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Leucine kinetics during feeding in normal newborns
S C Denne1, E M Rossi, S C Kalhan
1Department of Pediatrics, Indiana University School of Medicine, Indianapolis 46202-5210.
Pediatric Research
|July 1, 1991
Summary
Newborns increase protein synthesis during feeding, not by reducing protein breakdown, to gain mass. This study measured leucine metabolism in fed versus fasted infants.
Area of Science:
- Neonatal nutrition
- Metabolic research
- Protein metabolism
Background:
- Understanding leucine and protein metabolism is crucial for neonatal growth.
- Feeding significantly impacts metabolic processes in newborns.
- Previous studies focused on fasting states, necessitating research on fed states.
Purpose of the Study:
- To investigate the effects of feeding on leucine and protein metabolism in term newborns.
- To compare leucine kinetics in fed versus fasted newborns.
- To determine the relationship between birth weight and leucine flux.
Main Methods:
- Utilized a prime-constant tracer infusion of 1-13C leucine.
- Employed respiratory calorimetry to measure metabolic rates.
- Compared leucine kinetics in 11 fed newborns with data from previously studied fasting newborns.
Main Results:
- Fed newborns exhibited significantly higher nonoxidative leucine disposal rates, indicating increased protein synthesis (170 +/- 13 mumol/kg/h vs. 129 +/- 9 mumol/kg/h).
- Leucine oxidation and leucine release from protein were similar between fed and fasting groups.
- A positive correlation was observed between birth weight and leucine flux in both feeding and fasting states.
Conclusions:
- Newborns primarily achieve protein accretion through enhanced protein synthesis rather than reduced protein breakdown.
- Established an estimate for minimal leucine intake required to offset oxidative losses (816 mumol/kg/d).
- The correlation between birth weight and leucine flux may reflect variations in prenatal nutrient availability.