The objective of the present study was to identify postprandial molecular events associated with dietary fish oil level in rainbow trout using trout cDNA microarray tools (9 K). Our genomics data showed that relatively few hepatic genes (n=41) are differentially expressed between fish fed a high fat diet compared to those fed a diet without added fish oil. We then focus our analysis of specific events involved in intermediary metabolism by analysing them using qRT-PCR. Removal of fish oil was associated with higher lipid biosynthesis (reflected by the fatty acid synthase gene) and lower lipid catabolism (reflected by the acyl-CoA oxidase gene). More interestingly, some genes involved in proteasomal-dependant proteolysis (proteasome and ubiquitin ligase genes) were down regulated in fish fed without fish oil, suggesting a relationship between dietary lipid intake and regulation of hepatic protein metabolism in rainbow trout. (c) 2008 Elsevier B.V. All rights reserved.