The size and morphology of mitochondria are very heterogeneous and correlates well with their healthy functioning. In many pathological conditions, mitochondrial morphology is altered due to impaired mitochondrial dynamics (a collective term for mitochondrial fusion and fission) and dysfunction. The current study aimed at identifying the role of microRNA-128 (miR-128) in regulating mitochondrial biogenesis. Previously, peroxisome proliferator activator receptor γ coactivator 1α (PGC1α) has been shown to co-activate key intermediates of mitochondrial biogenesis, function, and dynamics; however, the upstream regulatory network remains largely unknown. We, herein using in silico analysis followed by in vitro experiments in C2C12 myoblasts, showed that miR-128 reduces mitochondrial biogenesis by directly targeting PGC1α. The expression of downstream genes, nuclear respiratory factors 1 and 2 (NRF1 and NRF2, respectively), and mitochondrial transcription factor A (TFAM) were decreased in C2C12 myoblasts upon overexpression of miR-128. Also, miR-128 is shown to promote mitochondrial dysfunction by directly targeting NADH Dehydrogenase (Ubiquinone) Fe-S Protein 4 (NDUFS4). The mitochondrial dynamics and morphology were impaired post miR-128 overexpression, as revealed by downregulation of fusion proteins (mitofusin1 and 2, i.e., MFN1 and MFN2, respectively) and upregulation of fission protein (dynamin-related protein 1, i.e., DRP1). Conversely, inhibition of miR-128 expression improved mitochondrial biogenesis, function, and dynamics, as evidenced by increased mitochondrial mass and ATP production after antimiR-128 treatment. Our findings reveal that inhibition of miR-128 can be a new potential target for reversing the effects of metabolic disorders of skeletal muscle as observed during many pathophysiological conditions such as obesity and type II diabetes.

线粒体的大小和形态非常不同，并且与它们的健康功能密切相关。在许多病理情况下，由于线粒体动力学受损（线粒体融合和裂变的统称）和功能障碍，线粒体形态发生改变。目前的研究旨在确定 microRNA-128 (miR-128) 在调节线粒体生物发生中的作用。以前，过氧化物酶体增殖物激活剂受体 γ 共激活剂 1α (PGC1α) 已被证明可共同激活线粒体生物发生、功能和动力学的关键中间体。然而，上游监管网络在很大程度上仍然未知。我们在此使用计算机分析，然后在 C2C12 成肌细胞中进行体外实验，表明 miR-128 通过直接靶向 PGC1α 减少线粒体生物发生。在 miR-128 过表达后，C2C12 成肌细胞中下游基因、核呼吸因子 1 和 2（分别为 NRF1 和 NRF2）和线粒体转录因子 A (TFAM) 的表达降低。此外，显示 miR-128 通过直接靶向 NADH 脱氢酶（泛醌）Fe-S 蛋白 4 (NDUFS4) 促进线粒体功能障碍。线粒体动力学和形态在 miR-128 过表达后受损，如融合蛋白（mitofusin1 和 2，即分别为 MFN1 和 MFN2）的下调和裂变蛋白（dynamin-related protein 1，即 DRP1）的上调所示。相反，抑制 miR-128 表达改善了线粒体的生物发生、功能和动力学，抗 miR-128 治疗后线粒体质量和 ATP 产生增加就证明了这一点。