Ronald Wanders - Academia.edu (original) (raw)

Papers by Ronald Wanders

Sub-cellular biochemistry, 2013

Peroxisomes play a key role in human physiology as exemplified by the devastating consequences of... more Peroxisomes play a key role in human physiology as exemplified by the devastating consequences of a defect in peroxisome biogenesis as observed in patients affected by Zellweger syndrome. The main metabolic functions of peroxisomes in humans include: (1) fatty acid beta-oxidation; (2) etherphospholipid synthesis; (3) bile acid synthesis; (4) fatty acid alpha-oxidation, and (5) glyoxylate detoxification. Since peroxisomes lack a citric acid cycle and respiratory chain like mitochondria do, metabolism in peroxisomes requires continued cross-talk with other organelles, notably mitochondria and the endoplasmic reticulum in order to allow continued metabolism of the products generated by peroxisomes. Many of the metabolites which require peroxisomes for homeostasis, are involved in signal transduction pathways. These include the primary bile acids; platelet activating factor; plasmalogens, N-acylglycines and N-acyltaurines; docosahexaenoic acid as well as multiple prostanoids. The current state of knowledge in this area will be discussed in this review.

Springer eBooks, Sep 13, 2006

Advances in Experimental Medicine and Biology, 2002

ABSTRACT

Inborn Metabolic Diseases, 2016

Inherited Metabolic Diseases, 2016

Enzymes are the ultimate catalysts of chemical reactions and thus form the essence of metabolic p... more Enzymes are the ultimate catalysts of chemical reactions and thus form the essence of metabolic pathways to ensure metabolic homeostasis. This occurs in close conjunction with the multiple transmembrane metabolite transporters which allow enzymes localized in different compartments within each individual cell to interact with one another. Until recently, enzymology was the obligatory, second step in the diagnostic algorithm aimed to identify the underlying defect in any patient suspected to suffer from an inborn error of metabolism (IEM) as a logical follow-up of metabolic investigations. This classical approach has led to the discovery of numerous inborn errors of metabolism. The introduction of sophisticated, highly accurate, and fast DNA sequencing technologies has revolutionized the field of inborn errors of metabolism and DNA sequencing may soon be the first line of investigation, especially in patients with an undefined set of signs and symptoms. Although these new developments will definitely change the sequence of events in the diagnosis of patients suspected to suffer from an inborn error of metabolism, enzymological studies will remain of crucial importance since it is the only way to resolve the functional consequences of the DNA variants found upon whole exome or whole genome sequencing in close conjunction with metabolite studies in such patients. We will describe the importance of enzymology for the diagnosis of patients affected by a peroxisomal disorder, a disorder of mitochondrial beta-oxidation, a defect in oxidative phosphorylation (OXPHOS), or a lysosomal disorder.

Movement Disorders, 2016

Background: Recessive mutations in the 3hydroxyisobutyryl-CoA hydrolase gene (HIBCH) are associat... more Background: Recessive mutations in the 3hydroxyisobutyryl-CoA hydrolase gene (HIBCH) are associated with a rare neurodegenerative disease that affects the basal ganglia. Most patients die during infancy or early childhood. Here we describe 5 adolescent and adult patients from 2 unrelated families, who presented with a movement disorder and MRI features suggestive of Leigh syndrome. Methods: Clinical and metabolic assessment was followed by autozygosity mapping and whole exome and Sanger sequencing. HIBCH enzyme activity and the bioenergetic profile were determined in patient fibroblasts. Results: The movement disorder was dominated by ataxia in one family and by dystonia in the other. All affected family members carried the identical homozygous c.913A>G (p.T305A) HIBCH mutation. Enzyme activity was reduced, and a valine challenge reduced the oxygen consumption rate. Conclusions: We report the first adult patients with HIBCH deficiency and a disease course much milder than previously reported, thereby expanding the HIBCHassociated phenotypic spectrum. V

Plant Physiology, 2016

Cofactors such as NAD, AMP, and Coenzyme A (CoA) are essential for a diverse set of reactions and... more Cofactors such as NAD, AMP, and Coenzyme A (CoA) are essential for a diverse set of reactions and pathways in the cell. Specific carrier proteins are required to distribute these cofactors to different cell compartments, including peroxisomes. We previously identified a peroxisomal transport protein in Arabidopsis (Arabidopsis thaliana) called the peroxisomal NAD carrier (PXN). When assayed in vitro, this carrier exhibits versatile transport functions, e.g. catalyzing the import of NAD or CoA, the exchange of NAD/NADH, and the export of CoA. These observations raise the question about the physiological function of PXN in plants. Here, we used Saccharomyces cerevisiae to address this question. First, we confirmed that PXN, when expressed in yeast, is active and targeted to yeast peroxisomes. Secondl, detailed uptake analyses revealed that the CoA transport function of PXN can be excluded under physiological conditions due to its low affinity for this substrate. Third, we expressed PXN in diverse mutant yeast strains and investigated the suppression of the mutant phenotypes. These studies provided strong evidences that PXN was not able to function as a CoA transporter or a redox shuttle by mediating a NAD/NADH exchange, but instead catalyzed the import of NAD into peroxisomes against AMP in intact yeast cells.

American journal of medical genetics. Part A, Jan 23, 2016

Normal cognitive outcome in a PEX6 deficient girl despite neonatal multisystem presentation.

Molecular & cellular proteomics : MCP, Jan 28, 2015

The protein substrates of SIRT5-regulated lysine malonylation (Kmal) remain unknown, hindering it... more The protein substrates of SIRT5-regulated lysine malonylation (Kmal) remain unknown, hindering its functional analysis. In this report, we carried out proteomic screening, identifying 4042 Kmal sites on 1426 proteins in mouse liver, and 4943 Kmal sites on 1822 proteins in human fibroblasts. Elevated malonyl-CoA in Malonyl-CoA decarboxylase (MCD) deficient cells induces Kmal levels in substrate proteins. We identified 461 Kmal sites showing more than 2-fold increase in response to MCD deficiency, as well as 1452 Kmal sites detected only in MCD-/- fibroblast but not MCD+/+ cells, suggesting a pathogenic role of Kmal in MCD deficiency. Cells with increased lysine malonylation displayed impaired mitochondrial function and fatty acid oxidation, suggesting that lysine malonylation plays a role in pathophysiology of malonic aciduria. Our study establishes an association between Kmal and a genetic disease, and offers a rich resource for elucidating the contribution of the Kmal pathway and m...

Journal of inherited metabolic disease, Jan 19, 2015

We describe the natural history of patients with a Zellweger spectrum disorder (ZSD) surviving in... more We describe the natural history of patients with a Zellweger spectrum disorder (ZSD) surviving into adulthood. Retrospective cohort study in patients with a genetically confirmed ZSD. All patients (n = 19; aged 16-35 years) had a follow-up period of 1-24.4 years (mean 16 years). Seven patients had a progressive disease course, while 12 remained clinically stable during follow-up. Disease progression usually manifests in adolescence as a gait disorder, caused by central and/or peripheral nervous system involvement. Nine were capable of living a partly independent life with supported employment. Systematic MRI review revealed T2 hyperintense white matter abnormalities in the hilus of the dentate nucleus and/or peridentate region in nine out of 16 patients. Biochemical analyses in blood showed abnormal peroxisomal biomarkers in all patients in infancy and childhood, whereas in adolescence/adulthood we observed normalization of some metabolites. The patients described here represent a d...

Journal of Biological Chemistry, 2006

X-linked adrenoleukodystrophy (X-ALD) is a severe neurodegenerative disorder biochemically charac... more X-linked adrenoleukodystrophy (X-ALD) is a severe neurodegenerative disorder biochemically characterized by elevated levels of very long-chain fatty acids (VLCFA). Excess levels of VLCFAs are thought to play an important role in the pathogenesis of X-ALD. Therefore, therapeutic approaches for X-ALD are focused on the reduction or normalization of VLCFAs. In this study, we investigated an alternative oxidation route for VLCFAs, namely-oxidation. The results described in this study show that VLCFAs are substrates for the-oxidation system in human liver microsomes. Moreover, VLCFAs were not only converted into-hydroxy fatty acids, but they were also further oxidized to dicarboxylic acids via cytochrome P450-mediated reactions. High sensitivity toward the specific P450 inhibitor 17-octadecynoic acid suggested that-hydroxylation of VLCFAs is catalyzed by P450 enzymes belonging to the CYP4A/F subfamilies. Studies with individually expressed human recombinant P450 enzymes revealed that two P450 enzymes, i.e. CYP4F2 and CYP4F3B, participate in the-hydroxylation of VLCFAs. Both enzymes belong to the cytochrome P450 4F subfamily and have a high affinity for VLCFAs. In summary, this study demonstrates that VLCFAs are substrates for the human-oxidation system, and for this reason, stimulation of the in vivo VLCFA-oxidation pathway may provide an alternative mode of treatment to reduce the levels of VLCFAs in patients with X-ALD. In mammalian cells, fatty acid oxidation plays a major role in the production of energy, particularly in the heart and skeletal muscle, and is the main energy source during periods of fasting. Both mitochondria and peroxisomes are capable of degrading saturated fatty acids via ␤-oxidation. Short-, medium-, and long-chain saturated fatty acids are degraded predominantly by mitochondria, whereas very long-chain fatty acids (VLCFA, 2 Ͼ22 carbons) are ␤-oxidized exclusively in peroxisomes (1, 2). Moreover, peroxisomes also metabolize certain branched chain fatty acids, bile acid precursors, eicosanoids, and dicarboxylic acids (3).

Journal of Clinical Investigation, 1994

We examined the enzyme protein and biosynthesis of human trifunctional protein harboring enoyl-Co... more We examined the enzyme protein and biosynthesis of human trifunctional protein harboring enoyl-CoA hydratase, 3-hydroxyacyl-CoA dehydrogenase, and 3-ketoacyl-CoA thiolase activity in cultured skin fibroblasts from two patients with longchain 3-hydroxyacyl-CoA dehydrogenase deficiency. The following results were obtained. (a) In cells from patient 1, immunoblot analysis and pulse-chase experiments indicated that the content of trifunctional protein was < 10% of that in control cells, due to a very rapid degradation of protein newly synthesized in the mitochondria. The diminution of trifunctional protein was associated with a decreased activity of enoyl-CoA hydratase, 3-hydroxyacyl-CoA dehydrogenase, and 3-ketoacyl-CoA thiolase, when measured using medium-chain to long-chain substrates. (b) In cells from patient 2, the rate of degradation of newly synthesized trifunctional protein was faster than that in control cells, giving rise to a trifunctional protein amounting to 60% of the control levels. The 3-hydroxyacyl-CoA dehydrogenase activity with medium-chain to longchain substrates was decreased drastically, with minor changes in activities of the two other enzymes. These data suggest a subtle abnormality of trifunctional protein in cells from patient 2. Taken together, the results obtained show that in both patients, long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency is caused by an abnormality in the trifunctional protein, even though there is a heterogeneity in both patients.

Journal of Inherited Metabolic Disease, 2005

Sjögren-Larsson syndrome (SLS) is a metabolic disorder characterized by ichthyosis, mental retard... more Sjögren-Larsson syndrome (SLS) is a metabolic disorder characterized by ichthyosis, mental retardation and spastic diplegia or tetraplegia. The biochemical defect has been identified as a deficiency of fatty aldehyde dehydrogenase (FALDH), which is part of an enzyme complex that converts fatty alcohols into fatty acids. Making use of the finding that FALDH is also involved in the degradation of phytol, we set up an enzymatic assay for the prenatal diagnosis of SLS in cultured chorionic villus fibroblasts (CVF) based on a deficiency in the conversion of phytol to phytenic acid. FALDH activity was assessed by incubating fibroblast homogenates with phytol in the presence of NAD+, followed by hexane extraction of the samples and quantification of phytenic acid production by gas chromatography-mass spectrometry (GC-MS). FALDH activity could be detected in cultured CVF cells derived from control fetuses and the activity was found to be markedly deficient in cultured CVF cells derived from an affected SLS fetus. The new assay described in this paper has advantages over previous assays and we conclude that it may well contribute to the prenatal detection of SLS.

Journal of inherited metabolic disease, 1999

In recent years tremendous progress has been made with respect to the enzymology of the mitochond... more In recent years tremendous progress has been made with respect to the enzymology of the mitochondrial fatty acid beta-oxidation machinery and defects therein. Firstly, a number of new mitochondrial beta-oxidation enzymes have been identified, including very-long-chain acyl-CoA dehydrogenase (VLCAD) and mitochondrial trifunctional protein (MTP). Secondly, the introduction of tandem MS for the analysis of plasma acylcarnitines has greatly facilitated the identification of patients with a defect in fatty acid oxidation (FAO). These two developments explain why the number of defined FAO disorders has increased dramatically, making FAO disorders the most rapidly growing group of inborn errors of metabolism. In this review we describe the current state of knowledge of the enzymes involved in the mitochondrial oxidation of straight-chain, branched-chain and (poly)unsaturated fatty acyl-CoAs as well as disorders of fatty acid oxidation. The laboratory diagnosis of these disorders is describ...

Inherited Metabolic Diseases, 2010

Enzyme functions in a particular metabolic pathway are best described by K m and V max values. Th... more Enzyme functions in a particular metabolic pathway are best described by K m and V max values. The central parameter in metabolic flux analysis is that of control strength, alternatively called flux control coefficient. It is described by the flux control coefficient which is set between 0 and 1. A flux control coefficient of 1 means that the particular enzyme has full control of flux through the pathway, whereas a flux control coefficient of 0 implies that the particular enzyme exerts virtually no control of flux. In any patient with a Zellweger spectrum-like phenotype in which very long-chain fatty acids have been found abnormal, a full enzymatic study in fibroblasts is warranted in order to resolve whether the patient has a defect in the biogenesis of peroxisomes or is affected by a single peroxisomal enzyme deficiency. The introduction of tandem mass spectrometry has revolutionized the diagnosis of fatty acid oxidation (FAO) disorders. Acylcarnitine analysis is the first-line test in patients suspected to suffer from an FAO disorder. If abnormal, enzyme studies should be performed to resolve the underlying enzymatic defect. Biochemical diagnostics of mitochondrial disorders usually involves a broad screening of mitochondrial enzyme activities and analysis of fluxes through the citric acid cycle and oxi-dative phosphorylation system. The analysis of fluxes can only be performed in freshly obtained tissue samples (usually muscle). Determination of the activity of lysosomal enzymes in leukocytes, plasma or dried blood spots, or in fibroblasts is the core in the laboratory diagnosis of lysosomal storage disorders.

Orphanet Journal of Rare Diseases, 2016

A call from the EU for the setup of European Reference Networks (ERNs) is expected to be launched... more A call from the EU for the setup of European Reference Networks (ERNs) is expected to be launched in the first quarter of 2016. ERNs are intended to improve the care for patients with low prevalent or rare diseases throughout the EU by, among other things, facilitating the pooling and exchange of experience and knowledge and the development of protocols and guidelines. In the past, for example where costly orphan drugs have been concerned, industry has played an important role in facilitating consensus meetings and publication of guidelines. The ERNs should provide a unique opportunity for healthcare professionals and patients to lead these activities in an independent way. However, currently costs for networking activities are not to be covered by EU funds and alternative sources of funding are being explored. There is growing concern that any involvement of the industry in the funding of ERNs and their core activities may create a risk of undue influence. To date, the European Commission has not been explicit in how industry will be engaged in ERNs. We believe that public funding and a conflict of interest policy are needed at the level of the ERNs, Centers of Expertise (CEs), healthcare professionals and patient organizations with the aim of maintaining scientific integrity and independence. Specific attention is needed where it concerns the development of clinical practice guidelines. A proposal for a conflict of interest policy is presented, which may support the development of a framework to facilitate collaboration, safeguard professional integrity and to establish and maintain public acceptability and trust among patients, their organizations and the general public.

Biochimica et Biophysica Acta (BBA) - Molecular Cell Research, 2006

Peroxisomal disorders are a group of inherited diseases in man in which either peroxisome biogene... more Peroxisomal disorders are a group of inherited diseases in man in which either peroxisome biogenesis or one or more peroxisomal functions are impaired. The peroxisomal disorders identified to date are usually classified in two groups including: (1) the disorders of peroxisome biogenesis, and (2) the single peroxisomal enzyme deficiencies. This review is focused on the second group of disorders, which currently includes ten different diseases in which the mutant gene affects a protein involved in one of the following peroxisomal functions: (1) ether phospholipid (plasmalogen) biosynthesis; (2) fatty acid beta-oxidation; (3) peroxisomal alpha-oxidation; (4) glyoxylate detoxification, and (5) H 2 O 2 metabolism.

Refsum disease is characterized by anosmia and early-onset retinitis pigmentosa, which are both u... more Refsum disease is characterized by anosmia and early-onset retinitis pigmentosa, which are both universal findings with variable combinations of neuropathy, deafness, ataxia, and ichthyosis. Onset of symptoms ranges from age seven months to older than age 50 years. Cardiac arrhythmia and heart failure caused by cardiomyopathy are potentially severe health problems which develop later in life. The diagnosis of Refsum disease is suspected on the basis of clinical findings and a plasma phytanic acid concentration greater than 200 µmol/L in most affected individuals. Confirmation of the diagnosis requires either (1) molecular genetic testing to identify biallelic pathogenic variants in either PHYH (encoding phytanoyl-CoA hydroxylase), which accounts for more than 90% of Refsum disease, or PEX7 (encoding the PTS2 receptor), which accounts for less than 10% of Refsum disease; or (2) enzyme analysis to identify deficiency of either phytanoyl-CoA hydroxylase enzyme activity or the peroxisome-targeting signal type 2 receptor. Treatment of manifestations: Dietary restriction of phytanic acid intake helps resolve ichthyosis, sensory neuropathy, and ataxia. Supportive treatment includes hydrating creams for ichthyosis and drugs for cardiac arrhythmias and cardiomyopathy. Plasmapheresis or lipid apheresis is used for acute arrhythmias or extreme weakness. A high-calorie diet prevents mobilization of phytanic acid into the plasma. Agents/circumstances to avoid: Fasting and/or sudden weight loss; ibuprofen. Evaluation of relatives at risk: Testing of sibs of a proband ensures early treatment to reduce plasma phytanic acid concentration before symptoms occur. Refsum disease is inherited in an autosomal recessive manner. At conception, each sib of an affected individual has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25%

Methods in molecular biology (Clifton, N.J.), 2017

The peroxisomal disorders (PDs) are a heterogeneous group of genetic diseases in man caused by an... more The peroxisomal disorders (PDs) are a heterogeneous group of genetic diseases in man caused by an impairment in peroxisome biogenesis or one of the metabolic functions of peroxisomes. Thanks to the revolutionary technical developments in gene sequencing methods and their increased use in patient diagnosis, the field of genetic diseases in general and peroxisomal disorders in particular has dramatically changed in the last few years. Indeed, several novel peroxisomal disorders have been identified recently and in addition it has been realized that the phenotypic spectrum of patients affected by a PD keeps widening, which makes clinical recognition of peroxisomal patients increasingly difficult. Here, we describe these new developments and provide guidelines for the clinical and laboratory diagnosis of peroxisomal patients.

Molecular Machines Involved in Peroxisome Biogenesis and Maintenance, 2014

Peroxisomes play a crucial role in cellular metabolism as exemplified by the devastating conseque... more Peroxisomes play a crucial role in cellular metabolism as exemplified by the devastating consequences caused by deficiencies of one or more peroxisomal enzymes in humans. The major metabolic functions of peroxisomes in humans include fatty acid beta-oxidation, etherphospholipid biosynthesis, fatty acid alpha-oxidation; glyoxylate detoxification, bile acid synthesis, l-pipecolic acid oxidation, and docosahexaenoic acid (DHA) formation. Except from the bile acids which are true metabolic end products of bile acid formation in the liver as generated in peroxisomes, all the other products of peroxisome metabolism are not true end products but require continued metabolism in other organelles to reach their final fate. This explains the crosstalk between peroxisomes and other subcellular organelles notably mitochondria and the endoplasmic reticulum. In this review we will discuss the metabolic functions of peroxisomes in humans and the crosstalk with other subcellular organelles. In addition we will discuss the pathophysiological consequences of genetic defects in peroxisome metabolism.