Week 9. Appetite

Question 1

What does leptin do?

Answer 1

decreases appetite

Question 2

What are second order hormones?

Answer 2

LHA releases orexins –> stimulate appetite

PVN releases NPs that decrease food intake

Question 3

Outline the function of ARC.

Answer 3

Arcuate nucleus.

• at the base of the hypothalamus, where the BBB is broken
• signals from periphery can enter

Question 4

What does insulin do when directly added to brain?

Answer 4

decreases food intake

Question 5

How is cephalic phase detected?

Answer 5

Stretch receptors in stomach detect empty stomach and low blood sugar

Question 6

What does cholecystokinin (CCK) do?

Answer 6

• released from duodenum in response to fat

- reduces food intake by activating melacortin pathway in hypothalamus

Question 7

Define the cephalic phase?

Answer 7

Pre injestion/hunger phase

Question 8

When is peptide YY released?

Answer 8

Made in response to food entering GI tract

Produced at same time and in proportion to GLP1

Question 9

How are leptin and insulin similar?

Answer 9

• both circulate in proportion to fat levels
• both decrease food intake
• body can become resistant to both

Question 10

What are first order hormones?

Answer 10

• ARC contains two clusters of hormones
• ones that secret NPY –> increase appetite

Neurones that secret melanocortins - suppress appetite

Question 11

What is neuropeptide Y(NPY)?

Answer 11

• potently stimulates food intake

- but knocking out gene has no effect on appetite

Question 12

Outline the function of PVN.

Answer 12

Paraventricular nucleus.

• integrating centre
• most number of peptides regulating appetite produced here

Question 13

What is the intestinal phase?

Answer 13

Induction of satiation

Question 14

Why do diets fail?

Answer 14

10 week low calorie diet resets homeostatic peptides.

• increase in ghrelin
• decrease in satiety hormones
• 30% increase in weight after diet

Question 15

Outline the function of VMN.

Answer 15

Ventromedial nucleus.

• largest nuclei
• satiety centre
• site of action for peptides

Question 16

What is ghrelin and when is it released?

Answer 16

• secreted by gastric mucous in empty stomach
• peaks when fasting just before a meal
• function is to ensure you eat enough fat

Question 17

Outline the function of LHA.

Answer 17

Lateral hypothalamic area

- only one that produces peptides that cause hunger

Question 18

What is the pattern of hunger. Define each stage.

Answer 18

1. hunger - desire to eat (anything)
2. appetite - desire to eat specific food or nutrient
3. Satiation - desire to stop eating at the end of the meal
4. satiety - delaying the next meal

Question 19

Where is leptin produced?

Answer 19

adipose tissue

Question 20

Where does the input into the hypothalamus come from?

Answer 20

• neural input from cerebral cortex and limbic system
• peptide hormones from GI tract
• adipocytokines from adipose

Question 21

What is Agouti related peptide?

Answer 21

• stimulates food intake

- antagonist in melacortin system

Question 22

What compounds are related to hedonic behaviour?

Answer 22

Dopamine –> mood and addiction. Associated with wanting sweet things
Serotonine –> feel good hormone.
Endocannaboids –> pain, appetite, memory
- antagonists will reduce food intake

Question 23

What is alpha melanocyte stimulating hormone (αMSH)?

Answer 23

• inhibits food intake

- agonist in melacortin system

Question 24

Which nutrients are the most satiating?

Answer 24

Protein - most satiating
complex carbohydrate - satiating
fat - makes you want to eat more

Question 25

What hormone imbalances exist in obese people?

Answer 25

Less PYY satiation hormones.

Unclear pattern of ghrelin.

Question 26

What are the motor events of the cephalic phase?

Answer 26

• relaxation of sphincter

- gall bladder contractions

Question 27

Name six things about glucagon like peptide 1 (GLP1)

Answer 27

• proglucagon gene
• expressed in pancreas –> cleaved to form glucagon
• also expressed in intestinal L cells
• decreases food intake by reducing gut motility
• encourages energy expenditure

Question 28

What happens to leptin and ghrelin in obese people?

Answer 28

Leptin and ghrelin –> homeostatic control of appetite

- in obese people, leptin stops working but ghrelin doesn’t

Question 29

Which receptor in the brain does insulin bind to?

Answer 29

tyrosine kinase receptors

Question 30

What is the gastric phase?

Answer 30

Consumption stage, release of gut and neuro peptides

Question 31

What do insulin antibodies do to appetite?

Answer 31

increase it

Question 32

What is the glucostatic theory?

Answer 32

• glucose levels ultimately control feeding and satiety centre

Question 33

What are the secretory events of the cephalic phase?

Answer 33

• saliva
• pepsinogen
• pancreatic enzymes

Question 34

What is the lipostatic theory?

Answer 34

• level of body fat regulates feeding and satiety

Question 35

What is the difference between insulin and leptin?

Answer 35

Insulin:
Weight gain –> increased insulin and resistance
Weight loss –> decrease in insulin

Leptin:
As weight decreases, leptin dissociates from fat levels
- drop in leptin far greater than drop in body fat

Question 36

How to peripheral signals interact with each other?

Answer 36

Release of ghrelin –> hunger –> stretch receptors in stomach activated –> parasympathetic nervous system –> increase in gastric secretions –> food –> stomach lining stretches –> CCK released