Activation of glycogen synthase in myocardium induced by intermittent hypoxia is much lower in fasted than in fed rats.
Activation of glycogen synthase in myocardium induced by intermittent hypoxia is much lower in fasted than in fed rats.
复制标题
间歇性缺氧引起的心肌糖原合成酶的激活在禁食大鼠中比在进食大鼠中低得多。
DOI：
10.1152/ajpendo.00486.2006
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发表时间：
2007
期刊：
影响因子：
--
通讯作者：
Liu,Zhenqi
中科院分区：
文献类型：
--
作者：
Wu,Yangsong;Wang,Hong;Brautigan,DavidL;Liu,Zhenqi
Obstructive sleep apnea is characterized by intermittent obstruction of the upper airway, which leads to intermittent hypoxia. Myocardial glycogen is a major energy resource for heart during hypoxia. Previous studies have demonstrated that intermittent hypoxia rapidly degrades myocardial glycogen and activates glycogen synthase (GS). However, the underlying mechanisms remain undefined. Because sleep apnea/intermittent hypoxia usually happens at night, whether intermittent hypoxia leads to GS activation in the postabsorptive state is not known. In the present study, male adult rats were studied after either an overnight fast or ad libitum feeding with or without intermittent ventilatory arrest (3 90-s periods at 10-min intervals). Hearts were quickly excised and freeze-clamped. Intermittent hypoxia induced a significant decrease in myocardial glycogen content in fed rats and stimulated GS in both fasted and fed rats. However, the portion of GS in the active form increased by ∼38% in fasted rats compared with a larger, ∼130% increase in fed rats. The basal G-6-Pcontent was comparable in fasted and fed animals and increased approximately threefold after hypoxia. The basal phosphorylation states of Akt and GSK-3β and the activity of protein phosphatase 1 (PP1) were comparable between fasted and fed control rats. Hypoxia significantly increased Akt phosphorylation and PP1 activity only in fed rats. In contrast, hypoxia did not induce significant change in GSK-3β phosphorylation in either fasted or fed rats. We conclude that hypoxia activates GS in fed rat myocardium through a combination of rapid glycogenolysis, elevated local G-6-Pcontent, and increased PP1 activity, and fasting attenuates this action independent of local G-6-Pcontent.
