Heritability and mechanisms of n-3 long chain polyunsaturated fatty acid deposition in the flesh of Atlantic salmon

Abstract

N-3 long chain polyunsaturated fatty acids (n-3LC-PUFA) are essential components of vertebrate membrane lipids and are crucially deficient in modern Western diets. The main human dietary source for n-3LC-PUFA is fish and seafood, particularly oily fish and over 50% of global fish production is currently supplied by aquaculture. However, increasing pressure to include vegetable oils, which are devoid of n-3LC-PUFA, in aquaculture feeds reduces the content of these crucial nutrients in farmed fish flesh. The aim of this study was to measure the heritability and infer mechanisms determining flesh n-3LC-PUFA content in Atlantic salmon. This was achieved by analysing flesh lipid parameters in 48 families of Atlantic salmon, and by measuring differences in hepatic mRNA expression in families with high and low flesh n-3LC-PUFA. The results show that flesh n-3LC-PUFA level is a highly heritable trait (h2 = 0.77±0.14) and indicate the involvement of increased lipid transport, most likely in the form of very low density lipoprotein (VLDL) from liver. This increase in lipid transport may be associated with increased activity of a transcription factor, hepatic nuclear factor 4α (HNF4α), possibly as a result of family differences in transforming growth factor β1 (Tgfβ1) signalling. This study paves the way for identification of quantitative trait loci and gene interaction networks that are associated with levels of n-3LC-PUFA in fish flesh. Such markers can be used to assist the sustainable production of Atlantic salmon and provide optimal levels of critical nutrients for human consumers.