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.
Patients with oxidative phosphorylation (OxPhos) defects causing mitochondrial diseases appear particularly vulnerable to infections. Although OxPhos defects modulate cytokine production in vitro and ...in animal models, little is known about how circulating leukocytes of patients with inherited mitochondrial DNA (mtDNA) defects respond to acute immune challenges. In a small cohort of healthy controls (
n
= 21) and patients (
n
= 12) with either the m.3243A > G mutation or single, large-scale mtDNA deletions, we examined (i) cytokine responses (IL-6, TNF-α, IL-1β) in response to acute lipopolysaccharide (LPS) exposure and (ii) sensitivity to the immunosuppressive effects of glucocorticoid signaling (dexamethasone) on cytokine production. In dose–response experiments to determine the half-maximal effective LPS concentration (EC
50
), relative to controls, leukocytes from patients with mtDNA deletions showed 74–79% lower responses for IL-6 and IL-1β (p
IL-6
= 0.031, p
IL-1β
= 0.009). Moreover, whole blood from patients with mtDNA deletions (p
IL-6
= 0.006), but not patients with the m.3243A > G mutation, showed greater sensitivity to the immunosuppressive effects of dexamethasone. Together, these ex vivo data provide preliminary evidence that some systemic OxPhos defects may compromise immune cytokine responses and increase the sensitivity to immune cytokine suppression by glucocorticoids. Further work in larger cohorts is needed to define the nature of immune dysregulation in patients with mitochondrial disease, and their potential implications for disease phenotypes.
Key messages
Little is known about leukocyte cytokine responses in patients with mitochondrial diseases.
Leukocytes of patients with mtDNA deletions show blunted LPS sensitivity and cytokine responses.
Leukocytes of patients with mtDNA deletions are more sensitive to glucocorticoid-mediated IL-6 suppression.
Work in larger cohorts is needed to delineate potential immune alterations in mitochondrial diseases.
Abstract
Background: Glut1 deficiency syndrome (Glut1DS) is caused by mutations in SLC2A1 on chromosome 1p34.2, which impairs transmembrane glucose transport across the blood brain barrier resulting ...in hypoglycorrhachia and decreased glucose availability for brain metabolism. This causes a drug-resistant, metabolic epilepsy due to energy deficiency. Standard treatment for Glut1DS is the ketogenic diet (KD) but treatment options are limited if patients fail the KD. Diazoxide, which inhibits insulin release, was used sparingly in the past for a few Glut1DS patients to increase blood glucose levels and thus intracerebral glucose levels. Unfortunately, their treatment was complicated by unacceptable persistent hyperglycemia with blood glucoses in the 300s to 500s. We investigated the use of a continuous glucose monitor (CGM) to enable titration of diazoxide therapy in a patient with KD-resistant Glut1DS.
Clinical Case: A 14-year-old girl with Glut1DS (c.398_399delGCinsTT:p.Lys133Phe) failed the KD due to severe nausea, vomiting, abdominal pain, and hypertriglyceridemia. Laboratory tests revealed CSF glucose of 36 mg/dL when blood glucose was 93 mg/dL. Over the course of 3 hospitalizations targeting blood glucose levels in the range of 120-180 mg/dL with diazoxide, EEG seizure activity decreased from 3 to 0 absence seizures per hour. CGM placement during the third hospitalization showed an average interstitial glucose of 157 mg/dL with glucose variability of 20.8% on diazoxide dose of 7.3 mg/kg/day. After discharge, CGM has been used to adjust diazoxide doses 2-4 times a week to achieve target interstitial glucoses of 140-180 mg/dL. Repeat laboratory tests revealed CSF glucose of 55 mg/dL when interstitial glucose was 158 mg/dL. Current diazoxide dose is 7.9 mg/kg/day and most recent hemoglobin A1c was 5.4%.
Conclusions: This is the first report demonstrating CGM as a tool facilitating the safe initiation and real-time titration of diazoxide in Glut1DS patients who have failed the KD. Diazoxide addresses neuroglycopenia more physiologically by raising blood glucose levels and subsequently intracerebral glucose levels. CGM allows for more accurate titration of blood glucose with diazoxide while avoiding complications of hyperglycemia and thus introduces the possibility of diazoxide becoming a standard of care for Glut1DS. More broadly, CGM provides a valuable tool for the management of other disorders of glucose transport and carbohydrate metabolism.
Abstract 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 (Glut1DS) is a brain energy failure syndrome caused by impaired glucose transport across brain tissue barriers. Glucose diffusion across tissue barriers is facilitated by a ...family of proteins including glucose transporter type 1 (Glut1). Patients are treated effectively with ketogenic diet therapies (KDT) that provide a supplemental fuel, namely ketone bodies, for brain energy metabolism. The increasing complexity of Glut1DS, since its original description in 1991, now demands an international consensus statement regarding diagnosis and treatment. International experts (n = 23) developed a consensus statement utilizing their collective professional experience, responses to a standardized questionnaire, and serial discussions of wide‐ranging issues related to Glut1DS. Key clinical features signaling the onset of Glut1DS are eye‐head movement abnormalities, seizures, neurodevelopmental impairment, deceleration of head growth, and movement disorders. Diagnosis is confirmed by the presence of these clinical signs, hypoglycorrhachia documented by lumbar puncture, and genetic analysis showing pathogenic SLC2A1 variants. KDT represent standard choices with Glut1DS‐specific recommendations regarding duration, composition, and management. Ongoing research has identified future interventions to restore Glut1 protein content and function. Clinical manifestations are influenced by patient age, genetic complexity, and novel therapeutic interventions. All clinical phenotypes will benefit from a better understanding of Glut1DS natural history throughout the life cycle and from improved guidelines facilitating early diagnosis and prompt treatment. Often, the presenting seizures are treated initially with antiseizure drugs before the cause of the epilepsy is ascertained and appropriate KDT are initiated. Initial drug treatment fails to treat the underlying metabolic disturbance during early brain development, contributing to the long‐term disease burden. Impaired development of the brain microvasculature is one such complication of delayed Glut1DS treatment in the postnatal period. This international consensus statement should facilitate prompt diagnosis and guide best standard of care for Glut1DS throughout the life cycle.
Spinal muscular atrophy (SMA) was added to the Recommended Uniform Screening Panel (RUSP) in July 2018, following FDA approval of the first effective SMA treatment, and demonstration of feasibility ...of high-throughput newborn screening using a primary molecular assay. SMA newborn screening was implemented in New York State (NYS) on 1 October 2018.
Screening was conducted using DNA extracted from dried blood spots with a multiplex real-time quantitative polymerase chain reaction (qPCR) assay targeting the recurrent SMN1 exon 7 gene deletion.
During the first year, 225,093 infants were tested. Eight screened positive, were referred for follow-up, and confirmed to be homozygous for the deletion. Infants with two or three copies of the SMN2 gene, predicting more severe, earlier-onset SMA, were treated with antisense oligonucleotide and/or gene therapy. One infant with ≥4 copies SMN2 also received gene therapy.
Newborn screening permits presymptomatic SMA diagnosis, when treatment initiation is most beneficial. At 1 in 28,137 (95% confidence interval CI: 1 in 14,259 to 55,525), the NYS SMA incidence is 2.6- to 4.7-fold lower than expected. The low SMA incidence is likely attributable to imprecise and biased estimates, coupled with increased awareness, access to and uptake of carrier screening, genetic counseling, cascade testing, prenatal diagnosis, and advanced reproductive technologies.
Impaired glucose transport across the blood‐brain barrier results in Glut‐1 deficiency syndrome (Glut‐1 DS, OMIM 606777), characterized by infantile seizures, developmental delay, acquired ...microcephaly, spasticity, ataxia, and hypoglycorrhachia. We studied 16 new Glut‐1 deficiency syndrome patients focusing on clinical and laboratory features, molecular genetics, genotype–phenotype correlation, and treatment. These patients were classified phenotypically into three groups. The mean cerebrospinal fluid glucose concentration was 33.1 ± 4.9mg/dl equal to 37% of the simultaneous blood glucose concentration. The mean cerebrospinal fluid lactate concentration was 1.0 ± 0.3mM, which was less than the normal mean value of 1.63mM. The mean Vmax for the 3‐O‐methyl‐D‐glucose uptake into erythrocytes was 996 fmol/106 red blood cells per second, significantly less (54 ± 11%; t test, p < 0.05) than the mean control value of 1,847. The mean Km value for the patient group (1.4 ± 0.5mM) was similar to the control group (1.7 ± 0.5mM; t test, p > 0.05). We identified 16 rearrangements, including seven missense, one nonsense, one insertion, and seven deletion mutations. Fourteen were novel mutations. There were no obvious correlations between phenotype, genotype, or biochemical measures. The ketogenic diet produced good seizure control. Ann Neurol 2005;57:111–118
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.
Spinal muscular atrophy (SMA) was added to the Recommended Uniform Screening Panel in July 2018 largely on the basis of the availability and efficacy of newly approved disease-modifying therapies. ...New York State (NYS) started universal newborn screening for SMA in October 2018. The authors report the findings from the first 3 years of screening.
Statewide neonatal screening was conducted using DNA extracted from dried blood spots using a real-time quantitative PCR assay. Retrospective follow-up data were collected from 9 referral centers across the state on 34 infants.
In the first 3 years since statewide implementation, nearly 650,000 infants have been screened for SMA. Thirty-four babies screened positive and were referred to a neuromuscular specialty care center. The incidence remains lower than previously predicted. The majority (94%), including all infants with 2-3 copies of survival motor neuron (
2, have received treatment. Among treated infants, the overwhelming majority (94%; 30/32) have received gene replacement. All infants in this cohort with 3 copies of
are clinically asymptomatic posttreatment based on early clinical follow-up data. Infants with 2 copies of
are more variable in their outcomes. Electrodiagnostic outcomes data obtained from a subgroup of patients (n = 11) demonstrated either improvement or no change in compound muscle action potential (CMAP) amplitude at last clinical follow-up compared with pretreatment baseline. Most infants were treated before 6 weeks of age (median = 34.5 days of life; range 11-180 days). Delays and barriers to treatment identified by treating clinicians followed 2 broad themes: medical and nonmedical. Medical delays most commonly reported were the presence of AAV9 antibodies and elevated troponin I levels. Nonmedical barriers included delays in obtaining insurance and insurance policies regarding specific treatment modalities.
The findings from the NYS cohort of newborn screen-identified infants are consistent with other reports of improved outcomes from early diagnosis and treatment. Additional biomarkers of motor neuron health including EMG can potentially be helpful in detecting preclinical decline.
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