Lack of effect of recombinant human growth hormone (GH) on muscle morphology and GH-insulin-like growth factor expression in resistance-trained elderly men.
Vastus lateralis muscle samples were obtained by needle biopsy from 18 healthy elderly men (65-82 yr) participating in a double blind, placebo (PL)-controlled trial of recombinant human GH (rhGH) and exercise and assessed for muscle morphology and skeletal muscle tissue expression of GH and insulin-like growth factors (IGFs). Subjects initially underwent progressive resistance training for 14 weeks and were then randomized to receive either rhGH (0.02 mg/kg BW.day, sc) or PL while undertaking a further 10 weeks of training. Muscle samples were obtained at baseline and at 14 and 24 weeks. The mean (+/- SEM) cross-sectional areas of type I and II fibers were similar (type I, 3891 +/- 167 microns2; type II, 3985 +/- 200 microns2) at baseline and increased (P < 0.01) by 16.2 +/- 4.1% and 11.8 +/- 3.8%, respectively, after the initial 14-week training period. After treatment (weeks 14-24), two-way repeated measures ANOVA revealed a main effect of time for type I (P < 0.01) and type II fibers (P < 0.05), but no group effect or interaction. The increase in cross-sectional area for the PL group was significant (P = 0.01) for type I (11.5 +/- 3.6%) and approached significance (P = 0.06) for type II fibers (11.1 +/- 5.6%). For rhGH, the change in type I (6.3 +/- 5.9%) and II (7.1 +/- 5.2%) fiber area was not significant. No apparent change in tissue GH receptor, IGF-I, IGF-I receptor, IGF-II, or IGF-II receptor messenger ribonucleic acids occurred as a result of exercise after the 14-week pretreatment period or after treatment with rhGH or PL. These results indicate that rhGH administration in exercising elderly men does not augment muscle fiber hypertrophy or tissue GH-IGF expression and suggests that deficits in the GH-IGF-I axis with aging do not inhibit the skeletal muscle tissue response to training.
Musculoskeletal Research Laboratory, Veterans Affairs Medical Center, Palo Alto, California 94304, USA.
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Taaffe
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Jin
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Hoffman
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Marcus
D000368:Aged; D000369:Aged, 80 and over; D001483:Base Sequence; D004311:Double-Blind Method; D015870:Gene Expression / Q000187:drug effects; D013006:Growth Hormone / Q000235:genetics / Q000494:pharmacology*; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D010806:Physical Education and Training; D012333:RNA, Messenger / Q000032:analysis; D017451:Receptors, Somatomedin / Q000235:genetics*; D011986:Receptors, Somatotropin / Q000235:genetics; D011994:Recombinant Proteins / Q000494:pharmacology; D013002:Somatomedins / Q000235:genetics*
D012333:RNA, Messenger; D017451:Receptors, Somatomedin; D011986:Receptors, Somatotropin; D011994:Recombinant Proteins; D013002:Somatomedins; D013006:Growth Hormone