20. Acute Regulation of Glucose

Question 1

How are B-cells stimulated to release insulin?

Answer 1

1. Detection - blood glucose is picked up by B-cells via GLUT-2 transporters and used to make ATP
2. Depolarisation - ATP production blocks K+ pump in the cell causing the membrane to depolarise
3. Release - Calcium influx causes exocytosis of insulin.

Question 2

There is a greater spike in insulin levels after taking IV glucose rather than orally.
True or False?

Answer 2

FALSE

insulin levels are much higher after taking glucose orally.

Question 3

Why is there a difference between insulin levels when glucose is taken orally vs. IV?

Answer 3

ACh & CCK signals from the GI tract also stimulate insulin release from B-cells.
IV glucose does not induce these signals, so there is less overall insulin release.

Question 4

Is insulin secretion driven by the sympathetic or parasympathetic nervous system?

Answer 4

Parasympathetic nervous system

Question 5

How marker can you use to measure endogenous insulin production? (how much insulin someone makes themselves)

Answer 5

C peptide (cleaved off of proinsulin to form insulin)

Question 6

What is the receptor for insulin?

Answer 6

Tyrosine kinase receptor

Question 7

Liver cells contain GLUT-4 transporters.

True or False?

Answer 7

FALSE

only GLUT-2

Question 8

What effects does insulin have on the liver?

Answer 8

1. ↑ glycogenesis
2. ↑ VLDL production
3. gluconeogenesis inhibited
4. Ketone body production inhibited

Question 9

What effects does insulin have on muscle?

Answer 9

1. GLUT-4 inserted to increase glucose uptake
2. ↑ glycogenesis
3. ↑ lipogenesis
4. ↑ protein synthesis

Question 10

What effect does insulin have on fat (adipocytes)?

Answer 10

1. GLUT-4 inserted to increase glucose uptake
2. ↑ lipogenesis
3. ↓ export of fatty acids + glycerol into blood

Question 11

What effect does glucagon have on the liver?

Answer 11

1. ↑ glycogenolysis

2. ↑ gluconeogenesis

Question 12

Glucagon is a GPCR.

True or False?

Answer 12

TRUE

Question 13

What effect does glucagon have on fat and muscle?

Answer 13

Fat = lipolysis
Muscle = proteolysis

Question 14

Somatostatin inhibits:
CCK, secretin, gastrin, insulin, glucagon.
True or False?

Answer 14

TRUE

Question 15

Exercise releases adrenaline, what effect does this have on metabolism?

Answer 15

1. ↑ glucose production in liver
2. glycogen breakdown in muscle
3. GLUT-4 insertion
4. Fatty acid release from adipocytes

Question 16

What does a high urine volume and the presence of glucose indicate?

Answer 16

Diabetes mellitus.

Lack of insulin action cause high plasma glucose levels which is lost in urine, water follows by osmosis.

Question 17

Why do people with type 1 diabetes lose weight?

Answer 17

Cannot produce enough insulin due to B-cell destruction by immune system.
Therefore there is more glucagon present that insulin.
Leading to:
lipolysis, proteolysis, gluconeogenesis, ketogenesis.

Question 18

What is the issue in type 2 diabetes?

Answer 18

Insulin resistance

Question 19

What is the difference between type 1 & 2 diabetes management?

Answer 19

Type 1: always need insulin.

Type 2: Diets to reverse problem, drugs to enhance insulin secretion and sensitivity.

Question 20

Where is insulin produced?

Answer 20

β-cells in the Islets of Langerhans in pancreas

Question 21

Where is glucagon produced?

Answer 21

α-cells in the Islets of Langerhans in pancreas