Dissertation der Graduate School of Systemic Neurosciences der Ludwig-Maximillians-Universität München Hedonic interruption of the physiological controls of eating: sites and mechanisms ESTE LEIDMAA PhD Thesis 5th of Febuary 2016 Thesis Advisory Committee Professor Osborne Almeida (Supervisor) Professor Christophe Magnan (2nd reviewer) Professor Heidrun Potschka Dr. Susanne E La Fleur (External reviewer) Prof. Harald Luksch (Reviewer from GSN) Date of the thesis defence: 22.06.2016 Pühendusega minu perele Table of Contents Table of Contents ........................................................................................................................... List of Abbreviations ...................................................................................................................... i Abstract ............................................................................................................................................ 5 Chapter 1. General Introduction ...................................................................................................... 7 1.1. Feeding – an essential behaviour .................................................................................... 8 1.1.1. Meeting the energy demands of brain and body ....................................................... 8 1.1.2. Overeating and obesity ............................................................................................. 10 1.1.3. Pathological consequences of obesity ...................................................................... 13 1.2. Endocrine regulation of food intake ............................................................................. 15 1.2.1. Hunger signals (ghrelin, distention, glucocorticoids) ............................................... 15 1.2.2. Energy and nutrient signals and sensing .................................................................. 17 1.2.3. Endocrine signals of satiety to the brain .................................................................. 21 1.3. From neural circuits and behavioural mechanisms to metabolic homeostasis ............ 29 1.3.1. Central reception and integration of peripheral signals........................................... 30 1.3.2. Sensory and behavioural circuits and mechanisms regulating food ingestion ........ 36 1.3.3 The apparent conflict between hedonic and homeostatic mechansims ................. 45 1.4. Aims of this thesis ......................................................................................................... 50 Chapter 2. Food Choice under Different Physiological States ........................................................ 51 Abstract ...................................................................................................................................... 52 2.1 Introduction ....................................................................................................................... 53 2.2 Materials and Methods ..................................................................................................... 53 2.3 Results ............................................................................................................................... 58 2.4. Discussion ...................................................................................................................... 66 Chapter 3. Mechanisms Responsible for Hedonic Overriding of Leptin Signals ............................ 71 Abstract ...................................................................................................................................... 72 3.1. Introduction .................................................................................................................. 73 3.2. Materials and Methods ................................................................................................. 74 3.3. Results ........................................................................................................................... 80 3.3.1. Identification of brain areas that may mediate hedonic eating ............................... 80 3.3.2. Leptin does not suppress palatable food (PF) intake ............................................... 84 3.4. Discussion ...................................................................................................................... 90 3.5. Supplementary observations ........................................................................................ 94 Chapter 4. Potential of Galanin to Restore Anorexigenic Effects of Leptin During Exposure to a Hedonic Food ............................................................................................................................... 101 Abstract .................................................................................................................................... 102 4.1 Introduction .................................................................................................................... 103 4.2 Materials and Methods ................................................................................................... 104 4.3 Results ............................................................................................................................. 106 4.4 Discussion ....................................................................................................................... 109 Chapter 5. General Discussion ..................................................................................................... 113 Acknowlegements .................................................................................................................... 127 Curriculum Vitae ...................................................................................................................... 129 Publications .............................................................................................................................. 133 Affidavit .................................................................................................................................... 135 List of author contributions ..................................................................................................... 137 References ................................................................................................................................... 139 LIST OF ABBREVIATIONS 2-way ANOVA Two factor analysis of variance 2-AG 2-arachidonoyl-sn-glycerol 3V Third (III) ventricle 5-HT 5-hydroxy-tryptamine, serotonin 5-HT2A 5-hydroxy-tryptamine receptor 2A α-MSH α -melanocyte-stimulating hormone Acetyl-CoA Acetyl coenzyme A ACTH Adrenal corticotropin releasing hormone AGEs Advanced glycosylated end products AgRP Agouti-related peptide AP Area postarema ARC Arcuate nucleus ATP Adenosine triphosphate BAT Brown adipose tissue BBB Blood-brain barrier BMI Body mass index BNST Bed nucleus of the stria terminalis BW Body weight CART Cocaine- and amphetamine-regulated transcript CB1 Cannabinoid receptor 1 CeA Central amygdala CCK Cholecystokinin CNVII Cranial nerve VII CNS Central nervous system CRH Corticotropin releasing hormone DA Dopamine DAB Diaminobenzidine DMH Dorsomedial hypothalamus DMNX Dorsal motor nucleus of the vagus DREADD Designer receptor exclusively activated by designer drugs ER Endoplasmic reticulum ERK1/2 Extracellular signal-regulated kinase-1 and -2 Exp 1 Experiment 1 i FAs Fatty acids FI Food intake FITC Fluorescein isothiocyanate FEOs Food-entrainable oscillators fMRI Functional magnetic resonance imaging FTO Fat mass and obesity-associated gene GABA Gamma-aminobutyric acid Gal Galanin Gal1R Galanin receptor 1 GCTA Genome-wide Complex Trait Analysis GHS-R Growth hormone secretagogue receptor GIP Glucose-dependent insulinotropic polypeptide GLP-1 Glucagon-like peptide 1 GLUT4 glucose transporter 4 GPCR G-protein coupled receptor GWAS Genome-wide association studies HDL High density lipoprotein HF High-fat HFD High-fat diet HPA axis Hypothalamic pituitary adrenal axis ICV Intra-cerebroventricular IHC Immunohistochemistry i.p. Intraperitoneal ISHH In situ hybridization histochemistry IRS Insulin receptor substrate proteins JAK2 Janus kinase-2 KO Knock-out LC Locus coeruleus LDL Low density lipoprotein LF Low-fat LepRb Long isoform of leptin receptor LH Lateral hypothalamus M Mean (average value) MC4R Melanocortin receptor 4 MCH Melanin-concentrating hormone ii MOR µ-opioid receptors mPFC Medial prefrontal cortex mRNA Messenger RNA MUFAs Monounsaturated fatty acids MZ Monozygotic NAc Nucleus accumbens NPY Neuropeptide Y NTS Nucleus of the solitary tract (Nucleus tractus solitarius) OECD Organization for Economic Cooperation & Development OEA Oleoylethanolamide OFC Orbitofrontal cortex OX Orexin OXM Oxyntomodulin OXY Oxytocin PBN Parabranchial nucleus PF Palatable food PI3k Phosphatidylinositol-3 kinase POMC Proopiomelanocortin PPARα Peroxisome proliferation activating receptor alpha PUFAs Polyunsaturated fatty acids PVN Paraventricular nucleus PYY Peptide tyrosine-tyrosine WHO World Health Organisation RNA Ribonucleic acid SC Standard chow SCN Suprachiasmatic nucleus SD Standard deviation of mean SEM Standard error of the mean SNPs Single nucleotide polymorphisms SOCS-3 Suppressor of cytokine signalling 3 STAT3 Signal transducer and activator of transcription 3 T2DM Type 2 diabetes mellitus TRH Thyrotropin releasing hormone TNFα Tumor necrosis factor alpha TZDs Thiazolidinediones iii VMH Ventromedial hypothalamus VLDL Very low density lipoprotein