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To report a novel mutation associated with developmental delay, epilepsy, and neonatal diabetes—DEND Syndrome, responsive to a novel management combination. We describe the investigation, treatment, and genetic diagnosis of a newborn diagnosed with DEND syndrome. The patient was found to be de-novo heterozygous for pathogenic KCNJ11 missense variant: c.190G > A, p. (Val64Met), associated with DEND syndrome, responsive to a combination of super high doses of sulfonylurea (SU) and oral high-dose steroids. A single case was reported so far due to this mutation, presenting with severe DEND syndrome, treated by insulin only. His phenotypic description and management during 18 months, demonstrates this mutation is responsive to super-high doses of SU combined with high dose 6 weeks steroids protocol. We have identified a heterozygous missense mutation as the etiology for severe DEND syndrome in a one-day old neonate, presenting with asymptomatic hyperglycemia, responsive to a novel management combination.

Developmental delay, epilepsy, and neonatal diabetes (DEND) syndrome, the most severe end of neonatal diabetes mellitus, is caused by mutation in the ATP-sensitive potassium (KATP) channel. In addition to diabetes, DEND patients present muscle weakness as one of the symptoms, and although the muscle weakness is considered to originate in the brain, the pathological effects of mutated KATP channels in skeletal muscle remain elusive. Here, we describe the local effects of the KATP channel on muscle by expressing the mutation present in the KATP channels of the DEND syndrome in the murine skeletal muscle cell line C2C12 in combination with computer simulation. The present study revealed that the DEND mutation can lead to a hyperpolarized state of the muscle cell membrane, and molecular dynamics simulations based on a recently reported high-resolution structure provide an explanation as to why the mutation reduces ATP sensitivity and reveal the changes in the local interactions between ATP molecules and the channel.

Background There are very few reports pertaining to Indian patients with neonatal diabetes mellitus (NDM). Activating or gain of function mutations of KATP channel genes namely KCNJ11 and ABCC8 are most predominant cause of permanent neonatal diabetes mellitus (PNDM). Objectives To identify the genotype-phenotype correlation of KATP channel gene defects in a large series of (n = 181) Indian PNDM patients. Methods Direct sequencing of all exons of KCNJ11 and ABCC8 genes in all 181 patients with PNDM were performed. Clinical and biochemical data were collected. Results We have identified the molecular basis of KATP -NDM in 39 out of 181 patients (22%). Of these, 20 had KCNJ11 mutations and 19 had ABCC8 mutations, thus comprising 51% of KCNJ11 and 49% of ABCC8. There were four novel mutations (D1128Tfs*16, Y1287C, S1422T, and H1537R) in ABCC8 gene. Three patients with KCNJ11 mutations had developmental delay with DEND syndrome. In patients with ABCC8 mutations developmental delay was seen in seven out of 19 (36.8%). Of this, three patients (15.7%) had DEND phenotype and four (21%) had iDEND. Of the 39 patients, 33 (84%) patients were shifted to sulfonylurea therapy (glibenclamide). Of this, 19(57.5%) patients harbored KCNJ11 mutations and 14(42.1%) ABCC8 mutations. Conclusions This is the first largest study in NDM patients in India demonstrating the importance of KATP channel gene mutation screening in PNDM and efficacy of glibenclamide for Indian patients with KATP -PNDM. The success rate of transfer is more in patients with KCNJ11 mutations compared with those with ABCC8 mutations.

Significance Gain-of-function (GOF) mutations in the ATP-sensitive potassium (K ATP ) channel cause neonatal diabetes, with some individuals exhibiting developmental delay, epilepsy, and neonatal diabetes (DEND) syndrome. In this study, we uncover the direct effects of neuronal expression of K ATP -GOF mutations, and not diabetes per se, on the neurological features of DEND. Our results show a close link between neuronal K ATP -GOF expression and cognitive dysfunction in DEND and reveal that antidiabetic sulfonylureas, which successfully treat diabetes, mitigate some sensorimotor problems but not cognitive deficits. These results have critical implications for humans, revealing the need for novel drugs to treat learning and memory deficits not only for K ATP -induced DEND but also for other pathologies arising from altered ion channels in the brain.

To explore the relationship of phenotype and genotype of neonatal diabetes mellitus (NDM) in southwestern China. Sixteen cases of NDM admitted to Children’s Hospital of Chongqing Medical University from May 2009 to May 2019 were included in this study. The clinical features of the included infants were retrospectively analyzed. Peripheral blood samples of the patients and their parents were collected for mutation detection. Among the 16 cases of NDM, 8 cases were permanent neonatal diabetes mellitus (PNDM) (including 3 clinical syndromes), and 3 cases were transient neonatal diabetes mellitus (TNDM). Mutation detection was performed in six cases. The mutation genes and their loci were FOXP3 p.V408M, KCNJ11 p.C166Y, ABCC8 p.S830P, KCNJ11 p.I182T, KCNJ11 p.G334D, and ZFP57 p.R125X,412. ABCC8 p.S830P was the new found pathogenic site of gene mutation. According to the clinical features and follow-up results, one case was diagnosed as IPEX syndrome, two as DEND syndrome, two as simple PNDM, and one as TNDM. All the TNDM could spontaneously alleviate and then insulin was withdrawn. In PNDM, 75% of those with KATP channel gene mutation could be completely or partially converted to oral sulfonylureas treatment, however, the rest cases needed lifelong insulin replacement therapy. The clinical manifestations and treatment regimens of patients with NDM vary according to the type of gene mutation. Even the same mutant genotype has differences in phenotype and response to treatment.

Mutations in KCNJ11 gene cause a variety of persistent neonatal diabetes mellitus syndromes (PNDM), with and without developmental delay and epilepsy presentations (developmental delay, epilepsy, and neonatal diabetes - DEND Syndrome). We report a heterozygous mutation for pathogenic KCNJ11 missense variant: c.190G>A, p. (Val64Met), reported once so far, associated with severe epilepsy and neurological deterioration phenotype, responsive to a combination of super high doses of Glibenclamide (Sulfonylurea) and oral steroids. We had the patient attached to continuous glucose monitoring, performed electroencephalogramic tracings, magnetic resonance imaging and whole exome sequencing on parents and patient DNA and Sanger sequencing (SS) on candidate gene mutations. His phenotypic description and management during 18 months, demonstrates this mutation is responsive to super-high doses of SU combined with high dose 6 weeks steroids protocol. In conclusion, we have identified a de novo heterozygous missense mutation as the etiology for severe DEND syndrome in a one day old neonate, presenting with asymptomatic hyperglycemia, responsive to a novel management combination.

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.

In this study, we present a case of developmental delay, epilepsy and neonatal diabetes (DEND) syndrome in a young male patient with the R50P mutation located in the Kir6.2 subunit of the ATP-sensitive K(+) (KATP) channel. Whereas most patients with DEND syndrome are resistant to sulfonylurea therapy, our patient was responsive to sulfonylurea, lacked the most common neurological symptoms, such as epilepsy, but refused to drink water. His serum electrolytes and plasma osmolarity were normal but the serum vasopressin level was increased. To investigate the underlying mechanism of his water intake disorder, a 5 μL aliquot of 340 μM KATP channel opener diazoxide or 100 μM KATP channel inhibitor glibenclamide was injected into the third ventricle of the rat brain, and water intake was monitored. Although the injection of glibenclamide had no effect, injection of diazoxide significantly increased water intake by about 1.5 fold without affecting food intake. This result indicates that the KATP channel activity in the brain may have an influence on water intake. Here, we present the first case of a DEND syndrome-afflicted patient with water intake disorder and increased serum vasopressin level, possibly related to altered KATP channel activity.

The ATP-sensitive potassium (KATP) channel formed by the inwardly rectifying potassium channel Kir6.2 and the sulfonylurea receptor 1 (SUR1) plays a key role in regulating insulin secretion. Genetic mutations in KCNJ11 or ABCC8 which encode Kir6.2 and SUR1 respectively are major causes of insulin secretion disorders: those causing loss of channel function lead to congenital hyperinsulinism, whereas those causing gain of channel function result in neonatal diabetes and in some cases developmental delay, epilepsy, and neonatal diabetes, referred to as the DEND syndrome. Understanding how disease mutations disrupt channel expression and function is important for disease diagnosis and for devising effective therapeutic strategies. Here, we describe a workflow including several biochemical and functional assays to assess the effects of mutations on channel expression and function.

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.

BACKGROUND: Patients with permanent neonatal diabetes usually present within the first three months of life and require insulin treatment. In most, the cause is unknown. Because ATP-sensitive potassium (K(ATP)) channels mediate glucose-stimulated insulin secretion from the pancreatic beta cells, we hypothesized that activating mutations in the gene encoding the Kir6.2 subunit of this channel (KCNJ11) cause neonatal diabetes. METHODS: We sequenced the KCNJ11 gene in 29 patients with permanent neonatal diabetes. The insulin secretory response to intravenous glucagon, glucose, and the sulfonylurea tolbutamide was assessed in patients who had mutations in the gene. RESULTS: Six novel, heterozygous missense mutations were identified in 10 of the 29 patients. In two patients the diabetes was familial, and in eight it arose from a spontaneous mutation. Their neonatal diabetes was characterized by ketoacidosis or marked hyperglycemia and was treated with insulin. Patients did not secrete insulin in response to glucose or glucagon but did secrete insulin in response to tolbutamide. Four of the patients also had severe developmental delay and muscle weakness; three of them also had epilepsy and mild dysmorphic features. When the most common mutation in Kir6.2 was coexpressed with sulfonylurea receptor 1 in Xenopus laevis oocytes, the ability of ATP to block mutant K(ATP) channels was greatly reduced. CONCLUSIONS: Heterozygous activating mutations in the gene encoding Kir6.2 cause permanent neonatal diabetes and may also be associated with developmental delay, muscle weakness, and epilepsy. Identification of the genetic cause of permanent neonatal diabetes may facilitate the treatment of this disease with sulfonylureas.

Inwardly rectifying potassium channels (Kir channels) control cell membrane K + fluxes and electrical signaling in diverse cell types. Heterozygous mutations in the human Kir6.2 gene ( KCNJ11 ), the pore-forming subunit of the ATP-sensitive (K ATP ) channel, cause permanent neonatal diabetes mellitus (PNDM). For some mutations, PNDM is accompanied by marked developmental delay, muscle weakness, and epilepsy (severe disease). To determine the molecular basis of these different phenotypes, we expressed wild-type or mutant (R201C, Q52R, or V59G) Kir6.2/sulfonylurea receptor 1 channels in Xenopus oocytes. All mutations increased resting whole-cell K ATP currents by reducing channel inhibition by ATP, but, in the simulated heterozygous state, mutations causing PNDM alone (R201C) produced smaller K ATP currents and less change in ATP sensitivity than mutations associated with severe disease (Q52R and V59G). This finding suggests that increased K ATP currents hyperpolarize pancreatic beta cells and impair insulin secretion, whereas larger K ATP currents are required to influence extrapancreatic cell function. We found that mutations causing PNDM alone impair ATP sensitivity directly (at the binding site), whereas those associated with severe disease act indirectly by biasing the channel conformation toward the open state. The effect of the mutation on ATP sensitivity in the heterozygous state reflects the different contributions of a single subunit in the Kir6.2 tetramer to ATP inhibition and to the energy of the open state. Our results also show that mutations in the slide helix of Kir6.2 (V59G) influence the channel kinetics, providing evidence that this domain is involved in Kir channel gating, and suggest that the efficacy of sulfonylurea therapy in PNDM may vary with genotype.

Neonatal diabetes is a genetically heterogeneous disorder with nine different genetic aetiologies reported to date. Heterozygous activating mutations in the KCNJ11 gene encoding Kir6.2, the pore-forming subunit of the ATP-sensitive potassium (K(ATP)) channel, are the most common cause of permanent neonatal diabetes. The sulphonylurea receptor (SUR) SUR1 serves as the regulatory subunit of the K(ATP) channel in pancreatic beta cells. We therefore hypothesized that activating mutations in the ABCC8 gene, which encodes SUR1, might cause neonatal diabetes. We identified a novel heterozygous mutation, F132L, in the ABCC8 gene of a patient with severe developmental delay, epilepsy and neonatal diabetes (DEND syndrome). This mutation had arisen de novo and was not present in 150 control chromosomes. Residue F132 shows evolutionary conservation across species and is located in the first set of transmembrane helices (TMD0) of SUR1, which is proposed to interact with Kir6.2. Functional studies of recombinant K(ATP) channels demonstrated that F132L markedly reduces the sensitivity of the K(ATP) channel to inhibition by MgATP and this increases the whole-cell K(ATP) current. The functional consequence of this ABCC8 mutation mirrors that of KCNJ11 mutations causing neonatal diabetes and provides new insights into the interaction of Kir6.2 and SUR1. As SUR1 is expressed in neurones as well as in beta cells, this mutation can account for both neonatal diabetes and the neurological phenotype. Our results demonstrate that SUR1 mutations constitute a new genetic aetiology for neonatal diabetes and that they act by reducing the K(ATP) channel's ATP sensitivity.

Heterozygous, activating mutations of KCNJ11 encoding the pore-forming subunit (Kir 6.2) of the ATP-sensitive potassium channel (KATP) are the most prevalent cause of diabetes with onset in the first 6 months of life [1]. Rarely, KCNJ11 mutations are associated with diabetes that presents later in childhood or adulthood [2]. Kir6.2 is expressed not only in the pancreatic beta cell, but also in skeletal muscle, peripheral nerves, and especially brain [3], likely the explanation for a more severe condition termed developmental delay, epilepsy, and neonatal diabetes (DEND syndrome) that can result from rare KCNJ11 missense mutations [3, 4]. Patients with DEND syndrome have motor and speech delay and are often unable to talk and walk without aid. In addition, they suffer from epilepsy that generally occurs before 1 yr of age [3, 4]. In contrast, an intermediate form of the syndrome (iDEND), i.e.. with no epilepsy. is more frequent and less severe [1, 3, 5-8]. Identification of KCNJ11 mutations has important therapeutic consequences, as most patients respond to oral treatment with the sulfonylurea (SU) class of anti-diabetic drugs and can be totally weaned from insulin injections, reaching an excellent, long-lasting metabolic control [9-11]. In addition, motor function and other neurological consequences may be improved by SU treatment [3, 7, 12-14], although some patients with DEND may fail to favorably respond even to very high doses of SU [4, 9].

Non-technical summary Neonatal diabetes is a rare genetic form of diabetes that develops within the first 6 months of life. It is often caused by genetic defects (mutations) in a specialised membrane protein known as the KATP channel. This protein acts as a tiny pore in the membrane of the insulin-secreting cells in the pancreas and its opening and closing is regulated by blood glucose levels. Low blood glucose holds the pore open and prevents insulin secretion whereas high blood sugar leads to channel closure and insulin secretion. We identified a novel mutation (Kir6.2-W68R) that prevents channel closure and insulin secretion, and so results in neonatal diabetes. Detailed molecular studies showed that channel opening and closing is disrupted, suggesting Kir6.2-W68 may act as a channel ‘gatekeeper’. Our results also indicated that the mutant channel could be shut by sulphonylurea drugs, which enabled the patient to transfer from insulin injections to tablet therapy. Abstract We identified a novel heterozygous mutation, W68R, in the Kir6.2 subunit of the ATP-sensitive potassium (KATP) channel, in a patient with transient neonatal diabetes. This tryptophan is absolutely conserved in mammalian Kir channels. The functional effects of mutations at residue 68 of Kir6.2 were studied by heterologous expression in Xenopus oocytes, and by homology modelling. We found the Kir6.2-W68R mutation causes a small reduction in ATP inhibition in the heterozygous state and an increase in the whole-cell KATP current. This can explain the clinical phenotype of the patient. The effect of the mutation was not charge or size dependent, the order of potency for ATP inhibition being W

Interest in Morvan's disease or syndrome has grown, owing to its close links with various potassium channelopathies. Potassium is crucial for gating mechanisms (channel opening and closing), and especially for repolarization. Defective potassium regulation can lead to neuronal hyperexcitability. There are three families of potassium channels: voltage-gated potassium channels or VGKC (Kv1.1-Kv1.8), inward rectifier K+ channels (Kir), and two-pore channels (K2p). VGK channels are the commonest, and especially those belonging to the Shaker group (neuromyotonia and Morvan's syndrome, limbic encephalitis, and type 1 episodic ataxia). Brain and heart K+ channelopathies are a separate group due to KCNQ1 mutation (severe type 2 long QT syndrome). Kv7 channel mutations (in KNQ2 and KCNQ3) are responsible for benign familial neonatal seizures. Mutation of the Ca+ activated K+ channel gene causes epilepsy and paroxysmal dyskinesia. Inward rectifier K+ channels regulate intracellular potassium levels. The DEND syndrome, a treatable channelopathy of the brain and pancreas, is due to KCNJ1 mutation. Andersen's syndrome, due to KCNJ2 mutation, is characterized by periodic paralysis, cardiac arrythmia, and dysmorphia. Voltage-insensitive K2p channelopathies form a final group.

Assembly of an inward rectifier K+ channel pore (Kir6.1/Kir6.2) and an adenosine triphosphate (ATP)-binding regulatory subunit (SUR1/SUR2A/SUR2B) forms ATP-sensitive K+ (KATP) channel heteromultimers, widely distributed in metabolically active tissues throughout the body. KATP channels are metabolism-gated biosensors functioning as molecular rheostats that adjust membrane potential-dependent functions to match cellular energetic demands. Vital in the adaptive response to (patho)physiological stress, KATP channels serve a homeostatic role ranging from glucose regulation to cardioprotection. Accordingly, genetic variation in KATP channel subunits has been linked to the etiology of life-threatening human diseases. In particular, pathogenic mutations in KATP channels have been identified in insulin secretion disorders, namely, congenital hyperinsulinism and neonatal diabetes. Moreover, KATP channel defects underlie the triad of developmental delay, epilepsy, and neonatal diabetes (DEND syndrome). KATP channelopathies implicated in patients with mechanical and/or electrical heart disease include dilated cardiomyopathy (with ventricular arrhythmia; CMD1O) and adrenergic atrial fibrillation. A common Kir6.2 E23K polymorphism has been associated with late-onset diabetes and as a risk factor for maladaptive cardiac remodeling in the community-at-large and abnormal cardiopulmonary exercise stress performance in patients with heart failure. The overall mutation frequency within KATP channel genes and the spectrum of genotype–phenotype relationships remain to be established, while predicting consequences of a deficit in channel function is becoming increasingly feasible through systems biology approaches. Thus, advances in molecular medicine in the emerging field of human KATP channelopathies offer new opportunities for targeted individualized screening, early diagnosis, and tailored therapy.

ATP-sensitive potassium (K(ATP)) channels play a key role in glucose-dependent insulin secretion in pancreatic beta-cells. Recently, activating mutations in beta-cell K(ATP) channels were found to be an important cause of neonatal diabetes. In some patients, these mutations may also affect K(ATP) channel function in muscles, nerves and brain which can result in a severe disease termed DEND syndrome (Developmental delay, Epilepsy and Neonatal Diabetes). This review focuses on mutations in the pore-forming K(ATP) channel subunit (Kir6.2) that cause neonatal diabetes and discusses recent advances in our understanding of clinical features of neonatal diabetes, its underlying molecular mechanisms and their impact on treatment.

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.

Activating mutations in the Kir6.2 subunit of the adenosine triphosphate-sensitive potassium (KATP) channel is a cause of neonatal diabetes associated with various neurological disorders that include developmental delay, epilepsy, and neonatal diabetes (known together as DEND syndrome). This article reports a girl who developed infantile spasms and early onset diabetes mellitus at the age of 3 months and revealed DEND syndrome with a heterozygous activating mutation in Kir6.2. Infantile spasms with hypsarrhythmia on the electroencephalogram were severe and refractory to steroids. Steroids combined with oral sulfonylurea, a drug that closes the ATP-sensitive potassium channel by an independent mechanism, allowed partial and transitory control of the epilepsy. However, the child still exhibited severe encephalopathy and died of aspiration pneumonia. The role of oral sulfonylurea as an anticonvulsant in DEND syndrome associated with Kir6.2 mutation is discussed.

Activating mutations in the genes encoding the ATP-sensitive potassium (K(ATP)) channel subunits Kir6.2 and SUR1 are a common cause of neonatal diabetes. Here, we analyse the molecular mechanism of action of the heterozygous mutation F132L, which lies in the first set of transmembrane helices (TMD0) of SUR1. This mutation causes severe developmental delay, epilepsy and permanent neonatal diabetes (DEND syndrome). We show that the F132L mutation reduces the ATP sensitivity of K(ATP) channels indirectly, by altering the intrinsic gating of the channel. Thus, the open probability is markedly increased when Kir6.2 is co-expressed with mutant TMD0 alone or with mutant SUR1. The F132L mutation disrupts the physical interaction between Kir6.2 and TMD0, but does not alter the plasmalemma channel density. Our results explain how a mutation in an accessory subunit can produce enhanced activity of the K(ATP) channel pore (formed by Kir6.2). They also provide further evidence that interactions between TMD0 of SUR1 and Kir6.2 are critical for K(ATP) channel gating and identify a residue crucial for this interaction at both physical and functional levels.

Mutations in the pancreatic ATP-sensitive K+ channel (KATP channel) cause permanent neonatal diabetes mellitus (PNDM) in humans. All of the KATP channel mutations examined result in decreased ATP inhibition, which in turn is predicted to suppress insulin secretion. Here we describe a patient with severe PNDM, which includes developmental delay and epilepsy, in addition to neonatal diabetes (developmental delay, epilepsy, and neonatal diabetes [DEND]), due to a G334D mutation in the Kir6.2 subunit of KATP channel. The patient was wholly unresponsive to sulfonylurea therapy (up to 1.14 mg · kg−1 · day−1) and remained insulin dependent. Consistent with the putative role of G334 as an ATP-binding residue, reconstituted homomeric and mixed WT+G334D channels exhibit absent or reduced ATP sensitivity but normal gating behavior in the absence of ATP. In disagreement with the sulfonylurea insensitivity of the affected patient, the G334D mutation has no effect on the sulfonylurea inhibition of reconstituted channels in excised patches. However, in macroscopic rubidium-efflux assays in intact cells, reconstituted mutant channels do exhibit a decreased, but still present, sulfonylurea response. The results demonstrate that ATP-binding site mutations can indeed cause DEND and suggest the possibility that sulfonylurea insensitivity of such patients may be a secondary reflection of the presence of DEND rather than a simple reflection of the underlying molecular basis.

Aims/hypothesis Activating mutations in the KCNJ11 gene encoding the Kir6.2 subunit of the K-ATP channels in pancreatic beta cells are a common cause of neonatal diabetes. One-third of patients also have developmental delay, which probably results from mutated K-ATP channels in muscle, nerve and brain. Sulfonylureas, which bind to the sulfonylurea receptor 1 subunit of the K-ATP channel, can replace insulin injections in patients with KCNJ11 mutations. The aim of this study was to investigate the long-term outcome and impact on neurological features of sulfonylurea treatment.Methods We report the response to sulfonylurea treatment in a boy with neonatal diabetes and marked developmental delay resulting from the KCNJ11 mutation V59M.Results Glibenclamide (glyburide) treatment was started at 23 months and resulted in insulin being discontinued, lower overall glycaemia, reduced glucose fluctuations and reduced hypoglycaemia. Good control (HbA(1c) 6.5%) was maintained 2 years after discontinuing insulin, despite a reduction in the glibenclamide dose (from 0.41 to 0.11 mg center dot kg(-1)center dot day(-1)). Within 1 month of starting glibenclamide there was marked improvement in motor function, resulting in the patient progressing from being unable to stand unaided to walking independently, but there was no improvement in mental function.Conclusions/interpretation This 2-year follow-up of a patient highlights that sulfonylurea treatment can result in prolonged, excellent glycaemic control and may improve motor features, but not mental features, associated with KCNJ11 mutations. This suggests that the neurological actions of sulfonylurea are initially principally on peripheral (nerve or muscle) rather than on central (brain) K-ATP channels. Early molecular diagnosis is important in patients with neonatal diabetes and neurological features.

Background The ATP-sensitive potassium (KATP) channel, composed of the beta-cell proteins sulfonylurea receptor (SUR1) and inward-rectifying potassium channel subunit Kir6.2, is a key regulator of insulin release. It is inhibited by the binding of adenine nucleotides to subunit Kir6.2, which closes the channel, and activated by nucleotide binding or hydrolysis on SUR1, which opens the channel. The balance of these opposing actions determines the low open-channel probability, PO, which controls the excitability of pancreatic beta cells. We hypothesized that activating mutations in ABCC8, which encodes SUR1, cause neonatal diabetes. Methods We screened the 39 exons of ABCC8 in 34 patients with permanent or transient neonatal diabetes of unknown origin. We assayed the electrophysiologic activity of mutant and wild-type KATP channels. Results We identified seven missense mutations in nine patients. Four mutations were familial and showed vertical transmission with neonatal and adult-onset diabetes; the remain...

Closure of ATP-sensitive K+ channels (KATP channels) in response to metabolically generated ATP or binding of sulfonylurea drugs stimulates insulin release from pancreatic β-cells. Heterozygous gain-of-function mutations in the KCJN11 gene encoding the Kir6.2 subunit of this channel are found in ∼47% of patients diagnosed with permanent diabetes at transient neonatal diabetes > permanent neonatal diabetes > DEND syndrome channels. Sulfonylureas still close mutated KATP channels, and many patients can discontinue insulin injections and show improved glycemic control when treated with high-dose sulfonylurea tablets. In conclusion, the finding that Kir6.2 mutations can cause neonatal diabetes has enabled a new therapeutic approach and shed new light on the structure and function of the Kir6.2 subunit of the KATP channel.

Permanent neonatal diabetes (PNDM) is diagnosed in the first three months of life and is a major management problem as patients require lifelong insulin injections. Recently, activating mutations in the KCNJ11 gene which encodes the Kir6.2 subunit of the KATP channels in the pancreatic beta-cells were found to be an important cause of PNDM. The mutated KATP channels do not close in the presence of adenosine triphosphate (ATP) so the beta-cell membrane is hyperpolarized and insulin secretion does not occur. Some patients have DEND syndrome (developmental delay, epilepsy and neonatal diabetes) with the neurological features arising from mutated KATP channels in muscle, nerve and brain. Defining a genetic aetiology has not only given insights into clinical classification and disease mechanism, but has also influenced treatment. Sulphonylureas, by binding the sulphonylurea receptor, can close the KATP channel. This has led to patients who were insulin-dependent being able to discontinue insulin injections and achieve excellent control with sulphonylurea tablets. In this article we discuss the work that established Kir6.2 mutations as a common cause of neonatal diabetes, the clinical features, the underlying mechanism and the impact on patient treatment.

Permanent neonatal diabetes mellitus (PNDM) is a rare condition characterized by severe hyperglycemia constantly requiring insulin treatment from its onset. Complete deficiency of glucokinase (GCK) can cause PNDM; however, the genetic etiology is unknown in most PNDM patients. Recently, heterozygous activating mutations of KCNJ11, encoding Kir6.2, the pore forming subunit of the ATP-dependent potassium (KATP) channel of the pancreatic b-cell, were found in patients with PNDM. Closure of the KATP channel exerts a pivotal role in insulin secretion by modifying the resting membrane potential that leads to insulin exocytosis. We screened the KCNJ11 gene in 12 Italian patients with PNDM (onset within 3 months from birth) and in six patients with non-autoimmune, insulin-requiring diabetes diagnosed during the first year of life. Five different heterozygous mutations were identified: c.149G>C (p.R50P), c.175G>A (p.V59M), c.509A>G (p.K170R), c.510G>C (p.K170N), and c.601C>T (p.R201C) in eight patients with diabetes diagnosed between day 3 and 182. Mutations at Arg50 and Lys170 residues are novel. Four patients also presented with motor and/or developmental delay as previously reported. We conclude that KCNJ11 mutations are a common cause of PNDM either in isolation or associated with developmental delay. Permanent diabetes of non autoimmune origin can present up to 6 months from birth in individuals with KCNJ11 and EIF2AK3 mutations. Therefore, we suggest that the acronym PNDM be replaced with the more comprehensive permanent diabetes mellitus of infancy (PDMI), linking it to the gene product (e.g., GCK-PDMI, KCNJ11-PDMI) to avoid confusion between patients with early-onset, autoimmune type 1 diabetes. Hum Mutat 25:22–27, 2005. r 2004 Wiley-Liss, Inc.

Permanent neonatal diabetes mellitus (PNDM) is a rare form of diabetes characterized by insulin-requiring hyperglycemia that is diagnosed within the first months of life. Recently, activating mutations in the gene encoding the ATP-sensitive potassium-channel subunit Kir6.2 were identified in 10 PNDM patients. Tolbutamide-stimulated insulin secretion, demonstrated in 3 of these patients suggested that some PNDM patients may respond to oral sulfonylurea treatment. In this report, we describe an infant with PNDM due to an arginine-to-histidine substitution at position 201 (R201H) of the gene encoding Kir6.2. After insulin pump therapy for six months, he was shifted to oral glybenclamide therapy at a daily dose of 0.8 mg/kg. Basal c-peptide level increased by two fold during glybenclamide treatment, but no further elevation was observed following intravenous glucose administration. Outpatient, continuous glucose monitoring while on a normal infant diet demonstrated a marked improvement in glycemic control. This study demonstrates the feasibility of oral sulfonylurea treatment in PNDM patients with Kir6.2 mutations even during infancy, and the superiority of this approach over insulin administration.

To the Editor: Permanent neonatal diabetes mellitus (PNDM) is mainly caused by activating mutations in the KCNJ11 or ABCC8 genes, encoding respectively the Kir6.2 and sulfonylurea receptor (SUR)1 subunits of the KATP channels in the pancreatic beta cells [1–3]. Developmental delay, epilepsy and neonatal diabetes syndrome (DEND) represents the most severe clinical form of PNDM [4]. Besides diabetes mellitus patients exhibit severe developmental delay, hypotonia and therapy-resistant epilepsy. As KCNJ11 and ABCC8 are expressed in neuronal tissue the neurological features in DEND syndrome are postulated to result from mutated KATP channels in the brain. Only a few cases of DEND syndrome have been described. More common is a milder clinical picture, without generalised epilepsy and with less severe developmental delay, referred to as intermediate DEND. Since 2006 many patients with PNDM due to KCNJ11 and ABCC8 mutations have been completely transferred from insulin to sulfonylurea drugs [5, 6]. However, in DEND syndrome only cases of intermediate DEND were sulfonylurea-responsive [7, 8]. Shimomura and colleagues reported the first patient with severe DEND syndrome, due to a KCNJ11 mutation, who did completely switch to sulfonylurea drugs [4]. Here we report a case of DEND syndrome due to a novel ABCC8 mutation and successful transfer to sulfonylurea treatment. A boy was born as second child of non-consanguineous white parents following an uneventful pregnancy and spontaneous term delivery. His birthweight was low (2,700 g, −2 standard deviation score [SDS]). At 7 weeks of age he presented with failure to thrive (weight 3,140 g, −3.8 SDS), severe hyperglycaemia (blood glucose 42 mmol/l), glucosuria, and ketoacidosis. Physical examination revealed severe generalised hypotonia without dysmorphic features or other abnormalities. Islet cell auto antibodies, serum insulin and C-peptide were undetectable. Abdominal ultrasound examination demonstrated a normally developed pancreas. Neonatal diabetes mellitus was concluded and continuous intravenous insulin therapy was started followed by continuous subcutaneous insulin pump therapy. This resulted in good glycaemic control without significant hypoglycaemia. At the age of 5 months HbA1c was 7.2% and catch-up growth (weight −2 SDS) was observed. On the tenth day of admission, at the age of 2 months, he developed frequent subtle seizures unresponsive to increasing doses of the anti-epileptic drug phenobarbital. EEG examination showed a burst-suppression pattern (abnormal for the age of 8.5 weeks) and epileptic discharges later on. At the age of 3 months the seizures progressed to infantile spasms and EEG examination demonstrated a slowed high-voltage background pattern with multifocal epileptic discharges consistent with hypsarrhythmia and unresponsive to various antiepileptic drugs (phenobarbital, nitrazepam, adrenocorticotropic hormone and vigabatrin). At age 5 months the boy was severely hypotonic, with no visual contact, no babbling, hardly any facial expression and a psychomotor developmental age of 1 month. Magnetic resonance imaging of the brain at that age demonstrated no structural abnormalities but mild atrophy of frontal–temporal regions. DEND syndrome was suspected and the boy was tested for KATP channel defects. Genomic DNA isolated from peripheral lymphocytes was analysed by direct sequencing of all coding sequences as well as the relevant intron/exon boundaries. The KCNJ11 sequence was wild type. In exon 1 of the ABCC8 gene a monoallelic missense mutation was present (c.145A > T) that changed amino acid residue 49 from isoleucine to phenylalanine (p.I49F). This nucleotide change was not previously reported in any single-nucleotide polymorphism or mutation database, was absent in 70 control alleles and also absent in genomic DNA from both parents, indicating a de novo mutation. In an attempt to influence both glycaemic control and neurological abnormalities, at the age of 5.5 months oral glibenclamide therapy was started in a daily dose of 0.2 mg/kg body mass in two doses followed by weekly increments of 0.2 mg/kg−1 day−1. The insulin dose could gradually be reduced and after 2 months, at a glibenclamide dose of 1.6 mg/kg, insulin therapy was stopped. Side effects of glibenclamide treatment were not noticed, and there were no episodes of hypoglycaemia. Gradually the daily glibenclamide dose was tapered and at the age of 17 months he continued to have excellent glycaemic control with 1.0 mg/kg (HbA1c 5.6%). No improvement was observed in seizure control despite anti-epileptic drug treatment with high dose vigabatrin and levetiracetam. At the age of 26 months his functional psychomotor age was 3 months and he continued to have infantile spasms with unchanged EEG hypsarrhythmia. To our knowledge, this is the first report of a DEND patient with an ABCC8 mutation who successfully transfers to sulfonylurea therapy. Although functional studies were not performed the mutation is likely to be the molecular origin of the patient’s DEND syndrome, as it is a de novo mutation in a child of unaffected parents and affects an amino acid residue that shows evolutionary conservation across species. Based on the topology suggested by Conti and colleagues, amino acid residue 49 is located either in the N-terminal extracellular region or in the first predicted transmembrane domain [9]. The in silico prediction programs SIFT and PolyPhen both predicted that substitution at position 49 from isoleucine to phenylalanine would affect protein function. The excellent response to sulfonylurea treatment provides further evidence for the pathogenicity of the mutation. Shimomura and colleagues reported the first patient with severe DEND syndrome, due to a KCNJ11 mutation, who completely switched to sulfonylurea drugs [4]. Their patient also showed neurological improvement on a dose of 2.3 mg/kg, suggesting that such extremely high doses might influence neurological symptoms. In our case glucose values dropped to 3.5 mmol/l with a sulfonylurea dose of 1.6 mg/kg and further increasing the sulfonylurea dosage was thought to be contraindicated by the risk of hypoglycaemia. As the main aim in the treatment of DEND syndrome is to influence neurological dysfunction, perhaps increasing sulfonylurea doses should have been considered together with an additional treatment to prevent hypoglycaemia. Furthermore it could be speculated that rather than a drug that targets both SUR1 and SUR2 isoforms, such as glibenclamide, a SUR1-specific drug, such as gliclazide, might influence neurological symptoms more effectively as only SUR1 isoforms are present in neuronal KATP channels. It is not clear to what extent sulfonylurea drugs are hindered by the blood–brain barrier. Administering sulfonylurea drugs at a very young age, when the blood–brain barrier is still immature, might lead to better brain penetration than at later ages. This case report emphasises the importance of early genetic analysis in all cases of neonatal diabetes mellitus, including the most severely affected patients with DEND syndrome as in this group, sulfonylurea treatment may also completely restore glucose homeostasis. The effect on neurological features is a field of future research perhaps aiming at improved blood–brain barrier penetrance of sulfonylurea drugs and allowing higher doses by alternatively handling hypoglycaemia.

Introduction Benign familial neonatal seizures (BFNS) are a distinct epilepsy syndrome with selflimited seizures starting in the first days of life. The majority of cases is caused by mutations in the genes KCNQ2 and KCNQ3, encoding the voltage gated potassium channels Kv7.2 and Kv7.3. Methods and results We report on a family (index patient and his mother) with a phenotype, consisting of benign neonatal convulsions in association with transient neonatal diabetes mellitus. Sequencing of neonatal diabetes-related genes revealed the mutation p.R1379H (c.4139G>A) in ABCC8, encoding the regulating sulfonylurea receptor subunit of the ATP-sensitive potassium channel. Discussion The mutation in our family has been previously described in patients with transient neonatal diabetes mellitus (TNDM) and maturity onset diabetes of the young. While mutations in the K-ATP channel are known to cause a severe neurological disorder with developmental delay, epilepsy and neonatal diabetes (DEND syndrome), our family is the first report of associated benign familial neonatal seizures.

Mutations in the KCNJ11 gene are responsible for the majority of permanent neonatal diabetes mellitus (PNDM) cases. Some mutations in this gene, including p.Q52R, are associated with the developmental delay, epilepsy, neonatal diabetes (DEND) syndrome. We describe a patient with PNDM who had no neurological finding although she was determined to have a novel mutation (p.Q52L) in the same residue of the KCNJ11 as in the previously reported cases with DEND syndrome. This case suggests that not all Q52 mutations in the KCNJ11 gene are necessarily related to DEND syndrome.

To the Editor Diabetes caused by severe mutations in beta cell genes is usually diagnosed as neonatal diabetes [1] or MODY [2]. Activating mutations in KCJN11, the gene encoding the ATP-sensitive potassium channel subunit Kir6.2, have been described in very-early-onset diabetes ( A) was found in a single patient. This child was born at 40 weeks’ gestation and weighed 2,450 g. He was diagnosed with diabetes during the third week of life based on a plasma glucose of 35–50 mmol/l, without ketoacidosis, which was measured when he presented with pneumonia and bilateral acute otitis media. The patient was treatedwith insulin, with a dose of 0.7–1.0 U/kg used initially and subsequently decreased. At 9 years, 11 months he weighed 27.5 kg and his daily insulin requirement was 7 U (0.25 U/kg) as a single morning injection of intermediate-acting insulin. Despite little modification to his diet he rarely experienced hyperglycaemia above 11 mmol/l, and had an HbA1c level of 6.6%. These observations suggested endogenous beta cell function, which was confirmed by a fasting plasma C-peptide of 443 pmol/l (glucose 6.7 mmol/l) and an increase in plasma insulin concentration of 70 pmol/l during an IVGTT (Fig. 1). As patients with Kir6.2 diabetes may respond to sulphonylureas, we assessed whether this patient could successfully transfer to sulphonylurea tablets [3, 4]. Glipizide gastrointestinal therapeutic system (GITS), a controlledrelease sulphonylurea, was introduced [5]. A dose of 5 mg was administered for 2 days, then 10 mg; insulin was simultaneously slowly withdrawn over a period of 5 days. As the patient experienced a few mild hypoglycaemic episodes during the first 2 days after the discontinuation of insulin the glipizide GITS dose was decreased to 5 mg. While on this dose, a day profile of his capillary glucose concentrations revealed that they were between 4 and 6 mmol/l; a result confirmed by a 72-h record obtained using a continuous glucose monitoring system (Medtronic, Northridge, CA, USA). The IVGTT was repeated 3 weeks after a stable glipizide dose was achieved. At this time the patient’s fasting glucose level was 5.4mmol/l, and his C-peptide level was 347 pmol/l. T. Klupa and E. L. Edghill contributed equally to this work

Permanent Neonatal Diabetes Mellitus (PNDM), is a rare monogenic disorder, caused by activating mutations of the KATP channel. The most severe clinical form of PNDM presents as Developmental delay, Epilepsy and Neonatal Diabetes (DEND) syndrome. Diagnosis is confirmed by genetic mutation testing. Oral sulfonylurea therapy improves neurological outcome.

Results The age at diagnosis was between 0.5 and 5 month, the median was 3 month. 7 cases (58.3%) were SGA. Infection occurred in 7 cases, 4 cases with convulsion and 8 cases with ketoacidosis. The mean HbA1c at diagnosis was 10.0% (7.4%~13.7%). Insulin treatment was started in all 12 patients, the initial dose was 1.0~1.2IU/kg/d, 6 cases were treated with glyburide after the acute phase, only one boy who diagnosed as DEND syndrome reached euglycemia. 2 cases stopped glyburide because of gastrointestinal adverse reaction. Among the 12 cases followed up, 7 had PNDM, 4 had TNDM, 1 case lost following, 2 cases died, one was the DEND syndrome patient died of DKA, the other died of hepatic and renal failure at the age of 1 year and 6 months. One had skeletal dysplasia and diagnosed as Wolcott-Rallison syndrome. The blood glucose of most patients was well controlled. KCNJ11c.175G>A (V59M) and KCNJ11c.601C>A (R201H) mutation were found in two patients.

Permanent neonatal diabetes mellitus (PNDM) is caused by mutations in the ATP-sensitive potassium channel (KATP channel) subunits. Developmental delay, epilepsy, and neonatal diabetes (DEND) syndrome is the most severe form of PNDM and is characterized by various neurologic features. We report on a patient with DEND syndrome following initial misdiagnosis with type 1 DM, who was successfully switched from insulin to sulfonylurea therapy. A 50-day-old male presented with fever and seizure, complicated by persistent hyperglycemia. Insulin therapy was initiated. At 10 months of age, the patient was unable to hold his head up and make eye contact with others. At 17.9 years of age, direct sequencing of KCNJ11 identified a heterozygous mutation of c.602G>A (p.R201H). Since then, treatment with gliclazide was initiated and the insulin dose was gradually reduced. Following 3 months, insulin was discontinued with a gliclazide dose of 2.4 mg/kg. The patient continued to have excellent glycemic control with a glycated hemoglobin (HbA1c) level of 5.8% after 5 months. However, the patient's psychomotor retardation did not improve. This study reports the first case of DEND syndrome in Korea caused by a KCNJ11 mutation and emphasizes the necessity to screen mutations in KATP channel genes in patients with neonatal diabetes.