Lecture 16: Endocrine Pancreas

Question 1

What hormones does the endocrine pancreas release and from where?

Answer 1

Alpha Cells: Glucagon
Beta Cells: Insulin and C peptide
Delta Cells: Somatostatin
F cells: pancreatic polypeptide (satiety signal)

Question 2

Endocrine cells of the pancreas are arranged in clusters called what?

Answer 2

Islets of Langerhans

Question 3

What do delta cells look like?

Answer 3

Neuronal

-send dendrite like cells to beta cells

Question 4

How do endocrine cells of the pancreas communicate with each other?

Answer 4

Gap junctions

Question 5

How does blood flow in the endocrine pancreas?

Answer 5

Starts at the center of the islet and flows to the periphery

Question 6

What type of hormone is insulin: catabolic or anabolic?

Answer 6

Anabolic

• promotes glucose uptake
• promotes glycogenesis, lipogenesis, and protein synthesis

Question 7

What is a peptide hormone?

Answer 7

2 chains linked by disulfide bridges

Question 8

What is the difference between preproinsulin, proinsulin, and insulin?

Answer 8

Preproinsulin: Signal Peptide + A and B chains + C peptide (no disulfide bonds)

Proinsulin: A and B chains + C peptide

Insulin: A and B chains

Question 9

What is the significance of C peptide?

Answer 9

Marker of endogenous insulin secretion

-normally, secreted in equimolar quantities of insulin

Question 10

Where are GLUT-2 transporters normally found?

Answer 10

Liver (main)

Pancreatic Beta Cells

Question 11

Describe how insulin is released from beta cells?

Answer 11

1. Glucose enters via GLUT-2
2. GLU –> GLU-6-Phosphate (promotes ATP production)
3. ATP closes inward-rectifying potassium channels (cell becomes more negative)
4. Plasma membrane is depolarized
5. Voltage gated calcium channels open
6. Calcium enters cells to release insulin

Question 12

Why are sulfonylurea receptors targeted for type II diabetes treatment?

Answer 12

Increased membrane depolarization causes increased calcium entry –> more insulin released

Question 13

Describe the biphasic model of insulin release.

Answer 13

First phase: rapid release of insulin

Second phase: slow release of insulin

Question 14

In diabetic individuals, which phase of insulin secretion does not work?

Answer 14

First phase

Question 15

After insulin receptors are phosphorylated and complete their downstream pathways, what vesicle is translocated to the membrane?

Answer 15

GLUT 4

Question 16

Other than insulin, activation of what can result in GLUT 4 translocation?

Answer 16

Activation of AMP-kinase

-muscle contractions stimulate this process

Question 17

What inhibits insulin secretion?

Answer 17

Somatostatin

Question 18

What activates glucagon secretion?

Answer 18

Decreased glucose levels
CCK
β-adrenergic agonists

Question 19

What inhibits glucagon secretion?

Answer 19

Insulin (main)
Somatostatin
Fatty Acids
Ketoacids

Question 20

What is the physiology behind Type I diabetes?

Answer 20

Destruction of β-cells

-increased blood glucose, fatty acids, and keto acids

Question 21

In type I diabetes, do patients have hyperkalemia or hypokalemia?

Answer 21

Hyperkalemia

-insulin plays a role in Na+/K+ ATPase (not working properly)

Question 22

What is the physiology behind Type II diabetes?

Answer 22

Insulin resistance

-exhaustion of β-cells

Question 23

Describe obesity induced insulin resistance.

Answer 23

Decreased GLUT-4 uptake of glucose

-more insulin and glucose in blood

Question 24

What are incretin hormones?

Answer 24

Stimulate insulin secretion to lower blood glucose levels.

• released after eating from beta cells
• intestine derived hormone (GLP-1, GIP)