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Luengo-Pérez LM, Fernández-Bueso M, Guzmán-Carmona C, López-Navia A, García-Lobato C. Morphofunctional Assessment beyond Malnutrition: Fat Mass Assessment in Adult Patients with Phenylketonuria-Systematic Review. Nutrients 2024; 16:1833. [PMID: 38931188 PMCID: PMC11206948 DOI: 10.3390/nu16121833] [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: 05/12/2024] [Revised: 06/04/2024] [Accepted: 06/07/2024] [Indexed: 06/28/2024] Open
Abstract
Morphofunctional assessment was developed to evaluate disease-related malnutrition. However, it can also be used to assess cardiometabolic risk, as excess adiposity increases this risk. Phenylketonuria (PKU) is the most prevalent inherited metabolic disease among adults, and obesity in PKU has recently gained interest, although fat mass correlates better with cardiometabolic risk than body mass index. In this systematic review, the objective was to assess whether adult patients with PKU have higher fat mass than healthy controls. Studies of adult PKU patients undergoing dietary treatment in a metabolic clinic reporting fat mass were included. The PubMed and EMBASE databases were searched. Relevance of articles, data collection, and risk of bias were evaluated by two independent reviewers. Ten articles were evaluated, six with a control group, including 310 subjects with PKU, 62 with mild hyperphenylalaninemia, and 157 controls. One study reported a significant and four a tendency towards an increased fat mass in all patients or only females with PKU. Limitations included not having a healthy control group, not reporting sex-specific results and using different techniques to assess fat mass. Evaluation of fat mass should be included in the morphofunctional assessment of cardiometabolic risk in adult patients with PKU.
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Affiliation(s)
- Luis M. Luengo-Pérez
- Medical Sciences Department, Faculty of Medicine and Health Sciences, University of Extremadura, 06006 Badajoz, Spain
- Clinical Nutrition and Dietetics Unit, Endocrinology and Nutrition Section, Badajoz University Hospital, 06008 Badajoz, Spain; (M.F.-B.); (C.G.-L.)
| | - Mercedes Fernández-Bueso
- Clinical Nutrition and Dietetics Unit, Endocrinology and Nutrition Section, Badajoz University Hospital, 06008 Badajoz, Spain; (M.F.-B.); (C.G.-L.)
| | - Carlos Guzmán-Carmona
- Endocrinology and Nutrition, Don Benito-Villanueva de la Serena Hospital Complex, 06400 Don Benito, Spain; (C.G.-C.); (A.L.-N.)
| | - Ana López-Navia
- Endocrinology and Nutrition, Don Benito-Villanueva de la Serena Hospital Complex, 06400 Don Benito, Spain; (C.G.-C.); (A.L.-N.)
| | - Claudia García-Lobato
- Clinical Nutrition and Dietetics Unit, Endocrinology and Nutrition Section, Badajoz University Hospital, 06008 Badajoz, Spain; (M.F.-B.); (C.G.-L.)
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Trefz F, Frauendienst-Egger G, Dienel G, Cannet C, Schmidt-Mader B, Haas D, Blau N, Himmelreich N, Spraul M, Freisinger P, Dobrowolski S, Berg D, Pilotto A. Does hyperphenylalaninemia induce brain glucose hypometabolism? Cerebral spinal fluid findings in treated adult phenylketonuric patients. Mol Genet Metab 2024; 142:108464. [PMID: 38537426 DOI: 10.1016/j.ymgme.2024.108464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2024] [Revised: 03/21/2024] [Accepted: 03/22/2024] [Indexed: 05/08/2024]
Abstract
Despite numerous studies in human patients and animal models for phenylketonuria (PKU; OMIM#261600), the pathophysiology of PKU and the underlying causes of brain dysfunction and cognitive problems in PKU patients are not well understood. In this study, lumbar cerebral spinal fluid (CSF) was obtained immediately after blood sampling from early-treated adult PKU patients who had fasted overnight. Metabolite and amino acid concentrations in the CSF of PKU patients were compared with those of non-PKU controls. The CSF concentrations and CSF/plasma ratios for glucose and lactate were found to be below normal, similar to what has been reported for glucose transporter1 (GLUT1) deficiency patients who exhibit many of the same clinical symptoms as untreated PKU patients. CSF glucose and lactate levels were negatively correlated with CSF phenylalanine (Phe), while CSF glutamine and glutamate levels were positively correlated with CSF Phe levels. Plasma glucose levels were negatively correlated with plasma Phe concentrations in PKU subjects, which partly explains the reduced CSF glucose concentrations. Although brain glucose concentrations are unlikely to be low enough to impair brain glucose utilization, it is possible that the metabolism of Phe in the brain to produce phenyllactate, which can be transported across the blood-brain barrier to the blood, may consume glucose and/or lactate to generate the carbon backbone for glutamate. This glutamate is then converted to glutamine and carries the Phe-derived ammonia from the brain to the blood. While this mechanism remains to be tested, it may explain the correlations of CSF glutamine, glucose, and lactate concentrations with CSF Phe.
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Affiliation(s)
- Friedrich Trefz
- Heidelberg University, Medical Faculty of Heidelberg, Center for Child and Adolescent Medicine, Division of Child Neurology and Metabolic Medicine, Heidelberg, Germany.
| | | | - Gerald Dienel
- Department of Neurology, University of Arkansas for Medical Sciences, Little Rock, AR, United States; Department of Cell Biology and Physiology, University of New Mexico, Albuquerque, NM, United States
| | | | - Brigitte Schmidt-Mader
- Heidelberg University, Medical Faculty of Heidelberg, Center for Child and Adolescent Medicine, Division of Child Neurology and Metabolic Medicine, Heidelberg, Germany
| | - Dorothea Haas
- Heidelberg University, Medical Faculty of Heidelberg, Center for Child and Adolescent Medicine, Division of Child Neurology and Metabolic Medicine, Heidelberg, Germany
| | - Nenad Blau
- University Children's Hospital Zürich, Zürich, Switzerland
| | | | | | - Peter Freisinger
- Klinikum Reutlingen, Department of Pediatrics, Reutlingen, Germany
| | - Steven Dobrowolski
- Department of Pathology, University of Pittsburgh, School of Medicine, Pittsburgh, PA 15224, United States
| | - Daniela Berg
- Department of Neurology, University Hospital of Schleswig-Holstein, Kiel, Germany
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Cannet C, Bayat A, Frauendienst-Egger G, Freisinger P, Spraul M, Himmelreich N, Kockaya M, Ahring K, Godejohann M, MacDonald A, Trefz F. Phenylketonuria (PKU) Urinary Metabolomic Phenotype Is Defined by Genotype and Metabolite Imbalance: Results in 51 Early Treated Patients Using Ex Vivo 1H-NMR Analysis. Molecules 2023; 28:4916. [PMID: 37446577 DOI: 10.3390/molecules28134916] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2023] [Revised: 06/13/2023] [Accepted: 06/14/2023] [Indexed: 07/15/2023] Open
Abstract
Phenylketonuria (PKU) is a rare metabolic disorder caused by mutations in the phenylalanine hydroxylase gene. Depending on the severity of the genetic mutation, medical treatment, and patient dietary management, elevated phenylalanine (Phe) may occur in blood and brain tissues. Research has recently shown that high Phe not only impacts the central nervous system, but also other organ systems (e.g., heart and microbiome). This study used ex vivo proton nuclear magnetic resonance (1H-NMR) analysis of urine samples from PKU patients (mean 14.9 ± 9.2 years, n = 51) to identify the impact of elevated blood Phe and PKU treatment on metabolic profiles. Our results found that 24 out of 98 urinary metabolites showed a significant difference (p < 0.05) for PKU patients compared to age-matched healthy controls (n = 51) based on an analysis of urinary metabolome. These altered urinary metabolites were related to Phe metabolism, dysbiosis, creatine synthesis or intake, the tricarboxylic acid (TCA) cycle, end products of nicotinamide-adenine dinucleotide degradation, and metabolites associated with a low Phe diet. There was an excellent correlation between the metabolome and genotype of PKU patients and healthy controls of 96.7% in a confusion matrix model. Metabolomic investigations may contribute to a better understanding of PKU pathophysiology.
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Affiliation(s)
| | - Allan Bayat
- Kennedy Centre, Center for PKU, 2600 Glostrup, Denmark
| | | | - Peter Freisinger
- Department of Pediatrics, School of Medicine, University of Tübingen, 72074 Tübingen, Germany
| | | | | | - Musa Kockaya
- Private Pediatric Practice, 68307 Mannheim, Germany
| | | | | | - Anita MacDonald
- Dietetic Department, Birmingham Children's Hospital, Birmingham B4 6NH, UK
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Gama MI, Pinto A, Daly A, Rocha JC, MacDonald A. The Impact of the Quality of Nutrition and Lifestyle in the Reproductive Years of Women with PKU on the Long-Term Health of Their Children. Nutrients 2022; 14:nu14051021. [PMID: 35267995 PMCID: PMC8912747 DOI: 10.3390/nu14051021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Revised: 02/24/2022] [Accepted: 02/24/2022] [Indexed: 11/29/2022] Open
Abstract
A woman’s nutritional status before and during pregnancy can affect the health of her progeny. Phenylketonuria (PKU), a rare disorder causing high blood and brain phenylalanine (Phe) concentrations, is associated with neurocognitive disability. Lifelong treatment is mainly dietetic with a Phe-restricted diet, supplemented with a low-Phe protein substitute. Treatment adherence commonly decreases in adolescence, with some adults ceasing dietary treatment. In maternal PKU, elevated blood Phe is harmful to the fetus so a strict Phe-restricted diet must be re-established preconception, and this is particularly difficult to achieve. A woman’s reproductive years introduces an opportunity to adopt healthier behaviours to prepare for successful pregnancies and positive health outcomes for both themselves and their children. Several factors can influence the health status of women with PKU. Political, socioeconomic, and individual food and lifestyle choices affect diet quality, metabolic control, and epigenetics, which then pre-condition the overall maternal health and long-term health of the child. Here, we reflect on a comprehensive approach to treatment and introduce practical recommendations to optimize the wellbeing of women with PKU and the resultant health of their children.
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Affiliation(s)
- Maria Inês Gama
- Nutrition & Metabolism, NOVA Medical School, Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Campo dos Mártires da Pátria 130, 1169-056 Lisboa, Portugal; (M.I.G.); (J.C.R.)
| | - Alex Pinto
- Birmingham Women’s and Children’s Hospital, Birmingham B4 6NH, UK; (A.P.); (A.D.)
| | - Anne Daly
- Birmingham Women’s and Children’s Hospital, Birmingham B4 6NH, UK; (A.P.); (A.D.)
| | - Júlio César Rocha
- Nutrition & Metabolism, NOVA Medical School, Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Campo dos Mártires da Pátria 130, 1169-056 Lisboa, Portugal; (M.I.G.); (J.C.R.)
- Reference Centre of Inherited Metabolic Diseases, Centro Hospitalar Universitário de Lisboa Central, 1169-045 Lisboa, Portugal
- CINTESIS—Center for Health Technology and Services Research, NOVA Medical School, Campo dos Mártires da Pátria 130, 1169-056 Lisboa, Portugal
| | - Anita MacDonald
- Birmingham Women’s and Children’s Hospital, Birmingham B4 6NH, UK; (A.P.); (A.D.)
- Correspondence:
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Lipids and phenylketonuria: Current evidences pointed the need for lipidomics studies. Arch Biochem Biophys 2020; 688:108431. [DOI: 10.1016/j.abb.2020.108431] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Revised: 05/06/2020] [Accepted: 05/20/2020] [Indexed: 02/06/2023]
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Cannet C, Pilotto A, Rocha JC, Schäfer H, Spraul M, Berg D, Nawroth P, Kasperk C, Gramer G, Haas D, Piel D, Kölker S, Hoffmann G, Freisinger P, Trefz F. Lower plasma cholesterol, LDL-cholesterol and LDL-lipoprotein subclasses in adult phenylketonuria (PKU) patients compared to healthy controls: results of NMR metabolomics investigation. Orphanet J Rare Dis 2020; 15:61. [PMID: 32106880 PMCID: PMC7047385 DOI: 10.1186/s13023-020-1329-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2019] [Accepted: 02/07/2020] [Indexed: 12/22/2022] Open
Abstract
Background Phenylketonuria (PKU; OMIM#261600) is a rare metabolic disorder caused by mutations in the phenylalanine hydroxylase (PAH) gene resulting in high phenylalanine (Phe) in blood and brain. If not treated early this results in intellectual disability, behavioral and psychiatric problems, microcephaly, motor deficits, eczematous rash, autism, seizures, and developmental problems. There is a controversial discussion of whether patients with PKU have an additional risk for atherosclerosis due to interference of Phe with cholesterol synthesis and LDL-cholesterol regulation. Since cholesterol also plays a role in membrane structure and myelination, better insight into the clinical significance of the impact of Phe on lipoprotein metabolism is desirable. In 22 treated PKU patients (mean age 38.7 years) and 14 healthy controls (mean age 35.2 years), we investigated plasma with NMR spectroscopy and quantified 105 lipoprotein parameters (including lipoprotein subclasses) and 24 low molecular weight parameters. Analysis was performed on a 600 MHz Bruker AVANCE IVDr spectrometer as previously described. Results Concurrent plasma Phe in PKU patients showed a wide range with a mean of 899 μmol/L (50–1318 μmol/L). Total cholesterol and LDL-cholesterol were significantly lower in PKU patients versus controls: 179.4 versus 200.9 mg/dL (p < 0.02) and 79.5 versus 104.1 mg/dL (p < 0.0038), respectively. PKU patients also had lower levels of 22 LDL subclasses with the greatest differences in LDL2 Apo-B, LDL2 Particle Number, LDL2-phospholipids, and LDL2-cholesterol (p < 0.0001). There was a slight negative correlation of total cholesterol and LDL-cholesterol with concurrent Phe level. VLDL5-free cholesterol, VLDL5-cholesterol, VLDL5-phospholipids, and VLDL4-free cholesterol showed a significant (p < 0.05) negative correlation with concurrent Phe level. There was no difference in HDL and their subclasses between PKU patients and controls. Tyrosine, glutamine, and creatinine were significantly lower in PKU patients compared to controls, while citric and glutamic acids were significantly higher. Conclusions Using NMR spectroscopy, a unique lipoprotein profile in PKU patients can be demonstrated which mimics a non-atherogenic profile as seen in patients treated by statins.
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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
| | - Júlio César Rocha
- Center for Health Technology and Services Research (CINTESIS), Porto, Portugal.,Nutrition & Metabolism, NOVA Medical School, Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Lisbon, Portugal
| | | | | | - Daniela Berg
- Department of Neurology, University-Hospital-Schleswig-Holstein, Christian-Albrechts-University, Kiel, Germany
| | - Peter Nawroth
- Department of Endocrinology and Metabolism, University Hospital, Heidelberg, Germany
| | - Christian Kasperk
- Department of Endocrinology and Metabolism, University Hospital, Heidelberg, Germany
| | - Gwendolyn Gramer
- Department of Pediatrics, Centre for Pediatric and Adolescent Medicine, Division of Neuropaediatrics and Metabolic Medicine, University Hospital, Heidelberg, Germany
| | - Dorothea Haas
- Department of Pediatrics, Centre for Pediatric and Adolescent Medicine, Division of Neuropaediatrics and Metabolic Medicine, University Hospital, Heidelberg, Germany
| | - David Piel
- Pediatrics, Reutlingen Hospital, Reutlingen, Germany
| | - Stefan Kölker
- Department of Pediatrics, Centre for Pediatric and Adolescent Medicine, Division of Neuropaediatrics and Metabolic Medicine, University Hospital, Heidelberg, Germany
| | - Georg Hoffmann
- Department of Pediatrics, Centre for Pediatric and Adolescent Medicine, Division of Neuropaediatrics and Metabolic Medicine, University Hospital, Heidelberg, Germany
| | | | - Friedrich Trefz
- Department of Pediatrics, Centre for Pediatric and Adolescent Medicine, Division of Neuropaediatrics and Metabolic Medicine, University Hospital, Heidelberg, Germany. .,Metabolic Consulting, Reutlingen, Germany.
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Demmelmair H, MacDonald A, Kotzaeridou U, Burgard P, Gonzalez-Lamuno D, Verduci E, Ersoy M, Gokcay G, Alyanak B, Reischl E, Müller-Felber W, Faber FL, Handel U, Paci S, Koletzko B. Determinants of Plasma Docosahexaenoic Acid Levels and Their Relationship to Neurological and Cognitive Functions in PKU Patients: A Double Blind Randomized Supplementation Study. Nutrients 2018; 10:nu10121944. [PMID: 30544518 PMCID: PMC6316534 DOI: 10.3390/nu10121944] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2018] [Revised: 11/07/2018] [Accepted: 11/30/2018] [Indexed: 01/03/2023] Open
Abstract
Children with phenylketonuria (PKU) follow a protein restricted diet with negligible amounts of docosahexaenoic acid (DHA). Low DHA intakes might explain subtle neurological deficits in PKU. We studied whether a DHA supply modified plasma DHA and neurological and intellectual functioning in PKU. In a double-blind multicentric trial, 109 PKU patients were randomized to DHA doses from 0 to 7 mg/kg&day for six months. Before and after supplementation, we determined plasma fatty acid concentrations, latencies of visually evoked potentials, fine and gross motor behavior, and IQ. Fatty acid desaturase genotypes were also determined. DHA supplementation increased plasma glycerophospholipid DHA proportional to dose by 0.4% DHA per 1 mg intake/kg bodyweight. Functional outcomes were not associated with DHA status before and after intervention and remained unchanged by supplementation. Genotypes were associated with plasma arachidonic acid levels and, if considered together with the levels of the precursor alpha-linolenic acid, also with DHA. Functional outcomes and supplementation effects were not significantly associated with genotype. DHA intakes up to 7 mg/kg did not improve neurological functions in PKU children. Nervous tissues may be less prone to low DHA levels after infancy, or higher doses might be required to impact neurological functions. In situations of minimal dietary DHA, endogenous synthesis of DHA from alpha-linolenic acid could relevantly contribute to DHA status.
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Affiliation(s)
- Hans Demmelmair
- Division Metabolic and Nutritional Medicine, LMU-Ludwig-Maximilians-Universität Munich, Dr. von Hauner Children's Hospital, 80337 Munich, Germany.
| | | | - Urania Kotzaeridou
- Division of Neuropediatrics and Metabolic Medicine, Heidelberg University Hospital, 69120 Heidelberg, Germany.
| | - Peter Burgard
- Division of Neuropediatrics and Metabolic Medicine, Heidelberg University Hospital, 69120 Heidelberg, Germany.
| | | | - Elvira Verduci
- Department of Pediatrics, San Paolo Hospital Milano, 20142 Milano, Italy.
| | - Melike Ersoy
- Department of Pediatric Nutrition and Metabolism, Istanbul Medical Faculty, Istanbul University, 34093 Istanbul, Turkey.
| | - Gulden Gokcay
- Department of Pediatric Nutrition and Metabolism, Istanbul Medical Faculty, Istanbul University, 34093 Istanbul, Turkey.
| | - Behiye Alyanak
- Department of Child Psychiatry, Istanbul Medical Faculty, Istanbul University, 34093 Istanbul, Turkey.
| | - Eva Reischl
- Research Unit of Molecular Epidemiology, Institute of Epidemiology, Helmholtz Zentrum München, 85764 Neuherberg, Germany.
| | - Wolfgang Müller-Felber
- Division Metabolic and Nutritional Medicine, LMU-Ludwig-Maximilians-Universität Munich, Dr. von Hauner Children's Hospital, 80337 Munich, Germany.
| | - Fabienne Lara Faber
- Division Metabolic and Nutritional Medicine, LMU-Ludwig-Maximilians-Universität Munich, Dr. von Hauner Children's Hospital, 80337 Munich, Germany.
| | - Uschi Handel
- Division Metabolic and Nutritional Medicine, LMU-Ludwig-Maximilians-Universität Munich, Dr. von Hauner Children's Hospital, 80337 Munich, Germany.
| | - Sabrina Paci
- Department of Pediatrics, San Paolo Hospital Milano, 20142 Milano, Italy.
| | - Berthold Koletzko
- Division Metabolic and Nutritional Medicine, LMU-Ludwig-Maximilians-Universität Munich, Dr. von Hauner Children's Hospital, 80337 Munich, Germany.
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Montoya Parra GA, Singh RH, Cetinyurek-Yavuz A, Kuhn M, MacDonald A. Status of nutrients important in brain function in phenylketonuria: a systematic review and meta-analysis. Orphanet J Rare Dis 2018; 13:101. [PMID: 29941009 PMCID: PMC6020171 DOI: 10.1186/s13023-018-0839-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Accepted: 06/05/2018] [Indexed: 01/08/2023] Open
Abstract
Background Despite early and ongoing dietary management with a phe-restricted diet, suboptimal neuropsychological function has been observed in PKU. The restrictive nature of the PKU diet may expose patients to sub-optimal nutritional intake and deficiencies which may impact normal brain function. A systematic review of the published literature was carried out, where possible with meta-analysis, to compare the status of nutrients (Nutrients: DHA, EPA phospholipids, selenium, vitamins B6, B12, E, C, A, D, folic acid, choline, uridine, calcium, magnesium, zinc, iron, iodine and cholesterol) known to be important for brain development and functioning between individuals with PKU and healthy controls. Results Of 1534 publications identified, 65 studies met the entry criteria. Significantly lower levels of DHA, EPA and cholesterol were found for PKU patients compared to healthy controls. No significant differences in zinc, vitamins B12, E and D, calcium, iron and magnesium were found between PKU patients and controls. Because of considerable heterogeneity, the meta-analyses findings for folate and selenium were not reported. Due to an insufficient number of publications (< 4) no meta-analysis was undertaken for vitamins A, C and B6, choline, uridine, iodine and phospholipids. Conclusions The current data show that PKU patients have lower availability of DHA, EPA and cholesterol. Compliance with the phe-restricted diet including the micronutrient fortified protein substitute (PS) is essential to ensure adequate micronutrient status. Given the complexity of the diet, patients’ micronutrient and fatty acid status should be continuously monitored, with a particular focus on patients who are non-compliant or poorly compliant with their PS. Given their key role in brain function, assessment of the status of nutrients where limited data was found (e.g. choline, iodine) should be undertaken. Standardised reporting of studies in PKU would strengthen the output of meta-analysis and so better inform best practice for this rare condition. Electronic supplementary material The online version of this article (10.1186/s13023-018-0839-x) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Gina A Montoya Parra
- Danone Nutricia Research, Nutricia Advanced Medical Nutrition, Utrecht, The Netherlands.
| | - Rani H Singh
- Metabolic Genetics and Nutrition Program, Emory University, Atlanta, GA, USA
| | | | - Mirjam Kuhn
- Danone Nutricia Research, Nutricia Advanced Medical Nutrition, Utrecht, The Netherlands
| | - Anita MacDonald
- Department of Metabolic Diseases, Birmingham Children's Hospital, Birmingham, UK
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