Sialic acid content of low density lipoprotein and its relation to lipid concentrations and metabolism of low density lipoprotein and cholesterol

Transcription

1 Sili id ontent of low density lipoprotein nd its reltion to lipid onentrtions nd metolism of low density lipoprotein nd holesterol Nin Lindohm, Helen Gylling, nd Ttu A. Miettinen 1 Deprtment of Mediine, University of Helsinki, FIN HYKS Helsinki, Finlnd Astrt A low sili id ontent in low density lipoprotein (LDL) hs een ssoited with therogeniity nd oronry rtery disese (CAD) in mny ut not ll studies. We investigted ssoitions of the sili id-to-polipoprotein B (pob) rtio of LDL with lipoprotein lipid onentrtions, kinetis of LDL, metolism of holesterol, nd the presene of CAD in 98 sujets (, n 56;, n 42). The sili id rtios of totl, dense, nd very dense LDL were lower in the thn sujets, espeilly t high sili id rtios. The LDL sili id rtio ws inversely ssoited with respetive lipid nd pob onentrtions nd positively with lipid-to-pob rtios of LDL. The trnsport rtes (TRs) for totl nd dense LDL pob were negtively ssoited with their sili id rtios. The sili id rtio of dense LDL, ut not tht of totl LDL, ws inversely orrelted with serum levels of holesterol preursor sterols, inditors of holesterol synthesis, nd positively with serum levels of plnt sterols, inditors of holesterol sorption. In ddition, the TR for dense LDL ws positively orrelted with holesterol synthesis. In onlusion, low LDL sili id rtio ws ssoited with CAD, high numers of smll LDL prtiles, nd high TR for LDL pob, nd in dense LDL lso with high synthesis nd low sorption of holesterol. Lindohm, N., H. Gylling, nd T. A. Miettinen. Sili id ontent of low density lipoprotein nd its reltion to lipid onentrtions nd metolism of low density lipoprotein nd holesterol. J. Lipid Res : oronry rtery disese (CAD) hs een shown to e sili id poor ompred with LDL from helthy ontrols in some (7 9, 13) ut not ll (14 16) studies. Thus, the role of the sili id ontent of LDL in therogenesis is somewht ontroversil, ut s whole, erlier studies suggest tht the sili id ontent of LDL might ffet its ility to use therogenesis. Only few studies of limited numer of ptients hve investigted the effet of the sili id ontent of LDL on its metolism in vivo. Mlmendier et l. (17) showed tht desilyltion inresed the toli rte of LDL. However, in Type II dieti ptients the sili id-to-pob rtio of dense LDL ws positively relted to its frtionl toli rte (14), while in nondieti sujets (18) the rtio ws not ssoited with LDL pob tolism; however, the lower the sili id rtio, the higher the prodution rte of dense LDL pob. Assoitions of LDL sili id ontent with the metolism of holesterol hve not een previously investigted. Vrile findings out the importne of LDL sili id ontent provoked us to investigte ssoitions of the sili id ontent of totl LDL nd its sufrtions with the presene of CAD, lipoprotein lipid onentrtions, kinetis of LDL, nd metolism of holesterol in lrge group of hyperholesterolemi sujets without nd with CAD. pob lthosterol plnt sterol holes- Supplementry key words terol sorption PATIENTS AND METHODS Sili ids re loted in the terminl ends of mny rohydrte hins of glyolipids nd glyoproteins, inluding polipoprotein B (pob) (1, 2). Desilyltion of low density lipoprotein (LDL) hs een shown to inrese its inding to rteril proteoglyns (3) nd its uptke into ells (4 7). In ddition, strong negtive orreltion hs een reported etween the sili id ontent of LDL nd the mount of holesterol umulted intrellulrly (7 10). However, two other studies reported no effet of the sili id ontent of LDL on its inding nd degrdtion in ells (11, 12). LDL of minly mle ptients with Ptients Ninety-eight sujets, 53 women nd 45 men, were reruited for the study from the outptient lini of our hospitl. Fifty-six sujets ( ), 30 men nd 26 women, were dignosed with CAD on the sis of history of myordil infrtion (n 37), oronry ngiogrphy (n 14), or exerise iyle test (n 5), Arevitions: BMI, ody mss index; CAD, oronry rtery disese; FCR, frtionl toli rte; Lp[], lipoprotein []; LDL, low density lipoprotein; TR, trnsport rte. 1 To whom orrespondene should e ddressed Journl of Lipid Reserh Volume 41, 2000

2 while the remining 42 sujets ( ) hd no symptoms or mnifesttions of CAD on linil interview nd exmintion, or s reveled y eletrordiogrm (ECG). None of the sujets hd dietes mellitus or gstrointestinl, liver, or kidney disese. Three women hd een reeiving thyroxin tretment for hypothyroidism, nd they hd een euthyroid for severl yers. The sujets were not tking ny lipid-lowering medition t the time of the study. Sujets hd een ounseled t lest 6 months erlier to dhere to low-ft, low-holesterol diet, nd they hd done so. Forty-four sujets were tking et-loking gents, 6 sujets were tking thizide diuretis, nd 15 of the 53 women were reeiving hormone replement therpy. Twentyfour sujets were urrent smokers. All the sujets gve informed onsent to prtiipte in the study. The study protool ws epted y the ethis ommittee of our hospitl. Methods Blood smples were drwn fter 12-h fst. Serum lipoproteins were seprted y ultrentrifugtion (19). After totl LDL hd een seprted, it ws further frtionted into three sufrtions: light (d g/ml), dense (d g/ ml), nd very dense (d g/ml) in 60 Ti fixed-ngle rotor (Bekmn Instruments, Fullerton, CA) for 44 h t 58,000 rpm nd 10 C, s desried in detil previously (20). Totl nd free holesterol, triglyerides, phospholipids, pob, nd lipoprotein [] (Lp[]) in serum nd lipoproteins were nlyzed with ommeril kits (Boehringer Dignosti, Mnnheim, Germny; Wko Phrmeutils, Kyoto, Jpn; Orion Dignosti, Espoo, Finlnd; nd Merodi AB, Uppsl, Sweden). Sili id ws nlyzed from totl LDL nd its sufrtions y the modified resorinol method (21, 22), using N-etylneurmini id (Sigm, St. Louis, MO) s the stndrd. In the following, the sili id ontent of LDL is expressed s its rtio to pob nd is referred to s the sili id rtio. To exmine differenes in nd sujets t different sili id levels, oth nd sujets were divided into qurtiles y the sili id rtios of totl nd dense LDL, with equl numers of sujets in eh qurtile (Q 1 Q 4 from low to high sili id rtios). In 82 sujets, serum nonholesterol sterols, inluding the holesterol preursor sterols 8 -lthosterol, desmosterol, nd lthosterol, the plnt sterols mpesterol nd sitosterol, nd hoestnol were determined in nonsponifile serum extrts y gs liquid hromtogrphy on 50-m long SE-30 pillr y olumn (23). Beuse they re trnsported in serum y lipoproteins, like holesterol, the onentrtions of the nonholesterol sterols re highly dependent on serum holesterol levels. Thus, the vlues re expressed s 10 2 mmol/mol of serum holesterol, i.e., s rtios to holesterol, to eliminte the effet of vrition in holesterol levels. Of the totl 98 sujets, 58 rndomly seleted sujets volunteered to prtiipte in the lipoprotein kineti study. First, 50 ml of fsted EDTA plsm ws drwn, nd totl (d g/ml) nd dense (d g/ml) LDL were seprted y seril density ultrentrifugtions. Totl LDL pob ws iodinted with 131 I, nd dense LDL pob with 125 I, y modifition of the iodine monohloride method (24, 25). Approximtely 1 mg of mixture of the utologous leled totl nd dense LDL pob ws mixed with 5% humn serum lumin, filtered, nd injeted into eh ptient. Three dys efore the injetion the sujets strted to tke perorl potssium iodide. The totl mount of rdiotivity did not exeed 60 Ci. After the injetion, lood smples were olleted for 14 dys nd ounted. The die-wy urves were onstruted from plsm for 131 I-leled LDL nd 125 I-leled dense LDL. Frtionl toli rtes (FCRs) for totl nd dense LDL pob were determined using TABLE 1. Vrile Clinil hrteristis in nd groups nd in the omined group (n 42) two-pool model (26). Trnsport rtes (TRs) were lulted y multiplying the FCRs y the pool size, whih ws the poprotein plsm onentrtion multiplied y pproximted plsm volume, i.e., 4.5% of ody weight. Sttistis Groups were tested for signifint differenes y nlysis of vrine, Chi-squre test, nd Student s two-tiled t test. Correltions were nlyzed y lulting the Spermns rnk-order orreltion oeffiient. A stepwise logisti regression nlysis ws rried out with the presene of CAD s the dependent vrile, nd LDL holesterol nd triglyeride onentrtions, the LDL sili id rtio, nd the FCR nd TR for LDL pob s the independent vriles. To explin vriility in the LDL sili id rtio, stepwise regression nlysis ws used with the presene of CAD, the onentrtions of holesterol nd triglyerides in LDL, nd the FCR nd TR for LDL pob s the independent vriles. A P vlue less thn 0.05 ws onsidered signifint. RESULTS (n 56) Comined (n 98) Age, yers BMI, kg/m Wist-to-hip rtio Femles/mles 27/15 26/30 53/45 ApoE phenotype 3/2, 4/ / /3, 4/ Vlues represent mens SE. The sili id rtios of totl LDL nd its sufrtions were similr in mles nd femles nd in smokers nd nonsmokers (dt not shown). In the whole study group nd in the group, the sili id rtios of totl LDL nd its sufrtions were not ffeted y et-loker tretment ( vs g/mg in totl LDL in users vs. nonusers), ut in totl LDL of hypertensive sujets tking et-lokers (n 6) it ws lower thn in sujets not tking et-lokers (n 34) TABLE 2. Sili id rtio per pob in totl LDL nd its sufrtions in nd sujets (n 42) Sili Aid Rtio (n 56) g/mg pob Totl LDL Light LDL Dense LDL Very dense LDL Vlues represent mens SE. Lindohm, Gylling, nd Miettinen Sili id in LDL nd metolism of LDL nd holesterol 1111

3 TABLE 3. Sili id rtios per pob in totl nd dense LDL of nd sujets in qurtiles (Q 1 Q 4 ) divided for oth groups seprtely ording to the sili id rtios of totl nd dense LDL, respetively Sili Aid Rtio g/mg pob Totl LDL Q Q d Q d Q Dense LDL Q Q Q d Q d Vlues represent mens SE. d P ( g/mg vs g/mg, respetively, P 0.01). Use of thizide diuretis or, mong femles, tht of hormone replement therpy hd no effet on the LDL sili id rtio (dt not shown). Age, ody mss index (BMI), sex, or poe phenotype distriutions were not ssoited with the sili id rtios of totl LDL nd its sufrtions, nd they were similr in the nd groups (Tle 1). The men sili id rtios of totl LDL nd its dense nd very dense sufrtions Vrile were lower in thn sujets (Tle 2). When the nd sujets were oth divided into qurtiles ording to the sili id rtios of totl nd dense LDL, the rtios were mrkedly lower in thn sujets of the three highest qurtiles ut not in those of the lowest qurtile (Tle 3). In very low density lipoprotein (VLDL) nd LDL, the onentrtions of ll the lipids, nd those of holesterol nd phospholipids lso in serum, were negtively ssoited with the sili id rtio of totl LDL. Conentrtions of pob in serum nd LDL lso hd strong inverse ssoitions with the sili id rtio of totl LDL, while the respetive orreltions with high density lipoprotein (HDL) lipids nd serum Lp[] were insignifint (Tle 4). Similr negtive orreltions with lipid nd pob onentrtions were seen in the light nd dense LDL sufrtions, ut not in the very dense frtion (Tle 5, Fig. 1 for dense LDL pob). The lipids per pob in totl, dense, nd very dense LDL were positively ssoited with the sili id rtio of LDL. sujets hd higher holesterol level in totl nd light LDL thn sujets, ut otherwise the lipid levels of the two groups were roughly similr. The rtios of nonholesterol sterols to holesterol did not differ etween (n 33) nd (n 49) sujets (dt not shown), nd did not ssoite with the sili id rtio of totl LDL. However, the sili id rtio of dense LDL ws negtively orrelted with 8 -lthosterol, desmosterol, nd lthosterol rtios (r 0.389, P 0.001; r 0.244, P 0.05; nd r 0.311, P 0.01, respe- TABLE 4. Serum nd lipoprotein lipid nd pob onentrtions nd serum Lp[] onentrtion in nd sujets nd in ll sujets omined, nd their orreltion oeffiients with the sili id rtio of totl LDL for the omined group (n 42) (n 56) Comined (n 98) Correltion Coeffiient (n 98) Cholesterol, mmol/l Serum d VLDL IDL LDL d HDL Triglyerides, mmol/l Serum VLDL IDL LDL HDL Phospholipids, mg/dl Serum VLDL IDL LDL d HDL Serum pob, mg/dl d LDL pob, mg/dl d Serum Lp(), U/L Vlue represent mens SE. d P Journl of Lipid Reserh Volume 41, 2000

4 TABLE 5. Lipid nd poprotein onentrtions of LDL sufrtions nd lipid-to-pob rtios of totl LDL nd its sufrtions in nd sujets nd in the omined group, nd their orreltion oeffiients with the sili id rtio of totl LDL for the omined group Vrile (n 42) (n 56) Comined (n 98) Correltion Coeffiient (n 98) Light LDL Cholesterol, mmol/l Triglyerides, mmol/l Phospholipids, mg/dl ApoB, mg/dl Dense LDL Cholesterol, mmol/l Triglyerides, mmol/l Phospholipids, mg/dl ApoB, mg/dl d Very dense LDL Cholesterol, mmol/l Triglyerides, mmol/l Phospholipids, mg/dl ApoB, mg/dl Totl LDL, per pob Cholesterol Triglyerides Phospholipids d Light LDL, per pob Cholesterol Triglyerides Phospholipids Dense LDL, per pob Cholesterol Triglyerides Phospholipids Very dense LDL, per pob Cholesterol d Triglyerides Phospholipids d Vlues represent mens SE. d P tively) (in Fig. 2 shown for lthosterol), nd positively with mpesterol, sitosterol, nd holestnol rtios (r 0.219, P 0.05; r 0.239, P 0.05; nd r 0.407, P 0.001, respetively) (in Fig. 2 shown for holestnol). In Fig. 2 it n lso e seen tht t high dense LDL sili id rtios ( 40 g/mg), sujets hd lower lthosterol rtios thn sujets ( vs , 10 2 mmol/mol holesterol, P 0.05). A totl of 58 study sujets volunteered for the kineti studies. They hd higher BMI, higher triglyeride levels in serum nd ll lipoproteins ( vs mmol/l in serum, P 0.001), nd higher men sili id rtio in totl LDL thn the nonprtiipnts ( vs g/mg, P 0.001). Similr to the totl study group, in the kineti study prtiipnts holesterol nd pob onentrtions of oth totl nd dense LDL hd inverse ssoitions with the sili id rtio of totl LDL (Tle 6). FCRs were not signifintly ssoited with LDL sili id rtios, while the TRs for totl nd dense LDL pob were negtively orrelted with the sili id rtios of totl nd dense LDL (Fig. 3). The ssoitions of the kineti prmeters with the sili id rtio were similr in dense s in totl LDL, nd in dense LDL the orreltion etween the sili id rtio nd the TR ws even stronger thn in totl LDL. Furthermore, the TR for dense LDL pob hd signifint positive orreltions with 8 -lthosterol nd Fig. 1. Correltion etween dense LDL sili id-to-pob rtio nd dense LDL pob onentrtion. (losed irles), n 56, r 0.657, P 0.001, y 0.84x 74.7; (open irles), n 42, r 0.619, P 0.001, y 0.63x 67.9; omined group, N 98, r 0.633, P 0.001, y 0.70x Lindohm, Gylling, nd Miettinen Sili id in LDL nd metolism of LDL nd holesterol 1113

5 of CAD ws the dependent vrile, the only step explining its vriility ws the LDL holesterol onentrtion (R ), wheres the sili id rtio of totl LDL nd the TR or FCR for LDL pob did not ontriute. Fig. 2. Correltion etween dense LDL sili id-to-pob rtio nd (A) serum lthosterol-to-holesterol rtio ( sujets [losed irles], n 49, r 0.547, P 0.001, y 3.26x 297; sujets [open irles], n 33, r 0.107, NS; omined group, N 82, r 0.311, P 0.01, y 1.09x 235) nd (B) serum holestnol-to-holesterol rtio ( sujets [losed irles], n 49, r 0.395, P 0.01, y 1.44x 66.0; sujets [open irles], n 33, r 0.356, P 0.05, y 0.47x 102.9; omined group, N 82, r 0.407, P 0.001, y 0.79x 88.6). lthosterol rtios (r nd r 0.307, respetively, P 0.05 for oth), nd negtive orreltion with the holestnol rtio (r 0.410, P 0.01). In ontrst to the totl study group, the sili id rtios of totl nd dense LDL did not differ signifintly in the kineti study etween nd sujets (P 0.07 in dense LDL), ut the sujets hd higher holesterol nd pob onentrtions in oth totl nd dense LDL (Tle 6). They lso hd higher TRs for totl nd dense LDL pob, this eing seen only in the two highest sili id qurtiles. The FCRs did not differ etween nd groups. The stepwise regression nlysis showed tht oth the TR (step 1, R ) nd the FCR (step 2, R ) for totl LDL pob ounted for the vriility in LDL sili id rtio, ut the presene of CAD nd the onentrtions of holesterol nd triglyerides in LDL did not ontriute to the result. Furthermore, when the presene DISCUSSION The min new oservtions in the present study were tht the LDL sili id-to-pob rtio ws lower in sujets thn in sujets espeilly t high sili id rtios, nd tht it ws negtively ssoited with serum nd LDL holesterol nd pob levels nd with the TR for LDL pob, nd the rtio of dense LDL lso with holesterol synthesis. The result of the present study prtly supports the theory tht the sili id ontent of LDL might ffet its therogeniity nd thus predispose to the development of CAD. However, t low totl nd dense LDL sili id rtios (in Q 1 ), nd sujets hd similr men sili id rtios, while t higher vlues (Q 2 Q 4 ) ptients hd lower men sili id rtios thn did sujets. This implies tht in popultions with low LDL sili id rtios nd sujets hve similr sili id rtios in LDL. This ould, in ft, prtly explin the inonsistenies of previous studies in showing differenes in the LDL sili id rtio etween nd sujets. A reltively wek ssoition of the sili id rtio with CAD ws lso indited y the finding tht in stepwise logisti regression nlysis only the onentrtion of holesterol in LDL, nd not its sili id rtio, ws ssoited with the presene of CAD. In greement with the present findings, ut in ontrst to mny other oservtions (18, 27), negtive orreltions of LDL sili id rtios with serum nd LDL holesterol levels hve een reported in one erlier study (28). Serum nd LDL pob levels, remrkle risk ftors for CAD (29), nd triglyeride onentrtions lso exhiited inverse orreltions with sili id rtios, the ltter finding oserved erlier lso y others (15, 28). In the light nd dense LDL sufrtions, the numer of prtiles s indited y pob onentrtion ws negtively ssoited with the LDL sili id rtio. In the dense nd very dense LDL sufrtions the size of the prtiles, shown y their lipid-to-pob rtios, ws positively relted to the sili id rtios. These differenes in the LDL sufrtions resulted in the sili id rtio of totl LDL eing negtively relted to the lipid nd pob onentrtions nd positively to the rtios of lipids to pob. This suggests tht low LDL sili id rtio is ssoited with lrge numer of reltively smll LDL prtiles, generlly known to e therogeni (30), nd is in onordne with n erlier finding tht sujets with smll dense LDL hve lower LDL sili id ontent (28). Lp[] is highly silylted (31) nd overlps with the density rnge of LDL (32). High levels of Lp[] hve een ssoited with theroslerosis (33). If LDL ws ontminted with even smll mounts of Lp[], the sili id ontent of LDL would proly e inresed. Aord Journl of Lipid Reserh Volume 41, 2000

6 TABLE 6. Kinetis of totl nd dense LDL pob in,, nd ll study sujets prtiipting in the kineti study, nd their orreltion oeffiients with sili id-to-pob rtio of totl LDL Vrile (n 37) (n 21) Comined (n 58) Correltion Coeffiient (n 58) Age, yers BMI, kg/m Totl LDL Cholesterol, mmol/l ApoB, mg/dl d Sili id rtio, g/mg FCR, pools/dy TR, mg/kg/dy Dense LDL Cholesterol, mmol/l ApoB, mg/dl d Sili id rtio, g/mg FCR, pools/dy TR, mg/kg/dy FCR, Frtionl toli rte; TR, trnsport rte. Vlues represent mens SE. d P ingly, it ould e ssumed tht CAD ptients would hve higher LDL sili id ontent. However, even though the ptients tended to hve higher men serum Lp[] level, they hd lower LDL sili id rtios thn did sujets, nd there ws no orreltion etween the LDL sili id rtio nd serum onentrtion of Lp[] in the present study, finding onsistent with previous results (15). This strongly suggests tht the possile ontmintion of LDL with Lp[] ws negligile or, in the se of rel ontmintion, the differene in LDL sili id rtio etween nd sujets would e even higher. Furthermore, our mesurements of Lp[] in LDL sufrtions showed tht only minority of sujets with very high serum Lp[] levels hd smll mounts of Lp[] in the dense nd very dense LDL sufrtions. Fig. 3. Correltion etween dense LDL sili id-to-pob rtio nd dense LDL trnsport rte (TR). sujets (losed irles), n 20, r 0.147, NS; sujets (open irles), n 37, r 0.543, P 0.001, y 0.049x 5.89; omined group, N 57, r 0.456, P 0.001, y 0.053x Serum rtios of the holesterol preursor sterols 8 - lthosterol, desmosterol, nd lthosterol to holesterol reflet holesterol synthesis, while the rtios of the plnt sterols mpesterol nd sitosterol nd tht of holestnol reflet holesterol sorption (34). The orreltions of the dense LDL sili id rtio with serum nonholesterol sterol rtios in the whole study group indite tht low sili id rtio in dense LDL ws ssoited with high synthesis nd low sorption of holesterol, whih in turn were ssoited with high TR for dense LDL pob. This opposes the results of erlier studies, where high TR for LDL pob ws ssoited with high holesterol sorption (35, 36). At high dense LDL sili id rtios, sujets hd lower holesterol synthesis thn did sujets, in ordne with n erlier finding tht low holesterol synthesis predisposes to CAD (37). The ssoition of high-level LDL prodution with low LDL sili id rtio, seen lso in our erlier study (18), ould indite tht more sili id-poor thn sili idrih VLDL nd intermedite density lipoprotein (IDL) were onverted to LDL, or tht sili id-rih lipoproteins were lered more vidly from the irultion efore onversion to LDL. The ft tht the negtive ssoition etween LDL prodution nd the LDL sili id rtio is even stronger for dense LDL n explin, in prt, the ssoition etween the dense LDL sili id rtio nd holesterol metolism, s holesterol synthesis nd the TR for dense LDL pob were positively orrelted. Thus, the more holesterol is synthesized, the more dense LDL is produed, nd the lower is its sili id rtio. The finding tht the TRs for totl nd dense LDL pob were higher in sujets ompred with sujets is onsistent with n erlier study (38), nd suggests tht high prodution of LDL pob n e onsidered therogeni. The differene etween nd sujets eing found only in the highest two sili id qur- Lindohm, Gylling, nd Miettinen Sili id in LDL nd metolism of LDL nd holesterol 1115

7 tiles n e explined y the ft tht the negtive ssoition etween the sili id rtio nd the TR for dense LDL pob ws signifint only for the sujets (Fig. 3). FCRs for totl nd dense LDL pob were not signifintly ssoited with their sili id rtios, lthough there ws tendeny towrd positive orreltion etween the LDL sili id rtio nd the FCR for LDL pob (r 0.241, P 0.08). Suh orreltion ws seen in our previous study (14), in whih the sili id rtio nd the FCR for dense LDL pob were positively orrelted in dieti sujets, ut ompred with the present nondieti popultion they hd exeptionlly high LDL sili id rtios. Interestingly, however, in the stepwise regression nlysis of the present study, the FCR for LDL pob, on entering the model, explined the vriility of the LDL sili id rtio long with the TR for LDL pob. This suggests tht oth the prodution nd tolism of LDL re ssoited to some extent with its sili id rtio. A reson for the lower sili id rtios in the LDL of rther thn ptients ould e in the differing lipoprotein metolism in these groups. Speifilly, the higher prodution nd similr lerne of LDL pob in sujets ompred with sujets, whih indites longer residene time in the irultion for LDL, ould llow more time for desilyltion of LDL. The mehnism of this desilyltion is not known, ut silidse is n enzyme with the ility to remove sili id residues from rohydrte hins, nd its onentrtion in serum hs een found to e higher in thn in sujets (39). In onlusion, low sili id rtio in totl nd dense LDL ws ssoited with CAD, with high numers of smll LDL prtiles, nd with high trnsport rte for totl nd dense LDL pob. In ddition, low sili id rtio in dense LDL seemed to e ssoited with high synthesis nd low sorption of holesterol. The uthors wish to thnk Ms. Leen Kipiinen, Pi Hoffström, Orvokki Ahlroos, Anne Honkonen, Tin Nieminen, Ritv Nissilä, nd Leen Sikko for expert tehnil ssistne. The Finnish Medil Foundtion nd Helsinki University Centrl Hospitl re thnked for finnil support. Mnusript reeived 4 Jnury 2000 nd in revised form 10 Mrh REFERENCES 1. Swminthn, N., nd F. Aldjem The monoshride omposition nd sequene of the rohydrte moiety of humn serum low density lipoproteins. Biohemistry. 15: Tniguhi, T., Y. Ishikw, M. Tsunemitsu, nd H. Fukuzki The strutures of the sprgine-linked sugr hins of humn polipoprotein B-100. Arh. Biohem. Biophys. 273: Cmejo, G., A. López, F. López, nd J. Quiñones Intertion of low density lipoproteins with rteril proteoglyns. The role of hrge nd sili id ontent. Atheroslerosis. 55: Dy, C. E Control of the intertion of holesterol ester-rih lipoproteins with rteril reeptors. Atheroslerosis. 25: Filipovi, I., G. Shwrzmnn, W. Mrz, H. Wiegndt, nd E. Buddeke Sili-id ontent of low-density lipoproteins ontrols their inding nd uptke y ultured ells. Eur. J. Biohem. 93: Filipovi, I., nd E. Buddeke Desilized low-density lipoprotein regultes holesterol metolism in reeptor-defiient firolsts. Eur. J. Biohem. 101: Orekhov, A. N., V. V. Tertov, D. N. Mukhin, nd I. A. Mikhilenko Modifition of low density lipoprotein y desilyltion uses lipid umultion in ultured ells: Disovery of desilylted lipoprotein with ltered ellulr metolism in the lood of therosleroti ptients. Biohem. Biophys. Res. Commun. 162: Orekhov, A. N., V. V. Tertov, nd D. N. Mukhin Desilylted low density lipoprotein nturlly ourring modified lipoprotein with therogeni poteny. Atheroslerosis. 86: Tertov, V. V., A. N. Orekhov, I. A. Soenin, Z. A. Gsov, E. G. Popov, A. A. Yroslvov, nd V. N. Smirnov Three types of nturlly ourring modified lipoproteins indue intrellulr lipid umultion due to lipoprotein ggregtion. Cir. Res. 71: Orekhov, A. N., V. V. Tertov, I. A. Soenin, V. N. Smirnov, D. P. Vi, J. Guevr, Jr., A. M. Gotto, Jr., nd J. D. Morrisett Sili id ontent of humn low density lipoproteins ffets their intertion with ell reeptors nd intrellulr lipid umultion. J. Lipid Res. 33: Shiremn, R. B., nd W. R. Fisher The sene of role for the rohydrte moiety in the inding of polipoprotein B to the low density lipoprotein reeptor. Biohim. Biophys. At. 572: Attie, A. D., D. B. Weinstein, H. H. Freeze, R. C. Pittmn, nd D. Steinerg Unltered tolism of desilylted low-density lipoprotein in the pig nd in ultured rt heptoytes. Biohem. J. 180: Ruellnd, A., G. Gllou, B. Legrs, F. Pillrd, nd L. Clore LDL sili id ontent in ptients with oronry rtery disese. Clin. Chim. At. 221: Meljärvi, N., H. Gylling, nd T. A. Miettinen Sili ids nd the metolism of low density lipoprotein. J. Lipid Res. 37: Chppey, B., I. Myr, P. Girl, G. Kerhro, M. C. Plinfosse, J. Levenson, A. Simon, N. Motti, nd the PCVMETRA Group Evlution of the sili id ontent of LDL s mrker of oronry lifition nd extroronry theroslerosis in symptomti hyperholesterolemi sujets. Arteriosler. Throm. Vs. Biol. 15: Chppey, B., B. Beyssen, E. Foos, F. Ledru, J. L. Guermonprez, J. C. Gux, nd I. Myr Sili id ontent of LDL in oronry rtery disese: No evidene of desilyltion in sujets with oronry stenosis nd inresed levels in sujets with extensive theroslerosis nd ute myordil infrtion. Reltion etween desilyltion nd in vitro peroxidtion. Arteriosler. Throm. Vs. Biol. 18: Mlmendier, C. L., C. Delroix, nd M. Fontine Effet of sili id removl on humn low density lipoprotein tolism in vivo. Atheroslerosis. 37: Lindohm, N., H. Gylling, T. E. Miettinen, nd T. A. Miettinen Sili id ontent of LDL nd lipoprotein metolism in omined hyperlipidemi nd primry moderte hyperholesterolemi. Clin. Chim. At. 285: Lipid Reserh Clinis Progrm Mnul of Lortory Opertions. Lipid nd Lipoprotein Anlysis. Ntionl Institutes of Helth. DHEW Pulition No (NIH) Bethesd, MD. 1: Gylling, H., H. Vnhnen, nd T. A. Miettinen Effets of ketoonzole on holesterol preursors nd low density lipoprotein kinetis in hyperholesterolemi. J. Lipid Res. 34: Svennerholm, L Quntittive estimtion of sili ids. II. A olorimetri resorinol-hydrohlori id method. Biohim. Biophys. At. 24: Miettinen, T., nd I-T. Tkki-Luukkinen Use of utyl ette in determintion of sili id. At Chem. Snd. 13: Miettinen, T. A Cholesterol metolism during ketokonzole tretment in mn. J. Lipid Res. 29: MFrlne, A. S Effiient tre-lelling of proteins with iodine. Nture. 182: Bilheimer, D. W., S. Eisenerg, nd R. I. Levy The metolism of very low density lipoprotein proteins. I. Preliminry in vitro nd in vivo oservtions. Biohim. Biophys. At. 260: Mtthews, C. M. E The theory of trer experiments with 131 I-lelled plsm proteins. Phys. Med. Biol. 2: Journl of Lipid Reserh Volume 41, 2000

8 27. Millr, J. S., V. Aner, J. Shepherd, nd C. J. Pkrd Sili id-ontining omponents of lipoproteins influene lipoprotein proteoglyn intertions. Atheroslerosis. 145: L Belle, M., nd R. M. Kruss Differenes in rohydrte ontent of low density lipoproteins ssoited with low density lipoprotein sulss ptterns. J. Lipid Res. 31: Snidermn, A., S. Shpiro, D. Mrpole, B. Skinner, B. Teng, nd P. O. Kwiterovih, Jr Assoition of oronry theroslerosis with hyperpoetlipoproteinemi [inresed protein ut norml holesterol levels in humn plsm low density (et) lipoproteins]. Pro. Ntl. Ad. Si. USA. 77: Kruss, R. M Heterogeneity of plsm low-density lipoproteins nd theroslerosis risk. Curr. Opin. Lipidol. 5: Ehnholm, C., H. Groff, O. Renkonen, nd K. Simons Protein nd rohydrte omposition of Lp() lipoprotein from humn plsm. Biohemistry. 11: Sttler, W., G. M. Kostner, G. Weg, nd H. Esteruer Oxidtion of lipoprotein Lp(): omprison with low-density lipoproteins. Biohim. Biophys. At. 1081: Utermnn, G The mysteries of lipoprotein(). Siene. 246: Miettinen, T. A., R. S. Tilvis, nd Y. A. Kesäniemi Serum plnt sterols nd holesterol preursors reflet holesterol sorption nd synthesis in volunteers of rndomly seleted mle popultion. Am. J. Epidemiol. 131: Miettinen, T. A., H. Gylling, H. Vnhnen, nd A. Ollus Cholesterol sorption, elimintion, nd synthesis relted to LDL kinetis during vrying ft intke in men with different poprotein E phenotypes. Arteriosler. Throm. 12: Gylling, H., T. Strnderg, R. Tilvis, nd T. A. Miettinen Regultion of serum holesterol level in middle-ged nd elderly men. Reltion of holesterol sorption nd synthesis to lipoprotein metolism. Arteriosler. Throm. 14: Miettinen, T. A, nd H. Gylling Mortlity nd holesterol metolism in fmilil hyperholesterolemi. Long-term follow-up of 96 ptients. Arterioslerosis. 8: Kesäniemi, Y. A., nd S. M. Grundy Overprodution of low density lipoproteins ssoited with oronry hert disese. Arterioslerosis. 3: Sonmez, H., S. Suer, T. Ulutin, E. Kokoglu, nd N. Uisik The reltionship of vrious ftors in the pthogenesis of theroslerosis. Clin. Appl. Throm. Hemostsis. 4: Lindohm, Gylling, nd Miettinen Sili id in LDL nd metolism of LDL nd holesterol 1117