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

Surgical treatment of congenital hyperinsulinism

A multidisciplinary approach to patients with congenital hyperinsulinism (HI) can distinguish focal from diffuse HI, localize focal lesions, and permit partial pancreatectomy with cure in almost all focal patients. Surgery does not cure diffuse disease but can help prevent severe hypoglycemia and brain damage. Surgery can be curative for insulinoma and for some cases of atypical HI.

Surgical treatment of congenital hyperinsulinism: Results from 500 pancreatectomies in neonates and children

BACKGROUND

Congenital Hyperinsulinism (HI) causes severe hypoglycemia in neonates and children. We reviewed our experience with pancreatectomy for the various types of HI.

METHODS

From 1998 to 2018, 500 patients with HI underwent pancreatectomy: 246 for focal HI, 202 for diffuse HI, 37 for atypical HI (16 for Localized Islet Nuclear Enlargement [LINE], 21 for Beckwith-Wiedemann Syndrome), and 15 for insulinoma. Focal HI neonates were treated with partial pancreatectomy. Patients with diffuse HI who failed medical management underwent near-total (98%) pancreatectomy. Atypical HI patients had pancreatectomies tailored to the PET scan and biopsy findings.

RESULTS

The vast majority of pancreatectomies for focal HI were < 50%, and many were 2%-10%. 97% of focal HI patients are cured. For diffuse disease patients, 31% were euglycemic, 20% were hyperglycemic, and 49% required treatment for hypoglycemia; the incidence of diabetes increased with long-term follow-up. All 15 insulinoma patients were cured.

CONCLUSIONS

Our approach to patients with focal HI can distinguish focal from diffuse HI, localize focal lesions, and permit partial pancreatectomy with cure in almost all focal patients. Surgery does not cure diffuse disease but can help prevent severe hypoglycemia and brain damage. Surgery can be curative for insulinoma and for some cases of atypical HI.

LEVEL OF EVIDENCE

Level IV.

Congenital Hyperinsulinism in China: A Review of Chinese Literature Over the Past 15 Years

OBJECTIVE

Congenital hyperinsulinism (CHI) is a rare but severe cause of hypoglycemia. The present study investigates the clinical presentation, therapeutic outcomes and genetic mutations of CHI in Chinese individuals over the past 15 years.

METHODS

The authors retrospectively reviewed one case in their department and 206 cases reported from January 2002 to October 2016 in China. PubMed, Ovid Medline, Springer and Wanfang Database, CBMD database, and CKNI database were the sources used to collect the data.

RESULTS

In total, 207 cases were recruited. Of these, the ages of 100 (48.3%) were within the 4th week after birth. Seventy-seven cases (37.2%) were born large for gestational age (LGA). Seizures occurred in 140 cases (67.6%). Among 140 cases (67.6%) who were administered diazoxide treatment, 90 (64.3%) were responsive. Seven cases (3.4%) received octreotide treatment and 19 cases (9.2%) underwent surgery. 63/129 cases (48.8%) were detected to have gene mutations, including ABCC8 (69.8%), KCNJ11 (12.7%), GLUD1, GCK, HADH, and HNF4A. Among the diazoxide-unresponsive cases, gene mutations were detected in 20/36 (55.6%) cases with ABCC8 and in 2 (5.6%) cases with KCNJ11. Among the diazoxide-responsive cases, gene mutations were detected in 8 patients with ABCC8, 4 with KCNJ11, 5 with GLUD1, and 1 with GCK.

CONCLUSION

The present study indicates that most CHI cases occurred in neonates and that 1/3 of the cases were born LGA. ABCC8 and KCNJ11 are the most common gene mutations. More than half of the diazoxide-unresponsive CHI detected mutations are in ABCC8 and KCNJ11 genes. The GLUD1 gene mutations cause diazoxide-responsive CHI. Identifying the gene mutations can assist in the diagnosis and treatment of CHI.

Clinical practice guidelines for congenital hyperinsulinism

Congenital hyperinsulinism is a rare condition, and following recent advances in diagnosis and treatment, it was considered necessary to formulate evidence-based clinical practice guidelines reflecting the most recent progress, to guide the practice of neonatologists, pediatric endocrinologists, general pediatricians, and pediatric surgeons. These guidelines cover a range of aspects, including general features of congenital hyperinsulinism, diagnostic criteria and tools for diagnosis, first- and second-line medical treatment, criteria for and details of surgical treatment, and future perspectives. These guidelines were generated as a collaborative effort between The Japanese Society for Pediatric Endocrinology and The Japanese Society of Pediatric Surgeons, and followed the official procedures of guideline generation to identify important clinical questions, perform a systematic literature review (April 2016), assess the evidence level of each paper, formulate the guidelines, and obtain public comments.

The value of radiologic interventions and (18)F-DOPA PET in diagnosing and localizing focal congenital hyperinsulinism: systematic review and meta-analysis

PURPOSE

This systematic review and meta-analysis aimed to quantify the diagnostic performance of pancreatic venous sampling (PVS), selective pancreatic arterial calcium stimulation with hepatic venous sampling (ASVS), and (18)F-DOPA positron emission tomography (PET) in diagnosing and localizing focal congenital hyperinsulinism (CHI).

PROCEDURES

This systematic review and meta-analysis was conducted according to the PRISMA statement. PubMed, EMBASE, SCOPUS and Web of Science electronic databases were systematically searched from their inception to November 1, 2011. Using predefined inclusion and exclusion criteria, two blinded reviewers selected articles. Critical appraisal ranked the retrieved articles according to relevance and validity by means of the QUADAS-2 criteria. Pooled data of homogeneous study results estimated the sensitivity, specificity, likelihood ratios and diagnostic odds ratio (DOR).

RESULTS

(18)F-DOPA PET was superior in distinguishing focal from diffuse CHI (summary DOR, 73.2) compared to PVS (summary DOR, 23.5) and ASVS (summary DOR, 4.3). Furthermore, it localized focal CHI in the pancreas more accurately than PVS and ASVS (pooled accuracy, 0.82 vs. 0.76, and 0.64, respectively). Important limitations comprised the inclusion of studies with small sample sizes, high probability of bias and heterogeneity among their results. Studies with small sample sizes and high probability of bias tended to overestimate the diagnostic accuracy.

CONCLUSIONS

This systematic review and meta-analysis found evidence for the superiority of (18)F-DOPA PET in diagnosing and localizing focal CHI in patients requiring surgery for this disease.

Persistent hyperinsulinemic hypoglycemia of infancy: An overview of current concepts

Persistent hyperinsulinemic hypoglycemia of infancy (PHHI) is relatively rare but one of the most important causes of severe neonatal hypoglycemia. Recognition of this entity becomes important due to the fact that the hypoglycemia is so severe and frequent that it may lead to severe neurological damage in the infant manifesting as mental or psychomotor retardation or even a life-threatening event if not recognized and treated effectively in time. Near-total pancreatectomy may be required for patients with intractable hypoglycemia despite medical treatment; however, that may result in diabetes mellitus or recurrent postoperative hypoglycemia. This review aims to consolidate the traditional concepts and current information related to the pathogenesis and management of PHHI.

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.

Role of 18F-DOPA PET/CT imaging in congenital hyperinsulinism

Congenital hyperinsulinism is a leading cause of severe hypoglycaemia in the newborn period. There are two (diffuse and focal) histological subtypes of congenital hyperinsulinism. The diffuse form affects the entire pancreas and if medically unresponsive will require a near total (95%-98%) pancreatectomy. The focal form affects only a small region of the pancreas (with the rest of the pancreas being normal in endocrine and exocrine function) and only requires a limited pancreatectomy. This limited section of the focal lesion has the potential for curing the patient. Thus the pre-operative differentiation of these two subgroups is extremely important. Recent advances in Fluorine-18-L-dihydroxyphenylalanine positron emission tomography ((18)F-DOPA PET/CT) have radically changed the clinical approach to patient with congenital hyperinsulinism. In most patients this novel imaging technique is able to offer precise pre-operative localisation of the focal lesion, thus guiding the extent of surgical resection.

Necrotizing enterocolitis in neonates receiving octreotide for the management of congenital hyperinsulinism

The somatostatin analog octreotide was used for the first time in the treatment of an infant with congenital hyperinsulinism in 1986. Since then, it is commonly used in the management of congenital hyperinsulinemic hypoglycemias. Despite a wide variety of potential adverse reactions, octreotide is generally well tolerated. It has been extensively demonstrated that octreotide reduces the splanchnic blood flow in a dose-dependent manner, affecting the entire gastrointestinal tract, and some concern has been recently raised regarding the potential implications of this effect in the development of necrotizing enterocolitis in neonates receiving octreotide for the management of congenital hyperinsulinism. The aim of this report is to present a series of patients treated at our institution in which we observed this association, and review the current related literature.

Extremes of clinical and enzymatic phenotypes in children with hyperinsulinism caused by glucokinase activating mutations

OBJECTIVE

Heterozygous activating mutations of glucokinase have been reported to cause hypoglycemia attributable to hyperinsulinism in a limited number of families. We report three children with de novo glucokinase hyperinsulinism mutations who displayed a spectrum of clinical phenotypes corresponding to marked differences in enzyme kinetics.

RESEARCH DESIGN AND METHODS

Mutations were directly sequenced, and mutants were expressed as glutathionyl S-transferase-glucokinase fusion proteins. Kinetic analysis of the enzymes included determinations of stability, activity index, the response to glucokinase activator drug, and the effect of glucokinase regulatory protein.

RESULTS

Child 1 had an ins454A mutation, child 2 a W99L mutation, and child 3 an M197I mutation. Diazoxide treatment was effective in child 3 but ineffective in child 1 and only partially effective in child 2. Expression of the mutant glucokinase ins454A, W99L, and M197I enzymes revealed a continuum of high relative activity indexes in the three children (26, 8.9, and 3.1, respectively; wild type = 1.0). Allosteric responses to inhibition by glucokinase regulatory protein and activation by the drug RO0281675 were impaired by the ins454A but unaffected by the M197I mutation. Estimated thresholds for glucose-stimulated insulin release were more severely reduced by the ins454A than the M197I mutation and intermediate in the W99L mutation (1.1, 3.5, and 2.2 mmol/l, respectively; wild type = 5.0 mmol/l).

CONCLUSIONS

These results confirm the potency of glucokinase as the pancreatic beta-cell glucose sensor, and they demonstrate that responsiveness to diazoxide varies with genotype in glucokinase hyperinsulinism resulting in hypoglycemia, which can be more difficult to control than previously believed.

Localization of insulinomas to regions of the pancreas by intraarterial calcium stimulation: the NIH experience

CONTEXT

Selective intraarterial calcium injection of the major pancreatic arteries with hepatic venous sampling [calcium arterial stimulation (CaStim)] has been used as a localizing tool for insulinomas at the National Institutes of Health (NIH) since 1989. The accuracy of this technique for localizing insulinomas was reported for all cases until 1996.

OBJECTIVES

The aim of the study was to assess the accuracy and track record of the CaStim over time and in the context of evolving technology and to review issues related to result interpretation and procedure complications. CaStim was the only invasive preoperative localization modality used at our center. Endoscopic ultrasound (US) was not studied.

DESIGN AND SETTING

We conducted a retrospective case review at a referral center.

PATIENTS

Twenty-nine women and 16 men (mean age, 47 yr; range, 13-78) were diagnosed with an insulinoma from 1996-2008.

INTERVENTION

A supervised fast was conducted to confirm the diagnosis of insulinoma. US, computed tomography (CT), magnetic resonance imaging (MRI), and CaStim were used as preoperative localization studies. Localization predicted by each preoperative test was compared to surgical localization for accuracy.

MAIN OUTCOME

We measured the accuracy of US, CT, MRI, and CaStim for localization of insulinomas preoperatively.

RESULTS

All 45 patients had surgically proven insulinomas. Thirty-eight of 45 (84%) localized to the correct anatomical region by CaStim. In five of 45 (11%) patients, the CaStim was falsely negative. Two of 45 (4%) had false-positive localizations.

CONCLUSION

The CaStim has remained vastly superior to abdominal US, CT, or MRI over time as a preoperative localizing tool for insulinomas. The utility of the CaStim for this purpose and in this setting is thus validated.

Clinical characteristics and biochemical mechanisms of congenital hyperinsulinism associated with dominant KATP channel mutations

Congenital hyperinsulinism is a condition of dysregulated insulin secretion often caused by inactivating mutations of the ATP-sensitive K+ (KATP) channel in the pancreatic beta cell. Though most disease-causing mutations of the 2 genes encoding KATP subunits, ABCC8 (SUR1) and KCNJ11 (Kir6.2), are recessively inherited, some cases of dominantly inherited inactivating mutations have been reported. To better understand the differences between dominantly and recessively inherited inactivating KATP mutations, we have identified and characterized 16 families with 14 different dominantly inherited KATP mutations, including a total of 33 affected individuals. The 16 probands presented with hypoglycemia at ages from birth to 3.3 years, and 15 of 16 were well controlled on diazoxide, a KATP channel agonist. Of 29 adults with mutations, 14 were asymptomatic. In contrast to a previous report of increased diabetes risk in dominant KATP hyperinsulinism, only 4 of 29 adults had diabetes. Unlike recessive mutations, dominantly inherited KATP mutant subunits trafficked normally to the plasma membrane when expressed in COSm6 cells. Dominant mutations also resulted in different channel-gating defects, as dominant ABCC8 mutations diminished channel responses to magnesium adenosine diphosphate or diazoxide, while dominant KCNJ11 mutations impaired channel opening, even in the absence of nucleotides. These data highlight distinctive features of dominant KATP hyperinsulinism relative to the more common and more severe recessive form, including retention of normal subunit trafficking, impaired channel activity, and a milder hypoglycemia phenotype that may escape detection in infancy and is often responsive to diazoxide medical therapy, without the need for surgical pancreatectomy.

Hyperinsulinism in Infancy and Childhood: When an Insulin Level Is Not Always Enough

Background: Hypoglycemia in infants and children can lead to seizures, developmental delay, and permanent brain damage. Hyperinsulinism (HI) is the most common cause of both transient and permanent disorders of hypoglycemia. HI is characterized by dysregulated insulin secretion, which results in persistent mild to severe hypoglycemia. The various forms of HI represent a group of clinically, genetically, and morphologically heterogeneous disorders.

Content: Congenital hyperinsulinism is associated with mutations of SUR-1 and Kir6.2, glucokinase, glutamate dehydrogenase, short-chain 3-hydroxyacyl-CoA dehydrogenase, and ectopic expression on β-cell plasma membrane of SLC16A1. Hyperinsulinism can be associated with perinatal stress such as birth asphyxia, maternal toxemia, prematurity, or intrauterine growth retardation, resulting in prolonged neonatal hypoglycemia. Mimickers of hyperinsulinism include neonatal panhypopituitarism, drug-induced hypoglycemia, insulinoma, antiinsulin and insulin-receptor stimulating antibodies, Beckwith-Wiedemann Syndrome, and congenital disorders of glycosylation. Laboratory testing for hyperinsulinism may include quantification of blood glucose, plasma insulin, plasma β-hydroxybutyrate, plasma fatty acids, plasma ammonia, plasma acylcarnitine profile, and urine organic acids. Genetic testing is available through commercial laboratories for genes known to be associated with hyperinsulinism. Acute insulin response (AIR) tests are useful in phenotypic characterization. Imaging and histologic tools are also available for diagnosing and classifying hyperinsulinism. The goal of treatment in infants with hyperinsulinism is to prevent brain damage from hypoglycemia by maintaining plasma glucose levels above 700 mg/L (70 mg/dL) through pharmacologic or surgical therapy.

Summary: The management of hyperinsulinism requires a multidisciplinary approach that includes pediatric endocrinologists, radiologists, surgeons, and pathologists who are trained in diagnosing, identifying, and treating 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.

Mechanisms of Disease: advances in diagnosis and treatment of hyperinsulinism in neonates

Hyperinsulinism is the single most common mechanism of hypoglycemia in neonates. Dysregulated insulin secretion is responsible for the transient and prolonged forms of neonatal hypoglycemia, and congenital genetic disorders of insulin regulation represent the most common of the permanent disorders of hypoglycemia. Mutations in at least five genes have been associated with congenital hyperinsulinism: they encode glucokinase, glutamate dehydrogenase, the mitochondrial enzyme short-chain 3-hydroxyacyl-CoA dehydrogenase, and the two components (sulfonylurea receptor 1 and potassium inward rectifying channel, subfamily J, member 11) of the ATP-sensitive potassium channels (K(ATP) channels). K(ATP) hyperinsulinism is the most common and severe form of congenital hyperinsulinism. Infants suffering from K(ATP) hyperinsulinism present shortly after birth with severe and persistent hypoglycemia, and the majority are unresponsive to medical therapy, thus requiring pancreatectomy. In up to 40-60% of the children with K(ATP) hyperinsulinism, the defect is limited to a focal lesion in the pancreas. In these children, local resection results in cure with avoidance of the complications inherent to a near-total pancreatectomy. Hyperinsulinism can also be part of other disorders such as Beckwith-Wiedemann syndrome and congenital disorders of glycosylation. The diagnosis and management of children with congenital hyperinsulinism requires a multidisciplinary approach to achieve the goal of therapy: prevention of permanent brain damage due to recurrent hypoglycemia.

Clinical features and morphological characterization of 10 patients with noninsulinoma pancreatogenous hypoglycaemia syndrome (NIPHS)

OBJECTIVE

Noninsulinoma pancreatogenous hypoglycaemia syndrome (NIPHS), characterized by postprandial neuroglycopaenia, negative prolonged fasts and negative perioperative localization studies for insulinoma, but positive selective arterial calcium stimulation tests and nesidioblastosis in the gradient-guided resected pancreas, is a rare hypoglycaemic disorder of undetermined aetiology. We analysed the clinical, morphological and immunohistological features to further clarify the aetiology and pathogenesis of this rare disease.

PATIENTS

Ten consecutive patients with NIPHS (nine men and one woman, aged 29-78 years) were included in the study. Six of the 10 received a gradient-guided subtotal (70%) or distal (50%) pancreatectomy. In the remaining four patients, diazoxide treatment was initiated and the precise mechanism of its action was assessed by meal tests.

RESULTS

All of the patients showed a combination of postprandial neuroglycopaenia, negative prolonged fasts (except one patient) and negative localization studies for insulinoma, but positive calcium stimulation tests and nesidioblastosis in the gradient-guided resected pancreas. Immunohistological studies of the resected pancreatic tissues revealed neither an increased rate of proliferation of beta-cells nor an abnormal synthesis and/or processing of either proinsulin or amylin. Evidence of overexpression of the two pancreatic differentiation factors, PDX-1 and Nkx-6.1, as well as the calcium sensing receptor (CaSR) was absent. Nevertheless, abnormal expression of islet neogenesis-associated protein (INGAP), a human cytokine expressed only in the presence of islet neogenesis, in ducts and/or islets, was identified in three of the five patients studied. All of the six patients who received a surgical operation were relieved of further neuroglycopaenic attacks, but one patient who received a subtotal pancreatectomy developed diabetes. In the remaining four patients who received diazoxide treatment, hypoglycaemic episodes were satisfactorily controlled with an attenuated response of beta-cell peptides to meal stimulation.

CONCLUSIONS

Our results strengthen the existence of this unique clinical hypoglycaemic syndrome from beta-cell hyperfunction as well as the value of the selective arterial calcium stimulation test in its correct diagnosis and localization. The mechanisms underlying beta-cell hyperfunction and release of insulin to calcium, however, remain poorly characterized. Nevertheless, in a subset of patients with NIPHS, there exists some, as yet undefined, pancreatic humoral/paracrine factor(s) other than proinsulin, amylin, PDX-1, Nkx-6.1 and possibly glucagon-like peptide-1 (GLP-1) that are capable of inducing the INGAP gene and, if activated, will initiate ductal proliferation and islet neogenesis. As for the treatment, we recommend that diazoxide be tried first in each patient and, should it fail, a gradient-guided subtotal or distal pancreatectomy be attempted.

Recent advances in hyperinsulinemic hypoglycemia of infancy

Hyperinsulinemia-induced hypoglycemia is the most common cause of persistent hypoglycemia in adults, children, and infants. Our understanding of the disorders responsible for this type of hypoglycemia has been increasing due to the recent discoveries in the molecular and biochemical regulation of insulin secretion. In this article, we review the current knowledge of the pathophysiology, clinical presentation, and diagnosis of disorders that cause hyperinsulinemic hypoglycemia of infancy. We highlight the distinction between the diffuse and focal forms of the disease, especially the promising results with (18)F-L-dopa positive emission tomography (PET) scanning for preoperative localization and distinction to guide the extent of surgical removal of pancreatic tissue that may result in cure rather than persistence of disturbed carbohydrate metabolism.

CONCLUSION

Despite all these discoveries, much remains to be learned, as currently about one third of infants with hyperinsulinemic hypoglycemia have no identifiable cause.

Clinical features and insulin regulation in infants with a syndrome of prolonged neonatal hyperinsulinism

OBJECTIVES

To characterize the clinical features and insulin regulation in infants with hypoglycemia due to prolonged neonatal hyperinsulinism.

STUDY DESIGN

Data were collected on 26 infants with hypoglycemia due to neonatal hyperinsulinism that later resolved. Acute insulin response (AIR) tests to calcium, leucine, glucose, and tolbutamide were performed in 11 neonates. Results were compared to children with genetic hyperinsulinism due to mutations of the adenosine triphosphate-dependent potassium (K(ATP)) channel and glutamate dehydrogenase (GDH).

RESULTS

Among the 26 neonates, there were significantly more males, small-for-gestational-age infants, and cesarean deliveries. Only 5 of the 26 had no identifiable risk factor. Hyperinsulinism was diagnosed at a median age of 13 days (range, 2 to 180 days) and resolved by a median age of 181 days (range, 18 to 403 days). Diazoxide was effective in 19 of the 21 neonates treated. In the 11 neonates tested, the AIRs to calcium, leucine, glucose, and tolbutamide resembled those in normal controls and differed from genetic hyperinsulinism due to K(ATP) channel and GDH mutations.

CONCLUSIONS

We define a syndrome of prolonged neonatal hyperinsulinism that is responsive to diazoxide, persists for several months, and resolves spontaneously. AIR tests suggest that both the K(ATP) channel and GDH have normal function.

Serum glucagon counterregulatory hormonal response to hypoglycemia is blunted in congenital hyperinsulinism

The mechanisms involved in the release of glucagon in response to hypoglycemia are unclear. Proposed mechanisms include the activation of the autonomic nervous system via glucose-sensing neurons in the central nervous system, via the regulation of glucagon secretion by intra-islet insulin and zinc concentrations, or via direct ionic control, all mechanisms that involve high-affinity sulfonylurea receptor/inwardly rectifying potassium channel-type ATP-sensitive K(+) channels. Patients with congenital hyperinsulinism provide a unique physiological model to understand glucagon regulation. In this study, we compare serum glucagon responses to hyperinsulinemic hypoglycemia versus nonhyperinsulinemic hypoglycemia. In the patient group (n = 20), the mean serum glucagon value during hyperinsulinemic hypoglycemia was 17.6 +/- 5.7 ng/l compared with 59.4 +/- 7.8 ng/l in the control group (n = 15) with nonhyperinsulinemic hypoglycemia (P < 0.01). There was no difference between the serum glucagon responses in children with diffuse, focal, and diazoxide-responsive forms of hyperinsulinism. The mean serum epinephrine and norepinephrine concentrations in the hyperinsulinemic group were 2,779 +/- 431 pmol/l and 2.9 +/- 0.7 nmol/l and appropriately rose despite the blunted glucagon response. In conclusion, the loss of ATP-sensitive K(+) channels and or elevated intraislet insulin cannot explain the blunted glucagon release in all patients with congenital hyperinsulinism. Other possible mechanisms such as the suppressive effect of prolonged hyperinsulinemia on alpha-cell secretion should be considered.

Genotype-phenotype correlations in children with congenital hyperinsulinism due to recessive mutations of the adenosine triphosphate-sensitive potassium channel genes

Congenital hyperinsulinism (HI) is most commonly caused by recessive mutations of the pancreatic beta-cell ATP-sensitive potassium channel (K(ATP)), encoded by two genes on chromosome 11p, SUR1 and Kir6.2. The two mutations that have been best studied, SUR1 g3992-9a and SUR1 delF1388, are null mutations yielding nonfunctional channels and are characterized by nonresponsiveness to diazoxide, a channel agonist, and absence of acute insulin responses (AIRs) to tolbutamide, a channel antagonist, or leucine. To examine phenotypes of other K(ATP) mutations, we measured AIRs to calcium, leucine, glucose, and tolbutamide in infants with recessive SUR1 or Kir6.2 mutations expressed as diffuse HI (n = 8) or focal HI (n = 14). Of the 24 total mutations, at least seven showed evidence of residual K(ATP) channel function. This included positive AIR to both tolbutamide and leucine in diffuse HI cases or positive AIR to leucine in focal HI cases. One patient with partial K(ATP) function also responded to treatment with the channel agonist, diazoxide. Six of the seven patients with partial defects had amino acid substitutions or insertions; whereas, the other patient was compound heterozygous for two premature stop codons. These results indicate that some K(ATP) mutations can yield partially functioning channels, including cases of hyperinsulinism that are fully responsive to diazoxide therapy.

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.

Congenital Hyperinsulinism

Most cases of congenital hyperinsulinism (HI) manifest as either a diffuse or focal form. Diffuse HI is characterized by the presence of enlarged islet cell nuclei, defined as those occupying an area 3 times larger than the surrounding nuclei, throughout the pancreas, and usually requires near total pancreatectomy. Focal HI contains, within an otherwise normal pancreas with islet cell nuclei of normal size, a focus of adenomatous hyperplasia characterized by endocrine cell overgrowth occupying more than 40% of a given area. This form of HI is amenable to partial pancreatectomy. The current study assesses whether intraoperative frozen section evaluation can distinguish the 2 forms and guide the extent of pancreatectomy. By frozen section analysis, diffuse HI is diagnosed when enlarged islet cell nuclei are present in random intraoperative biopsies from the head, body, and tail of the pancreas. Focal HI is suggested when random biopsies contain no large islet cell nuclei, prompting a further search for a focal lesion. Fifty-two HI patients who underwent pancreatectomy from October 1, 1998 to September 30, 2002 were reviewed. On permanent sections, 18 were classified as diffuse HI, 30 had focal HI, and 4 could not be categorized as either. Among 18 diffuse HI patients, 17 were correctly diagnosed by frozen section; all underwent near total pancreatectomy. One case was interpreted as not belonging to typical diffuse or focal HI; however, the permanent sections showed diffuse HI. Twenty-six of 30 focal HI cases were correctly diagnosed by frozen section. The remaining 4 focal HI cases posed diagnostic difficulties on frozen sections because of one the following reasons: 1) presence of equivocally large islet cell nuclei or rare truly large islet cell nuclei in areas nonadjacent to the focal lesion, and 2) large and/or ill defined focus of adenomatous hyperplasia. Twenty-one of 30 focal HI patients eventually had 10% to 93% (mean, 41.8%) of their pancreas resected. In addition to cases typical for diffuse and focal HI, there were 4 other cases whose pancreata did not fit well with either category. These pancreata showed islet cell nuclear enlargement, as characteristically seen in diffuse HI, but only in confined areas of the pancreas. Examination of routinely processed tissue confirmed frozen section findings in all 4 cases. Intraoperative frozen section evaluation, therefore, can assume an essential role in identifying patients with focal HI to limit the extent of pancreatectomy. However, a small number of cases with unusual histology warrant caution when performing frozen section evaluation.

Blood Glucose Control During Selective Arterial Stimulation and Venous Sampling for Localization of Focal Hyperinsulinism Lesions in Anesthetized Children

Surgical management of congenital hyperinsulinism is improved by accurate localization of small, focal dysregulated pancreatic lesions using the arterial stimulation and venous sampling (ASVS) test, which can demonstrate increased hepatic venous insulin concentrations after selective arterial injections of calcium. However, anesthesia-related increases in blood glucose can induce insulin secretion, making it difficult to interpret ASVS test data. In this retrospective study, we examined the effect of anesthetic interventions on blood glucose concentrations in 68 children undergoing ASVS testing. We considered only the glucose concentrations observed before calcium stimulation in the final analysis. The choice of drugs for induction (sevoflurane, propofol, or thiopentone), maintenance inhaled anesthetics (sevoflurane, desflurane, or isoflurane), and the use of caudal epidural bupivacaine were not associated with significant differences in the mean blood glucose concentration before ASVS. However, patients receiving remifentanil infusions had smaller mean glucose concentrations (80 +/- 18 versus 100 +/- 44 mg x dl(-1), P = 0.01). These concentrations were also significantly smaller if tracheal intubation was delayed for at least 10 min after induction while patients received inhaled anesthetics via a face mask along with remifentanil infusions (79 +/- 14 for delayed intubation versus 95 +/- 39 mg x dl(-1) for early intubation, respectively, P = 0.03). The percentage increase in glucose concentrations from preintubation values was significantly smaller in these subjects (3.7% +/- 21.9% for delayed intubation versus 31.7% +/- 60.4% for early intubation, P = 0.02). We conclude that the anesthetic management protocol for these patients should include the use of remifentanil infusions and the administration of inhaled anesthetics and remifentanil infusions for a minimum of 10 min to establish a deep plane of anesthesia before tracheal intubation.

Differential diagnosis and management of neonatal hypoglycemia

Persistent hypoglycemia in the neonate is most often caused by hyperinsulinemia. Recent discoveries in the molecular and biochemical regulation of insulin secretion have increased dramatically our understanding of disorders responsible for syndromes of hyperinsulinemic hypoglycemia. This article focuses on defects and disorders of the KATP channel, activating mutation of glucokinase and glutamate dehydrogenase, and other disorders that may be associated with specific phenotypes to permit appropriate targeted therapies. It is essential to evaluate these entities carefully because of the emerging evidence that at least half, if not more, have focal disease, which can be cured by local excision rather than diffuse disease, which may not be cured even after near total pancreatectomy with risk for future diabetes. Delay in diagnosis may be associated with developmental delay. The mechanisms of hypoglycemia remain incompletely understood.

A multidisciplinary approach to the focal form of congenital hyperinsulinism leads to successful treatment by partial pancreatectomy

BACKGROUND/PURPOSE

Congenital hyperinsulinism (HI) causes severe hypoglycemia in neonates and infants. Recessive mutations of the beta-cell K(ATP) channel genes cause diffuse HI, whereas loss of heterozygosity together with inheritance of a paternal mutation cause focal adenomatous HI. Although these 2 forms of HI are clinically identical, focal HI can be cured surgically. The authors reviewed their experience with partial pancreatectomy for focal HI.

METHODS

From December 1998 to January 2003, 38 patients (ages 2 weeks to 14 months; median age, 10 weeks) were treated with partial pancreatectomy for focal HI. Before surgery, patients had localization studies using selective arterial calcium stimulation with venous sampling or transhepatic portal venous sampling. At operation, the focal lesion was found using the preoperative localization data and multiple pancreatic biopsies with frozen section analysis, followed by partial pancreatectomy. A complete response at follow-up was defined as no requirement for glycemic medications, no continuous tube feedings, and no diabetes mellitus.

RESULTS

Nineteen pancreatic focal lesions were in the head; 15 were in the neck, body, or tail; and 4 had more extensive involvement. Lesions that required substantial resection of the pancreatic head underwent Roux-en-Y pancreaticojejunostomy to preserve the normal body and tail. Lesions of the body or tail were usually treated with partial distal pancreatectomy. Ninety-two percent (35 of 38) of patients had a complete response to surgery. Three patients have required glycemic medications. No patient is diabetic. Surgical complications included additional resection for residual disease (3), small bowel obstruction requiring laparotomy and enterolysis (2), and chylous ascites (3) that resolved with medical management.

CONCLUSIONS

A multidisciplinary approach to patients with the focal form of congenital hyperinsulinism can distinguish focal from diffuse disease, localize focal lesions, and permit partial pancreatectomy with cure in most patients.

Genetics and pathophysiology of hyperinsulinism in infancy

Hyperinsulinism in infancy (HI) is a condition of neonates and early childhood. For many years the pathophysiology of this potentially lethal disorder was unknown. Advances in the genetics, histopathology and molecular physiology of this disease have now provided insights into the causes of beta-cell dysfunction and revealed levels of diversity far in excess of our previous knowledge. These include defects in ion channel subunit genes and mutations in several enzymes associated with beta-cell metabolism and anaplerosis. In most cases, beta-cell pathophysiology leads to an alteration in the function of ATP-sensitive K(+) channels. This can manifest as 'channelopathies' of K(ATP) channels through gene defects in ABCC8 and KCNJ11 (Ch.11p15); or as a result of 'metabolopathies' through defects in the genes encoding glucokinase (GCK, Ch.7p15-p13), glutamate dehydrogenase (GLUD1, Ch.10q23.3) and short-chain L-3-hydroxyacyl-CoA dehydrogenase (HADHSC, Ch.4q22-q26). This review focuses upon the relationship between the causes of HI and therapeutic options.

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.

Clinical and molecular characterization of a dominant form of congenital hyperinsulinism caused by a mutation in the high-affinity sulfonylurea receptor

Recessive mutations of sulfonylurea receptor 1 (SUR1) and potassium inward rectifier 6.2 (Kir6.2), the two adjacent genes on chromosome 11p that comprise the beta-cell plasma membrane ATP-sensitive K(+) (K(ATP)) channels, are responsible for the most common form of congenital hyperinsulinism in children. The present study was undertaken to identify the genetic defect in a family with dominantly inherited hyperinsulinism affecting five individuals in three generations. Clinical tests were carried out in three of the patients using acute insulin responses (AIRs) to intravenous stimuli to localize the site of defect in insulin regulation. The affected individuals showed abnormal positive calcium AIR, normal negative leucine AIR, subnormal positive glucose AIR, and impaired tolbutamide AIR. This AIR pattern suggested a K(ATP) channel defect because it resembled that seen in children with recessive hyperinsulinism due to two common SUR1 mutations, g3992-9a and delPhe1388. Genetic linkage to the K(ATP) locus was established using intragenic polymorphisms. Mutation analysis identified a novel trinucleotide deletion in SUR1 exon 34 that results in the loss of serine 1387. Studies of delSer1387 in COSm6 cells confirmed that the expressed mutant protein assembles with Kir6.2 and trafficks to the plasma membrane, but it had no (86)Rb efflux ion transport activity. These results indicate that hyperinsulinism in this family is caused by a SUR1 mutation that is expressed dominantly rather than recessively.

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.

Persistent hyperinsulinaemic hypoglycaemia

Congenital hyperinsulinism (CI) is the most important cause of hypoglycaemia in early infancy. The inappropriate oversecretion of insulin is responsible for profound hypoglycaemias which require aggressive treatment to prevent severe and irreversible brain damage. Hypoglycaemia have a neonatal or infancy onset. Medical treatment with diazoxide is first used to treat CI, but patients who are medically resistant (mostly of neonatal-onset) require pancreatectomy. CI is a heterogeneous disorder with two histopathological lesions, diffuse and focal which are clinically indistinguishable. Only diazoxide-sensitive neonates should be orientated to transient hyperinsulinism or hyperinsulinism-hyperammonemia syndrome. Focal CI is characterized by a sporadic somatic islet-cell hyperplasia. Diffuse CI corresponds to a functional abnormality of insulin secretion in the whole pancreas and involves several genes with different transmissions. The knowledge of both focal and diffuse lesions is very important. Focal lesions are effectively treated by limited pancreatic resection while diffuse lesions which are unresponsive to drug or dietary treatment require extensive pancreatectomy with high risk of diabetes mellitus.

Acute insulin responses to leucine in children with the hyperinsulinism/hyperammonemia syndrome

Mutations of glutamate dehydrogenase cause the hyperinsulinism/hyperammonemia syndrome by desensitizing glutamate dehydrogenase to allosteric inhibition by GTP. Normal allosteric activation of glutamate dehydrogenase by leucine is thus uninhibited, leading us to propose that children with hyperinsulinism/hyperammonemia syndrome will have exaggerated acute insulin responses to leucine in the postabsorptive state. As hyperglycemia increases beta-cell GTP, we also postulated that high glucose concentrations would extinguish abnormal responsiveness to leucine in hyperinsulinism/hyperammonemia syndrome patients. After an overnight fast, seven hyperinsulinism/hyperammonemia syndrome patients (aged 9 months to 29 yr) had acute insulin responses to leucine performed using an iv bolus of L-leucine (15 mg/kg) administered over 1 min and plasma insulin measurements obtained at -10, -5, 0, 1, 3, and 5 min. The acute insulin response to leucine was defined as the mean increase in insulin from baseline at 1 and 3 min after an iv leucine bolus. The hyperinsulinism/hyperammonemia syndrome group had excessively increased insulin responses to leucine (mean +/- SEM, 73 +/- 21 microIU/ml) compared with the control children and adults (n = 17) who had no response to leucine (1.9 +/- 2.7 microU/ml; P < 0.05). Four hyperinsulinism/hyperammonemia syndrome patients then had acute insulin responses to leucine repeated at hyperglycemia (blood glucose, 150-180 mg/dl). High blood glucose suppressed their abnormal baseline acute insulin responses to leucine of 180, 98, 47, and 28 microU/ml to 73, 0, 6, and 19 microU/ml, respectively. This suppression suggests that protein-induced hypoglycemia in hyperinsulinism/hyperammonemia syndrome patients may be prevented by carbohydrate loading before protein consumption.