α‐Linolenic acid does not contribute appreciably to docosahexaenoic acid within brain phospholipids of adult rats fed a diet enriched in docosahexaenoic acid

Abstract

Adult male unanesthetized rats, reared on a diet enriched in both a-linolenic acid (a-LNA) and docosahexaenoic acid (DHA), were infused intravenously for 5 min with [1-14 C]a-LNA. Timed arterial samples were collected until the animals were killed at 5 min and the brain was removed after microwaving. Plasma and brain lipid concentrations and radioactivities were measured. Within plasma lipids, > 99% of radioactivity was in the form of unchanged [1-14 C]a-LNA.Eighty-six per cent of brain radioactivity at 5 min was present as b-oxidation products, whereas the remainder was mainly in 'stable' phospholipid or triglyceride as a-LNA or DHA.Equations derived from kinetic modeling demonstrated that unesterified unlabeled a-LNA rapidly enters brain from plasma, but that its incorporation into brain phospholipid and triglyceride, as in the form of synthesized DHA, is £ 0.2% of the amount that enters the brain. Thus, in rats fed a diet containing large amounts of both a-LNA and DHA, the a-LNA that enters brain from plasma largely undergoes b-oxidation, and is not an appreciable source of DHA within brain phospholipids.

RETRACTED ARTICLE: Aging decreases rate of docosahexaenoic acid synthesis-secretion from circulating unesterified α-linolenic acid by rat liver

“…Fischer-344 (CDF) male rats aged 10, 20, and 30 months were obtained from rodent colonies at the National Institute on Aging (Bethesda, MD) and were maintained on an NIH-31 diet. The diet contained soybean oil and fishmeal and had 4% by weight crude fat (Demar et al 2005). As reported, saturated and monounsaturated fatty acids contributed 20.1% and 22.5%, respectively, to its total fatty acid content.…”

“…Although this study focused on n-3 PUFA kinetics and concentrations, future studies should test the effects of aging on n-6 PUFA liver kinetics. Rates of incorporation of unesterified circulating DHA and AA into brain reflect their respective rates of loss from brain due to metabolism, as the shorter chain PUFAs that enter brain largely undergo rapid oxidation (Demar et al 2005;DeMar et al 2006;Chen et al 2009;Chen et al 2011). As biomarkers of brain PUFA integrity, unesterified plasma DHA and AA concentrations may be more informative than the respective esterified concentrations (Kuriki et al 2003;Rapoport et al 2011).…”

“…DHA may be obtained directly from dietary sources, such as fish or fish products, or it can be synthesized from its nutritionally essential plant-derived precursor, α-linolenic acid (18:3n-3, α-LNA), through a series of elongation and desaturation steps (Sprecher 2000). The major site of DHA synthesis is the liver, whereas brain or heart synthesis is much less (Scott and Bazan 1989;Demar et al 2005;Igarashi et al 2007;Igarashi et al 2008;Rapoport et al 2010).…”

“…The brain obtains DHA directly from the plasma unesterified fatty acid pool, which is maintained in part by hydrolysis of circulating esterified fatty acids synthesized and secreted by the liver, and by adipose triglyceride lipolysis (Demar et al 2005;Gavino and Gavino 1992;Chen et al 2008;Rahman et al 2010a;Song et al 2010;Gao et al 2011). Newly synthesized DHA in liver is secreted into the plasma in triglyceride and phospholipid-rich lipoproteins, which can undergo lipolysis by a DHA-selective endothelial lipase (Chen and Subbaiah 2007).…”

Docosahexaenoic acid is a beneficial replacement treatment for spinocerebellar ataxia 38

“…The endogenous synthesis of DHA within the brain is low compared with its uptake from dietary and/or liver sources 15, 16. DHA is a well‐known dietary supplement, well tolerated at high dosage and with the ability to cross the blood–brain barrier by passive and active transport 17, 18, 19…”