Hargreaves M, Angus D, Howlett K, Conus N M, Febbraio M
Department of Physiology, University of Melbourne, Parkville, Australia.
J Appl Physiol (1985). 1996 Oct;81(4):1594-7. doi: 10.1152/jappl.1996.81.4.1594.
To identify the mechanism underlying the exaggerated hyperglycemia during exercise in the heat, six trained men were studied during 40 min of cycling exercise at a workload requiring 65% peak pulmonary oxygen uptake (VO2peak) on two occasions at least 1 wk apart. On one occasion, the ambient temperature was 20 degrees C [control (Con)], whereas on the other, it was 40 degrees C [high temperature (HT)]. Rates of glucose appearance and disappearance were measured by using a primed continuous infusion of [6,6-2H]glucose No differences in oxygen uptake during exercise were observed between trials. After 40 min of exercise, heart rate, rectal temperature, respiratory exchange ratio, and plasma lactate were all higher in HT compared with Con (P < 0.05). Plasma glucose levels were similar at rest (Con, 4.54 +/- 0.19 mmol/l; HT, 4.81 +/- 0.19 mmol/l) but increased to a greater extent during exercise in HT (6.96 +/- 0.16) compared with Con (5.45 +/- 0.18; P < 0.05). This was the result of a higher glucose rate of appearance in HT during the last 30 min of exercise. In contrast, the glucose rate of disappearance and metabolic clearance rate were not different at any time point during exercise. Plasma catecholamines were higher after 10 and 40 min of exercise in HT compared with Con (P < 0.05), whereas plasma glucagon, cortisol, and growth hormone were higher in HT after 40 min. These results indicate that the hyperglycemia observed during exercise in the heat is caused by an increase in liver glucose output without any change in whole body utilization.
为了确定在热环境中运动期间高血糖症加剧的潜在机制，对6名经过训练的男性进行了研究，他们在至少相隔1周的两个时间段进行了40分钟的骑自行车运动，运动强度为峰值肺摄氧量（VO2peak）的65%。一次，环境温度为20摄氏度[对照（Con）]，而另一次，环境温度为40摄氏度[高温（HT）]。通过使用[6,6-2H]葡萄糖的首剂量连续输注来测量葡萄糖的出现率和消失率。两次试验之间运动期间的摄氧量没有差异。运动40分钟后，与对照相比，高温组的心率、直肠温度、呼吸交换率和血浆乳酸均更高（P<0.05）。静息时血浆葡萄糖水平相似（对照，4.54±0.19 mmol/l；高温，4.81±0.19 mmol/l），但与对照（5.45±0.18；P<0.05）相比，高温环境下运动期间血浆葡萄糖水平升高幅度更大（6.96±0.16）。这是运动最后30分钟内高温组葡萄糖出现率更高的结果。相比之下，运动期间任何时间点的葡萄糖消失率和代谢清除率均无差异。与对照相比，高温组运动10分钟和40分钟后血浆儿茶酚胺更高（P<0.05），而高温组运动40分钟后血浆胰高血糖素、皮质醇和生长激素更高。这些结果表明，在热环境中运动期间观察到的高血糖症是由肝脏葡萄糖输出增加引起的，而全身利用率没有任何变化。
