出版社：American Society for Biochemistry and Molecular Biology
摘要：Rates of conversion of -linolenic acid (-LNA, 18:3n-3) to docosahexaenoicacid (DHA, 22:6n-3) by the mammalian brain and the brain's abilityto upregulate these rates during dietary deprivation of n-3polyunsaturated fatty acids (PUFAs) are unknown. To answer thesequestions, we measured conversion coefficients and rates inpost-weaning rats fed an n-3 PUFA deficient (0.2% -LNA of totalfatty acids, no DHA) or adequate (4.6% -LNA, no DHA) diet for15 weeks. Unanesthetized rats in each group were infused intravenouslywith [1-14C]-LNA, and their arterial plasma and microwaved brainscollected at 5 minutes were analyzed. The deficient comparedwith adequate diet reduced brain DHA by 37% and increased brainarachidonic (20:4n-6) and docosapentaenoic (22:5n-6) acids.Only 1% of plasma [1-14C]-LNA entering brain was converted toDHA with the adequate diet, and conversion coefficients of -LNAto DHA were unchanged by the deficient diet. In summary, thebrain's ability to synthesize DHA from -LNA is very low andis not altered by n-3 PUFA deprivation. Because the liver'sreported ability is much higher, and can be upregulated by thedeficient diet, DHA converted by the liver from circulatingLNA is the source of the brain's DHA when DHA is not in thediet.Supplementary key words n-3 polyunsaturated fatty acid • diet • elongation • fatty acid • synthesis
Abbreviations: AA, arachidonic acid; DHA, docosahexaenoic acid; DPA, docosapentaenoic acid; EPA, eicosapentaenoic acid; FAME, fatty acid methyl ester; LA, linoleic acid; -LNA, -linolenic acid
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