The independent effects of heat application on muscle growth program associated mRNA and protein phosphorylation

The development and maintenance of skeletal muscle is crucial for the support of daily function. Recent evidence suggests that genes coded for proteins associated with the human muscle growth program (myogenic and proteolytic genes) are sensitive to local heat application. Therefore, the purpose of this investigation was to determine the effect of 4 hours of local heat application to the vastus lateralis at rest on acute phosphorylation (mTOR Ser2448 , p70-S6K1 Thr389 , and 4E-BP1 Thr47/36 ) and gene expression changes for proteins associated with the muscle growth program. Intramuscular temperature of the HOT limb was 1.2 ± 0.2 °C higher than CON limb after 4 h of local heating. However, this local heat stimulus did not influence transcription of genes associated with myogenesis ( MSTN , p = 0.321; MYF5 , p =0.445; MYF6 , p = 0.895; MEF2a , p = 0.809; MYO-G , p = 0.766; MYO-D1 , p = 0.118; RPS3 , p = 0.321; and RPL-3L , p = 0.577), proteolysis ( Atrogin-1 , p = 0.573; FOXO3a , p = 0.452; MURF-1 , p = 0.284), nor protein phosphorylation (mTOR Ser2448 , p = 0.981; P70-S6K1 Thr389 , p = 0.583; 4E-BP1 Thr37/46 , p = 0.238) associated with the muscle growth program. These findings suggest little to no association between the local application of heat, at rest, and the activation of the observed muscle growth program-related markers.