V. Castagne et al., EFFECTS OF DIET-INDUCED HYPERTHREONINEMIA .1. AMINO-ACID LEVELS IN THE CENTRAL-NERVOUS-SYSTEM AND PERIPHERAL-TISSUES, Life sciences, 53(24), 1993, pp. 1803-1810
Rats were fed four levels of threonine (Thr, 0.4, 0.6, 0.8, and 5.8g/1
00 g diet). After two weeks, Thr, serine (Ser), and glycine (Gly) leve
ls were measured in plasma, liver, muscle, and central nervous system.
The diet containing 5.8 g/100 g of Thr elevated Thr and Gly concentra
tions in plasma and nervous tissue in comparison with a standard diet.
In muscle and liver, Thr concentrations were also raised but Gly leve
ls did not change. The hepatic Thr dehydratase activity was enhanced.
Diets containing moderate Thr quantities (0.6 and 0.8 g/100 g) induced
slight elevations of Thr levels in all tissues. Gly concentrations we
re not modified. The activity of hepatic Thr dehydratase was diminishe
d. Our results show that a high dietary content of Thr (15 times the n
ormal levels) elevates Gly levels in various tissues, including the br
ain. On the contrary, diets containing 2 to 4 times the normal levels
of Thr induce a weak hyperthreoninemia insufficient to modify brain Gl
y.