{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,6]],"date-time":"2026-03-06T13:09:38Z","timestamp":1772802578045,"version":"3.50.1"},"reference-count":37,"publisher":"Oxford University Press (OUP)","issue":"8","license":[{"start":{"date-parts":[[2013,8,1]],"date-time":"2013-08-01T00:00:00Z","timestamp":1375315200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/academic.oup.com\/journals\/pages\/open_access\/funder_policies\/chorus\/standard_publication_model"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2013,8,1]]},"abstract":"<jats:sec><jats:title>BACKGROUND<\/jats:title><jats:p>Coenzyme Q10 (CoQ10) is an essential part of the mitochondrial respiratory chain. Unlike most other respiratory chain disorders, CoQ10 deficiency is potentially treatable. We aimed to develop and validate an accurate liquid chromatography\u2013tandem mass spectrometry (LC-MS\/MS) method for the determination of mitochondrial CoQ10 in clinical samples.<\/jats:p><\/jats:sec><jats:sec><jats:title>METHODS<\/jats:title><jats:p>We used mitochondria isolated from muscle biopsies of patients (n = 166) suspected to have oxidative phosphorylation deficiency. We also used fibroblast mitochondria from 1 patient with CoQ10 deficiency and 3 healthy individuals. Samples were spiked with nonphysiologic CoQ10-[2H6] internal standard, extracted with 1-propanol and with ethanol and hexane (2 mL\/5 mL), and CoQ10 quantified by LC-MS\/MS. The method and sample stability were validated. A reference interval was established from the patient data.<\/jats:p><\/jats:sec><jats:sec><jats:title>RESULTS<\/jats:title><jats:p>The method had a limit of quantification of 0.5 nmol\/L. The assay range was 0.5\u20131000 nmol\/L and the CVs were 7.5%\u20138.2%. CoQ10 was stable in concentrated mitochondrial suspensions. In isolated mitochondria, the mean ratio of CoQ10 to citrate synthase (CS) activity (CoQ10\/CS) was 1.7 nmol\/U (95% CI, 1.6\u20131.7 nmol\/U). We suggest a CoQ10\/CS reference interval of 1.1\u20132.8 nmol\/U for both sexes and all ages. The CoQ10\/CS ratio was 5-fold decreased in fibroblast mitochondria from a patient with known CoQ10 deficiency due to recessive prenyl (decaprenyl) diphosphate synthase, subunit 2 (PDSS2) mutations.<\/jats:p><\/jats:sec><jats:sec><jats:title>CONCLUSIONS<\/jats:title><jats:p>Normalization of mitochondrial CoQ10 concentration against citrate synthase activity is likely to reflect most accurately the CoQ10 content available for the respiratory chain. Our assay and the established reference range should facilitate the diagnosis of respiratory chain disorders and treatment of patients with CoQ10 deficiency.<\/jats:p><\/jats:sec>","DOI":"10.1373\/clinchem.2012.200196","type":"journal-article","created":{"date-parts":[[2013,5,3]],"date-time":"2013-05-03T03:53:27Z","timestamp":1367553207000},"page":"1260-1267","source":"Crossref","is-referenced-by-count":15,"title":["Mitochondrial Coenzyme Q10 Determination by Isotope-Dilution Liquid Chromatography\u2013Tandem Mass Spectrometry"],"prefix":"10.1093","volume":"59","author":[{"given":"Outi","family":"Itkonen","sequence":"first","affiliation":[{"name":"HUSLAB, Helsinki University Central Hospital"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Anu","family":"Suomalainen","sequence":"first","affiliation":[{"name":"HUSLAB, Helsinki University Central Hospital"},{"name":"Research Programs Unit, Molecular Neurology, Biomedicum-Helsinki, University of Helsinki, and"},{"name":"Department of Neurology, Helsinki University Central Hospital, Helsinki, Finland"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ursula","family":"Turpeinen","sequence":"first","affiliation":[{"name":"HUSLAB, Helsinki University Central Hospital"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"286","published-online":{"date-parts":[[2013,8,1]]},"reference":[{"key":"2020022705334023700_B1","doi-asserted-by":"crossref","first-page":"358","DOI":"10.1111\/j.1432-1033.1973.tb02767.x","article-title":"The kinetics of the redox reactions of ubiquinone related to the electron-transport activity in the respiratory chain","volume":"34","author":"Kroger","year":"1973","journal-title":"Eur J Biochem"},{"key":"2020022705334023700_B2","doi-asserted-by":"crossref","first-page":"11126","DOI":"10.1073\/pnas.89.23.11126","article-title":"Requirement for coenzyme Q in plasma membrane electron transport","volume":"89","author":"Sun","year":"1992","journal-title":"Proc Natl Acad Sci U S A"},{"key":"2020022705334023700_B3","doi-asserted-by":"crossref","first-page":"11409","DOI":"10.1016\/S0021-9258(19)38410-8","article-title":"The protonmotive Q cycle. 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