Congenital hyperinsulinism is a group of genetic disorders that cause hypoglycemia in infants and children. "The hypoglycemia is quite dangerous and can cause seizures and permanent brain damage if not promptly detected and treated," says Charles A. Stanley, of the Children's Hospital of Philadelphia. "In its various forms, congenital hyperinsulinism is the most common and most difficult cause of hypoglycemia in young infants."
The majority of cases of congenital hyperinsulinism appear to be due to defects in insulin secretion by pancreatic cells. Currently, it is thought that mutations in any of four different genes can cause the disorder. One of these genes codes for an enzyme called glutamate dehydrogenase. This enzyme is stimulated by the amino acid leucine, meaning that protein meals that contain leucine lead to activation of glutamate dehydrogenase, which in turn triggers the release of insulin from pancreatic cells.
"The glutamate dehydrogenase mutations that cause hyperinsulinism are amino acid mis-sense mutations that impair the sensitivity of the enzyme to inhibition," explains Stanley. "As a result, glutamate dehydrogenase enzyme activity cannot be turned off and this leads to excessive release of insulin and hypoglycemia."
In order to understand how amino acids stimulate insulin and the role of glutamate dehydrogenase in this pathway, Stanley and his colleagues at the University of Pennsylvania generated transgenic mice that had a mutation in their gene for glutamate dehydrogenase. The resulting mice had hypoglycemia, confirming that the mutation can cause disease.
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Contact: Nicole Kresge
nkresge@asbmb.org
301-634-7415
American Society for Biochemistry and Molecular Biology
24-May-2006