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Effects of a GTP-insensitive mutation of glutamate dehydrogenase on insulin secretion in transgenic mice.
- Source :
-
The Journal of biological chemistry [J Biol Chem] 2006 Jun 02; Vol. 281 (22), pp. 15064-72. Date of Electronic Publication: 2006 Mar 30. - Publication Year :
- 2006
-
Abstract
- Glutamate dehydrogenase (GDH) plays an important role in insulin secretion as evidenced in children by gain of function mutations of this enzyme that cause a hyperinsulinism-hyperammonemia syndrome (GDH-HI) and sensitize beta-cells to leucine stimulation. GDH transgenic mice were generated to express the human GDH-HI H454Y mutation and human wild-type GDH in islets driven by the rat insulin promoter. H454Y transgene expression was confirmed by increased GDH enzyme activity in islets and decreased sensitivity to GTP inhibition. The H454Y GDH transgenic mice had hypoglycemia with normal growth rates. H454Y GDH transgenic islets were more sensitive to leucine- and glutamine-stimulated insulin secretion but had decreased response to glucose stimulation. The fluxes via GDH and glutaminase were measured by tracing 15N flux from [2-15N]glutamine. The H454Y transgene in islets had higher insulin secretion in response to glutamine alone and had 2-fold greater GDH flux. High glucose inhibited both glutaminase and GDH flux, and leucine could not override this inhibition. 15NH4Cl tracing studies showed 15N was not incorporated into glutamate in either H454Y transgenic or normal islets. In conclusion, we generated a GDH-HI disease mouse model that has a hypoglycemia phenotype and confirmed that the mutation of H454Y is disease causing. Stimulation of insulin release by the H454Y GDH mutation or by leucine activation is associated with increased oxidative deamination of glutamate via GDH. This study suggests that GDH functions predominantly in the direction of glutamate oxidation rather than glutamate synthesis in mouse islets and that this flux is tightly controlled by glucose.
- Subjects :
- Adenosine Diphosphate metabolism
Adenosine Triphosphate metabolism
Animals
Calcium Signaling drug effects
Glucose pharmacology
Glutamate Dehydrogenase antagonists & inhibitors
Glutamate Dehydrogenase metabolism
Glutamine pharmacology
Guanosine Triphosphate pharmacology
Humans
Hyperinsulinism enzymology
Hyperinsulinism genetics
Hyperinsulinism physiopathology
In Vitro Techniques
Insulin Secretion
Islets of Langerhans drug effects
Islets of Langerhans enzymology
Islets of Langerhans metabolism
Kinetics
Leucine pharmacology
Mice
Mice, Inbred C57BL
Mice, Transgenic
Models, Biological
Recombinant Proteins antagonists & inhibitors
Recombinant Proteins genetics
Recombinant Proteins metabolism
Glutamate Dehydrogenase genetics
Insulin metabolism
Mutation
Subjects
Details
- Language :
- English
- ISSN :
- 0021-9258
- Volume :
- 281
- Issue :
- 22
- Database :
- MEDLINE
- Journal :
- The Journal of biological chemistry
- Publication Type :
- Academic Journal
- Accession number :
- 16574664
- Full Text :
- https://doi.org/10.1074/jbc.M600994200