33 Physiology of Insulin Secretion

Question 1

How many islets are in the pancreas?

Answer 1

3 million islets

Question 2

Total weight of endocrine pancreas

Answer 2

1 g

Question 3

Most abundant cell type in pancreatic islets

Answer 3

Beta cells (60%)

Question 4

Glucose transporter in beta cells

Answer 4

GLUT2

Question 5

First rate limiting step in the glycolytic pathway

Answer 5

Phosphorylation of glucose to glucose-6-phosphate

Question 6

Enzyme that mediates phosphorylation of glucose

Answer 6

Glucokinase

Question 7

Effect of sympathetic stimulation to insulin and glucagon secretion

Answer 7

Inhibits insulin secretion
Potentiates glucagon secretion
(Alpha 2 mediated NE release)

Question 8

Effect of parasympathetic stimulation to insulin and glucagon secretion

Answer 8

Enhances insulin and glucagon release
(M3 mediated)

Question 9

Most beta-cell neogenesis occurs during this period

Answer 9

Preterm

Question 10

Most beta cell neogenesis occurs during:

Answer 10

Preterm

Question 11

Full complement of beta cells is established within how many years of life

Answer 11

5 years

Question 12

Average lifetime of beta cells

Answer 12

25 years

Question 13

Estimated pancreatic insulin content

Answer 13

200-250 units

Question 14

Number of secretory granules within beta cell cytoplasm

Answer 14

5000-8000

Question 15

Insulin granule half life

Answer 15

<5 days

Question 16

Proportion of renal C-peptide uptake that is excreted intact

Answer 16

15%

Question 17

Fraction of portal insulin that is removed by the liver in its first pass

Answer 17

65% (50-70%)

Question 18

Overall contribution of the liver to insulin clearance (first pass plus recirculation)

Answer 18

80%

Question 19

Among antidiabetic agents, this drug class is known to reduce insulin clearance

Answer 19

Sulphonylurea

Question 20

Contribution of first phase insulin secretion in suprabasal secretion during 2 hour OGTT

Answer 20

10% or ~3 nmol/m2

Question 21

Pulse intervals of insulin secretion

Answer 21

5-14 mins

Question 22

Slower ultradian cycles of insulin secretion

Answer 22

80-180 mins

Question 23

First phase insulin secretion lasts for how long

Answer 23

5-8 mins

Question 24

Phenomenon that describes that plasma glucose and insulin secretory responses are attenuated during the second, as compared to with the first meal

Answer 24

Staub-Traugott effect

Question 25

Product of insulin secretion and sensitivity indices

Answer 25

Disposition index

Question 26

In individuals with IGT, AIR compensation is reduced until insulin sensitivity drops below:

Answer 26

50 mcmol.min-1.kgFFM.nM-1

Question 27

NGT/ IFG/ IGT/ T2D:
Highest total insulin output (2 hours)

Answer 27

IGT