King Grub
2013-06-12, 14:44
The striated muscle activator of Rho signaling (STARS) pathway is suggested to provide a link between external stress responses and transcriptional regulation in muscle. However, the sensitivity of STARS signaling to different mechanical stress has not been investigated. In a comparative study, we examined the regulation of the STARS signaling pathway in response to unilateral resistance exercise performed as either eccentric (ECC) or concentric (CONC) contractions as well as prolonged training; with and without whey protein supplementation. Skeletal muscle STARS, myocardian-related transcription factor-A (MRTF-A) and serum response factor (SRF) mRNA and protein, as well as muscle cross sectional area and maximal voluntary contraction were measured. A single-bout of exercise produced increases in STARS and SRF mRNA and decreases in MRTF-A mRNA with both ECC and CONC exercise, however with an enhanced response occurring following ECC exercise. A 31% increase in STARS protein was observed exclusively after CONC exercise (p<0.001), while pSRF protein levels increased similarly by 48 % with both CONC and ECC exercise (p<0.001). Prolonged ECC and CONC training equally stimulated muscle hypertrophy as well as a 125 and 99 % increases in MRTF-A protein, respectively (p<0.001). No changes occurred for total SRF protein. There was no effect of whey protein supplementation. These results show that resistance exercise provides an acute stimulation of the STARS pathway in a contraction mode-dependent manner. The more pronounced acute exercise responses when compared to accumulated training responses suggest that STARS signaling is primarily involved in the initial phase of exercise-induced muscle adaptations.
J Physiol. 2013 Jun 10. Effect of resistance exercise contraction mode and protein supplementation on members of the STARS signaling pathway.
J Physiol. 2013 Jun 10. Effect of resistance exercise contraction mode and protein supplementation on members of the STARS signaling pathway.