S. Feurte et al., Is the early increase in leptinemia one of the anorectic signals induced by an essential amino acid-deficient diet in the rat?, ENDOCRINOL, 141(10), 2000, pp. 3916-3919
Rats start decreasing their food intake as early as 70 min after the first
ingestion of a food deficient in threonine. A decrease of the limiting esse
ntial amino acid (EAA) in the plasma was proposed to be the first anorectic
signal. Because many hormones regulate feeding behavior, we studied the ef
fect of a meal (46 kJ) that was either devoid of threonine or was corrected
for the deficiency, on plasma leptin, insulin and glucagon levels using a
radio-immunoassay, at 0 to 180 min after the meal. One hour after ingestion
of the threonine-devoid meal, a larger increase in insulinemia (22+/-1 vs.
15+/-1 mu U/ml) and leptinemia (7.8+/-0.5 vs. 4.4+/-0.6 ng/ml; p<0.001) wa
s observed than after ingestion of the corrected meal. The area under the c
urve of the threonine-devoid meal group was 3 and 1.34 fold larger than for
the corrected meal group for insulin and leptin respectively. Glucagonemia
was not different between the two groups. We propose that the rise in lept
inemia, perhaps in synergy with rise in plasma insulin, might serve as one
early signal to brain structures, participating in the anorectic mechanism
following ingestion of an EAA-deficient diet.