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Metabolic responses to alanine in small-for-gestational age infants: developmental aspects
Insights
Small-for-gestational age (SGA) infants show altered alanine metabolism compared to adults. Hypoglycemic SGA infants exhibit impaired glucose regulation after alanine administration, which normalizes with improved blood glucose levels.
Area of Science:
- Biochemistry
- Neonatology
- Pediatric Endocrinology
Background:
- Small-for-gestational age (SGA) is associated with metabolic disturbances in newborns.
- Alanine plays a crucial role in glucose homeostasis, particularly in neonates.
Purpose of the Study:
- To investigate the metabolic response to an intravenous alanine tolerance test in small-for-gestational age (SGA) infants.
- To compare alanine metabolism and its effect on glucose and pyruvate levels in normoglycemic and hypoglycemic SGA infants versus healthy adults.
Main Methods:
- Intravenous alanine tolerance test administered to 14 SGA infants (normoglycemic and hypoglycemic) and 4 healthy adult volunteers.
- Measurement of plasma alanine disappearance rate (K value), plasma pyruvate, and blood glucose levels before and after alanine infusion.
Main Results:
- Apparent K values for alanine disappearance were lower in SGA infants (3%/min in normoglycemic, 2.2%/min in hypoglycemic) compared to adults (5.6%/min).
- Plasma pyruvate increased post-alanine in all SGA infants.
- Hypoglycemic SGA infants showed a tendency for blood glucose to decrease after alanine, while normoglycemic infants and adults showed an increase.
- Normalization of blood glucose in previously hypoglycemic SGA infants led to a glucose profile similar to normoglycemic infants.
Conclusions:
- SGA infants, particularly those who are hypoglycemic, exhibit altered alanine metabolism and impaired glucose regulation.
- Alanine's effect on blood glucose is dependent on the infant's glycemic status.
- Metabolic normalization in SGA infants is associated with improved glucose response to alanine challenges.
Abstract:
14 small-for-gestational age (SGA) infants and 4 healthy adult volunteers were subjected to an intravenous alanine tolerance test. In normoglycemic SGA infants studied during the first 6 days of life, the apparent K value for the disappearance rate of alanine was 3%/min. In 6 hypoglycemic patients studied between day 1 and day 12 the corresponding K value was 2.2%/min. In adult volunteers a K value of 5.6%/min was obtained. Plasma pyruvate increased after alanine in both normoglycemic and hypoglycemic SGA infants. The blood glucose tended to decrease after the alanine load in the hypoglycemic infants, whereas an increase was observed in infants with normoglycemia. On reexamination of 4 hypoglycemic SGA infants after the blood glucose concentration had normalized, a blood glucose profile approaching that of normoglycemic infants was recorded.