Leptin in the ovine fetus correlates with fetal and placental size

OBJECTIVE: The purpose of this study was to detect the presence of leptin a nd its receptor in ovine fetal tissues and to examine the relationship betw een circulating leptin concentrations and fetal and placental weights on ge stational day 138 (GD138) of ovine pregnancy (term, 145 days), STUDY DESIGN: Pregnant sheep (n = 18) were instrumented on GD 110 to facili tate measurement and chronic reduction of uterine blood flow and produce in trauterine growth restriction. Four animals that served as controls were eu thanized on GD 138 to obtain fetal tissues to determine the presence of ovi ne leptin and its receptor by reverse transcriptase-polymerase chain reacti on. Seven instrumented animals were randomized into the control group, and 7 instrumented animals were randomized into the uterine blood flow restrict ed group (reduction equaled approximately 50% on GD 138). Maternal and feta l blood samples were obtained on day 138 to measure plasma leptin concentra tions, and animals were euthanized for the determination of fetal morphomet rics and placental weight. RESULTS: Expression of RNA for ovine leptin and its receptor were observed in fetal liver, skeletal muscle, kidney, heart, and placenta. Fetal body we ight, ponderal index, and placental weight were significantly decreased by approximately 40% in the blood flow restricted group as compared with contr ols, Fetal leptin concentrations were increased by 45% in the uteroplacenta l blood flow restricted group (P = .01). Maternal leptin concentrations wer e not significantly different between the 2 groups and did not correlate wi th fetal concentrations. Fetal leptin concentrations had an inverse relatio nship with uterine blood flow (r = -0.73; P = .004), fetal body weight (r = -0.78; P = .002), and placental weight (r = -0.68; P = .01). CONCLUSION: Ovine fetal tissues express RNA for leptin and its receptor. Ci rculating leptin concentrations in the ovine intrauterine growth restrictio n fetus were significantly elevated on gestational day 138 compared with co ntrols. Fetal leptin concentrations were inversely related to uterine blood flow and fetal and placental weight. These findings suggest that fetal lep tin may be involved in an adaptive response to intrauterine growth restrict ion.