Plasma branched-chain keto acids in burn patients.

Plasma branched-chain keto acids (BCKA) and glucose-alanine cycle-related substances were measured in venous and arterial blood following burn injury. It was found that the three BCKA diminished with a minimum on day 7 while pyruvate increased. Alanine and glutamate + glutamine also decreased but plasma branched-chain amino acids (BCAA) did not vary. BCKA and gluconeogenic amino acids were liberated by peripheral tissues whereas BCAA were not. By analogy with the fate of alanine, a reduction in plasma BCKA associated with a high release by peripheral tissues might involve an increase in their hepatic metabolism. The BCKA would then give rise to ketone bodies used by the peripheral tissue. This step would complete the glucose-alanine cycle described by Cahill in hypercatabolic states where energy requirements are intense and similar to those found in burn injuries.