Association of serum osteoprotegerin with vascular calcification in patients with type 2 diabetes

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.

Soluble CD14 and Osteoprotegerin Associate with Ankle-Brachial Index as a Measure of Arterial Stiffness in Patients with Mild-to-Moderate Chronic Kidney Disease in a Five-Year Prospective Study

INTRODUCTION

Vascular lesions and arterial stiffness appear at early stages of chronic kidney disease (CKD) and follow an accelerated course with disease progression, contributing to high cardiovascular mortality. There are limited prospective data on mechanisms contributing to progression of arterial stiffness in mild-to-moderate CKD (stages 2-3).

METHODS

We applied an affinity proteomics approach to identify candidates of circulating biomarkers with potential impact on vascular lesions in CKD and selected soluble cluster of differentiation 14 (sCD14), angiogenin (ANG), and osteoprotegerin (OPG) for further analysis. We studied their association with ankle-brachial index (ABI) and carotid intima-media thickness, as measures of arteriosclerosis and atherosclerosis, respectively, in 48 patients with CKD stages 2-3, who were prospectively followed and intensively treated for 5 years, and 44 healthy controls.

RESULTS

Concentrations of sCD14 (p < 0.001), ANG (p < 0.001), and OPG (p < 0.05) were higher in patients with CKD 2-3 at baseline, and sCD14 (p < 0.001) and ANG (p < 0.001) remained elevated in CKD patients at follow-up. There were positive correlations between ABI and sCD14 levels (r = 0.36, p = 0.01) and between ABI and OPG (r = 0.31, p = 0.03) at 5 years. The changes in sCD14 during follow-up correlated to changes in ABI from baseline to 5 years (r = 0.41, p = 0.004).

CONCLUSION

Elevated levels of circulating sCD14 and OPG in patients with CKD 2-3 were significantly associated with ABI, a measure of arterial stiffness. An increase in sCD14 over time in CKD 2-3 patients was associated with a corresponding increase in ABI. Further studies are needed to examine if early intensive multifactorial medication to align with international treatment targets may influence cardiovascular outcomes.

Association between serum osteoprotegerin level and renal prognosis in nondialysis patients with chronic kidney disease in the Korean Cohort Study for Outcomes in Patients with Chronic Kidney Disease (the KNOW-CKD Study)

Background

Osteoprotegerin is an important regulator of bone metabolism and vascular calcification. The association between serum osteoprotegerin level and chronic kidney disease (CKD) progression has not been elucidated. We investigated the prognostic value of serum osteoprotegerin levels in nondialysis CKD patients.

Methods

We analyzed 2,082 patients enrolled in the Korean Cohort Study for Outcomes in Patients with CKD between 2011 and 2016. Patients were divided into quartiles by their serum osteoprotegerin levels. The primary outcome was the occurrence of ≥1 of the following: dialysis initiation, kidney transplantation, a two-fold increase in serum creatinine level from baseline, or a 50% decrease in the estimated glomerular filtration rate (eGFR). Cox proportional hazard regression models were used to investigate the prognostic value of the serum osteoprotegerin level to CKD progression.

Results

The median follow-up period was 48.9 months, and 641 patients (30.8%) experienced the primary outcome. The hazard ratio of serum osteoprotegerin for renal progression in the full extended Cox proportional hazard model was 1.064 (95% confidence interval, 1.041–1.088). Subgroup analyses by age, presence of diabetes, and eGFR showed significant results consistent with the overall analysis results.

Conclusion

Serum osteoprotegerin level is independently associated with renal prognosis and could have prognostic importance in CKD progression.

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

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

Osteoprotegerin levels in children with subclinical hypothyroidism

AIM

In this study, we investigated the osteoprotegerin (OPG) and soluble receptor activator of nuclear factor-kappa Β ligand (sRANKL) serum levels in association with thyroid function in children with subclinical hypothyroidism.

METHODS

In 143 children and adolescents with subclinical hypothyroidism and 343 with normal thyroid function, age, height, weight and pubertal status were recorded and TSH, free thyroxine (FT4), anti-thyroid antibodies, OPG and sRANKL were measured in serum. Multiple linear regression was used for the statistical analysis with P < .05.

RESULTS

Children with subclinical hypothyroidism had higher TSH and lower FT4 serum levels than the control group (P < .05). Both groups had similar BMI Z-score, OPG and sRANKL serum levels. After multiple regression analysis, in children with subclinical hypothyroidism, OPG was negatively associated with FT4 (P < .05) whilst no association was observed between OPG and sRANKL, as well as between FT4 serum levels and RANKL.

CONCLUSION

Osteoprotegerin levels in children with subclinical hypothyroidism do not differ from those of euthyroid children. However, there is a negative association between FT4 and OPG levels observed only in the SH group. Considering the link between vascular dysfunction and alterations in osteoprotegerin levels, further research is needed to establish the role of childhood subclinical hypothyroidism in the long-term cardiovascular risk.

Biomarkers of vascular calcification in serum

Over the last decades, the association between vascular calcification (VC) and all-cause/cardiovascular mortality, especially in patients with high atherogenic status, such as those with diabetes and/or chronic kidney disease, has been repeatedly highlighted. For over a century, VC has been noted as a passive, degenerative, aging process without any treatment options. However, during the past decades, studies confirmed that mineralization of the arteries is an active, complex process, similar to bone genesis and formation. The main purpose of this review is to provide an update of the existing biomarkers of VC in serum and develop the various pathogenetic mechanisms underlying the calcification process, including the pivotal roles of matrix Gla protein, osteoprotegerin, bone morphogenetic proteins, fetuin-a, fibroblast growth-factor-23, osteocalcin, osteopontin, osteonectin, sclerostin, pyrophosphate, Smads, fibrillin-1 and carbonic anhydrase II.

Predictive Value of Osteoprotegerin for Detecting Coronary Artery Calcification in Type 2 Diabetes Mellitus Patients in Correlation with Extent of Calcification Detected by Multidetector Computed Tomography

Background:

Osteoprotegerin (OPG) is a tumor necrosis factor receptor super-family member. It specifically acts on bone by increasing bone mineral density and bone volume. Recent studies have evidenced its close relation to the development of atherosclerosis and plaque destabilization. Elevated OPG level has also been associated with the degree of coronary calcification in the general population and it has been considered to be a marker of coronary atherosclerosis.

Objective:

The aim of this study was to determine the relation between OPG levels and Coronary Artery Calcification score (CACs) in Type 2 diabetic patients in comparison to healthy controls.

Methods:

Our study included 45 type 2 diabetic patients (mean age 51.7 years; 51.1% male) without evidence of previous CVD and 45 healthy age and sex matched subjects as control. All participants were subjected to full history, full examination and lab investigations. Serum OPG concentration was measured by an enzyme-linked immunosorbent assay (ELISA) and CAC imaging was performed using non contrast Multi detector CT of the heart.

Results:

Significant CAC (<10 Agatston units) was seen in 23 patients (51.11 %).

:

OPG was significantly high in diabetic patients in comparison to controls with mean 12.9±5.7 pmol/l in cases, and 8.6±0.5 pmol/l in controls (P value < 0.001).

:

The Coronary Artery Calcification Score (CACS) was positively correlated with age and duration of diabetes. The OPG was positively correlated with age, fasting blood sugar and duration of diabetes. The CACS showed a significantly positive correlation with OPG.

Conclusion:

Findings suggested that increasing in serum OPG was consistent with CAC and could be used for the early diagnosis of subclinical atherosclerosis.

Association between bone metabolism regulators and arterial stiffness in type 2 diabetes patients

BACKGROUND AND AIM

Osteopontin (OPN), osteonectin (ON) and osteocalcin (OC) play an important role in the development of vascular calcifications, but it is unclear whether these bone metabolism regulators contribute to the development of arterial stiffness in type 2 diabetes patients. We therefore aim to determine the relationship between plasma concentrations of OPN, ON, OC and arterial stiffness in type 2 diabetes patients.

METHODS

Cross-sectional study of 1003 type 2 diabetes patients included in the Second Manifestations of ARTerial disease (SMART)-cohort. Generalized linear models were used to evaluate the relation between plasma levels of OPN, ON and OC and arterial stiffness as measured by pulse pressure (PP), ankle-brachial index (ABI) (≥0.9), carotid artery distension and an arterial stiffness summary score. Analyses were adjusted for age, sex, kidney function, diabetes duration and diastolic blood pressure. Higher OPN plasma levels were significantly related to a lower ABI (β-0.013; 95%CI -0.024 to -0.002) and a higher arterial stiffness summary score (OR1.24; 95%CI 1.03-1.49). OPN levels were not related to PP (β 0.59; 95%CI -0.63-1.81) or absolute carotid artery distention (β -7.03; 95%CI -20.00-5.93). ON and OC plasma levels were not related to any of the arterial stiffness measures.

CONCLUSION

Only elevated plasma levels of OPN are associated with increased arterial stiffness in patients with type 2 diabetes as measured by the ankle-brachial index and arterial stiffness summary score. These findings indicate that OPN may be involved in the pathophysiology of arterial stiffness and call for further clinical investigation.

Osteoprotegerin and Myocardial Fibrosis in Patients with Aortic Stenosis

Left ventricular myocardial fibrosis in patients with aortic stenosis (AS) confers worse prognosis. Plasma osteoprotegerin (OPG), a cytokine from the TNF receptor family, correlates with the degree of valve calcification in AS, reflecting the activity of the tissue RANKL/RANK/OPG (receptor activator of nuclear factor κΒ ligand/RANK/osteoprotegerin) axis, and is associated with poorer outcomes in AS. Its association with myocardial fibrosis is unknown. We hypothesised that OPG levels would reflect the extent of myocardial fibrosis in AS. We included 110 consecutive patients with AS who had undergone late-gadolinium contrast enhanced cardiovascular magnetic resonance (LGE-CMR). Patients were characterised according to pattern of fibrosis (no fibrosis, midwall fibrosis, or chronic myocardial infarction fibrosis). Serum OPG was measured with ELISA and compared between groups defined by valve stenosis severity. Some 36 patients had no fibrosis, 38 had midwall fibrosis, and 36 had chronic infarction. Patients with midwall fibrosis did not have higher levels of OPG compared to those without fibrosis (6.78 vs. 5.25 pmol/L, p = 0.12). There was no difference between those with midwall or chronic myocardial infarction fibrosis (6.78 vs. 6.97 pmol/L, p = 0.27). However, OPG levels in patients with chronic myocardial infarction fibrosis were significantly higher than those without fibrosis (p = 0.005).

Diabetes confers in vitro calcific potential on serum which associates with in vivo vascular calcification

Although vascular calcification (VC) is prevalent in Type 2 diabetes mellitus (T2DM), underlying mechanisms remain unclear. Neither is it known whether T2DM confers calcific potential (CP) on serum, enabling it to induce VC outside the disease milieu. We, therefore, investigated the CP of serum from controls and subjects with T2DM with and without in vivo VC. Samples from 20 healthy controls and 44 age- and sex-matched patients with T2DM with modification of diet in renal disease estimated glomerular filtration rate (MDRD-4 eGFR) > 60 ml·min-1 were analysed for CP using rat aortic smooth muscle cells in vitro CT scans of femoral arteries identified individuals with in vivo calcification. Serum from subjects with T2DM revealed significantly greater CP than controls. This was further enhanced in the presence of in vivo VC. Addition of β-glycerophosphate (β-GP) plus CaCl2 increased the CP of T2DM serum but not of controls. Along with age, CP was an independent predictor of the presence of VC. In receiver operator curve (ROC) analysis, CP was a significant predictor of femoral arterial VC (C-statistic 0.70: P=0.009). The distribution of CP was bimodal around a cutoff of 100 nmoles of Ca2+ protein mg-1, with a higher proportion of Type 2 diabetes subjects with in vivo calcification (T2DM+) sera above the cutoff value. This group also showed elevated levels of osteoprotegerin (OPG) and matrix Gla protein (MGP). Diabetes confers CP on the serum which is enhanced by the presence of in vivo VC. The CP acquired may be dependent on levels of OPG and MGP. These findings may be clinically relevant for early identification of individuals at risk of VC and for informing therapeutic strategies.

Osteoprotegerin is a Better Serum Biomarker of Coronary Artery Calcification than Osteocalcin in Type 2 Diabetes

OBJECTIVE

Coronary artery calcification (CAC) is a prominent feature of atherosclerosis and is associated with cardiovascular events. In vitro studies have suggested that osteoprotegerin (OPG) and osteocalcin (OC) exert anticalcification potential in the vessel wall. The objective of this study was to investigate the association of CAC and serum bone biomarkers in persons with type 2 diabetes.

METHODS

We examined 50 individuals with type 2 diabetes. CAC imaging was performed by multidetector computed tomography. CAC scores ≥10, expressed in Agatston units, were considered abnormal. OC, undercarboxylated OC (ucOC), and OPG levels were determined by enzyme-linked immunosorbent assay.

RESULTS

Abnormal CAC scores were found for 64% of the study cohort. OPG levels were significantly elevated (5.5 ± 2.0 pmol/L vs. 4.2 ± 1.7 pmol/L; P = .026) for those with abnormal CAC scores. No univariate differences were found for OC or ucOC. Logistic regression analyses revealed that an increase in serum OPG level was significantly associated with an increase in CAC score (odds ratio, 3.324; 95% confidence interval, 1.321 to 8.359; P = .011). Longer duration of diabetes was a significant covariate (P = .026), whereas nonsignificant covariates in the final model were age, gender, systolic blood pressure, body mass index, insulin resistance determined by the homeostasis model assessment for insulin resistance, leptin, adiponectin, and glycemic control. The Nagelkerke R2 for the model was 0.66. Neither OC nor ucOC were significantly associated with elevated CAC scores.

CONCLUSION

Our results suggest that OPG is a more useful serum biomarker than OC or ucOC for identifying those at increased risk of arterial calcification in type 2 diabetes.

Is rationale to decrease serum osteoprotegerin and fetuin-A in type 2 diabetes mellitus patients?

Fetuin-A and osteoprotegerin (OPG) are considered biomarkers of atherosclerosis, vascular calcification, inflammation in subjects with type 2 diabetes mellitus (T2DM) with possible predictive value. Recent clinical studies have been shown that fetuin-A and OPG could be helpful for cardiovascular risk stratification in T2DM. Therefore, fetuin-A and OPG may offer protection against atherosclerosis and vascular calcification. However, clinical implication of decreased serum concentrations of these biomarkers in T2DM during treatment with thiazolidinediones, in particular pioglitazone, and metformin is not fully understood. The relation of thiazolidinediones- and metformin- induced post-treatment serum levels of fetuin-A and OPG to changes in CV risk requires more investigations.

Influence of Type 2 Diabetes on Prevalence of Key Periodontal Pathogens, Salivary Matrix Metalloproteinases, and Bone Remodeling Markers in Sudanese Adults with and without Chronic Periodontitis

This study compared the influence of type 2 diabetes on the occurrence of six periodontal pathogens in plaque samples of patients with and without chronic periodontitis. Levels of salivary MMP-8, MMP-9, RANKL, and OPG were also investigated. The study enrolled 31 patients with type 2 diabetes and chronic periodontitis (DM + CP), 29 with chronic periodontitis (CP), and 20 with type 2 diabetes (DM). Questionnaire-guided interviews were conducted and plaque index, bleeding on probing, and pocket depth were recorded. Polymerase chain reaction (PCR) was utilized to determine the prevalence of the bacteria. The levels of salivary molecules were determined by enzyme immunosorbent assay (ELISA). The CP group had the highest prevalence of P. gingivalis (81.5%), followed by the DM + CP (59.3%) and DM (55.0%) groups (P > 0.05). Similar trends were observed for P. intermedia and T. denticola. The prevalence of T. forsythia was 100% in both periodontitis groups compared to 90% in the DM group. There were no significant differences between the groups regarding the concentrations of MMP-8, MMP-9, or OPG. RANKL concentrations were below the detection limit. Our data show that type 2 diabetes has no significant influence on the prevalence of the investigated periodontal pathogens, or the levels of salivary MMP-8, MMP-9, and OPG.

Association of osteoprotegerin with impaired glucose regulation and microalbuminuria: the REACTION study

BACKGROUND

High osteoprotegerin (OPG) has been reported in association with insulin resistance and type 2 diabetes. We aimed to evaluate the association of serum OPG with impaired glucose regulation (IGR) and microalbuminuria among middle-aged and older Chinese.

METHODS

Serum OPG was measured in 599 individuals with normal glucose regulation, 730 with impaired glucose regulation and 327 newly diagnosed patients with diabetes. Serum OPG was measured using ELISA methods and urine albumin/creatinine ratio was used to determine the urinary albumin excretion.

RESULTS

Serum OPG levels were significantly higher in subjects with isolated impaired fasting glucose, isolated impaired glucose tolerance, combined impaired fasting glucose/impaired glucose tolerance and diabetes than in those with normal glucose regulation, whereas serum OPG levels were not different in the four groups with dysregulation of glucose metabolism. OPG was associated with a higher risk for IGR (OR 1.108 for each 0.1 μg/l increase in OPG, 95% CI 1.009-1.117, p = 0.01) after adjustment for gender, age, BMI, current smoking and alcohol intake, family history of diabetes, homeostasis model assessment of insulin resistance (HOMA-IR), lipid profile; the corresponding OR of combined impaired glucose regulation and type 2 diabetes was 1.121 (95% CI 1.101-1.141, p = 0.0005). OPG was associated with the risk of microalbuminuria (OR 1.025, 95% CI 1.006-1.044, p = 0.02) after adjustment for gender, age, current smoking, current alcohol intake, family history of diabetes, BMI, waist/hip ratio, HOMA-IR, eGFR and lipid profile.

CONCLUSIONS

Serum OPG level is closely and independently associated with IGR and is an independent risk factor for microalbuminuria.

Increased FGF23 serum level is associated with unstable carotid plaque in type 2 diabetic subjects with internal carotid stenosis

Background

The object of this study was to investigate the potential role of FGF23 on plaque stability in type 2 diabetic patients with internal carotid artery stenosis.

Methods

In this retrospective observational study, we analyzed FGF23 serum level in 361 type 2 diabetic patients with internal carotid artery stenosis undergoing carotid endarterectomy and in 598 diabetic controls without carotid atherosclerosis.

Results

We found that FGF23 median serum levels was significantly higher in patients than in diabetic controls [67.7 (59.5–77.8) pg/mL and 43.89 (37.5–50.4), P < 0.001] and was significantly and independently associated with unstable plaque in patients with internal carotid artery stenosis [OR, 5,71 (95 % CI, 2.09–15.29].

Conclusions

We have found, for the first time, that FGF23 could be associated with unstable plaque in type 2 diabetic patients with internal carotid artery stenosis.

Relationship between serum osteocalcin level and carotid intima-media thickness in a metabolically healthy Chinese population

Background

The relationship between osteocalcin and atherosclerosis remains unclear. This might be due to different degrees of confounding from factors that are associated with serum osteocalcin level, such as metabolic-related variables. This study aimed to investigate the relationship between serum osteocalcin level and carotid intima-media thickness (C-IMT) in a metabolically healthy population.

Methods

A total of 476 subjects with normal values for weight, glucose tolerance, blood pressure, and lipids (age range, 20–75 years; 155 men, 201 premenopausal women, 120 postmenopausal women) from the Shanghai Obesity Study were recruited for this cross-sectional study. Subjects with a history of cardiovascular disease or carotid plaque were excluded. C-IMT was measured by ultrasonography. Serum osteocalcin level was assessed by an electrochemiluminescence immunoassay.

Results

Median C-IMT in the entire study population was 0.55 mm with an interquartile range of 0.50–0.60 mm. C-IMT in premenopausal women was significantly lower than that in men and postmenopausal women (all P < 0.001). The median (interquartile range) of serum osteocalcin level in the entire population was 17.02 (13.31–21.47) ng/mL. Serum osteocalcin level in postmenopausal women was significantly higher than that in men and premenopausal women (all P < 0.001), while the level of serum osteocalcin in men was also significantly higher than that in premenopausal women (P < 0.001). No significant correlation was found between C-IMT and serum osteocalcin level in either men or postmenopausal women. There was a significant, inverse correlations between C-IMT and serum osteocalcin level in premenopausal women after adjustment of age, but this association was eliminated after adjustment for other confounding factors.

Conclusions

Serum osteocalcin level was not independently associated with C-IMT in a metabolically healthy Chinese population.

Role of osteoprotegerin in vascular disorders of the end-stage renal disease patients

AIM

To assess the osteoprotegerin (OPG) relationship with cardiovascular complications in hemodialysis (HD) patients.

METHODS

The study included 87 HD patients. Clinical characteristics, ankle-arm index (AAI), OPG and mineral markers levels were recorded. Arterial intimal calcification (AIC) and arterial medial calcification (AMC) were registered.

RESULTS

OPG levels were increased in HD patients. Patients with AIC (p = 0.006)/ AMC (p = 0.01) had higher OPG levels. OPG did not have any relation with cardiovascular diseases. OPG correlated positively with age, increased HD vintage and inversely with albumin and AAI. OPG has not been a risk factor for VC or cardiovascular disease.

CONCLUSION

OPG rising could be a reaction in defense to vascular aggression, because OPG was associated with VC, but not with vascular disease.

Vascular calcification: from pathophysiology to biomarkers

The link between vascular calcification (VC) and increased mortality is now well established. Over time, as clinical importance of this phenomenon has begun to be fully considered, scientists have highlighted more and more physiopathological mechanisms and signaling pathways that underlie VC. Several conditions such as diabetes, dyslipidemia and renal diseases are undoubtedly identified as predisposing factors. But even if the process is better understood, many questions still remain unanswered. This review briefly develops the various theories that attempt to explain mineralization genesis. Nonetheless, the main purpose of the article is to provide a profile of the various existing biomarkers of VC. Indeed, in the past years, a lot of inhibitors and promoters, which form a dense and interconnected network, were identified. Given importance to assess and control mineralization process, a focusing on accumulated knowledge of each marker seemed to be necessary. Therefore, we tried to define their respective role in the physiopathology and how they can contribute to calcification risk assessment. Among these, Klotho/fibroblast growth factor-23, fetuin-A, Matrix Gla protein, Bone morphogenetic protein-2, osteoprotegerin, osteopontin, osteonectin, osteocalcin, pyrophosphate and sclerostin are specifically discussed.

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.

Exenatide can inhibit calcification of human VSMCs through the NF-kappaB/RANKL signaling pathway

Background

Arterial calcification is an important pathological change of diabetic vascular complication. Osteoblastic differentiation of vascular smooth muscle cells (VSMCs) plays an important cytopathologic role in arterial calcification. The glucagon-like peptide-1 receptor agonists (GLP-1RA), a novel type of antidiabetic drugs, exert cardioprotective effects through the GLP-1 receptor (GLP-1R). However, the question of whether or not GLP-1RA regulates osteoblastic differentiation and calcification of VSMCs has not been answered, and the associated molecular mechanisms have not been examined.

Methods

Calcifying VSMCs (CVSMCs) were isolated from cultured human arterial smooth muscle cells through limiting dilution and cloning. The extent of matrix mineralization was measured by Alizarin Red S staining. Protein expression and phosphorylation were detected by Western blot. Gene expression of receptor activator of nuclear factor-κB ligand (RANKL) was silenced by small interference RNA (siRNA).

Results

Exenatide, an agonist of GLP-1 receptor, attenuated β-glycerol phosphate (β-GP) induced osteoblastic differentiation and calcification of human CVSMCs in a dose- and time-dependent manner. RANKL siRNA also inhibited osteoblastic differentiation and calcification. Exenatide decreased the expression of RANKL in a dose-dependent manner. 1,25 vitD₃ (an activator of RANKL) upregulated, whereas BAY11-7082 (an inhibitor of NF-κB) downregulated RANKL, alkaline phosphatase (ALP), osteocalcin (OC), and core binding factor α1 (Runx2) protein levels and reduced mineralization in human CVSMCs. Exenatide decreased p-NF-κB and increased p-AMPKα levels in human CVSMCs 48 h after treatment. Significant decrease in p-NF-κB (p-Ser²⁷⁶, p-Ser⁵³⁶) level was observed in cells treated with exenatide or exenatide + BAY11-7082.

Conclusion

GLP-1RA exenatide can inhibit human VSMCs calcification through NF-κB/RANKL signaling.

Enhancing of women functional status with metabolic syndrome by cardioprotective and anti-inflammatory effects of combined aerobic and resistance training

These data describe the effects of combined aerobic plus resistance training (CT) with regards to risk factors of metabolic syndrome (MetS), quality of life, functional capacity, and pro- and anti-inflammatory cytokines in women with MetS. In this context, thirteen women (35.4 ± 6.2 yr) completed 10 weeks of CT consisting of three weekly sessions of ~60 min aerobic training (treadmill at 65-70% of reserve heart rate, 30 min) and resistance training (3 sets of 8-12 repetitions maximum for main muscle groups). Dependent variables were maximum chest press strength; isometric hand-grip strength; 30 s chair stand test; six minute walk test; body mass; body mass index; body adiposity index; waist circumference; systolic (SBP), diastolic and mean blood pressure (MBP); blood glucose; HDL-C; triglycerides; interleukins (IL) 6, 10 and 12, osteoprotegerin (OPG) and serum nitric oxide metabolite (NOx); quality of life (SF-36) and Z-Score of MetS. There was an improvement in muscle strength on chest press (p = 0.009), isometric hand-grip strength (p = 0.03) and 30 s chair stand (p = 0.007). There was a decrease in SBP (p = 0.049), MBP (p = 0.041), Z-Score of MetS (p = 0.046), OPG (0.42 ± 0.26 to 0.38 ± 0.19 ng/mL, p<0.05) and NOx (13.3 ± 2.3 µmol/L to 9.1 ± 2.3 µmol/L; p<0.0005). IL-10 displayed an increase (13.6 ± 7.5 to 17.2 ± 12.3 pg/mL, p < 0.05) after 10 weeks of training. Combined training also increased the perception of physical capacity (p = 0.011). This study endorses CT as an efficient tool to improve blood pressure, functional capacity, quality of life and reduce blood markers of inflammation, which has a clinical relevance in the prevention and treatment of MetS.

Antihypertensive medications, bone mineral density, and fractures: a review of old cardiac drugs that provides new insights into osteoporosis

Osteoporosis is increasing in prevalence and importance as society's age, with the clinical consequence of fractures of the hip, spine, and upper extremity, leading to impaired quality of life, loss of function and independence, and increased morbidity and mortality. A major risk factor for osteoporosis is older age, and cardiovascular diseases also share this risk factor; therefore, osteoporosis and cardiovascular disease often coexist and share risk factors. Medications used for the treatment of cardiovascular diseases, in particular antihypertensive drugs, have been shown in a variety of studies of varying designs to modulate bone health in both a positive or negative manner. In this article, we reviewed the pharmacology, potential mechanisms, and possible effects on bone mineral density and fracture risk of commonly prescribed antihypertensive medications, including thiazide and non-thiazide diuretics, beta-blockers, calcium channel blockers, renin-angiotensin-aldosterone system agents, and nitrates.

Medial vascular calcification revisited: review and perspectives

Vascular calcifications (VCs) are actively regulated biological processes associated with crystallization of hydroxyapatite in the extracellular matrix and in cells of the media (VCm) or intima (VCi) of the arterial wall. Both patterns of VC often coincide and occur in patients with type II diabetes, chronic kidney disease, and other less frequent disorders; VCs are also typical in senile degeneration. In this article, we review the current state of knowledge about the pathology, molecular biology, and nosology of VCm, expand on potential mechanisms responsible for poor prognosis, and expose some of the directions for future research in this area.

Vascular calcification in patients with type 2 diabetes: the involvement of matrix Gla protein

BACKGROUND

Matrix Gla protein (MGP) is an important inhibitor of calcification. The objective of the present study of patients with type 2 diabetes and normal or slightly altered kidney function was to evaluate levels of inactive, dephospho-uncarboxylated MGP(dp-ucMGP) and total uncarboxylated MGP(t-ucMGP) and assess their links with biological and clinical parameters (including peripheral vascular calcification).

METHODS

The DIACART study is a cross-sectional cohort study of 198 patients with type 2 diabetes and normal or slightly altered kidney function. Matrix Gla protein levels were measured with an ELISA and all patients underwent multislice spiral computed tomography scans to score below-knee arterial calcification.

RESULTS

In the study population as a whole, the mean dp-ucMGP and t-ucMGP levels were 627 ± 451 pM and 4868 ± 1613 nM, respectively. Glomerular filtration rate, age and current vitamin K antagonist use were independently associated with dp-ucMGP levels. When the study population was divided according to the median peripheral arterial calcification score, patients with the higher score displayed significantly lower t-ucMGP and significantly higher dp-ucMGP levels. Furthermore, plasma dp-ucMGP was positively associated with the peripheral arterial calcification score (independently of age, gender, previous cardiovascular disease and t-ucMGP levels).

CONCLUSIONS

High dp-ucMGP levels were independently associated with below-knee arterial calcification score in patients with type 2 diabetes and normal or slightly altered kidney function. The reversibility of the elevation of dp-ucMGP levels and the latter's relationship with clinical events merit further investigation.

Osteocalcin attenuates high fat diet-induced impairment of endothelium-dependent relaxation through Akt/eNOS-dependent pathway

Background

Recent studies have demonstrated a protective effect of osteocalcin (OCN) on glucose homeostasis and metabolic syndrome. However, its role in vascular function remains unknown. This study investigated the contribution of OCN to the pathogenesis of endothelial dysfunction in the thoracic aorta of apolipoprotein E-deficient (ApoE-KO) mice.

Methods

Eight-week-old ApoE–KO mice were given chow or high fat diet (HFD) for 12 weeks with or without daily intraperitoneal injection of OCN. Intraperitoneal glucose tolerance test (IPGTT), insulin tolerance test (ITT),measurement of serum lipid profiles and blood pressure were carried out. Endothelium-dependent relaxation (EDR) was measured by wire myography. Human umbilical vein endothelial cells (HUVECs) were used to study the role of OCN on eNOS levels in vitro. PI3K inhibitor (LY294002) and Akt inhibitor V were used ex-vivo to determine whether PI3K/Akt/eNOS contributes to the beneficial effect of OCN for the vascular or not.

Results

Daily injections of OCN can significantly improve lipid metabolism, glucose tolerance and insulin sensitivity in ApoE-KO mice. In ApoE-KO mice fed with HFD, the OCN-treated mice displayed an improved acetylcholine-stimulated EDR compared to the vehicle-treated group. In addition, compared to vehicle-treated HUVECs, OCN-treated HUVECs displayed increased activation of the Akt-eNOS signaling pathway, as evidenced by significantly higher levels of phosphorylated Akt and eNOS. Furthermore, a similar beneficial effect of OCN on thoracic aorta was observed using ex vivo organ culture of isolated mouse aortic segment. However, this effect was attenuated upon co-incubation with PI3K inhibitor or Akt inhibitor V.

Conclusions

Our study demonstrates that OCN has an endothelial-protective effect in atherosclerosis through mediating the PI3K/Akt/eNOS signaling pathway.

Neuropathy and the vascular-bone axis in diabetes: lessons from Charcot osteoarthropathy

Emerging evidence from the last two decades has shown that vascular calcification (VC) is a regulated, cell-mediated process orchestrated by vascular smooth muscle cells (VSMCs) and that this process bears many similarities to bone mineralization. While many of the mechanisms driving VSMC calcification have been well established, it remains unclear what factors in specific disease states act to promote vascular calcification and in parallel, bone loss. Diabetes is a condition most commonly associated with VC and bone abnormalities. In this review, we describe how factors associated with the diabetic milieu impact on VSMCs, focusing on the role of oxidative stress, inflammation, impairment of the advanced glycation end product (AGE)/receptor for AGE system and, importantly, diabetic neuropathy. We also explore the link between bone and VC in diabetes with a specific emphasis on the receptor activator of nuclear factor κβ ligand/osteoprotegerin system. Finally, we describe what insights can be gleaned from studying Charcot osteoarthropathy, a rare complication of diabetic neuropathy, in which the occurrence of VC is frequent and where bone lysis is extreme.

Associations of fetuin-A and osteoprotegerin with arterial stiffness and early atherosclerosis in chronic hemodialysis patients

BACKGROUND

Cardiovascular morbidity and mortality remains excessive in patients with chronic kidney disease. The association of vascular changes with regulators of extraosseous calcification in this patient population is still under investigation. The aim of the present study was to investigate the associations of the calcification inhibitor fetuin-A, and the anti-osteoclastic factor osteoprotegerin (OPG) with vascular pathology in chronic hemodialysis patients.

METHODS

In this cross-sectional study including 81 stable chronic hemodialysis patients, we measured carotid-to-femoral pulse wave velocity (cfPWV) with applanation tonometry, reflecting arterial stiffness, and common carotid intima-media thickness (ccIMT), a surrogate of early atherosclerosis, as well as serum levels of fetuin-A and OPG. Co-morbidities, traditional cardiovascular risk factors, inflammatory markers and mineral-bone disease serology parameters were also recorded.

RESULTS

cfPWV correlated inversely with fetuin-A (r=-0.355, p=0.001) and positively with OPG (r=0.584, p<0.001). In multilinear regression analysis including age, gender, diabetes, cardiovascular disease, hypertension, pulse pressure, LDL, logCRP, both fetuin-A and OPG were independently associated with cfPWV (p=0.024 and p=0.041 respectively). ccIMT was negatively associated with fetuin-A (r=-0.312, p=0.005) and positively with OPG (r=0.521, p<0.0001); however these associations lost statistical significance after adjustment for age.

CONCLUSION

In chronic hemodialysis patients both fetuin-A and OPG levels are independently associated with arterial stiffness but not with early atherosclerotic vascular changes.