Composition of Lipoproteins:
- Consists of non-polar core (Mainly Triglycerides and cholesteryl esters)
- A single surface layer of amphipathic phospholipids and cholesterol
- Protein moiety are known as Apoprotein or Apolipoprotein
- Protein and lipid contents vary
Synthesis of Chylomicrons and VLDL:
Metabolism of Chylomicrons:
- Synthesised in intestine
- Transport TAG (Triacylglycerol) to tissues and deliver remaining cholesterol & cholesterol ester to the liver.
Metabolism of VLDL, LDL and IDL:
- VLDL is synthesised in liver and converted to LDL which contain an increased proportion of cholesterol & cholesteryl ester (due to loss of TAG).
- Transport TAG and cholesterol from liver to tissues.
- Cholesterol in LDL referred to as “bad cholesterol” since LDLs are implicated in atherosclerosis
Metabolism of HDL (High Density Lipoprotein):
- HDL carries “used” cholesterol (as CE) back to the liver. Also donate some CE to circulating VLDL for redistribution to tissues.
- HDL taken up by liver and degraded. The cholesterol is excreted as bile salts or repackaged in VLDL for distribution to tissues.
- Cholesterol synthesis in the liver is regulated by the cholesterol arriving through HDL (and dietary cholesterol returned by chylomicron remnants).
- Cholesterol (CE) in HDL is referred to as “good cholesterol”.
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