Enhanced nutrient supply to very low birth weight infants is associated with higher blood amino acid concentrations and improved growth

Abstract

Background & aims: Customized nutrient supply is vital to ensure optimal growth among very low birth weight infants (birth weight < 1500 g). The supply of amino acids is especially important due to their impact on protein synthesis and growth. The objectives of this study were to evaluate the impact of enhanced nutrition on growth, blood concentrations of amino acids, and explore possible associations between amino acid concentrations and common neonatal morbidities. We hypothesized higher amino acids levels and growth velocity among infants on enhanced nutrient supply.

Methods: This randomized controlled trial was performed in three university neonatal intensive care units in Oslo, Norway. Fifty very low birth weight infants were randomized to a control or intervention group. Within 24 h after birth, infants in the intervention group received enhanced supply of energy, amino acids, lipids, long-chain polyunsaturated fatty acids and vitamin A, whereas the control group received a standard nutrient supply. The intervention continued until 52 weeks postmenstrual age or until a body weight of 5.5 kg was reached. Amino acid analyses were performed at birth, day 3, 5 weeks of age and 5 months corrected age. Detailed information about nutrient intake, morbidities, blood amino acid concentrations and growth velocity were collected from 44 infants (6 infants excluded). High-performance liquid chromatography was used for amino acid analysis.

Results: The intervention group (n = 23) received higher supply of proteins, with higher blood concentrations of amino acids measured at 5 weeks of age, and improved growth velocity (mean 17.4 vs 14.3 g/kg/day, p < 0.001) at 36 weeks postmenstrual age, compared to the control group (n = 21). The correlation between concentrations of branched chain amino acids (leucine, isoleucine and valine) and growth was stronger and more positive among infants: a) in the control group (correlation coefficient ≥ 0.68, p ≤ 0.004); b) born with birth weight appropriate for gestational age (correlation coefficient ≥ 0.53, p ≤ 0.009) and c) not diagnosed with septicemia (correlation coefficient ≥ 0.63, p ≤ 0.005).

Conclusion: Enhanced nutrient supply to very low birth weight infants led to higher blood amino acid concentrations and improved growth. The correlations between amino acid concentrations and growth velocity were weaker in the intervention group as compared to the control group. This could reflect an upper threshold for protein synthesis and growth with our intervention, whereas a potential for further growth with increasing amino acid supply was possible for the control group.

Clinical trial registration no: NCT01103219.

Keywords: Amino acids; Growth and nutrition; Premature infants.