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Studies on the analysis of 25-hydroxyvitamin D(3) by isotope-dilution liquid chromatography-tandem mass spectrometry using enzyme-assisted derivatisation.

ABSTRACT: The total serum concentration of 25-hydroxyvitamins D (25-hydroxyvitamin D3 and 25-hydroxyvitamin D2) is currently used as an indicator of vitamins D status. Vitamins D insufficiency is claimed to be associated with multiple diseases, thus accurate and precise reference methods for the quantification of 25-hydroxyvitamins D are needed. Here we present a novel enzyme-assisted derivatisation method for the analysis of vitamins D metabolites in adult serum utilising 25-[26,26,26,27,27,27-(2)H6]hydroxyvitamin D3 as the internal standard. Extraction of 25-hydroxyvitamins D from serum is performed with acetonitrile, which is shown to be more efficient than ethanol. Cholesterol oxidase is used to oxidize the 3?-hydroxy group in the vitamins D metabolites followed by derivatisation of the newly formed 3-oxo group with Girard P reagent. 17?-Hydroxysteroid dehydrogenase type 10 is shown to oxidize selectively the 3?-hydroxy group in the 3?-hydroxy epimer of 25-hydroxyvitamin D3. Quantification is achieved by isotope-dilution liquid chromatography-tandem mass spectrometry. Recovery experiments for 25-hydroxyvitamin D3 performed on adult human serum give recovery of 102-106%. Furthermore in addition to 25-hydroxyvitamin D3, 24,25-dihydroxyvitamin D3 and other uncharacterised dihydroxy metabolites, were detected in adult human serum.

SUBMITTER: Abdel-Khalik J

PROVIDER: S-EPMC4000436 | biostudies-literature | 2014 Apr

REPOSITORIES: biostudies-literature

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Studies on the analysis of 25-hydroxyvitamin D(3) by isotope-dilution liquid chromatography-tandem mass spectrometry using enzyme-assisted derivatisation.

Abdel-Khalik Jonas J Crick Peter J PJ Carter Graham D GD Makin Hugh L HL Wang Yuqin Y Griffiths William J WJ

Biochemical and biophysical research communications 20140130 3

The total serum concentration of 25-hydroxyvitamins D (25-hydroxyvitamin D3 and 25-hydroxyvitamin D2) is currently used as an indicator of vitamins D status. Vitamins D insufficiency is claimed to be associated with multiple diseases, thus accurate and precise reference methods for the quantification of 25-hydroxyvitamins D are needed. Here we present a novel enzyme-assisted derivatisation method for the analysis of vitamins D metabolites in adult serum utilising 25-[26,26,26,27,27,27-(2)H6]hydr ...[more]

PMID: 24486315

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Project description:The inaccuracy of routine serum 25-hydroxyvitamin D measurements hampers the interpretation of data in patient care and public health research. We developed and validated a candidate reference measurement procedure (RMP) for highly accurate quantitation of two clinically important 25-hydroxyvitamin D metabolites in serum, 25-hydroxyvitamin D2 [25(OH)D2] and 25-hydroxyvitamin D3 [25(OH)D3]. The two compounds of interest together with spiked deuterium-labeled internal standards [d 3-25(OH)D2 and d 6-25(OH)D3] were extracted from serum via liquid-liquid extraction. The featured isotope-dilution LC-MS/MS method used reversed-phase chromatography and atmospheric pressure chemical ionization in positive ion mode. A pentafluorophenylpropyl-packed UHPLC column together with isocratic elution allowed for complete baseline resolution of 25(OH)D2 and 25(OH)D3 from their structural C-3 isomers within 12 min. We evaluated method trueness, precision, potential interferences, matrix effects, limits of quantitation, and measurement uncertainty. Calibration materials were, or were traceable to, NIST Standard Reference Materials 2972. Within-day and total imprecision (CV) averaged 1.9 and 2.0% for 25(OH)D3, respectively, and 2.4 and 3.5% for 25(OH)D2, respectively. Mean trueness was 100.3% for 25(OH)D3 and 25(OH)D2. The limits of quantitation/limits of detection were 4.61/1.38 nmol/L for 25(OH)D3 and 1.46/0.13 nmol/L for 25(OH)D2. When we compared our RMP results to an established RMP using 40 serum samples, we found a nonsignificant mean bias of 0.2% for total 25(OH)D. This candidate RMP for 25(OH)D metabolites meets predefined method performance specifications (?5% total CV and ?1.7% bias) and provides sufficient sample throughput to meet the needs of the Centers for Disease Control and Prevention Vitamin D Standardization Certification Program. Graphical abstract Bias assessment using NIST standard reference materials. Legend CDC mean mass fractions (ng/g) ± U 95 (6 replicates per mean). NIST-certified mass fractions (ng/g) ± U 95 from the Certificates of Analysis.

Project description:Oxidative stress (OS) plays a major role in the pathogenesis of various diseases in humans. OS is a result of an imbalance between reactive oxygen species (ROS) and the biologically available antioxidants that prevent or repair damage that ROS inflict on the host cells. ROS are naturally generated during normal mitochondrial respiration and by oxidative burst during the immune response. Many factors may influence OS, including genetics, diet, exercise, and exposure to environmental toxicants (e.g., tobacco smoke). A nonenzymatic peroxidation product of arachidonic acid (AA), 8-iso-PGF2? (8-isoprostane), is a validated biomarker of OS that is present in urine as both glucuronide conjugate and free acid. Previous studies report that the conjugated forms of 8-isoprostane can vary between 30 and 80% of the total 8-isoprostane levels. By hydrolyzing the conjugated forms, it is possible to obtain a total (free + conjugated) measurement of 8-isoprostane in urine samples. Here, we describe a robust, automated, and high-throughput method for measuring total urinary 8-isoprostane using a polymeric weak anion-exchange solid-phase extraction (SPE) and isotope-dilution ultrahigh performance liquid chromatography electrospray ionization-tandem mass spectrometry (UHPLC-MS/MS). This method, using a 96-well plate platform, showed good sensitivity (8.8 pg/mL LOD) and used only 400 ?L of the sample volume with a cycle time of 11 min. The inter- and intraday precision, calculated from 20 repeated measurements of two quality control pools, varied from 4 to 10%. Accuracy, calculated from the recovery percentage at three spiking levels, ranged from 92.7 to 106.7%. We modified this method to allow for the exclusive measurement of free 8-isoprostane by removing the hydrolysis step. We measured both free and total 8-isoprostane in urine collected from 30 cigarette smokers (free: 460 ± 78.8 pg/mL; total: 704 ± 108 pg/mL) and 30 nonusers of tobacco products (free: 110 ± 24.2 pg/mL; total: 161 ± 38.7 pg/mL). This method is robust, accurate, and easily adaptable for large population studies.

Dataset Information

Studies on the analysis of 25-hydroxyvitamin D(3) by isotope-dilution liquid chromatography-tandem mass spectrometry using enzyme-assisted derivatisation.

Publications

Studies on the analysis of 25-hydroxyvitamin D(3) by isotope-dilution liquid chromatography-tandem mass spectrometry using enzyme-assisted derivatisation.

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