title: Coordinated increase in skeletal muscle fiber area and expression of IGF-I with resistance exercise in elderly post-operative patients.
abstract: Hypertrophy of developing skeletal muscle involves stimulation by insulin-like growth factor-I (IGF-I), however, the role of IGF-I in adult muscle is less clarified. In the present study, the mRNA splice variants of IGF-I (IGF-IEa and MGF) and the changes in muscle fiber cross sectional area after 12 weeks of training were studied in elderly post-operative patients. About 28 subjects, 14 men and 14 women (age 69, range 60-86 years) were randomized to unilateral resistance training (RT: 3/week), electrical stimulation (ES: 1h/day) or functional exercises (FE: 1h/day). The non-operated-side served as a within subject control. Muscle biopsies were obtained from the vastus lateralis of both limbs at +2d post-operative (baseline), at 5 weeks and 12 weeks post-surgery to analyze for changes in type 1 and type 2 muscle fiber area. Changes in expression levels of IGF-I mRNA isoforms were determined using real-time RT-PCR, normalized to the ribosomal protein large protein 0 (RPLP0) mRNA and presented relative to the control-side. At baseline there was no difference between the three groups in muscle fiber area or resting levels of IGF-IEa and MGF. RT resulted in a significant increase in muscle fiber area of type 1 (+17%, p<0.05) and type 2 (+36%, p<0.05) parallel to an increase in the expression of IGF-IEa and MGF, in contrast to ES and FE. The present study demonstrates that resistance training initiated in the acute post-operative phase is highly effective in increasing mean fiber area and in addition induces marked increases in the expression of IGF-I splice variants, supporting the idea that IGF-I is involved in regulating muscle hypertrophy.
authors.affiliation: Institute of Sports Medicine, Bispebjerg Hospital, University of Copenhagen, Denmark. csuetta@gmail.com
authors.forename: Charlotte
authors.initials: C
authors.lastname: Suetta
authors.forename: Christoffer
authors.initials: C
authors.lastname: Clemmensen
authors.forename: Jesper L
authors.initials: JL
authors.lastname: Andersen
authors.forename: S Peter
authors.initials: SP
authors.lastname: Magnusson
authors.forename: Peter
authors.initials: P
authors.lastname: Schjerling
authors.forename: Michael
authors.initials: M
authors.lastname: Kjaer
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000534:rehabilitation; D048429:Cell Size; D005260:Female; D015870:Gene Expression; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000235:genetics* / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D018485:Muscle Fibers, Skeletal / Q000166:cytology* / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000166:cytology / Q000378:metabolism; D011184:Postoperative Period; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D055070:Resistance Training; D015854:Up-Regulation / Q000502:physiology
chemical_list: D020033:Protein Isoforms; D007334:Insulin-Like Growth Factor I