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Molecular mechanisms of glucose toxicity and lipotoxicity in insulin-secreting cells

Research Project

Project/Area Number 10671069
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeSingle-year Grants
Section一般
Research Field Metabolomics
Research InstitutionOsaka University

Principal Investigator

NAMBA Mitsuyoshi  Osaka University Graduate School of Medicine, Lecturer, 医学系研究科, 講師 (00183533)

Co-Investigator(Kenkyū-buntansha) YAMASAKI Tomoyuki  Osaka University Medical School, Assistant Proffessor, 医学部, 助手 (00303975)
KITOJIMA Koichi  Osaka University Graduate School of Medicine, Assistant Proffessor, 医学系研究科, 助手 (00314310)
NAKAJIMA Hiromu  Osaka University Graduate School of Medicine, Assistant Proffessor, 医学系研究科, 助手 (50252680)
Project Period (FY) 1998 – 1999
Project Status Completed (Fiscal Year 1999)
Budget Amount *help
¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1999: ¥1,000,000 (Direct Cost: ¥1,000,000)
Keywordsglucose toxicity / insulin secretion / GFAT / MIN6 / free fatty acids / lipotoxicity
Research Abstract

Glucose-6-phosphatase (G-6-Pasc) hydrolyzes glucose-6-phosphate to glucose, reciprocal to the so-called glucose sensor, glucokinase, in pancreatic beta cells. To study the role of G-6-Pase in glucose-stimulated insulin secretion from beta cells, we have introduced the rat G-6-Pase catalytic subunit cDNA and have established permanent clones with 3-, 7-, and 24-fold G-6-Pase activity of mouse beta cell line MIN6. In these clones, glucose usage and ATP production in the presence of 5.5 or 25 mM glucose were reduced, and glucose-stimulated insulin secretion was decreased proportionally to the increased G-6-Pase activity. In addition, insulin secretory capacity in response to D-fructose and pyruvate was unchanged, however, 25 mM glucose-stimulated insulin secretion and intracellular calcium response were completely inhibited. In the clone with 24-fold G-6-Pasc activity, changes in intracellular NAD(P)H autofluorescence in response to 25 mM glucose were reduced, but the changes with 20 mM f … More ructose and 20 mM pyruvatc were not altered. Stable overexpression of G-6-Pasc in beta cells resulted in the attenuation of the overall glucose-stimulated metabolic responses corresponding to the degree of overexpression. This particular experimental manipulation shows that the possibility exists of modulating glucose stimulated insulin release by thoroughly altering the glucose cycling at the GK/G-6-Pase step.
Moreover, to analyze the molecular mechanisms of lipotoxicity, we here studied the impact of FFA on glucose and lipid metabolism in pancreatic beta cells with special reference to insulin secretion. Pancreatic beta cell line MIN6 was exposed to various concentrations of palmitate for 3 days. Glucose-stimulated insulin secretion and insulin content were decreased corresponding to the concentration of the palmitate exposed. Glycolytic flux and ATP synthesis was unchanged, but pyruvate flux into mitochondria was decreased. Pyruvate carboxylase was decreased at the protein level, which was restored by the removal of palmitate or the inhibition of beta oxidation.
Intracellular content of triglyceride and FFA were elevated, beta oxidation was increased, and de novo lipogenesis from glucose was decreased. Though NADPH content was decreased, malic enzyme activity was unaffected. The malic enzyme inhibitor alone inhibited insulin response to glucose. From these results, we conclude that the decreased pyruvate flux into mitochondria would play a critical role in the inhibition of glucose stimulated insulin secretion by long term exposure of FFA. Less

Report

(3 results)
  • 1999 Annual Research Report   Final Research Report Summary
  • 1998 Annual Research Report
  • Research Products

    (21 results)

All Other

All Publications (21 results)

  • [Publications] Iizuka, K., et al.: "Stable overexpression of the G6Pase catalytic subunit attenuates glucose sensitivity of lnsulin secretion from a mouse pancreatic data cell line"J. Endocrinol. (印刷中). (2000)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1999 Final Research Report Summary
  • [Publications] Yang, Q., et al.: "Structure/function studies of hepatocyte nuclear factor-1α, a diabes-associated transcription factor"Biochem. Biophys. Res. Commun.. 266・1. 196-202 (1999)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1999 Final Research Report Summary
  • [Publications] Yoshiuchi, I., et al.: "Three new mutations in the hepatocyte nuclear factor-1α gene in Japanese subjects with diabetes mellitus : Clinical features and functional characterization"Diabetologia. 42・5. 621-626 (1999)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1999 Final Research Report Summary
  • [Publications] Okita, K., et al.: "Human insulin gene is a target of hepatocyte nuclear factor-1α(HUF-1α) and HNF-1β"Biochem. Biophys. Res. Commun.. 263・2. 566-569 (1999)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1999 Final Research Report Summary
  • [Publications] Miyagawa, J., et al.: "Immunohistochemical localization of betacellalin, a new member of EGF family, in normal human pancreas and islet tumor cells"Endocrine J.. 46・6. 755-764 (1999)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1999 Final Research Report Summary
  • [Publications] K. Iizuka, H. Nakajima, A. Ono, K. Okita, J. Miyazaki, J. Miyagawa, M. Namba, T. Hanafusa and Y. Matsuzawa: "Stable overexpression of the glucose-6-phosphatase catalytic subunit attenuates glucose sensitivity of insulin secretion from a mouse pancreatic beta cell line."J. Endocrinol.. (in press).

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1999 Final Research Report Summary
  • [Publications] I. Yoshiuchi, K. Yamagata, Q. Yang, H. Iwahashi, K. Okita, K. Yamamoto, T. Oue, A. Imagawa, T. Hamaguchi, T. Yamasaki, Y. Horikawa, T. Satoh, H. Nakajima, J. Miyazaki, S. Higashiyama, J. Miyagawa, M. Namba, T. Hanafusa, Y. Matsuzawa: "Three new mutations in the hepatocyte nuclear factor-la gene in Japanese subjects with diabetes mellitus : Clinical features and functional characterization."Diabetologia. 42(5). 621-626 (1999)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1999 Final Research Report Summary
  • [Publications] Q. Yang, K. Yamagata, K. Yamamoto, J. Miyagawa, J. Takeda, N. Iwasaki, H. Iwahashi, I. Yoshiuchi, M. Namba, J. Miyazaki, T. Hanafusa, Y. Matsuzawa: "Structure/function studies of hepatocyte nuclear factor-1α, a diatetes-associated transcription factor."Biochem. Biophys. Res. Commun. 266(1). 196-202 (1999)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1999 Final Research Report Summary
  • [Publications] J. Miyagawa, T. Hanafusa, R. Sasada, K. Yamamoto, K. Igarashi, K. Yamamori, M. Seno, H. Tada, M. Li, T. Nammo, K. Yamamgata, H. Nakajima, M. Namba, M. Kuwajima, Y. Matsuzawa: "Immunohistochemical localization of Betacellulin, a new member of EGF family, in normal human pancreas and islet tumor cells."Endocrine J.. 46(6). 755-764 (1999)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1999 Final Research Report Summary
  • [Publications] K. Okita, Q. Yang, K. Yamagata, K. A. Hangenfeldt, J. Miyagawa, Y. Kajimoto, H. Nakajima, M. Namba, C. B. Wollheim, T. Hanafusa, Y. Matsuzawa: "Human insulin gene is a target gene of hepatocyte nuclear factor-1α (HNF-1α) and HNF-1β."Biochem. Biophys. Res. Commun.. 263(2). 566-569 (1999)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1999 Final Research Report Summary
  • [Publications] Iizuka K.et al.: "Stable over expression of the G6Pase catalytic subunit attenuates glucose sensibility of insulin secretion from a mouse pancreatic data cell line"J. Endocrinol.. 印刷中. (2000)

    • Related Report
      1999 Annual Research Report
  • [Publications] Yang Q.Et al.: "Structure/function studies of hepatocyte nuclear factor-lα , a diabes-associated transcription factor"Biochem. Biophys. Res. Commun.. 266・1. 196-202 (1999)

    • Related Report
      1999 Annual Research Report
  • [Publications] Yoshiuchi I.et al.: "Three new mutations in the hepatocyte nuclear factor-lα gene in Japanese subjects with diabetes mallitus : Clinical features and functional characterization."Diabetologia. 42・5. 621-626 (1999)

    • Related Report
      1999 Annual Research Report
  • [Publications] Okita K.et al.: "Human insulin gene is a target of hepatocyte nuclear factor-lα(HNF-lα) and HNF-lβ"Biochem. Biophys. Res. Commun.. 263・2. 566-569 (1999)

    • Related Report
      1999 Annual Research Report
  • [Publications] Miyagawa J.et al.: "Immunohistochemical localization of betacellulin, a new nembar of EGF family, in normal human pancreas and islet tumor cells"Endocrine J.. 46・6. 755-764 (1999)

    • Related Report
      1999 Annual Research Report
  • [Publications] Yamagata,K.,et al.: "Matatim P291 fsinsC in the Trenscriptia factor Hepatocyte Nuclaer Factor-1 of is Dominant Negative." Diabetes. 47・8. 1231-1235 (1998)

    • Related Report
      1998 Annual Research Report
  • [Publications] Iwahashi,H.,et al.: "Molecnlor mechanisms of pancreatic beta-cell destraction in antoimmune diabetes:potential targets for preventive thempy." Cytokines,Cellular&Molecular Therapy. 4. 45-51 (1998)

    • Related Report
      1998 Annual Research Report
  • [Publications] Yoshiuchi,I.,et al.: "Matation/polymorphism scanning of Glucose-6-phesphate Gene Promoter in Noxinsalla-dependent Diabetes Mellitas Patients." J.Clin.Endocrinol.Metab.83・3. 1016-1019 (1998)

    • Related Report
      1998 Annual Research Report
  • [Publications] Kuwajima,M.,et al.: "Charaderistic of cardiac Hypertriphy in the Jurenile Visceral steatosis Mouse with systemic Cornitine Deficioncy." J.Mol.Cell.Cardiol.30・4. 773-781 (1998)

    • Related Report
      1998 Annual Research Report
  • [Publications] 山崎知行 ら: "糖尿病の病因仮説としての糖新生系酵素の発現調節異常の検証" 日本臨床代謝学会記録. 35. 81- (1998)

    • Related Report
      1998 Annual Research Report
  • [Publications] Iwahashi,H.,et al.: "Emerging therapentic strategles in autoimnune diabetes:etiology,prodiction,prevention and cure." Emerging Therapentic Targets. 印刷中. (1999)

    • Related Report
      1998 Annual Research Report

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Published: 1999-04-01   Modified: 2016-04-21  

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