Lipoprotein Metabolism

Question 1

What happens when you remove cholesterol from a diet

Answer 1

The liver will start producing it

Question 2

Are triglycerides, phospholipids and cholesterol soluble or insoluble in blood

Answer 2

Insoluble

Question 3

What apolipoprotein do LDLs and VLDLs contain

Answer 3

Apolipoprotein B - looser to allow LDL particles to be bigger

Question 4

What apolipoprotein do HDLs contain

Answer 4

Apolipoprotein A - lots of kinks, tight sphere

Question 5

What do receptors in the liver bind to on lipoproteins

Answer 5

Apolipoprotein

Question 6

What’s the role of lipoproteins

Answer 6

Carry fat in the bloodstream

Question 7

What are VLDLs

Answer 7

Very low density lipoproteins

Question 8

Features of VLDLs

Answer 8

Rich in TAG
> 30nm
Atherogenic (contribute to disease)

Question 9

Features of LDLs

Answer 9

Rich in cholesterol
20-22nm
Atherogenic (contributes to disease)

Question 10

Features of HDLs

Answer 10

Rich in protein and phospholipid
9-15nm
Anti-atherogenic (reverse disease process)

Question 11

When is the production of the LDL receptor inhibited

Answer 11

When cholesterol accumulates

Question 12

What happens to damaged cholesterol

Answer 12

It’s consumed by macrophages

Question 13

How does HDL inhibit atherosclerotic process

Answer 13

• Inhibits expression of adhesion molecules
• Inhibits oxidation of LDL
• Promote cholesterol efflux (can take cholesterol out an artery and into liver)

Question 14

What changes in the transport of TAG after eating

Answer 14

Increased circulating TAG -> Increased TAG transported as VLDL

Question 15

Where do TAG-rich VLDLs unload TAG onto

Answer 15

Onto HDLs and LDLs

Question 16

What catabolises TAG-rich HDLs

Answer 16

Kidney, leading to fewer HDLs

Question 17

What does TAG get hydrolysed in

Answer 17

TAG-rich LDLs, leading to smaller and more dense LDLs (more dangerous)

Question 18

What is postprandial lipaemia

Answer 18

The elevation of lipid in the circulation seen in the hours after eating a fat-containing meal

Question 19

What happens to the intramuscular level of fat during exercise

Answer 19

It drops

Question 20

Light exercise reduces TAG response after a moderate-fat meal
This could be driven by a number of mechanisms

Answer 20

• Greater LPL activity to restore intramuscular TAG
• Less hepatic VLDL secretion as more fat is being oxidised
• Greater blood flow to previously exercised muscle and the liver

Question 21

How does training improve lipoprotein lipase activity in skeletal muscle and adipose tissue

Answer 21

• Improved delivery of FFA to active muscle
• Improved clearance of circulating triglycerides (postprandial). CVD patients show lower TAG clearance rates after a fatty meal

Question 22

How does insulin resistance impact TG

Answer 22

Decreases TG clearance
Increases FFA release
This is particularly a problem in the post-prandial state

Question 23

What does hormone sensitive lipase (HSL) do

Answer 23

Breaks stored TG and releases into circulation