Adiponectin serum concentrations in newborn at delivery appear to be of fetal origin

Adiponectin (APN) may play a role in adapting energy metabolism at the maternal-fetal unit. The aim of the study was to investigate the relationship between placental APN mRNA expression, maternal serum APN concentration and umbilical cord serum APN concentration in full-term healthy newborns.

Serum APN levels were compared in 46 samples (23 from healthy newborns; gestational age 37.0 to 41.5 weeks) and their mothers (n=23). The APN concentration was measured using enzyme linked immunosorbent assay (ELISA). We analyzed the mRNA expression profile of APN in 22 placenta tissue samples using real time polymerase chain reaction (RT-PCR).

The highest APN serum concentrations were found in umbilical cord blood, these were significantly higher than maternal APN levels (mean concentration±SD; 38.48±12.8 vs. 6.6±2.3 μg/mL, p<0.001). Otherwise, there were no significant correlation between maternal APN and umbilical cord APN concentration. APN gene expression was very low and only found in 8 out of 22 placentas. There were no significant correlation between placental APN mRNA and umbilical cord serum APN or maternal serum APN concentration. Umbilical cord APN concentrations were positively associated with birth weight (r=0.535; p=0.012) and gestational age (r=0.559; p=0.013). Maternal APN concentration revealed a negative correlation between maternal body weight (r=-0.623; p=0.009) and body mass index (BMI) (r=-0.634; p=0.008) at delivery. Additionally, no significant correlation was found between newborn birth weight and maternal weight.

This study suggests that high serum APN concentrations in umbilical cord blood are not regulated by placental APN mRNA gene expression. The high concentration of APN in cord blood is independent from maternal APN concentration, suggesting an important physiological role of APN and implicating that umbilical APN concentration reflects its exclusive production by fetal tissues.