Circulating apelin concentrations in mother/infant pairs at term

Aim: To prospectively investigate circulating concentrations of the adipokine and angiogenic factor apelin in mother/infant pairs and correlate them with respective insulin concentrations.

Methods: Plasma apelin concentrations were determined in 40 mothers and their singleton full-term foetuses and neonates on day 1 (N1) and 4 (N4) of life.

Results: Maternal apelin concentrations were lower compared to foetal, N1 and N4 ones (p < 0.001 in all cases). N1 apelin concentrations were lower compared to foetal and N4 ones (p = 0.002 and p = 0.005, respectively). Maternal apelin concentrations positively correlated with foetal, N1 and N4 concentrations (r= 0.663, p < 0.001, r= 0.486, p = 0.003, r= 0.484, p = 0.003, respectively). Foetal apelin concentrations positively correlated with N1 and N4 ones (r= 0.337, p = 0.044 and r= 0.574, p < 0.001, respectively). N1 apelin concentrations positively correlated with N4 ones (r= 0.513, p = 0.001). No association was found between apelin concentrations and birthweight, gender, parity or mode of delivery. No significant correlations were observed between apelin and insulin concentrations.

Conclusions: Concentrations of apelin are high in the foetus, possibly suggesting its potential role in intrauterine development. Apelin expression in placental tissue could account for its higher foetal concentrations and for its down-regulation soon after birth. The postnatal increase of apelin concentrations could presumably point to a gradual initiation of ex utero angiogenesis.