| 摘要: | 在日常生活中骨骼肌容易受到運動產生的機械力傷害而影響日常活動。因此，了解運動損傷後的肌肉修復機制極為重要。在先前的一項研究中，我們以生酮飲食作為飲食誘導肥胖小鼠的減重方式，發現生酮飲食顯著改善肥胖小鼠的耐力運動表現，並上調了參與脂質代謝的蛋白質表現。因此，我們假設脂肪酸可以減輕肌肉組織損傷並有助於肌肉修復。
本研究的主要目的是探討脂肪酸對肌肉修復的保護機制。最初，我們使用咖啡因和AMPK激活劑5-Aminoimidazole-4-carboxamide ribonucleotide (AICAR) 在C2C12成肌細胞分化的肌管中建立體外運動誘導的肌肉損傷 (EIMD) 模型。通過測量乳酸脫氫?滲漏 (LDH leakage) 確認肌肉損傷程度，結果表明咖啡因合適作為EIMD的體外模型。接下來，我們使用定量蛋白質組學分析瞭解咖啡因的影響，結果發現參與脂肪酸代謝的蛋白質以劑量依賴性方式增加，這表明補充脂肪酸可能減緩肌肉細胞受咖啡因影響所造成的損傷。為確認脂肪酸是否對EIMD具保護作用，我們比較不同脂肪酸，結果證實MCFA可預防咖啡因引起的肌肉損傷。為全面了解MCFA對咖啡因誘導EIMD的影響，我們在咖啡因介入下進行了定量蛋白質組學分析，並探討MCFA對低劑量 (0.5 mM) 和高劑量 (5 mM) 咖啡因介入的影響。在低劑量咖啡因組，兩種MCFA都會激活脂質儲存、穀胱甘?結合反應、TCA 循環和呼吸電子傳遞，然而在高劑量咖啡因組中介入MCFA的細胞仍增加了細胞凋亡相關蛋白表現。結果表明，MCFA可以在輕度損傷條件下從EIMD中拯救肌肉細胞，但無法防止嚴重損傷。此外，在低劑量咖啡因組中MCFA的介入增加了GST和SOD蛋白表現，這表明MCFA可能會誘導氧化壓力反應以緩解咖啡因造成的壓力，從而拯救肌肉細胞免受損傷。這些發現表明，MCFA通過線粒體促進能量代謝並緩解氧化壓力，從而有助於其對EIMD的保護作用。這項研究提供了一個體外平台，用於測試預防EIMD的介入方式、對鈣積累引起的肌肉損傷的分子見解，以及MCFA對EIMD的影響。
Skeletal muscle is prone to damage in daily life, particularly due to mechanical stress from exercise, which can impact daily activities. Therefore, understanding the mechanisms underlying muscle repair after exercise-induced damage is crucial. In a previous study, we observed that a ketogenic diet intervention, used for weight loss, significantly improved endurance exercise performance in diet-induced obese mice and upregulated proteins involved in lipid metabolism. Thus, we hypothesized that fatty acids may attenuate muscle tissue damage and aid in repair.
The main objective of this study was to investigate the protective mechanisms of fatty acids on muscle repair. Initially, we established in vitro exercise-induced muscle damage (EIMD) models in differentiated myotubes from C2C12 using caffeine and the AMPK activator 5-Aminoimidazole-4-carboxamide ribonucleoside (AICAR). The extent of muscle damage was confirmed by measuring LDH leakage, and the results indicated that caffeine was a suitable model for EIMD. Next, we examined the effects of caffeine using quantitative proteomics analysis and found that proteins involved in fatty acid metabolism increased in a dose-dependent manner, suggesting that fatty acid intervention might rescue muscle cells from caffeine-induced damage. To determine if fatty acids exert protective effects against EIMD, we compared different fatty acids, and then confirmed that co-treatment with MCFAs prevented caffeine-induced muscle damage. To comprehensively understand the effects of MCFAs on caffeine-induced EIMD, we performed quantitative proteomics analysis under two doses of caffeine treatment. We examined the effects of MCFAs on low-dose (0.5 mM) and high-dose (5 mM) caffeine treatments. Under low-dose caffeine treatment, both MCFAs activated lipid storage, glutathione conjugation, the TCA cycle, and respiratory electron transport. However, under high-dose caffeine treatment, MCFAs elevated the signaling of apoptosis. The results suggested that MCFAs can rescue muscle cells from EIMD under mild damage conditions but fail to protect against severe injury. MCFAs increased the protein expression of GST and SODs under low-dose caffeine treatment, suggesting MCFAs might trigger oxidative stress response to relieve the caffeine-caused stress thus rescue muscle cells from injury. These findings suggest that MCFAs promote energy metabolism through mitochondria-dependent processes and relieve oxidative stress, contributing to their protective effects on EIMD. This work provides an in vitro platform for testing interventions to prevent EIMD, molecular insights into calcium accumulation-induced muscle injury, and a systematic understanding of the effects of MCFAs on EIMD. |
