title: Effects of resistance training on expression of IGF-I splice variants in younger and older men.
abstract: Insulin-like growth factor-I (IGF-I) and its splice variants Insulin-like growth factor-I isoform Ea (IGF-IEa) and mechano growth factor (MGF) may play an important role in muscular adaptations to resistance training (RT) that may be modulated by ageing. It has been suggested that IGF-I induces cellular responses via AKT8 virus oncogene cellular homolog (Akt) and Extracellular signal-regulated kinase (Erk) signalling pathways. Therefore, resistance exercise-induced changes in skeletal muscle IGF-IEa and MGF messenger ribonucleic acid (mRNA), and MGF, Erk1/2, Akt and p70S6K protein expression were investigated before and after 21 weeks of RT in younger (YM, 20-34 yrs., n = 7) and older men (OM, 51-71 yrs., n = 10). Experimental resistance exercises (RE) of 5 × 10 repetition maximum leg presses were performed pre- and post-RT. Muscle biopsies were obtained before and 48 h after REs, to study the late response to muscle loading. The muscle proteins or mRNAs of interest were not systematically influenced by the REs or RT, except for MGF mRNA expression which was increased (p < .01) following RE before RT in OM. No differences were observed between YM and OM in any variables. This study demonstrated that basal levels or RE-induced responses in skeletal muscle MGF, Erk1/2, Akt and p70S6K protein levels or IGF-IEa and MGF mRNA expression did not differ between YM and OM, nor change systematically due to RT. Thus, ageing appears not to effect expression of the present signalling molecules involved in skeletal muscle hypertrophy.
authors.affiliation: a Department of Biology of Physical Activity and Neuromuscular Research Center , University of Jyväskylä , Jyväskylä , Finland.
authors.forename: Juha P
authors.initials: JP
authors.lastname: Ahtiainen
authors.affiliation: a Department of Biology of Physical Activity and Neuromuscular Research Center , University of Jyväskylä , Jyväskylä , Finland.
authors.forename: Juha J
authors.initials: JJ
authors.lastname: Hulmi
authors.affiliation: b LIKES Research Center for Sport and Health Sciences , Jyväskylä , Finland.
authors.forename: Maarit
authors.initials: M
authors.lastname: Lehti
authors.affiliation: c The Department of Human Sciences , The Ohio State University , OH , USA.
authors.forename: William J
authors.initials: WJ
authors.lastname: Kraemer
authors.affiliation: d Jyväskylä Central Hospital , Jyväskylä , Finland.
authors.forename: Kai
authors.initials: K
authors.lastname: Nyman
authors.affiliation: b LIKES Research Center for Sport and Health Sciences , Jyväskylä , Finland.
authors.forename: Harri
authors.initials: H
authors.lastname: Selänne
authors.affiliation: e Department of Medical Rehabilitation , Oulu University Hospital, Oulu and Institute of Health Sciences, University of Oulu , Oulu , Finland.
authors.forename: Markku
authors.initials: M
authors.lastname: Alen
authors.affiliation: b LIKES Research Center for Sport and Health Sciences , Jyväskylä , Finland.
authors.forename: Jyrki
authors.initials: J
authors.lastname: Komulainen
authors.affiliation: f Department of Health Sciences and Gerontology Research Centre , University of Jyväskylä , Jyväskylä , Finland.
authors.forename: Vuokko
authors.initials: V
authors.lastname: Kovanen
authors.affiliation: a Department of Biology of Physical Activity and Neuromuscular Research Center , University of Jyväskylä , Jyväskylä , Finland.
authors.forename: Antti A
authors.initials: AA
authors.lastname: Mero
authors.affiliation: g Department of Experimental Physiology, Medical School , National and Kapodistrian University of Athens , Athens , Greece.
authors.forename: Anastassios
authors.initials: A
authors.lastname: Philippou
authors.affiliation: f Department of Health Sciences and Gerontology Research Centre , University of Jyväskylä , Jyväskylä , Finland.
authors.forename: Eija K
authors.initials: EK
authors.lastname: Laakkonen
authors.affiliation: a Department of Biology of Physical Activity and Neuromuscular Research Center , University of Jyväskylä , Jyväskylä , Finland.
authors.forename: Keijo
authors.initials: K
authors.lastname: Häkkinen
mesh_terms: D000368:Aged; D000375:Aging / Q000502:physiology; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000502:physiology*; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D055070:Resistance Training; D015398:Signal Transduction / Q000502:physiology
chemical_list: D020033:Protein Isoforms; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I
keywords: Mechano growth factor; ageing; cell signalling; gene expression; muscle hypertrophy