期刊
LIPIDS
卷 49, 期 6, 页码 591-595出版社
WILEY
DOI: 10.1007/s11745-014-3902-y
关键词
Polyunsaturated fatty acid; Retroconversion; Docosapentaenoic acid (22:5n-6); Arachidonic acid
资金
- Valle international exchange program
- National Science Foundation [0642834]
- Academy of Finland [139786]
- Academy of Finland (AKA) [139786, 139786] Funding Source: Academy of Finland (AKA)
- Division Of Environmental Biology
- Direct For Biological Sciences [0642834] Funding Source: National Science Foundation
The aim of this study was to assess metabolic pathways for arachidonic acid (20:4n-6) biosynthesis in Daphnia magna. Neonates of D. magna were maintained on [C-13] enriched Scenedesmus obliquus and supplemented with liposomes that contained separate treatments of unlabeled docosapentaenoic acid (22:5n-6), 20:4n-6, linoleic acid (18:2n-6) or oleic acid (18:1n-9). Daphnia in the control treatment, without any supplementary fatty acids (FA) containing only trace amounts of 20:4n-6 (similar to 0.3 % of all FA). As expected, the highest proportion of 20:4n-6 (similar to 6.3 %) was detected in Daphnia that received liposomes supplemented with this FA. Higher availability of 18:2n-6 in the diet increased the proportion of 18:2n-6 in Daphnia, but the proportion of 20:4n-6 was not affected. Daphnia supplemented with 22:5n-6 contained similar to 3.5 % 20:4n-6 in the lipids and FA specific stable isotope analyses validated that the increase in the proportion of 20:4n-6 was due to retroconversion of unlabeled 22:5n-6. These results suggest that chain shortening of 22:5n-6 is a more efficient pathway to synthesize 20:4n-6 in D. magna than elongation and desaturation of 18:2n-6. These results may at least partially explain the discrepancies noticed between phytoplankton FA composition and the expected FA composition in freshwater cladocerans. Finally, retroconversion of dietary 22:5n-6 to 20:4n-6 indicates Daphnia efficiently retain long chain n-6 FA in lake food webs, which might be important for the nutritional ecology of fish.
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