Vukovich M D, Costill D L, Fink W J
Human Performance Laboratory, Ball State University, Muncie, IN 47306.
Med Sci Sports Exerc. 1994 Sep;26(9):1122-9.
This study investigated the effects of L-carnitine supplementation on muscle carnitine and glycogen content during submaximal exercise (EX). Triglycerides were evaluated by a fat feeding (90 g fat) and 3 h later subjects cycled for 60 min at 70% VO2max (CON). Muscle biopsies were obtained preexercise and after 30 and 60 min of EX. Blood samples were taken prior to and every 15 min of exercise. Subjects randomly completed two additional trials following 7 and 14 d of carnitine supplementation (6 g.d-1). During one of the two trials, subjects received 2000 units of heparin 15 min prior to EX to elevate FFA (CNhep); no heparin was administered during the other trial (CN). There were no differences in VO2, respiratory exchange ratio, heart rate, or g.min-1 of CHO and fat oxidized among the three trials. At rest serum total acid soluble (TASC) and free (FC) carnitine increased with supplementation (TASC; CON, 71.3 +/- 2.9; CN, 92.8 +/- 5.4; CNhep, 109.8 +/- 3.5 mumol.l-1) (FC; CON, 44.1 +/- 2.7; CN, 66.1 +/- 5.3; CNhep, 77.1 +/- 4.1 mumol.l-1). During EX, TASC remained stable, while FC decreased and short-chain acylcarnitine (SCAC) increased (P < 0.05). Muscle carnitine concentration at rest was unaffected by supplementation. During EX, muscle TASC did not change, FC decreased, and SCAC increased significantly in all three trials. Pre-EX and post-EX muscle glycogens were not different. Increased availability of serum carnitine does not result in an increase in muscle carnitine content nor does it alter lipid oxidation. It appears that there is an adequate amount of carnitine present within the mitochondria to support lipid oxidation.
本研究调查了补充左旋肉碱对次最大强度运动（EX）期间肌肉肉碱和糖原含量的影响。通过喂食脂肪（90克脂肪）评估甘油三酯，3小时后受试者以70%最大摄氧量（CON）进行60分钟的骑行。在运动前以及运动30分钟和60分钟后采集肌肉活检样本。在运动前和运动期间每隔15分钟采集血样。在补充肉碱（6克·天-1）7天和14天后，受试者随机完成另外两项试验。在两项试验中的一项中，受试者在运动前15分钟接受2000单位肝素以提高游离脂肪酸（CNhep）；在另一项试验中未给予肝素（CN）。三项试验之间在摄氧量、呼吸交换率、心率或碳水化合物和脂肪氧化的克·分钟-1方面没有差异。休息时，血清总酸溶性（TASC）和游离（FC）肉碱随着补充而增加（TASC；CON，71.3±2.9；CN，92.8±5.4；CNhep，109.8±3.5微摩尔·升-1）（FC；CON，44.1±2.7；CN，66.1±5.3；CNhep，77.1±4.1微摩尔·升-1）。在运动期间，TASC保持稳定，而FC下降，短链酰基肉碱（SCAC）增加（P<0.05）。休息时肌肉肉碱浓度不受补充的影响。在运动期间，所有三项试验中肌肉TASC没有变化，FC下降，SCAC显著增加。运动前和运动后肌肉糖原没有差异。血清肉碱可用性的增加不会导致肌肉肉碱含量增加，也不会改变脂质氧化。似乎线粒体中存在足够量的肉碱来支持脂质氧化。
