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Ziegler SG, Kim J, Ehmsen JT, Vernon HJ. Inborn errors of amino acid metabolism - from underlying pathophysiology to therapeutic advances. Dis Model Mech 2023; 16:dmm050233. [PMID: 37994477 PMCID: PMC10690057 DOI: 10.1242/dmm.050233] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Accepted: 10/19/2023] [Indexed: 11/24/2023] Open
Abstract
Amino acids are organic molecules that serve as basic substrates for protein synthesis and have additional key roles in a diverse array of cellular functions, including cell signaling, gene expression, energy production and molecular biosynthesis. Genetic defects in the synthesis, catabolism or transport of amino acids underlie a diverse class of diseases known as inborn errors of amino acid metabolism. Individually, these disorders are rare, but collectively, they represent an important group of potentially treatable disorders. In this Clinical Puzzle, we discuss the pathophysiology, clinical features and management of three disorders that showcase the diverse clinical presentations of disorders of amino acid metabolism: phenylketonuria, lysinuric protein intolerance and homocystinuria due to cystathionine β-synthase (CBS) deficiency. Understanding the biochemical perturbations caused by defects in amino acid metabolism will contribute to ongoing development of diagnostic and management strategies aimed at improving the morbidity and mortality associated with this diverse group of disorders.
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Affiliation(s)
- Shira G. Ziegler
- Department of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Jiyoung Kim
- Department of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Jeffrey T. Ehmsen
- Department of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
- Department of Internal Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Hilary J. Vernon
- Department of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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2
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Dobrowolski SF, Phua YL, Vockley J, Goetzman E, Blair HC. Phenylketonuria oxidative stress and energy dysregulation: Emerging pathophysiological elements provide interventional opportunity. Mol Genet Metab 2022; 136:111-117. [PMID: 35379539 PMCID: PMC9832337 DOI: 10.1016/j.ymgme.2022.03.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Revised: 03/24/2022] [Accepted: 03/25/2022] [Indexed: 01/13/2023]
Abstract
Phenylalanine hydroxylase (PAH) deficient phenylketonuria (PKU) is rightfully considered the paradigm treatable metabolic disease. Dietary substrate restriction (i.e. phenylalanine (Phe) restriction) was applied >60 years ago and remains the primary PKU management means. The traditional model of PKU neuropathophysiology dictates blood Phe over-representation directs asymmetric blood:brain barrier amino acid transport through the LAT1 transporter with subsequent increased cerebral Phe concentration and low concentrations of tyrosine (Tyr), tryptophan (Trp), leucine (Leu), valine (Val), and isoleucine (Ile). Low Tyr and Trp concentrations generate secondary serotonergic and dopaminergic neurotransmitter paucities, widely attributed as drivers of PKU neurologic phenotypes. White matter disease, a central PKU characteristic, is ascribed to Phe-mediated tissue toxicity. Impaired cerebral protein synthesis, by reduced concentrations of non-Phe large neutral amino acids, is another cited pathological mechanism. The PKU amino acid transport model suggests Phe management should be more efficacious than is realized, as even early identified, continuously treated patients that retain therapy compliance into adulthood, demonstrate neurologic disease elements. Reduced cerebral metabolism was an early-recognized element of PKU pathology. Legacy data (late 1960's to mid-1970's) determined the Phe catabolite phenylpyruvate inhibits mitochondrial pyruvate transport. Respirometry of Pahenu2 cerebral mitochondria have attenuated respiratory chain complex 1 induction in response to pyruvate substrate, indicating reduced energy metabolism. Oxidative stress is intrinsic to PKU and Pahenu2 brain tissue presents increased reactive oxygen species. Phenylpyruvate inhibits glucose-6-phosphate dehydrogenase that generates reduced niacinamide adenine dinucleotide phosphate the obligatory cofactor of glutathione reductase. Pahenu2 brain tissue metabolomics identified increased oxidized glutathione and glutathione disulfide. Over-represented glutathione disulfide argues for reduced glutathione reductase activity secondary to reduced NADPH. Herein, we review evidence of energy and oxidative stress involvement in PKU pathology. Data suggests energy deficit and oxidative stress are features of PKU pathophysiology, providing intervention-amenable therapeutic targets to ameliorate disease elements refractory to standard of care.
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Affiliation(s)
- Steven F Dobrowolski
- Department of Pathology, University of Pittsburgh, School of Medicine, Pittsburgh, PA 15224, United States of America.
| | - Yu Leng Phua
- Division of Medical Genetics, Children's Hospital of Pittsburgh, Pittsburgh, PA 15224, United States of America
| | - Jerry Vockley
- Division of Medical Genetics, Children's Hospital of Pittsburgh, Pittsburgh, PA 15224, United States of America
| | - Eric Goetzman
- Division of Medical Genetics, Children's Hospital of Pittsburgh, Pittsburgh, PA 15224, United States of America
| | - Harry C Blair
- Department of Pathology, University of Pittsburgh, School of Medicine, Pittsburgh, PA 15224, United States of America; Veteran's Affairs Medical Center, Pittsburgh, PA, United States of America
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3
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Winn SR, Dudley S, Scherer T, Rimann N, Thöny B, Boutros S, Krenik D, Raber J, Harding CO. Modeling the cognitive effects of diet discontinuation in adults with phenylketonuria (PKU) using pegvaliase therapy in PAH-deficient mice. Mol Genet Metab 2022; 136:46-64. [PMID: 35339387 PMCID: PMC9106909 DOI: 10.1016/j.ymgme.2022.03.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Revised: 03/14/2022] [Accepted: 03/15/2022] [Indexed: 10/18/2022]
Abstract
Existing phenylalanine hydroxylase (PAH)-deficient mice strains are useful models of untreated or late-treated human phenylketonuria (PKU), as most contemporary therapies can only be initiated after weaning and the pups have already suffered irreversible consequences of chronic hyperphenylalaninemia (HPA) during early brain development. Therefore, we sought to evaluate whether enzyme substitution therapy with pegvaliase initiated near birth and administered repetitively to C57Bl/6-Pahenu2/enu2 mice would prevent HPA-related behavioral and cognitive deficits and form a model for early-treated PKU. The main results of three reported experiments are: 1) lifelong weekly pegvaliase treatment prevented the cognitive deficits associated with HPA in contrast to persisting deficits in mice treated with pegvaliase only as adults. 2) Cognitive deficits reappear in mice treated with weekly pegvaliase from birth but in which pegvaliase is discontinued at 3 months age. 3) Twice weekly pegvaliase injection also prevented cognitive deficits but again cognitive deficits emerged in early-treated animals following discontinuation of pegvaliase treatment during adulthood, particularly in females. In all studies, pegvaliase treatment was associated with complete correction of brain monoamine neurotransmitter content and with improved overall growth of the mice as measured by body weight. Mean total brain weight however remained low in all PAH deficient mice regardless of treatment. Application of enzyme substitution therapy with pegvaliase, initiated near birth and continued into adulthood, to PAH-deficient Pahenu2/enu2 mice models contemporary early-treated human PKU. This model will be useful for exploring the differential pathophysiologic effects of HPA at different developmental stages of the murine brain.
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Affiliation(s)
- Shelley R Winn
- Department of Medical and Molecular Genetics, Oregon Health & Science University, Mailstop L-103, 3181 Sam Jackson Park Rd., Portland, OR 97239, USA
| | - Sandra Dudley
- Department of Medical and Molecular Genetics, Oregon Health & Science University, Mailstop L-103, 3181 Sam Jackson Park Rd., Portland, OR 97239, USA
| | - Tanja Scherer
- Department of Pediatrics, University of Zurich, Steinwiessstrasse 75, Zurich CH-8032, Switzerland
| | - Nicole Rimann
- Department of Pediatrics, University of Zurich, Steinwiessstrasse 75, Zurich CH-8032, Switzerland
| | - Beat Thöny
- Department of Pediatrics, University of Zurich, Steinwiessstrasse 75, Zurich CH-8032, Switzerland
| | - Sydney Boutros
- Department of Behavioral Neuroscience, Oregon Health & Science University, 3181 Sam Jackson Park Rd., Portland, OR 97239, USA
| | - Destine Krenik
- Department of Behavioral Neuroscience, Oregon Health & Science University, 3181 Sam Jackson Park Rd., Portland, OR 97239, USA
| | - Jacob Raber
- Department of Behavioral Neuroscience, Oregon Health & Science University, 3181 Sam Jackson Park Rd., Portland, OR 97239, USA; Departments of Neurology and Radiation Medicine, Division of Neuroscience, ONPRC, Oregon Health & Science University, 3181 Sam Jackson Park Rd., Portland, OR 97239, USA
| | - Cary O Harding
- Department of Medical and Molecular Genetics, Oregon Health & Science University, Mailstop L-103, 3181 Sam Jackson Park Rd., Portland, OR 97239, USA.
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Borges AC, Broersen K, Leandro P, Fernandes TG. Engineering Organoids for in vitro Modeling of Phenylketonuria. Front Mol Neurosci 2022; 14:787242. [PMID: 35082602 PMCID: PMC8784555 DOI: 10.3389/fnmol.2021.787242] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Accepted: 11/29/2021] [Indexed: 12/15/2022] Open
Abstract
Phenylketonuria is a recessive genetic disorder of amino-acid metabolism, where impaired phenylalanine hydroxylase function leads to the accumulation of neurotoxic phenylalanine levels in the brain. Severe cognitive and neuronal impairment are observed in untreated/late-diagnosed patients, and even early treated ones are not safe from life-long sequelae. Despite the wealth of knowledge acquired from available disease models, the chronic effect of Phenylketonuria in the brain is still poorly understood and the consequences to the aging brain remain an open question. Thus, there is the need for better predictive models, able to recapitulate specific mechanisms of this disease. Human induced pluripotent stem cells (hiPSCs), with their ability to differentiate and self-organize in multiple tissues, might provide a new exciting in vitro platform to model specific PKU-derived neuronal impairment. In this review, we gather what is known about the impact of phenylalanine in the brain of patients and highlight where hiPSC-derived organoids could contribute to the understanding of this disease.
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Affiliation(s)
- Alice C. Borges
- Department of Bioengineering and iBB – Institute for Bioengineering and Biosciences, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal
- Associate Laboratory i4HB – Institute for Health and Bioeconomy, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal
| | - Kerensa Broersen
- Department of Applied Stem Cell Technologies, Faculty of Science and Technology, Technical Medical Centre, University of Twente, Enschede, Netherlands
| | - Paula Leandro
- Faculty of Pharmacy, iMed.ULisboa - Research Institute for Medicines, Universidade de Lisboa, Lisbon, Portugal
| | - Tiago G. Fernandes
- Department of Bioengineering and iBB – Institute for Bioengineering and Biosciences, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal
- Associate Laboratory i4HB – Institute for Health and Bioeconomy, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal
- *Correspondence: Tiago G. Fernandes,
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Cannon Homaei S, Barone H, Kleppe R, Betari N, Reif A, Haavik J. ADHD symptoms in neurometabolic diseases: Underlying mechanisms and clinical implications. Neurosci Biobehav Rev 2021; 132:838-856. [PMID: 34774900 DOI: 10.1016/j.neubiorev.2021.11.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Revised: 11/09/2021] [Accepted: 11/09/2021] [Indexed: 12/16/2022]
Abstract
Neurometabolic diseases (NMDs) are typically caused by genetic abnormalities affecting enzyme functions, which in turn interfere with normal development and activity of the nervous system. Although the individual disorders are rare, NMDs are collectively relatively common and often lead to lifelong difficulties and high societal costs. Neuropsychiatric manifestations, including ADHD symptoms, are prominent in many NMDs, also when the primary biochemical defect originates in cells and tissues outside the nervous system. ADHD symptoms have been described in phenylketonuria, tyrosinemias, alkaptonuria, succinic semialdehyde dehydrogenase deficiency, X-linked ichthyosis, maple syrup urine disease, and several mitochondrial disorders, but are probably present in many other NMDs and may pose diagnostic and therapeutic challenges. Here we review current literature linking NMDs with ADHD symptoms. We cite emerging evidence that many NMDs converge on common neurochemical mechanisms that interfere with monoamine neurotransmitter synthesis, transport, metabolism, or receptor functions, mechanisms that are also considered central in ADHD pathophysiology and treatment. Finally, we discuss the therapeutic implications of these findings and propose a path forward to increase our understanding of these relationships.
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Affiliation(s)
- Selina Cannon Homaei
- Division of Psychiatry, Haukeland University Hospital, Norway; Department of Biomedicine, University of Bergen, Norway.
| | - Helene Barone
- Regional Resource Center for Autism, ADHD, Tourette Syndrome and Narcolepsy, Western Norway, Division of Psychiatry, Haukeland University Hospital, Norway.
| | - Rune Kleppe
- Division of Psychiatry, Haukeland University Hospital, Norway; Norwegian Centre for Maritime and Diving Medicine, Department of Occupational Medicine, Haukeland University Hospital, Norway.
| | - Nibal Betari
- Department of Biomedicine, University of Bergen, Norway.
| | - Andreas Reif
- Department of Psychiatry, Psychosomatic Medicine and Psychotherapy, University Hospital Frankfurt, Frankfurt am Main, Germany.
| | - Jan Haavik
- Division of Psychiatry, Haukeland University Hospital, Norway; Department of Biomedicine, University of Bergen, Norway.
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Dijkstra AM, van Vliet N, van Vliet D, Romani C, Huijbregts SCJ, van der Goot E, Hovens IB, van der Zee EA, Kema IP, Heiner-Fokkema MR, van Spronsen FJ. Correlations of blood and brain biochemistry in phenylketonuria: Results from the Pah-enu2 PKU mouse. Mol Genet Metab 2021; 134:250-256. [PMID: 34656426 DOI: 10.1016/j.ymgme.2021.09.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Revised: 09/12/2021] [Accepted: 09/18/2021] [Indexed: 11/30/2022]
Abstract
BACKGROUND In phenylketonuria (PKU), treatment monitoring is based on frequent blood phenylalanine (Phe) measurements, as this is the predictor of neurocognitive and behavioural outcome by reflecting brain Phe concentrations and brain biochemical changes. Despite clinical studies describing the relevance of blood Phe to outcome in PKU patients, blood Phe does not explain the variance in neurocognitive and behavioural outcome completely. METHODS In a PKU mouse model we investigated 1) the relationship between plasma Phe and brain biochemistry (Brain Phe and monoaminergic neurotransmitter concentrations), and 2) whether blood non-Phe Large Neutral Amino Acids (LNAA) would be of additional value to blood Phe concentrations to explain brain biochemistry. To this purpose, we assessed blood amino acid concentrations and brain Phe as well as monoaminergic neurotransmitter levels in in 114 Pah-Enu2 mice on both B6 and BTBR backgrounds using (multiple) linear regression analyses. RESULTS Plasma Phe concentrations were strongly correlated to brain Phe concentrations, significantly negatively correlated to brain serotonin and norepinephrine concentrations and only weakly correlated to brain dopamine concentrations. From all blood markers, Phe showed the strongest correlation to brain biochemistry in PKU mice. Including non-Phe LNAA concentrations to the multiple regression model, in addition to plasma Phe, did not help explain brain biochemistry. CONCLUSION This study showed that blood Phe is still the best amino acid predictor of brain biochemistry in PKU. Nevertheless, neurocognitive and behavioural outcome cannot fully be explained by blood or brain Phe concentrations, necessitating a search for other additional parameters. TAKE-HOME MESSAGE Blood Phe is still the best amino acid predictor of brain biochemistry in PKU. Nevertheless, neurocognitive and behavioural outcome cannot fully be explained by blood or brain Phe concentrations, necessitating a search for other additional parameters.
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Affiliation(s)
- Allysa M Dijkstra
- University of Groningen, University Medical Center Groningen, Beatrix Children's Hospital, Groningen, the Netherlands
| | - Ninke van Vliet
- University of Groningen, University Medical Center Groningen, Beatrix Children's Hospital, Groningen, the Netherlands
| | - Danique van Vliet
- University of Groningen, University Medical Center Groningen, Beatrix Children's Hospital, Groningen, the Netherlands
| | - Cristina Romani
- School of Life and Health Sciences, Aston University, Birmingham, UK
| | - Stephan C J Huijbregts
- Department of Clinical Child and Adolescent Studies-Neurodevelopmental Disorders, Faculty of Social Sciences, Leiden University, Leiden, the Netherlands
| | - Els van der Goot
- University of Groningen, Groningen Institute for Evolutionary Life Sciences (GELIFES), Department of Molecular Neurobiology, Groningen, the Netherlands
| | - Iris B Hovens
- University of Groningen, Groningen Institute for Evolutionary Life Sciences (GELIFES), Department of Molecular Neurobiology, Groningen, the Netherlands
| | - Eddy A van der Zee
- University of Groningen, Groningen Institute for Evolutionary Life Sciences (GELIFES), Department of Molecular Neurobiology, Groningen, the Netherlands
| | - Ido P Kema
- University of Groningen, University Medical Center Groningen, Department of laboratory Medicine, Groningen, the Netherlands
| | - M Rebecca Heiner-Fokkema
- University of Groningen, University Medical Center Groningen, Department of laboratory Medicine, Groningen, the Netherlands
| | - Francjan J van Spronsen
- University of Groningen, University Medical Center Groningen, Beatrix Children's Hospital, Groningen, the Netherlands.
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7
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Abstract
Phenylketonuria (PKU; also known as phenylalanine hydroxylase (PAH) deficiency) is an autosomal recessive disorder of phenylalanine metabolism, in which especially high phenylalanine concentrations cause brain dysfunction. If untreated, this brain dysfunction results in severe intellectual disability, epilepsy and behavioural problems. The prevalence varies worldwide, with an average of about 1:10,000 newborns. Early diagnosis is based on newborn screening, and if treatment is started early and continued, intelligence is within normal limits with, on average, some suboptimal neurocognitive function. Dietary restriction of phenylalanine has been the mainstay of treatment for over 60 years and has been highly successful, although outcomes are still suboptimal and patients can find the treatment difficult to adhere to. Pharmacological treatments are available, such as tetrahydrobiopterin, which is effective in only a minority of patients (usually those with milder PKU), and pegylated phenylalanine ammonia lyase, which requires daily subcutaneous injections and causes adverse immune responses. Given the drawbacks of these approaches, other treatments are in development, such as mRNA and gene therapy. Even though PAH deficiency is the most common defect of amino acid metabolism in humans, brain dysfunction in individuals with PKU is still not well understood and further research is needed to facilitate development of pathophysiology-driven treatments.
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Affiliation(s)
- Francjan J van Spronsen
- Beatrix Children's Hospital, University Medical Centre Groningen, University of Groningen, Groningen, Netherlands.
| | - Nenad Blau
- University Children's Hospital in Zurich, Zurich, Switzerland
| | - Cary Harding
- Department of Molecular and Medical Genetics and Department of Pediatrics, Oregon Health & Science University, Oregon, USA
| | | | - Nicola Longo
- Department of Pediatrics, University of Utah, Salt Lake City, Utah, USA
| | - Annet M Bosch
- University of Amsterdam, Department of Pediatrics, Division of Metabolic Disorders, Emma Children's Hospital, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
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Pilotto A, Blau N, Leks E, Schulte C, Deuschl C, Zipser C, Piel D, Freisinger P, Gramer G, Kölker S, Haas D, Burgard P, Nawroth P, Georg H, Scheffler K, Berg D, Trefz F. Cerebrospinal fluid biogenic amines depletion and brain atrophy in adult patients with phenylketonuria. J Inherit Metab Dis 2019; 42:398-406. [PMID: 30706953 DOI: 10.1002/jimd.12049] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/04/2018] [Accepted: 12/31/2018] [Indexed: 01/29/2023]
Abstract
Biogenic amines synthesis in phenylketonuria (PKU) patients with high phenylalanine (Phe) concentration is thought to be impaired due to inhibition of tyrosine and tryptophan hydroxylases and competition with amino acids at the blood-brain barrier. Dopamine and serotonin deficits might explain brain damage and progressive neuropsychiatric impairment in adult PKU patients. Ten early treated adult PKU patients (mean age 38.2 years) and 15 age-matched controls entered the study. Plasma and cerebrospinal fluid (CSF) Phe, 5-hydroxyindoleacetic acid (5-HIAA), 5-hydroxytryptophan (5-HTP), 3,4-dihydroxy-l-phenylalanine (l-DOPA) and homovanillic acid (HVA) were analyzed. Voxel-based morphometry statistical nonparametric mapping was used to test the age-corrected correlation between gray matter atrophy and CSF biogenic amines levels. 5-HIAA and 5-HTP were significantly reduced in PKU patients compared to controls. Significant negative correlations were found between CSF 5-HIAA, HVA, and 5-HTP and Phe levels. A decrease in 5-HIAA and 5-HTP concentrations correlated with precuneus and frontal atrophy, respectively. Lower HVA levels correlated with occipital atrophy. Biogenic amines deficits correlate with specific brain atrophy patterns in adult PKU patients, in line with serotonin and dopamine projections. These findings may support a more rigorous Phe control in adult PKU to prevent neurotransmitter depletion and accelerated brain damage due to aging.
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Affiliation(s)
- Andrea Pilotto
- Department of Neurodegeneration, Hertie Institute of Clinical Brain Research, University of Tübingen, Tübingen, Germany
- Neurology Unit, Department of Clinical and Experimental Sciences, University of Brescia, Brescia, Italy
- Parkinson's Disease Rehabilitation Centre, FERB ONLUS S. Isidoro Hospital, Trescore Balneario, Italy
| | - Nenad Blau
- Department of Pediatrics, Division for Neuropediatrics and Metabolic Medicine, University of Heidelberg, Heidelberg, Germany
| | - Edytha Leks
- Department of Biomedical Magnetic Resonance, University of Tübingen, Tübingen, Germany
| | - Claudia Schulte
- Department of Neurodegeneration, Hertie Institute of Clinical Brain Research, University of Tübingen, Tübingen, Germany
- German Center for Neurodegenerative Diseases, Department of Neurodegeneration, Tübingen, Germany
| | - Christian Deuschl
- Department of Neurodegeneration, Hertie Institute of Clinical Brain Research, University of Tübingen, Tübingen, Germany
- German Center for Neurodegenerative Diseases, Department of Neurodegeneration, Tübingen, Germany
| | - Carl Zipser
- Department of Neurology and Stroke, and Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
| | - David Piel
- Department of Endocrinology, Internal Medicine I, University of Heidelberg, Heidelberg, Germany
| | | | - Gwendolyn Gramer
- Department of Pediatrics, Division for Neuropediatrics and Metabolic Medicine, University of Heidelberg, Heidelberg, Germany
| | - Stefan Kölker
- Department of Pediatrics, Division for Neuropediatrics and Metabolic Medicine, University of Heidelberg, Heidelberg, Germany
| | - Dorothea Haas
- Department of Pediatrics, Division for Neuropediatrics and Metabolic Medicine, University of Heidelberg, Heidelberg, Germany
| | - Peter Burgard
- Department of Pediatrics, Division for Neuropediatrics and Metabolic Medicine, University of Heidelberg, Heidelberg, Germany
| | - Peter Nawroth
- Department of Endocrinology, Internal Medicine I, University of Heidelberg, Heidelberg, Germany
| | - Hoffmann Georg
- Department of Pediatrics, Division for Neuropediatrics and Metabolic Medicine, University of Heidelberg, Heidelberg, Germany
| | - Klaus Scheffler
- Department of Biomedical Magnetic Resonance, University of Tübingen, Tübingen, Germany
- Magnetic Resonance Centre, Max-Planck-Institute for Biological Cybernetics, Tübingen, Germany
| | - Daniela Berg
- Department of Neurodegeneration, Hertie Institute of Clinical Brain Research, University of Tübingen, Tübingen, Germany
- German Center for Neurodegenerative Diseases, Department of Neurodegeneration, Tübingen, Germany
- Department of Neurology, University-Hospital-Schleswig-Holstein, Christian-Albrechts-University, Kiel, Germany
| | - Friedrich Trefz
- Department of Pediatrics, Division for Neuropediatrics and Metabolic Medicine, University of Heidelberg, Heidelberg, Germany
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Luna-Munguia H, Zestos AG, Gliske SV, Kennedy RT, Stacey WC. Chemical biomarkers of epileptogenesis and ictogenesis in experimental epilepsy. Neurobiol Dis 2018; 121:177-186. [PMID: 30304705 DOI: 10.1016/j.nbd.2018.10.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Revised: 10/01/2018] [Accepted: 10/04/2018] [Indexed: 12/29/2022] Open
Abstract
Epilepsy produces chronic chemical changes induced by altered cellular structures, and acute ones produced by conditions leading into individual seizures. Here, we aim to quantify 24 molecules simultaneously at baseline and during periods of lowered seizure threshold in rats. Using serial hippocampal microdialysis collections starting two weeks after the pilocarpine-induced status epilepticus, we evaluated how this chronic epilepsy model affects molecule levels and their interactions. Then, we quantified the changes occurring when the brain moves into a pro-seizure state using a novel model of physiological ictogenesis. Compared with controls, pilocarpine animals had significantly decreased baseline levels of adenosine, homovanillic acid, and serotonin, but significantly increased levels of choline, glutamate, phenylalanine, and tyrosine. Step-wise linear regression identified that choline, homovanillic acid, adenosine, and serotonin are the most important features to characterize the difference in the extracellular milieu between pilocarpine and control animals. When increasing the hippocampal seizure risk, the concentrations of normetanephrine, serine, aspartate, and 5-hydroxyindoleacetic acid were the most prominent; however, there were no specific, consistent changes prior to individual seizures.
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Affiliation(s)
- Hiram Luna-Munguia
- Departamento de Neurobiologia Conductual y Cognitiva, Instituto de Neurobiologia, Universidad Nacional Autonoma de Mexico, Campus UNAM-Juriquilla, Queretaro, Mexico
| | - Alexander G Zestos
- Department of Chemistry, Center for Behavioral Neuroscience, American University, Washington D.C. 20016, USA
| | - Stephen V Gliske
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, USA; Department of Neurology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Robert T Kennedy
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA; Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109, USA
| | - William C Stacey
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, USA; Department of Neurology, University of Michigan, Ann Arbor, MI 48109, USA.
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10
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Belanger AM, Przybylska M, Gefteas E, Furgerson M, Geller S, Kloss A, Cheng SH, Zhu Y, Yew NS. Inhibiting neutral amino acid transport for the treatment of phenylketonuria. JCI Insight 2018; 3:121762. [PMID: 30046012 DOI: 10.1172/jci.insight.121762] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Accepted: 06/19/2018] [Indexed: 12/21/2022] Open
Abstract
The neuropathological effects of phenylketonuria (PKU) stem from the inability of the body to metabolize excess phenylalanine (Phe), resulting in accumulation of Phe in the blood and brain. Since the kidney normally reabsorbs circulating amino acids with high efficiency, we hypothesized that preventing the renal uptake of Phe might provide a disposal pathway that could lower systemic Phe levels. SLC6A19 is a neutral amino acid transporter responsible for absorption of the majority of free Phe in the small intestine and reuptake of Phe by renal proximal tubule cells. Transgenic KO mice lacking SLC6A19 have elevated levels of Phe and other amino acids in their urine but are otherwise healthy. Here, we crossed the Pahenu2 mouse model of PKU with the Slc6a19-KO mouse. These mutant/KO mice exhibited abundant excretion of Phe in the urine and an approximately 70% decrease in plasma Phe levels. Importantly, brain Phe levels were decreased by 50%, and the levels of key neurotransmitters were increased in the mutant/KO mice. In addition, a deficit in spatial working memory and markers of neuropathology were corrected. Finally, treatment of Pahenu2 mice with Slc6a19 antisense oligonucleotides lowered Phe levels. The results suggest that inhibition of SLC6A19 may represent a novel approach for the treatment of PKU and related aminoacidopathies.
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MESH Headings
- Amines
- Amino Acid Transport Systems, Neutral/analysis
- Amino Acid Transport Systems, Neutral/genetics
- Amino Acid Transport Systems, Neutral/metabolism
- Amino Acids, Neutral/blood
- Amino Acids, Neutral/metabolism
- Animals
- Astrocytes/metabolism
- Astrocytes/pathology
- Biological Transport/drug effects
- Brain/metabolism
- Disease Models, Animal
- Female
- Gene Expression Regulation
- Genetic Diseases, Inborn/therapy
- Kidney Tubules, Proximal/drug effects
- Kidney Tubules, Proximal/metabolism
- Male
- Memory, Short-Term
- Mice
- Mice, Knockout
- Morpholinos/pharmacology
- Oligonucleotides/pharmacology
- Phenylalanine/blood
- Phenylalanine/metabolism
- Phenylketonurias/pathology
- Phenylketonurias/therapy
- Renal Reabsorption/drug effects
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11
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Scherer T, Allegri G, Sarkissian CN, Ying M, Grisch-Chan HM, Rassi A, Winn SR, Harding CO, Martinez A, Thöny B. Tetrahydrobiopterin treatment reduces brain L-Phe but only partially improves serotonin in hyperphenylalaninemic ENU1/2 mice. J Inherit Metab Dis 2018; 41:709-718. [PMID: 29520738 PMCID: PMC6041158 DOI: 10.1007/s10545-018-0150-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Revised: 01/26/2018] [Accepted: 01/30/2018] [Indexed: 12/16/2022]
Abstract
Hyperphenylalaninemia (HPA) caused by hepatic phenylalanine hydroxylase (PAH) deficiency has severe consequences on brain monoamine neurotransmitter metabolism. We have studied monoamine neurotransmitter status and the effect of tetrahydrobiopterin (BH4) treatment in Pahenu1/enu2 (ENU1/2) mice, a model of partial PAH deficiency. These mice exhibit elevated blood L-phenylalanine (L-Phe) concentrations similar to that of mild hyperphenylalaninemia (HPA), but brain levels of L-Phe are still ~5-fold elevated compared to wild-type. We found that brain L-tyrosine, L-tryptophan, BH4 cofactor and catecholamine concentrations, and brain tyrosine hydroxylase (TH) activity were normal in these mice but that brain serotonin, 5-hydroxyindolacetic acid (5HIAA) and 3-methoxy-4-hydroxyphenylglycol (MHPG) content, and brain TH protein, as well as tryptophan hydroxylase type 2 (TPH2) protein levels and activity were reduced in comparison to wild-type mice. Parenteral L-Phe loading conditions did not lead to significant changes in brain neurometabolite concentrations. Remarkably, enteral BH4 treatment, which normalized brain L-Phe levels in ENU1/2 mice, lead to only partial recovery of brain serotonin and 5HIAA concentrations. Furthermore, indirect evidence indicated that the GTP cyclohydrolase I (GTPCH) feedback regulatory protein (GFRP) complex may be a sensor for brain L-Phe elevation to ameliorate the toxic effects of HPA. We conclude that BH4 treatment of HPA toward systemic L-Phe lowering reverses elevated brain L-Phe content but the recovery of TPH2 protein and activity as well as serotonin levels is suboptimal, indicating that patients with mild HPA and mood problems (depression or anxiety) treated with the current diet may benefit from supplementation with BH4 and 5-OH-tryptophan.
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Affiliation(s)
- Tanja Scherer
- Department of Pediatrics, Divisions of Metabolism and of Clinical Chemistry and Biochemistry, University of Zürich, Zürich, Switzerland
| | - Gabriella Allegri
- Department of Pediatrics, Divisions of Metabolism and of Clinical Chemistry and Biochemistry, University of Zürich, Zürich, Switzerland
| | | | - Ming Ying
- Department of Biomedicine and K.G. Jebsen Centre for Neuropsychiatric Disorders, University of Bergen, Bergen, Norway
| | - Hiu Man Grisch-Chan
- Department of Pediatrics, Divisions of Metabolism and of Clinical Chemistry and Biochemistry, University of Zürich, Zürich, Switzerland
| | - Anahita Rassi
- Department of Pediatrics, Divisions of Metabolism and of Clinical Chemistry and Biochemistry, University of Zürich, Zürich, Switzerland
| | - Shelley R Winn
- Department of Molecular and Medical Genetics, School of Medicine, Oregon Science & Health University, Portland, OR, USA
| | - Cary O Harding
- Department of Molecular and Medical Genetics, School of Medicine, Oregon Science & Health University, Portland, OR, USA
| | - Aurora Martinez
- Department of Biomedicine and K.G. Jebsen Centre for Neuropsychiatric Disorders, University of Bergen, Bergen, Norway.
| | - Beat Thöny
- Department of Pediatrics, Divisions of Metabolism and of Clinical Chemistry and Biochemistry, University of Zürich, Zürich, Switzerland.
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12
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Hawks ZW, Strube MJ, Johnson NX, Grange DK, White DA. Developmental Trajectories of Executive and Verbal Processes in Children with Phenylketonuria. Dev Neuropsychol 2018; 43:207-218. [PMID: 29432026 DOI: 10.1080/87565641.2018.1438439] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Phenylketonuria (PKU) is a hereditary disorder characterized by disrupted phenylalanine metabolism and cognitive impairment. However, the precise nature and developmental trajectory of this cognitive impairment remains unclear. The present study used a verbal fluency task to dissociate executive and verbal processes in children with PKU (n = 23; 7-18 years) and controls (n = 44; 7-19 years). Data were collected at three longitudinal timepoints over a three-year period, and the contributions of age, group, and their interaction to fluency performance were evaluated. Results indicated impairments in executive processes in children with PKU, which were exacerbated by declining metabolic control.
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Affiliation(s)
- Zoë W Hawks
- a Department of Psychological & Brain Sciences , Washington University , St. Louis , Missouri , United States of America
| | - Michael J Strube
- a Department of Psychological & Brain Sciences , Washington University , St. Louis , Missouri , United States of America
| | - Neco X Johnson
- a Department of Psychological & Brain Sciences , Washington University , St. Louis , Missouri , United States of America
| | - Dorothy K Grange
- b Department of Pediatrics , Washington University School of Medicine , St. Louis , Missouri , United States of America
| | - Desirée A White
- a Department of Psychological & Brain Sciences , Washington University , St. Louis , Missouri , United States of America.,b Department of Pediatrics , Washington University School of Medicine , St. Louis , Missouri , United States of America
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13
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Winn SR, Scherer T, Thöny B, Ying M, Martinez A, Weber S, Raber J, Harding CO. Blood phenylalanine reduction corrects CNS dopamine and serotonin deficiencies and partially improves behavioral performance in adult phenylketonuric mice. Mol Genet Metab 2018; 123:6-20. [PMID: 29331172 PMCID: PMC5786171 DOI: 10.1016/j.ymgme.2017.10.009] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 10/17/2017] [Accepted: 10/17/2017] [Indexed: 01/12/2023]
Abstract
Central nervous system (CNS) deficiencies of the monoamine neurotransmitters dopamine and serotonin have been implicated in the pathophysiology of neuropsychiatric dysfunction in human phenylketonuria (PKU). In this study, we confirmed the occurrence of brain dopamine and serotonin deficiencies in association with severe behavioral alterations and cognitive impairments in hyperphenylalaninemic C57BL/6-Pahenu2/enu2 mice, a model of human PKU. Phenylalanine-reducing treatments, including either dietary phenylalanine restriction or liver-directed gene therapy, initiated during adulthood were associated with increased brain monoamine content along with improvements in nesting behavior but without a change in the severe cognitive deficits exhibited by these mice. At euthanasia, there was in Pahenu2/enu2 brain a significant reduction in the protein abundance and maximally stimulated activities of tyrosine hydroxylase (TH) and tryptophan hydroxylase 2 (TPH2), the rate limiting enzymes catalyzing neuronal dopamine and serotonin synthesis respectively, in comparison to levels seen in wild type brain. Phenylalanine-reducing treatments initiated during adulthood did not affect brain TH or TPH2 content or maximal activity. Despite this apparent fixed deficit in striatal TH and TPH2 activities, initiation of phenylalanine-reducing treatments yielded substantial correction of brain monoamine neurotransmitter content, suggesting that phenylalanine-mediated competitive inhibition of already constitutively reduced TH and TPH2 activities is the primary cause of brain monoamine deficiency in Pahenu2 mouse brain. We propose that CNS monoamine deficiency may be the cause of the partially reversible adverse behavioral effects associated with chronic HPA in Pahenu2 mice, but that phenylalanine-reducing treatments initiated during adulthood are unable to correct the neuropathology and attendant cognitive deficits that develop during juvenile life in late-treated Pahenu2/enu2 mice.
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Affiliation(s)
- Shelley R Winn
- Department of Medical and Molecular Genetics, Oregon Health & Science University, Mailstop L-103, 3181 Sam Jackson Park Rd., Portland, OR 97239, USA
| | - Tanja Scherer
- Department of Pediatrics, University of Zurich, Steinweissstrasse 75, Zurich CH-8032, Switzerland
| | - Beat Thöny
- Department of Pediatrics, University of Zurich, Steinweissstrasse 75, Zurich CH-8032, Switzerland
| | - Ming Ying
- Department of Biomedicine, KG Jebsen Centre for Neuropsychiatric Disorders, University of Bergen, 5009 Bergen, Norway
| | - Aurora Martinez
- Department of Biomedicine, KG Jebsen Centre for Neuropsychiatric Disorders, University of Bergen, 5009 Bergen, Norway
| | - Sydney Weber
- Department of Behavioral Neuroscience, Oregon Health & Science University, 3181 Sam Jackson Park Rd., Portland, OR 97239, USA
| | - Jacob Raber
- Department of Behavioral Neuroscience, Oregon Health & Science University, 3181 Sam Jackson Park Rd., Portland, OR 97239, USA; Department of Neurology, Division of Neuroscience, ONPRC, Oregon Health & Science University, 3181 Sam Jackson Park Rd., Portland, OR 97239, USA; Department of Radiation Medicine, Division of Neuroscience, ONPRC, Oregon Health & Science University, 3181 Sam Jackson Park Rd., Portland, OR 97239, USA
| | - Cary O Harding
- Department of Medical and Molecular Genetics, Oregon Health & Science University, Mailstop L-103, 3181 Sam Jackson Park Rd., Portland, OR 97239, USA.
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14
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Boot E, Hollak CEM, Huijbregts SCJ, Jahja R, van Vliet D, Nederveen AJ, Nieman DH, Bosch AM, Bour LJ, Bakermans AJ, Abeling NGGM, Bassett AS, van Amelsvoort TAMJ, van Spronsen FJ, Booij J. Cerebral dopamine deficiency, plasma monoamine alterations and neurocognitive deficits in adults with phenylketonuria. Psychol Med 2017; 47:2854-2865. [PMID: 28552082 DOI: 10.1017/s0033291717001398] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
BACKGROUND Phenylketonuria (PKU), a genetic metabolic disorder that is characterized by the inability to convert phenylalanine to tyrosine, leads to severe intellectual disability and other cerebral complications if left untreated. Dietary treatment, initiated soon after birth, prevents most brain-related complications. A leading hypothesis postulates that a shortage of brain monoamines may be associated with neurocognitive deficits that are observable even in early-treated PKU. However, there is a paucity of evidence as yet for this hypothesis. METHODS We therefore assessed in vivo striatal dopamine D2/3 receptor (D2/3R) availability and plasma monoamine metabolite levels together with measures of impulsivity and executive functioning in 18 adults with PKU and average intellect (31.2 ± 7.4 years, nine females), most of whom were early and continuously treated. Comparison data from 12 healthy controls that did not differ in gender and age were available. RESULTS Mean D2/3R availability was significantly higher (13%; p = 0.032) in the PKU group (n = 15) than in the controls, which may reflect reduced synaptic brain dopamine levels in PKU. The PKU group had lower plasma levels of homovanillic acid (p < 0.001) and 3-methoxy-4-hydroxy-phenylglycol (p < 0.0001), the predominant metabolites of dopamine and norepinephrine, respectively. Self-reported impulsivity levels were significantly higher in the PKU group compared with healthy controls (p = 0.033). Within the PKU group, D2/3R availability showed a positive correlation with both impulsivity (r = 0.72, p = 0.003) and the error rate during a cognitive flexibility task (r = 0.59, p = 0.020). CONCLUSIONS These findings provide further support for the hypothesis that executive functioning deficits in treated adult PKU may be associated with cerebral dopamine deficiency.
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Affiliation(s)
- E Boot
- Department of Nuclear Medicine,Academic Medical Center,Amsterdam,The Netherlands
| | - C E M Hollak
- Division of Endocrinology and Metabolism, Department of Internal Medicine,Academic Medical Center,Amsterdam,The Netherlands
| | - S C J Huijbregts
- Department of Clinical Child and Adolescent Studies & Leiden,Institute for Brain and Cognition, Leiden University,Leiden,The Netherlands
| | - R Jahja
- Division of Metabolic Diseases,University of Groningen, University Medical Center Groningen, Beatrix Children's Hospital,Groningen,The Netherlands
| | - D van Vliet
- Division of Metabolic Diseases,University of Groningen, University Medical Center Groningen, Beatrix Children's Hospital,Groningen,The Netherlands
| | - A J Nederveen
- Department of Radiology,Academic Medical Center,Amsterdam,The Netherlands
| | - D H Nieman
- Department of Psychiatry,Academic Medical Center,Amsterdam,The Netherlands
| | - A M Bosch
- Department of Pediatrics,Emma Children's Hospital, Academic Medical Center,Amsterdam,The Netherlands
| | - L J Bour
- Department of Neurology and Clinical Neurophysiology,Academic Medical Center,Amsterdam,The Netherlands
| | - A J Bakermans
- Department of Radiology,Academic Medical Center,Amsterdam,The Netherlands
| | - N G G M Abeling
- Laboratory for Genetic Metabolic Diseases,Academic Medical Center,Amsterdam,The Netherlands
| | - A S Bassett
- The Dalglish Family 22q Clinic for Adults with 22q11.2 Deletion Syndrome, andCenter for Mental Health, University Health Network,Toronto, Ontario,Canada
| | - T A M J van Amelsvoort
- Department of Psychiatry and Psychology,Maastricht University,Maastricht,The Netherlands
| | - F J van Spronsen
- Division of Metabolic Diseases,University of Groningen, University Medical Center Groningen, Beatrix Children's Hospital,Groningen,The Netherlands
| | - J Booij
- Department of Nuclear Medicine,Academic Medical Center,Amsterdam,The Netherlands
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15
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Fiori E, Oddi D, Ventura R, Colamartino M, Valzania A, D’Amato FR, Bruinenberg V, van der Zee E, Puglisi-Allegra S, Pascucci T. Early-onset behavioral and neurochemical deficits in the genetic mouse model of phenylketonuria. PLoS One 2017; 12:e0183430. [PMID: 28850618 PMCID: PMC5574541 DOI: 10.1371/journal.pone.0183430] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Accepted: 08/01/2017] [Indexed: 11/19/2022] Open
Abstract
Phenylketonuria (PKU) is one of the most common human inborn errors of metabolism, caused by phenylalanine hydroxylase deficiency, leading to high phenylalanine and low tyrosine levels in blood and brain causing profound cognitive disability, if untreated. Since 1960, population is screened for hyperphenylalaninemia shortly after birth and submitted to early treatment in order to prevent the major manifestations of the disease. However, the dietetic regimen (phenylalanine free diet) is difficult to maintain, and despite the recommendation to a strict and lifelong compliance, up to 60% of adolescents partially or totally abandons the treatment. The development and the study of new treatments continue to be sought, taking advantage of preclinical models, the most used of which is the PAHenu2 (BTBR ENU2), the genetic murine model of PKU. To date, adult behavioral and neurochemical alterations have been mainly investigated in ENU2 mice, whereas there are no clear indications about the onset of these deficiencies. Here we investigated and report, for the first time, a comprehensive behavioral and neurochemical assay of the developing ENU2 mice. Overall, our findings demonstrate that ENU2 mice are significantly smaller than WT until pnd 24, present a significant delay in the acquisition of tested developmental reflexes, impaired communicative, motor and social skills, and have early reduced biogenic amine levels in several brain areas. Our results extend the understanding of behavioral and cerebral abnormalities in PKU mice, providing instruments to an early preclinical evaluation of the effects of new treatments.
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Affiliation(s)
- Elena Fiori
- Department of Psychology and Centro “Daniel Bovet”, Sapienza University, Rome, Italy
- Cell Biology and Neurobiology Institute, National Research Council, Rome, Italy
- European Brain Research Institute EBRI, Rome, Italy
- Fondazione Santa Lucia, IRCCS, Rome, Italy
| | - Diego Oddi
- Cell Biology and Neurobiology Institute, National Research Council, Rome, Italy
- Fondazione Santa Lucia, IRCCS, Rome, Italy
| | - Rossella Ventura
- Department of Psychology and Centro “Daniel Bovet”, Sapienza University, Rome, Italy
- Fondazione Santa Lucia, IRCCS, Rome, Italy
| | - Marco Colamartino
- Department of Psychology and Centro “Daniel Bovet”, Sapienza University, Rome, Italy
- Fondazione Santa Lucia, IRCCS, Rome, Italy
| | - Alessandro Valzania
- Department of Psychology and Centro “Daniel Bovet”, Sapienza University, Rome, Italy
- Fondazione Santa Lucia, IRCCS, Rome, Italy
| | - Francesca Romana D’Amato
- Cell Biology and Neurobiology Institute, National Research Council, Rome, Italy
- Fondazione Santa Lucia, IRCCS, Rome, Italy
| | - Vibeke Bruinenberg
- Molecular Neurobiology, GELIFES, University of Groningen, Groningen, The Netherlands
| | - Eddy van der Zee
- Molecular Neurobiology, GELIFES, University of Groningen, Groningen, The Netherlands
| | - Stefano Puglisi-Allegra
- Department of Psychology and Centro “Daniel Bovet”, Sapienza University, Rome, Italy
- Fondazione Santa Lucia, IRCCS, Rome, Italy
| | - Tiziana Pascucci
- Department of Psychology and Centro “Daniel Bovet”, Sapienza University, Rome, Italy
- Fondazione Santa Lucia, IRCCS, Rome, Italy
- * E-mail:
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16
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Abstract
Although serotonin neurotransmission has been implicated in several neurodevelopmental and psychological disorders, the factors that drive dysfunction of the serotonin system are poorly understood. Current research regarding the serotonin system revolves around its dysfunction in neuropsychiatric disorders, but there is no database collating genetic mutations that result in serotonin abnormalities. To bridge this gap, we developed a list of genes in mice that, when perturbed, result in altered levels of serotonin either in brain or blood. Due to the intrinsic limitations of search, the current list should be considered a preliminary subset of all relevant cases. Nevertheless, it offered an opportunity to gain insight into what types of genes have the potential to impact serotonin by using gene ontology (GO). This analysis found that genes associated with monoamine metabolism were more often associated with increases in brain serotonin than decreases. Speculatively, this could be because several pathways (and therefore many genes) are responsible for the clearance and metabolism of serotonin whereas only one pathway (and therefore fewer genes) is directly involved in the synthesis of serotonin. Another contributor could be cross talk between monoamine systems such as dopamine. In contrast, genes that were associated with decreases in brain serotonin were more likely linked to a developmental process. Sensitivity of serotonin neurons to developmental perturbations could be due to their complicated neuroanatomy or possibly they may be negatively regulated by dysfunction of their innervation targets. Thus, these observations suggest hypotheses regarding the mechanisms underlying the vulnerability of brain serotonin neurotransmission.
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Affiliation(s)
- Richard C. Tenpenny
- Department of Anesthesiology, Perioperative, and Pain
Medicine, Boston Children’s Hospital and Department of Anesthesia,
Harvard Medical School, 300 Longwood
Avenue, Boston, Massachusetts 02115, United States
| | - Kathryn G. Commons
- Department of Anesthesiology, Perioperative, and Pain
Medicine, Boston Children’s Hospital and Department of Anesthesia,
Harvard Medical School, 300 Longwood
Avenue, Boston, Massachusetts 02115, United States
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17
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Unbalance between Excitation and Inhibition in Phenylketonuria, a Genetic Metabolic Disease Associated with Autism. Int J Mol Sci 2017; 18:ijms18050941. [PMID: 28468253 PMCID: PMC5454854 DOI: 10.3390/ijms18050941] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 04/20/2017] [Accepted: 04/23/2017] [Indexed: 02/06/2023] Open
Abstract
Phenylketonuria (PKU) is the most common genetic metabolic disease with a well-documented association with autism spectrum disorders. It is characterized by the deficiency of the phenylalanine hydroxylase activity, causing plasmatic hyperphenylalaninemia and variable neurological and cognitive impairments. Among the potential pathophysiological mechanisms implicated in autism spectrum disorders is the excitation/inhibition (E/I) imbalance which might result from alterations in excitatory/inhibitory synapse development, synaptic transmission and plasticity, downstream signalling pathways, and intrinsic neuronal excitability. Here, we investigated functional and molecular alterations in the prefrontal cortex (pFC) of BTBR-Pahenu2 (ENU2) mice, the animal model of PKU. Our data show higher frequency of inhibitory transmissions and significant reduced frequency of excitatory transmissions in the PKU-affected mice in comparison to wild type. Moreover, in the pFC of ENU2 mice, we reported higher levels of the post-synaptic cell-adhesion proteins neuroligin1 and 2. Altogether, our data point toward an imbalance in the E/I neurotransmission favouring inhibition in the pFC of ENU2 mice, along with alterations of the molecular components involved in the organization of cortical synapse. In addition to being the first evidence of E/I imbalance within cortical areas of a mouse model of PKU, our study provides further evidence of E/I imbalance in animal models of pathology associated with autism spectrum disorders.
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18
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Abstract
Cerebral neurotransmitter (NT) deficiency has been suggested as a contributing factor in the pathophysiology of brain dysfunction in phenylketonuria (PKU), even in early-treated phenylketonuric patients. The study aimed to review dopamine and serotonin status in PKU, and the effect of the impaired neurotransmission. Several mechanisms are involved in the pathophysiology of PKU, primarily characterized by impaired dopamine and serotonin synthesis. These deficits are related to executive dysfunctions and social-emotional problems, respectively, in early treated patients. Blood phenylalanine is the main biomarker for treatment compliance follow-up, but further investigations and validation of peripheral biomarkers may be performed to monitor NT status. The development of new therapies is needed not only for decreasing blood and brain phenylalanine levels but also to improve NT syntheses.
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19
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Development of chemical isotope labeling liquid chromatography mass spectrometry for silkworm hemolymph metabolomics. Anal Chim Acta 2016; 942:1-11. [DOI: 10.1016/j.aca.2016.06.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2016] [Revised: 05/15/2016] [Accepted: 06/01/2016] [Indexed: 11/24/2022]
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20
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Abstract
Metabolic disorders comprise a large group of heterogeneous diseases ranging from very prevalent diseases such as diabetes mellitus to rare genetic disorders like Canavan Disease. Whether either of these diseases is amendable by gene therapy depends to a large degree on the knowledge of their pathomechanism, availability of the therapeutic gene, vector selection, and availability of suitable animal models. In this book chapter, we review three metabolic disorders of the central nervous system (CNS; Canavan Disease, Niemann-Pick disease and Phenylketonuria) to give examples for primary and secondary metabolic disorders of the brain and the attempts that have been made to use adeno-associated virus (AAV) based gene therapy for treatment. Finally, we highlight commonalities and obstacles in the development of gene therapy for metabolic disorders of the CNS exemplified by those three diseases.
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Affiliation(s)
- Dominic J Gessler
- University of Massachusetts Medical School, 368 Plantation Street, AS6-2049, Worcester, MA, 01605, USA
| | - Guangping Gao
- University of Massachusetts Medical School, 368 Plantation Street, AS6-2049, Worcester, MA, 01605, USA.
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21
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Winn SR, Scherer T, Thöny B, Harding CO. High dose sapropterin dihydrochloride therapy improves monoamine neurotransmitter turnover in murine phenylketonuria (PKU). Mol Genet Metab 2016; 117:5-11. [PMID: 26653793 PMCID: PMC4706464 DOI: 10.1016/j.ymgme.2015.11.012] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2015] [Accepted: 11/25/2015] [Indexed: 01/08/2023]
Abstract
Central nervous system (CNS) deficiencies of the monoamine neurotransmitters, dopamine and serotonin, have been implicated in the pathophysiology of neuropsychiatric dysfunction in phenylketonuria (PKU). Increased brain phenylalanine concentration likely competitively inhibits the activities of tyrosine hydroxylase (TH) and tryptophan hydroxylase (TPH), the rate limiting steps in dopamine and serotonin synthesis respectively. Tetrahydrobiopterin (BH4) is a required cofactor for TH and TPH activity. Our hypothesis was that treatment of hyperphenylalaninemic Pah(enu2/enu2) mice, a model of human PKU, with sapropterin dihydrochloride, a synthetic form of BH4, would stimulate TH and TPH activities leading to improved dopamine and serotonin synthesis despite persistently elevated brain phenylalanine. Sapropterin (20, 40, or 100mg/kg body weight in 1% ascorbic acid) was administered daily for 4 days by oral gavage to Pah(enu2/enu2) mice followed by measurement of brain biopterin, phenylalanine, tyrosine, tryptophan and monoamine neurotransmitter content. A significant increase in brain biopterin content was detected only in mice that had received the highest sapropterin dose, 100mg/kg. Blood and brain phenylalanine concentrations were unchanged by sapropterin therapy. Sapropterin therapy also did not alter the absolute amounts of dopamine and serotonin in brain but was associated with increased homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA), dopamine and serotonin metabolites respectively, in both wild type and Pah(enu2/enu2) mice. Oral sapropterin therapy likely does not directly affect central nervous system monoamine synthesis in either wild type or hyperphenylalaninemic mice but may stimulate synaptic neurotransmitter release and subsequent metabolism.
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Affiliation(s)
- Shelley R Winn
- Department of Molecular and Medical Genetics, Oregon Health & Science University, Mailstop L-103, 3181 Sam Jackson Park Rd., Portland, OR 97239, USA
| | - Tanja Scherer
- Department of Pediatrics, University of Zurich, Steinweissstrasse 75, Zurich CH-8032, Switzerland
| | - Beat Thöny
- Department of Pediatrics, University of Zurich, Steinweissstrasse 75, Zurich CH-8032, Switzerland
| | - Cary O Harding
- Department of Molecular and Medical Genetics, Oregon Health & Science University, Mailstop L-103, 3181 Sam Jackson Park Rd., Portland, OR 97239, USA.
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22
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Schuck PF, Malgarin F, Cararo JH, Cardoso F, Streck EL, Ferreira GC. Phenylketonuria Pathophysiology: on the Role of Metabolic Alterations. Aging Dis 2015; 6:390-9. [PMID: 26425393 DOI: 10.14336/ad.2015.0827] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Accepted: 08/27/2015] [Indexed: 11/01/2022] Open
Abstract
Phenylketonuria (PKU) is an inborn error of phenylalanine (Phe) metabolism caused by the deficiency of phenylalanine hydroxylase. This deficiency leads to the accumulation of Phe and its metabolites in tissues and body fluids of PKU patients. The main signs and symptoms are found in the brain but the pathophysiology of this disease is not well understood. In this context, metabolic alterations such as oxidative stress, mitochondrial dysfunction, and impaired protein and neurotransmitters synthesis have been described both in animal models and patients. This review aims to discuss the main metabolic disturbances reported in PKU and relate them with the pathophysiology of this disease. The elucidation of the pathophysiology of brain damage found in PKU patients will help to develop better therapeutic strategies to improve quality of life of patients affected by this condition.
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Affiliation(s)
- Patrícia Fernanda Schuck
- 1 Laboratório de Erros Inatos do Metabolismo, Unidade Acadêmica de Ciências da Saúde, Universidade do Extremo Sul Catarinense, Criciúma, SC, Brazil
| | - Fernanda Malgarin
- 1 Laboratório de Erros Inatos do Metabolismo, Unidade Acadêmica de Ciências da Saúde, Universidade do Extremo Sul Catarinense, Criciúma, SC, Brazil
| | - José Henrique Cararo
- 1 Laboratório de Erros Inatos do Metabolismo, Unidade Acadêmica de Ciências da Saúde, Universidade do Extremo Sul Catarinense, Criciúma, SC, Brazil
| | - Fabiola Cardoso
- 2 Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Emilio Luiz Streck
- 3 Laboratório de Bioenergética, Unidade Acadêmica de Ciências da Saúde, Universidade do Extremo Sul Catarinense, Criciúma, SC, Brazil
| | - Gustavo Costa Ferreira
- 2 Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
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23
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de Groot MJ, Sijens PE, Reijngoud DJ, Paans AM, van Spronsen FJ. Phenylketonuria: brain phenylalanine concentrations relate inversely to cerebral protein synthesis. J Cereb Blood Flow Metab 2015; 35:200-5. [PMID: 25352046 PMCID: PMC4426736 DOI: 10.1038/jcbfm.2014.183] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2014] [Revised: 08/19/2014] [Accepted: 09/04/2014] [Indexed: 11/09/2022]
Abstract
In phenylketonuria, elevated plasma phenylalanine concentrations may disturb blood-to-brain large neutral amino acid (LNAA) transport and cerebral protein synthesis (CPS). We investigated the associations between these processes, using data obtained by positron emission tomography with l-[1-(11)C]-tyrosine ((11)C-Tyr) as a tracer. Blood-to-brain transport of non-Phe LNAAs was modeled by the rate constant for (11)C-Tyr transport from arterial plasma to brain tissue (K1), while CPS was modeled by the rate constant for (11)C-Tyr incorporation into cerebral protein (k3). Brain phenylalanine concentrations were measured by magnetic resonance spectroscopy in three volumes of interest (VOIs): supraventricular brain tissue (VOI 1), ventricular brain tissue (VOI 2), and fluid-containing ventricular voxels (VOI 3). The associations between k3 and each predictor variable were analyzed by multiple linear regression. The rate constant k3 was inversely associated with brain phenylalanine concentrations in VOIs 2 and 3 (adjusted R(2)=0.826, F=19.936, P=0.021). Since brain phenylalanine concentrations in these VOIs highly correlated with each other, the specific associations of each predictor with k3 could not be determined. The associations between k3 and plasma phenylalanine concentration, K1, and brain phenylalanine concentrations in VOI 1 were nonsignificant. In conclusion, our study shows an inverse association between k3 and increased brain phenylalanine concentrations.
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Affiliation(s)
- Martijn J de Groot
- 1] Department of Metabolic Diseases, Beatrix Children's Hospital, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands [2] Department of Digestive and Metabolic Diseases, Center for Liver, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Paul E Sijens
- Department of Radiology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Dirk-Jan Reijngoud
- 1] Department of Digestive and Metabolic Diseases, Center for Liver, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands [2] Department of Laboratory Medicine, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Anne M Paans
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Francjan J van Spronsen
- 1] Department of Metabolic Diseases, Beatrix Children's Hospital, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands [2] Department of Digestive and Metabolic Diseases, Center for Liver, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
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Horling K, Schlegel G, Schulz S, Vierk R, Ullrich K, Santer R, Rune GM. Hippocampal synaptic connectivity in phenylketonuria. Hum Mol Genet 2014; 24:1007-18. [PMID: 25296915 DOI: 10.1093/hmg/ddu515] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
In humans, lack of phenylalanine hydroxylase (Pah) activity results in phenylketonuria (PKU), which is associated with the development of severe mental retardation after birth. The underlying mechanisms, however, are poorly understood. Mutations of the Pah gene in Pah(enu2)/c57bl6 mice result in elevated levels of phenylalanine in serum similar to those in humans suffering from PKU. In our study, long-term potentiation (LTP) and paired-pulse facilitation, measured at CA3-CA1 Schaffer collateral synapses, were impaired in acute hippocampal slices of Pah(enu2)/c57bl6 mice. In addition, we found reduced expression of presynaptic proteins, such as synaptophysin and the synaptosomal-associated protein 25 (SNAP-25), and enhanced expression of postsynaptic marker proteins, such as synaptopodin and spinophilin. Stereological counting of spine synapses at the ultrastructural level revealed higher synaptic density in the hippocampus, commencing at 3 weeks and persisting up to 12 weeks after birth. Consistent effects were seen in response to phenylalanine treatment in cultures of dissociated hippocampal neurones. Most importantly, in the hippocampus of Pah(enu2)/c57bl6 mice, we found a significant reduction in microglia activity. Reorganization of hippocampal circuitry after birth, namely synaptic pruning, relies on elimination of weak synapses by activated microglia in response to neuronal activity. Hence, our data strongly suggest that reduced microglial activity in response to impaired synaptic transmission affects physiological postnatal remodelling of synapses in the hippocampus and may trigger the development of mental retardation in PKU patients after birth.
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Affiliation(s)
- Katja Horling
- Institute of Neuroanatomy, Institute of Anatomy and Experimental Morphology and
| | | | | | | | - Kurt Ullrich
- Department of Pediatrics, University Medical Center Hamburg-Eppendorf, Hamburg 20246, Germany
| | - René Santer
- Department of Pediatrics, University Medical Center Hamburg-Eppendorf, Hamburg 20246, Germany
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Harding CO, Winn SR, Gibson KM, Arning E, Bottiglieri T, Grompe M. Pharmacologic inhibition of L-tyrosine degradation ameliorates cerebral dopamine deficiency in murine phenylketonuria (PKU). J Inherit Metab Dis 2014; 37:735-43. [PMID: 24487571 PMCID: PMC4119869 DOI: 10.1007/s10545-013-9675-2] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Revised: 12/18/2013] [Accepted: 12/30/2013] [Indexed: 12/22/2022]
Abstract
Monoamine neurotransmitter deficiency has been implicated in the etiology of neuropsychiatric symptoms associated with chronic hyperphenylalaninemia in phenylketonuria (PKU). Two proposed explanations for neurotransmitter deficiency in PKU include first, that chronically elevated blood L-phenylalanine (Phe) inhibits the transport of L-tyrosine (Tyr) and L-tryptophan (Trp), the substrates for dopamine and serotonin synthesis respectively, into brain. In the second hypothesis, elevated Phe competitively inhibits brain tyrosine hydroxylase (TH) and tryptophan hydroxylase (TPH) activities, the rate limiting steps in dopamine and serotonin synthesis. Dietary supplementation with large neutral amino acids (LNAA) including Tyr and Trp has been recommended for individuals with chronically elevated blood Phe in an attempt to restore amino acid and monoamine homeostasis in brain. As a potential alternative treatment approach, we demonstrate that pharmacologic inhibition of Tyr degradation through oral administration of nitisinone (NTBC) yielded sustained increases in blood and brain Tyr, decreased blood and brain Phe, and consequently increased dopamine synthesis in a murine model of PKU. Our results suggest that Phe-mediated inhibition of TH activity is the likely mechanism of impaired dopamine synthesis in PKU. Pharmacologic inhibition of Tyr degradation may be a promising adjunct therapy for CNS monoamine neurotransmitter deficiency in hyperphenylalaninemic individuals with PKU.
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Affiliation(s)
- Cary O Harding
- Department of Molecular and Medical Genetics, Oregon Health & Science University, Mailstop L-103, 3181 Sam Jackson Park Rd., Portland, OR, 97239, USA,
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Abhilash M, Alex M, Mathews VV, Nair RH. Chronic Effect of Aspartame on Ionic Homeostasis and Monoamine Neurotransmitters in the Rat Brain. Int J Toxicol 2014; 33:332-341. [DOI: 10.1177/1091581814537087] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Aspartame is one of the most widely used artificial sweeteners globally. Data concerning acute neurotoxicity of aspartame is controversial, and knowledge on its chronic effect is limited. In the current study, we investigated the chronic effects of aspartame on ionic homeostasis and regional monoamine neurotransmitter concentrations in the brain. Our results showed that aspartame at high dose caused a disturbance in ionic homeostasis and induced apoptosis in the brain. We also investigated the effects of aspartame on brain regional monoamine synthesis, and the results revealed that there was a significant decrease of dopamine in corpus striatum and cerebral cortex and of serotonin in corpus striatum. Moreover, aspartame treatment significantly alters the tyrosine hydroxylase activity and amino acids levels in the brain. Our data suggest that chronic use of aspartame may affect electrolyte homeostasis and monoamine neurotransmitter synthesis dose dependently, and this might have a possible effect on cognitive functions.
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Affiliation(s)
- M. Abhilash
- School of Biosciences, Mahatma Gandhi University, Kottayam, Kerala, India
| | - Manju Alex
- School of Biosciences, Mahatma Gandhi University, Kottayam, Kerala, India
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Sawin EA, Murali SG, Ney DM. Differential effects of low-phenylalanine protein sources on brain neurotransmitters and behavior in C57Bl/6-Pah(enu2) mice. Mol Genet Metab 2014; 111:452-61. [PMID: 24560888 PMCID: PMC3995025 DOI: 10.1016/j.ymgme.2014.01.015] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Accepted: 01/30/2014] [Indexed: 11/24/2022]
Abstract
Phenylketonuria (PKU) is an inborn error of metabolism caused by a deficiency of the enzyme phenylalanine hydroxylase, which metabolizes phenylalanine (phe) to tyrosine. A low-phe diet plus amino acid (AA) formula is necessary to prevent cognitive impairment; glycomacropeptide (GMP) contains minimal phe and provides a palatable alternative to the AA formula. Our objective was to assess neurotransmitter concentrations in the brain and the behavioral phenotype of PKU mice (Pah(enu2) on the C57Bl/6 background) and how this is affected by low-phe protein sources. Wild type (WT) and PKU mice, both male and female, were fed high-phe casein, low-phe AA, or low-phe GMP diets between 3 and 18 weeks of age. Behavioral phenotype was assessed using the open field and marble burying tests, and brain neurotransmitter concentrations were measured using HPLC with electrochemical detection system. Data were analyzed by 3-way ANOVA with genotype, sex, and diet as the main treatment effects. Brain mass and the concentrations of catecholamines and serotonin were reduced in PKU mice compared to WT mice; the low-phe AA and GMP diets improved these parameters in PKU mice. Relative brain mass was increased in female PKU mice fed the GMP diet compared to the AA diet. PKU mice exhibited hyperactivity and impaired vertical exploration compared to their WT littermates during the open field test. Regardless of genotype or diet, female mice demonstrated increased vertical activity time and increased total ambulatory and horizontal activity counts compared with male mice. PKU mice fed the high-phe casein diet buried significantly fewer marbles than WT control mice fed casein; this was normalized in PKU mice fed the low-phe AA and GMP diets. In summary, C57Bl/6-Pah(enu2) mice showed an impaired behavioral phenotype and reduced brain neurotransmitter concentrations that were improved by the low-phe AA or GMP diets. These data support lifelong adherence to a low-phe diet for PKU.
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Affiliation(s)
- Emily A Sawin
- Department of Nutritional Sciences, University of Wisconsin-Madison, WI 53706, USA.
| | - Sangita G Murali
- Department of Nutritional Sciences, University of Wisconsin-Madison, WI 53706, USA.
| | - Denise M Ney
- Department of Nutritional Sciences, University of Wisconsin-Madison, WI 53706, USA.
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Leuzzi V, Mannarelli D, Manti F, Pauletti C, Locuratolo N, Carducci C, Carducci C, Vanacore N, Fattapposta F. Age-related psychophysiological vulnerability to phenylalanine in phenylketonuria. Front Pediatr 2014; 2:57. [PMID: 25003100 PMCID: PMC4066367 DOI: 10.3389/fped.2014.00057] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/23/2013] [Accepted: 05/23/2014] [Indexed: 01/24/2023] Open
Abstract
BACKGROUND Phenylketonuria (PKU) is caused by the inherited defect of the phenylalanine hydroxylase enzyme, which converts phenylalanine (Phe) into tyrosine (Tyr). Neonatal screening programs and early treatment have radically changed the natural history of PKU. Nevertheless, an increased risk of neurocognitive and psychiatric problems in adulthood remains a challenging aspect of the disease. In order to assess the vulnerability of complex skills to Phe, we explored: (a) the effect of a rapid increase in blood Phe levels on event-related potentials (ERP) in PKU subjects during their second decade of life; (b) the association (if existing) between psychophysiological and neurocognitive features. METHODS Seventeen early-treated PKU subjects, aged 10-20, underwent ERP [mismatch negativity, auditory P300, contingent negative variation (CNV), and Intensity Dependence of Auditory Evoked Potentials] recording before and 2 h after an oral loading of Phe. Neurocognitive functioning, historical and concurrent biochemical values of blood Phe, Tyr, and Phe/Tyr ratio, were all included in the statistical analysis. RESULTS Event-related potential components were normally detected in all the subjects. In subjects younger than 13 CNV amplitude, W2-CNV area, P3b latency, and reaction times in motor responses were negatively influenced by Phe-loading. Independently from the psychophysiological vulnerability, some neurocognitive skills were more impaired in younger patients. No correlation was found between biochemical alterations and neurocognitive and psychophysiological findings. CONCLUSION The vulnerability of the emerging neurocognitive functions to Phe suggests a strict metabolic control in adolescents affected by PKU and a neurodevelopmental approach in the study of neurocognitive outcome in PKU.
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Affiliation(s)
- Vincenzo Leuzzi
- Department of Paediatrics, Child Neurology and Psychiatry, Sapienza Università di Roma , Rome , Italy
| | - Daniela Mannarelli
- Department of Neurology and Psychiatry, Sapienza Università di Roma , Rome , Italy
| | - Filippo Manti
- Department of Paediatrics, Child Neurology and Psychiatry, Sapienza Università di Roma , Rome , Italy
| | - Caterina Pauletti
- Department of Neurology and Psychiatry, Sapienza Università di Roma , Rome , Italy
| | - Nicoletta Locuratolo
- Department of Neurology and Psychiatry, Sapienza Università di Roma , Rome , Italy
| | - Carla Carducci
- Department of Experimental Medicine, Sapienza Università di Roma , Rome , Italy
| | - Claudia Carducci
- Department of Molecular Medicine, Sapienza Università di Roma , Rome , Italy
| | - Nicola Vanacore
- Centre for Epidemiology, Surveillance and Health Promotion (CNESPS), Istituto Superiore di Sanità , Rome , Italy
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Pascucci T, Giacovazzo G, Andolina D, Accoto A, Fiori E, Ventura R, Orsini C, Conversi D, Carducci C, Leuzzi V, Puglisi-Allegra S. Behavioral and neurochemical characterization of new mouse model of hyperphenylalaninemia. PLoS One 2013; 8:e84697. [PMID: 24376837 PMCID: PMC3869930 DOI: 10.1371/journal.pone.0084697] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Accepted: 11/18/2013] [Indexed: 11/19/2022] Open
Abstract
Hyperphenylalaninemia (HPA) refers to all clinical conditions characterized by increased amounts of phenylalanine (PHE) in blood and other tissues. According to their blood PHE concentrations under a free diet, hyperphenylalaninemic patients are commonly classified into phenotypic subtypes: classical phenylketonuria (PKU) (PHE > 1200 µM/L), mild PKU (PHE 600-1200 µM/L) and persistent HPA (PHE 120-600 µM/L) (normal blood PHE < 120 µM/L). The current treatment for hyperphenylalaninemic patients is aimed to keep blood PHE levels within the safe range of 120-360 µM/L through a PHE-restricted diet, difficult to achieve. If untreated, classical PKU presents variable neurological and mental impairment. However, even mildly elevated blood PHE levels, due to a bad compliance to dietary treatment, produce cognitive deficits involving the prefrontal cortical areas, extremely sensible to PHE-induced disturbances. The development of animal models of different degrees of HPA is a useful tool for identifying the metabolic mechanisms underlying cognitive deficits induced by PHE. In this paper we analyzed the behavioral and biochemical phenotypes of different forms of HPA (control, mild-HPA, mild-PKU and classic-PKU), developed on the base of plasma PHE concentrations. Our results demonstrated that mice with different forms of HPA present different phenotypes, characterized by increasing severity of behavioral symptoms and brain aminergic deficits moving from mild HPA to classical PKU forms. In addition, our data identify preFrontal cortex and amygdala as the most affected brain areas and confirm the highest susceptibility of brain serotonin metabolism to mildly elevated blood PHE.
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Affiliation(s)
- Tiziana Pascucci
- Dipartimento di Psicologia and Centro “Daniel Bovet”, Sapienza - Università di Roma, Roma, Italy
- Fondazione Santa Lucia, IRCCS, Roma, Italy
- * E-mail:
| | - Giacomo Giacovazzo
- Dipartimento di Psicologia and Centro “Daniel Bovet”, Sapienza - Università di Roma, Roma, Italy
- Fondazione Santa Lucia, IRCCS, Roma, Italy
| | - Diego Andolina
- Fondazione Santa Lucia, IRCCS, Roma, Italy
- Dipartimento di Scienze Cliniche Applicate e Biotecnologiche, University of L'Aquila, L'Aquila, Italy
| | - Alessandra Accoto
- Dipartimento di Psicologia and Centro “Daniel Bovet”, Sapienza - Università di Roma, Roma, Italy
- Fondazione Santa Lucia, IRCCS, Roma, Italy
| | - Elena Fiori
- Dipartimento di Psicologia and Centro “Daniel Bovet”, Sapienza - Università di Roma, Roma, Italy
- Fondazione Santa Lucia, IRCCS, Roma, Italy
| | - Rossella Ventura
- Dipartimento di Psicologia and Centro “Daniel Bovet”, Sapienza - Università di Roma, Roma, Italy
- Fondazione Santa Lucia, IRCCS, Roma, Italy
| | - Cristina Orsini
- Dipartimento di Psicologia and Centro “Daniel Bovet”, Sapienza - Università di Roma, Roma, Italy
- Fondazione Santa Lucia, IRCCS, Roma, Italy
| | - David Conversi
- Dipartimento di Psicologia and Centro “Daniel Bovet”, Sapienza - Università di Roma, Roma, Italy
- Fondazione Santa Lucia, IRCCS, Roma, Italy
| | - Claudia Carducci
- Dipartimento di Medicina sperimentale e Patologia, Sapienza - Università di Roma, Roma, Italy
| | - Vincenzo Leuzzi
- Dipartimento di Scienze Neurologiche, Psichiatriche e Riabilitative dell'Età Evolutiva, Università di Roma, Roma, Italy
| | - Stefano Puglisi-Allegra
- Dipartimento di Psicologia and Centro “Daniel Bovet”, Sapienza - Università di Roma, Roma, Italy
- Fondazione Santa Lucia, IRCCS, Roma, Italy
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Douglas TD, Jinnah HA, Bernhard D, Singh RH. The effects of sapropterin on urinary monoamine metabolites in phenylketonuria. Mol Genet Metab 2013; 109:243-50. [PMID: 23712020 DOI: 10.1016/j.ymgme.2013.04.017] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Revised: 04/24/2013] [Accepted: 04/24/2013] [Indexed: 11/28/2022]
Abstract
BACKGROUND Sapropterin dihydrochloride (BH4, tetrahydrobiopterin) can lower plasma phenylalanine (Phe) concentrations for a subset of patients with phenylketonuria (PKU), an inborn error of metabolism. Studies suggest that monoamine neurotransmitter concentrations are low in PKU patients. Sapropterin functions as a cofactor for hydroxylases specific to Phe, tyrosine, and tryptophan metabolism, pathways essential for catecholamine and serotonin synthesis. OBJECTIVE The objective of this study is to determine the impact of sapropterin on monoamine neurotransmitter status in patients with PKU. DESIGN 58 PKU subjects were provided 20 mg/kg of sapropterin for 1 month. Those who responded with at least a 15% decrease in plasma Phe received sapropterin for 1 year, while Non-responders discontinued it. After an additional 3 months, Responders who demonstrated increased Phe tolerance and decreased medical food dependence were classified as Definitive, whereas Responders unable to liberalize their diet without compromising plasma Phe control were identified as Provisional. At study visits, patients provided blood for plasma amino acids, 3-day diet records, and 12-hour urine samples analyzed for epinephrine (E), dopamine (DA), dihydroxyphenylacetate (DOPAC), homovanillic acid (HVA), 3-methoxytyramine (3MT), serotonin (5HT), and 5-hydroxyindole acetic acid (5HIAA) using HPLC with electrochemical detection. RESULTS Compared with healthy non-PKU controls, subjects with PKU had significantly lower baseline concentrations of DA, HVA, 3MT, 5HT, and 5HIAA (p < 0.001 for all). Medical food protein intake had a direct association with DA, HVA, 5HT, and 5HIAA during the study (p < 0.05 for all), while plasma Phe had an inverse association with these markers (p < 0.01 for all). DOPAC was also associated with plasma Phe throughout the year (p = 0.035), although not at baseline. Patients with PKU had a significant increase in HVA (p = 0.015) after 1 month of sapropterin. When stratifying by Responder and Non-Responder status, significance of HVA increase in Non-responders (p = 0.041) was confirmed, but not in Responders (p = 0.081). A declining trend in urinary 5HIAA, significant only after controlling for plasma Phe (p = 0.019), occurred for Definitive Responders during the 1-year study. CONCLUSION Urinary monoamine concentrations are low in patients with PKU and are influenced by oral sapropterin and medical food intake, highlighting the importance of these therapies to neurotransmitter metabolism in phenylketonuria.
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Affiliation(s)
- Teresa D Douglas
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA, USA.
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Pascucci T, Giacovazzo G, Andolina D, Conversi D, Cruciani F, Cabib S, Puglisi-Allegra S. In vivo catecholaminergic metabolism in the medial prefrontal cortex of ENU2 mice: an investigation of the cortical dopamine deficit in phenylketonuria. J Inherit Metab Dis 2012; 35:1001-9. [PMID: 22447154 PMCID: PMC3470696 DOI: 10.1007/s10545-012-9473-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/17/2011] [Revised: 02/27/2012] [Accepted: 02/29/2012] [Indexed: 11/19/2022]
Abstract
OBJECTIVE Phenylketonuria (PKU) is an inherited metabolic disease characterized by plasma hyperphenylalaninemia and several neurological symptoms that can be controlled by rigorous dietetic treatment. The cellular mechanisms underlying impaired brain functions are still unclear. It has been proposed, however, that phenylalanine interference in cognitive functions depends on impaired dopamine (DA) transmission in the prefrontal cortical area due to reduced availability of the precursor tyrosine. Here, using Pah(enu2) (ENU2) mice, the genetic murine model of PKU, we investigated all metabolic steps of catecholamine neurotransmission within the medial preFrontal Cortex (mpFC), availability of the precursor tyrosine, synthesis and release, to find an easy way to reinstate normal cortical DA neurotransmission. METHODS AND RESULTS Analysis of blood and brain levels of tyrosine showed reduced plasma and cerebral levels of tyrosine in ENU2 mice. Western blot analysis demonstrated deficient tyrosine hydroxylase (TH) protein levels in mpFC of ENU2 mice. Cortical TH activity, determined in vivo by measuring the accumulation of l-3,4-dihydroxyphenylalanine (L-DOPA) in mpFC after inhibition of L-aromatic acid decarboxylase with NSD-1015, was reduced in ENU2 mice. Finally, a very low dose of L-DOPA, which bypasses the phenylalanine-inhibited metabolic steps, restored DA prefrontal transmission to levels found in healthy mice. CONCLUSION The data suggests that a strategy of using tyrosine supplementation to treat PKU is unlikely to be effective, whereas small dose L-DOPA administration is likely to have a positive therapeutic effect.
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Affiliation(s)
- Tiziana Pascucci
- Department of Psychology and Centre Daniel Bovet, Sapienza University, via dei Marsi 78, 00185, Rome, Italy.
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Browne CA, Clarke G, Dinan TG, Cryan JF. An effective dietary method for chronic tryptophan depletion in two mouse strains illuminates a role for 5-HT in nesting behaviour. Neuropharmacology 2012; 62:1903-15. [DOI: 10.1016/j.neuropharm.2011.12.009] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2011] [Revised: 12/01/2011] [Accepted: 12/08/2011] [Indexed: 12/31/2022]
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Abstract
Phenylketonuria (PKU) is a common genetic disorder arising from a deficiency of phenylalanine hydroxylase. If left untreated, the accumulation of phenylalanine leads to brain damage and neuropsychological dysfunction. One of the abnormalities found in hyperphenylalaninemic patients and a mouse model of PKU is an aminergic deficit in the brain. We previously showed correction of hyperphenylalaninemia and concomitant behavioral recovery in PKU mice after liver-targeted gene transfer with a viral vector. Here, we addressed whether such a functional recovery was substantiated by an improved amine metabolism in the brain. After gene transfer, brain dopamine, norepinephrine, and serotonin levels in the PKU mice were significantly elevated to normal or near-normal levels, along with systemic improvement of phenylalanine catabolism. The results of biochemical analyses validated the efficacy of PKU gene therapy in the central nervous system.
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5-Hydroxytryptophan during critical postnatal period improves cognitive performances and promotes dendritic spine maturation in genetic mouse model of phenylketonuria. Int J Neuropsychopharmacol 2011; 14:479-89. [PMID: 21040618 PMCID: PMC3110346 DOI: 10.1017/s1461145710001288] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
Although phenylketonuria (PKU) is the most common genetic cause of mental retardation, the cellular mechanisms underlying impaired brain function are still unclear. Using PAHenu2 mice (ENU2), the genetic mouse model of PKU, we previously demonstrated that high phenylalanine levels interfere with brain tryptophan hydroxylase activity by reducing the availability of serotonin (5-hydroxytryptamine, 5-HT), crucial for maturation of neuronal connectivity in the prefrontal cortex (PFC), around the third postnatal week, a critical period for cortical maturation. 5-Hydroxytryptophan (5-HTP), the product of tryptophan hydroxylation, is known to be a better treatment to increase brain 5-HT levels. In this study we investigated the role of 5-HT during the early postnatal period in cognitive disturbances and in cortical dendritic alterations of PKU subjects by restoring temporarily (postnatal days 14-21) physiological brain levels of 5-HT in ENU2 through 5-HTP treatment. In adult ENU2 mice early 5-HTP treatment reverses cognitive deficits in spatial and object recognition tests accompanied by an increase in spine maturation of pyramidal neurons in layer V of the prelimbic/infralimbic area of the PFC, although locomotor deficits are not recovered by treatment. Taken together, our results support the hypothesis that mental retardation in PKU depends on reduced availability of brain 5-HT during critical developmental periods that interferes with cortical maturation and point to 5-HTP supplementation as a highly promising additional tool to heal PKU patients.
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van Spronsen FJ, de Groot MJ, Hoeksma M, Reijngoud DJ, van Rijn M. Large neutral amino acids in the treatment of PKU: from theory to practice. J Inherit Metab Dis 2010; 33:671-6. [PMID: 20976625 PMCID: PMC2992655 DOI: 10.1007/s10545-010-9216-1] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/11/2009] [Revised: 07/18/2010] [Accepted: 09/19/2010] [Indexed: 11/30/2022]
Abstract
Notwithstanding the success of the traditional dietary phenylalanine restriction treatment in phenylketonuria (PKU), the use of large neutral amino acid (LNAA) supplementation rather than phenylalanine restriction has been suggested. This treatment modality deserves attention as it might improve cognitive outcome and quality of life in patients with PKU. Following various theories about the pathogenesis of cognitive dysfunction in PKU, LNAA supplementation may have multiple treatment targets: a specific reduction in brain phenylalanine concentrations, a reduction in blood (and consequently brain) phenylalanine concentrations, an increase in brain neurotransmitter concentrations, and an increase in brain essential amino acid concentrations. These treatment targets imply different treatment regimes. This review summarizes the treatment targets and the treatment regimens of LNAA supplementation and discusses the differences in LNAA intake between the classical dietary phenylalanine-restricted diet and several LNAA treatment forms.
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Affiliation(s)
- Francjan J van Spronsen
- Department of Pediatrics, Division of Metabolic Diseases, Beatrix Children's Hospital, University Medical Center Groningen, University of Groningen, PO Box 30.001, 9700 RB, Groningen, The Netherlands.
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Schoemans R, Aigrot MS, Wu C, Marée R, Hong P, Belachew S, Josse C, Lubetzki C, Bours V. Oligodendrocyte development and myelinogenesis are not impaired by high concentrations of phenylalanine or its metabolites. J Inherit Metab Dis 2010; 33:113-20. [PMID: 20151197 PMCID: PMC3071566 DOI: 10.1007/s10545-010-9052-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/25/2009] [Revised: 01/11/2010] [Accepted: 01/13/2010] [Indexed: 10/19/2022]
Abstract
Phenylketonuria (PKU) is a metabolic genetic disease characterized by deficient phenylalanine hydroxylase (PAH) enzymatic activity. Brain hypomyelination has been reported in untreated patients, but its mechanism remains unclear. We therefore investigated the influence of phenylalanine (Phe), phenylpyruvate (PP), and phenylacetate (PA) on oligodendrocytes. We first showed in a mouse model of PKU that the number of oligodendrocytes is not different in corpus callosum sections from adult mutants or from control brains. Then, using enriched oligodendroglial cultures, we detected no cytotoxic effect of high concentrations of Phe, PP, or PA. Finally, we analyzed the impact of Phe, PP, and PA on the myelination process in myelinating cocultures using both an in vitro index of myelination, based on activation of the myelin basic protein (MBP) promoter, and the direct quantification of myelin sheaths by both optical measurement and a bioinformatics method. None of these parameters was affected by the increased levels of Phe or its derivatives. Taken together, our data demonstrate that high levels of Phe, such as in PKU, are unlikely to directly induce brain hypomyelination, suggesting involvement of alternative mechanisms in this myelination defect.
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Affiliation(s)
- Renaud Schoemans
- Human Genetics, GIGA-Research, University of Liège, Liège, Belgium
| | | | - Chaohong Wu
- Michtom School of Computer Science, Volen Center for Complex Systems, Room 261, Brandeis University, Waltham, MA 02454, USA
| | - Raphaël Marée
- Bioinformatics platform, GIGA-Research, University of Liège, Liège, Belgium
| | - Pengyu Hong
- Michtom School of Computer Science, Volen Center for Complex Systems, Room 261, Brandeis University, Waltham, MA 02454, USA
| | | | - Claire Josse
- Human Genetics, GIGA-Research, University of Liège, Liège, Belgium
| | | | - Vincent Bours
- Human Genetics, GIGA-Research, University of Liège, Liège, Belgium
- Genetics Center, CHU Liège, Liège, Belgium
- Department of Genetics, CHU Liège, Université de Liège B34, Avenue de l’hôpital 1, 4000 Liège, Belgique, Belgium
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37
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Li D, Gu X, Lu L, Liang L. Effects of phenylalanine on the survival and neurite outgrowth of rat cortical neurons in primary cultures: possible involvement of brain-derived neurotrophic factor. Mol Cell Biochem 2010; 339:1-7. [PMID: 20101519 DOI: 10.1007/s11010-009-0364-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2009] [Accepted: 12/16/2009] [Indexed: 12/15/2022]
Abstract
Phenylketonuria (PKU) is characterized by elevated levels of phenylalanine (Phe) in plasma and cerebrospinal fluid of PKU patients, leading to mental retardation. The developmental delay in the cerebral cortex is one of the characteristic pathologic changes in untreated phenylketonuria patients. This is thought to be due to the toxic effects of Phe and/or its metabolites; however, the underlying mechanisms are as yet unknown. In this study, using a model system in which cultured cortical neurons were induced with Phe, we observed that Phe inhibited the longest neurite outgrowth and induced the neuronal death. We further demonstrated that the expression of BDNF mRNA and protein was significantly decreased by Phe, together with a decrease in extracellular signal-regulated kinase (ERK) and Akt phosphorylation activity. There was no change in expression of TrkB mRNA and protein. Considering the important role of BDNF in normal brain development and function, these L: -Phe-induced changes in BDNF in PKU brain may be a critical element of the neurological symptoms of PKU.
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Affiliation(s)
- Duan Li
- Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Institute for Pediatric Research, 1665 Kong Jiang Rd, Shanghai 200092, China.
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38
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5-Hydroxytryptophan rescues serotonin response to stress in prefrontal cortex of hyperphenylalaninaemic mice. Int J Neuropsychopharmacol 2009; 12:1067-79. [PMID: 19664307 DOI: 10.1017/s1461145709990381] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Adult early treated hyperphenylalaninaemic patients can show specific deficits of prefrontal cortical functions. The development of additional therapeutic strategies for these patients requires the understanding of the mechanisms involved in phenylalanine-dependent impairment of fronto-cortical functions. We tested the hypothesis of phenylalanine interference with aminergic neurotransmission in the prefrontal cortex by evaluating, in vivo, amine release in adult Pah(enu2) mice, the genetic model of phenylketonuria. Mice of healthy background responded to a psychogenic stressor with the classic time-dependent increase of norepinephrine, dopamine and serotonin release from prefrontal cortical terminals. Neither the dopaminergic nor the serotoninergic responses were observable in the Pah(enu2) mice. Temporary reduction of circulating phenylalanine, by phenylalanine-free diet without amino- acid supplement, promoted recovery of the serotonin response only, demonstrating direct interference with serotonin synthesis in the mature brain. Evaluation of different steps of serotonin synthesis in the prefrontal cortex of hyperphenylalaninaemic mice demonstrated inhibition of cortical tryptophan hydroxylase activity. Finally, systemic administration of 5-hydroxytryptophan, the product of tryptophan hydroxylase activity, allowed frontal cortical serotonin response to stress in hyperphenylalaninaemic mice. Collectively, these results demonstrate that hyperphenylalaninaemia interferes with the ability of the mature prefrontal cortex to respond to psychological challenges, point to serotonin synthesis as the target of phenylalanine interference, and support the use of 5-hydroxytryptophan in lifelong treatment of hyperphenylalaninaemic subjects.
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39
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Fligny C, Hatia S, Amireault P, Mallet J, Côté F. Mammalian prenatal development: the influence of maternally derived molecules. Bioessays 2009; 31:935-43. [DOI: 10.1002/bies.200800217] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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40
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van Spronsen FJ, Hoeksma M, Reijngoud DJ. Brain dysfunction in phenylketonuria: is phenylalanine toxicity the only possible cause? J Inherit Metab Dis 2009; 32:46-51. [PMID: 19191004 DOI: 10.1007/s10545-008-0946-2] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/07/2008] [Revised: 10/16/2008] [Accepted: 11/20/2008] [Indexed: 11/25/2022]
Abstract
In phenylketonuria, mental retardation is prevented by a diet that severely restricts natural protein and is supplemented with a phenylalanine-free amino acid mixture. The result is an almost normal outcome, although some neuropsychological disturbances remain. The pathology underlying cognitive dysfunction in phenylketonuria is unknown, although it is clear that the high plasma concentrations of phenylalanine influence the blood-brain barrier transport of large neutral amino acids. The high plasma phenylalanine concentrations increase phenylalanine entry into brain and restrict the entry of other large neutral amino acids. In the literature, emphasis has been on high brain phenylalanine as the pathological substrate that causes mental retardation. Phenylalanine was found to interfere with different cerebral enzyme systems. However, apart from the neurotoxicity of phenylalanine, a deficiency of the other large neutral amino acids in brain may also be an important factor affecting cognitive function in phenylketonuria. Cerebral protein synthesis was found to be disturbed in a mouse model of phenylketonuria and could be caused by shortage of large neutral amino acids instead of high levels of phenylalanine. Therefore, in this review we emphasize the possibility of a different idea about the pathogenesis of mental dysfunction in phenylketonuria patients and the aim of treatment strategies. The aim of treatment in phenylketonuria might be to normalize cerebral concentrations of all large neutral amino acids rather than prevent high cerebral phenylalanine concentrations alone. In-depth studies are necessary to investigate the role of large neutral amino acid deficiencies in brain.
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Affiliation(s)
- F J van Spronsen
- Beatrix Children's Hospital, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
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41
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Pascucci T, Andolina D, Ventura R, Puglisi-Allegra S, Cabib S. Reduced availability of brain amines during critical phases of postnatal development in a genetic mouse model of cognitive delay. Brain Res 2008; 1217:232-8. [PMID: 18502400 DOI: 10.1016/j.brainres.2008.04.006] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2007] [Revised: 04/02/2008] [Accepted: 04/04/2008] [Indexed: 10/22/2022]
Abstract
Serotonin (5-HT), dopamine (DA) and noradrenaline (NE) play important roles in brain postnatal maturation. Therefore, deficits in brain availability of biogenic amines during critical developmental phases might underlie neurodevelopmental disturbances associated with cognitive impairment. To test this hypothesis we evaluated brain availability of 5-HT, DA and NE, of their immediate precursors 5-hydroxytryptophan and 3,4-dihydroxy-l-phenylalanine, and of large neutral amino acids phenylalanine, tyrosine and tryptophan, in developing PahEnu2 mice, the genetic model of Phenylketonuria (PKU) a cause of severe cognitive delay. We found deficits of brain amine levels in PKU pups between day 14 and 35 of postnatal life, when pups of the healthy background showed developmental peak increases of amines and precursors. 5-HT deficits were most pronounced, were unrelated with brain availability of the amino acid precursor tryptophan, but overlapped with peak brain phenylalanine concentrations and reduced availability of 5-HT direct precursor 5-hydroxytryptophan. These results identify a critical window of brain amine availability susceptible to disturbances in a genetic mouse model of pathological neurodevelopment and suggest a mechanism of interference with brain aminergic synthesis in PKU and non-PKU hyperphenylalaninemia.
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Affiliation(s)
- Tiziana Pascucci
- Dipartimento di Psicologia and Centro Daniel Bovet, Sapienza University, Rome, Italy.
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42
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Zhang Y, Zhang H, Yuan X, Gu X. Differential effects of phenylalanine on Rac1, Cdc42, and RhoA expression and activity in cultured cortical neurons. Pediatr Res 2007; 62:8-13. [PMID: 17515837 DOI: 10.1203/pdr.0b013e31806772be] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Phenylketonuria (PKU) is characterized by a high concentration of phenylalanine, which can lead to mental retardation. One of the characteristic pathologic changes in untreated phenylketonuria patients is a reduction in the number of axons, dendrites, and synapses in the brain. This is thought to be due to the toxic effects of phenylalanine and/or its metabolites, however, the underlying mechanism remains unclear. In this study, we observed that phenylalanine reduced the number of dendrites and dendritic spines in cultured neurons. We further demonstrated that phenylalanine down-regulated Rac1, Cdc42, and RhoA mRNA and protein expression. Pull-down assays indicated that phenylalanine caused a decrease in Rac1/Cdc42 activity but increased RhoA activity. Expression of a dominant negative RhoA or treatment with a Rho-associated kinase specific inhibitor, Y-27632, partly inhibited the phenylalanine-induced decrease in dendrite numbers. In conclusion, we have demonstrated that phenylalanine affects the expression and activity of Rac1, Cdc42, and RhoA. Furthermore, RhoA signaling is involved in the inhibitory effect of phenylalanine on dendritic branching. These results may provide an important insight into the molecular mechanism underlying phenylalanine-induced abnormalities of dendrites, specifically in phenylketonuria neuronal injury.
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Affiliation(s)
- Yongjun Zhang
- XinHua Hospital, Shanghai Institute for Pediatric Research, Shanghai Jiaotong University School of Medicine, Shanghai, 200092, China
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43
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Martynyuk AE, Ucar DA, Yang DD, Norman WM, Carney PR, Dennis DM, Laipis PJ. Epilepsy in Phenylketonuria: A Complex Dependence on Serum Phenylalanine Levels. Epilepsia 2007; 48:1143-50. [PMID: 17484755 DOI: 10.1111/j.1528-1167.2007.01115.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
PURPOSE Phenylketonuria (PKU) is a disorder of phenylalanine (Phe) metabolism that frequently results in epilepsy if a low Phe diet was not implemented at birth. The mechanisms by which Phe affects the brain are poorly understood. METHODS Audiogenic seizures (AGS) were studied in female homozygous Pah(enu2) BTBR (PKU) mice. RESULTS Adult PKU mice, 18-20 weeks of age, in contrast to wild-type and heterozygous counterparts, exhibited a full range of AGS. Younger PKU mice, 5-7 weeks of age, had higher serum Phe levels (2.22 +/- 0.20 mM) in comparison with the adult animals (1.72 +/- 0.05 mM) and were not susceptible to AGS. Among adult mice, animals susceptible to AGS had significantly lower serum Phe levels (1.62 +/- 0.06 mM) in comparison with those resistant to AGS (1.86 +/- 0.07 mM). Susceptibility to AGS tended to increase in the afternoon when serum Phe concentration decreased in comparison to evening and morning. Normalization of serum Phe level by instituting a low Phe diet generally prevented susceptibility to AGS within 12 h. Although return to a standard diet raised Phe levels to hyperphenylalaninemic within 12 h in animals treated with a low Phe diet for 2 weeks, more than 7 weeks were needed for a complete resumption of AGS. CONCLUSIONS Transient decrease in Phe levels within hyperphenylalaninemic range may be a necessary condition for PKU-related seizures to occur. A low Phe diet prevents susceptibility to seizures, which can resume with the significant delay after termination of dietary treatment.
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Affiliation(s)
- Anatoly E Martynyuk
- Department of Anesthesiology, University of Florida, Gainesville, FL 32610-0254, USA.
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44
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Abstract
To have more insight into the mechanism of neuronal injury in phenylketonuria (PKU) patients, gene expression profiles were studied in cell culture of embryonic rat cortical neurons induced by phenylalanine. Randomly chose cortical cultured for 3 days were treated by 0.9-mM phenylalanine for 12 h. Control group of the same batch was treated with the same volume of medium. Total RNA was extracted and hybridized with the Affymetrix gene chip U34 according to the protocol provided by the Affymetrix Company. Real-time PCR was used to further confirm the result. We found that the hybridization signals of 167 genes were increased among the total 1323 probes plotted on the chip. The 167 increased genes could be functionally categorized into signal transduction, neuron related, cytoskeleton, metabolism, ion channels, transcription factors, cytokines, and apoptosis related. Signals of seven probes were decreased, which accounted to 0.5% of the total number. A series of genes that were not reported previously were upregulated by phenylalanine, including Ca2+/calmodulin-dependent protein kinase, Brain type II (CaMK II), ras, P38, L-voltage dependent calcium channel, some genes related to vesicle formation and transmitter release, some glutamate receptor subunits and glutamate transporters. According to the gene expression profiles, it is likely that multiprocesses are involved in the neuronal injury induced by phenylalanine, such as the activation on of the NMDR-Ca2+-CaMK II-Ras-P38 axis, the abnormality in neurotransmitter release. Our study also suggests that the excitatory neurotransmitter glutamate may play a role in the neural pathology of PKU.
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Affiliation(s)
- Huiwen Zhang
- Department of Endocrinology and Genetic Metabolism, Xin Hua Hospital, Shanghai Institute for Pediatric Research, Shanghai Second Medical University, Shanghai 200092, People's Republic of China
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45
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Ormazabal A, Vilaseca MA, Pérez-Dueñas B, Lambruschini N, Gómez L, Campistol J, Artuch R. Platelet serotonin concentrations in PKU patients under dietary control and tetrahydrobiopterin treatment. J Inherit Metab Dis 2005; 28:863-70. [PMID: 16435178 DOI: 10.1007/s10545-005-0153-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/02/2005] [Accepted: 09/20/2005] [Indexed: 11/30/2022]
Abstract
Tetrahydrobiopterin (BH4) supplementation has been applied in PKU treatment, resulting in successful control of blood phenylalanine (Phe) concentrations. We evaluated serotonin status in PKU patients under classical dietary treatment (n = 40) and in a group of 11 PKU patients under BH4 treatment, both during a 6-month period. Platelet serotonin values were significantly lower in PKU patients under dietary treatment when compared with controls. A negative correlation was observed between plasma Phe and platelet serotonin concentrations (r = -0.367, p = 0.017) in PKU patients. Platelet serotonin concentration increased significantly after both 1 and 6 months of BH4 therapy when compared with baseline conditions (Wilcoxon test: p = 0.013 and p = 0.021, respectively), while no differences were observed when comparing plasma Phe concentrations at the different points. Our results indicate that PKU patients under classical treatment have decreased platelet serotonin concentrations, probably owing to continued high Phe values, while BH4 supplementation restored platelet serotonin values.
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Affiliation(s)
- A Ormazabal
- Department of Clinical Chemistry, Hospital Sant Joan de Déu, Esplugues, Barcelona, Spain
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46
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Mochizuki S, Mizukami H, Ogura T, Kure S, Ichinohe A, Kojima K, Matsubara Y, Kobayahi E, Okada T, Hoshika A, Ozawa K, Kume A. Long-term correction of hyperphenylalaninemia by AAV-mediated gene transfer leads to behavioral recovery in phenylketonuria mice. Gene Ther 2004; 11:1081-6. [PMID: 15057263 DOI: 10.1038/sj.gt.3302262] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Classical phenylketonuria (PKU) is a metabolic disorder caused by a deficiency of the hepatic enzyme phenylalanine hydroxylase (PAH). If untreated, accumulation of phenylalanine will damage the developing brain of affected individuals, leading to severe mental retardation. Here, we show that a liver-directed PAH gene transfer brought about long-term correction of hyperphenylalaninemia and behavioral improvement in a mouse model of PKU. A recombinant adeno-associated virus (AAV) vector carrying the murine PAH cDNA was constructed and administered to PAH-deficient mice (strain PAH(enu2)) via the portal vein. Within 2 weeks of treatment, the hyperphenylalaninemic phenotype improved and completely normalized in the animals treated with higher vector doses. The therapeutic effect persisted for 40 weeks in male mice, while serum phenylalanine concentrations in female animals gradually returned to pretreatment levels. Notably, this long-term correction of hyperphenylalaninemia was associated with a reversal of hypoactivity observed in PAH(enu2) mice. While locomotory activity over 24 h and exploratory behavior were significantly decreased in untreated PAH(enu2) mice compared with the age-matched controls, these indices were completely normalized in 12-month-old male PKU mice with lowered serum phenylalanine. These results demonstrate that AAV-mediated liver transduction ameliorated the PKU phenotype, including central nervous system dysfunctions.
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Affiliation(s)
- S Mochizuki
- Division of Genetic Therapeutics, Center for Molecular Medicine, Jichi Medical School, Tochigi, Japan
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47
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Abstract
Phenylketonuria is caused by specific mutations in the phenylalanine hydroxylase gene and is characterized by elevated blood phenylalanine levels, hypomyelination in forebrain structures, reduced dopamine levels, and cognitive difficulties. To determine whether brain tyrosine levels and/or myelination play a role in the up-regulation of dopamine, phenylketonuric mice were placed on a low phenylalanine diet for 4 weeks and as blood phenylalanine levels dropped to normal, the relationships between phenylalanine, tyrosine, dopamine, myelin proteins, and axonal proteins in frontal cortex and striatum were determined using gas chromatography mass spectrometry, histology, and western blotting techniques. Blood phenylalanine rapidly decreased from an eight-fold elevation to near control levels, and blood tyrosine gradually rose from about 50% to near normal values. In frontal cortex and striatum, phenylalanine levels dropped to 2- and 1.5-fold elevations above control, respectively, and tyrosine levels increased but remained less than 70% of control in both structures. In frontal cortex, increases in dopamine and myelin basic protein occurred in a similar biphasic pattern, reaching near normal levels by week 4. In striatum, dopamine and MBP dramatically increased to near normal levels in the first week. Myelination was confirmed histologically and by western blot quantification of phosphorylated neurofilaments. In summary, our results showed: (i) an increase in dopamine despite low brain tyrosine levels and (ii) similar recovery patterns for myelination and dopamine. Since myelin/axonal interactions trigger signaling pathways that result in axonal maturation, we speculate that this interaction also may trigger signals that up-regulate neurotransmitter synthesis.
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Affiliation(s)
- Bernadin Joseph
- Department of Neurology, The University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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