Essential fatty acids and lipid mediators

Abstract

Linoleic and α-linolenic acids are nutritionally essential and therefore called as essential fatty acids. In mammalian tissues, linoleic acid (18:2, ω6) can be converted to other ω6 polyunsaturated fatty acids (PUFAs) such as arachidonic acid (AA) (20:4), while α-linolenic acid (18:3, ω3) to other ω3 PUFAs such as eicosapentaenoic acid (20:5) and docosahexaenoic acid (22:6). One of the most important roles of these PUFAs is to serve as precursors of lipid mediators, which exert physiological actions through specific G protein-coupled receptors or nuclear receptors. Eicosanoids and endocannabinoids are two representative classes of lipid mediators metabolically related to AA. Eicosanoids include prostaglandins, thromboxanes, and leukotrienes, all of which are formed from AA by oxygenases like cyclooxygenase and 5-lipoxygenase, while endocannabinoids, which function as endogenous ligands of cannabinoid receptors, are the glyceryl ester or ethanolamide of AA (2-arachidonoylglycerol and anandamide, respectively). In this article, I will outline the progress in the studies on the metabolism and biological effects of eicosanoids and endocannabinoids during the past thirty years.