title: Oxidized proportion of muscle coenzyme Q10 increases with age in healthy children.
abstract: BACKGROUND
  Coenzyme Q10 (CoQ10) is synthesized in most human tissues, with high concentration in the skeletal muscle. CoQ10 functions in the mitochondrial respiratory chain and serves as a potent liphophilic antioxidant in membranes. CoQ10 deficiency impairs mitochondrial ATP synthesis and increases oxidative stress. It has been suggested that plasma CoQ10 status is not a robust proxy for the diagnosis of CoQ10 deficiency.
  
  
  METHODS
  We determined the concentration and redox-status of CoQ10 in plasma and muscle tissue from 140 healthy children (0.8-15.3 y) by high-performance liquid chromatography (HPLC) with electrochemical detection.
  
  
  RESULTS
  There was no correlation between CoQ10 concentration or redox status between plasma and muscle tissue. Lipid-related CoQ10 plasma concentrations showed a negative correlation with age (Spearman's, P ≤ 0.02), but there was no significant age-related correlation for muscle concentration. In muscle tissue, we found a distinct shift in the redox status in favor of the oxidized proportion with increasing age (Spearman's, P ≤ 0.00001). Reference values for muscle CoQ10 concentration (40.5 ± 12.2 pmol/mg wet tissue) and CoQ10 redox status (46.8 ± 6.8% oxidized within total) were established for healthy children.
  
  
  CONCLUSIONS
  The age-related redox shift in muscle tissue suggests changes in antioxidative defense during childhood. The reference values established here provide a necessary prerequisite for diagnosing early CoQ10 deficiency.
authors.affiliation: Children's Hospital Datteln, Witten-Herdecke University, Datteln, Germany.
authors.forename: Petra
authors.initials: P
authors.lastname: Niklowitz
authors.affiliation: Children's Hospital Datteln, Witten-Herdecke University, Datteln, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Scherer
authors.affiliation: Institute of Human Nutrition and Food Science, Molecular Prevention, Christian Albrechts University, Kiel, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Döring
authors.affiliation: Children's Hospital Datteln, Witten-Herdecke University, Datteln, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Paulussen
authors.affiliation: Children's Hospital Datteln, Witten-Herdecke University, Datteln, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Menke
mesh_terms: D000009:Abdominal Muscles / Q000201:enzymology* / Q000254:growth & development; D000293:Adolescent; D041923:Adolescent Development; D000367:Age Factors; D000375:Aging / Q000097:blood / Q000378:metabolism*; D002648:Child; D002657:Child Development; D002675:Child, Preschool; D002851:Chromatography, High Pressure Liquid; D055664:Electrochemical Techniques; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D007223:Infant; D008297:Male; D010084:Oxidation-Reduction; D012016:Reference Values; D014451:Ubiquinone / Q000031:analogs & derivatives* / Q000032:analysis / Q000097:blood; D015854:Up-Regulation
chemical_list: D014451:Ubiquinone; C024989:coenzyme Q10