Influence of pre-analytical and analytical factors on osteoprotegerin measurements

Reliability, stability during long-term storage, and intra-individual variation of circulating levels of osteopontin, osteoprotegerin, vascular endothelial growth factor-A, and interleukin-17A

BACKGROUND

Studies in many populations have reported associations between circulating cytokine levels and various physiological or pathological conditions. However, the reliability of cytokine measurements in population studies, which measure cytokines in multiple assays over a prolonged period, has not been adequately examined; nor has stability during sample storage or intra-individual variation been assessed.

METHODS

We assessed (1) analytical reliability in short- and long-term repeated measurements; (2) stability and analytical reliability during long-term sample storage, and (3) variability within individuals over seasons, of four cytokines-osteopontin (OPN), osteoprotegerin (OPG), vascular endothelial growth factor-A (VEGF-A), and interleukin-17A (IL-17A). Measurements in plasma or serum samples were made with commercial kits according to standard procedures. Estimation was performed by fitting a random or mixed effects linear model on the log scale.

RESULTS

In repeated assays over a short period, OPN, OPG, and VEGF-A had acceptable reliability, with intra- and inter-assay coefficients of variation (CV) less than 0.11. Reliability of IL-17A was poor, with inter- and intra-assay CV 0.85 and 0.43, respectively. During long-term storage, OPG significantly decayed (- 33% per year; 95% confidence interval [- 54, - 3.7]), but not OPN or VEGF-A (- 0.3% or - 6.3% per year, respectively). Intra- and inter-assay CV over a long period were comparable to that in a short period except for a slight increase in inter-assay CV of VEGF-A. Within-individual variation was small for OPN and VEGF-A, with intra-class correlations (ICC) 0.68 and 0.83, respectively, but large for OPG (ICC 0.11).

CONCLUSIONS

We conclude that OPN and VEGF-A can be reliably measured in a large population, that IL-17A is suitable only for small experiments, and that OPG should be assessed with caution due to degradation during storage and intra-individual variation. The overall results of our study illustrate the need for validation under relevant conditions when measuring circulating cytokines in population studies.

Prognostic role of osteoprotegerin and risk of coronary artery calcification: a systematic review and meta-analysis

Aim: Coronary artery calcification (CAC) is a predictor of atherosclerosis. However, the association of osteoprotegerin (OPG) with CAC is still controversial. Methods: Prospective cohort studies that provided odds ratios with 95% CIs were included from PubMed, Embase, Web of Science and Scopus through July 2022. Results: Out of 14 studies included in the systematic review, three studies with 7642 participants were included in the meta-analysis. The pooled odds ratio indicated a significant association between higher OPG levels and accelerated risk of CAC (1.15; 95% CI: 1.03-1.30; p < 0.001) with relatively no heterogeneity between studies (I² = 0%; p = 0.43). Conclusion: The results indicated that increased concentrations of OPG are positively associated with a 15% elevated odds of CAC after adjustment of major covariates.

Association between Serum Osteoprotegerin Levels and Severity of Coronary Artery Disease in Patients with Acute Myocardial Infarction

BACKGROUND

Osteoprotegerin (OPG), a glycoprotein of the tumour necrosis factor (TNF) superfamily, is one of the main biomarkers for vascular calcification.

AIM

We aimed to evaluate the association between serum OPG levels and extent of coronary lesions in patients with acute myocardial infarction (MI).

METHODS

Consecutive patients hospitalized for an acute MI who underwent coronary angiography were included. SYNTAX score was calculated to assess the severity of coronary artery disease. The population was analysed in low (5 (3-6)), medium (11 (9-13)) and high (20 (18-23)) tertiles of SYNTAX score.

RESULTS

Among the 378 patients included, there was a gradual increase in age, rate of diabetes, anterior wall location, and a reduction in left ventricular ejection fraction across the SYNTAX tertiles. OPG levels significantly increased across the tertiles (962 (782-1497), 1240 (870-1707), and 1464 (1011-2129) pg/mL, respectively (p < 0.001)). In multivariate analysis, OPG [OR(CI95%): 2.10 (1.29-3.49) 0.003], were associated with the high SYNTAX group, beyond hypercholesterolemia, CV history and reduced glomerular filtration rate.

CONCLUSION

We found an association between OPG levels and coronary lesions complexity patients with acute MI.

Osteoporosis Entwined with Cardiovascular Disease: The Implication of Osteoprotegerin and the Example of Statins

Beyond being epiphenomenon of shared epidemiological factors, the integration of Osteoporosis (OP) with Cardiovascular Disease (CVD) - termed "calcification paradox" - reflects a continuum of aberrant cardiometabolic status. The present review provides background knowledge on "calcification paradox", focusing on the endocrine aspect of vasculature orchestrated by the osteoblastic molecular fingerprint of vascular cells, acquired via imbalance among established modulators of mineralization. Osteoprotegerin (OPG), the well-established osteoprotective cytokine, has recently been shown to exert a vessel-modifying role. Prompted by this notion, the present review interrogates OPG as the potential missing link between OP and CVD. However, so far, the confirmation of this hypothesis is hindered by the equivocal role of OPG in CVD, being both proatherosclerotic and antiatherosclerotic. Further research is needed to illuminate whether OPG could be a biomarker of the "calcification paradox". Moreover, the present review brings into prominence the dual role of statins - cardioprotective and osteoprotective - as a potential illustration of the integration of CVD with OP. Considering that the statins-induced modulation of OPG is central to the statins-driven osteoprotective signalling, statins could be suggested as an illustration of the role of OPG in the bone/vessels crosstalk, if further studies consolidate the contribution of OPG to the cardioprotective role of statins. Another outstanding issue that merits further evaluation is the inconsistency of the osteoprotective role of statins. Further understanding of the varying bone-modifying role of statins, likely attributed to the unique profile of different classes of statins defined by distinct physicochemical characteristics, may yield tangible benefits for treating simultaneously OP and CVD.

Osteoprotegerin and Cardiovascular Events in High-Risk Populations: Meta-Analysis of 19 Prospective Studies Involving 27 450 Participants

Background Osteoprotegerin is a cytokine involved in bone metabolism as well as vascular calcification and atherogenesis. Although circulating osteoprotegerin levels are robustly associated with incident cardiovascular disease ( CVD ) in the general population, its relevance as a biomarker among populations at high CVD risk is less clear. Methods and Results Three independent reviewers systematically searched PubMed, EMBASE , and Web of Science to identify prospective studies that had recruited participants on the basis of having conditions related to high CVD risk. A total of 19 studies were eligible for inclusion, reporting on 27 450 patients with diabetes mellitus (2 studies), kidney disease (7 studies), preexisting heart disease (5 studies), or recent acute coronary syndromes (5 studies) at baseline. Over a mean follow-up of 4.2 years, 4066 CVD events were recorded. In a random-effects meta-analysis, the pooled risk ratio for CVD events comparing people in the top versus the bottom tertile of osteoprotegerin concentration was 1.30 (95% confidence interval, 1.12-1.50; P<0.001; I2=68.3%). There was evidence for presence of publication bias ( P value from Egger's test=0.013). Correction for publication bias using the trim-and-fill method reduced the risk ratio to 1.21 (95% confidence interval, 1.03-1.42; P<0.001). The risk ratios did not vary significantly by population type, geographical region, statistical adjustment, sample or assay type, age, sex, or length of follow-up. Conclusions In populations at high CVD risk, elevated circulating osteoprotegerin levels are associated with a higher risk for future CVD events. The magnitude of association appears weaker than in the general population.

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.

Diagnostic accuracy of the Coopscore© to predict liver fibrosis in human immunodeficiency virus/hepatitis B virus co-infection

Background Non-invasive methods for assessing liver fibrosis are increasingly used as an alternative to liver biopsy. Recently, a score-based biochemical blood test (Coopscore^©) was developed in a cohort of patients chronically infected with hepatitis C virus, showing higher diagnostic performances than Fibrometer®, Fibrotest®, Hepascore® and Fibroscan™. Here, we assess its performance in patients co-infected with the human immunodeficiency virus and hepatitis B virus. Methods Ninety-seven human immunodeficiency virus/hepatitis B virus co-infected patients with liver biopsies were included from a previously described cohort. Histological fibrosis staging using METAVIR criteria was used as the reference. Coopscore^©, Fibrotest®, Fibrometer®, Hepascore® and Zeng score were computed and compared with the Coopscore© using the Obuchowski index and area under the receiving operator characteristic curves. Results The distribution of liver fibrosis levels was as follows: F0-F1 ( n = 42), F2 ( n = 25), F3 ( n = 15) and F4 ( n = 15). The Obuchowski index was higher for Coopscore^© (0.774) than Fibrometer® (0.668), Hepascore® (0.690) and Zeng scores (0.704) ( P < 0.05), reflecting a better ability to discriminate between fibrosis stages. Similarly, when predicting significant fibrosis (≥F2), the AUROC was significantly greater for the Coopscore^© (0.836) than the Hepascore® (0.727) and Zeng scores (0.746), but not for the Fibrotest® (0.778, P = 0.14) or Fibrometer® (0.790, P = 0.19). The Coopscore^© did not show a higher capacity than other scores to predict advanced fibrosis (≥F3) or cirrhosis (F4). Conclusions This study supports the diagnostic value of the Coospcore^© in fibrosis staging among human immunodeficiency virus/hepatitis B virus co-infected patients, especially to predict significant fibrosis.

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 in Cardiometabolic Disorders

Osteoprotegerin (OPG), a glycoprotein traditionally implicated in bone remodelling, has been recently related to cardiovascular disease (CVD). Human studies show a positive relationship between circulating OPG, vascular damage, and CVD, and as such OPG has emerged as a potential biomarker for CVD. This review focuses on the relationship between circulating OPG and different endocrine cardiometabolic alterations such as type 1 and 2 diabetes. The association of OPG with diabetic complications (neuropathy, nephropathy, or retinopathy) as well as with atherosclerosis, coronary artery calcification, morbidity, and mortality is pointed out. Moreover, OPG modulation by different treatments is also established. Besides, other associated diseases such as obesity, hypertension, and metabolic syndrome, which are known cardiovascular risk factors, are also considered.