Whole body and leg acetate kinetics at rest, during exercise and recovery in humans.
We have used a constant [1,2-(13)C]acetate infusion (0.12 micromol x min(-1) x kg( 1)) for 2 h at rest, followed by 2 h of one-legged knee-extensor exercise at 65% of leg maximal workload, and 3 h of recovery in six post-absorptive volunteers to quantify whole-body and leg acetate kinetics and determine whether the whole-body acetate correction factor can be used to correct leg substrate oxidation. The acetate whole-body rate of appearance (R(a)) was not significantly different at rest, during exercise or during recovery (365-415 micromol x min(-1)). The leg net acetate uptake was similar at rest and during recovery (approximately 10 micromol x min(-1)), but increased approximately 5-fold with exercise. At rest the leg acetate uptake (approximately 15 micromol x min(-1)) and release (approximately 5 micromol x min(-1)) accounted for 4 and 1.5 % of whole-body acetate disposal (R(d)) and R(a), respectively. When the leg acetate kinetics were extrapolated to the total body skeletal muscle mass, then skeletal muscle accounted for approximately 16 and approximately 6% of acetate R(d) and R(a). With exercise, leg acetate uptake increased approximately 6-fold, whereas leg acetate release increased 9-fold compared with rest. Whole-body acetate carbon recovery increased with time of infusion at rest and during recovery from 21% after 1.5 h of infusion to 45% in recovery after 7 h of infusion. Leg and whole-body acetate carbon recovery were similar under resting conditions, both before and after exercise. During exercise whole-body acetate carbon recovery was approximately 75%, however, acetate carbon recovery of the active leg was substantially higher (approximately 100%). It is concluded that inactive skeletal muscle plays a minor role in acetate turnover. However, active skeletal muscle enhances several-fold acetate uptake and subsequent oxidation, as well as release and its contribution to whole-body acetate turnover. Furthermore, under resting conditions the whole-body acetate correction factor can be used to correct for leg, skeletal muscle, substrate oxidation, but not during exercise.
van Hall
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G
The Copenhagen Muscle Research Centre, University Hospital, DK-2100, Copenhagen, Denmark. gvhall@rh.dk
Sacchetti
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Rådegran
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G
D000085:Acetates / Q000097:blood / Q000378:metabolism*; D000328:Adult; D000465:Algorithms; D002245:Carbon Dioxide / Q000378:metabolism; D004032:Diet; D004734:Energy Metabolism / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D007700:Kinetics; D007866:Leg / Q000000981:diagnostic imaging / Q000502:physiology; D008297:Male; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging / Q000378:metabolism*; D010084:Oxidation-Reduction; D010168:Palmitates / Q000378:metabolism; D012146:Rest / Q000502:physiology*; D014463:Ultrasonography
D000085:Acetates; D010168:Palmitates; D002245:Carbon Dioxide