Effect of chronic protein ingestion on tyrosine and tryptophan levels and catecholamine and serotonin synthesis in rat brain. Nutr Neurosci 2011 Nov;14(6):260-7
Date
11/08/2011Pubmed ID
22053757DOI
10.1179/1476830511Y.0000000019Scopus ID
2-s2.0-81255195521 (requires institutional sign-in at Scopus site) 11 CitationsAbstract
OBJECTIVES: Previous studies have shown that brain tyrosine (TYR) levels and catecholamine synthesis rate increase in rats as chronic dietary protein content increases from 2 to 10% (% weight). A single protein, casein, was examined. The present study explores how TYR levels and catecholamine synthesis (and tryptophan (TRP) levels and serotonin synthesis) change when different proteins are ingested chronically over the same range of dietary protein contents.
METHODS: Male rats ingested for 8 days diets contain 2 or 10% protein (zein, gluten, casein, soy protein, or alpha-lactalbumin). On the last day, they were killed 2.5 hours into the dark period, 30 minutes after receiving an injection of m-hydroxybenzylhydrazine, an inhibitor of aromatic l-amino acid decarboxylase. Brain samples were analyzed for amino acids, including 5-hydroxytryptophan (index of serotonin synthesis rate) and dihydroxyphenylalanine (index of catecholamine synthesis rate), by HPLC-electrochemical detection.
RESULTS: TYR levels and catecholamine synthesis rate in brain were unaffected by the particular protein ingested. However, TRP levels and serotonin synthesis rate varied markedly, depending on the protein ingested, with effects being most prominent in the 10% protein groups. The effect of dietary protein on brain TRP correlated very highly with its effect on serotonin synthesis.
DISCUSSION: The results indicate that the protein ingested can chronically modify TRP levels and serotonin synthesis in brain, but not TYR levels or catecholamine synthesis, with effects most distinct at an adequate level of protein intake (10%).
Author List
Choi S, DiSilvio B, Fernstrom MH, Fernstrom JDAuthor
Sujean Choi PhD in the School of Allied Health department at Marquette UniversityMESH terms used to index this publication - Major topics in bold
5-HydroxytryptophanAnimals
Aromatic Amino Acid Decarboxylase Inhibitors
Brain
Caseins
Catecholamines
Cerebral Cortex
Diet, Protein-Restricted
Dietary Proteins
Dihydroxyphenylalanine
Enzyme Inhibitors
Hydrazines
Hypothalamus
Male
Protein Deficiency
Rats
Rats, Sprague-Dawley
Serotonin
Tryptophan
Tyrosine
