Ikeda Miu, Matsumoto Moe, Tamura Miki, Kobayashi Masaki, Iida Kaoruko
Department of Food and Nutritional Sciences, Graduate School of Humanities and Sciences, Ochanomizu University, Tokyo 1128610, Japan.
Mol Med Rep. 2025 Jul;32(1). doi: 10.3892/mmr.2025.13562. Epub 2025 May 16.
Skeletal muscle atrophy is often triggered by catabolic conditions such as fasting, malnutrition and chronic diseases; however, the efficacy of nutritional supplementation in maintaining muscle mass and preventing muscle atrophy remains controversial. The present study aimed to compare the inhibitory effects of various nutritional substrates on starvation‑induced catabolic changes and muscle cell atrophy. C2C12 muscle cells were starved for up to 24 h in medium lacking serum and main nutrients (glucose, glutamine and pyruvate). To assess the effects of exogenous substrates, the cells were incubated in starvation medium and individually supplemented with each of the following nutrients: Glucose, amino acids, fatty acids, lactate or ketone bodies. The expression of each gene and protein was analyzed by reverse transcription‑quantitative PCR and western blotting, respectively. Mitochondrial activity was determined by MTT assay and cell morphology was observed by immunofluorescence staining. The results revealed that starvation for >3 h suppressed mitochondrial activity, and after 5 h of starvation, the expression levels of several metabolic genes were increased; however, the levels of most, with the exception of Scot and , were suppressed after 24 h. Protein degradation and a decrease in protein synthesis were observed after 5 h of starvation, followed by autophagy with morphological atrophy at 24 h. Supplementation with specific substrates, with the exception of leucine, such as glucose, glutamine, lactic acid or α‑ketoglutarate, attenuated the suppression of mitochondrial activity, and altered gene expression, protein degradation and myotube atrophy in starved myotubes. Furthermore, the decrease in intracellular ATP production after 24 h of starvation was reversed by restoring glycolysis in glucose‑treated cells, and via an increase in mitochondrial respiration in cells treated with glutamine, lactic acid or α‑ketoglutarate. In conclusion, increasing the availability of glucose, glutamine, lactic acid or α‑ketoglutarate may be beneficial for countering muscle atrophy associated with inadequate nutrient intake.
骨骼肌萎缩通常由分解代谢状态引发，如禁食、营养不良和慢性疾病；然而，营养补充在维持肌肉质量和预防肌肉萎缩方面的功效仍存在争议。本研究旨在比较各种营养底物对饥饿诱导的分解代谢变化和肌肉细胞萎缩的抑制作用。将C2C12肌肉细胞在缺乏血清和主要营养物质（葡萄糖、谷氨酰胺和丙酮酸）的培养基中饥饿长达24小时。为了评估外源性底物的作用，将细胞在饥饿培养基中培养，并分别补充以下每种营养物质：葡萄糖、氨基酸、脂肪酸、乳酸或酮体。分别通过逆转录定量PCR和蛋白质印迹法分析每个基因和蛋白质的表达。通过MTT法测定线粒体活性，并通过免疫荧光染色观察细胞形态。结果显示，饥饿超过3小时会抑制线粒体活性，饥饿5小时后，几种代谢基因的表达水平升高；然而，除了Scot和 外，大多数基因的水平在24小时后受到抑制。饥饿5小时后观察到蛋白质降解和蛋白质合成减少，随后在24小时出现自噬并伴有形态学萎缩。补充特定底物，如葡萄糖、谷氨酰胺、乳酸或α-酮戊二酸（亮氨酸除外），可减轻线粒体活性的抑制，并改变饥饿肌管中的基因表达、蛋白质降解和肌管萎缩。此外，在葡萄糖处理的细胞中恢复糖酵解，以及在谷氨酰胺、乳酸或α-酮戊二酸处理的细胞中通过增加线粒体呼吸，可逆转饥饿24小时后细胞内ATP产生的减少。总之，增加葡萄糖、谷氨酰胺、乳酸或α-酮戊二酸的可用性可能有助于对抗与营养摄入不足相关的肌肉萎缩。
