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Unravelling the genetic causes of mosaic islet morphology in congenital hyperinsulinism

Congenital hyperinsulinism (CHI) causes dysregulated insulin secretion which can lead to life-threatening hypoglycaemia if not effectively managed. CHI can be sub-classified into three distinct groups: diffuse, focal and mosaic pancreatic disease. Whilst the underlying causes of diffuse and focal disease have been widely characterised, the genetic basis of mosaic pancreatic disease is not known. To gain new insights into the underlying disease processes of mosaic-CHI we studied the islet tissue histopathology derived from limited surgical resection from the tail of the pancreas in a patient with CHI. The underlying genetic aetiology was investigated using a combination of high depth next-generation sequencing, microsatellite analysis and p57kip2 immunostaining. Histopathology of the pancreatic tissue confirmed the presence of a defined area associated with marked islet hypertrophy and a cytoarchitecture distinct from focal CHI but compatible with mosaic CHI localised to a discrete region within the pancreas. Analysis of DNA extracted from the lesion identified a de novo mosaic ABCC8 mutation and mosaic paternal uniparental disomy which were not present in leukocyte DNA or the surrounding unaffected pancreatic tissue. This study provides the first description of two independent disease-causing somatic genetic events occurring within the pancreas of an individual with localised mosaic CHI. Our findings increase knowledge of the genetic causes of islet disease and provide further insights into the underlying developmental changes associated with β-cell expansion in CHI

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

This is the final version. Available from PLOS via the DOI in this record. 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.Wellcome Trus

Case report: maternal mosaicism resulting in inheritance of a novel GATA6 mutation causing pancreatic agenesis and neonatal diabetes mellitus.

Haploinsufficiency of the GATA6 transcription factor gene was recently found to be the most common cause of pancreatic agenesis, a rare cause of neonatal diabetes mellitus. Although most cases are de novo, we describe three siblings with inherited GATA6 haploinsufficiency and the rare finding of parental mosaicism.This article is freely available via Open Access. Click on the Additional Link above to access the full-text via the publisher's site

Treatment of hypoglycemia due to a rare pathogenic variant in AKT2 with waxy maize heat‐modified starch

Key Clinical Message The gain‐of‐function AKT2 c.49G>A variant causes hypoketotic hypoglycemia with variable associated features. Due to lack of effective medications, treatment is primarily supportive. This report suggests waxy maize heat is a viable treatment option. Abstract The serine–threonine kinase AKT2 is a critical mediator of insulin's anabolic effects, particularly cellular glucose uptake. The gain‐of‐function c.49G>A, p.(Glu17Lys) AKT2 variant results in hypoketotic hypoglycemia with suppressed insulin and free fatty acid levels due to constitutive activation of the insulin signaling cascade. Although biochemical similarities exist among the eight individuals identified to date, the associated phenotype varies considerably. Treatment of these patients remains challenging, consisting primarily of frequent feeds with uncooked cornstarch. We describe a female with hemihypertrophy, developmental delay, and dysmorphic features who presented to our center with hypoglycemic seizures at age 6 months. Critical sample revealed hypoketotic hypoglycemia, undetectable insulin, and suppressed free fatty acids. Molecular testing confirmed a pathogenic c.49G>A, p.(Glu17Lys) AKT2 mutation. Glycemic control was initially difficult to establish, with recurrent hypoglycemia despite high glucose infusion rates. Following in‐hospital administration of waxy maize heat‐modified starch at age 4‐years, she remained euglycemic overnight, despite a previous report showing no benefit compared to uncooked cornstarch in an infant with the same mutation. Our report suggests waxy maize heat‐modified starch is a viable treatment option for patients with activating c.49G>A AKT2 mutations and provides further evidence of a broad phenotypic spectrum

Decreased K_ATPChannel Activity Contributes to the Low Glucose Threshold for Insulin Secretion of Rat Neonatal Islets

Transitional hypoglycemia in normal newborns occurs in the first 3 days of life and has clinical features consistent with hyperinsulinism. We found a lower threshold for glucose-stimulated insulin secretion from freshly isolated embryonic day (E) 22 rat islets, which persisted into the first postnatal days. The threshold reached the adult level by postnatal day (P) 14. Culturing P14 islets also decreased the glucose threshold. Freshly isolated P1 rat islets had a lower threshold for insulin secretion in response to 2-aminobicyclo-(2, 2, 1)-heptane-2-carboxylic acid, a nonmetabolizable leucine analog, and diminished insulin release in response to tolbutamide, an inhibitor of β-cell K(ATP) channels. These findings suggested that decreased K(ATP) channel function could be responsible for the lower glucose threshold for insulin secretion. Single-cell transcriptomic analysis did not reveal a lower expression of K(ATP) subunit genes in E22 compared with P14 β cells. The investigation of electrophysiological characteristics of dispersed β cells showed that early neonatal and cultured cells had fewer functional K(ATP) channels per unit membrane area. Our findings suggest that decreased surface density of K(ATP) channels may contribute to the observed differences in glucose threshold for insulin release

Diazoxide‐induced pulmonary hypertension in hyperinsulinaemic hypoglycaemia: Recommendations from a multicentre study in the United Kingdom

Objective: Diazoxide is first-line treatment for hyperinsulinaemic hypoglycaemia (HH) but diazoxide-induced pulmonary hypertension (PH) can occur. We aim to characterize the incidence and risk factors of diazoxide-induced PH in a large HH cohort to provide recommendations for anticipating and preventing PH in diazoxide-treated patients with HH. Design and Patients: Retrospective cohort study involving four UK regional HH centres; review of case notes of HH patients on diazoxide. Measurements: The diagnosis of PH was based on clinical and echocardiography evidence. Patient and treatment-related risk factors were analysed for association. Results: Thirteen (6 men) of 177 HH diazoxide-treated patients developed PH, an incidence of 7%. In the PH group, HH was diagnosed at median (range) of 9 (1,180) days, with diazoxide commenced 4 (0,76) days from diagnosis and reaching a maximum dose of 7 (2.5,20) mg/kg/d. The majority (8 of 13 patients) developed PH within 2 weeks of diazoxide. Complete diazoxide withdrawal, but not dose reduction, led to PH resolution at 41 (3,959) days. In three patients, PH continued beyond 12 months. Risk factors for the development of PH included the presence of congenital heart disease (CHD) (P = .008), and total fluid volume exceeding 130 mL/kg/d in the immediate 24 hours preceding diazoxide (P = .019). Conclusion: Pulmonary hypertension can occur in 7% of diazoxide-treated HH patients. Risk factors include the presence of congenital heart disease and fluid overload. Recommendations include echocardiography and fluid restriction to 130 mL/kg/d prior to diazoxide treatment and immediate discontinuation of diazoxide if PH develops