blazyk lipid metab
TRANSCRIPT
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Lipid Met abolism in t he Liver
and I t s Role in Fat Digest ion
J ack Blazyk, Ph.D.Depar t ment of Biomedical Sciences
OU College of Ost eopat hic Medicine
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Lipid and Carbohydr at e Met abolism in t he Liver
I n t he f ed st at e,car bohydrat e can be
convert ed t o f at and
expor t ed via VLDL
I n t he f ast ed st at e,
f at t y acids ar e
oxidized t o pr oduceenergy and ket one
bodies ar e expor t edas f uel f or ot her
t issues
Cholest erol is t hepr ecur sor of bile
acids t hat ar e used inf at digest ion in t hegut
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Lipid Digest ion
Digest ive enzymesf r om t he pancreas ar e
act ivat ed by bile salt s
t o conver t TG t o f at t yacids and 2- MG
I nt est inal cells
r esynt hesize TG andexpor t chylomicr ons
int o cir culat ion
Most of t he bile salt s
ar e r et ur ned t o t he
liver f or r euse
M a r k s
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Bile Acids and Bile Salt s
H a r p e r s
Bile acids and bilesalt s ar e made in t he
liver f r om
cholest erol
The gall bladder
delivers bile salt s t ot he gut f or
emulsif icat ion
Bact eria modif y t hebile salt s and most is
reabsorbed by
int est inal cells
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Ent erohepat ic Cir culat ion
M a r k s - F i g . 3 4 . 2 0
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M e i s e n b e r g & S i m m o n s
Solubil it y of Cholest erol in Bile
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Overview of Cholest erol Tr anspor t
Cholest erol is est eri f ed
int r acellular ly by acyl-CoA:cholest er ol acylt r ansf erase or
by lecit hin: cholest erol
acylt r ansf erase in lipopr ot eins
Chylomicr ons pick up pr ot einsf r om HDL
The liver is t he maj or or gan in
which cholest erol is pr ocessed
Lipoprot eins car r y TG and
cholest erol t hrough t he
cir culat or y syst em
M e i s e n b e r g & S i m m o n s
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Lipopr ot eins
M e i s e n b e r g & S i m m o n s
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M e i s e n b e r g & S i m m o n s
Tr anspor t of Diet ar y Fat t o t he Liver
I nt est inal cells packagediet ar y f at (most ly TG)
int o chylomicr ons
Chylomicr ons pick up
pr ot eins f r om HDL
Lipopr ot ein l ipase (LPL)r emoves TG f or use in
t issues (Apo-C-I I act ivat es
LPL)
Chylomicr on r emnant s ar e
t aken up by t he liver
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Expor t of Fat f r om t he Liver
TG and cholest erol isexpor t ed f r om t he liver
as nascent VLDL
VLDL picks up pr ot einsf r om HDL
Lipoprot ein lipase (LPL)r emoves TG f or use in
t issues (Apo-C-I I
act ivat es LPL)
VLDL is t r ansf or med t o
LDL dur ing cir culat ion
LDL delivers cholest erol
t o t issues by recept or -
mediat ed upt ake
M e i s e n b e r g & S i m m o n s
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Role of HDL in Lipid Met abolism
Nascent HDL is expor t edf r om liver and int est inal
cells
Free cholest erol is picked
up f r om cells and ot her
lipoprot eins, along wit hot her component s
LCAT conver t s cholest erol
t o cholest erol est ers (CE)
CE is t r ansf err ed t o ot her
lipoprot eins
HDL r et ur ns cholest erol
t o t he liver
M e i s e n b e r g & S i m m o n s
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Bibliography
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G. Meisenber g, and W. H. Simmons, Pr inciples of Medical Biochemist r y, Mosby,1998
R. K. Mur r ay, D. K. Gr anner, P. A. Mayes, and V. W. Rodwell , Har per s
Biochemist r y, Applet on & Lange, 1999