lipoproteins and lipid transport
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Lipoproteinsandlipidtransport
AtifH.Khirelsied,B.Sc,M.Sc,Ph.D.
Departmentof
Biochemistry
FacultyofMedicineandHealthSciences
InternationalUniversityofAfrica,Khartoum,Sudan
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Lipoproteinsstructure
cholesteryl esters)
Apolipoproteins onthesurface
large:apoB (b
48
and
B
100)
atherogenic
, ,
C assi ie ont e asiso ensityan e ectrop oretic
mobility(VLDL;LDL;HDL)
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Compositionandphysicalpropertiesofhuman
li o roteins
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Lipoproteinsstructure
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Theapolipoproteins
Essentialcomponentsoflipoproteins.
Oftenreferredtoasapoproteins
Classifiedby
alphabetical
designation
(A
thru
E)
Responsibleforrecognitionofparticlebyreceptors.
Somehavecatalyticorcoenzymeactivity.
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Apoproteins ofhumanlipoproteins
AI(28,300) principalproteininHDL
90120mg%inplasma;activatesLCAT
AII(8,700) occursasdimer mainlyinHDL
30 50mg%;enhanceshepaticlipaseactivity
B48 (240,000) foundonlyinchylomicron
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Pro ertiesofthema orclassesofa oli o roteins
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Electrophorogram ofplasmaproteins
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Chylomicrons
Formedinthemucosalcellsintheintestine.
suclavian veins.
Degradedto
remnants
by
the
action
of
lipoprotein
cellsurface
Remnantsaretakenupbyliverparenchymal cellsdue
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Dietarycholesterolisabsorbedasesterandtransportedin
ch lomicrons
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Thechylomicrons
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Transferofapoproteins fromHDLtochylomicrons
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VeryLowDensityLipoprotein(VLDL)
ascent st en nteractw t togenerate
mature
VLDLs
(with
added
cholesterol,
apoC
II
and
ature
s
are
acte
upon
y
p to
generate
VLDLremnants(IDL)
IDL
are
further
degraded
by
hepatic
triglyceride
pase togenerate s
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ThefateofVLDL
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LDLreceptor
Receptora soca e B Ereceptor ecauseo itsabilitytorecognizeparticlescontainingbothapos B
,
B100/apo
E
binding
Theintracellulardomainisresponsibleforclustering
membrane
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Cholesteroluptakeby
receptormediated
endocytosis.
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HighDensityLipoproteins(HDL)
Severalsubfamiliesexist
.
Itinteractswithchylomicron remnantsand
lecithincholesterol
acyl transferase
(LCAT)
to
form
HDL3
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ThefunctionofHDL
Trans ersproteinstoot er ipoproteins
Picksupcholesterolfromcellmembranes
ConvertscholesteroltocholesterolestersviatheLCAT
reaction
ransportc o estero esterstot e ver re erre toas
reversecholesteroltrans ort
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ThefateofHDL
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Thelecithincholesteryl acyl transferase (LCAT)
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Thelecithincholesteryl acyl transferase (LCAT)
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ReversecholesteroltransportbyHDL
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Thefunctionof CETP
Thecholesterolestertransfer
protein(CETP).
CETPtransferscholesterolesters
rom o nexc ange
fortriacylglycerol (TG)
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Atherosclerosis
Hardeningofthearteriesduetothedepositionof
Heartdiseaseistheleadingcauseofdeath
Causedby
the
deposition
of
cholesteryl esters
on
the
Atherosclerosis
is
correlated
with
hi h
LDL
and
low
HDL
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Atherosclerosis
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Factorspromotingelevatedbloodlipids
age
men>45yearsofage;women>55yearsofage
smoking
h ertension>140 90mmH
lowHDL
cholesterol
obesity>30%overweight
diabetesmellitus
inactivity/lackofexercise
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Optimalanddesirable levelsofserumcholesterolandLDL
cholesterol
concentrations
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