Switching to sulphonylureas in children with iDEND syndrome caused by KCNJ11 mutations results in improved cerebellar perfusion

Genetic variant profiling of neonatal diabetes mellitus in Iranian patients: Unveiling 58 distinct variants in 14 genes

INTRODUCTION

Neonatal diabetes mellitus (NDM) is a rare non-immunological monogenic disorder characterized by hyperglycemic conditions primarily occurring within the first 6 months of life. The majority of cases are attributed to pathogenic variants in genes affecting beta-cell survival, insulin regulation, and secretion. This study aims to investigate the genetic landscape of NDM in Iran.

METHODS

We recruited a total of 135 patients who were initially diagnosed with diabetes at <12 months of age in Iran and referred to pediatric endocrinology clinics across the country. These patients underwent genetic diagnostic tests conducted by the Exeter Molecular Genetics Laboratory in the UK. The pathogenic variants identified were sorted and described based on type, pathogenicity (according to ACMG/AMP criteria), novelty, and the affected protein domain.

RESULTS

Genetic defects were identified in 93 probands, presenting various pathogenic abnormalities associated with NDM and its associated syndromes. 76% of the patients were born as a result of consanguineous marriage, and a familial history of diabetes was found in 43% of the cases. A total of 58 distinct variants in 14 different genes were discovered, including 20 variants reported for the first time. Causative variants were most frequently identified in EIF2AK3, KCNJ11, and ABCC8, respectively. Notably, EIF2AK3 and ABCC8 exhibited the highest number of novel variants.

DISCUSSION

These findings provide valuable insights into the genetic landscape of NDM in the Iranian population and contribute to the knowledge of novel pathogenic variants within known causative genes.

KATP Channels and the Metabolic Regulation of Insulin Secretion in Health and Disease: The 2022 Banting Medal for Scientific Achievement Award Lecture

Diabetes is characterized by elevation of plasma glucose due to an insufficiency of the hormone insulin and is associated with both inadequate insulin secretion and impaired insulin action. The Banting Medal for Scientific Achievement Commemorates the work of Sir Frederick Banting, a member of the team that first used insulin to treat a patient with diabetes almost exactly one hundred years ago on 11 January 1922. This article is based on my Banting lecture of 2022 and concerns the mechanism of glucose-stimulated insulin secretion from pancreatic β-cells, with an emphasis on the metabolic regulation of the KATP channel. This channel plays a central role in insulin release. Its closure in response to metabolically generated changes in the intracellular concentrations of ATP and MgADP stimulates β-cell electrical activity and insulin granule exocytosis. Activating mutations in KATP channel genes that impair the ability of the channel to respond to ATP give rise to neonatal diabetes. Impaired KATP channel regulation may also play a role in type 2 diabetes. I conjecture that KATP channel closure in response to glucose is reduced because of impaired glucose metabolism, which fails to generate a sufficient increase in ATP. Consequently, glucose-stimulated β-cell electrical activity is less. As ATP is also required for insulin granule exocytosis, both reduced exocytosis and less β-cell electrical activity may contribute to the reduction in insulin secretion. I emphasize that what follows is not a definitive review of the topic but a personal account of the contribution of my team to the field that is based on my Banting lecture.

Sulfonylurea for improving neurological features in neonatal diabetes: A systematic review and meta-analyses

OBJECTIVE

In monogenic diabetes due to KCNJ11 and ABCC8 mutations that impair KATP- channel function, sulfonylureas improve long-term glycemic control. Although KATP channels are extensively expressed in the brain, the effect of sulfonylureas on neurological function has varied widely. We evaluated published evidence about potential effects of sulfonylureas on neurological features, especially epilepsy, cognition, motor function and muscular tone, visuo-motor integration, and attention deficits in children and adults with KCNJ11 and ABCC8-related neonatal-onset diabetes mellitus.

RESEARCH DESIGN AND METHODS

We conducted a systematic review and meta-analyses of the literature (PROSPERO, CRD42021254782), including individual-patient data, according to PRISMA, using RevMan software. We also graded the level of evidence.

RESULTS

We selected 34 of 776 publications. The evaluation of global neurological function before and after sulfonylurea (glibenclamide) treatment in 114 patients yielded a risk difference (RD) of 58% (95%CI, 43%-74%; I²  = 54%) overall and 73% (95%CI, 32%-113%; I²  = 0%) in the subgroup younger than 4 years; the level of evidence was moderate and high, respectively. EEG studies of epilepsy showed a RD of 56% (95%CI, 23%-89%; I²  = 34%) in patients with KCNJ11 mutations, with a high quality of evidence. For hypotonia and motor function, the RDs were 90% (95%CI, 69%-111%; I²  = 0%) and 73% (95%CI, 35%-111%; I²  = 0%), respectively, with a high level of evidence.

CONCLUSIONS

Glibenclamide significantly improved neurological abnormalities in patients with neonatal-onset diabetes due to KCNJ11 or ABCC8 mutations. Hypotonia was the symptom that responded best. Earlier treatment initiation was associated with greater benefits.

Role of Actionable Genes in Pursuing a True Approach of Precision Medicine in Monogenic Diabetes

Monogenic diabetes is a genetic disorder caused by one or more variations in a single gene. It encompasses a broad spectrum of heterogeneous conditions, including neonatal diabetes, maturity onset diabetes of the young (MODY) and syndromic diabetes, affecting 1-5% of patients with diabetes. Some of these variants are harbored by genes whose altered function can be tackled by specific actions ("actionable genes"). In suspected patients, molecular diagnosis allows the implementation of effective approaches of precision medicine so as to allow individual interventions aimed to prevent, mitigate or delay clinical outcomes. This review will almost exclusively concentrate on the clinical strategy that can be specifically pursued in carriers of mutations in "actionable genes", including ABCC8, KCNJ11, GCK, HNF1A, HNF4A, HNF1B, PPARG, GATA4 and GATA6. For each of them we will provide a short background on what is known about gene function and dysfunction. Then, we will discuss how the identification of their mutations in individuals with this form of diabetes, can be used in daily clinical practice to implement specific monitoring and treatments. We hope this article will help clinical diabetologists carefully consider who of their patients deserves timely genetic testing for monogenic diabetes.

New insights into KATP channel gene mutations and neonatal diabetes mellitus

The ATP-sensitive potassium channel (K_ATP channel) couples blood levels of glucose to insulin secretion from pancreatic β-cells. K_ATP channel closure triggers a cascade of events that results in insulin release. Metabolically generated changes in the intracellular concentrations of adenosine nucleotides are integral to this regulation, with ATP and ADP closing the channel and MgATP and MgADP increasing channel activity. Activating mutations in the genes encoding either of the two types of K_ATP channel subunit (Kir6.2 and SUR1) result in neonatal diabetes mellitus, whereas loss-of-function mutations cause hyperinsulinaemic hypoglycaemia of infancy. Sulfonylurea and glinide drugs, which bind to SUR1, close the channel through a pathway independent of ATP and are now the primary therapy for neonatal diabetes mellitus caused by mutations in the genes encoding K_ATP channel subunits. Insight into the molecular details of drug and nucleotide regulation of channel activity has been illuminated by cryo-electron microscopy structures that reveal the atomic-level organization of the K_ATP channel complex. Here we review how these structures aid our understanding of how the various mutations in the genes encoding Kir6.2 (KCNJ11) and SUR1 (ABCC8) lead to a reduction in ATP inhibition and thereby neonatal diabetes mellitus. We also provide an update on known mutations and sulfonylurea therapy in neonatal diabetes mellitus.

Intellectual Disability and Potassium Channelopathies: A Systematic Review

Intellectual disability (ID) manifests prior to adulthood as severe limitations to intellectual function and adaptive behavior. The role of potassium channelopathies in ID is poorly understood. Therefore, we aimed to evaluate the relationship between ID and potassium channelopathies. We hypothesized that potassium channelopathies are strongly associated with ID initiation, and that both gain- and loss-of-function mutations lead to ID. This systematic review explores the burden of potassium channelopathies, possible mechanisms, advancements using animal models, therapies, and existing gaps. The literature search encompassed both PubMed and Embase up to October 2019. A total of 75 articles describing 338 cases were included in this review. Nineteen channelopathies were identified, affecting the following genes: KCNMA1, KCNN3, KCNT1, KCNT2, KCNJ10, KCNJ6, KCNJ11, KCNA2, KCNA4, KCND3, KCNH1, KCNQ2, KCNAB1, KCNQ3, KCNQ5, KCNC1, KCNB1, KCNC3, and KCTD3. Twelve of these genes presented both gain- and loss-of-function properties, three displayed gain-of-function only, three exhibited loss-of-function only, and one had unknown function. How gain- and loss-of-function mutations can both lead to ID remains largely unknown. We identified only a few animal studies that focused on the mechanisms of ID in relation to potassium channelopathies and some of the few available therapeutic options (channel openers or blockers) appear to offer limited efficacy. In conclusion, potassium channelopathies contribute to the initiation of ID in several instances and this review provides a comprehensive overview of which molecular players are involved in some of the most prominent disease phenotypes.

Intellectual Disability in KATP Channel Neonatal Diabetes

OBJECTIVE

Neonatal diabetes has been shown to be associated with high neuropsychiatric morbidity in a genotype-phenotype-dependent manner. However, the specific impact of different mutations on intellectual functioning is still insufficiently characterized. Specifically, only a small number of subjects with developmental delay have been comprehensively assessed, creating a knowledge gap about patients carrying the heaviest burden.

RESEARCH DESIGN AND METHODS

We assessed the intellectual functioning and mental health of the complete Norwegian population with K_ATP channel neonatal diabetes. Eight sulfonylurea-treated children (five with the p.V59M genotype [KCNJ11]) were assessed using age-matched control subjects with type 1 diabetes. The investigations included a physical and motor developmental examination, cerebral MRI, psychometrical examination, and questionnaires assessing intellectual capabilities and psychiatric morbidity.

RESULTS

A strong genotype-phenotype correlation was found, revealing the p.V59M genotype as highly associated with substantial intellectual disability, with no significant correlation with the time of sulfonylurea initiation. Consistent with previous studies, other genotypes were associated with minor cognitive impairment. Cerebral MRI verified normal brain anatomy in all but one child.

CONCLUSIONS

We here presented a comprehensive assessment of intellectual functioning in the largest cohort of p.V59M subjects to date. The level of intellectual disability revealed not only changes the interpretation of other psychological measures but downplays a strong protective effect of sulfonylurea. Within the scope of this study, we could not find evidence supporting an early treatment start to be beneficial, although a weaker effect cannot be ruled out.

Update of variants identified in the pancreatic β-cell KATP channel genes KCNJ11 and ABCC8 in individuals with congenital hyperinsulinism and diabetes

The most common genetic cause of neonatal diabetes and hyperinsulinism is pathogenic variants in ABCC8 and KCNJ11. These genes encode the subunits of the β-cell ATP-sensitive potassium channel, a key component of the glucose-stimulated insulin secretion pathway. Mutations in the two genes cause dysregulated insulin secretion; inactivating mutations cause an oversecretion of insulin, leading to congenital hyperinsulinism, whereas activating mutations cause the opposing phenotype, diabetes. This review focuses on variants identified in ABCC8 and KCNJ11, the phenotypic spectrum and the treatment implications for individuals with pathogenic variants.

Clinical Characteristics, Molecular Features, and Long-Term Follow-Up of 15 Patients with Neonatal Diabetes: A Single-Centre Experience

BACKGROUND

Diabetes diagnosed within the first 6 months of life is defined as neonatal diabetes mellitus (NDM). Mutations in the KCNJ11, ABCC8, and INS genes are the most common cause of permanent NDM. In populations with a high rate of consanguinity, Wolcott-Rallison syndrome caused by biallelic EIF2AK3 mutations is common.

METHODS

We studied the clinical characteristics and underlying genetic cause of disease in 15 individuals with diabetes onset before 6 months of age as defined by sustained hyperglycaemia requiring insulin treatment. Patients who had a remission of the diabetes, defined by a normal blood glucose and HbA1c value without insulin or sulphonylurea (SU) treatment, within the first 18 months of life were classified as having transient NDM (TNDM).

RESULTS

We report 15 patients with NDM from 14 unrelated families, including 10 with reported parental consanguinity. 1/15 patients had a remission of diabetes, leading to a diagnosis of TNDM. Mutations were detected in 80% (n = 12/15) of the cohort (ABCC8 [n = 4], PTF1A-distal enhancer [n = 3], KCNJ11 [n = 2], EIF2AK3 [n = 1], INS [n = 1], and SLC19A2 [n = 1]). All cases were initially treated with multiple dose insulin injections. One patient with an ABCC8 mutation transitioned from insulin to SU resulting in improved metabolic control at the age of 20 years.

CONCLUSION

Although the number of individuals born to consanguineous parents was considerably high in this cohort, KATP channel mutations (ABCC8/KCNJ11) were more common than EIF2AK3 mutations (n = 6 vs. n = 1). Genetic analyses should be performed in all NDM cases due to the potential impact on treatment and prognosis.

Precision Medicine: Long-Term Treatment with Sulfonylureas in Patients with Neonatal Diabetes Due to KCNJ11 Mutations

PURPOSE OF REVIEW

The goal of this review is to provide updates on the safety and efficacy of long-term sulfonylurea use in patients with KCNJ11-related diabetes. Publications from 2004 to the present were reviewed with an emphasis on literature since 2014.

RECENT FINDINGS

Sulfonylureas, often taken at high doses, have now been utilized effectively in KCNJ11 patients for over 10 years. Mild-moderate hypoglycemia can occur, but in two studies with a combined 975 patient-years on sulfonylureas, no severe hypoglycemic events were reported. Improvements in neurodevelopment and motor function after transition to sulfonylureas continue to be described. Sulfonylureas continue to be an effective, sustainable, and safe treatment for KCNJ11-related diabetes. Ongoing follow-up of patients in research registries will allow for deeper understanding of the facilitators and barriers to long-term sustainability. Further understanding of the effect of sulfonylurea on long-term neurodevelopmental outcomes, and the potential for adjunctive therapies, is needed.

Cognitive, Neurological, and Behavioral Features in Adults With KCNJ11 Neonatal Diabetes

OBJECTIVE

Central nervous system (CNS) features in children with permanent neonatal diabetes (PNDM) due to KCNJ11 mutations have a major impact on affected families. Sulfonylurea therapy achieves outstanding metabolic control but only partial improvement in CNS features. The effects of KCNJ11 mutations on the adult brain and their functional impact are not well understood. We aimed to characterize the CNS features in adults with KCNJ11 PNDM compared with adults with INS PNDM.

RESEARCH DESIGN AND METHODS

Adults with PNDM due to KCNJ11 mutations (n = 8) or INS mutations (n = 4) underwent a neurological examination and completed standardized neuropsychological tests/questionnaires about development/behavior. Four individuals in each group underwent a brain MRI scan. Test scores were converted to Z scores using normative data, and outcomes were compared between groups.

RESULTS

In individuals with KCNJ11 mutations, neurological examination was abnormal in seven of eight; predominant features were subtle deficits in coordination/motor sequencing. All had delayed developmental milestones and/or required learning support/special schooling. Half had features and/or a clinical diagnosis of autism spectrum disorder. KCNJ11 mutations were also associated with impaired attention, working memory, and perceptual reasoning and reduced intelligence quotient (IQ) (median IQ KCNJ11 vs. INS mutations 76 vs. 111, respectively; P = 0.02). However, no structural brain abnormalities were noted on MRI. The severity of these features was related to the specific mutation, and they were absent in individuals with INS mutations.

CONCLUSIONS

KCNJ11 PNDM is associated with specific CNS features that are not due to long-standing diabetes, persist into adulthood despite sulfonylurea therapy, and represent the major burden from KCNJ11 mutations.

To diet or not to diet in neonatal diabetes responding to sulfonylurea treatment

Background Neonatal diabetes mellitus (NDM) is defined as a monogenic form of diabetes that occurs in the first 6 months of life. As information on diet in NDM patients successfully treated with sulfonylurea is not yet available, we aimed to investigate the hypothesis that a carb-restricted diet is not needed in such cases. Case presentation In this case report, we present a successful implementation of a completely liberalized diet in a young patient with NDM, developmental delay and epilepsy (DEND syndrome), who was also switched to sulfonylurea treatment. The excellent metabolic control during follow-up despite completely ignoring any diet suggests that at least in some patients this approach might work. Conclusions If our proposed hypothesis is also confirmed by other reports, it might add significantly to the quality of life of these patients and broaden the knowledge in this medical field.

Genetic causes and treatment of neonatal diabetes and early childhood diabetes

Diabetes mellitus and impaired fasting glucose associated with single gene mutations are less rare than previously thought and may account for more than 6% of patients attending a pediatric diabetes clinic. The number of loci involved in monogenic diabetes exceed 25, and appropriate genetic diagnosis is crucial to direct therapy, for genetic counseling and for prognosis of short- and long-term complications. Among patients with neonatal diabetes (i.e. with onset within first 6 months of life) and patients with Maturity Onset Diabetes of the Young (MODY; an autosomal dominant form of diabetes), those carrying mutations in KCNJ11, ABCC8, HNF1A and HNF4A genes usually respond to oral therapy with sulphonylurea, while those bearing GCK mutations do not necessitate any treatment. Sensor-augmented continuous subcutaneous insulin infusion has been successfully employed in neonatal diabetes, and long-lasting effectiveness of sulfonylurea in KCNJ11 mutation carriers with neonatal diabetes well documented.

Future Roadmaps for Precision Medicine Applied to Diabetes: Rising to the Challenge of Heterogeneity

Precision medicine, the concept that specific treatments can be targeted to groups of individuals with specific genetic, cellular, or molecular features, is a key aspect of modern healthcare, and its use is rapidly expanding. In diabetes, the application of precision medicine has been demonstrated in monogenic disease, where sulphonylureas are used to treat patients with neonatal diabetes due to mutations in ATP-dependent potassium (K_ATP) channel genes. However, diabetes is highly heterogeneous, both between and within polygenic and monogenic subtypes. Making the correct diagnosis and using the correct treatment from diagnosis can be challenging for clinicians, but it is crucial to prevent long-term morbidity and mortality. To facilitate precision medicine in diabetes, research is needed to develop a better understanding of disease heterogeneity and its impact on potential treatments for specific subtypes. Animal models have been used in diabetes research, but they are not translatable to humans in the majority of cases. Advances in molecular genetics and functional laboratory techniques and availability and sharing of large population data provide exciting opportunities for human studies. This review will map the key elements of future diabetes research in humans and its potential for clinical translation to promote precision medicine in all diabetes subtypes.

Nuclear medicine of the cerebellum

Single-photon emission computed tomography (SPECT) and positron emission tomography (PET) with different radiotracers enable regional evaluation of blood flow and glucose metabolism, of receptors and transporters of several molecules, and of abnormal deposition of peptides and proteins in the brain. The cerebellum has been used as a reference region for different radiotracers in several disease conditions. Whole-brain voxel-wise analysis is not affected by a priori knowledge bias and should be preferred. SPECT and PET have contributed to establishing the cerebellum role in motion, cognition, and emotion control in physiologic and pathophysiologic conditions. The basic abnormal imaging findings include decreased or increased uptake of flow or metabolism tracers in the cerebellum alone or as part of a network. Decreased uptake is generally observed in primary structural damage of the cerebellum, but can also represent a distant effect of cerebral damage (crossed diaschisis). Increased uptake can be observed in Freidreich ataxia, inflammatory or immune-mediated diseases of the cerebellum, and in status epilepticus. The possibility is also recognized that primary structural damage of the cerebellum might determine distance effects on other brain structures (reversed diaschisis). So far, SPECT and PET have been predominantly used in clinical studies to investigate cerebellar changes in neurologic and psychiatric diseases and in connection with pharmacologic, transcranial magnetic stimulation, deep-brain stimulation, or surgical treatments.

KATP Channel Mutations and Neonatal Diabetes

Since the discovery of the KATP channel in 1983, numerous studies have revealed its physiological functions. The KATP channel is expressed in various organs, including the pancreas, brain and skeletal muscles. It functions as a "metabolic sensor" that converts the metabolic status to electrical activity. In pancreatic beta-cells, the KATP channel regulates the secretion of insulin by sensing a change in the blood glucose level and thus maintains glucose homeostasis. In 2004, heterozygous gain-of-function mutations in the KCNJ11 gene, which encodes the Kir6.2 subunit of the KATP channel, were found to cause neonatal diabetes. In some mutations, diabetes is accompanied by severe neurological symptoms [developmental delay, epilepsy, neonatal diabetes (DEND) syndrome]. This review focuses on mutations of Kir6.2, the pore-forming subunit and sulfonylurea receptor (SUR) 1, the regulatory subunit of the KATP channel, which cause neonatal diabetes/DEND syndrome and also discusses the findings of the pathological mechanisms that are associated with neonatal diabetes, and its neurological features.

Neonatal Diabetes and the KATP Channel: From Mutation to Therapy

Activating mutations in one of the two subunits of the ATP-sensitive potassium (K_ATP) channel cause neonatal diabetes (ND). This may be either transient or permanent and, in approximately 20% of patients, is associated with neurodevelopmental delay. In most patients, switching from insulin to oral sulfonylurea therapy improves glycemic control and ameliorates some of the neurological disabilities. Here, we review how K_ATP channel mutations lead to the varied clinical phenotype, how sulfonylureas exert their therapeutic effects, and why their efficacy varies with individual mutations.

Successful transition to sulfonylurea therapy in two Iraqi siblings with neonatal diabetes mellitus and iDEND syndrome due to ABCC8 mutation

Neonatal diabetes is a rare form of monogenic diabetes characterised by persistent hyperglycaemia during the first 6-9 months of age. About half of the cases of neonatal diabetes are transient forms resulting from mutations in the genes in the imprinted region of chromosome 6q24 and the other half are permanent forms. Activating mutations in the potassium ATP (KATP) channels encoded by the genes KCNJ11 and ABCC8 are responsible for the majority of permanent neonatal diabetes mellitus (PNDM). Mutations in KATP channels can be associated with Developmental delay, Epilepsy and Neonatal Diabetes (DEND) syndrome. Intermediate DEND (iDEND) syndrome is a rare mild form of DEND syndrome. Successful transition from insulin to sulphonyl urea (SU) agents in patients with PNDM due to KCNJ11 mutations and in patients with intermediate DEND syndrome due to KCNJ11 mutation have been reported in the literature. To our knowledge, the successful transition of PNDM with DEND due to ABCC8 mutation has only been reported only once before in the literature. We report the successful transition from insulin to SU in two Iraqi siblings with PNDM due to ABCC8 mutation, one with iDEND.

Patients with KCNJ11-related diabetes frequently have neuropsychological impairments compared with sibling controls

AIMS

KCNJ11-related diabetes is the most common form of permanent neonatal diabetes and has been associated with a spectrum of neurodevelopmental problems. We compared neurodevelopmental outcomes in patients with KCNJ11 mutations and their sibling controls.

METHODS

Through our Monogenic Diabetes Registry (http://monogenicdiabetes.uchicago.edu/), we evaluated 23 patients with KCNJ11 mutations with (n = 9) and without (n = 14) global developmental delay successfully treated with sulfonylurea and 20 healthy sibling controls, using a battery of targeted neuropsychological and behavioural assessments with scaled scores that are comparable across a wide range of ages.

RESULTS

Patients with KCNJ11-related diabetes without global developmental delay had significant differences compared with sibling controls on a range of assessments including IQ, measures of academic achievement and executive function. KCNJ11 patients with global delay exhibited significant differences in behavioural symptoms with a tendency to avoid social contact and displayed a reduced ability to adapt to new circumstances. Parents reported more immature behaviour, gross mood swings, bizarre thoughts, other unusual and severe behaviours, and there were also significant deficits in all subdomains of daily living skills.

CONCLUSIONS

This series represents the largest and most comprehensive study of neuropsychological and behavioural dysfunction of individuals with KCNJ11 diabetes and is the first to compare outcome with sibling controls. Our data demonstrate the variety of neurodevelopmental problems seen in those with KCNJ11 mutations, even in those without recognized global developmental delays. These data can be used to counsel families and guide structured neurodevelopmental assessments and treatments based on the initial genetic diagnosis in patients with neonatal diabetes.

Systemic Administration of Glibenclamide Fails to Achieve Therapeutic Levels in the Brain and Cerebrospinal Fluid of Rodents

Activating mutations in the Kir6.2 (KCNJ11) subunit of the ATP-sensitive potassium channel cause neonatal diabetes (ND). Patients with severe mutations also suffer from neurological complications. Glibenclamide blocks the open KATP channels and is the treatment of choice for ND. However, although glibenclamide successfully restores normoglycaemia, it has a far more limited effect on the neurological problems. To assess the extent to which glibenclamide crosses the blood-brain barrier (BBB) in vivo, we quantified glibenclamide concentrations in plasma, cerebrospinal fluid (CSF), and brain tissue of rats, control mice, and mice expressing a human neonatal diabetes mutation (Kir6.2-V59M) selectively in neurones (nV59M mice). As only small sample volumes can be obtained from rodents, we developed a highly sensitive method of analysis, using liquid chromatography tandem mass spectrometry acquisition with pseudo-selected reaction monitoring, achieving a quantification limit of 10ng/ml (20nM) glibenclamide in a 30μl sample. Glibenclamide was not detectable in the CSF or brain of rats after implantation with subcutaneous glibenclamide pellets, despite high plasma concentrations. Further, one hour after a suprapharmacological glibenclamide dose was administered directly into the lateral ventricle of the brain, the plasma concentration was twice that of the CSF. This suggests the drug is rapidly exported from the CSF. Elacridar, an inhibitor of P-glycoprotein and breast cancer resistance protein (major multidrug resistance transporters at the BBB), did not affect glibenclamide levels in CSF and brain tissue. We also identified a reduced sensitivity to volatile anaesthetics in nV59M mice and showed this was not reversed by systemic delivery of glibenclamide. Our results therefore suggest that little glibenclamide reaches the central nervous system when given systemically, that glibenclamide is rapidly removed across the BBB when given intracranioventricularly, and that any glibenclamide that does enter (and is below our detection limit) is insufficient to influence neuronal function as assessed by anaesthesia sensitivity.