Lipid Transport and Storage

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LIPID TRANSPORT AND STORAGE BIOMEDICAL IMPORTANCE Lipids are insoluble in water, w ater, or transport in t!e a"ueous plas#a, t!e$ are %o#bined wit! a#p!ipat!i% lipids and proteins to #a&e water'#is%ible lipoproteins( LIPIDS ARE TRNASPORTED IN T)E PLASMA AS LIPOPROTEINS *O+R MAOR LIPID CLASSI*ICATION CLASSI*ICATION -( tria%$l.l$%erol /-012 3( P!os!olipid /-412 5( C!olesterol /-412 4( C!olester$l ester /5012 6( *ree *att$ A%id /412 '#ost a%ti7e *O+R MAOR GRO+PS O* PLASMA LIPOPROTEINS -( C!$lo#i%rons 'deri7ed ro# intestinal absorption o tria%$l.l$%erol and ot!er lipids 3( 8er$'low 8er$'low densit$ lipoprotein 'deri7ed ro# li7er or t!e e9port o tria%$l.l$%erol 5( low'densit$ lipoprtoein 'representin. a inal sta.e in t!e %atabolis# o 8LDL 4( !i.!'densit$ lipoprotein 'in7ol7ed in %!olesterol transport also in 8LDL and %!$lo#i%rons #etabolsi# Tria%$.l$%erol 'predo#inant lipids in %!$lo#i%rons and 8LDL C!olesterol and p!osp!olipid 'predo#inant lipids in LDL and )DL CLASSI*ICATION ACCDG TO ELECTROP)ORETIC PROPERT PROP ERTIES IES -( alp!a'/)LD2 3( beta'/LDL2 5( pre'beta/8LDL2 LIPOPROTEINS CONSIST O* A NON POLAR CORE AND SINGLE S+R*ACAE S+R*ACAE LA:ER O* AMP)IPAT)IC AMP)IPAT)IC LIPIDS  Nonpolar lipid %ore surrounded b$ a sin.le sura%e la$er o a#p!ipat!i% p!osp!olipid and %!olesterol #ole%ule(

Apolipoprotein;Apoprotein 'protein #oiet$ o lipoprotein %onstitutin. ES T)E LIPOPROTEIN -( Apo As ')DL 3( Apo B /B'-==2 'LDL and also 8LDL 'one o t!e lon.est sin.le pol$peptide %!ains &nown B'4? '%!$lo#i%rons in intestine B'-== '%!$lo#i%rons in li7er  Roles o Apolipoprotein@ -( stru%tural /apo B2 3( En$#e %oa%tors %oa% tors /C'II or A'I2 En$#e In!ibitor /Apo A'II, Apo C'III, Apo C'I2 5( li.ands /apo B'-== and Apo'E2 *REE *ATT: *ATT: ACIDS ARE RAPIDL: METABOLI>ED **A 'arise in t!e plas#a ro# t!e brea&down o tria%$.l$%erol in adipose tissue or as a result o t!e a%tion o lipoprotein lipase on t!e plas#a plas#a a%$l.l$%erol 'ound in %o#bination wit! albu#in 're#o7ed ro# blood e9tre#el$ rapidl$ and o9idied or esteriied to or# tria%$.l$%erol in t!e tissue 'upta&e is dire%tl$ related to t!e plas#a **A %on%entration and t!us re.ulate lipol$sis Me#brane *att$ a%id Transporter Protein 'a%t as trans#e#brane %otransporter wit! Na *att$ a%id bindin. protein 'w!ere **A are bound on enterin. t!e %$tosol TRIAC:LGL:CEROL TRIAC:LGL:CEROL IS TRANSPORTED *ROM T)E INTESTINES IN C):LOMICRONS AND *ROM LI8ER IN 8ER: LO DENSIT: LIPOPROTEINS C!$lo#i%rons 'ound in %!$le /drainin. l$#p!ati%s o intestine2 'responsible or t!e transport o all dietar$ lipids to %ir%ulation 8LDL '!epati% in ori.in '7e!i%les o transport o tria%$l.l$%erol ro# t!e li7er to t!e e9tra!epati% tissue Abetalipoproteine#ia 'lipoproteins %ontainin. apoB are not or#ed and lipid lipid droplets a%%u#ulate in t!e intestine and li7er 

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C):LOMICRONS AND 8LDL ARE RAPIDL: CATABOLI>ED C!$lo#i%rons '%learan%e ro# blood is 7er$ rapid 'disappearan%e bein. under - !our in !u#ans 'lar.er parti%les are %atabolied #ore "ui%&l$ t!an s#aller '**A ro# %!$lo#i%rons .oes to@ ?=1 'adipose tissue, !eart and #us%le 3=1 'li7er  'li7er does not #etabolie nati7e %!$lo#i%rons or 8LDL si.nii%antl$ TRIAC:GL:CEROL O* C):LOMICRONS  8LDL ARE ):DROL:>ED B: LIPOPROTEIN LIPASE TO *ORM REMNANT LIPOPROTEINS Lipoprotein lipase 'walls o blood %apilaries '!eart, adipose tissue, spleen, lun., renal #edulla, aorta, diap!ra.#, la%tatin. #a##ar$ .land 'not a%ti7e adult li7er  )epati% lipase 'li7er sinusoids 'in7ol7ed in %!$lo#i%ron re#nants and )DL #etabolis# )eparin Ine%tion 'tri..ers release o t!ese en$#es ro# t!eir site o bindin. P!osp!olipids and apo C'II '%oa%tor or lipoprotein lipase a%ti7it$ Apo A'II and apo C'III 'in!ibitorF Redire%tion o ree att$ a%ids ro# adipose tissue to t!e !eart in star7ed state and in #a##ar$ .land in la%tation( 8LDL re%eptor 'pla$s an i#portant part in t!e deli7er$ o att$ a%ids ro# 8LDL tria%$l.l$%erol to adipo%$tes b$ bindin. 8LDL and brin.in. it into %lose %onta%t wit! lipoprotein Lipase Insullin 'en!an%e lipoproteins lipase s$nt!esis C!$lo#i%ron re#nant 'about !al t!e dia#eter o t!e  parent %!$lo#i%ron and relati7el$ enri%!ed in %!olesterol and %!olester$l esters be%ause o t!e loss o tria%$l.l$%erol 8LDL re#nants  inter#ediate Densit$ lipoprotein /IDL2 T)E LI8ER IS RESPONSIBLE *OR T)E +PTAHE O* REMNANT LIPOPROTEINS Apo E '#ediates upta&e 7ia 3 apo E'dependent re%eptors@

-( LDL /apo B'-==, E2 re%eptor  3( LRP'- /LDL re%eptor'related protein'-2 Dual role o )epati% lipase@ -( li.and 'a%ilitate re#nant upta&e 3( )$drolies re#nant tria%$l.l$%erol and  p!osp!olipids LDL IS METABOLI>ED 8IA LDL RECEPTOR  LDL /apo B'-==, E2 re%eptor 'li7er and e9tra!epati% tissue 5=1 'de.raded in t!e e9tra!epati% tissue