Skeletal muscle wasting drives negative clinical outcomes and is associated with a spectrum of pathologies including cancer. Cancer cachexia is a multi-factorial syndrome that encompasses skeletal muscle wasting and remains understudied, despite being a frequent and serious co-morbidity. Deviation from the homeostatic balance between breakdown and regeneration leads to muscle wasting disorders, such as cancer cachexia. Muscle stem cells (MuSCs) are the cellular compartment responsible for muscle regeneration, which makes MuSCs an intriguing target in the context of wasting muscle. Molecular studies investigating MuSCs and skeletal muscle wasting largely focus on transcriptional changes, but our group and others propose that metabolic changes are another layer of cellular regulation underlying MuSC dysfunction in cancer cachexia. In the present study, we combined gene expression and non-targeted metabolomic profiling of myoblasts exposed to wasting conditions (cancer cell conditioned media, CC-CM) to derive a more complete picture of the myoblast response to wasting factors. After mapping these features to annotated pathways, we found that more than half of the mapped pathways were amino acid-related, linking global amino acid metabolic disruption to conditioned media-induced myoblast defects. Notably, arginine metabolism was a highly enriched pathway in combined metabolomic and transcriptomic data. Arginine catabolism generates nitric oxide (NO), an important signaling molecule known to have negative effects on mature muscle. We hypothesize that tumor-derived disruptions in Nitric Oxide Synthase (NOS)2-regulated arginine catabolism impair differentiation of MuSCs. The work presented here further investigates the effect of NOS2 overactivity on myoblast proliferation and differentiation. We show that NOS2 inhibition is sufficient to rescue wasting phenotypes associated with inflammatory cytokines. Ultimately, this work provides new insights into MuSC biology and opens up potential therapeutic avenues for addressing disrupted MuSC dynamics in cancer cachexia.

骨骼肌萎缩会导致负面的临床结果，并与包括癌症在内的一系列病症相关。癌症恶病质是一种多因素综合症，包括骨骼肌萎缩，尽管是一种常见且严重的合并症，但仍未得到充分研究。偏离分解和再生之间的稳态平衡会导致肌肉萎缩症，例如癌症恶病质。肌肉干细胞 (MuSCs) 是负责肌肉再生的细胞区室，这使得 MuSCs 成为肌肉萎缩的一个有趣目标。研究 MuSC 和骨骼肌萎缩的分子研究主要集中在转录变化上，但我们小组和其他人提出，代谢变化是癌症恶病质中 MuSC 功能障碍的另一层细胞调节。在本研究中，我们将暴露于消耗条件（癌细胞条件培养基，CC-CM）的成肌细胞的基因表达和非靶向代谢组学分析相结合，以更全面地了解成肌细胞对消耗因素的反应。将这些特征映射到注释通路后，我们发现超过一半的映射通路与氨基酸相关，将全球氨基酸代谢破坏与条件培养基诱导的成肌细胞缺陷联系起来。值得注意的是，精氨酸代谢是组合代谢组学和转录组学数据中高度富集的途径。精氨酸分解代谢产生一氧化氮 (NO)，这是一种重要的信号分子，已知对成熟肌肉有负面影响。我们假设肿瘤衍生的一氧化氮合酶 (NOS)2 调节精氨酸分解代谢的破坏会损害 MuSC 的分化。这里介绍的工作进一步研究了 NOS2 过度活跃对成肌细胞增殖和分化的影响。我们表明 NOS2 抑制足以挽救与炎性细胞因子相关的消瘦表型。最终，这项工作为 MuSC 生物学提供了新的见解，并开辟了潜在的治疗途径，以解决癌症恶病质中 MuSC 动力学紊乱的问题。