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Whole body protein synthesis and energy expenditure in very low birth weight infants
Insights
This study investigated protein and energy metabolism in premature infants, finding that 75% of weight gain was lean tissue, crucial for growth. Protein synthesis and breakdown rates were quantified to understand nutrient utilization in these vulnerable infants.
Area of Science:
- Neonatal nutrition
- Pediatric metabolism
- Infant growth and development
Background:
- Very low birth weight (VLBW) infants (<1500g) experience rapid growth phases requiring precise nutritional support.
- Understanding whole body protein and energy metabolism is critical for optimizing growth and development in premature neonates.
Purpose of the Study:
- To investigate whole body protein synthesis and breakdown rates in VLBW infants during their rapid growth phase.
- To assess energy metabolism, including intake, expenditure, and retention, in VLBW infants.
- To determine the efficiency of nitrogen utilization and body composition changes in VLBW infants.
Main Methods:
- Studied ten VLBW infants during their first two months of life.
- Measured energy and protein intake, apparent digestibility, and expenditure.
- Utilized 15N glycine administration and urinary urea analysis to determine whole body protein synthesis and breakdown rates.
Main Results:
- Infants retained 41 kcal/kg/day, with 75% of weight gain being lean tissue.
- Apparent protein digestibility was 89%, with protein retention of 1.76 g/kg/day.
- Whole body protein synthesis averaged 11.2 g/kg/day and breakdown 9.4 g/kg/day.
Conclusions:
- VLBW infants demonstrate significant protein synthesis and breakdown during rapid growth.
- Energy and protein metabolism are crucial factors influencing lean tissue accretion in premature infants.
- Accurate assessment of metabolic processes aids in tailoring nutritional strategies for optimal VLBW infant outcomes.
Abstract:
The aim of the present work was to study whole body protein synthesis and breakdown, as well as energy metabolism, in very low birth weight premature infants (less than 1500 g) during their rapid growth phase. Ten very low birth weight infants were studied during their first and second months of life. They received a mean energy intake of 114 kcal/kg X day and 3 g protein/kg X day as breast milk or milk formula. The average weight gain was 15 g/kg X day. The apparent energy digestibility was 88%, i.e. 99 kcal/kg X day. Their resting postprandial energy expenditure was 58 kcal/kg X day, indicating that 41 kcal/kg X day was retained. The apparent protein digestibility was 89%, i.e. 2.65 g/kg X day. Their rate of protein oxidation was 0.88 g/kg X day so that protein retention was 1.76 g/kg X day. There was a linear relationship between N retention and N intake (r = 0.78, p less than 0.001). The slope of the regression line indicates a net efficiency of N utilization of 67%. Estimates of body composition from the energy balance, coupled with N balance method, showed that 25% of the gain was fat and 75% was lean tissue. Whole body protein synthesis and breakdown were determined using repeated oral administration of 15N glycine for 60-72 h, and 15N enrichment in urinary urea was measured. Protein synthesis averaged 11.2 g/kg X day and protein breakdown 9.4 g/kg X day. Muscular protein breakdown, as estimated by 3-methylhistidine excretion, contributed to 12% of the total protein breakdown.(ABSTRACT TRUNCATED AT 250 WORDS)