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[RC] Carbs/altered gene expression - Ridecamp Guest

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Authors LJ Cluberton, SL McGee, RM Murphy, M Hargreaves
Title   Effect of carbohydrate ingestion on exercise-induced alterations in 
metabolic gene expression
Full source     Journal of Applied Physiology, 2005, Vol 99, Iss 4, pp 1359-1363

Skeletal muscle possesses a high degree of plasticity and can adapt to both the 
physical and metabolic challenges that it faces. An acute bout of exercise is 
sufficient to induce the expression of a variety of metabolic genes, such as 
GLUT4, pyruvate dehydrogenase kinase 4 (PDK-4), uncoupling protein-3 (UCP3), 
and peroxisome proliferator-activated receptor-gamma coactivator 1 (PGC-1). 
Reducing muscle glycogen levels before exercise potentiates the effect of 
exercise on many genes. Similarly, altered substrate availability induces 
transcription of many of these genes. The purpose of this study was to 
determine whether glucose ingestion attenuates the exercise-induced increase in 
a variety of exercise-responsive genes. Six male subjects (28  7 yr; 83  3 kg; 
peak pulmonary oxygen uptake = 46  6 ml center dot kg(-1) center dot min(-1)) 
performed 60 min of cycling at 74  2% of peak pulmonary oxygen uptake on two 
separate occasions. On one occasion, subjects ingested a 6% carbohydrate drink. 
On the other occasion, subjects ingested an equal volume of a sweet placebo. 
Muscle samples were obtained from vastus lateralis at rest, immediately after 
exercise, and 3 h after exercise. PDK-4, UCP3, PGC-1, and GLUT4 mRNA levels 
were measured on these samples using real-time RT-PCR. Glucose ingestion 
attenuated (P < 0.05) the exercise-induced increase in PDK-4 and UCP3 mRNA. A 
similar trend (P = 0.09) was observed for GLUT4 mRNA. In contrast, PGC-1 mRNA 
increased following exercise to the same extent in both conditions. These data 
suggest that glucose availability can modulate the effect of exercise on 
metabolic gene expression.


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