PLACENTAL LEPTIN - AN IMPORTANT NEW GROWTH-FACTOR IN INTRAUTERINE ANDNEONATAL DEVELOPMENT

Background. Leptin, the protein product of the ob gene, is produced by the adipocyte and seems to function as a link between adiposity, sati ety, and activity. Leptin has also been found to be necessary for pube rtal development, conception, and pregnancy in mice, and is increased in prepubertal children, independent of adiposity, suggesting a role i n childhood growth and development. This study investigated 100 mother /newborn pairs to determine the role of leptin in neonatal development . Placental tissue was assayed for leptin mRNA to evaluate it as a sou rce of leptin production in utero. Methods. One hundred mother/newborn pairs were enrolled in this study. Radioimmunoassay was performed for leptin on maternal venous and newborn cord blood. Leptin concentratio ns were measured in 43 children in Tanner stages 1 and 2 as a control group. Placental tissue was obtained from five mothers and assayed for leptin mRNA by reverse transcription/polymerase chain reaction (RT/PC R). Human placental cell lines JAR and JEG-3 were also assayed for lep tin mRNA expression. Results. Leptin was present in all newborns studi ed at a mean concentration of 8.8 ng/mL (+/-9.6 standard deviations). Leptin concentrations in cord blood correlated with newborn weight (r = .51), body mass index (BMI) (r = .48), and arm fat (r = .42). There was no correlation between leptin and insulin. When statistically cova rying for adiposity for newborns and Tanner stages 1 and 2 children, n ewborns had greater concentrations of leptin (mean, 10.57 ng/mL) than children (mean, 3.04 ng/mL). Leptin was present in all mothers at a me an value of 28.8 ng/mL (+/-22.2 standard deviations). Leptin concentra tion correlated with prepregnancy BMI (r = .56), BMI at time of delive ry (r = .74), and arm fat (r = .73). Maternal leptin correlated with s erum insulin (r = .49). There was no correlation between maternal and newborn leptin concentrations. Thirteen percent of newborns had higher leptin concentrations than their mothers. Placental tissue from five separate placentas expressed leptin mRNA at comparable or greater leve ls than adipose tissue. Two human trophoblastic placental cell lines, JAR and JEG-3 also expressed leptin mRNA. Conclusions. The correlation between leptin and adiposity found in children and adults was also fo und in newborns. Serum leptin concentrations in newborns were increase d more than three-fold compared with children in Tanner stages 1 and 2 when controlling for adiposity, suggesting that leptin concentrations in the newborn are not explained by adiposity alone. Maternal leptin concentrations correlated with measures of adiposity at delivery but d id not correlate with newborn adiposity or leptin. Leptin mRNA was exp ressed both in placental tissue and in two human placental cell lines. These data suggest that leptin has a role in intrauterine and neonata l development and that the placenta provides a source of leptin for th e growing fetus.