title: Linoleic and α-linolenic acid as precursor and inhibitor for the synthesis of long-chain polyunsaturated fatty acids in liver and brain of growing pigs.
abstract: Studies suggested that in human adults, linoleic acid (LA) inhibits the biosynthesis of n-3 long-chain polyunsaturated fatty acids (LC-PUFA), but their effects in growing subjects are largely unknown. We used growing pigs as a model to investigate whether high LA intake affects the conversion of n-3 LC-PUFA by determining fatty acid composition and mRNA levels of Δ5- and Δ6 desaturase and elongase 2 and -5 in liver and brain. In a 2 × 2 factorial arrangement, 32 gilts from eight litters were assigned to one of the four dietary treatments, varying in LA and α-linolenic acid (ALA) intakes. Low ALA and LA intakes were 0.15 and 1.31, and high ALA and LA intakes were 1.48 and 2.65 g/kg BW0.75 per day, respectively. LA intake increased arachidonic acid (ARA) in liver. ALA intake increased eicosapentaenoic acid (EPA) concentrations, but decreased docosahexaenoic acid (DHA) (all P < 0.01) in liver. Competition between the n-3 and n-6 LC-PUFA biosynthetic pathways was evidenced by reductions of ARA (>40%) at high ALA intakes. Concentration of EPA (>35%) and DHA (>20%) was decreased by high LA intake (all P < 0.001). Liver mRNA levels of Δ5- and Δ6 desaturase were increased by LA, and that of elongase 2 by both ALA and LA intakes. In contrast, brain DHA was virtually unaffected by dietary LA and ALA. Generally, dietary LA inhibited the biosynthesis of n-3 LC-PUFA in liver. ALA strongly affects the conversion of both hepatic n-3 and n-6 LC-PUFA. DHA levels in brain were irresponsive to these diets. Apart from Δ6 desaturase, elongase 2 may be a rate-limiting enzyme in the formation of DHA.
authors.affiliation: Department of Animal Sciences, Animal Nutrition Group, Wageningen University, PO Box 338, 6700 AH, Marijkeweg 40, 6709 PG Wageningen, The Netherlands.
authors.forename: W
authors.initials: W
authors.lastname: Smink
authors.forename: W J J
authors.initials: WJ
authors.lastname: Gerrits
authors.forename: M
authors.initials: M
authors.lastname: Gloaguen
authors.forename: A
authors.initials: A
authors.lastname: Ruiter
authors.forename: J
authors.initials: J
authors.lastname: van Baal
mesh_terms: D000123:Acetyltransferases / Q000378:metabolism; D000704:Analysis of Variance; D000818:Animals; D053898:Biosynthetic Pathways / Q000502:physiology*; D001921:Brain / Q000378:metabolism*; D004281:Docosahexaenoic Acids / Q000378:metabolism; D015118:Eicosapentaenoic Acid / Q000378:metabolism; D044943:Fatty Acid Desaturases / Q000378:metabolism; D000081031:Fatty Acid Elongases; D005231:Fatty Acids, Unsaturated / Q000096:biosynthesis*; D019787:Linoleic Acid / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D034421:Sus scrofa / Q000378:metabolism*; D017962:alpha-Linolenic Acid / Q000378:metabolism*
chemical_list: D005231:Fatty Acids, Unsaturated; D017962:alpha-Linolenic Acid; D004281:Docosahexaenoic Acids; D019787:Linoleic Acid; D015118:Eicosapentaenoic Acid; D044943:Fatty Acid Desaturases; D000123:Acetyltransferases; D000081031:Fatty Acid Elongases