α-1 acid glycoprotein inhibits insulin responses by glucose oxidation, protein synthesis and protein breakdown in mouse C2C12 myotubes

Increased plasma α-1 acid glycoprotein (AGP) is correlated with reduced growth rates in neonatal swine. The specific physiological mechanisms contributing to this relationship are unknown. This study was performed to determine if AGP can modify muscle metabolism by examining glucose oxidation and protein synthesis in the C2C12 muscle cell line. Cells were used for experiments 4 days post-fusion as myotubes. Myotubes were exposed to AGP for 24 h, with the last 4 h used to monitor 14C-glucose oxidation or to measure protein synthesis by incorporation of 3H-tyrosine. Treatment of C2C12 myotubes with mouse AGP (100 µg/ml) reduced glucose oxidation (P