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 < 0.05). In response to ICV leptin, fetal swallowing remained significantly elevated at 2, 4 and 6 h (1.3 +/- 0.4, 1.4 +/- 0.3 and 1.5 +/- 0.2 swallows/min, respectively; p < 0.05 vs. control).


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.
Perinatal Research Laboratories, David Geffen School of Medicine, University of California at Los Angeles, California, USA.
M A
MA
El-Haddad
Y
Y
Ismail
L
L
Day
M  G
M
Ross
D000286:Administration, Sublingual; D000818:Animals; D003679:Deglutition / Q000187:drug effects / Q000502:physiology; D004576:Electromyography; D004947:Esophagus / Q000187:drug effects* / Q000196:embryology / Q000502:physiology*; D005260:Female; D005333:Fetus / Q000502:physiology*; D007276:Injections, Intraventricular; D020738:Leptin / Q000008:administration & dosage / Q000494:pharmacology*; D011247:Pregnancy; D012756:Sheep; D013395:Sucrose / Q000008:administration & dosage / Q000494:pharmacology*
D020738:Leptin; D013395:Sucrose