The Association Study On Genetic Polymophisms Of Interleukin-6and Its Receptor With Coronary Heart Disease

Objective To establish routine methods using high-resolution melting curve technology for detecting the gene polymorphisms of interleukin-6and its receptor, and to perform a case-control analysis for exploring the correlation between IL-6and its receptor gene polymorphisms (IL-6-174、-572、-597;IL-6R-183、-exon1、-exon2) and the susceptibility of coronary heart disease(CHD).Methods PCR-HRM assays were established for detecting six SNPs of IL-6-572G> C, IL-6-597G> A, IL-6-174G> C,IL,-6R-183G> A, IL-6R-exon1C> A and Il-6R-exon2A> T in231cases of CHD patients and275healthy control subjects from the Northwest Territories. The genomic DNA of all subjects were extracted using the Japanese Fujifilm company whole blood DNA extraction kit. IL-6and IL-6R gene polymorphism sites(IL-6-174、-572、-597;IL-6R-183、-exonl、-exon2) were genotyped with the PCR-HRM assays established in our laboratory. SHEsis online software was used to carry out Hardy-Weinberg equilibrium test in control group and analysis on the gene and genotype frequencies of all SNPs, as well as analysis on the haplotype of the SNPs located on the same chromosome. The statistical software SPSS18.0was used to fit the second category logistic regression models for exploring the relationship between mutations genotype and CHD risk by putting the three different genotypes of every SNP as independent variables, the wild homozygous type as benchmark, and other genotypes as dummy variable Conventional laboratory methods were used to detect the lipids:triglycerides(TG),total cholesterol(CHO), High-density lipoprotein(HDL) and Low-density lipoprotein(LDL) and hemagglutination marks:prothrombin time(PT), activated partial thromboplastin time(APTT), thrombin time(TT), plasma fibrinogen(FIB). Using SPSS18.0statistical software to analyze serological index of the case group and the gene polymorphism is related.Result (1) There was significant difference between the case and control groups about the IL-6-572gene and genotype frequencies (χ2=4.717, P=0.029; χ2=6.016, P=0.049). The two types of logistic regression model of the SNP showed that the CC genotype of the IL-6-572increases the risk of CHD (OR=1.935,95%CI:1.118-3.353).(2) There was differences of IL-6-597gene and genotype frequencies between the two groups (χ2=5.591, P=0.018;χ2=5.739, P=0.016). The result of logistic regression analysis on the SNP was statistically significant,GA genotype increases the risk of CHD(OR=2.651,95%CI:1.123-6.261).(3) The gene and genotype frequencies of IL-6R-exonl was statistically significant (χ2=5.758, P=0.016; χ2=6.548, P=0.037) between the case and control groups. Logistic regression analysis on the SNP showed that the mutant homozygous genotype CC may reduce the risk of CHD (OR=0.514,95%CI:0.305-0.866).(4) The genotype and gene frequencies of IL-6R-exon2has statistically different between the two groups (χ2=5.893, P=0.015;χ2=6.624, P=0.010). The result showed the AT genotype may increase the risk of CHD (OR=1.809,95%CI:1.164-2.811).(5) The genotype and gene frequencies of IL-6-174and IL-6-183were not statistically different between CHD patients and healthy controls (P>0.5).(6) The haplotype of IL-6-174,-572,-597were constructed and found to be of eight kinds, the CGG haplotype of which has significant difference between the case and control groups (χ2=4.18, P=0.040, OR=0.75); The haplotypes of IL-6R-183,-exonl,-exon2have eight kinds, the three haplotypes of AAA, ACT and GAA have significant difference between the case and control groups (χ2=12.468, P=0.0004, OR=3.213; χ2=7.681, P=0.0056, OR=0.601; χ2=4.385, P=0.036, OR=2.139).(7) The association study of IL-6and its receptor gene polymorphisms and CHD serological indictors (blood lipids, blood clot) showed that IL-6R-183related to blood clotting index INR and IL-6R-exonl associated with blood lipid index CHO and HDL.Conclusion Four SNPs of IL-6-572、IL-6-597、IL-6R-exon and IL,-6R-exon2are related to CHD susceptibility in Northwest Chinese population. The haplotype CGG of IL-6-174/-572/-597may reduce the risk of CHD development; and the haplotypes AAA and GAA of IL-6R-183/-exonl/-exon2may increase the risk of the occurrence of CHD, while the haplotype ACT may reduce the risk of CHD development. IL-6R gene polymorphisms are associated with the serological indictorsINR、CHO、HDL of CHD.