Regulation of appetite

Question 1

The obesogenic environment

Answer 1

Physical activity is discouraged and unhealthy food consumption is encouraged. Homes, schools communities ay encourage this environment; food industry – recipes high in sugar, salt and fat, large portion sizes, poor nutritional labelling, aggressive marketing of unhealthy food especially to children.

Question 2

Define appetite

Answer 2

Desire to eat food

Question 3

Define hunger

Answer 3

Need of eating

Question 4

Define anorexia

Answer 4

Lack of appetite

Question 5

Define satiety

Answer 5

Feeling of fullness - disappearance of appetite after a meal

Question 6

Define BMI

Answer 6

weight (kg) / ht (m^2)

Question 7

BMI <18.5

Answer 7

Underweight

Question 8

BMI 18.5 - 24.9

Answer 8

Normal

Question 9

BMI 25.0 - 29.9

Answer 9

Overweight

Question 10

BMI 30 - 39.9

Answer 10

Obese

Question 11

BMI >40

Answer 11

Morbidly obese

Question 12

What are the risks of obesity?

Answer 12

Type II diabetes
Hypertension
Coronary artery disease
Stroke
Osteoarthritis
Obstructive sleep apnoea

Question 13

What carcinomas are linked with obesity?

Answer 13

Breast
Endometrium
Prostate
Colon

Question 14

Visceral:subcutaneous fat ratio (V:S)

Answer 14

L1/L2 cuts above and below - volume calculated.

Question 15

What does weight regulation depend on?

Answer 15

Genes
Environment
Maintenance (homeostasis) system
Normal fat mass (-ve FB to maintenance)

Question 16

In an individual, weight is normally…

Answer 16

Remarkably constant - hardwired to maintain a specific weight.

Question 17

Maintaining fat mass

Answer 17

CNS increased food intake

Energy expenditure is reduced

Maintains a positive energy balance = fat stored which signals to CNS via insulin and leptin.

Lepin switches off Anabolic signals and on catabolic signals. No food intake and metabolic rate and physical activity is increased.

Fat is broken down.

Question 18

The satiety cascade

Answer 18

Internal physiological drive to eat
Feeling that prompts thought of food and motivates food consumption

External psychological drive to eat
Sometimes even in the absence of hunger (e.g buffet)

Question 19

Energy balance is influenced by

Answer 19

Insulin
Leptin
Adiponectin

TONIC

Question 20

Sensory and cognitive factors influencing satiety

Answer 20

Sensory and cognitive: sensation + prior beliefs + associations

Meal quality

Question 21

Post ingestive factors influencing satiety

Answer 21

Meal quantity

Stretch
Osmotic load
CCK
GLP-1
PYY
Ghrelin

Question 22

Post absorptive factors influencing satiety

Answer 22

Liver and metabolites
Nutrient status

Insulin
Oxidation
Glucose
AAs

Question 23

Which part of the brain plays a central role in appetite regulation?

Answer 23

Hypothalamus

Question 24

The hunger centre is located in

Answer 24

The Lateral hypothalamus

Question 25

The satiety centre is located in

Answer 25

The ventromedial hypothalamic nucleus

Question 26

Examples of central appetite controllers that increase appetite

Answer 26

NPY MCH AgRP (Agouti-related poeptide) Orexin Endocannabinoid

Question 27

Examples of central appetite controllers that decrease appetite

Answer 27

alpha -MSH CART (cocaine and amphetamine regulated transcript) GLP-1 Serotonin

Question 28

Leptin stimulates what?

Answer 28

POMC (pro-opiomelanocortin) /CART Inhibits PVN and PFA

Question 29

Leptin inhibits

Answer 29

NPY /AGRP Stimulates PVN and PFA

Question 30

Arcuate nucleus

Answer 30

It has fenestrated BBB - able to sample peripheral hormones.

Question 31

Leptin

Answer 31

Isolated in 1994 Greek ‘leptos’ - thin Expressed in white fat Binds to leptin receptor - cytokine receptor family - in hypothalamus Switches off appetite and is immunostimulatory ob/ob mouse - leptin deficient hyperphagic hyperinsulinaemic very obese Blood levels increase after meal Blood levels decrease after fasting

Question 32

Peptide YY

Answer 32

36 amino acids Structurally similar to NPY Binds NPY receptors secreted by neuroendocrine cells in ileum, pancreas and colon in response to food inhibits gastric motility reduces appetite

Question 33

CCK

Answer 33

1973 - administration - reduced feeding in rodents Receptors in pyloric sphincter - delays gastric emptying - gall bladder contraction - insulin release and via vagus - satiety

Question 34

Ghrelin

Answer 34

Isolated in 1999 28 amino acid Acyl side chain Expressed in stomach Action: stimulates - Growth hormone release - appetite - orexigenic Blood levels high when fasting, fall on re-feeding Levels lower after gastric bypass surgery ?use in anorexia/cachexia

Question 35

MCR1

Answer 35

Melanocytes Skin pigmentation (POMC deficiency = pale skin)

Question 36

MCR2

Answer 36

Adrenal Adrenal cortex - steroids (POMC deficiency = adrenal insufficiency)

Question 37

MCR3 and MCR4

Answer 37

Brain Satiety signalling (POMC deficiency = hyperphagia and obesisty)

Question 38

MCR5

Answer 38

Skin

Question 39

Leptin and insulin

Answer 39

Leptin and insulin: 1. Stimulate- POMC/CART neurons -> increased CART and alpha-MSH levels 2. Inhibit NPY/AgRP neurons -> decreased NPY and AgRP Net effect : ↑ Satiety and decreased Appetite

Question 40

Ghrelin

Answer 40

Stimulates NPY/AgRP = increased NPY and AgRP secretion Increased appetite

Question 41

PYY3-36 (homolog of NPY)

Answer 41

Binds to an inhibitory receptor on NPY/AgRP = decrease the secretion of NPY and AgRP therefore decrease appetite

Question 42

Fasted state

Answer 42

NYP up Glucose down Insuling down Ghrelin up Lepton down a-MSH down AgRP up Activated AMPK increased appetite and decreased Malonyl CoA.

Question 43

Fed state

Answer 43

NPY down Glucose up Insulin up Ghrelin down Leptin up a-MSH up AgRP down Deactivate AMPK decreased appetite and increased Malonyl CoA.

Question 44

The effects of incretins include

Answer 44

1. Blunting of glucagon 2. Beta-cell stimulation of insulin production 3. Improved satiety 4. Decreased gastric motility