Physical Activity and CVD Risk Factors: lipoprotein metabolism

Question 1

What is a lipoprotein?

Answer 1

When TGL, phospholipids, and cholesterol are packaged with proteins. They are made of a hydrophobic core (TGL and cholesterol esters) surrounded by amphipathic coat.

Question 2

What are chylomicrons and VLDL rich in?

Answer 2

TAG (>30nm)

Question 3

What are LDL rich in?

Answer 3

Cholesterol (20-22nm)

Question 4

What are HDL rich in?

Answer 4

Protein and phospholipid (9-15nm)

Question 5

If you have modified LDL (damaged cholesterol) in the intima, what effect does this have?

Answer 5

This will increase cytokines such as MCP-1. This will increase diapedesis. It can also accelerate maturation of monocytes to macrophages. It can also increase adhesion molecules.

Question 6

What is the most significant role of modified cholesterol?

Answer 6

Macrophages consume it in an UNCONTROLLED way.

Question 7

How do most cells inhibit production of LDL receptor when cholesterol accumulates?

Answer 7

LDL receptor synthesized inside the cell and moves to membrane. When LDL (containing cholesterol) attaches, cell takes cholesterol and uses it. If cholesterol levels rise above what cell needs, LDL receptor becomes inhibited.

Question 8

How do macrophages differentiate from normal cells in terms of cholesterol accumulation?

Answer 8

Scavenger receptors - Due to macrophages nature (to engulf pathogens), modified LDL will attach to scavenger receptors and be engulfed. Macrophage then has HUGE amounts of cholesterol, however scavenger receptors WILL NOT be turned off due to macrophages role.

Question 9

How does HDL inhibit atherosclerotic process?

Answer 9

• HDL promotes cholesterol efflux (take cholesterol out of artery wall and back into blood stream where its taken back to liver for excretion)
• HDL inhibits cholesterol oxidation
• HDL inhibits expression of adhesion molecules

Question 10

How does HDL cause cholesterol efflux?

Answer 10

Immature HDL in blood can take up free cholesterol in macrophage in tissue. This becomes fixed in HDL by enzyme LCAT

Question 11

What effect does exercise training have on blood lipid profiles (TC, LDL-C, TG, HDL-C)?

Answer 11

TC = decrease
LDL-C = decrease
TG = decrease
HDL-C = increase

Question 12

Does exercise have a direct impact on cholesterol?

Answer 12

No - however it reduces the amount of TAG in circulation and this has an impact on cholesterol.