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.

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 (Apoa1tm1Unc ) 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.

New therapeutic horizons for plasma phospholipid transfer protein (PLTP): Targeting endotoxemia, infection and sepsis.

Phospholipid Transfer Protein (PLTP) transfers amphiphilic lipids between circulating lipoproteins and between lipoproteins, cells and tissues. Indeed, PLTP is a major determinant of the plasma levels, turnover and functionality of the main lipoprotein classes: very low-density lipoproteins (VLDL), low-density lipoproteins (LDL) and high-density lipoproteins (HDL). To date, most attention has been focused on the role of PLTP in the context of cardiometabolic diseases, with additional insights in neurodegenerative diseases and immunity. Importantly, beyond its influence on plasma triglyceride and cholesterol transport, PLTP plays a key role in the modulation of the immune response, with immediate relevance to a wide range of inflammatory diseases including bacterial infection and sepsis. Indeed, emerging evidence supports the role of PLTP, in the context of its association with lipoproteins, in the neutralization and clearance of bacterial lipopolysaccharides (LPS) or endotoxins. LPS are amphipathic molecules originating from Gram-negative bacteria which harbor major pathogen-associated patterns, triggering an innate immune response in the host. Although the early inflammatory reaction constitutes a key step in the anti-microbial defense of the organism, it can lead to a dysregulated inflammatory response and to hemodynamic disorders, organ failure and eventually death. Moreover, and in addition to endotoxemia and acute inflammation, small amounts of LPS in the circulation can induce chronic, low-grade inflammation with long-term consequences in several metabolic disorders such as atherosclerosis, obesity and diabetes. After an updated overview of the role of PLTP in lipid transfer, lipoprotein metabolism and related diseases, current knowledge of its impact on inflammation, infection and sepsis is critically appraised. Finally, the relevance of PLTP as a new player and novel therapeutic target in the fight against inflammatory diseases is considered.

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.

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.

High plasma concentration of non-esterified polyunsaturated fatty acids is a specific feature of severe COVID-19 pneumonia.

COVID-19 pneumonia has specific features and outcomes that suggests a unique immunopathogenesis. Severe forms of COVID-19 appear to be more frequent in obese patients, but an association with metabolic disorders is not established. Here, we focused on lipoprotein metabolism in patients hospitalized for severe pneumonia, depending on COVID-19 status. Thirty-four non-COVID-19 and 27 COVID-19 patients with severe pneumonia were enrolled. Most of them required intensive care. Plasma lipid levels, lipoprotein metabolism, and clinical and biological (including plasma cytokines) features were assessed. Despite similar initial metabolic comorbidities and respiratory severity, COVID-19 patients displayed a lower acute phase response but higher plasmatic concentrations of non-esterified fatty acids (NEFAs). NEFA profiling was characterised by higher level of polyunsaturated NEFAs (mainly linoleic and arachidonic acids) in COVID-19 patients. Multivariable analysis showed that among severe pneumonia, COVID-19-associated pneumonia was associated with higher NEFAs, lower apolipoprotein E and lower high-density lipoprotein cholesterol concentrations, independently of body mass index, sequential organ failure (SOFA) score, and C-reactive protein levels. NEFAs and PUFAs concentrations were negatively correlated with the number of ventilator-free days. Among hospitalized patients with severe pneumonia, COVID-19 is independently associated with higher NEFAs (mainly linoleic and arachidonic acids) and lower apolipoprotein E and HDL concentrations. These features might act as mediators in COVID-19 pathogenesis and emerge as new therapeutic targets. Further investigations are required to define the role of NEFAs in the pathogenesis and the dysregulated immune response associated with COVID-19.Trial registration: NCT04435223.

Human apolipoprotein C1 transgenesis reduces atherogenesis in hypercholesterolemic rabbits.

BACKGROUND AND AIMS: Apolipoprotein (apo) C1 is a 6.6 kDa protein associated with HDL and VLDL. ApoC1 alters triglyceride clearance, and it also favors cholesterol accumulation in HDL, especially by inhibiting CETP in human plasma. Apart from studies in mice, which lack CETP, the impact of apoC1 on atherosclerosis in animal models expressing CETP, like in humans, is not known. This study aimed at determining the net effect of human apoC1 on atherosclerosis in rabbits, a species with naturally high CETP activity but with endogenous apoC1 without CETP inhibitory potential. METHODS: Rabbits expressing a human apoC1 transgene (HuApoC1Tg) were generated and displayed significant amounts of human apoC1 in plasma. RESULTS: After cholesterol feeding, atherosclerosis lesions were significantly less extensive (-22%, p < 0.05) and HDL displayed a reduced ability to serve as CETP substrates (-25%, p < 0.05) in HuApoC1Tg rabbits than in WT littermates. It was associated with rises in plasma HDL cholesterol level and PON-1 activity, and a decrease in the plasma level of the lipid oxidation markers 12(S)-HODE and 8(S)HETE. In chow-fed animals, the level of HDL-cholesterol was also significantly higher in HuApoC1Tg than in WT animals (0.83 ± 0.11 versus 0.73 ± 0.11 mmol/L, respectively, p < 0.05), and it was associated with significantly lower CETP activity (cholesteryl ester transfer rate, -10%, p < 0.05; specific CETP activity, -14%, p < 0.05). CONCLUSIONS: Constitutive expression of fully functional human apoC1 in transgenic rabbit attenuates atherosclerosis. It was found to relate, at least in part, to the inhibition of plasma CETP activity and to alterations in plasma HDL.

Human cholesteryl ester transfer protein lacks lipopolysaccharide transfer activity, but worsens inflammation and sepsis outcomes in mice.

Bacterial lipopolysaccharides (LPSs or endotoxins) can bind most proteins of the lipid transfer/LPS-binding protein (LT/LBP) family in host organisms. The LPS-bound LT/LBP proteins then trigger either an LPS-induced proinflammatory cascade or LPS binding to lipoproteins that are involved in endotoxin inactivation and detoxification. Cholesteryl ester transfer protein (CETP) is an LT/LBP member, but its impact on LPS metabolism and sepsis outcome is unclear. Here, we performed fluorescent LPS transfer assays to assess the ability of CETP to bind and transfer LPS. The effects of intravenous (iv) infusion of purified LPS or polymicrobial infection (cecal ligation and puncture [CLP]) were compared in transgenic mice expressing human CETP and wild-type mice naturally having no CETP activity. CETP displayed no LPS transfer activity in vitro, but it tended to reduce biliary excretion of LPS in vivo. The CETP expression in mice was associated with significantly lower basal plasma lipid levels and with higher mortality rates in both models of endotoxemia and sepsis. Furthermore, CETPTg plasma modified cytokine production of macrophages in vitro. In conclusion, despite having no direct LPS binding and transfer property, human CETP worsens sepsis outcomes in mice by altering the protective effects of plasma lipoproteins against endotoxemia, inflammation, and infection.

Inhibition of mitophagy drives macrophage activation and antibacterial defense during sepsis.

Mitochondria have emerged as key actors of innate and adaptive immunity. Mitophagy has a pivotal role in cell homeostasis, but its contribution to macrophage functions and host defense remains to be delineated. Here, we showed that lipopolysaccharide (LPS) in combination with IFN-γ inhibited PINK1-dependent mitophagy in macrophages through a STAT1-dependent activation of the inflammatory caspases 1 and 11. In addition, we demonstrated that the inhibition of mitophagy triggered classical macrophage activation in a mitochondrial ROS-dependent manner. In a murine model of polymicrobial infection (cecal ligature and puncture), adoptive transfer of Pink1-deficient bone marrow or pharmacological inhibition of mitophagy promoted macrophage activation, which favored bactericidal clearance and led to a better survival rate. Reciprocally, mitochondrial uncouplers that promote mitophagy reversed LPS/IFN-γ-mediated activation of macrophages and led to immunoparalysis with impaired bacterial clearance and lowered survival. In critically ill patients, we showed that mitophagy was inhibited in blood monocytes of patients with sepsis as compared with nonseptic patients. Overall, this work demonstrates that the inhibition of mitophagy is a physiological mechanism that contributes to the activation of myeloid cells and improves the outcome of sepsis.

The deficit in folate and vitamin B12 triggers liver macrovesicular steatosis and inflammation in rats with dextran sodium sulfate-induced colitis.

The risks of nonalcoholic steatohepatitis (NASH) and deficiency in vitamin B12 and folate (methyl donor deficiency, MDD) are increased in inflammatory bowel disease (IBD). We investigated the influence of MDD on NASH in rats with DSS-induced colitis. Two-month-old male Wistar rats were subjected to MDD diet and/or ingestion of DSS and compared to control animals. We studied steatosis, inflammation, fibrosis, plasma levels of metabolic markers, cytokines and lipopolysaccharide, and inflammatory pathways in liver. MDD triggered a severe macrovesicular steatosis with inflammation in DSS animals that was not observed in animals subjected to DSS or MDD only. The macrovesicular steatosis was closely correlated to folate, vitamin B12, homocysteine plasma level and liver S-adenosyl methionine/S-adenosyl homocysteine (SAM/SAH) ratio. Liver inflammation was evidenced by activation of nuclear factor kappa B (NFκB) pathway and nuclear translocation of NFκB phospho-p65. MDD worsened the increase of interleukin 1-beta (IL-1ß) and abolished the increase of IL10 produced by DSS colitis. It increased monocyte chemoattractant protein 1 (MCP-1). MDD triggers liver macrovesicular steatosis and inflammation through imbalanced expression of IL-1ß vs. IL10 and increase of MCP-1 in DSS colitis. Our results suggest evaluating whether IBD patients with MDD and increase of MCP-1 are at higher risk of NASH.

End-Stage Renal Disease-Associated Gut Bacterial Translocation: Evolution and Impact on Chronic Inflammation and Acute Rejection After Renal Transplantation.

Chronic inflammation in end-stage renal disease (ESRD) is partly attributed to gut bacterial translocation (GBT) due to loss of intestinal epithelium integrity. Increased levels of circulating lipopolysaccharide (LPS) -a surrogate marker of GBT- contribute to maintain a chronic inflammatory state. However, circulating LPS can be neutralized by lipoproteins and transported to the liver for elimination. While ESRD-associated GBT has been widely described, less is known about its changes and impact on clinical outcome after kidney transplantation (KT). One hundred and forty-six renal transplant recipients with serum samples obtained immediately before and 1 year after transplantation (1-Year post KT) were included. Intestinal epithelium integrity (iFABP), total LPS (by measuring 3-hydroxymyristate), LPS activity (biologically active LPS measured by the LAL assay), inflammatory biomarkers (sCD14 and cytokines), lipoproteins and LPS-binding proteins (LBP and phospholipid transfer protein [PLTP] activity) were simultaneously measured. At 1-Year post KT, iFABP decreased but remained higher than in normal volunteers. Total LPS concentration remained stable while LPS activity decreased. Inflammation biomarkers decreased 1-Year post KT. We concomitantly observed an increase in lipoproteins. Higher sCD14 levels before transplantation was associated with lower incidence of acute rejection. Although GBT remained stable after KT, the contemporary increase in lipoproteins could bind circulating LPS and contribute concomitantly to neutralization of LPS activity, as well as improvement in ESRD-associated chronic inflammation. Chronic exposure to LPS in ESRD could promote endotoxin tolerance and explain why patients with higher pre-transplant sCD14 are less prompt to develop acute rejection after transplantation.

Polysaccharide Chain Length of Lipopolysaccharides From Salmonella Minnesota Is a Determinant of Aggregate Stability, Plasma Residence Time and Proinflammatory Propensity in vivo.

Lipopolysaccharides (LPS) originate from the outer membrane of Gram-negative bacteria and trigger an inflammatory response via the innate immune system. LPS consist of a lipid A moiety directly responsible for the stimulation of the proinflammatory cascade and a polysaccharide chain of variable length. LPS form aggregates of variable size and structure in aqueous media, and the aggregation/disaggregation propensity of LPS is known as a key determinant of their biological activity. The aim of the present study was to determine to which extent the length of the polysaccharide chain can affect the nature of LPS structures, their pharmacokinetics, and eventually their proinflammatory properties in vivo. LPS variants of Salmonella Minnesota with identical lipid A but with different polysaccharide moieties were used. The physical properties of LPS aggregates were analyzed by zetametry, dynamic light scattering, and microscopy. The stability of LPS aggregates was tested in the presence of plasma, whole blood, and cultured cell lines. LPS pharmacokinetics was performed in wild-type mice. The accumulation in plasma of rough LPS (R-LPS) with a short polysaccharidic chain was lower, and its hepatic uptake was faster as compared to smooth LPS (S-LPS) with a long polysaccharidic chain. The inflammatory response was weaker with R-LPS than with S-LPS. As compared to S-LPS, R-LPS formed larger aggregates, with a higher hydrophobicity index, a more negative zeta potential, and a higher critical aggregation concentration. The lower stability of R-LPS aggregates could be illustrated in vitro by a higher extent of association of LPS to plasma lipoproteins, faster binding to blood cells, and increased uptake by macrophages and hepatocytes, compared to S-LPS. Our data indicate that a long polysaccharide chain is associated with the formation of more stable aggregates with extended residence time in plasma and higher inflammatory potential. These results show that polysaccharide chain length, and overall aggregability of LPS might be helpful to predict the proinflammatory effect that can be expected in experimental settings using LPS preparations. In addition, better knowledge and control of LPS aggregation and disaggregation might lead to new strategies to enhance LPS detoxification in septic patients.

Healthy adiposity and extended lifespan in obese mice fed a diet supplemented with a polyphenol-rich plant extract.

Obesity may not be consistently associated with metabolic disorders and mortality later in life, prompting exploration of the challenging concept of healthy obesity. Here, the consumption of a high-fat/high-sucrose (HF/HS) diet produces hyperglycaemia and hypercholesterolaemia, increases oxidative stress, increases endotoxaemia, expands adipose tissue (with enlarged adipocytes, enhanced macrophage infiltration and the accumulation of cholesterol and oxysterols), and reduces the median lifespan of obese mice. Despite the persistence of obesity, supplementation with a polyphenol-rich plant extract (PRPE) improves plasma lipid levels and endotoxaemia, prevents macrophage recruitment to adipose tissues, reduces adipose accumulation of cholesterol and cholesterol oxides, and extends the median lifespan. PRPE drives the normalization of the HF/HS-mediated functional enrichment of genes associated with immunity and inflammation (in particular the response to lipopolysaccharides). The long-term limitation of immune cell infiltration in adipose tissue by PRPE increases the lifespan through a mechanism independent of body weight and fat storage and constitutes the hallmark of a healthy adiposity trait.

Deletion of plasma Phospholipid Transfer Protein (PLTP) increases microglial phagocytosis and reduces cerebral amyloid-ß deposition in the J20 mouse model of Alzheimer's disease.

Plasma phospholipid transfer protein (PLTP) binds and transfers a number of amphipathic compounds, including phospholipids, cholesterol, diacylglycerides, tocopherols and lipopolysaccharides. PLTP functions are relevant for many pathophysiological alterations involved in neurodegenerative disorders (especially lipid metabolism, redox status, and immune reactions), and a significant increase in brain PLTP levels was observed in patients with Alzheimer's disease (AD) compared to controls. To date, it has not been reported whether PLTP can modulate the formation of amyloid plaques, i.e. one of the major histopathological hallmarks of AD. We thus assessed the role of PLTP in the AD context by breeding PLTP-deficient mice with an established model of AD, the J20 mice. A phenotypic characterization of the amyloid pathology was conducted in J20 mice expressing or not PLTP. We showed that PLTP deletion is associated with a significant reduction of cerebral Aß deposits and astrogliosis, which can be explained at least in part by a rise of Aß clearance through an increase in the microglial phagocytic activity and the expression of the Aß-degrading enzyme neprilysin. PLTP arises as a negative determinant of plaque clearance and over the lifespan, elevated PLTP activity could lead to a higher Aß load in the brain.

PhosphoLipid transfer protein (PLTP) exerts a direct pro-inflammatory effect on rheumatoid arthritis (RA) fibroblasts-like-synoviocytes (FLS) independently of its lipid transfer activity.

Rheumatoid arthritis (RA) is a chronic inflammatory rheumatic disease with modification of lipids profile and an increased risk of cardiovascular events related to inflammation. Plasma phospholipid transfer protein (PLTP) exerts a lipid transfer activity through its active form. PLTP can also bind to receptors such as ATP-binding cassette transporter A1 (ABCA1). In addition to its role in lipoprotein metabolism and atherosclerosis, the latest advances came in support of a complex role of PLTP in the regulation of the inflammatory response, both with pro-inflammatory or anti-inflammatory properties. The aim of the present study was to decipher the role of PLTP in joint inflammation and to assess its relevance in the context of RA. PLTP expression was examined by western-blot and by immunochemistry. ABCA1 expression was analyzed by flow cytometry. Lipid transfer activity of PLTP and pro-inflammatory cytokines were measured in sera and synovial fluid (SF) from RA patients and controls (healthy subjects or osteoarthritis patients [OA]). FLS were treated with both lipid-transfer active form and inactive form of recombinant human PLTP. IL-8, IL-6, VEGF and MMP3 produced by FLS were assessed by ELISA, and proliferation by measuring 3H-Thymidine incorporation. RA synovial tissues showed higher PLTP staining than OA and PLTP protein levels were also significantly higher in RA-FLS. In addition, RA, unlike OA patients, displayed elevated levels of PLTP activity in SF, which correlated with pro-inflammatory cytokines. Both lipid-transfer active and inactive forms of PLTP significantly increased the production of cytokines and proliferation of FLS. ABCA1 was expressed on RAFLS and PLTP activated STAT3 pathway. To conclude, PLTP is highly expressed in the joints of RA patients and may directly trigger inflammation and FLS proliferation, independently of its lipid transfer activity. These results suggest a pro-inflammatory role for PLTP in RA.

Enteroendocrine L Cells Sense LPS after Gut Barrier Injury to Enhance GLP-1 Secretion.

Glucagon-like peptide 1 (GLP-1) is a hormone released from enteroendocrine L cells. Although first described as a glucoregulatory incretin hormone, GLP-1 also suppresses inflammation and promotes mucosal integrity. Here, we demonstrate that plasma GLP-1 levels are rapidly increased by lipopolysaccharide (LPS) administration in mice via a Toll-like receptor 4 (TLR4)-dependent mechanism. Experimental manipulation of gut barrier integrity after dextran sodium sulfate treatment, or via ischemia/reperfusion experiments in mice, triggered a rapid rise in circulating GLP-1. This phenomenon was detected prior to measurable changes in inflammatory status and plasma cytokine and LPS levels. In human subjects, LPS administration also induced GLP-1 secretion. Furthermore, GLP-1 levels were rapidly increased following the induction of ischemia in the human intestine. These findings expand traditional concepts of enteroendocrine L cell biology to encompass the sensing of inflammatory stimuli and compromised mucosal integrity, linking glucagon-like peptide secretion to gut inflammation.

Recombinant human plasma phospholipid transfer protein (PLTP) to prevent bacterial growth and to treat sepsis.

Although plasma phospholipid transfer protein (PLTP) has been mainly studied in the context of atherosclerosis, it shares homology with proteins involved in innate immunity. Here, we produced active recombinant human PLTP (rhPLTP) in the milk of new lines of transgenic rabbits. We successfully used rhPLTP as an exogenous therapeutic protein to treat endotoxemia and sepsis. In mouse models with injections of purified lipopolysaccharides or with polymicrobial infection, we demonstrated that rhPLTP prevented bacterial growth and detoxified LPS. In further support of the antimicrobial effect of PLTP, PLTP-knocked out mice were found to be less able than wild-type mice to fight against sepsis. To our knowledge, the production of rhPLTP to counter infection and to reduce endotoxemia and its harmful consequences is reported here for the first time. This paves the way for a novel strategy to satisfy long-felt, but unmet needs to prevent and treat sepsis.

Brain Control of Plasma Cholesterol Involves Polysialic Acid Molecules in the Hypothalamus.

The polysialic acid (PSA) is a large glycan that is added to cell-surface proteins during their post-translational maturation. In the brain, PSA modulates distances between cells and controls the plasticity of the nervous system. In the hypothalamus, PSA is involved in many aspects of energy balance including food intake, osmoregulation, circadian rhythm, and sleep. In this work, we investigated the role of hypothalamic PSA in the regulation of plasma cholesterol levels and distribution. We report that HFD consumption in mice rapidly increased plasma cholesterol, including VLDL, LDL, and HDL-cholesterol. Although plasma VLDL-cholesterol was normalized within the first week, LDL and HDL were still elevated after 2 weeks upon HFD. Importantly, we found that hypothalamic PSA removal aggravated LDL elevation and reduced HDL levels upon HFD. These results indicate that hypothalamic PSA controls plasma lipoprotein profile by circumventing the rise of LDL-to-HDL cholesterol ratio in plasma during overfeeding. Although mechanisms by which hypothalamic PSA controls plasma cholesterol homeostasis remains to be elucidated, these findings also suggest that low level of hypothalamic PSA might be a risk factor for dyslipidemia and cardiovascular diseases.

Plasma phospholipid transfer protein (PLTP) modulates adaptive immune functions through alternation of T helper cell polarization.

OBJECTIVE: Plasma phospholipid transfer protein (PLTP) is a key determinant of lipoprotein metabolism, and both animal and human studies converge to indicate that PLTP promotes atherogenesis and its thromboembolic complications. Moreover, it has recently been reported that PLTP modulates inflammation and immune responses. Although earlier studies from our group demonstrated that PLTP can modify macrophage activation, the implication of PLTP in the modulation of T-cell-mediated immune responses has never been investigated and was therefore addressed in the present study. Approach and results: In the present study, we demonstrated that PLTP deficiency in mice has a profound effect on CD4+ Th0 cell polarization, with a shift towards the anti-inflammatory Th2 phenotype under both normal and pathological conditions. In a model of contact hypersensitivity, a significantly impaired response to skin sensitization with the hapten-2,4-dinitrofluorobenzene (DNFB) was observed in PLTP-deficient mice compared to wild-type (WT) mice. Interestingly, PLTP deficiency in mice exerted no effect on the counts of total white blood cells, lymphocytes, granulocytes, or monocytes in the peripheral blood. Moreover, PLTP deficiency did not modify the amounts of CD4+ and CD8+ T lymphocyte subsets. However, PLTP-deficiency, associated with upregulation of the Th2 phenotype, was accompanied by a significant decrease in the production of the pro-Th1 cytokine interleukin 18 by accessory cells. CONCLUSIONS: For the first time, this work reports a physiological role for PLTP in the polarization of CD4+ T cells toward the pro-inflammatory Th1 phenotype.