Maternal and neonatal irisin precursor gene FNDC5 polymorphism is associated with preterm birth.

Irisin is a novel secreted myokine, encoded by the fibronectin type III domain-containing protein 5 (FNDC5) precursor gene. Irisin plays a role in the female reproductive system in pregnancy and in embryonic development, and is associated with fetal size. It is expressed in the ovary, placenta and neonatal cord serum. We studied whether maternal and neonatal FNDC5 genetic polymorphisms are associated with preterm birth (PTB). Blood for DNA analysis was collected from Israeli mothers (n = 315) and from umbilical veins of their respected idiopathic preterm (24-36 weeks) and control term (>37 weeks) newborns (n = 161). Genotypes of maternal and neonatal FNDC5 polymorphisms (rs726344 and rs1746661) were determined by restriction fragment length polymorphism analysis. Genotype-phenotype associations were analyzed using SPSS program. The Frequency of FNCD5 rs726344 G alleles in the Israeli cohort is 82%. We found significant FNCD5 rs726344 genotype frequencies control and PTB groups. Women bearing the FNDC5 rs726344 GG genotype had 2.18 fold ([CI] 1.193-4.008, p = 0.01) higher chance to deliver at term compared to both AG and AA genotypes (adjusting to age, gravidity, parity, weight percentile per gestational age and gender of newborn). Neonates carrying the FNDC5 rs726344 GG genotype had 2.24 fold ([CI] 0.979-5.134, p = 0.05) higher chance to be born at term compared to either AG or AA genotypes (adjusting to parity, previous abortions and weight percentile per gestational age). There was no significant association of the rs1746661 polymorphism with PTB. Thus, we determined FNDC5 polymorphisms frequencies in the Israeli population and demonstrated that maternal and neonatal FNDC5 rs726344 polymorphism is significantly associated with increased risk for PTB.