2003 Fiscal Year Final Research Report Summary
Investigation of the roles of WFS1 and glutamate dehydorogenase on the pancreatic β-cell function and regulation of insulin secretion
| Project/Area Number |
14370338
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Metabolomics
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| Research Institution | Yamaguchi University |
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Principal Investigator |
TANIZAWA Yukio Yamaguchi University, Graduate School of Medicine, Department of Bio-Signal Analysis, Division of Molecular Analysis of Human. Disorders, Professor, 大学院・医学研究科, 教授 (00217142)
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| Co-Investigator(Kenkyū-buntansha) |
UEDA Kohei Yamaguchi University, Health Service Center, Research Associate, 保健管理センター, 助手 (50325221)
YUJIRI Toshiaki Yamaguchi University, Hospital, Assistant Professor, 医学部附属病院, 講師 (80346551)
MATSUBARA Atsushi Yamaguchi University, Hospital, Research Associate, 医学部附属病院, 助手 (40311815)
OHTA Yasuharu Yamaguchi University, Hospital, Clinical Fellow, 医学部附属病院, 医員(臨床)
TANABE Katsuya Yamaguchi University, Hospital, Clinical Fellow, 医学部附属病院, 医員(臨床)
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| Project Period (FY) |
2002 – 2003
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| Keywords | diabetes mellitus / insulin secretion / Wolfram syndrome / endoplasmic reticulum stress / glutamate dehydrogenase / hypoglycemia |
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| Research Abstract |
The WFSI gene encodes ar. endoplasmic reticulum (ER) membrane-resided protein, Homozygous loss of function mutations of the WFSI gene cause wolfram syndrome, characterized by insulin-defficient diabetes mellitus and optic atrophy. In the patient's islets, β-cells are selectively lost, In the current study, we demonstrated that β-cells were the major site of the WFSI expression. The WFSI expression was transcriptionally up-regulated by chemical insults inducing ER stress. Treatment of fibroblasts and MIN6 cells with reagents such as thapsigargin or tunicamycin increased WFSI mRNA and protein levels. The WFSI expression was also increased in the Akita mouse-derived insulin-2^<96Y/Y> insulinoma cells. In these cells, ER stress was intrinsically induced by the misfolded mutant insulin expression. The WFSI gene promoter-luciferase reporter system revealed that the human WFSI promoter was activated by chemically-induced ER stress in MIN6 cells, and the promoter was more active in the insulin
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-2^<96Y/Y> insulinoma cells than in insulin-2^<wild/wild> cells. Collectively, our data demonstrated that WFSI expression is associated with ER stress, and suggested functional link between WFSI and the ER stress responses. Loss of function mutations of WFSI gene may cause β-cell loss due to ER stress-induced apoptosis
Glutamate dehydrogenase (GDH) catalyzes reversible oxidative deamination of L-glutamate to α-ketoglutarate. Enzyme activity is regulated by several allosteric effectors. Gain-of function mutations of the GDH gene cause hyperinsulinism/hyper-ammonemia (HI/HA) syndrome. GDH266C is a constitutively activated mutant enzyme. By overexpressing GDH266C in MINE mouse insulinoma cells, we demonstrated unregulated elevation of GDH activity to render the cells responsive to glutamine in insulin secretion. Interestingly, at low glucose concentrations, basal insulin secretion was exaggerated in such cells. To clarify the role of GDH in the regulation of insulin secretion, we studied cellular glutamate metabolism using MIN6 cells overexpressing GDH266C (MIN6-GDH266C). Glutaminestimulated insulin secretion was associated with increased glutamine oxidation and decreased intracellular glutamate content. Similarly, at 5 mmol/l glucose without glutamine, glutamine oxidation also increased, and glutamate content decreased with exaggerated insulin secretion. Glucose oxidation was not altered. Insulin secretion profiles from GDH266C-overexpressing isolated rat pancreatic islets were similar to those from MIN6-GDH266C.These results demonstrate that upon activation, GDH oxidizes glutamate to α-ketoglutarate thereby stimulating insulin secretion by providing the TCA cycle with a substrate Less
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[Publications] Tanizawa Y, Nakai K, Sasaki T, Anno T, Ohta Y, Inoue H, Matsuo K, Koga M, Furukawa S, Oka Y.: "Unregulated elevation of glutamate dehydrogenase activity induces glutamine-stimulated insulin secretion : Identification and characterization of a GLUD 1 gene mutation, and insulin secretion studies with MIN6 cells overexpressing the mutant GDH"Diabetes. 51. 712-717 (2002)
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「研究成果報告書概要(欧文)」より
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[Publications] Ishihara H, Takeda S, Tamura A, Takahashi R, Yamaguchi S, Takei D, Yamada T, moue H, Soga H, Katagiri H, Tanizawa Y, Oka Y.: "Disruption of the WFS 1 gene in mice causes progressive β-cell loss and impaired stimulus-secretion coupling in insulin secretion"Hum Mol Genet.. 13. 1159-1170 (2004)
Description
「研究成果報告書概要(欧文)」より
