Soluble Activin Receptor Type Iib Increases Forward Pulling Tension In The Mdx Mouse

Introduction: In this study we investigated the action of RAP-031, a soluble activin receptor type IIB (ActRIIB) comprised of a form of the ActRIIB extracellular domain linked to a murine Fc, and the NF-kappa B inhibitor, ursodeoxycholic acid (UDCA), on the whole body strength of mdx mice. Methods: The whole body tension (WBT) method of assessing the forward pulling tension (FPT) exerted by dystrophic (mdx) mice was used. Results: RAP-031 produced a 41% increase in body mass and a 42.5% increase in FPT without altering the FPT normalized for body mass (WBT). Coadministration of RAP-031 with UDCA produced increases in FPT that were associated with an increase in WBT. Conclusions: Myostatin inhibition increases muscle mass without altering the fundamental weakness characteristic of dystrophic muscle. Cotreatment with an NF-kappa B inhibitor potentiates the effects of myostatin inhibition in improving FPT in mdx mice. Muscle Nerve 43: 694-699, 2011