Heat stress enhances mTOR signaling after resistance exercise in human skeletal muscle

Abstract

This study investigated the effect of heat stress (HS) on mammalian target of rapamycin (mTOR) signaling involved in translation initiation after resistance exercise in human skeletal muscle. Eight young male subjects performed four sets of six maximal repetitions of knee extension exercises, with or without HS, in a randomized crossover design. HS was applied to the belly of the vastus lateralis by using a microwave therapy unit prior to and during exercise. Muscle biopsies were taken from the vastus lateralis before, immediately after, and 1 h after exercise. HS significantly increased the phosphorylation of Akt/PKB, mTOR, and ribosomal protein S6 at 1 h after exercise (P < 0.05), and the 4E-BP1 phosphorylation level, which had initially decreased with exercise, had recovered by 1 h after exercise with HS. In addition, the phosphorylation of ribosomal S6 kinase 1 was significantly increased immediately after exercise with HS (P < 0.05). These results indicate that HS enhances mTOR signaling after resistance exercise in human skeletal muscle.

Whey peptide ingestion suppresses body fat accumulation in senescence-accelerated mouse prone 6 (SAMP6)

“…Western blot analysis was performed as previously described [18]. Frozen quadriceps muscles were minced, and a portion of the muscle was homogenized in 10 volumes of ice-cold homogenization buffer (50 mM HEPES, 4 mM EGTA, 10 mM EDTA, 50 mM b-glycerophosphate, 25 mM NaF, 5 mM Na 3 VO 4 , 0.1 % Triton-X100) containing the protease inhibitor cocktail Complete EDTA-free (Roche, Penzberg, Germany).…”

Heat stress and dehydration in adapting for performance: Good, bad, both, or neither?

“…Physiologically-relevant levels of heating increase the permeability of epithelial cell tight junctions of the gut in rats, 44 and in gut and kidney cell cultures 45,46 . Heat stress also stimulates the important signaling molecule, mTOR, 47,48 as well as glucose sensitivity at least in aged muscle, via HSP72 induction 49 . Contrary to this, hyperosmotic hypohydration may oppose both of these effects 50 via volume regulatory signaling mechanisms and/or oxidative stress.…”

“…Heating skeletal muscle either in the absence of exercise or after exercise can stimulate HSP72 and mTOR, 47 thereby protecting against disuse atrophy and enhancing muscle regrowth in rats 96 and producing hypertrophy in humans 97 . Heating of muscle might therefore seem attractive for strength athletes, but it should be noted that (i) heat per se is much less effective than exercise itself in conditioning muscle against mechanical overload, 98 (ii) when applied before exercise, heat actually preconditions muscle to become less perturbed 98 and thus less responsive to a short-term overload, 99 and (iii) HSP72 is stimulated by intense exercise as well.…”

Heat stress activates the Akt/mTOR signalling pathway in rat skeletal muscle

“…Moreover, we demonstrated that heat stress enhanced resistance exercise‐induced Akt/mTOR signalling activation in human skeletal muscle (Kakigi et al . ). These data indicate that temperature alterations may be important factors in the activation of Akt and its downstream targets independent of HSP expression in vivo .…”