Nitrogen and amino acid metabolism in adults with protein-calorie malnutrition.

Abstract

Nitrogen balance, plasma amino acidlevels, and amino acid balance across forearm tissues were studied in 17 adult patients with severe protein-calorie malnutrition in a Calcutta hospital. Patients were selected for the severity of their malnutrition and for absence of other diseases. During 2–4 mo of refeeding there was complete clinical recovery, including resolution of all signs of protein depletion. Plasma essential amino acids were very low in malnutrition and rose to normal during refeeding. Plasma glycine was high initially and after refeeding. Alanine and several other nonessential amino acids were normal in malnutrition and rose to high levels during refeeding. These results in adult malnutrition are similar to many of those reported in kwashiorkor, but they differ from results of studies of experimental starvation. The long duration of protein deprivation and the persistence of significant carbohydrate intake in malnutrition but not experimental starvation are probably factors that have important bearing on the differences between amino acid levels in these two conditions. Nitrogen balance was −2.4 g/day on a 2 g/day nitrogen intake initially and +6.6 g/day on a 24.7 g/day intake after refeeding. Both in malnutrition and after refeeding, postabsorptive plasma arteriovenous differences for several amino acids were small compared with values in normal Americans. These small differences reflected reduced net release of amino acids from forearm tissues in malnutrition and probably also after refeeding. Persistently subnormal amino acid release from peripheral tissues probably restricted the supply of amino acids to the liver for gluconeogenesis and thus played a role in overall nitrogen conservation. However, the presence of normal or greater postabsorptive plasma levels of alanine and other amino acids despite decreased release from peripheral tissues suggests that hepatic fractional extraction was diminished and that this was also important in the conservational adaptation to protein depletion. Nitrogen balance, plasma amino acidlevels, and amino acid balance across forearm tissues were studied in 17 adult patients with severe protein-calorie malnutrition in a Calcutta hospital. Patients were selected for the severity of their malnutrition and for absence of other diseases. During 2–4 mo of refeeding there was complete clinical recovery, including resolution of all signs of protein depletion. Plasma essential amino acids were very low in malnutrition and rose to normal during refeeding. Plasma glycine was high initially and after refeeding. Alanine and several other nonessential amino acids were normal in malnutrition and rose to high levels during refeeding. These results in adult malnutrition are similar to many of those reported in kwashiorkor, but they differ from results of studies of experimental starvation. The long duration of protein deprivation and the persistence of significant carbohydrate intake in malnutrition but not experimental starvation are probably factors that have important bearing on the differences between amino acid levels in these two conditions. Nitrogen balance was −2.4 g/day on a 2 g/day nitrogen intake initially and +6.6 g/day on a 24.7 g/day intake after refeeding. Both in malnutrition and after refeeding, postabsorptive plasma arteriovenous differences for several amino acids were small compared with values in normal Americans. These small differences reflected reduced net release of amino acids from forearm tissues in malnutrition and probably also after refeeding. Persistently subnormal amino acid release from peripheral tissues probably restricted the supply of amino acids to the liver for gluconeogenesis and thus played a role in overall nitrogen conservation. However, the presence of normal or greater postabsorptive plasma levels of alanine and other amino acids despite decreased release from peripheral tissues suggests that hepatic fractional extraction was diminished and that this was also important in the conservational adaptation to protein depletion.