Identification and profiling of targeted oxidized linoleic acid metabolites in rat plasma by quadrupole time-of-flight mass spectrometry

Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bethesda, MD, USA. .
Biomedical Chromatography (Impact Factor: 1.72). 04/2013; 27(4). DOI: 10.1002/bmc.2809
Source: PubMed


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.

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Available from: Ameer Taha, Oct 01, 2015
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    • "Likewise, 12/15-LOX-1 can oxidise the n-6 LA into 9-hydroperoxy-10E,12Z-octadecadienoic acid (9-HPODE) and 13S-hydroperoxy-9Z,11E-octadecadienoic acid (13-HPODE)( 61 ). Hydroperoxides can then be reduced to form hydroxyl intermediates (HETE and hydroxy-octadecadienoic acid (HODE)) and further dehydrogenated to form ketone intermediates (oxo-eicosatetraenoic acid (oxoETE) and oxo-octadecadienoic acid (oxoODE))( 62 ). n-3 Fatty acids also can be oxidised by COX and LOX to produce eicosanoids with more anti-inflammatory or resolving properties( 52 ). "
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