Unregulated Insulin Secretion Research Articles

Clinical Profile and Efficacy of Long-Acting Octreotide in Hyperinsulinemic Hypoglycaemia.

Hyperinsulinemic hypoglycaemia (HH) is characterised by unregulated insulin secretion, leading to persistent non-ketotic hypoglycaemia with a lack of alternate fuel that induces a severe risk for brain damage and neurodevelopmental abnormalities. Octreotide, a somatostatin analogue, has been effectively administered as subcutaneous injections or depot preparations in diazoxide-unresponsive HH. Children and infants with HH receiving short-acting octreotide injections were included. Anthropometric values, hypoglycaemic episodes, HbA1C, and side effects were noted from the records and were followed up for 12 months. Informed written consent was obtained from the parents before administration of a single dose of LAR (long-acting octreotide). Based on home-based glucose monitoring (HBGM), the dosage of LAR was modified, and short-acting octreotide was eventually withdrawn. The patients shared the injection's cost for cost-effectiveness. HH affects the quality of life (QoL) if not diagnosed and controlled adequately. A QoL questionnaire was given before starting LAR and after 6 months of receiving LAR, and the changes were noted accordingly. Twenty-two patients were diagnosed with HH, of which 11 infants and children were included in the study. Mutations were identified in 7 (63.63%) children. Daily octreotide could be tapered and stopped with the addition of sirolimus in one patient with an increasing dose of LAR to maintain euglycaemia. The hypoglycaemic episodes decreased with increasing dose of LAR with a decrease in the severity. Eight (72.7%) patients showed an improved lifestyle on LAR quantified through a QoL questionnaire. LAR was found effective in reducing hypoglycaemic episodes with no adverse effects. The patient's parent's satisfaction was higher. Given its high cost, this trial achieved cost-effectiveness by sharing a single sitting of LAR injection.

SAT149 In Vitro Characterization Of A Novel Long-acting Glucagon Analog (HM15136) And Its Potential Effect In Animal Models Of Chronic Hypoglycemic Diseases

Abstract Disclosure: J. Kim: Employee; Self; Hanmi Pharm. Co., Ltd. Y. Kim: Employee; Self; Hanmi Pharm. Co., Ltd. B. Ye: Employee; Self; Hanmi Pharm. Co., Ltd. W. Kim: Employee; Self; Hanmi Pharm. Co., Ltd. J. Kim: Employee; Self; Hanmi Pharm. Co., Ltd. S. Bae: Employee; Self; Hanmi Pharm. Co., Ltd. D. Kim: Employee; Self; Hanmi Pharm. Co., Ltd. S. Lee: Employee; Self; Hanmi Pharm. Co., Ltd. I. Choi: Employee; Self; Hanmi Pharm. Co., Ltd. Glucagon plays an essential role in glucose homeostasis, and has been used to treat acute hypoglycemia in diabetic patients. However, due to poor solubility and stability at physiological pH as well as short duration of action, its utility was hampered when managing chronic hypoglycemic diseases. One such example is congenital hyperinsulinism (CHI). CHI is a rare genetic disorder characterized by unregulated insulin secretion which leads to severe hypoglycemia especially during fasting condition. Another example is post-bariatric hypoglycemia (PBH) which can also lead to postprandial neuroglycopenia. Despite this life-threatening condition, no drugs are approved for CHI and/or PBH, and available glucagon therapies are very inefficient and inconvenient due to abovementioned limitations. Thus, to provide more optimal therapy for these chronic hypoglycemic diseases, a novel long-acting glucagon analog (HM15136) was developed. Here, we evaluated HM15136’s 1) solubility and stability at physiologic pH, 2) in vitro properties, and 3) potential therapeutic effect in animal models of CHI or PBH. First, we demonstrated improved solubility of HM15136 (≥150 vs. 0.03 mg/mL) at pH 7.0 and stability at day 20, compared to those of native glucagon. Next, in vitro cAMP assay was performed in CHO cells expressing human glucagon receptor (hGCGR), and HM15136 selectively activated hGCGR as a full agonist (EC50 = 0.024 vs. 0.003 nM; relative activity = ca.12.7%). In line with this, HM15136 promoted glycogenolysis and gluconeogenesis in rat primary hepatocytes in a dose dependent manner (relative potency = ca.20%), confirming glucose producing nature of HM15136. To investigate in vivo therapeutic effect on CHI and PBH, chronic hypoglycemia rats induced by SC infusion of insulin (CHI rats) and postprandial hypoglycemia rats induced by vertical sleeve gastrectomy (VSG rats) were established, respectively. Notably, HM15136 treatment significantly restored FBG by 37.3 ∼ 69.7% (p<0.05 ∼ 0.001) in CHI rats. Consistently, HM15136 treatment significantly prevented a massive BG reduction during MMTT in VSG rats (ΔBG between 0 and 45 min = +21 vs. -30 mg/dL, p<0.001). Furthermore, weekly dosing potential and BG elevation effect of HM15136 were also demonstrated in healthy human subjects (1). Based on these results, HM15136 could be a potential therapeutic option for chronic hypoglycemic diseases including CHI and PBH. Phase 2 clinical study in CHI subjects is on-going to assess the clinical relevance of these findings. Reference: (1) Diabetes Obes Metab. 2022 Mar; 23(3):411-20 Presentation: Saturday, June 17, 2023

Crosstalk between gut microbiota and antidiabetic drug action.

Type 2 diabetes (T2D) is a disorder characterized by chronic inflated blood glucose levels (hyperglycemia), at first due to insulin resistance and unregulated insulin secretion but with tendency towards global spreading. The gut microbiota is recognized to have an influence on T2D, although surveys have not formed a clear overview to date. Because of the interactions between gut microbiota and host homeostasis, intestinal bacteria are believed to play a large role in various diseases, including metabolic syndrome, obesity and associated disease. In this review, we highlight the animal and human studies which have elucidated the roles of metformin, α-glucosidase inhibitors, glucagon-like peptide-1 agonists, peroxisome proliferator-activated receptors γ agonists, inhibitors of dipeptidyl peptidase-4, sodium/glucose cotransporter inhibitors, and other less studied medications on gut microbiota. This review is dedicated to one of the most widespread diseases, T2D, and the currently used antidiabetic drugs and most promising new findings. In general, the gut microbiota has been shown to have an influence on host metabolism, food consumption, satiety, glucose homoeostasis, and weight gain. Altered intestinal microbiota composition has been noticed in cardiovascular diseases, colon cancer, rheumatoid arthritis, T2D, and obesity. Therefore, the main effect of antidiabetic drugs is on the microbiome composition, basically increasing the short-chain fatty acids-producing bacteria, responsible for losing weight and suppressing inflammation.

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 KATP 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.

Novel FOXA2 mutation causes Hyperinsulinism, Hypopituitarism with Craniofacial and Endoderm-derived organ abnormalities.

Congenital hypopituitarism (CH) is characterized by the deficiency of one or more pituitary hormones and can present alone or in association with complex disorders. Congenital hyperinsulinism (CHI) is a disorder of unregulated insulin secretion despite hypoglycaemia that can occur in isolation or as part of a wider syndrome. Molecular diagnosis is unknown in many cases of CH and CHI. The underlying genetic etiology causing the complex phenotype of CH and CHI is unknown. In this study, we identified a de novo heterozygous mutation in the developmental transcription factor, forkhead box A2, FOXA2 (c.505T>C, p.S169P) in a child with CHI and CH with craniofacial dysmorphic features, choroidal coloboma and endoderm-derived organ malformations in liver, lung and gastrointestinal tract by whole exome sequencing. The mutation is at a highly conserved residue within the DNA binding domain. We demonstrated strong expression of Foxa2 mRNA in the developing hypothalamus, pituitary, pancreas, lungs and oesophagus of mouse embryos using in situ hybridization. Expression profiling on human embryos by immunohistochemistry showed strong expression of hFOXA2 in the neural tube, third ventricle, diencephalon and pancreas. Transient transfection of HEK293T cells with Wt (Wild type) hFOXA2 or mutant hFOXA2 showed an impairment in transcriptional reporter activity by the mutant hFOXA2. Further analyses using western blot assays showed that the FOXA2 p.(S169P) variant is pathogenic resulting in lower expression levels when compared with Wt hFOXA2. Our results show, for the first time, the causative role of FOXA2 in a complex congenital syndrome with hypopituitarism, hyperinsulinism and endoderm-derived organ abnormalities.

Identification of the molecular dysfunction caused by glutamate dehydrogenase S445L mutation responsible for hyperinsulinism/hyperammonemia.

Congenital hyperinsulinism/hyperammonemia (HI/HA) syndrome gives rise to unregulated protein-induced insulin secretion from pancreatic beta-cells, fasting hypoglycemia and elevated plasma ammonia levels. Mutations associated with HI/HA were identified in the Glud1 gene, encoding for glutamate dehydrogenase (GDH). We aimed at identifying the molecular causes of dysregulation in insulin secretion and ammonia production conferred by the most frequent HI/HA mutation Ser445Leu. Following transduction with adenoviruses carrying the human GDH-wild type or GDH-S445L-mutant gene, immunoblotting showed efficient expression of the transgenes in all the investigated cell types. Enzymatic activity tested in INS-1E beta-cells revealed that the mutant was much more sensitive to the allosteric activator ADP, rendering it highly responsive to substrates. INS-1E cells expressing either the wild type or mutant GDH responded similarly to glucose stimulation regarding mitochondrial activation and insulin secretion. However, at basal glucose glutamine stimulation increased mitochondrial activity and insulin release only in the mutant cells. In mouse and human islets, expression of mutant GDH resulted in robust elevation of insulin secretion upon glutamine stimulation, not observed in control islets. Hepatocytes expressing either the wild type or mutant GDH produced similar levels of ammonia when exposed to glutamine, although alanine response was strongly elevated with the mutant form. In conclusion, the GDH-S445L mutation confers hyperactivity to this enzyme due to higher sensitivity to ADP allosteric activation. This renders beta-cells responsive to amino acid stimulation, explaining protein-induced hypoglycemia secondary to non-physiological insulin release. Hepatocytes carrying mutant GDH produced more ammonia upon alanine exposure, which underscores hyperammonemia developed by the patients.

Successful treatment of a newborn with congenital hyperinsulinism having a novel heterozygous mutation in the ABCC8 gene using subtotal pancreatectomy

Congenital hyperinsulinism (CHI) is the most common cause of persistent hypoglycemia in newborns and infants. CHI is characterized by unregulated secretion of insulin from pancreatic β cells. Here, we reported the case of a large-for-gestational-age, full-term newborn that suffered from CHI and developed severe and persistent hypoglycemia at an early stage of life. The infant was nearly unresponsive to medical treatment, which included continuous intravenous glucagon infusion, oral diazoxide, and nifedipine. After medical treatment had failed, an 18-fluoro L-3,4-dihydroxyphenylalanine positron emission tomography scan of the patient showed a focal lesion at the neck of the pancreas. The patient received subtotal pancreatectomy, and shortly after the procedure, the patient's blood sugar returned to the normal range. The patient was confirmed to have a novel heterozygous mutation at position c.2475+1G>A of the ABCC8 gene. This is the first report of a focal form of CHI in a patient in Taiwan, which had preoperatively been confirmed using 18-fluoro L-3,4-dihydroxyphenylalanine positron emission tomography.

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.

Noninsulinoma pancreatogenous hypoglycaemia in adults--a spotlight on its genetics.

Hyperinsulinaemic hypoglycaemia (HH) is also classically referred to as "nesidioblastosis". Heterogeneous clinical manifestation of the disease causes risk of late diagnosis or even misdiagnosis. In infants and children, it can lead to serious and permanent damage to the central nervous system, which leads to the manifesting mental retardation. HH is characterised by unregulated insulin secretion from pancreatic β-cells. This effect has been correlated with nine genes: ABCC8, KCNJ11, GCK, GLUD-1, HADH1, SLC16A1, HNF4A, HNF1A, and UCP2. Mutations in these genes were found in approximately 48% of cases. The genetic background of the remaining cases is unknown. Understanding the genetic basis of familial hyperinsulinism has changed the early look at the disease. It has allowed for the differentiation of specific types of the disease. Depending on which of the nine disease-associated loci bears a pathogenic mutation, they differ in phenotype and pattern of inheritance. This review provides a brief overview of the genetic mechanisms of HH and its possible clinical presentations.

Genotype and phenotype correlations in Iranian patients with hyperinsulinaemic hypoglycaemia.

BackgroundHyperinsulinaemic hypoglycaemia (HH) is a group of clinically and genetically heterogeneous disorders characterized by unregulated insulin secretion. Abnormalities in nine different genes (ABCC8, KCNJ11, GLUD1, GCK, HADH, SLC16A1, HNF4A, UCP2 and HNF1A) have been reported in HH, the most common being ABCC8 and KCNJ11. We describe the genetic aetiology and phenotype of Iranian patients with HH.MethodsRetrospective clinical, biochemical and genetic information was collected on 23 patients with biochemically confirmed HH. Mutation analysis was carried out for the ATP-sensitive potassium (KATP) channel genes (ABCC8 and KCNJ11), GLUD1, GCK, HADH and HNF4A.Results78 % of the patients were identified to have a genetic cause for HH. 48 % of patients had mutation in HADH, whilst ABCC8/KCNJ11 mutations were identified in 30 % of patients. Among the diazoxide-responsive patients (18/23), mutations were identified in 72 %. These include two novel homozygous ABCC8 mutations. Of the five patients with diazoxide-unresponsive HH, three had homozygous ABCC8 mutation, one had heterozygous ABCC8 mutation inherited from an unaffected father and one had homozygous KCNJ11 mutation. 52 % of children in our cohort were born to consanguineous parents. Patients with ABCC8/KCNJ11 mutations were noted to be significantly heavier than those with HADH mutation (p = 0.002). Our results revealed neurodevelopmental deficits in 30 % and epilepsy in 52 % of all patients.ConclusionsTo the best of our knowledge, this is the first study of its kind in Iran. We found disease-causing mutations in 78 % of HH patients. The predominance of HADH mutation might be due to a high incidence of consanguineous marriage in this population. Further research involving a larger cohort of HH patients is required in Iranian population.

Molecular mechanisms of congenital hyperinsulinism due to autosomal dominant mutations in ABCC8.

Congenital Hyperinsulinism (CHI) is a rare heterogeneous disease characterized by unregulated insulin secretion. Dominant mutations in ABCC8 causing medically unresponsive CHI have been reported; however, the molecular mechanisms are not clear. The molecular basis of medically unresponsive CHI due to dominant ABCC8 mutations has been studied in 10 patients, who were medically unresponsive to diazoxide (DZX), and nine of whom required a near-total pancreatectomy, and one partial pancreatectomy. DNA sequencing revealed seven dominant inactivating heterozygous missense mutations in ABCC8, including one novel and six previously reported but uncharacterized mutations. Two groups of mutations with different cellular mechanisms were characterized. Mutations in the transmembrane domain (TMD) were more responsive to channel activators such as DZX, MgADP and metabolic inhibition. The trafficking analysis has shown that nucleotide-binding domain two (NBD2) mutations are not retained in the endoplasmic reticulum (ER) and are present on the membrane. However, the TMD mutations were retained in the ER. D1506E was the most severe SUR1-NBD2 mutation. Homologous expression of D1506E revealed a near absence of KATP currents in the presence of DZX and intracellular MgADP. Heterozygous expression of D1506E showed a strong dominant-negative effect on SUR1\Kir6.2 currents. Overall, we define two groups of mutation with different cellular mechanisms. In the first group, channel complexes with mutations in NBD2 of SUR1 traffic normally but are unable to be activated by MgADP. In the second group, channels mutations in the TMD of SUR1 are retained in the ER and have variable functional impairment.

Molecular genetics, correlation between genotype and phenotype of 65 Vietnames patients with congenital hyperinsulinism

Hyperinsulinemic hypoglycemia (HH) is a consequence of unregulated insulin secretion by pancreatic β-cells. Congenital HH is caused by mutations in genes involved in regulation of insulin secretion (ABCC8, KCNJ11, GLUD1, CGK, HADH, SLC16A1, HNF4A and UCP2). Severe forms of congenital HH are caused by inactivating mutations in ABCC8 and KCNJ11, which encode the two components of the pancreatic β-cell ATP-sensitive potassium channel. Our aim is to identify mutations in the ABCC8 and KCNJ11, HNF4A and GLUD genes, and to describe genotype and phenotype correlations of Vietnamese children with congenital hyperinsulinism. A prospective study was conducted on 65 cases with congenital hyperinsulinism diagnosed and treated at the National Hospital of Pediatric from January 2007 to April 2014. Patients were selected by using inclusion criteria of Hussain K (2008). Mutations were identified in 32 cases (49.2%) including mutations of ABCC8 gene (28 cases; 43.1%), KCNJ11 (3 cases; 4.6%), HNF4A (1 case; 1.5%). 100% of cases with homozygous/compound heterozygous recessive mutations or one paternal dominant mutation of ABCC8 gene did not respond to diazoxide treatment and required 95% pancreatectomy. Molecular analysis using pancreas tissue after surgery from cases with one mutation of ABCC8 gene inherited from father confirmed focal lesion type. Other cases without identified mutations usually responded to diazoxide. In conclusions, children with congenital hyperinsulinism should be performed mutation analysis which helps in making diagnosis and treatment decision. Families of children with congenital hyperinsulinism should be given genetic counseling. Prenatal diagnosis should be performed as well as follow - up and treatment should be given to children with congenital hyperinsulinism immediately after birth.

Persistent hyperinsulinaemic hypoglycaemia in infancy

Persistent hyperinsulinaemic hypoglycaemia in infancy (PHHI) is a heterogeneous condition characterised by unregulated insulin secretion in response to a low blood glucose level. It is the most common cause of severe and persistent hypoglycaemia in neonates. It is extremely important to recognise this condition early and institute appropriate management to prevent significant brain injury leading to complications like epilepsy, cerebral palsy and neurological impairment. Histologically, PHHI is divided mainly into three types—diffuse, focal and atypical disease. Fluorine-18-l-3,4-dihydroxyphenylalanine positron emission tomography (18F-DOPA-PET/CT) scan allows differentiation between diffuse and focal diseases. The diffuse form is inherited in an autosomal recessive (or dominant) manner whereas the focal form is sporadic in inheritance and is localised to a small region of the pancreas. The molecular basis of PHHI involves defects in key genes (ABCC8, KCNJ11, GCK, SLC16A1, HADH, UCP2, HNF4A and GLUD1) that regulate insulin secretion. Focal lesions are cured by lesionectomy whereas diffuse disease (unresponsive to medical therapy) will require a near-total pancreatectomy with a risk of developing diabetes mellitus and pancreatic exocrine insufficiency. Open surgery is the traditional approach to pancreatic resection. However, recent advances in laparoscopic surgery have led to laparoscopic near-total pancreatectomy for diffuse lesions and laparoscopic distal pancreatectomy for focal lesions distal to the head of the pancreas.

Congenital hyperinsulinism: Role of fluorine-18L-3, 4 hydroxyphenylalanine positron emission tomography scanning.

Congenital hyperinsulinism (CHI) is a rare but complex heterogeneous disorder caused by unregulated secretion of insulin from the β-cells of the pancreas leading to severe hypoglycaemia and neuroglycopaenia. Swift diagnosis and institution of appropriate management is crucial to prevent or minimise adverse neurodevelopmental outcome in children with CHI. Histologically there are two major subtypes of CHI, diffuse and focal disease and the management approach will significantly differ depending on the type of the lesion. Patients with medically unresponsive diffuse disease require a near total pancreatectomy, which then leads on to the development of iatrogenic diabetes mellitus and pancreatic exocrine insufficiency. However patients with focal disease only require a limited pancreatectomy to remove only the focal lesion thus providing complete cure to the patient. Hence the preoperative differentiation of the histological subtypes of CHI becomes paramount in the management of CHI. Fluorine-18L-3, 4-hydroxyphenylalanine positron emission tomography ((18)F-DOPA-PET) is now the gold standard for pre-operative differentiation of focal from diffuse disease and localisation of the focal lesion. The aim of this review article is to give a clinical overview of CHI, then review the role of dopamine in β-cell physiology and finally discuss the role of (18)F-DOPA-PET imaging in the management of CHI.

Activating AKT2 Mutation: Hypoinsulinemic Hypoketotic Hypoglycemia

Hyperinsulinemic hypoglycemia (HH), characterized by unregulated insulin secretion, is an important cause of persistent and severe hypoglycemia. The biochemical picture of HH is hypoketotic hypo-fatty-acidemic hypoglycemia along with elevated serum insulin. Not infrequently, serum insulin might be undetectable in HH despite the presence of evidence of insulin action (suppressed ketogenesis and lipolysis). However, autonomous activity of the downstream insulin signaling pathway without the presence of the ligand (insulin) will give rise to the same clinical and biochemical picture, apart from undetectable serum insulin/C-peptide. AKT2, a serine/threonine protein kinase, is involved downstream to the insulin receptor in mediating the physiological effects of insulin. We describe the second report of an activating AKT2 mutation leading to hypoinsulinemic hypoketotic hypoglycemia. The proband presented with hemihypertrophy and symptomatic hypoglycemia. Investigations confirmed evidence of insulin action, despite absence of detectable serum insulin on multiple occasions. Molecular genetic testing for common causes of HH (ABCC8, KCNJ11, and GLUD1) was negative. Sequencing of AKT2 identified a de novo mosaic c.49G→A (p.E17K) mutation, consistent with the clinical and biochemical phenotype. This is the second report of an activating AKT2 mutation leading to hypoinsulinemic hypoketotic hypo-fatty-acidemic hypoglycemia. In patients presenting a clinical and biochemical picture of HH with undetectable serum insulin, consideration of autonomous activation of the downstream insulin signaling pathway should be made.

Molecular genetics and phenotype of 26 Vietnamese patients with congenital hyperinsulinism

Hyperinsulinemic hypoglycemia (HH) is a consequence of unregulated insulin secretion by pancreatic β-cells and is a major cause of hypoglycemic brain injury and mental retardation. Congenital HH is caused by mutations in genes involved in regulation of insulin secretion, seven of which have been identified (ABCC8, KCNJ11, GLUD1, CGK, HADH, SLC16A1 and HNF4A). Severe forms of congenital HH are caused by mutations in ABCC8 and KCNJ11, which encode the two components of the pancreatic β-cell ATP-sensitive potassium channel (sulfonylurea receptor SUR1 and the inwardly rectifying ion channel KIR6.2). Activating mutations in the subunit genes of ATP-sensitive potassium channel can result in monogenic diabetes, whereas inactivating mutations are the most common cause of congenital hyperinsulinism of infancy. We aim to identify mutations of ABCC8; KCNJ11 and HNF4A in Vietnamese patients with congenital HH, to describe the phenotype, and to evaluate outcome of these patients. This is a case series study including phenotype, genotype characteristics and outcome. Twenty six Vietnamese probands with congenital HH were analyzed for alterations in ABCC8; KCNJ11 and HNF4A. All exons of KCNJ11; ABCC8 and HNF4A genes were amplified from genomic DNA and directly sequenced. In patients with detected mutations, the parental origin of each mutation was determined. 13/26 cases with no identified mutations of ABCC8; KCNJ11 and HNF4A were stable with medical treatment (diazoxide-responsive congenital HH). Eleven probands had mutations in the ABCC8 and no mutation in the KCNJ11 and HNF4A. Six patients were homozygous or compound heterozygous for the mutations, indicating diffuse pancreatic disease. Their blood glucose levels were normal after nearly total pancreatectomy by laparoscopy. In five patients, heterozygous and paternally inherited mutations were found, suggesting focal disease before surgery. Of which one case had diffuse lesions on histopathology examination and normal blood glucose level after pancreatectomy, one case had diabetes after two days of surgery and stop of insulin injection after 6 months of treatment and one case still needs octreotide treatment for normal blood glucose levels. Altogether, 9 different ABCC8 mutations including three novel alterations (p.F686I, p.I395F and p.G1379S) and six reported mutations (p.F686S, IVS27-1G>A, p.R999X, c.1467+5G>A, p.R934X and p.S1387del) were identified. One case of responsive with diazoxide had partenal inherited mutation in KCNJ11 [c.482C>T (p.A161V)] and one case of responsive with diazoxide had a novel mutation and maternal inheritance in HNF4A [c.659T>C (p.L220P)]. Our results extend the knowledge of the molecular genetics, phenotype and outcome behind congenital HH in Vietnam.

Novel mutation c.597_598dup in exon 5 of ABCC8 gene causing congenital hyperinsulinism

Congenital hyperinsulinism (CHI), a clinically and genetically heterogeneous disease, characterized by the unregulated secretion of insulin from pancreatic β-cells, is the most common cause of persistent hypoglycemia in infancy. Early diagnosis and maintenance of normoglycaemia are essential to prevent adverse neurodevelopmental outcomes. The most common and severe forms of CHI are caused by inactivating mutations in ABCC8 and KCNJ11 genes, encoding the two subunits of the pancreatic β-cell ATP sensitive potassium channel (KATP). We report a case of neonatal CHI due to a novel homozygous recessive mutation in the ABCC8 gene.

The molecular mechanisms, diagnosis and management of congenital hyperinsulinism

Congenital hyperinsulinism (CHI) is the result of unregulated insulin secretion from the pancreatic β-cells leading to severe hypoglycaemia. In these patients it is important to make an accurate diagnosis and initiate the appropriate management so as to avoid hypoglycemic episodes and prevent the potentially associated complications like epilepsy, neurological impairment and cerebral palsy. At a genetic level abnormalities in eight different genes (ABCC8, KCNJ11, GLUD1, GCK, HADH, SLC16A1, HNF4A and UCP2) have been reported with CHI. Loss of function mutations in ABCC8/KCNJ11 lead to the most severe forms of CHI which are usually medically unresponsive. At a histological level there are two major subgroups, diffuse and focal, each with a different genetic etiology. The focal form is sporadic in inheritance and is localized to a small region of the pancreas whereas the diffuse form is inherited in an autosomal recessive (or dominant) manner. Imaging using a specialized positron emission tomography scan with the isotope fluroine-18 L-3, 4-dihydroxyphenyalanine (18F-DOPA-PET-CT) is used to accurately locate the focal lesion pre-operatively and if removed can cure the patient from hypoglycemia. Understanding the molecular mechanisms, the histological basis, improvements in imaging modalities and surgical techniques have all improved the management of patients with CHI.

Co-inheritance of two ABCC8 mutations causing an unresponsive congenital hyperinsulinism: Clinical and functional characterization of two novel ABCC8 mutations

Congenital hyperinsulinism (CHI) occurs as a consequence of unregulated insulin secretion from the pancreatic beta-cells. Severe recessive mutations and milder dominant mutations have been described in the ABCC8 and KCNJ11 genes encoding SUR1 and Kir6.2 subunits of the beta-cell ATP-sensitive K(+) channel. Here we report two patients with CHI unresponsive to medical therapy with diazoxide. Sequencing analysis identified a compound heterozygous mutation in ABCC8 in both patients. The first one is a carrier for the known mild dominant mutation p.Glu1506Lys jointly with the novel mutation p.Glu1323Lys. The second carries the p.Glu1323Lys mutation and a second novel mutation, p.Met1394Arg. Functional studies of both novel alleles showed reduced or null cell surface expression, typical of recessive mutations. Compound heterozygous mutations in congenital hyperinsulinism result in complex interactions. Studying these mechanisms can improve the knowledge of this disease and modify its therapy.

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.Conflict of interest:None declared.