PGRN-RIKEN: Identification of Genetic Predictors of ACE Inhibitor-Associated Angioedema

The purpose of this study is to identify genetic predictors of ACE inhibitor-associated angioedema. In addition to preventing the formation of the pressor angiotensin II, ACE inhibitors prevent the carboxyl-terminal degradation of the vasoactive substances bradykinin and substance P. Angioedema is hypothesized to result from defective amino-terminal degradation of bradykinin or substance P in patients in whom ACE is inhibited. For example, activity of dipeptidyl peptidase IV (DPP-IV), the enzyme responsible for the inactivation of substance P when ACE is inhibited, is decreased in patients with angioedema. In preliminary studies, we have identified SNPs in the DPP4 gene that associate with DPP-IV activity and, in blacks, with risk of angioedema. This project will use genome-wide genotyping to compare 250 cases and 568 ACE inhibitor-exposed control subjects (131 cases and 288 controls ascertained at Vanderbilt and 70 cases and 280 controls ascertained at the Marshfield Clinic). We plan a 2-stage analysis of associations between SNPs and angioedema - first, we will study DPP4 SNPs for association with angioedema and, second, we will explore associations using the full GWAS data set. Depending on the platform, additional DPP4 SNPs will be used to fully tag common genetic variants in both African American and European American samples. Based on the HapMap data, there are 14 tagging SNPs in people of European descent and 34 in Yoruba (selection criteria MAF>0.05 and r2>0.8). Cases were defined as having ACE inhibitor-associated angioedema if they had had swelling of the lips, throat, tongue or face while taking an ACE inhibitor but had never had angioedema while not taking an ACE inhibitor. For simplicity, intestinal edema was excluded. Control subjects were treated for at least 6 months with an ACE inhibitor without angioedema. Because black Americans are known to be overrepresented among patients with ACE inhibitor-associated angioedema, control subjects were prespecified to be 50% black American, 50% white American, and 50% female. At Vanderbilt, the medical history, including the history of angioedema, was confirmed by a research nurse or physician using a detailed case report form. Characteristics of Vanderbilt cases appear in the Table. At Marshfield, medical history will be confirmed by chart review. The Marshfield cohort is 98% white American and 57% female with a mean age of 47.2 years.]]>
Inclusion criteria Cases: 1) Men or women age 18 or older; 2) African- or Caucasian-Americans; 3) With angioedema, defined by swelling of the lips, tongue, pharynx, or face while taking an ACE inhibitor. Controls: 1) Men or women age 18 or older; 2) African- or Caucasian-Americans; 3) Taken and ACE inhibitor for at least 6 months and never experienced angioedema; 4) May include subjects who experienced cough. Exclusion criteria for all subjects 1) History of angioedema while not taking an ACE inhibitor; 2) Angioedema only involves the bowel; 3) Decreased C1 inhibitor or complement concentrations; 4) Mental conditions which render the subject unable to understand the nature, scope, and possible consequences of the study.]]>

本研究旨在识别血管紧张素转换酶（Angiotensin Converting Enzyme, ACE）抑制剂相关性血管性水肿的遗传预测因子。ACE抑制剂除可阻断升压物质血管紧张素II的生成外，还可抑制血管活性物质缓激肽与P物质的羧基末端降解。现有假说认为，血管性水肿的发生源于ACE受抑制患者体内缓激肽或P物质的氨基末端降解缺陷。例如，当ACE活性受抑制时负责灭活P物质的二肽基肽酶IV（Dipeptidyl peptidase IV, DPP-IV），其活性在血管性水肿患者中呈降低趋势。

在前期研究中，我们已发现DPP4基因上的单核苷酸多态性（Single Nucleotide Polymorphism, SNP）与DPP-IV活性相关，且在黑人人群中与血管性水肿风险存在关联。本项目将通过全基因组基因分型技术，对比250例病例与568例ACE抑制剂暴露对照受试者（其中范德堡大学招募131例病例、288例对照，马什菲尔德诊所招募70例病例、280例对照）。我们计划分两阶段开展SNP与血管性水肿的关联分析：第一阶段针对DPP4基因上的SNP进行血管性水肿关联研究；第二阶段则利用全基因组关联研究（Genome-Wide Association Study, GWAS）数据集全面探索关联位点。根据所用基因分型平台的差异，我们将补充检测额外的DPP4 SNPs，以实现非裔美国人和欧洲裔美国人样本中常见遗传变异的全覆盖标记。基于HapMap数据库数据，欧洲血统人群中存在14个标签SNP，约鲁巴血统人群中则存在34个（筛选标准为次要等位基因频率MAF>0.05且连锁不平衡r²>0.8）。

病例的定义为：服用ACE抑制剂期间出现嘴唇、咽喉、舌头或面部肿胀，且未服用ACE抑制剂时从未发生过血管性水肿。为简化研究分析，肠道源性水肿被排除出本研究范畴。对照受试者需服用ACE抑制剂至少6个月，且未发生过血管性水肿。鉴于已有研究证实非裔美国人在ACE抑制剂相关性血管性水肿患者中占比偏高，故预先设定对照受试者的构成比例为：非裔美国人、白人美国人各占50%，女性占比50%。

在范德堡大学，研究护士或医师将通过详细的病例报告表确认受试者的病史，包括血管性水肿病史。范德堡大学病例的相关特征详见附表。在马什菲尔德诊所，将通过病历回顾的方式确认受试者病史。马什菲尔德队列中98%为白人美国人，57%为女性，平均年龄为47.2岁。

### 纳入标准
#### 病例组
1. 年龄18周岁及以上的男性或女性；
2. 非裔或高加索裔美国人；
3. 服用ACE抑制剂期间出现以嘴唇、舌头、咽部或面部肿胀为表现的血管性水肿。

#### 对照组
1. 年龄18周岁及以上的男性或女性；
2. 非裔或高加索裔美国人；
3. 服用ACE抑制剂至少6个月且从未发生血管性水肿；
4. 曾出现咳嗽症状的受试者亦可纳入研究。

### 通用排除标准（所有受试者）
1. 未服用ACE抑制剂期间存在血管性水肿病史；
2. 仅肠道受累的血管性水肿；
3. C1抑制剂或补体浓度降低；
4. 存在精神疾病导致无法理解本研究的性质、范围及潜在后果。