How the brain controls food intake: the emerging role of the brain GLP-1 system in energy balance and autonomic control

Lead Research Organisation: Imperial College London
Department Name: Dept of Surgery and Cancer

Abstract

Obesity, diabetes and co-morbidities, such as hypertension, are a serious health burden for the patient and a strain on public resources. Promising drugs that might be beneficial for the treatment of these conditions are glucagon-like peptide 1 (GLP-1) analogues. GLP-1 is a hormone that is secreted from the gut after a meal. It is also produced in the brain. Its principal role is to improve the digestion of sugars, and to generate the sensation of fullness, or satiety. The aim of our project is to improve our knowledge of the relative importance of the brain and gut GLP-1 signalling in the control of blood sugar and food intake, and to clarify whether GLP-1 analogues, which are already in clinical use, activate the brain GLP-1 system.
Neurons that produce GLP-1 have been found in the brainstem. These cells send a network of nerve fibres to many parts of the brain, including the hypothalamus, a brain region implicated in the regulation of appetite. We hypothesise that it is GLP-1 released from these brainstem cells that mediates the satiety effects, some of the beneficial effects on blood glucose control, and further functions that are less well understood, such as in cardiovascular control, developing of hypertension, nausea and vomiting, and learning and memory. The proposed research will clarify the exact role of GLP-1 neurons in these effects and thus validate their importance as a drug target for treatment of metabolic disease.
We will use a gene therapy approach where new genes are delivered to GLP-1 cells in specific areas of the brain. These genes will produce proteins allowing cell-specific suppression (or alternatively increases) of the activity of GLP-1 cells with unprecendented temporal and spatial resolution. By measuring the effects of inhibiting or increasing activity of specific GLP-1-expressing cells on blood glucose control, food intake and behaviour, we will be able to tease out the exact physiological function played by GLP-1-expressing central neurons.
The primary aim of our project is to improve knowledge on the interaction between peripheral and central GLP-1 receptor activation. From this work we will learn whether interference with brain GLP-1 release is an important target for the treatment of obesity, diabetes and co-morbidities. These data will provide further insight into the clinical benefit of GLP-1-based treatments, possibly not only for patients with diabetes, but more generally in metabolic disease. Furthermore, it will provide information on the cause of undesired side effects such as nausea. Since GLP-1 analogues are already on the market for the treatment of type 2 diabetes in overweight patients, we expect that the knowledge from this project will feed into drug development and formulation, and thus an influence on therapy could be hoped for within 10 years.

Technical Summary

This proposal aims at characterising the exact physiological role of GLP-1 expressing neurons in the control of energy balance and autonomic functions. We will experimentally silence or activate GLP-1-expressing neuronal populations in vivo by using viral gene transfer. Specific targeting will be achieved by combining a transgenic mouse line that expresses Cre-recombinase selectively in cells that express GLP-1 or glucagon, with viral expression vectors that are only active in cells expressing Cre-recombinase (FLEX-switch technique). The adeno-associated virus (AAV)-based vectors are injected stereotaxically into the brain region containing GLP-1-expressing neurons and 2-5 weeks after the infections the animals will be tested for effects of GLP-1 neuron modulation on food intake, blood glucose control, cardiovascular and circadian activities. AAV vectors produced for this purpose will include those that inactivate or ablate GLP-1 cells permanently (Tetanus toxin light chain; Diphteria toxin A subunit), and those that inactivate GLP-1 cells transiently (Allatostatin receptor; DREADD hM4D) or activate GLP-1 neurons transiently (Channelrhodopsin2, DREADD hM3Dq), when the appropriate agonist is applied (allatostatin, clozapine-N-oxide or light, respectively). Generation of these tools will also greatly facilitate physiological in vivo studies of other specific cell populations in the CNS.
Food and water intake will be monitored using metabolic cages, blood glucose control will be evaluated with oral and intraperitoneal glucose tolerances tests, cardiovascular and respiratory activities will be assessed using standard physiological monitoring in anesthetised animals.
Our results will further define the physiological role of the GLP-1 neurons and provide crucial data on the usefulness of a GLP-1 based therapy for metabolic disease. They will also address the question whether overactivation of this system leads to emesis as observed with GLP-1 injection.

Planned Impact

The basic research we propose here is likely to significantly increase understanding of how GLP-1 affects energy balance and cardiovascular control. We expect these results to be of considerable nterest to the pharmaceutical industry. This is particularly likely becauseGLP-1 analogues are already in clinical use for the treatment of overweight diabetics. Indeed, Astra Zeneca agreed to sponsor a symposium on GLP-1 at the recent FEPS meeting in Istanbul that ST organised in collaboration with Frank Reimann from Cambridge University. Any intellectual property arising from this research grant will be exploited through Imperial College Innovations Ltd, the College's technology transfer company.
A benefit to the general population, in terms of improvements in healthcare, might be possible over a time-course of 10 years if our findings influence the availability of GLP-1 therapy for diabetic and for obese patients. Additionally, our research might identify new treatment strategies for metabolic disease, which could hopefully enter clinical practice over a 10-15 year time-course. This again would elicit interest from the pharmaceutical industry. Currently ~10% of the NHS budget (£9billion) is spent on the 2.6 million diabetics in the UK. Diabetes UK predicts this number to rise to 4 million by 2025, mainly due to an increased incidence of obesity, driven by increasingly sedentary lifestyles. In 2009 more than 60% of the adult UK population were overweight. The complications of these diseases include stroke, retinopathy, neuropathy, renal failure, cardiovascular disease and cancer. The increased prevalence of diabetes, obesity and co-morbidities was recently predicted to contribute to a lowered overall life expectancy in the UK (http://www.independent.co.uk/life-style/health-and-wellbeing/health-news/diabetes-may-cause-first-fall-in-life-expectancy-for-200-years-966914.html) for the first time in 200 years. GLP-1 analogues show great potential in the treatment of type 2 diaetics mainly due to their actions as insulin secretagogues and positive trophic effect on beta-cell mass. The anorexic effect of GLP-1 is mediated by central actions and so might be some of the insulin secretagogue effect. Since GLP-1 has various central effects (including induction of nausea and vomiting, in addition to satiety) exogenous application might be counterproductive. Our study of the endogenous source of GLP-1 in brain will educate us about the different pathways involved and thus clarify the role of central GLP-1 in satiety and blood glucose control. In particular, this work will address roadblocks in diabetes research as identified recently by the European Commission's Support Action "DIAMAP: A Road Map for Diabetes in Europe" (http://www.diamap.eu/) including "Determine central nervous master switches that control food intake and energy expenditure", which is identified as lacking "collaboration of researchers in related fields" and "available in vivo methodology and imaging techniques", both of which we are addressing with this proposal.

Publications

10 25 50
publication icon
Anesten F (2016) Preproglucagon neurons in the hindbrain have IL-6 receptor-a and show Ca2+ influx in response to IL-6. in American journal of physiology. Regulatory, integrative and comparative physiology

publication icon
Trapp S (2015) PPG neurons of the lower brain stem and their role in brain GLP-1 receptor activation. in American journal of physiology. Regulatory, integrative and comparative physiology

 
Description BHF studentship
Amount £114,000 (GBP)
Funding ID FS/14/43/30960 
Organisation Loughborough University 
Department British Heart Foundation National Centre for Physical Activity and Health (BHFNC)
Sector Academic/University
Country United Kingdom
Start 10/2014 
End 09/2017
 
Description Neuroendocrine Integration of Satiety and Food Reward
Amount $1,727,512 (USD)
Funding ID DK095757 
Organisation National Institutes of Health (NIH) 
Sector Public
Country United States
Start 05/2019 
End 05/2021
 
Description AMPK in central control of hepatic glucose production 
Organisation University of Toronto
Country Canada 
Sector Academic/University 
PI Contribution Generation and use of adenoviral constructs
Impact Publication in Diabetes 2010 (x2)
Start Year 2008
 
Description Cardiac preconditioning via vagal nerve activity 
Organisation University College London
Department Division of Biosciences
Country United Kingdom 
Sector Academic/University 
PI Contribution in vitro analysis of vagal activity
Collaborator Contribution provided model of hear failure
Impact Publications: Mastitskaya et al. (2012) Cardiovascular Research 95, 487-494. Machhada et al. (2015) Heart Rhythm 12, 2285-2293.
Start Year 2011
 
Description Collaboration on GLP-1 analogue action in mouse 
Organisation Novo Nordisk
Country Denmark 
Sector Public 
PI Contribution Analyse central effects of Novo Nordisk depeloped GLP-1 analogues
Collaborator Contribution provide chemical compounds
Impact not published yet
Start Year 2019
 
Description Collaboration with Linda Rinaman to investigate central GLP-1 cross-species 
Organisation Florida State University
Country United States 
Sector Academic/University 
PI Contribution Experimentation into mouse GLP-1 system to establish absence of GLP-1 receptors on GLP-1 producing neurons
Collaborator Contribution Similar experimentation on rat.
Impact Research paper (PMID: 30019398) Follow up funding from NIH 2R01DK095757
Start Year 2017
 
Description Conditional knockout mice 
Organisation Cochin Institute
Country France 
Sector Academic/University 
PI Contribution Generation of tissue specifi KO mice
Impact Publication in Diabetologia, 2010 (Sun et al)
 
Description Crosstalk between GLP-1 and Interleukin-6 in brain 
Organisation University of Gothenburg
Department Department of Physiology
Country Sweden 
Sector Academic/University 
PI Contribution Functional analysis of the response of GLP-1 producing neurons to interleukin; expertise with transgenic mice allowing identification and characterisation of GLP-1 producing and GLP-1 receptor expressing cells
Collaborator Contribution Expertise with interleukin in the brain
Impact 10.1152/ajpregu.00383.2015
Start Year 2015
 
Description D Bosco (Université de Genève) 
Organisation University of Geneva
Department Faculty of Diabetes
Country Switzerland 
Sector Academic/University 
PI Contribution Experiments for publications
Collaborator Contribution Experiments for publications
Impact Sorcin links pancreatic ß cell lipotoxicity to ER Ca2+ stores - Marmugi A et al - PMID: 26822088 Hypoxia lowers SLC30A8/ZnT8 expression and free cytosolic Zn2+ in pancreatic beta cells. Gerber PA et al PMID: 24865615 Incretin-modulated beta cell energetics in intact islets of Langerhans. Hodson DJ et al - PMID: 24766140 ADCY5 couples glucose to insulin secretion in human islets. Hodson DJ et al PMID: 24740569 Lipotoxicity disrupts incretin-regulated human ß cell connectivity. Hodson DJ et al - PMID: 24018562
Start Year 2013
 
Description Denton 
Organisation University of Bristol
Country United Kingdom 
Sector Academic/University 
PI Contribution Experiments for publications
Collaborator Contribution Experiments for publications
Impact manuscript (in press) Denton RM et al Biochem J 2016
Start Year 2014
 
Description Denton 
Organisation University of Pisa
Country Italy 
Sector Academic/University 
PI Contribution Experiments for publications
Collaborator Contribution Experiments for publications
Impact Sorcin links pancreatic ß cell lipotoxicity to ER Ca2+ stores - Marmugi A et al - PMID: 26822088 Hypoxia lowers SLC30A8/ZnT8 expression and free cytosolic Zn2+ in pancreatic beta cells. Gerber PA et al PMID: 24865615 Incretin-modulated beta cell energetics in intact islets of Langerhans. Hodson DJ et al - PMID: 24766140 ADCY5 couples glucose to insulin secretion in human islets. Hodson DJ et al PMID: 24740569 Lipotoxicity disrupts incretin-regulated human ß cell connectivity. Hodson DJ et al - PMID: 24018562
Start Year 2014
 
Description Functional characterisation of GLP-1 neurons 
Organisation University of Cambridge
Department Cambridge Institute for Medical Research (CIMR)
Country United Kingdom 
Sector Academic/University 
PI Contribution Devised experiments, conducted experiments, wrote publications
Collaborator Contribution Provision of transgenic mice that allows identification of GLP-1 neurons in vitro.
Impact Publications describing critical electrical and molecular properties of GLP-1 neurons (20522593, 21885869)
Start Year 2006
 
Description GLP-1 action in mesolimbic system 
Organisation Florida State University
Country United States 
Sector Academic/University 
PI Contribution -Electrophysiological characterisation of GLP-1 receptor expressing cells in the bed nucleus of the stria terminalis. -circuit mapping of GLP-1 projections to GLP-1R neurons and of GLP-1R cell projections from the bed nucleus of the stria terminalis
Collaborator Contribution Analysis of GLP-1 effects in the bed nucleus of the stria terminalis on food intake
Impact 10.1016/j.neuropharm.2017.12.007 follow-up funding from NIH: 2R01DK095757
Start Year 2016
 
Description GLP-1 in olfactory system 
Organisation Florida State University
Department Department of Biological Science
Country United States 
Sector Academic/University 
PI Contribution Providing morphological and cytochemical analysis of olfactory bulb tissue from transgenic mice
Collaborator Contribution Electrophysiological analysis of mitral cell activity under GLP-1
Impact Publication in Journal of Physiology
Start Year 2013
 
Description Generator of b-cell specfic knock-out mice for PASK 
Organisation AstraZeneca
Country United Kingdom 
Sector Private 
PI Contribution Design of PASK flox'd mice
Impact None as yet
Start Year 2009
 
Description Gerald Gradwohl (IGBMC) 
Organisation Institute of Genetics and Molecular and Cellular Biology (IGBMC)
Country France 
Sector Academic/University 
PI Contribution Experiments for publications
Collaborator Contribution Experiments for publications
Impact Piccard et al - http://www.ncbi.nlm.nih.gov/pubmed/25497096
Start Year 2015
 
Description Immunocytochemical characterisation of GLP-1 neurons 
Organisation Flinders University
Country Australia 
Sector Academic/University 
PI Contribution provision of fixed tissue from transgenic mice; intellectual lead
Collaborator Contribution Expertise in immunocytochemistry
Impact Publication that produces a detailed description of GLP-1 neuron distribution and projections in brain (21329743)
Start Year 2009
 
Description James Shapiro (Alberta) 
Organisation University of Alberta
Country Canada 
Sector Academic/University 
PI Contribution Experiments for publications
Collaborator Contribution Experiments for publications
Impact ADCY5 couples glucose to insulin secretion in human islets. Hodson DJ et al PMID: 24740569 Sorcin links pancreatic ß cell lipotoxicity to ER Ca2+ stores - Marmugi A et al - PMID: 26822088
Start Year 2014
 
Description Lorenzo Piemouti (Milan) 
Organisation University of Milan
Country Italy 
Sector Academic/University 
PI Contribution Experiments for publications
Collaborator Contribution Experiments for publications
Impact ADCY5 couples glucose to insulin secretion in human islets. Hodson DJ et al - PMID: 24740569 Sorcin links pancreatic ß cell lipotoxicity to ER Ca2+ stores. Marmugi A et al - PMID: 26822088
Start Year 2014
 
Description Piero Marchetti (Pisa) 
Organisation University of Pisa
Country Italy 
Sector Academic/University 
PI Contribution experiments for publications
Collaborator Contribution experiments for publications
Impact Sorcin links pancreatic ß cell lipotoxicity to ER Ca2+ stores - Marmugi A et al - PMID: 26822088 Hypoxia lowers SLC30A8/ZnT8 expression and free cytosolic Zn2+ in pancreatic beta cells. Gerber PA et al PMID: 24865615 Incretin-modulated beta cell energetics in intact islets of Langerhans. Hodson DJ et al - PMID: 24766140 ADCY5 couples glucose to insulin secretion in human islets. Hodson DJ et al PMID: 24740569 Lipotoxicity disrupts incretin-regulated human ß cell connectivity. Hodson DJ et al - PMID: 24018562
Start Year 2014
 
Description Role of AMPK in counter regulation 
Organisation Yale University
Country United States 
Sector Academic/University 
PI Contribution Provision of adenoviral constructs
Impact None as yet
Start Year 2008
 
Description Sekler 
Organisation Ben-Gurion University of the Negev
Country Israel 
Sector Academic/University 
PI Contribution Experiments for research paper
Collaborator Contribution Experiments for research paper
Impact Publication Pancreatic beta-cell Na+ channels control global Ca2+ signaling and oxidative metabolism by inducing Na+ and Ca2+ responses that are propagated into mitochondria. DOI - 10.1096/fj.13-248161
Start Year 2013
 
Description Yuval Dor (Israel) 
Organisation Open University of Israel
Country Israel 
Sector Academic/University 
PI Contribution Experiments for publications
Collaborator Contribution Experiments for publications
Impact LKB1 and AMPK differentially regulate pancreatic ß-cell identity - Kone M1 et al - FASEB J. 2014 Nov;28(11):4972-85. doi: 10.1096/fj.14-257667. Epub 2014 Jul 28. Loss of Liver Kinase B1 (LKB1) in Beta Cells Enhances Glucose-stimulated Insulin Secretion Despite Profound Mitochondrial Defects. Swisa A1et al - J Biol Chem. 2015 Aug 21;290(34):20934-46. doi: 10.1074/jbc.M115.639237. Epub 2015 Jul 2.
Start Year 2014
 
Description modulating brainstem neuron activity with viral gene transfer 
Organisation University College London
Department Department of Neuroscience, Physiology and Pharmacology
Country United Kingdom 
Sector Academic/University 
PI Contribution in vitro analysis
Collaborator Contribution in vivo analysis
Impact publications: Marina et al., 2010 Mastitskaya et al., 2012
Start Year 2010