Myogenic mRNA markers in young and old human skeletal muscle prior to and following sequential exercise bouts

Abstract

This study examined how multiple bouts of conventional resistance training affected the mRNA expression of transcripts and a protein associated with satellite cell activity in human skeletal muscle. Ten younger men (means± SE; age, 21.0± 0.5years; body mass, 82.3± 4.2kg; height, 178.4± 2.2cm; percent body fat, 15.4%± 2.9%) and 10 older men (age, 66.4± 1.6years; body mass, 94.2± 3.7kg; height, 180.9± 2.2cm; percent body fat, 27.4%± 1.8%) completed 3 lower-body workouts (Monday, Wednesday, Friday; 9 sets of 10 repetitions at 80% 1 repetition maximum). Vastus lateralis muscle biopsies were collected prior to intervention (T1), 48h following workout 1 (T2), 48h following workout 2 (T3), and 24h following workout 3 (T4). Real-time reverse transcription-polymerase chain reaction was performed to assess genes of interest, and muscle proliferating cell nuclear antigen (PCNA) was assessed using Western blotting. The CYCLIN D1 gene was expressed more highly in the older vs. younger men (p< 0.05), whereas the expression of all other genes and muscle PCNA were similar between age groups. MYOD mRNA expression increased at T2 (p< 0.05) and MHCEMB gene expression modestly increased (p< 0.05) at T4 relative to baseline expression values in the younger men. Baseline elevations in CYCLIN D1 mRNA expression in older persons may indicate that a compensatory expression of this transcript is occurring in an attempt to retain the muscle's proliferative potential. Increases in MYOD and MHCEMB indicate that 1 week of conventional resistance exercise may i crease myogenic activity, including satellite cell proliferation and differentiation, respectively, in younger men.