Metabolism of dietary alpha-linolenic acid vs. eicosapentaenoic acid in rat immune cell phospholipids during endotoxemia

Short-term (i.e., 3 d) continuous enteral feeding of diets containing eicos apentaenoic (EPA) and gamma-linolenic (CLA) polyunsaturated fatty acids (PU FA) to endotoxemic rats reduces the levels of arachidonic acid (AA) and lin oleic acid (LA) in alveolar macrophage (AM) and liver Kupffer and endotheli al (K&E) cell phospholipids with attendant decreases in prostaglandin forma tion by these cells in vitro. Diets that contain alpha-linolenic acid (LNA) as a substrate for endogenous formation of EPA may not be as effective in facilitating these immune cell modifications given the limited activity of Delta 6 desaturase. in the present study we compared the effectiveness of a n LNA-enriched diet vs. an (EPA + CLA)-enriched diet to displace phospholip id AA from AM and liver K&E cells in vivo in endotoxemic rats fed enterally for 3 or 6 d. We determined the fatty acid composition of AM and K&E cell phospholipids by gas chromatography. We found that AM and K&E cells from ra ts that had received the EPA + GLA diet for 3 d had significantly (P < 0.00 1) higher mole percentage of EPA and the CLA metabolite, dihomoGLA, than co rresponding cells from rats given the LNA diet or a control diet enriched w ith LA. Rats given the LNA diet had relatively low levels of stearidonic ac id, EPA and other n-3 PUFA, while rats given the LA diet had low revels of GLA and dihomoGLA. We conclude that diets enriched with LNA or LA may not b e as effective as those enriched with EPA + GLA for purposes of fostering i ncorporation of EPA or dihomoCLA into and displacement of AA from macrophag e phospholipids under pathophysiologic conditions commonly found in acutely septic patients.