Mutation-screening Analysis Of The LPL Gene In CHD Patients With Hypertriglyceridemia

Background and ObjectiveCoronary heart disease is one of the major diseases that threat human health. In thepathological process of coronary heart disease, abnormal lipid metabolism is the mainpathogenesis of coronary heart disease, and there is closely connection betweenhypertriglyceridemia and the occurrence and development of coronary heart disease.Studies have shown that hereditary hypertriglyceridemia can be caused by a variety ofgenetic mutations, and Lipoprotein lipase is the rate-limiting enzyme in the cause oftriglyceride metabolism. Recent studies indicate that mutations in the LPL gene play animportant role in the development of coronary heart disease. To explore the effect of LPLgene mutations and polymorphisms in the development of coronary heart disease, wescreened LPL gene mutations of HTG patients in CHD patients of Han-Chinese populationin Shandong province. The study aim is to find susceptibility genes of coronary heartdisease from the molecular level and provide a new target for the prevention and treatmentof coronary heart disease.Subjects and MethodsSubjects: the subjects of the patient group and normal control group are both fromLiaocheng People's Hospital. All subjects were Han-Chinese population. All wereexcluded from the disorders of liver, kidney, cancer and thyroid. There are120cases inCHD group, while there are118cases in the control group. It is comparable for age, sex,smoking prevalence, incidence of hypertension and other conditions between the twogroups through the statistical analysis. Methods: Patients and controls were asked to fill outan informed consent form. All of the subjects were fasted more than12hours and3ml ofvenous blood were collected in EDTAK2anticoagulant tube to extract genomic DNA. LPLgene fragment was amplified using the PCR method. The PCR product was sequencedthrough ABI3700facility. ResultsTwo kinds of mutations in exon8and exon9were identified in the patient group. Oneis Thr388?Thr mutation (c.1164C?A) in exon8mutation, which has not changed theamino acid sequence, so it is a synonymous mutation. Fifteen cases are heterozygousmutation and one case is homozygous mutation. The other is Ser447?Ter mutation(c.C1421?G) in exon9and it generates a stop codon.14patients have the heterozygousmutations and one patient has homozygous mutation. We also found intronic mutations asfollows: c.429+20A> C, c.430-6C> T,c.430-34C> A, c.775+3T> C,c.1140-7T> G, andall are heterozygous mutations. The reported mutations in lipoprotein lipase catalyticcenter Asp156-His241-Ser132(exon4and exon5) have not been found. In the normalcontrol group, the Ser447?Ter mutation was found in22cases, and all are heterozygousmutations. Since the mutation also exists in normal control, it is indicated that the mutationbelongs to gene polymorphism. We calculated the incidence of the above LPL genemutation and the results are as follows:1. The mutations of Thr388?Thr in exon8and Ser447?Ter in exon9in LPL genecoding region exist in Chinese Han population, and the distribution of Ser447?Ter inexon9are as follows: CC gene type accounts for84.45%(201cases), CG gene typeaccounts for15.13%(36cases), and GG gene type accounts for0.42%(1case) in alltesting crowd. The allele frequencies in the case group and normal control group accord tothe Hardy-Weinberg equilibrium (?2=0.46875,1.2471, df=1, P=0.9333,0.90678), andthe two groups can be considered to be representative of the population.2. The distribution difference of Ser447?Ter in the young group (<60years) and theolder group (?60years) was not statistically significant.(?2=1.743,0.044; df=2,1; P=0.418,0.835;)3. The distribution difference of Ser447?Ter in the male group and the female groupwas not statistically significant (?2=0.976,0.022:; df=2,1; P=0.614,0.882;)4. For Ser447?Ter of the LPL gene, the allele frequency differences between thecase group and the normal control group are not significant (?2=1.711, df=1, P=0.191).The three kinds of genotype frequencies differences in case group and the normal controlgroup are not significant (?2=3.164, df=2, P=0.206). The risk difference of coronaryheart disease in X genotype carriers and non-carriers is not significant.(OR=1.426;95%CI=0.729~2.788; P=0.298)ConclusionsIn this study we identified that the mutations of Thr388?Thr in exon8and Ser447 ?Ter in exon9existed in Shandong Han population. For the mutation of Ser447?Ter,there are no age and gender differences in the case group and the normal control group andthis indicates that the mutation belongs to gene polymorphisms. Also, it is found that theallele frequencies are different and the three kinds of genotype frequency differencesbetween the case group and the normal control group were not significant. This studyindicated that the incidence of Ser447?Ter mutation in case group is not significantlyhigher than that in normal control group, but other mutations in the LPL gene may play animportant role in the occurrence of hypertriglyceridemia. The increase of the sample size isneeded in the future further research to explore the mechanism of gene mutation.