Eicosapentaenoic acid eicosanoid metabolites

Fig. 1. The n-3/n-6 metabolic pathways. Precursors of the n-3 (18 3n-3, linolenic acid) and n-6 (18 2n-6, (/.-linoleic acid) are converted by a series of desaturation and (adding double bonds) and elongation (adding carbon atoms to the hydrocarbon backbone) reactions. Note that the same enzymes catalyze n-3 and n-6 desaturation and elongation reactions. Major metabolites are indicated. PUFAs with 20-carbon backbones (20 4n-6, arachidonic acid, and 20 5n-3, eicosapentaenoic acid) are precursors to the eicosanoids (prostaglandins, leukotrienes, thromboxanes). Docosahexaenoic acid (22 6n-3) is also indicated. Note that only a limited part of the metabolic pathway is shown in this figure.

In summary, eicosapentaenoic and docosahexaenoic acid competitively inhibit the utilization of arachidonic acid by the PGH synthase [25,81] and consequently decrease the available amount of metabolites of arachidonic acid, thus promoting the synthesis of biologically less active eicosanoids from eicosapentaenoic acid [29, 67, 81, 113]. 

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