The design of the energy metabolism system in striated muscle remains a major area of investigation. Here, we review our current understanding and emerging hypotheses regarding the metabolic support of muscle contraction. Maintenance of ATP free energy, so called energy homeostasis, via mitochondrial oxidative phosphorylation is critical to sustained contractile activity and this major design criterion is the focus of this review. Cell volume invested in mitochondria reduces the space available for generating contractile force, and this spatial balance between mitochondria and contractile elements to meet the varying sustained power demands across muscle types is another important design criterion. This is accomplished with remarkably similar mass-specific mitochondrial protein composition across muscle types, implying that it is the organization of mitochondria within the muscle cell that is critical to supporting sustained muscle function. Beyond the production of ATP, ubiquitous distribution of ATPases throughout the muscle requires rapid distribution of potential energy across these large cells. Distribution of potential energy has long been thought to occur primarily through facilitated metabolite diffusion but recent analysis has questioned the importance of this process under normal physiological conditions. Recent structural and functional studies have supported the hypothesis that the mitochondrial reticulum provides a rapid energy distribution system via the conduction of the mitochondrial membrane potential to maintain metabolic homeostasis during contractile activity. We extensively review this aspect of the energy metabolism design contrasting it with metabolite diffusion models and how mitochondrial structure can play a role in the delivery of energy in the striated muscle.

中文翻译：

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横纹肌细胞的能量代谢设计

横纹肌能量代谢系统的设计仍然是一个主要的研究领域。在这里，我们回顾了目前关于肌肉收缩代谢支持的理解和新的假设。通过线粒体氧化磷酸化维持 ATP 自由能，即所谓的能量稳态，对于持续收缩活动至关重要，这一主要设计标准是本次综述的重点。投入线粒体的细胞体积减少了可用于产生收缩力的空间，而线粒体和收缩元件之间的空间平衡以满足不同肌肉类型不同的持续功率需求是另一个重要的设计标准。这是通过跨肌肉类型的非常相似的质量特异性线粒体蛋白组成来实现的，这意味着肌肉细胞内的线粒体组织对于支持持续的肌肉功能至关重要。除了产生 ATP 之外，ATP 酶在整个肌肉中的普遍分布还需要势能在这些大细胞之间快速分布。长期以来，人们一直认为势能的分布主要是通过促进代谢物扩散而发生的，但最近的分析质疑了这一过程在正常生理条件下的重要性。最近的结构和功能研究支持了这样的假设：线粒体网通过线粒体膜电位的传导提供快速的能量分配系统，以维持收缩活动期间的代谢稳态。我们广泛回顾了能量代谢设计的这一方面，将其与代谢物扩散模型进行对比，以及线粒体结构如何在横纹肌的能量传递中发挥作用。