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Substrate utilization during the first weeks of life
P J Sauer1, V P Carnielli, E J Sulkers
1Department of Pediatrics, Erasmus University/Sophia Children's Hospital, Rotterdam, The Netherlands.
Insights
Preterm infants utilize both glucose and fat for energy after birth. Medium chain triglycerides (MCT) are efficiently oxidized and can replace glucose, while protein contributes minimally to energy expenditure.
Area of Science:
- Biochemistry
- Neonatal Physiology
- Nutritional Metabolism
Background:
- Substrate utilization shifts significantly after birth, with a transition from primarily glucose to a mix of glucose and fat.
- Understanding these metabolic changes is crucial for optimizing nutrition in preterm infants.
Purpose of the Study:
- To investigate substrate oxidation and turnover in preterm infants during the first day and weeks of life.
- To determine the relative contributions of glucose, fat, and protein to energy expenditure.
Main Methods:
- Studied substrate oxidation and turnover rates in preterm infants.
- Analyzed the utilization of glucose and different types of fats (MCTs, LCFAs).
Main Results:
- On the first day of life, infused glucose is partially oxidized and partially converted to fat.
- By day 7 and 28, fat oxidation accounts for nearly half of energy expenditure.
- Medium chain triglycerides (MCT) are oxidized more rapidly than long chain fatty acids (LCFAs) and can serve as a glucose alternative.
- Protein contributes a consistent, small percentage (approx. 7%) to energy expenditure.
Conclusions:
- Preterm infants exhibit distinct substrate utilization patterns post-birth.
- Fat, particularly MCTs, plays a significant role in energy provision for preterm infants.
- Nutritional strategies can leverage fat oxidation, especially MCTs, to meet the energy demands of preterm neonates.
Abstract:
It is assumed that substrate utilization changes markedly around birth, from mainly glucose utilization before, to glucose/fat utilization after birth. We studied substrate oxidation and turnover in preterm infants on the first day and during the first weeks of life. We found that only part of the glucose that is infused on the first day of life is oxidized, while glucose is also converted into fat at the same time. Almost half of the energy expenditure is provided by fat oxidation on day 7 and 28 of life. Fat oxidation is dependent on the type of fat oxidized; the rate of oxidation of medium chain triglycerides (MCT) is higher than that of long chain fatty acids. MCT can replace glucose as an energy source. Proteins contribute only to a small extent (approximately 7%) to the energy expenditure at all ages.