Lipid Transport

Question 1

What carries 98% of the lipids around the body? What carries the other 2%?

Answer 1

98%- lipoprotein

2%- albumin

Question 2

What is lipoprotein lipase?

Answer 2

Enzyme that hydrolyses triacylglycerol in lipoproteins.

Requires ApoC-II as cofactors

Found attached to surface of endothelial cells in capillaries

Question 3

What is hyperlipoproteinaemias?

Answer 3

Raised plasma level of one or more lipoprotein classes

Question 4

What causes hyperlipoproteinaemias?

Answer 4

Either over production of the lipoproteins or under removal of them

This may be as result of a defect in an enzyme, a receptors or an apoprotein

Question 5

What are the clinical signs of hypercholesterolaemia?

Answer 5

Cholesterol deposits around the body:

1. Xanthelasma - yellow patches on eyelids
2. Tendon xanthoma - nodules on tendons
3. Corneal arcus - obvious white circle around eye. Commoninolder people but if present in young could be a sign of high cholesterol

Question 6

What causes type 1 hyperlipoproteinaemia?

Answer 6

Defective LPL - results in the under removal of lipoproteins

Question 7

What causes type IIa hyperlipoproteinaemia?

Answer 7

Defective LDL receptors- results in the under removal of lipoproteins

*associated with coronary artery disease that may be severe

Question 8

What causes type III hyperlipoproteinaemia?

Answer 8

Defective apoprotein - apoE - results in the under removal of lipoproteins

*raised IDL and chylomicron remnants.
Associated with coronary artery disease
rare

Question 9

How does a raised serum LDL level cause atherosclerosis? And what are the consequences of that?

Answer 9

1. LDLs have a longer half life meaning they’re more susceptible to oxidative damages
2. The oxidised LDLs are phagocytosed by macrophages
3. Macrophages become foam cells (due to high lipid content)
4. Foam cells accumulate in intima of blood vessel forming a fatty streak
5. fatty streak evolves in atherosclerotic plaque
6. Grows and encroaches on lumen (get angina or…)
7. Ruptures= triggers acute thrombosis by activating platelets and clotting cascade (causing stroke/MI)

Question 10

Where does a fatty streak occur?

Answer 10

In the intima of blood vessel walls

Question 11

How do you treat hyperlipoproteinaemia?

Answer 11

1. Diet and lifestyle
2. (If no response to first treatment) drugs:
   - statins (reduce choleric synthesis by inhibiting HMG-CoA reductase) ie atorvastatin
   - bile salt sequestrants (bind bile salts in gi tract forcing liver to produce more and use more cholesterol) ie colestipol