Gomez Jose, Caro Pilar, Sanchez Ines, Naudi Alba, Jove Mariona, Portero-Otin Manuel, Lopez-Torres Monica, Pamplona Reinald, Barja Gustavo
Department of Animal Physiology II, Faculty of Biological Sciences, Complutense University, Madrid, Spain.
J Bioenerg Biomembr. 2009 Jun;41(3):309-21. doi: 10.1007/s10863-009-9229-3. Epub 2009 Jul 25.
Methionine restriction without energy restriction increases, like caloric restriction, maximum longevity in rodents. Previous studies have shown that methionine restriction strongly decreases mitochondrial reactive oxygen species (ROS) production and oxidative damage to mitochondrial DNA, lowers membrane unsaturation, and decreases five different markers of protein oxidation in rat heart and liver mitochondria. It is unknown whether methionine supplementation in the diet can induce opposite changes, which is also interesting because excessive dietary methionine is hepatotoxic and induces cardiovascular alterations. Because the detailed mechanisms of methionine-related hepatotoxicity and cardiovascular toxicity are poorly understood and today many Western human populations consume levels of dietary protein (and thus, methionine) 2-3.3 fold higher than the average adult requirement, in the present experiment we analyze the effect of a methionine supplemented diet on mitochondrial ROS production and oxidative damage in the rat liver and heart mitochondria. In this investigation male Wistar rats were fed either a L-methionine-supplemented (2.5 g/100 g) diet without changing any other dietary components or a control (0.86 g/100 g) diet for 7 weeks. It was found that methionine supplementation increased mitochondrial ROS generation and percent free radical leak in rat liver mitochondria but not in rat heart. In agreement with these data oxidative damage to mitochondrial DNA increased only in rat liver, but no changes were observed in five different markers of protein oxidation in both organs. The content of mitochondrial respiratory chain complexes and AIF (apoptosis inducing factor) did not change after the dietary supplementation while fatty acid unsaturation decreased. Methionine, S-AdenosylMethionine and S-AdenosylHomocysteine concentration increased in both organs in the supplemented group. These results show that methionine supplementation in the diet specifically increases mitochondrial ROS production and mitochondrial DNA oxidative damage in rat liver mitochondria offering a plausible mechanism for its hepatotoxicity.
在不限制能量的情况下限制蛋氨酸摄入，与限制热量摄入一样，可延长啮齿动物的最大寿命。先前的研究表明，限制蛋氨酸摄入能显著降低线粒体活性氧（ROS）的产生以及对线粒体DNA的氧化损伤，降低膜不饱和程度，并减少大鼠心脏和肝脏线粒体中五种不同的蛋白质氧化标记物。目前尚不清楚饮食中补充蛋氨酸是否会引发相反的变化，这一点也很有趣，因为过量的饮食蛋氨酸具有肝毒性并会引发心血管改变。由于与蛋氨酸相关的肝毒性和心血管毒性的详细机制尚不清楚，且如今许多西方人群摄入的膳食蛋白质（进而蛋氨酸）水平比成年人的平均需求量高2至3.3倍，因此在本实验中，我们分析了补充蛋氨酸的饮食对大鼠肝脏和心脏线粒体中ROS产生及氧化损伤的影响。在这项研究中，雄性Wistar大鼠被喂食添加L-蛋氨酸（2.5 g/100 g）的饮食，且不改变任何其他饮食成分，或喂食对照饮食（0.86 g/100 g），持续7周。结果发现，补充蛋氨酸会增加大鼠肝脏线粒体中的ROS生成和自由基泄漏百分比，但对大鼠心脏无此影响。与这些数据一致的是，线粒体DNA的氧化损伤仅在大鼠肝脏中增加，但在两个器官的五种不同蛋白质氧化标记物中均未观察到变化。饮食补充后，线粒体呼吸链复合物和凋亡诱导因子（AIF）的含量没有变化，而脂肪酸不饱和程度降低。补充组两个器官中的蛋氨酸、S-腺苷甲硫氨酸和S-腺苷高半胱氨酸浓度均升高。这些结果表明，饮食中补充蛋氨酸会特异性增加大鼠肝脏线粒体中的ROS产生和线粒体DNA氧化损伤，为其肝毒性提供了一个合理的机制。
