1
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Ghaderi S, Gholipour P, Komaki A, Shahidi S, Seif F, Bahrami-Tapehebur M, Salehi I, Zarei M, Sarihi A, Rashno M. Underlying mechanisms behind the neuroprotective effect of vanillic acid against diabetes-associated cognitive decline: An in vivo study in a rat model. Phytother Res 2024; 38:1262-1277. [PMID: 38185917 DOI: 10.1002/ptr.8111] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Revised: 11/01/2023] [Accepted: 12/16/2023] [Indexed: 01/09/2024]
Abstract
Hippocampal synaptic dysfunction, oxidative stress, neuroinflammation, and neuronal loss play critical roles in the pathophysiology of diabetes-associated cognitive decline (DACD). The study aimed to investigate the effects of vanillic acid (VA), a phenolic compound, against DACD and explore the potential underlying mechanisms. Following confirmation of diabetes, rats were treated with VA (50 mg/kg/day; P.O.) or insulin (6 IU/rat/day; S.C.) for 8 consecutive weeks. The cognitive performance of the rats was evaluated using passive-avoidance and water-maze tasks. Long-term potentiation (LTP) was induced at hippocampal dentate gyrus (DG) synapses in response to high-frequency stimulation (HFS) applied to the perforant pathway (PP) to evaluate synaptic plasticity. Oxidative stress factors, inflammatory markers, and histological changes were evaluated in the rat hippocampus. This study showed that streptozotocin (STZ)-induced diabetes caused cognitive decline that was associated with inhibition of LTP induction, suppression of enzymatic antioxidant activities, enhanced lipid peroxidation, elevated levels of inflammatory proteins, and neuronal loss. Interestingly, chronic treatment with VA alleviated blood glucose levels, improved cognitive decline, ameliorated LTP impairment, modulated oxidative-antioxidative status, inhibited inflammatory response, and prevented neuronal loss in diabetic rats at a level comparable to insulin therapy. The results suggest that the antihyperglycemic, antioxidative, anti-inflammatory, and neuroplastic properties of VA may be the mechanisms behind its neuroprotective effect against DACD.
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Affiliation(s)
- Shahab Ghaderi
- Department of Neuroscience, School of Science and Advanced Technologies in Medicine, Hamadan University of Medical Sciences, Hamadan, Iran
- Neurophysiology Research Center, Hamadan University of Medical Sciences, Hamadan, Iran
| | - Parsa Gholipour
- Neurophysiology Research Center, Hamadan University of Medical Sciences, Hamadan, Iran
| | - Alireza Komaki
- Department of Neuroscience, School of Science and Advanced Technologies in Medicine, Hamadan University of Medical Sciences, Hamadan, Iran
- Neurophysiology Research Center, Hamadan University of Medical Sciences, Hamadan, Iran
| | - Siamak Shahidi
- Department of Neuroscience, School of Science and Advanced Technologies in Medicine, Hamadan University of Medical Sciences, Hamadan, Iran
- Neurophysiology Research Center, Hamadan University of Medical Sciences, Hamadan, Iran
| | - Faezeh Seif
- Department of Basic Sciences, Shoushtar Faculty of Medical Sciences, Shoushtar, Iran
| | - Mohammad Bahrami-Tapehebur
- Department of Anatomy and Embryology, Faculty of Veterinary Medicine, Lorestan University, Khorramabad, Iran
| | - Iraj Salehi
- Neurophysiology Research Center, Hamadan University of Medical Sciences, Hamadan, Iran
| | - Mohammad Zarei
- Neurophysiology Research Center, Hamadan University of Medical Sciences, Hamadan, Iran
| | - Abdolrahman Sarihi
- Department of Neuroscience, School of Science and Advanced Technologies in Medicine, Hamadan University of Medical Sciences, Hamadan, Iran
- Neurophysiology Research Center, Hamadan University of Medical Sciences, Hamadan, Iran
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Bathla S, Datta D, Liang F, Barthelemy N, Wiseman R, Slusher BS, Asher J, Zeiss C, Ekanayake‐Alper D, Holden D, Terwilliger G, Duque A, Arellano J, van Dyck C, Bateman RJ, Xie Z, Nairn AC, Arnsten AFT. Chronic GCPII (glutamate-carboxypeptidase-II) inhibition reduces pT217Tau levels in the entorhinal and dorsolateral prefrontal cortices of aged macaques. ALZHEIMER'S & DEMENTIA (NEW YORK, N. Y.) 2023; 9:e12431. [PMID: 37915375 PMCID: PMC10617575 DOI: 10.1002/trc2.12431] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Revised: 09/28/2023] [Accepted: 09/30/2023] [Indexed: 11/03/2023]
Abstract
Introduction Current approaches for treating sporadic Alzheimer's disease (sAD) focus on removal of amyloid beta 1-42 (Aβ1-42) or phosphorylated tau, but additional strategies are needed to reduce neuropathology at earlier stages prior to neuronal damage. Longstanding data show that calcium dysregulation is a key etiological factor in sAD, and the cortical neurons most vulnerable to tau pathology show magnified calcium signaling, for example in dorsolateral prefrontal cortex (dlPFC) and entorhinal cortex (ERC). In primate dlPFC and ERC, type 3 metabotropic glutamate receptors (mGluR3s) are predominately post-synaptic, on spines, where they regulate cAMP-calcium signaling, a process eroded by inflammatory glutamate carboxypeptidase II (GCPII) actions. The current study tested whether enhancing mGluR3 regulation of calcium via chronic inhibition of GCPII would reduce tau hyperphosphorylation in aged macaques with naturally-occurring tau pathology. Methods Aged rhesus macaques were treated daily with the GCPII inhibitor, 2-MPPA (2-3-mercaptopropyl-penanedioic acid (2-MPPA)),Aged rhesus macaques were treated daily with the GCPII inhibitor, 2-MPPA (2-3-mercaptopropyl-penanedioic acid (2-MPPA)). Results Aged macaques that received 2-MPPA had significantly lower pT217Tau levels in dlPFC and ERC, and had lowered plasma pT217Tau levels from baseline. pT217Tau levels correlated significantly with GCPII activity in dlPFC. Both 2-MPPA- and vehicle-treated monkeys showed cognitive improvement; 2-MPPA had no apparent side effects. Exploratory CSF analyses indicated reduced pS202Tau with 2-MPPA administration, confirmed in dlPFC samples. Discussion These data provide proof-of-concept support that GCPII inhibition can reduce tau hyperphosphorylation in the primate cortices most vulnerable in sAD. GCPII inhibition may be particularly helpful in reducing the risk of sAD caused by inflammation. These data in nonhuman primates should encourage future research on this promising mechanism. Highlights Inflammation is a key driver of sporadic Alzheimer's disease.GCPII inflammatory signaling in brain decreases mGluR3 regulation of calcium.Chronic inhibition of GCPII inflammatory signaling reduced pT217Tau in aged monkeys.GCPII inhibition is a novel strategy to help prevent tau pathology at early stages.
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Affiliation(s)
- Shveta Bathla
- Departments of PsychiatryYale University School of MedicineNew HavenConnecticutUSA
| | - Dibyadeep Datta
- Departments of PsychiatryYale University School of MedicineNew HavenConnecticutUSA
- Departments of NeuroscienceYale University School of MedicineNew HavenConnecticutUSA
| | - Feng Liang
- Department of AnesthesiologyHarvard University School of MedicineBostonMassachusettsUSA
| | - Nicolas Barthelemy
- Department of NeurologyWashington University School of MedicineSt. LouisMissouriUSA
| | - Robyn Wiseman
- Department of Neurology, Johns Hopkins University Drug DiscoveryJohns Hopkins School of MedicineBaltimoreMarylandUSA
| | - Barbara S Slusher
- Department of Neurology, Johns Hopkins University Drug DiscoveryJohns Hopkins School of MedicineBaltimoreMarylandUSA
| | - Jennifer Asher
- Departments of Comparative MedicineYale University School of MedicineNew HavenConnecticutUSA
| | - Caroline Zeiss
- Departments of Comparative MedicineYale University School of MedicineNew HavenConnecticutUSA
| | - Dil Ekanayake‐Alper
- Departments of Comparative MedicineYale University School of MedicineNew HavenConnecticutUSA
| | - Daniel Holden
- Departments of RadiologyYale University School of MedicineNew HavenConnecticutUSA
| | - Gordon Terwilliger
- Departments of Comparative MedicineYale University School of MedicineNew HavenConnecticutUSA
| | - Alvaro Duque
- Departments of NeuroscienceYale University School of MedicineNew HavenConnecticutUSA
| | - Jon Arellano
- Departments of NeuroscienceYale University School of MedicineNew HavenConnecticutUSA
| | - Christopher van Dyck
- Departments of PsychiatryYale University School of MedicineNew HavenConnecticutUSA
| | - Randall J. Bateman
- Departments of RadiologyYale University School of MedicineNew HavenConnecticutUSA
| | - Zhongcong Xie
- Departments of Comparative MedicineYale University School of MedicineNew HavenConnecticutUSA
| | - Angus C. Nairn
- Departments of PsychiatryYale University School of MedicineNew HavenConnecticutUSA
| | - Amy F. T. Arnsten
- Departments of NeuroscienceYale University School of MedicineNew HavenConnecticutUSA
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3
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Alipour N, Fallahnezhad S, Bagheri J, Babaloo H, Tahmasebi F, Sazegar G, Haghir H. Increased Apoptosis in Subcortical Regions of The Visual Pathway in Offspring Born to Diabetic Rats. CELL JOURNAL 2023; 25:564-569. [PMID: 37641418 PMCID: PMC10542209 DOI: 10.22074/cellj.2023.1989649.1232] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Revised: 06/04/2023] [Accepted: 06/13/2023] [Indexed: 08/31/2023]
Abstract
OBJECTIVE Diabetes in pregnancy is a prevalent disease that can affect the central nervous system of the fetus by hyperglycemia. This study aimed to investigate the impact of maternal diabetes on neuronal apoptosis in the superior colliculus (SC) and the lateral geniculate nucleus (LGN) in male neonates born to diabetic mothers. MATERIALS AND METHODS In this experimental study, female adult rats were separated into three groups: control, diabetic (induced using an intraperitoneal injection of streptozotocin), and insulin-treated diabetic [diabetes controlled by subcutaneous neutral protamine hagedorn (NPH)-insulin injection]. Male neonates from each group were euthanized on 0, 7, and 14 postnatal days (P0, P7, and P14, respectively), and apoptotic cells were identified using TUNEL staining. RESULTS The numerical density per unit area (NA) of apoptotic cells was significantly higher in SC and the dorsal LGN (dLGN) in neonates born to the diabetic rats compared to the control group at P0, P7, and P14. However, insulin treatment normalized the number of apoptotic cells. CONCLUSION This study demonstrated that maternal diabetes increased apoptosis in dLGN and SC of male neonates at P0, P7, and P14.
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Affiliation(s)
- Nasim Alipour
- Department of Anatomy and Cell Biology, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Somaye Fallahnezhad
- Nervous System Stem Cell Research Center, Semnan University of Medical Sciences, Semnan, Iran
- Department of Anatomical Sciences, School of Medicine, Semnan University of Medical Sciences, Semnan, Iran
| | - Javad Bagheri
- Department of Anatomy and Cell Biology, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Hamideh Babaloo
- Department of Advanced Medical Sciences and Technologies, School of Paramedicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
- Medical Nanotechnology and Tissue Engineering Research Center, Yazd Reproductive Sciences Institute, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
| | - Fatemeh Tahmasebi
- Department of Anatomy and Cell Biology, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Ghasem Sazegar
- Department of Anatomy and Cell Biology, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Hossein Haghir
- Department of Anatomy and Cell Biology, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran.
- Medical Genetic Research Center (MGRC), School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
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Xue WJ, He CF, Zhou RY, Xu XD, Xiang LX, Wang JT, Wang XR, Zhou HG, Guo JC. High glucose and palmitic acid induces neuronal senescence by NRSF/REST elevation and the subsequent mTOR-related autophagy suppression. Mol Brain 2022; 15:61. [PMID: 35850767 PMCID: PMC9290252 DOI: 10.1186/s13041-022-00947-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Accepted: 07/04/2022] [Indexed: 11/10/2022] Open
Abstract
Cell senescence is a basic aging mechanism. Previous studies have found that the cellular senescence in adipose tissue and other tissues, such as the pancreas, muscle and liver, is associated with the pathogenesis and progression of type 2 diabetes; however, strong evidence of whether diabetes directly causes neuronal senescence in the brain is still lacking. In this study, we constructed a high glucose and palmitic acid (HGP) environment on PC12 neuronal cells and primary mouse cortical neurons to simulate diabetes. Our results showed that after HGP exposure, neurons exhibited obvious senescence-like phenotypes, including increased NRSF/REST level, mTOR activation and cell autophagy suppression. Downregulation of NRSF/REST could remarkably alleviate p16, p21 and γH2A.X upregulations induced by HGP treatment, and enhance mTOR-autophagy of neurons. Our results suggested that the diabetic condition could directly induce neuronal senescence, which is mediated by the upregulation of NRSF/REST and subsequent reduction of mTOR-autophagy.
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Affiliation(s)
- Wen-Jiao Xue
- Department of Translational Neuroscience, Jing'an District Centre Hospital of Shanghai, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, China
| | - Cheng-Feng He
- Department of Translational Neuroscience, Jing'an District Centre Hospital of Shanghai, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, China
| | - Ren-Yuan Zhou
- Department of Urology, Jing'an District Central Hospital, Fudan University, Shanghai, China
| | - Xiao-Die Xu
- Department of Translational Neuroscience, Jing'an District Centre Hospital of Shanghai, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, China
| | - Lv-Xuan Xiang
- Department of Translational Neuroscience, Jing'an District Centre Hospital of Shanghai, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, China
| | - Jian-Tao Wang
- Department of Geriatric Neurology of Huashan Hospital, National Clinical Research Center for Aging and Medicine, Fudan University, Shanghai, China
| | - Xin-Ru Wang
- Department of Geriatric Neurology of Huashan Hospital, National Clinical Research Center for Aging and Medicine, Fudan University, Shanghai, China
| | - Hou-Guang Zhou
- Department of Geriatric Neurology of Huashan Hospital, National Clinical Research Center for Aging and Medicine, Fudan University, Shanghai, China.
| | - Jing-Chun Guo
- Department of Translational Neuroscience, Jing'an District Centre Hospital of Shanghai, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, China.
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5
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Rhea EM, Banks WA, Raber J. Insulin Resistance in Peripheral Tissues and the Brain: A Tale of Two Sites. Biomedicines 2022; 10:1582. [PMID: 35884888 PMCID: PMC9312939 DOI: 10.3390/biomedicines10071582] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Revised: 06/27/2022] [Accepted: 06/29/2022] [Indexed: 12/12/2022] Open
Abstract
The concept of insulin resistance has been around since a few decades after the discovery of insulin itself. To allude to the classic Charles Dicken's novel published 62 years before the discovery of insulin, in some ways, this is the best of times, as the concept of insulin resistance has expanded to include the brain, with the realization that insulin has a life beyond the regulation of glucose. In other ways, it is the worst of times as insulin resistance is implicated in devastating diseases, including diabetes mellitus, obesity, and Alzheimer's disease (AD) that affect the brain. Peripheral insulin resistance affects nearly a quarter of the United States population in adults over age 20. More recently, it has been implicated in AD, with the degree of brain insulin resistance correlating with cognitive decline. This has led to the investigation of brain or central nervous system (CNS) insulin resistance and the question of the relation between CNS and peripheral insulin resistance. While both may involve dysregulated insulin signaling, the two conditions are not identical and not always interlinked. In this review, we compare and contrast the similarities and differences between peripheral and CNS insulin resistance. We also discuss how an apolipoprotein involved in insulin signaling and related to AD, apolipoprotein E (apoE), has distinct pools in the periphery and CNS and can indirectly affect each system. As these systems are both separated but also linked via the blood-brain barrier (BBB), we discuss the role of the BBB in mediating some of the connections between insulin resistance in the brain and in the peripheral tissues.
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Affiliation(s)
- Elizabeth M. Rhea
- Department of Medicine, Division of Gerontology and Geriatric Medicine, University of Washington, Seattle, WA 98195, USA; (E.M.R.); (W.A.B.)
- Geriatric Research Education and Clinical Center, Veterans Affairs Puget Sound Health Care System, Seattle, WA 98108, USA
| | - William A. Banks
- Department of Medicine, Division of Gerontology and Geriatric Medicine, University of Washington, Seattle, WA 98195, USA; (E.M.R.); (W.A.B.)
- Geriatric Research Education and Clinical Center, Veterans Affairs Puget Sound Health Care System, Seattle, WA 98108, USA
| | - Jacob Raber
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR 97239, USA
- Departments of Neurology and Radiation Medicine, Division of Neuroscience, ONPRC, Oregon Health & Science University, Portland, OR 97239, USA
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6
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Ridderinkhof KR, Krugers HJ. Horizons in Human Aging Neuroscience: From Normal Neural Aging to Mental (Fr)Agility. Front Hum Neurosci 2022; 16:815759. [PMID: 35845248 PMCID: PMC9277589 DOI: 10.3389/fnhum.2022.815759] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Accepted: 05/19/2022] [Indexed: 11/13/2022] Open
Abstract
While aging is an important risk factor for neurodegenerative disorders such as Alzheimer’s disease and Parkinson’s disease, age-related cognitive decline can also manifest without apparent neurodegenerative changes. In this review, we discuss molecular, cellular, and network changes that occur during normal aging in the absence of neurodegenerative disease. Emerging findings reveal that these changes include metabolic alterations, oxidative stress, DNA damage, inflammation, calcium dyshomeostasis, and several other hallmarks of age-related neural changes that do not act on their own, but are often interconnected and together may underlie age-related alterations in brain plasticity and cognitive function. Importantly, age-related cognitive decline may not be reduced to a single neurobiological cause, but should instead be considered in terms of a densely connected system that underlies age-related cognitive alterations. We speculate that a decline in one hallmark of neural aging may trigger a decline in other, otherwise thus far stable subsystems, thereby triggering a cascade that may at some point also incur a decline of cognitive functions and mental well-being. Beyond studying the effects of these factors in isolation, considerable insight may be gained by studying the larger picture that entails a representative collection of such factors and their interactions, ranging from molecules to neural networks. Finally, we discuss some potential interventions that may help to prevent these alterations, thereby reducing cognitive decline and mental fragility, and enhancing mental well-being, and healthy aging.
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Affiliation(s)
- K Richard Ridderinkhof
- Department of Psychology, University of Amsterdam, Amsterdam, Netherlands
- Amsterdam Center for Brain and Cognition (ABC), University of Amsterdam, Amsterdam, Netherlands
| | - Harm J Krugers
- Amsterdam Center for Brain and Cognition (ABC), University of Amsterdam, Amsterdam, Netherlands
- SILS-CNS, Faculty of Science, University of Amsterdam, Amsterdam, Netherlands
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7
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Brain Insulin Resistance: Focus on Insulin Receptor-Mitochondria Interactions. Life (Basel) 2021; 11:life11030262. [PMID: 33810179 PMCID: PMC8005009 DOI: 10.3390/life11030262] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Revised: 03/12/2021] [Accepted: 03/16/2021] [Indexed: 02/07/2023] Open
Abstract
Current hypotheses implicate insulin resistance of the brain as a pathogenic factor in the development of Alzheimer’s disease and other dementias, Parkinson’s disease, type 2 diabetes, obesity, major depression, and traumatic brain injury. A variety of genetic, developmental, and metabolic abnormalities that lead to disturbances in the insulin receptor signal transduction may underlie insulin resistance. Insulin receptor substrate proteins are generally considered to be the node in the insulin signaling system that is critically involved in the development of insulin insensitivity during metabolic stress, hyperinsulinemia, and inflammation. Emerging evidence suggests that lower activation of the insulin receptor (IR) is another common, while less discussed, mechanism of insulin resistance in the brain. This review aims to discuss causes behind the diminished activation of IR in neurons, with a focus on the functional relationship between mitochondria and IR during early insulin signaling and the related roles of oxidative stress, mitochondrial hypometabolism, and glutamate excitotoxicity in the development of IR insensitivity to insulin.
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8
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Frazier HN, Anderson KL, Ghoweri AO, Lin RL, Hawkinson TR, Popa GJ, Sompol P, Mendenhall MD, Norris CM, Thibault O. Molecular elevation of insulin receptor signaling improves memory recall in aged Fischer 344 rats. Aging Cell 2020; 19:e13220. [PMID: 32852134 PMCID: PMC7576226 DOI: 10.1111/acel.13220] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Revised: 07/16/2020] [Accepted: 07/22/2020] [Indexed: 12/24/2022] Open
Abstract
As demonstrated by increased hippocampal insulin receptor density following learning in animal models and decreased insulin signaling, receptor density, and memory decline in aging and Alzheimer's diseases, numerous studies have emphasized the importance of insulin in learning and memory processes. This has been further supported by work showing that intranasal delivery of insulin can enhance insulin receptor signaling, alter cerebral blood flow, and improve memory recall. Additionally, inhibition of insulin receptor function or expression using molecular techniques has been associated with reduced learning. Here, we sought a different approach to increase insulin receptor activity without the need for administering the ligand. A constitutively active, modified human insulin receptor (IRβ) was delivered to the hippocampus of young (2 months) and aged (18 months) male Fischer 344 rats in vivo. The impact of increasing hippocampal insulin receptor expression was investigated using several outcome measures, including Morris water maze and ambulatory gait performance, immunofluorescence, immunohistochemistry, and Western immunoblotting. In aged animals, the IRβ construct was associated with enhanced performance on the Morris water maze task, suggesting that this receptor was able to improve memory recall. Additionally, in both age-groups, a reduced stride length was noted in IRβ-treated animals along with elevated hippocampal insulin receptor levels. These results provide new insights into the potential impact of increasing neuronal insulin signaling in the hippocampus of aged animals and support the efficacy of molecularly elevating insulin receptor activity in vivo in the absence of the ligand to directly study this process.
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Affiliation(s)
| | - Katie L. Anderson
- Department of Pharmacology and Nutritional SciencesLexingtonKentuckyUSA
| | - Adam O. Ghoweri
- Department of Pharmacology and Nutritional SciencesLexingtonKentuckyUSA
| | - Ruei-Lung Lin
- Department of Pharmacology and Nutritional SciencesLexingtonKentuckyUSA
| | - Tara R. Hawkinson
- Department of Pharmacology and Nutritional SciencesLexingtonKentuckyUSA
| | - Gabriel J. Popa
- Department of Molecular and Cellular BiochemistryLexingtonKentuckyUSA
| | - Pradoldej Sompol
- Sanders-Brown Center on AgingUniversity of KentuckyLexingtonKentuckyUSA
| | | | | | - Olivier Thibault
- Department of Pharmacology and Nutritional SciencesLexingtonKentuckyUSA
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Thapak P, Bishnoi M, Sharma SS. Pharmacological Inhibition of Transient Receptor Potential Melastatin 2 (TRPM2) Channels Attenuates Diabetes-induced Cognitive Deficits in Rats: A Mechanistic Study. Curr Neurovasc Res 2020; 17:249-258. [DOI: 10.2174/1567202617666200415142211] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Revised: 03/02/2020] [Accepted: 03/07/2020] [Indexed: 02/08/2023]
Abstract
Background:
Diabetes is a chronic metabolic disorder affecting the central nervous system.
A growing body of evidence has depicted that high glucose level leads to the activation of the
transient receptor potential melastatin 2 (TRPM2) channels. However, there are no studies targeting
TRPM2 channels in diabetes-induced cognitive decline using a pharmacological approach.
Objective:
The present study intended to investigate the effects of 2-aminoethoxydiphenyl borate
(2-APB), a TRPM2 inhibitor, in diabetes-induced cognitive impairment.
Methods:
Streptozotocin (STZ, 50 mg/kg, i.p.) was used to induce diabetes in rats. Animals were
randomly divided into the treatment group, model group and age-matched control and pre se
group. 2-APB treatment was given for three weeks to the animals. After 10 days of behavioural
treatment, parameters were performed. Animals were sacrificed at 10th week of diabetic induction
and the hippocampus and cortex were isolated. After that, protein and mRNA expression study
was performed in the hippocampus. Acetylcholinesterase (AchE) activity was done in the cortex.
Results: :
Our study showed the 10th week diabetic animals developed cognitive impairment, which
was evident from the behavioural parameters. Diabetic animals depicted an increase in the TRPM2
mRNA and protein expression in the hippocampus as well as increased AchE activity in the cortex.
However, memory associated proteins were down-regulated, namely Ca2+/calmodulin-dependent
protein kinase II (CaMKII-Thr286), glycogen synthase kinase 3 beta (GSK-3β-Ser9), cAMP
response element-binding protein (CREB-Ser133), and postsynaptic density protein 95 (PSD-95).
Gene expression of parvalbumin, calsequestrin and brain-derived neurotrophic factor (BDNF)
were down-regulated while mRNA level of calcineurin A/ protein phosphatase 3 catalytic subunit
alpha (PPP3CA) was upregulated in the hippocampus of diabetic animals. A three-week treatment
with 2-APB significantly ameliorated the alteration in behavioural cognitive parameters in diabetic
rats. Moreover, 2-APB also down-regulated the expression of TRPM2 mRNA and protein in the
hippocampus as well as AchE activity in the cortex of diabetic animals as compared to diabetic
animals. Moreover, the 2-APB treatment also upregulated the CaMKII (Thr-286), GSK-3β (Ser9),
CREB (Ser133), and PSD-95 expression and mRNA levels of parvalbumin, calsequestrin, and
BDNF while mRNA level of calcineurin A was down-regulated in the hippocampus of diabetic
animals.
Conclusion: :
This study confirms the ameliorative effect of TRPM2 channel inhibitor in the diabetes-
induced cognitive deficits. Inhibition of TRPM2 channels reduced the calcium associated
downstream signaling and showed a neuroprotective effect of TRPM2 channels in diabetesinduced
cognitive impairment.
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Affiliation(s)
- Pavan Thapak
- Department of Pharmacology and Toxicology, National Institute of Pharmaceutical Education and Research (NIPER), Sector 67, S.A.S. Nagar, Punjab, India
| | - Mahendra Bishnoi
- National Agri-Food Biotechnology Institute, Sector 81, S.A.S. Nagar, Punjab, India
| | - Shyam S. Sharma
- Department of Pharmacology and Toxicology, National Institute of Pharmaceutical Education and Research (NIPER), Sector 67, S.A.S. Nagar, Punjab, India
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Ma WX, Tang J, Lei ZW, Li CY, Zhao LQ, Lin C, Sun T, Li ZY, Jiang YH, Jia JT, Liang CZ, Liu JH, Yan LJ. Potential Biochemical Mechanisms of Brain Injury in Diabetes Mellitus. Aging Dis 2020; 11:978-987. [PMID: 32765958 PMCID: PMC7390528 DOI: 10.14336/ad.2019.0910] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Accepted: 09/10/2019] [Indexed: 01/07/2023] Open
Abstract
The goal of this review was to summarize current biochemical mechanisms of and risk factors for diabetic brain injury. We mainly summarized mechanisms published in the past three years and focused on diabetes induced cognitive impairment, diabetes-linked Alzheimer’s disease, and diabetic stroke. We think there is a need to conduct further studies with increased sample sizes and prolonged period of follow-ups to clarify the effect of DM on brain dysfunction. Additionally, we also think that enhancing experimental reproducibility using animal models in conjunction with application of advanced devices should be considered when new experiments are designed. It is expected that further investigation of the underlying mechanisms of diabetic cognitive impairment will provide novel insights into therapeutic approaches for ameliorating diabetes-associated injury in the brain.
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Affiliation(s)
- Wei-Xing Ma
- 1Department of Pharmaceutical, University of North Texas Health Science Center, Fort Worth, Texas, USA.,2Chemical Engineering Institute, Qingdao University of Science and Technology, Qingdao, Shandong, China.,3Technological Center, Qingdao Customs, Qingdao, Shandong, China
| | - Jing Tang
- 3Technological Center, Qingdao Customs, Qingdao, Shandong, China
| | - Zhi-Wen Lei
- 3Technological Center, Qingdao Customs, Qingdao, Shandong, China
| | - Chun-Yan Li
- 1Department of Pharmaceutical, University of North Texas Health Science Center, Fort Worth, Texas, USA.,4Shantou University Medical College, Shantou, Guangdong, China
| | - Li-Qing Zhao
- 3Technological Center, Qingdao Customs, Qingdao, Shandong, China
| | - Chao Lin
- 3Technological Center, Qingdao Customs, Qingdao, Shandong, China
| | - Tao Sun
- 3Technological Center, Qingdao Customs, Qingdao, Shandong, China
| | - Zheng-Yi Li
- 3Technological Center, Qingdao Customs, Qingdao, Shandong, China
| | - Ying-Hui Jiang
- 3Technological Center, Qingdao Customs, Qingdao, Shandong, China
| | - Jun-Tao Jia
- 3Technological Center, Qingdao Customs, Qingdao, Shandong, China
| | - Cheng-Zhu Liang
- 3Technological Center, Qingdao Customs, Qingdao, Shandong, China
| | - Jun-Hong Liu
- 2Chemical Engineering Institute, Qingdao University of Science and Technology, Qingdao, Shandong, China
| | - Liang-Jun Yan
- 1Department of Pharmaceutical, University of North Texas Health Science Center, Fort Worth, Texas, USA
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11
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Thapak P, Bishnoi M, Sharma SS. Amelioration of diabetes-induced cognitive impairment by Transient Receptor Potential Vanilloid 2 (TRPV2) channel inhibitor: Behavioral and mechanistic study. Neurochem Int 2020; 139:104783. [PMID: 32652268 DOI: 10.1016/j.neuint.2020.104783] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Revised: 05/29/2020] [Accepted: 06/05/2020] [Indexed: 02/08/2023]
Abstract
Transient receptor potential (TRP) channels are Ca2+ permeable non-selective cation channels which play a pivotal role in diabetes and diabetic complications. Among diabetic complications, diabetes-induced cognitive impairment is a major CNS complication. The role of several TRP channels has been investigated extensively for their diverse Ca2+ regulating mechanism, and recently their role has been postulated in the progression of neurodegenerative disorders. However, the role of TRPV2 has not been investigated yet. Therefore, in the present study, the involvement of TRPV2 channels was investigated in diabetes-induced cognitive impairment using TRPV2 inhibitor, tranilast. High glucose exposure in rat C6 glial cells enhances the Ca2+-entry through TRPV2 channels. In our in-vivo study, diabetic rats showed increased gene and protein expression of TRPV2 in the hippocampus. Subsequent increase in the acetylcholinesterase activity in the cortex, as well as decrease in the phosphorylation of Ca2+/calmodulin-dependent protein kinase II (p-CaMKII-Thr-286), p-GSK-3β (Ser-9), p-CREB (Ser-133) and postsynaptic density protein 95 (PSD-95) in the hippocampus were also observed this led to the impairment in the learning and memory as evident from behavioral parameters such as Morris water maze test, passive avoidance and Y-maze test paradigm. Three-week treatment with tranilast (30 and 100 mg/kg, p.o.) showed improvement in learning and memory associated behaviours (Morris water maze test, passive avoidance, and Y-maze test) by increasing the p-CaMKII (Thr-286), p-GSK-3β (Ser-9), p-CREB (Ser-133) and PSD-95 in the hippocampus. Cortical acetylcholinesterase activity was also reduced by the tranilast. These findings depicted that TRPV2 inhibition may be an effective treatment strategy in diabetes-induced cognitive deficits.
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Affiliation(s)
- P Thapak
- Department of Pharmacology and Toxicology, National Institute of Pharmaceutical Education and Research (NIPER), S. A. S. Nagar, Punjab, India
| | - M Bishnoi
- National Agri-Food Biotechnology Institute (NABI), S. A. S. Nagar, Punjab, India
| | - S S Sharma
- Department of Pharmacology and Toxicology, National Institute of Pharmaceutical Education and Research (NIPER), S. A. S. Nagar, Punjab, India.
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12
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Frazier HN, Ghoweri AO, Anderson KL, Lin RL, Popa GJ, Mendenhall MD, Reagan LP, Craven RJ, Thibault O. Elevating Insulin Signaling Using a Constitutively Active Insulin Receptor Increases Glucose Metabolism and Expression of GLUT3 in Hippocampal Neurons. Front Neurosci 2020; 14:668. [PMID: 32733189 PMCID: PMC7358706 DOI: 10.3389/fnins.2020.00668] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Accepted: 06/02/2020] [Indexed: 12/31/2022] Open
Abstract
Insulin signaling is an integral component of healthy brain function, with evidence of positive insulin-mediated alterations in synaptic integrity, cerebral blood flow, inflammation, and memory. However, the specific pathways targeted by this peptide remain unclear. Previously, our lab used a molecular approach to characterize the impact of insulin signaling on voltage-gated calcium channels and has also shown that acute insulin administration reduces calcium-induced calcium release in hippocampal neurons. Here, we explore the relationship between insulin receptor signaling and glucose metabolism using similar methods. Mixed, primary hippocampal cultures were infected with either a control lentivirus or one containing a constitutively active human insulin receptor (IRβ). 2-NBDG imaging was used to obtain indirect measures of glucose uptake and utilization. Other outcome measures include Western immunoblots of GLUT3 and GLUT4 on total membrane and cytosolic subcellular fractions. Glucose imaging data indicate that neurons expressing IRβ show significant elevations in uptake and rates of utilization compared to controls. As expected, astrocytes did not respond to the IRβ treatment. Quantification of Western immunoblots show that IRβ is associated with significant elevations in GLUT3 expression, particularly in the total membrane subcellular fraction, but did not alter GLUT4 expression in either fraction. Our work suggests that insulin plays a significant role in mediating neuronal glucose metabolism, potentially through an upregulation in the expression of GLUT3. This provides further evidence for a potential therapeutic mechanism underlying the beneficial impact of intranasal insulin in the clinic.
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Affiliation(s)
- Hilaree N Frazier
- Department of Pharmacology and Nutritional Sciences, University of Kentucky College of Medicine, Lexington, KY, United States
| | - Adam O Ghoweri
- Department of Pharmacology and Nutritional Sciences, University of Kentucky College of Medicine, Lexington, KY, United States
| | - Katie L Anderson
- Department of Pharmacology and Nutritional Sciences, University of Kentucky College of Medicine, Lexington, KY, United States
| | - Ruei-Lung Lin
- Department of Pharmacology and Nutritional Sciences, University of Kentucky College of Medicine, Lexington, KY, United States
| | - Gabriel J Popa
- Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, Lexington, KY, United States
| | - Michael D Mendenhall
- Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, Lexington, KY, United States
| | - Lawrence P Reagan
- Department of Pharmacology, Physiology and Neuroscience, University of South Carolina School of Medicine, Columbia, SC, United States
| | - Rolf J Craven
- Department of Pharmacology and Nutritional Sciences, University of Kentucky College of Medicine, Lexington, KY, United States
| | - Olivier Thibault
- Department of Pharmacology and Nutritional Sciences, University of Kentucky College of Medicine, Lexington, KY, United States
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13
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Ibañez S, Luebke JI, Chang W, Draguljić D, Weaver CM. Network Models Predict That Pyramidal Neuron Hyperexcitability and Synapse Loss in the dlPFC Lead to Age-Related Spatial Working Memory Impairment in Rhesus Monkeys. Front Comput Neurosci 2020; 13:89. [PMID: 32009920 PMCID: PMC6979278 DOI: 10.3389/fncom.2019.00089] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Accepted: 12/18/2019] [Indexed: 01/04/2023] Open
Abstract
Behavioral studies have shown spatial working memory impairment with aging in several animal species, including humans. Persistent activity of layer 3 pyramidal dorsolateral prefrontal cortex (dlPFC) neurons during delay periods of working memory tasks is important for encoding memory of the stimulus. In vitro studies have shown that these neurons undergo significant age-related structural and functional changes, but the extent to which these changes affect neural mechanisms underlying spatial working memory is not understood fully. Here, we confirm previous studies showing impairment on the Delayed Recognition Span Task in the spatial condition (DRSTsp), and increased in vitro action potential firing rates (hyperexcitability), across the adult life span of the rhesus monkey. We use a bump attractor model to predict how empirically observed changes in the aging dlPFC affect performance on the Delayed Response Task (DRT), and introduce a model of memory retention in the DRSTsp. Persistent activity-and, in turn, cognitive performance-in both models was affected much more by hyperexcitability of pyramidal neurons than by a loss of synapses. Our DRT simulations predict that additional changes to the network, such as increased firing of inhibitory interneurons, are needed to account for lower firing rates during the DRT with aging reported in vivo. Synaptic facilitation was an essential feature of the DRSTsp model, but it did not compensate fully for the effects of the other age-related changes on DRT performance. Modeling pyramidal neuron hyperexcitability and synapse loss simultaneously led to a partial recovery of function in both tasks, with the simulated level of DRSTsp impairment similar to that observed in aging monkeys. This modeling work integrates empirical data across multiple scales, from synapse counts to cognitive testing, to further our understanding of aging in non-human primates.
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Affiliation(s)
- Sara Ibañez
- Department of Mathematics, Franklin and Marshall College, Lancaster, PA, United States
- Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, MA, United States
| | - Jennifer I. Luebke
- Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, MA, United States
| | - Wayne Chang
- Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, MA, United States
| | - Danel Draguljić
- Department of Mathematics, Franklin and Marshall College, Lancaster, PA, United States
| | - Christina M. Weaver
- Department of Mathematics, Franklin and Marshall College, Lancaster, PA, United States
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14
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Borshchev YY, Uspensky YP, Galagudza MM. Pathogenetic pathways of cognitive dysfunction and dementia in metabolic syndrome. Life Sci 2019; 237:116932. [PMID: 31606384 DOI: 10.1016/j.lfs.2019.116932] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Revised: 09/27/2019] [Accepted: 10/02/2019] [Indexed: 12/13/2022]
Abstract
The prevalence of dementia worldwide is growing at an alarming rate. A number of studies and meta-analyses have provided evidence for increased risk of dementia in patients with metabolic syndrome (MS) as compared to persons without MS. However, there are some reports demonstrating a lack of association between MS and increased dementia risk. In this review, taking into account the potential role of individual MS components in the pathogenesis of MS-related cognitive dysfunction, we considered the underlying mechanisms in arterial hypertension, diabetes mellitus, dyslipidemia, and obesity. The pathogenesis of dementia in MS is multifactorial, involving both vascular injury and non-ischemic neuronal death due to neurodegeneration. Neurodegenerative and ischemic lesions do not simply coexist in the brain due to independent evolution, but rather exacerbate each other, leading to more severe consequences for cognition than would either pathology alone. In addition to universal mechanisms of cognitive dysfunction shared by all MS components, other pathogenetic pathways leading to cognitive deficits and dementia, which are specific for each component, also play a role. Examples of such component-specific pathogenetic pathways include central insulin resistance and hypoglycemia in diabetes, neuroinflammation and adipokine imbalance in obesity, as well as arteriolosclerosis and lipohyalinosis in arterial hypertension. A more detailed understanding of cognitive disorders based on the recognition of underlying molecular mechanisms will aid in the development of new methods for prevention and treatment of devastating cognitive problems in MS.
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Affiliation(s)
- Yury Yu Borshchev
- Institute of Experimental Medicine, Almazov National Medical Research Center, Saint Petersburg, Russian Federation
| | - Yury P Uspensky
- Department of Faculty Therapy, Saint Petersburg State Pediatric Medical University, Saint Petersburg, Russian Federation
| | - Michael M Galagudza
- Laboratory of Digital and Display Holography, ITMO University, Russian Federation, Saint Petersburg, Russian Federation.
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15
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Verma N, Despa F. Contributing Factors to Diabetic Brain Injury and Cognitive Decline. Diabetes Metab J 2019; 43:560-567. [PMID: 31694078 PMCID: PMC6834839 DOI: 10.4093/dmj.2019.0153] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Accepted: 10/02/2019] [Indexed: 01/11/2023] Open
Abstract
The link of diabetes with co-occurring disorders in the brain involves complex and multifactorial pathways. Genetically engineered rodents that express familial Alzheimer's disease-associated mutant forms of amyloid precursor protein and presenilin 1 (PSEN1) genes provided invaluable insights into the mechanisms and consequences of amyloid deposition in the brain. Adding diabetes factors (obesity, insulin impairment) to these animal models to predict success in translation to clinic have proven useful at some extent only. Here, we focus on contributing factors to diabetic brain injury with the aim of identifying appropriate animal models that can be used to mechanistically dissect the pathophysiology of diabetes-associated cognitive dysfunction and how diabetes medications may influence the development and progression of cognitive decline in humans with diabetes.
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Affiliation(s)
- Nirmal Verma
- Department of Pharmacology and Nutritional Sciences, College of Medicine, University of Kentucky, Lexington, KY, USA
| | - Florin Despa
- Department of Pharmacology and Nutritional Sciences, College of Medicine, University of Kentucky, Lexington, KY, USA
- Department of Neurology, College of Medicine, University of Kentucky, Lexington, KY, USA.
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16
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Abstract
Cognitive dysfunction is increasingly recognized as an important comorbidity of diabetes mellitus. Different stages of diabetes-associated cognitive dysfunction exist, each with different cognitive features, affected age groups and prognoses and probably with different underlying mechanisms. Relatively subtle, slowly progressive cognitive decrements occur in all age groups. More severe stages, particularly mild cognitive impairment and dementia, with progressive deficits, occur primarily in older individuals (>65 years of age). Patients in the latter group are the most relevant for patient management and are the focus of this Review. Here, we review the evolving insights from studies on risk factors, brain imaging and neuropathology, which provide important clues on mechanisms of both the subtle cognitive decrements and the more severe stages of cognitive dysfunction. In the majority of patients, the cognitive phenotype is probably defined by multiple aetiologies. Although both the risk of clinically diagnosed Alzheimer disease and that of vascular dementia is increased in association with diabetes, the cerebral burden of the prototypical pathologies of Alzheimer disease (such as neurofibrillary tangles and neuritic plaques) is not. A major challenge for researchers is to pinpoint from the spectrum of diabetes-related disease processes those that affect the brain and contribute to development of dementia beyond the pathologies of Alzheimer disease. Observations from experimental models can help to meet that challenge, but this requires further improving the synergy between experimental and clinical scientists. The development of targeted treatment and preventive strategies will therefore depend on these translational efforts.
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Affiliation(s)
- Geert Jan Biessels
- Department of Neurology, Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, Netherlands.
| | - Florin Despa
- Department of Pharmacology and Nutritional Sciences and Department of Neurology, University of Kentucky, Lexington, KY, USA
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17
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Mattson MP, Arumugam TV. Hallmarks of Brain Aging: Adaptive and Pathological Modification by Metabolic States. Cell Metab 2018; 27:1176-1199. [PMID: 29874566 PMCID: PMC6039826 DOI: 10.1016/j.cmet.2018.05.011] [Citation(s) in RCA: 592] [Impact Index Per Article: 98.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Revised: 05/02/2018] [Accepted: 05/15/2018] [Indexed: 02/06/2023]
Abstract
During aging, the cellular milieu of the brain exhibits tell-tale signs of compromised bioenergetics, impaired adaptive neuroplasticity and resilience, aberrant neuronal network activity, dysregulation of neuronal Ca2+ homeostasis, the accrual of oxidatively modified molecules and organelles, and inflammation. These alterations render the aging brain vulnerable to Alzheimer's and Parkinson's diseases and stroke. Emerging findings are revealing mechanisms by which sedentary overindulgent lifestyles accelerate brain aging, whereas lifestyles that include intermittent bioenergetic challenges (exercise, fasting, and intellectual challenges) foster healthy brain aging. Here we provide an overview of the cellular and molecular biology of brain aging, how those processes interface with disease-specific neurodegenerative pathways, and how metabolic states influence brain health.
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Affiliation(s)
- Mark P Mattson
- Laboratory of Neurosciences, National Institute on Aging Intramural Research Program, Baltimore, MD, USA; Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
| | - Thiruma V Arumugam
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore; School of Pharmacy, Sungkyunkwan University, Suwon 16419, Republic of Korea
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18
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Zhang S, Chai R, Yang YY, Guo SQ, Wang S, Guo T, Xu SF, Zhang YH, Wang ZY, Guo C. Chronic diabetic states worsen Alzheimer neuropathology and cognitive deficits accompanying disruption of calcium signaling in leptin-deficient APP/PS1 mice. Oncotarget 2018; 8:43617-43634. [PMID: 28467789 PMCID: PMC5546429 DOI: 10.18632/oncotarget.17116] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Accepted: 04/03/2017] [Indexed: 02/06/2023] Open
Abstract
The coincidences between Alzheimer’s disease (AD) and type 2 diabetes mellitus (T2DM) are so compelling that it is attractive to speculate that diabetic conditions might aggravate AD pathologies by calcium dysfunction, although the understanding of the molecular mechanisms involved remains elusive. The present work was undertaken to investigate whether calcium dyshomeostasis is associated with the exacerbated Alzheimer-like cognitive dysfunction observed in diabetic conditions in APP/PS1-ob/ob mice, which were generated by crossing ob/ob mice with APP/PS1 mice. We confirmed that the diabetic condition can aggravate not only Aβ deposition but also tau phosphorylation, synaptic loss, neuronal death, and inflammation, exacerbating cognitive impairment in AD mice. More importantly, we found that the diabetic condition dramatically elevated calcium levels in APP/PS1 mice, thereby stimulating the phosphorylation of the calcium-dependent kinases. Our findings suggest that controlling over-elevation of intracellular calcium may provide novel insights for approaching AD in diabetic patients and delaying AD progression.
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Affiliation(s)
- Shuai Zhang
- College of Life and Health Sciences, Northeastern University, Shenyang, China
| | - Rui Chai
- College of Life and Health Sciences, Northeastern University, Shenyang, China
| | - Ying-Ying Yang
- College of Life and Health Sciences, Northeastern University, Shenyang, China
| | - Shi-Qi Guo
- College of Life and Health Sciences, Northeastern University, Shenyang, China
| | - Shan Wang
- College of Life and Health Sciences, Northeastern University, Shenyang, China
| | - Tian Guo
- College of Life and Health Sciences, Northeastern University, Shenyang, China
| | - Shuang-Feng Xu
- College of Life and Health Sciences, Northeastern University, Shenyang, China
| | - Yan-Hui Zhang
- College of Life and Health Sciences, Northeastern University, Shenyang, China
| | - Zhan-You Wang
- College of Life and Health Sciences, Northeastern University, Shenyang, China
| | - Chuang Guo
- College of Life and Health Sciences, Northeastern University, Shenyang, China
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19
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Cordner RD, Friend LN, Mayo JL, Badgley C, Wallmann A, Stallings CN, Young PL, Miles DR, Edwards JG, Bridgewater LC. The BMP2 nuclear variant, nBMP2, is expressed in mouse hippocampus and impacts memory. Sci Rep 2017; 7:46464. [PMID: 28418030 PMCID: PMC5394474 DOI: 10.1038/srep46464] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2016] [Accepted: 03/20/2017] [Indexed: 12/23/2022] Open
Abstract
The novel nuclear protein nBMP2 is synthesized from the BMP2 gene by translational initiation at an alternative start codon. We generated a targeted mutant mouse, nBmp2NLStm, in which the nuclear localization signal (NLS) was inactivated to prevent nuclear translocation of nBMP2 while still allowing the normal synthesis and secretion of the BMP2 growth factor. These mice exhibit abnormal muscle function due to defective Ca2+ transport in skeletal muscle. We hypothesized that neurological function, which also depends on intracellular Ca2+ transport, could be affected by the loss of nBMP2. Age-matched nBmp2NLStm and wild type mice were analyzed by immunohistochemistry, behavioral tests, and electrophysiology to assess nBMP2 expression and neurological function. Immunohistochemical staining of the hippocampus detected nBMP2 in the nuclei of CA1 neurons in wild type but not mutant mice, consistent with nBMP2 playing a role in the hippocampus. Mutant mice showed deficits in the novel object recognition task, suggesting hippocampal dysfunction. Electrophysiology experiments showed that long-term potentiation (LTP) in the hippocampus, which is dependent on intracellular Ca2+ transport and is thought to be the cellular equivalent of learning and memory, was impaired. Together, these results suggest that nBMP2 in the hippocampus impacts memory formation.
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Affiliation(s)
- Ryan D. Cordner
- Department of Microbiology and Molecular Biology, Brigham Young University, Provo, Utah, USA
| | - Lindsey N. Friend
- Department of Physiology and Developmental Biology, Brigham Young University, Provo, Utah, USA
| | - Jaime L. Mayo
- Department of Microbiology and Molecular Biology, Brigham Young University, Provo, Utah, USA
| | - Corinne Badgley
- Department of Physiology and Developmental Biology, Brigham Young University, Provo, Utah, USA
| | - Andrew Wallmann
- Department of Physiology and Developmental Biology, Brigham Young University, Provo, Utah, USA
| | - Conrad N. Stallings
- Department of Microbiology and Molecular Biology, Brigham Young University, Provo, Utah, USA
| | - Peter L. Young
- Department of Microbiology and Molecular Biology, Brigham Young University, Provo, Utah, USA
| | - Darla R. Miles
- Department of Microbiology and Molecular Biology, Brigham Young University, Provo, Utah, USA
| | - Jeffrey G. Edwards
- Department of Physiology and Developmental Biology, Brigham Young University, Provo, Utah, USA
| | - Laura C. Bridgewater
- Department of Microbiology and Molecular Biology, Brigham Young University, Provo, Utah, USA
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20
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Calcium Hypothesis of Alzheimer's disease and brain aging: A framework for integrating new evidence into a comprehensive theory of pathogenesis. Alzheimers Dement 2017; 13:178-182.e17. [PMID: 28061328 DOI: 10.1016/j.jalz.2016.12.006] [Citation(s) in RCA: 215] [Impact Index Per Article: 30.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
This article updates the Calcium Hypothesis of Alzheimer's disease and brain aging on the basis of emerging evidence since 1994 (The present article, with the subtitle "New evidence for a central role of Ca2+ in neurodegeneration," includes three appendices that provide context and further explanations for the rationale for the revisions in the updated hypothesis-the three appendices are as follows: Appendix I "Emerging concepts on potential pathogenic roles of [Ca2+]," Appendix II "Future studies to validate the central role of dysregulated [Ca2+] in neurodegeneration," and Appendix III "Epilogue: towards a comprehensive hypothesis.") (Marx J. Fresh evidence points to an old suspect: calcium. Science 2007; 318:384-385). The aim is not only to re-evaluate the original key claims of the hypothesis with a critical eye but also to identify gaps in knowledge required to validate relevant claims and delineate additional studies and/or data that are needed. Some of the key challenges for this effort included examination of questions regarding (1) the temporal and spatial relationships of molecular mechanisms that regulate neuronal calcium ion (Ca2+), (2) the role of changes in concentration of calcium ion [Ca2+] in various subcellular compartments of neurons, (3) how alterations in Ca2+ signaling affect the performance of neurons under various conditions, ranging from optimal functioning in a healthy state to conditions of decline and deterioration in performance during aging and in disease, and (4) new ideas about the contributions of aging, genetic, and environmental factors to the causal relationships between dysregulation of [Ca2+] and the functioning of neurons (see Appendices I and II). The updated Calcium Hypothesis also includes revised postulates that are intended to promote further crucial experiments to confirm or reject the various predictions of the hypothesis (see Appendix III).
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21
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Dietary Reversal Ameliorates Short- and Long-Term Memory Deficits Induced by High-fat Diet Early in Life. PLoS One 2016; 11:e0163883. [PMID: 27676071 PMCID: PMC5038939 DOI: 10.1371/journal.pone.0163883] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Accepted: 09/15/2016] [Indexed: 02/06/2023] Open
Abstract
A high-fat diet (HFD), one of the major factors contributing to metabolic syndrome, which is associated with an increased risk of neurodegenerative diseases, leads to insulin resistance and cognitive impairment. It is not known whether these alterations are improved with dietary intervention. To investigate the long-term impact of a HFD on hippocampal insulin signaling and memory, C57BL6 mice were placed into one of three groups based on the diet: a standard diet (control), a HFD, or a HFD for 16 weeks and then the standard diet for 8 weeks (HF16). HFD-induced impairments in glucose tolerance and hippocampal insulin signaling occurred concurrently with deficits in both short- and long-term memory. Furthermore, these conditions were improved with dietary intervention; however, the HFD-induced decrease in insulin receptor expression in the hippocampus was not altered with dietary intervention. Our results demonstrate that memory deficits due to the consumption of a HFD at an early age are reversible.
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22
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Kim H, Kang H, Heo RW, Jeon BT, Yi CO, Shin HJ, Kim J, Jeong SY, Kwak W, Kim WH, Kang SS, Roh GS. Caloric restriction improves diabetes-induced cognitive deficits by attenuating neurogranin-associated calcium signaling in high-fat diet-fed mice. J Cereb Blood Flow Metab 2016; 36:1098-110. [PMID: 26661177 PMCID: PMC4908619 DOI: 10.1177/0271678x15606724] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Accepted: 08/03/2015] [Indexed: 01/09/2023]
Abstract
Diabetes-induced cognitive decline has been recognized in human patients of type 2 diabetes mellitus and mouse model of obesity, but the underlying mechanisms or therapeutic targets are not clearly identified. We investigated the effect of caloric restriction on diabetes-induced memory deficits and searched a molecular mechanism of caloric restriction-mediated neuroprotection. C57BL/6 mice were fed a high-fat diet for 40 weeks and RNA-seq analysis was performed in the hippocampus of high-fat diet-fed mice. To investigate caloric restriction effect on differential expression of genes, mice were fed high-fat diet for 20 weeks and continued on high-fat diet or subjected to caloric restriction (2 g/day) for 12 weeks. High-fat diet-fed mice exhibited insulin resistance, glial activation, blood-brain barrier leakage, and memory deficits, in that we identified neurogranin, a down-regulated gene in high-fat diet-fed mice using RNA-seq analysis; neurogranin regulates Ca(2+)/calmodulin-dependent synaptic function. Caloric restriction increased insulin sensitivity, reduced high-fat diet-induced blood-brain barrier leakage and glial activation, and improved memory deficit. Furthermore, caloric restriction reversed high-fat diet-induced expression of neurogranin and the activation of Ca(2+)/calmodulin-dependent protein kinase II and calpain as well as the downstream effectors. Our results suggest that neurogranin is an important factor of high-fat diet-induced memory deficits on which caloric restriction has a therapeutic effect by regulating neurogranin-associated calcium signaling.
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Affiliation(s)
- Hwajin Kim
- Department of Anatomy and Convergence Medical Science, Institute of Health Sciences, Gyeongsang National University School of Medicine, Jinju, Republic of Korea
| | - Heeyoung Kang
- Department of Neurology, Institute of Health Sciences, Gyeongsang National University School of Medicine, Gyeongsang National University Hospital, Jinju, Republic of Korea
| | - Rok Won Heo
- Department of Anatomy and Convergence Medical Science, Institute of Health Sciences, Gyeongsang National University School of Medicine, Jinju, Republic of Korea
| | - Byeong Tak Jeon
- Department of Neurologic Surgery, Mayo Clinic College of Medicine, Rochester, USA
| | - Chin-Ok Yi
- Department of Anatomy and Convergence Medical Science, Institute of Health Sciences, Gyeongsang National University School of Medicine, Jinju, Republic of Korea
| | - Hyun Joo Shin
- Department of Anatomy and Convergence Medical Science, Institute of Health Sciences, Gyeongsang National University School of Medicine, Jinju, Republic of Korea
| | - Jeonghyun Kim
- Department of Medical Genetics, Ajou University School of Medicine, Suwon, Republic of Korea
| | - Seon-Yong Jeong
- Department of Medical Genetics, Ajou University School of Medicine, Suwon, Republic of Korea
| | | | - Won-Ho Kim
- Division of Metabolic Diseases, Center for Biomedical Sciences, National Institute of Health, Osong, Republic of Korea
| | - Sang Soo Kang
- Department of Anatomy and Convergence Medical Science, Institute of Health Sciences, Gyeongsang National University School of Medicine, Jinju, Republic of Korea
| | - Gu Seob Roh
- Department of Anatomy and Convergence Medical Science, Institute of Health Sciences, Gyeongsang National University School of Medicine, Jinju, Republic of Korea
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Virmani A, Pinto L, Bauermann O, Zerelli S, Diedenhofen A, Binienda ZK, Ali SF, van der Leij FR. The Carnitine Palmitoyl Transferase (CPT) System and Possible Relevance for Neuropsychiatric and Neurological Conditions. Mol Neurobiol 2015; 52:826-36. [PMID: 26041663 DOI: 10.1007/s12035-015-9238-7] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2015] [Indexed: 12/30/2022]
Abstract
The carnitine palmitoyl transferase (CPT) system is a multiprotein complex with catalytic activity localized within a core represented by CPT1 and CPT2 in the outer and inner membrane of the mitochondria, respectively. Two proteins, the acyl-CoA synthase and a translocase also form part of this system. This system is crucial for the mitochondrial beta-oxidation of long-chain fatty acids. CPT1 has two well-known isoforms, CPT1a and CPT1b. CPT1a is the hepatic isoform and CPT1b is typically muscular; both are normally utilized by the organism for metabolic processes throughout the body. There is a strong evidence for their involvement in various disease states, e.g., metabolic syndrome, cardiovascular diseases, and in diabetes mellitus type 2. Recently, a new, third isoform of CPT was described, CPT1c. This is a neuronal isoform and is prevalently localized in brain regions such as hypothalamus, amygdala, and hippocampus. These brain regions play an important role in control of food intake and neuropsychiatric and neurological diseases. CPT activity has been implicated in several neurological and social diseases mainly related to the alteration of insulin equilibrium in the brain. These pathologies include Parkinson's disease, Alzheimer's disease, and schizophrenia. Evolution of both Parkinson's disease and Alzheimer's disease is in some way linked to brain insulin and related metabolic dysfunctions with putative links also with the diabetes type 2. Studies show that in the CNS, CPT1c affects ceramide levels, endocannabionoids, and oxidative processes and may play an important role in various brain functions such as learning.
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Affiliation(s)
- Ashraf Virmani
- Research, Innovation and Development, Sigma-tau Health Science International BV, Utrecht, Netherlands,
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24
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Maimaiti S, Anderson KL, DeMoll C, Brewer LD, Rauh BA, Gant JC, Blalock EM, Porter NM, Thibault O. Intranasal Insulin Improves Age-Related Cognitive Deficits and Reverses Electrophysiological Correlates of Brain Aging. J Gerontol A Biol Sci Med Sci 2015; 71:30-9. [PMID: 25659889 DOI: 10.1093/gerona/glu314] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Accepted: 12/23/2014] [Indexed: 12/25/2022] Open
Abstract
Peripheral insulin resistance is a key component of metabolic syndrome associated with obesity, dyslipidemia, hypertension, and type 2 diabetes. While the impact of insulin resistance is well recognized in the periphery, it is also becoming apparent in the brain. Recent studies suggest that insulin resistance may be a factor in brain aging and Alzheimer's disease (AD) whereby intranasal insulin therapy, which delivers insulin to the brain, improves cognition and memory in AD patients. Here, we tested a clinically relevant delivery method to determine the impact of two forms of insulin, short-acting insulin lispro (Humalog) or long-acting insulin detemir (Levemir), on cognitive functions in aged F344 rats. We also explored insulin effects on the Ca(2+)-dependent hippocampal afterhyperpolarization (AHP), a well-characterized neurophysiological marker of aging which is increased in the aged, memory impaired animal. Low-dose intranasal insulin improved memory recall in aged animals such that their performance was similar to that seen in younger animals. Further, because ex vivo insulin also reduced the AHP, our results suggest that the AHP may be a novel cellular target of insulin in the brain, and improved cognitive performance following intranasal insulin therapy may be the result of insulin actions on the AHP.
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Affiliation(s)
- Shaniya Maimaiti
- Department of Pharmacology and Nutritional Sciences, University of Kentucky Medical Center, Lexington, Kentucky
| | - Katie L Anderson
- Department of Pharmacology and Nutritional Sciences, University of Kentucky Medical Center, Lexington, Kentucky
| | - Chris DeMoll
- Department of Pharmacology and Nutritional Sciences, University of Kentucky Medical Center, Lexington, Kentucky
| | - Lawrence D Brewer
- Department of Pharmacology and Nutritional Sciences, University of Kentucky Medical Center, Lexington, Kentucky
| | - Benjamin A Rauh
- Department of Pharmacology and Nutritional Sciences, University of Kentucky Medical Center, Lexington, Kentucky
| | - John C Gant
- Department of Pharmacology and Nutritional Sciences, University of Kentucky Medical Center, Lexington, Kentucky
| | - Eric M Blalock
- Department of Pharmacology and Nutritional Sciences, University of Kentucky Medical Center, Lexington, Kentucky
| | - Nada M Porter
- Department of Pharmacology and Nutritional Sciences, University of Kentucky Medical Center, Lexington, Kentucky
| | - Olivier Thibault
- Department of Pharmacology and Nutritional Sciences, University of Kentucky Medical Center, Lexington, Kentucky.
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Short-lived diabetes in the young-adult ZDF rat does not exacerbate neuronal Ca(2+) biomarkers of aging. Brain Res 2014; 1621:214-21. [PMID: 25451110 DOI: 10.1016/j.brainres.2014.10.052] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Revised: 10/24/2014] [Accepted: 10/26/2014] [Indexed: 12/31/2022]
Abstract
Results from clinical studies provide evidence that cognitive changes relatively late in life may be traced to antecedent conditions including diabetes, obesity, a sedentary lifestyle, and an atherogenic diet. As such, several traits of Type 2 diabetes (T2DM) could be considered pathogenic factors of aging, contributing to age-dependent cognitive decline and our susceptibility to Alzheimer's disease. It appears that both the duration of metabolic condition and the age of the individual, together can contribute to the potential impact on peripheral as well as brain health. Because of robust evidence that in animal models of aging, Ca(2+) dysregulation alters neuronal health, synaptic plasticity, and learning and memory processes, we tested the hypothesis that peripheral metabolic dysregulation could exacerbate Ca(2+) dysfunction in hippocampal CA1 neurons. Using intracellular/ extracellular electrophysiological and Ca(2+) imaging techniques, we show that Ca(2+)levels at rest or during synaptic stimulation, the Ca(2+)-dependent afterhyperpolarization, baseline field potentials, and short-term synaptic plasticity were not significantly altered in young-adult male Zucker diabetic fatty rats compare to their lean counterparts. Our observations suggest that early phases of T2DM characterized by high levels of glucose and insulin may be too transient to alter hippocampal CA1 physiology in this animal model of diabetes. These results are supported by clinical data showing that longer T2DM duration can have greater negative impact on cognitive functions. This article is part of a Special Issue entitled SI: Brain and Memory.
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26
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Niedowicz DM, Reeves VL, Platt TL, Kohler K, Beckett TL, Powell DK, Lee TL, Sexton TR, Song ES, Brewer LD, Latimer CS, Kraner SD, Larson KL, Ozcan S, Norris CM, Hersh LB, Porter NM, Wilcock DM, Murphy MP. Obesity and diabetes cause cognitive dysfunction in the absence of accelerated β-amyloid deposition in a novel murine model of mixed or vascular dementia. Acta Neuropathol Commun 2014; 2:64. [PMID: 24916066 PMCID: PMC4229778 DOI: 10.1186/2051-5960-2-64] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Accepted: 06/04/2014] [Indexed: 01/18/2023] Open
Abstract
Mid-life obesity and type 2 diabetes mellitus (T2DM) confer a modest, increased risk for Alzheimer's disease (AD), though the underlying mechanisms are unknown. We have created a novel mouse model that recapitulates features of T2DM and AD by crossing morbidly obese and diabetic db/db mice with APPΔNL/ΔNLx PS1P264L/P264L knock-in mice. These mice (db/AD) retain many features of the parental lines (e.g. extreme obesity, diabetes, and parenchymal deposition of β-amyloid (Aβ)). The combination of the two diseases led to additional pathologies-perhaps most striking of which was the presence of severe cerebrovascular pathology, including aneurysms and small strokes. Cortical Aβ deposition was not significantly increased in the diabetic mice, though overall expression of presenilin was elevated. Surprisingly, Aβ was not deposited in the vasculature or removed to the plasma, and there was no stimulation of activity or expression of major Aβ-clearing enzymes (neprilysin, insulin degrading enzyme, or endothelin-converting enzyme). The db/AD mice displayed marked cognitive impairment in the Morris Water Maze, compared to either db/db or APPΔNLx PS1P264L mice. We conclude that the diabetes and/or obesity in these mice leads to a destabilization of the vasculature, leading to strokes and that this, in turn, leads to a profound cognitive impairment and that this is unlikely to be directly dependent on Aβ deposition. This model of mixed or vascular dementia provides an exciting new avenue of research into the mechanisms underlying the obesity-related risk for age-related dementia, and will provide a useful tool for the future development of therapeutics.
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Mapping NAD(+) metabolism in the brain of ageing Wistar rats: potential targets for influencing brain senescence. Biogerontology 2013; 15:177-98. [PMID: 24337988 DOI: 10.1007/s10522-013-9489-5] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2013] [Accepted: 12/09/2013] [Indexed: 12/21/2022]
Abstract
Over the last decade, the importance of NAD(+) has expanded beyond its role as an essential cofactor for energy metabolism. NAD(+) has emerged as a major signalling molecule that serves as the sole substrate for several enzymatic reactions including the DNA repair enzyme, poly(ADP-ribose) polymerase (PARP), NAD-dependent protein deacetylases or CD38, and transcriptional factors by a new class of histone deacetylases known as sirtuins. NAD(+) levels are regulated by the metabolic status and cellular stress caused by oxidative stress and DNA damage. Since a detailed study of NAD(+) metabolism in the healthy ageing mammalian brain is nascent, we examined the effect of ageing on intracellular NAD(+) metabolism in different brain regions in female Wistar rats in young (3 months), middle aged (12 months) and older adults (24 months). Our results are the first to show a significant decline in intracellular NAD(+) levels and NAD:NADH ratio with ageing in the CNS, occurring in parallel to an increase in lipid peroxidation and protein oxidation (o- and m-tyrosine) and a decline in total antioxidant capacity. Hyperphosphorylation of H2AX levels was also observed together with increased PARP-1 and PARP-2 expression, and CD38 activity, concomitantly with reduced NAD(+) and ATP levels and SIRT1 function in the cortex, brainstem, hippocampus and cerebellum. Reduced activity of mitochondrial complex I-IV and impaired maximum mitochondrial respiration rate were also observed in the ageing rat brain. Among the multiple physiological pathways associated with NAD(+) catabolism, our discovery of CD38 as the major regulator of cellular NAD(+) levels in rat neurons indicates that CD38 is a promising therapeutic target for the treatment of age-related neurodegenerative diseases.
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