Lipid Transport Flashcards
Lipids are transported from
The gut to liver
The liver to non-hepatic tissue including adipoctyes
Non hepatic tissue back to liver
What are free fatty acids formed from?
Formed from triglycerides stored in adipose tissue
What are 5 types of lipoproteins characterised by centrifugation?
Chylomicrons Very low density lipoproteins (VLDL) Intermediate density lipoproteins (IDL) high density lipoproteins(HDL) Low density lipoproteins (LDL)
Describe the structure of lipoproteins?
Large protein= apolipoproteins
Hydrophilic region is exposed aqueous environment to blood
Hydrophobic region contained within structure
Single layer of lipid molecule
No hydrophobic core
Lipoprotein composition
More composition of TG, lower the density
Higher density, the more protein associated
Protein= apolipoproteins
What is function of apolipoproteins?
Structural
To solubilise lipids
Act as enzymes or enzyme cofactors
Tissue targeting => some apoproteins act as antagonist of receptors
Describe the structure of chylomicrons?
Low density due to high triglycerides
Contain fat soluble vitamins => vitamins A +E is important antioxidant preventing oxidation of lipids which are associated with heart disease
Chylomicrons remnants are largely protein content, little lipids. Short life cycle=> triglycerides is removed very quickly
VLDL
Where is it synthesised?
What metabolises it?
Synthesised in liver ER + Golgi released with B100 then acquire ApoE + C from HDL
Metabolised by LPL (lipoprotein lipase ?) as they circulate
Formation of VLDL is enhanced by….
Dietary carbohydrates
Circulating free fatty acid
Alcohol
Increase in insulin and decrease glucagon
What happens when VLDL loses triglycerides?
They change structure
Change in VLDL remnant => low lipid content
Some LDL used to form intermediate density lipoproteins
What is LDL?
Major carrier of cholesterol
Metabolised slowly (3 days)
Carry cholesterol to periphery + regulate de novo synthesis
What is HDL?
Made by de novo in liver + intestine by building from VLDL + chylomicrons + from free Apo1
Remove cholesterol from plasma
Contain enzyme lecithin cholesterol acyltransferase which esterifes cholesterol
Transported to liver + steroid producing cells
How is HDL important in cholesterol transfer?
HDL binds to lipoproteins + cells via ApoE
They return cholesterol to liver but transfer VLDLs and LDLs to cholesterol Ester transfer protein.
Require transporter ABCDA1 which transports cholesterol
What is HDL/LDL ratio used for?
Used to assess susceptibility to heart disease
HDL=GOOD cholesterol
LDL=BAD cholesterol
What do statins do?
Inhibit HMG-CoA reductase
Low intracellular cholesterol increases LDL receptor at cell surface
Leading to increase uptake of LDL
Lower circulating LDL
