Kim Jun Ho, Pan Jeong Hoon, Lee Eui Seop, Kim Young Jun
Department of Food and Biotechnology, Korea University, Sejong, 339-700, Republic of Korea.
Department of Food and Biotechnology, Korea University, Sejong, 339-700, Republic of Korea.
Biochem Biophys Res Commun. 2015 Aug 21;464(2):568-73. doi: 10.1016/j.bbrc.2015.07.009. Epub 2015 Jul 8.
L-Carnitine (LC), the bioactive form of carnitine, has been shown to play a key role in muscle fuel metabolism during exercise, resulting in increased fatty acid oxidation and energy expenditure. However, whether LC contributes to improved endurance exercise performance remains controversial. This study was designed to investigate the effects of LC administration on endurance capacity and energy metabolism in mice during treadmill exercise. Male C57BL/6 mice were divided into two groups (sedentary and exercise) and received daily oral administration of LC (150 mg/kg) or vehicle with a high-fat diet for 3 weeks. During the experimental period, all animals were trained three times a week on a motorized treadmill, and the total running time until exhaustion was used as the index of endurance capacity. LC administration induced a significant increase in maximum running time with a reduction of body fat compared with the control group when mice were subjected to programmed exercise. The serum levels of triglyceride, non-esterified fatty acid, and urea nitrogen were significantly lower in the LC group than the corresponding levels in the control group, while serum ketone body levels were higher in the LC group. Muscle glycogen content of LC administered-mice was higher than that of control mice, concomitant with reduced triglyceride content. Importantly, muscle mRNA and protein expressions revealed enhanced fatty acid uptake and oxidative metabolism and increased mitochondrial biogenesis by LC administration. These results suggest that LC administration promotes fat oxidation and mitochondrial biogenesis while sparing stored glycogen in skeletal muscle during prolonged exercise, resulting in enhanced endurance capacity.
左旋肉碱（LC）是肉碱的生物活性形式，已被证明在运动期间的肌肉燃料代谢中起关键作用，可导致脂肪酸氧化增加和能量消耗增加。然而，LC是否有助于提高耐力运动表现仍存在争议。本研究旨在调查给予LC对小鼠在跑步机运动期间耐力和能量代谢的影响。雄性C57BL/6小鼠分为两组（久坐组和运动组），并每日口服LC（150mg/kg）或载体，同时给予高脂饮食，持续3周。在实验期间，所有动物每周在电动跑步机上训练3次，将直至疲劳的总跑步时间用作耐力的指标。当小鼠进行程序化运动时，与对照组相比，给予LC可显著增加最大跑步时间并减少体脂。LC组的血清甘油三酯、非酯化脂肪酸和尿素氮水平显著低于对照组的相应水平，而LC组的血清酮体水平较高。给予LC的小鼠的肌肉糖原含量高于对照小鼠，同时甘油三酯含量降低。重要的是，肌肉mRNA和蛋白质表达显示，给予LC可增强脂肪酸摄取和氧化代谢，并增加线粒体生物发生。这些结果表明，给予LC可促进脂肪氧化和线粒体生物发生，同时在长时间运动期间节省骨骼肌中储存的糖原，从而提高耐力。
