Effect of total parenteral nutrition on whole body protein kinetics in cachectic patients with benign or malignant disease

The metabolic effects of total parenteral nutrition on malnourished cancer and noncancer patients were investigated by determining whole-body protein metabolism before and during intravenous nutritional support. The results were compared to similar studies reported in normal subjects. Primed-continuous infusion of 15N glycine was used and the isotopic enrichments in urinary urea and ammonia were measured. The end product average values were used in the calculation of whole body protein turnover. After 10 days of nutritional support in cancer and noncancer patients whole body protein breakdown decreased by 50% (p = 0.01), and 59% (p = 0.001), whereas protein synthesis decreased by 21% (p = 0.005) and 33% (p = 0.025), respectively. Protein turnover did not change in noncancer patients but increased by 15% (p = 0.005) in cancer patients. The efficiency of utilization of the endogenous supply of amino acids from the breakdown of body proteins for synthetic purposes was 77% in this group of subjects. The utilization efficiency of the intravenously infused amino acids for synthesis of body protein was 39% in cancer and noncancer patients but 51% (p less than 0.05) in normals. The data suggest that depleted patients synthesize proteins from intravenous amino acids less well than normals.