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Kibbey, R.G.* ; Choi, C.S.* ; Lee, H.Y.* ; Cabrera, O.* ; Pongratz, R.L.* ; Zhao, X.* ; Birkenfeld, A.L.* ; Li, C.* ; Berggren, P.O.* ; Stanley, C.* ; Shulman, G.I.*

Mitochondrial GTP insensitivity contributes to hypoglycemia in hyperinsulinemia hyperammonemia by inhibiting glucagon release.

Diabetes 63, 4218-4229 (2014)
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Open Access Green as soon as Postprint is submitted to ZB.
Mitochondrial GTP (mtGTP)-insensitive mutations in glutamate dehydrogenase (GDH(H454Y)) result in fasting and amino acid-induced hypoglycemia in hyperinsulinemia hyperammonemia (HI/HA). Surprisingly, hypoglycemia may occur in this disorder despite appropriately suppressed insulin. To better understand the islet-specific contribution, transgenic mice expressing the human activating mutation in β-cells (H454Y mice) were characterized in vivo. As in the humans with HI/HA, H454Y mice had fasting hypoglycemia, but plasma insulin concentrations were similar to the controls. Paradoxically, both glucose- and glutamine-stimulated insulin secretion were severely impaired in H454Y mice. Instead, lack of a glucagon response during hypoglycemic clamps identified impaired counterregulation. Moreover, both insulin and glucagon secretion were impaired in perifused islets. Acute pharmacologic inhibition of GDH restored both insulin and glucagon secretion and normalized glucose tolerance in vivo. These studies support the presence of an mtGTP-dependent signal generated via β-cell GDH that inhibits α-cells. As such, in children with activating GDH mutations of HI/HA, this insulin-independent glucagon suppression may contribute importantly to symptomatic hypoglycemia. The identification of a human mutation causing congenital hypoglucagonemic hypoglycemia highlights a central role of the mtGTP-GDH-glucagon axis in glucose homeostasis.
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Publication type Article: Journal article
Document type Scientific Article
ISSN (print) / ISBN 0012-1797
e-ISSN 1939-327X
Journal Diabetes
Quellenangaben Volume: 63, Issue: 12, Pages: 4218-4229 Article Number: , Supplement: ,
Publisher American Diabetes Association
Publishing Place Alexandria, VA.
Reviewing status Peer reviewed
Institute(s) Institute for Pancreatic Beta Cell Research (IPI)