title: Genotype-specific responses in Atlantic salmon (Salmo salar) subject to dietary fish oil replacement by vegetable oil: a liver transcriptomic analysis.
abstract: BACKGROUND
  Expansion of aquaculture is seriously limited by reductions in fish oil (FO) supply for aquafeeds. Terrestrial alternatives such as vegetable oils (VO) have been investigated and recently a strategy combining genetic selection with changes in diet formulations has been proposed to meet growing demands for aquaculture products. This study investigates the influence of genotype on transcriptomic responses to sustainable feeds in Atlantic salmon.
  
  
  RESULTS
  A microarray analysis was performed to investigate the liver transcriptome of two family groups selected according to their estimated breeding values (EBVs) for flesh lipid content, 'Lean' or 'Fat', fed diets containing either FO or a VO blend. Diet principally affected metabolism genes, mainly of lipid and carbohydrate, followed by immune response genes. Genotype had a much lower impact on metabolism-related genes and affected mostly signalling pathways. Replacement of dietary FO by VO caused an up-regulation of long-chain polyunsaturated fatty acid biosynthesis, but there was a clear genotype effect as fatty acyl elongase (elovl2) was only up-regulated and desaturases (Δ5 fad and Δ6 fad) showed a higher magnitude of response in Lean fish, which was reflected in liver fatty acid composition. Fatty acid synthase (FAS) was also up-regulated by VO and the effect was independent of genotype. Genetic background of the fish clearly affected regulation of lipid metabolism, as PPARα and PPARβ were down-regulated by the VO diet only in Lean fish, while in Fat salmon SREBP-1 expression was up-regulated by VO. In addition, all three genes had a lower expression in the Lean family group than in the Fat, when fed VO. Differences in muscle adiposity between family groups may have been caused by higher levels of hepatic fatty acid and glycerophospholipid synthesis in the Fat fish, as indicated by the expression of FAS, 1-acyl-sn-glycerol-3-phosphate acyltransferase and lipid phosphate phosphohydrolase 2.
  
  
  CONCLUSIONS
  This study has identified metabolic pathways and key regulators that may respond differently to alternative plant-based feeds depending on genotype. Further studies are required but data suggest that it will be possible to identify families better adapted to alternative diet formulations that might be appropriate for future genetic selection programmes.
authors: Institute of Aquaculture, University of Stirling, UK. sofia.morais@stir.ac.uk
authors: Sofia
authors: S
authors: Morais
authors: Jarunan
authors: J
authors: Pratoomyot
authors: John B
authors: JB
authors: Taggart
authors: James E
authors: JE
authors: Bron
authors: Derrick R
authors: DR
authors: Guy
authors: J Gordon
authors: JG
authors: Bell
authors: Douglas R
authors: DR
authors: Tocher
references: J Nutr. 2001 Apr;131(4):1129-32
references: 11285313
references: Cell. 1998 Jun 12;93(6):1031-41
references: 9635432
references: Vet Parasitol. 2011 Jan 10;175(1-2):141-50
references: 20947256
references: Lipids. 2004 Nov;39(11):1085-92
references: 15726823
references: Comp Biochem Physiol Part D Genomics Proteomics. 2011 Mar;6(1):62-9
references: 20451480
references: Prog Lipid Res. 1999 Sep-Nov;38(5-6):461-79
references: 10793891
references: J Lipid Res. 2005 Apr;46(4):706-15
references: 15654130
references: Mar Biotechnol (NY). 2009 Sep-Oct;11(5):627-39
references: 19184219
references: Clin Exp Immunol. 1994 Oct;98(1):12-6
references: 7923869
references: BMC Genomics. 2008 Oct 29;9:506
references: 18959775
references: Gene. 2008 Dec 1;425(1-2):69-78
references: 18762234
references: Comp Biochem Physiol B Biochem Mol Biol. 2009 Jun;153(2):171-7
references: 19258045
references: Mol Genet Metab. 2008 Feb;93(2):145-59
references: 18029214
references: Nucleic Acids Res. 2002 May 1;30(9):e36
references: 11972351
references: Comp Biochem Physiol B Biochem Mol Biol. 2009 Nov;154(3):255-63
references: 19563904
references: Biofactors. 2009 May-Jun;35(3):266-72
references: 19391122
references: Annu Rev Nutr. 2002;22:221-39
references: 12055344
references: Biochem J. 1999 Jun 15;340 ( Pt 3):677-86
references: 10359651
references: Br J Nutr. 2011 Nov;106(10):1457-69
references: 21736795
references: Am J Physiol Regul Integr Comp Physiol. 2008 Apr;294(4):R1154-64
references: 18234747
references: Biochem J. 1998 Aug 1;333 ( Pt 3):471-90
references: 9677303
references: J Lipid Res. 2003 Apr;44(4):686-95
references: 12562861
references: Endocrinology. 2005 Jul;146(7):3150-62
references: 15790725
references: Comp Biochem Physiol B Biochem Mol Biol. 2006 Oct;145(2):239-48
references: 16971150
references: Br J Nutr. 2006 Aug;96(2):299-309
references: 16923224
references: Am J Cardiol. 2006 Aug 21;98(4A):27i-33i
references: 16919514
references: J Biol Chem. 1957 May;226(1):497-509
references: 13428781
references: Toxicol In Vitro. 2008 Sep;22(6):1657-61
references: 18603400
references: Biochim Biophys Acta. 2011 Mar;1811(3):194-202
references: 21193059
references: Am J Physiol Gastrointest Liver Physiol. 2002 Feb;282(2):G338-48
references: 11804856
references: J Fish Biol. 2008 Jun;72(9):2071-2094
references: 19125201
references: Proc Natl Acad Sci U S A. 1998 Sep 15;95(19):11211-6
references: 9736715
references: Comp Biochem Physiol B Biochem Mol Biol. 2001 Jun;129(2-3):243-9
references: 11399456
references: Prog Lipid Res. 1996 Sep;35(3):227-41
references: 9082451
references: Age (Omaha). 1998 Jul;21(3):123-8
references: 23604370
references: Lipids. 2005 Jan;40(1):13-24
references: 15825826
references: BMC Genomics. 2008 Jun 24;9:299
references: 18577222
references: J Exp Med. 1997 May 19;185(10):1859-64
references: 9151711
references: J Nutr. 2005 Oct;135(10):2355-61
references: 16177195
references: Br J Nutr. 2000 Nov;84(5):619-28
references: 11177174
references: Biochem Soc Trans. 2002 Nov;30(Pt 6):1076-9
references: 12440976
references: Nat Genet. 2001 Dec;29(4):365-71
references: 11726920
references: Lipids. 2008 Sep;43(9):813-27
references: 18615261
references: Biochim Biophys Acta. 2005 May 1;1734(1):13-24
references: 15866479
references: Br J Nutr. 2010 Mar;103(6):851-61
references: 19943982
references: Am J Clin Nutr. 2006 Jun;83(6 Suppl):1505S-1519S
references: 16841861
references: Gen Comp Endocrinol. 2007 Oct-Dec;154(1-3):120-7
references: 17632107
references: Immunology. 1991 Jun;73(2):212-6
references: 1649125
references: Pharmacol Rev. 2003 Sep;55(3):551-71
references: 12869663
references: J Biochem Mol Biol. 2003 May 31;36(3):258-64
references: 12787479