Neonatology Fellow UIC University of Illinois at Chicago Chicago, Illinois, United States
Background: Tyrosine is a conditionally essential amino acid in preterm neonates and needs to be added to parenteral nutrition solutions (PNS). Roberts et al (2001) proposed that the tyrosine requirement of the parenterally fed term neonate to be 74 mg/kg/day, however the requirement for the premature infant is unknown. Achieving tyrosine goal concentrations is challenging due to its low solubility. Commercially available PNS use soluble precursors that are derivatives of tyrosine.TrophAmine® includes N-acetyl-tyrosine (NAT). NAT is poorly metabolized in parentally fed piglets, very low birth weight preterm infants and in adults. The urinary excretion of NAT in these groups are 65%, 40% and 35% of intake respectively. Studies have shown indirect evidence that NAT improves protein accretion in the preterm infant. TrophAmine given at goal of 3.5g/kg/day provides 84mg/kg/day of tyrosine, which surpasses the proposed tyrosine requirement although it's unknown how much is actually utilized in the preterm neonate as most tyrosine is given as NAT in TrophAmine.
Objective: We sought to determine if gestational age (GA) and birth weight (BW) influence urinary excretion of NAT. We hypothesized that neonates receiving total parenteral nutrition (TPN) with BW>= 1500g excrete less NAT than those with BW<1500g.
Design/Methods: Urine samples from infants born <32 weeks GA and with BW < 2000g were collected at days 1-3 of life. All patients received TPN containing 2.5, 2.7 and 3g/kg/da of protein on days of life 1, 2 and 3 respectively using 10% TrophAmine. Metabolomics was performed by Metabolon Inc. (North Carolina) as described previously (Miller et al., 2015). Raw biochemical values from mass spectrometry analysis were first median scaled and urine values were normalized to creatinine. Statistical analysis was conducted in R. A P-value less than 0.05 was considered significant.
Results: A total of 106 subjects were included in the study: 37 with BW <1000g (ELBW), 42 with BW 1000-1499g (VLBW) and 27 with BW 1500-2000g (LBW). Results were similar for ELBW and VLBW, therefore patients were grouped together for final analysis (EVLBW). Excretion of NAT and tyrosine were significantly higher in the EVLBW group in comparison with LBW group on all 3 days (p<0.01). Conclusion(s): ELBW and VLBW neonates receiving TPN have higher excretion of unchanged NAT than LBW neonates. This indicates that NAT requirements may be higher in ELBW and VLBW.
Authors/Institutions: Ana Taddei, University of Illinois at Chicago, Chicago, Illinois, United States; Caden Lambie, University of Wisconsin-Madison, Madison, Wisconsin, United States; Alan Schwartz, University of Illinois at Chicago, Chicago, Illinois, United States; Wenxiang Luo, University of Illinois at Chicago, Chicago, Illinois, United States; Nicole S. Glaser, University of Illinois at Chicago, Chicago, Illinois, United States; Katie Brenner, University of Wisconsin-Madison, Madison, Wisconsin, United States; Douglas Weibel, UW-Madison, Madison, Wisconsin, United States; De-Ann M. Pillers, University of Illinois, Chicago, Chicago, Illinois, United States
