Bioequivalence of Dietary α-Linolenic and Docosahexaenoic Acids as Sources of Docosahexaenoate Accretion in Brain and Associated Organs of Neonatal Baboons

Abstract

The dietary bioequivalence of alpha-linolenic (LNA) and docosahexaenoic acids (DHA) as substrates for brain and retinal n-3 fatty acid accretion during the brain growth spurt is reported for neonatal baboons who consumed a long-chain-polyunsaturate free commercial human infant formula with a n-6/n-3 ratio of 10:1. Neonates received oral doses of 13C-labeled fatty acids (LNA*) or (DHA*) at 4 wk of age, and at 6 wk brain (occipital cortex), retina, retinal pigment epithelium, liver, erythrocytes, and plasma were analyzed. In the brain, 1.71% of the preformed DHA* dose was detected, whereas 0.23% of the LNA* dose was detected as DHA*, indicating that preformed DHA is 7-fold more effective than LNA-derived DHA as a source for DHA accretion. In LNA*-dosed animals, DHA* was greater than 60% of labeled fatty acids in all tissues except erythrocytes, where docosapentaenoic acid was 55%. Estimates using dietary LNA levels as tracees indicate that brain turnover of DHA is less than 5% per week between weeks 4 and 6 of life. For retina and retinal pigment epithelium, preformed DHA was at levels 12-fold and 15-fold greater than LNA-derived DHA. Liver, plasma, and erythrocytes ratios were 27, 29, and 51, respectively, showing that these pools do not parallel tissue metabolism of a single dose of omega-3 fatty acids. The distributions of labeled fatty acids for LNA*-dosed animals were similar, in the order DHA > DPA > EPA > LNA, except for erythrocytes where docosapentaenoic acid predominated. These are the first direct measurements of the bioequivalence of DHA and LNA in neonatal primate brain and associated tissues.

Suckling Rats Actively Recycle Carbon from α-Linolenate into Newly Synthesized Lipids Even During Extreme Dietary Deficiency of n-3 Polyunsaturates

“…However, both pathways consume carbon from ␣-linolenate so this comparison does provide a reference point from which the impact of dietary or metabolic manipulation on relative synthesis of docosahexaenoate can be evaluated. The brain has a high requirement for docosahexaenoate but not for other n-3 PUFA, so the fact that 13 C incorporation into lipid products of recycling from ␣-linolenate normally exceeds by several fold ␣-linolenate conversion to docosahexaenoate supports other studies showing that incorporation of preformed (consumed) rather than endogenously synthesized docosahexaenoate is likely to be an important way for the brain to obtain docosahexaenoate (18,19). Why carbon recycling occurs so actively in the suckling period and in the face of high demand for docosahexaenoate is still unclear and will require further investigation.…”

Perinatal biochemistry and physiology of long-chain polyunsaturated fatty acids

“…85 and that fetal baboons can form DHA from an intravenous dose of [U -13 C]-LNA. 86 In the latter studies, approximately 0.6% of the LNA administered was recovered in brain DHA, whereas 4.6% of a dose of DHA was recovered in brain.…”

The influence of dietary docosahexaenoic acid and arachidonic acid on central nervous system polyunsaturated fatty acid composition

“…In a series of studies in primates [14][15][16][21][22][23], we investigated clinically relevant diets to further extend the findings of those studies and establish how CNS composition responds to diet and prematurity in perinatal baboons. We choose the baboon in part because it is an omnivorous primate with lipid metabolism similar to humans.…”