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Lipid biosynthesis enzyme Agpat5 in AgRP-neurons is required for insulin-induced hypoglycemia sensing and glucagon secretion. Nat Commun 2022; 13:5761. [PMID: 36180454 PMCID: PMC9525695 DOI: 10.1038/s41467-022-33484-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Accepted: 09/21/2022] [Indexed: 11/13/2022] Open
Abstract
The counterregulatory response to hypoglycemia that restores normal blood glucose levels is an essential physiological function. It is initiated, in large part, by incompletely characterized brain hypoglycemia sensing neurons that trigger the secretion of counterregulatory hormones, in particular glucagon, to stimulate hepatic glucose production. In a genetic screen of recombinant inbred BXD mice we previously identified Agpat5 as a candidate regulator of hypoglycemia-induced glucagon secretion. Here, using genetic mouse models, we demonstrate that Agpat5 expressed in agouti-related peptide neurons is required for their activation by hypoglycemia, for hypoglycemia-induced vagal nerve activity, and glucagon secretion. We find that inactivation of Agpat5 leads to increased fatty acid oxidation and ATP production and that suppressing Cpt1a-dependent fatty acid import into mitochondria restores hypoglycemia sensing. Collectively, our data show that AgRP neurons are involved in the control of glucagon secretion and that Agpat5, by partitioning fatty acyl-CoAs away from mitochondrial fatty acid oxidation and ATP generation, ensures that the fall in intracellular ATP, which triggers neuronal firing, faithfully reflects changes in glycemia. During hypoglycemia, glucagon secretion is part of the mechanism needed to restore normal blood glucose levels. Here, Strembitska et al. report that sensing of hypoglycemia by AgRP neurons requires Agpat5, an enzyme which prevents fatty acids from entering the mitochondria for ATP production, ensuring correct neuronal activation and glucagon secretion.
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Joly-Amado A, Soty M, Philippe E, Lacombe A, Castel J, Pillot B, Vily-Petit J, Zitoun C, Mithieux G, Magnan C. Portal Glucose Infusion, Afferent Nerve Fibers, and Glucose and Insulin Tolerance of Insulin-Resistant Rats. J Nutr 2022; 152:1862-1871. [PMID: 35511216 DOI: 10.1093/jn/nxac097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Revised: 01/19/2022] [Accepted: 04/26/2022] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND The role of hepatoportal glucose sensors is poorly understood in the context of insulin resistance. OBJECTIVES We assessed the effects of glucose infusion in the portal vein on insulin tolerance in 2 rat models of insulin resistance, and the role of capsaicin sensitive nerves in this signal. METHODS Male Wistar rats, 8 weeks old, weighing 250-275 g, were used. Insulin and glucose tolerance were assessed following a 4-hour infusion of either glucose or saline through catheterization in the portal vein in 3 paradigms. In experiment 1, for diet-induced insulin resistance, rats were fed either a control diet (energy content: proteins = 22.5%, carbohydrates = 64.1%, and lipids = 13.4%) or a high-fat diet (energy content: proteins = 15.3%, carbohydrates = 40.3%, and lipids =44.4%) for 4 months. In experiment 2, for centrally induced peripheral insulin resistance, catheters were inserted in the carotid artery to deliver either an emulsion of triglycerides [intralipid (IL)] or saline towards the brain for 24 hours. In experiment 3, for testing the role of capsaicin-sensitive nerves, experiment 2 was repeated following a periportal treatment with capsaicin or vehicle. RESULTS In experiment 1, when compared to rats fed the control diet, rats fed the high-fat diet exhibited decreased insulin and glucose tolerance (P ≤ 0.05) that was restored with a glucose infusion in the portal vein (P ≤ 0.05). In experiment 2, infusion of a triglyceride emulsion towards the brain (IL rats) decreased insulin and glucose tolerance and increased hepatic endogenous production when compared to saline-infused rats (P ≤ 0.05). Glucose infusion in the portal vein in IL rats restored insulin and glucose tolerance, as well as hepatic glucose production, to controls levels (P ≤ 0.05). In experiment 3, portal infusion of glucose did not increase insulin tolerance in IL rats that received a periportal pretreatment with capsaicin. CONCLUSIONS Stimulation of hepatoportal glucose sensors increases insulin tolerance in rat models of insulin resistance and requires the presence of capsaicin-sensitive nerves.
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Affiliation(s)
- Aurélie Joly-Amado
- Université de Paris, Functional and Adaptive Biology Unit, UMR (Unite Mixte de Recherche) 8251, CNRS (Centre National de la Recherche Scientifique), Paris, France
| | - Maud Soty
- Institut National de la Santé et de la Recherche Médicale, Lyon, France.,Université de Lyon, Lyon, France.,Université Lyon I, Villeurbanne, France
| | - Erwann Philippe
- Université de Paris, Functional and Adaptive Biology Unit, UMR (Unite Mixte de Recherche) 8251, CNRS (Centre National de la Recherche Scientifique), Paris, France
| | - Amelie Lacombe
- Université de Paris, Functional and Adaptive Biology Unit, UMR (Unite Mixte de Recherche) 8251, CNRS (Centre National de la Recherche Scientifique), Paris, France
| | - Julien Castel
- Université de Paris, Functional and Adaptive Biology Unit, UMR (Unite Mixte de Recherche) 8251, CNRS (Centre National de la Recherche Scientifique), Paris, France
| | - Bruno Pillot
- Institut National de la Santé et de la Recherche Médicale, Lyon, France.,Université de Lyon, Lyon, France.,Université Lyon I, Villeurbanne, France
| | - Justine Vily-Petit
- Institut National de la Santé et de la Recherche Médicale, Lyon, France.,Université de Lyon, Lyon, France.,Université Lyon I, Villeurbanne, France
| | - Carine Zitoun
- Institut National de la Santé et de la Recherche Médicale, Lyon, France.,Université de Lyon, Lyon, France.,Université Lyon I, Villeurbanne, France
| | - Gilles Mithieux
- Institut National de la Santé et de la Recherche Médicale, Lyon, France.,Université de Lyon, Lyon, France.,Université Lyon I, Villeurbanne, France
| | - Christophe Magnan
- Université de Paris, Functional and Adaptive Biology Unit, UMR (Unite Mixte de Recherche) 8251, CNRS (Centre National de la Recherche Scientifique), Paris, France
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3
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Garcia SM, Hirschberg PR, Sarkar P, Siegel DM, Teegala SB, Vail GM, Routh VH. Insulin actions on hypothalamic glucose-sensing neurones. J Neuroendocrinol 2021; 33:e12937. [PMID: 33507001 PMCID: PMC10561189 DOI: 10.1111/jne.12937] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Revised: 12/22/2020] [Accepted: 12/29/2020] [Indexed: 12/13/2022]
Abstract
Subsequent to the discovery of insulin 100 years ago, great strides have been made in understanding its function, especially in the brain. It is now clear that insulin is a critical regulator of the neuronal circuitry controlling energy balance and glucose homeostasis. This review focuses on the effects of insulin and diabetes on the activity and glucose sensitivity of hypothalamic glucose-sensing neurones. We highlight the role of electrophysiological data in understanding how insulin regulates glucose-sensing neurones. A brief introduction describing the benefits and limitations of the major electrophysiological techniques used to investigate glucose-sensing neurones is provided. The mechanisms by which hypothalamic neurones sense glucose are discussed with an emphasis on those glucose-sensing neurones already shown to be modulated by insulin. Next, the literature pertaining to how insulin alters the activity and glucose sensitivity of these hypothalamic glucose-sensing neurones is described. In addition, the effects of impaired insulin signalling during diabetes and the ramifications of insulin-induced hypoglycaemia on hypothalamic glucose-sensing neurones are covered. To the extent that it is known, we present hypotheses concerning the mechanisms underlying the effects of these insulin-related pathologies. To conclude, electrophysiological data from the hippocampus are evaluated aiming to provide clues regarding how insulin might influence neuronal plasticity in glucose-sensing neurones. Although much has been accomplished subsequent to the discovery of insulin, the work described in our review suggests that the regulation of central glucose sensing by this hormone is both important and understudied.
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Affiliation(s)
- Stephanie M Garcia
- Department of Pharmacology, Physiology and Neuroscience, Rutgers, New Jersey Medical School, The State University of New Jersey, Newark, NJ, USA
| | - Pamela R Hirschberg
- Department of Pharmacology, Physiology and Neuroscience, Rutgers, New Jersey Medical School, The State University of New Jersey, Newark, NJ, USA
| | - Pallabi Sarkar
- Department of Pharmacology, Physiology and Neuroscience, Rutgers, New Jersey Medical School, The State University of New Jersey, Newark, NJ, USA
| | - Dashiel M Siegel
- Department of Pharmacology, Physiology and Neuroscience, Rutgers, New Jersey Medical School, The State University of New Jersey, Newark, NJ, USA
| | - Suraj B Teegala
- Department of Pharmacology, Physiology and Neuroscience, Rutgers, New Jersey Medical School, The State University of New Jersey, Newark, NJ, USA
| | - Gwyndolin M Vail
- Department of Pharmacology, Physiology and Neuroscience, Rutgers, New Jersey Medical School, The State University of New Jersey, Newark, NJ, USA
| | - Vanessa H Routh
- Department of Pharmacology, Physiology and Neuroscience, Rutgers, New Jersey Medical School, The State University of New Jersey, Newark, NJ, USA
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4
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MacDonald AJ, Yang YHC, Cruz AM, Beall C, Ellacott KLJ. Brain-Body Control of Glucose Homeostasis-Insights From Model Organisms. Front Endocrinol (Lausanne) 2021; 12:662769. [PMID: 33868184 PMCID: PMC8044781 DOI: 10.3389/fendo.2021.662769] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Accepted: 03/12/2021] [Indexed: 12/15/2022] Open
Abstract
Tight regulation of blood glucose is essential for long term health. Blood glucose levels are defended by the correct function of, and communication between, internal organs including the gastrointestinal tract, pancreas, liver, and brain. Critically, the brain is sensitive to acute changes in blood glucose level and can modulate peripheral processes to defend against these deviations. In this mini-review we highlight select key findings showcasing the utility, strengths, and limitations of model organisms to study brain-body interactions that sense and control blood glucose levels. First, we discuss the large platform of genetic tools available to investigators studying mice and how this field may yet reveal new modes of communication between peripheral organs and the brain. Second, we discuss how rats, by virtue of their size, have unique advantages for the study of CNS control of glucose homeostasis and note that they may more closely model some aspects of human (patho)physiology. Third, we discuss the nascent field of studying the CNS control of blood glucose in the zebrafish which permits ease of genetic modification, large-scale measurements of neural activity and live imaging in addition to high-throughput screening. Finally, we briefly discuss glucose homeostasis in drosophila, which have a distinct physiology and glucoregulatory systems to vertebrates.
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Affiliation(s)
| | | | | | | | - Kate L. J. Ellacott
- Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, Exeter, United Kingdom
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5
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Malbert CH, Chauvin A, Horowitz M, Jones KL. Glucose Sensing Mediated by Portal Glucagon-Like Peptide 1 Receptor Is Markedly Impaired in Insulin-Resistant Obese Animals. Diabetes 2021; 70:99-110. [PMID: 33067312 DOI: 10.2337/db20-0361] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Accepted: 10/06/2020] [Indexed: 02/05/2023]
Abstract
The glucose portal sensor informs the brain of changes in glucose inflow through vagal afferents that require an activated glucagon-like peptide 1 receptor (GLP-1r). The GLP-1 system is known to be impaired in insulin-resistant conditions, and we sought to understand the consequences of GLP-1 resistance on glucose portal signaling. GLP-1-dependent portal glucose signaling was identified, in vivo, using a novel 68Ga-labeled GLP-1r positron-emitting probe that supplied a quantitative in situ tridimensional representation of the portal sensor with specific reference to the receptor density expressed in binding potential units. It also served as a map for single-neuron electrophysiology driven by an image-based abdominal navigation. We determined that in insulin-resistant animals, portal vagal afferents failed to inhibit their spiking activity during glucose infusion, a GLP-1r-dependent function. This reflected a reduction in portal GLP-1r binding potential, particularly between the splenic vein and the entrance of the liver. We propose that insulin resistance, through a reduction in GLP-1r density, leads to functional portal desensitization with a consequent suppression of vagal sensitivity to portal glucose.
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Affiliation(s)
| | - Alain Chauvin
- UEPR Unit, Department of Animal Physiology, INRAE, Saint-Gilles, France
| | - Michael Horowitz
- Centre of Research Excellence in Translating Nutritional Science to Good Health, Adelaide Medical School, The University of Adelaide, Adelaide, South Australia, Australia
| | - Karen L Jones
- Centre of Research Excellence in Translating Nutritional Science to Good Health, Adelaide Medical School, The University of Adelaide, Adelaide, South Australia, Australia
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6
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Donovan CM, Watts AG. Peripheral and central glucose sensing in hypoglycemic detection. Physiology (Bethesda) 2015; 29:314-24. [PMID: 25180261 DOI: 10.1152/physiol.00069.2013] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Hypoglycemia poses a serious threat to the integrity of the brain, owing to its reliance on blood glucose as a fuel. Protecting against hypoglycemia is an extended network of glucose sensors located within the brain and in the periphery that serve to mediate responses restoring euglycemia, i.e., counterregulatory responses. This review examines the various glucose sensory loci involved in hypoglycemic detection, with a particular emphasis on peripheral glucose sensory loci and their contribution to hypoglycemic counterregulation.
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Affiliation(s)
- Casey M Donovan
- Department of Biological Sciences, The Center for NeuroMetabolic Interactions, USC Dornsife College of Letters, Arts and Sciences, University of Southern California, Los Angeles, California
| | - Alan G Watts
- Department of Biological Sciences, The Center for NeuroMetabolic Interactions, USC Dornsife College of Letters, Arts and Sciences, University of Southern California, Los Angeles, California
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7
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Routh VH, Hao L, Santiago AM, Sheng Z, Zhou C. Hypothalamic glucose sensing: making ends meet. Front Syst Neurosci 2014; 8:236. [PMID: 25540613 PMCID: PMC4261699 DOI: 10.3389/fnsys.2014.00236] [Citation(s) in RCA: 122] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Accepted: 11/26/2014] [Indexed: 01/12/2023] Open
Abstract
The neuroendocrine system governs essential survival and homeostatic functions. For example, growth is needed for development, thermoregulation maintains optimal core temperature in a changing environment, and reproduction ensures species survival. Stress and immune responses enable an organism to overcome external and internal threats while the circadian system regulates arousal and sleep such that vegetative and active functions do not overlap. All of these functions require a significant portion of the body's energy. As the integrator of the neuroendocrine system, the hypothalamus carefully assesses the energy status of the body in order to appropriately partition resources to provide for each system without compromising the others. While doing so the hypothalamus must ensure that adequate glucose levels are preserved for brain function since glucose is the primary fuel of the brain. To this end, the hypothalamus contains specialized glucose sensing neurons which are scattered throughout the nuclei controlling distinct neuroendocrine functions. We hypothesize that these neurons play a key role in enabling the hypothalamus to partition energy to meet these peripheral survival needs without endangering the brain's glucose supply. This review will first describe the varied mechanisms underlying glucose sensing in neurons within discrete hypothalamic nuclei. We will then evaluate the way in which peripheral energy status regulates glucose sensitivity. For example, during energy deficit such as fasting specific hypothalamic glucose sensing neurons become sensitized to decreased glucose. This increases the gain of the information relay when glucose availability is a greater concern for the brain. Finally, changes in glucose sensitivity under pathological conditions (e.g., recurrent insulin-hypoglycemia, diabetes) will be addressed. The overall goal of this review is to place glucose sensing neurons within the context of hypothalamic control of neuroendocrine function.
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Affiliation(s)
- Vanessa H Routh
- Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers University Newark, NJ, USA
| | - Lihong Hao
- Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers University Newark, NJ, USA ; Department of Pharmacology and Physiology and Graduate School of the Biomedical Sciences, New Jersey Medical School, Rutgers University Newark, NJ, USA
| | - Ammy M Santiago
- Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers University Newark, NJ, USA ; Department of Pharmacology and Physiology and Graduate School of the Biomedical Sciences, New Jersey Medical School, Rutgers University Newark, NJ, USA
| | - Zhenyu Sheng
- Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers University Newark, NJ, USA
| | - Chunxue Zhou
- Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers University Newark, NJ, USA ; Department of Pharmacology and Physiology and Graduate School of the Biomedical Sciences, New Jersey Medical School, Rutgers University Newark, NJ, USA
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Ionut V, Castro AVB, Woolcott OO, Stefanovski D, Iyer MS, Broussard JL, Burch M, Elazary R, Kolka CM, Mkrtchyan H, Bediako IA, Bergman RN. Hepatic portal vein denervation impairs oral glucose tolerance but not exenatide's effect on glycemia. Am J Physiol Endocrinol Metab 2014; 307:E644-52. [PMID: 25117408 PMCID: PMC4200304 DOI: 10.1152/ajpendo.00244.2014] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The hepatoportal area is an important glucohomeostatic metabolic sensor, sensing hypoglycemia, hyperglycemia, and hormones such as glucagon-like peptide-1 (GLP-1). We have reported previously that activation of hepatoportal sensors by intraportal infusion of glucose and GLP-1 or by subcutaneous administration of GLP-1 receptor activator exenatide and of intraportal glucose improved glycemia independent of corresponding changes in pancreatic hormones. It is not clear whether this effect is mediated via the portal vein (PV) or by direct action on the liver itself. To test whether receptors in the PV mediate exenatide's beneficial effect on glucose tolerance, we performed 1) paired oral glucose tolerance tests (OGTT) with and without exenatide and 2) intravenous glucose tolerance tests before and after PV denervation in canines. Denervation of the portal vein affected oral glucose tolerance; post-denervation (POST-DEN) OGTT glucose and insulin AUC were 50% higher than before denervation (P = 0.01). However, portal denervation did not impair exenatide's effect to improve oral glucose tolerance (exenatide effect: 48 ± 12 mmol·l⁻¹·min before vs. 64 ± 26 mmol·l⁻¹·min after, P = 0.67). There were no changes in insulin sensitivity or secretion during IVGTTs. Portal vein sensing might play a role in controlling oral glucose tolerance during physiological conditions but not in pharmacological activation of GLP-1 receptors by exenatide.
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Affiliation(s)
| | | | | | | | | | | | - Miguel Burch
- Department of Surgery, Cedars Sinai Medical Center, Los Angeles, California
| | - Ram Elazary
- Department of Surgery, Cedars Sinai Medical Center, Los Angeles, California
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Kilpatrick LA, Coveleskie K, Connolly L, Labus JS, Ebrat B, Stains J, Jiang Z, Suyenobu BY, Raybould HE, Tillisch K, Mayer EA. Influence of sucrose ingestion on brainstem and hypothalamic intrinsic oscillations in lean and obese women. Gastroenterology 2014; 146:1212-21. [PMID: 24480616 PMCID: PMC4113508 DOI: 10.1053/j.gastro.2014.01.023] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/10/2013] [Revised: 01/06/2014] [Accepted: 01/14/2014] [Indexed: 12/21/2022]
Abstract
BACKGROUND & AIMS The study of intrinsic fluctuations in the blood oxygen level-dependent signal of functional magnetic resonance imaging can provide insight into the effect of physiologic states on brain processes. In an effort to better understand the brain-gut communication induced by the absorption and metabolism of nutrients in healthy lean and obese individuals, we investigated whether ingestion of nutritive and non-nutritive sweetened beverages differentially engages the hypothalamus and brainstem vagal pathways in lean and obese women. METHODS In a 2-day, double-blind crossover study, 11 lean and 11 obese healthy women underwent functional magnetic resonance imaging scans after ingestion of 2 beverages of different sucrose content, but identical sweetness. During scans, subjects rested with eyes closed. RESULTS Blood oxygen level-dependent fluctuations demonstrated significantly greater power in the highest frequency band (slow-3: 0.073-0.198 Hz) after ingestion of high-sucrose compared with low-sucrose beverages in the nucleus tractus solitarius for both groups. Obese women had greater connectivity between the right lateral hypothalamus and a reward-related brain region and weaker connectivity with homeostasis and gustatory-related brain regions than lean women. CONCLUSIONS In a functional magnetic resonance imaging study, we observed sucrose-related changes in oscillatory dynamics of blood oxygen level-dependent fluctuations in brainstem and hypothalamus in lean and obese women. The observed frequency changes are consistent with a rapid vagally mediated mechanism due to nutrient absorption, rather than sweet taste receptor activation. These findings provide support for altered interaction between homeostatic and reward networks in obese individuals.
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Affiliation(s)
- Lisa A. Kilpatrick
- Gail and Gerald Oppenheimer Family Center for Neurobiology of Stress, David Geffen School of Medicine, University of California, Los Angeles,Department of Medicine, Division of Digestive Diseases, University of California, Los Angeles
| | - Kristen Coveleskie
- Gail and Gerald Oppenheimer Family Center for Neurobiology of Stress, David Geffen School of Medicine, University of California, Los Angeles
| | - Lynn Connolly
- Gail and Gerald Oppenheimer Family Center for Neurobiology of Stress, David Geffen School of Medicine, University of California, Los Angeles,Department of Medicine, Division of Digestive Diseases, University of California, Los Angeles
| | - Jennifer S. Labus
- Gail and Gerald Oppenheimer Family Center for Neurobiology of Stress, David Geffen School of Medicine, University of California, Los Angeles,Department of Medicine, Division of Digestive Diseases, University of California, Los Angeles,Ahmanson-Lovelace Brain Mapping Center, Los Angeles, California,Brain Research Institute, University of California, Los Angeles, Los Angeles, California
| | - Bahar Ebrat
- Gail and Gerald Oppenheimer Family Center for Neurobiology of Stress, David Geffen School of Medicine, University of California, Los Angeles,Department of Medicine, Division of Digestive Diseases, University of California, Los Angeles
| | - Jean Stains
- Gail and Gerald Oppenheimer Family Center for Neurobiology of Stress, David Geffen School of Medicine, University of California, Los Angeles,Department of Medicine, Division of Digestive Diseases, University of California, Los Angeles
| | - Zhiguo Jiang
- Gail and Gerald Oppenheimer Family Center for Neurobiology of Stress, David Geffen School of Medicine, University of California, Los Angeles,Department of Medicine, Division of Digestive Diseases, University of California, Los Angeles
| | - Brandall Y. Suyenobu
- Gail and Gerald Oppenheimer Family Center for Neurobiology of Stress, David Geffen School of Medicine, University of California, Los Angeles,Department of Medicine, Division of Digestive Diseases, University of California, Los Angeles
| | - Helen E. Raybould
- Department of Anatomy, Physiology, and Cell Biology, School of Veterinary Medicine, University of California, Davis, Davis, California
| | - Kirsten Tillisch
- Gail and Gerald Oppenheimer Family Center for Neurobiology of Stress, David Geffen School of Medicine, University of California, Los Angeles,Department of Medicine, Division of Digestive Diseases, University of California, Los Angeles
| | - Emeran A. Mayer
- Gail and Gerald Oppenheimer Family Center for Neurobiology of Stress, David Geffen School of Medicine, University of California, Los Angeles,Department of Medicine, Division of Digestive Diseases, University of California, Los Angeles,Ahmanson-Lovelace Brain Mapping Center, Los Angeles, California,Department of Psychiatry, University of California, Los Angeles, Los Angeles, California,Brain Research Institute, University of California, Los Angeles, Los Angeles, California
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10
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Connolly L, Coveleskie K, Kilpatrick LA, Labus JS, Ebrat B, Stains J, Jiang Z, Tillisch K, Raybould HE, Mayer EA. Differences in brain responses between lean and obese women to a sweetened drink. Neurogastroenterol Motil 2013; 25:579-e460. [PMID: 23566308 PMCID: PMC4114731 DOI: 10.1111/nmo.12125] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2012] [Accepted: 02/14/2013] [Indexed: 01/14/2023]
Abstract
BACKGROUND Ingestion of sweet food is driven by central reward circuits and restrained by endocrine and neurocrine satiety signals. The specific influence of sucrose intake on central affective and reward circuitry and alterations of these mechanisms in the obese are incompletely understood. For this, we hypothesized that (i) similar brain regions are engaged by the stimulation of sweet taste receptors by sucrose and by non-nutrient sweeteners and (ii) during visual food-related cues, obese subjects show greater brain responses to sucrose compared with lean controls. METHODS In a double-blind, crossover design, 10 obese and 10 lean healthy females received a sucrose or a non-nutrient sweetened beverage prior to viewing food or neutral images. BOLD signal was measured using a 1.5 Tesla MRI scanner. KEY RESULTS Viewing food images after ingestion of either drink was associated with engagement of similar brain regions (amygdala, hippocampus, thalamus, anterior insula). Obese differed from lean subjects in behavioral and brain responses rating both beverages as less tasteful and satisfying, yet demonstrating greater brain responses. Obese subjects also showed engagement of an additional brain network (including anterior insula, anterior cingulate, hippocampus, and amygdala) only after sucrose ingestion. CONCLUSIONS & INFERENCES Obese subjects had a reduced behavioral hedonic response, yet a greater engagement of affective brain networks, particularly after sucrose ingestion, suggesting that in obese subjects, lingual and gut-derived signaling generate less central hedonic effects than food-related memories in response to visual cues, analogous to response patterns implicated in food addiction.
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Affiliation(s)
- L. Connolly
- Oppenheimer Family Center for Neurobiology of Stress, Los Angeles, CA, USA,Division of Digestive Diseases, Department of Medicine, David Geffen School of Medicine, UCLA, Los Angeles, CA, USA,Division of Digestive Diseases, David Geffen School of Medicine, UCLA, Los Angeles, CA, USA
| | - K. Coveleskie
- Oppenheimer Family Center for Neurobiology of Stress, Los Angeles, CA, USA
| | - L. A. Kilpatrick
- Oppenheimer Family Center for Neurobiology of Stress, Los Angeles, CA, USA,Division of Digestive Diseases, Department of Medicine, David Geffen School of Medicine, UCLA, Los Angeles, CA, USA,Division of Digestive Diseases, David Geffen School of Medicine, UCLA, Los Angeles, CA, USA
| | - J. S. Labus
- Oppenheimer Family Center for Neurobiology of Stress, Los Angeles, CA, USA,Division of Digestive Diseases, David Geffen School of Medicine, UCLA, Los Angeles, CA, USA,Division of Digestive Diseases, Department of Psychiatry, David Geffen School of Medicine, UCLA, Los Angeles, CA, USA
| | - B. Ebrat
- Oppenheimer Family Center for Neurobiology of Stress, Los Angeles, CA, USA,Division of Digestive Diseases, Department of Medicine, David Geffen School of Medicine, UCLA, Los Angeles, CA, USA,Division of Digestive Diseases, David Geffen School of Medicine, UCLA, Los Angeles, CA, USA
| | - J. Stains
- Oppenheimer Family Center for Neurobiology of Stress, Los Angeles, CA, USA,Division of Digestive Diseases, Department of Medicine, David Geffen School of Medicine, UCLA, Los Angeles, CA, USA,Division of Digestive Diseases, David Geffen School of Medicine, UCLA, Los Angeles, CA, USA
| | - Z. Jiang
- Oppenheimer Family Center for Neurobiology of Stress, Los Angeles, CA, USA,Division of Digestive Diseases, Department of Medicine, David Geffen School of Medicine, UCLA, Los Angeles, CA, USA,Division of Digestive Diseases, David Geffen School of Medicine, UCLA, Los Angeles, CA, USA
| | - K. Tillisch
- Oppenheimer Family Center for Neurobiology of Stress, Los Angeles, CA, USA,Division of Digestive Diseases, Department of Medicine, David Geffen School of Medicine, UCLA, Los Angeles, CA, USA,Division of Digestive Diseases, David Geffen School of Medicine, UCLA, Los Angeles, CA, USA
| | - H. E. Raybould
- Departments of Anatomy, Physiology and Cell Biology, UC Davis School of Veterinary Medicine, Davis, CA, USA
| | - E. A. Mayer
- Oppenheimer Family Center for Neurobiology of Stress, Los Angeles, CA, USA,Division of Digestive Diseases, Department of Medicine, David Geffen School of Medicine, UCLA, Los Angeles, CA, USA,Division of Digestive Diseases, David Geffen School of Medicine, UCLA, Los Angeles, CA, USA,Division of Digestive Diseases, Department of Psychiatry, David Geffen School of Medicine, UCLA, Los Angeles, CA, USA,Brain Research Institute, UCLA, Los Angeles, CA, USA,Division of Digestive Diseases, Department of Physiology, David Geffen School of Medicine, UCLA, Los Angeles, CA, USA
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Delaere F, Duchampt A, Mounien L, Seyer P, Duraffourd C, Zitoun C, Thorens B, Mithieux G. The role of sodium-coupled glucose co-transporter 3 in the satiety effect of portal glucose sensing. Mol Metab 2012; 2:47-53. [PMID: 24024129 DOI: 10.1016/j.molmet.2012.11.003] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Revised: 11/27/2012] [Accepted: 11/29/2012] [Indexed: 01/12/2023] Open
Abstract
Portal vein glucose sensors detect variations in glycemia to induce a nervous signal that influences food intake and glucose homeostasis. Previous experiments using high infusions of glucose suggested a metabolic sensing involving glucose transporter 2 (GLUT2). Here we evaluated the afferent route for the signal and candidate molecules for detecting low glucose fluxes. Common hepatic branch vagotomy did not abolish the anorectic effect of portal glucose, indicating dorsal transmission. GLUT2-null mice reduced their food intake in response to portal glucose signal initiated by protein-enriched diet. A similar response of Trpm5-null mice and portal infusions of sweeteners also excluded sugar taste receptors. Conversely, infusions of alpha-methylglucose, but not 3-O-methylglucose, decreased food intake, while phlorizin prevented the effect of glucose. This suggested sensing through SGLT3, which was expressed in the portal area. From these results we propose a finely tuned dual mechanism for portal glucose sensing that responds to different physiological conditions.
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Key Words
- (3-O-MDG), 3-O-methyl-d-glucopyranose
- (5-HT), 5-hydroxytryptamin/serotonin
- (EGP), endogenous glucose production
- (G6PC), glucose-6-phosphatase catalytic subunit
- (GAPDH), glyceraldehyde-3-phosphate dehydrogenase
- (GFAP), glial fibriallary acidic protein
- (GLP1), glucagon-like peptide 1
- (GLUT), glucose transporter
- (PED), protein-enriched diet
- (PGP9.5), protein gene product 9.5
- (SED), starch-enriched diet
- (SGLT), sodium glucose co-transporter
- (Trpm5), transient receptor potential melastin 5
- (αMDG), α-methylglucopyranoside
- Food intake
- Glucose metabolism
- Glucose sensing
- Peripheral nervous signal
- Portal vein
- SGLTs
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Affiliation(s)
- Fabien Delaere
- Institut National de la Santé et de la Recherche Médicale, U 855, Lyon 69372, France ; Université de Lyon, Lyon 69008, France ; Université Lyon 1, Villeurbanne 69622, France ; AgroParisTech, ENGREF, Paris F-75732, France
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12
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Routh VH, Donovan CM, Ritter S. 2. Hypoglycemia Detection. TRANSLATIONAL ENDOCRINOLOGY & METABOLISM 2012; 3:47-87. [PMID: 24910721 PMCID: PMC4045627 DOI: 10.1210/team.9781936704200.ch2] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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13
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Abstract
Neurons whose activity is regulated by glucose are found in a number of brain regions. Glucose-excited (GE) neurons increase while glucose-inhibited (GI) neurons decrease their action potential frequency as interstitial brain glucose levels increase. We hypothesize that these neurons evolved to sense and respond to severe energy deficit (e.g., fasting) that threatens the brains glucose supply. During modern times, they are also important for the restoration of blood glucose levels following insulin-induced hypoglycemia. Our data suggest that impaired glucose sensing by hypothalamic glucose sensing neurons may contribute to the syndrome known as hypoglycemia-associated autonomic failure in which the mechanisms which restore euglycemia following hypoglycemia become impaired. On the other hand, increased responses of glucose sensing neurons to glucose deficit may play a role in the development of Type 2 Diabetes Mellitus and obesity. This review will discuss the mechanisms by which glucose sensing neurons sense changes in interstitial glucose and explore the roles of these specialized glucose sensors in glucose and energy homeostasis.
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Affiliation(s)
- Vanessa H Routh
- Department of Pharmacology & Physiology, New Jersey Medical School (UMDNJ), Newark, NJ 07101, USA.
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14
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YAMADA H, IWAKI Y, KITAOKA R, FUJITANI M, SHIBAKUSA T, FUJIKAWA T, MATSUMURA S, FUSHIKI T, INOUE K. Blood Lactate Functions as a Signal for Enhancing Fatty Acid Metabolism during Exercise via TGF-^|^beta; in the Brain. J Nutr Sci Vitaminol (Tokyo) 2012. [DOI: 10.3177/jnsv.58.88] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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15
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Shin AC, Zheng H, Berthoud HR. An expanded view of energy homeostasis: neural integration of metabolic, cognitive, and emotional drives to eat. Physiol Behav 2009; 97:572-80. [PMID: 19419661 PMCID: PMC2765252 DOI: 10.1016/j.physbeh.2009.02.010] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2009] [Revised: 02/03/2009] [Accepted: 02/05/2009] [Indexed: 01/01/2023]
Abstract
The traditional view of neural regulation of body energy homeostasis focuses on internal feedback signals integrated in the hypothalamus and brainstem and in turn leading to balanced activation of behavioral, autonomic, and endocrine effector pathways leading to changes in food intake and energy expenditure. Recent observations have demonstrated that many of these internal signals encoding energy status have much wider effects on the brain, particularly sensory and cortico-limbic systems that process information from the outside world by detecting and interpreting food cues, forming, storing, and recalling representations of experience with food, and assigning hedonic and motivational value to conditioned and unconditioned food stimuli. Thus, part of the metabolic feedback from the internal milieu regulates food intake and energy balance by acting on extrahypothalamic structures, leading to an expanded view of neural control of energy homeostasis taking into account the need to adapt to changing conditions in the environment. The realization that metabolic signals act directly on these non-traditional targets of body energy homeostasis brings opportunities for novel drug targets for the fight against obesity and eating disorders.
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Affiliation(s)
- Andrew C Shin
- Neurobiology of Nutrition Laboratory, Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, Louisiana, USA
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16
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Rossetti P, Porcellati F, Lucidi P, Busciantella Ricci N, Candeloro P, Cioli P, Santeusanio F, Bolli GB, Fanelli CG. Portal vein glucose sensors do not play a major role in modulating physiological responses to insulin-induced hypoglycemia in humans. Diabetes 2009; 58:194-202. [PMID: 18852332 PMCID: PMC2606871 DOI: 10.2337/db08-0641] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
OBJECTIVE Experimental data from animal studies indicate that portal vein glucose sensors play a key role in the responses to slow-fall hypoglycemia. However, their role in modulating these responses in humans is not well understood. The aim of the present study was to examine in humans the potential role of portal vein glucose sensors in physiological responses to insulin-induced hypoglycemia mimicking the slow fall of insulin-treated diabetic subjects. RESEARCH DESIGN AND METHODS Ten nondiabetic subjects were studied on two different occasions during intravenous insulin (2 mU . kg(-1) . min(-1)) plus variable glucose for 160 minutes. In both studies, after 60 min of normal plasma glucose concentrations, hypoglycemia (47 mg/dl) was induced slowly (60 min) and maintained for 60 min. Hypoglycemia was preceded by the ingestion of either oral placebo or glucose (28 g) given at 30 min. RESULTS Plasma glucose and insulin were not different with either placebo or glucose (P > 0.2). Similarly, counterregulatory hormones, substrates, and symptoms were not different with either placebo or glucose. The Stroop color and colored words subtest of the Stroop test deteriorated less (P < 0.05) with glucose than placebo. CONCLUSIONS In contrast to animals, in humans, prevention of portal hypoglycemia with oral glucose from the beginning of insulin-induced slow-fall hypoglycemia has no effect on sympathoadrenal and symptomatic responses to hypoglycemia.
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Affiliation(s)
- Paolo Rossetti
- Department of Internal Medicine, University of Perugia, Perugia, Italy
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17
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Schmid SM, Jauch-Chara K, Hallschmid M, Oltmanns KM, Peters A, Born J, Schultes B. Lactate overrides central nervous but not beta-cell glucose sensing in humans. Metabolism 2008; 57:1733-9. [PMID: 19013298 DOI: 10.1016/j.metabol.2008.07.033] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/16/2008] [Accepted: 07/25/2008] [Indexed: 11/30/2022]
Abstract
Lactate has been shown to serve as an alternative energy substrate in the central nervous system and to interact with hypothalamic glucose sensors. On the background of marked similarities between central nervous and beta-cell glucose sensing, we examined whether lactate also interacts with pancreatic glucose-sensing mechanisms in vivo. The effects of intravenously infused lactate vs placebo (saline) on central nervous and pancreatic glucose sensing were assessed during euglycemic and hypoglycemic clamp experiments in 10 healthy men. The release of neuroendocrine counterregulatory hormones during hypoglycemia was considered to reflect central nervous glucose sensing, whereas endogenous insulin secretion as assessed by serum C-peptide levels served as an indicator of pancreatic beta-cell glucose sensing. Lactate infusion blunted the counterregulatory hormonal responses to hypoglycemia, in particular, the release of epinephrine (P = .007) and growth hormone (P = .004), so that higher glucose infusion rates (P = .012) were required to maintain the target blood glucose levels. In contrast, the decrease in C-peptide concentrations during the hypoglycemic clamp remained completely unaffected by lactate (P = .60). During euglycemic clamp conditions, lactate infusion did not affect the concentrations of C-peptide and of counterregulatory hormones, with the exception of norepinephrine levels that were lower during lactate than saline infusion (P = .049) independently of the glycemic condition. Data indicate that glucose sensing of beta-cells is specific to glucose, whereas glucose sensing at the central nervous level can be overridden by lactate, reflecting the brain's ability to rely on lactate as an alternative major energy source.
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Affiliation(s)
- Sebastian M Schmid
- Department of Internal Medicine I, University of Luebeck, D-23538 Luebeck, Germany
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18
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Ertl AC, Mann S, Richardson A, Briscoe VJ, Blair HB, Tate DB, Davis SN. Effects of oral carbohydrate on autonomic nervous system counterregulatory responses during hyperinsulinemic hypoglycemia and euglycemia. Am J Physiol Endocrinol Metab 2008; 295:E618-25. [PMID: 18612042 PMCID: PMC2536735 DOI: 10.1152/ajpendo.90470.2008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The effects of oral carbohydrate on modulating counterregulatory responses in humans remain undecided. This study's specific aim was to determine the effects of oral carbohydrate on autonomic nervous system (ANS) and neuroendocrine responses during hyperinsulinemic hypoglycemia and euglycemia. Nineteen healthy volunteers were studied during paired, single blind experiments. Nine subjects underwent two-step glucose clamps consisting of 60 min of euglycemia (5.0 mmol/l) followed by either 15 g of oral carbohydrate (cal) as orange juice or a noncaloric control (nocal) and subsequent 90 min of clamped hypoglycemia (2.9 mmol/l). Ten other subjects underwent two randomized 150-min hyperinsulinemic-euglycemic clamps with cal or nocal control administered at 60 min. Oral carbohydrate initially blunted (P < 0.05) epinephrine, norepinephrine, cortisol, glucagon, pancreatic polypeptide, muscle sympathetic nerve activity (MSNA), symptom, and systolic blood pressure responses during hypoglycemia. However, by the end of 90 min of hypoglycemia, plasma epinephrine and norepinephrine responses had rebounded and were increased (P < 0.05) compared with control. MSNA and cortisol levels remained suppressed during hypoglycemia (P < 0.05) after cal, whereas pancreatic polypeptide, glucagon, symptom, and blood pressure responses increased similar to control following initial suppression. Oral carbohydrate had no effects on neuroendocrine or ANS responses during hyperinsulinemic euglycemia. These results demonstrate that oral carbohydrate can have differential effects on the time course of ANS and neuroendocrine responses during hypoglycemia. We conclude that gastro-splanchnic-portal sensing of an amount of carbohydrate recommended for use in clinical practice for correction of hypoglycemia can have widespread and significant effects on central nervous system mediated counterregulatory responses in healthy humans.
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Affiliation(s)
- Andrew C Ertl
- Division of Diabetes, Endocrinology and Metabolism, Dept. of Medicine, 7465 MRB IV, Nashville, TN 37232-0475, USA
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Abstract
Food intake and energy expenditure are controlled by complex, redundant, and distributed neural systems that reflect the fundamental biological importance of adequate nutrient supply and energy balance. Much progress has been made in identifying the various hormonal and neural mechanisms by which the brain informs itself about availability of ingested and stored nutrients and, in turn, generates behavioral, autonomic, and endocrine output. While hypothalamus and caudal brainstem play crucial roles in this homeostatic function, areas in the cortex and limbic system are important for processing information regarding prior experience with food, reward, and emotion, as well as social and environmental context. Most vertebrates can store a considerable amount of energy as fat for later use, and this ability has now become one of the major health risks for many human populations. The predisposition to develop obesity can theoretically result from any pathological malfunction or lack of adaptation to changing environments of this highly complex system.
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Affiliation(s)
- Hans-Rudolf Berthoud
- Neurobiology of Nutrition Laboratory, Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, Louisiana, USA.
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Matveyenko AV, Bohland M, Saberi M, Donovan CM. Portal vein hypoglycemia is essential for full induction of hypoglycemia-associated autonomic failure with slow-onset hypoglycemia. Am J Physiol Endocrinol Metab 2007; 293:E857-64. [PMID: 17638706 DOI: 10.1152/ajpendo.00283.2007] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Antecedent hypoglycemia leads to impaired counterregulation and hypoglycemic unawareness. To ascertain whether antecedent portal vein hypoglycemia impairs portal vein glucose sensing, thereby inducing counterregulatory failure, we compared the effects of antecedent hypoglycemia, with and without normalization of portal vein glycemia, upon the counterregulatory response to subsequent hypoglycemia. Male Wistar rats were chronically cannulated in the carotid artery (sampling), jugular vein (glucose and insulin infusion), and mesenteric vein (glucose infusion). On day 1, the following three distinct antecedent protocols were employed: 1) HYPO-HYPO: systemic hypoglycemia (2.52 +/- 0.11 mM); 2) HYPO-EUG: systemic hypoglycemia (2.70 +/- 0.03 mM) with normalization of portal vein glycemia (portal vein glucose = 5.86 +/- 0.10 mM); and 3) EUG-EUG: systemic euglycemia (6.33 +/- 0.31 mM). On day 2, all groups underwent a hyperinsulinemic-hypoglycemic clamp in which the fall in glycemia was controlled so as to reach the nadir (2.34 +/- 0.04 mM) by minute 75. Counterregulatory hormone responses were measured at basal (-30 and 0) and during hypoglycemia (60-105 min). Compared with EUG-EUG, antecedent hypoglycemia (HYPO-HYPO) significantly blunted the peak epinephrine (10.44 +/- 1.35 vs. 15.75 +/- 1.33 nM: P = 0.01) and glucagon (341 +/- 16 vs. 597 +/- 82 pg/ml: P = 0.03) responses to next-day hypoglycemia. Normalization of portal glycemia during systemic hypoglycemia on day 1 (HYPO-EUG) prevented blunting of the peak epinephrine (15.59 +/- 1.43 vs. 15.75 +/- 1.33 nM: P = 0.94) and glucagon (523 +/- 169 vs. 597 +/- 82 pg/ml: P = 0.66) responses to day 2 hypoglycemia. Consistent with hormonal responses, the glucose infusion rate during day 2 hypoglycemia was substantially elevated in HYPO-HYPO (74 +/- 12 vs. 49 +/- 4 micromol x kg(-1) x min(-1); P = 0.03) but not HYPO-EUG (39 +/- 7 vs. 49 +/- 4 micromol x kg(-1) x min(-1): P = 0.36). Antecedent hypoglycemia local to the portal vein is required for the full induction of hypoglycemia-associated counterregulatory failure with slow-onset hypoglycemia.
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Affiliation(s)
- Aleksey V Matveyenko
- Department of Kinesiology, University of Southern California, Los Angeles, California 90089, USA
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Fukaya M, Mizuno A, Arai H, Muto K, Uebanso T, Matsuo K, Yamamoto H, Taketani Y, Doi T, Takeda E. Mechanism of rapid-phase insulin response to elevation of portal glucose concentration. Am J Physiol Endocrinol Metab 2007; 293:E515-22. [PMID: 17473051 DOI: 10.1152/ajpendo.00536.2006] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The hepatoportal region is important for glucose sensing; however, the relationship between the hepatoportal glucose-sensing system and the postprandial rapid phase of the insulin response has been unclear. We examined whether a rapid-phase insulin response to low amounts of intraportal glucose infusion would occur, compared that with the response to intrajugular glucose infusion in conscious rats, and assessed whether this sensing system was associated with autonomic nerve activity. The increases in plasma glucose concentration did not differ between the two infusions at 3 min, but the rapid-phase insulin response was detected only in the intraportal infusion. A sharp and rapid insulin response was observed at 3 min after intraportal infusion of a small amount of glucose but not after intrajugular infusion. Furthermore, this insulin response was also induced by intraportal fructose infusion but not by nonmetabolizable sugars. The rapid-phase insulin response at 3 min during intraportal infusion did not differ between rats that had undergone hepatic vagotomy or chemical sympathectomy with 6-hydroxydopamine compared with control rats, but this response disappeared in rats that had undergone chemical vagotomy with atropine. We conclude that the elevation of glucose concentration in the hepatoportal region induced afferent signals from undetectable sensors and that these signals stimulate pancreas to induce the rapid-phase insulin response via cholinergic nerve action.
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Affiliation(s)
- Makiko Fukaya
- Department of Clinical Nutrition, University of Tokushima School of Medicine, Tokushima, Japan.
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