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 GRß 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 4-7, and the mRNA expression levels of GRα and GRß were measured using RT-qPCR. The relative gene expression levels of GRα and GRß as the target genes normalized to actin beta as the endogenous control were calculated by the comparative cycle threshold method. RESULTS: The GRα/GRß 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/GRß expression ratio increased from day 0 to days 4-7 (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 suggest that glucocorticoid sensitivity in VLBW infants increases after birth and this rapid change may play a role in surviving critical postnatal events.