Lecture 32 - Feeding and weight control Flashcards Preview

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

Liver and stomach - CCK, Ghrelin

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


Ghrelin stimulates

hunger - food intake

neuropeptide Y - does the same in the brain


What do adiposity signals do?

Long-term - keep the body weight the same

Leptin Insulin


What is CCK?

Satiety signal acts quickly

released in periphery but GIT. acts on the vagus nerve

antagonism of peripheral CCKa receptors increases food intake


what is Ghrelin?

Increases appetite and body weight

Predominately synthesised in the stomach

plasma levels inversely proporitional to BMI

Receptors located in hypothalamus


What is Leptin?

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


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

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


What is synthesised in the arcuate nucleus?

Stimulating appetite
NPY/AGRP neurons - inhibited by Leptin

inhibiting appetite:
POMC/CART - stimulated by Leptin

Both inhibit food uptake


What is NPY?

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


NPY is one of the most potent...

appetite stimulating hormones known

stimulates feeling in satiated (full) animals - causes obesity

reduces energy expendature

Y1 and Y5 receptors are located


If leptin levels are low what happens in the hypothalamus?

less inhibition - more NPY being expressed


What is POMC?

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

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


What is alpha-MSH?

released in PVN

inhibits food intake predominantly via MC4-receptor

Increases energy expendature

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


Mutation in POMC or MC4R genes results in...

obesity - low levels of POMC


What is AGRP?

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)


over-expressionof AGRP results in ____



do the diapgram which integrates all this,,



Circulating leptin levels are proportional to...

fat mass


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

NPY and AGRP increased

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


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

NPY and AGRP decreased

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


What are the factors of obesity?

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


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


making purely genetic causes unlikely


What is the obesogenic environment?

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)


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

consumed after energy demands met

mjor contributing factor to obesity epidemic


the mesolimbic dompaminergic pathway activated in response to ...

palatable food

VTA to NAc

important for natural reward


How is the reward sdystem invovled in appetite?

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