The prevailing paradigm is that cardiac ANG II is synthesized in the extracellular space from components of the circulating and/or local renin-angiotensin system. The recent discovery of intracrine effects of ANG II led us to determine whether ANG II is synthesized intracellularly in neonatal rat ventricular myocytes (NRVM). NRVM, incubated in serum-free medium, were exposed to isoproterenol or high glucose in the absence or presence of candesartan, which was used to prevent angiotensin type 1 (AT1) receptor-mediated internalization of ANG II. ANG II was measured in cell lysates and the culture medium, which represented intra- and extracellularly synthesized ANG II, respectively. Isoproterenol increased ANG II concentration in cell lysates and medium of NRVM in the absence or presence of candesartan. High glucose markedly increased ANG II synthesis only in cell lysates in the absence and presence of candesartan. Western analysis showed increased intracellular levels of angiotensinogen, renin, and chymase in high-glucose-exposed cells. Confocal immunofluorocytometry confirmed the presence of ANG II in the cytoplasm and nucleus of high-glucose-exposed NRVM and along the actin filaments in isoproterenol-exposed cells. ANG II synthesis was dependent on renin and chymase in high-glucose-exposed cells and on renin and angiotensin-converting enzyme in isoproterenol-exposed cells. In summary, the site of ANG II synthesis, intracellular localization, and the synthetic pathway in NRVM are stimulus dependent. Significantly, NRVM synthesized and retained ANG II intracellularly, which redistributed to the nucleus under high-glucose conditions, suggesting a role for an intracrine mechanism in diabetic conditions.

No description available.

Chan Wai-Pong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves 114-135). / Abstracts in English and Chinese. / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- General review of pancreas --- p.1 / Chapter 1.2 --- The renin-angiotensin system (RAS) --- p.4 / Chapter 1.3 --- Tissue RAS --- p.12 / Chapter 1.4 --- Hypoxia and RAS --- p.21 / Chapter 1.5 --- Pancreatitis and RAS --- p.25 / Chapter 1.6 --- Aim of study --- p.27 / Chapter Chapter 2 --- Method / Chapter 2.1 --- Experimental animals and rat models --- p.30 / Chapter 2.2 --- Immunohistochemistry --- p.33 / Chapter 2.3 --- Semi-quantitative reverse transcriptase-polymase chain reaction (RT-PCR) --- p.37 / Chapter 2.4 --- Western blot analysis --- p.41 / Chapter 2.5 --- "Standard curve, quantitative competitive RT-PCR (SC-QC-RT-PCR)" --- p.45 / Chapter 2.6 --- Data analysis --- p.48 / Chapter Chapter 3 --- Result / Chapter 3.1 --- Existence of a local RAS in the rat pancreas --- p.49 / Chapter 3.2 --- Effect of chronic hypoxia on RAS expression in neonatal rat --- p.59 / Chapter 3.3 --- Effect of chronic hypoxia on RAS expression in mature rat --- p.72 / Chapter 3.4 --- Effect of experimental pancreatitis on RAS expression --- p.86 / Chapter Chapter 4 --- Discussion / Chapter 4.1 --- Existence of a local RAS in the rat pancreas --- p.97 / Chapter 4.2 --- Regulation of pancreatic RAS by chronic hypoxia --- p.101 / Chapter 4.3 --- Regulation of pancreatic RAS by pancreatitis --- p.106 / Chapter 4.4 --- Conclusion --- p.111 / Chapter 4.5 --- Further work --- p.112 / Chapter Chapter 5 --- References --- p.114

Lau Tung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 142-157). / Abstracts in English and Chinese. / Abstract --- p.i / 摘要 --- p.iii / Acknowledgements --- p.v / Table of Contents --- p.vi / List of Abreviations --- p.x / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Pancreas and its functions --- p.1 / Chapter 1.1.1 --- Structure of pancreas --- p.1 / Chapter 1.1.2 --- Exocrine function --- p.4 / Chapter 1.1.3 --- Endocrine function --- p.7 / Chapter 1.1.3.1 --- Pancreatic islet and islet cells --- p.7 / Chapter 1.1.3.2 --- Regulation of insulin secretion --- p.10 / Chapter 1.1.3.3 --- Mechanism for glucose-stimulated insulin release --- p.14 / Chapter 1.1.3.4 --- Bi-phase response of insulin secretion --- p.16 / Chapter 1.2 --- Pancreatic Renin-Angiotensin System --- p.19 / Chapter 1.2.1 --- Circulating RAS and local RAS --- p.19 / Chapter 1.2.2 --- RAS inhibitors --- p.25 / Chapter 1.2.2.1 --- Angiotensin converting enzyme inhibitor --- p.25 / Chapter 1.2.2.2 --- Non-specific Ang II receptor blocker --- p.28 / Chapter 1.2.2.3 --- Specific AT1 receptor antagonist --- p.29 / Chapter 1.2.2.4 --- Specific AT2 receptor antagonist --- p.30 / Chapter 1.2.3 --- RAS and Pancreas --- p.30 / Chapter 1.2.3.1 --- Expression and localization of pancreatic RAS --- p.30 / Chapter 1.2.3.2 --- Regulation of pancreatic RAS and its clinical relevance --- p.32 / Chapter 1.3 --- Islet Transplantation and RAS --- p.34 / Chapter 1.3.1 --- Whole pancreas and islet transplantation --- p.34 / Chapter 1.3.2 --- Problems encountered in islet transplantation --- p.36 / Chapter 1.3.3 --- Potential role of RAS in islet transplantation --- p.38 / Chapter 1.4 --- Diabetes Mellitus and RAS --- p.40 / Chapter 1.4.1 --- Diabetes Mellitus --- p.40 / Chapter 1.4.2 --- Type 1 diabetes and its animal model --- p.42 / Chapter 1.4.3 --- Type 2 diabetes and its animal model --- p.44 / Chapter 1.4.4 --- RAS blockade in diabetes patients --- p.46 / Chapter 1.4.5 --- Potential role of RAS in Diabetes Mellitus --- p.47 / Chapter 1.5 --- Aims of Study --- p.49 / Chapter Chapter 2 --- Materials and Methods / Chapter 2.1 --- Experimental animals and mouse models --- p.50 / Chapter 2.1.1 --- Experimental animals for islet isolation and transplantation --- p.50 / Chapter 2.1.2 --- Mouse model for type 2 diabetes --- p.51 / Chapter 2.2 --- Islet isolation and transplantation --- p.52 / Chapter 2.2.1 --- Enzymatic islet isolation --- p.52 / Chapter 2.2.2 --- Islet transplantation --- p.53 / Chapter 2.3 --- Biological assay on islet functions --- p.53 / Chapter 2.3.1 --- Measurement of islet insulin release --- p.53 / Chapter 2.3.2 --- Measurement of islet glucose oxidation rate --- p.56 / Chapter 2.3.3 --- Measurement of islet (pro)insulin biosynthesis --- p.59 / Chapter 2.3.4 --- Measurement of islet total protein synthesis --- p.60 / Chapter 2.4 --- Chronic losartan treatment --- p.62 / Chapter 2.5 --- Perfusion experiment of transplanted islet graft --- p.62 / Chapter 2.6 --- Insulin content of the islet graft --- p.63 / Chapter 2.7 --- Islet graft (pro)insulin and total protein biosynthesis --- p.64 / Chapter 2.8 --- Real-time RT-PCR Analysis --- p.64 / Chapter 2.8.1 --- Design of primers and probes --- p.67 / Chapter 2.8.2 --- Use of internal control --- p.69 / Chapter 2.8.3 --- RT-PCR reaction --- p.69 / Chapter 2.8.4 --- Calculation using the comparative CT method --- p.70 / Chapter 2.9 --- Western Blot Analysis --- p.71 / Chapter 2.10 --- Immunocytochemistry --- p.72 / Chapter 2.11 --- Statistical data analysis --- p.73 / Chapter Chapter 3 --- Results / Chapter 3 .1 --- Effect of Angiotensin II and Losartan on islet insulin release --- p.74 / Chapter 3.1.1 --- Insulin release from normal islets --- p.74 / Chapter 3.2 --- "Effect of Angiotensin II and Losartan on islet glucose oxidation rate, (pro)insulin and total protein biosynthesis" --- p.77 / Chapter 3.2.1 --- Glucose oxidation rate of isolated normal islets --- p.77 / Chapter 3.2.2 --- (pro)insulin and total protein biosynthesis of isolated normal islets --- p.77 / Chapter 3.3 --- Regulation of RAS components in islet transplantation --- p.81 / Chapter 3.3.1 --- Expression of RAS components in endogenous islets and transplanted islets --- p.81 / Chapter 3.3.2 --- Localization of AT1-receptor in endogenous islets --- p.87 / Chapter 3.3.3 --- Expression of AT1-receptor protein in endogenous and transplanted islets --- p.89 / Chapter 3.3.4 --- Relative abundance of RAS components in kidney and liver --- p.91 / Chapter 3.3.5 --- Insulin release from perfused transplanted islet graft --- p.93 / Chapter 3.3.5 --- (pro)insulin and total protein biosynthesis of transplanted islet graft --- p.96 / Chapter 3.4 --- Effect of Angiotensin II and losartan on diabetic islets --- p.99 / Chapter 3.4.1 --- Expression of RAS components in diabetic pancreas --- p.99 / Chapter 3.4.2 --- Localization of AT1 receptors in diabetic pancreas --- p.105 / Chapter 3.4.3 --- Insulin release from islets of type 2 diabetic mice --- p.107 / Chapter 3.4.4 --- (pro)insulin and total protein biosynthesis of islets from type 2 diabetic mice --- p.112 / Chapter Chapter 4 --- Discussion / Chapter 4.1 --- Effect of angiotensin II and losartan on islet insulin release --- p.116 / Chapter 4.2 --- Existence of local RAS in pancreatic islets --- p.119 / Chapter 4.3 --- Regulation of islet RAS components in transplanted islets --- p.122 / Chapter 4.4 --- Clinical relevance of islet RAS in transplantation --- p.125 / Chapter 4.5 --- Regulation of islet RAS by type 2 diabetes --- p.126 / Chapter 4.6 --- Clinical relevance of islet RAS in type 2 diabetes --- p.134 / Chapter 4.7 --- Conclusion --- p.140 / Chapter 4.8 --- Further studies --- p.141 / Chapter Chapter 5 --- Bibliography --- p.142

Thesis (M.Sc.)--University of Alberta, 2009. / A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science, Department of Physiology. Title from pdf file main screen (viewed on October 11, 2009). Includes bibliographical references.

published_or_final_version / Physiology / Doctoral / Doctor of Philosophy

Siu-Yin Sylvia Lam. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 123-140). / Abstracts in English and Chinese. / Abstract --- p.i / 摘要 --- p.iv / 英中譯名對照 --- p.vi / Acknowledgements --- p.vii / Table of Contents --- p.viii / Abbreviations --- p.xiii / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Overview of Carotid Body --- p.1 / Chapter 1.1.1 --- Type I Cells --- p.3 / Chapter 1.1.2 --- Type II Cells --- p.4 / Chapter 1.1.3 --- Blood Vessels --- p.5 / Chapter 1.1.4 --- Innervation --- p.5 / Chapter 1.1.5 --- Biochemistry --- p.6 / Chapter 1.1.6 --- Physiology and Function --- p.7 / Chapter 1.2 --- The Renin-Angiotensin System (RAS) --- p.8 / Chapter 1.2.1 --- Circulating RAS --- p.8 / Chapter 1.2.1.1 --- Angiotensinogen --- p.10 / Chapter 1.2.1.2 --- Renin --- p.10 / Chapter 1.2.1.3 --- Angiotensin I --- p.11 / Chapter 1.2.1.4 --- Angiotensin Converting Enzyme --- p.12 / Chapter 1.2.1.5 --- Angiotensin II --- p.12 / Chapter 1.2.1.6 --- Angiotensin II Receptors --- p.13 / Chapter 1.2.1.7 --- Angiotensin IV and Angiotensin IV Receptor --- p.15 / Chapter 1.2.2 --- Tissue RAS --- p.16 / Chapter 1.3 --- Hypoxia and Carotid Body --- p.18 / Chapter 1.4 --- Hypoxia and RAS --- p.21 / Chapter 1.5 --- Hypoxia and RAS in Carotid Body --- p.23 / Chapter 1.6 --- Aims of Study --- p.24 / Chapter 1.6.1 --- Existence of Functional Angiotensin II Receptors --- p.24 / Chapter 1.6.2 --- Regulation and Function of Angiotensin II Receptors by Chronic Hypoxia --- p.24 / Chapter 1.6.3 --- Existence of an Intrinsic Angiotensin-generating System --- p.25 / Chapter 1.6.4 --- Regulation of Local RAS by Chronic Hypoxia --- p.25 / Chapter 1.6.5 --- Studies of AT4 Receptor --- p.26 / Chapter Chapter 2 --- Materials and Methods / Chapter 2.1 --- Experimental Animals and Rat Models --- p.27 / Chapter 2.1.1 --- Rat Model of Chronic Hypoxia --- p.27 / Chapter 2.1.2 --- Isolation of Carotid Body --- p.28 / Chapter 2.2 --- Semi-quantitative Reverse Transcriptase-polymerase Chain Reaction (RT-PCR) --- p.30 / Chapter 2.2.1 --- Total RNA Extraction and Quantification --- p.30 / Chapter 2.2.2 --- Reverse Transcription (RT) --- p.31 / Chapter 2.2.3 --- Polymerase Chain Reaction (PCR) --- p.31 / Chapter 2.2.4 --- Gel Electrophoresis --- p.34 / Chapter 2.2.5 --- Optimization of Semi-quantitative RT-PCR for RAS Gene Analysis --- p.34 / Chapter 2.3 --- Northern Blotting --- p.35 / Chapter 2.3.1 --- Transfer of Denatured RNA to Nitrocellulose Membrane By Capillary Elution --- p.35 / Chapter 2.3.2 --- Hybridization --- p.36 / Chapter 2.4 --- In-situ Hybridization --- p.38 / Chapter 2.4.1 --- Linearization of Angiotensinogen cDNA --- p.38 / Chapter 2.4.2 --- Riboprobe Preparation --- p.38 / Chapter 2.4.3 --- Quantification and Gel Electrophoresis of Riboprobes --- p.39 / Chapter 2.4.4 --- In-situ Hybridization Histochemistry --- p.39 / Chapter 2.5 --- Immunohistochemistry --- p.42 / Chapter 2.5.1 --- Preparation of Cryosection --- p.42 / Chapter 2.5.2 --- Indirect Immunoperoxidase Staining --- p.42 / Chapter 2.5.3 --- Immunofluorescent Double Staining --- p.43 / Chapter 2.6 --- Western Blot Analysis --- p.45 / Chapter 2.6.1 --- Preparation of Angiotensinogen Protein --- p.45 / Chapter 2.6.2 --- Quantification of Protein Concentration --- p.45 / Chapter 2.6.3 --- Sample Preparation --- p.45 / Chapter 2.6.4 --- Sodium Dodecyl-sulphate Polyacrylamide Gel Electrophoresis (SDS-PAGE) --- p.46 / Chapter 2.6.5 --- Electroblotting and Immunodetection of Proteins --- p.46 / Chapter 2.7 --- Spectrofluorimetric Measurement and In-vitro Electrophysiology --- p.48 / Chapter 2.7.1 --- Dissociation of Carotid Body Type I Cells and Spectrofluorimetric Measurement --- p.48 / Chapter 2.7.2 --- In-vitro Electrophysiology --- p.49 / Chapter 2.8 --- Assay of ACE Activity --- p.51 / Chapter 2.8.1 --- Crude Membrane Preparation --- p.51 / Chapter 2.8.2 --- Basic Principle for ACE Activity Measurement --- p.51 / Chapter 2.8.3 --- Measurement of ACE Activity --- p.51 / Chapter 2.8.4 --- Fluorescence Measurement --- p.53 / Chapter 2.9 --- In-vitro Autoradiography and Fluorescence-labeled Binding Assay for Angiotensin IV --- p.54 / Chapter 2.9.1 --- Preparation of Frozen Tissue Sections --- p.54 / Chapter 2.9.2 --- Localization and Density of AT4 Receptor --- p.54 / Chapter 2.10 --- Statistics and Data Analysis --- p.57 / Chapter Chapter 3 --- Results / Chapter 3.1 --- Functional Expression of Angiotensin II Receptors --- p.58 / Chapter 3.1.1 --- [Ca2+]i Response to Angiotensin II --- p.58 / Chapter 3.1.2 --- Antagonistic Blockade of Angiotensin II Receptor Subtypes --- p.58 / Chapter 3.1.3 --- Expression of AT1 Receptors mRNA --- p.61 / Chapter 3.1.4 --- Cellular Localization of AT1 Receptors Protein --- p.61 / Chapter 3.2 --- Effect of Chronic Hypoxia on the Expression and Function of Angiotensin II Receptors --- p.64 / Chapter 3.2.1 --- Effect of Chronic Hypoxia on the Expression of AT1 Receptors --- p.64 / Chapter 3.2.2 --- Effect of Chronic Hypoxia on the Expression of AT2 Receptors --- p.67 / Chapter 3.2.3 --- Cellular Localization of the AT1 Receptor by Chronic Hypoxia --- p.69 / Chapter 3.2.4 --- Increase of Afferent Nerve Activities of the Carotid Body In-vitro by Angiotensin II --- p.71 / Chapter 3.2.5 --- Inhibition of Angiotensin II-mediated Response in Chronically Hypoxic Carotid Body by Losartan --- p.73 / Chapter 3.3 --- Evidence for the Existence of an Intrinsic Angiotensin-generating System --- p.75 / Chapter 3.3.1 --- Expression and Localization of Angiotensinogen mRNA --- p.75 / Chapter 3.3.2 --- Expression and Localization of Angiotensinogen Protein --- p.78 / Chapter 3.3.3 --- Expression of Renin mRNA --- p.81 / Chapter 3.3.4 --- Expression of ACE mRNA --- p.81 / Chapter 3.4 --- Effect of Chronic Hypoxia on the Locally-generated Angiotensin System --- p.85 / Chapter 3.4.1 --- Effect of Chronic Hypoxia on the Expression of Angiotensinogen mRNA --- p.85 / Chapter 3.4.2 --- Effect of Chronic Hypoxia on the Localization of Angiotensinogen mRNA --- p.87 / Chapter 3.4.3 --- Effect of Chronic Hypoxia on the Expression of Angiotensinogen Protein --- p.89 / Chapter 3.4.4 --- Effect of Chronic Hypoxia on the Expression of ACE --- p.91 / Chapter 3.5 --- Time-course Effect of Chronic Hypoxia on ACE Activity --- p.93 / Chapter 3.6 --- Preliminary Studies of AT4 Receptor --- p.98 / Chapter 3.6.1 --- In-vitro Autoradiographic Study of AT4 Receptors --- p.98 / Chapter 3.6.2 --- Localization of AT4 Receptors --- p.100 / Chapter Chapter 4 --- Discussion / Chapter 4.1 --- Functional Expression of Angiotensin II Receptors --- p.102 / Chapter 4.2 --- Upregulation and Function of Angiotensin II Receptors --- p.105 / Chapter 4.3 --- Existence of a Local RAS --- p.108 / Chapter 4.4 --- Regulation of the Local RAS --- p.112 / Chapter 4.5 --- Time-dependent Changes of ACE Activity --- p.155 / Chapter 4.6 --- Presence and Regulation of AT4 Receptor --- p.117 / Chapter 4.7 --- Conclusion --- p.120 / Chapter 4.8 --- Future Works --- p.121 / Chapter Chapter 5 --- References --- p.123

The apelin-apelin receptor (APLNR) system is an important regulator of cardiovascular homeostasis both in health and disease. Principal actions of the apelin-APLNR system are positive inotropism, vasodilatation, diuresis and a potential anti-inflammatory role in vascular tissue. The significance of this system is highlighted in heart failure and pulmonary hypertension. Preclinical models of these diseases report downregulation of apelin- APLNR, whilst knockout strains develop more severe phenotypes, more rapidly. Moreover treatment with exogenous apelin retards or prevents disease progression. In man plasma apelin concentrations are reduced in heart failure and vary with disease severity. Initial increases are reported in mild heart failure suggesting a compensatory role, but are depressed in severe heart failure. Limited data profile myocardial APLNR expression in heart failure and in keeping with plasma apelin concentrations, expression is reduced in severe heart failure. Of interest, the APLNR most closely resembles the angiotensin II type 1 receptor (AT1R), sharing similar tissue expression and sequence homology, but mediates opposing physiological actions. Furthermore, emerging preclinical data support receptor interactions between the APLNR and AT1R that modify their native signalling pathways. It is likely that the apelin-APLNR system serves to antagonise the renin-angiotensin system. Given the established role of angiotensin II, arguably the most important peptide in cardiovascular pathophysiology, any system influencing its actions merits further investigation. Current clinical studies are limited to 20 minutes infusions and understanding its cardiovascular effects requires more prolonged administration. There are concerns of tachyphylaxis and interaction with the renin-angiotensin-aldosterone system (RAAS), possibly reducing efficacy of APLNR agonism in clinical settings. In a series of randomised, blinded crossover clinical trials 60 healthy volunteers and 20 patients with chronic stable heart failure were enrolled to assess the effects of (Pyr1)apelin-13 infusion at rest, during acute and subacute infusion, exercise and upregulation of the renin-angiotensin system. I have identified that APLNR agonism is unaffected by prevailing levels of angiotensin II activity in local vascular beds and systemic haemodynamic infusions. Furthermore, the efficacy of (Pyr1)apelin-13 is retained in healthy volunteers and patients with chronic stable heart failure during acute and subacute infusions. Finally, systemic (Pyr1)apelin-13 does not alter exercise performance in healthy individuals. My findings support a role in targeting the APLNR in chronic heart failure and predict that efficacy will be retained in chronic dosing. Future research directed at other patient groups with ventricular dysfunction is merited, in order to further characterise the utility of this system. These studies are encouraging; however, longer term studies may reveal effects beyond haemodynamic alterations and examine the effects on cardiac fibrosis and endothelial function. A long acting agonist is required to fully evaluate the role of APLNR signalling in cardiovascular disease.

Fluid balance is critical for cells to maintain at homeostasis as disturbances in it can disrupt cellular function and consequently the physiology of an organism. Fluid loss for an organism can be classified as either intra- or extracellular, and it appears that different mechanisms have developed to restore homeostasis after intra- or extracellular dehydration. The renin-angiotensin system (RAS) has been shown to be an important mediator of extracellular dehydration induced fluid intake. Various lines of evidence have demonstrated the importance of the subfornical organ (SFO) to mediate fluid intake, especially due to the RAS, and we have shown that production and action of angiotensin (ANG) at the SFO is necessary for fluid intake due to ANG within the brain. Protein kinase C (PKC), specifically PKC-a;, is shown to be a necessary and sufficienty sufficient effector in the SFO to mediate brain angiotensin-II (ANG-II) polydipsia. It is also demonstrated that production of ANG from the SFO is sufficient to increase fluid intake through the ANG-II type 1 (AT1R) receptor and PKC. While production of ANG from the SFO is sufficient to increase fluid intake it is not sufficient to increase blood pressure, metabolism, or sodium appetite. Thus, production and action of ANG to activate PKC-a; is both necessary and sufficient to increase fluid intake at the SFO, and the fluid, pressor, and metabolic phenotypes of brain ANG through the SFO can be separated.

Leptin acts within the brain to increase resting metabolic rate (RMR) and blood pressure (BP). The renin-angiotensin system (RAS) elicits similar effects in the brain, as reviewed in chapter 1, and it has previously been shown that central angiotensin II type 1 (AT1) receptors are required for leptin-mediated inductions in sympathetic nerve activity to the brown adipose tissue. Thus, we hypothesize that the brain RAS mediates the metabolic effects of leptin. To investigate the interaction between the RAS and leptin, we generated the AT1ALepR-KO mouse which lacks the AT1A receptor in leptin-sensitive cells. In chapter 2, we demonstrated that stimulation of RMR by DOCA-salt and high fat diet requires AT1A receptors in leptin receptor-expressing cells and that these cells expressing both AT1A and the leptin receptor appear to be agouti related-peptide (AgRP) neurons. In chapter 3, we investigated the role of AT1A specifically in AgRP neurons by utilizing AT1AAgRP-KO mice. Similar to AT1ALepR-KO mice, AT1AAgRP-KO mice exhibited deficits in BAT SNA responses to leptin and induction of RMR by alpha melanocyte stimulating hormone. In chapter 4, we utilized a novel transgenic mouse model to demonstrate that microglia do not express the AT1A receptor under chow or high fat diet fed conditions. Taken together, we conclude that a subset of AgRP neurons, which express both the leptin receptor and the AT1A receptor, are critical for the control of sympathetic nerve activity and ultimately RMR.