[Osteoprotegerin: regulator, protector and marker]. / Osteoprotegerin: a regulátor, a protektor és a marker. Osszefoglalás irodalmi adatok és saját eredményeink alapján.

Experimental and clinical trials in the field of bone biology helped to clarify the role of receptors, which belong to the tumor necrosis factor family, such as osteoprotegerin and receptor activator of nuclear factor kappaB (RANK), in the regulation of bone remodeling. The ligand of the receptor activator of nuclear factor kappaB (RANKL) is a stimulator of bone resorption, while osteoprotegerin is the soluble "decoy" receptor to RANKL, protecting thereby bone from resorption. Pathological states of bone remodeling (like osteoporosis) are associated with imbalance in the activity of osteoprotegerin and the receptor activator of nuclear factor kappaB. Recent studies, however, also indicate that the osteoprotegerin/RANKL/RANK system has important roles in the regulation of the immune and vascular system as well. In this review we summarize the function and regulation of osteoprotegerin, its role in pathological states--primarily in cardiovascular diseases--and its relevance as a marker of cardiovascular risk. Finally, we present our prospective trial performed among the chronic dialyzed patients, where we examined the association between the cardiovascular mortality, osteoprotegerin levels and the arterial stiffness.

Serum osteoprotegerin level, carotid-femoral pulse wave velocity and cardiovascular survival in haemodialysis patients.

BACKGROUND: Osteoprotegerin (OPG) is a marker and regulator of arterial calcification, and it is related to cardiovascular survival in haemodialysis patients. The link between OPG and aortic stiffening--a consequence of arterial calcification--has not been previously evaluated in this population, and it is not known whether OPG-related mortality risk is mediated by arterial stiffening. METHODS: At baseline, OPG and aortic pulse wave velocity (PWV) were measured in 98 chronic haemodialysis patients who were followed for a median of 24 months. The relationship between OPG and PWV was assessed by multivariate linear regression. The role of PWV in mediating OPG related cardiovascular mortality was evaluated by including both OPG and PWV in the same survival model. RESULTS: At baseline mean (standard deviation) PWV was 11.2 (3.3) m/s and median OPG (interquartile range) was 11.1 (7.5-15.9) pmol/L. There was a strong, positive, linear relationship between PWV and lnOPG (P = 0.009, model R(2) = 0.540) independent of covariates. During follow-up 23 patients died of cardiovascular causes. In separate univariate survival models both PWV and lnOPG were related to cardiovascular mortality [hazard ratios 1.31 (1.14-1.50) and 8.96 (3.07-26.16), respectively]. When both PWV and lnOPG were entered into the same model, only lnOPG remained significantly associated with cardiovascular mortality [hazard ratio 1.11 (0.93-1.33) and 7.18 (1.89-27.25), respectively). CONCLUSION: In haemodialysis patients OPG is strongly related to PWV and OPG related cardiovascular mortality risk is, in part, mediated by increased PWV.

Effect of sevelamer on aortic pulse wave velocity in patients on hemodialysis: a prospective observational study.

Aortic stiffening and aortic calcification are risk factors for cardiovascular events in hemodialysis (HD) patients, and these 2 risk factors are interrelated. Sevelamer decreases aortic calcification but its effect on aortic stiffness has not been investigated previously. Thirteen HD patients commencing sevelamer treatment and 13 matched controls were followed for 11 months. Aortic pulse wave velocity (PWV), augmentation index (AIx), and levels of inhibitors of vascular calcification (fetuin-A, matrix-GLA-protein, osteoprotegerin/RANKL) were measured at baseline and at the end of follow-up, and the differences between the groups were compared. Determinants of the changes in PWV during follow-up were assessed by multivariate linear regression. At baseline, PWV was 9.93 (2.10) m/s in sevelamer-treated patients and 9.20 (2.84) m/s in control patients (p=0.464). By the end of follow-up, PWV decreased by 0.83 (2.3) m/s in sevelamer-treated patients while it increased by 0.93 (1.88) m/s in controls (p=0.042). The direction of changes in AIx were similar, but not statistically significant. There were no significant differences in the levels of inhibitors of calcification either at baseline or during follow-up. In multivariate linear regression sevelamer treatment, diabetes, heart rate, and C-reactive protein were related to the change in PWV. These data suggest that sevelamer treatment is associated with an improvement in aortic stiffness in HD patients, but it does not seem to affect serum levels of inhibitors of vascular calcification.

Intracardiac calcification is a marker of generalized atherosclerosis.

Aortic valve calcification (AVC) and carotid artery calcification (CAC) are considered to be markers of generalized atherosclerosis. However, the role of intracardiac calcification (ICC) (valvular and perivalvular calcification) is unclear. The objective of this retrospective study was to analyze the relationship between ICC and CAC, risk factors, and clinical atherosclerotic disease. Risk factors included age, sex, diabetes mellitus, hypercholesterolemia, and hypertension; clinical atherosclerosis comprised stroke, coronary artery disease, and peripheral artery disease. Between January 1, 2001, and January 1, 2004, all consecutive patients were enrolled into the study who underwent both carotid ultrasonography and transthoracic echocardiography examinations within 2 months. Patients with renal failure, substantial aortic stenosis, and carotid artery occlusion were excluded. There were 320 patients (104 men; mean +/- SEM age, 66.6 +/- 0.76 years). Positive results on carotid ultrasonography are defined as any CAC. Patients were categorized as having mild, moderate, or severe CAC. Positive results on transthoracic echocardiography were defined as any ICC; AVC was defined as mitral anulus calcification (MAC) or both. Intracardiac calcification was found in 181 patients, AVC in 51 patients, MAC in 48 patients, and calcification of both structures in 82 patients. Using multiple logistic regression analysis, ICC (odds ratio, 1.9), age (10-year periods) (odds ratio, 2.0), and the presence of peripheral artery disease (odds ratio, 1.7) were independent predictors of CAC. Carotid ultrasonography results were positive in 227 patients. For CAC, the sensitivities of AVC, MAC, both, and any ICC were 52.4%, 52.0%, 33.5%, and 71.2%, respectively, and the specificities were 84.9%, 87.1%, 92.5%, and 78.5%, respectively. The extension of ICC as 0, 1 location (AVC or MAC) , or 2 locations (AVC and MAC) was associated with the severity of CAC (P < .001, tau = 0.42). There was no difference between patients with AVC vs patients with MAC in the presence of different stages of CAC (P = .62). Intracardiac calcification (MAC or AVC) is an independent predictor of CAC as a marker of atherosclerosis, although the lack of ICC does not rule out atherosclerosis. Intracardiac calcification is related to CAC, with high specificity. The extension of ICC is related to the severity of atherosclerosis. Based on our results, antiatherothrombotic therapy should be considered in patients with ICC even before obtaining a positive carotid ultrasonography result.

Raloxifene lowers ischaemia susceptibility by increasing nitric oxide generation in the heart of ovariectomized rats in vivo.

We studied the effects of a 2-week period of oral raloxifene therapy on the cardiac level of nitric oxide (NO) and on the susceptibility to angina in ovariectomized rats. Ovariectomy decreased the activity of Ca2+-dependent nitric oxide synthase (NOS) in the left ventricle, an effect restored by raloxifene (0.2-5 mg kg(-1) day(-1)) or 17beta-oestradiol (0.3 mg kg(-1) day(-1)). Ovariectomy led to a significant ST segment depression after the injection of (1) ornithine-vasopressin (0.5 IU kg(-1), i.v.) or (2) epinephrine (10 microg kg(-1), i.v.), followed 30 s later by phentolamine (15 mg kg(-1), i.v.); both effects were reversed by raloxifene or 17beta-oestradiol treatment. Inhibition of nitric oxide synthase (with NG-nitro-L-arginine methyl ester [L-NAME]; 5 mg kg(-1), s.c.) augmented the ST segment depression in the ovariectomized rat and abolished the anti-ischaemic effect of 17beta-oestradiol or raloxifene. Thus, an oestrogen deficiency down-regulates the cardiac constitutive nitric oxide synthase, which increases the susceptibility of the heart to ishaemia because both actions can be blocked by exogenous administration of the natural oestrogen 17beta-oestradiol or the selective oestrogen-receptor modulator (SERM) raloxifene. In the present in vivo system, raloxifene exerts oestrogen-agonist properties.