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Barile M, Giancaspero TA, Leone P, Galluccio M, Indiveri C. Riboflavin transport and metabolism in humans. J Inherit Metab Dis 2016; 39:545-57. [PMID: 27271694 DOI: 10.1007/s10545-016-9950-0] [Citation(s) in RCA: 85] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/30/2016] [Revised: 05/12/2016] [Accepted: 05/19/2016] [Indexed: 12/17/2022]
Abstract
Recent studies elucidated how riboflavin transporters and FAD forming enzymes work in humans and create a coordinated flavin network ensuring the maintenance of cellular flavoproteome. Alteration of this network may be causative of severe metabolic disorders such as multiple acyl-CoA dehydrogenase deficiency (MADD) or Brown-Vialetto-van Laere syndrome. A crucial step in the maintenance of FAD homeostasis is riboflavin uptake by plasma and mitochondrial membranes. Therefore, studies on recently identified human plasma membrane riboflavin transporters are presented, together with those in which still unidentified mitochondrial riboflavin transporter(s) have been described. A main goal of future research is to fill the gaps still existing as for some transcriptional, functional and structural details of human FAD synthases (FADS) encoded by FLAD1 gene, a novel "redox sensing" enzyme. In the frame of the hypothesis that FADS, acting as a "FAD chaperone", could play a crucial role in the biogenesis of mitochondrial flavo-proteome, several basic functional aspects of flavin cofactor delivery to cognate apo-flavoenzyme are also briefly dealt with. The establishment of model organisms performing altered FAD homeostasis will improve the molecular description of human pathologies. The molecular and functional studies of transporters and enzymes herereported, provide guidelines for improving therapies which may have beneficial effects on the altered metabolism.
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Affiliation(s)
- Maria Barile
- Dipartimento di Bioscienze, Biotecnologie e Biofarmaceutica, Università degli Studi di Bari "Aldo Moro", via Orabona 4, I-70126, Bari, Italy.
| | - Teresa Anna Giancaspero
- Dipartimento di Bioscienze, Biotecnologie e Biofarmaceutica, Università degli Studi di Bari "Aldo Moro", via Orabona 4, I-70126, Bari, Italy
| | - Piero Leone
- Dipartimento di Bioscienze, Biotecnologie e Biofarmaceutica, Università degli Studi di Bari "Aldo Moro", via Orabona 4, I-70126, Bari, Italy
| | - Michele Galluccio
- Dipartimento DiBEST (Biologia, Ecologia, Scienze della Terra), Unità di Biochimica e Biotecnologie Molecolari, Università della Calabria, via Bucci 4c, I-87036, Arcavacata di Rende, Italy
| | - Cesare Indiveri
- Dipartimento DiBEST (Biologia, Ecologia, Scienze della Terra), Unità di Biochimica e Biotecnologie Molecolari, Università della Calabria, via Bucci 4c, I-87036, Arcavacata di Rende, Italy
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Olsen RKJ, Koňaříková E, Giancaspero TA, Mosegaard S, Boczonadi V, Mataković L, Veauville-Merllié A, Terrile C, Schwarzmayr T, Haack TB, Auranen M, Leone P, Galluccio M, Imbard A, Gutierrez-Rios P, Palmfeldt J, Graf E, Vianey-Saban C, Oppenheim M, Schiff M, Pichard S, Rigal O, Pyle A, Chinnery PF, Konstantopoulou V, Möslinger D, Feichtinger RG, Talim B, Topaloglu H, Coskun T, Gucer S, Botta A, Pegoraro E, Malena A, Vergani L, Mazzà D, Zollino M, Ghezzi D, Acquaviva C, Tyni T, Boneh A, Meitinger T, Strom TM, Gregersen N, Mayr JA, Horvath R, Barile M, Prokisch H. Riboflavin-Responsive and -Non-responsive Mutations in FAD Synthase Cause Multiple Acyl-CoA Dehydrogenase and Combined Respiratory-Chain Deficiency. Am J Hum Genet 2016; 98:1130-1145. [PMID: 27259049 PMCID: PMC4908180 DOI: 10.1016/j.ajhg.2016.04.006] [Citation(s) in RCA: 92] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Accepted: 04/13/2016] [Indexed: 12/27/2022] Open
Abstract
Multiple acyl-CoA dehydrogenase deficiencies (MADDs) are a heterogeneous group of metabolic disorders with combined respiratory-chain deficiency and a neuromuscular phenotype. Despite recent advances in understanding the genetic basis of MADD, a number of cases remain unexplained. Here, we report clinically relevant variants in FLAD1, which encodes FAD synthase (FADS), as the cause of MADD and respiratory-chain dysfunction in nine individuals recruited from metabolic centers in six countries. In most individuals, we identified biallelic frameshift variants in the molybdopterin binding (MPTb) domain, located upstream of the FADS domain. Inasmuch as FADS is essential for cellular supply of FAD cofactors, the finding of biallelic frameshift variants was unexpected. Using RNA sequencing analysis combined with protein mass spectrometry, we discovered FLAD1 isoforms, which only encode the FADS domain. The existence of these isoforms might explain why affected individuals with biallelic FLAD1 frameshift variants still harbor substantial FADS activity. Another group of individuals with a milder phenotype responsive to riboflavin were shown to have single amino acid changes in the FADS domain. When produced in E. coli, these mutant FADS proteins resulted in impaired but detectable FADS activity; for one of the variant proteins, the addition of FAD significantly improved protein stability, arguing for a chaperone-like action similar to what has been reported in other riboflavin-responsive inborn errors of metabolism. In conclusion, our studies identify FLAD1 variants as a cause of potentially treatable inborn errors of metabolism manifesting with MADD and shed light on the mechanisms by which FADS ensures cellular FAD homeostasis.
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MESH Headings
- Adult
- Blotting, Western
- Case-Control Studies
- Cells, Cultured
- Electron Transport
- Female
- Fibroblasts/drug effects
- Fibroblasts/metabolism
- Fibroblasts/pathology
- Flavin-Adenine Dinucleotide/metabolism
- Frameshift Mutation/genetics
- Gene Expression Profiling
- Humans
- Infant
- Infant, Newborn
- Liver/drug effects
- Liver/metabolism
- Liver/pathology
- Male
- Mitochondrial Diseases/drug therapy
- Mitochondrial Diseases/genetics
- Mitochondrial Diseases/pathology
- Multiple Acyl Coenzyme A Dehydrogenase Deficiency/drug therapy
- Multiple Acyl Coenzyme A Dehydrogenase Deficiency/genetics
- Multiple Acyl Coenzyme A Dehydrogenase Deficiency/pathology
- Muscle, Skeletal/drug effects
- Muscle, Skeletal/metabolism
- Muscle, Skeletal/pathology
- Mutagenesis, Site-Directed
- Nucleotidyltransferases/genetics
- Protein Binding
- RNA, Messenger/genetics
- Real-Time Polymerase Chain Reaction
- Reverse Transcriptase Polymerase Chain Reaction
- Riboflavin/pharmacology
- Skin/drug effects
- Skin/metabolism
- Skin/pathology
- Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
- Vitamin B Complex/pharmacology
- Young Adult
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Affiliation(s)
- Rikke K J Olsen
- Research Unit for Molecular Medicine, Department of Clinical Medicine, Aarhus University and University Hospital, 8200 Aarhus N, Denmark.
| | - Eliška Koňaříková
- Institute of Human Genetics, Technische Universität München, 81675 Munich, Germany; Institute of Human Genetics, Helmholtz Zentrum München, 85764 Neuherberg, Germany
| | - Teresa A Giancaspero
- Department of Biosciences, Biotechnology, and Biopharmaceutics, University of Bari Aldo Moro, 70125 Bari, Italy
| | - Signe Mosegaard
- Research Unit for Molecular Medicine, Department of Clinical Medicine, Aarhus University and University Hospital, 8200 Aarhus N, Denmark
| | - Veronika Boczonadi
- Wellcome Trust Centre for Mitochondrial Research, Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne NE1 3BZ, UK
| | - Lavinija Mataković
- Department of Paediatrics, Paracelsus Medical University, SALK Salzburg, 5020 Salzburg, Austria
| | - Alice Veauville-Merllié
- Service Maladies Héréditaires du Métabolisme et Dépistage Néonatal, Centre de Biologie et Pathologie Est, Centre Hospitalier Universitaire Lyon, 69500 Bron, France
| | - Caterina Terrile
- Institute of Human Genetics, Helmholtz Zentrum München, 85764 Neuherberg, Germany
| | - Thomas Schwarzmayr
- Institute of Human Genetics, Technische Universität München, 81675 Munich, Germany; Institute of Human Genetics, Helmholtz Zentrum München, 85764 Neuherberg, Germany
| | - Tobias B Haack
- Institute of Human Genetics, Technische Universität München, 81675 Munich, Germany; Institute of Human Genetics, Helmholtz Zentrum München, 85764 Neuherberg, Germany
| | - Mari Auranen
- Clinical Neurosciences, Neurology, University of Helsinki and Helsinki University Hospital, 340 Helsinki, Finland
| | - Piero Leone
- Department of Biosciences, Biotechnology, and Biopharmaceutics, University of Bari Aldo Moro, 70125 Bari, Italy
| | - Michele Galluccio
- Department DiBEST (Biology, Ecology, and Earth Sciences), University of Calabria, 87036 Arcavacata di Rende, Italy
| | - Apolline Imbard
- Biochemistry Hormonology Laboratory, Robert-Debré Hospital, 75019 Paris, France; Pharmacy Faculty, Paris Sud University, 92019 Chatenay-Malabry, France
| | - Purificacion Gutierrez-Rios
- Wellcome Trust Centre for Mitochondrial Research, Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne NE1 3BZ, UK; Centro Andaluz de Biología del Desarrollo, Universidad Pablo de Olavide, 41013 Seville, Spain
| | - Johan Palmfeldt
- Research Unit for Molecular Medicine, Department of Clinical Medicine, Aarhus University and University Hospital, 8200 Aarhus N, Denmark
| | - Elisabeth Graf
- Institute of Human Genetics, Helmholtz Zentrum München, 85764 Neuherberg, Germany
| | - Christine Vianey-Saban
- Service Maladies Héréditaires du Métabolisme et Dépistage Néonatal, Centre de Biologie et Pathologie Est, Centre Hospitalier Universitaire Lyon, 69500 Bron, France
| | - Marcus Oppenheim
- Neurometabolic Unit, National Hospital for Neurology and Neurosurgery, London WCIN 3BG, UK
| | - Manuel Schiff
- INSERM UMR 1141, Hôpital Robert Debré, 75019 Paris, France; Reference Center for Inherited Metabolic Diseases, Robert-Debré Hospital, Assistance Publique - Hôpitaux de Paris, 75019 Paris, France; Faculté de Médecine Denis Diderot, Université Paris Diderot (Paris 7), 75013 Paris, France
| | - Samia Pichard
- Reference Center for Inherited Metabolic Diseases, Robert-Debré Hospital, Assistance Publique - Hôpitaux de Paris, 75019 Paris, France
| | - Odile Rigal
- Biochemistry Hormonology Laboratory, Robert-Debré Hospital, 75019 Paris, France
| | - Angela Pyle
- Wellcome Trust Centre for Mitochondrial Research, Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne NE1 3BZ, UK
| | - Patrick F Chinnery
- Wellcome Trust Centre for Mitochondrial Research, Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne NE1 3BZ, UK; Department of Clinical Neurosciences, Cambridge Biomedical Campus, University of Cambridge, Cambridge CB2 0QQ, UK
| | | | - Dorothea Möslinger
- Department of Pediatrics, Medical University of Vienna, 1090 Vienna, Austria
| | - René G Feichtinger
- Department of Paediatrics, Paracelsus Medical University, SALK Salzburg, 5020 Salzburg, Austria
| | - Beril Talim
- Pathology Unit, Department of Pediatrics, Hacettepe University Children's Hospital, 06100 Ankara, Turkey
| | - Haluk Topaloglu
- Neurology Unit, Department of Pediatrics, Hacettepe University Children's Hospital, 06100 Ankara, Turkey
| | - Turgay Coskun
- Metabolism Unit, Department of Pediatrics, Hacettepe University Children's Hospital, 06100 Ankara, Turkey
| | - Safak Gucer
- Pathology Unit, Department of Pediatrics, Hacettepe University Children's Hospital, 06100 Ankara, Turkey
| | - Annalisa Botta
- Medical Genetics Section, Department of Biomedicine and Prevention, Tor Vergata University of Rome, 00133 Rome, Italy
| | - Elena Pegoraro
- Neuromuscular Center, Department of Neurosciences, University of Padova, 35129 Padova, Italy
| | - Adriana Malena
- Neuromuscular Center, Department of Neurosciences, University of Padova, 35129 Padova, Italy
| | - Lodovica Vergani
- Neuromuscular Center, Department of Neurosciences, University of Padova, 35129 Padova, Italy
| | - Daniela Mazzà
- Italy Institute of Medical Genetics, Catholic University of Roma, 00168 Rome, Italy
| | - Marcella Zollino
- Italy Institute of Medical Genetics, Catholic University of Roma, 00168 Rome, Italy
| | - Daniele Ghezzi
- Molecular Neurogenetics Unit, Foundation IRCCS Neurological Institute C. Besta, 20126 Milan, Italy
| | - Cecile Acquaviva
- Service Maladies Héréditaires du Métabolisme et Dépistage Néonatal, Centre de Biologie et Pathologie Est, Centre Hospitalier Universitaire Lyon, 69500 Bron, France
| | - Tiina Tyni
- Department of Pediatric Neurology, Hospital for Children and Adolescence, Helsinki University Central Hospital, 280 Helsinki, Finland
| | - Avihu Boneh
- Murdoch Childrens Research Institute and University of Melbourne, Melbourne, VIC 3010, Australia
| | - Thomas Meitinger
- Institute of Human Genetics, Technische Universität München, 81675 Munich, Germany; Institute of Human Genetics, Helmholtz Zentrum München, 85764 Neuherberg, Germany
| | - Tim M Strom
- Institute of Human Genetics, Technische Universität München, 81675 Munich, Germany; Institute of Human Genetics, Helmholtz Zentrum München, 85764 Neuherberg, Germany
| | - Niels Gregersen
- Research Unit for Molecular Medicine, Department of Clinical Medicine, Aarhus University and University Hospital, 8200 Aarhus N, Denmark
| | - Johannes A Mayr
- Department of Paediatrics, Paracelsus Medical University, SALK Salzburg, 5020 Salzburg, Austria
| | - Rita Horvath
- Wellcome Trust Centre for Mitochondrial Research, Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne NE1 3BZ, UK
| | - Maria Barile
- Department of Biosciences, Biotechnology, and Biopharmaceutics, University of Bari Aldo Moro, 70125 Bari, Italy.
| | - Holger Prokisch
- Institute of Human Genetics, Technische Universität München, 81675 Munich, Germany; Institute of Human Genetics, Helmholtz Zentrum München, 85764 Neuherberg, Germany
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53
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Significant clinical heterogeneity with similar ETFDH genotype in three Chinese patients with late-onset multiple acyl-CoA dehydrogenase deficiency. Neurol Sci 2016; 37:1099-105. [PMID: 27000805 DOI: 10.1007/s10072-016-2549-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2015] [Accepted: 03/04/2016] [Indexed: 10/22/2022]
Abstract
Late-onset multiple acyl-CoA dehydrogenase deficiency (MADD) with electron transfer flavoprotein dehydrogenase (ETFDH) gene mutations is the most common lipid storage myopathy (LSM) in China. Its clinical features vary widely and pose a challenge for diagnosis. We presented the significant clinical heterogeneity among three Chinese late-onset MADD patients with similar ETFDH genotype by collecting clinical information, muscle histology, and genetic analysis. Three novel compound heterozygous variants of ETFDH gene were identified: c.892C > T (p.Pro298Ser), c.453delA (p.Glu152ArgfsTer15), and c.449_453delTAACA (p.Leu150Ter). Moreover, all patients carried a hotspot mutation c.250G > A (p.Ala84Thr). Western blot analysis of the patients' muscular tissue showed a significantly reduced ETFDH expression, and normal electron transfer flavoprotein A (ETFA) and electron transfer flavoprotein B (ETFB) expression. Two patients with similar genotypes (c.453delA and c.449_453delTAACA) presented a significant clinical heterogeneity. Among them, one exhibited muscle weakness and exercise intolerance as initial and major symptoms, and the other showed episodic recurrent gastrointestinal symptoms before a serious muscle weakness appeared in later life. The novel variants in ETFDH and the corresponding clinical features enrich the variant spectrum of late-onset MADD and provide a new insight into the genotype-phenotype relationship. Late-onset MADD should be included in differential diagnosis for adult myopathy along with chronic digestive disease.
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54
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Lund M, Olsen RKJ, Gregersen N. A short introduction to acyl-CoA dehydrogenases; deficiencies and novel treatment strategies. Expert Opin Orphan Drugs 2015. [DOI: 10.1517/21678707.2015.1092869] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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55
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Olsen RKJ, Cornelius N, Gregersen N. Redox signalling and mitochondrial stress responses; lessons from inborn errors of metabolism. J Inherit Metab Dis 2015; 38:703-19. [PMID: 26025548 PMCID: PMC4493798 DOI: 10.1007/s10545-015-9861-5] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Revised: 04/25/2015] [Accepted: 05/07/2015] [Indexed: 12/14/2022]
Abstract
Mitochondria play a key role in overall cell physiology and health by integrating cellular metabolism with cellular defense and repair mechanisms in response to physiological or environmental changes or stresses. In fact, dysregulation of mitochondrial stress responses and its consequences in the form of oxidative stress, has been linked to a wide variety of diseases including inborn errors of metabolism. In this review we will summarize how the functional state of mitochondria -- and especially the concentration of reactive oxygen species (ROS), produced in connection with the respiratory chain -- regulates cellular stress responses by redox regulation of nuclear gene networks involved in repair systems to maintain cellular homeostasis and health. Based on our own and other's studies we re-introduce the ROS triangle model and discuss how inborn errors of mitochondrial metabolism, by production of pathological amounts of ROS, may cause disturbed redox signalling and induce chronic cell stress with non-resolving or compromised cell repair responses and increased susceptibility to cell stress induced cell death. We suggest that this model may have important implications for those inborn errors of metabolism, where mitochondrial dysfunction plays a major role, as it allows the explanation of oxidative stress, metabolic reprogramming and altered signalling growth pathways that have been reported in many of the diseases. It is our hope that the model may facilitate novel ideas and directions that can be tested experimentally and used in the design of future new approaches for pre-symptomatic diagnosis and prognosis and perhaps more effective treatments of inborn errors of metabolism.
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Affiliation(s)
- Rikke K J Olsen
- Research Unit for Molecular Medicine, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, 8200, Aarhus N, Denmark,
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56
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Koster KL, Sturm M, Herebian D, Smits SHJ, Spiekerkoetter U. Functional studies of 18 heterologously expressed medium-chain acyl-CoA dehydrogenase (MCAD) variants. J Inherit Metab Dis 2014; 37:917-28. [PMID: 24966162 DOI: 10.1007/s10545-014-9732-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Revised: 05/22/2014] [Accepted: 06/02/2014] [Indexed: 12/30/2022]
Abstract
Medium-chain acyl-coenzyme-A dehydrogenase (MCAD) catalyzes the first step of mitochondrial beta-oxidation for medium-chain acyl-CoAs. Mutations in the ACADM gene cause MCAD deficiency presenting with life-threatening symptoms during catabolism. Since fatty-acid-oxidation disorders are part of newborn screening (NBS), many novel mutations with unknown clinical relevance have been identified in asymptomatic newborns. Eighteen of these mutations were separately cloned into the human ACADM gene, heterologously overexpressed in Escherichia coli and functionally characterized by using different substrates, molecular chaperones, and measured at different temperatures. In addition, they were mapped to the three-dimensional MCAD structure, and cross-link experiments were performed. This study identified variants that only moderately affect the MCAD protein in vitro, such as Y42H, E18K, and R6H, in contrast to the remaining 15 mutants. These three mutants display residual octanoyl-CoA oxidation activities in the range of 22 % to 47 %, are as temperature sensitive as the wild type, and reach 100 % activity with molecular chaperone co-overexpression. Projection into the three-dimensional protein structure gave some indication as to possible reasons for decreased enzyme activities. Additionally, six of the eight novel mutations, functionally characterized for the first time, showed severely reduced residual activities < 5 % despite high expression levels. These studies are of relevance because they classify novel mutants in vitro on the basis of their corresponding functional effects. This basic knowledge should be taken into consideration for individual management after NBS.
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Affiliation(s)
- Kira-Lee Koster
- Department of General Pediatrics, Neonatology and Pediatric Cardiology, University Children's Hospital, Moorenstr.5, 40225, Duesseldorf, Germany
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57
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Carrozzo R, Torraco A, Fiermonte G, Martinelli D, Di Nottia M, Rizza T, Vozza A, Verrigni D, Diodato D, Parisi G, Maiorana A, Rizzo C, Pierri CL, Zucano S, Piemonte F, Bertini E, Dionisi-Vici C. Riboflavin responsive mitochondrial myopathy is a new phenotype of dihydrolipoamide dehydrogenase deficiency. The chaperon-like effect of vitamin B2. Mitochondrion 2014; 18:49-57. [PMID: 25251739 DOI: 10.1016/j.mito.2014.09.006] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Accepted: 09/15/2014] [Indexed: 11/18/2022]
Abstract
Dihydrolipoamide dehydrogenase (DLD, E3) is a flavoprotein common to pyruvate, α-ketoglutarate and branched-chain α-keto acid dehydrogenases. We found two novel DLD mutations (p.I40Lfs*4; p.G461E) in a 19 year-old patient with lactic acidosis and a complex amino- and organic aciduria consistent with DLD deficiency, manifesting progressive exertional fatigue. Muscle biopsy showed mitochondrial proliferation and lack of DLD cross-reacting material. Riboflavin supplementation determined the complete resolution of exercise intolerance with the partial restoration of the DLD protein and disappearance of mitochondrial proliferation in the muscle. Morphological and functional studies support the riboflavin chaperon-like role in stabilizing DLD protein with rescue of its expression in the muscle.
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Affiliation(s)
- Rosalba Carrozzo
- Unit of Molecular Medicine for Neuromuscular and Neurodegenerative Diseases, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy.
| | - Alessandra Torraco
- Unit of Molecular Medicine for Neuromuscular and Neurodegenerative Diseases, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
| | - Giuseppe Fiermonte
- Department of Biosciences, Biotechnologies and Biopharmaceutics, Laboratory of Biochemistry and Molecular Biology, University of Bari, Via E. Orabona 4, Bari, Italy
| | - Diego Martinelli
- Division of Metabolism, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
| | - Michela Di Nottia
- Unit of Molecular Medicine for Neuromuscular and Neurodegenerative Diseases, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
| | - Teresa Rizza
- Unit of Molecular Medicine for Neuromuscular and Neurodegenerative Diseases, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
| | - Angelo Vozza
- Department of Biosciences, Biotechnologies and Biopharmaceutics, Laboratory of Biochemistry and Molecular Biology, University of Bari, Via E. Orabona 4, Bari, Italy
| | - Daniela Verrigni
- Unit of Molecular Medicine for Neuromuscular and Neurodegenerative Diseases, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
| | - Daria Diodato
- Unit of Molecular Medicine for Neuromuscular and Neurodegenerative Diseases, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
| | - Giovanni Parisi
- Department of Biosciences, Biotechnologies and Biopharmaceutics, Laboratory of Biochemistry and Molecular Biology, University of Bari, Via E. Orabona 4, Bari, Italy
| | - Arianna Maiorana
- Division of Metabolism, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
| | - Cristiano Rizzo
- Department of Laboratory Medicine, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
| | - Ciro Leonardo Pierri
- Department of Biosciences, Biotechnologies and Biopharmaceutics, Laboratory of Biochemistry and Molecular Biology, University of Bari, Via E. Orabona 4, Bari, Italy
| | - Stefania Zucano
- Department of Biosciences, Biotechnologies and Biopharmaceutics, Laboratory of Biochemistry and Molecular Biology, University of Bari, Via E. Orabona 4, Bari, Italy
| | - Fiorella Piemonte
- Unit of Molecular Medicine for Neuromuscular and Neurodegenerative Diseases, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
| | - Enrico Bertini
- Unit of Molecular Medicine for Neuromuscular and Neurodegenerative Diseases, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
| | - Carlo Dionisi-Vici
- Division of Metabolism, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy.
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58
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Pey AL, Megarity CF, Timson DJ. FAD binding overcomes defects in activity and stability displayed by cancer-associated variants of human NQO1. Biochim Biophys Acta Mol Basis Dis 2014; 1842:2163-73. [PMID: 25179580 DOI: 10.1016/j.bbadis.2014.08.011] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2014] [Revised: 08/08/2014] [Accepted: 08/20/2014] [Indexed: 01/24/2023]
Abstract
NAD(P)H quinone oxidoreductase 1 is involved in antioxidant defence and protection from cancer, stabilizing the apoptosis regulator p53 towards degradation. Here, we studied the enzymological, biochemical and biophysical properties of two cancer-associated variants (p.R139W and p.P187S). Both variants (especially p.187S) have lower thermal stability and greater susceptibility to proteolysis compared to the wild-type. p.P187S also has reduced activity due to a lower binding affinity for the FAD cofactor as assessed by activity measurements and direct titrations. Native gel electrophoresis and dynamic light scattering also suggest that p.P187S has a higher tendency to populate unfolded states under native conditions. Detailed thermal stability studies showed that all variants irreversibly denature causing dimer dissociation, while addition of FAD restores the stability of the polymorphic forms to wild-type levels. The kinetic destabilization induced by polymorphisms as well as the kinetic protection exerted by FAD was confirmed by measuring denaturation kinetics at temperatures close to physiological. Our data suggest that the main molecular mechanisms associated with these cancer-related variants are their low binding affinity for FAD and/or kinetic instability. Thus, pharmacological chaperones may be useful in the treatment of patients bearing these polymorphisms.
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Affiliation(s)
- Angel L Pey
- Department of Physical Chemistry, Faculty of Sciences, University of Granada, Av. Fuentenueva s/n, 18071, Spain.
| | - Clare F Megarity
- School of Biological Sciences, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast BT9 7BL, UK
| | - David J Timson
- School of Biological Sciences, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast BT9 7BL, UK; Institute for Global Food Security, Queen's University Belfast, 18-30 Malone Road, Belfast BT9 5BN, UK.
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59
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Grünert SC. Clinical and genetical heterogeneity of late-onset multiple acyl-coenzyme A dehydrogenase deficiency. Orphanet J Rare Dis 2014; 9:117. [PMID: 25200064 PMCID: PMC4222585 DOI: 10.1186/s13023-014-0117-5] [Citation(s) in RCA: 129] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2014] [Accepted: 07/08/2014] [Indexed: 01/10/2023] Open
Abstract
BACKGROUND Multiple acyl-CoA dehydrogenase deficiency (MADD) is an autosomal recessive disorder caused by deficiency of electron transfer flavoprotein or electron transfer flavoprotein dehydrogenase. The clinical picture of late-onset forms is highly variable with symptoms ranging from acute metabolic decompensations to chronic, mainly muscular problems or even asymptomatic cases. METHODS All 350 cases of late-onset MADD reported in the literature to date have been analyzed and evaluated with respect to age at presentation, diagnostic delay, biochemical features and diagnostic parameters as well as response to treatment. RESULTS Mean age at onset was 19.2 years. The mean delay between onset of symptoms and diagnosis was 3.9 years. Chronic muscular symptoms were more than twice as common as acute metabolic decompensations (85% versus 33% of patients, respectively). 20% had both acute and chronic symptoms. 5% of patients had died at a mean age of 5.8 years, while 3% of patients have remained asymptomatic until a maximum age of 14 years. Diagnosis may be difficult as a relevant number of patients do not display typical biochemical patterns of urine organic acids and blood acylcarnitines during times of wellbeing. The vast majority of patients carry mutations in the ETFDH gene (93%), while mutations in the ETFA (5%) and ETFB (2%) genes are the exceptions. Almost all patients with late-onset MADD (98%) are clearly responsive to riboflavin. CONCLUSIONS Late-onset MADD is probably an underdiagnosed disease and should be considered in all patients with acute or chronic muscular symptoms or acute metabolic decompensation with hypoglycemia, acidosis, encephalopathy and hepatopathy. This may not only prevent patients from invasive diagnostic procedures such as muscle biopsies, but also help to avoid fatal metabolic decompensations.
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Affiliation(s)
- Sarah C Grünert
- Center of Pediatrics and Adolescent Medicine, University Hospital Freiburg, Freiburg, Germany.
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60
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Spectrum of metabolic myopathies. Biochim Biophys Acta Mol Basis Dis 2014; 1852:615-21. [PMID: 24997454 DOI: 10.1016/j.bbadis.2014.06.031] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Revised: 06/19/2014] [Accepted: 06/25/2014] [Indexed: 11/24/2022]
Abstract
Metabolic myopathies are disorders of utilization of carbohydrates or fat in muscles. The acute nature of energy failure is manifested either by a metabolic crisis with weakness, sometimes associated with respiratory failure, or by myoglobinuria. A typical disorder where permanent weakness occurs is glycogenosis type II (GSDII or Pompe disease) both in infantile and late-onset forms, where respiratory insufficiency is manifested by a large number of cases. In GSDII the pathogenetic mechanism is still poorly understood, and has to be attributed more to structural muscle alterations, possibly in correlation to macro-autophagy, rather than to energetic failure. This review is focused on recent advances about GSDII and its treatment, and the most recent notions about the management and treatment of other metabolic myopathies will be briefly reviewed, including glycogenosis type V (McArdle disease), glycogenosis type III (debrancher enzyme deficiency or Cori disease), CPT-II deficiency, and ETF-dehydrogenase deficiency (also known as riboflavin-responsive multiple acyl-CoA dehydrogenase deficiency or RR-MADD). The discovery of the genetic defect in ETF dehydrogenase confirms the etiology of this syndrome. Other metabolic myopathies with massive lipid storage and weakness are carnitine deficiency, neutral lipid storage-myopathy (NLSD-M), besides RR-MADD. Enzyme replacement therapy is presented with critical consideration and for each of the lipid storage disorders, representative cases and their response to therapy is included. This article is part of a Special Issue entitled: Neuromuscular Diseases: Pathology and Molecular Pathogenesis.
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Cornelius N, Corydon TJ, Gregersen N, Olsen RKJ. Cellular consequences of oxidative stress in riboflavin responsive multiple acyl-CoA dehydrogenation deficiency patient fibroblasts. Hum Mol Genet 2014; 23:4285-301. [PMID: 24698980 DOI: 10.1093/hmg/ddu146] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Mitochondrial dysfunction and oxidative stress are central to the molecular pathology of many human diseases. Riboflavin responsive multiple acyl-CoA dehydrogenation deficiency (RR-MADD) is in most cases caused by variations in the gene coding for electron transfer flavoprotein-ubiquinone oxidoreductase (ETF-QO). Currently, patients with RR-MADD are treated with high doses of riboflavin resulting in improvements of the clinical and biochemical profiles. However, in our recent studies of RR-MADD, we have shown that riboflavin treatment cannot fully correct the molecular defect in patient cells producing increased reactive oxygen species (ROS). In the current study, we aim to elucidate the cellular consequences of increased ROS by studying the cellular ROS adaption systems including antioxidant system, mitochondrial dynamics and metabolic reprogramming. We have included fibroblasts from six unrelated RR-MADD patients and two control fibroblasts cultivated under supplemented and depleted riboflavin conditions and with coenzyme Q10 (CoQ10) treatment. We demonstrated inhibition of mitochondrial fusion with increased fractionation and mitophagy in the patient fibroblasts. Furthermore, we indicated a shift in the energy metabolism by decreased protein levels of SIRT3 and decreased expression of fatty acid β-oxidation enzymes in the patient fibroblasts. Finally, we showed that CoQ10 treatment has a positive effect on the mitochondrial dynamic in the patient fibroblasts, indicated by increased mitochondrial fusion marker and reduced mitophagy. In conclusion, our results indicate that RR-MADD patient fibroblasts suffer from a general mitochondria dysfunction, probably initiated as a rescue mechanism for the patient cells to escape apoptosis as a result of the oxidative stress.
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Affiliation(s)
- Nanna Cornelius
- Research Unit for Molecular Medicine, Aarhus University Hospital and Department of Clinical Medicine, Aarhus University, Brendstrupgaardsvej 100, Aarhus 8200, Denmark and
| | - Thomas J Corydon
- Department of Biomedicine, Aarhus University, Aarhus 8000, Denmark
| | - Niels Gregersen
- Research Unit for Molecular Medicine, Aarhus University Hospital and Department of Clinical Medicine, Aarhus University, Brendstrupgaardsvej 100, Aarhus 8200, Denmark and
| | - Rikke K J Olsen
- Research Unit for Molecular Medicine, Aarhus University Hospital and Department of Clinical Medicine, Aarhus University, Brendstrupgaardsvej 100, Aarhus 8200, Denmark and
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62
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Pinto JT, Cooper AJL. From cholesterogenesis to steroidogenesis: role of riboflavin and flavoenzymes in the biosynthesis of vitamin D. Adv Nutr 2014; 5:144-63. [PMID: 24618756 PMCID: PMC3951797 DOI: 10.3945/an.113.005181] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Flavin-dependent monooxygenases and oxidoreductases are located at critical branch points in the biosynthesis and metabolism of cholesterol and vitamin D. These flavoproteins function as obligatory intermediates that accept 2 electrons from NAD(P)H with subsequent 1-electron transfers to a variety of cytochrome P450 (CYP) heme proteins within the mitochondria matrix (type I) and the (microsomal) endoplasmic reticulum (type II). The mode of electron transfer in these systems differs slightly in the number and form of the flavin prosthetic moiety. In the type I mitochondrial system, FAD-adrenodoxin reductase interfaces with adrenodoxin before electron transfer to CYP heme proteins. In the microsomal type II system, a diflavin (FAD/FMN)-dependent cytochrome P450 oxidoreductase [NAD(P)H-cytochrome P450 reductase (CPR)] donates electrons to a multitude of heme oxygenases. Both flavoenzyme complexes exhibit a commonality of function with all CYP enzymes and are crucial for maintaining a balance of cholesterol and vitamin D metabolites. Deficits in riboflavin availability, imbalances in the intracellular ratio of FAD to FMN, and mutations that affect flavin binding domains and/or interactions with client proteins result in marked structural alterations within the skeletal and central nervous systems similar to those of disorders (inborn errors) in the biosynthetic pathways that lead to cholesterol, steroid hormones, and vitamin D and their metabolites. Studies of riboflavin deficiency during embryonic development demonstrate congenital malformations similar to those associated with genetic alterations of the flavoenzymes in these pathways. Overall, a deeper understanding of the role of riboflavin in these pathways may prove essential to targeted therapeutic designs aimed at cholesterol and vitamin D metabolism.
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63
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Olsen RKJ, Brøner S, Sabaratnam R, Doktor TK, Andersen HS, Bruun GH, Gahrn B, Stenbroen V, Olpin SE, Dobbie A, Gregersen N, Andresen BS. TheETFDHc.158A>G Variation Disrupts the Balanced Interplay of ESE- and ESS-Binding Proteins thereby Causing Missplicing and Multiple Acyl-CoA Dehydrogenation Deficiency. Hum Mutat 2013; 35:86-95. [DOI: 10.1002/humu.22455] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Accepted: 09/25/2013] [Indexed: 12/19/2022]
Affiliation(s)
- Rikke K. J. Olsen
- Research Unit for Molecular Medicine; Aarhus University Hospital and Department of Clinical Medicine, Aarhus University; Aarhus Denmark
| | - Sabrina Brøner
- Department of Biochemistry and Molecular Biology; University of Southern Denmark; Odense Denmark
| | - Rugivan Sabaratnam
- Department of Biochemistry and Molecular Biology; University of Southern Denmark; Odense Denmark
| | - Thomas K. Doktor
- Department of Biochemistry and Molecular Biology; University of Southern Denmark; Odense Denmark
| | - Henriette S. Andersen
- Department of Biochemistry and Molecular Biology; University of Southern Denmark; Odense Denmark
| | - Gitte H. Bruun
- Department of Biochemistry and Molecular Biology; University of Southern Denmark; Odense Denmark
| | - Birthe Gahrn
- Research Unit for Molecular Medicine; Aarhus University Hospital and Department of Clinical Medicine, Aarhus University; Aarhus Denmark
| | - Vibeke Stenbroen
- Research Unit for Molecular Medicine; Aarhus University Hospital and Department of Clinical Medicine, Aarhus University; Aarhus Denmark
| | - Simon E. Olpin
- Department of Clinical Chemistry; The Children's Hospital; Sheffield United Kingdom
| | - Angus Dobbie
- Department of Clinical Genetics; St James's University Hospital; Leeds United Kingdom
| | - Niels Gregersen
- Research Unit for Molecular Medicine; Aarhus University Hospital and Department of Clinical Medicine, Aarhus University; Aarhus Denmark
| | - Brage S. Andresen
- Department of Biochemistry and Molecular Biology; University of Southern Denmark; Odense Denmark
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64
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Liang WC, Nishino I. Riboflavin-responsive multiple acyl-CoA dehydrogenase deficiency: A frequent condition in the southern Chinese population. ACTA ACUST UNITED AC 2013. [DOI: 10.1111/ncn3.45] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Wen-Chen Liang
- Department of Pediatrics; Kaohsiung Medical University Hospital; Kaohsiung Medical University; Kaohsiung Taiwan
- Department of Pediatrics; School of Medicine; College of Medicine; Kaohsiung Medical University; Kaohsiung Taiwan
| | - Ichizo Nishino
- Department of Neuromuscular Research; National Institute of Neuroscience; National Center of Neurology and Psychiatry; Tokyo Japan
- Department of Clinical Development; Translational Medical Center; National Center of Neurology and Psychiatry; Tokyo Japan
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65
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Angelini C, Nascimbeni AC, Semplicini C. Therapeutic advances in the management of Pompe disease and other metabolic myopathies. Ther Adv Neurol Disord 2013; 6:311-21. [PMID: 23997816 DOI: 10.1177/1756285613487570] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The world of metabolic myopathies has been dramatically modified by the advent of enzyme replacement therapy (ERT), the first causative treatment for glycogenosis type II (GSDII) or Pompe disease, which has given new impetus to research into that disease and also other pathologies. This article reviews new advances in the treatment of GSDII, the consensus about ERT, and its limitations. In addition, the most recent knowledge regarding the pathophysiology, phenotype, and genotype of the disease is discussed. Pharmacological, immunotherapy, nutritional, and physical/rehabilitative treatments for late-onset Pompe disease and other metabolic myopathies are covered, including treatments for defects in glycogen metabolism, such as glycogenosis type V (McArdle disease), and glycogenosis type III (debrancher enzyme deficiency), and defects in lipid metabolism, such as carnitine palmitoyltransferase II deficiency and electron transferring flavoprotein dehydrogenase deficiency, or riboflavin-responsive multiple acyl-CoA dehydrogenase deficiency.
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66
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Olpin SE. Pathophysiology of fatty acid oxidation disorders and resultant phenotypic variability. J Inherit Metab Dis 2013; 36:645-58. [PMID: 23674167 PMCID: PMC7101856 DOI: 10.1007/s10545-013-9611-5] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Revised: 03/27/2013] [Accepted: 04/10/2013] [Indexed: 12/16/2022]
Abstract
Fatty acids are a major fuel for the body and fatty acid oxidation is particularly important during fasting, sustained aerobic exercise and stress. The myocardium and resting skeletal muscle utilise long-chain fatty acids as a major source of energy. Inherited disorders affecting fatty acid oxidation seriously compromise the function of muscle and other highly energy-dependent tissues such as brain, nerve, heart, kidney and liver. Such defects encompass a wide spectrum of clinical disease, presenting in the neonatal period or infancy with recurrent hypoketotic hypoglycaemic encephalopathy, liver dysfunction, hyperammonaemia and often cardiac dysfunction. In older children, adolescence or adults there is often exercise intolerance with episodic myalgia or rhabdomyolysis in association with prolonged aerobic exercise or other exacerbating factors. Some disorders are particularly associated with toxic metabolites that may contribute to encephalopathy, polyneuropathy, axonopathy and pigmentary retinopathy. The phenotypic diversity encountered in defects of fat oxidation is partly explained by genotype/phenotype correlation and certain identifiable environmental factors but there remain many unresolved questions regarding the complex interaction of genetic, epigenetic and environmental influences that dictate phenotypic expression. It is becoming increasingly clear that the view that most inherited disorders are purely monogenic diseases is a naive concept. In the future our approach to understanding the phenotypic diversity and management of patients will be more realistically achieved from a polygenic perspective.
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Affiliation(s)
- Simon E Olpin
- Department of Clinical Chemistry, Sheffield Children's Hospital, Sheffield S10 2TH, UK.
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67
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Cornelius N, Byron C, Hargreaves I, Guerra PF, Furdek AK, Land J, Radford WW, Frerman F, Corydon TJ, Gregersen N, Olsen RKJ. Secondary coenzyme Q10 deficiency and oxidative stress in cultured fibroblasts from patients with riboflavin responsive multiple Acyl-CoA dehydrogenation deficiency. Hum Mol Genet 2013; 22:3819-27. [PMID: 23727839 DOI: 10.1093/hmg/ddt232] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Coenzyme Q10 (CoQ10) is essential for the energy production of the cells and as an electron transporter in the mitochondrial respiratory chain. CoQ10 links the mitochondrial fatty acid β-oxidation to the respiratory chain by accepting electrons from electron transfer flavoprotein-ubiquinone oxidoreductase (ETF-QO). Recently, it was shown that a group of patients with the riboflavin responsive form of multiple acyl-CoA dehydrogenation deficiency (RR-MADD) carrying inherited amino acid variations in ETF-QO also had secondary CoQ10 deficiency with beneficial effects of CoQ10 treatment, thus adding RR-MADD to an increasing number of diseases involving secondary CoQ10 deficiency. In this study, we show that moderately decreased CoQ10 levels in fibroblasts from six unrelated RR-MADD patients were associated with increased levels of mitochondrial reactive oxygen species (ROS). Treatment with CoQ10, but not with riboflavin, could normalize the CoQ10 level and decrease the level of ROS in the patient cells. Additionally, riboflavin-depleted control fibroblasts showed moderate CoQ10 deficiency, but not increased mitochondrial ROS, indicating that variant ETF-QO proteins and not CoQ10 deficiency are the causes of mitochondrial ROS production in the patient cells. Accordingly, the corresponding variant Rhodobacter sphaeroides ETF-QO proteins, when overexpressed in vitro, bind a CoQ10 pseudosubstrate, Q10Br, less tightly than the wild-type ETF-QO protein, suggesting that molecular oxygen can get access to the electrons in the misfolded ETF-QO protein, thereby generating superoxide and oxidative stress, which can be reversed by CoQ10 treatment.
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68
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Olsen RKJ, Cornelius N, Gregersen N. Genetic and cellular modifiers of oxidative stress: what can we learn from fatty acid oxidation defects? Mol Genet Metab 2013; 110 Suppl:S31-9. [PMID: 24206932 DOI: 10.1016/j.ymgme.2013.10.007] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Revised: 10/08/2013] [Accepted: 10/08/2013] [Indexed: 11/16/2022]
Abstract
During the last two decades the realization has emerged that the phenotype of the majority of inherited genetic diseases, including inborn errors of metabolism, cannot be predicted by the genotype identified in patients. This is true for PKU and in the majority of fatty acid oxidation (FAO) defects, where the genotypes identified in patients may be allocated into two groups. One comprising big deletions and small out-of-frame deletions/insertions as well as severe splice and stop codon changes, generally giving rise to no or very little protein product, and the other group, comprising small in-frame deletions/insertions and missense variations, resulting in misfolding proteins with varying stability. In all cases of FAO defects the pathophysiology may be due to energy insufficiency as well as toxic effects from accumulated enzyme substrates. In patients carrying missense variations, it may in addition be caused by the presence of misfolding proteins. A common effect of accumulated substrates and misfolding proteins is chronic oxidative stress, the severeness of which may depend on a complex interplay of modifying factors, including genetic, cellular, environmental and dietary. In this review we will discuss the hypothesis that especially the amounts of reactive oxygen species (ROS) and reactive nitrogen species (RNS), created in connection with the electron transport chain (ETC), are the driving forces in the balance between cell survival and death. In young and healthy cells small amounts of ROS function as signaling molecules, activating cell protection systems, such as protein quality networks, antioxidant enzymes and metabolic shift from ATP production by the ETC to glycolysis. In the sick and old cell, containing misfolding and damaged proteins, the dynamic range of these protecting systems are narrowed, and cells develop a state of chronic stress, which easier than young and healthy cells may initiate cell death programs like apoptosis and necrosis. We will discuss a wealth of literature that support this hypothesis, which - if supported by studies - is important for new treatment strategies. We conclude that crude antioxidant treatment may not be beneficial, since it may inhibit the survival stress responses. We discuss the ongoing studies to enhance the residual activity of mild misfolding enzyme proteins by cofactor or chemical chaperones or by inducing the transcription of FAO enzyme proteins by bezafibrate with respect to misfolding/distorted conformational proteins ability to create ROS, and the need to know the exact pathophysiological mechanisms in order to suggest new treatment regimes.
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Affiliation(s)
- Rikke Katrine Jentoft Olsen
- Research Unit for Molecular Medicine, Department of Clinical Medicine, Aarhus University and Aarhus University Hospital, Brendstrupgaardsvej 100, Aarhus, Denmark.
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