Cellular and Physiological Implications of Dietary Supplementation with Beta‐Hydroxy‐Beta‐Methylbutyrate and Beta‐Alanine in Late Middle‐Aged Mice

Abstract

Several studies suggest that the decline of muscle function with age can be mitigated by dietary supplementation with beta‐hydroxy‐beta‐methylbutyrate (HMB) or beta‐alanine (BA). The purposes of this study were to investigate the effects of: 1) HMB treatment on murine C2C12 myoblast and myotube cultures; and 2) dietary HMB, BA, and a combination thereof, on muscle contractility in late middle‐aged mice. In C2C12 myotubes, free acid HMB enhanced sarcoplasmic reticulum (SR) calcium release beyond vehicle control in the presence of three separate SR agonists (P<0.05, ANOVA). HMB also improved C2C12 myoblast viability (P<0.05) and proliferation (P=0.017). Furthermore, an ex vivo muscle contractility study was performed on 48 C57BL/6nTac male mice (19 months old at end of study). For 8 weeks, mice were fed control AIN‐93M diet containing calcium HMB monohydrate, BA, or the combination thereof. In EDL muscle, the combination of HMB and BA showed significant increases in relative force (88.6 ± 2.2 mN vs. 79.8 ± 2.4 mN, P=0.025) and specific force (12.2 ± 0.4 N/cm2 vs. 10.8 ± 0.4 N/cm2, P=0.021) at submaximal frequency of stimulation. At maximum frequency of stimulation, BA showed a significant force increase over the control diet (202.0 ± 3.4 mN vs. 188.2 ± 4.6 mN, P=0.023). Effects in soleus muscle did not achieve statistical significance. Our findings suggest calcium signaling as a key pathway contributing to beneficial effects of HMB and BA on skeletal muscle.