The role of skeletal muscle glycogen breakdown for regulation of insulin sensitivity by exercise.
The role of skeletal muscle glycogen breakdown for regulation of insulin sensitivity by exercise.
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DOI：
10.3389/fphys.2011.00112
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发表时间：
2011
影响因子：
4
通讯作者：
Lai YC
中科院分区：
文献类型：
--
作者：
Jensen J;Rustad PI;Kolnes AJ;Lai YC
糖原是哺乳动物体内碳水化合物的储存形式。在人类中，大部分糖原储存在骨骼肌（约500克）和肝脏（约100克）中。食物是在大餐中提供的，但血糖浓度必须保持在狭窄的范围内才能生存和保持健康。因此，身体必须应对碳水化合物过量的时期和没有补充的时期。当葡萄糖过量时，健康人迅速清除血糖，但胰岛素抵抗和2型糖尿病患者胰岛素刺激的葡萄糖处置减少。在高胰岛素正糖钳夹期间，健康受试者的70-90%的葡萄糖处置将作为肌糖原储存。骨骼肌中的糖原储存是有限的，因为有效的反馈介导的糖原合成酶抑制可以防止积累。当糖原储存被填满时，从头脂质合成有助于葡萄糖的处理。运动生理学家通常认为糖原的主要功能是能量底物。当运动强度超过最大摄氧量的70%（）时，糖原是主要的能量基质，当活跃肌肉中的糖原储存耗尽时，就会产生疲劳。运动后，糖原合成速度加快，以补充糖原储备，血糖是底物。事实上，胰岛素刺激的葡萄糖摄取和糖原合成在运动后会升高，从进化的角度来看，这有利于糖原的补充和为新的“战斗或逃跑”事件做准备。在现代社会中，运动后骨骼肌中储存的糖原减少，使碳水化合物被储存为肌糖原，防止葡萄糖被输送到脂质合成的通道中，长此以往，就会引起异位脂肪积累和胰岛素抵抗。运动后骨骼肌糖原的减少有助于饭后碳水化合物的健康储存，防止2型糖尿病的发生。
Glycogen is the storage form of carbohydrates in mammals. In humans the majority of glycogen is stored in skeletal muscles (∼500 g) and the liver (∼100 g). Food is supplied in larger meals, but the blood glucose concentration has to be kept within narrow limits to survive and stay healthy. Therefore, the body has to cope with periods of excess carbohydrates and periods without supplementation. Healthy persons remove blood glucose rapidly when glucose is in excess, but insulin-stimulated glucose disposal is reduced in insulin resistant and type 2 diabetic subjects. During a hyperinsulinemic euglycemic clamp, 70–90% of glucose disposal will be stored as muscle glycogen in healthy subjects. The glycogen stores in skeletal muscles are limited because an efficient feedback-mediated inhibition of glycogen synthase prevents accumulation. De novo lipid synthesis can contribute to glucose disposal when glycogen stores are filled. Exercise physiologists normally consider glycogen’s main function as energy substrate. Glycogen is the main energy substrate during exercise intensity above 70% of maximal oxygen uptake () and fatigue develops when the glycogen stores are depleted in the active muscles. After exercise, the rate of glycogen synthesis is increased to replete glycogen stores, and blood glucose is the substrate. Indeed insulin-stimulated glucose uptake and glycogen synthesis is elevated after exercise, which, from an evolutional point of view, will favor glycogen repletion and preparation for new “fight or flight” events. In the modern society, the reduced glycogen stores in skeletal muscles after exercise allows carbohydrates to be stored as muscle glycogen and prevents that glucose is channeled to de novo lipid synthesis, which over time will causes ectopic fat accumulation and insulin resistance. The reduction of skeletal muscle glycogen after exercise allows a healthy storage of carbohydrates after meals and prevents development of type 2 diabetes.