Lipoprotein Pathways and Cholesterol Part 2 Flashcards
ApoE
Ligand for LP receptors
Binds either of two LP receptors expressed in liver: LDL-R or LRP
LPL location
Capillary endothelia in fat and muscle
LCAT location
Bound to HDL in blood
Exogenous lipoprotein pathway –> CM & CMR
- Dietary fats digested & taken into enterocytes
- Enterocytes resynth lipids, then assemble & secrete CMs
3a. CM acted on by LPL in adipose capillaries until CII is released.
3b. CII collected by HDL
3c. CMR generated - CMR taken up by apoE binding to either LRP or LDL-R on liver cells
- CMRs disassembled
Endogenous LP pathway - delivering FA to adipose when g:i is low
- Liver assembles and secretes VLDL in response to liver TG
2a. LPL acts on VLDL until CII is released, generating IDL
2b. CII collected by HDL
LPL induced in adipose capillaries _____
by insulin, to store FA as TG
LPL induced in muscle capillaries _____
during fasting, to use FA for cellular fuel
Hepatic Lipase (HL) location
OUter hepatocyte surface
HL action
- w/o apo-p
- remove TG from IDL –> FA + glycerol until apoE falls off LP
Where does LDL go?
apoB100 binds to LDL-R
1/2 to liver
1/2 to peripheral cells (steroidogenic cells, macrophages)
LPL acts on ___ until ___ is released
VLDL
CII
Liver secretes ____ in response to liver TG
VLDL
Reverse Cholesterol Transport
- Liver secretes CE-poor HDL
- Chol is transported from peripheral cells by ABCA1 onto HDL surface
- LCAT converts surface chol into CE in HDL core –> CE rich HDL
- CE rich HDL delivers CE back to liver
What does liver do with CE rich HDL?
Liver converts chol –> BA (7alpha-OHase) then BA and some chol are secreted into bile.
How is Chol removed from body
Only via fecal elim of BA and chol
