Diabetes and endocrinology

Question 1

What are the main cells of the islets of langerhans?

Answer 1

Alpha - Glucagon :
Beta - Insulin:
Gamma - Pancreatic polypeptide:
Delta - Somatostatin

Question 2

Describe the blood supply to the islets

Answer 2

Afferent arterioles of pancreatic duodenal arteries

Nerves: Vagus nerve and middle splachnic nerves

Question 3

Describe the structure of insulin

Answer 3

51 amino acid sequence made of 2 chains joined by disulphide bonds

Pro insulin is cleaved to produce insulin and C peptide

Question 4

Why does glucagon secretion increase after a protein rich meal?

Answer 4

L arginine is a potent stimulator of glucagon

Question 5

Describe the functions of somatostatin

Answer 5

• Secreted in the fed state
• Released from delta cells
• Contracts pyloric sphincter, inhibits gastric acid secretion and reduces GI motility/secretion
• May slow nutrient absorption and hence a rise in BGC

Question 6

What stimulates insulin release?

Answer 6

Noradrenaline
High blood glucose: Induces exocytosis of insulin from beta cells and can induce the effects of amino acids and fatty acids
High dietry amino acids
Neural signals + incretins

Question 7

Describe the biphasic release of insulin

Answer 7

Insulin initially released from granules near cell surface more rapidly, granules further away from the surface release insulin more slowly

Question 8

How does insulin exocytosis occur?

Answer 8

Low ATP:ADP means Glucose enters cells via GLUT2 channel

Glucokinase phosphorylates glucose -> glucose-6-phosphate

Energy and ATP are produced which close K+ channels

Ca2+ channels open stimulating exocytosis of insulin granules to outside of cell

Question 9

What is the importance of cell to cell contact in the islets?

Answer 9

3D structure of clusters of endocrine cells is important to maintain the normal function for insulin secretion

When islets become disaggregated to a single cell they loose the ability to respond to glucose + the biphasic release of insulin

When the 3D structure returns glucose induced biphasic insulin release returns

Question 10

What transporter does the muscle and adipose tissue use and what is this uptake dependent on?

Answer 10

Glucose uptake is dependent on insulin

GLUT4

Question 11

Which organs are not dependent on insulin for glucose uptake and which transporter do they use?

Answer 11

Brain ( steady): GLUT3

Liver - ( Rapid): GLUT2

Question 12

Describe the basal bolus regimen in diabetes treatment

Answer 12

Basal = long acting insulin analogue 
Bolus = rapid acting insulin at meal time to deal with the correct glucose load