Chen C, Williams P F, Cooney G J, Caterson I D
Department of Endocrinology, Royal Prince Alfred Hospital, NSW, Australia.
Int J Obes Relat Metab Disord. 1992 Nov;16(11):913-21.
The circadian rhythm of glycogen metabolism in liver and skeletal muscle was studied in lean and gold thioglucose (GTG) induced-obese mice. The active forms of glycogen synthase (GSI) and phosphorylase (GPa) and the total activity of these enzymes were measured every three hours over a 24 h period in mice fed ad libitum. Hepatic and muscle glycogen content displayed a marked diurnal rhythm that was similar in lean and obese mice. In skeletal muscle the glycogen content, GSI and GPa were not significantly different in lean and obese animals over the 24 h period. The activities of muscle GSI and GPa were constant in both groups despite the diurnal variation in the muscle glycogen content. The absence of an increase in the glycogen content of skeletal muscle despite the pronounced hyperinsulinemia and hyperglycemia in the obese mice, may indicate the degree of insulin resistance in this tissue or the maximal capacity of muscle tissue to store glycogen. In liver, glycogen concentration and total glycogen storage were higher in obese mice. Unlike muscle, both hepatic GSI and GPa underwent significant changes in activity over the 24 h period. Hepatic GSI was lower and GPa was higher in obese mice. The circadian rhythm in enzyme activities was independent of both blood glucose and insulin levels. The total glycogen storage and the activities of total phosphorylase and GPa were significantly increased in the liver from GTG obese mice over a 24 h period and could be implicated in the development of insulin resistance and glucose intolerance in this model of obesity.
在瘦小鼠和金硫葡萄糖（GTG）诱导的肥胖小鼠中研究了肝脏和骨骼肌中糖原代谢的昼夜节律。在自由进食的小鼠中，在24小时内每三小时测量一次糖原合酶（GSI）和磷酸化酶（GPa）的活性形式以及这些酶的总活性。肝脏和肌肉糖原含量呈现出明显的昼夜节律，在瘦小鼠和肥胖小鼠中相似。在骨骼肌中，在24小时期间，瘦小鼠和肥胖小鼠的糖原含量、GSI和GPa没有显著差异。尽管肌肉糖原含量存在昼夜变化，但两组肌肉GSI和GPa的活性是恒定的。尽管肥胖小鼠存在明显的高胰岛素血症和高血糖症，但骨骼肌糖原含量没有增加，这可能表明该组织中的胰岛素抵抗程度或肌肉组织储存糖原的最大能力。在肝脏中，肥胖小鼠的糖原浓度和总糖原储存量更高。与肌肉不同，肝脏中的GSI和GPa在24小时内活性都发生了显著变化。肥胖小鼠的肝脏GSI较低，GPa较高。酶活性的昼夜节律与血糖和胰岛素水平无关。在24小时期间，GTG肥胖小鼠肝脏中的总糖原储存量以及总磷酸化酶和GPa的活性显著增加，这可能与该肥胖模型中胰岛素抵抗和葡萄糖不耐受的发展有关。
