19 | Appetite

Question 1

satiety

Answer 1

feeling of fullness

• peptides
• gastric distention

Question 2

satiety peptides

Answer 2

appetite-inhibitory peptides (released from GI)
-CCK (cholecystokinin)
-GLP-1 (glucagon like peptide, also incretin - improves glucose tolerance during a meal)
decrease appetite by delaying rate of gastric emptying, slowing return of hunger
major short-term endocrine regulators of appetite

Question 3

satiety signals (3)

Answer 3

• vagal pathways
• short acting
• define meal size and frequency

Question 4

ghrelin (4)

Answer 4

only gut peptide that increases appetite

• binds to appetite stimulator neurons in hypothalamus
• increases food intake and body weight
• decreases fat breakdown (dec. energy use)
• level inc before meal (hunger), fall after a meal (fed)

Question 5

insulin (3)

Answer 5

-responds to levels of nutrients, affects their metabolism/energy use
-crosses BBB, binds to hypothalamus neurons that suppress appetite
(dec meal size and freq is a way for insulin to dec BG)
-adiposity hormones, levels parallel amount of adipose

Question 6

adipose tissue

Answer 6

metabolic endocrine “organ”

• brown fat: rich in mitochondria, thermogenesis
• white fat: energy storage, breakdown releases FFA’s and glycerol. endocrine center. receptors for response to metabolic and endocrine signals. secretes hormones and cytokines. metabolism of steroid hormones.

Question 7

leptin

Answer 7

• secreted by adipose tissue
• binds to hypothalamus neurons, inhibits appetite
• many obese people are leptin (+ insulin) resistant, rather than deficient
• adiposity signal, levels correlate with adipose
• rapid drop during fasting, can influence other hormonal axes (loss of menstrual periods with strenuous exercise or malnutrition)

Question 8

longer term appetite regulators

Answer 8

leptin + insulin: inhibit appeptite

ghrelin: opposes action of leptin
- peripheral effectors

Question 9

exercise + energy homeostasis

Answer 9

-promotes negative energy balance (energy use > food intake, weight loss)
-improvees insulin sensitivity and glucose uptake in skeletal muscle, overcome insulin resistance
acute exercise:
-promotes post prandial levels of satiety peptides
-ghrelin levels may decrease
-leptin levels fall long term

Question 10

orexigenic circuit

Answer 10

appetite stimulating

• food intake, energy conservation signals
• activated by ghrelin
• inhibited by leptin

Question 11

anorexigenic circuit

Answer 11

appetite inhibiting

-activated by leptin

Question 12

hypothalamus

Answer 12

ARC region: anorexigenic and orexigenic nuerons
-receptors for ghrelin + leptin
-activation releases neuropeptides
-activate second order neurons associated with weight loss or gain pathways
-net signals to higher cortical centers and limbic system
(circuits active at same time, varying levels to fine tune appetite and energy use. prolonged imbalance - net weight gain or loss)

Question 13

hungry state

Answer 13

• inc ghrelin activates orexigenic receptors
• secrete neuropeptide Y (NPY) and agouti-related peptide (AgRP)
• activate second order neurons with NPY-R
• initiates feeding behaviors, metabolic processes

Question 14

fed state

Answer 14

• leptin activates anorexigenic receptors (and inhibit orexigenic)
• neurons release CART (cocaine + amphetamine related transcript) and POMC (pro-opiomelanocortin) peptides
• POMC cleaved to a-MSH, binds to melanocortin-rec on second order neurons
• inhibit feeding behavior, promote energy use
• path can be overriden by AgRp

Question 15

melanocortin receptor + obesity

Answer 15

-receptor defects
-chronic inhibition by AgRp
can cause obesity, interruption of anorexigenic signals

Question 16

visual cues

Answer 16

• tend to eat more with larger package, utensils, food portions
• cue of how much eaten can signal to stop eating

Question 17

energy density

Answer 17

• amount of energy/g of food (kcal/g)
• modulates overall energy intake
• low energy dense meal with comparable levels of fullness can decrease intake

Question 18

sensory perception

Answer 18

food taste, smell, appearance

-can influence palatability, and amount eaten

Question 19

Pima Indian study + thrifty gene hypothesis

Answer 19

Pima Indians - genetically predisposed to obesity + T2DM

• two genetically identical populations, one in S. Arizona, other in remote Mexico
• US group had more sedentary lifestyle, easier access to high cal, processed foods
• Mexican group had higher activity levels, consume lower-fat, traditional foods
• in Mexican group, obesity was uncommon and prevalence of T2DM was comparable to US population (8% overall)
• but in US group almost half had T2DM, and 95% of them were obese

support thrifty gene hypothesis:
ability to accumulate and retain stores of fat is adaptational in time of famine
-shows primary influence of environmental factors on genetic predisposition to obesity and T2DM

Question 20

metabolic syndrome

Answer 20

conditions that increase risk of coronary artery disease
-obesity
-hypertension
-T2DM
-cholesterol abnormalities
[high insulin levels, with inc fasting glucose or glucose intolerance and central obesity, abnormal cholesterol, or high BP]