Cholesteryl Ester Transfer Research Articles

Variants in the CETP gene affect levels of HDL cholesterol by reducing the amount, and not the specific lipid transfer activity, of secreted CETP.

Cholesteryl ester transfer protein (CETP) transfers cholesteryl esters in plasma from high density lipoprotein (HDL) to very low density lipoprotein and low density lipoprotein. Loss-of-function variants in the CETP gene cause elevated levels of HDL cholesterol. In this study, we have determined the functional consequences of 24 missense variants in the CETP gene. The 24 missense variants studied were the ones reported in the Human Gene Mutation Database and in the literature to affect HDL cholesterol levels, as well as two novel variants identified at the Unit for Cardiac and Cardiovascular Genetics, Oslo University Hospital in subjects with hyperalphalipoproteinemia. HEK293 cells were transiently transfected with mutant CETP plasmids. The amounts of CETP protein in lysates and media were determined by Western blot analysis, and the lipid transfer activities of the CETP variants were determined by a fluorescence-based assay. Four of the CETP variants were not secreted. Five of the variants were secreted less than 15% compared to the WT-CETP, while the other 15 variants were secreted in varying amounts. There was a linear relationship between the levels of secreted protein and the lipid transfer activities (r = 0.96, p<0.001). Thus, the secreted variants had similar specific lipid transfer activities. The effect of the 24 missense variants in the CETP gene on the lipid transfer activity was mediated predominantly by their impact on the secretion of the CETP protein. The four variants that prevented CETP secretion cause autosomal dominant hyperalphalipoproteinemia. The five variants that markedly reduced secretion of the respective variants cause mild hyperalphalipoproteinemia. The majority of the remaining 15 variants had minor effects on the secretion of CETP, and are considered neutral genetic variants.

Efficient energy transfer of Ce to Nd in SrF2 transparent ceramics for enhancing NIR emission

Efficient energy transfer of Ce to Nd in SrF2 transparent ceramics for enhancing NIR emission

Mixed effects and co-transfer of CeO2 NPs and arsenic in the pakchoi-snail food chain

Nanomaterial application in agriculture offers novel solutions for soil arsenic (As) pollution control, yet safety along the food chain is of concern. We comprehensively assessed CeO2 nanoparticles (NPs) foliar application effects on As uptake by pakchoi and their presence in the pakchoi-snail food chain. CeO2 NPs reduced As transfer from pakchoi roots to shoots by 37.9%, lowered As in snail foot by 39%, and halved human As exposure risk. The NPs alleviated pakchoi shoot As toxicity by regulating antioxidants, enhancing water use efficiency, and photosynthesis. CeO2 +As treatment raised GSH/GSSG ratios by 38.92%− 167.54%, leading to an increased AsIII/AsV ratio and inorganic As detoxification compared to As alone. Metabolomics revealed CeO2's rapid As response via phosphatidylinositol signaling. The enzyme-like activity of CeO2 NPs may drive these effects. While CeO2 foliar application accumulated Ce on pakchoi leaves, > 99% of Ce was excreted following snail consumption. Ce transfer from pakchoi leaves to snail foot was minimal (trophic transfer factor ∼0.00007) due to limited bioavailability. The target hazard quotient of Ce in pakchoi shoot (1.21 ± 0.18) and snails (0.0016 ± 0.0004) indicated low exposure risk, suggesting a ‘risk filter’ effect for CeO2. Our results contribute to the safe and sustainable application of CeO2 NPs in the future implication.

Bound Phospholipids Assist Cholesteryl Ester Transfer in the Cholesteryl Ester Transfer Protein.

Cholesteryl ester transfer protein (CETP) is a plasma glycoprotein that assists the transfer of cholesteryl esters (CEs) from antiatherogenic high-density lipoproteins (HDLs) to proatherogenic low-density lipoproteins (LDLs), initiating cholesterol plaques in the arteries. Consequently, inhibiting the activity of CETP is therefore being pursued as a novel strategy to reduce the risk of cardiovascular diseases (CVDs). The crystal structure of CETP has revealed the presence of two CEs running in the hydrophobic tunnel and two plugged-in phospholipids (PLs) near the concave surface. Other than previous animal models that rule out the PL transfer by CETP and PLs in providing the structural stability, the functional importance of bound phospholipids in CETP is not fully explored. Here, we employ a series of molecular dynamics (MD) simulations, steered molecular dynamics (SMD) simulations, and free energy calculations to unravel the effect of PLs on the functionality of the protein. Our results suggest that PLs play an important role in the transfer of neutral lipids by transforming the unfavorable bent conformation of CEs into a favorable linear conformation to facilitate the smooth transfer. The results also suggest that the making and breaking interactions of the hydrophobic tunnel residues with CEs with a combined effort from PLs are responsible for the transfer of CEs. Further, the findings demonstrate that the N-PL has a more pronounced effort on CE transfer than C-PL but efforts from both PLs are essential in the transfer. Thus, we propose that the functionally important PLs can be considered with potential research interest in targeting cardiovascular diseases.

Proprotein convertase subtilisin/kexin type 9 inhibitors: prospects for cholesterol-lowering therapy in type 2 diabetes

Diabetic dyslipoproteinemia (DLP), characterized by quantitative, qualitative, and kinetic changes in all major circulating lipids, contributes to an increased risk of atherosclerotic cardiovascular disease in patients with type 2 diabetes mellitus (DM). Inhibition of proprotein convertase subtilisin/kexin type 9 (PCSK9) by human monoclonal antibodies is a promising treatment for diabetic DLP. Several drugs differ in their mechanisms of inhibition of PCSK9 activity. The following groups are conditionally distinguished: PCSK9 monoclonal antibodies (anti-PCSK9 monoclonal antibodies): evolocumab, alirocumab, bococizumab (injectable); other injectable medications with different mechanism of actions (inclisiran, SPC4061, SPC5001, adnectin BMS-962476, LIB003, anti-PCSK9 vaccine; anti-PCSK9 vaccine (nanoparticle-based); orally administered drugs (PF-06446846, DS-9001a, SRT3025); cholesteryl ester transfer protein/PCSK9 inhibitors (anacetrapib, evacetrapib, torcetrapib, K-312). This review aims to discuss the role of alirocumab and evolocumab, fully humanized monoclonal antibodies, in the treatment of type 2 DM patients with DLP and to consider their effectiveness and safety. Strategy of search. Scopus, Science Direct (from Elsevier), and PubMed, including the Medline databases, were searched. The following keywords were used: autonomic nervous system, heart rate variability, baroreflex sensitivity, diabetic cardiac autonomic neuropathy, and MeSH terms. A manual search of the bibliography of publications was used to identify research results that could not be found with the online search. Statins are the first line of choice for treating DLP in patients with type 2 DM to reduce the risk of atherosclerotic cardiovascular disease. Ezetimibe is the next drug to be added if patients’ low-density lipoprotein cholesterol levels are higher than acceptable. In cases of failure of the combination of statins with ezetimibe, PCSK9 inhibitor is a reasonable and rational choice. Overall, clinical data suggest that PCSK9 inhibitors are well tolerated and provide a significant reduction in low-density lipoprotein cholesterol levels in type 2 DM patients with DLP in addition to high-intensity statin therapy. The use of PCSK9 inhibitors is not associated with impaired glycemic control or increased risk of diabetes development in individuals without previously diagnosed DM and may prevent or reduce subsequent cardiovascular events.

Utilizing the Energy Transfer of Ce4+– and Ce3+–Tb3+ to Boost the Luminescence Quantum Efficiency up to 100% in Borate Glass

Light-emitting glass shows potential to be used in high-power light-emitting diode (LED) devices because of its homogeneous emission, excellent thermal stability, and simple and low-cost fabrication procedures. The reported quantum efficiencies (QEs) of Ce3+-based luminescent glasses do not compete with those of phosphors because of their loose structures. In this study, a series of high-efficiency luminescent strontium borate (SBO) glasses SBO:Ce3+, Tb3+ are designed and developed. Our work skillfully takes advantage of the Tb3+ ion acquiring the transferred energy from nonluminescent Ce4+ and luminescent center Ce3+ ions, almost doubling their luminescence QE and achieving an astonishing QE of 100%. Also, their chrominance could be conveniently adjusted from blue to green through the white light region by increasing the amount of Tb3+. The optimal SBO:20% Ce3+, 15% Tb3+ glass also presents excellent thermal luminescence stability compared to commercial DS-200 phosphor. An assembled SBO-LED shows a bright greenish-white emission at 4 W of power.

Transfer of La, Ce, Sm and Yb to alfalfa and ryegrass from spiked soil and the role of Funneliformis mosseae.

Rare earth elements (REEs) are widely used in high-tech industries, and REE waste emissions have become a concern for ecosystems, food quality and human beings. Arbuscular mycorrhizal fungi (AMF) have repeatedly been reported to alleviate plant stress in metal-contaminated soils. To date, little information is available concerning the role of AMF in REE-contaminated soils. We recently showed that there was no transfer of Sm to alfalfa by Funneliformis mosseae, but only a single REE was examined, while light and heavy REEs are present in contaminated soils. To understand the role of AMF on the transfer of REEs to plants, we carried out an experiment using alfalfa (Medicago sativa) and ryegrass (Lolium perenne) in compartmented pots with separate bottom compartments that only were accessible by F. mosseae fungal hyphae. The bottom compartments contained a mixture of four REEs at equal concentrations (La, Ce, Sm and Yb). The concentration of REEs in plants was higher in roots than in shoots with higher REE soil-root than root-shoot transfer factors. Moreover, significantly higher light-REEs La and Ce were transferred to ryegrass shoots than Sm and the heavy-REE Yb, but this was not observed for alfalfa. Alfalfa dry weight was significantly increased by F. mosseae inoculation, but not ryegrass dry weight. For both plant species, there was significantly higher P uptake by the mycorrhizal plants than the nonmycorrhizal plants, but there was no significant transfer of La, Ce, Sm or Yb to alfalfa and ryegrass roots or shoots due to F. mosseae inoculation.

Abstract P112: A Simple, Rapid, And Sensitive Fluorescence-based Method To Assess Triacylglycerol Hydrolase Activities

Introduction: Lipases constitute an important class of water-soluble enzymes that catalyze the hydrolysis of hydrophobic triacylglycerol (TAG). Their activity is usually measured after isolation and quantification of the hydrolyzed free fatty acids. We have used NBD-labeled lipids previously to develop TAG, cholesteryl ester, and phospholipid transfer assays for microsomal triglyceride transfer protein. To date, however, NBD-labeled TAG (NBD-TAG) has not been used to assess the enzymatic activities of different lipases. Methods: We developed methods to measure lipase activities using adipose triglyceride lipase (ATGL), lipoprotein lipase (LpL), and pancreatic triglyceride lipase (PNLIP) as model lipases. In these assays, we incubated a source of ATGL, LpL, or PNLIP with substrate emulsions containing nitrobenzoxadiazole (NBD)-labeled TAG in phosphatidylcholine (PC) and phosphatidylinositol (PI), measured increases in NBD fluorescence with time, and calculated enzyme activities. Results: Incorporation of NBD-TAG into PC vesicles resulted in some hydrolysis; but required product isolation step to measure NBD fluorescence. However, incorporation of PI into these NBD-TAG/PC vesicles significantly increased substrate hydrolysis in time, protein, and substrate concentration dependent manner negating the need to isolate products to measure lipase activities. Further, increasing the ratio of NBD-TAG to PC enhanced substrate hydrolysis. Next, we tested specific lipase inhibitors and found that orlistat inhibits all three enzymes indicating that it is a pan-lipase inhibitor. Conclusions: We describe a simple, rapid fluorescence-based TAG hydrolysis assay to assess three major TAG hydrolases: ATGL localized intracellularly, LpL localized at the extracellular endothelium, and PNLIP produced and secreted from the pancreas into the intestinal lumen. The major advantages of this method are its speed, simplicity, and avoidance of a product isolation step. This assay is potentially applicable to a wide range of lipases and is amenable to high-throughput screening to discover novel modulators of triacylglycerol hydrolases, and in the diagnosis of diseases associated with increases in plasma lipase activities.

Electrochemistry of PUREX: R is for reduction and ion transfer

ABSTRACT The PUREX (Plutonium, Uranium, Reduction, EXtraction) process is the foundation of all industrial activities that involve the recycling of plutonium and uranium from used nuclear fuel. With over 70 years of research, engineering, and operations, it can be argued that little opportunity is left for further discovery and new fundamental understandings regarding PUREX, in general, and tri-n-butyl phosphate (TBP), in particular. Through use of an advanced electroanalytical approach, molecular-level insights regarding the back-extraction of Pu(IV) by reductive separation are reported. Studies of model PUREX systems, with lanthanide ions extracted into 20% TBP in n-dodecane, are used to demonstrate the approach. These studies reveal knowledge pertinent to mass-transfer aspects of the biphasic reductive stripping reaction central to the separation of U and Pu in PUREX. Two lanthanide ions – Ce(IV) and Yb(III) – were extracted from their concentrated solutions in aqueous 3 M HNO3 to expressly provide electrically conducting third phases to facilitate electrochemical data acquisition. To simplify the diabolically-complicated reductive separation aspects of PUREX, the controlled polarization of electrode surfaces was used to reduce Ce(IV) and Yb(III) in place of chemical reductants. Electroanalyses of the biphasic systems with Ce(IV) and Yb(III) using three-phase electrode differential pulse voltammetry demonstrate the effects of mass transfer across water–oil interfaces on the electrode potentials for the reduction to Ce(III) and Yb(II). These reductions trigger nitrate transfer out of the oil phase for Ce and proton transfer into the organic phase for Yb. This is in correlation with the transfer of the charge-neutral ion pairs Ce·3NO3 and Yb·2NO3 out of the oil phases. The differences in ion-transfer steps reflect significant variations in the equilibrium speciation of multinuclear Ce(IV) and mononuclear Yb(III) solvates of TBP in the oil phases and the loading of the organic phase.

Reduced Reverse Cholesterol Transport Efficacy in Healthy Men with Undesirable Postprandial Triglyceride Response.

Elevation of nonfasting triglyceride (TG) levels above 1.8 g/L (2 mmol/L) is associated with increased risk of cardiovascular diseases. Exacerbated postprandial hypertriglyceridemia (PP–HTG) and metabolic context both modulate the overall efficacy of the reverse cholesterol transport (RCT) pathway, but the specific contribution of exaggerated PP–HTG on RCT efficacy remains indeterminate. Healthy male volunteers (n = 78) exhibiting no clinical features of metabolic disorders underwent a postprandial exploration following consumption of a typical Western meal providing 1200 kcal. Subjects were stratified according to maximal nonfasting TG levels reached after ingestion of the test meal into subjects with a desirable PP–TG response (GLow, TG < 1.8 g/L, n = 47) and subjects with an undesirable PP–TG response (GHigh, TG > 1.8 g/L, n = 31). The impact of the degree of PP–TG response on major steps of RCT pathway, including cholesterol efflux from human macrophages, cholesteryl ester transfer protein (CETP) activity, and hepatic high-density lipoprotein (HDL)-cholesteryl ester (CE) selective uptake, was evaluated. Cholesterol efflux from human macrophages was not significantly affected by the degree of the PP–TG response. Postprandial increase in CETP-mediated CE transfer from HDL to triglyceride-rich lipoprotein particles, and more specifically to chylomicrons, was enhanced in GHigh vs. GLow. The hepatic HDL-CE delivery was reduced in subjects from GHigh in comparison with those from GLow. Undesirable PP–TG response induces an overall reduction in RCT efficacy that contributes to the onset elevation of both fasting and nonfasting TG levels and to the development of cardiometabolic diseases.

MnCeOx/diatomite catalyst for persulfate activation to degrade organic pollutants

Persulfate (PS)-based oxidation technologies are attracting increasing attentions in water treatment due to their high efficiency and stability. In this study, a novel diatomite supported MnCeOx composite (MnCeOx/diatomite) was prepared and characterized for activation of PS to degrade organic pollutants. Results indicated that diatomite not only dispersed MnCeOx and increased the specific surface area of catalyst, but also improved the low-valence metal site (Mn2+ and Ce3+) and reactive oxygen species site (–OH) of MnCeOx, thus enhancing the activities of MnCeOx. MnCeOx/diatomite/PS showed high efficiency for multiple dyes and pharmaceutical pollutants. Constant rate (k) of MnCeOx/diatomite (kMnCeOx/diatomite) was three times higher than the sum of constant rate of MnCeOx (kMnCeOx) and constant rate of diatomite (kdiatomite). In addition, MnCeOx/diatomite showed wide pH application (5–9). Cl− and NO32− had no effect while SO42− and humid acid had slightly negative effects on MnCeOx/diatomite/PS system. Moreover, MnCeOx/diatomite showed good reusability and stability. Mechanism analyses indicated that electron transfer of Mn and Ce attributed to the activation of PS and oxygen to produce free radicals. SO4−, OH and O2− on the surface of catalyst were the main active free radicals to attack pollutants.

ApoF knockdown increases cholesteryl ester transfer to LDL and impairs cholesterol clearance in fat-fed hamsters

Cholesteryl ester transfer protein (CETP) regulates intravascular lipoprotein metabolism. In vitro studies indicate that ApoF alters CETP function by inhibiting its activity with LDL. To explore in vivo the complexities driving ApoF's effects on CETP, we developed a siRNA-based hamster model of ApoF knockdown. In both male and female hamsters on chow- or fat-fed diets, we measured lipoprotein levels and composition, determined CETP-mediated transfer of cholesteryl esters (CEs) between lipoproteins, and quantified reverse cholesterol transport (RCT). We found that apoF knockdown in chow-fed hamsters had no effect on lipoprotein levels or composition, but these ApoF-deficient lipoproteins supported 50-100% higher LDL CETP activity in vitro. ApoF knockdown in fat-fed male hamsters created a phenotype in which endogenous CETP-mediated CE transfer from HDL to LDL increased up to 2-fold, LDL cholesterol increased 40%, HDL declined 25%, LDL and HDL lipid compositions were altered, and hepatic LDLR gene expression was decreased. Diet-induced hypercholesterolemia obscured this phenotype on occasion. In fat-fed female hamsters, ApoF knockdown caused similar but smaller changes in plasma CETP activity and LDL cholesterol. Notably, ApoF knockdown impaired HDL RCT in fat-fed hamsters but increased sterol excretion in chow-fed animals. These in vivo data validate in vitro findings that ApoF regulates lipid transfer to LDL. The consequences of ApoF knockdown on lipoproteins and sterol excretion depend on the underlying lipid status. By minimizing the transfer of HDL-derived CE to LDL, ApoF helps control LDL cholesterol levels when LDL clearance mechanisms are limiting.

Online mass spectrometry of CE (SDS)-separated proteins by two-dimensional capillary electrophoresis.

Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) is the fundamental technique for protein separation by size. Applying this technology in capillary format, gaining high separation efficiency in a more automated way, is a key technology for size separation of proteins in the biopharmaceutical industry. However, unequivocal identification by online mass spectrometry (MS) is impossible so far, due to strong interference in the electrospray process by SDS and other components of the SDS-MW separation gel buffer. Here, a heart-cut two-dimensional electrophoretic separation system applying an electrically isolated valve with an internal loop of 20nL is presented. The peak of interest in the CE (SDS) separation is transferred to the CZE-MS, where electrospray-interfering substances of the SDS-MW gel are separated prior to online electrospray ionization mass spectrometry. An online SDS removal strategy for decomplexing the protein-SDS complex is implemented in the second dimension, consisting of the co-injection of organic solvent and cationic surfactant. This online CE (SDS)-CZE-MS system allows MS characterization of proteoforms separated in generic CE (SDS), gaining additional separation in the CZE and detailed MS information. In general, the system can be applied to all kinds of proteins separated by CE (SDS). Here, we present results of the CE (SDS)-CZE-MS system on the analysis of several biopharmaceutically relevant antibody impurities and fragments. Additionally, the versatile application spectrum of the system is demonstrated by the analysis of extracted proteins from soybean flour. The online hyphenation of CE (SDS) resolving power and MS identification capabilities will be a powerful tool for protein and mAb characterization. Graphical abstract Two-dimensional capillary electrophoresis system hyphenated with mass spectrometry for the characterization of CE (SDS)-separated proteins. As first dimension, a generic and high MS-interfering CE (SDS) separation is performed for size separation. After heart-cut transfer of the unknown CE (SDS) protein peak, via a four-port nanoliter valve to a volatile electrolyte system as second dimension, interference-free mass spectrometric data of separated mAb fragments and soybean proteins are obtained.

Are Cerium Oxide Nanoparticles Transferred from Plants to the Aphid Myzus persicae (Hemiptera: Aphididae)?

In the last 20 yr, the production of nanoparticles has increased, although their effects on organisms and the environment are not well understood. This research evaluated the transfer of cerium oxide (nano-CeO2) nanoparticles in a terrestrial trophic chain formed by the producer Nicandra physaloides (L.) Gaertn. (Solanaceae) and a primary consumer, green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae), a generalist insect pest. Nicandra physaloides plants were treated by foliar spraying with nano-CeO2 (25 nm) aqueous suspensions (1, 10, 100, and 1,000 mg Ce L-1) and fed to the green peach aphid (M. persicae). The survival and fecundity of insects were evaluated. Microprobe X-ray fluorescence spectroscopy was used to verify the presence of Ce in plants and insects. It was possible to verify Ce in the oral cavity and digestive system of aphids fed on leaves previously treated with nano-CeO2 (1,000 mg CeL-1). Despite the transfer of Ce in this terrestrial trophic chain, the nanoparticles did not reduce survival and fecundity of aphids. Resumo Nas ultimas decadas, a producao de nanoparticulas tem aumentado; entretanto, seus efeitos em organismos e no meio ambiente ainda nao sao bem compreendidos. A transferencia de nanoparticulas de oxido de cerio (Nano-CeO2) em uma cadeia trofica terrestre, formada pelo produtor Nicandra physaloides (L.) Gaertn. (Solanaceae) e pelo consumidor primario, inseto-praga generalista, Myzus persicae (Sulz.) (Hemiptera, Aphididae), foi avaliada nesse trabalho. Plantas de N. physaloides foram submetidas a tratamento via pulverizacao foliar com suspensao aquosa de nano-CeO2, 25 nm (1, 10, 100, e 1.000 mg Ce L-1) e empregadas para alimentacao do pulgao verde (M. persicae). Empregando-se microanalise por espectroscopia de fluorescencia de raios-X foi possivel constatar a presenca de Ce nas plantas e insetos. Assim, o Ce foi observado na cavidade oral e sistema digestivo dos pulgoes que se alimentaram das folhas previamente tratadas com nano-CeO2 (1.000 mg CeL-1). Apesar da transferencia de Ce nessa cadeia trofica, nao foi constatada reducao na sobrevivencia e fecundidade dos afideos. Key Words: nanotechnology; Solanaceae; insect; trophic transfer; X-ray fluorescence spectroscopy View this article in BioOne

Steering the Lipid Transfer To Unravel the Mechanism of Cholesteryl Ester Transfer Protein Inhibition.

Human plasma cholesteryl ester transfer protein (CETP) mediates the transfer of neutral lipids from antiatherogenic high-density lipoproteins (HDLs) to proatherogenic low-density lipoproteins (LDLs). Recent cryo-electron microscopy studies have suggested that CETP penetrates its N- and C-terminal domains in HDL and LDL to form a ternary complex, which facilitates the lipid transfer between different lipoproteins. Inhibition of CETP lipid transfer activity has been shown to increase the plasma HDL-C levels and, therefore, became an effective strategy for combating cardiovascular diseases. Thus, understanding the molecular mechanism of inhibition of lipid transfer through CETP is of paramount importance. Recently reported inhibitors, torcetrapib and anacetrapib, exhibited low potency in addition to severe side effects, which essentially demanded a thorough knowledge of the inhibition mechanism. Here, we employ steered molecular dynamics simulations to understand how inhibitors interfere with the neutral lipid transfer mechanism of CETP. Our study revealed that inhibitors physically occlude the tunnel posing a high energy barrier for lipid transfer. In addition, inhibitors bring about the conformational changes in CETP that hamper CE passage and expose protein residues that disrupt the optimal hydrophobicity of the CE transfer path. The atomic level details presented here could accelerate the designing of safe and efficacious CETP inhibitors.

Antibodies Against the C-Terminus of ApoA-1 Are Inversely Associated with Cholesterol Efflux Capacity and HDL Metabolism in Subjects with and without Type 2 Diabetes Mellitus.

Background: We determined relationships of cholesterol efflux capacity (CEC), plasma cholesterol esterification (EST) and cholesteryl ester transfer (CET) with anti-c-terminus apoA-1 (Ac-terAA1) and anti-apolipoprotein (apo)-1 (AAA1) autoantibodies in subjects with and without Type 2 diabetes mellitus (T2D). Methods: In 75 T2D subjects and 75 nondiabetic subjects, Ac-terAA1 and AAA1 plasma levels were measured by enzyme-linked immunosorbent assay. CEC was measured as [3H]-cholesterol efflux from human cultured fibroblasts to diluted individual subject plasma. Plasma EST and CET were assayed by isotope methods. Results: Ac-terAA1 and AAA1 levels and were similar between T2D and control subjects. Univariate regression analysis (n = 150) demonstrated that Ac-terAA1 levels were inversely correlated with CEC, EST, CET, total cholesterol, non-HDL cholesterol, triglycerides and apolipoprotein B, (p < 0.05 to p < 0.01), but not with glucose and HbA1c. In separate multivariable linear regression models, CEC, EST and CET were inversely associated with Ac-terAA1 levels independently of age, sex, T2D and drug use (β = −0.186, p = 0.026; β = −0.261, p < 0.001; and β = −0.321, p < 0.001; respectively). These associations were lost after additional adjustment for non-HDL cholesterol and triglycerides. No associations were observed for AAA1. Conclusions: CEC, plasma EST and CET are inversely associated with Ac-terAA1 autoantibodies, conceivably attributable to an inverse relationship of these autoantibodies with apolipoprotein B-containing lipoproteins.

Changes in lecithin: cholesterol acyltransferase, cholesteryl ester transfer protein and paraoxonase-1 activities in patients with colorectal cancer

BackgroundPrevious studies revealed decreased level of high-density lipoprotein cholesterol (HDLC) as important factor for development of colorectal cancer (CRC). Quantity and structure of HDL particles depend on activities of lipid transfer proteins lecithin:cholesterol acyltransferase (LCAT) and cholesteryl ester transfer protein (CETP), but this topic is largely unexplored in CRC. The main objective of this study was to investigate activities of LCAT and CETP in patients with CRC. Additionally, we analyzed activity of paraoxonase-1 (PON-1), as a main carrier of HDL-antioxidant function. Materials and methodsNinety-nine CRC patients and 101 healthy individuals were included. LCAT and CETP activities were assessed by measuring rates of formation and transfer of cholesteryl esters. PON-1 paraoxonase and arylesterase activities were measured. ResultsLower levels of HDL-C (p < .001) were observed in cohort of patients, alongside with decreased LCAT (p < .050) and increased CETP activity (p < .050). Both PON-1 activities were diminished in CRC (p < .050 and p < .001 respectively). Univariate logistic regression singled out HDL-C level (OR = 0.218, p < .001), CETP activity (OR = 1.010, p < .01) and mass (OR = 0.994, p < .001) as possible markers of elevated CRC risk. CETP mass maintained its predictive significance when adjusted for traditional risk factors and level of oxidative stress (OR = 0.993, p < .001; OR = 0.982, p < .050, respectively). ConclusionOur results demonstrated increased CETP and decreased LCAT and PON-1 activities in CRC patients. In preliminary analysis CETP mass was identified as potential significant predictor of CRC development, suggesting that alterations in HDL-C levels, alongside with changes in HDL structure might have a role in carcinogenesis.

Abstract 390: A New Humanized Mouse Model to Study Lipid Abnormalities and HDL Function in Poorly Controlled Type 1 Diabetes Mellitus

Elevated plasma triglycerides (TG) and VLDL are often present in poorly controlled type 1 diabetes mellitus (T1DM). Furthermore, T1DM patients exhibit an increased risk of cardiovascular disease (CVD) despite normal or high HDL-cholesterol. There is a need for new mouse models to study T1DM lipid abnormalities because mice do not express cholesteryl ester transfer protein (CETP), which transfers cholesteryl ester (CE) from HDL to VLDL and other lipoproteins in exchange for TG, and because mice do not exhibit human-like HDL populations. To develop a physiologically relevant model, we crossed a virally-induced mouse model of T1DM ( Ldlr -/- ;Gp Tg ) deficient in the LDL receptor with human apolipoprotein A-I ( APOA1 ) transgenic mice. These mice (n=8-10) were injected with a liver-specific adeno-associated virus driving expression of human CETP, mimicking the human CETP activity/apoA-I ratio, and the 3 major human HDL subpopulations. Using this model ( APOA1 Tg ;Ldlr -/- ;Gp Tg ), we examined the impact of diabetes on dyslipidemia, HDL particle concentration (HDL-P), and serum HDL function. Induction of diabetes increased plasma TG and cholesterol, primarily due to an increase in VLDL, as compared with non-diabetic (ND) littermates. The dyslipidemia was associated with increases in hepatic TG content and hepatic TG production rate (2-fold over ND). Moreover, resident peritoneal macrophages from diabetic mice exhibited a 5-fold increase in CE loading, increased lipid raft content (20%), and increased Tnfa (3-fold) and Il1b mRNA (4-fold), as compared with ND littermates. In addition, T1DM mice had increased small, medium and large HDL-P (2-fold) concentrations compared with ND controls. Serum HDL from T1DM mice showed a significant increase in its cholesterol efflux capacity through both ABCA1 and ABCG1. Thus, in this humanized mouse model, poorly controlled T1DM leads to elevated plasma TG and VLDL due in part to increased hepatic TG production. This dyslipidemia is associated with higher HDL-P and an increase in serum HDL’s cholesterol efflux capacity, likely due to the increased plasma HDL-P. We have found similar changes in HDL concentration and function in humans with T1DM, suggesting that our mouse model might provide insights into CVD risk in T1DM patients.

Duality of statin action on lipoprotein subpopulations in the mixed dyslipidemia of metabolic syndrome: Quantity vs quality over time and implication of CETP

Statins impact the metabolism, concentrations, composition, and function of circulating lipoproteins. We evaluated time course relationships between statin-mediated reduction in atherogenic apolipoprotein B (ApoB)-containing particles and dynamic intravascular remodeling of ApoAI-containing lipoprotein subpopulations in the mixed dyslipidemia of metabolic syndrome. Insulin-resistant, hypertriglyceridemic, hypercholesterolemic, obese males (n=12) were treated with pitavastatin (4mg/d) and response evaluated at 6, 42, and 180days. Reduction in low-density lipoprotein (LDL) cholesterol, ApoB, and triglycerides (TGs) was essentially complete at 42days (-38%, -32%, and -35%, respectively); rapid reduction equally occurred in remnant cholesterol, ApoCII, CIII, and E levels (day 6; -35%, -50%, -23%, and -26%, respectively). Small dense LDLs (LDL4 and LDL5 subpopulations) predominated at baseline and were markedly reduced on treatment (-29% vs total LDL mass). Cholesteryl ester (CE) transfer protein activity and mass decreased progressively (-18% and -16%, respectively); concomitantly, TG depletion (up to -49%) and CE enrichment occurred in all high-density lipoprotein (HDL) particle subpopulations with normalization of CE/TG mass ratio at 180days. ApoAI was redistributed from LpAI to LpAI:AII particles in HDL2a and HDL3a subpopulations; ApoCIII was preferentially depleted from LpAI:AII-rich particles on treatment. Overall, statin action exhibits duality in mixed dyslipidemia, as CE transfer protein-mediated normalization of the HDL CE/TG core lags markedly behind subacute reduction in elevated levels of atherogenic ApoB-containing lipoproteins. Normalization of the HDL neutral lipid core is consistent with enhanced atheroprotective function. The HDL CE/TG ratio constitutes a metabolomic marker of perturbed HDL metabolism in insulin-resistant states, equally allowing monitoring of statin impact on HDL metabolism, structure, and function.

Cholesteryl ester transfer protein and its inhibitors

Most of the cholesterol in plasma is in an esterified form that is generated in potentially cardioprotective HDLs. Cholesteryl ester transfer protein (CETP) mediates bidirectional transfers of cholesteryl esters (CEs) and triglycerides (TGs) between plasma lipoproteins. Because CE originates in HDLs and TG enters the plasma as a component of VLDLs, activity of CETP results in a net mass transfer of CE from HDLs to VLDLs and LDLs, and of TG from VLDLs to LDLs and HDLs. As inhibition of CETP activity increases the concentration of HDL-cholesterol and decreases the concentration of VLDL- and LDL-cholesterol, it has the potential to reduce atherosclerotic CVD. This has led to the development of anti-CETP neutralizing monoclonal antibodies, vaccines, and antisense oligonucleotides. Small molecule inhibitors of CETP have also been developed and four of them have been studied in large scale cardiovascular clinical outcome trials. This review describes the structure of CETP and its mechanism of action. Details of its regulation and nonlipid transporting functions are discussed, and the results of the large scale clinical outcome trials of small molecule CETP inhibitors are summarized.