Stefan Farese

Nanoparticle-Based Test Measures Overall Propensity for Calcification in Serum

Vascular and soft tissue calcification contributes to cardiovascular morbidity and mortality in both the general population and CKD. Because calcium and phosphate serum concentrations are near supersaturation, the balance of inhibitors and promoters critically influences the development of calcification. An assay that measures the overall propensity for calcification to occur in serum may have clinical use. Here, we describe a nanoparticle-based assay that detects, in the presence of artificially elevated calcium and phosphate concentrations, the spontaneous transformation of spherical colloidal primary calciprotein particles (CPPs) to elongate crystalline secondary CPPs. We used characteristics of this transition to describe the intrinsic capacity of serum to inhibit the precipitation of calcium and phosphate. Using this assay, we found that both the sera of mice deficient in fetuin-A, a serum protein that inhibits calcification, and the sera of patients on hemodialysis have reduced intrinsic properties to inhibit calcification. In summary, we developed a nanoparticle-based test that measures the overall propensity for calcification in serum. The clinical use of the test requires evaluation in a prospective study.

Sodium thiosulfate prevents vascular calcifications in uremic rats

Accelerated vascular calcification is a severe complication of chronic kidney disease contributing to high morbidity and mortality in patients undergoing renal replacement therapy. Sodium thiosulfate is increasingly used for the treatment of soft tissue calcifications in calciphylaxis. Therefore, we determined whether it also prevents development of vascular calcifications in chronic kidney disease. We found that uremic rats treated by thiosulfate had no histological evidence of calcification in the aortic wall whereas almost three-fourths of untreated uremic rats showed aortic calcification. Urinary calcium excretion was elevated and the calcium content of aortic, heart, and renal tissue was significantly reduced in the thiosulfate-treated compared to non-treated animals. Sodium thiosulfate treatment transiently lowered plasma ionized calcium and induced metabolic acidosis. It also lowered bone strength in the treated animals compared to their normal controls. Hence, sodium thiosulfate prevented vascular calcifications in uremic rats, likely by enhancing acid- and/or chelation-induced urinary calcium loss. The negative impact on rat bone integrity necessitates a careful risk-benefit analysis before sodium thiosulfate can be used in individual human patients.

Serum Calcification Propensity Predicts All-Cause Mortality in Predialysis CKD

Medial arterial calcification is accelerated in patients with CKD and strongly associated with increased arterial rigidity and cardiovascular mortality. Recently, a novel in vitro blood test that provides an overall measure of calcification propensity by monitoring the maturation time (T50) of calciprotein particles in serum was described. We used this test to measure serum T50 in a prospective cohort of 184 patients with stages 3 and 4 CKD, with a median of 5.3 years of follow-up. At baseline, the major determinants of serum calcification propensity included higher serum phosphate, ionized calcium, increased bone osteoclastic activity, and lower free fetuin-A, plasma pyrophosphate, and albumin concentrations, which accounted for 49% of the variation in this parameter. Increased serum calcification propensity at baseline independently associated with aortic pulse wave velocity in the complete cohort and progressive aortic stiffening over 30 months in a subgroup of 93 patients. After adjustment for demographic, renal, cardiovascular, and biochemical covariates, including serum phosphate, risk of death among patients in the lowest T50 tertile was more than two times the risk among patients in the highest T50 tertile (adjusted hazard ratio, 2.2; 95% confidence interval, 1.1 to 5.4; P=0.04). This effect was lost, however, after additional adjustment for aortic stiffness, suggesting a shared causal pathway. Longitudinally, serum calcification propensity measurements remained temporally stable (intraclass correlation=0.81). These results suggest that serum T50 may be helpful as a biomarker in designing methods to improve defenses against vascular calcification.

Randomized, Double-Blind Comparative Trial of Subunit and Virosomal Influenza Vaccines for Immunocompromised Patients

BACKGROUND To our knowledge, no study to date has compared the effects of a subunit influenza vaccine with those of a virosomal influenza vaccine on immunocompromised patients. METHODS A prospective, double-blind, randomized study was conducted to compare the immunogenicity and reactogenicity of subunit and virosomal influenza vaccines for adult patients who had an immunosuppressive disease or who were immunocompromised as a result of treatment. RESULTS There were 304 patients enrolled in our study: 131 with human immunodeficiency virus (HIV) infection, 47 with a chronic rheumatologic disease, 74 who underwent a renal transplant, 47 who received long-term hemodialysis, and 5 who had some other nephrologic disease. There were 151 patients who received the subunit vaccine and 153 patients who received the virosomal vaccine. A slightly higher percentage of patients from the subunit vaccine group were protected against all 3 influenza vaccine strains after being vaccinated, compared with patients from the virosomal vaccine group (41% vs. 30% of patients; P = .03). Among HIV-infected patients, the level of HIV RNA, but not the CD4 cell count, was an independent predictor of vaccine response. Among renal transplant patients, treatment with mycophenolate significantly reduced the immune response to vaccination. The 2 vaccines were comparable with regard to the frequency and severity of local and systemic reactions within 7 days after vaccination. Disease-specific scores for the activity of rheumatologic diseases did not indicate flare-ups 4-6 weeks after vaccination. CONCLUSIONS For immunosuppressed patients, the subunit vaccine was slightly more immunogenic than the virosomal vaccine. The 2 vaccines were comparable with regard to reactogenicity. Vaccine response decreased with increasing degree of immune suppression. Among HIV-infected patients, the viral load, rather than the CD4 cell count, predicted the protective immune response to the vaccine. CLINICAL TRIALS REGISTRATION NCT00783380 .

Calcification Propensity and Survival among Renal Transplant Recipients

Calciprotein particle maturation time (T50) in serum is a novel measure of individual blood calcification propensity. To determine the clinical relevance of T50 in renal transplantation, baseline serum T50 was measured in a longitudinal cohort of 699 stable renal transplant recipients and the associations of T50 with mortality and graft failure were analyzed over a median follow-up of 3.1 years. Predictive value of T50 was assessed for patient survival with reference to traditional (Framingham) risk factors and the calcium-phosphate product. Serum magnesium, bicarbonate, albumin, and phosphate levels were the main determinants of T50, which was independent of renal function and dialysis vintage before transplant. During follow-up, 81 (12%) patients died, of which 38 (47%) died from cardiovascular causes. Furthermore, 45 (6%) patients developed graft failure. In fully adjusted models, lower T50 values were independently associated with increased all-cause mortality (hazard ratio, 1.43; 95% confidence interval, 1.11 to 1.85; P=0.006 per SD decrease) and increased cardiovascular mortality (hazard ratio, 1.55; 95% confidence interval, 1.04 to 2.29; P=0.03 per SD decrease). In addition to age, sex, and eGFR, T50 improved prognostication for all-cause mortality, whereas traditional risk factors or calcium-phosphate product did not. Lower T50 was also associated with increased graft failure risk. The associations of T50 with mortality and graft failure were confirmed in an independent replication cohort. In conclusion, reduced serum T50 was associated with increased risk of all-cause mortality, cardiovascular mortality, and graft failure and, of all tested parameters, displayed the strongest association with all-cause mortality in these transplant recipients.

Effect of Transcutaneous Electrical Muscle Stimulation and Passive Cycling Movements on Blood Pressure and Removal of Urea and Phosphate During Hemodialysis

BACKGROUND Intradialytic exercise has been described to improve blood pressure stability and dialysis efficacy. However, comorbid conditions in the dialysis population often preclude the widespread use of active intradialytic exercise. Therefore, we investigated the effect of intradialytic transcutaneous muscle stimulation (TEMS) and passive cycling movements (PCMs) on blood pressure and dialysis efficacy in patients. STUDY DESIGN Prospective, controlled, randomized, crossover investigation. SETTING & PARTICIPANTS Ten patients were randomly allocated to TEMS, PCMs, or no intervention (NI) for 9 consecutive dialysis sessions. INTERVENTION Participants were studied with NI, PCMs using a motor-driven ergometer, and bilateral TEMS of the leg musculature. Individual dialysis prescriptions were unchanged during the investigation. OUTCOMES & MEASUREMENTS The effect of TEMS and PCMs on blood pressure and dialysis efficacy in patients was assessed. RESULTS Mean blood pressure increased from 121/64 +/- 21/15 mm Hg with NI to 132/69 +/- 21/15 mm Hg (P < 0.001) during sessions with PCMs and 125/66 +/- 22/16 mm Hg (P < 0.05) during sessions with TEMS. Urea and phosphate removal during dialysis were significantly (P < 0.001) greater with TEMS (19.4 +/- 3.7 g/dialysis and 1,197 +/- 265 mg/dialysis) or PCMs (20.1 +/- 3.4 g/dialysis and 1,172 +/- 315 mg/dialysis) than with NI (15.1 +/- 3.9 g/dialysis and 895 +/- 202 mg/dialysis). Body weight, ultrafiltration, Kt/V, and increases in hemoglobin and albumin levels during dialysis did not differ among the NI, PCMs, and TEMS groups. LIMITATIONS The study design does not allow extension of the findings to prolonged treatment. CONCLUSION Future studies during longer observation periods will have to prove the persistence of these acute findings. Both TEMS and PCMs deserve future investigations in dialysis patients because they increase intradialytic blood pressure and facilitate urea and phosphate removal when applied short term.

Glycyrrhetinic acid food supplementation lowers serum potassium concentration in chronic hemodialysis patients

Hyperkalemia is a common life-threatening problem in hemodialysis patients. Because glycyrrhetinic acid (GA) inhibits the enzyme 11beta-hydroxy-steroid dehydrogenase II and thereby increases cortisol availability to the colonic mineralocorticoid receptor, it has the potential to lower serum potassium concentrations. To test this, 10 patients in a 6 month prospective, double-blind, placebo-controlled crossover study were given cookies or bread rolls supplemented with glycyrrhetinic acid or placebo. Twenty-four-hour blood pressure measurements were performed at baseline and week 6 and 12 of each treatment period. The ratio of plasma cortisol/cortisone was significantly increased in all patients on GA as compared to baseline or placebo, indicating appropriate enzyme inhibition. Nine of the 10 patients had a persistent decrease in predialysis serum potassium concentration. On GA, mean predialysis serum potassium was significantly lower than at baseline or on placebo. On placebo, serum potassium was significantly elevated above the upper limit of normal in 76% compared to 30% of measurements during GA treatment. Furthermore, on this treatment the frequency of severe hyperkalemia significantly decreased from 9% to 0.6%. No differences were found in parameters reflecting sodium retention. Although these studies show that prolonged GA supplementation persistently lowers serum potassium in dialysis patients, a long-term toxicity study will be mandatory before we recommend the routine use of this treatment.

Sodium Thiosulfate Pharmacokinetics in Hemodialysis Patients and Healthy Volunteers

BACKGROUND AND OBJECTIVES Vascular calcification is a major cause of morbidity and mortality in dialysis patients. Human and animal studies indicate that sodium thiosulfate (STS) may prevent the progression of vascular calcifications. The pharmacokinetics of STS in hemodialysis patients has not been investigated yet. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS STS was given intravenously to 10 hemodialysis patients on- and off-hemodialysis. Additionally, STS was applied to 9 healthy volunteers once intravenously and once orally. Thiosulfate concentrations were measured by using a specific and sensitive HPLC method. RESULTS In volunteers and patients, mean endogenous thiosulfate baseline concentrations were 5.5 ± 1.82 versus 7.1 ± 2.7 μmol/L. Renal clearance was high in volunteers (1.86 ± 0.45 ml/min per kg) and reflected GFR. Nonrenal clearance was slightly, but not significantly, higher in volunteers (2.25 ± 0.32 ml/min per kg) than in anuric patients (2.04 ± 0.72 ml/min per kg). Hemodialysis clearance of STS was 2.62 ± 1.01 ml/min per kg. On the basis of the nonrenal clearance and the thiosulfate steady-state serum concentrations, a mean endogenous thiosulfate generation rate of 14.6 nmol/min per kg was calculated in patients. After oral application, only 4% of STS was recovered in urine of volunteers, reflecting a low bioavailability of 7.6% (0.8% to 26%). CONCLUSIONS Given the low and variable bioavailability of oral STS, only intravenous STS should be prescribed today. The biologic relevance of the high hemodialysis clearance for the optimal time point of STS dosing awaits clarification of the mechanisms of action of STS.

Nocturnal dipping behaviour in normotensive white children and young adults in response to changes in salt intake

Background Nocturnal nondipping is a feature of salt-sensitive, hypertensive individuals. In normotensive children and adults, the impact of salt intake on circadian blood pressure (BP) rhythm is not well defined. Objective To test whether a high-salt diet abolishes nocturnal dipping in salt-sensitive, normotensive individuals. Methods In normotensive, healthy individuals dichotomized for age (children: n = 28, age 11.9 ± 0.8 years, 43% girls; adults: n = 41, age 25.7 ± 0.9 years, 46% women), 24-h ambulatory BP monitoring was performed and 24-h urine collections were obtained during the steady-state phase of a low and a high-salt diet. Salt-sensitivity was defined as at least 3-mmHg increase in 24-h mean arterial pressure during the high-salt diet. Results Salt-sensitive children and young adults (n = 11 in each group) and salt-resistant individuals (n = 17 children and n = 30 adults) were recruited. Circadian BP rhythm was maintained irrespective of age, salt intake and salt sensitivity. In contrast to the pronounced pressure response to high salt, a low-salt diet lowered the BP of salt-sensitive individuals as compared with salt-resistant individuals at daytime (SBP 107.6 ± 1.2 vs. 114.8 ± 1.6 mmHg, P = 0.002 in adults and SBP/DBP 103.1 ± 1.6/68.6 ± 1.5 vs. 111.2 ± 1.3/74.5 ± 1.1 mmHg, P = 0.005 in children), yet left night-time BP unchanged. Nonlinear mixed effects modelling indicated a steeper downward slope of BP from daytime to night-time in salt-sensitive as compared with salt-resistant children and all adults (P < 0.0015). Without exception, daytime mean arterial pressure disclosed salt-sensitive individuals upon salt loading. Conclusion Normotensive children and young adults maintain normal nocturnal BP dipping irrespective of salt intake and of individual salt sensitivity. Thus, daytime BP assessment is sufficient to characterize salt responsiveness in normotensive individuals.

Impact of daclizumab, low-dose cyclosporine, mycophenolate mofetil and steroids on renal function after kidney transplantation

BACKGROUND Early and long-term use of cyclosporine A (CsA) leads to increased risks of renal toxicity. We hypothesized that administration of daclizumab in combination with mycophenolate mofetil (MMF) allows a relevant reduction in the dose of CsA. METHODS We carried out a 3-year, prospective, randomized, controlled clinical multi-centre trial in 156 patients. The patients were randomized to standard treatment (CsA, MMF, steroids) or to high-dose daclizumab (first dose: 2 mg/kg), in combination with low-dose CsA, MMF and steroids. We maintained the mean CsA levels of daclizumab patients at 57% of standard patients (132 versus 216 ng/ml) on Day 7 post-transplant, and 84% by 6 months. RESULTS Primary outcome, creatinine clearance (with imputation of informative dropouts) at 12 months, was significantly better in daclizumab-treated (34 +/- 17) than standard patients (29 +/- 17; P = 0.028, two sided). Only 5 cases of BPAR were recorded in the daclizumab compared to 22 in the standard group (P = 0.0016). Daclizumab patients had 91% event-free survival after 1 year compared to 66% in standard patients (P = 0.00017). CONCLUSION We demonstrate here that high-dose daclizumab in combination with lower CsA levels in adult renal transplant recipients is as or more effective than standard regimen (CsA, MMF, steroids) and may result in better outcomes at 12 months post-transplant with no increase in adverse reactions.