Glutamine and skeletal muscle

Among the 20 amino acids in the genetic code, glutamine is the most abundant and versatile amino acid in the human body. Quantitatively, the main tissue for glutamine synthesis, storage, and release is the skeletal muscle. Through the intertissue metabolic flux, skeletal muscles constantly release glutamine and feed cells of the immune system, liver, and kidneys. Glutamine can donate nitrogen atoms to the synthesis of purines and pyrimidines, has antioxidant and antiinflammatory properties, and also can modulate the synthesis of heat shock proteins. During catabolic situations, such as sepsis and major infections, trauma, surgery, and after exhaustive physical exercise, glutamine concentration in plasma and tissues (especially in skeletal muscle) is severely compromised. In order to reverse this scenario, free and dipeptide forms of glutamine supplementation have been studied. In the present chapter, the importance of glutamine metabolic biochemistry in skeletal muscle and the increased interest in glutamine supplementation is discussed.