Dietary alpha-linolenic and linoleic acids competitively affect metabolism of polyunsaturated fatty acids in Arctic charr (Salvelinus alpinus).
We investigated the effects of various levels of dietary 18:2(n-6) (linoleic acid) and 18: 3(n-3) (alpha-linolenic acid) on the growth, feeding, body composition and metabolism of polyunsaturated fatty acids in liver and muscle of Arctic charr. Fish were fed 8 or 12 casein-based semipurified diets in two separate experiments for 12 or 14 wk, respectively. Low levels of dietary 18:2(n-6) and 18:3(n-3) supplemented with pure methyl esters or linseed (flax) oil had an additive effect on fish growth. For each 100 g of diet, the addition of 1.6-1.7 g of 18:3(n-3) and 2.6 g of 18:2(n-6) led to significantly lower fish growth compared with the treatment diets with lower amounts of 18:2(n-6). Whereas 18:2(n-6) was converted to 20:4(n-6) and 22: 5(n-6) in the absence or presence of dietary 18: 3(n-3), the dominant product of 18:3(n-3) conversion was consistently 22:6(n-3). High levels of dietary 18: 3(n-3) markedly inhibited the conversion of 18:2(n-6), whereas the inhibition of dietary 18:2(n-6) on 18: 3(n-3) conversion was noted only when the ratio of dietary 18:2(n-6) to 18:3(n-3) changed from 1.0 to 1.5. Feeding diets rich in 18:3(n-3) led to a marked accumulation of 18:3(n-3) and 18:4(n-3) in fish muscle but a negligible change in 20:5(n-3) and 22:6(n-3), regardless of the level of 18:3(n-3) in the diets.
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Department of Zoology, University of Manitoba, Winnipeg, Canada.
Dick
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D000818:Animals; D004041:Dietary Fats / Q000008:administration & dosage* / Q000494:pharmacology; D015525:Fatty Acids, Omega-3 / Q000378:metabolism; D043371:Fatty Acids, Omega-6; D005231:Fatty Acids, Unsaturated / Q000378:metabolism*; D019787:Linoleic Acid; D008041:Linoleic Acids / Q000008:administration & dosage / Q000494:pharmacology*; D008055:Lipids / Q000737:chemistry; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D009132:Muscles / Q000187:drug effects / Q000378:metabolism; D009929:Organ Size / Q000187:drug effects; D014337:Trout / Q000378:metabolism*; D017962:alpha-Linolenic Acid / Q000008:administration & dosage / Q000494:pharmacology*
D004041:Dietary Fats; D015525:Fatty Acids, Omega-3; D043371:Fatty Acids, Omega-6; D005231:Fatty Acids, Unsaturated; D008041:Linoleic Acids; D008055:Lipids; D017962:alpha-Linolenic Acid; D019787:Linoleic Acid