Oxidized derivatives of omega-3 fatty acids: identification of IPF3 alpha-VI in human urine.
Isoprostanes (iPs) are prostaglandin-like molecules derived from autoxidation of polyunsaturated fatty acids (PUFAs). Urinary iP levels have been used as indices of in vivo lipid peroxidation. Thus far, it has only been possible to measure iPs derived from arachidonic acid in urine, because levels of iPs/neuroprostanes (nPs) derived from omega 3-PUFAs have been found to be below detection limits of available assays. Because of the interest in omega3-PUFA dietary supplementation, we developed specific methods to measure nPF4 alpha-VI and iPF3 alpha-VI [derived from 4,7,10,13,16,19-docosahexaenoic acid (DHA) and 5,8,11,14,17-eicosapentaenoic acid (EPA)] using a combination of chemical synthesis, gas chromatography/mass spectrometry (GC/MS), and liquid chromatography tandem mass spectrometry (LC/MS/MS). Although nPF4 alpha-VI was below the detection limit of the assay, we conclusively identified iPF3 alpha-VI in human urine by GC/MS and LC/MS/MS. The mean levels in 26 subjects were approximately 300 pg/mg creatinine. Our failure to detect nPF4 alpha-VI may have been due to its rapid metabolism by beta-oxidation to iPF3 alpha-VI, which we showed to occur in rat liver homogenates. In contrast, iPF3 alpha-VI is highly resistant to beta-oxidation in vitro. Thus iPF3 alpha-VI can be formed by two mechanisms: i) direct autoxidation of EPA, and ii) beta-oxidation of nPF4 alpha-VI, formed by autoxidation of DHA. This iP may therefore serve as an excellent marker for the combined in vivo peroxidation of EPA and DHA.
Lawson
John A
JA
Institute for Translational Medicine and Therapeutics and Department of Pharmacology, The University of Pennsylvania, Philadelphia, PA 19104, USA.
Kim
Seongjin
S
Powell
William S
WS
FitzGerald
Garret A
GA
Rokach
Joshua
J
D000818:Animals; D002624:Chemistry, Clinical / Q000379:methods; D005227:Fatty Acids / Q000378:metabolism; D015525:Fatty Acids, Omega-3 / Q000378:metabolism* / Q000652:urine*; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D028421:Isoprostanes / Q000652:urine*; D008099:Liver / Q000378:metabolism; D008297:Male; D008956:Models, Chemical; D010100:Oxygen / Q000737:chemistry / Q000378:metabolism; D051381:Rats; D013997:Time Factors
D005227:Fatty Acids; D015525:Fatty Acids, Omega-3; D028421:Isoprostanes; D010100:Oxygen