Neonatal and very-early-onset diabetes mellitus

Genetic perspectives on childhood monogenic diabetes: Diagnosis, management, and future directions

Monogenic diabetes is caused by one or even more genetic variations, which may be uncommon yet have a significant influence and cause diabetes at an early age. Monogenic diabetes affects 1 to 5% of children, and early detection and gene-tically focused treatment of neonatal diabetes and maturity-onset diabetes of the young can significantly improve long-term health and well-being. The etiology of monogenic diabetes in childhood is primarily attributed to genetic variations affecting the regulatory genes responsible for beta-cell activity. In rare instances, mutations leading to severe insulin resistance can also result in the development of diabetes. Individuals diagnosed with specific types of monogenic diabetes, which are commonly found, can transition from insulin therapy to sulfonylureas, provided they maintain consistent regulation of their blood glucose levels. Scientists have successfully devised materials and methodologies to distinguish individuals with type 1 or 2 diabetes from those more prone to monogenic diabetes. Genetic screening with appropriate findings and interpretations is essential to establish a prognosis and to guide the choice of therapies and management of these interrelated ailments. This review aims to design a comprehensive literature summarizing genetic insights into monogenetic diabetes in children and adolescents as well as summarizing their diagnosis and mana-gement.

Structure based analysis of KATP channel with a DEND syndrome mutation in murine skeletal muscle

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 (K_ATP) 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 K_ATP channels in skeletal muscle remain elusive. Here, we describe the local effects of the K_ATP channel on muscle by expressing the mutation present in the K_ATP 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.

Postnatal growth of Infants with neonatal diabetes: insulin pump (CSII) versus Multiple Daily Injection (MDI) therapy

Background: Permanent neonatal diabetes mellitus (PNDM) is characterized by the onset of hyperglycemia within the first six months of life. Their diabetes is associated with partial or complete insulin deficiency with variable degree of intrauterine growth retardation. Insulin therapy corrects the hyperglycemia and results in improvement of growth. However, no studies have reported the longitudinal growth of these infants (head circumference, length and weight gain) after starting insulin therapy. Patients and methods: We assessed the growth parameters weight (Wt), Length (L) and head circumference (HC) in 9 infants with PNDM, during the first 2 years of their postnatal life. Five infants were on insulin pump therapy (CSII) and 4 were on multiple doses of insulin injection (MDI) therapy. Results: On insulin therapy for 20±4 months catch-up growth occurred in the majority of infants. L-SDS increased from -1.45 to -0.65 , HC-SDS from -2.3 to - 0.51 and Wt-SDS increased from -1.94 to - 0.7 at the end of the 20±4 months of age, after starting insulin therapy. Two out of 9 infants had a L-SDS <-2 , in 4 Wt-SDS was <-2 and in 1 the HC-SDS was <-2 at at 20±4 months of postnatal growth. The level of HbA_1c was lower in infants on CSII compared to those on MDI (9.6±1%) compared to those on MDI (10.2±2%). However, growth parameters improved significantly in both groups (CSII and MDI) with no significant difference among them. Conclusions: Infants with PNDM with positive anti-GAD and antiTPO were diagnosed later and their intra-uterine and postnatal growth differed compared to those with negative antibodies. The majority of infants with PNDM exhibited significant catch up growth within the first two years of life irrespective of the etiology of diabetes. HbA_1c appeared to be better in infants with PNDM on CSII therapy when compared to those on MDI therapy. (www.actabiomedica.it)

Transient Neonatal Diabetes due to a Mutation in KCNJ11 in a Child with Klinefelter Syndrome

Klinefelter syndrome is the most frequent chromosomal aneuploidy in males occurring in about 1 in 660 males. Epidemiological studies have demonstrated increased risk of type 1 diabetes and type 2 diabetes in adults with Klinefelter syndrome. There is only one previous report of neonatal diabetes in a patient with Klinefelter syndrome. We report transient neonatal diabetes due to a pathogenic heterozygous variant in KCNJ11 in a male infant with Klinefelter syndrome. A 78-day old male infant was noted to have sustained hyperglycemia with serum glucose ranging between 148 mg/dL (8.2 mmol/L) and 381 mg/dL (21.2 mmol/L) three days after undergoing a complete repair of an atrioventricular defect. Hemoglobin A1c was 6.6%. The patient was born at term with a birth weight of 2.16 kg following a pregnancy complicated by gestational diabetes that was controlled with diet. The patient was initially started on a continuous intravenous insulin drip and subsequently placed on subcutaneous insulin (glargine, human isophane and regular insulin). Insulin was gradually decreased and eventually discontinued at seven months of age. Chromosomal microarray at 11 weeks of age showed XXY and a panel-based, molecular test for neonatal diabetes revealed a pathogenic heterozygous variant c.685G>A (p.Glu229Lys) in KCNJ11. The patient is now 34 months old and continues to have normal fasting and post-prandial glucose and HbA1C levels. The patient will need prospective follow up for assessment of his glycemic status. To our knowledge this is the second reported case of neonatal diabetes in an infant with Klinefelter syndrome and the first due to a mutation in the KCNJ11 in a patient with Klinefelter syndrome.

Transient Neonatal Diabetes Mellitus: A Challenge and Opportunity for Specialized Nursing Care

Transient neonatal diabetes mellitus (TNDM) is a rare disorder, with a reported incidence of approximately 1 in 450,000 live births. It is characterized by insulin-requiring hyperglycemia in the neonatal period. The disease improves by early childhood, but the patient may relapse in later life. Diagnosis is made after genetic testing following presentation with hyperglycemia not conforming to Type 1 or Type 2 diabetes. Management is based on insulin and possible sulfonylurea administration. Three genetically distinct subtypes of TNDM are recognized. Type 1 TNDM is due to overexpression of genes at the 6q24 locus, whereas the 11p15 locus is involved in Type 2 and 3 TNDM. In this article the clinical presentation, management, and genetics of TNDM are discussed, particularly emphasizing the role of the neonatal nurse.

Epidemiology, clinical characteristics, and genetic etiology of neonatal diabetes in Japan

Neonatal diabetes mellitus (NDM) is a rare but potentially devastating metabolic disorder, with a reported incidence of one per 300 000-500 000 births generally, and hyperglycemia develops within the first 6 months of life. NDM is classified into two categories clinically. One is transient NDM (TNDM), in which insulin secretion is spontaneously recovered by several months of age, but sometimes recurs later, and the other is permanent NDM (PNDM), requiring lifelong medication. Recent molecular analysis of NDM identified at least 12 genetic abnormalities: chromosome 6q24, KCNJ11, ABCC8, INS, FOXP3, GCK, IPF1, PTF1A, EIF2AK3, GLUT2, HNF1β, and GLIS3. Of these, imprinting defects on chromosome 6q24 and the KCNJ11 mutation have been recognized as the major causes of TNDM and PNDM, respectively, in Caucasian subjects. Although the pathogenesis and epidemiology of NDM in Japan seem to be clinically distinct, they are still unclear. In this review, we summarize the epidemiology, clinical characteristics, and genetic etiology in Japanese patients with NDM compared with the data on Caucasian patients.

A seven weeks old baby with diabetic ketoacidosis: a case report

Diabetes mellitus is rare during infancy, however, it should be suspected in infants presenting with features consistent with sepsis and hyperglycemia. This is crucial in initiating the treatment of diabetes ketoacidosis which if delayed may result in significant morbidity and death.

Transient neonatal diabetes due to a missense mutation (E227K) in the gene encoding the ATP-sensitive potassium channel (KCNJ11)

Neonatal diabetes is a monogenic form of diabetes. Herein, we report on a newborn presenting diabetic ketoacidosis at 17 days of life. A KCNJ11 mutation was identified. In such cases, insulin can be replaced by sulfonylurea with a successful metabolic control, as an example of how molecular diagnosis may influence the clinical management of the disorder.

Clinical characteristics and molecular genetic analysis of 22 patients with neonatal diabetes from the South-Eastern region of Turkey: predominance of non-KATP channel mutations

BACKGROUND

Neonatal diabetes mellitus (NDM) is a rare form of monogenic diabetes and usually presents in the first 6 months of life. We aimed to describe the clinical characteristics and molecular genetics of a large Turkish cohort of NDM patients from a single centre and estimate an annual incidence rate of NDM in South-Eastern Anatolian region of Turkey.

DESIGN AND METHODS

NDM patients presenting to Diyarbakir Children State Hospital between 2010 and 2013, and patients under follow-up with presumed type 1 diabetes mellitus, with onset before 6 months of age were recruited. Molecular genetic analysis was performed.

RESULTS

Twenty-two patients (59% males) were diagnosed with NDM (TNDM-5; PNDM-17). Molecular genetic analysis identified a mutation in 20 (95%) patients who had undergone a mutation analysis. In transient neonatal diabetes (TNDM) patients, the genetic cause included chromosome 6q24 abnormalities (n=3), ABCC8 (n=1) and homozygous INS (n=1). In permanent neonatal diabetes (PNDM) patients, homozygous GCK (n=6), EIF2AK3 (n=3), PTF1A (n=3), and INS (n=1) and heterozygous KCNJ11 (n=2) mutations were identified. Pancreatic exocrine dysfunction was observed in patients with mutations in the distal PTF1A enhancer. Both patients with a KCNJ11 mutation responded to oral sulphonylurea. A variable phenotype was associated with the homozygous c.-331C>A INS mutation, which was identified in both a PNDM and TNDM patient. The annual incidence of PNDM in South-East Anatolian region of Turkey was one in 48 000 live births.

CONCLUSIONS

Homozygous mutations in GCK, EIF2AK3 and the distal enhancer region of PTF1A were the commonest causes of NDM in our cohort. The high rate of detection of a mutation likely reflects the contribution of new genetic techniques (targeted next-generation sequencing) and increased consanguinity within our cohort.

Permanent neonatal diabetes mellitus in China

Background

Permanent neonatal diabetes mellitus (PNDM) is a rare disease, which is defined as the onset of diabetes before the age of 6 months with persistence through life. Infants with KCNJ11 or ABCC8 genetic mutations may respond to oral sulfonylurea therapy. Currently, there are limited studies about the genetic analysis and long-term follow-up of PNDM.

Case presentation

We report four cases of PNDM. None of the infants or their parents had INS, KCNJ11, or ABCC8 genetic mutations. One infant underwent continuous subcutaneous insulin infusion (CSII) and the other infants underwent multiple injections of insulin (MII). In these infants, PNDM persisted from 35 months to 60 months of follow-up. Three infants maintained fairly stable blood sugar levels, and one infant had poor sugar control.

Conclusions

We suggest that all of the infants with PNDM should undergo genetic evaluation. For infants without KCNJ11 and ABCC8 genetic mutations, oral sulfonylurea should not be considered as treatment. CSII is a useful method for overcoming the difficulties of diabetes, and it may also improve the quality of life of both infants and their parents.

Genetic Counseling for Diabetes Mellitus

Most diabetes is polygenic in etiology, with (type 1 diabetes, T1DM) or without (type 2 diabetes, T2DM) an autoimmune basis. Genetic counseling for diabetes generally focuses on providing empiric risk information based on family history and/or the effects of maternal hyperglycemia on pregnancy outcome. An estimated one to five percent of diabetes is monogenic in nature, e.g., maturity onset diabetes of the young (MODY), with molecular testing and etiology-based treatment available. However, recent studies show that most monogenic diabetes is misdiagnosed as T1DM or T2DM. While efforts are underway to increase the rate of diagnosis in the diabetes clinic, genetic counselors and clinical geneticists are in a prime position to identify monogenic cases through targeted questions during a family history combined with working in conjunction with diabetes professionals to diagnose and assure proper treatment and familial risk assessment for individuals with monogenic diabetes.

Genes, assisted reproductive technology and trans-illumination

Genomic imprinting is a parent-of-origin allele-specific epigenetic process that is critical for normal development and health. The establishment and maintenance of normal imprinting is dependent on both cis-acting imprinting control centers, which are marked by differentially (parental allele specific) methylated marks, and trans mechanisms, which regulate the establishment and/or maintenance of the correct methylation epigenotype at the imprinting control centers. Studies of rare human imprinting disorders such as familial hydatidiform mole, Beckwith-Wiedemann syndrome and familial transient neonatal diabetes mellitus have enabled the identification of genetic (e.g., mutations in KHDC3L [C6ORF221], NLRP2 [NALP2], NLRP7 [NALP7] and ZFP57) and environmental (assisted reproductive technologies) factors that can disturb the normal trans mechanisms for imprinting establishment and/or maintenance. Here we review the clinical and molecular aspects of these imprinting disorders in order to demonstrate how the study of rare inherited disorders can illuminate the molecular characteristics of fundamental epigenetic processes, such as genomic imprinting.

Detection of KCNJ11 gene mutations in a family with neonatal diabetes mellitus: implications for therapeutic management of family members with long-standing disease

BACKGROUND

Activating mutations of potassium inwardly-rectifying channel, subfamily J, member 11 (KCNJ11), which encodes Kir6.2 (beta-cell adenosine triphosphate-sensitive potassium [K(ATP)] channel subunit), have been associated with neonatal diabetes mellitus (NDM) in different studies. Treatment with oral sulfonylureas in place of exogenous insulin injections results in improved glycemic control in most patients carrying these mutations. Exploration of genetic causes of NDM occurring before the age of 6 months has been proposed as an important issue in identification of monogenic forms of diabetes, which might be critical in their therapeutic management, as a consequence.

METHODS

Mutation screening of the KCNJ11 gene was carried out using PCR amplification followed by direct sequencing in three family members: the proband, ND1, diagnosed at 40 days of age (current age 7 years); his sibling, ND2, diagnosed at 2 years of age (current age 14 years); and their father, ND3, diagnosed at 15 years of age (current age 35 years), who had been exclusively treated with insulin. The effect of the E227K mutation was also examined in a homology model of Kir6.2.

RESULTS

Our results revealed the presence of the heterozygous missense mutation c. 679 G/A (E227K) in all three patients, who were all able to successfully transfer from insulin injections to an oral sulfonylurea, with improved glycemic control.

CONCLUSION

We found that three members of a family with highly variable age of onset of insulin-treated diabetes, diagnosed at 40 days, 2 years, and 15 years of age, all carried the E227K mutation in KCNJ11 and could switch to an oral sulfonylurea. This mutation has been previously reported in patients with permanent and transient NDM, as well as later-onset diabetes; this report adds to the variability in phenotypic presentation and further supports genetic testing in all diabetic members of any family affected by NDM.

The lessons of early-onset monogenic diabetes for the understanding of diabetes pathogenesis

Monogenic diabetes consists of different subtypes of single gene disorders comprising a large spectrum of phenotypes, namely neonatal diabetes mellitus or monogenic diabetes of infancy, dominantly inherited familial forms of early-onset diabetes (called Maturity-Onset Diabetes of the Young) and rarer diabetes-associated syndromic diseases. All these forms diagnosed at a very-young age are unrelated to auto-immunity. Their genetic dissection has revealed major genes in developmental and/or functional processes of the pancreatic β-cell physiology, and various molecular mechanisms underlying the primary pancreatic defects. Most of these discoveries have had remarkable consequences on the patients care and patient's long-term condition with outstanding examples of successful genomic medicine, which are highlighted in this chapter. Increasing evidence also shows that frequent polymorphisms in or near monogenic diabetes genes may contribute to adult polygenic type 2 diabetes. In this regard, unelucidated forms of monogenic diabetes represent invaluable models for identifying new targets of β-cell dysfunction.

Neonatal diabetes mellitus in China: a case report and review of the Chinese literature

To recognize the clinical characteristics and outcomes of neonatal diabetes mellitus (NDM), the authors retrospectively reviewed 1 NDM baby in their department and compared their data with 39 NDM cases reported in the available Chinese literature between January 1986 and December 2010. Most of the cases were located near the eastern and southern coasts of China, and clinical manifestation of 72.5% of the cases occurred in 4-week-old infants. Hyperglycemia and glycosuria findings were seen in all the patients and in 47.5% with intrauterine growth retardation. Moreover, 30.0% of the cases had polyuria, 52.5% had dehydration, and 47.5% had ketoacidosis. Cases with hyperglycemia, dehydration, and ketoacidosis recovered mostly. Ten NDM cases had persisted after 1 to 11 years of follow-up, 3 cases maintained normal blood sugar, and 7 cases had poor sugar control. NDM is a rare condition and early management includes fluid and insulin and later management depends on the transient or permanent nature of the condition.

Phenotype variability and neonatal diabetes in a large family with heterozygous mutation of the glucokinase gene

Monogenic diabetes caused by mutations in the glucokinase gene (GCK-MODY) is usually characterized by a mild clinical phenotype. The clinical course of diabetes may be, however, highly variable. The authors present a child with diabetes manifesting with ketoacidosis during the neonatal period, born in a large family with ten members bearing a heterozygous p.Gly223Ser mutation in GCK. DNA sequencing and multiplex ligation-dependent probe amplification were used to confirm GCK mutation and exclude other de novo mutations in other known genes associated with monogenic diabetes. Continuous glucose monitoring (CGM) was used to assess daily glycemic profiles. At the onset of diabetes the child had hyperglycemia 765 mg/dl with pH 7.09. Her glycated hemoglobin level was 8.6% (70.5 mmol/mol). The C-peptide level was below normal range (<0.5 pmol/ml) at onset, and the three- and 6-month follow-up examinations. Current evaluation at age 3 still showed unsatisfactory metabolic control with HbA1c level equal to 8.1% (65.0 mmol/mol). CGM data showed glucose concentrations profile similar to poorly controlled type 1 diabetes. The patient was confirmed to be heterozygous for the p.Gly223Ser mutation and did not show any point mutations or deletions within other monogenic diabetes genes. Other family members with p.Gly223Ser mutation had retained C-peptide levels and mild diabetes manageable with diet (five individuals), oral hypoglycemizing agents (five patients), or insulin (one patient). This mutation was absent within all healthy family members. Heterozygous mutations of the GCK gene may result in neonatal diabetes similar to type 1 diabetes, the cause of such phenotype variety is still unknown. The possibility of other additional, unknown mutations seems to be the most likely explanation for the unusual presentation of GCK-MODY.

Novel glucokinase mutations in patients with monogenic diabetes - clinical outline of GCK-MD and potential for founder effect in Slavic population

Glucokinase (GCK) gene mutations are the causative factor of GCK-MD (monogenic diabetes) characterized by a mild clinical phenotype and potential for insulin withdrawal. This study presents the results of a nationwide genetic screening for GCK-MD performed in Poland. A group of 194 patients with clinical suspicion of GCK-MD and 17 patients with neonatal diabetes were subjected to GCK sequencing. Patients negative for GCK mutations were subjected to multiplex ligation-dependent probe amplification (MLPA) to detect deletions or insertions. A total of 44 GCK heterozygous mutations were found in 68 probands (35%). Among those, 20 mutations were novel ones: A282fs, D198V, E158X, G246V, G249R, I348N, L165V, L315Q, M115I, N254S, P284fs, Q338P, R377L, R43C, R46S, S212fs, S212P, T255N, V406A and Y214D. No abnormalities were detected in MLPA analysis. Homozygous D278E mutation was found in one patient with neonatal diabetes. The most frequently observed combinations of symptoms typical for GCK-MD were mild diabetes and/or fasting hyperglycaemia (98.3%), positive C-peptide at diagnosis (76%) and dominant mode of inheritance (59%). This study outlines numerous novel mutations of the GCK gene present in white Caucasians of Slavic origin. Thorough clinical assessment of known factors associated with GCK-MD may facilitate patient selection.

Hyperglycaemia in preterm neonates: what to know, what to do

Neonatal hyperglycaemia is a frequent complication in VLBW infants during the first week of life. The more common causes include high glucose intake, stress situations such as sepsis, NEC, and surgical treatments, as well as the administration of vasoactive drugs and methylxanthines. The appropriate definition is unclear. Hyperglycaemia has been associated with increased mortality and major morbidities. There have been insufficient randomized clinical trials to help in clarifying which infants should be treated, and there are insufficient data on the pharmacokinetics of insulin in these vulnerable patients.

Functional analysis of Rfx6 and mutant variants associated with neonatal diabetes

Mutations in rfx6 were recently associated with Mitchell-Riley syndrome, which involves neonatal diabetes, and other digestive system defects. To better define the function of Rfx6 in early endoderm development we cloned the Xenopus homologue. Expression of rfx6 begins early, showing broad expression throughout the anterior endoderm; at later stages rfx6 expression becomes restricted to the endocrine cells of the gut and pancreas. Morpholino knockdown of rfx6 caused a loss of pancreas marker expression, as well as other abnormalities. Co-injection of exogenous wild-type rfx6 rescued the morpholino phenotype in Xenopus tadpoles, whereas attempts to rescue the loss-of-function phenotype using mutant rfx6 based on Mitchell-Riley patients were unsuccessful. To better define the pleiotropic effects, we performed microarray analyses of gene expression in knockdown foregut tissue. In addition to pancreatic defects, the microarray analyses revealed downregulation of lung, stomach and heart markers and an upregulation of kidney markers. We verified these results using RT-PCR and in situ hybridization. Based on the different rfx6 expression patterns and our functional analyses, we propose that rfx6 has both early and late functions. In early development Rfx6 plays a broad role, being essential for development of most anterior endodermal organs. At later stages however, Rfx6 function is restricted to endocrine cells.

Transienter neonataler Diabetes und Hypomethylierungssyndrome

Der transiente neonatale Diabetes (TNDM) ist definiert als Manifestation einer diabetogenen Stoffwechsellage in den ersten Lebenswochen und Normalisierung des Glukosestoffwechsels bis zum 18. Lebensmonat. Zu den klinischen Kardinalsymptomen zählen intrauterine Wachstumsverzögerung, Hyperglykämie und Dehydratation bei fehlender Ketoazidose. Die Ätiologie des TNDM ist sehr heterogen. In 70% der Fälle ist die Erkrankung mit Aberrationen in der Chromosomenregion 6q24 assoziiert. Diese Chromosomenregion enthält die genomisch geprägten Gene PLAGL1/ZAC und HYMAI. Durch eine paternale uniparentale Disomie 6 (upd(6)pat), eine paternale Duplikation der geprägten Region in 6q24 oder durch Imprintingdefekte des maternalen Allels kommt es zu einer Überexpression des paternal exprimierten Gens PLAGL1. Imprintingdefekte können isoliert oder im Rahmen eines Hypomethylierungssyndroms mit Beteiligung mehrerer geprägter Loci des Genoms auftreten. Hypomethylierung an multiplen Loci wurde bis jetzt bei Patienten mit TNDM, Silver-Russell-Syndrom (SRS) und Beckwith-Wiedemann-Syndrom (BWS) beobachtet. Das Wiederholungsrisiko hängt wesentlich von der Ursache des TNDM an. Chromosomale Aberrationen der Eltern unter Beteiligung des Chromosoms 6 erhöhen das Risiko sowohl für eine UPD des geprägten Bereichs in 6q24 als auch für eine paternale Duplikation. Jedoch entstehen sowohl UPD als auch Duplikationen zumeist de novo.

The molecular mechanisms and pharmacotherapy of ATP-sensitive potassium channel gene mutations underlying neonatal diabetes

Neonatal diabetes mellitus (NDM) is a monogenic disorder caused by mutations in genes involved in regulation of insulin secretion from pancreatic β-cells. Mutations in the KCNJ11 and ABCC8 genes, encoding the adenosine triphosphate (ATP)-sensitive potassium (K(ATP)) channel Kir6.2 and SUR1 subunits, respectively, are found in ∼50% of NDM patients. In the pancreatic β-cell, K(ATP) channel activity couples glucose metabolism to insulin secretion via cellular excitability and mutations in either KCNJ11 or ABCC8 genes alter K(ATP) channel activity, leading to faulty insulin secretion. Inactivation mutations decrease K(ATP) channel activity and stimulate excessive insulin secretion, leading to hyperinsulinism of infancy. In direct contrast, activation mutations increase K(ATP) channel activity, resulting in impaired insulin secretion, NDM, and in severe cases, developmental delay and epilepsy. Many NDM patients with KCNJ11 and ABCC8 mutations can be successfully treated with sulfonylureas (SUs) that inhibit the K(ATP) channel, thus replacing the need for daily insulin injections. There is also strong evidence indicating that SU therapy ameliorates some of the neurological defects observed in patients with more severe forms of NDM. This review focuses on the molecular and cellular mechanisms of mutations in the K(ATP) channel that underlie NDM. SU pharmacogenomics is also discussed with respect to evaluating whether patients with certain K(ATP) channel activation mutations can be successfully switched to SU therapy.

Neonatal diabetes mellitus accompanied by diabetic ketoacidosis and mimicking neonatal sepsis: a case report

Neonatal diabetes mellitus (DM) develops within the first six weeks of life with basic findings including dehydration, hyperglycaemia, and mild or no ketonemia/ketonuria. It can be either transient or permanent. Here, we report a case of a one-month-old infant with permanent neonatal diabetes, due to pancreatic hypoplasia, accompanied by diabetic ketoacidosis (DKA). The hyperglycaemia and ketoacidosis resolved by the 14(th) hour of treatment, consisting of IV insulin and rehydration. Subsequently, insulin treatment was continued with neutral protamine hagedorn (NPH) insulin. Breastfeeding was started and was continued at intervals of three hours. Following initiation of breastfeeding, the stools became watery, loose, yellow-green in color, and frequent (8-10 times a day). They contained no blood or mucus. Replacement of pancreatic enzymes resulted in decreased stool frequency. Neonatal DM due to pancreatic hypoplasia and associated with DKA may mimic sepsis and should be kept in mind in all newborns who present with fever, dehydration, and weight loss.

6q24 transient neonatal diabetes

Transient Neonatal Diabetes (type 1) is the commonest cause of diabetes presenting in the first week of life. The majority of infants recover by 3 months of age but are predisposed to developing type 2 diabetes in later life. It is associated with low birth weight but rapid catch up by 1 year of life. The condition is usually due to genetic or epigenetic aberrations at an imprinted locus on chromosome 6q24 and can be sporadic or inherited. Early diagnosis alters medical treatment strategies and differentiates it from other types of early onset diabetes. In some individuals, diabetes may be the initial presentation of a more complex imprinting disorder due to recessive mutations in the gene ZFP57 and may be associated with other developmental problems.

Neonatal hyperglycaemia: a challenging diagnosis

Neonatal diabetes mellitus (NDM) is a very rare disorder occurring between 1:400 000 and 1:500 000 live births and, until recently, little was known about this disease. The authors report a case of transient NDM in a 2-day-old female infant admitted in an intensive care unit with a blood glucose level greater than 400 mg/dl, glycosuria, ketonuria and with no evidence of autoimmunity. Treatment with insulin was necessary until the 51st day of life and many difficulties were found in the management of metabolic control because of the need for tiny quantities of insulin. Hyperglycaemia is sometimes routinely treated with insulin by neonatologists but after excluding the common causes of hyperglycaemia, NDM should be considered as a diagnostic possibility with clinical, genetic and therapeutic implications.

[Long-term follow-up of permanent neonatal diabetes in Tunisian infant]

Neonatal diabetes mellitus is a rare entity defined as hyperglycaemia occurring within the first 3 months of life that lasts for at least 2 weeks and requiring insulin therapy for unforeseeable duration. We report the case of a full-term female infant with permanent neonatal diabetes mellitus, stemming from consanguineous parents, born with severe intra-uterine growth retardation and birth weight of 1400 g. The patient presented on the 15th day of life a severe dehydration with a fever and ponderal loss of 14 %. The biology showed hyperglycaemia to 15 mmol/L, moderate metabolic acidosis, glucosuria and ketonuria. The diagnosis of neonatal diabetes mellitus was reserved, justifying its stake under insulin. Etiologic investigation showed a type HLA-DR4/DR8; anti-insulin antibodies were weakly positive, Langerhans islet cell and anti-GAD antibodies were negative. Abdominal magnetic resonance imaging scans, karyotype, molecular biology and chromatography of amino and organic acids did not show any abnormalities. During the first 2 years of age, the patient presented a big instability of glycaemia having required several hospitalizations. After 12 years of age, the patient is still under insulin with a satisfactory glycaemia balance and her growth is normal. Besides, she presents a microcephaly with a spastic walking. The search of neonatal diabetes mellitus must be systematic in front of any fetal hypotrophy allowing a premature coverage and a good prognosis.

A case report of neonatal diabetes due to neonatal hemochromatosis

A 6-week-old girl, the first child of non-consanguineous parents, was admitted to the hospital for evaluation of vomiting. She was small for gestational age (1500 g). On admission, she weighed 1830 g, and appeared dehydrated. The blood glucose was 880 mg/dL. Insulin and C-peptide levels were <1 microIU/ml and 0.1 pmol/L, respectively. Antibodies of diabetes were negative. The serum triglyceride level was markedly elevated (5322 mg/dL). After a few days of insulin therapy, the triglyceride levels dramatically decreased, but cholestasis persisted. A liver biopsy revealed diffuse iron deposition and the diagnosis of neonatal hemochromatosis was established. In neonatal hemochromatosis, diabetes may occur as a result of iron deposition in the pancreas. The coexistence of neonatal diabetes secondary to neonatal hemochromatosis with a fatal course during the infancy period has not been previously reported. In this report, an infant with neonatal diabetes secondary to neonatal hemochromatosis is presented as the first case in the literature involving the coexistence of these two conditions.

ATP-sensitive potassium channels in health and disease

The ATP-sensitive potassium (K(ATP)) channel plays a crucial role in insulin secretion and thus glucose homeostasis. K(ATP) channel activity in the pancreatic beta-cell is finely balanced; increased activity prevents insulin secretion, whereas reduced activity stimulates insulin release. The beta-cell metabolism tightly regulates K(ATP) channel gating, and if this coupling is perturbed, two distinct disease states can result. Diabetes occurs when the K(ATP) channel fails to close in response to increased metabolism, whereas congenital hyperinsulinism results when K(ATP) channels remain closed even at very low blood glucose levels. In general there is a good correlation between the magnitude of K(ATP) current and disease severity. Mutations that cause a complete loss of K(ATP) channels in the beta-cell plasma membrane produce a severe form of congenital hyperinsulinism, whereas mutations that partially impair channel function produce a milder phenotype. Similarly mutations that greatly reduce the ATP sensitivity of the K(ATP) channel lead to a severe form of neonatal diabetes with associated neurological complications, whilst mutations that cause smaller shifts in ATP sensitivity cause neonatal diabetes alone. This chapter reviews our current understanding of the pancreatic beta-cell K(ATP) channel and highlights recent structural, functional and clinical advances.

Update of mutations in the genes encoding the pancreatic beta-cell K(ATP) channel subunits Kir6.2 (KCNJ11) and sulfonylurea receptor 1 (ABCC8) in diabetes mellitus and hyperinsulinism

The beta-cell ATP-sensitive potassium (K(ATP)) channel is a key component of stimulus-secretion coupling in the pancreatic beta-cell. The channel couples metabolism to membrane electrical events bringing about insulin secretion. Given the critical role of this channel in glucose homeostasis it is therefore not surprising that mutations in the genes encoding for the two essential subunits of the channel can result in both hypo- and hyperglycemia. The channel consists of four subunits of the inwardly rectifying potassium channel Kir6.2 and four subunits of the sulfonylurea receptor 1 (SUR1). It has been known for some time that loss of function mutations in KCNJ11, which encodes for Kir6.2, and ABCC8, which encodes for SUR1, can cause oversecretion of insulin and result in hyperinsulinism of infancy, while activating mutations in KCNJ11 and ABCC8 have recently been described that result in the opposite phenotype of diabetes. This review focuses on reported mutations in both genes, the spectrum of phenotypes, and the implications for treatment on diagnosing patients with mutations in these genes.

The K(ATP) channel and neonatal diabetes

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.

Transient neonatal diabetes mellitus in an extremely preterm infant

The present report concerns transient neonatal diabetes mellitus in an extremely preterm infant (gestational age 27 weeks, birth weight 718 g). The patient had intrauterine growth retardation and developed hyperglycaemia on the first day of life. Insulin administration was discontinued on the 89th day of life, which was 1 day before the original due date. This case suggests that (a) insufficient insulin secretion started at least from the second trimester of the pregnancy, and (b) the duration needed for recovery of insulin secretion was not dependent on the maturity.

Association of the Kir6.2 E23K variant with reduced acute insulin response in African-Americans

CONTEXT

ATP-sensitive potassium channels are composed of pore-forming (Kir6.x) and regulatory sulfonylurea receptor (SURx) subunits and have been implicated in the maintenance of glucose homeostasis. Kir6.2 and SUR1 are expressed in a broad range of tissues, and no contemporary studies have addressed the physiological impact of variants in Hispanic-Americans and African-Americans carefully phenotyped for components of glucose homeostasis.

OBJECTIVE

The objective of this study was to evaluate two nonsynonymous variants in Kir6.2 (E23K) and SUR1 (A1369S) and determine their role in vivo.

DESIGN AND SETTING

The Insulin Resistance Atherosclerosis Family Study (IRAS-FS) is a community-based study of Hispanic-Americans (San Antonio, TX, and San Luis Valley, CO) and African-Americans (Los Angeles, CA).

PARTICIPANTS

A total of 1,040 Hispanic-Americans and 500 African-American individuals formed the basis of this study.

MAIN OUTCOME MEASURE(S)

The primary glucose homeostasis phenotypes of interest in this study were derived from the frequently sampled iv glucose tolerance test and included insulin sensitivity (S(I)), acute insulin response, and disposition index.

RESULTS

In African-Americans, both variants were associated with a significant reduction in insulin secretion in glucose-tolerant carriers of the minor alleles (additive P = 0.00053). S(I), a measure of insulin sensitivity, was not associated. In Hispanic-Americans, there was no association with measures of glucose homeostasis.

CONCLUSIONS

We conclude that variation marked by the Kir6.2 E23K and SUR1 A1369S mutations is associated with alterations in glucose-stimulated insulin secretion but not with other measures of glucose homeostasis in an African-American population.

Seven mutations in the human insulin gene linked to permanent neonatal/infancy-onset diabetes mellitus

Permanent neonatal diabetes mellitus (PNDM) is a rare disorder usually presenting within 6 months of birth. Although several genes have been linked to this disorder, in almost half the cases documented in Italy, the genetic cause remains unknown. Because the Akita mouse bearing a mutation in the Ins2 gene exhibits PNDM associated with pancreatic beta cell apoptosis, we sequenced the human insulin gene in PNDM subjects with unidentified mutations. We discovered 7 heterozygous mutations in 10 unrelated probands. In 8 of these patients, insulin secretion was detectable at diabetes onset, but rapidly declined over time. When these mutant proinsulins were expressed in HEK293 cells, we observed defects in insulin protein folding and secretion. In these experiments, expression of the mutant proinsulins was also associated with increased Grp78 protein expression and XBP1 mRNA splicing, 2 markers of endoplasmic reticulum stress, and with increased apoptosis. Similarly transfected INS-1E insulinoma cells had diminished viability compared with those expressing WT proinsulin. In conclusion, we find that mutations in the insulin gene that promote proinsulin misfolding may cause PNDM.

Neonatal and late-onset diabetes mellitus caused by failure of pancreatic development: report of 4 more cases and a review of the literature

OBJECTIVE

Permanent neonatal diabetes mellitus caused by developmental failure of the pancreas is rare. Thus far, only a few genetic causes have been reported. We now report the clinical and genetic aspects of 4 more cases of permanent neonatal diabetes mellitus caused by pancreatic agenesis or hypoplasia.

PATIENTS AND METHODS

All 4 of the patients were from consanguineous kinships, and all presented with diabetes mellitus and pancreatic exocrine insufficiency. Three patients had pancreatic agenesis, and 1 had pancreatic hypoplasia on computed tomography scan. DNA was extracted from blood samples of patients and unaffected family members. Specific genes were amplified by polymerase chain reaction and characterized by DNA sequencing.

RESULTS

Several genes that encode transcription factors that have known roles in pancreas development were characterized in the affected children and unaffected family members. These genes include Pdx1, the master regulator of pancreas development and beta-cell differentiation, and other transcription factors that are expressed early in pancreas development, namely, Ptf1a, Sox9, Sox17, Hnf6, and HlxB9. Several novel polymorphisms were found in our patients. However, these were also present in unaffected individuals. No disease-causing mutations were found in any of these genes.

CONCLUSIONS

These findings add to the 4 cases already in the literature in which the Pdx1 structural gene has been found to be normal in patients with pancreatic agenesis or hypoplasia. The analysis here has been extended to include the screening of 4 other candidate genes in addition to promoter elements upstream of the Pdx1. Two of the cases occurred in a sibling pair, and 2 were isolated, so there may be more than 1 etiology in the cases reported here.

Monogenic diabetes in the young, pharmacogenetics and relevance to multifactorial forms of type 2 diabetes

Most valuable breakthroughs in the genetics of type 2 diabetes for the past two decades have arisen from candidate gene studies and familial linkage analysis of maturity-onset diabetes of the young (MODY), an autosomal dominant form of diabetes typically occurring before 25 years of age caused by primary insulin secretion defects. Despite its low prevalence, MODY is not a single entity but presents genetic, metabolic and clinical heterogeneity. MODY can result from mutations in at least six different genes encoding the glucose sensor enzyme glucokinase and transcription factors that participate in a regulatory network essential for adult beta-cell function. Additional genes have been described in other discrete phenotypes or syndromic forms of diabetes. Whereas common variants in the MODY genes contribute very modestly to type 2 diabetes susceptibility in adults, major findings emerging from the advent of genome-wide association studies will deliver an increasing number of genes and new pathways for the pathological events of the disease.

Neonatal diabetes mellitus

An explosion of work over the last decade has produced insight into the multiple hereditary causes of a nonimmunological form of diabetes diagnosed most frequently within the first 6 months of life. These studies are providing increased understanding of genes involved in the entire chain of steps that control glucose homeostasis. Neonatal diabetes is now understood to arise from mutations in genes that play critical roles in the development of the pancreas, of beta-cell apoptosis and insulin processing, as well as the regulation of insulin release. For the basic researcher, this work is providing novel tools to explore fundamental molecular and cellular processes. For the clinician, these studies underscore the need to identify the genetic cause underlying each case. It is increasingly clear that the prognosis, therapeutic approach, and genetic counseling a physician provides must be tailored to a specific gene in order to provide the best medical care.

Insulin mutation screening in 1,044 patients with diabetes: mutations in the INS gene are a common cause of neonatal diabetes but a rare cause of diabetes diagnosed in childhood or adulthood

OBJECTIVE

Insulin gene (INS) mutations have recently been described as a cause of permanent neonatal diabetes (PND). We aimed to determine the prevalence, genetics, and clinical phenotype of INS mutations in large cohorts of patients with neonatal diabetes and permanent diabetes diagnosed in infancy, childhood, or adulthood.

RESEARCH DESIGN AND METHODS

The INS gene was sequenced in 285 patients with diabetes diagnosed before 2 years of age, 296 probands with maturity-onset diabetes of the young (MODY), and 463 patients with young-onset type 2 diabetes (nonobese, diagnosed <45 years). None had a molecular genetic diagnosis of monogenic diabetes.

RESULTS

We identified heterozygous INS mutations in 33 of 141 probands diagnosed at <6 months, 2 of 86 between 6 and 12 months, and none of 58 between 12 and 24 months of age. Three known mutations (A24D, F48C, and R89C) account for 46% of cases. There were six novel mutations: H29D, L35P, G84R, C96S, S101C, and Y103C. INS mutation carriers were all insulin treated from diagnosis and were diagnosed later than ATP-sensitive K(+) channel mutation carriers (11 vs. 8 weeks, P < 0.01). In 279 patients with PND, the frequency of KCNJ11, ABCC8, and INS gene mutations was 31, 10, and 12%, respectively. A heterozygous R6C mutation cosegregated with diabetes in a MODY family and is probably pathogenic, but the L68M substitution identified in a patient with young-onset type 2 diabetes may be a rare nonfunctional variant.

CONCLUSIONS

We conclude that INS mutations are the second most common cause of PND and a rare cause of MODY. Insulin gene mutation screening is recommended for all diabetic patients diagnosed before 1 year of age.

Neonatal diabetes: genetic implications in treatment

A 2-month-old newborn was diagnosed with diabetes mellitus presenting with ketoacidosis and negative islet antibodies. Genetic study revealed the R201C mutation of the KCNJ11 gene. In the last few years, the heterozygous activating mutation in KCNJ11 encoding the Kir6.2 subunit of the ATP-sensitive potassium (K(ATP)) channel has been shown to cause permanent neonatal diabetes. Diabetes results from impaired insulin secretion caused by failure of the beta cell-K(ATP) channel to close in response to increased intracellular ATP. Recent studies have demonstrated the effectiveness of oral sulfonylurea in the treatment of this disease. Sulfonylurea closes the K(ATP) channel by an ATP-independent route. Treatment with sulfonylurea in permanent neonatal diabetes has not yet been approved due to the lack of long-term studies in infants. However, the present case illustrates the importance of genetics to identify patients who may benefit from treatment.

Neonatal hyperglycaemia and abnormal development of the pancreas

Transient and permanent neonatal diabetes mellitus (TNDM and PNDM) are rare conditions occurring in around 1 per 300,000 live births. In TNDM, growth-retarded infants develop diabetes in the first few weeks of life, only to go into remission after a few months with possible relapse to permanent diabetes usually around adolescence or in adulthood. In PNDM, insulin secretory failure occurs in the late fetal or early postnatal period. The very recently elucidated mutations in KCNJ11 and ABCC8 genes, encoding the Kir6.2 and SUR1 subunits of the pancreatic K(ATP) channel involved in regulation of insulin secretion, account for a third to a half of the PNDM cases. Molecular analysis of chromosome 6 anomalies and the KCNJ11 and ABCC8 genes encoding Kir6.2 and SUR1 provides a tool for distinguishing transient from permanent neonatal diabetes mellitus in the neonatal period. Some patients (those with mutations in KCNJ11 and ABCC8) may be transferred from insulin therapy to sulphonylureas.

Mosaic paternal uniparental isodisomy and an ABCC8 gene mutation in a patient with permanent neonatal diabetes and hemihypertrophy

OBJECTIVE

Activating mutations in the KCNJ11 and ABCC8 genes encoding the Kir6.2 and SUR1 subunits of the pancreatic ATP-sensitive K(+) channel are the most common cause of permanent neonatal diabetes. In contrast to KCNJ11, where only dominant heterozygous mutations have been identified, recessively acting ABCC8 mutations have recently been found in some patients with neonatal diabetes. These genes are co-located on chromosome 11p15.1, centromeric to the imprinted Beckwith-Wiedemann syndrome (BWS) locus at 11p15.5. We investigated a male with hemihypertrophy, a condition classically associated with neonatal hyperinsulinemia and hypoglycemia, who developed neonatal diabetes at age 5 weeks.

RESEARCH DESIGN AND METHODS

The KCNJ11 and ABCC8 genes and microsatellite markers on chromosome 11 were analyzed in DNA samples from the patient and his parents.

RESULTS

A paternally inherited activating mutation (N72S) in the ABCC8 gene was identified in the proband. The mutation was present at 70% in the patient's leukocytes and 50% in buccal cells. Microsatellite analysis demonstrated mosaic segmental paternal uniparental isodisomy (UPD) of 11pter-11p14 in the proband that encompassed the ABCC8 gene and the BWS locus.

CONCLUSIONS

We report a patient with neonatal diabetes, hemihypertrophy, and relatively high birth weight resulting from telomeric segmental paternal UPD of chromosome 11, which unmasks a recessively acting gain-of-function mutation in the ABCC8 gene and causes deregulation of imprinted genes at the BWS locus on 11p15.5.

Molecular basis of neonatal diabetes in Japanese patients

CONTEXT

Neonatal diabetes mellitus (NDM) is classified clinically into a transient form (TNDM), in which insulin secretion recovers within several months, and a permanent form (PNDM), requiring lifelong medication. However, these conditions are genetically heterogeneous.

OBJECTIVE

Our objective was to evaluate the contribution of the responsible gene and delineate their clinical characteristics.

PATIENTS AND METHODS

The chromosome 6q24 abnormality and KCNJ11 and ABCC8 mutations were analyzed in 31 Japanese patients (16 with TNDM and 15 with PNDM). Moreover, FOXP3 and IPF1 mutations were analyzed in a patient with immune dysregulation, polyendocrinopathy, enteropathy X-linked syndrome and with pancreatic agenesis, respectively.

RESULTS

A molecular basis for NDM was found in 23 patients: 6q24 in eleven, KCNJ11 in nine, ABCC8 in two, and FOXP3 in one. All the patients with the 6q24 abnormality and two patients with the KCNJ11 mutation proved to be TNDM. Five mutations were novel: two (p.A174G and p.R50G) [corrected] in KCNJ11, two (p.A90V and p.N1122D) in ABCC8, and one (p.P367L) in FOXP3. Comparing the 6q24 abnormality and KCNJ11 mutation, there were some significant clinical differences: the earlier onset of diabetes, the lower frequency of diabetic ketoacidosis at onset, and the higher proportion of the patients with macroglossia at initial presentation in the patients with 6q24 abnormality. In contrast, two patients with the KCNJ11 mutations manifested epilepsy and developmental delay.

CONCLUSIONS

Both the 6q24 abnormality and KCNJ11 mutation are major causes of NDM in Japanese patients. Clinical differences between them could provide important insight into the decision of which gene to analyze in affected patients first.

Origin of de novo KCNJ11 mutations and risk of neonatal diabetes for subsequent siblings

CONTEXT

Activating mutations in the KCNJ11 gene, which encodes the Kir6.2 subunit of the pancreatic beta-cell K(ATP) channel, result in permanent and transient neonatal diabetes. The majority of KCNJ11 mutations are spontaneous, but the parental origin of these mutations is not known.

OBJECTIVE

Our objective was to determine the parental origin of de novo KCNJ11 mutations and investigate the possibility of mosaicism in transmitting parents.

DESIGN

We identified 68 index cases with a KCNJ11 mutation where neither parent was known to be affected. DNA was available from both parents of 41 probands. The parental origin of the mutation was determined in 18 families by examination of pedigrees, microsatellite analysis, or allele-specific PCR.

RESULTS

A nonsignificant excess of paternally derived mutations was found with 13 of 18 (72%) shown to have arisen on the paternal allele. There was no evidence to suggest an association with increased age at conception. In two families, there were half-siblings with permanent neonatal diabetes born to an unaffected father, suggesting germline mosaicism that was confirmed by the presence of the R201C mutation in one father's semen. Somatic mosaicism was detected in one unaffected mother, and this mutation will also be present in her germ cells.

CONCLUSION

De novo KCNJ11 mutations can arise either during gametogenesis or embryogenesis. The possibility of germline mosaicism means that future siblings are at increased risk of neonatal diabetes, and we recommend that molecular genetic testing is routinely offered at birth for subsequent siblings of children with de novo KCNJ11 mutations.

Diabetes and hypoglycaemia in young children and mutations in the Kir6.2 subunit of the potassium channel: therapeutic consequences

ATP-sensitive potassium channels (K(ATP)) couple cell metabolism to electrical activity by regulating potassium movement across the membrane. These channels are octameric complex with two kind of subunits: four regulatory sulfonylurea receptor (SUR) embracing four poreforming inwardly rectifying potassium channel (Kir). Several isoforms exist for each type of subunits: SUR1 is found in the pancreatic beta-cell and neurons, whereas SUR2A is in heart cells and SUR2B in smooth muscle; Kir6.2 is in the majority of tissues as pancreatic beta-cells, brain, heart and skeletal muscle, and Kir6.1 can be found in smooth vascular muscle and astrocytes. The K(ATP) channels play multiple physiological roles in the glucose metabolism regulation, especially in beta-cells where it regulates insulin secretion, in response to an increase in ATP concentration. They also seem to be critical metabolic sensors in protection against metabolic stress as hypo or hyperglycemia, hypoxia, ischemia. Persistent hyperinsulinemic hypoglycaemia (HI) of infancy is a heterogeneous disorder which may be divided into two histopathological forms (diffuse and focal lesions). Different inactivating mutations have been implicated in both forms: the permanent inactivation of the K(ATP) channels provokes inappropriate insulin secretion, despite low ATP. Diazoxide, used efficiently in certain cases of HI, opens the K(ATP) channels and therefore overpass the mutation effect on the insulin secretion. Conversely, several studies reported sequencing of KCNJ11, coding for Kir6.2, in patients with permanent neonatal diabetes mellitus and found different mutations in 30 to 50% of the cases. More than 28 heterozygous activating mutations have now been identified, the most frequent mutation being in the aminoacid R201. These mutations result in reduced ATP-sensitivity of the K(ATP) channels compared with the wild-types and the level of channel block is responsible for different clinical features: the "mild" form confers isolated permanent neonatal diabetes whereas the severe form combines diabetes and neurological symptoms such as epilepsy, deve-lopmental delay, muscle weakness and mild dimorphic features. Sulfonylureas close K(ATP) channels by binding with high affinity to SUR suggesting they could replace insulin in these patients. Subsequently, more than 50 patients have been reported as successfully and safely switched from subcutaneous insulin injections to oral sulfonylurea therapy, with an improvement in their glycated hemoglobin. We therefore designed a protocol to transfer and evaluate children who have insulin treated neonatal diabetes due to KCNJ11 mutation, from insulin to sulfonylurea. The transfer from insulin injections to oral glibenclamide therapy seems highly effective for most patients and safe. This shows how the molecular understan-ding of some monogenic form of diabetes may lead to an unexpected change of the treatment in children. This is a spectacular example by which a pharmacogenomic approach improves the quality of life of our young diabetic patients in a tremendous way.

Prevalence of permanent neonatal diabetes in Slovakia and successful replacement of insulin with sulfonylurea therapy in KCNJ11 and ABCC8 mutation carriers

CONTEXT

Mutations in the KCNJ11 and ABCC8 genes encoding the pancreatic beta-cell K(ATP) channel have recently been shown to be the most common cause of permanent neonatal diabetes mellitus (PNDM). Information regarding the frequency of PNDM has been based mainly on nonpopulation or short-term collections only. Thus, the aim of this study was to identify the incidence of PNDM in Slovakia and to switch patients to sulfonylurea (SU) where applicable.

DESIGN

We searched for PNDM patients in the Slovak Children Diabetes Registry. In insulin-treated patients who matched the clinical criteria for PNDM, the KCNJ11 or ABCC8 genes were sequenced, and mutation carriers were invited for replacement of insulin with SU.

RESULTS

Eight patients with diabetes onset before the sixth month of life without remission were identified since 1981, which corresponds to the PNDM incidence in Slovakia of one case in 215,417 live births. In four patients, three different KCNJ11 mutations were found (R201H, H46Y, and L164P). Three patients with the KCNJ11 mutations (R201H and H46Y) were switched from insulin to SU, decreasing their glycosylated hemoglobin from 9.3-11.0% on insulin to 5.7-6.6% on SU treatment. One patient has a novel V86A mutation in the ABCC8 gene and was also substituted with SU.

CONCLUSIONS

PNDM frequency in Slovakia is much higher (one in 215,417 live births) than previously suggested from international estimates (about one in 800,000). We identified one ABCC8 and four KCNJ11 mutation carriers, of whom four were successfully transferred to SU, dramatically improving their diabetes control and quality of life.