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Smith CJ, Sims SK, Nguyen S, Williams A, McLeod T, Sims-Robinson C. Intranasal insulin helps overcome brain insulin deficiency and improves survival and post-stroke cognitive impairment in male mice. J Neurosci Res 2023; 101:1757-1769. [PMID: 37571837 PMCID: PMC10664462 DOI: 10.1002/jnr.25237] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Revised: 07/16/2023] [Accepted: 07/22/2023] [Indexed: 08/13/2023]
Abstract
Obesity increases the risk for stroke and is associated with worse post-stroke outcomes; however, the mechanisms are poorly understood. Diet-induced obesity leads to insulin resistance and subsequently, brain insulin deficiency. The purpose of this study was to investigate the potential impact of brain insulin deficiency on post-stroke outcomes. To accomplish this, brain insulin levels were assessed in male C57BL/6J (B6) mice placed on either a standard diet or 54% kcal high-fat diet, a known model of insulin resistance. Mice were subjected to either a sham surgery (control) or 30-min middle cerebral artery occlusion to induce an ischemic stroke and administered either intranasal saline (0.9%) or intranasal insulin (1.75 U) twice daily for 5 days beginning on day 1 post-stroke. High-fat diet-induced brain insulin deficiency was associated with increased mortality, neurological and cognitive deficits. On the other hand, increasing brain insulin levels via intranasal insulin improved survival, neurological and cognitive function in high-fat diet mice. Our data suggests that brain insulin deficiency correlates with worse post-stroke outcomes in a diet-induced mouse model of insulin resistance and increasing brain insulin levels may be a therapeutic target to improve stroke recovery.
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Affiliation(s)
- Crystal J. Smith
- Department of Neurology, Medical University of South Carolina, Charleston, South Carolina, 29425 USA
- Department of Neurosciences, Medical University of South Carolina, Charleston, SC 29425 USA
| | - Serena-Kaye Sims
- Department of Neurology, Medical University of South Carolina, Charleston, South Carolina, 29425 USA
- Department of Biology, College of Charleston, Charleston, South Carolina, 29424 USA
| | - Stacy Nguyen
- Department of Neurology, Medical University of South Carolina, Charleston, South Carolina, 29425 USA
| | - Alexus Williams
- Department of Neurology, Medical University of South Carolina, Charleston, South Carolina, 29425 USA
| | - Taylor McLeod
- Department of Neurology, Medical University of South Carolina, Charleston, South Carolina, 29425 USA
- Department of Public Health Sciences, Medical University of South Carolina, Charleston, South Carolina 29425 USA
| | - Catrina Sims-Robinson
- Department of Neurology, Medical University of South Carolina, Charleston, South Carolina, 29425 USA
- Department of Neurosciences, Medical University of South Carolina, Charleston, SC 29425 USA
- Ralph H. Johnson Veterans Affairs Medical Center, Charleston, SC, 29401 USA
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2
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Watson LS, Wilken-Resman B, Williams A, DiLucia S, Sanchez G, McLeod TL, Sims-Robinson C. Hyperinsulinemia alters insulin receptor presentation and internalization in brain microvascular endothelial cells. Diab Vasc Dis Res 2022; 19:14791641221118626. [PMID: 35975361 PMCID: PMC9393688 DOI: 10.1177/14791641221118626] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Insulin receptors are internalized by endothelial cells to facilitate their physiological processes; however, the impact of hyperinsulinemia in brain endothelial cells is not known. Thus, the aim of this study was to elucidate the impact hyperinsulinemia plays on insulin receptor internalization through changes in phosphorylation, as well as the potential impact of protein tyrosine phosphatase 1B (PTP1B). Hippocampal microvessels were isolated from high-fat diet fed mice and assessed for insulin signaling activation, a process known to be involved with receptor internalization. Surface insulin receptors in brain microvascular endothelial cells were labelled to assess the role hyperinsulinemia plays on receptor internalization in response to stimulation, with and without the PTP1B antagonist, Claramine. Our results indicated that insulin receptor levels increased in tandem with decreased receptor signaling in the high-fat diet mouse microvessels. Insulin receptors of cells subjected to hyperinsulinemic treatment demonstrate splice variation towards decreased IR-A mRNA expression and demonstrate a higher membrane-localized proportion. This corresponded with decreased autophosphorylation at sites critical for receptor internalization and signaling. Claramine restored signaling and receptor internalization in cells treated with hyperinsulinemia. In conclusion, hyperinsulinemia impacts brain microvascular endothelial cell insulin receptor signaling and internalization, likely via alternative splicing and increased negative feedback from PTP1B.
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Affiliation(s)
- Luke S Watson
- Department of Neurology, Medical University of South
Carolina, Charleston, SC, USA
- Molecular and Cellular Biology and
Pathobiology Program, Medical University of South
Carolina, Charleston, SC, USA
| | - Brynna Wilken-Resman
- Molecular and Cellular Biology and
Pathobiology Program, Medical University of South
Carolina, Charleston, SC, USA
| | - Alexus Williams
- Molecular and Cellular Biology and
Pathobiology Program, Medical University of South
Carolina, Charleston, SC, USA
| | - Stephanie DiLucia
- Department of Neurology, Medical University of South
Carolina, Charleston, SC, USA
- Molecular and Cellular Biology and
Pathobiology Program, Medical University of South
Carolina, Charleston, SC, USA
| | - Guadalupe Sanchez
- Molecular and Cellular Biology and
Pathobiology Program, Medical University of South
Carolina, Charleston, SC, USA
| | - Taylor L McLeod
- Molecular and Cellular Biology and
Pathobiology Program, Medical University of South
Carolina, Charleston, SC, USA
| | - Catrina Sims-Robinson
- Molecular and Cellular Biology and
Pathobiology Program, Medical University of South
Carolina, Charleston, SC, USA
- Catrina Sims-Robinson, PhD, Molecular and
Cellular Biology and Pathobiology Program, Medical University of South Carolina,
96 Jonathan Lucas Street Suite 309D2 CSB, MSC 606, Charleston, SC 29425-2503,
USA.
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3
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Rebelos E, Rinne JO, Nuutila P, Ekblad LL. Brain Glucose Metabolism in Health, Obesity, and Cognitive Decline-Does Insulin Have Anything to Do with It? A Narrative Review. J Clin Med 2021; 10:jcm10071532. [PMID: 33917464 PMCID: PMC8038699 DOI: 10.3390/jcm10071532] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Revised: 04/01/2021] [Accepted: 04/02/2021] [Indexed: 12/13/2022] Open
Abstract
Imaging brain glucose metabolism with fluorine-labelled fluorodeoxyglucose ([18F]-FDG) positron emission tomography (PET) has long been utilized to aid the diagnosis of memory disorders, in particular in differentiating Alzheimer’s disease (AD) from other neurological conditions causing cognitive decline. The interest for studying brain glucose metabolism in the context of metabolic disorders has arisen more recently. Obesity and type 2 diabetes—two diseases characterized by systemic insulin resistance—are associated with an increased risk for AD. Along with the well-defined patterns of fasting [18F]-FDG-PET changes that occur in AD, recent evidence has shown alterations in fasting and insulin-stimulated brain glucose metabolism also in obesity and systemic insulin resistance. Thus, it is important to clarify whether changes in brain glucose metabolism are just an epiphenomenon of the pathophysiology of the metabolic and neurologic disorders, or a crucial determinant of their pathophysiologic cascade. In this review, we discuss the current knowledge regarding alterations in brain glucose metabolism, studied with [18F]-FDG-PET from metabolic disorders to AD, with a special focus on how manipulation of insulin levels affects brain glucose metabolism in health and in systemic insulin resistance. A better understanding of alterations in brain glucose metabolism in health, obesity, and neurodegeneration, and the relationships between insulin resistance and central nervous system glucose metabolism may be an important step for the battle against metabolic and cognitive disorders.
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Affiliation(s)
- Eleni Rebelos
- Turku PET Centre, University of Turku and Turku University Hospital, 20520 Turku, Finland; (E.R.); (J.O.R.); (P.N.)
| | - Juha O. Rinne
- Turku PET Centre, University of Turku and Turku University Hospital, 20520 Turku, Finland; (E.R.); (J.O.R.); (P.N.)
| | - Pirjo Nuutila
- Turku PET Centre, University of Turku and Turku University Hospital, 20520 Turku, Finland; (E.R.); (J.O.R.); (P.N.)
- Department of Endocrinology, Turku University Hospital, 20520 Turku, Finland
| | - Laura L. Ekblad
- Turku PET Centre, University of Turku and Turku University Hospital, 20520 Turku, Finland; (E.R.); (J.O.R.); (P.N.)
- Correspondence: ; Tel.: +358-2-3138721
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4
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Frazier HN, Ghoweri AO, Sudkamp E, Johnson ES, Anderson KL, Fox G, Vatthanaphone K, Xia M, Lin RL, Hargis-Staggs KE, Porter NM, Pauly JR, Blalock EM, Thibault O. Long-Term Intranasal Insulin Aspart: A Profile of Gene Expression, Memory, and Insulin Receptors in Aged F344 Rats. J Gerontol A Biol Sci Med Sci 2021; 75:1021-1030. [PMID: 31180116 DOI: 10.1093/gerona/glz105] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Indexed: 02/06/2023] Open
Abstract
Intranasal insulin is a safe and effective method for ameliorating memory deficits associated with pathological brain aging. However, the impact of different formulations and the duration of treatment on insulin's efficacy and the cellular processes targeted by the treatment remain unclear. Here, we tested whether intranasal insulin aspart, a short-acting insulin formulation, could alleviate memory decline associated with aging and whether long-term treatment affected regulation of insulin receptors and other potential targets. Outcome variables included measures of spatial learning and memory, autoradiography and immunohistochemistry of the insulin receptor, and hippocampal microarray analyses. Aged Fischer 344 rats receiving long-term (3 months) intranasal insulin did not show significant memory enhancement on the Morris water maze task. Autoradiography results showed that long-term treatment reduced insulin binding in the thalamus but not the hippocampus. Results from hippocampal immunofluorescence revealed age-related decreases in insulin immunoreactivity that were partially offset by intranasal administration. Microarray analyses highlighted numerous insulin-sensitive genes, suggesting insulin aspart was able to enter the brain and alter hippocampal RNA expression patterns including those associated with tumor suppression. Our work provides insights into potential mechanisms of intranasal insulin and insulin resistance, and highlights the importance of treatment duration and the brain regions targeted.
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Affiliation(s)
| | | | - Emily Sudkamp
- The College of Pharmacy, University of Kentucky, Lexington, Kentucky
| | | | | | - Grant Fox
- Department of Pharmacology and Nutritional Sciences
| | | | - Mengfan Xia
- Department of Pharmacology and Nutritional Sciences
| | | | | | | | - James R Pauly
- The College of Pharmacy, University of Kentucky, Lexington, Kentucky
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5
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Belsham DD, Dalvi PS. Insulin signalling in hypothalamic neurones. J Neuroendocrinol 2020; 33:e12919. [PMID: 33227171 DOI: 10.1111/jne.12919] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 11/02/2020] [Accepted: 11/04/2020] [Indexed: 12/15/2022]
Abstract
Subsequent to the discovery of insulin by Banting and Best in the Department of Physiology at the University of Toronto 100 years ago, the field of insulin signalling and action has grown at a remarkable pace. Yet, the recognition that insulin action in the brain is critical for whole body homeostasis has only recently been appreciated. The hypothalamus is a key region in the brain that responds to circulating insulin by engaging a complex signalling cascade resulting in the ultimate release of neuropeptides that control hunger and feeding. Disruption of this important feedback system can lead to a phenomenon called cellular insulin resistance, where the neurones cease to sense insulin. The factors contributing to insulin resistance, as well as the resulting detrimental effects, include the induction of neuroinflammation, endoplasmic reticulum stress and alterations in the architecture of the blood-brain barrier that allow transport of insulin into the brain. These manifestations usually change energy balance, causing weight gain, often resulting in obesity and its deadly comorbidities, including type 2 diabetes mellitus, cardiovascular disease and metabolic syndrome. Nonetheless, there is still hope because the signal transduction pathways can be targeted at a number of levels by neurone-specific therapeutics. With the advent of unique cell models for investigating the mechanisms involved in these processes, the discovery of novel targets is increasingly possible. Although we are still looking for a cure for diabetes, Banting and Best would be impressed at how far their discovery has advanced and the contemporary knowledge that has been accumulated based on insulin action.
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Affiliation(s)
- Denise D Belsham
- Departments of Physiology, Obstetrics and Gynaecology and Medicine, University of Toronto, Toronto, ON, Canada
| | - Prasad S Dalvi
- Biology Department, Morosky College of Health Professions and Sciences, Gannon University, Erie, PA, USA
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6
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Johnson AW, Snegovskikh D, Parikh L, DeAguiar RB, Han CS, Hwang JJ. Characterizing the Effects of Diabetes and Obesity on Insulin and Leptin Levels amongst Pregnant Women. Am J Perinatol 2020; 37:1094-1101. [PMID: 32120424 DOI: 10.1055/s-0040-1702988] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
OBJECTIVE In this study, we assess the impact of obesity and diabetes on maternal brain and periphery, as well as fetal exposure to insulin and leptin, and two hormones that play an important role in regulating energy homeostasis. STUDY DESIGN Fasting maternal plasma, fetal cord vein and artery plasma, and maternal cerebrospinal fluid (CSF) were collected in 37 women (12 lean, nondiabetic [prepregnancy body mass index (BMI): 22.9 ± 1.7 kg/m2]; 12 overweight/obese nondiabetic [BMI: 37.8 ± 7.3 kg/m2]; 13 gestational/type 2 diabetes mellitus [BMI: 29.8 ± 7.3 kg/m2]) with uncomplicated singleton pregnancies undergoing elective Cesarean delivery. HbA1C, insulin, glucose, and leptin levels were measured. RESULTS Compared with lean mothers, mothers with obesity and diabetes mellitus (DM) had significantly lower CSF-to-plasma ratios of insulin. Moreover, mothers with obesity and DM had significantly lower cord arterial and cord venous to maternal plasma ratios of insulin, but not leptin, compared with lean mothers. There were no differences in CSF and cord blood insulin and leptin levels between obese and DM mothers. CONCLUSION Compared with lean individuals, mothers with obesity and DM have relative deficiencies in insulin exposure. The patterns observed in mothers with obesity and diabetes were similar highlighting the importance of the maternal metabolic environment in obesity and suggesting obese patients warrant further clinical focus.
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Affiliation(s)
- Andrea W Johnson
- Department of Obstetrics, Gynecology and Reproductive Sciences, Section of Maternal-Fetal Medicine, Yale School of Medicine, New Haven, Connecticut
| | - Denis Snegovskikh
- Division of Obstetric and Gynecological Anesthesiology, Department of Anesthesiology, Yale School of Medicine, New Haven, Connecticut
| | - Lisa Parikh
- Department of Internal Medicine, Section of Endocrinology and Metabolism, Yale School of Medicine, New Haven, Connecticut
| | - Renata B DeAguiar
- Department of Internal Medicine, Section of Endocrinology and Metabolism, Yale School of Medicine, New Haven, Connecticut
| | - Christina S Han
- Department of Obstetrics, Gynecology and Reproductive Sciences, Section of Maternal-Fetal Medicine, Yale School of Medicine, New Haven, Connecticut
| | - Janice J Hwang
- Department of Internal Medicine, Section of Endocrinology and Metabolism, Yale School of Medicine, New Haven, Connecticut
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7
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Frazier HN, Ghoweri AO, Anderson KL, Lin RL, Popa GJ, Mendenhall MD, Reagan LP, Craven RJ, Thibault O. Elevating Insulin Signaling Using a Constitutively Active Insulin Receptor Increases Glucose Metabolism and Expression of GLUT3 in Hippocampal Neurons. Front Neurosci 2020; 14:668. [PMID: 32733189 PMCID: PMC7358706 DOI: 10.3389/fnins.2020.00668] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Accepted: 06/02/2020] [Indexed: 12/31/2022] Open
Abstract
Insulin signaling is an integral component of healthy brain function, with evidence of positive insulin-mediated alterations in synaptic integrity, cerebral blood flow, inflammation, and memory. However, the specific pathways targeted by this peptide remain unclear. Previously, our lab used a molecular approach to characterize the impact of insulin signaling on voltage-gated calcium channels and has also shown that acute insulin administration reduces calcium-induced calcium release in hippocampal neurons. Here, we explore the relationship between insulin receptor signaling and glucose metabolism using similar methods. Mixed, primary hippocampal cultures were infected with either a control lentivirus or one containing a constitutively active human insulin receptor (IRβ). 2-NBDG imaging was used to obtain indirect measures of glucose uptake and utilization. Other outcome measures include Western immunoblots of GLUT3 and GLUT4 on total membrane and cytosolic subcellular fractions. Glucose imaging data indicate that neurons expressing IRβ show significant elevations in uptake and rates of utilization compared to controls. As expected, astrocytes did not respond to the IRβ treatment. Quantification of Western immunoblots show that IRβ is associated with significant elevations in GLUT3 expression, particularly in the total membrane subcellular fraction, but did not alter GLUT4 expression in either fraction. Our work suggests that insulin plays a significant role in mediating neuronal glucose metabolism, potentially through an upregulation in the expression of GLUT3. This provides further evidence for a potential therapeutic mechanism underlying the beneficial impact of intranasal insulin in the clinic.
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Affiliation(s)
- Hilaree N Frazier
- Department of Pharmacology and Nutritional Sciences, University of Kentucky College of Medicine, Lexington, KY, United States
| | - Adam O Ghoweri
- Department of Pharmacology and Nutritional Sciences, University of Kentucky College of Medicine, Lexington, KY, United States
| | - Katie L Anderson
- Department of Pharmacology and Nutritional Sciences, University of Kentucky College of Medicine, Lexington, KY, United States
| | - Ruei-Lung Lin
- Department of Pharmacology and Nutritional Sciences, University of Kentucky College of Medicine, Lexington, KY, United States
| | - Gabriel J Popa
- Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, Lexington, KY, United States
| | - Michael D Mendenhall
- Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, Lexington, KY, United States
| | - Lawrence P Reagan
- Department of Pharmacology, Physiology and Neuroscience, University of South Carolina School of Medicine, Columbia, SC, United States
| | - Rolf J Craven
- Department of Pharmacology and Nutritional Sciences, University of Kentucky College of Medicine, Lexington, KY, United States
| | - Olivier Thibault
- Department of Pharmacology and Nutritional Sciences, University of Kentucky College of Medicine, Lexington, KY, United States
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8
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Buie JJ, Watson LS, Smith CJ, Sims-Robinson C. Obesity-related cognitive impairment: The role of endothelial dysfunction. Neurobiol Dis 2019; 132:104580. [PMID: 31454547 PMCID: PMC6834913 DOI: 10.1016/j.nbd.2019.104580] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2019] [Revised: 07/27/2019] [Accepted: 08/20/2019] [Indexed: 12/16/2022] Open
Abstract
Obesity is a global pandemic associated with macro- and microvascular endothelial dysfunction. Microvascular endothelial dysfunction has recently emerged as a significant risk factor for the development of cognitive impairment. In this review, we present evidence from clinical and preclinical studies supporting a role for obesity in cognitive impairment. Next, we discuss how obesity-related hyperinsulinemia/insulin resistance, systemic inflammation, and gut dysbiosis lead to cognitive impairment through induction of endothelial dysfunction and disruption of the blood brain barrier. Finally, we outline the potential clinical utility of dietary interventions, exercise, and bariatric surgery in circumventing the impacts of obesity on cognitive function.
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Affiliation(s)
- Joy Jones Buie
- WISSDOM Center, Medical University of South Carolina, Charleston, SC 29425, USA; Department of Neurology, Medical University of South Carolina, Charleston, SC 29425, USA
| | - Luke S Watson
- Department of Neurology, Medical University of South Carolina, Charleston, SC 29425, USA; Molecular and Cellular Biology and Pathobiology Program, Medical University of South Carolina, Charleston, SC 29425, USA
| | - Crystal J Smith
- Department of Neurology, Medical University of South Carolina, Charleston, SC 29425, USA; Department of Neurosciences, Medical University of South Carolina, Charleston, SC 29425, USA
| | - Catrina Sims-Robinson
- Department of Neurology, Medical University of South Carolina, Charleston, SC 29425, USA; Molecular and Cellular Biology and Pathobiology Program, Medical University of South Carolina, Charleston, SC 29425, USA; Department of Neurosciences, Medical University of South Carolina, Charleston, SC 29425, USA.
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9
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Frazier HN, Ghoweri AO, Anderson KL, Lin RL, Porter NM, Thibault O. Broadening the definition of brain insulin resistance in aging and Alzheimer's disease. Exp Neurol 2019; 313:79-87. [PMID: 30576640 PMCID: PMC6370304 DOI: 10.1016/j.expneurol.2018.12.007] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Revised: 12/05/2018] [Accepted: 12/17/2018] [Indexed: 12/17/2022]
Abstract
It has been >20 years since studies first revealed that the brain is insulin sensitive, highlighted by the expression of insulin receptors in neurons and glia, the presence of circulating brain insulin, and even localized insulin production. Following these discoveries, evidence of decreased brain insulin receptor number and function was reported in both clinical samples and animal models of aging and Alzheimer's disease, setting the stage for the hypothesis that neuronal insulin resistance may underlie memory loss in these conditions. The development of therapeutic insulin delivery to the brain using intranasal insulin administration has been shown to improve aspects of memory or learning in both humans and animal models. However, whether this approach functions by compensating for poorly signaling insulin receptors, for reduced insulin levels in the brain, or for reduced trafficking of insulin into the brain remains unclear. Direct measures of insulin's impact on cellular physiology and metabolism in the brain have been sparse in models of Alzheimer's disease, and even fewer studies have analyzed these processes in the aged brain. Nevertheless, recent evidence supports the role of brain insulin as a mediator of glucose metabolism through several means, including altering glucose transporters. Here, we provide a review of contemporary literature on brain insulin resistance, highlight the rationale for improving memory function using intranasal insulin, and describe initial results from experiments using a molecular approach to more directly measure the impact of insulin receptor activation and signaling on glucose uptake in neurons.
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Affiliation(s)
- Hilaree N Frazier
- University of Kentucky, Department of Pharmacology and Nutritional Sciences, 800 Rose St., Lexington, KY 40536, United States.
| | - Adam O Ghoweri
- University of Kentucky, Department of Pharmacology and Nutritional Sciences, 800 Rose St., Lexington, KY 40536, United States.
| | - Katie L Anderson
- University of Kentucky, Department of Pharmacology and Nutritional Sciences, 800 Rose St., Lexington, KY 40536, United States.
| | - Ruei-Lung Lin
- University of Kentucky, Department of Pharmacology and Nutritional Sciences, 800 Rose St., Lexington, KY 40536, United States.
| | - Nada M Porter
- University of Kentucky, Department of Pharmacology and Nutritional Sciences, 800 Rose St., Lexington, KY 40536, United States.
| | - Olivier Thibault
- University of Kentucky, Department of Pharmacology and Nutritional Sciences, 800 Rose St., Lexington, KY 40536, United States.
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10
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Woods SC, May AA, Liu M, Tso P, Begg DP. Using the cerebrospinal fluid to understand ingestive behavior. Physiol Behav 2017; 178:172-178. [PMID: 27923718 PMCID: PMC5944842 DOI: 10.1016/j.physbeh.2016.11.037] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Revised: 11/22/2016] [Accepted: 11/28/2016] [Indexed: 01/08/2023]
Abstract
The cerebrospinal fluid (CSF) offers a window into the workings of the brain and blood-brain barrier (BBB). Molecules that enter into the central nervous system (CNS) by passive diffusion or receptor-mediated transport through the choroid plexus often appear in the CSF prior to acting within the brain. Other molecules enter the CNS by passing through the BBB into the brain's interstitial fluid prior to appearing in the CSF. This pattern is also often observed for molecules synthesized by neurons or glia within the CNS. The CSF is therefore an important conduit for the entry and clearance of molecules into/from the CNS and thereby constitutes an important window onto brain activity and barrier function. Assessing the CSF basally, under experimental conditions, or in the context of challenges or metabolic diseases can provide powerful insights about brain function. Here, we review important findings made by our labs, as influenced by the late Randall Sakai, by interrogating the CSF.
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Affiliation(s)
- Stephen C Woods
- Department of Psychiatry and Behavioral Neuroscience, Metabolic Diseases Institute, University of Cincinnati College of Medicine, Cincinnati, OH, USA.
| | - Aaron A May
- Department of Pathology and Molecular Medicine, Metabolic Diseases Institute, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Min Liu
- Department of Pathology and Molecular Medicine, Metabolic Diseases Institute, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Patrick Tso
- Department of Pathology and Molecular Medicine, Metabolic Diseases Institute, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Denovan P Begg
- School of Psychology, University of New South Wales, Sydney, NSW 2052, Australia
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11
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Conde SV, Ribeiro MJ, Melo BF, Guarino MP, Sacramento JF. Insulin resistance: a new consequence of altered carotid body chemoreflex? J Physiol 2017; 595:31-41. [PMID: 27027507 PMCID: PMC5199745 DOI: 10.1113/jp271684] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2015] [Accepted: 03/11/2016] [Indexed: 01/22/2023] Open
Abstract
Metabolic diseases affect millions of individuals across the world and represent a group of chronic diseases of very high prevalence and relatively low therapeutic success, making them suitable candidates for pathophysiological studies. The sympathetic nervous system (SNS) contributes to the regulation of energy balance and energy expenditure both in physiological and pathological states. For instance, drugs that stimulate sympathetic activity decrease food intake, increase resting metabolic rate and increase the thermogenic response to food, while pharmacological blockade of the SNS has opposite effects. Likewise, dysmetabolic features such as insulin resistance, dyslipidaemia and obesity are characterized by a basal overactivation of the SNS. Recently, a new line of research linking the SNS to metabolic diseases has emerged with the report that the carotid bodies (CBs) are involved in the development of insulin resistance. The CBs are arterial chemoreceptors that classically sense changes in arterial blood O2 , CO2 and pH levels and whose activity is known to be increased in rodent models of insulin resistance. We have shown that selective bilateral resection of the nerve of the CB, the carotid sinus nerve (CSN), totally prevents diet-induced insulin resistance, hyperglycaemia, dyslipidaemia, hypertension and sympathoadrenal overactivity. These results imply that the beneficial effects of CSN resection on insulin action and glucoregulation are modulated by target-related efferent sympathetic nerves through a reflex that is initiated in the CBs. It also highlights modulation of CB activity as a putative future therapeutic intervention for metabolic diseases.
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Affiliation(s)
- Silvia V. Conde
- CEDOC, Centro Estudos Doenças Crónicas, NOVA Medical School, Faculdade de Ciências MédicasUniversidade Nova de LisboaLisboaPortugal
| | - Maria J. Ribeiro
- CEDOC, Centro Estudos Doenças Crónicas, NOVA Medical School, Faculdade de Ciências MédicasUniversidade Nova de LisboaLisboaPortugal
| | - Bernardete F. Melo
- CEDOC, Centro Estudos Doenças Crónicas, NOVA Medical School, Faculdade de Ciências MédicasUniversidade Nova de LisboaLisboaPortugal
| | - Maria P. Guarino
- CEDOC, Centro Estudos Doenças Crónicas, NOVA Medical School, Faculdade de Ciências MédicasUniversidade Nova de LisboaLisboaPortugal
- UIS‐Unidade de Investigação em Saúde – Escola Superior de Saúde de Leiria – Instituto Politécnico de LeiriaLeiriaPortugal
| | - Joana F. Sacramento
- CEDOC, Centro Estudos Doenças Crónicas, NOVA Medical School, Faculdade de Ciências MédicasUniversidade Nova de LisboaLisboaPortugal
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12
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O'Dell LE, Nazarian A. Enhanced vulnerability to tobacco use in persons with diabetes: A behavioral and neurobiological framework. Prog Neuropsychopharmacol Biol Psychiatry 2016; 65:288-96. [PMID: 26092247 DOI: 10.1016/j.pnpbp.2015.06.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Revised: 05/15/2015] [Accepted: 06/08/2015] [Indexed: 11/18/2022]
Abstract
Tobacco use significantly magnifies the negative health complications associated with diabetes. Although tobacco use is strongly discouraged in persons with diabetes, clinical evidence suggests that they often continue to smoke and have more difficulty quitting despite serious contraindications. Here, we suggest that a potential reason for enhanced vulnerability to tobacco use in persons with diabetes is greater rewarding effects of nicotine. This review summarizes pre-clinical evidence indicating that the rewarding effects of nicotine are enhanced in rodent models of type 1 and type 2 diabetes. We also provide a framework of neurobiological mechanisms that are posited to promote tobacco use in persons with diabetes. This framework suggests that diabetes induces a disruption in insulin signaling that leads to a suppression of dopamine systems in the mesolimbic reward pathway. Lastly, we consider the clinical implications of enhanced rewarding effects of nicotine that may promote tobacco use in persons with diabetes. The clinical efficacy of smoking cessation medications that enhance dopamine are important to consider, given that persons with diabetes may display disrupted dopaminergic mechanisms. Future work is needed to better understand the complex interaction of dopamine and insulin in order to develop better smoking cessation medications for persons with diabetes.
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Affiliation(s)
- Laura E O'Dell
- Department of Psychology, University of Texas at El Paso, 500 West University Avenue, El Paso, TX 79968, USA
| | - Arbi Nazarian
- Department of Pharmaceutical Sciences, Western University of Health Sciences, 309 East Second Street, Pomona, CA 91766, USA.
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13
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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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14
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Abstract
The pancreatic hormone insulin plays a well-described role in the periphery, based principally on its ability to lower circulating glucose levels via activation of glucose transporters. However, insulin also acts within the central nervous system (CNS) to alter a number of physiological outcomes ranging from energy balance and glucose homeostasis to cognitive performance. Insulin is transported into the CNS by a saturable receptor-mediated process that is proposed to be dependent on the insulin receptor. Transport of insulin into the brain is dependent on numerous factors including diet, glycemia, a diabetic state and notably, obesity. Obesity leads to a marked decrease in insulin transport from the periphery into the CNS and the biological basis of this reduction of transport remains unresolved. Despite decades of research into the effects of central insulin on a wide range of physiological functions and its transport from the periphery to the CNS, numerous questions remain unanswered including which receptor is responsible for transport and the precise mechanisms of action of insulin within the brain.
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Affiliation(s)
- Denovan P Begg
- School of Psychology, University of New South Wales (UNSW, Australia), Sydney, New South Wales, Australia.
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15
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Kealy J, Bennett R, Lowry JP. Real-time effects of insulin-induced hypoglycaemia on hippocampal glucose and oxygen. Brain Res 2014; 1598:76-87. [PMID: 25511995 DOI: 10.1016/j.brainres.2014.12.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2014] [Revised: 12/01/2014] [Accepted: 12/05/2014] [Indexed: 01/07/2023]
Abstract
The hippocampus plays a vital role in learning and memory and is susceptible to damage following hypoglycaemic shock. The effect of an acute administration of insulin on hippocampal function has been described in terms of behavioural deficits but its effect on hippocampal oxygen and glucose is unclear. Glucose oxidase biosensors (detecting glucose) and carbon paste electrodes (detecting oxygen) were implanted into the hippocampus of Sprague Dawley rats. Animals were allowed to recover and real-time recordings were made in order to determine the effects of fasting, insulin administration (15 U/kg; i.p.) and reintroduction of food on hippocampal oxygen and glucose. Fasting caused a significant decrease in hippocampal glucose over the course of 24h. Insulin administration produced a significant decrease in hippocampal glucose along with a significant increase in hippocampal oxygen. Finally, the reintroduction of food resulted in glucose levels significantly increasing along with a transient but significant increase in oxygen levels. The findings presented here suggest that even a single acute period of hypoglycaemia may substantially disrupt hippocampal oxygen and glucose and therefore affect hippocampal function.
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Affiliation(s)
- John Kealy
- Maynooth University Department of Chemistry, Maynooth University, Maynooth, Co. Kildare, Ireland.
| | - Rachel Bennett
- Maynooth University Department of Chemistry, Maynooth University, Maynooth, Co. Kildare, Ireland
| | - John P Lowry
- Maynooth University Department of Chemistry, Maynooth University, Maynooth, Co. Kildare, Ireland
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16
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Begg DP, Mul JD, Liu M, Reedy BM, D'Alessio DA, Seeley RJ, Woods SC. Reversal of diet-induced obesity increases insulin transport into cerebrospinal fluid and restores sensitivity to the anorexic action of central insulin in male rats. Endocrinology 2013; 154:1047-54. [PMID: 23337529 PMCID: PMC3578991 DOI: 10.1210/en.2012-1929] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Diet-induced obesity (DIO) reduces the ability of centrally administered insulin to reduce feeding behavior and also reduces the transport of insulin from the periphery to the central nervous system (CNS). The current study was designed to determine whether reversal of high-fat DIO restores the anorexic efficacy of central insulin and whether this is accompanied by restoration of the compromised insulin transport. Adult male Long-Evans rats were initially maintained on either a low-fat chow diet (LFD) or a high-fat diet (HFD). After 22 weeks, half of the animals on the HFD were changed to the LFD, whereas the other half continued on the HFD for an additional 8 weeks, such that there were 3 groups: 1) a LFD control group (Con; n = 18), 2) a HFD-fed, DIO group (n = 17), and 3) a HFD to LFD, DIO-reversal group (DIO-rev; n = 18). The DIO reversal resulted in a significant reduction of body weight and epididymal fat weight relative to the DIO group. Acute central insulin administration (8 mU) reduced food intake and caused weight loss in Con and DIO-rev but not DIO rats. Fasting cerebrospinal fluid insulin was higher in DIO than Con animals. However, after a peripheral bolus injection of insulin, cerebrospinal fluid insulin increased in Con and DIO-rev rats but not in the DIO group. These data provide support for previous reports that DIO inhibits both the central effects of insulin and insulin's transport to the CNS. Importantly, DIO-rev restored sensitivity to the effects of central insulin on food intake and insulin transport into the CNS.
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Affiliation(s)
- Denovan P Begg
- Departments of Psychiatry and Behavioral Neuroscience, University of Cincinnati, Cincinnati, OH 45237, USA.
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17
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Begg DP, Woods SC. Interactions between the central nervous system and pancreatic islet secretions: a historical perspective. ADVANCES IN PHYSIOLOGY EDUCATION 2013; 37:53-60. [PMID: 23471249 PMCID: PMC3776474 DOI: 10.1152/advan.00167.2012] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2012] [Accepted: 01/14/2013] [Indexed: 05/10/2023]
Abstract
The endocrine pancreas is richly innervated with sympathetic and parasympathetic projections from the brain. In the mid-20th century, it was established that α-adrenergic activation inhibits, whereas cholinergic stimulation promotes, insulin secretion; this demonstrated the importance of the sympathetic and parasympathetic systems in pancreatic endocrine function. It was later established that insulin injected peripherally could act within the brain, leading to the discovery of insulin and insulin receptors within the brain and the receptor-mediated transport of insulin into the central nervous system from endothelial cells. The insulin receptor within the central nervous system is widely distributed, reflecting insulin's diverse range of actions, including acting as an adiposity signal to reduce food intake and increase energy expenditure, regulation of systemic glucose responses, altering sympathetic activity, and involvement in cognitive function. As observed with central insulin administration, the pancreatic hormones glucagon, somatostatin, pancreatic polypeptide, and amylin can each also reduce food intake. Pancreatic and also gut hormones are released cephalically, in what is an important mechanism to prepare the body for a meal and prevent excessive postprandial hyperglycemia.
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Affiliation(s)
- Denovan P Begg
- Department of Psychiatry and Behavioral Neuroscience, University of Cincinnati, Cincinnati, OH 45237, USA
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18
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Arble DM, Sandoval DA. CNS control of glucose metabolism: response to environmental challenges. Front Neurosci 2013; 7:20. [PMID: 23550218 PMCID: PMC3581798 DOI: 10.3389/fnins.2013.00020] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2012] [Accepted: 02/04/2013] [Indexed: 01/07/2023] Open
Abstract
Over the last 15 years, considerable work has accumulated to support the role of the CNS in regulating postprandial glucose levels. As discussed in the first section of this review, the CNS receives and integrates information from afferent neurons, circulating hormones, and postprandially generated nutrients to subsequently direct changes in glucose output by the liver and glucose uptake by peripheral tissues. The second major component of this review focuses on the effects of external pressures, including high fat diet and changes to the light:dark cycle on CNS-regulating glucose homeostasis. We also discuss the interaction between these different pressures and how they contribute to the multifaceted mechanisms that we hypothesize contribute to the dysregulation of glucose in type 2 diabetes mellitus (T2DM). We argue that while current peripheral therapies serve to delay the progression of T2DM, generating combined obesity and T2DM therapies targeted at the CNS, the primary site of dysfunction for both diseases, would lead to a more profound impact on the progression of both diseases.
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Affiliation(s)
- Deanna M Arble
- Department of Medicine, University of Cincinnati Cincinnati, OH, USA
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19
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Woods SC. From conditioned hypoglycemia to obesity: following the data. Physiol Behav 2013; 121:19-24. [PMID: 23352822 DOI: 10.1016/j.physbeh.2013.01.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2012] [Accepted: 01/03/2013] [Indexed: 01/24/2023]
Abstract
While a graduate student in the late 1960s I trained rats to lower their blood glucose in response to an arbitrary cue, a phenomenon called conditioned hypoglycemia. Over many years as my colleagues and I attempted to understand the underlying physiology of conditioned insulin secretion and conditioned hypoglycemia, it became clear that there were many implications that were highly important, including the entry of insulin into the brain, the existence of insulin receptors in certain brain areas, neural reflexes that project to insulin-secreting B-cells in the pancreas, the entrainment of those reflexes to improve the efficiency of meal-taking, and the possibility of adiposity signals from the body to the brain that influence behavior and metabolism. This article summarizes how we tackled each of these areas of research.
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Affiliation(s)
- Stephen C Woods
- Department of Psychiatry and Behavioral Neuroscience, University of Cincinnati, 2170 East Galbraith Road, Cincinnati, OH 45237, USA.
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20
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Banks WA, Owen JB, Erickson MA. Insulin in the brain: there and back again. Pharmacol Ther 2012; 136:82-93. [PMID: 22820012 PMCID: PMC4134675 DOI: 10.1016/j.pharmthera.2012.07.006] [Citation(s) in RCA: 382] [Impact Index Per Article: 31.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2012] [Accepted: 07/03/2012] [Indexed: 12/12/2022]
Abstract
Insulin performs unique functions within the CNS. Produced nearly exclusively by the pancreas, insulin crosses the blood-brain barrier (BBB) using a saturable transporter, affecting feeding and cognition through CNS mechanisms largely independent of glucose utilization. Whereas peripheral insulin acts primarily as a metabolic regulatory hormone, CNS insulin has an array of effects on brain that may more closely resemble the actions of the ancestral insulin molecule. Brain endothelial cells (BECs), the cells that form the vascular BBB and contain the transporter that translocates insulin from blood to brain, are themselves regulated by insulin. The insulin transporter is altered by physiological and pathological factors including hyperglycemia and the diabetic state. The latter can lead to BBB disruption. Pericytes, pluripotent cells in intimate contact with the BECs, protect the integrity of the BBB and its ability to transport insulin. Most of insulin's known actions within the CNS are mediated through two canonical pathways, the phosphoinositide-3 kinase (PI3)/Akt and Ras/mitogen activated kinase (MAPK) cascades. Resistance to insulin action within the CNS, sometimes referred to as diabetes mellitus type III, is associated with peripheral insulin resistance, but it is possible that variable hormonal resistance syndromes exist so that resistance at one tissue bed may be independent of that at others. CNS insulin resistance is associated with Alzheimer's disease, depression, and impaired baroreceptor gain in pregnancy. These aspects of CNS insulin action and the control of its entry by the BBB are likely only a small part of the story of insulin within the brain.
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Affiliation(s)
- William A Banks
- Geriatrics Research Education and Clinical Center, Veterans Affairs Puget Sound Health Care Center, Seattle, WA, USA.
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21
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Abstract
Lipid sensing and insulin signaling in the brain independently triggers a negative feedback system to lower glucose production and food intake. Here, we discuss the underlying molecular and neuronal mechanisms of lipid sensing and insulin signaling in the hypothalamus and how these mechanisms are affected in response to high-fat feeding. We propose that high-fat feeding concurrently disrupts hypothalamic insulin-signaling and lipid-sensing mechanisms and that experiments aimed to restore both insulin action and lipid sensing in the brain could effectively lower glucose production and food intake to restore metabolic homeostasis in type 2 diabetes and obesity.
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Affiliation(s)
- Jessica T Y Yue
- Toronto General Research Institute, University Health Network, Toronto, Canada
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22
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Papazoglou I, Berthou F, Vicaire N, Rouch C, Markaki EM, Bailbe D, Portha B, Taouis M, Gerozissis K. Hypothalamic serotonin-insulin signaling cross-talk and alterations in a type 2 diabetic model. Mol Cell Endocrinol 2012; 350:136-44. [PMID: 22209745 DOI: 10.1016/j.mce.2011.12.007] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/22/2011] [Revised: 12/08/2011] [Accepted: 12/08/2011] [Indexed: 12/31/2022]
Abstract
Serotonin and insulin are key regulators of homeostatic mechanisms in the hypothalamus. However, in type 2 diabetes, the hypothalamic responsiveness to serotonin is not clearly established. We used a diabetic model, the Goto Kakizaki (GK) rats, to explore insulin receptor expression, insulin and serotonin efficiency in the hypothalamus and liver by means of Akt phosphorylation. Insulin or dexfenfluramine (stimulator of serotonin) treatment induced Akt phosphorylation in Wistar rats but not in GK rats that exhibit down-regulated insulin receptor. Studies in a neuroblastoma cell line showed that serotonin-induced Akt phosphorylation is PI3-kinase dependent. Finally, in response to food intake, hypothalamic serotonin release was reduced in GK rats, indicating impaired responsiveness of this neurotransmitter. In conclusion, hypothalamic serotonin as insulin efficiency is impaired in diabetic GK rats. The insulin-serotonin cross-talk and impairment observed is one potential key modification in the brain during the onset of diabetes.
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Affiliation(s)
- Ioannis Papazoglou
- CNRS, Center of Neurosciences Paris-Sud, UMR 8195, Orsay F-91405, France
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23
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Figlewicz DP, Sipols AJ. Energy regulatory signals and food reward. Pharmacol Biochem Behav 2010; 97:15-24. [PMID: 20230849 PMCID: PMC2897918 DOI: 10.1016/j.pbb.2010.03.002] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/07/2009] [Revised: 02/26/2010] [Accepted: 03/09/2010] [Indexed: 12/23/2022]
Abstract
The hormones insulin, leptin, and ghrelin have been demonstrated to act in the central nervous system (CNS) as regulators of energy homeostasis, acting at medial hypothalamic sites. Here, we summarize research demonstrating that, in addition to direct homeostatic actions at the hypothalamus, CNS circuitry that subserves reward and is also a direct and indirect target for the action of these endocrine regulators of energy homeostasis. Specifically, insulin and leptin can decrease food reward behaviors and modulate the function of neurotransmitter systems and neural circuitry that mediate food reward, the midbrain dopamine (DA) and opioidergic pathways. Ghrelin can increase food reward behaviors, and support midbrain DA neuronal function. We summarize discussion of behavioral, systems, and cellular evidence in support of the contributions of reward circuitry to the homeostatic roles of these hormones in the CNS. The understanding of neuroendocrine modulation of food reward, as well as food reward modulation by diet and obesity, may point to new directions for therapeutic approaches to overeating or eating disorders.
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Affiliation(s)
- Dianne P Figlewicz
- Metabolism/Endocrinology, VA Puget Sound Health Care System, Seattle Division, Seattle, WA 98108, USA.
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24
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Young CN, Deo SH, Chaudhary K, Thyfault JP, Fadel PJ. Insulin enhances the gain of arterial baroreflex control of muscle sympathetic nerve activity in humans. J Physiol 2010; 588:3593-603. [PMID: 20643774 DOI: 10.1113/jphysiol.2010.191866] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Recent animal studies indicate that insulin increases arterial baroreflex control of lumbar sympathetic nerve activity; however, the extent to which these findings can be extrapolated to humans is unknown. To begin to address this, muscle sympathetic nerve activity (MSNA) and arterial blood pressure were measured in 19 healthy subjects (27 ± 1 years) before, and for 120 min following, two common methodologies used to evoke sustained increases in plasma insulin: a mixed meal and a hyperinsulinaemic euglycaemic clamp. Weighted linear regression analysis between MSNA and diastolic blood pressure was used to determine the gain (i.e. sensitivity) of arterial baroreflex control of MSNA. Plasma insulin was significantly elevated within 30 min following meal intake (34 ± 6 uIU ml(1); P < 0.05) and remained above baseline for up to 120 min. Similarly, after meal intake, arterial baroreflex-MSNA gain for burst incidence and total MSNA was increased and remained elevated for the duration of the protocol (e.g. burst incidence gain: 3.29 ± 0.54 baseline vs. 5.64 ± 0.67 bursts (100 heart beats)(1) mmHg(1) at 120 min; P < 0.05). During the hyperinsulinaemic euglycaemic clamp, in which insulin was elevated to postprandial concentrations (42 ± 6 μIU ml(1); P < 0.05), while glucose was maintained constant, arterial baroreflex-MSNA gain was similarly enhanced (e.g. burst incidence gain: 2.44 ± 0.29 baseline vs. 4.74 ± 0.71 bursts (100 heart beats)(1) mmHg(1) at 120 min; P < 0.05). Importantly, during time control experiments, with sustained fasting insulin concentrations, the arterial baroreflex-MSNA gain remained unchanged. These findings demonstrate, for the first time in healthy humans, that increases in plasma insulin enhance the gain of arterial baroreflex control of MSNA.
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Affiliation(s)
- Colin N Young
- Department of Medical Pharmacology & Physiology, University of Missouri, Columbia, MO 65212, USA
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25
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Abstract
The hormones insulin, leptin, and ghrelin have been demonstrated to act in the central nervous system (CNS) as regulators of energy homeostasis, acting at medial hypothalamic sites. Here, we summarize research demonstrating that, in addition to direct homeostatic actions at the hypothalamus, CNS circuitry that subserves reward and is also a direct and indirect target for the action of these endocrine regulators of energy homeostasis. Specifically, insulin and leptin can decrease food reward behaviors and modulate the function of neurotransmitter systems and neural circuitry that mediate food reward, the midbrain dopamine (DA) and opioidergic pathways. Ghrelin can increase food reward behaviors, and support midbrain DA neuronal function. We summarize discussion of behavioral, systems, and cellular evidence in support of the contributions of reward circuitry to the homeostatic roles of these hormones in the CNS. The understanding of neuroendocrine modulation of food reward, as well as food reward modulation by diet and obesity, may point to new directions for therapeutic approaches to overeating or eating disorders.
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26
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Young CN, Deo SH, Kim A, Horiuchi M, Mikus CR, Uptergrove GM, Thyfault JP, Fadel PJ. Influence of endurance training on central sympathetic outflow to skeletal muscle in response to a mixed meal. J Appl Physiol (1985) 2010; 108:882-90. [PMID: 20110544 DOI: 10.1152/japplphysiol.01174.2009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Nutrient intake is accompanied by increases in central sympathetic outflow, a response that has been mainly attributed to insulin. Insulin-mediated sympathoexcitation appears to be blunted in insulin-resistant conditions, suggesting that aside from peripheral insulin insensitivity, such conditions may also impair the central action of insulin in mediating sympathetic activation. What remains unclear is whether an insulin-sensitive state, such as that induced by chronic endurance training, alters the central sympathetic effects of insulin during postprandial conditions. To examine this question plasma insulin and glucose, muscle sympathetic nerve activity (MSNA), heart rate, and arterial blood pressure were measured in 11 high-fit [HF; peak oxygen uptake (V(O(2peak))) 65.9 +/- 1.4 ml x kg(-1) x min(-1)] and 9 average-fit (AF; V(O(2peak)) 43.6 +/- 1.3 ml x kg(-1) x min(-1)) male subjects before and for 120 min after ingestion of a mixed meal drink. As expected, the insulin response to meal ingestion was lower in HF than AF participants (insulin area under the curve(0-120): 2,314 +/- 171 vs. 4,028 +/- 460 microIU x ml(-1) x 120(-1), HF vs. AF, P < 0.05), with similar plasma glucose responses between groups. Importantly, following consumption of the meal, the HF subjects demonstrated a greater rise in MSNA compared with the AF subjects (e.g., 120 min: Delta21 +/- 1 vs. 8 +/- 3 bursts/100 heart beats, HF vs. AF, P < 0.05). Furthermore, when expressed relative to plasma insulin, HF subjects exhibited a greater change in MSNA for any given change in insulin. Arterial blood pressure responses following meal intake were similar between groups. Collectively, these data suggest that, in addition to improved peripheral insulin sensitivity, endurance training may enhance the central sympathetic effect of insulin to increase MSNA following consumption of a mixed meal.
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Affiliation(s)
- Colin N Young
- Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO 65212, USA
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27
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The Brain-insulin Connection, Metabolic Diseases and Related Pathologies. DIABETES, INSULIN AND ALZHEIMER'S DISEASE 2010. [DOI: 10.1007/978-3-642-04300-0_2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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28
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Banks WA. Mouse models of neurological disorders: a view from the blood-brain barrier. Biochim Biophys Acta Mol Basis Dis 2009; 1802:881-8. [PMID: 19879356 DOI: 10.1016/j.bbadis.2009.10.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2009] [Revised: 10/20/2009] [Accepted: 10/23/2009] [Indexed: 12/16/2022]
Abstract
The number of disease models that involve an aspect of blood-brain barrier (BBB) dysregulation have increased tremendously. The main factors contributing to this expansion have been an increased number of diseases in which the BBB is known to be involved, an increase in the known functions of the BBB, and an increase in the number of models and tools with which those diverse functions can be studied. In many cases, the BBB may be a target of disease; current thinking would include hypertensive encephalopathy and perhaps stroke in this category. Another category are those diseases in which special attributes of the BBB may predispose to disease; for example, the ability of a pathogen to cross the BBB often depends on the pathogen's ability to invoke transcytotic pathways in the brain endothelial or choroid plexus cell. Of special interest are those diseases in which the BBB may be the primary seat of disease or play a major role in the onset or progression of the disease. An increasing number of diseases are so categorized in which BBB dysfunction or dysregulation plays a major role; this review highlights such roles for the BBB including those proposed for Alzheimer's disease and obesity.
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Affiliation(s)
- William A Banks
- GRECC, Veterans Affairs Medical Center-St. Louis and Saint Louis University School of Medicine, Division of Geriatrics, Department of Internal Medicine, 915 N. Grand Blvd, St. Louis, MO 63106, USA.
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29
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Sandoval DA, Obici S, Seeley RJ. Targeting the CNS to treat type 2 diabetes. Nat Rev Drug Discov 2009; 8:386-98. [PMID: 19404312 DOI: 10.1038/nrd2874] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Research on the role of peripheral organs in the regulation of glucose homeostasis has led to the development of various monotherapies that aim to improve glucose uptake and insulin action in these organs for the treatment of type 2 diabetes. It is now clear that the central nervous system (CNS) also plays an important part in orchestrating appropriate glucose metabolism, with accumulating evidence linking dysregulated CNS circuits to the failure of normal glucoregulatory mechanisms. There is evidence that there is substantial overlap between the CNS circuits that regulate energy balance and those that regulate glucose levels, suggesting that their dysregulation could link obesity and diabetes. These findings present new targets for therapies that may be capable of both inducing weight loss and improving glucose regulation.
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Affiliation(s)
- Darleen A Sandoval
- Department of Psychiatry, Genome Research Institute, University of Cincinnati, 2170 East Galbraith Road, Cincinnati, Ohio 45237, USA
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Woods SC, D'Alessio DA. Central control of body weight and appetite. J Clin Endocrinol Metab 2008; 93:S37-50. [PMID: 18987269 PMCID: PMC2585760 DOI: 10.1210/jc.2008-1630] [Citation(s) in RCA: 294] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/28/2008] [Accepted: 09/08/2008] [Indexed: 12/14/2022]
Abstract
CONTEXT Energy balance is critical for survival and health, and control of food intake is an integral part of this process. This report reviews hormonal signals that influence food intake and their clinical applications. EVIDENCE ACQUISITION A relatively novel insight is that satiation signals that control meal size and adiposity signals that signify the amount of body fat are distinct and interact in the hypothalamus and elsewhere to control energy homeostasis. This review focuses upon recent literature addressing the integration of satiation and adiposity signals and therapeutic implications for treatment of obesity. EVIDENCE SYNTHESIS During meals, signals such as cholecystokinin arise primarily from the GI tract to cause satiation and meal termination; signals secreted in proportion to body fat such as insulin and leptin interact with satiation signals and provide effective regulation by dictating meal size to amounts that are appropriate for body fatness, or stored energy. Although satiation and adiposity signals are myriad and redundant and reduce food intake, there are few known orexigenic signals; thus, initiation of meals is not subject to the degree of homeostatic regulation that cessation of eating is. There are now drugs available that act through receptors for satiation factors and which cause weight loss, demonstrating that this system is amenable to manipulation for therapeutic goals. CONCLUSIONS Although progress on effective medical therapies for obesity has been relatively slow in coming, advances in understanding the central regulation of food intake may ultimately be turned into useful treatment options.
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Affiliation(s)
- Stephen C Woods
- Department of Psychiatry, University of Cincinnati, Cincinnati, OH 45237, USA.
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Figlewicz DP, Benoit SC. Insulin, leptin, and food reward: update 2008. Am J Physiol Regul Integr Comp Physiol 2008; 296:R9-R19. [PMID: 18945945 DOI: 10.1152/ajpregu.90725.2008] [Citation(s) in RCA: 151] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The hormones insulin and leptin have been demonstrated to act in the central nervous system (CNS) as regulators of energy homeostasis at medial hypothalamic sites. In a previous review, we described new research demonstrating that, in addition to these direct homeostatic actions at the hypothalamus, CNS circuitry that subserves reward and motivation is also a direct and an indirect target for insulin and leptin action. Specifically, insulin and leptin can decrease food reward behaviors and modulate the function of neurotransmitter systems and neural circuitry that mediate food reward, i.e., midbrain dopamine and opioidergic pathways. Here we summarize new behavioral, systems, and cellular evidence in support of this hypothesis and in the context of research into the homeostatic roles of both hormones in the CNS. We discuss some current issues in the field that should provide additional insight into this hypothetical model. The understanding of neuroendocrine modulation of food reward, as well as food reward modulation by diet and obesity, may point to new directions for therapeutic approaches to overeating or eating disorders.
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Affiliation(s)
- Dianne P Figlewicz
- Metabolism/Endocrinology (151) VA Puget Sound Health Care System, 1660 So. Columbian Way, Seattle, WA 98108, USA.
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Sandoval D, Cota D, Seeley RJ. The integrative role of CNS fuel-sensing mechanisms in energy balance and glucose regulation. Annu Rev Physiol 2008; 70:513-35. [PMID: 17988209 DOI: 10.1146/annurev.physiol.70.120806.095256] [Citation(s) in RCA: 139] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The incidences of both obesity and type 2 diabetes mellitus are rising at epidemic proportions. Despite this, the balance between caloric intake and expenditure is tremendously accurate under most circumstances. Growing evidence suggests that nutrient and hormonal signals converge and directly act on brain centers, leading to changes in fuel metabolism and, thus, stable body weight over time. Growing evidence also suggests that these same signals act on the central nervous system (CNS) to regulate glucose metabolism independently. We propose that this is not coincidental and that the CNS responds to peripheral signals to orchestrate changes in both energy and glucose homeostasis. In this way the CNS ensures that the nutrient demands of peripheral tissues (and likely of the brain itself) are being met. Consequently, dysfunction of the ability of the CNS to integrate fuel-sensing signals may underlie the etiology of metabolic diseases such as obesity and diabetes.
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Affiliation(s)
- Darleen Sandoval
- Department of Psychiatry, Genome Research Institute, University of Cincinnati, Cincinnati, OH 45237, USA
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Woods SC, Lutz TA, Geary N, Langhans W. Pancreatic signals controlling food intake; insulin, glucagon and amylin. Philos Trans R Soc Lond B Biol Sci 2006; 361:1219-35. [PMID: 16815800 PMCID: PMC1642707 DOI: 10.1098/rstb.2006.1858] [Citation(s) in RCA: 167] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The control of food intake and body weight by the brain relies upon the detection and integration of signals reflecting energy stores and fluxes, and their interaction with many different inputs related to food palatability and gastrointestinal handling as well as social, emotional, circadian, habitual and other situational factors. This review focuses upon the role of hormones secreted by the endocrine pancreas: hormones, which individually and collectively influence food intake, with an emphasis upon insulin, glucagon and amylin. Insulin and amylin are co-secreted by B-cells and provide a signal that reflects both circulating energy in the form of glucose and stored energy in the form of visceral adipose tissue. Insulin acts directly at the liver to suppress the synthesis and secretion of glucose, and some plasma insulin is transported into the brain and especially the mediobasal hypothalamus where it elicits a net catabolic response, particularly reduced food intake and loss of body weight. Amylin reduces meal size by stimulating neurons in the hindbrain, and there is evidence that amylin additionally functions as an adiposity signal controlling body weight as well as meal size. Glucagon is secreted from A-cells and increases glucose secretion from the liver. Glucagon acts in the liver to reduce meal size, the signal being relayed to the brain via the vagus nerves. To summarize, hormones of the endocrine pancreas are collectively at the crossroads of many aspects of energy homeostasis. Glucagon and amylin act in the short term to reduce meal size, and insulin sensitizes the brain to short-term meal-generated satiety signals; and insulin and perhaps amylin as well act over longer intervals to modulate the amount of fat maintained and defended by the brain. Hormones of the endocrine pancreas interact with receptors at many points along the gut-brain axis, from the liver to the sensory vagus nerve to the hindbrain to the hypothalamus; and their signals are conveyed both neurally and humorally. Finally, their actions include gastrointestinal and metabolic as well as behavioural effects.
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Affiliation(s)
- Stephen C Woods
- Department of Psychiatry, University of Cincinnati, OH 45237 USA.
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Carvalheira JBC, Ribeiro EB, Araújo EP, Guimarães RB, Telles MM, Torsoni M, Gontijo JAR, Velloso LA, Saad MJA. Selective impairment of insulin signalling in the hypothalamus of obese Zucker rats. Diabetologia 2003; 46:1629-40. [PMID: 14600817 DOI: 10.1007/s00125-003-1246-x] [Citation(s) in RCA: 119] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/10/2003] [Revised: 08/04/2003] [Indexed: 02/07/2023]
Abstract
AIM/HYPOTHESIS By acting in the brain, insulin suppresses food intake. However, little is known with regard to insulin signalling in the hypothalamus in insulin-resistant states. METHODS Western blotting, immunohistochemistry and polymerase chain reaction assays were combined to compare in vivo hypothalamic insulin signalling through the PI3-kinase and MAP kinase pathways between lean and obese Zucker rats. RESULTS Intracerebroventricular insulin infusion reduced food intake in lean rats to a greater extent than that observed in obese rats, and pre-treatment with PI3-kinase inhibitors prevented insulin-induced anorexia. The relative abundance of IRS-2 was considerably higher than that of IRS-1 in hypothalamus of both lean and obese rats. Insulin-stimulated phosphorylation of IR, IRS-1/2, the associations of PI 3-kinase to IRS-1/2 and phosphorylation of Akt in hypothalamus were decreased in obese rats compared to lean rats. These effects seem to be mediated by increased phosphoserine content of IR, IRS-1/2 and decreased protein levels of IRS-1/2 in obese rats. In contrast, insulin stimulated the phosphorylation of MAP kinase equally in lean and obese rats. CONCLUSION/INTERPRETATION This study provides direct measurements of insulin signalling in hypothalamus, and documents selective resistance to insulin signalling in hypothalamus of Zucker rats. These findings provide support for the hypothesis that insulin could have anti-obesity actions mediated by the PI3-kinase pathway, and that impaired insulin signalling in hypothalamus could play a role in the development of obesity in this animal model of insulin-resistance.
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Affiliation(s)
- J B C Carvalheira
- Departamento de Clínica Médica, FCM, Universidade Estadual de Campinas (UNICAMP), 13081-970, Campinas, SP, Brasil
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Figlewicz DP. Adiposity signals and food reward: expanding the CNS roles of insulin and leptin. Am J Physiol Regul Integr Comp Physiol 2003; 284:R882-92. [PMID: 12626355 DOI: 10.1152/ajpregu.00602.2002] [Citation(s) in RCA: 163] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The hormones insulin and leptin have been proposed to act in the central nervous system (CNS) as adiposity signals as part of a theoretical negative feedback loop that senses the caloric stores of an animal and orchestrates adjustments in energy balance and food intake. Much research has provided support for both the existence of such a feedback loop and the specific roles that insulin and leptin may play. Most studies have focused on hypothalamic sites, which historically are implicated in the regulation of energy balance, and on the brain stem, which is a target for neural and humoral signals relating to ingestive acts. More recent lines of research, including studies from our lab, suggest that in addition to these CNS sites, brain reward circuitry may be a target for insulin and leptin action. These studies are reviewed together here with the goals of providing a historical overview of the findings that have substantiated the originally hypothesized negative feedback model and of opening up new lines of investigation that will build on these findings and allow further refinement of the model of adiposity signal/CNS feedback loop. The understanding of how motivational circuitry and its endocrine or neuroendocrine modulation contributes to normal energy balance regulation should expand possibilities for future therapeutic approaches to obesity and may lead to important insights into mental illnesses such as substance abuse or eating disorders.
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Affiliation(s)
- Dianne P Figlewicz
- Veterans Affairs Puget Sound Health Care System, Seattle Division, Seattle 98108, USA.
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Alemzadeh R, Holshouser S. Effect of diazoxide on brain capillary insulin receptor binding and food intake in hyperphagic obese Zucker rats. Endocrinology 1999; 140:3197-202. [PMID: 10385415 DOI: 10.1210/endo.140.7.6768] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Insulin is believed to act as a central adiposity signal by binding to hypothalamic and other brain insulin receptors. Entry of circulating insulin into the brain is accomplished by a saturable receptor-mediated transendothelial transport system and is believed to be impaired in hyperinsulinemic, insulin-resistant, and hyperphagic obese Zucker rats. Theoretically, if hyperinsulinemia is decreased simultaneously while brain capillary insulin binding is increased, uptake of insulin into the brain can be enhanced leading to reduced food intake. To test this hypothesis, we administered diazoxide (DZ, 150 mg/kg/day), an inhibitor of glucose-mediated insulin secretion, or vehicle (control) to 7-week-old female obese and lean Zucker rats for 4 weeks (n = 24-28/subgroup-strain). Animals were assigned to either fasted (FD) or free-fed (FF) protocol for determination of plasma and cerebrospinal fluid (CSF) insulin and brain capillary insulin binding at the end of 4 weeks. DZ obese consumed fewer calories (P<0.01) and gained less weight than control obese (P<0.01), whereas DZ lean had similar amounts of caloric intake and weight gain compared with lean controls. DZ obese had lower fasting and random plasma glucose than control obese (P<0.05). FD and FF DZ-treated obese and lean rats had lower plasma insulin than their respective obese (P<0.01) and lean (P<0.01) controls. FD and FF DZ-treated obese rats demonstrated higher CSF insulin (P<0.05) and CSF/ plasma insulin ratio (P<0.01) than their controls, while only FF DZ lean animals showed higher CSF/plasma insulin ratio (P<0.01) than their controls (P<0.05). This was associated with enhanced brain capillary insulin binding in FD and FF DZ-treated obese (P<0.01) and lean (P<0.05) animals compared with their respective controls. It was concluded that DZ treatment in obese Zucker rats caused a decrease in insulin secretion and partially reversed impaired insulin binding to brain capillaries, leading to enhanced brain insulin uptake, and resulted in reduced food intake and weight gain observed in these animals.
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Affiliation(s)
- R Alemzadeh
- Department of Pediatrics, University of Tennessee Medical Center, Knoxville 37920, USA.
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Pedrazzi P, Cattaneo L, Valeriani L, Boschi S, Cocchi D, Zoli M. Hypothalamic neuropeptide Y and galanin in overweight rats fed a cafeteria diet. Peptides 1998; 19:157-65. [PMID: 9437748 DOI: 10.1016/s0196-9781(97)00258-1] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
We evaluated neuropeptide Y (NPY) and galanin (GAL) immunoreactivity (IR) and mRNA in the paraventricular and arcuate nucleus, respectively, in rats that became overweight (Ov) or not (NOv) when fed a cafeteria diet. After 2 months of diet, NOv rats showed a significant increase in NPY IR, whereas Ov rats showed a significant increase in GAL mRNA levels. None of these changes was present in rats overfed for 6.5 months. These differential changes in hypothalamic GAL and NPY transmissions may contribute to the different susceptibility of the two rat subpopulations to the weight-promoting effects of the hypercaloric diet.
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Affiliation(s)
- P Pedrazzi
- Department of Biomedical Sciences, University of Modena, Italy
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Cattaneo L, De Gennaro Colonna V, Zoli M, Müller EE, Cocchi D. Hypothalamo-pituitary-IGF-1 axis in female rats made obese by overfeeding. Life Sci 1997; 61:881-9. [PMID: 9284081 DOI: 10.1016/s0024-3205(97)00590-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
A gender-related impairment of the somatotrophic axis is present in obese Zucker rats, female rats being better preserved than males. We showed that another animal model of obesity, i.e., male rats made obese by feeding a hypercaloric diet had a reduced function of somatotrophic axis which was likely related to impairment of gonadal function. Aim of this work was that of studying the function of somatotrophic axis in female overfed rats and comparing it to that of male rats of the previous study. Sprague-Dawley female rats were fed an energy-rich palatable diet for seven months. At the end of overfeeding, according to the degree of overweight, rats were divided into overtly obese (Obese), overweight (Overweight) and Non-Obese, i.e. rats whose weights were similar to those of controls. Rats fed ad libitum with the standard pellet chow served as controls (Controls). Acute administration of a supramaximal dose of GHRH (2 microg/rat, iv) elicited a plasma GH rise similar to that of Controls in all the groups, except in Obese which had a lower GH response. Growth hormone responses after GHRH administration were inversely related to plasma levels of free fatty acids (FFA). Pituitary GH content and gene expression as well as hypothalamic GHRH and SS mRNA content, were similar in all experimental groups and in Controls and the same was true for plasma concentrations of free IGF-I. These results indicate that, similarly to obese female Zucker rats, also overfed female rats had a better preservation of the somatotrophic axis than their male counterparts. In diet-induced obese rats, also the etiology of the impairment of somatotrophic axis seems to be gender-related i.e. due to a reduction of gonadal function in males and to an elevation of FFA in females.
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Affiliation(s)
- L Cattaneo
- Dept. Pharmacology, University of Milano
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Figlewicz DP, Schwartz MW, Seeley RJ, Chavez M, Baskin DG, Woods SC, Porte D. Endocrine regulation of food intake and body weight. THE JOURNAL OF LABORATORY AND CLINICAL MEDICINE 1996; 127:328-32. [PMID: 8656034 DOI: 10.1016/s0022-2143(96)90179-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- D P Figlewicz
- Department of Psychology, University of Washington, Seattle, USA
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Griffond B, Deray A, Nguyen NU, Colard C, Fellmann D. The synthesis of melanin-concentrating hormone is stimulated by ventromedial hypothalamic lesions in the rat lateral hypothalamus: a time-course study. Neuropeptides 1995; 28:267-75. [PMID: 7603587 DOI: 10.1016/0143-4179(95)90043-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The activity of melanin-concentrating (MCH) neurons, was investigated by immunocytochemical and hybridocytochemical techniques in male rats bearing limited lesions of the ventromedial hypothalamic nuclei (VMN). 2 days after operation, the abundance of immunoreactive cell bodies and fibres and the intensity of labelling seemed slightly decreased in lesioned rats as compared to controls while no significant difference could be detected in MCH gene expression. After 8 days, synthesis, storage and transport of MCH appeared strongly stimulated and this stimulation lasted until the end of the experiment (day 35), suggesting that VMN plays a physiological role in controlling MCH neuron activity.
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Affiliation(s)
- B Griffond
- C.N.R.S. URA 561, Laboratoire d'Histologie Embryologie Cytogénétique, Faculté de Médecine, Besançon, France
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