endocrine lecture2 Flashcards
How are insulin levels related to glucose levels?
they are directly coupled (high = high, low = low)
-if you uncouple them, thats diabetes
when the body has to produce more insulin than normal ni order to control glucose its called _____
insulin resistance
how do fatty acids in the blood affect insulin?
more fatty acids = more insulin resistance
what is the structure of insulin?
protein hormone with 2 chains (A chain and B chain) connected with di-sulfide bridges
what is pre-pro insulin?
A chain and B chain are linked together by “C-peptide”
what is pro insulin?
pre-pro insulin, minus the N-terminus of B chains
where is pro-insulin converted into insulin?
in the secretory vessicle, the C-peptide is cleaved
where is insulin produced?
beta cells in the islets of langerhans of the pancreas
what cell types are found in the islets of langerhans? what do they produce?
alpha cells = glucagon
beta cells = insulin
delta cells = somatostatin
pancreatic polypeptide cells = pancreatic polypeptide
where does the pancreas excrete its horones?
directly into portal circulation…. to the liver
C-peptide a great measure of _____ in the blood? Why?
- Great measure of Insulin.
- Because it doesnt get degraded by the liver on 1st pass
what are the things that trigger insulin release?
glucose
amino acids
what are the things that “modulate” the release of insulin?
- gut peptides from eating (these “potentiate” insulin release)
(ex. : VIP, glucagon like peptides)
what things inhibit insulin release?
-epinephrine (via alpha-adrenergic receptors)
epinephrine acts via ____ receptors
alpha-adrenergic
what 4 things happen to cause insulin release in response to increased glucose levels?
- glucose enters beta cell
- glucose metabolized into ATP
- increased ATP closes K+ channels
- depolarization open Ca++ channels… insulin exocytosis occurs
what are the 2 types of glucose transporters?
GLUT2 = independent of insulin GLUT4 = insulin dependent
which GLUT is found on pancreatic beta cells?
GLUT2 (independent of insulin)
what receptor does insulin bind to? what happens?
EGF family receptors (plasma membrane surface):
- autophosphorylates itself (tyrosine kinase)
- dimerizes itself
- phosphorylates IRS –> activates Pi3, MAPK, mTOR signal cascades
what are the 3 sites of insulin action?
Liver
Muscle
Adipose
what does insulin do to Liver?
Regulates enzymes which are responsible for catalyzing glucose storage pathways in the liver:
- glycogen creation
- triglyceride production (ex VLDL)
what GLUT does liver express? muscle? adipose?
liver = GLUT2 muscle = GLUT4 adipose = GLUT4
what does insulin do to the skeletal muscle?
binds to insulin receptors…. causing the expression of GLUT4 on the surface of the muscle cells which drives glucose into the cells
-results in glycogen and lactic acid
what does insulin do to the adipose tissue?
binds to insulin receptors… causing the expression of GLUT4 on the surface of the adipocytes which drives glucose into cells
- results in triacylglycerol and LPL increase
- LPL is an enzyme that converts blood VLDL into FFAs which are then stored in the adipocyte
- also inhibits “Hormone sensitive lipase” (an enzyme which breaks down fat into glycerol/FFAs)
