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 Ͻ45 years). None had a molecular genetic diagnosis of monogenic diabetes. RESULTS-We identified heterozygous INS mutations in 33 of141 probands diagnosed at Ͻ6 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 ϩ channel mutation carriers (11 vs. 8 weeks, P Ͻ 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.

BackgroundCongenital hyperinsulinism (CHI) is a clinically heterogeneous condition. Mutations in eight genes (ABCC8, KCNJ11, GLUD1, GCK, HADH, SLC16A1, HNF4A and HNF1A) are known to cause CHI.AimTo characterise the clinical and molecular aspects of a large cohort of patients with CHI.MethodologyThree hundred patients were recruited and clinical information was collected before genotyping. ABCC8 and KCNJ11 genes were analysed in all patients. Mutations in GLUD1, HADH, GCK and HNF4A genes were sought in patients with diazoxide-responsive CHI with hyperammonaemia (GLUD1), raised 3-hydroxybutyrylcarnitine and/or consanguinity (HADH), positive family history (GCK) or when CHI was diagnosed within the first week of life (HNF4A).ResultsMutations were identified in 136/300 patients (45.3%). Mutations in ABCC8/KCNJ11 were the commonest genetic cause identified (n=109, 36.3%). Among diazoxide-unresponsive patients (n=105), mutations in ABCC8/KCNJ11 were identified in 92 (87.6%) patients, of whom 63 patients had recessively inherited mutations while four patients had dominantly inherited mutations. A paternal mutation in the ABCC8/KCNJ11 genes was identified in 23 diazoxide-unresponsive patients, of whom six had diffuse disease. Among the diazoxide-responsive patients (n=183), mutations were identified in 41 patients (22.4%). These include mutations in ABCC8/KCNJ11 (n=15), HNF4A (n=7), GLUD1 (n=16) and HADH (n=3).ConclusionsA genetic diagnosis was made for 45.3% of patients in this large series. Mutations in the ABCC8 gene were the commonest identifiable cause. The vast majority of patients with diazoxide-responsive CHI (77.6%) had no identifiable mutations, suggesting other genetic and/or environmental mechanisms.

Concordance with growth hormone (GH) therapy in 75 children was objectively assessed using data on GP prescriptions over 12 months. 23% missed .2 injections/ week. Lower concordance was associated with longer duration on GH therapy (p,0.005), lack of choice of delivery device (p,0.005) and short prescription durations (p,0.005), and predicted lower height velocities (p,0.05).Concordance with drug therapy is often poor in chronic non-life-threatening conditions such as growth hormone (GH) deficiency.1 Motivation may be low as the benefits are not immediately apparent and daily subcutaneous injections may present a significant burden.Concordance with GH therapy has been related to patient and family education, timing and location of education sessions, and the type of healthcare professional providing the education.2 3 In a retrospective observational study we examined whether various differences in GH prescribing policies were associated with objectively measured treatment concordance and short-term growth outcomes. METHODSWe collected data on 75 GH deficient children receiving GH therapy who attended a regional paediatric endocrine clinic at Addenbrooke's Hospital, Cambridge during 1999-2003 We sent a postal questionnaire to the children's general practitioners (GPs) who issued the GH prescriptions under a shared care agreement. Data on 11 patients were obtained from an outreach clinic where GH prescriptions were provided directly by a designated local consultant paediatrician. The questionnaire requested details on the number of issued prescriptions and the total GH dose (or number of vials/cartridges) issued with each prescription during three specific 12-month periods (1999-2000, 2000-2001 and 2002-2003). Most of the data returned by GPs was in the form of computerised printouts. We approached 66 GP practices and 58 replied (response rate 88%).GH devices used included automatic injection devices (n = 38), manual injection pen devices (n = 33) and needle-free injection devices (n = 4). According to a gradual change in clinic policy, children had been either allocated to a specific GH device by the nurse specialist or consultant, or had been offered a free choice of devices. All children and parents received training on GH delivery from one nurse specialist (SB). Patients were seen in the regional clinic every 4-6 months for assessment of height by the nurse specialists and review of GH doses. ConcordanceConcordance was objectively assessed in each child by comparing total expected GH usage as documented in the clinic records and letters to the total amount of GH prescribed by GPs during a 12-month period. From the expected daily dose (mg/day) (A), the expected annual GH requirement for each patient (B) was calculated. The number of issued prescriptions and the number of vials provided with each prescription enabled calculation of the total amount of GH prescribed by the GP over the same 12-month period (C). The annual deficit (D) in GH prescribed compared to that expected was calculated as (D = B2C). ...

ObjectiveThe phenotype associated with heterozygous HNF4A gene mutations has recently been extended to include diazoxide responsive neonatal hypoglycemia in addition to maturity-onset diabetes of the young (MODY). To date, mutation screening has been limited to patients with a family history consistent with MODY. In this study, we investigated the prevalence of HNF4A mutations in a large cohort of patients with diazoxide responsive hyperinsulinemic hypoglycemia (HH).Subjects and methodsWe sequenced the ABCC8, KCNJ11, GCK, GLUD1, and/or HNF4A genes in 220 patients with HH responsive to diazoxide. The order of genetic testing was dependent upon the clinical phenotype.ResultsA genetic diagnosis was possible for 59/220 (27%) patients. KATP channel mutations were most common (15%) followed by GLUD1 mutations causing hyperinsulinism with hyperammonemia (5.9%), and HNF4A mutations (5%). Seven of the 11 probands with a heterozygous HNF4A mutation did not have a parent affected with diabetes, and four de novo mutations were confirmed. These patients were diagnosed with HI within the first week of life (median age 1 day), and they had increased birth weight (median +2.4 SDS). The duration of diazoxide treatment ranged from 3 months to ongoing at 8 years.ConclusionsIn this large series, HNF4A mutations are the third most common cause of diazoxide responsive HH. We recommend that HNF4A sequencing is considered in all patients with diazoxide responsive HH diagnosed in the first week of life irrespective of a family history of diabetes, once KATP channel mutations have been excluded.

Hyperinsulinaemic hypoglycaemia (HH) occurs as a consequence of unregulated insulin secretion from pancreatic beta cells. In the newborn period it is the most common cause of severe and persistent hypoglycaemia. As HH is a major risk factor for brain injury and subsequent neurodevelopment handicap, the identification, rapid diagnosis and prompt management of patients with HH is essential if brain damage is to be avoided. Advances in molecular genetics, radiological imaging techniques (such as fluorine-18 L-3, 4-dihydroxyphenylalanine positron emission tomography ((18F)DOPA-PET) scanning) and laparoscopic surgery have completely changed the clinical approach to infants with the severe congenital forms of HH. This review gives an outline of the clinical presentation, the diagnostic cascade, the underlying molecular mechanisms and the management of HH with a particular focus on congenital forms of hyperinsulinism.

Congenital hyperinsulinism (CHI) is biochemically characterised by the dysregulated secretion of insulin from pancreatic b-cells. It is a major cause of persistent hyperinsulinaemic hypoglycaemia (HH) in the newborn and infancy period. Genetically CHI is a heterogeneous condition with mutations in seven different genes described. The genetic basis of CHI involves defects in key genes which regulate insulin secretion from b-cells. Recessive inactivating mutations in ABCC8 and KCNJ11 (which encode the two subunits of the adenosine triphosphate sensitive potassium channels (ATP sensitive K ATP channels)) in b-cells are the most common cause of CHI. The other recessive form of CHI is due to mutations in HADH (encoding for-3-hydroxyacyl-coenzyme A dehydrogenase). Dominant forms of CHI are due to inactivating mutations in ABCC8 and KCNJ11, and activating mutations in GLUD1 (encoding glutamate dehydrogenase) and GCK (encoding glucokinase). Recently dominant mutations in HNF4A (encoding hepatocyte nuclear factor 4a) and SLC16A1 (encoding monocarboxylate transporter 1) have been described which lead to HH. Mutations in all these genes account for about 50% of the known causes of CHI. Histologically there are three (possibly others which have not been characterised yet) major subtypes of CHI: diffuse, focal and atypical forms. The diffuse form is inherited in an autosomal recessive (or dominant manner), the focal form being sporadic in inheritance. The diffuse form of the disease may require a near total pancreatectomy whereas the focal form requires a limited pancreatectomy potentially curing the patient. Understanding the genetic basis of CHI has not only provided novel insights into b-cell physiology but also aided in patient management and genetic counselling.

BackgroundActivating mutations in the GLUD1 gene (which encodes for the intra-mitochondrial enzyme glutamate dehydrogenase, GDH) cause the hyperinsulinism–hyperammonaemia (HI/HA) syndrome. Patients present with HA and leucine-sensitive hypoglycaemia. GDH is regulated by another intra-mitochondrial enzyme sirtuin 4 (SIRT4). Sirt4 knockout mice demonstrate activation of GDH with increased amino acid-stimulated insulin secretion.ObjectivesTo study the genotype–phenotype correlations in patients with GLUD1 mutations. To report the phenotype and functional analysis of a novel mutation (P436L) in the GLUD1 gene associated with the absence of HA.Patients and methodsTwenty patients with HI from 16 families had mutational analysis of the GLUD1 gene in view of HA (n=19) or leucine sensitivity (n=1). Patients negative for a GLUD1 mutation had sequence analysis of the SIRT4 gene. Functional analysis of the novel P436L GLUD1 mutation was performed.ResultsHeterozygous missense mutations were detected in 15 patients with HI/HA, 2 of which are novel (N410D and D451V). In addition, a patient with a normal serum ammonia concentration (21 μmol/l) was heterozygous for a novel missense mutation P436L. Functional analysis of this mutation confirms that it is associated with a loss of GTP inhibition. Seizure disorder was common (43%) in our cohort of patients with a GLUD1 mutation. No mutations in the SIRT4 gene were identified.ConclusionPatients with HI due to mutations in the GLUD1 gene may have normal serum ammonia concentrations. Hence, GLUD1 mutational analysis may be indicated in patients with leucine sensitivity; even in the absence of HA. A high frequency of epilepsy (43%) was observed in our patients with GLUD1 mutations.

OBJECTIVE-Mutations in the human HNF4A gene encoding the hepatocyte nuclear factor (HNF)-4␣ are known to cause maturity-onset diabetes of the young (MODY), which is characterized by autosomal-dominant inheritance and impaired glucose-stimulated insulin secretion from pancreatic ␤-cells. HNF-4␣ has a key role in regulating the multiple transcriptional factor networks in the islet. Recently, heterozygous mutations in the HNF4A gene were reported to cause transient hyperinsulinemic hypoglycemia associated with macrosomia.RESEARCH DESIGN AND METHODS-Three infants presented with macrosomia and severe hypoglycemia with a positive family history of MODY. The hypoglycemia was confirmed to be due to hyperinsulinism, and all three patients required diazoxide therapy to maintain normoglycemia. Two of the three infants are still requiring diazoxide therapy at 8 and 18 months, whereas one of them had resolution of hyperinsulinemic hypoglycemia at 32 months of age.RESULTS-Sequencing of the HNF4A gene identified heterozygous mutations in all three families. In family 1, a frameshift mutation L330fsdel17ins9 (c.987 1003del17ins9; p.Leu330fs) was present in the proband; a mutation affecting the conserved A nucleotide of the intron 2 branch site (c.264 -21AϾG) was identified in the proband of family 2; and finally a nonsense mutation, Y16X (c.48CϾG, p.Tyr16X), was found in the proband of family 3. (1,2). HNF-4␣ is a transcription factor of the nuclear hormone receptor superfamily and is expressed in liver, kidney, gut, and pancreatic islets (3). It plays a key role in the regulation of pancreatic insulin secretion. Loss-of-function HNF4A mutations have been identified in maturity-onset diabetes of the young (MODY) families in both coding and regulatory regions of the gene, including the P2 promoter region, which is suggested to be the primary transcriptional start site used in ␤-cells (4,5). MODY is characterized by an autosomal-dominant inheritance pattern and impaired glucose-stimulated insulin secretion from pancreatic ␤-cells (4). CONCLUSIONS-HeterozygousThe finding of transient mild hyperinsulinemic hypoglycemia is unexpected, since heterozygous mutations in the HNF4A gene lead to loss of glucose-induced insulin secretion with glucose intolerance in these patients. We now extend the observations of two previous studies (1,2) and report that heterozygous HNF4A mutations can cause macrosomia with severe and persistent hyperinsulinemic hypoglycemia as well as MODY in three families. RESEARCH DESIGN AND METHODSPatient 1. Patient 1 was born at 39 weeks' gestation with a birth weight of 5.9 kg after a vaginal delivery. The delivery was complicated with a prolonged second stage and shoulder dystocia. After delivery, the baby developed severe symptomatic hypoglycemia (jitteriness and irritability with a blood glucose concentration of 0.8 mmol/l). He required a continuous infusion of 25% dextrose delivering 25 mg ⅐ kg Ϫ1 ⅐ min Ϫ1 glucose, as well as an infusion of glucagon to maintain normoglycemia. Biochemical analysis showed an in...