Arch Iranian Med 2002: 5 (4): 230 - 234

ELEVATED LIPOPROTEIN(^) IN SYSTEMIC LUPUS

Seyed-Mohammad-Mansour Haeryfar MSc PhD*', Nayer Rassaian MD PIID**, Moha~n~nad Moslemizadeh MD***, Ladan Hoseini-Gohari PIID****

*Department of Microbiology and immunology, Dalhousie University, Halifax, Canada, **Department of Physiology, *** Department of Rheumatology, Shaheed Beheshti University of

Medical Sciences, ^***Department of Biochemistry, lran University of Medical Sciences, Tehran, lran

Background - The underlying mechanism(s) for the development of premature atherosclerosis in patients with systemic lupus erythematosus (SLE) is not precisely understood. In recent years, lipoprotein(a) [Lp(a)] has emerged as a valuable predictor as well as an independent risk factor for premature atherosclerosis. The objective of this study was to determine blood Lp(a) levels i n SLE patients, and to determine whether increased levels are a contributing factor to the development of atherosclerotic complications of SLE.

Methods - Serum Lp(a) levels were measured by enzyme immunoassay in 37 SLE patients, nine of their apparently healthy siblings and 35 healthy controls. Student's t test was used for statistical comparisons.

Results - Our data showed a higher frequency of enhanced Lp(a) levels (> 30 mg1dL) in SLE patients as cornpared with that observed in healthy controls (51.4% vs 25.7%). Analysis of lipid profiles i n SLE patients also revealed significantly higher levels of triglycerides as compared with controls (165 + 16 vs I00 f 6 mgIdL, p = 0.001). Serum Lp(a) levels were not different between patients with or without glucocorticoids, hospitalization and disease exacerbation (p values equal to 0.9, 0.7 and 0.6, respectively. Moreover, there was no significant difference in serum Lp(a) concentration between nine SLE patients and their siblings (34 i 11.8 vs 37.3 i 12.8 mgldL; p = 0.8).

Conclusion - Increased Lp(a) levels are more likely to be encountered in patients with SLE than in healthy subjects. Lp(a) blood levels in SLE, as in healthy individuals, seem to represent a aeneticallv redetermined trait

Keywords atherosclerosis a lipoproteins a lupus erythematosus

Introduction

P atients with systemic lupus erythema- tosus (SLE) exhibit a11 increased incidence of atherosclerotic and tlirombo-

embolic complications.' Atherosclerosis has been acknowledged as a major cause of death and morbidity in SLE ptients.'.' Tlie reason for development of premature atlierosclerosis in SLE is not precisely known, but the higher prevalence of atlierosclerotic progression may be ascribed to

Corrcspondmec: S M h l Haery/ur PhD, Deparin~eni of Microbiolo~ and inz,,trmology, Str Churles T ~ I ~ ~ L ' I Medico1 Bs~lding, Fmully of Medicine. DaN?ozaie Un,versily. Iloli/ox, Afovo Scorio. B3H 4H7 Ca,ta&. E-,r!ail: Iroen~k~rGidolco.

numerous factors including prlmary immunologic injury to blood vessels, presence of anti-pliospho- lipid antibodies, hypertension, vasculitis, duration of glucocorticoid therapy, and dyslipoprotein- e~nia.'.~.' Arteriovenous thrombosis is also a well- know^^ complication of SLE!

I11 recent years, there has been a considerable resurgence of iuterest in lipoprote~n(a) LLp(a)], as there is strong evidence that it represents an independent risk factor for preinature athem- sclerosis. Lp(a) is co~nposed of a low dens~ty lipoprotein (LDL) linked by disulfide bonds to apolipoprotein(a) [apo(a)], a high-molecular weight protein with striking liomology to a seriue

230 Archives ofIranian Medicine, Vol5, No 4, October 2002

S.M.M. Haeryfar, N. Rassaian, M. Moslemizadeh, et al

tease, plasininogen. The LDL-like property of (a) confers the particle an atherogenetic tential, while the similarity of the apo(a) subunit plasminogen could account for prothronibotic

Current information justifies the need to levels in patients who are

ceptible to atherosclerotic cardiovascular ase."n the other hand, it has been suggested

ed in i~nrnunologic mech- is important to compare

s with those in healthy Lp(a) levels should be ts' healthy siblings to

ere is a genetic tendency ards higher Lp(a) levels in lupus patients.

I Patients and Methods

ubjects Thirty-seven SLE patlents with a meall age of -

8 years (range, 13 - 53) including 32 wornen and men constituted the patient group. All paticnts dexhibited at least four of the revised criteria for e diagnosis of SLE" during the course of their sease. All had been admitted to the rheurnatology nters of tlie three main medical universities of ehran between April 1994 and October 1995, though they were froin different parts of Iran. wo sisters with inactive SLE were among the tients. Twenty-nine patients were talcing methyl- ednisolone and eight were not. None of them s receiving lipid-lo~vering dl-ugs. Sixteen tients had been hospitalized in rheurnatology ards because of an SLE flare-up, while 21 were

n during outpatient follow-up periods in the eumatology Clinic of Loghinan Hakim Gcneral spital. Within our outpatient group, 20 had

active SLE and only one had active disease cording to the lup~is activity criter-ia count scribed by Urowitz et al." None of the patients doverlau svndromes. In this studv, ixitieilts with

included because Lp(a) levels may change under these circumstance^.'".'^

The control group consisted of 35 healthy volunteers who had been referred to thc Iranian Reference Laboratory in order to undergo routine tests before marriage (opium test and Venereal Disease Research Laboratory test). An appropriate questionnaire was used to ensure that the control group included only healthy subjects. Despite the fact that Lp(a) concentration is not coi~elated with age or sex,'%ontrols and patients were matched for both age and sex. Because Lp(a) blood level is known to be transmitted as an autosomal dominant trait," Lp(a) blood levels were determined in our patients' healthy siblings. After a dctailed clinical examination, nine apparently healthy siblings (one for each patient) were selected, in whom there was no sign or symptom of clinical lupus.

Laboratory investigations Blood specimens were obtained after a 12-hour

fast. Serum Lp(a) was determined by sandwich enzyme-linked irnmunosorbent assay (ELISA) using an I~nmunozym Lp(a) kit provided as a gift by TMMUNO AG (Vienna; Austria). All known isoforms of Lp(a) were detectable by tlie anti- apo(a) polyclonal antibodies employed in this kit. Fnrthermorc, according to the manufacturer, cross- reactivity of Lp(a) with plasrninogen or LDL does not interfere with the test results. Toral serLlrn cholesterol, triglycerides (TG) and high-density lipoprotcin cholesterol ('IDL-C) were nleasured by enzymatic colorimetric methods using Technicon Itits purchased froni MAN Laboratories (Tehran, Iran). HDL-C was determined after precipitating very-low-density lipoprotein (VLDI.) and 12DL with a reagent containing dextran sulijte and magnesium chloride. VLDL-cholesterol (VLDL-C) was calculated by dividing the TG concelitration by 5 , and LDL-C uras calculated hy the Friedwald fom~ula,"~ where LDL-C = total cholesterol (TC) - (HDL-C + (TG/5)] . . . .

phrotic syndrome, diabetes mellitus, hyper- or pothysoidism were not included because of Statistical ar~alysis

ported changes in plasma Lp(a) levels related or Data were cornpal-ed using Student's I test and

condary to these conditions."~" A pregnant 1' vdlucs lcss than 0.05 were considered statistically

man and a patlent with Budd-Chiari syr~dro~ne significant. All analyses were performed using

re also excluded from this study because of the SPSSIPC+ software (version 6.1). Thc results are uchat,ons or plasma L ~ ( ~ ) lcvcls during expressed as mean i standard error (SE).

egnancy and the fact that the liver is iiivolved the synthesis of Idp(a)," respectively. In Results

dition, those patients who had undergone emodialysis or recent surgical operations were not 'Thcrc was a strong trend toward abnonna~~y

A v c l ~ i i ~ ~ ~ s q f ' l i r i n i o i ~ hlclellicine. Vol 5 , No 4, Oclober LOO2 231

Elevated Lipoprotein(a) in Systemic Lupus Erythematosus

.-y

? 40 - U) - $ 30 m - - E 20 0 J

E 10 2

0

Patients Controls

50

40

30

20

10

0

Patients Controls

Figure 1. Lipoprotein(a) [Lp(a)] concentration in SLE patients and controls. A) There was a trend toward higher Lp(a) blood levels in SLE patients as compared with controls (38.5 + 6.4 vs 24.5 + 4.3 mgldL, p = 0.07). B) Elevated Lp(a) levels (> 30 mgldL) were also more frequent in SLE patients (51.4% vs 25.7%).

Lp(a) concentrations in SLE patients as compared with controls, although tlie observed difference did not reach statistical significance (38.5 t- 6.4 vs 24.4 i 4.3 mgIdL; p = 0.07) (Figure IA). However, the frequency o f high Lp(a) levels (> 30 mg/dL) was twice as high in patients with SLE than in healthy s~~bjects (Figure 1B).

There was no difference in mean serum Lp(a) levels between patients with and without gluco- corticoid tlierapy 02 = 0.9), liospitalized and nonhospitalized patients (p = 0.7), and those with and without active disease (p = 0.6) (Table I). We found raised scruln lcvels o f T G and VLDL-C in SLE patients as compared with contl.ols (165 i I 6 vs 100 * 6 1n8/dL and 33 + 3 vs 20 f I mddl,, respecti\iely; p = 0.001), wliicli is consistent wit11 the so-called "lupus pattern" o f dyslipo- proteincmia.

Forthermore, the statistical correlation analyses o f the data revealed no significant differences between patients on or not on gl~tcocorticoid therapy in terms o f serum levels o f TC, TG, HDL- C, LDL-C and VLDL-C.

'To explore a possible genetic basis for high blood Lp(a) levels i n SLE patients, serum l,p(a) concentrations o f ninc SLE patients were directly coinpared with those o f nine o f their apparently

Table 1 . Serum lipoprotein(a) levels (mg/dL) of hospitalization and disease activity.

healthy siblings. N o difference in mean Lp(a) lcvels was noted between these two groups (34 i 11.8 nigidL vs 37.3 + 12.8 ~ng/dL; IJ = 0.8). Furthennore, two sistcrs wi th inactive SLE had quite similar serum Lp(a) concentrations (92.2 mg/dL and 88.3 mg/dL).

Discussion

Atherosclerotic and tliromboc~nbolic proble~ns are among the life-threatening, long-term complications o f SLE. Dyslipoproteillc~nia is widely recognized as a risk factor for vascnlal. disease in I L I ~ U S . ~ , ~ ' Serum samplcs from SLE patients have been shown to stitnulate the accumulation o f cholesterol in cultured smooth tnuscle cells o f the aorta. Such all atherogenic effect o f lupus sera was attributed to the presence o f LDL-containing immune complexes." McGregor et al reported SLE cases with elevated apolipoprotein B levels i n spite o f normal blood levels o f cholesterol and LDL-C. ?'hey suggested that SI,E patients may have abnormally dense particles o f LDL.'

The LDL-l ike molecule Lp(a) has become a focus o f attention due to tlie possibility that levels

SLE patients in relation to glucocorticoid therapy,

~p

Variable --- Yes (n, FIM) No (11, FIM) 11 Vuhrc

MP therapy 38.1 i 2.7 (29, 25M) 39.9 L 14.9 (8, 7/11 0.9

Hospitalization 35.85 10.7 (16, 1412) 40.6% 8(21, 1813) 0.7

Active disease - - 34.9 1 10.2 (17. 1512) 41.6 1 8.3 (20, 1713) - 0.6 il= n i ~ ~ n b c r of snbjccts: F - ltlnalc, M = miilc: MP = melhylprednisrrlonc.

232 Archives of lrunian Medicine, Vol 5 , No 4, October 2002

S.M.M. Haeryfar, N. Rassaian, M. Moslemizadeh, et al

circulatiiig Lp(a) represent an independent risk factor for coronary vascular disease of greater predictive potential than other lipoprotein traits.23 Elevated Lp(a) levels in lupus patients have been previously reported.'.24 Lp(a) blood levels in our study patients tended to be higher than in controls, although such a difference did not reach statistical significance possibly because of the relatively small number of patients examined. Alternatively, it may reflect genetic or population-based differences between the patients in this study and those in earlier similar studies, as Lp(a) levels are known to vary widely among various ethnic groups." The latter possibility is supported by a recent study conducted in Tehran, in which Lp(a) serum levcls were not diffcrent between patients with angina pectoris and healthy contro~s.'~ Nevertheless, our results clearly indicate a higher 5equency of increased Lp(a) levels (> 30 mg1dL) in SLE patients. The clinical importance of Lp(a) in SLE are emphasized by the results of a retrospective study in which there were higher levels of Lp(a) in eight SLE patients with myocardial andlor cerebral infarction than in eight SLE patients with no history of infarction."

Lp(a) concentrations are not affected by most phamacologic agents. However, the general consensus is that the identification of elevated Lp(a) levels in a patient should prolilpt the clinician to search for and climinate modifiable risk factors such as cigarette smoking, arterial hypertension, diabetes mellitus and hyper- cho~esterolemia.'~~'" Furthermore, because the cardio-vascular risk of Lp(a) increases when plasma levels of LDL-C arc also high,'*." I.DI.-C concentrations can be lowered therapeutically at the appropriate timc.

The effect of glucocorticoid therapy on blood Lp(a) levels has been an issue of controvcrsy. In this study, there was no difference in I.p(a) concentration between patients with and without glucocorticoid therapy, nor was there any significant correlation between Lp(a) levels and methylprednisolone dosage. This is in agreement with the results of Matsuda et al\nd Rorha el al," but not with those of another rcport wherein reductions in serum Lp(a) levels following glucocorticoid therapy was found in a small group of Further studies on greater numbers of lupus patients are required to clarify whether or not glucocorticoid therapy can actually alter Lp(a) blood levels.

Our finding that I>p(a) lcvels did not differ

between those patients with and those without active disease lend support to the results of Borha et a ~ , ' ~ indicating that the acute phase reactant-like property of lp(a)I6 is unlikely to he responsible for raised Lp(a) levels encountcred in SLE patients.

Plasma Lp(a) levels are known to be genetically determined, as supported by familial and twin studies."~oever, no attenipts to correlate Lp(a) blood levels of SLE patients with those of their healthy siblings have ever been made. Our results extend the existing literature in that Lp(a) blood levels arc not different between lupus patients and their healthy siblings. In fact, in our exa~iiination of lupus patients and their healthy siblings, 50% of the pairs showed almost identical Lp(a) levels. Bcsides, two sisters (aged 34 a~id 39) with inactive SLE, taking the same daily dosage of n~ethylprednisolone (2.5 mglday), had very similar serum Lp(a) concentrations (92.2 and 88.3 mg/dL, respectively). Thus, it could be concluded that the higher frequency of elevated Lp(a) lcvels in lupus patients as compared with healthy subjects represents a phenotypic expression of a related genetic trait. This is by no means a cause and cffcct relationship. Rather, these data may provide a clue to a genetic tendency toward higher Lp(a) levels in patients with SLE. More detailed and controlled investigations on greater numbers of cases are warranted. Thc evel--enigmatic physiologic role and other Cunctional aspects of Lp(a), as well as its modifications manifested in other autoimmune conditions, also remain to be elucidated.

Acknowledgment

The atcthors ~vi.sh to thank Dr. Eilrl D. Sih~ern~ai~ of'the University qf' Tol.orlto.for uiticui reidew of' this mnntr.script. This study IYCIS nznrle l~ossibfe hy a generous gijt of uir iini?luirozym Lp(l1) 1cit.fio111 IMMUNO AG. Vienna, Az~stiia.

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27 Ka\vai S. Mizushiti~a Y. IK;~buraki J. Iticrcasctl E~MII

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angiogmphically-assessed coronary :~ihcrusclcror~s Dc~,~ctidcncc rm serttrn I .DL Icvcls, ,4/hr!ro.~~cln.o.si.v. iR66: 62: 2 4 9 57.

31 Aoki K. Kuwai S. Glucocortimid rhcr;~~). dccrc;isc$

234 Arrhivcs of Irfinririt Afilcrlrcnrc. V o l 5, h o 4. Octobe~ 2002