First report of glucose transporter 1 deficiency syndrome in Korea with a novel splice site mutation

Ketogenic diet for infants with epilepsy: A literature review

The ketogenic diet (KD) is an established, nonpharmacological treatment for drug-resistant epilepsy (DRE). Actually, KD and its variants have been shown to be elective and resolute for patients with glucose transporter type 1 (GLUT1) deficiency. The aim of this review was to study the use of KD and its variants in infancy, including the neonatal age, and demonstrate the safety and efficacy of this treatment in patients with the age of 0-23 months affected by DRE already subjected to pharmacological approach attempts. A literature search was conducted using PubMed as the medical database source. We used the age limit of 0-23 months, and we considered only articles published between the years 2015 and 2018, in light of increasing interest worldwide in the use of KD and its variants to manage DRE. We included 52 publications: 1 Cochrane study, 22 retrospective studies, 9 prospective studies, 4 randomized controlled trials (RCTs), 12 clinical cases, and 4 clinical reviews. Literature data showed that KD and its variants are safe and useful in patients with the age of 0-23 months with DRE. Classical KD is of first choice in the treatment of GLUT1 deficiency. Earlier introduction of KD in GLUT1 promises a better outcome and a decrease in seizure frequency in these patients.

Evaluation of non-coding variation in GLUT1 deficiency

AIM

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.

METHOD

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.

RESULTS

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.

INTERPRETATION

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.

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

AIM

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.

METHOD

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.

RESULTS

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.

INTERPRETATION

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.