Serum lipoprotein(a) level is increased in patients with systemic lupus erythematosus irrespective of positivity of antiphospholipid antibodies

Echocardiographic findings, lipids and lipoprotein(a) in patients with systemic lupus erythematosus

Cardiac involvement, evaluated by echo-doppler-cardiography, occurred in 41 of 50 (82%) patients with systemic lupus erythematosus (SLE). Valvular pathology with aortic cusp sclerosis was the most prevalent finding irrespective of age. This finding, suggestive of atherosclerotic heart disease, was supported by increased levels of cholesterol and triglycerides in these patients. There was no significant increase in Lp(a) in the whole patient group, but Lp(a) was raised in patients with proteinuria. Forty percent of the SLE patients had pericarditis. Twelve patients with hypertension and/or mitral regurgitation had increased dimensions of left ventricle, left atrium or interventricular septum while 15 of 50 patients had isolated increase of these parameters. Localized hypokinesia was found in nine patients. Reduced cardiac index was found in five patients with SLE. There was no association between valvular disease, increased pulmonary artery pressure, and anticardiolipin antibodies.

Lipoprotein(a) in health and disease

Lipoprotein(a) [Lp(a)] represents an LDL-like particle to which the Lp(a)-specific apolipoprotein(a) is linked via a disulfide bridge. It has gained considerable interest as a genetically determined risk factor for atherosclerotic vascular disease. Several studies have described a correlation between elevated Lp(a) plasma levels and coronary heart disease, stroke, and peripheral atherosclerosis. In healthy individuals, Lp(a) plasma concentrations are almost exclusively controlled by the apo(a) gene locus on chromosome 6q2.6-q2.7. More than 30 alleles at this highly polymorphic gene locus determine a size polymorphism of apo(a). There exists an inverse correlation between the size (molecular weight) of apo(a) isoforms and Lp(a) plasma concentrations. The standardization of Lp(a) quantification is still an unresolved task due to the large particle size of Lp(a), the presence of two different apoproteins [apoB and apo(a)], and the large size polymorphism of apo(a) and its homology with plasminogen. A working group sponsored by the IFCC is currently establishing a stable reference standard for Lp(a) as well as a reference method for quantitative analysis. Aside from genetic reasons, abnormal Lp(a) plasma concentrations are observed as secondary to various diseases. Lp(a) plasma levels are elevated over controls in patients with nephrotic syndrome and patients with end-stage renal disease. Following renal transplantation, Lp(a) concentrations decrease to values observed in controls matched for apo(a) type. Controversial data on Lp(a) in diabetes mellitus result mainly from insufficient sample sizes of numerous studies. Large studies and those including apo(a) phenotype analysis came to the conclusion that Lp(a) levels are not or only moderately elevated in insulin-dependent patients. In noninsulin-dependent diabetics, Lp(a) is not elevated. Conflicting data also exist from studies in patients with familial hypercholesterolemia. Several case-control studies reported elevated Lp(a) levels in those patients, suggesting a role of the LDL-receptor pathway for degradation of Lp(a). However, recent turnover studies rejected that concept. Moreover, family studies also revealed data arguing against an influence of the LDL receptor for Lp(a) concentrations. Several rare diseases or disorders, such as LCAT- and LPL-deficiency as well as liver diseases, are associated with low plasma levels or lack of Lp(a).