Brass E P, Hiatt W R
Department of Medicine, Case Western Reserve University, Cleveland, Ohio 44106-4981.
Life Sci. 1994;54(19):1383-93. doi: 10.1016/0024-3205(94)00593-1.
Carnitine is an important cofactor for normal cellular metabolism. Optimal utilization of fuel substrates for ATP generation by skeletal muscle during exercise is dependent on adequate carnitine stores. During short periods of exercise the skeletal muscle carnitine pool is largely segregated from extracellular carnitine. In normal human subjects, only minimal changes in the muscle carnitine pool are observed during exercise at work loads below the lactate threshold. In contrast, at work-loads above the lactate threshold the muscle total carnitine is redistributed from carnitine to acetylcarnitine, with the acetylcarnitine content correlated with the muscle acetyl-CoA and lactate contents. In contrast, in patients with peripheral arterial disease, an accumulation of acylcarnitines is observed at all work loads. Patients with chronic renal failure who are on hemodialysis demonstrate a poor exercise capability which is correlated with a decrease in muscle carnitine content. Carnitine supplementation has been shown to improve exercise tolerance in both peripheral arterial disease and hemodialysis patients. Further work is needed to define the mechanism by which exogenous carnitine improves exercise performance in order to better define potential patient populations for therapy and to facilitate optimal dosing regimens.
肉碱是正常细胞代谢的重要辅助因子。运动期间骨骼肌通过利用燃料底物生成三磷酸腺苷（ATP）的最佳效率取决于充足的肉碱储备。在短时间运动期间，骨骼肌中的肉碱池在很大程度上与细胞外肉碱分隔开来。在正常人体中，在低于乳酸阈值的工作负荷下运动时，肌肉肉碱池仅有微小变化。相反，在高于乳酸阈值的工作负荷下，肌肉总肉碱会从肉碱重新分布为乙酰肉碱，乙酰肉碱含量与肌肉乙酰辅酶A和乳酸含量相关。相比之下，外周动脉疾病患者在所有工作负荷下均观察到酰基肉碱的积累。接受血液透析的慢性肾衰竭患者表现出较差的运动能力，这与肌肉肉碱含量降低有关。已证明补充肉碱可改善外周动脉疾病患者和血液透析患者的运动耐力。需要进一步开展研究以确定外源性肉碱改善运动表现的机制，从而更好地确定潜在的治疗患者群体并制定最佳给药方案。
