L-Tryptophan: Basic Metabolic Functions, Behavioral Research and Therapeutic Indications

Abstract

An essential component of the human diet, L-tryptophan is critical in a number of metabolic functions and has been widely used in numerous research and clinical trials. This review provides a brief overview of the role of L-tryptophan in protein synthesis and a number of other metabolic functions. With emphasis on L-tryptophan’s role in synthesis of brain serotonin, details are provided on the research uses of L-tryptophan, particularly L-tryptophan depletion, and on clinical trials that have been conducted using L-tryptophan supplementation. The ability to change the rates of serotonin synthesis in the brain by manipulating concentrations of serum tryptophan is the foundation of much research. As the sole precursor of serotonin, experimental research has shown that L-tryptophan’s role in brain serotonin synthesis is an important factor involved in mood, behavior, and cognition. Furthermore, clinical trials have provided some initial evidence of L-tryptophan’s efficacy for treatment of psychiatric disorders, particularly when used in combination with other therapeutic agents.

Estudo Do L-Triptofano Na Depressão Ocorrida Pela Doença De Alzheimer Em Modelos Experimentais

“…A existência de glicocorticoides ou corticosteroides também pode estar envolvida na depressão, visto que seu excesso restringe os níveis de dopamina 13,14 . A serotonina ou 5-hidroxitriptamina (5-HT) é sintetizada nos neurônios da rafe presentes no tronco cerebral através da hidroxilação e descarboxilação do L-triptofanoaminoácido essencial considerado o único precursor da 5-HT produzido tanto no sistema nervoso central (SNC) quanto perifericamente, além de ter função na formação das proteínas e metabólitos como a quinurenina [15][16][17] . Por meio de uma rede difusa dentro do SNC o sistema serotoninérgico é encarregado por regular diversas funções, entre elas, o sono, apetite, temperatura, humor e cognição 16 .…”

Amino Acid Composition of Ten Fish Species from Hel River, North-East India

“…Methionine is used for treating liver disorders, improving wound healing, and treating depression, alcoholism, allergies, asthma, copper poisoning, radiation side effects, schizophrenia, drug withdrawal, and Parkinson's disease [2,3,13]. Tryptophan is the precursor of serotonin, melatonin, tryptamine, and kynurenine and it plays an important role in the functioning of neurotransmitters [14]. Tryptophan supplement is used in treatment of pain, insomnia, depression, seasonal affective disorder, bulimia, premenstrual dysphoric disorder, hyperactivity disorder, and chronic fatigue [2,14].…”

The Urinary Ratio of 3-Hydroxykynurenine/3-Hydroxyanthranilic Acid Is an Index to Predicting the Adverse Effects of D-Tryptophan in Rats

“…In a dynamic equilibrium of protein metabolism, it is believed that .90% of l-Trp ingested is catabolized by the l-Trp-Kyn pathway (30,31). We measured the levels of metabolites of Trp when rats were fed d-Trp.…”