endocrine lecture2

Question 1

How are insulin levels related to glucose levels?

Answer 1

they are directly coupled (high = high, low = low)

-if you uncouple them, thats diabetes

Question 2

when the body has to produce more insulin than normal ni order to control glucose its called _____

Answer 2

insulin resistance

Question 3

how do fatty acids in the blood affect insulin?

Answer 3

more fatty acids = more insulin resistance

Question 4

what is the structure of insulin?

Answer 4

protein hormone with 2 chains (A chain and B chain) connected with di-sulfide bridges

Question 5

what is pre-pro insulin?

Answer 5

A chain and B chain are linked together by “C-peptide”

Question 6

what is pro insulin?

Answer 6

pre-pro insulin, minus the N-terminus of B chains

Question 7

where is pro-insulin converted into insulin?

Answer 7

in the secretory vessicle, the C-peptide is cleaved

Question 8

where is insulin produced?

Answer 8

beta cells in the islets of langerhans of the pancreas

Question 9

what cell types are found in the islets of langerhans? what do they produce?

Answer 9

alpha cells = glucagon
beta cells = insulin
delta cells = somatostatin
pancreatic polypeptide cells = pancreatic polypeptide

Question 10

where does the pancreas excrete its horones?

Answer 10

directly into portal circulation…. to the liver

Question 11

C-peptide a great measure of _____ in the blood? Why?

Answer 11

• Great measure of Insulin.

- Because it doesnt get degraded by the liver on 1st pass

Question 12

what are the things that trigger insulin release?

Answer 12

glucose

amino acids

Question 13

what are the things that “modulate” the release of insulin?

Answer 13

• gut peptides from eating (these “potentiate” insulin release)
  (ex. : VIP, glucagon like peptides)

Question 14

what things inhibit insulin release?

Answer 14

-epinephrine (via alpha-adrenergic receptors)

Question 15

epinephrine acts via ____ receptors

Answer 15

alpha-adrenergic

Question 16

what 4 things happen to cause insulin release in response to increased glucose levels?

Answer 16

1. glucose enters beta cell
2. glucose metabolized into ATP
3. increased ATP closes K+ channels
4. depolarization open Ca++ channels… insulin exocytosis occurs

Question 17

what are the 2 types of glucose transporters?

Answer 17

GLUT2 = independent of insulin
GLUT4 = insulin dependent

Question 18

which GLUT is found on pancreatic beta cells?

Answer 18

GLUT2 (independent of insulin)

Question 19

what receptor does insulin bind to? what happens?

Answer 19

EGF family receptors (plasma membrane surface):

• autophosphorylates itself (tyrosine kinase)
• dimerizes itself
• phosphorylates IRS –> activates Pi3, MAPK, mTOR signal cascades

Question 20

what are the 3 sites of insulin action?

Answer 20

Liver
Muscle
Adipose

Question 21

what does insulin do to Liver?

Answer 21

Regulates enzymes which are responsible for catalyzing glucose storage pathways in the liver:

• glycogen creation
• triglyceride production (ex VLDL)

Question 22

what GLUT does liver express? muscle? adipose?

Answer 22

liver = GLUT2
muscle = GLUT4
adipose = GLUT4

Question 23

what does insulin do to the skeletal muscle?

Answer 23

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

Question 24

what does insulin do to the adipose tissue?

Answer 24

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)

Question 25

what are the main hormones which oppose insulin?

Answer 25

Glucagon***
epinephrine
GH