Atherosclerosis and Lipid-lowering pharm Flashcards
Atherosclerosis is a degenerative and inflammatory disease that causes the ________ and ________ of vessels.
Thickening and loss of elasticity
In which part of vessels does atherosclerosis most commonly occur?
Medium and large arteries, most commonly where they bifurcate/branch
What are 4 constitutional risk factors for atherosclerosis?
1) Age
2) Male gender
3) FHx
4) Genetics
What are 4 modifiable risk factors for atherosclerosis?
1) HLD
2) HTN
3) DM
4) Smoking
In which layer of vessels do atheroma form?
Tunica intima
What are the 3 principal components of atheromas?
1) Fibrous cap: Smooth muscle cells, macrophages, T cells
2) ECM (collagen, elastic fibers, proteoglycans)
3) Necrotic center: Intra and extracellular lipids, cell debris, cholesterol
What are 3 complications of atherosclerosis?
1) Vessel wall thickening → ↓ tissue perfusion → ischemia
2) Loss of elasticity → aneurysm, rupture, hemorrhage
3) Endothelial change → thrombosis
What are the different types of atherosclerotic lesions?
Early: fatty streak
Established: Atheromatous plaque (friable, prone to complications)
Complicated
What are 3 forms of chronic atherosclerotic stenosis?
1) Stable angina
2) Chronic IHD
3) Bowel Ischemia
4) Ischemic encephalopathy
5) Intermittent claudication
What are the 5 forms of acute plaque change?
1) Rupture
2) Fissure
3) Erosion
4) Ulceration
5) Hemorrhage
How do px with acute plaque changes normally present?
Intermittent claudication:
- pain in calf, thigh, butt, induced by exercise, relieved by rest
- progressive worsening
Unstable plaques are often (smaller/larger) and have (more/less) fibrous tissue than stable plaques.
Smaller and less fibrous tissue
What are the factors that determine the stability of a plaque?
1) Intrinsic:
- structure and composition (<fibrous → ↑unstable)
- ↑ MMP by macrophages → ↑ collagen and ECM degradation → ↑unstable
- ↓ TIMP by macrophage/endothelial/smooth muscle → ↓ MMP inhibition → ↑unstable
2) Extrinsic:
- ↑BP → ↑unstable
- Platelet reactivity → ↑prothrombotic → ↑unstable
What is the pathogenesis of atherosclerosis?
1) Chronic endothelial injury (by hemodynamic factors, HLD, Smoking, etc.)
2) Lipids accumulate in tunica intima + endothelial dysfunction
3) Macrophage adhesion/activation by VCAM-1 → Inflammation
4) Smooth muscle recruitment by inflammation (by cytokines/growth factors)
5) Macrophages engulf but cannot digest excess oxidised LDL → foam cells
6) Smooth muscle secrete ECM and engulf lipids → fibrous cap
7) Structural change of vessel wall
How do foam cells form in artheromas?
Circulating monocytes adhere to dysfunctional vessel wall by VCAM-1 → activated
→ recruit inflammatory cells → recruit more macrophages (+ve feedback)
→ macrophages engulf but cannot digest excess LDLs that have been oxidised by free radicals
→ foam cells
How does hyperlipidaemia lead to atherosclerotic plaque?
↑LDLs → ↑circulating apoproteins
+ endothelial injury → ↑ lipids accumulate in tunica intima
The greater the triglyceride content in lipoproteins, the (higher/lower) the density of lipoproteins.
↑ triglyceride → ↓ density
The greater the protein content in lipoproteins, the (higher/lower) the density of lipoproteins.
↑ protein → ↑ density
What are chylomicrons?
From in mucosal epithelia of small intestine and contain mainly dietary lipids
- transported to adipose tissue for storage
What are VLDLs?
Very low density lipoproteins
- synthesised in hepatocytes
- contain mainly endogenous lipids
- FA used for storage by adipocytes and muscle cells for ATP
What are ILDLs?
Intermediate low density lipoproteins
- triglyceride depletion of VLDLs
- taken up my liver for reprocessing
- form LDL after further triglyceride depletion
What are LDLs?
Low density lipoproteins
- deposit cholesterol in and around smooth muscle fibers in arteries → fatty plaque → ↑CAD risk
What are HDLs?
High density lipoproteins
- made in liver
- removes excess cholesterol from cell and transport to liver for elimination → ↓CAD risk
How is exogenous triglycerides/cholesterol transported in tissues?
1) core triglycerides in chylomicrons (from small intestine) hydrolysed by lipoprotein lipase
2) tissues take up free FAs
3) chylomicron remnants bind to hepatocyte receptors and get endocytosed
4) cholesterol is stored, oxidised to bile acids, or secreted in bile unaltered
5) can also enter endogenous pathway in VLDL
How is endogenous triglycerides/cholesterol transported in tissues?
1) cholesterol/synthesised triglycerides transported from liver as VLDL to muscle and adipose tissue
2) triglycerides hydrolysed → FA enter tissues
3) VLDL → ILDL → LDL
4) Cells take up LDL by endocytosis via LDL receptors that recognise LDL apolipoproteins
5) cholesterol can return to plasma from tissues in HDLs
What are the 6 types of dyslipidaemias?
Type 1: ↑ Chylomicrons
Type 2a: ↑ LDL
Type 2b: ↑ LDL, ↑ VLDL
Type 3: ↑ ILDL
Type 4: ↑VLDL
Type 5: Chylomicrons
(decreasing risk of Cholesterol, except type 1)