Fatty acid utilisation and metabolism in caecal enterocytes of rainbow trout (Oncorhynchus mykiss) fed dietary fish or copepod oil

Abstract

A combined fatty acid metabolism assay was employed to determine fatty acid uptake and relative utilisation in enterocytes isolated from the pyloric caeca of rainbow trout. In addition, the effect of a diet high in long-chain monoenoic fatty alcohols present as wax esters in oil derived from Calanus finmarchicus, compared to a standard fish oil diet, on caecal enterocyte fatty acid metabolism was investigated. The diets were fed for 8 weeks before caecal enterocytes from each dietary group were isolated and incubated with [1-14 C]fatty acids: 0, 18:1n-9, 18:2n-6, 18:3n-3, 20:1n-9, 20:4n-6, 20:5n-3, and 22:6n-3 Recovery of labelled 18:1n-9 in exported TAG was 3-fold greater than any other fatty acid which could be due to multiple esterification on the glycerol 'backbone' and/or increased export. Approximately 20-40% of fatty acids taken up were β-oxidised, and was highest with 20:4n-6. Oxidation of 20:5n-3 and 22:6n-3 was also surprisingly high, although 22:6n-3 oxidation was mainly attributed to retroconversion to 20:5n-3. Metabolic modification of fatty acids by elongation-desaturation was generally low at <10% of [1-14 C]fatty acid uptake.Dietary copepod oil had generally little effect on fatty acid metabolism in enterocytes, 3 although it stimulated the elongation and desaturation of 16:0 and elongation of 18:1n-9, with radioactivity recovered in longer n-9 monoenes. The monoenoic fatty acid, 20:1n-9, abundant in copepod oil as the homologous alcohol, was poorly utilised with 80% of uptake remaining unesterified in the enterocyte. However, the fatty acid composition of pyloric caeca was not influenced by dietary copepod oil.4

Localization of Fatty Acids with Selective Chain Length by Imaging Time‐of‐Flight Secondary Ion Mass Spectrometry

“…This is supported by a study on fatty acid uptake by caecal enterocytes, which showed that esterification into cellular lipids was seen highest in 16:0 and C18 fatty acids. The overall utilization of fatty acids in phospholipid synthesis was seen low, but highest with 16:0 (Oxley et al, 2005). Dietary essential fatty acids have been shown to be important in mucosal defense and restitution.…”

Nutritional and environmental regulation of the synthesis of highly unsaturated fatty acids and of fatty-acid oxidation in Atlantic salmon (Salmo salar L.) enterocytes and hepatocytes

“…With the importance of lipid as an energy source in most fish species, particularly salmonids and marine fish, there have been several studies on fatty acid oxidation in fish (Crockett and Sidell 1993;Kiessling and Kiessling 1993;Frøyland et al 1998Frøyland et al , 2000Fjermestad et al 2000;Torstensen et al 2000;Nanton et al 2003;Vegusdal et al 2004;Oxley et al 2005;Stubhaug et al 2005aStubhaug et al ,b,c, 2006.…”

“…This is based on studies measuring β-oxidation capacity using subcellular fractions, in which long-chain monenes were preferred over PUFA as substrates in fish (Henderson and Sargent 1985;Kiessling and Kiessling 1993;Henderson 1996;Frøyland et al 2000). However, recent intact cell studies, which measure relative fates of fatty acids taken up by the cells, have suggested that PUFA can be relatively more oxidized than 18:1n-9 in salmonid hepatocytes or enterocytes (Oxley et al 2005;Stubhaug et al 2005c). In contrast, in the trial with salmon postsmolts mentioned above, there was a tendency for β-oxidation in liver in salmon fed VOs to be higher than in fish fed FO in the autumn after transfer, but by the following spring there was no difference in β-oxidation capacity in liver between fish fed FO or VO (Stubhaug et al 2005a).…”

Fish oil replacement in finfish nutrition

“…The lipid and fatty acid composition of the intestinal cells can be significantly modified by the dietary lipid and fatty acid composition (Caballero et al. 2003; Oxley et al. 2005a; Ruyter et al.…”