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Appettite regulation
Magdalena Warchoł, Msc, PhD
Department of Physiology
Plan of what you will know after class
What is appetite?
Brain control of appetite
Hormones that regulate appetite, and their basic modes of action
Other factors regulating food intake
How is it in obesity?
Why do we eat?
Energy hemeostasis
CARBOHYDRATES
PROTEINS
FATS
• FOOD
INTAKE
metabolism
• ENERGY
BODY FUNCTIONS
STORE
• UNDERNUTRION
/OBESITY
The use of consumed food
73%
HEAT
protein
metabolism,
muscles
activity
27%
for cells
activities of
various organs
and tissues of
the body
Energy balance is the key
What are adipocytes?
Adipose tissue is an anatomical term for loose
connective tissue composed of fat storing cells
(adipocytes)
White adipose tissue
- store fatty acids in the form of triglycerides food reserve
- thermally insulates the organism
- like any tissue - source of first messengers
(hormones and cytokines) that diffuse into the
body
Leptin is produced by adipose
tissue
Adipocytes also produce: inflammatory
cytokines: TNF-α and IL-6
- an excess of adipose tissue - chronic
mild inflammatory state referred to as
the “metabolic syndrome”
- an excess of fully loaded adipocytes the release of free fatty acids - rise to
insulin resistance
contributing to the
late onset diabetes (type II) in obese
people
Obesity and leptin
9.3 calories of excess energy - 1
gram of fat is stored
studies have shown that new
adipocytes can differentiate from
fibroblast-like preadipocytes at
any period of life
An extremely obese person - 4x
adipocytes, each containing 2x
more lipids
How much food do we need?
variability in the amount of energy storage (i.e., fat mass)
an adequate energy supply is necessary for survival
powerful physiological control systems - adequate energy intake
deficits of energy stores activate mechanisms that cause hunger
athletes
6000/7000
kcal/day
Sedentary
individuals
2000kcal/day
Appetite
Appetite – desire for food, felt as hunger
• Regulate adequate energy intake to maintain metabolic
needs
Appetite is different from hunger
• Hunger – physical need to eat
When we lose weight – our body response is to conserve energy
and boost appetite – yo-yo effect
The Hypothalamus Contains Hunger
and Satiety Centers
Control of food intake
• Lateral nuclei of the hypothalamus – hunger
center
• Stimulation of this area – hyperphagia
• Destruction of LHA - inanition
• Ventromedial nuclei/paraventricular nuclei –
satiety center
• Stimulation – aphagia
• Destruction – voracious eating
THIS CENTERS REGULATES FOOD INTAKE AND
ENERGY EXPENDITURE
hunger
FROM: Gross P., Jean-Baptiste F.,
Siba Lemba T.A., Zoror K., Singaling
by ghrelin, insulin and leptin in
hyphothalamus. Obesity Project
2009 – Universite Bordeaux.
Feedback mechanisms for
control of food intake
1. Neural signals from gastrointestinal
tract – sensory information about
stomach filling
2. Chemical signals from nutrients in the
blood – glucose, amino acids, fatty
acids – signify satiety
3. Signals from gastrointestinal hormones
4. Signals from hormones released by
adipose tissue
5. Signals from the cerebral cortex - sight,
smell, taste
The hypothalamic melanocortin
system
• POMC neurons release α- MSH
• α- MSH acts on melanocortin receptors(MCR)
• at least 5 subtypes of MCR exist
• MCR-3 and MCR-4 – important in food intake
•
reduced food intake, increased energy expenditure
•
increased food intake, reduced energy expenditure
• mutations of MCR-4 – most common genetic cause of obesity, 5-6% severe
obesity in children
• excesive activation – may be associated with anorexia
Regulation of the Quantity of Food Intake
short-term – prevents
overaeting at each meal
Gastrointestinal Filling Inhibits
Feeding
Mechanoreceptors and
Chemoreceptors of
gastrointestinal tract
Leptin-Ghrelin „tango”
„oral factors”
long-term – maintains
energy stores in body
Fat stores – leptin from
adipocytes
Glucose metabolism - Insulin
from β-cells
Ghrelin – when the fat stores are
too low
Why do we need both, short- and
long-term regulation?
LONG-TERM
SHORT-TERM
• maintain constant stores of nutrients in
the tissues
• preventing from being too low or too
high
• eating the right amount at each meal
• prevent from eating too much important for metabolic storage systems
Grelin
 mainly released by oxintic cells of stomach
Blood levles rise during fasting
Peak just before eating
 rapidly after meal
Orexigenic hormone
The physiological role – still discussed, some
studies about ghrelin role in the early
development
Tacheoesophageal fistula
 food intake inhibition
 despite the gastrointestinal
tract is not filled at all
 „oral factors” – chewing,
salivation, swallowing, tasting
– measure food intake
 After a certain amount passes
– hypothalamic feeding
centers are inhibited
 Intermediate- and long-term
regulation – energy stores can
modulate food intake at meal
Long-term regulation - summary
When the energy stores of the body
fall below normal, the feeding
centers of the hypothalamus and
other areas of the brain become
highly active, and the person
exhibits increased hunger, as well
as the behavior of searching for
food. Conversely, when the energy
stores (mainly the fat stores) are
already abundant, the person
usually loses the sensation of
hunger and develops a state of
satiety.
Thank you for your attention!