The Effect of Heat Stress on Heat Shock Protein Expression and Hypertrophy Related Signaling in the Skeletal Muscle of Trained Individuals

Am J Physiol Regul Integr Comp Physiol. 2023 Oct 16. doi: 10.1152/ajpregu.00031.2023. Online ahead of print.ABSTRACTMuscle mass is balanced between hypertrophy and atrophy by cellular processes, including activation of the Akt-mTOR signaling cascade. Stressors apart from exercise and nutrition, such as heat stress, can stimulate the heat shock protein A (HSPA) and C (HSPC) families alongside hypertrophic signaling factors and muscle growth. The effects of heat stress on HSP expression and Akt-mTOR activation in human skeletal muscle, and their magnitude of activation compared to known hypertrophic stimuli is unclear. Here we show a single session of whole-body heat stress followed by resistance exercise increases the expression of HSPA as well as activation of the Akt-mTOR cascade in skeletal muscle compared to resistance exercise in a healthy, resistance trained population. Heat stress alone may also exert similar effects, though the responses are notably variable and require further investigation. Additionally, acute heat stress in C2C12 muscle cells enhanced myotube growth and myogenic fusion, albeit to a lesser degree than growth factor mediated hypertrophy. Though the mechanisms by which heat stress stimulates hypertrophy related signaling and the potential mechanistic role of HSPs remain unclear, these findings provide additional evidence implicating heat stress as a novel growth stimulus when combined with resistance exercise in human skeletal muscle and alone in isola...
Source: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology - Category: Physiology Authors: Source Type: research