AJP - Regulatory, Integrative and Comparative Physiology, Vol 236, Issue 5 307-R311, Copyright © 1979 by American Physiological Society
Diabetes, dietary tryptophan, and protein intake regulation in weanling rats
T. L. Woodger, A. Sirek and G. H. Anderson
The effects of streptozotocin-induced diabetes and tryptophan content of
the protein fed on protein intake regulation by weanling rats selecting
from 10 and 60% casein diets were evaluated. In uncompensated diabetes the
ratio of tryptophan to other selected neutral amino acids in plasma and
brain tryptophan were reduced, protein intake per unit of body weight was
increased, and serotonin, 5-hydroxyindoleacetic acid, and norepinephrine
were unaffected. Enrichment of the tryptophan content of the ingested
protein caused a decrease in protein, but not energy consumption of both
diabetic and nondiabetic rats. The reduction in protein intake correlated
inversely with increases in the tryptophan content relative to the neutral
amino acids in plasma and with increases in brain tryptophan and serotonin
levels in both diabetic and nondiabetic rats. The data suggest that
protein-feeding behavior is regulated by a mechanism that includes brain
serotonergic activity with insulin, through its influence on circulating
amino acids, determining the quantity of protein consumed in relation to
body weight.
