A polymorphism in the ABCG1 promoter is functionally associated with coronary artery disease in a Chinese Han population

Adrenal Abcg1 Controls Cholesterol Flux and Steroidogenesis

Cholesterol is the precursor of all steroids, but how cholesterol flux is controlled in steroidogenic tissues is poorly understood. The cholesterol exporter ABCG1 is an essential component of the reverse cholesterol pathway and its global inactivation results in neutral lipid redistribution to tissue macrophages. The function of ABCG1 in steroidogenic tissues, however, has not been explored. To model this, we inactivated Abcg1 in the mouse adrenal cortex, which led to an adrenal-specific increase in transcripts involved in cholesterol uptake and de novo synthesis. Abcg1 inactivation did not affect adrenal cholesterol content, zonation, or serum lipid profile. Instead, we observed a moderate increase in corticosterone production that was not recapitulated by the inactivation of the functionally similar cholesterol exporter Abca1. Altogether, our data imply that Abcg1 controls cholesterol uptake and biosynthesis and regulates glucocorticoid production in the adrenal cortex, introducing the possibility that ABCG1 variants may account for physiological or subclinical variation in stress response.

ATP-binding cassette transporter G1 (ABCG1) polymorphisms in pregnant women with gestational diabetes mellitus

CONTEXT AND OBJECTIVES

Gestational diabetes mellitus (GDM) is the most common metabolic disorder in pregnancy, and it often leads to adverse pregnancy outcomes and seriously harms the health of mothers and infants. ATP-binding cassette transporter G1 (ABCG1) plays critical roles in high-density lipoprotein (HDL) metabolism and reverse cholesterol transport. This study was designed to explore the relevance of the ABCG1 polymorphisms in the atherometabolic risk in GDM.

STUDY DESIGN

The case-control population consists of 1504 subjects. The rs2234715 and rs57137919 single nucleotide polymorphisms (SNPs) were genotyped using PCR and DNA sequencing, and clinical and metabolic parameters were determined.

RESULTS

The genotype distributions of the two SNPs showed no difference between the GDM patient and control groups. However, the rs57137919 polymorphism was associated with total cholesterol (TC), and diastolic blood pressure (DBP) levels in patients with GDM. Moreover, subgroup analysis showed that this polymorphism was associated with ApoA1 and DBP levels in overweight/obese patients with GDM, while it was associated with TC, and gestational weight gain (GWG) in non-obese patients with GDM. Meanwhile, the rs2234715 polymorphism was found to be associated with neonatal birth height in non-obese patients with GDM.

CONCLUSIONS

The two polymorphisms in the ABCG1 have an influence on atherometabolic traits, GWG, and fetal growth in GDM, depending on the BMI of the patients.

Association of methylation status of ABCA1/G1 genes with the risk of coronary artery disease

Background

ATP-binding cassette transporters A1/G1 (ABCA1/G1) is a main regulator of HDL (high-density lipoprotein) formation and reverse cholesterol transport. Impaired ABCA1/G1 genes function may seriously affect cholesterol homeostasis, leading to increased risk of cardiovascular disease. In the present study, the association of ABCA1/G1 genes methylation status with the risk of coronary artery disease (CAD), risk factors of CAD, and serum level of lipid parameters was investigated.

This study was conducted on 70 CAD patients and 40 control subjects. All CAD subjects with diabetes mellitus were excluded. The promoter methylation status of ABCA1/G1 genes was determined by the methylation-specific polymerase chain reaction (MS-PCR) method and serum lipid parameters were assessed using commercial kits.

Results

ABCA1 promoter methylation was higher in CAD group compared to the control participants (80% vs. 60%). Hypermethylation of the ABCA1 gene significantly increases the risk of CAD in the total population (OR 3.886, 95% CI (1.181–12.791), p = 0.026). ABCG1 methylation status showed no difference between CAD and control subjects. In addition, no significant association was noted between methylation status of ABCA1/G1 and serum level of lipid profile.

Conclusions

Altogether, our study shows that ABCA1 gene promoter hypermethylation may increase the risk of CAD, which may help identify people at risk of developing CAD.

Genetic variations in ABCA1/G1 associated with plasma lipid levels and risk of ischemic stroke

BACKGROUND

ATP binding cassette transporters ABCA1 and ABCG1 play a crucial role in cholesterol efflux and reverse cholesterol transport (RCT), thereby rendering ischemic stroke (IS) susceptibility. Variants of ABCA1/G1 have been implicated in etiology of IS. This study aimed to investigate the association between single-nucleotide polymorphisms (SNPs) of ABCA1/G1 with plasma lipid variability and the risk of IS in Chinese Han Population.

METHODS

Totally 249 IS patients and 226 healthy controls were enrolled and 10 SNPs of ABCA1/G1 were screened for genotyping by kompetitive allele-specific polymerase chain reaction (KASP) and validated by sanger sequencing. The logistic regression analysis was performed to identify risk alleles of IS and appropriate genetic model. The genetic risk scores (GRS) and predicted risks for all individuals was computed. Based on different plasma lipid levels, we applied stratified analyses for subgroups. Linkage disequilibrium (LD) test was used to explore different functional haplotype combinations. Association between specific allele or genotype of the SNPs of ABCA1/G1 and plasma lipid or lipoproteins levels were also investigated.

RESULTS

Besides total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C), significant differences of clinical data were observed between IS and control group. The rare GG genotype frequencies of rs4149338 on ABCA1 was higher in IS patients than those in controls (11.4%, 4.6%, respectively, P = 0.037). Frequencies of rs57137919 on ABCG1 for rare AA genotype was lower in IS group than those in control group (4.6%, 13.3%, respectively, P = 0.030). GRS showed ability to discriminate IS patients and controls (AUC = 0.633, P < 0.001). Haplotype A-A (rs4149339-rs4149338) was correlated with reduced risk of IS (P = 0.023). Association analysis showed that subjects with rare AA genotype of rs57137919 had the lowest LDL-C levels while rare GG genotype of rs4149338 had lower TC level than those with AA genotype. The mRNA expression of ABCG1 was higher in IS patients, especially in the patients with frequent GG genotype of rs57137919, and was positively correlated with higher ABCG1 expression level and plasma LDL-C level.

CONCLUSIONS

Polymorphisms of ABCA1/G1 associated with varieties of plasma lipid levels and risk of IS.

Effects of ABCG1 knockout on proteomic composition of HDL in mice on a chow diet and a High-Fat Diet

ATP-binding cassette transporter G1 (ABCG1) is a cellular transmembrane protein that transports oxysterol efflux from cells to high-density lipoprotein (HDL) particles in the plasma. Previous studies have demonstrated that an ABCG1 deficiency exerts an antiatherosclerotic function through the effects of oxysterol accumulation in cells to enhance apoptosis and regulate inflammatory processes. However, whether the deficiency of ABCG1 and the corresponding changes in the efflux of oxysterols could take a series of impacts on the proteomic composition of HDL remains unclear. Here, plasma HDL of ABCG1(-/-) mice and their wild-type controls on a normal chow diet (NCD) or a high-fat diet (HFD) were isolated by ultracentrifugation. The proportion of 7-ketocholesterol and the proteomic composition of samples were comparatively analyzed by LC-MS/MS. In NCD-fed mice, lipid metabolism-related protein (arachidonate 12-lipoxygenase) and antioxidative protein (pantetheinase) exhibited increased accumulation, and inflammatory response protein (alpha-1-antitrypsin) was decreased in accumulation in ABCG1(-/-) mice HDL. In HFD-fed mice, fewer proteins were detected than that of NCD-fed mice. The ABCG1(-/-) mice HDL exhibited increased accumulation of lipid metabolism-related proteins (e.g., carboxylesterase 1C, apolipoprotein (apo)C-4) and decreased accumulation of alpha-1-antitrypsin, as well as significantly reduced proportion of 7-ketocholesterol. Additionally, positive correlations were found between 7-ketocholesterol and some essential proteins on HDL, such as alpha-1-antitrypsin, apoA-4, apoB-100 and serum amyloid A. These results suggest a detrimental impact of oxysterols on HDL composition, which might affect the antiatherosclerotic properties of HDL. This article is protected by copyright. All rights reserved.

Genomic Variants and Multilevel Regulation of ABCA1, ABCG1, and SCARB1 Expression in Atherogenesis

Atheroprotective properties of human plasma high-density lipoproteins (HDLs) are determined by their involvement in reverse cholesterol transport (RCT) from the macrophage to the liver. ABCA1, ABCG1, and SR-BI cholesterol transporters are involved in cholesterol efflux from macrophages to lipid-free ApoA-I and HDL as a first RCT step. Molecular determinants of RCT efficiency that may possess diagnostic and therapeutic meaning remain largely unknown. This review summarizes the progress in studying the genomic variants of ABCA1, ABCG1, and SCARB1, and the regulation of their function at transcriptional and post-transcriptional levels in atherosclerosis. Defects in the structure and function of ABCA1, ABCG1, and SR-BI are caused by changes in the gene sequence, such as single nucleotide polymorphism or various mutations. In the transcription initiation of transporter genes, in addition to transcription factors, long noncoding RNA (lncRNA), transcription activators, and repressors are also involved. Furthermore, transcription is substantially influenced by the methylation of gene promoter regions. Post-transcriptional regulation involves microRNAs and lncRNAs, including circular RNAs. The potential biomarkers and targets for atheroprotection, based on molecular mechanisms of expression regulation for three transporter genes, are also discussed in this review.

Atrial Natriuretic Peptide Inhibited ABCA1/G1-dependent Cholesterol Efflux Related to Low HDL-C in Hypertensive Pregnant Patients

Objective: It has been reported that atrial natriuretic peptide (ANP) regulates lipid metabolism by stimulating adipocyte browning, lipolysis, and lipid oxidation, and by impacting the secretion of adipokines. In our previous study, we found that the plasma ANP concentration of hypertensive disorders of pregnancy (HDP) was significantly increased in comparison to that of normotensive pregnancy patients. Thus, this study’s objective was to investigate the lipid profile in patients with HDP and determine the effects of ANP on the cholesterol efflux in THP-1 macrophages.

Methods: A total of 265 HDP patients and 178 normotensive women as the control group were recruited. Clinical demographic characteristics and laboratory profile data were collected. Plasma total triglycerides (TGs), total cholesterol (TC), low-density cholesterol (LDL-C), and high-density cholesterol (HDL-C) were compared between the two groups. THP-1 monocytes were incubated with different concentrations of ANP. ATP-binding cassette transporter A1 (ABCA1) and ATP-binding cassette transporter G1 (ABCG1) mRNA and protein were evaluated. ABCA1- and ABCG1-mediated cholesterol efflux to apolipoprotein A-Ⅰ (apoA-Ⅰ) and HDL, respectively, were measured by green fluorescent labeled NBD cholesterol. Natriuretic peptide receptor A (NPR-A) siRNA and specific agonists of the peroxisome proliferator–activated receptor-γ (PPAR-γ) and liver X receptor α (LXRα) were studied to investigate the mechanism involved.

Results: Plasma TG, TC, LDL-C, and LDL-C/HDL-C were significantly increased, and HDL-C was significantly decreased in the HDP group in comparison to the control (all p < 0.001). ANP inhibited the expression of ABCA1 and ABCG1 at both the mRNA and protein levels in a dose-dependent manner. The functions of ABCA1- and ABCG1-mediated cholesterol efflux to apoA-I and HDL were significantly decreased. NPR-A siRNA further confirmed that ANP binding to its receptor inhibited ABCA1/G1 expression through the PPAR-γ/LXRα pathway.

Conclusions: ABCA1/G1 was inhibited by the stimulation of ANP when combined with NPR-A through the PPAR-γ/LXRα pathway in THP-1 macrophages. The ABCA1/G1-mediated cholesterol efflux was also impaired by the stimulation of ANP. This may provide a new explanation for the decreased level of HDL-C in HDP patients.

Effects of a nurse-led eHealth cardiac rehabilitation programme on health outcomes of patients with coronary heart disease: A randomised controlled trial

BACKGROUND

The uptake of and adherence to cardiac rehabilitation remain suboptimal despite its apparent health benefits in modifying risk factors and slowing disease progression. eHealth refers to the use of information and communication technologies for health-related purposes. It is a promising approach for improving participation in cardiac rehabilitation by enabling instant contact, hypermedia information delivery, technology-monitored functionalities and individualised progress monitoring.

AIMS

To evaluate the effects of a nurse-led eHealth cardiac rehabilitation (NeCR) system on health behaviours, cardiac self-efficacy, anxiety and depression, health-related quality of life, risk parameters and unplanned use of care services for people with coronary heart disease.

DESIGN

A single-blinded randomised controlled trial design was used.

METHODS

The study randomly assigned 146 patients hospitalised for coronary heart disease to receive either the NeCR intervention or the usual care. Underpinned by social cognitive theory, the intervention commenced before hospital discharge with an in-person session by the nurse to identify individualised self-care needs, set goals and develop an action plan to enhance behavioural risk factor modification and orientate the patient to the use of the information and communication technology platform for cardiac rehabilitation. After discharge, the e-platform helped patients gain knowledge of disease management and monitor goal attainment for health behavioural changes. The nurse provided feedback on the patients' goal attainment and lifestyle modifications on a weekly basis in a small group format through the WeChat platform, thus also mobilising peer influence. Data for lifestyle behaviours, physiological risk parameters and clinical outcomes were collected at baseline and at 6 and 12 weeks post-intervention.

RESULTS

At 6 weeks post-intervention, participants in the intervention group showed significant improvement in the number of steps/day (β = 2628.48, p = .022), the number of minutes/week sitting (β = -640.30, p = .006) and their health-promoting lifestyle profile (β = 25.17, p < .001) compared with the control group. Improvements in the number of steps/day (β = 2520.00, p = .006), the number of minutes/week sitting (β = -719.73, p = .004) and health-promoting lifestyle (β = 16.09, p < .001) were sustained until the 12-week post-intervention endpoint. Moreover, participants showed significantly greater improvement in self-efficacy (β = 0.61, p = .005) and health-related quality of life (mean difference = 0.56, p < .001) than the control group at the study endpoint.

CONCLUSIONS

The findings of this study demonstrate the effectiveness of the NeCR intervention in modifying behavioural risk factors and improving health-related quality of life. These findings also provide insights into the application of eHealth nursing interventions to enhance the rehabilitation of patients with coronary heart disease.

TRIAL REGISTRATION

ChiCTR1800020411.

Mammalian ABCG-transporters, sterols and lipids: To bind perchance to transport?

Members of the ATP binding cassette (ABC) transporter family perform a critical function in maintaining lipid homeostasis in cells as well as the transport of drugs. In this review, we provide an update on the ABCG-transporter subfamily member proteins, which include the homodimers ABCG1, ABCG2 and ABCG4 as well as the heterodimeric complex formed between ABCG5 and ABCG8. This review focusses on progress made in this field of research with respect to their function in health and disease and the recognised transporter substrates. We also provide an update on post-translational regulation, including by transporter substrates, and well as the involvement of microRNA as regulators of transporter expression and activity. In addition, we describe progress made in identifying structural elements that have been recognised as important for transport activity. We furthermore discuss the role of lipids such as cholesterol on the transport function of ABCG2, traditionally thought of as a drug transporter, and provide a model of potential cholesterol binding sites for ABCG2.

Is it possible ABC transporters genetic variants influence the outcomes of a weight-loss diet in obese women?

ATP-Binding Cassette (ABC) transporters are involved in cholesterol metabolism and their dysfunctions could lead to obesity-associated complications. It was investigated whether SNPs in the ABCA1 (rs1800977 and rs2230806), ABCA7 (rs2279796) and ABCG1 (rs692383 and rs3827225) genes can modulate the responsiveness of 137 obese women to a weight-loss dietary intervention. Thus, anthropometric and lipid profiles were collected at baseline and after nine weeks of a calorie-restricted diet of 600kcal per day and participants were genotyped for the ABC genes SNPs. Regarding the transversal analysis, the ABCA7 rs2279796 GG genotype was associated with higher levels of total cholesterol and LDL-c at baseline (p = 0.044 for both). Association between ABCG1 rs692383 AA genotype and lower BMI were found in the post-diet moment, however, statistical significance was lost after multi-test correction. Regarding the longitudinal analysis, after multi-test correction, the association remained between ABCG1 rs692383 G allele and HDL-c levels: G allele carriers had a lower HDL-c reduction (p = 0.043). Results suggest the standard weight-loss diet applied in this study could attenuate the ABCA7 rs2279796 GG genotype effects found at baseline and non-dyslipidemic obese women with ABCG1 rs692383 G allele are benefitting from the diet with a lower reduction in HDL-c levels.

A Promoter Polymorphism (Rs57137919) of ABCG1 Gene Influence on Blood Lipoprotein in Chinese Han Population

BACKGROUND

Adenosine triphosphate-binding cassette subfamily G member 1 (ABCG1) has the function of transporting free intracellular cholesterol to extracellular high-density lipoprotein (HDL) particles, which play a crucial role in atherosclerosis. The goal of this study is to examine the relationship between the polymorphisms of the ABCG1 gene promoter region and ischemic stroke.

METHODS

In the present study, a case-control association study was designed to identify 3 single-nucleotide polymorphisms (SNPs; rs5713919, rs1378577, and rs1893590), which were located in the promoter region of ABCG1 gene by kompetitive allele-specific polymerase chain reaction genotyping approach. The in vitro luciferase assay was done to estimate the effect of rs5713919 on gene expression. Finally, the relationships of 3 SNPs of ABCG1 gene with plasma lipids and lipoproteins were investigated in this Chinese cohort.

RESULTS

The correlation analysis between lipids and genotypes showed that the rs57137919 locus genotype was significantly associated with HDL cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C) levels (P = 0.021 and P = 0.017, respectively), and the GA and AA genotypes had higher HDL-C levels than the GG genotype.

CONCLUSIONS

Our study provides evidence that ABCG1 promoter region polymorphism rs57137919 has an influence on plasma HDL-C and LDL-C levels in Chinese Han population.

New candidate genes for ST-elevation myocardial infarction

BACKGROUND

Despite extensive research in atherosclerosis, the mechanisms of coronary atherothrombosis in ST-elevation myocardial infarction (STEMI) patients are undetermined.

OBJECTIVES

Our aim was to find candidate genes involved in STEMI by analysing leucocyte gene expression in STEMI patients, without the influence of secondary inflammation from innate immunity, which was assumed to be a consequence rather than the cause of coronary atherothrombosis.

METHODS

Fifty-one patients were included at coronary angiography because of STEMI. Arterial blood was sampled in the acute phase (P1), at 24-48 h (P2) and at 3 months (P3). Leucocyte RNA was isolated and gene expression analysis was performed by Affymetrix Human Transcriptome Array 2.0. By omission of up- or downregulated genes at P2, secondary changes from innate immunity were excluded. Genes differentially expressed in P1 when compared to the convalescent sample in P3 were determined as genes involved in STEMI.

RESULTS

Three genes were upregulated at P1 compared to P3; ABCG1 (P = 5.81 × 10^-5 ), RAB20 (P = 3.69 × 10^-5 ) and TMEM2 (P = 7.75 × 10^-6 ) whilst four were downregulated; ACVR1 (P = 9.01 × 10^-5 ), NFATC2IP (P = 8.86 × 10^-5 ), SUN1 (P = 3.87 × 10^-5 ) and TTC9C (P = 7.18 × 10^-6 ). These genes were also highly expressed in carotid atherosclerotic plaques.

CONCLUSIONS

We found seven genes involved in STEMI. The study is unique regarding the blood sampling in the acute phase and omission of secondary expressed genes from innate immunity. However, the results need to be replicated by future studies.

Lipid trafficking in cardiovascular disease

The reduction of plasma apolipoprotein B (apoB) containing lipoproteins has long been pursued as the main modifiable risk factor for the development of cardiovascular disease (CVD). This has led to an intense search for strategies aiming at reducing plasma apoB-lipoproteins, culminating in reduction of overall CV risk. Despite 3 decades of progress, CVD remains the leading cause of morbidity and mortality worldwide and, as such, new therapeutic targets are still warranted. Clinical and preclinical research has moved forward from the original concept, under which some lipids must be accumulated and other removed to achieve the ideal condition in disease prevention, into the concept that mechanisms that orchestrate lipid movement between lipoproteins, cells and organelles is equally involved in CVD. As such, this review scrutinizes potentially atherogenic changes in lipid trafficking and assesses the molecular mechanisms behind it. New developments in risk assessment and new targets for the mitigation of residual CVD risk are also addressed.

TIMD4 rs6882076 SNP Is Associated with Decreased Levels of Triglycerides and the Risk of Coronary Heart Disease and Ischemic Stroke

Background: The T-cell immunoglobulin and mucin domain 4 gene (TIMD4) rs6882076 single nucleotide polymorphism (SNP) has been associated with serum total cholesterol, low-density lipoprotein cholesterol and triglycerides (TG) levels, but the results are inconsistent. Moreover, little is known about such association in Chinese populations. The aim of this study was to detect the association of the TIMD4 rs6882076 SNP and serum lipid levels and the risk of coronary heart disease (CHD) and ischemic stroke (IS) in a Southern Chinese Han population. Methods: Genotypes of the TIMD4 rs6882076 SNP in 1765 unrelated subjects (CHD, 581; IS, 559 and healthy controls, 625) were determined by the Snapshot Technology. Results: The genotypic and allelic frequencies of the TIMD4 rs6882076 SNP were different between the CHD/IS patients and controls (P < 0.05 for all). The subjects with CT/TT genotypes were associated with decreased risk of CHD (P = 0.014 for CT/TT vs. CC genotypes, P = 0.010 for T vs. C alleles) and IS (P = 0.003 for CT/TT vs. CC genotypes; P = 0.016 for T vs. C alleles). The T allele carriers in healthy controls were also associated with decreased levels of serum TG. Conclusions: The results of the present study suggest that the TIMD4 rs6882076 SNP is associated with decreased risk of CHD and IS in our study population. It is likely to decrease the CHD and IS risk by reducing serum TG levels.

Analysis of differential gene expression by RNA-seq data in ABCG1 knockout mice

AIMS

The previous studies on ABCG1 using genetically modified mice showed inconsistent results on atherosclerosis. The aim of this study was to determine whether accurate target knockout of ABCG1 would result in transcriptional changes of other atherosclerosis-related genes.

METHODS

ABCG1 knockout mouse model was obtained by precise gene targeting without affecting non-target DNA sequences in C57BL/6 background. The wildtype C57BL/6 mice were regarded as control group. 12-week-old male mice were used in current study. We performed whole transcriptome analysis on the peripheral blood mononuclear cells obtained from ABCG1 knockout mice (n = 3) and their wildtype controls (n = 3) by RNA-seq.

RESULTS

Compared with wildtype group, 605 genes were modified at the time of ABCG1 knockout and expressed differentially in knockout group, including 306 up-regulated genes and 299 down-regulated genes. 54 genes were associated with metabolism regulation, of which 13 were related to lipid metabolism. We also found some other modified genes in knockout mice involved in cell adhesion, leukocyte transendothelial migration and apoptosis, which might also play roles in the process of atherosclerosis. 7 significantly enriched GO terms and 19 significantly enriched KEGG pathways were identified, involving fatty acid biosynthesis, immune response and intracellular signal transduction.

CONCLUSIONS

ABCG1 knockout mice exhibited an altered expression of multiple genes related to many aspects of atherosclerosis, which might affect the further studies to insight into the effect of ABCG1 on atherosclerosis with this animal model.

ANGPTL4 variants and their haplotypes are associated with serum lipid levels, the risk of coronary artery disease and ischemic stroke and atorvastatin cholesterol-lowering responses

Background

This study aimed to assess the association between the angiopoietin-like protein 4 gene (ANGPTL4) single nucleotide polymorphisms (SNPs) and serum lipid levels, the risk of coronary artery disease (CAD) and ischemic stroke (IS), and response to atorvastatin therapy in a Southern Chinese Han population.

Methods

Genotypes of the ANGPTL4 rs4076317, rs7255436, rs1044250 and rs2967605 SNPs in 1,654 unrelated subjects (CAD, 568; IS, 537; and controls, 549) were determined by the Snapshot technology. Another group of 724 hyperlipidemic patients was selected and treated with atorvastatin calcium tablet 20 mg/day for 8 weeks.

Results

The rs2967605 CT/TT genotypes were associated with a decreased risk of CAD (adjusted OR = 0.68, 95% CI = 0.47-0.99, P = 0.043 for CT/TT vs. CC) and IS (adjusted OR = 0.55, 95% CI = 0.38-0.80, P = 0.020 for CT/TT vs. CC). There was no significant association between the four SNPs and angiographic severity of CAD. The subjects with the rs4076317 CG/CC genotypes in controls had higher total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) levels than the subjects with the GG genotype (P < 0.001; a P < 0.0018 was regarded statistically significant by the Bonferroni correction). The subjects with rs4076317CG/GG genotypes had lower TC and LDL-C levels than the subjects with CC genotype after atorvastatin treatment (P < 0.001).

Conclusions

The observed associations suggest that the ANGPTL4 variants have a potential role on serum lipid levels and atherosclerosis-related diseases in the Chinese Han population, especially the ANGPTL4 rs4076317 and rs2967605 SNPs.

The effects of cigarette smoking and smoking cessation on high-density lipoprotein functions: implications for coronary artery disease

BACKGROUND

Smoking cessation was associated with improved prognosis of coronary artery disease. This study was designed to investigate the effect of smoking cessation on high-density lipoprotein functionality in coronary artery disease patients.

METHODS

In this prospective, randomized and parallel controlled study, coronary artery disease smokers ( n = 28) and healthy smokers ( n = 30) were divided into smoking cessation group and continuous smoking group, respectively. Blood samples were collected before and after three-month smoking cessation. Plasma high-density lipoprotein was isolated by density gradient centrifugation. The ability of high-density lipoprotein against copper-induced oxidation of lipoprotein was determined to evaluate the antioxidative property of high-density lipoprotein, and the macrophage migration inhibited by high-density lipoprotein was tested to identify the antichemotactic property of high-density lipoprotein. High-density lipoprotein-induced macrophage cholesterol efflux was measured by fluorescence spectrometry using NBD cholesterol analogue. Healthy non-smoking volunteers were enrolled as the baseline control.

RESULTS

The baseline antioxidative, antichemotactic ability of high-density lipoprotein and high-density lipoprotein-induced cellular cholesterol efflux in coronary artery disease smokers and healthy smokers were significantly attenuated when compared with those in healthy non-smokers. After three-month smoking cessation, both the antioxidative ability and antichemotactic ability of high-density lipoprotein were improved significantly in coronary artery disease smokers. However, high-density lipoprotein-induced cellular cholesterol efflux was not increased by smoking cessation. In in vitro experiments, carbon monoxide reduced the antioxidative ability and nicotine enhanced the antichemotactic ability of high-density lipoprotein.

CONCLUSIONS

Smoking cessation is an effective measure to improve high-density lipoprotein functions in coronary artery disease smokers. Our study re-emphasizes the importance of smoking cessation in the secondary prevention of coronary artery disease.

Development of a Polymerase Chain Reaction/Ligase Detection Reaction Assay for Detection of CYP2C19 Polymorphisms

AIMS

Cytochrome P450 2C19 (CYP2C19) genotypes are associated with differential drug metabolism. The aim of this study was to establish a reliable assay for CYP2C19 genotyping based on a polymerase chain reaction/ligase detection reaction (PCR-LDR).

MATERIALS AND METHODS

Specific primers and probes were designed to detect CYP2C19*1, *2, *3, and *17. A control for each allele was prepared and used for performance evaluation. A total of 200 clinical samples were analyzed using the PCR-LDR assay and Sanger sequencing.

RESULTS

The detection limit of the PCR-LDR assay was 2 ng/μL of genomic DNA. Common interfering substances in the blood did not affect the results of the detection. For the clinical samples, the results of the PCR-LDR and the Sanger sequencing were identical. Among the 200 patients, 104 (52%) were wild type (*1/*1), 64 (32%) were *1/*2, 16 (8%) were *1/*3, 8 (4%) were *2/*2, 7 (3.5%) were *2/*3, and 1 (0.5%) was *1/*7. No *3/*3 genotype was detected in these patients.

CONCLUSION

This PCR-LDR assay is reliable for the detection of CYP2C19 genotypes in a clinical setting. It will be a useful tool to screen for CYP2C19 loss-of-function alleles in patients before clopidogrel and proton pump inhibitor treatment.

Toll-like receptor 4 rs11536889 is associated with angiographic extent and severity of coronary artery disease in a Chinese population

Toll-like receptor 4 (TLR4) is a key modulator in many inflammation-related diseases. Polymorphisms in the TLR4 gene may alter TLR4 expression and affect the extent and severity of coronary artery disease (CAD). We analyzed 3 polymorphisms of TLR4 in 607 Chinese subjects who underwent coronary arteriography. Blood samples were collected to identify the polymorphisms. We evaluated the relationships between the polymorphisms and the number of vessels involved in coronary stenosis, Gensini scores, and Duke prognostic scores. We found that rs11536889 was associated with an increased risk of 3-vessel disease. When subjects with 3-vessel disease were compared to subjects with nonsignificant CAD, rs11536889 variant genotypes were associated with an increased risk of 3-vessel disease (GC/CC vs. GG: OR=2.06, 95%CI=1.21-3.51). When subjects with 3-vessel disease were compared to subjects with 1-vessel disease, rs11536889 variant genotypes were associated with an increased risk of 3-vessel disease (GC vs. GG: OR=2.14, 95%CI=1.20-3.79; GC/CC vs. GG: OR=2.06, 95%CI=1.20-3.54). When subjects with 3-vessel disease were compared to subjects with non-3-vessel disease, rs11536889 variant genotypes were associated with an increased risk of 3-vessel disease (GC vs. GG: OR=1.76, 95%CI=1.12-2.75; GC/CC vs. GG: OR=1.83, 95%CI=1.19-2.82). The TLR4 rs11536889 polymorphism was also related to Gensini score (P=0.02). The Gensini score was higher in subjects with the variant CC and GC/CC genotype than in subjects with the wild GG genotype (61.28 1.84 and 57.6434.82 vs. 51.2734.57). Our results demonstrate that TLR4 rs11536889 polymorphism is a novel genetic factor in the development of CAD, influencing the extent and severity of CAD.

Association between the TIMD4-HAVCR1 variants and serum lipid levels, coronary heart disease and ischemic stroke risk and atorvastatin lipid-lowering efficacy

Little is known about the association of the TIMD4 (T-cell immunoglobulin and mucin domain 4 gene)-HAVCR1 (hepatitis A virus cellular receptor 1) variants and lipid metabolism, the risk of coronary heart disease (CHD) and ischemic stroke (IS). The present study aimed to determine the TIMD4-HAVCR1 variants, their haplotypes and gene–environment interactions on serum lipid levels, the risk of CHD and IS, and the lipid-lowering efficacy of atorvastatin in a southern Chinese Han population. Genotypes of three variants in 622 controls, 579 CHD, and 546 IS patients were determined by the Snapshot technology. Atorvastatin calcium tablet (20 mg/day) was given in 724 hyperlipidemic patients for 8 weeks after genotyping. The rs12522248 genotypic and allelic frequencies were different between controls and patients, and were associated with the risk of CHD and IS. The rs1501908G-rs12522248T-rs2036402T haplotype was associated with an increased risk of CHD; the G-C-T haplotype was associated with lower risk of CHD; and the C-C-C haplotype was associated with an increased risk of IS. Variants and their haplotypes in controls were associated with triglyceride (rs1501908), low-density lipoprotein cholesterol (LDL-C, rs1501908, G-T-T), high-density lipoprotein cholesterol (HDL-C, rs12522248, C-C-C) and the ratio of total cholesterol (TC) to HDL-C (C-C-C). Interactions of rs1501908- and rs2036402-alcohol (HDL-C); rs1501908- and rs12522248-high body mass index (hBMI, ≥24 kg/m²; TC); and TIMD4-HAVCR1 variants-atorvastatin on several lipid parameters were detected. Interactions of rs12522248TC/CC-hBMI, G-T-T-, and C-C-C-smoking on the risk of CHD; and C-C-C-smoking, C-C-C-, and G-C-T-hBMI on the risk of IS were also observed. These findings suggest that the TIMD4-HAVCR1 variants may be the genetic risk factors for CHD and IS.

Blood-Based DNA Methylation Biomarkers for Type 2 Diabetes: Potential for Clinical Applications

Type 2 diabetes (T2D) is a leading cause of death and disability worldwide. It is a chronic metabolic disorder that develops due to an interplay of genetic, lifestyle, and environmental factors. The biological onset of the disease occurs long before clinical symptoms develop, thus the search for early diagnostic and prognostic biomarkers, which could facilitate intervention strategies to prevent or delay disease progression, has increased considerably in recent years. Epigenetic modifications represent important links between genetic, environmental and lifestyle cues and increasing evidence implicate altered epigenetic marks such as DNA methylation, the most characterized and widely studied epigenetic mechanism, in the pathogenesis of T2D. This review provides an update of the current status of DNA methylation as a biomarker for T2D. Four databases, Scopus, Pubmed, Cochrane Central, and Google Scholar were searched for studies investigating DNA methylation in blood. Thirty-seven studies were identified, and are summarized with respect to population characteristics, biological source, and method of DNA methylation quantification (global, candidate gene or genome-wide). We highlight that differential methylation of the TCF7L2, KCNQ1, ABCG1, TXNIP, PHOSPHO1, SREBF1, SLC30A8, and FTO genes in blood are reproducibly associated with T2D in different population groups. These genes should be prioritized and replicated in longitudinal studies across more populations in future studies. Finally, we discuss the limitations faced by DNA methylation studies, which include including interpatient variability, cellular heterogeneity, and lack of accounting for study confounders. These limitations and challenges must be overcome before the implementation of blood-based DNA methylation biomarkers into a clinical setting. We emphasize the need for longitudinal prospective studies to support the robustness of the current findings of this review.

Critical Role of the Human ATP-Binding Cassette G1 Transporter in Cardiometabolic Diseases

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

The effect of MVK-MMAB variants, their haplotypes and G×E interactions on serum lipid levels and the risk of coronary heart disease and ischemic stroke

Aim

This study aimed to detect the association of the mevalonate kinase (MVK) and methylmalonic aciduria (cobalamin deficiency) cblB type (MMAB) gene variants, their haplotypes, and gene-environment (G×E) interactions on serum lipid levels and the risk of coronary heart disease (CHD) and ischemic stroke (IS) in a Chinese Han population.

Methods

Genotyping of the rs3759387, rs7134594, rs877710 and rs9593 SNPs in 846 CHD and 869 IS patients and 847 healthy controls was performed by PCR-RFLP and Sanger sequencing. Logistic regression and factor regression were used to investigate the association of 4 MVK-MMAB SNPs and serum lipid levels and the risk of CHD and IS.

Results

The genotypic and allelic frequencies of the rs3759387 and rs7134594 SNPs differed between controls and patients (P < 0.0125-0.001). The rs3759387 SNP was associated with the risk of CHD and IS in different genetic models. The A-T-G-A and C-T-C-T haplotypes were associated with increased risk of CHD. The haplotype of A-T-G-A was associated with an increased risk of IS, whereas the C-T-G-A haplotype was associated with a decreased risk of IS. Interactions of C-T-C-T-smoking or C-T-C-T-age on the risk of CHD, and A-T-G-A-hypertension or A-T-G-A-age on the risk of IS were also observed. The subjects with the rs3759387AA genotype in controls had lower high-density lipoprotein cholesterol (HDL-C) levels than did the subjects with AC/CC genotypes. Several SNPs interacted with alcohol consumption and cigarette smoking to increase serum HDL-C and apolipoprotein A1 levels, but they interacted with body mass index ≥ 24 kg/m² to decrease serum HDL-C and apolipoprotein A1 levels.

Conclusion

Several MVK-MMAB variants, especially the rs3759387 SNP, 4 main haplotypes, and G×E interactions were associated with serum lipid levels and the risk of CHD and IS in a Chinese Han population.

Promoter Polymorphism of Toll-Like Receptor 4 is Associated with a Decreased Risk of Coronary Artery Disease: A Case-Control Study in the Chinese Han Population

Background

Coronary artery disease (CAD) is considered a chronic inflammatory disease of the blood vessels. Toll-like receptor 4 (TLR4) is a transmembrane receptor involved in inflammatory reactions. The aim of this study was to determine the association between polymorphisms in the promoter region and 3′-untranslated region (3′-UTR) of TLR4, and the associated CAD risk.

Material/Methods

This study enrolled 424 participants with CAD and 424 controls without CAD. The polymorphisms in the promoter region and 3′-UTR of TLR4 were identified from the HapMap database, including rs10116253, rs10983755, and rs11536889. Genomic DNA was extracted from peripheral blood. Polymerase chain reaction-restriction fragment length polymorphism was performed to identify genotype polymorphisms. Relative luciferase activity was measured using the dual-luciferase reporter assay system.

Results

TLR4 rs10116253 in the promoter region was associated with CAD risk. The variant (CC+TC) genotypes of rs10116253 were associated with a decreased CAD risk (OR 95% CI 0.73 (0.54–0.98), p=0.034). In the stratification analyses, the variant (CC+TC) genotypes of rs10116253 were observed to have a relationship with decreased CAD risk in the male subgroup (OR: 95% CI 0.68 (0.48–0.98), p=0.041). Moreover, the variant CC and (CC+TC) genotypes of rs10116253 were correlated with a decreased CAD risk in participants younger than 60-year-old (TC: OR (95% CI 0.62 (0.39–0.98), p=0.042; TC+CC: OR 95% CI 0.63 (0.41–0.98), p=0.039). Regarding rs10116253, the luciferase activity of the mutant C allele construct was lower than that of the wild T allele construct (5.215±0.009 vs. 5.304±0.041; p=0.087).

Conclusions

The results provided evidence of an association between the TLR4 rs10116253 in the promoter region and a reduced risk of CAD.

ATP Binding Cassette Transporter ABCA7 Regulates NKT Cell Development and Function by Controlling CD1d Expression and Lipid Raft Content

ABCA7 is an ABC transporter expressed on the plasma membrane, and actively exports phospholipid complexes from the cytoplasmic to the exocytoplasmic leaflet of membranes. Invariant NKT (iNKT) cells are a subpopulation of T lymphocytes that recognize glycolipid antigens in the context of CD1d-mediated antigen presentation. In this study, we demonstrate that ABCA7 regulates the development of NKT cells in a cell-extrinsic manner. We found that in Abca7^−/− mice there is reduced expression of CD1d accompanied by an alteration in lipid raft content on the plasma membrane of thymocytes and antigen presenting cells. Together, these alterations caused by absence of ABCA7 negatively affect NKT cell development and function.

Loss of ABCG1 influences regulatory T cell differentiation and atherosclerosis

ATP-binding cassette transporter G1 (ABCG1) promotes cholesterol accumulation and alters T cell homeostasis, which may contribute to progression of atherosclerosis. Here, we investigated how the selective loss of ABCG1 in T cells impacts atherosclerosis in LDL receptor-deficient (LDLR-deficient) mice, a model of the disease. In LDLR-deficient mice fed a high-cholesterol diet, T cell-specific ABCG1 deficiency protected against atherosclerotic lesions. Furthermore, T cell-specific ABCG1 deficiency led to a 30% increase in Treg percentages in aorta and aorta-draining lymph nodes (LNs) of these mice compared with animals with only LDLR deficiency. When Abcg1 was selectively deleted in Tregs of LDLR-deficient mice, we observed a 30% increase in Treg percentages in aorta and aorta-draining LNs and reduced atherosclerosis. In the absence of ABCG1, intracellular cholesterol accumulation led to downregulation of the mTOR pathway, which increased the differentiation of naive CD4 T cells into Tregs. The increase in Tregs resulted in reduced T cell activation and increased IL-10 production by T cells. Last, we found that higher ABCG1 expression in Tregs was associated with a higher frequency of these cells in human blood samples. Our study indicates that ABCG1 regulates T cell differentiation into Tregs, highlighting a pathway by which cholesterol accumulation can influence T cell homeostasis in atherosclerosis.

MADD-FOLH1 Polymorphisms and Their Haplotypes with Serum Lipid Levels and the Risk of Coronary Heart Disease and Ischemic Stroke in a Chinese Han Population

This study aimed to detect the association of the MADD-FOLH1 single nucleotide polymorphisms (SNPs) and their haplotypes with the risk of coronary heart disease (CHD) and ischemic stroke (IS) in a Chinese Han population. Six SNPs of rs7395662, rs326214, rs326217, rs1051006, rs3736101, and rs7120118 were genotyped in 584 CHD and 555 IS patients, and 596 healthy controls. The genotypic and allelic frequencies of the rs7395662 SNP were different between controls and patients, and the genotypes of the rs7395662 SNP were associated with the risk of CHD and IS in different genetic models. Six main haplotypes among the rs1051006, rs326214, rs326217, rs3736101, and rs7120118 SNPs were detected in our study population, the haplotypes of G-G-T-G-C and G-A-T-G-T were associated with an increased risk of CHD and IS, respectively. The subjects with rs7395662GG genotype in controls had higher triglyceride (TG) and lower high-density lipoprotein cholesterol (HDL-C) levels than the subjects with AA/AG genotypes. Several SNPs interacted with alcohol consumption to influence serum TG (rs326214, rs326217, and rs7120118) and HDL-C (rs7395662) levels. The SNP of rs3736101 interacted with cigarette smoking to modify serum HDL-C levels. The SNP of rs1051006 interacted with body mass index ≥24 kg/m² to modulate serum low-density lipoprotein cholesterol levels. The interactions of several haplotypes and alcohol consumption on the risk of CHD and IS were also observed.

SNP-SNP Interaction between TLR4 and MyD88 in Susceptibility to Coronary Artery Disease in the Chinese Han Population

The toll-like receptor 4 (TLR4)-myeloid differentiation factor 88 (MyD88)-dependent signaling pathway plays a role in the initiation and progression of coronary artery disease (CAD). We investigated SNP-SNP interactions between the TLR4 and MyD88 genes in CAD susceptibility and assessed whether the effects of such interactions were modified by confounding risk factors (hyperglycemia, hyperlipidemia and Helicobacter pylori (H. pylori) infection). Participants with CAD (n = 424) and controls (n = 424) without CAD were enrolled. Polymerase chain restriction-restriction fragment length polymorphism was performed on genomic DNA to detect polymorphisms in TLR4 (rs10116253, rs10983755, and rs11536889) and MyD88 (rs7744). H. pylori infections were evaluated by enzyme-linked immunosorbent assays, and the cardiovascular risk factors for each subject were evaluated clinically. The significant interaction between TLR4 rs11536889 and MyD88 rs7744 was associated with an increased CAD risk (p value for interaction = 0.024). In conditions of hyperglycemia, the interaction effect was strengthened between TLR4 rs11536889 and MyD88 rs7744 (p value for interaction = 0.004). In hyperlipidemic participants, the interaction strength was also enhanced for TLR4 rs11536889 and MyD88 rs7744 (p value for interaction = 0.006). Thus, the novel interaction between TLR4 rs11536889 and MyD88 rs7744 was related with an increased risk of CAD, that could be strengthened by the presence of hyperglycemia or hyperlipidemia.

LXR Agonism Upregulates the Macrophage ABCA1/Syntrophin Protein Complex That Can Bind ApoA-I and Stabilized ABCA1 Protein, but Complex Loss Does Not Inhibit Lipid Efflux

Macrophage ABCA1 effluxes lipid and has anti-inflammatory activity. The syntrophins, which are cytoplasmic PDZ protein scaffolding factors, can bind ABCA1 and modulate its activity. However, many of the data assessing the function of the ABCA1-syntrophin interaction are based on overexpression in nonmacrophage cells. To assess endogenous complex function in macrophages, we derived immortalized macrophages from Abca1(+/+) and Abca1(-/-) mice and show their phenotype recapitulates primary macrophages. Abca1(+/+) lines express the CD11B and F4/80 macrophage markers and markedly upregulate cholesterol efflux in response to LXR nuclear hormone agonists. In contrast, immortalized Abca1(-/-) macrophages show no efflux to apoA-I. In response to LPS, Abca1(-/-) macrophages display pro-inflammatory changes, including an increased level of expression of cell surface CD14, and 11-26-fold higher levels of IL-6 and IL-12 mRNA. Given recapitulation of phenotype, we show with these lines that the ABCA1-syntrophin protein complex is upregulated by LXR agonists and can bind apoA-I. Moreover, in immortalized macrophages, combined α1/β2-syntrophin loss modulated ABCA1 cell surface levels and induced pro-inflammatory gene expression. However, loss of all three syntrophin isoforms known to bind ABCA1 did not impair lipid efflux in immortalized or primary macrophages. Thus, the ABCA1-syntrophin protein complex is not essential for ABCA1 macrophage lipid efflux but does directly interact with apoA-I and can modulate the pool of cell surface ABCA1 stabilized by apoA-I.

Association of polymorphisms in the MAFB gene and the risk of coronary artery disease and ischemic stroke: a case-control study

BACKGROUND

The v-maf avian musculoaponeurotic fibrosarcoma oncogene homolog B gene (MAFB) has been associated with serum lipid levels in the Eurpean population, but little is known about such association in the Chinese population or in atherosclerosis-related patients. Therefore, the purpose of the present study was to assess the association of the single nucleotide polymorphisms (SNPs) in the MAFB and serum lipid levels and the risk of coronary artery disease (CAD) and ischemic stroke (IS) in the Chinese population.

METHODS

A total of 1,065 unrelated patients (CAD, 525 and IS, 540) and 539 healthy controls were recruited in this study. Genotypes of the MAFB rs2902940 and rs6102059 SNPs were determined by the Snapshot technology platform.

RESULTS

The rs2902940AA genotype was associated with an increased risk of CAD (adjusted OR = 1.63, 95% CI = 1.07-2.48, P = 0.023) and IS (adjusted OR = 1.69, 95% CI = 1.09-2.61, P = 0.017). The rs2902940GA/AA genotypes were also associated with an increased risk of CAD (adjusted OR = 1.56, 95% CI = 1.04-2.32, P = 0.030 for GA/AA vs. GG) and IS (adjusted OR = 1.72, 95% CI = 1.14-2.60, P = 0.010 for GA/AA vs. GG). Significant interactions were observed only in those with higher body mass index (BMI), hypertension and diabetes (P < 0.05). The subjects with rs2902940GA/AA genotypes in controls had lower serum ApoAI levels than the subjects with GG genotype (P = 0.024).

CONCLUSIONS

The rs2902940A allele carriers in the MAFB conferred a decreased serum ApoAI level in controls and an increased risk of CAD and IS. The rs2902940GA/AA genotypes interacted with higher BMI, hypertension and diabetes to contribute the risk of CAD and IS.

Association of ATP-Binding Cassette Transporter G1 Polymorphisms with Risk of Ischemic Stroke in the Chinese Han Population

BACKGROUND

The adenosine triphosphate (ATP)-binding cassette transporter G1 (ABCG1), a member of the superfamily of ATP-binding cassette transporters, is involved in the transport of cholesterol and phospholipids in macrophages. As such, ABCG1 plays a crucial role in the development of atherosclerosis in humans. In this study, we investigate the association between ABCG1 polymorphisms and the risk of developing ischemic stroke in a Chinese Han population.

METHODS

This case-control study included 389 ischemic stroke patients and 380 healthy subjects. ABCG1 rs1378577 and rs57137919 polymorphisms were analyzed by a polymerase chain reaction-ligation detection reaction.

RESULTS

We found that the genotypic distribution and allelic frequency of these polymorphisms were similar in patients and controls. In a subgroup with hypertriglyceridemia (144 patients and 115 controls), the frequency of rs1378577 GG genotype and G allele as well as rs57137919 AA genotype was lower in the patient group compared with that in the control group (P = .018, P = .035, and P = .023, respectively). Logistic regression analysis revealed a reduced risk of ischemic stroke in a recessive model for both rs1378577 and rs57137919. Subtype analyses demonstrated that rs1378577 TG and GG genotypes and the G allele were associated with reduced risk of atherothrombotic stroke (P = .030, P = .006, and P = .004, respectively), even after adjusting for confounding factors in a dominant model.

CONCLUSIONS

Data from the present study demonstrate that ABCG1 polymorphisms are associated with reduced risk of developing ischemic stroke in hypertriglyceridemic population and atherothrombotic stroke in this cohort of Chinese Han population.

The implication of cigarette smoking and cessation on macrophage cholesterol efflux in coronary artery disease patients

We investigated ATP-binding cassette transporters A1/G1 expression and function in mediating cholesterol efflux by examining the macrophages of cigarette-smoking patients with coronary artery disease (CAD) before and after smoking abstinence. Peripheral blood monocyte cells were collected from nonsmokers (n = 17), non-CAD (NCAD) smokers (n = 35), and CAD smokers (n = 32) before and after 3 months of smoking cessation. We found that the ABCA1 expression level was lower in macrophages from NCAD and CAD smokers than from nonsmokers at baseline. The ABCA1 function of mediating cholesterol efflux was reduced in NCAD and CAD smokers as compared with nonsmokers. After 3 months of smoking cessation, ABCA1 expression and function were improved in CAD smokers. However, ABCG1 expression and function did not change after smoking cessation. Furthermore, ABCA1 expression was inhibited by tar in human acute monocytic leukemia cell line THP-1-derived macrophages through the inhibition of liver X receptors. Nicotine and carbon monoxide did not inhibit ABCA1 expression. Our results indicate that chronic cigarette smoking impaired ABCA1-mediated cholesterol efflux in macrophages and that tobacco abstinence reversed the function and expression of ABCA1, especially in CAD patients. It was tobacco tar, rather than nicotine or carbon monoxide, that played a major role in the tobacco-induced disturbance of cellular cholesterol homeostasis.

DNA methylation of lipid-related genes affects blood lipid levels

BACKGROUND

Epigenetic mechanisms might be involved in the regulation of interindividual lipid level variability and thus may contribute to the cardiovascular risk profile. The aim of this study was to investigate the association between genome-wide DNA methylation and blood lipid levels high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triglycerides, and total cholesterol. Observed DNA methylation changes were also further analyzed to examine their relationship with previous hospitalized myocardial infarction.

METHODS AND RESULTS

Genome-wide DNA methylation patterns were determined in whole blood samples of 1776 subjects of the Cooperative Health Research in the Region of Augsburg F4 cohort using the Infinium HumanMethylation450 BeadChip (Illumina). Ten novel lipid-related CpG sites annotated to various genes including ABCG1, MIR33B/SREBF1, and TNIP1 were identified. CpG cg06500161, located in ABCG1, was associated in opposite directions with both high-density lipoprotein cholesterol (β coefficient=-0.049; P=8.26E-17) and triglyceride levels (β=0.070; P=1.21E-27). Eight associations were confirmed by replication in the Cooperative Health Research in the Region of Augsburg F3 study (n=499) and in the Invecchiare in Chianti, Aging in the Chianti Area study (n=472). Associations between triglyceride levels and SREBF1 and ABCG1 were also found in adipose tissue of the Multiple Tissue Human Expression Resource cohort (n=634). Expression analysis revealed an association between ABCG1 methylation and lipid levels that might be partly mediated by ABCG1 expression. DNA methylation of ABCG1 might also play a role in previous hospitalized myocardial infarction (odds ratio, 1.15; 95% confidence interval=1.06-1.25).

CONCLUSIONS

Epigenetic modifications of the newly identified loci might regulate disturbed blood lipid levels and thus contribute to the development of complex lipid-related diseases.

HDL biogenesis, remodeling, and catabolism

In this chapter, we review how HDL is generated, remodeled, and catabolized in plasma. We describe key features of the proteins that participate in these processes, emphasizing how mutations in apolipoprotein A-I (apoA-I) and the other proteins affect HDL metabolism. The biogenesis of HDL initially requires functional interaction of apoA-I with the ATP-binding cassette transporter A1 (ABCA1) and subsequently interactions of the lipidated apoA-I forms with lecithin/cholesterol acyltransferase (LCAT). Mutations in these proteins either prevent or impair the formation and possibly the functionality of HDL. Remodeling and catabolism of HDL is the result of interactions of HDL with cell receptors and other membrane and plasma proteins including hepatic lipase (HL), endothelial lipase (EL), phospholipid transfer protein (PLTP), cholesteryl ester transfer protein (CETP), apolipoprotein M (apoM), scavenger receptor class B type I (SR-BI), ATP-binding cassette transporter G1 (ABCG1), the F1 subunit of ATPase (Ecto F1-ATPase), and the cubulin/megalin receptor. Similarly to apoA-I, apolipoprotein E and apolipoprotein A-IV were shown to form discrete HDL particles containing these apolipoproteins which may have important but still unexplored functions. Furthermore, several plasma proteins were found associated with HDL and may modulate its biological functions. The effect of these proteins on the functionality of HDL is the topic of ongoing research.

Association between ABCG1 polymorphism rs1893590 and high-density lipoprotein (HDL) in an asymptomatic Brazilian population

ATP binding cassette transporter G1 (ABCG1) promotes lipidation of nascent high-density lipoprotein (HDL) particles, acting as an intracellular transporter. SNP rs1893590 (c.-204A > C) of ABCG1 gene has been previously studied and reported as functional over plasma HDL-C and lipoprotein lipase activity. This study aimed to investigate the relationships of SNP rs1893590 with plasma lipids and lipoproteins in a large Brazilian population. Were selected 654 asymptomatic and normolipidemic volunteers from both genders. Clinical and anthropometrical data were taken and blood samples were drawn after 12 h fasting. Plasma lipids and lipoproteins, as well as HDL particle size and volume were determined. Genomic DNA was isolated for SNP rs1893590 detection by TaqMan(®) OpenArray(®) Real-Time PCR Plataform (Applied Biosystems). Mann-Whitney U, Chi square and two-way ANOVA were the used statistical tests. No significant differences were found in the comparison analyses between the allele groups for all studied parameters. Conversely, significant interactions were observed between SNP and age over plasma HDL-C, were volunteers under 60 years with AA genotype had increased HDL-C (p = 0.048). Similar results were observed in the group with body mass index (BMI) < 25 kg/m(2), where volunteers with AA genotype had higher HDL-C levels (p = 0.0034), plus an increased HDL particle size (p = 0.01). These findings indicate that SNP rs1893590 of ABCG1 has a significant impact over HDL-C under asymptomatic clinical conditions in an age and BMI dependent way.

High-density lipoprotein and atherosclerosis: Roles of lipid transporters

Various previous studies have found a negative correlation between the risk of cardiovascular events and serum high-density lipoprotein (HDL) cholesterol levels. The reverse cholesterol transport, a pathway of cholesterol from peripheral tissue to liver which has several potent antiatherogenic properties. For instance, the particles of HDL mediate to transport cholesterol from cells in arterial tissues, particularly from atherosclerotic plaques, to the liver. Both ATP-binding cassette transporters (ABC) A1 and ABCG1 are membrane cholesterol transporters and have been implicated in mediating cholesterol effluxes from cells in the presence of HDL and apolipoprotein A-I, a major protein constituent of HDL. Previous studies demonstrated that ABCA1 and ABCG1 or the interaction between ABCA1 and ABCG1 exerted antiatherosclerotic effects. As a therapeutic approach for increasing HDL cholesterol levels, much focus has been placed on increasing HDL cholesterol levels as well as enhancing HDL biochemical functions. HDL therapies that use injections of reconstituted HDL, apoA-I mimetics, or full-length apoA-I have shown dramatic effectiveness. In particular, a novel apoA-I mimetic peptide, Fukuoka University ApoA-I Mimetic Peptide, effectively removes cholesterol via specific ABCA1 and other transporters, such as ABCG1, and has an antiatherosclerotic effect by enhancing the biological functions of HDL without changing circulating HDL cholesterol levels. Thus, HDL-targeting therapy has significant atheroprotective potential, as it uses lipid transporter-targeting agents, and may prove to be a therapeutic tool for atherosclerotic cardiovascular diseases.

ABCB1 C3435T polymorphism and the risk of ischemic heart disease: a meta-analysis

ATP binding cassette transporter 1 (ABCB1) plays a critical role in the development and progression of cardiovascular disease. Emerging evidence suggests that common functional polymorphisms in the ABCB1 gene might have an impact on an individual's susceptibility to ischemic heart disease, but individually published results are inconclusive. The MEDLINE (1966-2013), the Cochrane Library Database (Issue 12, 2013), EMBASE (1980-2013), CINAHL (1982-2013), Web of Science (1945-2013), and the Chinese Biomedical Database (CBM; 1982-2013) were searched without language restrictions. Meta-analysis was performed with the use of the STATA statistical software. Odds ratios (OR) with their 95% confidence intervals (95% CIs) were calculated. Seven case-control studies with a total of 2310 myocardial infarction (MI) patients and 10,506 acute coronary syndrome (ACS) patients met the inclusion criteria. Our meta-analysis results indicated that ABCB1 C3435T polymorphism may be associated with an increased risk of MI and ACS, especially among Asian populations (T allele vs. C allele: OR=1.40, 95% CI=1.31-1.49, ph=0.058). Meta-regression analyses showed that clinical subtype and ethnicity may be the main sources of heterogeneity (T allele vs. C allele: OR=1.16, 95% CI=0.97-1.37, ph=0.036). Our findings provide empirical evidence that ABCB1 C3435T polymorphism may contribute to the risk of MI and ACS, especially among Caucasian populations. Thus, detection of ABCB1 C3435T polymorphism may be a promising biomarker for the early detection of MI and ACS.

Attenuated macrophage cholesterol efflux function in patients with obstructive sleep apnea-hypopnea syndrome

BACKGROUND

Obstructive sleep apnea-hypopnea syndrome (OSAHS) is associated with premature atherosclerosis. However, the associated mechanism remains unknown. This study investigates the expression of adenosine triphosphate (ATP)-binding cassette transporter protein A1 (ABCA1) and cellular cholesterol efflux in cultured macrophages from OSAHS patients.

METHODS

Of the 18 subjects enrolled in this study, six subjects with apnea-hypopnea index (AHI) <5 were placed into the control group, and 12 subjects with AHI ≥5 were placed into the OSAHS group. Peripheral blood mononuclear cells (PBMCs) from each subject were isolated, purified, cultured, and differentiated into macrophages in vitro. ABCA1 mRNA and protein expression were evaluated by reverse transcription PCR and Western Blot, respectively. Both ABCA1-mediated and autologous serum induced cholesterol efflux were measured by isotopic cholesterol efflux assays.

RESULTS

The levels of AHI and high sensitivity C-reactive protein (hsCRP) were significantly higher in the OSAHS group than in the control group. ABCA1 mRNA and protein expressions in PBMCs-derived macrophages were significantly reduced in patients with OSAHS compared to that in controls (p < 0.05). Both ABCA1-mediated and autologous serum-induced cholesterol efflux were significantly lower in the OSAHS group than that in the control group (p = 0.033 and p = 0.01, respectively). Pearson's correlation analysis revealed a negative correlation between AHI and the mRNA (r = -0.7726, p = 0.0007) and protein (r = -0.8112, p = 0.0044) expression of ABCA1, a positive correlation between ABCA1-mediated cholesterol efflux and the minimum oxygen saturation (r = 0.7954, p < 0.0001), and a negative correlation between AHI and autologous serum induced cholesterol efflux (r = -0.7756, p = 0.0002).

CONCLUSION

ABCA1 expression and cellular cholesterol efflux in macrophages were significantly decreased in OSAHS patients, which closely correlated with the severity of disease. Our findings provide meaningful insights into the mechanism of atherogenesis in OSAHS patients.

ABCG1 rs57137919G>a polymorphism is functionally associated with varying gene expression and apoptosis of macrophages

ATP-binding cassette transporter G1 (ABCG1) is a transmembrane cholesterol transporter involved in macrophage sterol homeostasis, reverse cholesterol transport (RCT), and atherosclerosis. The role of ABCG1 in atherosclerosis remains controversial, especially in animal models. Our previous study showed that single nucleotide polymorphism rs57137919 (-367G>A) in the ABCG1 promoter region was associated with reduced risk for atherosclerotic coronary artery disease (CAD). This study was designed to provide functional evidence for the role of rs57137919G>A in atherosclerosis in humans. We combined in vitro and ex vivo studies using cell lines and human monocyte-derived macrophages to investigate the functional consequences of the promoter polymorphism by observing the effects of the rs57137919A allele on promoter activity, transcription factor binding, gene expression, cholesterol efflux, and apoptosis levels. The results showed that the rs57137919A allele was significantly associated with decreased ABCG1 gene expression possibly due to the impaired ability of protein-DNA binding. ABCG1-mediated cholesterol efflux decreased by 23% with rs57137919 A/A versus the G/G genotype. Cholesterol-loaded macrophage apoptosis was induced 2-fold with the A/A genotype compared with the G/G genotype. Proapoptotic genes Bok and Bid mRNA levels were significantly increased in macrophages from the A/A genotype compared with those from the G/G genotype. These findings demonstrated that the ABCG1 promoter rs57137919G>A variant had an allele-specific effect on ABCG1 expression and was associated with an increased apoptosis in cholesterol-loaded macrophages, providing functional evidence to explain the reduced risk for atherosclerosis in subjects with the ABCG1 promoter rs57137919A allele as reported in our previous study.

Genes in the high-density lipoprotein metabolic pathway in age-related macular degeneration and polypoidal choroidal vasculopathy

PURPOSE

To investigate the associations of genetic variants in the high-density lipoprotein (HDL) metabolism pathway with neovascular age-related macular degeneration (AMD) and polypoidal choroidal vasculopathy (PCV).

DESIGN

Cross-sectional, case-control association study.

PARTICIPANTS

A Chinese case-control group of 200 neovascular AMD patients, 233 PCV patients, and 275 control subjects.

METHODS

Eight single nucleotide polymorphisms (SNPs) from 6 genes of the HDL metabolism pathway and 2 known AMD-associated SNPs, rs800292 (from complement factor H [CFH]) and rs11200638 (from HtrA serine peptidase 1 [HTRA1]), were genotyped in all study subjects using the TaqMan genotyping technology (Applied Biosystems, Foster City, CA).

MAIN OUTCOME MEASURES

Allele and genotypic frequencies of selected SNPs.

RESULTS

The SNP rs3764261 in the cholesteryl ester transfer protein (CETP) gene was associated significantly with neovascular AMD (P = 1.82×10(-4); odds ratio [OR], 1.89) and PCV (P = 4.04×10(-4); OR, 1.80). The associations remained significant after adjusting for the CFH SNP rs800292 and the HTRA1 SNP rs11200638. A significant interaction between the CETP SNP rs3764261 and the CFH SNP rs800292 existed in both neovascular AMD and PCV, the rs800292 G allele conferring a significantly increased risk of the diseases only in individuals carrying the risk allele T of rs3764261. A borderline association was detected between the ATP-binding cassette, subfamily G, member 1 (ABCG1) gene SNP rs57137919 and PCV (P = 0.03).

CONCLUSIONS

Our results showed that CETP is a susceptibility gene for neovascular AMD and PCV and that ABCG1 a putative gene for PCV. CETP exerts a modifying effect on CFH in the genetic risk. Our data suggest a link of the HDL metabolism pathway with neovascular AMD and PCV.

Epipolymorphisms within lipoprotein genes contribute independently to plasma lipid levels in familial hypercholesterolemia

Gene polymorphisms associated so far with plasma lipid concentrations explain only a fraction of their heritability, which can reach up to 60%. Recent studies suggest that epigenetic modifications (DNA methylation) could contribute to explain part of this missing heritability. We therefore assessed whether the DNA methylation of key lipoprotein metabolism genes is associated with high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) and triglyceride levels in patients with familial hypercholesterolemia (FH). Untreated FH patients (61 men and 37 women) were recruited for the measurement of blood DNA methylation levels at the ABCG1, LIPC, PLTP and SCARB1 gene loci using bisulfite pyrosequencing. ABCG1, LIPC and PLTP DNA methylation was significantly associated with HDL-C, LDL-C and triglyceride levels in a sex-specific manner (all P<0.05). FH subjects with previous history of coronary artery disease (CAD) had higher LIPC DNA methylation levels compared with FH subjects without CAD (P = 0.02). Sex-specific multivariable linear regression models showed that new and previously reported epipolymorphisms (ABCG1-CpGC3, LIPC-CpGA2, mean PLTP-CpGC, LPL-CpGA3, CETP-CpGA2, and CETP-CpGB2) significantly contribute to variations in plasma lipid levels (all P<0.001 in men and P<0.02 in women), independently of traditional predictors such as age, waist circumference, blood pressure, fasting plasma lipids and glucose levels. These results suggest that epigenetic perturbations of key lipoprotein metabolism genes are associated with plasma lipid levels, contribute to the interindividual variability and might partially explain the missing heritability of plasma lipid levels, at least in FH.

ABCB1 C3435T polymorphism and the risk of coronary heart disease: a meta-analysis

BACKGROUND

ATP-binding cassette transporter 1 (ABCB1) plays a critical role in the development and progression of cardiovascular disease. Emerging evidence suggests that common functional polymorphisms in the ABCB1 gene might have an impact on an individual's susceptibility to coronary heart disease (CHD), but individually published results are inconclusive. This meta-analysis aimed to derive a more precise estimation of the relationship between ABCB1 C3435T polymorphism and CHD risk.

METHOD

An extensive literary search for relevant studies was conducted in PubMed, Embase, Web of Science, Cochrane Library, CISCOM, CINAHL, Google Scholar, China BioMedicine (CBM), and China National Knowledge Infrastructure (CNKI) databases from their inception through August 1st, 2013. Meta-analysis was performed using the STATA 12.0 software. The crude odds ratio (OR) with 95% confidence interval (CI) were calculated.

RESULTS

Seven clinical studies were included with a total of 13,074 CHD patients, including 378 variant angina pectoris (VAP) patients, 2290 myocardial infarction (MI) patients, and 10,406 acute coronary syndrome (ACS) patients. Our meta-analysis results indicated that ABCB1 C3435T polymorphism may be associated with an increased risk of CHD, especially for MI and ACS among Caucasian populations. However, no statistically significant association was found between ABCB1 C3435T polymorphism and VAP risk, especially among Asian populations. Meta-regression analyses showed that clinical subtype and ethnicity may be the main sources of heterogeneity. No publication bias was detected in this meta-analysis.

CONCLUSION

The current meta-analysis suggests that ABCB1 C3435T polymorphism may contribute to the risk of CHD, especially for MI and ACS, among Caucasian populations. Thus, detection of ABCB1 C3435T polymorphism may be a promising biomarker for the early detection of CHD.

HMG-CoA reductase inhibitors, simvastatin and atorvastatin, downregulate ABCG1-mediated cholesterol efflux in human macrophages

Recent studies showed that statins reduce ATP-binding cassette transporter A1 expression and ATP-binding cassette transporter A1-mediated cholesterol efflux in macrophages, whereas the effect of statins on ATP-binding cassette transporter G1 (ABCG1), another important lipid transporter, is still unclear. Here, we investigated the expression and functionality of ABCG1 on statins in THP-1-derived macrophages and human peripheral blood mononuclear cells. Simvastatin and atorvastatin were used in this study. Treatment with statins significantly decreased ABCG1-mediated cholesterol efflux in human macrophages (from 33.8% ± 2.8% of control to 22.9% ± 1.7% of 10 µM simvastatin or to 23.3% ± 3.3% of 10 µM atorvastatin; P < 0.01, n = 4), whereas the protein expression of ABCG1 remained unaltered on statins. Further analysis revealed that 2 major ABCG1 isoforms responded to statins differently. The expression of ABCG1-S, which exhibited higher activity in cholesterol efflux than ABCG1-L, was significantly decreased on statins compared with increased expression of ABCG1-L. The results suggested that the proportion change of ABCG1 isoform expressions could contribute to reduced ABCG1 functionality under treatment with statins. The effects of statins on ABCG1 isoform expression and functionality were reversed by low-dose liver X receptor agonist, TO-901317, indicating that statins' downregulation of ABCG1 functionality was likely through liver X receptor-dependent pathway. In conclusion, simvastatin and atorvastatin decreased ABCG1-mediated cholesterol efflux in human macrophages without alteration of total ABCG1 protein level. The proportion change of ABCG1 isoforms expressions may be involved in the down-regulation of ABCG1 functionality by statins, which provided a novel mechanism for the regulation of ABCG1 activity.

CHD@ZJU: a knowledgebase providing network-based research platform on coronary heart disease

Coronary heart disease (CHD), the leading cause of global morbidity and mortality in adults, has been reported to be associated with hundreds of genes. A comprehensive understanding of the CHD-related genes and their corresponding interactions is essential to advance the translational research on CHD. Accordingly, we construct this knowledgebase, CHD@ZJU, which records CHD-related information (genes, pathways, drugs and references) collected from different resources and through text-mining method followed by manual confirmation. In current release, CHD@ZJU contains 660 CHD-related genes, 45 common pathways and 1405 drugs accompanied with >8000 supporting references. Almost half of the genes collected in CHD@ZJU were novel to other publicly available CHD databases. Additionally, CHD@ZJU incorporated the protein-protein interactions to investigate the cross-talk within the pathways from a multi-layer network view. These functions offered by CHD@ZJU would allow researchers to dissect the molecular mechanism of CHD in a systematic manner and therefore facilitate the research on CHD-related multi-target therapeutic discovery. Database URL: http://tcm.zju.edu.cn/chd/

The transcription levels of ABCA1, ABCG1 and SR-BI are negatively associated with plasma CRP in Chinese populations with various risk factors for atherosclerosis

ATP binding cassette transporters (ABCA1, ABCG1) and scavenger receptor class B type I (SR-BI) are the three most important cellular cholesterol transporters that may prevent atherogenesis. The aim of this study was to investigate whether they were altered in Chinese populations with various risk factors for atherosclerosis and their potential associations with C-reactive protein (CRP). Healthy female controls (n = 30) and populations with various risk factors for atherosclerosis, such as type 2 diabetes (n = 17), hypertension (n = 12), overweight/obesity (n = 10), incipient nephropathy (n = 10), postmenopausal women (n = 9), male (n = 19), ageing male (n = 22), or smoking (n = 16), were recruited. ABCA1, ABCG1 and SR-BI mRNA levels in peripheral monocytes was determined. ABCG1 was decreased in all the risk populations except ageing. ABCA1 was decreased in all the risk populations except diabetes and male. SR-BI was decreased in those with overweight/obesity and incipient nephropathy. Circulating CRP was increased almost in all the risk populations except in males. The levels of ABCA1, ABCG1 and SR-BI were reduced in those with subclinically high CRP, and negatively associated with CRP level. These data indicates that ABCA1, ABCG1, and SR-BI are reduced in various populations under subclinically inflammatory conditions, which may potentially lead to impairing reverse cholesterol transport and developing atherosclerosis.

Human ATP-binding cassette G1 controls macrophage lipoprotein lipase bioavailability and promotes foam cell formation

OBJECTIVE

The physiological function of the ATP-binding cassette G1 (ABCG1) transporter in humans is not yet elucidated, as no genetic disease caused by ABCG1 mutations has been documented. The goal of our study was, therefore, to investigate the potential role(s) of ABCG1 in lipid metabolism in humans.

METHODS AND RESULTS

Here we report that among the 104 polymorphisms present in the ABCG1 gene, the analysis of the frequent functional rs1893590 and rs1378577 single nucleotide polymorphisms located in the regulatory region of ABCG1 in the Regression Growth Evaluation Statin Study population revealed that both ABCG1 single nucleotide polymorphisms were significantly associated with plasma lipoprotein lipase (LPL) activity. Moreover, we observed that plasma LPL activity was modestly reduced in Abcg1(-/-) mice as compared with control mice. Adipose tissue and skeletal muscle are the major tissues accounting for levels and activity of plasma LPL in the body. However, beyond its lipolytic action in the plasma compartment, LPL was also described to act locally at the cellular level. Thus, macrophage LPL was reported to promote foam cell formation and atherosclerosis in vivo. Analysis of the relationship between ABCG1 and LPL in macrophages revealed that the knockdown of ABCG1 expression (ABCG1 knockdown) in primary cultures of human monocyte-derived macrophages using small interfering RNAs led to a marked reduction of both the secretion and activity of LPL. Indeed, LPL was trapped at the cell surface of ABCG1 knockdown human monocyte-derived macrophages, likely in cholesterol-rich domains, thereby reducing the bioavailability and activity of LPL. As a consequence, LPL-mediated lipid accumulation in human macrophage foam cells in the presence of triglyceride-rich lipoproteins was abolished when ABCG1 expression was repressed.

CONCLUSIONS

We presently report that ABCG1 controls LPL activity and promotes lipid accumulation in human macrophages in the presence of triglyceride-rich lipoproteins, thereby suggesting a potential deleterious role of macrophage ABCG1 in metabolic situations associated with high levels of circulating triglyceride-rich lipoproteins together with the presence of macrophages in the arterial wall.