Osteoprotegerin as a marker of atherosclerosis: a systematic update

The Role of the Receptor Activator of Nuclear Factor Kappa-B Ligand/Osteoprotegerin Ratio in Vascular Diseases: A Therapeutic Approach

Cardiovascular and bone diseases contribute independently to mortality and global health. The exact mechanisms involved in the pathophysiology shared between bone and vascular diseases are not well defined. Endothelial cells and osteoblasts communicate during osteogenesis, thus establishing a connection between angiogenesis and osteogenesis. One shared mechanism may involve osteoprotegerin (OPG) and its ligand Receptor Activator of NF-κB Ligand (RANKL). The RANKL/OPG ratio is an important modulator for the skeletal, immunological, and vascular systems. OPG levels are elevated due to either osteogenic causes or inflammatory responses in the vasculature. The data obtained from clinical and in vitro studies support the role of the RANKL/OPG ratio as a potential marker for the progression of endothelial damage. Therefore, determining the therapeutic approaches for the targeting RANKL/OPG ratio and evaluating its usage as a biomarker in cardiovascular and bone pathophysiology are needed. By integrating the protective and disease-causing role of OPG with its ligand, this review outlines the role of the RANKL/OPG ratio at the molecular level. We also consider targeted therapeutic approaches.

Secondary Prevention and Extreme Cardiovascular Risk Evaluation (SEVERE-1), Focus on Prevalence and Associated Risk Factors: The Study Protocol

INTRODUCTION

Despite significant improvement in secondary CardioVascular (CV) preventive strategies, some acute and chronic coronary syndrome (ACS and CCS) patients will suffer recurrent events (also called "extreme CV risk"). Recently new biochemical markers, such as uric acid (UA), lipoprotein A [Lp(a)] and several markers of inflammation, have been described to be associated with CV events recurrence. The SEcondary preVention and Extreme cardiovascular Risk Evaluation (SEVERE-1) study will accurately characterize extreme CV risk patients enrolled in cardiac rehabilitation (CR) programs.

AIM

 Our aims will be to describe the prevalence of extreme CV risk and its association with newly described biochemical CV risk factors.

AIM

Our aims will be to describe the prevalence of extreme CV risk and its association with newly described biochemical CV risk factors.

METHODS

We will prospectively enrol 730 ACS/CCS patients at the beginning of a CR program. Extreme CV risk will be retrospectively defined as the presence of a previous (within 2 years) CV events in the patients' clinical history. UA, Lp(a) and inflammatory markers (interleukin-6 and -18, tumor necrosis factor alpha, C-reactive protein, calprotectin and osteoprotegerin) will be assessed in ACS/CCS patients with extreme CV risk and compared with those without extreme CV risk but also with two control groups: 1180 hypertensives and 765 healthy subjects. The association between these biomarkers and extreme CV risk will be assessed with a multivariable model and two scoring systems will be created for an accurate identification of extreme CV risk patients. The first one will use only clinical variables while the second one will introduce the biochemical markers. Finally, by exome sequencing we will both evaluate polygenic risk score ability to predict recurrent events and perform mendellian randomization analysis on CV biomarkers.

CONCLUSIONS

Our study proposal was granted by the European Union PNRR M6/C2 call. With this study we will give definitive data on extreme CV risk prevalence rising attention on this condition and leading cardiologist to do a better diagnosis and to carry out a more intensive treatment optimization that will finally leads to a reduction of future ACS recurrence. This will be even more important for cardiologists working in CR that is a very important place for CV risk definition and therapies refinement.

Markers of Restenosis after Percutaneous Transluminal Balloon Angioplasty in Patients with Critical Limb Ischemia

Among cardiovascular diseases, chronic obliterating lesions of the arteries of lower extremities, which are one of the important problems of modern healthcare, are distinguished. In most cases, the cause of damage to the arteries of lower extremities is atherosclerosis. The most severe form is chronic ischemia, characterized by pain at rest and ischemic ulcers, ultimately increasing the risk of limb loss and cardiovascular mortality. Therefore, patients with critical limb ischemia need limb revascularization. Percutaneous transluminal balloon angioplasty is one of the least invasive and safe approaches, with advantages for patients with comorbidities. However, after this procedure, restenosis is still possible. Early detection of changes in the composition of some molecules as markers of restenosis will help screen patients at the risk of restenosis, as well as find ways to apply efforts for further directions of inhibition of this process. The purpose of this review is to provide the most important and up-to-date information on the mechanisms of restenosis development, as well as possible predictors of their occurrence. The information collected in this publication may be useful in predicting outcomes after surgical treatment and will also find new ways for the target implication to the mechanisms of development of restenosis and atherosclerosis.

Association of serum levels of osteopontin and osteoprotegerin with adverse outcomes after endovascular revascularisation in peripheral artery disease

Background

Osteoprotegerin (OPG) and osteopontin (OPN) are vascular calcification inhibitors with a known role in the atherosclerotic and inflammatory process. We investigated their relationship with adverse outcomes (restenosis/adverse cardiovascular events) after endovascular revascularisation of patients with peripheral arterial disease (PAD).

Methods

203 consecutive patients were enrolled in the PAD group (PADG) and 78 age and sex-matched subjects with less than two cardiovascular risk factors served as control group (COG). PADG underwent standard medical assessment at baseline and 12 months after the procedure. During follow up major adverse cardiovascular events (MACEs) including arterial restenosis with need for reintervention were documented and the PADG was divided accordingly into two subgroups.

Results

During 12-month follow-up, 82 MACE were recorded (MACE subgroup). The rest of 124 PAD patients remained free of MACE (non-MACE subgroup). At baseline, OPG (9.89 ± 2.85 ng/ml vs 3.47 ± 1.95 ng/ml, p < 0.001) and OPN (79.99 ± 38.29 ng/ml vs 35.21 ± 14.84 ng/ml, p < 0.001) levels were significantly higher in PADG compared to COG, as well as in MACE subgroup compared to non-MACE subgroup (13.29 ± 3.23 ng/ml vs 10.86 ± 3 ng/ml and 96.45 ± 40.12 ng/ml vs 78.1 ± 38.29 ng/ml, respectively). An independent association of PAD with OPG and OPN was found in the whole patient cohort. Although OPG and OPN were significantly related to MACE incidence in the univariate analysis, multiple logistic regression analysis failed to detect any independent predictor of MACE within the PADG.

Conclusion

Baseline high OPG and OPN levels were independently associated with PAD presence. Even higher levels of those biomarkers were detected among PAD patients with MACE, however, their prognostic role should be further clarified.

Serum osteoprotegerin levels, endothelial function and carotid intima-media thickness in type 2 diabetic patients

OBJECTIVES

Osteoprotegerin (OPG), a well-known protein that inhibits osteoclast formation and activity, might also be a potential marker for identifying patients with high cardiovascular risk. This study aimed to compare OPG levels, FMD, and CIMT measurements in subjects with vs. without diabetes and investigate the association of serum osteoprotegerin level with the early atherosclerotic markers, endothelial function, and carotid intima-media thickness (CIMT) in patients with type 2 diabetes mellitus (DM2).

METHODS

Forty-nine patients with DM2 (F/M: 26/23, 49.3 ± 10.0 years) and 45 healthy volunteers (F/M: 26/19, 48.3 ± 7.5 years) were included in this cross-sectional study. Serum OPG levels were measured by solid-phase enzyme-linked immunosorbent assay (ELISA). Fasting plasma glucose (FPG) and HbA1c levels were measured. CIMT was measured by B-mode ultrasound, and endothelial function was evaluated via flow-mediated dilation (FMD) of the brachial artery with Doppler ultrasonography.

RESULTS

Serum OPG levels were significantly higher in patients with DM2 (617.0 ± 111.0 pg/mL) compared to controls (481.0 ± 96.0 pg/mL, p < 0.001). While CIMT in diabetic patients (0.65 + 0.13 mm) was higher than controls (0.54 ± 0.10 mm, p = 0.009), FMD measurement was lower in DM2 group (4.2% ± 3.1 mm vs. 7.6% ± 4.1 mm, p = 0.01). Univariate analysis showed that OPG was associated with the presence of diabetes (OR: 6.999, p = 0.001, R²: 15.1%) and hypertension (OR = 6.925, p = 0.001, R²: 13.2%). There was no relationship between OPG levels and CIMT or FMD.

CONCLUSION

Osteoprotegerin and CIMT levels were increased, and FMD measurements were decreased in patients with DM2. No association between CIMT, FMD, and OPG measurements was observed. The presence of DM and hypertension were associated with circulating OPG levels.

High levels of osteoprotegerin are associated with coronary artery calcification in patients suspected of a chronic coronary syndrome

Plasma osteoprotegerin (OPG) and vascular smooth muscle cell (VSMC) derived extracellular vesicles (EVs) are important regulators in the process of vascular calcification (VC). In population studies, high levels of OPG are associated with events. In animal studies, however, high OPG levels result in reduction of VC. VSMC-derived EVs are assumed to be responsible for OPG transport and VC but this role has not been studied. For this, we investigated the association between OPG in plasma and circulating EVs with coronary artery calcium (CAC) as surrogate for VC in symptomatic patients. We retrospectively assessed 742 patients undergoing myocardial perfusion imaging (MPI). CAC scores were determined on the MPI-CT images using a previously developed automated algorithm. Levels of OPG were quantified in plasma and two EV-subpopulations (LDL and TEX), using an electrochemiluminescence immunoassay. Circulating levels of OPG were independently associated with CAC scores in plasma; OR 1.39 (95% CI 1.17–1.65), and both EV populations; EV-LDL; OR 1.51 (95% CI 1.27–1.80) and EV-TEX; OR 1.21 (95% CI 1.02–1.42). High levels of OPG in plasma were independently associated with CAC scores in this symptomatic patient cohort. High levels of EV-derived OPG showed the same positive association with CAC scores, suggesting that EV-derived OPG mirrors the same pathophysiological process as plasma OPG.

The role of osteoprotegerin (OPG) in fibrosis: its potential as a biomarker and/or biological target for the treatment of fibrotic diseases

Fibrosis is defined by excessive formation and accumulation of extracellular matrix proteins, produced by myofibroblasts, that supersedes normal wound healing responses to injury and results in progressive architectural remodelling. Fibrosis is often detected in advanced disease stages when an organ is already severely damaged and can no longer function properly. Therefore, there is an urgent need for reliable and easily detectable markers to identify and monitor fibrosis onset and progression as early as possible; this will greatly facilitate the development of novel therapeutic strategies. Osteoprotegerin (OPG), a well-known regulator of bone extracellular matrix and most studied for its role in regulating bone mass, is expressed in various organs and functions as a decoy for receptor activator of nuclear factor kappa-B ligand (RANKL) and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). Recently, OPG has been linked to fibrosis and fibrogenesis, and has been included in a panel of markers to diagnose liver fibrosis. Multiple studies now suggest that OPG may be a general biomarker suitable for detection of fibrosis and/or monitoring the impact of fibrosis treatment. This review summarizes our current understanding of the role of OPG in fibrosis and will discuss its potential as a biomarker and/or novel therapeutic target for fibrosis.

The role of serum osteoprotegerin level in diagnosis of disease and determining cardiovascular risk of polycystic ovary syndrome

Objective: Although animal studies claim that osteoprotegerin (OPG) is preventive on this system, there are conflicting results in human studies. The aim of this study was to investigate the role of OPG in the diagnosis and determination of cardivovascular risk in patients with polycystic ovary syndrome (PCOS), which is a multisystem effective disease.Method: The study was performed on 28 premenopausal healthy female volunteers and 57 newly diagnosed PCOS patients in 2017. Anamnesis was obtained, body mass indexes were calculated, laboratory tests required for diagnosis and differential diagnosis of PCOS and suprapubic ovarian ultrasonography were performed, serum OPG level was studied by enzyme-linked immunosorbent assay.Results: OPG levels were similar in PCOS and control groups and there was no significant difference (49.392 ± 10.973 pg/ml vs 49.567 ± 13.57 pg/ml, p = .815). Correlation analysis showed a positive correlation between OPG and total testosterone levels in the PCOS group (r = 0.277, p = .045). No significant relationship with cardiovascular and metabolic parameters was detected.Conclusion: No difference was found between PCOS patients and control groups in terms of OPG levels. Therefore, it is thought that OPG level cannot be used in the diagnosis of the disease. There was no significant relationship between cardiometabolic parameters.

Serum osteoprotegerin level is positively associated with peripheral artery disease in patients with peritoneal dialysis

Osteoprotegerin (OPG) is a potential biomarker of cardiovascular disease complications and severity. Peripheral arterial disease (PAD) is associated with an increased risk of death in patients on peritoneal dialysis (PD). Therefore, this study aimed to evaluate the relationship between serum OPG levels and PAD by measuring the ankle-brachial index (ABI) of patients on PD. A commercial enzyme-linked immunosorbent assay kit was used to measure OPG values. Left or right ABI values of <0.9 were categorized as the low ABI group. Among 70 patients on PD, 13 (18.6%) were categorized in the low ABI group. Patients in the low ABI group had higher prevalence of diabetes mellitus (p = .044) and higher serum C-reactive protein (CRP) (p < .001) and OPG levels (p < .001) but lower creatinine (p = .013) and peritoneal Kt/V (p = .048) levels than those in the normal ABI group. Results of multivariable logistic regression analysis revealed that OPG [adjusted odds ratio (aOR) 1.027, 95% confidence interval (CI) 1.010-1.045, p = .002] and CRP (aOR 1.102, 95% CI 1.006-1.207, p = .037) levels were independent predictors of PAD in patients on PD. OPG can also be used to predict PAD development with the area under the receiver operating characteristic curve of 0.823 (95% CI: 0.714-0.904, p < .001) in patients on PD. Therefore, serum OPG and CRP levels can be considered as risk factors for PAD development in patients on PD.

Osteoprotegerin SNP associations with coronary artery disease and ischemic stroke risk: a meta-analysis

Osteoprotegerin (OPG) is involved in the development of atherosclerosis and cardio-cerebrovascular disease. The goal of this meta-analysis was to evaluate the association of OPG single nucleotide polymorphisms (SNPs) with coronary artery disease (CAD) and ischemic stroke. A total of 15 eligible studies were extracted from electronic databases. Odds ratios (ORs) were presented, with 95% confidence intervals (CIs), to assess the associations. Meta-analysis was conducted using MetaGenyo, STATA, and Comprehensive Meta-Analysis. Meta-analysis of our data showed that the OPG SNP T950C was significantly associated with increased CAD risk among Asians via recessive (OR 1.55, 95% CI 1.18–2.04, P=0.002), CC vs TT (OR 1.57, 95% CI 1.16–2.11, P=0.003) and allelic (OR 1.21, 95% CI 1.05–1.38, P=0.007) models. No strong associations were observed for the OPG SNP G1181C, T245G and G209A with CAD risk. When evaluating the OPG SNP T245G and T950C associations with ischemic stroke, we found the OPG SNP T245G to be significantly associated with increased risk of ischemic stroke among Chinese via recessive (OR 1.53, 95% CI 1.02–2.29, P=0.039) and CC vs AA (OR 1.61, 95% CI 1.07–2.42, P=0.021) models. Our results suggested that the OPG SNP T950C was associated with increased risk of CAD among Asians, and the OPG SNP T245G was associated with enhanced ischemic stroke risk among Chinese.

Towards identification of novel putative biomarkers for infective endocarditis by serum proteomic analysis

INTRODUCTION

Infective endocarditis (IE) has high mortality, partly due to delayed diagnosis. No biomarker can identify IE in patients with fever and clinical picture of infection. To find putative biomarkers we analyzed serum levels of two proteins found in cardiac valves, fibulin-1 (n=696) and osteoprotegerin (n=689) among patients on clinical suspicion of IE. Proteomic analyses were performed in 24 patients with bacteremia, 12 patients with definite IE and 12 patients with excluded IE.

METHODS

Fibulin-1 and osteoprotegerin were studied by enzyme linked immunosorbent assay (ELISA). Proteomic analyses were conducted by 2-dimensional polyacrylamid gel electrophoresis (2D-PAGE) and label-free quantitative liquid chromatography - tandem mass spectrometry (LFQ LC-MS/MS). Controls for 2D 2D-PAGE and LFQ LC-MS/MS had bacteremia and excluded IE.

RESULTS

Osteoprotegerin levels were significantly increased in IE patients compared with non-IE patients. Fibulin-1 showed no difference. 2D-PAGE showed significant differences of 6 proteoforms: haptoglobin, haptoglobin-related protein, α-2-macroglobulin, apolipoprotein A-I and ficolin-3. LFQ LC-MS/MS analysis revealed significant level changes of 7 proteins: apolipoprotein L1, complement C1q subcomponent B and C, leukocyte immunoglobulin-like receptor subfamily A member 3, neuropilin-2, multimerin-1 and adiponectin.

CONCLUSIONS

The concentration changes in a set of proteoforms/proteins suggest that stress and inflammation responses are perturbed in patients with IE compared to patients with bacteremia without IE.

Bone Morphogenetic Protein-2 and Osteopontin Gene Expression in Epicardial Adipose Tissue from Patients with Coronary Artery Disease Is Associated with the Presence of Calcified Atherosclerotic Plaques

PURPOSE

It has been proposed that the cardiovascular effects of obesity are related to epicardial adipose tissue (EAT), which seems to play an active role on the development and calcification of atherosclerotic plaques, but the mechanisms are still unknown. Therefore, the aim of this study was to determine whether the EAT expresses the genes of calcifying factors and whether such expression is associated with the body mass index (BMI) and with the presence of coronary artery calcium (CAC) in patients with coronary artery disease (CAD).

PATIENTS AND METHODS

Forty-three patients with CAD were enrolled specifically for this study, and their CAC score and EAT volume were determined by computed tomography. As the group of comparison, 41 patients with aortic valve stenosis and CAC = 0 were included (control group). A representative subgroup of 16 CAD patients and 23 controls were selected to obtain EAT biopsies during the chirurgical procedure from the atrio-interventricular groove. The mRNA expression of bone morphogenetic protein-2 and -4 (BMP-2, BMP-4), osteopontin (OPN), osteonectin (ON), and osteoprotegerin (OPG) in EAT was determined by qPCR.

RESULTS

The gene expression of OPN and BMP-2 was 70% and 52% higher in the EAT from CAD patients than that in controls, respectively, whereas the expression of OPG, ON, and BMP-4 was similar in both groups. The EAT volume positively correlated with OPG and with the BMI, suggesting a relationship of obesity with local higher expression of calcifying genes in the coronary territory. The logistic regression analysis showed that high levels of both OPN and BMP-2 increased about 6 and 8 times the odds of coronary calcification (CAC score > 0), respectively.

CONCLUSION

EAT correlated with BMI and expressed the mRNA of calcifying genes but only OPN and BMP-2 expression was higher in CAD patients. Higher levels of both OPN and BMP-2 statistically determined the presence of calcium in coronary arteries of CAD patients.

Peripheral artery disease and osteoporosis: Not only age‑related (Review)

Osteoporosis and atherosclerosis are two chronic degenerative diseases that share several biochemical pathways and risk factors. Previous studies have associated osteoporosis with carotid atherosclerosis, cardiovascular mortality and stroke, but data on the relationship with peripheral artery disease are few and conflicting. The OPG/RANK/RANKL system and Wnt/beta catenin signaling seem to be deeply involved in the pathogenesis of bone alterations and atherosclerotic processes also affect arteries of the lower extremities. Hypovitaminosis D could also play a role in the relationship of these two diseases. New and larger studies are necessary to shed light on this association and to design new drugs able to act in both these chronic degenerative diseases.

Elevated Circulating Osteoprotegerin Levels in the Plasma of Hemodialyzed Patients With Severe Artery Calcification

We studied the correlations between circulating osteoprotegerin (OPG) level and radial artery calcification (RAC) assessed histologically and carotid artery intima-media thickness (CCA-IMT). Moreover, we studied the relationship between OPG levels and all-cause and cardiovascular (CV) mortality during a 5-year observation period. The study comprised 59 CKD patients (36 hemodialyzed (HD), 23 predialysis). The biochemical parameters included: creatinine, calcium, phosphate, intact parathormone, C-reactive protein, interleukin-6, tumor necrosis factor receptor II (TNFRII), transforming growth factor-β, hepatocyte growth factor, fibroblast growth factor 23, osteonectin (ON), osteopontin, osteoprotegerin, and osteocalcin. CCA-IMT and the presence of atherosclerotic plaques was assessed by ultrasound. Fragments of radial artery obtained during creation of HD access were prepared for microscopy and stained for calcifications with alizarin red. RAC was detected in 34 patients (58%). In multiple regression adjusted for dialysis status, TNFRII, ON and Framingham risk score (FRS) were identified as the independent predictors of OPG. Serum OPG above the median value of 7.55 pmol/L significantly predicted the presence of RAC in simple logistic regression (OR 5.33; 95%CI 1.39-20.4; P = 0.012) and in multiple logistic regression adjusted for FRS, dialysis status and CCA-IMT values (OR 6.56; 95%CI 1.06-40.6; P = 0.036). OPG levels above the median were associated with higher CCA-IMT values (1.02 ± 0.10 vs. 0.86 ± 0.13; P < 0.001) and predicted the presence of atherosclerotic plaques in carotid artery (OR 14.4; 95%CI 2.84-72.9; P < 0.001), independently of FRS, dialysis status and RAC. In this study, elevated serum OPG levels correlated with higher CCA-IMT, the presence of atherosclerotic plaques and the severity of the RAC independently of each other. During follow-up, 25 patients (42%) died, including 21 due to CV causes. In multiple Cox regression, OPG above the median predicted overall survival independently of dialysis status, Framingham risk score, CCA-IMT above the median value, and the presence of atherosclerotic plaques in CCA, but not independently of RAC. We postulate that circulating OPG may play a dual role as a marker for both medial arterial calcification and atherosclerosis, hence it seems to be a valuable tool for assessing CV risk in patients with CKD. OPG might be an early indicator of all-cause mortality in CKD patients with advanced medial arterial calcification.

The Role of Osteoprotegerin as a Cardioprotective Versus Reactive Inflammatory Marker: the Chicken or the Egg Paradox

Cardiovascular disease is one of the most frequent causes of mortality and morbidity worldwide. Several variables have been identified as risk factors for cardiovascular disease. Recently, the role of receptor activator of nuclear factor kappa B, receptor activator of nuclear factor kappa B ligand, and the osteoprotegerin system has been recognized as more important in the pathogenesis of cardiovascular disease. Besides their roles in the regulation of bone resorption, these molecules have been reported to be associated with the pathophysiology of cardiovascular disease. There are conflicting data regarding the impact of osteoprotegerin, a glycoprotein with a regulatory role in the cardiovascular system. The aim of this review is to discuss the current knowledge and the role of osteoprotegerin in cardiovascular disease.

Osteoprotegerin concentration and risk of cardiovascular outcomes in nine general population studies: Literature-based meta-analysis involving 26,442 participants

Background

Recent experimental and epidemiological studies have suggested that osteoprotegerin, a key regulator in bone metabolism, may be involved in vascular calcification and atherosclerosis. Our aim was to reliably quantify the associations of osteoprotegerin concentration and incidence of first-ever cardiovascular disease outcomes in the general population.

Methods

Using the electronic databases MEDLINE, EMBASE and Web of Science (January 1975 and April 2017, no language restrictions), nine relevant studies were identified involving a total of 26,442 participants recruited from the general population. Over a mean follow-up of 8.5 years, 2,160 cardiovascular disease, 2,123 coronary heart disease, and 1,102 stroke outcomes were recorded. Study-specific risk ratios were combined with random-effects meta-analysis.

Results

When comparing individuals in the top with those in the bottom third of osteoprotegerin concentration, the combined risk ratio was 1.83 (95% confidence interval: 1.46, 2.30; P<0.001; I² = 76.8%) for cardiovascular disease, 1.72 for coronary heart disease (1.26, 2.37; P = 0.001; I² = 83.5%), and 1.58 for stroke (1.18, 2.12; P = 0.002; I² = 65.2%). Associations appeared stronger at younger age (P = 0.018 for cardiovascular disease), in studies that did not employ statistical adjustment (P = 0.023 for cardiovascular disease and 0.018 for coronary heart disease), and potentially in studies that measured osteoprotegerin in plasma rather than in serum (P = 0.005 for cardiovascular disease and 0.018 for coronary heart disease). Magnitudes of associations did not differ according to the proportion of males, geographical region, or osteoprotegerin assay manufacturer. There was no evidence for publication bias for any of the outcomes assessed (all P>0.05).

Conclusions

Elevated osteoprotegerin concentration is associated with an increased risk of incident cardiovascular disease in the general population. The mechanisms underlying this observation deserve further investigation.

Relationship of serum osteoprotegerin with arterial stiffness, preclinical atherosclerosis, and disease activity in patients with ankylosing spondylitis

Patients with ankylosing spondylitis (AS) reportedly have a higher mortality and morbidity risk. Osteoprotegerin (OPG) was recently defined as an important cardiovascular (CV) marker in the general population. We aimed to assess the relationship of serum OPG levels with arterial stiffness, carotid intima media thickness (CIMT), and clinical and laboratory data in AS patients. We examined 60 AS patients without CV disease or risk factors and 50 healthy controls. Disease activity was evaluated using the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and the Ankylosing Spondylitis Disease Activity Score (ASDAS), whereas functional capacity was evaluated using the Bath Ankylosing Spondylitis Functional Index (BASFI). Serum OPG levels were measured with the enzyme-linked immunosorbent assay. Carotid-femoral pulse wave velocity (PWV) was used as an indicator of arterial stiffness, whereas CIMT (examined via carotid ultrasonography) was used to evaluate preclinical atherosclerosis. The mean serum OPG level, PWV, and CIMT were significantly higher in AS patients than in controls (106.7 ± 50.9 vs. 58.1 ± 12.7 pg/mL; 7.4 ± 1.8 vs. 6.2 ± 1.2 m/s; 0.72 ± 0.13 vs. 0.57 ± 0.07 mm, respectively; P < 0.001 for all). In AS patients, the serum OPG levels were not significantly correlated with PWV and CIMT but were significantly correlated with erthrocyte sedimentation rate, BASFI, and ASDAS. AS patients without CV disease or risk exhibited high OPG levels and increased PWV and CIMT values. Although OPG levels were not significantly correlated with PWV or CIMT, future long-term follow-up studies will help define the predictive value of OPG in these patients.

Relationship of osteoprotegerin to pulse wave velocity and carotid intima-media thickness in rheumatoid arthritis patients

OBJECTIVE

Osteoprotegerin (OPG) is considered an important biomarker in cardiovascular (CV) disease. CV disease is the most common cause of mortality in patients with rheumatoid arthritis (RA), a consequence of accelerated atherosclerosis. The present study aimed to evaluate the relationship of serum OPG levels to arterial stiffness, carotid intima-media thickness (CIMT), and clinical and laboratory indices in RA patients.

PATIENTS AND METHODS

Included in the study were 68 RA patients with no history or signs of CV disease and 48 healthy subjects Disease activity was assessed by the 28-joint disease activity score (DAS28) in RA patients. Serum OPG level was measured using enzyme-linked immunosorbent assay (ELISA). Carotid femoral pulse wave velocity (PWV) was measured as an index of arterial stiffness and CIMT was evaluated by carotid ultrasonography.

RESULTS

The mean serum OPG level was significantly higher in RA patients than controls (p < 0.001). Mean PWV and CIMT were also significantly increased in RA patients compared to controls (both p < 0.001). In RA patients, serum OPG level was significantly correlated with PWV and CIMT, as well as rheumatoid factor (RF) and anti-cyclic citrullinated peptide (anti-CCP) antibody; but not with DAS28, high-sensitivity C-reactive protein (hsCRP), or erythrocyte sedimentation rate.

CONCLUSION

Serum OPG levels were increased and correlated with CIMT and PWV in RA patients. In addition to PWV and CIMT, OPG may be a useful biomarker for CV risk management in RA patients.

From bones to blood pressure, developing novel biologic approaches targeting the osteoprotegein pathway for pulmonary vascular disease

Osteoprotegerin (tnfsf11b, OPG) is a soluble member of the TNF superfamily originally described as an important regulator of osteoclastogenesis almost 20 years ago. OPG is a heparin-binding secreted glycoprotein that exists as a 55–62 kDa monomer or a 110–120 kDa disulphide-linked homodimer. Acting as a soluble decoy receptor for RANKL, OPG actively regulates RANK signalling, and thereby osteoclastogenesis. OPG has subsequently been shown to also be a decoy receptor TNF related apoptosis inducing-ligand (tnfsf10, TRAIL, Apo2L). TRAIL is a type II transmembrane protein that is widely expressed in a variety of human tissues, including the spleen, lung, and prostate. Through binding to TRAIL, OPG can inhibit TRAIL-induced apoptosis of cancer cells. More recently, OPG has been demonstrated to be secreted by, and influence, vascular smooth muscle cells phenotype particularly related to vascular calcification and pulmonary vascular remodelling. In pulmonary artery smooth muscle cell (PASMC) suppression of BMP, induction of 5-HT and IL-1 signalling have been shown to stimulate the release of OPG in vitro, which causes cell migration and proliferation. Patients with idiopathic PAH (IPAH) demonstrate increased circulating and tissue levels of OPG, and circulating serum levels predict survival. In pre-clinical models, OPG levels correlate with disease severity. Since OPG is a naturally circulating protein, we are investigating the potential of novel biologic antibody therapies to rescue PAH phenotype in disease models. Further pre-clinical and mechanistic data are forthcoming, but we believe current published data identify OPG as an exciting and novel therapeutic target in PAH.

Low-dose hydrocortisone replacement is associated with improved arterial stiffness index and blood pressure dynamics in severely adrenocorticotrophin-deficient hypopituitary male patients

OBJECTIVE

Increased cardiovascular and cerebrovascular morbidity and mortality in hypopituitary subjects may be linked to inappropriate glucocorticoid exposure; however, the pathophysiology remains unclear. We aimed to examine the effect of three commonly prescribed hydrocortisone (HC) regimens on vascular risk factors.

DESIGN

An open crossover study randomising ten hypopituitary men with severe adrenocorticotrophic hormone deficiency to three HC dose regimens: dose A (20mg mane and 10mg tarde), dose B (10mg mane and 10mg tarde) and dose C (10mg mane and 5mg tarde).

METHODS

Following 6 weeks on each regimen, participants underwent 24-h serum cortisol sampling, 24-h ambulatory blood pressure (BP) measurements, calculation of the Ambulatory Arterial Stiffness Index (AASI), oral glucose tolerance testing and fasting serum osteoprotegerin (OPG) sampling.

RESULTS

There were no differences in 24-h BP between dose regimens and controls; however, low-dose HC replacement (dose C) was associated with the lowest AASI, indicating a less stiff arterial tree (P<0.05) compared with the other dose regimens. Loss of the physiologic nocturnal BP dip was more common in higher HC replacement regimens, although only significant for dose B compared with dose C (P=0.03). Twenty per cent of patients had abnormal glucose tolerance, but this was unrelated to dose regimen. OPG correlated strongly with 24-h BP in those on dose A only (r=0.65, P=0.04).

CONCLUSION

Currently prescribed HC replacement doses do not result in significant differences in absolute BP levels or improvements in insulin sensitivity. However, lower HC doses may result in lower arterial stiffness and a more physiological nocturnal BP dip. Long-term studies are required to confirm these findings and evaluate their impact on vascular morbidity in this patient group.

High circulating osteoprotegerin levels are associated with non-zero blood groups

BACKGROUND

Osteoprotegerin (OPG) and von Willebrand factor (VWF) form complex within endothelial cells and following secretion. The nature of blood group antigens strongly influences the levels of circulating VWF, but there is no available data concerning its ascendancy on OPG levels. We aimed to assess the relationship of AB0 blood groups with OPG, VWF levels (VWF: Ag) and collagen binding activity (VWF: CB) in peripheral arterial disease (PAD) patients.

METHODS

Functional and laboratory parameters of 105 PAD patients and 109 controls were examined. Results of OPG, VWF: Ag, VWF: CB (ELISA-s) were analysed by comparative statistics, together with clinical data.

RESULTS

OPG levels were higher in patients than in controls (4.64 ng/mL vs. 3.68 ng/mL, p < 0.001). Among patients elevation was marked in the presence of critical limb ischemia (5.19 ng/mL vs. 4.20 ng/mL, p = 0.011). The OPG in patients correlated positively with VWF: Ag and VWF: CB (r = 0.26, p = 0.008; r = 0.33, p = 0.001) and negatively with ankle-brachial pressure index (r = -0.22, p = 0.023). Furthermore, OPG was significantly elevated in non-0 blood groups compared to 0-groups both in patients and controls (4.95 ng/mL vs. 3.90 ng/mL, p = 0.012 and 4.09 ng/mL vs. 3.40 ng/mL, p = 0.002).

CONCLUSIONS

OPG levels are associated to blood group phenotypes and higher in non-0 individuals. Increased OPG levels in PAD characterize disease severity. The significant correlation between OPG and VWF:CB might have functional importance in an atherothrombosis-prone biological environment.

Osteoprotegerin, but Not Receptor Activator for Nuclear Factor-κB Ligand, is Associated With Subclinical Coronary Atherosclerosis in HIV-Infected Men

CONTEXT

Abnormalities in the osteoprotegerin (OPG)/receptor activator of nuclear factor-κB ligand (RANKL) axis have been observed in HIV-infected persons and have been implicated in cardiovascular disease (CVD) pathogenesis in the general population.

OBJECTIVE

To determine associations of serum OPG and RANKL concentrations with HIV infection and subclinical atherosclerosis.

DESIGN

Cross-sectional study nested within the Multicenter AIDS Cohort Study.

SETTING

Four US academic medical centers.

PARTICIPANTS

There were 578 HIV-infected and 344 HIV-uninfected men.

MAIN OUTCOME MEASURES

Coronary artery calcium (CAC) was measured by noncontrast cardiac computed tomography, and coronary stenosis and plaque characteristics (composition, presence, and extent) were measured by coronary computed tomography angiography. All statistical models were adjusted for traditional CVD risk factors.

RESULTS

OPG concentrations were higher, and RANKL concentrations were lower among HIV-infected men compared with HIV-uninfected men (P < 0.0001 each). Among HIV-infected men, higher OPG concentrations were associated with the presence of CAC, mixed plaque, and coronary stenosis >50%, but not with plaque extent. In contrast, among HIV-uninfected men, higher OPG concentrations were associated with the extent of both CAC and calcified plaque, but not with their presence. RANKL concentrations were not associated with plaque presence or the extent among HIV-infected men, but among HIV-uninfected men, lower RANKL concentrations were associated with greater extent of CAC and total plaque.

CONCLUSIONS

OPG and RANKL are dysregulated in HIV-infected men, and their relationship to the presence and extent of subclinical atherosclerosis varies by HIV status. The role of these biomarkers in CVD pathogenesis and risk prediction may be different in HIV-infected men.

Relationship of osteoprotegerin to pulse wave velocity and carotid intima-media thickness in rheumatoid arthritis patients

OBJECTIVE

Osteoprotegerin (OPG) is considered an important biomarker in cardiovascular (CV) disease. CV disease is the most common cause of mortality in patients with rheumatoid arthritis (RA), a consequence of accelerated atherosclerosis. The present study aimed to evaluate the relationship of serum OPG levels to arterial stiffness, carotid intima-media thickness (CIMT), and clinical and laboratory indices in RA patients.

PATIENTS AND METHODS

Included in the study were 68 RA patients with no history or signs of CV disease and 48 healthy subjects Disease activity was assessed by the 28-joint disease activity score (DAS28) in RA patients. Serum OPG level was measured using enzyme-linked immunosorbent assay (ELISA). Carotid femoral pulse wave velocity (PWV) was measured as an index of arterial stiffness and CIMT was evaluated by carotid ultrasonography.

RESULTS

The mean serum OPG level was significantly higher in RA patients than controls (p < 0.001). Mean PWV and CIMT were also significantly increased in RA patients compared to controls (both p < 0.001). In RA patients, serum OPG level was significantly correlated with PWV and CIMT, as well as rheumatoid factor (RF) and anti-cyclic citrullinated peptide (anti-CCP) antibody; but not with DAS28, high-sensitivity C-reactive protein (hsCRP), or erythrocyte sedimentation rate.

CONCLUSION

Serum OPG levels were increased and correlated with CIMT and PWV in RA patients. In addition to PWV and CIMT, OPG may be a useful biomarker for CV risk management in RA patients.

Association of plasma osteoprotegerin levels with the severity of lower extremity arterial disease in patients with type 2 diabetes

Background

Osteoprotegerin (OPG) is a member of the tumor necrosis factor receptor superfamily and suggested as a marker of atherosclerosis. However, little is known about the association between plasma OPG levels and lower extremity arterial disease. We investigated whether plasma OPG levels were associated with the presence and severity of lower extremity arterial disease in patients with type 2 diabetes.

Methods

This was a study of 712 patients with type 2 diabetes aged 40 years or older. Plasma OPG was measured using ELISA. The lower extremity arterial disease was diagnosed by high-frequency color Doppler ultrasonic.

Results

Of 712 patients, 505 (70.9 %) had lower extremity arterial stenosis. OPG levels were significantly increased in patients with lower extremity arterial stenosis [1.89 (1.48-2.41) vs. 2.39 (1.82-3.33) ng/mL, p < 0.001]. Plasma OPG levels increased gradually with increasing severity of lower extremity arterial stenosis (p < 0.001 for trend), after adjustment for traditional cardiovascular risk factors such as age, gender, smoking, total cholesterol, high-density lipoprotein (HDL) cholesterol, C-reactive protein (CRP), body mass index (BMI), systolic blood pressure(SBP). The risk of lower extremity arterial disease was increased (OR = 1.17, 95 % CI 1.09 –1.28, p < 0.001) with each standard deviation (SD) higher level of OPG in patients with type 2 diabetes after adjustment for traditional CVD risk factors.

Conclusions

Plasma OPG levels were significantly associated with the presence and severity of lower extremity arterial disease. Our results suggest that OPG is an important plasma biomarker of lower extremity arterial disease in type 2 diabetes.

Serum osteopontin levels are upregulated and predict disability after an ischaemic stroke

BACKGROUND

After an acute ischaemic stroke (AIS), several inflammatory biomarkers have been investigated, but their predictive role on functional recovery remains to be validated. Here, we investigated the prognostic relevance of biomarkers related to atherosclerotic plaque calcification, such as osteopontin (OPN), osteoprotegerin (OPG) and the receptor activator of nuclear factor kappa-B ligand (RANKL) in a cohort of patients with AIS (n = 90) during 90-day follow-up.

MATERIALS AND METHODS

Radiological and clinical examinations as well as blood sampling were performed at admission and at days 1, 7 and 90 from the event. Validated scores [such as modified Rankin scale (mRS) and the National Institutes of Health Stroke Scale (NIHSS)] were used to assess poststroke outcome. Serum levels of OPN, OPG and RANKL were measured by colorimetric enzyme-linked immunosorbent assay (ELISA).

RESULTS

When compared to the admission, OPN serum levels increased at day 7. Serum OPN levels at this time point were positively correlated with both ischaemic lesion volume and NIHSS at days 7 and 90. A cut-off of 30.53 ng/mL was identified for serum OPN by receiver operating characteristic (ROC) curve analysis. Adjusted logistic regression showed that serum OPN levels at day 7 predicted worse mRS at day 90 [OR 4.13 (95% CI 1.64-10.36); P = 0.002] and NIHSS [1.49 (95% CI 1.16-1.99); P = 0.007], independently of age, gender, hypertension and thrombolysis.

CONCLUSIONS

Serum levels of OPN, but not OPG and RANKL, peaked at day 7 after AIS and predicted worse neurological scores. Therefore, OPN might have a pathophysiological and clinical relevance after AIS.

Meta-analysis of genome-wide association studies identifies two loci associated with circulating osteoprotegerin levels

Osteoprotegerin (OPG) is involved in bone homeostasis and tumor cell survival. Circulating OPG levels are also important biomarkers of various clinical traits, such as cancers and atherosclerosis. OPG levels were measured in serum or in plasma. In a meta-analysis of genome-wide association studies in up to 10 336 individuals from European and Asian origin, we discovered that variants >100 kb upstream of the TNFRSF11B gene encoding OPG and another new locus on chromosome 17q11.2 were significantly associated with OPG variation. We also identified a suggestive locus on chromosome 14q21.2 associated with the trait. Moreover, we estimated that over half of the heritability of OPG levels could be explained by all variants examined in our study. Our findings provide further insight into the genetic regulation of circulating OPG levels.

Changes of plasma concentration of osteoprotegerin and its association with endothelial dysfunction before and after hypouricemic therapy in patients with hyperuricemia

OBJECTIVE

Osteoprotegerin (OPG) is a secreted glycoprotein in the regulation of bone turnover. Recently, many studies showed that OPG acts as an important regulatory molecule in the vascular systems. Our objective was to examine the plasma OPG levels alteration and its association with endothelial function before and after hypouricemic therapy in patients with hyperuricemia.

METHODS

Thirty patients (28 males and 2 females, serum uric acid > 7.0 mg/dl) with hyperuricemia were selected. Thirty healthy individuals (28 males and 2 females) with normal serum uric acid were also selected as control. Patients were administered with hypouricemic therapy for 6 months. Plasma OPG concentration was measured in duplicate using a sandwich ELISA and high-resolution ultrasound was used to measure brachial artery diameter at rest, after reactive hyperemia and after sublingual glyceryltrinitrate.

RESULTS

Plasma OPG levels in patients with hyperuricemia before hypouricemic therapy was significantly higher than those in controls (3.39 ± 0.25 vs. 2.05 ± 0.74 ng/L, p < 0.01). After hypouricemic therapy, OPG levels decreased markedly (2.54 ± 0.38 ng/L, p < 0.01). Flow-mediated dilation (FMD) in patients with hyperuricemia was 3.07 ± 1. 23%, which was significantly lower than that in control subjects (4.62 ± 0.69%, p < 0.01), and it improved significantly after hypouricemic therapy (3.91 ± 1.37%, p < 0.01). The absolute changes in OPG showed a significant positive correlation with the changes in serum uric acid (p < 0.05) and negative correlation with the changes in FMD (p < 0.01) in patients with hyperuricemia during the course of hypouricemic therapy.

CONCLUSION

The current study demonstrates that plasma OPG levels increased significantly in patients with hyperuricemia and decreased significantly after hypouricemic therapy, and are correlated with FMD. These findings support the growing concept that elevated plasma OPG levels may be involved with the development of endothelial dysfunction in patients with hyperuricemia.

Influence of pre-analytical and analytical factors on osteoprotegerin measurements

INTRODUCTION

Osteoprotegerin (OPG), an osteoclastogenesis inhibitor implicated in bone remodelling, has emerged as a potential biomarker for cardiovascular disease. In order to implement OPG determination in the clinical laboratory, it is crucial to identify the most appropriate specimen type, preparation and measurement conditions. The present study focuses on identifying the pre-analytical variables that may influence OPG measurements.

METHODS

Serum and plasma (in EDTA, heparin and citrate) were collected from 45 healthy volunteers (men (n=21, 46.7%), women (n=24, 53.3%)). OPG was analysed by ELISA. The influence of the centrifugation speed, the number of freeze-thaw cycles, delay in sample processing, thermo-stability and endogenous interfering agents (haemolysis, triglycerides, bilirubin, cholesterol and RANKL) were studied.

RESULTS

OPG concentrations were significantly lower (p<0.0001) in serum (1015±357 pg/mL) than in all plasma samples (1314±448 pg/mL in EDTA, 1209±417 pg/mL in heparin and 1260±498 pg/mL in citrate). Increasing centrifugation speed (200 g to 3000 g) did not change serum OPG concentration (p=0.88). However, OPG concentration significantly increased when centrifuged serum samples were stored at 48 h at room temperature (p<0.0001). Repeated freeze-thaw cycles did not modify OPG levels until 4 cycles (p<0.0001). Increasing time before processing the samples (2 h and 6 h) raised OPG concentrations both at room temperature (p<0.0001) or 4°C (p<0.001). Positive concentration-dependent interference of triglycerides was found in the analysed pooled samples; however, OPG concentrations were falsely diminished with haemoglobin interference. Bilirubin, cholesterol and RANKL did not interfere with OPG measurements.

Increased calcification in osteoprotegerin-deficient smooth muscle cells: Dependence on receptor activator of NF-κB ligand and interleukin 6

OBJECTIVE

Vascular calcification is highly correlated with cardiovascular disease morbidity and mortality. Osteoprotegerin (OPG) is a secreted decoy receptor for receptor activator of NF-κB ligand (RANKL). Inactivation of OPG in apolipoprotein E-deficient (ApoE-/-) mice increases lesion size and calcification. The mechanism(s) by which OPG is atheroprotective and anticalcific have not been entirely determined. We investigated whether OPG-deficient vascular smooth muscle cells (VSMCs) are more susceptible to mineralization and whether RANKL mediates this process.

RESULTS

Lesion-free aortas from 12-week-old ApoE-/-OPG-/- mice had spotty calcification, an appearance of osteochondrogenic factors and a decrease of smooth muscle markers when compared to ApoE-/-OPG+/+ aortas. In osteogenic conditions, VSMCs isolated from ApoE-/-OPG-/- (KO-VSMC) mice deposited more calcium than VSMCs isolated from ApoE-/-OPG+/+ (WT-VSMC) mice. Gene expression and biochemical analysis indicated accelerated osteochondrogenic differentiation. Ablation of RANKL signaling in KO-VSMCs rescued the accelerated calcification. While WT-VSMCs did not respond to RANKL treatment, KO-VSMCs responded with enhanced calcification and the upregulation of osteochondrogenic genes. RANKL strongly induced interleukin 6 (IL-6), which partially mediated RANKL-dependent calcification and gene expression in KO-VSMCs.

CONCLUSIONS

OPG inhibits vascular calcification by regulating the procalcific effects of RANKL on VSMCs and is thus a possible target for therapeutic intervention.

Effects of combination therapy with olmesartan and azelnidipine on serum osteoprotegerin in patients with hypertension

BACKGROUND

Vascular calcification is a potent predictor of plaque instability and cardiac events. Osteoprotegerin (OPG), well-known vascular calcification mediator, is a signaling molecule involved in bone remodeling, which has been implicated in the regulation of vascular calcification and atherogenesis. The purpose of this study was to compare the combination treatments of olmesartan/azelnidipine and olmesartan/diuretics on serum bone-related markers in patients with essential hypertension.

METHODS AND RESULTS

A total of 48 patients with hypertension treated with 20 mg olmesartan were randomized to receive combination treatment with 16 mg azelnidipine (O/A group) or diuretics (1 mg indapamide; O/D group) for 12 months. Osteoprotegerin, matrix metalloproteinase 2 (MMP-2), and high-sensitive CRP (hs-CRP) were measured after 3 and 12 months of treatment. Cardio-ankle vascular index (CAVI) was measured as the arterial stiffness using a VaSera CAVI instrument at the same time points. In both groups, the systolic and diastolic blood pressure reduction is similar. Serum OPG, MMP-2, and hs-CRP were significantly decreased at 12 months in the O/A group (P < .05), while there were no significant reductions in the O/D group. CAVI was significantly improved at 12 months in both the treatment groups. The improvement in CAVI was significantly greater in the O/A group than in the O/D group.

CONCLUSION

Azelnidipine, but not indapamide, combined with olmesartan, improved arterial stiffness and were associated with significant decrease in OPG, MMP-2, and hs-CRP concentrations. These results suggest that the beneficial effects of the combination treatments of olmesartan/azelnidipine on arterial stiffness are mediated by alteration in bone-remodeling and inflammatory markers.