Food Intake and Energy Homeostasis Flashcards
What is BMI and what do we use it for?
Body Mass Index: used as a crude measure of obesity (kg/m2)
-measure to roughly determine if someone is obese or not
What is excluded from BMI measurement?
Doesn’t take into account muscle mass
What would be a better ratio to look at if we were to determine if someone is obese or not?
Ratio between Hips and git visceral fat to determine if you are at a risk of developing a condition that could kill you
How is obesity defined?
Having an abnormal or excess fat accumulation that presents a risk to an individuals health
(BMI 30+)
How prevalent is obesity in North America?
Obesity rates have increased 35% in the last 50 years
There is no sex discrimination when it comes to obesity
There has been a 80% increase in adult obesity rates
There has been a 300% increase in child obesity rates
What is energy balance?
Energy balance= energy intake-energy expenditure
How do we manipulate energy balance to lose or gain weight?
To lose we need to increase energy expenditure and decrease energy intake
To gain weight we need to increase energy intake and decrease energy expenditure
What are environmental/lifestyle factors that affect how much and what food we intake?
Taste& Smell- taking in energy when we dont need too
Availability- always aruond
Clock- daily schedule regardless if we need it
Social Habits and cues- events providing food when you have already eaten
Cost/reward optimization
What are individual predisposition/wirings that affect what food and how much we take in?
Genetic- predisposed to want to heart more. Hormones are released in excess or out of whack
Epigenetic: While in the womb, there was a change in condition that when you were born, you were more likely to eat more
Imprinted
Early Life events
What are the physiological events that affect how much and what to eat?
Internal Milieu nutrient sending (through organs)
Nutrient Partitioning
Energy Out
What can e do to these physiological process in our body?
We can over ride them in which we can then eat more than we need
What is the main physiological signal for food intake?
Negative feedback control system
What is an example of a negative feedback system control for food intake?
We are Hungry> We Eat> Increasing adipose tissue> Increasing leptin being released> Leptin is understood in the Satiety Centre (Arcuate Nucleus)> Tells body you are full> Stop eating> decrease adipose levels and leptin> Feeding centre turned on (lateral hypothalamus and Paraventricular nucleus)> Cycle repeats
- Once the arcuate nuclei receives the signal from leptin, the feeding centre (lateral hypothalamus and paraventricular nuclei) are shut of
Why is the feeding centre shut off when leptin signals are circulating?
If you have too much leptin, the arcuate shuts off the the lateral hypothalamus and paraventricular nucleus because these 2 areas are related to hunger
What is the amount of adipose (fat) proportional too?
The amount of leptin hormone you have
What tissue releases the peptide leptin?
White adipose tissue releases leptin into circulation
What does leptin trigger in the brain?
POMC Neurons
AgRP/NPY Neurons
-the amount of leptin affects each pathway differently
Describe the POMC neural pathway?
Adipose releases Leptin. Triggers POMC neutrons to release alpha-MSH hormones. Which work at receptors MC4-R at the paraventricular nucleus. This can affect energy expenditure and therefore affect energy homeostasis
Describe the AgRP/NPY neural pathway
Adipose releases Leptin. Triggers AgRP/NPY neutrons to release the hormone NPY-R. This hormone works on receptors in the dorsomedial hypothalamic nucleus. This can affect food intake
What is the Lateral hypothalamus and what does it have an affect on in the neural pathways?
Is the feeding centre in the brain
-NPR-Y hormones have an affect in this nucleus and can influence food intake
What happens when there is an acute increase in leptin?
Increase adipose
Increases Leptin
Activates POMC neurons (to shut down food intake)
MSH hormone turn on MC4-R Receptors
Energy Expenditure will increase beaqcuse we have too much
*At the same time the AgRP/NPY pathway is inhibited and affects how fast the hormones work
If the POMC pathway is activated why is the AgRP/NPY pathway inactivated when there is an acute increase in leptin?
Neurons are shut down completely so they have no affect on the release of hormone and the receptor
What happens when there is an acute decrease in leptin?
Decrease Adipose
Decrease in Leptin released
AgRP/NPY neurons activates
Neurons Stimulate NPY-R receptors in the Dorsalmedial hypothalamic nucleus
Food Intake increases
Shuts down communication between paraventricular nuclei to decrease energy expenditure
* at the same time the POMC pathway is inactivated which also leads to decreased energy expenditure
How are the AgRP/NPY neurons activated?
They are not, they are tonically active (they are always on but can be inactivated/muted to see reduced effects)
-once the POMC pathway is removed, the AgRP/NPY neurons are able to go full force ahead
What happens when there is a chronic increase in leptin?
The pathways will act the same way as if the person had decreased leptin levels in their system
-Leptin doesn’t exert the effects that leptin should at the POMC neurons
How could someone become leptin resistant?
Decrease number of receptors
Decreased sensitivity of receptors
Not enough carrier proteins for leptin across BBB
What is leptin resistance associated with?
Only neurons involved in feeding (POMC & AgRP), NOT in neurons in the SNS control throughout the brain
What can leptin resistance lead to?
Obesity and hypertension because leptin is still present and exerting effects but something in the body is not seeing/registering that it is there. Body won’t take the appropriate actions and people will continue eating and BP will go up
What is the normal function of the MC4-R receptor and what happens when it doesn’t work?
Normal: Able to receive input from alpha-MSH transmitter and increases energy expenditure
Not working: Pathway might still be working but MC4-R is not able to receive/interpret signals. Leads to a decrease in energy expenditure
-will retain more weight and not burn a lot of calories
When the MC4-R recpeort isn’t working, is that due to environmental factors or genetics?
Genetic disorder of a non-functional MC4-R receptor and can result in obesity
What is the lateral hypothalamic nucleus?
Houses the neurotransmitter orexin which regulates appetite
What does chronic leptin resistance lead to?
Leads to constant SNS hypertension
What is Orexin?
Neurotransmitter that stimulates food intake
-found in lateral hypothalamic neurons
What is NPY?
Neurons and neurotransmitter that stimulates food
-found intake found in the the arcuate nucleus
What is POMC?
Neurons that produce neurotransmitters Alpha-MSH which inhibits food intake and activates energy expenditure
-found in the arcuate nucleus
What is the Paraventricular Nucleus?
Activates pathways for energy expenditure
-activates SNS as a results of increased alpha-MSH
What is the Arcuate Nucleus?
Satiety centre which respond to leptin
What is the Lateral Hypothalamus?
Feeding centre activates food intake
-responds to leptin
