Ch. 18: Lipids III: Plasma Lipoproteins Flashcards
Apoliproteins: ApoA-I
Associated lipoprotein?
Function/characteristics?
HDL
Activates lecithin:cholesterol acyltransferase (LCAT)
Apoliproteins: ApoB-48
Associated lipoprotein?
Function/characteristics?
Chylomicrons
Derived from apoB-100 gene via RNA editing in intestinal epithelium
Lacks LDL receptor-binding domain of apoB-100
Apoliproteins: ApoB-100
Associated lipoprotein?
Function/characteristics?
VLDL, IDL, LDL
Binds to LDL receptor
Apoliproteins: ApoC-I
Associated lipoprotein?
Function/characteristics?
Chylomicrons, VLDL, IDL, HDL
May also activate lecithin:cholesterol acyltransferase (LCAT)
Apoliproteins: ApoC-II
Associated lipoprotein?
Function/characteristics?
Chylomicrons, VLDL, IDL, HDL
Activates lipoprotein lipase (LPL)
Apoliproteins: ApoC-III
Associated lipoprotein?
Function/characteristics?
Chylomicrons, VLDL, IDL, HDL
inhibits lipoprotein lipase (LPL)
Apoliproteins: ApoD
Associated lipoprotein?
Function/characteristics?
HDL
Associated with lecithin:cholesterol acyltransferase (LCAT)
Apoliproteins: ApoE
Associated lipoprotein?
Function/characteristics?
Chylomicron remnants, VLDL, IDL, HDL
Binds to LDL receptor
Lipoprotein lipase (LPL):
What time of enzyme is this?
In what tissues is it concentrated?
What is its function?
Serine esterase
Muscle & adipose tissue
Main enzyme in processing chylomicrons & VLDL (via hydrolysis of FAs from TAGs)
Hepatic lipase:
What are its functions?
What does it respond positively to? Negatively to?
Continues lipolysis of VLDL & IDL ➡️ LDL
Hydrolyzes PLs and HDL-TAGs
➕: androgens
➖: ⬆️ estrogen
Lecithin:cholesterol acyltransferase (LCAT):
What does it circulate with?
What is its function?
HDL, LDL, ApoD, Cholesteryl ester transfer protein (CETP)
Transfers LCFAs from PLs to cholesterol ➡️ forms cholesterol esters (for storage & transport in lipoprotein core)
Acyl-CoA:cholesterol acyltransferase (ACAT):
Location?
What is its function?
Intracellular enzyme
Esterifies free cholesterol via linking to an FA ➡️ for storage in liver parenchymal cells
What is the forward cholesterol transport pathway?
Transport cholesterol from liver ➡️ peripheral cells & tissues
(via VLDL ➡️ IDL ➡️ LDL)
What is the reverse cholesterol transport pathway?
Transport of cholesterol from extrahepatic tissues ➡️ liver, for excretion in bile
(via HDL)
Hyperlipoproteinemia: phenotype I
Lipoprotein in excess?
Chylomicrons
Hyperlipoproteinemia: phenotype IIa
Lipoprotein in excess?
LDL
Hyperlipoproteinemia: phenotype IIb
Lipoprotein in excess?
LDL
VLDL
Hyperlipoproteinemia: phenotype III
Lipoprotein in excess?
Beta-VLDL
Hyperlipoproteinemia: phenotype IV
Lipoprotein in excess?
VLDL
Hyperlipoproteinemia: phenotype V
Lipoprotein in excess?
Chylomicrons
VLDL
Lipid-lowering drugs: Cholestyramine & colestipol
Characteristics/Function?
Non-absorbable resins
Interrupt enterohepatic circulation of bile acids
Lipid-lowering drugs: Nicotinic acid
Characteristics/Function?
➖ hepatic secretion of VLDL, suppresses mobilization of FAs ➡️ ⬇️ VLDL & LDL
Lipid-lowering drugs: Clofibrate, gemfibrozil
Characteristics/Function?
➕ LPL ➡️ rapid turnover of VLDL
Gemfibrozil: ➖ VLDL secretion
Lipid-lowering drugs: Probucol
Characteristics/Function?
Blocks intestinal cholesterol transport ➡️ ⬇️ plasma cholesterol (no effect on TAG)
⬇️ HDL cholesterol levels
Lipid-lowering drugs: Statins
Characteristics/Function?
➖ regulatory step of cholesterol biosynthesis
➖ hepatic cholesterol synthesis, upregulates LDL receptor activity ➡️ ⬇️ serum cholesterol & LDL cholesterol
