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Differential effects of short-term ? agonist and growth hormone treatments on expression of myosin heavy chain IIB and associated metabolic genes in sheep muscle

Hemmings, K. M.; Daniel, Zoe C.T.R.; Buttery, P. J.; Parr, T.; Brameld, John M.

Differential effects of short-term ? agonist and growth hormone treatments on expression of myosin heavy chain IIB and associated metabolic genes in sheep muscle Thumbnail


K. M. Hemmings

Zoe C.T.R. Daniel

P. J. Buttery

Professor of Nutritional Biochemistry

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Professor of Nutritional Biochemistry


Growth hormone (GH) and ? agonists increase muscle mass, but the mechanisms for this response are unclear and the magnitude of response is thought to vary with age of animal. To investigate the mechanisms driving the muscle response to these agents, we examined the effects of short-term (6 day) administration of GH or cimaterol (a ?2-adrenergic agonist, BA) on skeletal muscle phenotype in both young (day 60) and mature (day 120) lambs. Expression of myosin heavy chain (MyHC) isoforms were measured in Longissimus dorsi (LD), Semitendinosus (ST) and Supraspinatus (SS) muscles as markers of fibre type and metabolic enzyme activities were measured in LD. To investigate potential mechanisms regulating the changes in fibre type/metabolism, expression or activity of a number of signalling molecules were examined in LD. There were no effects of GH administration on MyHC isoform
expression at either the mRNA or protein level in any of the muscles. However, BA treatment induced a proportional change in MyHC mRNA expression at both ages, with the %MyHCI and/or IIA mRNA being significantly decreased in all three muscles and % MyHCIIX/IIB mRNA significantly increased in the LD and ST. BA treatment induced de novo expression of MyHCIIB mRNA in LD, the fastest isoform not normally expressed in sheep LD, as well as increasing expression in the other two muscles. In the LD, the
increased expression of the fastest MyHC isoforms (IIX and IIB) was associated with a decrease in isocitrate dehydrogenase activity, but no change in lactate dehydrogenase activity, indicating a reduced capacity for oxidative metabolism. In both young and mature lambs, changes in expression of metabolic regulatory factors were observed that might induce these changes in muscle
metabolism/fibre type. In particular, BA treatment decreased PPAR-? coactivator-1? mRNA and increased receptor-interacting protein 140 mRNA. The results suggest that the two agents work via different mechanisms or over different timescales, with only BA inducing changes in muscle mass and transitions to a faster, less oxidative fibre type after a 6-day treatment.

Journal Article Type Article
Acceptance Date Aug 13, 2014
Online Publication Date Sep 12, 2014
Publication Date 2015-02
Deposit Date Aug 15, 2017
Publicly Available Date Aug 15, 2017
Journal Animal
Print ISSN 1751-7311
Electronic ISSN 1751-732X
Publisher Cambridge University Press
Peer Reviewed Peer Reviewed
Volume 9
Issue 2
Pages 285-294
Keywords ? agonist, growth hormone, muscle fibre type, myosin heavy chain, sheep
Public URL
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Additional Information License: © The Animal Consortium 2014This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (, which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited.


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