遗传背景对痛风和/或高尿酸血症影响的初探

【作者】 张冰清；

【导师】 曾学军；

【作者基本信息】 北京协和医学院 ， 临床医学， 2013， 博士

【摘要】 背景：随着生活水平和健康意识的提高,高尿酸血症和痛风的患病率呈逐年上升的趋势,流行病学和实验室研究均发现高尿酸血症与心血管疾病有密切联系。临床中观察到一个家庭中有三例女性出现绝经前发病的痛风,这和我们已经知晓的高尿酸血症和痛风的常见危险因素——女性通常在绝经后发病迥然不同,特别是其中一例发病年龄仅为16岁,提示遗传因素可能参与发病。遗传因素是高尿酸血症和痛风已知的重要危险因素,遗传背景可能是导致疾病个体化的原因之一。全基因组连锁分析(Genome-Wide Association Study, GWAS)发现了众多与血尿酸水平和痛风相关的位点,然而临床观察到的现象往往是遗传因素与环境因素共同作用的结果,且多数情况下环境因素所占权重更大,因此GWAS研究发现的遗传高危位点目前尚未应用于解释特定人群痛风和高尿酸血症的发生并指导临床实践。本次研究,我们旨在对于上述问题开展初步的探索。目的：1)通过对一个绝经前发病女性痛风家庭的遗传学研究,探索与高尿酸血症和痛风相关的遗传因素；2)在人群中初步探索痛风高危位点ABCG2SNP rs2231142遗传多态性对高尿酸血症的影响,以及其它危险因素对遗传因素影响的可能交互作用。方法：1)收集该家庭的病史、体格检查和实验室检查等临床资料,等位基因共享实验和外显子基因测序研究家族性青年性高尿酸性肾病的致病基因UMOD, RENIN, HNF1B和HNFJ3,以及Lesch-Nyhan综合征的致病基因HPRT1;外显子测序筛查痛风和高尿酸血症的相关位点ABCG2、SLC2A9、SLC22A12。2)利用我院2008年职工健康体检样本,选择去除肌酐清除率小于30ml/min/1.73m2的高尿酸血症样本(高尿酸血症组),在性别、年龄、肌酐清除率和体质指数匹配的尿酸正常者中按照1：1～1：2比例随机抽取正常对照(正常对照组),采用ARMS-PCR法检测rs2231142位点的基因型。配对回归分析和交互分析研究该人群中rs2231142的基因型分布、A基因频率、A等位基因对高尿酸血症的相关性以及其他因素与该位点的交互作用。结果：1)该家庭共四代,收集到完整临床信息和血样者共11人,男性6人,女性5人。痛风患者共3人,均为绝经前女性,男性成员均无痛风或高尿酸血症。等位基因共享实验显示RENIN基因在该家庭中存在共享,其他基因无共享,基因测序显示RENIN, UMOD无有意义突变。HPRT1基因测序无突变。先症者的ABCG2, SLC2A9和SLC22A12基因存在多个遗传多态性位点(single nucleotide polymorphism, SNP),其中包括一个高尿酸血症保护位点和高危危险rs2231137和rs2231142。该家庭中其他成员均存在上述位点。2)本研究对象总体高尿酸血症共296人,去除肌酐清除率<30ml/min/1.73m2者和不能完全匹配者后,高尿酸血症组共196人,正常对照288人。配对研究人群总体的rs2231142的A等位基因频率为30.79%,高尿酸血症组和尿酸正常组A等位基因频率存在显著差异(分别为39.03%和25.17%,p<0.01)；A等位基因与高尿酸血症显著相关,OR=3.35(95%CI2.10-5.33,p<0.01)；相比CC基因型,CA基因型和AA基因型发生高尿酸血症的OR分别为3.19(95%CI：1.99-5.12,p<0.01)和4.85(95%CI2.13-11.00,p<0.01)；调整血脂、血压、血糖后,A等位基因的高尿酸血症相对风险为3.37(95%CI2.07-5.47,p<0.01)。亚组分析显示：在男性、青年男性、老年女性,慢性肾功能(CKD)3期肾功能者,BMI<28kg/m2者,A基因对高尿酸血症的影响更加明显,但这种影响在年轻女性中不明显。结论：1)在此例绝经前女性痛风家庭中,普遍存在高尿酸血症和痛风的危险位点,ABCG2SNP rs2231142,但排除了目前已知的单基因遗传病。2)在特定研究人群中将性别、年龄、肌酐清除率、体质指数均匹配后,ABCG2SNPrs2231142的A等位基因是高尿酸血症的独立危险因素,且随着A等位基因数目增多,高尿酸血症的风险呈增高趋势。性别、年龄、肌酐清除率和体质指数可能对A等位基因与高尿酸血症的相关性产生修饰作用。3)A基因与高尿酸血症的相关性在年轻女性中不明显,提示年轻女性中可能存在保护因素影响这种基因的作用。更多还原

【Abstract】 BackgroundWith the improving quality of life, the world has seen increasing prevalence of gout and hyperuricemia. Both epidemiology and bench work have demonstrated significant association between hyperuricemia and cardiovascular disease. We found a family characterized with three female gout patients attacked before menopause, which was in contrast with the well-known risk factors of gout and hyperuricemia that women usually do not have gout until menopause, particularly one patient had gout attack as early as16years, highly implicating the involvement genetic factors.Genetic are important risk factors for hyperuricemia and gout, and possibly one of the reasons that cause the variation of gout disease. Genome-Wide Association Study (GWAS) have identified multiple loci associated with gout and hyperuricemia. However what we see in the clinic is often the result of both nature and nurture, and more often than not, nurture is more predominant. Therefore, there are still gap between the findings of GWAS and its application in a specific population, and even further to be transformed into clinical practice. In light of these, we performed the following series of work.Object:1) To explore the genetic factors related to gout and hyperuricemia in a female premenopausal gout family.2) To explore the association between gout risky loci ABCG2rs2231142polymorphism and hyperuricemia in a population, and the possible interaction between other risk factors and genetic factors.Method:1) Collecting medical history, physical examination and laboratory examination of this family. Allele sharing examination and exon sequencing were applied to study the causative genes of familial juvenile hyperuricemia nephropathy, including UMOD, RENIN, HNF1B and HNFJ3, as well as the causative gene of Lesch-Nayhn syndrome-HPRT1. ABCG2, SLC2A9, and SLC22A12were screened by exon sequencing.2) Based on the cohort of the2008faculty annual health examination of PUMCH, exclude hyperuricemia with GFR less than30ml/min/1.73m2(NHUA), normal uricemic control group (NUA) were randomly selected after matching with the NHUA group by sex, age, CKD and BMI. SNP rs2231142were identified by ARMS-PCR. Paired logistic regression and interaction analysis were used to study the genotype distribution of rs2231142, the A allele frequency, the association between A allele and hyperuricemia, and the interaction of other risk factors with the rs2231142risk A allele.Results:1) The family was composed of4generations with21family members, clinical information and genetic study was focused on11members, including6male members and5female members. All three gout patients were female, attacked before menopause; and none of the male family members were affected. RENIN gene was found to be shared in this family by allele sharing experiment, but was found to be normal by exon sequencing. UMOD was not shared and found to be spared with mutations by exon sequencing. HPRT1gene was proved to be normal. Multiple single nucleotide polymorphisms of gene ABCG2, SLC2A9and SLC22A12were found in the one patient, including one locus known to be highly associated with gout, the SNP rs2231142of the gene ABCG2. Nearly all of the family members carry this risk allele.2) A total of296were found to be hyperuricemia in the total cohort. After excluding those with GFR<30ml/min/1.73m2,196hyperuricemic samples were enrolled in the pair group (NHUA);288normal uricemic controls were selected (NUA), matched with hyperuricemic group by sex, age, CKD and BMI. The total A allele frequency of the pair group were30.79%. The A allele frequency was significantly higher in the NHUA group than the NUA group (39.03%v.s.25.17%, p<0.001). The A allele were significantly associated with hyperuricemia (OR=3.35,95%CI2.10-5.33, p<0.01); compared to CC genotype, the risk of hyperuricemia rendered by CA genotype and AA genotype were3.19(95%CI:1.99-5.12, p<0.01) and4.85(95%CI2.13-11.00, p<0.01). After adjustment of dyslipidemia, hypertension and hyperglycemia, the OR of A allele was3.37(95%CI2.07-5.47, p<0.01). Subgroup analysis showed that in young male, old female, those in CKD3and those with BMI<28kg/m2, the relative risk contributed by A allele was more significant, but the increased risk by A allele was not so obvious in young female. Conclusion:1) In this premenopausal gout family, all the known gout causative genes were excluded as the culprit of this family. ABCG2SNP rs2231142was found in both the female patients and male healthy members of this family.2) In this nested case-control study, after matching with sex, age, CKD and BMI, ABCG2SNP rs2231142A allele was proved to be an independent risk factor for hyperuricemia, and the risk of hyperuricemia tends to increase with increasing number of the risk A allele. Sex, age, CKD and BMI might modify the risk conducted by A allele.3) The risk conducted by A allele toward hyperuricemia was relatively insignificant in young female, indicating a protective factor that might overwhelm the risk of SNP rs2231142A allele.更多还原