Lecture 32 - Feeding and weight control

Question 1

What are the short term satiety signals and what produces them?

Answer 1

Liver and stomach - CCK, Ghrelin

Vagus sends info to medulla to alter food intake - then goes to hypothalamus

Question 2

Ghrelin stimulates

Answer 2

hunger - food intake

neuropeptide Y - does the same in the brain

Question 3

What do adiposity signals do?

Answer 3

Long-term - keep the body weight the same

Leptin Insulin

Question 4

What is CCK?

Answer 4

Satiety signal acts quickly

released in periphery but GIT. acts on the vagus nerve

antagonism of peripheral CCKa receptors increases food intake

Question 5

what is Ghrelin?

Answer 5

Increases appetite and body weight

Predominately synthesised in the stomach

plasma levels inversely proporitional to BMI

Receptors located in hypothalamus

Question 6

What is Leptin?

Answer 6

Secreted predominately from fat cells

plasma levels proportional to BMI and fat

Crosses BBB via a saturable process

receptors located in hypothalamus

inhibits food intake via CNS mechanism

Question 7

What relevance does Leptin or Leptin deficiency have in obesity worldwide?

Answer 7

only relevant in a very small number of pateints - mainly other things

Question 8

What is synthesised in the arcuate nucleus?

Answer 8

Stimulating appetite
NPY/AGRP neurons - inhibited by Leptin

inhibiting appetite:
POMC/CART - stimulated by Leptin

Both inhibit food uptake

Question 9

What is NPY?

Answer 9

member of pancreatic polypeptide family
stimuates apetite, unlike other members of the family

Other members
Peptide YY - GIT
Pancreatic polypeptide - PANCREATIC ISLETs

Theses circulate and act acutely to inhibit food intake

Question 10

NPY is one of the most potent…

Answer 10

appetite stimulating hormones known

stimulates feeling in satiated (full) animals - causes obesity

reduces energy expendature

Y1 and Y5 receptors are located

Question 11

If leptin levels are low what happens in the hypothalamus?

Answer 11

less inhibition - more NPY being expressed

Question 12

What is POMC?

Answer 12

Located in vairous regions in the brain but in particular the arcuate neurons -

undergoes post-translational processing to cause the producgtion of alpha-MSH

Question 13

What is alpha-MSH?

Answer 13

released in PVN

inhibits food intake predominantly via MC4-receptor

Increases energy expendature

levels are regualted by feeding status and leptin (same as NPY)

Question 14

Mutation in POMC or MC4R genes results in…

Answer 14

obesity - low levels of POMC

Question 15

What is AGRP?

Answer 15

Endogenous antagonist at MC4R

inhibits a-MSH from binding to MC4R
-increases food intake
reduces energy expendature

level regualted by feed status and Leptin (again)

Question 16

over-expressionof AGRP results in ____

Answer 16

obesity

Question 17

do the diapgram which integrates all this,,

Answer 17

now

Question 18

Circulating leptin levels are proportional to…

Answer 18

fat mass

Question 19

What does Low Leptin (from decrease in fat mass) lead to…

Answer 19

NPY and AGRP increased

POMC decreased (decrease in a-MSH released) - increased body weight

Question 20

What does High Leptin (from increase in fat mass) lead to…

Answer 20

NPY and AGRP decreased

POMC increased (increase in a-MSH released - decreased body weight)

Question 21

What are the factors of obesity?

Answer 21

Genes
sleep deprivation - increase in Grehlin
food intake
physical activity
socioeconomic status
cultural

Question 22

While certain genes increase the susceptibility to obesity, the prevalence of obesity has almost ____ since 1980,

Answer 22

doubled

making purely genetic causes unlikely

Question 23

What is the obesogenic environment?

Answer 23

Decline in physical activity

• decrease in rates of exercise
• increase in technology to complete activityof daily living, TV, computers

Food portion size - mistake quantity for quality

comsumption of suger-sweetened beverages

consmption of palatable energy-dense foods

• high fat/super
• cheaper (SES)

Question 24

Bland foods not eaten in excess but what about palatable foods?

Answer 24

consumed after energy demands met

mjor contributing factor to obesity epidemic

Question 25

the mesolimbic dompaminergic pathway activated in response to …

Answer 25

palatable food

VTA to NAc

important for natural reward

Question 26

How is the reward sdystem invovled in appetite?

Answer 26

hnger enhances activation of meso-limbic pathway

leptin inhibits activity of VTA neurons
- VTA neurons express leptin receptor

Ghrelin stimulates activity of VTA dopaminergic neurons
- VTA neuron express ghrelin receptor
increases rewarding value of food