The effect of statins on blood gene expression in COPD

Background: COPD is currently the fourth leading cause of death worldwide and predicted to rank third by 2020. Statins are commonly used lipid lowering agents with documented benefits on cardiovascular morbidity and mortality, and have also been shown to have pleiotropic effects including anti-inflammatory and anti-oxidant activity. Objective: Identify a gene signature associated with statin use in the blood of COPD patients, and identify molecular mechanisms and pathways underpinning this signature that could explain any potential benefits in COPD. Methods: Whole blood gene expression was measured on 168 statin users and 452 non-users from the ECLIPSE (Evaluation of COPD Longitudinally to Identify Predictive Surrogate Endpoints) study. Gene expression was measured using the Affymetrix Human Gene 1.1 ST microarray chips. Factor Analysis for Robust Microarray Summarization (FARMS) was used to process the expression data and to filter out non-informative probe sets. Differential gene expression analysis was undertaken using the Linear Models for Microarray data (Limma) package adjusting for propensity score and employing a surrogate variable analysis. Similarity of the expression signal with published gene expression profiles was performed in ProfileChaser. Results: 18 genes were differentially expressed between statin users and non-users at a false discovery rate of 10%. Top genes included LDLR, ABCA1, ABCG1, MYLIP, SC4MOL, and DHCR24. The 18 genes were significantly enriched in pathways and biological processes related to cholesterol homeostasis and metabolism, and were enriched for transcription factor binding sites for sterol regulatory element binding protein 2 (SREBP-2). The resulting gene signature showed correlation with Huntington disease, Parkinson’s disease and acute myeloid leukemia. Conclusion: Statins gene signature was not enriched in any pathways related to respiratory diseases, beyond the drug’s effect on cholesterol homeostasis. Study subjects were a subset of those with COPD from the Evaluation of COPD Longitudinally to Identify Predictive Surrogate Endpoints (ECLIPSE) study (Vestbo et al.), funded by GlaxoSmithKline (GSK Study No. SCO104960, NCT00292552). ECLIPSE is a non-interventional, observational, multicentre, three-year study in people with COPD. Blood was collected in PAXGene tubes and frozen at -80oC. In this work we have looked at the effect of statins on gene expression in 620 subjects of whom 168 were statin users. ECLIPSE study was described in: Vestbo J, Anderson W, Coxson HO, et al.: Evaluation of COPD Longitudinally to Identify Predictive Surrogate End-points (ECLIPSE). Eur Respir J. 2008;31(4):869-73

背景：目前慢性阻塞性肺疾病（Chronic Obstructive Pulmonary Disease, COPD）是全球第四大致死性疾病，预计到2020年将升至第三位。他汀类药物是临床常用的降脂制剂，已被证实可降低心血管疾病的发病率与死亡率，同时还具备多种多效性作用，包括抗炎与抗氧化活性。
目的：筛选与慢性阻塞性肺疾病患者血液中他汀类药物使用相关的基因特征，并阐明支撑该特征的分子机制与通路，以解释他汀类药物对慢性阻塞性肺疾病的潜在获益。
方法：本研究依托慢性阻塞性肺疾病纵向评估以识别预测性替代终点（Evaluation of COPD Longitudinally to Identify Predictive Surrogate Endpoints, ECLIPSE）研究队列，对168名他汀类药物使用者与452名非使用者的全血基因表达量进行检测。基因表达量检测采用Affymetrix Human Gene 1.1 ST微阵列芯片。使用稳健微阵列汇总因子分析（Factor Analysis for Robust Microarray Summarization, FARMS）对表达数据进行处理，并过滤掉无信息的探针集。差异基因表达分析采用微阵列数据线性模型（Linear Models for Microarray data, Limma）工具包，校正倾向得分并采用替代变量分析方法。使用ProfileChaser工具对表达信号与已发表的基因表达谱进行相似性比对。
结果：在10%的错误发现率（false discovery rate, FDR）阈值下，共筛选出18个在他汀类药物使用者与非使用者间存在差异表达的基因。排名靠前的基因包括LDLR、ABCA1、ABCG1、MYLIP、SC4MOL与DHCR24。这18个基因显著富集于胆固醇稳态与代谢相关的通路及生物学过程，同时其转录因子结合位点富集于固醇调节元件结合蛋白2（sterol regulatory element binding protein 2, SREBP-2）。该基因特征与亨廷顿病、帕金森病及急性髓系白血病的表达谱存在显著相关性。
结论：除他汀类药物对胆固醇稳态的作用外，其相关基因特征未富集于任何呼吸系统疾病相关通路。本研究受试者来自慢性阻塞性肺疾病纵向评估以识别预测性替代终点（ECLIPSE）研究的亚队列（Vestbo等），该研究由葛兰素史克（GlaxoSmithKline, GSK）资助（GSK研究编号：SCO104960，临床试验编号：NCT00292552）。ECLIPSE研究是一项非干预性、观察性多中心三年期队列研究，纳入对象为慢性阻塞性肺疾病患者。血液样本采集于PAXGene采血管，并于-80℃冻存。本研究共纳入620名受试者，其中168名使用他汀类药物，旨在分析他汀类药物对其基因表达的影响。ECLIPSE研究详情已发表于：Vestbo J, Anderson W, Coxson HO, et al.: Evaluation of COPD Longitudinally to Identify Predictive Surrogate End-points (ECLIPSE). Eur Respir J. 2008;31(4):869-73