Coenzyme Q10 quantification in muscle, fibroblasts and cerebrospinal fluid by liquid chromatography/tandem mass spectrometry using a novel deuterated internal standard.

RATIONALE: 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.

The effect of ascorbate and ubiquinone supplementation on plasma and CSF total antioxidant capacity.

Free radicals are thought to be involved in the onset of neuronal disturbances such as Alzheimer's disease, Parkinson's disease, and neuronal ceroid lipofuscinosis. It is also assumed that they play a role in cerebral injury caused by ischemia or trauma. Plasma and cerebrospinal fluid (CSF), Total (peroxyl) Radical-trapping Antioxidant Parameter (TRAP), and the known antioxidant components of TRAP, for instance, ascorbic acid, uric acid, protein sulfhydryl groups, tocopherol, and ubiquinol were analyzed and the remaining unidentified fragment was calculated in five healthy volunteers before and after 4 weeks of ascorbate and ubiquinone (Q-10) supplementation. In CSF, TRAP was significantly lower than in plasma. The major contributor to plasma's antioxidant capacity was uric acid (UA), whereas in CSF it was ascorbic acid (AA). In CSF, AA concentrations were four times higher than in plasma. Oral supplementation of AA (500 mg/d first 2 weeks, 1,000 mg/d following 2 weeks) and Q-10 (100 mg/d first 2 weeks, 300 mg/d following 2 weeks) induced a significant increase in plasma AA and Q-10. Surprisingly, in spite of the high lipophilicity of Q-10, its concentration did not change in CSF. The supplementation of AA increased its concentration in CSF by 28% (p < .05). However, the increase in AA did not result in an increase in CSF TRAP. This indicates that AA had lost one-third of its radical trapping capacity as compared to that in plasma. The facts that AA is the highest contributor to CSF TRAP and its effect on TRAP is concentration dependent could indicate that the peroxyl radical-trapping capacity of CSF is buffered by AA.