title: Effect of naringenin on brain insulin signaling and cognitive functions in ICV-STZ induced dementia model of rats.
abstract: Recent evidence indicates that severe abnormalities in brain glucose/energy metabolism and insulin signaling have been documented to take a pivotal role in early sporadic Alzheimer's disease pathology. It has been reported that naringenin (NAR), derived from citrus aurantium, exhibits antioxidant potential and protects the brain against neurodegeneration. The current study was designed to further investigate the protective effect of the NAR on neurodegeneration in a rat model of AD induced by an intracerebroventricular (ICV) injection of streptozotocin (STZ), and to determine whether this neuroprotective effect was associated with brain insulin signaling. Rats were injected bilaterally with ICV-STZ (3 mg/kg), while sham rats received the same volume of vehicle and then supplemented with NAR (25, 50 mg, 100 mg/kg, respectively) for 3 weeks. The ICV-STZ injected rats did not have elevated blood glucose levels. 21 days following ICV-STZ injection, rats treated with NAR had better learning and memory performance in the Morris water maze test compared with rats treated with saline. We demonstrated that NAR increased the mRNA expression of INS and INSR in cerebral cortex and hippocampus. In addition, NAR reversed ICV-STZ induced Tau hyper-phosphorylation in both hippocampus and cerebral cortex through downregulation of glycogen synthase kinase-3β (GSK-3β) activity, a key kinase in the insulin signaling. Brain levels of Abeta, which were elevated in ICV-STZ rats, were significantly reduced in NAR-treated rats via upregulation of insulin degrading enzyme. These effects were mediated by increased insulin and insulin receptors expression in the brain, suggesting that insulin sensitizer agents might have therapeutic efficacy in early AD.
authors: Department of Physiology, Research Center of Neuroscience, Chongqing Medical University, Chongqing, 400016, China.
authors: Wenqing
authors: W
authors: Yang
authors: Jing
authors: J
authors: Ma
authors: Zheng
authors: Z
authors: Liu
authors: Yongliang
authors: Y
authors: Lu
authors: Bin
authors: B
authors: Hu
authors: Huarong
authors: H
authors: Yu
mesh_terms: D016229:Amyloid beta-Peptides / Q000378:metabolism; D000818:Animals; D001786:Blood Glucose / Q000187:drug effects; D001921:Brain / Q000187:drug effects* / Q000503:physiopathology*; D003071:Cognition / Q000187:drug effects / Q000502:physiology; D003072:Cognition Disorders / Q000188:drug therapy / Q000503:physiopathology; D003704:Dementia / Q000188:drug therapy* / Q000503:physiopathology*; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D057967:Infusions, Intraventricular; D061385:Insulins / Q000378:metabolism*; D008297:Male; D018782:Maze Learning / Q000187:drug effects / Q000502:physiology; D010446:Peptide Fragments / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D011897:Random Allocation; D017207:Rats, Sprague-Dawley; D011972:Receptor, Insulin / Q000378:metabolism; D065852:Spatial Memory / Q000187:drug effects / Q000502:physiology; D013311:Streptozocin; D016875:tau Proteins / Q000378:metabolism
chemical_list: D016229:Amyloid beta-Peptides; D001786:Blood Glucose; D061385:Insulins; C489131:Mapt protein, rat; D010446:Peptide Fragments; D012333:RNA, Messenger; C075222:amyloid beta-protein (1-42); D016875:tau Proteins; D013311:Streptozocin; D011972:Receptor, Insulin; D000071679:Glycogen Synthase Kinase 3 beta; C000605508:Gsk3b protein, rat; D038362:Glycogen Synthase Kinase 3