Uncovering microdeletions in patients with severe Glut-1 deficiency syndrome using SNP oligonucleotide microarray analysis

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.

Solute carrier transporter disease and developmental and epileptic encephalopathy

The International League Against Epilepsy officially revised its classification in 2017, which amended "epileptic encephalopathy" to "developmental and epileptic encephalopathy". With the development of genetic testing technology, an increasing number of genes that cause developmental and epileptic encephalopathies are being identified. Among these, solute transporter dysfunction is part of the etiology of developmental and epileptic encephalopathies. Solute carrier transporters play an essential physiological function in the human body, and their dysfunction is associated with various human diseases. Therefore, in-depth studies of developmental and epileptic encephalopathies caused by solute carrier transporter dysfunction can help develop new therapeutic modalities to facilitate the treatment of refractory epilepsy and improve patient prognosis. In this article, the concept of transporter protein disorders is first proposed, and nine developmental and epileptic encephalopathies caused by solute carrier transporter dysfunction are described in detail in terms of pathogenesis, clinical manifestations, ancillary tests, and precise treatment to provide ideas for the precise treatment of epilepsy.

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.

Language regression, hemichorea and focal subclinical seizures in a 6-year-old girl with GLUT-1 deficiency

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A 6 year old girl with progressive speech difficulties, new abnormal movements, olfactory hallucinations

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Choreiform movement of her right hemibody along with her face and tongue

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Seizures were noted during sleep without clinical correlate, progressing to awake subclinical seizures

Impact of MCT1 Haploinsufficiency on the Mouse Retina

The monocarboxylate transporter 1 (MCT1) is highly expressed in the outer retina, suggesting that it plays a critical role in photoreceptors. We examined MCT1 ^+/- heterozygotes, which express half of the normal complement of MCT1. The MCT1 ^+/- retina developed normally and retained normal function, indicating that MCT1 is expressed at sufficient levels to support outer retinal metabolism.

Diagnosing Glucose Transporter 1 Deficiency at Initial Presentation Facilitates Early Treatment

OBJECTIVE

To profile the initial clinical events of glucose transporter 1 deficiency syndrome (Glut1 DS) in order to facilitate the earliest possible diagnosis.

STUDY DESIGN

We retrospectively reviewed 133 patients with Glut1 DS from a single institution. Family interviews and medical record reviews identified the first clinical event(s) reported by the caregivers.

RESULTS

Average age of the first event was 8.15 ± 11.9 months (range: 0.01-81). Ninety-one patients experienced the first symptom before age 6 months (68%). Thirty-three additional patients (25%) presented before age 2 years. Only 9 patients (7%), reported the first event after age 2 years. Seizures were the most common first event (n = 81, 61%), followed by eye movement abnormalities (n = 51, 38%) and changes in muscle strength and tone (n = 30, 22%). Eye movement abnormalities, lower cerebrospinal fluid glucose values, and lower Columbia Neurological Scores correlated with earlier onset of the first event (r: -0.17, 0.22, and 0.25 respectively, P < .05). There was no correlation with age of first event and red blood cell glucose uptake or mutation type.

CONCLUSIONS

Glut1 DS is a treatable cause of infantile onset encephalopathy. Health care providers should recognize the wide spectrum of paroxysmal events that herald the clinical onset of Glut1 DS in early infancy to facilitate prompt diagnosis, immediate treatment, and improved long-term outcome.

GLUT1 deficiency syndrome: an update

INTRODUCTION

Glucose transporter type 1 deficiency syndrome is caused by heterozygous, mostly de novo, mutations in the SLC2A1 gene encoding the glucose transporter GLUT1. Mutations in this gene limit brain glucose availability and lead to cerebral energy deficiency.

STATE OF THE ART

The phenotype is characterized by the variable association of mental retardation, acquired microcephaly, complex motor disorders, and paroxysmal manifestations including seizures and non-epileptic paroxysmal episodes. Clinical severity varies from mild motor dysfunction to severe neurological disability. In patients with mild phenotypes, paroxysmal manifestations may be the sole manifestations of the disease. In particular, the diagnosis should be considered in patients with paroxysmal exercise-induced dyskinesia or with early-onset generalized epilepsy. Low CSF level of glucose, relative to blood level, is the best biochemical clue to the diagnosis although not constantly found. Molecular analysis of the SLC2A1 gene confirms the diagnosis. Ketogenic diet is the cornerstone of the treatment and implicates a close monitoring by a multidisciplinary team including trained dieticians. Non-specific drugs may be used as add-on symptomatic treatments but their effects are often disappointing.

CONCLUSION

Glucose transporter type 1 deficiency syndrome is likely under diagnosed due to its complex and pleiotropic phenotype. Proper identification of the affected patients is important for clinical practice since the disease is treatable.

Phenotypic spectrum of glucose transporter type 1 deficiency syndrome (Glut1 DS)

Glut1 deficiency syndrome (Glut1 DS) was originally described in 1991 as a developmental encephalopathy characterized by infantile onset refractory epilepsy, cognitive impairment, and mixed motor abnormalities including spasticity, ataxia, and dystonia. The clinical condition is caused by impaired glucose transport across the blood brain barrier. The past 5 years have seen a dramatic expansion in the range of clinical syndromes that are recognized to occur with Glut1 DS. In particular, there has been greater recognition of milder phenotypes. Absence epilepsy and other idiopathic generalized epilepsy syndromes may occur with seizure onset in childhood or adulthood. A number of patients present predominantly with movement disorders, sometimes without any accompanying seizures. In particular, paroxysmal exertional dyskinesia is now a well-documented clinical feature that occurs in individuals with Glut1 DS. A clue to the diagnosis in patients with paroxysmal symptoms may be the triggering of episodes during fasting or exercise. Intellectual impairment may range from severe to very mild. Awareness of the broad range of potential clinical phenotypes associated with Glut1 DS will facilitate earlier diagnosis of this treatable neurologic condition. The ketogenic diet is the mainstay of treatment and nourishes the starving symptomatic brain during development.

Rosiglitazone attenuates hyperglycemia-enhanced hemorrhagic transformation after transient focal ischemia in rats

Hemorrhagic transformation (HT) has been claimed to represent the most feared complication of treatment with intravenous tissue plasminogen activator (t-PA) therapy. In this study, we tested the effect of rosiglitazone on HT in a rat focal cerebral ischemia model. Male Sprague-Dawley rats received an injection of 50% dextrose (6ml/kg intraperitoneally) and were subjected to middle cerebral artery occlusion (MCAO) 10 min later, with the regional cerebral blood flow monitored in vivo by laser-Doppler-flowmetry. Two groups were included: rosiglitazone treatment and vehicle group. In the treatment group, after 1.5h of ischemia, rosiglitazone (2mg/kg) was administered at the onset of reperfusion. Neurobehavioral scores, infarct volume, hemoglobin leakage, hemorrhage rate, the expression of collagen IV and glucose transporter 1 (GLUT1) were measured at 24h after ischemia. Rosiglitazone improved neurobehavioral deficits, reduced infarct volume and hemorrhage rate, and inhibited hemoglobin leakage, when compared with the vehicle group. In addition, it increased the expression of collagen IV and GLUT1 compared to the vehicle group. Our results suggest that rosiglitazone attenuated the hyperglycemia-induced HT after MCAO, possibly by preservation of GLUT1 expression.

Lack of SLC2A1 (glucose transporter 1) mutations in 30 Italian patients with alternating hemiplegia of childhood

Alternating hemiplegia of childhood is a rare, predominantly sporadic disorder. Diagnosis is clinical, and little is known about genetics. Glucose transporter 1 deficiency syndrome shares with alternating hemiplegia of childhood paroxysmal and nonparoxysmal symptoms. The aim of the study was to investigate glucose transporter 1 mutations in 30 Italian patients. Genetic material was analyzed by DNA amplification and glucose transporter 1 region sequencing. Mutational analysis findings of the SLC2A1 gene were negative in all patients. The pattern of movement disorders was reviewed. Interictal dystonia and multiple paroxysmal events were typical of alternating hemiplegia of childhood. In conclusion, alternating hemiplegia of childhood is a heterogeneous clinical condition, and although glucose transporter 1 deficiency can represent an undiagnosed cause of this disorder, mutational analysis is not routinely recommended. Alternatively, a careful clinical analysis and the 3-O-methyl-D-glucose uptake test can allow prompt identification of a subgroup of patients with alternating hemiplegia of childhood treatable with a ketogenic diet.

Allelic variations of glut-1 deficiency syndrome: the chinese experience

Glucose transporter type 1 deficiency syndrome is characterized by infantile onset seizures, development delay, movement disorders, and acquired microcephaly. The phenotype includes allelic variants such as intermittent ataxia, choreoathetosis, dystonia, and alternating hemiplegia of childhood with or without epilepsy. Dystonias involve allelic variants of glucose transporter type 1 deficiency syndrome. Three Chinese patients presented with paroxysmal behavioral disturbance, weakness, ataxia (especially after fasting), and exercise intolerance. Electroencephalogram findings did not correlate with clinical manifestations. Cranial magnetic resonance imaging produced normal results or mild hypomyelination. Hypoglycorrhachia was evident in all cases. Cerebrospinal fluid glucose ranged from 1.63-2.45 mmol/L. Erythrocyte 3-O-methyl-d-glucose uptake was decreased to 58% in patient 1. Three SLC2A1 disease-causing mutations (761delA, P383H, and R400C) were observed. No patient tolerated ketogenic diets. Two patients responded to frequent meals with snacks. Cerebrospinal fluid evaluation constitutes the diagnostic testing permitting early treatment of glucose transporter type 1 deficiency syndrome. Early diagnosis and treatment improve prognoses.

Glut1 deficiency syndrome and erythrocyte glucose uptake assay

OBJECTIVE

The Glut1 deficiency syndrome (Glut1 DS) phenotype has expanded dramatically since first described in 1991. Hypoglycorrhachia and decreased erythrocyte 3-OMG uptake are confirmatory laboratory biomarkers. The objective is to expand previous observations regarding the diagnostic value of the uptake assay.

METHODS

One hundred and nine suspected cases of Glut-1 DS were studied. All cases had a consistent clinical picture and hypoglycorrhachia. The uptake assay was decreased in 74 cases (group 1) and normal in 35 cases (group 2). We identified disease-causing mutations in 70 group 1 patients (95%) and one group 2 patient (3%).

RESULTS

The cut-off for an abnormally low uptake value was increased from 60% to 74% with a corresponding sensitivity of 99% and specificity of 100%. The correlation between the uptake values for the time-curve and the kinetic concentration curve were strongly positive (R(2) = 0.85). Significant group differences were found in CSF glucose and lactate values, tone abnormalities, and degree of microcephaly. Group 2 patients were less affected in all domains. We also noted a significant correlation between the mean erythrocyte 3-OMG uptake and clinical severity (R(2) = 0.94).

INTERPRETATION

These findings validate the erythrocyte glucose uptake assay as a confirmatory functional test for Glut1 DS and as a surrogate marker for GLUT1 haploinsufficiency.

Glut1 deficiency: when to suspect and how to diagnose?

Impaired glucose transport across the blood-brain barrier results in GLUT1 deficiency syndrome (GLUT1-DS), characterized by infantile seizures, developmental delay, acquired microcephaly, spasticity, ataxia, and hypoglycorrhachia. A part from this classic phenotype, clinical conditions associated with a deficiency of GLUT1 are highly variable and several atypical variants have been described; in particular, patients with movement disorders, but without seizures, with paroxysmal exertion-induced dyskinesia, have been reported. Most patients carry heterozygous de novo mutations in the GLUT1-gene but autosomal dominant and recessive transmission has been identified. Diagnosis is based on low cerebrospinal fluid glucose, in the absence of hypoglycemia, and it is confirmed by molecular analysis of the GLUT1-gene and by glucose uptake studies and immunoreactivity in human erythrocytes. Treatment with a ketogenic diet results in marked improvement of seizures and movement disorders. This review summarizes recent advances in understanding of GLUT1-DS and highlights the diagnostic and therapeutic approach to GLUT1-DS.

SLC2A1 gene analysis of Japanese patients with glucose transporter 1 deficiency syndrome

Glucose transporter 1 deficiency syndrome (Glut1-DS) is a congenital metabolic disorder characterized by refractory seizures with early infantile onset, developmental delay, movement disorders and acquired microcephaly. Glut1-DS is caused by heterozygous abnormalities of the SLC2A1 (Glut1) gene, whose product acts to transport glucose into the brain across the blood-brain barrier. We analyzed the SLC2A1 gene in 12 Japanese Glut1-DS patients who were diagnosed by characteristic clinical symptoms and hypoglycorrhachia as follows: all patients had infantile-onset seizures and mild to severe developmental delay, and ataxia was detected in 11 patients. For the 12 patients, we identified seven different mutations (three missense, one nonsense, two frameshift and one splice-site) in exons and exon-intron boundaries of the SLC2A1 gene by direct sequencing, of which six were novel mutations. Of the remaining five patients who had no point mutations and underwent investigation by multiplex ligation-dependent probe amplification, a complex abnormality with deletion and duplication was identified in one patient: this is the first case of such recombination of the SLC2A1 gene. Changes in regulatory sequences in the promoter region or genes other than SLC2A1 might be responsible for onset of Glut1-DS in the other four patients (33%) without SLC2A1 mutation.

Dystonic tremor caused by mutation of the glucose transporter gene GLUT1

Glucose transporter 1 deficiency syndrome (GLUT1-DS) is due to heterozygous mutation of the glucose transporter type 1 gene (GLUT1/SLC2A1). GLUT1-DS is characterized by movement disorders, including paroxysmal exercise-induced dystonia (PED), as well as seizures, mental retardation and hypoglycorrhachia. Tremor was recently shown to be part of the phenotype, but its clinical and electrophysiological features have not yet been described in detail, and GLUT1 tremor reports are rare. We describe two patients, a young woman and her mother, who were referred to us for tremor. We also systematically review published cases of GLUT1-DS with tremor (14 cases, including ours), focusing on clinical features. In most cases (10/14), the tremor, which involved the limbs and voice, fulfilled clinical criteria for dystonic tremor (DT), occurring in body areas affected by dystonia. Tremor was the only permanent symptom in 2 cases. Recordings, reported here for the first time, showed an irregular 6- to 8.5-Hz tremor compatible with DT in our two patients. These findings show that tremor, and particularly DT, may be a presenting symptom of GLUT1-DS. Patients who present with dystonic tremor, with or without mental retardation, seizures, movement disorders and/or a family history, should therefore be screened for GLUT1-DS.

Impairment of brain endothelial glucose transporter by methamphetamine causes blood-brain barrier dysfunction

BACKGROUND

Methamphetamine (METH), an addictive psycho-stimulant drug with euphoric effect is known to cause neurotoxicity due to oxidative stress, dopamine accumulation and glial cell activation. Here we hypothesized that METH-induced interference of glucose uptake and transport at the endothelium can disrupt the energy requirement of the blood-brain barrier (BBB) function and integrity. We undertake this study because there is no report of METH effects on glucose uptake and transport across the blood-brain barrier (BBB) to date.

RESULTS

In this study, we demonstrate that METH-induced disruption of glucose uptake by endothelium lead to BBB dysfunction. Our data indicate that a low concentration of METH (20 μM) increased the expression of glucose transporter protein-1 (GLUT1) in primary human brain endothelial cell (hBEC, main component of BBB) without affecting the glucose uptake. A high concentration of 200 μM of METH decreased both the glucose uptake and GLUT1 protein levels in hBEC culture. Transcription process appeared to regulate the changes in METH-induced GLUT1 expression. METH-induced decrease in GLUT1 protein level was associated with reduction in BBB tight junction protein occludin and zonula occludens-1. Functional assessment of the trans-endothelial electrical resistance of the cell monolayers and permeability of dye tracers in animal model validated the pharmacokinetics and molecular findings that inhibition of glucose uptake by GLUT1 inhibitor cytochalasin B (CB) aggravated the METH-induced disruption of the BBB integrity. Application of acetyl-L-carnitine suppressed the effects of METH on glucose uptake and BBB function.

CONCLUSION

Our findings suggest that impairment of GLUT1 at the brain endothelium by METH may contribute to energy-associated disruption of tight junction assembly and loss of BBB integrity.