Energy metabolism profile of the effects of amino acid treatment on skeletal muscle cells: Leucine inhibits glycolysis of myotubes

Abstract Amino acids are not only components of proteins, but can also be metabolized to energy substances or be utilized as signaling molecules. However, the basic knowledge of the relationship between amino acids treatment and energy metabolism is still insufficient. In the present study, we profiled whether amino acids (essential amino acids and alanine) treatment can affect the energy metabolism (glycolysis, mitochondrial respiration) of cultured skeletal muscle cells. C2C12 myoblasts and differentiated myotubes were treated with 5 mM each amino acid for 1 hour, then the energy metabolism was measured by using extracellular flux analyzer. Although all the amino acids treatment could not affect the energy metabolism of C2C12 myoblasts, leucine, isoleucine, lysine, phenylalanine and histidine decreased the ECAR (ExtraCellular Acidification Rate), an indirect indicator of glycolysis, in differentiated myotubes without alteration of OCR (Oxygen Consumption Rate), an indirect indicator of mitochondrial respiration. By Glycolysis stress test, we found that leucine treatment inhibited glycolysis of myotubes when the substrate of glycolysis is sufficient in cultured media. The inhibitory effect of glycolysis by leucine was not canceled by Rapamycin (an inhibitor for mTOR). But, BT2 (an inhibitor for BCKDC kinase) increased BCAAs catabolism which decreased the glycolysis of myotubes. Our findings complement the basic knowledge of amino acids treatment on energy metabolism of cultured skeletal muscle cells and suggest the inhibitory effects of glycolysis by BCAAs catabolism.