Adaptive responses of GLUT-4 and citrate synthase in fast-twitch muscle of voluntary running rats.

Glucose transporter (GLUT-4) protein, hexokinase, and citrate synthase (proteins involved in oxidative energy production from blood glucose catabolism) increase in response to chronically elevated neuromuscular activity. It is currently unclear whether these proteins increase in a coordinated manner in response to this stimulus. Therefore, voluntary wheel running (WR) was used to chronically overload the fast-twitch rat plantaris muscle and the myocardium, and the early time courses of adaptative responses of GLUT-4 protein and the activities of hexokinase and citrate synthase were characterized and compared. Plantaris hexokinase activity increased 51% after just 1 wk of WR, whereas GLUT-4 and citrate synthase were increased by 51 and 40%, respectively, only after 2 wk of WR. All three variables remained comparably elevated (+50-64%) through 4 wk of WR. Despite the overload of the myocardium with this protocol, no substantial elevations in these variables were observed. These findings are consistent with a coordinated upregulation of GLUT-4 and citrate synthase in the fast-twitch plantaris, but not in the myocardium, in response to this increased neuromuscular activity. Regulation of hexokinase in fast-twitch muscle appears to be uncoupled from regulation of GLUT-4 and citrate synthase, as increases in the former are detectable well before increases in the latter.

[1]  E. Henriksen,et al.  Cardiac protein content and synthesis in vivo after voluntary running or head-down suspension. , 1994, Journal of applied physiology.

[2]  A. Halseth,et al.  Early alterations in soleus GLUT-4, glucose transport, and glycogen in voluntary running rats. , 1994, Journal of applied physiology.

[3]  G. Cartee,et al.  Exercise training does not compensate for age-related decrease in myocardial GLUT-4 content. , 1994, Journal of applied physiology.

[4]  D. Pette,et al.  Low-frequency stimulation of rat fast-twitch muscle enhances the expression of hexokinase II and both the translocation and expression of glucose transporter 4 (GLUT-4). , 1994, European journal of biochemistry.

[5]  R. Farrar,et al.  Effect of chronic electrical stimulation on GLUT-4 protein content in fast-twitch muscle. , 1993, The American journal of physiology.

[6]  J. Ivy,et al.  Effects of exercise training on skeletal muscle glucose uptake and transport. , 1993, The American journal of physiology.

[7]  E. Horton,et al.  Glucose Transporter Number, Function, and Subcellular Distribution in Rat Skeletal Muscle After Exercise Training , 1992, Diabetes.

[8]  C. Slentz,et al.  Glucose transporters and maximal transport are increased in endurance-trained rat soleus. , 1992, Journal of applied physiology.

[9]  D. James,et al.  Exercise training, glucose transporters, and glucose transport in rat skeletal muscles. , 1992, The American journal of physiology.

[10]  T. Walters,et al.  Influence of electrical stimulation on a fast-twitch muscle in aging rats. , 1991, Journal of applied physiology.

[11]  D. James,et al.  Effect of denervation or unweighting on GLUT-4 protein in rat soleus muscle. , 1991, Journal of applied physiology.

[12]  W. Kraus,et al.  Mitochondrial biogenesis in striated muscles: rapid induction of citrate synthase mRNA by nerve stimulation. , 1991, The American journal of physiology.

[13]  W. Kraus,et al.  Intracellular Signals Mediating Contraction-Induced Changes in the Oxidative Capacity of Skeletal Muscle , 1990 .

[14]  T. Ohkuwa,et al.  Effect of endurance training on glucose transport capacity and glucose transporter expression in rat skeletal muscle. , 1990, The American journal of physiology.

[15]  D. James,et al.  Effects of Exercise Training on Insulin-Regulatable Glucose-Transporter Protein Levels in Rat Skeletal Muscle , 1990, Diabetes.

[16]  G. Reaven,et al.  Effects of insulin on carbohydrate and protein metabolism in voluntary running rats. , 1990, The American journal of physiology.

[17]  F. E. Weber,et al.  Changes in free and bound forms and total amount of hexokinase isozyme II of rat muscle in response to contractile activity. , 1990, European journal of biochemistry.

[18]  W. Haskell,et al.  Differences in insulin-induced glucose uptake and enzyme activity in running rats. , 1990, Journal of applied physiology.

[19]  H. Rupp,et al.  Differential effect of physical exercise routines on ventricular myosin and peripheral catecholamine stores in normotensive and spontaneously hypertensive rats. , 1989, Circulation research.

[20]  D. James,et al.  Molecular cloning and characterization of an insulin-regulatable glucose transporter , 1989, Nature.

[21]  W. Haskell,et al.  Variations in running activity and enzymatic adaptations in voluntary running rats. , 1989, Journal of applied physiology.

[22]  S Salmons,et al.  Adaptation of skeletal muscle to increased contractile activity. Expression nuclear genes encoding mitochondrial proteins. , 1987, The Journal of biological chemistry.

[23]  M. Danson,et al.  Citrate synthase. , 2020, Current topics in cellular regulation.

[24]  F. Booth,et al.  Biochemical adaptations to endurance exercise in muscle. , 1976, Annual review of physiology.

[25]  J. Scheuer,et al.  Experimental observations on the effects of physical training upon intrinsic cardiac physiology and biochemistry. , 1974, The American journal of cardiology.

[26]  U. K. Laemmli,et al.  Cleavage of Structural Proteins during the Assembly of the Head of Bacteriophage T4 , 1970, Nature.

[27]  E. Racker,et al.  Regulatory mechanisms in carbohydrate metabolism. VII. Hexokinase and phosphofructokinase. , 1965, The Journal of biological chemistry.