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Congenital hyperinsulinism caused by hexokinase I expression or glucokinase-activating mutation in a subset of ?-cells.

ABSTRACT: Congenital hyperinsulinism causes persistent hypoglycemia in neonates and infants. Most often, uncontrolled insulin secretion (IS) results from a lack of functional K(ATP) channels in all ?-cells or only in ?-cells within a resectable focal lesion. In more rare cases, without K(ATP) channel mutations, hyperfunctional islets are confined within few lobules, whereas hypofunctional islets are present throughout the pancreas. They also can be cured by selective partial pancreatectomy; however, unlike those with a K(ATP) focal lesion, they show clinical sensitivity to diazoxide. Here, we characterized in vitro IS by fragments of pathological and adjacent normal pancreas from six such cases. Responses of normal pancreas were unremarkable. In pathological region, IS was elevated at 1 mmol/L and was further increased by 15 mmol/L glucose. Diazoxide suppressed IS and tolbutamide antagonized the inhibition. The most conspicuous anomaly was a large stimulation of IS by 1 mmol/L glucose. In five of six cases, immunohistochemistry revealed undue presence of low-K(m) hexokinase-I in ?-cells of hyperfunctional islets only. In one case, an activating mutation of glucokinase (I211F) was found in pathological islets only. Both abnormalities, attributed to somatic genetic events, may account for inappropriate IS at low glucose levels by a subset of ?-cells. They represent a novel cause of focal congenital hyperinsulinism.

SUBMITTER: Henquin JC

PROVIDER: S-EPMC3636634 | biostudies-literature | 2013 May

REPOSITORIES: biostudies-literature

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Congenital hyperinsulinism caused by hexokinase I expression or glucokinase-activating mutation in a subset of β-cells.

Henquin Jean-Claude JC Sempoux Christine C Marchandise Joelle J Godecharles Sebastien S Guiot Yves Y Nenquin Myriam M Rahier Jacques J

Diabetes 20121228 5

Congenital hyperinsulinism causes persistent hypoglycemia in neonates and infants. Most often, uncontrolled insulin secretion (IS) results from a lack of functional K(ATP) channels in all β-cells or only in β-cells within a resectable focal lesion. In more rare cases, without K(ATP) channel mutations, hyperfunctional islets are confined within few lobules, whereas hypofunctional islets are present throughout the pancreas. They also can be cured by selective partial pancreatectomy; however, unlik ...[more]

PMID: 23274908

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Project description:The importance of glucokinase (GK) in the regulation of insulin secretion has been highlighted by the phenotypes of individuals with activating and inactivating mutations in the glucokinase gene (GCK). Here we report 10 individuals with congenital hyperinsulinism (HI) caused by eight unique activating mutations of GCK. Six are novel and located near previously identified activating mutations sites. The first recognized episode of hypoglycemia in these patients occurred between birth and 24 years, and the severity of the phenotype was also variable. Mutant enzymes were expressed and purified for enzyme kinetics in vitro. Mutant enzymes had low glucose half-saturation concentration values and an increased enzyme activity index compared with wild-type GK. We performed functional evaluation of islets from the pancreata of three children with GCK-HI who required pancreatectomy. Basal insulin secretion in perifused GCK-HI islets was normal, and the response to glyburide was preserved. However, the threshold for glucose-stimulated insulin secretion in perifused glucokinase hyperinsulinism (GCK-HI) islets was decreased, and glucagon secretion was greatly suppressed. Our evaluation of novel GCK disease-associated mutations revealed that the detrimental effects of these mutations on glucose homeostasis can be attributed not only to a lowering of the glucose threshold of insulin secretion but also to a decreased counterregulatory glucagon secretory response.Article highlightsOur evaluation of six novel and two previously published activating GCK mutations revealed that the detrimental effects of these mutations on glucose homeostasis can be attributed not only to a lowering of the glucose threshold of insulin secretion but also to a decreased counterregulatory glucagon secretory response. These studies provide insights into the pathophysiology of GCK-hyperinsulinism and the dual role of glucokinase in β-cells and α-cells to regulate glucose homeostasis.

Project description:INTRODUCTION:Congenital hyperinsulinism is a rare inherited disease caused by mutations in genes responsible for ?-cell's function in glucose hemostasis leading to profound and recurrent hypoglycemia. The incidence of the disease is about 1 in 50000 newborns. Mutations in at least 8 genes have been reported to cause congenital hyperinsulinism. Mutations in ABCC8 gene are the most common cause of the disease that account for approximately 40% of cases. Less frequently KCNJ11 gene mutations are responsible for the disease. Mutations in other genes such as HADH account for smaller fractions of cases. In nearly half of the cases the cause remains unknown. CASE PRESENTATION:During the period between 2005 and 2010, a total of six patients with persistent hyperinsulinism were investigated at Mofid Children's Hospital. In this study all of the patients had early onset hyperinsulinemia. Five patients had consanguineous parents. After failure of medical treatment in three patients, They were undergone pancreatectomy. Two diffuse types and one focal type had been recognized in pathological analysis of intra-operative frozen specimens of pancreas in these patients. Genetic analysis was performed using polymerase chain reaction followed by Sanger sequencing for ABCC8, KCNJ11and HADH genes. In five patients homozygous mutations in these genes were identified that indicated an autosomal recessive pattern of inheritance. In one patient a heterozygous mutation in ABCC8 was identified, indicating possible autosomal dominant inheritance of the disease. CONCLUSIONS:Congenital hyperinsulinism can have different inheritance pattern. Autosomal recessive inheritance is more common but less frequently autosomal dominant inheritance can be seen. It appears that mutations in ABCC8 gene can show both autosomal recessive and autosomal dominant inheritance of the disease. PCR followed by Sanger sequencing proved to be an efficient method for mutation detection in three investigated genes. Despite early diagnosis, psychomotor retardation was seen in two patients.

Dataset Information

Congenital hyperinsulinism caused by hexokinase I expression or glucokinase-activating mutation in a subset of ?-cells.

Publications

Congenital hyperinsulinism caused by hexokinase I expression or glucokinase-activating mutation in a subset of β-cells.

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