Single Nucleotide Polymorphisms In The Cholesteryl Ester Transfer Protein Gene And Their Association With Coronary Heart Disease In Chinese

Molecular epidemiological studies have demonstrated that cholesteryl ester transfer protein (CETP) gene is one of the susceptibility genes for coronary heart disease (CHD). CETP mediates the exchange of cholesteryl ester and triglyceride between HDL and apo-B containing lipoproteins, i.e., LDL and VLDL, in the plasma. Via this exchange, the protein can modulate the concentration, composition and particle size of HDL and plays a key role in reverse cholesterol transport from peripheral tissues to the liver. Thus, CETP is considered to be one of the main determinants of HDL and LDL level in the plasma and acts an important part in the pathogenesis of CHD. A number of single nucleotide polymorphisms (SNPs) in the gene coding for CETP have so far been identified which were related to the development of CHD. In the present study, the association analyses between these known SNPs in the CETP gene and CHD were performed and whole-gene screening for the possible new SNPs was conducted in a Chinese population including 203 CHD patients and 209 controls using polymerase chain reaction, restriction fragment length polymorphism, denaturing high performance liquid chromatography, molecular cloning and DNA sequencing techniques. The results were as follows:1. Two of 7 known SNPs in the CETP gene, IVS14 +1 G/A and R451Q, have not been found in the 412 subjects, indicating that they are rare in Chinese Han population.2. Among the known SNPs, the differences in allele frequencies and genotype frequencies of D442G between the CHD group and the control group were significant ( P = 0.043ï¼›P = 0.035 ), and the frequency of 442G allele was significantly higher in CHD patients than that in controls, which suggested that 442G allele was likely to be related to the development of CHD.3. Through whole CETP gene screening including promoter region, all 16 exons and adjacent intronic regions, 5501 bp in total, 12 novel SNPs were identified. Among them, 2 were in promoter region, 1 in 5' untranslated region and 9 in introns, and 4 were transitions and 8 transversions.4. The genotype and allele frequencies of the 5 newly found SNPs, namely - 645 A/C and - 174 G/C in promoter region, + 9907 T/A in intron 7, + 13044 A/T in intron 9 and + 19323 T/A in intron 11, were significantly different between the patients and the controls ( P < 0.05 ).5. In CHD patients, the frequencies of heterozygote of - 645 A/C and - 174 G/C polymorphisms were significantly higher in the subgroup with TC / HDL-C > 5 than that with TC / HDL-C < 5, suggesting that - 645 C and - 174 C alleles were associated with higher TC / HDL-C ratio.6. Three novel SNPs were found to be related to the variation of the plasma lipid level in male CHD patients: - 645 A was associated with higher HDL-C, - 174 G related to higher HDL-C and TC, and +19323 T associated with lower LDL-C level.7. The pairwise linkage disequilibrium analyses of the 5 new SNPs with significantly different allele frequencies between the CHD patients and controls revealed that - 645 A/C and - 174 G/C polymorphisms in promoter region werein linkage disequilibrium ( D' = 0.344984, P = 0.0000 ).8. Haplotype analyses with EH program demonstrated that the distribution of 5 of 6 haplotypes with frequencies > 0.01 consisting 3 SNPs was significantly different between CHD and control groups ( P < 0.05 or P < 0.01 ). Also the distribution of 4 of 8 haplotypes with frequencies > 0.01 of 5 SNPs was significantly different between CHD and control groups ( P < 0.05 or P < 0.01 ).9. The frequencies of haplotypes containing - 645 C allele were higher or significantly higher, whereas the frequencies of haplotypes containing - 645 A allele were lower or significantly lower in patient group than that in control group in various SNP combinations, indicating that the - 645 A/C polymorphism was closely associated with CHD.