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Expression of IGF-I splice variants in young and old human skeletal muscle after high resistance exercise

Hameed, M; Orrell, RW; Cobbold, M; Goldspink, G; Harridge, SDR; (2003) Expression of IGF-I splice variants in young and old human skeletal muscle after high resistance exercise. J PHYSIOL-LONDON , 547 (1) 247 - 254. 10.1113/jphysiol.2002.032136.

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Abstract

The mRNA expression of two splice variants of the insulin-like growth factor-I (IGF-I) gene, IGF-IEa and mechano growth factor (MGF), were studied in human skeletal muscle. Subjects (eight young, aged 25-36 years, and seven elderly, aged 70-82 years) completed 10 sets of six repetitions of single legged knee extensor exercise at 80% of their one repetition maximum. Muscle biopsy samples were obtained from the quadriceps muscle of both the control and exercised legs 2.5 h after completion of the exercise bout. Expression levels of the IGF-I mRNA transcripts were determined using real-time quantitative RT-PCR with specific primers. The resting levels of MGF were significantly (similar to100-fold) lower than those of the IGF-IEa isoform. No difference was observed between the resting levels of the two isoforms between the two subject groups. High resistance exercise resulted in a significant increase in MGF mRNA in the young, but not in the elderly subjects. No changes in IGF-IEa mRNA levels were observed as a result of exercise in either group. The mRNA levels of the transcription factor MyoD were greater at rest in the older subjects (P < 0.05), but there was no significant effect of the exercise bout. Electrophoretic separation of myosin heavy chain (MHC) isoforms showed the older subjects to have a lower (P< 0.05) percentage of MHC-II isoforms than the young subjects. However, no association was observed between the composition of the muscle and changes in the IGF-I isoforms with exercise. The data from this study show an attenuated MGF response to high resistance exercise in the older subjects, indicative of age-related desensitivity to mechanical loading. The data in young subjects indicate that the MGF and IGF-IEa isoforms are differentially regulated in human skeletal muscle.

Type: Article
Title: Expression of IGF-I splice variants in young and old human skeletal muscle after high resistance exercise
DOI: 10.1113/jphysiol.2002.032136
Keywords: GROWTH-FACTOR-I, TRAPEZIUS MUSCLE, ELDERLY-PEOPLE, SINGLE FIBERS, STRENGTH, HYPERTROPHY, STIMULATION, STRETCH, DIFFERENTIATION, REGENERATION
UCL classification: UCL > School of Life and Medical Sciences
UCL > School of Life and Medical Sciences > Faculty of Brain Sciences
UCL > School of Life and Medical Sciences > Faculty of Brain Sciences > Institute of Neurology
UCL > School of Life and Medical Sciences > Faculty of Brain Sciences > Institute of Neurology > Clinical Neuroscience
UCL > School of Life and Medical Sciences > Faculty of Life Sciences
UCL > School of Life and Medical Sciences > Faculty of Medical Sciences
UCL > School of Life and Medical Sciences > Faculty of Medical Sciences > Surgery and Interventional Science (Division of)
URI: http://discovery.ucl.ac.uk/id/eprint/185436
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