T. Tokuda et al., The changes in body weight and plasma metabolite levels during leptin injection are caused by the reduction of food intake in sheep, ANIM SCI, 70, 2000, pp. 343-348
Leptin is thought to act on the central nervous system as an important regu
lator of food intake and body weight in mice. To examine the actions of lep
tin in sheep, we injected recombinant mouse leptin into the lateral cerebra
l ventricle of ewes. Six ewes were intracerebroventricularly cannulated and
given free access to forage and wafer. The ewes were injected with phospha
te-buffered saline (PBS) as a vehicle for 5 days through the cannula and th
en with PBS + leptin for 7 days consecutively Although food intake and body
weight did not change during PBS injection, the administration of leptin d
ecreased food intake and body weight. Plasma glucose levels decreased and p
lasma non-esterified fatty acid levels increased on the last few days of le
ptin administration. Approximately 2 weeks after normal food intake was rec
overed, the amount of diet was individually reduced in accordance with the
recorded food intake during the leptin administration in each sheep. During
food restriction, body weight and plasma metabolite concentrations were si
milarly changed as during the leptin-administration period. These results i
ndicate that leptin decreases food intake in sheep. Moreover, it is likely
that the changes in body weight and plasma metabolites were mainly induced
by the suppression of food intake during leptin injection.