Hyperlipidaemias Flashcards
What is atherosclerosis?
build up of plaque in arteries = thickening or hardening of arteries
What are the stages of atherosclerosis?
- LDLs travel through endothelial barrier lumen
- LDL oxidised
- macrophages attracted to oxidied LDL, also enter artery wall
- macrophage phagocytose oxidised LDL = foam cell
- foam cells expand
- undergo death, release lipid content = recruitment of inflammatory cytokines
- growth factors released = smooth muscle proliferation = ⬆ collagen synthesis = hardening of plaque - plaque-> narrowing of artery
- plaque can rupture -> thrombosis = risk of clots
what is foam cell filled with?
lipids
whats plaque in wall (atherosclerosis) made of? 5
dead foam cells foam cells immune cells collagen smooth muscle cells
What is the structure of lipoproteins?
lipid core of trigl + cholesterol esters
coat containing apoproteins - mediate binding of lipoproteins with tissues in body using receptors on those tissues
what about a lipoprotein affects which tissue and receptor it will bind to?
coat containing apoproteins- type affects..
name some lipproteins
chylomicrons
VLDL
LDL
HDL
transport pathways of lipoproteins?
exogenous
endogenous
Which lipid pathway involves lipids in the diet?
exogenous
What are lipids (TGs and cholesterol esters) emulsified by in the GIT?
bile acids
lipids are emsulsified in the GIT.. what are absorbed into?
chylomicrons
Explain how a foam cell is formed?
- LDL travels through endothelial barrier -> lining of artery
- LDL oxidised
- macrophages attracted and enter lining
- macrophages phagocytose oxidised LDL forming a foam cell
What do foam cells do after they are formed?
- continue to expand
- undergo death
- release lipid content and recruit inflammatory cytokines
- release growth factors
- smooth muscle proliferates
- increased collagen synthesis
- plaque hardens
What is the consequence of plaque rupturing?
thrombosis
Describe the exogenous lipid pathway
involves lipid in the diet
emulsified by bile acids in the GIT
lipids absorbed into chylomicons
triglycerides hydrolysed by lipoportein lipase, produces free fatty acids = absorbed and stored in fat and muscle tissues
chylomicron remnants - taken up by hepatocytes = store of cholesterol
Describe the endogenous lipid pathway
liver
makes C and TG from exogenous pathway
lipids excreted into VLDL
TGS hydrolysed by same enzyme, fatty acids produced and stored in tissues
LDLS now contain mainly cholesterol esters
extrahepatic
cholesterol from cell turnover absorbed into HDL
cholesterol esters transferred to LDL and VLDL
increased HDL promotes LDL removal
What are TGs hydrolysed by to produce free fatty acids?
lipoprotein lipase
Where are free fatty acids absorbed and stored?
fat and muscle tissues
What are chylomicrons an excess of?
TG
what are chylomicron REMNANTS an excess of and how do they appear in liver?
CE (cholesterol)
yellow!
What are chylomicrons taken up in order to contribute to the store in the liver?
hepatocytes
Endogenous pathway:
2 sites
liver
extrahepatic (reverse cholesterol transport)
liver makes cholesterol (C) and TG + C from what pathway?
exogenous
What is Acetyl co enzyme A converted to in the liver?
what enz is involved?
ACoA —- > MVA (Mevalonate)
HMG CoA reductase
After mevalonate is formed what gets secreted into VLDLs?
lipids (both TG and cholesterol esters CE)
In the endogenous pathway VLDLs travel through muscle and fat tissue and bind to receptors on the wall of muscle and fat tissue. What are they hydrolysed to?
free fatty acids
What do LDLs mostly contain at the end of the endogenous pathway in the liver?
cholesterol esters
The extra hepatic pathway is called the reverse cholesteral transport. What is absorbed into HDL from cell turnover?
cholesterol
and from developing plaques
HDLs contain cholesterol esters in the extra hepatic pathway but do not travel. What happens to them instead?
transferred to VLDLs and LDLs via CETP, change in apoprotein = more likely to be taken up by hepatocytes due to ⬆ levels of HDLs
Give 3 uses of LDLs in the body?
membranes, steroids and bile acids