The role of ATP-binding-cassette-transporter-A1 (ABCA1) gene polymorphism on coronary artery disease risk

Role of ABCA1 in Cardiovascular Disease

Cholesterol homeostasis plays a significant role in cardiovascular disease. Previous studies have indicated that ATP-binding cassette transporter A1 (ABCA1) is one of the most important proteins that maintains cholesterol homeostasis. ABCA1 mediates nascent high-density lipoprotein biogenesis. Upon binding with apolipoprotein A-I, ABCA1 facilitates the efflux of excess intracellular cholesterol and phospholipids and controls the rate-limiting step of reverse cholesterol transport. In addition, ABCA1 interacts with the apolipoprotein receptor and suppresses inflammation through a series of signaling pathways. Thus, ABCA1 may prevent cardiovascular disease by inhibiting inflammation and maintaining lipid homeostasis. Several studies have indicated that post-transcriptional modifications play a critical role in the regulation of ABCA1 transportation and plasma membrane localization, which affects its biological function. Meanwhile, carriers of the loss-of-function ABCA1 gene are often accompanied by decreased expression of ABCA1 and an increased risk of cardiovascular diseases. We summarized the ABCA1 transcription regulation mechanism, mutations, post-translational modifications, and their roles in the development of dyslipidemia, atherosclerosis, ischemia/reperfusion, myocardial infarction, and coronary heart disease.

Remembering your A, B, C's: Alzheimer's disease and ABCA1

The function of ATP binding cassette protein A1 (ABCA1) is central to cholesterol mobilization. Reduced ABCA1 expression or activity is implicated in Alzheimer's disease (AD) and other disorders. Therapeutic approaches to boost ABCA1 activity have yet to be translated successfully to the clinic. The risk factors for AD development and progression, including comorbid disorders such as type 2 diabetes and cardiovascular disease, highlight the intersection of cholesterol transport and inflammation. Upregulation of ABCA1 can positively impact APOE lipidation, insulin sensitivity, peripheral vascular and blood–brain barrier integrity, and anti-inflammatory signaling. Various strategies towards ABCA1-boosting compounds have been described, with a bias toward nuclear hormone receptor (NHR) agonists. These agonists display beneficial preclinical effects; however, important side effects have limited development. In particular, ligands that bind liver X receptor (LXR), the primary NHR that controls ABCA1 expression, have shown positive effects in AD mouse models; however, lipogenesis and unwanted increases in triglyceride production are often observed. The longstanding approach, focusing on LXRβ vs. LXRα selectivity, is over-simplistic and has failed. Novel approaches such as phenotypic screening may lead to small molecule NHR modulators that elevate ABCA1 function without inducing lipogenesis and are clinically translatable.

Common gene polymorphism in ATP-binding cassette transporter A1 and coronary artery disease: A genetic association study and a structural analysis

ATP-binding cassette transporter A1 (ABCA1) has a crucial role in removing intracellular cholesterol and plays a protective role against atherosclerosis. Therefore, genetic polymorphisms in this gene may alter the susceptibility to coronary artery disease (CAD). This study was aimed to examine the association of rs2230806 (c.1051 G > A; p.R219K) variation in the ABCA1 gene with CAD in a case-control design which was followed by a meta-analysis and in silico approach. In the case-control study, 300 subjects including 150 individuals with CAD and 150 healthy controls were recruited. The c.1051 G > A genotyping was done by polymerase chain reaction-restriction fragment length polymorphism method. In the meta-analysis, eligible studies were collected from PubMed, Google Scholar, and ScienceDirect databases and pooled odds ratio, heterogeneity, publication bias, and sensitivity analyses were carried. Finally, some bioinformatics tools were employed to assess the impacts of p.R219K variation on ABCA1 protein structure. Our case-control examination showed a statistically significant association between c.1051 G > A genetic polymorphism and CAD risk. In addition, the meta-analysis showed reliable significant associations between c.1051 G > A transition and risk of CAD in the Caucasian population. In silico analysis showed that the p.R219K substitution could alter the secondary structure, hydrophobicity pattern, and Ramachandran plot of ABCA1. These findings elucidate that the c.1051 G > A variation could be a genetic risk factor for CAD and it could be considered as a prognostic and predictive biomarker for susceptible individuals.

Effect of adiponectin on macrophage reverse cholesterol transport in adiponectin-/- mice and its mechanism

The objective of the present study was to investigate the effect of adiponectin (APN) on macrophage reverse cholesterol transport (RCT) in adiponectin-/- knockout mice (APN-/-mice) and its possible anti-atherosclerotic mechanism. A total of 30 male APN-/-mice were randomly divided into the control group and four intervention groups. The intervention groups were treated with intraperitoneal injections of APN, at doses of 50, 150, 200 and 250 µg/(kg/day), respectively, for 4 weeks. The control group received normal saline. After 4 weeks, serum lipid levels were measured, the degree of severity of atherosclerotic lesions was observed by light microscopy, the ³H-TC (APN-/-mice treated with intraperitoneal injections of ³H-TC-labeled macrophages) radioactivity in serum, liver, and feces, and the expression of ABCA1 mRNA and protein in liver were determined. Compared with the control group, serum triglycerides, total cholesterol, and low-density lipoproteins levels in the intervention groups were significantly decreased, while high-density lipoprotein was increased. The severity of aortic atherosclerotic lesions in the intervention groups was milder than in the control group, which had obvious aortic atherosclerotic lesions, large lipid deposition on vessel walls, and the formation of atheromatous plaques. In the intervention groups, serum ³H-TC content was significantly decreased (P<0.05), but the ³H-TC content in liver and feces was significantly increased (P<0.05). The levels of ABCA1 mRNA in liver of the intervention groups were significantly increased in a dose-dependent manner. In conclusion, APN can promote RCT and intracellular cholesterol efflux by upregulating the expression of ABCA1, to delay the occurrence and development of atherosclerosis.

Evaluation of Adenosine Triphosphate-Binding Cassette Transporter A1 (ABCA1) R219K and C-Reactive Protein Gene (CRP) +1059G/C Gene Polymorphisms in Susceptibility to Coronary Heart Disease

Background

This meta-analysis investigated the correlation of ABCA1 R219K and CRP +1059G/C gene polymorphisms with susceptibility to coronary heart disease (CHD).

Material/Methods

We searched PubMed, Springer link, Wiley, EBSCO, Ovid, Wanfang database, VIP database, and China National Knowledge Infrastructure (CNKI) databases to retrieve published studies by keyword. Searches were filtered using our stringent inclusion and exclusion criteria. Resultant high-quality data collected from the final selected studies were analyzed using Comprehensive Meta-analysis 2.0 software. Eleven case-control studies involving 3053 CHD patients and 3403 healthy controls met our inclusion criteria. Seven studies were conducted in Asian populations, 3 studies were done in Caucasian populations, and 1 was in an African population.

Results

Our major finding was that ABCA1 R219K polymorphism increased susceptibility to CHD in allele model (OR=0.729, 95% CI=0.559~0.949, P=0.019) and dominant model (OR=0.698, 95% CI=0.507~0.961, P=0.027). By contrast, we were unable to find any significant association between the CRP +1059G/C polymorphism and susceptibility to CHD (allele model: OR=1.170, 95% CI=0.782~1.751, P=0.444; dominant model: OR=1.175, 95% CI=0.768~1.797, P=0.457).

Conclusions

This meta-analysis provides convincing evidence that polymorphism of ABCA1 R219K is associated with susceptibility to CHD while the CRP +1059G/C polymorphism appears to have no correlation with susceptibility to CHD.

Influence of ATP-binding cassette transporter 1 R219K and M883I polymorphisms on development of atherosclerosis: a meta-analysis of 58 studies

Background

Numerous epidemiological studies have evaluated the associations between ATP-binding cassette transporter 1 (ABCA1) R219K (rs2230806) and M883I (rs4149313) polymorphisms and atherosclerosis (AS), but results remain controversial. The purpose of the present study is to investigate whether these two polymorphisms facilitate the susceptibility to AS using a meta-analysis.

Methods

PubMed, Embase, Web of Science, Medline, Cochrane database, Clinicaltrials.gov, Current Controlled Trials, Chinese Clinical Trial Registry, CBMdisc, CNKI, Google Scholar and Baidu Library were searched to get the genetic association studies. All statistical analyses were done with Stata 11.0.

Results

Forty-seven articles involving 58 studies were included in the final meta-analysis. For the ABCA1 R219K polymorphism, 42 studies involving 12,551 AS cases and 19,548 controls were combined showing significant association between this variant and AS risk (for K allele vs. R allele: OR = 0.77, 95% CI = 0.71–0.84, P<0.01; for K/K vs. R/R: OR = 0.60, 95% CI = 0.51–0.71, P<0.01; for K/K vs. R/K+R/R: OR = 0.69, 95% CI = 0.60–0.80, P<0.01; for K/K+R/K vs. R/R: OR = 0.74, 95% CI = 0.66–0.83, P<0.01). For the ABCA1 M883I polymorphism, 16 studies involving 4,224 AS cases and 3,462 controls were combined. There was also significant association between the variant and AS risk (for I allele vs. M allele: OR = 0.85, 95% CI = 0.77–0.95, P<0.01).

Conclusions

The present meta-analysis suggested that the ABCA1 R219K and M883I polymorphisms were associated with the susceptibility to AS. However, due to the high heterogeneity in the meta-analysis, the results should be interpreted with caution.

Involvement of ATP-binding cassette, subfamily A polymorphism with susceptibility to coronary artery disease

Coronary artery disease (CAD) is one of the leading causes of mortality in developed countries. Adenosine triphosphate (ATP)-binding cassette A1 (ABCA1) belongs to the superfamily of membrane proteins that function as a key factor in the regulation of plasma high-density lipoprotein cholesterol (HDL-C) and the metabolism of apolipoprotein A-I (Apo AI). The role of this gene in CAD remains controversial. The aim of this study was to investigate the frequency of single-nucleotide polymorphism (SNP) rs2230806 in the ABCA1 gene of 120 CAD patients and 100 age-matched, healthy controls using restriction fragment length polymorphism and direct sequencing. Total serum cholesterol, HDL-C and serum triglyceride levels were also assayed. Low-density lipoprotein cholesterol (LDL-C) was calculated using the Friedewald formula. When compared, the G allele occurred significantly more frequently in CAD patients compared to the control subjects. The odds ratio (OR) for CAD conferred by carrying the ABCA1 G allele was 2.362 [95% confidence interval (CI) 0.9055-6.161] (P<0.08). The K variant of SNP rs2230806 in the G allele was associated with a decrease in HDL-C levels, but an increased frequency of CAD. In conclusion, the results showed that SNP rs2230806 in the ABCA1 gene is significantly associated with the incidence of CAD. Homozygosity for the G allelic variant in CAD patients may be associated with an increased risk of CAD/MI.

Genetic variation of the ATP-binding cassette transporter A1 and susceptibility to coronary heart disease

ATP-binding cassette transporter A1 (ABCA1) is a member of a superfamily of membrane proteins that has attracted considerable attention as a candidate gene for coronary heart disease (CHD) based on its enzyme function as a key factor in regulating plasma HDL-C and apo A-I metabolism. It has been suggested that polymorphisms in the ABCA1 gene are risk factors for CHD, but a large number of studies have reported apparently conflicting results. To investigate this inconsistency and derive a more precise estimation of the relationship, a meta-analysis of 14,040 cases and 28,607 controls from 31 published case-control studies was performed. Five potential sources of heterogeneity including ethnicity, source of control, sample size, HWE status and genotyping method of study were also assessed. Overall, significantly decreased CHD risk was associated with 219K allele of R219K polymorphism when all studies were pooled into the meta-analysis. In the subgroup analysis by ethnicity, significantly decreased risks were found in Asians and other ethnic population for the polymorphism in all genetic models; while no significant associations were found among Caucasians. When stratified by source of controls, both population and hospital based studies get consistent positive results. However, no significant results were observed for I883M polymorphism of ABCA1 in all genetic models. In conclusion, this meta-analysis suggests that K allele of ABCA1 R219K polymorphism is a protective factor associated with decreased CHD susceptibility, but these associations vary in different ethnic populations.