Beneficial Effect of Increased Tryptophan Intake on Its Metabolism and Mental State of the Elderly

Abstract

The elderly often suffer from sleep disorders and depression, which contribute to mood disorders. In our previous work, we showed that elderly individuals with mood disorders had a lower intake of TRP and recommended a TRP-based dietary intervention to improve the mental state of such individuals. In this work, we assessed the impact of a TRP-rich diet on the mental state of, and TRP metabolism in, elderly individuals with mood disorders. Forty elderly individuals with depression and sleep disorders and an equal number of elderly subjects without mood disorders were enrolled in this study. TRP intake was evaluated with the nutrition calculator. Patients with mood disorders had a lower TRP intake than their normal counterparts and received a TRP-rich diet with TRP content of 25 mg per kilogram of the body per day for 12 weeks. The mental state was assessed before and after this dietary intervention with the Hamilton Depression Rating Scale (HAM-D) and the Insomnia Severity Index (ISI). At those times, urinary levels of TRP and its metabolites 5-hydroxyindoleacetic acid (5-HIAA), L-kynurenine (KYN), kynurenic acid (KYNA), and quinolinic acid (QA) were determined by liquid chromatography with tandem mass spectrometry and related to creatinine level. After TRP-based dietary intervention, the score of ISI and HAM-D decreased by more than half. A correlation analysis reveals that TRP, 5-HIAA, and KYNA might have anti-depressive action, while KYN and QA—pro-depressive. The levels of TRP, 5-HIAA, and KYNA in urine of mood disorder patients increased, while the levels of KYN and QA decreased. In conclusion, dietary consumption of adequate amount of tryptophan has a beneficial effect on mental health of the elderly with mood disorders and improves metabolism of this amino acid. Therefore, a TRP-enriched diet may be considered as a component of the treatment of elderly individuals with mood disorders.

Circular RNAs Mediate the Effects of Dietary Tryptophan on the Transformation of Muscle Fiber Types in Weaned Piglets

“…The current study sought to elucidate the mechanism underlying the regulation of muscle fiber type transformation by circRNAs in weaned piglets fed a diet high in Trp. Trp is an essential amino acid that is employed for protein synthesis, and its total concentration in the body is the lowest among all the amino acids; therefore, Trp plays a rate-limiting role in protein synthesis . In addition, Trp is also involved in the kynurenine and 5-HT metabolic pathways and is a substrate for the synthesis of the coenzyme nicotinamide adenine dinucleotide as well as melatonin .…”

“…Trp is an essential amino acid that is employed for protein synthesis, and its total concentration in the body is the lowest among all the amino acids; therefore, Trp plays a rate-limiting role in protein synthesis. 26 In addition, Trp is also involved in the kynurenine and 5-HT metabolic pathways and is a substrate for the synthesis of the coenzyme nicotinamide adenine dinucleotide as well as melatonin. 27 Trp and its metabolites play important physiological roles in a variety of biological processes associated with cell growth and the maintenance of metabolic homeostasis through the regulation of certain signaling pathways and may contribute to the process of muscle development and myofiber type transformation.…”

Microbiota, Tryptophan and Aryl Hydrocarbon Receptors as the Target Triad in Parkinson’s Disease—A Narrative Review

“…A study in 40 elderly persons with insomnia or depression revealed that patients’ initial dietary Trp intake is low, their urinary excretion of KYNA is unaltered and excretion of KYN and QUIN is high. A prolonged, 12-week intake of 25 mg/kg of Trp daily resulted in mood improvement and increased elimination of Trp but reduced the elimination of KYN and QUIN with urine [ 151 ]. A double-blind, placebo-controlled study showed prominent increases in plasma KYN, KYNA and 5-HIAA, occurring 4 h after the oral administration of a single dose of Trp (6 g) to patients with schizophrenia as well as in healthy individuals [ 152 , 153 ].…”

Recent Advances in Current Uptake Situation, Metabolic and Nutritional Characteristics, Health, and Safety of Dietary Tryptophan

“…17 To investigate the safety of Trp, researchers recruited participants to assess the effects of a Trp-rich diet on mental status and Trp metabolism in older adults with mood disorders, in which the participants consumed 25 mg/kg per day for 12 weeks. 18 After the test, correlation analysis showed that Trp, 5-hydroxyindole acetic acid (5-HIAA), and KA might have antidepressant effects, while KYN and quinolinic acid (QA) might have pro-depressant effects. It is also concluded that moderate dietary intake of Trp is beneficial for the mental health of elders with mood disorders by improving the metabolism of Trp.…”