Lipoproteins

Question 1

Apo A1

Answer 1

• most abundant in HDL
• synthesized by liver and intestine
• activates LCAT, which transfers FA from lecithin to cholesterol to make CE, involved in maturation of HDL
• involved in RCT (facilitates transfer of cell cholesterol by ABCA1 to HDL and delivery of CE and free cholesterol on HDL to the liver through SR-B1)
• antiatherogenic?

Question 2

Apo AII

Answer 2

• synthesized mostly in the liver
• present with A1 in some HDL
• activates lipoprotein lipase and inhibits LCAT
• proatherogenic?

Question 3

ApoB-100

Answer 3

• produced in liver
• binds to lipids from microsomal triglyceride transfer protein (MTP) to assemble VLDL
• 1 copy of ApoB-100 for each VLDL
• relationship is retained as LPs are metabolized to IDL and LDL
• numbers in plasma reflect particle number
• higher levels associated with CVD

Question 4

Apo-B-48

Answer 4

• truncated form of 100
• 48%
• involved in chylo metabolism, not recognized by LDL receptor

Question 5

Apo Cs

Answer 5

• can be exchanged freely among LP particles
• important for TG metabolism
• interfere with recognition of ApoE or displace ApoE from lipoproteins
• CII activates LPL and III inhibits LPL

Question 6

ApoE

Answer 6

• associated with all LPs except LDL
• recognized by LDLR and LRP (LDL receptor related protein)
• mediates the hepatic uptake of chylos and VLDL remnants as well as IDL
• responsible for clearance of intestinal derived LPs after a meal and for the clearance of VLDL and IDL before they are converted to LDL
• E2, 3, 4
• E3 is common
• E2 risk for type III hyperlipidemia (increased chylos and VLDL)
• E4 associated with Alzheimers

Question 7

PSCK9

Answer 7

• proprotein convertase subtilisin/Kexin 9
• protein that modulates LDLR
• upregulation causes degradation of LDLR and elevation of LDL
• downregulation does opposite and is associated with lifelong decrease in LDL and lower risk of CAD

Question 8

LRP

Answer 8

-LDL receptor related protein
-apoE receptor or CMR receptor
0mediates uptake of chyl remnants and VLDL
-recognizes apoE but notB
-mediates metabolism of major E containing LPs- chylos, IDL

Question 9

scavenger receptor A

Answer 9

• uptake of oxidized LDL into macrophages
• high cholesterol doesn’t stop it
• foam cells and fatty streaks

Question 10

scavenger receptor B

Answer 10

• CD36 and SR-B1
• uptake of cholesterol by liver and steroid producing cells
• depends in part on scavenger receptor class

Question 11

standard fasting lipid panel

Answer 11

• total cholesterol
• triglycerides
• HDL-C (after precipitation of ApoB)
• VLDL-C (TG/5)
• LDL-C- Fiedewals
• non-HDL cholesterol (total-HDL-C)