Peptide mixtures for enteral and parenteral nutrition

This article reviews the work concerning intestinal absorption of amino acids from a mixture of 12 glycyl-dipeptides in human jejunum as well as nutritional efficacy and safety of different dipeptide mixtures as the nitrogen source of total parenteral nutrition in baboons. Using a segmental perfusion technique, amino acid absorption rates were generally greater and less selective from the dipeptide mixture as compared to the corresponding free amino acid mixture. This can only be explained as a result of peptide uptake by a system that has greater transport capacity than amino acid carrier systems, thus minimizing competition among its substrates. To assess the efficacy and safety of dipeptides as substrates for total parenteral nutrition, the effects of intravenous infusion of two different synthetic dipeptide mixtures as well as a dipeptide supplemented free amino acid mixture on a range of parameters of nutrition, metabolism and organ function were investigated. In each experiment the corresponding free amino acid mixtures served as control. In three experiments in baboons with the period of parenteral nutrition being 1 or 4 weeks, respectively, all dipeptides were efficiently utilized, as evidenced by only trace concentrations of dipeptides in plasma and urine. With a dipeptide supplemented amino acid solution as well as with complete dipeptide mixtures serving as the sole source of nitrogen of parenteral solutions, parameters of nutrition, metabolism and organ function were well maintained. No adverse effects of the dipeptides occurred. These experiments provide the information needed for further investigation of dipeptides as a substrate of enteral and parenteral nutrition in man.