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Valle A, Castillo P, García-Rodríguez A, Palou A, Palou M, Picó C. Brain-Derived Neurotrophic Factor as a Potential Mediator of the Beneficial Effects of Myo-Inositol Supplementation during Suckling in the Offspring of Gestational-Calorie-Restricted Rats. Nutrients 2024; 16:980. [PMID: 38613013 PMCID: PMC11013066 DOI: 10.3390/nu16070980] [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: 02/28/2024] [Revised: 03/21/2024] [Accepted: 03/23/2024] [Indexed: 04/14/2024] Open
Abstract
This study aims to investigate the potential mechanisms underlying the protective effects of myo-inositol (MI) supplementation during suckling against the detrimental effects of fetal energy restriction described in animal studies, particularly focusing on the potential connections with BDNF signaling. Oral physiological doses of MI or the vehicle were given daily to the offspring of control (CON) and 25%-calorie-restricted (CR) pregnant rats during suckling. The animals were weaned and then fed a standard diet until 5 months of age, when the diet was switched to a Western diet until 7 months of age. At 25 days and 7 months of age, the plasma BDNF levels and mRNA expression were analyzed in the hypothalamus and three adipose tissue depots. MI supplementation, especially in the context of gestational calorie restriction, promoted BDNF secretion and signaling at a juvenile age and in adulthood, which was more evident in the male offspring of the CR dams than in females. Moreover, the CR animals supplemented with MI exhibited a stimulated anorexigenic signaling pathway in the hypothalamus, along with improved peripheral glucose management and enhanced browning capacity. These findings suggest a novel connection between MI supplementation during suckling, BDNF signaling, and metabolic programming, providing insights into the mechanisms underlying the beneficial effects of MI during lactation.
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Affiliation(s)
- Ana Valle
- Laboratory of Molecular Biology, Nutrition and Biotechnology (Group of Nutrigenomics, Biomarkers and Risk Evaluation), University of the Balearic Islands, 07122 Palma, Spain
- Health Research Institute of the Balearic Islands (IdISBa), 07010 Palma, Spain
- Artificial Intelligence Research Institute of the Balearic Islands (IAIB), 07122 Palma, Spain
- CIBER de Fisiopatología de la Obesidad y Nutrición (CIBEROBN), 28029 Madrid, Spain
| | - Pedro Castillo
- Laboratory of Molecular Biology, Nutrition and Biotechnology (Group of Nutrigenomics, Biomarkers and Risk Evaluation), University of the Balearic Islands, 07122 Palma, Spain
- Health Research Institute of the Balearic Islands (IdISBa), 07010 Palma, Spain
- Artificial Intelligence Research Institute of the Balearic Islands (IAIB), 07122 Palma, Spain
- CIBER de Fisiopatología de la Obesidad y Nutrición (CIBEROBN), 28029 Madrid, Spain
| | - Adrián García-Rodríguez
- Laboratory of Molecular Biology, Nutrition and Biotechnology (Group of Nutrigenomics, Biomarkers and Risk Evaluation), University of the Balearic Islands, 07122 Palma, Spain
- Health Research Institute of the Balearic Islands (IdISBa), 07010 Palma, Spain
- Artificial Intelligence Research Institute of the Balearic Islands (IAIB), 07122 Palma, Spain
- CIBER de Fisiopatología de la Obesidad y Nutrición (CIBEROBN), 28029 Madrid, Spain
| | - Andreu Palou
- Laboratory of Molecular Biology, Nutrition and Biotechnology (Group of Nutrigenomics, Biomarkers and Risk Evaluation), University of the Balearic Islands, 07122 Palma, Spain
- Health Research Institute of the Balearic Islands (IdISBa), 07010 Palma, Spain
- Artificial Intelligence Research Institute of the Balearic Islands (IAIB), 07122 Palma, Spain
- CIBER de Fisiopatología de la Obesidad y Nutrición (CIBEROBN), 28029 Madrid, Spain
| | - Mariona Palou
- Laboratory of Molecular Biology, Nutrition and Biotechnology (Group of Nutrigenomics, Biomarkers and Risk Evaluation), University of the Balearic Islands, 07122 Palma, Spain
- Health Research Institute of the Balearic Islands (IdISBa), 07010 Palma, Spain
- Artificial Intelligence Research Institute of the Balearic Islands (IAIB), 07122 Palma, Spain
- CIBER de Fisiopatología de la Obesidad y Nutrición (CIBEROBN), 28029 Madrid, Spain
| | - Catalina Picó
- Laboratory of Molecular Biology, Nutrition and Biotechnology (Group of Nutrigenomics, Biomarkers and Risk Evaluation), University of the Balearic Islands, 07122 Palma, Spain
- Health Research Institute of the Balearic Islands (IdISBa), 07010 Palma, Spain
- Artificial Intelligence Research Institute of the Balearic Islands (IAIB), 07122 Palma, Spain
- CIBER de Fisiopatología de la Obesidad y Nutrición (CIBEROBN), 28029 Madrid, Spain
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Ehrhardt RA, Giesy SL, Hileman SM, Houseknecht KL, Boisclair YR. Effects of the central melanocortin system on feed intake, metabolic hormones and insulin action in the sheep. J Anim Sci 2023; 101:skad398. [PMID: 38035762 PMCID: PMC10734672 DOI: 10.1093/jas/skad398] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Accepted: 11/29/2023] [Indexed: 12/02/2023] Open
Abstract
Voluntary feed intake is insufficient to meet the nutrient demands associated with late pregnancy in prolific ewes and early lactation in high-yielding dairy cows. Under these conditions, peripheral signals such as growth hormone and ceramides trigger adaptations aimed at preserving metabolic well-being. Recent work in rodents has shown that the central nervous system-melanocortin (CNS-MC) system, consisting of alpha-melanocyte-stimulating hormone (α-MSH) and agouti-related peptide (AGRP) acting respectively as agonist and antagonist on central MC receptors, contributes to the regulation of some of the same adaptations. To assess the effects of the CNC-MC on peripheral adaptations in ruminants, ewes were implanted with an intracerebroventricular cannula in the third ventricle and infused over days with artificial cerebrospinal fluid (aCSF), the α-MSH analog melanotan-I (MTI), or AGRP. Infusion of MTI at 0.03 nmol/h reduced intake, expressed as a fold of maintenance energy requirement (M), from 1.8 to 1.1 M (P < 0.0001), whereas AGRP at 0.3 nmol/h increased intake from 1.8 to 2.0 M (P < 0.01); these doses were used in all subsequent experiments. To assess the effect of MTI on plasma variables, sheep were fed ad libitum and infused with aCSF or MTI or pair-fed to MTI-treated sheep and infused with aCSF (aCSFPF). Feed intake of the MTI and aCSFPF groups was 40% lower than the aCSF group (P < 0.0001). MTI increased plasma triiodothyronine and thyroxine in an intake-independent manner (P < 0.05 or less) but was devoid of effects on plasma glucose, insulin, and cortisol. None of these variables were altered by AGRP infusion in sheep fed at a fixed intake of 1.6 M. To assess the effect of CNS-MC activation on insulin action, ewes were infused with aCSF or MTI over the last 3 d of a 14-d period when energy intake was limited to 0.3 M and studied under basal conditions and during hyperinsulinemic-euglycemic clamps. MTI had no effect on plasma glucose, plasma insulin, or glucose entry rate under basal conditions but blunted the ability of insulin to inhibit endogenous glucose production during hyperinsulinemic-euglycemic clamps (P < 0.0001). Finally, MTI tended to reduce plasma leptin in sheep fed at 0.3 M (P < 0.08), and this effect became significant at 0.6 M (P < 0.05); MTI had no effect on plasma adiponectin irrespective of feeding level. These data suggest a role for the CNC-MC in regulating metabolic efficiency and peripheral insulin action.
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Affiliation(s)
- Richard A Ehrhardt
- Department of Animal Science, Michigan State University, East Lansing, MI 48824, USA
- Department of Large Animal Clinical Sciences, Michigan State University, East Lansing, MI 48824, USA
| | - Sarah L Giesy
- Department of Animal Science, Cornell University, Ithaca, NY 14853, USA
| | - Stanley M Hileman
- Department of Physiology, Pharmacology, and Toxicology, West Virginia University, Morgantown, WV 26506, USA
| | - Karen L Houseknecht
- Department of Biomedical Sciences, University of New England, Portland, ME 04103, USA
| | - Yves R Boisclair
- Department of Animal Science, Cornell University, Ithaca, NY 14853, USA
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Optogenetic stimulation of the liver-projecting melanocortinergic pathway promotes hepatic glucose production. Nat Commun 2020; 11:6295. [PMID: 33293550 PMCID: PMC7722761 DOI: 10.1038/s41467-020-20160-w] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Accepted: 11/18/2020] [Indexed: 12/18/2022] Open
Abstract
The central melanocortin system plays a fundamental role in the control of feeding and body weight. Proopiomelanocortin (POMC) neurons in the arcuate nucleus of the hypothalamus (ARC) also regulate overall glucose homeostasis via insulin-dependent and -independent pathways. Here, we report that a subset of ARC POMC neurons innervate the liver via preganglionic parasympathetic acetylcholine (ACh) neurons in the dorsal motor nucleus of the vagus (DMV). Optogenetic stimulation of this liver-projecting melanocortinergic pathway elevates blood glucose levels that is associated with increased expression of hepatic gluconeogenic enzymes in female and male mice. Pharmacological blockade and knockdown of the melanocortin-4 receptor gene in the DMV abolish this stimulation-induced effect. Activation of melanocortin-4 receptors inhibits DMV cholinergic neurons and optogenetic inhibition of liver-projecting parasympathetic cholinergic fibers increases blood glucose levels. This elevated blood glucose is not due to altered pancreatic hormone release. Interestingly, insulin-induced hypoglycemia increases ARC POMC neuron activity. Hence, this liver-projecting melanocortinergic circuit that we identified may play a critical role in the counterregulatory response to hypoglycemia. Hypothalamic melanocortin neurons regulate systemic glucose homeostasis through incompletely understood pathways. Here, the authors show that a subset of pro-opiomelanocortin neurons innervate the liver via preganglionic parasympathetic cholinergic neurons in the dorsal motor nucleus of the vagus and that stimulation of this pathway elevates blood glucose levels
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Wong JC, Shapiro L, Thelin JT, Heaton EC, Zaman RU, D'Souza MJ, Murnane KS, Escayg A. Nanoparticle encapsulated oxytocin increases resistance to induced seizures and restores social behavior in Scn1a-derived epilepsy. Neurobiol Dis 2020; 147:105147. [PMID: 33189882 DOI: 10.1016/j.nbd.2020.105147] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Revised: 10/14/2020] [Accepted: 10/23/2020] [Indexed: 02/06/2023] Open
Abstract
Oxytocin (OT) has broad effects in the brain and plays an important role in cognitive, social, and neuroendocrine function. OT has also been identified as potentially therapeutic in neuropsychiatric disorders such as autism and depression, which are often comorbid with epilepsy, raising the possibility that it might confer protection against the behavioral and seizure phenotypes in epilepsy. Dravet syndrome (DS) is an early-life encephalopathy associated with prolonged and recurrent early-life febrile seizures (FSs), treatment-resistant afebrile epilepsy, and cognitive and behavioral deficits. De novo loss-of-function mutations in the voltage-gated sodium channel SCN1A are the main cause of DS, while genetic epilepsy with febrile seizures plus (GEFS+), also characterized by early-life FSs and afebrile epilepsy, is typically caused by inherited mutations that alter the biophysical properties of SCN1A. Despite the wide range of available antiepileptic drugs, many patients with SCN1A mutations do not achieve adequate seizure control or the amelioration of associated behavioral comorbidities. In the current study, we demonstrate that nanoparticle encapsulation of OT conferred robust and sustained protection against induced seizures and restored more normal social behavior in a mouse model of Scn1a-derived epilepsy. These results demonstrate the ability of a nanotechnology formulation to significantly enhance the efficacy of OT. This approach will provide a general strategy to enhance the therapeutic potential of additional neuropeptides in epilepsy and other neurological disorders.
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Affiliation(s)
- Jennifer C Wong
- Department of Human Genetics, Emory University, Atlanta, GA, United States of America.
| | - Lindsey Shapiro
- Department of Human Genetics, Emory University, Atlanta, GA, United States of America
| | - Jacquelyn T Thelin
- Department of Human Genetics, Emory University, Atlanta, GA, United States of America
| | - Elizabeth C Heaton
- Department of Human Genetics, Emory University, Atlanta, GA, United States of America
| | - Rokon U Zaman
- Department of Pharmaceutical Sciences, Mercer University, Atlanta, GA, United States of America
| | - Martin J D'Souza
- Department of Pharmaceutical Sciences, Mercer University, Atlanta, GA, United States of America
| | - Kevin S Murnane
- Department of Pharmaceutical Sciences, Mercer University, Atlanta, GA, United States of America
| | - Andrew Escayg
- Department of Human Genetics, Emory University, Atlanta, GA, United States of America
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Chen B, Vavrek M, Gundersdorf R, Zhong W, Cancilla MT. Combining MALDI mass spectrometry imaging and droplet-base surface sampling analysis for tissue distribution, metabolite profiling, and relative quantification of cyclic peptide melanotan II. Anal Chim Acta 2020; 1125:279-287. [PMID: 32674774 DOI: 10.1016/j.aca.2020.05.050] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Revised: 04/30/2020] [Accepted: 05/21/2020] [Indexed: 12/21/2022]
Abstract
Peptides have become a fast-growing segment of the pharmaceutical industry over the past few decades. It is essential to develop cutting edge analytical techniques to support the discovery and development of peptide therapeutics, especially to examine their absorption, distribution, metabolism and excretion (ADME) properties. Herein, we utilized two label-free mass spectrometry (MS) based techniques to investigate representative challenges in developing therapeutic peptides, such as tissue distribution, metabolic stability and clearance. A tool proof-of-concept cyclic peptide, melanotan II, was used in this study. Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI), which is a well-developed label-free imaging technique, was used to map the detailed molecular distribution of melanotan II and its metabolites. Droplet-based liquid microjunction surface sampling liquid chromatography-high resolution mass spectrometry (LMJ-SSP-LC-HRMS) was used in combination with MALDI-MSI to rapidly profile molecular information and provide structural insights on drug and metabolites. Using both techniques in parallel allowed a more comprehensive and complementary data set than using either technique independently. We envision MALDI-MSI and droplet-based LMJ-SSP-LC-HRMS, which can be used in combination or as standalone techniques, to become valuable tools for assessing the in vivo fate of peptide therapeutics in support of drug discovery and development.
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Affiliation(s)
- Bingming Chen
- Department of Pharmacokinetics, Pharmacodynamics & Drug Metabolism (PPDM), Merck & Co., Inc., 2000 Galloping Hill Rd, Kenilworth, NJ, 07033, USA.
| | - Marissa Vavrek
- Department of Pharmacokinetics, Pharmacodynamics & Drug Metabolism (PPDM), Merck & Co., Inc., 2000 Galloping Hill Rd, Kenilworth, NJ, 07033, USA
| | - Richard Gundersdorf
- Department of Pharmacokinetics, Pharmacodynamics & Drug Metabolism (PPDM), Merck & Co., Inc., 2000 Galloping Hill Rd, Kenilworth, NJ, 07033, USA
| | - Wendy Zhong
- Analytical Research & Development, Merck & Co., Inc., 2000 Galloping Hill Rd, Kenilworth, NJ, 07033, USA
| | - Mark T Cancilla
- Department of Pharmacokinetics, Pharmacodynamics & Drug Metabolism (PPDM), Merck & Co., Inc., 2000 Galloping Hill Rd, Kenilworth, NJ, 07033, USA.
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Pozo M, Claret M. Hypothalamic Control of Systemic Glucose Homeostasis: The Pancreas Connection. Trends Endocrinol Metab 2018; 29:581-594. [PMID: 29866501 DOI: 10.1016/j.tem.2018.05.001] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Revised: 05/10/2018] [Accepted: 05/12/2018] [Indexed: 12/22/2022]
Abstract
Maintenance of glucose homeostasis is mandatory for organismal survival. It is accomplished by complex and coordinated interplay between glucose detection mechanisms and multiple effector systems. The brain, in particular homeostatic regions such as the hypothalamus, plays a crucial role in orchestrating such a highly integral response. We review here current understanding of how the hypothalamus senses glucose availability and participates in systemic glucose homeostasis. We provide an update of the relevant signaling pathways and neuronal subsets involved, as well as of the mechanisms modulating metabolic processes in peripheral tissues such as liver, skeletal muscle, fat, and especially the pancreas. We also discuss the relevance of these networks in human biology and prevalent metabolic conditions such as diabetes and obesity.
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Affiliation(s)
- Macarena Pozo
- Neuronal Control of Metabolism (NeuCoMe) Laboratory, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), 08036 Barcelona, Spain
| | - Marc Claret
- Neuronal Control of Metabolism (NeuCoMe) Laboratory, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), 08036 Barcelona, Spain; Centro de Investigación Biomédica en Red (CIBER) de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), 08036 Barcelona, Spain.
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Chen KY, Muniyappa R, Abel BS, Mullins KP, Staker P, Brychta RJ, Zhao X, Ring M, Psota TL, Cone RD, Panaro BL, Gottesdiener KM, Van der Ploeg LHT, Reitman ML, Skarulis MC. RM-493, a melanocortin-4 receptor (MC4R) agonist, increases resting energy expenditure in obese individuals. J Clin Endocrinol Metab 2015; 100:1639-45. [PMID: 25675384 PMCID: PMC4399297 DOI: 10.1210/jc.2014-4024] [Citation(s) in RCA: 125] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
CONTEXT Activation of the melanocortin-4 receptor (MC4R) with the synthetic agonist RM-493 decreases body weight and increases energy expenditure (EE) in nonhuman primates. The effects of MC4R agonists on EE in humans have not been examined to date. OBJECTIVE, DESIGN, AND SETTING In a randomized, double-blind, placebo-controlled, crossover study, we examined the effects of the MC4R agonist RM-493 on resting energy expenditure (REE) in obese subjects in an inpatient setting. STUDY PARTICIPANTS AND METHODS Twelve healthy adults (6 men and 6 women) with body mass index of 35.7 ± 2.9 kg/m(2) (mean ± SD) received RM-493 (1 mg/24 h) or placebo by continuous subcutaneous infusion over 72 hours, followed immediately by crossover to the alternate treatment. All subjects received a weight-maintenance diet (50% carbohydrate, 30% fat, and 20% protein) and performed 30 minutes of standardized exercise daily. Continuous EE was measured on the third treatment day in a room calorimeter, and REE in the fasting state was defined as the mean of 2 30-minute resting periods. RESULTS RM-493 increased REE vs placebo by 6.4% (95% confidence interval, 0.68-13.02%), on average by 111 kcal/24 h (95% confidence interval, 15-207 kcal, P = .03). Total daily EE trended higher, whereas the thermic effect of a test meal and exercise EE did not differ significantly. The 23-hour nonexercise respiratory quotient was lower during RM-493 treatment (0.833 ± 0.021 vs 0.848 ± 0.022, P = .02). No adverse effect on heart rate or blood pressure was observed. CONCLUSIONS Short-term administration of the MC4R agonist RM-493 increases REE and shifts substrate oxidation to fat in obese individuals.
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Affiliation(s)
- Kong Y Chen
- Diabetes, Endocrinology, and Obesity Branch (K.Y.C., R.M., B.S.A., K.P.M., P.S., R.J.B., X.Z., M.R., T.L.P., M.L.R., M.C.S.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892; Department of Molecular Physiology and Biophysics (R.D.C., B.L.P.), Vanderbilt University School of Medicine, Nashville, Tennessee 37232; and Rhythm Pharmaceuticals (K.M.G., L.H.T.V.d.P.), Boston, Massachusetts 02116
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Fosgerau K, Raun K, Nilsson C, Dahl K, Wulff BS. Novel α-MSH analog causes weight loss in obese rats and minipigs and improves insulin sensitivity. J Endocrinol 2014; 220:97-107. [PMID: 24204009 PMCID: PMC3888513 DOI: 10.1530/joe-13-0284] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Obesity is a major burden to people and to health care systems around the world. The aim of the study was to characterize the effect of a novel selective α-MSH analog on obesity and insulin sensitivity. The subchronic effects of the selective MC4-R peptide agonist MC4-NN1-0182 were investigated in diet-induced obese (DIO) rats and DIO minipigs by assessing the effects on food intake, energy consumption, and body weight. The acute effect of MC4-NN1-0182 on insulin sensitivity was assessed by a euglycemic-hyperinsulinemic clamp study in normal rats. Three weeks of treatment of DIO rats with MC4-NN1-0182 caused a decrease in food intake and a significant decrease in body weight 7±1%, P<0.05 compared with 3±1% increase with the vehicle control. In DIO minipigs, 8 weeks of treatment with MC4-NN1-0182 resulted in a body weight loss of 13.3±2.5 kg (13±3%), whereas the vehicle control group had gained 3.7±1.4 kg (4±1%). Finally, clamp studies in normal rats showed that acute treatment with MC4-NN1-0182 caused a significant increase in glucose disposal (Rd) compared with vehicle control (Rd, mg/kg per min, 17.0±0.7 vs 13.9±0.6, P<0.01). We demonstrate that treatment of DIO rats or minipigs with a selective MC4-R peptide agonist causes weight loss. Moreover, we have demonstrated weight-independent effects on insulin sensitivity. Our observations identify MC4 agonism as a viable target for the treatment of obesity and insulin resistance.
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Affiliation(s)
- Keld Fosgerau
- Novo Nordisk Diabetes Research Unit, Novo Nordisk A/S, Novo Nordisk Park, DK-2760 Maaloev, Denmark
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La Fleur SE, Fliers E, Kalsbeek A. Neuroscience of glucose homeostasis. HANDBOOK OF CLINICAL NEUROLOGY 2014; 126:341-51. [PMID: 25410233 DOI: 10.1016/b978-0-444-53480-4.00026-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Plasma glucose concentrations are homeostatically regulated and maintained within strict boundaries. Several mechanisms are in place to increase glucose output when glucose levels in the circulation drop as a result of glucose utilization, or to decrease glucose output and increase tissue glucose uptake to prevent hyperglycemia. Although the term homeostasis mostly refers to stable levels, the blood glucose concentrations fluctuate over the day/night cycle, with the highest concentrations occurring just prior to the activity period in anticipation of increased caloric need. In this chapter we describe how the brain, particularly the hypothalamus, is involved in both the daily rhythm of plasma glucose concentrations and acute glucose challenges.
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Affiliation(s)
- S E La Fleur
- Department of Endocrinology and Metabolism, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - E Fliers
- Department of Endocrinology and Metabolism, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - A Kalsbeek
- Department of Endocrinology and Metabolism, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
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Tao YX, Liang XF. G Protein-Coupled Receptors as Regulators of Glucose Homeostasis and Therapeutic Targets for Diabetes Mellitus. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2014; 121:1-21. [DOI: 10.1016/b978-0-12-800101-1.00001-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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Coppari R, Bjørbæk C. Leptin revisited: its mechanism of action and potential for treating diabetes. Nat Rev Drug Discov 2012; 11:692-708. [PMID: 22935803 PMCID: PMC4019022 DOI: 10.1038/nrd3757] [Citation(s) in RCA: 204] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Since the discovery of leptin in 1994, we now have a better understanding of the cellular and molecular mechanisms underlying its biological effects. In addition to its established anti-obesity effects, leptin exerts antidiabetic actions that are independent of its regulation of body weight and food intake. In particular, leptin can correct diabetes in animal models of type 1 and type 2 diabetes. In addition, long-term leptin replacement therapy improves glycaemic control, insulin sensitivity and plasma triglycerides in patients with severe insulin resistance due to lipodystrophy. These results have spurred enthusiasm for the use of leptin therapy to treat diabetes. Here, we review the current understanding of the glucoregulatory functions of leptin, emphasizing its central mechanisms of action and lessons learned from clinical studies, and discuss possible therapeutic applications of leptin in the treatment of type 1 and type 2 diabetes.
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Affiliation(s)
- Roberto Coppari
- Department of Internal Medicine, Division of Hypothalamic Research, The University of Texas Southwestern Medical Center, Dallas TX, 75390, USA
- Department of Cellular Physiology and Metabolism, Faculty of Medicine, University of Geneva, 1211 Geneva, Switzerland
- The Center for Epigenetics and Metabolism, University of California Irvine, Irvine, CA, 92697, USA
| | - Christian Bjørbæk
- Department of Medicine, Division of Endocrinology and Metabolism, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston MA, 02215, USA
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Coomans CP, Biermasz NR, Geerling JJ, Guigas B, Rensen PCN, Havekes LM, Romijn JA. Stimulatory effect of insulin on glucose uptake by muscle involves the central nervous system in insulin-sensitive mice. Diabetes 2011; 60:3132-40. [PMID: 22028182 PMCID: PMC3219951 DOI: 10.2337/db10-1100] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
OBJECTIVE Insulin inhibits endogenous glucose production (EGP) and stimulates glucose uptake in peripheral tissues. Hypothalamic insulin signaling is required for the inhibitory effects of insulin on EGP. We examined the contribution of central insulin signaling on circulating insulin-stimulated tissue-specific glucose uptake. RESEARCH DESIGN AND METHODS Tolbutamide, an inhibitor of ATP-sensitive K(+) channels (K(ATP) channels), or vehicle was infused into the lateral ventricle in the basal state and during hyperinsulinemic-euglycemic conditions in postabsorptive, chow-fed C57Bl/6J mice and in postabsorptive C57Bl/6J mice with diet-induced obesity. Whole-body glucose uptake was measured by d-[(14)C]glucose kinetics and tissue-specific glucose uptake by 2-deoxy-d-[(3)H]glucose uptake. RESULTS During clamp conditions, intracerebroventricular administration of tolbutamide impaired the ability of insulin to inhibit EGP by ∼20%. In addition, intracerebroventricular tolbutamide diminished insulin-stimulated glucose uptake in muscle (by ∼59%) but not in heart or adipose tissue. In contrast, in insulin-resistant mice with diet-induced obesity, intracerebroventricular tolbutamide did not alter the effects of insulin during clamp conditions on EGP or glucose uptake by muscle. CONCLUSIONS Insulin stimulates glucose uptake in muscle in part through effects via K(ATP) channels in the central nervous system, in analogy with the inhibitory effects of insulin on EGP. High-fat diet-induced obesity abolished the central effects of insulin on liver and muscle. These observations stress the role of central insulin resistance in the pathophysiology of diet-induced insulin resistance.
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Affiliation(s)
- Claudia P Coomans
- Department of Endocrinology and Metabolic Disorders, Leiden University Medical Center, Leiden, the Netherlands.
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Coomans CP, Geerling JJ, Guigas B, van den Hoek AM, Parlevliet ET, Ouwens DM, Pijl H, Voshol PJ, Rensen PCN, Havekes LM, Romijn JA. Circulating insulin stimulates fatty acid retention in white adipose tissue via KATP channel activation in the central nervous system only in insulin-sensitive mice. J Lipid Res 2011; 52:1712-22. [PMID: 21700834 DOI: 10.1194/jlr.m015396] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Insulin signaling in the central nervous system (CNS) is required for the inhibitory effect of insulin on glucose production. Our aim was to determine whether the CNS is also involved in the stimulatory effect of circulating insulin on the tissue-specific retention of fatty acid (FA) from plasma. In wild-type mice, hyperinsulinemic-euglycemic clamp conditions stimulated the retention of both plasma triglyceride-derived FA and plasma albumin-bound FA in the various white adipose tissues (WAT) but not in other tissues, including brown adipose tissue (BAT). Intracerebroventricular (ICV) administration of insulin induced a similar pattern of tissue-specific FA partitioning. This effect of ICV insulin administration was not associated with activation of the insulin signaling pathway in adipose tissue. ICV administration of tolbutamide, a K(ATP) channel blocker, considerably reduced (during hyperinsulinemic-euglycemic clamp conditions) and even completely blocked (during ICV administration of insulin) WAT-specific retention of FA from plasma. This central effect of insulin was absent in CD36-deficient mice, indicating that CD36 is the predominant FA transporter in insulin-stimulated FA retention by WAT. In diet-induced insulin-resistant mice, these stimulating effects of insulin (circulating or ICV administered) on FA retention in WAT were lost. In conclusion, in insulin-sensitive mice, circulating insulin stimulates tissue-specific partitioning of plasma-derived FA in WAT in part through activation of K(ATP) channels in the CNS. Apparently, circulating insulin stimulates fatty acid uptake in WAT but not in BAT, directly and indirectly through the CNS.
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Affiliation(s)
- Claudia P Coomans
- Departments of Endocrinology and Metabolic Diseases, Leiden University Medical Center, Leiden, The Netherlands.
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14
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Claret M, Smith MA, Knauf C, Al-Qassab H, Woods A, Heslegrave A, Piipari K, Emmanuel JJ, Colom A, Valet P, Cani PD, Begum G, White A, Mucket P, Peters M, Mizuno K, Batterham RL, Giese KP, Ashworth A, Burcelin R, Ashford ML, Carling D, Withers DJ. Deletion of Lkb1 in pro-opiomelanocortin neurons impairs peripheral glucose homeostasis in mice. Diabetes 2011; 60:735-45. [PMID: 21266325 PMCID: PMC3046834 DOI: 10.2337/db10-1055] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE AMP-activated protein kinase (AMPK) signaling acts as a sensor of nutrients and hormones in the hypothalamus, thereby regulating whole-body energy homeostasis. Deletion of Ampkα2 in pro-opiomelanocortin (POMC) neurons causes obesity and defective neuronal glucose sensing. LKB1, the Peutz-Jeghers syndrome gene product, and Ca(2+)-calmodulin-dependent protein kinase kinase β (CaMKKβ) are key upstream activators of AMPK. This study aimed to determine their role in POMC neurons upon energy and glucose homeostasis regulation. RESEARCH DESIGN AND METHODS Mice lacking either Camkkβ or Lkb1 in POMC neurons were generated, and physiological, electrophysiological, and molecular biology studies were performed. RESULTS Deletion of Camkkβ in POMC neurons does not alter energy homeostasis or glucose metabolism. In contrast, female mice lacking Lkb1 in POMC neurons (PomcLkb1KO) display glucose intolerance, insulin resistance, impaired suppression of hepatic glucose production, and altered expression of hepatic metabolic genes. The underlying cellular defect in PomcLkb1KO mice involves a reduction in melanocortin tone caused by decreased α-melanocyte-stimulating hormone secretion. However, Lkb1-deficient POMC neurons showed normal glucose sensing, and body weight was unchanged in PomcLkb1KO mice. CONCLUSIONS Our findings demonstrate that LKB1 in hypothalamic POMC neurons plays a key role in the central regulation of peripheral glucose metabolism but not body-weight control. This phenotype contrasts with that seen in mice lacking AMPK in POMC neurons with defects in body-weight regulation but not glucose homeostasis, which suggests that LKB1 plays additional functions distinct from activating AMPK in POMC neurons.
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Affiliation(s)
- Marc Claret
- Laboratory of Diabetes and Obesity, Endocrinology and Nutrition Unit, Institut d'Investigacions Biomèdiques August Pi i Sunyer, Hospital Clinic de Barcelona, Barcelona, Spain
- Corresponding author: Dominic J. Withers, , or Marc Claret,
| | - Mark A. Smith
- Metabolic Signalling Group, Medical Research Council (MRC) Clinical Sciences Centre, Imperial College London, London, U.K
- Biomedical Research Institute, Ninewells Hospital and Medical School, University of Dundee, Dundee, U.K
| | - Claude Knauf
- Institut National de la Santé et de la Recherche Médicale U858, Institut de Médecine Moléculaire de Rangueil, Toulouse, France
| | - Hind Al-Qassab
- Metabolic Signalling Group, Medical Research Council (MRC) Clinical Sciences Centre, Imperial College London, London, U.K
| | - Angela Woods
- Cellular Stress Group, MRC Clinical Sciences Centre, Imperial College London, London, U.K
| | - Amanda Heslegrave
- Cellular Stress Group, MRC Clinical Sciences Centre, Imperial College London, London, U.K
| | - Kaisa Piipari
- Metabolic Signalling Group, Medical Research Council (MRC) Clinical Sciences Centre, Imperial College London, London, U.K
| | - Julian J. Emmanuel
- Centre for Diabetes and Endocrinology, Rayne Institute, University College London, London, U.K
| | - André Colom
- Institut National de la Santé et de la Recherche Médicale U858, Institut de Médecine Moléculaire de Rangueil, Toulouse, France
| | - Philippe Valet
- Institut National de la Santé et de la Recherche Médicale U858, Institut de Médecine Moléculaire de Rangueil, Toulouse, France
| | - Patrice D. Cani
- Louvain Drug Research Institute, Unit of Pharmacokinetics, Metabolism, Nutrition, and Toxicology, Université Catholique de Louvain, Brussels, Belgium
| | - Ghazala Begum
- Faculties of Life Sciences and Medical and Human Sciences, Manchester Academic Health Sciences Centre, University of Manchester, Manchester, U.K
| | - Anne White
- Faculties of Life Sciences and Medical and Human Sciences, Manchester Academic Health Sciences Centre, University of Manchester, Manchester, U.K
| | - Phillip Mucket
- Cellular Stress Group, MRC Clinical Sciences Centre, Imperial College London, London, U.K
| | - Marco Peters
- Centre for the Cellular Basis of Behaviour, Institute of Psychiatry, King’s College London, London, U.K
| | - Keiko Mizuno
- Centre for the Cellular Basis of Behaviour, Institute of Psychiatry, King’s College London, London, U.K
| | - Rachel L. Batterham
- Centre for Diabetes and Endocrinology, Rayne Institute, University College London, London, U.K
| | - K. Peter Giese
- Centre for the Cellular Basis of Behaviour, Institute of Psychiatry, King’s College London, London, U.K
| | - Alan Ashworth
- The Breakthrough Breast Cancer Research Centre, Institute of Cancer Research, London, U.K
| | - Remy Burcelin
- Institut National de la Santé et de la Recherche Médicale U858, Institut de Médecine Moléculaire de Rangueil, Toulouse, France
| | - Michael L. Ashford
- Biomedical Research Institute, Ninewells Hospital and Medical School, University of Dundee, Dundee, U.K
| | - David Carling
- Cellular Stress Group, MRC Clinical Sciences Centre, Imperial College London, London, U.K
| | - Dominic J. Withers
- Metabolic Signalling Group, Medical Research Council (MRC) Clinical Sciences Centre, Imperial College London, London, U.K
- Corresponding author: Dominic J. Withers, , or Marc Claret,
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15
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Tanida M, Shintani N, Hashimoto H. The melanocortin system is involved in regulating autonomic nerve activity through central pituitary adenylate cyclase-activating polypeptide. Neurosci Res 2011; 70:55-61. [PMID: 21291921 DOI: 10.1016/j.neures.2011.01.014] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2010] [Revised: 01/20/2011] [Accepted: 01/24/2011] [Indexed: 10/18/2022]
Abstract
Pituitary adenylate cyclase-activating polypeptide (PACAP) is a peptidergic neurotransmitter that is highly expressed in the nervous system. We have previously reported that a central injection of PACAP leads to changes in the autonomic nervous system tones including sympathetic excitation and parasympathetic inhibition. An anatomical study revealed that melanocortin and PACAP are colocalized in some hypothalamic nuclei. Here, we investigated the possible role of the melanocortin system in autonomic control by PACAP using SHU9119, an antagonist of the melanocortin receptors (MC3-R/MC4-R). Pretreatment with SHU-9119 did not affect the activating neural responses of adrenal, renal, and lumbar sympathetic nerves following a PACAP injection However, SHU9119 significantly eliminated the suppressing effect of a PACAP injection on gastric vagal nerve activity and excitation effects on liver and brown adipose tissue sympathetic nerve activities. These results suggest that the brain melanocortin system might play a key role in the control of thermogenic sympathetic outflows and digestive parasympathetic outflow by PACAP, but this system does not participate in the central effects of PACAP on cardiovascular function and neural activities of renal, adrenal, and lumbar sympathetic nerves.
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Affiliation(s)
- Mamoru Tanida
- Department of Biomedical Sciences, College of Life Sciences, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga 525-8577, Japan.
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16
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Kalsbeek A, Bruinstroop E, Yi CX, Klieverik LP, La Fleur SE, Fliers E. Hypothalamic control of energy metabolism via the autonomic nervous system. Ann N Y Acad Sci 2010; 1212:114-29. [PMID: 21070249 DOI: 10.1111/j.1749-6632.2010.05800.x] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The hypothalamic control of hepatic glucose production is an evident aspect of energy homeostasis. In addition to the control of glucose metabolism by the circadian timing system, the hypothalamus also serves as a key relay center for (humoral) feedback information from the periphery, with the important role for hypothalamic leptin receptors as a striking example. The hypothalamic biological clock uses its projections to the preautonomic hypothalamic neurons to control the daily rhythms in plasma glucose concentration, glucose uptake, and insulin sensitivity. Euglycemic, hyperinsulinemic clamp experiments combined with either sympathetic-, parasympathetic-, or sham-denervations of the autonomic input to the liver have further delineated the hypothalamic pathways that mediate the control of the circadian timing system over glucose metabolism. In addition, these experiments clearly showed both that next to the biological clock peripheral hormones may "use" the preautonomic neurons in the hypothalamus to affect hepatic glucose metabolism, and that similar pathways may be involved in the control of lipid metabolism in liver and white adipose tissue.
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Affiliation(s)
- A Kalsbeek
- Department of Endocrinology and Metabolism, Academic Medical Center (AMC), University of Amsterdam, Meibergdreef 9, Amsterdam, the Netherlands.
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17
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Abstract
The melanocortin-4 receptor (MC4R) was cloned in 1993 by degenerate PCR; however, its function was unknown. Subsequent studies suggest that the MC4R might be involved in regulating energy homeostasis. This hypothesis was confirmed in 1997 by a series of seminal studies in mice. In 1998, human genetic studies demonstrated that mutations in the MC4R gene can cause monogenic obesity. We now know that mutations in the MC4R are the most common monogenic form of obesity, with more than 150 distinct mutations reported thus far. This review will summarize the studies on the MC4R, from its cloning and tissue distribution to its physiological roles in regulating energy homeostasis, cachexia, cardiovascular function, glucose and lipid homeostasis, reproduction and sexual function, drug abuse, pain perception, brain inflammation, and anxiety. I will then review the studies on the pharmacology of the receptor, including ligand binding and receptor activation, signaling pathways, as well as its regulation. Finally, the pathophysiology of the MC4R in obesity pathogenesis will be reviewed. Functional studies of the mutant MC4Rs and the therapeutic implications, including small molecules in correcting binding and signaling defect, and their potential as pharmacological chaperones in rescuing intracellularly retained mutants, will be highlighted.
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Affiliation(s)
- Ya-Xiong Tao
- Department of Anatomy, Physiology, and Pharmacology, Auburn University, Alabama 36849-5519, USA.
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18
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D'Agostino G, Diano S. Alpha-melanocyte stimulating hormone: production and degradation. J Mol Med (Berl) 2010; 88:1195-201. [PMID: 20617297 DOI: 10.1007/s00109-010-0651-0] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2010] [Revised: 06/21/2010] [Accepted: 06/24/2010] [Indexed: 10/19/2022]
Abstract
Proopiomelanocortin (POMC) is a polypeptide hormone precursor that is expressed in the brain and in peripheral tissues such as in the pituitary gland, immune system, and skin. In the brain, POMC is processed to form several peptides including alpha-melanocyte stimulating hormone (α-MSH). alpha-MSH is expressed in the hypothalamic arcuate nucleus and in the nucleus tractus solitarius of the brainstem where it has a crucial role in the regulation of metabolic functions. Specifically, α-MSH is an anorexigenic peptide. Its production and maturation processes have been shown to be regulated according to the metabolic condition of the organism. This review summarizes our current knowledge on α-MSH processing including its maturation and degradation processes and pharmacological aspects of its manipulation.
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Affiliation(s)
- Giuseppe D'Agostino
- Program in Integrative Cell Signaling and Neurobiology of Metabolism, Yale University School of Medicine, New Haven, CT 06520, USA
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19
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Pro-opiomelanocortin gene transfer to the nucleus of the solitary track but not arcuate nucleus ameliorates chronic diet-induced obesity. Neuroscience 2010; 169:1662-71. [PMID: 20538045 DOI: 10.1016/j.neuroscience.2010.06.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2010] [Revised: 05/27/2010] [Accepted: 06/01/2010] [Indexed: 11/20/2022]
Abstract
Short-term pharmacological melanocortin activation deters diet-induced obesity (DIO) effectively in rodents. However, whether central pro-opiomelanocortin (POMC) gene transfer targeted to the hypothalamus or hindbrain nucleus of the solitary track (NTS) can combat chronic dietary obesity has not been investigated. Four-weeks-old Sprague-Dawley rats were fed a high fat diet for 5 months, and then injected with either the POMC or control vector into the hypothalamus or NTS, and body weight and food intake recorded for 68 days. Insulin sensitivity, glucose metabolism and adrenal indicators of central sympathetic activation were measured, and voluntary wheel running (WR) assessed. Whereas the NTS POMC-treatment decreased cumulative food consumption and caused a sustained weight reduction over 68 days, the hypothalamic POMC-treatment did not alter cumulative food intake and produced weight loss only in the first 25 days. At death, only the NTS-POMC rats had a significant decrease in fat mass. They also displayed enhanced glucose tolerance, lowered fasting insulin and increased QUICK value, and elevated adrenal indicators of central sympathetic activation. Moreover, the NTS-POMC animals exhibited a near 20% increase in distance ran relative to the respective controls, but the ARC-POMC rats did not. In conclusion, POMC gene transfer to the NTS caused modest anorexia, persistent weight loss, improved insulin sensitivity, and increased propensity for WR in DIO rats. These metabolic improvements may involve stimulation of energy expenditure via centrally regulated sympathetic outflow. The similar POMC treatment in the hypothalamus had minimal long-term physiological or metabolic impact. Thus, melanocortin activation in the brainstem NTS region effectively ameliorates chronic dietary obesity whilst that in the hypothalamus fails to do so.
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20
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Zhang Y, Collazo R, Gao Y, Li G, Scarpace PJ. Intermittent MTII application evokes repeated anorexia and robust fat and weight loss. Peptides 2010; 31:639-43. [PMID: 20034526 PMCID: PMC2860181 DOI: 10.1016/j.peptides.2009.12.019] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2009] [Revised: 12/12/2009] [Accepted: 12/13/2009] [Indexed: 10/20/2022]
Abstract
Central melanocortins (MC) evoke potent but transient anorectic responses with tachyphylaxis developing within days. We hypothesized that intermittent therapy using the MC analog, melanotan II (MTII), would minimize the tachyphylaxis and enhance the long-term efficacy of MTII treatment. F344/BN rats were infused with MTII or vehicle into the lateral ventricle by mini pump for 14 days. Half the MTII-infused rats were then given vehicle (MTII-On/Off), while the remaining received fresh MTII (MTII-On) for 10 days. Finally, pumps in both groups were replaced with ones containing fresh MTII for an additional 6 days. The first MTII application induced a 30% food reduction that attenuated within 5 days. Reapplication of MTII in MTII-On/Off rats, after the off period, invoked a new and equally robust anorectic response while continuation of MTII supplement in the MTII-On group did not change food intake from the control level. Body weights decreased similarly in both MTII groups at termination (day 30). Hypothalamic MC3 receptor, AgRP, and POMC expressions were unchanged, but MC4 receptor expression was diminished by 25%, and adiposity reduced by 80% in both MTII groups. Acetyl-CoA carboxylase 1 phosphorylation was elevated in perirenal fat by over 10 fold with either MTII treatment. In conclusion, intermittent MTII treatment preserves anorectic responses but does not prevent tachyphylaxis, whereas constant MTII application blunts further food response after the initial tachyphylaxis. Either form of MTII administration results in significant weight and adiposity reductions, involving perhaps fatty acid oxidation within specific adipose tissues.
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Affiliation(s)
- Yi Zhang
- Research Department, Malcom Randall Veterans Affairs Medical Center-NF/SG HSC, Rm E585-1, 1601 SW Archer Road, Gainesville, FL 32608, USA.
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21
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Toda C, Shiuchi T, Lee S, Yamato-Esaki M, Fujino Y, Suzuki A, Okamoto S, Minokoshi Y. Distinct effects of leptin and a melanocortin receptor agonist injected into medial hypothalamic nuclei on glucose uptake in peripheral tissues. Diabetes 2009; 58:2757-65. [PMID: 19752162 PMCID: PMC2780865 DOI: 10.2337/db09-0638] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
OBJECTIVE The medial hypothalamus mediates leptin-induced glucose uptake in peripheral tissues, and brain melanocortin receptors (MCRs) mediate certain central effects of leptin. However, the contributions of the leptin receptor and MCRs in individual medial hypothalamic nuclei to regulation of peripheral glucose uptake have remained unclear. We examined the effects of an injection of leptin and the MCR agonist MT-II into medial hypothalamic nuclei on glucose uptake in peripheral tissues. RESEARCH DESIGN AND METHODS Leptin or MT-II was injected into the ventromedial (VMH), dorsomedial (DMH), arcuate nucleus (ARC), or paraventricular (PVH) hypothalamus or the lateral ventricle (intracerebroventricularly) in freely moving mice. The MCR antagonist SHU9119 was injected intracerebroventricularly. Glucose uptake was measured by the 2-[(3)H]deoxy-d-glucose method. RESULTS Leptin injection into the VMH increased glucose uptake in skeletal muscle, brown adipose tissue (BAT), and heart, whereas that into the ARC increased glucose uptake in BAT, and that into the DMH or PVH had no effect. SHU9119 abolished these effects of leptin injected into the VMH. Injection of MT-II either into the VMH or intracerebroventricularly increased glucose uptake in skeletal muscle, BAT, and heart, whereas that into the PVH increased glucose uptake in BAT, and that into the DMH or ARC had no effect. CONCLUSIONS The VMH mediates leptin- and MT-II-induced glucose uptake in skeletal muscle, BAT, and heart. These effects of leptin are dependent on MCR activation. The leptin receptor in the ARC and MCR in the PVH regulate glucose uptake in BAT. Medial hypothalamic nuclei thus play distinct roles in leptin- and MT-II-induced glucose uptake in peripheral tissues.
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Affiliation(s)
- Chitoku Toda
- Department of Physiological Sciences, Graduate University for Advanced Studies (Sokendai), Hayama, Kanagawa, Japan
- Division of Endocrinology and Metabolism, Department of Developmental Physiology, National Institute for Physiological Sciences, Okazaki, Aichi, Japan
| | - Tetsuya Shiuchi
- Department of Physiological Sciences, Graduate University for Advanced Studies (Sokendai), Hayama, Kanagawa, Japan
- Division of Endocrinology and Metabolism, Department of Developmental Physiology, National Institute for Physiological Sciences, Okazaki, Aichi, Japan
| | - Suni Lee
- Division of Endocrinology and Metabolism, Department of Developmental Physiology, National Institute for Physiological Sciences, Okazaki, Aichi, Japan
| | - Maya Yamato-Esaki
- Department of Physiological Sciences, Graduate University for Advanced Studies (Sokendai), Hayama, Kanagawa, Japan
- Division of Endocrinology and Metabolism, Department of Developmental Physiology, National Institute for Physiological Sciences, Okazaki, Aichi, Japan
| | - Yusuke Fujino
- Division of Endocrinology and Metabolism, Department of Developmental Physiology, National Institute for Physiological Sciences, Okazaki, Aichi, Japan
- Department of Internal Medicine 1, Faculty of Medicine, Oita University, Hasama, Oita, Japan
| | - Atsushi Suzuki
- Division of Endocrinology and Metabolism, Department of Developmental Physiology, National Institute for Physiological Sciences, Okazaki, Aichi, Japan
| | - Shiki Okamoto
- Department of Physiological Sciences, Graduate University for Advanced Studies (Sokendai), Hayama, Kanagawa, Japan
- Division of Endocrinology and Metabolism, Department of Developmental Physiology, National Institute for Physiological Sciences, Okazaki, Aichi, Japan
| | - Yasuhiko Minokoshi
- Department of Physiological Sciences, Graduate University for Advanced Studies (Sokendai), Hayama, Kanagawa, Japan
- Division of Endocrinology and Metabolism, Department of Developmental Physiology, National Institute for Physiological Sciences, Okazaki, Aichi, Japan
- Corresponding author: Yasuhiko Minokoshi,
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22
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Leptin-dependent control of glucose balance and locomotor activity by POMC neurons. Cell Metab 2009; 9:537-47. [PMID: 19490908 PMCID: PMC2730605 DOI: 10.1016/j.cmet.2009.05.003] [Citation(s) in RCA: 171] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2008] [Revised: 11/12/2008] [Accepted: 05/12/2009] [Indexed: 01/16/2023]
Abstract
Leptin plays a pivotal role in regulation of energy balance. Via unknown central pathways, leptin also affects peripheral glucose homeostasis and locomotor activity. We hypothesized that, specifically, pro-opiomelanocortin (POMC) neurons mediate those actions. To examine this possibility, we applied Cre-Lox technology to express leptin receptors (ObRb) exclusively in POMC neurons of the morbidly obese, profoundly diabetic, and severely hypoactive leptin receptor-deficient Lepr(db/db) mice. Here, we show that expression of ObRb only in POMC neurons leads to a marked decrease in energy intake and a modest reduction in body weight in Lepr(db/db) mice. Remarkably, blood glucose levels are entirely normalized. This normalization occurs independently of changes in food intake and body weight. In addition, physical activity is greatly increased despite profound obesity. Our results suggest that leptin signaling exclusively in POMC neurons is sufficient to stimulate locomotion and prevent diabetes in the severely hypoactive and hyperglycemic obese Lepr(db/db) mice.
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23
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Abstract
The PI3K-Akt-FoxO1 pathway contributes to the actions of insulin and leptin in several cell types, including neurons in the CNS. However, identifying these actions in chemically identified neurons has proven difficult. To address this problem, we have developed a reporter mouse for monitoring PI3K-Akt signaling in specific populations of neurons, based on FoxO1 nucleocytoplasmic shuttling. The reporter, FoxO1 fused to green fluorescent protein (FoxO1GFP), is expressed under the control of a ubiquitous promoter that is silenced by a loxP flanked transcriptional blocker. Thus, the expression of the reporter in selected cells is dependent on the action of Cre recombinase. Using this model, we found that insulin treatment resulted in the nuclear exclusion of FoxO1GFP within POMC and AgRP neurons in a dose- and time-dependent manner. FoxO1GFP nuclear exclusion was also observed in POMC neurons following in vivo administration of insulin. In addition, leptin induced transient nuclear export of FoxO1GFP in POMC neurons in a dose dependent manner. Finally, insulin-induced nuclear export was impaired in POMC neurons by pretreatment with free fatty acids, a paradigm known to induce insulin resistance in peripheral insulin target tissues. Thus, our FoxO1GFP mouse provides a tool for monitoring the status of PI3K-Akt signaling in a cell-specific manner under physiological and pathophysiological conditions.
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24
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Zhou L, Sutton GM, Rochford JJ, Semple RK, Lam DD, Oksanen L, Thornton-Jones ZD, Clifton PG, Yueh CY, Evans ML, McCrimmon R, Elmquist JK, Butler AA, Heisler LK. Serotonin 2C receptor agonists improve type 2 diabetes via melanocortin-4 receptor signaling pathways. Cell Metab 2007; 6:398-405. [PMID: 17983585 PMCID: PMC2075535 DOI: 10.1016/j.cmet.2007.10.008] [Citation(s) in RCA: 172] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/28/2006] [Revised: 08/16/2007] [Accepted: 10/15/2007] [Indexed: 11/18/2022]
Abstract
The burden of type 2 diabetes and its associated premature morbidity and mortality is rapidly growing, and the need for novel efficacious treatments is pressing. We report here that serotonin 2C receptor (5-HT(2C)R) agonists, typically investigated for their anorectic properties, significantly improve glucose tolerance and reduce plasma insulin in murine models of obesity and type 2 diabetes. Importantly, 5-HT(2C)R agonist-induced improvements in glucose homeostasis occurred at concentrations of agonist that had no effect on ingestive behavior, energy expenditure, locomotor activity, body weight, or fat mass. We determined that this primary effect on glucose homeostasis requires downstream activation of melanocortin-4 receptors (MC4Rs), but not MC3Rs. These findings suggest that pharmacological targeting of 5-HT(2C)Rs may enhance glucose tolerance independently of alterations in body weight and that this may prove an effective and mechanistically novel strategy in the treatment of type 2 diabetes.
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MESH Headings
- Absorptiometry, Photon
- Animals
- Blotting, Western
- Diabetes Mellitus, Type 2/drug therapy
- Diabetes Mellitus, Type 2/metabolism
- Diabetes Mellitus, Type 2/physiopathology
- Gene Expression/drug effects
- Glucose/metabolism
- Glucose Intolerance
- Glucose Tolerance Test
- Homeostasis/drug effects
- Immunohistochemistry
- Insulin/blood
- Male
- Mice
- Mice, Knockout
- Mice, Obese
- Neurons/drug effects
- Neurons/metabolism
- Piperazines/pharmacology
- Polymerase Chain Reaction
- Pro-Opiomelanocortin/genetics
- Receptor, Melanocortin, Type 4/chemistry
- Receptor, Melanocortin, Type 4/metabolism
- Receptor, Melanocortin, Type 4/physiology
- Serotonin 5-HT2 Receptor Agonists
- Serotonin Receptor Agonists/pharmacology
- Signal Transduction/drug effects
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Affiliation(s)
- Ligang Zhou
- Department of Clinical Biochemistry, Addenbrooke's Hospital, University of Cambridge, Cambridge CB2 2QQ, UK
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Gregory M. Sutton
- Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, LA 70808, USA
| | - Justin J. Rochford
- Department of Clinical Biochemistry, Addenbrooke's Hospital, University of Cambridge, Cambridge CB2 2QQ, UK
| | - Robert K. Semple
- Department of Clinical Biochemistry, Addenbrooke's Hospital, University of Cambridge, Cambridge CB2 2QQ, UK
| | - Daniel D. Lam
- Department of Clinical Biochemistry, Addenbrooke's Hospital, University of Cambridge, Cambridge CB2 2QQ, UK
| | - Laura J. Oksanen
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA
| | | | - Peter G. Clifton
- Department of Psychology, Sussex University, Brighton BN1 9QG, UK
| | - Chen-Yu Yueh
- Department of Medicine, Addenbrooke's Hospital, University of Cambridge, Cambridge CB2 2QQ, UK
| | - Mark L. Evans
- Department of Medicine, Addenbrooke's Hospital, University of Cambridge, Cambridge CB2 2QQ, UK
| | - Rory J. McCrimmon
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Joel K. Elmquist
- Division of Hypothalamic Research and the Departments of Internal Medicine and Pharmacology, The University of Texas Southwestern Medical Center, Dallas, TX 75390-9051, USA
| | - Andrew A. Butler
- Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, LA 70808, USA
| | - Lora K. Heisler
- Department of Clinical Biochemistry, Addenbrooke's Hospital, University of Cambridge, Cambridge CB2 2QQ, UK
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25
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Lee M, Kim A, Chua SC, Obici S, Wardlaw SL. Transgenic MSH overexpression attenuates the metabolic effects of a high-fat diet. Am J Physiol Endocrinol Metab 2007; 293:E121-31. [PMID: 17374695 DOI: 10.1152/ajpendo.00555.2006] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To determine whether long-term melanocortinergic activation can attenuate the metabolic effects of a high fat diet, mice overexpressing an NH(2)-terminal POMC transgene that includes alpha- and gamma(3)-MSH were studied on either a 10% low-fat diet (LFD) or 45% high-fat diet (HFD). Weight gain was modestly reduced in transgenic (Tg-MSH) male and female mice vs. wild type (WT) on HFD (P < 0.05) but not LFD. Substantial reductions in body fat percentage were found in both male and female Tg-MSH mice on LFD (P < 0.05) and were more pronounced on HFD (P < 0.001). These changes occurred in the absence of significant feeding differences in most groups, consistent with effects of Tg-MSH on energy expenditure and partitioning. This is supported by indirect calorimetry studies demonstrating higher resting oxygen consumption and lower RQ in Tg-MSH mice on the HFD. Tg-MSH mice had lower fasting insulin levels and improved glucose tolerance on both diets. Histological and biochemical analyses revealed that hepatic fat accumulation was markedly reduced in Tg-MSH mice on the HFD. Tg-MSH also attenuated the increase in corticosterone induced by the HFD. Higher levels of Agrp mRNA, which might counteract effects of the transgene, were measured in Tg-MSH mice on LFD (P = 0.02) but not HFD. These data show that long-term melanocortin activation reduces body weight, adiposity, and hepatic fat accumulation and improves glucose metabolism, particularly in the setting of diet-induced obesity. Our results suggest that long-term melanocortinergic activation could serve as a potential strategy for the treatment of obesity and its deleterious metabolic consequences.
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Affiliation(s)
- Michelle Lee
- Department of Medicine, Columbia University College of Physicians and Surgeons, 630 West 168th St., New York, NY 10032, USA
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26
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Tanaka T, Masuzaki H, Yasue S, Ebihara K, Shiuchi T, Ishii T, Arai N, Hirata M, Yamamoto H, Hayashi T, Hosoda K, Minokoshi Y, Nakao K. Central melanocortin signaling restores skeletal muscle AMP-activated protein kinase phosphorylation in mice fed a high-fat diet. Cell Metab 2007; 5:395-402. [PMID: 17488641 DOI: 10.1016/j.cmet.2007.04.004] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/25/2006] [Revised: 01/22/2007] [Accepted: 04/17/2007] [Indexed: 11/19/2022]
Abstract
Little is known about the role of the central melanocortin system in the control of fuel metabolism in peripheral tissues. Skeletal muscle AMP-activated protein kinase (AMPK) is activated by leptin and serves as a master regulator of fatty acid beta-oxidation. To elucidate an unidentified role of the central melanocortin system in muscle AMPK regulation, we treated conscious, unrestrained mice intracerebroventricularly with the melanocortin agonist MT-II or the antagonist SHU9119. MT-II augmented phosphorylation of AMPK and its target acetyl-CoA carboxylase (ACC) independent of caloric intake. Conversely, AMPK/ACC phosphorylation by leptin was abrogated by the coadministration of SHU9119 or in KKA(y) mice, which centrally express endogenous melanocortin antagonist. Importantly, high-fat-diet-induced attenuation of AMPK/ACC phosphorylation in leptin-overexpressing transgenic mice was not reversed by central leptin but was markedly restored by MT-II. Our data provide evidence for the critical role of the central melanocortin system in the leptin-skeletal muscle AMPK axis and highlight the system as a therapeutic target in leptin resistance.
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Affiliation(s)
- Tomohiro Tanaka
- Department of Medicine and Clinical Science, Kyoto University Graduate School of Medicine, Kyoto 606-8507, Japan
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27
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Banno R, Arima H, Hayashi M, Goto M, Watanabe M, Sato I, Ozaki N, Nagasaki H, Ozaki N, Oiso Y. Central administration of melanocortin agonist increased insulin sensitivity in diet-induced obese rats. FEBS Lett 2007; 581:1131-6. [PMID: 17321524 DOI: 10.1016/j.febslet.2007.02.019] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2007] [Revised: 02/09/2007] [Accepted: 02/09/2007] [Indexed: 01/21/2023]
Abstract
In this study, we examined the effects of intracerebroventricular administration of melanotan II (MTII), a melanocortin agonist, on insulin sensitivity in diet-induced obese (DIO) rats. Although MTII treatment significantly decreased food intake and body weight for 10 days, there was no significant difference in body weight between MTII and pair-fed groups. The insulin tolerance test showed that insulin sensitivity was significantly improved in the MTII group compared to the pair-fed group. Furthermore, MTII treatment increased the number of small-sized adipocytes in epididymal white adipose tissues, suggesting that MTII increased insulin sensitivity through action on the white adipose tissues in DIO rats.
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Affiliation(s)
- Ryoichi Banno
- Department of Endocrinology and Diabetes, Field of Internal Medicine, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8550, Japan
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28
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Heijboer AC, Pijl H, Van den Hoek AM, Havekes LM, Romijn JA, Corssmit EPM. Gut-brain axis: regulation of glucose metabolism. J Neuroendocrinol 2006; 18:883-94. [PMID: 17076764 DOI: 10.1111/j.1365-2826.2006.01492.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Obesity and type II diabetes mellitus have reached epidemic proportions. From this perspective, knowledge about the regulation of satiety and food intake is more important than ever. The gut releases several peptides upon feeding, which affect hypothalamic pathways involved in the regulation of satiety and metabolism. Within the hypothalamus, there are complex interactions between many nuclei of which the arcuate nucleus is considered as one of the most important hypothalamic centres that regulates food intake. The neuropeptides, which are present in the hypothalamus and are involved in regulating food intake, also play a key role in regulating glucose metabolism and energy expenditure. In synchrony with the effects of those neuropeptides, gastrointestinal hormones also affect glucose metabolism and energy expenditure. In this review, the effects of the gastrointestinal hormones ghrelin, cholecystokinin, peptide YY, glucagon-like peptide, oxyntomodulin and gastric inhibitory polypeptide on glucose and energy metabolism are reviewed. These gut hormones affect glucose metabolism at different levels: by altering food intake and body weight, and thereby insulin sensitivity; by affecting gastric delay and gut motility, and thereby meal-related fluctuations in glucose levels; by affecting insulin secretion, and thereby plasma glucose levels, and by affecting tissue specific insulin sensitivity of glucose metabolism. These observations point to the notion of a major role of the gut-brain axis in the integrative physiology of whole body fuel metabolism.
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Affiliation(s)
- A C Heijboer
- Department of Endocrinology and Metabolic Diseases, Leiden University Medical Center, Leiden, The Netherlands
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29
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Adan RAH, Tiesjema B, Hillebrand JJG, la Fleur SE, Kas MJH, de Krom M. The MC4 receptor and control of appetite. Br J Pharmacol 2006; 149:815-27. [PMID: 17043670 PMCID: PMC2014686 DOI: 10.1038/sj.bjp.0706929] [Citation(s) in RCA: 178] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Mutations in the human melanocortin (MC)4 receptor have been associated with obesity, which underscores the relevance of this receptor as a drug target to treat obesity. Infusion of MC4R agonists decreases food intake, whereas inhibition of MC receptor activity by infusion of an MC receptor antagonist or with the inverse agonist AgRP results in increased food intake. This review addresses the role of the MC system in different aspects of feeding behaviour. MC4R activity affects meal size and meal choice, but not meal frequency, and the type of diet affects the efficacy of MC4R agonists to reduce food intake. The central sites involved in the different aspects of feeding behaviour that are affected by MC4R signalling are being unravelled. The paraventricular nucleus plays an important role in food intake per se, whereas MC signalling in the lateral hypothalamus is associated with the response to a high fat diet. MC4R signalling in the brainstem has been shown to affect meal size. Further genetic, behavioural and brain-region specific studies need to clarify how the MC4R agonists affect feeding behaviour in order to determine which obese individuals would benefit most from treatment with these drugs. Application of MCR agonists in humans has already revealed side effects, such as penile erections, which may complicate introduction of these drugs in the treatment of obesity.
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MESH Headings
- Agouti-Related Protein
- Animals
- Anti-Obesity Agents/pharmacology
- Appetite Depressants/pharmacology
- Appetite Regulation/drug effects
- Brain/metabolism
- Diet
- Energy Intake
- Feeding Behavior
- Food Preferences
- Humans
- Intercellular Signaling Peptides and Proteins/genetics
- Intercellular Signaling Peptides and Proteins/metabolism
- Ligands
- Melanocortins/metabolism
- Mice
- Mice, Transgenic
- Mutation
- Nutritional Physiological Phenomena
- Obesity/genetics
- Obesity/metabolism
- Obesity/physiopathology
- Pro-Opiomelanocortin/genetics
- Pro-Opiomelanocortin/metabolism
- Receptor, Melanocortin, Type 3/genetics
- Receptor, Melanocortin, Type 3/metabolism
- Receptor, Melanocortin, Type 4/drug effects
- Receptor, Melanocortin, Type 4/genetics
- Receptor, Melanocortin, Type 4/metabolism
- Signal Transduction/drug effects
- Time Factors
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Affiliation(s)
- R A H Adan
- Rudolf Magnus Institute of Neuroscience, Department of Pharmacology and Anatomy, University Medical Centre Utrecht, Utrecht, The Netherlands.
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30
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Phan LK, Chung WK, Leibel RL. The mahoganoid mutation (Mgrn1md) improves insulin sensitivity in mice with mutations in the melanocortin signaling pathway independently of effects on adiposity. Am J Physiol Endocrinol Metab 2006; 291:E611-20. [PMID: 16638826 DOI: 10.1152/ajpendo.00034.2006] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mahoganoid (Mgrn1(md)) is a mutation of the mahogunin (Mgrn1) gene. The hypomorphic allele suppresses the yellow pigmentation and obesity of the A(y) mouse that ubiquitously overexpresses agouti signaling protein (ASP). To assess the physiological effects of MGRN1 on energy and glucose homeostasis, we generated animals doubly mutant for Mgrn1(md) and A(y), Lep(ob), or a null allele of Mc4r, and diet-induced obesity (DIO) mice segregating for Mgrn1(md). Mgrn1(md) suppressed the obesity, hyperglycemia, and hyperinsulinemia of A(y) mice. Mgrn1(md) suppressed A(y)-induced obesity by reducing food intake, and reduced adiposity in Lep(ob)/Lep(ob) females, but did not alter the body weight or body composition of mice fed a high-fat diet. There was no effect of Mgrn1(md) on weight gain, body composition, energy intake, or energy expenditure in Mc4r-null animals. Mgrn1(md) reduced circulating insulin concentrations in DIO, A(y), and Mc4r-null but not Lep(ob)/Lep(ob) mice. The effect of Mgrn1(md) on circulating insulin concentrations was not due primarily to reductions in fat mass, since the plasma insulin concentrations of Mgrn1(md) mice segregating for either A(y) or Mc4r-null alleles, adjusted for fat mass and plasma glucose, were reduced compared with A(y) and Mc4r mice, respectively. The effect of Mgrn1(md) on insulin sensitivity of Mc4r-null mice suggests that Mgrn1(md) may be increasing insulin sensitivity via the hypothalamic melanocortin-3 receptor pathway.
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MESH Headings
- Adiposity/genetics
- Adiposity/physiology
- Agouti Signaling Protein
- Animals
- Blood Glucose/metabolism
- Body Weight/physiology
- Eating/physiology
- Female
- Genotype
- Insulin/blood
- Insulin Resistance/physiology
- Intercellular Signaling Peptides and Proteins/genetics
- Leptin/blood
- Leptin/genetics
- Male
- Mice
- Mice, Inbred C3H
- Mice, Inbred C57BL
- Mice, Inbred Strains
- Mice, Knockout
- Mice, Mutant Strains
- Mice, Obese
- Mutation/genetics
- Obesity/etiology
- Obesity/genetics
- Obesity/physiopathology
- Receptor, Melanocortin, Type 4/genetics
- Receptor, Melanocortin, Type 4/physiology
- Signal Transduction/genetics
- Signal Transduction/physiology
- Ubiquitin-Protein Ligases/genetics
- Ubiquitin-Protein Ligases/physiology
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Affiliation(s)
- Loan K Phan
- Department of Pediatrics, Columbia University, New York, NY, USA
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31
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Abstract
Obesity is a major public health concern and environmental factors are involved in its development. The hypothalamus is a primary site for the integration of signals for the regulation of energy homeostasis. Dysregulation of these pathways can lead to weight loss or gain. Some drugs in development can have favourable effects on body weight, acting on some of these pathways and leading to responses resulting in weight loss. Strategies for the management of weight reduction include exercise, diet, behavioural therapy, drug therapy and surgery. Investigational antiobesity medications can modulate energy homeostasis by stimulating catabolic or inhibiting anabolic pathways. Investigational drugs stimulating catabolic pathways consist of leptin, agonists of melanocortin receptor-4, 5-HT and dopamine; bupropion, growth hormone fragments, cholecystokinin subtype 1 receptor agonist, peptide YY3-36, oxyntomodulin, ciliary neurotrophic factor analogue, beta3-adrenergic receptor agonists, adiponectin derivatives and glucagon-like peptide-1. On the other hand, investigational drugs inhibiting anabolic pathways consist of the ghrelin receptor, neuropeptide Y receptor and melanin-concentrating hormone-1 antagonists; somatostatin analogues, peroxisome proliferator-activated receptor-gamma and -beta/delta antagonists, gastric emptying retardation agents, pancreatic lipase inhibitors, topiramate and cannabinoid-1 receptor antagonists. These differing approaches are reviewed and commented on in this article.
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MESH Headings
- Animals
- Anti-Obesity Agents/pharmacology
- Anti-Obesity Agents/therapeutic use
- Body Weight
- Drugs, Investigational/pharmacology
- Drugs, Investigational/therapeutic use
- Energy Metabolism
- Humans
- Hypothalamus/drug effects
- Hypothalamus/metabolism
- Leptin/genetics
- Leptin/pharmacology
- Leptin/therapeutic use
- Obesity/drug therapy
- Obesity/metabolism
- Peroxisome Proliferator-Activated Receptors/drug effects
- Peroxisome Proliferator-Activated Receptors/metabolism
- Randomized Controlled Trials as Topic
- Receptor, Melanocortin, Type 4/agonists
- Receptor, Melanocortin, Type 4/metabolism
- Receptor, Serotonin, 5-HT1B/metabolism
- Receptor, Serotonin, 5-HT2C/metabolism
- Receptors, G-Protein-Coupled/antagonists & inhibitors
- Receptors, G-Protein-Coupled/metabolism
- Receptors, Ghrelin
- Receptors, Neuropeptide Y/antagonists & inhibitors
- Receptors, Neuropeptide Y/metabolism
- Recombinant Proteins/pharmacology
- Recombinant Proteins/therapeutic use
- Serotonin 5-HT1 Receptor Agonists
- Serotonin 5-HT2 Receptor Agonists
- Serotonin Receptor Agonists/pharmacology
- Serotonin Receptor Agonists/therapeutic use
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Affiliation(s)
- Marcio C Mancini
- Sao Paulo University, Obesity & Metabolic Syndrome Group of the Endocrinology & Metabology Service, Faculty of Medicine, Hospital das Clínicas, Sao Paulo, Brazil.
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32
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Tallam LS, da Silva AA, Hall JE. Melanocortin-4 receptor mediates chronic cardiovascular and metabolic actions of leptin. Hypertension 2006; 48:58-64. [PMID: 16754792 DOI: 10.1161/01.hyp.0000227966.36744.d9] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
This study tested whether the melanocortin 4-receptor (MC4R) is essential for the chronic cardiovascular and metabolic actions of leptin. Twenty- to 22-week-old male wild-type (WT) C57BL/6J and obese MC4R (-/-) mice (N=5 to 6 per group) were implanted with radiotelemetric transmitters and catheters for measuring mean arterial pressure (MAP) and heart rate 24 hours per day and intravenous infusions. After a 3-day stable control period, leptin was infused (2 microg/kg per minute IV) for 7 days in WT, obese ad libitum-fed MC4R (-/-), and nonobese pair-fed MC4R (-/-) mice. WT mice receiving vehicle for 7 days served as controls. MC4 (-/-) mice were 30% heavier and had 4- and 11-fold increases in plasma insulin and leptin levels, respectively, compared with WT mice. Despite obesity, MAP and heart rate tended to be lower in MC4R (-/-) mice compared with WT mice. Chronic leptin infusion in the different groups increased plasma leptin levels to 45 to 65 ng/mL. Seven-day leptin infusion in WT mice increased MAP by 12+/-3 mm Hg despite a 35% reduction in food intake and an 8% reduction in body weight. Leptin did not alter plasma glucose but reduced plasma insulin in WT mice (5.9+/-1.0 versus 3.0+/-0.5 microU/mL). These cardiovascular and metabolic actions of leptin were abolished in obese and nonobese MC4R (-/-) mice. These data suggest that MC4R deficiency, and not obesity-induced leptin resistance, abolished the cardiovascular and metabolic actions of leptin in obese MC4R (-/-) mice. Thus, a functional MC4R is essential for the chronic cardiovascular and metabolic actions of leptin.
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Affiliation(s)
- Lakshmi S Tallam
- Department of Physiology, School of Medicine, University of Mississippi Medical Center, Jackson, Miss 39216, USA
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Heijboer AC, van den Hoek AM, Parlevliet ET, Havekes LM, Romijn JA, Pijl H, Corssmit EPM. Ghrelin differentially affects hepatic and peripheral insulin sensitivity in mice. Diabetologia 2006; 49:732-8. [PMID: 16485139 DOI: 10.1007/s00125-006-0138-2] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/03/2005] [Accepted: 11/19/2005] [Indexed: 10/25/2022]
Abstract
AIMS/HYPOTHESIS This study was conducted to evaluate the effects of ghrelin on insulin's capacity to suppress endogenous glucose production and promote glucose disposal in mice. To establish whether the growth hormone secretagogue (GHS) receptor can mediate the putative effect of ghrelin on the action of insulin, we also determined the metabolic effects of growth hormone releasing peptide 6 (GHRP-6), a specific GHS receptor agonist. In addition, we explored the biological significance of des-ghrelin (unacylated ghrelin) in this experimental context. MATERIALS AND METHODS Vehicle (n=8), ghrelin (n=9), GHRP-6 (n=9), des-ghrelin (n=8) or a combination of des-ghrelin and ghrelin (n=7) were infused i.v. for 3 h. Simultaneously, endogenous glucose production and glucose disposal were measured by (14)C-glucose dilution during a hyperinsulinaemic-euglycaemic clamp. Tissue-specific glucose uptake in muscle and adipose tissue was measured using (3)H-2-deoxyglucose. RESULTS During hyperinsulinaemia, glucose disposal was 31% higher in mice treated with ghrelin than in those treated with vehicle (77+/-16 and 59+/-8 micromol kg(-1) h(-1), respectively, p<0.05). This was in accordance with enhanced 2-deoxyglucose uptake in muscle in ghrelin-treated animals. In contrast, endogenous glucose production was less effectively suppressed by insulin during ghrelin infusion (46+/-22 vs 71+/-11% in controls, p<0.05). GHRP-6 did not affect insulin action. Des-ghrelin hampered insulin's capacity to inhibit endogenous glucose production, whereas it did not affect glucose disposal. The restraining effects of des-ghrelin and ghrelin on hepatic insulin action were abolished by simultaneous administration of both peptides. CONCLUSIONS/INTERPRETATION Ghrelin hampers insulin's capacity to suppress endogenous glucose production, whereas it reinforces the action of insulin on glucose disposal, independently of food intake and body weight. These metabolic effects are unlikely to be mediated by the GHS receptor. Furthermore, simultaneous administration of des-ghrelin abolishes the inhibitory effect of ghrelin on hepatic insulin action.
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Affiliation(s)
- A C Heijboer
- Department of Endocrinology and Metabolic Diseases, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands.
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