Abstract
Muscle atrophy is a concern in various health conditions, such as aging, cancer, and diabetes. As such, finding effective therapies to treat muscle loss is of significant value. The best treatment for muscle atrophy is exercise. However, many with these conditions either cannot or will not exercise. This highlights the value of finding an effective pharmacologic therapy. AMP-activated protein kinase (AMPK) is one of the best-characterized exercise-responsive molecular signals. Despite suppressing muscle synthesis acutely, chronic AMPK activation has been shown to prevent muscle loss in wasting conditions. Our collaborator company, Biolexis Therapeutics, has identified MLX-0871 as a novel AMPK-activating oral small molecule, which we have utilized in these studies. PURPOSE: To determine whether intermittent AMPK activation would increase cultured myotube size and anabolic signaling. METHODS: Experiment 1: We treated primary human myotubes for two hours daily for three consecutive days with vehicle control (DMSO) or 50 or 100 uM MLX-0871. A day after the final treatment, myotube diameter was measured, and phosphorylation of AMPK target proteins and the anabolic markers p70 ribosomal protein S6 kinase (S6k) and ribosomal protein S6 (rpS6) were measured by western blotting. Experiment 2: We treated primary human myotubes with 50 uM MLX-0871 or DMSO for one hour, withdrawing myotubes from treatment at 0, 30, 60, 120, or 240 minutes before lysis, then assessed them for phosphorylation of AMPK target proteins, S6k and rpS6. RESULTS: Treatment with 50 uM and 100 uM MLX-0871 increased myotube diameter by 20.6% and 29.6%, respectively, compared to the control. No significant differences in S6k or rpS6 were observed 24 hours after the final treatment. However, in experiment 2, S6k phosphorylation was increased by 90%, and rpS6 tended to increase two hours after withdrawal of MLX-0871. CONCLUSION: Our findings indicate that anabolic signaling rebounds above basal levels about 2 hours after AMPK activation with MLX-0871. This may contribute to the increased muscle fiber size we saw with chronic AMPK activation.
Recommended Citation
Stark, Isaac S.; Summers, Abigail E.; Barbeau, Jack E.; Secrist, Neal A.; and Thomson, David M.
(2024)
"Intermittent AMP-activated Protein Kinase Activation Promotes Myotube Hypertrophy,"
International Journal of Exercise Science: Conference Proceedings: Vol. 14:
Iss.
4, Article 56.
Available at:
https://digitalcommons.wku.edu/ijesab/vol14/iss4/56