Appetite Regulation Flashcards
what are examples of energy intake?
eating
what are examples of energy expenditure?
physical activity
metabolism
thermogenesis (internal heat production)
what happens when intake > expenditure?
TG storage
weight gain
what happens when intake < expenditure?
TG breakdown
weight loss
weight refers to the amount of _____ and NOT ____
amount of fat tissue - adiposity
NOT the total body weight
why is weight gain strongly “defended” biologically?
our bodies have evolved to conserve energy/weight but once we gain weight, we stay fat
what are 2 examples of energy imbalance leading to serious diseases?
obesity
type 2 diabetes mellitus (T2DM)
energy balance is regulated by multiple pathways, both _____ and _____
afferent and efferent
what are some examples of things that convey information about meal status (fed/hungry states)?
nutrient sensing (glucose, lipids)
CNS/PNS
hormones
what is the job of the hypothalamus?
point of convergence for appetite pathways and major locus for their integration
major peripheral systems in appetite regulation include ______. give some examples
organs/systems involved in absorption and storage of nutrients
olfactory, gustatory, GI, pancreas, liver, muscle, adipose tissue, bone
peripheral signals relay to ___ and ____ to influence behavioral and physiological responses
higher cortical centers and limbic system
T/F: hypothalamus and brainstem are ONLY stimulated by peripheral hormones and neural signals from endocrine tissues
FALSE - both stimulated and inhibited
what does the stomach have/do to send out a “fullness” signal?
stomach contains stretch receptors (gastric distension)
what are the 2 things responsible for satiation?
- release of satiety peptides from GI tract
2. gastric distension
what are 2 satiety gut peptides?
where are they secreted from?
what do they do?
cholecystokinin (CCK)
glucagon-like peptide 1 (GLP1)
secreted from stomach and intestines
act as hormones/neuropeptides that generate signals via vagal pathways
signals mediated by satiety peptides are typically ____ and _____
short acting
define meal size and frequency
how do most satiety peptides decrease appetite?
by delaying the rate of gastric emptying
slowing the return of hunger
what is bariatric surgery?
gastric bypass surgery - restricts/reroutes the GI tract
in addition to its appetite suppression effects, GLP1 is also an ____
incretin - peptide hormone that stimulates insulin secretion (improving glucose tolerance during a meal)
what are gliptins?
a new family of drugs used to treat T2DM by increasing GLP1 activity
ghrelin is NOT a ____ but it is unique as the only gut peptide to ______.
satiety peptide
increases appetite
how is ghrelin an appetite stimulator? (nervous system)
what does it increase/decrease in the body?
binds to appetite stimulatory neurons in hypothalamus
increases food intake and body weight
decreases fat breakdown (decrease energy expenditure)
what are the levels of ghrelin before and after a meal?
high ghrelin before a meal (hunger state)
low ghrelin immediately after a meal (fed state)
what are the results of vaccines against ghrelin?
reduced food intake (in rodents)
what kind of peptide is ghrelin?
gut
NOT SATIETY
what kind of peptide hormone is insulin?
pancreatic peptide hormone
what are the 3 things insulin does to control appetite?
- insulin responds to minute-minute basis based on nutrient levels –> changes nutrient metabolism and thus, energy expenditure
- insulin crosses BBB and binds to appetite suppressing receptors on hypothalamus
- insulin is also an adiposity hormone –> basal hormone levels parallel amount of adipose tissue in body
ex. high fat levels (obesity) = high basal levels of insulin
T/F: reducing meal size and frequency is another way for insulin to reduce glucose in the bloodstream
TRUE
what is obesity commonly associated with?
what is that then closely associated with?
obesity –> hyperinsulinemia –> insulin resistance, obesity, T2DM
T/F: adipose tissue is a complex and highly metabolic endocrine “organ”
TRUE
what are the two forms of adipose tissue and their function?
BAT (brown) - lots of mitochondria, thermogenesis
WAT (white) - energy storehouse, breakdown of stored fat releases fatty acids and glycerol, endocrine center, secretes hormones and cytokines
T/F: adipose tissue is involved in the metabolism of steroid hormones
TRUE
Leptin, from the greek word meaning ___, is secreted by _____.
thin
adipose tissue
leptin binds to receptors on hypothalamus and causes what?
appetite inhibition
T/F: leptin can serve as an anti-obesity drug
FALSE - obesity is closely associated with leptin resistance in obese patients
T/F: leptin cannot be used as an anti-obesity drug because obese patients have leptin resistance
TRUE
what are the two gene mutations for leptin?
what were the experimental findings?
leptin deficiency - obese mice became normal weight and had reduced appetite when injected with exogenous leptin, works with humans with leptin deficiency
leptin receptor deficiency - no change in obesity with treatment with exogenous leptin due to leptin resistance in obese patients/mice, most common in human obesity
like insulin, leptin is also a ______, and its concentrations correlate with body fat levels. most obesity is associated with high levels of ___ and ____. during fasting, leptin levels are ____, much more quickly than would be expected from weight loss.
adiposity signal
insulin and leptin
reduced
what happens when leptin levels are too low? (reduced fat stores because leptin is adiposity signal)
hypothalamic amenorrhea - loss of menstrual period due to too much exercise or malnutrition, can occur if leptin is too low –> maybe to prevent pregnancy during illness or famine
what are the short and long term effects of appetite regulation?
short term - satiety peptides (CCK, GLP1)
long term - leptin, insulin, ghrelin
____ and _____ act synergistically to inhibit appetite whereas ghrelin opposes the action of _____
insulin and leptin
leptin
physical exercise promotes a _____ energy balance which means…..
negative energy balance - expenditure > intake, weight loss
what does acute exercise do to levels of satiety peptides and ghrelin?
increase satiety peptide post-prandial levels
ghrelin levels stay the same or decrease
what happens to leptin levels with long term exercise?
leptin levels decrease
think about it like this: leptin decreases because it is an adiposity signal, so fat stores decreased due to exercise
exercise improves ___ sensitivity and ___ uptake into skeletal muscle, which helps to overcome ____ resistance. exercise is therefore prescribed in the treatments of ____ and _____, for appetite control, weight reduction, and decreased _____ resistance.
insulin sensitivity
glucose uptake
insulin resistance
obesity and T2DM
insulin resistance
what are the roles of the two main neuronal circuits of the hypothalamus?
drives food intake and determining whether fat is stored or used for fuel
what are the two neuronal circuits of the hypothalamus?
where in the hypothalamus do these circuits signal?
- orexigenic - appetite stimulating
- anorexigenic - appetite inhibiting
in the ARC region of the hypothalamus
ghrelin, leptin, insulin act via _____ whereas satiety peptides act via ____
ARC
vagal pathway
appetite regulatory hormones bind to their receptors which releases ____, which then target _______ neurons associated with weight loss/gain pathways
neuropeptides
secondary
what is composed of the brain’s reward center?
higher cortical center and limbic system
T/F: both hypothalamic neuronal circuits are active at the same time but vary in levels to fine tune appetite and energy usage
TRUE
T/F: only the anorxigenic hypothalamic neuronal circuit is active all the time to inhibit appetite (prevents over-eating)
FALSE - both neuronal circuits (orexigenic, anorxigenic) are active at the same time
Insulin and PYY are (orexigenic/anorexigenic)
anorexigenic
both are appetite INHIBITING
in the hungry state, ghrelin levels are (elevated/reduced) and activate receptors on (anorexigenic/orexigenic) ARC neurons, signaling the need for (increased/decreased) food intake and energy conservation. the ghrelin receptors then activate 2 more neuropeptides _____ and _____. these neuropeptides bind to secondary neurons expressing ____ receptor. Activation of this receptors increases food ____ and reduces energy _____.
elevated orexigenic increased neuropeptide Y (NPY) and agouti-related peptide (AgRP) NCY receptor food intake energy expenditure
leptin (activates/inhibits) orexigenic ARC neurons so they do not release neuropeptides ____ and ____.
inhibits (leptin is appetite-inhibiting)
NPY and AgRP
in the fed state, appetite inhibitory neurons like leptin and insulin (activate/inhibit) (orexigenic/anorexigenic) circuits in the hypothalamus. the same hormones that inhibit ARC orexigenic neurons also (stimulate/inhibit) anorexigenic neurons. These neurons release 2 neuropeptides ____ and ____.
inhibit
orexigenic
stimulate
cocaine and amphetamine-related transcript (CART) and pro-opiomelanocortin (POMC)
POMC is proteolytically process in the _____ and produces hormone ______, which binds to melanocortin receptors on secondary neurons. This activates downstream pathways that (activate/inhibit) food intake and promotes energy _____. This pathway can be overriden by ____, a component of the orexigenic system. it inhibits _____ receptors on secondary neurons.
hypothalamus alpha-melanocyte-stimulating hormone inhibit expenditure AgRP melanocortin receptors
Melanocortin receptor defects or chronic inhibition of these receptors by AgRP are both causes of _____
obestiy
prolonged imbalance of energy intake/expenditure causes net weight ____ and ____
weight gain or loss
what are the 3 environmental factors influencing appetite?
- visual cues
- energy density
- sensory perception
T/F: environmental factors only affect sub-conscious cognitive functioning related to food intake
FALSE - both conscious and sub-conscious
how does visual cues affect food intake: what makes people eat more? does education help? what helps determine when people stop eating? how do children tend to overeat?
visual cues like portion size, packaging
education does not mediate a visual cue effect –> nutrition experts overeat too when given a larger bowl
visual cue of how much food has been eaten
if they are taught to ignore signs of fullness
what is energy density?
amount of energy per gram of food (calorie)
regarding energy density, adults claim what after meals of differing energy density?
how can low-energy dense first course help to decrease energy intake while making the person feel full?
hint: ex. (eating vegetable soup before a meal)
adults claim equal fullness after meals of varying energy density
lowers energy intake at a meal while providing comparable levels of fullness as a high-energy meal
(eating vegetable soup before a meal)
how can sensory perception affect food intake:
what makes people eat more?
how does palatability or amount of food eaten affect satiation after a meal?
food that has good taste, smell, appearance, texture
it is not sure
what were the results of the Pima Indians experiment? what did it prove?
2 genetically identical native groups in different locations, US and Mexico
US pima group had higher access to fatty foods and had more of a sedentary lifestyle –> 50% T2DM and 90% obesity
Mexican pima group were more active and ate healthier –> lower obesity/T2DM statistics
What is the thrifty gene hypothesis?
idea that the ability to accumulate and retain fat stores is adaptational in times of famine
basically –> weight is both environmental and genetic
T/F: certain ethnic groups are at increased risk for insulin resistance and T2DM
TRUE - minority groups like black, latinos, asians, native americans
What are some risk factors for T2DM?
family history obesity lack of activity impaired glucose tolerance giving birth to baby > 9 pounds > 45 years old metabolic syndrome
What is metabolic syndrome?
cluster of conditions (like diabesity, hypertension, cholesterol abnormalities) that increase risk of coronary artery disease
T/F: metabolic syndrome shows a low correlation with obesity
FALSE - high correlation
increase risk of coronary heart disease with increased obesity levels
what are hormonal vs neural examples of appetite inhibition?
hormonal - satiety peptides
neural - gastric distension (full –> no more eating)
what are hormonal vs neural examples of appetite stimulation?
hormonal - ghrelin
neural - gastric emptying
what are some pancreatic endocrine peptides?
insulin
glucagon
pancreatic polypeptide
amylin
define resistance to a hormone
lack of response to hormone (usually hormone levels are high)
What is the most abundant neuropeptide in the brain?
NPY
T/F: NPY decreases with prolonged stress
FALSE - increases
What is one of the most potent and long-lasting appetite stimulators?
AgRP
What does ARC stand for?
arcuate region of the brain
What does AgRP inhibit?
Melanocortin receptors (MCR)
T/F: CART is only distributed in the hypothalamus in the brain
FALSE - distributed everywhere in the brain but concentrated in the hypothalamus
What neurons secrete POMC?
ARC neurons
what gene deficiency causes obesity?
is it dominant or recessive?
MC4R deficiency = obesity
dominant
What are some things associated with metabolic syndrome? (FYI: to be considered MS, needs 3 or more of these things)
high insulin, glucose intolerance, fasting glucose high TG or low HDL obesity cholesterol abnormalities BP > 140/90 without treatment
NPY and AgRP are appetite….
stimulating
CART and POMC are appetite…
inhibiting
