title: Characterization of plasma acylcarnitines in patients under valproate monotherapy using ESI-MS/MS.
abstract: OBJECTIVE
  The effect of administration of the antiepileptic drug valproate (VPA), on the composition of the plasma acylcarnitine profile (including free carnitine) was investigated.
  
  
  METHODS
  Plasma samples were obtained from 18 individuals (13 males:5 females; 15-65 y) on long-term treatment with VPA (resulting in plasma levels of 14.6-135.0 mg/L; therapeutic conc.: 40-100 mg/L). Acylcarnitines (AC) in plasma were quantified by electrospray tandem mass spectrometry (ESI-MS/MS).
  
  
  RESULTS
  VPA was found to increase the levels (mean +/- SD, microM) of 3-hydroxy-isovalerylcarnitine (0.10 +/- 0.04; controls: 0.02-0.06), C14:2 acylcarnitine (0.11 +/- 0.05; controls: 0.02-0.08), propylglutarylcarnitine (0.06 +/- 0.05; controls: 0.00-0.04), and C18-0H-acylcarnitine (0.09 +/- 0.05; controls: 0.00-0.04). The free carnitine (C) (42.2 +/- 9.0; controls: 22.3-54.9) and the total carnitine (52.3 +/- 10.1; controls: 26.5-73.6) were not significantly altered by VPA. Other AC (C2-C18, monounsaturated and hydroxylated) were all within the control range and especially no increase of C8 (valproyl) carnitine was observed. A positive correlation was found between the ratios [AC] / [C] (p < 0.05) or [long-chain AC (C10-C18)] / [C] (p < 0.09) with the plasma VPA concentration.
  
  
  CONCLUSIONS
  The unequivocal increase in 3-hydroxy-isovalerylcarnitine is consistent with the increase of 3-hydroxy-isovaleric acid observed in urine of VPA treated patients. This finding suggests an interaction mechanism of VPA with specific enzymes, namely involved in leucine metabolism. Adult patients under VPA monotherapy do not suffer from carnitine deficiency; the effect of the accumulating acylcarnitines is ill-defined.
authors.affiliation: Department of Clinical Chemistry and Paediatrics, University of Amsterdam, Academic Medical Centre, Amsterdam, The Netherlands.
authors.forename: M F
authors.initials: MF
authors.lastname: Silva
authors.forename: J
authors.initials: J
authors.lastname: Selhorst
authors.forename: H
authors.initials: H
authors.lastname: Overmars
authors.forename: A H
authors.initials: AH
authors.lastname: van Gennip
authors.forename: M
authors.initials: M
authors.lastname: Maya
authors.forename: R J
authors.initials: RJ
authors.lastname: Wanders
authors.forename: I T
authors.initials: IT
authors.lastname: de Almeida
authors.forename: M
authors.initials: M
authors.lastname: Duran
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000927:Anticonvulsants / Q000494:pharmacology*; D002331:Carnitine / Q000031:analogs & derivatives* / Q000097:blood*; D005260:Female; D006801:Humans; D007930:Leucine / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D063991:Mitochondrial Trifunctional Protein; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D014631:Valerates / Q000652:urine; D014635:Valproic Acid / Q000494:pharmacology*
chemical_list: C098116:3-hydroxyisovalerylcarnitine; D000927:Anticonvulsants; D009097:Multienzyme Complexes; D014631:Valerates; C116917:acylcarnitine; C004961:beta-hydroxyisovaleric acid; D014635:Valproic Acid; D063991:Mitochondrial Trifunctional Protein; D007930:Leucine; D002331:Carnitine