Whole body and leg acetate kinetics at rest, during exercise and recovery in humans.

摘要

We have used a constant [1,2-(13)C]acetate infusion (0.12 &mgr;mol min(-1) 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 &mgr;mol min(-1)). The leg net acetate uptake was similar at rest and during recovery (~10 &mgr;mol min(-1)), but increased ~5-fold with exercise. At rest the leg acetate uptake (~15 &mgr;mol min(-1)) and release (~5 &mgr;mol 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 ~16 and ~6 % of acetate R(d) and R(a).With exercise, leg acetate uptake increased ~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 ~75 %, however, acetate carbon recovery of the active leg was substantially higher (~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.