Leeuwenburgh C, Wagner P, Holloszy J O, Sohal R S, Heinecke J W
Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Arch Biochem Biophys. 1997 Oct 1;346(1):74-80. doi: 10.1006/abbi.1997.0297.
Oxidative damage, particularly to proteins, has been widely postulated to be a major causative factor in the loss of functional capacity during senescence. The nature of the various mechanisms that may contribute to protein oxidation is only partially understood. In this study, concentrations of two markers for oxidative damage, o,o'-dityrosine and o-tyrosine, were determined using stable isotope dilution gas chromatography-mass spectrometry in four tissues of the mouse, namely heart, skeletal muscle, brain, and liver, during youth (4 months old), adulthood (14 months old), and old (30 months old) age. A comparison was made between mice that had access to unlimited calories with those that were restricted to 60% of the caloric intake of the ad libitum regimen. Caloric restriction of this magnitude extends the average and maximum life span of mice by approximately 40%. In vitro studies demonstrated that o,o'-dityrosine was generated selectively in proteins exposed to tyrosyl radical. o-Tyrosine increased in proteins oxidized with hydroxyl radical, which also resulted in a variable increase in o,o'-dityrosine. In mice fed ad libitum, levels of o,o'-dityrosine increased with age in cardiac and skeletal muscle but not in liver or brain. In contrast, o-tyrosine levels did not rise with age in any of the tissues examined. These results suggest that tyrosyl radical-induced protein oxidation increases selectively with age in skeletal muscle and heart. Caloric restriction prevented the increase in o,o'-dityrosine levels in cardiac and skeletal muscle but did not influence o-tyrosine levels in any of the four tissues. This selective increase in o,o'-dityrosine levels and its prevention by a life-prolonging caloric restriction regimen raise the possibility that oxidation of muscle proteins by tyrosyl radical contributes to the deterioration of cardiac and skeletal muscle function with advancing age.
氧化损伤，尤其是对蛋白质的氧化损伤，已被广泛假定为衰老过程中功能能力丧失的主要致病因素。对于可能导致蛋白质氧化的各种机制的本质，目前仅了解一部分。在本研究中，使用稳定同位素稀释气相色谱 - 质谱法测定了小鼠四个组织（即心脏、骨骼肌、脑和肝脏）在青年期（4个月大）、成年期（14个月大）和老年期（30个月大）时氧化损伤的两个标志物——邻，邻'-二酪氨酸和邻酪氨酸的浓度。对可获取无限热量的小鼠与热量摄入限制在自由摄食方案热量摄入60%的小鼠进行了比较。这种程度的热量限制使小鼠的平均寿命和最大寿命延长了约40%。体外研究表明，邻，邻'-二酪氨酸是在暴露于酪氨酰自由基的蛋白质中选择性产生的。在用羟基自由基氧化的蛋白质中，邻酪氨酸增加，这也导致邻，邻'-二酪氨酸有不同程度的增加。在自由摄食的小鼠中，心脏和骨骼肌中邻，邻'-二酪氨酸的水平随年龄增加，而肝脏和脑中则没有。相比之下，在所检查的任何组织中，邻酪氨酸水平均未随年龄升高。这些结果表明，酪氨酰自由基诱导的蛋白质氧化在骨骼肌和心脏中随年龄选择性增加。热量限制阻止了心脏和骨骼肌中邻，邻'-二酪氨酸水平的升高，但不影响四个组织中任何一个组织的邻酪氨酸水平。邻，邻'-二酪氨酸水平的这种选择性增加及其通过延长寿命的热量限制方案得到预防，增加了酪氨酰自由基对肌肉蛋白质的氧化导致心脏和骨骼肌功能随着年龄增长而恶化的可能性。
