Early posttransplant serum osteoprotegerin levels predict long-term (8-year) patient survival and cardiovascular death in renal transplant patients

Recent Insights in Noninvasive Diagnostic for the Assessment of Kidney and Cardiovascular Outcome in Kidney Transplant Recipients

Kidney transplantation improves quality of life and prolongs survival of patients with end-stage kidney disease. However, kidney transplant recipients present a higher risk for cardiovascular events compared to the general population. Risk assessment for graft failure as well as cardiovascular events is still based on invasive procedures. Biomarkers in blood and urine, but also new diagnostic approaches like genetic or molecular testing, can be useful tools to monitor graft function and to identify patients of high cardiovascular risk. Many biomarkers have been introduced, whereas most of these biomarkers have not been implemented in clinical routine. Here, we discuss recent developments in biomarkers and diagnostic models in kidney transplant recipients. Because many factors impact graft function and cardiovascular risk, it is most likely that no biomarker will meet the highest demands and standards. We advocate to shift focus to the identification of patients benefitting from molecular and genetic testing as well as from analysis of more specific biomarkers instead of finding one biomarker fitting to all patients.

Association of Serum Osteoprotegerin With Vascular Calcification, and Cardiovascular and Graft Outcomes in Kidney Transplant Patients: Results From the KNOW-KT

BACKGROUND

Vascular calcification and stiffness contribute to increased cardiovascular morbidity in patients with chronic kidney disease. This study investigated associations between serum osteoprotegerin (OPG) levels and vascular calcification or stiffness to assess cardiovascular and graft outcomes in kidney transplant patients.

METHODS

The KoreaN cohort study for Outcome in patients With Kidney Transplantation was a prospective multicenter cohort study. Serum OPG levels were measured at baseline and 3 y after transplantation in 1018 patients. Patients were classified into high and low OPG groups according to median serum OPG levels. The median follow-up duration was 93.5 mo.

RESULTS

The mean age was 45.8 ± 11.7 y and 62.9% were men. Patients with high OPG had significantly higher coronary artery calcium scores, abdominal aortic calcification scores, and brachial-ankle pulse wave velocities than those with lower OPG; these parameters remained significant for 5 y after transplantation. The 3-y OPG levels were lower than baseline values ( P  < 0.001) and were positively correlated ( r  = 0.42, P  < 0.001). Multivariate Cox regression analysis showed that high OPG levels were significantly associated with posttransplant cardiovascular events ( P  = 0.008) and death-censored graft loss ( P  = 0.004). Similar findings regarding posttransplant cardiovascular events ( P  = 0.012) and death-censored graft loss ( P  = 0.037) were noted in patients with high OPG at the 3-y follow-up. Mediation analyses revealed that coronary artery calcium scores, abdominal aortic calcification scores, and brachial-ankle pulse wave velocities could act as mediators between serum OPG levels and posttransplant cardiovascular events.

CONCLUSIONS

Serum OPG concentration is associated with vascular calcification and stiffness and could be a significant risk factor for cardiovascular outcomes and graft loss in patients undergoing kidney transplantation.

Pathophysiology and Clinical Impacts of Chronic Kidney Disease on Coronary Artery Calcification

The global prevalence of chronic kidney disease (CKD) has increased in recent years. Adverse cardiovascular events have become the main cause of life-threatening events in patients with CKD, and vascular calcification is a risk factor for cardiovascular disease. Vascular calcification, especially coronary artery calcification, is more prevalent, severe, rapidly progressive, and harmful in patients with CKD. Some features and risk factors are unique to vascular calcification in patients with CKD; the formation of vascular calcification is not only influenced by the phenotypic transformation of vascular smooth muscle cells, but also by electrolyte and endocrine dysfunction, uremic toxin accumulation, and other novel factors. The study on the mechanism of vascular calcification in patients with renal insufficiency can provide a basis and new target for the prevention and treatment of this disease. This review aims to illustrate the impact of CKD on vascular calcification and to discuss the recent research data on the pathogenesis and factors involved in vascular calcification, mainly focusing on coronary artery calcification, in patients with CKD.

Association of Circulating Osteoprotegerin Level with Blood Pressure Variability in Patients with Chronic Kidney Disease

Circulating osteoprotegerin (OPG) is a biomarker for cardiovascular complications that are closely related to chronic kidney disease (CKD). To investigate the association between circulating OPG level with long-term visit-to-visit blood pressure variability (BPV) in patients with pre-dialysis CKD, a total of 1855 subjects with CKD from stage 1 to pre-dialysis stage 5 from a prospective cohort were analyzed. Long-term visit-to-visit BPV was determined by average real variability (ARV), standard deviation (SD), and coefficient of variation (CoV) of systolic and diastolic blood pressure (SBP and DBP). ARV of SBP (Adjusted β coefficient 0.143, 95% confidence interval 0.021 to 0.264) was significantly associated with serum OPG level. Although SD and CoV of SBP were not significantly associated with serum OPG level in multivariate linear regression analyses, restricted cubic spline visualized the linear correlation of serum OPG level with all of ARV, SD, and CoV. The association between serum OPG level and DBP variability was not significant. Subgroup analyses revealed that the association of serum OPG with BPV is more prominent in the subjects with Charlson comorbidity index ≤3 and in the subjects without history of diabetes mellitus. In conclusion, circulating OPG level is potentially associated with long-term visit-to-visit BPV in patients with pre-dialysis CKD.

Association between serum osteoprotegerin level and mortality in kidney transplant recipients - a prospective observational cohort study

Paradoxically, higher serum levels of osteoprotegerin (OPG: a vascular calcification inhibitor) have been associated with increased arterial stiffness, risk of cardiovascular disease and all-cause mortality. A few studies reported that post-transplant OPG levels are associated with mortality in kidney transplant (KT) recipients. In this study, this association was assessed in a cohort of prevalent KT recipients, adjusting for previously untested potential confounders, including fibroblast growth factor 23 (FGF23) and interleukin 6 (IL-6). Socio-demographic and clinical parameters, medical and transplant history, and laboratory data were collected from 982 prevalent KT recipients. The association between serum OPG and all-cause mortality over a 6-year follow-up period was examined using Kaplan-Meier survival curves and multivariable-adjusted Cox regression models. Participants with high serum OPG were more likely female, older, deceased donor KT recipients and have more comorbidity, lower eGFR, higher FGF23, higher IL-6, and longer dialysis vintage. Each 1 pmol/l higher serum OPG level was associated with a 49% higher risk of mortality (hazard ratio (HR) [95% confidence interval (CI)]: 1.49 [1.40-1.61]). This association persisted after adjusting for confounders (HR [95% CI]: 1.20 [1.10-1.30]). In conclusion, serum OPG was associated with all-cause mortality independent of several novel confounders in prevalent KT recipients.

Bone biomarkers in de novo renal transplant recipients

Successful kidney transplantation (partly) corrects the physiologic and metabolic abnormalities driving chronic kidney disease - mineral and bone disorders. At the same time, renal transplant recipients are exposed to immunosuppressive agents that may affect bone metabolism. Bone biomarkers have been suggested as surrogates of or adjuncts to bone biopsy and imaging techniques to assess bone health and to classify risk of bone loss and fractures. Bone biomarkers may be classified as circulating factors that affect bone metabolism (commonly referred to as bone metabolism markers) or that reflect bone cell number and/or activity (commonly referred to as bone turnover markers). A growing body of evidence shows that successful renal transplantation has a major impact on both bone metabolism and bone turnover. Analytical issues, including the cross-reactivity with fragments, complicate the interpretation of bone biomarkers, especially in the setting of a rapid changing kidney function, as is the case after successful renal transplantation. Overall, bone turnover seems to decline following renal transplantation, but inter-individual variability is substantial. Preliminary evidence indicates that bone biomarkers may be useful in guiding mineral and bone therapy in renal transplant recipients.

Prognostic value of bone- and vascular-derived molecular biomarkers in hemodialysis and renal transplant patients: a systematic review and meta-analysis

Background

Patients undergoing hemodialysis and kidney graft recipients are high-risk populations for cardiovascular and all-cause mortality. Fibroblast growth factor 23 (FGF23), osteoprotegerin (OPG), RANK ligand, osteopontin (OPN), Klotho protein and bone morphogenetic protein-7 (BMP-7) are bone- and vascular-derived molecular biomarkers that have been shown to be associated with cardiovascular surrogate end points; however, currently available data on the prognostic value of these biomarkers is inconsistent. The aim of the present study was to conduct a systematic review and meta-analysis in order to summarize the available evidence on the association of molecular biomarkers with mortality in individuals undergoing hemodialysis and renal transplant patients.

Methods

Two databases (MEDLINE and Embase) were systematically searched. Studies were eligible if the association of biomarker and mortality was reported as time-to-event data [hazard Ratio (HR)] or as effect size with a fixed time of follow-up [odds Ratio (OR)]. Abstracted HRs were converted onto a standard scale of effect and combined using a random effects model.

Results

From a total of 1170 studies identified in initial searches, 21 met the inclusion criteria. In hemodialysis patients, comparing the lower third with the upper third of baseline FGF23 distribution, pooled HRs (95% confidence intervals) were 1.94 (1.47, 2.56) for all-cause mortality and 2.4 (1.64, 3.51) for cardiovascular mortality. For the same comparison of baseline OPG distribution, pooled HRs were 1.8 (0.95, 3.39) for all-cause mortality and 2.53 (1.29, 4.94) for cardiovascular mortality. Reported risk estimates of RANK ligand, OPN, Klotho protein and BMP-7 were not suitable for pooling; however, only Klotho protein was significantly related to mortality. For kidney graft recipients, four studies that investigated the relationship of FGF23 and OPG with mortality were identified, all of which reported a significant association.

Conclusions

In hemodialysis patients, FGF23 is a predictor of all-cause and cardiovascular mortality, whereas the predictive value of OPG is restricted to cardiovascular mortality. Further studies are needed in order to gain insight into the prognostic value of these biomarkers in renal transplant recipients.

Elevated serum osteoprotegerin may predict peripheral arterial disease after kidney transplantation: a single-center prospective cross-sectional study in Taiwan

Background

Osteoprotegerin (OPG) is a potential biomarker for severity and complications of cardiovascular diseases. Peripheral arterial disease (PAD) is associated with an increased risk of death in kidney transplantation (KT) patients. This prospective cross-sectional study evaluated the relationship between serum OPG and PAD in KT patients.

Methods

Seventy-four KT patients were enrolled for this PAD study. Fasting blood samples were obtained to measure serum OPG levels by using enzyme-linked immunosorbent assay kits. The ankle-brachial index (ABI) of less than 0.9 was applied for PAD diagnosis.

Results

Thirteen patients (17.6%) were diagnosed with PAD. Diabetes (P = 0.025), smoking (P = 0.010), and increased OPG levels (P = 0.001) were significantly more frequent in the PAD group. Multivariate logistic regression analysis showed that serum OPG (odds ratio [OR], 1.336; 95% CI [1.108–1.611]; P = 0.002) and diabetes (OR, 7.120; 95% CI [1.080–46.940]; P = 0.041) were independent predictors of PAD in KT patients. The area under the receiver operating characteristic (ROC) curve determined that the probability of a serum OPG level of 7.117 pg/L in predicting PAD in KT patients was 0.799 (95% CI [0.690–0.884]; P < 0.001).

Discussion

Exploration of reliable biomarkers for early identification of vascular risk is crucial for KT patients. Elevated serum OPG levels may predict PAD in KT patients with cutoff value of 7.117 pg/L.

Serum osteoprotegerin and renal function in the general population: the Tromsø Study

Background

Serum osteoprotegerin (OPG) is elevated in patients with chronic kidney disease (CKD) and increases with decreasing renal function. However, there are limited data regarding the association between OPG and renal function in the general population. The aim of the present study was to explore the relation between serum OPG and renal function in subjects recruited from the general population.

Methods

We conducted a cross-sectional study with 6689 participants recruited from the general population in Tromsø, Norway. Estimated glomerular filtration rate (eGFR) was calculated using the Chronic Kidney Disease Epidemiology Collaboration equations. OPG was modelled both as a continuous and categorical variable. General linear models and linear regression with adjustment for possible confounders were used to study the association between OPG and eGFR. Analyses were stratified by the median age, as serum OPG and age displayed a significant interaction on eGFR.

Results

In participants ≤62.2 years with normal renal function (eGFR ≥90 mL/min/1.73 m²) eGFR increased by 0.35 mL/min/1.73 m² (95% CI 0.13–0.56) per 1 standard deviation (SD) increase in serum OPG after multiple adjustment. In participants older than the median age with impaired renal function (eGFR <90 mL/min/1.73 m²), eGFR decreased by 1.54 (95% CI −2.06 to −1.01) per 1 SD increase in serum OPG.

Conclusions

OPG was associated with an increased eGFR in younger subjects with normal renal function and with a decreased eGFR in older subjects with reduced renal function. Our findings imply that the association between OPG and eGFR varies with age and renal function.

High Serum Osteoprotegerin Is Associated with Arterial Stiffness in Kidney Transplant Patients

Osteoprotegerin (OPG) is a cytokine that regulates bone resorption by inhibiting osteoclastogenesis, and OPG has been implicated in the process that causes vascular stiffness. An increase in serum OPG level has been associated with the development of arterial stiffness. Kidney transplant (KT) patients are susceptible to aortic stiffness, which is considered to be a predictor of cardiovascular events in this patient population. Carotid-femoral pulse wave velocity (cfPWV) has emerged as a gold standard for non-invasive evaluation of aortic stiffness. The aim of this study was to evaluate the relationship between serum OPG concentration and cfPWV among KT patients. Fasting blood samples were obtained from 57 KT patients and their cfPWV was measured using applanation tonometry. The serum OPG levels were measured using an enzyme-linked immunosorbent assay. Univariable linear regression analysis showed that the cfPWV in KT patients was significantly and positively correlated with age, body weight, waist circumference, body mass index, log-creatinine, systolic blood pressure, diastolic blood pressure, pulse pressure, and the log-OPG concentration. KT patients with metabolic syndrome had higher cfPWV values than those without metabolic syndrome (P = 0.036), which indicates a higher incidence of aortic stiffness in this patient population. Multivariable forward stepwise linear regression analysis of the significant variables showed that the log-OPG (P = 0.001), the log-creatinine (P = 0.004), and the SBP (P = 0.005) remained as independent and positive predictors of cfPWV values. These findings indicate that serum OPG levels are positively associated with cfPWV in KT patients.

Receptor activator of nuclear factor κB ligand/osteoprotegerin axis and vascular calcifications in patients with chronic kidney disease

Vascular calcifications are commonly observed in patients with chronic kidney disease (CKD) and contribute to the excessive cardiovascular morbidity and mortality rates observed in these patients populations. Although the pathogenetic mechanisms are not yet fully elucidated, recent evidence suggests a link between bone metabolism and the development and progression of vascular calcifications. Moreover, accumulating data indicate that receptor activator of nuclear factor κB ligand/osteoprotegerin axis which plays essential roles in the regulation of bone metabolism is also involved in extra-osseous bone formation. Further studies are required to establish the prognostic significance of the above biomarkers as predictors of the presence and severity of vascular calcifications in CKD patients and of cardiovascular morbidity and mortality. Moreover, randomized clinical trials are needed to clarify whether inhibition of osteoclast activity will protect from vascular calcifications.

Serum osteoprotegerin levels associated with the aortic augmentation index in renal transplant recipients

OBJECTIVES

Arterial stiffness is recognized as an independent risk factor for cardiovascular morbidity and mortality. Recent studies found that osteoprotegerin (OPG) is associated with arterial stiffness and may reflect endothelial dysfunction. The aim of this study was to evaluate the relationship between fasting serum OPG levels and the aortic augmentation index (AIx) in renal transplant recipients.

MATERIALS AND METHODS

Fasting blood samples were obtained from 66 renal transplant recipients. The aortic AIx was measured using a validated tonometry system (SphygmoCor). Serum OPG levels were measured using a commercial enzyme-linked immunosorbent assay kit.

RESULTS

Univariate linear analysis of the aortic AIx in renal transplant recipients revealed that body fat mass (r = 0.377, p = 0.002), aortic diastolic blood pressure (DBP; r = 0.307, p = 0.020), triglycerides (r = 0.260, p = 0.035), and logarithmically transformed OPG (log-OPG, r = 0.402, p < 0.001) were positively correlated, whereas height (r = 0.361, p = 0.004) and body weight (r = 0.212, p = 0.041) were negatively correlated with the aortic AIx in renal transplant recipients. Multivariate forward stepwise linear regression analysis of the factors significantly associated with the aortic AIx showed that log-OPG (R2 = 0.213, p < 0.001), height (R2 = 0.081, p = 0.009), and aortic DBP (R2 = 0.058, p = 0.022) were independent predictors of the aortic AIx in renal transplant recipients.

CONCLUSION

These results suggest that the serum fasting OPG level is associated with the aortic AIx in renal transplant recipients.

Serum osteoprotegerin is associated with pulse pressure in kidney transplant recipients

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

Elevated Circulating Osteoprotegerin and Renal Dysfunction Predict 15-Year Cardiovascular and All-Cause Mortality: A Prospective Study of Elderly Women

Background

Data on the predictive role of estimated glomerular filtration rate (eGFR) and osteoprotegerin (OPG) for cardiovascular (CVD) and all-cause mortality risk have been presented by our group and others. We now present data on the interactions between OPG with stage I to III chronic kidney disease (CKD) for all-cause and CVD mortality.

Methods and Results

The setting was a 15-year study of 1,292 women over 70 years of age initially randomized to a 5-year controlled trial of 1.2 g of calcium daily. Serum OPG and creatinine levels with complete mortality records obtained from the Western Australian Data Linkage System were available. Interactions were detected between OPG levels and eGFR for both CVD and all-cause mortality (P < 0.05). Compared to participants with eGFR ≥60ml/min/1.73m² and low OPG, participants with eGFR of <60ml/min/1.73m² and elevated OPG had a 61% and 75% increased risk of all-cause and CVD mortality respectively (multivariate-adjusted HR, 1.61; 95% CI, 1.27-2.05; P < 0.001 and HR, 1.75; 95% CI, 1.22-2.55; P = 0.003). This relationship with mortality was independent of decline in renal function (P<0.05). Specific causes of death in individuals with elevated OPG and stage III CKD highlighted an excess of coronary heart disease, renal failure and chronic obstructive pulmonary disease deaths (P < 0.05).

Conclusion

The association between elevated OPG levels with CVD and all-cause mortality was more evident in elderly women with poorer renal function. Assessment of OPG in the context of renal function may be important in studies investigating its relationship with all-cause and CVD mortality.

Increased osteoprotegerin predicts poor virological outcome during anticytomegalovirus therapy in solid organ transplant recipients

BACKGROUND

Cytomegalovirus (CMV) infection involves interaction between endothelial cells and leukocyte subsets that may promote vascular inflammation and lead to treatment failure in infected individuals. Osteoprotegerin is a marker of vascular and systemic inflammation but has not been investigated in relation to treatment outcome during CMV infection.

METHODS

We investigated whether circulating levels of osteoprotegerin are related to features of CMV disease and treatment outcomes during CMV infection in 291 solid organ transplant recipients receiving valganciclovir or ganciclovir in an international multicenter trial of CMV disease treatment (the VICTOR study).

RESULTS

Elevated plasma osteoprotegerin was associated with (i) certain disease characteristics including presence of tissue invasive disease (P<0.05) and increased viral load at baseline (P<0.05), (ii) poor virological outcome at day 49 after anti-CMV therapy, (iii) increased plasma levels of markers of inflammation (pentraxin 3 and C-reactive protein) and endothelial cell activation (von Willebrand factor) both at baseline and during follow-up.

CONCLUSION

Our finding indicates that elevated osteoprotegerin levels in solid organ transplant recipients with CMV infection may reflect vascular inflammation and is associated with late virological outcome in these patients.

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.

Serum osteoprotegerin is associated with vascular stiffness and the onset of new cardiovascular events in hemodialysis patients

BACKGROUND/AIMS

Osteoprotegerin (OPG) and fetuin-A are vascular calcification regulators that may be related to high cardiovascular (CV) mortality in hemodialysis (HD) patients. We evaluated the relationship between OPG, fetuin-A, and pulse wave velocity (PWV), a marker of vascular stiffness, and determined whether OPG and fetuin-A were independent predictors of CV events in HD patients.

METHODS

We conducted a prospective observational study in 97 HD patients. OPG and fetuin-A were measured at baseline and arterial stiffness was evaluated by PWV. All patients were stratified into tertiles according to serum OPG levels.

RESULTS

A significant trend was observed across increasing serum OPG concentration tertiles for age, HD duration, systolic blood pressure, cholesterol, triglycerides, and PWV. Multiple linear regression analysis revealed that diabetes (β = 0.430, p = 0.000) and OPG levels (β = 0.308, p = 0.003) were independently associated with PWV. The frequency of new CV events was significantly higher in the upper OPG tertiles compared with those in the lower OPG tertiles. In Cox proportional hazards analysis, upper tertiles of OPG levels were significantly associated with CV events (hazard ratio = 4.536, p = 0.011).

CONCLUSIONS

Serum OPG, but not fetuin-A, levels were closely associated with increased vascular stiffness, and higher OPG levels may be independent predictors of new CV events in HD patients.

Calcium and osteoprotegerin levels predict the progression of the abdominal aortic calcifications after kidney transplantation

Background

Vascular calcifications (VCs) are a cardiovascular risk factor in patients affected by chronic kidney disease and after kidney transplantation (KTx). We evaluated the prevalence of VCs at the abdominal aortic site in KTx patients at the time of transplantation and 1 year after KTx, exploring the possibly associated factors.

Methods

In 107 transplanted patients, the following parameters were evaluated at the first and twelfth month after KTx: the aortic calcification index (ACI), fibroblast growth factor 23, osteoprotegerin (OPG), fetuin A, and clinical and biochemical parameters. Patients were followed up for 2 years after KTx.

Results

At the time of KTx, 60% of patients had some degree of VC (ACI>0), whereas 40% had no VC. One year after KTx, VCs worsened in 26% of patients, whereas in 74%, VCs remained stable or improved. The progression of VC was observed almost exclusively in patients with a positive ACI score at the first month. At the multivariate analysis, serum calcium, OPG, and estimated glomerular filtration rate were the only variables independently associated with the progression of VC.

Conclusions

VCs at the aortic site are frequent in KTx patients, and in a significant percentage of them, they tend to progress even in the short time. High levels of serum calcium and OPG are significantly associated with the progression of VCs. Whether these associations are based on a cause-effect relationship and their correction might impact on the calcification process could be ascertained by prospective interventional studies.

Cardiovascular risk assessment in children with chronic kidney disease

Chronic kidney disease (CKD) is a major factor contributing to cardiovascular (CV) morbidity and mortality with the highest risk in patients on dialysis. An estimation of CV risk is important not only to identify potential modifiable risk factors but also to evaluate the effect of treatments aimed to reduce the risk. Non-invasive methods of measuring vascular changes and circulating biomarkers are available to assess the presence and severity of cardiovascular damage. These include measures of structural (carotid intima-media thickness and coronary artery calcification score) and functional (aortic pulse wave velocity, 24-h ambulatory blood pressure monitoring, ambulatory arterial stiffness index, heart rate variability and flow-mediated dilatation) changes in the vessel wall. In addition, a number of circulating biomarkers of vascular damage and its progression have been studied. Many of these tests are well validated as surrogate markers of future cardiovascular events and death in adult CKD patients, but need technical adaptation, standardization and validation for use in children. With our current state of knowledge, these are best reserved for research studies and scarce clinical resources may be better utilized for preventative strategies to reduce the modifiable risk factors for calcification from early CKD stages.

Osteoprotegerin as a predictor of renal and cardiovascular outcomes in renal transplant recipients: follow-up data from the ALERT study

BACKGROUND

In patients with chronic kidney disease, vascular calcification contributes to increased cardiovascular (CV) morbidity and mortality. CV risk remains high after successful renal transplantation. Osteoprotegerin (OPG) is a glycoprotein, involved in the regulation of the vascular calcification process. Previous studies have shown that elevated OPG is predictive of mortality in high-risk populations. The aim of this study was to investigate the prognostic value of OPG for graft function, CV events and all-cause death, in a large transplant cohort.

METHODS

OPG was measured at baseline in renal transplant recipients enrolled in the Assessment of Lescol in Renal Transplantation (ALERT) study, a randomized placebo-controlled intervention study comparing fluvastatin and placebo. Patients were followed for 6.7 years with evaluation of pre-specified end points, graft loss, graft function, CV events and death.

RESULTS

OPG was analysed in 1889 renal transplant recipients, with a mean value of 4.69 ± 1.85 pg/L. The number of renal and CV events increased by quartiles of OPG. In the multivariate analysis, OPG in the fourth as compared to first quartile was an independent predictor of graft failure or doubling of serum creatinine [hazard ratio (HR) 2.20 (1.56-3.11), P < 0.001], major CV events [HR 2.40 (1.58-3.64), P < 0.001], cardiac mortality [HR 2.80 (1.32-5.94), P = 0.007] and all-cause mortality [HR 2.31 (1.53-3.49), P < 0.001].

CONCLUSION

In a large cohort of kidney transplant patients with long-term follow-up, OPG was independently associated with renal events, CV events and mortality.

Subclinical rejection in renal transplants is associated with low serum mannose-binding lectin levels

Surveillance biopsies have contributed to the understanding of the natural history of renal allograft lesions. Subclinical rejection, defined as the presence of histological lesions, indistinguishable from acute rejection in stable grafts, is associated with progression of interstitial fibrosis and tubular atrophy. The prevalence of subclinical rejection has decreased as more powerful immunosuppressive treatments have been introduced, suggesting that subclinical rejection represents the degree of control of the alloimmune response. However, non-immune factors such as donor age are also associated with the prevalence of subclinical rejection, suggesting that kidneys from older donors are more susceptible to insult and have a reduced capacity for tissue regeneration. Innate immunity has a crucial role in the modulation of the inflammatory response during infection and tissue damage. Mannose-binding lectin (MBL) is an innate immune protein, the polymorphisms of which are associated with infection, low-grade inflammation, diabetes, and cardiovascular disease. However, the relationship between MBL and disease is complex. For example, low MBL level is associated with higher risk for diabetes, whereas in patients with diabetes, high MBL level is associated with more severe renal damage. In renal transplant patients, low MBL levels are associated with an increased prevalence of infection and diabetes, whereas high MBL levels are associated with shortened graft survival. Although MBL is not clearly associated with prevalence of acute rejection, surveillance biopsy studies have shown that low MBL levels are associated with subclinical rejection in kidney and the heart, suggesting that MBL modulates the injury–repair process of the allograft.

Impact of sirolimus, tacrolimus and mycophenolate mofetil on osteoclastogenesis--implications for post-transplantation bone disease

BACKGROUND

Post-transplantation bone disease is associated with a high degree of morbidity including pain and fractures. Glucocorticoid-induced osteoporosis on top of pre-existing renal osteodystrophy is considered the major pathogenic factor, while the role of non-glucocorticoid immunosuppressants is less well defined.

METHODS

In this study, we investigated the influence of sirolimus (SRL) versus calcineurin inhibitor (CI)-based immunosuppressive regimens on biomarkers of bone resorption in renal transplant patients. In addition, the impact of SRL, tacrolimus and mycophenolate mofetil (MMF) on osteoclast activation and function was assessed in cell culture systems.

RESULTS

Using this approach, we demonstrated reduced serum levels of bone resorption markers in patients treated with SRL after kidney transplantation compared to a CI-based regimen. In line with this observation, we detected profoundly reduced osteoclast differentiation and subsequently diminished hydroxyapatite resorption in the presence of SRL compared to MMF and tacrolimus in vitro. Moreover, SRL significantly reduced osteoclast precursor proliferation in vitro compared to tacrolimus and led to augmented apoptosis in osteoclast precursors.

CONCLUSIONS

Taken together, SRL was shown to inhibit osteoclast formation in vivo and in vitro. SRL thus may have the potential to balance osteoclast promoting effects of glucocorticoids and CI, thereby counteracting the development of accelerated osteoporosis in renal transplant recipients.

Osteoprotegerin and progression of coronary and aortic calcifications in chronic kidney disease

Vascular calcifications (VCs) are important predictors of cardiovascular mortality in patients with chronic kidney disease (CKD). We have shown previously that osteoprotegerin (OPG), a potential early biomarker for VC, was an independent predictor of mortality in CKD patients. The aim of our study was to follow longitudinally coronary and aortic VCs. VCs were measured using Siemens 16 detector CT in a group of predialysis and hemodialyzed patients before and after a follow-up of 4 years. Some of these patients were transplanted in the meantime. Renal function, calcium, phosphate, iPTH, hs-CRP (high sensitive protein C reactive), and OPG serum levels were also compared. VCs progressed in predialysis, hemodialyzed, and transplanted patients but the progression was not the same in all arterial beds. A progression of coronary calcifications was observed in predialysis and transplanted patients, while aortic calcifications worsened significantly only in hemodialyzed patients. OPG serum levels and hs-CRP were significantly lower among transplanted patients. We concluded that VC depends on the severity of the kidney disease. Transplanted patients are not protected from VC, yet their OPG serum levels were significantly lower, suggesting that there is no link between between OPG levels and severity of VC. Longer follow-up of these patients would be necessary to assess whether a decline in OPG correlates with better survival.

Osteoprotegerin and mortality in type 2 diabetic patients

OBJECTIVE

Plasma osteoprotegerin (OPG) is an emerging strong and independent predictor of cardiovascular disease (CVD) in high-risk populations. OPG is a bone-related glycopeptide produced by vascular smooth muscle cells, and increased plasma OPG levels may reflect arterial vascular damage. We aimed to investigate the prognostic value of OPG in relation to all-cause and cardiovascular mortality in a cohort of type 2 diabetic patients.

RESEARCH DESIGN AND METHODS

In a prospective observational follow-up study, 283 type 2 diabetic patients (172 men; aged 53.9 ± 8.8 years) were followed for a median of 16.8 years (range 0.2-23.0). Baseline plasma OPG concentrations were determined by immunoassay.

RESULTS

During follow-up, 193 (68%) patients died. High versus low levels of OPG predicted all-cause mortality (covariate-adjusted for urinary albumin excretion rate [UAER], estimated glomerular filtration rate, and conventional risk factors); hazard ratio (HR) 1.81 [95% CI 1.21-2.69]. The all-cause predictive effect of OPG was independent of NH(2)-terminal pro-brain natriuretic peptide (NT-proBNP) and was also useful within groups divided according to level of UAER. In total, 103 (73%) patients died because of CVD. High and medium versus low levels of OPG predicted cardiovascular mortality (unadjusted HR 1.86 [95% CI 1.07-3.23] and 3.51 [2.10-5.85], respectively). However, after adjustment for the covariates, HRs were no longer significant.

CONCLUSIONS

Elevated plasma OPG is a strong predictor of all-cause mortality in type 2 diabetic patients. The effect of OPG on all-cause mortality was independent of conventional cardiovascular risk factors, UAER, and NT-proBNP levels.

Prognostic value of osteoprotegerin in chronic heart failure: The GISSI-HF trial

BACKGROUND

Circulating levels of osteoprotegerin (OPG), a member of the tumor necrosis factor receptor superfamily, is predictive of death and hospitalization for heart failure after acute coronary syndrome. The association between OPG and outcome in patients with chronic heart failure (CHF) is unknown.

METHODS

Plasma OPG levels at baseline were assessed in 1,229 patients with CHF recruited from 51 clinical centers and included in the Gruppo Italiano per lo Studio della Sopravvivenza nell'Infarto Miocardico-Heart Failure (GISSI-HF) trial. Patients were randomized to n-3 polyunsaturated fatty acids (1 g/d) or rosuvastatin (10 mg/d) versus placebo. Osteoprotegerin was analyzed by enzyme-linked immunosorbent assay. The association between OPG and outcome was assessed by Cox proportional hazards regression models.

RESULTS

During a median follow-up time of 3.9 years, 332 patients died; and 791 patients died or were hospitalized because of cardiovascular causes. By univariate analysis, baseline OPG levels were strongly associated with the incidence of death (hazard ratio {HR} [95% CI] 1.53 [1.40-1.67] per 1-SD increase in log OPG). After adjustment for conventional risk markers, OPG remained a significant predictor of death (HR [95% CI] 1.20 [1.06-1.35], P < .001). Similar findings were observed for the composite end point (HR [95% CI] 1.34 [1.07-1.69], P = .012).

CONCLUSION

In patients with CHF, OPG is associated with the incidence of death independently of conventional cardiovascular risk factors.

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.

A cohort study of the effects of serum osteoprotegerin and osteoprotegerin gene polymorphisms on cardiovascular mortality in elderly women

OBJECTIVE

To investigate the role of serum osteoprotegerin (OPG) and OPG gene polymorphisms in relation to cardiovascular (CV) and all-cause mortality in elderly women.

BACKGROUND

The OPG/RANK/RANKL plays a vital role in bone cell biology. It has also been detected in myocardial tissue and atherosclerotic plaques. In some population studies, OPG and OPG gene polymorphisms have been associated with CV disease risk.

DESIGN, MEASUREMENTS AND RESULTS

In an 8.5-year cohort population study of 1333 postmenopausal women mean age 75.2 ± 2.7 years, serum OPG concentrations above the median were associated with an increased risk of all-cause [odds ratio (OR) 1.39 (1.04-1.85)], and in particular CV mortality [OR 1.83 (1.10-3.05)], before and after adjusting for age, BMI, treated hypertension, diabetes, hypercholesterolemia, previous HRT use, calcium supplementation and smoking. Genotyping the OPG gene did not provide further information on the association between OPG and CV risk or mortality events.

CONCLUSIONS

Raised osteoprotegerin appears to be an independent risk factor for total and CV death and thus has potential as a useful biomarker of risk as well as a potential target for therapeutic intervention.

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.

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.

Elevated osteoprotegerin is associated with all-cause mortality in CKD stage 4 and 5 patients in addition to vascular calcification

BACKGROUND

Cardiovascular disease is the leading cause of death in the chronic kidney disease (CKD) population. The mechanisms of vascular damage are not fully understood. The objective of this study was to prospectively investigate the importance of novel mediators of vascular damage, in conjunction with vascular calcification (VC), on survival.

METHODS

A total of 134 subjects [60 haemodialysis (HD), 28 peritoneal dialysis (PD) and 46 CKD stage 4] were studied. All survivors completed 40 months of follow-up. VC was measured using multi-slice spiral CT of the superficial femoral artery. Circulating osteoprotegerin (OPG), Fetuin-A and high sensitivity C-reactive protein (hs-CRP) were measured in addition to standard clinical biochemical analysis.

RESULTS

After a 40-month follow-up, 31 patients had died (27 men and 4 women). Of 31 subjects, 31 had evidence of significant VC. The majority of deaths were in the HD group (48%), 36% were PD subjects and 16% were CKD subjects. The outcome of interest was survival at the end of follow-up. Multivariate logistical regression analysis revealed male gender [OR 8.06 (1.34-48.450) P = 0.02], OPG >25 pmol/L [OR 5.31(1.35-20.88) P = 0.02] and hypoalbuminaemia [OR 0.26 (0.12-0.56) P < 0.01], were associated with increased odds of death.

CONCLUSION

We have previously reported that VC and low albumin predict death in CKD stages 4 and 5 over a 2-year follow-up period. These data show that OPG, independent of CRP, is also associated with a negative outcome. The mechanisms remain to be elucidated; however, it is likely that they are associated with vascular damage through mechanisms in addition to VC.

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

AIMS/HYPOTHESIS

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

METHODS

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

RESULTS

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

CONCLUSIONS/INTERPRETATION

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

Impact of the complement lectin pathway on cytomegalovirus disease early after kidney transplantation

BACKGROUND

This study retrospectively investigated the association between pre-transplant levels of mannose-binding lectin (MBL) plus the associated serine protease (MASP)-2 and the occurrence of cytomegalovirus (CMV) infection and symptomatic CMV disease during the first 12 weeks after kidney transplantation. Materials and methods. Altogether 159 consecutive single kidney transplant recipients were included. The patients were screened for CMV pp65 antigenaemia every second week. No CMV prophylaxis or pre-emptive treatment was given. MBL and MASP-2 were measured in samples taken at transplantation and 10 weeks later.

RESULTS

CMV infection, defined as at least one positive test, was found in 95 patients (59.8%). MBL and MASP-2 measured at transplantation were similar in patients with and without CMV infection. The incidence of CMV infection was also similar in 36 patients (58.3%) with pre-transplant MBL levels below the reference level (500 microg/L) and in patients with higher MBL levels (60.2%). Symptomatic CMV disease was diagnosed in 35 patients (22%), and MASP-2 levels at transplantation in the lower quartile range (<or=148 microg/L) was significantly associated with CMV disease during the first 12 weeks, P = 0.028. MBL levels decreased significantly from transplantation to 10 weeks later, and median (interquartile range) fell from 2597 (526-4939) microug/L to 1520 (270-3069) microg/L (P < 0.001). In contrast, MASP-2 levels increased significantly from 252 (148-382) microg/L to 380 (302-492) microg/L (P < 0.001).

CONCLUSION

Pre-transplant MBL levels do not influence the incidence of any CMV infection or symptomatic CMV disease during the first 12 weeks after kidney transplantation. However, low MASP-2 levels may play a role in the development of symptomatic CMV disease.

Serum osteoprotegerin level, carotid-femoral pulse wave velocity and cardiovascular survival in haemodialysis patients

BACKGROUND

Osteoprotegerin (OPG) is a marker and regulator of arterial calcification, and it is related to cardiovascular survival in haemodialysis patients. The link between OPG and aortic stiffening--a consequence of arterial calcification--has not been previously evaluated in this population, and it is not known whether OPG-related mortality risk is mediated by arterial stiffening.

METHODS

At baseline, OPG and aortic pulse wave velocity (PWV) were measured in 98 chronic haemodialysis patients who were followed for a median of 24 months. The relationship between OPG and PWV was assessed by multivariate linear regression. The role of PWV in mediating OPG related cardiovascular mortality was evaluated by including both OPG and PWV in the same survival model.

RESULTS

At baseline mean (standard deviation) PWV was 11.2 (3.3) m/s and median OPG (interquartile range) was 11.1 (7.5-15.9) pmol/L. There was a strong, positive, linear relationship between PWV and lnOPG (P = 0.009, model R(2) = 0.540) independent of covariates. During follow-up 23 patients died of cardiovascular causes. In separate univariate survival models both PWV and lnOPG were related to cardiovascular mortality [hazard ratios 1.31 (1.14-1.50) and 8.96 (3.07-26.16), respectively]. When both PWV and lnOPG were entered into the same model, only lnOPG remained significantly associated with cardiovascular mortality [hazard ratio 1.11 (0.93-1.33) and 7.18 (1.89-27.25), respectively).

CONCLUSION

In haemodialysis patients OPG is strongly related to PWV and OPG related cardiovascular mortality risk is, in part, mediated by increased PWV.

Vascular calcification inhibitors in relation to cardiovascular disease with special emphasis on fetuin-A in chronic kidney disease

The mortality rate is extremely high in chronic kidney disease (CKD), primarily due to the high prevalence of cardiovascular disease (CVD) in this patient group. Apart from traditional Framingham risk factors, evidences suggest that nontraditional risk factors, such as inflammation, oxidative stress, endothelial dysfunction, and vascular calcification also contribute to this extremely high risk of CVD. Disturbance in the mineral metabolism, especially in the ions of Ca and PO4, are linked to enhanced calcification of blood vessels. Although the mechanism(s) of this enhanced calcification process are not fully understood, current knowledge suggests that a large number (and an imbalance between them) of circulating promoters and inhibitors of the calcification process, that is, fetuin-A (or alpha 2-Heremans-Schmid glycoprotein, AHSG), matrix-Gla protein (MGP), osteoprotegerin (OPG), osteopontin (OPN), bone morphogenetic proteins (BMPs), and inorganic pyrophosphate (PPi), are involved in the deterioration of vascular tissue. Thus, an imbalance in these factors may contribute to the high prevalence of vascular complications in CKD patients. Among these mediators, studies on fetuin-A deserve further attention as clinical studies consistently show that fetuin-A deficiency is associated with vascular calcification, all-cause and cardiovascular mortality in CKD patients. Both chronic inflammation and the uremic milieu per se may contribute to fetuin-A depletion, as well as specific mutations in the AHSG gene. Recent experimental and clinical studies also suggest an intriguing link between fetuin-A, insulin resistance, and the metabolic syndrome.

Vascular calcification and uremia: what do we know?

In the last decade, the nephrology community has focused its attention on the main cause of morbidity and mortality in chronic renal failure patients: cardiovascular disease. In addition, recent studies pointed out that vascular calcification (VC) is a major cause of cardiovascular disease in the dialysis population. Interestingly, the pathogenesis of VC and soft tissue calcification in chronic kidney disease (CKD) has been extensively investigated. Nowadays we know that VC is associated not only with passive calcium phosphate deposition, but also with an active, cell-mediated process. To better understand the pathogenesis of VC in CKD, numerous regulatory proteins have been studied, because of their ability to inhibit mineral deposition in the vessels. We here examine the state of the art of those substances recognized as regulatory key factors in preventing VC in uremic conditions, such as fetuin A (alpha2-Heremans-Schmid glycoprotein), matrix gamma-carboxyglutamic acid protein, pyrophosphate, osteoprotegerin and bone morphogenetic protein. We conclude that at present it is too early to introduce these novel markers into clinical practice.

Low pretransplantation mannose-binding lectin levels predict superior patient and graft survival after simultaneous pancreas-kidney transplantation

Simultaneous pancreas-kidney transplantation (SPKT) is the treatment of choice for patients with type 1 diabetes and renal failure. However, this procedure is characterized by a high rate of postoperative infections, acute rejection episodes, and cardiovascular mortality. The lectin pathway of complement activation contributes to cardiovascular disease in diabetes and may play an important role in inflammatory damage after organ transplantation. This study therefore sought to determine how mannose-binding lectin (MBL), a major recognition molecule of the lectin pathway of complement activation, influences outcome after SPKT. MBL serum levels were determined in 99 and MBL genotypes in 97 consecutive patients who received an SPKT from 1990 through 2000 and related to patient and graft survival. At 12 yr, cumulative death-censored kidney graft survival was 87.5% in patients with an MBL level <400 ng/ml and 74.8% in the group with MBL levels >400 ng/ml (P = 0.021). Pancreas graft survival was significantly better in patients with low MBL levels (P = 0.016). MBL levels >400 ng/ml were associated with a hazard ratio of 6.28 for patient death (95% confidence interval 1.8 to 20.3; P = 0.003). Accordingly, survival was significantly better in recipients with MBL gene polymorphisms associated with low MBL levels. These findings identify MBL as a potential risk factor for graft and patient survival in SPKT. It is hypothesized that MBL contributes to the pathogenesis of inflammation-induced vascular damage both in the transplanted organs and in the recipient's native blood vessels.

Effects of non-steroid immunosuppressive drugs on insulin secretion in transplantation

Post-transplantation diabetes (PTD) is a serious complication in organ transplantation: not only does it increase the risk of graft dysfunction; it also increases cardiovascular morbidity and mortality. PTD incidence is correlated with age, non-Caucasian ethnic background, a family history of diabetes, excess weight, hepatitis C infection and steroid boluses for potential rejection. Different mechanisms might explain post-transplantation glucose metabolism disorders: ischemia-reperfusion disorders, whether renal, hepatic or cardiac, are responsible for insulin-resistance, which is increased by post-transplantation steroids; the detrimental effect of non-steroid immunosuppressive drugs on insulin-secretion could also be involved, especially with calcineurin inhibitors. In vivo and in vitro studies have shown that tacrolimus has inhibitory effects on insulin-secretion, while these effects are less obvious for cyclosporin, and were mainly demonstrated in vitro. Mycophenolate has no overt effect on insulin-secretion. Sirolimus and everolimus, two mTOR inhibitors, have shown controversial results in this realm. The effects of sirolimus (most often studied mTOR inhibitor) appear to depend on serum levels, cell type (ss cell or cell line), species (human or animal) and also environmental nutrients. At therapeutic concentrations, a stimulatory effect on insulin secretion was observed on human beta cells. This might explain the success of islet cell transplantation with the Edmonton protocol. Finally, steroids are mainly detrimental because they accentuate insulin resistance whereas anticalcineurins, in particular tacrolimus, lower insulin synthesis.

Serum levels of calcification inhibition proteins and coronary artery calcium score: comparison between transplantation and dialysis

Vascular calcifications in CKD are now linked to serum alterations of both divalent ions and calcification inhibitory proteins. Due to possible biochemical differences between dialysis (D) and transplantation (Tx), we examined the entity and severity of these biochemical modifications and of coronary artery calcium score separately in these two populations. We assayed, besides standard markers of inflammation, divalent ions and serum levels of fetuin, matrix Gla protein (MGP) and osteoprotegerin (OPG), in 51 Tx patients (age 45 +/- 12 years; 30 males, 21 females; previous D duration 4.8 +/- 4.2 years; Tx since 6.6 +/- 5.5 years; Cr 1.8 +/- 0.6 mg/dl) and in 49 D patients (age 49 +/- 14 years; 30 males,19 females; D duration 5.6 +/- 4.8 years). Additionally, coronary calcium score (AS) was evaluated by cardiac multi-slice CT. Compared with D patients, Tx patients had better values of divalent ions and inflammation markers, and lower prevalence (65 vs. 86%; p < 0.02) and severity (AS = 570 +/- 1,637 vs. 1,311 +/- 3,128; p < 0.008) of coronary calcification. In addition, a tendency toward normalization for all of the three calcification inhibitory proteins was evident. In both Tx and D, AS correlated with age and OPG (Tx: r(s) = 0.439, p < 0.001, and r(s) = 0.510, p < 0.0001; D: r(s) = 0.471, p < 0.001, and r(s) = 0.403, p < 0.005, respectively); in D patients, a correlation was present also with D duration (r(s) = 0.435; p < 0.002), other markers of inflammation and, notably, fetuin (r(s) = -0.442; p < 0.002). Regression analysis selected previous time on D in Tx patients (r(m) = 0.400; p < 0.004), and C-reactive protein and OPG in D patients (r(m) = 0.518; p < 0.004) as the most predictive parameters of AS. Discriminant analysis confirmed the major role of age and D duration in the appearance of AS and evidenced male gender as a distinct risk condition. At variance, Tx duration was never associated with AS. In conclusion, as compared to D, renal Tx patients show serum levels of calcification inhibition proteins and of divalent ions closer to normal. As this is associated with a lower prevalence and severity of AS, it is suggested that Tx antagonize the accelerating role of D in the progression of vascular calcification. Assessment of both coronary calcifications and serum levels of calcification inhibitory proteins may be of value to identify those subjects at higher risk of development and progression of vascular lesions, among whom males have the highest rate.