Insulin counter-regulatory hormones Flashcards
Which hormone controls blood glucose levels during fasting?
Glucagon
Actives processes to release glucose and fatty acids
Which cell in the Islets of Langerhans produces glucagon?
Alpha cells
Describe the structure of glucagon
29aa peptide
When is glucagon secreted?
When blood glucose levels are too low
Increase in blood amino acids
During exercise
Which molecules inhibit glucagon secretion?
Insulin
Somatostatin
What type of receptor is the glucagon receptor?
G protein coupled receptor
What happens to Gluconeogenesis and Lipolysis when no insulin is being secereted? (inhibited or not inhibited)
Insulin usually inhibits these processes. When there is no insulin there is no inhibition
Gluconeogenesis is not inhibited by insulin
Lipolysis is not inhibited by insulin
Which biomarker is used to monitor insulin concentration in the blood
Monitor the C- peptide level
1 C peptide 1 Insulin molecule
What effect does glucagon have on gluconeogenesis and glycolysis? Where in the body are these effects exerted?
increases gluconeogenesis and inhibits glycolysis in the liver
What happens to triglyceride stores during fasting? Relate to insulin and glucagon.
Lipolysis occurs-
Break down of triglycerides
(Hormone sensitive lipase is inhibited by insulin and activated by glucagon/PKA)
What happens to beta oxidation in a fasted state where glucagon concentration is high.
β oxidation is inhibited-
Malonyl-CoA inhibits transport of FFAs into mitochondria via CPT-1
Glucagon stimulates CPT-1
During fasting, what happens to the Acetyl-CoA which can not enter the TCA cycle? Where does this Acetyl-CoA come from?
Converted into ketone bodies
It comes from fatty acid breakdown which occurs during prolonged fasting
State the 3 types of ketone bodies
Acetoacetate
Acteone
Beta-hydroxybutyrate
Where are adrenocortical hormones released from?
The adrenal medulla in the adrenal gland
Name two physiological states can lead to the release of catecholamines?
Stress
Hypoglycaemia
Which amino acids are used to produce the monamines for catecholamines?
phenylalanine and tyrosine
Which molecules are broken down in short term stress and in long term stress?
Short term- liver converts glucagon to glucose which is released into the blood
Long term- Protein and fats are converted to glucose or broken down for energy
Where and how are Glucocorticoids released?
Where- Adrenal cortex in the adrenal gland
How- The cortex has many low density lipoprotein receptors. These enable cholesteral uptake for steroid hormone synthesis
Which hormone stimulates the release of cortisol? Where is this hormon produced?
adrenocorticotropic hormone
The pituitary
What are the metabolic functions of cortisol? List 4
It enhances gluconeogenesis
It inhibits glucose uptake
(and utilisation)
It stimulates muscle proteolysis
It stimulates adipose-tissue lipolysis
(rapid mobilisation of amino acids and fatty acid stores)
Which proteins are not broken down (mobilised) by cortisol?
Functional proteins-
Muscle contractile proteins
Neuronal proteins
How does cortisol help to resist stress and inflammation?
For stress it maintains blood pressure
For inflammation it suppresses it
What happens to your muscles when cortisol is elevated for prolonged periods of time?
Muscle wasting occurs due to proteolysis
What effect do growth hormones have on adipose tissues?
- Increases lipolysis
- Reduces glucose uptake
- Reduces lipogenesis
- Reduces the re-esterification of free fatty acids
- reduces body fat mass
When can ketone bodies by produced?
Starvation (prolonged fasting)
prolonged exercise
What effect do growth hormones have on skeletal muscle?
Reduces glucose uptake in skeletal muscle
Increases the activity of LPL’s
Increases beta oxidation
What effect do growth hormones have on the liver function?
Increases VLDL secretion from liver
Increases HL activity
Reduces PPARa expression
Increases production and uptake of IDL, LDL and HDL
Name the two types of thyroid hormones
Tetraiodothyronine, thyroxine (T4) and Triiodothyronine (T3)
What is the intracellular function of thyroid hormones?
activate nuclear receptors and transcription of large number of genes
Which thyrpid hormone is more potent and by how much?
T3 is about 4 times more potent than T4
Describe the difference in the concentrations of the two thyroid hormones within the tissues and within the blood
T4 is higher in the blood and T3 is higher in the tissues
This is because T4 concentration is higher in blood and it converted into T3 at the tissues
What is the main function of thyroid hormones. Describe 3 metabolic actions of thyroid hormones which enable this to occur.
Increase the basal metabolic rate
- Increase in the number and activity of mitochondria
Increases the rate of ATP synthesis - Stimulation of carbohydrate metabolism
Rapid glucose uptake
Enhanced glycolysis and gluconeogenesis
Increased insulin secretion - Stimulation of fat metabolism
Lipid mobilised rapidly from fat tissue
Increased fatty acids concentration in the plasma
What are incretins? Give 2 examples
Gastrointestinal hormones
- Glucagon-like peptide-1
- Gastric inhibitory peptide
What is the definition of hypoglycaemia?
any abnormally low plasma glucose concentration
that exposes the subject to potential harm” with a proposed threshold
plasma glucose value <70 mg/dL (<3.9 mmol/L)
Describe 5 causes of hypoglycemia
High insulin doses
Alcohol excess (inhibition of gluconeogenesis)
Insulinoma (A tumour of pancreatic β cells)
Excessive exercise (Leading to increased glucose utilisation)
Reactive hypoglycaemia (Excessive insulin secretion in response to a high carbohydrate meal in the pre-diabetic condition)
List 6 symptoms of mild hypoglycaemia
Trembling, palpitation, sweating, anxiety, hunger, tingling
List 6 symptoms of severe hypoglycaemia
Confusion, disorientation, convulsion, fitting, seizures,
loss of consciousness, coma
What happens in prolonged hypoglycaemia? What is the consequence of this?
Growth hormone and cortisol are secreted –
they decrease the rate of glucose utilisation
by most cells converting to fat utilisation?
neuroglycopaenia
(shortage of glucose for the brain)
Brain damage
Loss of cognitive function, seizures and coma
