Publications by authors named "Stephan Kemp"

70 Publications

Metabolic rerouting via SCD1 induction impacts X-linked adrenoleukodystrophy.

J Clin Invest 2021 Apr;131(8)

Laboratory Genetic Metabolic Diseases, Department of Clinical Chemistry, Amsterdam UMC, Amsterdam Gastroenterology & Metabolism, University of Amsterdam, Amsterdam, Netherlands.

X-linked adrenoleukodystrophy (ALD) is a progressive neurodegenerative disease caused by mutations in ABCD1, the peroxisomal very long-chain fatty acid (VLCFA) transporter. ABCD1 deficiency results in accumulation of saturated VLCFAs. A drug screen using a phenotypic motor assay in a zebrafish ALD model identified chloroquine as the top hit. Chloroquine increased expression of stearoyl-CoA desaturase-1 (scd1), the enzyme mediating fatty acid saturation status, suggesting that a shift toward monounsaturated fatty acids relieved toxicity. In human ALD fibroblasts, chloroquine also increased SCD1 levels and reduced saturated VLCFAs. Conversely, pharmacological inhibition of SCD1 expression led to an increase in saturated VLCFAs, and CRISPR knockout of scd1 in zebrafish mimicked the motor phenotype of ALD zebrafish. Importantly, saturated VLCFAs caused ER stress in ALD fibroblasts, whereas monounsaturated VLCFA did not. In parallel, we used liver X receptor (LXR) agonists to increase SCD1 expression, causing a shift from saturated toward monounsaturated VLCFA and normalizing phospholipid profiles. Finally, Abcd1-/y mice receiving LXR agonist in their diet had VLCFA reductions in ALD-relevant tissues. These results suggest that metabolic rerouting of saturated to monounsaturated VLCFAs may alleviate lipid toxicity, a strategy that may be beneficial in ALD and other peroxisomal diseases in which VLCFAs play a key role.
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http://dx.doi.org/10.1172/JCI142500DOI Listing
April 2021

MRI surveillance of boys with X-linked adrenoleukodystrophy identified by newborn screening: Meta-analysis and consensus guidelines.

J Inherit Metab Dis 2020 Dec 29. Epub 2020 Dec 29.

Division of Neurogenetics and The Moser Center for Leukodystrophies, Kennedy Krieger Institute, Johns Hopkins University, Baltimore, Maryland, USA.

Background: Among boys with X-Linked adrenoleukodystrophy, a subset will develop childhood cerebral adrenoleukodystrophy (CCALD). CCALD is typically lethal without hematopoietic stem cell transplant before or soon after symptom onset. We sought to establish evidence-based guidelines detailing the neuroimaging surveillance of boys with neurologically asymptomatic adrenoleukodystrophy.

Methods: To establish the most frequent age and diagnostic neuroimaging modality for CCALD, we completed a meta-analysis of relevant studies published between January 1, 1970 and September 10, 2019. We used the consensus development conference method to incorporate the resulting data into guidelines to inform the timing and techniques for neuroimaging surveillance. Final guideline agreement was defined as >80% consensus.

Results: One hundred twenty-three studies met inclusion criteria yielding 1285 patients. The overall mean age of CCALD diagnosis is 7.91 years old. The median age of CCALD diagnosis calculated from individual patient data is 7.0 years old (IQR: 6.0-9.5, n = 349). Ninety percent of patients were diagnosed between 3 and 12. Conventional MRI was most frequently reported, comprised most often of T2-weighted and contrast-enhanced T1-weighted MRI. The expert panel achieved 95.7% consensus on the following surveillance parameters: (a) Obtain an MRI between 12 and 18 months old. (b) Obtain a second MRI 1 year after baseline. (c) Between 3 and 12 years old, obtain a contrast-enhanced MRI every 6 months. (d) After 12 years, obtain an annual MRI.

Conclusion: Boys with adrenoleukodystrophy identified early in life should be monitored with serial brain MRIs during the period of highest risk for conversion to CCALD.
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http://dx.doi.org/10.1002/jimd.12356DOI Listing
December 2020

Evolution of adrenoleukodystrophy model systems.

J Inherit Metab Dis 2020 Dec 29. Epub 2020 Dec 29.

Department of Pediatric Neurology, Emma Children's Hospital, Amsterdam UMC, Amsterdam Leukodystrophy Center, Amsterdam Neuroscience, University of Amsterdam, Amsterdam, The Netherlands.

X-linked adrenoleukodystrophy (ALD) is a neurometabolic disorder affecting the adrenal glands, testes, spinal cord and brain. The disease is caused by mutations in the ABCD1 gene resulting in a defect in peroxisomal degradation of very long-chain fatty acids and their accumulation in plasma and tissues. Males with ALD have a near 100% life-time risk to develop myelopathy. The life-time prevalence to develop progressive cerebral white matter lesions (known as cerebral ALD) is about 60%. Adrenal insufficiency occurs in about 80% of male patients. In adulthood, 80% of women with ALD also develop myelopathy, but adrenal insufficiency or cerebral ALD are very rare. The complex clinical presentation and the absence of a genotype-phenotype correlation are complicating our understanding of the disease. In an attempt to understand the pathophysiology of ALD various model systems have been developed. While these model systems share the basic genetics and biochemistry of ALD they fail to fully recapitulate the complex neurodegenerative etiology of ALD. Each model system recapitulates certain aspects of the disorder. This exposes the complexity of ALD and therefore the challenge to create a comprehensive model system to fully understand ALD. In this review, we provide an overview of the different ALD modeling strategies from single-celled to multicellular organisms and from in vitro to in vivo approaches, and introduce how emerging iPSC-derived technologies could improve the understanding of this highly complex disorder.
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http://dx.doi.org/10.1002/jimd.12357DOI Listing
December 2020

The variability conundrum in neurometabolic degenerative diseases.

Mol Genet Metab 2020 12 6;131(4):367-369. Epub 2020 Nov 6.

Department of Pediatric Neurology, Amsterdam Leukodystrophy Center, Emma Children's Hospital, Amsterdam Neuroscience, Amsterdam University Medical Centers, University of Amsterdam, the Netherlands; Department of Clinical Chemistry, Laboratory Genetic Metabolic Diseases, Amsterdam University Medical Centers, Amsterdam Gastroenterology & Metabolism, University of Amsterdam, Amsterdam, the Netherlands.

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http://dx.doi.org/10.1016/j.ymgme.2020.11.002DOI Listing
December 2020

Plasma NfL and GFAP as biomarkers of spinal cord degeneration in adrenoleukodystrophy.

Ann Clin Transl Neurol 2020 11 13;7(11):2127-2136. Epub 2020 Oct 13.

Department of Paediatric Neurology, Amsterdam Leukodystrophy Center, Emma Children's Hospital, Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, The Netherlands.

Objective: To explore the potential of neurofilament light (NfL) and glial fibrillary acidic protein (GFAP) as biomarkers of spinal cord degeneration in adrenoleukodystrophy, as objective treatment-outcome parameters are needed.

Methods: Plasma NfL and GFAP levels were measured in 45 male and 47 female ALD patients and compared to a reference cohort of 73 healthy controls. For male patients, cerebrospinal fluid (CSF) samples (n = 33) and 1-year (n = 39) and 2-year (n = 18) follow-up data were also collected. Severity of myelopathy was assessed with clinical parameters: Expanded Disability Status Scale (EDSS), Severity Scoring system for Progressive Myelopathy (SSPROM), and timed up-and-go.

Results: NfL and GFAP levels were higher in male (P < 0.001, effect size (partial ƞ ) NfL = 0.49, GFAP = 0.13) and female (P < 0.001, effect size NfL = 0.19, GFAP = 0.23) patients compared to controls; levels were higher in both symptomatic and asymptomatic patients. In male patients, NfL levels were associated with all three clinical parameters of severity of myelopathy (EDSS, SSPROM, and timed up-and go), while GFAP in male and NfL and GFAP in female patients were not. Changes in clinical parameters during follow-up did not correlate with (changes in) NfL or GFAP levels. Plasma and CSF NfL were strongly correlated (r = 0.60, P < 0.001), but plasma and CSF GFAP were not (r = 0.005, P = 0.98).

Interpretation: Our study illustrates the potential of plasma NfL as biomarker of spinal cord degeneration in adrenoleukodystrophy, which was superior to plasma GFAP in our cohort.
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http://dx.doi.org/10.1002/acn3.51188DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7664277PMC
November 2020

Targeting foam cell formation in inflammatory brain diseases by the histone modifier MS-275.

Ann Clin Transl Neurol 2020 11 30;7(11):2161-2177. Epub 2020 Sep 30.

Department of Pathobiology of the Nervous System, Centre for Brain Research, Medical University of Vienna, Vienna, 1090, Austria.

Objective: To assess class I-histone deacetylase (HDAC) inhibition on formation of lipid-accumulating, disease-promoting phagocytes upon myelin load in vitro, relevant for neuroinflammatory disorders like multiple sclerosis (MS) and cerebral X-linked adrenoleukodystrophy (X-ALD).

Methods: Immunohistochemistry on postmortem brain tissue of acute MS (n = 6) and cerebral ALD (n = 4) cases to analyze activation and foam cell state of phagocytes. RNA-Seq of in vitro differentiated healthy macrophages (n = 8) after sustained myelin-loading to assess the metabolic shift associated with foam cell formation. RNA-Seq analysis of genes linked to lipid degradation and export in MS-275-treated human HAP1 cells and RT-qPCR analysis of HAP1 cells knocked out for individual members of class I HDACs or the corresponding enzymatically inactive knock-in mutants. Investigation of intracellular lipid/myelin content after MS-275 treatment of myelin-laden human foam cells. Analysis of disease characteristic very long-chain fatty acid (VLCFA) metabolism and inflammatory state in MS-275-treated X-ALD macrophages.

Results: Enlarged foam cells coincided with a pro-inflammatory, lesion-promoting phenotype in postmortem tissue of MS and cerebral ALD patients. Healthy in vitro myelin laden foam cells upregulated genes linked to LXRα/PPARγ pathways and mimicked a program associated with tissue repair. Treating these cells with MS-275, amplified this gene transcription program and significantly reduced lipid and cholesterol accumulation and, thus, foam cell formation. In macrophages derived from X-ALD patients, MS-275 improved the disease-associated alterations of VLCFA metabolism and reduced the pro-inflammatory status of these cells.

Interpretation: These findings identify class I-HDAC inhibition as a potential novel strategy to prevent disease promoting foam cell formation in CNS inflammation.
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http://dx.doi.org/10.1002/acn3.51200DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7664285PMC
November 2020

Comparison of the Diagnostic Performance of C26:0-Lysophosphatidylcholine and Very Long-Chain Fatty Acids Analysis for Peroxisomal Disorders.

Front Cell Dev Biol 2020 29;8:690. Epub 2020 Jul 29.

Department of Clinical Chemistry, Laboratory Genetic Metabolic Diseases, Amsterdam UMC, Amsterdam Gastroenterology and Metabolism, University of Amsterdam, Amsterdam, Netherlands.

Peroxisomes are subcellular organelles that are involved in various important physiological processes such as the oxidation of fatty acids and the biosynthesis of bile acids and plasmalogens. The gold standard in the diagnostic work-up for patients with peroxisomal disorders is the analysis of very long-chain fatty acid (VLCFA) levels in plasma. Alternatively, C26:0-lysophosphatidylcholine (C26:0-LPC) can be measured in dried blood spots (DBS) using liquid chromatography tandem mass spectrometry (LC-MS/MS); a fast and easy method but not yet widely used. Currently, little is known about the correlation of C26:0-LPC in DBS and C26:0-LPC in plasma, and how C26:0-LPC analysis compares to VLCFA analysis in diagnostic performance. We investigated the correlation between C26:0-LPC levels measured in DBS and plasma prepared from the same blood sample. For this analysis we included 43 controls and 38 adrenoleukodystrophy (ALD) (21 males and 17 females) and 33 Zellweger spectrum disorder (ZSD) patients. In combined control and patient samples there was a strong positive correlation between DBS C26:0-LPC and plasma C26:0-LPC, with a Spearman's rank correlation coefficient of (114) = 0.962, < 0.001. These data show that both plasma and DBS are suitable to determine blood C26:0-LPC levels and that there is a strong correlation between C26:0-LPC levels in both matrices. Following this, we investigated how VLCFA and C26:0-LPC analysis compare in diagnostic performance for 67 controls, 26 ALD males, 19 ALD females, and 35 ZSD patients. For C26:0-LPC, all ALD and ZSD samples had C26:0-LPC levels above the upper limit of the reference range. For C26:0, one out of 67 controls had C26:0 levels above the upper reference range. For 1 out of 26 (1/26) ALD males, 1/19 ALD females and 3/35 ZSD patients, the C26:0 concentration was within the reference range. The C26:0/C22:0 ratio was within the reference range for 0/26 ALD males, 1/19 ALD females and 2/35 ZSD patients. Overall, these data demonstrate that C26:0-LPC analysis has a superior diagnostic performance compared to VLCFA analysis (C26:0 and C26:0/C22:0 ratio) in all patient groups. Based on our results we recommend implementation of C26:0-LPC analysis in DBS and/or plasma in the diagnostic work-up for peroxisomal disorders.
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http://dx.doi.org/10.3389/fcell.2020.00690DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7438929PMC
July 2020

Postural Body Sway as Surrogate Outcome for Myelopathy in Adrenoleukodystrophy.

Front Physiol 2020 17;11:786. Epub 2020 Jul 17.

Department of Pediatric Neurology, Amsterdam Leukodystrophy Center, Emma Children's Hospital, Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, Netherlands.

Background: Myelopathy is the core clinical manifestation of adrenoleukodystrophy (ALD), which is the most common peroxisomal disorder. Development of therapies requires sensitive and clinically relevant outcome measures. Together with spastic paraparesis, balance disturbance is the main cause of disability from myelopathy in ALD. In this cross-sectional study, we evaluated whether postural body sway - a measure of balance - could serve as a surrogate outcome in clinical trials.

Methods: Forty-eight male ALD patients and 49 age-matched healthy male controls were included in this study. We compared sway amplitude and sway path of ALD patients to controls. We then correlated the body sway parameters showing the largest between-group differences with clinical measures of severity of myelopathy. To correct for age, we performed multiple linear regression analysis with age and severity of myelopathy as independent variables.

Results: All body sway parameters were significantly higher in patients than in controls, with medium to large effect sizes ( = 0.43-0.66, < 0.001). In the subgroup of asymptomatic patients, body sway amplitude was also higher, but the difference with controls was smaller than for symptomatic patients (effect size = 0.38-0.46). We found moderate to strong correlations between body sway amplitude and clinical severity of myelopathy ( = 0.40-0.79, < 0.005). After correction for age, severity of myelopathy was a significant predictor of body sway amplitude in all regression models.

Conclusions: These results indicate that postural body sway may serve as a surrogate outcome for myelopathy in ALD. Such outcomes are important to evaluate new therapies in clinical trials. Further longitudinal studies are needed and ongoing in this cohort.
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http://dx.doi.org/10.3389/fphys.2020.00786DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7379508PMC
July 2020

Multi-Omic Approach to Identify Phenotypic Modifiers Underlying Cerebral Demyelination in X-Linked Adrenoleukodystrophy.

Front Cell Dev Biol 2020 25;8:520. Epub 2020 Jun 25.

Center for Molecular Medicine and Therapeutics, BC Children's Hospital Research Institute, University of British Columbia, Vancouver, BC, Canada.

X-linked adrenoleukodystrophy (ALD) is a peroxisomal metabolic disorder with a highly complex clinical presentation. ALD is caused by mutations in the gene, and is characterized by the accumulation of very long-chain fatty acids in plasma and tissues. Disease-causing mutations are 'loss of function' mutations, with no prognostic value with respect to the clinical outcome of an individual. All male patients with ALD develop spinal cord disease and a peripheral neuropathy in adulthood, although age of onset is highly variable. However, the lifetime prevalence to develop progressive white matter lesions, termed cerebral ALD (CALD), is only about 60%. Early identification of transition to CALD is critical since it can be halted by allogeneic hematopoietic stem cell therapy only in an early stage. The primary goal of this study is to identify molecular markers which may be prognostic of cerebral demyelination from a simple blood sample, with the hope that blood-based assays can replace the current protocols for diagnosis. We collected six well-characterized brother pairs affected by ALD and discordant for the presence of CALD and performed multi-omic profiling of blood samples including genome, epigenome, transcriptome, metabolome/lipidome, and proteome profiling. In our analysis we identify discordant genomic alleles present across all families as well as differentially abundant molecular features across the omics technologies. The analysis was focused on univariate modeling to discriminate the two phenotypic groups, but was unable to identify statistically significant candidate molecular markers. Our study highlights the issues caused by a large amount of inter-individual variation, and supports the emerging hypothesis that cerebral demyelination is a complex mix of environmental factors and/or heterogeneous genomic alleles. We confirm previous observations about the role of immune response, specifically auto-immunity and the potential role of PFN1 protein overabundance in CALD in a subset of the families. We envision our methodology as well as dataset has utility to the field for reproducing previous or enabling future modifier investigations.
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http://dx.doi.org/10.3389/fcell.2020.00520DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7330173PMC
June 2020

Adrenoleukodystrophy Newborn Screening in the Netherlands (SCAN Study): The X-Factor.

Front Cell Dev Biol 2020 17;8:499. Epub 2020 Jun 17.

Department of Clinical Chemistry, Laboratory Genetic Metabolic Diseases, Amsterdam UMC, Amsterdam Gastroenterology and Metabolism, University of Amsterdam, Amsterdam, Netherlands.

X-linked adrenoleukodystrophy (ALD) is a devastating metabolic disorder affecting the adrenal glands, brain and spinal cord. Males with ALD are at high risk for developing adrenal insufficiency or progressive cerebral white matter lesions (cerebral ALD) at an early age. If untreated, cerebral ALD is often fatal. Women with ALD are not at risk for adrenal insufficiency or cerebral ALD. Newborn screening for ALD in males enables prospective monitoring and timely therapeutic intervention, thereby preventing irreparable damage and saving lives. The Dutch Ministry of Health adopted the advice of the Dutch Health Council to add a boys-only screen for ALD to the newborn screening panel. The recommendation made by the Dutch Health Council to only screen boys, without gathering any unsolicited findings, posed a challenge. We were invited to set up a prospective pilot study that became known as the SCAN study (SCreening for ALD in the Netherlands). The objectives of the SCAN study are: (1) designing a boys-only screening algorithm that identifies males with ALD and without unsolicited findings; (2) integrating this algorithm into the structure of the Dutch newborn screening program without harming the current newborn screening; (3) assessing the practical and ethical implications of screening only boys for ALD; and (4) setting up a comprehensive follow-up that is both patient- and parent-friendly. We successfully developed and validated a screening algorithm that can be integrated into the Dutch newborn screening program. The core of this algorithm is the "X-counter." The X-counter determines the number of X chromosomes without assessing the presence of a Y chromosome. The X-counter is integrated as second tier in our 4-tier screening algorithm. Furthermore, we ensured that our screening algorithm does not result in unsolicited findings. Finally, we developed a patient- and parent-friendly, multidisciplinary, centralized follow-up protocol. Our boys-only ALD screening algorithm offers a solution for countries that encounter similar ethical considerations, for ALD as well as for other X-linked diseases. For ALD, this alternative boys-only screening algorithm may result in a more rapid inclusion of ALD in newborn screening programs worldwide.
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http://dx.doi.org/10.3389/fcell.2020.00499DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7311642PMC
June 2020

Vorinostat in the acute neuroinflammatory form of X-linked adrenoleukodystrophy.

Ann Clin Transl Neurol 2020 05 2;7(5):639-652. Epub 2020 May 2.

Department of Pathobiology of the Nervous System, Center for Brain Research, Medical University of Vienna, Vienna, Austria.

Objective: To identify a pharmacological compound targeting macrophages, the most affected immune cells in inflammatory X-linked adrenoleukodystrophy (cerebral X-ALD) caused by ABCD1 mutations and involved in the success of hematopoietic stem cell transplantation and gene therapy.

Methods: A comparative database analysis elucidated the epigenetic repressing mechanism of the related ABCD2 gene in macrophages and identified the histone deacetylase (HDAC) inhibitor Vorinostat as a compound to induce ABCD2 in these cells to compensate for ABCD1 deficiency. In these cells, we investigated ABCD2 and pro-inflammatory gene expression, restoration of defective peroxisomal β-oxidation activity, accumulation of very long-chain fatty acids (VLCFAs) and their differentiation status. We investigated ABCD2 and pro-inflammatory gene expression, restoration of defective peroxisomal ß-oxidation activity, accumulation of very long-chain fatty acids (VLCFA) and differentiation status. Three advanced cerebral X-ALD patients received Vorinostat and CSF and MRI diagnostics was carried out in one patient after 80 days of treatment.

Results: Vorinostat improved the metabolic defects in X-ALD macrophages by stimulating ABCD2 expression, peroxisomal ß-oxidation, and ameliorating VLCFA accumulation. Vorinostat interfered with pro-inflammatory skewing of X-ALD macrophages by correcting IL12B expression and further reducing monocyte differentiation. Vorinostat normalized the albumin and immunoglobulin CSF-serum ratios, but not gadolinium enhancement upon 80 days of treatment.

Interpretation: The beneficial effects of HDAC inhibitors on macrophages in X-ALD and the improvement of the blood-CSF/blood-brain barrier are encouraging for future investigations. In contrast with Vorinostat, less toxic macrophage-specific HDAC inhibitors might improve also the clinical state of X-ALD patients with advanced inflammatory demyelination.
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http://dx.doi.org/10.1002/acn3.51015DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7261758PMC
May 2020

Spinal cord atrophy as a measure of severity of myelopathy in adrenoleukodystrophy.

J Inherit Metab Dis 2020 07 1;43(4):852-860. Epub 2020 Mar 1.

Department of Pediatric Neurology, Emma Children's Hospital, Amsterdam University Medical Centers, Amsterdam, The Netherlands.

All men and most women with X-linked adrenoleukodystrophy (ALD) develop myelopathy in adulthood. As clinical trials with new potential disease-modifying therapies are emerging, sensitive outcome measures for quantifying myelopathy are needed. This prospective cohort study evaluated spinal cord size (cross-sectional area - CSA) and shape (eccentricity) as potential new quantitative outcome measures for myelopathy in ALD. Seventy-four baseline magnetic resonance imaging (MRI) scans, acquired in 42 male ALD patients and 32 age-matched healthy controls, and 26 follow-up scans of ALD patients were included in the study. We used routine T -weighted MRI sequences to measure mean CSA, eccentricity, right-left and anteroposterior diameters in the cervical spinal cord. We compared MRI measurements between groups and correlated CSA with clinical outcome measures of disease severity. Longitudinally, we compared MRI measurements between baseline and 1-year follow-up. CSA was significantly smaller in patients compared to controls on all measured spinal cord levels (P < .001). The difference was completely explained by the effect of the symptomatic subgroup. Furthermore, the spinal cord showed flattening (higher eccentricity and smaller anteroposterior diameters) in patients. CSA correlated strongly with all clinical measures of severity of myelopathy. There was no detectable change in CSA after 1-year follow-up. The cervical spinal cord in symptomatic ALD patients is smaller and flattened compared to controls, possibly due to atrophy of the dorsal columns. CSA is a reliable marker of disease severity and can be a valuable outcome measure in long-term follow-up studies in ALD. SYNOPSIS: A prospective cohort study in 42 adrenoleukodystrophy (ALD) patients and 32 controls demonstrated that the spinal cord cross-sectional area of patients is smaller compared to healthy controls and correlates with severity of myelopathy in patients, hence it could be valuable as a much needed surrogate outcome measure.
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http://dx.doi.org/10.1002/jimd.12226DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7383492PMC
July 2020

Longitudinal diffusion MRI as surrogate outcome measure for myelopathy in adrenoleukodystrophy.

Neurology 2019 12 12;93(23):e2133-e2143. Epub 2019 Nov 12.

From the Department of Paediatric Neurology, Emma Children's Hospital (I.C.H., W.J.C.v.B., J.M.B.W.V., M.E.), Laboratory Genetic Metabolic Diseases (S.K.), and Department of Biomedical Engineering & Physics (M.W.A.C.), Amsterdam UMC, University of Amsterdam, the Netherlands.

Objective: To prospectively determine the potential of diffusion MRI (dMRI) of the cervical spinal cord and the corticospinal tracts in brain as surrogate outcome measure for progression of myelopathy in men with adrenoleukodystrophy, as better outcome measures to quantify progression of myelopathy would enable clinical trials with fewer patients and shorter follow-up.

Methods: Clinical assessment of myelopathy included Expanded Disability Status Scale (EDSS), Severity Scoring System for Progressive Myelopathy (SSPROM), Timed Up-and-Go, and 6-Minute Walk Test. Applied dMRI metrics included fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity.

Results: Data were available for 33 controls and 52 patients. First, cross-sectionally, differences between groups (controls vs patients; controls vs asymptomatic patients vs symptomatic patients) were statistically significant for fractional anisotropy, mean diffusivity, and radial diffusivity in spinal cord and brain corticospinal tracts (effect size 0.31-0.68). Correlations between dMRI metrics and clinical measures were moderate to strong (correlation coefficient 0.35-0.60). Second, longitudinally (n = 36), change on clinical measures was significant after 2-year follow-up for EDSS, SSPROM, and Timed Up-and-Go ( ≤ 0.021, effect size ≤0.14). Change on brain fractional anisotropy and radial diffusivity was slightly larger ( ≤ 0.002, effect sizes 0.16-0.28). In addition, a statistically significant change was detectable in asymptomatic patients using brain dMRI and not using the clinical measures. Change on clinical measures did not correlate to change on dMRI metrics.

Conclusion: Although effect sizes were small, our prospective data illustrate the potential of dMRI as surrogate outcome measure for progression of myelopathy in men with adrenoleukodystrophy.
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http://dx.doi.org/10.1212/WNL.0000000000008572DOI Listing
December 2019

Disease progression in women with X-linked adrenoleukodystrophy is slow.

Orphanet J Rare Dis 2019 02 7;14(1):30. Epub 2019 Feb 7.

Department of Pediatric Neurology/Emma Children's Hospital, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.

Background: Over 80% of women with X-linked adrenoleukodystrophy (ALD) develop spinal cord disease in adulthood for which treatment is supportive only. For future clinical trials quantitative data on disease progression rates are essential. Moreover, diagnosis can be challenging in ALD women, as the most important diagnostic biomarker is normal in 15-20%. Better biomarkers are needed. The purpose of this single centre cross-sectional follow-up study in women with ALD was to assess whether Expanded Disability Status Scale (EDSS), AMC Linear Disability Scale (ALDS) and Short Form (36) Health Survey (SF-36) can detect disease progression and to model the effect of age and duration of symptoms on the rate of progression. Moreover, we performed a pilot study to assess if a semi-targeted lipidomics approach can identify possible new diagnostic biomarkers.

Results: In this study 46 women (baseline clinical data published by our group previously) were invited for a follow-up visit. Newly identified women at our center were also recruited. We analysed 65 baseline and 34 follow-up assessments. Median time between baseline and follow-up was 7.8 years (range 6.4-8.7). Mean age at baseline was 49.2 ± 14.2 years, at follow-up 55.4 ± 10.1. EDSS increased significantly (+ 0.08 points/year), but the other outcome measures did not. Increasing age and duration of symptoms were associated with more disability. For the pilot study we analysed plasma of 20 ALD women and 10 controls with ultra-high performance liquid chromatography coupled to high-resolution mass spectrometry, which identified 100 potential biomarker ratios with strong differentiating properties and non-overlapping data distributions between ALD women and controls.

Conclusions: Progression of spinal cord disease can be detected with EDSS, but not with ALDS or SF-36 after a follow-up period of almost 8 years. Moreover, age and the duration of symptoms seem positively associated with the rate of progression. Although a significant progression was measurable, it was below the rate generally conceived as clinically relevant. Therefore, EDSS, ALDS and SF-36 are not suitable as primary outcome measures in clinical trials for spinal cord disease in ALD women. In addition, a semi-targeted lipidomics approach can identify possible new diagnostic biomarkers for women with ALD.
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http://dx.doi.org/10.1186/s13023-019-1008-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6367840PMC
February 2019

Translational Metabolism: A multidisciplinary approach towards precision diagnosis of inborn errors of metabolism in the omics era.

J Inherit Metab Dis 2019 03 5;42(2):197-208. Epub 2019 Feb 5.

Laboratory Genetic Metabolic Diseases, Department of Clinical Chemistry, Emma Children's Hospital, Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, The Netherlands.

The laboratory diagnosis of inborn errors of metabolism has been revolutionized in recent years, thanks to the amazing developments in the field of DNA sequencing including whole exome and whole genome sequencing (WES and WGS). Interpretation of the results coming from WES and/or WGS analysis is definitely not trivial especially since the biological relevance of many of the variants identified by WES and/or WGS, have not been tested experimentally and prediction programs like POLYPHEN-2 and SIFT are far from perfect. Correct interpretation of WES and/or WGS results can only be achieved by performing functional studies at multiple levels (different metabolomics platforms, enzymology, in vitro and in vivo flux analysis), often requires studies in model organisms like zebra fish, Caenorhabditis elegans, Saccharomyces cerevisiae, mutant mice and others, and also requires the input of many different disciplines to make this Translational Metabolism approach effective.
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http://dx.doi.org/10.1002/jimd.12008DOI Listing
March 2019

Progression of myelopathy in males with adrenoleukodystrophy: towards clinical trial readiness.

Brain 2019 02;142(2):334-343

Department of Paediatric Neurology/Emma Children's Hospital, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands.

Males with adrenoleukodystrophy develop progressive myelopathy causing severe disability later in life. No treatment is currently available, but new disease-modifying therapies are under development. Knowledge of the natural history of the myelopathy is of paramount importance for evaluation of these therapies in clinical trials, but prospective data on disease progression are lacking. We performed a prospective observational cohort study to quantify disease progression over 2 years of follow-up. Signs and symptoms, functional outcome measures and patient-reported outcomes were assessed at baseline, 1 and 2 years of follow-up. We included 46 male adrenoleukodystrophy patients (median age 45.5 years, range 16-71). Frequency of myelopathy at baseline increased with age from 30.8% (<30 years) to 94.7% (>50 years). Disease progression was measured in the patients who were symptomatic at baseline (n = 24) or became symptomatic during follow-up (n = 1). Significant progression was detected with the functional outcome measures and quantitative vibration measurements. Over 2 years of follow-up, Expanded Disability Status Score increased by 0.34 points (P = 0.034), Severity Scoring system for Progressive Myelopathy decreased by 2.78 points (P = 0.013), timed up-and-go increased by 0.82 s (P = 0.032) and quantitative vibration measurement at the hallux decreased by 0.57 points (P = 0.040). Changes over 1-year follow-up were not significant, except for the 6-minute walk test that decreased by 19.67 meters over 1 year (P = 0.019). None of the patient-reported outcomes were able to detect disease progression. Our data show that progression of myelopathy in adrenoleukodystrophy can be quantified using practical and clinically relevant outcome measures. These results will help in the design of clinical trials and the development of new biomarkers for the myelopathy of adrenoleukodystrophy.10.1093/brain/awy299_video1awy299media15995811923001.
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http://dx.doi.org/10.1093/brain/awy299DOI Listing
February 2019

Intrathecal Adeno-Associated Viral Vector-Mediated Gene Delivery for Adrenomyeloneuropathy.

Hum Gene Ther 2019 05 18;30(5):544-555. Epub 2018 Dec 18.

1 Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.

Mutations in the gene encoding the peroxisomal ATP-binding cassette transporter () cause elevations in very long-chain fatty acids (VLCFAs) and the neurodegenerative disease adrenoleukodystrophy (ALD). In most adults, this manifests as the spinal cord axonopathy adrenomyeloneuropathy (AMN). A challenge in virus-based gene therapy in AMN is how to achieve functional gene correction to the entire spinal cord while minimizing leakage into the systemic circulation, which could contribute to toxicity. In the present study, we used an osmotic pump to deliver adeno-associated viral (AAV) vector into the lumbar cerebrospinal fluid space in mice. We report that slow intrathecal delivery of recombinant AAV serotype 9 (rAAV9) achieves efficient gene transfer across the spinal cord and dorsal root ganglia as demonstrated with two different transgenes, and . In the mouse, gene correction after continuous rAAV9-CBA-h delivery led to a 20% decrease in VLCFA levels in spinal cord compared with controls. The major cell types transduced were astrocytes, vascular endothelial cells, and neurons. Importantly, rAAV9 delivered intrathecally by osmotic pump, in contrast to bolus injection, reduced systemic leakage into peripheral organs, particularly liver and heart tissue.
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http://dx.doi.org/10.1089/hum.2018.079DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6909708PMC
May 2019

The Natural History of Adrenal Insufficiency in X-Linked Adrenoleukodystrophy: An International Collaboration.

J Clin Endocrinol Metab 2019 01;104(1):118-126

Department of Neurology, Massachusetts General Hospital, Boston, Massachusetts.

Context: Primary adrenal insufficiency is an important clinical manifestation of X-linked adrenoleukodystrophy (ALD). Other manifestations include spinal cord disease and/or inflammatory demyelinating cerebral disease. Implementation of newborn screening requires natural history data to develop follow-up recommendations.

Objective: To delineate the natural history of adrenal insufficiency in male patients with ALD and to assess associations between the risk for developing adrenal insufficiency, spinal cord disease, or cerebral disease and plasma C26:0/C22:0 and C24:0/C22:0 ratios, which are diagnostic biomarkers for ALD.

Design: Retrospective review of medical records.

Setting: Two international tertiary referral centers of expertise for ALD.

Patients: Male patients with ALD followed at the centers between 2002 and 2016.

Main Outcome Measures: The primary endpoint was adrenal insufficiency; secondary endpoints were spinal cord and cerebral disease.

Results: Data on 159 male patients was available. The probability of developing adrenal insufficiency was described with survival analysis. Median time until adrenal insufficiency was 14 years (95% CI, 9.70 to 18.30 years). The cumulative proportion of patients who developed adrenal insufficiency was age-dependent and highest in early childhood [0 to 10 years, 46.8% (SEM 0.041%); 11 to 40 years, 28.6% (SEM, 0.037%); >40 years, 5.6% (SEM, 0.038%)]. No association between clinical manifestations and plasma ratios was detected with Cox model or Spearman correlation.

Conclusions: Lifetime prevalence of adrenal insufficiency in male patients with ALD is ~80%. Adrenal insufficiency risk is time-dependent and warrants age-dependent follow-up. Besides on-demand testing if symptoms manifest, we suggest a minimum of adrenal testing every 4 to 6 months for patients age ≤10 years, annual testing for those age 11 to 40 years, and solely on-demand testing for those age >40 years.
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http://dx.doi.org/10.1210/jc.2018-01307DOI Listing
January 2019

Stability of the ABCD1 Protein with a Missense Mutation: A Novel Approach to Finding Therapeutic Compounds for X-Linked Adrenoleukodystrophy.

JIMD Rep 2019 21;44:23-31. Epub 2018 Jun 21.

Department of Biological Chemistry, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan.

Mutations in the ABCD1 gene that encodes peroxisomal ABCD1 protein cause X-linked adrenoleukodystrophy (X-ALD), a rare neurodegenerative disorder. More than 70% of the patient fibroblasts with this missense mutation display either a lack or reduction of the ABCD1 protein because of posttranslational degradation. In this study, we analyzed the stability of the missense mutant ABCD1 proteins (p.A616T, p.R617H, and p.R660W) in X-ALD fibroblasts and found that the mutant ABCD1 protein p.A616T has the capacity to recover its function by incubating at low temperature. In the case of such a mutation, chemical compounds that stabilize mutant ABCD1 proteins could be therapeutic candidates. Here, we prepared CHO cell lines stably expressing ABCD1 proteins with a missense mutation in fusion with green fluorescent protein (GFP) at the C-terminal. The stability of each mutant ABCD1-GFP in CHO cells was similar to the corresponding mutant ABCD1 protein in X-ALD fibroblasts. Furthermore, it is of interest that the GFP at the C-terminal was degraded together with the mutant ABCD1 protein. These findings prompted us to use CHO cells expressing mutant ABCD1-GFP for a screening of chemical compounds that can stabilize the mutant ABCD1 protein. We established a fluorescence-based assay method for the screening of chemical libraries in an effort to find compounds that stabilize mutant ABCD1 proteins. The work presented here provides a novel approach to finding therapeutic compounds for X-ALD patients with missense mutations.
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http://dx.doi.org/10.1007/8904_2018_118DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6323035PMC
June 2018

Comparison of C26:0-carnitine and C26:0-lysophosphatidylcholine as diagnostic markers in dried blood spots from newborns and patients with adrenoleukodystrophy.

Mol Genet Metab 2017 12 28;122(4):209-215. Epub 2017 Oct 28.

Laboratory Genetic Metabolic Diseases, Department of Pediatrics, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands; Laboratory Genetic Metabolic Diseases, Departments of Clinical Chemistry, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands; Department of Pediatrics, Emma Children's Hospital, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands; Department of Pediatric Neurology, Emma Children's Hospital, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands. Electronic address:

X-linked adrenoleukodystrophy (ALD) is the most common leukodystrophy with a birth incidence of 1:14,700 live births. The disease is caused by mutations in ABCD1 and characterized by very long-chain fatty acids (VLCFA) accumulation. In childhood, male patients are at high-risk to develop adrenal insufficiency and/or cerebral demyelination. Timely diagnosis is essential. Untreated adrenal insufficiency can be life-threatening and hematopoietic stem cell transplantation is curative for cerebral ALD provided the procedure is performed in an early stage of the disease. For this reason, ALD is being added to an increasing number of newborn screening programs. ALD newborn screening involves the quantification of C26:0-lysoPC in dried blood spots which requires a dedicated method. C26:0-carnitine, that was recently identified as a potential new biomarker for ALD, has the advantage that it can be added as one more analyte to the routine analysis of amino acids and acylcarnitines already in use. The first objective of this study was a comparison of the sensitivity of C26:0-carnitine and C26:0-lysoPC in dried blood spots from control and ALD newborns both in a case-control study and in newborns included in the New York State screening program. While C26:0-lysoPC was elevated in all ALD newborns, C26:0-carnitine was elevated only in 83%. Therefore, C26:0-carnitine is not a suitable biomarker to use in ALD newborn screen. In women with ALD, plasma VLCFA analysis results in a false negative result in approximately 15-20% of cases. The second objective of this study was to compare plasma VLCFA analysis with C26:0-carnitine and C26:0-lysoPC in dried blood spots of women with ALD. Our results show that C26:0-lysoPC was elevated in dried blood spots from all women with ALD, including from those with normal plasma C26:0 levels. This shows that C26:0-lysoPC is a better and more accurate biomarker for ALD than plasma VLCFA levels. We recommend that C26:0-lysoPC be added to the routine biochemical array of diagnostic tests for peroxisomal disorders.
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http://dx.doi.org/10.1016/j.ymgme.2017.10.012DOI Listing
December 2017

Lipid-induced endoplasmic reticulum stress in X-linked adrenoleukodystrophy.

Biochim Biophys Acta Mol Basis Dis 2017 09 27;1863(9):2255-2265. Epub 2017 Jun 27.

Department of Clinical Chemistry, Laboratory Genetic Metabolic Diseases, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands; Department of Pediatrics, Emma Children's Hospital, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands. Electronic address:

X-linked adrenoleukodystrophy (ALD) is a progressive neurodegenerative disease that is caused by mutations in the ABCD1 gene and characterized by elevated levels of very long-chain fatty acids (VLCFA) in plasma and tissues, with the most pronounced increase in the central nervous system. Virtually all male patients develop adrenal insufficiency and myelopathy (adrenomyeloneuropathy), but a subset develops a fatal cerebral demyelinating disease (known as cerebral ALD). Female patients may also develop myelopathy, but adrenal insufficiency or leukodystrophy are very rare. ALD has been associated with mitochondrial dysfunction, oxidative stress and bioenergetic failure, but the mechanism by which VLCFA accumulation triggers these effects has not been resolved thus far. In this study, we used primary human fibroblasts from normal subjects and ALD patients to investigate whether VLCFA can induce endoplasmic reticulum stress. We show that saturated VLCFA (C26:0) induce endoplasmic reticulum stress in fibroblasts from ALD patients, but not in controls. Furthermore, there is a clear correlation between the chain-length of the fatty acid and the induction of endoplasmic reticulum stress. Exposure of ALD fibroblasts to C26:0, resulted in increased expression of additional endoplasmic reticulum stress markers (EDEM1, GADD34 and CHOP) and in lipoapoptosis. This new insight into the underlying mechanism of VLCFA-induced toxicity is of great importance for the development of a disease modifying treatment for ALD aimed at the normalization of VLCFA levels in tissues.
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http://dx.doi.org/10.1016/j.bbadis.2017.06.003DOI Listing
September 2017

Method for Measurement of Peroxisomal Very Long-Chain Fatty Acid Beta-Oxidation and De Novo C26:0 Synthesis Activity in Living Cells Using Stable-Isotope Labeled Docosanoic Acid.

Methods Mol Biol 2017 ;1595:45-54

Laboratory Genetic Metabolic Diseases (F0-226), Departments of Pediatrics and Clinical Chemistry, Academic Medical Center, University of Amsterdam, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands.

Peroxisomes are present in virtually every eukaryotic cell type with the exception of the mature erythrocyte. In higher eukaryotes, one of the main functions of peroxisomes is lipid metabolism by means of beta-oxidation of very long-chain fatty acids (VLCFA; ≥22 carbon atoms). A dysfunction in peroxisomal VLCFA beta-oxidation results in elevated VLCFA levels in cells, tissue, and plasma. Here, we describe a straightforward and sensitive method to measure peroxisomal beta-oxidation capacity in living cells using stable-isotope labeled docosanoic acid (D-C22:0).
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http://dx.doi.org/10.1007/978-1-4939-6937-1_5DOI Listing
May 2017

CYP4F2 affects phenotypic outcome in adrenoleukodystrophy by modulating the clearance of very long-chain fatty acids.

Biochim Biophys Acta 2016 10 15;1862(10):1861-70. Epub 2016 Jul 15.

INSERM U986, Le Kremlin-Bicêtre, Paris, France.

X-linked adrenoleukodystrophy (ALD) is a severe neurodegenerative disorder caused by the accumulation of very long-chain fatty acids (VLCFA) due to mutations in the ABCD1 gene. The phenotypic spectrum ranges from a fatal cerebral demyelinating disease in childhood (cerebral ALD) to a progressive myelopathy without cerebral involvement in adulthood (adrenomyeloneuropathy). Because ABCD1 mutations have no predictive value with respect to clinical outcome a role for modifier genes was postulated. We report that the CYP4F2 polymorphism rs2108622 increases the risk of developing cerebral ALD in Caucasian patients. The rs2108622 polymorphism (c.1297G>A) results in an amino acid substitution valine for methionine at position 433 (p.V433M). Using cellular models of VLCFA accumulation, we show that p.V433M decreases the conversion of VLCFA into very long-chain dicarboxylic acids by ω-oxidation, a potential escape route for the deficient peroxisomal β-oxidation of VLCFA in ALD. Although p.V433M does not affect the catalytic activity of CYP4F2 it reduces CYP4F2 protein levels markedly. These findings open perspectives for therapeutic interventions in a disease with currently limited treatment options.
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http://dx.doi.org/10.1016/j.bbadis.2016.07.006DOI Listing
October 2016

Adrenoleukodystrophy - neuroendocrine pathogenesis and redefinition of natural history.

Nat Rev Endocrinol 2016 10 17;12(10):606-15. Epub 2016 Jun 17.

Department of Pediatrics, Academisch Medisch Centrum, University of Amsterdam Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands.

X-Linked adrenoleukodystrophy (ALD) is a peroxisomal metabolic disorder with a highly complex clinical presentation. ALD is caused by mutations in the ABCD1 gene, which leads to the accumulation of very long-chain fatty acids in plasma and tissues. Virtually all men with ALD develop adrenal insufficiency and myelopathy. Approximately 60% of men develop progressive cerebral white matter lesions (known as cerebral ALD). However, one cannot identify these individuals until the early changes are seen using brain imaging. Women with ALD also develop myelopathy, but generally at a later age than men and adrenal insufficiency or cerebral ALD are very rare. Owing to the multisystem symptomatology of the disease, patients can be assessed by the paediatrician, general practitioner, endocrinologist or a neurologist. This Review describes current knowledge on the clinical presentation, diagnosis and treatment of ALD, and highlights gaps in our knowledge of the natural history of the disease owing to an absence of large-scale prospective cohort studies. Such studies are necessary for the identification of new prognostic biomarkers to improve care for patients with ALD, which is particularly relevant now that newborn screening for ALD is being introduced.
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http://dx.doi.org/10.1038/nrendo.2016.90DOI Listing
October 2016

C26:0-Carnitine Is a New Biomarker for X-Linked Adrenoleukodystrophy in Mice and Man.

PLoS One 2016 28;11(4):e0154597. Epub 2016 Apr 28.

Laboratory Genetic Metabolic Diseases, Departments of Pediatrics and Clinical Chemistry, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.

X-linked adrenoleukodystrophy (ALD), a progressive neurodegenerative disease, is caused by mutations in ABCD1 and characterized by very-long-chain fatty acids (VLCFA) accumulation. Virtually all males develop progressive myelopathy (AMN). A subset of patients, however, develops a fatal cerebral demyelinating disease (cerebral ALD). Hematopoietic stem cell transplantation is curative for cerebral ALD provided the procedure is performed in an early stage of the disease. Unfortunately, this narrow therapeutic window is often missed. Therefore, an increasing number of newborn screening programs are including ALD. To identify new biomarkers for ALD, we developed an Abcd1 knockout mouse with enhanced VLCFA synthesis either ubiquitous or restricted to oligodendrocytes. Biochemical analysis revealed VLCFA accumulation in different lipid classes and acylcarnitines. Both C26:0-lysoPC and C26:0-carnitine were highly elevated in brain, spinal cord, but also in bloodspots. We extended the analysis to patients and confirmed that C26:0-carnitine is also elevated in bloodspots from ALD patients. We anticipate that validation of C26:0-carnitine for the diagnosis of ALD in newborn bloodspots may lead to a faster inclusion of ALD in newborn screening programs in countries that already screen for other inborn errors of metabolism.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0154597PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4849772PMC
April 2017

Pathogenicity of novel ABCD1 variants: The need for biochemical testing in the era of advanced genetics.

Mol Genet Metab 2016 06 3;118(2):123-7. Epub 2016 Apr 3.

Laboratory Genetic Metabolic Diseases, Departments of Pediatrics and Clinical Chemistry, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands; Departments of Pediatrics and Pediatric Neurology, Emma Children's Hospital, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands. Electronic address:

X-linked adrenoleukodystrophy (ALD), a progressive neurodegenerative disease, is caused by mutations in ABCD1 and characterized by very-long-chain fatty acids (VLCFA) accumulation. In male patients, an increased plasma VLCFA levels in combination with a pathogenic mutation in ABCD1 confirms the diagnosis. Recent studies have shown that many women with ALD also develop myelopathy. Correct diagnosis is important for management including genetic counseling. Diagnosis in women can only be confirmed when VLCFA levels are elevated or when a known pathogenic ABCD1 mutation is identified. However, in 15-20% of women with ALD VLCFA plasma levels are not elevated. Demonstration that a novel sequence variant is pathogenic can be a challenge when VLCFA levels are in the normal range. Here we report two women with a clinical presentation compatible with ALD, an ABCD1 variation (p.Arg17His and p.Ser358Pro) of unknown significance, but with normal VLCFA levels. We developed a diagnostic test that is based on generating clonal cell lines that express only one of the two alleles. Subsequent biochemical studies enabled us to show that the two sequence variants were not pathogenic, thereby excluding the diagnosis ALD in these women. We conclude that the clonal approach is an important addition to the existing diagnostic array.
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http://dx.doi.org/10.1016/j.ymgme.2016.03.009DOI Listing
June 2016

Enzymatic characterization of ELOVL1, a key enzyme in very long-chain fatty acid synthesis.

Biochim Biophys Acta 2015 Feb 11;1851(2):231-7. Epub 2014 Dec 11.

Genetic Metabolic Diseases, Department of Pediatrics/Emma Children's Hospital, Academic Medical Center, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands; Genetic Metabolic Diseases, Department of Clinical Chemistry, Academic Medical Center, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands. Electronic address:

X-linked adrenoleukodystrophy (X-ALD) is a neurometabolic disease that is caused by mutations in the ABCD1 gene. ABCD1 protein deficiency impairs peroxisomal very long-chain fatty acid (VLCFA) degradation resulting in increased cytosolic VLCFA-CoA levels, which are further elongated by the VLCFA-specific elongase, ELOVL1. In adulthood, X-ALD most commonly manifests as a gradually progressive myelopathy (adrenomyeloneuropathy; AMN) without any curative or disease modifying treatments. We recently showed that bezafibrate reduces VLCFA accumulation in X-ALD fibroblasts by inhibiting ELOVL1. Although, in a clinical trial, bezafibrate was unable to lower VLCFA levels in plasma or lymphocytes in X-ALD patients, inhibition of ELOVL1 remains an attractive therapeutic option. In this study, we investigated the kinetic characteristics of ELOVL1 using X-ALD fibroblasts and microsomal fractions from ELOVL1 over-expressing HEK293 cell lines and analyzed the inhibition kinetics of a series of fibrates. Our data show that the CoA esters of bezafibrate and gemfibrozil reduce chain elongation by specifically inhibiting ELOVL1. These fibrates can therefore serve as lead compounds for the development of more potent and more specific inhibitors for ELOVL1.
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http://dx.doi.org/10.1016/j.bbalip.2014.12.005DOI Listing
February 2015

Hematopoietic cell transplantation does not prevent myelopathy in X-linked adrenoleukodystrophy: a retrospective study.

J Inherit Metab Dis 2015 Mar 9;38(2):359-61. Epub 2014 Dec 9.

Department of Neurology, Medical Center Alkmaar, Alkmaar, The Netherlands.

Background: X-linked adrenoleukodystrophy (X-ALD) is a peroxisomal metabolic disorder. Male patients develop adrenocortical insufficiency (80 % before 18 years), a chronic myelopathy (adrenomyeloneuropathy (AMN); all in adulthood), or progressive cerebral demyelination (cerebral ALD; 40 % before 18 years). Cerebral ALD is treated with haematopoetic cell transplantation (HCT). It is unknown if AMN still develops in patients with X-ALD that underwent HCT for cerebral ALD in childhood.

Patients And Methods: A retrospective observational study was performed by selecting all adult patients with X-ALD in our cohort that underwent HCT in childhood.

Results: This retrospective study found that three out of five patients in our cohort who underwent HCT in childhood developed signs of myelopathy in adulthood.

Conclusion: These data suggest that HCT for cerebral ALD in childhood does not prevent the onset of AMN in X-ALD in adulthood.
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http://dx.doi.org/10.1007/s10545-014-9797-1DOI Listing
March 2015