Session 7: Control of Appetite Flashcards
In order to maintain a stable body weight, what must be true about energy intake and energy expenditure?
Energy intake must be equal to energy expenditure
What makes up energy expenditure?
- Basal Metabolic Rate (BMR)
- Physical Activity Level (PAL)
- Diet-induced thermogenesis (DIT)
What indicates increased energy stores and body weight?
Energy intake > Energy expenditure
What indicates decreased energy stores and body weight?
Energy intake < Energy expenditure
Where is the appetite control centre located in the brain?
Arcuate nucleus within the hypothalamus
What are the two types of neurones in the arcuate nucleus of the hypothalamus?
- Primary neurones
- Secondary neurones
What do primary neurones in the arcuate nucleus of the hypothalamus do?
Sense metabolites in blood and respond to hormones
What do secondary neurones in the arcuate nucleus of the hypothalamus do?
Receive input from primary neurones and coordinate a response
What are the two types of primary neurone in the arcuate nucleus of the hypothalamus?
- Stimulatory (orexigenic) neurons
- Inhibitory (anorexigenic) neurons
What do stimulatory (orexigenic) primary neurons release?
- Neuropeptide Y (NPY)
- Agouti-related peptide (AgRP)
These promote hunger
What do inhibitory (anorexigenic) primary neurons release?
- Pro-opiomelanocortin (POMC)
- Cocaine and amphetamine-related transcript (CART)
These promote satiety
Pro-opiomelanocortin (POMC) is cleaved to what?
α-melanocyte stimulating hormone (α-MSH) = this promotes satiety
Which major nerve do secondary neurons in the arcuate nucleus of the hypothalamus receive input from?
Vagus nerve
What peripheral signal stimulates appetite?
Ghrelin (released by stomach)
List some peripheral signals involved in suppressing appetite and their sources.
Leptin (adipose)
Insulin (pancreas)
Amylin (pancreas)
Glucagon-like peptide, GLP-1 (ileum, colon)
Peptide YY, PYY (ileum, colon)
What is leptin?
- Polypeptide hormone (145 a.a. long)
- Released from white adipocytes
- Overall effect = appetite suppression
Which primary neurons does leptin activate?
Leptin stimulates the inhibitory primary neurons (anorexigenic) and inhibits the stimulatory primary neurons (orexigenic)
Blood levels of leptin correlate with what?
The amount of adipose tissue in the body
Leptin increases the expression of what protein in mitochondria of brown adipose tissue (BAT)?
Uncoupling protein
What polypeptide hormone is used to treat obese patients who lack the hormone?
Leptin
What is insulin?
- Polypeptide hormone (55 a.a. long)
- Released from pancreas (beta cells)
- Overall effect = appetite suppression
What is amylin?
- Polypeptide hormone (37 a.a. long)
- Released from pancreas (beta cells)
- Overall effect = appetite suppression
What effects does amylin have to achieve suppression of appetite?
1) Decreases glucagon secretion
2) Slows gastric emptying
Overall effect = appetite suppression
List the signals from the body to the hypothalamus.
1) Leptin = suppressing (adipocytes)
2) Insulin = suppressing (pancreas)
3) Amylin = suppressing (pancreas)
List the signals from the gut to the hypothalamus.
1) Peptide YY = suppressing (ileum/colon)
2) Ghrelin = stimulating (stomach)
What is peptide YY?
- Polypeptide hormone (36 a.a. long)
- Released from ileum/colon
- Overall effect = appetite suppression
What is ghrelin?
- Polypeptide hormone (28 a.a. long)
- Released from stomach when empty
- Overall effect = appetite stimulation
What other signals are released from the large intestine that help suppress appetite?
- Oxyntomodulin = suppresses appetite
- Glucagon-like peptide (GLP-1) = suppresses appetite
What other signals are released from the small intestine that help suppress appetite?
- Cholecystokinin (CKK) = suppresses appetite
- Gastric inhibitory protein (GIP) = suppresses appetite
What other signals are released from adipose tissue that help regulate appetite?
- Adiponectin
- Resistin
- Visfatin
What other signals are released from the pancreas that help regulate appetite?
- Pancreatic polypeptide (PP)
- Enterostatin
What are the three types of bariatric surgery?
- Reducing the size of the stomach with an implanted medical device (gastric band)
- Removing a portion of the stomach (sleeve gastrectomy)
- Resecting and rerouting the small intestine to a small stomach pouch (gastric bypass)
Where is glucagon-like peptide 1 (GLP-1) released from?
Ileum, colon
What are the effects of GLP-1 on maintaining glucose homeostasis?
- Increases insulin sensitivity
- Stimulates beta cells in pancreas to proliferate.
- Beta cells increase in number and more insulin is produced by the body
Name the two regulatory systems involved in the regulation of appetite.
Episodic
Hedonic
What is the episodic regulatory system of appetite?
- Senses blood fuels, metabolites and peripheral signals coming from the gut and responds
- Senses tonic signals such as insulin and leptin and responds
- Senses central signals (neurotransmitters) and responds
What is the hedonic regulatory system of appetite?
- Relating to reward
- Operates on reward signals/mediators
Which regulatory system has a tendency to over-ride the other for appetite regulation?
The hedonic regulatory system has a tendency to over-ride the episodic regulatory system for appetite regulation
What signals are involved in the episodic homeostatic regulatory system of appetite?
- Tonic signals from adipose tissue = information about how much energy we have in the body (leptin/insulin)
- Episodic signals from gut = (ghrelin, enterostatin, cholecystokinin, oxyntomodulin, GLP-1, orexins)
- Typical episodic signals = (blood/liver metabolites)
Where are the neurons in the hedonic regulatory system reward pathways mainly found in the brain?
- Hippocampus
- Nucleus accumbens
- Amygdala
What neurotransmitters are involved in the hedonic regulatory system reward pathways?
- Opioids
- GABA
- Glutamate
- Cannabinoids
What are other players in the hedonic regulatory system of appetite?
- Orexin-A
- Serotonin
What dietary changes would you recommend for a person who is overweight?
- Calorie restriction
- Low-fat diet
- Increased physical activity
What psychological intervention might you recommend for a person who is obese adjunct to their diet and exercise modifications?
CBT
What adjunctive pharmacotherapy options would you recommend for an individual who is obese?
GLP-1 receptor agonists
- Semaglutide
- Liraglutide
Gastric and pancreatic lipase inhibitor
- Orlistat
How does Orlistat work?
Inhibits gastric and pancreatic lipase so it prevents absorption of fats from our diet
What might you recommend for someone who is morbidly obese and resistant to treatment?
Bariatric surgery
How does the hypothalamus control the release of hormones from the anterior pituitary?
By secreting neurohormones
GLUT4 is specific for which tissues?
b) Adipose tissue and skeletal muscle
