Significant association between low-molecular-weight apolipoprotein(a) isoforms and intermittent claudication

Small apolipoprotein(a) isoforms may predict primary patency following peripheral arterial revascularization

Background

High lipoprotein (a) [Lp(a)] is associated with adverse limb events in patients undergoing lower extremity revascularization. Lp(a) levels are genetically pre-determined, with LPA gene encoding for two apolipoprotein (a) [apo(a)] isoforms. Isoform size variations are driven by the number of kringle IV type 2 (KIV-2) repeats. Lp(a) levels are inversely correlated with isoform size. In this study, we examined the role of Lp(a) levels, apo(a) size, and inflammatory markers with lower extremity revascularization outcomes.

Methods

Twenty-five subjects with chronic peripheral arterial disease (PAD) underwent open or endovascular lower extremity revascularization (mean age, 66.7 ± 9.7 years; Female = 12; Male = 13; Black = 8; Hispanic = 5; and White = 12). Pre- and postoperative medical history, self-reported symptoms, ankle-brachial indices (ABIs), and lower extremity duplex ultrasounds were obtained. Plasma Lp(a), apoB100, lipid panel, and pro-inflammatory markers (IL-6, IL-18, hs-CRP, TNFα) were assayed preoperatively. Isoform size was estimated using gel electrophoresis and weighted isoform size (wIS) calculated based on % isoform expression. Firth logistic regression was used to examine the relationship between Lp(a) levels and wIS with procedural outcomes: symptoms (better/worse), early primary patency at 2 to 4 weeks, ABIs, and reintervention within 3 to 6 months. We controlled for age, sex, history of diabetes, smoking, statin, antiplatelet, and anticoagulation use.

Results

Median plasma Lp(a) level was 108 (interrquartile range, 44-301) nmol/L. The mean apoB100 level was 168.0 ± 65.8 mg/dL. These values were not statistically different among races. We found no association between Lp(a) levels and wIS with measured plasma pro-inflammatory markers. However, smaller apo(a) wIS was associated with occlusion of the treated lesion(s) in the postoperative period (odds ratio, 1.97; 95% confidence interval, 1.01-3.86; P < .05). The relationship of smaller apo(a) wIS with reintervention was not as strong (odds ratio, 1.57; 95% confidence interval, 0.96-2.56; P = .07). We observed no association between wIS with patient reported symptoms or change in ABIs.

Conclusions

In this small study, subjects with smaller apo(a) isoform size undergoing peripheral arterial revascularization were more likely to experience occlusion in the postoperative period and/or require reintervention. Larger cohort studies identifying the mechanism and validating these preliminary data are needed to improve understanding of long-term peripheral vascular outcomes.

Small apolipoprotein(a) isoforms may predict primary patency following peripheral arterial revascularization

Background

High lipoprotein (a) [Lp(a)] is associated with adverse limb events in patients undergoing lower extremity revascularization. Lp(a) levels are genetically pre-determined, with LPA gene encoding for two apolipoprotein (a) [apo(a)] isoforms. Isoform size variations are driven by the number of kringle IV type 2 (KIV-2) repeats. Lp(a) levels are inversely correlated with isoform size. In this study, we examined the role of Lp(a) levels, apo(a) size and inflammatory markers with lower extremity revascularization outcomes.

Methods

25 subjects with chronic peripheral arterial disease (PAD), underwent open or endovascular lower extremity revascularization (mean age of 66.7±9.7 years; F=12, M=13; Black=8, Hispanic=5, and White=12). Pre- and post-operative medical history, self-reported symptoms, ankle brachial indices (ABIs), and lower extremity duplex ultrasounds were obtained. Plasma Lp(a), apoB100, lipid panel, and pro-inflammatory markers (IL-6, IL-18, hs-CRP, TNFα) were assayed preoperatively. Isoform size was estimated using gel electrophoresis and weighted isoform size ( wIS ) calculated based on % isoform expression. Firth logistic regression was used to examine the relationship between Lp(a) levels, and wIS with procedural outcomes: symptoms (better/worse), primary patency at 2-4 weeks, ABIs, and re-intervention within 3-6 months. We controlled for age, sex, history of diabetes, smoking, statin, antiplatelet and anticoagulation use.

Results

Median plasma Lp(a) level was 108 (44, 301) nmol/L. The mean apoB100 level was 168.0 ± 65.8 mg/dL. These values were not statistically different among races. We found no association between Lp(a) levels and w IS with measured plasma pro-inflammatory markers. However, smaller apo(a) wIS was associated with occlusion of the treated lesion(s) in the postoperative period [OR=1.97 (95% CI 1.01 - 3.86, p<0.05)]. The relationship of smaller apo(a) wIS with re-intervention was not as strong [OR=1.57 (95% CI 0.96 - 2.56), p=0.07]. We observed no association between wIS with patient reported symptoms or change in ABIs.

Conclusions

In this small study, subjects with smaller apo(a) isoform size undergoing peripheral arterial revascularization were more likely to experience occlusion in the perioperative period and/or require re-intervention. Larger cohort studies identifying the mechanism and validating these preliminary data are needed to improve understanding of long-term peripheral vascular outcomes.

Key Findings

25 subjects with symptomatic PAD underwent open or endovascular lower extremity revascularization in a small cohort. Smaller apo(a) isoforms were associated with occlusion of the treated lesion(s) within 2-4 weeks [OR=1.97 (95% CI 1.01 - 3.86, p<0.05)], suggesting apo(a) isoform size as a predictor of primary patency in the early period after lower extremity intervention.

Take Home Message

Subjects with high Lp(a) levels, generally have smaller apo(a) isoform sizes. We find that, in this small cohort, patients undergoing peripheral arterial revascularization subjects with small isoforms are at an increased risk of treated vessel occlusion in the perioperative period.

Table of Contents Summary

Subjects with symptomatic PAD requiring lower extremity revascularization have high median Lp(a) levels. Individuals with smaller apo(a) weighted isoform size (wIS) have lower primary patency rates and/or require re-intervention.

The association of lipoprotein(a) and apolipoprotein(a) phenotypes with peripheral artery disease

AIM

Lipoprotein(a) [Lp(a)] is an independent risk factor of coronary heart disease (CHD) and myocardial infarction. Data about the role of Lp(a) in the development of peripheral artery disease (PAD) is controversial and uncertain. The aim of the study was to evaluate the association between Lp(a), apolipoprotein(a) [apo(a)] phenotypes and PAD.

MATERIALS AND METHODS

The study included 998 patients (707 male and 291 female, average age 60±12). The patients were divided into 4 groups depending on the presence or absence PAD and CHD: group I (n=188, PAD+CHD+), group II (n=78, PAD+CHD-), group III (n=407, PAD-CHD+), group IV (n=325, PAD-CHD-).

RESULTS

The level of Lp(a) was significantly higher in groups I, II, III in comparison with patients of control group (group IV): 34 [15; 80], 30 [10; 49], 22 [8; 60] mg/dl vs. 15 [6; 35] mg/dl respectively, p<0.01 in all cases. Lp(a) level was higher in the group I than in the other groups (p<0.05). The prevalence of elevated Lp(a) level (≥ 30 mg/dl) was significantly higher in groups I, II, III than in control group: 54%, 50%, 43% respectively vs. 30%, p<0.01 in all cases. The prevalence of Lp(a) ≥ 30 mg/dl was more frequent in the group with PAD and CHD than in the group with CHD and without PAD (p=0.02). The odds ratio (OR) of PAD in the presence of elevated Lp(a) level was 1.9 (95%CI, 1.4-2.5, p<0.01). Low molecular weight (LMW) apo(a) phenotype was met more frequently in groups I, II, III compared to group IV: 46%, 56%, 52% respectively vs. 28%, p<0.01. LMW apo(a) in the patients without CHD was associated with PAD (OR 3.3; 95% CI, 1.6-6.8, p<0.01), and there was no association with the patients with CHD. In logistic regression analysis adjusted for age, sex, hypertension, obesity, smoking, diabetes, LDL-C, Lp(a) and LMW apo(a) phenotype were independent predictors of PAD when included separately.

CONCLUSION

Elevated level of Lp(a) and LMW apo(a) phenotype are independent risk factors of PAD. The level of Lp(a) in the patients with PAD and CHD was higher than in the case of isolated lesion of each vascular pool. Higher level of Lp(a) is associated with more severe atherosclerosis involving more than one vascular pools.

Lipoprotein (a) as a cause of cardiovascular disease: insights from epidemiology, genetics, and biology

Human epidemiologic and genetic evidence using the Mendelian randomization approach in large-scale studies now strongly supports that elevated lipoprotein (a) [Lp(a)] is a causal risk factor for cardiovascular disease, that is, for myocardial infarction, atherosclerotic stenosis, and aortic valve stenosis. The Mendelian randomization approach used to infer causality is generally not affected by confounding and reverse causation, the major problems of observational epidemiology. This approach is particularly valuable to study causality of Lp(a), as single genetic variants exist that explain 27-28% of all variation in plasma Lp(a). The most important genetic variant likely is the kringle IV type 2 (KIV-2) copy number variant, as the apo(a) product of this variant influences fibrinolysis and thereby thrombosis, as opposed to the Lp(a) particle per se. We speculate that the physiological role of KIV-2 in Lp(a) could be through wound healing during childbirth, infections, and injury, a role that, in addition, could lead to more blood clots promoting stenosis of arteries and the aortic valve, and myocardial infarction. Randomized placebo-controlled trials of Lp(a) reduction in individuals with very high concentrations to reduce cardiovascular disease are awaited. Recent genetic evidence documents elevated Lp(a) as a cause of myocardial infarction, atherosclerotic stenosis, and aortic valve stenosis.

Lipoprotein (a): a Unique Independent Risk Factor for Coronary Artery Disease

The current epidemic affecting Indians is coronary artery disease (CAD), and is currently one of the most common causes of mortality and morbidity in developed and developing countries. The higher rate of CAD in Indians, as compared to people of other ethnic origin, may indicate a possible genetic susceptibility. Hence, Lp(a), an independent genetic risk marker for atherosclerosis and cardiovascular disease assumes great importance. Lp(a), an atherogenic lipoprotein, contains a cholesterol rich LDL particle, one molecule of apolipoprotein B-100 and a unique protein, apolipoprotein (a) which distinguishes it from LDL. Apo(a) is highly polymorphic and an inverse relationship between Lp(a) concentration and apo(a) isoform size has been observed. This is genetically controlled suggesting a functional diversity among the apo(a) isoforms. The LPA gene codes for apo(a) whose genetic heterogeneity is due to variations in its number of kringles. The exact pathogenic mechanism of Lp(a) is still not completely elucidated, but the structural homology of Lp(a) with LDL and plasmin is possibly responsible for its acting as a link between atherosclerosis and thrombosis. Upper limits of normal Lp(a) levels have not been defined for the Indian population. A cut off limit of 20 mg/dL has been suggested while for the Caucasian population it is 30 mg/dL. Though a variety of assays are available for its measurement, standardization of the analytical method is highly complicated as a majority of the methods are affected by the heterogeneity in apo(a) size. No therapeutic drug selectively targets Lp(a) but recently, new modifiers of apo(a) synthesis are being considered.

Lipoprotein (a) concentrations, apolipoprotein (a) phenotypes, and peripheral arterial disease in three independent cohorts

Aims

The relevance of lipoprotein(a) [Lp(a)] concentrations and low-molecular-weight (LMW) apo(a) phenotypes in peripheral arterial disease (PAD) has only been investigated by few studies. Therefore, we analysed this association in three independent cohorts and performed a Mendelian Randomization approach using instrumental variable regression.

Methods and results

Lp(a) concentrations, apo(a) phenotypes, and one SNP in the LPA gene (rs10455872) were measured in the CAVASIC study, including 241 male patients with intermittent claudication and 246 age- and diabetes-matched controls as well as in the two population-based studies KORA F3 (n = 3184) and KORA F4 (n = 3080). In KORA F3/F4, 109/80 persons suffered from intermittent claudication, 200/144 from PAD, and 128/103 showed an ankle–brachial index (ABI) <0.9. In CAVASIC, adjusted logistic regression analyses revealed significant associations between an increase of log-Lp(a) per one standard deviation (SD) (OR = 1.28, P = 0.02) as well as LMW apo(a) phenotypes and symptomatic PAD (OR = 1.65, P = 0.03). Linear regression models with continuous ABI showed a significant association in the combined analyses of KORA F3/F4: an increase in log-Lp(a) per one SD (β = −0.006, P = 0.005) and the presence of LMW apo(a) phenotypes (β = −0.011, P = 0.02) or the minor allele of rs10455872 (ß = −0.016, P = 0.03) were associated with a decrease in ABI in the fully adjusted linear and instrumental variable regression models.

Conclusion

Analyses in three independent populations showed significant associations of Lp(a) concentrations, LMW apo(a) phenotypes, and rs10455872 with PAD. This points to a causal relationship between Lp(a) and PAD since the genetically determined apo(a) phenotypes and SNP alleles are indeed associated with PAD.

Genetic determinants of the ankle-brachial index: a meta-analysis of a cardiovascular candidate gene 50K SNP panel in the candidate gene association resource (CARe) consortium

BACKGROUND

Candidate gene association studies for peripheral artery disease (PAD), including subclinical disease assessed with the ankle-brachial index (ABI), have been limited by the modest number of genes examined. We conducted a two stage meta-analysis of ∼50,000 SNPs across ∼2100 candidate genes to identify genetic variants for ABI.

METHODS AND RESULTS

We studied subjects of European ancestry from 8 studies (n=21,547, 55% women, mean age 44-73 years) and African American ancestry from 5 studies (n=7267, 60% women, mean age 41-73 years) involved in the candidate gene association resource (CARe) consortium. In each ethnic group, additive genetic models were used (with each additional copy of the minor allele corresponding to the given beta) to test each SNP for association with continuous ABI (excluding ABI>1.40) and PAD (defined as ABI<0.90) using linear or logistic regression with adjustment for known PAD risk factors and population stratification. We then conducted a fixed-effects inverse-variance weighted meta-analyses considering a p<2×10(-6) to denote statistical significance.

RESULTS

In the European ancestry discovery meta-analyses, rs2171209 in SYTL3 (β=-0.007, p=6.02×10(-7)) and rs290481 in TCF7L2 (β=-0.008, p=7.01×10(-7)) were significantly associated with ABI. None of the SNP associations for PAD were significant, though a SNP in CYP2B6 (p=4.99×10(-5)) was among the strongest associations. These 3 genes are linked to key PAD risk factors (lipoprotein(a), type 2 diabetes, and smoking behavior, respectively). We sought replication in 6 population-based and 3 clinical samples (n=15,440) for rs290481 and rs2171209. However, in the replication stage (rs2171209, p=0.75; rs290481, p=0.19) and in the combined discovery and replication analysis the SNP-ABI associations were no longer significant (rs2171209, p=1.14×10(-3); rs290481, p=8.88×10(-5)). In African Americans, none of the SNP associations for ABI or PAD achieved an experiment-wide level of significance.

CONCLUSIONS

Genetic determinants of ABI and PAD remain elusive. Follow-up of these preliminary findings may uncover important biology given the known gene-risk factor associations. New and more powerful approaches to PAD gene discovery are warranted.

Increased serum lipoprotein(a) concentrations and low molecular weight phenotypes of apolipoprotein(a) are associated with symptomatic peripheral arterial disease

BACKGROUND

Increased concentrations of lipoprotein(a) [Lp(a)] have been considered a genetically determined risk factor for coronary artery and cerebrovascular disease. Only 2 small and conflicting studies have investigated the possibility of an association of peripheral arterial disease (PAD) with high serum Lp(a) concentrations and low molecular weight (LMW) phenotypes of apolipoprotein(a) [apo(a)].

METHODS

We measured serum concentrations of Lp(a) and apo(a) phenotypes in 213 patients with symptomatic PAD and 213 controls matched for sex, age (within 2 years), and presence of diabetes.

RESULTS

Patients with PAD showed significantly higher median serum concentrations of Lp(a) (76 vs 47 mg/L; P = 0.003) and a higher frequency of LMW apo(a) phenotypes (41% vs 26%; P = 0.002) than controls. After adjustment for several potential confounders, increased Lp(a) concentrations (>195 mg/L, i.e., 75th percentile of the entire study sample) and LMW apo(a) phenotypes were significant predictors of PAD, with odds ratios of 3.73 (95% CI 2.08-6.67; P <0.001) and 2.21 (95% CI 1.33-3.67; P = 0.002), respectively.

CONCLUSIONS

In this study sample, both increased serum concentrations of Lp(a) and the presence of LMW apo(a) phenotypes were associated with the presence of symptomatic PAD independent of traditional and nontraditional cardiovascular risk factors. Because PAD is considered an indicator of systemic atherosclerotic disease, our results suggest a possible role of Lp(a) as a genetically determined marker for systemic atherosclerosis.

Lipoprotein(a): A Unique Risk Factor for Cardiovascular Disease

Lipoprotein(a) (Lp(a)) is present in humans and primates. It has many properties in common with low-density lipoprotein, but contains a unique protein moiety designated apo(a), which is linked to apolipoprotein B-100 by a single disulfide bond. International standards for Lp(a) measurement and optimized Lp(a) assays insensitive to isoform size are not yet widely available. Lp(a) is a risk factor for coronary artery disease, and smaller size apo(a) is associated with coronary artery disease. The physiologic role of Lp(a) is unknown.

Lipoprotein(a) and Thrombocytes: Potential Mechanisms Underlying Cardiovascular Risk

Plasma levels of lipoprotein(a), Lp(a), is an independent risk factor for cardiovascular disease. Lp(a) has many properties in common with low-density lipoprotein (LDL), including a cholesteryl ester-rich lipid core and the presence of one copy of apolipoprotein B-100; both apoB-100 and the lipid core are pro-atherogenic. In addition, Lp(a) contains a unique hydrophilic, carbohydrate-rich protein, apo(a), linked to apoB through a single disulfide bond connecting the C-terminal regions of the two proteins. The similarities between apolipoprotein(a), apo(a), and plasminogen has initiated numerous studies on the possible role of Lp(a) as a prothrombotic agent. Studies to date suggest that Lp(a) has antifibrinolytic and procoagulant properties. In this review, we summarize recent studies focused on the interaction between Lp(a) and platelets. Collectively, results to date illustrate that thrombogenicity associated with Lp(a) could be due to risk associated with the LDL moiety, with the apo(a) moiety, or from the combination of those in Lp(a). Present findings suggest that the various components of Lp(a) may impact to a varying degree on different underlying pathways involved in platelet activation and aggregation. On balance, results indicate an effect by Lp(a) on platelet function and future studies focused on specific Lp(a) components, such as the role of apo(a) and of the LDL-like lipid moiety, are needed.

Lipoprotein(a): an elusive cardiovascular risk factor

Lipoprotein (a) [Lp(a)], is present only in humans, Old World nonhuman primates, and the European hedgehog. Lp(a) has many properties in common with low-density lipoprotein (LDL) but contains a unique protein, apo(a), which is structurally different from other apolipoproteins. The size of the apo(a) gene is highly variable, resulting in the protein molecular weight ranging from 300 to 800 kDa; this large variation may be caused by neutral evolution in the absence of any selection advantage. Apo(a) influences to a major extent metabolic and physicochemical properties of Lp(a), and the size polymorphism of the apo(a) gene contributes to the pronounced heterogeneity of Lp(a). There is an inverse relationship between apo(a) size and Lp(a) levels; however, this pattern is complex. For a given apo(a) size, there is a considerable variation in Lp(a) levels across individuals, underscoring the importance to assess allele-specific Lp(a) levels. Further, Lp(a) levels differ between populations, and blacks have generally higher levels than Asians and whites, adjusting for apo(a) sizes. In addition to the apo(a) size polymorphism, an upstream pentanucleotide repeat (TTTTA(n)) affects Lp(a) levels. Several meta-analyses have provided support for an association between Lp(a) and coronary artery disease, and the levels of Lp(a) carried in particles with smaller size apo(a) isoforms are associated with cardiovascular disease or with preclinical vascular changes. Further, there is an interaction between Lp(a) and other risk factors for cardiovascular disease. The physiological role of Lp(a) is unknown, although a majority of studies implicate Lp(a) as a risk factor.

The apolipoprotein(a) size polymorphism is associated with nephrotic syndrome

BACKGROUND

The atherogenic serum lipoprotein(a) [Lp(a)] is significantly elevated in patients with nephrotic syndrome. The underlying mechanism for this elevation is poorly understood.

METHODS

We investigated in 207 patients with nondiabetic nephrotic syndrome and 274 controls whether the apolipoprotein(a) [apo(a)] kringle-IV repeat polymorphism explains the elevated Lp(a) levels in these patients.

RESULTS

Patients showed a tremendous elevation of Lp(a) concentrations when compared to controls (mean 60.4 vs. 20.0 mg/dL and median 29.8 vs. 6.4 mg/dL, P < 0.0001). Primary and secondary causes contributed to this elevation. The primary causes became apparent by a markedly elevated number of low-molecular-weight apo(a) phenotypes which are usually associated with high Lp(a) levels. This frequency was 35.7% in patients compared to only 24.8% in controls (P= 0.009). In addition, secondary causes by the pathogenetic mechanisms of the nephrotic syndrome itself resulted in a different increase of Lp(a) in the various apo(a) isoform groups. Based on the measured Lp(a) concentrations in each subject, we calculated separately the Lp(a) concentrations arising from the two expressed isoforms by estimating the relative proportion of the two serum isoforms in the sodium dodecyl sulfate (SDS) agarose gel electrophoresis. Low-molecular-weight isoforms were associated with 40% to 75% elevated Lp(a) concentrations when compared to matched isoforms from controls. High-molecular-weight apo(a) isoforms showed 100% to 500% elevated Lp(a) levels compared to matched isoforms from controls. The severity of the nephrotic syndrome as well as the degree of renal impairment did not influence the Lp(a) concentrations.

CONCLUSION

The tremendously increased Lp(a) levels in nephrotic syndrome ar caused by primary genetic as well as disease-related mechanisms.

Effect of Aspirin Treatment on Serum Concentrations of Lipoprotein(a) in Patients with Atherosclerotic Diseases

Background: Increased serum lipoprotein(a) [Lp(a)] is an independent risk factor for atherosclerosis. We previously reported that aspirin reduced Lp(a) production by cultured hepatocytes via the reduction of apolipoprotein(a) [apo(a)] gene transcription.

Methods: We evaluated both the effect of aspirin treatment (81 mg/day) on serum Lp(a) concentrations and the correlation between the degree of reduction in serum Lp(a) and the type of apo(a) isoform in 70 patients with coronary artery disease or cerebral infarction.

Results: Aspirin lowered serum Lp(a) concentrations to ∼80% of the baseline values in patients with high Lp(a) concentrations (&gt;300 mg/L). The percentage of decrease in serum Lp(a) was larger in patients with high Lp(a) than in patients with low Lp(a) (&lt;300 mg/L), irrespective of apo(a) isoform size. The decreases in serum Lp(a) in high Lp(a) patients with both the high-molecular-weight and the low-molecular-weight isoforms were positively correlated with the baseline Lp(a) concentrations.

Conclusions: Because the secretory efficiencies of apo(a) in the same isoform are likely to be similar, the difference in serum Lp(a) concentrations in patients having the same apo(a) isoform depends on the transcriptional activity of the apo(a) gene. These findings suggest that aspirin decreases serum Lp(a) concentrations via a decrease in apo(a) gene transcription more effectively in patients with high transcriptional activity of this gene.

Influence of lipoprotein(a) on restenosis after femoropopliteal percutaneous transluminal angioplasty in Type 2 diabetic patients

OBJECTIVE

The influence of vascular morphology and metabolic parameters including lipoprotein(a) (Lp(a)) on restenosis after peripheral angioplasty has been compared in Type 2 diabetes (DM) vs. non-diabetic patients (ND).

RESEARCH DESIGN AND METHODS

The clinical course and risk profile of 132 (54 DM vs. 78 ND) patients with peripheral arterial occlusive disease (PAD) were observed prospectively following femoropopliteal angioplasty (PTA). Clinical examination, oscillometry, ankle brachial blood pressure index (ABI) and the toe systolic blood pressure index (TSPI) were used during follow-up. Duplex sonography and reangiography were also used to verify suspected restenosis or reocclusion.

RESULTS

At the time of intervention patients with DM had a lower median Lp(a) of 9 vs. 15 mg/dl (P < 0.01) in patients without diabetes. Recurrence within 1 year after PTA occurred in 25 diabetic (= 46%, Lp(a) 12 mg/dl) and 30 non-diabetic (= 38%, Lp(a) 48 mg/dl) patients. DM patients with 1 year's patency had a median Lp(a) of 7 vs. 11 mg/dl in non-diabetic patients (P < 0.05). However, 12 months after angioplasty Lp(a) correlated negatively with the ABI (r = -0.44, P < 0.01) in diabetic and in non-diabetic patients (r = -0.20, P < 0.05). The probability of recurrence after PTA continuously increased with higher levels of Lp(a) in each subgroup of patients.

CONCLUSIONS

Our data indicate that Lp(a) is generally lower in those with peripheral arterial occlusive disease and Type 2 diabetes than in non-diabetic individuals. The increased risk for restenosis with rising levels of Lp(a) is set at a lower Lp(a) in diabetes and may be more harmful for diabetic patients.

Inhibition of fibrinolysis by lipoprotein(a)

A high plasma concentration of lipoprotein Lp(a) is now considered to be a major and independent risk factor for cerebro- and cardiovascular atherothrombosis. The mechanism by which Lp(a) may favour this pathological state may be related to its particular structure, a plasminogen-like glycoprotein, apo(a), that is disulfide linked to the apo B100 of an atherogenic LDL-like particle. Apo(a) exists in several isoforms defined by a variable number of copies of plasminogen-like kringle 4 and single copies of kringle 5 and the catalytic region. At least one of the plasminogen-like kringle 4 copies present in apo(a) (kringle IV type 10) contains a lysine binding site (LBS) that is similar to that of plasminogen. This structure allows binding of these proteins to fibrin and cell membranes. Plasminogen thus bound is cleaved at Arg561-Val562 by plasminogen activators and transformed into plasmin. This mechanism ensures fibrinolysis and pericellular proteolysis. In apo(a) a Ser-Ile substitution at the Arg-Val plasminogen activation cleavage site prevents its transformation into a plasmin-like enzyme. Because of this structural/functional homology and enzymatic difference, Lp(a) may compete with plasminogen for binding to lysine residues and impair, thereby, fibrinolysis and pericellular proteolysis. High concentrations of Lp(a) in plasma may, therefore, represent a potential source of antifibrinolytic activity. Indeed, we have recently shown that during the course of the nephrotic syndrome the amount of plasminogen bound and plasmin formed at the surface of fibrin are directly related to in vivo variations in the circulating concentration of Lp(a) (Arterioscler. Thromb. Vasc. Biol., 2000, 20: 575-584; Thromb. Haemost., 1999, 82: 121-127). This antifibrinolytic effect is primarily defined by the size of the apo(a) polymorphs, which show heterogeneity in their fibrin-binding activity--only small size isoforms display high affinity binding to fibrin (Biochemistry, 1995, 34: 13353-13358). Thus, in heterozygous subjects the amount of Lp(a) or plasminogen bound to fibrin is a function of the affinity of each of the apo(a) isoforms and of their concentration relative to each other and to plasminogen. The real risk factor is, therefore, the Lp(a) subpopulation with high affinity for fibrin. According to this concept, some Lp(a) phenotypes may not be related to atherothrombosis and, therefore, high Lp(a) in some individuals might not represent a risk factor for cardiovascular disease. In agreement with these data, it has been recently reported that Lp(a) particles containing low molecular mass apo(a) emerged as one of the leading risk conditions in advanced stenotic atherosclerosis (Circulation, 1999, 100: 1154-1160). The predictive value of high Lp(a) as a risk factor, therefore, depends on the relative concentration of Lp(a) particles containing small apo(a) isoforms with the highest affinity for fibrin. Within this context, the development of agents able to selectively neutralise the antifibrinolytic activity of Lp(a), offers new perspectives in the prevention and treatment of the cardiovascular risk associated with high concentrations of thrombogenic Lp(a).

Relationship of lipoprotein(a) to variables of coagulation in hypertensive subjects

BACKGROUND

Coagulation factors are independent predictors of cardiovascular damage in the general population. The purpose of this study was to investigate the relationships between general cardiovascular risk factors, lipoprotein(a) (Lp(a)), and some hemostatic variables, and to characterize the isoforms of apolipoprotein(a) (apo(a)) in hypertensive subjects.

METHODS

Plasma lipids, apolipoproteins, Lp(a), apo(a) isoforms, fibrinogen, and parameters that directly reflect the coagulation activation were measured in 389 untreated essential hypertensive patients recruited at a hypertension clinic. Hypertensive patients were compared with 323 normotensive controls.

RESULTS

In normotensive subjects, Lp(a) concentrations were significantly correlated with fibrinogen (r = 0.138; P < 0.02) but not D-dimer (r = 0.074; not significant). In hypertensive subjects, log Lp(a) concentrations were significantly correlated with age (r = 0.127; P < 0.02), apo-B (r = 0.128; P < 0.02), plasma fibrinogen (r = 0.193; P < 0.001), and fibrin D-dimer (r = 0.200; P < 0.001) levels, but not with body mass index, blood pressure, cholesterol, triglycerides, apo-AI, prothrombin fragment 1 + 2, and antithrombin III. The relationship of Lp(a) with fibrinogen (male: r = 0.198, P < 0.002; female: r = 0.177, P < 0.01) and D-dimer (male: r = 0.211, P < 0.002; female: r = 0.188, P < 0.01) was significant in both sexes, whereas the relationship of Lp(a) with age and apo-B was found only in males. Multivariate analysis showed that both fibrinogen and D-dimer were independently related with Lp(a). Elevated fibrinogen, D-dimer, and Lp(a) levels were significantly and independently associated with clinical evidence of atherosclerotic disease. Apo(a) phenotypes were analyzed to investigate the genetic background of the relationships between Lp(a) and coagulation parameters. In both hypertensive and normotensive subjects, Lp(a) levels were inversely correlated with apo(a) isoform protein size, whereas fibrinogen and D-dimer concentrations were comparable in patients with apo(a) isoforms of different size.

CONCLUSIONS

The relationship between Lp(a) and clotting variables is significantly stronger in hypertensive than in normotensive subjects, providing a compelling argument for accelerated progression of atherothrombosis in these patients.

Effect of apolipoprotein E polymorphism on serum lipid, lipoproteins, and atherosclerosis in hemodialysis patients

Atherosclerosis and cardiovascular disease are the main causes of death in hemodialysis patients. Possession of the apolipoprotein E4 (ApoE4) allele has been associated with increased levels of serum lipids and with coronary and carotid artery atherosclerosis. We investigated the possible relationship between ApoE polymorphism and atherosclerosis risk factors in hemodialysis patients. Two hundred sixty-nine hemodialysis patients (115 women, 154 men) were included in our study. The mean patient age and mean hemodialysis duration were 45.8 +/- 15.3 years and 52.6 +/- 40.6 months, respectively. Testing was done on all patients to determine ApoE genotype and serum levels of total cholesterol (T-Cho), low-density lipoprotein (LDL-C), high-density cholesterol (HDL-C), triglyceride (TG), lipoprotein (a) (Lp[a]), intact parathormone (iPTH), and fibrinogen. ApoE genotype was identified with the polymerase chain reaction. Ultrasonographic measurement of carotid artery intima media thickness (IMT) was used to diagnose atherosclerosis. We also analyzed ApoE polymorphism and risk factors such as age, gender, duration of hemodialysis, smoking, and hypertension in relation to the presence of atherosclerosis. Serum T-Cho and LDL-C levels were higher in patients with the ApoE4/3 phenotype than in those with ApoE3/3 and ApoE3/2 phenotypes (P < 0.05). However, there was no statistically significant link between ApoE polymorphism and serum levels of TG, HDL-C, or Lp(a) (P > 0.05). Apart from a relationship with age and duration of hemodialysis (P < 0.05), we found no significant association between atherosclerosis and ApoE polymorphism or the other risk factors analyzed (P > 0.05). In conclusion, although ApoE polymorphism significantly affects serum levels of T-Cho and LDL-C in hemodialysis patients, this study indicates that ApoE polymorphism is not associated with the presence of atherosclerosis in these individuals. The high incidence of atherosclerosis in these patients underlines the need for further research on other possible causative factors.

Lipoprotein (a), haemostatic variables and cardiovascular damage in hypertensive patients

OBJECTIVE

Lipoproteins and coagulation factors are independent predictors of atherothrombotic events in the general population and their interaction may contribute to the development of cardiovascular damage. This study was designed to assess relationships between lipoproteins, haemostatic variables, and atherosclerotic complications in hypertensive patients.

METHODS

In 389 untreated essential hypertensive patients recruited at a hypertension clinic, we measured plasma lipids, apolipoproteins, lipoprotein (a), apolipoprotein (a) isoforms, fibrinogen, and parameters that directly reflect the coagulation activation. Hypertensive patients were compared to 92 normotensive controls.

RESULTS

Univariate analysis showed log lipoprotein (a) concentrations to be significantly correlated with age (P< 0.02), apolipoprotein B (P< 0.02), plasma fibrinogen (P< 0.001), and fibrin D-dimer (P< 0.001) levels, but not with body mass index, blood pressure, dietary fat intake, cholesterol, triglycerides, apolipoprotein Al, prothrombin fragment 1 + 2, and antithrombin III. The relationship of lipoprotein (a) with fibrinogen and D-dimer was present in both sexes, whereas the relationship of lipoprotein (a) with age and apolipoprotein B was found only in males. Multiple regression analysis showed that both fibrinogen and D-dimer were independently related with lipoprotein (a). Elevated fibrinogen, D-dimer, and lipoprotein (a) levels were significantly and independently associated with clinical evidence of atherosclerotic disease. To investigate whether the relationships of lipoprotein (a) with coagulation parameters are genetically determined, we analysed apolipoprotein (a) phenotypes in a subset of 188 hypertensive patients. While lipoprotein (a) levels were inversely correlated with apolipoprotein (a) isoform protein size, both fibrinogen and D-dimer concentrations were comparable in patients with apolipoprotein (a) isoforms of different size.

CONCLUSIONS

This study demonstrates a relationship between lipoprotein (a) and clotting variables in hypertensive patients that may contribute to atherosclerotic damage in these patients. There is no evidence of a genetic background for this relationship.

Lipoprotein(a) serum concentrations and apolipoprotein(a) phenotypes in mild and moderate renal failure

High lipoprotein(a) (Lp(a)) serum concentrations and the underlying apolipoprotein(a) (apo(a)) phenotypes are risk factors for cardiovascular disease in the general population as well as in patients with renal disease. Lp(a) concentrations are markedly elevated in patients with end-stage renal disease. However, nothing is known about the changes of Lp(a) depending on apo(a) size polymorphism in the earliest stages of renal impairment. In this study, GFR was measured by iohexol technique in 227 non-nephrotic patients with different degrees of renal impairment and was then correlated with Lp(a) serum concentrations stratified according to low (LMW) and high (HMW) molecular weight apo(a) phenotypes. Lp(a) increased significantly with decreasing GFR. Such an increase was dependent on apo(a) phenotype. Only renal patients with HMW apo(a) phenotypes expressed higher median Lp(a) concentrations, i.e., 6.2 mg/dl at GFR >90 ml/min per 1.73 m2, 14.2 at GFR 45 to 90 ml/min per 1.73 m2, and 18.0 mg/dl at GFR <45 ml/min per 1.73 m2. These values were markedly different when compared with apo(a) phenotype-matched control subjects who had a median level of 4.4 mg/dl (ANOVA, linear relationship, P < 0.001). In contrast, no significant differences were observed at different stages of renal function in patients with LMW apo(a) phenotypes when compared with phenotype-matched control subjects. The elevation of Lp(a) was independent of the type of primary renal disease and was not related to the concentration of C-reactive protein. Multiple linear regression analysis found that the apo(a) phenotype and GFR were significantly associated with Lp(a) levels. Non-nephrotic-range proteinuria modified the association between GFR and Lp(a) levels. In summary, an increase of Lp(a) concentrations, compared with apo(a) phenotype-matched control subjects, is seen in non-nephrotic patients with primary renal disease even in the earliest stage when GFR is not yet subnormal. This change is found only in subjects with HMW apo(a) phenotypes, however.

Influence of systemic factors on pre-existing intimal hyperplasia and their effect on the outcome of infrainguinal arterial reconstruction with vein

BACKGROUND

The association between raised levels of homocysteine, fibrinogen and lipoprotein (a), and the presence of pre-existing intimal hyperplasia (IH) in vein has not been assessed. The positive association between such hyperplasia and graft failure following infrainguinal arterial reconstruction, and between lipoprotein (a) and graft failure, is disputed. The influence of homocysteine on outcome has not been investigated prospectively.

METHODS

Fifty-seven patients (63 grafts) undergoing infrainguinal arterial reconstruction with saphenous vein were studied. Homocysteine, fibrinogen and lipoprotein (a) levels were measured, and a vein biopsy was taken at operation. Patients underwent graft surveillance and outcome at 12 months was determined.

RESULTS

Fifty-seven per cent of patients had hyperhomocysteinaemia. Patients with pre-existing IH had significantly higher homocysteine levels. There was no association between homocysteine and outcome, or between fibrinogen and pre-existing IH or outcome. Lipoprotein (a) levels were significantly lower in patients with pre-existing disease, and were lower, but not significantly, in those whose grafts failed. The correlation between pre-existing IH and vein graft failure was highly significant.

CONCLUSION

Hyperhomocysteinaemia is associated with peripheral vascular disease and the development of pre-existing IH in vein, which itself is associated with vein graft failure.

Lipoprotein(a) and apolipoprotein(a) isoforms and proteinuria in patients with moderate renal failure

BACKGROUND

Atherosclerotic diseases are a major cause of death in patients with renal failure. Increased serum concentrations of lipoprotein(a) [Lp(a)] have been established as a genetically controlled risk factor for these diseases and have been demonstrated in patients with moderate renal failure, suggesting that this lipoprotein contributes to the increased cardiovascular risk seen in these patients. Variable alleles at the apolipoprotein(a) [apo(a)] gene locus are the main determinants of the serum Lp(a) level in the general population. The purpose of this study was to investigate apo(a) isoforms in patients with moderate renal failure and mild proteinuria (less than 1.0 g/day).

METHODS

In 250 consecutive subjects recruited at a hypertension clinic, we assessed the renal function by 24-hour creatinine clearance, proteinuria, and microalbuminuria, as well as the prevalence of atherosclerotic disease, and we also measured apo(a) isoforms, serum albumin, and Lp(a) concentrations.

RESULTS

Moderate impairment of renal function (creatinine clearance, 30 to 89 ml/min per 1.73 m2 of body surface area) was found in 97 patients. Lp(a) levels were significantly greater in patients with moderate renal failure (21.7+/-23.9 mg/dl) as compared with patients with normal renal function (15.6+/-16.4 mg/dl, P<0.001), and an inverse correlation was observed between log Lp(a) and creatinine clearance (r = -0.181, P <0.01). However, no difference was found in the frequency of low molecular weight apo(a) isoforms between patients with normal (25.5%) and impaired (27.8%) renal function. Only patients with the smallest size apo(a) isoforms exhibited significantly elevated levels of Lp(a), whereas the large-size isoforms had similar concentrations in patients with normal and impaired renal function. No significant relationship was found between serum Lp(a) and proteinuria. Clinical and laboratory evidence of one or more events attributed to atherosclerosis was found in 9.8% of patients with normal renal function and 25.8% of patients with moderate renal failure (P<0.001).

CONCLUSIONS

These results indicate that renal failure per se or other genes beside the apo(a) gene locus are responsible for the elevation of serum Lp(a) levels in patients with moderate impairment of renal function. The elevation of Lp(a) levels occurs independently of the level of proteinuria and may contribute to the risk for atherosclerotic disease in these patients.

Lipoprotein(a) plasma concentrations after renal transplantation: a prospective evaluation after 4 years of follow-up

The highly atherogenic lipoprotein(a) [Lp(a)] is significantly elevated in patients with renal disease. It is discussed controversially whether Lp(a) concentrations decrease after renal transplantation and whether the mode of immunosuppressive therapy influences the Lp(a) concentrations. In a prospective study the Lp(a) concentrations before and on average 48 months after renal transplantation were measured in 145 patients. The determinants of the relative changes of Lp(a) concentrations were investigated in a multivariate analysis. Patients treated by CAPD showed a larger decrease of Lp(a) than hemodialysis patients, reflecting their markedly higher Lp(a) levels before transplantation. The relative decrease of Lp(a) was higher with increasing Lp(a) concentrations before transplantation in combination with an increasing molecular weight of apolipoprotein(a) [apo(a)]. That means that the relative decrease of Lp(a) is related to the Lp(a) concentration and the apo(a) size polymorphism. With increasing proteinuria and decreasing glomerular filtration rate, the relative decrease of Lp(a) became less pronounced. Neither prednisolone nor cyclosporine (CsA) had a significant impact on the Lp(a) concentration changes. Azathioprine (Aza) was the only immunosuppressive drug which had a dose-dependent influence on the relative decrease of Lp(a) levels. These data clearly demonstrate a decrease of Lp(a) following renal transplantation which is caused by the restoration of kidney function. The relative decrease is influenced by Aza but not by CsA or prednisolone.

The low molecular weight apo(a) phenotype is an independent predictor for coronary artery disease in hemodialysis patients: a prospective follow-up

Patients with end-stage renal disease treated by hemodialysis have a tremendous risk for cardiovascular complications that cannot be explained by traditional atherosclerosis risk factors. Lipoprotein(a) (Lp(a)), a risk factor for these complications in the general population, is significantly elevated in these patients. In this study, it was determined whether Lp(a) and/or the genetically determined apo(a) phenotype are risk predictors for the development of coronary artery disease in these patients. A cohort of 440 unselected hemodialysis patients were followed for a period of 5 yr independent of the cause of renal disease, duration of preceding treatment, and the preexistence of coronary artery disease at study entry. Coronary events defined as definite myocardial infarction, percutaneous transluminal coronary angioplasty, aortocoronary bypass, or a stenosis >50% in the coronary angiography were the main outcome measure. Sixty-six (15%) of the 440 patients suffered a coronary event during follow-up. In univariate analysis, patients with events were significantly older and showed a trend to lower HDL cholesterol concentrations, and higher apolipoprotein B and Lp(a) concentrations without reaching significance. Apo(a) phenotypes of low molecular weight, however, were significantly more frequent in patients with compared to those without events (43.9% versus 21.9%, P<0.001). The other lipids, lipoproteins, and apolipoproteins were similar in both groups. Multiple Cox proportional hazards regression analysis found age and the apo(a) phenotype to be the best predictors for coronary events during the observation period, independent of whether patients with a preexisting coronary artery disease or an age >65 yr at the study entry or both were excluded from the analysis. Diabetes mellitus was a risk factor only in presence of a low molecular weight apo(a) phenotype. The genetically determined apo(a) phenotype is a strong and independent predictor for coronary events in hemodialysis patients. Apo(a) phenotyping might be helpful to identify hemodialysis patients at high risk for coronary artery disease.

Lipoprotein(a) and dietary proteins: casein lowers lipoprotein(a) concentrations as compared with soy protein

BACKGROUND

Substitution of soy protein for casein in the diet decreases LDL cholesterol and increases HDL cholesterol. How the 2 proteins affect lipoprotein(a) [Lp(a)], an independent risk factor for coronary artery disease, is unknown.

OBJECTIVE

We compared the effects of dietary soy protein and casein on plasma Lp(a) concentrations.

DESIGN

Nine normolipidemic men were studied initially while consuming their habitual, self-selected diets, and then, in a crossover design, while consuming 2 liquid-formula diets containing either casein or soy protein. The dietary periods lasted 45 d (n = 7) or 33 d (n = 2). Fasting total cholesterol, LDL-cholesterol, HDL-cholesterol, triacylglycerol, and Lp(a) concentrations were measured throughout.

RESULTS

After 30 d of each diet, the mean concentration of Lp(a) was not significantly different after the soy-protein and self-selected diets. However, Lp(a) decreased by an average of 50% (P < 0.001) after the casein diet as compared with concentrations after both the soy-protein and self-selected diets. Two weeks after subjects switched from the self-selected to the soy-protein diet, Lp(a) increased by 20% (P = 0.065), but subsequently decreased to baseline. In contrast, the switch to the casein diet did not cause an increase in Lp(a), but instead a continuing decrease in mean concentrations to 65% below baseline (P < 0.0002). Total cholesterol, LDL cholesterol, and HDL cholesterol were significantly lower > or =30 d after both the casein and soy-protein diets than after the self-selected diet (P < 0.001). HDL cholesterol was 11% higher after the soy-protein diet than after the casein diet (P < 0.002), but LDL cholesterol, total cholesterol, and triacylglycerol were not significantly different after the casein and soy-protein diets.

CONCLUSION

These findings indicate that soy protein may have an Lp(a)-raising effect, potentially detrimental to its use in antiatherogenic diets.

Is lipoprotein(a) an independent risk factor for ischemic heart disease in men? The Quebec Cardiovascular Study

OBJECTIVES

This study was undertaken to determine whether lipoprotein(a) [Lp(a)] is an independent risk factor for ischemic heart disease (IHD) and to establish the relation of Lp(a) to the other lipid fractions.

BACKGROUND

Several, but not all, studies have shown that elevated Lp(a) concentrations may be associated with IHD; very few have been prospective.

METHODS

A 5-year prospective follow-up study was conducted in 2,156 French Canadian men 47 to 76 years old, without clinical evidence of IHD. Lipid measurements obtained at baseline included total cholesterol, low density lipoprotein (LDL) cholesterol, high density lipoprotein (HDL) cholesterol, apoprotein B and Lp(a). During the follow-up period, there were 116 first IHD events (myocardial infarction, angina, death). Adjusted proportional hazards models were used to estimate the relative risk for the different variables. The cohort was also classified according to Lp(a) levels and other lipid risk factor tertiles to evaluate the relation of elevated Lp(a) levels to these risk factors. A cutoff value of 30 mg/dl was used for Lp(a). Risk ratios were calculated using the group with low Lp(a) levels and the first tertile of lipid measures as a reference.

RESULTS

Lp(a) was not an independent risk factor for IHD but seemed to increase the deleterious effects of mildly elevated LDL cholesterol and elevated total cholesterol and apoprotein B levels and seemed to counteract the beneficial effects associated with elevated HDL cholesterol levels.

CONCLUSIONS

In this cohort, Lp(a) was not an independent risk factor for IHD but appeared to increase the risk associated with other lipid risk factors.

CI-1011 lowers lipoprotein(a) and plasma cholesterol concentrations in chow-fed cynomolgus monkeys

Lipoprotein(a) (Lp(a)), which is generated through the covalent association of apolipoprotein(a) (apo(a)) and apo B-100-LDL, is an independent risk factor for several vascular diseases. Therefore, there is interest in developing therapies for lowering Lp(a). This investigation was carried out to determine the effect of CI-1011, a potent lipid regulator in rodents, on Lp(a) and other lipid parameters in cynomolgus monkeys (Macaca fascicularis). Nine healthy male monkeys on a normal chow diet were orally treated with CI-1011 at 30 mg/kg per day for 3 weeks. Lp(a) and total cholesterol levels were significantly decreased after 1 week and maximally reduced to 68 and 73% of control levels, respectively, after 3 treatment weeks. The decreases in total cholesterol were mainly due to changes in low density lipoprotein (LDL). The LDL:HDL ratio decreased by 30%. Triglycerides were unaffected by treatment. Lp(a) and total cholesterol levels returned to pretreatment values after stopping treatment suggesting a direct effect of the compound on their inhibition. Further studies demonstrated that CI-1011 was effective at a low dose of 3 mg/kg per day after 1 week of administration. CI-1011 also decreased apo B-100 to 80% of control levels, but this change was not sufficient to account for the Lp(a) lowering. There was also no correlation between the changes in Lp(a) and apo B-100 levels. Treatment of cynomolgus monkey primary hepatocyte cultures with CI-1011 resulted in a dose-dependent inhibition of Lp(a) levels suggesting a direct hepatic effect of the compound. Western blot analysis of the samples showed that changes in Lp(a) were associated mainly with decreased apo(a) (47%), but not apo B-100 (17%). These results demonstrate that CI-1011 effectively decreases Lp(a) levels both in vivo and in vitro.

Increased plasma concentrations of LDL-unbound apo(a) in patients with end-stage renal disease

Lipoprotein(a) [Lp(a)] and its characteristic glycoprotein apolipoprotein(a) [apo(a)] are risk factors for atherosclerosis in the general population. Patients with renal disease show an elevation of Lp(a). Recent studies have described an arteriovenous difference of Lp(a) in the renovascular bed as well as the plasma-derived fragmented LDL-unbound apo(a) in urine, suggesting that the kidney is involved in the metabolism of Lp(a). We therefore investigated whether patients with chronic renal failure have higher levels of LDL-unbound apo(a) and whether this could account for the increased Lp(a) concentrations in these patients. In addition, we studied the possible generation of apo(a) fragments in vitro by mimicking uremic plasma conditions and by investigating the assembly of Lp(a) in cell culture experiments. Patients treated by hemodialysis (N = 185) and by continuous ambulatory peritoneal dialysis (CAPD; N = 20) had markedly elevated absolute (1.22 +/- 1.55 mg/dl and 2.14 +/- 2.86 mg/dl) as well as relative (7.5% and 7.3%) amounts of LDL-unbound apo(a) in comparison to controls (0.46 +/- 0.48 mg/dl or 4.5%). Following renal transplantation the absolute amount decreased significantly. Lp(a) plasma concentration was the most important determining variable for the absolute amount of LDL-unbound apo(a) and showed a positive correlation in both hemodialysis patients (r = 0.85) and controls (r = 0.92). In vitro experiments demonstrated that "uremization" of plasma samples did not generate a higher amount of LDL-unbound apo(a). Although LDL of renal patients has different chemical and structural properties as compared to control LDL, the extracellular assembly of Lp(a) did not differ between patients and controls. Therefore, the higher amounts of LDL-unbound apo(a) found in renal disease are not caused by an impaired assembly of Lp(a), but rather indicate a catabolic role of the kidney for LDL-unbound apo(a) as was already shown for Lp(a). Despite a small contribution, these elevated levels cannot explain the higher Lp(a) values found in patients with end-stage renal disease.

Structural basis for the pathophysiology of lipoprotein(a) in the athero-thrombotic process

Lipoprotein Lp(a) is a major and independent genetic risk factor for atherosclerosis and cardiovascular disease. The essential difference between Lp(a) and low density lipoproteins (LDL) is apolipoprotein apo(a), a glycoprotein structurally similar to plasminogen, the precursor of plasmin, the fibrinolytic enzyme. This structural homology endows Lp(a) with the capacity to bind to fibrin and to membrane proteins of endothelial cells and monocytes, and thereby to inhibit plasminogen binding and plasmin generation. The inhibition of plasmin generation and the accumulation of Lp(a) on the surface of fibrin and cell membranes favor fibrin and cholesterol deposition at sites of vascular injury. Moreover, insufficient activation of TGF-beta due to low plasmin activity may result in migration and proliferation of smooth muscle cells into the vascular intima. These mechanisms may constitute the basis of the athero-thrombogenic mode of action of Lp(a). It is currently accepted that this effect of Lp(a) is linked to its concentration in plasma. An inverse relationship between Lp(a) concentration and apo(a) isoform size, which is under genetic control, has been documented. Recently, it has been shown that inhibition of plasminogen binding to fibrin by apo(a) is also inversely associated with isoform size. Specific point mutations may also affect the lysine-binding function of apo(a). These results support the existence of functional heterogeneity in apolipoprotein(a) isoforms and suggest that the predictive value of Lp(a) as a risk factor for vascular occlusive disease would depend on the relative concentration of the isoform with the highest affinity for fibrin.

LDL-unbound apolipoprotein(a) and carotid atherosclerosis in hemodialysis patients

High lipoprotein(a) [Lp(a)] plasma concentrations, which are genetically determined by apo(a) size polymorphism, are directly associated with an increased risk for atherosclerosis. Patients with end-stage renal disease (ESRD), who show an enormous prevalence of cardiovascular disease, have elevated plasma concentrations of Lp(a). In recent studies we were able to show that apo(a) size polymorphism is a better predictor for carotid atherosclerosis and coronary artery disease in hemodialysis patients than concentrations of Lp(a) and other lipoproteins. Less than 5% of apo(a) in plasma exists in a low-density lipoprotein (LDL)-unbound form. This "free" apo(a) consists mainly of disintegrated apo(a) molecules of different molecular weight, ranging from about 125 to 360 kDa. LDL-unbound apo(a) molecules are elevated in patients with ESRD. The aim of this study was therefore to investigate whether the LDL-unbound form of apo(a) contributes to the prediction of carotid atherosclerosis in a group of 153 hemodialysis patients. The absolute amount of LDL-unbound apo(a) showed a trend to increasing values with the degree of carotid atherosclerosis, but the correlation of Lp(a) plasma concentrations with atherosclerosis was more pronounced. In multivariate analysis the two variables were related to neither the presence nor the degree of atherosclerosis. Instead, the apo(a) phenotype took the place of Lp(a) and LDL-unbound apo(a). After adjustment for other variables, the odds ratio for carotid atherosclerosis in patients with a low molecular weight apo(a) phenotype was about 5 (p<0.01). This indicates a strong association between the apo(a) phenotype and the prevalence of carotid atherosclerosis. Finally, multivariate regression analysis revealed age, angina pectoris and the apo(a) phenotype as the only significant predictors of the degree of atherosclerosis in these patients. In summary, it seems that LDL-unbound apo(a) levels do not contribute to the prediction of carotid atherosclerosis in hemodialysis patients. However, this does not mean that "free", mainly disintegrated, apo(a) has no atherogenic potential.

Lipoprotein (a) and its relationship to risk factors and severity of atherosclerotic peripheral vascular disease

OBJECTIVES

To determine the significance of Lipoprotein (a) (Lp(a)) as a risk factor for atherosclerotic lower limb peripheral vascular disease (PVD), and its relationship to other demographic and biochemical variables and disease pattern and severity.

DESIGN

Prospective case-control study.

MATERIAL AND METHODS

Demographic and biochemical risk factors, lipoprotein fractions and Lp(a) were measured in 200 patients with PVD and 200 age- and sex-matched control subjects. Lp(a) levels were correlated with traditional risk factors and clinical and vascular laboratory disease parameters.

RESULTS

Patients with PVD have a higher incidence of smoking, hypertension, and diabetes mellitus; and had significantly higher levels of serum cholesterol, triglycerides, LDL, VLDL, apolipoprotein B, fasting glucose, fibrinogen, plasminogen, haematocrit, white cell and platelet counts; but lower levels of HDL and apolipoprotein A1. Fasting Lp (a) concentration is an independent risk factor for PVD and is significantly higher in the patients (median = 26.1 mg/dl [4.8-195], mean = 36.5 +/- 32.6 mg/dl) than in controls (median = 18.2 mg/dl [5.4-216], mean = 27.2 +/- 28.1 mg/dl; p < 0.0001). In patients with PVD, Lp(a) correlated positively with plasma LDL, cholesterol, fibrinogen, renal disease, and apolipoprotein B. Fasting levels of > 24 mg/dl incurred a two-fold increase in risk of PVD. Patients with a higher Lp(a) have a significantly higher incidence of resting pain and ulcerations, and regression analysis confirmed smoking and Lp(a) level to be associated with the SVS category of disease severity.

CONCLUSIONS

Lipoprotein (a) is a significant independent risk factor for PVD. Lp(a) levels correlated with LDL, cholesterol, fibrinogen, apolipoprotein B and disease severity. An elevated Lp(a) level may be associated with more severe forms of PVD.

Pentaerythritol tetranicotinate (niceritrol) decreases plasma lipoprotein(a) levels

We determined the most effective dosage of pentaerythritol tetranicotinate (niceritrol) to reduce plasma lipoprotein(a) [Lp(a)] levels in 44 Japanese patients (16 men and 28 women; mean age, 59.2 +/- 10.8 years) with hyperlipidemia types IIa, IIb, and IV. Patients received oral niceritrol at a dosage of 750 mg (3 tablets)/d for 8 weeks, followed by 1,500 mg (6 tablets)/d for 8 weeks. Administration of niceritrol 750 mg/d for 8 weeks decreased total and low-density lipoprotein (LDL) cholesterol in patients with type IIa hyperlipidemia and decreased triglycerides in patients with type IV hyperlipidemia, but did not affect Lp(a). However, niceritrol 1,500 mg/d for 8 weeks decreased Lp(a) in patients with initial Lp(a) levels greater than 30 mg/dL in addition to decreasing total and LDL cholesterol and triglycerides. These results suggest that the effective dosage of niceritrol to reduce the serum Lp(a) concentration in Japanese hyperlipidemic patients with a high Lp(a) level (> or = 30 mg/dL) is greater than 1,500 mg/d.

Elevated lipoprotein(a) and increased incidence of restenosis after femoropopliteal PTA. Rationale for the higher risk of recurrence in females?

It has been shown that the incidence of recurrent stenosis following successful percutaneous transluminal coronary angioplasty (PTCA) is correlated with serum Lipoprotein(a) [Lp(a)] levels. The aim of the present study was to examine the influence of Lp(a) on restenosis after primary successful femoropopliteal PTA. One hundred and thirty nine consecutive patients with peripheral arterial occlusive disease (PAOD) and successful femoropopliteal PTA were studied. Follow-up included clinical examination and non-invasive laboratory testing (pulse volume recordings, ankle-brachial arterial pressure measurement) in every patient before and after 1, 3, 6 and 12 months following intervention. Duplex sonography was performed 1 year after PTA. Suspicion of restenosis (> or = 50% diameter reduction) was verified by angiography. Lp(a) was determined using ELISA technique (mg/dl). Twelve months after successful PTA no restenosis was found in 82 patients (59%: group A). The one-year recurrence rate of 41% (group B) was due to significant restenosis in 35 patients (25%) and reocclusion in 22 patients (16%). The corresponding mean values +/- S.E.M. for Lp(a) were as follows: group A, 28 +/- 5.3; group B 59 +/- 11 (P < 0.01). Women showed a higher frequency of recurrences (55%) versus men (30%, P < 0.01) also corresponding with a high Lp(a) level (51.8 +/- 8 versus 32.7 +/- 5; P < 0.05). Furthermore Lp(a) aggravated the well known increased risk for recurrence in multiple stenoses or occlusions of > or = 5 cm in length. There were no significant differences between groups A and B with respect to age, diabetes, hyperlipidaemia, obesity and cigarette smoking. The results support the view that Lp(a) is an independent risk factor for recurrence after PTA in the femoropopliteal area. It might also be a causal basis for the higher incidence of recurrences in female PAOD patients.

Evaluation of the coagulation and fibrinolytic systems in men with intermittent claudication

The authors evaluated elements of the coagulation and fibrinolytic systems in 18 male patients with intermittent claudication vs 19 men matched for risk factors who served as controls. Prothrombin time and activated partial thromboplastin time did not significantly differ in the patients and the controls. The plasminogen level in the two groups was not significantly different. The level of lipoprotein(a) was significantly higher in the patients than in the controls. The levels of antigen and the activity of protein C did not differ significantly between the two groups. The thrombomodulin level was significantly higher in the patients than in the controls. There were no significant differences between the two groups in the levels of alpha 2-macroglobulin, C1-inactivator, or antithrombin III. The levels of fibrinogen and alpha 1-antitrypsin were significantly higher in the patients vs the controls. Significantly lower levels of alpha 2-plasmin inhibitor and higher levels of alpha 2-plasmin inhibitor/plasmin complex and thrombin/antithrombin III complex were found in the patients vs the controls. These findings suggest that the levels of thrombin/antithrombin III complex, alpha 2-plasmin inhibitor/plasmin complex, and thrombomodulin may perhaps serve as indicators for injury to the peripheral endothelium and that the coagulation and fibrinolytic systems may be activated in patients with intermittent claudication.

Lipoprotein(a) in renal disease

Lipoprotein(a) [Lp(a)] is a genetically determined risk factor for atherosclerotic vascular disease. Several studies have described a correlation between high 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 apolipoprotein(a) [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. Average Lp(a) levels are high in individuals with low molecular weight isoforms and low in those with high molecular weight isoforms. Mean Lp(a) plasma levels are elevated over controls in patients with renal disease. Patients with nephrotic syndrome exhibit excessively high Lp(a) plasma concentrations, which can be reduced with antiproteinuric treatment. The mechanism underlying this elevation is unclear, but the general increase in protein synthesis caused by the liver due to high urinary protein loss is a likely explanation. Patients with end-stage renal disease (ESRD) also have elevated Lp(a) levels. These are even higher in patients treated by continuous ambulatory peritoneal dialysis than in those receiving hemodialysis. Lipoprotein(a) concentrations decrease to values observed in controls matched for apo(a) type following renal transplantation. This clearly demonstrates the nongenetic origin of Lp(a) elevation in ESRD. Both the increase in ESRD and the decrease following renal transplantation are apo(a) phenotype dependent. Only patients with high molecular weight phenotypes show the described changes in Lp(a) levels. In patients with low molecular weight types the Lp(a) concentrations remain unchanged during both phases of renal disease. As in the general population, Lp(a) is a risk factor for cardiovascular events in ESRD patients. In this patient group the apo(a) phenotype seems to be equally or better predictive of the degree of atherosclerosis than is Lp(a) concentration. Further prospective studies will be necessary to confirm these observations. Whether Lp(a) also plays a key role in the pathogenesis and progression of renal diseases needs further study. Controversial data on the role of the kidney in Lp(a) metabolism result from insufficient sample sizes of several studies. Due to the broad range and skewed distribution of Lp(a) plasma concentrations, large study groups must be investigated to obtain reliable results.

Lipoprotein (a), homocysteine, and hypercoagulable states in young men with premature peripheral atherosclerosis: a prospective, controlled analysis

PURPOSE

Elevated lipoprotein (a) (Lp[a]) lipoprotein, total homocysteine, and hypercoagulable states (HCS) have all been implicated as risk factors for premature-onset atherosclerosis. This study was performed to determine the prevalence of these abnormalities in young men with chronic lower extremity ischemia (peripheral vascular disease [PVD]) and to determine their relative strengths as risk factors for premature peripheral atherosclerosis.

METHODS

We analyzed 50 young white men (aged 45 years or younger at onset of symptoms) and compared them with 45 age-matched white male control subjects.

RESULTS

Atherosclerotic risk factors were similar in both groups. The mean (+/- SEM) Lp(a) lipoprotein level was 36 +/- 6 mg/dl among the study patients, compared with 14 +/- 2 mg/dl among control subjects (p = 0.02, Mann-Whitney). Twenty (40%) study patients and seven (16%) control subjects had Lp(a) lipoprotein levels of 30 mg/dl or greater (atherosclerotic risk threshold) (p = 0.01, odds ratio = 3.62, confidence interval (CI) 1.4 to 9.5). Positive HCS panels (antiphospholipid antibodies or deficiencies in antithrombin III, protein C, or protein S) were nearly twice as prevalent in study patients (n = 15, 30%) as in controls (n = 8, 18%), but this difference did not achieve statistical significance. The mean total plasma homocysteine level among the study patients was 15.9 +/- 0.9 mumol/L, which was not significantly different from the mean control value of 14.7 +/- 0.7 mumol/L. Lp(a) lipoprotein was related to risk of premature PVD through a linear logistic relationship (p = 0.003, odds ratio per each 1 mg/dl Lp(a) change was 1.03, CI 1.0 to 1.1). Multivariate analysis with stepwise logistic regression selected two variables: Lp(a) lipoprotein > or = 30 mg/dl (p = 0.01, odds ratio = 3.6, CI 1.3 to 9.9) and family history (p = 0.07, odds ratio = 2.2, CI 0.9 to 5.3). Tests of interaction demonstrated no effect between Lp(a) lipoprotein, HCS, and homocysteine.

CONCLUSIONS

Lp(a) lipoprotein of 30 mg/dl or greater is an independent risk factor for premature peripheral atherosclerosis in men. None of the other examined variables exhibited a significant association with premature PVD.

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).

A unique pattern of apo(a) polymorphism in an isolated east Greenlandic Inuit (Eskimo) population

Eskimos of the east coast of Greenland very rarely had contacts with Caucasians until late in the 19th century. Their genes are therefore likely to be similar to those in the original Eskimo gene pool. We have compared serum concentrations of Lp(a) and apo(a) phenotypes in 78 East Greenland Eskimos (EGE) with those in Eskimos from Western Greenland (WGE) (n = 100) and Caucasian Danes (n = 466). Lp(a) levels were higher in EGE (median: 11.9 mg/dl [95% CI: 9.1-16.4]) than in Danes (p < 0.01), (median: 6.3 mg/dl [95% CI: 5.5-7.3]) and WGE (p < 0.01), (median: 7.8 mg/dl [95% CI: 5.7-10.2]). Lp(a) concentrations above 30 mg/dl were (p < 0.05) more common in EGE (19%) than in WGE (9%) and similar (p = 0.89) to those in Danes (20%). Apo(a) molecules as small as S2 or smaller (S1, B and F) were present in 26% of Danes and in 3% of WGE but were absent in EGE (p < 0.01). In contrast, a large apo(a) variant (VS4) was present in 54% of EGE and 62% of WGE, whereas it was very rare in Danes (2%). Lp(a) concentrations were inversely associated with apo(a) size in EGE (p < 0.05), WGE (p < 0.01) and Danes (p < 0.01), but EGE with S3 or S4 had significantly higher Lp(a) levels than Danes (p < 0.05) with the same phenotypes.

Elevated levels of lipoprotein (a) in association with cerebrovascular saccular aneurysmal disease

The relationship between cerebrovascular aneurysmal disease and atherosclerosis remains unclear. Elevated serum levels of lipoprotein (a) (Lp[a]), are an independent risk factor for atherosclerosis. We measured serum Lp(a) levels in 50 patients who had angiographically proven saccular aneurysmal disease and who were free of clinically significant atheromatous disease (as judged by their medical histories and the results of physical examination, electrocardiography, and carotid angiography). The Lp(a) serum levels in these patients were compared with the Lp(a) serum levels in a group of 42 normal healthy controls. Serum Lp(a) levels in the patients was 20.1 +/- 0.42 mg/dl (median +/- standard error); however, median serum Lp(a) in the control subjects was 10.8 +/- 0.47 mg/dl (P < 0.01). Among females, the difference in serum Lp(a) levels was significant; the levels were 22.2 +/- 0.6 for female patients (n = 29) and 9.5 +/- 0.53 in female control subjects (n = 26) (P < 0.005). The most significant difference (P < 0.002) was seen in females < 50 years old (14 patients, 10 control subjects). No significant differences were seen in the Lp(a) serum levels between 21 male patients and 16 male control subjects. Lp(a) levels above the threshold level (30 mg/dl) were found in 20 patients and 7 control subjects (chi 2 = 5.99, P < 0.02); 12 female patients and 3 female control subjects (chi 2 = 6.16, P < 0.02; 8 male patients and 4 male control subjects (this difference was not significant). These results indicate either that cerebrovascular aneurysmal disease and subclinical atherosclerosis are related or that Lp(a) is a risk factor for vasculopathies other than atheroma.

Serum Lp(a) lipoprotein levels in patients with coronary artery disease and the influence of long-term n-3 fatty acid supplementation

The serum levels of Lp(a) lipoprotein (Lp(a)) were determined preoperatively in 601 patients with coronary artery disease, undergoing bypass operations. Compared with a reference group of 99 apparently healthy individuals, the Lp(a) levels were higher in the patient group (7.7 mg dl-1 vs. 5.1 mg dl-1, p = 0.012). In the patient group, there was a weak, but significant negative correlation between the Lp(a) levels and age (r = -0.10, p = 0.017), and in both groups the women had higher Lp(a) levels than the men. In the patients we found no significant correlations between Lp(a) and other serum lipids or lipoproteins, nor between Lp(a) and variables in the fibrinolytic system. We investigated the long-term effects of supplementation with n-3 polyunsaturated fatty acids (n-3 PUFAs) on the Lp(a) concentrations. Postoperatively, in a randomized fashion, 280 of the patients received 4 g of an n-3 PUFA concentrate (containing > 85% of long-chain n-3 PUFAs) per day, whereas 269 patients comprised the control group. The fatty acids in serum phospholipids were monitored, and a significant increase in the phospholipid n-3 fatty acids was noted in the n-3 PUFA group, as opposed to the virtually unchanged amounts in the control group. The Lp(a) levels were determined again after 6 months, and, compared with the control group, n-3 PUFA supplementation had no overall effect on the serum Lp(a) levels.

Lipoprotein(a) distribution in a French Canadian population and its relation to intermittent claudication (the Québec Cardiovascular Study)

This study was undertaken to evaluate the distribution and the relation of lipoprotein(a) (Lp[a]) concentration with intermittent claudication in a cohort of men aged 35 to 64 years, randomly selected in 1974 and followed until 1990. In 1985, blood samples for a complete fasting lipid profile and Lp(a) were obtained in 2,424 men representing 62% of the living cohort. The diagnosis of intermittent claudication was made by trained nurses using a standardized questionnaire and confirmed by a cardiologist. Lp(a) distribution did not change with age and was similar to that of other Caucasian populations. Because Lp(a) concentration did not vary with age, its relation to the incidence of intermittent claudication was assessed for the years 1974 to 1990. The incidence of intermittent claudication was 42 of 10,000 person-years. The 113 men with intermittent claudication, in contrast to men without this symptomatology, were older at entry (49 +/- 7 vs 45 +/- 7 years), and had higher systolic pressure (144 +/- 20 vs 136 +/- 16 mmHg) and Lp(a) levels (46 +/- 45 vs 33 +/- 35 mg/dl) (all p < 0.05). There was also a significantly greater prevalence of smoking and diabetes among men with intermittent claudication. The risk of intermittent claudication was doubled in men in the second and third tertiles of Lp(a) concentration (p < 0.001). Thus, high Lp(a) levels constitute a significant risk for intermittent claudication in this population.

Influence of serum lipoprotein(a) and homocyst(e)ine levels on graft patency after coronary artery bypass grafting

High serum levels of lipoprotein(a) and homocyst(e)ine are considered independent risk factors for atherothrombotic disease. In a prospective study in patients undergoing coronary artery bypass grafting, the preoperatively determined lipoprotein(a) and homocyst(e)ine levels were related to the frequency of 1-year graft occlusion. A cohort of 610 patients who underwent coronary artery bypass surgery was followed through the first postoperative year. Shunt angiography was performed in 581 patients (95%) at a mean of 12.1 +/- 1.5 months after the operation. The serum levels of lipoprotein(a) (n = 570) and homocyst(e)ine (n = 565) in patients with occluded internal mammary artery (IMA) grafts were not significantly different from the levels in those with open IMA grafts. Also, the serum lipoprotein(a) and homocyst(e)ine levels in patients with > or = 1 occluded vein graft were not significantly different from those in patients with all vein grafts patent. This study also determined the incidence of graft occlusion in quartiles of the lipoprotein(a) and homocyst(e)ine levels, respectively, and tested for linear trends. No significant trends in the incidence of graft occlusion were found, but the number of patients with vein graft occlusions was higher in the lowest quartile of lipoprotein(a) than that in the upper 3 quartiles (odds ratio, 1.82, 95% confidence interval, 1.21 to 2.74, p = 0.0025). Controlling for background variables in multivariate models only slightly modified the results. Thus, apart from an unexplained excess of vein graft occlusions in the lowest quartile of lipoprotein(a) levels, no association between the preoperative serum lipoprotein(a) or homocyst(e)ine levels and the frequency of 1-year graft occlusion could be demonstrated.

Evidence that apolipoprotein(a) phenotype is a risk factor for coronary artery disease in men < 55 years of age

Whereas the importance of plasma lipoprotein(a) [Lp(a)] levels as a risk factor for premature coronary artery disease (CAD) is certain, it is not clear if the apolipoprotein(a) [apo(a)] phenotype plays an additional and independent role. To investigate the possible effect of apo(a) phenotype on premature CAD (in patients < 55 years of age), plasma Lp(a) concentrations, the apo(a) phenotypes, and their relation with many recognized CAD risk factors were examined in 96 non-diabetic male patients with angiographically defined CAD and in 83 age-matched male control subjects with no angiographic evidence of CAD. Results demonstrate that patients with premature CAD are characterized by higher Lp(a) levels (24 +/- 21 vs 17 +/- 15 mg/dl, p < 0.01) and a higher frequency of S2 phenotype (32% vs 15%, p < 0.01). Patients with an S2 phenotype exhibited significantly higher plasma Lp(a) concentrations than control subjects with the same isoform (37 +/- 22 vs 22 +/- 17 mg/dl, p < 0.05). A significant correlation was found between apo B and Lp(a) levels in patients with an S2 phenotype. In addition, patients had a low frequency of S1 and S4, and a high frequency of double-band phenotypes of apo(a). Multivariate analysis did not demonstrate an independent role for apo(a) phenotype as a risk factor for premature CAD. In conclusion, CAD patients < 55 years of age have a very different pattern of apo(a) phenotypes than subjects with no angiographic evidence of CAD; this study confirms the hypothesis that apo(a) phenotype may play an additional role in the etiology of premature CAD.

The relationship between serum levels of lipoprotein(a) and proteins associated with the acute phase response

The association of serum lipoprotein(a) (Lp(a)) with inflammation was investigated in a primarily rheumatologic study group (n = 570; 202 males and 368 females) by studying the relationship between serum levels of Lp(a) and a panel of acute phase proteins (C-reactive protein (CRP), alpha 1-antitrypsin (AAT), alpha 1-acid glycoprotein (AGP), haptoglobin (HPT), complement components 3 and 4 (C3, C4), prealbumin (PAL), albumin (ALB) and transferrin (TRF)). Lp(a) data were adjusted for age and sex, but not clinical condition as no significant differences in Lp(a) levels were observed, using analysis of variance, among the 15 diagnostic categories in the study group. Univariate analyses revealed significant positive associations between Lp(a) levels and levels of C4, AGP, C3 and HPT. Multivariate analysis revealed that C4 and AGP (in descending order of significance) were significant independent predictors of Lp(a) concentration, together accounting for 2.9% of the variability in Lp(a) concentration in the present study group. The data indicate that confounding effects of an acute phase response should be considered in epidemiologic studies, if a high prevalence of inflammation is suspected.