title: Upregulated liver conversion of alpha-linolenic acid to docosahexaenoic acid in rats on a 15 week n-3 PUFA-deficient diet.
abstract: We quantified incorporation rates of plasma-derived alpha-linolenic acid (alpha-LNA, 18:3n-3) into "stable" liver lipids and the conversion rate of alpha-LNA to docosahexaenoic acid (DHA, 22:6n-3) in male rats fed, after weaning, an n-3 PUFA-adequate diet (4.6% alpha-LNA, no DHA) or an n-3 PUFA-deficient diet (0.2% alpha-LNA, no DHA) for 15 weeks. Unanesthetized rats were infused intravenously with [1-14C]alpha-LNA, and arterial plasma was sampled until the liver was microwaved at 5 min. Unlabeled alpha-LNA and DHA concentrations in arterial plasma and liver were reduced >90% by deprivation, whereas unlabeled arachidonic acid (20:4n-6) and docosapentaenoic acid (22:5n-6) concentrations were increased. Deprivation did not change alpha-LNA incorporation coefficients into stable liver lipids but increased synthesis-incorporation coefficients of DHA from alpha-LNA by 6.6-, 8.4-, and 2.3-fold in triacylglycerol, phospholipid, and cholesteryl ester, respectively. Assuming that synthesized-incorporated DHA eventually would be secreted within lipoproteins, calculated liver DHA secretion rates equaled 2.19 and 0.82 micromol/day in the n-3 PUFA-adequate and -deprived rats, respectively. These rates exceed the published rates of brain DHA consumption by 6- and 10-fold, respectively, and should be sufficient to maintain normal and reduced brain DHA concentrations, respectively, in the two dietary conditions.
authors.affiliation: Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bethesda, MD 20892, USA. mikii@mail.nih.gov
authors.forename: Miki
authors.initials: M
authors.lastname: Igarashi
authors.forename: James C
authors.initials: JC
authors.lastname: DeMar
authors.forename: Kaizong
authors.initials: K
authors.lastname: Ma
authors.forename: Lisa
authors.initials: L
authors.lastname: Chang
authors.forename: Jane M
authors.initials: JM
authors.lastname: Bell
authors.forename: Stanley I
authors.initials: SI
authors.lastname: Rapoport
mesh_terms: D000818:Animals; D001711:Biotransformation; D004281:Docosahexaenoic Acids / Q000378:metabolism*; D005231:Fatty Acids, Unsaturated / Q000172:deficiency* / Q000494:pharmacology; D008099:Liver / Q000378:metabolism*; D008297:Male; D023421:Models, Animal; D051381:Rats; D017962:alpha-Linolenic Acid / Q000378:metabolism*
chemical_list: D005231:Fatty Acids, Unsaturated; D017962:alpha-Linolenic Acid; D004281:Docosahexaenoic Acids