The muscle-hypertrophic effect of clenbuterol is additive to the hypertrophic effect of myostatin suppression.

INTRODUCTION In this study we investigated the combined effect of myostatin (MSTN) suppression and β-agonist (clenbuterol) administration on muscle hypertrophy and the phosphorylation of muscle 4E-BP1 and p70S6k, two downstream effectors of the Akt/mTOR anabolic pathway. METHODS Female heterozygous MSTN-prodomain transgenic mice (an MSTN suppression model) and wild-type littermates were given 0 or 20 ppm of clenbuterol (CL) in their drinking water, and muscle samples were collected at 1 and 2 weeks after treatment. RESULTS CL increased body and muscle mass in both genotypes. Levels of phosphorylated muscle 4E-BP1 and p70S6k were higher in MSTN-prodomain transgenic mice than in wild-type mice. CL increased the phosphorylation of 4E-BP1 and p70S6k in both genotypes. CONCLUSIONS The muscle-hypertrophic effect of CL is additive to the effect of MSTN suppression. The combination of MSTN suppression and treatment with β-agonists may be an effective therapeutic approach to combat muscle-wasting conditions.