Tryptophan-restriction diets help to maintain L-tryptophan homeostasis in tryptophan 2,3-dioxygenase knockout mice.
We hypothesized that the requirements of essential nutrients are dependent upon catabolic abilities. Mice lacking L-tryptophan 2,3-dioxygenase (TDO) are available. The body concentration of L-tryptophan (L-Trp) has been reported to be higher in TDO-deficient mice than in wild-type (WT) mice. We examined the requirement of an appropriate L-Trp level for TDO-deficient mice using several biomarkers. TDO-deficient mice were fed a 10% amino-acid mixture diet containing 0.06%, 0.08%, and 0.17% L-Trp. WT mice fed a 0.17% Trp diet (standard diet) were used as control mice. The concentrations of L-Trp and its metabolites via serotonin were higher in TDO-deficient mice fed the 0.17% L-Trp diet than in WT mice fed the standard diet, but the concentrations were almost identical between TDO-deficient mice fed the 0.06% L-Trp diet and WT mice fed the standard diet. Therefore, as hypothesized, requirements of essential nutrients are dependent on catabolic abilities.
Department of Nutrition, School of Human Cultures, the University of Shiga Prefecture, Hikone, Shiga, Japan.
Akihiro
A
Maeta
Tsutomu
T
Fukuwatari
Hiroshi
H
Funakoshi
Toshikazu
T
Nakamura
Katsumi
K
Shibata
0.06% L-Trp diet; TDO-deficient mice; tryptophan; wild-type mice