• Kaoru Kimura, Xian Wu Cheng, Aiko Inoue, Lina Hu, Teruhiko Koike, and Masafumi Kuzuya.
• Department of Community Healthcare & Geriatrics, Nagoya University Graduate School of Medicine, Nagoya, Japan.
• Nutr Res. 2014 Apr 1; 34 (4): 368-74.

Abstractβ-Hydroxy-β-methylbutyrate (HMB) prevents deleterious muscle responses under pathological conditions, including tumor- and chronic steroid therapy-related muscle losses. Here, we investigated the hypothesis that HMB may modulate the balance between protein synthesis and degradation in the PI3K/Akt-mediated mammalian target of rapamycin (mTOR) and FoxO1/FoxO3a-dependent mechanisms in differentiated C2C12 muscle cells. We also tested the effect of HMB on the expression of MuRF-1 and atrogin-1 in response to the inflammatory stress. β-Hydroxy-β-methylbutyrate up-regulated phosphorylation of Akt and mTOR, and these effects were completely abolished in the presence of PI3K inhibitor LY294002. β-Hydroxy-β-methylbutyrate also up-regulated FoxO1 and FoxO3a phosphorylation, and these changes were inhibited by LY294002. Although, unexpectedly, HMB failed to reduce the expressions of atrophy-related atrogin-1 messenger RNA and the protein response to the proinflammatory cytokines tumor necrosis factor α plus interferon γ, HMB did attenuate the MuRF-1 expression. Thus, HMB appears to restore the balance between intracellular protein synthesis and proteolysis, likely via activation of the PI3K/Akt-dependent mTOR and FoxO1/FoxO3a signaling pathway and the reduction of tumor necrosis factor α/interferon γ-induced MuRF-1 expression, thereby ameliorating aging-related muscle atrophy.Copyright © 2014 Elsevier Inc. All rights reserved.

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