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Peripheral hyperinsulinemia promotes tau phosphorylation in vivo
Susanna Freude1, Leona Plum, Jessika Schnitker
1Department of Internal Medicine II, LFI 4/061, University of Cologne, Kerpener Str. 62, D-50937 Cologne, Germany.
Diabetes
|November 25, 2005
Summary
Peripheral insulin directly impacts brain insulin signaling and tau phosphorylation, linking type 2 diabetes to neurodegeneration. This study reveals how insulin resistance may accelerate Alzheimer's disease progression.
Area of Science:
- Neuroscience
- Endocrinology
- Molecular Biology
Background:
- Cerebral insulin receptors regulate energy and neurodegeneration.
- Insulin resistance in type 2 diabetes increases Alzheimer's disease risk.
- Hyperphosphorylated tau in neurofibrillary tangles is key to neurodegeneration.
Purpose of the Study:
- To investigate if peripheral hyperinsulinemia alters in vivo cerebral insulin signaling and tau phosphorylation.
- To elucidate the direct effects of peripheral insulin on brain pathways linked to neurodegeneration.
Main Methods:
- Peripheral insulin stimulation in mice.
- Analysis of insulin receptor signaling pathways (tyrosine phosphorylation, MAPK, PI3K).
- Measurement of tau phosphorylation at Ser202.
- Immunostaining for phospho-FoxO1 and PI-3,4,5-phosphate.
- Utilizing neuronal/brain-specific insulin receptor knockout mice.
Main Results:
- Insulin stimulation rapidly increased cerebral insulin receptor signaling and tau phosphorylation.
- Phosphorylation occurred throughout the brain, not limited by the blood-brain barrier.
- Knockout of brain insulin receptors abolished these effects, confirming direct brain targeting.
Conclusions:
- Peripherally administered insulin directly targets the brain.
- Rapid cerebral insulin receptor signaling and tau phosphorylation occur in vivo.
- Provides new insights into the link between type 2 diabetes and neurodegeneration.