Therapy for persistent hyperinsulinemic hypoglycemia of infancy. Understanding the responsiveness of beta cells to diazoxide and somatostatin

Genome-wide Survival Analysis for Macular Neovascularization Development in Central Serous Chorioretinopathy Revealed Shared Genetic Susceptibility with Polypoidal Choroidal Vasculopathy

PURPOSE

To identify susceptibility genes for macular neovascularization (MNV) development in central serous chorioretinopathy (CSC).

DESIGN

Genome-wide survival analysis using a longitudinal cohort study.

PARTICIPANTS

We included 402 and 137 patients with CSC but without MNV at their first visit from the Kyoto CSC Cohort and Kobe CSC dataset, respectively. All patients underwent detailed ophthalmologic examinations, including multimodal imaging, such as fundus autofluorescence, spectral-domain optical coherence tomography, and fluorescein angiography/indocyanine green angiography and/or optimal coherence tomography angiography.

METHODS

We conducted a genome-wide survival analysis using the Kyoto CSC Cohort. We applied the Cox proportional hazard model to adjust for age, sex, and the first principal component. Single nucleotide polymorphisms (SNPs) with P-values <1.0×10^-5 were carried forward to the replication in the Kobe CSC dataset. Moreover, we evaluated the contribution of previously-reported age-related macular degeneration (AMD) susceptibility loci. We used FUMA and ToppFun for the functional enrichment analysis.

MAIN OUTCOME MEASURES

The association between SNPs and MNV development in patients with CSC.

RESULTS

Rs370974631 near ARMS2 displayed a genome-wide significant association in the meta-analysis of discovery and replication result (hazard ratio [HR]_meta = 3.63; P_meta = 5.76×10^-9). Among previously-reported AMD susceptibility loci, we additionally identified CFH rs800292 (HR = 0.39, P = 2.55×10^-4), COL4A3 rs4276018 (HR = 0.26, P = 1.56×10^-3), and B3GALTL rs9564692 (HR = 0.56, P = 8.30×10^-3) as susceptibility loci for MNV development in CSC. The functional enrichment analysis revealed significant enrichment of eight pathways (GO:0051561, GO:0036444, GO:0008282, GO:1990246, GO:0015272, GO:0030955, GO:0031420, and GO:0005242) related to ion transport.

CONCLUSIONS

ARMS2, CFH, COL4A3, and B3GALTL were identified as susceptibility genes for MNV development in CSC. The aforementioned four genes are known as susceptibility genes for AMD, whereas COL4A3 and B3GALTL were previously reported to be polypoidal choroidal vasculopathy (PCV)-specific susceptibility genes. Our findings revealed the shared genetic susceptibility between PCV and MNV secondary to CSC.

Phosphomannomutase 2 hyperinsulinemia: Recent advances of genetic pathogenesis, diagnosis, and management

Congenital hyperinsulinemia (CHI), is a clinically heterogeneous disorder that presents as a major cause of persistent and recurrent hypoglycemia during infancy and childhood. There are 16 subtypes of CHI-related genes. Phosphomannomutase 2 hyperinsulinemia (PMM2-HI) is an extremely rare subtype which is first reported in 2017, with only 18 families reported so far. This review provides a structured description of the genetic pathogenesis, and current diagnostic and therapeutic advances of PMM2-HI to increase clinicians' awareness of PMM2-HI.

Genetic pathogenesis, diagnosis, and treatment of short-chain 3-hydroxyacyl-coenzyme A dehydrogenase hyperinsulinism

Congenital hyperinsulinism (CHI), a major cause of persistent and recurrent hypoglycemia in infancy and childhood. Numerous pathogenic genes have been associated with 14 known genetic subtypes of CHI. Adenosine triphosphate-sensitive potassium channel hyperinsulinism (KATP-HI) is the most common and most severe subtype, accounting for 40–50% of CHI cases. Short-chain 3-hydroxyacyl-coenzyme A dehydrogenase hyperinsulinism (SCHAD-HI) is a rare subtype that accounts for less than 1% of all CHI cases that are caused by homozygous mutations in the hydroxyacyl-coenzyme A dehydrogenase (HADH) gene. This review provided a systematic description of the genetic pathogenesis and current progress in the diagnosis and treatment of SCHAD-HI to improve our understanding of this disease.

Necrotising enterocolitis in newborns receiving diazoxide

BACKGROUND

Frequent and severe gastrointestinal disturbances have been reported with the use of diazoxide in adults and older children. However, no studies have investigated the incidence of necrotising enterocolitis (NEC) in diazoxide-exposed newborns.

OBJECTIVE

To evaluate a possible association between diazoxide treatment for neonatal hypoglycaemia and the occurrence of NEC.

DESIGN

Multicentre retrospective cohort study.

SETTING

Three tertiary neonatal intensive care units in Toronto, Canada.

PATIENTS

All patients treated with diazoxide for persistent hypoglycaemia between July 2012 and June 2017 were included. Overall incidence of NEC during those years on the participating units was obtained for comparison from the Canadian Neonatal Network database.

MAIN OUTCOME

Incidence of NEC after diazoxide exposure.

RESULTS

Fifty-five neonates were exposed to diazoxide during the study period. Eighteen patients (33%) showed signs of feeding intolerance, and 7 developed NEC (13%). A diagnosis of NEC was more prevalent in the diazoxide-exposed, as compared with non-exposed infants of similar gestational age (OR 5.07, 95% CI 2.27 to 11.27; p<0.001), and greatest among infants born at 33-36 weeks' gestation (OR 13.76, 95% CI 3.77 to 50.23; p<0.001). All but one of the neonates diagnosed with NEC developed the disease within 7 days from initiation of diazoxide treatment.

CONCLUSION

The present data suggest a possible association between diazoxide exposure and the development of NEC in neonates. Further evaluation of the diazoxide-associated risk of NEC in neonates treated for persistent hypoglycaemia is warranted.

Somatostatin analogues for the treatment of hyperinsulinaemic hypoglycaemia

Hyperinsulinaemic hypoglycaemia (HH) is a biochemical finding of low blood glucose levels due to the dysregulation of insulin secretion from pancreatic β-cells. Under normal physiological conditions, glucose metabolism is coupled to β-cell insulin secretion so that blood glucose levels are maintained within the physiological range of 3.5-5.5 mmol/L. However, in HH this coupling of glucose metabolism to insulin secretion is perturbed so that insulin secretion becomes unregulated. HH typically occurs in the neonatal, infancy and childhood periods and can be due to many different causes. Adults can also present with HH but the causes in adults tend to be different. Somatostatin (SST) is a peptide hormone that is released by the delta cells (δ-cells) in the pancreas. It binds to G protein-coupled SST receptors to regulate a variety of location-specific and selective functions such as hormone inhibition, neurotransmission and cell proliferation. SST plays a potent role in the regulation of both insulin and glucagon secretion in response to changes in glucose levels by negative feedback mechanism. The half-life of SST is only 1-3 min due to quick degradation by peptidases in plasma and tissues. Thus, a direct continuous intravenous or subcutaneous infusion is required to achieve the therapeutic effect. These limitations prompted the discovery of SST analogues such as octreotide and lanreotide, which have longer half-lives and therefore can be administered as injections. SST analogues are used to treat different forms of HH in children and adults and therapeutic effect is achieved by suppressing insulin secretion from pancreatic β-cells by complex mechanisms. These treatments are associated with several side effects, especially in the newborn period, with necrotizing enterocolitis being the most serious side effect and hence SS analogues should be used with extreme caution in this age group.

Heterozygous Insulin Receptor (INSR) Mutation Associated with Neonatal Hyperinsulinemic Hypoglycaemia and Familial Diabetes Mellitus: Case Series

Mutations in the insulin receptor (INSR) gene are associated with insulin resistance and hyperglycaemia. Various autosomal dominant heterozygous INSR mutations leading to hyperinsulinemic hypoglycaemia (HH) have been described in adults and children (more than 3 years of age) but not in the neonatal period. Family 1: A small for gestational age (SGA) child born to a mother with gestational diabetes presented with persistent hypoglycaemia, was diagnosed with HH and responded well to diazoxide treatment. Diazoxide was gradually weaned and discontinued by 8 months of age. Later, the younger sibling had a similar course of illness. On genetic analysis a heterozygous INSR missense variant p.(Met1180Lys) was found in the siblings, mother and grandfather but not in the father. Family 2: A twin preterm and SGA baby presented with persistent hypoglycaemia, which was confirmed as HH. He responded to diazoxide, which was subsequently discontinued by 10 weeks of life. Genetic analysis revealed a novel heterozygous INSR missense variant p.(Arg1119Gln) in the affected twin and the mother. Family 3: An SGA child presented with diazoxide responsive HH. Diazoxide was gradually weaned and discontinued by 9 weeks of age. Genetic analysis revealed a novel heterozygous INSR p.(Arg1191Gln) variant in the proband and her father. We report, for the first time, an association of INSR mutation with neonatal HH responsive to diazoxide therapy that resolved subsequently. Our case series emphasizes the need for genetic analysis and long-term follow up of these patients.

Necrotizing enterocolitis following diazoxide therapy for persistent neonatal hypoglycemia

Recalcitrant neonatal hypoglycemia poses a treatment challenge for clinicians. When a patient’s hypoglycemia does not respond to dextrose infusion, several medication options are available, including diazoxide(1,2). Several side effects of diazoxide are described in the literature, including fluid retention with the risk of development of congestive heart failure(3,4). We describe a case of necrotizing enterocolitis in a patient with Beckwith-Wiedemann Syndrome with persistent neonatal hypoglycemia who was treated with increasing doses of diazoxide.

Congenital Hyperinsulinemic Hypoglycemia and Hyperammonemia due to Pathogenic Variants in GLUD1

Congenital hyperinsulinism (CHI) is a clinically and genetically heterogeneous disorder, characterized by dysregulated insulin secretion. Pathogenic variants in at least twelve different genes (ABCC8, KCNJ11, GLUD1, GCK, HADH, SLC16A1, HNF4A, HNF1A, UCP2, TRMT10A HK1, and PGM1) are known to cause CHI. Pathogenic variants in the GLUD1 gene, which encodes the enzyme glutamate dehydrogenase (GDH), account for 5% of the cases of congenital hyperinsulinemic hypoglycemia. Pathogenic variants in GLUD1 typically present in late infancy, are diet and/or diazoxide-responsive and cause protein-induced hyperinsulinemic hypoglycemia as insulin secretion is triggered by allosteric activation of GDH by leucine. The authors are presenting three unrelated Indian children, who manifested with fasting as well as dietary protein induced hypoglycemia in late infancy, and were diagnosed to have hyperinsulinemic hyperammonemic hypoglycemia due to pathogenic variants in GLUD1. Although the hypoglycemia responded to diazoxide, delayed diagnosis and irregular treatment had resulted in neurological problems in two of the three children. Early identification, appropriate dietary modifications and regular treatment with diazoxide can prevent adverse neurological outcome.

Sporadic Insulinoma Presenting as Early Morning Night Terrors

A 16-year-old boy with a recent diagnosis of night terrors was evaluated for recurrent early morning hypoglycemia after an early morning seizure. Evaluation in clinic with critical laboratories identified hyperinsulinemic hypoglycemia. Additional investigation revealed a sporadic insulinoma as the etiology of his hypoglycemia and all symptoms were resolved after pancreaticoduodenectomy. The importance of obtaining critical laboratory samples is highlighted and appropriate radiologic, medical, and pathologic testing is discussed. We additionally review the medical and surgical management of hyperinsulinemic hypoglycemia. A discussion of multiple endocrine neoplasia type 1 associated insulinomas is included as well. This case highlights the importance of considering hypoglycemia in the evaluation of night terrors and new-onset seizures.

Establishment and Application of in Vitro Membrane Potential Assays in Cell Lines with Endogenous or Recombinant Expression of ATP-Sensitive Potassium Channels (Kir6.2/SUR1) Using a Fluorescent Probe Kit

The flow of current through the adenosine triphosphate (ATP)-sensitive potassium channel (KATP) of the isoform Kir6.2/SUR1 regulates the resting membrane potential in the pancreatic β-cell. In combination with the cellular glucose metabolism, it is an important minute-to-minute regulator of insulin secretion and whole-body glucose homeostasis. The same KATPisoform is further reported to be present in glucagon-secreting α-cells, intestinal L-cells, and glucose-responsive neurons in the hypothalamus. All in all, this makes Kir6.2/SUR1 an interesting drug target. Using a commercially available fluorescent membrane potential probe kit and a conventional 96-well fluorescence plate reader, the authors have developed and established qualitative membrane potential assays used to screen for potassium channel closers (KCCs) and openers (KCOs) in insulin- and glucagon-secreting cell lines as well as in cells with recombinant expression of the human Kir6.2/SUR1 channel complex. Both glucose- and KCC-induced depolarization could be demonstrated. The magnitudes of these responses and KCO-induced repolarization at high glucose displayed some variation between the different cell lines but a similar rank order of test compounds. Some cell types required the presence of a KCC, such as tolbutamide, to display significant effects of KCOs. The authors find that robust and reliable functional in vitro assays compatible with medium-throughput screening and high-throughput screening can be developed as a base for finding new, more potent, and isoform-selective KCCs and KCOs.

Congenital hyperinsulinemia with grade 4 intraventricular hemorrhage: a case report with a 2-year follow-up

Massive intraventricular hemorrhage associated with hypoglycemia has rarely been reported. We present a late preterm baby girl with severe hypoglycemia after birth. Despite high glucose infusion rates, her glucose levels remained in the 30s to 50s (mg/dL) during the first week of life with a brief period of normoglycemia. On day 2, her computed tomography scan of head showed extensive intraventricular hemorrhage with intraparenchymal extension, which was reported as unexpected for an infant born close to term. She was diagnosed with congenital hyperinsulinemia. Her glucose levels normalized on diazoxide therapy started on day 6. In the absence of any other clear cause, the massive brain hemorrhage was thought to be secondary to prolonged severe hypoglycemia the infant suffered. She remains in global developmental delay at her age at 26 months. This case highlights the importance of early referral of neonatal hypoglycemia for prompt diagnosis and management to avoid the consequences of prolonged low blood glucose.

Management strategies for neonatal hypoglycemia

While hypoglycemia occurs commonly among neonates, treatment can be challenging if hypoglycemia persists beyond the first few days of life. This review discusses the available treatment options for both transient and persistent neonatal hypoglycemia. These treatment options include dextrose infusions, glucagon, glucocorticoids, diazoxide, octreotide, and nifedipine. A stepwise, practical approach to the management of these patients is offered.

Treatment of hyperinsulinemic hypoglycemia because of diffuse nesidioblastosis with nifedipine after surgical therapies in a newborn

Recent studies have demonstrated a role for calcium channel blocking agents in the treatment of persistent hyperinsulinemic hypoglycemia of newborns. We report a newborn infant with persistent hyperinsulinemic hypoglycemia whom we successfully treated with oral nifedipine alone after surgical therapies. A 4-day-old male infant was referred with intractable hypoglycemia and seziures. Normoglycaemia could be maintained only by the intravenous infusion of glucose at a rate of 20 mg/kg per minute. Persistent hyperinsulinemic hypoglycemia of newborn was diagnosed from an inappropriately raised plasma insulin concentration (44 mU/L) at the time of hypoglycemia. Medical treatments led to only a mild reduction in the intravenous glucose requirement; an 85-90% pancreatectomy was performed and histological "diffuse nesidioblastosis" was confirmed. However, despite all the medical treatments after the first pancreatectomy, the hyperinsulinemic hypoglycemia persisted and a second 95% pancreatectomy was performed. After the second pancreatectomy, persistent hyperinsulinemic hypoglycemia was treated with somatostatin and diazoxide, but led to no reduction in the intravenous glucose requirement. We report the case of an infant who had persistent hypoglycemia after two subtotal pancreatic resections but subsequently became normoglycemic on treatment with nifedipine (2 mg/kg per day). The patient was discharged home on oral nifedipine. Calcium channel blocking agents cuold be used with efficacy and safety in recurrent persistent hyperinsulinemic hypoglycemia.

Hyperinsulinaemic hypoglycaemia:genetic mechanisms, diagnosis and management

Hyperinsulinaemic hypoglycaemia (HH) is characterized by unregulated insulin secretion from pancreatic β-cells. Untreated hypoglycaemia in infants can lead to seizures, developmental delay, and subsequent permanent brain injury. Early identification and meticulous managementof these patients is vital to prevent neurological insult. Mutations in eight different genes (ABCC8, KCNJ11, GLUD1, CGK, HADH, SLC16A1, HNF4A and UCP2) have been identified to date in patients with congenital forms of hyperinsulinism (CHI). The most severe forms of CHI are due to mutations in ABCC8 and KCJN11, which encode the two components of pancreatic β-cell ATP-sensitive potassium channel. Recent advancement in understanding the genetic aetiology, histological characterisation into focal and diffuse variety combined with improved imaging (such as fluorine 18 L-3, 4-dihydroxyphenylalanine positron emission tomography 18F-DOPA-PET scanning) and laparoscopic surgical techniques have greatly improved management. In adults, HH can be due to an insulinoma, pancreatogenous hypoglycaemic syndrome, post gastric-bypass surgery for morbid obesity as well as to mutations in insulin receptor gene. This review provides an overview of the molecular basis of CHI and outlines the clinical presentation, diagnostic criteria, and management of these patients.

Hypothalamic Obesity following Craniopharyngioma Surgery: Results of a Pilot Trial of Combined Diazoxide and Metformin Therapy

Objective. To assess the effect of combined diazoxide-metformin therapy in obese adolescents treated for craniopharyngioma. Design. A prospective open-label 6-month pilot treatment trial in 9 obese subjects with craniopharyngioma. Diazoxide (2 mg/kg divided b.i.d., maximum 200 mg/day) and metformin (1000 mg b.i.d.). Whole body insulin sensitivity index (WBISI) and area-under-the-curve insulin (AUC(ins)) were calculated. Results. Seven subjects completed: 4M/3F, mean ± SD age 15.4 ± 2.9 years, weight 99.7 ± 26.3 kg, BMI 35.5 ± 5.6 kg/m(2), and BMI SDS 2.3 ± 0.3. Two were withdrawn due to vomiting and peripheral edema. Of participants completing the study, the mean ± SD weight gain, BMI, and BMI SDS during the 6 months were reduced compared to the 6 months prestudy (+1.2 ± 5.9 versus +9.5 ± 2.7 kg, P = .004; -0.3 ± 2.3 versus +2.2 ± 1.5 kg/m(2), P = .04; -0.04 ± 0.15 versus +0.11 ± 0.08, P = .021, resp.). AUC(ins) correlated with weight loss (r = 0.82, P = .02) and BMI decrease (r = 0.96, P = .009). Conclusion. Combined diazoxide-metformin therapy was associated with reduced weight gain in patients with hypothalamic obesity. AUC(ins) at study commencement predicted effectiveness of the treatment.

Fluorine-18 DOPA-PET and PET/CT Imaging in Congenital Hyperinsulinism

Congenital hyperinsulinism is the principle cause of hypoglycemia during infancy but successful treatment is difficult and persistent hypoglycemia carries the risk of neurologic damage. Focal and diffuse abnormalities are the common forms of hyperinsulinism. Identification and localization of focal hyperinsulinism can be cured by partial pancreatectomy. It has been shown that affected pancreatic areas utilize LDOPA in a higher rate than normal pancreatic tissue and, thus, labeling L-DOPA with fluorine-18 (FDOPA) allows functional mapping of hyperinsulinism using PET. This article presents a fundamental overview of the genetics background, pathology, management, and the role of FDOPA-PET imaging in hyperinsulinism.

Neonatal hyperinsulinism: clinicopathologic correlation

Neonatal hyperinsulinism is a life-threatening disease that, when treated by total pancreatectomy, leads to diabetes and pancreatic insufficiency. A more conservative approach is now possible since the separation of the disease into a nonrecurring focal form, which is cured by partial surgery, and a diffuse form, which necessitates total pancreas removal only in cases of medical treatment failure. The pathogenesis of the disease is now divided into K-channel disease (hyperinsulinemic hypoglycemia, familial [HHF] 1 and 2), which can mandate surgery, and other metabolic causes, HHF 3 to 6, which are treated medically in most patients. The diffuse form is inherited as a recessive gene on chromosome 11, whereas most cases of the focal form are caused by a sulfonylurea receptor 1 defect inherited from the father, which is associated with a loss of heterozygosity on the corresponding part of the mother's chromosome 11. The rare bifocal forms result from a maternal loss of heterozygosity specific to each focus. Paternal disomy of chromosome 11 is a rare cause of a condition similar to Beckwith-Wiedemann syndrome. A preoperative PET scan with fluorodihydroxyphenylalanine and perioperative frozen-section confirmation are the types of studies done before surgery when needed. Adult variants of the disease are less well defined at the present time.

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.

Somatostatin Analogue Mimics Acute Ischemic Preconditioning in a Rat Model of Myocardial Infarction

We tested the hypothesis that octreotide, a somatostatin analogue, can mimic ischemic preconditioning (PC) to provide cardioprotection against myocardial infarction. An ischemia-reperfusion model of adult Wistar rats was used. Infarct size was expressed as a percentage of the area at risk under different treatment protocols. Octreotide PC (35 microg/Kg 20 minutes before ischemia-reperfusion) significantly decreased infarct size (18 +/- 4%) versus control (60 +/- 7%). The somatostatin receptor antagonist cyclo-somatostatin (0.5 mg/Kg) could blunt the above cardioprotection. Administration of either chelerythrine (a protein kinase C inhibitor, 2 mg/Kg) or genistein (a tyrosine kinase inhibitor, 5 mg/Kg) could also block octreotide PC (54 +/- 7% and 58 +/- 6%, respectively). Pretreatment with the mitochondrial ATP-sensitive potassium channel antagonist 5-hydroxydecanoic acid (5-HD) and the sarcolemmal ATP-sensitive potassium channel antagonist glibenclamide could abolish the effects of octreotide PC (54 +/- 6% and 52 +/- 6%). Chelerythrine, however, had no effect on octreotide PC. In conclusion, the present study demonstrates that octreotide can mimic ischemic PC to reduce infarct size. Acute effects of octreotide PC involve the activation of protein kinase C, tyrosine kinase C, and mitochondrial ATP-sensitive potassium channels, but not systemic IGF-I activation.

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.

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.

Epinephrine-induced hyperpolarization of islet cells without KATP channels

This study examines the effect of epinephrine, a known physiological inhibitor of insulin secretion, on the membrane potential of pancreatic islet cells from sulfonylurea receptor-1 (ABCC8)-null mice (Sur1KO), which lack functional ATP-sensitive K+ (KATP) channels. These channels have been argued to be activated by catecholamines, but epinephrine effectively inhibits insulin secretion in both Sur1KO and wild-type islets and in mice. Isolated Sur1KO beta-cells are depolarized in both low (2.8 mmol/l) and high (16.7 mmol/l) glucose and exhibit Ca(2+)-dependent action potentials. Epinephrine hyperpolarizes Sur1KO beta-cells, inhibiting their spontaneous action potentials. This effect, observed in standard whole cell patches, is abolished by pertussis toxin and blocked by BaCl2. The epinephrine effect is mimicked by clonidine, a selective alpha2-adrenoceptor agonist and inhibited by alpha-yohimbine, an alpha2-antagonist. A selection of K+ channel inhibitors, tetraethylammonium, apamin, dendrotoxin, iberiotoxin, E-4130, chromanol 293B, and tertiapin did not block the epinephrine-induced hyperpolarization. Analysis of whole cell currents revealed an inward conductance of 0.11 +/- 0.04 nS/pF (n = 7) and a TEA-sensitive outward conductance of 0.55 +/- 0.08 nS/pF (n = 7) at -60 and 0 mV, respectively. Guanosine 5'-O-(3-thiotriphosphate) (100 microM) in the patch pipette did not significantly alter these currents or activate novel inward-rectifying K+ currents. We conclude that epinephrine can hyperpolarize beta-cells in the absence of KATP channels via activation of low-conductance BaCl2-sensitive K+ channels that are regulated by pertussis toxin-sensitive G proteins.

Oscillations of membrane potential and cytosolic Ca(2+) concentration in SUR1(-/-) beta cells

AIMS/HYPOTHESIS

SUR1(ABCC8)(-/-) mice lacking functional K(ATP) channels are an appropriate model to test the significance of K(ATP) channels in beta-cell function. We examined how this gene deletion interferes with stimulus-secretion coupling. We tested the influence of metabolic inhibition and galanin, whose mode of action is controversial.

METHODS

Plasma membrane potential (Vm) and currents were measured with microelectrodes or the patch-clamp technique; cytosolic Ca(2+) concentrations ([Ca(2+)](c)) and mitochondrial membrane potential (DeltaPsi) were measured using fluorescent dyes.

RESULTS

In contrast to the controls, SUR1(-/-) beta cells showed electrical activity even at a low glucose concentration. Continuous spike activity was measured with the patch-clamp technique, but with microelectrodes slow oscillations in Vm consisting of bursts of Ca(2+)-dependent action potentials were detected. [Ca(2+)](c) showed various patterns of oscillations or a sustained increase. Sodium azide did not hyperpolarize SUR1(-/-) beta cells. The depolarization of DeltaPsi evoked by sodium azide was significantly lower in SUR1(-/-) than SUR1(+/+) cells. Galanin transiently decreased action potential frequency and [Ca(2+)](c) in cells from both SUR1(-/-) and SUR1(+/+) mice.

CONCLUSION/INTERPRETATION

The strong dependence of Vm and [Ca(2+)](c) on glucose concentration observed in SUR1(+/+) beta cells is disrupted in the knock-out cells. This demonstrates that both parameters oscillate in the absence of functional K(ATP) channels. The lack of effect of metabolic inhibition by sodium azide shows that in SUR1(-/-) beta cells changes in ATP/ADP no longer link glucose metabolism and Vm. The results with galanin suggest that this peptide affects beta cells independently of K(ATP) currents and thus could contribute to the regulation of beta-cell function in SUR1(-/-) animals.

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.

Somatostatin receptors

In 1972, Brazeau et al. isolated somatostatin (somatotropin release-inhibiting factor, SRIF), a cyclic polypeptide with two biologically active isoforms (SRIF-14 and SRIF-28). This event prompted the successful quest for SRIF receptors. Then, nearly a quarter of a century later, it was announced that a neuropeptide, to be named cortistatin (CST), had been cloned, bearing strong resemblance to SRIF. Evidence of special CST receptors never emerged, however. CST rather competed with both SRIF isoforms for specific receptor binding. And binding to the known subtypes with affinities in the nanomolar range, it has therefore been acknowledged to be a third endogenous ligand at SRIF receptors. This review goes through mechanisms of signal transduction, pharmacology, and anatomical distribution of SRIF receptors. Structurally, SRIF receptors belong to the superfamily of G protein-coupled (GPC) receptors, sharing the characteristic seven-transmembrane-segment (STMS) topography. Years of intensive research have resulted in cloning of five receptor subtypes (sst(1)-sst(5)), one of which is represented by two splice variants (sst(2A) and sst(2B)). The individual subtypes, functionally coupled to the effectors of signal transduction, are differentially expressed throughout the mammalian organism, with corresponding differences in physiological impact. It is evident that receptor function, from a physiological point of view, cannot simply be reduced to the accumulated operations of individual receptors. Far from being isolated functional units, receptors co-operate. The total receptor apparatus of individual cell types is composed of different-ligand receptors (e.g. SRIF and non-SRIF receptors) and co-expressed receptor subtypes (e.g. sst(2) and sst(5) receptors) in characteristic proportions. In other words, levels of individual receptor subtypes are highly cell-specific and vary with the co-expression of different-ligand receptors. However, the question is how to quantify the relative contributions of individual receptor subtypes to the integration of transduced signals, ultimately the result of collective receptor activity. The generation of knock-out (KO) mice, intended as a means to define the contributions made by individual receptor subtypes, necessarily marks but an approximation. Furthermore, we must now take into account the stunning complexity of receptor co-operation indicated by the observation of receptor homo- and heterodimerisation, let alone oligomerisation. Theoretically, this phenomenon adds a novel series of functional megareceptors/super-receptors, with varied pharmacological profiles, to the catalogue of monomeric receptor subtypes isolated and cloned in the past. SRIF analogues include both peptides and non-peptides, receptor agonists and antagonists. Relatively long half lives, as compared to those of the endogenous ligands, have been paramount from the outset. Motivated by theoretical puzzles or the shortcomings of present-day diagnostics and therapy, investigators have also aimed to produce subtype-selective analogues. Several have become available.

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.

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.

Tissue-specific deletion of Foxa2 in pancreatic beta cells results in hyperinsulinemic hypoglycemia

We have used conditional gene ablation to uncover a dramatic and unpredicted role for the winged-helix transcription factor Foxa2 (formerly HNF-3 beta) in pancreatic beta-cell differentiation and metabolism. Mice that lack Foxa2 specifically in beta cells (Foxa2(loxP/loxP); Ins.Cre mice) are severely hypoglycemic and show dysregulated insulin secretion in response to both glucose and amino acids. This inappropriate hypersecretion of insulin in the face of profound hypoglycemia mimics pathophysiological and molecular aspects of familial hyperinsulinism. We have identified the two subunits of the beta-cell ATP-sensitive K(+) channel (K(ATP)), the most frequently mutated genes linked to familial hyperinsulinism, as novel Foxa2 targets in islets. The Foxa2(loxP/loxP); Ins.Cre mice will serve as a unique model to investigate the regulation of insulin secretion by the beta cell and suggest the human FOXA2 as a candidate gene for familial hyperinsulinism.

Peripheral channelopathies as targets for potassium channel openers

Potassium channel openers (KCOs) are important tools that are often used to gain a greater understanding of K(+) channels. Agents that can induce or maintain the opening of K(+) channels also offer a therapeutic approach to controlling of cell excitability and offer a means of producing stability in biological systems. The pathogenesis of a broad range of peripheral disorders (e.g., LQT syndrome, hypokalemic periodic paralysis, hyperinsulinism in infancy and erectile dysfunction) are associated with dysfunctional K(+) channels due to mutations in genes encoding channel proteins. The therapeutic potential of KCOs in peripheral K(+) channelopathies is discussed. The identification of K(+) channel subtype-specific openers offers discrete modulation of cellular systems creating a realistic therapeutic advance in the treatment of K(+) channelopathies.

When it is more than transient neonatal hypoglycemia: hyperinsulinemia--a case study challenge

Persistent uncontrolled neonatal hypoglycemia may cause irreversible brain damage. Hyperinsulinemia is a rare cause of persistent hypoglycemia, diagnosed by excluding other etiologies. Inappropriately high fasting serum insulin levels with concurrent hypoglycemia confirm the diagnosis. Initial interventions for hyperinsulinemia are conservative. The first line of therapy is administration of adequate intravenous (i.v.) glucose to maintain serum or whole blood glucose levels at or greater than 40 mg/dl. When enteral feedings are tolerated, schedules and caloric concentration are adjusted. Pharmacologic therapy is added to facilitate weaning from i.v. glucose. The drug of first choice is diazoxide. Octreotide is added if diazoxide therapy fails. Partial or complete pancreatectomy is the final treatment option. Nursing care for infants with hyperinsulinemia must also focus on the support and education of families. Family education must be individualized and should cover feeding regimes, administration of medication, proper use of equipment, and care during illness.

Hyperinsulinism of infancy: the regulated release of insulin by KATP channel-independent pathways

Hyperinsulinism of infancy (HI) is a congenital defect in the regulated release of insulin from pancreatic beta-cells. Here we describe stimulus-secretion coupling mechanisms in beta-cells and intact islets of Langerhans isolated from three patients with a novel SUR1 gene defect. 2154+3 A to G SUR1 (GenBank accession number L78207) is the first report of familial HI among nonconsanguineous Caucasians identified in the U.K. Using patch-clamp methodologies, we have shown that this mutation is associated with both a decrease in the number of operational ATP-sensitive K+ channels (KATP channels) in beta-cells and impaired ADP-dependent regulation. There were no apparent defects in the regulation of Ca2+- and voltage-gated K+ channels or delayed rectifier K+ channels. Intact HI beta-cells were spontaneously electrically active and generating Ca2+ action currents that were largely insensitive to diazoxide and somatostatin. As a consequence, when intact HI islets were challenged with glucose and tolbutamide, there was no rise in intracellular free calcium ion concentration ([Ca2+]i) over basal values. Capacitance measurements used to monitor exocytosis in control and HI beta-cells revealed that there were no defects in Ca2+-dependent exocytotic events. Finally, insulin release studies documented that whereas tolbutamide failed to cause insulin secretion as a consequence of impaired [Ca2+]i signaling, glucose readily promoted insulin release. Glucose was also found to augment the actions of protein kinase C- and protein kinase A-dependent agonists in the absence of extracellular Ca2+. These findings document the relationship between SUR1 gene defects and insulin secretion in vivo and in vitro and describe for the first time KATP channel-independent pathways of regulated insulin secretion in diseased human beta-cells.

Management of hyperinsulinism in infancy and childhood

Hyperinsulinism (HI) in infancy presents a formidable challenge for the paediatrician as it is one of the most difficult problems to manage in contemporary paediatric endocrinology. Although there have been major advances in understanding the condition over the last five years, the neurological outcome remains poor choice, and the choice of treatments continue to be unsatisfactory. This review article updates the management of HI derived from a Consensus Workshop held by the European Network for Research into Hyperinsulinism (ENRHI) in 1999.

A recessive contiguous gene deletion causing infantile hyperinsulinism, enteropathy and deafness identifies the Usher type 1C gene

Usher syndrome type 1 describes the association of profound, congenital sensorineural deafness, vestibular hypofunction and childhood onset retinitis pigmentosa. It is an autosomal recessive condition and is subdivided on the basis of linkage analysis into types 1A through 1E. Usher type 1C maps to the region containing the genes ABCC8 and KCNJ11 (encoding components of ATP-sensitive K + (KATP) channels), which may be mutated in patients with hyperinsulinism. We identified three individuals from two consanguineous families with severe hyperinsulinism, profound congenital sensorineural deafness, enteropathy and renal tubular dysfunction. The molecular basis of the disorder is a homozygous 122-kb deletion of 11p14-15, which includes part of ABCC8 and overlaps with the locus for Usher syndrome type 1C and DFNB18. The centromeric boundary of this deletion includes part of a gene shown to be mutated in families with type 1C Usher syndrome, and is hence assigned the name USH1C. The pattern of expression of the USH1C protein is consistent with the clinical features exhibited by individuals with the contiguous gene deletion and with isolated Usher type 1C.

Calcium-stimulated insulin secretion in diffuse and focal forms of congenital hyperinsulinism

OBJECTIVES

To identify infants with hyperinsulinism caused by defects of the beta-cell adenosine triphosphate-dependent potassium channel complex and to distinguish focal and diffuse forms of hyperinsulinism caused by these mutations.

STUDY DESIGN

The acute insulin response to intravenous calcium stimulation (CaAIR) was determined in 9 patients <20 years with diffuse hyperinsulinism caused by defective beta-cell sulfonylurea receptor (SUR1(-/-)), 3 patients with focal congenital hyperinsulinism (6 weeks to 18 months), a 10-year-old with insulinoma, 5 with hyperinsulinism/hyperammonemia syndrome caused by defective glutamate dehydrogenase (6 months to 28 years), 4 SUR1(+/-) heterozygotes with no symptoms, and 9 normal adults. Three infants with congenital focal disease, 1 with diffuse hyperinsulinism, and the child with insulinoma underwent selective pancreatic intra-arterial calcium stimulation with hepatic venous sampling.

RESULTS

Children with diffuse SUR1(-/-) disease and infants with congenital focal hyperinsulinism responded to CaAIR, whereas the normal control group, patients with hyperinsulinism/hyperammonemia syndrome, and SUR1(+/-) carriers did not. Selective arterial calcium stimulation of the pancreas with hepatic venous sampling revealed selective, significant step-ups in insulin secretion that correlated anatomically with the location of solitary lesions confirmed surgically in 2 of 3 infants with congenital focal disease and in the child with insulinoma. Selective arterial calcium stimulation of the pancreas with hepatic venous sampling demonstrated markedly elevated baseline insulin levels throughout the pancreas of the infant with diffuse hyperinsulinism.

CONCLUSIONS

The intravenous CaAIR is a safe and simple test for identifying infants with diffuse SUR1(-/-) hyperinsulinism or with focal congenital hyperinsulinism. Preoperative selective arterial calcium stimulation of the pancreas with hepatic venous sampling can localize focal lesions causing hyperinsulinism in children. The combination of these calcium stimulation tests may help distinguish focal lesions suitable for cure by local surgical resection.

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.

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.

Practical management of hyperinsulinism in infancy

Hyperinsulinism in infancy is one of the most difficult problems to manage in contemporary paediatric endocrinology. Although the diagnosis can usually be achieved without difficulty, it presents the paediatrician with formidable day to day management problems. Despite recent advances in understanding the pathophysiology of hyperinsulinism, the neurological outcome remains poor, and there is often a choice of unsatisfactory treatments, with life long sequelae for the child and his or her family. This paper presents a state of the art overview on management derived from a consensus workshop held by the European network for research into hyperinsulinism (ENRHI). The consensus is presented as an educational aid for paediatricians and children's nurses. It offers a practical guide to management based on the most up to date knowledge. It presents a proposed management cascade and focuses on the clinical recognition of the disease, the immediate steps that should be taken to stabilise the infant during diagnostic investigations, and the principles of definitive treatment.

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.

Persistent hyperinsulinemic hypoglycemia of infancy: long-term outcome following subtotal pancreatectomy

BACKGROUND

Persistent hyperinsulinemic hypoglycemia of infancy (PHHI) is the most common cause of persistent hypoglycemia in infants. The current standard treatment is subtotal pancreatectomy (Px). However, the long-term outcome following surgery needs further attention.

METHODS

We analyzed 10 children (7 M, 3 F) with PHHI who underwent partial (65-80%) and subtotal (81-95%) Px. Follow-up ranged from 2 to 9.4 yr (mean = 4.2 yr). We divided them into 2 groups based upon the age at onset of hypoglycemia: early (< 1 mo) and late (> or = 1 mo).

RESULTS

The seven patients in the early-onset group underwent 85-95% Px between ages of 18 d and 3 mo. Three of them initially treated by 85-90% Px had persistent hypoglycemia postoperatively. Two out of three required a 2nd operation with 95% Px for controlling hypoglycemia, though both still had persistent hypoglycemia and required medication to control blood glucose. The remaining four had 95% Px and had maintained euglycemia postoperatively. One patient developed diabetes 6 yr after surgery. Six of seven patients had delayed development and subnormal IQ. Three patients of the late-onset group (3 mo, 6 mo and 4 yr) underwent partial Px (80%, 65% and 65%, respectively) and maintained euglycemia postoperatively. Despite 65% Px, one developed diabetes 3 yr after surgery.

CONCLUSIONS

These results suggest that children with early-onset hypoglycemia have more severe hyperinsulinism than those with late-onset hypoglycemia. The former require 95% Px for maintaining euglycemia, but long-term complications with diabetes may be common. In contrast, the latter require lower percentage Px which may reduce the incidence of diabetes in the future.

Recent advancements in pediatric toxicology

Ingestion of potentially poisonous agents is a common reason for children to present to an emergency department. The clinician must decide whether gastrointestinal decontamination is indicated for these patients. The controversy over the type of gastrointestinal decontamination is resolving and recent recommendations are reviewed. Also two new antidotes, fomepizole for toxic alcohols and octreotide for sulfonylureas, are reviewed.

Hyperinsulinemic hypoglycemia of infancy. Recent insights into ATP-sensitive potassium channels, sulfonylurea receptors, molecular mechanisms, and treatment

Persistent hyperinsulinemic hypoglycemia of infancy (PHHI), previously termed "nesidioblastosis," is an important cause of hypoglycemia in infancy and childhood. Recent studies have defined this syndrome at the molecular, genetic, and clinical level. This article reviews the genetic and molecular basis of these entities, describes their clinical manifestations, and discusses the rationales for available therapeutic options.

Channelopathies of inwardly rectifying potassium channels

Mutations in genes encoding ion channels have increasingly been identified to cause disease conditions collectively termed channelopathies. Recognizing the molecular basis of an ion channel disease has provided new opportunities for screening, early diagnosis, and therapy of such conditions. This synopsis provides an overview of progress in the identification of molecular defects in inwardly rectifying potassium (Kir) channels. Structurally and functionally distinct from other channel families, Kir channels are ubiquitously expressed and serve functions as diverse as regulation of resting membrane potential, maintenance of K(+) homeostasis, control of heart rate, and hormone secretion. In humans, persistent hyperinsulinemic hypoglycemia of infancy, a disorder affecting the function of pancreatic beta cells, and Bartter's syndrome, characterized by hypokalemic alkalosis, hypercalciuria, increased serum aldosterone, and plasma renin activity, are the two major diseases linked so far to mutations in a Kir channel or associated protein. In addition, the weaver phenotype, a neurological disorder in mice, has also been associated with mutations in a Kir channel subtype. Further genetic linkage analysis and full understanding of the consequence that a defect in a Kir channel would have on disease pathogenesis are among the priorities in this emerging field of molecular medicine.

Hypoglycemia in infants and children

Hypoglycemia is more common in the pediatric patient than in adults. This article discusses the many diagnoses that can be associated with hypoglycemia in infancy and childhood. A guide to help practitioners evaluate such patients and suggested treatments for many of these disorders are provided. As genetic diagnosis continues to develop, it is anticipated that the list of specific disorders associated with hypoglycemia in infancy and childhood will increase.