Sclerostin Serum Levels and Vascular Calcification Progression in Prevalent Renal Transplant Recipients

CONTEXT

Vascular calcification (VC) is prevalent and progressive in renal transplant recipients (RTRs). Recent cross-sectional data suggest that activated Wnt signaling contributes to VC.

OBJECTIVE

The objective was to investigate whether circulating levels of the Wnt antagonist sclerostin associate with progression of VC.

DESIGN

This was a post hoc analysis of the longitudinal observational Brussels Renal Transplant Cohort study.

SETTING

The setting was a tertiary care academic hospital.

PATIENTS

Coronary artery calcification and aorta calcification were measured by multislice spiral computerized tomography in 268 prevalent RTRs (age, 53 ± 13 y; 61% male) at baseline and remeasured in 189 patients after a median follow-up of 4.4 years. Baseline serum sclerostin levels were assessed on stored blood samples. Regression analysis was performed to identify determinants of baseline VC and progression.

MAIN OUTCOME MEASURE

The main outcome measure was progression of VC.

RESULTS

VC was present in up to 84% of participants at baseline. Almost half of the patients showed progression of VC, according to Hokanson criteria. The cross-sectional analysis at baseline demonstrated a direct association between sclerostin levels and VC score in univariate analysis, which became inverse after adjustment for age, gender and PTH level. Remarkably, a lower sclerostin level was identified as an independent determinant of a higher baseline aorta calcification score in the final regression model. Moreover, baseline sclerostin levels showed an inverse association with VC progression, at least after adjustment for traditional risk factors.

CONCLUSIONS

Serum sclerostin levels inversely associated with VC burden and progression in prevalent RTRs after adjustment for traditional risk factors. Our data corroborate previous findings in nontransplanted chronic kidney disease patients and support the notion that sclerostin may be up-regulated in the vascular wall during the VC process as part of a local counterregulatory mechanism directed to suppress VC. Additional clinical and experimental data are required for confirmation.

The effect of anastomosis time on outcome in recipients of kidneys donated after brain death: a cohort study

Whether warm ischemia during the time to complete the vascular anastomoses determines renal allograft function has not been investigated systematically. We investigated the effect of anastomosis time on allograft outcome in 669 first, single kidney transplantations from brain-dead donors. Anastomosis time independently increased the risk of delayed graft function (odds ratio per minute [OR] 1.05, 95% confidence interval [CI] 1.02-1.07, p < 0.001) and independently impaired allograft function after transplantation (p = 0.009, mixed-models repeated-measures analysis). In a subgroup of transplant recipients, protocol-specified biopsies at 3 months (n = 186), 1 year (n = 189), and 2 years (n = 153) were blindly reviewed. Prolonged anastomosis time independently increased the risk of interstitial fibrosis and tubular atrophy on these protocol-specified biopsies posttransplant (p < 0.001, generalized linear models). In conclusion, prolonged anastomosis time is not only detrimental for renal allograft outcome immediately after transplantation, also longer-term allograft function and histology are affected by the duration of this warm ischemia.

Safety and efficacy of different lanreotide doses in the treatment of polycystic liver disease: pooled analysis of individual patient data

BACKGROUND

Long-acting lanreotide (LAN) 120 mg every 4 weeks reduces liver volume (LV) in patients with polycystic liver diseases (PCLD). Animal studies demonstrated that the inhibition of hepatic and renal cystogenesis is dose dependent.

AIM

To investigate the safety and efficacy of two different LAN doses in PCLD patients.

METHODS

The 6-month results of the LOCKCYST I trial, its extension study and the LOCKCYST II trial were pooled. LV at baseline and month 6 was measured by CT-scan and blindly re-analysed by two independent radiologists.

RESULTS

The study population [132 treatment periods, age 49 years (IQR: 45-55), 114 women] consisted of three groups. Each received treatment every 4 weeks during 6 months: placebo (n = 26); LAN 90 mg (n = 55) or LAN 120 mg (n = 51). The inter-observer variability and agreement in the calculation of LV were excellent. Severe side effects occurred with placebo, LAN 90 mg and LAN 120 mg in respectively 0%, 7% and 16%. Change in LV's after 6 months in these three groups were respectively: increase of +36 mL [(-45)-(+138)]; decrease of -82 mL [(-285)-(+92)] and decrease of -123 mL [(-312)-(+4)] (Kruskal-Wallis One Way anova on Ranks; P = 0.002). Based on ROC analysis, a reduction of ≥120 mL in LV has a positive predictive value of 64% for improving symptoms (ROC analysis AUC: 0.729; sensitivity 73%, specificity 69%, P < 0.0001).

CONCLUSIONS

Both LAN 90 mg and LAN 120 mg reduce liver volume. LAN 90 mg has less side effects. This suggests that in case of intolerance to LAN 120 mg, a dose reduction to LAN 90 mg is meaningful.

Combined kidney and intestinal transplantation in patients with enteric hyperoxaluria secondary to short bowel syndrome

Kidney transplantation is the treatment of choice for end-stage renal disease whereas indications for intestinal transplantation are currently restricted to patients with irreversible small bowel failure and severe complications of total parenteral nutrition (mostly shortage and infection of venous accesses, major electrolyte disturbances and liver failure). Enteric hyperoxaluria is secondary to certain intestinal diseases like intestinal resections, chronic inflammatory bowel disease and other malabsorption syndromes and can lead to end-stage renal disease requiring kidney transplantation. We report two patients suffering from renal failure due to enteric hyperoxaluria (secondary to extensive intestinal resection) in whom we elected to replace not only the kidney but also the intestine to prevent recurrence of hyperoxaluria in the transplanted kidney.

Post-streptococcal glomerulonephritis: not an extinct disease!

We present the case of a 29-year-old type 1 diabetic patient with the diagnosis of acute post-streptococcal glomerulonephritis. The incidence of this textbook example of acute glomerulonephritis has dropped dramatically in the developed world during the past decades due to the more widespread use of antibiotics. However, the present case illustrates that it is not an extinct disease and that clinicians should be aware of this entity. Particular attention is needed for the fact that the clinical context in which the disease occurs may be different from the classical "post-angina" presentation.

Chronic histological damage in early indication biopsies is an independent risk factor for late renal allograft failure

The impact of early histological lesions of renal allografts on long-term graft survival remains unclear. We included all renal allograft recipients transplanted at a single center from 1991 to 2001 (N = 1197). All indication biopsies performed within the first year after transplantation were rescored according to the current Banff classification. Mean follow-up time was 14.8 ± 2.80 years. In multivariate Cox proportional hazards analysis, arteriolar hyalinosis and transplant glomerulopathy were independently associated with death-censored graft survival, adjusted for baseline demographic covariates. Arteriolar hyalinosis correlated with interstitial fibrosis, tubular atrophy, mesangial matrix increase, vascular intimal thickening and glomerulosclerosis. Clustering of the patients according to these chronic lesions, reflecting the global burden of chronic injury, associated better with long-term graft survival than each of the chronic lesions separately. Early chronic histological damage was an independent risk factor for late graft loss, irrespective whether a specific, progressive disease was diagnosed or not, while T cell-mediated rejection did not. We conclude that individual chronic lesions like arteriolar hyalinosis, tubular atrophy, interstitial fibrosis, glomerulosclerosis, mesangial matrix increase and vascular intimal thickening cannot be seen as individual entities. The global burden of early chronic histological damage within the first year after transplantation importantly affects the fate of the allografts.

Measuring the glomerular filtration rate in different age groups using iohexol, the protocol from the Belgian iohexol study

OBJECTIVES

Measuring the exact glomerular filtration rate (GFR) is difficult. Iohexol can be used instead of inulin or labeled EDTA or DTPA. In recent years, different studies have validated GFR-estimating equations in adults. Validation of these estimations in adolescents and elderly is lacking. With this study, we aim to develop a simplified (only 1-3 blood collections) iohexol protocol to measure the true GFR for patients of all ages and try to develop GFR-estimating equations for adolescents and the elderly.

DESIGN AND SETTING

Participants of different ages will be recruited: 50 adolescent (14-18 years) and 30 adults (20-65 years), 60 elderly (65-80 years) and 60 very elderly (80+ years old) stratified based on their GFR. Biometric data, serum creatinine and cystatin C will be measured. After injecting 5 mL iohexol, 9 blood samples will be taken between 20 and 360 min. First, the GFR will be calculated by using the double exponential decay method and different GFRs based on 1-3 blood samples, which will be compared with the GFR of the abovementioned 9 samples. Second, the GFR will be calculated by using new and existing equations and compared to the true GFR.

DISCUSSION

The availability of a reliable GFR measurement is important in situations such as screening patients for kidney donation or when taking potentially nephrotoxic treatments. This study will allow us to develop a simplified protocol for measuring the true GFR in all ages and will allow us to validate existing equations and develop new eGFR equations for adolescents and the elderly.

Systematic review: the pathophysiology and management of polycystic liver disease

BACKGROUND

Polycystic liver diseases (PCLD) represent a group of genetic disorders in which cysts occur solely in the liver, or together with renal cysts. Most of the patients with PCLD are asymptomatic, however, in some patients, expansion of liver cysts causes invalidating abdominal symptoms.

AIM

To provide a systemic review on the pathophysiology and management of PCLD.

METHODS

A PubMed search was undertaken to identify relevant literature using search terms including polycystic liver disease, pathophysiology, surgical and medical management.

RESULTS

The most common complication in patients with PCLD is extensive hepatomegaly, which may lead to malnutrition and can be lethal. Conservative surgical approaches are only partially effective and do not change the natural course of the disease. Liver transplantation has been successfully performed in PCLD, however, in an era of organ shortage, medical management needs to be evaluated. A better understanding of the pathophysiology and the availability of animal models have already identified promising drugs. Abnormalities in cholangiocyte proliferation/apoptosis and enhanced fluid secretion are key factors in the pathophysiology. It has been demonstrated in rodents and in humans that somatostatin analogues diminish liver volume. The role of the inhibitors of the mammalian target of rapamycin (mTOR) in the management of PCLD is still under investigation.

CONCLUSIONS

The exact pathophysiology of polycystic liver disease still remains unclear. In symptomatic patients, none of the currently available surgical options except liver transplantation have been shown to change the natural course of the disease. The use of somatostatin analogues has been shown to diminish liver volume.

Fluctuations of haemoglobinaemia in chronic haemodialysis patients

In March 2008 and June 2009, an ad hoc working group of nephrologists discussed the status of anaemia therapy with erythropoiesis-stimulating agents [ESA] in patients on chronic haemodialysis, the phenomenon of fluctuations of haemoglobinaemia, and the need for individualisation of ESA treatment. The working group put together the following statements: (1) ESAs increase the haemoglobin concentration and adaptations of the ESA dose adjust the response according to a negative-feedback loop. The long lag time between an ESA dose change and its effect on erythropoiesis is cumbersome. The optimal haemoglobin target concentration is different for every haemodialysis patient; the lowest haemoglobin concentration upon which one could consistently demonstrate a positive subjective and objective clinical benefit in chronic dialysis is 11 g/dL, in contrast to the lowest haemoglobin concentration of 10 g/dL recommended in the current EMEA label for ESAs. (2) Intra-individual fluctuation of haemoglobinaemia over time is unavoidable, not only due to the ESA dose/haemoglobin response interaction, but also, and more importantly, due to the occurrence of acute illnesses and exacerbations of co-morbid conditions. Many different methodologies to characterise haemoglobin variability have been described but there is currently no universally applied definition of the phenomenon. (3) An impact of the haemoglobin level and the amplitude of the haemoglobin fluctuations on patient outcome has been observed. Without disclosing any causal relationship, worse outcomes were associated with haemoglobin fluctuations around the lower target level, but later on, more simply linked to the relative time spent below the haemoglobin concentration of 11 g/dL and to the administration of inappropriately high ESA doses in order to achieve the recommended haemoglobin target range. A plausible mechanism might be that acute illnesses blunt the patients' basal ESA sensitivity; this leads to subnormal and/or varying haemoglobin levels, currently initiating an ESA dose increase. The longer it takes the patient to recover from the acute illness, the more the prolongation of the clinically poor condition is to some extent maintained by the persistence of low haemoglobinaemia and/or by the administration of high ESA doses, and, as such, on their turn possibly contributing to an ultimate poor outcome. In the absence of clinical trials, recommendations should be offered how to proceed with the administration of ESAs as optimal as possible in periods of clinical instability.

Localization, etiology and impact of calcium phosphate deposits in renal allografts

Hypercalcemia, hypophosphatemia and renal phosphate wasting are common after kidney transplantation. Animal data suggest that these alterations in mineral metabolism may contribute to calcium phosphate (CaPhos) deposition in the kidney and renal dysfunction. We tested the hypothesis that CaPhos deposition is highly prevalent in the early posttransplant period and is related to a disturbed mineral metabolism. For this purpose, biomarkers of mineral metabolism and renal calcium and phosphorus handling were prospectively assessed in 201 renal transplant recipients. CaPhos deposits were observed in 4.6, 30.4 and 24.7% of protocol biopsies obtained at the time of engraftment, and 3 and 12 months thereafter, respectively. In multivariate logistic regression analysis, high calcium and low serum phosphorus levels were independently associated with renal CaPhos deposition at month 3. The extent of CaPhos deposition correlated significantly with the severity of mineral metabolism disturbances. Renal function after a mean follow-up of 33 months was similar in patients with and without CaPhos deposition at month 3. In conclusion, our data demonstrate that CaPhos deposition is highly prevalent in the early posttransplant period and suggest that a disordered mineral metabolism is implicated in its pathogenesis. The clinical relevance of CaPhos deposition remains to be established.

Free p-cresol is associated with cardiovascular disease in hemodialysis patients

Cardiovascular disease (CVD) is highly prevalent in chronic kidney disease, suggesting that molecules retained in uremia might contribute to this increased risk. We explored the relationship between p-cresol, a protein-bound uremic retention solute, and CVD by comparing the strength of this relationship relative to traditional and novel cardiovascular risk factors. Univariate Cox proportional hazard analysis showed that the free serum p-cresol concentration was significantly associated with CVD when the primary end point was the time to the first cardiovascular event. In multivariate analysis, free p-cresol was significantly associated with CVD in non-diabetics. In diabetic patients, however, a significant relationship between p-cresol and cardiovascular events could not be demonstrated despite their having significantly higher p-cresol levels. Our study shows that free p-cresol is a novel cardiovascular risk factor in non-diabetic hemodialysis patients.

Influenza vaccination is efficacious and safe in renal transplant recipients

Whether influenza vaccination in solid-organ transplant recipients is efficacious remains a controversial issue. Furthermore, theoretical concerns have been raised regarding the safety of vaccination as it might trigger rejection of the allograft. The present prospective trial is aimed at investigating the antibody response and safety of influenza vaccination in renal transplant recipients (RTR). A total of 165 RTR and 41 healthy volunteers were vaccinated with a standard trivalent inactivated influenza vaccine. Hemagglutination-inhibiting (HI) antibodies were quantified before and 1 month after vaccination. Seroprotection (SP) and seroresponse (SR) were defined as a titer > or =40 and a 4-fold rise in HI titer, respectively. Similar SR rates were observed in both groups. Postvaccination SP rates in RTR amounted to 92.7%, 78.7% and 82.9% for A/H1N1, A/H3N2 and B, respectively. High baseline SP rates, most probably reflecting frequent preimmunizations, explain partly the high postvaccination SP rates. SR rate was independently and inversely associated with baseline SP rate. Mycophenolate mofetil (MMF) usage was associated with a 2.6-5-fold lower SR. Nonetheless, these patients showed good postvaccination SP rates. A booster dose did not enhance SP or SR rates. Influenza vaccination neither affected allograft function nor caused rejection episodes. In conclusion, influenza vaccination is efficacious and safe in renal transplantation.

Major coagulation disturbances during fractionated plasma separation and adsorption

Fractionated Plasma Separation and Adsorption (FPSA) is a novel nonbiologic detoxification system for the removal of protein-bound solutes. FPSA is used to bridge patients during fulminant liver failure, either to functional recovery or to liver transplantation. Besides liver failure associated protein bound solutes, several important uremic retention solutes share important protein binding. We observed repeated occlusive thrombosis of the arterio-venous conduit during FPSA in hemodialysis (HD) patients, resulting in acute loss of function. A major reduction of several coagulation factors was demonstrated, exceeding 50% for factor II, factor X and protein C. Broad disturbances of the coagulation system were confirmed in FPSA treated liver failure patients. An ex vivo recirculation model demonstrated nonspecific adsorption of coagulation factors protein S and protein C on the anion exchange cartridge. Direct contact between fractionated plasma and the Prometh02 anion exchanger causes significant adsorption of procoagulant and anti-coagulant factors, associated with clinically relevant adverse events.

Superior dialytic clearance of β2-microglobulin and p-cresol by high-flux hemodialysis as compared to peritoneal dialysis

Both residual renal and dialytic clearance confer to the total solute clearance in dialysis patients. Dialytic clearances of the middle molecule beta-microglobulin (beta(2)M) and the protein-bound solute p-cresol (pcr) are generally believed to be higher with peritoneal dialysis (PD) as compared to hemodialysis (HD). Supportive data, however, are lacking. We performed a single-center cross-sectional observational study including 70 unselected patients treated with either high-flux HD (n=20) or PD (n=50). Mid-day serum levels (PD) and time-averaged concentrations (HD) of the water-soluble solutes urea nitrogen, creatinine and phosphate, the middle molecule beta(2)M, and the protein-bound solute pcr were determined. Dialytic solute clearances (l/week/1.73 m(2)) were calculated from total dialysate collection during the mid-week session in HD and 24 h dialysate collection in PD. Renal clearances were calculated for each of the respective solutes from a timed urine collection. Total clearances were obtained by summation. HD delivered significantly higher clearances of all retention solutes studied. This superiority was especially pronounced for pcr (30.9+/-62.7 vs 4.4+/-2.3, HD vs PD, P<0.0001) and beta(2)M (28.6+/-6.6 vs 5.8+/-3.1, HD vs PD, P<0.0001). Renal clearances, conversely, were significantly higher in patients on PD. Serum levels of all solutes but pcr were significantly lower in HD than in PD. Both a higher residual renal function and a lower generation rate contribute to the lower pcr levels in PD. In conclusion, superior dialytic clearance of both water-soluble solutes, beta(2)M, and pcr is achieved by high-flux HD as compared to PD.

Free serum concentrations of the protein-bound retention solute p-cresol predict mortality in hemodialysis patients

Based on in vitro data, protein-bound uremic retention solutes have increasingly been recognized to play a pathophysiological role in the uremic syndrome. p-Cresol, a representative of this group of molecules, has been shown to be implicated in uremic immunodeficiency and endothelial dysfunction, potentially linking its serum levels to mortality. Thus far, however, no clinical information on this issue is available. To determine the relationship between p-cresol and all-cause mortality, 175 prevalent hemodialysis (HD) patients were enrolled in a prospective study. At baseline, serum levels of the water-soluble solutes urea, creatinine, and phosphate, the middle molecule beta2-microglobulin, total and free concentrations of the protein-bound solute p-cresol, and several risk factors for mortality were evaluated. During a median follow-up of 34 months, 60 patients died. Baseline comorbidity (Davies score) (hazard ratio (HR), 1.49; 95% confidence interval (95% CI), 1.19-1.86), impaired nutritional status (HR, 4.22; 95% CI, 2.15-8.29), time since initiation of dialysis (HR, 0.98; 95% CI, 0.97-1.00), and higher free concentrations of the protein-bound solute p-cresol (HR, 2.28; 95% CI, 1.12-4.64) were independently associated with mortality (multivariate Cox proportional hazards analysis). Our data suggest that free serum levels of p-cresol, a representative of the protein-bound uremic retention solutes, are associated with mortality in HD patients. These findings may encourage nephrologists to widen their field of interest beyond the scope of small water-soluble uremic solutes and middle molecules.

Acarbose treatment lowers generation and serum concentrations of the protein-bound solute p-cresol: a pilot study

Several protein-bound uremic retention solutes (including p-cresol) originate from colonic bacterial fermentation of protein. Higher colonic availability of carbohydrates drives this process towards lower production of toxic metabolites. Small intestinal alpha-glucosidase inhibitors like Acarbose (Glucobay) enhance the amount of undigested carbohydrates reaching the colon. We studied the effect of Acarbose on generation and serum concentrations of p-cresol. Nine healthy volunteers (age 25 (22-36) years) with a creatinine clearance of 89.6 ml/min/1.73 m(2) (85.5-116.4) were treated with Acarbose for 3 weeks. Dose was gradually increased to reach 300 mg/day after 1 week. Blood sampling, 24-h urine and stool collections on 3 consecutive days were performed before and during the last days of the treatment period. p-Cresol generation was estimated from mean 24-h urinary elimination. Gastrointestinal side effects, if present, were mild to moderate. Serum concentrations of p-cresol declined significantly after Acarbose treatment (before: 1.14 mg/l (0.93-3.03); after: 1.11 mg/l (0.31-1.82); P=0.047). Urinary excretion of p-cresol, reflecting its colonic generation rate, was significantly lower after treatment (before: 29.93 mg/day (6.79-75.19); after: 10.54 mg/day (1.08-30.85); P=0.031). The fecal excretion of nitrogen increased after treatment (before: 1.04 g/day (0.47-2.29); after: 1.99 g/day (0.76-3.08); P=0.047). This pilot study suggests that Acarbose treatment lowers generation and serum concentrations of the protein-bound uremic solute p-cresol. Although further confirmation is warranted, the data may point to a novel treatment option for chronic kidney disease patients in view of the potential toxic effects of p-cresol and related substances.