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Okazaki T, Hifumi T, Kawakita K, Shishido H, Ogawa D, Okauchi M, Shindo A, Kawanishi M, Tamiya T, Kuroda Y. Blood Glucose Variability: A Strong Independent Predictor of Neurological Outcomes in Aneurysmal Subarachnoid Hemorrhage. J Intensive Care Med 2016; 33:189-195. [PMID: 27630011 DOI: 10.1177/0885066616669328] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
PURPOSE In patients with aneurysmal subarachnoid hemorrhage (SAH), increased glucose variability (GV) is associated with increased mortality and cerebral infarction; however, there are no reports demonstrating an association between GV and neurological outcome. This study investigated whether GV had an independent effect on neurological outcomes in patients with SAH in the intensive care unit. MATERIALS AND METHODS Consecutive adult patients hospitalized with SAH between January 1, 2009, and May 31, 2015 (N = 122) were retrospectively reviewed. Univariate/multivariate analyses were performed to identify independent predictors of poor neurological outcome. Patients were divided according to the mean glucose level (80-139 vs 140-200 mg/dL) and further subdivided using quartiles (Q) of the standard deviation (SD, representing variability) of the glucose level (Q1, Q2 + 3, and Q4). RESULTS Unfavorable neurological outcomes occurred in 44.2% of the patients. On multiple regression analysis, age, Hunt and Kosnik grade, SD of glucose (odds ratio [OR], 1.09; 95% confidence interval [CI], 1.02-1.17; P < .01), and minimum blood glucose level (OR, 0.95; 95% CI, 0.91-0.99; P < .01) were significantly associated with unfavorable neurological outcomes. Both groups (mean glucose levels: 80-139 and 140-200 mg/dL groups) had increasing unfavorable neurological outcomes with increasing SD of glucose (Q1, 15.0%; Q2 + 3, 40.0%; Q4, 52.4% and Q1, 44.4%; Q2 + 3, 50%; Q4, 88.9% in the 80-139 and 140-200 mg/dL groups, respectively). Patients with minimum glucose of <90 mg/dL comprised >50% of unfavorable neurological outcome. CONCLUSION Increased GV was an independent predictor of unfavorable neurological outcomes in patients with SAH.
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Affiliation(s)
- Tomoya Okazaki
- 1 Emergency Medical Center, Kagawa University Hospital, Kagawa, Japan.,Dr. Okazaki and Dr. Hifumi contributed equally to this work
| | - Toru Hifumi
- 1 Emergency Medical Center, Kagawa University Hospital, Kagawa, Japan.,Dr. Okazaki and Dr. Hifumi contributed equally to this work
| | - Kenya Kawakita
- 1 Emergency Medical Center, Kagawa University Hospital, Kagawa, Japan
| | - Hajime Shishido
- 1 Emergency Medical Center, Kagawa University Hospital, Kagawa, Japan
| | - Daisuke Ogawa
- 2 Department of Neurosurgery, Kagawa University Hospital, Kagawa, Japan
| | - Masanobu Okauchi
- 2 Department of Neurosurgery, Kagawa University Hospital, Kagawa, Japan
| | - Atsushi Shindo
- 2 Department of Neurosurgery, Kagawa University Hospital, Kagawa, Japan
| | | | - Takashi Tamiya
- 2 Department of Neurosurgery, Kagawa University Hospital, Kagawa, Japan
| | - Yasuhiro Kuroda
- 1 Emergency Medical Center, Kagawa University Hospital, Kagawa, Japan
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152
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Insulin-Independent GABAA Receptor-Mediated Response in the Barrel Cortex of Mice with Impaired Met Activity. J Neurosci 2016; 36:3691-7. [PMID: 27030755 DOI: 10.1523/jneurosci.0006-16.2016] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2016] [Accepted: 02/22/2016] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED Autism spectrum disorder (ASD) is a neurodevelopmental disorder caused by genetic variants, susceptibility alleles, and environmental perturbations. The autism associated geneMETtyrosine kinase has been implicated in many behavioral domains and endophenotypes of autism, including abnormal neural signaling in human sensory cortex. We investigated somatosensory thalamocortical synaptic communication in mice deficient in Met activity in cortical excitatory neurons to gain insights into aberrant somatosensation characteristic of ASD. The ratio of excitation to inhibition is dramatically increased due to decreased postsynaptic GABAAreceptor-mediated inhibition in the trigeminal thalamocortical pathway of mice lacking active Met in the cerebral cortex. Furthermore, in contrast to wild-type mice, insulin failed to increase GABAAreceptor-mediated response in the barrel cortex of mice with compromised Met signaling. Thus, lacking insulin effects may be a risk factor in ASD pathogenesis. SIGNIFICANCE STATEMENT A proposed common cause of neurodevelopmental disorders is an imbalance in excitatory neural transmission, provided by the glutamatergic neurons, and the inhibitory signals from the GABAergic interneurons. Many genes associated with autism spectrum disorders impair synaptic transmission in the expected cell type. Previously, inactivation of the autism-associated Met tyrosine kinase receptor in GABAergic interneurons led to decreased inhibition. In thus report, decreased Met signaling in glutamatergic neurons had no effect on excitation, but decimated inhibition. Further experiments indicate that loss of Met activity downregulates GABAAreceptors on glutamatergic neurons in an insulin independent manner. These data provide a new mechanism for the loss of inhibition and subsequent abnormal excitation/inhibition balance and potential molecular candidates for treatment or prevention.
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153
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Pinheiro BS, Lemos C, Neutzling Kaufmann F, Marques JM, da Silva-Santos CS, Carvalho E, Mackie K, Rodrigues RJ, Cunha RA, Köfalvi A. Hierarchical glucocorticoid-endocannabinoid interplay regulates the activation of the nucleus accumbens by insulin. Brain Res Bull 2016; 124:222-30. [PMID: 27208730 DOI: 10.1016/j.brainresbull.2016.05.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Revised: 05/16/2016] [Accepted: 05/17/2016] [Indexed: 12/28/2022]
Abstract
Here we asked if insulin activation of the nucleus accumbens in vitro is reflected by an increase in (3)H-deoxyglucose ([(3)H]DG) uptake, thus subserving a new model to study molecular mechanisms of central insulin actions. Additionally, we investigated the dependence of this insulin effect on endocannabinoids and corticosteroids, two major culprits in insulin resistance. We found that in acute accumbal slices, insulin (3 and 300nM but not at 0.3nM) produced an increase in [(3)H]DG uptake. The synthetic cannabinoid agonist, WIN55212-2 (500nM) and the glucocorticoid dexamethasone (10μM), impaired insulin (300nM) action on [(3)H]DG uptake. The glucocorticoid receptor (GcR) antagonist, mifepristone (10μM) prevented dexamethasone from inhibiting insulin's action. Strikingly, this anti-insulin action of dexamethasone was also blocked by two CB1 cannabinoid receptor (CB1R) antagonists, O-2050 (500nM) and SR141716A (500nM), as well as by tetrahydrolipstatin (10μM), an inhibitor of diacylglycerol lipases-the enzymes responsible for the synthesis of the endocannabinoid, 2-arachidonoyl-glycerol (2-AG). On the other hand, the blockade of the post-synaptic 2-AG metabolizing enzymes, α,β-serine hydrolase domain 6/12 by WWL70 (1μM) also prevented the action of insulin, probably via increasing endogenous 2-AG tone. Additionally, an anti-insulin receptor (InsR) antibody immunoprecipitated CB1Rs from accumbal homogenates, indicating a physical complexing of CB1Rs with InsRs that supports their functional interaction. Altogether, insulin stimulates glucose uptake in the nucleus accumbens. Accumbal GcR activation triggers the synthesis of 2-AG that in turn binds to the known CB1R-InsR heteromer, thus impeding insulin signaling.
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Affiliation(s)
- Bárbara S Pinheiro
- CNC, Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Cristina Lemos
- CNC, Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal
| | | | - Joana M Marques
- CNC, Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Carla S da Silva-Santos
- CNC, Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Eugénia Carvalho
- CNC, Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Ken Mackie
- Department of Psychological and Brain Sciences, Gill Center for Biomolecular Science, Indiana University, Bloomington, IN, USA
| | - Ricardo J Rodrigues
- CNC, Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal; Institute for Interdisciplinary Research, University of Coimbra, 3030-789 Coimbra, Portugal
| | - Rodrigo A Cunha
- CNC, Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal; FMUC, Faculty of Medicine, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Attila Köfalvi
- CNC, Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal; Institute for Interdisciplinary Research, University of Coimbra, 3030-789 Coimbra, Portugal.
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154
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The glucagon-like peptide 1 (GLP) receptor as a therapeutic target in Parkinson's disease: mechanisms of action. Drug Discov Today 2016; 21:802-18. [DOI: 10.1016/j.drudis.2016.01.013] [Citation(s) in RCA: 188] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Revised: 12/03/2015] [Accepted: 01/25/2016] [Indexed: 02/06/2023]
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155
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Affiliation(s)
| | - Vera Novak
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
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156
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Insulin Stimulates S100B Secretion and These Proteins Antagonistically Modulate Brain Glucose Metabolism. Neurochem Res 2016; 41:1420-9. [PMID: 26875731 DOI: 10.1007/s11064-016-1851-y] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2015] [Revised: 01/21/2016] [Accepted: 01/26/2016] [Indexed: 12/24/2022]
Abstract
Brain metabolism is highly dependent on glucose, which is derived from the blood circulation and metabolized by the astrocytes and other neural cells via several pathways. Glucose uptake in the brain does not involve insulin-dependent glucose transporters; however, this hormone affects the glucose influx to the brain. Changes in cerebrospinal fluid levels of S100B (an astrocyte-derived protein) have been associated with alterations in glucose metabolism; however, there is no evidence whether insulin modulates glucose metabolism and S100B secretion. Herein, we investigated the effect of S100B on glucose metabolism, measuring D-(3)H-glucose incorporation in two preparations, C6 glioma cells and acute hippocampal slices, and we also investigated the effect of insulin on S100B secretion. Our results showed that: (a) S100B at physiological levels decreases glucose uptake, through the multiligand receptor RAGE and mitogen-activated protein kinase/ERK signaling, and (b) insulin stimulated S100B secretion via PI3K signaling. Our findings indicate the existence of insulin-S100B modulation of glucose utilization in the brain tissue, and may improve our understanding of glucose metabolism in several conditions such as ketosis, streptozotocin-induced dementia and pharmacological exposure to antipsychotics, situations that lead to changes in insulin signaling and extracellular levels of S100B.
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157
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Pang Y, Lin S, Wright C, Shen J, Carter K, Bhatt A, Fan LW. Intranasal insulin protects against substantia nigra dopaminergic neuronal loss and alleviates motor deficits induced by 6-OHDA in rats. Neuroscience 2016; 318:157-65. [PMID: 26777890 DOI: 10.1016/j.neuroscience.2016.01.020] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Revised: 12/22/2015] [Accepted: 01/08/2016] [Indexed: 01/04/2023]
Abstract
Protection of substantia nigra (SN) dopaminergic (DA) neurons by neurotrophic factors (NTFs) is one of the promising strategies in Parkinson's disease (PD) therapy. A major clinical challenge for NTF-based therapy is that NTFs need to be delivered into the brain via invasive means, which often shows limited delivery efficiency. The nose to brain pathway is a non-invasive brain drug delivery approach developed in recent years. Of particular interest is the finding that intranasal insulin improves cognitive functions in Alzheimer's patients. In vitro, insulin has been shown to protect neurons against various insults. Therefore, the current study was designed to test whether intranasal insulin could afford neuroprotection in the 6-hydroxydopamine (6-OHDA)-based rat PD model. 6-OHDA was injected into the right side of striatum to induce a progressive DA neuronal lesion in the ipsilateral SN pars compact (SNc). Recombinant human insulin was applied intranasally to rats starting from 24h post lesion, once per day, for 2 weeks. A battery of motor behavioral tests was conducted on day 8 and 15. The number of DA neurons in the SNc was estimated by stereological counting. Our results showed that 6-OHDA injection led to significant motor deficits and 53% of DA neuron loss in the ipsilateral side of injection. Treatment with insulin significantly ameliorated 6-OHDA-induced motor impairments, as shown by improved locomotor activity, tapered/ledged beam-walking performance, vibrissa-elicited forelimb-placing, initial steps, as well as methamphetamine-induced rotational behavior. Consistent with behavioral improvements, insulin treatment provided a potent protection of DA neurons in the SNc against 6-OHDA neurotoxicity, as shown by a 74.8% increase in tyrosine hydroxylase (TH)-positive neurons compared to the vehicle group. Intranasal insulin treatment did not affect body weight and blood glucose levels. In conclusion, our study showed that intranasal insulin provided strong neuroprotection in the 6-OHDA rat PD model, suggesting that insulin signaling may be a novel therapeutic target in broad neurodegenerative disorders.
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Affiliation(s)
- Y Pang
- Department of Pediatrics, University of Mississippi Medical Center, Jackson, MS 39216, United States.
| | - S Lin
- Department of Pediatrics, University of Mississippi Medical Center, Jackson, MS 39216, United States
| | - C Wright
- Department of Pediatrics, University of Mississippi Medical Center, Jackson, MS 39216, United States
| | - J Shen
- Department of Pediatrics, University of Mississippi Medical Center, Jackson, MS 39216, United States
| | - K Carter
- Department of Pediatrics, University of Mississippi Medical Center, Jackson, MS 39216, United States
| | - A Bhatt
- Department of Pediatrics, University of Mississippi Medical Center, Jackson, MS 39216, United States
| | - L-W Fan
- Department of Pediatrics, University of Mississippi Medical Center, Jackson, MS 39216, United States
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158
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Lazard D, Vardi P, Bloch K. Anti-diabetic and neuroprotective effects of pancreatic islet transplantation into the central nervous system. Diabetes Metab Res Rev 2016; 32:11-20. [PMID: 25708430 DOI: 10.1002/dmrr.2644] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Accepted: 02/19/2015] [Indexed: 12/19/2022]
Abstract
During the last decades, the central nervous system (CNS) was intensively tested as a site for islet transplantation in different animal models of diabetes. Immunoprivilege properties of intracranial and intrathecal sites were found to delay and reduce rejection of transplanted allo-islets and xeno-islets, especially in the form of dispersed single cells. Insulin released from islets grafted in CNS was shown to cross the blood-brain barrier and to act as a regulator of peripheral glucose metabolism. In diabetic animals, sufficient nutrition and oxygen supply to islets grafted in the CNS provide adequate insulin response to increase glucose level resulting in rapid normoglycemia. In addition to insulin, pancreatic islets produce and secrete several other hormones, as well as neurotrophic and angiogenic factors with potential neuroprotective properties. Recent experimental studies and clinical trials provide a strong support for delivery of islet-derived macromolecules to CNS as a promising strategy to treat various brain disorders. This review article focuses mainly on analysis of current status of intracranial and intrathecal islet transplantations for treatment of experimental diabetes and discusses the possible neuroprotective properties of grafted islets into CNS as a novel therapeutic approach to brain disorders with cognitive dysfunctions characterized by impaired brain insulin signalling. Copyright © 2015 John Wiley & Sons, Ltd.
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MESH Headings
- Animals
- Blood-Brain Barrier
- Brain
- Central Nervous System
- Diabetes Mellitus, Type 1/blood
- Diabetes Mellitus, Type 1/complications
- Diabetes Mellitus, Type 1/metabolism
- Diabetes Mellitus, Type 1/surgery
- Diabetes Mellitus, Type 2/blood
- Diabetes Mellitus, Type 2/complications
- Diabetes Mellitus, Type 2/metabolism
- Diabetes Mellitus, Type 2/surgery
- Diabetic Neuropathies/prevention & control
- Disease Models, Animal
- Humans
- Hyperglycemia/prevention & control
- Hypoglycemia/prevention & control
- Insulin/metabolism
- Insulin Resistance
- Insulin Secretion
- Islets of Langerhans Transplantation/adverse effects
- Spinal Cord
- Subarachnoid Space
- Transplantation, Heterologous/adverse effects
- Transplantation, Heterotopic/adverse effects
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Affiliation(s)
- Daniel Lazard
- Laboratory of Diabetes and Obesity Research, Felsenstein Medical Research Center, Sackler School of Medicine, Tel Aviv University, Petah Tikva, Israel
| | - Pnina Vardi
- Laboratory of Diabetes and Obesity Research, Felsenstein Medical Research Center, Sackler School of Medicine, Tel Aviv University, Petah Tikva, Israel
| | - Konstantin Bloch
- Laboratory of Diabetes and Obesity Research, Felsenstein Medical Research Center, Sackler School of Medicine, Tel Aviv University, Petah Tikva, Israel
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159
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Rosiglitazone improves learning and memory ability in rats with type 2 diabetes through the insulin signaling pathway. Am J Med Sci 2015; 350:121-8. [PMID: 25973687 DOI: 10.1097/maj.0000000000000499] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Diabetes mellitus (DM) is associated with moderate cognitive deficits and neurophysiologic and structural changes in the brain, a condition that is referred to as diabetic encephalopathy. This study was performed to investigate the effect of rosiglitazone (RSG) on learning and memory in rats with DM and elucidate possible mechanisms underlying this condition. Thirty-two male Sprague-Dawley rats were randomly divided into 4 groups: control (C, n = 8), DM (n = 8), RSG-administered control (C + RSG, n = 8) and RSG-administered DM groups (DM + RSG, n = 8). At 8 weeks after drug administration, Morris water maze was used to perform a training and probe trial to detect spatial learning and memory abilities. Western blot and immunohistochemistry were also used to detect changes in proteins involved in the insulin signal transduction pathway, such as the insulin receptor, insulin receptor substrate-1, protein kinase B, phosphorylated cAMP response element-binding protein and B-cell lymphoma 2, in the hippocampus of the rats. This study found that RSG could normalize the impaired insulin signal transduction in type 2 DM. The authors showed that RSG modulated the central insulin signaling axis.
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160
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Differential interaction of Apolipoprotein-E isoforms with insulin receptors modulates brain insulin signaling in mutant human amyloid precursor protein transgenic mice. Sci Rep 2015; 5:13842. [PMID: 26346625 PMCID: PMC4561911 DOI: 10.1038/srep13842] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Accepted: 08/07/2015] [Indexed: 12/12/2022] Open
Abstract
It is unclear how human apolipoprotein E4 (ApoE4) increases the risk for Alzheimer’s disease (AD). Although Aβ levels can lead to insulin signaling impairment, these experiments were done in the absence of human ApoE. To examine ApoE role, we crossed the human ApoE-targeted replacement mice with mutant human amyloid precursor protein (APP) mice. In 26 week old mice with lower Aβ levels, the expression and phosphorylation of insulin signaling proteins remained comparable among APP, ApoE3xAPP and ApoE4xAPP mouse brains. When the mice aged to 78 weeks, these proteins were markedly reduced in APP and ApoE4xAPP mouse brains. While Aβ can bind to insulin receptor, how ApoE isoforms modulate this interaction remains unknown. Here, we showed that ApoE3 had greater association with insulin receptor as compared to ApoE4, regardless of Aβ42 concentration. In contrast, ApoE4 bound more Aβ42 with increasing peptide levels. Using primary hippocampal neurons, we showed that ApoE3 and ApoE4 neurons are equally sensitive to physiological levels of insulin. However, in the presence of Aβ42, insulin failed to elicit a downstream response only in ApoE4 hippocampal neurons. Taken together, our data show that ApoE genotypes can modulate this Aβ-mediated insulin signaling impairment.
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161
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Duarte JMN. Metabolic Alterations Associated to Brain Dysfunction in Diabetes. Aging Dis 2015; 6:304-21. [PMID: 26425386 DOI: 10.14336/ad.2014.1104] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Accepted: 11/04/2014] [Indexed: 12/13/2022] Open
Abstract
From epidemiological studies it is known that diabetes patients display increased risk of developing dementia. Moreover, cognitive impairment and Alzheimer's disease (AD) are also accompanied by impaired glucose homeostasis and insulin signalling. Although there is plenty of evidence for a connection between insulin-resistant diabetes and AD, definitive linking mechanisms remain elusive. Cerebrovascular complications of diabetes, alterations in glucose homeostasis and insulin signalling, as well as recurrent hypoglycaemia are the factors that most likely affect brain function and structure. While difficult to study in patients, the mechanisms by which diabetes leads to brain dysfunction have been investigated in experimental models that display phenotypes of the disease. The present article reviews the impact of diabetes and AD on brain structure and function, and discusses recent findings from translational studies in animal models that link insulin resistance to metabolic alterations that underlie brain dysfunction. Such modifications of brain metabolism are likely to occur at early stages of neurodegeneration and impact regional neurochemical profiles and constitute non-invasive biomarkers detectable by magnetic resonance spectroscopy (MRS).
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Affiliation(s)
- João M N Duarte
- Laboratory for Functional and Metabolic Imaging (LIFMET), École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
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162
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Exendin-4, a glucagon-like peptide-1 receptor agonist, reduces Alzheimer disease-associated tau hyperphosphorylation in the hippocampus of rats with type 2 diabetes. J Investig Med 2015; 63:267-72. [PMID: 25479064 DOI: 10.1097/jim.0000000000000129] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
BACKGROUND Impaired insulin signaling pathway in the brain in type 2 diabetes (T2D) is a risk factor for Alzheimer disease (AD). Glucagon-like peptide-1 (GLP-1) and its receptor agonist are widely used for treatment of T2D. Here we studied whether the effects of exendin-4 (EX-4), a long-lasting GLP-1 receptor agonist, could reduce the risk of AD in T2D. MATERIALS AND METHODS Type 2 diabetes rats were injected with EX-4 for 28 consecutive days. Blood glucose and insulin levels, as well as GLP-1 and insulin in cerebrospinal fluid, were determined during the experiment. The phosphorylation level of tau at individual phosphorylation sites, the activities of phosphatidylinositol 3 kinase/protein kinase B (PI3K/AKT), and glycogen synthase kinase-3β (GSK-3β) were analyzed with Western blots. RESULTS The levels of phosphorylated tau protein at site Ser199/202 and Thr217 level in the hippocampus of T2D rats were found to be raised notably and evidently decreased after EX-4 intervention. In addition, brain insulin signaling pathway was ameliorated after EX-4 treatment, and this result was reflected by a decreased activity of PI3K/AKT and an increased activity of GSK-3β in the hippocampus of T2D rats as well as a rise in PI3K/AKT activity and a decline in GSK-3β activity after 4 weeks intervention of EX-4. CONCLUSIONS These results demonstrate that multiple days with EX-4 appears to prevent the hyperphosphorylation of AD-associated tau protein due to increased insulin signaling pathway in the brain. These findings support the potential use of GLP-1 for the prevention and treatment of AD in individuals with T2D.
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163
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Garwood CJ, Ratcliffe LE, Morgan SV, Simpson JE, Owens H, Vazquez-Villaseñor I, Heath PR, Romero IA, Ince PG, Wharton SB. Insulin and IGF1 signalling pathways in human astrocytes in vitro and in vivo; characterisation, subcellular localisation and modulation of the receptors. Mol Brain 2015; 8:51. [PMID: 26297026 PMCID: PMC4546315 DOI: 10.1186/s13041-015-0138-6] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Accepted: 08/02/2015] [Indexed: 12/20/2022] Open
Abstract
Background The insulin/IGF1 signalling (IIS) pathways are involved in longevity regulation and are dysregulated in neurons in Alzheimer’s disease (AD). We previously showed downregulation in IIS gene expression in astrocytes with AD-neuropathology progression, but IIS in astrocytes remains poorly understood. We therefore examined the IIS pathway in human astrocytes and developed models to reduce IIS at the level of the insulin or the IGF1 receptor (IGF1R). Results We determined IIS was present and functional in human astrocytes by immunoblotting and showed astrocytes express the insulin receptor (IR)-B isoform of Ir. Immunocytochemistry and cell fractionation followed by western blotting revealed the phosphorylation status of insulin receptor substrate (IRS1) affects its subcellular localisation. To validate IRS1 expression patterns observed in culture, expression of key pathway components was assessed on post-mortem AD and control tissue using immunohistochemistry. Insulin signalling was impaired in cultured astrocytes by treatment with insulin + fructose and resulted in decreased IR and Akt phosphorylation (pAkt S473). A monoclonal antibody against IGF1R (MAB391) induced degradation of IGF1R receptor with an associated decrease in downstream pAkt S473. Neither treatment affected cell growth or viability as measured by MTT and Cyquant® assays or GFAP immunoreactivity. Discussion IIS is functional in astrocytes. IR-B is expressed in astrocytes which differs from the pattern in neurons, and may be important in differential susceptibility of astrocytes and neurons to insulin resistance. The variable presence of IRS1 in the nucleus, dependent on phosphorylation pattern, suggests the function of signalling molecules is not confined to cytoplasmic cascades. Down-regulation of IR and IGF1R, achieved by insulin + fructose and monoclonal antibody treatments, results in decreased downstream signalling, though the lack of effect on viability suggests that astrocytes can compensate for changes in single pathways. Changes in signalling in astrocytes, as well as in neurons, may be important in ageing and neurodegeneration. Electronic supplementary material The online version of this article (doi:10.1186/s13041-015-0138-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Claire J Garwood
- Sheffield Institute for Translational Neuroscience, Department of Neuroscience, The University of Sheffield, 385a Glossop Road, Sheffield, S10 2HQ, UK
| | - Laura E Ratcliffe
- Sheffield Institute for Translational Neuroscience, Department of Neuroscience, The University of Sheffield, 385a Glossop Road, Sheffield, S10 2HQ, UK
| | - Sarah V Morgan
- Sheffield Institute for Translational Neuroscience, Department of Neuroscience, The University of Sheffield, 385a Glossop Road, Sheffield, S10 2HQ, UK
| | - Julie E Simpson
- Sheffield Institute for Translational Neuroscience, Department of Neuroscience, The University of Sheffield, 385a Glossop Road, Sheffield, S10 2HQ, UK
| | - Helen Owens
- Sheffield Institute for Translational Neuroscience, Department of Neuroscience, The University of Sheffield, 385a Glossop Road, Sheffield, S10 2HQ, UK
| | - Irina Vazquez-Villaseñor
- Sheffield Institute for Translational Neuroscience, Department of Neuroscience, The University of Sheffield, 385a Glossop Road, Sheffield, S10 2HQ, UK
| | - Paul R Heath
- Sheffield Institute for Translational Neuroscience, Department of Neuroscience, The University of Sheffield, 385a Glossop Road, Sheffield, S10 2HQ, UK
| | - Ignacio A Romero
- Biomedical Research Network, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK
| | - Paul G Ince
- Sheffield Institute for Translational Neuroscience, Department of Neuroscience, The University of Sheffield, 385a Glossop Road, Sheffield, S10 2HQ, UK
| | - Stephen B Wharton
- Sheffield Institute for Translational Neuroscience, Department of Neuroscience, The University of Sheffield, 385a Glossop Road, Sheffield, S10 2HQ, UK.
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164
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Pandey SP, Singh HK, Prasad S. Alterations in Hippocampal Oxidative Stress, Expression of AMPA Receptor GluR2 Subunit and Associated Spatial Memory Loss by Bacopa monnieri Extract (CDRI-08) in Streptozotocin-Induced Diabetes Mellitus Type 2 Mice. PLoS One 2015; 10:e0131862. [PMID: 26161865 PMCID: PMC4498885 DOI: 10.1371/journal.pone.0131862] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Accepted: 06/09/2015] [Indexed: 01/21/2023] Open
Abstract
Bacopa monnieri extract has been implicated in the recovery of memory impairments due to various neurological disorders in animal models and humans. However, the precise molecular mechanism of the role of CDRI-08, a well characterized fraction of Bacopa monnieri extract, in recovery of the diabetes mellitus-induced memory impairments is not known. Here, we demonstrate that DM2 mice treated orally with lower dose of CDRI-08 (50- or 100 mg/kg BW) is able to significantly enhance spatial memory in STZ-DM2 mice and this is correlated with a significant decline in oxidative stress and up regulation of the AMPA receptor GluR2 subunit gene expression in the hippocampus. Treatment of DM2 mice with its higher dose (150 mg/kg BW or above) shows anti-diabetic effect in addition to its ability to recover the spatial memory impairment by reversing the DM2-induced elevated oxidative stress and decreased GluR2 subunit expression near to their values in normal and CDRI-08 treated control mice. Our results provide evidences towards molecular basis of the memory enhancing and anti diabetic role of the Bacopa monnieri extract in STZ-induced DM2 mice, which may have therapeutic implications.
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MESH Headings
- Animals
- Bacopa/chemistry
- CA3 Region, Hippocampal/drug effects
- CA3 Region, Hippocampal/metabolism
- Diabetes Mellitus, Experimental/drug therapy
- Diabetes Mellitus, Experimental/metabolism
- Diabetes Mellitus, Experimental/psychology
- Diabetes Mellitus, Type 2/drug therapy
- Diabetes Mellitus, Type 2/metabolism
- Diabetes Mellitus, Type 2/psychology
- Drug Evaluation, Preclinical
- Gene Expression/drug effects
- Hypoglycemic Agents/pharmacology
- Hypoglycemic Agents/therapeutic use
- Male
- Malondialdehyde/metabolism
- Maze Learning
- Memory Disorders/drug therapy
- Memory Disorders/metabolism
- Mice
- Oxidative Stress
- Plant Extracts/pharmacology
- Plant Extracts/therapeutic use
- Receptors, AMPA/genetics
- Receptors, AMPA/metabolism
- Spatial Memory/drug effects
- Streptozocin
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Affiliation(s)
- Surya P. Pandey
- Biochemistry & Molecular Biology Lab, Centre of Advanced Study in Zoology, Banaras Hindu University, Varanasi, 221005, Uttar Pradesh, India
| | - Hemant K. Singh
- Lumen Research Foundation, Ashok Nagar, Chennai, 600083, Tamilnadu, India
| | - S. Prasad
- Biochemistry & Molecular Biology Lab, Centre of Advanced Study in Zoology, Banaras Hindu University, Varanasi, 221005, Uttar Pradesh, India
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165
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Kornelius E, Lin C, Chang H, Li H, Huang W, Yang Y, Lu Y, Peng C, Huang C. DPP-4 Inhibitor Linagliptin Attenuates Aβ-induced Cytotoxicity through Activation of AMPK in Neuronal Cells. CNS Neurosci Ther 2015; 21:549-57. [PMID: 26010513 PMCID: PMC5033019 DOI: 10.1111/cns.12404] [Citation(s) in RCA: 98] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Revised: 04/05/2015] [Accepted: 04/15/2015] [Indexed: 12/13/2022] Open
Abstract
AIM It is now clear that insulin signaling has important roles in regulation of neuronal functions in the brain. Dysregulation of brain insulin signaling has been linked to neurodegenerative disease, particularly Alzheimer's disease (AD). In this regard, there is evidence that improvement of neuronal insulin signaling has neuroprotective activity against amyloid β (Aβ)-induced neurotoxicity for patients with AD. Linagliptin is an inhibitor of dipeptidylpeptidase-4 (DPP-4), which improves impaired insulin secretion and insulin downstream signaling in the in peripheral tissues. However, whether the protective effects of linagliptin involved in Aβ-mediated neurotoxicity have not yet been investigated. METHODS In the present study, we evaluated the mechanisms by which linagliptin protects against Aβ-induced impaired insulin signaling and cytotoxicity in cultured SK-N-MC human neuronal cells. RESULTS Our results showed that Aβ impairs insulin signaling and causes cell death. However, linagliptin significantly protected against Aβ-induced cytotoxicity, and prevented the activation of glycogen synthase kinase 3β (GSK3β) and tau hyperphosphorylation by restoring insulin downstream signaling. Furthermore, linagliptin alleviated Aβ-induced mitochondrial dysfunction and intracellular ROS generation, which may be due to the activation of 5' AMP-activated protein kinase (AMPK)-Sirt1 signaling. This upregulation of Sirt1 expression was also observed in diabetic patients with AD coadministration of linagliptin. CONCLUSIONS Taken together, our findings suggest linagliptin can restore the impaired insulin signaling caused by Aβ in neuronal cells, suggesting DPP-4 inhibitors may have therapeutic potential for reducing Aβ-induced impairment of insulin signaling and neurotoxicity in AD pathogenesis.
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Affiliation(s)
- Edy Kornelius
- Division of Endocrinology and MetabolismDepartment of Internal MedicineChung Shan Medical University HospitalTaichungTaiwan
- Institute of MedicineChung Shan Medical UniversityTaichungTaiwan
| | - Chih‐Li Lin
- Institute of MedicineChung Shan Medical UniversityTaichungTaiwan
- Department of Medical ResearchChung Shan Medical University HospitalTaichungTaiwan
| | - Hsiu‐Han Chang
- Institute of MedicineChung Shan Medical UniversityTaichungTaiwan
| | - Hsin‐Hua Li
- Institute of MedicineChung Shan Medical UniversityTaichungTaiwan
| | - Wen‐Nung Huang
- Institute of MedicineChung Shan Medical UniversityTaichungTaiwan
| | - Yi‐Sun Yang
- Division of Endocrinology and MetabolismDepartment of Internal MedicineChung Shan Medical University HospitalTaichungTaiwan
- Institute of MedicineChung Shan Medical UniversityTaichungTaiwan
| | - Ying‐Li Lu
- Division of Endocrinology and MetabolismDepartment of Internal MedicineChung Shan Medical University HospitalTaichungTaiwan
- Institute of MedicineChung Shan Medical UniversityTaichungTaiwan
| | - Chiung‐Huei Peng
- Division of Basic Medical ScienceHungkuang UniversityTaichungTaiwan
| | - Chien‐Ning Huang
- Division of Endocrinology and MetabolismDepartment of Internal MedicineChung Shan Medical University HospitalTaichungTaiwan
- Institute of MedicineChung Shan Medical UniversityTaichungTaiwan
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166
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Gong Y, Ma Y, Sinyuk M, Loganathan S, Thompson RC, Sarkaria JN, Chen W, Lathia JD, Mobley BC, Clark SW, Wang J. Insulin-mediated signaling promotes proliferation and survival of glioblastoma through Akt activation. Neuro Oncol 2015; 18:48-57. [PMID: 26136493 DOI: 10.1093/neuonc/nov096] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Accepted: 05/07/2015] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND Metabolic complications such as obesity, hyperglycemia, and type 2 diabetes are associated with poor outcomes in patients with glioblastoma. To control peritumoral edema, use of chronic high-dose steroids in glioblastoma patients is common, which can result in de novo diabetic symptoms. These metabolic complications may affect tumors via profound mechanisms, including activation of insulin receptor (InsR) and the related insulin-like growth factor 1 receptor (IGF1R) in malignant cells. METHODS In the present study, we assessed expression of InsR in glioblastoma surgical specimens and glioblastoma response to insulin at physiologically relevant concentrations. We further determined whether genetic or pharmacological targeting of InsR affected oncogenic functions of glioblastoma in vitro and in vivo. RESULTS We showed that InsR was commonly expressed in glioblastoma surgical specimens and xenograft tumor lines, with mitogenic isoform-A predominating. Insulin at physiologically relevant concentrations promoted glioblastoma cell growth and survival, potentially via Akt activation. Depletion of InsR impaired cellular functions and repressed orthotopic tumor growth. The absence of InsR compromised downstream Akt activity, but yet stimulated IGF1R expression. Targeting both InsR and IGF1R with dual kinase inhibitors resulted in effective blockade of downstream signaling, loss of cell viability, and repression of xenograft tumor growth. CONCLUSIONS Taken together, our work suggests that glioblastoma is sensitive to the mitogenic functions of insulin, thus significant insulin exposure imposes risks to glioblastoma patients. Additionally, dual inhibition of InsR and IGF1R exhibits promise for treating glioblastoma.
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Affiliation(s)
- Yuanying Gong
- Department of Neurological Surgery (Y.G., Y.M., R.C.T., S.W.C., J.W.), Department of Molecular Physiology and Biophysics (W.C.), Department of Neurology (S.W.C.), Department of Pathology, Microbiology and Immunology (B.C.M.), and Department of Cancer Biology and Department of Pharmacology, Vanderbilt University, Nashville, Tennessee (J.W.); Department of Cellular and Molecular Medicine, Cleveland Clinic, Cleveland, Ohio (M.S., J.D.L.); Department of Neuroscience and Pharmacology, Meharry Medical College, Nashville, Tennessee (S.L.); Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (J.N.S.)
| | - Yufang Ma
- Department of Neurological Surgery (Y.G., Y.M., R.C.T., S.W.C., J.W.), Department of Molecular Physiology and Biophysics (W.C.), Department of Neurology (S.W.C.), Department of Pathology, Microbiology and Immunology (B.C.M.), and Department of Cancer Biology and Department of Pharmacology, Vanderbilt University, Nashville, Tennessee (J.W.); Department of Cellular and Molecular Medicine, Cleveland Clinic, Cleveland, Ohio (M.S., J.D.L.); Department of Neuroscience and Pharmacology, Meharry Medical College, Nashville, Tennessee (S.L.); Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (J.N.S.)
| | - Maksim Sinyuk
- Department of Neurological Surgery (Y.G., Y.M., R.C.T., S.W.C., J.W.), Department of Molecular Physiology and Biophysics (W.C.), Department of Neurology (S.W.C.), Department of Pathology, Microbiology and Immunology (B.C.M.), and Department of Cancer Biology and Department of Pharmacology, Vanderbilt University, Nashville, Tennessee (J.W.); Department of Cellular and Molecular Medicine, Cleveland Clinic, Cleveland, Ohio (M.S., J.D.L.); Department of Neuroscience and Pharmacology, Meharry Medical College, Nashville, Tennessee (S.L.); Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (J.N.S.)
| | - Sudan Loganathan
- Department of Neurological Surgery (Y.G., Y.M., R.C.T., S.W.C., J.W.), Department of Molecular Physiology and Biophysics (W.C.), Department of Neurology (S.W.C.), Department of Pathology, Microbiology and Immunology (B.C.M.), and Department of Cancer Biology and Department of Pharmacology, Vanderbilt University, Nashville, Tennessee (J.W.); Department of Cellular and Molecular Medicine, Cleveland Clinic, Cleveland, Ohio (M.S., J.D.L.); Department of Neuroscience and Pharmacology, Meharry Medical College, Nashville, Tennessee (S.L.); Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (J.N.S.)
| | - Reid C Thompson
- Department of Neurological Surgery (Y.G., Y.M., R.C.T., S.W.C., J.W.), Department of Molecular Physiology and Biophysics (W.C.), Department of Neurology (S.W.C.), Department of Pathology, Microbiology and Immunology (B.C.M.), and Department of Cancer Biology and Department of Pharmacology, Vanderbilt University, Nashville, Tennessee (J.W.); Department of Cellular and Molecular Medicine, Cleveland Clinic, Cleveland, Ohio (M.S., J.D.L.); Department of Neuroscience and Pharmacology, Meharry Medical College, Nashville, Tennessee (S.L.); Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (J.N.S.)
| | - Jann N Sarkaria
- Department of Neurological Surgery (Y.G., Y.M., R.C.T., S.W.C., J.W.), Department of Molecular Physiology and Biophysics (W.C.), Department of Neurology (S.W.C.), Department of Pathology, Microbiology and Immunology (B.C.M.), and Department of Cancer Biology and Department of Pharmacology, Vanderbilt University, Nashville, Tennessee (J.W.); Department of Cellular and Molecular Medicine, Cleveland Clinic, Cleveland, Ohio (M.S., J.D.L.); Department of Neuroscience and Pharmacology, Meharry Medical College, Nashville, Tennessee (S.L.); Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (J.N.S.)
| | - Wenbiao Chen
- Department of Neurological Surgery (Y.G., Y.M., R.C.T., S.W.C., J.W.), Department of Molecular Physiology and Biophysics (W.C.), Department of Neurology (S.W.C.), Department of Pathology, Microbiology and Immunology (B.C.M.), and Department of Cancer Biology and Department of Pharmacology, Vanderbilt University, Nashville, Tennessee (J.W.); Department of Cellular and Molecular Medicine, Cleveland Clinic, Cleveland, Ohio (M.S., J.D.L.); Department of Neuroscience and Pharmacology, Meharry Medical College, Nashville, Tennessee (S.L.); Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (J.N.S.)
| | - Justin D Lathia
- Department of Neurological Surgery (Y.G., Y.M., R.C.T., S.W.C., J.W.), Department of Molecular Physiology and Biophysics (W.C.), Department of Neurology (S.W.C.), Department of Pathology, Microbiology and Immunology (B.C.M.), and Department of Cancer Biology and Department of Pharmacology, Vanderbilt University, Nashville, Tennessee (J.W.); Department of Cellular and Molecular Medicine, Cleveland Clinic, Cleveland, Ohio (M.S., J.D.L.); Department of Neuroscience and Pharmacology, Meharry Medical College, Nashville, Tennessee (S.L.); Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (J.N.S.)
| | - Bret C Mobley
- Department of Neurological Surgery (Y.G., Y.M., R.C.T., S.W.C., J.W.), Department of Molecular Physiology and Biophysics (W.C.), Department of Neurology (S.W.C.), Department of Pathology, Microbiology and Immunology (B.C.M.), and Department of Cancer Biology and Department of Pharmacology, Vanderbilt University, Nashville, Tennessee (J.W.); Department of Cellular and Molecular Medicine, Cleveland Clinic, Cleveland, Ohio (M.S., J.D.L.); Department of Neuroscience and Pharmacology, Meharry Medical College, Nashville, Tennessee (S.L.); Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (J.N.S.)
| | - Stephen W Clark
- Department of Neurological Surgery (Y.G., Y.M., R.C.T., S.W.C., J.W.), Department of Molecular Physiology and Biophysics (W.C.), Department of Neurology (S.W.C.), Department of Pathology, Microbiology and Immunology (B.C.M.), and Department of Cancer Biology and Department of Pharmacology, Vanderbilt University, Nashville, Tennessee (J.W.); Department of Cellular and Molecular Medicine, Cleveland Clinic, Cleveland, Ohio (M.S., J.D.L.); Department of Neuroscience and Pharmacology, Meharry Medical College, Nashville, Tennessee (S.L.); Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (J.N.S.)
| | - Jialiang Wang
- Department of Neurological Surgery (Y.G., Y.M., R.C.T., S.W.C., J.W.), Department of Molecular Physiology and Biophysics (W.C.), Department of Neurology (S.W.C.), Department of Pathology, Microbiology and Immunology (B.C.M.), and Department of Cancer Biology and Department of Pharmacology, Vanderbilt University, Nashville, Tennessee (J.W.); Department of Cellular and Molecular Medicine, Cleveland Clinic, Cleveland, Ohio (M.S., J.D.L.); Department of Neuroscience and Pharmacology, Meharry Medical College, Nashville, Tennessee (S.L.); Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (J.N.S.)
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Candeias EM, Sebastião IC, Cardoso SM, Correia SC, Carvalho CI, Plácido AI, Santos MS, Oliveira CR, Moreira PI, Duarte AI. Gut-brain connection: The neuroprotective effects of the anti-diabetic drug liraglutide. World J Diabetes 2015; 6:807-827. [PMID: 26131323 PMCID: PMC4478577 DOI: 10.4239/wjd.v6.i6.807] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Revised: 01/30/2015] [Accepted: 05/18/2015] [Indexed: 02/05/2023] Open
Abstract
Long-acting glucagon-like peptide-1 (GLP-1) analogues marketed for type 2 diabetes (T2D) treatment have been showing positive and protective effects in several different tissues, including pancreas, heart or even brain. This gut secreted hormone plays a potent insulinotropic activity and an important role in maintaining glucose homeostasis. Furthermore, growing evidences suggest the occurrence of several commonalities between T2D and neurodegenerative diseases, insulin resistance being pointed as a main cause for cognitive decline and increased risk to develop dementia. In this regard, it has also been suggested that stimulation of brain insulin signaling may have a protective role against cognitive deficits. As GLP-1 receptors (GLP-1R) are expressed throughout the central nervous system and GLP-1 may cross the blood-brain-barrier, an emerging hypothesis suggests that they may be promising therapeutic targets against brain dysfunctional insulin signaling-related pathologies. Importantly, GLP-1 actions depend not only on the direct effect mediated by its receptor activation, but also on the gut-brain axis involving an exchange of signals between both tissues via the vagal nerve, thereby regulating numerous physiological functions (e.g., energy homeostasis, glucose-dependent insulin secretion, as well as appetite and weight control). Amongst the incretin/GLP-1 mimetics class of anti-T2D drugs with an increasingly described neuroprotective potential, the already marketed liraglutide emerged as a GLP-1R agonist highly resistant to dipeptidyl peptidase-4 degradation (thereby having an increased half-life) and whose systemic GLP-1R activity is comparable to that of native GLP-1. Importantly, several preclinical studies showed anti-apoptotic, anti-inflammatory, anti-oxidant and neuroprotective effects of liraglutide against T2D, stroke and Alzheimer disease (AD), whereas several clinical trials, demonstrated some surprising benefits of liraglutide on weight loss, microglia inhibition, behavior and cognition, and in AD biomarkers. Herein, we discuss the GLP-1 action through the gut-brain axis, the hormone’s regulation of some autonomic functions and liraglutide’s neuroprotective potential.
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168
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Bedse G, Di Domenico F, Serviddio G, Cassano T. Aberrant insulin signaling in Alzheimer's disease: current knowledge. Front Neurosci 2015; 9:204. [PMID: 26136647 PMCID: PMC4468388 DOI: 10.3389/fnins.2015.00204] [Citation(s) in RCA: 196] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Accepted: 05/22/2015] [Indexed: 12/18/2022] Open
Abstract
Alzheimer's disease (AD) is the most common form of dementia affecting elderly people. AD is a multifaceted pathology characterized by accumulation of extracellular neuritic plaques, intracellular neurofibrillary tangles (NFTs) and neuronal loss mainly in the cortex and hippocampus. AD etiology appears to be linked to a multitude of mechanisms that have not been yet completely elucidated. For long time, it was considered that insulin signaling has only peripheral actions but now it is widely accepted that insulin has neuromodulatory actions in the brain. Insulin signaling is involved in numerous brain functions including cognition and memory that are impaired in AD. Recent studies suggest that AD may be linked to brain insulin resistance and patients with diabetes have an increased risk of developing AD compared to healthy individuals. Indeed insulin resistance, increased inflammation and impaired metabolism are key pathological features of both AD and diabetes. However, the precise mechanisms involved in the development of AD in patients with diabetes are not yet fully understood. In this review we will discuss the role played by aberrant brain insulin signaling in AD. In detail, we will focus on the role of insulin signaling in the deposition of neuritic plaques and intracellular NFTs. Considering that insulin mitigates beta-amyloid deposition and phosphorylation of tau, pharmacological strategies restoring brain insulin signaling, such as intranasal delivery of insulin, could have significant therapeutic potential in AD treatment.
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Affiliation(s)
- Gaurav Bedse
- Department of Physiology and Pharmacology "V. Erspamer," Sapienza University of Rome Rome, Italy ; Department of Biochemical Sciences, Sapienza University of Rome Rome, Italy
| | - Fabio Di Domenico
- Department of Biochemical Sciences, Sapienza University of Rome Rome, Italy
| | - Gaetano Serviddio
- Department of Medical and Surgical Sciences, University of Foggia Foggia, Italy
| | - Tommaso Cassano
- Department of Clinical and Experimental Medicine, University of Foggia Foggia, Italy
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Lioutas VA, Alfaro-Martinez F, Bedoya F, Chung CC, Pimentel DA, Novak V. Intranasal Insulin and Insulin-Like Growth Factor 1 as Neuroprotectants in Acute Ischemic Stroke. Transl Stroke Res 2015; 6:264-75. [PMID: 26040423 DOI: 10.1007/s12975-015-0409-7] [Citation(s) in RCA: 79] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2015] [Revised: 04/16/2015] [Accepted: 05/13/2015] [Indexed: 12/22/2022]
Abstract
Treatment options for stroke remain limited. Neuroprotective therapies, in particular, have invariably failed to yield the expected benefit in stroke patients, despite robust theoretical and mechanistic background and promising animal data. Insulin and insulin-like growth factor 1 (IGF-1) play a pivotal role in critical brain functions, such as energy homeostasis, neuronal growth, and differentiation. They may exhibit neuroprotective properties in acute ischemic stroke based upon their vasodilatory, anti-inflammatory and antithrombotic effects, as well as improvements of functional connectivity, neuronal metabolism, neurotransmitter regulation, and remyelination. Intranasally administered insulin has demonstrated a benefit for prevention of cognitive decline in older people, and IGF-1 has shown potential benefit to improve functional outcomes in animal models of acute ischemic stroke. The intranasal route presents a feasible, tolerable, safe, and particularly effective administration route, bypassing the blood-brain barrier and maximizing distribution to the central nervous system (CNS), without the disadvantages of systemic side effects and first-pass metabolism. This review summarizes the neuroprotective potential of intranasally administered insulin and IGF-1 in stroke patients. We present the theoretical background and pathophysiologic mechanisms, animal and human studies of intranasal insulin and IGF-1, and the safety and feasibility of intranasal route for medication administration to the CNS.
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Affiliation(s)
- Vasileios-Arsenios Lioutas
- Department of Neurology, Division of Cerebrovascular Diseases, Beth Israel Deaconess Medical Center, 330 Brookline Avenue, Palmer 127, Boston, MA, 02215, USA,
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Giustina A, Berardelli R, Gazzaruso C, Mazziotti G. Insulin and GH-IGF-I axis: endocrine pacer or endocrine disruptor? Acta Diabetol 2015; 52:433-43. [PMID: 25118998 DOI: 10.1007/s00592-014-0635-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Accepted: 07/23/2014] [Indexed: 12/13/2022]
Abstract
Growth hormone/insulin-like growth factor (IGF) axis may play a role in maintaining glucose homeostasis in synergism with insulin. IGF-1 can directly stimulate glucose transport into the muscle through either IGF-1 or insulin/IGF-1 hybrid receptors. In severely decompensated diabetes including diabetic ketoacidosis, plasma levels of IGF-1 are low and insulin delivery into the portal system is required to normalize IGF-1 synthesis and bioavailability. Normalization of serum IGF-1 correlated with the improvement of glucose homeostasis during insulin therapy providing evidence for the use of IGF-1 as biomarker of metabolic control in diabetes. Taking apart the inherent mitogenic discussion, diabetes treatment using insulins with high affinity for the IGF-1 receptor may act as an endocrine pacer exerting a cardioprotective effect by restoring the right level of IGF-1 in bloodstream and target tissues, whereas insulins with low affinity for the IGF-1 receptor may lack this positive effect. An excessive and indirect stimulation of IGF-1 receptor due to sustained and chronic hyperinsulinemia over the therapeutic level required to overtake acute/chronic insulin resistance may act as endocrine disruptor as it may possibly increase the cardiovascular risk in the short and medium term and mitogenic/proliferative action in the long term. In conclusion, normal IGF-1 may be hypothesized to be a good marker of appropriate insulin treatment of the subject with diabetes and may integrate and make more robust the message coming from HbA1c in terms of prediction of cardiovascular risk.
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Affiliation(s)
- Andrea Giustina
- Chair of Endocrinology and Metabolism, University of Brescia - A.O. Spedali Civili di Brescia, 25123, Brescia, Italy,
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171
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Kim B, Feldman EL. Insulin resistance as a key link for the increased risk of cognitive impairment in the metabolic syndrome. Exp Mol Med 2015; 47:e149. [PMID: 25766618 PMCID: PMC4351418 DOI: 10.1038/emm.2015.3] [Citation(s) in RCA: 208] [Impact Index Per Article: 23.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Accepted: 11/19/2014] [Indexed: 02/07/2023] Open
Abstract
Metabolic syndrome (MetS) is a cluster of cardiovascular risk factors that includes obesity, diabetes, and dyslipidemia. Accumulating evidence implies that MetS contributes to the development and progression of Alzheimer's disease (AD); however, the factors connecting this association have not been determined. Insulin resistance (IR) is at the core of MetS and likely represent the key link between MetS and AD. In the central nervous system, insulin plays key roles in learning and memory, and AD patients exhibit impaired insulin signaling that is similar to that observed in MetS. As we face an alarming increase in obesity and T2D in all age groups, understanding the relationship between MetS and AD is vital for the identification of potential therapeutic targets. Recently, several diabetes therapies that enhance insulin signaling are being tested for a potential therapeutic benefit in AD and dementia. In this review, we will discuss MetS as a risk factor for AD, focusing on IR and the recent progress and future directions of insulin-based therapies.
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Affiliation(s)
- Bhumsoo Kim
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
| | - Eva L Feldman
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
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Tetrahydroxystilbene glucoside extends mouse life span via upregulating neural klotho and downregulating neural insulin or insulin-like growth factor 1. Neurobiol Aging 2015; 36:1462-70. [DOI: 10.1016/j.neurobiolaging.2014.11.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2013] [Revised: 10/26/2014] [Accepted: 11/04/2014] [Indexed: 02/08/2023]
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Chandramohan R, Pari L, Rathinam A, Sheikh BA. Tyrosol, a phenolic compound, ameliorates hyperglycemia by regulating key enzymes of carbohydrate metabolism in streptozotocin induced diabetic rats. Chem Biol Interact 2015; 229:44-54. [PMID: 25641191 DOI: 10.1016/j.cbi.2015.01.026] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Revised: 01/02/2015] [Accepted: 01/21/2015] [Indexed: 12/23/2022]
Abstract
The present study was designed to evaluate the effects of tyrosol, a phenolic compound, on the activities of key enzymes of carbohydrate metabolism in the control and streptozotocin-induced diabetic rats. Diabetes mellitus was induced in rats by a single intraperitoneal injection of streptozotocin (40 mg/kg body weight). Experimental rats were administered tyrosol 1 ml intra gastrically at the doses of 5, 10 and 20mg/kg body weight and glibenclamide 1 ml at a dose of 600 μg/kg body weight once a day for 45 days. At the end of the experimental period, diabetic control rats exhibited significant (p<0.05) increase in plasma glucose, glycosylated hemoglobin with significant (p<0.05) decrease in plasma insulin, total hemoglobin and body weight. The activities of key enzymes of carbohydrate metabolism such as phosphoenolpyruvate carboxykinase, fructose-1,6-bisphosphatase and glucose-6-phosphatase were significantly (p<0.05) increased and the activities of hexokinase and glucose-6-phosphate dehydrogenase were significantly (p<0.05) decreased in the liver and kidney of diabetic control rats. Further, antioxidants were lowered in diabetic control rats. A significant (p<0.05) decline in glycogen level in the liver and muscle and glycogen synthase activity in the liver and a significant (p<0.05) increase in the activity of liver glycogen phosphorylase were observed in diabetic control rats compared to normal control rats. Oral administration of tyrosol to diabetic rats reversed all the above mentioned biochemical parameters to near normal in a dose dependent manner. Tyrosol at a dose of 20mg/kg body weight showed the highest significant effect than the other two doses. Immunohistochemical staining of pancreas revealed that tyrosol treated diabetic rats showed increased insulin immunoreactive β-cells, which confirmed the biochemical findings. The observed results were compared with glibenclamide, a standard oral hypoglycemic drug. The results of the present study suggest that tyrosol decreases hyperglycemia, by its antioxidant effect.
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Affiliation(s)
- Ramasamy Chandramohan
- Department of Biochemistry and Biotechnology, Faculty of Science, Annamalai University, Annamalainagar 608002, Tamilnadu, India
| | - Leelavinothan Pari
- Department of Biochemistry and Biotechnology, Faculty of Science, Annamalai University, Annamalainagar 608002, Tamilnadu, India.
| | - Ayyasamy Rathinam
- Department of Biochemistry and Biotechnology, Faculty of Science, Annamalai University, Annamalainagar 608002, Tamilnadu, India
| | - Bashir Ahmad Sheikh
- Department of Biochemistry and Biotechnology, Faculty of Science, Annamalai University, Annamalainagar 608002, Tamilnadu, India
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Akintola AA, van Heemst D. Insulin, aging, and the brain: mechanisms and implications. Front Endocrinol (Lausanne) 2015; 6:13. [PMID: 25705204 PMCID: PMC4319489 DOI: 10.3389/fendo.2015.00013] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Accepted: 01/21/2015] [Indexed: 12/12/2022] Open
Abstract
There is now an impressive body of literature implicating insulin and insulin signaling in successful aging and longevity. New information from in vivo and in vitro studies concerning insulin and insulin receptors has extended our understanding of the physiological role of insulin in the brain. However, the relevance of these to aging and longevity remains to be elucidated. Here, we review advances in our understanding of the physiological role of insulin in the brain, how insulin gets into the brain, and its relevance to aging and longevity. Furthermore, we examine possible future therapeutic applications and implications of insulin in the context of available models of delayed and accelerated aging.
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Affiliation(s)
- Abimbola A. Akintola
- Department of Gerontology and Geriatrics, Leiden University Medical Center, Leiden, Netherlands
- *Correspondence: Abimbola A. Akintola, Department of Gerontology and Geriatrics, Leiden University Medical Center, C7-124, Albinusdreef 2, Leiden 2333 ZA, Netherlands e-mail:
| | - Diana van Heemst
- Department of Gerontology and Geriatrics, Leiden University Medical Center, Leiden, Netherlands
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175
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Gallardo-Moreno GB, González-Garrido AA, Gudayol-Ferré E, Guàrdia-Olmos J. Type 1 Diabetes Modifies Brain Activation in Young Patients While Performing Visuospatial Working Memory Tasks. J Diabetes Res 2015; 2015:703512. [PMID: 26266268 PMCID: PMC4525461 DOI: 10.1155/2015/703512] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Revised: 06/30/2015] [Accepted: 07/01/2015] [Indexed: 12/23/2022] Open
Abstract
In recent years, increasing attention has been paid to the effects of Type 1 Diabetes (T1D) on cognitive functions. T1D onset usually occurs during childhood, so it is possible that the brain could be affected during neurodevelopment. We selected young patients of normal intelligence with T1D onset during neurodevelopment, no complications from diabetes, and adequate glycemic control. The purpose of this study was to compare the neural BOLD activation pattern in a group of patients with T1D versus healthy control subjects while performing a visuospatial working memory task. Sixteen patients and 16 matched healthy control subjects participated. There was no significant statistical difference in behavioral performance between the groups, but, in accordance with our hypothesis, results showed distinct brain activation patterns. Control subjects presented the expected activations related to the task, whereas the patients had greater activation in the prefrontal inferior cortex, basal ganglia, posterior cerebellum, and substantia nigra. These different patterns could be due to compensation mechanisms that allow them to maintain a behavioral performance similar to that of control subjects.
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Affiliation(s)
- Geisa B. Gallardo-Moreno
- Instituto de Neurociencias, Universidad de Guadalajara, Francisco de Quevedo 180, Colonia Arcos Vallarta, 44130 Guadalajara, JAL, Mexico
- *Geisa B. Gallardo-Moreno:
| | - Andrés A. González-Garrido
- Instituto de Neurociencias, Universidad de Guadalajara, Francisco de Quevedo 180, Colonia Arcos Vallarta, 44130 Guadalajara, JAL, Mexico
| | - Esteban Gudayol-Ferré
- Facultad de Psicología, Universidad Michoacana de San Nicolás de Hidalgo, Francisco Villa 450, 58120 Morelia, MICH, Mexico
| | - Joan Guàrdia-Olmos
- Facultat de Psicologia, Universitat de Barcelona, Institut de Recerca en Cervell, Cognició i Conducta (IR3C), Passeig de la Vall d'Hebron 171, 08035 Barcelona, Spain
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176
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Cabral A, De Francesco PN, Perello M. Brain circuits mediating the orexigenic action of peripheral ghrelin: narrow gates for a vast kingdom. Front Endocrinol (Lausanne) 2015; 6:44. [PMID: 25870587 PMCID: PMC4378314 DOI: 10.3389/fendo.2015.00044] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Accepted: 03/11/2015] [Indexed: 11/26/2022] Open
Affiliation(s)
- Agustina Cabral
- Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology [Argentine Research Council (CONICET) and Scientific Research Commission, Province of Buenos Aires (CIC-PBA)], Buenos Aires, Argentina
| | - Pablo N. De Francesco
- Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology [Argentine Research Council (CONICET) and Scientific Research Commission, Province of Buenos Aires (CIC-PBA)], Buenos Aires, Argentina
| | - Mario Perello
- Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology [Argentine Research Council (CONICET) and Scientific Research Commission, Province of Buenos Aires (CIC-PBA)], Buenos Aires, Argentina
- *Correspondence: ;
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177
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Kapogiannis D, Boxer A, Schwartz JB, Abner EL, Biragyn A, Masharani U, Frassetto L, Petersen RC, Miller BL, Goetzl EJ. Dysfunctionally phosphorylated type 1 insulin receptor substrate in neural-derived blood exosomes of preclinical Alzheimer's disease. FASEB J 2014; 29:589-96. [PMID: 25342129 DOI: 10.1096/fj.14-262048] [Citation(s) in RCA: 250] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Insulin resistance causes diminished glucose uptake in similar regions of the brain in Alzheimer's disease (AD) and type 2 diabetes mellitus (DM2). Brain tissue studies suggested that insulin resistance is caused by low insulin receptor signaling attributable to its abnormal association with more phospho (P)-serine-type 1 insulin receptor substrate (IRS-1) and less P-tyrosine-IRS-1. Plasma exosomes enriched for neural sources by immunoabsorption were obtained once from 26 patients with AD, 20 patients with DM2, 16 patients with frontotemporal dementia (FTD), and matched case control subjects. At 2 time points, they were obtained from 22 others when cognitively normal and 1 to 10 yr later when diagnosed with AD. Mean exosomal levels of extracted P-serine 312-IRS-1 and P-pan-tyrosine-IRS-1 by ELISA and the ratio of P-serine 312-IRS-1 to P-pan-tyrosine-IRS-1 (insulin resistance factor, R) for AD and DM2 and P-serine 312-IRS-1 and R for FTD were significantly different from those for case control subjects. The levels of R for AD were significantly higher than those for DM2 or FTD. Stepwise discriminant modeling showed correct classification of 100% of patients with AD, 97.5% of patients with DM2, and 84% of patients with FTD. In longitudinal studies of 22 patients with AD, exosomal levels of P-serine 312-IRS-1, P-pan-tyrosine-IRS-1, and R were significantly different 1 to 10 yr before and at the time of diagnosis compared with control subjects. Insulin resistance reflected in R values from this blood test is higher for patients with AD, DM2, and FTD than case control subjects; higher for patients with AD than patients with DM2 or FTD; and accurately predicts development of AD up to 10 yr prior to clinical onset.
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Affiliation(s)
| | - Adam Boxer
- Memory and Aging Center, Department of Neurology, and
| | - Janice B Schwartz
- Jewish Home of San Francisco, San Francisco, California, USA; Department of Medicine, University of California-San Francisco Medical Center, San Francisco, California, USA
| | - Erin L Abner
- Sanders-Brown Center on Aging, University of Kentucky, Lexington, Kentucky, USA; and
| | - Arya Biragyn
- Intramural Research Program, National Institute on Aging, Baltimore, Maryland, USA
| | - Umesh Masharani
- Jewish Home of San Francisco, San Francisco, California, USA
| | - Lynda Frassetto
- Jewish Home of San Francisco, San Francisco, California, USA
| | | | | | - Edward J Goetzl
- Intramural Research Program, National Institute on Aging, Baltimore, Maryland, USA; Jewish Home of San Francisco, San Francisco, California, USA; Department of Medicine, University of California-San Francisco Medical Center, San Francisco, California, USA;
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178
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Disability in patients with multiple sclerosis: influence of insulin resistance, adiposity, and oxidative stress. Nutrition 2014; 30:268-73. [PMID: 24484677 DOI: 10.1016/j.nut.2013.08.001] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2013] [Revised: 06/06/2013] [Accepted: 08/04/2013] [Indexed: 01/05/2023]
Abstract
OBJECTIVE The aims of the present study were to report the prevalence of insulin resistance (IR) in patients with multiple sclerosis (MS); to verify differences in metabolic and inflammatory biomarkers, and oxidative stress in patients with MS with or without IR; and to assess if IR and adiposity are associated with disability in these patients. METHODS The study enrolled 110 patients with MS and 175 healthy individuals. Patients with MS were divided in those with IR (n = 44) and those without (n = 66). Metabolic and inflammatory markers, oxidative stress, and disability were evaluated by the Extended Disability Status Scale (EDSS). RESULTS IR prevalence was verified in 40% of the patients with MS and in 21.1% of the control group (odds ratio, 2.48; 95% confidence interval, 1.469-4.210; P = 0.0006). Patients with the disease and IR showed higher EDSS (P = 0.031), interleukin (IL)-6 (P = 0.028), IL-17 (P = 0.006), oxidative stress evaluated by tert-butyl hydroperoxide-initiated chemiluminescence (P = 0.029), and advanced oxidation protein products (P = 0.025) than those patients without IR. The multivariate analysis showed that disability was associated with IR evaluated by homeostasis model assessment of insulin resistance (P = 0.030) and adiposity evaluated by waist circumference (P = 0.0179) and body mass index (P = 0.0033). CONCLUSION This is the first study to demonstrate an increase IR prevalence and the association between IR and adiposity with disability assessed by EDSS in patients with MS. IR seems to be associated with chronic inflammatory process and oxidative stress in patients with MS. More studies are warranted to elucidate the mechanisms by which IR and adiposity could contribute to the progression and disability in patients with MS.
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179
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Kuang H, Sun M, Lv J, Li J, Wu C, Chen N, Bo L, Wei X, Gu X, Liu Z, Mao C, Xu Z. Hippocampal apoptosis involved in learning deficits in the offspring exposed to maternal high sucrose diets. J Nutr Biochem 2014; 25:985-90. [DOI: 10.1016/j.jnutbio.2014.04.012] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2013] [Revised: 03/28/2014] [Accepted: 04/26/2014] [Indexed: 01/24/2023]
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180
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Spielman LJ, Little JP, Klegeris A. Inflammation and insulin/IGF-1 resistance as the possible link between obesity and neurodegeneration. J Neuroimmunol 2014; 273:8-21. [PMID: 24969117 DOI: 10.1016/j.jneuroim.2014.06.004] [Citation(s) in RCA: 125] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2013] [Revised: 06/03/2014] [Accepted: 06/04/2014] [Indexed: 12/17/2022]
Abstract
Obesity is a growing epidemic that contributes to several brain disorders including Alzheimer's, Parkinson's, and Huntington's diseases. Obesity could promote these diseases through several different mechanisms. Here we review evidence supporting the involvement of two recently recognized factors linking obesity with neurodegeneration: the induction of pro-inflammatory cytokines and onset of insulin and insulin-like growth factor 1 (IGF-1) resistance. Excess peripheral pro-inflammatory mediators, some of which can cross the blood brain barrier, may trigger neuroinflammation, which subsequently exacerbates neurodegeneration. Insulin and IGF-1 resistance leads to weakening of neuroprotective signaling by these molecules and can contribute to onset of neurodegenerative diseases.
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Affiliation(s)
- Lindsay J Spielman
- Department of Biology, University of British Columbia Okanagan Campus, 3333 University Way, Kelowna, BC, V1V 1V7 Canada
| | - Jonathan P Little
- School of Health and Exercise Sciences, University of British Columbia Okanagan Campus, 3333 University Way, Kelowna, BC, V1V 1V7 Canada
| | - Andis Klegeris
- Department of Biology, University of British Columbia Okanagan Campus, 3333 University Way, Kelowna, BC, V1V 1V7 Canada.
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181
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Lazcano Z, Solis O, Bringas ME, Limón D, Diaz A, Espinosa B, García-Peláez I, Flores G, Guevara J. Unilateral injection of Aβ25-35in the hippocampus reduces the number of dendritic spines in hyperglycemic rats. Synapse 2014; 68:585-594. [DOI: 10.1002/syn.21770] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2014] [Accepted: 07/15/2014] [Indexed: 02/05/2023]
Affiliation(s)
- Zayda Lazcano
- Laboratorio de Neuropsiquiatría; Instituto de Fisiología Benemérita Universidad Autónoma de Puebla; Puebla México
| | - Oscar Solis
- Laboratorio de Neuropsiquiatría; Instituto de Fisiología Benemérita Universidad Autónoma de Puebla; Puebla México
| | - María Elena Bringas
- Laboratorio de Neuropsiquiatría; Instituto de Fisiología Benemérita Universidad Autónoma de Puebla; Puebla México
| | - Daniel Limón
- Laboratorio de Neurofarmacología, Facultad de Ciencias Químicas; Benemérita Universidad Autónoma de Puebla; Puebla México
| | - Alfonso Diaz
- Departamento de Farmacia, Facultad de Ciencias Químicas; Benemérita Universidad Autónoma de Puebla; Puebla México
- Laboratorio Experimental de Enfermedades Neurodegenerativas; Instituto Nacional de Neurología y Neurocirugía; Ciudad de México Distrito Federal México
- Departamento de Bioquímica, Facultad de Medicina; Universidad Nacional Autónoma de México; Ciudad de México Distrito Federal México
| | - Blanca Espinosa
- Laboratorio de Bioquímica, Instituto Nacional de Enfermedades Respiratorias; Ciudad de México Distrito Federal México
| | - Isabel García-Peláez
- Departamento de Biología Celular y Tisular, Facultad de Medicina; Universidad Nacional Autónoma de México; Ciudad de México Distrito Federal México
| | - Gonzalo Flores
- Laboratorio de Neuropsiquiatría; Instituto de Fisiología Benemérita Universidad Autónoma de Puebla; Puebla México
| | - Jorge Guevara
- Departamento de Bioquímica, Facultad de Medicina; Universidad Nacional Autónoma de México; Ciudad de México Distrito Federal México
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182
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Chmiel-Perzyńska I, Perzyński A, Urbańska EM. Experimental diabetes mellitus type 1 increases hippocampal content of kynurenic acid in rats. Pharmacol Rep 2014; 66:1134-9. [PMID: 25443746 DOI: 10.1016/j.pharep.2014.07.014] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Revised: 07/24/2014] [Accepted: 07/28/2014] [Indexed: 10/24/2022]
Abstract
BACKGROUND Diabetes mellitus (DM) is frequently associated with peripheral and central complications and has recently emerged as a risk factor for cognitive impairment and dementia. Kynurenic acid (KYNA), a unique tryptophan derivative, displays pleiotropic effects including blockade of ionotropic glutamate and α7 nicotinic receptors. Here, the influence of experimental diabetes on KYNA synthesis was studied in rat brain. METHODS DM was induced by i.p. administration of streptozotocin (STZ). Five weeks later, KYNA content and the activity of semi-purified kynurenine aminotransferases (KATs) were measured in frontal cortex, hippocampus and striatum of diabetic and insulin-treated rats, using HPLC-based methods. RESULTS Hippocampal but not cortical or striatal KYNA concentration was considerably increased during DM, either untreated or treated with insulin (220% and 170% of CTR, respectively). The activity of kynurenine aminotransferase I (KAT I) was not affected by DM in all of the studied structures. KAT II activity was moderately increased in cortex (145% of CTR) and hippocampus (126% of CTR), but not in striatum of diabetic animals. Insulin treatment normalized cortical but not hippocampal KAT II activity. CONCLUSIONS A novel factor potentially implicated in diabetic hippocampal dysfunction has been identified. Observed increase of KYNA level may stem from the activation of endogenous neuroprotection, however, it may also have negative impact on cognition.
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Affiliation(s)
| | | | - Ewa M Urbańska
- Medical University of Lublin, Lublin, Poland; Institute of Agricultural Medicine, Lublin, Poland.
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183
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Zhang J, Liu F. Tissue-specific insulin signaling in the regulation of metabolism and aging. IUBMB Life 2014; 66:485-95. [PMID: 25087968 DOI: 10.1002/iub.1293] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2014] [Accepted: 07/14/2014] [Indexed: 12/30/2022]
Abstract
In mammals, insulin signaling regulates glucose homeostasis and plays an essential role in metabolism, organ growth, development, fertility, and lifespan. The defects in this signaling pathway contribute to various metabolic diseases such as type 2 diabetes, polycystic ovarian disease, hypertension, hyperlipidemia, and atherosclerosis. However, reducing the insulin signaling pathway has been found to increase longevity and delay the aging-associated diseases in various animals, ranging from nematodes to mice. These seemly paradoxical findings raise an interesting question as to how modulation of the insulin signaling pathway could be an effective approach to improve metabolism and aging. In this review, we summarize current understanding on tissue-specific functions of insulin signaling in the regulation of metabolism and lifespan. We also discuss the potential benefits and limitations in modulating tissue-specific insulin signaling pathway to improve metabolism and healthspan.
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Affiliation(s)
- Jingjing Zhang
- Metabolic Syndrome Research Center, Key Laboratory of Diabetes Immunology, Ministry of Education; Diabetes Center, Institute of Metabolism and Endocrinology, Second Xiangya Hospital, Central South University, Changsha, Hunan, China
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184
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Duarte J, Schuck PF, Wenk GL, Ferreira GC. Metabolic disturbances in diseases with neurological involvement. Aging Dis 2014; 5:238-55. [PMID: 25110608 DOI: 10.14336/ad.2014.0500238] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2013] [Revised: 11/26/2013] [Accepted: 11/27/2013] [Indexed: 12/19/2022] Open
Abstract
Degeneration of specific neuronal populations and progressive nervous system dysfunction characterize neurodegenerative diseases, including Alzheimer's disease and Parkinson's disease. These findings are also reported in inherited diseases such as phenylketonuria and glutaric aciduria type I. The involvement of mitochondrial dysfunction in these diseases was reported, elicited by genetic alterations, exogenous toxins or buildup of toxic metabolites. In this review we shall discuss some metabolic alterations related to the pathophysiology of diseases with neurological involvement and aging process. These findings may help identifying early disease biomarkers and lead to more effective therapies to improve the quality of life of the patients affected by these devastating illnesses.
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Affiliation(s)
| | - Patrícia F Schuck
- Laboratory of inborn errors of metabolism, Universidade do Extremo Sul Catarinense, Brazil
| | - Gary L Wenk
- Department of Psychology, The Ohio State University, Columbus, OH 43210, USA
| | - Gustavo C Ferreira
- Laboratory of inborn errors of metabolism, Universidade do Extremo Sul Catarinense, Brazil
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185
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Sebastião I, Candeias E, Santos MS, de Oliveira CR, Moreira PI, Duarte AI. Insulin as a Bridge between Type 2 Diabetes and Alzheimer Disease - How Anti-Diabetics Could be a Solution for Dementia. Front Endocrinol (Lausanne) 2014; 5:110. [PMID: 25071725 PMCID: PMC4086025 DOI: 10.3389/fendo.2014.00110] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/21/2014] [Accepted: 06/24/2014] [Indexed: 12/13/2022] Open
Abstract
Type 2 diabetes (T2D) and Alzheimer disease (AD) are two major health issues nowadays. T2D is an ever increasing epidemic, affecting millions of elderly people worldwide, with major repercussions in the patients' daily life. This is mostly due to its chronic complications that may affect brain and constitutes a risk factor for AD. T2D principal hallmark is insulin resistance which also occurs in AD, rendering both pathologies more than mere unrelated diseases. This hypothesis has been reinforced in the recent years, with a high number of studies highlighting the existence of several common molecular links. As such, it is not surprising that AD has been considered as the "type 3 diabetes" or a "brain-specific T2D," supporting the idea that a beneficial therapeutic strategy against T2D might be also beneficial against AD. Herewith, we aim to review some of the recent developments on the common features between T2D and AD, namely on insulin signaling and its participation in the regulation of amyloid β (Aβ) plaque and neurofibrillary tangle formation (the two major neuropathological hallmarks of AD). We also critically analyze the promising field that some anti-T2D drugs may protect against dementia and AD, with a special emphasis on the novel incretin/glucagon-like peptide-1 receptor agonists.
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Affiliation(s)
- Inês Sebastião
- Center for Neuroscience and Cell Biology (CNC), University of Coimbra, Coimbra, Portugal
- Department of Life Sciences, University of Coimbra, Coimbra, Portugal
- Institute for Interdisciplinary Research (IIIUC), University of Coimbra, Coimbra, Portugal
| | - Emanuel Candeias
- Center for Neuroscience and Cell Biology (CNC), University of Coimbra, Coimbra, Portugal
- Institute for Interdisciplinary Research (IIIUC), University of Coimbra, Coimbra, Portugal
| | - Maria S. Santos
- Center for Neuroscience and Cell Biology (CNC), University of Coimbra, Coimbra, Portugal
- Department of Life Sciences, University of Coimbra, Coimbra, Portugal
- Institute for Interdisciplinary Research (IIIUC), University of Coimbra, Coimbra, Portugal
| | - Catarina R. de Oliveira
- Center for Neuroscience and Cell Biology (CNC), University of Coimbra, Coimbra, Portugal
- Institute of Biochemistry, Faculty of Medicine, University of Coimbra, Coimbra, Portugal
| | - Paula I. Moreira
- Center for Neuroscience and Cell Biology (CNC), University of Coimbra, Coimbra, Portugal
- Institute of Physiology, Faculty of Medicine, University of Coimbra, Coimbra, Portugal
| | - Ana I. Duarte
- Center for Neuroscience and Cell Biology (CNC), University of Coimbra, Coimbra, Portugal
- Institute for Interdisciplinary Research (IIIUC), University of Coimbra, Coimbra, Portugal
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186
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Roberts RO, Knopman DS, Cha RH, Mielke MM, Pankratz VS, Boeve BF, Kantarci K, Geda YE, Jack CR, Petersen RC, Lowe VJ. Diabetes and elevated hemoglobin A1c levels are associated with brain hypometabolism but not amyloid accumulation. J Nucl Med 2014; 55:759-64. [PMID: 24652830 PMCID: PMC4011952 DOI: 10.2967/jnumed.113.132647] [Citation(s) in RCA: 116] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
UNLABELLED Dysfunctional insulin signaling may affect brain metabolism or amyloid deposition. We investigated the associations of type 2 diabetes with amyloid accumulation measured using (11)C-Pittsburgh compound B ((11)C-PiB) and brain hypometabolism measured using (18)F-FDG PET. METHODS We studied a sample of nondemented participants from the population-based Mayo Clinic Study of Aging. All subjects underwent MR imaging, amyloid PET, and (18)F-FDG PET. Alzheimer disease (AD) signature and region-of-interest (ROI) measures for (11)C-PiB retention ratio and (18)F-FDG ratio were measured. Diabetes was assessed from the Rochester Epidemiology Project medical records linkage system. RESULTS Among 749 participants (median age, 79.0 y; 56.5% men, 81.0% cognitively normal; 20.6% diabetic individuals), (18)F-FDG hypometabolism ((18)F-FDG ratio < 1.31) in the AD signature meta-ROI was more common in diabetic individuals (48.1%) than in nondiabetic individuals (28.9%; P < 0.001). The median (18)F-FDG ratio was lower in diabetic individuals than in nondiabetic individuals in the AD signature meta-ROI (1.32 vs. 1.40, P < 0.001) and in the angular (1.40 vs. 1.48, P < 0.001) and posterior cingulate gyri ROIs (1.63 vs. 1.72, P < 0.001). The odds ratio (OR) for abnormal AD signature (18)F-FDG hypometabolism was elevated (2.28; 95% confidence interval [CI], 1.56-3.33) in diabetic individuals versus nondiabetic individuals after adjustment for age, sex, and education and after additional adjustment for apolipoprotein ε4 allele, glycemic level, and cognitive status (OR, 1.69; 95% CI, 1.10-2.60). However, the AD signature (11)C-PiB retention ratio was similar in diabetic individuals versus nondiabetic individuals (OR, 1.03; 95% CI, 0.71-1.51; P = 0.87). In post hoc analyses in nondiabetic individuals, a 1% increase in hemoglobin A1c was associated with greater AD signature hypometabolism in cognitively normal subjects (OR, 1.93; 95% CI, 1.03-3.62; P = 0.04) and in the total cohort (OR 1.59; 95% CI, 0.92-2.75; P = 0.10). CONCLUSION Diabetes and poor glycemic control in nondiabetic individuals may enhance glucose hypometabolism in AD signature regions. These factors should be investigated in longitudinal studies for their role in detecting onset of symptoms in AD.
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Affiliation(s)
- Rosebud O. Roberts
- Department of Health Sciences Research, Mayo Clinic, Rochester, MN
- Department of Neurology, Mayo Clinic, Rochester, MN
| | | | - Ruth H. Cha
- Department of Health Sciences Research, Mayo Clinic, Rochester, MN
| | | | | | | | | | - Yonas E. Geda
- Department of Psychiatry & Psychology, and Department of Neurology, Mayo Clinic, Scottsdale, AZ
| | | | - Ronald C. Petersen
- Department of Health Sciences Research, Mayo Clinic, Rochester, MN
- Department of Neurology, Mayo Clinic, Rochester, MN
| | - Val J. Lowe
- Department of Radiology, Mayo Clinic, Rochester, MN
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187
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Song J, Lee WT, Park KA, Lee JE. Association between risk factors for vascular dementia and adiponectin. BIOMED RESEARCH INTERNATIONAL 2014; 2014:261672. [PMID: 24860814 PMCID: PMC4016875 DOI: 10.1155/2014/261672] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Revised: 03/27/2014] [Accepted: 03/30/2014] [Indexed: 01/06/2023]
Abstract
Vascular dementia is caused by various factors, including increased age, diabetes, hypertension, atherosclerosis, and stroke. Adiponectin is an adipokine secreted by adipose tissue. Adiponectin is widely known as a regulating factor related to cardiovascular disease and diabetes. Adiponectin plasma levels decrease with age. Decreased adiponectin increases the risk of cardiovascular disease and diabetes. Adiponectin improves hypertension and atherosclerosis by acting as a vasodilator and antiatherogenic factor. Moreover, adiponectin is involved in cognitive dysfunction via modulation of insulin signal transduction in the brain. Case-control studies demonstrate the association between low adiponectin and increased risk of stroke, hypertension, and diabetes. This review summarizes the recent findings on the association between risk factors for vascular dementia and adiponectin. To emphasize this relationship, we will discuss the importance of research regarding the role of adiponectin in vascular dementia.
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Affiliation(s)
- Juhyun Song
- Department of Anatomy, Yonsei University College of Medicine, 50 Yonsei-ro, Seoul 120-752, Republic of Korea
| | - Won Taek Lee
- Department of Anatomy, Yonsei University College of Medicine, 50 Yonsei-ro, Seoul 120-752, Republic of Korea
| | - Kyung Ah Park
- Department of Anatomy, Yonsei University College of Medicine, 50 Yonsei-ro, Seoul 120-752, Republic of Korea
| | - Jong Eun Lee
- Department of Anatomy, Yonsei University College of Medicine, 50 Yonsei-ro, Seoul 120-752, Republic of Korea
- BK21 Plus Project for Medical Sciences and Brain Research Institute, Yonsei University College of Medicine, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-752, Republic of Korea
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Insulin, IGF-1 and GLP-1 signaling in neurodegenerative disorders: targets for disease modification? Prog Neurobiol 2014; 118:1-18. [PMID: 24582776 DOI: 10.1016/j.pneurobio.2014.02.005] [Citation(s) in RCA: 171] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Revised: 02/09/2014] [Accepted: 02/20/2014] [Indexed: 12/13/2022]
Abstract
Insulin and Insulin Growth Factor-1 (IGF-1) play a major role in body homeostasis and glucose regulation. They also have paracrine/autocrine functions in the brain. The Insulin/IGF-1 signaling pathway contributes to the control of neuronal excitability, nerve cell metabolism and cell survival. Glucagon like peptide-1 (GLP-1), known as an insulinotropic hormone has similar functions and growth like properties as insulin/IGF-1. Growing evidence suggests that dysfunction of these pathways contribute to the progressive loss of neurons in Alzheimer's disease (AD) and Parkinson's disease (PD), the two most frequent neurodegenerative disorders. These findings have led to numerous studies in preclinical models of neurodegenerative disorders targeting insulin/IGF-1 and GLP-1 signaling with currently available anti-diabetics. These studies have shown that administration of insulin, IGF-1 and GLP-1 agonists reverses signaling abnormalities and has positive effects on surrogate markers of neurodegeneration and behavioral outcomes. Several proof-of-concept studies are underway that attempt to translate the encouraging preclinical results to patients suffering from AD and PD. In the first part of this review, we discuss physiological functions of insulin/IGF-1 and GLP-1 signaling pathways including downstream targets and receptors distribution within the brain. In the second part, we undertake a comprehensive overview of preclinical studies targeting insulin/IGF-1 or GLP-1 signaling for treating AD and PD. We then detail the design of clinical trials that have used anti-diabetics for treating AD and PD patients. We close with future considerations that treat relevant issues for successful translation of these encouraging preclinical results into treatments for patients with AD and PD.
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189
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El Khoury NB, Gratuze M, Papon MA, Bretteville A, Planel E. Insulin dysfunction and Tau pathology. Front Cell Neurosci 2014; 8:22. [PMID: 24574966 PMCID: PMC3920186 DOI: 10.3389/fncel.2014.00022] [Citation(s) in RCA: 81] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Accepted: 01/16/2014] [Indexed: 01/26/2023] Open
Abstract
The neuropathological hallmarks of Alzheimer's disease (AD) include senile plaques of β-amyloid (Aβ) peptides (a cleavage product of the Amyloid Precursor Protein, or APP) and neurofibrillary tangles (NFT) of hyperphosphorylated Tau protein assembled in paired helical filaments (PHF). NFT pathology is important since it correlates with the degree of cognitive impairment in AD. Only a small proportion of AD is due to genetic variants, whereas the large majority of cases (~99%) is late onset and sporadic in origin. The cause of sporadic AD is likely to be multifactorial, with external factors interacting with biological or genetic susceptibilities to accelerate the manifestation of the disease. Insulin dysfunction, manifested by diabetes mellitus (DM) might be such factor, as there is extensive data from epidemiological studies suggesting that DM is associated with an increased relative risk for AD. Type 1 diabetes (T1DM) and type 2 diabetes (T2DM) are known to affect multiple cognitive functions in patients. In this context, understanding the effects of diabetes on Tau pathogenesis is important since Tau pathology show a strong relationship to dementia in AD, and to memory loss in normal aging and mild cognitive impairment. Here, we reviewed preclinical studies that link insulin dysfunction to Tau protein pathogenesis, one of the major pathological hallmarks of AD. We found more than 30 studies reporting Tau phosphorylation in a mouse or rat model of insulin dysfunction. We also payed attention to potential sources of artifacts, such as hypothermia and anesthesia, that were demonstrated to results in Tau hyperphosphorylation and could major confounding experimental factors. We found that very few studies reported the temperature of the animals, and only a handful did not use anesthesia. Overall, most published studies showed that insulin dysfunction can promote Tau hyperphosphorylation and pathology, both directly and indirectly, through hypothermia.
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Affiliation(s)
- Noura B El Khoury
- Département de Psychiatrie et Neurosciences, Faculté de Médecine, Université Laval Québec, QC, Canada ; Axe Neurosciences, Centre Hospitalier de l'Université Laval Québec, QC, Canada
| | - Maud Gratuze
- Département de Psychiatrie et Neurosciences, Faculté de Médecine, Université Laval Québec, QC, Canada ; Axe Neurosciences, Centre Hospitalier de l'Université Laval Québec, QC, Canada
| | - Marie-Amélie Papon
- Axe Neurosciences, Centre Hospitalier de l'Université Laval Québec, QC, Canada
| | - Alexis Bretteville
- Axe Neurosciences, Centre Hospitalier de l'Université Laval Québec, QC, Canada
| | - Emmanuel Planel
- Département de Psychiatrie et Neurosciences, Faculté de Médecine, Université Laval Québec, QC, Canada ; Axe Neurosciences, Centre Hospitalier de l'Université Laval Québec, QC, Canada
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190
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Mechanisms of action of brain insulin against neurodegenerative diseases. J Neural Transm (Vienna) 2014; 121:611-26. [PMID: 24398779 DOI: 10.1007/s00702-013-1147-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Accepted: 12/17/2013] [Indexed: 12/13/2022]
Abstract
Insulin, a pancreatic hormone, is best known for its peripheral effects on the metabolism of glucose, fats and proteins. There is a growing body of evidence linking insulin action in the brain to neurodegenerative diseases. Insulin present in central nervous system is a regulator of central glucose metabolism nevertheless this glucoregulation is not the main function of insulin in the brain. Brain is known to be specifically vulnerable to oxidative products relative to other organs and altered brain insulin signaling may cause or promote neurodegenerative diseases which invalidates and reduces the quality of life. Insulin located within the brain is mostly of pancreatic origin or is produced in the brain itself crosses the blood-brain barrier and enters the brain via a receptor-mediated active transport system. Brain Insulin, insulin receptor and insulin receptor substrate-mediated signaling pathways play important roles in the regulation of peripheral metabolism, feeding behavior, memory and maintenance of neural functions such as neuronal growth and differentiation, neuromodulation and neuroprotection. In the present review, we would like to summarize the novel biological and pathophysiological roles of neuronal insulin in neurodegenerative diseases and describe the main signaling pathways in use for therapeutic strategies in the use of insulin to the cerebral tissues and their biological applications to neurodegenerative diseases.
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Bloemer J, Bhattacharya S, Amin R, Suppiramaniam V. Impaired insulin signaling and mechanisms of memory loss. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2014; 121:413-49. [PMID: 24373245 DOI: 10.1016/b978-0-12-800101-1.00013-2] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Insulin is secreted from the β-cells of the pancreas and helps maintain glucose homeostasis. Although secreted peripherally, insulin also plays a profound role in cognitive function. Increasing evidence suggests that insulin signaling in the brain is necessary to maintain health of neuronal cells, promote learning and memory, decrease oxidative stress, and ultimately increase neuronal survival. This chapter summarizes the different facets of insulin signaling necessary for learning and memory and additionally explores the association between cognitive impairment and central insulin resistance. The role of impaired insulin signaling in the advancement of cognitive dysfunction is relevant to the current debate of whether the shared pathophysiological mechanisms between diabetes and cognitive impairment implicate a direct relationship. Here, we summarize a vast amount of literature that suggests a strong association between impaired brain insulin signaling and cognitive impairment.
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Affiliation(s)
- Jenna Bloemer
- Department of Pharmacal Sciences, Harrison School of Pharmacy, Auburn University, Auburn, Alabama, USA
| | - Subhrajit Bhattacharya
- Department of Pharmacal Sciences, Harrison School of Pharmacy, Auburn University, Auburn, Alabama, USA
| | - Rajesh Amin
- Department of Pharmacal Sciences, Harrison School of Pharmacy, Auburn University, Auburn, Alabama, USA
| | - Vishnu Suppiramaniam
- Department of Pharmacal Sciences, Harrison School of Pharmacy, Auburn University, Auburn, Alabama, USA
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Persiyantseva NA, Storozhevykh TP, Senilova YE, Gorbacheva LR, Pinelis VG, Pomytkin IA. Mitochondrial H2O2 as an enable signal for triggering autophosphorylation of insulin receptor in neurons. J Mol Signal 2013; 8:11. [PMID: 24094269 PMCID: PMC3817577 DOI: 10.1186/1750-2187-8-11] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2013] [Accepted: 10/03/2013] [Indexed: 11/22/2022] Open
Abstract
Background Insulin receptors are widely distributed in the brain, where they play roles in synaptic function, memory formation, and neuroprotection. Autophosphorylation of the receptor in response to insulin stimulation is a critical step in receptor activation. In neurons, insulin stimulation leads to a rise in mitochondrial H2O2 production, which plays a role in receptor autophosphorylation. However, the kinetic characteristics of the H2O2 signal and its functional relationships with the insulin receptor during the autophosphorylation process in neurons remain unexplored to date. Results Experiments were carried out in culture of rat cerebellar granule neurons. Kinetic study showed that the insulin-induced H2O2 signal precedes receptor autophosphorylation and represents a single spike with a peak at 5–10 s and duration of less than 30 s. Mitochondrial complexes II and, to a lesser extent, I are involved in generation of the H2O2 signal. The mechanism by which insulin triggers the H2O2 signal involves modulation of succinate dehydrogenase activity. Insulin dose–response for receptor autophosphorylation is well described by hyperbolic function (Hill coefficient, nH, of 1.1±0.1; R2=0.99). N-acetylcysteine (NAC), a scavenger of H2O2, dose-dependently inhibited receptor autophosphorylation. The observed dose response is highly sigmoidal (Hill coefficient, nH, of 8.0±2.3; R2=0.97), signifying that insulin receptor autophosphorylation is highly ultrasensitive to the H2O2 signal. These results suggest that autophosphorylation occurred as a gradual response to increasing insulin concentrations, only if the H2O2 signal exceeded a certain threshold. Both insulin-stimulated receptor autophosphorylation and H2O2 generation were inhibited by pertussis toxin, suggesting that a pertussis toxin-sensitive G protein may link the insulin receptor to the H2O2-generating system in neurons during the autophosphorylation process. Conclusions In this study, we demonstrated for the first time that the receptor autophosphorylation occurs only if mitochondrial H2O2 signal exceeds a certain threshold. This finding provides novel insights into the mechanisms underlying neuronal response to insulin. The neuronal insulin receptor is activated if two conditions are met: 1) insulin binds to the receptor, and 2) the H2O2 signal surpasses a certain threshold, thus, enabling receptor autophosphorylation in all-or-nothing manner. Although the physiological rationale for this control remains to be determined, we propose that malfunction of mitochondrial H2O2 signaling may lead to the development of cerebral insulin resistance.
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Thambisetty M, Jeffrey Metter E, Yang A, Dolan H, Marano C, Zonderman AB, Troncoso JC, Zhou Y, Wong DF, Ferrucci L, Egan J, Resnick SM, O'Brien RJ. Glucose intolerance, insulin resistance, and pathological features of Alzheimer disease in the Baltimore Longitudinal Study of Aging. JAMA Neurol 2013; 70:1167-72. [PMID: 23897112 PMCID: PMC3934653 DOI: 10.1001/jamaneurol.2013.284] [Citation(s) in RCA: 116] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
IMPORTANCE Peripheral glucose homeostasis has been implicated in the pathogenesis of Alzheimer disease (AD). The relationship among diabetes mellitus, insulin, and AD is an important area of investigation. However, whether cognitive impairment seen in those with diabetes is mediated by excess pathological features of AD or other related abnormalities, such as vascular disease, remains unclear. OBJECTIVE To investigate the association between serial measures of glucose intolerance and insulin resistance and in vivo brain β-amyloid burden, measured with carbon 11–labeled Pittsburgh Compound B (11C-PiB), and AD pathology at autopsy. DESIGN Scores calculated from the Consortium to Establish a Registry for Alzheimer’s Disease (CERAD) and Braak criteria were correlated with measures of hyperglycemia, hyperinsulinemia, glucose intolerance, and insulin resistance in 197 participants who underwent autopsy after death and who had undergone 2 or more oral glucose tolerance tests (OGTT) using grouped analyses and a continuous mixed-models analysis. The same measures of glucose intolerance and insulin resistance were also correlated with brain 11C-PiB retention in an additional 53 living subjects from the Baltimore Longitudinal Study of Aging neuroimaging study. SETTING Prospective, serially assessed cohort of community-dwelling subjects. PARTICIPANTS Cohort 1 consisted of 197 participants enrolled in the Baltimore Longitudinal Study of Aging who had 2 or more OGTTs during life and a complete brain autopsy after death. Cohort 2 consisted of 53 living subjects who had 2 or more OGTTs and underwent brain 11C-PiB positron emission tomography. EXPOSURES Autopsy and 11C-PiB positron emission tomography. MAIN OUTCOMES AND MEASURES The correlation of brain markers of AD, including CERAD score, Braak score, and 11C-PiB retention, with serum markers of glucose homeostasis using grouped and continuous mixed-models analyses. RESULTS We found no significant correlations between measures of brain AD pathology or 11C-PiB β-amyloid load and glucose intolerance or insulin resistance in subjects who had a mean (SD) of 6.4 (3.2) OGTTs during 22.1 (8.0) years of follow-up. Thirty subjects with frank diabetes mellitus who received medications also had AD pathology scores that were similar to those of the cohort as a whole. CONCLUSIONS AND RELEVANCE In this prospective cohort with multiple assessments of glucose intolerance and insulin resistance, measures of glucose and insulin homeostasis are not associated with AD pathology and likely play little role in AD pathogenesis. Long-term therapeutic trials are important to elucidate this issue.
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Sugimoto K, Baba M, Suzuki S, Yagihashi S. The impact of low-dose insulin on peripheral nerve insulin receptor signaling in streptozotocin-induced diabetic rats. PLoS One 2013; 8:e74247. [PMID: 24023699 PMCID: PMC3758356 DOI: 10.1371/journal.pone.0074247] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Accepted: 07/31/2013] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND The precise mechanisms of the neuroprotective effects of insulin in streptozotocin (STZ)-induced diabetic animals remain unknown, but altered peripheral nerve insulin receptor signaling due to insulin deficiency might be one cause. METHODOLOGY AND PRINCIPAL FINDINGS Diabetes was induced in 10-week-old, male Wistar rats by injecting them with STZ (45 mg/kg). They were assigned to one group that received half of an insulin implant (∼1 U/day; I-group, n = 11) or another that remained untreated (U-group, n = 10) for 6 weeks. The controls were age- and sex-matched, non-diabetic Wistar rats (C-group, n = 12). Low-dose insulin did not change haemoglobin A1c, which increased by 136% in the U-group compared with the C-group. Thermal hypoalgesia and mechanical hyperalgesia developed in the U-group, but not in the I-group. Sensory and motor nerve conduction velocities decreased in the U-group, whereas sensory nerve conduction velocity increased by 7% (p = 0.0351) in the I-group compared with the U-group. Western blots showed unaltered total insulin receptor (IR), but a 31% decrease and 3.1- and 4.0-fold increases in phosphorylated IR, p44, and p42 MAPK protein levels, respectively, in sciatic nerves from the U-group compared with the C-group. Phosphorylated p44/42 MAPK protein decreased to control levels in the I-group (p<0.0001). CONCLUSIONS AND SIGNIFICANCE Low-dose insulin deactivated p44/42 MAPK and ameliorated peripheral sensory nerve dysfunction in rats with STZ-induced diabetes. These findings support the notion that insulin deficiency per se introduces impaired insulin receptor signaling in type 1 diabetic neuropathy.
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MESH Headings
- Animals
- Behavior, Animal/drug effects
- Blotting, Western
- Body Weight/drug effects
- Diabetes Mellitus, Experimental/drug therapy
- Diabetes Mellitus, Experimental/metabolism
- Diabetes Mellitus, Experimental/pathology
- Diabetes Mellitus, Experimental/physiopathology
- Dose-Response Relationship, Drug
- Fluorescent Antibody Technique
- Ganglia, Spinal/drug effects
- Ganglia, Spinal/enzymology
- Ganglia, Spinal/pathology
- Insulin/administration & dosage
- Insulin/pharmacology
- Insulin/therapeutic use
- Male
- Mitogen-Activated Protein Kinase 3/metabolism
- Myelin Sheath/metabolism
- Neural Conduction/drug effects
- Nociception/drug effects
- Phosphorylation/drug effects
- Rats
- Rats, Wistar
- Receptor, Insulin/metabolism
- Sciatic Nerve/drug effects
- Sciatic Nerve/metabolism
- Sciatic Nerve/physiopathology
- Signal Transduction/drug effects
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Affiliation(s)
- Kazuhiro Sugimoto
- Department of Laboratory Medicine, Hirosaki University Graduate School of Medicine, Hirosaki, Japan
- Diabetes Center, Ohta Nishinouchi Hospital, Koriyama, Japan
| | - Masayuki Baba
- Department of Neurology, Aomori Prefectural Central Hospital, Aomori, Japan
| | - Susumu Suzuki
- Diabetes Center, Ohta Nishinouchi Hospital, Koriyama, Japan
| | - Soroku Yagihashi
- Department of Pathology and Molecular Medicine, Hirosaki University Graduate School of Medicine, Hirosaki, Japan
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195
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Rhee YH, Choi M, Lee HS, Park CH, Kim SM, Yi SH, Oh SM, Cha HJ, Chang MY, Lee SH. Insulin concentration is critical in culturing human neural stem cells and neurons. Cell Death Dis 2013; 4:e766. [PMID: 23928705 PMCID: PMC3763456 DOI: 10.1038/cddis.2013.295] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Revised: 06/27/2013] [Accepted: 07/15/2013] [Indexed: 12/25/2022]
Abstract
Cell culture of human-derived neural stem cells (NSCs) is a useful tool that contributes to our understanding of human brain development and allows for the development of therapies for intractable human brain disorders. Human NSC (hNSC) cultures, however, are not commonly used, mainly because of difficulty with consistently maintaining the cells in a healthy state. In this study, we show that hNSC cultures, unlike NSCs of rodent origins, are extremely sensitive to insulin, an indispensable culture supplement, and that the previously reported difficulty in culturing hNSCs is likely because of a lack of understanding of this relationship. Like other neural cell cultures, insulin is required for hNSC growth, as withdrawal of insulin supplementation results in massive cell death and delayed cell growth. However, severe apoptotic cell death was also detected in insulin concentrations optimized to rodent NSC cultures. Thus, healthy hNSC cultures were only produced in a narrow range of relatively low insulin concentrations. Insulin-mediated cell death manifested not only in all human NSCs tested, regardless of origin, but also in differentiated human neurons. The underlying cell death mechanism at high insulin concentrations was similar to insulin resistance, where cells became less responsive to insulin, resulting in a reduction in the activation of the PI3K/Akt pathway critical to cell survival signaling.
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Affiliation(s)
- Y-H Rhee
- Department of Biochemistry and Molecular Biology, College of Medicine, Hanyang University, Seoul, Korea
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196
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Majo VJ, Arango V, Simpson NR, Prabhakaran J, Kassir SA, Underwood MD, Bakalian M, Canoll P, Mann JJ, Dileep Kumar JS. Synthesis and in vitro evaluation of [18F]BMS-754807: a potential PET ligand for IGF-1R. Bioorg Med Chem Lett 2013; 23:4191-4. [PMID: 23743281 PMCID: PMC4820059 DOI: 10.1016/j.bmcl.2013.05.026] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Revised: 04/30/2013] [Accepted: 05/07/2013] [Indexed: 12/13/2022]
Abstract
Radiosynthesis and in vitro evaluation of [(18)F](S)-1-(4-((5-cyclopropyl-1H-pyrazol-3-yl)amino)pyrrolo[2,1-f][1,2,4]triazin-2-yl)-N-(6-fluoropyridin-3-yl)-2-methylpyrrolidine-2-carboxamide ([(18)F]BMS-754807 or [(18)F]1) a specific IGF-1R inhibitor was performed. [(18)F]1 demonstrated specific binding in vitro to human cancer tissues. Synthesis of reference standard 1 and corresponding bromo derivative (1a), the precursor for radiolabeling were achieved from 2,4-dichloropyrrolo[2,1-f][1,2,4]triazine (4) in three steps with 50% overall yield. The radioproduct was obtained in 8% yield by reacting 1a with [(18)F]TBAF in DMSO at 170°C at high radiochemical purity and specific activity (1-2Ci/μmol, N=10). The proof of concept of IGF-IR imaging with [(18)F]1 was demonstrated by in vitro autoradiography studies using pathologically identified surgically removed grade IV glioblastoma, breast cancer and pancreatic tumor tissues. These studies indicate that [(18)F]1 can be a potential PET tracer for monitoring IGF-1R.
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Affiliation(s)
- Vattoly J. Majo
- Division of Molecular Imaging and Neuropathology, Department of Psychiatry, Columbia University College of Physicians and Surgeons, NY, USA
| | - Victoria Arango
- Division of Molecular Imaging and Neuropathology, Department of Psychiatry, Columbia University College of Physicians and Surgeons, NY, USA
- New York State Psychiatric Institute, NY, USA
| | | | - Jaya Prabhakaran
- Division of Molecular Imaging and Neuropathology, Department of Psychiatry, Columbia University College of Physicians and Surgeons, NY, USA
| | | | - Mark D. Underwood
- Division of Molecular Imaging and Neuropathology, Department of Psychiatry, Columbia University College of Physicians and Surgeons, NY, USA
- New York State Psychiatric Institute, NY, USA
| | | | - Peter Canoll
- Department of Pathology, College of Physicians and Surgeons, NY, USA
| | - J. John Mann
- Division of Molecular Imaging and Neuropathology, Department of Psychiatry, Columbia University College of Physicians and Surgeons, NY, USA
- New York State Psychiatric Institute, NY, USA
- Department of Radiology, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA
| | - J. S. Dileep Kumar
- Division of Molecular Imaging and Neuropathology, Department of Psychiatry, Columbia University College of Physicians and Surgeons, NY, USA
- New York State Psychiatric Institute, NY, USA
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197
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Chen Z, Zhong C. Decoding Alzheimer's disease from perturbed cerebral glucose metabolism: implications for diagnostic and therapeutic strategies. Prog Neurobiol 2013; 108:21-43. [PMID: 23850509 DOI: 10.1016/j.pneurobio.2013.06.004] [Citation(s) in RCA: 435] [Impact Index Per Article: 39.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2013] [Revised: 06/03/2013] [Accepted: 06/18/2013] [Indexed: 12/14/2022]
Abstract
Alzheimer's disease (AD) is an age-related devastating neurodegenerative disorder, which severely impacts on the global economic development and healthcare system. Though AD has been studied for more than 100 years since 1906, the exact cause(s) and pathogenic mechanism(s) remain to be clarified. Also, the efficient disease-modifying treatment and ideal diagnostic method for AD are unavailable. Perturbed cerebral glucose metabolism, an invariant pathophysiological feature of AD, may be a critical contributor to the pathogenesis of this disease. In this review, we firstly discussed the features of cerebral glucose metabolism in physiological and pathological conditions. Then, we further reviewed the contribution of glucose transportation abnormality and intracellular glucose catabolism dysfunction in AD pathophysiology, and proposed a hypothesis that multiple pathogenic cascades induced by impaired cerebral glucose metabolism could result in neuronal degeneration and consequently cognitive deficits in AD patients. Among these pathogenic processes, altered functional status of thiamine metabolism and brain insulin resistance are highly emphasized and characterized as major pathogenic mechanisms. Finally, considering the fact that AD patients exhibit cerebral glucose hypometabolism possibly due to impairments of insulin signaling and altered thiamine metabolism, we also discuss some potential possibilities to uncover diagnostic biomarkers for AD from abnormal glucose metabolism and to develop drugs targeting at repairing insulin signaling impairment and correcting thiamine metabolism abnormality. We conclude that glucose metabolism abnormality plays a critical role in AD pathophysiological alterations through the induction of multiple pathogenic factors such as oxidative stress, mitochondrial dysfunction, and so forth. To clarify the causes, pathogeneses and consequences of cerebral hypometabolism in AD will help break the bottleneck of current AD study in finding ideal diagnostic biomarker and disease-modifying therapy.
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Affiliation(s)
- Zhichun Chen
- Department of Neurology, Zhongshan Hospital, Fudan University, Shanghai, China
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198
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Medhi B, Chakrabarty M. Insulin resistance: an emerging link in Alzheimer's disease. Neurol Sci 2013; 34:1719-25. [PMID: 23670236 DOI: 10.1007/s10072-013-1454-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2013] [Accepted: 05/06/2013] [Indexed: 12/18/2022]
Abstract
Relentless progression of Alzheimer's disease (AD) poses a grave situation for the biomedical community to tackle. Agents starting as hot favorites in clinical trials have failed in later stages and it is time we reconsidered our approaches to intervene the disease. Quite some interesting work in the last decade has introduced a new school of thought which factors in neuronal glycemic imbalance as a major component for the development of AD. Insulin resistance in the brain has brought forward subsequent sequelae which might work towards amyloid accretion and/or tau hyperphosphorylation. It is also pointed out that insulin works by distributing iron to neuronal tissue and an insulin resistant state throws it off gear leading to iron overloading of neurons which is ultimately detrimental. A relatively recent investigation finds the role of c-Jun-N-terminal kinase (JNK3) in AD which also seems to bear a link with insulin resistance.
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Affiliation(s)
- Bikash Medhi
- Department of Pharmacology, Postgraduate Institute of Medical Education and Research, Research Block B, 4th Floor, Room No. 4043, Chandigarh, 160012, India,
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199
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200
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Emmanuel Y, Cochlin LE, Tyler DJ, de Jager CA, David Smith A, Clarke K. Human hippocampal energy metabolism is impaired during cognitive activity in a lipid infusion model of insulin resistance. Brain Behav 2013; 3:134-44. [PMID: 23533158 PMCID: PMC3607154 DOI: 10.1002/brb3.124] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/25/2012] [Revised: 11/11/2012] [Accepted: 12/23/2012] [Indexed: 11/13/2022] Open
Abstract
Neuronal glucose uptake was thought to be independent of insulin, being facilitated by glucose transporters GLUT1 and GLUT3, which do not require insulin signaling. However, it is now known that components of the insulin-mediated glucose uptake pathway, including neuronal insulin synthesis and the insulin-dependent glucose transporter GLUT4, are present in brain tissue, particularly in the hippocampus. There is considerable recent evidence that insulin signaling is crucial to optimal hippocampal function. The physiological basis, however, is not clear. We propose that while noninsulin-dependent GLUT1 and GLUT3 transport is adequate for resting needs, the surge in energy use during sustained cognitive activity requires the additional induction of insulin-signaled GLUT4 transport. We studied hippocampal high-energy phosphate metabolism in eight healthy volunteers, using a lipid infusion protocol to inhibit insulin signaling. Contrary to conventional wisdom, it is now known that free fatty acids do cross the blood-brain barrier in significant amounts. Energy metabolism within the hippocampus was assessed during standardized cognitive activity. (31)Phosphorus magnetic resonance spectroscopy was used to determine the phosphocreatine (PCr)-to-adenosine triphosphate (ATP) ratio. This ratio reflects cellular energy production in relation to concurrent cellular energy expenditure. With lipid infusion, the ratio was significantly reduced during cognitive activity (PCr/ATP 1.0 ± 0.4 compared with 1.4 ± 0.4 before infusion, P = 0.01). Without lipid infusion, there was no reduction in the ratio during cognitive activity (PCr/ATP 1.5 ± 0.3 compared with 1.4 ± 0.4, P = 0.57). This provides supporting evidence for a physiological role for insulin signaling in facilitating increased neuronal glucose uptake during sustained cognitive activity. Loss of this response, as may occur in type 2 diabetes, would lead to insufficient neuronal energy availability during cognitive activity.
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Affiliation(s)
- Yaso Emmanuel
- Cardiac Metabolism Research Group Department of Physiology, Anatomy and Genetics, University of OxfordOxford, United Kingdom
- Oxford Centre for Clinical Magnetic Resonance Research (OCMR), University of OxfordOxford, United Kingdom
- Oxford Project to Investigate Memory and Ageing (OPTIMA) Nuffield Department of Medicine, University of OxfordOxford, United Kingdom
| | - Lowri E Cochlin
- Cardiac Metabolism Research Group Department of Physiology, Anatomy and Genetics, University of OxfordOxford, United Kingdom
- Oxford Centre for Clinical Magnetic Resonance Research (OCMR), University of OxfordOxford, United Kingdom
| | - Damian J Tyler
- Cardiac Metabolism Research Group Department of Physiology, Anatomy and Genetics, University of OxfordOxford, United Kingdom
- Oxford Centre for Clinical Magnetic Resonance Research (OCMR), University of OxfordOxford, United Kingdom
| | - Celeste A de Jager
- Oxford Project to Investigate Memory and Ageing (OPTIMA) Nuffield Department of Medicine, University of OxfordOxford, United Kingdom
| | - A David Smith
- Oxford Project to Investigate Memory and Ageing (OPTIMA) Nuffield Department of Medicine, University of OxfordOxford, United Kingdom
| | - Kieran Clarke
- Cardiac Metabolism Research Group Department of Physiology, Anatomy and Genetics, University of OxfordOxford, United Kingdom
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