Insulin counter-regulatory hormones Flashcards
What are the key properties of glucagon?
29 amino acid peptide
made by alpha cells in islets of langerhans in the pancreas
How is glucagon formed?
preproglucagon -> proglucagon -> glucagon
In what conditions are glucagon secreted?
low blood glucose levels
increase amino acid levels (arginine and alanine)
exercise
What is the glucagon receptor like?
7 fold transmembrane GPCR receptor
How does glucagon signalling work?
glucagon binds to the GPCR receptor -> activates cAMP -> protein kinase A activation -> phosphorylates phosphorylase kinase -> glycogen phosphorylase converts glycogen to glucose-6-phosphate
What are the effects of glucagon?
glycogenolysis amino acid uptake gluconeogenesis glycolysis inhibited (PFK1 inhibited) lipolysis (HSL activation) ketogenesis beta oxidation of fatty acids (CPT-1 activation)
What happens in prolonged fasting?
oxaloacetate replaces amino acids for gluconeogenesis
formation of acetoacetate (ketone) inhibited by glucagon so don’t get excess cholesterol or TGA
What are the adrenocortical hormones?
Steroid hormones - mineralocorticoids, glucocorticoids, androgens
What are the main examples of catecholamines?
Epinephrine (adrenaline), norepinephrine (noradrenaline) and dopamine
Where are catecholamines and glucocorticoids made?
- adrenal gland medulla (catecholamines)
- adrenal cortex (glucocorticoids)
What is the function of catecholamines?
Released during stress/hypoglycaemia
ST: increase glucose and lipid levels
Inhibit insulin secretion, glycogenolysis, glucagon secretion, lipolysis
What is the function of glucocorticoids?
Steroid hormone
LT: protein and lipid use
What is ACTH, what does it do?
Glucocorticoid
released in anterior pituitary gland causing cortisol secretion which maintains bp and inflammation and:
Allows gluconeogenesis, inhibits glucose uptake, allows muscle proteolysis -> muscle wasting, allows lipolysis
Where are growth hormones found and what do they do?
In adipose tissue -> lipolysis, decreased glucose uptake, decreased lipogenesis
In skeletal muscle -> decreased glucose uptake, increased lipoprotein lipase activity
Liver -> increased VLDL secretion, HDL and LDL production and secretion
What is the function of thyroid hormones?
increase metabolic rate
increase mitochondrial number and activity = increased ATP synthesis
Glucose uptake, glycolysis, gluconeogenesis, insulin secretion
lipids mobilised from adipose so increased fatty acid concentration
