Enzymatic regulation of glucose disposal in human skeletal muscle after a high-fat, low-carbohydrate diet.
Whole body glucose disposal and skeletal muscle hexokinase, glycogen synthase (GS), pyruvate dehydrogenase (PDH), and PDH kinase (PDK) activities were measured in aerobically trained men after a standardized control diet (Con; 51% carbohydrate, 29% fat, and 20% protein of total energy intake) and a 56-h eucaloric, high-fat, low-carbohydrate diet (HF/LC; 5% carbohydrate, 73% fat, and 22% protein). An oral glucose tolerance test (OGTT; 1 g/kg) was administered after the Con and HF/LC diets with vastus lateralis muscle biopsies sampled pre-OGTT and 75 min after ingestion of the oral glucose load. The 90-min area under the blood glucose and plasma insulin concentration vs. time curves increased by 2-fold and 1.25-fold, respectively, after the HF/LC diet. The pre-OGTT fraction of GS in its active form and the maximal activity of hexokinase were not affected by the HF/LC diet. However, the HF/LC diet increased PDK activity (0.19 +/- 0.05 vs. 0.08 +/- 0.02 min(-1)) and decreased PDH activation (0.38 +/- 0.08 vs. 0.79 +/- 0.10 mmol acetyl-CoA.kg wet muscle(-1).min(-1)) before the OGTT vs. Con. During the OGTT, GS and PDH activation increased by the same magnitude in both diets, such that PDH activation remained lower during the HF/LC OGTT (0.60 +/- 0.11 vs. 1.04 +/- 0.09 mmol acetyl-CoA.kg(-1).min(-1)). These data demonstrate that the decreased glucose disposal during the OGTT after the 56-h HF/LC diet was in part related to decreased oxidative carbohydrate disposal in skeletal muscle and not to decreased glycogen storage. The rapid increase in PDK activity during the HF/LC diet appeared to account for the reduced potential for oxidative carbohydrate disposal.
Dept. of Human Biology and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
Tanya L
TL
Pehleman
Sandra J
SJ
Peters
George J F
GJ
Heigenhauser
Lawrence L
LL
Spriet
D000222:Adaptation, Physiological / Q000502:physiology; D000328:Adult; D001786:Blood Glucose / Q000032:analysis*; D004040:Dietary Carbohydrates / Q000378:metabolism*; D004041:Dietary Fats / Q000378:metabolism*; D015444:Exercise / Q000502:physiology; D005080:Exercise Test; D006801:Humans; D008297:Male; D009124:Muscle Proteins / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000502:physiology*; D010088:Oxidoreductases / Q000378:metabolism*; D005082:Physical Exertion / Q000502:physiology*
D001786:Blood Glucose; D004040:Dietary Carbohydrates; D004041:Dietary Fats; D009124:Muscle Proteins; D010088:Oxidoreductases