scholarly journals Dietary whey protein increases liver and skeletal muscle glycogen levels in exercise-trained rats

2005 ◽  
Vol 93 (4) ◽  
pp. 439-445 ◽  
Author(s):  
Masashi Morifuji ◽  
Kensuke Sakai ◽  
Chiaki Sanbongi ◽  
Katsumi Sugiura
Keyword(s):  
Skeletal Muscle ◽  
Whey Protein ◽  
Muscle Glycogen ◽  
Dietary Protein ◽  
Glycogen Content ◽  
Glycogen Synthase ◽  
Casein Diet ◽  
Skeletal Muscle Glycogen ◽  
Protein Group ◽  
Glycogen Synthase Activity

We investigated the effect of different types of dietary protein on glycogen content in liver and skeletal muscle of exercise-trained rats. Twenty-four male Sprague-Dawley rats (approximately 100 g; n 6 per group) were divided into sedentary or exercise-trained groups with each group being fed either casein or whey protein as the source of dietary protein. Rats in the exercised groups were trained during 2 weeks using swimming exercise for 120 min/d, 6 d/week. Exercise training resulted in an increase in the skeletal muscle glycogen content. Furthermore, the whey protein group significantly increased the skeletal muscle glycogen content compared with the casein group. The increase in glycogen content in liver was significantly greater in rats fed the whey protein diet compared with those fed the casein diet. We also found that the whey protein diet increased the activity of liver glucokinase, whereas it decreased the activities of 6-phosphofructokinase and pyruvate kinase compared with the casein diet. However, hepatic total glycogen synthase activity and mRNA expression were similar with the two diets. In the skeletal muscle, whey protein decreased only 6-phosphofructokinase activity compared with casein. Total glycogen synthase activity in the skeletal muscle in the whey protein group was significantly higher than that in the casein group. The present study is the first to demonstrate that a diet based on whey protein may increase glycogen content in liver and skeletal muscle of exercise-trained rats. We also observed that whey protein regulated glycogen metabolism in these two tissues by different mechanisms.

Effect of hypercorticism on regulation of skeletal muscle glycogen metabolism by epinephrine

1992 ◽  
Vol 262 (4) ◽  
pp. E434-E439 ◽  
Author(s):  
L. Coderre ◽  
A. K. Srivastava ◽  
J. L. Chiasson
Keyword(s):  
Skeletal Muscle ◽  
Muscle Glycogen ◽  
Glycogen Content ◽  
Activity Ratio ◽  
Glycogen Synthase ◽  
Glycogen Metabolism ◽  
Dexamethasone Treatment ◽  
Fed State ◽  
Glycogen Concentration ◽  
Glycogen Synthase Activity

The effect of hypercorticism on the regulation of glycogen metabolism by epinephrine was examined in skeletal muscles using a hindlimb perfusion technique. Rats were injected with either saline or dexamethasone (0.4 mg.kg-1.day-1) for 14 days and were studied in the fed and fasted (24 h) states under saline or epinephrine (10(-7) M) treatment. In the fed state, dexamethasone administration did not affect basal glycogen concentration but decreased glycogen synthase activity ratio in white and red gastrocnemius muscles. Epinephrine failed to decrease glycogen content despite the expected activation of glycogen phosphorylase in the fed dexamethasone-treated rats. Dexamethasone treatment resulted in a threefold increase in the level of muscle adenosine, a phosphorylase a inhibitor. In control rats, fasting was associated with a decrease in muscle glycogen concentration (P less than 0.01) and with an increase in the glycogen synthase activity ratio. Dexamethasone treatment, however, totally abolished both the decreased muscle glycogen content and glycogen synthase activation observed in fasting controls. In the dexamethasone-treated group, fasting restored the glycogenolytic effect of epinephrine. Interestingly, it was associated with decreased muscle adenosine concentrations. These data indicate that, in the fed state, dexamethasone treatment inhibits skeletal muscle glycogenolysis in response to epinephrine despite phosphorylase activation and glycogen synthase inactivation. It is suggested that this abnormality could be due to the inhibition of phosphorylase a by increased muscle adenosine levels.

Time course of insulin sensitivity and skeletal muscle glycogen synthase activity after a single bout of exercise in horses

2007 ◽  
Vol 103 (3) ◽  
pp. 1063-1069 ◽  
Author(s):  
Shannon E. Pratt ◽  
Raymond J. Geor ◽  
Lawrence L. Spriet ◽  
L. Jill McCutcheon
Keyword(s):  
Skeletal Muscle ◽  
Insulin Sensitivity ◽  
Muscle Glycogen ◽  
Time Course ◽  
Glycogen Content ◽  
Activity Ratio ◽  
Glycogen Synthase ◽  
Muscle Glycogen Content ◽  
Skeletal Muscle Glycogen ◽  
Single Bout

The time course of insulin sensitivity, skeletal muscle glycogen and GLUT4 content, and glycogen synthase (GS) activity after a single bout of intense exercise was examined in eight horses. On separate days, a euglycemic-hyperinsulinemic clamp (EHC) was undertaken at 0.5, 4, or 24 h after exercise or after 48 h of rest [control (Con)]. There was no increase in mean glucose infusion rate (GIR) with exercise (0.5-, 4-, and 24-h trials), and GIR was significantly decreased at 0.5 h postexercise (GIR: 8.6 ± 2.7, 6.7 ± 2.0, 9.0 ± 2.0, and 10.6 ± 2.2 mg·kg−1·min−1 for Con and at 0.5, 4, and 24 h, respectively). Before each EHC, muscle glycogen content (mmol glucosyl units/kg dry muscle) was higher ( P < 0.05) for Con (565 ± 102) than for other treatments (317 ± 84, 362 ± 79, and 382 ± 74 for 0.5, 4, and 24 h, respectively) and muscle GLUT4 content was unchanged. Pre-EHC active-to-total GS activity ratio was higher ( P < 0.05) at 0.5, 4, and 24 h after exercise than in Con. Post-EHC active GS and GS activity ratio were higher ( P < 0.05) in Con and at 24 h. There was a significant inverse correlation ( r = −0.43, P = 0.02) between glycogen content and GS activity ratio but no relationship between GS activity and GIR. The lack of increase in insulin sensitivity, determined by EHC, after exercise that resulted in a significant reduction in muscle glycogen content is consistent with the slow rate of muscle glycogen resynthesis observed in equine studies.

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