n the liver transcriptome of both rainbow trout and Atlantic salmon. However, there are few data on the interaction between genotype and dietary fatty acid composition. In this respect, microarrays have great potential for application as hypothesis generating tools. The objective of the present study was to investi gate nutrient genotype interactions in two groups of Atlantic salmon families, Lean and Fat, fed diets where FO was completely replaced by a VO blend. The knowl edge gained concerning how this substitution affects hepatic metabolism and, furthermore, how these effects may depend on the genetic background of the fish, not only informs our understanding of lipid metabolism more generally but is also highly relevant to the strategy of genetic selection for families better adapted to alterna tive and more sustainable feed formulations in the future.

A previous study has already focused on hepatic choles terol and lipoprotein metabolism, which was shown to present a significant diet �� genotype interaction, while here we will present more broadly the effects of the fac tors diet and genotype. Entinostat Results Microarray results Two way ANOVA of the cDNA microarray dataset returned a high number of features showing evidence of differential expression for each factor 713 for diet and 788 for genotype and hence a more detailed analysis was restricted to the top 100 most significant hits for each factor, which were then categorised according to function. The functional category most affected by diet was that of metabolism, while immune response and intracellular trafficking were also affected.

Within lipid metabolism, the affected genes are involved in PUFA, fatty acid and cholesterol biosynthesis, gly cerophospholipid metabolism and acylglycerol homeostasis. Some genes related to carbohydrate metabolism, implicated in glycolysis, glutamine fructose 6 phosphate and glycerol 3 phosphate metabolism, such as alpha enolase, gluta mine fructose 6 phosphate transaminase 1 and glycerol kinase, respectively, were also identified as being significantly affected by diet. Genotype had a lower impact on metabolism related genes and affected mostly genes involved in signalling. Regarding lipid metabolism, pri mary roles of affected genes are in glycerophospholipid metabolism, fatty acid transport and lipoprotein metabolism.

In addi tion, both factors had an effect on a relatively high number of transcription related genes. Detailed lists of the top 100 most significant genes for diet and geno type, organised by biological function and including the normalised expression ratio between treatments, are shown in Tables 1 and 2, respectively. Gene Ontology enrichment analysis, which enables the identification of GO terms significantly enriched in the input entity list when compared to the whole array dataset, was per formed for both factors, providing evidence for which biological processes may be particularly altered in the experimental conditions being compared. For die