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Diabetes 54:3343-3348, 2005
© 2005 by the American Diabetes Association, Inc.

Peripheral Hyperinsulinemia Promotes Tau Phosphorylation In Vivo

Susanna Freude1,2, Leona Plum1,2,3, Jessika Schnitker1, Uschi Leeser1,2, Michael Udelhoven1,2, Wilhelm Krone1,2, Jens C. Bruning2,3, and Markus Schubert1,2

1 Department of Internal Medicine II, University of Cologne, Cologne, Germany
2 Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
3 Department of Mouse Genetics and Metabolism, Institute for Genetics, University of Cologne, Cologne, Germany

Cerebral insulin receptors play an important role in regulation of energy homeostasis and development of neurodegeneration. Accordingly, type 2 diabetes characterized by insulin resistance is associated with an increased risk of developing Alzheimer’s disease. Formation of neurofibrillary tangles, which contain hyperphosphorylated tau, represents a key step in the pathogenesis of neurodegenerative diseases. Here, we directly addressed whether peripheral hyperinsulinemia as one feature of type 2 diabetes can alter in vivo cerebral insulin signaling and tau phosphorylation. Peripheral insulin stimulation rapidly increased insulin receptor tyrosine phosphorylation, mitogen-activated protein kinase and phosphatidylinositol (PI) 3-kinase pathway activation, and dose-dependent tau phosphorylation at Ser202 in the central nervous system. Phospho-FoxO1 and PI-3,4,5-phosphate immunostainings of brains from insulin-stimulated mice showed neuronal staining throughout the brain, not restricted to brain areas without functional blood-brain barrier. Importantly, in insulin-stimulated neuronal/brain-specific insulin receptor knockout mice, cerebral insulin receptor signaling and tau phosphorylation were completely abolished. Thus, peripherally injected insulin directly targets the brain and causes rapid cerebral insulin receptor signal transduction and site-specific tau phosphorylation in vivo, revealing new insights into the linkage of type 2 diabetes and neurodegeneration.

Address correspondence and reprint requests to Markus Schubert, MD, Department of Internal Medicine II, LFI 4/061, University of Cologne, Kerpener Str. 62, D-50937 Cologne, Germany. E-mail: markus.schubert{at}uni-koeln.de

Abbreviations: BBB, blood-brain barrier; CNS, central nervous system; CSF, cerebrospinal fluid; Erk, extracellular regulated kinase; GSK, glycogen synthase kinase; NIRKO, neuronal/brain-specific insulin receptor knockout; PI, phosphatidylinositol; PIP3, PI-3,4,5-phosphate; TBS, Tris-buffered saline


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Diabetes Diabetes Care Clinical Diabetes Diabetes Spectrum
Copyright © 2005 by the American Diabetes Association.