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Badawy AAB. Tryptophan Metabolism: A Versatile Area Providing Multiple Targets for Pharmacological Intervention. EGYPTIAN JOURNAL OF BASIC AND CLINICAL PHARMACOLOGY 2019; 9:10.32527/2019/101415. [PMID: 31105983 PMCID: PMC6520243 DOI: 10.32527/2019/101415] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The essential amino acid L-tryptophan (Trp) undergoes extensive metabolism along several pathways, resulting in production of many biologically active metabolites which exert profound effects on physiological processes. The disturbance in Trp metabolism and disposition in many disease states provides a basis for exploring multiple targets for pharmaco-therapeutic interventions. In particular, the kynurenine pathway of Trp degradation is currently at the forefront of immunological research and immunotherapy. In this review, I shall consider mammalian Trp metabolism in health and disease and outline the intervention targets. It is hoped that this account will provide a stimulus for pharmacologists and others to conduct further studies in this rich area of biomedical research and therapeutics.
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Linden M, Helmbold K, Kempf J, Sippas S, Filss C, Langen KJ, Eisert A, Zepf FD. Dietary tryptophan depletion in humans using a simplified two amino acid formula - a pilot study. Food Nutr Res 2016; 60:29272. [PMID: 27989269 PMCID: PMC5165058 DOI: 10.3402/fnr.v60.29272] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2015] [Revised: 09/26/2016] [Accepted: 11/03/2016] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Acute tryptophan depletion (ATD) is a well-established dietary method in translational brain research used to briefly lower central nervous serotonin (5-hydroxytryptamine (5-HT)) synthesis. A simplified two amino acid ATD formula (ATDPHE/LEU) was developed while reducing the overall amount of amino acids (AAs), with the objective of administration especially in children and adolescents in future studies. OBJECTIVE This study investigated tryptophan (TRP) influx rates across the blood-brain barrier (BBB) after dietary ATDPHE/LEU administration relative to the ATD Moja-De protocol that has been established for use in children and adolescents. DESIGN Seventy-two healthy adults (50% females) were randomized into four groups and administered ATD Moja-De, its TRP-balanced control condition (BAL), ATDPHE/LEU, or its respective control mixture (BALPHE/LEU) in a counterbalanced, double-blind, between-subjects design. Blood samples were collected at baseline and at hourly intervals for 6 h after AA intake. Questionnaires about mood, taste, and challenge tolerance were completed at fixed time points. RESULTS Both challenge mixtures significantly reduced central nervous TRP influx as calculated by Michaelis-Menten kinetics relative to baseline and the respective control conditions with only mild and comparable side effects. A greater decline in TRP influx over the BBB after ATDPHE/LEU administration when compared with ATD Moja-De was detected without group effects for taste, challenge tolerance, and mood. There was unintended initial short increase in plasma TRP concentrations observed after ATDPHE/LEU intake, and a possible redistribution between free and protein-bound TRP triggered by protein synthesis stimulated by the ingested AAs may account for this finding. Moreover, a decline in TRP influx after BALPHE/LEU administration over a 6-h period was observed, and the large amount of PHE in the BALPHE/LEU mixture may be a possible explanation for this particular phenomenon, which could have led to an unexpected increase in displacement of TRP at the BBB in this control condition. CONCLUSIONS This pilot study provides preliminary evidence for the possibility of lowering TRP influx as calculated by Michaelis-Menten kinetics into the brain by using a simplified ATD protocol in humans. The simplified composition of only two AAs, the lower overall AA amount, and the appropriate tolerance are characteristics of the newly developed ATDPHE/LEU protocol. Future studies focusing on the effects of the ATDPHE/LEU protocol and its respective control condition on CSF 5-HIAA concentrations, as well as neurochemical studies in rodents, are needed to further validate this newly developed AA mixture before definite conclusions about its usability in ATD-related research in humans, its specificity, and additional effects can be made.
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Affiliation(s)
- Maike Linden
- Clinic for Child and Adolescent Psychiatry, Psychosomatics and Psychotherapy, RWTH Aachen University, Aachen, Germany.,JARA Translational Brain Medicine, Jülich Aachen Research Alliance, Jülich, Germany
| | - Katrin Helmbold
- Clinic for Child and Adolescent Psychiatry, Psychosomatics and Psychotherapy, RWTH Aachen University, Aachen, Germany.,JARA Translational Brain Medicine, Jülich Aachen Research Alliance, Jülich, Germany
| | - Janina Kempf
- Clinic for Child and Adolescent Psychiatry, Psychosomatics and Psychotherapy, RWTH Aachen University, Aachen, Germany.,JARA Translational Brain Medicine, Jülich Aachen Research Alliance, Jülich, Germany.,Faculty of Arts and Social Sciences, Maastricht University, Maastricht, The Netherlands
| | - Shabnam Sippas
- Clinic for Child and Adolescent Psychiatry, Psychosomatics and Psychotherapy, RWTH Aachen University, Aachen, Germany.,JARA Translational Brain Medicine, Jülich Aachen Research Alliance, Jülich, Germany.,Faculty of Arts and Social Sciences, Maastricht University, Maastricht, The Netherlands
| | - Christian Filss
- Section JARA-Brain, Jülich-Aachen Research Alliance (JARA), Jülich, Germany
| | - Karl-Josef Langen
- Section JARA-Brain, Jülich-Aachen Research Alliance (JARA), Jülich, Germany.,Institute of Neuroscience and Medicine (INM-3, -4, -5), Research Centre Jülich, Jülich, Germany.,Department of Nuclear Medicine, RWTH Aachen University Hospital, Aachen, Germany
| | - Albrecht Eisert
- Department of Pharmacy, RWTH Aachen University, Aachen, Germany
| | - Florian Daniel Zepf
- Clinic for Child and Adolescent Psychiatry, Psychosomatics and Psychotherapy, RWTH Aachen University, Aachen, Germany.,JARA Translational Brain Medicine, Jülich Aachen Research Alliance, Jülich, Germany.,Centre and Discipline of Child and Adolescent Psychiatry, Psychosomatics and Psychotherapy, School of Psychiatry and Clinical Neurosciences & School of Paediatrics and Child Health, Faculty of Medicine, Dentistry and Health Sciences, The University of Western Australia, Perth, Australia.,Specialised Child and Adolescent Mental Health Services (CAMHS), Department of Health in Western Australia, Perth, Australia;
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Badawy AAB, Dougherty DM. Assessment of the Human Kynurenine Pathway: Comparisons and Clinical Implications of Ethnic and Gender Differences in Plasma Tryptophan, Kynurenine Metabolites, and Enzyme Expressions at Baseline and After Acute Tryptophan Loading and Depletion. Int J Tryptophan Res 2016; 9:31-49. [PMID: 27547036 PMCID: PMC4981220 DOI: 10.4137/ijtr.s38189] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2016] [Revised: 07/17/2016] [Accepted: 07/19/2016] [Indexed: 12/24/2022] Open
Abstract
Tryptophan (Trp) metabolism via the kynurenine pathway (KP) was assessed in normal healthy US volunteers at baseline and after acute Trp depletion (ATD) and acute Trp loading (ATL) using amino acid formulations. The hepatic KP accounts for ~90% of overall Trp degradation. Liver Trp 2,3-dioxygenase (TDO) contributes ~70% toward Trp oxidation, with the remainder achieved by subsequent rate-limiting enzymes in the KP. TDO is not influenced by a 1.15 g Trp load, but is maximally activated by a 5.15 g dose. We recommend a 30 mg/kg dose for future ATL studies. ATD activates TDO and enhances the Trp flux down the KP via its leucine component. Higher plasma free [Trp] and lower total [Trp] are observed in women, with no gender differences in kynurenines. Kynurenic acid is lower in female Caucasians, which may explain their lower incidence of schizophrenia. African-American and Hispanic women have a lower TDO and Trp oxidation relative to free Trp than the corresponding men. African-American women have a potentially higher 3-hydroxyanthranilic acid/anthranilic acid ratio, which may protect them against osteoporosis. Future studies of the KP in relation to health and disease should focus on gender and ethnic differences.
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Affiliation(s)
- Abdulla A-B Badawy
- School of Health Sciences, Cardiff Metropolitan University, Cardiff, Wales, UK
| | - Donald M Dougherty
- Department of Psychiatry, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
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Badawy AAB. Tryptophan metabolism, disposition and utilization in pregnancy. Biosci Rep 2015; 35:e00261. [PMID: 26381576 PMCID: PMC4626867 DOI: 10.1042/bsr20150197] [Citation(s) in RCA: 112] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Revised: 08/27/2015] [Accepted: 09/16/2015] [Indexed: 12/26/2022] Open
Abstract
Tryptophan (Trp) requirements in pregnancy are several-fold: (1) the need for increased protein synthesis by mother and for fetal growth and development; (2) serotonin (5-HT) for signalling pathways; (3) kynurenic acid (KA) for neuronal protection; (4) quinolinic acid (QA) for NAD(+) synthesis (5) other kynurenines (Ks) for suppressing fetal rejection. These goals could not be achieved if maternal plasma [Trp] is depleted. Although plasma total (free + albumin-bound) Trp is decreased in pregnancy, free Trp is elevated. The above requirements are best expressed in terms of a Trp utilization concept. Briefly, Trp is utilized as follows: (1) In early and mid-pregnancy, emphasis is on increased maternal Trp availability to meet the demand for protein synthesis and fetal development, most probably mediated by maternal liver Trp 2,3-dioxygenase (TDO) inhibition by progesterone and oestrogens. (2) In mid- and late pregnancy, Trp availability is maintained and enhanced by the release of albumin-bound Trp by albumin depletion and non-esterified fatty acid (NEFA) elevation, leading to increased flux of Trp down the K pathway to elevate immunosuppressive Ks. An excessive release of free Trp could undermine pregnancy by abolishing T-cell suppression by Ks. Detailed assessment of parameters of Trp metabolism and disposition and related measures (free and total Trp, albumin, NEFA, K and its metabolites and pro- and anti-inflammatory cytokines in maternal blood and, where appropriate, placental and fetal material) in normal and abnormal pregnancies may establish missing gaps in our knowledge of the Trp status in pregnancy and help identify appropriate intervention strategies.
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Affiliation(s)
- Abdulla A-B Badawy
- School of Health Sciences, Cardiff Metropolitan University, Western Avenue, Cardiff CF5 2YB, Wales, U.K.
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Sánchez CL, Van Swearingen AED, Arrant AE, Biskup CS, Kuhn CM, Zepf FD. Simplified dietary acute tryptophan depletion: effects of a novel amino acid mixture on the neurochemistry of C57BL/6J mice. Food Nutr Res 2015; 59:27424. [PMID: 26278978 PMCID: PMC4538305 DOI: 10.3402/fnr.v59.27424] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2015] [Revised: 06/24/2015] [Accepted: 06/24/2015] [Indexed: 01/10/2023] Open
Abstract
BACKGROUND Diet and nutrition can impact on the biological processes underpinning neuropsychiatric disorders. Amino acid (AA) mixtures lacking a specific neurotransmitter precursor can change the levels of brain serotonin (5-HT) or dopamine (DA) in the central nervous system. The availability of these substances within the brain is determined by the blood-brain barrier (BBB) that restricts the access of peripheral AA into the brain. AA mixtures lacking tryptophan (TRP) compete with endogenous TRP for uptake into the brain across the BBB, which in turn leads to a decrease in central nervous 5-HT synthesis. OBJECTIVE The present study compared the effects of a simplified acute tryptophan depletion (SATD) mixture in mice on blood and brain serotonergic and dopaminergic metabolites to those of a commonly used acute tryptophan depletion mixture (ATD Moja-De) and its TRP-balanced control (BAL). DESIGN The SATD formula is composed of only three large neutral AAs: phenylalanine (PHE), leucine (LEU), and isoleucine (ILE). BAL, ATD Moja-De, or SATD formulas were delivered to adult male C57BL/6J mice by gavage. TRP, monoamines, and their metabolites were quantified in blood and brain regions (hippocampus, frontal cortex, amygdala, caudate putamen, and nucleus accumbens). RESULTS Both ATD Moja-De and SATD significantly decreased levels of serum and brain TRP, as well as brain 5-HIAA and 5-HT compared with BAL. SATD reduced HVA levels in caudate but did not alter total DA levels or DOPAC. SATD decreased TRP and serotonergic metabolites comparably to ATD Moja-De administration. CONCLUSION A simplified and more palatable combination of AAs can manipulate serotonergic function and might be useful to reveal underlying monoamine-related mechanisms contributing to different neuropsychiatric disorders.
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Affiliation(s)
- Cristina L Sánchez
- Clinic for Child and Adolescent Psychiatry, Psychosomatics and Psychotherapy, JARA Brain, RWTH Aachen University, Aachen, Germany.,Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA
| | | | - Andrew E Arrant
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA
| | - Caroline S Biskup
- Clinic for Child and Adolescent Psychiatry, Psychosomatics and Psychotherapy, JARA Brain, RWTH Aachen University, Aachen, Germany
| | - Cynthia M Kuhn
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA
| | - Florian D Zepf
- Clinic for Child and Adolescent Psychiatry, Psychosomatics and Psychotherapy, JARA Brain, RWTH Aachen University, Aachen, Germany.,Department of Child and Adolescent Psychiatry, School of Paediatrics and Child Health & School of Psychiatry and Clinical Neurosciences, Faculty of Medicine, Dentistry and Health Sciences, The University of Western Australia, Perth, WA, Australia.,Specialised Child and Adolescent Mental Health Services (CAHMS), Department of Health, Perth, WA, Australia;
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Badawy AAB, Dougherty DM. Standardization of formulations for the acute amino acid depletion and loading tests. J Psychopharmacol 2015; 29:363-71. [PMID: 25586395 PMCID: PMC5516789 DOI: 10.1177/0269881114565141] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The acute tryptophan depletion and loading and the acute tyrosine plus phenylalanine depletion tests are powerful tools for studying the roles of cerebral monoamines in behaviour and symptoms related to various disorders. The tests use either amino acid mixtures or proteins. Current amino acid mixtures lack specificity in humans, but not in rodents, because of the faster disposal of branched-chain amino acids (BCAAs) by the latter. The high content of BCAA (30-60%) is responsible for the poor specificity in humans and we recommend, in a 50g dose, a control formulation with a lowered BCAA content (18%) as a common control for the above tests. With protein-based formulations, α-lactalbumin is specific for acute tryptophan loading, whereas gelatine is only partially effective for acute tryptophan depletion. We recommend the use of the whey protein fraction glycomacropeptide as an alternative protein. Its BCAA content is ideal for specificity and the absence of tryptophan, tyrosine and phenylalanine render it suitable as a template for seven formulations (separate and combined depletion or loading and a truly balanced control). We invite the research community to participate in standardization of the depletion and loading methodologies by using our recommended amino acid formulation and developing those based on glycomacropeptide.
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Affiliation(s)
| | - Donald M Dougherty
- Department of Psychiatry, University of Texas Health Sciences Center at San Antonio, 7703 Floyd Curl Drive, Mail Code 7793, San Antonio, Texas, 78229, USA
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Badawy AAB, Lake SL, Dougherty DM. Mechanisms of the pellagragenic effect of leucine: stimulation of hepatic tryptophan oxidation by administration of branched-chain amino acids to healthy human volunteers and the role of plasma free tryptophan and total kynurenines. Int J Tryptophan Res 2014; 7:23-32. [PMID: 25520560 PMCID: PMC4259507 DOI: 10.4137/ijtr.s18231] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2014] [Revised: 09/12/2014] [Accepted: 10/03/2014] [Indexed: 01/23/2023] Open
Abstract
The pellagragenic effect of leucine (Leu) has been proposed to involve modulation of L-tryptophan (Trp) metabolism along the hepatic kynurenine pathway. Here, we discuss some of the mechanisms suggested and report the effects in healthy volunteers of single doses of Leu (4.05-6.75 g) administered in a 16-amino acid mixture on concentrations of plasma Trp and its kynurenine metabolites. Flux of Trp through Trp 2,3-dioxygenase (TDO) is dose-dependently enhanced most probably by Leu and can be attributed to TDO activation. Trp oxidation is better expressed using plasma total kynure-nines, rather than kynurenine, and free, rather than total, Trp. Increased hepatic Trp oxidation may be an additional mechanism of action of branched-chain amino acids in the acute Trp depletion test. Inhibition of intestinal absorption or hepatic uptake of Trp by Leu can be excluded. Potential mechanisms of the aggravation of pellagra symptoms by Leu are discussed.
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Affiliation(s)
- Abdulla A-B Badawy
- School of Health Sciences, Cardiff Metropolitan University, Western Avenue, Cardiff, Wales, UK
| | - Sarah L Lake
- Department of Psychiatry, University of Texas Health Sciences Center at San Antonio, San Antonio, TX, USA
| | - Donald M Dougherty
- Department of Psychiatry, University of Texas Health Sciences Center at San Antonio, San Antonio, TX, USA
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Sobczak S, Schruers K. Can formulation affect tryptophan depletion results? Hints from studies in experimental panic. J Psychopharmacol 2014; 28:486-90. [PMID: 24429220 DOI: 10.1177/0269881113517954] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
RATIONALE Acute Tryptophan Depletion (ATD) is a specific serotonergic challenge tool. Central serotonergic effects of different ATD procedures are possibly not those that are usually assumed. OBJECTIVES In this paper we review data of ATD in an experimental fear model to investigate whether and how methodological differences may affect fear outcomes. Next we point to discrepancies of studies in our laboratory in order to test the hypotheses formulated in the review. METHODS Literature was searched in PubMed and MEDLINE and studies of our laboratory were compared. RESULTS Eight studies were included in the review: five in patients with panic disorder, three in healthy individuals. Methodologically the studies in our laboratory were quite similar except for the applied ATD mixtures. CONCLUSIONS ATD exerts fear-enhancing effects in patients with panic disorders, more than in healthy individuals. However, our findings are inconclusive. The discrepant findings of studies in our laboratory can possibly be explained by differences in the ATD mixtures used. We suggest mechanisms as to how these might have affected the central availability of tryptophan and hence serotonin.
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Affiliation(s)
- Sjacko Sobczak
- 1Mondriaan Department of Old Age Psychiatry/Department of Psychiatry and Neuropsychology, Maastricht University, Maastricht, The Netherlands
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Badawy AAB. Tryptophan and inhibitors of tryptophan 2,3-dioxygenase as antidepressants: reply. J Psychopharmacol 2014; 28:169-72. [PMID: 24449217 DOI: 10.1177/0269881113512044] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Appropriate amino acid mixtures for tryptophan depletion and tyrosine/phenylalanine depletion and the safety of long-term amino acid depletion in humans: reply. Psychopharmacology (Berl) 2013; 230:673-6. [PMID: 24241688 DOI: 10.1007/s00213-013-3357-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2013] [Accepted: 11/02/2013] [Indexed: 10/26/2022]
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Dietary manipulation of serotonergic and dopaminergic function in C57BL/6J mice with amino acid depletion mixtures. J Neural Transm (Vienna) 2013; 121:153-62. [PMID: 24061481 DOI: 10.1007/s00702-013-1083-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Accepted: 08/14/2013] [Indexed: 01/24/2023]
Abstract
Amino acid (AA) depletion techniques have been used to decrease serotonin (5-HT) and/or dopamine (DA) synthesis after administration of a tryptophan (acute tryptophan depletion, ATD) or phenylalanine/tyrosine-free (phenylalanine-tyrosine depletion, PTD) AA formula and are useful as neurochemical challenge procedures to study the impact of DA and 5-HT in patients with neuropsychiatric disorders. We recently demonstrated that the refined Moja-De ATD paradigm decreases brain 5-HT synthesis in humans and mice and lowers brain 5-HT turnover. In the present study we validated the neurochemical effects of three developed AA formulas on brain 5-HT and DA function in mice. To distinguish the direct and indirect effects of such mixtures on 5-HT and DA and to determine whether additive depletion of both could be obtained simultaneously, we compared the effects of ATD for 5-HT, PTD for DA, and a combined monoamine depletion mixture (CMD) compared to a control condition consisting of a balanced amino acid mixture. Food-deprived male C57BL/6J mice were gavaged with AA mixtures. Serum and brain samples were collected and analyzed for determination of tryptophan (Trp), tyrosine (Tyr), 5-HT, 5-HIAA, DA, DOPAC and HVA levels. ATD was the most effective at decreasing Trp, 5-HT and 5-HIAA. In contrast, PTD reduced Tyr globally but HVA only in certain brain regions. Although CMD affected both 5-HT and DA synthesis, it was less effective when compared with ATD or PTD alone. The present results demonstrate that two newly developed PTD and CMD formulas differentially impact brain 5-HT and DA synthesis relative to 5-HT-specific ATD Moja-De. Different effects on 5-HT and DA function by these mixtures suggest that the exact composition may be a critical determinant for effectiveness with respect to the administered challenge procedure.
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Badawy A. Novel nutritional treatment for manic and psychotic disorders: a review of tryptophan and tyrosine depletion studies and the potential of protein-based formulations using glycomacropeptide. Psychopharmacology (Berl) 2013; 228:347-58. [PMID: 23828158 DOI: 10.1007/s00213-013-3191-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/21/2013] [Accepted: 06/08/2013] [Indexed: 12/21/2022]
Abstract
RATIONALE Current amino acid (AA) mixtures used in acute tryptophan (Trp) and tyrosine (Tyr) plus phenylalanine (Phe) depletion and loading tests are unpalatable and lack specificity. Specificity is improved by reducing content of branched-chain amino acids (BCAA) and palatability to a certain extent by dose reduction. OBJECTIVES This study aims to identify a palatable naturally occurring alternative(s) to amino acids with the desired BCAA content for use in the above tests. METHODS A palatable alternative lacking in Trp, Tyr and Phe has been identified in the whey protein fraction caseino-glycomacropeptide (c-GMP). The absence of these three aromatic amino acids renders GMP suitable as a template for seven formulations for separate and combined depletion or loading and a placebo control. The absence of Phe and Tyr enables GMP to provide a unique nutritional therapy of manic and psychotic disorders by inhibition of cerebral dopamine synthesis and release and possibly also by enhancing glutamatergic function, in general, and in patients resistant to anti-psychotic medication, in particular. RESULTS Seven GMP-based formulations for the above tests are proposed, two of which can be used in the above nutritional therapy and a third formulation as a placebo control in clinical trials. CONCLUSIONS Development of these formulations should advance the above research and diagnostic tests, open new avenues for neuroscience research on monoamine function, and improve the therapy of bipolar and psychotic disorders and enhance the quality of life of sufferers.
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Affiliation(s)
- Abdulla Badawy
- School of Health Sciences, Cardiff Metropolitan University, Western Avenue, Cardiff, CF5 2YB, Wales, UK.
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van der Plasse G, Feenstra MGP. WITHDRAWN: Is acute tryptophan depletion a valid method to assess central serotonergic function? Neurosci Biobehav Rev 2011:S0149-7634(11)00053-4. [PMID: 21435352 DOI: 10.1016/j.neubiorev.2011.03.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2010] [Revised: 02/16/2011] [Accepted: 03/15/2011] [Indexed: 10/18/2022]
Abstract
This article has been withdrawn at the request of the editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy.
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Affiliation(s)
- Geoffrey van der Plasse
- Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Department of Psychiatry, PO Box 85500, 3508 GAUtrecht,The Netherlands
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