Exercise type and volume alter signaling pathways regulating skeletal muscle glucose uptake and protein synthesis

Purpose

The aim of this study was to compare activation of cellular signaling pathways regulating protein synthesis and glucose uptake in skeletal muscle between resistance and endurance exercise. Moreover, the effect of resistance exercise volume was examined.

Methods

Three groups of male volunteers (26 ± 3 years) were examined: 5 × 10 repetition maximum (RM) resistance exercise (RE) with leg press device (5 × 10 RE; n = 8), 10 × 10 RE (n = 11), and endurance exercise (strenuous 50-min walking with extra load on a treadmill; EE; n = 8). Muscle biopsies were obtained from m.vastus lateralis 30 min pre- and post-exercise.

Results

Downstream markers of mTORC1, p-p70S6K^{Thr421/Ser424} and p-rpS6^Ser240/244, increased more after 10 × 10 RE than after 5 × 10 RE (p < 0.05) and EE (p < 0.01–0.001). Exercise-induced changes in p-IRS-I^Ser636/639 that inhibit IRS-I signaling via negative feedback from hyperactivated mTORC1 signaling were greater (p < 0.05) after 10 × 10 RE compared with 5 × 10 RE and EE. The changes in energy sensor p-AMPKα^Thr172 were greater after 10 × 10 RE and EE (p < 0.05–0.01) than after 5 × 10 RE. A major regulator of glucose uptake in muscle, p-AS160^Thr642, increased more after 10 × 10 RE than after 5 × 10 RE (p < 0.01) and EE (p < 0.05).

Conclusion

10 × 10 RE induced greater activation of important signaling proteins regulating glucose uptake (p-AS160) and protein synthesis (p-p70S6K, p-rpS6) than 5 × 10 RE and EE. The present findings further suggest that, especially after 10 × 10 RE, IRS-I signaling is downregulated and that AS160 is activated through AMPK signaling pathway.