Howlett K, Angus D, Proietto J, Hargreaves M
Department of Physiology, The University of Melbourne, Parkville 3052, Australia.
J Appl Physiol (1985). 1998 Apr;84(4):1413-7. doi: 10.1152/jappl.1998.84.4.1413.
This study examined the effect of increased blood glucose availability on glucose kinetics during exercise. Five trained men cycled for 40 min at 77 +/- 1% peak oxygen uptake on two occasions. During the second trial (Glu), glucose was infused at a rate equal to the average hepatic glucose production (HGP) measured during exercise in the control trial (Con). Glucose kinetics were measured by a primed continuous infusion of D-[3-3H]glucose. Plasma glucose increased during exercise in both trials and was significantly higher in Glu. HGP was similar at rest (Con, 11.4 +/- 1.2; Glu, 10.6 +/- 0.6 micromol . kg-1 . min-1). After 40 min of exercise, HGP reached a peak of 40.2 +/- 5.5 micromol . kg-1 . min-1 in Con; however, in Glu, there was complete inhibition of the increase in HGP during exercise that never rose above the preexercise level. The rate of glucose disappearance was greater (P < 0.05) during the last 15 min of exercise in Glu. These results indicate that an increase in glucose availability inhibits the rise in HGP during exercise, suggesting that metabolic feedback signals can override feed-forward activation of HGP during strenuous exercise.
本研究考察了运动期间血糖可利用性增加对葡萄糖动力学的影响。五名受过训练的男性在两种情况下以峰值摄氧量的77±1%进行了40分钟的骑行。在第二次试验（Glu）期间，以等于在对照试验（Con）中运动期间测得的平均肝葡萄糖生成（HGP）的速率输注葡萄糖。通过对D-[3-3H]葡萄糖进行单次静脉注射后持续输注来测量葡萄糖动力学。在两次试验中，运动期间血浆葡萄糖均升高，且在Glu试验中显著更高。静息时HGP相似（Con组，11.4±1.2；Glu组，10.6±0.6微摩尔·千克-1·分钟-1）。运动40分钟后，Con组的HGP达到峰值40.2±5.5微摩尔·千克-1·分钟-1；然而，在Glu组中，运动期间HGP的增加完全受到抑制，从未超过运动前水平。在Glu试验中，运动最后15分钟期间葡萄糖消失速率更高（P<0.05）。这些结果表明，葡萄糖可利用性的增加会抑制运动期间HGP的升高，这表明在剧烈运动期间，代谢反馈信号可以超越HGP的前馈激活。
