GLUT1 deficiency syndrome--2007 update

The diagnostic and prognostic role of cerebrospinal fluid biomarkers in glucose transporter 1 deficiency: a systematic review

The purpose of this study is to investigate the diagnostic and prognostic role of cerebrospinal fluid (CSF) biomarkers in the diagnostic work-up of glucose transporter 1 (GLUT1) deficiency. Reported here is a systematic review according to PRISMA guidelines collecting clinical and biochemical data about all published patients who underwent CSF analysis. Clinical phenotypes were compared between groups defined by the levels of CSF glucose (≤ 2.2 mmol/L versus > 2.2 mmol/L), CSF/blood glucose ratio (≤ 0.45 versus > 0.45), and CSF lactate (≤ 1 mmol/L versus > 1 mmol/L). Five hundred sixty-two patients fulfilled the inclusion criteria with a mean age at the diagnosis of 8.6 ± 6.7 years. Patients with CSF glucose ≤ 2.2 mmol/L and CSF/blood glucose ratio ≤ 0.45 presented with an earlier onset of symptoms (16.4 ± 22.0 versus 54.4 ± 45.9 months, p < 0.01; 15.7 ± 23.8 versus 40.9 ± 38.0 months, p < 0.01) and received an earlier molecular genetic confirmation (92.1 ± 72.8 versus 157.1 ± 106.2 months, p < 0.01). CSF glucose ≤ 2.2 mmol/L was consistently associated with response to ketogenic diet (p = 0.018) and antiseizure medications (p = 0.025). CSF/blood glucose ratio ≤ 0.45 was significantly associated with absence seizures (p = 0.048), paroxysmal exercise-induced dyskinesia (p = 0.046), and intellectual disability (p = 0.016) while CSF lactate > 1 mmol/L was associated with a response to antiseizure medications (p = 0.026) but not to ketogenic diet.Conclusions:This systematic review supported the diagnostic usefulness of lumbar puncture for the early identification of patients with GLUT1 deficiency responsive to treatments especially if they present with co-occurring epilepsy, movement, and neurodevelopmental disorders. What is Known: • Phenotypes of GLUT1 deficiency syndrome range between early epileptic and developmental encephalopathy to paroxysmal movement disorders and developmental impairment What is New: • CSF blood/glucose ratio may predict better than CSF glucose the diagnosis in children presenting with early onset absences • CSF blood/glucose ratio may predict better than CSF glucose the diagnosis in children presenting with paroxysmal exercise induced dyskinesia and intellectual disability. • CSF glucose may predict better than CSF blood/glucose and lactate the response to ketogenic diet and antiseizure medications.

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.

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.

Clinical application of trio-based whole-exome sequencing in idiopathic generalized epilepsy

PURPOSE

Idiopathic generalized epilepsies (IGEs) are a common group of genetic generalized epilepsies with high genetic heterogeneity and complex inheritance. However, the genetic basis is still largely unknown. This study aimed to explore the genetic etiologies in IGEs.

METHODS

Trio-based whole-exome sequencing was performed in 60 cases with IGEs. The pathogenicity of candidate genetic variants was evaluated by the criteria of the American College of Medical Genetics and Genomics (ACMG), and the clinical causality was assessed by concordance between the observed phenotype and the reported phenotype.

RESULTS

Seven candidate variants were detected in seven unrelated cases with IGE (11.7%, 7/60). According to ACMG, a de novo SLC2A1 (c.376C>T/p.Arg126Cys) variant identified in childhood absence epilepsy was evaluated as pathogenic with clinical concordance. Six variants were assessed to be uncertain significance by ACMG, but then considered causative after evaluation of clinical concordance. These variants included CLCN4 hemizygous variant (c.2044G>A/p.Glu682Lys) and IQSEC2 heterozygous variant (c.4315C>T/p.Pro1439Ser) in juvenile absence epilepsy, EFHC1 variant (c.1504C>T/p.Arg502Trp) and CACNA1H (c.589G>T/p.Ala197Ser) both with incomplete penetrance in juvenile myoclonic epilepsy, and GRIN2A variant (c.2011C>G/p.Gln671Glu) and GABRB1 variant (c.1075G>A/p.Val359Ile) both co-segregated with juvenile myoclonic epilepsy. Among them, GABRB1 was for the first time identified as potential novel causative gene for IGE.

SIGNIFICANCE

Considering the genetic heterogeneity and complex inheritance of IGEs, a comprehensive evaluation combined the ACMG scoring and assessment of clinical concordance is suggested for the pathogenicity analysis of variants identified in clinical screening. GABRB1 is probably a novel causative gene for IGE, which warrants further studies.

Evaluating the efficacy of a ketogenic diet in managing drug resistant paediatric DEDPC5-related epilepsy

AIM

To evaluate the effectiveness of the ketogenic diet treatment in a cohort of patients with drug-resistant epilepsy with a mutation in the DEPDC5 gene.

MATERIALS AND METHODS

We followed four paediatric patients with drug resistant DEPDC5-related epilepsy through a ketogenic diet (KD) treatment course. We analyzed the following parameters of their clinical profiles: past medical history, clinical characteristics of seizure morphology, EEG records pre- and post-KD treatment, the results of MRI head and neurological and psychological examinations (pre-treatment and throughout treatment course). We evaluated the effectiveness of previous therapeutic approaches and the current treatment with ketogenic diet alongside results of neuroimaging studies. Effect of KD on co-morbid behavioural and psychiatric symptoms, as well as adverse effects from KD were also assessed.

RESULTS

In three patients, the introduction of the ketogenic diet resulted in the cessation of seizures, while in 1 patient with co-morbid cortical dysplasia, epileptic seizures of lesser severity returned after an initial seizure-free period of several weeks. Further, 1 patient was able to transition to a KD-only treatment regimen. The remaining patients were able to reduce the number of antiseizure medicine (ASM) to a monotherapy. In all cases we observed improvements in EEG results. Our cohort included one patient whose MRI head showed cortical dysplasia. However, no patients demonstrated any neurological signs in neurological examination. Psychological examination showed normal intellectual development in all patients, although behavioral disorders and difficulties at school were observed. The introduction of KD treatment correlated with improvement in school performance and improved behavioral regulation. No clinically significant adverse events were observed.

CONCLUSIONS

KD seems to be both effective and well tolerated in young patients with DEPDC5-related epilepsy, both as a monotherapy and as an adjunct to ASM. We recommend an early adoption of this therapeutic approach in this patient demographic. Our results demonstrate that the positive effects of KD treatment encompass improvements in general functioning, particularly in the context of school performance and behavior, in addition to the achievement of good seizure control.

Proteomic alterations in the brain and blood-brain barrier during brain Aβ accumulation in an APP knock-in mouse model of Alzheimer's disease

BACKGROUND

Blood-brain barrier (BBB) dysfunction is supposed to be an early event in the development of Alzheimer's disease (AD). This study aimed to investigate the relationship between BBB alterations and AD progression in terms of amyloid-β peptide (Aβ) accumulation in the brains of humanized amyloid precursor protein knock-in (APP-KI) mice.

METHODS

Brain Aβ accumulation was examined using immunohistochemical analysis. Alterations in differentially expressed proteins were determined using sequential window acquisition of all theoretical fragment ion mass spectroscopy (SWATH-MS)-based quantitative proteomics, and Metascape, STRING, Gene Ontology, and KEGG were used for network analyses of altered biological pathways and processes. Statistical significance was determined using the unpaired two-tailed Student's t-test and Welch's t-test for two groups and one-way analysis of variance followed by Tukey's test for more than two groups. Correlations between two groups were determined using Pearson's correlation analysis.

RESULTS

Brain Aβ accumulation in APP-KI mice was detectable at 2 months, increased significantly at 5 months, and remained elevated at 12 months of age. The levels of differentially expressed proteins in isolated brain capillaries were higher in younger mice, whereas those in the brain were higher in older mice. Network analyses indicated changes in basement membrane-associated and ribosomal proteins in the brain capillaries. There were no significant changes in key proteins involved in drug or Aβ transport at the BBB. In contrast, solute carrier transporter levels in astrocytes, microglia, and neurons were altered in the brain of older mice. Moreover, the levels of the lipid transporters Apoe and Apoj were upregulated in both the brain and isolated brain capillaries after Aβ accumulation.

CONCLUSIONS

Our results suggest that changes in the brain occurred after advanced Aβ accumulation, whereas initial Aβ accumulation was sufficient to cause alterations in the BBB. These findings may help elucidate the role of BBB alterations in AD progression and predict the distribution of drugs across the BBB in the brain of patients with AD.

Quantitative determination of SLC2A1 variant functional effects in GLUT1 deficiency syndrome

OBJECTIVE

The goal of this study is to demonstrate the utility of a growth assay to quantify the functional impact of single nucleotide variants (SNVs) in SLC2A1, the gene responsible for Glut1DS.

METHODS

The functional impact of 40 SNVs in SLC2A1 was quantitatively determined in HAP1 cells in which SLC2A1 is required for growth. Donor libraries were introduced into the endogenous SLC2A1 gene in HAP1-Lig4KO cells using CRISPR/Cas9. Cell populations were harvested and sequenced to quantify the effect of variants on growth and generate a functional score. Quantitative functional scores were compared to 3-OMG uptake, SLC2A1 cell surface expression, CADD score, and clinical data, including CSF/blood glucose ratio.

RESULTS

Nonsense variants (N = 3) were reduced in cell culture over time resulting in negative scores (mean score: -1.15 ± 0.17), whereas synonymous variants (N = 10) were not depleted (mean score: 0.25 ± 0.12) (P < 2e-16). Missense variants (N = 27) yielded a range of functional scores including slightly negative scores, supporting a partial function and intermediate phenotype. Several variants with normal results on either cell surface expression (p.N34S and p.W65R) or 3-OMG uptake (p.W65R) had negative functional scores. There is a moderate but significant correlation between our functional scores and CADD scores.

INTERPRETATION

Cell growth is useful to quantitatively determine the functional effects of SLC2A1 variants. Nonsense variants were reliably distinguished from benign variants in this in vitro functional assay. For facilitating early diagnosis and therapeutic intervention, future work is needed to determine the functional effect of every possible variant in SLC2A1.

GLUT1-DS Italian registry: past, present, and future: a useful tool for rare disorders

BACKGROUND

GLUT1 deficiency syndrome is a rare, genetically determined neurological disorder for which Ketogenic Dietary Treatment represents the gold standard and lifelong treatment. Patient registries are powerful tools providing insights and real-world data on rare diseases.

OBJECTIVE

To describe the implementation of a national web-based registry for GLUT1-DS.

METHODS

This is a retrospective and prospective, multicenter, observational registry developed in collaboration with the Italian GLUT1-DS association and based on an innovative, flexible and configurable cloud computing technology platform, structured according to the most rigorous requirements for the management of patient's sensitive data. The Glut1 Registry collects baseline and follow-up data on the patient's demographics, history, symptoms, genotype, clinical, and instrumental evaluations and therapies.

RESULTS

Five Centers in Italy joined the registry, and two more Centers are currently joining. In the first two years of running, data from 67 patients (40 females and 27 males) have been collected. Age at symptom onset was within the first year of life in most (40, 60%) patients. The diagnosis was formulated in infancy in almost half of the cases (34, 51%). Symptoms at onset were mainly paroxysmal (mostly epileptic seizure and paroxysmal ocular movement disorder) or mixed paroxysmal and fixed symptoms (mostly psychomotor delay). Most patients (53, 79%) are currently under Ketogenic dietary treatments.

CONCLUSIONS

We describe the principles behind the design, development, and deployment of the web-based nationwide GLUT1-DS registry. It represents a stepping stone towards a more comprehensive understanding of the disease from onset to adulthood. It also represents a virtuous model from a technical, legal, and organizational point of view, thus representing a possible paradigmatic example for other rare disease registry implementation.

Association between cerebrospinal fluid parameters and developmental and neurological status in glucose transporter 1 deficiency syndrome

OBJECTIVE

In glucose transporter 1 deficiency syndrome (Glut1DS), cerebrospinal fluid glucose (CSFG) and CSFG to blood glucose ratio (CBGR) show significant differences among groups classified by phenotype or genotype. The purpose of this study was to investigate the association between these biochemical parameters and Glut1DS severity.

METHODS

The medical records of 45 patients who visited Osaka University Hospital between March 2004 and December 2021 were retrospectively examined. Neurological status was determined using the developmental quotient (DQ), assessed using the Kyoto Scale of Psychological Development 2001, and the Scale for the Assessment and Rating of Ataxia (SARA). CSF parameters included CSFG, CBGR, and CSF lactate (CSFL).

RESULTS

CSF was collected from 41 patients, and DQ and SARA were assessed in 24 and 27 patients, respectively. Simple regression analysis showed moderate associations between neurological status and biochemical parameters. CSFG resulted in a higher R² than CBGR in these analyses. CSF parameters acquired during the first year of life were not comparable to those acquired later. CSFL was measured in 16 patients (DQ and SARA in 11 and 14 patients, respectively). Although simple regression analysis also showed moderate associations between neurological status and CSFG and CSFL, the multiple regression analysis for DQ and SARA resulted in strong associations through the use of a combination of CSFG and CSFL as explanatory variables.

CONCLUSION

The severity of Glut1DS can be predicted from CSF parameters. Glucose and lactate are independent contributors to the developmental and neurological status in Glut1DS.

Establishment of a flow cytometry screening method for patients with glucose transporter 1 deficiency syndrome

Objective

We assessed the usefulness of flow cytometry as a functional assay to measure glucose transporter 1 (GLUT1) levels on the surface of red blood cells (RBCs) from Japanese patients with glucose transporter 1 deficiency syndrome (Glut1DS).

Methods

We recruited 13 genetically confirmed Glut1DS patients with a solute carrier family 2 member 1 (SLC2A1) mutation (eight missense, one frameshift, two nonsense, and two deletion) and one clinically suspected Glut1DS-like patient without an SLC2A1 mutation, and collected whole blood with informed consent. We stained pelleted RBCs (1 μL) from the patients with a Glut1.RBD ligand and anti-glycophorin A antibody, which recognizes a human RBC membrane protein, and analyzed the cells using flow cytometry.

Results

Relative GLUT1 levels quantified by flow cytometry in 11 of 13 patients with definite Glut1DS were 90% below those of healthy controls. Relative GLUT1 levels were not reduced in two of 13 Glut1DS patients who had a missense mutation and no intellectual disability and one Glut1DS-like patient without an SLC2A1 mutation. Relative GLUT1 levels were significantly reduced in Glut1DS patients with an SLC2A1 mutation, more severe intellectual disability, and spasticity.

Conclusions

This method to detect GLUT1 levels on RBCs is simple and appears to be an appropriate screening assay to identify severe Glut1DS patients in the early stage before the development of irreversible neurologic damage caused by chronic hypoglycorrhachia.

A Mixed-Lipid Diet (Medium-Chain and Long-Chain Triglycerides) for Better Tolerability and Efficiency in Pediatric Epilepsy Patients

Purpose: In the past, the use of medium-chain triglycerides (MCTs) for a ketogenic diet (KD) was expected to improve both patients’ and caregivers’ adherence to treatment, but many gastrointestinal problems have been reported. Through a calculated partial administration of MCTs in a KD, we aimed to reduce these complications, while maintaining acceptable seizure reduction. Methods: At a tertiary referral center for pediatric patients with epilepsy, MCT oil was given in a 1:1 ratio with long-chain triglycerides to patients on KDs. Patients who began the diet from February 2019 to February 2020 were reviewed retrospectively, and 47 patients with at least 3 months of follow-up records were enrolled in the studyResults: Overall, 29.8% of patients on a KD with an adjusted MCT ratio experienced complications, such as gastrointestinal symptoms and behavioral food refusal, compared to 63.0% of prior KD patients. The mean seizure reduction rate was 68.45%±40.61%, which was not significantly different from the comparison group’s rate of 64.84%±34.24%. Conclusion: Adjusted MCT incorporation into a KD showed comparable seizure control results, with better tolerability of the diet.

Quantitation of Lactate in Cerebrospinal Fluid Using Liquid Chromatography-Electrospray-Tandem Mass Spectrometry

We describe a simple stable isotope dilution method for accurate and precise measurement of cerebrospinal fluid (CSF) lactate as a clinical diagnostic test. Lactate is produced from cellular metabolism, primarily in muscle cells, and provides a source of energy especially during instances of low oxygen levels. Measurement of lactate in CSF provides diagnostic information regarding the body's oxidative metabolism including diagnosis of lactate acidosis, aiding in the diagnosis of blood-brain barrier glucose transporter defect and differentiation between bacterial and viral meningitis. Determination of lactate in CSF (20 μL) was performed utilizing high-performance liquid chromatography coupled with electrospray positive ionization tandem mass spectrometry (HPLC-ESI-MS/MS). Lactate in CSF is determined by a 1:10 dilution with internal standard (sodium lacate-d3) and injected directly onto the HPLC-ESI-MS/MS system. Each assay is quantified using a six-point standard curve (0.625-20 mM) and has an analytical measurement range of 0.3-20 mM.

A mathematical model of GLUT1 modulation in rods and RPE and its differential impact in cell metabolism

We present a mathematical model of key glucose metabolic pathways in two cells of the human retina: the rods and the retinal pigmented epithelium (RPE). Computational simulations of glucose transporter 1 (GLUT1) inhibition in the model accurately reproduce experimental data from conditional knockout mice and reveal that modification of GLUT1 expression levels of both cells differentially impacts their metabolism. We hypothesize that, under glucose scarcity, the RPE's energy producing pathways are altered in order to preserve its functionality, impacting the photoreceptors' outer segment renewal. On the other hand, when glucose is limited in the rods, aerobic glycolysis is preserved, which maintains the lactate contribution to the RPE.

Head circumference in glucose transporter 1 deficiency syndrome: Normal for individuals, abnormal as a group

In the literature, microcephaly is considered as part of the classical phenotype of glucose transporter 1 deficiency syndrome (GLUT1DS), and previous cohort studies reported a prevalence of microcephaly of around 50%. In our clinical experience, however, only very few patients with GLUT1DS appear to have microcephaly. Therefore, we conducted an observational study among a large cohort of Dutch patients with GLUT1DS to investigate the prevalence of microcephaly, defined as < 2 standard deviations (SD) below the mean. We analysed the head circumference of 54 patients and found a prevalence of microcephaly at last known measurement of 6.5%. Notably, none of the patients had a head circumference < -3 SD. However, we learned that 75.9% of the patients had a head circumference below 0 SD. This study shows that microcephaly occurs less often than previously thought in patients with GLUT1DS, and that primary or secondary microcephaly does not seem to be a sign for clinicians to suspect GLUT1DS. As a group, however, patients with GLUT1DS seem to have decreased head circumference compared to healthy individuals and as such, our study suggests that early brain development and brain growth may be compromised in GLUT1DS.

Microcephaly in Neurometabolic Diseases

Neurometabolic disorders are an important group of diseases that mostly occur in neonates and infants. They are mainly due to the lack or dysfunction of an enzyme or cofactors necessary for a specific biochemical reaction, which leads to a deficiency of essential metabolites in the brain. This, in turn, can cause certain neurometabolic diseases. Disruption of metabolic pathways, and the inhibition at earlier stages, may lead to the storage of reaction intermediates, which are often toxic to the developing brain. Symptoms are caused by the progressive deterioration of mental, motor, and perceptual functions. The authors review the diseases with microcephaly, which may be one of the most visible signs of neurometabolic disorders.

Clinical and Genetic Characteristics of Chinese Children With GLUT1 Deficiency Syndrome: Case Report and Literature Review

Objective: GLUT1 deficiency syndrome (GLUT1-DS) is a rare, treatable neurometabolic disorder. However, its diagnosis may be challenging due to the various and evolving phenotypes. Here we report the first Chinese familial cases with genetically confirmed GLUT1-DS and analyze the characteristics of Chinese children with GLUT1-DS from clinical, laboratory, and genetic aspects.

Methods: We reported a Chinese family with three members affected with GLUT1-DS and searched for relevant articles up to September 2020 from PubMed, WOS, CNKI, and WanFang databases. A total of 30 Chinese patients diagnosed with GLUT1-DS (three newly identified patients in one family and 27 previously reported ones) were included and analyzed in this study.

Results: The median age of onset of the 30 patients (male: 18, female: 12) was 8.5 months (range, 33 days to 10 years). Epileptic seizures were found in 25 patients, most with generalized tonic–clonic and focal ones. Movement disorders were found in 20 patients—frequently with ataxia and dystonia, developmental delay in 25 patients, and microcephaly only in six patients. The cerebrospinal fluid (CSF) analysis showed decreased CSF glucose (median: 1.63 mmol/L, range: 1.1–2.6 mmol/L) and glucose ratio of CSF to blood (median: 0.340; range: 0.215–0.484). The genetic testing performed in 28 patients revealed 27 cases with pathogenic variations of the SLC2A1 gene, including 10 missense, nine frameshift, three nonsense, three large fragment deletions, and two splice-site mutations. Most patients had a good response to the treatment of ketogenic diet or regular diet with increased frequency. Although three patients in this Chinese family carried the same pathogenic mutation c.73C > T (p.Q25X) in the SLC2A1 gene, their symptoms and responses to treatment were not exactly the same.

Conclusion: The clinical manifestations of GLUT1-DS are heterogeneous, even among family members sharing the same mutation. For children with unexplained epileptic seizures, developmental delay, and complex movement disorders, detection of low CSF glucose or SLC2A1 gene mutations is helpful for the diagnosis of GLUT1-DS. Early initiation of ketogenic diet treatment significantly improves the symptoms and prognosis of GLUT1-DS.

Recent aspects of ketogenic diet in neurological disorders

The ketogenic diet (KD) is a high-fat, low-carbohydrate diet, in which fat is used as the primary energy source through the production of ketone bodies (KBs) in place of glucose. The KD was formally introduced in 1921 to mimic the biochemical changes associated with fasting and gained recognition as a potent treatment for pediatric epilepsy in the mid-1990s. The clinical and basic scientific knowledge that supports the anti-seizure efficacy, safety, and feasibility of using the KD in patients with epilepsy is huge. Additionally, the International Ketogenic Diet Study Group’s consensus guidelines provide practical information in 2009 and 2018. The KD is a broad-spectrum therapy for drug resistant epilepsy and is gaining attention as a potential therapy for other neurological disorders. This article will review recent aspects on the use of the KD, including its mechanisms of action, KD alternatives, expanding its use across different age groups and regions, its use as a treatment for other neurologic disorders, and future research subjects.

Dietary-Induced Ketogenesis: Adults Are Not Children

There is increasing interest in the use of a ketogenic diet for various adult disorders; however, the ability of adults to generate ketones is unknown. Our goal was to challenge the hypothesis that there would be no difference between adults and children regarding their ability to enter ketosis. Methods: Two populations were studied, both treated with identical very low-carbohydrate high-fat diets: a retrospective series of children with epilepsy or/and metabolic disorders (2009–2016) and a prospective clinical trial of adults with glioblastoma. Dietary intake was assessed based upon written food diaries and 24-h dietary recall. Ketogenic ratio was calculated according to [grams of fat consumed]/[grams of carbohydrate and protein consumed]. Ketone levels (β-hydroxybutyrate) were measured in blood and/or urine. Results: A total of 168 encounters amongst 28 individuals were analyzed. Amongst both children and adults, ketone levels correlated with nutritional ketogenic ratio; however, the absolute ketone levels in adults were approximately one quarter of those seen in children. This difference was highly significant in a multivariate linear regression model, p < 0.0001. Conclusions: For diets with comparable ketogenic ratios, adults have lower blood ketone levels than children; consequently, high levels of nutritional ketosis are unobtainable in adults.

GLUT1 Deficiency Syndrome-Early Treatment Maintains Cognitive Development? (Literature Review and Case Report)

Glucose transporter type 1 (GLUT1) is the most important energy carrier of the brain across the blood-brain barrier, and a genetic defect of GLUT1 is known as GLUT1 deficiency syndrome (GLUT1DS). It is characterized by early infantile seizures, developmental delay, microcephaly, ataxia, and various paroxysmal neurological phenomena. In most cases, GLUT1DS is caused by heterozygous single-nucleotide variants (SNVs) in the SLC2A1 gene that provoke complete or severe impairment of the functionality and/or expression of GLUT1 in the brain. Despite the rarity of these diseases, GLUT1DS is of high clinical interest since a very effective therapy, the ketogenic diet, can improve or reverse symptoms, especially if it is started as early as possible. We present a clinical phenotype, biochemical analysis, electroencephalographic and neuropsychological features of an 11-month-old boy with myoclonic seizures, hypogammaglobulinemia, and mildly impaired gross motor development. Using sequence analysis and deletion/duplication testing, deletion of an entire coding sequence in the SLC2A1 gene was detected. Early introduction of a modified Atkins diet maintained a seizure-free period without antiseizure medications and normal cognitive development in the follow-up period. Our report summarizes the clinical features of GLUT1 syndromes and discusses the importance of early identification and molecular confirmation of GLUT1DS as a treatable metabolic disorder.

Varied phenotypic spectrum presenting of paroxysmal exercise-induced dyskinesia: a Turkish family with SLC2A1 mutation

INTRODUCTION

Paroxysmal exercise-induced dyskinesia (PED) is characterized by repeated episodes of involuntary movement disorders that are typically caused by prolonged walking or running and mostly caused by SLC2A1 gene mutations. Phenotypes vary from focal dystonia, ataxia, tremor, and complex non-kinesigenic movements to other movement disorders in patients with SLC2A1 mutation. Also, SLC2A1 mutations carriers may present with also other phenotypes such as epileptic seizure and migraine.

CASE REPORTS

We report five patients with various phenotypic spectrums of PED in a Turkish family. Whole exome sequencing revealed a likely pathogenic synonymous variant p.Ser324Ser (c.972G > A) in the SLC2A1 gene (ENST00000426263.3) and the variant segregated in all affected family members. Also, other than PED, the phenotypical spectrum of affected individuals in this family includes epilepsy, mental retardation, and weakness.

CONCLUSIONS

We concluded that family members with the same SLC2A1 gene mutation may show very heterogenous phenotypes. Clinicians should be aware of wide variety of symptoms of the patients with PED. We also emphasized that even if a mutation in the coding sequence does not make an amino acid change, it may cause the disease.

Intra-cisterna magna delivery of an AAV vector with the GLUT1 promoter in a pig recapitulates the physiological expression of SLC2A1

Glucose transporter 1 deficiency syndrome (GLUT1DS) is caused by haplo-insufficiency of SLC2A1, which encodes GLUT1, resulting in impaired hexose transport into the brain. Previously, we generated a tyrosine-mutant AAV9/3 vector in which SLC2A1 was expressed under the control of the endogenous GLUT1 promoter (AAV-GLUT1), and confirmed the improved motor function and cerebrospinal fluid glucose levels of Glut1-deficient mice after cerebroventricular injection of AAV-GLUT1. In preparation for clinical application, we examined the expression of transgenes after intra-cisterna magna injection of AAV-GFP (tyrosine-mutant AAV9/3-GFP with the CMV promoter) and AAV-GLUT1. We injected AAV-GFP or AAV-GLUT1 (1.63 × 10¹² vector genomes/kg) into the cisterna magna of pigs to compare differential promoter activity. After AAV-GFP injection, exogenous GFP was expressed in broad areas of the brain and peripheral organs. After AAV-GLUT1 injection, exogenous GLUT1 was expressed predominantly in the brain. At the cellular level, exogenous GLUT1 was mainly expressed in the endothelium, followed by glia and neurons, which was contrasted with the neuronal-predominant expression of GFP by the CMV promotor. We consider intra-cisterna magna injection of AAV-GLUT1 to be a feasible approach for gene therapy of GLUT1DS.

Incidence and Characteristics of Kidney Stones in Patients on Ketogenic Diet: A Systematic Review and Meta-Analysis

Very-low-carbohydrate diets or ketogenic diets are frequently used for weight loss in adults and as a therapy for epilepsy in children. The incidence and characteristics of kidney stones in patients on ketogenic diets are not well studied. Methods: A systematic literature search was performed, using MEDLINE, EMBASE, and Cochrane Database of Systematic Reviews from the databases’ inception through April 2020. Observational studies or clinical trials that provide data on the incidence and/or types of kidney stones in patients on ketogenic diets were included. We applied a random-effects model to estimate the incidence of kidney stones. Results: A total of 36 studies with 2795 patients on ketogenic diets were enrolled. The estimated pooled incidence of kidney stones was 5.9% (95% CI, 4.6–7.6%, I2 = 47%) in patients on ketogenic diets at a mean follow-up time of 3.7 +/− 2.9 years. Subgroup analyses demonstrated the estimated pooled incidence of kidney stones of 5.8% (95% CI, 4.4–7.5%, I2 = 49%) in children and 7.9% (95% CI, 2.8–20.1%, I2 = 29%) in adults, respectively. Within reported studies, 48.7% (95% CI, 33.2–64.6%) of kidney stones were uric stones, 36.5% (95% CI, 10.6–73.6%) were calcium-based (CaOx/CaP) stones, and 27.8% (95% CI, 12.1–51.9%) were mixed uric acid and calcium-based stones, respectively. Conclusions: The estimated incidence of kidney stones in patients on ketogenic diets is 5.9%. Its incidence is approximately 5.8% in children and 7.9% in adults. Uric acid stones are the most prevalent kidney stones in patients on ketogenic diets followed by calcium-based stones. These findings may impact the prevention and clinical management of kidney stones in patients on ketogenic diets.

Transient hypoglycorrhachia with paroxysmal abnormal eye movement in early infancy

Paroxysmal abnormal eye movement in early infancy is one of the initial symptoms of glucose transporter 1 deficiency syndrome (GLUT1DS). We describe four early infants with transient hypoglycorrhachia presenting with abnormal eye movements. Their symptoms disappeared after the introduction of a ketogenic diet (KD), and their development was normal. Since no variants in SLC2A1 were detected, the CSF-to-blood glucose ratios (C/B) were re-examined, and within normal range. None of the four patients displayed recurrent symptoms after withdrawal from the KD. Because long-term KD has potential adverse effects and could affect the quality of life of patients and their families, re-examination of CSF glucose during late infancy should be considered in the case of absence of the SLC2A1 pathogenic variant.

Functional characterization and tissue localization of the facilitative glucose transporter GLUT12

Facilitative glucose transporters (GLUTs) play crucial roles in glucose utilization and homeostasis. GLUT12 was initially isolated as a novel GLUT4-like transporter involved in insulin-dependent glucose transport. However, tissue distribution and biochemical properties of GLUT12 are not well understood. In this study, we investigated the basic kinetic properties and tissue distribution of GLUT12. Human GLUT12 and GLUT1 were overexpressed and purified using Ni-NTA column chromatography. Reconstituted proteoliposomes showed time-dependent d-glucose transport activity, which was inhibited by phloretin and dehydroascorbate. Dose dependence of glucose transport revealed a KM and Vmax values of 6.4 mM and 1.2 μmol/mg/min, respectively, indicating that GLUT12 is a high-affinity type GLUT. Glucose transport by GLUT12 was inhibited by ATP and glucose-1-phosphate, glucose-6-phosphate and disaccharides (properties similar to those of GLUT1). Indirect immunohistochemistry revealed the distribution of mouse GLUT12 in the apical region of distal tubules and collecting ducts in the kidney and epithelial cells of the jejunum. In addition to these cells, GLUT12 was present in chromaffin cells in the adrenal medulla, the anterior pituitary lobe, as well as the thyroid and pyloric glands. These tissue distributions suggest a unique function of GLUT12, besides that of an insulin-dependent glucose transport.

Ketogenic Diet Therapies for Seizures and Status Epilepticus

Ketogenic diet therapies are high-fat, low-carbohydrate diets designed to mimic a fasting state. Although initially developed nearly one century ago for seizure management, most clinical trials for the management of drug-resistant epilepsy in children as well as adults have been conducted over the last 3 decades. Moreover, ketogenic diets offer promising new adjunctive strategies in the critical care setting for the resolution of acute status epilepticus when traditional antiseizure drugs and anesthetic agents fail. Here, we review the history of ketogenic diet development, the clinical evidence supporting its use for the treatment of drug-resistant epilepsy in children and adults, and the early evidence supporting ketogenic diet feasibility, safety, and potential efficacy in the management of status epilepticus.

Modulation of Glucose Availability and Effects of Hypo- and Hyperglycemia on Status Epilepticus: What We Do Not Know Yet?

Status epilepticus (SE) can lead to serious neuronal damage and act as an initial trigger for epileptogenic processes that may lead to temporal lobe epilepsy (TLE). Besides promoting neurodegeneration, neuroinflammation, and abnormal neurogenesis, SE can generate an extensive hypometabolism in several brain areas and, consequently, reduce intracellular energy supply, such as adenosine triphosphate (ATP) molecules. Although some antiepileptic drugs show efficiency to terminate or reduce epileptic seizures, approximately 30% of TLE patients are refractory to regular antiepileptic drugs (AEDs). Modulation of glucose availability may provide a novel and robust alternative for treating seizures and neuronal damage that occurs during epileptogenesis; however, more detailed information remains unknown, especially under hypo- and hyperglycemic conditions. Here, we review several pathways of glucose metabolism activated during and after SE, as well as the effects of hypo- and hyperglycemia in the generation of self-sustained limbic seizures. Furthermore, this study suggests the control of glucose availability as a potential therapeutic tool for SE.

The role of molecular analysis of SLC2A1 in the diagnostic workup of glucose transporter 1 deficiency syndrome

The study aimed to investigate the role of molecular analysis of SLC2A1 in the diagnostic workup of glucose transporter 1 deficiency syndrome (Glut1DS). During 2006-2020, we received 100 requests for SLC2A1 variant analysis of patients clinically suspected for Glut1DS. Pathogenic variants were detected in 37 patients, among whom 11 were familial cases. Most patients presented with epilepsy (n = 31; 84%), movement disorders (MD) (n = 28; 76%), and intellectual disabilities (ID) (n = 29; 78%). Moreover, paroxysmal dyskinesias (PD) (n = 10; 27%) were more frequently seen in familial cases (55%) than in sporadic cases (15%) (p < .05). The Glut1DS patients with ID typically had either epilepsy or MD. The presence of MD, particularly when associated with epilepsy or ID, indicated Glut1DS (p < .05). The cerebrospinal fluid (CSF) glucose levels were at or below the 10th percentile in all 32 SLC2A1-positive patients but only in 16 of 52 (31%) SLC2A1-negative patients (p < .05). Thus, CSF analysis is an essential tool in the diagnostic workup of Glut1DS. SLC2A1 molecular analysis should be performed in patients with a family history of Glut1DS or with at least one of the following clinical features, such as epilepsy, MD, and PD with or without ID, and low CSF glucose level. This would help in precise molecular diagnosis of the disease and facilitate effective treatment and appropriate genetic counseling.

Erythroid glucose transport in health and disease

Glucose transport is intimately linked to red blood cell physiology. Glucose is the unique energy source for these cells, and defects in glucose metabolism or transport activity are associated with impaired red blood cell morphology and deformability leading to reduced lifespan. In vertebrate erythrocytes, glucose transport is mediated by GLUT1 (in humans) or GLUT4 transporters. These proteins also account for dehydroascorbic acid (DHA) transport through erythrocyte membrane. The peculiarities of glucose transporters and the red blood cell pathologies involving GLUT1 are summarized in the present review.

Animal Models of Metabolic Epilepsy and Epilepsy Associated Metabolic Dysfunction: A Systematic Review

Epilepsy is a serious neurological disorder affecting around 70 million people globally and is characterized by spontaneous recurrent seizures. Recent evidence indicates that dysfunction in metabolic processes can lead to the alteration of neuronal and network excitability, thereby contributing to epileptogenesis. Developing a suitable animal model that can recapitulate all the clinical phenotypes of human metabolic epilepsy (ME) is crucial yet challenging. The specific environment of many symptoms as well as the primary state of the applicable neurobiology, genetics, and lack of valid biomarkers/diagnostic tests are the key factors that hinder the process of developing a suitable animal model. The present systematic review summarizes the current state of available animal models of metabolic dysfunction associated with epileptic disorders. A systematic search was performed by using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) model. A range of electronic databases, including google scholar, Springer, PubMed, ScienceDirect, and Scopus, were scanned between January 2000 and April 2020. Based on the selection criteria, 23 eligible articles were chosen and are discussed in the current review. Critical analysis of the selected literature delineated several available approaches that have been modeled into metabolic epilepsy and pointed out several drawbacks associated with the currently available models. The result describes available models of metabolic dysfunction associated with epileptic disorder, such as mitochondrial respiration deficits, Lafora disease (LD) model-altered glycogen metabolism, causing epilepsy, glucose transporter 1 (GLUT1) deficiency, adiponectin responsive seizures, phospholipid dysfunction, glutaric aciduria, mitochondrial disorders, pyruvate dehydrogenase (PDH) α-subunit gene (PDHA1), pyridoxine dependent epilepsy (PDE), BCL2-associated agonist of cell death (BAD), Kcna1 knock out (KO), and long noncoding RNAs (lncRNA) cancer susceptibility candidate 2 (lncRNA CASC2). Finally, the review highlights certain focus areas that may increase the possibilities of developing more suitable animal models and underscores the importance of the rationalization of animal models and evaluation methods for studying ME. The review also suggests the pressing need of developing precise robust animal models and evaluation methods for investigating ME.

Glucose transporter 1 deficiency syndrome: nutritional and growth pattern phenotypes at diagnosis

BACKGROUND/OBJECTIVES

Glucose Transporter 1 Deficiency Syndrome (GLUT1-DS; OMIM #606777) is a rare disease caused by dominant mutations in SLC2A1 encoding GLUT1, which is a ubiquitous transporter of glucose across plasma membranes, particularly across the blood-brain barrier. Hypoglycorrhachia symptoms are the cornerstones of GLUT1-DS, but delayed growth has also been suggested. This led us to investigate, at diagnosis, the relationship between the glycemia/glycorrhachia ratio and the nutritional and growth pattern phenotype of 30 GLUT-DS patients.

SUBJECTS/METHODS

An assessment was made of body weight (BW), body length/height (BL, BH) and body composition by anthropometry and DEXA, and the results put with BL and BW at birth, genetic target, glycemia, insulinemia, and glycorrhachia values.

RESULTS

At birth, 21% of patients had a BW below -1.645 z-score, whereas no patients had BL below the reference values. At diagnosis 23% of the patients had an impaired nutritional status, 19.2% and 3.8% being respectively underweight and overweight/obese; 10%, all under 10 years old, had BL/BH below -1.645 z-score, with no specific features related to body composition. Finally, there was no association between glycemia, glycorrhachia, and growth phenotype.

CONCLUSIONS

GLUT1-DS is associated with impaired BW but not BL intrauterine growth, with a slower than normal pattern of growth rather than growth failure. These data could be useful for the interpretation of any long-term effects of the ketogenic diet, e.g. nutritional and growth pattern decline.

Variety of symptoms of GLUT1 deficiency syndrome in three-generation family

OBJECTIVE

Glucose transporter type 1 deficiency (G1D) syndrome is generally a genetic disorder because of a mutation of the SLC2A1 gene. The clinical picture of G1D is heterogeneous. The aim of this paper was to present the case of G1D, recognized in a three-generation family, caused by missense mutation p.Arg92Trp in SLC2A1 gene, and showing high clinical heterogeneity and evolution of symptoms over time.

METHODS

Three-generation family members, showing symptoms suggesting G1D, have been characterized in terms of the clinical picture, electroencephalogram (EEG) recordings, brain neuroimaging, and the psychological assessment data. All subjects were offered genetic testing of the SLC2A1 gene.

RESULTS

We sequenced the SLC2A1 gene in the proband of the family and identified the c.274C > T variant (p.Arg92Trp). The presence of the same mutation was confirmed in all affected family members; however, significant variations in the clinical picture among them were observed. In addition to the typical symptoms for G1D (e.g., epilepsy, intellectual disability), patients presented movement disorders, stiffness, and dysarthria, as well as psychiatric symptoms. After using the ketogenic diet, epileptic seizures disappeared, but the rest of the symptoms were resistant to treatment.

CONCLUSIONS

Despite the same underlying mutation, clinical symptoms may vary among members of one family. Different clinical symptoms are observed depending on the patient's age. Not all symptoms occur in all patients within one family despite the same genetic background. However, the importance of early therapy for the clinical course of the disease requires further study.

The evolving indications of KD therapy

Despite the rapid increase of clinical and basic-science knowledge on ketogenic diet therapies over the past years, it has not always been easy to determine the adequate indications of this treatment. Over the nearly 100 years of use, from being a last resource in the therapeutic algorithm, the diet has become one of the four main treatments for patients with difficult-to-control epilepsy together with antiepileptic drugs, surgery, and vagus nerve stimulation. The use of the diet has also changed. The current paper will briefly discuss the history of the diet together with a review of the literature regarding its most important indications and how they have evolved. The concept of the importance of defining the type of seizure, type of syndrome, and etiology in the selection of patients and timing of diet initiation has been gaining importance. This paper explores how the indications of the diet changed together with the shifting focus of epilepsy teams towards its use in different types of epilepsy and epilepsy syndromes and according to etiologies and as an alternative option in refractory and superrefractory status epilepticus.

Mechanistic Insights into Protein Stability and Self-aggregation in GLUT1 Genetic Variants Causing GLUT1-Deficiency Syndrome

Human sodium-independent glucose cotransporter 1 (hGLUT1) has been studied for its tetramerization and multimerization at the cell surface. Homozygous or compound heterozygous mutations in hGLUT1 elicit GLUT1-deficiency syndrome (GLUT1-DS), a metabolic disorder, which results in impaired glucose transport into the brain. The reduced cell surface expression or loss of function have been shown for some GLUT1 mutants. However, the mechanism by which deleterious mutations affect protein structure, conformational stability and GLUT1 oligomerization is not known and require investigation. In this review, we combined previous knowledge of GLUT1 mutations with hGLUT1 crystal structure to analyze native interactions and several natural single-point mutations. The modeling of native hGLUT1 structure confirmed the roles of native residues in forming a range of side-chain interactions. Interestingly, the modeled mutants pointed to the formation of a variety of non-native novel interactions, altering interaction networks and potentially eliciting protein misfolding. Self-aggregation of the last part of hGLUT1 was predicted using protein aggregation prediction tool. Furthermore, an increase in aggregation potential in the aggregation-prone regions was estimated for several mutants suggesting increased aggregation of misfolded protein. Protein stability change analysis predicted that GLUT1 mutant proteins are unstable. Combining GLUT1 oligomerization behavior with our modeling, aggregation prediction, and protein stability analyses, this work provides state-of-the-art view of GLUT1 genetic mutations that could destabilize native interactions, generate novel interactions, trigger protein misfolding, and enhance protein aggregation in a disease state.

Biochemical assessment of patients following ketogenic diets for epilepsy: Current practice in the UK and Ireland

Objective

Biochemical assessment is recommended for patients prior to initiating and following a ketogenic diet (KD). There is no published literature regarding current practice in the UK and Ireland. We aimed to explore practice in comparison with international guidelines, determine approximate costs of biochemical testing in KD patients across the UK and Ireland, and promote greater consistency in KD services nationally.

Methods

A survey was designed to determine the biochemical tests requested for patients at baseline, 3, 6, 12, 18, and 24 months + on KD. The survey was circulated to 39 centers across the UK and Ireland.

Results

Sixteen centers completed the survey. Full blood count, electrolytes, calcium, liver function tests (LFTs), lipid profile, and vitamin D were requested at all centers at baseline, in keeping with international guidelines. Bicarbonate, total protein, and urinalysis were less consistently requested. Magnesium and zinc were requested by all centers, despite not being specifically recommended for pre‐diet evaluation in guidelines. Urea and electrolyte profiles and some LFTs were consistently requested at follow‐up, in accordance with guidelines. Other LFTs and renal tests, full blood count, lipid profile, acylcarnitine profile, selenium, vitamin D, and urinalysis were less consistently requested at follow‐up. The mean costs of the lowest and highest number of tests requested at baseline in our participating centers were £167.54 and £501.93; the mean costs of the lowest and highest number of tests requested at 3‐month follow‐up were £19.17 and £450.06.

Significance

Biochemical monitoring of KD patients varies widely across the UK and Ireland and does not fully correspond to international best practice guidelines. With an ongoing drive for cost‐effectiveness within health care, further work is needed to streamline practice while ensuring patient safety.

Cerebral palsy: not always what it seems

Cerebral palsy (CP) is not a disease, but a neurological syndrome, a combination of signs and symptoms, some of which may occur in neurodegenerative or metabolic disorders, particularly those with an onset in the first 2 years of life. There are many different causes of the syndrome. All children with CP should undergo brain MRI, even with an identified antenatal or perinatal insult. Children with CP should be referred to a paediatric neurologist or a clinical geneticist, or both, if appropriate and particularly in the absence of a known perinatal cerebral insult, with brain MRI that is reported to be normal, a progression in, or new, signs or where there is a reported 'family history of CP'. Finally, a few of the CP syndromes may be readily treatable and potentially prevent irreversible neurological and cognitive impairment.

Quality of Life in Chronic Ketogenic Diet Treatment: The GLUT1DS Population Perspective

BACKGROUND

Glucose transporter type 1 deficiency syndrome (GLUT1DS) is a rare, genetically determined neurological disorder, for which Ketogenic Diet (KD) represents the gold standard life-long treatment. The aim of this study is to investigate health related quality of life in a well characterized cohort of patients affected by GLUT1DS treated with KD, evaluating factors that can influence patients' and parents' quality of life perception.

METHODS

This is a double center exploratory research study. A postal survey with auto-administrable questionnaires was conducted among 17 subjects (aged 3-22 years) with diagnosis of GLUT1DS, receiving a stable KD treatment for more than 1 year. The Pediatric Quality of Life Inventory (PedsQL) 4.0 Generic Core Scales was adopted. Clinical variables analyzed in relation to quality of life were frequency of epileptic seizures and movement disorder since KD introduction, presence of intellectual disability (ID), and KD ratio.

RESULTS

Quality of life global scores were impaired both in parents' and children's perspectives, with a significant concordance. Taking into consideration subscales, the average was 64.17 (range 10-100) for physical functioning, 74.23 (range 30-100) for emotional functioning, 62.64 (range 10-100) for social functioning, and 56 (range 15-92) for school functioning.

CONCLUSIONS

In patients with GLUT1DS the quality of life perception is comparable to that of other patients with chronic disease. In our sample, the presence of movement disorder seems to be a crucial element in quality of life perception.

The role of mutations associated with familial neurodegenerative disorders on blood-brain barrier function in an iPSC model

Background

Blood–brain barrier dysfunction is associated with many late-stage neurodegenerative diseases. An emerging question is whether the mutations associated with neurodegenerative diseases can independently lead to blood–brain barrier (BBB) dysfunction. Studies from patient-derived induced pluripotent stem cells suggest that mutations associated with neurodegenerative disease are non-cell autonomous, resulting in gain of toxic function in derived neurons and astrocytes. Here we assess whether selected mutations associated with neurodegenerative diseases can contribute to impairment of the blood–brain barrier.

Methods

We assessed barrier function of confluent monolayers of human brain microvascular endothelial cells (hBMECs) derived from induced pluripotent stem cells (iPSC) from three healthy individuals and eight individuals with neurodegenerative disease. We systematically assessed protein and gene expression of BBB biomarkers, transendothelial resistance (TEER), permeability of Lucifer yellow, permeability of d-glucose, permeability of rhodamine 123, the efflux ratio of rhodamine 123, and P-gp inhibition using Tariquidar for confluent monolayers of human brain microvascular endothelial cell (hBMECs).

Results

We provide evidence supporting the hypothesis that mutations associated with neurodegenerative disease can independently cause BBB dysfunction. These functional changes are not catastrophic since barrier breakdown would result in BBB impairment during development. Synergistic interactions between non-cell autonomous cerebrovascular dysfunction and the effects of gain-of-toxic function in neurons (e.g. toxic oligomers) are likely to increase disease burden through a positive feedback mechanism.

Conclusions

These results suggest that the accumulation of defects in brain microvascular endothelial cells may ultimately lead to impairment of the BBB. Small changes in barrier function over time could lead to accumulated defects that result in positive feedback to unrelated central nervous system diseases.

Electronic supplementary material

The online version of this article (10.1186/s12987-019-0139-4) contains supplementary material, which is available to authorized users.

Total Intravenous Anesthesia in GLUT1 Deficiency Syndrome Patient: A Case Report

Patient: Female, 2

Final Diagnosis: GLUT1 deficiency syndrome

Symptoms: Mastoiditis

Medication: —

Clinical Procedure: General anesthesia

Specialty: Anesthesiology

Failure of ketogenic diet therapy in GLUT1 deficiency syndrome

PURPOSE

Epilepsy in GLUT1 deficiency syndrome is generally drug-resistant; ketogenic diet (KD) therapy is the mainstay of therapy, as production of ketones provides the brain with an alternative energy source, bypassing the defect in GLUT1. Failure of KD therapy and risk factors for failure have been sparsely published.

METHODS

We performed a retrospective study of GLUT1DS patients with refractory epilepsy failing on KD therapy, to identify their clinical characteristics.

RESULTS

Failure of the ketogenic diet was due to KD inefficacy (poor effect despite adequate ketosis), as well as intolerance and an inability to attain ketosis. Our cohort of seven patients in whom KD therapy failed stood out for their advanced age at seizure onset, i.e. almost 4 years vs 8 months in large series, female sex, as well as their advanced age at diagnosis and initiation of KD therapy. EEG recordings during KD therapy can aid in the assessment of effectiveness of the KD therapy.

CONCLUSIONS

GLUT1DS is generally described as a treatable disorder and existing case series do not provide details of treatment failure. In select patients with GLUT1DS, KD therapy fails, rendering GLUT1DS an essentially untreatable disorder. Failure of the ketogenic diet was due to KD inefficacy (poor effect despite adequate ketosis), as well as intolerance and an inability to attain ketosis. Failure to reduce seizure frequency with deterioration of the EEG findings should lead to consideration of cessation of KD therapy.

Glucose Transporter Type 1 Deficiency Syndrome: Developmental Delay and Early-Onset Ataxia in a Novel Mutation of the SLC2A1 Gene

Glucose transporter type 1 deficiency syndrome (GLUT1-DS) was first described by De Vivo in 1991, and the classic clinical manifestations include infantile epilepsy, developmental delay, and acquired microcephaly. A neurological complex disorder including elements of hypotonia, spasticity, ataxia, and dystonia can frequently be present. GLUT1-DS is an inborn error of metabolism caused by impaired glucose transport through blood–brain barrier in the majority of patients because of mutation of solute carrier family 2 (facilitated glucose transporter) member 1 gene (SLC2A1), encoding the transporter protein. We report a 6-year-old girl with GLUT1-DS, which is caused by a novel heterozygous variant c.109dupC of the SLC2A1 gene. The dominating clinical features were ataxia, epilepsy started at 4 years, acquired microcephaly, and mild intellectual disability. Treatment with ketogenic diet showed clinical improvement with the reduction of ataxia and seizure control in a 10-month follow-up period.

Optimal clinical management of children receiving dietary therapies for epilepsy: Updated recommendations of the International Ketogenic Diet Study Group

Ketogenic dietary therapies (KDTs) are established, effective nonpharmacologic treatments for intractable childhood epilepsy. For many years KDTs were implemented differently throughout the world due to lack of consistent protocols. In 2009, an expert consensus guideline for the management of children on KDT was published, focusing on topics of patient selection, pre‐KDT counseling and evaluation, diet choice and attributes, implementation, supplementation, follow‐up, side events, and KDT discontinuation. It has been helpful in outlining a state‐of‐the‐art protocol, standardizing KDT for multicenter clinical trials, and identifying areas of controversy and uncertainty for future research. Now one decade later, the organizers and authors of this guideline present a revised version with additional authors, in order to include recent research, especially regarding other dietary treatments, clarifying indications for use, side effects during initiation and ongoing use, value of supplements, and methods of KDT discontinuation. In addition, authors completed a survey of their institution's practices, which was compared to responses from the original consensus survey, to show trends in management over the last 10 years.

10 patients, 10 years - Long term follow-up of cardiovascular risk factors in Glut1 deficiency treated with ketogenic diet therapies: A prospective, multicenter case series

BACKGROUND AND AIMS

Glut1 Deficiency (Glut1D) is caused by impaired glucose transport into brain. The resulting epileptic encephalopathy and movement disorders can be treated effectively by high-fat carbohydrate-restricted ketogenic diet therapies (KDT) mimicking fasting and providing ketones as an alternative cerebral fuel. Recently 6-24 months follow-ups of epileptic patients reported elevated blood lipids and intima thickening of the carotid artery raising concerns about potential cardiovascular risks by KDT. To clarify potential cardiovascular risks we performed a prospective 10 year follow up of 10 Glut1D patients.

METHODS

Between August 2001 and January 2016 we enrolled Glut1D patients on KDT at two hospitals in Germany in this prospective, multicenter case series. The minimal follow up was 10 years. Standard deviation scores (SDS) of body mass index (BMI), total cholesterol (TC), HDL-/LDL cholesterol, and triglycerides (TG) before initiation of KDT were compared with respective values at 6 months, 2, 5 years, and 10 years after initiation. After 10 years on KDT cardiovascular risk, assessed by BMI, carotid intima-media thickness (CIMT) measurement, and blood pressure, was compared to a healthy reference population (n = 550).

RESULTS

Baseline and 10 year follow-up investigations were available for 10 individuals with Glut1D on KDT. After two years on KDT BMI increased significantly, while total cholesterol, HDL-cholesterol, and LDL-cholesterol decreased. Within 3-5 years on KDT these differences disappeared, and after 10 years blood lipid parameters reflected the situation at initiation of KDT. Prior to KDT one child had dyslipidaemia, but no child after 10 years on KDT. No significant differences were observed with respect to BMI SDS (p = 0.26), CIMT (p = 0.63) or systolic and diastolic blood pressure (SDS p = 0.11 and p = 0.37, respectively) in Glut1D children treated with KDT for at least 10 years compared to healthy controls.

CONCLUSIONS

In contrast to previous short-term reports on adverse effects of KDT, 10-year follow-up did not identify cardiovascular risks of dietary treatment for Glut1D.

Membrane Phase-Dependent Occlusion of Intramolecular GLUT1 Cavities Demonstrated by Simulations

Experimental evidence has shown a close correlation between the composition and physical state of the membrane bilayer and glucose transport activity via the glucose transporter GLUT1. Cooling alters the membrane lipids from the fluid to gel phase, and also causes a large decrease in the net glucose transport rate. The goal of this study is to investigate how the physical phase of the membrane alters glucose transporter structural dynamics using molecular-dynamics simulations. Simulations from an initial fluid to gel phase reduce the size of the cavities and tunnels traversing the protein and connecting the external regions of the transporter and the central binding site. These effects can be ascribed solely to membrane structural changes since in silico cooling of the membrane alone, while maintaining the higher protein temperature, shows protein structural and dynamic changes very similar to those observed with uniform cooling. These results demonstrate that the protein structure is sensitive to the membrane phase, and have implications for how transmembrane protein structures respond to their physical environment.