title: Identification and profiling of targeted oxidized linoleic acid metabolites in rat plasma by quadrupole time-of-flight mass spectrometry.
abstract: Linoleic acid (LA) and LA-esters are the precursors of LA hydroperoxides, which are readily converted to 9- and 13-hydroxy-​octadecadienoic acid (HODE) and 9- and 13-oxo-​octadecadienoic acid (oxo ODE) metabolites in vivo. These four oxidized LA metabolites (OXLAMs) have been implicated in a variety of pathological conditions. Therefore, their accurate measurement may provide mechanistic insights into disease pathogenesis. Here we present a novel quadrupole time-of-flight mass spectrometry (Q-TOFMS) method for quantitation and identification of target OXLAMs in rat plasma. In this method, the esterified OXLAMs were base-hydrolyzed and followed by liquid-liquid extraction. Quantitative analyses were based on one-point standard addition with isotope dilution. The Q-TOFMS data of target metabolites were acquired and multiple reaction monitoring extracted-ion chromatograms were generated post-acquisition with a 10 ppm extraction window. The limit of quantitation was 9.7-35.9 nmol/L depending on the metabolite. The method was reproducible with a coefficient of variation of <18.5%. Mean concentrations of target metabolites in rat plasma were 57.8, 123.2, 218.1 and 57.8 nmol/L for 9-HODE, 13-HODE, 9-oxoODE and 13-oxoODE, respectively. Plasma levels of total OXLAMs were 456.9 nmol/L, which correlated well with published concentrations obtained by gas chromatography/mass spectrometry (GC/MS). The concentrations were also obtained utilizing a standard addition curve approach. The calibration curves were linear with correlation coefficients of >0.991. Concentrations of 9-HODE, 13-HODE, 9-oxoODE and 13-oxoODE were 84.0, 138.6, 263.0 and 69.5 nmol/L, respectively, which were consistent with the results obtained from one-point standard addition. Target metabolites were simultaneously characterized based on the accurate Q-TOFMS data. This is the first study of secondary LA metabolites using Q-TOFMS. Published 2012. This article is a U.S. Government work and is in the public domain in the USA.
authors.affiliation: Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Zhi-Xin
authors.initials: ZX
authors.lastname: Yuan
authors.forename: Stanley I
authors.initials: SI
authors.lastname: Rapoport
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Soldin
authors.forename: Alan T
authors.initials: AT
authors.lastname: Remaley
authors.forename: Ameer Y
authors.initials: AY
authors.lastname: Taha
authors.forename: Matthew
authors.initials: M
authors.lastname: Kellom
authors.forename: Jianghong
authors.initials: J
authors.lastname: Gu
authors.forename: Maureen
authors.initials: M
authors.lastname: Sampson
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Ramsden
mesh_terms: D000818:Animals; D002853:Chromatography, Liquid / Q000379:methods; D057230:Limit of Detection; D008041:Linoleic Acids / Q000097:blood*; D044243:Linoleic Acids, Conjugated / Q000097:blood*; D008042:Linolenic Acids / Q000097:blood*; D051381:Rats; D015203:Reproducibility of Results; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D008041:Linoleic Acids; D044243:Linoleic Acids, Conjugated; D008042:Linolenic Acids; C024347:9-hydroxy-10,12-octadecadienoic acid; C064441:13-oxo-9,11-octadecadienoic acid; C024348:13-hydroxy-9,11-octadecadienoic acid; C062143:9-oxo-10,12-octadecadienoic acid