AMP-activated protein kinase (AMPK) but not mammalian target of rapamycine complex 1/ Ribosomal protein S6 kinase beta-1 (mTOR/ S6K1) activity was regulated by leucine in HepG2 cells. (A) Western blots and densitometry analysis of leucine-supplemented HepG2 cells stained for p-mTOR and p-S6K1 and (B) p-AMPK. (C) Effect of leucine supplementation on myostatin (MSTN) mRNA level. Values are the presented as mean ± SEM. Statistical significance relative to untreated control, *P <0.05, (n =3).