[Total parenteral nutrition of premature infants: metabolic effects of an exogenous supply of L-aspartic acid and L-glutamic acid]

Abstract

Within the scope of clinically indicated total parenteral nutrition of premature infants, a comparative randomized study was performed to examine--by means of nitrogen-balance studies and determination of the free amino acids in the serum--the metabolic effects of absent or parallel intake of 1.140 mumol L-aspartic acid plus 2.160 mumol L-glutamic acid per kg body weight per day in complete L-amino acid solutions with a comparative E/T-ratio and with identical intake of all other nutrients adapted to the requirement. 1. The nitrogen balance level was not affected by the absent or parallel intake of the dicarbonic acids. 2. Intravenous intakes of glycine plus L-serine, which are higher than 2.5 mmol per kg body weight and day, caused statistically significant increased serum concentrations of glycine and L-serine. Such intakes are obviously above the physiologic regulation range. 3. The absent intake of L-aspartic acid and L-glutamic acid resulted in parallel, statistically significant reduced serum concentrations of aspartic acid and asparagine as well as in homeostatic serum concentrations of glutamic acid and glutamine. Despite the only 15-20% higher intake of proline, alanine and arginine under the infusion regimen lacking dicarbonic acids, there was a parallel, statistically significant marked increase in the serum concentrations of proline, alanine, arginine and methionine as well as a statistically significant marked decrease in those of taurine. Under the infusion regimen containing dicarbonic acids exclusively, constant homeostatic serum concentrations of these amino acids as well as of aspartic acid and glutamic acid were measured. 4. A direct or indirect effect of the exogenous supply of L-aspartic acid and/or L-glutamic acid on the homeostasis of aspartic acid and asparagine, on the endogenous turnover of L-alanine and L-proline as well as on the physiologic course of the Krebs-Henseleit cycle and of the "transsulfuration pathway" must be discussed. 5. Since the supply rates of L-aspartic acid plus L-glutamic acid chosen in series 2 (when continuously administered during 24-hour periods) apparently do not cause any disturbance in amino-acid homeostasis, it is established that under the nutritional conditions given this intake lies within the respective physiologic regulation range and therefore is atoxic.