衰老机制及其学说

不同物种,同一个体的不同组织和细胞,它们的衰老速度并不相同。究其原因,遗传与环境都能影响衰老的进程。个体的平均寿命和物种的最高寿限可以从不同侧面反映衰老的进程。目前认为平均寿命主要与环境相关,而物种最高寿限与遗传相关。从两者的关系看,不良环境影响是通过对遗传物质或其产物的作用而影响衰老的进程。从遗传因素看,衰老并非由单一基因或单一作用所决定,而是一连串基因激活和阻抑及其通过各自产物相互作用的结果。DNA（特别是线粒体DNA）并不像原先设想的那样稳定,目前业已证明,包括基因在内的遗传控制体系可受内、外环境,特别是氧自由基等损伤因素的影响,从而加速衰老的进程。

Mechanisms of aging and its theories

The velocity of aging is rather different in various species, and even in various tissues and cells of the same individual. Both genetic and environmental factors affect aging process. It is evident that life expectancy mainly relates to environment, while maximum life-span of a species more depends on its genetic background. Poor environment possibly affects genes or their products and then influences the process of human senescence. As aspect of genetic causes, aging is not totally depends on one gene, but rather on the interaction of networks of activated or repressed genes and their products. DNA(especially, mitochondrial DNA)is not as stable as previously conceived. The stability of genetic substance, including genes, could be affected by stresses from external or internal environment, which are particularly induced by harmful substances, such as reactive oxygen species, leading to accelerate aging process.