Circumventing Cardiovascular Calamities: The Dawn of ANGPTL3 Blockade in Severe Dyslipidemia Management.

The landscape of severe dyslipidemia treatment is undergoing a remarkable transformation with the advent of angiopoietin-like 3 (ANGPTL3) inhibitors. ANGPTL3, a pivotal regulator of lipoprotein lipase and endothelial lipase, orchestrates the catabolism of triglyceride-rich and high-density lipoproteins, thus playing a critical role in lipid homeostasis. This review article examines the therapeutic potential of ANGPTL3 blockade and its implications for patients with severe dyslipidemias, particularly those unresponsive to traditional lipid-lowering regimens. We delve into the molecular mechanisms by which ANGPTL3 influences lipid metabolism and appraise the clinical utility of emerging therapeutics, such as monoclonal antibodies and antisense oligonucleotides. Moreover, we discuss the impact of ANGPTL3 inhibition on cardiovascular risk factors and project its promising role in reducing cardiovascular morbidity and mortality. The narrative synthesizes data from recent clinical trials, including the efficacy and safety profiles of ANGPTL3 inhibitors, and forecasts the potential of these agents to revolutionize the management of dyslipidemic conditions. The advent of ANGPTL3-targeted therapies signifies a potential breakthrough in the therapeutic armamentarium against complex lipid disorders, heralding a new era of precision medicine in cardiovascular risk mitigation.

In Silico Description of the Direct Inhibition Mechanism of Endothelial Lipase by ANGPTL3.

Angiopoietin-like protein 3 (ANGPTL3) is a plasmatic protein that plays a crucial role in lipoprotein metabolism by inhibiting the lipoprotein lipase (LPL) and the endothelial lipase (EL) responsible for the hydrolysis of phospholipids on high-density lipoprotein (HDL). Interest in developing new pharmacological therapies aimed at inhibiting ANGPTL3 has been growing due to the hypolipidemic and antiatherogenic profile observed in its absence. The goal of this study was the in silico characterization of the interaction between ANGPTL3 and EL. Because of the lack of any structural information on both the trimeric coiled-coil N-terminal domain of ANGPTL3 and the EL homodimer as well as data regarding their interactions, the first step was to obtain the three-dimensional model of these two proteins. The models were then refined via molecular dynamics (MD) simulations and used to investigate the interaction mechanism. The analysis of interactions in different docking poses and their refinement via MD allowed the identification of three specific glutamates of ANGPTL3 that recognize a positively charged patch on the surface of EL. These ANGPTL3 key residues, i.e., Glu154, Glu157, and Glu160, could form a putative molecular recognition site for EL. This study paves the way for future investigations aimed at confirming the recognition site and at designing novel inhibitors of ANGPTL3.

Expression of Placental Lipid Transporters in Pregnancies Complicated by Gestational and Type 1 Diabetes Mellitus.

The objective of the study was to assess the expression of proteins responsible for placental lipid transport in term pregnancies complicated by well-controlled gestational (GDM) and type 1 diabetes mellitus (PGDM). A total of 80 placental samples were obtained from patients diagnosed with PGDM (n = 20), GDM treated with diet (GDMG1, n = 20), GDM treated with diet and insulin (GDMG2, n = 20), and a non-diabetic control group (n = 20). Umbilical and uterine artery blood flows were assessed by means of ultrasound in the period prior to delivery and computer-assisted quantitative morphometry of immunostained placental sections was performed to determine the expression of selected proteins. The morphometric analysis performed for the vascular density-matched placental samples demonstrated a significant increase in the expression of fatty acid translocase (CD36), fatty acid binding proteins (FABP1, FABP4 and FABP5), as well as a decrease in the expression of endothelial lipase (EL) and fatty acid transport protein (FATP4) in the PGDM-complicated pregnancies as compared to the GDMG1 and control groups (p < 0.05). No significant differences with regard to the placental expression of lipoprotein lipase (LPL) and FATP6 protein between GDM/PGDM and non-diabetic patients were noted. Maternal pre-pregnancy weight, body mass index, placental weight as well as the expression of LPL and FABP4 were selected by the linear regression model as the strongest contributors to the fetal birth weight. To conclude, in placentas derived from pregnancies complicated by well-controlled PGDM, the expression of several lipid transporters, including EL, CD36, FATP4, FABP1, FABP4 and FABP5, is altered. Nonetheless, only LPL and FABP4 were significant predictors of the fetal birth weight.

A novel fully human anti-NT-ANGPTL3 antibody from phage display library exhibits potent ApoB, TG, and LDL-C lowering activities in hyperlipidemia mice.

Dyslipidemia is characterized by elevated plasma levels of low-density lipoprotein cholesterol (LDL-C), triglycerides (TG), and TG-rich lipoprotein (TGRLs) in circulation, and is closely associated with the incidence and development of cardiovascular disease. Angiopoietin-like protein 3 (ANGPTL3) deficiency has been identified as a cause of familial combined hypolipidemia in humans, which allows it to be an important therapeutic target for reducing plasma lipids. Here, we report the discovery and characterization of a novel fully human antibody F1519-D95aA against N-terminal ANGPTL3 (NT-ANGPTL3), which potently inhibits NT-ANGPTL3 with a KD as low as 9.21 nM. In hyperlipidemic mice, F1519-D95aA shows higher apolipoprotein B (ApoB) and TG-lowering, and similar LDL-C reducing activity as compared to positive control Evinacumab (56.50% vs 26.01% decrease in serum ApoB levels, 30.84% vs 25.28% decrease in serum TG levels, 23.32% vs 22.52% decrease in serum LDLC levels, relative to vehicle group). Molecular docking and binding energy calculations reveal that the F1519-D95aA-ANGPTL3 complex (10 hydrogen bonds, -65.51 kcal/mol) is more stable than the Evinacumab-ANGPTL3 complex (4 hydrogen bonds, -63.76 kcal/mol). Importantly, F1519-D95aA binds to ANGPTL3 with different residues in ANGPTL3 from Evinacumab, suggesting that F1519-D95aA may be useful for the treatment of patients resistant to Evinacumab. In conclusion, F1519-D95aA is a novel fully human anti-NT-ANGPTL3 antibody with potent plasma ApoB, TG, and LDL-C lowering activities, which can potentially serve as a therapeutic agent for hyperlipidemia and relevant cardiovascular diseases.

Multivessel Coronary Artery Disease Complicated by Diabetes Mellitus Has a Relatively Small Effect on Endothelial and Lipoprotein Lipases Expression in the Human Atrial Myocardium and Coronary Perivascular Adipose Tissue.

Endothelial (EL) and lipoprotein (LPL) lipases are enzymes involved in lipoproteins metabolism and formation of atherosclerosis, a pathological feature of coronary artery disease (CAD). This paper examines the role of the lipases in the right atrial appendage (RAA) and coronary perivascular adipose tissue (PVAT) of patients with CAD alone or with accompanying diabetes. Additionally, correlation analysis for plasma concentration of the lipases, apolipoproteins (ApoA-ApoJ) and blood lipids (Chol, HDL-C, LDL-C, TAG) was performed. We observed that CAD had little effect on the lipases gene/protein levels in the RAA, while their transcript content was elevated in the PVAT of diabetic CAD patients. Interestingly, the RAA was characterized by higher expression of EL/LPL (EL: +1-fold for mRNA, +5-fold for protein; LPL: +2.8-fold for mRNA, +12-fold for protein) compared to PVAT. Furthermore, ApoA1 plasma concentration was decreased, whereas ApoC1 and ApoH were increased in the patients with CAD and/or diabetes. The concentrations of ApoC3 and ApoD were strongly positively correlated with TAG content in the blood, and the same was true for ApoB with respect to LDL-C and total cholesterol. Although plasma concentrations of EL/LPL were elevated in the patients with diabetes, CAD alone had little effect on blood, myocardial and perivascular fat expression of the lipases.

Endothelial Lipase Variant, T111I, Does Not Alter Inhibition by Angiopoietin-like Proteins.

High levels of HDL-C are correlated with a decreased risk of cardiovascular disease. HDL-C levels are modulated in part by the secreted phospholipase, endothelial lipase (EL), which hydrolyzes the phospholipids of HDL and decreases circulating HDL-C concentrations. A 584C/T polymorphism in LIPG, the gene which encodes EL, was first identified in individuals with increased HDL levels. This polymorphism results in a T111I point mutation the EL protein. The association between this variant, HDL levels, and the risk of coronary artery disease (CAD) in humans has been extensively studied, but the findings have been inconsistent. In this study, we took a biochemical approach, investigating how the T111I variant affected EL activity, structure, and stability. Moreover, we tested whether the T111I variant altered the inhibition of phospholipase activity by angiopoietin-like 3 (ANGPTL3) and angiopoietin-like 4 (ANGPTL4), two known EL inhibitors. We found that neither the stability nor enzymatic activity of EL was altered by the T111I variant. Moreover, we found no difference between wild-type and T111I EL in their ability to be inhibited by ANGPTL proteins. These data suggest that any effect this variant may have on HDL-C levels or cardiovascular disease are not mediated through alterations in these functions.

Associations between Endothelial Lipase and Apolipoprotein B-Containing Lipoproteins Differ in Healthy Volunteers and Metabolic Syndrome Patients.

The association between serum levels of endothelial lipase (EL) and the serum levels and composition of apolipoprotein B (apoB)-containing lipoproteins in healthy subjects and patients with metabolic syndrome (MS) remained unexplored. Therefore, in the present study, we determined the serum levels and lipid content of apoB-containing lipoproteins using nuclear magnetic resonance (NMR) spectroscopy and examined their association with EL serum levels in healthy volunteers (HVs) and MS patients. EL was significantly negatively correlated with the serum levels of cholesterol in large very low-density lipoprotein (VLDL) particles, as well as with total-cholesterol-, free-cholesterol-, triglyceride-, and phospholipid-contents of VLDL and intermediate-density lipoprotein particles in MS patients but not in HVs. In contrast, EL serum levels were significantly positively correlated with the serum levels of apoB, triglycerides, and phospholipids in large low-density lipoprotein particles in HVs but not in MS patients. EL serum levels as well as the serum levels and lipid content of the majority of apoB-containing lipoprotein subclasses were markedly different in MS patients compared with HVs. We conclude that EL serum levels are associated with the serum levels and lipid content of apoB-containing lipoproteins and that these associations are markedly affected by MS.

Associations between Endothelial Lipase, High-Density Lipoprotein, and Endothelial Function Differ in Healthy Volunteers and Metabolic Syndrome Patients.

Metabolic syndrome (MS) is characterized by endothelial- and high-density lipoprotein (HDL) dysfunction and increased endothelial lipase (EL) serum levels. We examined the associations between EL serum levels, HDL (serum levels, lipid content, and function), and endothelial function in healthy volunteers (HV) and MS patients. Flow-mediated dilation (FMD), nitroglycerin-mediated dilation (NMD), serum levels of HDL subclasses (measured by nuclear magnetic resonance (NMR) spectroscopy), and EL serum levels differed significantly between HV and MS patients. The serum levels of triglycerides in large HDL particles were significantly positively correlated with FMD and NMD in HV, but not in MS patients. Cholesterol (C) and phospholipid (PL) contents of large HDL particles, calculated as HDL1-C/HDL1-apoA-I and HDL1-PL/HDL1-apoA-I, respectively, were significantly negatively correlated with FMD in HV, but not in MS patients. Cholesterol efflux capacity and arylesterase activity of HDL, as well as EL, were correlated with neither FMD nor NMD. EL was significantly negatively correlated with HDL-PL/HDL-apoA-I in HV, but not in MS patients, and with serum levels of small dense HDL containing apolipoprotein A-II in MS patients, but not in HV. We conclude that MS modulates the association between HDL and endothelial function, as well as between EL and HDL. HDL cholesterol efflux capacity and arylesterase activity, as well as EL serum levels, are not associated with endothelial function in HV or MS patients.

Proprotein Convertase Subtilisin/Kexin 6 in Cardiovascular Biology and Disease.

Proprotein convertase subtilisin/kexin 6 (PCSK6) is a secreted serine protease expressed in most major organs, where it cleaves a wide range of growth factors, signaling molecules, peptide hormones, proteolytic enzymes, and adhesion proteins. Studies in Pcsk6-deficient mice have demonstrated the importance of Pcsk6 in embryonic development, body axis specification, ovarian function, and extracellular matrix remodeling in articular cartilage. In the cardiovascular system, PCSK6 acts as a key modulator in heart formation, lipoprotein metabolism, body fluid homeostasis, cardiac repair, and vascular remodeling. To date, dysregulated PCSK6 expression or function has been implicated in major cardiovascular diseases, including atrial septal defects, hypertension, atherosclerosis, myocardial infarction, and cardiac aging. In this review, we describe biochemical characteristics and posttranslational modifications of PCSK6. Moreover, we discuss the role of PCSK6 and related molecular mechanisms in cardiovascular biology and disease.

ANGPTL3 as a Drug Target in Hyperlipidemia and Atherosclerosis.

PURPOSE OF REVIEW: Elevated low-density lipoprotein cholesterol (LDL-C) and triglyceride-rich lipoproteins (TRLs) or remnants are important risk factors for the development of atherosclerotic cardiovascular disease (ASCVD). The ongoing challenge of not being able to achieve recommended LDL-C targets despite maximally tolerated lipid-lowering therapy (LLT) has led to the development of novel therapeutic agents including angiopoietin-like 3 (ANGPTL3) inhibitors. RECENT FINDINGS: ANGPTL3 is a glycoprotein produced by the liver that inhibits lipoprotein lipase and endothelial lipase. Data from genetic and clinical studies have shown that a lower ANGPTL3 level is associated with lower plasma LDL-C, triglyceride (TG), and other lipoproteins. Pharmacological inactivation of ANGPTL3 with the monoclonal antibody, evinacumab, results in a 50% reduction in LDL-C, even in patients with homozygous familial hypercholesterolemia (HoFH). The safe and effective targeted delivery of nucleic acid-based therapies will shape the future of the lipid arena. ANGPTL3 is a novel target in lipoprotein metabolism, targeting not only LDL-C via an LDL-receptor (LDLR) independent mechanism but also TRLs and carries a significant promise for further ASCVD risk reduction.

Plasma HDL pattern, cholesterol efflux and cholesterol loading capacity of serum in carriers of a novel missense variant (Gly176Trp) of endothelial lipase.

BACKGROUND: Loss of function variants of LIPG gene encoding endothelial lipase (EL) are associated with primary hyperalphalipoproteinemia (HALP), a lipid disorder characterized by elevated plasma levels of high density lipoprotein cholesterol (HDL-C). OBJECTIVE: Aim of the study was the phenotypic and genotypic characterization of a family with primary HALP. METHODS: HDL subclasses distribution was determined by polyacrylamide gradient gel electrophoresis. Serum content of preß-HDL was assessed by (2D)-electrophoresis. Cholesterol efflux capacity (CEC) of serum mediated by ABCA1, ABCG1 or SR-BI was assessed using cells expressing these proteins. Cholesterol loading capacity (CLC) of serum was assayed using cultured human macrophages. Next generation sequencing was used for DNA analysis. Plasma EL mass was determined by ELISA. RESULTS: Three family members had elevated plasma HDL-C, apoA-I and total phospholipids, as well as a reduced content of preß-HDL. These subjects were heterozygous carriers of a novel variant of LIPG gene [c.526 G>T, p.(Gly176Trp)] found to be deleterious in silico. Plasma EL mass in carriers was lower than in controls. CEC of sera mediated by ABCA1 and ABCG1 transporters was substantially reduced in the carriers. This effect was maintained after correction for serum HDL concentration. The sera of carriers were found to have a higher CLC in cultured human macrophages than control sera. CONCLUSION: The novel p.(Gly176Trp) variant of endothelial lipase is associated with changes in HDL composition and subclass distribution as well as with functional changes affecting cholesterol efflux capacity of serum which suggest a defect in the early steps of revere cholesterol transport.

An updated ANGPTL3-4-8 model as a mechanism of triglyceride partitioning between fat and oxidative tissues.

In mammals, triglyceride (TG), the main form of lipids for storing and providing energy, is stored in white adipose tissue (WAT) after food intake, while during fasting it is routed to oxidative tissues (heart and skeletal muscle) for energy production, a process referred to as TG partitioning. Lipoprotein lipase (LPL), a rate-limiting enzyme in this fundamental physiological process, hydrolyzes circulating TG to generate free fatty acids that are taken up by peripheral tissues. The postprandial activity of LPL declines in oxidative tissues but rises in WAT, directing TG to WAT; the reverse is true during fasting. However, the molecular mechanism in regulating tissue-specific LPL activity during the fed-fast cycle has not been completely understood. Research on angiopoietin-like (ANGPTL) proteins (A3, A4, and A8) has resulted in an ANGPTL3-4-8 model to explain the TG partitioning between WAT and oxidative tissues. Food intake induces A8 expression in the liver and WAT. Liver A8 activates A3 by forming the A3-8 complex, which is then secreted into the circulation. The A3-8 complex acts in an endocrine manner to inhibit LPL in oxidative tissues. WAT A8 forms the A4-8 complex, which acts locally to block A4's LPL-inhibiting activity. Therefore, the postprandial activity of LPL is low in oxidative tissues but high in WAT, directing circulating TG to WAT. Conversely, during fasting, reduced A8 expression in the liver and WAT disables A3 from inhibiting oxidative-tissue LPL and restores WAT A4's LPL-inhibiting activity, respectively. Thus, the fasting LPL activity is high in oxidative tissues but low in WAT, directing TG to the former. According to the model, we hypothesize that A8 antagonism has the potential to simultaneously reduce TG and increase HDL-cholesterol plasma levels. Future research on A3, A4, and A8 can hopefully provide more insights into human health, disease, and therapeutics.

Angiopoietin-like protein 4 (ANGPTL4) is an inhibitor of endothelial lipase (EL) while the ANGPTL4/8 complex has reduced EL-inhibitory activity.

We previously demonstrated that angiopoietin-like protein 8 (ANGPTL8) forms ANGPTL3/8 and ANGPTL4/8 complexes that increase with feeding to direct fatty acids (FA) toward adipose tissue through differential modulation of lipoprotein lipase (LPL) activity. Each complex correlated inversely with high density lipoprotein cholesterol (HDL) in control subjects. We thus investigated ANGPTL3/8 and ANGPTL4/8 levels in type 2 diabetes patients, who can present with decreased HDL. While ANGPTL3/8 levels in type 2 diabetes patients were similar to those previously observed in normal controls, ANGPTL4/8 levels were roughly twice as high as those in control subjects. Concentrations of ANGPTL3/8 and ANGPTL4/8 in type 2 diabetes patients were inversely correlated with HDL, with the correlation being significant for ANGPTL4/8. We therefore measured the ability of the various ANGPTL proteins and complexes to inhibit endothelial lipase (EL), the enzyme which hydrolyzes phospholipids (PL) in HDL. While confirming ANGPTL3 as an EL inhibitor, we found that ANGPTL4 was a more potent EL inhibitor than ANGPTL3. Interestingly, we observed that while ANGPTL3/8 had increased EL-inhibitory activity compared to ANGPTL3 alone, ANGPTL4/8 exhibited decreased potency in inhibiting EL compared to ANGPTL4 alone. Together, these results show for the first time that ANGPTL4 is a more potent EL inhibitor than ANGPTL3 and suggest a possible reason for why ANGPTL4/8 levels are correlated inversely with HDL.

Angiopoietin-like 3 inhibition of endothelial lipase is not modulated by angiopoietin-like 8.

High plasma triglyceride (TG) levels and low HDL-C levels are risk factors for atherosclerosis and cardiovascular disease. Both plasma TG and HDL-C levels are regulated in part by the circulating inhibitor, angiopoietin-like 3 (ANGPTL3). ANGPTL3 inhibits the phospholipase, endothelial lipase (EL), which hydrolyzes the phospholipids of HDL, thus decreasing plasma HDL levels. ANGPTL3 also inhibits LPL, the lipase primarily responsible for the clearance of TGs from the circulation. Previous studies have shown that ANGPTL3 requires complex formation with the related ANGPTL protein, angiopoietin-like 8 (ANGPTL8), to efficiently inhibit LPL, but the role of ANGPTL8 in EL inhibition is not known. In this study, we characterized inhibition and binding of EL by ANGPTL3 and investigated the role of ANGPTL8 in EL inhibition. We found that inhibition of EL by ANGPTL3 was dose dependent and temperature dependent. Interestingly, this inhibition was diminished when EL was bound to endothelial cells or in the presence of heparin. Unlike previous findings with LPL, we found that ANGPTL8 did not significantly alter the binding or the inhibition of EL by ANGPTL3. In addition, we found that a common ANGPTL8 variant, which encodes an R59W mutation, altered the ability of ANGPTL3 to bind and inhibit LPL but not EL. Together, our data indicate that ANGPTL8 is not necessary for EL inhibition. We conclude that ANGPTL8 is specific for the regulation of TG-rich lipoproteins through the LPL pathway and that therapeutically targeting ANGPTL8 for the treatment of hypertriglyceridemia or cardiovascular disease may have different outcomes than targeting ANGPTL3.

Treadmill Running Changes Endothelial Lipase Expression: Insights from Gene and Protein Analysis in Various Striated Muscle Tissues and Serum.

Endothelial lipase (EL) is an enzyme capable of HDL phospholipids hydrolysis. Its action leads to a reduction in the serum high-density lipoprotein concentration, and thus, it exerts a pro-atherogenic effect. This study examines the impact of a single bout exercise on the gene and protein expression of the EL in skeletal muscles composed of different fiber types (the soleus-mainly type I, the red gastrocnemius-mostly IIA, and the white gastrocnemius-predominantly IIX fibers), as well as the diaphragm, and the heart. Wistar rats were subjected to a treadmill run: (1) t = 30 [min], V = 18 [m/min]; (2) t = 30 [min], V = 28 [m/min]; (3) t = 120 [min], V = 18 [m/min] (designated: M30, F30, and M120, respectively). We established EL expression in the total muscle homogenates in sedentary animals. Resting values could be ordered with the decreasing EL protein expression as follows: endothelium of left ventricle > diaphragm > red gastrocnemius > right ventricle > soleus > white gastrocnemius. Furthermore, we observed that even a single bout of exercise was capable of inducing changes in the mRNA and protein level of EL, with a clearer pattern observed for the former. After 30 min of running at either exercise intensity, the expression of EL transcript in all the cardiovascular components of muscles tested, except the soleus, was reduced in comparison to the respective sedentary control. The protein content of EL varied with the intensity and/or duration of the run in the studied whole tissue homogenates. The observed differences between EL expression in vascular beds of muscles may indicate the muscle-specific role of the lipase.

Potential role of hepatic lipase in the accretion of docosahexaenoic acid (DHA) by the brain.

DHA (docosahexaenoic acid) is an essential fatty acid that is required for the normal development and function of the brain. Because of its inability to synthesize adequate amounts of DHA from the precursors, the brain has to acquire DHA from plasma through the blood brain barrier (BBB). Recent studies demonstrated the presence of a transporter at the BBB that specifically transports DHA into the brain in the form of lysophosphatidylcholine (LPC-DHA). However, the mechanism by which LPC-DHA is generated in the plasma is not known. Our previous studies showed that there are at least three different enzymes - lecithin cholesterol acyltransferase (LCAT), endothelial lipase (EL), and hepatic lipase (HL), which can generate LPC-DHA from sn-2 DHA phosphatidylcholine. Here we determined the relative contributions of these enzymes in the delivery of DHA to the brain by measuring the brain DHA levels in the mice deficient in each of these enzymes. The results show that the brain DHA levels of LCAT-deficient mice or EL-deficient mice were not significantly lower than those of their littermates. However, brain DHA was significantly decreased in HL deficient mice (13.5% of total fatty acids) compared to their littermates (17.1%) (p < 0.002), and further decreased to 8.3% of total fatty acids in mice deficient in both HL and EL. These results suggest that HL activity may be the major source for the generation of LPC-DHA in the plasma necessary for transport into the brain, and EL might contribute to this process in the absence of HL.

Roles of endothelial lipase gene related single nucleotide polymorphisms in patients with coronary artery disease.

The current work focused on evaluating the roles of endothelial lipase gene (LIPG) related single nucleotide polymorphisms (SNPs) in patients with coronary artery disease (CAD). This study involved 1,883 subjects with 959 CAD patients and 924 healthy controls. Data were harvested to assess the association of LIPG related SNPs including rs3744841, rs3744843, rs3813082 and rs2000813 with the risk of CAD. The CC + AC genotype in rs3813082 played a protective role for CAD [odds ratio (OR) = 0.709, P = 0.039]. Differences existed in apolipoprotein-A1 (Apo-A1) and high-density lipoprotein-cholesterol (HDL-C) levels in rs3744843 variant between control and CAD groups. The rs3744841 variant increased the levels of total cholesterol (TC), HDL-C, low-density lipoprotein cholesterol (LDL-C), Apo-A1 and Lipoprotein a (LPa) in the CAD group and TC, LDL-C, HDL-C, Apo-B, Apo-A1 in the control group. The triglyceride (TG) level was lower in rs2000813 variant in the CAD group and elevated in the control group. The rs2000813 variant decreased the number of vascular stenosis while rs3744843 and rs3744841 variants increased the number of vascular stenosis in CAD patients. This study explored the roles of LIPG related SNPs in CAD, showing that CC + AC genotype in rs3813082 was a protective factor for CAD. The rs3744843, rs3744841 and rs2000813 variants were associated with the levels of lipid parameters in CAD patients. The rs3744843, rs3744841 and rs2000813 variants influenced the number of vascular stenosis in CAD patients. The results of our study might be a promising reference for preventing CAD.

The Endothelium Is Both a Target and a Barrier of HDL's Protective Functions.

The vascular endothelium serves as a barrier between the intravascular and extravascular compartments. High-density lipoproteins (HDL) have two kinds of interactions with this barrier. First, bloodborne HDL must pass the endothelium to access extravascular tissues, for example the arterial wall or the brain, to mediate cholesterol efflux from macrophages and other cells or exert other functions. To complete reverse cholesterol transport, HDL must even pass the endothelium a second time to re-enter circulation via the lymphatics. Transendothelial HDL transport is a regulated process involving scavenger receptor SR-BI, endothelial lipase, and ATP binding cassette transporters A1 and G1. Second, HDL helps to maintain the integrity of the endothelial barrier by (i) promoting junction closure as well as (ii) repair by stimulating the proliferation and migration of endothelial cells and their progenitor cells, and by preventing (iii) loss of glycocalix, (iv) apoptosis, as well as (v) transmigration of inflammatory cells. Additional vasoprotective functions of HDL include (vi) the induction of nitric oxide (NO) production and (vii) the inhibition of reactive oxygen species (ROS) production. These vasoprotective functions are exerted by the interactions of HDL particles with SR-BI as well as specific agonists carried by HDL, notably sphingosine-1-phophate (S1P), with their specific cellular counterparts, e.g., S1P receptors. Various diseases modify the protein and lipid composition and thereby the endothelial functionality of HDL. Thorough understanding of the structure-function relationships underlying the multiple interactions of HDL with endothelial cells is expected to elucidate new targets and strategies for the treatment or prevention of various diseases.

Endothelial Lipase Is Involved in Cold-Induced High-Density Lipoprotein Turnover and Reverse Cholesterol Transport in Mice.

The physiologic activation of thermogenic brown and white adipose tissues (BAT/WAT) by cold exposure triggers heat production by adaptive thermogenesis, a process known to ameliorate hyperlipidemia and protect from atherosclerosis. Mechanistically, it has been shown that thermogenic activation increases lipoprotein lipase (LPL)-dependent hydrolysis of triglyceride-rich lipoproteins (TRL) and accelerates the generation of cholesterol-enriched remnants and high-density lipoprotein (HDL), which promotes cholesterol flux from the periphery to the liver. HDL is also subjected to hydrolysis by endothelial lipase (EL) (encoded by LIPG). Genome-wide association studies have identified various variants of EL that are associated with altered HDL cholesterol levels. However, a potential role of EL in BAT-mediated HDL metabolism has not been investigated so far. In the present study, we show that in mice, cold-stimulated activation of thermogenic adipocytes induced expression of Lipg in BAT and inguinal WAT but that loss of Lipg did not affect gene expression of thermogenic markers. Furthermore, in both wild type (WT) and Lipg-deficient mice, activation of thermogenesis resulted in a decline of HDL cholesterol levels. However, cold-induced remodeling of the HDL lipid composition was different between WT and Lipg-deficient mice. Notably, radioactive tracer studies with double-labeled HDL indicated that cold-induced hepatic HDL cholesterol clearance was lower in Lipg-deficient mice. Moreover, this reduced clearance was associated with impaired macrophage-to-feces cholesterol transport. Overall, these data indicate that EL is a determinant of HDL lipid composition, cholesterol flux, and HDL turnover in conditions of high thermogenic activity.