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Normothermic perfusion provides a means to rescue steatotic liver grafts, including by pharmacological defatting. In this study, we tested the potential of new drug combinations to trigger defatting in three human culture models, primary hepatocytes with induced steatosis, primary hepatocytes isolated from steatotic liver, and precision-cut liver slices (PCLS) of steatotic liver. Forskolin, L-carnitine and a PPARα agonist were all combined with rapamycin, an immunosuppressant that induces autophagy, in a D-FAT cocktail. D-FAT was tested alone or in combination with necrosulfonamide, an inhibitor of mixed lineage kinase domain like pseudokinase involved in necroptosis. Within 24 h, in all three models, D-FAT induced a decrease in triglyceride content by 30%, attributable to an upregulation of genes involved in free fatty acid β-oxidation and autophagy, and a downregulation of those involved in lipogenesis. Defatting was accompanied by a decrease in endoplasmic reticulum stress and in the production of reactive oxygen species. The addition of necrosulfonamide increased the efficacy of defatting by 8%-12% in PCLS, with a trend towards increased autophagy. In conclusion, culture models, notably PCLS, are insightful to design strategies for liver graft rescue. Defatting can be rapidly achieved by combinations of drugs targeting mitochondrial oxidative metabolism, macro-autophagy and lipogenesis., Summary: This study describes a defatting cocktail that has been proven to function in three relevant steatotic human culture models without cytotoxicity, and which could be employed in the reduction of steatosis in donor livers during liver transplantation.

Aims SR-B1 is a cholesterol transporter that exerts anti-atherogenic properties in liver and peripheral tissues in mice. Bone marrow (BM) transfer studies suggested an atheroprotective role in cells of haematopoietic origin. Here, we addressed the specific contribution of SR-B1 in the monocyte/macrophage. Methods and results We generated mice deficient for SR-B1 in monocytes/macrophages (Lysm-Cre × SR-B1f/f) and transplanted their BM into Ldlr−/− mice. Fed a cholesterol-rich diet, these mice displayed accelerated aortic atherosclerosis characterized by larger macrophage-rich areas and decreased macrophage apoptosis compared with SR-B1f/f transplanted controls. These findings were reproduced in BM transfer studies using another atherogenic mouse recipient (SR-B1 KOliver × Cholesteryl Ester Transfer Protein). Haematopoietic reconstitution with SR-B1−/− BM conducted in parallel generated similar results to those obtained with Lysm-Cre × SR-B1f/f BM; thus suggesting that among haematopoietic-derived cells, SR-B1 exerts its atheroprotective role primarily in monocytes/macrophages. Consistent with our in vivo data, free cholesterol (FC)-induced apoptosis of macrophages was diminished in the absence of SR-B1. This effect could not be attributed to differential cellular cholesterol loading. However, we observed that expression of apoptosis inhibitor of macrophage (AIM) was induced in SR-B1-deficient macrophages, and notably upon FC-loading. Furthermore, we demonstrated that macrophages were protected from FC-induced apoptosis by AIM. Finally, AIM protein was found more present within the macrophage-rich area of the atherosclerotic lesions of SR-B1-deficient macrophages than controls. Conclusion Our findings suggest that macrophage SR-B1 plays a role in plaque growth by controlling macrophage apoptosis in an AIM-dependent manner.

Background: Low concentrations of high-density lipoprotein cholesterol (HDL-C) represent a well-established cardiovascular risk factor. Paradoxically, extremely high HDL-C levels are equally associated with elevated cardiovascular risk, resulting in the U-shape relationship of HDL-C with cardiovascular disease. Mechanisms underlying this association are presently unknown. We hypothesised that the capacity of high-density lipoprotein (HDL) to acquire free cholesterol upon triglyceride-rich lipoprotein (TGRL) lipolysis by lipoprotein lipase underlies the non-linear relationship between HDL-C and cardiovascular risk. Methods: To assess our hypothesis, we developed a novel assay to evaluate the capacity of HDL to acquire free cholesterol (as fluorescent TopFluor® cholesterol) from TGRL upon in vitro lipolysis by lipoprotein lipase. Results: When the assay was applied to several populations markedly differing in plasma HDL-C levels, transfer of free cholesterol was significantly decreased in low HDL-C patients with acute myocardial infarction (−45%) and type 2 diabetes (–25%), and in subjects with extremely high HDL-C of >2.59 mmol/L (>100 mg/dL) (−20%) versus healthy normolipidaemic controls. When these data were combined and plotted against HDL-C concentrations, an inverse U-shape relationship was observed. Consistent with these findings, animal studies revealed that the capacity of HDL to acquire cholesterol upon lipolysis was reduced in low HDL-C apolipoprotein A-I knock-out mice and was negatively correlated with aortic accumulation of [3H]-cholesterol after oral gavage, attesting this functional characteristic as a negative metric of postprandial atherosclerosis. Conclusions: Free cholesterol transfer to HDL upon TGRL lipolysis may underlie the U-shape relationship between HDL-C and cardiovascular disease, linking HDL-C to triglyceride metabolism and atherosclerosis. Fil: Feng, Ma. Inserm; Francia. Université Pierre et Marie Curie; Francia Fil: Darabi, Maryam. Université Pierre et Marie Curie; Francia. Inserm; Francia Fil: Tubeuf, Emilie. Inserm; Francia. Université Pierre et Marie Curie; Francia Fil: Canicio, Aurélie. Université Pierre et Marie Curie; Francia. Inserm; Francia Fil: Lhomme, Marie. Institute Of Cardiometabolism And Nutrition; Francia Fil: Frisdal, Eric. Inserm; Francia. Université Pierre et Marie Curie; Francia Fil: Lanfranchi Lebreton, Sandrine. Université Pierre et Marie Curie; Francia Fil: Matheron, Lucrèce. Université Pierre et Marie Curie; Francia Fil: Rached, Fabiana. Université Pierre et Marie Curie; Francia. Inserm; Francia Fil: Ponnaiah, Maharajah. Institute Of Cardiometabolism And Nutrition; Francia Fil: Serrano, Carlos V.. Instituto Do Coracao Do Hospital Das Clinicas; Brasil Fil: Santos, Raul D.. Instituto Do Coracao Do Hospital Das Clinicas; Brasil Fil: Brites, Fernando Daniel. Universidad de Buenos Aires; Argentina. Instituto Do Coracao Do Hospital Das Clinicas; Brasil Fil: Bolbach, Gerard. Université Pierre et Marie Curie; Francia Fil: Gautier, Emmanuel. Université Pierre et Marie Curie; Francia. Inserm; Francia Fil: Huby, Thierry. Inserm; Francia. Université Pierre et Marie Curie; Francia Fil: Carrie, Alain. Inserm; Francia. Université Pierre et Marie Curie; Francia Fil: Bruckert, Eric. Inserm; Francia. Université Pierre et Marie Curie; Francia Fil: Guerin, Maryse. Université Pierre et Marie Curie; Francia. Inserm; Francia Fil: Couvert, Philippe. Inserm; Francia. Université Pierre et Marie Curie; Francia Fil: Giral, Philippe. Université Pierre et Marie Curie; Francia. Inserm; Francia Fil: Lesnik, Philippe. Université Pierre et Marie Curie; Francia. Inserm; Francia Fil: Le Goff, Wilfried. Université Pierre et Marie Curie; Francia. Inserm; Francia Fil: Guillas, Isabelle. Inserm; Francia. Université Pierre et Marie Curie; Francia Fil: Kontush, Anatol. Inserm; Francia. Université Pierre et Marie Curie; Francia

Objective— Erdheim-Chester disease (ECD) is a rare non-Langerhans cell histiocytosis characterized by the infiltration of multiple tissues with lipid-laden histiocytes. Cardiovascular involvement is frequent in ECD and leads to a severe prognosis. The objective of this study was to determine whether an alteration of lipid metabolism participates in the lipid accumulation in histiocytes and the cardiovascular involvement in ECD. Approach and Results— An analysis of plasma lipid levels indicated that male ECD patients carrying the BRAF V600E (B-Raf proto-oncogene, serine/threonine kinase) mutation exhibited hypoalphalipoproteinemia, as demonstrated by low plasma HDL-C (high-density lipoprotein cholesterol) levels. Capacity of sera from male BRAF V600E ECD patients to mediate free cholesterol efflux from human macrophages was reduced compared with control individuals. Cardiovascular involvement was detected in 84% of the ECD patients, and we reported that the presence of the BRAF V600E mutation and hypoalphalipoproteinemia is an independent determinant of aortic infiltration in ECD. Phenotyping of blood CD14 + cells, the precursors of histiocytes, enabled the identification of a specific inflammatory signature associated with aortic infiltration which was partially affected by the HDL phenotype. Finally, the treatment with vemurafenib, an inhibitor of the BRAF V600E mutation, restored the defective sera cholesterol efflux capacity and reduced the aortic infiltration. Conclusions— Our findings indicate that hypoalphalipoproteinemia in male ECD patients carrying the BRAF V600E mutation favors the formation of lipid-laden histiocytes. In addition, we identified the BRAF status and the HDL phenotype as independent determinants of the aortic involvement in ECD with a potential role of HDL in modulating the infiltration of blood CD14 + cells into the aorta.

International audience; Mutations in the a disintegrin and metalloproteinase with thrombospondin motif-like 2 ( ADAMTSL2) gene are responsible for the autosomal recessive form of geleophysic dysplasia, which is characterized by short stature, short extremities, and skeletal abnormalities. However, the exact function of ADAMTSL2 is unknown. To elucidate the role of this protein in skeletal development, we generated complementary knockout (KO) mouse models with either total or chondrocyte Adamtsl2 deficiency. We observed that the Adamtsl2 KO mice displayed skeletal abnormalities reminiscent of the human phenotype. Adamtsl2 deletion affected the growth plate formation with abnormal differentiation and proliferation of chondrocytes. In addition, a TGF-β signaling impairment in limbs lacking Adamtsl2 was demonstrated. Further investigations revealed that Adamtsl2 KO chondrocytes failed to establish a microfibrillar network composed by fibrillin1 and latent TGF-β binding protein 1 fibrils. Chondrocyte Adamtsl2 KO mice also exhibited dwarfism. These studies uncover the function of Adamtsl2 in the maintenance of the growth plate ECM by modulating the microfibrillar network.-Delhon, L., Mahaut, C., Goudin, N., Gaudas, E., Piquand, K., Le Goff, W., Cormier-Daire, V., Le Goff, C. Impairment of chondrogenesis and microfibrillar network in Adamtsl2 deficiency.

International audience; Background Factor V (FV) is a circulating protein primarily synthesized in the liver, and mainly present in plasma. It is a major component of the coagulation process. Objective To detect novel genetic loci participating to the regulation of FV plasma levels. Methods We conducted the first Genome Wide Association Study on FV plasma levels in a sample of 510 individuals and replicated the main findings in an independent sample of 1156 individuals. Results In addition to genetic variations at the F5 locus, we identified novel associations at the PLXDC2 locus, with the lead PLXDC2 rs927826 polymorphism explaining ~3.7% (P = 7.5 × 10−15 in the combined discovery and replication samples) of the variability of FV plasma levels. In silico transcriptomic analyses in various cell types confirmed that PLXDC2 expression is positively correlated to F5 expression. SiRNA experiments in human hepatocellular carcinoma cell line confirmed the role of PLXDC2 in modulating factor F5 gene expression, and revealed further influences on F2 and F10 expressions. Conclusion Our study identified PLXDC2 as a new molecular player of the coagulation process.

Cardiogenics Consortium, IDEM Leducq Consortium CADGenomics; International audience; Macrophages are key players involved in numerous pathophysiological pathways and an in-depth characterization of their gene regulatory networks can help in better understanding how their dysfunction may impact on human diseases. We here conducted a cross-species network analysis of macrophage gene expression data between human and mouse to identify conserved networks across both species, and assessed whether such networks could reveal new disease-associated regulatory mechanisms. From a sample of 684 individuals processed for genome-wide macrophage gene expression profiling, we identified 27 groups of coexpressed genes (modules). Six modules were found preserved (P , 10 24) in macrophages from 86 mice of the Hybrid Mouse Diversity Panel. One of these modules was significantly [false discovery rate (FDR) = 8.9 · 10 211 ] enriched for genes belonging to the oxidative phosphorylation (OXPHOS) pathway. This pathway was also found significantly (FDR , 10 24) enriched in susceptibility genes for Alzheimer, Parkinson, and Huntington diseases. We further conducted an expression quantitative trait loci analysis to identify SNP that could regulate macrophage OXPHOS gene expression in humans. This analysis identified the PARK2 rs192804963 as a transacting variant influencing (minimal P-value = 4.3 · 10 28) the expression of most OXPHOS genes in humans. Further experimental work demonstrated that PARK2 knockdown expression was associated with increased OXPHOS gene expression in THP1 human macrophages. This work provided strong new evidence that PARK2 participates to the regulatory networks associated with oxidative phosphorylation and suggested that PARK2 genetic variations could act as a trans regulator of OXPHOS gene macrophage expression in humans.

Cardiospondylocarpofacial (CSCF) syndrome is characterized by growth retardation, dysmorphic facial features, brachydactyly with carpal-tarsal fusion and extensive posterior cervical vertebral synostosis, cardiac septal defects with valve dysplasia, and deafness with inner ear malformations. Whole-exome sequencing identified heterozygous MAP3K7 mutations in six distinct CSCF-affected individuals from four families and ranging in age from 5 to 37 years. MAP3K7 encodes transforming growth factor β (TGF-β)-activated kinase 1 (TAK1), which is involved in the mitogen-activated protein kinase (MAPK)-p38 signaling pathway. MAPK-p38 signaling was markedly altered when expression of non-canonical TGF-β-driven target genes was impaired. These findings support the loss of transcriptional control of the TGF-β-MAPK-p38 pathway in fibroblasts obtained from affected individuals. Surprisingly, although TAK1 is located at the crossroad of inflammation, immunity, and cancer, this study reports MAP3K7 mutations in a developmental disorder affecting mainly cartilage, bone, and heart.

Reconstituted forms of HDL (rHDL) are under development for infusion as a therapeutic approach to attenuate atherosclerotic vascular disease and to reduce cardiovascular risk following acute coronary syndrome and ischemic stroke. Currently available rHDL formulations developed for clinical use contain apolipoprotein A-I (apoA-I) and one of the major lipid components of HDL, either phosphatidylcholine or sphingomyelin. Recent data have established that quantitatively minor molecular constituents of HDL particles can strongly influence their anti-atherogenic functionality. Novel rHDL formulations displaying enhanced biological activities, including cellular cholesterol efflux, may therefore offer promising prospects for the development of HDL-based, anti-atherosclerotic therapies. Indeed, recent structural and functional data identify phosphatidylserine as a bioactive component of HDL; the content of phosphatidylserine in HDL particles displays positive correlations with all metrics of their functionality. This review summarizes current knowledge of structure-function relationships in rHDL formulations, with a focus on phosphatidylserine and other negatively-charged phospholipids. Mechanisms potentially underlying the atheroprotective role of these lipids are discussed and their potential for the development of HDL-based therapies highlighted.

International audience; Kupffer cells (KCs) are liver-resident macrophages that self-renew by proliferation in the adult independently from monocytes. However, how they are maintained during non-alcoholic steatohepatitis (NASH) remains ill defined. We found that a fraction of KCs derived from Ly-6C+ monocytes during NASH, underlying impaired KC self-renewal. Monocyte-derived KCs (MoKCs) gradually seeded the KC pool as disease progressed in a response to embryo-derived KC (EmKC) death. Those MoKCs were partly immature and exhibited a pro-inflammatory status compared to EmKCs. Yet, they engrafted the KC pool for the long term as they remained following disease regression while acquiring mature EmKC markers. While KCs as a whole favored hepatic triglyceride storage during NASH, EmKCs promoted it more efficiently than MoKCs, and the latter exacerbated liver damage, highlighting functional differences among KCs with different origins. Overall, our data reveal that KC homeostasis is impaired during NASH, altering the liver response to lipids, as well as KC ontogeny.

High density lipoproteins (HDL) are key components of reverse cholesterol transport pathway. HDL removes excessive cholesterol from peripheral cells, including macrophages, providing protection from cholesterol accumulation and conversion into foam cells, which is a key event in pathogenesis of atherosclerosis. The mechanism of cellular cholesterol efflux stimulation by HDL involves interaction with the ABCA1 lipid transporter and ensuing transfer of cholesterol to HDL particles. In this study, we looked for additional proteins contributing to HDL-dependent cholesterol efflux. Using RNAseq, we analyzed mRNAs induced by HDL in human monocyte-derived macrophages and identified three genes, fatty acid desaturase 1 (FADS1), insulin induced gene 1 (INSIG1), and the low-density lipoprotein receptor (LDLR), expression of which was significantly upregulated by HDL. We individually knocked down these genes in THP-1 cells using gene silencing by siRNA, and measured cellular cholesterol efflux to HDL. Knock down of FADS1 did not significantly change cholesterol efflux (p = 0.70), but knockdown of INSIG1 and LDLR resulted in highly significant reduction of the efflux to HDL (67% and 75% of control, respectively, p 0.001). Importantly, the suppression of cholesterol efflux was independent of known effects of these genes on cellular cholesterol content, as cells were loaded with cholesterol using acetylated LDL. These results indicate that HDL particles stimulate expression of genes that enhance cellular cholesterol transfer to HDL.

Objective- Erdheim-Chester disease (ECD) is a rare non-Langerhans cell histiocytosis characterized by the infiltration of multiple tissues with lipid-laden histiocytes. Cardiovascular involvement is frequent in ECD and leads to a severe prognosis. The objective of this study was to determine whether an alteration of lipid metabolism participates in the lipid accumulation in histiocytes and the cardiovascular involvement in ECD. Approach and Results- An analysis of plasma lipid levels indicated that male ECD patients carrying the BRAF

Background The Middle East region is characterized by low levels of high-density lipoprotein cholesterol (HDL-C). To date, no genetic study has investigated the cause of low HDL-C in the Lebanese population. Objective Our objective was to study the genetic causes for hypoalphalipoproteinemia in a Lebanese family with extremely low HDL-C levels. Methods We sequenced the ABCA1 gene and evaluated cholesterol efflux, inflammatory, and metabolic profiles in the proband and his family. Results We identified the first Lebanese pathogenic variant in ABCA1 gene causing Tangier disease in a consanguineous family. The proband carried a novel homozygous pathogenic variant p.Gly592Asp in exon 14 of ABCA1, which segregated with the disease in the family. Functional study of the p.Gly592Asp pathogenic variant revealed that lipid-free apolipoprotein A-I–dependent cholesterol efflux was completely abolished in cholesterol-loaded human monocytes-derived macrophages isolated from the proband when compared to controls. Systemic inflammatory and metabolic assessments showed that plasma cytokines (MCP-1, MIP-1α, IL-6, CRP, TNF-α), adhesion molecules (ICAM-1, VCAM-1, E-selectin), inflammatory soluble receptors (sIL-6r, sTNFRI, sTNFRII), and metabolic markers (Insulin, C-peptide) were elevated in the proband when compared to controls. Noninvasive cardiovascular investigation revealed the presence of premature artery lesions in the proband. Conclusions It is the first case of Tangier disease reported in Lebanon harboring a novel pathogenic variant in ABCA1. Further genetic research is needed in the Middle East where the consanguinity rate is elevated, to understand the cause of the highly prevalent dyslipidemia. This will help guiding the early diagnosis, management, and prevention of cardiovascular complications.

Background Neutrophilic dermatoses refer to a group of cutaneous inflammatory disorders characterized by neutrophilic infiltration of the skin. Neutrophilic dermatoses have been reported in association with various conditions including autoimmune diseases, inflammatory bowel diseases, and neoplasia. In the later condition, myeloproliferative disorders and monoclonal gammopathy (monoclonal immunoglobulin [MIg]) are the most frequent. Only few data are available in case of neutrophilic dermatoses associated with MIg regarding the pathophysiology and the clinical outcome. Objective We sought to gain further insight into clinical and biological aspects of neutrophilic dermatoses associated with MIg. Methods We report a retrospective series of 26 patients with neutrophilic dermatoses associated with MIg focusing on clinical and biological aspects, with a study of a large panel of cytokines, chemokines, and adhesion molecules. Results This study reveals an association between MIg IgA isotype and neutrophilic dermatoses, and a specific inflammatory pattern including elevated interleukin 6, vascular endothelial growth factor, monocyte chemotactic protein-1, epidermal growth factor, and intercellular adhesion molecule-1. Limitations This is a retrospective study from a single institution with a limited number of participants. Conclusion Our data highlight a strong association between IgA isotype and neutrophilic dermatoses, and the existence of a specific inflammatory profile involving several molecules.

International audience; Despite considerable progress in the management of major risk factors over recent decades, cardiovascular diseases (CVD) attributable to atherosclerosis are still a predominant cause of death worldwide. This is due, in large part, to the expansion of risk factors related to obesity such as insulin resistance and diabetes [1]. In fact, the risk of developing CVD in adults with diabetes is two to four times higher than in those without diabetes. Moreover, it is well established that insulin resistance and hyperglycemia promote atherosclerosis, leading to coronary artery disease. Yet the underlying mechanisms linking diabetes and atherosclerosis are still not completely understood. To overcome this lack of understanding, numerous studies have been conducted, using mouse models with targeted deletion in intimal cells, to evaluate the impact of impaired insulin signaling at the level of the arterial wall on atherosclerosis development and progression [2]. Taken together, this work highlights the critical consequences of altered insulin signaling, in both macrophages and endothelial cells, in atherogenesis and the formation of advanced plaques. In humans, comparative analyses of atherosclerotic plaques from diabetic and non-diabetic individuals have revealed some important differences in the quality and composition of plaques between these groups. Lesions from diabetic patients are characterized by a larger necrotic core, increased inflammation, neovascularization, intra-plaque hemorrhage, and calcification [3], [4], [5], [6] and [7]. Higher macrophage and T-cell content, along with increased proportions of apoptotic macrophages and smooth muscle cells, may contribute to this larger necrotic area [4] and [8]. When combined with the increased prevalence of thin-cap fibroatheroma and fibrocalcific atheroma, observed using Virtual Histology intravascular ultrasound in vessels of diabetic patients [5], these alterations of plaque morphology may explain the higher risk of acute coronary syndrome in diabetic patients. Indeed, coronary lesions of patients with diabetes mellitus are more vulnerable to rupture and subsequent thrombosis [3] and [6].

ATP-binding cassette G1 (ABCG1) is a member of the large family of ABC transporters which are involved in the active transport of many amphiphilic and lipophilic molecules including lipids, drugs or endogenous metabolites. It is now well established that ABCG1 promotes the export of lipids, including cholesterol, phospholipids, sphingomyelin and oxysterols, and plays a key role in the maintenance of tissue lipid homeostasis. Although ABCG1 was initially proposed to mediate cholesterol efflux from macrophages and then to protect against atherosclerosis and cardiovascular diseases (CVD), it becomes now clear that ABCG1 exerts a larger spectrum of actions which are of major importance in cardiometabolic diseases (CMD). Beyond a role in cellular lipid homeostasis, ABCG1 equally participates to glucose and lipid metabolism by controlling the secretion and activity of insulin and lipoprotein lipase. Moreover, there is now a growing body of evidence suggesting that modulation of ABCG1 expression might contribute to the development of diabetes and obesity, which are major risk factors of CVD. In order to provide the current understanding of the action of ABCG1 in CMD, we here reviewed major findings obtained from studies in mice together with data from the genetic and epigenetic analysis of ABCG1 in the context of CMD.

International audience; Vitamin E membrane transport has been shown to involve the cholesterol transporters SR-BI, ABCA1 and NPC1L1. Our aim was to investigate the possible participation of another cholesterol transporter in cellular vitamin E efflux: ABCG1. In Abcg1-deficient mice, vitamin E concentration was reduced in plasma lipoproteins whereas most tissues displayed a higher vitamin E content compared to wild-type mice. alpha- and gamma-tocopherol efflux was increased in CHO cells overexpressing human ABCG1 compared to control cells. Conversely, alpha- and gamma-tocopherol efflux was decreased in ABCG1-knockdown human cells (Hep3B hepatocytes and THP-1 macrophages). Interestingly, alpha- and gamma-tocopherol significantly downregulated ABCG1 and ABCA1 expression levels in Hep3B and THP-1, an effect confirmed in vivo in rats given vitamin E for 5 days. This was likely due to reduced LXR activation by oxysterols, as Hep3B cells and rat liver treated with vitamin E displayed a significantly reduced content in oxysterols compared to their respective controls. Overall, the present study reveals for the first time that ABCG1 is involved in cellular vitamin E efflux. (C) 2014 Elsevier B.V. All rights reserved.

Omega-3 fatty acids (n-3) FA are reported to be protective against cardiovascular disease (CVD), notably through their beneficial action on atherosclerosis development. In this context dietary intake of long-chain marine eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) is recommended and randomised trials largely support that EPA and DHA intake is associated with a reduction of CVD. However, mechanisms governing the atheroprotective action of n-3 FA are still unclear and numerous studies using mouse models conducted so far do not allow to reach a precise view of the cellular and molecular effects of n-3 FA on atherosclerosis. In the current issue of Atherosclerosis , Chang et al. provide important new information on the anti-atherogenic properties of n-3 FA by analysing the incremental replacement of saturated FA by pure fish oil as a source of EPA and DHA in Ldlr −/− mice fed a high fat/high cholesterol diet.

Objectives To identify key determinants of plasma endogenous CETP activity and threshold value of plasma CETP activity associated with high cardiovascular risk. Methods Endogenous plasma CETP activity was measured in a total of 1403 individuals. Results Multivariate analysis revealed that 23.5% of endogenous CETP activity variability was explained by plasma LDL-C (12.0%), HDL-C (6.4%) and TG (4.4%) whereas sex and BMI accounted together for only 0.7% of its variability. Scoring patients for cardiovascular risk on the basis of their plasma lipid levels (TC, TG, LDL-C and HDL-C), revealed that patients with high cardiovascular risk (score ≥3) displayed a mean endogenous plasma CETP activity above 34%. Conclusion Plasma CETP activity represents a potent indicator of cardiovascular risk in patients with metabolic disorders since it integrates major independent risk factors.

Variants in the CETP and the LIPC genes, encoding cholesteryl ester transfer protein and hepatic lipase, respectively, are associated with high levels of HDL-cholesterol or hyperalphalipoproteinemia (HALP). Recently, we have identified three novel variants in the CETP promoter and two novel variants in LIPC in Thai subjects with HALP. In this study, we investigated the functions of these 5 variants in vitro.For CETP promoter variants, we used site-directed mutagenesis, transient expression in HepG2 cells and luciferase reporter assay. For LIPC variants, cDNA was cloned and mutagenesis for missense variants was performed before expression in HepG2 cells.The transcriptional activities of -49GT,-70CT, and -372CT CETP promoter variants were markedly reduced (5%, 8% and 30%, respectively, compared to that of the wild-type, P0.001). For LIPC variants, hepatic lipase activities in the lysates of cells transfected with c.421AG (p.G141S) and c.517GA (p.V173M) variants were 41% and 46%, respectively, compared to that of the wild-type (P0.05).The recently-identified variants in the CETP promoter and in the LIPC gene may contribute to HALP. Our result may have a diagnostic application in the genetic evaluation of subjects with high HDL-cholesterol levels.

Objective— The physiological function of the ATP–binding cassette G1 (ABCG1) transporter in humans is not yet elucidated, as no genetic disease caused by ABCG1 mutations has been documented. The goal of our study was, therefore, to investigate the potential role(s) of ABCG1 in lipid metabolism in humans. Methods and Results— Here we report that among the 104 polymorphisms present in the ABCG1 gene, the analysis of the frequent functional rs1893590 and rs1378577 single nucleotide polymorphisms located in the regulatory region of ABCG1 in the Regression Growth Evaluation Statin Study population revealed that both ABCG1 single nucleotide polymorphisms were significantly associated with plasma lipoprotein lipase (LPL) activity. Moreover, we observed that plasma LPL activity was modestly reduced in Abcg1 −/− mice as compared with control mice. Adipose tissue and skeletal muscle are the major tissues accounting for levels and activity of plasma LPL in the body. However, beyond its lipolytic action in the plasma compartment, LPL was also described to act locally at the cellular level. Thus, macrophage LPL was reported to promote foam cell formation and atherosclerosis in vivo. Analysis of the relationship between ABCG1 and LPL in macrophages revealed that the knockdown of ABCG1 expression (ABCG1 knockdown) in primary cultures of human monocyte–derived macrophages using small interfering RNAs led to a marked reduction of both the secretion and activity of LPL. Indeed, LPL was trapped at the cell surface of ABCG1 knockdown human monocyte–derived macrophages, likely in cholesterol-rich domains, thereby reducing the bioavailability and activity of LPL. As a consequence, LPL–mediated lipid accumulation in human macrophage foam cells in the presence of triglyceride-rich lipoproteins was abolished when ABCG1 expression was repressed. Conclusion— We presently report that ABCG1 controls LPL activity and promotes lipid accumulation in human macrophages in the presence of triglyceride-rich lipoproteins, thereby suggesting a potential deleterious role of macrophage ABCG1 in metabolic situations associated with high levels of circulating triglyceride-rich lipoproteins together with the presence of macrophages in the arterial wall.

Background The identification of mutations in PCSK9 (proprotein convertase subtilisin kexin9) in autosomal dominant hypercholesterolemia (ADH), has revealed the existence of a new player in cholesterol homeostasis. PCSK9 has been shown to enhance the degradation of the LDL receptor (LDLR) at the cell surface. Gain-of-function mutations of PCSK9 induce ADH and are very rare, but their identification is crucial in studying PCSK9's role in hypercholesterolemia, its detailed trafficking pathway and its impact on the LDLR. Methods In order to identify new mutations and understand the exact mechanisms of action of mutated PCSK9, PCSK9 was sequenced in 75 ADH patients with no mutations in the LDLR or APOB genes. Functional analyses in cell culture were conducted and the impact of novel PCSK9 mutations on the quantitative and qualitative features of lipoprotein particles and on the HDL-mediated cellular cholesterol efflux was studied. Results Among these 75 ADH probands with no mutations in the LDLR or APOB genes, four gain-of-function mutations of PCSK9 were identified, of which two were novel: the p.Leu108Arg and the p.Asp35Tyr substitutions. In vitro studies of their consequences on the activity of PCSK9 on cell surface levels of LDLR showed that the p.Leu108Arg mutation clearly results in a gain-of-function, while the p.Asp35Tyr mutation created a novel Tyr-sulfation site, which may enhance the intracellular activity of PCSK9. Conclusion These data further contribute to the characterization of PCSK9 mutations and to better understanding of the impact on cholesterol metabolism of this new therapeutic target.

Objective To evaluate the impact of CETP inhibition on the capacity of individual postprandial HDL subspecies to promote key steps of the reverse cholesterol transport pathway. Methods The capacity of HDL particles to mediate cellular free cholesterol efflux and selective hepatic uptake of cholesteryl esters was evaluated throughout postprandial phase (0–8h) following consumption of a standardised mixed meal before and after treatment for 6 weeks with atorvastatin alone (10mg/d) and subsequently with combination torcetrapib/atorvastatin (60/10mg/d) in 16 patients displaying low HDL-C levels ( Results The larger HDL2b and HDL2a subfraction displayed a superior capacity to mediate cellular free cholesterol efflux via both SR-BI and ABCG1-dependent pathways than smaller HDL3 subspecies. CETP inhibition specifically enhanced the capacity of HDL2b subfraction for both SR-BI and ABCG1 dependent efflux. However, only the SR-BI-dependent efflux to HDL2b subspecies can be further enhanced during postprandial lipemia following CETP inhibition. Concomitantly, postprandial lipemia was associated with a reduced capacity of total HDL particles to deliver cholesteryl esters to hepatic cells in a drug independent manner. Conclusion CETP inhibition specifically improves postprandial SR-BI and ABCG1-dependent efflux to larger HDL2b subspecies. In addition, CETP inhibition improves HDL-CE delivery to hepatic cells and maintains an efficient direct return of cholesteryl esters to the liver during postprandial lipemia.

Myhre syndrome (MIM 139210) is a developmental disorder characterized by short stature, short hands and feet, facial dysmorphism, muscular hypertrophy, deafness and cognitive delay. Using exome sequencing of individuals with Myhre syndrome, we identified SMAD4 as a candidate gene that contributes to this syndrome on the basis of its pivotal role in the bone morphogenetic pathway (BMP) and transforming growth factor (TGF)-β signaling. We identified three distinct heterozygous missense SMAD4 mutations affecting the codon for Ile500 in 11 individuals with Myhre syndrome. All three mutations are located in the region of SMAD4 encoding the Mad homology 2 (MH2) domain near the site of monoubiquitination at Lys519, and we found a defect in SMAD4 ubiquitination in fibroblasts from affected individuals. We also observed decreased expression of downstream TGF-β target genes, supporting the idea of impaired TGF-β-mediated transcriptional control in individuals with Myhre syndrome.

Cholesterol-laden monocyte-derived macrophages are phagocytic cells characteristic of early and advanced atherosclerotic lesions. Interleukin-6 (IL-6) is a macrophage secretory product that is abundantly expressed in atherosclerotic plaques but whose precise role in atherogenesis is unclear. The capacity of macrophages to clear apoptotic cells, through the efferocytosis mechanism, as well as to reduce cellular cholesterol accumulation contributes to prevent plaque progression and instability. By virtue of its capacity to promote cellular cholesterol efflux from phagocyte-macrophages, ABCA1 was reported to reduce atherosclerosis. We demonstrated that lipid loading in human macrophages was accompanied by a strong increase of IL-6 secretion. Interestingly, IL-6 markedly induced ABCA1 expression and enhanced ABCA1-mediated cholesterol efflux from human macrophages to apoAI. Stimulation of ABCA1-mediated cholesterol efflux by IL-6 was, however, abolished by selective inhibition of the Jak-2/Stat3 signaling pathway. In addition, we observed that the expression of molecules described to promote efferocytosis, i.e. c-mer proto-oncogene-tyrosine kinase, thrombospondin-1, and transglutaminase 2, was significantly induced in human macrophages upon treatment with IL-6. Consistent with these findings, IL-6 enhanced the capacity of human macrophages to phagocytose apoptotic cells; moreover, we observed that IL-6 stimulates the ABCA1-mediated efflux of cholesterol derived from the ingestion of free cholesterol-loaded apoptotic macrophages. Finally, the treatment of human macrophages with IL-6 led to the establishment of an anti-inflammatory cytokine profile, characterized by an increased secretion of IL-4 and IL-10 together with a decrease of that of IL-1β. Taken together, our results indicate that IL-6 favors the elimination of excess cholesterol in human macrophages and phagocytes by stimulation of ABCA1-mediated cellular free cholesterol efflux and attenuates the macrophage proinflammatory phenotype. Thus, high amounts of IL-6 secreted by lipid laden human macrophages may constitute a protective response from macrophages to prevent accumulation of cytotoxic-free cholesterol. Such a cellular recycling of free cholesterol may contribute to reduce both foam cell formation and the accumulation of apoptotic bodies as well as intraplaque inflammation in atherosclerotic lesions.

Objective— Low high-density lipoprotein (HDL) cholesterol levels are frequently observed in familial hypercholesterolemia (FH) and might be associated with functional alterations of HDL particles that may influence their efficaciousness in the reverse cholesterol transport pathway. Methods and Results— We evaluated key steps of the reverse cholesterol transport, ie, cellular free cholesterol efflux, cholesteryl ester transfer protein-mediated cholesteryl ester (CE) transfer from HDL to apolipoprotein B–containing lipoproteins, and hepatic HDL-CE uptake, in patients displaying FH (n=12) and in healthy normolipidemic control subjects (n=12). Large HDL2 particles isolated from FH patients displayed a reduced capacity to mediate free cholesterol efflux via both scavenger receptor-BI– and ABCG1–dependent pathways. A significant inverse relationship between scavenger receptor-BI–dependent HDL2 efflux capacity and carotid intima-media thickness ( r =−0.473; P =0.0186), as well as between ABCG1-dependent HDL2 efflux capacity and carotid intima-media thickness ( r =−0.485; P =0.0212), was detected. We also observed an elevated cholesteryl ester transfer protein-mediated CE transfer from HDL2 and HDL3 particles to low-density lipoprotein and a reduced capacity of HDL particles to deliver CEs to the liver. Conclusion— We demonstrated that the centripetal movement of cholesterol from peripheral tissues, including the vessel wall, to feces is defective in FH, thereby emphasizing its atherogenicity.

Objectives To identify the genetic variant in the CETP gene of the proband with high HDL-C and low CETP activity and to investigate whether HDL from the CETP-deficient subject was dysfunctional in the reverse cholesterol transport (RCT) pathway. Methods We sequenced the CETP gene and assessed its promoter activity. Cholesterol efflux and hepatic cholesteryl ester delivery studies were also performed using the proband's HDL. Results A proband was a compound heterozygote for a known D459G variant and a novel 18-bp deletion mutation in the CETP promoter. This promoter mutation markedly reduced the transcriptional activity in HepG2 cells. HDL2 from this subject increased SR-BI-mediated cholesterol efflux, whereas cholesteryl ester delivery into hepatocytes was maintained. Conclusion A novel deletion mutation in the CETP promoter is associated with high HDL-C and decreased promoter activity. HDL from this CETP-deficient subject was not dysfunctional in mediating two main steps of RCT assessed in vitro.

Objective— Therapeutic strategies to raise low plasma HDL-cholesterol levels, with concomitant normalization of the intravascular metabolism, physicochemical properties, and antiatherogenic function of HDL particles, are a major focus in atherosclerosis prevention. Methods and Results— Patients displaying Type IIB hyperlipidemia (n=14) and healthy controls (n=11) were recruited. After drug washout, dyslipidemic patients first received atorvastatin (10 mg/d) for 6 weeks and subsequently torcetrapib/atorvastatin (60/10 mg/d) for the same period. Partial CETP inhibition markedly reduced supranormal CE transfer rates to normal levels from HDL3 (−58%; P P P P Conclusion— CETP inhibition partially corrected the abnormal physicochemical and functional properties of HDL2 and HDL3 particles in type IIB hyperlipidemia. Enhanced hepatic selective uptake of HDL-CE may compensate for attenuated indirect CE transfer to apoB-containing lipoproteins via CETP attributable to torcetrapib.

We evaluated the impact of gender differences in both the quantitative and qualitative features of HDL subspecies on cellular free cholesterol efflux through the scavenger receptor class B type I (SR-BI), ABCA1, and ABCG1 pathways. For that purpose, healthy subjects (30 men and 26 women) matched for age, body mass index, triglyceride, apolipoprotein A-I, and high density lipoprotein-cholesterol (HDL-C) levels were recruited. We observed a significant increase (+14%; P < 0.03) in the capacity of whole sera from women to mediate cellular free cholesterol efflux via the SR-BI-dependent pathway compared with sera from men. Such enhanced efflux capacity resulted from a significant increase in plasma levels of large cholesteryl ester-rich HDL2 particles (+20%; P < 0.04) as well as from an enhanced capacity (+14%; P < 0.03) of these particles to mediate cellular free cholesterol efflux via SR-BI. By contrast, plasma from men displayed an enhanced free cholesterol efflux capacity (+31%; P < 0.001) via the ABCA1 transporter pathway compared with that from women, which resulted from a 2.4-fold increase in the plasma level of prebeta particles (P < 0.008). Moreover, in women, SR-BI-mediated cellular free cholesterol efflux was significantly correlated with plasma HDL-C (r = 0.72, P < 0.0001), whereas this relationship was not observed in men. In conclusion, HDL-C level may not represent the absolute indicator of the efficiency of the initial step of the reverse cholesterol transport.

International audience; Aims: Macrophage apoptosis is a prominent feature of atherosclerosis, yet whether cell death-protected macrophages would favour the resolution of already established atherosclerotic lesions, and thus hold therapeutic potential, remains unknown.Methods and results: We irradiated then transplanted into Apoe(-/-) or LDLr(-/-) recipient mice harbouring established atherosclerotic lesions, bone marrow cells from mice displaying enhanced macrophage survival through overexpression of the antiapoptotic gene hBcl-2 (Mø-hBcl2 Apoe(-/-) or Mø-hBcl2 Apoe(+/+) LDLr(-/-)). Both recipient mice exhibited decreased lesional apoptotic cell content and reduced necrotic areas when repopulated with Mø-hBcl2 mouse-derived bone marrow cells. In contrast, only LDLr(-/-) recipients showed a reduction in plasma cholesterol levels and in atherosclerotic lesions. The absence of significant reduction of plasma cholesterol levels in the context of apoE deficiency highlighted macrophage-derived apoE as key in both the regulation of plasma and tissue cholesterol levels and the progression of pre-existing lesion. Accordingly, hBcl2 expression in macrophages was associated with larger pools of Kupffer cells and Ly-6C(low) monocytes, both high producers of apoE. Additionally, increased Kupffer cells population was associated with improved clearance of apoptotic cells and modified lipoproteins.Conclusion: Collectively, these data show that promoting macrophage survival provides a supplemental source of apoE, which hinders pre-existing plaque progression.

Objectives— Postprandial atherogenic lipoproteins, characterizing high-risk patients, correlate positively with cardiovascular events. Although the effect of niacin on fasting lipids is well established, its impact on atheroprotective reverse cholesterol transport (RCT) pathway and on functional features of circulating lipoproteins during the postprandial state remains indeterminate. Approach and Results— We evaluated RCT pathway during postprandial phase in dyslipidemic patients displaying a low high-density lipoprotein (HDL) cholesterol phenotype. Ten subjects on stable statin therapy received 1 g/20 mg extended-release niacin/laropiprant (ERN/LRPT) for 4 weeks followed by 2 g/40 mg ERN/LRPT for additional 8 weeks. At each experimental period, postprandial hypertriglyceridemia and major steps of RCT, including cholesterol efflux from human macrophages, cholesteryl ester transfer protein–mediated cholesteryl ester transfer, and hepatic HDL-cholesteryl ester selective uptake were evaluated. Equally, the capacity of postprandial HDL particles isolated from patients before and after ERN/LRPT treatment to mediate RCT to feces was evaluated in vivo in human apolipoprotein B/cholesteryl ester transfer protein double transgenic mouse model. Compared with baseline, ERN/LRPT significantly reduced postprandial hypertriglyceridemia (incremental area under the curve-triglyceride: −53%; P =0.02). Postprandial increase in endogenous plasma cholesteryl ester transfer protein activity was completely abolished after ERN/LRPT treatment. Despite a slight reduction in plasma cholesterol efflux capacity from human THP-1 macrophages, evaluation of global RCT efficacy by combining both ex vivo and in vivo approaches indicate that postprandial HDL particles formed under ERN/LRPT therapy displayed a greater capacity for HDL-mediated RCT to feces. Conclusions— ERN/LRPT treatment efficiently attenuates atherogenic postprandial lipemia and stimulates HDL-mediated cholesterol return to the liver and elimination into feces during postprandial phase, thus maintaining an efficient removal of cholesterol from the body.

Rationale: High-density lipoprotein (HDL) is a heterogeneous population of particles. Differences in the capacities of HDL subfractions to remove cellular cholesterol may explain variable correlations between HDL-cholesterol and cardiovascular risk and inform future targets for HDL-related therapies. The ATP binding cassette transporter A1 (ABCA1) facilitates cholesterol efflux to lipid-free apolipoprotein A-I, but the majority of apolipoprotein A-I in the circulation is transported in a lipidated state and ABCA1-dependent efflux to individual HDL subfractions has not been systematically studied. Objective: Our aims were to determine which HDL particle subfractions are most efficient in mediating cellular cholesterol efflux from foam cell macrophages and to identify the cellular cholesterol transporters involved in this process. Methods and Results: We used reconstituted HDL particles of defined size and composition, isolated subfractions of human plasma HDL, cell lines stably expressing ABCA1 or ABCG1, and both mouse and human macrophages in which ABCA1 or ABCG1 expression was deleted. We show that ABCA1 is the major mediator of macrophage cholesterol efflux to HDL, demonstrating most marked efficiency with small, dense HDL subfractions (HDL3b and HDL3c). ABCG1 has a lesser role in cholesterol efflux and a negligible role in efflux to HDL3b and HDL3c subfractions. Conclusions: Small, dense HDL subfractions are the most efficient mediators of cholesterol efflux, and ABCA1 mediates cholesterol efflux to small dense HDL and to lipid-free apolipoprotein A-I. HDL-directed therapies should target increasing the concentrations or the cholesterol efflux capacity of small, dense HDL species in vivo.

The importance of ATP-Binding Cassette G1 (ABCG1) transporter in obesity was recently brought to light by recent findings uncovering its key role in adipogenesis with physiopathological consequences in human obesity. Thus, silencing of ABCG1 expression using an RNAi approach allows inhibition of adipocyte differentiation and maturation leading to reduction of fat mass growth in vivo in mice. Studies of ABCG1 in obese subjects validated its deleterious role in the context of obesity, suggesting that adipose tissue ABCG1 could be a potential therapeutic target in obese patients. Here, we discuss the potential feasibility of such strategy and provide a brief overview of critical issues to be considered.

The role of the ATP-binding cassette G1 (ABCG1) transporter in human pathophysiology is still largely unknown. Indeed, beyond its role in mediating free cholesterol efflux to HDL, the ABCG1 transporter equally promotes lipid accumulation in a triglyceride (TG)-rich environment through regulation of the bioavailability of lipoprotein lipase (LPL). Because both ABCG1 and LPL are expressed in adipose tissue, we hypothesized that ABCG1 is implicated in adipocyte TG storage and therefore could be a major actor in adipose tissue fat accumulation. Silencing of Abcg1 expression by RNA interference in 3T3-L1 preadipocytes compromised LPL-dependent TG accumulation during the initial phase of differentiation. Generation of stable Abcg1 knockdown 3T3-L1 adipocytes revealed that Abcg1 deficiency reduces TG storage and diminishes lipid droplet size through inhibition of Pparγ expression. Strikingly, local inhibition of adipocyte Abcg1 in adipose tissue from mice fed a high-fat diet led to a rapid decrease of adiposity and weight gain. Analysis of two frequent ABCG1 single nucleotide polymorphisms (rs1893590 [A/C] and rs1378577 [T/G]) in morbidly obese individuals indicated that elevated ABCG1 expression in adipose tissue was associated with increased PPARγ expression and adiposity concomitant to increased fat mass and BMI (haplotype AT>GC). The critical role of ABCG1 in obesity was further confirmed in independent populations of severe obese and diabetic obese individuals. This study identifies for the first time a major role of adipocyte ABCG1 in adiposity and fat mass growth and suggests that adipose ABCG1 might represent a potential therapeutic target in obesity.

We performed a strain intercross between two apoE-deficient mouse strains with a large difference in lesion susceptibility and measured aortic root lesion area in 98 female F2 progeny. Total RNA was prepared from bone marrow-derived macrophages, and RNA from the five mice with the smallest and largest lesions were used for microarray gene expression profiling. Remarkably, approximately 5% of the 12,288 expressed transcripts were differentially expressed in the atherosclerosis-susceptible and atherosclerosis-resistant bone marrow-derived macrophages (unadjusted p < 0.05), thus defining the transcriptome of macrophages associated with atherosclerosis susceptibility. Using more stringent criteria of twofold or greater change and p < 0.01, 116 and 70 transcripts were overexpressed in lesion-prone and lesion-resistant bone marrow-derived macrophages, respectively. Transcription factor binding site analysis identified two promoter elements that were found more often in the genes overexpressed in the large-lesion group, and one promoter element that was found more often in the small-lesion group. The combination of this expression profiling data with the genetic method of quantitative trait locus mapping should give powerful insights into the genes that affect atherosclerosis susceptibility in mice.

Objective— To determine the mechanism by which expression of the murine ABCA1 gene is highly induced by cAMP analogues. Methods and Results— ABCA1 mRNA turnover cannot account for its induction by cAMP. Thus cAMP induction of ABCA1 mRNA occurs at a transcriptional level. Shotgun cloning DNA fragments from the murine ABCA1 locus identified a strong cAMP responsive enhancer located in the first intron, which led to 25- to 100-fold cAMP-mediated induction of reporter gene activity. Deletions and mutations of this enhancer led to the identification a cAMP-responsive element (CRE) that was essential for the cAMP induction. Furthermore, the capacity of this CRE site to mediate the cAMP induction required the presence of a STAT3/4 element located 81 bp away. A dominant-negative CREB expression vector inhibited the cAMP induction of ABCA1, demonstrating that CREB was required for cAMP induction of ABCA1 expression in RAW264.7 cells. Conclusion— Phospho-CREB1 controls the cAMP-mediated induction of murine ABCA1 gene expression through a CRE site acting in cooperation with a nearby STAT element. This CRE site is not conserved in the human ABCA1 gene, explaining why human ABCA1 is not strongly stimulated by cAMP analogs.

The multidrug resistance P-glycoprotein (P-gp) was recently proposed to redistribute cholesterol in the plasma membrane, suggesting that P-gp could modulate cholesterol efflux to cholesterol acceptors. To address this hypothesis and to reevaluate the role of P-gp in cholesterol homeostasis, we first analyzed the role of P-gp expression on cholesterol efflux in P-gp stably transfected drug-selected LLC-MDR1 cells. Cholesterol efflux to methyl-beta-cyclodextrin (CD) was 4-fold higher in LLC-MDR1 cells compared with control LLC-PK1 cells, indicating that the accessible pool of plasma membrane cholesterol was increased by P-gp expression. However, using the P-gp-inducible cells lines HeLa MDR-Tet and 77.1 MDR-Tet, cholesterol efflux to CD, apolipoprotein A-I, or HDL was not associated with P-gp expression. In addition, we did not observe any effect of P-gp expression on cellular free and esterified cholesterol content, cholesteryl ester uptake from LDL and HDL particles, or acyl-CoA:cholesterol acyltransferase activity. Therefore, we conclude that P-gp expression does not play a major role in cholesterol homeostasis in P-gp-inducible cells and that the effects of P-gp on cholesterol homeostasis previously described in drug-selected cells might result from non-P-gp pathways that were also induced by selection for drug resistance.

The cholesteryl ester transfer protein (CETP) plays a key role in reverse cholesterol transport in mediating the transfer of cholesteryl ester from HDL to atherogenic apolipoprotein B-containing lipoproteins (VLDL, IDL, and LDL). Variation in plasma CETP mass in both normolipidemic and dyslipidemic individuals may reflect differences in CETP gene expression. As the 5' flanking sequence up to 3.4 kb of the human CETP gene contributes to transcriptional activity and tissue-specific gene expression, we evaluated the role of the distal promoter region in the modulation of CETP gene expression. In transfection experiments in HepG2 cells, we presently demonstrate that an Alu repeat (-2,153/-2,414) acts as a repressive element, whereas a binding site for the orphan nuclear receptor CYP7A promoter binding factor (CPF), at position -1,042, facilitates activation of human CETP promoter activity. Cotransfection of liver receptor homolog, the mouse homologue of CPF in HEK293 cells that lack CPF, indicated that the -1,042 CPF site is sufficient to induce CPF-mediated activation of CETP promoter activity. Taken together, our results indicate that the distal-promoter region is a major component in the modulation of human CETP promoter activity, and that it may contribute to the liver-specific expression of the CETP gene.

The effect of atorvastatin, at 10 mg or 40 mg for 6 wk, on lipid and lipoprotein metabolism during the postprandial phase in subjects (n = 11) displaying type IIB hyperlipidemia was evaluated. The postprandial increment in area under the curve above baseline concentrations in type IIB subjects was significantly decreased by atorvastatin for plasma triglyceride (A10: -42% and A40: -55%, P < 0.01), chylomicrons (CMs) (A10: -24% and A40: -40%, P < 0.03) and VLDL-1 (A10: -54% and A40: -52%, P < 0.02). Before atorvastatin therapy, postprandial cholesteryl ester (CE) transfer from high-density lipoprotein (HDL) to CMs (2.5-fold; P < 0.005), very low-density lipoprotein (VLDL)-1 (1.8-fold; P < 0.005), VLDL-2 (1.4-fold; P < 0.05), and intermediate-density lipoproteins (1.4-fold; P < 0.05) were significantly increased 4 h postprandially. Following statin treatment, the postprandial transfer of CE from HDL to triglyceride-rich lipoproteins (TRLs) at the 4-h time point was significantly reduced at 10 mg/d (-26%; P < 0.05) and at 40 mg/d (-24%; P < 0.05), compared with that before treatment. Such postprandial increase in CE transferred from HDLs to TRLs arose exclusively from accelerated CE transfer from HDLs to CMs (2.5-fold; P < 0.005). In conclusion, atorvastatin attenuates the abnormal intravascular remodeling of postprandial TRL particles via marked reduction in CE transfer in type IIB hyperlipidemia and diminishes the postprandial formation and accumulation of CMs and VLDL-1.

Type IIB hyperlipidemia is associated with premature vascular disease, an atherogenic lipoprotein phenotype characterised by elevated levels of triglyceride-rich VLDL and small dense LDL, together with subnormal levels of HDL. The dose-dependent and independent effects of a potent HMGCoA reductase inhibitor, Atorvastatin, at daily doses of 10 and 40 mg, were evaluated on triglyceride-rich lipoprotein subclasses (VLDL-1, VLDL-2 and IDL), on the major LDL subclasses (light LDL, LDL-1+LDL-2, d: 1.019–1.029 g/ml; intermediate LDL, LDL-3, d: 1.029–1.039 g/ml and small dense LDL, LDL-4+LDL+5, d: 1.039–1.063 g/ml), on CETP-mediated cholesteryl ester transfer from HDL to apoB-containing lipoproteins, on phospholipid transfer protein activity and on plasma-mediated cellular cholesterol efflux in patients (n=10) displaying type IIB hyperlipidemia. Plasma concentrations of triglyceride-rich lipoprotein subclasses (TRL: VLDL-1, Sf 60–400; VLDL-2, Sf 20–60 and IDL, Sf 12–20) and of LDL (d: 1.019–1.063 g/ml) were markedly diminished after 6 weeks of statin treatment at 10 mg per day (−31 and −36%, respectively; P

The plasma cholesteryl ester transfer protein (CETP) plays a key role in reverse cholesterol transport (RCT) by mediating the transfer of cholesteryl ester (CE) from high-density lipoprotein (HDL) to atherogenic ApoB-containing lipoproteins, including VLDL, IDL and LDL. We describe a new polymorphism located at position −971 in the human CETP gene promoter, which corresponds to a G/A substitution at a potential Ava I restriction site. The relationship between the −971G/A polymorphism, plasma lipid parameters and plasma CETP concentration was evaluated in the Etude Cas-Temoins de l'Infarctus du Myocarde (control–myocardial infarction cases) cohort, and revealed that the −971G/A polymorphism (A allele frequency: 0.491) was significantly associated with both plasma high-density lipoprotein cholesterol (HDL-C) levels and CETP concentration ( P =0.006 and 0.009, respectively). Subjects with genotype −971GG displayed both low HDL-C levels and high plasma CETP concentration, while genotype −971AA subjects displayed the inverse relationship. Evaluation of potential interactions between the −971G/A and the −629C/A or TaqIB polymorphisms demonstrated that the −971G/A polymorphism interacts significantly with the functional −629C/A site and the TaqIB polymorphism with respect to plasma HDL-C levels ( P =0.0014 and 0.012, respectively), but does not affect plasma CETP concentration. These results clearly suggest that the interaction between the 971G/A polymorphism and either the −629C/A or the TaqIB polymorphism on plasma CETP concentration is different than that implicated in HDL-C levels. Transient transfection of HepG2 cells revealed that the −971G/A polymorphism did not modulate transcriptional activity of the human CETP gene promoter. The −971G/A promoter polymorphism therefore constitutes a non-functional marker. Furthermore, the observed effects of the −971G/A polymorphism on both plasma CETP concentration and HDL-C levels are due to functional variants in linkage disequilibrium with it. Our findings strongly suggest the existence of as yet unidentified functional polymorphisms in the CETP gene promoter that could explain the association between specific polymorphisms of the CETP gene and both plasma HDL-C and CETP concentrations.

Nuclear Liver X Receptors activation by synthetic agonists was proven to be atheroprotective in mice; an effect likely based on stimulation of cellular cholesterol efflux from arterial macrophages. However, mechanisms involved in free cholesterol efflux from mouse macrophages appear distinct from those operating in human macrophages. The objective of this study was to decipher precise cellular mechanisms controlling free cholesterol efflux from human macrophages upon LXR stimulation. In THP-1 and human monocyte-derived macrophages (HMDM), treatment with the LXR agonist GW3965 efficiently induced ARL7 expression (6-fold, p Specific targeting of each LXR isoforms, LXRα and LXRβ, by RNAi revealed that LXRα silencing in THP-1 and HMDM reduced significantly expression of cholesterol transporters ABCA1, ABCG1 and receptor SR-BI/Cla-1 mRNA levels, as well as free cholesterol efflux to apoA1 (-30%, p We conclude that LXR-mediated stimulation of cholesterol efflux from human macrophages is a two-steps mechanism. First, LXR activation promotes ARL7-dependent free cholesterol transport to plasma membrane, mostly in lipid raft domains. Then, membrane free cholesterol is exported to apoA1 and HDL acceptors through ABCA1; this latter step being controlled selectively by LXRα.

Introduction: The role of niacin has been called into question by recent outcome trials showing no benefit on cardiovascular events. Still, for certain high risk patients not achieving their LDL-C target niacin remains a significant therapeutic option. Hypothesis: Although the effect of niacin on fasting lipids is well established, its impact on cholesterol efflux and lipoprotein metabolism during the atherogenic postprandial state remains indeterminate. Methods: We evaluated the effect of extended-release niacin with laropiprant (ERN/LRP) on postprandial lipoprotein metabolism in 10 subjects on stable statin therapy. All subjects received 1g/20mg ERN/LRP for 4 weeks and then 2 g/40mg ERN/LRP for 8 weeks. At each experimental period, all patients consumed a standardized test meal (1100kcal). Postprandial hypertriglyceridemia (HTG) and plasma efflux capacity through THP-1 macrophages and cellular models overexpressing ABCA1, ABCG1 and SR-BI were evaluated. Results: Compared with baseline, ERN/LRP significantly improved postprandial HTG by reducing the area under the curve AUC for chylomicrons (-50%, p=0.004), VLDL-1 (-43%, p=0.0001) and VLDL-2 (-28%, p=0.01). These latter reductions induce a concomitant decrease in CETP activity during the postprandial state (-11.7%;p=0.03, -12%;p=0.01, -18%;p=0.0003, -13%;p=0.0006, 2h, 4h, 6h and 8h respectively after fat load). Plasma cholesterol efflux capacity from human THP-1 macrophages was reduced throughout the postprandial phase (AUC:-20%, p=0.05) following ERN/LRP therapy as a result of a specific reduction in ABCA1 dependent efflux pathway (AUC:-10%; p Conclusions: ERN/LRP treatment reduces physiological triglyceride rich lipoproteins synthesis which indirectly results in a significant reduction in CETP activity. By this mechanism, intravascular remodeling of HDL is altered, thus affecting regeneration of ApoA1/preβ-HDL, the preferential cellular cholesterol acceptors via ABCA1 pathway. We conclude that Niacin therapy is associated with an overall reduction in the early step of RCT representing therefore one potential mechanistic hypothesis for the disappointing results in recent clinical trials

Objectives CETP or HL deficiencies lead to a marked increase in HDL-C levels however the atheroprotective effect of this phenotype, in particular the ability of HDL particles to remove cholesterol from human macrophages, remains to be determined. Methods We measured cholesterol efflux from human THP-1 macrophages to total plasma or to isolated HDL subfractions in patients with HALP carrying molecular defect in either the CETP or LIPC gene. Results We demonstrate that HALP is associated with an increased plasma cholesterol efflux capacity from human macrophages. This observation is primarily related to a stimulation of both SR-BI and ABCA1 dependent efflux pathways as a result of quantitative elevation in HDL2 and enhanced intrinsic capacity of HDL3 subspecies, respectively. Conclusion HDL particles from HALP patients with molecular defect within either CETP or LIPC gene are not dysfunctional and are efficient to stimulate cholesterol efflux from human macrophages.

International audience; Hepatitis C virus (HCV) establishes infection using host lipid metabolism pathways that are thus considered potential targets for indirect anti-HCV strategies. HCV enters the cell via clathrin-dependent endocytosis, interacting with several receptors, and virus-cell fusion, which depends on acidic pH and the integrity of cholesterol-rich domains of the hepatocyte membrane. The ATP-binding Cassette Transporter A1 (ABCA1) mediates cholesterol efflux from hepatocytes to extracellular Apolipoprotein A1 and moves cholesterol within cell membranes. Furthermore, it generates high-density lipoprotein (HDL) particles. HDL protects against arteriosclerosis and cardiovascular disease. We show that the up-regulation of ABCA1 gene expression and its cholesterol efflux function in Huh7.5 hepatoma cells, using the liver X receptor (LXR) agonist GW3965, impairs HCV infection and decreases levels of virus produced. ABCA1-stimulation inhibited HCV cell entry, acting on virus-host cell fusion, but had no impact on virus attachment, replication, or assembly/secretion. It did not affect infectivity or properties of virus particles produced. Silencing of the ABCA1 gene and reduction of the specific cholesterol efflux function counteracted the inhibitory effect of the GW3965 on HCV infection, providing evidence for a key role of ABCA1 in this process. Impaired virus-cell entry correlated with the reorganisation of cholesterol-rich membrane microdomains (lipid rafts). The inhibitory effect could be reversed by an exogenous cholesterol supply, indicating that restriction of HCV infection was induced by changes of cholesterol content/distribution in membrane regions essential for virus-cell fusion. Stimulation of ABCA1 expression by GW3965 inhibited HCV infection of both human primary hepatocytes and isolated human liver slices. This study reveals that pharmacological stimulation of the ABCA1-dependent cholesterol efflux pathway disrupts membrane cholesterol homeostasis, leading to the inhibition of virus-cell fusion and thus HCV cell entry. Therefore besides other beneficial roles, ABCA1 might represent a potential target for HCV therapy.

Objective— High-density lipoprotein (HDL) displays multiple atheroprotective activities and is highly heterogeneous in structure, composition, and function; the molecular determinants of atheroprotective functions of HDL are incompletely understood. Because phospholipids represent a major bioactive lipid component of HDL, we characterized the phosphosphingolipidome of major normolipidemic HDL subpopulations and related it to HDL functionality. Approach and Results— Using an original liquid chromatography–mass spectrometry/mass spectrometry methodology for phospholipid and sphingolipid profiling, 162 individual molecular lipid species were quantified across the 9 lipid subclasses, in the order of decreasing abundance, phosphatidylcholine>sphingomyelin>lysophosphatidylcholine>phosphatidylethanolamine>phosphatidylinositol>ceramide>phosphatidylserine>phosphatidylglycerol>phosphatidic acid. When data were expressed relative to total lipid, the contents of lysophosphatidylcholine and of negatively charged phosphatidylserine and phosphatidic acid increased progressively with increase in hydrated density of HDL, whereas the proportions of sphingomyelin and ceramide decreased. Key biological activities of HDL subpopulations, notably cholesterol efflux capacity from human THP-1 macrophages, antioxidative activity toward low-density lipoprotein oxidation, antithrombotic activity in human platelets, cell-free anti-inflammatory activity, and antiapoptotic activity in endothelial cells, were predominantly associated with small, dense, protein-rich HDL3. The biological activities of HDL particles were strongly intercorrelated, exhibiting significant correlations with multiple components of the HDL phosphosphingolipidome. Specifically, the content of phosphatidylserine revealed positive correlations with all metrics of HDL functionality, reflecting enrichment of phosphatidylserine in small, dense HDL3. Conclusions— Our structure–function analysis thereby reveals that the HDL lipidome may strongly affect atheroprotective functionality.

Objective— We investigated the impact of several genetic variants located in genes encoding for proteins involved in biogenesis, maturation, and intravascular remodeling of high density lipoprotein (HDL) particles on plasma efflux capacity. Approach and Results— The capacity of whole-plasma to mediate cholesterol efflux from cholesterol-loaded human THP-1 macrophages was measured in 846 individuals (450 men and 396 women). We demonstrated that rs17231506 ( CETP c.–1337 C>T), rs2230806 ( ABCA1 p.R219K), rs1799837 ( APOA1 c.–75 G>A), rs5086 ( APOAII c.–265 T>C), and rs1800588 ( LIPC c.–514 C>T) single nucleotide polymorphisms (SNPs) significantly modulate the capacity of whole-plasma to mediate cholesterol efflux from human macrophages in a sex-dependent manner. Such associations were independent of circulating plasma lipid levels (HDL-cholesterol, triglyceride, low density lipoprotein-cholesterol). In women, we identified the APOA1 c.–75 G>A and the LIPC c.–514 C>T variants as major contributors of interindividual variability of plasma efflux capacity, whereas the ABCA1 p.R219K and the APOAII c.–265 T>C SNPs mostly contribute to total variance of plasma efflux capacity in men. Multiple regression analyses revealed that the 7 SNPs tested accounted together for approximately 6% of total plasma efflux capacity. We demonstrated that genetically determined plasma efflux capacity represents a better predictor of macrophage cholesterol removal, as compared with plasma HDL-cholesterol levels. Conclusions— Genetic variants located within genes encoding proteins involved in HDL metabolism significantly impact plasma efflux capacity independently of variation in plasma HDL-cholesterol levels.

Objective— We aim to identify the impact of endogenous cholesteryl ester transfer protein (CETP) activity on plasma capacity to mediate free cholesterol efflux from human macrophages. Methods and Results— Endogenous plasma CETP activity was measured in a population of 348 women. We defined a low CETP group corresponding to subjects displaying an endogenous plasma CETP activity within the first tertile and a high CETP group corresponding to subjects with an endogenous plasma CETP activity within the third tertile. Subjects from the high CETP activity group displayed a significant increase in the capacity of their plasma (+8.2%; P =0.001) to mediate cholesterol efflux from human acute monocytic leukemia cell line human macrophages and from ATP-binding cassette transporter A1-dependent pathway (+23.4%; P =0.0001) as compared with those from the low CETP activity group. Multivariate analyses revealed that the impact of CETP activity was independent of plasma lipids levels. Pre–β1-high-density lipoprotein concentrations were significantly elevated (+29.6%; P =0.01) in the high CETP activity group as compared with the low CETP activity group. A positive correlation between pre–β1-high-density lipoprotein levels and plasma efflux efficiency from human acute monocytic leukemia cell line human macrophages was observed ( r =0.29, P =0.02). Conclusion— CETP leading to the improvement of plasma efflux capacity, as a result of efficient pre–β-high-density lipoprotein formation and ATP-binding cassette transporter A1 efflux, should be preserved to prevent lipid accumulation in human macrophages.

In familial hypercholesterolemia (FH), low HDL cholesterol (HDL-C) levels are associated with functional alterations of HDL particles that reduce their capacity to mediate the reverse cholesterol transport (RCT) pathway. The objective of this study was to evaluate the consequences of LDL apheresis on the effi cacy of the RCT pathway in FH patients. LDL apheresis markedly reduced abnormal accel- erated cholesteryl ester transfer protein (CETP) -mediated cholesteryl ester (CE) transfer from HDL to LDL, thus reducing their CE content. Equally, we observed a major decrease ( 53%; P < 0.0001) in pre- 1-HDL levels. The capacity of whole plasma to mediate free cholesterol effl ux from human macrophages was reduced ( 15%; P < 0.02) following LDL apheresis. Such reduction resulted from a marked decrease in the ABCA1-dependent effl ux ( 71%; P < 0.0001) in the scavenger receptor class B type I-dependent effl ux ( 21%; P < 0.0001) and in the ABCG1-dependent pathway ( 15%; P < 0.04). However, HDL particles isolated from FH patients before and after LDL apheresis displayed a similar capacity to mediate cellular free cholesterol effl ux or to deliver CE to hepatic cells. We demonstrate that rapid removal of circulating lipoprotein particles by LDL apheresis transitorily reduces RCT. However, LDL aphere- sis is without impact on the intrinsic ability of HDL particles to promote either cellular free cholesterol effl ux from mac- rophages or to deliver CE to hepatic cells. —Orsoni, A., E. F. Villard, E. Bruckert, P. Robillard, A. Carrie, D. Bonnefont- Rousselot, M. J. Chapman, G. M. Dallinga-Thie, W. Le Goff, and M. Guerin. Impact of LDL apheresis on atheroprotec- tive reverse cholesterol transport pathway in familial hyper- cholesterolemia. J. Lipid Res . 2012. 53: 767-775.