Université de Lyon, Ecologie des Hydrosystèmes Naturels et Anthropisés, Université Lyon 1; Ecole Nationale des Travaux Publics de l'Etat; Centre National de la Recherche Scientifique, Villeurbanne, France.
Am J Physiol Regul Integr Comp Physiol. 2013 Nov 1;305(9):R1065-75. doi: 10.1152/ajpregu.00137.2013. Epub 2013 Sep 4.
The ontogeny of pectoralis muscle bioenergetics was studied in growing Adélie penguin chicks during the first month after hatching and compared with adults using permeabilized fibers and isolated mitochondria. With pyruvate-malate-succinate or palmitoyl-carnitine as substrates, permeabilized fiber respiration markedly increased during chick growth (3-fold) and further rose in adults (1.4-fold). Several markers of muscle fiber oxidative activity (cytochrome oxidase, citrate synthase, hydroxyl-acyl-CoA dehydrogenase) increased 6- to 19-fold with age together with large rises in intermyofibrillar (IMF) and subsarcolemmal (SS) mitochondrial content (3- to 5-fold) and oxidative activities (1.5- to 2.4-fold). The proportion of IMF relative to SS mitochondria increased with chick age but markedly dropped in adults. Differences in oxidative activity between mitochondrial fractions were reduced in adults compared with hatched chicks. Extrapolation of mitochondrial to muscle respirations revealed similar figures with isolated mitochondria and permeabilized fibers with carbohydrate-derived but not with lipid-derived substrates, suggesting diffusion limitations of lipid substrates with permeabilized fibers. Two immunoreactive fusion proteins, mitofusin 2 (Mfn2) and optic atrophy 1 (OPA1), were detected by Western blots on mitochondrial extracts and their relative abundance increased with age. Muscle fiber respiration was positively related with Mfn2 and OPA1 relative abundance. Present data showed by two complementary techniques large ontogenic increases in muscle oxidative activity that may enable birds to face thermal emancipation and growth in childhood and marine life in adulthood. The concomitant rise in mitochondrial fusion protein abundance suggests a role of mitochondrial networks in the skeletal muscle processes of bioenergetics that enable penguins to overcome harsh environmental constraints.
成体企鹅胸肌生物能量发生的个体发育过程。利用通透性纤维和分离的线粒体比较了刚出壳 1 个月的阿德利企鹅幼雏和成体企鹅。利用丙酮酸-苹果酸-琥珀酸或棕榈酰肉碱作为底物，通透性纤维呼吸在幼雏生长过程中显著增加（3 倍），而成体进一步增加（1.4 倍）。随着年龄的增长，几种肌肉纤维氧化活性标志物（细胞色素氧化酶、柠檬酸合酶、羟基酰基辅酶 A 脱氢酶）增加了 6-19 倍，同时肌间纤维（IMF）和肌小节下（SS）线粒体含量（3-5 倍）和氧化活性（1.5-2.4 倍）大幅增加。IMF 相对于 SS 线粒体的比例随幼雏年龄的增长而增加，但在成体中明显下降。与刚出壳的幼雏相比，成年个体线粒体各部分之间的氧化活性差异减小。与分离的线粒体和通透性纤维相比，利用碳水化合物衍生而不是脂质衍生底物， extrapolation 线粒体到肌肉呼吸揭示了类似的数字，表明通透性纤维对脂质底物的扩散限制。Western blot 检测到线粒体提取物中有两种免疫反应性融合蛋白，即线粒体融合蛋白 2（Mfn2）和视神经萎缩蛋白 1（OPA1），它们的相对丰度随年龄增加而增加。肌肉纤维呼吸与 Mfn2 和 OPA1 的相对丰度呈正相关。本研究通过两种互补技术表明，肌肉氧化活性在个体发育过程中发生了显著增加，这可能使鸟类能够在童年时期应对热释放和生长，以及在成年后应对海洋生活。线粒体融合蛋白丰度的同时增加表明线粒体网络在企鹅骨骼肌生物能量学过程中的作用，使企鹅能够克服恶劣的环境限制。
