2005 Fiscal Year Final Research Report Summary
Pathogenesis and treatment of diabetic nephropathy
| Project/Area Number |
16590786
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Kidney internal medicine
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| Research Institution | Kyoto University |
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Principal Investigator |
ARAI Hidenori Kyoto University, Graduate School of Medicine, Assistant Professor, 医学研究科, 講師 (60232021)
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| Project Period (FY) |
2004 – 2005
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| Keywords | diabetic nephropathy / Akt / mTOR / Gas6 / mesangial cell |
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| Research Abstract |
Background. We have already reported that Gas6 is involved in glomerular hypertrophy observed in diabetic nephropathy. However, the molecular mechanisms involved in glomerular hypertrophy are still unknown, especially in vivo.
Methods. In vivo, diabetes was induced in rats and mice by streptozotocin (STZ) and the activation of the Akt/mTOR pathway was examined in glomeruli. In vitro, mesangial hypertrophy was assessed by [^3H]leucine incorporation and measuring cell areas.
Results. Akt, p70 S6 kinase, and 4E-BP-1 were induced and phosphorylated in rat glomerular lysates after 12 weeks of STZ injection when mesangial and glomerular hypertrophy was observed. We then examined the role of Gas6 by treating STZ-rats with warfarin and found that warfarin treatment inhibited the phosphorylation of these molecules as well as the hypertrophy. We next examined whether high glucose stimulation can induce the expression of Gas6/Axl in mesangial cells. Stimulation of the cells with 25 mmol/l of glucose increased the expression of Gas6/Axl and mesangial cell size compared with that with 5.6 mmol/l of glucose. This hypertrophic effect was abolished in mesangial cells derived from Gas6 knockout mice. We also found that LY294002 and rapamycin blocked Gas6-induced activation of the Akt/mTOR pathway and mesangial hypertrophy. Furthermore, less phosphorylated Akt-positive or 4E-BP-1-positive areas were found in STZ-treated Gas6 knockout mice than in STZ-treated wild type mice.
Conclusions. Our study indicates that the Akt/mTOR pathway is a key signaling cascade in Gas6-mediated mesangial and glomerular hypertrophy and revealed a crucial role of Gas6/Axl and the Akt/mTOR pathway in the development of diabetic nephropathy.
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