title: Effect of carbohydrate ingestion on exercise-induced alterations in metabolic gene expression.
abstract: 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.kg(-1).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.
authors.affiliation: Centre for Physical Activity and Nutrition, School of Exercise and Nutrition Sciences, Deakin University, Burwood, Victoria, Australia.
authors.forename: Laura J
authors.initials: LJ
authors.lastname: Cluberton
authors.forename: Sean L
authors.initials: SL
authors.lastname: McGee
authors.forename: Robyn M
authors.initials: RM
authors.lastname: Murphy
authors.forename: Mark
authors.initials: M
authors.lastname: Hargreaves
mesh_terms: D000328:Adult; D001628:Beverages; D001642:Bicycling / Q000502:physiology*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D004040:Dietary Carbohydrates / Q000494:pharmacology*; D015870:Gene Expression / Q000187:drug effects; D051275:Glucose Transporter Type 4 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007473:Ion Channels; D008297:Male; D024101:Mitochondrial Proteins; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D052097:Quadriceps Muscle / Q000378:metabolism*; D012333:RNA, Messenger / Q000037:antagonists & inhibitors / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D000071247:Uncoupling Protein 3
chemical_list: D002352:Carrier Proteins; D004040:Dietary Carbohydrates; D051275:Glucose Transporter Type 4; D007473:Ion Channels; D024101:Mitochondrial Proteins; D012333:RNA, Messenger; C495692:SLC2A4 protein, human; D014157:Transcription Factors; C000604392:UCP3 protein, human; D000071247:Uncoupling Protein 3; C111264:peroxisome-proliferator-activated receptor-gamma coactivator-1; D011494:Protein Kinases; C403287:pyruvate dehydrogenase kinase 4