线粒体DNA总体水平或可预测个体的死亡风险

  近日，来自约翰霍普金斯大学的研究人员通过研究发现，个体机体细胞中的线粒体DNA的总量或可帮助预测个体的死亡率；研究者表示，个体机体血液中的线粒体DNA总量可以直接反应出机体的虚弱程度，而线粒体DNA也是在机体出现症状之前反应个体死亡和虚弱性总体风险的一个很好的预测工具。

  研究者表示，本文研究为我们理解机体老化进程，同时为开发新型检测手段来帮助鉴别处于风险的个体提供了一定的帮助；研究者Dan Arking说道，线粒体DNA或许是一种很有用的生物标志物来用于进行机体老化的研究，线粒体并不像其它细胞结构，其有自身独特的DNA，即2-10个小型环状的染色体，可以编码37个实现染色体功能的基因，依赖于细胞对能量的需求程度，每个细胞中大约有10个至成千个线粒体。

  此前研究中研究者认为线粒体DNA的遗传改变可以增加老年个体机体的虚弱程度并且降低肌肉力量，从医学角度来讲机体虚弱是一种老化的症状，主要包括能量降低、活动水平降低及体重下降；本文中为了检测这种关联，研究人员从20世纪80年代末期进行了两项大型研究，从收集的血液样本中来分析个体细胞中的线粒体DNA的含量。

  通过计算每一份样本线粒体DNA中核DNA的含量后，研究者测定了参与者机体的虚弱及健康状况；结果显示，相比非虚弱个体而言，虚弱个体机体的线粒体DNA总量要比前者少9%，Arking表示，线粒体DNA水平的下降和较差的健康情况直接相关，随着年龄增长，我们机体的能量也会逐渐下降，从而使得机体对各种健康问题和疾病易感。

  最后研究者希望通过对线粒体DNA含量的测定可以帮助检测个体机体虚弱和死亡的风险，同时也可以帮助医生们及时采取治疗措施来抑制个体疾病的发生，为改善个体老化后的机体健康状况带来一定的帮助。（转化医学网360zhyx.com）

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Association of mitochondrial DNA levels with frailty and all-cause mortality
Journal of Molecular Medicine doi:10.1007/s00109-014-1233-3
Foram N. Ashar, Anna Moes, Ann Z. Moore, Megan L. Grove, Paulo H. M. Chaves, Josef Coresh, Anne B. Newman, Amy M. Matteini, Karen Bandeen-Roche, Eric Boerwinkle, Jeremy D. Walston, Dan E. Arking
Mitochondrial function is altered with age and variants in mitochondrial DNA (mtDNA) modulate risk for several age-related disease states. However, the association of mtDNA copy number, a readily available marker which reflects mitochondrial depletion, energy reserves, and oxidative stress, on aging and mortality in the general population has not been addressed. To assess the association between mtDNA copy number and two primary outcomes—prevalent frailty and all-cause mortality—we utilize data from participants who were from two multicenter, multiethnic, community-based, prospective studies—the Cardiovascular Health Study (CHS) (1989–2006) and the Atherosclerosis Risk in Communities (ARIC) study (1987–2013). A total of 4892 participants (43.3 % men) from CHS and 11,509 participants (44.9 % men) from ARIC self-identifying as white or black were included in the analysis. mtDNA copy number, the trait of interest, was measured using a qPCR-based method in CHS and an array-based method in ARIC from DNA isolated from whole blood in participants from both cohorts. In race-stratified meta-analyses, we observe a significant inverse association of mtDNA copy number with age and higher mtDNA copy number in women relative to men. Lower mtDNA copy number was also significantly associated with prevalent frailty in white participants from CHS (OR 0.91, 95 % CI 0.85–0.97). Additionally, mtDNA copy number was a strong independent predictor of all-cause mortality in an age- and sex-adjusted, race-stratified analysis of 16,401 participants from both cohorts with a pooled hazard ratio of 1.47 (95 % CI 1.33–1.62) for the lowest quintile of mtDNA copy number relative to the highest quintile.