Muscle enzyme activity in humans: role of substrate availability and training.
To study the effect of nutrient intake (substrate flux) and training on muscle enzyme activities, 36 untrained healthy men adapted for 7 wk to a fat-rich or a carbohydrate-rich diet. Ten of the 18 subjects on each diet completed an endurance training program, and the remaining 8 served as controls. Maximal oxygen uptake was increased (11%) in the trained groups (P < 0.05). Irrespective of training, beta-hydroxyacyl-CoA-dehydrogenase activity in the vastus lateralis muscle was significantly increased by an average of 25% after adaptation to a fat-rich diet and was unchanged after adaptation to a carbohydrate-rich diet. In contrast, irrespective of diet, muscle citrate synthase activity and hexokinase activity were increased (P < 0.05) after adaptation to training by 17 and 18% in the group fed the carbohydrate, rich diet and by 17 and 12% in the group fed the fat-rich diet, respectively, and were unchanged in the two control groups. We suggest that diet can affect muscle enzymatic adaptation, presumably through an effect on the substrate flux.
Helge
J W
JW
Copenhagen Muscle Research Centre, August Krogh Institute, University of Copenhagen, Denmark.
Kiens
B
B
D015094:3-Hydroxyacyl CoA Dehydrogenases / Q000378:metabolism; D000328:Adult; D001706:Biopsy; D002950:Citrate (si)-Synthase / Q000378:metabolism; D004040:Dietary Carbohydrates / Q000378:metabolism; D004041:Dietary Fats / Q000378:metabolism; D004044:Dietary Proteins / Q000378:metabolism; D002149:Energy Intake; D006593:Hexokinase / Q000378:metabolism; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000201:enzymology*; D010809:Physical Fitness
D004040:Dietary Carbohydrates; D004041:Dietary Fats; D004044:Dietary Proteins; D015094:3-Hydroxyacyl CoA Dehydrogenases; D002950:Citrate (si)-Synthase; D006593:Hexokinase