Notch, Numb and Numb-like responses to exercise-induced muscle damage in human skeletal muscle.

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findingsWhat is the central question of this study? Do Notch, Numb and Numb-like expression change in human skeletal muscle after exercise-induced muscle damage? What are the main finding and its importance? Notch gene expression trends toward an increase in response to an acute bout of exercise-induced muscle damage, while Numb and Numb-like expression does not change. These results suggest that human skeletal muscle response to exercise-induced muscle damage is dynamic and may differ from Drosophila and rodent models. Furthermore, the timing of muscle biopsies, training status and muscle damage protocols should be considered. ABSTRACT: This investigation examined changes in the gene and protein expression of Notch, Numb and Numb-like (Numbl) in human skeletal muscle after an acute bout of eccentric exercise-induced muscle damage. Twelve recreationally active male subjects participated in this study. These individuals completed seven sets of 10 repetitions of eccentric leg extension at 120% of one-repetition max with 2 min of rest period between sets. Four muscle biopsies of the vastus lateralis were collected: before exercise (Pre), and 3 h, 2 days and 5 days post-muscle damage. Biopsy samples were used to probe Notch, Numb and Numbl utilizing western blot and RT-qPCR techniques. The results were analysed using a one-way repeated-measures ANOVA. Notch1 mRNA expression trended toward a significant increase from Pre to 2 days post-muscle damage from baseline measures (P = 0.087), while Numb (P = 0.804) and Numbl (P = 0.480) expression was unaltered post-muscle damage. There were no significant differences in protein expression post-muscle damage for any of the proteins. These results suggest that exercise-induced muscle damage, via eccentric exercise, slightly elevates Notch1 mRNA expression.