相同基因突变家族性高胆固醇血症患者低密度脂蛋白胆固醇水平差异的甲基化机制研究

Methylation mechanism of the expressional difference of low-density lipoprotein cholesterol in familial hypercholesterolemia patients with same gene mutation

目的探讨相同基因突变[低密度脂蛋白受体(LDL-R) A606T基因突变]的家族性高胆固醇血症(FH)患者低密度脂蛋白胆固醇水平差异的机制。方法选取2016年1月至2017年3月在首都医科大学附属北京安贞医院门诊临床和基因诊断确诊为FH的杂合患者10例,依据低密度脂蛋白胆固醇(LDL-C)水平,分为高LDL-C组(LDL-C≥5 mmol/L,6例)和低LDL-C组(LDL-C <5 mmol/L,4例)。提取2组外周血淋巴细胞中的DNA。Illumina公司Human Methylation 850K甲基化芯片检测2组CpG岛甲基化谱的差异。实时荧光定量聚合酶链反应(RT-PCR)检测差异基因mRNA表达水平;酶联免疫吸附试验(ELISA)检测血浆差异基因蛋白水平。结果全基因组甲基化芯片初步筛选结果显示,与低LDL-C组相比,高LDL-C组胆固醇7α-羟化酶(CYP27A1)基因表现为高甲基化。RT-PCR和ELISA检测结果显示,高LDL-C组的CYP27A1 mRNA及CYP27A1蛋白表达水平较低LDL-C组低[(0. 041±0. 013)比(1. 011±0. 076),(136±12)μg/L比(174±26)μg/L](均P <0. 05)。结论 LDL-R A606T突变的FH患者的CYP27A1 mRNA和CYP27A1蛋白表达水平均降低,与该基因甲基化水平增高有关,CYP27A1基因甲基化异常可能参与FH患者的血脂代谢。

Objective To investigate the mechanism of the expressional difference of low-density lipoprotein cholesterol(LDL-C)in familial hypercholesterolemia(FH)patients with low-density lipoprotein receptor(LDL-R)gene A606T mutation.Methods Ten heterozygous patients with FH diagnosed by clinical manifestations and genetic detection in Beijing Anzhen Hospital,Capital Medical University from January 2016 to March 2017 were divided into high LDL-C group(LDL-C≥5 mmol/L,6 cases)and low LDL-C group(LDL-C<5 mmol/L,4 cases).DNA methylation of CpG island in peripheral blood was detected by the Illumina Human Methylation850 K Bead Chip.Expressions of mRNA and protein of the differential gene were determined by real-time fluorescence quantitative polymerase chain reaction(RT-PCR)and enzyme linked immunosorbent assay(ELISA).Results Genome-wide methylation screening showed that cholesterol-7α-hydroxylase(CYP27A1)gene was hypermethylated in the high LDL-C group.RT-PCR and ELISA revealed that CYP27A1 mRNA and protein expression in the high LDL-C group were significantly lower than those in the low LDL-C group[(0.041±0.013)vs(1.011±0.076),(136±12)μg/L vs(174±26)μg/L](both P<0.05).Conclusion FH patients with LDL-R A606T mutation have low expressions of CYP27A1 mRNA and protein,which is related with its hypermethylation;the abnormal methylation of CYP27A1 gene may be involved in lipid metabolism in FH patients.