Fatty acid metabolism in isolated enterocytes from salmonid fish.

Abstract

Considering the results found, through in vivo experimentation, that intestine of trout and specifically pyloric caeca was an important site of metabolic activity (Bell et al., 2003c), it was contemplated to begin with a research project to demonstrate and establish the rate in which n-3 HUFA are synthesised by intestinal cells using in vitro assays. The aim of the research work was to determine the importance of intestine and caecal enterocytes in fatty acid metabolism in salmonids, focusing on their potential role in HUFA synthesis and the effects of replacement of fish oil (FO) with vegetable oils (VO) in the diets. The results of the investigation gave answer to the most important questions about intestinal metabolism of fatty acids and brought suggestions for future research work. A simple method for the isolation of viable enterocytes from salmonids suitable for use in both laboratory and fish farm conditions was established, and a method to analyse desaturation/elongation and P-oxidation activities in a single combined assay was developed. Pyloric caeca enterocytes were found to be more active than other intestinal tissues tested in terms of HUFA synthesis capacity and they were used for the evaluation of the following dietary trials. The performance of the HUFA synthesis assay in the enterocyte preparations was determined under a variety of parameters to standardize an assay protocol for use in all comparative studies. Regarding the effect of replacing FO with VO in diets for salmonids on fatty acid metabolism in enterocytes it was found that VO (a blend) can be good substitute for FO and can be use by the salmon industry without compromising the standard of quality of the product. Caecal enterocytes were not more active than hepatocytes and, irrespective of the diet, the primary fate of the substrate was P-oxidation rather than HUFA synthesis. HUFA synthesis in enterocytes and hepatocytes, increased in fish fed VO compared to fish fed FO and fish fed VO increased fatty acid oxidation activity in enterocytes whereas there was no dietary effect in hepatocytes.