Study On The Association Of LCAT Gene Polymorphisms With The Susceptibility Of Coronary Artery Diease

Coronary artery disease (CAD) is one of the leading causes of death worldwide. It is a complex disease resulting from numerous gene-gene and gene-environment interactions. It is commonly accepted that dyslipidemia, including elevated levels of atherogenic lipoproteins and/or reduced levels of high-density lipoprotein (HDL), is a prerequisite for most forms of CAD. Moreover, epidemiological studies over the past 50 years have revealed that multiple genes, especially those involved in lipid metabolism, are responsible of the genetic .susceptibility of CAD.Lecithin: cholesterol acyltransferase (LCAT), which is a pivotal enzyme in reverse cholestelrol transport (RCT), plays a key role in cholesterol and HDL metabolism. Therefore, LCAT is thought to be one of the candidate genes associated with dyslipidemia and CAD, as well as a putative new target for gene therapy to prevent CAD.In post-genomic era, studies on association of sequencevariation with phenotype are the main subject of medical genetics. Single nucleotide polymorphisms (SNPs), the third-generation genetic marker, possess the characteristic of large numbers and dispersed distribution. SNPs, especially those in the coding regions (cSNPs) and gene regulatory elements are implicated as a causative factor in human genetic disease. Association study based on population level may find the possible SNP and/or haplotype associated with the disease. They are of importance for clarifying the genetic pathology of some polygenic inheritance disease.To further our understanding of the possible role-played by SNPs of the LCAT gene in dyslipidemia and CAD; first, we examined the distribution of 3 known SNPs (608OT, 911T>C and 1188OT) of LCAT gene in 203 Chinese patients with CAD and 209 controls by PCR-RFLP. Second, we screened the unknown SNPs of the LCAT gene by high-throughput denaturing high-performance liquid chromatography (DHPLC), and further confirmed by DNA sequencing and RFLP assay. Finally, we analyzed the association of these SNPs with lipid metabolism in patients with CAD.As to the 3 known cSNPs, the frequency of 608T allele was significantly higher in controls than that in patients (P=0. 034). Further statistical analysis suggested that 608T was associated with higher plasma HDL-C level in CAD patients. The other two polymorphisms 911T>C and 188C>T were not found.By DHPLC, sequencing and RFLP, a novel cSNP 511OT (P143L) in exon 4 of the LCAT gene was discovered in CAD patients with frequency of 5.79% (nine males and two females), and was not found in 209 controls. The patients were divided into two subgroups, that is LHDL (low HDL-C level) and NHDL (normal HDL-C level) subgroups according to NCEP-ATPIII criteria. The genotype and allele distribution of 511OT (P143L) was significantly (P<0. 04) higher in the LHDL subgroup than in the NHDL-C subgroup in both male patients and all CAD patients. And 511C>T (P143L) was also found to be significantly (P<0.01) associated with the low HDL-C level phenotype in both male patients and all CAD patients, with odds-ratios of 7. 003 (95% CI 2. 243-21. 859) and 5. 754 (95% CI 1. 893-13. 785) respectively. Thus, the 511C>T (P143L) polymorphism may be related to decreased HDL-C levels, leading to increased risk of dyslipidemia and CAD in Chinese.Another novel cSNP 1230A>G (S383G) in exon 6 was found to be no significant difference between the control and CAD group. In addition, cSNP 52T>A (L-11Q) in exon 1 and 1278OT (R399C) in exon 6 was found with frequency less than 1% and they are not discussed in detail.