A novel marker of atherosclerosis: To treat or not to treat?
Dimitris Tousoulis
, Nikolaos Papageorgiou, Emmanuel Androulakis, Christodoulos Stefanadis
1st Cardiology Department, Athens University Medical School, Hippokration Hospital, Greece
a r t i c l e i n f o
 Article history:
Received 14 August 2012Accepted 26 September 2012Available online 24 October 2012
AtherosclerosisLipoprotein-associated phospholipase A2In
ammationCardiovascular disease
1. Introduction
ammatory process contributes signi
cantly to the initiation,progression and rupture of atherosclerotic plaques [1]. A numberof classicalongwithnovel,whicharestillunderinvestigation,in
amma-tory biomarkers, have been proposed during the last years, evaluatingthecontributionofin
ammatorybiomarkersmaybeabletopredictcardio-vascular disease (CVD) events [2]. Thus, apart from the widely studiedC-reactiveprotein(CRP)andamongseveralnovelbiomarkersexaminedfortheirroleinCVD,lipoprotein-associatedphospholipaseA2(Lp-PLA2)is an emerging in
ammatory marker playing a key role in vascular in-
ammation and importantly in atherosclerosis evolution (Fig. 1). Morespeci
cally,Lp-PLA2isanenzymethathydrolyzesphospholipidstogen-eratelysophospholipidsaswellasoxidizedfreefattyacids,whilehavingapredictiveroleforfutureCVDevents.Althoughthereisanencouragingamount of Lp-PLA2-associated data, little is known about the involve-ment of Lp-PLA2 in the pathophysiology of atherosclerosis, CVD riskprediction, its association with cardiovascular indices and its poten-tial as a therapeutic target for future medical treatments.In this issue of the
 Charniot et al. [3] aimed to assess rela-tionshipsbetween Lp-PLA2levels,cardiac disease and treatmentsandto evaluate the association of Lp-PLA2 levels with the severity of angiographic coronary artery disease (CAD) and the extracoronaryatherosclerosis. They reported that interpretation of Lp-PLA2 levelsneeds a good assessment of cardiac parameters and treatments, espe-cially statins and ACEi/ARA2. In addition, Lp-PLA2 levels are signi
-cantly associated with coronary heart disease and with the extension
ofextracoronarydiseaseafteradjustmentforageandgender.However,the exact role of Lp-PLA2 as a prognostic biomarker and as a targetbiomarker is not well elucidated.
2. Lp-PLA2, a novel marker 
Lipoprotein-associated phospholipase A2 is a 45.4-kDa protein andalso a calcium-associated member of the phospholipase A2 family.This in
ammatory biomarker is secreted mainly by macrophages,T-lymphocytes and monocytes as well as mast cells and data haveshownthatitisenhancedinatheroscleroticlesions,especiallyincomplexvulnerableplaquesandimportantlyinthincapcoronarylesionspronetorupture [4].Two-thirds of the Lp-PLA2 plasma isoform primarily bound tolow-density lipoprotein cholesterol (LDL-c), while the other third isdistributed between high-density lipoprotein cholesterol (HDL-c) HDL and very low-density lipoprotein (VLDL) [4]. Low-density lipoproteincholesterolappearstobeacirculatingreservoir,inwhichLp-PLA2isin-active until the oxidative modi
cation of LDL. Following LDL oxidation,Lp-PLA2 cleaves an oxidized phosphatidylcholine component of the li-poprotein particle generating lysophosphatidylcholine and oxidizedfattyacid,whichare pro-in
ammatory andpro-atherogenic mediators.
3. Evidence from large scale studies
SeveralstudieshaveexaminedthepredictiveroleofLp-PLA2incor-onary events (Table 1). In the ARIC trial [5], the authors prospectively found that Lp-PLA2 levels were increased in subjects who developedCAD. In addition to the classic risk factors, both levels of Lp-PLA2 andhighsensitivityCRPwerehigherinpatientswithCVDeventscomparedtothosewhodidnotexperienceCVDevents.ItwasshownthatLp-PLA2was independent of CRP and body mass index, thus being superiorin terms of speci
city to CRP as subjects presenting with abdominaladiposity had enhanced expression of CRP and pro-in
ammatory cyto-kines. Interestingly, increased Lp-PLA2 was signi
cantly related to adouble risk of CVD event, implicating that that Lp-PLA2 may be usefulin classifying intermediate risk individuals in high or low risk status.According to the data derived from the MONICA study [6] enhancedconcentrations of Lp-PLA2 and CRP were additional risk factors forCAD events.Of great importance were the scienti
c data coming from theWOSCOPS study [7]. Prior to the aforementioned studies, the WOSCOPSreported that Lp-PLA2 is a potential biomarker for CVD risk assessment.In addition, increased Lp-PLA2 levels have a predictive value for cardio-vasculareventsindependentlyofotherin
ammatorymarkersinahigherrisk population of men with hyperlipidemia [8]. Thus, a 60% statistically
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cantincreaseinriskbetweenthehighestandthelowestquintileof Lp-PLA2 was found. Despite the signi
cant relations of Lp-PLA2 withtotal and LDL, Lp-PLA2 levels were independent of age, body massindex, blood pressure or smoking.Several other studies have reported the predictive value of Lp-PLA2to identify residual risk in high risk individuals [9]. However, Lp-PLA2levels during the early phase of the acute coronary syndromes werenot associated with the risk for recurrent events [10]. Moreover, meta-analyses have tried to enlighten the role of this in
ammatory molecule.In a cohort of more than 20,000 patients from large epidemiologicalstudies [11], increased Lp-PLA2 levels were independently associatedwith CVD events, while from the early studies it was shown thatLp-PLA2 may be also an attractive novel therapeutic target [12].
4. Recent data highlighting the role of Lp-PLA2 in atherosclerosis
Apartfromthepromisingresultsfromlargeepidemiologicalstudies,recent studies have aimed to examine the potential pathophysiologicalrole of Lp-PLA2 in CVD and the potential agents aiming to that. Whileevaluating the known results of previous large scale studies Kleber etal. [13] demonstrated that Lp-PLA2 levels predict risk for total and CVDmortality independently from established risk factors and indicatedrisk for CVD death even in patients with high CRP levels. Recently,otherstudiesaimedtoinvestigatetherole ofLp-PLA2intransient ische-mic attack patients and to examine their association with recurrentstroke [14]. The authors found that Lp-PLA2 mass and activity werehigher in transient ischemic patients in the control group. Duringfollow-up Lp-PLA2 activity of >207 nmol/ml/min was a signi
cant pre-dictorforrecurrentstroke[14]implyingapotentialroleintheearlyeval-uationofsuchpatients.Furtherstudieshavedemonstratedthatintype1diabetes Lp-PLA2 mass was marginally higher and Lp-PLA2 activitywas signi
cantly lower than in those without diabetes as well as agreaterproportion ofthose withprogression of coronarycalci
cationin type 1 diabetes compared with those without diabetes. Lp-PLA2 ac-tivitywasindependentlyassociated withprogressionofcoronarycalci-
cation in multivariate analysis. However, LpPLA2 mass was notsigni
cantly associated with progression of coronary calci
cationin this cohort [15]. Moreover, other studies have shown thatLp-PLA2 expression increases dramatically during human monocyte tomacrophage differentiation and further in in
ammatory macrophagesand foam like cells [16]. Despite only a marginal association of singlenucleotide polymorphisms in PLA2G7 with Lp-PLA2 activity or mass,numerous PLA2G7 single nucleotide polymorphisms were associatedwith coronary artery calci
cation [16]. Charniot et al. [3] reported that in healthy controls, mean Lp-PLA2 level correlated with age, bodymass index, smoking, history of hypertension but not with diabetes,gender,creatinineorNewYorkHeartAssociationstatus.Inmultivariateanalysis Lp-PLA2 was associated with total cholesterol, LDL-cholesteroland apoB but not with Lp(a).AsmorestudieshighlightfurthertheroleofLp-PLA2inatherosclero-sistheaimofthecurrentandfuturestudiesistoevaluatetheroleofthisin
ammatory marker in hypolipidemic therapy. Statins and darapladibare the most potent agents targeting Lp-PLA2. High-dose atorvastatinsigni
cantly reduced sPLA2 and Lp-PLA2 mass and activity after acutecoronary syndromes and mitigated the risk of death associated withsPLA2 mass suggesting that atorvastatin may exert antiin
ammatoryeffects on phospholipases which contribute to its therapeutic bene
tafter acute coronary syndromes [17]. Importantly, the relationship be-tween circulating Lp-PLA2 levels and coronary plaque volume has not
      L     p   -      P      L      A      2
Lyso-PCT-cell activationleukocyte recruitment Plaque destabilizationVSMC proliferation and migrationPlatelet recruitment and activation
Fig. 1.
 Lp-PLA2 mediates in
ammatory process.
 Table 1
Major large scale studies evaluating the predictive value of Lp-PLA2.Study Subjects Events OR/HR or RR (95% CI)Ballantyne et al. [5] Healthy subjects CAD events 1.15 (0.8
1.6)2.08 (1.2
3.6)Koenig et al. [6] Hypercholesterolemia CAD events 1.21 (1.01
1.5)Packard et al. [7] Hyperlipidemia CAD events 1.80 (1.3
2.6)Winkler et al. [20] DM II CAD 2.09 (1.0
4.2)Persson et al. [21] Healthy MI 1.54 (1.1
2.2)Kiechl et al. [22] Healthy CAD events 1.4 (1.1
1.4)Khuseyinova [23] CAD CAD 1.91 (1.12
3.28)Koenig et al. [24] ACS CAD 2.09 (1.10
3.96)Gerber et al. [25] ACS Death 4.93 (2.10
11.6)O'Donoghueetal.[10] ACS CAD events 1.33 (1.01
1.74)Sabatine et al. [26] CAD MI 1.41 (1.17
1.70)Mockel et al. [27] ACS CAD events 2.60 (1.1
6.6)Oldgren et al. [28] ACS CAD events 1.40 (0.77
2.5)Abbreviations: DM: diabetes mellitus; MI: myocardial infarction; ACS: acute coronarysyndromes; OR: odds ratio; RR: relative risk; HR: hazard ratio; CI: con
dence intervals;CAD: coronary artery disease.214
been well clari
ed in patients with acute coronary syndromes [18].Therefore,Dohietal.[18]demonstratedthatLp-PLA2levelssigni
cantlydecreased between baseline and six months of follow-up, while the ab-solute change in plaque volume also signi
cantly correlated with thechange in Lp-PLA2 levels. In the study of Charniot et al. [3] it was foundthat Lp-PLA2 levels were signi
cantly higher in patients with CAD thanin patients without CAD and signi
cantly higher in patients with themost extensive angiographic CAD. Patients with heart failure, sepsis oraortic aneurysm had increased Lp-PLA2 levels compared to controlsand interestingly, in patients with carotid artery disease, Lp-PLA2 signif-icantly increased with the severity of atherosclerosis.Furthermore, experimental data have shown that administrationof darapladib daily for 6 weeks, although not affecting body weightand serum lipids levels, reduced serum Lp-PLA2 activity signi
cantly aswellasCRPandinterleukin-6[19].Interestingly,theplaqueareathroughthe arch to the abdominal aorta was reduced in the darapladib group,while the macrophage content was decreased and collagen content wasincreased in atherosclerotic lesions at the aortic sinus in the darapladibgroup compared with the vehicle group. It is also worth mentioningthat the samestudy revealed lowerexpressionof monocyte chemotacticprotein-1, vascular cell adhesion molecule 1 and tumor necrosis factoralpha after darapladib [19]. Additional data to the current knowledgehave been provided by Charniot et al. [3] as Lp-PLA2 was signi
cantlyassociated with treatments such as statins and ACEi/ARA2 but not withb-blockers, antiaggregant drugs or diuretics.
5. Challenging role of novel biomarkers: time for Lp-PLA2?
Thereis a continuous seek of new riskfactorsthat predictCVD andcan be incorporated into risk assessment algorithms. Although sever-al molecules seem to play a central pathogenic role in atherogenesis,this does not necessarily mean that they are suitable parameters forrisk prediction. Moreover, a proposed biomarker should not only pro-vide independentinformation on CVD risk, but alsobe easyto measureusing inexpensive and standardized commercial assays that have lowvariability,arerelativelystable,andexhibitminimalcircadianvariation.Lp-PLA2isnotyetwellvalidatedtobeusedindailyclinicalpracticeandfurther studies are required to con
rm its clinical utility as a predictorbiomarker. Furthermore, in
ammatory process is multifactorial andthus, inhibiting just one mediator does not warrant the achievementof a signi
cant total antiin
ammatory improvement.
6. Conclusions
Recent evidence suggests that Lp-PLA2 plays an important role in thepathophysiology of atherosclerosis and may have predictive value forfuture cardiovascular events. The available data suggest that Lp-PLA2couldbeamorevascular-speci
cmarkercomparedtoC-reactiveprotein,but there are still issues pending as regards to the available assays/measurements of this protein, especially at low plasma concentrations.The studies already conducted have demonstrated that Lp-PLA2 may bea target of lipid-lowering drugs such as statins and novel includingdarapladib aiming further to plaque formation. Although the majorityoftheresultsareinfavortothesigni
cantroleofLp-PLA2incardiovas-cular disease, the available data remain limited. Therefore, more welldesigned large scale randomized trials, especially in humans are re-quired to investigate further and evaluate the atherosclerotic mecha-nisms associated with Lp-PLA2 and its potential role as a therapeutictarget for cardiovascular agents.
The authors of this manuscript have certi
ed that they complywith the Principles of Ethical Publishing in the International Journalof Cardiology.
[1] Greenland P, Knoll MD, Stamler J, et al. Major risk factors as antecedents of fataland nonfatal coronary heart disease events. JAMA 2003;290:891-7.[2] Tousoulis D, Charakida M, Stefanadis C. Endothelial function and in
ammation incoronary artery disease. Heart 2006;92:441-4.[3] Charniot JC, Khani-Bittar R, Albertini JP, et al. Interpretation of lipoprotein-associated phospholipase A2 levels is in
uenced by cardiac disease, comorbidities,extension of atherosclerosis and treatments. Int J Cardiol, http://dx.doi.org/10.1016/ j.ijcard.2012.09.054.[4] Zalewski A, Macphee C. Role of lipoprotein-associated phospholipase A2 inatherosclerosis: biology, epidemiology, and possible therapeutic target. ArteriosclerThromb Vasc Biol 2005;25:923-31.[5] Ballantyne CM, Hoogeveen RC, Bang H, et al. Lipoprotein-associated phospholipaseA2, high sensitivity C-reactive protein, and risk for incident coronary heart diseasein middle aged men and women in the Atherosclerosis Risk in Communities(ARIC) study. Circulation 2004;109:837-42.[6] Koenig W, Khuseyinova N, Löwel H, Trischler G, Meisinger C. Lipoprotein-associatedphospholipaseA2addstoriskpredictionofincidentcoronaryeventsbyC-reactivepro-teininapparentlyhealthymiddle-agedmenfromthegeneralpopulation:resultsfromthe 14-year follow-up ofa large cohort from southern Germany(MONICA-Augsburg).Circulation 2004;110:1903-8.[7] PackardCJ,O'ReillyDS,CaslakeMJ,etal.Lipoprotein-associatedphospholipaseA2,asanindependent predictor of coronary heart disease. N Engl J Med 2000;343:1148-55.[8] CorsettiJP,RainwaterDL,MossAJ,Zareba W,SparksCE.Highlipoprotein-associatedphospholipase A2 is a risk factor for recurrent coronary events in postinfarction pa-tients. Clin Chem 2006;52:1331-8.[9] May HT, Horne BD, Anderson JL, et al. Lipoprotein-associated phospholipase A2independently predicts the angiographic diagnosis of coronary artery diseaseand coronary death. Am Heart J 2006;152:997
1003.[10] O'Donoghue M, Morrow DA, Sabatine MS, et al. Lipoprotein-associated phospho-lipase A2 and its association with cardiovascular outcomes in patients with acutecoronary syndromes in the PROVE IT-TIMI 22 (PRavastatin Or ator-VastatinEvaluation and Infection Therapy-Thrombolysis In Myocardial Infarction) Trial.Circulation 2006;113:1745-52.[11] Garza CA, Montori VM, McConnell JP, Somers VK, Kullo IJ, Lopez-Jimenez F. Associa-tionbetweenlipoprotein-associatedphospholipaseA2andcardiovasculardisease:asystematic review. Mayo Clin Proc 2007;82:159-65.[12] Serruys PW, García-García HM, Buszman P, et al. Integrated Biomarker and ImagingStudy-2 Investigators. Effects of the direct lipoprotein-associated phospholipaseA(2) inhibitor darapladib on human coronary atherosclerotic plaque. Circulation2008;118:1172-82.[13] KleberME,WolfertRL,DeMoisslGD,etal. Lipoprotein associated phospholipase A2concentration predicts total and cardiovascular mortality independently of established risk factors (The Ludwigshafen Risk and Cardiovascular Health Study).Clin Lab 2011;57:659-67.[14] Delgado P, Chacón P, Penalba A, et al. Lipoprotein-associated phospholipase A(2)activity is associated with large-artery atherosclerotic etiology and recurrentstroke in TIA patients. Cerebrovasc Dis 2012;33:150-8.[15] KinneyGL,Snell-BergeonJK,MaahsDM,etal.Lipoprotein-associatedphospholipaseAactivity predicts progression of subclinical coronary atherosclerosis. Diabetes TechnolTher 2011;13:381-7.[16] FergusonJF,Hinkle CC,MehtaNN,etal.Translationalstudiesoflipoprotein-associatedphospholipase A in in
ammation and atherosclerosis. J Am Coll Cardiol 2012;59:764-72.[17] RyuSK,MallatZ,BenessianoJ,etal.MyocardialIschemiaReductionWithAggressiveCholesterol Lowering (MIRACL) Trial Investigators. Phospholipase A2 enzymes,high-dose atorvastatin, and prediction of ischemic events after acute coronary syn-dromes. Circulation 2012;125:757-66.[18] Dohi T, Miyauchi K, Okazaki S, et al. Decreased circulating lipoprotein-associatedphospholipase A2 levels are associated with coronary plaque regression in patientswith acute coronary syndrome. Atherosclerosis 2011;219:907-12.[19] WangWY,ZhangJ,WuWY,etal.Inhibitionoflipoprotein-associatedphospholipaseA2 ameliorates in
ammation and decreases atherosclerotic plaque formation inApoE-de
cient mice. PLoS One 2011;6:e23425.[20] Winkler K, Abletshauser C, Friedrich I, Hoffmann MM, Wieland H, März W.Fluvastatin slow-release lowers platelet-activating factor acetyl hydrolase activity:a placebo-controlled trial in patients with type 2 diabetes. J Clin Endocrinol Metab2004;89:1153-9.[21] Persson M, Hedblad B, Nelson JJ, Berglund G. MALMO elevated Lp-PLA2 levels addprognostic information to the metabolic syndrome on incidence of cardiovascularevents among middle-aged nondiabetic subjects. Arterioscler Thromb Vasc Biol2007;27:1411-6.[22] Kiechl S, Willeit J, Mayr M, et al. Oxidized phospholipids, lipoprotein(a),lipoprotein-associated phospholipase A2 activity, and 10-year cardiovascularoutcomes: prospective results from the Bruneck study. Arterioscler ThrombVasc Biol 2007;27:1788-95.[23] Khuseyinova N, Imhof A, Rothenbacher D, et al. Association between Lp-PLA2 andcoronary arterydisease: focuson itsrelationship with lipoproteins andmarkersof in
ammation and hemostasis (HELICOR). Atherosclerosis 2005;182:181-8.[24] Koenig W, Twardella D, Brenner H, Rothenbacher D. Lipoprotein associated phos-pholipase A2 predicts future cardiovascular events in patients with coronaryheart disease independently of traditional risk factors, markers of in
ammation,renal function and hemodynamic stress (KAROLA). Arterioscler Thromb VascBiol 2006;26:1586-93.215
[25] GerberY,McConnellJP,JaffeAS,WestonSA,KillianJM,RogerVL.Lipoprotein-associatedphospholipase A2 and prognosis after myocardial infarction in the community.Arterioscler Thromb Vasc Biol 2006;26:2517-22.[26] SabatineMS,MorrowDA,O'DonoghueM,etal.forthePEACEInvestigators.Prognos-ticutilityoflipoprotein-associatedphospholipaseA2forcardiovascularoutcomesinpatientswithstablecoronaryarterydisease.ArteriosclerThrombVascBiol2007;27:2463-9.[27] Mockel M, Muller R, Vollert JO, et al. Lipoprotein-associated phospholipase A2 forearly risk strati
cation in patients with suspected acute coronary syndrome: amulti-marker approach: the North Wuerttemberg and Berlin Infarction Study-II(NOBIS-II). Clin Res Cardiol 2007;96:604-12.[28] Oldgren J, James SK, Siegbahn A, Wallentin L. Lipoprotein-associated phospholipaseA2 does not predict mortality or new ischaemic events in acute coronary syndromepatients. Eur Heart J 2007;28:699-704.216
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