Blazyk Lipid Metab

8/2/2019 Blazyk Lipid Metab

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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


2/13


3/13

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



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Lipopr ot eins



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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



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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



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Bibliography

D. B. Marks, A. D. Marks, and C. M. Smit h, Basic Medical Biochemist r y: AClinical Approach, Wil liams & Wi lkins, 1996

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

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Blazyk Lipid Metab