Supplementary Material for: Glucocorticoid receptor expression pattern in very low-birth weight infants changes drastically within the first week of life

Introduction
We herein examined changes in expression levels of the glucocorticoid receptor subtypes GRα and GRβ in very low-birth weight (VLBW) and term infants to clarify time-dependent changes in glucocorticoid sensitivity after birth.

Methods
Whole blood samples were collected at birth and on postnatal days 4 to 7, and the mRNA expression levels of GRα and GRβ were measured using RT-qPCR. The relative gene expression levels of GRα and GRβ as the target genes normalized to actin beta as the endogenous control were calculated by the comparative cycle threshold method.

Results
The GRα/GRβ expression ratio at birth was significantly lower in 32 VLBW cesarean section (CS) infants than in term planned CS infants (median (IQR), 1.5 (1.1-1.8)- and 1.1 (0.7-1.6)-fold change, p <0.05). Furthermore, the GRα/GRβ expression ratio increased from day 0 to days 4 to 7 (1.0 (0.6-1.4)- and 1.7 (0.6-1.4)-fold change, p <0.01) in 43 VLBW infants.

Discussion / Conclusion
The present results suggests that glucocorticoid sensitivity in VLBW infants increases after birth and this rapid change may play a role in surviving critical postnatal events.