Effect of intravenous L-carnitine on carnitine homeostasis and fuel metabolism during exercise in humans.
This study was undertaken to challenge the hypothesis that short-term administration of carnitine during exercise can modify skeletal muscle carnitine homeostasis and fuel metabolism in normal humans. With a randomized, blinded, crossover design, subjects received carnitine or placebo at the start of a bicycle ergometer exercise session. During the 2 hours after intravenous administration of 185 mumol/kg carnitine, carnitine kinetics could be described with a central compartment volume of distribution of 200 ml/kg, a total clearance from this compartment of 1.9 ml/min/kg, and a renal clearance of 1.3 ml/min/kg. Carnitine administration had no effect on muscle total carnitine content or the workload-dependent accumulation of acylcarnitines in skeletal muscle. Carnitine had no effect on the respiratory exchange ratio, muscle lactate accumulation, plasma lactate concentration, muscle glycogen utilization, or plasma beta-hydroxybutyrate concentration during exercise. Thus the skeletal muscle carnitine pool is segregated from dramatic changes in the plasma carnitine pool, and short-term administration of carnitine has no significant effect on fuel metabolism during exercise in humans.
Brass
E P
EP
Department of Medicine, Case Western Reserve University, Cleveland.
Hoppel
C L
CL
Hiatt
W R
WR
D000328:Adult; D002331:Carnitine / Q000008:administration & dosage / Q000378:metabolism* / Q000494:pharmacology*; D004734:Energy Metabolism / Q000187:drug effects; D015444:Exercise / Q000502:physiology*; D006706:Homeostasis / Q000187:drug effects; D006801:Humans; D007275:Injections, Intravenous; D008297:Male; D009132:Muscles / Q000378:metabolism; D012016:Reference Values; D016037:Single-Blind Method
D002331:Carnitine