Mélanie Boël, Caroline Romestaing, Claude Duchamp, Frédéric Veyrunes, Sabrina Renaud, Damien Roussel, Yann Voituron
Laboratoire d'Ecologie des Hydrosystèmes Naturels et Anthropisés (UMR CNRS 5023), Université Claude Bernard Lyon1, Université de Lyon; Bd du 11 novembre 1918, Bât. Darwin C; 69622 Villeurbanne Cedex, France.
Institut des Sciences de l'Evolution de Montpellier (UMR CNRS 5554), Université Montpellier, IRD, EPHE; 34095 Montpellier, France.
J Exp Biol. 2020 Jan 1. doi: 10.1242/jeb.215558.
Mass-specific metabolic rate negatively co-varies with body mass from the whole-animal to the mitochondrial levels. Mitochondria are the mainly consumers of oxygen inspired by mammals to generate ATP or compensate energetic losses dissipated as the form of heat (proton leak) during oxidative phosphorylation. Consequently, ATP synthesis and proton leak thus compete for the same electrochemical gradient. Because proton leak co-varies negatively with body mass, it is unknown if extremely small mammals further decouple their mitochondria to maintain their body temperature or if they implement metabolic innovations to ensure cellular homeostasis. The present study investigates the impact of body mass variation on cellular and mitochondrial functioning in small mammals, comparing the two extremely small African pygmy mice (Mus mattheyi, approx. 5 g and Mus minutoides, approx. 7 g) with the larger house mouse (Mus musculus, approx. 22 g). Oxygen consumption rates were measured from the animal to the mitochondrial levels. We also measured mitochondrial ATP synthesis in order to appreciate the mitochondrial efficiency (ATP/O). At the whole-animal scale, mass- and surface-specific metabolic rates co-varied negatively with body mass, whereas this was not necessarily the case at cellular and mitochondrial levels. M. mattheyi had generally the lowest cellular and mitochondrial fluxes, depending on the tissue considered (liver or skeletal muscle), as well as having higher efficient muscle mitochondria than the other two species. M. mattheyi presents metabolic innovations to ensure its homeostasis, by generating more ATP per oxygen consumed.
从整体动物到线粒体水平，单位质量代谢率与体重呈负相关。线粒体是哺乳动物吸入氧气的主要消耗者，用于生成三磷酸腺苷（ATP）或补偿氧化磷酸化过程中以热量形式（质子泄漏）耗散的能量损失。因此，ATP合成和质子泄漏竞争相同的电化学梯度。由于质子泄漏与体重呈负相关，目前尚不清楚极小的哺乳动物是否会进一步使线粒体解偶联以维持体温，或者它们是否会采用代谢创新来确保细胞内稳态。本研究调查了体重变化对小型哺乳动物细胞和线粒体功能的影响，将两种极小的非洲侏儒小鼠（马修侏鼠，约5克和小侏鼠，约7克）与较大的家鼠（小家鼠，约22克）进行比较。测量了从动物到线粒体水平的耗氧率。我们还测量了线粒体ATP合成，以评估线粒体效率（ATP/O）。在整体动物水平上，单位质量和单位表面积代谢率与体重呈负相关，而在细胞和线粒体水平上不一定如此。根据所考虑的组织（肝脏或骨骼肌），马修侏鼠通常具有最低的细胞和线粒体通量，并且其肌肉线粒体效率高于其他两个物种。马修侏鼠通过每消耗一分子氧气产生更多的ATP，呈现出代谢创新以确保其体内稳态。
