The impact of a ketogenic diet and liver dysfunction on serum very long-chain fatty acids levels

Safety and tolerance of the ketogenic diet in patients with Zellweger Syndrome

Zellweger Syndrome is a peroxisomal disorder that can lead to elevation of long chain fatty acids and epilepsy, which can be drug resistant. The treatment of drug resistant epilepsy can include the ketogenic diet in appropriately chosen patients. Typically, the ketogenic diet is contraindicated in individuals with defects in fatty acid metabolism because of the diet's reliance on medium and long chain fatty acids. To our knowledge this is the first publication outlining the use of the ketogenic diet in patients with defects in beta oxidation of very long chain fatty acids. We present two patients with Zellweger Syndrome who were placed on a ketogenic diet for drug resistant epilepsy. Safety and tolerance of the ketogenic diet in patients with Zellweger Syndrome.

ABCD1 Gene Mutations: Mechanisms and Management of Adrenomyeloneuropathy

Pathogenic variants in the ABCD1 gene on the X chromosome may result in widely heterogenous phenotypes, including adrenomyeloneuropathy (AMN). Affected males typically present in their third or fourth decade of life with progressive lower limb weakness and spasticity, and may develop signs and symptoms of adrenal insufficiency and/or cerebral demyelination. Heterozygous females may be asymptomatic, but may develop a later-onset and more slowly progressive spastic paraparesis. In this review, we describe the clinical presentation of AMN, as well as its diagnosis and management. The role of rehabilitative therapies and options for management of spasticity are highlighted.

Core outcome set development for childhood epilepsy treated with ketogenic diet therapy: Results of a scoping review and parent interviews

PURPOSE

Clinical trials on childhood epilepsy treated with ketogenic diet (KD) use a wide range of outcomes, however, patients and decision-makers often do not perceive the outcomes used as the most important. We sought parental opinion on outcomes of importance and compared these to outcomes reported in published research.

METHODS

Ethical approval (London-Surrey-REC19/LO/1680). A scoping review identified outcomes reported in previous studies of childhood epilepsy and KD. Parents were recruited from nine KD centres (UK), charities and social media (international), then interviewed (Jan-April 2020) to explore priority outcomes. Content analysis identified all outcomes in transcripts. Parent identified outcomes were compared with those in the scoping review. Outcomes were collated and grouped into domains according to the COMET Taxonomy.

RESULTS

Of 2663 articles;147 met inclusion criteria. 921 verbatim outcomes were sorted into 90 discrete outcomes, reduced to 70 in consultation with the study advisory group, then classified into 21 domains. Parents (n = 21) identified 39 outcomes as important from the scoping review and seven new outcomes. They prioritised both physiological and functional outcomes in contrast to past studies, which prioritised physiological outcomes.

CONCLUSION

Little consistency exists in the outcomes used in childhood epilepsy and KD research. Those traditionally used do not adequately reflect parents' important outcomes for their child. Clinical trials should consider the broader priorities of parents when choosing outcomes, in particular, functional outcomes. Identified outcomes will inform an international two-round Delphi-study with parent, professional and researcher participants to develop a core outcome set for this clinical area (COMET registration #1116).

Changes in the Serum Fatty Acid Profile After Anhepatic Phase of Orthotopic Liver Transplantation Procedure

During orthotopic liver transplantation (OLT), the patients’ body remains deprived of this organ for some time, which could cause critical changes in the levels of various metabolites in the circulation, including fatty acids. Thus, the aim of this study was to determine whether the liver transplantation procedure leads to significant changes in the FA profile in serum lipids after the anhepatic phase. Our gas chromatography–mass spectrometry analysis revealed that after transplantation, serum levels of myristic and palmitic acids significantly decreased, whereas serum levels of very long-chain FAs containing 20 or more carbons in their chains were increased. These results indicate that the anhepatic phase during liver transplantation produces significant changes in serum fatty acid levels, and emphasizes the role of the liver in the metabolism of very long-chain fatty acids.

The Impact of Kidney Transplantation on the Serum Fatty Acid Profile in Patients with End-Stage Kidney Disease

Epidemiological data indicate that metabolic disturbances and increased cardiovascular risk in renal transplant patients are a significant and common problem. Therefore, it is important to search for new solutions and, at the same time, counteract the negative effects of currently used therapies. In this study, we examined the effect of kidney transplantation on the serum levels of fatty acids (FAs) in order to assess the role of these compounds in the health of transplant patients. The FA profile was analyzed by gas chromatography-mass spectrometry in the serum of 35 kidney transplant recipients, just before transplantation and 3 months later. The content of total n-3 polyunsaturated FAs (PUFAs) decreased after transplantation (3.06 ± 0.13% vs. 2.66 ± 0.14%; p < 0.05). The total amount of ultra-long-chain FAs containing 26 and more carbon atoms was significantly reduced (0.08 ± 0.009% vs. 0.05 ± 0.007%; p < 0.05). The desaturation index (18:1/18:0) increased after transplantation (3.92 ± 0.11% vs. 4.36 ± 0.18%; p < 0.05). The study showed a significant reduction in n-3 PUFAs in renal transplant recipients 3 months after transplantation, which may contribute to increased cardiovascular risk in this patient population.

Quantification of Very-Long-Chain and Branched-Chain Fatty Acids in Plasma by Liquid Chromatography-Tandem Mass Spectrometry

Peroxisomal disorders are a heterogeneous group of genetic disorders caused by impaired peroxisomal biogenesis or by defects in single peroxisomal proteins. The most common peroxisomal disorders are Zellweger spectrum disorders (ZSDs), due to pathogenic variants in one of the 13 PEX genes, and X-linked adrenoleukodystrophy/adrenomyeloneuropathy (X-ALD/AMN), due to pathogenic variants in ATP-binding cassette transporter type D1 (ABCD1) gene. Peroxisomes perform multiple essential cellular functions, including β-oxidation of very-long-chain fatty acids (VLCFAs), pristanic acid and some bile acid intermediates, and α-oxidation of phytanic acid. In most patients, abnormal levels of VLCFAs and/or branched-chain fatty acids (BCFAs, e.g., phytanic and pristanic acids) are present; hence, measuring these analytes is critical when suspecting a peroxisomal disorder. This chapter describes a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to quantify VLCFAs and BCFAs in plasma or serum for the diagnosis of peroxisomal disorders. The method consists of an acid hydrolysis step to release the fatty acids from their coenzyme A esters followed by derivatization using oxalyl chloride, dimethylaminoethanol, and then methyl iodide. The trimethyl-amino-ethyl (TMAE) iodide ester derivatives are analyzed using UPLC-MS/MS in positive electrospray ionization and multiple reaction-monitoring (MRM) mode. Quantitation is performed using a five-point calibration curve after normalizing with deuterated internal standards.

False-positive very long-chain fatty acids in a case of autoimmune adrenal insufficiency

BACKGROUND

X-linked adrenoleukodystrophy (ALD) affects up to 25% of boys diagnosed with adrenal insufficiency in childhood. Because early identification of these individuals can be lifesaving, all boys with new-onset primary adrenal insufficiency should be tested for ALD with a plasma very long-chain fatty acid (VLCFA) level. While plasma VLCFA is a diagnostic test with high sensitivity and specificity, false-positive results have been reported in individuals on a ketogenic diet.

CASE PRESENTATION

We present a case of an 11-year-old boy with new-onset primary adrenal insufficiency due to autoimmune adrenalitis who was initially found to have elevated VLCFA levels, suggestive of ALD, that normalized on repeat testing.

CONCLUSIONS

As advances in gene therapy and newborn screening for ALD expand, VLCFA testing may increase, and clinicians should be aware that testing during the initial presentation of primary adrenal insufficiency may lead to false-positive results and associated psychosocial distress.

The Changing Face of Adrenoleukodystrophy

Adrenoleukodystrophy (ALD) is a rare X-linked disorder of peroxisomal oxidation due to mutations in ABCD1. It is a progressive condition with a variable clinical spectrum that includes primary adrenal insufficiency, myelopathy, and cerebral ALD. Adrenal insufficiency affects over 80% of ALD patients. Cerebral ALD affects one-third of boys under the age of 12 and progresses to total disability and death without treatment. Hematopoietic stem cell transplantation (HSCT) remains the only disease-modifying therapy if completed in the early stages of cerebral ALD, but it does not affect the course of adrenal insufficiency. It has significant associated morbidity and mortality. A recent gene therapy clinical trial for ALD reported short-term MRI and neurological outcomes comparable to historical patients treated with HSCT without the associated adverse side effects. In addition, over a dozen states have started newborn screening (NBS) for ALD, with the number of states expecting to double in 2020. Genetic testing of NBS-positive neonates has identified novel variants of unknown significance, providing further opportunity for genetic characterization but also uncertainty in the monitoring and therapy of subclinical and/or mild adrenal insufficiency or cerebral involvement. As more individuals with ALD are identified at birth, it remains uncertain if availability of matched donors, transplant (and, potentially, gene therapy) centers, and specialists may affect the timely treatment of these individuals. As these promising gene therapy trials and NBS transform the clinical management and outcomes of ALD, there will be an increasing need for the endocrine management of presymptomatic and subclinical adrenal insufficiency. (Endocrine Reviews 41: 1 - 17, 2020).

Zellweger Syndrome Disorders: From Severe Neonatal Disease to Atypical Adult Presentation

Zellweger syndrome disorders (ZSD) is the principal group of peroxisomal disorders characterized by a defect of peroxisome biogenesis due to mutations in one of the 13 PEX genes. The clinical spectrum is very large with a continuum from antenatal forms to adult presentation. Whereas biochemical profile in body fluids is classically used for their diagnosis, the revolution of high-throughput sequencing has extended the knowledge about these disorders. The aim of this review is to offer a large panorama on molecular basis, clinical presentation and treatment of ZSD, and to update the diagnosis strategy of these disorders in the era of next-generation sequencing (NGS).

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.

Mild Zellweger syndrome due to a novel PEX6 mutation: correlation between clinical phenotype and in silico prediction of variant pathogenicity

Zellweger syndrome (ZS) is a consequence of a peroxisome biogenesis disorder (PBD) caused by the presence of a pathogenic mutation in one of the 13 genes from the PEX family. ZS is a severe multisystem condition characterized by neonatal appearance of symptoms and a shorter life. Here, we report a case of ZS with a mild phenotype, due to a novel PEX6 gene mutation. The patient presented subtle craniofacial dysmorphic features and slightly slower psychomotor development. At the age of 2 years, he was diagnosed with adrenal insufficiency, hypoacusis, and general deterioration. Magnetic resonance imaging showed a symmetrical hyperintense signal in the frontal and parietal white matter. Biochemical tests showed elevated liver transaminases, elevated serum very long chain fatty acids, and phytanic acid. After the death of the child at the age of 6 years, molecular diagnostics were continued in order to provide genetic counseling for his parents. Next generation sequencing (NGS) analysis with the TruSight One™ Sequencing Panel revealed a novel homozygous PEX6 p.Ala94Pro mutation. In silico prediction of variant severity suggested its possible benign effect. To conclude, in the milder phenotypes, adrenal insufficiency, hypoacusis, and leukodystrophy together seem to be pathognomonic for ZS.

Absence of biochemical evidence at an early age delays diagnosis in a patient with a clinically severe peroxisomal biogenesis disorder

Analysis of the plasma levels of very long chain fatty acids (VLCFA) is a primary screening method for peroxisomal disorders and usually identifies severe peroxisomal biogenesis defects reliably. We report a patient presenting with typical facial stigmata, a treatment resistant seizure disorder and polymicrogyria, whose plasma VLCFA levels were within normal limits until the age of 18 months. Only thereafter an elevation was found. Subsequent enzymatic and molecular genetic analysis revealed compound heterozygous mutations in the PEX6 gene. In conclusion, normal VLCFA levels do not necessarily exclude global peroxisomal biogenesis defects and the analysis should be repeated subsequently. Persisting clinical suspicion justifies further enzymatic and molecular evaluation.

Peroxisome biogenesis disorders in the Zellweger spectrum: An overview of current diagnosis, clinical manifestations, and treatment guidelines

Peroxisome biogenesis disorders in the Zellweger spectrum (PBD-ZSD) are a heterogeneous group of genetic disorders caused by mutations in PEX genes responsible for normal peroxisome assembly and functions. As a result of impaired peroxisomal activities, individuals with PBD-ZSD can manifest a complex spectrum of clinical phenotypes that typically result in shortened life spans. The extreme variability in disease manifestation ranging from onset of profound neurologic symptoms in newborns to progressive degenerative disease in adults presents practical challenges in disease diagnosis and medical management. Recent advances in biochemical methods for newborn screening and genetic testing have provided unprecedented opportunities for identifying patients at the earliest possible time and defining the molecular bases for their diseases. Here, we provide an overview of current clinical approaches for the diagnosis of PBD-ZSD and provide broad guidelines for the treatment of disease in its wide variety of forms. Although we anticipate future progress in the development of more effective targeted interventions, the current guidelines are meant to provide a starting point for the management of these complex conditions in the context of personalized health care.