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Nitrogen balance and protein turnover during the growth failure in newly born low-birth-weight infants
Insights
Growth failure in low-birth-weight infants is not due to inadequate protein turnover. Insufficient energy and protein intake impacts high protein turnover rates, affecting protein balance in newborns.
Area of Science:
- Neonatal Nutrition
- Infant Metabolism
- Pediatric Gastroenterology
Background:
- Low-birth-weight (LBW) infants, including small-for-gestational-age (SGA) and appropriate-for-gestational-age (AGA) infants, often experience growth failure.
- Understanding nutrient assimilation and metabolic responses in the first week of life is crucial for optimizing infant growth.
- Protein turnover is a key indicator of metabolic status and growth potential in neonates.
Purpose of the Study:
- To investigate weight gain, nitrogen balance, and protein turnover in LBW, SGA, and AGA infants during the first week of life.
- To determine the relationship between energy and protein intake and growth parameters.
- To elucidate the mechanisms underlying growth failure in these vulnerable infants.
Main Methods:
- Measurement of weight gain, nitrogen balance, and energy/protein intake in 14 LBW, 5 SGA, and 9 AGA infants.
- Enteral feeding was adjusted based on individual infant assimilation capacity.
- Protein synthesis and degradation rates were quantified using intragastric infusion of [1-13C]leucine.
Main Results:
- Mean gross energy intake was 334 KJ/kg and protein intake was 1.75 g/kg/day.
- Four infants gained weight, while ten lost weight, correlating with intake and nitrogen balance.
- Protein synthesis and degradation rates were approximately 50% higher than in older preterm infants and not correlated with nitrogen balance.
Conclusions:
- Growth failure in LBW infants is not linked to insufficient overall protein turnover rates.
- Inadequate energy and protein intake appears to influence high protein turnover rates.
- Small alterations in protein synthesis and/or degradation, driven by insufficient intake, may lead to changes in protein balance and growth failure.
Abstract:
Weight gain, nitrogen balance, protein turnover, and energy and protein intakes were measured during the first week of life of 14 low-birth-weight (LBW) infants, 5 small-for-gestational-age (SGA) infants and 9 appropriate-for-gestational-age (AGA) infants enterally fed at rates determined by the infants ability to assimilate feed. Mean gross intakes were 334 KJ and 1.75 g/kg protein; 4 infants were increasing and 10 were losing weight at rates proportional to gross energy and protein intakes and to nitrogen balance (0.031 g protein balance/g wt gain). Rates of protein synthesis and degradation measured by an intragastric infusion of [1-13C]leucine, averaged 14.5 and 15.9 g protein.kg-1.d-1, some 50% higher than previously reported in older preterm infants and not correlated with nitrogen balance. The growth failure of these infants was not associated with inadequate overall rates of protein turnover, but appeared to reflect an influence of the insufficient energy and protein intakes on the high rates of protein turnover, inducing changes in protein balance in either direction through relatively small changes in protein synthesis and/or degradation.