GLUT1 Deficiency Research Articles

Stroke-like episodes add to the phenotypic spectrum of GLUT1 deficiency syndrome

Stroke-like episodes add to the phenotypic spectrum of GLUT1 deficiency syndrome

The face of Glut1-DS patients: A 3D Craniofacial Morphometric Analysis.

Glut1 deficiency syndrome (Glut1-DS) is a neurological and metabolic disorder caused by impaired transport of glucose across the blood brain barrier (BBB). Mutations on the SCL2A1 gene encoding the glucose transporter protein in the BBB cause the syndrome, which encompasses epilepsy, movement disorders, and mental delay. Such variability of symptoms presents an obstacle to early diagnosis. The patients seem to share some craniofacial features, and identification and quantification of these could help in prompt diagnosis and clinical management. We performed a three-dimensional morphometric analysis of the faces of 11 female Glut1-DS patients using a stereophotogrammetric system. Data were analyzed using both inter-landmark distances and Principal Component Analysis. Compared with data collected from age-, sex-, and ethnicity-matched control subjects, common and homogenous facial features were identified among patients, which were mainly located in the mandible and the eyes. Glut1-DS patients had a more anterior chin; their mandibular body was longer but the rami were shorter, with a reduced gonial angle; they had smaller and down-slanted eyes with a reduced intercanthal distance. This study highlights the importance of morphometric analysis for defining the facial anatomical characteristics of the syndrome better, potentially helping clinicians to diagnose Glut1-DS. Improved knowledge of the facial anatomy of these patients can provide insights into their facial and cerebral embryological development, perhaps further clarifying the molecular basis of the syndrome. Clin. Anat. 30:644-652, 2017. © 2017 Wiley Periodicals, Inc.

Brain metabolism in health, aging, andneurodegeneration.

Brain cells normally respond adaptively to bioenergetic challenges resulting from ongoing activity in neuronal circuits, and from environmental energetic stressors such as food deprivation and physical exertion. At the cellular level, such adaptive responses include the "strengthening" of existing synapses, the formation of new synapses, and the production of new neurons from stem cells. At the molecular level, bioenergetic challenges result in the activation of transcription factors that induce the expression of proteins that bolster the resistance of neurons to the kinds of metabolic, oxidative, excitotoxic, and proteotoxic stresses involved in the pathogenesis of brain disorders including stroke, and Alzheimer's and Parkinson's diseases. Emerging findings suggest that lifestyles that include intermittent bioenergetic challenges, most notably exercise and dietary energy restriction, can increase the likelihood that the brain will function optimally and in the absence of disease throughout life. Here, we provide an overview of cellular and molecular mechanisms that regulate brain energy metabolism, how such mechanisms are altered during aging and in neurodegenerative disorders, and the potential applications to brain health and disease of interventions that engage pathways involved in neuronal adaptations to metabolic stress.

GLUT1-deficiency syndrome: Report of a four-generation Norwegian family with a mild phenotype.

Glucose transporter type 1 deficiency syndrome (GLUT1-DS) is a rare metabolic encephalopathy with a wide variation of clinical phenotypes. Familial variants are often milder than de novo cases, and may therefore remain undiagnosed. The aim of this study was to characterize the clinical course of GLUT1-DS in a four-generation Norwegian family where the oldest generations had never received any treatment. Through interviews and clinical investigations, we characterized a family of 26 members, where 11 members had symptoms strongly suggesting GLUT1-DS. All members were offered genetic testing of the SLC2A1 gene. Affected members were offered treatment with ketogenic diet, and the effect of the treatment was registered. We sequenced the SLC2A1 gene in 13 members, and found that 10, all with symptoms, had the c.823G>A (p.Ala275Thr) variant. All affected members had experienced early-onset epilepsy, paroxysmal exercise-induced dyskinesias, and most had mild learning disability. Moreover, some had symptoms and signs of a distal neuropathy in addition to reduced sense of orientation and excessive daytime sleep. Their load of symptoms had decreased over the years, although that they never had received any treatment. Nevertheless, those who started dietary treatment all experienced an improved quality of life. We report a four-generation family with GLUT1-DS where the disease has a mild course, even when untreated. In addition to classical GLUT1-DS features, we also describe symptoms which have never been reported in GLUT1-DS previously. As such, this family extends the phenotypic spectrum of GLUT1-DS and underlines the importance of diagnosing also relatively mildly affected patients, even in adult life, as they also seem to benefit from dietary treatment.

Evaluation of GLUT1 variation in non-acquired focal epilepsy

Brain glucose transport is dependent on glucose transporter 1 (GLUT1), encoded by the solute carrier family 2 member 1 (SLC2A1) gene. Mutations in SLC2A1 cause GLUT1 deficiency which is characterized by a broad spectrum of neurological phenotypes including generalized epilepsy, motor disorders, developmental delay and microcephaly. Recent case reports suggest SLC2A1 mutations can contribute to non-acquired focal epilepsy (NAFE) but interrogation of a large patient cohort has not been reported. We studied 200 patients with NAFE (126 with temporal lobe epilepsy) comprising 104 females and 96 males with a mean age of onset of 18 years. Polymerase chain reaction (PCR) and Sanger sequencing was performed to detect variants in all 10 coding exons and splice site regions of the SLC2A1 gene. We did not detect any pathogenic mutations in SLC2A1 in this cohort. Our data suggests that the frequency of GLUT1 mutations in NAFE is low. Limitations of this study include the mean age of onset and cohort size. Future research should focus on subpopulations of focal epilepsy with lower age of seizure onset particularly with co-existent movement disorders in which GLUT1 mutations may play a more important role.

Upstream SLC2A1 translation initiation causes GLUT1 deficiency syndrome.

Glucose transporter type 1 deficiency syndrome (GLUT1DS) is a neurometabolic disorder with a complex phenotypic spectrum but simple biomarkers in cerebrospinal fluid. The disorder is caused by impaired glucose transport into the brain resulting from variants in SCL2A1. In 10% of GLUT1DS patients, a genetic diagnosis can not be made. Using whole-genome sequencing, we identified a de novo 5'-UTR variant in SLC2A1, generating a novel translation initiation codon, severely compromising SLC2A1 function. This finding expands our understanding of the disease mechanisms underlying GLUT1DS and encourages further in-depth analysis of SLC2A1 non-coding regions in patients without variants in the coding region.

Alternating Hemiplegia of Childhood in an Infant with Symptoms Resembling Glucose Transporter 1 Deficiency

AbstractGlucose transporter type 1 (glut1) deficiency syndrome presents with developmental delay, microcephaly, and recurrent seizures during infancy, as well as cerebrospinal fluid (CSF) hypoglycorrhachia and mutations in the SLC2A1 gene. We describe a baby with microcephaly, global developmental delay, seizures from 3 months of age, and CSF glucose in the lower limit of normal range, with heterozygous p.Glu815Lys mutation of the ATP1A3 gene and no mutation in the SLC2A1 gene. Mutations in ATP1A3 gene are associated with alternating hemiplegia of childhood (AHC). Interestingly the baby developed episodes of recurrent bouts of alternating hemiplegia from 13 months of age. The case is reported to highlight ATP1A3 mutation as a probable etiology for glut1 deficiency like syndrome and AHC. A brief review of literature emphasizing the overlapping paroxysmal and nonparoxysmal symptoms of the two conditions is also included.

Brain microvasculature defects and Glut1 deficiency syndrome averted by early repletion of the glucose transporter-1 protein

Haploinsufficiency of the SLC2A1 gene and paucity of its translated product, the glucose transporter-1 (Glut1) protein, disrupt brain function and cause the neurodevelopmental disorder, Glut1 deficiency syndrome (Glut1 DS). There is little to suggest how reduced Glut1 causes cognitive dysfunction and no optimal treatment for Glut1 DS. We used model mice to demonstrate that low Glut1 protein arrests cerebral angiogenesis, resulting in a profound diminution of the brain microvasculature without compromising the blood–brain barrier. Studies to define the temporal requirements for Glut1 reveal that pre-symptomatic, AAV9-mediated repletion of the protein averts brain microvasculature defects and prevents disease, whereas augmenting the protein late, during adulthood, is devoid of benefit. Still, treatment following symptom onset can be effective; Glut1 repletion in early-symptomatic mutants that have experienced sustained periods of low brain glucose nevertheless restores the cerebral microvasculature and ameliorates disease. Timely Glut1 repletion may thus constitute an effective treatment for Glut1 DS.

Gene therapy for a mouse model of glucose transporter-1 deficiency syndrome

ObjectiveWe generated an adeno-associated virus (AAV) vector in which the human SLC2A1 gene was expressed under the synapsin I promoter (AAV-hSLC2A1) and examined if AAV-hSLC2A1 administration can lead to functional improvement in GLUT1-deficient mice. MethodsAAV-hSLC2A1 was injected into heterozygous knock-out murine Glut1 (GLUT1+/−) mice intraperitoneally (systemic; 1.85×1011vg/mouse) or intra-cerebroventricularly (local; 1.85×1010vg/mouse). We analyzed GLUT1 mRNA and protein expression, motor function using rota-rod and footprint tests, and blood and cerebrospinal fluid (CSF) glucose levels. ResultsVector-derived RNA was detected in the cerebrum for both injection routes. In the intra-cerebroventricular injection group, exogenous GLUT1 protein was strongly expressed in the cerebral cortex and hippocampus near the injection site. In the intraperitoneal injection group, exogenous GLUT1 protein was mildly expressed in neural cells throughout the entire central nervous system. The motor function test and CSF/blood glucose ratio were significantly improved following intra-cerebroventricular injection. ConclusionsAAV-hSLC2A1 administration produced exogenous GLUT1 in neural cells and improved CSF glucose levels and motor function of heterozygous knock-out murine Glut1 mice.

Brain correlates of spike and wave discharges in GLUT1 deficiency syndrome

PurposeTo provide imaging biomarkers of generalized spike-and-wave discharges (GSWD) in patients with GLUT1 deficiency syndrome (GLUT1DS).MethodsEighteen GLUT1DS patients with pathogenetic mutation in SLC2A1 gene were studied by means of Video-EEG simultaneously recorded with functional MRI (VideoEEG-fMRI). A control group of sex and age-matched patients affected by Genetic Generalized Epilepsy (GGE) with GSWD were investigated with the same protocol. Within and between groups comparison was performed as appropriated. For GLUT1DS, correlations analyses between the contrast of interest and the main clinical measurements were provided.ResultsEEG during fMRI revealed interictal GSWD in 10 GLUT1DS patients. Group-level analysis showed BOLD signal increases at the premotor cortex and putamen. With respect to GGE, GLUT1DS patients demonstrated increased neuronal activity in the putamen, precuneus, cingulate cortex, SMA and paracentral lobule. Whole-brain correlation analyses disclosed a linear relationship between the GSWD-related BOLD changes and the levels of glycorrhachia at diagnosis over the sensory-motor cortex and superior parietal lobuli.ConclusionThe BOLD dynamics related to GSWD in GLUT1DS are substantially different from typical GGE showing the former an increased activity in the premotor-striatal network and a decrease in the thalamus. The revealed hemodynamic maps might represent imaging biomarkers of GLUT1DS, being potentially useful for a precocious diagnosis of this genetic disorder.

Short-term impact of a classical ketogenic diet on gut microbiota in GLUT1 Deficiency Syndrome: A 3-month prospective observational study

Background&aimsThe classical ketogenic diet (KD) is a high-fat, very low-carbohydrate normocaloric diet used for drug-resistant epilepsy and Glucose Transporter 1 Deficiency Syndrome (GLUT1 DS). In animal models, high fat diet induces large alterations in microbiota producing deleterious effects on gut health. We carried out a pilot study on patients treated with KD comparing their microbiota composition before and after three months on the diet. MethodsSix patients affected by GLUT1 DS were asked to collect fecal samples before and after three months on the diet. RT – PCR analysis was performed in order to quantify Firmicutes, Bacteroidetes, Bifidobacterium spp., Lactobacillus spp., Clostridium perfringens, Enterobacteriaceae, Clostridium cluster XIV, Desulfovibrio spp. and Faecalibacterium prausnitzii. ResultsCompared with baseline, there were no statistically significant differences at 3 months in Firmicutes and Bacteroidetes. However fecal microbial profiles revealed a statistically significant increase in Desulfovibrio spp. (p = 0.025), a bacterial group supposed to be involved in the exacerbation of the inflammatory condition of the gut mucosa associated to the consumption of fats of animal origin. ConclusionsA future prospective study on the changes in gut microbiota of all children with epilepsy started on a KD is warranted. In patients with dysbiosis demonstrated by fecal samples, it my be reasonable to consider an empiric trial of pre or probiotics to potentially restore the «ecological balance» of intestinal microbiota.

Is ketogenic diet treatment hepatotoxic for children with intractable epilepsy?

PurposeLong-term ketogenic diet (KD) treatment has been shown to induce liver steatosis and gallstone formation in some in vivo and clinical studies. The aim of this retrospective study was to evaluate the hepatic side effects of KD in epileptic children. MethodA total of 141 patients (mean age: 7.1±4.1years [2–18 years], 45.4% girls), receiving KD at least one year for intractable epilepsy due to different diagnoses (congenital brain defects, GLUT-1 deficiency, West syndrome, tuberous sclerosis, hypoxic brain injury, etc.) were included in the study. Serum triglyceride, cholesterol, aminotransferase, bilirubin, protein and albumin levels and abdominal ultrasonography were recorded before and at 1, 3, 6, and 12 months following after diet initiation. ResultsThe mean duration of KD was 15.9±4.3months. At one month of therapy, three patients had elevated alanine and aspartate aminotransferase levels. These patients were receiving ketogenic diet for Doose syndrome, idiopathic epilepsy and GLUT-1 deficiency. Hepatosteatosis was detected in three patients at 6 months of treatment. Two of these patients were treated with KD for the primary diagnosis of tuberous sclerosis and one for Landau Kleffner syndrome. Cholelithiasis was detected in two patients at 12 months of treatment. They were receiving treatment for West syndrome and hypoxic brain injury sequelae. ConclusionLong-term ketogenic diet treatment stimulates liver parenchymal injury, hepatic steatosis and gallstone formation. Patients should be monitored by screening liver enzymes and abdominal ultrasonography in order to detect these side effects.

Epilepsy in Inborn Errors of Metabolism With Therapeutic Options

Inborn errors of metabolism (IEM) are rare conditions that represent more than 1000 diseases, with a global prevalence of approximately 1:2000 individuals. Approximately, 40%-60% of IEM may present with epilepsy as one of the main neurologic signs. Epilepsy in IEM may appear at any age (fetal, newborn, infant, adolescent, or even adult). Different pathophysiological mechanisms may be responsible for the clinical phenotype, such as disturbances in energy metabolism (mitochondrial and fatty oxidation disorders, GLUT-1, and cerebral creatine deficiency), accumulation of complex molecules (lysosomal storage disorders), toxic mechanisms (organic acidurias and urea cycle disorders), or impairment of neurotransmission. Early diagnosis and, in some cases, an effective treatment may result in an excellent evolution of the IEM, in particularly seizure control. This review attempts to delineate a summary of IEM that may present with seizures or epilepsy and emphasizes the management in treatable conditions.

Experience in the Use of a Ketogenic Diet in a Patient with Type I Glucose Transporter Deficiency Syndrome (clinical observations)

This report presents our experience of the use of a ketogenic diet (KD) in the treatment of drug-resistant epilepsy in a patient with type I glucose transporter deficiency syndrome (GLUT1). The patient was a nineyear-old boy suffering from refractory epilepsy with frequent repeated myoclonic seizures due to GLUT1. Use of a KD was found to be highly effective in the treatment of this disease. Complete recovery from epileptic seizures and EEG anomalies was obtained by day 10 from the beginning of the KD. At three months, there were improvements in the cognitive domain and in the child’s verbal development. Anticonvulsants were withdrawn on the basis of the stable remission of epileptic seizures. This was followed by further improvements in intellectual functions and the psychoemotional domain; the child became able to attend a special school. At the time of writing the patient had been on the diet for one year three months. The improvements persisted and observations continue. Thus, a ketogenic diet was highly effective and is perhaps the only method currently available for the treatment of GLUT1.

A 23 years follow-up study identifies GLUT1 deficiency syndrome initially diagnosed as complicated hereditary spastic paraplegia

Glucose transporter 1 (GLUT1) deficiency syndrome (GLUT1DS) was initially described in the early 90s as a sporadic clinical condition, characterized by seizures, motor and intellectual impairment with variable clinical presentation, and without a known genetic cause. Although causative mutations in SLC2A1 were later identified and much more is known about the disease, it still remains largely underdiagnosed. In the current study, a previously described Italian family was re-analyzed using whole exome sequencing and clinically re-evaluated. Affected individuals presented with spastic paraplegia as a predominant symptom, with epilepsy and intellectual disability, inherited as an autosomal dominant trait with variable clinical presentation. While a novel variant of hereditary spastic paraplegia (HSP) was initially hypothesized in this family, previous linkage studies of known HSP genes did not identify the genetic cause. Exome-sequencing study identified a p.Arg126Cys mutation in the SLC2A1 gene, encoding GLUT1, which segregated with the affected members of the family. The diagnosis of GLUT1DS was further confirmed by cerebrospinal fluid analysis, and treatment was started with good initial response. The description of this large family provides further clinical information on this rare disease. It also offers an example of how GLUT1DS can be challenging to diagnose, and emphasizes the importance of lumbar puncture in the workflow of similar syndromes. Finally, it suggests that analysis of SLC2A1 should be considered in the diagnostic work up of HSP, especially if it is associated with epilepsy.

The changing face of dietary therapy for epilepsy.

Ketogenic diet is an established and effective non-pharmacologic treatment for drug-resistant epilepsy. Ketogenic diet represents the treatment of choice for GLUT-1 deficiency syndrome and pyruvate dehydrogenase complex deficiency. Infantile spasms, Dravet syndrome and myoclonic-astatic epilepsy are epilepsy syndromes for which ketogenic diet should be considered early in the therapeutic pathway. Recently, clinical indications for ketogenic diet have been increasing, as there is emerging evidence regarding safety and effectiveness. Specifically, ketogenic diet response has been investigated in refractory status epilepticus and encephalopathy with status epilepticus during sleep. New targets in neuropharmacology, such as mitochondrial permeability transition, are being studied and might lead to using it effectively in other neurological diseases. But, inefficient connectivity and impaired ketogenic diet proposal limit ideal availability of this therapeutic option. Ketogenic diet in Italy is not yet considered as standard of care, not even as a therapeutic option for many child neurologists and epileptologists. The aim of this review is to revisit ketogenic diet effectiveness and safety in order to highlight its importance in drug-resistant epilepsy and other neurological disorders. • Ketogenic diet efficacy is now described in large case series, with adequate diet compliance and side effects control. • Ketogenic diet is far from being attempted as a first line therapy. Its availability varies worldwide. What is New: • New pharmacological targets such as mitochondrial permeability transition and new epileptic syndromes and etiologies responding to the diet such as refractory status epilepticus are being pointed out. • Ketogenic diet can function at its best when used as a tailor-made therapy. Fine tuning is crucial.

Cognitive and neurodevelopmental comorbidities in paediatric epilepsy.

Cognitive and behavioural comorbidities are often seen in children with epilepsy, and are more common and severe in refractory epilepsy. These comorbidities are associated with worse quality of life, increased behavioural and language problems and worse social skills, all of which adversely affect long-term psychosocial functioning. To enable early intervention and therapy, children and teens with epilepsy should be periodically screened for cognitive comorbidities. The location of the epileptic focus can, to a certain degree, predict the type(s) of comorbidity; however, the spectrum of disability is often broad, presumably because focal perturbations can cause network dysfunction. Comorbidities often result from underlying structural or functional pathology that has led to seizures. In selected cases, therapy targeting the underlying cause, such as the ketogenic diet for GLUT1 deficiency syndromes, may be remarkably effective in ameliorating both seizures and cognitive concerns. In many cases, however, cognitive impairment persists despite seizure control. In epileptic encephalopathies, frequent seizures and/or interictal epileptiform abnormalities exacerbate neurocognitive dysfunction, owing to synaptic reorganization or impaired neurogenesis, or to other effects on developing neural circuits, and prompt initiation of effective antiepileptic therapy is essential to limit cognitive comorbidities.

Use of modified Atkins diet in glucose transporter type 1 deficiency syndrome.

Glucose transporter type 1 deficiency syndrome (GLUT1-DS) results from impaired glucose transport into the brain, and is treated with a ketogenic diet. A few reports have suggested effectiveness of treatment using the modified Atkins diet (MAD). We aimed to assess the efficacy of MAD as a treatment for GLUT1-DS. We evaluated the efficacy of MAD in 10 patients (four males, six females; mean age at diagnosis [SD] 6.2y [1.7], min-max: 4mo-12y) with GLUT1-DS. MAD was started at diagnosis in eight patients, including two infants. The mean duration (SD) under MAD was 2.5 [0.6] years (range 6mo-6y). Seven patients with epilepsy started MAD at GLUT1-DS diagnosis, and all experienced improvements in their epilepsy: five out of seven were seizure-free at M1, and three out of six at M3 and M6. The initiation of MAD allowed symptoms to be controlled in the three patients with movement disorders but without seizures. Two patients switched from the ketogenic diet to MAD. This switch was not responsible for the recurrence of any symptoms, and led to improvements in both physical abilities and growth parameters. MAD, which is a less restrictive and more palatable diet than the ketogenic diet, seems to have comparable effectiveness. Moreover, a switch from the ketogenic diet to MAD appears to be beneficial for patients with GLUT1-DS.

Evaluation of non-coding variation in GLUT1 deficiency.

Loss-of-function mutations in SLC2A1, encoding glucose transporter-1 (GLUT-1), lead to dysfunction of glucose transport across the blood-brain barrier. Ten percent of cases with hypoglycorrhachia (fasting cerebrospinal fluid [CSF] glucose <2.2mmol/L) do not have mutations. We hypothesized that GLUT1 deficiency could be due to non-coding SLC2A1 variants. We performed whole exome sequencing of one proband with a GLUT1 phenotype and hypoglycorrhachia negative for SLC2A1 sequencing and copy number variants. We studied a further 55 patients with different epilepsies and low CSF glucose who did not have exonic mutations or copy number variants. We sequenced non-coding promoter and intronic regions. We performed mRNA studies for the recurrent intronic variant. The proband had a de novo splice site mutation five base pairs from the intron-exon boundary. Three of 55 patients had deep intronic SLC2A1 variants, including a recurrent variant in two. The recurrent variant produced less SLC2A1 mRNA transcript. Fasting CSF glucose levels show an age-dependent correlation, which makes the definition of hypoglycorrhachia challenging. Low CSF glucose levels may be associated with pathogenic SLC2A1 mutations including deep intronic SLC2A1 variants. Extending genetic screening to non-coding regions will enable diagnosis of more patients with GLUT1 deficiency, allowing implementation of the ketogenic diet to improve outcomes.

Atypical Manifestations in Glut1 Deficiency Syndrome

Glucose transporter type 1 deficiency syndrome is a genetically determined, treatable, neurologic disorder that is caused by an insufficient transport of glucose into the brain. It is caused by a mutation in the SCL2A1 gene, which is so far the only known to be associated with this condition. Glucose transporter type 1 deficiency syndrome consists of a wide clinical spectrum that usually presents with cognitive impairment, epilepsy, paroxysmal exercise-induced dyskinesia, acquired microcephaly, hemolytic anemia, gait disturbance, and dyspraxia in different combinations. However, there are other clinical manifestations that we consider equally peculiar but that have so far been poorly described in literature. In this review, supported by a video contribution, we will accurately describe this type of clinical manifestation such as oculogyric crises, weakness, paroxysmal kinesigenic and nonkinesigenic dyskinesia in order to provide an additional instrument for a correct, rapid diagnosis.