Effects of gamma-linolenic acid and docosahexaenoic acid in formulae on brain fatty acid composition in artificially reared rats

This study evaluated the effects of dietary supplementation with gamma-lino lenic acid (GLA, 18:3n-6) and docosahexaenoic acid (DHA, 22:6n-3) on the fa tty acid composition of the neonatal brain in gastrostomized rat pups reare d artificially from days 5-18. These pups were fed rat milk substitutes con taining fats that provided 10% linoleic acid and 1% a linolenic acid (% fat ty acids) and, using a 2 x 3 factorial design, one of two levels of DHA (0. 5 and 2.5%), and one of three levels of GLA (0.5, 1.0, and 3.0%). A seventh artificially reared group served as a reference group and was fed 0.5% DHA and 0.5% arachidonic acid (AA, 20:4n-6); these levels are within the range of those found in rat milk. The eighth group, the suckled control group, w as reared by nursing dams fed a standard American Institute of Nutrition 93 M chow. The fatty acid composition of the phosphatidylethanolamine, phospha tidylcholine, and phosphatidylserine/phosphatidylinositol membrane fraction s of the forebrain on day 18 reflected the dietary composition in that high levels of dietary DHA resulted in increases in DHA but decreases in 22:4n- 6 and 22:5n-6 in brain. High levels of GLA increased 22:4n-6 but, in contra st to previous findings with high levels of AA, did not decrease levels of DHA. These results suggest that dietary CLA, during development, differs fr om high dietary levels of AA in that it does not lead to reductions in brai n DHA.