Sulphur-containing amino acids, glutathione and the modulation of inflammation

The diet of industrialised countries is usually rich in amino acids, which are partly used as a source of calories. However, metabolic alterations are observed in diseased patients and a preferential retention of Sulphurated Amino Acids (SAA) occurs during the inflammatory response. It has been demonstrated in an acute sepsis phase model in rats that the metabolism of L-Cysteine (Cys) is modified. Glutathione (GSH) concentration is greater in the liver, kidneys and other organs and Cys incorporation into proteins is higher in the spleen and lungs. In the plasma Acute Phase Proteins are released while Albumin is decreased. The proinflammatory cytokines such as Interleukin-1, Interleukin-6 and TNF-alpha are the main initiators altering protein and amino acid metabolism. L-Methionine (Met) conversion to Cys is impaired under stress, such as in premature infants or AIDS patients. Thus, the metabolic flow through the trans-sulphuration pathway may be inadequate to meet the Cys demand under critical conditions. These altered biochemical rules during inflammation weaken the anti-oxiding functions, while the extra-supply of SAA under inflammatory conditions may help restore homeostasis.