High Incidence of Heterozygous ABCC8 and HNF1A Mutations in Czech Patients With Congenital Hyperinsulinism

International Guidelines for the Diagnosis and Management of Hyperinsulinism

BACKGROUND

Hyperinsulinism (HI) due to dysregulation of pancreatic beta-cell insulin secretion is the most common and most severe cause of persistent hypoglycemia in infants and children. In the 65 years since HI in children was first described, there has been a dramatic advancement in the diagnostic tools available, including new genetic techniques and novel radiologic imaging for focal HI; however, there have been almost no new therapeutic modalities since the development of diazoxide.

SUMMARY

Recent advances in neonatal research and genetics have improved our understanding of the pathophysiology of both transient and persistent forms of neonatal hyperinsulinism. Rapid turnaround of genetic test results combined with advanced radiologic imaging can permit identification and localization of surgically-curable focal lesions in a large proportion of children with congenital forms of HI, but are only available in certain centers in "developed" countries. Diazoxide, the only drug currently approved for treating HI, was recently designated as an "essential medicine" by the World Health Organization but has been approved in only 16% of Latin American countries and remains unavailable in many under-developed areas of the world. Novel treatments for HI are emerging, but they await completion of safety and efficacy trials before being considered for clinical use.

KEY MESSAGES

This international consensus statement on diagnosis and management of HI was developed in order to assist specialists, general pediatricians, and neonatologists in early recognition and treatment of HI with the ultimate aim of reducing the prevalence of brain injury caused by hypoglycemia. A previous statement on diagnosis and management of HI in Japan was published in 2017. The current document provides an updated guideline for management of infants and children with HI and includes potential accommodations for less-developed regions of the world where resources may be limited.

An insulin hypersecretion phenotype precedes pancreatic β cell failure in MODY3 patient-specific cells

MODY3 is a monogenic hereditary form of diabetes caused by mutations in the transcription factor HNF1A. The patients progressively develop hyperglycemia due to perturbed insulin secretion, but the pathogenesis is unknown. Using patient-specific hiPSCs, we recapitulate the insulin secretion sensitivity to the membrane depolarizing agent sulfonylurea commonly observed in MODY3 patients. Unexpectedly, MODY3 patient-specific HNF1A^+/R272C β cells hypersecrete insulin both in vitro and in vivo after transplantation into mice. Consistently, we identified a trend of increased birth weight in human HNF1A mutation carriers compared with healthy siblings. Reduced expression of potassium channels, specifically the K_ATP channel, in MODY3 β cells, increased calcium signaling, and rescue of the insulin hypersecretion phenotype by pharmacological targeting ATP-sensitive potassium channels or low-voltage-activated calcium channels suggest that more efficient membrane depolarization underlies the hypersecretion of insulin in MODY3 β cells. Our findings identify a pathogenic mechanism leading to β cell failure in MODY3.

New approaches to screening and management of neonatal hypoglycemia based on improved understanding of the molecular mechanism of hypoglycemia

For the past 70 years, controversy about hypoglycemia in newborn infants has focused on a numerical "definition of neonatal hypoglycemia", without regard to its mechanism. This ignores the purpose of screening newborns for hypoglycemia, which is to identify those with pathological forms of hypoglycemia and to prevent hypoglycemic brain injury. Recent clinical and basic research indicates that the three major forms of neonatal hypoglycemia are caused by hyperinsulinism (recognizing also that other rare hormonal or metabolic conditions may also present during this time frame). These include transitional hypoglycemia, which affects all normal newborns in the first few days after birth; perinatal stress-induced hypoglycemia in high-risk newborns, which afflicts ∼1 in 1,200 newborns; and genetic forms of congenital hyperinsulinism which afflict ∼1 in 10,000-40,000 newborns. (1) Transitional hyperinsulinism in normal newborns reflects persistence of the low glucose threshold for insulin secretion during fetal life into the first few postnatal days. Recent data indicate that the underlying mechanism is decreased trafficking of ATP-sensitive potassium channels to the beta-cell plasma membrane, likely a result of the hypoxemic state of fetal life. (2) Perinatal stress-induced hyperinsulinism in high-risk infants appears to reflect an exaggeration of this normal low fetal glucose threshold for insulin release due to more severe and prolonged exposure to perinatal hypoxemia. (3) Genetic hyperinsulinism, in contrast, reflects permanent genetic defects in various steps controlling beta-cell insulin release, such as inactivating mutations of the K _ATP-channel genes. The purpose of this report is to review our current knowledge of these three major forms of neonatal hyperinsulinism as a foundation for the diagnosis and management of hypoglycemia in newborn infants. This includes selection of appropriate interventions based on underlying disease mechanism; combined monitoring of both plasma glucose and ketone levels to improve screening for infants with persistent forms of hypoglycemia; and ultimately to ensure that infants at risk of persistent hyperinsulinemic hypoglycemia are recognized prior to discharge from the nursery.

Report of Prolonged Neonatal Hypoglycemia in Three Infants of Mothers With Variants in HNF1A

Background/Objective

Genetic variants in hepatic nuclear factor 1α (HNF1A) cause maturity-onset diabetes of the young (MODY). We sought to examine whether HNF1A MODY variants also cause neonatal hypoglycemia.

Case Report

We present 3 infants with variants in HNF1A shared with their mothers. The infants experienced neonatal hypoglycemia, 2 extending beyond 1 year and the third resolving by 28 days, and all were large for gestational age (birth weights of >99th percentile). In 2 cases, genetic testing for neonatal hypoglycemia revealed pathogenic variants in HNF1A; 1 mother was previously diagnosed with HNF1A MODY, and the other's genetic testing and ultimate MODY diagnosis were prompted by her child's hypoglycemia workup. In the third case, the infant's persistent hypoglycemia prompted genetic testing, revealing an HNF1A variant of uncertain significance, which was then identified in the mother.

Discussion

Genetic variants causing HNF1A MODY have not been definitively linked to neonatal hypoglycemia or fetal overgrowth in utero. MODY caused by HNF1A is clinically similar to that caused by HNF4A, for which a causal relationship with neonatal hypoglycemia is more certain. Case reports have previously implicated variants in HNF1A in congenital hyperinsulinism; however, these cases have generally not been in families with MODY. The cases presented here suggest that HNF1A variants causing MODY may also cause neonatal hypoglycemia.

Conclusion

Although confounding factors make the assessment of neonatal hypoglycemia challenging, these cases offer potential support for single genetic variants in HNF1A causing both MODY and neonatal hypoglycemia, with associated fetal overgrowth in utero.

Congenital hyperinsulinism: recent updates on molecular mechanisms, diagnosis and management

Congenital hyperinsulinism (CHI) is a rare disease characterized by an unregulated insulin release, leading to hypoglycaemia. It is the most frequent cause of persistent and severe hypoglycaemia in the neonatal period and early childhood. Mutations in 16 different key genes (ABCC8, KCNJ11, GLUD1, GCK, HADH, SLC16A1, UCP2, HNF4A, HNF1A, HK1, KCNQ1, CACNA1D, FOXA2, EIF2S3, PGM1 and PMM2) that are involved in regulating the insulin secretion from pancreatic β-cells have been described to be responsible for the underlying molecular mechanisms of CHI. CHI can also be associated with specific syndromes and can be secondary to intrauterine growth restriction (IUGR), maternal diabetes, birth asphyxia, etc. It is important to diagnose and promptly initiate appropriate management as untreated hypoglycaemia can be associated with significant neurodisability. CHI can be histopathologically classified into diffuse, focal and atypical forms. Advances in molecular genetics, imaging techniques (18F-fluoro-l-dihydroxyphenylalanine positron emission tomography/computed tomography scanning), novel medical therapies and surgical advances (laparoscopic pancreatectomy) have changed the management and improved the outcome of patients with CHI. This review article provides an overview of the background, clinical presentation, diagnosis, molecular genetics and therapy for children with different forms of CHI.

Congenital Hyperinsulinism: Current Laboratory-Based Approaches to the Genetic Diagnosis of a Heterogeneous Disease

Congenital hyperinsulinism is characterised by the inappropriate release of insulin during hypoglycaemia. This potentially life-threatening disorder can occur in isolation, or present as a feature of syndromic disease. Establishing the underlying aetiology of the hyperinsulinism is critical for guiding medical management of this condition especially in children with diazoxide-unresponsive hyperinsulinism where the underlying genetics determines whether focal or diffuse pancreatic disease is present. Disease-causing single nucleotide variants affecting over 30 genes are known to cause persistent hyperinsulinism with mutations in the KATP channel genes (ABCC8 and KCNJ11) most commonly identified in children with severe persistent disease. Defects in methylation, changes in chromosome number, and large deletions and duplications disrupting multiple genes are also well described in congenital hyperinsulinism, further highlighting the genetic heterogeneity of this condition. Next-generation sequencing has revolutionised the approach to genetic testing for congenital hyperinsulinism with targeted gene panels, exome, and genome sequencing being highly sensitive methods for the analysis of multiple disease genes in a single reaction. It should though be recognised that limitations remain with next-generation sequencing with no single application able to detect all reported forms of genetic variation. This is an important consideration for hyperinsulinism genetic testing as comprehensive screening may require multiple investigations.

Maturity Onset Diabetes of the Young-New Approaches for Disease Modelling

Maturity-onset diabetes of the young (MODY) is a genetically heterogeneous group of monogenic endocrine disorders that is characterised by autosomal dominant inheritance and pancreatic β-cell dysfunction. These patients are commonly misdiagnosed with type 1 or type 2 diabetes, as the clinical symptoms largely overlap. Even though several biomarkers have been tested none of which could be used as single clinical discriminator. The correct diagnosis for individuals with MODY is of utmost importance, as the applied treatment depends on the gene mutation or is subtype-specific. Moreover, in patients with HNF1A-MODY, additional clinical monitoring can be included due to the high incidence of vascular complications observed in these patients. Finally, stratification of MODY patients will enable better and newer treatment options for MODY patients, once the disease pathology for each patient group is better understood. In the current review the clinical characteristics and the known disease-related abnormalities of the most common MODY subtypes are discussed, together with the up-to-date applied diagnostic criteria and treatment options. Additionally, the usage of pluripotent stem cells together with CRISPR/Cas9 gene editing for disease modelling with the possibility to reveal new pathophysiological mechanisms in MODY is discussed.

A Review of Functional Characterization of Single Amino Acid Change Mutations in HNF Transcription Factors in MODY Pathogenesis

Mutations in HNF transcription factor genes cause the most common subtypes of maturity-onset of diabetes of youth (MODY), a monogenic form of diabetes mellitus. Mutations in the HNF1-α, HNF4-α, and HNF1-β genes are primarily considered as the cause of MODY3, MODY1, and MODY5 subtypes, respectively. Although patients with different subtypes display similar symptoms, they may develop distinct diabetes-related complications and require different treatments depending on the type of the mutation. Genetic analysis of MODY patients revealed more than 400 missense/nonsense mutations in HNF1-α, HNF4-α, and HNF1-β genes, however only a small portion of them are functionally characterized. Evaluation of nonsense mutations are more direct as they lead to premature stop codons and mostly in mRNA decay or nonfunctional truncated proteins. However, interpretation of the single amino acid change (missense) mutation is not such definite, as effect of the variant may vary depending on the location and also the substituted amino acid. Mutations with benign effect on the protein function may not be the pathologic variant and further genetic testing may be required. Here, we discuss the functional characterization analysis of single amino acid change mutations identified in HNF1-α, HNF4-α, and HNF1-β genes and evaluate their roles in MODY pathogenesis. This review will contribute to comprehend HNF nuclear family-related molecular mechanisms and to develop more accurate diagnosis and treatment based on correct evaluation of pathologic effects of the variants.

Congenital Hyperinsulinism Caused by Novel Homozygous KATP Channel Gene Variants May Be Linked to Unexplained Neonatal Deaths among Kurdish Consanguineous Families

INTRODUCTION

Neonatal hypoglycemia due to congenital hyperinsulinism (CHI) is a potentially life-threatening condition. Biallelic pathogenic variants in KATP channel subunit genes (ABCC8, KCNJ11), causing severe forms of CHI, are more prevalent in regions with a significant rate of consanguinity and may lead to unexplained neonatal deaths. We hypothesized that KATP channel gene variants are the cause of CHI in three unrelated children from consanguineous Kurdish families with histories of four unexplained neonatal deaths with convulsions.

CASES

(1) A girl presented on the 6th day of life with recurrent hypoglycemic convulsions (blood glucose 2.05 mmol/L, insulin 58 mIU/L, C-peptide 2,242 pmol/L). (2) A girl with severe developmental delay was diagnosed with CHI at 3 years of age (blood glucose 2.78 mmol/L, insulin 8.1 mIU/L, C-peptide 761 pmol/L) despite a history of recurrent hypoglycemia since neonatal age. (3) A girl presented at 3 weeks of age with convulsions and unconsciousness (blood glucose 2.5 mmol/L, insulin 14.6 mIU/L, C-peptide 523 pmol/L). Coding regions of the ABCC8 and KCNJ11 genes were tested by Sanger sequencing. Potential variants were evaluated using the American College of Medical Genetics standards. Three novel causative homozygous variants were found - p.Trp514Ter in the ABCC8 gene (Pt2), and p.Met1Val (Pt1) and p.Tyr26Ter (Pt3) in the KCNJ11 gene.

CONCLUSION

CHI caused by KATP channel variants was elucidated in three children, providing a highly probable retrospective diagnosis for their deceased siblings. Future lives can be saved by timely diagnosis of CHI when encountering a neonate with unexplained seizures or other signs of recurrent and/or persistent hypoglycemia.

Long-Term Outcome and Treatment in Persistent and Transient Congenital Hyperinsulinism: A Finnish Population-Based Study

CONTEXT

The management of congenital hyperinsulinism (CHI) has improved.

OBJECTIVE

To examine the treatment and long-term outcome of Finnish patients with persistent and transient CHI (P-CHI and T-CHI).

DESIGN

A population-based retrospective study of CHI patients treated from 1972 to 2015.

PATIENTS

106 patients with P-CHI and 132 patients with T-CHI (in total, 42 diagnosed before and 196 after year 2000) with median follow-up durations of 12.5 and 6.2 years, respectively.

MAIN OUTCOME MEASURES

Recovery, diabetes, pancreatic exocrine dysfunction, neurodevelopment.

RESULTS

The overall incidence of CHI (n = 238) was 1:11 300 live births (1972-2015). From 2000 to 2015, the incidence of P-CHI (n = 69) was 1:13 500 and of T-CHI (n = 127) 1:7400 live births. In the 21st century P-CHI group, hyperinsulinemic medication was initiated and normoglycemia achieved faster relative to earlier. Of the 74 medically treated P-CHI patients, 68% had discontinued medication. Thirteen (12%) P-CHI patients had partial pancreatic resection and 19 (18%) underwent near-total pancreatectomy. Of these, 0% and 84% developed diabetes and 23% and 58% had clinical pancreatic exocrine dysfunction, respectively. Mild neurological difficulties (21% vs 16%, respectively) and intellectual disability (9% vs 5%, respectively) were as common in the P-CHI and T-CHI groups. However, the 21st century P-CHI patients had significantly more frequent normal neurodevelopment and significantly more infrequent diabetes and pancreatic exocrine dysfunction compared with those diagnosed earlier.

CONCLUSIONS

Our results demonstrated improved treatment and long-term outcome in the 21st century P-CHI patients relative to earlier.

Hyperinsulinemic hypoglycemia in children and adolescents: Recent advances in understanding of pathophysiology and management

Hyperinsulinemic hypoglycemia (HH) is characterized by unregulated insulin release, leading to persistently low blood glucose concentrations with lack of alternative fuels, which increases the risk of neurological damage in these patients. It is the most common cause of persistent and recurrent hypoglycemia in the neonatal period. HH may be primary, Congenital HH (CHH), when it is associated with variants in a number of genes implicated in pancreatic development and function. Alterations in fifteen genes have been recognized to date, being some of the most recently identified mutations in genes HK1, PGM1, PMM2, CACNA1D, FOXA2 and EIF2S3. Alternatively, HH can be secondary when associated with syndromes, intra-uterine growth restriction, maternal diabetes, birth asphyxia, following gastrointestinal surgery, amongst other causes. CHH can be histologically characterized into three groups: diffuse, focal or atypical. Diffuse and focal forms can be determined by scanning using fluorine-18 dihydroxyphenylalanine-positron emission tomography. Newer and improved isotopes are currently in development to provide increased diagnostic accuracy in identifying lesions and performing successful surgical resection with the ultimate aim of curing the condition. Rapid diagnostics and innovative methods of management, including a wider range of treatment options, have resulted in a reduction in co-morbidities associated with HH with improved quality of life and long-term outcomes. Potential future developments in the management of this condition as well as pathways to transition of the care of these highly vulnerable children into adulthood will also be discussed.

Congenital hyperinsulinism due to mutations in HNF1A

Congenital hyperinsulinism is a rare but significant cause of severe and persistent hypoglycaemia in infancy. Although a biphasic phenotype of congenital hyperinsulinism in infancy followed by Maturity-Onset Diabetes of the Young (MODY) in later life has been established for HNF4A, the existence of a similar phenotype for a related MODY gene, HNF1A, is less clear. We describe two cases of congenital hyperinsulinism in association with dominantly inherited variants in HNF1A. They presented in the early neonatal period with unequivocal biochemical evidence of congenital hyperinsulinism and persistence into childhood with ongoing need for medical therapy. Both cases inherited HNF1A variants from a parent with a diabetes phenotype consistent with MODY, without obesity, insulin resistance or other metabolic syndrome features. In the first case, a paternally inherited novel c.-230_-101del variant was found that deletes the minimal promoter region presumably required for HNF1A expression. In the second case, a maternally inherited missense variant (c.713G>T, p.(Arg238Met)) was identified. This variant is predicted to cause haploinsufficiency via aberrant splicing and has previously been associated with MODY but not congenital hyperinsulinism. Our cases further strengthen the evidence for HNF1A as a CHI-causing gene requiring long-term follow-up.

Functional Analyses of HNF1A-MODY Variants Refine the Interpretation of Identified Sequence Variants

CONTEXT

While rare variants of the hepatocyte nuclear factor-1 alpha (HNF1A) gene can cause maturity-onset diabetes of the young (HNF1A-MODY), other variants can be risk factors for the development of type 2 diabetes. As has been suggested by the American College of Medical Genetics (ACMG) guidelines for variant interpretation, functional studies provide strong evidence to classify a variant as pathogenic.

OBJECTIVE

We hypothesized that a functional evaluation can improve the interpretation of the HNF1A variants in our Czech MODY Registry.

DESIGN, SETTINGS, AND PARTICIPANTS

We studied 17 HNF1A variants that were identified in 48 individuals (33 female/15 male) from 20 Czech families with diabetes, using bioinformatics in silico tools and functional protein analyses (transactivation, protein expression, DNA binding, and nuclear localization).

RESULTS

Of the 17 variants, 12 variants (p.Lys120Glu, p.Gln130Glu, p.Arg131Pro, p.Leu139Pro, p.Met154Ile, p.Gln170Ter, p.Glu187SerfsTer40, p.Phe215SerfsTer18, p.Gly253Arg, p.Leu383ArgfsTer3, p.Gly437Val, and p.Thr563HisfsTer85) exhibited significantly reduced transcriptional activity or DNA binding (< 40%) and were classified as (likely) pathogenic, 2/17 variants were (likely) benign and 3/17 remained of uncertain significance. Functional analyses allowed for the reclassification of 10/17 variants (59%). Diabetes treatment was improved in 20/29 (69%) carriers of (likely) pathogenic HNF1A variants.

CONCLUSION

Functional evaluation of the HNF1A variants is necessary to better predict the pathogenic effects and to improve the diagnostic interpretation and treatment, particularly in cases where the cosegregation or family history data are not available or where the phenotype is more diverse and overlaps with other types of diabetes.

Clinical and Genetic Characterization of 153 Patients with Persistent or Transient Congenital Hyperinsulinism

CONTEXT

Major advances have been made in the genetics and classification of congenital hyperinsulinism (CHI).

OBJECTIVE

To examine the genetics and clinical characteristics of patients with persistent and transient CHI.

DESIGN

A cross-sectional study with the register data and targeted sequencing of 104 genes affecting glucose metabolism.

PATIENTS

Genetic and phenotypic data were collected from 153 patients with persistent (n = 95) and transient (n = 58) CHI diagnosed between 1972 and 2015. Of these, 86 patients with persistent and 58 with transient CHI participated in the analysis of the selected 104 genes affecting glucose metabolism, including 10 CHI-associated genes, and 9 patients with persistent CHI were included because of their previously confirmed genetic diagnosis.

MAIN OUTCOME MEASURES

Targeted next-generation sequencing results and genotype-phenotype associations.

RESULTS

Five novel and 21 previously reported pathogenic or likely pathogenic variants in ABCC8, KCNJ11, GLUD1, GCK, HNF4A, and SLC16A1 genes were found in 68% (n = 65) and 0% of the patients with persistent and transient CHI, respectively. KATP channel mutations explained 82% of the mutation positive cases.

CONCLUSIONS

The genetic variants found in this nationwide CHI cohort are in agreement with previous studies, mutations in the KATP channel genes being the major causes of the disease. Pathogenic CHI-associated variants were not identified in patients who were both diazoxide responsive and able to discontinue medication within the first 4 months. Therefore, our results support the notion that genetic testing should be focused on patients with inadequate response or prolonged need for medication.

Using referral rates for genetic testing to determine the incidence of a rare disease: The minimal incidence of congenital hyperinsulinism in the UK is 1 in 28,389

Congenital hyperinsulinism (CHI) is a significant cause of hypoglycaemia in neonates and infants with the potential for permanent neurologic injury. Accurate calculations of the incidence of rare diseases such as CHI are important as they inform health care planning and can aid interpretation of genetic testing results when assessing the frequency of variants in large-scale, unselected sequencing databases. Whilst minimal incidence rates have been calculated for four European countries, the incidence of CHI in the UK is not known. In this study we have used referral rates to a central laboratory for genetic testing and annual birth rates from census data to calculate the minimal incidence of CHI within the UK from 2007 to 2016. CHI was diagnosed in 278 individuals based on inappropriately detectable insulin and/or C-peptide measurements at the time of hypoglycaemia which persisted beyond 6 months of age. From these data, we have calculated a minimum incidence of 1 in 28,389 live births for CHI in the UK. This is comparable to estimates from other outbred populations and provides an accurate estimate that will aid both health care provision and interpretation of genetic results, which will help advance our understanding of CHI.

Hyperinsulinaemic hypoglycaemia-an overview of a complex clinical condition

Hyperinsulinaemic hypoglycaemia (HH) is a major cause of hypoglycaemia in the neonatal period, infancy and childhood. It is caused by unsuppressed insulin secretion in the setting of hypoglycaemia and carries a high risk of significant neurological sequelae, such as cognitive impairment. Genetic mutations have been implicated in the pathogenesis of the condition. Other causes include intra-uterine growth retardation, perinatal asphyxia, maternal diabetes mellitus and syndromes, such as Beckwith-Wiedemann. Based on the aetiology, the clinical presentation can range from absence of symptoms to the typical adrenergic symptoms and coma and even death. The diagnosis is based on biochemical findings and the gold-standard imaging technique is 18F-DOPA PET/CT scanning. Treatment options involve medications, such as diazoxide, nifedipine, glucagon and octreotide, as well as surgery. Novel treatment, such as long-acting octreotide, lanreotide and sirolimus, may be used as an alternative to pancreatectomy. Potential future medical treatments include exendin, a GLP-1 receptor antagonist, and glucagon infusion via a pump.Conclusion: Advances in the fields of genetic testing, imaging techniques and medical treatment are beginning to provide novel insights into earlier detection, less invasive treatment approaches and fewer complications associated with the complex entity of hyperinsulinaemic hypoglycaemia. What is Known: • HH is caused by dysregulated insulin release from the β cell due to genetic mutations and carries a risk for complications, such as neurocognitive impairment. 18F-DOPA PET/CT scanning is presented as the gold-standard imaging technique currently in children with hyperinsulinaemic hypoglycaemia. • Clinical presentation is heterogeneous and treatment options include medical therapy and pancreatectomy. What is New: • 18F-DOPA PET/CT is indicated in suspected focal CHI due to paternal transmitted mutations in ABCC8 or KCNJ11. • Novel treatment options have been introduced, such as long-acting octreotide, lanreotide, sirolimus and selective nonpeptide somatostatin receptor subtype 5 (SSTR5) agonists. Future medical treatments include exendin, a GLP-1 antagonist, and glucagon infusion via a pump. However, all these options are off-label at present.

The Genetic and Molecular Mechanisms of Congenital Hyperinsulinism

Congenital hyperinsulinism (CHI) is a heterogenous and complex disorder in which the unregulated insulin secretion from pancreatic beta-cells leads to hyperinsulinaemic hypoglycaemia. The severity of hypoglycaemia varies depending on the underlying molecular mechanism and genetic defects. The genetic and molecular causes of CHI include defects in pivotal pathways regulating the secretion of insulin from the beta-cell. Broadly these genetic defects leading to unregulated insulin secretion can be grouped into four main categories. The first group consists of defects in the pancreatic K_ATP channel genes (ABCC8 and KCNJ11). The second and third categories of conditions are enzymatic defects (such as GDH, GCK, HADH) and defects in transcription factors (for example HNF1α, HNF4α) leading to changes in nutrient flux into metabolic pathways which converge on insulin secretion. Lastly, a large number of genetic syndromes are now linked to hyperinsulinaemic hypoglycaemia. As the molecular and genetic basis of CHI has expanded over the last few years, this review aims to provide an up-to-date knowledge on the genetic causes of CHI.

Congenital hyperinsulinism treated by surgical resection of the hyperplastic lesion which had been preoperatively diagnosed by 18F-DOPA PET examination in Japan: a nationwide survey

PURPOSE

Congenital hyperinsulinism is a rare disease, and the newly developed 18 fluoro-_L-dihydroxyphenylalanine-positron emission tomography (18F-DOPA PET) examination can detect hyperplastic lesions. Our purpose was to report the results of a nationwide survey on surgical treatment of congenital hyperinsulinism in Japan.

METHODS

A questionnaire was sent to the 159 accredited and affiliated training institutes certified as pediatric surgical institutes by the Japanese Association of Pediatric Surgeons, asking if they had encountered patients who underwent surgical treatment for congenital hyperinsulinism after 18F-DOPA PET examination from 2000 to 2017. Six institutes answered that they had treated such cases, and the total number of cases was 14.

RESULTS

18F-DOPA PET examination detected the focal lesion in 12 of the 14 cases. 18F-DOPA PET examination could accurately determine the site of the hyperplastic lesion in the pancreas in 11 (91.7%) of the 12 cases. All cases underwent surgical resection of the hyperplastic lesion at under 2 years of age.

CONCLUSION

Surgical resection of a focal hyperplastic lesion in the pancreas was a safe and effective treatment if the hyperplastic lesion was a focal lesion. However, it is necessary to check the exact distribution of the lesion by intraoperative pathologic examination of frozen sections.

Clinical heterogeneity of hyperinsulinism due to HNF1A and HNF4A mutations

BACKGROUND

Dominant inactivating mutations in HNF1A and HNF4A have been described to cause hyperinsulinism (HI) before evolving to diabetes. However, information available in the literature regarding the clinical phenotype is limited.

OBJECTIVE

To report the prevalence of HNF1A and HNF4A mutations in a large cohort of children with HI, and to describe their genotypes and phenotypes.

DESIGN

Retrospective descriptive study.

METHODS

Medical records were reviewed to extract clinical information. Mutation analysis was carried out for 8 genes associated with HI (ABCC8, KCNJ11, GLUD1, GCK, HADH, HNF4A, HNF1A, and UCP2).

RESULTS

HNF1A and HNF4A mutations were identified in 5.9% (12 out of 204; HNF1A = 7, HNF4A = 5) of diazoxide-responsive HI probands. The clinical phenotypes were extremely variable. Two children showed evidence of ketone production during hypoglycemia, a biochemical profile atypical for hyperinsulinism. At the time of analysis, diazoxide was discontinued in 5 children at a median age of 6.8 years. None had developed diabetes mellitus at a median age of 7.0 years.

CONCLUSIONS

Given the heterogeneous clinical phenotypes of HNF1A- and HNF4A-HI, all children with transient, diazoxide-responsive HI without clear history of perinatal stress, should be screened for HNF1A and HNF4A mutations as it predicts the clinical course and affects the subsequent management plan.

Neonatal hypoglycemia, early-onset diabetes and hypopituitarism due to the mutation in EIF2S3 gene causing MEHMO syndrome

Recently, the genetic cause of several syndromic forms of glycemia dysregulation has been described. One of them, MEHMO syndrome, is a rare X-linked syndrome recently linked to the EIF2S3 gene mutations. MEHMO is characterized by Mental retardation, Epilepsy, Hypogonadism/hypogenitalism, Microcephaly, and Obesity. Moreover, patients with MEHMO had also diabetes and endocrine phenotype, but detailed information is missing. We aimed to provide more details on the endocrine phenotype in two previously reported male probands with MEHMO carrying a frame-shift mutation (I465fs) in the EIF2S3 gene. Both probands had a neonatal hypoglycemia, early onset insulin-dependent diabetes, and hypopituitarism due to dysregulation and gradual decline of peptide hormone secretion. Based on the clinical course in our two probands and also in previously published patients, neonatal hypoglycemia followed by early-onset diabetes and hypopituitarism may be a consistent part of the MEHMO phenotype.

Congenital Hyperinsulinism: Diagnosis and Treatment Update

Pancreatic β-cells are finely tuned to secrete insulin so that plasma glucose levels are maintained within a narrow physiological range (3.5-5.5 mmol/L). Hyperinsulinaemic hypoglycaemia (HH) is the inappropriate secretion of insulin in the presence of low plasma glucose levels and leads to severe and persistent hypoglycaemia in neonates and children. Mutations in 12 different key genes (ABCC8, KCNJ11, GLUD1, GCK, HADH, SLC16A1, UCP2, HNF4A, HNF1A, HK1, PGM1 and PMM2) that are involved in the regulation of insulin secretion from pancreatic β-cells have been described to be responsible for the underlying molecular mechanisms leading to congenital HH. In HH due to the inhibitory effect of insulin on lipolysis and ketogenesis there is suppressed ketone body formation in the presence of hypoglycaemia thus leading to increased risk of hypoglycaemic brain injury. Therefore, a prompt diagnosis and immediate management of HH is essential to avoid hypoglycaemic brain injury and long-term neurological complications in children. Advances in molecular genetics, imaging techniques (18F-DOPA positron emission tomography/computed tomography scanning), medical therapy and surgical advances (laparoscopic and open pancreatectomy) have changed the management and improved the outcome of patients with HH. This review article provides an overview to the background, clinical presentation, diagnosis, molecular genetics and therapy in children with different forms of HH.

Could a combination of heterozygous ABCC8 and KCNJ11 mutations cause congenital hyperinsulinism?

BACKGROUND

Congenital hyperinsulinism (CHI) is frequently caused by mutations in one of the KATP channel subunits encoded by the genes ABCC8 and KCNJ11. The effect of simultaneous mutations in both of these genes on the pancreatic β-cell function is not known and patients with CHI carrying both ABCC8 and KCNJ11 mutations have not yet been reported. We questioned if a combination of heterozygous mutations in the ABCC8 and KCNJ11 genes could also lead to β-cell dysfunction presenting as CHI.

METHODS

As a model, we used a patient with transient CHI that paternally inherited novel heterozygous mutations in ABCC8 (p.Tyr1293Asp) and KCNJ11 (p.Arg50Trp) genes. The pathogenic effects on the pancreatic β-cells function were examined in an in vitro functional study using radioactive rubidium efflux assay.

RESULTS

We showed that the activation of the mutated KATP channels by diazoxide was decreased by 60.9% in the channels with the heterozygous combination of both mutations compared to the wild type channels. This could indicate the pathogenic effect on the pancreatic β-cell function leading to CHI although conclusive evidence is needed to be added.

CONCLUSIONS

Our findings may widen the spectrum of genetic causes of CHI and suggest a novel pathogenic mechanism of CHI that must however, be further investigated.

Hyperinsulinaemic hypoglycaemia in children and adults

Pancreatic β cells are functionally programmed to release insulin in response to changes in plasma glucose concentration. Insulin secretion is precisely regulated so that, under normal physiological conditions, fasting plasma glucose concentrations are kept within a narrow range of 3·5-5·5 mmol/L. In hyperinsulinaemic hypoglycaemia, insulin secretion becomes dysregulated (ie, uncoupled from glucose metabolism) so that insulin secretion persists in the presence of low plasma glucose concentrations. Hyperinsulinaemic hypoglycaemia is the most common cause of severe and persistent hypoglycaemia in neonates and children. At a molecular level, mutations in nine different genes can lead to the dysregulation of insulin secretion and cause this disorder. In adults, hyperinsulinaemic hypoglycaemia accounts for 0·5-5·0% of cases of hypoglycaemia and can be due either to β-cell tumours (insulinomas) or β-cell hyperplasia. Rapid diagnosis and prompt management of hyperinsulinaemic hypoglycaemia is essential to avoid hypoglycaemic brain injury, especially in the vulnerable neonatal and childhood periods. Advances in the field of hyperinsulinaemic hypoglycaemia include use of rapid molecular genetic testing for the disease, application of novel imaging techniques (6-[fluoride-18]fluoro-levodopa [¹⁸F-DOPA] PET-CT and glucagon-like peptide 1 (GLP-1) receptor imaging), and development of novel medical treatments (eg, long-acting octreotide formulations, mTOR inhibitors, and GLP-1 receptor antagonists) and surgical therapies (eg, laparoscopic surgery).

Diagnosis and treatment of hyperinsulinaemic hypoglycaemia and its implications for paediatric endocrinology

Glucose homeostasis requires appropriate and synchronous coordination of metabolic events and hormonal activities to keep plasma glucose concentrations in a narrow range of 3.5–5.5 mmol/L. Insulin, the only glucose lowering hormone secreted from pancreatic β-cells, plays the key role in glucose homeostasis. Insulin release from pancreatic β-cells is mainly regulated by intracellular ATP-generating metabolic pathways. Hyperinsulinaemic hypoglycaemia (HH), the most common cause of severe and persistent hypoglycaemia in neonates and children, is the inappropriate secretion of insulin which occurs despite low plasma glucose levels leading to severe and persistent hypoketotic hypoglycaemia. Mutations in 12 different key genes (ABCC8, KCNJ11, GLUD1, GCK, HADH, SLC16A1, UCP2, HNF4A, HNF1A, HK1, PGM1 and PMM2) constitute the underlying molecular mechanisms of congenital HH. Since insulin supressess ketogenesis, the alternative energy source to the brain, a prompt diagnosis and immediate management of HH is essential to avoid irreversible hypoglycaemic brain damage in children. Advances in molecular genetics, imaging methods (¹⁸F–DOPA PET-CT), medical therapy and surgical approach (laparoscopic and open pancreatectomy) have changed the management and improved the outcome of patients with HH. This up to date review article provides a background to the diagnosis, molecular genetics, recent advances and therapeutic options in the field of HH in children.

Heterogeneity in phenotype of hyperinsulinism caused by activating glucokinase mutations: a novel mutation and its functional characterization

BACKGROUND

Mutations in the GCK gene lead to different forms of glucokinase (GCK)-disease, activating mutations cause hyperinsulinaemic hypoglycaemia while inactivating mutations cause monogenic diabetes. Hyperinsulinism (HI) is a heterogeneous condition with a significant genetic component. The major causes are channelopathies, the other forms are rare and being caused by mutations in genes such as GCK.

OBJECTIVE

To describe the clinical and genetic presentation of four families with activating GCK mutations, and to explore the pathogenicity of the novel mutation identified through functional studies.

RESULTS

Four cases of HI with mutations in GCK were identified. These include one novel mutation (p.Trp99Cys). Functional analysis of the purified mutant fusion protein glutathione-S-transferase (GST)-GCK-p.Trp99Cys demonstrated that p.Trp99Cys is an activating mutation as it induces a higher affinity for glucose and increases the relative activity index more than 11 times. Moreover, the thermal stability of the mutant protein was similar to that of its wild type. All patients were responsive to diazoxide treatment. One of the mutations arose de novo, and two were dominantly inherited, although only one of them from an HI affected parent. The age of presentation in our cases varied widely from the neonatal period to adulthood.

CONCLUSION

The clinical phenotype of the GCK activating mutation carriers was heterogeneous, the severity of symptoms and age at presentation varied markedly between affected individuals, even within the same family. The novel activating GCK mutation (p.Trp99Cys) has a strong activating effect in vitro although it has been identified in one case of a milder and late-onset form of HI.

Hyperinsulinemic Hypoglycemia - The Molecular Mechanisms

Under normal physiological conditions, pancreatic β-cells secrete insulin to maintain fasting blood glucose levels in the range 3.5-5.5 mmol/L. In hyperinsulinemic hypoglycemia (HH), this precise regulation of insulin secretion is perturbed so that insulin continues to be secreted in the presence of hypoglycemia. HH may be due to genetic causes (congenital) or secondary to certain risk factors. The molecular mechanisms leading to HH involve defects in the key genes regulating insulin secretion from the β-cells. At this moment, in time genetic abnormalities in nine genes (ABCC8, KCNJ11, GCK, SCHAD, GLUD1, SLC16A1, HNF1A, HNF4A, and UCP2) have been described that lead to the congenital forms of HH. Perinatal stress, intrauterine growth retardation, maternal diabetes mellitus, and a large number of developmental syndromes are also associated with HH in the neonatal period. In older children and adult's insulinoma, non-insulinoma pancreatogenous hypoglycemia syndrome and post bariatric surgery are recognized causes of HH. This review article will focus mainly on describing the molecular mechanisms that lead to unregulated insulin secretion.