title: Muscle fibre size optimisation provides flexibility for energy budgeting in calorie-restricted coho salmon transgenic for growth hormone.
abstract: Coho salmon (Oncorhynchus kisutch) transgenic for growth hormone (GH) show substantially faster growth than wild-type (WT) fish. We fed GH-transgenic salmon either to satiation (1 year; TF) or the same smaller ration of wild-type fish (2 years; TR), resulting in groups matched for body size to WT salmon. The myotomes of TF and WT fish had the same number and size distribution of muscle fibres, indicating a twofold higher rate of fibre recruitment in the GH transgenics. Unexpectedly, calorie restriction was found to decrease the rate of fibre production in transgenics, resulting in a 20% increase in average fibre size and reduced costs of ionic homeostasis. Genes for myotube formation were downregulated in TR relative to TF and WT fish. We suggest that muscle fibre size optimisation allows the reallocation of energy from maintenance to locomotion, explaining the observation that calorie-restricted transgenics grow at the same rate as WT fish whilst exhibiting markedly higher foraging activity.
authors.affiliation: Scottish Oceans Institute, School of Biology, University of St Andrews, St Andrews, KY16 8LB, UK iaj@standrews.ac.uk.
authors.forename: Ian A
authors.initials: IA
authors.lastname: Johnston
authors.affiliation: Scottish Oceans Institute, School of Biology, University of St Andrews, St Andrews, KY16 8LB, UK.
authors.forename: Daniel Garcia
authors.initials: DG
authors.lastname: de la Serrana
authors.affiliation: Fisheries and Oceans Canada, 4160 Marine Drive, West Vancouver, BC V7V 1N6, Canada.
authors.forename: Robert H
authors.initials: RH
authors.lastname: Devlin
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D031204:Caloric Restriction; D002149:Energy Intake; D013006:Growth Hormone / Q000235:genetics / Q000378:metabolism*; D006706:Homeostasis / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000378:metabolism; D018482:Muscle, Skeletal / Q000254:growth & development* / Q000378:metabolism*; D017684:Oncorhynchus kisutch / Q000235:genetics* / Q000254:growth & development*
chemical_list: D013006:Growth Hormone
keywords: Growth; Myotube formation; Optimal fibre size hypothesis; Transgenesis
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