401
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Physical Activity Protects the Human Brain against Metabolic Stress Induced by a Postprandial and Chronic Inflammation. Behav Neurol 2015; 2015:569869. [PMID: 26074674 PMCID: PMC4436444 DOI: 10.1155/2015/569869] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Accepted: 04/27/2015] [Indexed: 12/19/2022] Open
Abstract
In recent years, it has become clear that chronic systemic low-grade inflammation is at the root of many, if not all, typically Western diseases associated with the metabolic syndrome. While much focus has been given to sedentary lifestyle as a cause of chronic inflammation, it is less often appreciated that chronic inflammation may also promote a sedentary lifestyle, which in turn causes chronic inflammation. Given that even minor increases in chronic inflammation reduce brain volume in otherwise healthy individuals, the bidirectional relationship between inflammation and sedentary behaviour may explain why humans have lost brain volume in the last 30,000 years and also intelligence in the last 30 years. We review evidence that lack of physical activity induces chronic low-grade inflammation and, consequently, an energy conflict between the selfish immune system and the selfish brain. Although the notion that increased physical activity would improve health in the modern world is widespread, here we provide a novel perspective on this truism by providing evidence that recovery of normal human behaviour, such as spontaneous physical activity, would calm proinflammatory activity, thereby allocating more energy to the brain and other organs, and by doing so would improve human health.
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402
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Wang D, Yan J, Chen J, Wu W, Zhu X, Wang Y. Naringin Improves Neuronal Insulin Signaling, Brain Mitochondrial Function, and Cognitive Function in High-Fat Diet-Induced Obese Mice. Cell Mol Neurobiol 2015; 35:1061-71. [PMID: 25939427 DOI: 10.1007/s10571-015-0201-y] [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: 03/12/2015] [Accepted: 04/24/2015] [Indexed: 12/20/2022]
Abstract
The epidemic and experimental studies have confirmed that the obesity induced by high-fat diet not only caused neuronal insulin resistance, but also induced brain mitochondrial dysfunction as well as learning impairment in mice. Naringin has been reported to posses biological functions which are beneficial to human cognitions, but its protective effects on HFD-induced cognitive deficits and underlying mechanisms have not been well characterized. In the present study Male C57BL/6 J mice were fed either a control or high-fat diet for 20 weeks and then randomized into four groups treated with their respective diets including control diet, control diet + naringin, high-fat diet (HFD), and high-fat diet + naringin (HFDN). The behavioral performance was assessed by using novel object recognition test and Morris water maze test. Hippocampal mitochondrial parameters were analyzed. Then the protein levels of insulin signaling pathway and the AMP-activated protein kinase (AMPK) in the hippocampus were detected by Western blot method. Our results showed that oral administration of naringin significantly improved the learning and memory abilities as evidenced by increasing recognition index by 52.5% in the novel object recognition test and inducing a 1.05-fold increase in the crossing-target number in the probe test, and ameliorated mitochondrial dysfunction in mice caused by HFD consumption. Moreover, naringin significantly enhanced insulin signaling pathway as indicated by a 34.5% increase in the expression levels of IRS-1, a 47.8% decrease in the p-IRS-1, a 1.43-fold increase in the p-Akt, and a 1.89-fold increase in the p-GSK-3β in the hippocampus of the HFDN mice versus HFD mice. Furthermore, the AMPK activity significantly increased in the naringin-treated (100 mg kg(-1) d(-1)) group. These findings suggest that an enhancement in insulin signaling and a decrease in mitochondrial dysfunction through the activation of AMPK may be one of the mechanisms that naringin improves cognitive functions in HFD-induced obese mice.
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Affiliation(s)
- Dongmei Wang
- Department of Pathogen Biology, Medical College, Henan University of Science and Technology, No.6, Anhui Road, Jianxi District, Luoyang, 471003, China.
| | - Junqiang Yan
- Department of Neurology, The First Affiliated Hospital of Henan University of Science and Technology, Jinghua Road 24, Luoyang, 471003, China
| | - Jing Chen
- Department of Neurology, The Second Affiliated Hospital of Zhengzhou University, Jingba Road 2, Zhengzhou, 450014, China
| | - Wenlan Wu
- Department of Pathogen Biology, Medical College, Henan University of Science and Technology, No.6, Anhui Road, Jianxi District, Luoyang, 471003, China
| | - Xiaoying Zhu
- Department of Pathogen Biology, Medical College, Henan University of Science and Technology, No.6, Anhui Road, Jianxi District, Luoyang, 471003, China
| | - Yong Wang
- Department of Pathogen Biology, Medical College, Henan University of Science and Technology, No.6, Anhui Road, Jianxi District, Luoyang, 471003, China
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403
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Identification of early transcriptome signatures in placenta exposed to insulin and obesity. Am J Obstet Gynecol 2015; 212:647.e1-11. [PMID: 25731694 DOI: 10.1016/j.ajog.2015.02.026] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2014] [Revised: 12/22/2015] [Accepted: 02/25/2015] [Indexed: 12/21/2022]
Abstract
OBJECTIVE The purpose of this study was to investigate the effects of insulin on human placental transcriptome and biological processes in first-trimester pregnancy. STUDY DESIGN Maternal plasma and placenta villous tissue were obtained at the time of voluntary termination of pregnancy (7-12 weeks) from 17 lean (body mass index, 20.9±1.5 kg/m2) and 18 obese (body mass index, 33.5±2.6 kg/m2) women. Trophoblast cells were immediately isolated for in vitro treatment with insulin or vehicle. Patterns of global gene expression were analyzed using genome microarray profiling after hybridization to Human Gene 1.1 ST and real time reverse transcription-polymerase chain reaction. RESULTS The global trophoblast transcriptome was qualitatively separated in insulin-treated vs untreated trophoblasts of lean women. The number of insulin-sensitive genes detected in the trophoblasts of lean women was 2875 (P<.001). Maternal obesity reduced the number of insulin-sensitive genes recovered by 30-fold. Insulin significantly impaired several gene networks regulating cell cycle and cholesterol homeostasis but did not modify pathways related to glucose transport. Obesity associated with high insulin and insulin resistance, but not maternal hyperinsulinemia alone, impaired the global gene profiling of early gestation placenta, highlighting mitochondrial dysfunction and decreased energy metabolism. CONCLUSION We report for the first time that human trophoblast cells are highly sensitive to insulin regulation in early gestation. Maternal obesity associated with insulin resistance programs the placental transcriptome toward refractoriness to insulin with potential adverse consequences for placental structure and function.
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404
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Leiria LOS, Arantes-Costa FM, Calixto MC, Alexandre EC, Moura RF, Folli F, Prado CM, Prado MA, Prado VF, Velloso LA, Donato J, Antunes E, Martins MA, Saad MJA. Increased airway reactivity and hyperinsulinemia in obese mice are linked by ERK signaling in brain stem cholinergic neurons. Cell Rep 2015; 11:934-943. [PMID: 25937275 DOI: 10.1016/j.celrep.2015.04.012] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2014] [Revised: 01/01/2015] [Accepted: 04/03/2015] [Indexed: 01/09/2023] Open
Abstract
Obesity is a major risk factor for asthma, which is characterized by airway hyperreactivity (AHR). In obesity-associated asthma, AHR may be regulated by non-TH2 mechanisms. We hypothesized that airway reactivity is regulated by insulin in the CNS, and that the high levels of insulin associated with obesity contribute to AHR. We found that intracerebroventricular (ICV)-injected insulin increases airway reactivity in wild-type, but not in vesicle acetylcholine transporter knockdown (VAChT KD(HOM-/-)), mice. Either neutralization of central insulin or inhibition of extracellular signal-regulated kinases (ERK) normalized airway reactivity in hyperinsulinemic obese mice. These effects were mediated by insulin in cholinergic nerves located at the dorsal motor nucleus of the vagus (DMV) and nucleus ambiguus (NA), which convey parasympathetic outflow to the lungs. We propose that increased insulin-induced activation of ERK in parasympathetic pre-ganglionic nerves contributes to AHR in obese mice, suggesting a drug-treatable link between obesity and asthma.
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Affiliation(s)
- Luiz O S Leiria
- Department of Internal Medicine, Faculty of Medical Sciences, State University of Campinas, Campinas, SP 13083-887, Brazil
| | - Fernanda M Arantes-Costa
- Department of Medicine, School of Medicine, University of São Paulo, São Paulo, SP 01246-904, Brazil
| | - Marina C Calixto
- Department of Pharmacology, Faculty of Medical Sciences, State University of Campinas, Campinas, SP 13083-881, Brazil
| | - Eduardo C Alexandre
- Department of Pharmacology, Faculty of Medical Sciences, State University of Campinas, Campinas, SP 13083-881, Brazil
| | - Rodrigo F Moura
- Department of Internal Medicine, Faculty of Medical Sciences, State University of Campinas, Campinas, SP 13083-887, Brazil; Obesity and Comorbidities Research Center (O.C.R.C.), State University of Campinas, Campinas, SP 13083-887, Brazil
| | - Franco Folli
- Department of Internal Medicine, Faculty of Medical Sciences, State University of Campinas, Campinas, SP 13083-887, Brazil; Obesity and Comorbidities Research Center (O.C.R.C.), State University of Campinas, Campinas, SP 13083-887, Brazil; Division of Diabetes, Department of Medicine, University of Texas Health Science Center at San Antonio, TX 78229-3900, USA
| | - Carla M Prado
- Department of Biological Science, Federal University of São Paulo, Diadema, SP 09972-270, Brazil
| | - Marco Antonio Prado
- Robarts Research Institute, Department of Anatomy & Cell Biology and Department of Physiology and Pharmacology, University of Western Ontario, London, ON 5015, Canada
| | - Vania F Prado
- Robarts Research Institute, Department of Anatomy & Cell Biology and Department of Physiology and Pharmacology, University of Western Ontario, London, ON 5015, Canada
| | - Licio A Velloso
- Department of Internal Medicine, Faculty of Medical Sciences, State University of Campinas, Campinas, SP 13083-887, Brazil; Obesity and Comorbidities Research Center (O.C.R.C.), State University of Campinas, Campinas, SP 13083-887, Brazil
| | - José Donato
- Department of Physiology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP 05508-000, Brazil
| | - Edson Antunes
- Department of Pharmacology, Faculty of Medical Sciences, State University of Campinas, Campinas, SP 13083-881, Brazil
| | - Milton A Martins
- Department of Medicine, School of Medicine, University of São Paulo, São Paulo, SP 01246-904, Brazil
| | - Mario J A Saad
- Department of Internal Medicine, Faculty of Medical Sciences, State University of Campinas, Campinas, SP 13083-887, Brazil; Obesity and Comorbidities Research Center (O.C.R.C.), State University of Campinas, Campinas, SP 13083-887, Brazil.
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405
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Abstract
Diabetes mellitus, particularly type 2 diabetes, is a risk factor for dementia and this holds true for incident vascular dementia and Alzheimer's disease. Cerebrovascular complications of diabetes and chronic mild inflammation in insulin resistant states partly account for this increased risk. In addition, cellular resistance to the trophic effects of insulin on neurons and glial cells favor the accumulation of toxic metabolic products, such as amyloid and hyperphosphorylated tau protein (pTau). Weight loss frequently precedes overt cognitive symptoms of Alzheimer's disease. This results in an increased risk of hypoglycemic episodes in stable diabetic patients who are on suitably adjusted doses of oral insulin or insulinotropic antidiabetic drugs. In turn, hypoglycemic episodes may induce further damage in the vulnerable brains of type 2 diabetes patients. Patients with unexplained weight loss, hypoglycemic episodes and subjective memory complaints must be screened for dementia. Once dementia has been diagnosed the goals of diabetes management must be reevaluated as prevention of hypoglycemia becomes more important than tight metabolic control. As weight loss accelerates the rate of cognitive decline, nutritional goals must aim at stabilizing body weight. There is no available evidence on whether drug treatment of diabetes in middle-aged persons can help to prevent dementia; however, physical exercise, mental activity and higher education have preventive effects on the risk of dementia in later life. In addition, nutritional recommendations that are effective in preventing cardiovascular events have also been shown to reduce the risk of dementia.
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Affiliation(s)
- D Kopf
- Klinik für Geriatrie, Kath. Marienkrankenhaus, Alfredstr. 9, 22087, Hamburg, Deutschland,
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406
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Insulin resistance in brain alters dopamine turnover and causes behavioral disorders. Proc Natl Acad Sci U S A 2015; 112:3463-8. [PMID: 25733901 DOI: 10.1073/pnas.1500877112] [Citation(s) in RCA: 285] [Impact Index Per Article: 31.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Diabetes and insulin resistance are associated with altered brain imaging, depression, and increased rates of age-related cognitive impairment. Here we demonstrate that mice with a brain-specific knockout of the insulin receptor (NIRKO mice) exhibit brain mitochondrial dysfunction with reduced mitochondrial oxidative activity, increased levels of reactive oxygen species, and increased levels of lipid and protein oxidation in the striatum and nucleus accumbens. NIRKO mice also exhibit increased levels of monoamine oxidase A and B (MAO A and B) leading to increased dopamine turnover in these areas. Studies in cultured neurons and glia cells indicate that these changes in MAO A and B are a direct consequence of loss of insulin signaling. As a result, NIRKO mice develop age-related anxiety and depressive-like behaviors that can be reversed by treatment with MAO inhibitors, as well as the tricyclic antidepressant imipramine, which inhibits MAO activity and reduces oxidative stress. Thus, insulin resistance in brain induces mitochondrial and dopaminergic dysfunction leading to anxiety and depressive-like behaviors, demonstrating a potential molecular link between central insulin resistance and behavioral disorders.
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407
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Buysschaert M, Medina JL, Bergman M, Shah A, Lonier J. Prediabetes and associated disorders. Endocrine 2015; 48:371-93. [PMID: 25294012 DOI: 10.1007/s12020-014-0436-2] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/02/2014] [Accepted: 09/20/2014] [Indexed: 12/14/2022]
Abstract
Prediabetes represents an elevation of plasma glucose above the normal range but below that of clinical diabetes. Prediabetes includes individuals with IFG, IGT, IFG with IGT and elevated HbA1c levels. Insulin resistance and β-cell dysfunction are characteristic of this disorder. The diagnosis of prediabetesis is vital as both IFG and IGT are indeed well-known risk factors for type 2 diabetes with a greater risk in the presence of combined IFG and IGT. Furthermore, as will be illustrated in this review, prediabetes is associated with associated disorders typically only considered in with established diabetes. These include cardiovascular disease, periodontal disease, cognitive dysfunction, microvascular disease, blood pressure abnormalities, obstructive sleep apnea, low testosterone, metabolic syndrome, various biomarkers, fatty liver disease, and cancer. As the vast majority of individuals with prediabetes are unaware of their diagnosis, it is therefore vital that the associated conditions are identified, particularly in the presence of mild hyperglycemia, so they may benefit from early intervention.
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Affiliation(s)
- Martin Buysschaert
- Department of Endocrinology and Diabetology, University Clinic Saint-Luc, Université Catholique de Louvain, Brussels, Belgium
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408
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Cardiotrophin-1 (CT-1) Improves High Fat Diet-Induced Cognitive Deficits in Mice. Neurochem Res 2015; 40:843-53. [DOI: 10.1007/s11064-015-1535-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2014] [Revised: 01/29/2015] [Accepted: 02/04/2015] [Indexed: 01/12/2023]
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409
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Clemmensen C, Müller TD, Finan B, Tschöp MH, DiMarchi R. Current and Emerging Treatment Options in Diabetes Care. Handb Exp Pharmacol 2015; 233:437-59. [PMID: 25903416 DOI: 10.1007/164_2015_7] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Diabetes constitutes an increasing threat to human health, particularly in newly industrialized and densely populated countries. Type 1 and type 2 diabetes arise from different etiologies but lead to similar metabolic derangements constituted by an absolute or relative lack of insulin that results in elevated plasma glucose. In the last three decades, a set of new medicines built upon a deeper understanding of physiology and diabetic pathology have emerged to enhance the clinical management of the disease and related disorders. Recent insights into insulin-dependent and insulin-independent molecular events have accelerated the generation of a series of novel medicinal agents, which hold the promise for further advances in the management of diabetes. In this chapter, we provide a historical context for what has been accomplished to provide perspective for future research and novel emerging treatment options.
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Affiliation(s)
- Christoffer Clemmensen
- Institute for Diabetes and Obesity and Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Neuherberg, Germany.,Division of Metabolic Diseases, Department of Medicine, Technische Universität München, Munich, Germany
| | - Timo D Müller
- Institute for Diabetes and Obesity and Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Neuherberg, Germany.,Division of Metabolic Diseases, Department of Medicine, Technische Universität München, Munich, Germany
| | - Brian Finan
- Institute for Diabetes and Obesity and Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Neuherberg, Germany.,Division of Metabolic Diseases, Department of Medicine, Technische Universität München, Munich, Germany
| | - Matthias H Tschöp
- Institute for Diabetes and Obesity and Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Neuherberg, Germany. .,Division of Metabolic Diseases, Department of Medicine, Technische Universität München, Munich, Germany.
| | - Richard DiMarchi
- Department of Chemistry, Indiana University, Bloomington, IN, USA
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410
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Stelzhammer V, Ozcan S, Gottschalk MG, Steeb H, Hodes GE, Guest PC, Rahmoune H, Wong EH, Russo SJ, Bahn S. Central and peripheral changes underlying susceptibility and resistance to social defeat stress – A proteomic profiling study. ACTA ACUST UNITED AC 2015. [DOI: 10.1016/j.dineu.2015.08.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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411
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Takach O, Gill TB, Silverman MA. Modulation of insulin signaling rescues BDNF transport defects independent of tau in amyloid-β oligomer-treated hippocampal neurons. Neurobiol Aging 2014; 36:1378-82. [PMID: 25543463 DOI: 10.1016/j.neurobiolaging.2014.11.018] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2014] [Revised: 10/21/2014] [Accepted: 11/25/2014] [Indexed: 10/24/2022]
Abstract
Defective brain insulin signaling contributes to the cognitive deficits in Alzheimer's disease (AD). Amyloid-beta oligomers (AβOs), the primary neurotoxin implicated in AD, downregulate insulin signaling by impairing protein kinase B/AKT, thereby overactivating glycogen synthase kinase-3β. By this mechanism, AβOs may also impair axonal transport before tau-induced cytoskeletal collapse and cell death. Here, we demonstrate that a constitutively active form of protein kinase B/AKT prevents brain-derived neurotrophic factor (BDNF) transport defects in AβO-treated primary neurons from wild type (tau(+/+)) and tau knockout (tau(-/-)) mice. Remarkably, inhibition of glycogen synthase kinase-3β rescues BDNF transport defects independent of tau. Furthermore, exendin-4, an anti-diabetes agent, restores normal BDNF axonal transport by stimulating the glucagon-like peptide-1 receptor to activate the insulin pathway. Collectively, our findings indicate that normalized insulin signaling can both prevent and reverse BDNF transport defects in AβO-treated neurons. Ultimately, this work may reveal novel therapeutic targets that regulate BDNF trafficking, promote its secretion and uptake, and prolong neuronal survival during AD progression.
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Affiliation(s)
- Oliver Takach
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Trevor B Gill
- Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Michael A Silverman
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada; Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada.
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412
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Differential effects of angiopoietin-like 4 in brain and muscle on regulation of lipoprotein lipase activity. Mol Metab 2014; 4:144-50. [PMID: 25685701 PMCID: PMC4314546 DOI: 10.1016/j.molmet.2014.11.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/09/2014] [Revised: 11/03/2014] [Accepted: 11/05/2014] [Indexed: 12/30/2022] Open
Abstract
OBJECTIVE Lipoprotein lipase (LPL) is a key regulator of circulating triglyceride rich lipoprotein hydrolysis. In brain LPL regulates appetite and energy expenditure. Angiopoietin-like 4 (Angptl4) is a secreted protein that inhibits LPL activity and, thereby, triglyceride metabolism, but the impact of Angptl4 on central lipid metabolism is unknown. METHODS We induced type 1 diabetes by streptozotocin (STZ) in whole-body Angptl4 knockout mice (Angptl4(-/-) ) and their wildtype littermates to study the role of Angptl4 in central lipid metabolism. RESULTS In type 1 (streptozotocin, STZ) and type 2 (ob/ob) diabetic mice, there is a ~2-fold increase of Angptl4 in the hypothalamus and skeletal muscle. Intracerebroventricular insulin injection into STZ mice at levels which have no effect on plasma glucose restores Angptl4 expression in hypothalamus. Isolation of cells from the brain reveals that Angptl4 is produced in glia, whereas LPL is present in both glia and neurons. Consistent with the in vivo experiment, in vitro insulin treatment of glial cells causes a 50% reduction of Angptl4 and significantly increases LPL activity with no change in LPL expression. In Angptl4(-/-) mice, LPL activity in skeletal muscle is increased 3-fold, and this is further increased by STZ-induced diabetes. By contrast, Angptl4(-/-) mice show no significant difference in LPL activity in hypothalamus or brain independent of diabetic and nutritional status. CONCLUSION Thus, Angptl4 in brain is produced in glia and regulated by insulin. However, in contrast to the periphery, central Angptl4 does not regulate LPL activity, but appears to participate in the metabolic crosstalk between glia and neurons.
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Key Words
- ARC, arcuate nucleus
- AgRP, agouti-related protein
- Angptl4
- Angptl4, angiopoietin-like 4
- CART, cocaine-and-amphetamine-regulated transcript
- CNS, central nervous system
- FFA, free fatty acid
- LPL, lipoprotein lipase
- Lipid metabolism
- Lipoprotein lipase
- NPY, neuropeptide-Y
- POMC, pro-opiomelanocortin
- STZ, streptozotocin
- TG, triglyceride
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413
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Insulin resistance in Alzheimer's disease. Neurobiol Dis 2014; 72 Pt A:92-103. [PMID: 25237037 DOI: 10.1016/j.nbd.2014.09.001] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2014] [Revised: 09/02/2014] [Accepted: 09/05/2014] [Indexed: 12/16/2022] Open
Abstract
Insulin is a key hormone regulating metabolism. Insulin binding to cell surface insulin receptors engages many signaling intermediates operating in parallel and in series to control glucose, energy, and lipids while also regulating mitogenesis and development. Perturbations in the function of any of these intermediates, which occur in a variety of diseases, cause reduced sensitivity to insulin and insulin resistance with consequent metabolic dysfunction. Chronic inflammation ensues which exacerbates compromised metabolic homeostasis. Since insulin has a key role in learning and memory as well as directly regulating ERK, a kinase required for the type of learning and memory compromised in early Alzheimer's disease (AD), insulin resistance has been identified as a major risk factor for the onset of AD. Animal models of AD or insulin resistance or both demonstrate that AD pathology and impaired insulin signaling form a reciprocal relationship. Of note are human and animal model studies geared toward improving insulin resistance that have led to the identification of the nuclear receptor and transcription factor, peroxisome proliferator-activated receptor gamma (PPARγ) as an intervention tool for early AD. Strategic targeting of alternate nodes within the insulin signaling network has revealed disease-stage therapeutic windows in animal models that coalesce with previous and ongoing clinical trial approaches. Thus, exploiting the connection between insulin resistance and AD provides powerful opportunities to delineate therapeutic interventions that slow or block the pathogenesis of AD.
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