Stefanetti, R. J, Zacharewicz, E., Della Gatta, P. A, Garnham, A., Russell, A. P & Lamon, S. (2014). Ageing has no effect on the regulation of the ubiquitin proteasome-related genes and proteins following resistance exercise. Frontiers in Physiology,5 1-10. Switzerland: Frontiers Research Foundation. Retrieved from https://doi.org/10.3389/fphys.2014.00030
Skeletal muscle atrophy is a critical component of the ageing process. Age-related muscle wasting is due to disrupted muscle protein turnover, a process mediated in part by the ubiquitin proteasome pathway ( UPP ). Additionally, older subjects have been observed to have an attenuated anabolic response, at both the molecular and physiological levels, following a single-bout of resistance exercise ( RE ). We investigated the expression levels of the UPP-related genes and proteins involved in muscle protein degradation in 10 older ( 60–75 years ) vs. 10 younger ( 18–30 years ) healthy male subjects at basal as well as 2 h after a single-bout of RE. MURF1, atrogin-1 and FBXO40, their substrate targets PKM2, myogenin, MYOD, MHC and EIF3F as well as MURF1 and atrogin-1 transcriptional regulators FOXO1 and FOXO3 gene and/or protein expression levels were measured via real time PCR and western blotting, respectively. At basal, no age-related difference was observed in the gene/protein levels of atrogin-1, MURF1, myogenin, MYOD and FOXO1/3. However, a decrease in FBXO40 mRNA and protein levels was observed in older subjects, while PKM2 protein was increased. In response to RE, MURF1, atrogin-1 and FBXO40 mRNA were upregulated in both the younger and older subjects, with changes observed in protein levels. In conclusion, UPP-related gene/protein expression is comparably regulated in healthy young and old male subjects at basal and following RE. These findings suggest that UPP signaling plays a limited role in the process of age-related muscle wasting. Future studies are required to investigate additional proteolytic mechanisms in conjunction with skeletal muscle protein breakdown ( MPB ) measurements following RE in older vs. younger subjects.
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