The collagen derived dipeptide hydroxyprolyl-glycine promotes C2C12 myoblast differentiation and myotube hypertrophy

The majority of studies on possible roles for collagen hydrolysates in human health have focused on their effects on bone and skin. Hydroxyprolyl-glycine (Hyp-Gly) was recently identified as a novel collagen hydrolysate-derived dipeptide in human blood. However, any possible health benefits of Hyp-Gly remain unclear. Here, we report the effects of Hyp-Gly on differentiation and hypertrophy of murine skeletal muscle C2C12 cells. Hyp-Gly increased the fusion index, the myotube size, and the expression of the myotube-specific myosin heavy chain (MyHC) and tropomyosin structural proteins. Hyp-Gly increased the phosphorylation of Akt, mTOR, and p70S6K in myoblasts, whereas the phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 inhibited their phosphorylation by Hyp-Gly. LY294002 and the mammalian target of rapamycin (mTOR) inhibitor rapamycin repressed the enhancing effects of Hyp-Gly on MyHC and tropomyosin expression. The peptide/histidine transporter 1 (PHT1) was highly expressed in both myoblasts and myotubes, and co-administration of histidine inhibited Hyp-Gly-induced phosphorylation of p70S6K in myoblasts and myotubes. These results indicate that Hyp-Gly can induce myogenic differentiation and myotube hypertrophy and suggest that Hyp-Gly promotes myogenic differentiation by activating the PI3K/Akt/mTOR signaling pathway, perhaps depending on PHT1 for entry into cells.