Rasmussen Ulla F, Krustrup Peter, Kjaer Michael, Rasmussen Hans N
Department of Biochemistry, August Krogh Institute, University of Copenhagen, Universitetsparken 13, Copenhagen, Denmark.
Exp Gerontol. 2003 Aug;38(8):877-86. doi: 10.1016/s0531-5565(03)00092-5.
The mitochondrial theory of aging was tested with optimised preparation techniques. Mitochondria were isolated from approximately 90 mg quadriceps muscle from healthy humans at age 70+ and 20+. The content of mitochondrial protein was approximately 10 mg g(-1) muscle and the yields were approximately 40%. The mitochondrial integrity was high as judged from the respiratory control and P/O ratios. No general membrane alterations or changes in the cytochrome contents were observed. BSA decreased the non-phosphorylating rates of respiration equally in both age groups. Thirteen different enzyme activities were assayed and normalised to protein content and citrate synthase activity. Most of the critical levels for detection of declines were <10%. In the 70+ group, the activity for fatty acid oxidation was decreased by approximately 20%. Two inherently low activities associated with oxidation of sarcoplasmic NADH were also decreased, probably related to the age change of fibre types. The remaining activities measured, e.g. those of pyruvate dehydrogenase, tricarboxylic acid cycle, respiratory chain, and ATP synthesis, were not observed to be lowered. Thus, the central bioenergetic systems appeared unaltered with age. The obvious discord with reported age declines of human skeletal muscle mitochondrial function is discussed. It is concluded that the present results are incompatible with the mitochondrial theory of aging.
采用优化的制备技术对衰老的线粒体理论进行了验证。从70岁及以上和20岁及以上健康人的约90毫克股四头肌中分离出线粒体。线粒体蛋白含量约为10毫克/克肌肉，产率约为40%。从呼吸控制和P/O比值判断，线粒体完整性较高。未观察到一般的膜改变或细胞色素含量的变化。牛血清白蛋白在两个年龄组中均同等程度地降低了非磷酸化呼吸速率。测定了13种不同的酶活性，并将其标准化为蛋白质含量和柠檬酸合酶活性。大多数检测到下降的临界水平<10%。在70岁及以上组中，脂肪酸氧化活性降低了约20%。与肌浆NADH氧化相关的两种固有低活性也降低了，这可能与纤维类型的年龄变化有关。所测量的其余活性，例如丙酮酸脱氢酶、三羧酸循环、呼吸链和ATP合成的活性，未观察到降低。因此，核心生物能量系统似乎不会随年龄而改变。讨论了与报道的人类骨骼肌线粒体功能随年龄下降明显不一致的情况。得出的结论是，目前的结果与衰老的线粒体理论不相符。
