Transient tachypnea of the newborn (TTN): A role for polymorphisms in the beta-adrenergic receptor (ADRB) encoding genes?

Aim: Transient tachypnea of the newborn (TTN) is a common cause of early respiratory distress in the neonatal period of term infants. Delayed resorption of foetal lung fluid after birth is considered as the main pathophysiological factor. As resorption of foetal lung fluid is a catecholamine dependent process, we aimed at investigating, whether beta 1- and beta 2-adrenoreceptor (ADRB1, ADRB2) polymorphisms, known to alter catecholamine activity, are operative in TTN. Methods: DNA was collected for genotyping from 73 term newborns suffering from TTN and 55 healthy controls from a Caucasian cohort. Results: TTN infants were more likely to be male (70% vs. 49%; p < 0.05), had a lower mean birthweight (3120 +/- 450 vs. 3396 +/- 504 g; p < 0.001) and gestational age (GA) (38.4 +/- 1.2 vs. 39.4 +/- 1.3 weeks; p < 0.001) and were more often delivered by caesarean section (CS) (71% vs. 26%; p < 0.001). The beta 1Ser49Gly polymorphism differed significantly between cases and controls. Multivariate analysis provided beta 1Gly49 homozygotes with higher risk for TTN (OR 18.5; 95%CI 1.5-229; p = 0.023) than beta 1Ser49 allele carrier. Further analysis showed significant association of T-47C, A46G, C79G and C491T (TACC) haplotype in ADRB2 gene with TTN (p = 0.048). Conclusion: We conclude that beta 1Gly49 homozygosity and TACC haplotype of ADRB2 gene, both loss-of-function genetic variations, may predispose to TTN.