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Keywords:

  • cardiovascular disease;
  • mortality;
  • myocardial infarction;
  • osteoprotegerin;
  • stroke

Abstract

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Disclosure of Conflict of Interests
  8. References

Summary. Background: Osteoprotegerin (OPG) concentration in serum is associated with the presence and severity of atherosclerosis. Objective: To investigate the association between serum osteoprotegerin and the risk of a future myocardial infarction, ischemic stroke and mortality in a general population. Patients/methods: OPG was measured in serum collected from 6265 subjects recruited from a general population without a prior myocardial infarction and ischemic stroke (the Tromsø Study). Incident myocardial infarction, ischemic stroke and mortality were registered during follow-up. Cox regression models were used to estimate crude and adjusted hazard ratios and 95% confidence intervals (HR; 95% CI). Results: There were 575 myocardial infarctions, 284 ischemic strokes and 824 deaths (146 deaths as a result of ischemic heart disease, 78 deaths because of stroke and 600 deaths due to other causes) in the cohort during a median of 10.6 years of follow-up. Serum OPG (per SD [1.13 ng mL−1] increase in OPG) was associated with an increased risk of a myocardial infarction (1.20; 1.11–1.31), ischemic stroke (1.32; 1.18–1.47), total mortality (1.34; 1.26–1.42), death because of ischemic heart disease, (1.35; 1.18–1.54), stroke (1.44; 1.19–1.75) and non-vascular causes (1.31; 1.22–1.41) after adjustment for age, gender, current smoking, systolic blood pressure, body mass index, high density lipoprotein cholesterol, total cholesterol, creatinine, high sensitivity C-reactive protein (CRP) and diabetes mellitus or HbA1c > 6.1%. No association was detected between OPG and incident hemorrhagic stroke (1.02; 0.73–1.43). Conclusions: Serum OPG was associated with future risk of myocardial infarction, ischemic stroke, total mortality, mortality of ischemic heart disease, stroke and of non-vascular causes independent of traditional cardiovascular risk factors.


Introduction

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Disclosure of Conflict of Interests
  8. References

Osteoprotegerin (OPG), a member of the tumor necrosis factor (TNF) receptor superfamily [1], is a decoy receptor for receptor activator for nuclear factor kappa β ligand (RANKL) and TNF-related apoptosis-inducing ligand (TRAIL) [2,3]. OPG inhibits ligation of RANKL and TRAIL to their cognate receptors with subsequent regulation of bone formation and resorption [1], modulation of the immune system [4] and promotion of cell survival [3]. Many cells within the cardiovascular system, for example, arterial smooth muscle cells, endothelial cells and megakaryocytes [2,5,6], express and secrete OPG into the circulation.

There is growing evidence to support that serum OPG is a marker of cardiovascular diseases. Patients with stable coronary heart disease (CHD), acute CHD, CHD complicated with heart failure, and symptomatic carotid atherosclerosis have increased serum OPG levels [7–11]. Serum levels of OPG are also associated with CHD, all-cause and cardiovascular mortality in other groups of patients, for example, renal failure [12]. However, limited data are available on the impact of OPG to predict the future risk of an incident myocardial infarction, stroke and mortality. In postmenopausal women (n = 490), serum OPG was associated with a risk of fatal ischemic stroke, cardiovascular mortality and all-cause mortality, but not with nonfatal ischemic strokes [13]. In the Offspring cohort of the Framingham Heart Study (n = 3250) significant associations between serum OPG levels and cardiovascular disease (CVD) and OPG and mortality were reported [14]. CVD events included fatal (n = 6) and nonfatal (n = 58) myocardial infarction, coronary insufficiency (n = 6), heart failure (n = 40) and stroke (n = 33) [14]. Serum OPG was also an independent risk factor for cardiovascular disease and vascular mortality in the Bruneck study (n = 915) [15]. In the latter population-based cohort, cardiovascular disease was a composite of transient ischemic attacks, ischemic stroke, myocardial infarction, peripheral artery disease, revascularization procedures and vascular deaths as a result of limited number of events [15]. Nested case–control studies in general populations have reported an association between serum OPG and CHD [16] and no association between serum OPG and ischemic stroke [17].

In order to establish serum OPG as a risk factor for cardiovascular diseases (e.g. myocardial infarction and stroke) in a general population, it is warranted to conduct population-based cohort studies with a sample size large enough to assess the impact of OPG on incident clinical events and mortality. The present large population-based cohort study (n = 6265) was conducted to investigate the impact of serum OPG levels on incident myocardial infarction, stroke (ischemic and hemorrhagic), and mortality during 12 years of follow-up.

Methods

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Disclosure of Conflict of Interests
  8. References

Study population

Participants were recruited from the fourth survey of the Tromsø Study (conducted in 1994–95), a single-center prospective, population-based study, with repeated health surveys of inhabitants in Tromsø, Norway. All inhabitants aged 55–74 years and 5–10% samples in other 5-year age groups (25–54 years and 75–85 years) were invited to take part. Seventy-eight percent (n = 6899) of invited subjects attended. Fifty-seven subjects did not give written consent, and 13 subjects were not officially registered inhabitants of the municipality of Tromsø at baseline and were excluded. Subjects with a known history of myocardial infarction (n = 378), ischemic stroke (n = 79) or both (n = 20) were excluded. Serum samples were missing for 87 subjects. Thus, 6265 subjects (3294 women and 2971 men) were included in our prospective study. Informed written consent was obtained from all participants, and the study was approved by the regional committee for research ethics. Incident cardiovascular events and mortality among the participants were recorded from the date of enrollment through to the end of follow-up, 31 December 2005.

Medical history, blood collection and measurements

Information on study participants was obtained by a self-administrated questionnaire, anthropometric measurements and measurements of non-fasting blood samples [18]. In brief, non-fasting blood samples were collected from an antecubital vein, serum prepared by centrifugation after 1 h respite at room temperature. OPG concentrations were analyzed in previously unthawed serum aliquots stored at −70 °C for 12 years by an ELISA assay (R&D Systems, Abingdon, UK) with mouse anti-human OPG as a capture antibody. Biotinylated goat anti-human OPG and streptavidin horseradish peroxidase were used for detection. The intra- and interassay coefficients of variation (CV) in our laboratory were 6.5% and 9.3%, respectively. The analysis was performed according to the manufacturer’s instruction. Between-assay variations in OPG were adjusted for by use of an internal standard. All samples were analyzed in duplicate and the mean value is used in this report. Serum lipids [total and high-density lipoprotein (HDL) cholesterol and triglycerides], HbA1c, fibrinogen, hs-CRP, creatinine and hematological variables were assessed as previously described [18].

End point assessment

Adjudication of hospitalized and out-of hospital events was performed by an independent endpoint committee and based on data from hospital and out-of hospital journals, autopsy records and death certificates. The national 11-digit identification number allowed linkage to national and local diagnosis registries. Cases of incident myocardial infarction and ischemic stroke were identified by linkage to the discharge diagnosis registry at the University Hospital of North Norway (UNN) with search for ICD 9 codes 410–414, and 430–438 in the period 1994–98 and thereafter ICD 10 codes I20–I25 and I60–I69. UNN is the only hospital in the area serving the Tromsø population. The hospital medical records were retrieved for case validation. Slightly modified WHO MONICA/MORGAM criteria for myocardial infarction were used and included clinical symptoms and signs, findings in electrocardiograms (ECG), values of cardiac biomarkers and autopsy reports when applicable (http://www.ktl.fi/publications/morgam/manual/followup/form22.htm). An ischemic stroke was defined according to the WHO definition [19] only when computed tomography (CT) or magnetic resonance imaging (MRI) scans had ruled out a brain hemorrhage. Further, linkage to the National Causes of Death Registry at Statistics Norway allowed identification of fatal incident cases of myocardial infarction and ischemic stroke that occurred as out-of-hospital deaths, including deaths that occurred outside of Tromsø, as well as information on all-cause mortality. Information from the death certificates was used to collect relevant information of the event from additional sources such as autopsy reports and records from nursing homes, ambulance services and general practitioners. The Norwegian Registry of Vital Statistics provided information on emigration and death.

Statistical analyzes

Continuous variables are presented as means [95% confidence interval (CI), or standard deviation [SD]], and categorical data as number or percentage. Multivariable linear or logistic regression models were used for gender and age adjustment, and to test for linear trends across tertiles of OPG for continuous and binary data, respectively. For each participant, person years of follow-up were calculated from the date of blood sampling in 1994–95, until the date of an event, the date the participant moved from the municipality of Tromsø, died or until the end of the study period (31 December 2005). Cox-proportional hazard regression models were used to estimate hazard ratios (HR), with 95% CI for the following events: incident myocardial infarction, ischemic stroke and hemorrhagic stroke. HR with 95% CI for total mortality, death of ischemic heart disease (IHD), stroke and death of noncardiovascular disease (nonIHD and stroke) were also calculated. OPG was both categorized (tertiles) and treated as a continuous variable in analyzes. Crude analyzes, adjustment for age and gender and further adjustments were carried out for cardiovascular risk factors, and for variables previously shown to be associated with OPG (creatinine and self-reported diabetes mellitus or HbA1c > 6.1%). The addition of fibrinogen to the multivariable models did not significantly change the risk estimates. Possible two-way interactions between gender, or age, with OPG was assessed by including cross-product terms to the models. The proportional hazard assumption was verified by evaluating the parallelism between the curves of the log-log survivor function for tertiles of OPG. Subjects with incomplete data for the assessed covariates were excluded from the multivariable models. The distribution of OPG was moderately skewed in the population; however, log-transformation of OPG did not significantly influence the results of the statistical analyzes. The statistical analyzes were performed using spss software for Windows, version 16.0 (SPSS, Inc., Chicago, IL, USA). Two-sided Pvalues < 0.05 were considered statistically significant.

Results

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Disclosure of Conflict of Interests
  8. References

Characteristics of participants at baseline (1994–95), including traditional cardiovascular risk factors across tertiles of OPG, are shown in Table 1. Age, blood pressures, HDL cholesterol, HbA1c, fibrinogen, hsCRP, the percentage of women, smokers and subjects with diabetes mellitus increased, whereas BMI and triglycerides decreased, significantly across tertiles of serum OPG.

Table 1.   Distribution of baseline characteristics across tertiles of osteoprotegerin (OPG) adjusted for age and gender (n = 6265). Continuous variables are reported as mean with 95% confidence intervals (CIs) and categorical values as percentage. The Tromsø Study
 OPG tertilesP (trend)
T1 (0.46–2.78 ng mL−1)T2 (2.79–3.55 ng mL−1)T3 (3.56–25.81 ng mL−1)
  1. BP, blood pressure; DM, diabetes mellitus; HDL, high-density lipoprotein. *Adjusted for gender. Adjusted for age.

Number of subjects208820892088 
Age (years)*53.6 (53.2–54.0)61.5 (61.1–61.9)66.7 (66.3–67.1)< 0.001
Gender (% men)56.146.238.9< 0.001
Current smoker (%)25.431.134.2< 0.001
Body mass index (kg m−2)26.3 (26.1–26.5)26.0 (25.8–26.1)25.5 (25.4–25.7)< 0.001
Systolic BP (mm Hg)142 (141–143)144 (143–145)148 (148–149)< 0.001
Diastolic BP (mm Hg)82 (82–83)83 (82–84)84 (84–85)< 0.001
Total cholesterol (mmol L−1)6.61 (6.55–6.66)6.78 (6.73–6.84)6.71 (6.65–6.77)0.025
HDL cholesterol (mmol L−1)1.49 (1.47–1.51)1.55 (1.53–1.56)1.58 (1.56–1.59)< 0.001
Triglycerides (mmol L−1)1.65 (1.61–1.69)1.58 (1.55–1.62)1.57 (1.53–1.61)0.023
HbAlc (%)5.41 (5.37–5.44)5.45 (5.42–5.48)5.54 (5.51–5.57)< 0.001
Fibrinogen (g L−1)3.23 (3.19–3.27)3.38 (3.34–3.41)3.53 (3.50–3.57)< 0.001
C-reactive protein (mg L−1)2.24 (1.94–2.54)2.47 (2.20–2.75)3.21 (2.92–3.51)< 0.001
Creatinine (μmol L−1)78.3 (77.5–79.1)77.1 (76.4–77.8)79.0 (78.3–79.8)0.18
DM or HbA1c > 6.1 (%)5.15.38.9< 0.001
DM (self-reported) (%)1.31.73.6< 0.001

There were 641 incident myocardial infarction events, 317 incident ischemic stroke events and a total of 910 deaths during 60 878 person-years of follow-up (median 10.6 years). The overall crude incidence rates of myocardial infarction, ischemic stroke and death were 10.9, 5.3 and 14.9 per 1000 person-years, respectively. Serum OPG was associated with risk of incident myocardial infarction and ischemic stroke in crude and adjusted models irrespective of whether OPG was treated as a continuous or categorized variable (tertiles) (Table 2 and Fig. 1). The cumulative survival without myocardial infarction and ischemic stroke stratified by OPG tertiles are shown in Fig. 2, panel A and B, respectively. Subjects in the upper tertile of OPG had a significantly higher risk of clinical events during follow-up than subjects in the lowest tertile (Table 2 and Fig. 2). OPG showed a significant interaction (P = 0.011) with gender for ischemic stroke as an endpoint. The risk estimate for ischemic stroke was higher in women, HR 1.44 (95% CI 1.22–1.69) per SD increase in OPG than in men, HR 1.25 (95% CI 1.07–1.47) after adjustment. No association was found between serum OPG and the risk of hemorrhagic stroke (HR 1.02; 95% CI 0.73–1.43) (Fig. 1).

Table 2.   Hazard ratios with 95% confidence intervals (HR, 95% CI) of myocardial infarction (n = 6264), ischemic stroke (n = 6260) and total mortality (n = 6265) calculated for osteoprotegerin (OPG) tertile groups and per SD (1.13 ng mL−1) increase in OPG levels. The Tromsø Study
 OPG levelsP (trend)SD OPGP-value
Tertile 1Tertile 2Tertile 3
  1. Model 1: Adjusted for age and gender. Model 2: Adjusted for age, gender, current smoking, systolic blood pressure, body mass index, high-density lipoprotein cholesterol, total cholesterol, creatinine, diabetes mellitus or HbA1C > 6.1% and high sensitive C-reactive protein. *n = 5699, events 575. n = 5696, events 284. n = 5700, events 824.

Incident myocardial infarction
 Eventsn = 130n = 200n = 311 n = 641 
 Unadjusted1.01.58 (1.26–1.97)2.67 (2.17–3.28)< 0.0011.25 (1.21–1.29)< 0.001
 Model 11.01.14 (0.91–1.44)1.59 (1.25–2.02)< 0.0011.24 (1.17–1.31)< 0.001
 Model 2*1.01.03 (0.80–1.31)1.36 (1.05–1.76)0.0081.20 (1.11–1.31)< 0.001
Incident ischemic stroke
 Eventsn = 41n = 105n = 171 n = 317 
 Unadjusted1.02.65 (1.85–3.80)4.72 (3.35–6.63)< 0.0011.28 (1.24–1.33)< 0.001
 Model 11.01.76 (1.21–2.56)2.39 (1.62–3.52)< 0.0011.30 (1.21–1.40)< 0.001
 Model 21.01.55 (1.04–2.30)2.03 (1.35–3.06)0.0011.32 (1.18–1.47)< 0.001
Total mortality
 Eventsn = 124n = 255n = 531 n = 910 
 Unadjusted1.02.09 (1.69–2.59)4.69 (3.86–5.71)< 0.0011.30 (1.28–1.33)< 0.001
 Model 11.01.28 (1.02–1.60)2.06 (1.65–2.58)< 0.0011.35 (1.30–1.40)< 0.001
 Model 21.01.18 (0.94–1.49)1.63 (1.28–2.06)< 0.0011.34 (1.26–1.42)< 0.001
image

Figure 1.  Osteoprotegerin and the risk of incident disease and mortality Hazard ratios (HR) with 95% confidence intervals per standard deviation osteoprotegerin for incident disease (top) and mortality (bottom). HRs are adjusted for age, gender, current smoking, systolic blood pressure, body mass index, high-density lipoprotein cholesterol, total cholesterol, creatinine, diabetes mellitus or HbA1C > 6.1% and high sensitive C-reactive protein.

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image

Figure 2.  Osteoprotegerin and long-term cumulative survival stratified by tertiles of serum osteoprotegerin (tertile 1; — tertile 2; ········, tertile 3; –––) Panel A; incident myocardial infarction, P for trend = 0.008, panel B; incident ischemic stroke, P for trend = 0.001, panel C; total mortality (All cause mortality) P for trend < 0.001. Adjusted for age, gender, current smoking, systolic blood pressure, body mass index, high-density lipoprotein cholesterol, total cholesterol, creatinine, diabetes mellitus or HbA1C > 6.1% and high sensitive C-reactive protein.

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Serum levels of OPG predicted total mortality in crude analyzes and after adjustments (Table 2, Figs 1 and 2). OPG was associated with death from ischemic heart disease (HR 1.35; 95% CI 1.18–1.54) and stroke (HR 1.44; 95% CI 1.19–1.75) (Fig. 1). Mortality from non-vascular causes was also predicted by serum OPG in crude (data not shown) and adjusted analysis (HR 1.31; 95% CI 1.22–1.41) (Fig. 1). There were no statistical significant interactions between OPG and age in the models.

Discussion

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Disclosure of Conflict of Interests
  8. References

The present population based cohort study with 12 years follow-up revealed that serum OPG was significantly associated with incident myocardial infarction, ischemic stroke and total mortality independent of traditional cardiovascular risk factors. Subjects with serum OPG levels in the upper tertile had a 1.4-, 2.0- and 1.6-fold increased risk of myocardial infarction, ischemic stroke and total mortality, respectively, compared with subjects in the lowest tertile. Furthermore, serum OPG differentiated between risk of hemorrhagic and ischemic strokes. This may suggest that OPG acts as a specific predictor for atherothrombotic cardiovascular diseases. Similar risk estimates for non-vascular-, ischemic heart disease- and stroke-related mortality may suggest that OPG also predicts other diseases with fatal outcome.

Previous studies have reported various associations between serum OPG and incident ischemic strokes and cerebrovascular deaths [13,17,20], whereas most [13–16,20], but not all [21] prospective studies showed that OPG predicted cardiovascular events and mortality. Thus, it has been suggested that the differential impact of OPG on risk of myocardial infarction and ischemic stroke reflected different pathogenic processes for the two disease entities [17]. In the present study, however, the risk estimate was even higher for ischemic stroke than for myocardial infarction. Serum OPG was not merely an unspecific risk marker of cerebrovascular events as a result of its ability to discriminate between thromboembolic and bleeding events. No association between OPG and non-vascular mortality was reported in the Bruneck study [15]. In contrast, we found similar and significant risk estimates for vascular and non-vascular mortality in our large, population- based cohort. The reason(s) for the apparent discrepancies between our and previous studies may be related to differences in study populations, sample size, event rates and study design.

Several lines of evidence support the concept that OPG is a marker (or inhibitor) rather than a mediator of cardiovascular disease. First, proinflammatory cytokines such as interleukin-1β and TNF-α are known to induce OPG expression in human vascular smooth muscle cells [22]. Second, atherosclerosis is a chronic inflammatory condition [23] and previous studies have shown elevated levels of OPG in the presence of coronary artery disease (CAD) and an increase in OPG with the severity of the disease [7,8]. Third, serum OPG is significantly associated with most cardiovascular risk factors [7,8,15,21] (see also Table 1). Fourth, interventional studies in animal models revealed OPG as an inhibitor rather than mediator of atherosclerosis [24–26], and prospective cohort studies in humans have shown that OPG was not associated with novel plaque formation [15,18] and had a modest [15] if any [18] impact on plaque growth.

A clear temporal sequence between exposure and outcome is a prerequisite to establish OPG as a risk factor of cardiovascular diseases and mortality. Our findings that elevated serum OPG preceded incident cardiovascular events and mortality in a general population independent of traditional risk factors suggests that serum OPG is also a mediator of cardiovascular diseases and mortality. However, the mechanism(s) by which OPG promotes cardiovascular disease and mortality is not known, but OPG may influence plaque morphology [27] and vulnerability [28] by inducing increased expression of matrix metalloproteinases [26,29], apoptotic and chemotactic effects of its own or by inhibiting ligation of RANKL and TRAIL to their cognate receptors [2,3]. Furthermore, elevated serum OPG levels may also play an important role in thrombogenesis. Previous studies have shown that OPG is colocalized with von Willebrand factor (VWF) in endothelial cells, remains complexed after secretion from endothelial cells [30] and is correlated with VWF in plasma from CAD patients [31].

In the present study, OPG showed similar risk estimates for death of ischemic heart disease, stroke and non-vascular causes. These findings may indicate that OPG is a marker for other diseases as well as cardiovascular disease. This could be biologically plausible given the pleiotropic effects of the TRAIL/OPG/RANKL system, affecting the immune system, the skeletal system, the cardiovascular system and cell survival (apoptosis). Inhibition of central hubs such as nuclear factor κB in chronic inflammation may render subjects susceptible to opportunistic infections and impair tumor surveillance [32]. Given the pleiotropic effects of the TRAIL/OPG/RANKL system, therapeutic interventions affecting OPG and/or ligation of RANKL and TRAIL to their cognate receptors may also be associated with side effects which could be beneficial or harmful. However, more knowledge about the biological role of increased circulating OPG (causal relationship vs. compensatory mechanism) and long-term follow-up studies are needed to address this question.

The strengths of the present study are its population-based and prospective design, the high number of participants, high attendance rate and long-term follow-up as well as the completeness of end-point registration and validation. Study limitations, even though potential confounders and assumptions for statistical models were carefully checked, it is not possible to completely rule out residual uncontrolled confounding because of error in the measurement of the covariates or confounding by some other unmeasured factor. It is uncertain whether our findings in a European Caucasian population apply to other ethnical groups. Serum samples were kept frozen for 12 years at −70 °C without any freezing-thawing cycles before measurement of OPG. However, others have reported long-term stability of OPG measurements in serum samples stored at −70 °C [15].

In conclusion, in this prospective large population-based study, the serum OPG level was associated with incident myocardial infarction, incident ischemic stroke and mortality independent of traditional cardiovascular risk factors. Serum OPG also showed similar risk estimates for vascular- and non-vascular mortality, suggesting that OPG may also play a role in the pathogenesis of other fatal diseases.

Disclosure of Conflict of Interests

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Disclosure of Conflict of Interests
  8. References

CART was supported by an independent grant from Pfizer AS.

References

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Disclosure of Conflict of Interests
  8. References
  • 1
    Simonet WS, Lacey DL, Dunstan CR, Kelley M, Chang MS, Luthy R, Nguyen HQ, Wooden S, Bennett L, Boone T, Shimamoto G, DeRose M, Elliott R, Colombero A, Tan HL, Trail G, Sullivan J, Davy E, Bucay N, Renshaw-Gegg L, et al. Osteoprotegerin: a novel secreted protein involved in the regulation of bone density. Cell 1997; 89: 30919.
  • 2
    Yasuda H, Shima N, Nakagawa N, Yamaguchi K, Kinosaki M, Mochizuki S-i, Tomoyasu A, Yano K, Goto M, Murakami A, Tsuda E, Morinaga T, Higashio K, Udagawa N, Takahashi N, Suda T. Osteoclast differentiation factor is a ligand for osteoprotegerin/osteoclastogenesis-inhibitory factor and is identical to TRANCE/RANKL. PNAS 1998; 95: 3597602.
  • 3
    Emery JG, McDonnell P, Burke MB, Deen KC, Lyn S, Silverman C, Dul E, Appelbaum ER, Eichman C, DiPrinzio R, Dodds RA, James IE, Rosenberg M, Lee JC, Young PR. Osteoprotegerin Is a Receptor for the Cytotoxic Ligand TRAIL. J Biol Chem 1998; 273: 143637.
  • 4
    Reid P, Holen I. Pathophysiological roles of osteoprotegerin (OPG). Eur J Cell Biol 2009; 88: 117.
  • 5
    Malyankar UM, Scatena M, Suchland KL, Yun TJ, Clark EA, Giachelli CM. Osteoprotegerin is an alpha vbeta 3-induced, NF-kappa B-dependent Survival Factor for Endothelial Cells. J Biol Chem 2000; 275: 2095962.
  • 6
    Bord S, Frith E, Ireland DC, Scott MA, Craig JI, Compston JE. Synthesis of osteoprotegerin and RANKL by megakaryocytes is modulated by oestrogen. Br J Haematol 2004; 126: 24451.
  • 7
    Jono S, Ikari Y, Shioi A, Mori K, Miki T, Hara K, Nishizawa Y. Serum osteoprotegerin levels are associated with the presence and severity of coronary artery disease. Circulation 2002; 106: 11924.
  • 8
    Schoppet M, Sattler AM, Schaefer JR, Herzum M, Maisch B, Hofbauer LC. Increased osteoprotegerin serum levels in men with coronary artery disease. J Clin Endocrinol Metab 2003; 88: 10248.
  • 9
    Crisafulli A, Micari A, Altavilla D, Saporito F, Sardella A, Passaniti M, Raffa S, D’Anneo G, Luca F, Mioni C, Arrigo F, Squadrito F. Serum levels of osteoprotegerin and RANKL in patients with ST elevation acute myocardial infarction. Clin Sci (Lond) 2005; 109: 38995.
  • 10
    Ueland T, Jemtland R, Godang K, Kjekshus J, Hognestad A, Omland T, Squire IB, Gullestad L, Bollerslev J, Dickstein K, Aukrust P. Prognostic value of osteoprotegerin in heart failure after acute myocardial infarction. J Am Coll Cardiol 2004; 44: 19706.
  • 11
    Golledge J, McCann M, Mangan S, Lam A, Karan M. Osteoprotegerin and Osteopontin Are Expressed at High Concentrations Within Symptomatic Carotid Atherosclerosis. Stroke 2004; 35: 163641.
  • 12
    Nybo M, Rasmussen LM. The capability of plasma osteoprotegerin as a predictor of cardiovascular disease: a systematic literature review. Eur J Endocrinol 2008; 159: 6038.
  • 13
    Browner WS, Lui LY, Cummings SR. Associations of serum osteoprotegerin levels with diabetes, stroke, bone density, fractures, and mortality in elderly women. J Clin Endocrinol Metab 2001; 86: 6317.
  • 14
    Lieb W, Gona P, Larson MG, Massaro JM, Lipinska I, Keaney JF Jr, Rong J, Corey D, Hoffmann U, Fox CS, Vasan RS, Benjamin EJ, O’Donnell CJ, Kathiresan S. Biomarkers of the Osteoprotegerin Pathway. Clinical Correlates, Subclinical Disease, Incident Cardiovascular Disease, and Mortality. Arterioscler Thromb Vasc Biol 2010; 30: 184954.
  • 15
    Kiechl S, Schett G, Wenning G, Redlich K, Oberhollenzer M, Mayr A, Santer P, Smolen J, Poewe W, Willeit J. Osteoprotegerin is a risk factor for progressive atherosclerosis and cardiovascular disease. Circulation 2004; 109: 217580.
  • 16
    Semb AG, Ueland T, Aukrust P, Wareham NJ, Luben R, Gullestad L, Kastelein JJ, Khaw KT, Boekholdt SM. Osteoprotegerin and soluble receptor activator of nuclear factor-kappaB ligand and risk for coronary events: a nested case-control approach in the prospective EPIC-Norfolk population study 1993-2003. Arterioscler Thromb Vasc Biol 2009; 29: 97580.
  • 17
    Nybo M, Johnsen SP, Dethlefsen C, Overvad K, Tjonneland A, Jorgensen JO, Rasmussen LM. Lack of observed association between high plasma osteoprotegerin concentrations and ischemic stroke risk in a healthy population. Clin Chem 2008; 54: 196974.
  • 18
    Vik A, Mathiesen EB, Johnsen SH, Brox J, Wilsgaard T, Njolstad I, Hansen JB. Serum osteoprotegerin, sRANKL and carotid plaque formation and growth in a general population – The Tromso Study. J Thromb Haemost 2010; 8: 898905.
  • 19
    WHO MONICA Project Principal Investigators. The World Health Organization MONICA Project (monitoring trends and determinants in cardiovascular disease): a major international collaboration. J Clin Epidemiol 1988; 41: 10514.
  • 20
    Ueland T, Wilson SG, Islam FMA, Mullin B, Devine A, Bollerslev J, Zhu K, Prince RL. A cohort study of the effects of serum osteoprotegerin and osteoprotegerin gene polymorphisms on cardiovascular mortality in elderly women. Clin Endocrinol 2009; 71: 82833.
  • 21
    Omland T, Ueland T, Jansson AM, Persson A, Karlsson T, Smith C, Herlitz J, Aukrust P, Hartford M, Caidahl K. Circulating osteoprotegerin levels and long-term prognosis in patients with acute coronary syndromes. J Am Coll Cardiol 2008; 51: 62733.
  • 22
    Zhang J, Fu M, Myles D, Zhu X, Du J, Cao X, Chen YE. PDGF induces osteoprotegerin expression in vascular smooth muscle cells by multiple signal pathways. FEBS Lett 2002; 521: 1804.
  • 23
    Libby P, Ridker PM, Maseri A. Inflammation and atherosclerosis. Circulation 2002; 105: 113543.
  • 24
    Bucay N, Sarosi I, Dunstan CR, Morony S, Tarpley J, Capparelli C, Scully S, Tan HL, Xu W, Lacey DL, Boyle WJ, Simonet WS. Osteoprotegerin-deficient mice develop early onset osteoporosis and arterial calcification. Genes Dev 1998; 12: 12608.
  • 25
    Morony S, Tintut Y, Zhang Z, Cattley RC, Van G, Dwyer D, Stolina M, Kostenuik PJ, Demer LL. Osteoprotegerin inhibits vascular calcification without affecting atherosclerosis in ldlr(−/−) mice. Circulation 2008; 117: 41120.
  • 26
    Bennett BJ, Scatena M, Kirk EA, Rattazzi M, Varon RM, Averill M, Schwartz SM, Giachelli CM, Rosenfeld ME. Osteoprotegerin inactivation accelerates advanced atherosclerotic lesion progression and calcification in older ApoE−/− mice. Arterioscler Thromb Vasc Biol 2006; 26: 211724.
  • 27
    Vik A, Mathiesen EB, Noto AT, Sveinbjornsson B, Brox J, Hansen JB. Serum osteoprotegerin is inversely associated with carotid plaque echogenicity in humans. Atherosclerosis 2007; 191: 12834.
  • 28
    Kadoglou NP, Gerasimidis T, Golemati S, Kapelouzou A, Karayannacos PE, Liapis CD. The relationship between serum levels of vascular calcification inhibitors and carotid plaque vulnerability. J Vasc Surg 2008; 47: 5562.
  • 29
    Fiotti N, Altamura N, Orlando C, Simi L, Reimers B, Pascotto P, Zingone B, Pascotto A, Serio M, Guarnieri G, Giansante C. Metalloproteinases-2, -9 and TIMP-1 expression in stable and unstable coronary plaques undergoing PCI. Int J Cardiol 2008; 127: 3507.
  • 30
    Zannettino AC, Holding CA, Diamond P, Atkins GJ, Kostakis P, Farrugia A, Gamble J, To LB, Findlay DM, Haynes DR. Osteoprotegerin (OPG) is localized to the Weibel-Palade bodies of human vascular endothelial cells and is physically associated with von Willebrand factor. J Cell Physiol 2005; 204: 71423.
  • 31
    Breland UM, Hollan I, Saatvedt K, Almdahl SM, Damas JK, Yndestad A, Mikkelsen K, Forre OT, Aukrust P, Ueland T. Inflammatory markers in patients with coronary artery disease with and without inflammatory rheumatic disease. Rheumatology (Oxford) 2010; 6: 111827.
  • 32
    Libby P. How our growing understanding of inflammation has reshaped the way we think of disease and drug development. Clin Pharmacol Ther 2010; 87: 38991.