Osteoprotegerin is associated with silent coronary artery disease in high-risk but asymptomatic type 2 diabetic patients

Does Improvement of Glycemic Control Cause Acute Charcot Foot in Patients with Diabetes?

Recent studies have suggested that improved glycemic control in patients with diabetes may cause acute Charcot foot. To conduct a narrative review of studies investigating whether improved glycemic control in patients with diabetes causes acute Charcot foot.Publications found by searching PubMed, EMBASE, and Cochrane Library as well as reference lists of identified publications were reviewed.Very few publications were found, primarily consisting of case reports and case studies without control groups, documenting instances where cases of acute Charcot foot had been preceded by improved glycemic control. Recent large multicenter randomized placebo-controlled clinical trials of anti-hyperglycemic agents in patients with diabetes, where significant improvement of glycemic control occurred, have not reported incidences of acute Charcot foot.There is so far no solid evidence to suggest that improvement of glycemic control in patients with diabetes causes acute Charcot foot.

Osteoprotegerin/Receptor Activator of Nuclear Factor-Kappa B Ligand/Receptor Activator of Nuclear Factor-Kappa B Axis in Obesity, Type 2 Diabetes Mellitus, and Nonalcoholic Fatty Liver Disease

PURPOSE OF REVIEW

To summarize evidence on the potential involvement of the osteoprotegerin (OPG)/receptor activator of nuclear factor-kappa B (NF-κΒ) ligand (RANKL)/receptor activator of NF-κΒ (RANK) axis in the pathogenesis of metabolic diseases.

RECENT FINDINGS

The OPG-RANKL-RANK axis, which has been originally involved in bone remodeling and osteoporosis, is now recognized as a potential contributor in the pathogenesis of obesity and its associated comorbidities, i.e., type 2 diabetes mellitus and nonalcoholic fatty liver disease. Besides bone, OPG and RANKL are also produced in adipose tissue and may be involved in the inflammatory process associated with obesity. Metabolically healthy obesity has been associated with lower circulating OPG concentrations, possibly representing a counteracting mechanism, while elevated serum OPG levels may reflect an increased risk of metabolic dysfunction or cardiovascular disease. OPG and RANKL have been also proposed as potential regulators of glucose metabolism and are potentially involved in the pathogenesis of type 2 diabetes mellitus. In clinical terms, type 2 diabetes mellitus has been consistently associated with increased serum OPG concentrations. With regard to nonalcoholic fatty liver disease, experimental data suggest a potential contribution of OPG and RANKL in hepatic steatosis, inflammation, and fibrosis; however, most clinical studies showed reduction in serum concentrations of OPG and RANKL. The emerging contribution of the OPG-RANKL-RANK axis to the pathogenesis of obesity and its associated comorbidities warrants further investigation by mechanistic studies and may have potential diagnostic and therapeutic implications.

miR-145 improves metabolic inflammatory disease through multiple pathways

Chronic inflammation plays a pivotal role in insulin resistance and type 2 diabetes, yet the mechanisms are not completely understood. Here, we demonstrated that serum LPS levels were significantly higher in newly diagnosed diabetic patients than in normal control. miR-145 level in peripheral blood mononuclear cells decreased in type 2 diabetics. LPS repressed the transcription of miR-143/145 cluster and decreased miR-145 levels. Attenuation of miR-145 activity by anti-miR-145 triggered liver inflammation and increased serum chemokines in C57BL/6 J mice. Conversely, lentivirus-mediated miR-145 overexpression inhibited macrophage infiltration, reduced body weight, and improved glucose metabolism in db/db mice. And miR-145 overexpression markedly reduced plaque size in the aorta in ApoE-/- mice. Both OPG and KLF5 were targets of miR-145. miR-145 repressed cell proliferation and induced apoptosis partially by targeting OPG and KLF5. miR-145 also suppressed NF-κB activation by targeting OPG and KLF5. Our findings provide an association of the environment with the progress of metabolic disorders. Increasing miR-145 may be a new potential therapeutic strategy in preventing and treating metabolic diseases such as type 2 diabetes and atherosclerosis.

Circulating Levels of Osteoprotegerin, Osteocalcin and Osteopontin in Patients with Rheumatoid Arthritis: A Systematic Review and Meta-Analysis

OBJECTIVE

Currently published data regarding the potential role of osteoprotegerin (OPG), osteocalcin (OCN) and osteopontin (OPN) for the discrimination between rheumatoid arthritis (RA) and osteoarthritis (OA) are contradictory. To derive a more precise evaluation, a meta-analysis was performed.

METHODS

Published literatures comparing plasma/serum OPG, OCN and OPN levels between RA group and OA controls were searched in PubMed, Embase and the Cochrane Library. The Newcastle-Ottawa Scale was used to assess the study quality. Pooled standard mean difference (SMD) with 95% confidence interval (CI) was calculated by random-effect model analysis. Heterogeneity test was performed by the Q statistic and quantified using I².

RESULTS

Nine studies including 438 RA patients and 255 OA patients were finally incorporated in the meta-analysis after examining title, type, abstracts and full text. The results showed that RA patients had higher plasma/serum OPN (pooled SMD = -2.57, 95% CI = -4.72 to -0.41) levels when compared to OA patients. No significant difference in plasma/serum OPG (pooled SMD = -0.29, 95% CI = -1.07‒0.49) and OCN (pooled SMD = -0.09, 95% CI = -0.48‒0.31) levels were found between RA patients and OA patients. Subgroup analysis indicated that plasma/serum OPG levels had no significant differences between RA patients and OA patients in Europe and Asian.

CONCLUSIONS

Overall, there is no significant difference in circulating OPG and OCN levels between RA patients and OA patients. However, plasma/serum OPN level is significantly higher in RA patients compared with OA patients.

The Role of Osteoprotegerin as a Cardioprotective Versus Reactive Inflammatory Marker: the Chicken or the Egg Paradox

Cardiovascular disease is one of the most frequent causes of mortality and morbidity worldwide. Several variables have been identified as risk factors for cardiovascular disease. Recently, the role of receptor activator of nuclear factor kappa B, receptor activator of nuclear factor kappa B ligand, and the osteoprotegerin system has been recognized as more important in the pathogenesis of cardiovascular disease. Besides their roles in the regulation of bone resorption, these molecules have been reported to be associated with the pathophysiology of cardiovascular disease. There are conflicting data regarding the impact of osteoprotegerin, a glycoprotein with a regulatory role in the cardiovascular system. The aim of this review is to discuss the current knowledge and the role of osteoprotegerin in cardiovascular disease.

Osteoprotegerin Disruption Attenuates HySu-Induced Pulmonary Hypertension Through Integrin αvβ3/FAK/AKT Pathway Suppression

BACKGROUND

Pulmonary arterial remodeling characterized by increased vascular smooth muscle proliferation is commonly seen in life-threatening disease, pulmonary arterial hypertension (PAH). Clinical studies have suggested a correlation between osteoprotegerin serum levels and PAH severity. Here, we aimed to invhestigate vascular osteoprotegerin expression and its effects on pulmonary arterial smooth muscle cell proliferation in vitro and in vivo, as well as examine the signal transduction pathways mediating its activity.

METHODS AND RESULTS

Serum osteoprotegerin levels were significantly elevated in patients with PAH and correlated with disease severity as determined by the World Health Organization (WHO) functional classifications and 6-minute walking distance tests. Similarly, increased osteoprotegerin expression was observed in the pulmonary arteries of hypoxia plus SU5416- and monocrotaline-induced PAH animal models. Moreover, osteoprotegerin disruption attenuated hypoxia plus SU5416-induced PAH progression by reducing pulmonary vascular remodeling, whereas lentiviral osteoprotegerin reconstitution exacerbated PAH by increasing pulmonary arterial smooth muscle cell proliferation. Furthermore, pathway analysis revealed that osteoprotegerin induced pulmonary arterial smooth muscle cell proliferation by interacting with integrin α_vβ₃ to elicit downstream focal adhesion kinase and AKT pathway activation.

CONCLUSIONS

Osteoprotegerin facilitates PAH pathogenesis by regulating pulmonary arterial smooth muscle cell proliferation, suggesting that it may be a potential biomarker and therapeutic target in this disease.

Evolution of silent myocardial ischaemia prevalence and cardiovascular disease risk factor management in Type 2 diabetes over a 10-year period: an observational study

AIMS

To assess the evolution of silent myocardial ischaemia prevalence and of cardiovascular disease risk factor management over 10 years in people with Type 2 diabetes.

METHODS

This repeated cross-sectional study prospectively included 770 people with Type 2 diabetes who presented at our centre in the period 1999-2009. All had at least one additional cardiovascular disease risk factor, no history of coronary disease and were screened for silent myocardial ischaemia using myocardial perfusion imaging. The prevalence of silent myocardial ischaemia, clinical and biological variables and treatments were collected and compared among participants screened in three periods: 1999 to 2002; 2003 to 2005; and 2006 to 2009. We also identified predictive factors for silent myocardial ischaemia.

RESULTS

Participants had a mean ± sd age of 62.3 ± 9.3 years, 57.4% were men and the mean time from diagnosis of diabetes was 13.4 ± 9.3 years. Overall, silent myocardial ischaemia screening was positive in 13.9% of participants. This prevalence decreased sharply over the 10-year study period (22.6% in 1999-2002, 13.7% in 2003-2005 and 5.9% in 2006-2009; P<0.0001). In parallel, diastolic and systolic blood pressure, HbA_1c and LDL cholesterol significantly decreased and glitazone and statin use increased (all P<0.001). Male gender, peripheral artery disease, diastolic blood pressure >80 mmHg and LDL cholesterol >2.6 mmol/l were independently associated with silent myocardial ischaemia. Further adjustment showed the screening period had a significant effect, which erased the effects of diastolic blood pressure and LDL cholesterol.

CONCLUSIONS

The prevalence of silent myocardial ischaemia decreased sharply over time, and control of the main cardiovascular disease risk factors improved. Although the causality link cannot be established, the present study supports current recommendations advocating glycaemic control and intensive management of cardiovascular factors instead of systematic screening.

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.

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.

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 and sclerostin in chronic kidney disease prior to dialysis: potential partners in vascular calcifications

BACKGROUND

Osteoprotegerin (OPG), sclerostin and DKK1 constitute opposite bone turnover inhibitors, OPG inhibiting osteoclastogenesis while sclerostin and DKK1 exerting their inhibitory effects on osteoblastogenesis. Both proteins have been recognized as strong risk factors of vascular calcifications in non-dialysis chronic kidney disease (ND-CKD) patients. The aim of this study was to investigate the relationships between these inhibitors and coronary artery calcifications (CAC) in this population.

METHODS

A total of 241 ND-CKD patients [143 males; 69.0 (25.0-95.0) years; median estimated glomerular filtration rate using CKD-EPI 35.1 (6.7-120.1) mL/min/1.73 m(2)] were enrolled in this cross-sectional study. All underwent chest multidetector computed tomography for CAC scoring. OPG, sclerostin, DKK1 and mineral metabolism markers including PTH and bone alkaline phosphatase were measured. Logistic regression analyses were used to study the relationships between CAC and these markers.

RESULTS

Decline in renal function was associated with a significant increase in OPG and sclerostin while a slight but significant decrease in DKK1 was observed. The main crude associations with presence of CAC were a high level of OPG [OR = 2.55 95% confidence interval (95% CI) (1.35-4.82) for a level ranging from 6.26 to 9.15 pmol/L and OR = 5.74 95% CI (2.87-11.5) for a level ≥9.15 pmol/L; P < 0.0001] and a high level of sclerostin [OR = 2.64 95% CI (1.39-5.00) for a level ranging from 0.748 to 1.139 ng/mL and OR = 3.78 95% CI (1.96-7.31) for a level ≥1.139 ng/mL; P = 0.0002]. A logistic regression model clearly showed that the risk to present CAC was significantly increased when both OPG (≥6.26 pmol/L) and sclerostin (≥0.748 ng/mL) levels were high [crude model: OR = 11.47 95% CI (4.54-29.0); P < 0.0001; model adjusted for age, gender, diabetes, body mass index and smoking habits: OR = 5.69 95% CI (1.76-18.4); P = 0.02]. No association between DKK1 and presence of CAC was observed.

CONCLUSIONS

Our results strongly suggest that bone turnover inhibitors, OPG and sclerostin, are independently associated with CAC with potential additive effects in ND-CKD patients.

Role of plaque calcification regulators osteoprotegerin and matrix Gla-proteins in stable angina and acute myocardial infarction

AIM

To assess serum levels of the plaque calcification regulators osteoprotegerin (OPG) and Matrix Gla-proteins (MGP) in individuals with stable angina and acute myocardial infarction submitted to coronary angiography and their relation to coronary artery disease burden.

METHODS

The study included 40 individuals affected by ST-elevation myocardial infarction (STEMI) and 40 individuals with stable angina who all underwent coronary angiography, with evaluation of the extent of coronary artery disease by Syntax Score calculation and measurement of serum OPG and MGP levels. Osteoporosis was excluded by femoral and vertebral computerized bone mineralometry.

RESULTS

Serum OPG and MGP levels were respectively 3.87 ± 1.07 pmol/l and 6.80 ± 2.43 nmol/l in the stable angina group, 7.57 ± 1.5 pmol/l and 7.18 ± 1.93 nmol/l in the STEMI group (P < 0.01 and P = 0.33, respectively). Pearson correlation coefficient for OPG and Syntax Score, MGP and Syntax score was respectively 0.79 (P < 0.01) and 0.18 (P = 0.22) in the stable angina group, -0.03 (P = 0.43) and 0.10 (P = 0.5) in the STEMI group.Serum OPG and MGP levels were respectively 5.52 ± 1.02 pmol/l and 7.56 ± 1.42 nmol/l in diabetics, 4.3 ± 0.8 pmol/l and 6.52 ± 1.14 nmol/l in nondiabetics (P < 0.05; P < 0.05).

CONCLUSION

OPG, in a relatively small group of patients with stable angina, correlates proportionally with the extent of coronary artery disease (CAD), as evaluated by the Syntax Score. Higher serum OPG levels can be observed in individuals with STEMI regardless of CAD burden. As for MGP, a potential role as marker of plaque calcification remains unproven.

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.

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.

Association between osteoprotegerin gene polymorphisms and cardiovascular disease in type 2 diabetic patients

Osteoprotegerin (OPG) gene polymorphisms (T245G, T950C and G1181C) have been associated with osteoporosis and early predictors of cardiovascular disease. The aim of this study was to evaluate whether these polymorphisms contribute to cardiovascular disease (CVD) in type 2 diabetic patients. We performed a case-control study with 178 CVD subjects with diabetes and 312 diabetic patients without CVD to assess the impact of variants of the OPG gene on the risk of CVD. The OPG gene polymorphisms were analyzed by using the polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP). There was no significant association between the T245G and G1181C polymorphisms and CVD in the additive genetic model (OR = 0.96, 95% CI 0.64–1.45, p = 0.79; OR = 1.06, 95% CI 0.81–1.39, p = 0.65, respectively). However, the C allele of the T950C polymorphism was independently associated with a risk of CVD in type 2 diabetic patients in this genetic model (OR = 1.38, 95% CI 1.07–1.80, p = 0.01). This study provides evidence that the C allele of the T950C polymorphism is associated with increased risk of CVD in diabetic patients. However, well-designed prospective studies with a larger sample size are needed to validate these results.

The role of osteoprotegerin in cardiovascular disease

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Secretion patterns of circulating osteoprotegerin and response to acute and chronic energy deprivation in young healthy adults

INTRODUCTION

Osteoprotegerin (OPGN) is a bone-remodeling marker that is associated with various metabolic and vascular complications. Cross-sectional studies in humans have demonstrated an inverse association between leptin, a marker of energy sufficiency, and OPGN. The physiology of OPGN has not been fully elucidated to date. We thus aim to elucidate 1) whether OPGN levels exhibit any gender dimorphism or day/night secretion pattern; and 2) whether there is any effect of acute and/or chronic energy deprivation on its circulating levels and whether such effects are mediated through leptin.

MATERIALS AND METHODS

Study A: To evaluate OPGN secretion patterns and OPGN response to acute energy deprivation, we studied 12 healthy subjects under three different conditions for 72 h-in the isocaloric fed state, and during a fasting state with administration of either placebo or metreleptin in replacement doses. Blood samples were obtained every 15 min and pooled hourly during the last 24 h of the study. Study B: To evaluate the effect of chronic energy deprivation on OPGN secretion, we measured its levels in 14 obese subjects before and during weight loss after bariatric surgery.

RESULTS

OPGN levels exhibited a statistically significant (P < 0.01), albeit clinically limited in magnitude, day/night variation pattern in both genders (R(2) = 14.68%; 10.7-14.8% reduction with lower levels around 1600-1800 h; P < 0.01). Males had lower OPGN levels compared to females (1.81 ± 0.04 vs. 3.65 ± 0.07 pmol/liter; P < 0.001). Three days of fasting with either placebo or metreleptin administration did not change OPGN levels. OPGN levels did not change during bariatric surgery-induced weight loss.

CONCLUSIONS

OPGN levels are lower in men and exhibit a statistically significant, albeit clinically limited in magnitude, day/night secretion pattern. Neither acute nor chronic energy deprivation leading to significant weight loss has any effects on OPGN levels. Nomenclature Comment: Use of the terms "circadian" and "day/night variation" is meant as follows: Circadian pattern is a functional term that implies a rhythm that has been proven to be regulated by the innate circadian apparatus (anatomical and/or molecular). Conversely, day/night variation pattern is a descriptive term that refers to serum levels that vary during a day, usually in a periodic fashion. It is not known whether this variation is an innate property of the organ that secretes this hormone or whether it is determined by exogenous factors.

Bone biomarkers help grading severity of coronary calcifications in non dialysis chronic kidney disease patients

Background

Osteoprotegerin (OPG) and fibroblast growth factor-23 (FGF23) are recognized as strong risk factors of vascular calcifications in non dialysis chronic kidney disease (ND-CKD) patients. The aim of this study was to investigate the relationships between FGF23, OPG, and coronary artery calcifications (CAC) in this population and to attempt identification of the most powerful biomarker of CAC: FGF23? OPG?

Methodology/Principal Findings

195 ND-CKD patients (112 males/83 females, 70.8 [27.4–94.6] years) were enrolled in this cross-sectional study. All underwent chest multidetector computed tomography for CAC scoring. Vascular risk markers including FGF23 and OPG were measured. Logistic regression analyses were used to study the potential relationships between CAC and these markers.

The fully adjusted-univariate analysis clearly showed high OPG (≥10.71 pmol/L) as the only variable significantly associated with moderate CAC ([100–400[) (OR = 2.73 [1.03;7.26]; p = 0.04). Such association failed to persist for CAC scoring higher than 400. Indeed, severe CAC was only associated with high phosphate fractional excretion (FEPO₄) (≥38.71%) (OR = 5.47 [1.76;17.0]; p = 0.003) and high FGF23 (≥173.30 RU/mL) (OR = 5.40 [1.91;15.3]; p = 0.002). In addition, the risk to present severe CAC when FGF23 level was high was not significantly different when OPG was normal or high. Conversely, the risk to present moderate CAC when OPG level was high was not significantly different when FGF23 was normal or high.

Conclusions

Our results strongly suggest that OPG is associated to moderate CAC while FGF23 rather represents a biomarker of severe CAC in ND-CKD patients.

The role of serum osteoprotegerin and S-100 protein levels in patients with acute ischaemic stroke: determination of stroke subtype, severity and mortality

This study investigated correlations between mortality, stroke subtype and stroke severity with serum osteoprotegerin (OPG) and S-100 protein levels prior to the treatment of patients admitted to the emergency department and diagnosed with ischaemic stroke. Pretreatment serum samples were collected from patients (n = 90) to determine OPG and S-100 protein levels. Age- and sex-matched healthy individuals (n = 16) served as controls. Compared with controls, OPG and S-100 protein levels were significantly higher in the cardioembolic and atherothrombotic stroke groups. Within the stroke group, OPG levels were significantly higher in the cardioembolic and atherothrombotic stroke groups compared with the transient ischaemic attack (TIA) group. S-100 protein levels were significantly higher in the atherothrombotic stroke group than in the lacunar stroke and TIA groups, and in the cardioembolic stroke group compared with the lacunar stroke group. Serum OPG and S-100 protein levels were significantly higher in patients who died compared with survivors. In predicting stroke subtype and severity, although both OPG and S-100 protein levels were indicators, S-100 protein was more valuable for mortality prediction.

[Rheumatoid arthritis: a cardiovascular disease?]

Mortality in rheumatoid arthritis (RA) is doubled when compared to the general population. This excess in mortality can be explained in half of cases by cardiovascular (CV) events. The risk of myocardial infarction is increased by about 60% in RA. Mortality secondary to cerebrovascular stroke is increased by 50% even if the incidence of stroke is not increased. Indeed, the risk of fatal CV events is increased in RA when compared to the general population. The increased CV risk cannot be explained only by traditional CV risk factors, even if smoking and changes in lipid profile may be implied. It is mainly related to the chronic inflammatory condition that causes many metabolic disturbances. Other parameters such as treatments used in RA also play a role. Thus, it is essential for proper management of RA patients to be aware of this risk and to treat any modifiable CV risk factors.

Osteoprotegerin and coronary artery disease in type 2 diabetic patients with microalbuminuria

Objective

Plasma osteoprotegerin (P-OPG) is an independent predictor of cardiovascular disease in diabetic and other populations. OPG is a bone-related glycopeptide produced by vascular smooth muscle cells and increased P-OPG may reflect arterial damage. We investigated the correlation between P-OPG and coronary artery disease (CAD) in asymptomatic type 2 diabetic patients with microalbuminuria.

Methods

P-OPG was measured in 200 asymptomatic diabetic patients without known cardiac disease. Patients with P-NT-proBNP >45.2 ng/l and/or coronary calcium score (CCS) ≥400 were stratified as high risk of CAD (n = 133), and all other patients as low risk patients (n = 67). High risk patients were examined by myocardial perfusion imaging (MPI; n = 109), and/or CT-angiography (n = 20), and/or coronary angiography (CAG; n = 86). Significant CAD was defined by presence of significant myocardial perfusion defects at MPI and/or >70% coronary artery stenosis at CAG.

Results

Significant CAD was demonstrated in 70 of the high risk patients and of these 23 patients had >70% coronary artery stenosis at CAG. Among high risk patients, increased P-OPG was an independent predictor of significant CAD (adjusted odds ratio [CI] 3.11 [1.01-19.54] and 3.03 [1.00-9.18] for second and third tertile vs.first tertile P-OPG, respectively) and remained so after adjustments for NT-proBNP and CCS. High P-OPG was also associated with presence of >70% coronary artery stenosis(adjusted odds ratio 14.20 [1.35-148.92] for third vs. first tertile P-OPG), and 91% of patients with low (first tertile) P-OPG did not have >70% coronary artery stenosis.

Conclusions

Elevated P-OPG is an independent predictor of the presence of CAD in asymptomatic type 2 diabetic patients with microalbuminuria.

Association of plasma osteoprotegerin and adiponectin with arterial function, cardiac function and metabolism in asymptomatic type 2 diabetic men

BACKGROUND

Osteoprotegerin (OPG), a soluble member of the tumor necrosis factor receptor superfamily, is linked to cardiovascular disease. Negative associations exist between circulating OPG and cardiac function. The adipocytokine adiponectin (ADPN) is downregulated in type 2 diabetes mellitus (T2DM) and coronary artery disease and shows an inverse correlation with insulin sensitivity and cardiovascular disease risk. We assessed the relationship of plasma OPG and ADPN and arterial function, cardiac function and myocardial glucose metabolism in T2DM.

METHODS

We included 78 asymptomatic men with uncomplicated, well-controlled T2DM, without inducible ischemia, assessed by dobutamine-stress echocardiography, and 14 age-matched controls. Cardiac function was measured by magnetic resonance imaging, myocardial glucose metabolism (MMRglu) by 18F-2-fluoro-2-deoxy-D-glucose positron emission tomography. OPG and ADPN levels were measured in plasma.

RESULTS

T2DM patients vs. controls showed lower aortic distensibility, left ventricular (LV) volumes, impaired LV diastolic function and MMRglu (all P < 0.05). In T2DM men vs. controls, OPG levels were higher (P = 0.02), whereas ADPN concentrations were decreased (P = 0.04). OPG correlated inversely with aortic distensibility, LV volumes and E/A ratio (diastolic function), and positively with LV mass/volume ratio (all P < 0.05). Regression analyses showed the associations with aortic distensibility and LV mass/volume ratio to be independent of age-, blood pressure- and glycated hemoglobin (HbA1c). However, the associations with LV volumes and E/A ratio were dependent of these parameters. ADPN correlated positively with MMRglu (P < 0.05), which, in multiple regression analysis, was dependent of whole-body insulin sensitivity, HbA1c and waist.

CONCLUSIONS

OPG was inversely associated with aortic distensibility, LV volumes and LV diastolic function, while ADPN was positively associated with MMRglu. These findings indicate that in asymptomatic men with uncomplicated T2DM, OPG and ADPN may be markers of underlying mechanisms linking the diabetic state to cardiac abnormalities.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN53177482.

Similar to adiponectin, serum levels of osteoprotegerin are associated with obesity in healthy subjects

An increase in serum osteoprotegerin (OPG) is associated with type 2 diabetes mellitus, the severity of vascular calcification, and coronary artery disease. Obesity is a risk factor for diabetes and cardiovascular disease, but little is known about the relationship between OPG and obesity. The purpose of this study was to determine if changes in body mass index (BMI) and insulin sensitivity influence circulating OPG in healthy subjects. A total of 100 subjects (36 lean, 41 overweight, and 23 obese) with normal glucose tolerance, blood pressure, and electrocardiogram stress test result volunteered for this study. Insulin sensitivity was estimated using a 2-hour oral glucose tolerance test with oral glucose insulin sensitivity analysis. Osteoprotegerin, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL),soluble receptor activator of nuclear factor-κβ ligand (sRANKL), and adiponectin were analyzed using commercially available enzyme-linked immunosorbent assays. Osteoprotegerin (P < .01) and adiponectin (P < .001) were significantly decreased in the obese compared with lean subjects. There was no significant difference between BMI categories for TRAIL or sRANKL. Controlling for age and sex, there was a significant correlation between OPG and adiponectin (r = 0.391, P < .001), BMI (r = -0.331, P < .001), waist circumference (r = -0.268, P < .01), homeostasis model assessment of insulin resistance (r = -0.222, P < .05), and oral glucose insulin sensitivity (r = 0.221, P < .05). Both OPG and adiponectin were negatively correlated with body weight, BMI, waist circumference, and fasting plasma insulin while being positively correlated with insulin sensitivity (P < .05). Controlling for age, sex, and BMI, TRAIL was positively related to fat mass (r = 0.373, P < .001) and waist circumference (r = 0.257, P < .05). In contrast to patients with type 2 diabetes mellitus, circulating OPG is lower in obese, but otherwise healthy subjects and is positively correlated with indices of insulin sensitivity.

Relationship between serum osteoprotegerin, glycemic control, renal function and markers of atherosclerosis in type 2 diabetes

We aimed to investigate the relationship between serum osteoprotegerin (OPG) level and glycemic control, lipids, renal function, microalbuminuria, insulin resistance and markers of atherosclerosis including C-reactive protein (CRP), fibrinogen and erythrocyte sedimentation rate (ESR) in patients with type 2 diabetes mellitus (DM). A total of 166 patients (99 women and 67 men) with type 2 DM were recruited in the study. Serum OPG level was higher in poorly controlled diabetic patients (HbA(1c) ≥ 7%) than in well-controlled diabetic patients (HbA(1c) < 7%) [4.0 (3.6-5.0) and 3.5 (2.9-4.4) pmol/L, p = 0.02]. There was no difference between the patients with and without microalbuminuria with respect to OPG levels (p > 0.05). LogOPG was correlated with age (r = 0.47, p = 0.0001). After adjustment for age, sex and BMI, logOPG correlated positively with fasting blood glucose (FBG) (r = 0.28, p = 0.001), prandial blood glucose (PBG) (r = 0.22, p = 0.009), glycated hemoglobin (HbA(1c)) (r = 0.26, p = 0.002), logHOMA-IR (r = 0.30, p = 0.006), fibrinogen (r = 0.17, p = 0.04), mean albumin excretion rate (MAER) (r = 0.20, p = 0.01) and negatively with creatinine clearance (r = - 0.20, p = 0.01). Regression analysis revealed that logOPG was independently associated with age (p = 0.0001), HbA(1c) (p = 0.01) and MAER (p = 0.02) (r(2) = 0.25). In conclusion; we found that serum OPG levels are increased in poorly controlled type 2 DM and associated with age, glycemic control and microalbuminuria.

Effect of pioglitazone on serum concentrations of osteoprotegerin in patients with type 2 diabetes mellitus

OBJECTIVE

Osteoprotegerin (OPG) acts as an important regulatory molecule in atherosclerosis. Recent studies report that thiazolidinediones could affect OPG expression. We investigated the relationship between OPG and inflammatory cytokines and the effects of pioglitazone (a PPARγ (PPARG) agonist) versus metformin on serum OPG levels in type 2 diabetic patients.

DESIGN AND METHODS

Sixty-seven type 2 diabetic patients were included in this study. They were assigned to pioglitazone (15 mg/day, n=34) or metformin (1000 mg/day, n=33) during 24 weeks. Various anthropometric and metabolic parameters, OPG, interleukin 6 (IL6), C-reactive protein (CRP), adiponectin, and homeostasis model assessment of insulin resistance (HOMA-IR), were measured at baseline and at 6 months of treatment.

RESULTS

Serum OPG levels correlated significantly with fasting plasma glucose (FPG), HbAlc, HOMA-IR, IL6, and CRP, and inversely correlated with adiponectin after adjusting for age (P<0.05). Multiple regression analysis showed that FPG, HbAlc, and adioponectin were independently correlated with OPG level. After 6 months of treatment, the reduction in FPG and HbAlc levels was similar between the two groups. Pioglitazone treatment significantly increased body mass index (P<0.05) and waist circumference (P<0.05) and decreased triglycerides (P<0.05) and HOMA-IR (P<0.01). The adiponectin concentration was increased (P<0.05), and OPG and CRP levels were decreased in the pioglitazone group (P<0.05), but were unchanged in the metformin group. The changes in serum OPG in the pioglitazone group showed significant correlation with changes in FPG, HbAlc, and adiponectin.

CONCLUSIONS

In type 2 diabetic patients, pioglitazone decreases OPG levels, and this decrease in OPG levels might be associated with the increase in adiponectin.

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.

Fetuin-mineral complex reflects extraosseous calcification stress in CKD

Fetuin-A is an important inhibitor of extraosseous calcification, but some of the studies that used ELISAs did not identify a significant relationship between serum fetuin-A levels and vascular calcification in patients with chronic kidney disease (CKD). Here, we used centrifugation to separate a fetuin-mineral complex (FMC) composed of fetuin-A, fibrinogen, fibronectin-1, and calcium from the serum of hemodialysis patients. In addition, we analyzed serum fetuin-A levels of 73 patients with diabetes and CKD (predialysis) after centrifugation. Fetuin-A concentrations were significantly lower in supernatants than in serum from patients at any stage of CKD, indicating systemic circulation of FMC in these patients. With greater severity of CKD, the contribution of FMC to total fetuin-A increased. Despite the absence of a correlation between serum fetuin-A and coronary artery calcification scores (CACS), supernatant fetuin-A negatively correlated with CACS and the extent to which centrifugation reduced fetuin-A (reduction ratio [RR]) positively correlated with CACS. In a longitudinal study of 12 hemodialysis patients with secondary hyperparathyroidism, parathyroidectomy and cinacalcet therapy each significantly reduced the RR without changing supernatant fetuin-A levels after 1 month, suggesting a reduction in FMC. Moreover, the magnitude of cinacalcet-induced reduction in parathyroid hormone correlated with the decrease in RR but not with changes in serum or supernatant fetuin-A. These data suggest that a quantitative measure of FMC, not supernatant or serum fetuin-A as measured in previous studies, reflects extraosseous calcification stress.

Lovastatin raises serum osteoprotegerin level in people with type 2 diabetic nephropathy

OBJECTIVES

Osteoprotegerin (OPG), a glycoprotein, is a member of the tumor necrotizing factor alpha receptor super-family. By considering the possible role of OPG in cardiovascular disease (CVD), higher incidence of CVD in people with type 2 diabetic nephropathy (T2DN), and anti-atherosclerotic effects of statins, the present study aimed to investigate the effects of lovastatin on serum levels of OPG and soluble receptor activator of nuclear factor-κB ligand (sRANKL) in people with T2DN.

DESIGN AND METHODS

Thirty patients completed the study course, out of 38 adult male patients with T2DN who were initially enrolled. Lovastatin, 20mg/d, was administered for 90 days. Afterwards, lovastatin was withdrawn for the next 30 days. Serum levels of OPG and sRANKL were measured using commercial ELISA kits at baseline, after 90 days of intervention, and after 30 days of withdrawal of lovastatin.

RESULTS

Serum level of OPG was significantly increased (10.76 ± 16.44) and decreased (-7.38 ± 11.98) during 90 days of intervention and 30 days of withdrawal periods, respectively, while, sRANKL level was significantly decreased (-1192.08 ± 578.20) and increased (4418.67 ± 2124.66) during the same periods, respectively.

CONCLUSIONS

Lovastatin therapy increased serum OPG level and decreased sRANKL level in people with T2DN. The withdrawal of lovastatin decreased serum OPG level, while sRANKL level was extensively increased.

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.

TNF-alpha modulates the migratory response of mesenchymal stem cells to TRAIL

The number of circulating mesenchymal stem cells (MSC), analyzed after acute myocardial infarction (AMI), was lower in AMI patients who developed heart failure (HF) in the follow-up. Conversely, the circulating levels of tumor necrosis factor (TNF)-alpha, and osteoprotegerin (OPG) were higher in AMI patients who developed HF with respect to the patients who did not develop HF. In vitro exposure to TNF-alpha enhanced the migration of MSC in response to TNF-related apoptosis-inducing ligand (TRAIL) and significantly increased the release of OPG by endothelial cells. On the contrary, OPG dose-dependently neutralized the in vitro pro-migratory activity of TRAIL. Thus, TNF-alpha exhibits opposite effects on MSC migration driven by TRAIL: it is capable of potentiating MSC migration as well as of inhibiting MSC migration as an indirect consequence of OPG induction, which might result in a suboptimal recruitment of circulating MSC after AMI in those patients who develop HF in the follow-up.

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.

Medial arterial calcification in diabetes and its relationship to neuropathy

Calcification of the media of arterial walls is common in diabetes and is particularly associated with distal symmetrical neuropathy. Arterial calcification also complicates chronic kidney disease and is an independent risk factor for cardiovascular and all-cause mortality. The term calcification is not strictly accurate because the morphological changes incorporate those of new bone formation, i.e. ossification. The processes are complex, but are closely related to those involved in bone homeostasis, and it is relevant that calcification of the arterial wall and osteopenia often co-exist. One particular factor linked to the development of arterial calcification is distal symmetrical neuropathy; indeed, it has been suggested that neuropathy explains the distal distribution of arterial calcification in diabetes. It has also been suggested that the link with neuropathy results from loss of neuropeptides, such as calcitonin gene-related peptide, which are inherently protective. The association between distal symmetrical neuropathy and calcification of the arterial wall highlights the fact that neuropathy may be an independent risk factor for cardiovascular mortality.

Evolution of coronary artery calcifications following kidney transplantation: relationship with osteoprotegerin levels

We prospectively assessed the evolution of coronary artery calcification (CAC) and osteoprotegerin (OPG) levels after renal transplantation (RT). Eighty-three recipients were followed-up prospectively during 1 year. Blood was collected before (baseline) and after RT for determination of mineral metabolism parameters including OPG. CAC was measured by multidetector computed tomography at transplantation (baseline) and 1 year later. Progression of CAC was defined as a difference between the follow-up square-root transformed volume (SRV) and the baseline SRV >or= 2.5. By multivariate analysis, baseline OPG level, age and low LDL levels were significantly associated with baseline CAC. RT was accompanied by mineral metabolism improvement with a decrease of OPG from 955 [395-5652] to 527 [217-1818] pg/mL and parathyroid hormone from 94 [1-550] to 62 [16-410] pg/mL. Thirty-one percent of patients did not exhibit CAC at baseline. CAC diminished in 14.5%, stabilized in 59.2% and progressed in 26.3% of patients. Baseline CAC was associated with progression (OR 2.92 [1.02-8.36]). No significant association was found between OPG and CAC progression despite a higher baseline OPG level in progressors (1046 [456-3285]) vs. non-progressors (899 [396-5952] pg/mL). CAC at baseline, but not 1 year after RT, is independently associated with baseline OPG; posttransplant CAC progression is predicted by baseline CAC score.

Myocardial ischemia, carotid, and peripheral arterial disease and their interrelationship in type 2 diabetes patients

BACKGROUND

Cardiovascular disease (CVD) is the leading cause of death in type 2 diabetes mellitus (T2DM) patients. We examined the relationship between CVD in different vascular territories.

METHODS

T2DM patients without known or suspected CVD (n = 305) referred consecutively to a diabetes clinic for the first time and age-matched nondiabetic reference subjects (n = 40) were screened for myocardial ischemia, carotid, and peripheral arterial disease by means of myocardial perfusion scintigraphy, carotid artery ultrasonography, and peripheral ankle and toe systolic blood pressure measurements.

RESULTS

In the T2DM patients, the prevalence of myocardial ischemia, carotid, and peripheral arterial disease was 30%, 42%, and 15%, respectively, almost three times higher than in the reference subjects (P = 0.007, P = 0.001, and P = 0.09, respectively). T2DM patients with myocardial ischemia, carotid, or peripheral arterial disease had a significantly increased risk of CVD in other vascular territories as well (OR: 1.99, 2.09, and 3.09, respectively). However, 40%, 52%, and 22% of the T2DM patients with myocardial ischemia, carotid, or peripheral arterial disease demonstrated exclusively this particular type of CVD manifestation.

CONCLUSIONS

In T2DM patients, signs of CVD in one vascular territory carry a significantly increased risk of CVD in other territories, although many patients only presented one manifestation.

Plasma osteoprotegerin is an independent risk factor for mortality and an early biomarker of coronary vascular calcification in chronic kidney disease

BACKGROUND

Cardiovascular disease is the major cause of morbidity and mortality in chronic kidney disease (CKD) and early biomarkers are required which can predict disease and death in such patients. The aim of our study was to investigate if osteoprotegerin (OPG) could be a predictor of coronary artery calcification (CAC) and mortality in CKD.

METHODS

A total of 77 outpatients (32 with pre-dialysis CKD and 45 undergoing hemodialysis) were followed-up during 2 years. Measurements of CAC were performed using Siemens Multidetector CT software and calcium scores were measured according to the Agatston method.

RESULTS

OPG was an independent predictor of the Agatston score for CAC and correlated with the degree of CAC in pre-dialysis patients. A two-sample t-test characterized survivors as having a better glomerular filtration rate, lower Agatston scores, and lower serum levels of OPG. Kaplan-Meier survival curves separated survivors from non-survivors at plasma OPG cut-off levels of <3.1 ng/mL. A multivariable logistic regression analysis showed that OPG was an independent predictor of mortality from all causes in CKD patients.

CONCLUSIONS

OPG predicted mortality in CKD patients and could be a valuable biomarker in early detection of CAC in these patients.

Associations of coronary artery calcification and carotid intima-media thickness with plasma concentrations of vascular calcification inhibitors in type 2 diabetic patients

Vascular calcification is frequently accompanied by intima-media thickening, but the associations among these atherosclerotic features and bone-related peptides in diabetic patients are unclear. We enrolled 168 type 2 diabetic patients and 40 non-diabetic subjects consecutively admitted to our hospital. Mean intima-media thickness (mean-IMT) in common carotid arteries was measured by B-mode ultrasonography. Agatston coronary artery calcium score (CACS) was obtained using multidetector-row computed tomography (MDCT). Plasma bone-related peptides osteopontin and osteoprotegerin levels were measured. Diabetic patients had higher mean-IMT (p=0.0002) and log(CACS+1) (p<0.0001) and similar bone-related peptides compared to non-diabetic subjects. In diabetic patients classified into tertiles according to their CACS levels, those with the highest scores showed the highest mean-IMT (p=0.0004) and bone-related peptides (p<0.05) among the groups. log(CACS+1) and mean-IMT were associated (p<0.0001) and were positively correlated with osteopontin (p<0.01) and osteoprotegerin (p<0.01) in diabetic patients. Multivariate analyses revealed that the significant independent determinants of log(CACS+1) were age, duration of diabetes and osteopontin (p<0.0001) and those of mean-IMT were age, hypertension, osteopontin and osteoprotegerin (p<0.0001), respectively. We have demonstrated that vascular calcification in type 2 diabetic patients is frequently accompanied by intima-media thickening, and osteopontin may act as a vascular calcification inhibitor by increasing intima-media thickness.

A cut-off value of plasma osteoprotegerin level may predict the presence of coronary artery calcifications in chronic kidney disease patients

BACKGROUND

Expression of bone proteins resulting from transdifferentiation of vascular smooth muscle cells into osteoblasts suggests that vascular calcifications are a bioactive process. Osteoprotegerin (OPG) could play a key role in bone-vascular calcification imbalance and could be a marker of vascular calcification extent and progression. The purpose of this study was to evaluate relationships between vascular risk biomarkers (including classic risk factors and OPG) and coronary artery calcification (CAC) extent in chronic kidney disease (CKD) patients and to establish within the markers the appropriate cut-off value to predict CAC.

METHODS

A total of 133 non-dialyzed CKD patients at various stages of kidney disease [75 males/58 females, median age: 69.9 (27.4-94.6)] were enrolled, excluding extrarenal replacement therapy patients. All underwent chest multidetector computed tomography for CAC scoring. Blood samples were collected for measurement of vascular risk markers (kidney disease, inflammation, nutrition, calcium phosphate and OPG). A potential relationship between CAC and these biological markers was investigated, and a receiver-operating characteristic (ROC) curve was designed thereafter to identify a cut-off value of involved markers that best predicted the presence of CAC.

RESULTS

After adjustment for age, diabetes, smoking and gender, among biological markers, only low-estimated glomerular filtration rate using Modification of Diet in Renal Disease [OR = 3.63 (1.10-12.02)], high FEPO(4) [OR = 3.99 (1.17-13.6)] and high OPG levels [OR = 8.54 (2.14-34.11)] were associated with the presence of CAC. A protective effect of 1.25(OH)(2) vitamin D [OR = 0.20 (0.05-0.79)] and LDL cholesterol [OR = 0.27 (0.08-0.94)] on CAC was also observed. ROC curve analysis showed that the OPG best cut-off value predicting CAC was 757.7 pg/mL.

CONCLUSION

These results suggest that a CAC increase is strongly associated with a plasma OPG increase in CKD patients. The values of OPG >757.7 pg/mL allow us to predict the presence of CAC in these patients.

Association of serum osteoprotegerin with ankle-brachial index and urine albumin: creatinine ratio in African-Americans and non-Hispanic whites

Osteoprotegerin (OPG), a member of tumor necrosis factor receptor superfamily, has been implicated in vascular disease. We investigated the association of serum OPG with the ankle-brachial index (ABI) and urine albumin:creatinine ratio (UACR), in a bi-ethnic cohort of 1324 African-Americans (mean age 64 years, 71% women) and 1237 non-Hispanic whites (mean age 59 years, 57% women) belonging to hypertensive sibships. Serum levels of OPG were measured by solid phase sandwich immunoassay. ABI was measured using a standard protocol and peripheral arterial disease (PAD) defined as ABI<0.90. UACR was expressed as mg albumin/gm creatinine. Multivariable regression analysis using generalized estimating equations (GEE) were performed to assess whether serum OPG levels were associated with ABI and UACR. After adjustment for conventional risk factors (age, sex, diabetes, waist circumference, history of smoking, total and HDL cholesterol, hypertension), prior history of myocardial infarction or stroke, and medication (renin-angiotensin-aldosterone system inhibitors, statins, aspirin, estrogen) use, higher OPG levels were significantly associated with lower ABI and higher UACR in African-Americans (P=0.001 and P<0.0001, respectively) and non-Hispanic whites (P=0.017 and P=0.002, respectively); the association remained significant after further adjustment for plasma C-reactive protein (CRP) in both ethnic groups. In multivariable logistic regression analysis, higher OPG levels were associated with PAD in African-Americans, independent of the covariates listed above (P=0.026); the association remained significant after additional adjustment for plasma CRP (P=0.047). In non-Hispanic whites, the association of higher OPG levels with PAD was of borderline significance after adjustment for the relevant covariates (P=0.106). We conclude that higher OPG levels are associated with lower ABI and higher UACR, independent of conventional risk factors and plasma CRP.

Association between plasma osteoprotegerin concentrations and urinary albumin excretion in Type 2 diabetes

AIMS

Osteoprotegerin (OPG) is a recently identified inhibitor of bone resorption. Recent studies indicate that OPG is also associated with endothelial dysfunction in Type 2 diabetes. The aim was to investigate the relationship between plasma OPG levels and urinary albumin excretion (UAE) in Type 2 diabetic patients.

METHODS

This study included 154 newly diagnosed Type 2 diabetic patients and 46 healthy subjects. Plasma OPG and 24-h UAE were measured. High-resolution ultrasound was used to measure flow-mediated (endothelium-dependent arterial) dilation (FMD).

RESULTS

Compared with the normoalbuminuric subgroup, OPG levels in the microalbuminuric subgroup were significantly higher, and OPG levels in macroalbuminuria subgroup were significantly higher than those in the normoalbuminuria and albuminuria subgroups. Multiple regression analysis showed that only FMD (r = -0.26), C-reactive protein (r = 0.23), fasting blood glucose (r = 0.25), 2-h blood glucose (r = 0.21), HbA(1c) (r = 0.28), UAE (r = 0.27) and retinopathy (r = 0.27) were significant factors associated with OPG. Pearson's correlation analyses showed a positive correlation between OPG and logUAE (r = 0.440) and negative correlations between OPG and FMD (r = -0.284), and between FMD and logUAE (r = -0.602).

CONCLUSIONS

Plasma OPG levels are significantly associated with UAE in Type 2 diabetic patients.

Effects of pravastatin on serum osteoprotegerin levels in patients with hypercholesterolemia and type 2 diabetes

Osteoprotegerin is a secretory glycoprotein. Recent experimental findings have suggested that osteoprotegerin may protect against vascular calcification and/or atherosclerosis. In humans, osteoprotegerin levels are positively correlated with the presence and severity of coronary artery disease and the progression of atherosclerosis. However, it is unclear how osteoprotegerin levels are regulated. Statins are known to have beneficial pleiotropic effects against atherosclerosis beyond their lipid-lowering effects. In this study, we examined whether treatment with pravastatin can alter osteoprotegerin levels in patients with hypercholesterolemia and type 2 diabetes. Osteoprotegerin levels were significantly increased from 6.64 +/- 2.18 pmol/L at baseline to 7.08 +/- 2.29 pmol/L (P = .024) after 3-month treatment with pravastatin. These increases in osteoprotegerin levels remained after 6 months of treatment (7.05 +/- 2.22 pmol/L, P = .026). These findings suggest that pravastatin may exert its pleiotropic effects in part through alteration of osteoprotegerin levels.

Serum osteoprotegerin is associated with carotid intima media thickness in women with previous gestational diabetes

Circulating levels of osteoprotegerin (OPG) have been shown to be increased in patients with cardiovascular disorders and diabetes. The aim of this study was to determine serum OPG levels in women with previous gestational diabetes (GDM), and to investigate the relationship between OPG and carotid intima media thickness (IMT) and circulating cardiovascular risk factors. Serum OPG was measured in 46 women with previous GDM and 30 age-matched healthy controls. Carotid IMT was evaluated. Serum lipid, insulin and hsCRP levels, plasma fibrinogen, vWF and PAI-1 levels were measured. Serum OPG levels tended to be increased in women with previous GDM (p=0.058). Carotid IMT was increased in the study group. Women with previous GDM had elevated levels of hsCRP and PAI-1. OPG levels were positively correlated with age, fasting and post-load glucose levels, hsCRP, and carotid IMT. Multiple regression analysis showed that serum OPG was a statistically significant predictor for elevated carotid IMT. Our results revealed that OPG levels tended to be elevated in women with previous GDM. Significant association of OPG with carotid IMT suggested that OPG might play a role in the pathogenesis of endothelial dysfunction in women with previous GDM.