Atherosclerosis and lipid metabolism

Question 1

Describe the exogenous pathway of lipid metabolism?

Answer 1

Absorption of fats from the diet.

Dietary triglycerides and cholesterol are broken down and packaged into chylomicrons (these are large structures)

The chylomicrons are then broken down lipids and into chylomicron remnants. This is catalysed by lipases.

These products can then end up in the adipose tissue and in the blood vessels.

NOTE: most of the lipids in our body are endogenous

Question 2

What is reverse cholesterol transport?

Answer 2

Cholesterol is taken out of blood vessels and foam cells (smooth muscles or macrophages stuffed full of lipids + cholesterol)

Conversion of HDL to LDL

Question 3

Describe the stages of atherosclerosis?

Answer 3

LDL gets into the endothelium

You get release of growth factors and cytokines, which attract inflammatory cells such as monocytes

Then you get the formation of foam cells in the endothelium, which are macrophages that contain a lot of lipid (cholesterol or cholesterol esters)

There will also be proliferation of fibroblasts and smooth muscle cells - this expands the plaque

Question 4

Describe endothelial dysfunction in atherosclerosis?

Answer 4

Endothelial dysfunction in atherosclerosis is characterised by a series of early changes that precede lesion formation

• Increased endothelial permeability
• Regulation of endothelial adhesion molecules
• Leukocyte adhesion
• Migration of leukocytes into the artery wall