Control of blood glucose & endocrine pancreas

Question 1

How does glucose get into cells?

Answer 1

→ Secondary active transport
→ SGLT 1
→ Sodium transports glucose into the cell

Question 2

How does glucose get reabsorbed in the kidney?

Answer 2

→ SGLT 1 and SGLT2

Question 3

Where is GLUT 1 found and in what ranges does it work?

Answer 3

→ In the brain + erythrocytes
→ High affinity for glucose
→ Constant uptake at 2-6mM

Question 4

Where is GLUT 2 found and what is the affinity like?

Answer 4

→ liver,kidney,pancreas,gut
→ Low affinity
→ Transport rate increases with glucose concentration

Question 5

Where is GLUT 3 found and what is its affinity?

Answer 5

→Brain

→ High affinity

Question 6

Where is GLUT 4 found and what is its affinity?

Answer 6

→ muscle and adipose tissue
→ Medium affinity
→ Insulin recruits transporters

Question 7

What does high affinity mean?

Answer 7

→ rate of transport does not depend on the concentration

Question 8

What are the islets of Langerhans?

Answer 8

→ Clusters of endocrine cells surrounded by an exocrine pancreas

Question 9

what do alpha cells in the pancreas produce?

Answer 9

→ Glucagon

Question 10

What do beta cells in the pancreas produce?

Answer 10

→ Insulin

Question 11

What do the delta cells in the pancreas produce?

Answer 11

→ Somatostatin

Question 12

What are the steps for insulin production?

Answer 12

1) original transcript is pre-pro insulin
2) Signal sequence is removed ( in RER)
3) Transferred to Golgi apparatus
4) Peptidases break off the C peptide leaving an A and B chain linked by disulfide bonds

Question 13

For every mole that is secreted of insulin how many C peptides do you get?

Answer 13

one

Question 14

What is the clinical significance of C peptide

Answer 14

→ It is inert

→ good index of insulin circulation

Question 15

What is the blood supply of the pancreas?

Answer 15

→ Branches of celiac, superior mesenteric and splenic arteries

Question 16

What is the venous drainage of the pancreas?

Answer 16

→ Into the portal system

Question 17

Describe the path insulin takes

Answer 17

→ Insulin is secreted in circulation
→ drained into portal vein
→ Metabolized by the liver
→ remainder is diluted in circulation

Question 18

Where is the insulin most concentrated?

Answer 18

→ in the portal vein

Question 19

Why is C peptide a more accurate index of insulin secretion?

Answer 19

→ It is not metabolized by the liver

Question 20

What stimulates the secretion of insulin from Beta cells ?

Answer 20

→ rise in plasma glucose 
→ amino acids - arginine
→ Glucagon 
→ Parasympathetic effects
→ Incretin hormones

Question 21

What inhibits insulin?

Answer 21

→ Alpha adrenergic receptors

→ somatostatin

Question 22

What stimulates glucagon secretion from alpha cells?

Answer 22

→ Amino acids
→ beta adrenergic
→ parasympathetic

Question 23

What inhibits glucagon secretion?

Answer 23

→ Plasma glucose
→ Somatostatin
→ Insulin

Question 24

How do beta cells sense a rise in glucose?

Answer 24

→ Increase in glucose through the GLUT 2
→ glucose is metabolized into ATP
→ ATP closes a K+/ATP channel
→ Depolarized the cell
→ Activates VG calcium channels
→ rise in iCa stimulates vesicular release of insulin

Question 25

What family is the insulin receptor a part of?

Answer 25

→ Tyrosine Kinase

Question 26

How does the insulin receptor work?

Answer 26

→ Insulin binds

→ Starts many protein activation cascades

Question 27

What are the protein cascades activated by the insulin receptor?

Answer 27

→ Translocation of the GLUT 4 transporter to plasma membrane and influx of glucose
→ Glycogen synthesis
→ Glyolysis
→ Fatty acid synthesis

Question 28

What enzyme starts lipogenesis and how?

Answer 28

→ACC starts lipogenesis

→ Insulin reduces PKA which inhibits ACC

Question 29

Why is insulin resistance not down to one reason?

Answer 29

→ could be something highly selective

→ because there are many intracellular pathways

Question 30

How does the glucagon receptor work?

Answer 30

→ Glucagon binds to its receptor
→ Adenylate cyclase converts ATP to cAMP
→ PKA is activated

Question 31

How do insulin counter regulatory hormones work?

Answer 31

→ phosphorylation of enzymes