What is Tyrosine?
This post was written with Consensus AI Academic Search Engine – please read our Disclaimer at the end of this article. Tyrosine is a non-essential amino acid that plays a crucial role in the production of several important neurotransmitters. It is found in various protein-rich foods and is a precursor to catecholamines, including dopamine, norepinephrine, and epinephrine. This article explores the biochemical significance of tyrosine, its effects on cognitive and physical performance, and its potential as a biomarker for intestinal injury. Other names include: 2-Acetylamino-3-(4-Hydroxyphenyl)-Propanoic Acid, Acetyl-L-Tyrosine, Acétyl-L-Tyrosine, L-Tyrosine, N-Acetyl L-Tyrosine, N-Acetyl-L-Tyrosine, N-Acétyl L-Tyrosine, N-Acetyl-Tyrosine, N-Acétyl-Tyrosine, Tirosina, Tyr, Tyrosinum, 2-amino-3-(4-hydroxyphenyl)propionic acid.
Biochemical Significance
Tyrosine is synthesized in the body from phenylalanine, another amino acid. It is a precursor to several neurotransmitters that are vital for brain function. The conversion of tyrosine to dopamine, norepinephrine, and epinephrine involves several enzymatic steps, making it a key player in the catecholaminergic system3.
Cognitive Performance of Tyrosine
Positive Effects
Tyrosine has been shown to enhance cognitive flexibility, particularly under conditions of high cognitive demand. In a study involving a task-switching paradigm, tyrosine supplementation reduced switching costs, thereby promoting cognitive flexibility. This suggests that tyrosine can help replenish cognitive resources, especially in demanding situations2.
Negative Effects
Contrary to some findings, other studies have shown that tyrosine can negatively affect cognitive performance under certain conditions. For instance, a study found that tyrosine worsened cognitive flexibility when participants were subjected to high cognitive load, indicating that the effects of tyrosine may vary depending on the type of stressor1.
Physical Performance
Tyrosine has also been investigated for its effects on physical performance, particularly under stress. One study tested the effects of tyrosine ingestion on cognitive and physical performance during a military-based protocol in the heat. Despite significant elevations in serum tyrosine levels, no improvements were observed in cognitive function or physical performance, suggesting that tyrosine may not be effective in all stressful conditions5.
Tyrosine as a Biomarker
Tyrosine has potential as a biomarker for severe intestinal injury during ischemia. In a study involving anesthetized rabbits, tyrosine concentrations in the gut luminal perfusate increased significantly during severe intestinal ischemia. This indicates that tyrosine could serve as a useful indicator of intestinal villus compromise4.
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Uses of Tyrosine
Cognitive Flexibility and Performance
Tyrosine supplementation can improve cognitive flexibility and reduce switching costs in task-switching paradigms, indicating enhanced cognitive control1.
It can also enhance working memory performance in multitasking environments, suggesting its utility in maintaining cognitive function under stress8.
Tyrosine has been shown to improve stopping unwanted actions, enhancing inhibitory control without affecting response execution speed9.
Stress Reduction
Tyrosine reduces symptoms, adverse moods, and performance impairments in stressful conditions such as cold and hypoxia3.
It can mitigate physiological and behavioral decrements induced by cardiovascular stress, such as lower body negative pressure6.
Tyrosine supplementation has been associated with reduced physiological arousal, including heart rate and pupil dilation variability, which may contribute to improved decision-making under stress2.
Cognitive Performance Under Stress
Tyrosine can ameliorate performance declines during extended wakefulness and sleep deprivation, suggesting its potential to counteract cognitive fatigue10.
It has been found to improve cognitive function and depressive mood in patients with severe anorexia nervosa, indicating its potential benefits in clinical settings5.
Mixed Findings on Cognitive Load
While some studies show that tyrosine improves cognitive performance under high cognitive demands, others indicate that it may worsen cognitive flexibility under such conditions4.
In older adults, tyrosine’s effects on proactive response inhibition and associated brain activation can be age-dependent, sometimes leading to detrimental outcomes7.
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Adverse Effects of Tyrosine
Cognitive Performance Under Stress
Tyrosine can worsen cognitive flexibility under high cognitive load conditions, contrary to expectations of improvement1.
In older adults, tyrosine negatively affects proactive response slowing and associated brain activation, with more pronounced detrimental effects as age increases4.
Neurochemical and Behavioral Effects
Tyrosine ingestion leads to a short-lasting increase in plasma catecholamines (norepinephrine, epinephrine, dopamine) and a decrease in DOPAC levels, indicating acute effects on catecholamine systems2.
Acute tyrosine depletion, which reduces dopamine neurotransmission, does not significantly alter mood, memory, attention, or behavioral inhibition in healthy individuals6.
Cardiovascular and Autonomic Responses
In Parkinson’s disease patients, tyrosine supplementation did not significantly affect blood pressure or autonomic responses during exercise, although it increased plasma tyrosine levels9.
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How has Tyrosine Improved Patient Outcomes?
Oxidative Stress and Infection Outcomes
Tyrosine nitrosylation is associated with better short-term clinical outcomes in patients with community-acquired pneumonia, reducing the risk of death or ICU admission within 30 days1.
Cancer Treatment Efficacy
Tyrosine kinase inhibitors (TKIs) have been linked to improved overall survival and progression-free survival in patients with advanced hepatocellular carcinoma and non-small cell lung cancer2 5.
The combination of metformin with EGFR-TKIs significantly improves progression-free survival and overall survival in patients with advanced lung adenocarcinoma7.
A medication management service improves adherence to TKIs and clinical outcomes in patients with chronic myeloid leukemia6.
Cognitive and Psychological Benefits
Tyrosine supplementation improves cognitive function and mood in patients with anorexia nervosa and children with phenylketonuria3 4.
Tyrosine depletion can attenuate the psychostimulant effects of methamphetamine and reduce mania severity in patients with manic illness10.
Depression
A study found no significant antidepressant activity of tyrosine in patients with major depression, despite changes in biochemical markers9.
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Tyrosine Mechanisms of Action
Neurotransmitter Precursor Role
Tyrosine increases brain dopamine levels, which can enhance cognitive functions such as working memory and inhibitory control, particularly under high cognitive demands4 6 7.
Hormonal Effects
Tyrosine stimulates the secretion of prolactin and thyrotrophin (TSH) but does not affect adrenocorticotrophic hormone (ACTH), cortisol, growth hormone, or gonadotrophins under normal conditions. However, when combined with an α2-adrenoceptor antagonist, it can stimulate ACTH and noradrenaline secretion1.
Cognitive Performance
Tyrosine supplementation can improve cognitive flexibility and inhibitory control, but its effects can vary depending on the type of cognitive load and individual genetic differences in dopamine receptor function4 6 7.
Insulin Signaling
Tyrosine kinase activity is crucial in insulin signaling, with changes in diet affecting insulin sensitivity and glucose metabolism through modulation of tyrosine kinase activity2.
Immune and Inflammatory Responses
Tyrosine kinase 2 (TYK2) inhibitors have shown efficacy in treating conditions like psoriasis and psoriatic arthritis by modulating cytokine signaling pathways3 9.
Redox Regulation
Protein tyrosine phosphatase 1B (PTP1B) activity, which counter-regulates insulin signaling, is influenced by dietary selenium through redox mechanisms, affecting liver triglyceride concentrations5.
Cardiovascular Effects
Tyrosine kinase signaling is involved in the regulation of vascular function, including the expression of endothelial nitric oxide synthase (eNOS), which is crucial for maintaining vascular reactivity10.
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Common Complaints Associated with Tyrosine
Oxidative Stress and Metabolic Disruptions
Administration of oxidized tyrosine (O-Tyr) and its product dityrosine (Dityr) in mice leads to increased oxidative damage to proteins and lipids, reduced antioxidant capacity, and suppressed antioxidant enzyme mRNA expression. This results in enhanced fatty acid oxidation, glycolysis, glucose-alanine cycle, and tricarboxylic acid (TCA) cycle metabolism, along with induced oxidative stress responses and altered gut microbiota functions1.
Cognitive Performance Under Stress
Tyrosine administration has been shown to negatively affect cognitive flexibility under high cognitive load conditions. Instead of improving performance, tyrosine worsened cognitive flexibility in a randomized, double-blind, placebo-controlled experiment involving healthy volunteers2.
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Disclaimer
The content presented in this blog is generated by Consensus, an AI-powered academic search engine, and is based on publicly available scientific literature. While every effort is made to provide accurate, up-to-date, and well-researched information, the content is intended for informational and educational purposes only. It does not constitute medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional before making any decisions regarding medical conditions, treatments, or medications. The AI system’s analysis may not cover all perspectives, emerging research, or individual cases, and it is not a substitute for professional expertise. Neither the blog publisher nor the developers of the AI-powered search engine are responsible for any actions taken based on the information provided in this content. Use of this information is at your own risk. Citations to the original scientific studies are included for reference, but these studies should be reviewed in full and interpreted with the guidance of a healthcare or research professional.
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