Document Detail


GH administration changes myosin heavy chain isoforms in skeletal muscle but does not augment muscle strength or hypertrophy, either alone or combined with resistance exercise training in healthy elderly men.
MedLine Citation:
PMID:  11836279     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
GH administration, either alone or combined with resistance exercise training (RT), has attracted interest as a means of increasing muscle mass and strength in the elderly. In the present study, 31 healthy, elderly men [age, 74 +/- 1 yr (mean +/- SEM)] were assigned to either RT [3 sessions/wk, 3-5 sets of 8-12 repetition maximum (RM)/session] + placebo (n = 8), RT + GH (n = 8), GH (n = 8), or placebo (n = 7) in a randomized, placebo-controlled, double-blinded (RT + placebo and RT + GH) or single-blinded (GH or placebo) design. Measurements of: 1) isokinetic quadriceps muscle strength; 2) quadriceps muscle power; 3) quadriceps muscle fiber type, size, and myosin heavy chain (MHC) composition; 4) quadriceps cross-sectional area (CSA) [nuclear magnetic resonance imaging (NMRI)]; 5) body composition (dual-energy x-ray absorptiometry scanning); and 6) GH-related serum markers were performed at baseline and after 12 wk. The final GH dose was 1.77 +/- 0.18 IU x d(-1) (approximately 7.2 +/- 0.8 microg x kg(-1) x d(-1)). GH alone had no effect on isokinetic quadriceps muscle strength, power, CSA, or fiber size. However, a substantial increase in MHC 2X isoform was observed with GH administration alone, and this may be regarded as a change into a more youthful MHC composition, possibly induced by the rejuvenating of systemic IGF-I levels. RT + placebo caused substantial increases in quadriceps isokinetic strength, power, and CSA; but these RT induced improvements were not further augmented by additional GH administration. In the RT + GH group, there was a significant decrease in MHC 1 and 2X isoforms, whereas MHC 2A increased. RT, therefore, seems to overrule the changes in MHC composition induced by GH administration alone. Changes in body composition confirmed previous reports of decreased fat mass, increased fat-free mass, and unchanged bone mineral content with GH administration. A high incidence of side effects was reported. Our results do not support a role for GH as a means of increasing muscle strength or mass, either alone or combined with RT, in healthy elderly men; although GH administration alone may induce changes in MHC composition.
Authors:
Kai Henrik Wiborg Lange; Jesper Løvind Andersen; Nina Beyer; Fredrik Isaksson; Benny Larsson; Michael Højby Rasmussen; Anders Juul; Jens Bülow; Michael Kjaer
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Publication Detail:
Type:  Clinical Trial; Journal Article; Randomized Controlled Trial; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Journal of clinical endocrinology and metabolism     Volume:  87     ISSN:  0021-972X     ISO Abbreviation:  J. Clin. Endocrinol. Metab.     Publication Date:  2002 Feb 
Date Detail:
Created Date:  2002-02-11     Completed Date:  2002-03-01     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  0375362     Medline TA:  J Clin Endocrinol Metab     Country:  United States    
Other Details:
Languages:  eng     Pagination:  513-23     Citation Subset:  AIM; IM    
Affiliation:
Sports Medicine Research Unit, Bispebjerg Hospital, DK-2400 Copenhagen NV, Denmark. klange@dadlnet.dk
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MeSH Terms
Descriptor/Qualifier:
Absorptiometry, Photon
Aged
Aged, 80 and over
Blood / metabolism
Dose-Response Relationship, Drug
Growth Hormone / administration & dosage,  adverse effects,  therapeutic use*
Humans
Hypertrophy
Magnetic Resonance Spectroscopy
Male
Muscle Contraction
Muscle Fibers, Skeletal / classification,  ultrastructure
Muscle, Skeletal / drug effects*,  pathology,  physiopathology*
Myosin Heavy Chains / metabolism*
Physical Education and Training*
Protein Isoforms / metabolism
Torque
Weight Lifting*
Chemical
Reg. No./Substance:
0/Myosin Heavy Chains; 0/Protein Isoforms; 9002-72-6/Growth Hormone

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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