MARKED ENRICHMENT OF THE ALKENYLACYL SUBCLASS OF PLASMA ETHANOLAMINE GLYCEROPHOSPHOLIPID WITH EICOSAPENTAENOIC ACID IN HUMAN-SUBJECTS CONSUMING A FISH-OIL CONCENTRATE

Alteration in human platelet fatty acid levels with the consumption of fish oils containing eicosapentaenoic acid (EPA, 20:5n-3) and docosah exaenoic acid (DHA, 22:6n-3) have been well documented, but changes in the fatty acid composition of plasma plasmalogenic phospholipid under similar circumstances have not been delineated. In the present study, subjects consumed the fish oil concentrate (MaxEPA) for 6 wk followed immediately by a 6-wk recovery period with no fish oil ingestion. Pla sma total choline glycerophospholipid (GPC) and ethanolamine glyceroph ospholipid (GPE) subclasses isolated from blood samples obtained at 0, 3, 6, 9 and 12 wk of the experimental period were analyzed for fatty acid composition via thin-layer and gas-liquid chromatographic techniq ues. Consumption of fish oil for 3 or 6 wk significantly elevated the content of n-3 fatty acids while concomitantly decreasing n-6 fatty ac id levels in plasma total GPC and in diacyl and alkenylacyl (plasmalog en) GPE. Alkenylacyl GPE exhibited the greatest alteration of both n-3 and n-6 fatty acid levels. Following 6 wk of supplementation with fis h oil, EPA rose by 24.6 mol% in alkenylacyl GPE compared to increases of 6.7 and 7.1 mol% in diacyl GPE and total GPC, respectively. The inc rease in EPA (from 5.0 to 29.6 mol%) in plasma alkenylacyl GPE represe nts amongst the highest enrichment of EPA in any lipid yet reported in human subjects. DHA also rose by 8.0, 4.8, and 3.1 mol% in alkenylacy l GPE, diacyl GPE, and total GPC, respectively. Alkenylacyl GPE exhibi ted the greatest mol% decline (by 18.7 mol%) in arachidonic acid (AA, 20:4n-6) following 6 wk of fish oil supplementation. The corresponding decreases of AA in diacyl GPE and total GPC were 8.7 and 1.8 mol%, re spectively Following the 6 wk recovery period, n-3 and n-6 fatty acid levels had returned to pre-supplementation values. The marked enrichme nt of alkenylacyl GPE in n-3 fatty acids, especially EPA, may be of si gnificance with respect to a unique role for this plasma phospholipid subclass in attenuating certain lipoprotein-mediated cardiovascular ef fects as observed with fish/fish oil consumption.