Endo 15: Endocrine control of food intake

Question 1

What is the input to the hypothalamus

Answer 1

GHRELIN, PYY & other gut hormones

Neural input from the periphery and other brain regions

LEPTIN

Question 2

What are the outputs of hypothalamus

Answer 2

Food Intake
and
Energy Expenditure (TRH)

Question 3

Why is paraventricular nucleus important

Answer 3

Releases TRH

Question 4

Where is arcuate

Answer 4

Bottom of hypothalamus next to the 3V

Question 5

How does arcuate receive hormonal input. What function does arcuate nucleus serve

Answer 5

Incomplete blood brain barrier, allows access to peripheral hormones.
(circumventricular)

Integrates peripheral and central feeding signals.

Question 6

What are the key neuronal populations in the arcuate nucleus

Answer 6

Stimulatory (NPY/Agrp neuron)

Inhibitory (POMC neuron)

Question 7

How is POMC used in different brain areas

Answer 7

pituitary cut up to ACTH

Hypothalamus cut up to MSH

Question 8

What hormone is present in the paraventricular nucleus and the function

Answer 8

MC4R…. reduces appetite

Question 9

How does POMC neuronal bodies affect paraventricular nucleus

Answer 9

Releases a-MSH to stimulate PVN to decrease food intake

Question 10

How to AGRP/NPY affect PVN

Answer 10

releases AGRP which inhibits MCR4 so increased appetite

Question 11

T/F NPY and Agrp mutatuons are responsible for obesity prevalence

Answer 11

F!! POMC deficiency and MC4-R mutations cause morbid obesity, but NOT responsle for obesity prevalence

Question 12

What does the hypothalamus receive signal from

Answer 12

From leptin, the gut and brainstem as well as cortical regions

Question 13

What is the ob gene, what occurs in deficiency

Answer 13

Ob gene codes for leptin in ob/ob mouse there is no leptin, nothing to tell the brain that there are adequate fat stores in the adipose tissue

Profoundly obese.
Hyperphagia.
Diabetic.
Decreased body temperature.
Decreased energy expenditure.

Question 14

What is leptin, where is it released, and where are its receptors

Answer 14

Leptin released from WHITE adipose tissue

Leptin receptors in the hypothalamus (Ob-R)

Question 15

How does leptin work on the hypothalamus

Answer 15

Activates POMC and inhibits NPY/AgRP neurons.

Question 16

What is the effect of central or peripheral administration of leptin in those who have deficiency

Answer 16

Central or peripheral administration decreases food intake and increases thermogenesis.

Question 17

What will leptin be when body fat is

a) high
b) low

Answer 17

a) high when body fat high

b) low when body fat low

Question 18

With obese humans, what are leptin levels like

Answer 18

Most obese humans have high leptin (high fat mass)….

Question 19

Can leptin be used as a weight control drug

Answer 19

No, leptin is ineffective as a weight control drug.

the brain is now unresponsive to leptin because it’s been high due to high adiposity

Question 20

What is the role of inslin in food intake.

T/F insulin secretion from the pancreas increases in proportion to body adiposity

Answer 20

Insulin circulates at levels proportional to body fat.

Receptors in the hypothalamus.

Central administration reduces food intake.

T! Glucose-induced insulin secretion from the pancreas increases in proportion to body adiposity, owing to the capability of expanding fat stores to induce resistance to insulin’s glucose-lowering effects.

Question 21

What is the body’s largest endocrine organ

Answer 21

The gut

Question 22

How many gut hormones are there

Answer 22

20+

Question 23

What do gut hormones control

Answer 23

gut motility, secretion of other hormones, appetite.

Question 24

Rlease of gut hormone is regulaated by what

Answer 24

Release regulated by gut nutrient content.

Question 25

How dows grehlin impact appetite. Where is grehln released

Answer 25

Released in stomach It stimulates NPY/Agrp Imhibits POMC INCREASES appetite

Question 26

What type of hormone makes you feel full?

Answer 26

PYY (satiety)

Question 27

How does PYY work and where is it released

Answer 27

Released from L cells in intestine Inhibits NPY release. Stimulates POMC neurons. Decreases appetite.

Question 28

What is GLP1 and what is the effect on appetite T/f: GLP1 is made from the same gene as glucagon. PYY also comes from this gene.

Answer 28

Gut hormone coded for by the preproglucagon gene and released post-prandially in the L cells by the gut F: glucagon, glp1 and glp2 from same gene but PYY from elsewhere

Question 29

What type of hormone is GLP1..... explain this hormone type

Answer 29

Hormones that Are released after eating Augment insulin secretion from b islet cells

Question 30

2 functions of GLP-1

Answer 30

Well characterised incretin role and also reduces food intake.

Question 31

Are there therapeutic uses of GLP1

Answer 31

GLP-1 agonists are injectable only or DPP-4 inhibitors (DPP-4 endogenousl breaks down GLP-1, so these drugs prevent breakdown)

Question 32

Why is it difficult to give injection for GLP-1 How is GLP-1 agonists used in type II diabtetes

Answer 32

Very short lives as they're peptide hormones so are broken down,,,, haf life just 1 minute, so can be modified to saxenda (which is modified GLP so longer lived) Used in type II diab. because they can cause increased release of insulin to control sugar and also inhiit appetpite Also have recently been licensed for obesity treatment

Question 33

Coud PYY3-36 be used a as a drug target

Answer 33

No because narrow therapeutic window and cause nausea above this, and no efffect below it

Question 34

What is thrify vs drift gene

Answer 34

thrifty gene stated that those who had genes that caused storage of fat were selected for as starvation was a big problem in cave men times. This shows as Populations historically prone to starvation become most obese when exposed to Western diet and sedentary life-style (e.g. Pima Indians, Pacific Islanders). drfity gene says that there is normal distribution of body mass, as if you are too fat you are eaten and if you are too thin then you starve. BUT then 20,000 years ago people learnt to defend against predators so obesity isn't selected against.... so body fat was then a neutral change/genetic drift.... In a healthy environment those genetically prone will have same BMI as everyone else but in toxic environment i.e. like the western fat diet one, then these people will put on lots of weight

Question 35

Which gene codes for leptin

Answer 35

The Ob gene