Maintenance of Arachidonic Acid and Evidence of Δ5 Desaturation in Cats Fed γ-Linolenic and Linoleic Acid Enriched Diets

Cats have limited Delta 6 desaturase activity. However, gamma-linolenate (GLA) feeding may by-pass the Delta 6 desaturase step allowing arachidonate (ARA) accumulation via Delta 5-desaturation. Alternatively, high dietary linoleate (LNA) may induce limited Delta 6 desaturase also resulting in ARA accumulation. Fatty acid profiles were determined after feeding high LNA, high GLA, or adequate LNA diets. Adult female cats (n = 29) were assigned to one of three groups and fed for 8 weeks. Plasma samples were collected at weeks 0, 2, 4 and 8 for plasma triacylglycerol (TAG), total cholesterol (TC), lipoprotein (LP), and plasma and red blood cell membrane phospholipid fatty acid determinations. Time, but no diet, effects were observed for TAG, TC, and LP fractions at weeks 2 and 4 with significant increases likely due to increased dietary fat. However, all values were within feline normal limits. The GLA diet resulted in increased dihomo-gamma-linolenic acid (DGLA) and ARA as early as week 2, supporting a a dagger 5 desaturase. Further evidence of Delta 5 desaturase was found at high dietary LNA with the appearance of a novel fatty acid, 20:3 a dagger 7, 11, 14, apparently formed via a dagger 5 desaturation and chain elongation of LNA. However, Delta 6 desaturase induction at high dietary LNA concentration was not observed. Cats are able to maintain plasma and red blood cell ARA when fed a practical diet containing GLA using what appears to be an active Delta 5 desaturase enzyme.