Plasma osteoprotegerin levels are associated with glycaemic status, systolic blood pressure, kidney function and cardiovascular morbidity in type 1 diabetic patients

Rapid correction of chronic hyperglycemia and bone remodeling, warning against overdoing

It is widely recognized that chronic hyperglycemia decreases bone quality, although little is known about the impact of the rapid correction of chronic hyperglycemia on the quality of bone remodeling. This spotlight article explores this correlation by focusing on the stages of bone remodeling linked to glucose levels.

Osteoprotegerin and Inflammation in Incident Peritoneal Dialysis Patients

Objectives: Osteoprotegerin (OPG) is a member of the tumor necrosis factor receptor family involved in processes in many inflammatory states. OPG concentration is enhanced in the majority of chronic kidney disease (CKD) patients and those undergoing renal replacement therapy. The aim of the study was to assess the relation of OPG and chronic inflammation in peritoneal dialysis (PD) patients and to evaluate whether OPG concentrations in plasma and dialysate were related to plasma and dialysate levels of proinflammatory mediators (interleukin 6 (IL-6), high-sensitivity C-reactive protein (hsCRP), interleukin 33 (IL-33) and interleukin 1 receptor-like 1IL-1RL1 (IL-1RL1, sST2)). Methods: The study included 37 patients of the Peritoneal Dialysis Center, Department of Nephrology, Transplantology and Internal Medicine, Szczecin, Poland, 4-6 weeks after the onset of peritoneal dialysis therapy. During a peritoneal equilibration test, plasma (at 2 h) and dialysate (at 4 h) OPG, IL-33, 1IL-1RL1 (sST2), IL-6 and hsCRP concentrations were determined. Results: Plasma concentration of OPG did not correlate with dialysate OPG level (Rs = 0.04, p = 0.8). There was a strong positive correlation between plasma OPG concentrations and plasma IL-1RL1 (sST2) (Rs = 0.41; p = 0.01), plasma IL-6 (Rs = 0.38; p = 0.01) and plasma hsCRP (Rs = 0.35; p = 0.02). Dialysate OPG concentrations were positively associated with dialysate IL-1RL1 (sST2) (Rs = 0.37; p = 0.02) and dialysate IL-6 levels (Rs = 0.44; p = 0.005). Multivariate analysis showed that higher IL-1RL1 (sST2) (ß = +0.38, p = 0.006), higher plasma hsCRP (ß = +0.32, p = 0.02) and older age (ß = +0.35, p = 0.01) were independent determinants of higher plasma OPG concentration and that higher concentrations of dialysate IL-6 (ß = +0.37, p = 0.02) were independent determinants of higher dialysate OPG concentration. Conclusions: Both plasma and dialysate OPG levels are associated with the severity of systemic and local inflammation illustrated by the plasma and dialysate concentrations of IL-1RL1 (sST2), hsCRP and IL-6, suggesting that OPG might have a pivotal role in explaining the milieu of systemic and intraperitoneal inflammation.

Advanced Glycation End Products, Bone Health, and Diabetes Mellitus

Advanced glycation end products (AGEs), the compounds resulting from the non-enzymatic glycosylation between reducing sugars and proteins, are derived from food or produced de novo. Over time, more and more endogenous and exogenous AGEs accumulate in various organs such as the liver, kidneys, muscle, and bone, threatening human health. Among these organs, bone is most widely reported. AGEs accumulating in bone reduce bone strength by participating in bone structure formation and breaking bone homeostasis by binding their receptors to alter the proliferation, differentiation, and apoptosis of cells involved in bone remodeling. In this review, we summarize the research about the effects of AGEs on bone health and highlight their associations with bone health in diabetes patients to provide some clues toward the discovery of new treatment and prevention strategies for bone-related diseases caused by AGEs.

Circulating Osteoprotegerin in Chronic Kidney Disease and All-Cause Mortality

BACKGROUND

Chronic kidney disease (CKD) is associated with cardiovascular disease (CKD), mineral and bone disorder (CKD-MBD) and high mortality. Bone-related factors such as osteopontin (OPN), osteocalcin (OC), osteoprotegerin (OPG) and fibroblast growth factor 23 (FGF23) were linked to cardiovascular complications of CKD and are expected to have predictive value in CKD patients.

PURPOSE

The aim of this study was to assess the relationship of OPN, OC, OPG and FGF23 to clinical characteristics and to evaluate their ability to predict mortality in patients with different CKD stages.

METHODS

The following study groups were enrolled: subjects with end-stage renal disease (38 ESRD), CKD stages 3 and 4 (19 CKD3-4) and non-CKD controls (19), respectively. Blood was withdrawn once to perform the measurements and cardiac computed tomography was used to evaluate coronary calcium score (CS). Patients were followed for 5 years for the ascertainment of their all-cause mortality.

RESULTS

Serum OPN, OC and OPG concentrations increased significantly along with the progression of renal disease. We found a significant positive correlation among these proteins. Additionally, OPN and OPG were significantly and positively correlated to CS. Serum OPG revealed the strongest correlation to the calcium turnover markers of GFR decline and was significantly associated with an increased risk of death in subjects with CKD3-4 or ESRD (HR 5.8, CI 95%).

CONCLUSION

Single measurement of osteoprotegerin is associated with 5-year all-cause mortality in patients with CKD3-4 or ESRD. We suggest assessing its concentration, preferably in combination with calcium score, to stratify mortality risks in CKD patients.

Investigating potential protein markers of cardiovascular disease in children with type 1 diabetes mellitus

BACKGROUND

Type 1 diabetes mellitus (T1DM) is a metabolic disease characterized by dysglycaemia. Cardiovascular disease (CVD) is a major complication among T1DM patients and the leading cause of mortality later in life.

METHODS

The study subjects consisted of T1DM children with poor glycemic control (HbA1c > 7.5%) and healthy age and gender matched controls. Venous blood samples were collected and tested by utilizing a novel immunoassay panel with 96 protein biomarkers. Data were analyzed using non-linear regression analysis and the expression of biomarkers was compared between T1DM and healthy control groups using an unpaired student's t-test. Dynamic principal component analysis (PCA) was operated based on the differentially expressed proteins.

RESULTS

Ten T1DM children and 10 healthy controls were analyzed. Twelve CVD markers show significant differential expression between T1DM patients and healthy controls (p < 0.05). Dynamic PCA clustering based on differentially expressed proteins demonstrated an obvious clustering between the two populations.

CONCLUSIONS

This preliminary study reveals the feasibility of utilizing a novel immunoassay panel to investigate potential biomarkers for predicting incipient CVD in children with T1DM. In future, longitudinal studies are required to track the relationships between measurements of the selected protein markers and the development of CVD in T1DM patients.

Serum Osteoprotegerin and Carotid Intima-Media Thickness Are Related to High Arterial Stiffness in Heart Failure with Reduced Ejection Fraction

Arterial stiffness (AS) is a complex vascular phenomenon with consequences for central hemodynamics and left-ventricular performance. Circulating biomarkers have been associated with AS; however, their value in heart failure is poorly characterized. Our aim was to evaluate the clinical and biomarker correlates of AS in the setting of heart failure with reduced ejection fraction (HFrEF). In 78 hospitalized, hemodynamically stable patients (20 women, 58 men, mean age 65.8 ± 1.41 years) with HFrEF, AS was measured using aortic pulse wave velocity (PWV). Serum OPG, RANKL, sclerostin, and DKK-1 were determined, and the relationships between the clinical variables, vascular-calcification-related biomarkers, and PWV were evaluated by correlation analysis and linear and logistic regression models. OPG and the OPG/RANKL ratio were significantly higher in the group of patients (n = 37, 47.4%) with increased PWV (>10 m/s). PWV was positively correlated with age, left-ventricular ejection fraction, and carotid intima-media thickness (cIMT), and negatively correlated with the glomerular filtration rate. OPG and cIMT were significantly associated with PWV in the logistic regression models when adjusted for hypertension, EF, and the presence of atherosclerotic manifestations. Elevated serum OPG, together with cIMT, were significantly related to increased AS in the setting of HFrEF.

Association between Osteoprotegerin and Charcot Neuroarthropathy: a systematic review

AIMS

Osteoprotegerin (OPG) has been associated with Charcot Neuroarthropathy (CN); however, three studied OPG polymorphisms (1181C > G, 245A > C and 950 T > C) have yielded conflicting results. Therefore, this meta-analysis was conducted to determine the difference in serum OPG concentrations between healthy controls and diabetics with and without CN and the effect OPG polymorphisms have on CN development.

METHODS

PubMed, LILAC, SCOPUS, and EBSCO databases and retrieved publications' bibliographies were searched for studies that examined for OPG and CN. Depending on the heterogeneity, fixed or random effects were used to calculate the pooled odds ratio (OR) or standard difference in means (SDM) with 95% confidence intervals (95%CI) for 5 genetic models (heterozygous, homozygous, dominant, recessive, and allelic) and serum concentrations, respectively.

RESULTS

Seven publications (12 studies) demonstrated that serum OPG concentrations were more elevated in subjects with CN (SDM = 0.719, 95%CI = 0.555-0.883, p < 0.001). When CN was compared to healthy controls or diabetics, the difference was more prominent for healthy controls (SDM = 1.043, 95%CI = 0.676-1.409, p < 0.001) than diabetics (SDM = 0.639, 95%CI = 0.456-0.821, p < 0.001) and the SDM difference was significant (p = 0.013). Using 6 publications (9 studies), neither the 1181C > G or the 950 T > C polymorphisms showed any significant associations for any genetic model. For the 245A > C polymorphism, only the homozygous genetic model showed a significant association between the polymorphism and CN (OR = 2.850, 95%CI: 1.051-7.729, p = 0.040).

CONCLUSIONS

Here, we determined a potential correlation between the CN and serum OPG concentrations and that only the CC genotype of the 245A > C polymorphism showed an increased risk of developing CN.

Plasma circulating miR-23~27~24 clusters correlate with the immunometabolic derangement and predict C-peptide loss in children with type 1 diabetes

AIMS/HYPOTHESIS

We aimed to analyse the association between plasma circulating microRNAs (miRNAs) and the immunometabolic profile in children with type 1 diabetes and to identify a composite signature of miRNAs/immunometabolic factors able to predict type 1 diabetes progression.

METHODS

Plasma samples were obtained from children at diagnosis of type 1 diabetes (n = 88) and at 12 (n = 32) and 24 (n = 30) months after disease onset and from healthy control children with similar sex and age distribution (n = 47). We quantified 60 robustly expressed plasma circulating miRNAs by quantitative RT-PCR and nine plasma immunometabolic factors with a recognised role at the interface of metabolic and immune alterations in type 1 diabetes. Based on fasting C-peptide loss over time, children with type 1 diabetes were stratified into the following groups: those who had lost >90% of C-peptide compared with diagnosis level; those who had lost <10% of C-peptide; those showing an intermediate C-peptide loss. To evaluate the modulation of plasma circulating miRNAs during the course of type 1 diabetes, logistic regression models were implemented and the correlation between miRNAs and immunometabolic factors was also assessed. Results were then validated in an independent cohort of children with recent-onset type 1 diabetes (n = 18). The prognostic value of the identified plasma signature was tested by a neural network-based model.

RESULTS

Plasma circulating miR-23~27~24 clusters (miR-23a-3p, miR-23b-3p, miR-24-3p, miR-27a-3p and miR-27b-3p) were upmodulated upon type 1 diabetes progression, showed positive correlation with osteoprotegerin (OPG) and were negatively correlated with soluble CD40 ligand, resistin, myeloperoxidase and soluble TNF receptor in children with type 1 diabetes but not in healthy children. The combination of plasma circulating miR-23a-3p, miR-23b-3p, miR-24-3p, miR-27b-3p and OPG, quantified at disease onset, showed a significant capability to predict the decline in insulin secretion 12 months after disease diagnosis in two independent cohorts of children with type 1 diabetes.

CONCLUSIONS/INTERPRETATIONS

We have pinpointed a novel miR-23a-3p/miR-23b-3p/miR-24-3p/miR-27b-3p/OPG plasma signature that may be developed into a novel blood-based method to better stratify patients with type 1 diabetes and predict C-peptide loss.

TRAIL, OPG, and TWEAK in kidney disease: biomarkers or therapeutic targets?

Ligands and receptors of the tumor necrosis factor (TNF) superfamily regulate immune responses and homeostatic functions with potential diagnostic and therapeutic implications. Kidney disease represents a global public health problem, whose prevalence is rising worldwide, due to the aging of the population and the increasing prevalence of diabetes, hypertension, obesity, and immune disorders. In addition, chronic kidney disease is an independent risk factor for the development of cardiovascular disease, which further increases kidney-related morbidity and mortality. Recently, it has been shown that some TNF superfamily members are actively implicated in renal pathophysiology. These members include TNF-related apoptosis-inducing ligand (TRAIL), its decoy receptor osteoprotegerin (OPG), and TNF-like weaker inducer of apoptosis (TWEAK). All of them have shown the ability to activate crucial pathways involved in kidney disease development and progression (e.g. canonical and non-canonical pathways of the transcription factor nuclear factor-kappa B), as well as the ability to regulate cell proliferation, differentiation, apoptosis, necrosis, inflammation, angiogenesis, and fibrosis with double-edged effects depending on the type and stage of kidney injury. Here we will review the actions of TRAIL, OPG, and TWEAK on diabetic and non-diabetic kidney disease, in order to provide insights into their full clinical potential as biomarkers and/or therapeutic options against kidney disease.

Contribution of biomarkers for pancreatic cancer-associated new-onset diabetes to pancreatic cancer screening

BACKGROUND

Pancreatic cancer (PaC) is one of the deadliest types of tumor, and it is regarded as a fatal disease, with a 5-year survival rate less than 10%. Most clinical diagnoses for PaC are made at an advanced stage because of the insidious onset of the disease, which leads to an extremely poor prognosis.

RECENT FINDINGS

The relationship between diabetes mellitus (DM) and PaC has been established by several decades of research, and the prevalence of DM in patients with PaC has been reported to be 40%, with half of the patients having developed new-onset DM within 2 years or less. Increasing evidence suggests that new-onset DM is associated with a high prevalence of PaC, and PaC resection ameliorates DM. Therefore, screening for PaC may be needed in patients with newly developed DM.

PURPOSE

The objective of this review was to present our current understanding of biomarkers for PaC-associated new-onset DM (PCAND), to offer a perspective on the prospects and problems of using this strategy for early screening to differentiate PCAND from new-onset type 2 DM not associated with PaC and to suggest candidate biomarkers to use for PaC screening in patients with new-onset DM. Finding sensitive and specific biomarkers to manage these patients constitutes a challenge for the research community and for public health policies.

Carotid intima media thickness and associations with serum osteoprotegerin and s-RANKL in children and adolescents with type 1 diabetes mellitus with increased risk for endothelial dysfunction

Background Although carotid intima media thickness (CIMT) is an established marker of endothelial dysfunction, limited data exist on relative laboratory biomarkers in youngsters with type 1 diabetes mellitus (T1DM). Our aim was to study CIMT and the biomarkers of the osteoprotegerin (OPG)/RANKL system in young T1DM patients and controls, and also in subgroups of patients with increased risk for endothelial dysfunction, such as those with overweight/obesity, poor metabolic control or the presence of microalbuminuria. Methods CIMT and OPG/RANKL of 56 T1DM children and adolescents were compared to 28 healthy controls. Results Anthropometric, laboratory, CIMT and OPG/RANKL measurements were similar between patients and controls. Overweight/obese patients had greater CIMT than the normal weight ones (0.50 vs. 0.44 mm, p=0.001). Microalbuminuric patients had greater CIMT (0.49 vs. 0.44 mm, p=0.035) than the normoalbuminuric ones, with no difference in terms of OPG/RANKL. In the microalbuminuric group, OPG (r=-0.90, p=0.036) and RANKL (r=-0.92, p=0.024) were significantly negatively associated with CIMT. Following linear regression analysis, in the total patients group, microalbuminuria was the only factor significantly associated with CIMT (beta±SE: 0.050±0.021, p=0.035), body mass index (BMI)-z-scores were negatively associated with OPG (beta±SE: -0.25±0.12, p=0.05), while in the microalbuminuric group, CIMT was negatively associated with OPG (beta±SE: -0.070±0.019, p=0.036). During the forward stepwise procedure, microalbuminuria and age were the only variables negatively associated with RANKL (b=-0.334, p=0.034, b=-35.95, p=0.013, respectively). Conclusions In T1DM pediatric patients, overweight/obesity and microalbuminuria were associated with greater CIMT and with impaired OPG/RANKL levels, as biochemical indices of calcification of the atherosclerotic plaque.

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.

Association between low bone mass and the serum RANKL and OPG in patients with nephrolithiasis

Background

Nephrolithiasis is a risk factor for Osteopenia and osteoporosis. Receptor activator of nuclear factor kappaB ligand (RANKL) and osteoprotegerin (OPG) regulate bone remodeling and osteoclastogenesis. This study aimed to evaluate the relation between serum OPG, RANKL concentration, and bone mineral density (BMD) in patients with kidney stone disease.

Methods

Forty-four nephrolithiasis patients with either low bone mass or normal BMD (considered control group) were enrolled in this study. BMD was measured at lumbar spine (L1-L4) and femoral neck by dual-energy X-ray absorptiometry (DEXA). The serum OPG and RANKL were determined using the ELISA method.

Results

The median levels of serum OPG were significantly higher in nephrolithiasis patients with low bone mass compared to the nephrolithiasis patients with normal BMD (3.9 pmol/l versus 3.1 pmol/l; P = 0.03), respectively. Negative correlation was detected between bone densities of femoral neck and OPG in patients with nephrolithiasis (r = −.0344, P = 0.02).

Conclusion

The present study showed that high serum fasting OPG levels may be indicative of femoral neck BMD in patients with nephrolithiasis.

Diabetic macular oedema: under-represented in the genetic analysis of diabetic retinopathy

Diabetic retinopathy, a complication of both type 1 and type 2 diabetes, is a complex disease and is one of the leading causes of blindness in adults worldwide. It can be divided into distinct subclasses, one of which is diabetic macular oedema. Diabetic macular oedema can occur at any time in diabetic retinopathy and is the most common cause of vision loss in patients with type 2 diabetes. The purpose of this review is to summarize the large number of genetic association studies that have been performed in cohorts of patients with type 2 diabetes and published in English-language journals up to February 2017. Many of these studies have produced positive associations with gene polymorphisms and diabetic retinopathy. However, this review highlights that within this large body of work, studies specifically addressing a genetic association with diabetic macular oedema, although present, are vastly under-represented. We also highlight that many of the studies have small patient numbers and that meta-analyses often inappropriately combine patient data sets. We conclude that there will continue to be conflicting results and no meaningful findings will be achieved if the historical approach of combining all diabetic retinopathy disease states within patient cohorts continues in future studies. This review also identifies several genes that would be interesting to analyse in large, well-defined cohorts of patients with diabetic macular oedema in future candidate gene association studies.

Significant Association between OPG/TNFRSF11B Variant and Common Complex Ischemic Stroke

BACKGROUND

The serum level of osteoprotegerin (encoded by OPG or TNFRSF11B) was previously shown to be increased in patients with ischemic stroke. A single nucleotide polymorphism rs3134069 in the TNFRSF11B gene was previously associated with ischemic stroke in a population of diabetic patients in Italy. It remains to be determined whether rs3134069 is associated with ischemic stroke in the general population or populations without diabetes.

MATERIALS AND METHODS

We genotyped rs3134069 and performed a case-control association study to test whether rs3134069 is associated with ischemic stroke in 2 independent Chinese Han populations, including a China-Central population with 1629 cases and 1504 controls and a China-Northern population with 1206 cases and 720 controls.

RESULTS

rs3134069 showed significant association with ischemic stroke in the China-Central population (P = 9.24 × 10^-3, odds ratio [OR] = 1.50). The association was replicated in the independent China-Northern population (P = 2.45 × 10^-4, OR = 1.53). The association became more significant in the combined population (P = 7.09 × 10^-6, OR = 1.41). The associations remained significant in the male population, female population, and population without type 2 diabetes. Our expression quantitative trait loci analysis found that the minor allele C of rs3134069 was significantly associated with a decreasedexpression level of TNFRSF11B (P = .002).

CONCLUSIONS

This study demonstrates that rs3134069 in TNFRSF11B increases risk of ischemic stroke by decreasing TNFRSF11B expression.

Is cardiovascular disease in patients with diabetes associated with serum levels of MMP-2, LOX, and the elastin degradation products ELM and ELM-2?

BACKGROUND

Diabetes mellitus type 2 (T2DM) is a significant risk factor for the development of cardiovascular diseases (CVDs). In a previous microarray study of internal mammary arteries from patients with and without T2DM, we observed several elastin-related genes with altered mRNA-expression in diabetic patients, namely matrix metalloproteinase 2 (MMP-2), lysyl oxidase (LOX) and elastin itself. In this study we investigate whether the serum concentrations of elastin-related proteins correlate to signs of CVD in patients with T2DM.

METHODS

Blood samples from 302 type 2 diabetic patients were analysed for MMP-2, LOX, and the elastin degradation products ELM and ELM2. The results were investigated for correlations to signs of CVD in different vascular territories, as determined by myocardial perfusion scintigraphy, carotid artery thickness and ankle-brachial blood pressure index.

RESULTS

T2DM patients with peripheral arterial disease (low ankle-brachial index) (PAD) display higher levels of MMP-2 and ELM compared to patients without PAD. However, none of the proteins or degradation products correlated with myocardial ischemia or a combined measure of CVD-signs, including myocardial ischemia, increased carotid thickness and decreased ankle-brachial blood pressure.

CONCLUSIONS

Our results suggest that the diabetic environment affects the circulating amounts of MMP-2 and ELM in patients with PAD. However, the same connection could not be seen in diabetic patients with CVD broadly identified in three vascular territories. LOX and ELM-2 did not correlate to any type of CVD. Overall, serum levels of elastin-related molecules are only remotely related to CVD in type 2 diabetes.

Circulating osteoprotegerin is associated with chronic kidney disease in hypertensive patients

Background

Osteoprotegerin (OPG) is a glycoprotein that plays an important regulatory role in the skeletal, vascular, and immune system. It has been shown that OPG predicts chronic kidney disease (CKD) in diabetic patients. We hypothesized that OPG could be a risk marker of CKD development also in non-diabetic hypertensive patients.

Methods

A case-control study was carried out to measure circulating OPG levels in 42 hypertensive patients with CKD and in 141 hypertensive patients without CKD. A potential relationship between OPG and the presence of CKD was investigated and a receiver-operating characteristic (ROC) curve was designed thereafter to identify a cut-off value of OPG that best explained the presence of CKD. Secondly, to evaluate whether OPG increase could affect the kidney, 18 C57BL/6J mice were randomized to be treated with saline or recombinant OPG every 3 weeks for 12 weeks.

Results

Circulating OPG levels were significantly higher in hypertensive patients with CKD, and there was a significant inverse association between OPG and renal function, that was independent from other variables. ROC analysis showed that OPG levels had a high statistically predictive value on CKD in hypertensive patients, which was greater than that of hypertension. The OPG best cut-off value associated with CKD was 1109.19 ng/L. In the experimental study, OPG delivery significantly increased the gene expression of pro-inflammatory and pro-fibrotic mediators, as well as the glomerular nitrosylation of proteins.

Conclusions

This study shows that OPG is associated with CKD in hypertensive patients, where it might have a higher predictive value than that of hypertension for CKD development. Secondly, we found that OPG delivery significantly increased the expression of molecular pathways involved in kidney damage. Further longitudinal studies are needed not only to evaluate whether OPG predicts CKD development but also to clarify whether OPG should be considered a risk factor for CKD.

Electronic supplementary material

The online version of this article (doi:10.1186/s12882-017-0625-3) contains supplementary material, which is available to authorized users.

Osteoprotegerin, RANKL, ADMA, and Fetuin-A serum levels in children with type I diabetes mellitus

INTRODUCTION

Patients with type I diabetes mellitus (T1DM) have increased incidence of atherosclerosis and cardiovascular disease. Although these complications are unusual in children with T1DM, prevention, and early intervention could decrease morbidity and mortality. Osteoprotegerin (OPG), asymmetric dimethylarginine (ADMA), and Fetuin-A have been associated with increased cardiovascular risk (CVR). Increased OPG and ADMA, and decreased or increased Fetuin-A serum levels have been associated with increased CVR.

AIM

Because patients with T1DM have higher CVR we investigated OPG, ADMA, and Fetuin-A, in children with T1DM.

METHODS

We determined the serum levels of OPG, receptor activator of nuclear factor-κB ligand (RANKL), ADMA, and Fetuin-A by enzyme-linked immunosorbent assay (ELISA) in 56 children with T1DM aged 12.1 ± 3.4 yr and in 46 normal control children, (C) aged 11.3 ± 3.0 yr.

RESULTS

Serum OPG levels were significantly increased in patients with T1DM (3.352 ± 0.73 pmol/L) compared with C (2.75 ± 0.67 pmol/L, p < 0.0001) but RANKL did not change. ADMA was significantly decreased in T1DM compared with C (0.68 ± 0.13 µmol/L versus 0.82 ± 0.18 µmol/L, p < 0.0001). Fetuin-A was similar in T1DM (0.551 ± 0.13 g/L) and C (0.540 ± 0.11 g/L) subjects. OPG was positively associated with glycosylated hemoglobin A1c (p < 0.001) and negatively associated with BMI (p < 0.01). ADMA and Fetuin-A were not associated with A1c and ADMA was only negatively associated with age (p < 0.05).

CONCLUSION

OPG is increased, ADMA is decreased, but RANKL and Fetuin-A are unchanged in T1DM children. Whereas increased OPG has been firmly related to increased CVR, more studies, especially longitudinal studies, are needed to delineate the role and clinical significance of decreased ADMA and if Fetuin-A has any role in T1DM.

Ghrelin attenuates vascular calcification in diabetic patients with amputation

Vascular calcification is established to be a critical factor in diabetes mellitus, which causes cardiovascular and amputation complication of diabetic patients. OPG/RANKL/RANK axis serves as a regulatory role in vascular calcification. Ghrelin, an endogenous ligand of growth hormone secretagogue receptor (GHSR), has been reported to exhibit potent cardiovascular protective effects. However, the role of ghrelin in the regulation of diabetic vascular calcification is still elusive. Here, we reported the role of ghrelin and its relationship with OPG/RANKL/RANK system in patients with diabetic foot amputation. In vivo and in vitro investigations were performed. Sixty type 2 diabetic patients with foot amputation were enrolled in vivo investigation, and they were divided into three groups through Doppler ultrasound: mild stenosis group (n=20), moderate stenosis group (n=20), and severe stenosis/occlusion group (n=20). Morphological analysis results showed diffused calcium depositions in the anterior tibial artery of diabetic amputees. Compared with the mild and moderate stenosis group, the severe stenosis/occlusion group had more spotty calcium depositions in atherosclerotic plaques. Western blot analysis indicated the expressions of osteoprotegerin (OPG) and ghrelin were downregulated, while the expression of receptor activator of nuclear factor kappa B ligand (RANKL) was upregulated with the vascular stenosis aggravation. Pearson correlation analysis revealed a negative correlation between calcium content and ghrelin levels (r=-0.58, P<0.001), as well as the ghrelin levels and sRANKL levels (r=-0.57, P<0.001). Meanwhile, OPG levels were positively correlated with ghrelin levels (r=0.63, P<0.001). From in vitro investigation, we found that the high-glucose (HG), high-lipid (HL), and β-glycerophosphate (β-GP) considerably increased the total calcium content, ALP activity, and expression of osteogenic markers in vascular smooth muscle cells (VSMCs). Ghrelin blunted calcification in a dose-dependent manner. In addition, ghrelin upregulated OPG expression and downregulated RANKL expression in VSMC calcification when anti-OPG antibody and RANKL were performed. Collectively, we therefore conclude serum ghrelin level may be a predictor of diabetic vascular calcification. The possible mechanism may be related with OPG/RANKL signal.

Osteoprotegerin as a marker of cardiovascular risk in children and adolescents with type 1 diabetes

BACKGROUND

Elevated osteoprotegerin (OPG) levels have been reported in patients with diabetes complications. We investigated whether plasma OPG levels can be used as a marker of cardiovascular risk in children and adolescents with type 1 diabetes (T1D).

METHODS

Plasma blood samples were obtained from 243 subjects (143 children and adolescents with T1D and 100 healthy controls). OPG concentrations were measured by enzyme-linked immunosorbent assay (ELISA) method. All data were analyzed by using PASW statistics 18.

RESULTS

A significant higher plasma OPG level was found in children with T1D compared to controls (p < 0.001). A significant increase of OPG levels has been related to the glucose level ≥ 7 mmol/L (2.44 [0.01-6.22] vs. 2.16 [0.13-6.22] pmol/L, p = 0.019), microalbuminuria ≥ 30 mg/24 h (3.71 [0.160-6.03] vs. 2.26 [0.01-6.22] pmol/L, p < 0.001), and cystatin-C ≥ 0.789 mg/L (2.64 [0.37-6.22] vs. 2.11 [0.01-5.82] pmol/L, p < 0.001). We noted a significant higher frequency of children with increased cystatin-C levels in the group with elevated plasma level of OPG compared with those with normal levels (49 vs. 18%, respectively) with an odds ratio (OR) = 4.42 [1.41-13.84] (p = 0.006). We showed a significant increase of OPG levels when the number of cardiovascular risk factors exceeds 3 (p = 0.001).

CONCLUSION

OPG may be a potential biomarker of cardiovascular risk in T1D. Implementation of OPG determination in the clinical laboratory setting would be useful in order to better stratify patients and to assess the most adequate treatment.

Glucagon-like peptide-1(GLP-1) receptor agonists: potential to reduce fracture risk in diabetic patients?

This review summarizes current knowledge about glucagon-like peptide 1 receptor agonists (GLP-1 RA) and their effects on bone metabolism and fracture risk. Recent in vivo and in vitro experiments indicated that GLP-1 RA could improve bone metabolism. GLP-1 could affect the fat-bone axis by promoting osteogenic differentiation and inhibiting adipogenic differentiation of bone mesenchymal precursor cells (BMSCs), which express the GLP-1 receptor. GLP-1 RA may also influence the balance between osteoclasts and osteoblasts, thus leading to more bone formation and less bone resorption. Wnt/β-catenin signalling is involved in this process. Mature osteocytes, which also express the GLP-1 receptor, produce sclerostin which inhibits Wnt/β-catenin signalling by binding to low density lipoprotein receptor-related protein (LRP) 5 and preventing the binding of Wnt. GLP-1 RA also decreases the expression of sclerostin (SOST) and circulating levels of SOST. In addition, GLP-1 receptors are expressed in thyroid C cells, where GLP-1 induces calcitonin release and thus indirectly inhibits bone resorption. Furthermore, GLP-1 RA influences the osteoprotegerin(OPG)/receptor activator of nuclear factor-κB ligand (RANKL)/receptor activator of nuclear factor-κB (RANK) system by increasing OPG gene expression, and thus reverses the decreased bone mass in rats models. However, a recent meta-analysis and a cohort study did not show a significant relationship between GLP-RA use and fracture risk. Future clinical trials will be necessary to investigate thoroughly the relationship between GLP-1 RA use and fracture risk in diabetic patients.

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

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

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.

Roles and Clinical Applications of OPG and TRAIL as Biomarkers in Cardiovascular Disease

Cardiovascular diseases (CVD) remain the major cause of death and premature disability in Western societies. Assessing the risk of CVD is an important aspect in clinical decision-making. Among the growing number of molecules that are studied for their potential utility as CVD biomarkers, a lot of attention has been focused on osteoprotegerin (OPG) and its ligands, which are receptor activator of nuclear factor κB ligand (RANKL) and TNF-related apoptosis-inducing ligand. Based on the existing literature and on our experience in this field, here we review what the possible roles of OPG and TRAIL in CVD are and their potential utility as CVD biomarkers.

Amlodipine and atorvastatin improved hypertensive cardiac hypertrophy through regulation of receptor activator of nuclear factor kappa B ligand/receptor activator of nuclear factor kappa B/osteoprotegerin system in spontaneous hypertension rats

The present study aims to study the role of receptor activator of nuclear factor kappa B ligand/receptor activator of nuclear factor kappa B/osteoprotegerin (RANKL/RANK/OPG) system in cardiac hypertrophy in a spontaneous hypertension rat (SHR) model and the effects of amlodipine and atorvastatin intervention. Thirty-six-week-old male SHRs were randomly divided into four groups: 1) SHR control group; 2) amlodipine alone (10 mg/kg/d) group, 3) atorvastatin alone (10 mg/kg/d) group, 4) combination of amlodinpine and atorvastatin (10 mg/kg/d for each) group. Same gender, weight, and age of Wistar-Kyoto (WKY) rats with normal blood pressure were used as normal control. Drugs were administered by oral gavage over 12 weeks. The thicknesses of left ventricle walls, left ventricle weight, and cardiac function were measured by transthoracic echocardiography. Left ventricular pressure and function were assessed by hemodynamic examination. Cardiomyocyte hypertrophy and collagen accumulation in cardiac tissue were measured by hematoxylin and eosin (HE) and Masson staining, respectively. The hydroxyproline content of cardiac tissue was examined by biochemistry technique. RANKL, RANK and OPG mRNA, protein expression and tissue localization were studied by RT-PCR, Immunohistochemistry and Western blot. Treatment with amlodipine or atorvastatin alone significantly decreased left ventricular mass index, cardiomyocyte cross-sectional area and interstitial fibrosis in SHR (each P < 0.05). Moreover, combined amlodipine and atorvastatin treatment induced significant reversal of left ventricular hypertrophy and decreased cardiomyocyte cross-sectional area and interstitial fibrosis in SHR to a greater extent than each agent alone (P < 0.05). Compared with WKY rats, the myocardial expression of RANKL, RANK, and OPG was increased. Both amlodipine and atorvastatin reduced RANKL, RANK, and OPG expression, with the best effects seen with the combination. Based on our results, activation of the RANKL/RANK/OPG system may be an important factor leading to ventricular remodeling in SHR rats. Amlodipine and atorvastatin could improve ventricular remodeling in SHR rats through intervention with the RANKL/RANK/OPG system.

Cardiac hypertrophy is exacerbated in aged mice lacking the osteoprotegerin gene

AIMS

Osteoprotegerin (OPG) may play a role in the progression of cardiac hypertrophy and heart failure. However, its pathophysiological role in changes in cardiac structure and function with ageing remains to be elucidated.

METHODS AND RESULTS

We conducted experiments using 2.5- and 12-month-old OPG(-/-) mice and age-matched wild-type (WT) mice and compared the morphology and function of the left ventricle (LV). Both 2.5- and 12-month-old OPG(-/-) mice showed a higher systolic blood pressure and a greater heart weight/body weight ratio than age-matched WT mice. Twelve-month-old OPG(-/-) mice had a significantly larger LV chamber and reduced wall thickness compared with age-matched WT mice, and contractile function was decreased. The morphological differences were accompanied by an increase in the number of apoptotic cells and activation of tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) in the LV of 12-month-old OPG(-/-) mice. Correspondingly, OPG small interfering RNA induced the expressions of TRAIL and cleaved caspase-3 in cultured cardiac myocytes. In addition, these mice revealed a decrease in interstitial fibrosis, activation of matrix metalloproteinase (MMP)-2 and tissue inhibitors of MMP-1 and -2, and inactivation of procollagen α1 synthesis. Moreover, intraperitoneal administration of recombinant OPG to either 2.5- or 12-month-old OPG(-/-) mice for 28 days led to partial improvement of LV structure and function without affecting systolic blood pressure.

CONCLUSION

These results suggest that OPG plays a role in preserving myocardial structure and function with ageing through a reduction in apoptosis and preservation of the matrix structure. In addition, this appears to be independent of effects on the vasculature.

Cardiovascular disease and type 1 diabetes: prevalence, prediction and management in an ageing population

Cardiovascular disease (CVD) is a major cause of mortality in type 1 diabetes mellitus (T1D). However, evidence of its risks and management is often extrapolated from studies in type 2 diabetic (T2D) patients or the general population. This approach is unsatisfactory given that the underlying pathology, demographics and natural history of the disease differ between T1D and T2D. Furthermore, with a rising life expectancy, a greater number of T1D patients are exposed to the cardiovascular (CV) risk factors associated with an ageing population. The aim of this review is to examine the existing literature around CVD in T1D. We pay particular attention to CVD prevalence, how well we manage risk, potential biomarkers, and whether the studies included the older aged patients (defined as aged over 65). We also discuss approaches to the management of CV risk in the older aged. The available data suggest a significant CVD burden in patients with T1D and poor management of CV risk factors. This is underpinned by a poor evidence base for therapeutic management of CV risk specifically for patients with T1D, and in the most relevant population - the older aged patients. We would suggest that important areas remain to be addressed, particularly exploring the risks and benefits of therapeutic approaches to CVD management in the older aged.

Serum osteoprotegerin is associated with pulse pressure in kidney transplant recipients

Pulse pressure (PP) reflects increased large artery stiffness, which is caused, in part, by arterial calcification in patients with chronic kidney disease. PP has been shown to predict both cardiovascular and cerebrovascular events in various patient populations, including kidney transplant (KTX) recipients. Osteoprotegerin (OPG) is a marker and regulator of arterial calcification, and it is related to cardiovascular survival in hemodialysis patients. Here we tested the hypothesis that OPG is associated with increased pulse pressure. We cross-sectionally analyzed the association between serum OPG and PP in a prevalent cohort of 969 KTX patients (mean age: 51 +/- --13 years, 57% male, 21% diabetics, mean eGFR 51 +/- 20 ml/min/1.73 m2). Independent associations were tested in a linear regression model adjusted for multiple covariables. PP was positively correlated with serum OPG (rho = 0.284, p < 0.001). Additionally, a positive correlation was seen between PP versus age (r = 0.358, p < 0.001), the Charlson Comorbidity Index (r = 0.232, p < 0.001), serum glucose (r = 0.172, p < 0.001), BMI (r = 0.133, p = 0.001) and serum cholesterol (r = 0.094, p = 0.003). PP was negatively correlated with serum Ca, albumin and eGFR. The association between PP and OPG remained significant after adjusting for multiple potentially relevant covariables (beta = 0.143, p < 0.001). We conclude that serum OPG is independently associated with pulse pressure in kidney transplant recipients.

Comparative effects of metformin and pioglitazone on fetuin-A and osteoprotegerin concentrations in patients with newly diagnosed diabetes: A randomized clinical trial

AIMS

Fetuin-A is a circulating glycoprotein capable of inhibiting insulin signaling both in vivo and in vitro and is positively associated with insulin resistance. Osteoprotegerin (OPG) acts as a regulatory molecule with increased levels in the early stages of diabetes and atherosclerosis, and is also associated with insulin resistance. We investigated the effects of pioglitazone and metformin as representative insulin-sensitizing therapies on fetuin-A and OPG levels.

MATERIALS AND METHODS

In a randomized clinical trial setting (NCT02027103), 88 patients with newly diagnosed type 2 diabetes were randomly assigned to pioglitazone (30 mg/day, n=46) or metformin (1000 mg/day, n=42) for 12 weeks. Various anthropometric and metabolic parameters, fetuin-A, OPG, highly sensitive C-reactive protein (hsCRP), and homeostasis model assessment of insulin resistance (HOMA-IR) were measured at baseline and after three months.

RESULTS

The reduction in fasting plasma glucose and haemoglobin A1c levels was comparable in the two arms. Pioglitazone resulted in a significant reduction in both fetuin-A and OPG in men, but only fetuin-A in women. Metformin was only effective in lowering OPG levels in women. When compared, both medications were equally effective with regard to fetuin-A and OPG reduction in women (p=0.413 and 0.359, respectively). In men, pioglitazone more effectively decreased fetuin-A levels in both uni- (p=0.011) and multivariate models (p=0.015) and OPG levels in only uni- (p=0.023) but not the multivariate model (p=0.547).

CONCLUSIONS

Metformin and pioglitazone differentially affect fetuin-A and osteoprotegrin levels in diabetic women and men. The level of change may not necessarily be associated with the amelioration of insulin resistance.

Osteoprotegerin is up-regulated in pancreatic cancers and correlates with cancer-associated new-onset diabetes

New-onset diabetes might help to yield biomarkers for the early diagnosis of pancreatic cancer (PaC). In this study, we computationally predicted and experimentally validated osteoprotegerin (OPG) being associated with pancreatic cancer related new-onset diabetes. We first performed a meta-analysis on microarray datasets to search for genes specifically highly expressed in PaC, and then filtered for cytokines involved in islet dysfunction. The expression of OPG in PaC and normal pancreas were validated by immunohistochemistry. Serum OPG levels in healthy controls, non-cancerous diabetes and PaC patients with or without diabetes were detected by enzyme-linked immunosorbent assay (ELISA). In silico assay found that OPG up-regulated in PaC tissues in comparison to normal pancreas. Immunohistochemical data further confirmed that OPG was overexpressed in PaC samples. Furthermore, increased expression of OPG in PaC tissues correlated to the occurrence of new-onset diabetes, and adversely affected the patients&apos; overall survival in both univariate and multivariate analysis. In addition, the serum levels of OPG were significantly higher in pancreatic cancer patients with new-onset diabetes than other groups including pancreatic patients without diabetes, new-onset type 2 diabetes and healthy controls. In conclusion, there is a close association between OPG and pancreatic cancer related new-onset diabetes, and OPG might serve as a potential biomarker for the early diagnosis of pancreatic cancer from populations with new-onset diabetes.

Prevalence and correlates of mitral annular calcification in adults with chronic kidney disease: Results from CRIC study

BACKGROUND

Risk factors for mitral annular calcification (MAC) and cardiovascular disease (CVD) demonstrate significant overlap in the general population. The aim of this paper is to determine whether there are independent relationships between MAC and demographics, traditional and novel CVD risk factors using cardiac CT in the Chronic Renal Insufficiency Cohort (CRIC) in a cross-sectional study.

METHODS

A sample of 2070 subjects underwent coronary calcium scanning during the CRIC study. Data were obtained for each participant at time of scan.

SUBJECTS

were dichotomized into the presence and absence of MAC. Differences in baseline demographic and transitional risk factor data were evaluated across groups. Covariates used in multivariable adjustment were age, gender, BMI, HDL, LDL, lipid lowering medications, smoking status, family history of heart attack, hypertension, diabetes mellitus, phosphate, PTH, albuminuria, and calcium.

RESULTS

Our study consisted of 2070 subjects, of which 331 had MAC (prevalence of 16.0%). The mean MAC score was 511.98 (SD 1368.76). Age and white race remained independently associated with presence of MAC. Decreased GFR was also a risk factor. African American and Hispanic race, as well as former smoking status were protective against MAC. In multivariable adjusted analyses, the remaining covariates were not significantly associated with MAC. Among renal covariates, elevated phosphate was significant.

CONCLUSION

In the CRIC population, presence of MAC was independently associated with age, Caucasian race, decreased GFR, and elevated phosphate. These results are suggested by mechanisms of dysregulation of inflammation, hormones, and electrolytes in subjects with renal disease.

Plasma osteoprotegerin concentrations in type 1 diabetic patients with albuminuria

BACKGROUND

Osteoprotegerin (OPG) is a recently identified inhibitor of bone resorption. Recent studies indicate that OPG is also associated with endothelial dysfunction in diabetes.

AIM

To investigate the relationship between plasma OPG levels and urinary albumin excretion (UAE) in type 1 diabetes.

METHODS

A total of 80 type 1 diabetic subjects and 40 control subjects were enrolled. Diabetic subjects were divided into a normoalbuminuric group and a microalbuminuric group according to urinary albumin excretion rate (UAER). Plasma OPG level was measured by enzyme-linked immunoassay.

RESULTS

The plasma OPG levels were significantly elevated in patients with microalbuminuria (176.39±25.05pg/ml) compared with patients with normoalbuminuria (154.73±16.66pg/ml) and control subjects (44.76±8.7pg/ml). The plasma OPG level had a positive correlation with patients' age, duration of disease, HbA1C and UAER.

CONCLUSIONS

Plasma OPG levels are significantly associated with UAE in patients with type 1 diabetes. These findings may support the concept that elevated plasma OPG may be associated with diabetic angiopathy.

Association of gene polymorphisms in RANKL/RANK/OPG system with hypertension and blood pressure in Chinese women

Recent studies have revealed that the receptor activator of nuclear factor-kappa B ligand/RANK/osteoprotegerin (RANKL/RANK/OPG) system has an important role in vascular calcification, which is contributory to various cardiovascular diseases and intimately linked to the regulation of blood pressure. Therefore, we performed a case-control study to investigate the associations of 21 single-nucleotide polymorphisms (SNPs) in the TNFSF11, TNFRSF11A and TNFRSF11B genes in the RANKL/RANK/OPG system with hypertension and blood pressure in post-menopausal Chinese women. In this study, 503 hypertensive patients and 509 normal controls were recruited. Genotyping was performed using the high-throughput Sequenom genotyping platform. The results showed that two SNPs (rs6567270 and rs4603673) in the TNFRSF11A were associated with hypertension (P=0.010 and P=0.013, respectively) and systolic blood pressure (P=0.024 and P=0.023, respectively). One SNP (rs9646629) in the TNFRSF11A showed significant association with diastolic blood pressure (P=0.031). The results of this study suggest that TNFRSF11A but not TNFSF11 and TNFRSF11B genetic variation is associated with hypertension and blood pressure in Chinese women. The findings provide additional support for the genetic role of RANKL/RANK/OPG system in hypertension and blood pressure regulation.

Long Term Effect of High Glucose and Phosphate Levels on the OPG/RANK/RANKL/TRAIL System in the Progression of Vascular Calcification in rat Aortic Smooth Muscle Cells

Osteoprotegerin (OPG), receptor activator of NF-κB ligand (RANKL)/receptor activator of NF-κB (RANK) axis, and TNF-related apoptosis-inducing ligand (TRAIL) participate in vascular calcification process including atherosclerosis, but their contributions under high glucose (HG) and phosphate (HP) condition for a long-term period (more than 2 weeks) have not been fully determined. In this study, we evaluated the effects of HG and HP levels over 2 or 4 weeks on the progression of vascular calcification in rat vascular smooth muscle cells (VSMCs). Calcium deposition in VSMCs was increased in medium containing HG (30 mmol/L D-glucose) with β-glycerophosphate (β-GP, 12 mmol/L) after 2 weeks and increased further after 4 weeks. OPG mRNA and protein expressions were unchanged in HG group with or without β-GP after 2 weeks. However, after 4 weeks, OPG mRNA and protein expressions were significantly lower in HG group with β-GP. No significant expression changes were observed in RANKL, RANK, or TRAIL during the experiment. After 4 weeks of treatment in HG group containing β-GP and rhBMP-7, an inhibitor of vascular calcification, OPG expressions were maintained. Furthermore, mRNA expression of alkaline phosphatase (ALP), a marker of vascular mineralization, was lower in the presence of rhBMP-7. These results suggest that low OPG levels after long term HG and phosphate stimulation might reduce the binding of OPG to RANKL and TRAIL, and these changes could increase osteo-inductive VSMC differentiation, especially vascular mineralization reflected by increased ALP activity during vascular calcification.

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.

RANKL-OPG and RAGE modulation in vascular calcification and diabetes: novel targets for therapy

Type 2 diabetes is associated with increased cardiovascular morbidity and mortality and early vascular ageing. This takes the form of atherosclerosis, with progressive vascular calcification being a major complication in the pathogenesis of this disease. Current research and drug targets in diabetes have hitherto focused on atherosclerosis, but vascular calcification is now recognised as an independent predictor of cardiovascular morbidity and mortality. An emerging regulatory pathway for vascular calcification in diabetes involves the receptor activator for nuclear factor κB (RANK), RANK ligand (RANKL) and osteoprotegerin (OPG). Important novel biomarkers of calcification are related to levels of glycation and inflammation in diabetes. Several therapeutic strategies could have advantageous effects on the vasculature in patients with diabetes, including targeting the RANKL and receptor for AGE (RAGE) signalling pathways, since there has been little success-at least in macrovascular outcomes-with conventional glucose-lowering therapy. There is substantial and relevant clinical and basic science evidence to suggest that modulating RANKL-RANK-OPG signalling, RAGE signalling and the associated proinflammatory milieu alters the natural course of cardiovascular complications and outcomes in people with diabetes. However, further research is critically needed to understand the precise mechanisms underpinning these pathways, in order to translate the anti-calcification strategies into patient benefit.

Osteoprotegerin CGA haplotype protection against cerebrovascular complications in anti-CCP negative patients with rheumatoid arthritis

Introduction

Rheumatoid arthritis is an inflammatory disease with high incidence of cardiovascular disease due to accelerated atherosclerosis. Osteoprotegerin (OPG) has been associated with increased risk of atherosclerotic disease in the general population. Several polymorphisms in the OPG gene with functional effects on cardiovascular disease in non-rheumatic individuals have been described. Therefore, we aimed to analyze the effect of three of these functional OPG polymorphisms on the risk of cardiovascular disease in a large and well-characterized cohort of Spanish patients with rheumatoid arthritis.

Methods

Three OPG gene variants (rs3134063, rs2073618 and rs3134069) were genotyped by TaqMan assays in 2027 Spanish patients with rheumatoid arthritis. Anti-cyclic citrullinated peptide (anti-CCP) antibody testing was positive in 997 of 1714 tested. Also, 18.3% of the whole series had experienced cardiovascular events, including 5.4% with cerebrovascular accidents. The relationship between OPG variants and cardiovascular events was assessed using Cox regression.

Results

No association between OPG gene variants and cardiovascular disease was observed in the whole group of rheumatoid arthritis patients or in anti-CCP positive patients. Nevertheless, a protective effect of CGA haplotype on the risk of cardiovascular disease in general, and specifically in the risk of cerebrovascular complications after adjusting for sex, age at disease diagnosis and traditional cardiovascular risk factors was disclosed in anti-CCP negative patients (HR = 0.54; 95%CI: 0.31–0.95; p = 0.032 and HR = 0.17; 95%CI: 0.04–0.78; p = 0.022, respectively).

Conclusion

Our results indicate a protective effect of the OPG CGA haplotype on cardiovascular risk, mainly due to a protective effect against cerebrovascular events in anti-CCP negative rheumatoid arthritis patients.

Osteoprotegerin is associated with subclinical left ventricular systolic dysfunction in diabetic hypertensive patients: a speckle tracking study

BACKGROUND

Recently, the role of osteoprotegerin (OPG) in the pathogenesis of heart failure through different mechanisms has received much attention. Subclinical changes in left ventricular (LV) function can be identified using quantification of myocardial strain, and global longitudinal strain (GLS) is a superior predictor of outcomes than ejection fraction. We hypothesized that increased OPG levels could predict subclinical LV systolic dysfunction in treated diabetic hypertensive patients with preserved LV ejection fraction.

METHODS

The study was composed of 86 diabetic hypertensive and 30 nondiabetic hypertensive patients. All patients underwent echocardiography and venous blood samples were taken for determination of OPG. The relation between OPG levels and LV GLS was investigated using 2-dimensional speckle tracking echocardiography.

RESULTS

Diabetic hypertensive patients had higher diastolic peak early/early diastolic tissue velocity and lower systolic tissue velocity, GLS, GLS rate systolic, and GLS rate early diastolic than nondiabetic hypertensive patients (P = 0.009, P = 0.049, P < 0.001, P = 0.004, and P < 0.001, respectively). Diabetic hypertensive patients were divided into 2 groups according to median GLS value (> 18.5 and ≤ 18.5). The patients with GLS ≤ 18.5 had higher diastolic blood pressure (mm Hg; P = 0.048), OPG (pmol/L; P < 0.001), and hemoglobin A1c (%; P = 0.042) values than those with GLS > 18.5. In multivariate logistic regression analysis, OPG was found to be an independent predictor of impaired GLS (P = 0.001). Receiver operating characteristic curve analysis revealed that OPG values of > 6.45 (pmol/L) identified the patients with GLS ≤ 18.5.

CONCLUSIONS

Plasma OPG values could predict subclinical LV systolic dysfunction in diabetic hypertensive patients.

Osteoprotegerin increases in metabolic syndrome and promotes adipose tissue proinflammatory changes

BACKGROUND

Inflammation is believed to link obesity to insulin resistance, as in the setting of metabolic syndrome (MetS). Osteoprotegerin (OPG) is a soluble protein that seems to exert proatherogenic and prodiabetogenic effects. This study aims at determining OPG levels in MetS and whether OPG might contribute to MetS development and progression.

METHODOLOGY/PRINCIPAL FINDINGS

Circulating OPG was measured in 46 patients with MetS and 63 controls, and was found significantly elevated in those with MetS. In addition, circulating and tissue OPG was significantly increased in high-fat diet (HFD) fed C57BL6 mice, which is one of the animal models for the study of MetS. To evaluate the consequences of OPG elevation, we delivered this protein to C57BL6 mice, finding that it promoted systemic and adipose tissue proinflammatory changes in association with metabolic abnormalities.

CONCLUSIONS/SIGNIFICANCE

These data suggest that OPG may trigger adipose tissue proinflammatory changes in MetS/HFD-induced obesity.

The osteoprotegerin/tumor necrosis factor related apoptosis-inducing ligand axis in the kidney

PURPOSE OF REVIEW

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a cytokine belonging to the TNF superfamily. TRAIL may modulate cell survival and proliferation through interaction with two different receptors, TRAIL-R1 and TRAIL-R2. The actions of TRAIL are regulated by three decoy receptors, TRAIL-R3, TRAIL-R4 and osteoprotegerin (OPG). There is evidence that both TRAIL and OPG are expressed by renal cells. The OPG/TRAIL axis has been recently linked to the pathogenesis of renal damage and, in particular, diabetic nephropathy.

RECENT FINDINGS

In patients with kidney diseases, serum TRAIL and OPG levels are increased in parallel and are significantly associated with each other. In diabetic nephropathy, the renal expression of TRAIL and OPG is elevated, and in tubular cells proinflammatory cytokines enhance TRAIL expression. Additionally, a high-glucose microenvironment sensitizes tubular cells to apoptosis induced by TRAIL, whereas OPG counteracts the actions of TRAIL in cultured cells.

SUMMARY

It seems that the expression and levels of TRAIL and OPG at serum and kidney levels are crucial for the pathogenesis of kidney diseases, and in particular diabetic nephropathy. Although further studies are necessary to clarify the exact role of the OPG/TRAIL axis in the kidney, this system seems to hold promise to provide therapeutic approaches for the management of renal damage.

VIDEO ABSTRACT AVAILABLE

See the Video Supplementary Digital Content 1 (http://links.lww.com/CONH/A5).

Osteoporosis, fractures, and diabetes

It is well established that osteoporosis and diabetes are prevalent diseases with significant associated morbidity and mortality. Patients with diabetes mellitus have an increased risk of bone fractures. In type 1 diabetes, the risk is increased by ∼6 times and is due to low bone mass. Despite increased bone mineral density (BMD), in patients with type 2 diabetes the risk is increased (which is about twice the risk in the general population) due to the inferior quality of bone. Bone fragility in type 2 diabetes, which is not reflected by bone mineral density, depends on bone quality deterioration rather than bone mass reduction. Thus, surrogate markers and examination methods are needed to replace the insensitivity of BMD in assessing fracture risks of T2DM patients. One of these methods can be trabecular bone score. The aim of the paper is to present the present state of scientific knowledge about the osteoporosis risk in diabetic patient. The review also discusses the possibility of problematic using the study conclusions in real clinical practice.

Osteoprotegerin and kidney disease

Vascular calcification in chronic kidney disease (CKD) patients is associated to increased mortality. Osteoprotegerin (OPG) is a soluble tumor necrosis factor (TNF) superfamily receptor that inhibits the actions of the cytokines receptor activator of nuclear factor kappa-B ligand (RANKL) and TNF-related apoptosis-inducing ligand (TRAIL) by preventing their binding to signaling receptors in the cell membrane. OPG-deficient mice display vascular calcification while OPG prevented calcification of cultured vascular smooth muscle cells and protected kidney cells from TRAIL-induced death. OPG may be a biomarker in patients with kidney disease. Circulating OPG is increased in predialysis, dialysis and transplant CKD patients and may predict vascular calcification progression and patient survival. By contrast, circulating OPG is decreased in nephrotic syndrome. In addition, free and exosome-bound urinary OPG is increased in human kidney disease. Increased urinary OPG has been associated with lupus nephritis activity. Despite the association of high OPG levels with disease, experimental functional information available suggests that OPG might be protective in kidney disease and in vascular injury in the context of uremia. Thus, tissue injury results in increased OPG, while OPG may protect from tissue injury. Recombinant OPG was safe in phase I randomized controlled trials. Further research is needed to fully define the therapeutic and biomarker potential of OPG in patients with kidney disease.

The relation between carotid intima media thickness and serum osteoprotegerin levels in nonalcoholic fatty liver disease

AIM

This study was designed to evaluate carotid intima media thickness (CIMT) and serum osteoprotegerin (OPG) levels in nonalcoholic fatty liver disease (NAFLD) in comparison to healthy controls and to investigate factors predicting the CIMT increase.

MATERIALS AND METHODS

A total of 60 outpatients [median (min-max) age 44.5 (24.0-65.0) years, 63.3% were females] diagnosed with NAFLD via ultrasonography performed during their admission to our hospital for any reason and 30 control subjects [median (min-max) age 39.5 (24.0-57.0) years, 73.3% were females] with normal liver echogenicity in ultrasonography were included in this study. Data on demographic characteristics, anthropometric measurements, biochemical and hematological tests, CIMT measurement, serum levels for OPG, and predictive factors for the CIMT increase were collected.

RESULTS

Median (min-max) CIMT [0.60 (0.40-1.10) vs. 0.50 (0.30-0.60), P<0.001) and OPG (pg/mL) [65.0 (18.1-272.8) vs. 32.0 (10.1-82.3), P<0.001] levels were significantly higher in NAFLD patients compared to controls, while there was a significant positive correlation between CIMT and serum OPG (r=0.42, P<0.001). Mean CIMT value was determined to increase significantly by 0.001 cm (P=0.001) for each 1 pg/mL of increase in OPG levels, by 0.103 cm (P<0.001) in case of concomitant NAFLD (P<0.001), and by 0.006 cm (P<0.001) for each 1 pg/mL of increase in urea levels.

CONCLUSION

Our findings indicate higher levels of serum OPG and CIMT in patients with NAFLD compared to controls along with a positive correlation between serum OPG and CIMT levels. High levels of serum OPG, presence of NAFLD, and high levels of serum urea seem to be the independent risk factors predictive for the CIMT increase.

TNFRSF11B polymorphisms are associated with metabolic traits in Uyghur and Han ethnic groups

Abstract Introduction: To test whether genetic variants of osteoprotegerin gene (TNFRSF11B) affect metabolic traits (body mass index [BMI], glucose, triglyceride, total cholesterol) and bone mass traits.

METHODS

We conducted a population based association study to investigate associations of eight tagging single nucleotide polymorphisms (tSNPs) of the TNFRSF11B gene with the aforementioned traits in a Chinese Han population and an ethnic group admixed with Caucasians and Asians - Uyghur. The associations between the tSNPs and bone mass density (BMD) were also tested in Han population.

RESULTS

We found that SNP rs3102727, located in the first intron of the TNFRSF11B gene, was significantly associated with triglyceride levels in Uyghur population and Han population simultaneously. T allele of the rs3102727 variant was associated with a 0.10 mmol/L and 0.09 mmol/L lower level of triglyceride than C allele in Uyghur (p = 0.019) and Han subjects (p = 0.037), respectively. In addition, the T allele is also associated with a lower level of hip BMD (p = 0.025) and total BMD (p = 0.048). Further, we found significant associations between SNP rs11573869 and BMI in Uyghur subjects and SNP rs3134062 with hip BMD in Han sbujects. Rs11573869-T allele was associated with a 0.81 kg/m(2) lower level of BMI than C allele (p = 0.002) and the hip BMD decreases with the copy of rs3134062-T allele increases (p = 0.002).

CONCLUSION

We detected novel associations between TNFRSF11B polymorphisms and metabolic traits in Uyghur and Han populations. In addition, we found associations between TNFRSF11B polymorphisms and bone mass traits in Han population.

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.

SNP rs2073618 of the osteoprotegerin gene is associated with diabetic retinopathy in Slovenian patients with type 2 diabetes

Recent studies indicate that osteoprotegerin (OPG) acts as an important regulatory molecule in the vasculature. Also, a strong association was observed between circulation OPG and microvascular complication. By considering the possible role of OPG in diabetic retinopathy (DR) we examined two of the most studied polymorphisms of the OPG genes rs2073618 (located in exon I) and rs3134069 (located in the promoter region) and their relation to DR in Slovenian patients with type 2 diabetes. Logistic regression analysis demonstrated that the carriers of the CC genotype had a 2.2 higher risk for DR than those with either the CG genotype or the GG genotype (codominant model for rs2073618). Furthermore, the combined effect of single nucleotide polymorphisms (SNPs) rs2073618 and rs3134069 on the DR was stronger than that of each SNP alone. The odds ratio (OR) for individuals with CC genotype (rs2073618) and AA genotype (rs3134069) compared with carriers of CG/GG (rs2073618) + AA (rs3134069) was 2.54 (95% CI = 1.26–5.13, P = 0.01). To conclude, these results indicate that SNPs in the OPG gene may be implicated in the pathogenesis of DR.