Mutations in the gene encoding peroxisomal alpha-methylacyl-CoA racemase cause adult-onset sensory motor neuropathy

Alpha-methyl acetyl-coA racemase deficiency. Magnetic resonance imaging findings of three patients with encephalopathy, epilepsy, and stroke-like episodes

Alpha-methyl acyl-CoA racemase deficiency (AMACRD) is a rare peroxisomal disorder that results in the accumulation of pristanic acid and 16 cases have been reported in the literature. Here, we present three additional patients, two confirmed by genomic study and one suspected. Three siblings who were born to healthy unrelated parents developed recurrent episodes of encephalopathy, seizures, and behavioral disturbances. In all 3, brain MRI showed lesions in the thalami, cerebral peduncles, and mesencephalic tegmentum, as well as brain volume loss. In addition, one patient had a chronic hemispheric infarct and an acute contralateral infarct, and another had a subacute infarct involving multiple vascular territories without abnormalities on MR angiography.

Disorders of fatty acid homeostasis

Humans derive fatty acids (FA) from exogenous dietary sources and/or endogenous synthesis from acetyl-CoA, although some FA are solely derived from exogenous sources ("essential FA"). Once inside cells, FA may undergo a wide variety of different modifications, which include their activation to their corresponding CoA ester, the introduction of double bonds, the 2- and ω-hydroxylation and chain elongation, thereby generating a cellular FA pool which can be used for the synthesis of more complex lipids. The biological properties of complex lipids are very much determined by their molecular composition in terms of the FA incorporated into these lipid species. This immediately explains the existence of a range of genetic diseases in man, often with severe clinical consequences caused by variants in one of the many genes coding for enzymes responsible for these FA modifications. It is the purpose of this review to describe the current state of knowledge about FA homeostasis and the genetic diseases involved. This includes the disorders of FA activation, desaturation, 2- and ω-hydroxylation, and chain elongation, but also the disorders of FA breakdown, including disorders of peroxisomal and mitochondrial α- and β-oxidation.

Analysis of enzyme reactions using NMR techniques: A case study with α-methylacyl-CoA racemase (AMACR)

α-Methylacyl-CoA racemase (AMACR; P504S) catalyzes the conversion of R-2-methylacyl-CoA esters into their corresponding S-2-methylacyl-CoA epimers enabling their degradation by β-oxidation. The enzyme also catalyzes the key epimerization reaction in the pharmacological activation pathway of ibuprofen and related drugs. AMACR protein levels and enzymatic activity are increased in prostate cancer, and the enzyme is a recognized drug target. Key to the development of novel treatments based on AMACR inhibition is the development of functional assays. Synthesis of substrates and purification of recombinant human AMACR are described. Incubation of R- or S-2-methylacyl-CoA esters with AMACR in vitro resulted in formation of epimers (at a near 1-1 ratio at equilibrium) via removal of their α-protons to form an enolate intermediate followed by reprotonation. Conversion can be conveniently followed by incubation in buffer containing 2H2O followed by 1H NMR analysis to monitor conversion of the α-methyl doublet to a single peak upon deuterium incorporation. Incubation of 2-methylacyl-CoA esters containing leaving groups results in an elimination reaction, which was also characterized by 1H NMR. The synthesis of substrates, including a double labeled substrate for mechanistic studies, and subsequent analysis is also described.

Autoantibody Positivity in Two Bahraini Siblings With a Novel Alpha-Methylacyl-CoA Racemase Mutation

Bile acid synthesis disorders (BASD) are a group of rare autosomal recessive disorders. Of the nine different versions, BASD type 4 is characterized by a gene mutation in alpha-methylacyl-CoA racemase (AMACR), which is located on chromosome 5p13. These disorders generally present with a normal gamma-glutamyl transferase with cholestasis, absence of pruritis, and malabsorption of fat, which can lead to fat-soluble vitamin deficiencies. In adulthood, patients usually develop neurological sequelae. Initial testing can be done through the measurement of urine metabolites; however, confirmation of the diagnosis is achieved through whole exome sequencing. Treatment involves supplementation of oral cholic acid and modification of diet. Only 23 patients with this disease have been described. Here, we report two cases of siblings from a family in Bahrain with a novel AMACR mutation and a unique association with autoimmune antibodies alongside a literature review.

Evaluating the strength of evidence for genes implicated in peroxisomal disorders using the ClinGen clinical validity framework and providing updates to the peroxisomal disease nomenclature

Peroxisomal disorders are heterogeneous in nature, with phenotypic overlap that is indistinguishable without molecular testing. Newborn screening and gene sequencing for a panel of genes implicated in peroxisomal diseases are critical tools for the early and accurate detection of these disorders. It is therefore essential to evaluate the clinical validity of the genes included in sequencing panels for peroxisomal disorders. The Peroxisomal Gene Curation Expert Panel (GCEP) assessed genes frequently included on clinical peroxisomal testing panels using the Clinical Genome Resource (ClinGen) gene-disease validity curation framework and classified gene-disease relationships as Definitive, Strong, Moderate, Limited, Disputed, Refuted, or No Known Disease Relationship. Subsequent to gene curation, the GCEP made recommendations to update the disease nomenclature and ontology in the Monarch Disease Ontology (Mondo) database. Thirty-six genes were assessed for the strength of evidence supporting their role in peroxisomal disease, leading to 36 gene-disease relationships, after two genes were removed for their lack of a role in peroxisomal disease and two genes were curated for two different disease entities each. Of these, 23 were classified as Definitive (64%), one as Strong (3%), eight as Moderate (23%), two as Limited (5%), and two as No known disease relationship (5%). No contradictory evidence was found to classify any relationships as Disputed or Refuted. The gene-disease relationship curations are publicly available on the ClinGen website (https://clinicalgenome.org/affiliation/40049/). The changes to peroxisomal disease nomenclature are displayed on the Mondo website (http://purl.obolibrary.org/obo/MONDO_0019053). The Peroxisomal GCEP-curated gene-disease relationships will inform clinical and laboratory diagnostics and enhance molecular testing and reporting. As new data will emerge, the gene-disease classifications asserted by the Peroxisomal GCEP will be re-evaluated periodically.

Dysfunctional peroxisomal lipid metabolisms and their ocular manifestations

Retina is rich in lipids and dyslipidemia causes retinal dysfunction and eye diseases. In retina, lipids are not only important membrane component in cells and organelles but also fuel substrates for energy production. However, our current knowledge of lipid processing in the retina are very limited. Peroxisomes play a critical role in lipid homeostasis and genetic disorders with peroxisomal dysfunction have different types of ocular complications. In this review, we focus on the role of peroxisomes in lipid metabolism, including degradation and detoxification of very-long-chain fatty acids, branched-chain fatty acids, dicarboxylic acids, reactive oxygen/nitrogen species, glyoxylate, and amino acids, as well as biosynthesis of docosahexaenoic acid, plasmalogen and bile acids. We also discuss the potential contributions of peroxisomal pathways to eye health and summarize the reported cases of ocular symptoms in patients with peroxisomal disorders, corresponding to each disrupted peroxisomal pathway. We also review the cross-talk between peroxisomes and other organelles such as lysosomes, endoplasmic reticulum and mitochondria.

Late onset AMACR deficiency with metabolic stroke-like episodes and seizures

Alpha-methylacyl-CoA racemase (AMACR) deficiency is a rare peroxisomal disorder causing pristanic acid accumulation. Only 16 cases have been described so far. A female in her seventh decade presented with episodes of dysphasia, headache and sensory disturbance inconsistent with migraine, epilepsy or transient ischaemic attack. An MRI demonstrated unusual changes in the pons, red nuclei, thalami and white matter. Mitochondrial disease was suspected but detailed testing was negative. After eight years of symptoms, she developed a febrile encephalopathy with hemispheric dysfunction, focal convulsive seizures and coma. Her condition stabilised after one month. Lacosamide was continued for seizure prevention. The diagnosis remained elusive until whole genome sequencing revealed AMACR deficiency. Pristanic acid levels were highly elevated and dietary modification was recommended. Genetic peroxisomal disorders can present in older age; our patient is the oldest in the AMACR deficiency literature. Novel features in our case include central apnoea, dystonia and rapid eye movement behaviour disorder.

Diagnosis and treatment of an inborn error of bile acid synthesis type 4: A case report

BACKGROUND

Inborn error of bile acid synthesis type 4 is a peroxisomal disease with impaired bile acid synthesis caused by a-methylacyl-CoA racemase (AMACR) gene mutation. The disease is usually found in children with mild to severe liver disease, cholestasis and poor fat-soluble vitamin absorption. At present, there is no report of inborn errors of bile acid synthesis type 4 in adults with liver disease and poor fat-soluble vitamin absorption.

CASE SUMMARY

A 71-year-old man was hospitalized in our department for recurrent liver dysfunction. The clinical manifestations were chronic liver disease and yellow skin and sclera. Serum transaminase, bilirubin and bile acid were abnormally increased; and fat-soluble vitamins decreased. Liver cirrhosis and ascites were diagnosed by computed tomography. The patient had poor coagulation function and ascites and did not undergo liver puncture. Genetic testing showed AMACR gene missense mutation. The patient was diagnosed with inborn error of bile acid synthesis type 4. He was treated with ursodeoxycholic acid, liver protection and vitamin supplementation, and jaundice of the skin and sclera was reduced. The indicators of liver function and the quality of life were significantly improved.

CONCLUSION

When adults have recurrent liver function abnormalities, physicians should be alert to genetic diseases and provide timely treatment.

Episodic hyperCKaemia may be a feature of α-methylacyl-coenzyme A racemase deficiency

α-methylacyl-CoA racemase (AMACR) deficiency is a rare disorder, affecting peroxisomal metabolism of pristanic acid, with ten published adult cases. We describe an AMACR deficiency case with a clinical presentation dominated by episodic hyperCKaemia, suggesting that myopathic features of AMACR should be considered.

Racemases and epimerases operating through a 1,1-proton transfer mechanism: reactivity, mechanism and inhibition

Racemases and epimerases catalyse changes in the stereochemical configurations of chiral centres and are of interest as model enzymes and as biotechnological tools. They also occupy pivotal positions within metabolic pathways and, hence, many of them are important drug targets. This review summarises the catalytic mechanisms of PLP-dependent, enolase family and cofactor-independent racemases and epimerases operating by a deprotonation/reprotonation (1,1-proton transfer) mechanism and methods for measuring their catalytic activity. Strategies for inhibiting these enzymes are reviewed, as are specific examples of inhibitors. Rational design of inhibitors based on substrates has been extensively explored but there is considerable scope for development of transition-state mimics and covalent inhibitors and for the identification of inhibitors by high-throughput, fragment and virtual screening approaches. The increasing availability of enzyme structures obtained using X-ray crystallography will facilitate development of inhibitors by rational design and fragment screening, whilst protein models will facilitate development of transition-state mimics.

Peroxisomal Disorders and Their Mouse Models Point to Essential Roles of Peroxisomes for Retinal Integrity

Peroxisomes are multifunctional organelles, well known for their role in cellular lipid homeostasis. Their importance is highlighted by the life-threatening diseases caused by peroxisomal dysfunction. Importantly, most patients suffering from peroxisomal biogenesis disorders, even those with a milder disease course, present with a number of ocular symptoms, including retinopathy. Patients with a selective defect in either peroxisomal α- or β-oxidation or ether lipid synthesis also suffer from vision problems. In this review, we thoroughly discuss the ophthalmological pathology in peroxisomal disorder patients and, where possible, the corresponding animal models, with a special emphasis on the retina. In addition, we attempt to link the observed retinal phenotype to the underlying biochemical alterations. It appears that the retinal pathology is highly variable and the lack of histopathological descriptions in patients hampers the translation of the findings in the mouse models. Furthermore, it becomes clear that there are still large gaps in the current knowledge on the contribution of the different metabolic disturbances to the retinopathy, but branched chain fatty acid accumulation and impaired retinal PUFA homeostasis are likely important factors.

RNA-Seq based genetic variant discovery provides new insights into controlling fat deposition in the tail of sheep

Genetic basis of fat deposition in sheep tail have not been completely elucidated yet. Understanding the genetic mechanisms controlling fat-tail size can improve breeding strategies to modulate fat deposition. RNA sequencing has made it possible to discover genetic variants that may underlie various phenotypic differences. Hence, to identify genetic variants that are important for describing different fat-tail phenotypes in sheep, RNA sequencing was used for single nucleotide polymorphism (SNP) calling in two Iranian sheep breeds (Lori-Bakhtiari, fat-tailed; n = 4, vs Zel, thin-tailed; n = 4). Using a stringent pipeline, a total of 112,344 known SNPs were genotyped, of which 30,550 and 42,906 SNPs were shared by at least two Lori-Bakhtiari and Zel, respectively. Comparing these SNPs showed 2,774 (including 209 missense and 25 deleterious SNPs) and 10,470 (including 1,054 missense and 116 deleterious SNPs) breed-specific SNPs in Lori-Bakhtiari and Zel sheep, respectively. Potential breed-specific SNPs were detected by considering those located in QTL regions associated with fatness or reported as important candidates in previous similar studies. Of the breed-specific SNPs, 724 and 2,905 were located in the QTL regions. Functional enrichment analysis of the affected genes revealed several enriched gene ontologies and KEGG pathways related to fat metabolism. Based on the results, several affected genes were proposed to be strongly linked with fat deposition such as DGAT2, ACSL1, ACACA, ADIPOQ, ACLY, FASN, CPT2, SCD, ADCY6, PER3, CSF1R, SLC22A4, GFPT1, CDS2, BMP6, ACSS2, ELOVL6, HOXA10 and FABP4. Moreover, several SNPs were found in the candidate genes related to fatty acid oxidation introducing them as promising candidates responsible for lower fat content in tail of Zel. Our findings provided new insights into the genetic mechanisms of fat deposition in sheep, which can serve to designing appropriate breeding programs.

Current Knowledge on the Function of α-Methyl Acyl-CoA Racemase in Human Diseases

Branched chain fatty acids perform very important functions in human diet and drug metabolism. they cannot be metabolized in mitochondria and are instead processed and degraded in peroxisomes due to the presence of methyl groups on the carbon chains. Oxidative degradation pathways for lipids include α- and β-oxidation and several pathways. In all metabolic pathways, α-methyl acyl-CoA racemase (AMACR) plays an essential role by regulating the metabolism of lipids and drugs. AMACR regulates β-oxidation of branched chain lipids in peroxisomes and mitochondria and promotes chiral reversal of 2-methyl acids. AMACR defects cause sensory-motor neuronal and liver abnormalities in humans. These phenotypes are inherited and are caused by mutations in AMACR. In addition, AMACR has been found to be overexpressed in prostate cancer. In addition, the protein levels of AMACR have increased significantly in many types of cancer. Therefore, AMACR may be an important marker in tumors. In this review, a comprehensive overview of AMACR studies in human disease will be described.

Effects of dietary phytol on tissue accumulation of phytanic acid and pristanic acid and on the tissue lipid profiles in mice

Recent in vitro evidence suggests that the phytol-derived fatty acids, phytanic acid (PA) and pristanic acid (PrA), are components of animal products with the potential to cause both beneficial and harmful effects on human health. In this study, we investigated the in vivo tissue accumulation of PA and PrA and the changes in tissue lipid profiles, using mice fed a phytol-containing diet. After 4 weeks of treatment with a diet containing 1.0% phytol, plasma, adipose tissue, liver, and brain were collected and their lipid profiles were biochemically and gas-chromatographically determined. Dietary phytol caused PA and PrA accumulation in the adipose tissue and liver but not in the brain, and reduced plasma and liver triacylglycerol levels. Phytol intake also decreased the fatty acid concentrations in the adipose tissue, especially polyunsaturated fatty acids such as linoleic acid, but increased the concentrations of these fatty acids in the liver. However, dietary phytol had a low impact on the brain lipid profile. This study suggests that dietary phytol intake caused accumulation of PA and PrA and modified lipid profiles in the adipose tissue and liver, but that the brain is an insusceptible tissue to dietary phytol-induced changes.

Fatty Acid Oxidation in Peroxisomes: Enzymology, Metabolic Crosstalk with Other Organelles and Peroxisomal Disorders

Peroxisomes play a central role in metabolism as exemplified by the fact that many genetic disorders in humans have been identified through the years in which there is an impairment in one or more of these peroxisomal functions, in most cases associated with severe clinical signs and symptoms. One of the key functions of peroxisomes is the β-oxidation of fatty acids which differs from the oxidation of fatty acids in mitochondria in many respects which includes the different substrate specificities of the two organelles. Whereas mitochondria are the main site of oxidation of medium-and long-chain fatty acids, peroxisomes catalyse the β-oxidation of a distinct set of fatty acids, including very-long-chain fatty acids, pristanic acid and the bile acid intermediates di- and trihydroxycholestanoic acid. Peroxisomes require the functional alliance with multiple subcellular organelles to fulfil their role in metabolism. Indeed, peroxisomes require the functional interaction with lysosomes, lipid droplets and the endoplasmic reticulum, since these organelles provide the substrates oxidized in peroxisomes. On the other hand, since peroxisomes lack a citric acid cycle as well as respiratory chain, oxidation of the end-products of peroxisomal fatty acid oxidation notably acetyl-CoA, and different medium-chain acyl-CoAs, to CO₂ and H₂O can only occur in mitochondria. The same is true for the reoxidation of NADH back to NAD⁺. There is increasing evidence that these interactions between organelles are mediated by tethering proteins which bring organelles together in order to allow effective exchange of metabolites. It is the purpose of this review to describe the current state of knowledge about the role of peroxisomes in fatty acid oxidation, the transport of metabolites across the peroxisomal membrane, its functional interaction with other subcellular organelles and the disorders of peroxisomal fatty acid β-oxidation identified so far in humans.

Potential Involvement of Peroxisome in Multiple Sclerosis and Alzheimer's Disease : Peroxisome and Neurodegeneration

Peroxisomopathies are rare diseases due to dysfunctions of the peroxisome in which this organelle is either absent or with impaired activities. These diseases, at the exception of type I hyperoxaluria and acatalasaemia, affect the central and peripheral nervous system. Due to the significant impact of peroxisomal abnormalities on the functioning of nerve cells, this has led to an interest in peroxisome in common neurodegenerative diseases, such as Alzheimer's disease and multiple sclerosis. In these diseases, a role of the peroxisome is suspected on the basis of the fatty acid and phospholipid profile in the biological fluids and the brains of patients. It is also speculated that peroxisomal dysfunctions could contribute to oxidative stress and mitochondrial alterations which are recognized as major players in the development of neurodegenerative diseases. Based on clinical and in vitro studies, the data obtained support a potential role of peroxisome in Alzheimer's disease and multiple sclerosis.

Laboratory diagnosis of disorders of peroxisomal biogenesis and function: a technical standard of the American College of Medical Genetics and Genomics (ACMG)

Peroxisomal disorders are a clinically and genetically heterogeneous group of diseases caused by defects in peroxisomal biogenesis or function, usually impairing several metabolic pathways. Peroxisomal disorders are rare; however, the incidence may be underestimated due to the broad spectrum of clinical presentations. The inclusion of X-linked adrenoleukodystrophy to the Recommended Uniform Screening Panel for newborn screening programs in the United States may increase detection of this and other peroxisomal disorders. The current diagnostic approach relies heavily on biochemical genetic tests measuring peroxisomal metabolites, including very long-chain and branched-chain fatty acids in plasma and plasmalogens in red blood cells. Molecular testing can confirm biochemical findings and identify the specific genetic defect, usually utilizing a multiple-gene panel or exome/genome approach. When next-generation sequencing is used as a first-tier test, evaluation of peroxisome metabolism is often necessary to assess the significance of unknown variants and establish the extent of peroxisome dysfunction. This document provides a resource for laboratories developing and implementing clinical biochemical genetic testing for peroxisomal disorders, emphasizing technical considerations for sample collection, test performance, and result interpretation. Additionally, considerations on confirmatory molecular testing are discussed.

Oxysterols as lipid mediators: Their biosynthetic genes, enzymes and metabolites

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Pathways of oxysterol biosynthesis.

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Pathways of oxysterol metabolism.

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Oxysterols as bioactive molecules.

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Disorders of oxysterol metabolism.

There is growing evidence that oxysterols are more than simple metabolites in the pathway from cholesterol to bile acids. Recent data has shown oxysterols to be ligands to nuclear receptors and to G protein-coupled receptors, modulators of N-methyl-d-aspartate receptors and regulators of cholesterol biosynthesis. In this mini-review we will discuss the biosynthetic mechanisms for the formation of different oxysterols and the implication of disruption of these mechanisms in health and disease.

The cholic acid extension study in Zellweger spectrum disorders: Results and implications for therapy

INTRODUCTION

Currently, no therapies are available for Zellweger spectrum disorders (ZSDs), a group of genetic metabolic disorders characterised by a deficiency of functional peroxisomes. In a previous study, we showed that oral cholic acid (CA) treatment can suppress bile acid synthesis in ZSD patients and, thereby, decrease plasma levels of toxic C₂₇ -bile acid intermediates, one of the biochemical abnormalities in these patients. However, no effect on clinically relevant outcome measures could be observed after 9 months of CA treatment. It was noted that, in patients with advanced liver disease, caution is needed because of possible hepatotoxicity.

METHODS

An extension study of the previously conducted pretest-posttest design study was conducted including 17 patients with a ZSD. All patients received oral CA for an additional period of 12 months, encompassing a total of 21 months of treatment. Multiple clinically relevant parameters and markers for bile acid synthesis were assessed after 15 and 21 months of treatment.

RESULTS

Bile acid synthesis was still suppressed after 21 months of CA treatment, accompanied with reduced levels of C₂₇ -bile acid intermediates in plasma. These levels significantly increased again after discontinuation of CA. No significant changes were found in liver tests, liver elasticity, coagulation parameters, fat-soluble vitamin levels or body weight.

CONCLUSIONS

Although CA treatment did lead to reduced levels of toxic C₂₇ -bile acid intermediates in ZSD patients without severe liver fibrosis or cirrhosis, no improvement of clinically relevant parameters was observed after 21 months of treatment. We discuss the implications for CA therapy in ZSD based on these results.

Loss of Enzymes in the Bile Acid Synthesis Pathway Explains Differences in Bile Composition among Mammals

Bile acids are important for absorbing nutrients. Most mammals produce cholic and chenodeoxycholic bile acids. Here, we investigated genes in the bile acid synthesis pathway in four mammals that deviate from the usual mammalian bile composition. First, we show that naked-mole rats, elephants, and manatees repeatedly inactivated CYP8B1, an enzyme uniquely required for cholic acid synthesis, which explains the absence of cholic acid in these species. Second, no gene-inactivating mutations were found in any pathway gene in the rhinoceros, a species that lacks bile acids, indicating an evolutionarily recent change in its bile composition. Third, elephants and/or manatees that also lack bile acids altogether have lost additional nonessential enzymes (SLC27A5, ACOX2). Apart from uncovering genomic differences explaining deviations in bile composition, our analysis of bile acid enzymes in bile acid-lacking species suggests that essentiality prevents gene loss, while loss of pleiotropic genes is permitted if their other functions are compensated by functionally related proteins.

Clinical and Neuroimaging Spectrum of Peroxisomal Disorders

Peroxisomes play vital roles in a broad spectrum of cellular metabolic pathways. Defects in genes encoding peroxisomal proteins can result in a wide array of disorders, depending upon the metabolic pathways affected. These disorders can be broadly classified into 2 main groups; peroxisome biogenesis disorders (PBDs) and single peroxisomal enzyme deficiencies. Peroxisomal enzyme deficiencies are result of dysfunction of a specific metabolic pathway, while PBDs are due to generalized peroxisomal dysfunction. Mutations in PEX1 gene are the most common cause of PBDs, accounting for two-thirds of cases. Peroxisomal fission defects is a recently recognized entity, included under the subgroup of PBDs. The aim of this article is to provide a comprehensive review on the clinical and neuroimaging spectrum of peroxisomal disorders.

The peroxisome: an update on mysteries 2.0

Peroxisomes are key metabolic organelles, which contribute to cellular lipid metabolism, e.g. the β-oxidation of fatty acids and the synthesis of myelin sheath lipids, as well as cellular redox balance. Peroxisomal dysfunction has been linked to severe metabolic disorders in man, but peroxisomes are now also recognized as protective organelles with a wider significance in human health and potential impact on a large number of globally important human diseases such as neurodegeneration, obesity, cancer, and age-related disorders. Therefore, the interest in peroxisomes and their physiological functions has significantly increased in recent years. In this review, we intend to highlight recent discoveries, advancements and trends in peroxisome research, and present an update as well as a continuation of two former review articles addressing the unsolved mysteries of this astonishing organelle. We summarize novel findings on the biological functions of peroxisomes, their biogenesis, formation, membrane dynamics and division, as well as on peroxisome-organelle contacts and cooperation. Furthermore, novel peroxisomal proteins and machineries at the peroxisomal membrane are discussed. Finally, we address recent findings on the role of peroxisomes in the brain, in neurological disorders, and in the development of cancer.

Inborn Errors of Bile Acid Metabolism

Inborn errors of bile acid metabolism are rare causes of neonatal cholestasis and liver disease in older children and adults. The diagnosis should be considered in the context of hyperbilirubinemia with normal serum bile acids and made by urinary liquid secondary ionization mass spectrometry or DNA testing. Cholic acid is an effective treatment of most single-enzyme defects and patients with Zellweger spectrum disorder with liver disease.

Expanding the concept of peroxisomal diseases and efficient diagnostic system in Japan

The concept of peroxisomal diseases is expanding because of improvements in diagnostic technology based on advanced biochemical analysis and development of next-generation sequencing. For quicker and more accurate diagnosis of as many patients as possible, we developed a new diagnostic system combining the conventional diagnostic system and comprehensive mutational analysis by whole-exome sequencing in Japan. Adrenoleukodystrophy (ALD) is the most common peroxisomal disease. In the cerebral type of ALD, hematopoietic stem cell transplantation is the only treatment in the early stage, and thus prompt diagnosis will improve the prognosis of affected patients. Furthermore, it is also important to identify pre-symptomatic patients by family analysis of probands by providing appropriate disease information and genetic counseling, which will also lead to early intervention. Here, we summarize current information related to peroxisomal diseases and ALD and introduce our efficient diagnostic system for use in Japan, which resulted in the diagnosis of 73 Japanese patients with peroxisome biogenesis disorders, 16 with impaired β-oxidation of fatty acids, three with impaired etherphospholipid biosynthesis, and 191 Japanese families with ALD so far.

Plasma lipidomics as a diagnostic tool for peroxisomal disorders

Peroxisomes are ubiquitous cell organelles that play an important role in lipid metabolism. Accordingly, peroxisomal disorders, including the peroxisome biogenesis disorders and peroxisomal single-enzyme deficiencies, are associated with aberrant lipid metabolism. Lipidomics is an emerging tool for diagnosis, disease-monitoring, identifying lipid biomarkers, and studying the underlying pathophysiology in disorders of lipid metabolism. In this study, we demonstrate the potential of lipidomics for the diagnosis of peroxisomal disorders using plasma samples from patients with different types of peroxisomal disorders. We show that the changes in the plasma profiles of phospholipids, di- and triglycerides, and cholesterol esters correspond with the characteristic metabolite abnormalities that are currently used in the metabolic screening for peroxisomal disorders. The lipidomics approach, however, gives a much more detailed overview of the metabolic changes that occur in the lipidome. Furthermore, we identified novel unique lipid species for specific peroxisomal diseases that are candidate biomarkers. The results presented in this paper show the power of lipidomics approaches to enable the specific diagnosis of different peroxisomal disorders.

Autosomal-recessive cerebellar ataxias

The autosomal-recessive cerebellar ataxias comprise more than half of the known genetic forms of ataxia and represent an extensive group of clinically heterogeneous disorders that can occur at any age but whose onset is typically prior to adulthood. In addition to ataxia, patients often present with polyneuropathy and clinical symptoms outside the nervous system. The most common of these diseases is Friedreich ataxia, caused by mutation of the frataxin gene, but recent advances in genetic analysis have greatly broadened the ever-expanding number of causative genes to over 50. In this review, the clinical neurogenetics of the recessive cerebellar ataxias will be discussed, including updates on recently identified novel ataxia genes, advancements in unraveling disease-specific molecular pathogenesis leading to ataxia, potential treatments under development, technologic improvements in diagnostic testing such as clinical exome sequencing, and what the future holds for clinicians and geneticists.

Exome sequences of multiplex, multigenerational families reveal schizophrenia risk loci with potential implications for neurocognitive performance

Schizophrenia is a serious mental illness, involving disruptions in thought and behavior, with a worldwide prevalence of about one percent. Although highly heritable, much of the genetic liability of schizophrenia is yet to be explained. We searched for susceptibility loci in multiplex, multigenerational families affected by schizophrenia, targeting protein-altering variation with in silico predicted functional effects. Exome sequencing was performed on 136 samples from eight European-American families, including 23 individuals diagnosed with schizophrenia or schizoaffective disorder. In total, 11,878 non-synonymous variants from 6,396 genes were tested for their association with schizophrenia spectrum disorders. Pathway enrichment analyses were conducted on gene-based test results, protein-protein interaction (PPI) networks, and epistatic effects. Using a significance threshold of FDR < 0.1, association was detected for rs10941112 (p = 2.1 × 10-5 ; q-value = 0.073) in AMACR, a gene involved in fatty acid metabolism and previously implicated in schizophrenia, with significant cis effects on gene expression (p = 5.5 × 10-4 ), including brain tissue data from the Genotype-Tissue Expression project (minimum p = 6.0 × 10-5 ). A second SNP, rs10378 located in TMEM176A, also shows risk effects in the exome data (p = 2.8 × 10-5 ; q-value = 0.073). PPIs among our top gene-based association results (p < 0.05; n = 359 genes) reveal significant enrichment of genes involved in NCAM-mediated neurite outgrowth (p = 3.0 × 10-5 ), while exome-wide SNP-SNP interaction effects for rs10941112 and rs10378 indicate a potential role for kinase-mediated signaling involved in memory and learning. In conclusion, these association results implicate AMACR and TMEM176A in schizophrenia risk, whose effects may be modulated by genes involved in synaptic plasticity and neurocognitive performance.

Genetic testing for Refsum disease

We reviewed the scientific literature and disease guidelines in order to summarize the clinical utility of genetic testing for Refsum disease. The disease has autosomal recessive inheritance, unknown prevalence, and is caused by variations in PEX7 and PHYH genes. Clinical diagnosis is based on clinical findings, ophthalmological examination, electroretinography, optical coherence tomography and phytanic acid assay. The genetic test is useful for confirming diagnosis, for differential diagnosis, couple risk assessment and access to clinical trials.

Peripheral neuropathy in complex inherited diseases: an approach to diagnosis

Peripheral neuropathy is a common finding in patients with complex inherited neurological diseases and may be subclinical or a major component of the phenotype. This review aims to provide a clinical approach to the diagnosis of this complex group of patients by addressing key questions including the predominant neurological syndrome associated with the neuropathy, for example, spasticity, the type of neuropathy and the other neurological and non-neurological features of the syndrome. Priority is given to the diagnosis of treatable conditions. Using this approach, we associated neuropathy with one of three major syndromic categories: (1) ataxia, (2) spasticity and (3) global neurodevelopmental impairment. Syndromes that do not fall easily into one of these three categories can be grouped according to the predominant system involved in addition to the neuropathy, for example, cardiomyopathy and neuropathy. We also include a separate category of complex inherited relapsing neuropathy syndromes, some of which may mimic Guillain-Barré syndrome, as many will have a metabolic aetiology and be potentially treatable.

Liver and the defects of cholesterol and bile acids biosynthesis: Rare disorders many diagnostic pitfalls

In recent decades, biotechnology produced a growth of knowledge on the causes and mechanisms of metabolic diseases that have formed the basis for their study, diagnosis and treatment. Unfortunately, it is well known that the clinical features of metabolic diseases can manifest themselves with very different characteristics and escape early detection. Also, it is well known that the prognosis of many metabolic diseases is excellent if diagnosed and treated early. In this editorial we briefly summarized two groups of inherited metabolic diseases, the defects of cholesterol biosynthesis and those of bile acids. Both groups show variable clinical manifestations but some clinical signs and symptoms are common in both the defects of cholesterol and bile acids. The differential diagnosis can be made analyzing sterol profiles in blood and/or bile acids in blood and urine by chromatographic techniques (GC-MS and LC-MS/MS). Several defects of both biosynthetic pathways are treatable so early diagnosis is crucial. Unfortunately their diagnosis is made too late, due either to the clinical heterogeneity of the syndromes (severe, mild and very mild) that to the scarcity of scientific dissemination of these rare diseases. Therefore, the delay in diagnosis leads the patient to the medical observation when the disease has produced irreversible damages to the body. Here, we highlighted simple clinical and laboratory descriptions that can potentially make you to suspect a defect in cholesterol biosynthesis and/or bile acids, as well, we suggest appropriate request of the laboratory tests that along with common clinical features can help to diagnose these defects.

Identification and diagnostic value of phytanoyl- and pristanoyl-carnitine in plasma from patients with peroxisomal disorders

Phytanic acid is a branched-chain fatty acid, the level of which is elevated in patients with a variety of peroxisomal disorders, including Refsum disease, and Rhizomelic chondrodysplasia punctata type 1 and 5. Elevated levels of both phytanic and pristanic acid are found in patients with Zellweger Spectrum Disorders, and pristanic acid is elevated in patients with α-methylacyl-CoA racemase deficiency. For the diagnosis of peroxisomal disorders, a variety of metabolites can be measured in blood samples from suspected patients, including very long-chain fatty acids, phytanic and pristanic acid. Based on the fact that very long-chain fatty acylcarnitines are elevated in tissues and plasma from patients with certain peroxisomal disorders, we investigated whether phytanoyl- and pristanoyl-carnitine are also present in plasma from patients with different peroxisomal disorders. Our study shows that phytanoyl- and pristanoyl-carnitine are indeed present in plasma samples from patients with different types of peroxisomal disorders, but only when the total plasma levels of their corresponding fatty acids, phytanic acid and pristanic acid, are markedly elevated. We conclude that the measurement of phytanoyl- and pristanoyl-carnitine is not sensitive and specific enough to use these acylcarnitines as conclusive diagnostic markers for peroxisomal disorders.

Bile acid analysis in human disorders of bile acid biosynthesis

Bile acids facilitate the absorption of lipids in the gut, but are also needed to maintain cholesterol homeostasis, induce bile flow, excrete toxic substances and regulate energy metabolism by acting as signaling molecules. Bile acid biosynthesis is a complex process distributed across many cellular organelles and requires at least 17 enzymes in addition to different metabolite transport proteins to synthesize the two primary bile acids, cholic acid and chenodeoxycholic acid. Disorders of bile acid synthesis can present from the neonatal period to adulthood and have very diverse clinical symptoms ranging from cholestatic liver disease to neuropsychiatric symptoms and spastic paraplegias. This review describes the different bile acid synthesis pathways followed by a summary of the current knowledge on hereditary disorders of human bile acid biosynthesis with a special focus on diagnostic bile acid profiling using mass spectrometry.

Inherited ichthyosis: Syndromic forms

Among diseases that cause ichthyosis as one of the symptoms, there are some diseases that induce abnormalities in organs other than the skin. Of these, diseases with characteristic signs are regarded as syndromes. Although these syndromes are very rare, Netherton syndrome, Sjögren-Larsson syndrome, Conradi-Hünermann-Happle syndrome, Dorfman-Chanarin syndrome, ichthyosis follicularis, atrichia and photophobia (IFAP) syndrome, and Refsum syndrome have been described in texts as representative ones. It is important to know the molecular genetics and pathomechanisms in order to establish an effective therapy and beneficial genetic counseling including a prenatal diagnosis.

Expression of Alpha Methylacyl CoA Racemase (AMACR) in Gastric Adenocarcinoma and Its Correlation with Helicobacter pylori Infection

INTRODUCTION

Gastric cancer develops in a multistep progression and is determined by genetic and environmental factors. Over-expression of Alpha Methylacyl CoA Racemase (AMACR) is useful in diagnosis of prostate cancer. There is plenty of genetic alteration that occurs in gastric adenocarcinoma. The present study was planned to determine if AMACR can be used as a diagnostic marker in gastric adenocarcinoma similar to prostate cancer.

AIM

To study the expression of AMACR in gastric adenocarcinoma and correlate its expression with density of Helicobacter pylori.

MATERIALS AND METHODS

This cross-sectional, prospective study was conducted from August 2013-2015. Fifty gastric cancer biopsies were taken. Adjacent biopsy from normal/reactive mucosa was also taken from 21 cases. Samples were stained with H&E for morphological details, Loeffler's methylene blue for Helicobacter pylori and immunohistochemistry (IHC) was done to check for the expression of AMACR proteins. Statistical analysis was done using chi square test, Spearman's correlation coefficient and Fisher's exact test. The p-value ≤ 0.05 was taken as critical level of significance.

RESULTS

Overexpression of AMACR was observed in 88.89% of intestinal type and 78.05% of diffuse type adenocarcinoma. AMACR expression was significantly less in adjacent reactive/dysplastic mucosa. Helicobacter pylori were seen in 8/9 (88.89%) and 35/41(85.36%) cases of intestinal adenocarcinoma and diffuse adenocarcinoma respectively. When grades of Helicobacter pylori were compared with the positivity of AMACR, no significant association and correlation was found.

CONCLUSION

The expression of AMACR in neoplastic tissue was significantly higher as compared to adjacent dysplastic, reactive or normal tissue. Thus, IHC for AMACR can be used for differentiating the cases of reactive atypia from early neoplastic lesions similar to its role in prostatic tissue. Helicobacter pylori does not affect the expression of AMACR in neoplastic gastric lesions.

ACOX2 deficiency: A disorder of bile acid synthesis with transaminase elevation, liver fibrosis, ataxia, and cognitive impairment

Acyl CoA Oxidase 2 (ACOX2) encodes branched-chain acyl-CoA oxidase, a peroxisomal enzyme believed to be involved in the metabolism of branched-chain fatty acids and bile acid intermediates. Deficiency of this enzyme has not been described previously. We report an 8-y-old male with intermittently elevated transaminase levels, liver fibrosis, mild ataxia, and cognitive impairment. Exome sequencing revealed a previously unidentified homozygous premature termination mutation (p.Y69*) in ACOX2 Immunohistochemistry confirmed the absence of ACOX2 expression in the patient's liver, and biochemical analysis showed marked elevation of intermediate bile acids upstream of ACOX2. These findings define a potentially treatable inborn error of bile acid biosynthesis caused by ACOX2 deficiency.

Peroxisomes in brain development and function

Peroxisomes contain numerous enzymatic activities that are important for mammalian physiology. Patients lacking either all peroxisomal functions or a single enzyme or transporter function typically develop severe neurological deficits, which originate from aberrant development of the brain, demyelination and loss of axonal integrity, neuroinflammation or other neurodegenerative processes. Whilst correlating peroxisomal properties with a compilation of pathologies observed in human patients and mouse models lacking all or individual peroxisomal functions, we discuss the importance of peroxisomal metabolites and tissue- and cell type-specific contributions to the observed brain pathologies. This enables us to deconstruct the local and systemic contribution of individual metabolic pathways to specific brain functions. We also review the recently discovered variability of pathological symptoms in cases with unexpectedly mild presentation of peroxisome biogenesis disorders. Finally, we explore the emerging evidence linking peroxisomes to more common neurological disorders such as Alzheimer’s disease, autism and amyotrophic lateral sclerosis. This article is part of a Special Issue entitled: Peroxisomes edited by Ralf Erdmann.

AMACR amplification and overexpression in primary imatinib-naïve gastrointestinal stromal tumors: a driver of cell proliferation indicating adverse prognosis

Non-random gains of chromosome 5p have been observed in clinically aggressive gastrointestinal stromal tumors, whereas the driving oncogenes on 5p remain to be characterized. We used an integrative genomic and functional approach to identify amplified oncogenes on 5p and to evaluate the relevance of AMACR amplification at 5p13.3 and its overexpression in gastrointestinal stromal tumors. Thirty-seven tumor samples, imatinib-sensitive GIST882 cell line, and imatinib-resistant GIST48 cell line were analyzed for DNA imbalances using array-based genomic profiling. Forty-one fresh tumor samples of various risk categories were enriched for pure tumor cells by laser capture microdissection and quantified for AMACR mRNA expression. AMACR-specific fluorescence in situ hybridization and immunohistochemistry were both informative in tissue microarray sections of 350 independent primary gastrointestinal stromal tumors, including 213 cases with confirmed KIT /PDGFRA genotypes. To assess the oncogenic functions of AMACR, GIST882 and GIST48 cell lines were stably silenced against their endogenous AMACR expression. In 59% of cases featuring 5p gains, two major amplicons encompassed discontinuous chromosomal regions that were differentially overrepresented in high-risk cases, including the one harboring the mRNA-upregulated AMACR gene. Gene amplification was detected in 19.7% of cases (69/350) and strongly related to protein overexpression (p<0.001), although 52% of AMACR-overexpressing cases exhibited no amplification. Both gene amplification and protein overexpression were significantly associated with epithelioid histology, larger size, increased mitoses, higher risk levels, and unfavorable genotypes (all p≤0.03). They were also independently predictive of decreased disease-free survival (overexpression, p<0.001; amplification, p=0.020) in the multivariate analysis. Concomitant with downregulated cyclin D1, cyclin E, and CDK4, AMACR knockdown suppressed cell proliferation and induced G₁-phase arrest, but did not affect apoptosis in both GIST882 and GIST48 cells. In conclusion, AMACR amplification is a mechanism driving increased mRNA and protein expression and conferring aggressiveness through heightened cell proliferation in gastrointestinal stromal tumors.

Pristanic acid provokes lipid, protein, and DNA oxidative damage and reduces the antioxidant defenses in cerebellum of young rats

Zellweger syndrome (ZS) and some peroxisomal diseases are severe inherited disorders mainly characterized by neurological symptoms and cerebellum abnormalities, whose pathogenesis is poorly understood. Biochemically, these diseases are mainly characterized by accumulation of pristanic acid (Prist) and other fatty acids in the brain and other tissues. In this work, we evaluated the in vitro influence of Prist on redox homeostasis by measuring lipid, protein, and DNA damage, as well as the antioxidant defenses and the activities of aconitase and α-ketoglutarate dehydrogenase in cerebellum of 30-day-old rats. The effect of Prist on DNA damage was also evaluated in blood of these animals. Some parameters were also evaluated in cerebellum from neonatal rats and in cerebellum neuronal cultures. Prist significantly increased malondialdehyde (MDA) levels and carbonyl formation and reduced sulfhydryl content and glutathione (GSH) concentrations in cerebellum of young rats. It also caused DNA strand damage in cerebellum and induced a high micronuclei frequency in blood. On the other hand, this fatty acid significantly reduced α-ketoglutarate dehydrogenase and aconitase activities in rat cerebellum. We also verified that Prist-induced increase of MDA levels was totally prevented by melatonin and attenuated by α-tocopherol but not by the nitric oxide synthase inhibitor N(ω)-nitro-L-arginine methyl ester, indicating the involvement of reactive oxygen species in this effect. Cerebellum from neonate rats also showed marked alterations of redox homeostasis, including an increase of MDA levels and a decrease of sulfhydryl content and GSH concentrations elicited by Prist. Finally, Prist provoked an increase of dichlorofluorescein (DCFH) oxidation in cerebellum-cultivated neurons. Our present data indicate that Prist compromises redox homeostasis in rat cerebellum and blood and inhibits critical enzymes of the citric acid cycle that are susceptible to free radical attack. The present findings may contribute to clarify the pathogenesis of the cerebellar alterations observed in patients affected by ZS and some peroxisomal disorders in which Prist is accumulated.

"Role of peroxisomes in human lipid metabolism and its importance for neurological development"

Peroxisomes play a crucial role in normal neurological development as exemplified by the devastating neurological consequences of a defect in the biogenesis of peroxisomes as in Zellweger syndrome. The underlying basis for the important role of peroxisomes in neurological development resides in the fact that peroxisomes catalyze a number of physiological functions, notably involving the metabolism of different lipids. Indeed, peroxisomes catalyse the beta-oxidative breakdown of certain fatty acids including: (1.) the very long-chain fatty acids C22:0, C24:0, and C26:0; (2.) pristanic acid and (3.) the bile acid intermediates di- and trihydroxycholestanoic acid which cannot be oxidized in mitochondria. Furthermore, peroxisomes catalyze the synthesis of a particular type of lipids, i.e. ether-linked phospholipids, which are highly abundant in brain, especially in myelin. The current state of knowledge with respect to the metabolic role of peroxisomes will be described in this paper with particular emphasis on the role of peroxisomes in brain.

The clinical spectrum of inherited diseases involved in the synthesis and remodeling of complex lipids. A tentative overview

Over one hundred diseases related to inherited defects of complex lipids synthesis and remodeling are now reported. Most of them were described within the last 5 years. New descriptions and phenotypes are expanding rapidly. While the associated clinical phenotype is currently difficult to outline, with only a few patients identified, it appears that all organs and systems may be affected. The main clinical presentations can be divided into (1) Diseases affecting the central and peripheral nervous system. Complex lipid synthesis disorders produce prominent motor manifestations due to upper and/or lower motoneuron degeneration. Motor signs are often complex, associated with other neurological and extra-neurological signs. Three neurological phenotypes, spastic paraparesis, neurodegeneration with brain iron accumulation and peripheral neuropathies, deserve special attention. Many apparently well clinically defined syndromes are not distinct entities, but rather clusters on a continuous spectrum, like for the PNPLA6-associated diseases, extending from Boucher-Neuhauser syndrome via Gordon Holmes syndrome to spastic ataxia and pure hereditary spastic paraplegia; (2) Muscular/cardiac presentations; (3) Skin symptoms mostly represented by syndromic (neurocutaneous) and non syndromic ichthyosis; (4) Retinal dystrophies with syndromic and non syndromic retinitis pigmentosa, Leber congenital amaurosis, cone rod dystrophy, Stargardt disease; (5) Congenital bone dysplasia and segmental overgrowth disorders with congenital lipomatosis; (6) Liver presentations characterized mainly by transient neonatal cholestatic jaundice and non alcoholic liver steatosis with hypertriglyceridemia; and (7) Renal and immune presentations. Lipidomics and molecular functional studies could help to elucidate the mechanism(s) of dominant versus recessive inheritance observed for the same gene in a growing number of these disorders.

An overview of inborn errors of complex lipid biosynthesis and remodelling

In a review published in 2012, we delineated 14 inborn errors of metabolism (IEM) related to defects in biosynthesis of complex lipids, particularly phospholipids and sphingolipids (Lamari et al 2013). Given the numerous roles played by these molecules in membrane integrity, cell structure and function, this group of diseases is rapidly expanding as predicted. Almost 40 new diseases related to genetic defects in enzymes involved in the biosynthesis and remodelling of phospholipids, sphingolipids and complex fatty acids are now reported. While the clinical phenotype associated with these defects is currently difficult to outline, with only a few patients identified to date, it appears that all organs and systems may be affected - central and peripheral nervous system, eye, muscle, skin, bone, liver, immune system, etc. This chapter presents an introductive overview of this new group of IEM. More broadly, this special issue provides an update on other IEM involving complex lipids, namely dolichol and isoprenoids, glycolipids and congenital disorders of glycosylation, very long chain fatty acids and plasmalogens. Likewise, more than 100 IEM may actually lead to primary or secondary defects of complex lipids synthesis and remodelling. Because of the implication of several cellular compartments, this new group of disorders affecting the synthesis and remodelling of complex molecules challenges our current classification of IEM still largely based on cellular organelles--i.e. mitochondrial, lysosomal, peroxisomal disorders. While most of these new disorders have been identified by next generation sequencing, we wish to emphasize the promising role of lipidomics in deciphering their pathophysiology and identifying therapeutic targets.

FUNDUS FINDINGS IN A PATIENT WITH α-METHLYACYL-COA RACEMASE DEFICIENCY

PURPOSE

To describe the ocular findings in a patient with α-methylacyl-CoA racemase deficiency.

METHODS

Case report.

RESULTS

A 45-year-old white man presented with seizures, hemiparesis, and altered mental status. As a part of an extensive investigation, an ophthalmic evaluation was performed. Funduscopic examination of both eyes showed a bull's-eye pattern pigmentary maculopathy. Fluorescein angiography demonstrated a prominent choroidal circulation without dye leakage. Optical coherence tomography showed a significant thinning of the macula with moderate nerve fiber layer loss. Serum pristanic levels were significantly elevated, and α-methylacyl-CoA racemase deficiency was confirmed by urine and bile analysis. The patient's clinical condition improved after plasma exchange and dietary restriction of fatty acids.

CONCLUSION

α-Methylacyl-CoA racemase deficiency is a rare peroxisomal enzyme disorder previously described in only six patients, two of whom had pigmentary retinopathies. This article describes the third patient with retinopathy and the first with published fundus findings.

AMACR overexpression as a poor prognostic factor in patients with nasopharyngeal carcinoma

The molecular prognostic adjunct in patients with nasopharyngeal carcinomas (NPCs) still remains obscured. Through data mining from published transcriptomic database, alpha-methylacyl-CoA racemase (AMACR) was first identified as a differentially upregulated gene in NPC tissues, which is a key enzyme for isometric conversion of fatty acids entering the β-oxidation. Given the roles of AMACR in prognostication and frontline therapeutic regimen of common carcinomas, such as prostate cancer, we explored AMACR immunoexpression status and its clinical significance in NPC patients. AMACR immunohistochemistry was retrospectively performed and analyzed using H-score for biopsy specimens from 124 NPC patients who received standard treatment without distant metastasis at initial diagnosis. Those cases with H-score larger than the median value were construed as featuring AMACR overexpression. The findings were correlated with the clinicopathological variables, disease-specific survival (DSS), distant metastasis-free survival (DMFS), and local recurrence-free survival (LRFS). Endogenous AMACR protein expressions were assessed by real-time reverse-transcription polymerase chain reaction (RT-PCR) and Western blotting in NPC cells and non-neoplastic mucosal cells. AMACR overexpression was significantly associated with increment of primary tumor status (P = 0.009) and univariately predictive of adverse outcomes for DSS, DMFS, and LRFS. In the multivariate comparison, AMACR overexpression still remained prognostically independent to portend worse DSS (P = 0.006, hazard ratio = 2.129), DMFS (P = 0.001, hazard ratio = 2.795), and LRFS (P = 0.041, hazard ratio = 2.009), together with advanced American Joint of Cancer Committee (AJCC) stages III-IV. Compared with non-neoplastic cells, both HONE1 and TW01 NPC cells demonstrated markedly increased AMACR expression. AMACR overexpression was identified as an important prognosticator and a potential therapeutic target in the future.