Relationships of osteoprotegerin with albuminuria and asymmetric dimethylarginine in essential hypertension: integrating vascular dysfunction

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.

The role of osteoprotegerin in cardiovascular disease

Osteoprotegerin (OPG) is a 401 amino acid N-glycosylated protein, which is highly expressed in a large number of tissues. OPG mainly binds to two ligands, i.e. RANKL (receptor activator of nuclear factor κB ligand) and TRAIL (tumor necrosis factor- related apoptosis-inducing ligand). Upon binding to the former ligand, OPG inhibits the activation of osteoclasts and promotes apoptosis of osteoclasts, whereas the binding of OPG with TRAIL prevents apoptosis of tumor cells. There is now emerging evidence that OPG participates in the pathogenesis of atherosclerosis and cardiovascular diseases by amplifying the adverse effects of inflammation and several traditional risk factors such as hyperlipidemia, endothelial dysfunction, diabetes mellitus, and hypertension. Some epidemiological studies also showed a positive association between OPG levels and cardiovascular morbidity and mortality. The aim of this article is to provide an overview of the main biochemical, physiological, and pathological aspects of OPG biology in cardiovascular disease.

Osteoprotegerin, leptin and IL-6: association with silent myocardial ischemia in type 2 diabetes mellitus

BACKGROUND

Diabetic patients often exhibit severe, asymptomatic coronary artery disease (CAD). The relationship between osteoprotegerin (OPG), inflammatory markers and silent myocardial ischemia remains to be elucidated.

METHODS

We recruited 45 type 2 diabetic patients and 33 healthy controls and assessed them for silent myocardial ischemia (SMI) by myocardial perfusion imaging. Patient blood was tested for OPG, IL-6 and leptin concentrations.

RESULTS

OPG, leptin and IL-6 levels were found significantly elevated in diabetic patients (p < 0.001, p < 0.01, p < 0.05). Based on our classification of presence/absence of SMI in our diabetic group, we found that there was a significant association between SMI and the biomarkers IL-6 (p < 0.001), leptin (p < 0.001) and OPG (p < 0.05). In multivariate regression analyses, OPG was found to be significantly related to diabetes mellitus and to SMI. Age, sex and smoking increased the association between OPG and SMI.

CONCLUSION

High OPG, leptin and IL-6 levels are associated with the presence and severity of SMI in type 2 diabetic patients.