Dyck D J, Peters S J, Wendling P S, Chesley A, Hultman E, Spriet L L
School of Human Biology, University of Guelph, Ontario, Canada.
Am J Physiol. 1996 Jan;270(1 Pt 1):E116-25. doi: 10.1152/ajpendo.1996.270.1.E116.
This study examined muscle glycogenolysis and the regulation of glycogen phosphorylase (Phos) activity during 15 min of cycling at 85% of maximal O2 consumption (VO2max) in control and high free fatty acid (FFA; Intralipid-heparin) conditions in 11 subjects. Muscle biopsies were sampled at rest and 1, 5, and 15 min of exercise, and glycogen Phos transformation state (%Phos alpha), substrate (Pi, glycogen), and allosteric regulator (ADP, AMP, IMP) contents were measured. Infusion of intralipid elevated plasma FFA from 0.32 +/- 0.04 mM at rest to 1.00 +/- 0.04 mM just before exercise and 1.12 +/- 0.10 mM at 14 min of exercise. In the control trial, plasma FFA were 0.36 +/- 0.04 mM at rest and unchanged at the end of exercise (0.34 +/- 0.03 mM). Seven subjects used less muscle glycogen (46.7 +/- 7.6%, mean +/- SE) during the Intralipid trial, and four did not respond. In subjects who spared glycogen, glycogen Phos transformation into the active (alpha) form was unaffected by high FFA except for a nonsignificant reduction during the initial 5 min of exercise. Total AMP and IMP contents were not significantly different during exercise between trials, but total ADP was significantly lower with Intralipid only at 15 min. The calculated free ADP, AMP, and Pi contents were lower with Intralipid but not significantly different. However, when the present results were pooled with the data from a previous study using the same protocol [Dyck et al., Am. J. Physiol. 265 (Endocrinol, Metab. 28): E852-E859, 1993], the free ADP, AMP, and Pi contents of all subjects who spared glycogen (n = 13) were significantly lower at 15 min in the Intralipid trial. The findings suggest that the elevation of plasma FFA during intense cycling spares muscle glycogen by posttransformational regulation of Phos. This may be due to blunted increases in the contents of AMP, an allosteric activator of Phos alpha, and Pi, a substrate for Phos.
本研究在11名受试者处于对照和高游离脂肪酸（FFA；脂质乳剂-肝素）状态下，于最大摄氧量（VO2max）的85%强度进行15分钟骑行期间，检测了肌肉糖原分解及糖原磷酸化酶（Phos）活性的调节情况。在静息状态以及运动1、5和15分钟时采集肌肉活检样本，测量糖原Phos转化状态（%Phosα）、底物（无机磷酸、糖原）和变构调节物（ADP、AMP、肌苷酸）的含量。输注脂质乳剂使静息时血浆FFA从0.32±0.04 mM升高至运动前的1.00±0.04 mM以及运动14分钟时的1.12±0.10 mM。在对照试验中，静息时血浆FFA为0.36±0.04 mM，运动结束时无变化（0.34±0.03 mM）。7名受试者在脂质乳剂试验期间肌肉糖原消耗较少（46.7±7.6%，平均值±标准误），4名受试者无此反应。在节省糖原的受试者中，除运动最初5分钟有不显著的降低外，糖原Phos向活性（α）形式的转化不受高FFA影响。试验期间运动过程中总AMP和肌苷酸含量无显著差异，但脂质乳剂组仅在15分钟时总ADP显著降低。计算得出的游离ADP、AMP和无机磷酸含量脂质乳剂组较低，但无显著差异。然而，当将本研究结果与之前采用相同方案的一项研究[戴克等人，《美国生理学杂志》265（内分泌学、代谢28）：E852 - E859，1993]的数据合并时，脂质乳剂试验中所有节省糖原的受试者（n = 13）在15分钟时的游离ADP、AMP和无机磷酸含量均显著降低。这些发现表明，在剧烈骑行过程中血浆FFA升高通过对Phos的转化后调节节省了肌肉糖原。这可能是由于Phosα的变构激活剂AMP以及Phos的底物无机磷酸含量的增加受到抑制。
