title: Hyperinsulinemic hypoglycemia syndrome associated with mutations in the human insulin receptor gene: report of two cases.
abstract: Insulinoma and insulin or insulin receptor (IR) autoantibodies are the main causes of hyperinsulinemic hypoglycemia in adults, but the exact cause in other cases remains obscure. This study is to determine the genetic basis of hyperinsulinemic hypoglycemia in two cases without the above abnormalities. Sequence analysis of IR gene in two patients with adult-onset hyperinsulinemic hypoglycemia and their relatives were performed, and the mutant gene observed in one case was analyzed. Both cases had normal levels of fasting plasma glucose (FPG), fasting hyperinsulinemia, low insulin sensitivity, and hypoglycemia with excessive insulin secretion during oral glucose tolerance test (OGTT). Both reported adult-onset postprandial hypoglycemic symptoms. In one patient, a missense mutation (Arg256Cys) was detected in both alleles of the IR gene, and his parents had the same mutation in only one allele but no hypoglycemia. The other had a novel nonsense mutation (Trp1273X) followed by a mutation (Gln1274Lys) in one allele, and his 9-year old son had the same mutation in one allele, together with hyperinsulinemic hypoglycemia during OGTT. Overexpression experiments of the mutant gene found in Case 1 in mammalian cells showed abnormal processing of the IR protein and demonstrated reduced function of Akt/Erk phosphorylation by insulin in the cells. In two cases of hyperinsulinemic hypoglycemia in adults, we found novel mutations in IR gene considered to be linked to hypoglycemia. We propose a disease entity of adult-onset hyperinsulinemic hypoglycemia syndrome associated with mutations in IR gene.
authors.affiliation: Department of Metabolic Medicine, Graduate School of Medicine, Osaka University, Suita, Osaka, Japan.
authors.forename: Yohei
authors.initials: Y
authors.lastname: Kuroda
authors.forename: Hiromi
authors.initials: H
authors.lastname: Iwahashi
authors.forename: Ikuo
authors.initials: I
authors.lastname: Mineo
authors.forename: Kenji
authors.initials: K
authors.lastname: Fukui
authors.forename: Atsunori
authors.initials: A
authors.lastname: Fukuhara
authors.forename: Ryuya
authors.initials: R
authors.lastname: Iwamoto
authors.forename: Akihisa
authors.initials: A
authors.lastname: Imagawa
authors.forename: Iichiro
authors.initials: I
authors.lastname: Shimomura
mesh_terms: D000328:Adult; D017668:Age of Onset; D000595:Amino Acid Sequence; D001483:Base Sequence; D002648:Child; D005260:Female; D057809:HEK293 Cells; D006801:Humans; D006946:Hyperinsulinism / Q000150:complications / Q000235:genetics*; D007003:Hypoglycemia / Q000150:complications / Q000235:genetics*; D008297:Male; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D009679:Nuclear Family; D011972:Receptor, Insulin / Q000235:genetics*; D013577:Syndrome
chemical_list: D011972:Receptor, Insulin