Role Of Cholesteryl Ester Transfer Protein Research Articles

Novel Role of CETP in Macrophages: Reduction of Mitochondrial Oxidants Production and Modulation of Cell Immune-Metabolic Profile.

Plasma cholesteryl ester transfer protein (CETP) activity diminishes HDL-cholesterol levels and thus may increase atherosclerosis risk. Experimental evidence suggests CETP may also exhibit anti-inflammatory properties, but local tissue-specific functions of CETP have not yet been clarified. Since oxidative stress and inflammation are major features of atherogenesis, we investigated whether CETP modulates macrophage oxidant production, inflammatory and metabolic profiles. Comparing macrophages from CETP-expressing transgenic mice and non-expressing littermates, we observed that CETP expression reduced mitochondrial superoxide anion production and H2O2 release, increased maximal mitochondrial respiration rates, and induced elongation of the mitochondrial network and expression of fusion-related genes (mitofusin-2 and OPA1). The expression of pro-inflammatory genes and phagocytic activity were diminished in CETP-expressing macrophages. In addition, CETP-expressing macrophages had less unesterified cholesterol under basal conditions and after exposure to oxidized LDL, as well as increased HDL-mediated cholesterol efflux. CETP knockdown in human THP1 cells increased unesterified cholesterol and abolished the effects on mitofusin-2 and TNFα. In summary, the expression of CETP in macrophages modulates mitochondrial structure and function to promote an intracellular antioxidant state and oxidative metabolism, attenuation of pro-inflammatory gene expression, reduced cholesterol accumulation, and phagocytosis. These localized functions of CETP may be relevant for the prevention of atherosclerosis and other inflammatory diseases.

Abstract 397: Transgenic Expression of Cholesteryl Ester Transfer Protein in Female Mice Disrupts Liver and Plasma Triglyceride Metabolism With Estrogen Treatment in a Liver Network Involving Estrogen Receptor Alpha and Small Heterodimer Partner

Background: Triglycerides are an important risk factor for cardiovascular disease, especially in women. Hormone replacement therapy raises triglycerides (TG) in postmenopausal women, but mechanisms responsible remain poorly understood. Cholesteryl Ester Transfer Protein (CETP) is a serum protein that shuttles TG and cholesteryl ester between lipoproteins in humans and plays an important role in lipoprotein metabolism. The role of CETP in regulating whole body triglyceride homeostasis remains unclear. Mice (which naturally lack CETP) expressing a transgenic copy of CETP or their wild-type (WT) littermates were used to determine the role of CETP in regulating plasma and liver TG metabolism in response to estrogen. Methods and Results: Female CETP and WT mice were ovariectomized and given vehicle or estrogen treatment. Estrogen raised plasma TG in CETP females, but not in WT females. CETP expression impaired TG clearance independent of estrogen. Estrogen treatment raised very-low density lipoprotein (VLDL) TG production in CETP females, but not in WT females. Estrogen treatment augmented mRNA expression and protein activity of VLDL assembly and secretion targets (Apob, Mttp, PDI) in CETP females, but not in WT females. Additionally, CETP expression lowered liver TG content and increased mRNA expression of TG oxidation targets (Ppara, Acox1, Acadm, Cpt2). Deletion of liver estrogen receptor alpha prevented CETP-mediated decreases in liver TG content and increases in mRNA expression of TG oxidation targets. Liver-specific deletion of estrogen receptor alpha did not attenuate estrogen-mediated increases in plasma TG and VLDL-TG production in female mice expressing CETP. Deletion of liver small heterodimer partner attenuated CETP-mediated increases in plasma TG and VLDL-TG production with estrogen treatment. Deletion of small heterodimer partner also attenuated CETP-mediated increases in mRNA expression and protein activity of VLDL synthesis and assembly targets with estrogen treatment. Conclusion: These studies indicate several novel functions of CETP in regulating plasma and liver TG homeostasis. We also discovered that CETP expression in female mice also augments several aspects of estrogen action in liver that impact liver TG biology.

High level of serum cholesteryl ester transfer protein in active hepatitis C virus infection.

To determine the significance of cholesteryl ester transfer protein (CETP) in lipoprotein abnormalities in chronic hepatitis C virus (HCV) infection. We evaluated the significance of the serum concentration of CETP in 110 Japanese patients with chronic HCV infection. Fifty-five patients had active HCV infection, and HCV eradication had been achieved in 55. The role of CETP in serum lipoprotein abnormalities, specifically, in triglyceride (TG) concentrations in the four major classes of lipoproteins, was investigated using Pearson correlations in conjunction with multiple regression analysis and compared them between those with active HCV infection and those in whom eradication had been achieved. The serum CETP levels of patients with active HCV infection were significantly higher than those of patients in whom HCV eradication was achieved (mean ± SD, 2.84 ± 0.69 μg/mL vs 2.40 ± 1.00 μg/mL, P = 0.008). In multiple regression analysis, HCV infection status (active or eradicated) was an independent factor significantly associated with the serum CETP level. TG concentrations in low-density lipoprotein (mean ± SD, 36.25 ± 15.28 μg/mL vs 28.14 ± 9.94 μg/mL, P = 0.001) and high-density lipoprotein (HDL) (mean ± SD, 25.9 ± 7.34 μg/mL vs 17.17 ± 4.82 μg/mL, P < 0.001) were significantly higher in patients with active HCV infection than in those in whom HCV eradication was achieved. The CETP level was strongly correlated with HDL-TG in patients with active HCV infection (R = 0.557, P < 0.001), whereas CETP was not correlated with HDL-TG in patients in whom HCV eradication was achieved (R = -0.079, P = 0.56). Our results indicate that CETP plays a role in abnormalities of lipoprotein metabolism in patients with chronic HCV infection.

Anacetrapib for the treatment of dyslipidaemia: the last bastion of the cholesteryl ester transfer protein inhibitors?

ABSTRACTIntroduction: Inhibition of cholesteryl ester transfer protein (CETP) has emerged as a potential way to decrease cardiovascular risk by raising high density lipoprotein (HDL) cholesterol and lowering low density lipoprotein (LDL) cholesterol concentrations. However, high profile withdrawals of several CETP inhibitors have cast doubt over this hypothesis. Despite this concern, anacetrapib appears to be safe, well-tolerated and delivers a substantial increases in HDL cholesterol and reductions in LDL cholesterol as monotherapy and when combined with a statin.Areas covered: We discuss the role of CETP and HDL cholesterol as therapeutic targets, describe the pharmacokinetics and pharmacodynamics of anacetrapib, as well as report on the recent clinical trials.Expert opinion: The focus of CETP inhibition has shifted from HDL cholesterol-raising to LDL cholesterol-lowering. Although anacetrapib appears to be safe and is effective in altering lipid-related biochemical parameters of interest, its effect on cardiovascular outcomes remains unknown. Extrapolation of LDL cholesterol lowering to improved cardiovascular outcomes is not possible, because LDL and HDL functionality in the setting of anacetrapib treatment is unclear. The results of the phase III REVEAL randomised controlled trial will be critical for anacetrapib to establish a place in clinical care.

Is Cholesteryl Ester Transfer Protein Inhibition an Effective Strategy to Reduce Cardiovascular Risk? CETP as a Target to Lower CVD Risk: Suspension of Disbelief?

The notion that cardiovascular disease (CVD) remains a major burden to global morbidity and mortality has driven the quest for novel pharmaceutical agents to further reduce CVD risk. In this respect, cholesteryl ester transfer protein (CETP) has gained considerable interest, ever since one of the first descriptions in the 1980s that low CETP levels attributed to deleterious mutations in CETP were associated with longevity,1 a finding that was later suggested to result from higher high-density lipoprotein (HDL) cholesterol (-C) levels.2 The role of HDL as a causal determinant in CVD risk, however, has not been established, and HDL-C levels might very well be a risk marker rather than a risk factor.3,4 Response by Barter et al on p 440 It is striking that 2 decades after the first description of the potential beneficial effects of CETP mutations, the effect of CETP on CVD risk remains inconclusive, and this, by itself, suggests that CETP may not be an attractive therapeutic target for the prevention of CVD. The hypothesis that CETP inhibition would result in CVD risk reduction has been questioned in the past. Fielding and Havel,5 leading scientists in HDL metabolism, suggested that the increase in HDL-C induced by CETP inhibition could be misleading and in fact not be associated with CVD risk reduction. HDL particles formed on CETP inhibition are cholesteryl ester enriched and may lose their antiatherogenic bioactivity. Apart from insights from HDL metabolism, data derived from animal studies, large prospective human population studies, and clinical trials have generated conflicting results with respect to the role of CETP in CVD risk. We set out to summarize the published data that cast doubt on CETP as a therapeutic target to lower CVD risk. We focus on data derived from animal and human studies and …

Evacetrapib is a novel, potent, and selective inhibitor of cholesteryl ester transfer protein that elevates HDL cholesterol without inducing aldosterone or increasing blood pressure

Cholesteryl ester transfer protein (CETP) catalyses the exchange of cholesteryl ester and triglyceride between HDL and apoB containing lipoprotein particles. The role of CETP in modulating plasma HDL cholesterol levels in humans is well established and there have been significant efforts to develop CETP inhibitors to increase HDL cholesterol for the treatment of coronary artery disease. These efforts, however, have been hampered by the fact that most CETP inhibitors either have low potency or have undesirable side effects. In this study, we describe a novel benzazepine compound evacetrapib (LY2484595), which is a potent and selective inhibitor of CETP both in vitro and in vivo. Evacetrapib inhibited human recombinant CETP protein (5.5 nM IC(50)) and CETP activity in human plasma (36 nM IC(50)) in vitro. In double transgenic mice expressing human CETP and apoAI, evacetrapib exhibited an ex vivo CETP inhibition ED(50) of less than 5 mg/kg at 8 h post oral dose and significantly elevated HDL cholesterol. Importantly, no blood pressure elevation was observed in rats dosed with evacetrapib at high exposure multiples compared with the positive control, torcetrapib. In addition, in a human adrenal cortical carcinoma cell line (H295R cells), evacetrapib did not induce aldosterone or cortisol biosynthesis whereas torcetrapib dramatically induced aldosterone and cortisol biosynthesis. Our data indicate that evacetrapib is a potent and selective CETP inhibitor without torcetrapib-like off-target liabilities. Evacetrapib is currently in phase II clinical development.

Human cholesteryl ester transfer protein enhances insulin-mediated glucose uptake in adipocytes

Aims Adipose tissue plays an important role in the pathogenesis of insulin resistance, obesity, and Type-2 diabetes. Human adipocytes express abundant cholesteryl ester transfer protein (CETP). However, the function and role of CETP in regulating lipoprotein metabolism are mostly unknown. In this study, we examined whether CETP affected the insulin-mediated responses in adipocytes. Main methods Because mouse 3T3-L1 preadipocytes do not express CETP, we established a stable cell line expressing human CETP by transfecting the cells with pcDNA3.1/human CETP. We used a standard approach to differentiate the cells into mature adipocytes, and we examined the cholesterol balance and insulin responses. Key findings The human CETP stable cell line expressed stable levels of CETP without affecting the expression of either peroxisome proliferator-activated receptor-gamma (PPARγ) or glucose transporter-4 (GLUT4) throughout cell differentiation. CETP expression significantly increased the level of both total and free cholesterol in the mature adipocytes. Upon insulin stimulation, CETP expressing cells had significantly higher protein kinase B (Akt) phosphorylation and 2- 3H-deoxyglucose uptake, as compared with 3T3-L1 cells and cells transfected with control vector. Significance Human CETP expression increased cellular cholesterol levels and enhanced insulin-stimulated Akt phosphorylation and glucose uptake in adipocytes. Thus, CETP may modulate glucose metabolism and insulin action in addition to its effects on lipoprotein metabolism.

P260 CETP EXPRESSION REVERSES THE RECONSTITUTED HDL-INDUCED INCREASE IN VLDL

Human data suggest that reconstituted HDL (rHDL) infusion can induce atherosclerosis regression. Studies in mice indicated that rHDL infusion adversely affects VLDL levels, but this effect is less apparent in humans. This discrepancy may be explained by the fact that humans, in contrast to mice, express cholesteryl ester transfer protein (CETP). The aim of this study was to investigate the role of CETP in the effects of rHDL on VLDL metabolism by using APOE*3-Leiden (E3L) mice, a well-established model for human-like lipoprotein metabolism. At 1 h after injection, rHDL increased plasma VLDL-C and TG in E3L mice, but not in E3L mice cross-bred onto a human CETP background (E3L.CETP mice). This initial raise in VLDL, caused by competition between rHDL and VLDL for LPLmediated TG hydrolysis, was thus prevented by CETP. At 24 h after injection, rHDL caused a second increase in VLDL-C and TG in E3L mice, whereas rHDL had even decreased VLDL in E3L.CETP mice. This secondary raise in VLDL was due to increased hepatic VLDL-TG production. Collectively, we conclude that CETP protects against the rHDL-induced increase in VLDL. We anticipate that studies evaluating the anti-atherosclerotic efficacy of rHDL in mice that are naturally deficient for CETP should be interpreted with caution, and that treatment of atherogenic dyslipidemia by rHDL should not be combined with agents that aggressively reduce CETP activity. Copyright © 2011 by the American Society for Biochemistry and Molecular Biology, Inc.

Association of Taq 1B CETP polymorphism with insulin and HOMA levels in the population of the Canary Islands

Background and aims Cholesteryl ester transfer protein (CETP) is an enzyme with a key role in lipoprotein metabolism. A common genetic polymorphism, the Taq 1B, influences CETP activity and HDL-cholesterol levels, with individual homozygotes for the B1 allele exhibiting higher enzyme activity and lower HDL-cholesterol levels than carriers of at least one B2 allele. Our aim was to analyze the influence of Taq 1B CETP polymorphism on cardiovascular risk factors in a representative sample of adult subjects from Canary population. Methods and result A total of 518 adult subjects from the Canary Islands, enrolled in a nutritional survey (the ENCA study), were included. The Taq 1B polymorphism was analyzed by PCR–RFLP. Compared with individuals with at least one B2 allele, and after adjusting for age, sex, BMI, waist perimeter, smoking and alcohol intake, carriers of the B1B1 genotype showed lower HDL-cholesterol levels (geometric mean (95% CI): 46.6 (44.5–48.8) vs. 50.6 (49.1–52.9) mg/dl; P = 0.003); and higher insulin (geometric mean (95% CI): 11.1 (10.5–11.9) vs. 10.0 (9.5–10.5 μU/ml; P = 0.008) and HOMA levels (geometric mean (95% CI): 2.3 (2.1–2.5) vs. 2.1 (1.9–2.1); P = 0.009). In addition, the B1B1 genotype was more frequent in individuals who had low levels of HDL-cholesterol according to the National Cholesterol Education Program Adult Treatment Panel III (NCEP-ATP III) criteria (Odds Ratio (OR): 1.563; 95% CI: 1.04–2.34; P = 0.030), and in those included in the upper quartile of insulinemia (OR: 1.90; 95% CI: 1.20–3.03; P = 0.007) and HOMA (OR: 1.61; 95% CI: 1.02–2.57; P = 0.043). Conclusion The observed influence of Taq 1B polymorphism on insulin levels and HOMA highlights the possible role of CETP in the regulation of glucose homeostasis.

Elevated cholesteryl ester transfer protein concentration is associated with an increased risk for cardiovascular disease in women, but not in men, with Type 2 diabetes: the Hoorn Study

Cholesteryl ester transfer protein (CETP) exchanges neutral lipids between lipoproteins. As the role of CETP in the atherogenic process is still not fully clarified, we studied the association of CETP concentration with the prevalence of cardiovascular disease (CVD) and with intima-media thickness of the carotid artery (IMT) in subjects with normal glucose tolerance (NGT), impaird fasting glucose and/or impaired glucose tolerance (IFG/IGT) and Type 2 diabetes mellitus. Subjects (n = 566) were recruited from the 2000-2001 follow-up examination of the Hoorn study. CETP concentration was determined by immunoassay. CVD was defined as self-reported history of arterial surgery, cerebral vascular event, amputation, angina, claudication, possible infarction, measured ankle-brachial index < 0.90 or ECG abnormalities. The right common carotid artery IMT was measured by ultrasound at 10 mm proximal to the carotid bulb. In men, CETP concentration was not associated with CVD, irrespective of glucose tolerance status. In women with NGT or IGT, there was also no relationship. However, in women with Type 2 diabetes, the risk of CVD was increased in those with high CETP concentration [odds ratio = 3.34 (1.56; 7.14)]. No statistically significant association was found between CETP concentration and IMT in the entire cohort. In an elderly Caucasian population, associations of CETP concentration with CVD were dependent on glucose tolerance status and gender. The finding that high CETP concentration was strongly associated with increased prevalence of CVD in women with Type 2 diabetes warrants further investigation.

Oral Cholesteryl Ester Transfer Protein (CETP) Inhibitors: A Potential New Approach for Treating Coronary Artery Disease

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The relationship between cholesteryl ester transfer protein levels and risk factor profile in patients with familial hypercholesterolemia

Background: Cholesteryl ester transfer protein (CETP) mediates the transfer of neutral lipids between lipoproteins. The role of CETP in atherogenesis is controversial. To better understand the relationships between plasma CETP levels, lipoproteins and atherosclerosis, we assessed these parameters in patients with an enhanced risk for atherosclerosis. Methods and results: We investigated 281 patients with familial hypercholesterolemia (FH) in which the effects of two statins were compared in a 2-year, randomized, double-blinded study. Patients were stratified in quartiles according to their CETP baseline levels. In addition to correlations with decreased high-density lipoprotein cholesterol (HDL-c), increased low-density lipoprotein cholesterol (LDL-c) and enhanced triglyceride levels, higher CETP levels were also associated with reduced HDL particle size, and smaller and denser LDL. Statins reduced plasma CETP levels and atherogenic lipoproteins. Nevertheless, baseline CETP concentration was positively associated with IMT after 2 years of therapy. Conclusion: This study provides evidence that CETP levels are associated with a more atherogenic lipid profile and increased progression of atherosclerosis. Statin treatment improved the lipoprotein profile in FH patients, but to a lesser extent in those with high CETP levels. These findings might imply that statin treatment does not entirely counteract the lipoprotein abnormalities associated with high CETP levels.

Contribution of Cholesteryl Ester Transfer Protein and Lecithin:Cholesterol Acyltransferase to HDL Size Distribution

High‐density lipoproteins (HDL) includes a heterogeneous class of lipoproteins grouped into various subclasses that seem to have different antiatherogenic function. Cholesteryl ester transfer protein (CETP) and lecithin cholesterol acyltransferase (LCAT) play an active role in HDL remodeling. This study was designed to define the role of CETP and LCAT activities on HDL‐cholesterol (HDL‐C) plasma levels and HDL size distribution, as determined by nondenaturating polyacrylamide gradient gel electrophoresis in 47 clinically healthy Mexican individuals without personal and family history of coronary heart disease. Surprisingly, plasma activities of CETP (29 ± 4.1% of transfer) and LCAT (4.8 ± 2.2% of esterification) did not correlate either with HDL‐C plasma levels or with any other lipid parameter, indicating the poor contribution of these proteins to the lipid profile. The CETP activity showed a negative correlation with small HDL3b (r = − 0476, P < 0.05), whereas LCAT was positively associated with this HDL subclass (r = 0.466, P < 0.05). The LCAT showed a negative correlation with large HDL2a (r = − 0.674, P < 0.005). Nevertheless, when the LCAT/CETP ratio was calculated, we observed that the higher the ratio, the greater the relative proportion of small HDL3b (r = 0.551, P < 0.05) and HDL3c (r = 0.477, P < 0.05). These results suggest that the balance of LCAT and CETP activities have a great impact in the plasma HDL size distribution.

Deficiency of choresteryl ester transfer protein and gene polymorphisms of lipoprotein lipase and hepatic lipase are not associated with longevity.

Cholesteryl ester transfer protein (CETP) is one of the key proteins in reverse cholesterol transport (RCT). The role of CETP in atherosclerosis remains controversial. In this study we investigated the associations between polymorphisms of CETP (mutations in intron 14 and exon 15, and Taq1B), hepatic lipase (C-514T), lipoprotein lipase ( PvuII and HindIII), and ATP-binding cassette transporter 1 (R219K) loci and longevity in 256 centenarians and 190 healthy younger controls. Although heterozygous CETP deficiency and the B2 allele of the Taq1B polymorphism was consistently associated with higher HDL-C concentrations both in centenarians and controls, the allelic frequencies of those polymorphisms did not differ between the two groups. The allelic frequencies of other gene polymorphisms in RCT were not different between the two groups. Centenarians with lipoprotein lipase P(-/-) genotype had significantly higher HDL-C concentration than those with P(-/+) or with P(+/+), in contrast, there was no such a relationship among controls. In stepwise multiple regression analysis, serum albumin, CETP deficiency and lipoprotein lipase PvuII genotype were independently associated with HDL-C in centenarians. Sex, CETP deficiency, and the Taq1B genotype were also independently associated with HDL-C; however, lipoprotein lipase PvuII genotype had no significant effect on their HDL-C in controls. In conclusion, we observed that CETP deficiency and other gene polymorphisms in RCT have no impact on longevity for Japanese centenarians.

A cholesteryl ester transfer protein inhibitor attenuates atherosclerosis in rabbits.

Cholesteryl ester transfer protein (CETP) is a plasma protein that mediates the exchange of cholesteryl ester in high-density lipoprotein (HDL) for triglyceride in very low density lipoprotein (VLDL). This process decreases the level of anti-atherogenic HDL cholesterol and increases pro-atherogenic VLDL and low density lipoprotein (LDL) cholesterol, so CETP is potentially atherogenic. On the other hand, CETP could also be anti-atherogenic, because it participates in reverse cholesterol transport (transfer of cholesterol from peripheral cells through the plasma to the liver). Because the role of CETP in atherosclerosis remains unclear, we have attempted to develop a potent and specific CETP inhibitor. Here we describe CETP inhibitors that form a disulphide bond with CETP, and present one such inhibitor (JTT-705) that increases HDL cholesterol, decreases non-HDL cholesterol and inhibits the progression of atherosclerosis in rabbits. Our findings indicate that CETP may be atherogenic in vivo and that JTT-705 may be a potential anti-atherogenic drug.

Secretion of preβ HDL increases with the suppression of cholesteryl ester transfer protein in Hep G2 cells

Preβ HDL are small, protein rich lipoproteins that are predominantly composed of apo A-I, without apo A-II. Preβ HDL are secreted from the liver as nascent HDL and/or are produced in the incubated plasma by cholesteryl ester transfer protein (CETP). However, the role of CETP in the secretion of HDL from the liver has yet to be determined. In the present study, we examined the effect of the suppression of hepatic CETP by antisense oligodeoxynucleotides (ODNs) against CETP targeted to the liver on the secretion of apo A-I using a Hep G2 cell culture. The ODNs against CETP were coupled to asialoglycoprotein (ASOR) carrier molecules, which serve as an important method for the regulation of liver gene expression. Hep G2 cells were cultured in DMEM supplemented with 10% FBS. After 2 days, the medium was changed to DMEM with EGF and the cells were divided into three groups. The control group received saline, while the sense group was mixed with the sense ODNs complex and the antisense group was mixed with the antisense ODNs complex, respectively, for 2 days. Both the hepatic CETP mRNA and the CETP mass in the medium in the antisense group decreased significantly more than in the sense and the control groups (CETP mass: 1.697±0.410 ng/mg cell protein vs. 2.367±0.22 and 2.360±0.139, n=3 in each determination). In contrast, both the hepatic apo A-I mRNA and the apo A-I mass in the medium in the antisense group were significantly higher than those in the sense and the control groups (apo A-I mass; 1.877±0.215 μg/mg cell protein vs. 1.213±0.282 and 1.097±0.144, n=3 in each determination). The increase in apo A-I was mainly due to the increase in preβ apo A-I. These findings may partly explain why HDL and apo A-I increase in patients with CETP deficiency, while also indicating the possibility that the original level of preβ HDL is sufficient in such patients.

Cholesteryl ester transfer protein and its plasma regulator: lipid transfer inhibitor protein.

The interconnections between cholesteryl ester transfer protein (CETP) expression and lipid metabolism, and the possible roles of CETP in atherogenesis are examined. The importance of lipid transfer inhibitor protein in modulating CETP activity is detailed, and the consequences of this inhibitory activity on CETP-mediated events are proposed.