Data from: Individuals with higher metabolic rates have lower levels of reactive oxygen species hydrogen peroxide in vivo

There is increasing interest in the effect of energy metabolism on oxidative stress, but much ambiguity over the relationship between the rate of oxygen consumption and the generation of reactive oxygen species (ROS). Production of ROS (such as hydrogen peroxide, H2O2) in the mitochondria is primarily inferred indirectly from measurements in vitro, which may not reflect actual ROS production in living animals. Here, we measured in vivo H2O2 content using the recently developed MitoB probe that becomes concentrated in the mitochondria of living organisms, where it is converted by H2O2 into an alternative form termed MitoP; the ratio of MitoP/MitoB indicates the level of mitochondrial H2O2 in vivo. Using the brown trout Salmo trutta, we tested whether this measurement of in vivo H2O2 content over a 24 h-period was related to interindividual variation in standard metabolic rate (SMR). We showed that the H2O2 content varied up to 26-fold among fish of the same age and under identical environmental conditions and nutritional states. Interindividual variation in H2O2 content was unrelated to mitochondrial density but was significantly associated with SMR: fish with a higher mass-independent SMR had a lower level of H2O2. The mechanism underlying this observed relationship between SMR and in vivo H2O2 content requires further investigation, but may implicate mitochondrial uncoupling which can simultaneously increase SMR but reduce ROS production. To our knowledge, this is the first study in living organisms to show that individuals with higher oxygen consumption rates can actually have lower levels of H2O2.

当前，能量代谢对氧化应激的影响愈发受到学界关注，但耗氧速率与活性氧（reactive oxygen species, ROS）生成之间的关联仍存在诸多未明确之处。线粒体中活性氧（如过氧化氢，H₂O₂）的生成量，目前主要通过体外（in vitro）实验进行间接推断，此类结果或无法反映活体动物体内真实的ROS生成情况。本研究借助新近开发的MitoB探针，对体内（in vivo）的H₂O₂含量进行检测：该探针可在活生物体的线粒体中富集，并被H₂O₂转化为名为MitoP的异构体；通过计算MitoP与MitoB的比值，即可反映活体线粒体中H₂O₂的水平。本研究以褐鳟（Salmo trutta）为实验对象，探究了24小时周期内的体内H₂O₂含量与标准代谢率（standard metabolic rate, SMR）的个体间差异是否存在关联。实验结果显示，在年龄一致、环境条件与营养状态均相同的个体间，H₂O₂含量的差异最高可达26倍。H₂O₂含量的个体差异与线粒体密度无显著关联，但与SMR存在明显相关性：经体重校正的SMR越高的个体，其H₂O₂水平越低。上述SMR与体内H₂O₂含量之间的关联机制仍需进一步探究，但其可能涉及线粒体解偶联作用——该作用可同时提升SMR并减少ROS的生成。据我们所知，本研究是首个在活体生物中证实“耗氧速率更高的个体，其H₂O₂水平反而更低”的相关研究。