title: Coenzyme Q10 quantification in muscle, fibroblasts and cerebrospinal fluid by liquid chromatography/tandem mass spectrometry using a novel deuterated internal standard.
abstract: BACKGROUND
  Neurological dysfunction is common in primary coenzyme Q10 (2,3-dimethoxy, 5-methyl, 6-polyisoprene parabenzoquinone; CoQ10 ; ubiquinone) deficiencies, the most readily treatable subgroup of mitochondrial disorders. Therapeutic benefit from CoQ10 supplementation has also been noted in other neurodegenerative diseases. CoQ10 can be measured by high-performance liquid chromatography (HPLC) in plasma, muscle or leucocytes; however, there is no reliable method to quantify CoQ10 in cerebrospinal fluid (CSF). Additionally, many methods use CoQ9 , an endogenous ubiquinone in humans, as an internal standard.
  
  
  METHODS
  Deuterated CoQ10 (d6 -CoQ10 ) was synthesised by a novel, simple, method. Total CoQ10 was measured by liquid chromatography/tandem mass spectrometry (LC/MS/MS) using d6 -CoQ10 as internal standard and 5 mM methylamine as an ion-pairing reagent. Chromatography was performed using a Hypsersil GOLD C4 column (150 × 3 mm, 3 µm).
  
  
  RESULTS
  CoQ10 levels were linear over a concentration range of 0-200 nM (R(2) = 0.9995). The lower limit of detection was 2 nM. The inter-assay coefficient of variation (CV) was 3.6% (10 nM) and 4.3% (20 nM), and intra-assay CV 3.4% (10 nM) and 3.6% (20 nM). Reference ranges were established for CoQ10 in CSF (5.7-8.7 nM; n = 17), fibroblasts (57.0-121.6 pmol/mg; n = 50) and muscle (187.3-430.1 pmol/mg; n = 15).
  
  
  CONCLUSIONS
  Use of d6 -CoQ10 internal standard has enabled the development of a sensitive LC/MS/MS method to accurately determine total CoQ10 levels. Clinical applications of CSF CoQ10 determination include identification of patients with cerebral CoQ10 deficiency, and monitoring CSF CoQ10 levels following supplementation.
authors.affiliation: Department of Molecular Neuroscience, UCL Institute of Neurology, London, UK.
authors.forename: Kate E C
authors.initials: KE
authors.lastname: Duberley
authors.forename: Iain P
authors.initials: IP
authors.lastname: Hargreaves
authors.forename: Korn-Anong
authors.initials: KA
authors.lastname: Chaiwatanasirikul
authors.forename: Simon J R
authors.initials: SJ
authors.lastname: Heales
authors.forename: John M
authors.initials: JM
authors.lastname: Land
authors.forename: Shamima
authors.initials: S
authors.lastname: Rahman
authors.forename: Kevin
authors.initials: K
authors.lastname: Mills
authors.forename: Simon
authors.initials: S
authors.lastname: Eaton
mesh_terms: D000293:Adolescent; D000328:Adult; D002478:Cells, Cultured; D002648:Child; D002675:Child, Preschool; D002851:Chromatography, High Pressure Liquid / Q000379:methods / Q000592:standards; D003903:Deuterium / Q000032:analysis; D005260:Female; D005347:Fibroblasts / Q000737:chemistry*; D006801:Humans; D007223:Infant; D057230:Limit of Detection; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000737:chemistry*; D010084:Oxidation-Reduction; D012015:Reference Standards; D053719:Tandem Mass Spectrometry / Q000379:methods* / Q000592:standards; D014451:Ubiquinone / Q000031:analogs & derivatives* / Q000032:analysis / Q000134:cerebrospinal fluid; D055815:Young Adult
chemical_list: D014451:Ubiquinone; D003903:Deuterium; C024989:coenzyme Q10