Journal
AMERICAN JOURNAL OF PHYSIOLOGY-ENDOCRINOLOGY AND METABOLISM
Volume 281, Issue 6, Pages E1151-E1158Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/ajpendo.2001.281.6.E1151
Keywords
pyruvate dehydrogenase kinase 2; pyruvate dehydrogenase kinase 4; respiratory exchange ratio; pyruvate dehydrogenase activity; mitochondria
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The increase in skeletal muscle pyruvate dehydrogenase kinase (PDK) activity was measured in skeletal muscle of six healthy males after a eucaloric high-fat/low-carbohydrate (HF/LC; 5% carbohydrate, 73% fat, and 22% protein of total energy intake) diet compared with a standardized prediet (50% carbohdyrate, 30% fat, and 21% protein). Biopsies were obtained from the vastus lateralis muscle after 3 days on the prediet (day 0) and after 1, 2, and 3 days of the HF/LC diet. Intact mitchondria were extracted from fresh muscle and analyzed for PDK activity and Western blotting of PDK2 and PDK4 protein. A second biopsy was taken at each time point and frozen for Northern blot analysis of PDK2 and PDK4 mRNAs. PDK activity increased in a linear fashion over the 3-day HF/LC diet and was significantly higher than control by 1 day. PDK activity was 0.09 +/-0.03, 0.18 +/-0.05, 0.30 +/-0.07, and 0.37 +/-0.09 min(-1) at 0, 1, 2, and 3 days, respectively. PDK4 protein and mRNA increased maximally by day 1, and PDK2 protein and mRNA were unaffected by the HF/LC diet. Resting respiratory exchange ratios decreased after 1 day of the HF/LC diet (from 0.79 +/-0.02 to 0.72 +/-0.02) and remained depressed throughout the 3-day dietary intervention (0.68 +/-0.01). The immediate shift to fat utilization was accompanied by increased blood glycerol, beta -hydroxybutyrate, and plasma free fatty acid concentrations. These results suggest that the continuing increase in PDK activity over the 3-day HF/LC diet is not due to increasing PDK protein beyond 1 day. This could be due to the contribution of another isoform to the total PDK activity or to a continual increase in PDK4 or PDK2 specific activity.
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