Association Study Of Polymorphisms In ABCG1 Gene And Coronary Atherosclerotic Disease

[Background]Coronary atherosclerotic disease (CAD) has a severely high prevalence and lethality, while a main underlying pathology is atherosclerosis. Consistent and compelling evidence has demonstrated association between lipoprotein-associated lipid concentrations and cardiovascular disease incidence. Whereas high concentrations of LDL cholesterol are associated with increased risk of CAD, high concentrations of HDL cholesterol are associated with decreased risk of CAD. Still, family studies suggest that about half of the variation in these traits is genetically determined, and it is clear that LDL cholesterol, HDL cholesterol and triglyceride concentrations are strongly influenced by the genetic constitution of each individual. Furthermore, genetic variants that increase LDL cholesterol concentrations have also been associated with increased susceptibility to coronary heart disease.ABCA1, ABCG1, two members of the ATP-binding cassette (ABC) transporter family, have been implicated in the transport of sterols and lipids across cell membranes. Single nucleotide polymorphisms (SNP) in ABCA1 contribute to variation in HDL cholesterol concentrations and the risk of CAD. While the role of ABCG1 in atherosclerotic development remains unclear, only a moderate increase or actually decreased atherosclerotic lesions in atherogenic mouse models were reported transplanted with bone marrow from ABCG1(?)mice. The fact that total body ABCG1 expression protects against early atherosclerotic lesion development suggested ABCG1 played a protective role against atherosclerosis.[Objective]The population based case-control association study was carried out to explore the association of polymorphisms in ABCG1 gene and coronary atherosclerotic disease in Chinese Han population. To determine the effect of ABCG1 transcription in promoter SNPs by in vitro assay.[Methods]1.541 patients with CAD and 649 healthy controls from Chinese Han population were interviewed. The genomic DNA was extracted from the white blood cells in peripheral blood.2. Five SNPs, rs4148082, rs1893590, rs1378577 in the promoter, rs225374 in intron 7, and rs1044317 in the 3'untranslated region (3'UTR) of ABCG1 were genotyped using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay.3. The genotype frequencies and allele frequencies of each polymorphism were calculated for Hardy-Weinberg equilibrium (HWE). Estimate linkage disequilibrium between each polymorphisms. Logistic regression analysis was applied to determinationed the genetic model associated with CAD.4. The sequence of ABCG1 promoter was analysised with Mat Inspector software. Firefly luciferase reporter constructs were generated with different haplotype of ABCG1 promoter based on the genotype results. Recombination constructs were transient transfected into Hela and HEK293T cells to assaying for the luciferase activity.[Results]1. All the SNPs were in HWE in the CAD patients and the healthy controls, respectively. rs4148082, rs1893590, rsl378577 in the promoter show a strong linkage disequilibrium each other, and almost no linkage disequilibrium was found between rs225374, rs1044317 and any other SNPs.2. For rs4148082, rs1893590, rs1378577 in the promoter, neither genotype nor allele was statistically different between CAD patients and healthy controls. For rs225374, the frequency of allele C was statistically higher in the CAD patients in comparison to the healthy controls (OR=1.186,95%CI:1.009-1.394, P=0.039). For rs1044317, A statistically higher prevalence risk allele A was found in the CAD patients in comparison to the healthy controls (OR=1.187,95%CI: 1.009-1.397, P=0.039).3. In case-only association study, rs4148082, rs1893590, rs1378577 in the promoter showed a statistically association in female subgoup between the high Gensini score subgroup and the low Gensini score subgroup. No statistically difference was found in rs225374, rs1044317.4. Luciferase activity assay show that promoter of haplotype GCG constructed by rs4148082, rsl893590, rs1378577 has a statistically lower activity than promoter of haplotype GAT, while activity of promoter of haplotype GAG has no statistically difference with promoter of haplotype GCG.[Conclusions]1. rs225374, rs1044317 in ABCG1 gene could be associated with the susceptibility of CAD in Chinese Han population.2. rs4148082, rs1893590, rs1378577 in the promoter of ABCG1 could be associated with the severity of CAD in Chinese Han female.3. The allele G of rsl378577 has the down regulation effect of ABCG1 transcription but not rs1893590.