Which is an abnormal lipoprotein?
Ans. is 'a' i.e., Lipoprotein-X* IDL or Intermediate Density Lipoprotein is a normal lipoprotein formed from VLDL. IDL then gets converted to LDL.* So LDL is also a normal lipoprotein which carries cholesterol ester and has apo B100 as its apoprotein* Lipoprotein(a) is a lipoprotein subclass. It has LDL like particle attached to apo(a) attached to apoBlOO# This apo(a) is a plasminogen analogue and hence it competitively inhibits tissue plasminogen activator. As plasmin is not formed, there is decreased fibrinolysis.# It stimulates the release of plasminogen activator inhibitor as well.# Hence thrombogenesis is favoured.# Apo (a) is also a carrier of cholesterol.# It also stimulates the release of proinflammatory cytokines.# Put together, Lipoprotein(a) is a normal lipoprotein which favours atherogenesis.# Concentration of Lp(a) is heritable. Depending upon the number of kringle domains present in apo(a), the rate of synthesis is variable. More the number of kringle domains, longer will be the time taken for synthesis and lesser will be the concentration of Lipoprotein(a) in circulation.# Lesser Lipoprotein(a) is favourable.* Lipoprotein- X is the abnormal discoidal lipoprotein that is present either in obstructive jaundice or in LCAT deficiency]# Lipoprotein-X has only phospholipid and cholesterol, both of which are amphipathic. Because there are no non polar lipids like cholesterol ester and triacylglycerol, there is no non polar lipid core in the centre to form a spheroidal lipoprotein.# Such abnormal lipoproteins are found in obstructive jaundice. Because in obstructive jaundice, the VLDL gets effluxed back into circulation, wherein they interact with plasma protein like albumin to lose the non polar lipids and form a discoidal Lipoprotein - X# They are also found in LCAT or Lecithin Cholesterol Acyl Transferase deficiency. Because LCAT is the enzyme which converts discoidal HDL to Spheroidal HDL# Hence Lipoprotein-X is an abnormal lipoprotein
Lipoprotein-X
Lipoprotein(a)
IDL
LDL
Lipids