Trappe S. Proteolytic gene expression differs at rest and after resistance exercise between young and old women. J Gerontol A Biol Sci Med Sci

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-a (TNF-a) 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 6 1 years, thigh muscle 89 6 4 cm2) and young women (YW: n 8, 23 6 2 years, thigh muscle 122 6 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 ma