Unopposed appetite (orexigenic) mechanisms in the near-term ovine fetus: central leptin does not inhibit sucrose ingestion

Objective: Leptin is produced in adipocytes and is present in the term fetus. In the adult, leptin acts centrally to inhibit neuropeptide Y-induced carbohydrate intake. We sought to examine if central leptin alters fetal ingestion of oral sucrose in the near-term ovine fetus.

Methods: Five pregnant ewes and fetuses were prepared with fetal vascular, sublingual and intracerebroventricular (ICV) catheters and esophageal electromyogram electrodes, and studied at 132?±?1 days' gestation (term 145–150 days). Following a 2-h baseline period, 10% sucrose was infused sublingually (0.25?ml/min) for the duration of the study. At time 4?h, leptin (0.075?mg/kg) was administered ICV and fetal swallowing was monitored for an additional 6?h.

Results: During the basal period, fetal swallowing averaged 0.7?±?0.1 swallows/min. Fetal swallowing increased significantly in response to 10% sucrose (1.2?±?0.1 swallows/min; p?p?Conclusions: These results indicate that central leptin inhibition of sucrose ingestion is not functional in the near-term fetus. We speculate that a leptin-mediated anorexigenic response is not present at birth, such that unopposed appetite stimulatory mechanisms in the newborn may facilitate rapid newborn weight gain despite high body fat levels.