Possible Interaction: Tryptophan and Valine

“Other large neutral amino acids, namely valine , isoleucine, leucine and phenylalanine affect precursor availability by competing with tryptophan and tyrosine for the transport system across the blood brain barrier.”

“Twenty healthy newborns (two to three days of age) were randomly assigned to receive a feeding consisting either of tryptophan in 10 per cent glucose or valine in 5 per cent glucose valine competes with tryptophan for entry into the brain).”

“In both craniotomy groups, preoperative levels of tryptophan and valine were significantly decreased whereas glutamate, alanine, and arginine were significantly increased relative to the reference group.”

“Fasting plasma tryptophan (TRP) levels and ratios of total plasma … neutral amino acids (LNAAs)--tyrosine, phenylalanine, leucine, isoleucine, and valine--… tryptophan for passage across the blood-brain barrier were found to be significantly lower in … depression compared with 29 normal subjects and 21 patients with obsessive-compulsive disorder (OCD).”

“Since isoleucine, leucine, and valine are important competitors of tryptophan uptake at the blood-brain barrier, these observations suggest a possible mechanism for the therapeutic activity of Li, i.e., the enhancement of brain serotonin levels.”

“The other major factor that is thought to influence the levels of brain tryptophan is the concentration of the other neutral amino acids (leucine, isoleucine, valine , tyosine and phenylalanine) which compete with tryptophan for transport into the brain (Fernstrom & Wurtman, 1972).”

“In conclusion, an interaction exists between dietary supply of Val and Trp on the zootechnical performance of post-weaning piglets and dietary AA excess for Ile, Leu and His, reduces growth performance of piglets in low-protein diets, independent of the dietary level of Val.”

“These data support the view that the substitution of tryptophan by valine at this position may contribute to the lower stability of R17.”

“ Valine pretreatment, which blocks TRP entry into the brain, completely prevented FA-induced brain TRP and brain 5-HIAA increases.”

“Coadministration of valine with tryptophan attenuates these effects even in animals receiving methiothepin pretreatment.”