Counter regulatory hormones Flashcards
Briefly state how metabolism works during fasting
- Inhibition of insulin secretion
- Low glucose levels
- No glycogen or triglyceride synthesis
Which hormones promotes the processes usually supressed by insulin in starvation
Glucagon
Briefly describe the graphical relationship between glucagon and insulin
If glucose and insulin go up, glucagon goes down and vice versaq
Which cells secrete glucagon
Alpha cells
Describe the structure of glucagon hormone
Peptide hormone made up of only 1 cchain
29 amino acids
When is glucagon secreted
When blood glucose levels are low
How is glucagon stored
In granules
Name 3 things that stimulate glucagon secretion
Low blood glucose
Increased blood amino acid
Exercise
What are normal fasting levels of glucose
80-90mg/ 100ml
Which blood amino acids particularly regulate glucagon secretion
Alanine and arginine
What type of receptor in the glucagon receptor
G protein coupled receptor
What is the first thing that happens when glucagon binds to the glucagon receptor
- G protein splits off
- Starts the cascade
What is the end point of the cascade in glucagon receptor signalling pathway
Production of cAMP which activates protein kinase A
Protein kinase A activates signal
Increases breakdown of glycogen to stop glycogen synthesis
What is the effect of PKA on the liver
Stimulates liver to make glucose via gluconeogenesis
Stops glycolysis
Does glucagon increase or decrease glycogenolysis
Increases
How long does it take for glycogen stores to be broken down
24 hours
What molecules can the liver use for gluconeogenesis
Carbon based subtrates (amino acids, glycerol)
How is gluconeogenesis not inhibited during fasting
Combination of reduced insulin and increased glucagon
What is the effect of glucagon in the liver
Increased gluconeogenesis and inhibits glycolysis
How does glucagon increase gluconeogenesis and inhibit glycolysis in the liver
- Inhibition of PFK-1 through modulation of fructose-2,6-bisphosphate levels
- Inhibition of pyruvate kinase
What mediates the action of glucagon in the liver
Protein kinase A
Does glucagon increase or decrease the uptake of amino acids into the liver
Increase
What inhibits/ activates hormone sensitive lipase
Inhibited by insulin
Acitvated by glucagon/ PKA
What does hormone sensitive lipase do
Initiate lipolysis
How can fatty acids be used to generate ATP
Enters the krebs cycle
What mediates the fatty acids shuttle system
Cpt-1
Does insulin supress or promote the action of Cpt-1? What about glucagon?
Insulin- suppresses
Glucagon- promotes
What is the effect of glucagons inhibition of cpt-1
- Allows breakdown of triglycerides to be broken down because activates hormone sensitive lipase needed to break it down
- Also allows passage across mitochondria membrane
Overall, what hormones suppress and promotes fatty acid oxidation
Glucagon- promotes
Insulin- suppresses
What is acetyl- CoA converted to in prolonged fasting
Ketone bodies
Name 2 hormones that inhibits glucagon secretion
Insulin
Somantostatin
How is cAMP used to regulate glucagon secretion
Insulin converts cAMP to AMP which can’t signal anymore so there is no glucagon action
Is it catecholamines or glucocorticoids that have a long term effect
Glucocorticoids
What is the effect of catecholamines
Stimulates glycogen breakdown from the liver1q
When are catecholamines released
Response to stress of hypoglycaemia
What are monoamines of catecholamine synthesised from
Phenylalanine
Tyrosine
State the metabolic action of epineprhine
Inhibits insulin secretion
Stimulates glycogenolysis in liver and muscle
Stimulates glucagon secretion
Increases lipolysis
Consequence of epinephrine release in terms of blood levels
Increased blood glucose and fatty acids levels
What kind of hormones are glucocorticoids
Steroid
How are adrenal cortex cells adapted for steroid hormone production
Many LDL receptors enabliing cholesterol uptake for steroid hormones synthesis
What is cortisol released in response to
ACTH
State the metabolic actions of cortisol
- Enhances gluconeogenesis
- Inhibits glucose uptake
- Stimulates muscle proteolysis
- Stimulates adipose tissue lipolysis
Why does cortisol produce long term responses
Because is hydrophobic so can pass through the cell membrane
Binds to nuclear receptor
What happens if levels of cortisol are high for a long time
induce proteolysis and muscle wasting
Does growth hormone act more like insulin or glucagon
Glucagon
Are cortisol and epinephrine secreted in hypo or hyper glycaemia
Hypo
Where are incretins found in the body
Gastro-intestinal hormones
Where is GLP-1 secreted
From the L cell
4 actions of GLP-1
Inhibits glucagon secretion and hepatic glucose production
Augments glucose induced insulin secretion
Slow gastric emptying
Promotes satiety
