title: Nitro-fatty acids occur in human plasma in the picomolar range: a targeted nitro-lipidomics GC-MS/MS study.
abstract: First studies on the occurrence of nitrated fatty acids in plasma of healthy subjects revealed basal concentrations of 600 nM for free/nonesterified nitro-oleic acid (NO(2)-OA) as measured by liquid chromatography tandem mass spectrometry (LC-MS/MS). We recently showed by a gas chromatography tandem mass spectrometry (GC-MS/MS) method the physiological occurrence of two isomers, i.e., 9-NO(2)-OA and 10-NO(2)-OA, at mean basal plasma concentrations of 880 and 940 pM, respectively. In consideration of this large discrepancy we modified our originally reported method by replacing solid-phase extraction (SPE) by solvent extraction with ethyl acetate and by omitting the high-performance liquid chromatography (HPLC) step for a more direct detection and with the potential for lipidomics studies. Intra-assay imprecision and accuracy of the modified method in human plasma were 1-34% and 91-221%, respectively, for added NO(2)-OA concentrations in the range 0-3,000 pM. This method provided basal plasma concentrations of 306 +/- 44 pM for 9-NO(2)-OA and 316 +/- 33 pM for 10-NO(2)-OA in 15 healthy subjects. Nitro-arachidonic acid and nitro-linolenic acid were not detectable in the plasma samples. In summary, our studies show 9-NO(2)-OA and 10-NO(2)-OA as endogenous nitrated fatty acids in human plasma in the pM range; HPLC is recommendable as a sample clean-up step for reliable quantification of nitro-oleic acids by GC-MS/MS.
authors.affiliation: Institute of Clinical Pharmacology, Hannover Medical School, Carl-Neuberg-Strasse 1, 30625, Hannover, Germany. tsikas.dimitros@mh-hannover.de
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Tsikas
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Zoerner
authors.forename: Anja
authors.initials: A
authors.lastname: Mitschke
authors.forename: Frank-Mathias
authors.initials: FM
authors.lastname: Gutzki
mesh_terms: D005227:Fatty Acids / Q000097:blood*; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D006801:Humans; D009574:Nitro Compounds / Q000097:blood*; D012680:Sensitivity and Specificity; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D005227:Fatty Acids; D009574:Nitro Compounds
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