title: Phasing of muscle gene expression with fasting-induced recovery growth in Atlantic salmon.
abstract: BACKGROUND
  Many fish species experience long periods of fasting in nature often associated with seasonal reductions in water temperature and prey availability or spawning migrations. During periods of nutrient restriction, changes in metabolism occur to provide cellular energy via catabolic processes. Muscle is particularly affected by prolonged fasting as myofibrillar proteins act as a major energy source. To investigate the mechanisms of metabolic reorganisation with fasting and refeeding in a saltwater stage of Atlantic salmon (Salmo salar L.) we analysed the expression of genes involved in myogenesis, growth signalling, lipid biosynthesis and myofibrillar protein degradation and synthesis pathways using qPCR.
  
  
  RESULTS
  Hierarchical clustering of gene expression data revealed three clusters. The first cluster comprised genes involved in lipid metabolism and triacylglycerol synthesis (ALDOB, DGAT1 and LPL) which had peak expression 3-14d after refeeding. The second cluster comprised ADIPOQ, MLC2, IGF-I and TALDO1, with peak expression 14-32d after refeeding. Cluster III contained genes strongly down regulated as an initial response to feeding and included the ubiquitin ligases MuRF1 and MAFbx, myogenic regulatory factors and some metabolic genes.
  
  
  CONCLUSIONS
  Early responses to refeeding in fasted salmon included the synthesis of triacylglycerols and activation of the adipogenic differentiation program. Inhibition of MuRF1 and MAFbx respectively may result in decreased degradation and concomitant increased production of myofibrillar proteins. Both of these processes preceded any increase in expression of myogenic regulatory factors and IGF-I. These responses could be a necessary strategy for an animal adapted to long periods of food deprivation whereby energy reserves are replenished prior to the resumption of myogenesis.
authors.affiliation: Gatty Marine Laboratory, School of Biology, University of St Andrews, St Andrews, Fife, KY16 8LB, UK. iaj@st-andrews.ac.uk.
authors.forename: Neil I
authors.initials: NI
authors.lastname: Bower
authors.forename: Richard G
authors.initials: RG
authors.lastname: Taylor
authors.forename: Ian A
authors.initials: IA
authors.lastname: Johnston
references.citation: Prog Lipid Res. 1996;35(2):169-201
references.pmid: 8944226
references.citation: Bioinformatics. 2004 Jun 12;20(9):1453-4
references.pmid: 14871861
references.citation: Proc Natl Acad Sci U S A. 2004 Dec 28;101(52):18135-40
references.pmid: 15601779
references.citation: Curr Opin Genet Dev. 1996 Aug;6(4):445-53
references.pmid: 8791524
references.citation: Comp Biochem Physiol B Biochem Mol Biol. 2006 Oct;145(2):239-48
references.pmid: 16971150
references.citation: Comp Biochem Physiol B Biochem Mol Biol. 2001 Jun;129(2-3):207-19
references.pmid: 11399452
references.citation: J Mol Biol. 2005 Jul 22;350(4):713-22
references.pmid: 15967462
references.citation: Annu Rev Nutr. 1998;18:353-83
references.pmid: 9706229
references.citation: Int J Biochem Cell Biol. 2005 Oct;37(10):1974-84
references.pmid: 16087388
references.citation: EMBO J. 2008 Apr 23;27(8):1266-76
references.pmid: 18354498
references.citation: Science. 2001 Nov 23;294(5547):1704-8
references.pmid: 11679633
references.citation: J Exp Biol. 2007 Aug;210(Pt 16):2781-94
references.pmid: 17690225
references.citation: Comp Biochem Physiol A Comp Physiol. 1986;85(3):445-50
references.pmid: 2878772
references.citation: Eur J Cell Biol. 1985 Nov;39(1):112-7
references.pmid: 3910436
references.citation: Clin Chem. 2009 Apr;55(4):611-22
references.pmid: 19246619
references.citation: FASEB J. 2001 Jul;15(9):1589-91
references.pmid: 11427495
references.citation: Biochem Biophys Res Commun. 2005 Nov 18;337(2):540-50
references.pmid: 16202386
references.citation: Genome Biol. 2002 Jun 18;3(7):RESEARCH0034
references.pmid: 12184808
references.citation: Am J Physiol Regul Integr Comp Physiol. 2008 Jul;295(1):R329-35
references.pmid: 18434442
references.citation: J Lipid Res. 2005 Jul;46(7):1369-79
references.pmid: 15834118
references.citation: J Biol Chem. 1985 May 25;260(10):6054-9
references.pmid: 2581946
references.citation: J Endocrinol. 2006 Oct;191(1):15-24
references.pmid: 17065385
references.citation: FEBS Lett. 2006 Sep 18;580(21):4996-5002
references.pmid: 16930594
references.citation: Comp Biochem Physiol B Biochem Mol Biol. 2006 May;144(1):119-27
references.pmid: 16545592
references.citation: Dev Dyn. 2008 Jun;237(6):1682-90
references.pmid: 18489000
references.citation: Nat Cell Biol. 2001 Nov;3(11):1009-13
references.pmid: 11715022
references.citation: Endocrinology. 1993 Feb;132(2):770-80
references.pmid: 8381074
references.citation: Crit Rev Clin Lab Sci. 1992;29(3-4):243-68
references.pmid: 1489519
references.citation: Mol Cell. 2004 May 7;14(3):395-403
references.pmid: 15125842
references.citation: BMC Genomics. 2007 Nov 28;8:438
references.pmid: 18045468
references.citation: J Mol Biol. 2008 Jun 13;379(4):666-77
references.pmid: 18468620
references.citation: Nature. 2001 Sep 13;413(6852):179-83
references.pmid: 11557984
references.citation: Med Res Rev. 2005 Jan;25(1):49-65
references.pmid: 15389734
references.citation: J Lipid Res. 1971 Mar;12(2):179-91
references.pmid: 4396562
references.citation: Fish Physiol Biochem. 2008 Jun;34(2):103-16
references.pmid: 18649028
references.citation: J Biol Chem. 1996 Dec 20;271(51):32994-3001
references.pmid: 8955144
references.citation: Nat Cell Biol. 2002 Sep;4(9):648-57
references.pmid: 12172553
references.citation: Semin Cell Dev Biol. 2005 Aug-Oct;16(4-5):585-95
references.pmid: 16099183
references.citation: Endocrinology. 2005 Aug;146(8):3547-57
references.pmid: 15878958
references.citation: Anim Behav. 1997 Dec;54(6):1405-12
references.pmid: 9521797
references.citation: Biochem Biophys Res Commun. 1999 Mar 16;256(2):257-62
references.pmid: 10079172
references.citation: J Exp Biol. 2003 Apr;206(Pt 8):1337-51
references.pmid: 12624169
references.citation: J Biol Chem. 2005 Jan 28;280(4):2847-56
references.pmid: 15531760
references.citation: Cell Metab. 2007 Nov;6(5):376-85
references.pmid: 17983583
references.citation: Int Rev Cytol. 2005;243:215-85
references.pmid: 15797461
references.citation: Gen Comp Endocrinol. 2007 Feb;150(3):462-72
references.pmid: 17196198
references.citation: Gen Comp Endocrinol. 2003 Jun 15;132(2):209-15
references.pmid: 12812767
references.citation: J Mol Biol. 2008 Mar 7;376(5):1224-36
references.pmid: 18222470
references.citation: J Biol Chem. 2007 Mar 16;282(11):7991-6
references.pmid: 17244624
references.citation: J Exp Biol. 2008 Dec;211(Pt 24):3859-70
references.pmid: 19043058
references.citation: Cell. 2005 Nov 18;123(4):569-80
references.pmid: 16286006
references.citation: Endocr Rev. 2004 Oct;25(5):807-30
references.pmid: 15466941
references.citation: Mol Cell Biochem. 1999 Nov;201(1-2):1-10
references.pmid: 10630616
references.citation: J Biol Chem. 2002 Dec 27;277(52):50876-84
references.pmid: 12407108