Osteoprotegerin is an independent predictor of vascular events in Finnish adults with type 1 diabetes

Comparison of novel markers of metabolic complications and cardiovascular risk factors between obese non-diabetic and obese type 1 diabetic children and young adults

Introduction

For the past years, the prevalence of obesity is growing in the general population of children, as well as among diabetic patients, resulting in increased risk of cardiovascular complications. Type 1 diabetes mellitus (T1DM) is one of the most common chronic diseases in children and young adults, leading to decreased life quality and lifespan, with obesity being recognized recently as a major contributing factor to these health problems. The objective of this study was to analyze and compare the selected novel markers for metabolic complications of obesity and vascular risk factors between obese non-diabetic and obese T1DM children and young adults.

Methods

One hundred four subjects, aged between 10 and 24 years (31 with T1DM and excessive body weight, 41 with obesity without diabetes, and 32 with T1DM and normal weight), and 32 matched lean controls were included in the study. Clinical characteristics, blood pressure measurements, daily requirement for insulin, HbA1c%, plasma lipids, fetuin-A, E-selectin, and osteoprotegerin levels were compared with respect to body mass index (BMI), body mass index standard deviation score (BMI-SDS), and carotid intima-media thickness (cIMT) of common carotid arteries.

Results

Patients with T1DM and excessive body weight compared to non-diabetic obese subjects had similar values of systolic blood pressure (125.6 ± 8.2 vs. 127.3 ± 12.9 mmHg, p = 0.515), diastolic blood pressure (78.19 ± 7.03 vs. 78.02 ± 8.01 mmHg, p = 0.918), cholesterol (175.26 ± 34.1 vs. 163.51 ± 26.08 mg/dl, p = 0.102), LDL (108.03 ± 32.55 vs. 112.22 ± 26.36 mg/dl, p = 0.548), and triglyceride levels (118.19 ± 71.20 vs. 117 ± 55.80 mg/dl, p = 0.937); all values were found to be higher compared to non-obese T1DM and healthy controls. HbA1c level and insulin resistance indices were significantly worse in T1DM obese vs. T1DM non-obese patients. Fetuin-A levels were higher among obese non-diabetic patients (p = 0.01), and E-selectin and osteoprotegerin levels were similar in both groups with obesity, but higher than in the reference group. There were no statistical differences in cIMT with T1DM with normal weight, excessive weight, and non-diabetic obese children; however, the cIMT value was higher compared to the reference group.

Discussion

Novel markers of metabolic complications of obesity are similar between obese T1DM and non-diabetic subjects. Obesity in patients with T1DM results in worse metabolic control, insulin resistance, and increased risk for vascular complications.

The roles of osteoprotegerin in cancer, far beyond a bone player

Osteoprotegerin (OPG), also known as tumor necrosis factor receptor superfamily member 11B (TNFRSF11B), is a member of the tumor necrosis factor (TNF) receptor superfamily. Characterized by its ability to bind to receptor activator of nuclear factor kappa B ligand (RANKL), OPG is critically involved in bone remodeling. Emerging evidence implies that OPG is far beyond a bone-specific modulator, and is involved in multiple physiological and pathological processes, such as immunoregulation, vascular function, and fibrosis. Notably, numerous preclinical and clinical studies have been conducted to assess the participation of OPG in tumorigenesis and cancer development. Mechanistic studies have demonstrated that OPG is involved in multiple hallmarks of cancer, including tumor survival, epithelial to mesenchymal transition (EMT), neo-angiogenesis, invasion, and metastasis. In this review, we systematically summarize the basis and advances of OPG from its molecular structure to translational applications. In addition to its role in bone homeostasis, the physiological and pathological impacts of OPG on human health and its function in cancer progression are reviewed, providing a comprehensive understanding of OPG. We aim to draw more attention to OPG in the field of cancer, and to propose it as a promising diagnostic or prognostic biomarker as well as potential therapeutic target for cancer.

Circulating Osteoprotegerin in Chronic Kidney Disease and All-Cause Mortality

BACKGROUND

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

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

AIMS/HYPOTHESIS

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

METHODS

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

RESULTS

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

CONCLUSIONS/INTERPRETATIONS

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

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

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

Calcification biomarkers and vascular dysfunction in obesity and type 2 diabetes: influence of oral hypoglycemic agents

Vascular aging in obesity and type 2 diabetes (T2D) is associated with progressive vascular calcification, an independent predictor of morbidity and mortality. Pathways for vascular calcification modulate bone matrix deposition, thus regulating calcium deposits. We investigated the association between biomarkers of vascular calcification and vasodilator function in obesity or T2D, and whether antidiabetic therapies favorably impact those markers. Circulating levels of proteins involved in vascular calcification, such as osteopontin (OPN), osteoprotegerin (OPG), regulated on activation, normal T cell expressed and secreted (RANTES), and fetuin-A were measured in lean subjects, individuals with metabolically healthy obesity (MHO), and patients with metabolically unhealthy obesity (MUO) or T2D. Vasodilator function was assessed by infusion of ACh and sodium nitroprusside (SNP). Circulating levels of OPN were higher in the MUO/T2D group than in lean subjects (P < 0.05); OPG and RANTES were higher in MUO/T2D group than in the other groups (both P < 0.001); fetuin-A was not different between groups (P > 0.05); vasodilator responses to either ACh or SNP were impaired in both MUO/T2D and MHO compared with lean subjects (all P < 0.001). In patients with T2D who were enrolled in the intervention trial, antidiabetic treatment with glyburide, metformin, or pioglitazone resulted in a significant reduction of circulating OPG (P = 0.001), without changes in the other biomarkers and vasodilator responses (all P > 0.05). In conclusion, obese patients with MUO/T2D have elevated circulating OPN, OPG, and RANTES; in these patients, antidiabetic treatment reduces only circulating OPG. Further study is needed to better understand the mechanisms of vascular calcifications in obesity and diabetes.

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

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

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

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

Osteoprotegerin and Cardiovascular Events in High-Risk Populations: Meta-Analysis of 19 Prospective Studies Involving 27 450 Participants

Background Osteoprotegerin is a cytokine involved in bone metabolism as well as vascular calcification and atherogenesis. Although circulating osteoprotegerin levels are robustly associated with incident cardiovascular disease ( CVD ) in the general population, its relevance as a biomarker among populations at high CVD risk is less clear. Methods and Results Three independent reviewers systematically searched PubMed, EMBASE , and Web of Science to identify prospective studies that had recruited participants on the basis of having conditions related to high CVD risk. A total of 19 studies were eligible for inclusion, reporting on 27 450 patients with diabetes mellitus (2 studies), kidney disease (7 studies), preexisting heart disease (5 studies), or recent acute coronary syndromes (5 studies) at baseline. Over a mean follow-up of 4.2 years, 4066 CVD events were recorded. In a random-effects meta-analysis, the pooled risk ratio for CVD events comparing people in the top versus the bottom tertile of osteoprotegerin concentration was 1.30 (95% confidence interval, 1.12-1.50; P<0.001; I2=68.3%). There was evidence for presence of publication bias ( P value from Egger's test=0.013). Correction for publication bias using the trim-and-fill method reduced the risk ratio to 1.21 (95% confidence interval, 1.03-1.42; P<0.001). The risk ratios did not vary significantly by population type, geographical region, statistical adjustment, sample or assay type, age, sex, or length of follow-up. Conclusions In populations at high CVD risk, elevated circulating osteoprotegerin levels are associated with a higher risk for future CVD events. The magnitude of association appears weaker than in the general population.

Differential Association of Microvascular Attributions With Cardiovascular Disease in Patients With Long Duration of Type 1 Diabetes

OBJECTIVE

Independent association of chronic kidney disease (CKD) and proliferative diabetic retinopathy (PDR) with cardiovascular disease (CVD) has not been established. In the Joslin 50-Year Medalist study, characterizing individuals with type 1 diabetes for 50 years or more, we examined the associations of CKD and PDR with CVD, which was validated by another cohort with type 1 diabetes from Finland.

RESEARCH DESIGN AND METHODS

This cross-sectional study characterized U.S. residents (n = 762) with type 1 diabetes of 50 years or longer (Medalists) at a single site by questionnaire, clinical, ophthalmic, and laboratory studies. A replication cohort (n = 675) from the longitudinal Finnish Diabetic Nephropathy Study (FinnDiane) was used. CKD and PDR were defined as estimated glomerular filtration rate <45 mL/min/1.73 m² (CKD stage 3b) and according to the Early Treatment Diabetic Retinopathy Study (ETDRS) protocol, respectively. CVD was based on questionnaires and/or hospital discharge registers. Associations of CVD status with CKD and PDR were analyzed by multivariable logistic regression.

RESULTS

CVD prevalence in the Medalists with CKD and without PDR (+CKD/-PDR) (n = 30) and CVD prevalence in the -CKD/+PDR group (n = 339) were half the prevalence in the +CKD/+PDR group (n = 66) (34.5% and 42.8% vs. 68.2%, P = 0.002). PDR status was independently associated with CVD (odds ratio 0.21 [95% CI 0.08-0.58], P = 0.003) in patients with CKD. Among the Finnish cohort, a trend toward a lower prevalence of CVD in the +CKD/-PDR group (n = 21) compared with the +CKD/+PDR group (n = 170) (19.1% vs. 37.1%, P = 0.10) was also observed.

CONCLUSIONS

Absence of PDR in people with type 1 diabetes and CKD was associated with a decreased prevalence of CVD, suggesting that common protective factors for PDR and CVD may exist.

Cardiovascular risk assessment in osteoporotic patients using osteoprotegerin as a reliable predictive biochemical marker

Osteoprotegerin (OPG), a member of the tumour necrosis factor receptor (TNFR) superfamily of proteins known to be involved in a large number of biological systems, plays a pivotal role in bone remodelling. In addition to the roles of OPG in bone metabolism, it has been reported to be associated with a high cardiovascular risk in patients with metabolic syndrome. In most cases, the exact functions of OPG remain to be established; however, the widespread expression of OPG suggests that this molecule may have multiple biological activities, mainly in the cardiometabolic environment. The aim of this study was to evaluate the value of OPG as a predictive marker for cardiovascular and metabolic risk in osteoporotic patients. The study group comprised patients with osteoporosis, in order to evaluate the association between OPG serum levels and cardiovascular pathology. Our results revealed significant correlations between classical biochemical bone and metabolic parameters, such as osteocalcin and parathyroid hormone with lipid and glucose biomarkers, sustaining the crosstalk between calcium and bone parameters and cardiovascular risk. The OPG serum level proved to have a significant and independent predictive value for metabolic syndrome (MetS) as a cardiovascular risk standard in osteoporotic patients. The OPG serum levels were increased in patients with MetS as a protective response against the atherosclerotic lesions. The serum levels of 25-hydroxy vitamin D had significant and independent predictive value for cardiovascular and metabolic risk in our subjects, sustaining the active role of vitamin D beyond the area of bone metabolism.

Circulating osteoprotegerin is associated with chronic kidney disease in hypertensive patients

Background

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

Methods

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

Results

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

Conclusions

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

Electronic supplementary material

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Identification of Patients Affected by Mitral Valve Prolapse with Severe Regurgitation: A Multivariable Regression Model

Background. Mitral valve prolapse (MVP) is the most common cause of severe mitral regurgitation. Besides echocardiography, up to now there are no reliable biomarkers available for the identification of this pathology. We aim to generate a predictive model, based on circulating biomarkers, able to identify MVP patients with the highest accuracy. Methods. We analysed 43 patients who underwent mitral valve repair due to MVP and compared to 29 matched controls. We assessed the oxidative stress status measuring the oxidized and the reduced form of glutathione by liquid chromatography-tandem mass spectrometry method. Osteoprotegerin (OPG) plasma levels were measured by an enzyme-linked immunosorbent assay. The combination of these biochemical variables was used to implement several logistic regression models. Results. Oxidative stress levels and OPG concentrations were significantly higher in patients compared to control subjects (0.116 ± 0.007 versus 0.053 ± 0.013 and 1748 ± 100.2 versus 1109 ± 45.3 pg/mL, respectively; p < 0.0001). The best regression model was able to correctly classify 62 samples out of 72 with accuracy in terms of area under the curve of 0.92. Conclusions. To the best of our knowledge, this is the first study to show a strong association between OPG and oxidative stress status in patients affected by MVP with severe regurgitation.

High osteoprotegerin is associated with development of foot ulcer in type 1 diabetes

BACKGROUND AND AIM

The bone-related peptide osteoprotegerin has been linked to vascular calcification and peripheral vascular disease. We investigated the association between osteoprotegerin and development of foot complications in persons with type 1 diabetes.

MATERIALS AND METHODS

Prospective observational study of 573 persons with type 1 diabetes, 225 women; age [mean±SD] 42.3±10.3years. Plasma osteoprotegerin was measured by ELISA.

RESULTS

Median (IQR) osteoprotegerin was 2.80(2.35-3.63)μg/L and follow-up time (median (range)) was 12.7(0.1-15.6)years. Endpoints included: new foot ulceration (n=153), Charcot foot (n=14), vascular surgery/amputation (n=53), loss of foot pulse (n=57), and peripheral neuropathy (n=99). In unadjusted analyses, higher osteoprotegerin was associated with development of all endpoints (p≤0.026). Higher osteoprotegerin remained associated with development of foot ulcer, and the combination of vascular surgery/amputation, loss of foot pulse and neuropathy (p≤0.001) in a sex and age adjusted model. After further adjustment (nephropathy status, smoking, HbA_1c, systolic blood pressure, serum cholesterol, high sensitivity C-reactive protein, eGFR, and presence of neuropathy and/or claudication and/or foot ulcer at baseline), higher osteoprotegerin remained associated with development of foot ulcer (HR (95% CI) per doubling: 1.75 (1.04-2.97); p=0.037).

CONCLUSION

Higher osteoprotegerin levels were associated with development of foot ulcer, even after comprehensive adjustment.

Aspects of Hyperglycemia Contribution to Arterial Stiffness and Cardiovascular Complications in Patients With Type 1 Diabetes

Controlling the blood glucose level is of outmost importance for the prevention of the micro- and macrovascular diabetic complications observed in patients with type 1 diabetes (T1D). Although the pathogenesis behind the complex cascade of complications is far from solved, one possible mechanism could be a negative effect of glucose on the arteries resulting in a stiffening of the arteries and ultimately in vascular complications. Intriguingly, patients with T1D have been shown to suffer from premature arterial aging compared to nondiabetic subjects-an association that is even more evident in the presence of diabetic complications such as diabetic nephropathy. Arterial stiffness has in several patient populations been shown to independently predict cardiovascular disease. However, interventional studies aimed at attenuating arterial stiffness to reduce cardiovascular disease in T1D are yet to come. Moreover, most of the data on pharmacological treatments of arterial stiffening are directed toward pathophysiological pathways other than hyperglycemia. Interestingly, the sodium-glucose transport-2 (SGLT2) inhibitor empagliflozin was recently shown to reduce both blood pressure and arterial stiffness in patients with type 2 diabetes. Whether, these effects can also be replicated in patients with T1D is an intriguing question. Tight metabolic and antihypertensive control are still of central importance for the prevention and the treatment of diabetic complications. However, the need for a noninvasive intermediate marker to identify at risk patients for aggressive treatment is evident. One such tool might be arterial stiffness linking diabetes to increased cardiovascular risk. Future research efforts exploring large-scale databases will play a key role in the identification of other clinically useful markers.

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.

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.

Osteocalcin, adipokines and their associations with glucose metabolism in type 1 diabetes

To determine osteocalcin (OC) and adipokines in type 1 diabetes (T1D) and healthy controls, and to explore possible associations between glucose and bone metabolism, body composition and adipokines. Serum levels of total OC, undercarboxylated (UC-OC), leptin, adiponectin, and other parameters of glucose and bone metabolism were measured in 128 patients with T1D (mean duration 21.2years) and in 77 healthy controls, matched for gender, age, and body mass index (BMI). Partial correlations (adjusted for age and gender) with parameters of body composition (BMI, fat body mass [derived from bone mineral density scans]), glycaemic control (hemoglobin A1c (HbA1c), daily insulin dose in T1D), skeletal homeostasis (osteoprotegerin (OPG), receptor activator of NF-κB ligand (RANKL), all measured in serum), and serum insulin-like growth factor 1 (IGF-1) were also examined. Independent predictors of total and UC-OC were then explored. Total OC was lower in males with T1D (16.3±6.4 vs. 22.2±9.9ng/ml; p=0.001), whereas UC-OC did not show group differences. Adiponectin was higher in T1D patients, both for males and females (8.9±6.6 vs. 5.7±2.5μg/ml; p=0.004 and 13.8±6.4 vs. 8.8±4.0μg/ml; p<0.001). IGF-1 was lower only in females with T1D (146.6±68.8 vs. 203.0±74.4ng/ml; p<0.001). BMI and fat body mass were similar in T1D and controls. In T1D patients, total OC was inversely correlated with BMI and HbA1c, and UC-OC inversely correlated with HbA1c. In T1D patients, leptin positively correlated with BMI, fat body mass and daily insulin dose, while adiponectin inversely correlated with BMI and daily insulin dose. Multivariate regression modelling showed that determinants of higher total OC levels were male gender (p=0.04, ß-coefficient=2.865) and lower HbA1c (p=0.04, ß-coefficient=-0.117), whereas determinants of UC-OC levels were T1D (p=0.016, ß-coefficient=2.015), higher IGF-1 (p=0.004, ß-coefficient=0.011) and lower HbA1c (p=0.011, ß-coefficient=- 0.061). Total OC and UC-OC are associated with good glycaemic control in T1D, with gender-specific differences for total-OC. The association of leptin and adiponectin with glycaemic control, as observed in controls, does not seem to be a feature in T1D, although both adipokines appear to be related to the insulin demand. This article is part of a Special Issue entitled "Bone and diabetes".

Recent Progress in Stem Cell Therapy for Diabetic Nephropathy

BACKGROUND

Diabetic nephropathy (DN) represents the leading cause of end-stage renal disease. Current therapeutic strategies for DN are very limited, and none of them can stop end-stage renal disease progression. Stem cell-based therapy showed encouraging outcomes in kidney disease, including experimental DN.

SUMMARY

Both podocytes and proximal tubular epithelial cells play key roles in the pathogenesis of DN and, accordingly, could be regarded as treatment targets. Multiple kinds of stem cells contribute to the regeneration of the injured kidney, including embryonic stem cells (ESCs), mesenchymal stem cells, and induced pluripotent stem cells (iPSCs). Stem cells exert reparatory effects mainly by homing to injured sites, directing differentiation, paracrine action, and immunoregulation. However, poor survival after transplantation under diabetic conditions and unsatisfactory animal models of advanced DN are major obstacles for achieving an efficacious therapeutic effect from stem cell transplantation. Recently, remarkable progress has been made both in the direct differentiation of human ESCs and iPSCs into renal cells and in the generation of tissue- and patient-specific iPSCs, offering a powerful tool to investigate DN mechanisms and to identify the ideal candidate cell for future clinical application.

KEY MESSAGE

This review provides updated information on recent progress and limitations of stem cell-based therapy for DN.

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

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

Association of plasma osteoprotegerin levels with the severity of lower extremity arterial disease in patients with type 2 diabetes

Background

Osteoprotegerin (OPG) is a member of the tumor necrosis factor receptor superfamily and suggested as a marker of atherosclerosis. However, little is known about the association between plasma OPG levels and lower extremity arterial disease. We investigated whether plasma OPG levels were associated with the presence and severity of lower extremity arterial disease in patients with type 2 diabetes.

Methods

This was a study of 712 patients with type 2 diabetes aged 40 years or older. Plasma OPG was measured using ELISA. The lower extremity arterial disease was diagnosed by high-frequency color Doppler ultrasonic.

Results

Of 712 patients, 505 (70.9 %) had lower extremity arterial stenosis. OPG levels were significantly increased in patients with lower extremity arterial stenosis [1.89 (1.48-2.41) vs. 2.39 (1.82-3.33) ng/mL, p < 0.001]. Plasma OPG levels increased gradually with increasing severity of lower extremity arterial stenosis (p < 0.001 for trend), after adjustment for traditional cardiovascular risk factors such as age, gender, smoking, total cholesterol, high-density lipoprotein (HDL) cholesterol, C-reactive protein (CRP), body mass index (BMI), systolic blood pressure(SBP). The risk of lower extremity arterial disease was increased (OR = 1.17, 95 % CI 1.09 –1.28, p < 0.001) with each standard deviation (SD) higher level of OPG in patients with type 2 diabetes after adjustment for traditional CVD risk factors.

Conclusions

Plasma OPG levels were significantly associated with the presence and severity of lower extremity arterial disease. Our results suggest that OPG is an important plasma biomarker of lower extremity arterial disease in type 2 diabetes.

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.

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

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

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

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

VIDEO ABSTRACT AVAILABLE

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

Osteoprotegerin and kidney disease

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

Osteoprotegerin (OPG) as a biomarker for diabetic cardiovascular complications

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