INSULIN

Question 1

Half life of insulin

Answer 1

5-6 min

Question 2

Uses of C peptide

Answer 2

Assessment of Beta cell function
Distinguish between endogenous and exogenous hyperinsulinemia

Question 3

Factors the promote insulin secretion

Answer 3

Glucose
Fatty acids
Ketones
Amino acids

Question 4

Why does oral glucose have a higher insulinotropic effect than IV glucose

Answer 4

Due to the incretin effect

Question 5

Which adrenergic receptors promote and inhibit insulin secretion

Answer 5

Alpha-2 inhibits secretion
Beta-2 promotes secretion

Question 6

Effect of vagal nerve stimulation on insulin release

Answer 6

Promotes insulin secretion

Question 7

What effect does any condition that activates sympathetic system have on insulin release

Answer 7

Inhibits it through alpha2 receptor activation

Question 8

What is the rate limiting step in glucose metabolism in the beta cells

Answer 8

Phosphorylation by Glucokinase (Hexokinase IV)

Question 9

The different forms insulin goes through during secretion

Answer 9

Insulin is initially synthesized as preproinsulin
Preproinsulin is cleaved to produce proinsulin
Proinsulin is then cleaved to Insulin and C peptide

Question 10

Parts of preproinsulin

Answer 10

Single peptide (SP)
B chain
C-peptide
A chain

Question 11

Are the actions of insulin anabolic or catabolic

Answer 11

Anabolic

Question 12

Functions of insulin

Answer 12

Stimulates glycogenesis, lipogenesis, protein synthesis and inhibits their catabolism

Inhibits gluconeogenesis

Stimulates transport of substrates and ions into cells

Question 13

What type of receptor is the insulin receptor

Answer 13

Kinase linked receptor

Question 14

Types of kinase linked receptors

Answer 14

Receptor tyrosine kinases

Serine/thréonine kinases

Cytokine receptor

Question 15

Examples of receptor tyrosine kinases

Answer 15

EGF, FGF, insulin receptors , NGF, Toll like receptors

Question 16

Examples of serine/threonine kinases

Answer 16

Transforming growth factor

Question 17

Effect of insulin oh glycogen synthase

Answer 17

Insulin enhances the activity of glycogen synthase

Question 18

Which hormones stimulate insulin secretion

Answer 18

Glucagon
Growth Hormone
Corticotrophin
Placenta Lactogen
Secretin
Gastrin
Cholecystokinin
Catecholamines

Question 19

Which hormones stimulate insulin secretion

Answer 19

Glucagon
Growth Hormone
Corticotrophin
Placenta Lactogen
Secretin
Gastrin
Cholecystokinin
Catecholamines
Incretins

Question 20

How does hypoxia affect insulin release

Answer 20

Inhibits insulin release

Question 21

Name the incretins

Answer 21

GIP- Gastric inhibitory peptide or Glucose dependent insulinotropic peptide

GLP-1 - Glucagon-like peptide-1

Question 22

Functions of the incretins

Answer 22

Increase insulin secretion
Prevent beta cell apoptosis
Inhibit glucagon release
Increases satiety
Reduce gastric emptying time

Question 23

Which enzyme inactives the incretins

Answer 23

DPP-4
Dipeptidyl peptidase-4

Question 24

Explain the incretin effect

Answer 24

Oral glucose intake elicits a higher insulin response compared to IV glucose that produces the same levels of serum glucose levels.

Question 25

Source of the incretins

Answer 25

GIP - K cells of the duodenum and jéjunum
GLP- 1- L cells of the ileum and colon

Question 26

Structure of insulin

Answer 26

51 amino acids
A chain - 21 amino acids
B chain - 30 amino acids

Question 27

How is insulin release in response to glucose

Answer 27

Biphasic insuline response
Initial repaid release in the first 2 minutes
Second release 5-10 mins later

Question 28

How is glucose different from other products in stimulating insulin release

Answer 28

Only glucose stimulates synthesis of insulin