Gamma-linolenoyl-CoA (6,9,12-20:3(n-6)) is rapidly elongated to dihomo-gamma-linolenoyl-CoA (DGL-CoA; 8,11,14-20:3(n-6)) by the action of C18-PUFA-specific elongase 5 (ELOVL5). Two carbon atoms are added during this reaction. DGL-CoA later undergoes desaturation to form arachidonic acid (AA, 5,8,11,14-20:4(n-6)).
Depending on the cell type, DGL-CoA can also be metabolized by cyclooxygenases and lipoxygenases to produce anti-inflammatory eicosanoids (prostaglandins of series 1 (PGE1) and 15-hydroxyeico- satrienoic acid (15-HETrE)). GLA and these two oxidative metabolites exert clinical effects in a variety of diseases, including suppression of chronic inflammation, vasodilation and lowering of blood pressure, inhibition of platelet aggregation and thrombosis. (Fan et al. 2001, Fan & Chapkin 1998, Kapoor & Huang. 2006)