Pathophysiological roles of osteoprotegerin (OPG). Eur J Cell Biol. 2009;88:1-17. [PMID: 18707795 DOI: 10.1016/j.ejcb.2008.06.004]

RANK-RANKL-OPG Axis in MASLD: Current Evidence Linking Bone and Liver Diseases and Future Perspectives

Metabolic dysfunction-associated steatotic liver disease (MASLD)-and its worse form, metabolic-associated steatohepatitis (MASH), characterised by inflammation and liver damage-corresponds to the liver's involvement in metabolic syndrome, which constitutes an economic burden for healthcare systems. However, the biomolecular pathways that contribute to steatotic liver disease are not completely clear. Abnormalities of bone metabolism are frequent in people affected by metabolic liver disease, with reduced bone density and an increased risk of fracture. Receptor activator of NF-κB (RANK), receptor activator of NF-κB ligand (RANKL), and osteoprotegerin(OPG) are critical regulators of bone metabolism, performing pleiotropic effects, and may have potential involvement in metabolic disorders like MASLD, resulting in a topic of great interest and intrigue. This narrative review aims to investigate this potential role and its implications in MASLD development and progression and in hepatocellular carcinoma, which represents its worst complication.

Osteoprotegerin is an Early Marker of the Fibrotic Process and of Antifibrotic Treatment Responses in Ex Vivo Lung Fibrosis

BACKGROUND

Lung fibrosis is a chronic lung disease with a high mortality rate with only two approved drugs (pirfenidone and nintedanib) to attenuate its progression. To date, there are no reliable biomarkers to assess fibrosis development and/or treatment effects for these two drugs. Osteoprotegerin (OPG) is used as a serum marker to diagnose liver fibrosis and we have previously shown it associates with lung fibrosis as well.

METHODS

Here we used murine and human precision-cut lung slices to investigate the regulation of OPG in lung tissue to elucidate whether it tracks with (early) fibrosis development and responds to antifibrotic treatment to assess its potential use as a biomarker.

RESULTS

OPG mRNA expression in murine lung slices was higher after treatment with profibrotic cytokines TGFβ1 or IL13, and closely correlated with Fn and PAI1 mRNA expression. More OPG protein was released from fibrotic human lung slices than from the control human slices and from TGFβ1 and IL13-stimulated murine lung slices compared to control murine slices. This OPG release was inhibited when murine slices were treated with pirfenidone or nintedanib. OPG release from human fibrotic lung slices was inhibited by pirfenidone treatment.

CONCLUSION

OPG can already be detected during the early stages of fibrosis development and responds, both in early- and late-stage fibrosis, to treatment with antifibrotic drugs currently on the market for lung fibrosis. Therefore, OPG should be further investigated as a potential biomarker for lung fibrosis and a potential surrogate marker for treatment effect.

Molecular Pathways of Vulnerable Carotid Plaques at Risk of Ischemic Stroke: A Narrative Review

The concept of vulnerable carotid plaques is pivotal in understanding the pathophysiology of ischemic stroke secondary to large-artery atherosclerosis. In macroscopic evaluation, vulnerable plaques are characterized by one or more of the following features: microcalcification; neovascularization; lipid-rich necrotic cores (LRNCs); intraplaque hemorrhage (IPH); thin fibrous caps; plaque surface ulceration; huge dimensions, suggesting stenosis; and plaque rupture. Recognizing these macroscopic characteristics is crucial for estimating the risk of cerebrovascular events, also in the case of non-significant (less than 50%) stenosis. Inflammatory biomarkers, such as cytokines and adhesion molecules, lipid-related markers like oxidized low-density lipoprotein (LDL), and proteolytic enzymes capable of degrading extracellular matrix components are among the key molecules that are scrutinized for their associative roles in plaque instability. Through their quantification and evaluation, these biomarkers reveal intricate molecular cross-talk governing plaque inflammation, rupture potential, and thrombogenicity. The current evidence demonstrates that plaque vulnerability phenotypes are multiple and heterogeneous and are associated with many highly complex molecular pathways that determine the activation of an immune-mediated cascade that culminates in thromboinflammation. This narrative review provides a comprehensive analysis of the current knowledge on molecular biomarkers expressed by symptomatic carotid plaques. It explores the association of these biomarkers with the structural and compositional attributes that characterize vulnerable plaques.

TRAIL-induced apoptosis and proteasomal activity - Mechanisms, signalling and interplay

Programmed cell death, in particular apoptosis, is essential during development and tissue homeostasis, and also is the primary strategy to induce cancer cell death by cytotoxic therapies. Precision therapeutics targeting TRAIL death receptors are being evaluated as novel anti-cancer agents, while in parallel highly specific proteasome inhibitors have gained approval as drugs. TRAIL-dependent signalling and proteasomal control of cellular proteostasis are intricate processes, and their interplay can be exploited to enhance therapeutic killing of cancer cells in combination therapies. This review provides detailed insights into the complex signalling of TRAIL-induced pathways and the activities of the proteasome. It explores their core mechanisms of action, pharmaceutical druggability, and describes how their interplay can be strategically leveraged to enhance cell death responses in cancer cells. Offering this comprehensive and timely overview will allow to navigate the complexity of the processes governing cell death mechanisms in TRAIL- and proteasome inhibitor-based treatment conditions.

Plasma osteoprotegerin predicts adverse cardiovascular events in stable coronary artery disease: the PEACE trial

Background

Osteoprotegerin (OPG) is a secretory glycoprotein and participates in the progression of atherosclerotic lesions. We aim to explore the relationship between OPG and the prognosis of coronary artery disease (CAD).

Methods

Plasma OPG concentrations were measured in 3,766 patients with stable CAD enrolled in the PEACE trial. The PEACE trial (NCT00000558) group followed up the patients and examined their future clinical outcomes.

Results

In summary, 208 (5.5%) primary outcomes occurred, 295 patients (7.8%) died from all-cause death, 128 (3.4%) died from cardiovascular causes, and 94 (2.5%) experienced heart failure during a median follow-up of 1,892 days. In addition, we found that higher plasma levels of OPG were associated with a higher incidence of all-cause death, cardiovascular death, and heart failure, even after adjusting clinical cofounders.

Conclusion

It was demonstrated that elevated plasma OPG levels were associated with an increased incidence of all-cause death, cardiovascular death, and heart failure in patients with stable CAD.

Systematic Review Registration

https://clinicaltrials.gov/ct2/show/NCT00000558?term=NCT00000558&draw=2&rank=1, identifier: NCT00000558.

Advanced applications of strontium-containing biomaterials in bone tissue engineering

Strontium (Sr) and strontium ranelate (SR) are commonly used therapeutic drugs for patients suffering from osteoporosis. Researches have showed that Sr can significantly improve the biological activity and physicochemical properties of materials in vitro and in vivo. Therefore, a large number of strontium containing biomaterials have been developed for repairing bone defects and promoting osseointegration. In this review, we provide a comprehensive overview of Sr-containing biomaterials along with the current state of their clinical use. For this purpose, the different types of biomaterials including calcium phosphate, bioactive glass, and polymers are discussed and provided future outlook on the fabrication of the next-generation multifunctional and smart biomaterials.

Progranulin, a moderator of estrogen/estrogen receptor α binding, regulates bone homeostasis through PERK/p-eIF2 signaling pathway

Under normal conditions, the human body employs the synergistic action of osteoblasts and osteoclasts to maintain a dynamic balance between bone formation and resorption. Bone homeostasis plays a very important role in the process of bone formation. Various bone diseases can occur if bone homeostasis is disrupted. In this study, the serum estrogen levels were significantly increased in the granulin (GRN)-deficient mice and PGRN regulates the binding of estrogen and estrogen receptor α (ERα) and then affects estrogen's ability to regulate bone formation and resorption. In addition, this study also explored the role that PGRN plays in regulating bone homeostasis by affecting the binding of estrogen and estrogen receptors through the protein kinase R-like endoplasmic reticulum kinase/phosphorylation of the eukaryotic initiation factor 2 signaling pathway. In summary, we confirmed the important role of PGRN in regulating the estrogen (E2)/ERα signal in maintaining bone homeostasis. Our findings may provide a new strategy for the treatment of osteoporosis and maintaining bone homeostasis. KEY MESSAGES: PGRN is a molecular regulator of the binding of E2 and ERα signal in maintaining bone homeostasis. PGRN plays in regulating bone homeostasis through the PERK/p-eIF2α signaling pathway. The best therapeutic effect of PGRN in osteoporosis is associated with different concentration of E2.

Elevated Serum Osteoprotegerin is Associated with Reduced Risks of Albuminuria and CKD Progression in Patients with Type 2 Diabetes

OBJECTIVE

To analyze the correlation between serum osteoprotegerin (OPG) level and chronic kidney disease (CKD) at different CKD stages in patients with type 2 diabetes.

METHODS

All subjects were hospitalized patients with type 2 diabetes. Medical history collection, physical examinations, and blood and urine samples testing were performed. Stages of CKD (G1-5) were defined by eGFR, groups of persistent albuminuria (normal, microalbuminuria and massive albuminuria) were divided by UACR, and categories of CKD progression risks (low, moderate and high or very high risk) were recommended by the Kidney Disease: Improving Global Outcomes (KDIGO). Serum OPG level was determined by enzyme-linked immunosorbent assay in the central laboratory.

RESULTS

Four hundred and eighty-four patients were included in the study. The average level of OPG of all subjects was 941.30 (547.53-1332.62) pg/mL. The levels of OPG decreased gradually with the aggravation of albuminuria (P = 0.007, P _{for trend}=0.003) and CKD progression (P = 0.001, P _{for trend}=0.001). No differences were found between OPG levels and stages of CKD (P = 0.31). After the adjustment, each 100 pg/mL increase in OPG levels could reduce the risk of massive albuminuria (OR 0.92, 95% CI 0.86-0.99, P = 0.02) and the high or very high risk of CKD progression (OR 0.94, 95% CI 0.89-0.99, P = 0.04) by multivariate logistic regression analysis. No correlations were found between OPG and stages of CKD.

CONCLUSION

In patients with type 2 diabetes, elevated serum osteoprotegerin is associated with albuminuria and the risk of CKD progression, and may delay the progression of CKD.

Association of Metabolic Dysfunction-Associated Fatty Liver Disease and Liver Stiffness With Bone Mineral Density in American Adults

CONTEST

The relationship between metabolic dysfunction-associated fatty liver disease (MAFLD) and liver stiffness and bone mineral density (BMD) remains unclear.

OBJECTIVES

We aimed to investigate the association between MAFLD and liver stiffness and BMD in the United States population.

METHODS

A cross-sectional study among 2031 participants over 50 years old in the National Health and Nutrition Examination Survey (NHANES) 2017-2018 was performed. All patients underwent vibration controlled transient elastography (VCTE) and dual-energy x-ray absorptiometry (DXA). The linear and logistic regression model were used to analyze the association between the MAFLD and liver stiffness and osteoporosis, with adjustments for known covariates. Furthermore, the sensitive analyses were conducted to explore the relationship between MAFLD and liver stiffness and whole osteoporosis (include femoral and lumbar osteoporosis).

RESULTS

MAFLD was prevalent in the study population, with a prevalence of 50.9% for men and 40.7% for women. The multiple linear models demonstrated positive associations between MAFLD and liver stiffness and total femur BMD, femur neck BMD, trochanter BMD, intertrochanter BMD. In multiple logistic regression models, both MAFLD and significant liver fibrosis were negatively associated with femoral osteoporosis (OR=0.41, 95% CI: 0.27 to 0.63; OR=0.67, 95% CI: 0.33-1.37, respectively). Nonetheless, when BMI was adjusted, the association between MAFLD and liver stiffness and osteoporosis became insignificant. Besides, as showed in the sensitive analyses, the relationship between MAFLD and liver stiffness and whole osteoporosis were stable.

CONCLUSIONS

These results suggest that MAFLD and liver stiffness were associated with higher femoral and lumbar bone mineral density in individuals aged over 50 years. But the results may be confounded by BMI.

Butyrate Inhibits Osteoclast Activity In Vitro and Regulates Systemic Inflammation and Bone Healing in a Murine Osteotomy Model Compared to Antibiotic-Treated Mice

Short-chain fatty acids (SCFAs) produced by the gut microbiota have previously been demonstrated to play a role in numerous chronic inflammatory diseases and to be key mediators in the gut-bone signaling axis. However, the role of SCFAs in bone fracture healing and its impact on systemic inflammation during the regeneration process has not been extensively investigated yet. The aim of this study was to first determine the effects of the SCFA butyrate on key cells involved in fracture healing in vitro, namely, osteoclasts and mesenchymal stromal cells (MSCs), and second, to assess if butyrate supplementation or antibiotic therapy impacts bone healing, systemic immune status, and inflammation levels in a murine osteotomy model. Butyrate significantly reduced osteoclast formation and resorption activity in a dose-dependent manner and displayed a trend for increased calcium deposits in MSC cultures. Numerous genes associated with osteoclast differentiation were differentially expressed in osteoclast precursor cells upon butyrate exposure. In vivo, antibiotic-treated mice showed reduced SCFA levels in the cecum, as well as a distinct gut microbiome composition. Furthermore, circulating proinflammatory TNFα, IL-17a, and IL-17f levels, and bone preserving osteoprotegerin (OPG), were increased in antibiotic-treated mice compared to controls. Antibiotic-treated mice also displayed a trend towards delayed bone healing as revealed by reduced mineral apposition at the defect site and higher circulating levels of the bone turnover marker PINP. Butyrate supplementation resulted in a lower abundance of monocyte/macrophages in the bone marrow, as well as reduced circulating proinflammatory IL-6 levels compared to antibiotic- and control-treated mice. In conclusion, this study supports our hypothesis that SCFAs, in particular butyrate, are important contributors to successful bone healing by modulating key cells involved in fracture healing as well as systemic inflammation and immune responses.

Nanomaterial-induced mesenchymal stem cell differentiation into osteoblast for counteracting bone resorption in the osteoporotic rats

The current approach was designed to unearth the therapeutic potential of osteoblasts infusion, yielded from cultivating rat mesenchymal stem cells of bone marrow source in osteogenic differentiation media supplied with either hydroxyapatite nanoparticles (HA-NPs), chitosan/hydroxyapatite nanomaterials (C/HA-NPs), or chitosan nanoparticles, in the osteoporotic rats. The successful migration of the osteoblasts to the diseased bones of rats in C/HA-NPs and HA-NPs groups was evidenced by PCR screening of the Y-linked sex-determining gene (SRY) in the femoral bone tissue. Serum bone biomarker levels and gene expression patterns of cathepsin K, receptor activator of nuclear factor kappa B ligand (RANKL), and osteoprotegerin (OPG) were assessed. Additionally, histological examination of the femoral bone tissues of rats was performed. The current outcomes revealed that osteoblast implantation, resulted from C/HA-NPs or HA-NPs group, significantly lessened bone sialoprotein level. In Addition, it yielded a significant decline in the gene expression patterns of cathepsin K, RANKL, and RANKL/OPG proportion as well as up-regulation in BMP-2 and Runx-2 gene expression levels as opposed to the untreated ovariectomized animals. Moreover, it could restrain bone resorption and refine bone histoarchitecture. Conclusively, this study sheds light on the therapeutic significance of osteoblasts transplantation in alleviating the intensity of the bone remodeling cycle, consequently representing a hopeful therapeutic approach for primary osteoporosis.

Biomolecules Orchestrating Cardiovascular Calcification

Vascular calcification, once considered a degenerative, end-stage, and inevitable condition, is now recognized as a complex process regulated in a manner similar to skeletal bone at the molecular and cellular levels. Since the initial discovery of bone morphogenetic protein in calcified human atherosclerotic lesions, decades of research have now led to the recognition that the regulatory mechanisms and the biomolecules that control cardiovascular calcification overlap with those controlling skeletal mineralization. In this review, we focus on key biomolecules driving the ectopic calcification in the circulation and their regulation by metabolic, hormonal, and inflammatory stimuli. Although calcium deposits in the vessel wall introduce rupture stress at their edges facing applied tensile stress, they simultaneously reduce rupture stress at the orthogonal edges, leaving the net risk of plaque rupture and consequent cardiac events depending on local material strength. A clinically important consequence of the shared mechanisms between the vascular and bone tissues is that therapeutic agents designed to inhibit vascular calcification may adversely affect skeletal mineralization and vice versa. Thus, it is essential to consider both systems when developing therapeutic strategies.

Circulating mRNA and plasma levels of osteoprotegerin and receptor activator of NF-κB ligand in nonalcoholic fatty liver disease

Pathogenesis of the beginning and progression of nonalcoholic fatty liver disease (NAFLD) has not been clarified exactly. The osteoprotegerin (OPG)/receptor activator of NF-κB ligand (RANKL) axis seems to play an imperative function in the onset and progression of this disease. The goal of the present study was to investigate the peripheral blood mononuclear cell (PBMC) expression and plasma levels of RANKL and OPG cytokines in NAFLD patients and compare them with healthy group. Plasma levels of OPG and RANKL were determined with ELISA kits in 57 men with NAFLD and 25 healthy men as controls. Biochemical and anthropometric parameters tests were also evaluated in the study groups. RANKL and OPG mRNA contents were evaluated by quantitative RT-PCR. OPG contents were markedly decreased in NAFLD patients as compared with healthy patients [1.43 (1.05-5.45)] versus [2.94 (1.76-4.73)] ng/mL; P = 0.007). The levels of RANKL were significantly reduced in NAFLD patients [74.00 (56.26-203.52) ng/mL] than in healthy patients [119.37 (83.71-150.13) ng/mL]; (P = 0.03). Also, OPG and RANKL gene expression were significantly decreased in NAFLD patients in comparison with the control group (P < 0.05). Moreover, receiver operating characteristic curve indicated that OPG may have a good capability to discriminate between NAFLD patients and normal individuals. A positive correlation was observed between OPG and RANKL in plasma sample (r = 0.495) (P = 0.000). Decreased plasma levels and gene expression of RANKL and OPG cytokines in NAFLD patients indicate that there is a relationship between these cytokines and the pathology of NAFLD disease. Confirmation of this association as well as the mechanism and role of these cytokines in NAFLD require further studies.

Osteopontin and osteoprotegerin in atherosclerotic plaque - are they significant markers of plaque vulnerability?

Atherosclerosis (ATS) is still considered as a major, global health problem. For a deeper understanding of its pathogenesis, in the last years the research was translated from tissue visible events to molecular mechanisms. Osteopontin (OPN) and osteoprotegerin (OPG) are two molecules that have been associated with the initiation and progression of ATS lesions. The aim of our study was to assess the OPN and OPG expression in advanced stages of carotid ATS, to analyze the correlation between these markers and the ultrasonographic plaque properties, pointing out the identification of possible patterns that can predict plaque vulnerability and risks of restenosis. The study group comprised 49 consecutive patients (38 males and 11 females) diagnosed with carotid stenotic lesions by using ultrasonography. The carotid endarterectomy specimens were standardly processed for histopathological and immunohistochemical exams. The OPN and OPG expression was semi-quantitatively assessed. Our results sustained the relationship between histological American Heart Association (AHA) type and ultrasonographic classification (echogenic versus echolucent) (p<0.001). The semi-quantitative analysis showed that in most cases (31 plaques) OPG and OPN had opposite expressions, whereas in the remaining cases (18 plaques) the expression was similar. There were no correlations between low versus high expression of intra-plaque OPN and OPG (p=0.335). We found significant correlation for OPN and plaque echogenicity (p=0.011), but not for OPG (p=0.079). OPN expression (low versus high) was correlated with plaque type (stable versus unstable) (p=0.036), plaque ulceration (p=0.009) and inflammation (p<0.001). OPG expression (low versus high) did not reveal statistically significant differences with plaque type (stable versus unstable) and vulnerability plaque parameters, respectively. OPG and OPN co-exist in carotid atherosclerotic plaque demonstrating a modulatory role in inflammatory and calcification processes. OPG is strongly expressed in stable, calcified plaques, while OPN is poorly expressed in calcified plaques and in plaques without hemorrhage, ulceration, inflammation, or necrosis. Starting from the molecular mechanisms, further studies of biomarkers are important to identify new therapeutic resources meant to prevent and treat vascular calcification.

Predictive Value of Osteoprotegerin and Neutrophil Gelatinase-associated Lipocalin on Multiple Organ Failure in Multiple Trauma

BACKGROUND/AIM

Multiple organ dysfunction syndrome (MODS) is the leading cause of late posttraumatic mortality. This study analyzed the prognostic values of osteoprotegerin (OPG) and neutrophil gelatinase-associated lipocalin (NGAL/lipocalin 2) compared to interleukin-6 (IL-6) in multiply injured patients.

PATIENTS AND METHODS

A retrospective observational cohort study on multiply injured patients with an injury severity score (ISS) of ≥16 was performed. OPG, NGAL and IL-6 blood concentrations were measured. Statistical analysis comprised receiver-operating-characteristic (ROC) analysis with the corresponding area under the curve (AUC).

RESULTS

Thirty-nine patients with a mean ISS of 34±11 were included. Fourteen patients (36%) developed MODS and 8 patients (21%) died. Plasma levels of NGAL, OPG, and IL-6 were significantly elevated in the MODS+ group. Each biomarker positively correlated with MODS score and diagnosis of MODS.

CONCLUSION

NGAL and OPG might be indicative of MODS and could have the potential to be biomarkers in the early detection of patients at risk of posttraumatic MODS.

Circulating Osteoprotegerin Levels Independently Predict All-cause Mortality in Patients with Chronic Kidney Disease: a Meta-analysis

Background: Studies have shown inconsistent results regarding the association between circulating osteoprotegerin (OPG) levels and all-cause mortality in patients with chronic kidney disease (CKD). The aim of this meta-analysis is to investigate the association between circulating OPG levels and all-cause mortality in patients with CKD. Methods: The PubMed, EMBASE and Cochrane Library databases were searched for eligible studies investigating the association between circulating OPG levels and all-cause mortality in patients with CKD. Pooled hazard ratios (HRs) and the corresponding 95% confidence intervals (CIs) were calculated using a random effects model. Results: In all, 13 studies that included 2,895 patients with CKD were included in this analysis. According to the meta-analysis, patients with the highest circulating OPG level had a significantly higher risk of all-cause mortality (7 studies; the adjusted HR, 1.88; 95% CI, 1.45 - 2.44) compared with patients with the lower circulating OPG level. An increase of 1 pmol/L in the circulating OPG level was associated with a 6% increased risk of all-cause mortality (7 studies; the adjusted HR, 1.06; 95% CI, 1.03-1.10). A subgroup analysis by dialysis methods suggested that an elevated circulating OPG level was independently associated with all-cause mortality in the HD only population. Conclusion: Elevated circulating OPG levels independently predict an increased risk of all-cause mortality in patients with CKD, especially in the HD only population.

Nonalcoholic fatty liver disease and alcoholic liver disease: metabolic diseases with systemic manifestations

The progression of liver disease is portrayed by several common, overarching signs and symptoms. Classically, these include findings such as spider angiomata, jaundice, palmar erythema, and as cirrhosis decompensates, ascites, variceal hemorrhage (VH), hepatic encephalopathy (HE), and hepatocellular carcinoma (HCC). Aside from these universal hallmarks among cirrhotics, patients with nonalcoholic fatty liver disease (NAFLD) and alcoholic liver disease (ALD) harbor their own distinct systemic associations and manifestations. NAFLD is tightly linked to metabolic syndrome, which appears to be a driving force for a multitude of comorbidities, such as insulin resistance, cardiovascular disease, chronic kidney disease (CKD), obstructive sleep apnea (OSA), as well as increased malignancy risk. ALD also maintains a variety of comorbidities congruent with systemic effects of chronic alcohol use. These findings are highlighted by cardiovascular conditions, neuronal damage, myopathy, nutritional deficiencies, chronic pancreatitis, in addition to increased malignancy risk. While a general, guideline-driven management for all cirrhotic patients remains imperative for minimizing risk of complications, a tailored treatment strategy is useful for patients with NAFLD and ALD who entertain their own constellation of unique systemic manifestations.

Osteoprotegerin Assessment Improves Prediction of Mortality in Stroke Patients

BACKGROUND

Elevated circulating osteoprotegerin (OPG) level is associated with an increased risk of hospitalization for ischemic stroke and coronary artery disease. The aim of the present study was to analyze whether OPG assessment may improve the prediction of mortality in patients with stroke.

PATIENTS AND METHODS

Serum OPG, fetuin A, 25-OH-D3, intact parathyroid hormone levels were assessed in serum samples which were left over after routine tests in a hospital laboratory. This assessment was conducted in 240 consecutive patients with acute ischemic stroke, admitted within 24hours after the onset of symptoms to the Stroke Unit. Mortality data were obtained from the local registry office.

RESULTS

The mean OPG serum level was 14.6 ± 6.0pmol/L (range: 3.7-43.4). There were no significant differences in the OPG values between men and women (13.9 ± 5.0 versus 15.1 ± 6.7 pmol/L; P = .12). Therefore, tertiles were calculated for the whole group. During the follow-up, 85 (35.4%) patients died and 92 (38.3%) died or had recurrent stroke. OPG level appeared a significant predictors of death and composite end-point (death/recurrent stroke), in addition to the well-established once (age, atrial fibrillation, diabetes RANKIN at admission and discharge, severity of stroke). In multivariable stepwise backward analyses, the OPG level persisted as a significant and independent predictor of death (hazard ratio [HR] = 1.084 (95% confidence intervals: 1.036-1.134)] and composite and point (HR = 1.082 [1.037-1.129]).

CONCLUSIONS

OPG level may be considered as a predictor of mortality in stroke patients.

Emerging role of testosterone in pancreatic β-cell function and insulin secretion

One of the most sexually dimorphic aspects of metabolic regulation is the bidirectional modulation of glucose homeostasis by testosterone in male and females. Severe testosterone deficiency predisposes men to type 2 diabetes (T2D), while in contrast, androgen excess predisposes women to hyperglycemia. The role of androgen deficiency and excess in promoting visceral obesity and insulin resistance in men and women respectively is well established. However, although it is established that hyperglycemia requires β cell dysfunction to develop, the role of testosterone in β cell function is less understood. This review discusses recent evidence that the androgen receptor (AR) is present in male and female β cells. In males, testosterone action on AR in β cells enhances glucose-stimulated insulin secretion by potentiating the insulinotropic action of glucagon-like peptide-1. In females, excess testosterone action via AR in β cells promotes insulin hypersecretion leading to oxidative injury, which in turn predisposes to T2D.

The Anti-Inflammatory Effects of Testosterone

Low plasma testosterone (T) levels correlated with metabolic syndrome, cardiovascular diseases, and increased mortality risk. T exerts a significant effect on the regulation of adipose tissue accumulation, and in the glucose and lipids metabolism. Adipocytes are the primary source of the most important adipokines responsible for inflammation and chronic diseases. This review aims to analyze the possible effect of T on the regulation of the proinflammatory cytokines secretion.

A systematic literature search on MEDLINE, Google Scholar, and Cochrane using the combination of the following keywords: “testosterone” with “inflammation,” “cytokines,” “adiponectin, CRP, IL-1B, IL-6, TNFα, leptin” was conducted. Sixteen articles related to the effect of low T level and 18 to the effect of T therapy on proinflammatory cytokine were found.

T exerts a significant inhibitory effect on adipose tissue formation and the expression of various adipocytokines, such as leptin, TNF-α, IL-6, IL-1, and is positively correlated with adiponectin level, whereas a low T level is correlated with increased expression of markers of inflammation. Further studies are necessary to investigate the role of T, integrated with weight loss and physical activity, on its action on the mechanisms of production and regulation of proinflammatory cytokines.

Role of osteoprotegerin/receptor activator of nuclear factor kappa B/receptor activator of nuclear factor kappa B ligand axis in nonalcoholic fatty liver disease

Concomitantly with the increase in the prevalences of overweight/obesity, nonalcoholic fatty liver disease (NAFLD) has worldwide become the main cause of chronic liver disease in both adults and children. Patients with fatty liver display features of metabolic syndrome (MetS), like insulin resistance (IR), glucose intolerance, hypertension and dyslipidemia. Recently, epidemiological studies have linked obesity, MetS, and NAFLD to decreased bone mineral density and osteoporosis, highlighting an intricate interplay among bone, adipose tissue, and liver. Osteoprotegerin (OPG), an important symbol of the receptor activator of nuclear factor-B ligand/receptor activator of nuclear factor kappa B/OPG system activation, typically considered for its role in bone metabolism, may also play critical roles in the initiation and perpetuation of obesity-related comorbidities. Clinical data have indicated that OPG concentrations are associated with hypertension, left ventricular hypertrophy, vascular calcification, endothelial dysfunction, and severity of liver damage in chronic hepatitis C. Nonetheless, the relationship between circulating OPG and IR as a key feature of MetS as well as between OPG and NAFLD remains uncertain. Thus, the aims of the present review are to provide the existent knowledge on these associations and to discuss briefly the underlying mechanisms linking OPG and NAFLD.

Combination of biomarkers of vascular calcification and sTWEAK to predict cardiovascular events in chronic kidney disease

BACKGROUND AND AIMS

Vascular calcification (VC) and atherosclerosis are associated with an increased cardiovascular morbimortality in chronic kidney disease (CKD). Osteoprotegerin (OPG) and osteopontin (OPN) are involved in both VC and CKD. Soluble tumor necrosis factor-like weak inducer of apoptosis (sTWEAK) has been related to cardiovascular disease. We hypothesized that OPG, OPN and sTWEAK levels may be associated with a higher prevalence of cardiovascular outcomes in patients with CKD.

METHODS

The presence of calcified or non-calcified atherosclerotic plaques was assessed in 1043 stage 3 to 5D CKD patients from The NEFRONA Study. Biochemical measurements and OPG, OPN and sTWEAK serum levels were analyzed. Patients were followed for cardiovascular outcomes (41 ± 16 months).

RESULTS

At recruitment, 26% of CKD patients had VC. The adjusted odds ratios for having VC were 2.22 (1.32-3.75); p=.003 for OPG, and 0.45 (0.24-0.84); p=.01 for sTWEAK concentrations. After follow-up, 95 CV events occurred. In a Cox model, patients with OPG or OPN above and sTWEAK below their optimal cut-off points had an adjusted higher risk of cardiovascular events [HR: 2.10 (1.49-3.90); p=.02; 1.65 (1.02-2.65); p=.04; 2.05 (1.28-3.29), p=.003; respectively]. When CKD patients were grouped according to the number of biomarkers above (OPG and OPN) or below (sTWEAK) their cut-off points, the combination of these biomarkers showed the highest risk for cardiovascular events [HR: 9.46 (3.80-23.5) p < .001]. A composite score of these three biomarkers increased the C-statistic and net reclassification index beyond conventional risk factors and VC.

CONCLUSIONS

The combination of OPG, OPN and sTWEAK increased the predictability of cardiovascular outcomes.

Interdependence between osteoprotegerin and active von Willebrand factor in long-term cardiovascular mortality prediction in patients undergoing percutaneous coronary intervention

The interdependence of the predictive accuracy of serum osteoprotegerin (OPG) and von Willebrand factor (vWF) levels for long-term cardiovascular outcomes has not been investigated so far. This was a prospective observational cohort study in 361 patients with coronary artery disease undergoing percutaneous coronary intervention (PCI). Baseline levels of OPG, vWF, active vWF (act vWF) and ristocetin cofactor activity (vWF:RICO) were measured. Cardiovascular mortality was recorded over a median of five years. OPG concentrations >3.7 µg/ml emerged as the strongest predictor of cardiovascular (CV) death: 30 % of patients died during the five-year follow-up in this group, as compared to 10 % in patients with OPG ≤3.7 µg/ml (p<0.001). Act vWF had a significant prognostic impact on CV mortality when OPG levels were low (≤3.7 µg/ml): patients with act vWF concentration >1 µg/ml died in 14 %, whereas those with act vWF values ≤1 µg/ml had a mortality rate of 1 % (p=0.015). We stratified patients into three groups: high OPG, low OPG/high act vWF and low OPG/low act vWF. Patients with high OPG values had a 13-fold higher risk for CV death than those with low OPG/low act vWF concentrations (adj. HR: 12.6; 95 %CI: 1.7–94.7; p=0.014), and a two-fold higher risk as compared to those patients with low OPG/high act vWF concentrations (adj. HR: 2.0; 95 %CI: 1.1–3.7; p=0.03) in the adjusted Cox regression analysis. In conclusion, elevated OPG at the time of PCI was a strong independent predictor of five-years cardiovascular mortality, whereas act vWF had a significant prognostic impact on CV mortality when OPG levels were low.

Unbalanced Vitreous Levels of Osteoprotegerin, RANKL, RANK, and TRAIL in Proliferative Diabetic Retinopathy

PURPOSE

We investigated the expression of the proinflammatory and proangiogenic factor osteoprotegerin (OPG) and its ligands, receptor activator of nuclear factor-κB ligand (RANKL), tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), and the receptor RANK in proliferative diabetic retinopathy (PDR).

MATERIALS AND METHODS

Vitreous samples from PDR and nondiabetic control patients and epiretinal membranes from PDR patients were studied by enzyme-linked immunosorbent assay, immunohistochemistry, and Western blot analysis.

RESULTS

Vascular endothelial growth factor, OPG, and soluble RANK levels in vitreous samples from PDR patients were significantly higher than that in nondiabetic controls. Soluble TRAIL levels were significantly lower in PDR patients than that in nondiabetic control, whereas soluble RANKL levels did not differ significantly. RANKL, RANK, and TRAIL were expressed in vascular endothelial cells, myofibroblasts, and CD45-expressing leukocytes in PDR epiretinal membranes.

CONCLUSIONS

Dysregulated expression of OPG/RANKL/RANK pathway and TRAIL might be related to inflammation and angiogenesis in PDR.

Osteoprotegerin-Knockout Mice Developed Early Onset Root Resorption

INTRODUCTION

Recent studies indicate that the osteoprotegerin (OPG)/RANKL/RANK pathway takes part in root resorption. However, the relationship between OPG and root resorption is vague. The purpose of our study was to investigate the role of OPG in root resorption.

METHODS

The first molars of the mandibles of osteoprotegerin-knockout (Opg-KO) mice and wild-type (WT) mice were evaluated by micro-computed tomography, histology, and immunohistochemistry at 4, 6, 26, and 52 weeks. To detect the activity of the osteoclasts, we induced bone marrow macrophages into osteoclast-like cells from Opg-KO mice and wild-type mice in vitro and then compared their osteoclast activities. To evaluate the cementum quality, an osteoclast-cementum co-culture model was established in vitro.

RESULTS

In Opg-KO mice, root resorption began at the age of 4 weeks. At 6 weeks the cementum damage extended to the coronal and apical regions, and at 52 weeks the damage reached the predentin. At all observed stages, more tartrate-resistant acid phosphatase (TRAP)-positive cells were found on the surface of cementum in Opg-KO mice. In vitro, the mRNA levels of cathepsin K, TRAP, matrix metalloproteinase-9, and matrix metalloproteinase-1, as well as the protein expression of nuclear factor of activated T cell 1 and TRAP, increased significantly in osteoclast-like cells from Opg-KO mice. In addition, the cementum resorption pits of Opg-KO mice were larger when co-cultured with osteoclast-like cells.

CONCLUSIONS

Our study demonstrated that loss of OPG led to root resorption via increasing activation of osteoclasts and reducing mineralization of cementum.

Androgen receptor-deficient islet β-cells exhibit alteration in genetic markers of insulin secretion and inflammation. A transcriptome analysis in the male mouse

AIMS

Testosterone action is mediated via the androgen receptor (AR). We have reported that male mice lacking AR selectively in β-cells (βARKO^-/y) develop decreased glucose-stimulated insulin secretion (GSIS), producing glucose intolerance. We showed that testosterone action on AR in β-cells amplifies the insulinotropic action of GLP-1 on its receptor via a cAMP-dependent protein kinase-A pathway.

METHODS

To investigate AR-dependent gene networks in β-cells, we performed a high throughput whole transcriptome sequencing (RNA-Seq) in islets from male βARKO^-/y and control mice.

RESULTS

We identified 214 differentially expressed genes (DEGs) (158 up- and 56 down-regulated) with a false discovery rate (FDR) < 0.05 and a fold change (FC) > 2. Our analysis of individual transcripts revealed alterations in β-cell genes involved in cellular inflammation/stress and insulin secretion. Based on 312 DEGs with an FDR < 0.05, the pathway analysis revealed 23 significantly enriched pathways, including cytokine-cytokine receptor interaction, Jak-STAT signaling, insulin signaling, MAPK signaling, type 2 diabetes (T2D) and pancreatic secretion. The gene ontology analysis confirmed the results of the individual DEGs and the pathway analysis in showing enriched biological processes encompassing inflammation, ion transport, exocytosis and insulin secretion.

CONCLUSIONS

AR-deficient islets exhibit altered expression of genes involved in inflammation and insulin secretion demonstrating the importance of androgen action in β-cell health in the male with implications for T2D development in men.

Cardiac biomarkers in dialysis

Cardiovascular disease is the major cause of death, accounting for approximately 40 percent of all-cause mortality in patients receiving either hemodialysis or peritoneal dialysis. Cardiovascular risk stratification is an important aspect of managing dialysis patients as it enables early identification of high-risk patients, so therapeutic interventions can be optimized to lower cardiovascular morbidity and mortality. Biomarkers can detect early stages of cardiac injury so timely intervention can be provided. The B-type natriuretic peptides (Brain Natriuretic peptide [BNP] and N-terminal pro-B-type natriuretic peptide [NT-proBNP]) and troponins have been shown to predict mortality in dialysis patients. Suppression of tumorigenicity 2 (ST2) and galectin-3 are new emerging biomarkers in the field of heart failure in both the general and dialysis populations. This article aims to discuss the current evidence regarding cardiac biomarker use to diagnose myocardial injury and monitor the risk of major adverse cardiovascular events in patients undergoing dialysis.

Association of Osteoprotegerin with Obesity, Insulin Resistance and Non-Alcoholic Fatty Liver Disease in Children

BACKGROUND

Osteoprotegerin (OPG) is a member of the tumor necrosis factor superfamily. Reduced OPG levels are related to obesity, insulin resistance, and non-alcoholic fatty liver disease (NAFLD).

OBJECTIVES

The aim of this study was to evaluate the relationship between OPG levels, obesity, insulin resistance, and NAFLD in pediatric patients.

METHODS

This was a prospective, cross-sectional, controlled study that was conducted in the department of pediatrics at Bagcilar training and research hospital in Istanbul, Turkey, between April and August 2015. The study was performed on 107 children with obesity and 37 controls aged 5 - 17 years. In the obese subset, 62 patients had NAFLD. Homeostatic model assessment-insulin resistance (HOMA-IR) was used to calculate insulin resistance. Insulin resistance was defined as a HOMA-IR value greater than 2.5. Plasma OPG levels were measured using enzyme-linked immunosorbent assays. NAFLD was diagnosed by hepatic ultrasound.

RESULTS

The mean age was 11.25 ± 3.38 years in the patient group and 10.41 ± 3.15 years in the control group. The OPG level in the obese group with the mean of 55.20 ± 24.55 pg/mL (median = 48.81 pg/mL) was significantly lower than that in the control group with the mean of 70.78 ± 33.41 pg/mL (median = 64.57 pg/mL) (P = 0.0001). The optimal cut-off point (sensitivity, specificity) of the OPG level for the diagnosis of obesity was ≤ 46, 19 pg/mL. According to logistic regression analysis, fasting insulin (P = 0.036) and OPG (P = 0.01) levels were most affected by obesity. In the obese patients, who had HOMA-IR < 2.5, the mean level of OPG was 58.91 ± 6.88729 pg/mL (median = 49.55). In the obese patients, who had HOMA-IR ≥ 2.5, the mean level of OPG was 54.19 ± 22.21 pg/mL (median = 48.47). No significant correlations were found between OPG and HOMA-IR (P = 0.791). No statistically significant difference was observed in the mean OPG between patients with hepatosteatosis (mean = 54.55 ± 25.01 pg/mL) (median = 49.46) and those without the disease (56.30 ± 24.02 pg/mL) (mean = 48.34) (P = 0.089).

CONCLUSIONS

We confirmed that serum OPG concentrations reduce in obese children. However, no correlation was identified between OPG and insulin resistance. OPG levels are not meaningful in the diagnosis of NAFLD in children with obesity.

Breast cancer cells and bone marrow mesenchymal stromal cells: a regulated modulation of the breast tumor in the context of immune response

OBJECTIVE

The role of direct cell-cell interactions mediating selective bone metastasis by breast cancer cells (BCCs) niche is still mostly unknown.

MATERIALS AND METHODS

Conditioned medium and direct cell-cell contacts experiments were used to investigate the effect of bone marrow-derived mesenchymal stromal cells (MSCs), osteoprogenitor-like cells (MG-63) and osteosarcoma cells (SaOS-2) on luminal-like (MCF-7) and basal-like (MDA-MB-231) BCCs flow cytometry was used to assess the purity of isolated BCCs and osteoblasts. Expression of osteoblastic markers was investigated by semi-quantitative RT-PCR. RANKL and OPG levels were measured by ELISA.

RESULTS

Conditioned medium from MSCs and osteoblasts induced the expression of osteoblastic markers in BCCs. While co-culture assays with SaOS-2 increased the expression of osteoblastic markers in MCF-7 cells, SaOS-2 cell conditioned medium increased the expression of RANKL, PTHrP, VEGF and NOGGIN in MCF-7 cells. Co-cultures with either MG-63 cells or MSCs induced OPG and MMP-2 in both tumor cell lines. Interestingly, conditioned medium from co-cultures of MSCs and MDA-MB-231 cells significantly decreased the proliferation of activated T lymphocytes which was reversed by addition of anti-OPG antibodies to the co-cultures.

CONCLUSION

Our data suggest that MSCs strongly contribute to the adaptation and invasiveness of breast cancer cells in skeletal tissues.

Osteoprotegerin: A novel biomarker for inflammatory bowel disease and gastrointestinal carcinoma

Osteoprotegerin (OPG) is a member of the tumor necrosis factor receptor superfamily of proteins. Although initial data illustrated the key role that OPG plays in bone turnover, numerous recent reports indicate that OPG is also an important factor in inflammatory pathways and tumor cell survival. OPG contributes directly to inflammatory processes and has been evaluated as a novel non-invasive biomarker of gut inflammation. Furthermore, OPG affects cell turn-over, differentiation, death, and survival via extracellular pathways, correlating with worse prognosis in inflammatory bowel diseases and several gastrointestinal carcinomas. It is now clear that OPG has multiple functions and characteristics. This review gives an overview of OPG, highlights its roles in different extracellular pathways, and outlines how OPG could be used as a novel non-invasive biological marker in inflammatory bowel diseases and gastrointestinal carcinomas.

Plasma osteoprotegerin levels are inversely associated with nonalcoholic fatty liver disease in patients with type 2 diabetes: A case-control study in China

OBJECTIVE

Osteoprotegerin (OPG), a soluble member of the tumor necrosis factor (TNF) receptor superfamily, is a decoy receptor for the receptor activator of nucleus factor-κB ligand (RANKL) and TNF-related apoptosis-inducing ligand (TRAIL). OPG has an effect on systemic insulin sensitivity and glucose homeostasis. The objective of this study was to evaluate the relationship between plasma osteoprotegerin (OPG) levels and nonalcoholic fatty liver disease (NAFLD) in patients with type 2 diabetes.

MATERIALS/METHODS

A case-control study was performed with 746 patients with type 2 diabetes. Of the study population, 367 patients had B-mode ultrasound-proven NAFLD and 379 were controls. The plasma OPG levels were measured using ELISA methods. NAFLD was diagnosed by hepatic ultrasound after the exclusion of alcohol abuse and other liver diseases.

RESULTS

The OPG levels were significantly decreased in patients with NAFLD (2.3±1.1μg/L vs. 2.8±1.3μg/L, p=3.75×10(5)) compared to controls. Pearson correlation analysis showed that the OPG levels were associated with age and systolic blood pressure (both p<0.05). The participants in the lowest OPG quartile had a significantly increased risk for NAFLD (OR=3.49, 95% CI 1.86-6.94) after adjusting for potential cofounders.

CONCLUSIONS

The plasma OPG level is negatively associated with NAFLD independent of potential cofounders.

Higher Levels of Osteoprotegerin and Immune Activation/Immunosenescence Markers Are Correlated with Concomitant Bone and Endovascular Damage in HIV-Suppressed Patients

HIV-infected patients appear to have a significantly greater risk of non-AIDS comorbidities such as osteoporosis and atherosclerosis. Subjects with osteoporosis are at a higher risk of developing cardiovascular disease than those with normal bone mass, therefore a possible relation between these two conditions can be hypothesized. In the setting of HIV infection, several factors might contribute to bone disease and endothelial dysfunction. The aim of our study was to evaluate the relationship between bone and cardiovascular disease and to investigate the role of traditional factors, T-cell phenotype and osteoprotegerin in HIV positive subjects on effective antiretroviral therapy. We included 94 HIV positive subjects on antiretroviral therapy with virological suppression and 41 healthy subjects matched for age and gender as a control group. Carotid-Intima Media Thickness (c-IMT) and bone mineral density (BMD) were performed by ultrasound and DEXA, respectively. CD4+/CD8+ T-cell activation, senescence and osteoprotegerin plasma levels were measured by flow-cytometry and ELISA, respectively. Among HIV positive patients, 56.4% had osteopenia/osteoporosis and 45.7% had pathological c-IMT (>0.9 mm). Subjects with pathological c-IMT and BMD exhibited higher CD4+ and CD8+ activated, CD8+ senescent and osteoprotegerin than subjects with normal c-IMT and BMD. HIV positive subjects with osteopenia/osteoporosis had higher c-IMT than subjects with normal BMD, and linear regression analysis showed a negative correlation between BMD and c-IMT. Several factors are implicated in the pathogenesis of non-AIDS comorbidities in HIV positive patients. Osteoprotegerin together with inflammation and immunosenescence in HIV positive patients could affect bone and vascular system and could be considered as a possible common link between these two diseases.

Biomarkers of Metabolic Syndrome: Biochemical Background and Clinical Significance

Biomarkers of the metabolic syndrome are divided into four subgroups. Although dividing them in groups has some limitations, it can be used to draw some conclusions. In a first part, the dyslipidemias and markers of oxidative stress are discussed, while inflammatory markers and cardiometabolic biomarkers are reviewed in a second part. For most of them, the biochemical background and clinical significance are discussed, although here also a well-cut separation cannot always be made. Altered levels cannot always be claimed as the cause, risk, or consequence of the syndrome. Several factors are interrelated to each other and act in a concerted, antagonistic, synergistic, or modulating way. Most important conclusions are summarized at the end of every reviewed subgroup. Genetic biomarkers or influences of various food components on concentration levels are not included in this review article.

Auricular ossification: A newly recognized feature of osteoprotegerin-deficiency juvenile Paget disease

We report auricular ossification (AO) affecting the elastic cartilage of the ear as a newly recognized feature of osteoprotegerin (OPG)-deficiency juvenile Paget disease (JPD). AO and auricular calcification refer interchangeably to rigid pinnae, sparing the ear lobe, from various etiologies. JPD is a rare Mendelian disorder characterized by elevated serum alkaline phosphatase activity accompanied by skeletal pain and deformity from rapid bone turnover. Autosomal recessive transmission of loss-of-function mutations within TNFRSF11B encoding OPG accounts for most JPD (JPD1). JPD2 results from heterozygous constitutive activation of TNFRSF11A encoding RANK. Other causes of JPD remain unknown. In 2007, we reported a 60-year-old man with JPD1 who described hardening of his external ears at age 45 years, after 4 years of treatment with bisphosphonates (BPs). Subsequently, we noted rigid pinnae in a 17-year-old boy and 14-year-old girl, yet pliable pinnae in a 12-year-old boy, each with JPD1 and several years of BP treatment. Cranial imaging indicated cortical bone within the pinnae of both teenagers. Radiologic studies of our three JPD patients without mutations in TNFRSF11B showed normal auricles. Review of the JPD literature revealed possible AO in several reports. Two of our JPD1 patients had experienced difficult tracheal intubation, raising concern for mineralization of laryngeal elastic cartilage. Thus, AO is a newly recognized feature of JPD1, possibly exacerbated by BP treatment. Elastic cartilage at other sites in JPD1 might also ossify, and warrants investigation.

HIGHER SERUM OSTEOPROTEGERIN LEVELS IN SUBJECTS WITH THYROID NODULES

OBJECTIVE

A recent study demonstrated that osteoprotegerin (OPG) could be expressed both in benign and malignant thyroid tissue. However, epidemiologic studies investigating the association between serum OPG and thyroid nodules are not available. The objective of this study was to determine whether serum OPG is associated with thyroid nodules.

METHODS

We measured serum OPG, total triiodothyronine, total thyroxine, free triiodothyronine, free thyroxine, thyrotropin, antithyroid peroxidase antibodies, thyrotropin-receptor antibodies, antithyroglobulin antibodies, and thyroglobulin in 1,120 Chinese participants in a cross-sectional community-based study performed in downtown Shanghai. Thyroid nodule was diagnosed by thyroid ultrasonographic examination.

RESULTS

The serum OPG levels were significantly increased in nodule-positive subjects compared to nodule-negative subjects (2.8 ± 1.2 ng/mL versus 2.1 ± 1.0 ng/mL; P<.001). After multiple adjustments, the odds ratios were substantially higher for thyroid nodule (odds ratio, 3.09; 95% confidence interval, 1.60 to 5.97) in the highest OPG quartile compared with those in the lowest quartile. These associations remained significant after further adjustment for potential confounders. Multivariate linear regression analysis demonstrated that age (P = .015) and OPG (P = .003) were independently associated with thyroid nodule.

CONCLUSION

Serum OPG is elevated significantly in subjects with thyroid nodules among middle-aged and elderly individuals.

St. John's Wort (Hypericum perforatum) stimulates human osteoblastic MG-63 cell proliferation and attenuates trabecular bone loss induced by ovariectomy

BACKGROUND/OBJECFTIVES

The effect of St. John's Wort extract (SJW) on MG-63 cell proliferation and trabecular bone loss induced by ovariectomy was examined.

MATERIALS/METHODS

Proliferation, expression of estrogen receptor (ER) α and ER β, and gene expressions of osteoprotegerin (OPG), osteocalcin (OC) and alkaline phosphatase (ALP) were examined in MG-63 cells treated with or without SJW. Ovariectomized rats were treated with SJW at the dose of 100 or 200 mg/kg/day, β-estradiol-3-benzoate (E2), or vehicle only (OVX-C), and sham operated rats were treated with vehicle only (Sham-C). Serum ALP and C-telopeptide (CTX), and femoral trabecular bone loss were examined.

RESULTS

SJW increased MG-63 cell proliferation and expression of ER α and ER β, and positive effect was shown on gene expressions of ALP, OC and OPG. SJW also showed estrogen like effect on bone associated with slowing down in trabecular bone loss. Histopathology by H&E showed rats treated with SJW displayed denser structure in metaphyseal region of distal femur compared with rats in OVX-C. SJW was shown to reduce serum CTX in OVX rats.

CONCLUSION

The present study provides new insight in preventing estrogen deficiency induced bone loss of SJW and possibility for its application in bone health supplement.

Nonalcoholic fatty liver disease and decreased bone mineral density: is there a link?

PURPOSE

Liver diseases are associated with decreased bone mineral density (BMD) and evidence suggests that nonalcoholic fatty liver disease (NAFLD) affects several extra-hepatic organs, interacting with the regulation of multiple endocrine and metabolic pathways. This review focuses on the rapidly expanding body of evidence that supports a strong association between NAFLD and the risk of decreased BMD, expression of low bone mass (osteoporosis), or reduced mineralization (osteomalacia).

METHODS

We identified studies by searching PubMed for original articles published in English through March 2015 using the keywords "nonalcoholic fatty liver disease" or "fatty liver" combined with "bone mineral density", "osteoporosis", or "osteomalacia".

RESULTS

Recent cross-sectional and case-control studies involving both adults and children have consistently shown that patients with NAFLD exhibit a greater prevalence of decreased BMD compared with age-, sex-, and body mass index-matched healthy controls. Accumulating clinical and experimental evidence suggests that NAFLD may contribute to the pathophysiology of low BMD, possibly through the direct contribution of NAFLD to whole-body and hepatic insulin resistance and/or the systemic release of multiple pro-inflammatory, pro-coagulant, and pro-fibrogenic mediators.

CONCLUSIONS

Although more research is needed before firm conclusions can be drawn, it appears that there is a non-chance, statistical association between NAFLD and low BMD. This finding argues for more careful monitoring and evaluation of BMD among patients with NAFLD. The potential contribution of NAFLD itself to the development and progression of decreased BMD warrants further study.

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.

Serum osteoprotegerin and future risk of cancer and cancer-related mortality in the general population: the Tromsø study

The purpose was to investigate the association between serum osteoprotegerin (OPG) and risk of incident cancer and cancer mortality in a general population. OPG was measured in serum collected from 6,279 subjects without prior cancer recruited from a general population. Incident cancer and cancer-related mortality were registered from inclusion in 1994-95 until end of follow-up December 31, 2008. Cox regression models were used to estimate crude and adjusted (for age, sex and other confounders) hazard ratios and 95% confidence intervals (HR 95% CI). There were 948 incident cancers and 387 deaths in the cohort during 71,902 person-years of follow up (median 13.5 years). Subjects with serum OPG in the upper tertile had 79% higher risk of incident gastrointestinal cancer than those in the lowest tertile (HR 1.79, 95% CI 1.19-2.67). In women <60 years, serum OPG (per SD 0.81 ng/ml) was associated with reduced risk of incident cancer (all cancers merged; 0.73; 0.57-0.94) and breast cancer (0.51; 0.31-0.83) after adjustment. Subjects in the upper tertile of OPG had higher risk of cancer-related mortality (1.63; 1.16-2.28), particularly mortality from cancer in the gastrointestinal system (2.28; 1.21-4.28) compared to those in the lowest OPG tertile. No significant association was detected between OPG and risk of death from cancer in the respiratory system or death from prostatic cancer. Our findings from a large population based cohort study suggest that serum OPG was associated with increased risk of incident gastrointestinal cancer, inversely associated with breast cancer, and predicts cancer-related mortality.

Immune activation, immunosenescence, and osteoprotegerin as markers of endothelial dysfunction in subclinical HIV-associated atherosclerosis

HIV-infected patients have a significantly greater risk of cardiovascular disease. Several markers including osteoprotegerin have been shown to be involved in the development and progression of atherosclerosis. We investigated the relationship between T-cell phenotype, osteoprotegerin, and atherosclerosis evaluated by carotid intima-media thickness (c-IMT) in 94 HIV+ patients on suppressive antiretroviral therapy with Framingham score <10%. As for the control group, 24 HIV-negative subjects were enrolled. c-IMT was assessed by ultrasound. CD4+/CD8+ T-cell activation (CD38+ HLADR+) and senescence (CD57+ CD28−) were measured by flow cytometry. IL-6 and OPG levels were measured by ELISA kit. c-IMT was higher in HIV+ than in controls. Among HIV+ patients, 44.7% had pathological c-IMT (≥0.9 mm). CD8+ T-cell activation and senescence and OPG plasma levels were higher in HIV+ patients than in controls. Subjects with pathological c-IMT exhibited higher CD8+ immune activation and immunosenescence and OPG levels than subjects with normal c-IMT. Multivariate analysis showed that age, CD8+ CD38+ HLADR+, and CD8+ CD28− CD57+ were independently associated with pathological c-IMT. Several factors have been implicated in the pathogenesis of atherosclerosis in HIV patients. Immune activation and immunosenescence of CD8+ T cell together with OPG plasma levels might be associated with the development and progression of early atherosclerosis, even in the case of viral suppression.

Age and menopausal status affect osteoprotegerin and osteocalcin levels in women differently, irrespective of thyroid function

Osteoprotegerin (OPG) and osteocalcin (OC) are essential bone proteins. Recent studies have demonstrated that they are not secreted solely by bone cells; they play roles in the vascular function and energy metabolism, and they are influenced by multiple factors. The aim of the current study was to investigate the influence of menopause and age on OPG and OC in women with different thyroid-stimulating hormone (TSH) 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.

High osteoprotegerin levels predict MACCE in STEMI patients, but are not associated with myocardial salvage

OBJECTIVES

High circulating levels of osteoprotegerin (OPG) carry prognostic impact in cohorts with various cardiovascular diagnoses. With the present study, we aim to investigate the role of OPG within the scale of myocardial damage.

DESIGN

This study includes 219 consecutive patients with acute ST-elevation myocardial infarction randomized to primary percutaneous coronary intervention (pPCI) or pPCI and remote ischemic per-conditioning. Salvage index via myocardial single-photon emission CT assessment (data available in 61% of the patients) was performed, and derived from Day 1 (myocardial area at risk) and Day 30 (final infarct size). Plasma OPG levels were measured using an in-house immunoassay. A combined end-point of all-mortality, myocardial infarction, stroke, readmission for heart failure and ischemic stroke/transient ischemic attack (Major Adverse Cardiac and Cerebrovascular Events [MACCE]) was used for follow-up; 45 (38-48 months).

RESULTS

High OPG levels were associated with the severity of cardiovascular disease. During follow-up, OPG was a predictor of MACCE (unadjusted, HR: 2.1, 95% CI: 1.14-3.85, P = 0.017). Adjustments for age, gender, and body mass index preserved the independent predictive power of OPG. However, OPG levels were neither associated with salvage index nor with the final infarct size. Remote ischemic per-conditioning had no effect on OPG levels.

CONCLUSION

Despite absent association between OPG levels and the scale of myocardial damage, high OPG levels predict a significantly increased risk of MACCE.

RANKL inhibitors induce osteonecrosis of the jaw in mice with periapical disease

Antiresorptive medications are essential in treating diseases of pathologic osteoclastic bone resorption, including bone cancer and osteoporosis. Bisphosphonates (BPs) are the most commonly used antiresorptives in clinical practice. Although inhibition of bone resorption is important in regulating unwanted malignant and metabolic osteolysis, BP treatment is associated with potential side effects, including osteonecrosis of the jaws (ONJ). Recently, non-BP antiresorptive medications targeting osteoclastic function and differentiation, such as denosumab, have entered the clinical arena. Denosumab treatment results in a similar rate of ONJ as BPs. Animal models of ONJ, using high-dose BP treatment in combination with tooth extraction or dental disease, provide valuable tools and insight in exploring ONJ pathophysiology. However, the ability of other antiresorptives to induce ONJ-like lesions in animal models has not been explored. Such studies would be beneficial in providing support for the role of osteoclast inhibition in ONJ pathogenesis versus a direct BP effect on oral tissues. Here, we tested the ability of the receptor activator of NF-κB ligand (RANKL) inhibitors RANK-Fc (composed of the extracellular domain of RANK fused to the fragment crystallizable [Fc] portion of immunoglobulin G [IgG]) and OPG-Fc (composed of the RANKL-binding domains of osteoprotegerin [OPG] linked to the Fc portion of IgG) to induce ONJ in mice in the presence of periapical disease, but in the absence of dental extractions. We demonstrate radiographic evidence of ONJ in RANK-Fc-treated and OPG-Fc-treated mice, including inhibition of bone loss, increased bone density, lamina dura thickening, and periosteal bone deposition. These findings closely resembled the radiographic appearance of an ONJ patient on denosumab treatment. Histologic examination revealed that RANK-Fc treatment and OPG-Fc treatment resulted in absence of osteoclasts, periosteal bone formation, empty osteocytic lacunae, osteonecrosis, and bone exposure. In conclusion, we have successfully induced ONJ in mice with periapical disease, using potent osteoclast inhibitors other than BPs. Our findings, coupled with ONJ animal models using high-dose BPs, suggest that osteoclast inhibition is pivotal to the pathogenesis of ONJ.

Biomarkers of vascular calcification and mortality in patients with ESRD

BACKGROUND

Vascular calcification is common among patients undergoing dialysis and is associated with mortality. Factors such as osteoprotegerin (OPG), osteopontin (OPN), bone morphogenic protein-7 (BMP-7), and fetuin-A are involved in vascular calcification.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

OPG, OPN, BMP-7, and fetuin-A were measured in blood samples from 602 incident dialysis patients recruited from United States dialysis centers between 1995 and 1998 as part of the Choices for Healthy Outcomes In Caring for ESRD Study. Their association with all-cause and cardiovascular mortality were assessed using Cox proportional hazards models adjusted for demographic characteristics, comorbidity, serum phosphate, and calcium. An interaction with diabetes was tested because of its known association with vascular calcification. Predictive accuracy of selected biomarkers was explored by C-statistics in nested models with training and validation subcohorts.

RESULTS

Higher OPG and lower fetuin-A levels were associated with higher mortality over up to 13 years of follow-up (median, 3.4 years). The adjusted hazard ratios (HR) for highest versus lowest tertile were 1.49 (95% confidence interval [95% CI], 1.08 to 2.06) for OPG and 0.69 (95% CI, 0.52 to 0.92) for fetuin-A. In stratified models, the highest tertile of OPG was associated with higher mortality among patients without diabetes (HR, 2.42; 95% CI, 1.35 to 4.34), but not patients with diabetes (HR, 1.26; 95% CI, 0.82 to 1.93; P for interaction=0.001). In terms of cardiovascular mortality, higher fetuin-A was associated with lower risk (HR, 0.85 per 0.1 g/L: 95% CI, 0.75 to 0.96). In patients without diabetes, higher OPG was associated with greater risk (HR for highest versus lowest tertile, 2.91; 95% CI, 1.06 to 7.99), but not in patients with diabetes or overall. OPN and BMP-7 were not independently associated with outcomes overall. The addition of OPG and fetuin-A did not significantly improve predictive accuracy of mortality.

CONCLUSIONS

OPG and fetuin-A may be risk factors for all-cause and cardiovascular mortality in patients undergoing dialysis, but do not improve risk prediction.

Osteoprotegerin (OPG) as a biomarker for diabetic cardiovascular complications

Osteoprotegerin (OPG) is a glycoprotein involved in bone metabolisms and with a regulatory role in immune, skeletal and vascular systems. Recently, circulating OPG levels have emerged as independent biomarkers of cardiovascular disease (CVD) in patients with acute or chronic heart disease, as well as in the healthy population. Furthermore, OPG has been implicated in various inflammations and linked to diabetes and poor glycaemic control. This review focuses on the relations between circulating OPG levels and cardiovascular complications, with special emphasis on diabetic patients. OPG levels were observed to increase concurrently with the severity of diabetic complications, that is, with the highest circulating OPG levels observed in diabetic patients dying from CVD. Although the clinical prognostic use of OPG may seem far away, OPG does look promising as a biomarker in order to help the cardiologist to a better risk-stratification of the patients.