人老化的理論得到統一：細胞核及線立體都和老化有關（圖）

線粒體 (mitochondria) 存在於大多數真核細胞內，是細胞生命能量ATP的製造來源，為細胞的新陳代謝提供充足能量，所以線粒體在科學界也有細胞“動力工廠”之稱。人體衰老與線粒體關係密不可分。氧自由基 [reactive oxygen species (ROS)] 讓線粒體受損並無法得到修複，最終導致細胞因能量下降而趨向衰亡，使人體細胞老化速度不斷加劇。

另外一項老化的機製，與細胞核 (nucleus) 內承載遺傳基因的染色體終端 (telomere) 消耗有關。染色體的終端隨著細胞分裂的次數不斷減短，減短到一定程度時，細胞便停止分裂。所以染色體終端的長度，可能就是生命的定時器，它告訴細胞什麽時候該停止分裂了。

線粒體老化機製和細胞核老化機製之間的關係是怎樣的呢？在最近一期的《自然》雜誌中有新的研究進展。



With age, telomere damage in the nucleus triggers the activation of p53, which can have different effects. In proliferative cells, p53 halts both cell growth and DNA replication, potentially causing apoptotic cell death. Sahin et al.report that p53 also represses the expression of PGC-1 in mitochondria, reducing the function and number of these organelles, and so leading to age-related dysfunction of mitochondrion-rich, quiescent tissues. The mitochondrial derangements driven by loss of PGC-1 activity may independently lower the threshold for the generation of toxic intermediates such as reactive oxygen species (ROS), which damage mitochondrial DNA, thus setting up a vicious cycle of further mitochondrial dysfunction.


-  Daniel P. Kelly1. Cell biology: Ageing theories unified. Nature Year published: (2011)Published online 09 February 2011
 
http://www.nature.com/nature/journal/vaop/ncurrent/full/nature09896.html?WT.ec_id=NATURE-20110210