β-hydroxy-β-methylbutyrate (HMB), a leucine catabolite, has been shown to prevent exercise-induced protein degradation and muscle damage. We hypothesized that HMB would directly regulate muscle-cell proliferation and differentiation and would attenuate apoptosis, the latter presumably underlying satellite-cell depletion during muscle degradation or atrophy. Adding various concentrations of HMB to serum-starved myoblasts induced cell proliferation and MyoD expression as well as the phosphorylation of MAPK/ERK. HMB induced differentiation-specific markers, increased IGF-I mRNA levels and accelerated cell fusion. Its inhibition of serum-starvation- or staurosporine-induced apoptosis was reflected by less apoptotic cells, reduced BAX expression and increased levels of Bcl-2 and Bcl-X. Annexin V staining and flow cytometry analysis showed reduced staurosporine-induced apoptosis in human myoblasts in response to HMB. HMB enhanced the association of the p85 subunit of PI3K with tyrosine-phosphorylated proteins. HMB elevated Akt phosphorylation on Thr308 and Ser473 and this was inhibited by Wortmannin, suggesting that HMB acts via Class I PI3K. Blocking of the PI3K/Akt pathway with specific inhibitors revealed its requirement in mediating the promotive effects of HMB on muscle cell differentiation and fusion. These direct effects of HMB on myoblast differentiation and survival resembling those of IGF-I, at least in culture, suggest its positive influence in preventing muscle wasting.
|Original language||American English|
|Number of pages||9|
|Journal||Biochimica et Biophysica Acta - Molecular Cell Research|
|State||Published - May 2009|
Bibliographical noteFunding Information:
We thank Bruce Paterson for the anti-chicken myogenin antibody. This study was supported by a grant from the EEU 6th Framework Program Network of Excellence MYORES (contract 511978), the AFM (Association Française contre les Myopathies), INSERM, University Pierre et Marie Curie, the ARCUS Région Ile de France/Ministère des Affaires Etrangères/UPMC, and the Capes-Cofecub and FIOCRUZ/INSERM joint programs.
- Skeletal muscle