Kiens B
Copenhagen Muscle Research Centre, August Krogh Institute, University of Copenhagen, Denmark.
Med Sci Sports Exerc. 1997 May;29(5):640-5. doi: 10.1097/00005768-199705000-00009.
Older studies of humans seem to suggest a correlation between free fatty acid (FFA) turnover and oxidation on the one hand and plasma FFA concentration on the other hand during submaximal exercise. However, recent studies, in which higher concentrations of plasma FFA have been reached during prolonged submaximal exercise, have revealed a levelling off in net uptake in spite of increasing plasma FFA concentrations. Furthermore, this relationship between FFA concentration and FFA uptake and oxidation is altered by endurance training. These recent findings in humans support the notion from other cell types that transmembrane fatty acid transport is not only by simple diffusion, but predominantly carrier-mediated. During prolonged submaximal knee-extension exercise it has been demonstrated that the total oxidation of fatty acids was approximately 60% higher in trained subjects than in nontrained subjects. The training-induced adaptations responsible for this increased utilization of plasma fatty acids by the muscle could be located at several steps from the mobilization of fatty acids to skeletal muscle metabolism in the mitochondria. In this paper regulation at the transport steps and also at various metabolic steps is discussed.
早期对人类的研究似乎表明，在次最大运动期间，一方面游离脂肪酸（FFA）周转与氧化之间存在关联，另一方面与血浆FFA浓度也存在关联。然而，近期的研究发现，在长时间的次最大运动中，尽管血浆FFA浓度不断升高，但净摄取量却趋于平稳。此外，耐力训练会改变FFA浓度与FFA摄取及氧化之间的这种关系。人类的这些最新发现支持了来自其他细胞类型的观点，即跨膜脂肪酸转运不仅通过简单扩散，而且主要是载体介导的。在长时间的次最大伸膝运动中，已证明训练有素的受试者脂肪酸的总氧化量比未训练的受试者高出约60%。训练引起的适应性变化导致肌肉对血浆脂肪酸的利用率提高，这一过程可能发生在从脂肪酸动员到线粒体中骨骼肌代谢的多个步骤中。本文将讨论转运步骤以及各种代谢步骤的调节。
