Amyotrophic Lateral Sclerosis (ALS) is a multisystemic neurodegenerative disorder, with accumulating evidence indicating metabolic disruptions in the skeletal muscle preceding disease symptoms, rather than them manifesting as a secondary consequence of motor neuron (MN) degeneration. Hence, energy homeostasis is deeply implicated in the complex physiopathology of ALS and skeletal muscle has emerged as a key therapeutic target. Here, we describe intrinsic abnormalities in ALS skeletal muscle, both in patient-derived muscle cells and in muscle cell lines with genetic knockdown of genes related to familial ALS, such as TARDBP (TDP-43) and FUS. We found a functional impairment of myogenesis that parallels defects of glucose oxidation in ALS muscle cells. We identified FOXO1 transcription factor as a key mediator of these metabolic and functional features in ALS muscle, via gene expression profiling and biochemical surveys in TDP-43 and FUS-silenced muscle progenitors. Strikingly, inhibition of FOXO1 mitigated the impaired myogenesis in both the genetically modified and the primary ALS myoblasts. In addition, specific in vivo conditional knockdown of TDP-43 or FUS orthologs (TBPH or caz) in Drosophila muscle precursor cells resulted in decreased innervation and profound dysfunction of motor nerve terminals and neuromuscular synapses, accompanied by motor abnormalities and reduced lifespan. Remarkably, these phenotypes were partially corrected by foxo inhibition, bolstering the potential pharmacological management of muscle intrinsic abnormalities associated with ALS. The findings demonstrate an intrinsic muscle dysfunction in ALS, which can be modulated by targeting FOXO factors, paving the way for novel therapeutic approaches that focus on the skeletal muscle as complementary target tissue.

肌萎缩侧索硬化症 (ALS) 是一种多系统神经退行性疾病，越来越多的证据表明，疾病症状出现之前骨骼肌代谢紊乱，而不是运动神经元 (MN) 变性的继发后果。因此，能量稳态与 ALS 复杂的病理生理学密切相关，骨骼肌已成为关键的治疗靶点。在这里，我们描述了 ALS 骨骼肌的内在异常，包括患者来源的肌肉细胞和具有家族性 ALS 相关基因（例如TARDBP (TDP-43) 和FUS）基因敲除的肌肉细胞系。我们发现肌生成的功能障碍与 ALS 肌肉细胞中葡萄糖氧化缺陷相似。通过 TDP-43 和 FUS 沉默的肌肉祖细胞的基因表达谱和生化调查，我们确定 FOXO1 转录因子是 ALS 肌肉中这些代谢和功能特征的关键介导者。引人注目的是，FOXO1 的抑制减轻了转基因 ALS 成肌细胞和原代 ALS 成肌细胞中受损的肌生成。此外，果蝇肌肉前体细胞中 TDP-43 或 FUS 直系同源物（ TBPH或caz ）的特定体内条件敲低导致运动神经末梢和神经肌肉突触的神经支配减少和严重功能障碍，并伴有运动异常和寿命缩短。值得注意的是，这些表型通过Foxo抑制得到部分纠正，增强了与 ALS 相关的肌肉内在异常的潜在药物管理。 研究结果表明，ALS 存在内在的肌肉功能障碍，这种功能障碍可以通过针对 FOXO 因子进行调节，从而为专注于将骨骼肌作为补充靶组织的新型治疗方法铺平了道路。