ABCD1 Mutation Research Articles

A Novel Mouse Model for Cerebral Inflammatory Demyelination in X-Linked Adrenoleukodystrophy: Insights into Pathogenesis and Potential Therapeutic Targets.

X-linked adrenoleukodystrophy (ALD) is caused by mutations in ABCD1, a peroxisomal gene. More than half of males with an ABCD1 mutation develop inflammatory cerebral demyelination (cALD), but underlying mechanisms remain unknown and therapies are limited. We sought to develop and characterize a mouse model of cALD to facilitate study of disease mechanisms and therapy development. We used immunoassays and immunohistochemistry to assess novel (interleukin 18 [IL-18]) and established molecular markers in cerebrospinal fluid (CSF) and postmortem brain tissue from cALD patients. We generated a cALD phenotype in Abcd1-knockout mice using a 2-hit method that combines cuprizone and experimental autoimmune encephalomyelitis models. We then used magnetic resonance imaging (MRI) and immunohistochemistry to assess the fidelity of cALD molecular markers in the mice. Human and mouse cALD lesions shared histologic features of myelin phagocytosis, myelin loss, abundant microglial activation, T and B-cell infiltration, and astrogliosis. Compared to wild-type controls, Abcd1-knockout mice displayed more cerebral demyelination, blood-brain barrier disruption, and perivascular immune cell infiltration. This enhanced inflammatory response was associated with higher levels of fibrin deposition, oxidative stress, demyelination, and axonal injury. IL-18 immunoreactivity co-localized with perivascular monocytes/macrophages in both human and mouse brain tissue. In cALD patients, CSF IL-18 levels correlated with MRI lesion severity. Our results suggest loss of Abcd1 function in mice predisposes to more severe blood-brain barrier disruption, cerebral inflammation driven by the infiltration of peripheral immune cells, demyelination, and axonal damage, replicating human cALD features. This novel mouse model could shed light on cALD mechanisms and accelerate cALD therapy development. ANN NEUROL 2024.

Adrenoleukodystrophy an Overview

Adrenoleukodystrophy (ALD) is a rare X-linked peroxisomal oxidation disease caused by mutations in ABCD1. It presents with various clinical manifestations, including cerebral ALD, myelopathy, and primary adrenal insufficiency. About 80% of ALD patients suffer from adrenal insufficiency, and cerebral ALD affects one-third of boys under twelve, progressing to total impairment and death without treatment. Hematopoietic stem cell transplantation (HSCT) is the only disease-modifying treatment for early-stage cerebral ALD, but it does not halt adrenal insufficiency progression and carries significant morbidity and mortality risks. A recent gene therapy clinical trial showed short-term MRI and neurological outcomes equivalent to past HSCT treatments without the adverse side effects. Additionally, over a dozen states have initiated newborn screening (NBS) for ALD, with the number expected to triple by 2020. Genetic testing of NBS-positive newborns has identified novel variations of unknown significance, raising questions about monitoring and treating preclinical or moderate adrenal insufficiency or cerebral involvement. This presents further opportunities for genetic characterization. The availability of matching donors, transplant centers, and specialists will impact prompt treatment for those diagnosed with ALD at birth. As NBS and gene therapy trials improve ALD's clinical management and prognosis, endocrine management of presymptomatic and subclinical adrenal insufficiency will become increasingly important.

In vivo adenine base editing rescues adrenoleukodystrophy in a humanized mouse model

X-linked adrenoleukodystrophy (ALD), an inherited neurometabolic disorder caused by mutations in ABCD1, which encodes the peroxisomal ABC transporter, mainly affects the brain, spinal cord, adrenal glands, and testes. In ALD patients, very long-chain fatty acids (VLCFAs) fail to enter the peroxisome and undergo subsequent β-oxidation, resulting in their accumulation in the body. It has not been tested whether in vivo base editing or prime editing can be harnessed to ameliorate ALD. We developed a humanized mouse model of ALD by inserting a human cDNA containing the pathogenic variant into the mouse Abcd1 locus. The humanized ALD model showed increased levels of VLCFAs. To correct the mutation, we tested both base editing and prime editing and found that base editing using ABE8e(V106W) could correct the mutation in patient-derived fibroblasts at an efficiency of 7.4%. Adeno-associated virus (AAV)-mediated systemic delivery of NG-ABE8e(V106W) enabled robust correction of the pathogenic variant in the mouse brain (correction efficiency: ∼5.5%), spinal cord (∼5.1%), and adrenal gland (∼2%), leading to a significant reduction in the plasma levels of C26:0/C22:0. This established humanized mouse model and the successful correction of the pathogenic variant using a base editor serve as a significant step towards treating human ALD disease.

Central precocious puberty in a boy with X-linked adrenoleukodystrophy caused by a novel ABCD1 mutation

X-linked adrenoleukodystrophy (X-ALD) is a rare genetic disorder caused by pathogenic variants in the ABCD1 gene. The symptoms include primary adrenal insufficiency (PAI), progressive spinal cord disease, inflammatory demyelinating cerebral disease, and primary hypogonadism. It is exceptionally rare that pediatric PAI is accompanied by central precocious puberty (CPP). The purpose of this study was to better understand the diversity of clinical manifestations of X-ALD and to identify the ABCD1 gene mutation in a case of a boy with X-ALD accompanied by CPP. We collected clinical, laboratory and imaging data, and used whole-exome sequencing (WES) analysis to evaluate the pathogenicity of the variant. We also predicted the potential deleterious effects of the novel mutation using Mutation Taster and generated three-dimensional protein structures using Swiss-Model and PyMOL Viewer software. The patient presented with PAI accompanied by CPP. Adrenal gland CT revealed adrenal hypoplasia. Gonadotropin-releasing hormone stimulation tests revealed CPP. WES revealed a novel variant (c.1376dup) in the ABCD1 gene, which resulted in a reading frameshift and a premature termination codon (p.Leu461ProfsTer95). Sanger sequencing confirmed that the variant was inherited from his heterozygous mother. Mutation Taster predicted that the variant could be harmful. The overall three-dimensional structures of the mutant wild-type proteins were visually distinct. Our results shed light on additional aspects of X-ALD. The premature activation of the hypothalamic-pituitary-gonadal axis may possibly be related to the pathogenic ABCD1 gene mutation.

Role of Basal Forebrain Neurons in Adrenomyeloneuropathy in Mice and Humans.

X-linked adrenoleukodystrophy is caused by mutations in the peroxisomal half-transporter ABCD1. The most common manifestation is adrenomyeloneuropathy, a hereditary spastic paraplegia of adulthood. The present study set out to understand the role of neuronal ABCD1 in mice and humans with adrenomyeloneuropathy. Neuronal expression of ABCD1 during development was assessed in mice and humans. ABCD1-deficient mice and human brain tissues were examined for corresponding pathology. Next, we silenced ABCD1 in cholinergic Sh-sy5y neurons to investigate its impact on neuronal function. Finally, we tested adeno-associated virus vector-mediated ABCD1 delivery to the brain in mice with adrenomyeloneuropathy. ABCD1 is highly expressed in neurons located in the periaqueductal gray matter, basal forebrain and hypothalamus. In ABCD1-deficient mice (Abcd1-/y), these structures showed mild accumulations of α-synuclein. Similarly, healthy human controls had high expression of ABCD1 in deep gray nuclei, whereas X-ALD patients showed increased levels of phosphorylated tau, gliosis, and complement activation in those same regions, albeit not to the degree seen in neurodegenerative tauopathies. Silencing ABCD1 in Sh-sy5y neurons impaired expression of functional proteins and decreased acetylcholine levels, similar to observations in plasma of Abcd1-/y mice. Notably, hind limb clasping in Abcd1-/y mice was corrected through transduction of ABCD1 in basal forebrain neurons following intracerebroventricular gene delivery. Our study suggests that the basal forebrain-cortical cholinergic pathway may contribute to dysfunction in adrenomyeloneuropathy. Rescuing peroxisomal transport activity in basal forebrain neurons and supporting glial cells might represent a viable therapeutic strategy. ANN NEUROL 2024;95:442-458.

ABCD1 Transporter Deficiency Results in Altered Cholesterol Homeostasis.

X-linked adrenoleukodystrophy (X-ALD), the most common peroxisomal disorder, is caused by mutations in the peroxisomal transporter ABCD1, resulting in the accumulation of very long-chain fatty acids (VLCFA). Strongly affected cell types, such as oligodendrocytes, adrenocortical cells and macrophages, exhibit high cholesterol turnover. Here, we investigated how ABCD1 deficiency affects cholesterol metabolism in human X-ALD patient-derived fibroblasts and CNS tissues of Abcd1-deficient mice. Lipidome analyses revealed increased levels of cholesterol esters (CE), containing both saturated VLCFA and mono/polyunsaturated (V)LCFA. The elevated CE(26:0) and CE(26:1) levels remained unchanged in LXR agonist-treated Abcd1 KO mice despite reduced total C26:0. Under high-cholesterol loading, gene expression of SOAT1, converting cholesterol to CE and lipid droplet formation were increased in human X-ALD fibroblasts versus healthy control fibroblasts. However, the expression of NCEH1, catalysing CE hydrolysis and the cholesterol transporter ABCA1 and cholesterol efflux were also upregulated. Elevated Soat1 and Abca1 expression and lipid droplet content were confirmed in the spinal cord of X-ALD mice, where expression of the CNS cholesterol transporter Apoe was also elevated. The extent of peroxisome-lipid droplet co-localisation appeared low and was not impaired by ABCD1-deficiency in cholesterol-loaded primary fibroblasts. Finally, addressing steroidogenesis, progesterone-induced cortisol release was amplified in X-ALD fibroblasts. These results link VLCFA to cholesterol homeostasis and justify further consideration of therapeutic approaches towards reducing VLCFA and cholesterol levels in X-ALD.

CO110 Hospitalizations, Clinical Characteristics and Mortality in Adults with Adrenomyeloneuropathy (AMN): A Retrospective Study

Adrenomyeloneuropathy (AMN) is a rare neurodegenerative X-linked disease caused by mutations in ABCD1 that cause progressive myeloneuropathy, spastic paraparesis, sensory ataxia, loss of mobility, incontinence, and sexual dysfunction. This study sought to examine for the first time hospitalizations, clinical characteristics, and mortality in adults with AMN in the US.

EE373 The Economic Impact of Adrenomyeloneuropathy (AMN) on Direct Medical Costs in Commercially Insured US Adults: A Retrospective Study

Adrenomyeloneuropathy (AMN) is the most common manifestation of X-linked adrenoleukodystrophy (X-ALD), a rare neurodegenerative disease caused by mutations in ABCD1, featuring progressive myeloneuropathy, spastic paraparesis, sensory ataxia, loss of mobility, incontinence, and sexual dysfunction. Presentation, onset and clinical manifestations vary between men and women. This study sought to quantify for the first time the impact of AMN on healthcare costs in commercially insured adults, both male and female, in the US.

Teaching Neuro Images : MRI findings in X-linked adrenoleukodystrophy

A 6-year-old boy presented with 4 months progressive verbal comprehension difficulties, declining school performance, strabismus, and visual impairment. General examination noted moderate hypotension and hyperpigmented skin. Pertinent neurologic examination abnormalities included difficulty with comprehension, decreased visual acuity (20/50 bilaterally), disconjugate gaze, bilateral dysmetria, and unsteady gait. CSF protein was elevated (1.82 g/L). Brain MRI showed posterior cerebrum and brainstem abnormalities consistent with adrenoleukodystrophy1 (figure). Morning cortisol was decreased (21 nM) and adrenocorticotrophic hormone stimulation test confirmed adrenal insufficiency. Diagnosis was confirmed by very long chain fatty acid analysis (elevated C26:0/C22:0 and C24:0/C22:0 ratios) and identification of pathogenic ABCD1 mutation.

Novel mutations in the ABCD1 gene caused adrenomyeloneuropathy in the Chinese population.

As a rare genetic disease, adrenomyeloneuropathy (AMN) is the most common adult phenotype of X-linked adrenoleukodystrophy (X-ALD). Mutations in the ABCD1 gene have been identified to cause AMN. We applied clinical evaluation, laboratory tests, and neuroimaging on three patients with progressive spastic paraparesis. In genetic analysis, we investigated ABCD1 gene mutations by whole-exome sequencing and Sanger sequencing. Bioinformatics tools were used to predict the effects of identified ABCD1 mutations on the protein. All three patients were men with adult-onset disease, mainly characterized by progressive spastic paraparesis. Among them, two patients had peripheral neuropathy and one patient had signs of adrenal insufficiency. All three patients showed cerebral involvement on brain MRI, while two patients were found with diffuse cord atrophy on spinal MRI. High-VLCFA levels in plasma, as well as C24:0/C22:0 and C26:0/C22:0 ratios, were found in all three patients. In addition, three different ABCD1 mutations were identified in three unrelated Chinese families, including one known mutation (c.1415_1416delAG) and two novel mutations (c.217C>T and c.160_170delACGCAGGAGGC). Based on the clinical assessment, radiographic, biochemical, and genetic testing, the final diagnosis was AMN in these patients with spastic paraparesis. This study reported three patients with AMN and identified two novel mutations in the ABCD1 in the Chinese population. Our finding emphasized that X-ALD is an important cause of adult-onset spastic paraplegia. Thus, neuroimaging, VLCFA testing, and especially the detection of the ABCD1 gene have important implications for the etiological diagnosis of adult patients with spastic paraplegia.

Adrenoleukodystrophy Protein (ALDP) Antibody Formation and Graft Loss in Gene Therapy for Adrenoleukodystrophy

A nine-year boy with adrenoleukodystrophy (ALD) due to an ABCD1 whole gene deletion was diagnosed with the active cerebral form of disease characterized by demyelination and gadolinium enhancement on brain MRI. Allogeneic hematopoietic stem cell transplant (HCT) or lentiviral correction of autologous CD34+cell-based gene therapy (GT) are the only known mechanisms to arrest the progression of cerebral disease. He was treated with GCSF/plerixafor to mobilize autologous CD34+ cells which were then transduced with the ABCD1 expressing lentiviral vector. He received myeloablative conditioning with busulfan and fludarabine followed by lentivirus-based GT. Initial viral copy number (VCN) was 0.8592 in whole blood at 30 days post HCT and MRI's showed disease stabilization with significant decrease in gadolinium enhancement at 60 and 100 days after GT. Unfortunately, VCN then declined and subsequent MRI's showed re-emergence of gadolinium enhancement and disease progression at 6 months after GT. Antibodies to the ABCD1 gene product (ALDP) were detected in the patient's plasma by immunoblot at 9 months after GT. Antisera also showed specific reactivity to human peroxisomes in immunofluorescence assays, suggesting that generation of an immune response had occurred following GT. Evaluation of pre-GT plasma did not find any anti-ALDP. Evaluation of post HCT plasma from other patients undergoing either GT or allo-HCT did not show anti-ALPD reactivity suggesting this was a unique phenomenon to this patient. Peptide mapping indicated the antisera bound mostly to the C-terminal portion of ALDP in five distinct peptide regions. Subtyping of the antibody indicated it was IgG and not IgM at 9 months post GT. Specific anti-ALDP IgG Subtypes detected were IgG1 and IgG3. Immune adjuvant therapy using rituximab and daratumumab failed to significantly reduce plasma reactivity to ALDP. Due to disease advancement on MRI, an allogeneic HCT was performed approximately 12 months after initial GT with an 5/6 HLA matched umbilical cord blood unit. Donor neutrophil engraft occurred on day +17, donor platelet engraftment occurred on day +35. Chimerism studies revealed 100% engraftment in CD33+cells and 90% engraftment in CD3+ cells by 60 days post HCT. The MRI's at 30-, 60-, and 100-days post allo-HCT showed stabilizing cerebral disease and fading gadolinium enhancement. Importantly, plasma collected at 30-, 60-days, and 100-days post allo-HCT showed no reactivity to ALPD. Conclusion. This is the first case of anti-ALDP antibodies occurring after gene therapy for cerebral ALD. Antibody generation may have been related to the unique ABCD1 whole gene deletion condition within this child which is very rare as the majority of ALD patients have missense or non-sense mutations in ABCD1. Whether anti-ALDP presence was a causal or an unrelated phenomenon to the loss of the autologous vector-containing cells is not currently known at the time of submission. These findings highlight to need to scrutinize patients prior to before and after GT for the presence of antibody to the protein product being introduced. This may be especially important in the case where the patient's immune system has never seen the protein (like in this case of a whole gene deletion) and therefore would have never been "educated".

Peroxisome Metabolism Contributes to PIEZO2-Mediated Mechanical Allodynia.

Mutations in the peroxisomal half-transporter ABCD1 cause X-linked adrenoleukodystrophy, resulting in elevated very long-chain fatty acids (VLCFA), progressive neurodegeneration and an associated pain syndrome that is poorly understood. In the nervous system of mice, we found ABCD1 expression to be highest in dorsal root ganglia (DRG), with satellite glial cells (SGCs) displaying higher expression than neurons. We subsequently examined sensory behavior and DRG pathophysiology in mice deficient in ABCD1 compared to wild-type mice. Beginning at 8 months of age, Abcd1−/y mice developed persistent mechanical allodynia. DRG had a greater number of IB4-positive nociceptive neurons expressing PIEZO2, the mechanosensitive ion channel. Blocking PIEZO2 partially rescued the mechanical allodynia. Beyond affecting neurons, ABCD1 deficiency impacted SGCs, as demonstrated by high levels of VLCFA, increased glial fibrillary acidic protein (GFAP), as well as genes disrupting neuron-SGC connectivity. These findings suggest that lack of the peroxisomal half-transporter ABCD1 leads to PIEZO2-mediated mechanical allodynia as well as SGC dysfunction. Given the known supportive role of SGCs to neurons, this elucidates a novel mechanism underlying pain in X-linked adrenoleukodystrophy.

Novel RAB3GAP1 Mutation in the First Tunisian Family With Warburg Micro Syndrome.

Warburg Micro syndrome (WARBM) is a rare autosomal recessive genetic disease characterized by ocular, neurologic, and endocrine anomalies. WARBM is a phenotypically and genetically heterogeneous syndrome caused by mutations in RAB3GAP1, RAB3GAP2, RAB18, and TBC1D20. Here we present the clinical and genetic characterization of a consanguineous Tunisian family with a WARBM phenotype presenting two pathogenic variations, one of which is on RAB3GAP1.We applied whole-exome sequencing (WES) to two affected young males presenting a WARBM-compatible phenotype.We reveal a new variation in RAB3GAP1 (NM_012233.3: c.297del, p.Gln99fs) and another variation in ABCD1 (NM_000033: c.896A>G, p.His299Arg). Each of these mutations, which in silico predictions concluded as being pathogenic variations, affects a critical protein region. Both affected males presented a WARBM-compatible phenotype, with severe intellectual disability, severe developmental delay, postnatal growth delay, postnatal microcephaly, congenital bilateral cataracts, general hypotonia, and a thin corpus callosum without a splenium. However, intrafamilial clinical heterogeneity was present, since only the oldest child had large ears, microphthalmia, foot deformities, and a genital anomaly, and only the youngest child had microcornea. Despite the mutation identified in ABCD1, our patients did not have any X-linked symptoms of adrenoleukodystrophy disorder that are usually caused by ABCD1 mutations, which prompted our interest in clinical monitoring.WES analysis of a consanguineous Tunisian family with WARBM revealed a novel variation in RAB3GAP1 (NM_012233.3: c.297del, p.Gln99fs) that is most likely pathogenic and allowed us to confirm the diagnosis of WARBM.

Generation of mutation-corrected induced pluripotent stem cell lines derived from adrenoleukodystrophy patient by using homology directed repair

X-linked adrenoleukodystrophy (ALD) caused by the ABCD1 mutation, is the most common inherited peroxisomal disease. Previously, we generated an ALD patient-derived SCHi001-A iPSC model. In this study, we have performed the first genome editing of ALD patient-derived SCHi001-A iPSCs using homology-directed repair (HDR). The mutation site, c.1534G > A [GenBank: NM_000033.4], was corrected by introducing ssODN and the CRISPR/Cas9 system. The cell line exhibited normal iPSC plulipotency marker expression following genome editing. Mutation-corrected iPSCs from SCHi001-A iPSC line can be used in research into the pathophysiology of and therapeutics for ALD.

Novel RAB3GAP1 Mutation in the First Tunisian Family With Warburg Micro Syndrome.

Background and PurposeWarburg Micro syndrome (WARBM) is a rare autosomal recessive genetic disease characterized by ocular, neurologic, and endocrine anomalies. WARBM is a phenotypically and genetically heterogeneous syndrome caused by mutations in RAB3GAP1, RAB3GAP2, RAB18, and TBC1D20. Here we present the clinical and genetic characterization of a consanguineous Tunisian family with a WARBM phenotype presenting two pathogenic variations, one of which is on RAB3GAP1.MethodsWe applied whole-exome sequencing (WES) to two affected young males presenting a WARBM-compatible phenotype.ResultsWe reveal a new variation in RAB3GAP1 (NM_012233.3: c.297del, p.Gln99fs) and another variation in ABCD1 (NM_000033: c.896A>G, p.His299Arg). Each of these mutations, which in silico predictions concluded as being pathogenic variations, affects a critical protein region. Both affected males presented a WARBM-compatible phenotype, with severe intellectual disability, severe developmental delay, postnatal growth delay, postnatal microcephaly, congenital bilateral cataracts, general hypotonia, and a thin corpus callosum without a splenium. However, intrafamilial clinical heterogeneity was present, since only the oldest child had large ears, microphthalmia, foot deformities, and a genital anomaly, and only the youngest child had microcornea. Despite the mutation identified in ABCD1, our patients did not have any X-linked symptoms of adrenoleukodystrophy disorder that are usually caused by ABCD1 mutations, which prompted our interest in clinical monitoring.ConclusionsWES analysis of a consanguineous Tunisian family with WARBM revealed a novel variation in RAB3GAP1 (NM_012233.3: c.297del, p.Gln99fs) that is most likely pathogenic and allowed us to confirm the diagnosis of WARBM.

Investigating ABCD1 mutations in a Taiwanese cohort with hereditary spastic paraplegia phenotype

BackgroundAdrenoleukodystrophy (ALD) is an X-linked peroxisomal disorder caused by mutations in the ABCD1 gene. The clinical manifestations of ALD vary widely with some patients presenting with adrenomyeloneuropathy (AMN) that resembles the phenotype of hereditary spastic paraplegia (HSP). The aim of this study is to investigate the frequency, spectrum, and clinical features of ABCD1 mutations in Taiwanese patients with HSP phenotype. MethodsMutational analysis of the ABCD1 gene was performed in 230 unrelated Taiwanese patients with clinically suspected HSP by targeted resequencing. Clinical, electrophysiological, and neuroimaging features of the patients carrying an ABCD1 pathogenic mutation were characterized. ResultsTen different ABCD1 mutations were identified in eleven patients, including two novel mutations (p.Q177Pfs*17 and p.Y357*) and eight ever reported in ALD cases of other ethnicities. All patients were male and exhibited slowly progressive spastic paraparesis with onset ages ranging from 21 to 50 years. Most of them had additional non-motor symptoms, including autonomic dysfunction in nine patients, sensory deficits in seven, premature baldness in seven, skin hyperpigmentation in five, psychiatric symptoms in one and cerebellar ataxia in one. Seven of the ten patients who ever received nerve conduction studies showed axonal polyneuropathy. Magnetic resonance imaging (MRI) revealed diffuse spinal cord atrophy in seven patients, cerebral white matter hyperintensity in one patient, and cerebellar involvement in one patient. ConclusionsABCD1 mutations account for 4.8% (11/230) of the cases with HSP phenotype in Taiwan. This study highlights the importance to consider ABCD1 mutations in patients with clinically suspected HSP of unknown genetic causes.

Adrenoleukodystrophy as a Cause of Spastic Paraparesis and Hyperpigmentation

Background: X-linked Adrenoleukodystrophy (X-ALD) is caused by an abnormal gene mutation on the X chromosome which codes for an abnormal ABC transporter, preventing transport of very long chain fatty acids (VLCFAs) into peroxisomes for beta oxidation. These VLCFAs, unable to be broken down, thus accumulate in the CNS, adrenal cortex, and Leydig cells of the testes. The clinical presentation depends upon the anatomical involvement, which most often includes the CNS and adrenal glands, and can be a cause of adrenomyeloneuropathy (AMN) or adrenal insufficiency.Case Report: We report a 44 year old male who presented with 9 years of progressive spastic paraparesis. Physical exam was significant for lower extremity spasticity, 3/5 bilateral lower extremity weakness, and hyperpigmentation. His initial work-up for autoimmune disease, MRI brain, and lumbar puncture were unremarkable, and genetic testing for Hereditary Spastic Paraparesis was negative. However, due to advancing symptoms over the years with progression of spasticity, polyneuropathy, development of erectile dysfunction and significant hyperpigmentation, re-evaluation with MRI brain and EMG revealed diffuse symmetrical cerebral and cerebellar volume loss and axonal motor peripheral neuropathy, respectively. Due to hyperpigmentation, further work-up for VLCFAs was positive and presence of the ABCD1 mutation confirmed the diagnosis of X-ALD. Evaluation of adrenal glands yielded high ACTH of >2000 pg/mL (normal: 7.2–63.3) and low AM cortisol of 2.5 ug/dL (normal: 6.2–19.4). Insignificant increase of cortisol from 2.5 ug/dL to 2.7 ug/dL with cosyntropin confirmed primary adrenal insufficiency as the cause of hyperpigmentation with elevated ACTH. Surprisingly, his testosterone level was normal at 542 (normal: 250–1100 ng/dL) and suggestive of Leydig cell-sparing and neuropathy-induced erectile dysfunction. The patient was started on hydrocortisone for adrenal insufficiency with improvement in his fatigue and feelings of well-being. He received physical therapy and is being monitored closely for progression of AMN by Neurology.Conclusion: Our case suggests that ALD should be considered in the differential diagnosis of unexplained paraparesis with associated hyperpigmentation in males. Moreover, timely diagnosis and medical intervention can prevent life-threatening adrenal crisis in such patients.

Metabolic rerouting via SCD1 induction impacts X-linked adrenoleukodystrophy.

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.

Generation of two human induced pluripotent stem cell lines derived from two X-linked adrenoleukodystrophy patients with ABCD1 mutations

Adrenoleukodystrophy (ALD) is an X-linked genetic disorder, characterized by demyelination in the central nervous system and adrenal insufficiency. Human induced pluripotent stem cell (hiPSC) lines derived from two Japanese male patients with ALD were generated from skin fibroblasts using retroviral vectors. The generated hiPSC lines showed self-renewal and pluripotency, and carried either a missense or a nonsense mutation in ABCD1 gene. Since the molecular pathogenesis caused by ABCD1 dysfunction remains unclear, these cell resources provide useful tools to establish disease models and to develop new therapies for X-ALD.

Defining diagnostic cutoffs in neurological patients for serum very long chain fatty acids (VLCFA) in genetically confirmed X-Adrenoleukodystrophy

X-linked Adrenoleukodystrophy (X-ALD) is caused by mutations in the ABCD1 gene resulting in the accumulation of very long chain fatty acids (VLCFA). X-ALD is the most common peroxisomal disorder with adult patients (male and female) presenting with progressive spastic paraparesis with bladder disturbance, sensory ataxia with impaired vibration sense, and leg pain. 80% of male X-ALD patients have an adrenal failure, while adrenal dysfunction is rare in women with X-ALD. The objective of this study was to define optimal serum VLCFA cutoff values in patients with X-ALD-like phenotypes for the differentiation of genetically confirmed X-ALD and Non-X-ALD individuals. Three groups were included into this study: a) X-ALD cases with confirmed ABCD1 mutations (n = 34) and two Non-X-ALD cohorts: b) Patients with abnormal serum VCLFA levels despite negative testing for ABCD1 mutations (n = 15) resulting from a total of 1,953 VLCFA tests c) Phenotypically matching patients as Non-X-ALD controls (n = 104). Receiver operating curve analysis was used to optimize VLCFA cutoff values, which differentiate patients with genetically confirmed X-ALD and Non-X-ALD individuals. The serum concentration of C26:0 was superior to C24:0 for the detection of X-ALD. The best differentiation of Non-X-ALD and X-ALD individuals was obtained with a cutoff value of < 1.0 for the C24:0/C22:0 ratio resulting in a sensitivity of 97%, a specificity of 94.1% and a positive predictive value (PPV) of 83.8% for true X-ALD. Our findings further suggested a cutoff of < 0.02 for the ratio C26:0/C22:0 leading to a sensitivity of 90.9%, a specificity of 95.0%, and a PPV of 80.6%. Pearson correlation indicated a significant positive association between total blood cholesterol and VLCFA values. Usage of serum VLCFA are economical and established biomarkers suitable for the guidance of genetic testing matching the X-ALD phenotype. We suggest using our new optimized cutoff values, especially the two ratios (C24:0/C22:0 and C26:0/C22:0), in combination with standard lipid profiles.