| Abstract
| - Background. Skeletal muscle atrophy in rodents is associated with increased gene expression of proteolytic markers muscle-RING-finger protein 1 (MuRF-1) and atrogin-1. In humans with age-related muscle atrophy, known as sarcopenia, little is known about these key proteolytic biomarkers. Therefore, the purpose of this investigation was 2-fold: (i) measure messenger RNA (mRNA) expression of proteolytic genes MuRF-1, atrogin-1, forkhead box (FOXO)3A, and tumor necrosis factor-α (TNF-α) in young and old women at rest, and (ii) measure these proteolytic genes in response to an acute resistance exercise (RE) bout, a known hypertrophic stimulus. Methods. A group of old women (OW: n = 6, 85 ± 1 years, thigh muscle = 89 ± 4 cm2) and young women (YW: n = 8, 23 ± 2 years, thigh muscle = 122 ± 6 cm2) performed three sets of 10 knee extensions at 70% of one-repetition maximum. Muscle biopsies were taken from the vastus lateralis before and 4 hours after RE. Using real-time reverse transcription-polymerase chain reaction (RT-PCR), mRNA was amplified and normalized to GAPDH. Results. At rest, OW expressed higher mRNA levels of MuRF-1 (p =.04) and FOXO3A (p =.001) compared to YW. In response to RE, there was an age effect (p =.01) in the induction of atrogin-1 (OW: 2.5-fold). Both YW and OW had an induction (p =.001) in MuRF-1 (YW: 3.6-fold; OW: 2.6-fold) with RE. Conclusions. These data show that the regulation of ubiquitin proteasome-related genes involved with muscle atrophy are altered in very old women (> 80 years). This finding is manifested both at rest and in response to RE, which may contribute to the large degree of muscle loss with age.
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