The effects of a diet rich in fish oil on human neutrophils: identification of leukotriene B5 as a metabolite.

Diets that are enriched with fish oil have been shown to alter arachidonic acid metabolism via the cyclooxygenase pathway. Recently it has been shown that one of the major component fatty acids of fish oil, eicosapentaenoate (EPA), is a substrate for the leukotriene B (LTB) pathway when added exogenously to human neutrophils in vitro. We fed a diet that contained 8-10gm/day of EPA to four human subjects for three weeks and compared the arachidonate metabolism of their neutrophils to the same functions while the subjects were on their usual diet. The fish oil-supplementation increased neutrophil EPA content from undetectable levels to 7.4 +/- 2.4% (p less than 0.01, expressed as % of total fatty acid), and decreased arachidonate from 15.4 +/- 2.3% to 12.8 +/- 2.3% (p less than 0.05). Leukotriene B5 was identified as a metabolite during the fish oil-diet by its chromatographic profile and mass spectrum. During the experimental diet LTB4, decreased from 160 +/- 37 ng/10(7) neutrophils to 120 +/- 12 (p less than 0.05), and LTB5 increased from 0 to 39 +/- 9 ng/10(7) neutrophils (p less than 0.005). The diet had no effect on neutrophil aggregation or adherence to nylon fibers.