Beta-hydroxy-beta-methylbutyrate (HMB) stimulates myogenic cell proliferation, differentiation and survival via the MAPK/ERK and PI3K/Akt pathways.
Beta-hydroxy-beta-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.
Kornasio
Reut
R
Department of Animal Sciences, The Hebrew University of Jerusalem, P.O. Box 12, Rehovot 76100, Israel.
Riederer
Ingo
I
Butler-Browne
Gillian
G
Mouly
Vincent
V
Uni
Zehava
Z
Halevy
Orna
O
D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002645:Chickens; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000187:drug effects* / Q000502:physiology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D014631:Valerates / Q000378:metabolism / Q000494:pharmacology*; D051020:bcl-X Protein / Q000378:metabolism
D015415:Biomarkers; D019253:Proto-Oncogene Proteins c-bcl-2; D014631:Valerates; D051020:bcl-X Protein; C004961:beta-hydroxyisovaleric acid; D007334:Insulin-Like Growth Factor I; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; D020928:Mitogen-Activated Protein Kinases