Increased very long chain fatty acids in patients on a ketogenic diet: a cause of diagnostic confusion

Lipidomic biomarkers in plasma correlate with disease severity in adrenoleukodystrophy

BACKGROUND

X-linked adrenoleukodystrophy (ALD) is a neurometabolic disorder caused by pathogenic variants in ABCD1 resulting very long-chain fatty acids (VLCFA) accumulation in plasma and tissues. Males can present with various clinical manifestations, including adrenal insufficiency, spinal cord disease, and leukodystrophy. Female patients typically develop spinal cord disease and peripheral neuropathy. Predicting the clinical outcome of an individual patient remains impossible due to the lack of genotype-phenotype correlation and predictive biomarkers.

METHODS

The availability of a large prospective cohort of well-characterized patients and associated biobank samples allowed us to investigate the relationship between lipidome and disease severity in ALD. We performed a lipidomic analysis of plasma samples from 24 healthy controls, 92 male and 65 female ALD patients.

RESULTS

Here we show that VLCFA are incorporated into different lipid classes, including lysophosphatidylcholines, phosphatidylcholines, triglycerides, and sphingomyelins. Our results show a strong association between higher levels of VLCFA-containing lipids and the presence of leukodystrophy, adrenal insufficiency, and severe spinal cord disease in male ALD patients. In female ALD patients, VLCFA-lipid levels correlate with X-inactivation patterns in blood mononuclear cells, and higher levels are associated with more severe disease manifestations. Finally, hematopoietic stem cell transplantation significantly reduces, but does not normalize, plasma C26:0-lysophosphatidylcholine levels in male ALD patients. Our findings are supported by the concordance of C26:0-lysophosphatidylcholine and total VLCFA analysis with the lipidomics results.

CONCLUSIONS

This study reveals the profound impact of ALD on the lipidome and provides potential biomarkers for predicting clinical outcomes in ALD patients.

Identification of a Novel Non-Canonical Splice-Site Variant in ABCD1

Cerebral adrenoleukodystrophy (CALD) is a fatal genetic disease characterized by rapid, devastating neurological decline, with a narrow curative treatment window in the early stage. Non-canonical splice-site (NCSS) variants can easily be missed during genomic DNA analyses, and only a few of them in ABCD1 have been explored. Here, we studied a Chinese patient with clinical features similar to those of early-stage CALD but with a negative molecular diagnosis and a sibling who had presumably died of CALD. Trio-based whole-exome sequencing (trio-WES) and RNA sequencing (RNA-Seq) revealed a novel hemizygote NCSS variant c.901-25_901-9 del in ABCD1 intron 1, resulting in a complex splicing pattern. The in vitro minigene assay revealed that the c.901-25_901-9 del construct contained two aberrant transcripts that caused skipping of exon 2 and a small 48-bp deletion on left of the same exon. We identified a novel NCSS variant, that extends the spectrum of the known ABCD1 variants, and demonstrated the pathogenicity of this gene variant. Our findings highlight the importance of combining RNA-Seq and WES techniques for prompt diagnosis of leukodystrophy with NCSS variants.

Very-Long-Chain Fatty Acids Quantification by Gas-Chromatography Mass Spectrometry

Abnormal accumulation of very-long-chain fatty acids (VLCFAs), defined as molecules with greater than 22 carbons, and branched-chain fatty acids, pristanic and phytanic acids, is characteristic of inborn errors of peroxisomal biogenesis or function. X-linked adrenoleukodystrophy, Zellweger spectrum disorders, rhizomelic chondrodysplasia punctata, and Refsum syndrome can be diagnosed biochemically by quantitation of these metabolites in plasma. Ratios of C24/C22 and C26/C22 can help improve detection of X-linked adrenoleukodystrophy. Analysis using gas-chromatography mass spectrometry (GC/MS) after acid/base hydrolysis, organic solvent extraction, and derivatization is an established method for clinical diagnostics. This chapter describes detailed steps to process plasma samples for GC/MS analysis.

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.

Very long chain acylcarnitines and lysophosphatidylcholines in screening of peroxisomal disease in children by tandem mass spectrometry

To investigate the value of very long chain acylcarnitine (VLCAC) and lysophosphatidylcholine (LPC) in screening of peroxisomal disease in children. Eighteen children with peroxisomal disease, including 14 cases of X-linked adrenoleukodystrophy (X-ALD group) and 4 cases of Zellweger syndrome (ZS group) diagnosed based on clinical symptoms, MRI and genetic tests were enrolled in the study; and 200 healthy children were selected as control group. Samples of dried blood spots were collected from all subjects, VLCAC and LPC in dried blood spots were extracted by solvent containing internal isotopic standards hexacosanoylcarnitine (H-C26) and C26:0 lysophosphatidylcholine (H-C26:0-LPC). The eicosanoylcarnitine (C20), docosanoylcarnitine (C22), tetracosanoylcarnitine (C24), hexacosanoylcarnitine (C26), C20:0 lysophosphatidylcholine (C20:0-LPC), C22:0 lysophosphatidylcholine (C22:0-LPC), C24:0 lysophosphatidylcholine (C24:0-LPC) and C26:0 lysophosphatidylcholine (C26:0-LPC) were detected by tandem mass spectrometry (MS/MS). The above 8 indicators and the ratios were compared among the groups using Kruskal-Wallis test and Mann-Whitney test; the contribution of each index to the disease were analyzed by partial least square method. Except C24:0-LPC/C20:0-LPC, there were significant differences in all indicators and ratios among all groups (<0.05 or <0.01). There were differences in most indicators and ratios between X-ALD group and the control group, as well as between ZS group and the control group, but there was no difference between the X-ALD group and the ZS group. PLS-DA analysis showed that the peroxisome disease group (including X-ALD group and ZS group) and the control group were able to be completely separated, and C26 had the highest variable importance for the projection (VIP) value. MS/MS detection of VLCAC and LPC can be used as a screening method for peroxisomal disease, and C26 may be a sensitive indicator for diagnosis.

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.

Endocrine dysfunction in adrenoleukodystrophy

X-linked adrenoleukodystrophy (ALD) is a peroxisomal disorder caused by mutations in the ABCD1 gene and characterized by impaired very long-chain fatty acid beta-oxidation. Clinically, male patients develop adrenal failure and a progressive myelopathy in adulthood, although age of onset and rate of progression are highly variable. Additionally, 40% of male patients develop a leukodystrophy (cerebral ALD) before the age of 18 years. Women with ALD also develop a myelopathy but generally at a later age than men and with slower progression. Adrenal failure and leukodystrophy are exceedingly rare in women. Allogeneic hematopoietic cell transplantation (HCT), or more recently autologous HCT with ex vivo lentivirally transfected bone marrow, halts the leukodystrophy. Unfortunately, there is no curative treatment for the myelopathy. In the following chapter, the biochemistry, pathology, and clinical spectrum of ALD are discussed in detail.

The peroxisomal disorder spectrum and Heimler syndrome: Deep phenotyping and review of the literature

The spectrum of peroxisomal disorders is wide and comprises individuals that die in the first year of life, as well as people with sensorineural hearing loss, retinal dystrophy and amelogenesis imperfecta. In this article, we describe three patients; two diagnosed with Heimler syndrome and a third one with a mild-intermediate phenotype. We arrived at these diagnoses by conducting complete ophthalmic (National Eye Institute), auditory (National Institute of Deafness and Other Communication Disorders), and dental (National Institute of Dental and Craniofacial Research) evaluations, as well as laboratory and genetic testing. Retinal degeneration with macular cystic changes, amelogenesis imperfecta, and sensorineural hearing loss were features shared by the three patients. Patients A and C had pathogenic variants in PEX1 and Patient B, in PEX6. Besides analyzing these cases, we review the literature regarding mild peroxisomal disorders, their pathophysiology, genetics, differential diagnosis, diagnostic methods, and management. We suggest that peroxisomal disorders are considered in every child with sensorineural hearing loss and retinal degeneration. These patients should have a dental evaluation to rule out amelogenesis imperfecta as well as audiologic examination and laboratory testing including peroxisomal biomarkers and genetic testing. Appropriate diagnosis can lead to better genetic counseling and management of the associated comorbidities.

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).

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

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

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).

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

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

Clinical and Laboratory Diagnosis of Peroxisomal Disorders

The peroxisomal disorders (PDs) are a heterogeneous group of genetic diseases in man caused by an impairment in peroxisome biogenesis or one of the metabolic functions of peroxisomes. Thanks to the revolutionary technical developments in gene sequencing methods and their increased use in patient diagnosis, the field of genetic diseases in general and peroxisomal disorders in particular has dramatically changed in the last few years. Indeed, several novel peroxisomal disorders have been identified recently and in addition it has been realized that the phenotypic spectrum of patients affected by a PD keeps widening, which makes clinical recognition of peroxisomal patients increasingly difficult. Here, we describe these new developments and provide guidelines for the clinical and laboratory diagnosis of peroxisomal patients.

The important role of biochemical and functional studies in the diagnostics of peroxisomal disorders

Peroxisomes are dynamic organelles that play an essential role in a variety of metabolic pathways. Peroxisomal dysfunction can lead to various biochemical abnormalities and result in abnormal metabolite levels, such as increased very long-chain fatty acid or reduced plasmalogen levels. The metabolite abnormalities in peroxisomal disorders are used in the diagnostics of these disorders. In this paper we discuss in detail the different diagnostic tests available for peroxisomal disorders and focus specifically on the important role of biochemical and functional studies in cultured skin fibroblasts in reaching the right diagnosis. Several examples are shown to underline the power of such studies.

Endocrine Dysfunction in X-Linked Adrenoleukodystrophy

X-linked adrenoleukodystrophy (X-ALD) is caused by mutations in the ABCD1 gene and leads to an elevation of very-long-chain fatty acids (VLCFA). The accumulation of the VLCFA and the associated oxidative stress can present with a spectrum of significant neurologic disease, adrenal insufficiency, and testicular dysfunction in males with ABCD1 gene mutations. Much of the published literature for X-ALD has focused on the associated devastating progressive neurologic conditions. The purpose of this review is to summarize the concerns for endocrine dysfunction associated with X-ALD and provide guidance for monitoring and management of adrenal insufficiency.

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.

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

Peroxisomes play an essential role in mammalian cellular metabolism, particularly in oxidation fatty acid pathways. Serum very long-chain fatty acids (VLCFA), the main biochemical diagnostic parameters for peroxisomal disorders, were examined in 25 neurological patients with epilepsy on a ketogenic diet and 27 patients with liver dysfunction. The data show that patients on a ketogenic diet have increased levels of C22:0 and C24:0, but not C26:0, and normal C24:0/C22:0 and C26:0/C22:0. Patients with liver insufficiency showed a slightly elevated level of C26:0, a normal level of C24:0 and a decreased level of C22:0; thus in 21/27 the ratio of C24:0/C22:0 was increased and 15/27 the ratio of C26:0/C22:0 was increased.

Peanut consumption increases levels of plasma very long chain fatty acids in humans

Peanut consumption has been suspected of raising plasma very long chain fatty acid (VLCFA) levels in humans. The effect of peanut consumption on VLCFAs was studied in six human subjects. After 3 to 4h of peanut butter ingestion, plasma C26:0 and C26:0/C22:0 were found to be significantly elevated to levels seen in patients with peroxisomal disorders. These levels returned to normal within 12h. Peanut consumption needs to be accounted for when interpreting VLCFAs.

X-linked adrenoleukodystrophy (X-ALD): clinical presentation and guidelines for diagnosis, follow-up and management

X-linked adrenoleukodystrophy (X-ALD) is the most common peroxisomal disorder. The disease is caused by mutations in the ABCD1 gene that encodes the peroxisomal membrane protein ALDP which is involved in the transmembrane transport of very long-chain fatty acids (VLCFA; ≥C22). A defect in ALDP results in elevated levels of VLCFA in plasma and tissues. The clinical spectrum in males with X-ALD ranges from isolated adrenocortical insufficiency and slowly progressive myelopathy to devastating cerebral demyelination. The majority of heterozygous females will develop symptoms by the age of 60 years. In individual patients the disease course remains unpredictable. This review focuses on the diagnosis and management of patients with X-ALD and provides a guideline for clinicians that encounter patients with this highly complex disorder.

Investigational methods for peroxisomal disorders

Peroxisomes play an important role in cellular metabolism. Defects in peroxisome assembly or of a single peroxisomal pathway are associated with a wide variety of inherited disorders, including X-linked adrenoleukodystrophy, Zellweger spectrum disorders, rhizomelic chondrodysplasia punctata, and Refsum disease. A group of peroxisome-specific biomarkers has been shown to be characteristic of specific defects. Patients with defects in peroxisome fatty acid beta-oxidation accumulate very long-chain fatty acids (VLCFA), patients with defects in plasmalogen synthesis are deficient in erythrocyte membrane plasmalogens, and patients with mislocalized pipecolic acid oxidase accumulate pipecolic acid in body fluids. This unit describes three protocols that can be used to measure plasma VLCFA, erythrocyte plasmalogens, and plasma or urine pipecolic acid by capillary gas chromatography (GC) or GC-mass spectrometry. These techniques can be used to identify the majority of patients with known neurogenetic peroxisome disorders.

Peroxisome biogenesis disorders

Defects in PEX genes impair peroxisome assembly and multiple metabolic pathways confined to this organelle, thus providing the biochemical and molecular bases of the peroxisome biogenesis disorders (PBD). PBD are divided into two types--Zellweger syndrome spectrum (ZSS) and rhizomelic chondrodysplasia punctata (RCDP). Biochemical studies performed in blood and urine are used to screen for the PBD. DNA testing is possible for all of the disorders, but is more challenging for the ZSS since 12 PEX genes are known to be associated with this spectrum of PBD. In contrast, PBD-RCDP is associated with defects in the PEX7 gene alone. Studies of the cellular and molecular defects in PBD patients have contributed significantly to our understanding of the role of each PEX gene in peroxisome assembly.

[Ketogenic regime as anti-epileptic treatment: its use in 29 epileptic children]

INTRODUCTION

The ketogenic diet is a treatment option for patient with intractable or refractory epilepsy. It is a high-fat, low protein, low carbohydrate diet developed in 1920s. Recent research publications and media interest have renewed debate on the merits of ketogenic diet.

POPULATION

We report our experience with 29 children suffering from refractory epilepsy, treated with the ketogenic diet. No surgical option was available. Modalities are explained.

RESULTS

The ketogenic diet improved seizure control in 12/29 cases. It appeared effective in infants with infantile spasms. Refractory-status epilepticus responded to the ketogenic diet (3/6 cases). Migrating partial seizures in infancy were always refractory to the diet. Compliance with the diet was good. Adverse effects must be compared with the toxicity of antiepileptic drugs. One child had hypokaliemia with cardiac complication.

CONCLUSION

The ketogenic diet should be continued during one or 2 years when it is effective. It should be considered as an alternative therapy for children with refractory epilepsy.

Comparison of the anticonvulsant efficacies and neurotoxic effects of valproic acid, phenytoin, and the ketogenic diet

PURPOSE

The purpose of this study was to measure quantitatively the effectiveness of the ketogenic diet (KD) in comparison to two clinically important anticonvulsant drugs (AEDs), valproic acid (VPA) and phenytoin (PHT), and to evaluate possible associated neurotoxicity.

METHODS

Rats were maintained on either a calorie-restricted, KD or calorie-restricted, rodent-chow diet for 3-5 weeks, after which neurobehavioral and seizure testing was completed. AEDs (either VPA or PHT) were injected acutely at the time to peak effect before neurotoxic and seizure assessment. Seizures were induced by timed infusion of pentylenetetrazole (PTZ) and maximal electroshock (MES).

RESULTS

VPA protected from both MES- and PTZ-induced seizures, whereas the KD only elevated PTZ seizure threshold; PHT only attenuated MES-induced seizures. The KD was as effective as a high dose of VPA (i.e., 300 mg/kg) and combined treatment (i.e., KD + VPA) showed an additive increase in PTZ seizure threshold. No observed neurobehavioral deficits were associated with either diet treatment; however, drug-related side effects were noted with high doses of either VPA or PHT.

CONCLUSIONS

These data suggest that the KD ranks among VPA and PHT as an effective treatment for seizures, without observed drug-associated neurobehavioral contraindications. In combination with AEDs, our results indicate that the KD plus VPA work synergistically to increase seizure threshold, whereas the KD plus PHT may be complementary, elevating seizure threshold (KD) and reducing seizure severity (PHT). These findings may provide insights into future directions for rational polytherapy; however, it is important to be aware that the KD has been shown to elevate VPA-induced hepatotoxicity.

The ketogenic diet: an effective medical therapy with side effects

Attention is directed to the fact that the ketogenic diet is much less toxic than some of the medications currently used in the treatment of epilepsy. (Dr Samuel Livingston, 1972) 1

The ketogenic diet... is an effective and safe medical treatment for epilepsy, but it must be judiciously applied and carefully monitored. (Drs Doug R. Nordli and Daryl C. DeVivo, 2001)2

Plasma very long chain fatty acids in 3,000 peroxisome disease patients and 29,000 controls

The assay of plasma very long chain fatty acids (VLCFAs), developed in our laboratory in 1981, has become the most widely used procedure for the diagnosis of X-linked adrenoleukodystrophy (X-ALD) and other peroxisomal disorders. We present here our 17 years' experience with this assay. Three VLCFA parameters, the level of hexacosanoic acid (C26:0), the ratio of C26:0 to tetracosanoic acid (C24:0), and of C26:0 to docosanoic acid (C22:0), were measured in 1,097 males (hemizygotes) with X-ALD, 1,282 women heterozygous for this disorder, including 379 obligate heterozygotes, 797 patients with other peroxisomal disorders, and 29,600 control subjects. All X-ALD hemizygotes who had not previously received Lorenzo's oil or a diet with a high erucic acid content had increased VLCFA levels, but the application of a discriminant function based on all three measurements is required to avoid the serious consequences of a false-negative result. VLCFA levels are increased at day of birth, thus providing the potential for neonatal mass screening, are identical in the childhood and adult forms, and do not change with age. Eighty-five percent of obligate heterozygotes had abnormally high VLCFA levels, but a normal result does not exclude carrier status. VLCFA levels were increased in all patients homozygous for Zellweger syndrome, neonatal adrenoleukodystrophy, infantile Refsum's disease, and in patients with deficiencies of peroxisomal acyl-coenzyme A oxidase, bifunctional enzyme, and 3-oxoacyl-coenzyme A thiolase. In these patients the degree of VLCFA excess correlated with clinical severity.

Role of the ketogenic diet in children with intractable seizures

OBJECTIVE

To provide a review of the mechanism of action, clinical efficacy, adverse effects, drug interactions, and therapeutic considerations associated with the use of a ketogenic diet to manage patients with intractable seizures.

DATA SOURCES

A MEDLINE search from January 1966 to the present and relevant articles from journals were reviewed.

DATA SYNTHESIS

The ketogenic diet has been used as a treatment modality since the early 1920s to control intractable seizures. The exact mechanism of action is unknown. Overall, uncontrolled clinical studies have reported that approximately one-third of patients with intractable seizures have become seizure-free on the ketogenic diet. Common adverse events attributed to the diet include dehydration, gastrointestinal symptoms, hypoglycemia, as well as carnitine and vitamin deficiencies. Cognitive effects, hyperlipidemia, impaired neutrophil function, urolithiasis, optic neuropathy, osteoporosis, and protein deficiency may also occur in some patients. Carbohydrate content and drug formulation in the selection of medications while on the diet are important. Acetazolamide, phenobarbital, and valproic acid have been reported to interact with the ketogenic diet. Medications that cause carnitine deficiency or influence carbohydrate metabolism should also be used with caution. The carbohydrate content of drugs in various therapeutic classes is presented to aid in the selection of the most appropriate drug and formulation for patients on the ketogenic diet. The success of the diet in controlling intractable seizures is related to the patient's close adherence to the diet. Minimizing carbohydrate ingestion from medications along with a multidisciplinary team approach to the selection and monitoring of the diet are important to the success of the ketogenic diet in controlling seizures.

CONCLUSIONS

The ketogenic diet has shown promising results in controlling intractable seizures; however, carefully controlled clinical trials are needed to better assess the efficacy of the diet during its use and after discontinuation.