Alanine

Alanine is a non-essential amino acid central to the glucose-alanine (Cahill) cycle, by which exercising muscle exports amino nitrogen to the liver for gluconeogenesis while disposing of pyruvate generated by glycolysis. Salivary alanine reflects the intensity of muscle glycolytic flux and inter-organ nitrogen shuttling during exercise. Felig and Wahren (1971) established the marked rise in alanine release from working muscle that defines this cycle.