title: Patients with medium-chain acyl-coenzyme a dehydrogenase deficiency have impaired oxidation of fat during exercise but no effect of L-carnitine supplementation.
abstract: BACKGROUND
  It is not clear to what extent skeletal muscle is affected in patients with medium-chain acyl-coenzyme A dehydrogenase deficiency (MCADD). l-Carnitine is commonly used as a supplement in patients with MCADD, although its beneficial effect has not been verified.
  
  
  METHODS
  We investigated (1) fuel utilization during prolonged low-intensity exercise in patients with MCADD and (2) the influence of 4 weeks of oral l-carnitine supplementation on fuel utilization during exercise.
  
  
  METHODS
  Four asymptomatic patients with MCADD and 11 untrained, healthy, age- and sex-matched control subjects were included. The subjects performed a 1-hour cycling test at a constant workload corresponding to 55% of Vo2max, while fat and carbohydrate metabolism was assessed, using the stable isotope technique and indirect calorimetry. The patients ingested 100 mg/kg/d of l-carnitine for 4 weeks, after which the cycling tests were repeated.
  
  
  RESULTS
  At rest, palmitate oxidation and total fatty acid oxidation (FAO) rates were similar in patients and healthy control subjects. During constant workload cycling, palmitate oxidation and FAO rates increased in both groups, but increased 2 times as much in healthy control subjects as in patients (P = .007). Palmitate oxidation and FAO rates were unchanged by the l-carnitine supplementation.
  
  
  CONCLUSIONS
  Our results indicate that patients with MCADD have an impaired ability to increase FAO during exercise but less so than that observed in patients with a number of other disorders of fat oxidation, which explains the milder skeletal muscle phenotype in MCADD. The use of carnitine supplementation in MCADD cannot be supported by the present findings.
authors: Neuromuscular Research Unit, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark. karen_lindhardt@hotmail.com
authors: K L
authors: KL
authors: Madsen
authors: N
authors: N
authors: Preisler
authors: M C
authors: MC
authors: Orngreen
authors: S P
authors: SP
authors: Andersen
authors: J H
authors: JH
authors: Olesen
authors: A M
authors: AM
authors: Lund
authors: J
authors: J
authors: Vissing
mesh_terms: D042964:Acyl-CoA Dehydrogenase / Q000172:deficiency / Q000378:metabolism; D000293:Adolescent; D000328:Adult; D002331:Carnitine / Q000008:administration & dosage / Q000494:pharmacology*; D019587:Dietary Supplements; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D017079:Exercise Tolerance / Q000187:drug effects / Q000502:physiology; D005260:Female; D006801:Humans; D050356:Lipid Metabolism / Q000187:drug effects / Q000502:physiology*; D008052:Lipid Metabolism, Inborn Errors / Q000378:metabolism*; D008297:Male; D010084:Oxidation-Reduction / Q000187:drug effects; D012107:Research Design; D055815:Young Adult
chemical_list: D042964:Acyl-CoA Dehydrogenase; D002331:Carnitine