Peter Santer

Osteoprotegerin Is a Risk Factor for Progressive Atherosclerosis and Cardiovascular Disease

Background—Osteoprotegerin is a novel member of the tumor necrosis factor receptor superfamily and a soluble decoy receptor of the receptor activator of nuclear factor-κB ligand. Recent experimental research has implicated osteoprotegerin in atherogenesis, but epidemiological confirmation of this concept is sparse. Methods and Results—As part of the prospective, population-based Bruneck Study, severity, initiation, and progression of atherosclerosis were assessed in carotid arteries. Cases of incident cardiovascular disease and vascular mortality were carefully recorded over a 10-year period (1990 to 2000). Osteoprotegerin levels were measured in samples obtained at baseline and during follow-up. Serum osteoprotegerin showed a strong association with numerous vascular risk factors, including age, diabetes, markers of systemic inflammation, chronic infection, and smoking. In multivariate analyses, osteoprotegerin was significantly related to severity and 10-year progression of carotid atherosclerosis. Furthermore, a high level of osteoprotegerin was an independent risk factor for incident cardiovascular disease (adjusted relative risk for the top versus bottom tertile group for osteoprotegerin 2.2 [1.3 to 3.8]; P =0.001) and vascular mortality (adjusted relative risk for the top versus bottom tertile group for osteoprotegerin 3.1 [1.2 to 8.2]; P =0.010) but not for mortality due to nonvascular causes. Conclusions—Osteoprotegerin is an independent risk factor for the progression of atherosclerosis and onset of cardiovascular disease.

Role of Lipoprotein(a) and Apolipoprotein(a) Phenotype in Atherogenesis Prospective Results From the Bruneck Study

BACKGROUND Experimental studies have suggested both atherogenic and thrombogenic properties of lipoprotein(a) [Lp(a)], depending on Lp(a) plasma concentrations and varying antifibrinolytic capacity of apolipoprotein(a) [apo(a)] isoforms. Epidemiological studies may contribute to assessment of the relevance of these findings in the general population. METHODS AND RESULTS This study prospectively investigated the association between Lp(a) plasma concentrations, apo(a) phenotypes, and the 5-year progression of carotid atherosclerosis assessed by high-resolution duplex ultrasound in a random sample population of 826 individuals. We differentiated early atherogenesis (incident nonstenotic atherosclerosis) from advanced (stenotic) stages in atherosclerosis that originate mainly from atherothrombotic mechanisms. Lp(a) plasma concentrations predicted the risk of early atherogenesis in a dose-dependent fashion, with this association being confined to subjects with LDL cholesterol levels above the population median (3.3 mmol/L). Apo(a) phenotypes were distributed similarly in subjects with and without early carotid atherosclerosis. In contrast, apo(a) phenotypes of low molecular weight emerged as one of the strongest risk predictors of advanced stenotic atherosclerosis, especially when associated with high Lp(a) plasma concentrations (odds ratio, 6.4; 95% CI, 2.8 to 14. 9). CONCLUSIONS Lp(a) is one of the few risk factors capable of promoting both early and advanced stages of atherogenesis. Lp(a) plasma concentrations predicted the risk of early atherogenesis synergistically with high LDL cholesterol. Low-molecular-weight apo(a) phenotypes with a putatively high antifibrinolytic capacity in turn emerged as one of the leading risk conditions of advanced stenotic stages of atherosclerosis.

Lipidomics Profiling and Risk of Cardiovascular Disease in the Prospective Population-Based Bruneck Study

Background— The bulk of cardiovascular disease risk is not explained by traditional risk factors. Recent advances in mass spectrometry allow the identification and quantification of hundreds of lipid species. Molecular lipid profiling by mass spectrometry may improve cardiovascular risk prediction. Methods and Results— Lipids were extracted from 685 plasma samples of the prospective population-based Bruneck Study (baseline evaluation in 2000). One hundred thirty-five lipid species from 8 different lipid classes were profiled by shotgun lipidomics with the use of a triple-quadrupole mass spectrometer. Levels of individual species of cholesterol esters (CEs), lysophosphatidylcholines, phosphatidylcholines, phosphatidylethanolamines (PEs), sphingomyelins, and triacylglycerols (TAGs) were associated with cardiovascular disease over a 10-year observation period (2000–2010, 90 incident events). Among the lipid species with the strongest predictive value were TAGs and CEs with a low carbon number and double-bond content, including TAG(54:2) and CE(16:1), as well as PE(36:5) (P=5.1×10−7, 2.2×10−4, and 2.5×10−3, respectively). Consideration of these 3 lipid species on top of traditional risk factors resulted in improved risk discrimination and classification for cardiovascular disease (cross-validated &Dgr;C index, 0.0210 [95% confidence interval, 0.0010-0.0422]; integrated discrimination improvement, 0.0212 [95% confidence interval, 0.0031-0.0406]; and continuous net reclassification index, 0.398 [95% confidence interval, 0.175-0.619]). A similar shift in the plasma fatty acid composition was associated with cardiovascular disease in the UK Twin Registry (n=1453, 45 cases). Conclusions— This study applied mass spectrometry-based lipidomics profiling to population-based cohorts and identified molecular lipid signatures for cardiovascular disease. Molecular lipid species constitute promising new biomarkers that outperform the conventional biochemical measurements of lipid classes currently used in clinics.

Oxidation-Specific Biomarkers, Prospective 15-Year Cardiovascular and Stroke Outcomes, and Net Reclassification of Cardiovascular Events

OBJECTIVES This study sought to assess the long-term predictive value and net reclassification for risk of cardiovascular disease (CVD) of biomarkers reflecting oxidation-specific epitopes (OSEs). BACKGROUND OSEs are immunogenic, proinflammatory, and proatherogenic. The long-term predictive value and net reclassification of OSEs for risk of CVD events are not known. METHODS Oxidized phospholipids on apolipoprotein B-100 (OxPL/apoB) and immunoglobulin (Ig)-G (IgG) and IgM autoantibodies to malondialdehyde-modified, low-density lipoprotein (MDA-LDL) and copper-oxidized LDL (Cu-OxLDL) were measured in 765 subjects in 1995 and 656 subjects in 2000 in the Bruneck study, representing 45- to 84-year-old men and women from the general community. RESULTS Over 15 years of follow-up, 138 subjects reached the primary endpoint of incident CVD (ischemic stroke, myocardial infarction, new-onset unstable angina, acute coronary interventions, and vascular death). In a multivariable Cox model, the highest tertile of OxPL/apoB was associated with higher risk of CVD (hazard ratio [HR]: 2.4; 95% confidence interval [CI]: 1.5 to 3.7) and stroke (HR: 3.6; 95% CI: 1.8 to 7.4) compared with the lowest tertile. IgG Cu-OxLDLs were associated with higher risk of CVD, whereas IgM MDA-LDLs were associated with lower risk. Using OxPL/apoB, IgG Cu-OxLDL, and IgM MDA-LDL variables, the area under the curve (AUC) for CVD risk prediction increased from 0.664 (95% CI: 0.629 to 0.697) to 0.705 (95% CI: 0.672 to 0.737) (p = 0.048). The net reclassification index (NRI) was 0.163 (p = 0.0044) and 0.332 (p < 0.0001) in all subjects (n = 765) and in subjects with intermediate risk (n = 305), respectively. Of 627 subjects who remained free of CVD, 108 were correctly reclassified to a lower risk category, and 83 were reclassified to a higher category (categories: 15-year risk <15%, 15% to 30%, >30%). CONCLUSIONS OSE biomarkers predict 15-year CVD and stroke outcomes and provide potential clinical utility by reclassifying a significant proportion of individuals into higher or lower risk categories after traditional risk assessment.

Soluble Receptor Activator of Nuclear Factor-κB Ligand and Risk for Cardiovascular Disease

Background— Overexpression of receptor activator of nuclear factor-&kgr;B ligand (RANKL) is a prominent feature of vulnerable atherosclerotic lesions prone to rupture and was thought to contribute to the transition from a stable to an unstable plaque phenotype in both human and murine atherosclerosis because of its ability to promote matrix degradation, monocyte/macrophage chemotaxis, and vascular calcification. Methods and Results— The Bruneck Study is a prospective, population-based survey of men and women 40 to 79 years of age at the 1990 baseline examination. Levels of soluble RANKL and other variables were assessed in 909 subjects (1990). All cases of cardiovascular disease were carefully recorded between 1990 and 2005. During follow-up, cardiovascular disease (defined as ischemic stroke and transient ischemic attack, myocardial infarction, and vascular death) manifested in 124 of the 909 subjects. Baseline serum level of RANKL emerged as a highly significant predictor of vascular risk (adjusted hazard ratio per 1-unit increase in soluble RANKL, 1.27; 95% confidence interval, 1.16 to 1.40; P<0.001). Predictive significance was independent of that afforded by the classic vascular risk factors, C-reactive protein, osteoprotegerin concentration, and severity of carotid atherosclerosis. Findings were internally consistent and robust in a variety of sensitivity analyses. Notably, soluble RANKL was not associated with carotid or femoral artery atherosclerosis. Conclusions— Our study lends large-scale epidemiological support to a role for RANKL in cardiovascular disease. In the absence of a significant association between RANKL and atherosclerosis, the idea that RANKL promotes plaque destabilization and rupture is a highly appealing concept.

Marburg I Polymorphism of Factor VII–Activating Protease A Prominent Risk Predictor of Carotid Stenosis

Background—Atherothrombosis is a main pathomechanism in the evolution of vessel stenosis and is counteracted by endogenous fibrinolysis. Recently, the plasmatic serine protease “factor seven–activating protease” (FSAP) was recognized as a potent activator of prourokinase in vitro. The Marburg I polymorphism of FSAP impairs this potential and may thus facilitate arterial thrombosis. Methods and Results—This analysis of the Bruneck Study involved 810 men and women aged 40 to 79 years. The ultrasound-based atherosclerosis progression model (5-year follow-up) permits differentiation between early atherogenesis and the advanced stenotic stages of carotid artery disease. The FSAP Marburg I polymorphism was found in 37 subjects (carriage rate 4.4%). Individuals with this genetic variant showed a prominently reduced in vitro capacity to activate prourokinase. No relation was found to exist between the Marburg I polymorphism and early atherogenesis. In contrast, it emerged as a strong and independent risk predictor of incident/progressive carotid stenosis (multivariate odds ratio [95%CI], 6.6 [1.6 to 27.7]). This finding equally applied to subjects with and without co-segregation of the Marburg II polymorphism. The risk profile of advanced atherogenesis further includes cigarette smoking, high lipoprotein(a), the factor V Leiden mutation, low antithrombin III, high fibrinogen, and diabetes. Conclusions—In concert with other genetic and acquired conditions known to interfere with coagulation or fibrinolysis, the Marburg I polymorphism of FSAP, which attenuates its capacity to activate prourokinase, is a significant risk predictor for the evolution and progression of carotid stenosis.

Lipoprotein(a) and Asymptomatic Carotid Artery Disease Evidence of a Prominent Role in the Evolution of Advanced Carotid Plaques: The Bruneck Study

BACKGROUND AND PURPOSE Elevated levels of lipoprotein(a) [Lp(a)] have been reported in association with symptomatic coronary and carotid artery disease. Relevancy of Lp(a) as a risk predictor of presymptomatic atherosclerosis in general populations is not well established. METHODS Serum Lp(a) distribution and its relation to sonographically assessed carotid atherosclerosis were examined in a random sample of 885 men and women aged 40 to 79 years (Bruneck Study). RESULTS Logistic regression analysis revealed a binary-type association between Lp(a) and carotid artery disease, with the threshold level of Lp(a) for an enhanced atherosclerosis risk defined at 32 mg/dL. The strength of relation increased with advancing severity of carotid atherosclerosis (odds ratios for Lp(a), 1.8 for nonstenotic and 4.7 for stenotic carotid artery disease; P < .001). Lp(a) was unaffected by environmental factors except for a significant decrease in women taking hormone replacement therapy (P < .05). In a multivariate approach, Lp(a) turned out to be an independently significant predictor of carotid atherosclerosis (P < .001). No differential effect of Lp(a) on atherosclerosis (effect modification) was observed for sex, age, low-density lipoprotein cholesterol, apolipoprotein A-I and B, fasting glucose, diabetes, or hypertension. However, the Lp(a)-atherosclerosis relation was significantly modified by fibrinogen (P < .01) and antithrombin III (P < .05). CONCLUSIONS The present study demonstrates a strong and independent association between elevated Lp(a) levels and carotid atherosclerosis in a large randomized population and provides evidence of a potential role of Lp(a) in the evolution of carotid stenosis. Apart from atherogenicity of Lp(a) cholesterol, interference with fibrinolysis of atheroma-associated clots and fibrin deposits in the arterial wall may achieve pathophysiological significance.

Signature of circulating microRNAs in osteoarthritis

BACKGROUND Osteoarthritis is the most common form of arthritis and a major socioeconomic burden. Our study is the first to explore the association between serum microRNA levels and the development of severe osteoarthritis of the knee and hip joint in the general population. METHODS We followed 816 Caucasian individuals from 1995 to 2010 and assessed joint arthroplasty as a definitive outcome of severe osteoarthritis of the knee and hip. After a microarray screen, we validated 12 microRNAs by real-time PCR in the entire cohort at baseline. RESULTS In Cox regression analysis, three microRNAs were associated with severe knee and hip osteoarthritis. let-7e was a negative predictor for total joint arthroplasty with an adjusted HR of 0.75 (95% CI 0.58 to 0.96; p=0.021) when normalised to U6, and 0.76 (95% CI 0.6 to 0.97; p=0.026) after normalisation to the Ct average. miRNA-454 was inversely correlated with severe knee or hip osteoarthritis with an adjusted HR of 0.77 (95% CI 0.61 to 0.97; p=0.028) when normalised to U6. This correlation was lost when data were normalised to Ct average (p=0.118). Finally, miRNA-885-5p showed a trend towards a positive relationship with arthroplasty when normalised to U6 (HR 1.24; 95% CI 0.95 to 1.62; p=0.107) or to Ct average (HR 1.30; 95% CI 0.99 to 1.70; p=0.056). CONCLUSIONS Our study is the first to identify differentially expressed circulating microRNAs in osteoarthritis patients necessitating arthroplasty in a large, population-based cohort. Among these microRNAs, let-7e emerged as potential predictor for severe knee or hip osteoarthritis.

Asymmetric and symmetric dimethylarginines are of similar predictive value for cardiovascular risk in the general population

OBJECTIVES Asymmetric dimethylarginine (ADMA) has raised considerable interest, as it is an endogenous inhibitor of nitric oxide synthesis. While increased plasma levels of ADMA have been reported in different cardiovascular disease states, its association with symmetric dimethylarginine (SDMA) has not been evaluated in a prospective population-based study. METHODS AND RESULTS We performed a mass spectrometry-based analysis of ADMA and SDMA in the plasma of 572 participants of the Bruneck study. Levels of ADMA and SDMA were significantly correlated with each other (r=0.189, p<0.001). Age and parameters of renal function, however, showed a stronger influence on SDMA than on ADMA. Both ADMA and SDMA were predictive of cardiovascular disease in multivariate analysis and the associated hazard ratios over the 5-year observation period were of similar strength: 3.86 (1.36-10.9) and 7.91 (1.94-32.3) for ADMA and SDMA, respectively (p=0.011 and 0.004). Separate analyses focused on quintile groups of SDMA revealed that the increase in cardiovascular risk was mainly confined to the top category (>0.80 micromol/L). CONCLUSION This study argues against an exclusive ADMA effect in mediating cardiovascular risk. Instead, SDMA, its supposedly inactive counterpart, has similar diagnostic value in this large prospective cohort.

Poor Response to Activated Protein C as a Prominent Risk Predictor of Advanced Atherosclerosis and Arterial Disease

BACKGROUND The potential role of activated protein C (APC) resistance in arterial thrombosis and disease is a matter of ongoing controversy. METHODS AND RESULTS In the present population-based survey, a random sample of 826 men and women underwent high-resolution duplex ultrasound scanning of the carotid and femoral arteries. Response to APC was expressed in APC ratios. Subjects were tested for the factor V Leiden mutation. The risk of carotid stenosis increased gradually with decreasing response to APC (adjusted OR [95% CI] for a 1-U decrease of response to APC, 1.6 [1. 2 to 2.2]), as did the risk of femoral artery stenosis (1.7 [1.3 to 2.3]) and prevalent cardiovascular disease (1.4 [1.1 to 2.0]). The association between low APC ratio and atherosclerotic vascular disease applied equally to subjects with the factor V Leiden mutation and those without. Our study identified various nongenetic determinants of poor response to APC in the general population, including behavioral, hormonal, and environmental factors. CONCLUSIONS The present study revealed an independent and gradual association between low response to APC and both advanced atherosclerosis (stenosis) and arterial disease. Resistance to APC due to factor V Leiden mutation was only one facet of this relationship.