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Basal insulin secretion and erythrocyte insulin binding in preterm and term newborn infants
Insights
Newborn infants show increased insulin binding to erythrocytes, suggesting a mechanism for insulin
Area of Science:
- Endocrinology
- Neonatal Physiology
- Metabolic Research
Background:
- Insulin plays a crucial role in growth and metabolism.
- Understanding insulin's role in newborns is vital for neonatal care.
- Erythrocyte insulin receptors offer a measurable indicator of insulin activity.
Purpose of the Study:
- To investigate the ontogeny of insulin secretion and erythrocyte insulin receptors in newborns.
- To compare insulin binding in preterm infants, term infants, and adults.
- To explore the relationship between insulin binding, gestational age, and birth weight.
Main Methods:
- Measured plasma immunoreactive insulin and C-peptide concentrations in cord blood.
- Quantified [125I]-insulin binding to erythrocytes in preterm infants, term infants, and adults.
- Analyzed correlations between insulin/C-peptide levels, birth weight, gestational age, and insulin binding.
Main Results:
- Newborns had lower C-peptide concentrations and insulin/C-peptide ratios than adults.
- Insulin binding to erythrocytes was significantly higher in newborns compared to adults.
- Erythrocytes from preterm infants showed higher insulin binding than term infants, correlated negatively with gestational age.
- Increased binding in term infants was due to higher receptor concentration; in preterm infants, it was due to increased concentration and affinity.
Conclusions:
- Basal insulin secretion appears similar in preterm and term infants.
- Insulin clearance is likely decreased in newborn infants.
- Elevated erythrocyte insulin binding in newborns may facilitate insulin's growth-stimulatory effects during fetal development.
Abstract:
To study the ontogeny of the insulin secretion and the erythrocyte insulin receptor we measured plasma immunoreactive insulin and C-peptide concentrations and the binding of [125I]-insulin to the erythrocytes in cord blood from 16 preterm and 16 term infants. 20 normal-weight adults were also studied. The C-peptide concentrations and the molar ratio of C-peptide to insulin were lower in the newborn infants than in the adults. The immunoreactive insulin correlated positively with birth weight in the term infants. The insulin binding to erythrocytes from the newborn infants was increased when compared to the adults. Erythrocytes from the preterm infants bound more insulin than the cells from the term infants. There was a strong negative correlation between insulin binding and gestational age. In the term infants, plasma C-peptide correlated negatively with the insulin binding. The increased binding to erythrocytes from the term infants was due to an increase in the receptor concentration. The high insulin binding in the preterm infants was a result of both an increased receptor concentration and affinity. These data suggest that the basal insulin secretion is similar in preterm and term infants and that the clearance of insulin is decreased in newborn infants. The increased insulin binding in newborn infants may be a mechanism by which the growth stimulatory effect of insulin in fetal life is mediated.