble into nanoparticles. The study investigated the efficacy of the M2e-LS nanoparticle vaccine in mice. Mice immunized with M2e-LS nanoparticles exhibited significantly higher levels of intracellular cytokines than those receiving soluble M2e proteins. The M2e-LS protein exhibited robust immunogenicity and provided 100% protection against cross-clade influenza.

Risk factors and prognostic value of endotoxemia in patients with acute myocardial infarction

Background

There is increasing evidence regarding the association between endotoxemia and the pathogenesis of atherosclerosis and myocardial infarction (MI). During the acute phase of MI, endotoxemia might increase inflammation and drive adverse cardiovascular (CV) outcomes. We aimed to explore the risk factors and prognostic value of endotoxemia in patients admitted for acute MI.

Methods

Patients admitted to the coronary care unit of Dijon University Hospital for type 1 acute MI between 2013 and 2015 were included. Endotoxemia, assessed by plasma lipopolysaccharide (LPS) concentration, was measured by mass spectrometry. Major adverse CV events were recorded in the year following hospital admission.

Results

Data from 245 consecutive MI patients were analyzed. LPS concentration at admission markedly increased with age and diabetes. High LPS concentration was correlated with metabolic biomarkers (glycemia, triglyceride, and total cholesterol) but not with CV (troponin Ic peak and N-terminal pro-brain natriuretic peptide) or inflammatory biomarkers (C-reactive protein, IL6, IL8, and TNFα). LPS concentration was not associated with in-hospital or 1-year outcomes.

Conclusions

In patients admitted for MI, higher levels of endotoxins were related to pre-existing conditions rather than acute clinical severity. Therefore, endotoxins measured on the day of MI could reflect metabolic chronic endotoxemia rather than MI-related acute gut translocation.

Soluble CD14 produced by bovine mammary epithelial cells modulates their response to full length LPS

Bovine mastitis remains a major disease in cattle world-wide. In the mammary gland, mammary epithelial cells (MEC) are sentinels equipped with receptors allowing them to detect and respond to the invasion by bacterial pathogens, in particular Escherichia coli. Lipopolysaccharide (LPS) is the major E. coli motif recognized by MEC through its interaction with the TLR4 receptor and the CD14 co-receptor. Previous studies have highlighted the role of soluble CD14 (sCD14) in the efficient recognition of LPS molecules possessing a full-length O-antigen (LPSS). We demonstrate here that MEC are able to secrete CD14 and are likely to contribute to the presence of sCD14 in milk. We then investigated how sCD14 modulates and is required for the response of MEC to LPSS. This study highlights the key role of sCD14 for the full activation of the Myd88-independent pathway by LPSS. We also identified several lncRNA that are activated in MEC in response to LPS, including one lncRNA showing homologies with the mir-99a-let-7c gene (MIR99AHG). Altogether, our results show that a full response to LPS by mammary epithelial cells requires sCD14 and provide detailed information on how milk sCD14 can contribute to an efficient recognition of LPS from coliform pathogens.

Diet modulates strongyle infection and microbiota in the large intestine of horses

The use of anthelminthic drugs has several drawbacks, including the selection of resistant parasite strains. Alternative avenues to mitigate the negative effects of helminth infection involve dietary interventions that might affect resistance and/or tolerance by improving host immunity, modulating the microbiota, or exerting direct anthelmintic effects. The aim of this study was to assess the impact of diet on strongyle infection in horses, specifically through immune-mediated, microbiota-mediated, or direct anthelmintic effects. Horses that were naturally infected with strongyles were fed either a high-fiber or high-starch diet, supplemented with either polyphenol-rich pellets (dehydrated sainfoin) or control pellets (sunflower and hay). When horses were fed a high-starch diet, they excreted more strongyle eggs. Adding sainfoin in the high-starch diet reduced egg excretion. Additionally, sainfoin decreased larval motility whatever the diet. Moreover, the high-starch diet led to a lower fecal bacterial diversity, structural differences in fecal microbiota, lower fecal pH, lower blood acetate, and lower hematocrit compared to the high-fiber diet. Circulating levels of Th1 and Th2 cytokines, lipopolysaccharides, procalcitonin, and white blood cells proportions did not differ between diets. Overall, this study highlights the role of dietary manipulations as an alternative strategy to mitigate the effect of helminth infection and suggests that, in addition to the direct effects, changes in the intestinal ecosystem are the possible underlying mechanism.

Diversity, Complexity, and Specificity of Bacterial Lipopolysaccharide (LPS) Structures Impacting Their Detection and Quantification

Endotoxins are toxic lipopolysaccharides (LPSs), extending from the outer membrane of Gram-negative bacteria and notorious for their toxicity and deleterious effects. The comparison of different LPSs, isolated from various Gram-negative bacteria, shows a global similar architecture corresponding to a glycolipid lipid A moiety, a core oligosaccharide, and outermost long O-chain polysaccharides with molecular weights from 2 to 20 kDa. LPSs display high diversity and specificity among genera and species, and each bacterium contains a unique set of LPS structures, constituting its protective external barrier. Some LPSs are not toxic due to their particular structures. Different, well-characterized, and highly purified LPSs were used in this work to determine endotoxin detection rules and identify their impact on the host. Endotoxin detection is a major task to ensure the safety of human health, especially in the pharma and food sectors. Here, we describe the impact of different LPS structures obtained under different bacterial growth conditions on selective LPS detection methods such as LAL, HEK-blue TLR-4, LC-MS2, and MALDI-MS. In these various assays, LPSs were shown to respond differently, mainly attributable to their lipid A structures, their fatty acid numbers and chain lengths, the presence of phosphate groups, and their possible substitutions.

Endotoxin Translocation Is Increased in Broiler Chickens Fed a Fusarium Mycotoxin-Contaminated Diet

Broiler chickens in livestock production face numerous challenges that can impact their health and welfare, including mycotoxin contamination and heat stress. In this study, we aimed to investigate the combined effects of two mycotoxins, deoxynivalenol (DON) and fumonisins (FBs), along with short-term heat stress conditions, on broiler gut health and endotoxin translocation. An experiment was conducted to assess the impacts of mycotoxin exposure on broilers, focusing on intestinal endotoxin activity, gene expression related to gut barrier function and inflammation, and the plasma concentration of the endotoxin marker 3-OH C14:0 either at thermoneutral conditions or short-term heat stress conditions. Independently of heat stress, broilers fed DON-contaminated diets exhibited reduced body weight gain during the starter phase (Day 1-12) compared to the control group, while broilers fed FB-contaminated diets experienced decreased body weight gain throughout the entire trial period (Day 1-24). Furthermore, under thermoneutral conditions, broilers fed DON-contaminated diets showed an increase in 3-OH C14:0 concentration in the plasma. Moreover, under heat stress conditions, the expression of genes related to gut barrier function (Claudin 5, Zonulin 1 and 2) and inflammation (Toll-like receptor 4, Interleukin-1 beta, Interleukin-6) was significantly affected by diets contaminated with mycotoxins, depending on the gut segment. This effect was particularly prominent in broilers fed diets contaminated with FBs. Notably, the plasma concentration of 3-OH C14:0 increased in broilers exposed to both DON- and FB-contaminated diets under heat stress conditions. These findings shed light on the intricate interactions between mycotoxins, heat stress, gut health, and endotoxin translocation in broiler chickens, highlighting the importance of understanding these interactions for the development of effective management strategies in livestock production to enhance broiler health and welfare.

Excess of body weight is associated with accelerated T-cell senescence in hospitalized COVID-19 patients

BACKGROUND

Several risk factors have been involved in the poor clinical progression of coronavirus disease-19 (COVID-19), including ageing, and obesity. SARS-CoV-2 may compromise lung function through cell damage and paracrine inflammation; and obesity has been associated with premature immunosenescence, microbial translocation, and dysfunctional innate immune responses leading to poor immune response against a range of viruses and bacterial infections. Here, we have comprehensively characterized the immunosenescence, microbial translocation, and immune dysregulation established in hospitalized COVID-19 patients with different degrees of body weight.

RESULTS

Hospitalised COVID-19 patients with overweight and obesity had similarly higher plasma LPS and sCD14 levels than controls (all p < 0.01). Patients with obesity had higher leptin levels than controls. Obesity and overweight patients had similarly higher expansions of classical monocytes and immature natural killer (NK) cells (CD56+CD16-) than controls. In contrast, reduced proportions of intermediate monocytes, mature NK cells (CD56+CD16+), and NKT were found in both groups of patients than controls. As expected, COVID-19 patients had a robust expansion of plasmablasts, contrasting to lower proportions of major T-cell subsets (CD4 + and CD8+) than controls. Concerning T-cell activation, overweight and obese patients had lower proportions of CD4+CD38+ cells than controls. Contrasting changes were reported in CD25+CD127low/neg regulatory T cells, with increased and decreased proportions found in CD4+ and CD8+ T cells, respectively. There were similar proportions of T cells expressing checkpoint inhibitors across all groups. We also investigated distinct stages of T-cell differentiation (early, intermediate, and late-differentiated - TEMRA). The intermediate-differentiated CD4 + T cells and TEMRA cells (CD4+ and CD8+) were expanded in patients compared to controls. Senescent T cells can also express NK receptors (NKG2A/D), and patients had a robust expansion of CD8+CD57+NKG2A+ cells than controls. Unbiased immune profiling further confirmed the expansions of senescent T cells in COVID-19.

CONCLUSIONS

These findings suggest that dysregulated immune cells, microbial translocation, and T-cell senescence may partially explain the increased vulnerability to COVID-19 in subjects with excess of body weight.

Plasma citrulline concentration and plasma LPS detection among critically ill patients a prospective observational study

PURPOSE

Gut can be a source of sepsis but sepsis itself can induce gut dysfunction. We aimed to study whether plasma citrulline, a marker of enterocyte mass, was correlated with plasma lipopolysaccharide, a potential marker of bacterial translocation among critically ill patients.

MATERIALS AND METHODS

Critically ill patients admitted to the ICU. Plasma citrulline and plasma LPS concentration and activity were measured at ICU admission. Patients were compared according to the presence of sepsis at ICU admission.

RESULTS

109 critically ill patients, with SOFA score 8 [6-12], were prospectively included. Sixty six patients (61%) had sepsis at ICU admission. There was no correlation between plasma citrulline concentration and plasma LPS concentration or activity. However, sepsis at ICU admission was associated with a lower plasma citrulline concentration (13.4 μmol.L-1 vs 21.3 μmol.L-1, p = 0.02). Plasma LPS activity was significantly higher among patients with abdominal sepsis compared to patients with extra-abdominal sepsis (1.04 EU/mL vs 0.63, p = 0.01).

CONCLUSIONS

Plasma citrulline is not associated with the level of plasma LPS but is strongly decreased among septic patients. Detection of LPS is ubiquitous among critically ill patients but abdominal sepsis is associated with increased plasma LPS activity compared to extra-abdominal sepsis.

Advances in endotoxin analysis

The outer membrane of gram-negative bacteria is primarily composed of lipopolysaccharide (LPS). In addition to protection, LPS defines the distinct serogroups used to identify bacteria specifically. Furthermore, LPS also act as highly potent stimulators of innate immune cells, a phenomenon essential to understanding pathogen invasion in the body. The complex multi-step process of LPS binding to cells involves several binding partners, including LPS binding protein (LBP), CD14 in both membrane-bound and soluble forms, membrane protein MD-2, and toll-like receptor 4 (TLR4). Once these pathways are activated, pro-inflammatory cytokines are eventually expressed. These binding events are also affected by the presence of monomeric or aggregated LPS. Traditional techniques to detect LPS include the rabbit pyrogen test, the monocyte activation test and Limulus-based tests. Modern approaches are based on protein, antibodies or aptamer binding. Recently, novel techniques including electrochemical methods, HPLC, quartz crystal microbalance (QCM), and molecular imprinting have been developed. These approaches often use nanomaterials such as gold nanoparticles, quantum dots, nanotubes, and magnetic nanoparticles. This chapter reviews current developments in endotoxin detection with a focus on modern novel techniques that use various sensing components, ranging from natural biomolecules to synthetic materials. Highly integrated and miniaturized commercial endotoxin detection devices offer a variety of options as the scientific and technologic revolution proceeds.

Pneumococcal pneumonia and endotoxemia: An experimental and clinical reappraisal

BACKGROUND

Circulating endotoxins could result from bacterial digestive translocation during sepsis, thus contributing to uncontrolled systemic inflammation, leading in turn to organ dysfunction. We addressed this issue in the setting of severe pneumococcal pneumonia.

METHODS

Endotoxemia was measured in a clinically relevant rabbit model of ventilated pneumococcal pneumonia and in 110 patients with bacteraemic pneumonia, using a patented mass spectrometry (LC-MS/MS) method for detection of 3-OH fatty acids (C10, C12, C14, C16 and C18), which are molecules bound to the lipid A motif of LPS.

RESULTS

Whereas higher levels of systemic inflammation and organ dysfunctions were found, there was no significant difference in lipopolysaccharide concentrations when infected rabbits were compared to non-infected ones, or when patients were compared to healthy volunteers.

CONCLUSIONS

Seemingly, endotoxins do not drive the overwhelming inflammation associated with severe forms of pneumococcal pneumonia.

The transplantation of the gut microbiome of fat-1 mice protects against colonic mucus layer disruption and endoplasmic reticulum stress induced by high fat diet

High-fat diets alter gut barrier integrity, leading to endotoxemia by impacting epithelial functions and inducing endoplasmic reticulum (ER) stress in intestinal secretory goblet cells. Indeed, ER stress, which is an important contributor to many chronic diseases such as obesity and obesity-related disorders, leads to altered synthesis and secretion of mucins that form the protective mucus barrier. In the present study, we investigated the relative contribution of omega-3 polyunsaturated fatty acid (PUFAs)-modified microbiota to alleviating alterations in intestinal mucus layer thickness and preserving gut barrier integrity. Male fat-1 transgenic mice (exhibiting endogenous omega-3 PUFAs tissue enrichment) and wild-type (WT) littermates were fed either an obesogenic high-fat diet (HFD) or a control diet. Unlike WT mice, HFD-fed fat-1 mice were protected against mucus layer alterations as well as an ER stress-mediated decrease in mucin expression. Moreover, cecal microbiota transferred from fat-1 to WT mice prevented changes in the colonic mucus layer mainly through colonic ER stress downregulation. These findings highlight a novel feature of the preventive effects of omega-3 fatty acids against intestinal permeability in obesity-related conditions.

Association of Age-Related Macular Degeneration with a Blood Biomarker of Lipopolysaccharide, a Gut Bacterial Proinflammatory Toxin

Purpose

Chronic inflammation, immune dysregulation, and oxidative stress are major drivers of age-related macular degeneration (AMD) pathogenesis. Lipopolysaccharide (LPS) is a potent proinflammatory toxin originating from gut bacteria. We assessed the association of a blood biomarker of LPS exposure with incident AMD.

Methods

The Alienor Study is a prospective population-based study, including 963 residents of Bordeaux (France), aged 73 years or more at baseline. Esterified 3-hydroxy fatty acids (3-OH FAs) were measured from blood samples as a proxy of LPS burden. AMD was graded from color retinal photographs and spectral domain optical coherence tomography, performed every two years from 2006 to 2017. Cox proportional hazards models were used to estimate associations of between esterified 3-OH FAs, using 722 eyes at risk for incident early AMD and 981 eyes at risk for incident advanced AMD.

Results

Higher esterified 3-OH FAs were associated with incident early AMD after adjusting for age and gender (hazard ratio [HR] = 1.21 for 1 standard deviation [SD] increase; 95% confidence interval [CI], 1.01-1.45; P = 0.04) but not with incident advanced AMD (HR = 1.03 for 1 SD increase; 95% CI, 0.73-1.45; P = 0.86). These associations remained stable after multivariate adjustment and imputation for missing covariates (early AMD HR = 1.22 for 1 SD increase; 95% CI, 1.01-1.46; P = 0.04; advanced AMD HR = 0.98 for 1 SD increase; 95% CI, 0.69-1.38; P = 0.91).

Conclusions

This study evidenced an association between higher esterified 3-OH FAs and incident early AMD, suggesting that exposure to LPS may be involved in the early pathophysiological processes of AMD.

An early glycolysis burst in microglia regulates mitochondrial dysfunction in oligodendrocytes under neuroinflammation

Metabolism and energy processes governing oligodendrocyte function during neuroinflammatory disease are of great interest. However, how varied cellular environments affect oligodendrocyte activity during neuroinflammation is unknown. We demonstrate that activated microglial energy metabolism controls oligodendrocyte mitochondrial respiration and activity. Lipopolysaccharide/interferon gamma promote glycolysis and decrease mitochondrial respiration and myelin protein synthesis in rat brain glial cells. Enriched microglia showed an early burst in glycolysis. In microglia-conditioned medium, oligodendrocytes did not respire and expressed less myelin. SCENITH revealed metabolic derangement in microglia and O4-positive oligodendrocytes in endotoxemia and experimental autoimmune encephalitogenic models. The early burst of glycolysis in microglia was mediated by PDPK1 and protein kinase B/AKT signaling. We found that microglia-produced NO and itaconate, a tricarboxylic acid bifurcated metabolite, reduced mitochondrial respiration in oligodendrocytes. During inflammation, we discovered a signaling pathway in microglia that could be used as a therapeutic target to restore mitochondrial function in oligodendrocytes and induce remyelination.

Endotoxemia in Acute Heart Failure and Cardiogenic Shock: Evidence, Mechanisms and Therapeutic Options

Acute heart failure and cardiogenic shock are frequently occurring and deadly conditions. In patients with those conditions, endotoxemia related to gut injury and gut barrier dysfunction is usually described as a driver of organ dysfunction. Because endotoxemia might reciprocally alter cardiac function, this phenomenon has been suggested as a potent vicious cycle that worsens organ perfusion and leading to adverse outcomes. Yet, evidence beyond this phenomenon might be overlooked, and mechanisms are not fully understood. Subsequently, even though therapeutics available to reduce endotoxin load, there are no indications to treat endotoxemia during acute heart failure and cardiogenic shock. In this review, we first explore the evidence regarding endotoxemia in acute heart failure and cardiogenic shock. Then, we describe the main treatments for endotoxemia in the acute setting, and we present the challenges that remain before personalized treatments against endotoxemia can be used in patients with acute heart failure and cardiogenic shock.

Hepatotoxicity of polymeric proanthocyanidins is caused by translocation of bacterial lipopolysaccharides through impaired gut epithelium

Polymeric proanthocyanidins (P-PAC) induced hepatotoxicity in C57BL/6 mice. Mice were supplemented with P-PAC alone or with a mixture of probiotic bacteria (PB), Lactobacillus, Bifidobacterium, and Akkermansia muciniphila for 14 consecutive days. The liver tissues of sacrificed mice were analyzed by mass spectrometry to identify and quantify the P-PAC metabolites. Potential P-PAC metabolites, 2-hydroxyphenylacetic acid and pyrocatechol were detected in higher concentrations and 4-hydroxybenzoic acid was detected exclusively in the mice supplemented with P-PAC and PB. Supplementation with P-PAC alone or with PB caused no shift in the α-diversity of mice gut microbiota. P-PAC induced nonalcoholic steatohepatitis in mice through increasing liver exposure to intestinal bacterial lipopolysaccharides by reducing expression of gut epithelial tight junction proteins, claudin-3 and occludin. Lipopolysaccharide concentrations in the livers of mice supplemented with P-PAC were significantly high compared to the control mice. Furthermore, P-PAC downregulated the expressions of claudin-3 and claudin-4 tight junction proteins in cultured Caco-2 cell monolayers. PB biotransformed P-PAC into bioavailable metabolites and potentially reduced the toxicity of P-PAC. The toxicity of P-PAC and their synbiotics need to be critically evaluated for the safety of human consumption.

Gut-derived low-grade endotoxaemia, atherothrombosis and cardiovascular disease

Systemic inflammation has been suggested to have a pivotal role in atherothrombosis, but the factors that trigger systemic inflammation have not been fully elucidated. Lipopolysaccharide (LPS) is a component of the membrane of Gram-negative bacteria present in the gut that can translocate into the systemic circulation, causing non-septic, low-grade endotoxaemia. Gut dysbiosis is a major determinant of low-grade endotoxaemia via dysfunction of the intestinal barrier scaffold, which is a prerequisite for LPS translocation into the systemic circulation. Experimental studies have demonstrated that LPS is present in atherosclerotic arteries but not in normal arteries. In atherosclerotic plaques, LPS promotes a pro-inflammatory status that can lead to plaque instability and thrombus formation. Low-grade endotoxaemia affects several cell types, including leukocytes, platelets and endothelial cells, leading to inflammation and clot formation. Low-grade endotoxaemia has been described in patients at risk of or with overt cardiovascular disease, in whom low-grade endotoxaemia was associated with atherosclerotic burden and its clinical sequelae. In this Review, we describe the mechanisms favouring the development of low-grade endotoxaemia, focusing on gut dysbiosis and changes in gut permeability; the plausible biological mechanisms linking low-grade endotoxaemia and atherothrombosis; the clinical studies suggesting that low-grade endotoxaemia is a risk factor for cardiovascular events; and the potential therapeutic tools to improve gut permeability and eventually eliminate low-grade endotoxaemia.

Endotoxin in Sepsis: Methods for LPS Detection and the Use of Omics Techniques

Lipopolysaccharide (LPS) or endotoxin, the major cell wall component of Gram-negative bacteria, plays a pivotal role in the pathogenesis of sepsis. It is able to activate the host defense system through interaction with Toll-like receptor 4, thus triggering pro-inflammatory mechanisms. A large amount of LPS induces inappropriate activation of the immune system, triggering an exaggerated inflammatory response and consequent extensive organ injury, providing the basis of sepsis damage. In this review, we will briefly describe endotoxin's molecular structure and its main pathogenetic action during sepsis. In addition, we will summarize the main different available methods for endotoxin detection with a special focus on the wider spectrum offered by omics technologies (genomics, transcriptomics, proteomics, and metabolomics) and promising applications of these in the identification of specific biomarkers for sepsis.

Increased Weight Gain and Insulin Resistance in HF-Fed PLTP Deficient Mice Is Related to Altered Inflammatory Response and Plasma Transport of Gut-Derived LPS

Bacterial lipopolysaccharides (LPS, endotoxins) are found in high amounts in the gut lumen. LPS can cross the gut barrier and pass into the blood (endotoxemia), leading to low-grade inflammation, a common scheme in metabolic diseases. Phospholipid transfer protein (PLTP) can transfer circulating LPS to plasma lipoproteins, thereby promoting its detoxification. However, the impact of PLTP on the metabolic fate and biological effects of gut-derived LPS is unknown. This study aimed to investigate the influence of PLTP on low-grade inflammation, obesity and insulin resistance in relationship with LPS intestinal translocation and metabolic endotoxemia. Wild-type (WT) mice were compared with Pltp-deficient mice (Pltp-KO) after a 4-month high-fat (HF) diet or oral administration of labeled LPS. On a HF diet, Pltp-KO mice showed increased weight gain, adiposity, insulin resistance, lipid abnormalities and inflammation, together with a higher exposure to endotoxemia compared to WT mice. After oral administration of LPS, PLTP deficiency led to increased intestinal translocation and decreased association of LPS to lipoproteins, together with an altered catabolism of triglyceride-rich lipoproteins (TRL). Our results show that PLTP, by modulating the intestinal translocation of LPS and plasma processing of TRL-bound LPS, has a major impact on low-grade inflammation and the onset of diet-induced metabolic disorders.

Possible mediators of metabolic endotoxemia in women with obesity and women with obesity-diabetes in The Gambia

AIMS/HYPOTHESIS

Translocation of bacterial debris from the gut causes metabolic endotoxemia (ME) that results in insulin resistance, and may be on the causal pathway to obesity-related type 2 diabetes. To guide interventions against ME we tested two hypothesised mechanisms for lipopolysaccharide (LPS) ingress: a leaky gut and chylomicron-associated transfer following a high-fat meal.

METHODS

In lean women (n = 48; fat mass index (FMI) 9.6 kg/m2), women with obesity (n = 62; FMI 23.6 kg/m2) and women with obesity-diabetes (n = 38; FMI 24.9 kg/m2) we used the lactulose-mannitol dual-sugar permeability test (LM ratio) to assess gut integrity. Markers of ME (LPS, EndoCAb IgG and IgM, IL-6, CD14 and lipoprotein binding protein) were assessed at baseline, 2 h and 5 h after a standardised 49 g fat-containing mixed meal. mRNA expression of markers of inflammation, macrophage activation and lipid metabolism were measured in peri-umbilical adipose tissue (AT) biopsies.

RESULTS

The LM ratio did not differ between groups. LPS levels were 57% higher in the obesity-diabetes group (P < 0.001), but, contrary to the chylomicron transfer hypothesis, levels significantly declined following the high-fat challenge. EndoCAb IgM was markedly lower in women with obesity and women with obesity-diabetes. mRNA levels of inflammatory markers in adipose tissue were consistent with the prior concept that fat soluble LPS in AT attracts and activates macrophages.

CONCLUSIONS/INTERPRETATION

Raised levels of LPS and IL-6 in women with obesity-diabetes and evidence of macrophage activation in adipose tissue support the concept of metabolic endotoxemia-mediated inflammation, but we found no evidence for abnormal gut permeability or chylomicron-associated post-prandial translocation of LPS. Instead, the markedly lower EndoCAb IgM levels indicate a failure in sequestration and detoxification.

Norepinephrine Inhibits Lipopolysaccharide-Stimulated TNF-α but Not Oxylipin Induction in n-3/n-6 PUFA-Enriched Cultures of Circumventricular Organs

Sensory circumventricular organs (sCVOs) are pivotal brain structures involved in immune-to-brain communication with a leaky blood-brain barrier that detect circulating mediators such as lipopolysaccharide (LPS). Here, we aimed to investigate the potential of sCVOs to produce n-3 and n-6 oxylipins after LPS-stimulation. Moreover, we investigated if norepinephrine (NE) co-treatment can alter cytokine- and oxylipin-release. Thus, we stimulated rat primary neuroglial sCVO cultures under n-3- or n-6-enriched conditions with LPS or saline combined with NE or vehicle. Supernatants were assessed for cytokines by bioassays and oxylipins by HPLC-MS/MS. Expression of signaling pathways and enzymes were analyzed by RT-PCR. Tumor necrosis factor (TNF)α bioactivity and signaling, IL-10 expression, and cyclooxygenase (COX)2 were increased, epoxide hydroxylase (Ephx)2 was reduced, and lipoxygenase 15-(LOX) was not changed by LPS stimulation. Moreover, LPS induced increased levels of several n-6-derived oxylipins, including the COX-2 metabolite 15d-prostaglandin-J2 or the Ephx2 metabolite 14,15-DHET. For n-3-derived oxylipins, some were down- and some were upregulated, including 15-LOX-derived neuroprotectin D1 and 18-HEPE, known for their anti-inflammatory potential. While the LPS-induced increase in TNFα levels was significantly reduced by NE, oxylipins were not significantly altered by NE or changes in TNFα levels. In conclusion, LPS-induced oxylipins may play an important functional role in sCVOs for immune-to-brain communication.

Evidence for Constitutive Microbiota-Dependent Short-Term Control of Food Intake in Mice: Is There a Link with Inflammation, Oxidative Stress, Endotoxemia, and GLP-1?

Aims: Although prebiotics, probiotics, and fecal transplantation can alter the sensation of hunger and/or feeding behavior, the role of the constitutive gut microbiota in the short-term regulation of food intake during normal physiology is still unclear. Results: An antibiotic-induced microbiota depletion study was designed to compare feeding behavior in conventional and microbiota-depleted mice. Tissues were sampled to characterize the time profile of microbiota-derived signals in mice during consumption of either standard or high-fat food for 1 h. Pharmacological and genetic tools were used to evaluate the contribution of postprandial endotoxemia and inflammatory responses in the short-term regulation of food intake. We observed constitutive microbial and macronutrient-dependent control of food intake at the time scale of a meal; that is, within 1 h of food introduction. Specifically, microbiota depletion increased food intake, and the microbiota-derived anorectic effect became significant during the consumption of high-fat but not standard food. This anorectic effect correlated with a specific postprandial microbial metabolic signature, and did not require postprandial endotoxemia or an NOD-, LRR-, and Pyrin domain-containing protein 3-inflammasome-mediated inflammatory response. Innovation and Conclusion: These findings show that the gut microbiota controls host appetite at the time scale of a meal under normal physiology. Interestingly, a microbiota-derived anorectic effect develops specifically with a high-fat meal, indicating that gut microbiota activity is involved in the satietogenic properties of foods. Antioxid. Redox Signal. 37, 349-369.

High-density lipoprotein infusion protects from acute graft-versus-host disease in experimental allogeneic hematopoietic cell transplantation

Acute graft-versus-host disease (aGVHD) is a major limitation of the therapeutic potential of allogeneic hematopoietic cell transplantation. Lipopolysaccharides (LPS) derived from intestinal gram-negative bacteria are well-known aGVHD triggers and amplifiers. Here, we explored the LPS metabolism in aGVHD mouse models using an innovative quantification method. We demonstrated that systemic LPS accumulation after transplantation was due, at least partly, to a defect in its clearance through lipoprotein-mediated transport to the liver (i.e., the so-called reverse LPS transport). After transplantation, reduced circulating HDL concentration impaired LPS neutralization and elimination through biliary flux. Accordingly, HDL-deficient (Apoa1^tm1Unc ) recipient mice developed exacerbated aGVHD. Repeated administration of HDL isolated from human plasma significantly decreased the mortality and the severity of aGVHD. While the potential role of HDL in scavenging circulating LPS was examined in this study, it appears that HDL plays a more direct immunomodulatory role by limiting or controlling aGVHD. Notably, HDL infusion mitigated liver aGVHD by diminishing immune infiltration (e.g., interferon-γ-secreting CD8⁺ T cells and non-resident macrophages), systemic and local inflammation (notably cholangitis). Hence, our results revealed the interest of HDL-based therapies in the prevention of aGVHD.

Effect of a Hemodialysis Session on Markers of Inflammation and Endotoxin

Background

People receiving hemodialysis (HD) treatment have higher cardiovascular morbidity and mortality, ascribed to an increased prevalence of traditional cardiovascular risk factors. However, the role of nontraditional risk factors, such as inflammation, has become increasingly recognized. The origin of this inflammation remains elusive and one putative cause is elevated levels of circulating bacterial endotoxin.

Methods

In this study, serum concentrations of endotoxin and inflammatory biomarkers, including high-sensitivity C-reactive protein (hsCRP), interleukin-6 (IL-6), interleukin-1β (IL1β), ferritin and tumor necrosis factor (TNF), were measured in 30 adults receiving HD and 10 healthy individuals without kidney disease. In people receiving HD, samples were collected immediately before dialysis (preHD), after dialysis (postHD), and 48 hours after (postHD_48hrs).

Results

Endotoxin was detectable in only 1 of 90 samples analyzed. There were no significant differences in serum hsCRP, IL1β, and IL6 levels, before and after dialysis. Serum TNF levels decreased significantly from 30.9 (8.0, 39.5) pg/mL preHD to 13.9 (8.5, 17.3) pg/mL post-HD (p=0.002) and then increased back to 27.37 (14.5, 35) pg/mL 2 days later (p < 0.001). Ferritin increased from 1153 ng/mL (782, 1458) preHD to 1313 ng/mL (657, 1638) post HD (p < 0.001) and then decreased back to 1186 ng/mL (754, 1597) (p=0.66) postHD_48hrs. Compared to controls, people receiving HD had significantly elevated levels of hsCRP [6.16 mg/L (2.1, 16.8) vs. 1.1 mg/L (0.81, 3.63) p=0.015], IL1β [1.5 pg/mL (0.05, 2.51) vs. 0.5 pg/mL (1.81, 2.95) p ≤ 0.001], and ferritin [1153 (782, 1458) vs. 132.9 (111, 257) ng/mL p ≤ 0.001], but comparable levels of in IL6 [6.15 pg/mL (4.82, 9.12) vs. 7.49 pg/mL (4.56, 10.39), p=0.77] and TNF [27.35 pg/mL ± 17.48 vs. 17.87 pg/mL ± 12.28, p < 0.12]. In conclusion, people on HD have elevated levels of inflammatory biomarkers, which are not associated with endotoxemia (which is rare) or the dialysis procedure.

Lipopolysaccharide and the gut microbiota: Considering structural variation

Systemic inflammation is associated with chronic disease and is purported to be a main pathogenic mechanism underlying metabolic conditions. Microbes harbored in the host gastrointestinal tract release signaling byproducts from their cell wall, such as lipopolysaccharides (LPS), which can act locally and, after crossing the gut barrier and entering circulation, also systemically. Defined as metabolic endotoxemia, elevated concentrations of LPS in circulation are associated with metabolic conditions and chronic disease. As such, measurement of LPS is highly prevalent in animal and human research investigating these states. Indeed, LPS can be a potent stimulant of host immunity but this response depends on the microbial species' origin, a parameter often overlooked in both preclinical and clinical investigations. Indeed, the lipid A portion of LPS is mutable and comprises the main virulence and endotoxic component, thus contributing to the structural and functional diversity among LPSs from microbial species. In this review, we discuss how such structural differences in LPS can induce differential immunological responses in the host.

Periodontitis and cardiometabolic disorders: The role of lipopolysaccharide and endotoxemia

Lipopolysaccharide is a virulence factor of gram-negative bacteria with a crucial importance to the bacterial surface integrity. From the host's perspective, lipopolysaccharide plays a role in both local and systemic inflammation, activates both innate and adaptive immunity, and can trigger inflammation either directly (as a microbe-associated molecular pattern) or indirectly (by inducing the generation of nonmicrobial, danger-associated molecular patterns). Translocation of lipopolysaccharide into the circulation causes endotoxemia, which is typically measured as the biological activity of lipopolysaccharide to induce coagulation of an aqueous extract of blood cells of the assay. Apparently healthy subjects have a low circulating lipopolysaccharide activity, since it is neutralized and cleared rapidly. However, chronic endotoxemia is involved in the pathogenesis of many inflammation-driven conditions, especially cardiometabolic disorders. These include atherosclerotic cardiovascular diseases, obesity, liver diseases, diabetes, and metabolic syndrome, where endotoxemia has been recognized as a risk factor. The main source of endotoxemia is thought to be the gut microbiota. However, the oral dysbiosis in periodontitis, which is typically enriched with gram-negative bacterial species, may also contribute to endotoxemia. As endotoxemia is associated with an increased risk of cardiometabolic disorders, lipopolysaccharide could be considered as a molecular link between periodontal microbiota and cardiometabolic diseases.

Characterization of the LPS and 3OHFA Contents in the Lipoprotein Fractions and Lipoprotein Particles of Healthy Men

Atherosclerosis is a chronic inflammatory disease that is caused by the accumulation of LDL particles in the intima, causing the activation of immune cells and triggering an inflammatory response. LPS is a potent activator of the innate immune response and it can be transported by lipoproteins. Since humans are much more sensitive to LPS than other mammals, and very low amounts of LPS can elicit an immune response, the aim of this study is to characterize the distribution of LPS and its immunogenic portion (3OHFAs) among lipoprotein types of healthy men. We separated lipoprotein fractions by ultracentrifugation and the amount of each 3OHFA was measured by MS in each lipoprotein fraction to calculate LPS concentration. Lipoprotein particle concentration was measured by NMR. LDL and HDL fractions transported the highest concentration of LPS (35.7% and 31.5%, respectively), but VLDL particles carried more LPS molecules per particle (0.55 molecules/particle) than LDL or HDL (p < 0.01). The distribution of LPS and all 3OHFAs among lipoprotein fractions showed high interindividual variability, suggesting that they may be studied as a potential biomarker. This may help understand the role of LPS in atherosclerosis in those cases where the disease cannot be explained by traditional risk factors.

Regulation of blood-brain barrier integrity by microbiome-associated methylamines and cognition by trimethylamine N-oxide

BACKGROUND

Communication between the gut microbiota and the brain is primarily mediated via soluble microbe-derived metabolites, but the details of this pathway remain poorly defined. Methylamines produced by microbial metabolism of dietary choline and L-carnitine have received attention due to their proposed association with vascular disease, but their effects upon the cerebrovascular circulation have hitherto not been studied.

RESULTS

Here, we use an integrated in vitro/in vivo approach to show that physiologically relevant concentrations of the dietary methylamine trimethylamine N-oxide (TMAO) enhanced blood-brain barrier (BBB) integrity and protected it from inflammatory insult, acting through the tight junction regulator annexin A1. In contrast, the TMAO precursor trimethylamine (TMA) impaired BBB function and disrupted tight junction integrity. Moreover, we show that long-term exposure to TMAO protects murine cognitive function from inflammatory challenge, acting to limit astrocyte and microglial reactivity in a brain region-specific manner.

CONCLUSION

Our findings demonstrate the mechanisms through which microbiome-associated methylamines directly interact with the mammalian BBB, with consequences for cerebrovascular and cognitive function. Video abstract.

Endotoxin Mass Concentration in Plasma Is Associated With Mortality in a Multicentric Cohort of Peritonitis-Induced Shock

Objectives: To investigate the association of plasma LPS mass with mortality and inflammation in patients with peritonitis-induced septic shock (SS). Design: Longitudinal endotoxin and inflammatory parameters in a multicentric cohort of SS. Patients: Protocolized post-operative parameters of 187 SS patients collected at T1 (12 h max post-surgery) and T4 (24 h after T1). Intervention: Post-hoc analysis of ABDOMIX trial. Measurements and Results: Plasma concentration of LPS mass as determined by HPLC-MS/MS analysis of 3-hydroxymyristate, activity of phospholipid transfer protein (PLTP), lipids, lipoproteins, IL-6, and IL-10. Cohort was divided in low (LLPS) and high (HLPS) LPS levels. The predictive value for mortality was tested by multivariate analysis. HLPS and LLPS had similar SAPSII (58 [48.5; 67]) and SOFA (8 [6.5; 9]), but HLPS showed higher death and LPS to PLTP ratio (p < 0.01). LPS was stable in HLPS, but it increased in LLPS with a greater decrease in IL-6 (p < 0.01). Dead patients had a higher T1 LPS (p = 0.02), IL-6 (<0.01), IL-10 (=0.01), and day 3 SOFA score (p = 0.01) than survivors. In the group of SAPSII > median, the risk of death in HLPS (38%) was higher than in LLPS (24%; p < 0.01). The 28-day death was associated only with SAPSII (OR 1.06 [1.02; 1.09]) and HLPS (OR 2.47 [1; 6.11]) in the multivariate model. In HLPS group, high PLTP was associated with lower plasma levels of IL-6 (p = 0.02) and IL-10 (p = 0.05). Conclusions: Combination of high LPS mass concentration and high SAPS II is associated with elevated mortality in peritonitis-induced SS patients.

Genetic Profile of Endotoxemia Reveals an Association With Thromboembolism and Stroke

Background Translocation of lipopolysaccharide from gram-negative bacteria into the systemic circulation results in endotoxemia. In addition to acute infections, endotoxemia is detected in cardiometabolic disorders, such as cardiovascular diseases and obesity. Methods and Results We performed a genome-wide association study of serum lipopolysaccharide activity in 11 296 individuals from 6 different Finnish study cohorts. Endotoxemia was measured by limulus amebocyte lysate assay in the whole population and by 2 other techniques (Endolisa and high-performance liquid chromatography/tandem mass spectrometry) in subpopulations. The associations of the composed genetic risk score of endotoxemia and thrombosis-related clinical end points for 195 170 participants were analyzed in FinnGen. Lipopolysaccharide activity had a genome-wide significant association with 741 single-nucleotide polymorphisms in 5 independent loci, which were mainly located at genes affecting the contact activation of the coagulation cascade and lipoprotein metabolism and explained 1.5% to 9.2% of the variability in lipopolysaccharide activity levels. The closest genes included KNG1, KLKB1, F12, SLC34A1, YPEL4, CLP1, ZDHHC5, SERPING1, CBX5, and LIPC. The genetic risk score of endotoxemia was associated with deep vein thrombosis, pulmonary embolism, pulmonary heart disease, and venous thromboembolism. Conclusions The biological activity of lipopolysaccharide in the circulation (ie, endotoxemia) has a small but highly significant genetic component. Endotoxemia is associated with genetic variation in the contact activation pathway, vasoactivity, and lipoprotein metabolism, which play important roles in host defense, lipopolysaccharide neutralization, and thrombosis, and thereby thromboembolism and stroke.

Increased LPS levels coexist with systemic inflammation and result in monocyte activation in severe COVID-19 patients

Mucosal barrier alterations may play a role in the pathogenesis of several diseases, including COVID-19. In this study we evaluate the association between bacterial translocation markers and systemic inflammation at the earliest time-point after hospitalization and at the last 72 h of hospitalization in survivors and non-survivors COVID-19 patients. Sixty-six SARS-CoV-2 RT-PCR positive patients and nine non-COVID-19 pneumonia controls were admitted in this study. Blood samples were collected at hospital admission (T1) (Controls and COVID-19 patients) and 0-72 h before hospital discharge (T2, alive or dead) to analyze systemic cytokines and chemokines, lipopolysaccharide (LPS) concentrations and soluble CD14 (sCD14) levels. THP-1 human monocytic cell line was incubated with plasma from survivors and non-survivors COVID-19 patients and their phenotype, activation status, TLR4, and chemokine receptors were analyzed by flow cytometry. COVID-19 patients presented higher IL-6, IFN-γ, TNF-α, TGF-β1, CCL2/MCP-1, CCL4/MIP-1β, and CCL5/RANTES levels than controls. Moreover, LPS and sCD14 were higher at hospital admission in SARS-CoV-2-infected patients. Non-survivors COVID-19 patients had increased LPS levels concomitant with higher IL-6, TNF-α, CCL2/MCP-1, and CCL5/RANTES levels at T2. Increased expression of CD16 and CCR5 were identified in THP-1 cells incubated with the plasma of survivor patients obtained at T2. The incubation of THP-1 with T2 plasma of non-survivors COVID-19 leads to higher TLR4, CCR2, CCR5, CCR7, and CD69 expression. In conclusion, the coexistence of increased microbial translocation and hyperinflammation in patients with severe COVID-19 may lead to higher monocyte activation, which may be associated with worsening outcomes, such as death.

Increased Phospholipid Transfer Protein Activity Is Associated With Markers of Enhanced Lipopolysaccharide Clearance in Human During Cardiopulmonary Bypass

Introduction: Lipopolysaccharide (LPS) is a component of gram-negative bacteria, known for its ability to trigger inflammation. The main pathway of LPS clearance is the reverse lipopolysaccharide transport (RLT), with phospholipid transfer protein (PLTP) and lipoproteins playing central roles in this process in experimental animal models. To date, the relevance of this pathway has never been studied in humans. Cardiac surgery with cardiopulmonary bypass is known to favor LPS digestive translocation. Our objective was to determine whether pre-operative PLTP activity and triglyceride or cholesterol-rich lipoprotein concentrations were associated to LPS concentrations in patients undergoing cardiac surgery with cardiopulmonary bypass. Methods: A post-hoc analysis was conducted on plasma samples obtained from patients recruited in a randomized controlled trial.Total cholesterol, high density lipoprotein cholesterol (HDLc), low density lipoprotein cholesterol (LDLc), triglyceride and PLTP activity were measured before surgery. LPS concentration was measured by mass spectrometry before surgery, at the end of cardiopulmonary bypass and 24 h after admission to the intensive care unit. Results: High PLTP activity was associated with lower LPS concentration but not with inflammation nor post-operative complications. HDLc, LDLc and total cholesterol were not associated with LPS concentration but were lower in patients developing post-operative adverse events. HDLc was negatively associated with inflammation biomarkers (CRP, PCT). Triglyceride concentrations were positively correlated with LPS concentration, PCT and were higher in patients with post-operative complications. Conclusion: Our study supports the role of PLTP in LPS elimination and the relevance of RLT in human. PLTP activity, and not cholesterol rich lipoproteins pool size seemed to be the limiting factor for RLT. PLTP activity was not directly related to post-operative inflammation and adverse events, suggesting that LPS clearance is not the main driver of inflammation in our patients. However, HDLc was associated with lower inflammation and was associated with favorable outcomes, suggesting that HDL beneficial anti-inflammatory effects could be, at least in part independent of LPS clearance.

Deciphering Microbial Metal Toxicity Responses via Random Bar Code Transposon Site Sequencing and Activity-Based Metabolomics

To uncover metal toxicity targets and defense mechanisms of the facultative anaerobe Pantoea sp. strain MT58 (MT58), we used a multiomic strategy combining two global techniques, random bar code transposon site sequencing (RB-TnSeq) and activity-based metabolomics. MT58 is a metal-tolerant Oak Ridge Reservation (ORR) environmental isolate that was enriched in the presence of metals at concentrations measured in contaminated groundwater at an ORR nuclear waste site. The effects of three chemically different metals found at elevated concentrations in the ORR contaminated environment were investigated: the cation Al³⁺, the oxyanion CrO₄^2-, and the oxycation UO₂²⁺. Both global techniques were applied using all three metals under both aerobic and anaerobic conditions to elucidate metal interactions mediated through the activity of metabolites and key genes/proteins. These revealed that Al³⁺ binds intracellular arginine, CrO₄^2- enters the cell through sulfate transporters and oxidizes intracellular reduced thiols, and membrane-bound lipopolysaccharides protect the cell from UO₂²⁺ toxicity. In addition, the Tol outer membrane system contributed to the protection of cellular integrity from the toxic effects of all three metals. Likewise, we found evidence of regulation of lipid content in membranes under metal stress. Individually, RB-TnSeq and metabolomics are powerful tools to explore the impact various stresses have on biological systems. Here, we show that together they can be used synergistically to identify the molecular actors and mechanisms of these pertubations to an organism, furthering our understanding of how living systems interact with their environment. IMPORTANCE Studying microbial interactions with their environment can lead to a deeper understanding of biological molecular mechanisms. In this study, two global techniques, RB-TnSeq and activity metabolomics, were successfully used to probe the interactions between a metal-resistant microorganism, Pantoea sp. strain MT58, and metals contaminating a site where the organism can be located. A number of novel metal-microbe interactions were uncovered, including Al³⁺ toxicity targeting arginine synthesis, which could lead to a deeper understanding of the impact Al³⁺ contamination has on microbial communities as well as its impact on higher-level organisms, including plants for whom Al³⁺ contamination is an issue. Using multiomic approaches like the one described here is a way to further our understanding of microbial interactions and their impacts on the environment overall.

Mediterranean diet and prudent diet are both associated with low circulating esterified 3-hydroxy fatty acids, a proxy of LPS burden, among older adults

BACKGROUND

LPS-type endotoxins, naturally found in the gut microbiota, are recognized as triggers of inflammation and emerge as detrimental factors of healthy aging. Nutrition represents a promising strategy to reduce LPS burden, yet little is known about the relation of diet to circulating LPS concentrations.

OBJECTIVE

The aim was to evaluate the associations between food groups, dietary patterns, and circulating 3-hydroxy fatty acids (3-OH FAs), a proxy of LPS burden.

METHODS

In a cross-sectional study of 698 French older community-dwelling individuals, 3-OH FA concentrations were measured by LC-tandem MS. Dietary patterns were determined using food-frequency questionnaires. Adherence to a Mediterranean-type diet was computed according to the consumption of 8 food groups (fruits, vegetables, legumes, cereals, fish, olive oil, meat, and dairy products) and alcohol intake (range: 0, low adherence, to 18, high adherence). Three a posteriori dietary patterns were derived from factor analysis: complex carbohydrate (rich in rice, pasta, eggs, poultry, and potatoes), traditional (rich in alcohol, meat, processed meats-cold cuts, and legumes), and prudent (rich in vegetables and fruits and low in cookies) diets. Linear regression models were applied.

RESULTS

The frequency of consumption of each food group was not associated with 3-OH FA concentrations. Greater adherence to both the Mediterranean diet and the prudent diet were associated with lower circulating 3-OH FAs (β [95% CI] for each additional point of score: -0.12 [-0.22, -0.01] and -0.27 [-0.48, -0.07], respectively). In contrast, greater adherence to the traditional diet was associated with higher concentration of 3-OH FAs (β [95% CI] 0.22 [0.001, 0.46]). The adherence to the complex-carbohydrate diet was not associated with 3-OH FA concentrations.

CONCLUSIONS

Based on 2 complementary approaches, the identified plant-based dietary patterns were associated with lower 3-OH FA concentrations, and thus a lower LPS burden, which is considered a potent trigger of inflammatory response.

Endotoxin Removal in Septic Shock with the Alteco LPS Adsorber Was Safe But Showed no Benefit Compared to Placebo in the Double-Blind Randomized Controlled Trial-the Asset Study

PURPOSE

Lipopolysaccharides (LPS) are presumed to contribute to the inflammatory response in sepsis. We investigated if extracorporeal Alteco LPS Adsorber for LPS removal in early gram-negative septic shock was feasible and safe. Also, effects on endotoxin level, inflammatory response, and organ function were assessed.

METHODS

A pilot, double-blinded, randomized, Phase IIa, feasibility clinical investigation was undertaken in six Scandinavian intensive care units aiming to allocate 32 septic shock patients with abdominal or urogenital focus on LPS Adsorber therapy or a Sham Adsorber, therapy without active LPS binding. The study treatment was initiated within 12 h of inclusion and given for 6 h daily on first 2 days. LPS was measured in all patients.

RESULTS

The investigation was terminated after 527 days with eight patients included in the LPS Adsorber group and seven in the Sham group. Twenty-one adverse effects, judged not to be related to the device, were reported in three patients in the LPS Adsorber group and two in the Sham group. Two patients in the Sham group and no patients in the LPS Adsorber group died within 28 days. Plasma LPS levels were low without groups differences during or after adsorber therapy. The changes in inflammatory markers and organ function were similar in the groups.

CONCLUSIONS

In a small cohort of patients with presumed gram-negative septic shock, levels of circulating endotoxin were low and no adverse effects within 28 days after LPS adsorber-treatment were observed. No benefit compared with a sham device was seen when using a LPS adsorber in addition to standard care.

TRIAL REGISTRATION

Clinicaltrials.gov NCT02335723. Registered: November 28, 2014.

Intestinal Microbial-tissue Complex and Chronic Heart Failure (part 1): Pathogenesis

Antigenic and metabolic integration of the intestinal microbiota into the homeostasis of the human body is a factor that claims to play a key role in the pathogenesis of cardiovascular diseases. It acquires special significance against the background of the decrease in blood circulation and congestion in the digestive system during chronic heart failure. Aim of the review is analysis and synthesis of studies results on the role of intestinal microbiocenosis in the pathogenesis of heart remodeling and chronic heart failure. The search for articles was conducted in databases eLIBRARY.RU and Medline for the key terms "gut microbiota (microbiome, microbiocenosis)", "dysbiosis (dysbacteriosis)", "excessive bacterial growth syndrome", "lipopolysaccharide (endotoxin)", "trimethylamine-N-oxide" in combination with the terms "heart failure", "myocardial remodeling", "myocardium" in Russian and English, respectively. We selected articles containing the results of clinical and experimental studies published from 1995 to 2020. Review articles were considered only on the subject of the cited original publications. Most researchers have established the relationship between chronic heart failure and dysfunction and changes in the qualitative and quantitative composition of intestinal microbiocenosis. As negative changes, it is customary to note the proliferation of gram-negative opportunistic bacteria with concomitant endotoxinemia and a decrease in the pool of commensal microbiota. The available data suggest that the participation of the intestinal microbial-tissue complex in the pathogenesis of chronic heart failure and heart remodeling is realized through the activation of a local and then systemic inflammatory response, accompanied by cardiodepressive action of pro-inflammatory cytokines and universal proliferation factors, an imbalance of matrix metalloproteinases and their inhibitors, the initiation of apoptosis, fibrosis, and loss of contractile myocardium. Besides, a decrease in the production of short-chain and polyunsaturated fatty acids and vitamins by the commensal microbiota may be associated with changes in the electrical properties of cardiomyocyte membranes, a decrease in the systolic function of the left ventricle of the heart, and an increase in the risk of sudden cardiac death. It's also shown that the direct cardiotoxic effect of microbial molecules (lipopolysaccharides, peptidoglycans, trimethylamine-N-oxide, etc.), which interact with the receptors of cardiomyocytes and microenvironment cells, can cause the development of myocardial remodeling and its dysfunction. Recent studies have established mechanisms of myocardial remodeling mediated by microbial molecules, which may be associated with new strategies for the treatment and prevention of heart failure.

Endotoxin contamination of engineered nanomaterials: Overcoming the hurdles associated with endotoxin testing

Nanomaterials are highly susceptible to endotoxin contamination due their large surface-to-volume ratios and endotoxins propensity to associate readily to hydrophobic and cationic surfaces. Additionally, the stability of endotoxin ensures it cannot be removed efficiently through conventional sterilization techniques such as autoclaving and ionizing radiation. In recent times, the true significance of this hurdle has come to light with multiple reports from the United States Nanotechnology Characterization Laboratory, in particular, along with our own experiences of endotoxin testing from multiple Horizon 2020-funded projects which highlight the importance of this issue for the clinical translation of nanomaterials. Herein, we provide an overview on the topic of endotoxin contamination of nanomaterials intended for biomedical applications. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Toxicology and Regulatory Issues in Nanomedicine > Regulatory and Policy Issues in Nanomedicine.

New Insights on End-Stage Renal Disease and Healthy Individual Gut Bacterial Translocation: Different Carbon Composition of Lipopolysaccharides and Different Impact on Monocyte Inflammatory Response

Chronic kidney disease induces disruption of the intestinal epithelial barrier, leading to gut bacterial translocation. Here, we appreciated bacterial translocation by analyzing circulating lipopolysaccharides (LPS) using two methods, one measuring only active free LPS, and the other quantifying total LPS as well as LPS lipid A carbon chain length. This was done in end-stage renal disease (ESRD) patients and healthy volunteers (HV). We observed both higher LPS concentration in healthy volunteers and significant differences in composition of translocated LPS based on lipid A carbon chain length. Lower LPS activity to mass ratio and higher concentration of high-density lipoproteins were found in HV, suggesting a better plasma capacity to neutralize LPS activity. Higher serum concentrations of soluble CD14 and pro-inflammatory cytokines in ESRD patients confirmed this hypothesis. To further explore whether chronic inflammation in ESRD patients could be more related to LPS composition rather than its quantity, we tested the effect of HV and patient sera on cytokine secretion in monocyte cultures. Sera with predominance of 14-carbon chain lipid A-LPS induced higher secretion of pro-inflammatory cytokines than those with predominance of 18-carbon chain lipid A-LPS. TLR4 or LPS antagonists decreased LPS-induced cytokine production by monocytes, demonstrating an LPS-specific effect. Thereby, septic inflammation observed in ESRD patients may be not related to higher bacterial translocation, but to reduced LPS neutralization capacity and differences in translocated LPS subtypes.

Intra-Abdominal Lipopolysaccharide Clearance and Inactivation in Peritonitis: Key Roles for Lipoproteins and the Phospholipid Transfer Protein

Introduction

During peritonitis, lipopolysaccharides (LPS) cross the peritoneum and pass through the liver before reaching the central compartment. The aim of the present study was to investigate the role of lipoproteins and phospholipid transfer protein (PLTP) in the early stages of LPS detoxification.

Material and Methods

Peritonitis was induced by intra-peritoneal injection of LPS in mice. We analyzed peritoneal fluid, portal and central blood. Lipoprotein fractions were obtained by ultracentrifugation and fast protein liquid chromatography. LPS concentration and activity were measured by liquid chromatography coupled with mass spectrometry and limulus amoebocyte lysate. Wild-type mice were compared to mice knocked out for PLTP.

Results

In mice expressing PLTP, LPS was able to bind to HDL in the peritoneal compartment, and this was maintained in plasma from portal and central blood. A hepatic first-pass effect of HDL-bound LPS was observed in wild-type mice. LPS binding to HDL resulted in an early arrival of inactive LPS in the central blood of wild-type mice.

Conclusion

PLTP promotes LPS peritoneal clearance and neutralization in a model of peritonitis. This mechanism involves the early binding of LPS to lipoproteins inside the peritoneal cavity, which promotes LPS translocation through the peritoneum and its uptake by the liver.

Lactobacillus stress protein GroEL prevents colonic inflammation

BACKGROUND

We previously showed that supernatants of Lactobacillus biofilms induced an anti-inflammatory response by affecting the secretion of macrophage-derived cytokines, which was abrogated upon immunodepletion of the stress protein GroEL.

METHODS

We purified GroEL from L. reuteri and analysed its anti-inflammatory properties in vitro in human macrophages isolated from buffy coats, ex vivo in explants from human biopsies and in vivo in a mouse model of DSS induced intestinal inflammation. As a control, we used GroEL purified (LPS-free) from E. coli.

RESULTS

We found that L. reuteri GroEL (but not E. coli GroEL) inhibited pro-inflammatory M1-like macrophages markers, and favored M2-like markers. Consequently, L. reuteri GroEL inhibited pro-inflammatory cytokines (TNFα, IL-1β, IFNγ) while favouring an anti-inflammatory secretome. In colon tissues from human biopsies, L. reuteri GroEL was also able to decrease markers of inflammation and apoptosis (caspase 3) induced by LPS. In mice, we found that rectal administration of L. reuteri GroEL (but not E. coli GroEL) inhibited all signs of haemorrhagic colitis induced by DSS including intestinal mucosa degradation, rectal bleeding and weight loss. It also decreased intestinal production of inflammatory cytokines (such as IFNγ) while increasing anti-inflammatory IL-10 and IL-13. These effects were suppressed when animals were immunodepleted in macrophages. From a mechanistic point of view, the effect of L. reuteri GroEL seemed to involve TLR4, since it was lost in TRL4-/- mice, and the activation of a non-canonical TLR4 pathway.

CONCLUSIONS

L. reuteri GroEL, by affecting macrophage inflammatory features, deserves to be explored as an alternative to probiotics.

The Tryptophan/Kynurenine Pathway: A Novel Cross-Talk between Nutritional Obesity, Bariatric Surgery and Taste of Fat

Diet-induced obesity (DIO) reduces the orosensory perception of lipids in rodents and in some humans. Although bariatric surgery partially corrects this alteration, underlying mechanisms remain poorly understood. To explore whether metabolic changes might explain this fat taste disturbance, plasma metabolome analyses, two-bottle choice tests and fungiform papillae (Fun) counting were performed in vertical sleeve gastrectomized (VSG) mice and sham-operated controls. An exploratory clinic study was also carried out in adult patients undergone a VSG. In mice, we found that (i) the VSG reduces both the plasma neurotoxic signature due to the tryptophan/kynurenine (Trp/Kyn) pathway overactivation and the failure of fat preference found in sham-operated DIO mice, (ii) the activity of Trp/Kyn pathway is negatively correlated to the density of Fun, and (iii) the pharmacological inhibition of the Kyn synthesis mimics in non-operated DIO mice the positive effects of VSG (i.e., decrease of Kyn synthesis, increase of Fun number, improvement of the fat taste perception). In humans, a reduction of the plasma Kyn level is only found in patients displaying a post-surgery improvement of their fat taste sensitivity. Altogether these data provide a plausible metabolic explanation to the degradation of the orosensory lipid perception observed in obesity.