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

Weighted gene co-expression network analysis identified hub genes critical to fatty acid composition in Gushi chicken breast muscle

BACKGROUND

The composition and content of fatty acids in the breast muscle are important factors influencing meat quality. In this study, we investigated the fatty acid composition and content in the breast muscle of Gushi chickens at different developmental stages (14 weeks, 22 weeks, and 30 weeks). Additionally, we utilized transcriptomic data from the same tissue and employed WGCNA and module identification methods to identify key genes associated with the fatty acid composition in Gushi chicken breast muscle and elucidate their regulatory networks.

RESULTS

Among them, six modules (blue, brown, green, light yellow, purple, and red modules) showed significant correlations with fatty acid content and metabolic characteristics. Enrichment analysis revealed that these modules were involved in multiple signaling pathways related to fatty acid metabolism, including fatty acid metabolism, PPAR signaling pathway, and fatty acid biosynthesis. Through analysis of key genes, we identified 136 genes significantly associated with fatty acid phenotypic traits. Protein-protein interaction network analysis revealed that nine of these genes were closely related to fatty acid metabolism. Additionally, through correlation analysis of transcriptome data, we identified 51 key ceRNA regulatory networks, including six central genes, 7 miRNAs, and 28 lncRNAs.

CONCLUSION

This study successfully identified key genes closely associated with the fatty acid composition in Gushi chicken breast muscle, as well as their post-transcriptional regulatory networks. These findings provide new insights into the molecular regulatory mechanisms underlying the flavor characteristics of chicken meat and the composition of fatty acids in the breast muscle.

Therapeutic Role of ELOVL in Neurological Diseases

Fatty acids play an important role in controlling the energy balance of mammals. De novo lipogenesis also generates a significant amount of lipids that are endogenously produced in addition to their ingestion. Fatty acid elongation beyond 16 carbons (palmitic acid), which can lead to the production of very long chain fatty acids (VLCFA), can be caused by the rate-limiting condensation process. Seven elongases, ELOVL1-7, have been identified in mammals and each has a unique substrate specificity. Researchers have recently developed a keen interest in the elongation of very long chain fatty acids protein 1 (ELOVL1) enzyme as a potential treatment for a variety of diseases. A number of neurological disorders directly or indirectly related to ELOVL1 involve the elongation of monounsaturated (C20:1 and C22:1) and saturated (C18:0-C26:0) acyl-CoAs. VLCFAs and ELOVL1 have a direct impact on the neurological disease. Other neurological symptoms such as ichthyotic keratoderma, spasticity, and hypomyelination have also been linked to the major enzyme (ELOVL1). Recently, ELOVL1 has also been heavily used to treat a number of diseases. The current review focuses on in-depth unique insights regarding the role of ELOVL1 as a therapeutic target and associated neurological disorders.

Elongases of Long-Chain Fatty Acids ELO2 and ELO9 Are Involved in Cuticle Formation and Function in Fecundity in the Yellow Fever Mosquito, Aedes aegypti

Long-chain fatty acid elongases (ELOs) play important roles in the metabolism of fatty acids in insects. In this study, the genes for two elongases from Aedes aegypti were identified, AeELO2 and AeELO9. Quantitative real time PCR showed that AeELO2 and AeELO9 are expressed at all developmental stages and some body parts, but with different expression patterns. RNAi-mediated knockdown of AeELO2 and AeELO9 was performed to investigate their roles in the development, growth, osmotic balance, and cold tolerance of Ae. aegypti. Knockdown of AeELO2 slowed larval growth and development by causing molting abnormalities. Additionally, 33% ± 3.3% of adults died during oviposition, accompanied by an abnormal extension of cuticles in AeELO2-dsRNA knockdown mosquitos. Knockdown of AeEL09 resulted in abnormal balance of cuticular osmotic pressure and a reduction in egg production. The maximal mRNAs of AeELO2 and AeELO9 were detected in eggs at 72 h after oviposition. Moreover, AeELO2 knockdown reduced the egg hatching rates and AeELO9 knockdown larvae did not develop well. In summary, AeELO2 is involved in larval molting and growth, and its knockdown affects the flexibility and elasticity of adult mosquito cuticles. AeELO9 regulates cold tolerance, osmotic balance, and egg development in Ae. aegypti.

Long-chain polyunsaturated fatty acid biosynthesis in a land-crab with advanced terrestrial adaptations: Molecular cloning and functional characterization of two fatty acyl elongases

Depending on the presence and activities of the front-end fatty acyl desaturases and elongation of very long-chain fatty acid (Elovl) enzymes, animals have different capacities for long-chain (≥C₂₀) polyunsaturated fatty acids (LC-PUFA) biosynthesis. Successful land colonisation in brachyuran crabs requires a shift towards terrestrial food chain with limited LC-PUFA availability. We cloned and functionally characterised two elovl genes from the purple land crab Gecarcoidea lalandii. The two Elovl contained all the necessary motifs of a typical polyunsaturated fatty acids (PUFA) Elovl and phylogenetically clustered in the Elovl1 and Elovl6 clades, respectively. The G. lalandii Elovl1 elongated saturated fatty acids, with low activities towards C20 and C22 PUFA substrates. Moreover, the G. lalandii Elovl6 was particularly active in the elongation of C18 PUFA, although it also recognised monounsaturated fatty acids as substrates for elongation. Collectively, the herein characterised G. lalandii elovl paralogues fulfil all the elongation steps involved in the LC-PUFA biosynthetic pathways. Tissue distribution of the G. lalandii elovl genes, along with the FA composition analyses, suggest the hepatopancreas and gill as key metabolic sites for fatty acid elongation. However, current data suggest that G. lalandii is unable to rely solely on biosynthesis to fulfil LC-PUFA requirements, since front-end desaturase appears to be absent in this species and other decapods.

3-Hydroxyacyl-CoA dehydratase 2 deficiency confers resistance to diet-induced obesity and glucose intolerance

Obesity and associated complications are becoming a pandemic. Inhibiting fatty acid synthesis and elongation is an important intervention for the treatment of obesity. Despite intensive investigations, many potential therapeutic targets have yet to be discovered. In this study, decreased expression of Hacd2 (a newly found enzyme in fatty acid elongation) was found in HFD induced mice and loss of Hacd2 expression in the liver protected mice against HFD induced obesity as well as associated fatty liver disease and diabetes. Additionally, further study indicated that hepatic HACD2 deficiency increased energy expenditure by upregulating the transcription of thermogenic programming genes. Our results suggest that HACD2 may be a promising therapeutic target for the management of obesity and associated metabolic diseases.

Discovery of Novel, Orally Bioavailable Pyrimidine Ether-Based Inhibitors of ELOVL1

In our efforts to identify novel small molecule inhibitors for the treatment of adrenoleukodystrophy (ALD), we conducted a high-throughput radiometric screen for inhibitors of elongation of very long chain fatty acid 1 (ELOVL1) enzyme. We developed a series of highly potent, central nervous system (CNS)-penetrant pyrimidine ether-based compounds with favorable pharmacokinetics culminating in compound 22. Compound 22 is a selective inhibitor of ELOVL1, reducing C26:0 VLCFA synthesis in ALD patient fibroblasts and lymphocytes in vitro. Compound 22 reduced C26:0 lysophosphatidyl choline (LPC), a subtype of VLCFA, in the blood of ATP binding cassette transporter D1 (ABCD1) KO mice, a murine model of ALD to near wild-type levels. Compound 22 is a low-molecular-weight, potent ELOVL1 inhibitor that may serve as a useful tool for exploring therapeutic approaches to the treatment of ALD.

Discovery and Optimization of Pyrazole Amides as Inhibitors of ELOVL1

Accumulation of very long chain fatty acids (VLCFAs) due to defects in ATP binding cassette protein D1 (ABCD1) is thought to underlie the pathologies observed in adrenoleukodystrophy (ALD). Pursuing a substrate reduction approach based on the inhibition of elongation of very long chain fatty acid 1 enzyme (ELOVL1), we explored a series of thiazole amides that evolved into compound 27─a highly potent, central nervous system (CNS)-penetrant compound with favorable in vivo pharmacokinetics. Compound 27 selectively inhibits ELOVL1, reducing C26:0 VLCFA synthesis in ALD patient fibroblasts, lymphocytes, and microglia. In mouse models of ALD, compound 27 treatment reduced C26:0 VLCFA concentrations to near-wild-type levels in blood and up to 65% in the brain, a disease-relevant tissue. Preclinical safety findings in the skin, eye, and CNS precluded progression; the origin and relevance of these findings require further study. ELOVL1 inhibition is an effective approach for normalizing VLCFAs in models of ALD.

Evolution of adrenoleukodystrophy model systems

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

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.

Lipids and cancer: Emerging roles in pathogenesis, diagnosis and therapeutic intervention

With the advent of effective tools to study lipids, including mass spectrometry-based lipidomics, lipids are emerging as central players in cancer biology. Lipids function as essential building blocks for membranes, serve as fuel to drive energy-demanding processes and play a key role as signaling molecules and as regulators of numerous cellular functions. Not unexpectedly, cancer cells, as well as other cell types in the tumor microenvironment, exploit various ways to acquire lipids and extensively rewire their metabolism as part of a plastic and context-dependent metabolic reprogramming that is driven by both oncogenic and environmental cues. The resulting changes in the fate and composition of lipids help cancer cells to thrive in a changing microenvironment by supporting key oncogenic functions and cancer hallmarks, including cellular energetics, promoting feedforward oncogenic signaling, resisting oxidative and other stresses, regulating intercellular communication and immune responses. Supported by the close connection between altered lipid metabolism and the pathogenic process, specific lipid profiles are emerging as unique disease biomarkers, with diagnostic, prognostic and predictive potential. Multiple preclinical studies illustrate the translational promise of exploiting lipid metabolism in cancer, and critically, have shown context dependent actionable vulnerabilities that can be rationally targeted, particularly in combinatorial approaches. Moreover, lipids themselves can be used as membrane disrupting agents or as key components of nanocarriers of various therapeutics. With a number of preclinical compounds and strategies that are approaching clinical trials, we are at the doorstep of exploiting a hitherto underappreciated hallmark of cancer and promising target in the oncologist's strategy to combat cancer.

The effects of chronic cadmium exposure on Bufo gargarizans larvae: Histopathological impairment, gene expression alteration and fatty acid metabolism disorder in the liver

Cadmium (Cd) a highly toxic metal to human and wildlife health and it is hazardous to both terrestrial and aquatic life. In this study, we used RNA sequencing analysis to examine the effects of chronic cadmium exposure on liver lipid metabolism of Bufo gargarizans larvae. Tadpoles were exposed to cadmium concentrations at 0, 5, 10, 50, 100 and 200 μg L^-1 from Gosner stage 26-42 of metamorphic climax. The results showed high dose cadmium (50, 100 and 200 μg L^-1) caused obvious histological changes characterized by hepatocytes deformation, nuclear pyknosis, increasing melanomacrophage centers (MMCs) and aggregated lipid droplets. Moreover, transcriptome analysis showed that liver function was seriously affected by cadmium exposure. Furthermore, high dose cadmium significantly upregulated the mRNA expression of elongation of very-long-chain fatty acids 1 (ELOVL1), Mitochondrial trans-2-enoyl-CoA reductase (MECR), Trans-2, 3-enoyl-CoA reductase (TER) and Hydroxysteroid (17β) dehydrogenase type 12 (HSD17B12) which are related with fatty acid synthesis. Meanwhile, mRNA levels of genes related with fat acid oxidation such as acetyl-CoA acyltransferase 2 (ACAA2) and enoyl-coenzyme A (CoA) hydratase short chain 1 (ECHS1) were significantly upregulated while the expression of Acyl-coA thioesterase 1 (ACOT1), 3-hydroxyacyl-CoA dehydrogenase (HADH), Palmitoyl-protein thioesterase 1(PPT1) and Acetyl-CoA acyltransferase 1(ACAA1) was significantly downregulated by high dose cadmium exposure. Furthermore, the mRNA level of ATP-binding cassette subfamily B member 11 (ABCB11) related with bile secretion was significantly decreased exposed to high dose cadmium. Our results suggested cadmium can cause liver dysfunction by inducing histopathological damages, genetic expression alterations and fatty acid metabolism disorder.

Probing the effects of hexavalent chromium exposure on histology and fatty acid metabolism in liver of Bufo gargarizans tadpoles

Hexavalent chromium is one of the major detrimental heavy metal pollutants. B. gargarizans tadpoles were treated with different concentrations of Cr⁶⁺ (0, 13, 52, 104, 208, and 416 μg Cr⁶⁺ L^-1) from Gs 2 to Gs 42. The effect of Cr⁶⁺ on histopathological alterations and transcript levels of fatty acid metabolism-related genes as well as fatty acids composition and content in liver were examined. Histopathological changes were observed in liver at 52, 104, 208, and 416 μg Cr⁶⁺ L^-1. Moreover, RT-qPCR analyses showed the downregulated mRNA levels of the genes related to fatty acid synthesis (SCD, MECR, TECR and ELOVL1) and fatty acid β-oxidation (ACOT1, PPT1, HADH and ACAA2) at 416 μg Cr⁶⁺ L^-1. However, the mRNA expression of fatty acid β-oxidation-related genes (ECHS1, HADHA and ACAA1) were significantly upregulated at 13, 52, 104, 208 and 416 μg Cr⁶⁺ L^-1. In situ hybridization revealed BSEP was expressed in hepatocyte nucleus and plasma membrane, and HSD17B12 was abundantly expressed in the plasma membrane. The HSD17B12 mRNA levels were significantly upregulated in tadpoles exposed to all Cr⁶⁺ treatment groups, while the BSEP mRNA levels were downregulated at 104, 208 and 416 μg Cr⁶⁺ L^-1 groups compared to control. In addition, an increase in polyunsaturated fatty acids and a decrease in monounsaturated fatty acids were found in 52, 104 and 416 μg Cr⁶⁺ L^-1 groups. Overall, chronic exposure to Cr⁶⁺ may suppress fatty acid synthesis, disturb fatty acid β-oxidation, aggravate disorders of hepatic function and induce hepatic impairment in B. gargarizans tadpoles.

Whole blood microRNA expression associated with stroke: Results from the Framingham Heart Study

Emerging evidence suggests microRNAs (miRNAs) may play an important role in explaining variation in stroke risk and recovery in humans, yet there are still few longitudinal studies examining the association between whole blood miRNAs and stroke. Accounting for multiple testing and adjusting for potentially confounding technical and clinical variables, here we show that whole blood miR-574-3p expression was significantly lower in participants with chronic stroke compared to non-cases. To explore the functional relevance of our findings, we analyzed miRNA-mRNA whole blood co-expression, pathway enrichment, and brain tissue gene expression. Results suggest miR-574-3p is involved in neurometabolic and chronic neuronal injury response pathways, including brain gene expression of DBNDD2 and ELOVL1. These results suggest miR-574-3p plays a role in regulating chronic brain and systemic cellular response to stroke and thus may implicate miR-574-3p as a partial mediator of long-term stroke outcomes.

Exogenous Addition of 25-Hydroxycholesterol Reduces Level of Very Long-Chain Fatty Acids in X-Linked Adrenoleukodystrophy

X‐Linked adrenoleukodystrophy (X‐ALD) is a severe metabolic disorder characterized by the accumulation of very long‐chain fatty acids (VLCFAs). Recently, we demonstrated that levels of 25‐hydroxycholesterol (25‐HC) and cholesterol 25‐hydroxylase (CH25H) were found to be elevated in X‐ALD. Herein, we report that the exogenous addition of 25‐HC significantly reduces C26:0 levels in X‐ALD patient‐derived fibroblasts and oligodendrocytes differentiated from induced pluripotent stem cells (iPSCs) derived from X‐ALD patients. Moreover, 25‐HC treatment was found to down‐regulate the expression of ELOVL1, a key enzyme for the synthesis of C26. In addition, activation of liver X receptor (LXR), a molecular target of endogenous 25‐HC, also reduced C26:0 level. The reduction of C26:0 levels by 25‐HC treatment might result, at least partially, from the decrease of ELOVL1 expression as well as the activation of LXR. Our findings could provide a better understanding of the role of 25‐HC in X‐ALD and useful information to find therapeutic agents to treat X‐ALD.

Dominant ELOVL1 mutation causes neurological disorder with ichthyotic keratoderma, spasticity, hypomyelination and dysmorphic features

BACKGROUND

Ichthyosis and neurological involvement occur in relatively few known Mendelian disorders caused by mutations in genes relevant both for epidermis and neural function.

OBJECTIVES

To identify the cause of a similar phenotype of ichthyotic keratoderma, spasticity, mild hypomyelination (on MRI) and dysmorphic features (IKSHD) observed in two unrelated paediatric probands without family history of disease.

METHODS

Whole exome sequencing was performed in both patients. The functional effect of prioritised variant in ELOVL1 (very-long-chain fatty acids (VLCFAs) elongase) was analysed by VLCFA profiling by gas chromatography-mass spectrometry in stably transfected HEK2932 cells and in cultured patient's fibroblasts.

RESULTS

Probands shared novel heterozygous ELOVL1 p.Ser165Phe mutation (de novo in one family, while in the other family, father could not be tested). In transfected cells p.Ser165Phe: (1) reduced levels of FAs C24:0-C28:0 and C26:1 with the most pronounced effect for C26:0 (P=7.8×10^-6 vs HEK293 cells with wild type (wt) construct, no difference vs naïve HEK293) and (2) increased levels of C20:0 and C22:0 (P=6.3×10^-7, P=1.2×10^-5, for C20:0 and C22:0, respectively, comparison vs HEK293 cells with wt construct; P=2.2×10^-7, P=1.9×10^-4, respectively, comparison vs naïve HEK293). In skin fibroblasts, there was decrease of C26:1 (P=0.014), C28:0 (P=0.001) and increase of C20:0 (P=0.033) in the patient versus controls. There was a strong correlation (r=0.92, P=0.008) between the FAs profile of patient's fibroblasts and that of p.Ser165Phe transfected HEK293 cells. Serum levels of C20:0-C26:0 FAs were normal, but the C24:0/C22:0 ratio was decreased.

CONCLUSION

The ELOVL1 p.Ser165Phe mutation is a likely cause of IKSHD.

Effect of Lorenzo's Oil on Hepatic Gene Expression and the Serum Fatty Acid Level in abcd1-Deficient Mice

Lorenzo's oil is known to decrease the saturated very long chain fatty acid (VLCFA) level in the plasma and skin fibroblasts of X-linked adrenoleukodystrophy (ALD) patients. However, the involvement of Lorenzo's oil in in vivo fatty acid metabolism has not been well elucidated. To investigate the effect of Lorenzo's oil on fatty acid metabolism, we analyzed the hepatic gene expression together with the serum fatty acid level in Lorenzo's oil-treated wild-type and abcd1-deficient mice. The change in the serum fatty acid level in Lorenzo's oil-treated abcd1-defcient mice was quite similar to that in the plasma fatty acid level in ALD patients supplemented with Lorenzo's oil. In addition, we found that the hepatic gene expression of two peroxisomal enzymes, Dbp and Scp2, and three microsomal enzymes, Elovl1, 2, and 3, were significantly stimulated by Lorenzo's oil. Our findings indicate that Lorenzo's oil activates hepatic peroxisomal fatty acid β-oxidation at the transcriptional level. In contrast, the transcriptional stimulation of Elovl1, 2, and 3 by Lorenzo's oil does not cause changes in the serum fatty acid level. It seems likely that the inhibition of these elongation activities by Lorenzo's oil results in a decrease in saturated VLCFA. Thus, these results not only contribute to a clarification of the mechanism by which the saturated VLCFA level is reduced in the serum of ALD patients by Lorenzo's oil-treatment, but also suggest the development of a new therapeutic approach to peroxisomal β-oxidation enzyme deficiency, especially mild phenotype of DBP deficiency.

Adrenoleukodystrophy - neuroendocrine pathogenesis and redefinition of natural history

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

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

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

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.

Brain microsomal fatty acid elongation is increased in abcd1-deficient mouse during active myelination phase

The dysfunction of ABCD1, a peroxisomal ABC protein, leads to the perturbation of very long chain fatty acid (VLCFA) metabolism and is the cause of X-linked adrenoleukodystrophy. Abcd1-deficient mice exhibit an accumulation of saturated VLCFAs, such as C26:0, in all tissues, especially the brain. The present study sought to measure microsomal fatty acid elongation activity in the brain of wild-type (WT) and abcd1-deficient mice during the course of development. The fatty acid elongation activity in the microsomal fraction was measured by the incorporation of [2-(14)C]malonyl-CoA into fatty acids in the presence of C16:0-CoA or C20:0-CoA. Cytosolic fatty acid synthesis activity was completely inhibited by the addition of N-ethylmaleimide (NEM). The microsomal fatty acid elongation activity in the brain was significantly high at 3 weeks after birth and decreased substantially at 3 months after birth. Furthermore, we detected two different types of microsomal fatty acid elongation activity by using C16:0-CoA or C20:0-CoA as the substrate and found the activity toward C20:0-CoA in abcd1-deficient mice was higher than the WT 3-week-old animals. These results suggest that during the active myelination phase the microsomal fatty acid elongation activity is stimulated in abcd1-deficient mice, which in turn perturbs the lipid composition in myelin.

Induced pluripotent stem cell models of Zellweger spectrum disorder show impaired peroxisome assembly and cell type-specific lipid abnormalities

Introduction

Zellweger spectrum disorder (PBD-ZSD) is a disease continuum caused by mutations in a subset of PEX genes required for normal peroxisome assembly and function. They highlight the importance of peroxisomes in the development and functions of the central nervous system, liver, and other organs. To date, the underlying bases for the cell-type specificity of disease are not fully elucidated.

Methods

Primary skin fibroblasts from seven PBD-ZSD patients with biallelic PEX1, PEX10, PEX12, or PEX26 mutations and three healthy donors were transduced with retroviral vectors expressing Yamanaka reprogramming factors. Candidate induced pluripotent stem cells (iPSCs) were subject to global gene expression, DNA methylation, copy number variation, genotyping, in vitro differentiation and teratoma formation assays. Confirmed iPSCs were differentiated into neural progenitor cells (NPCs), neurons, oligodendrocyte precursor cells (OPCs), and hepatocyte-like cell cultures with peroxisome assembly evaluated by microscopy. Saturated very long chain fatty acid (sVLCFA) and plasmalogen levels were determined in primary fibroblasts and their derivatives.

Results

iPSCs were derived from seven PBD-ZSD patient-derived fibroblasts with mild to severe peroxisome assembly defects. Although patient and control skin fibroblasts had similar gene expression profiles, genes related to mitochondrial functions and organelle cross-talk were differentially expressed among corresponding iPSCs. Mitochondrial DNA levels were consistent among patient and control fibroblasts, but varied among all iPSCs. Relative to matching controls, sVLCFA levels were elevated in patient-derived fibroblasts, reduced in patient-derived iPSCs, and not significantly different in patient-derived NPCs. All cell types derived from donors with biallelic null mutations in a PEX gene showed plasmalogen deficiencies. Reporter gene assays compatible with high content screening (HCS) indicated patient-derived OPC and hepatocyte-like cell cultures had impaired peroxisome assembly.

Conclusions

Normal peroxisome activity levels are not required for cellular reprogramming of skin fibroblasts. Patient iPSC gene expression profiles were consistent with hypotheses highlighting the role of altered mitochondrial activities and organelle cross-talk in PBD-ZSD pathogenesis. sVLCFA abnormalities dramatically differed among patient cell types, similar to observations made in iPSC models of X-linked adrenoleukodystrophy. We propose that iPSCs could assist investigations into the cell type-specificity of peroxisomal activities, toxicology studies, and in HCS for targeted therapies for peroxisome-related disorders.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-015-0149-3) contains supplementary material, which is available to authorized users.

Peroxisome biogenesis in mammalian cells: The impact of genes and environment

The initiation and progression of many human diseases are mediated by a complex interplay of genetic, epigenetic, and environmental factors. As all diseases begin with an imbalance at the cellular level, it is essential to understand how various types of molecular aberrations, metabolic changes, and environmental stressors function as switching points in essential communication networks. In recent years, peroxisomes have emerged as important intracellular hubs for redox-, lipid-, inflammatory-, and nucleic acid-mediated signaling pathways. In this review, we focus on how nature and nurture modulate peroxisome biogenesis and function in mammalian cells. First, we review emerging evidence that changes in peroxisome activity can be linked to the epigenetic regulation of cell function. Next, we outline how defects in peroxisome biogenesis may directly impact cellular pathways involved in the development of disease. In addition, we discuss how changes in the cellular microenvironment can modulate peroxisome biogenesis and function. Finally, given the importance of peroxisome function in multiple aspects of health, disease, and aging, we highlight the need for more research in this still understudied field.

Inhibition of Mammalian Target of Rapamycin Complex 1 (mTORC1) Downregulates ELOVL1 Gene Expression and Fatty Acid Synthesis in Goat Fetal Fibroblasts

Elongation of very-long-chain fatty acids 1 (ELOVL1) is a ubiquitously expressed gene that belongs to the ELOVL family and regulates the synthesis of very-long-chain fatty acids (VLCFAs) and sphingolipids, from yeast to mammals. Mammalian target of rapamycin complex 1 (mTORC1) is a central regulator of cell metabolism and is associated with fatty acids synthesis. In this study, we cloned the cDNA that encodes Cashmere goat (Capra hircus) ELOVL1 (GenBank Accession number KF549985) and investigated its expression in 10 tissues. ELOVL1 cDNA was 840 bp, encoding a deduced protein of 279 amino acids, and ELOVL1 mRNA was expressed in a wide range of tissues. Inhibition of mTORC1 by rapamycin decreased ELOVL1 expression and fatty acids synthesis in Cashmere goat fetal fibroblasts. These data show that ELOVL1 expression is regulated by mTORC1 and that mTORC1 has significant function in fatty acids synthesis in Cashmere goat.