The <scp>AMPK</scp> allosteric activator <scp>MK</scp> ‐8722 improves the histology and spliceopathy in myotonic dystrophy type 1 ( <scp>DM1</scp> ) skeletal muscle

Multiple signaling pathways have been reported to be altered in Myotonic Dystrophy type 1 (DM1) skeletal muscle, contributing to pathogenicity. In particular, previous work established that AMPK signaling, a key sensor of energy metabolism, is repressed in DM1 mouse muscle and that activating AMPK through exercise and/or with pharmacological activators is beneficial for the DM1 muscle phenotype. Here, we explored the effects of a newer, more specific allosteric AMPK activator acting directly on AMPK. We treated male and female HSA^LR mice for 1 and 4 weeks with a daily injection of the allosteric activator MK-8722, the AMP mimetic AICAR, or vehicle. Our results show that 1 and 4 weeks of treatment with MK-8722 improves alternative splicing toward wild-type levels in male and female HSA^LR muscle. However, the effects of MK-8722 were more modest compared to AICAR. In contrast, 4 weeks of treatment with MK-8722 improved muscle histology to a greater extent than AICAR. As expected with AMPK activation, 4 weeks of treatment with MK-8722 and AICAR promoted the expression of slower, more oxidative fibers. Finally, acute injections of MK-8722 and AICAR triggered the rapid and transient increase in phospho-AMPK in muscle. However, the peak of AMPK phosphorylation was lower with MK-8722 compared to AICAR, thereby explaining the more modest effects of AMPK allosteric activation. Altogether, our data demonstrate that chronic activation of AMPK with specific pharmacological activators is beneficial for the DM1 muscle. They further indicate that at least a portion of the beneficial effects seen following the administration of these drugs occurs through AMPK.