Lipoprotein-associated Phospholipase A <sub> 2 </ Sub> (lp-pla <sub> 2 </ Sub>) Gene Polymorphism And Coronary Heart Disease Associated With Research

BackgroundThe coronary atherosclerotic disease (CAD) is a polygenic disease. The genetic factors play a key role in the development of atherosclerotic plaque and its complications. Theoretically, the investigation of genetic risk factors of CAD is very important for prevention and treatment of the CAD.The oxidation and inflammation contribute to the formation and development of atherosclerosis. The phospholipids are oxidized by the oxidized lipids (such as fatty acids) in the LDL and the consequent peroxides result in the formation of LDL with a mild modification and initiate a series of procedures to form the early fatty streaks, which finally accelerate the development of atherosclerosis with the accumulation of lipid peroxides. The high-density lipoprotein, which is smallest in size and highest in density, is considered to exhibit capability of anti-atherosclerosis, because of its effect of promoting the reverse cholesterol transport as well as its capability of anti-oxidation and anti-inflammation. Several enzymes included in HDL participate in this function, one of which is lipoprotein-associated phospholipase A₂ (Lp-PLA₂).Lp-PLA₂ is a subtype of phospholipase superfamily, also known as platelet activating factor-acetylhydrolase (PAF-AH). The epidemiology studies demonstrate that there is an association of the level of Lp-PLA₂ with the risk of CAD; however, it remains unknown that if this phenomena is a response to the stimulation of inflammation of atherosclerosis or a direct cause of atherosclerosis or the marker of risks. On one hand, the Lp-PLA₂ can hydrolyze the platelet activating factor (PAF) and the oxidized lipid products induced by the oxidation of LDL or oxidative stress, which therefore is considered to have the capability of anti-atherosclerosis. On the other hand, studies have revealed that the Lp-PLA₂ may hydrolyze oxidized phospholipids to generate lysophosphatidyl choline (lyso-PC) and free oxidized fatty acids, both of which play a critical role in atherogenesis.The investigations of the genetic polymorphism of Lp-PLA₂ have demonstrated that the polymorphisms of V279F on the exon 9 and A379V on the exon 11 have functional effect, and are associated with CAD. No studies with large sample have been conducted to investigate the association of the polymorphism of Lp-PLA₂ gene with CAD in Chinese Han people. Therefore, our study will focus on polymorphism of V279F and A379V of Lp-PLA₂ gene in the patients with CAD and the healthy control, and the associations of polymorphism and the onset/ severity of CAD.Objective1. The study is designed to investigate the polymorphism of V279F on exon 9 and A379V on 11 exon of Lp-PLAV2 in Chinese CAD patients, compared with healthy control; also to compare and analyze the difference of the distribution of genotype and allele between these two populations.2. To analyze the association of the polymorphism of V279F and A379V of Lp-PLA₂ with traditional risk factors, lipid profile and disease severity of CAD patients in Chinese Han people. Also to identify the role of Lp-PLA₂ in CAD progression.Method1. The patients were recruited in Peking Union Medical Hospital and FuWai Cardiovascular Disease Hospital from 03/2007 to 04/2008. Inclusion criterion was the presence of typical angina pectoris with a diameter stenosis >50% in at least one major coronary artery, or the presence of MI history. Age-matched healthy control without CAD, DM and hyperlipidemia were recruited from the health examination department of PUMC. Demographic features and traditional risk factors of CAD, including age, sex, smoking, family history, past history (with or without HTN, DM or hyperlipidemia) and lipid profile were collected. The result of CAG and the MI history were also collected to evaluate the severity of CAD.2. The venous blood samples were drawn after an overnight fast. The genomic DNA was extracted from the whole blood cells using phenol-chloroform method.3. Genotyping for V279F polymorphism on exon 9 and A379V polymorphism on 11 exon of Lp-PLA₂ were determined for each subject using Taqman(?) probe allele discrimination method. The frequencies of genotypes and alleles were analyzed and compared between CAD patients and healthy control.4. The associations of SNPs with phenotypes were analyzed using relevant statistical methods.Result1. Total 806 patients (age of 61.51±10.74, F:M=620:186) and 482 healthy subjects (age of 61.63±8.41, F:M=264:218) were included. Those two groups were age matched, but had significant difference in sex (p<0.001). The comparison of traditional risk factors indicated that CAD patients had significantly greater level of BMI, FBG and HsCRP, lower level of HDL-C and ApoA1, and higher prevalence rate of HTN, than healthy control.2. There was a significantly higher prevalence of the VF+FF genotype and F279 allele of Lp-PLA₂ V279F in CAD patients compared with healthy control. The frequencies of VF+FF genotype of those two groups were 13.6% and 9.3% respectively (p=0.024), and F279 allele were 6.9% and 4.9% respectively (p=0.037). The distribution of A379V variant was similar between CAD patients and healthy control. SHESIS haplotype analysis identified that, among the haplotype formed by those two variants TC haplotype was associated with CAD (OR= 1.449, 95%CI[1.019-2.061 ], p=0.038).3. The prevalence of VF+FF genotype and F279 allele of V279F locus was significantly higher in the subpopulation with multi-vessel coronary disease, compared with healthy control. The frequencies of VF+FF genotype and F279 allele in this subpopulation were 15.2% and 7.7% with p-value 0.005 and 0.009 respectively. Those frequencies were also significantly higher than single-vessel coronary disease subpopulation.4. The VF+FF genotype and F279 allele were also significantly more frequent in patients with a diameter stenosis >70% in at least one major coronary artery. The frequencies of VF+FF and F allele were 14.1% (p=0.013) and 7.1% (p=0.025), respectively.5. The V379 allele of A379V was significantly more frequent in patients with MI histories (18.7%), compared with patients without MI histories (14.8%), p=0.038. Also, the prevalence of VV genotype was significantly higher in patients with MI histories (3.3% vs.1.2%, p=0.043).6. The Comparison between patients with/without DM or HTN didn't reveal any significant difference of the distribution of V279F and A379V variants.7. Logistic regression analysis showed the V279F polymorphism was positively associated with CAD. The VF+FF individuals had a significantly higher risk of CAD compared with VV individuals, even after adjusted for sex, BMI and HTN (OR=1.611, 95% CI[1.020, 2.545], P=0.041) . The risk analysis of MI in CAD patients revealed A379V polymorphism was positively associated with MI. The AV +VV individuals had a significantly higher risk of MI compared with AA individuals, even after adjusted for sex, BMI, smoking, HsCRP, HDL-C and LDL-C (OR=1.596, 95%CI[1.104,2.306], P=0.013) .8. The association analysis of lipid profile and genotype showed AV+VV individuals in CAD group had significantly higher level of LDL-C and ApoB, compared with AA individuals (the level of LDL-C was 2.63mmol/l and 2.48 mmol/l respectively, p=0.030; and the level of ApoB was 0.88mmol/l and 0.81mmol/l, p=0.018). But the same difference was not identified in healthy control population.Conclusion1. Lp-PLA₂ V279F polymorphism is associated with CAD. The VF+FF genotype are more frequent in CAD patients, compared with healthy control. The individuals with F279 allele have increased risk of CAD and more severe coronary atherosclerosis.2. The study didn't reveal the association of Lp-PLA₂ A379V polymorphism with CAD, but had identified this polymorphism is significantly associated with MI of CAD patients. The VV genotype and V379 allele are more frequent in patients with MI histories than patients without MI histories. The AV+VV individuals have increased risk of MI.3. The individuals with AV+VV genotype of Lp-PLA₂ A379V in CAD patients had significantly higher level of LDL-C and ApoB, compared with AA individuals4. The TC haplotype formed by V279F and A379V of Lp-PLA₂ is associated with CAD.