METABOLIC CHANGES INDUCED BY MAXIMAL EXERCISE IN HUMAN-SUBJECTS FOLLOWING L-CARNITINE ADMINISTRATION

In double-blind cross-over experiments, ten moderately trained male subjects were submitted to two bouts of maximal cycle ergometer exercise separated by a 3 day interval. Each subject was randomly given either l-carnitine (2 g) or placebo orally 1 h before the beginning of rach exercise session. At rest l-carnitine supplementation resulted in an increase of plasma-free carnitine without a change in acid-soluble carnitine esters. Treatment with l-carnitine induced a significant post-exercise decrease of plama lactate and pyruvate and a concurrent increase of acetylcarnitine. The determination of the individual carnitine esters in urine collected for 24 h after the placebo exercise trial revealed a decrease of acetyl carnitine and a parallel increase of a C4 carnitine ester, probably isobutyrylcarnitine. Conversely, acetylcarnitine was strongly increased and C4 compounds were almost suppressed in the l-carnitine loading trial. These results suggest that l-carnitine administration prior to high-intensity exercise stimulates pyruvate dehydrogenase activity, thus diverting pyruvate from lactate to acetylcarnitine formation. © 1990.