Responses of Chick Myoblast Proliferation to Branched-Chain Amino Acids in a Three-Component System

This study investigated the combined effect of branched-chain amino acids (BCAAs), valine (Val), leucine (Leu), and isoleucine (Ile) on chick myoblast proliferation and associated gene expression within a three-component system. Isolated myoblasts were incubated in 22 different culture media, designed using a {3, 5} simplex lattice design to cover the entire range of compositions for each BCAA. The proliferation was estimated based on cell quantities after 72 h of incubation. The proliferation data under different BCAA combinations were fitted using Scheffé's seven-term special cubic model for three components. The response surfaces of proliferation showed a convex configuration, with increases in Ile leading to a decrease in proliferation. The maximal proliferation was observed at Leu and Val proportions of 3:7 and 1:1 in an Ile-free medium, as measured by the DNA assay and water-soluble tetrazolium salt (WST-8) assay, respectively. These findings suggest that Val has a greater influence than Leu on myoblast proliferation, particularly in DNA content. The responses of myoblast proliferation-associated factors, Pax7 and p21, corresponded to the proliferation evaluated with DNA and WST-8 assays, respectively. These results indicate that the growth of chick myoblast cells is affected by the combination of BCAAs in a three-component system.