Mitochondrial DNA heteroplasmy and risk for atherosclerotic cardiovascular disease (ASCVD)

心血管疾病（CVD）仍然是全球死亡率和发病率的主要原因。我们有 先前证明，线粒体DNA拷贝数（mtDNA-CN），这反映了高度的 每个细胞线粒体基因组数量的变化（10到100）是CVD的一个新的风险因素。中 前瞻性队列分析包括21，870名参与者，mtDNA-CN下降1个标准差 与CVD风险增加1.23（95%CI 1.19 - 1.26）相关。此外，直接的临床效用是 证明，将mtDNA-CN添加到2013年ACC/AHA合并队列方程中， 10年动脉粥样硬化CVD风险显著提高了推荐的敏感性和特异性， 开始他汀治疗虽然mtDNA-CN捕获线粒体的数量，但较高的mtDNA-CN水平 与线粒体功能的增加有关，这种测量没有考虑到 线粒体线粒体DNA异质性，这是普遍观察到的，并随着年龄的增长而积累， 可能对线粒体功能产生负面影响。因此，我们假设mtDNA的作用- CN对心血管疾病风险的影响将直接受到异质性水平的影响，并且更高水平的异质性将 是CVD的独立危险因素。为了检验这一假设，我们将首先使用ARIC、CHS、FHS、 梅萨和RS队列（n= 23，954; 6，048起新发CVD事件），以确定基线 线粒体DNA异质性与CVD事件的措施。其次，mtDNA异质性的变化可能反映了 正在进行的疾病过程（例如炎症），因此我们将使用从初始基线访视收集的DNA 沿着每个队列最多2次随访访视（n= 7，364，3，430起CVD事件），以评估纵向 mtDNA异质性的改变影响未来CVD的风险。第三，一个潜在的后果是， 由体细胞突变引起的线粒体功能是线粒体产生的上调。 因此，在高异质性存在下，高mtDNA-CN实际上可能是有害的而不是保护性的。 因此，我们建议将这些措施联合收割机，并评估其在改善ACC/AHA风险评分中的作用。 最后，我们将在功能上描述mtDNA异质性的后果， 通过mitoTALEN操纵特定mtDNA遗传变异的水平。我们将进一步探讨 异质性对细胞核DNA甲基化和基因表达的影响 表达，两者均被mtDNA-CN修饰。该提案利用了5个完善的队列， 在超过20年的随访中，约6000例CVD事件，以及一套全面的功能性 验证实验，以阐明mtDNA异质性在CVD风险中的作用。异质性和线粒体DNA- CN很容易在全血中测量，全血是一种高度相关的组织，在发展中起主要作用， CVD。更重要的是，这两项指标代表了一种新的风险因素， 这一发现证实了心血管疾病的危险因素，因此开辟了新的预防或治疗策略的可能性。

Cardiovascular disease (CVD) continues to be a leading cause of mortality and morbidity worldwide. We have previously demonstrated that mitochondrial DNA copy number (mtDNA-CN), which reflects the high degree of variation in the number of mitochondrial genomes per cell (10s to 100s), is a novel risk factor for CVD. In a prospective cohort analysis including 21,870 participants, a 1 standard deviation decrease in mtDNA-CN was associated with a 1.23 (95%CI 1.19 to 1.26) increased risk of CVD. Moreover, a direct clinical utility was demonstrated, with the addition of mtDNA-CN to the 2013 ACC/AHA Pooled Cohorts Equations for estimating 10-yr atherosclerotic CVD risk significantly improving both sensitivity and specificity for the recommendations on initiating statin therapy. While mtDNA-CN captures the quantity of mitochondria, and higher mtDNA-CN levels are associated with increased mitochondrial function this measurement does not take into account the quality of the mitochondria. Mitochondrial DNA heteroplasmy, which is universally observed and accumulates with age, is likely to have negative consequences for mitochondrial function. Thus, we hypothesize that the effect of mtDNA- CN on CVD risk will be directly impacted by levels of heteroplasmy, and that higher levels of heteroplasmy will be an independent risk factor for CVD. To test this hypothesis, we will first use the combined ARIC, CHS, FHS, MESA and RS cohorts (n=23,954; 6,048 incident CVD events), to determine the association of baseline measures of mtDNA heteroplasmy with incident CVD. Second, changes in mtDNA heteroplasmy may reflect ongoing disease processes (e.g. inflammation), and thus we will use DNA collected from the initial baseline visit along with up to 2 follow-up visits in each cohort (n=7,364, 3,430 incident CVD events) to assess how longitudinal changes in mtDNA heteroplasmy influence future CVD risk. Third, one potential consequence of decreased mitochondrial function arising from somatic mutation is an upregulation in the production of mitochondria. Therefore, high mtDNA-CN in the presence of high heteroplasmy may actually be harmful rather than protective. Thus, we propose to combine these measures and assess their role in improving the ACC/AHA risk score. Finally, we will functionally characterize the consequences of mtDNA heteroplasmy by introducing and manipulating the levels of specific mtDNA genetic variants through mitoTALENs. We will further explore a plausible biological mechanism testing the impact of heteroplasmy on nuclear DNA methylation and gene expression, both of which are modified by mtDNA-CN. This proposal leverages 5 well-established cohorts, with ~6000 cases of incident CVD in over 20 years of follow-up, together with a comprehensive set of functional validation experiments, to elucidate the role of mtDNA heteroplasmy in CVD risk. Both heteroplasmy and mtDNA- CN are readily measured in whole blood, a highly relevant tissue that plays a primary role in the development of CVD. More importantly, these two measures represent a novel class of risk factors not captured by any of the established CVD risk factors and therefore opens the potential for novel preventive or therapeutic strategies.