Changes of osteoprotegerin before and after insulin therapy in type 1 diabetic patients

Impact of the Rapid Normalization of Chronic Hyperglycemia on the Receptor Activator of Nuclear Factor-Kappa B Ligand and the Osteoprotegerin System in Patients Living with Type 2 Diabetes: RANKL-GLYC Study

The RANKL-GLYC study aims to explore the impact of the rapid correction of chronic hyperglycemia on the receptor activator of nuclear factor-kappa B ligand (RANKL) and its antagonist osteoprotegerin (OPG). RANKL and OPG are considered the main factors in the pathophysiology of Charcot neuroarthropathy, a devastating complication of the joints that remains poorly understood. The study began recruiting patients in September 2021 and ends in June 2022; the final study results are scheduled for January 2023.

The influence of vitamin D administration on the clinical presentation, body mass index, and osteoprotegerin (OPG) level in a sample of Egyptian children with familial Mediterranean fever

Background

Familial Mediterranean fever (FMF) is autosomal recessive chronic disease represents by recurring attacks of polyserositis, fever, and joint pain. Vitamin D deficiency in FMF children has been recently mentioned in literature and linked to delayed physical growth. Osteoporosis in FMF patients can be linked to low levels of vitamin D, too. Osteoprotegerin (OPG) might be used as an indicator for osteoporosis. Therefore, this work aimed to investigate the impact of vitamin D administration on clinical status, BMI, and bone mineral density represented by alterations in the OPG serum levels in a group of Egyptian children with FMF. This was a prospective longitudinal study carried out on 33 children, aged 4–16 years, with FMF cases. Patients were on colchicine 0.5–2 mg/day and received vitamin D3 oral drops 2800 IU/ml; each drop contains 100 IU in a dose of 600 IU/day for 6 months. The effect of vitamin D administration was evaluated clinically, anthropometrically and by assessment of serum vitamin D and osteoprotegerin at baseline and 6 months later.

Results

Serum vitamin D levels were below the normal range before intervention and showed significant improvement (p < 0.001) 6 months after intervention. Significant increase in both BMI Z scores (p < 0.05) and OPG serum levels and improvement in the clinical status as illustrated by significant decrease in the number of cases with fever, arthritis, and abdominal pain and significant decrease in the frequency and duration of the attacks (p < 0.001).

Conclusion

Our results intensely indicate that vitamin D supplementation improved the clinical condition, BMI, and bone mineral density in children with FMF.

Serum osteoprotegerin levels, endothelial function and carotid intima-media thickness in type 2 diabetic patients

OBJECTIVES

Osteoprotegerin (OPG), a well-known protein that inhibits osteoclast formation and activity, might also be a potential marker for identifying patients with high cardiovascular risk. This study aimed to compare OPG levels, FMD, and CIMT measurements in subjects with vs. without diabetes and investigate the association of serum osteoprotegerin level with the early atherosclerotic markers, endothelial function, and carotid intima-media thickness (CIMT) in patients with type 2 diabetes mellitus (DM2).

METHODS

Forty-nine patients with DM2 (F/M: 26/23, 49.3 ± 10.0 years) and 45 healthy volunteers (F/M: 26/19, 48.3 ± 7.5 years) were included in this cross-sectional study. Serum OPG levels were measured by solid-phase enzyme-linked immunosorbent assay (ELISA). Fasting plasma glucose (FPG) and HbA1c levels were measured. CIMT was measured by B-mode ultrasound, and endothelial function was evaluated via flow-mediated dilation (FMD) of the brachial artery with Doppler ultrasonography.

RESULTS

Serum OPG levels were significantly higher in patients with DM2 (617.0 ± 111.0 pg/mL) compared to controls (481.0 ± 96.0 pg/mL, p < 0.001). While CIMT in diabetic patients (0.65 + 0.13 mm) was higher than controls (0.54 ± 0.10 mm, p = 0.009), FMD measurement was lower in DM2 group (4.2% ± 3.1 mm vs. 7.6% ± 4.1 mm, p = 0.01). Univariate analysis showed that OPG was associated with the presence of diabetes (OR: 6.999, p = 0.001, R²: 15.1%) and hypertension (OR = 6.925, p = 0.001, R²: 13.2%). There was no relationship between OPG levels and CIMT or FMD.

CONCLUSION

Osteoprotegerin and CIMT levels were increased, and FMD measurements were decreased in patients with DM2. No association between CIMT, FMD, and OPG measurements was observed. The presence of DM and hypertension were associated with circulating OPG levels.

Acute Hyperinsulinemia Alters Bone Turnover in Women and Men With Type 1 Diabetes

Type 1 diabetes (T1D) increases fracture risk across the lifespan. The low bone turnover associated with T1D is thought to be related to glycemic control, but it is unclear whether peripheral hyperinsulinemia due to dependence on exogenous insulin has an independent effect on suppressing bone turnover. The purpose of this study was to test the bone turnover marker (BTM) response to acute hyperinsulinemia. Fifty‐eight adults aged 18 to 65 years with T1D over 2 years were enrolled at seven T1D Exchange Clinic Network sites. Participants had T1D diagnosis between age 6 months to 45 years. Participants were stratified based on their residual endogenous insulin secretion measured as peak C‐peptide response to a mixed meal tolerance test. BTMs (CTX, P1NP, sclerostin [SCL], osteonectin [ON], alkaline phosphatase [ALP], osteocalcin [OCN], osteoprotegerin [OPG], osteopontin [OPN], and IGF‐1) were assessed before and at the end of a 2‐hour hyperinsulinemic‐euglycemic clamp (HEC). Baseline ON (r = −0.30, p = .022) and OCN (r = −0.41, p = .002) were negatively correlated with age at T1D diagnosis, but baseline BTMs were not associated with HbA1c. During the HEC, P1NP decreased significantly (−14.5 ± 44.3%; p = .020) from baseline. OCN, ON, and IGF‐1 all significantly increased (16.0 ± 13.1%, 29.7 ± 31.7%, 34.1 ± 71.2%, respectively; all p < .001) during the clamp. The increase in SCL was not significant (7.3 ± 32.9%, p = .098), but the decrease in CTX (−12.4 ± 48.9, p = .058) neared significance. ALP and OPG were not changed from baseline (p = .23 and p = .77, respectively). Baseline ON and SCL were higher in men, but OPG was higher in women (all p ≤ .029). SCL was the only BTM that changed differently in women than men. There were no differences in baseline BTMs or change in BTMs between C‐peptide groups. Exogenous hyperinsulinemia acutely alters bone turnover, suggesting a need to determine whether strategies to promote healthy remodeling may protect bone quality in T1D. © 2020 American Society for Bone and Mineral Research © 2020 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

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.

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.

Intravascular haemolysis in severe Plasmodium knowlesi malaria: association with endothelial activation, microvascular dysfunction, and acute kidney injury

Plasmodium knowlesi occurs throughout Southeast Asia, and is the most common cause of human malaria in Malaysia. Severe disease in humans is characterised by high parasite biomass, reduced red blood cell deformability, endothelial activation and microvascular dysfunction. However, the roles of intravascular haemolysis and nitric oxide (NO)-dependent endothelial dysfunction, important features of severe falciparum malaria, have not been evaluated, nor their role in acute kidney injury (AKI). In hospitalised Malaysian adults with severe (n = 48) and non-severe (n = 154) knowlesi malaria, and in healthy controls (n = 50), we measured cell-free haemoglobin (CFHb) and assessed associations with the endothelial Weibel–Palade body (WPB) constituents, angiopoietin-2 and osteoprotegerin, endothelial and microvascular function, and other markers of disease severity. CFHb was increased in knowlesi malaria in proportion to disease severity, and to a greater extent than previously reported in severe falciparum malaria patients from the same study cohort. In knowlesi malaria, CFHb was associated with parasitaemia, and independently associated with angiopoietin-2 and osteoprotegerin. As with angiopoietin-2, osteoprotegerin was increased in proportion to disease severity, and independently associated with severity markers including creatinine, lactate, interleukin-6, endothelial cell adhesion molecules ICAM-1 and E-selectin, and impaired microvascular reactivity. Osteoprotegerin was also independently associated with NO-dependent endothelial dysfunction. AKI was found in 88% of those with severe knowlesi malaria. Angiopoietin-2 and osteoprotegerin were both independent risk factors for acute kidney injury. Our findings suggest that haemolysis-mediated endothelial activation and release of WPB constituents is likely a key contributor to end-organ dysfunction, including AKI, in severe knowlesi malaria.

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.

Does the OPG/RANKL system contribute to the bone-vascular axis in chronic kidney disease? A systematic review

Vascular calcification (VC) is highly prevalent in patients with chronic kidney disease (CKD) and is strongly associated with cardiovascular mortality and morbidity. Accumulating evidence over the past decade has challenged the hypothesis of close interaction between bone and VC what raises the possibility of a common underlying pathophysiological mechanism. Lately, bone regulatory proteins such as: osteoprotegerin (OPG) and Receptor Activator for Nuclear Factor κB Ligand (RANKL) has attracted attention of researchers as a possible key mediators of bone-vascular calcification imbalance. The literature search was carried out using the MEDLINE/PubMed database and a combination of keywords and MeSH terms, and only papers published since January 2005 to July 2016 were selected. The search resulted in 562 potential articles. After selection according to the eligibility criteria, 107 studies fulfilled were included (102 full texts and 5 was case reports). OPG and RANKL plays essential role in the regulation of bone metabolism and may be regarded as a possible link between VC, bone and mineral metabolism in CKD patients. Further studies are required to determine the diagnostic significance of these proteins in evaluation of progression and severity of VC process in CKD patients. Finally, the efficacy and safety, especially in regard to VC, of anti-RANKL therapy in CKD patients requires well-designed prospective, randomized trials.

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.

Higher levels of s-RANKL and osteoprotegerin in children and adolescents with type 1 diabetes mellitus may indicate increased osteoclast signaling and predisposition to lower bone mass: a multivariate cross-sectional analysis

Simultaneous lower bone mineral density, metabolic bone markers, parathyroid hormone (PTH), magnesium, insulin-like growth factor 1 (IGF1), and higher levels of total soluble receptor activator of nuclear factor-kappa B ligand (s-RANKL), osteoprotegerin (OPG), and alkaline phosphatase (ALP) are indicative of lower osteoblast and increased osteoclast signaling in children and adolescents with type 1 diabetes mellitus, predisposing to adult osteopenia and osteoporosis.

INTRODUCTION

Type 1 diabetes mellitus (T1DM) is a risk factor for reduced bone mass, disrupting several bone metabolic pathways. We aimed at identifying association patterns between bone metabolic markers, particularly OPG, s-RANKL, and bone mineral density (BMD) in T1DM children and adolescents, in order to study possible underlying pathophysiologic mechanisms of bone loss.

METHODS

We evaluated 40 children and adolescents with T1DM (mean ± SD age 13.04 ± 3.53 years, T1DM duration 5.15 ± 3.33 years) and 40 healthy age- and gender-matched controls (aged12.99 ± 3.3 years). OPG, s-RANKL, osteocalcin, C-telopeptide cross-links (CTX), IGF1, electrolytes, PTH, and total 25(OH)D were measured, and total body along with lumbar spine BMD were evaluated with dual energy X-ray absorptiometry (DXA). Multivariate regression and factor analysis were performed after classic inference.

RESULTS

Patients had significantly lower BMD, with lower bone turnover markers, PTH, magnesium, and IGF1 than controls, indicating lower osteoblast signaling. Higher levels of total s-RANKL, OPG, and total ALP were observed in patients, with log(s-RANKL) and OPG correlation found only in controls, possibly indicating increased osteoclast signaling in patients. Coupling of bone resorption and formation was observed in both groups. Multivariate regression confirmed simultaneous lower bone turnover, IGF1, magnesium, and higher total s-RANKL, OPG, and ALP in patients, while factor analysis indicated possible activation of RANK/RANKL/OPG system in patients and its association with magnesium and IGF1. Patients with longer disease duration or worse metabolic control had lower BMD.

CONCLUSIONS

T1DM children and adolescents have impaired bone metabolism which seems to be multifactorial. Reduced osteoblast and increased osteoclast signaling, resulting from multiple simultaneous disturbances, could lead to reduced peak bone accrual in early adulthood, predisposing to adult osteopenia and osteoporosis.

The effects of insulin and liraglutide on osteoprotegerin and vascular calcification in vitro and in patients with type 2 diabetes

OBJECTIVE

Vascular calcification (VC) is inhibited by the glycoprotein osteoprotegerin (OPG). It is unclear whether treatments for type 2 diabetes are capable of promoting or inhibiting VC. The present study examined the effects of insulin and liraglutide on i) the production of OPG and ii) the emergence of VC, both in vitro in human aortic smooth muscle cells (HASMCs) and in vivo in type 2 diabetes.

DESIGN/METHODS

HASMCs were exposed to insulin glargine or liraglutide, after which OPG production, alkaline phosphatase (ALP) activity and levels of Runx2, ALP and bone sialoprotein (BSP) mRNA were measured. A prospective, nonrandomised human subject study was also conducted, in which OPG levels and coronary artery calcification (CAC) were measured in a type 2 diabetes population before and 16 months after the commencement of either insulin or liraglutide treatment and in a control group that took oral hypoglycemics only.

RESULTS

Exposure to insulin glargine, but not liraglutide, was associated with significantly decreased OPG production (11 913±1409 pg/10(4) cells vs 282±13 pg/10(4) cells, control vs 10 nmol/l insulin, P<0.0001), increased ALP activity (0.82±0.06 IU/10(4) cells vs 2.40±0.16 IU/10(4) cells, control vs 10 nmol/l insulin, P<0.0001) and increased osteogenic gene expression by HASMCs. In the clinical study (n=101), insulin treatment was associated with a significant reduction in OPG levels and, despite not achieving full statistical significance, a trend towards increased CAC in patients.

CONCLUSION

Exogenous insulin down-regulated OPG in vitro and in vivo and promoted VC in vitro. Although neither insulin nor liraglutide significantly affected CAC in the present pilot study, these data support the establishment of randomised trials to investigate medications and VC in diabetes.

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.

Osteoprotegerin is independently associated with metabolic syndrome and microvascular complications in type 2 diabetes mellitus

AIMS

Osteoprotegerin (OPG) is a glycoprotein from tumour necrosis factor receptor superfamily, responsible for osteoclastogenesis inhibition and associated with arterial calcification and stiffness. We describe the association between metabolic syndrome (MS) and OPG in type 2 diabetes mellitus patients.

METHODOLOGY

We consecutively enrolled 1220 patients from our institution's Diabetes Centre from August 2011. Anthropometric data such as fasting blood/urine were obtained, and OPG was measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Mean (standard deviation (SD)) of age and diabetes duration was 57.4 (10.9) years and 11.2 (8.9) years, respectively. Prevalence of MS was 64.3% (95% confidence interval (CI): 61.3%-67.2%) and associated with significantly higher OPG (5.44 vs 4.47 pmol/L) and microvascular complications. The presence of microvascular complications was associated with higher OPG: nephropathy (5.54 (2.20) vs 4.65 (1.70) pmol/L, p < 0.0001), neuropathy (6.33 (2.64) vs 5.06 (1.91) pmol/L, p < 0.0001) and retinopathy (6.08 (2.47) vs 5.00 (1.95) pmol/L, p < 0.0001). After adjusting for age, gender, ethnicity, glucose and microvascular complications, OPG remained an independent predictor of MS: (odds ratio (OR) = 1.102 (95% CI: 1.015-1.196), p = 0.021).

CONCLUSION

Higher OPG levels were associated with risk of MS and microvascular complications. Studies are needed to test whether OPG could be a useful biomarker identifying patients at risk of vascular complications and whether further exploration of this pathway may lead novel therapeutic options.

Contrast agent suppresses endothelium-dependent arterial dilation after digital subtraction angiography procedure in patients with diabetic foot

Recent studies showed that contrast agents can induce renal injury. Thus, the present study was designed to assess whether the contrast agents used during digital subtraction angiography (DSA) procedure can damage endothelium. Fow-mediated endothelium-dependent vasodilation (FMD) was measured at baseline, 1, 3, and 7 days after DSA in 198 subjects with diabetic foot. We also measured the levels of thiobarbituric acid-reactive substances (TBARS) and von Willebrand factor (vWF), interleukin (IL)-6, tumor necrosis factor (TNF)-α, and C-reactive protein (CRP). Compared with baseline (3.60 ± 0.47 %), FMD at 1 day decreased (2.74 ± 0.47 %), and increased significantly from 1 to 3 days (p < 0.01), and returned to baseline level at 7 days after DSA. The plasma TBARS increased at 1 day and decreased from 1 to 3 days (p < 0.01), and returned to baseline level at 7 days after DSA. CRP, IL-6, and TNF-α had similar changes before and after DSA procedure. FMD was significantly correlated to vWF, IL-6, TNF-α, CRP, and TBARS (p < 0.01). A negative correlation between contrast volume and FMD, positive correlation between contrast volume and vWF, TBARS, CRP, IL-6 at 1 or 3 days after DSA exist in diabetic group (p < 0.05). Contrast medium suppresses FMD, probably through an increased production of oxygen-derived free radicals and inflammation although adequate hydration was given in type 2 diabetes. Therefore, an effective prophylaxis should allow to prevent this complication.

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.

Association of serum and vitreous concentrations of osteoprotegerin with diabetic retinopathy

BACKGROUND

Angiogenesis is involved in the pathogenesis of diabetic retinopathy. Osteoprotegerin, a recently identified glycoprotein belonging to the tumour necrosis factor receptor superfamily, has been implicated to be correlated with angiogenesis. This study aims to determine whether serum and vitreous concentrations of osteoprotegerin are associated with diabetic retinopathy.

METHODS

This study consisted of 254 diabetic patients (100 without diabetic retinopathy, 64 with non-proliferative diabetic retinopathy and 90 with proliferative diabetic retinopathy) and 62 control subjects. Serum and vitreous concentrations of osteoprotegerin were evaluated using enzyme-linked immunosorbent assay method.

RESULTS

Serum and vitreous osteoprotegerin concentrations in proliferative diabetic retinopathy patients were significantly elevated compared with those of the other three groups. Non-proliferative diabetic retinopathy patients showed elevated concentrations of serum and vitreous osteoprotegerin compared with patients without diabetic retinopathy. In addition, control subjects had significantly lower serum and vitreous osteoprotegerin concentrations compared with diabetic patients without retinopathy, non-proliferative diabetic retinopathy patients and proliferative diabetic retinopathy patients.

CONCLUSIONS

Serum and vitreous osteoprotegerin concentrations are associated with the presence and severity of diabetic retinopathy.

Comparison of osteoprotegerin and vascular endothelial growth factor in normoalbuminuric Type 1 diabetic and control subjects

BACKGROUND

The aim of the current study was to evaluate the association of osteoprotegerin and vascular endothelial growth factor (VEGF) with glycemic indices and diabetes status.

METHODS

A total of 44 normoalbuminuric Type 1 diabetic patients and 44 healthy control subjects, matched for age, body mass index, sex ratio, and lipid measures were enrolled. Univariate and multivariate logistic regression analyses were used to determine the association of osteoprotegerin and VEGF with diabetes status. Further, linear regression analysis was performed to investigate the roles of osteoprotegerin and VEGF as determinants of glycated hemoglobin (HbA1c).

RESULTS

Osteoprotegerin and VEGF were significantly elevated in diabetic subjects (2.76±0.85 vs 2.26±0.75 pmol/l and 187.1±92.7 vs 125.9±52.3 pg/ml, respectively, p<0.01) and were positively correlated with glycemic indices (i.e. fasting plasma glucose and HbA1c, p<0.001). After controlling for possible confounding factors, odds ratios (confidence interval) of osteoprotegerin and VEGF for diabetes were 2.532 (1.003-6.392) and 1.021 (1.002-1.041), respectively (p<0.05). Further, linear regression analysis revealed that the association of osteoprotegerin with HbA1c is independent of VEGF and vice versa (p<0.001).

CONCLUSION

Osteoprotegerin and VEGF are elevated in normoalbuminuric Type 1 diabetic subjects and are independently associated with glycemic indices and diabetes status.

The role of osteoprotegerin in cardiovascular disease

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

Receptor activator of nuclear factor-κB ligand (RANKL) and its relationship to coronary atherosclerosis in HIV patients

HIV-infected individuals have an increased prevalence of coronary artery disease. Receptor activator of nuclear factor-κB ligand (RANKL) and osteoprotegerin have been postulated as mediators of vascular calcification. 78 HIV-infected men and 32 healthy controls without history of coronary artery disease were prospectively recruited to undergo cardiac computed tomography and computed tomography angiography to assess coronary artery calcium and plaque burden. Soluble receptor activator of nuclear factor-κB ligand was lower in HIV-infected individuals than controls [2.52 (1.08-3.98) vs. 3.33 (2.44-4.64) pg/mL, P = 0.01, median (IQR) respectively]. Soluble receptor activator of nuclear factor-κB ligand was negatively associated with the number of coronary segments with plaque (Spearman ρ = -0.41, P < 0.001) and Agatston calcium score (ρ = -0.30, P < 0.01) in HIV-infected individuals even after adjusting for traditional cardiovascular risk factors.

Osteoprotegerin as a marker of atherosclerosis in diabetic patients

Atherosclerosis is the principal cause of cardiovascular disease (CVD) and has many risk factors, among which is diabetes. Osteoprotegerin (OPG) is a soluble glycoprotein, involved in bone metabolism. OPG is also found in other tissues, and studies have shown that it is expressed in vascular smooth muscle cells. OPG has been implicated in various inflammations and also has been linked to diabetes mellitus. Increased serum OPG levels were found in patients with diabetes and poor glycemic control. Furthermore, prepubertal children with type 1 diabetes have significantly increased OPG levels. Receptor activator of nuclear factor kappa-B ligand (RANKL) is not found in the vasculature in normal conditions, but may appear in calcifying areas. OPG and RANKL are important regulators of mineral metabolism in both bone and vascular tissues. Few data are available on the relationship between plasma OPG/RANKL levels and endothelial dysfunction as assessed using noninvasive methods like ultrasound indexes, neither in the general population nor, more specifically, in diabetic patients. The aim of our review study was to investigate, based on the existing data, these interrelationships in order to identify a means of predicting, via noninvasive methods, later development of endothelial dysfunction and vascular complications in diabetic patients.

Osteoprotegerin, Soluble Receptor Activator of Nuclear Factor- κ B Ligand, and Subclinical Atherosclerosis in Children and Adolescents with Type 1 Diabetes Mellitus

Aims. To evaluate carotid intima-media thickness (cIMT) and biomarkers of the osteoprotegerin/receptor activator of nuclear factor- κ B ligand (OPG/RANKL) system in type 1 diabetes (T1DM) children and adolescents and controls. Subjects and Methods. Fifty six T1DM patients (mean ± SD age: 12.0 ± 2.7 years, diabetes duration: 5.42 ± 2.87 years and HbA1c: 8.0 ± 1.5%) and 28 healthy matched controls, were studied with anthropometric and laboratory measurements, including serum OPG, soluble RANKL (sRANKL) and cIMT. Results. Anthropometric, laboratory, and cIMT measurements were similar between T1DM youngsters and controls. However patients with longer diabetes duration (>/7.0 years) had indicatively higher cIMT (cIMT = 0.49 vs 0.44 mm, P 0.072) and triglyceride levels than the rest of the patients (93.7 vs 64.6 mg/dl, P 0.025). Both in the total study population (β 0.418, P 0.027) and among T1DM patients separately (β 0.604, P 0.013), BMI was the only factor associated with cIMT. BMI was further associated with OPG in both groups (β -0.335, P 0.003 and β -0.356, P 0.008 respectively), while sRANKL levels were not associated with any factor. Conclusions. BMI was the strongest independent predictor of cIMT among the whole population, and especially in diabetics, suggesting a possible synergistic effect of diabetes and adiposity on atherosclerotic burden. BMI was overall strongly associated with circulating OPG, but the causes of this association remain unclear.

Comparison of osteoprotegerin to traditional atherosclerotic risk factors and high-sensitivity C-reactive protein for diagnosis of atherosclerosis

Atherosclerosis is the main cause of cardiovascular disease, but the extent of atherosclerosis in individual patients is difficult to estimate. A biomarker of the atherosclerotic burden would be very valuable. The aim of the present study was to evaluate the association of plasma osteoprotegerin (OPG) to clinical and subclinical atherosclerotic disease in a large community-based, cross-sectional population study. In the Copenhagen City Heart Study, OPG concentrations were measured in 5,863 men and women. A total of 494 participants had been hospitalized for ischemic heart disease or ischemic stroke, and compared to controls, this group with clinical atherosclerosis had higher mean OPG (1,773 vs 1,337 ng/L, p <0.001) and high-sensitivity C-reactive protein (2.3 vs 1.6 mg/L, p <0.001). In a multivariate model with age, gender, body mass index, hypertension, diabetes, hypercholesterolemia, smoking status, estimated glomerular filtration rate, high-sensitivity C-reactive protein, and OPG, OPG remained significantly associated with clinical atherosclerosis (p <0.01); high-sensitivity C-reactive protein, in contrast, did not (p = 0.74). In the control group without clinical atherosclerosis, OPG was independently associated with hypertension, diabetes, hypercholesterolemia, smoking, and subclinical peripheral atherosclerosis as measured by ankle brachial index. For each doubling of the plasma OPG concentration, the risk for subclinical peripheral atherosclerosis increased by 50% (p <0.001) after multivariate adjustment. In conclusion, OPG appears to be a promising biomarker of atherosclerosis that is independently associated with traditional risk factors of atherosclerosis, subclinical peripheral atherosclerosis, and clinical atherosclerotic disease such as ischemic heart disease and ischemic stroke.

Increased osteoprotegerin levels in women with previous gestational diabetes developing metabolic syndrome

Osteoprotegerin (OPG), a novel soluble member of tumour necrosis factor receptor superfamily, has been shown to link cardiovascular disorders. The aim of this study is to investigate the potential relationship between serum OPG levels, cardiovascular risk factors and metabolic syndrome in a relatively large group of women with previous GDM. In this cross-sectional case-control study, 128 women with previous GDM and 67 age-matched controls were enrolled. Subjects were evaluated for the diagnosis of metabolic syndrome according to the criteria of the American Heart Association (AHA). Fasting glucose, insulin, serum lipids, CRP and OPG were assayed. HOMA score was calculated. Carotid intima media thickness (IMT) was measured. There was no significant increase in OPG levels in women with previous GDM when compared to controls. On the other hand, women with previous GDM developing metabolic syndrome had higher OPG levels than those without metabolic syndrome and healthy controls. Serum OPG levels were associated with obesity, insulin resistance, serum CRP and carotid IMT. Serum OPG is related to cardiovascular risk factors and metabolic syndrome, and might be involved in the development of cardiovascular disorders in women with previous GDM.

Low serum osteoprotegerin levels in normoalbuminuric type 1 diabetes mellitus

The aim of this study is to establish whether abnormal mineral metabolism is present in patients with type 1 DM with normal renal function and in the absence of microalbuminuria. Serum levels of 1,25-dihydroxyvitamin D, osteoprotegerin (OPG) and receptor activator for nuclear factor kappa β ligand (RANKL) and other determinants of bone metabolism were measured in 35 patients with type 1 DM and in 25 age-, sex- and ethnicity-matched healthy controls. Serum OPG (1.98 vs. 2.98 pmol/l: P = 0.001), 1,25-dihydroxyvitamin D (41.1 vs. 48.2 pmol/l: P = 0.035) and magnesium (0.84 vs. 0.89 mmol/l P = 0.029) levels were significantly lower in patients with type 1 DM compared to normal controls. RANKL levels were similar in both groups. The groups did not differ with respect to calcium, phosphate, PTH, 25-hydroxyvitamin D, tubular reabsorption of phosphate and cross-linked N-telopeptides of type 1-collagen levels. Abnormalities of mineral metabolism including low serum OPG and 1,25-dihydroxyvitamin D levels occur in patients with type 1 DM with normal renal function and in the absence of microalbuminuria. These abnormalities may promote altered bone metabolism and vascular pathology.

Osteoprotegerin and biomarkers of vascular inflammation in type 2 diabetes

BACKGROUND

Osteoprotegerin (OPG), receptor activator for nuclear factor kappa beta ligand (RANKL) and tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) are newly discovered members of the tumour necrosis factor-alpha receptor superfamily. While their role in bone metabolism is well described, their function within the vasculature is poorly understood. OPG inhibits vascular calcification in vitro and high serum levels have been demonstrated in type 2 diabetes, but serum RANKL and TRAIL and their potential correlation with well-established biomarkers of subclinical vascular inflammation such as high-sensitivity C-reactive protein (hsCRP) and interleukin-6 (IL-6) have not been described.

METHODS

Sixty-two patients with well-controlled type 2 diabetes and an age, gender and body mass index-matched group of 58 healthy individuals were recruited. Serum OPG, RANKL and TRAIL were measured using commercial enzyme-linked immunosorbent assays, as were hsCRP and IL-6.

RESULTS

Serum OPG, IL-6 and hsCRP levels, but not RANKL or TRAIL, were higher in patients with type 2 diabetes mellitus than in healthy controls, after adjustment for age and gender. After exclusion of diabetes patients with a history of micro- or macrovascular disease, OPG remained significantly higher in those with diabetes, but IL-6 and hsCRP levels were no longer elevated. There was a positive correlation between OPG and IL-6 in the group as a whole, but no correlation was found between RANKL or TRAIL and either hsCRP or IL-6.

CONCLUSION

OPG, but not RANKL or TRAIL, is significantly increased in type 2 diabetes. Higher OPG (but not IL-6 or hsCRP) in those without vascular disease suggests these biomarkers reflect separate pathophysiological processes in the vasculature.

Osteoprotegerin as a predictor of coronary artery disease and cardiovascular mortality and morbidity

Osteoprotegerin (OPG) is a glycoprotein that acts as a decoy receptor for receptor activator of nuclear factor kappaB ligand (RANKL) and tumor necrosis factor-related apoptosis-inducing ligand. The OPG/RANKL/receptor activator of nuclear factor kappaB axis plays an important regulatory role in the skeletal, immune, and vascular systems. The protective role of OPG, in animal models, against vascular calcification has not been replicated in human trials; moreover, increased OPG levels have been consistently associated with the incidence and prevalence of coronary artery disease. There seems to be some dichotomy in the role of OPG, RANKL, and tumor necrosis factor-related apoptosis-inducing ligand in atherosclerosis and plaque stability. In this review, we integrate the findings from some of the important studies and try to draw conclusions with a view to gaining some insight into the complex interactions of the OPG/RANKL/receptor activator of nuclear factor kappaB axis and tumor necrosis factor-related apoptosis-inducing ligand in the pathophysiology of atherosclerosis.

Osteoprotegerin in relation to type 2 diabetes mellitus and the metabolic syndrome in postmenopausal women

Osteoprotegerin (OPG) is an inhibitor of bone resorption. Circulating levels of OPG seem to be elevated in patients with cardiovascular disorders and diabetes. The relationship between OPG and the metabolic syndrome has never been studied in postmenopausal women. In a population-based study, 382 Iranian postmenopausal women were randomly selected. Cardiovascular risk factors, high-sensitivity C-reactive protein, and OPG were measured. The diabetes classification and the metabolic syndrome definition were based on the criteria of the American Diabetes Association and the National Cholesterol Education Program-Adult Treatment Panel III, respectively. The mean serum OPG level was higher in those with type 2 diabetes mellitus than those without diabetes (4.33 +/- 1.70 vs 3.84 +/- 1.76 pmol/L, P = .016). In multiple logistic regression analysis, type 2 diabetes mellitus showed a significant association with serum OPG levels when adjustments were made for age, high-sensitivity C-reactive protein, and cardiovascular risk factors (odds ratio = 2.21; confidence interval, 1.34-3.66; P = .002). No significant difference was found between the mean serum OPG levels of those with the metabolic syndrome and those without the metabolic syndrome. Mean OPG levels did not differ significantly between subjects with and without hypertension, dyslipidemia, glucose intolerance, or abdominal obesity according to the National Cholesterol Education Program-Adult Treatment Panel III criteria. In conclusion, circulating OPG levels are significantly associated with diabetes, independent of cardiovascular risk factors in postmenopausal women. However, OPG levels have no correlation with the metabolic syndrome or its components. Further studies are warranted to determine the pathophysiologic origin of elevated OPG in type 2 diabetes mellitus.

Diabetic angiopathy, the complement system and the tumor necrosis factor superfamily

Among the most serious consequences of diabetes mellitus is the development of diabetic angiopathy, of which the clinical features are cardiovascular disease, retinopathy, nephropathy and neuropathy. Diabetic kidney problems affect up to one third of all patients with diabetes mellitus and are a major cause of end-stage renal failure. Although a huge number of pharmaceutical interventions are available today, diabetic angiopathy remains a leading cause of mortality and morbidity in diabetes mellitus, therefore, an urgent need exists to develop new therapeutic strategies. Recent data support the hypothesis that dysregulation of the complement system and of members of the tumor necrosis factor (TNF) superfamily may be involved in the development of diabetic vascular complications. The mannose-binding lectin pathway-an overall regulatory component of the complement system-is a particularly promising biomarker as it is directly involved in the development of diabetic angiopathy. In addition, two components of the TNF superfamily, namely TRAIL (tumor necrosis factor-related apoptosis-inducing ligand) and osteoprotegerin, may be involved in the pathogenesis of diabetic angiopathy. Several ways of specifically manipulating the complement and TNF superfamily systems already exist, but whether or not these drugs provide new targets for intervention for late diabetic complications is still to be revealed.

Plasma osteoprotegerin levels predict cardiovascular and all-cause mortality and deterioration of kidney function in type 1 diabetic patients with nephropathy

AIMS/HYPOTHESIS

The bone-related peptide osteoprotegerin is produced by vascular cells and is involved in the process of vascular calcification. The aim of this study was to investigate the predictive value of plasma levels of osteoprotegerin in relation to mortality, cardiovascular events and deterioration in kidney function in patients with type 1 diabetes.

METHODS

This prospective observational follow-up study included 397 type 1 diabetic patients with overt diabetic nephropathy (243 men; age [mean+/-SD] 42.1 +/- 10.6 years, duration of diabetes 28.3 +/- 9.9 years, GFR 67 +/- 28 ml min(-1) 1.73 m(2)) and a group of 176 patients with longstanding type 1 diabetes and persistent normoalbuminuria (105 men; age 42.6 +/- 9.7 years, duration of diabetes 27.6 +/- 8.3 years).

RESULTS

The median (range) follow-up period was 11.3 (0.0-12.9) years. Among patients with diabetic nephropathy, individuals with high osteoprotegerin levels (fourth quartile) had significantly higher all-cause mortality than patients with low levels (first quartile) (covariate-adjusted hazard ratio [HR] 3.00 [1.24-7.27]). High osteoprotegerin levels also predicted cardiovascular mortality (covariate-adjusted HR 4.88 [1.57-15.14]). Furthermore, patients with high osteoprotegerin levels had significantly higher risk of progression to end-stage renal disease than patients with low levels (covariate-adjusted HR 4.32 [1.45-12.87]). In addition, patients with high levels of plasma osteoprotegerin had an elevated rate of decline in GFR.

CONCLUSIONS/INTERPRETATION

High levels of osteoprotegerin predict all-cause and cardiovascular mortality in patients with diabetic nephropathy. Furthermore, high levels of osteoprotegerin predict deterioration of kidney function towards end-stage renal disease.

The causes of the Charcot syndrome

The Charcot syndrome is a rare complication of neuropathy in diabetes and is characterized by an acute inflammatory episode of the foot that is associated with variable degrees of dislocation, fracture, and deformity. It has no single cause but represents the final common pathway in people who are predisposed to its development by the varying overlap of several different factors. The association of the active phase of the disease with inflammation, increasing osteopenia, and increasing calcification of the arterial walls strongly suggests, however, the involvement of the receptor activator of nuclear factor-kappaB ligand (RANKL)/osteoprotegerin (OPG) cytokine pathway, which is closely involved in all three processes. The evidence for increased expression of RANKL and OPG in diabetes and neuropathy as well as its potential significance is reviewed.