title: Peripheral hyperinsulinemia promotes tau phosphorylation in vivo.
abstract: 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.
authors.affiliation: Department of Internal Medicine II, LFI 4/061, University of Cologne, Kerpener Str. 62, D-50937 Cologne, Germany.
authors.forename: Susanna
authors.initials: S
authors.lastname: Freude
authors.forename: Leona
authors.initials: L
authors.lastname: Plum
authors.forename: Jessika
authors.initials: J
authors.lastname: Schnitker
authors.forename: Uschi
authors.initials: U
authors.lastname: Leeser
authors.forename: Michael
authors.initials: M
authors.lastname: Udelhoven
authors.forename: Wilhelm
authors.initials: W
authors.lastname: Krone
authors.forename: Jens C
authors.initials: JC
authors.lastname: Bruning
authors.forename: Markus
authors.initials: M
authors.lastname: Schubert
mesh_terms: D000818:Animals; D001921:Brain / Q000503:physiopathology; D003924:Diabetes Mellitus, Type 2 / Q000503:physiopathology; D003929:Diabetic Neuropathies / Q000503:physiopathology; D004195:Disease Models, Animal; D006946:Hyperinsulinism / Q000503:physiopathology*; D007328:Insulin / Q000494:pharmacology / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D010766:Phosphorylation; D010768:Phosphoserine / Q000378:metabolism; D010769:Phosphothreonine / Q000378:metabolism; D011972:Receptor, Insulin / Q000187:drug effects / Q000502:physiology; D015398:Signal Transduction; D016875:tau Proteins / Q000378:metabolism*
chemical_list: D007328:Insulin; D016875:tau Proteins; D010769:Phosphothreonine; D010768:Phosphoserine; D011972:Receptor, Insulin