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.

Lipid intensive drug therapy for sepsis pilot: A Bayesian phase I clinical trial

OBJECTIVES

Cholesterol may be protective in sepsis. Patients with early sepsis may have critically low cholesterol levels that are associated with poor outcomes. The study objective was to test the safety of a fish oil-containing lipid injectable emulsion for stabilizing early cholesterol levels in sepsis.

METHODS

Phase I Bayesian optimal interval design trial of adult patients with septic shock (Sequential Organ Failure Assessment score ≥4 or vasopressor dependence). Using sequential dose escalation, participants received 2 doses of 1.0 to 1.6 g/kg of lipid emulsion (Smoflipid 20% lipid emulsion) within 48 hours of enrollment. Cholesterol levels, function, and organ failure were assessed serially during the first 7 days of hospital admission.

MEASUREMENTS AND MAIN RESULTS

A total of 10 patients with septic shock were enrolled. One patient withdrew for social reasons. Another patient had an unrelated medical complication and received 1 drug dose. Of 9 patients, mean age was 58 years (SD 16), median Sequential Organ Failure Assessment was 8, and 28-day mortality was 30%. No serious adverse events related to lipid infusion occurred. The six occurrences of non-serious adverse events possibly related to lipid infusion included hyperglycemia (1), elevated triglycerides (3), anemia (1), and vascular access redness/pain (1) for all doses. The mean change in total cholesterol levels from enrollment was -7 (SD 16.6) at 48 hours and 14 (SD 25.2) at 7 days.

CONCLUSIONS

Fish oil-containing lipid emulsion administration during early septic shock was safe. Further studies are needed to assess effects on cholesterol levels, function, and organ failure.

CLINICAL TRIAL REGISTRATION

NCT03405870.

Period prevalence and mortality rates associated with hypocholesterolaemia in dogs and cats: 1,375 cases

To determine the period prevalence of hypocholesterolaemia and the associated mortality rates in dogs and cats at a university teaching hospital. The secondary aim was to identify disease processes associated with hypocholesterolaemia.

MATERIALS AND METHODS

Medical records over a 5-year period were reviewed to determine the severity of hypocholesterolaemia and its associated mortality rate. Medical records of animals with moderate to severe hypocholesterolaemia (<2.59 mmol/L in dogs, <1.81 mmol/L in cats) were analysed further. Animals with hospital-acquired hypocholesterolaemia were identified.

RESULTS

Among 16,977 dogs and 3,788 cats that had at least one cholesterol measurement, the period prevalence of hypocholesterolaemia was 7.0% in dogs and 4.7% in cats. The mortality rate of hypocholesteraemic dogs and cats was 12% in both species which was significantly higher than that of animals with normal serum cholesterol. The degree of hypocholesterolaemia was significantly associated with mortality. Dogs, but not cats, with hospital-acquired hypocholesterolaemia had a higher mortality rate than those presenting with hypocholesterolaemia. Disease of hepatic, gastrointestinal and lymphoreticular systems were most commonly associated with hypocholesterolaemia, and infectious and neoplastic disease were the most commonly associated pathophysiologic processes in both species. Lymphoma was over-represented in dogs with neoplasia.

CLINICAL SIGNIFICANCE

Hypocholesterolaemia is not a frequent abnormality but was associated with mortality in this study and may be a negative prognostic indicator. It is not known if hypocholesterolaemia is simply a marker for disease severity, or if it is has active physiologic effects contributing to poor outcomes.

Classical Activation of Macrophages Leads to Lipid Droplet Formation Without de novo Fatty Acid Synthesis

Altered lipid metabolism in macrophages is associated with various important inflammatory conditions. Although lipid metabolism is an important target for therapeutic intervention, the metabolic requirement involved in lipid accumulation during pro-inflammatory activation of macrophages remains incompletely characterized. We show here that macrophage activation with IFNγ results in increased aerobic glycolysis, iNOS-dependent inhibition of respiration, and accumulation of triacylglycerol. Surprisingly, metabolite tracing with ¹³C-labeled glucose revealed that the glucose contributed to the glycerol groups in triacylglycerol (TAG), rather than to de novo synthesis of fatty acids. This is in stark contrast to the otherwise similar metabolism of cancer cells, and previous results obtained in activated macrophages and dendritic cells. Our results establish a novel metabolic pathway whereby glucose provides glycerol to the headgroup of TAG during classical macrophage activation.

Biphasic adaptative responses in VLDL metabolism and lipoprotein homeostasis during Gram-negative endotoxemia

Dyslipidemia and hepatic overproduction of very low density lipoprotein (VLDL) are hallmarks of the septic response, yet the underlying mechanisms are not fully defined. We evaluated the lipoprotein subclasses profile and hepatic VLDL assembly machinery over 24 h in fasted LPS-treated rats. The response of serum non-esterified fatty acids (NEFA) and glucose to endotoxin was biphasic, with increased levels of NEFA and hypoglycemia in the first 12 h-phase, and low NEFA and high glucose in the second 12 h-phase. Hypertriglyceridemia was more marked in the first 12 h (6.8-fold), when triglyceride abundance increased in all lipoprotein subclasses, and preferentially in large VLDL. The abundance of medium-sized VLDL and the increase in the number of VLDL particles was higher in the second phase (10-fold vs 5-fold in the first phase); however, apoB gene transcript abundance increased only in the second phase. Analysis of putative pre-translational mechanisms revealed that neither increased Apob transcription rate nor increased transcript binding to mRNA stabilizing HuR (Hu antigen R) protein paralleled the increase in apoB transcripts. In conclusion, endotoxin challenge induces increases in plasma NEFA and large, triglyceride-rich VLDL. After approximately 12 h, the triglyceride-rich VLDLs are replaced by medium-sized, triglyceride-poor VLDL particles. Hepatic apoB mRNA abundance also increases during the second period, suggesting a role for apoB protein expression in the acute reaction against sepsis.

Apolipoprotein CI stimulates the response to lipopolysaccharide and reduces mortality in Gram‐negative sepsis

Gram-negative sepsis is a major death cause in intensive care units. Accumulating evidence indicates the protective role of plasma lipoproteins such as high-density lipoprotein (HDL) in sepsis. It has recently been shown that septic HDL is almost depleted from apolipoprotein CI (apoCI), suggesting that apoCI may be a protective factor in sepsis. Sequence analysis revealed that apoCI possesses a highly conserved consensus KVKEKLK binding motif for lipopolysaccharide (LPS), an outer-membrane component of gram-negative bacteria. Through avid binding to LPS involving this motif, apoCI improved the presentation of LPS to macrophages in vitro and in mice, thereby stimulating the inflammatory response to LPS. Moreover, apoCI dose-dependently increased the early inflammatory response to Klebsiella pneumoniae-induced pneumonia, reduced the number of circulating bacteria, and protected mice against fatal sepsis. Our data support the hypothesis that apoCI is a physiological protector against infection by enhancing the early inflammatory response to LPS and suggest that timely increase of apoCI levels could be used to efficiently prevent and treat early sepsis.

Benefit of farnesoid X receptor inhibition in obstructive cholestasis

The nuclear hormone receptors farnesoid X receptor (FXR) and pregnane X receptor have been implicated in regulating bile acid, lipid, carbohydrate, and xenobiotic metabolism. Bile duct ligation was used to increase endogenous bile acids and evaluate the roles of these receptors in modulating cholestatic liver injury. FXR knockout (KO) mice were found to be protected from obstructive cholestasis. Concurrent deletion of FXR also could ameliorate an increase in liver injury that is seen usually in pregnane X receptor KO mice with cholestasis. Mechanisms proposed for this protection include the lowering of bile acid concentrations and altered expression of the hepatic transporters Mdr1, Mdr2, BSEP, and Mrp4. FXR KO mice also exhibit a biphasic lipid profile after bile duct ligation, with an increase in high-density lipoprotein cholesterol and triglycerides by day 6. The expression of apolipoprotein AV was reduced in these mice, implicating FXR in triglyceride regulation. We show that FXR modulates cholestasis by controlling bile acids within the hepatocyte and is involved in bile acid synthesis, bile excretion via BSEP, and serum export via Mrp4. This study strongly suggests a potential clinical role for FXR antagonists in the treatment of obstructive cholestatic liver disorders.