Effect of dietary docosaheaxenoic acid on the net accumulation of docosaheaxenoic acid biosynthesized from alpha-linolenic acid in organs of young rat

James C. DeMar . Jr, Carmine DiMartino, Adam W. Baca, William Lefkowitz, and Norman Salem . Jr

Lab Membrane Biochemistry & Biophysics, NIAAA, NIH, Bethesda, MD 20892-9410

Corresponding Author: nsalem{at}martek.com

Docosahexaenoic acid (DHA), a long chain n-3 polyunsaturated fatty acid important for nervous system function, may be obtained directly from the diet or synthesized in vivo from dietary alpha-linolenic acid (LNA). We addressed whether the synthesis of DHA is regulated by the availability of dietary DHA in artificially reared rat pups, during development from p8 to p28. One group of rat pups was continuously fed deuterium-labeled LNA (d5-LNA) as the only source of n-3 PUFA (d5-LNA diet) and a second both d5-LNA and unlabeled DHA (d5-LNA + DHA diet). The rat pups were sacrificed after feeding these diets for the 20 d growth period and the total amount of d5-DHA (newly synthesized DHA) as well as other n-3 fatty acid intermediates present in various tissues comprising the whole body was quantified. In the d5-LNA+ DHA group, the presence of dietary DHA led to a marked decrease (3-5 fold) in the total amount of d5-DHA that accumulated in brain, bone, digestive tract, heart, kidney, liver, lung, skeletal muscle, plasma, retina, skin, spleen, and testes, but not in adipose. Overall, DHA accretion from d5-DHA was generally diminished by the dietary availability of preformed DHA, as preformed DHA was found to be the predominant source of tissue DHA. When preformed DHA was unavailable, d5-DHA and unlabeled DHA were preferentially accreted in some tissues along with a net loss of unlabeled DHA from other organs during the course of this 20 d long feeding study.

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