Nesidioblastosis of the pancreas: definition of the syndrome and the management of the severe neonatal hyperinsulinaemic hypoglycaemia

When is it best to discontinue diazoxide in children with persistent hyperinsulinaemic hypoglycaemia and negative genetics for KATP channel gene variants?

Diazoxide is the first-line treatment in children with hyperinsulinaemic hypoglycaemia (HH); however, limited information is available on the duration of diazoxide treatment in children who require over 2 years of it. Hence, we retrospectively reviewed the clinical and biochemical aspects, as well as the duration of therapy and neurodevelopmental assessment, in genetically uncharacterised diazoxide-responsive HH patients admitted to a tertiary hospital over the last 16 years, who had successfully discontinued diazoxide and remained euglycaemic. To exclude transient HH forms, only patients that required diazoxide for over 2 years were studied. We identified a total of 17 patients (70% males), in whom HH was diagnosed between 1 day and 18 months of age, and 88% were born at term with a median birth weight of 3.79 kg. All children responded to diazoxide at a median dose of 11.5 mg/kg/day, and it was stopped at a median age of 8.5 years, with a median duration of therapy of 7.25 years. The cases that required diazoxide the longest manifested no specific biochemical or clinical characteristics. Fasting tests performed after diazoxide discontinuation showed no longer requirement of diazoxide in all the cases. A total of 64.7% of the children showed mild to moderate developmental delay. Therefore, it seems that long-term resolution of HH in children with negative genetics for K_ATP channel genes who required diazoxide for over 2 years will ensue, and thus regular evaluation is crucial. The possible molecular mechanisms involved are unclear.

Infant Death Following Home Birth: A Case Report of Fatal Neonatal Hypoglycemia

Infants born to diabetic mothers are at increased risk for symptomatic hypoglycemia and death after birth. A 36-year-old G4P3 mother with a history of gestational diabetes and newly diagnosed type II insulin-dependent diabetes gave birth at home, in the care of a midwife, to a macrosomic infant girl (10 lbs.). Several hours after birth, the infant became lethargic and was found to be hypoglycemic (blood sugar: 28 mg/dL). Glucose and sugar water were administered by the midwife; however, the infant continued to decompensate. Emergency medical services were called, and the infant was transported to the hospital where, despite resuscitative efforts, she died. An autopsy and review of the literature was performed. At autopsy, characteristic features of maternal-fetal glucose dysregulation were identified, including fetal macrosomia, cardiomegaly, hepatomegaly, and severe pancreatic islet cell hypertrophy/hyperplasia. Developmental abnormalities and other potential causes of death were not identified. Although deaths due to hypoglycemia cannot be reliably diagnosed postmortem using vitreous glucose levels, a clinical history of maternal glucose dysregulation in combination with certain gross and histologic findings should prompt a pathologist to consider maternal-fetal glucose dysregulation as a diagnosis of exclusion and cause of death.

Investigation of Archived Formalin-Fixed Paraffin-Embedded Pancreatic Tissue with Whole-Genome Gene Expression Microarray

The use of formalin-fixed, paraffin-embedded (FFPE) tissue overcomes the most prominent issues related to research on relatively rare diseases: limited sample size, availability of control tissue, and time frame. The use of FFPE pancreatic tissue in GEM may be especially challenging due to its very high amounts of ribonucleases compared to other tissues/organs. In choosing pancreatic tissue, we therefore indirectly address the applicability of other FFPE tissues to gene expression microarray (GEM). GEM was performed on archived, routinely fixed, FFPE pancreatic tissue from patients with congenital hyperinsulinism (CHI), insulinoma, and deceased age-appropriate neonates, using whole-genome arrays. Although ribonuclease-rich, we obtained biologically relevant and disease-specific, significant genes; cancer-related genes; genes involved in (a) the regulation of insulin secretion and synthesis, (b) amino acid metabolism, and (c) calcium ion homeostasis. These results should encourage future research and GEM studies on FFPE tissue from the invaluable biobanks available at the departments of pathology worldwide.

In vitro insulin secretion by pancreatic tissue from infants with diazoxide-resistant congenital hyperinsulinism deviates from model predictions

Congenital hyperinsulinism (CHI) is the major cause of persistent neonatal hypoglycemia. CHI most often occurs due to mutations in the ABCC8 (which encodes sulfonylurea receptor 1) or KCNJ11 (which encodes the potassium channel Kir6.2) gene, which result in a lack of functional KATP channels in pancreatic β cells. Diffuse forms of CHI (DiCHI), in which all β cells are abnormal, often require subtotal pancreatectomy, whereas focal forms (FoCHI), which are characterized by localized hyperplasia of abnormal β cells, can be cured by resection of the lesion. Here, we characterized the in vitro kinetics of insulin secretion by pancreatic fragments from 6 DiCHI patients and by focal lesion and normal adjacent pancreas from 18 FoCHI patients. Responses of normal pancreas were similar to those reported for islets from adult organ donors. Compared with normal pancreas, basal insulin secretion was elevated in both FoCHI and DiCHI tissue. Affected tissues were heterogeneous in their secretory responses, with increased glucose levels often producing a rapid increase in insulin secretion that could be followed by a paradoxical decrease below prestimulatory levels. The KATP channel blocker tolbutamide was consistently ineffective in stimulating insulin secretion; conversely, the KATP channel activator diazoxide often caused an unanticipated increase in insulin secretion. These observed alterations in secretory behavior were similar in focal lesion and DiCHI tissue, and independent of the specific mutation in ABCC8 or KCNJ11. They cannot be explained by classic models of β cell function. Our results provide insight into the excessive and sometimes paradoxical changes in insulin secretion observed in CHI patients with inactivating mutations of KATP channels.

Morphologic analysis of focal and diffuse forms of congenital hyperinsulinism

Congenital hyperinsulinism is clinically characterized by an inappropriate insulin secretion resulting in recurrent severe hypoglycemia. Nesidioblastosis, the proliferation of islet cells budding off from ducts, has been considered for years as the histologic lesion responsible for the syndrome. In our morphologic studies, we demonstrate that nesidioblastosis is not specific of the disease, which is actually not a single entity. Indeed, we recognize the existence of 2 different forms-a diffuse form and a focal form-and demonstrate that they can be differentiated by morphologic criteria, even on frozen sections during surgery. This histologic distinction directs the therapeutic approach because the patients experiencing the focal form of the syndrome can be completely cured by a very limited pancreatectomy. Molecular findings confirmed the reliability of this histologic distinction, showing a specific background for each form.

Glucose metabolism and neurological outcome in congenital hyperinsulinism

Advances in imaging and surgical techniques allow a complete cure for children with focal-type congenital hyperinsulinism (CHI). In contrast, management of diffuse-type CHI remains a matter of controversy. To prevent hypoglycemic brain damage, extensive surgery has been recommended in the past, resulting in diabetes. On the basis of 2 data sets of patients with congenital hyperinsulinism, the German registry for CHI with 235 patients (ages 1 day to 19 years) and the diabetes treatment register (Diabetes Patienten-Verlaufsdokumentationssystem initiative), a follow-up study was initiated for diabetes mellitus and the intellectual and physical development as well as motor function. In our ongoing study, we investigated 20 patients with CHI (12 male, mean ages 9.9 years). Six of 20 patients had undergone subtotal pancreatectomy. In early infantile development (0-3 years) we observed a trend to motor and speech delay. In early childhood (2.5-7 years) there appeared a trend to an advantage of results of nonverbal tasks compared with verbal tasks. Before 1990 most patients (∼75%) were treated by subtotal pancreatectomy; since 2000, a more conservative approach is obvious (4/68). All patients with diabetes (n = 25) developed the condition after undergoing subtotal pancreatectomy. No spontaneous manifestation of diabetes was noted before adulthood. There was a wide range of age (0-17.7 years) at manifestation indicating a long period during which glucose tolerance is compensated. Compared with >40.000 children with type 1 diabetes mellitus from the Diabetes Patienten-Verlaufsdokumentationssystem registry, we found significant differences with a tendency for being overweight as well as small stature. Mean daily insulin dose and HbA1c was comparable in both groups.

Anemia and neutropenic fever with high dose diazoxide treatment in a case with hyperinsulinism due to Munchausen by proxy

BACKGROUND

The etiology of hyperinsulinemic hypoglycemia in adolescents is similar to that of adults. Patients resistant to medical treatment may undergo pancreatectomy. Diazoxide is the mainstay of medical treatment. Rarely bone marrow suppression is reported due to diazoxide.

PATIENT

An adolescent with severe hyperinsulinemic hypoglycemia was referred for pancreatectomy after she was treated with high doses of diazoxide, octreotide and glucose. She developed anemia and febrile neutropenia in the course of diazoxide treatment that resolved with cessation of medication. The cause of the hyperinsulinemia proved to be classical Munchausen by proxy.

CONCLUSION

This is the first report of bone marrow suppression involving erythroid series by diazoxide. Follow-up of blood count may be considered in patients on high dosages since anemia may be dose dependent. Munchausen by proxy poses a serious threat to children with significant morbidity and mortality. Awareness and a high index of suspicion in clinical settings with unusual causes are the mainstay for the diagnosis.

Generation and characterization of human insulin-releasing cell lines

Background

The in vitro culture of insulinomas provides an attractive tool to study cell proliferation and insulin synthesis and secretion. However, only a few human beta cell lines have been described, with long-term passage resulting in loss of insulin secretion. Therefore, we set out to establish and characterize human insulin-releasing cell lines.

Results

We generated ex-vivo primary cultures from two independent human insulinomas and from a human nesidioblastosis, all of which were cultured up to passage number 20. All cell lines secreted human insulin and C-peptide. These cell lines expressed neuroendocrine and islets markers, confirming the expression profile found in the biopsies. Although all beta cell lineages survived an anchorage independent culture, none of them were able to invade an extracellular matrix substrate.

Conclusion

We have established three human insulin-releasing cell lines which maintain antigenic characteristics and insulin secretion profiles of the original tumors. These cell lines represent valuable tools for the study of molecular events underlying beta cell function and dysfunction.

Hyperinsulinemic hypoglycemia with nesidioblastosis: histologic features and growth factor expression

Hypoglycemia secondary to nesidioblastosis is rare in adults, and the pathogenesis of this condition is unknown. To determine factors leading to nesidioblastosis in adults, we analyzed 36 cases of nesidioblastosis including 27 cases of postgastric bypass nesidioblastosis and 9 cases of idiopathic nesidioblastosis in adults by immunohistochemistry using antibodies to insulin-like growth factor 1, insulin-like growth factor 2 (IGF2), insulin-like growth factor one receptor-alpha epidermal growth factor receptor, transforming growth factor-beta1 and 2, and transforming growth factor-beta receptor type 3. Fifty-two surgically excised pancreatic specimens from patients with benign exocrine tumors and no evidence of hypoglycemia were used as controls. There was increased IGF2, insulin-like growth factor receptor 1 receptor-alpha and transforming growth factor-beta receptor 3 expression in islets from nesidioblastosis patients compared to controls. Peliosis-type vascular ectasia was more common in nesidioblastosis patients compared to controls. These findings suggest that increased production of growth factors and growth factor receptors may contribute to the development of nesidioblastosis in adults.

Chronic antidiabetic sulfonylureas in vivo: reversible effects on mouse pancreatic beta-cells

BACKGROUND

Pancreatic beta-cell ATP-sensitive potassium (K ATP) channels are critical links between nutrient metabolism and insulin secretion. In humans, reduced or absent beta-cell K ATP channel activity resulting from loss-of-function K ATP mutations induces insulin hypersecretion. Mice with reduced K ATP channel activity also demonstrate hyperinsulinism, but mice with complete loss of K ATP channels (K ATP knockout mice) show an unexpected insulin undersecretory phenotype. Therefore we have proposed an "inverse U" hypothesis to explain the response to enhanced excitability, in which excessive hyperexcitability drives beta-cells to insulin secretory failure without cell death. Many patients with type 2 diabetes treated with antidiabetic sulfonylureas (which inhibit K ATP activity and thereby enhance insulin secretion) show long-term insulin secretory failure, which we further suggest might reflect a similar progression.

METHODS AND FINDINGS

To test the above hypotheses, and to mechanistically investigate the consequences of prolonged hyperexcitability in vivo, we used a novel approach of implanting mice with slow-release sulfonylurea (glibenclamide) pellets, to chronically inhibit beta-cell K ATP channels. Glibenclamide-implanted wild-type mice became progressively and consistently diabetic, with significantly (p < 0.05) reduced insulin secretion in response to glucose. After 1 wk of treatment, these mice were as glucose intolerant as adult K ATP knockout mice, and reduction of secretory capacity in freshly isolated islets from implanted animals was as significant (p < 0.05) as those from K ATP knockout animals. However, secretory capacity was fully restored in islets from sulfonylurea-treated mice within hours of drug washout and in vivo within 1 mo after glibenclamide treatment was terminated. Pancreatic immunostaining showed normal islet size and alpha-/beta-cell distribution within the islet, and TUNEL staining showed no evidence of apoptosis.

CONCLUSIONS

These results demonstrate that chronic glibenclamide treatment in vivo causes loss of insulin secretory capacity due to beta-cell hyperexcitability, but also reveal rapid reversibility of this secretory failure, arguing against beta-cell apoptosis or other cell death induced by sulfonylureas. These in vivo studies may help to explain why patients with type 2 diabetes can show long-term secondary failure to secrete insulin in response to sulfonylureas, but experience restoration of insulin secretion after a drug resting period, without permanent damage to beta-cells. This finding suggests that novel treatment regimens may succeed in prolonging pharmacological therapies in susceptible individuals.

Pulmonary hypertension, heart failure and neutropenia due to diazoxide therapy

Primary persistent hyperinsulinaemic hypoglycaemia is characterised by clinical symptoms that occur when blood glucose levels drop below the normal range. Diazoxide treatment remains the mainstay of medical therapy. Tolerance of diazoxide is usually excellent, but several side effects of this drug have been described. We present a 4-month-old girl who developed pulmonary hypertension, heart failure and neutropenia during diazoxide therapy. Diazoxide toxicity was suspected and the drug was withdrawn on day 13. During the next 3 days, respiratory and haemodynamic status dramatically improved and she was weaned from mechanical ventilation. Control white blood cell count was 8800 cells/mm(3) and a new echocardiography showed modreduction of pulmonary artificial pressure to 20 mmHg and resolution of atrial and ventricular enlargement. Paediatric physicians should be in mind of pulmonary hypertension, heart failure and neutropenia developing during diazoxide therapy.

beta-cell hyperexcitability: from hyperinsulinism to diabetes

Nutrient oxidation in beta cells generates a rise in [ATP]:[ADP] ratio. This reduces K(ATP) channel activity, leading to depolarization, activation of voltage-dependent Ca(2+) channels, Ca(2+) entry and insulin secretion. Consistent with this paradigm, loss-of-function mutations in the genes (KCNJ11 and ABCC8) that encode the two subunits (Kir6.2 and SUR1, respectively) of the ATP-sensitive K(+) (K(ATP)) channel underlie hyperinsulinism in humans, a genetic disorder characterized by dysregulated insulin secretion. In mice with genetic suppression of K(ATP) channel subunit expression, partial loss of K(ATP) channel conductance also causes hypersecretion, but unexpectedly, complete loss results in an undersecreting, mildly glucose-intolerant phenotype. When challenged by a high-fat diet, normal mice and mice with reduced K(ATP) channel density respond with hypersecretion, but mice with more significant or complete loss of K(ATP) channels cross over, or progress further, to an undersecreting, diabetic phenotype. It is our contention that in mice, and perhaps in humans, there is an inverse U-shaped response to hyperexcitabilty, leading first to hypersecretion but with further exacerbation to undersecretion and diabetes. The causes of the overcompensation and diabetic susceptibility are poorly understood but may have broader implications for the progression of hyperinsulinism and type 2 diabetes in humans.

Long-term in vitro growth of human insulin-secreting insulinoma cells

OBJECTIVE

Long-term in vitro maintenance of human insulin-secreting insulinoma cells.

METHODS

(1) Cell culture of ex vivo-derived insulinoma cell suspensions from 8 individual human donors, using various cell culture medium supplementations; (2) determination of insulin synthesis and secretion using immunocytochemistry and insulin and pro-insulin radioimmunoassays; (3) nestin-immunostaining of long-term in vitro grown insulinoma cell suspensions, and (4) phase-contrast light microscopy for analyzing the in vitro growth characteristics of the insulinoma cells.

RESULTS

(1) Parallel persistence of in vitro insulinoma cell proliferation as well as insulin-synthesizing and -secreting capacity depended on both the co-culture of insulinoma cells with human fibroblasts and the supplementation of the cell culture medium with tissue culture supernatant derived from the rodent pituitary adenoma cell line GH-3; (2) immunostaining for insulin and secretagogin confirmed the neuroendocrine origin of the insulinoma cells grown in vitro; (3) insulin secretion capability persisted up to an observation period of 25 weeks; (4) insulin secretion rates after 6 weeks of in vitro growth ranged from 3.5 to 83.3 muU/ml/h/60,000 cells plated, and (5) after long-term in vitro growth of insulinoma-derived cell suspensions with persistent insulin-secreting capacity, nestin staining was observed predominantly in co-cultured fibroblasts.

CONCLUSION

Our data describe for the first time the long-term in vitro culture of insulin-secreting human insulinomas and highlight the importance of beta-cell trophic factors for insulinoma cell growth.

From congenital hyperinsulinism to diabetes mellitus: the role of pancreatic beta-cell KATP channels

Pancreatic beta-cell adenosine triphosphate (ATP)-sensitive potassium (K(ATP)) channels play a pivotal role in linking glucose metabolism to regulated insulin secretion. K(ATP) channels are hetero-octameric complexes comprising two subunits Kir6.2 and sulfonylurea receptor 1 (SUR1). Changes in the intracellular concentration of nucleotides (ATP) cause alterations in the resting and opening state of the K(ATP) channels. Loss-of-function mutations in the genes encoding the two subunits of K(ATP) channels lead to the most common form of congenital hyperinsulinism (CHI). This causes persistent and severe hypoglycemia in the neonatal and infancy period. CHI can cause mental retardation and epilepsy if not treated properly. On the other hand, now there is evidence of an association between polymorphisms in the Kir6.2 gene and type 2 diabetes mellitus, mutations in the Kir6.2 gene and neonatal diabetes mellitus, and mutations in the SUR1 gene and diabetes mellitus. Interestingly, for reasons that are unclear at present, mice knockout models of K(ATP) channels are different from the human phenotype of CHI. This article is a review focusing on how abnormalities in the pancreatic beta-cell K(ATP) channels can lead to severe hypoglycemia on the one hand and diabetes mellitus on the other.

Genotypes of the pancreatic beta-cell K-ATP channel and clinical phenotypes of Japanese patients with persistent hyperinsulinaemic hypoglycaemia of infancy

OBJECTIVE

Persistent hyperinsulinaemic hypoglycaemia of infancy (PHHI) is a disorder of glucose metabolism that is characterized by dysregulated secretion of insulin from pancreatic beta-cells. This disease has been reported to be associated with mutations of the sulfonylurea receptor SUR1 (ABCC8) or the inward-rectifying potassium channel Kir6.2 (KCNJ11), which are two subunits of the pancreatic beta-cell ATP-sensitive potassium channel.

PATIENTS AND METHODS

In 14 Japanese PHHI patients, all exons of SUR1 and Kir6.2 genes were analysed by polymerase chain reaction (PCR) and direct sequencing. Four patients responded to diazoxide, and nine patients underwent a subtotal pancreatectomy. Histologically, seven patients were diagnosed to have a focal form and two a diffuse form of the disease.

RESULTS

We found nine novel mutations in the SUR1 gene and two in the Kir6.2 gene. In the SUR1 gene mutations, three were nonsense mutations (Y512X, Y1354X and G1469X), one was a one-base deletion in exon 7, and two were missense mutations in the nucleotide-binding domain 2 (K1385Q, R1487K). The other three mutations occurred in introns 14, 29 and 36, which might cause aberrant splicing of RNA. Two siblings in one family were heterozygotes for a missense mutation, K1385Q, which was maternally inherited. In Kir6.2 gene screening, one patient was found to be a compound heterozygote of a missense mutation (R34H) and a one-base deletion (C344fs/ter).

CONCLUSION

The novel mutations reported here could be pathological candidates for PHHI in Japan. They also reveal that SUR1 and Kir6.2 mutations in the Japanese population exhibit heterogeneity and that they occurred at a frequency similar to other genetic populations.

Contemporary strategies in the diagnosis and management of neonatal hyperinsulinaemic hypoglycaemia

Congenital hyperinsulinism (CHI) is a genetically and phenotypically diverse syndrome. Key management issues involve early diagnosis by ensuring that appropriate samples are taken at the point of hypoglycaemia, prevention of recurrent hypoglycaemia, and detailed characterisation of the clinical, biochemical, and genetic features of each case. Infants with persistent diazoxide resistant CHI require evaluation at specialist referral centres equipped to differentiate those with focal (fo-HI) and diffuse (di-HI) pancreatic disease. Fo-HI is treated with selective pancreatic resection but di-HI is treated by surgery only if intensive medical management regimes are not efficacious.

Hyperinsulinism of infancy: novel ABCC8 and KCNJ11 mutations and evidence for additional locus heterogeneity

Hyperinsulinism of infancy is a genetically heterogeneous disease characterized by dysregulation of insulin secretion resulting in severe hypoglycemia. To date, mutations in five different genes, the sulfonylurea receptor (SUR1, ABCC8), the inward rectifying potassium channel (K(IR)6.2, KCNJ11), glucokinase (GCK), glutamate dehydrogenase (GLUD1), and short-chain 3-hydroxyacyl-coenzyme A dehydrogenase (SCHAD), have been implicated. Previous reports suggest that, in 40% of patients, no mutation can be identified in any of these genes, suggesting additional locus heterogeneity. However, previous studies did not screen all five genes using direct sequencing, the most sensitive technique available for mutation detection. We selected 15 hyperinsulinism of infancy patients and systematically sequenced the promoter and all coding exons and intron/exon boundaries of ABCC8 and KCNJ11. If no mutation was identified, the coding sequence and intron/exon boundaries of GCK, GLUD1, and SCHAD were sequenced. Seven novel mutations were found in the ABCC8 coding region, one mutation was found in the KCNJ11 coding region, and one novel mutation was found in each of the two promoter regions screened. Functional studies on beta-cells from six patients showed abnormal ATP-sensitive K+ channel function in five of the patients; the sixth had normal channel activity, and no mutations were found. Photolabeling studies using a reconstituted system showed that all missense mutations altered intracellular trafficking. Each of the promoter mutations decreased expression of a reporter gene by about 60% in a heterologous expression system. In four patients (27%), no mutations were identified. Thus, further genetic heterogeneity is suggested in this disorder. These patients represent a cohort that can be used for searching for mutations in other candidate genes.

Hyperinsulinaemic hypoglycaemia in infancy and childhood--resolving the enigma

Children with severe hypoglycaemia due to persistent hyperinsulinism in infancy (HI) generate some of the most formidable problems of management in contemporary paediatric endocrinology. Until recently its pathophysiology was an enigma, although it was thought to be due to an anatomical abnormality in the islets of Langerhans (so called 'nesidioblastosis'). During the last 6 years there has been an explosion of knowledge providing fundamental insights into the pathological mechanisms underpinning the abnormal insulin secretion. This knowledge has been facilitated by ENRHI, a programme of research funded by the European Union, which brings together clinicians and basic scientists from 14 different countries. This collaboration encompasses clinical paediatric endocrinology, intracellular biochemistry, membrane physiology and molecular biology. This collaboration has resulted in numerous publications generating new insights into the pathophysiology of HI and represents a paradigm for collaboration in paediatric endocrinology. This review article is based on a plenary lecture delivered at the European Society for Paediatric Endocrinology meeting in Montreal on behalf of the European Network for Research into Hyperinsulinism of Infancy (ENRHI).

A case of severe diazoxide toxicity

Hyperinsulism is a rare cause of persistent hypoglycemia in the neonatal period. Therapy can be accomplished either surgically or pharmacologically. Diazoxide treatment remains the mainstay of medical therapy. Tolerance of diazoxide is usually excellent, but several adverse effects of this drug have been described. A case of severe diazoxide intoxication with fluid retention, congestive heart failure, and respiratory failure is reported. The patient was a 43-day-old infant, affected by persistent and severe hypoglycemia. After the diagnosis, hyperinsulinism was established he was treated with diazoxide (17 mg x kg(-1) daily) and octreotide (12 microg x kg(-1) daily). A few days later he presented with hepatomegaly, severe fluid retention, diffuse edema, congestive heart failure, and respiratory failure requiring mechanical ventilation. After introduction of ACE inhibitors he developed acute renal failure. The clinical condition worsened and he developed pulmonary hypertension requiring high-frequency oscillatory ventilation. Diazoxide was stopped on the 12th day in spite of poor control of blood sugar. During the next 5 days his hemodynamic status dramatically improved and he was weaned from catecholamines: he lost weight, had a negative fluid balance, and the edema disappeared, a normal diuresis resumed and renal function improved. Improvement of respiratory patterns and gas exchange made it possible to switch back to conventional ventilation and then to extubate the patient. Echocardiography demonstrated reduction of the PA pressure to normal and resolution of atrial enlargement. The patient was scheduled for elective subtotal pancreatectomy. Diagnosis and management of diazoxide intoxication are discussed.

Urinary α-ketoglutarate is elevated in patients with hyperinsulinism-hyperammonemia syndrome

BACKGROUND

Congenital hyperinsulinism (CHI) is the most frequent cause of recurrent episodes of hypoglycemia in infancy and results from different underlying genetic defects. The hyperinsulinism-hyperammonemia syndrome (HHS) has been shown to result from dominant germ line mutations within the glutamate dehydrogenase gene (GLUD1, OMIM *138130). Diagnosis of this entity is of clinical importance since invasive diagnostic procedures which are performed to identify focal pancreatic lesions are not necessary in HHS. Therefore, we investigated whether urinary concentration of alpha-ketoglutarate (alpha-KG) is elevated in patients with hyperinsulinism.

METHODS

Excretion of alpha-KG was measured by gas-chromatography/mass spectrometry (GC/MS) in eight patients with an activating GLUD1 mutation and 90 controls.

RESULTS

Urinary alpha-KG was significantly elevated in seven of eight patients when compared to controls. Hyperammonemia was found in six of the eight patients with HHS. No relation was found between the underlying GLUD1 mutation and the level of urinary alpha-KG as well as the presence or absence of hyperammonemia.

CONCLUSION

Urinary alpha-KG is elevated in most patients with HHS and should be included in the work-up of patients with hyperinsulinism.

Hyperinsulinism in Infancy: From Basic Science to Clinical Disease

Dunne, Mark J., Karen E. Cosgrove, Ruth M. Shepherd, Albert Aynsley-Green, and Keith J. Lindley. Hyperinsulinism in Infancy: From Basic Science to Clinical Disease. Physiol Rev 84: 239–275, 2004; 10.1152/physrev.00022.2003.—Ion channelopathies have now been described in many well-characterized cell types including neurons, myocytes, epithelial cells, and endocrine cells. However, in only a few cases has the relationship between altered ion channel function, cell biology, and clinical disease been defined. Hyperinsulinism in infancy (HI) is a rare, potentially lethal condition of the newborn and early childhood. The causes of HI are varied and numerous, but in almost all cases they share a common target protein, the ATP-sensitive K+channel. From gene defects in ion channel subunits to defects in β-cell metabolism and anaplerosis, this review describes the relationship between pathogenesis and clinical medicine. Until recently, HI was generally considered an orphan disease, but as parallel defects in ion channels, enzymes, and metabolic pathways also give rise to diabetes and impaired insulin release, the HI paradigm has wider implications for more common disorders of the endocrine pancreas and the molecular physiology of ion transport.

Hyperinsulinaemic hypoglycaemia in preterm neonates

Hyperinsulinism in infancy (HI) is an important cause of severe and recurrent hypoglycaemia in newborn infants. It usually appears in infants born at term, and only one case of its occurrence in a prematurely born infant has been reported as an incidental finding. This is a report of seven infants born at 31-36 weeks gestation who experienced severe persistent hyperinsulinism. Two infants were large for dates. All infants were difficult to manage, suggesting that the occurrence of HI with prematurity may be associated with a particularly aggressive illness. HI should be considered in the differential diagnosis of severe hypoglycaemia in preterm infants.

Surgery of persistent hyperinsulinaemic hypoglycaemia

Hyperinsulinism (HI) is the commonest cause of persistent or recurrent hypoglycaemia in childhood. HI is genetically and phenotypically diverse. Key management issues involve early diagnosis by insuring that appropriate investigations are undertaken at the point of hypoglycaemia, prevention of recurrent hypoglycaemia and clinical, biochemical and genetic characterisation of the HI syndrome. Children with persistent diazoxide resistant HI require investigation at specialist centres to differentiate those with a generalised disorder of the pancreas (diffuse HI; di-HI) from those with localised abnormalities within the pancreas (focal HI; fo-HI). Fo-HI may be managed by selective pancreatic resection of the focal abnormality. Di-HI is only managed by surgery if combination drug therapies are unable to prevent hypoglycaemia. Pancreatic beta-cell dysfunction persists following subtotal pancreatectomy of di-HI.

The outcome in Australian children with hyperinsulinism of infancy: early extensive surgery in severe cases lowers risk of diabetes

AIMS

Hyperinsulinism of infancy (HI) is characterized by unregulated insulin secretion in the presence of hypoglycaemia, often resulting in brain damage. Pancreatic resection for control of hypoglycaemia is frequently resisted because of the risk of diabetes mellitus (DM). We investigated retrospectively 62 children with HI from nine Australian treatment centres born between 1972 and 1998, comparing endocrine and neurological outcome in 28 patients receiving medical therapy alone with 34 who required pancreatic resection to control their hypoglycaemia.

METHODS

History, treatment and clinical course were ascertained from file audit and interview. Risk of DM (hazard ratio) attributable to age at surgery (< vs. > or = 100 days at last pancreatectomy) and extent of resection (< vs. > or = 95%) were calculated using Cox proportional hazards regression and categorical variables compared by the chi2-test. Neurological outcome (normal, mild deficit or severe deficit) was derived from the most authoritative source.

RESULTS

Surgically treated patients had a greater birthweight, earlier presentation and higher plasma insulin levels. Of 18 infants < 100 days and 16 > or = 100 days of age at surgery, four (all > or = 100 days) became diabetic as an immediate consequence of surgery and five (two < 100 days and three > or = 100 days) became diabetic 7-18 years later. Surgery > or = 100 days and pancreatectomy > or = 95% were associated with development of diabetes (HR = 12.61, CI 1.53-104.07 and HR = 7.03, CI 1.43-34.58, respectively). Neurodevelopmental outcome was no different between the surgical and medical groups with 44% overall with neurological deficits. Patients euglycaemic within 35 days of the first symptom of hypoglycaemia (Group A) had a better neurodevelopmental outcome than those still hypoglycaemic > 35 days from first presentation (Group B) (P = 0.007). Prolonged hypoglycaemia in Group B was due either to delayed diagnosis or to need for repeat surgery because of continued hypoglycaemia. Within Group A, medically treated patients (who presented later with apparently milder disease) had a higher incidence of neurodevelopmental deficit (n = 15, four mild, three severe deficit) compared with surgically treated patients (n = 18, two mild, none severe deficit) (P < 0.025).

CONCLUSIONS

Poor neurodevelopmental outcome remains a major problem in hyperinsulinism of infancy. Risk of diabetes mellitus with pancreatectomy varies according to age at surgery and extent of resection. Patients presenting early with severe disease have a better neurodevelopmental outcome and lower risk of diabetes if they are treated with early extensive surgery.

Characterisation of new KATP-channel mutations associated with congenital hyperinsulinism in the Finnish population

AIMS/HYPOTHESIS

ATP-sensitive potassium (K(ATP)) channels are crucial for the regulation of insulin secretion from pancreatic beta cells and mutations in either the Kir6.2 or SUR1 subunit of this channel can cause congenital hyperinsulinism (CHI). The aim of this study was to analyse the functional consequences of four CHI mutations (A1457T, V1550D and L1551V in SUR1, and K67N in Kir6.2) recently identified in the Finnish population.

METHODS

Wild type or mutant Kir6.2 and SUR1 subunits were coexpressed in Xenopus oocytes. The functional properties of the channels were examined by measuring currents in intact oocytes or giant inside-out membrane patches. Surface expression was measured by enzyme-linked immunosorbance assay, using HA-epitope-tagged subunits.

RESULTS

Two mutations (A1457T and V1550D) prevented trafficking of the channel to the plasma membrane. The L1551V mutation reduced surface expression 40-fold, and caused loss of MgADP and diazoxide activation. Both these factors will contribute to the lack of K(ATP) current activation observed in response to metabolic inhibition in intact oocytes. The L1551V mutation also increased the channel open probability, thereby producing a reduction in ATP-sensitivity (from 10 micro mol/l to 120 micro mol/l). The fourth mutation (K67N mutation in Kir6.2) did not affect surface expression nor alter the properties of K(ATP) channels in excised patches, but resulted in a reduced K(ATP) current amplitude in intact cells on metabolic inhibition, through an unidentified mechanism.

CONCLUSION/INTERPRETATION

The four CHI mutations disrupted K(ATP) channel activity by different mechanisms. Our results are discussed in relation to the CHI phenotype observed in patients with these mutations.

A new subtype of autosomal dominant diabetes attributable to a mutation in the gene for sulfonylurea receptor 1

BACKGROUND

ATP-sensitive potassium (KATP) channels are major regulators of glucose-induced insulin secretion in pancreatic beta cells. We have described a dominant heterozygous mutation--E1506K--in the sulfonylurea receptor 1 (SUR1) gene (ABCC8) in a Finnish family, which leads to congenital hyperinsulinaemia due to reduction of K(ATP)-channel activity. We aimed to characterise glucose metabolism in adults heterozygous for the E1506K mutation.

METHODS

Glucose tolerance was assessed by an oral glucose tolerance test, insulin secretion by the intravenous glucose tolerance test and hyperglycaemic clamp, and insulin sensitivity by hyperinsulinaemic euglycaemic clamp in 11 people heterozygous for the E1506K mutation and 19 controls.

FINDINGS

Four people who were heterozygous for the SUR1 E1506K mutation had diabetes, five had impaired glucose tolerance, one had impaired fasting glucose, and one had normal glucose tolerance. Although glucose-induced, first-phase insulin secretion was normal in children younger than 10 years of age who were heterozygous for the SUR1 E1506K mutation (n=2; 66 and 334 pmol/L), it fell rapidly after puberty (n=3; 12-32 pmol/L), and was almost completely lost in adulthood (n=11; 12-32 pmol/L). Furthermore, these heterozygous people had a substantial reduction in maximum glucose-stimulated insulin secretion during hyperglycemic clamp (carriers without diabetes 422 pmol/L; carriers with diabetes 97 pmol/L). By contrast, insulin sensitivity (M/I value) was normal in carriers of the E1506K mutation who did not have diabetes and was reduced by 15% in those who were heterozygous with diabetes (0.07 in those without diabetes and 0.05 in those with the disorder; not significantly different from controls).

INTERPRETATION

Heterozygous E1506K substitution in the SUR1 gene causes congenital hyperinsulinism in infancy, loss of insulin secretory capacity in early adulthood, and diabetes in middle-age. This variant represents a new subtype of autosomal dominant diabetes.

Hyperinsulinism induced by targeted suppression of beta cell KATP channels

ATP-sensitive K+ (K(ATP)) channels couple cell metabolism to electrical activity. To probe the role of K(ATP) in glucose-induced insulin secretion, we have generated transgenic mice expressing a dominant-negative, GFP-tagged K(ATP) channel subunit in which residues 132-134 (Gly-Tyr-Gly) in the selectivity filter were replaced by Ala-Ala-Ala, under control of the insulin promoter. Transgene expression was confirmed by both beta cell-specific green fluorescence and complete suppression of channel activity in those cells ( approximately 70%) that did fluoresce. Transgenic mice developed normally with no increased mortality and displayed normal body weight, blood glucose levels, and islet architecture. However, hyperinsulinism was evident in adult mice as (i) a disproportionately high level of circulating serum insulin for a given glucose concentration ( approximately 2-fold increase in blood insulin), (ii) enhanced glucose-induced insulin release from isolated islets, and (iii) mild yet significant enhancement in glucose tolerance. Enhanced glucose-induced insulin secretion results from both increased glucose sensitivity and increased release at saturating glucose concentration. The results suggest that incomplete suppression of K(ATP) channel activity can give rise to a maintained hyperinsulinism.

Early brain atrophy in persistent hyperinsulinemic hypoglycemia of infancy

We present two siblings with persistent hyperinsulinemic hypoglycemia of infancy, accelerated intrauterine growth and early neonatal brain atrophy. Fetal plasma glucose and insulin levels in the second sibling revealed normoglycemia despite hyperinsulinemia. The absence of intrauterine hypoglycemia suggests that the brain damage is not secondary to hypoglycemia and other etiologies must be considered.

K(ATP) channels and insulin secretion disorders

ATP-sensitive potassium (K(ATP)) channels are inhibited by intracellular ATP and activated by ADP. Nutrient oxidation in beta-cells leads to a rise in [ATP]-to-[ADP] ratios, which in turn leads to reduced K(ATP) channel activity, depolarization, voltage-dependent Ca(2+) channel activation, Ca(2+) entry, and exocytosis. Persistent hyperinsulinemic hypoglycemia of infancy (HI) is a genetic disorder characterized by dysregulated insulin secretion and, although rare, causes severe mental retardation and epilepsy if left untreated. The last five or six years have seen rapid advance in understanding the molecular basis of K(ATP) channel activity and the molecular genetics of HI. In the majority of cases for which a genotype has been uncovered, causal HI mutations are found in one or the other of the two genes, SUR1 and Kir6.2, that encode the K(ATP) channel. This article will review studies that have defined the link between channel activity and defective insulin release and will consider implications for future understanding of the mechanisms of control of insulin secretion in normal and diseased states.

Oral beta-hydroxybutyrate supplementation in two patients with hyperinsulinemic hypoglycemia: monitoring of beta-hydroxybutyrate levels in blood and cerebrospinal fluid, and in the brain by in vivo magnetic resonance spectroscopy

In persistent hyperinsulinemic hypoglycemia of infancy, ketone body concentrations are abnormally low at times of hypoglycemia, depriving the brain of its most important alternative fuel. The neuroprotective effect of endogenous ketone bodies is evidenced by animal and human studies, but knowledge about exogenous supply is limited. Assuming that exogenous ketone body compounds as a dietetic food might replace this alternative energy source for the brain, we have monitored the fate of orally supplemented DL sodium beta-hydroxybutyrate (beta-OHB) in two 6-mo-old infants with persistent hyperinsulinemic hypoglycemia for 5 and 7 mo, while on frequent tube-feedings and treatment with octreotide. Near total (95%) pancreatectomy had been ineffective in one patient and was refused in the other. In blood, concentrations of beta-OHB increased to levels comparable to a 16- to 24-h fast while on DL sodium beta-OHB 880 to 1000 mg/kg per day. In cerebrospinal fluid, concentrations of beta-OHB increased to levels comparable to a 24- to 40-h fast, after single dosages of 4 and 8 g, respectively. High ratios of beta-OHB to acetoacetate indicated exogenous origin of beta-OHB. An increase of intracerebral concentrations of beta-OHB could be demonstrated by repetitive single-voxel proton magnetic resonance spectroscopy by a clear doublet at 1.25 ppm. Oral DL sodium beta-OHB was tolerated without side effects. This first report on oral supplementation of DL sodium beta-OHB in two patients with persistent hyperinsulinemic hypoglycemia demonstrates effective uptake across the blood-brain barrier and could provide the basis for further evaluation of the neuroprotective effect of beta-OHB in conditions with hypoketotic hypoglycemia.

Identification of a familial hyperinsulinism-causing mutation in the sulfonylurea receptor 1 that prevents normal trafficking and function of KATP channels

Mutations in the pancreatic ATP-sensitive potassium (K(ATP)) channel subunits sulfonylurea receptor 1 (SUR1) and the inwardly rectifying potassium channel Kir6.2 cause persistent hyperinsulinemic hypoglycemia of infancy. We have identified a SUR1 mutation, L1544P, in a patient with the disease. Channels formed by co-transfection of Kir6.2 and the mutant SUR1 in COS cells have reduced response to MgADP ( approximately 10% that of the wild-type channels) and reduced surface expression ( approximately 19% that of the wild-type channels). However, the steady-state level of the SUR1 protein is unaffected. Treating cells with lysosomal or proteasomal inhibitors did not improve surface expression of the mutant channels, suggesting that increased degradation of mutant channels by either pathway is unlikely to account for the reduced surface expression. Removal of the RKR endoplasmic reticulum retention/retrieval trafficking motif in either SUR1 or Kir6.2 increased the surface expression of the mutant channel by approximately 35 and approximately 20%, respectively. The simultaneous removal of the RKR motif in both channel subunits restored surface expression of the mutant channel to the wild-type channel levels. Thus, the L1544P mutation may interfere with normal trafficking of K(ATP) channels by causing improper shielding of the RKR endoplasmic reticulum retention/retrieval trafficking signals in the two channel subunits.

Insulin receptor activation inhibits insulin secretion from human islets of Langerhans

There is no consensus on the role of insulin secreted from pancreatic beta-cells in regulating its own secretion, either in rodent islets or in human islets. We have now investigated whether there is an autocrine signalling role for insulin in human islets by determining insulin receptor expression and assessing the effects of insulin receptor activation using a non-peptidyl insulin mimetic termed L-783,281. Human insulin receptor mRNA was detected by PCR amplification of human islet cDNA, and translation of the message in human islets was confirmed by Western blotting. Perifusion experiments revealed that both glucose-stimulated and basal insulin secretion were significantly inhibited following human islet insulin receptor activation with L-783,281, and that signalling through phosphatidylinositol 3-kinase (PI 3-kinase) was responsible, at least in part, for this inhibitory effect. These studies indicate that human islets express insulin receptors and that they are functionally coupled to a PI 3-kinase-dependent inhibition of insulin secretion.

Ten years' experience of persistent hyperinsulinaemic hypoglycaemia of infancy

OBJECTIVE

To review the presentation, management and outcome of persistent hyperinsulinaemic hypoglycaemia of infancy seen at the Royal Alexandra Hospital for Children over a 10 year period.

METHODOLOGY

A retrospective review of 20 subjects was performed. As well as laboratory data, data were collected on clinical presentation, medical and surgical management and developmental outcome.

RESULTS

Twenty subjects (11 male) were identified with presentation at a median age of 1.5 months (range 0-10 months), with 10 (50%) presenting in the first week of life. Only 20% of patients were large for gestational age. Diagnosis was made on the basis of high glucose requirements and inappropriately high insulin levels at the time of hypoglycaemia. Eight (40%) responded well to diazoxide treatment alone, seven (35%) received diazoxide in combination with other short-term medical therapy initially and five (25%) required pancreatectomy (repeat surgery in three). Those who required surgery had a higher mean birth weight. Infants presenting in the first week of life were less likely to respond to diazoxide. At the time of last review, eight (40%) of those treated medically had ceased all treatment. Two of the five cases requiring pancreatectomy now require insulin treatment. Neurodevelopmental assessment was normal in 11 (55%), mild delay was found in six (30%) and moderate or severe delay was found in three (15%).

CONCLUSIONS

Persistent hyperinsulinaemic hypoglycaemia of infancy remains a major diagnostic and management challenge. Early suspicion and recognition is critical with definitive investigation and medical therapy to avoid hypoglycaemia, with pancreatectomy in medically unresponsive cases. Normal neurodevelopmental outcome was found in only 55% of cases.

Subtotal pancreatectomy for hypoglycemia due to congenital hyperinsulinism: long-term follow-up of neurodevelopmental and pancreatic function

OBJECTIVE

To evaluate neurodevelopmental status as well as endocrine and exocrine pancreatic function in children who have undergone subtotal pancreatectomy for hypoglycemia due to congenital hyperinsulinism.

PATIENTS AND METHODS

Out of 15 identified patients, eight children (mean age 12.7 +/- 0.8 yr) participated in detailed psychometric testing and studies assessing glucose homeostasis, secretion of proinsulin, insulin, glucagon and C-peptide during a test meal. Additionally, a 24-h fast, glucagon challenge test, 72-h stool collection, and ultrasonography of the pancreatic remnant were performed.

RESULTS

Five of the 15 initially identified children had seizure disorders, including two with mental retardation. Diabetes developed in two of 15 children. All eight children investigated in the present study had evidence for attentional control impairment and 50% had subnormal intellectual functioning. Two had symptomatic hypoglycemia during the 24-h fast, while one had an elevated fasting glucose concentration. Four children, including the latter patient, had proinsulin/insulin ratios resembling patients with type 2 diabetes. Exocrine pancreatic function was normal in all eight children. No correlation was found between pancreatic endocrine function and pancreatic remnant size, nor between multiple pre- and postoperative factors (i.e., age at diagnosis and surgery) and neurodevelopmental outcome.

CONCLUSION

While severe mental retardation or diabetes occurred infrequently in our patient population compared with previous reports, all of the studied children had subtle anomalies in their cognitive performance tests and the majority had endocrine test results indicative of abnormal insulin secretion and stressed pancreatic beta cells. Although partial pancreatectomy remains the treatment of choice after medical therapy fails, improved therapeutic means are necessary to achieve better clinical outcome.

Exercise induced hypoglycaemic hyperinsulinism

BACKGROUND

Hyperinsulinism in childhood is often caused by genetic defects involving the regulation of insulin secretion leading to recurrent episodes of hypoglycaemia. We report two patients with exercise induced hypoglycaemia.

METHODS

Standardised short exercise tests with frequent blood glucose and plasma insulin measurements were performed in the patients and young healthy controls.

RESULTS

Short term exercise resulted in insulin induced hypoglycaemia 15 to 50 minutes after the end of exercise. A massive burst of insulin secretion was observed within a few minutes of the start of exercise in both patients. By contrast glucose and insulin concentrations remained unchanged in healthy controls.

CONCLUSIONS

Hyperinsulinaemic hypoglycaemia after moderate physical exercise represents a rarely described phenotype of hyperinsulinism with an as yet unknown defect in the regulation of insulin secretion. It should be suspected in individuals with recurrent exercise related syncope or disturbance of consciousness.

Defective trafficking and function of KATP channels caused by a sulfonylurea receptor 1 mutation associated with persistent hyperinsulinemic hypoglycemia of infancy

The ATP-sensitive potassium channel (K(ATP)) regulates insulin secretion in pancreatic beta cells. Loss of functional K(ATP) channels because of mutations in either the SUR1 or Kir6.2 channel subunit causes persistent hyperinsulinemic hypoglycemia of infancy (PHHI). We investigated the molecular mechanism by which a single phenylalanine deletion in SUR1 (DeltaF1388) causes PHHI. Previous studies have shown that coexpression of DeltaF1388 SUR1 with Kir6.2 results in no channel activity. We demonstrate here that the lack of functional expression is due to failure of the mutant channel to traffic to the cell surface. Trafficking of K(ATP) channels requires that the endoplasmic reticulum-retention signal, RKR, present in both SUR1 and Kir6.2, be shielded during channel assembly. To ask whether DeltaF1388 SUR1 forms functional channels with Kir6.2, we inactivated the RKR signal in DeltaF1388 SUR1 by mutation to AAA (DeltaF1388 SUR1(AAA)). Inactivation of similar endoplasmic reticulum-retention signals in the cystic fibrosis transmembrane conductance regulator has been shown to partially overcome the trafficking defect of a cystic fibrosis transmembrane conductance regulator mutation, DeltaF508. We found that coexpression of DeltaF1388 SUR1(AAA) with Kir6.2 led to partial surface expression of the mutant channel. Moreover, mutant channels were active. Compared with wild-type channels, the mutant channels have reduced ATP sensitivity and do not respond to stimulation by MgADP or diazoxide. The RKR --> AAA mutation alone has no effect on channel properties. Our results establish defective trafficking of K(ATP) channels as a molecular basis of PHHI and show that F1388 in SUR1 is critical for normal trafficking and function of K(ATP) channels.

Histologic findings in persistent hyperinsulinemic hypoglycemia of infancy: Australian experience

Persistent hyperinsulinemic hypoglycemia of infancy (PHHI) is characterized by hyperinsulinism and profound hypoglycemia, with most children requiring pancreatic resection. The histological classification of PHHI is controversial. Most authors acknowledge the existence of focal areas of islet cell proliferation (adenomatosis) in 30%-50% of cases and a diffuse disorganisation of islet architecture, termed "nesidiodysplasia," in others. De Lonlay et al. reported that cases with adenomatosis are focal with normal remainder of pancreas and that focal and diffuse disease can be differentiated intraoperatively, on the basis of increased beta-cell nuclear size found only in the diffusely abnormal pancreas. We have examined pancreatic histology in a blinded controlled study of PHHI patients. Pancreatic tissue was obtained at autopsy from 60 normal subjects (age 17 weeks gestation to 76 years) and from surgical specimens of 31 PHHI patients. Sections from PHHI subjects (n = 294 blocks) and control sections were stained with hematoxylin and eosin, insulin, glucagon, somatostatin, NSE, cytokeratin 19, and vimentin. Three sections from each PHHI patient were randomly chosen for further analysis. Age-matched control (n = 34) and PHHI sections (n = 66) were examined, with the identity of subjects concealed. A diagnosis of normal histology, adenomatosis, or diffuse nesidiodysplasia was recorded for each section. The presence of large beta-cell nuclei (>19 microm), ductuloinsular complexes, and centroacinar cell proliferation was noted. Of a total of 65 subjects examined (34 control and 31 PHHI), 37 subjects were identified as normal on both sections examined. All the control cases were correctly identified as normal and none had large beta-cell nuclei or centroacinar cell proliferation. Of 31 PHHI patients, 28 were identified as abnormal, either on the basis of abnormal architecture and/or abnormally large beta-cell nuclei. Three patients were identified as normal in both sections. Fifteen of 31 patients had diffuse nesidiodysplasia only. Of 13 patients with areas of adenomatosis, 2 had resection of a nodule with adenomatosis present in most of the tissue removed at surgery. Nine patients had a diagnosis of adenomatosis in one section and a diagnosis of diffuse nesidiodysplasia in the other sections from nonadjacent pancreas. Only 2 of 31 PHHI cases had adenomatosis on one section examined and normal pancreas on the other section examined. Large beta-cell nuclei were variably found in PHHI sections. Only 5 of 15 patients with diffuse nesidiodysplasia had large nuclei in both sections examined. Centroacinar cell proliferation was identified in 12 PHHI subjects, 6 with adenomatosis and diffuse nesidiodysplasia and 6 with diffuse changes only. It was patchy in distribution within sections and present in only one section in 7 of the 12 subjects. In summary, we have shown that a blinded observer could differentiate control and PHHI pancreatic tissue. Only 2 of 31 patients (6%) had focal adenomatosis with normal nonadjacent pancreas, the majority (24 of 31) had diffuse nesidiodysplasia affecting the remainder of their pancreas, with 38% (9 of 24) also having areas of adenomatosis. Large beta-cell nuclei did not reliably identify those with diffuse disease in this study. There was evidence of significant ductal and centroacinar proliferation in 39% of PHHI cases, which was not observed in any of the controls. We have shown that PHHI subjects have a spectrum of pancreatic histological abnormalities, from no abnormality to diffuse subtle changes to florid adenomatosis. Patients could not be segregated into subtypes for different operative intervention despite the availability of full immunohistochemical staining.

Neonatal hypoglycaemia and withdrawal symptoms after exposure in utero to valproate

AIMS

To define, in a prospective study, the risk of hypoglycaemia-defined as blood glucose concentration < 1.8 mmol/l-in term infants exposed in utero to valproate and to describe the withdrawal symptoms.

METHODS

Twenty epileptic women were treated with valproate only during pregnancy and two were treated with valproate and carbamazepine. In the first trimester, the daily median dose of valproate was 1.0 g (range 0.3-4.2) and in the third trimester 1.2 g (range 0.3-4.8).

RESULTS

Thirteen of the 22 infants became hypoglycaemic. One infant had eight episodes of hypoglycaemia, one had three episodes, two had two episodes, and nine had one episode each. The lowest blood glucose concentration was 1.0 mmol/l. All episodes were asymptomatic. The maternal mean plasma concentration of total valproate during the third trimester correlated negatively with blood glucose concentration one hour after delivery (p < 0.0003) and with the development of hypoglycaemia (p < 0.0001). There was no evidence for hyperinsulinaemia as the cause of hypoglycaemia. Ten infants developed withdrawal symptoms, which correlated positively with the mean dose of valproate in the third trimester and the concentration of the free fraction of valproate in maternal plasma at delivery (p < 0.02).

CONCLUSIONS

Infants exposed to valproate in utero had a significantly elevated risk of hypoglycaemia, and withdrawal symptoms were often observed.

Congenital hyperinsulinism: molecular basis of a heterogeneous disease

Congenital hyperinsulinism (CHI) is a disease phenotype characterized by increased, usually irregular, insulin secretion leading to hypoglycemia, coma, and severe brain damage, left untreated. Hyperinsulinism may be caused by a range of biochemical disturbances and molecular defects. In pancreatic beta cells, insulin secretion is stimulated by closure of the ATP-dependent potassium channel (K(ATP) channel). K(ATP) channel is a complex composed of at least two subunits: the sulfonylurea receptor SUR1 and Kir6.2, an inward rectifier K+ channel member. Mutations in both subunits have been identified in patients with the autosomal recessive form of hyperinsulinism, including 28 different mutations in the SUR1 gene and two mutations in the Kir6.2 gene. These mutations co-segregated with disease phenotype, also known as persistent hyperinsulinemic hypoglycemia of infancy (PHHI), and with attenuated K(ATP) channel function. Inadequately high insulin secretion in one family with an autosomal dominant mode of inheritance is caused by a mutation in the glucokinase gene, resulting in increased affinity of the enzyme for glucose. Five different mutations have been identified in the glutamate dehydrogenase gene, resulting in overactivity of this enzyme and causing a syndrome of hyperinsulinism and hyperammonemia. In 13 cases, hyperinsulinism was caused by one or more focal pancreatic lesions with specific loss of maternal alleles of the imprinted chromosome region 11p15. In five patients, this loss of heterozygosity unmasked a paternally inherited recessive SUR1 mutation. The new molecular approaches in PHHI give further insight into the mechanism of pancreatic beta cell insulin secretion. The heterogeneous group of patients with CHI may now be classified according to their basic defects in the four different genes, with potential implications for a more specific treatment.

Intragenic single nucleotide polymorphism haplotype analysis of SUR1 mutations in familial hyperinsulinism

Familial hyperinsulinism (HI; MIM# 256450) is an autosomal recessive disorder of pancreatic beta-cell function, characterized by inadequate suppression of insulin secretion despite severe recurrent fasting hypoglycemia. Subtotal pancreatectomy is frequently required to prevent permanent neurologic sequelae. The incidence of HI in the Caucasian population is estimated at 1:50,000, however an apparent increased incidence among Ashkenazi Jews and Saudi Arabian Arabs has been reported. A locus for HI was assigned by linkage analyses to human chromosome 11p15.1. The sulfonylurea receptor (MIM# 600509, SUR1) and the potassium channel, inwardly rectifying, subfamily J member 11 (MIM# 600937, KIR6.2) genes, 2 components of the beta-cell K(ATP) channel, are clustered in this chromosomal region, and mutations in these genes have been implicated in HI. We previously demonstrated that two mutations in the SUR1 gene are present on approximately 88% of HI-associated chromosomes in Ashkenazi Jewish patients. Haplotype analysis with microsatellite markers flanking the gene revealed that one mutation (delF1388), reported only in Ashkenazi probands, occurred on two related extended haplotypes. By contrast, the second, more common mutation (3992-9g-->a) was associated with nine different intergenic haplotypes and has been reported in non-Jewish HI patients as well. In this study, we evaluated disease-associated chromosomes from 41 Ashkenazi Jewish and 2 non-Jewish HI patients carrying the 3992-9g-->a mutation by assessing haplotypes defined by nine common single nucleotide polymorphisms (SNPs), six in the SUR1 gene, and three in the KIR6.2 gene. Our results indicate that all 54 chromosomes carrying the 3992-9g-->a mutation in the Jewish patients appear to have originated from one founder mutation, whereas the same mutation on chromosomes from non-Jewish patients originated independently. Furthermore, our findings have implications concerning the HI-associated chromosomes on which no mutation has been identified.

Hyperinsulinism of the newborn

Neonatal hyperinsulinism (HI) is a clinical syndrome of pancreatic beta-cell dysfunction characterized by failure to suppress insulin secretion in the presence of hypoglycemia. Although rare, it is the most common cause for persistent hypoglycemia in the newborn period. Treatment can be extremely difficult, and partial pancreatectomy is frequently required to prevent recurrent hypoglycemia and irreversible brain damage. In the last 5 years much has been learned about the pathophysiology of this disease. In most patients, the disease is caused by recessive mutations in either of the 2 functional subunits of the beta-cell KATP channel (SUR1 or Kir6.2). Although in most families, the disease is transmitted as an autosomal recessive trait, a novel form of transmission, resulting in focal involvement of the pancreas has recently been described. Not all patients with HI have mutations in the KATP channel genes. An activating mutation in the "glucose sensor" glucokinase has recently been reported in one family with diazoxide-responsive autosomal dominant hyperinsulinemic hypoglycemia. Also, a new syndrome of hyperinsulinism associated with benign hyperammonemia was recently described and found to be caused by activating mutations in the glutamate dehydrogenase (GDH) gene (GLUD-1). Thus, the clinical syndrome of HI can be caused by mutations in 4 different genes and can be transmitted as either a recessive or a dominant trait. These findings aid in the therapeutic decision-making process and improve the accuracy and precision of genetic counseling. Despite these recent discoveries, however, the metabolic origin of the disease is still unknown in about 50% of cases.

Targeted overactivity of beta cell K(ATP) channels induces profound neonatal diabetes

A paradigm for control of insulin secretion is that glucose metabolism elevates cytoplasmic [ATP]/[ADP] in beta cells, closing K(ATP) channels and causing depolarization, Ca2+ entry, and insulin release. Decreased responsiveness of K(ATP) channels to elevated [ATP]/[ADP] should therefore lead to decreased insulin secretion and diabetes. To test this critical prediction, we generated transgenic mice expressing beta cell K(ATP) channels with reduced ATP sensitivity. Animals develop severe hyperglycemia, hypoinsulinemia, and ketoacidosis within 2 days and typically die within 5. Nevertheless, islet morphology, insulin localization, and alpha and beta cell distributions were normal (before day 3), pointing to reduced insulin secretion as causal. The data indicate that normal K(ATP) channel activity is critical for maintenance of euglycemia and that overactivity can cause diabetes by inhibiting insulin secretion.

Hyperinsulinism of infancy: towards an understanding of unregulated insulin release. European Network for Research into Hyperinsulinism in Infancy

Insulin is synthesised, stored, and secreted from pancreatic beta cells. These are located within the islets of Langerhans, which are distributed throughout the pancreas. Less than 2% of the total pancreas is devoted to an endocrine function. When the mechanisms that control insulin release are compromised, potentially lethal diseases such as diabetes and neonatal hypoglycaemia are manifest. This article reviews the physiology of insulin release and illustrates how defects in these processes will result in the pathophysiology of hyperinsulinism of infancy.

Ions, genes and insulin release: from basic science to clinical disease. Based on the 1998 R. D. Lawrence Lecture

In 1968, reports of the first microelectrode recordings of insulin-secreting cells were published. Thirty years later it is now established that electrical responses of beta-cells play a critical role in stimulus-secretion coupling. It is now also clear that defects in ion channel genes compromise the mechanisms which govern secretion and lead to the onset of disease. Here, the physiology of insulin release is reviewed in the context of ion channels, the ionic control of insulin release and the pathophysiology of hyperinsulinism of infancy.

Engineering a glucose-responsive human insulin-secreting cell line from islets of Langerhans isolated from a patient with persistent hyperinsulinemic hypoglycemia of infancy

Persistent hyperinsulinemic hypoglycemia of infancy (PHHI) is a neonatal disease characterized by dysregulation of insulin secretion accompanied by profound hypoglycemia. We have discovered that islet cells, isolated from the pancreas of a PHHI patient, proliferate in culture while maintaining a beta cell-like phenotype. The PHHI-derived cell line (NES2Y) exhibits insulin secretory characteristics typical of islet cells derived from these patients, i.e. they have no K(ATP) channel activity and as a consequence secrete insulin at constitutively high levels in the absence of glucose. In addition, they exhibit impaired expression of the homeodomain transcription factor PDX1, which is a key component of the signaling pathway linking nutrient metabolism to the regulation of insulin gene expression. To repair these defects NES2Y cells were triple-transfected with cDNAs encoding the two components of the K(ATP) channel (SUR1 and Kir6.2) and PDX1. One selected clonal cell line (NISK9) had normal K(ATP) channel activity, and as a result of changes in intracellular Ca(2+) homeostasis ([Ca(2+)](i)) secreted insulin within the physiological range of glucose concentrations. This approach to engineering PHHI-derived islet cells may be of use in gene therapy for PHHI and in cell engineering techniques for administering insulin for the treatment of diabetes mellitus.