Investigating the Combined Effects of Mechanical Stress and Nutrition on Muscle Hypertrophic Signals Using Contractile 3D-Engineered Muscle (3D-EM)

Since 3D-EM closely resembles in vivo muscles, the aim of this study was to investigate the effects of exercise (electrical pulse stimulation (EPS)) and nutrition (maca), which contains triterpenes, on muscle hypertrophy by using 3D-EM for the first time. The 3D-EM was composed of C2C12 cells and type 1 collagen gel, was differentiated for 14 days, and was divided into four groups: control, maca, EPS, and maca + EPS. The medium was replaced every two days before each EPS intervention, and the concentration of maca in the culture solution was 1 mg/mL. The intervention conditions of the EPS were 30 V, 1 Hz, and 2 ms (24 h on, 24 h off, for one week). The expression levels of proteins were examined by Western blotting. The intervention of maca and EPS upregulated the expression of MHC-fast/slow (both p < 0.05) compared with the control group, and the addition of maca had no effect on the phosphorylation of mTOR (p = 0.287) but increased the AMPK phosphorylation (p = 0.001). These findings suggest that intervention with maca and EPS has a positive effect on muscle hypertrophy, which has a positive impact on sarcopenia. However, the underlying mechanisms remain to be further explored.