Glut1 Deficiency Syndrome (Glut1DS): State of the art in 2020 and recommendations of the international Glut1DS study group

Clinical and genetic analysis of children with glucose transporter type 1 deficiency syndrome

Glucose transporter type 1 deficiency syndrome (GLUT1-DS) is a rare metabolic encephalopathy with a wide variety of clinical phenotypes. In the present study, 15 patients diagnosed with GLUT1-DS were selected, all of whom had obvious clinical manifestations and complete genetic testing. Their clinical data and genetic reports were collated. All patients were provided with a ketogenic diet (KD) and an improvement in their symptoms was observed during a follow-up period of up to 1 year. The results revealed that the 15 cases had clinical symptoms, such as convulsions or dyskinesia. Although none had a cerebrospinal fluid/glucose ratio <0.4, the genetic report revealed that all had the solute carrier family 2 member 1 gene variant, and their clinical symptoms basically improved following the use of the KD. GLUT1-DS is a genetic metabolic disease that causes a series of neurological symptoms due to glucose metabolism disorders in the brain. Low glucose levels in cerebrospinal fluid and genetic testing are key diagnostic criteria, and the KD is a highly effective treatment option. By summarizing and analyzing patients with GLUT1-DS, summarizing clinical characteristics and expanding their gene profile, the findings of the present study may be of clinical significance for the early recognition and diagnosis of the disease, so as to conduct early treatment and shorten the duration of brain energy deficiency. This is of utmost importance for improving the prognosis and quality of life of affected children.

Nice to know 2: The impact of NICE guidelines on ketogenic diet services in the UK and Ireland - An update

BACKGROUND

Ketogenic diet therapy (KDT) has been recommended as a treatment for drug-resistant epilepsy in children and young people since 2012 in the National Institute for Health and Care Excellence Clinical Guidelines for Epilepsies. The Ketogenic Dietitians Research Network completed a survey in 2017 to assess the impact of these guidelines.

METHODS

An online survey was circulated to ketogenic dietitians across the UK and Ireland. The results were compared with those of the 2017 survey.

RESULTS

The number of individuals following KDT was 854, comprising an increase of 13% since 2017. Service sizes ranged widely, with 1-74 (median 16) patients on the diet. Of 36 services, 30 had a waiting list, ranging from 2 to 67 (median 9) patients. The classical diet continued to be the most common KDT used (58% of patients). Ten services reported use of a new flexible medium chain triglyceride protocol. Some 48% of patients (n = 427) had been following the KDT for over 2 years, comprising an 18% increase since 2017. Of these, 68 (15.9%) had attempted to wean off KDT but had to re-start as a result of a deterioration in seizures.

CONCLUSIONS

The number of individuals following medical KDT remains stable. Referral numbers and waiting lists remain high, highlighting that KDT is still a well-recognised treatment option for drug-resistant epilepsy. The types of KDT used are similar to previous years, although increasingly flexible protocols are being adopted. Longer-term use of KDT is increasing, with a proportion of patients requiring long-term use to maintain seizure control.

Dietary management and access to treatment for patients with glucose deficiency syndrome type 1: an overview review with focus on the European regulatory framework

BACKGROUND

Glut-1 deficiency Syndrome (GLUT-1 DS) is a rare disease caused by a mutation in the SLC2A1 gene that codes for the glucose transporter protein GLUT-1 DS. Currently, there is no indicated drug therapy for this condition and ketogenic diet (KD) is the most effective remedy to treat it.

OBJECTIVE

The objective of this study was to review the published literature that evaluated the effectiveness of KD in the dietary management of GLUT-1 DS syndrome, describing the state-of-the-art the treatment pathway for patients with GLUT-1 DS syndrome in light of the current European regulatory framework within the National Health Services.

METHODS

The literature search was carried out on September 10, 2023, and all studies conducted in humans diagnosed with GLUT-1 deficiency syndrome and treated with KD were included.

RESULTS

A total of 156 scientific papers have been extracted. Applying the exclusion criteria, 38 articles have been considered eligible. In 29 out of 38 studies, the main outcome for determining the efficacy of KD was the measurement of the number of epileptic seizures, demonstrating that patients treated with KD experienced improvements with a clear reduction in the number of epileptic attacks. Currently, in the European Union, only one country provides full reimbursement by the national health system for KD.

DISCUSSION

Although they are crucial for the treatment of GLUT-1 DS, according with current food regulations, KD are not evaluated on the basis of an unambiguous efficacy result, but only on the basis of safety. As a result, it is desirable to carry out clinical studies in the coming years based on the determination of efficacy in target populations, also in view of the marketing of these products on the European market.

Glucose transporter-1 deficiency syndrome with extreme phenotypic variability in a five-generation family carrying a novel SLC2A1 variant

BACKGROUND AND PURPOSE

Glucose transporter-1 (GLUT1) deficiency syndrome (GLUT1-DS) is a metabolic disorder due to reduced expression of GLUT1, a glucose transporter of the central nervous system. GLUT1-DS is caused by heterozygous SLC2A1 variants that mostly arise de novo. Here, we report a large family with heterogeneous phenotypes related to a novel SLC2A1 variant.

METHODS

We present clinical and genetic features of a five-generation family with GLUT1-DS.

RESULTS

The 14 (nine living) affected members had heterogeneous phenotypes, including seizures (11/14), behavioral disturbances (5/14), mild intellectual disability (3/14), and/or gait disabilities (2/14). Brain magnetic resonance imaging revealed hippocampal sclerosis in the 8-year-old proband, who also had drug-responsive absences associated with attention-deficit/hyperactivity disorder. His 52-year-old father, who had focal epilepsy since childhood, developed paraparesis related to a reversible myelitis associated with hypoglycorrhachia. Molecular study detected a novel heterozygous missense variant (c.446C>T) in exon 4 of SLC2A1 (NM: 006516.2) that cosegregated with the illness. This variant causes an amino acid replacement (p.Pro149Leu) at the fourth transmembrane segment of GLUT1, an important domain located at its catalytic core.

CONCLUSIONS

Our study illustrates the extremely heterogenous phenotypes in familial GLUT1-DS, ranging from milder classic phenotypes to more subtle neurological disorder including paraparesis. This novel SLC2A1 variant (c.446C>T) provides new insight into the pathophysiology of GLUT1-DS.

The use of ketogenic diets in children living with drug-resistant epilepsy, glucose transporter 1 deficiency syndrome and pyruvate dehydrogenase deficiency: A scoping review

BACKGROUND

The ketogenic diet (KD) is a high fat, moderate protein and very low carbohydrate diet. It can be used as a medical treatment for drug-resistant epilepsy (DRE), glucose transporter 1 deficiency syndrome and pyruvate dehydrogenase deficiency. The aim of this scoping review was to map the KD literature, with a focus on epilepsy and associated metabolic conditions, to summarise the current evidence-base and identify any gaps.

METHODS

This review was conducted using JBI scoping review methodological guidance and the PRISMA extension for scoping reviews reporting guidance. A comprehensive literature search was conducted in September 2021 and updated in February 2024 using MEDLINE, CINAHL, AMED, EmBASE, CAB Abstracts, Scopus and Food Science Source databases.

RESULTS

The initial search yielded 2721 studies and ultimately, data were extracted from 320 studies that fulfilled inclusion criteria for the review. There were five qualitative studies, and the remainder were quantitative, including 23 randomised controlled trials (RCTs) and seven quasi-experimental studies. The USA published the highest number of KD studies followed by China, South Korea and the UK. Most studies focused on the classical KD and DRE. The studies key findings suggest that the KD is efficacious, safe and tolerable.

CONCLUSIONS

There are opportunities available to expand the scope of future KD research, particularly to conduct high-quality RCTs and further qualitative research focused on the child's needs and family support to improve the effectiveness of KDs.

Stroke and Stroke-Like Episodes: Recurrent Manifestations in GLUT1 Deficiency Syndrome

BACKGROUND

Since the initial description of glucose transporter-1 deficiency syndrome (Glut1-DS) the phenotype of the condition has expanded, even leading to the recognition of atypical manifestations. We report on eight patients with Glut1-DS who experienced at least one episode of acute focal neurological deficits.

METHODS

We conducted a retrospective analysis, collecting clinical, electrophysiological, neuroradiological, and genetic information. We focused in particular on three well-documented cases.

RESULTS

Among 42 patients with Glut1-DS, eight individuals aged between six and 38 years presented with an acute onset of neurological disturbances: dysarthria/aphasia, oral dyskinesia, swallowing difficulties, paresthesia, facial palsy, hemi/monoplegia, vomiting, headache, and behavioral disturbances. When performed, magnetic resonance imaging (MRI) revealed signs of venous congestion and hypoperfusion and electroencephalography showed focal contralateral slowing. Deficits were transient in all patients but one. Four patients (50%) were on a ketogenic diet (KD), and two of these patients had lower than usual ketonemia levels during the episode. In two patients, MRI demonstrated the presence of an ischemic brain lesion.

CONCLUSIONS

In Glut1-DS, stroke-like episodes are a recurrent manifestation, particularly during early adulthood, and they were reported in 19% of the patients in our cohort. Stroke mimics should be considered a key feature of Glut1-DS, as other paroxysmal disorders. It remains to be established whether a KD can prevent the recurrence of episodes and, if so, at what level of ketosis. Further observations are needed to confirm the correlation between Glut1-DS and ischemic stroke.

PURA and GLUT1: Sweet partners for brain health

PURA, also known as Pur-alpha, is an evolutionarily conserved DNA/RNA-binding protein crucial for various cellular processes, including DNA replication, transcriptional regulation, and translational control. Comprising three PUR domains, it engages with nucleic acids and has a role in protein-protein interactions. The manifestation of PURA syndrome, arising from mutations in the PURA gene, presents neurologically with developmental delay, hypotonia, and seizures. In our prior work from 2018, we highlighted the unique case of a PURA patient displaying hypoglycorrhachia, suggesting a potential association with GLUT1 dysfunction in this syndrome. In this current study, we expand the patient cohort with PURA mutations exhibiting hypoglycorrhachia and aim to unravel the molecular basis of this phenomenon. We established an in vitro model in HeLa cells to modulate PURA expression and investigated GLUT1 function and expression. Our findings indicate that PURA levels directly impact glucose uptake through the functioning of GLUT1, without influencing significantly GLUT1 expression. Moreover, our study reveals evidence for a possible physical interaction between PURA and GLUT1, demonstrated by colocalization and co-immunoprecipitation of both proteins. Computational analyses, employing molecular dynamics, further corroborates these findings, demonstrating that PURA:GLUT1 interactions are plausible, and that the stability of the complex is altered when PURA is truncated and/or mutated. In conclusion, our results suggest that PURA plays a pivotal role in driving the function of GLUT1 for glucose uptake, potentially forming a regulatory complex. Additional investigations are warranted to elucidate the precise mechanisms governing this complex and its significance in ensuring proper GLUT1 function.

The 2017 and 2022 ILAE epilepsy classification systems identify needs and opportunities in care: A paediatric hospital-based study

OBJECTIVES

There is a paucity of studies reporting the epilepsy spectrum using the 2017 and 2022 ILAE classification systems in everyday clinical practice. To identify gaps and opportunities in care we evaluated a hospital-based cohort applying these epilepsy classification systems, including aetiology and co-morbidity, and the utility of molecular genetic diagnosis to identify available precision therapies.

METHODS

Cross sectional retrospective study of all children with epilepsy (≤16 years) attending University Hospital Galway (2017-2022). Data collection and analysis of each case was standardised to ensure a systematic approach and application of the recent ILAE categorisation and terminology (2017 and 2022). Ethics approval was obtained.

RESULTS

Among 356 children, epilepsy was classified as focal (46.1 %), generalised (38.8 %), combined (6.2 %), and unknown (9 %). Epilepsy syndrome was determined in 145/356 (40.7 %), comprising 24 different syndromes, most commonly SeLECTS (9 %), CAE (7 %), JAE (6.2 %) and IESS (5.9 %). New aetiology-specific syndromes were identified (e.g. CDKL5-DEE). Molecular diagnosis was confirmed in 19.9 % (n = 71) which encompassed monogenic (13.8 %) and chromosomopathy/CNV (6.2 %). There was an additional 35.7 % (n = 127) of patients who had a presumed genetic aetiology of epilepsy. Remaining aetiology included structural (18.8 %, n = 67), infectious (2 %, n = 7), metabolic (1.7 %, n = 6) and unknown (30.3 %, n = 108). Encephalopathy categorisation was determined in 182 patients (DE in 38.8 %; DEE in a further 11.8 %) associated with a range of co-morbidities categorised as global delay (29.2 %, n = 104), severe neurological impairment (16.3 %, n = 58), and ASD (14.6 %, n = 52). Molecular-based "precision therapy" was deemed available in 21/356 (5.9 %) patients, with "molecular precision" approach utilised in 13/356 (3.7 %), and some benefit noted in 6/356 (1.7 %) of overall cohort or 6/71 (8.5 %) of the molecular cohort.

CONCLUSION

Applying the latest ILAE epilepsy classification systems allow comparison across settings and identifies a major neuro-developmental co-morbidity rate and a large genetic aetiology. We identified very few meaningful molecular-based disease modifying "precision therapies". There is a monumental gap between aetiological identification, and impact of meaningful therapies, thus the new 2017/2022 classification clearly identifies the major challenges in the provision of routine epilepsy care.

Triheptanoin Did Not Show Benefit versus Placebo for the Treatment of Paroxysmal Movement Disorders in Glut1 Deficiency Syndrome: Results of a Randomized Phase 3 Study

BACKGROUND

Paroxysmal movement disorders are common in Glut1 deficiency syndrome (Glut1DS). Not all patients respond to or tolerate ketogenic diets.

OBJECTIVES

The objective was to evaluate the effectiveness and safety of triheptanoin in reducing the frequency of disabling movement disorders in patients with Glut1DS not receiving a ketogenic diet.

METHODS

UX007G-CL301 was a randomized, double-blind, placebo-controlled, phase 3 crossover study. After a 6-week run-in, eligible patients were randomized 1:1 to the first sequence (triheptanoin/placebo or placebo/triheptanoin) titration plus maintenance, followed by washout and the opposite sequence titration plus maintenance. The placebo (safflower oil) matched the appearance, taste, and smell of triheptanoin. Open-label triheptanoin was administered in the extension. The frequency of disabling paroxysmal movement disorder events per 4 weeks (recorded by diary during maintenance; primary endpoint) was assessed by Wilcoxon rank-sum test.

RESULTS

Forty-three patients (children, n = 16; adults, n = 27) were randomized and treated. There was no difference between triheptanoin and placebo in the mean (interquartile range) number of disabling paroxysmal movement disorder events (14.3 [4.7-38.3] vs. 11.8; [3.2-28.7]; Hodges-Lehmann estimated median difference: 1.46; 95% confidence interval, -1.12 to 4.36; P = 0.2684). Treatment-emergent adverse events were mild/moderate in severity and included diarrhea, vomiting, upper abdominal pain, headache, and nausea. Two patients discontinued the study because of non-serious adverse events that were predominantly gastrointestinal. The study was closed early during the open-label extension because of lack of effectiveness. Seven patients continued to receive triheptanoin compassionately.

CONCLUSION

There were no significant differences between the triheptanoin and placebo groups in the frequency of disabling movement disorder events during the double-blind maintenance period. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Case for supporting astrocyte energetics in glucose transporter 1 deficiency syndrome

In glucose transporter 1 deficiency syndrome (Glut1DS), glucose transport into brain is reduced due to impaired Glut1 function in endothelial cells at the blood-brain barrier. This can lead to shortages of glucose in brain and is thought to contribute to seizures. Ketogenic diets are the first-line treatment and, among many beneficial effects, provide auxiliary fuel in the form of ketone bodies that are largely metabolized by neurons. However, Glut1 is also the main glucose transporter in astrocytes. Here, we review data indicating that glucose shortage may also impact astrocytes in addition to neurons and discuss the expected negative biochemical consequences of compromised astrocytic glucose transport for neurons. Based on these effects, auxiliary fuels are needed for both cell types and adding medium chain triglycerides (MCTs) to ketogenic diets is a biochemically superior treatment for Glut1DS compared to classical ketogenic diets. MCTs provide medium chain fatty acids (MCFAs), which are largely metabolized by astrocytes and not neurons. MCFAs supply energy and contribute carbons for glutamine and γ-aminobutyric acid synthesis, and decanoic acid can also block α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid glutamate receptors. MCTs do not compete with metabolism of ketone bodies mostly occurring in neurons. Triheptanoin, an anaplerotic but also gluconeogenic uneven MCT, may be another potential addition to ketogenic diets, although maintenance of "ketosis" can be difficult. Gene therapy has also targeted both endothelial cells and astrocytes. Other approaches to increase fuel delivery to the brain currently investigated include exchange of Glut1DS erythrocytes with healthy cells, infusion of lactate, and pharmacological improvement of glucose transport. In conclusion, although it remains difficult to assess impaired astrocytic energy metabolism in vivo, astrocytic energy needs are most likely not met by ketogenic diets in Glut1DS. Thus, we propose prospective studies including monitoring of blood MCFA levels to find optimal doses for add-on MCT to ketogenic diets and assessing of short- and long-term outcomes.

Unraveling unmet needs in ketogenic dietary services: An ERN EpiCARE survey

The implementation and potential of ketogenic dietary therapies (KDTs) have changed over time. The organization of KDT services, the availability of multidisciplinary teams, resources and support for patients and families still vary widely around the world. This diversity is reflected by a lack of consistency in reported outcomes, optimization of using KDT and KDT compliance. To highlight the unmet needs for KDT services, the ERN EpiCARE Ketogenic Dietary Therapy Special Interest Group (KDT SIG) conducted an online survey on KDT implementation and utilization, addressing the following topics: Use and completeness of guidelines and protocols; assessment of compliance and outcome parameters, sustainability and inclusivity in daily life. Consistently reported unmet needs included the lack of psychological support and resources to measure and improve adherence to KDT, the lack of inclusion strategies, and shared guidelines and protocols adapting to specific needs. Future interventions should focus primarily on educational and informative measures together with creation of shared protocols for complex care. PLAIN LANGUAGE SUMMARY: This study provides the results of a survey compiled by clinicians and patients representatives belonging to ERN Epicare, designed to unravel unmet needs from both patients' and healthcare practitioners' perspectives during ketogenic dietary therapies (KDT) provision. Importantly, results show the need to create new shared protocols and guidelines meant for KDT use in complex care situations and to develop future strategies initiatives to support patients improving their social inclusivity.

Neurodevelopment Is Dependent on Maternal Diet: Placenta and Brain Glucose Transporters GLUT1 and GLUT3

Glucose is the primary energy source for most mammalian cells and its transport is affected by a family of facilitative glucose transporters (GLUTs) encoded by the SLC2 gene. GLUT1 and GLUT3, highly expressed isoforms in the blood-brain barrier and neuronal membranes, respectively, are associated with multiple neurodevelopmental disorders including epilepsy, dyslexia, ADHD, and autism spectrum disorder (ASD). Dietary therapies, such as the ketogenic diet, are widely accepted treatments for patients with the GLUT1 deficiency syndrome, while ameliorating certain symptoms associated with GLUT3 deficiency in animal models. A ketogenic diet, high-fat diet, and calorie/energy restriction during prenatal and postnatal stages can also alter the placental and brain GLUTs expression with long-term consequences on neurobehavior. This review focuses primarily on the role of diet/energy perturbations upon GLUT isoform-mediated emergence of neurodevelopmental and neurodegenerative disorders.

GLUT1DS focus on dysarthria

RESEARCH PURPOSE

GLUT1 deficiency syndrome (GLUT1DS) is a rare genetic disorder caused by a mutation in the SLC2A1 gene that limits the transport of glucose across the blood-brain barrier. Speech disorders and dysarthria are typical findings in patients with GLUT1DS, but have never been deeply phenotyped. The aim of the present study was to characterize speech abilities in a sample of patients with GLUT1DS.

RESULTS

30 patients with GLUT1DS were recruited. We reported impairments in different speech and oromotor domains: the speech was characterized by dysarthria, inaccurate articulation of consonants, abnormal nasal resonance, errors in intonation and prosody and low intelligibility. We observed difficulties in motor planning and programming. Moreover, we observed a significant difference between the dysarthric level of impairment with genotype groups.

CONCLUSIONS

The presence of a speech disorder in patients with GLUT1DS represents a core feature of the syndrome. Our findings suggest that patients with GLUT1DS would benefit from a comprehensive neurocognitive assessment to detect strengths and weaknesses of the speech profile. Understanding the speech and language phenotype in GLUT1DS is critical for planning early intervention to positively influence the global development of patients with GLUT1DS.

The Assessment of the Efficacy, Safety, and Challenges of Ketogenic Diet Therapy in Children with Epilepsy: The First Experience of a Single Center

Background and Objectives: Ketogenic diet therapy (KDT) has been used as a non-pharmacological treatment for childhood refractory epilepsy. Its efficacy and safety have been described in numerous studies and reviews. However, there have been fewer studies evaluating the challenges experienced by patients and their family members when starting KDT. When implementing a new treatment method, challenges arise for both the healthcare professionals and patients, making it important to summarize the initial results and compare them with the experiences of other centers. To analyze and evaluate the efficacy and safety of KDT in children with epilepsy, as well as to consider the challenges faced by their parents/caregivers. Materials and Methods: A retrospective analysis of patients' data (N = 30) and an analysis of the completed questionnaires of the parents/caregivers (N = 22) occurred. Results: In the study group, 66.7% of the patients had a >50% decrease in seizure frequency, and 2/3 of them had a >90% decrease in seizure frequency or were seizure-free, which enabled reducing the anti-seizure medications in 36.4% of the patients, as well as reducing the hospital visits. Cognitive improvement and better alertness were subjectively reported by 59.1% of the parents/caregivers. No dangerous long-term adverse effects of KDT have been observed in the study group. The patients with generalized epilepsy experienced significantly more adverse events. Most of the adverse effects of KDT were related to the digestive system, but usually they were temporary and controllable. The challenges of the parents/caregivers were mostly related to social life issues and financial difficulties; the medical-related challenges were minimal. Conclusions: KDT is an effective and safe treatment option for children with drug-resistant epilepsy, and the challenges faced by families are resolvable. In order to ensure effective KDT, a multidisciplinary team is required. This would ensure smooth and comprehensive care and the timely resolution of emerging problems. The cooperation of the families undergoing KDT is also important, enabling them to share their experiences.

Analysis of dietary fats intake and lipid profile in Chilean patients with glucose transport type 1 deficiency syndrome: similarities and differences with the reviewed literature

Introduction

Glucose transporter type 1 deficiency syndrome (GLUT1-DS) is a neurological disorder caused by mutations in the SLC2A1 gene. The main treatment is ketogenic diet therapy (KDT), which changes the brain's energy substrate from glucose to ketone bodies. The diet controls seizures, but there may be side effects such as dyslipidemia. This study aimed to describe the type of fats ingested by the Chilean cohort of patients with GLUT1-DS and analyze for alterations in the lipid profile.

Methods

A GLUT1-DS group and a control group were formed, each with 13 subjects who were matched by age, gender, and nutritional status. Anthropometry, dietary intake, including types of fat, and blood tests were evaluated (lipid and liver profile, and 25-hydroxyvitamin D levels).

Results

A high-fat diet, especially saturated fat, was identified in the GLUT1-DS group (38% of total calories), with the use of medium-chain triglycerides (17% of total calories). In addition, GLUT1-DS participants had a higher intake of monounsaturated (MUFA) and polyunsaturated (PUFA) fats and adequate consumption of omega-3 (2% of total calories). Despite the GLUT1-DS group receiving on average 80% of its total energy as fats, it is important to highlight that 50% are MUFA+PUFA fats, there were no significant differences in the lipid and liver profile compared to the control group.

Conclusion

KDT did not negatively impact lipid profile, despite a high intake of fats. It is important to monitor lipid profiles, in a personalized and constant manner, to prevent future nutritional risks.

Brain energy metabolism: A roadmap for future research

Although we have learned much about how the brain fuels its functions over the last decades, there remains much still to discover in an organ that is so complex. This article lays out major gaps in our knowledge of interrelationships between brain metabolism and brain function, including biochemical, cellular, and subcellular aspects of functional metabolism and its imaging in adult brain, as well as during development, aging, and disease. The focus is on unknowns in metabolism of major brain substrates and associated transporters, the roles of insulin and of lipid droplets, the emerging role of metabolism in microglia, mysteries about the major brain cofactor and signaling molecule NAD+, as well as unsolved problems underlying brain metabolism in pathologies such as traumatic brain injury, epilepsy, and metabolic downregulation during hibernation. It describes our current level of understanding of these facets of brain energy metabolism as well as a roadmap for future research.

Ketogenic diet therapy in children with epilepsy caused by SLC2A1 mutations: a single-center single-arm retrospective study

BACKGROUND

This retrospective study assessed the efficacy and safety of ketogenic diet therapies in children with epilepsy caused by SLC2A1 genetic mutations and glucose transporter type 1 deficiency syndrome.

METHODS

Pediatric patients with epilepsy symptoms admitted to our medical center between January 2017 and October 2021 were included if they presented with an SLC2A1 genetic mutation on whole-exome sequencing. We analyzed the patients' convulsions and treatment with antiepileptic drugs. The patients were followed up at different time periods after ketogenic diet therapies.

RESULTS

Six patients with SLC2A1 mutations were included in this study. The patients had seizures of different types and frequencies, and they took antiepileptic drugs to relieve their symptoms. They were then treated with a ketogenic diet for at least four months. We analyzed epilepsy control rates at 1, 2, 3, 6, and 12 months after ketogenic diet treatment. All patients were seizure-free within a month of receiving the diet therapy. All patients were followed up for six months, three were followed up for 12 months after the treatment, and there was no recurrence of epilepsy during this period. After antiepileptic drug withdrawal, none of the patients experienced seizure relapse when receiving ketogenic diet treatment alone. No severe adverse events occurred during the therapy.

CONCLUSIONS

Ketogenic diet therapy is very effective and safe for the treatment of epilepsy caused by SLC2A1 mutations. Therefore, patients with glucose transporter type 1 deficiency syndrome caused by SLC2A1 mutations should begin ketogenic diet treatment as soon as possible.

Does hyperphenylalaninemia induce brain glucose hypometabolism? Cerebral spinal fluid findings in treated adult phenylketonuric patients

Despite numerous studies in human patients and animal models for phenylketonuria (PKU; OMIM#261600), the pathophysiology of PKU and the underlying causes of brain dysfunction and cognitive problems in PKU patients are not well understood. In this study, lumbar cerebral spinal fluid (CSF) was obtained immediately after blood sampling from early-treated adult PKU patients who had fasted overnight. Metabolite and amino acid concentrations in the CSF of PKU patients were compared with those of non-PKU controls. The CSF concentrations and CSF/plasma ratios for glucose and lactate were found to be below normal, similar to what has been reported for glucose transporter1 (GLUT1) deficiency patients who exhibit many of the same clinical symptoms as untreated PKU patients. CSF glucose and lactate levels were negatively correlated with CSF phenylalanine (Phe), while CSF glutamine and glutamate levels were positively correlated with CSF Phe levels. Plasma glucose levels were negatively correlated with plasma Phe concentrations in PKU subjects, which partly explains the reduced CSF glucose concentrations. Although brain glucose concentrations are unlikely to be low enough to impair brain glucose utilization, it is possible that the metabolism of Phe in the brain to produce phenyllactate, which can be transported across the blood-brain barrier to the blood, may consume glucose and/or lactate to generate the carbon backbone for glutamate. This glutamate is then converted to glutamine and carries the Phe-derived ammonia from the brain to the blood. While this mechanism remains to be tested, it may explain the correlations of CSF glutamine, glucose, and lactate concentrations with CSF Phe.

[Fourteenth Jesús Culebras Lecture. Ketogenic diet, a half-discovered treatment]

Introduction

The ketogenic diet was an amazing approach to treating epilepsy from its beginning. The body undergoes a change in obtaining energy, going from depending on carbohydrates to depending on fats, and then a whole series of biochemical routes are launched that, independently but also complementary, give rise to a set of effects that benefit the patient. This search for its mechanism of action, of devising how to improve compliance and take advantage of it for other diseases has marked its trajectory. This article briefly reviews these aspects, emphasizing the importance of continuing to carry out basic and clinical research so that this treatment can be applied with solid scientific bases.

Differentiating non-epileptic seizures from epileptic seizures in Glut1 deficiency syndrome

AIM

To investigate the clinical characteristics of non-epileptic seizures due to transient brain dysfunction caused by energy deficiency after prolonged fasting or exercise in individuals with glucose transporter type 1 deficiency syndrome (Glut1DS), and then elucidate further the seizure features to distinguish non-epileptic seizures from epileptic seizures.

METHOD

This retrospective case-control study included 57 non-epileptic seizures and 23 epileptic seizures (control group) in 14 individuals (11 males, three females; aged 5-44 years, median = 20 years) with Glut1DS, all with a heterozygous pathogenic SLC2A1 mutation.

RESULTS

Non-epileptic seizures were classified as paroxysmal altered consciousness (n = 8), movement disorders (n = 35) (eye-head movements, ataxia, spasticity, weakness, involuntary movement), dysaesthesia (n = 8), and vomiting (n = 6) at the peak ages at onset of 5 to 10 years. Ketogenic diet therapy was effective in 33 of 43 (77%) non-epileptic seizures. Providing supplementary food before high-impact exercise or during attacks prevented or mitigated non-epileptic seizures in some individuals. Glut1DS-associated non-epileptic seizures are fundamentally situation-related seizures with specific provoking and ameliorating factors. Non-epileptic seizures can be distinguished from epileptic seizures by the absence of complete consciousness loss and rapid postictal recovery despite prolonged seizures.

INTERPRETATION

Non-epileptic seizures are not well recognized but require different therapeutic approaches compared to epileptic seizures. Awareness of the differentiation of non-epileptic seizures from epileptic seizures is essential when performing preventive or therapeutic decision-making for acute exacerbation seizures.

Care of pharmaco-resistant absence seizures in childhood

In childhood absence epilepsy, pharmaco-resistance occurs in 20-30% of patients. In that situation, glucose transporter type 1 deficiency has to be ruled out, especially if absences started before the age of four years and if neurological signs are present. If ethosuximide, valproate and lamotrigine have failed in monotherapy or in association, there are currently no valuable therapeutic options. The same rules apply for epilepsy with myoclonic absences. Importantly, arguments supporting that making the patient seizure-free will improve eventual associated cognitive deficits such as attention deficit are very weak. Therefore, limiting the cognitive side effects of the anti-epileptic drugs has always to be a priority when faced with typical refractory absences in childhood. In epilepsy with eyelid myoclonia, the majority of patients are pharmaco-resistant. However, absence seizures, if present, tend to be very brief, and seizures are limited in many patients to eyelid myoclonia that eventually do not affect their quality of life and are well attenuated by wearing blue lenses. Atypical absences occurring in the course a developmental and/or epileptic encephalopathy are often pharmaco-resistant. In that situation, characterizing the type of epilepsy syndrome and searching for a specific genetic or structural etiology are needed to offer the best therapeutic options to the patient.

GLUT-1DS resistant to ketogenic diet: from clinical feature to in silico analysis. An exemplificative case report with a literature review

Glucose transporter type 1 deficiency syndrome (GLUT-1DS) is characterized by alterations in glucose translocation through the blood-brain barrier (BBB) due to mutation involving the GLUT-1 transporter. The fundamental therapy is ketogenic diet (KD) that provide an alternative energetic substrate - ketone bodies that across the BBB via MCT-1 - for the brain. Symptoms are various and include intractable seizure, acquired microcephalia, abnormal ocular movement, movement disorder, and neurodevelopment delay secondary to an energetic crisis for persistent neuroglycopenia. KD is extremely effective in controlling epileptic seizures and has a positive impact on movement disorders and cognitive impairment. Cases of KD resistance are rare, and only a few of them are reported in the literature, all regarding seizure. Our study describes a peculiar case of GLUT-1DS due to a new deletion involving the first codon of SLC2A1 gene determining a loss of function with a resistance to KD admitted to hospital due to intractable episodes of dystonia. This patient presented a worsening of symptomatology at higher ketonemia values but without hyperketosis and showed a complete resolution of symptomatology while maintaining low ketonemia values. Our study proposes an in-silico genomic and proteomic analysis aimed at explaining the atypical response to KD exhibited by our patient. In this way, we propose a new clinical and research approach based on precision medicine and molecular modelling to be applied to patients with GLUT-1DS resistant to first-line treatment with ketogenic diet by in silico study of genetic and altered protein product.

Expanding the Spectrum of Stress-Induced Childhood-Onset Neurodegeneration with Variable Ataxia and Seizures (CONDSIAS)

Stress-induced childhood-onset neurodegeneration with variable ataxia and seizures (CONDSIAS) is an extremely rare, autosomal recessive neurodegenerative disorder. It is caused by biallelic pathogenic variants in the ADPRS gene, which encodes an enzyme involved in DNA repair, and is characterized by exacerbations in relation to physical or emotional stress, and febrile illness. We report a 24-year-old female, who was compound heterozygous for two novel pathogenic variants revealed by whole exome sequencing. Additionally, we summarize the published cases of CONDSIAS. In our patient, onset of symptoms occurred at 5 years of age and consisted of episodes of truncal dystonic posturing, followed half a year later by sudden diplopia, dizziness, ataxia, and gait instability. Progressive hearing loss, urinary urgency, and thoracic kyphoscoliosis ensued. Present neurological examination revealed dysarthria, facial mini-myoclonus, muscle weakness and atrophy of hands and feet, leg spasticity with clonus, truncal and appendicular ataxia, and spastic-ataxic gait. Hybrid [18F]-fluorodeoxyglucose (FDG) positron emission tomography/magnetic resonance imaging (PET/MRI) of the brain revealed cerebellar atrophy, particularly of the vermis, with corresponding hypometabolism. MRI of the spinal cord showed mild atrophy. After informed consent from the patient, we initiated experimental, off-label treatment with minocycline, a poly-ADP-polymerase (PARP) inhibitor, which has shown beneficial effects in a Drosophila fly model. The present case report expands the list of known pathogenic variants in CONDIAS and presents details of the clinical phenotype. Future studies will reveal whether PARP inhibition is an effective treatment strategy for CONDIAS.

Novel insight into GLUT1 deficiency syndrome: screening for emotional and behavioral problems in youths following ketogenic diet

BACKGROUND

Glucose transporter type 1 deficiency syndrome (GLUT1DS) is a rare disorder with a broad spectrum of neurological manifestations. The ketogenic diet (KD) is, to date, the gold standard treatment. Behavioral problems, well recognized in patients with chronic conditions, have not been, so far, deeply investigated in GLUT1DS patients. We performed an exploratory study to assess the risk of emotional and behavioral problems and investigated the potential role of influencing factors related to the pathology itself or KD treatment.

METHODS

This was a mono-center retrospective study involving youths with GLUT1Ds treated with KD and a group of migraine patients age- and gender-matched. Patients were included if the main caregiver completed the Child Behavior Check List 6-18 (CBCL). Descriptive statistics for demographic and clinical data and questionnaire scores were computed. Correlational analyses were used to assess the potential associations of clinical variables and age and time from KD introduction with CBCL scores in GLUT1DS patients.

RESULTS

We enrolled nine youths with GLUT1DS and 9 with migraine. In the GLUT1DS group, none of the mean scores of the CBCL items fell within the borderline/clinical range, except for social problems located in the borderline range. Investigation for influencing factors revealed the patient's age related to withdrawn/depressive (r=0.709, P=0.032) and social problems (r=.684, P=0.042). Time from the introduction of KD was related to social problems (r=.827, P=0.006). From the comparison with the scores obtained from migraine patients, significantly higher scores emerged in the latter group in internalizing problems (Z=-2.48, P=0.01), externalizing problems (Z=-3.49, P<0.001), anxious/depressed subscale (Z=-2.37, P=0.014), somatic complaints subscale (Z=-2.624, P=0.008), aggressive behavior subscale (Z=-2.539, P=0.011).

CONCLUSIONS

Although highly exploratory in its nature, this study provides a novel insight into GLUT1DS. Our data suggested that the risk for internalizing problems in GLUT1DS youths was related to higher age and higher time elapsed from KD introduction. They occurred at a sub-clinical level, making them difficult to detect, if not expressly and systematically investigated.

The landscape of drug resistant absence seizures in adolescents and adults: Pathophysiology, electroclinical spectrum and treatment options

The persistence of typical absence seizures (AS) in adolescence and adulthood may reduce the quality of life of patients with genetic generalized epilepsies (GGEs). The prevalence of drug resistant AS is probably underestimated in this patient population, and treatment options are relatively scarce. Similarly, atypical absence seizures in developmental and epileptic encephalopathies (DEEs) may be unrecognized, and often persist into adulthood despite improvement of more severe seizures. These two seemingly distant conditions, represented by typical AS in GGE and atypical AS in DEE, share at least partially overlapping pathophysiological and genetic mechanisms, which may be the target of drug and neurostimulation therapies. In addition, some patients with drug-resistant typical AS may present electroclinical features that lie in between the two extremes represented by these generalized forms of epilepsy.

Leukodystrophy with Macrocephaly, Refractory Epilepsy, and Severe Hyponatremia-The Neonatal Type of Alexander Disease

INTRODUCTION

Alexander disease (AxD) is a rare neurodegenerative condition that represents the group of leukodystrophies. The disease is caused by GFAP mutation. Symptoms usually occur in the infantile age with macrocephaly, developmental deterioration, progressive quadriparesis, and seizures as the most characteristic features. In this case report, we provide a detailed clinical description of the neonatal type of AxD.

METHOD

Next-Generation Sequencing (NGS), including a panel of 49 genes related to Early Infantile Epileptic Encephalopathy (EIEE), was carried out, and then Whole Exome Sequencing (WES) was performed on the proband's DNA extracted from blood.

CASE DESCRIPTION

In the first weeks of life, the child presented with signs of increased intracranial pressure, which led to ventriculoperitoneal shunt implementation. Recurrent focal-onset motor seizures with secondary generalization occurred despite phenobarbital treatment. Therapy was modified with multiple anti-seizure medications. In MRI contrast-enhanced lesions in basal ganglia, midbrain and cortico-spinal tracts were observed. During the diagnostic process, GLUT-1 deficiency, lysosomal storage disorders, organic acidurias, and fatty acid oxidation defects were excluded. The NGS panel of EIEE revealed no abnormalities. In WES analysis, GFAP missense heterozygous variant NM_002055.5: c.1187C>T, p.(Thr396Ile) was detected, confirming the diagnosis of AxD.

CONCLUSION

AxD should be considered in the differential diagnosis in all neonates with progressive, intractable seizures accompanied by macrocephaly.

Ketogenic diet for epilepsy and obesity: Is it the same?

The term "ketogenic diet" (KD) is used for a wide variety of diets with diverse indications ranging from obesity to neurological diseases, as if it was the same diet. This terminology is confusing for patients and the medical and scientific community. The term "ketogenic" diet implies a dietary regimen characterized by increased levels of circulating ketone bodies that should be measured in blood (beta-hydroxybutyrate), urine (acetoacetate) or breath (acetone) to verify the "ketogenic metabolic condition". Our viewpoint highlights that KDs used for epilepsy and obesity are not the same; the protocols aimed at weight loss characterized by low-fat, low-CHO and moderate/high protein content are not ketogenic by themselves but may become mildly ketogenic when high calorie restriction is applied. In contrast, there are standardized protocols for neurological diseases treatment for which ketosis has been established to be part of the mechanism of action. Therefore, in our opinion, the term ketogenic dietary therapy (KDT) should be reserved to the protocols considered for epilepsy and other neurological diseases, as suggested by the International Study Group in 2018. We propose to adjust the abbreviations in VLCHKD for Very Low CarboHydrate Ketogenic Diet and VLEKD for Very Low Energy Ketogenic Diet, to clarify the differences in dietary composition. We recommend that investigators describe the researchers describing efficacy or side effects of KDs, to clearly specify the dietary protocol used with its unique acronym and level of ketosis, when ketosis is considered as a component of the diet's mechanism of action.

Oberg, Clark RD, Wenman C, Loughlin S, Saad R, Ashraf T, Male A, Tadros S, Boostani R, Abdel-Salam GM, Zaki M, Abdalla E, Manzini MC, Pehlivan D, Posey JE, Gibbs RA, Houlden H, Alkuraya FS, Bujakowska K, Maroofian R, Lupski JR, Nguyen LN. Biallelic variation in the choline and ethanolamine transporter FLVCR1 underlies a pleiotropic disease spectrum from adult neurodegeneration to severe developmental disorders

FLVCR1 encodes Feline leukemia virus subgroup C receptor 1 (FLVCR1), a solute carrier (SLC) transporter within the Major Facilitator Superfamily. FLVCR1 is a widely expressed transmembrane protein with plasma membrane and mitochondrial isoforms implicated in heme, choline, and ethanolamine transport. While Flvcr1 knockout mice die in utero with skeletal malformations and defective erythropoiesis reminiscent of Diamond-Blackfan anemia, rare biallelic pathogenic FLVCR1 variants are linked to childhood or adult-onset neurodegeneration of the retina, spinal cord, and peripheral nervous system. We ascertained from research and clinical exome sequencing 27 individuals from 20 unrelated families with biallelic ultra-rare missense and predicted loss-of-function (pLoF) FLVCR1 variant alleles. We characterize an expansive FLVCR1 phenotypic spectrum ranging from adult-onset retinitis pigmentosa to severe developmental disorders with microcephaly, reduced brain volume, epilepsy, spasticity, and premature death. The most severely affected individuals, including three individuals with homozygous pLoF variants, share traits with Flvcr1 knockout mice and Diamond-Blackfan anemia including macrocytic anemia and congenital skeletal malformations. Pathogenic FLVCR1 missense variants primarily lie within transmembrane domains and reduce choline and ethanolamine transport activity compared with wild-type FLVCR1 with minimal impact on FLVCR1 stability or subcellular localization. Several variants disrupt splicing in a mini-gene assay which may contribute to genotype-phenotype correlations. Taken together, these data support an allele-specific gene dosage model in which phenotypic severity reflects residual FLVCR1 activity. This study expands our understanding of Mendelian disorders of choline and ethanolamine transport and demonstrates the importance of choline and ethanolamine in neurodevelopment and neuronal homeostasis.

Transcellular Barriers to Glucose Delivery in the Body

Glucose is the universal fuel of most mammalian cells, and it is largely replenished through dietary intake. Glucose availability to tissues is paramount for the maintenance of homeostatic energetics and, hence, supply should match demand by the consuming organs. In its journey through the body, glucose encounters cellular barriers for transit at the levels of the absorbing intestinal epithelial wall, the renal epithelium mediating glucose reabsorption, and the tight capillary endothelia (especially in the brain). Glucose transiting through these cellular barriers must escape degradation to ensure optimal glucose delivery to the bloodstream or tissues. The liver, which stores glycogen and generates glucose de novo, must similarly be able to release it intact to the circulation. We present the most up-to-date knowledge on glucose handling by the gut, liver, brain endothelium, and kidney, and discuss underlying molecular mechanisms and open questions. Diseases associated with defects in glucose delivery and homeostasis are also briefly addressed. We propose that the universal problem of sparing glucose from catabolism in favor of translocation across the barriers posed by epithelia and endothelia is resolved through common mechanisms involving glucose transfer to the endoplasmic reticulum, from where glucose exits the cells via unconventional cellular mechanisms.

Treatable inherited metabolic epilepsies

Inherited metabolic epilepsies (IMEs) represent inherited metabolic disorders predominately presenting with seizures. While most IMEs are currently managed with symptomatic and supportive therapies, some are amenable to disorder-specific targeted treatments. In most cases, these treatments are effective only if given in a narrow time window early in the lives of affected patients. Hence, prompt recognition of treatable inherited metabolic epilepsies at an early age and as soon as symptoms appear has paramount importance. Herein, we provide an overview of inherited metabolic epilepsies, which presently have established targeted treatments showing clinical efficacy in reducing seizure burden and improving neurodevelopmental outcomes. These therapeutic modalities range from specific diets, vitamins, and supplementation of organic compounds to synthetic pharmacological agents and novel genetic-based therapies that alter the biochemical pathways of these disorders at the cellular or molecular level, steering them to their normal function.

Complete absence of GLUT1 does not impair human terminal erythroid differentiation

The Glucose transporter 1 (GLUT1) is one of the most abundant proteins within the erythrocyte membrane and is required for glucose and dehydroascorbic acid (Vitamin C precursor) transport. It is widely recognized as a key protein for red cell structure, function, and metabolism. Previous reports highlighted the importance of GLUT1 activity within these uniquely glycolysis-dependent cells, in particular for increasing antioxidant capacity needed to avoid irreversible damage from oxidative stress in humans. However, studies of glucose transporter roles in erythroid cells are complicated by species-specific differences between humans and mice. Here, using CRISPR-mediated gene editing of immortalized erythroblasts and adult CD34+ hematopoietic progenitor cells, we generate committed human erythroid cells completely deficient in expression of GLUT1. We show that absence of GLUT1 does not impede human erythroblast proliferation, differentiation, or enucleation. This work demonstrates for the first-time generation of enucleated human reticulocytes lacking GLUT1. The GLUT1-deficient reticulocytes possess no tangible alterations to membrane composition or deformability in reticulocytes. Metabolomic analyses of GLUT1-deficient reticulocytes reveal hallmarks of reduced glucose import, downregulated metabolic processes and upregulated AMPK-signalling, alongside alterations in antioxidant metabolism, resulting in increased osmotic fragility and metabolic shifts indicative of higher oxidant stress. Despite detectable metabolic changes in GLUT1 deficient reticulocytes, the absence of developmental phenotype, detectable proteomic compensation or impaired deformability comprehensively alters our understanding of the role of GLUT1 in red blood cell structure, function and metabolism. It also provides cell biological evidence supporting clinical consensus that reduced GLUT1 expression does not cause anaemia in GLUT1 deficiency syndrome.

Amino acid ratio combinations as biomarkers for discriminating patients with pyruvate dehydrogenase complex deficiency from other inborn errors of metabolism

BACKGROUND

Pyruvate dehydrogenase complex deficiency (PDCD) is a mitochondrial neurometabolic disorder of energy deficit, with incidence of about 1 in 42,000 live births annually in the USA. The median and mean ages of diagnosis of PDCD are about 12 and 31 months, respectively. PDCD is a major cause of primary lactic acidosis with concomitant elevation in blood alanine (Ala) and proline (Pro) concentrations depending on phenotypic severity. Alanine/Leucine (Ala/Leu) ≥4.0 and Proline/Leucine (Pro/Leu) ≥3.0 combination cutoff from dried blood spot specimens was used as a biomarker for early identification of neonates/infants with PDCD. Further investigations were needed to evaluate the sensitivity (SN), specificity (SP), and clinical utility of such amino acid (AA) ratio combination cutoffs in discriminating PDCD from other inborn errors of metabolism (IEM) for early identification of such patients.

METHODS

We reviewed medical records of patients seen at UPMC in the past 11 years with molecularly or enzymatically confirmed diagnosis. We collected plasma AA analysis data from samples prior to initiation of therapeutic interventions such as total parenteral nutrition and/or ketogenic diet. Conditions evaluated included organic acidemias, primary mitochondrial disorders (MtDs), fatty acid oxidation disorders (FAOD), other IEMs on current newborn screening panels, congenital cardiac great vessel anomalies, renal tubular acidosis, and non-IEMs. The utility of specific AA ratio combinations as biomarkers were evaluated using receiver operating characteristic curves, correlation analysis, principal component analysis, and cutoff SN, SP, and positive predictive value determined from 201 subjects with broad age range.

RESULTS

Alanine/Lysine (Ala/Lys) and Ala/Leu as well as (Ala + Pro)/(Leu + Lys) and Ala/Leu ratio combinations effectively discriminated subjects with PDCD from those with other MtDs and IEMs on current newborn screening panels. Specific AA ratio combinations were significantly more sensitive in identifying PDCD than Ala alone or combinations of Ala and/or Pro in the evaluated cohort of subjects. Ala/Lys ≥3.0 and Ala/Leu ≥5.0 as well as (Ala + Pro)/(Leu + Lys) ≥2.5 and Ala/Leu ≥5.0 combination cutoffs identified patients with PDCD with 100% SN and ~85% SP.

CONCLUSIONS

With the best predictor of survival and positive cognitive outcome in PDCD being age of diagnosis, PDCD patients would benefit from use of such highly SN and SP AA ratio combination cutoffs as biomarkers for early identification of at-risk newborns, infants, and children, for early intervention(s) with known and/or novel therapeutics for this disorder.

From diagnosis to treatment in genetic epilepsies: Implementation of precision medicine in real-world clinical practice

The implementation of whole exome sequencing (WES) has had a major impact on the diagnostic yield of genetic testing in individuals with epilepsy. The identification of a genetic etiology paves the way to precision medicine: an individualized treatment approach, based on the disease pathophysiology. The aim of this retrospective cohort study was to: (1) determine the diagnostic yield of WES in a heterogeneous cohort of individuals with epilepsy referred for genetic testing in a real-world clinical setting, (2) investigate the influence of epilepsy characteristics on the diagnostic yield, (3) determine the theoretical yield of treatment changes based on genetic diagnosis and (4) explore the barriers to implementation of precision medicine. WES was performed in 247 individuals with epilepsy, aged between 7 months and 68 years. In 34/247 (14 %) a (likely) pathogenic variant was identified. In 7/34 (21 %) of these individuals the variant was found using a HPO-based filtering. Diagnostic yield was highest for individuals with an early onset of epilepsy (39 %) or in those with a developmental and epileptic encephalopathy (34 %). Precision medicine was a theoretical possibility in 20/34 (59 %) of the individuals with a (likely) pathogenic variant but implemented in only 11/34 (32 %). The major barrier to implementation of precision treatment was the limited availability or reimbursement of a given drug. These results confirm the potential impact of genetic analysis on treatment choices, but also highlight the hurdles to the implementation of precision medicine. To optimize precision medicine in real-world practice, additional endeavors are needed: unifying definitions of precision medicine, establishment of publicly accessible databases that include data on the functional effect of gene variants, increasing availability and reimbursement of precision therapeutics, and broadening access to innovative clinical trials.

Effects of Sodium Lactate Infusion in Two Girls with Glucose Transporter 1 Deficiency Syndrome

BACKGROUND

Glucose is an important fuel for the brain. In glucose transporter 1 deficiency syndrome (GLUT1DS), the transport of glucose across the blood-brain barrier is limited. Most individuals with GLUT1DS present with developmental problems, epilepsy, and (paroxysmal) movement disorders, and respond favorably to the ketogenic diet. Similar to ketones, lactate is an alternative energy source for the brain. The aim of this study is to investigate whether intravenous infusion of sodium lactate in children with GLUT1DS has beneficial effects on their epilepsy.

METHODS

We performed a proof of principle study with two subjects with GLUT1DS who were not on a ketogenic diet and suffered from absence epilepsy. After overnight fasting, sodium lactate (600 mmol/L) was infused during 120 minutes, under video electroencephalographic (EEG) recording and monitoring of serum lactate, glucose, electrolytes, and pH. Furthermore, the EEGs were compared with pre-/postprandial EEGs of both subjects, obtained shortly before the study.

RESULTS

Fasting EEGs of both subjects showed frequent bilateral, frontocentral polyspike and wave complexes. In one subject, no more epileptic discharges were seen postprandially and after the start of lactate infusion. The EEG of the other subject did not change, neither postprandially nor after lactate infusion. Serum pH, lactate, and sodium changed temporarily during the study.

CONCLUSION

This study suggests that sodium lactate infusion is possible in individuals with GLUT1DS, and may have potential therapeutic effects. Cellular abnormalities, beyond neuronal energy failure, may contribute to the underlying disease mechanisms of GLUT1DS, explaining why not all individuals respond to the supplementation of alternative energy sources.

Clinical and biochemical footprints of inherited metabolic diseases. XV. Epilepsies

We provide a comprehensive overview of inherited metabolic disorders (IMDs) in which epilepsy is a prominent manifestation. Our unique database search has identified 256 IMDs associated with various types of epilepsies, which we classified according to the classic pathophysiology-based classification of IMDs, and according to selected seizure-related factors (neonatal seizures, infantile spasms, myoclonic seizures, and characteristic EEG patterns) and treatability for the underlying metabolic defect. Our findings indicate that inherited metabolic epilepsies are more likely to present in the neonatal period, with infantile spasms or myoclonic seizures. Additionally, the ∼20% of treatable inherited metabolic epilepsies found by our search were mainly associated with the IMD groups of "cofactor and mineral metabolism" and "Intermediary nutrient metabolism." The information provided by this study, including a comprehensive list of IMDs with epilepsy stratified according to age of onset, and seizure type and characteristics, along with an overview of the key clinical features and proposed diagnostic and therapeutic approaches, may benefit any epileptologist and healthcare provider caring for individuals with metabolic conditions.

The cation-leaky hereditary stomatocytosis syndromes: A tale of six proteins

This review concerns a series of dominantly inherited haemolytic anaemias in which the membrane of the erythrocyte 'leaks' the univalent cations, compromising the osmotic stability of the cell. The majority of the conditions are explained by mutations in one of six genes, coding for multispanning membrane proteins of different structure and function. These are: RhAG, coding for an ammonium carrier; SLC4A1, coding for the band 3 anion exchanger; PIEZO1, coding for a mechanosensitive cation channel; GLUT1, coding for a glucose transporter; KCNN4, coding for an internal-calcium-activated potassium channel; and ABCB6, coding for a porphyrin transporter. This review describes the five clinical syndromes associated with genetic defects in these genes and their variable genotype/phenotype relationships.

The Modified Atkins Diet for Epilepsy: Two Decades of an "Alternative" Ketogenic Diet Therapy

In 2003, the first case series of six patients treated with an Atkins diet for epilepsy was published in the journal Neurology. The concept was a simple, outpatient-initiated diet in which ketosis could be maintained by eating high-fat foods while tracking and limiting daily carbohydrate counts based on food ingredient labels. Twenty years later, after dozens of studies encompassing hundreds of patients, including several randomized controlled trials, the Modified Atkins Diet is a proven method of providing ketogenic dietary therapy for epilepsy. It is a diet therapy of choice for adolescents and adults, is being investigated for new-onset epilepsy, and is researched for neurological conditions other than epilepsy. Adverse effects do exist but may be less common than the classic ketogenic diet. This review will cover the history, clinical trials, implementation, current utilization, and future directions of this "alternative" ketogenic diet therapy on its 20-year anniversary.

Inborn Errors of Metabolism with Ataxia: Current and Future Treatment Options

A number of hereditary ataxias are caused by inborn errors of metabolism (IEM), most of which are highly heterogeneous in their clinical presentation. Prompt diagnosis is important because disease-specific therapies may be available. In this review, we offer a comprehensive overview of metabolic ataxias summarized by disease, highlighting novel clinical trials and emerging therapies with a particular emphasis on first-in-human gene therapies. We present disease-specific treatments if they exist and review the current evidence for symptomatic treatments of these highly heterogeneous diseases (where cerebellar ataxia is part of their phenotype) that aim to improve the disease burden and enhance quality of life. In general, a multimodal and holistic approach to the treatment of cerebellar ataxia, irrespective of etiology, is necessary to offer the best medical care. Physical therapy and speech and occupational therapy are obligatory. Genetic counseling is essential for making informed decisions about family planning.

A concise study of acetazolamide in glucose transporter type 1 deficiency (G1D) epilepsy

Epilepsy constitutes the most common paroxysmal manifestation of glucose transporter type 1 deficiency (G1D) and is generally considered medication-refractory. It can also prove therapeutic diet-resistant. We examined acetazolamide effects in G1D motivated by several longstanding and recent observations: First, the electrographic spike-waves characteristic of absence seizures often resemble those of G1D and, since the 1950s, they have occasionally been treated successfully with acetazolamide, well before G1D was segregated from absence epilepsy as a distinct syndrome. Second, synaptic inhibitory neuron failure characterizes G1D and, in other experimental models, this can be ameliorated by drugs that modify cellular chloride gradient such as acetazolamide. Third, acetazolamide potently stimulates model cell glucose transport in vitro. Seventeen antiepileptic drug or therapeutic diet-refractory individuals with G1D treated with acetazolamide were thus identified via medical record review complemented by worldwide individual survey. Acetazolamide was tolerated and decreased seizures in 76% of them, with 58% of all persons studied experiencing seizure reductions by more than one-half, including those who first manifested myoclonic-astatic epilepsy or infantile spams. Eighty-eight percent of individuals with G1D continued taking acetazolamide for over 6 months, indicating sustained tolerability and efficacy. The results provide a novel avenue for the treatment and mechanistic investigation of G1D.

Neurological Applications of Celery (Apium graveolens): A Scoping Review

Apium graveolens is an indigenous plant in the family Apiaceae, or Umbelliferae, that contains many active compounds. It has been used traditionally to treat arthritic conditions, gout, and urinary infections. The authors conducted a scoping review to assess the quality of available evidence on the overall effects of celery when treating neurological disorders. A systematic search was performed using predetermined keywords in selected electronic databases. The 26 articles included upon screening consisted of 19 in vivo studies, 1 published clinical trial, 4 in vitro studies and 2 studies comprising both in vivo and in vitro methods. A. graveolens and its bioactive phytoconstituent, 3-n-butylphthalide (NBP), have demonstrated their effect on neurological disorders such as Alzheimer's disease, Parkinson's disease, stroke-related neurological complications, depression, diabetes-related neurological complications, and epilepsy. The safety findings were minimal, showing that NBP is safe for up to 18 weeks at 15 mg/kg in animal studies, while there were adverse effects (7%) reported when consuming NBP for 24 weeks at 600 mg daily in human trials. In conclusion, the safety of A. graveolens extract and NBP can be further investigated clinically on different neurological disorders based on their potential role in different targeted pathways.

Experimental pharmacology: Targeting metabolic pathways

Since the discovery of the treatment for Wilson disease a growing number of treatable inherited dystonias have been identified and their search and treatment have progressively been implemented in the clinics of patients with dystonia. While waiting for gene therapy to be more widely and adequately translated into the clinical setting, the efforts to divert the natural course of dystonia reside in unveiling its pathogenesis. Specific metabolic treatments can rewrite the natural history of the disease by preventing neurotoxic metabolite accumulation or interfering with the cell accumulation of damaging metabolites, restoring energetic cell fuel, supplementing defective metabolites, and supplementing the defective enzyme. A metabolic derangement of cell homeostasis is part of the progression of many non-metabolic genetic lesions and could be the target for possible metabolic approaches. In this chapter, we provided an update on treatment strategies for treatable inherited dystonias and an overview of genetic dystonias with new experimental therapeutic approaches available or close to clinical translation.

Ketogenic dietary therapies in epilepsy: recommendations of the Italian League against Epilepsy Dietary Therapy Study Group

A stepwise increase in the utilization of ketogenic dietary therapies for drug-resistant epilepsy has been observed in Italy in the last decade, although it is still considered often underused in many centers when compared to other countries. The Dietary Therapy Study Group of the Italian League against Epilepsy proposes practical recommendations to improve shared knowledge and facilitate the application of ketogenic dietary therapies, optimizing its efficacy and tolerability. The experts involved (11 child neuropsychiatrists, two adult neurologists, one psychologist, one pharmacologist, one pediatric endocrinologist, one representative of patients' associations, and three dietitians and clinical nutritionists) responded to a survey on current clinical practice issues and were asked to discuss controversial topics related to supplementation, long-term maintenance, transition, and a multidisciplinary approach to ketogenic dietary therapies. Practical indications for patient selection, diet initiation, management, side effects prevention, and follow-up are provided.

Uncommon use of intermittent glucose administration for infrequent non-epileptic paroxysmal events in GLUT1-DS

The ketogenic diet is the treatment of GLUT1 deficiency syndrome that provides an alternative energy source for the brain. However, there are some limitations, including compliance issues as well as patients who do not respond to the ketogenic diet. We report the case of two patients that were not on any particular diet. Both experienced infrequent paroxysmal non-epileptic events (acute ataxia and exercise-induced dystonia). Intermittent glucose intake prior to physical activity for exercise-induced symptoms and at the onset of symptoms for acute ataxia showed consistent and reproducible improvement of the symptoms. Our observations raised the question of developing a new treatment strategy with the induction of a sustained increase in blood glucose. For now, the use of this strategy should be limited to a small group of GLUT1-DS patients who are not on a ketogenic diet.

Nutritional Intervention Through Ketogenic Diet in GLUT1 Deficiency Syndrome

Glucose transporter type 1 (GLUT1) deficiency syndrome (DS) is a metabolic brain disorder caused by a deficiency resulting from SLC2A1 gene mutation and is characterized by abnormal brain metabolism and associated metabolic encephalopathy. Reduced glucose supply to the brain leads to brain damage, resulting in delayed neurodevelopment in infancy and symptoms such as eye abnormalities, microcephaly, ataxia, and rigidity. Treatment options for GLUT1 DS include ketogenic diet (KD), pharmacotherapy, and rehabilitation therapy. Of these, KD is an essential and the most important treatment method as it promotes brain neurodevelopment by generating ketone bodies to produce energy. This case is a focused study on intensive KD nutritional intervention for an infant diagnosed with GLUT1 DS at Gangnam Severance Hospital from May 2022 to January 2023. During the initial hospitalization, nutritional intervention was performed to address poor intake via the use of concentrated formula and an attempt was made to introduce complementary feeding. After the second hospitalization and diagnosis of GLUT1 DS, positive effects on the infant's growth and development, nutritional status, and seizure control were achieved with minimal side effects by implementing KD nutritional intervention and adjusting the type and dosage of anticonvulsant medications. In conclusion, for patients with GLUT1 DS, it is important to implement a KD with an appropriate ratio of ketogenic to nonketogenic components to supply adequate energy. Furthermore, individualized and intensive nutritional management is necessary to improve growth, development, and nutritional status.

Systemic Reduction of Glut1 Normalizes Retinal Dysfunction, Inflammation, and Oxidative Stress in the Retina of Spontaneous Type 2 Diabetic Mice

Defects in the light-evoked responses of the retina occur early in the sequalae of diabetic retinopathy (DR). These defects, identified through the electroretinogram (ERG), represent dysfunction of retinal neurons and the retinal pigment epithelium and are commonly identifiable at the timing of, or almost immediately following, diabetes diagnosis. Recently, systemic reduction of the facilitated glucose transporter type 1, Glut1, in type 1 diabetic mice was shown to reduce retinal sorbitol accumulation, mitigate ERG defects, and prevent retinal oxidative stress and inflammation. Herein, the study investigated whether systemic reduction of Glut1 also diminished hallmarks of DR in type 2 diabetic mice. Transgenic nondiabetic Leprdb/+ and spontaneously diabetic Leprdb/db mice that expressed wild-type (Glut1+/+) or systemically reduced levels of Glut1 (Glut1+/-) were aged and subjected to standard strobe flash electroretinography and c-wave analysis before evaluation of inflammatory cytokines and oxidative stress molecules. Although Leprdb/dbGlut1+/- mice still displayed overt obesity and diabetes, no scotopic, photopic, or c-wave ERG defects were present through 16 weeks of age, and expression of inflammatory cytokines and oxidative stress molecules was also normalized. These findings suggest that systemic reduction of Glut1 is sufficient to prevent functional retinal pathophysiology in type 2 diabetes. Targeted, moderate reductions of Glut1 or inhibition of Glut1 activity in the retina of diabetic patients should be considered as a novel therapeutic strategy to prevent development and progression of DR.

Dietary carbohydrates in the management of epilepsy

PURPOSE OF REVIEW

The role of dietary carbohydrates in the management of epilepsy is intrinsically linked to the ketogenic diet. The ketogenic diet has been in use for well over a century now. There have been numerous adaptations to the diet. It is crucial to understand the indications and role of the ketogenic diet in the management of epilepsy.

RECENT FINDINGS

There have been new studies that have looked at the role of ketogenic ratios in seizure control. In addition, there has been new evidence in the role of using the ketogenic diet therapy instead of antiseizure medications. These data highlight that the ketogenic diet should be tailored for patients and caregivers. When used appropriately, it can result in a significant improvement in seizure control as well as cognitive and developmental gains.

SUMMARY

The ketogenic diet therapy has undergone numerous revisions and reiterations from its initial reported use in patients a century ago. This has enabled us to tailor the diet specific to each patient's underlying diagnosis.