Appetite and Food Intake: Central Control, Second Edition

325 Pages·2017·15.57 MB·English

by  Harris

Appetite and Food Intake
Central Control, Second Edition
http://taylorandfrancis.com
Appetite and Food Intake
Central Control, Second Edition
Edited by
Ruth B.S. Harris
CRC Press
Taylor & Francis Group
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Library of Congress Cataloging‑in‑Publication Data
Names: Harris, Ruth B. S.
Title: Appetite and food intake : central control / [edited by] Ruth B.S. Harris.
Description: Second edition. | Boca Raton : CRC Press, 2017. | Previous edition:
Appetite and food intake : behavioral and physiological considerations / edited by
Ruth B.S. Harris, Richard D. Mattes (Boca Raton : CRC Press, 2008). | Includes
bibliographical references.
Identifiers: LCCN 2016045823 | ISBN 9781498723169 (hardback : alk. paper)
Subjects: LCSH: Ingestion--Regulation. | Appetite--Physiological aspects. | Appetite
disorders. | Food habits--Psychological aspects.
Classification: LCC QP147 .A66 2017 | DDC 612.3/1--dc23
LC record available at https://lccn.loc.gov/2016045823
Visit the Taylor & Francis Web site at
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Contents
Preface......................................................................................................................vii
Contributors ..............................................................................................................xi
Chapter 1 Appetite Control in C. elegans .............................................................1
Kristen Davis, Mi Cheong Cheong, Ji Su Park, and Young-Jai You
Chapter 2 Central and Peripheral Regulation of Appetite and Food Intake
in Drosophila .....................................................................................17
Audrey Branch and Ping Shen
Chapter 3 The Hamster as a Model for Human Ingestive Behavior ...................39
Ruth B.S. Harris
Chapter 4 Beyond Homeostasis: Understanding the Impact
of Psychosocial Factors on Appetite Using Nonhuman Primate
Models ................................................................................................67
Mark E. Wilson and Vasiliki Michopoulos
Chapter 5 Untangling Appetite Circuits with Optogenetics
and Chemogenetics ............................................................................91
Michael J. Krashes
Chapter 6 The Use of Functional Magnetic Resonance Imaging
in the Study of Appetite and Obesity ...............................................117
Selin Neseliler, Jung-Eun Han, and Alain Dagher
Chapter 7 Development of Hypothalamic Circuits That Control Food
Intake and Energy Balance ..............................................................135
Sebastien G. Bouret
Chapter 8 Maternal and Epigenetic Factors That Influence Food Intake
and Energy Balance in Offspring .....................................................155
Lin Song, Miranda D. Johnson, and Kellie L.K. Tamashiro
v
vi Contents
Chapter 9 Monitoring and Maintenance of Brain Glucose Supply:
Importance of Hindbrain Catecholamine Neurons
in This Multifaceted Task ................................................................177
Sue Ritter
Chapter 10 Hindbrain Astrocyte Glucodetectors and Counterregulation ..........205
Richard C. Rogers, David H. McDougal, and Gerlinda E. Hermann
Chapter 11 Vagal Afferent Signaling and the Integration of Direct
and Indirect Controls of Food Intake ...............................................229
Robert C. Ritter, Carlos A. Campos, Jason Nasse,
and James H. Peters
Chapter 12 Energy Metabolism and Appetite Control: Separate Roles
for Fat-Free Mass and Fat Mass in the Control of Food Intake
in Humans ........................................................................................259
Mark Hopkins and John E. Blundell
Chapter 13 Pharmacotherapy for Weight Loss ...................................................277
Thomas A. Lutz and Lori Asarian
Index ......................................................................................................................297
Preface
Obesity is recognized as a global health issue that is associated with increased risk for
chronic disease and results in increased morbidity and mortality. Excessive weight
gain is a significant health issue for all westernized societies, but the United States
has one of the highest rates of overweight in the world, with more than two-thirds of
the adult population classified as overweight or obese. This means that the number of
individuals maintaining a healthy weight is in a minority. Conceptually, it is easy to
reduce body weight by lowering energy intake and increasing expenditure; in reality,
weight-loss programs that depend upon dietary and behavioral changes have very
low rates of success, especially over the long-term. Successful strategies can only be
developed if the scientific rationale is reliable, which emphasizes the need to gain a
better and more detailed understanding of the complex and integrated mechanisms
that influence appetite, food choice, food consumption, and energy expenditure.
During the past two decades, gastric bypass surgery has emerged as the most effec-
tive treatment for obesity, but this major surgery is associated with multiple risks and
emphasizes the need for less invasive treatments and strategies to reverse weight gain
or to reduce incidence of weight gain in the first place.
The first edition of this book reviewed knowledge on the intake of micronutri-
ents and macronutrients, food choice, and opposing views on whether or not there
are mechanisms that control food intake. An emphasis was placed on perspectives
gained from the use of animal models versus human trials, and a large majority
of the information remains current, making it unnecessary to simply update these
chapters. Therefore, I have taken the opportunity with this second edition to focus
on current and emerging areas of interest in the control of food intake and energy
balance, spanning the advantages of new and continuously developing technologies
in animal and human studies to novel perspectives on which aspect of body composi-
tion is being sensed and controlled.
The first section of the book is devoted to some less common models that are being
used to investigate the control of food intake. Conservancy of neural circuits and neu-
ropeptides across species allows the use of simple systems, such as Caenorhabditis
elegans and Drosophila, to elucidate the role of specific neurotransmitters in differ-
ent aspects of ingestive behavior, taking advantage of relatively simple circuitry and
in-depth knowledge of the genome of the organism. At a different level, hamsters
provide a rodent model for investigating neuropeptides that drive food aquisition,
and the data illustrate a striking similarity between hormones and neurotransmit-
ters that influence foraging and hoarding with those identified as important to con-
summatory behavior, even though these two components of ingestive behavior are
under independent control. In contrast to the work with the simple models such as
C. elegans, group housed nonhuman primates provide a unique opportunity for test-
ing the impact of social environment on food choice and consumption that is directly
relevant to the human situation. Although not easily available to all investigators, it
is clear that we can learn an enormous amount from animal models other than the
commonly used rats and mice.
vii
viii Preface
In the last decade, there have been major advances in technologies that facili-
tate manipulation of specific central control systems. The ability to induce or knock
down expression of neuropeptides in select populations of neurons in adult animals
has helped eliminate the possibility of compensation for prenatal genetic modifica-
tions. Acute activation or inhibition of neurons based on neuroanatomic location and
neuropeptide expression with designer receptors exclusively activated by designer
drug or optogentics has resulted in elegant experiments that confirm the functional
and anatomic integration of different control systems. The limitations associated
with the use of these invasive procedures in humans are partially compensated for
by functional magnetic resonance imaging, which identifies brain areas that are acti-
vated by food cues and how this is influenced by internal energy status, emotional
status, and external environment. These elegant techniques have supported rapid
and unprecedented progress in the identification of the neuronal circuitry that drives
ingestive behavior.
In parallel with the progress made at the molecular and cellular level, there has
been a growing appreciation of the influence of environment on development and
on long-term risk for chronic disease, including diabetes and obesity. Grounded in
earlier human studies that defined the impact of severe food deprivation during ges-
tation on lifelong risk for disease in the offsping, recent animal studies have explored
mechanisms that mediate the effects of the developmental environment, including
diet and maternal and paternal energy status, on the physiology and behavior of both
the immediate offspring and of future generations. Two chapters summarize current
investigations of how energy balance is influenced by epigenetics and by the impact
of prenatal and neonatal environment on the development of hypothalamic circuits
that influence food intake.
Historically, a majority of research investigating the central control of food intake
has focused on the hypothalamus, but now there is a growing appreciation for the
critical role played by the hindbrain, which integrates information from higher
brain areas with that coming from the periphery to determine an appropriate feed-
ing response. Until recently, investigation of the long-term signals that represent the
energy balance status of an organism has been independent of the study of short-
term gastrointestinal and sensory signals that influence meal size and frequency.
The hindbrain plays a major role in integrating these different types of information
and allows changes in body energy stores to influence feeding behavior. Control of
ingestive behavior is essential for homeostasis and one parameter that is critical for
survival is control of blood and brain glucose. Two chapters address the association
between glucostasis and ingestion. One focuses on the identification of brain areas
and neuronal cell types that are glucose sensitive. The second reviews new evidence
that astrocytes play a critical role in responding to changes in central glucose con-
centration, representative of a new and growing appreciation for the functionality of
glia in physiologic control systems.
Traditionally, it has been concluded that food intake is controlled to maintain
body energy stores in the form of fat. A challenge to this perspective is provided
based on evidence from past and present studies that fat-free mass may drive day-
to-day changes in food intake, whereas body fat correlates with intake over a period
of days or weeks. It is proposed that fat-free mass is the primary determinant of
Preface ix
resting metabolic rate, which is the major component of energy expenditure under
normal conditions and most closely predicts energy intake on a daily basis. Thus,
daily energy intake is linked to fat-free mass with the opportunity for modulation by
the amount of energy stored as fat. The final chapter reviews current drugs available
for treating obesity, focusing on those that influence food intake and food choice with
an emphasis on combination therapies. The fairly small number of approved and
effective medications illustrates the difficulty in developing a pharmacological treat-
ment for a highly complex system that not only integrates many different types of
information associated with food-related decisions but also justifies the exploration
of combining drugs with synergystic activity. It also highlights the need for further
investigation of the systems that influence food intake so that less invasive, but effec-
tive treatments can be developed to alleviate the reliance for body weight control
on gastric bypass surgery. This intervention is not covered in this book, primarily
because the restraint of food intake is due to imposition of a physical limitation on
eating, rather than direct manipulation of a control system that has been implicated
in maintenance of energy balance. There is, however, a large and growing literature
on the physiological, psychological, and behavioral benefits and limitations of the
procedure, which is providing unexpected insight into the influence of the gut on
metabolism.
The summary of some of the current trends in research on ingestive behavior in
this edition should be considered a companion to the first edition, in which there
was an emphasis on the knowledge gaps between basic and applied research. It also
should provide a useful, although not exhaustive, reference for students and other
professionals who need an overview of aspects of the control of ingestive behavior
that are outside their area of specialization. Many of the chapters provide a historic
overview of key observations that were made in a specific areas of research, which
gives a valuable perspective and context not only to those chapters but also to the
field in general. In addition, some of the topics addressed by the authors included
in this book should increase awareness of the value of different approaches to com-
mon issues encountered in the study of ingestion. As you go through the chapters
presented here, it is clear that there is a significant degree of cross-reference and of
reliance on similar established observations, emphasizing that no individual area
within the study of appetite and ingestive behavior can stand alone.