Cord Blood from SGA Preterm Infants Exhibits Increased GLUT4 mRNA Expression

Abstract

Background Insulin and insulin-like growth factor (IGF) signaling plays an important role in prenatal and postnatal growth and glucose metabolism. Both smallfor-gestational age (SGA) and preterm infants have abnormal growth and glucose metabolism. However, the underlying mechanism remains unknown. Recently, we showed that term SGA infants have abnormal insulin/ IGF signaling in cord blood. In this study, we examined whether preterm infants show similar aberrations in cord blood insulin/IGF signaling. Methods A total of 41 preterm cord blood samples were collected. Blood glucose, insulin, IGF-1, and C-peptide concentrations were measured, and mRNA expression of IGF1R, INSR, IRS1, IRS2, and SLC2A4 (i.e., GLUT4) was analyzed by quantitative reversetranscription PCR. Results This study included 34 appropriate-forgestational age (AGA) and 7 SGA preterm neonates. No hyperinsulinemia or any differences in IGF1R or INSR mRNA expression were detected between the two groups. However, GLUT4 mRNA levels were increased in preterm SGA. Moreover, the expression level in hypoglycemic preterm SGA was significantly higher than that in hypoglycemic preterm AGA. IRS2 mRNA expression did not show a statistically significant difference between preterm SGA and AGA neonates. Conclusion SGA preterm birth does not induce hyperinsulinemia; however, it modifies insulin/IGF signaling components such as GLUT4 in umbilical cord blood. Our study suggests that prematurity or adaptation to malnutrition alters the insulin/IGF signaling pathway.

Cord-Blood Derived Chemistry Reference Values in Preterm Infants for Sodium, Chloride, Potassium, Glucose, and Creatinine

“…Cord glucose values in term babies were previously found to be similar to their respective mothers (14) with values of 4.0+/-0.6mmol/L, comparable to our findings of 4.0+/-1.3mmol/L (Table 4) (7). It is not surprising to see lower glucose values in multiples, C/s deliveries and SGA infants, with additive effects (25). Multiples are limited by substrate with more than one fetus needing to be sustained.…”

“…C/s deliveries are more likely to occur in pathologic pregnancies, have mothers fasting, and emergencies, all of which use up substrates, and SGA by definition includes infants who are in a situation of lacking nutritional reserves. 25 Interestingly, none of the perinatal pathologic conditions we investigated other than SGA were associated with low glucose levels which might be because of multiples, C/s deliveries and SGA having stronger influence. In contrast, others have observed in term babies after pregnancy complicated by PIH cord glucose levels higher than their normal counterparts.…”

“…Multiples are limited by substrate with more than one fetus needing to be sustained. C/s deliveries are more likely to occur in pathologic pregnancies, have mothers fasting, and emergencies, all of which use up substrates, and SGA by definition includes infants who are in a situation of lacking nutritional reserves (25). Interestingly, none of the perinatal pathologic conditions we investigated other than SGA were associated with low glucose levels which might be because of multiples, C/s deliveries and SGA having stronger influence.…”

“…7 It is not surprising to see lower glucose values in multiples, C/s deliveries, and SGA infants, with additive effects. 25 Multiples are limited by substrate with more than one fetus needing to be sustained. C/s deliveries are more likely to occur in pathologic pregnancies, have mothers fasting, and emergencies, all of which use up substrates, and SGA by definition includes infants who are in a situation of lacking nutritional reserves.…”