Endocrinology

Question 1

Regarding metabolism in the fed state, where are glucose and AAs transported

Answer 1

From intestine to the blood

Question 2

Regarding metabolism in the fed state, where are dietary lipids transported

Answer 2

From the lymphatic system to the blood

Question 3

What does insulin stimulate

Answer 3

Storage of fuels and synthesis of proteins

Question 4

What is the fuel reserve of a well-fed human

Answer 4

161,000 kcal

Question 5

Energy needed for a 24 hr period

Answer 5

1600-6000 kcal

• sufficient reserves for starvation up to 1-3 months
• however glucose reserves are exhausted < 1 day

Question 6

Even under starvation what must the blood-glucose level be above

Answer 6

40 mg/100 ml

Question 7

In prolonged starvation, what is the first priority

Answer 7

Sufficient glucose for brain, nervous tissue, RBC

Question 8

In prolonged starvation, what is the 2nd priority

Answer 8

Preserve protein - lipolysis & gluconeogenesis

Question 9

After 3 days of starvation what do the brain and heart start to do

Answer 9

Use ketones as fuel

Question 10

After several weeks of starvation, what is the major fuel of the brain

Answer 10

Ketone bodies

Question 11

What happens when TAG stores must be used (prolonged starvation)

Answer 11

Increase protein degraded

Decrease heart, liver and kidney function

Question 12

What happens to 1. Glucose 2. Ketone body and 3. FA conc in plasma during starvation

Answer 12

1. Decreases but remains above 3-4 mM
2. Increases rapidly
   3, Increases slowly

Question 13

Decreasing order of total body metabolic fuel

Answer 13

1. Fat
2. Protein
3. Muscle glycogen
4. Hepatic glycogen
5. Circulating nutrients

Question 14

Decreasing order of circulating fuel

Answer 14

1. glucose

2. TAGs & free FAs

Question 15

What is the exocrine pancreas associated with

Answer 15

Acini - digestion (99%)

Question 16

What is the endocrine pancreas associated with

Answer 16

Islets of Langerhans - control of blood glucose (1%)

Question 17

What do the beta cells of the islets of langerhans release

Answer 17

Insulin (see photo)

Question 18

What do the alpha cells of the islets of langerhans release

Answer 18

glucagon (see photo)

Question 19

What do the gamma cells of the islets of langerhans release

Answer 19

Somatostatin

Question 20

Where are pancreatic polypeptides found and what do they do

Answer 20

Found between acinar cells and inhibit pancreatic secretion of fluid

Question 21

What is optimal blood glucose concentration

Answer 21

Normal fasting level = 90-100mg/100 mls (5mM)

Question 22

Effect of an increase in glucose on insulin

Answer 22

Increased insulin

Question 23

Effect of a decrease in glucose on insulin

Answer 23

Decreased insulin

Question 24

Vascularisation of islets

Answer 24

Richly vascularised

- 1-2% of pancreas but 10-15% pancreatic blood flow

Question 25

Effect of increasing plasma AAs on insulin

Answer 25

Large increase in insulin

Question 26

Effect of increasing free FAs on insulin

Answer 26

Increase in insulin

Question 27

Effect of increasing Glucagon on insulin

Answer 27

Increase in insulin

Question 28

Effect of increasing GH & GIT hormones on insulin

Answer 28

Increase in insulin

Question 29

What are the islets modulated by

Answer 29

ANS innervation - modulate insulin and glucagon secretion

Question 30

Which has a greater effect - orally administered glucose or IV administered glucose

Answer 30

Orally administered | - glucagon, glucagon derivatives, secretin, cholecystokinin & gastric inhibitory peptide stimulate insulin secretion

Question 31

What is the incretin effect

Answer 31

Gut-derived factors that enhance glucose-stimulated insulin secretion from the islet beta-cell ie a graph re-iterating that oral glucose has a greater effect than IV glucose infusion

Question 32

Where is Glucagon-like polypeptide 1 (GLP-1) synthesised

Answer 32

Within L cells located predominantly in ileum and colon & a lesser number in the duodenum and jejunum

Question 33

What does GLP-1 do

Answer 33

- stimulates insulin secretion - suppresses glucagon secretion - slows gastric emptying - reduces food intake - increases beta cell mass - maintains beta cell function (decreases beta cell apoptosis) - improves insulin sensitivity (muscle) - enhances glucose disposal (decreases glucose production in liver) - Increases cardiac protection and CO - decreases appetite - increases neuroprotection

Question 34

What effect of GLP-1 is preserved in type 2 diabetes

Answer 34

Glucose lowering effects

Question 35

1. Tissue distribution & 2. Special properties of GLUT 1

Answer 35

1. Most cells 2. High capacity Relatively low Km (5mM) => high substrate affinity

Question 36

1. Tissue distribution & 2. Special properties of GLUT 2

Answer 36

``` 1. Liver beta cells hypothalamus basolateral membrane of SI 2. High capacity but low affinity => high Km (15-20mM) Part of the glucose sensor in beta-cells ```

Question 37

1. Tissue distribution & 2. Special properties of GLUT 3

Answer 37

1. Neurons Placenta testes 2. Low Km (1mM) and high capacity

Question 38

1. Tissue distribution & 2. Special properties of GLUT 4

Answer 38

``` 1. Skeletal muscle Cardiac muscle Fat 2. Activated by insulin Km = 5mM ```

Question 39

1. Tissue distribution & 2. Special properties of GLUT 5

Answer 39

1. SI mucosal surface sperm 2. Primarily fructose carrier in intestine