Metabolic consequences of obesity

Question 1

Are adipose tissues energy stores?

Answer 1

Yes, they can store vast amounts of energy HOWEVER this is not their only role.

Question 2

Other than storage, what are other functions of adipose tissues?

Answer 2

Can produce proteins (leptin, adiponectin etc) which act like hormones

Question 3

Describe how insulin works on a cell.

Answer 3

Insulin will attach to insulin receptor, causing it to express its tyrosine (amino acid) and phosphorylate. IRS-1 binds to it, also causing IRS-1 to phosphorylate. This then switches on PI3kinase which subsequently phosphorylates PIP2 to PIP3. PIP3 switches on a number of proteins (namely PKB/akt) which cause vesicles of GLUT4 transporters to move to the membrane, where they fuse.

Question 4

What is the difference in insulin stimulated tyrosine phosphorylation of insulin receptor and IRS-1 in obese and lean people?

Answer 4

Insulin stimulated tyrosine phosphorylation of insulin receptor and IRS-1 was far lower in obese muscle.

Question 5

What happens to amino acid phosphorylation when there is increased fat derivatives in the cell?

Answer 5

There is an increased serine phosphorylation, and a decreased tyrosine phosphorylation (meaning tyrosine cant be phosphorylated)

Question 6

What impact does insulin have on LPL?

Answer 6

Positive effect - increased fat clearance from blood stream

Insulin resistant = can’t clear blood of TG

Question 7

What impact does insulin have on HSL?

Answer 7

Inhibitory - helps keep fat partitioned away

Question 8

What does leptin do?

Answer 8

Insulin desensitising

Question 9

Do people with Type-2 diabetes have high or low levels of leptin?

Answer 9

High

Question 10

What is the relationship between BMI and adiponectin levels?

Answer 10

The greater the BMI, the less adiponectin.

Question 11

Can fat be oxidised in the cytosol of a cell?

Answer 11

No - Fat HAS to be oxidised in the mitochondria

Question 12

How does fat enter the mitochondria in order to be oxidised?

Answer 12

CPT1 protein

Question 13

How is malonyl-CoA formed and what does it do?

Answer 13

Acetyl-CoA converts to malonyl-CoA, via ACC protein.

Malonyl-CoA reduces CPT1 protein.

Question 14

How does adiponectin reduce malonyl-CoA content?

Answer 14

Through cascade events - adiponectin causes AMPK phosphorylation, which subsequently causes ACC phosphorylation, causing us NOT to produce malonyl-CoA

Question 15

What effect does training have on TNF?

Answer 15

Reduces it

Question 16

What effect does adiponectin have on TNF?

Answer 16

Increase