Sylvie Dusilová-Sulková

Paricalcitol (19-nor-1,25-dihydroxyvitamin D2) and calcitriol (1,25-dihydroxyvitamin D3) exert potent immunomodulatory effects on dendritic cells and inhibit induction of antigen-specific T cells

Paricalcitol (19-nor-1,25/OH(2)/D(2)), a second generation vitamin D receptor (VDR) activator, is a synthetic analogue of vitamin D3. In contrast to calcitriol, paricalcitol has a reduced effect on intestinal calcium resorption thus avoiding undesirable hypercalcemia. Information about immunomodulatory activity of paricalcitol is scarce. In this study we show that, in all investigated aspects, paricalcitol retains significant immunomodulatory activity, comparable to calcitriol. Both VDR agonists impaired differentiation of immature dendritic cells (DCs) from monocytes. The presence of VDR agonists during DC differentiation abolished their capacity to be activated and, despite potent Toll-like receptor mediated stimulation, VDR agonist-treated DCs remained in the immature state. In accordance with these findings, VDR-treated DCs produced no bioactive IL-12 and had a significantly decreased capacity to induce antigen-specific T cells while the capacity to induce functional Tregs remained unchanged when compared to control DCs. As DCs and T cells play an important role in the pathogenesis of atherosclerosis, in end-stage renal disease patients, paricalcitol should be a VDR agonist of choice for the reduction of the risk of atherosclerosis due to its immunomodulatory effect proven in this study and known limited hypercalcemic effect. The immunomodulatory potency of paricalcitol makes it a drug of interest in the therapy of chronic immune-mediated inflammatory diseases.

No Benefit of Hemodiafiltration over Hemodialysis in Lowering Elevated Levels of Asymmetric Dimethylarginine in ESRD Patients

Background: It has been suggested that hemodiafiltration (HDF) is more efficient than hemodialysis (HD) in lowering plasma levels of the endogenous nitric oxide synthase inhibitor asymmetric dimethylarginine (ADMA), which is a strong and independent predictor of overall mortality in ESRD patients. Methods/Patients: Twenty ESRD patients (11 women) were studied during both a single online HDF session and a single HD session. In each patient, ADMA, L-arginine, SDMA, β2-microglobulin and urea were measured at several time points. Results: Although HDF was clearly superior to HD in decreasing plasma β2-microglobulin, there was no difference in the elimination characteristics of ADMA. However, HDF but not HD eliminated the nitric oxide synthase substrate L-arginine, making HD superior in increasing the L-arginine/ADMA ratio. Conclusion: Neither HD nor HDF sufficiently removes the putative uremic toxin ADMA. The clinical significance of HD better improving the L-arginine/ADMA ratio (parameter of NO production) as compared to HDF needs to be determined.

Plasma albumin levels correlate with decreased microcirculation and the development of skin defects in hemodialyzed patients

OBJECTIVES Difficulty healing wounds and skin defects is a frequent problem in patients on chronic hemodialysis (HD) because of malnutrition, inflammation, and atherosclerosis (MIA) syndrome. The aim of the present study was to estimate the influence of peripheral blood flow changes during HD on the development of foot defects and its relationship to plasma albumin levels. METHODS Peripheral skin blood flow was measured using a laser Doppler line scanner in 10 different areas of the dorsal part of the instep and the toes of each foot before and during HD with ultrafiltration (897 +/- 465 mL/procedure) in 31 HD patients (10 female, 21 male; age 36-79 y, body mass index = 28 +/- 5.0). No skin defects or apparent acute disease or infection were detected in any patient at the time of laser Doppler line scanner measurement. The feet of the patients were clinically re-examined carefully over the next 18 mo. RESULTS We found a significant and constant decrease of skin blood flow during the HD procedure (P < 0.001). Skin blood flow was significantly correlated with serum albumin level both before HD (r = 0.36, P = 0.05) and during HD (r = 0.47, P = 0.007). Skin defects developed in 11 patients, with significantly lower skin blood flow during the 18-mo follow-up period. A significantly larger number of patients who had normal perfusion remained defect-free in comparison to patients with critical perfusion (93% versus 38%, P = 0.002, Kaplan-Meier analysis). CONCLUSION Skin blood flow may be impaired in HD patients. The apparent malnutrition and inflammation in HD patients are likely responsible for the decreased skin blood flow and the development of the difficulty to heal skin defects and wounds.

Fibroblast growth factor 23 and matrix-metalloproteinases in patients with chronic kidney disease: are they associated with cardiovascular disease?

Background: High cardiovascular risk in patients with chronic kidney disease (CKD) may be related to mineral disorder and microinflammation. Fibroblast growth factor 23 (FGF-23) is a phosphatonin and inhibitor of calcitriol synthesis, which is associated with poor prognosis in CKD patients starting dialysis. Matrix-metalloproteinases (MMP-2, MMP-9) contribute to myocardial remodeling and arterial calcification. FGF-23 and MMPs levels are altered in CKD, however, little is known about their association and relation to cardiovascular (CV) disease. Methods: Standard laboratory parameters, plasma levels of MMP-2, MMP-9, FGF-23, PAPP-A and CV disease history were assessed in 80 patients with CKD 1–5 and 44 healthy control subjects. Results: FGF-23 and MMP-2 (assessed by ELISA) were higher in CKD patients compared to controls. FGF-23 increased from CKD 3, whereas MMP-2 increased only in CKD 5. FGF-23 was positively associated with MMP-2, adjusted to age, eGFR, phosphatemia, calcitriol and parathormone. FGF-23 independently correlated with parathormone and inversely with calcitriol, whereas MMP-2 was related to phosphatemia. FGF-23 was higher in subjects with a history of CV disease compared to those free of such history (559.0 vs.184.0 RU/ml), adjusted to age and eGFR. Conclusion: Our data suggest a possible relationship between FGF-23, MMP-2 and CV disease in CKD. Potential causality of this association remains to be elucidated.

Design and challenges of the Randomized Evaluation of Normal versus Augmented Level Replacement Therapy (RENAL) Trial: high-dose versus standard-dose hemofiltration in acute renal failure

Background/Aims: The optimal dose of renal replacement therapy (RRT) in acute renal failure (ARF) is uncertain. Methods: The Randomized Evaluation of Normal versus Augmented Level Replacement Therapy Trial tests the hypothesis that higher dose continuous veno-venous hemodiafiltration (CVVHDF) at an effluent rate of 40 ml/kg/h will increase survival compared to CVVHDF at 25 ml/kg/h of effluent dose. Results: This trial is currently randomizing critically ill patients in 35 intensive care units in Australia and New Zealand with a planned sample size of 1,500 patients. This trial will be the largest trial ever conducted on acute blood purification in critically ill patients. Conclusion: A trial of this magnitude and with demanding technical requirements poses design difficulties and challenges in the logistics, conduct, data collection, data analysis and monitoring. Our report will assist in the development of future trials of blood purification in intensive care. This study was registered with ClinicalTrials.gov (NCT00221013).

Pregnancy-Associated Plasma Protein A as an Independent Mortality Predictor in Long-Term Hemodialysis Patients

Background/Aims: Pregnancy-associated plasma protein A (PAPP-A) is a biomarker related to vascular damage. The aim of the study was to focus on PAPP-A and related parameters and their relationship to the prognosis of long-term hemodialysis (HD) patients. Methods: This is a prospective observational cohort study which included 261 long-term HD patients followed up for 5 years and 66 healthy subjects. PAPP-A, placental growth factor (PlGF), matrix metalloproteinase 2 and 9 (MMP-2, MMP-9), insulin-like growth factor 1 (IGF-1), insulin-like growth factor binding protein-4 (IGFBP-4), and cardiac, nutritional and inflammatory parameters were measured at the beginning of the study and tested as predictors of mortality. Results: PAPP-A, PlGF, IGF-1, IGFBP-4 and MMP-2 were significantly increased in HD patients compared to controls (PAPP-A 27.6 ± 15.5 mIU/l in HD vs. 9.4 ± 2.5 mIU/l in controls, p < 0.001). Increased PAPP-A was a significant independent predictor of overall mortality and mortality due to infection in the multivariate Cox analysis [HR (95% CI): 1.237 (1.060–1.444), p = 0.007, and 1.416 (1.115–1.798), p = 0.004, per standard deviation, respectively]. PAPP-A was not related to cardiovascular mortality. Conclusion: Increased PAPP-A is a significant independent predictor of overall mortality and mortality due to infection but it was not related to cardiovascular mortality in this study.

Vitamin D Binding Protein Is Not Involved in Vitamin D Deficiency in Patients with Chronic Kidney Disease

Objective. This study was designed to evaluate vitamin D status with separate determination of 25-OH D2 and 25-OH D3 and its relationship to vitamin D binding protein (VDBP) in patients with chronic kidney disease (CKD) and long-term haemodialysis patients (HD). Methods. 45 CKD patients, 103 HD patients, and 25 controls (C) were included. Plasma vitamin D concentrations were determined using chromatography and VDBP in serum and urine in CKD using enzyme immunoassay. Results. Plasma vitamin D levels were lower in CKD (30.16 ± 16.74 ng/mL) and HD (18.85 ± 15.85 ng/mL) versus C (48.72 ± 18.35 ng/mL), P < 0.0001. 25-OH D3 was the dominant form of vitamin D. Serum VDBP was higher in CKD (273.2 ± 93.8 ug/mL) versus C (222 ± 87.6 ug/mL) and HD (213.8 ± 70.9 ug/mL), P = 0.0003. Vitamin D/VDBP ratio was the highest in C and the lowest in HD; however, there was no correlation between vitamin D and VDBP. Urinary concentration of VDBP in CKD (0.25 ± 0.13 ug/mL) correlated with proteinuria (r = 0.43, P = 0.003). Conclusions. Plasma levels of vitamin D are decreased in CKD patients and especially in HD patients. 25-OH D3 was the major form of vitamin D. Despite urinary losses of VDBP, CKD patients had higher serum VDBP concentrations, indicating compensatory enhanced production. Vitamin D binding protein is not involved in vitamin D deficiency.

EN-RAGE (extracellular newly identified receptor for advanced glycation end-products binding protein) and mortality of long-term hemodialysis patients: Aprospective observational cohort study

OBJECTIVES EN-RAGE is extracellular newly identified receptor for advanced glycation end-products binding protein playing a role in inflammation. The aim was to test the relationship of EN-RAGE to prognosis of long-term hemodialysis patients (HD). DESIGN AND METHODS This is a prospective observational cohort study in 261 HD patients followed up for five years. Laboratory parameters were measured at the beginning of the study. RESULTS EN-RAGE was slightly but unsignificantly increased in HD patients compared with healthy controls and correlated significantly with inflammatory markers. Univariate Cox analysis demonstrated EN-RAGE as a significant predictor for mortality due to infection (HR (95%CI): 1.305 (1.063-1.602), per standard deviation, p=0.01), but this significance disappeared in multivariate Cox analysis when CRP was included into the model. CONCLUSIONS Our study demonstrates EN-RAGE as an inflammatory biomarker. It is related to mortality of HD patients due to infection, but in our study, it did not provide additional information to CRP.

Vitamin D metabolism and vitamin D traditional and nontraditional, target organs: implications for kidney patients.

Vitamin D plays an absolute essential role in human physiology. More than 60 types of cells possess vitamin D receptors (VDR) and more than 200 genes represent the target for VDR activation. The principle of the biological effect of vitamin D is gene control. In general, VDR activation inhibits cell differentiation and proliferation while promoting cell maturation and it also participates in the regulation of apoptosis (programmed cell death). Conventionally, vitamin D status is assessed according to the serum 25-hydroxyvitamin D concentration. Values between 30-60 ng/ml (70-150 nmol/l) are optimal. Low vitamin D status is associated with bone and mineral disturbances and also with many other pathological conditions. Studies have described association with susceptibility to some infections; higher risk of autoimmune diseases, association with some malignancies and many other complications. Low vitamin D status is common, but usually underestimated. The native vitamin D undergoes two-step hydroxylation to become biologically active. The second metabolic conversion is dependent on functional renal parenchyma. In advanced stages of chronic kidney disease (CKD) the renal activation of vitamin D sharply decreases regardless of the stores of native vitamin D, resulting in low concentration of active vitamin D. The parathyroid hyperactivity in advanced CKD represents the approved indication for pharmacological VDR activation. The therapeutic window of nonselective VDR activators is narrow. On the contrary, the effect of selective VDR activators (paricalcitol) in the intestine is much lower and therefore the activators are safer in terms of maintaining serum concentration of calcium and phosphate. Several recent observational studies demonstrated survival benefits of selective VDR activation in CKD patients. Theoretically, these drugs may, at least, partly cover the need for the systemic activation of VDR in kidney patients, but this assumption must be carefully examined. At present, the possible cardioprotectivity, renoprotectivity and other benefits of selective VDR activators are being intensively studied.

Effect of Hemodiafiltration on Pregnancy-Associated Plasma Protein A (PAPP-A) and Related Parameters

Background. Dialysis patients are at high risk of vascular/cardiovascular complications with multifactorial pathogenesis, and pregnancy-associated plasma protein A (PAPP-A) is one of the new markers related to cardiovascular risk. Because hemodiafiltration (HDF) is supposed to be better for cardiovascular status, the aim of this study was to describe whether it has any advantage concerning changes of PAPP-A and related molecules during the session in comparison with hemodialysis (HD). Methods. The studied group consisted of 20 chronic hemodialysis patients. In each patient, PAPP-A and related parameters—IGFBP-4 (insulin like growth factor binding protein), IGF-I (insulin like growth factor), and two MMPs (matrix metalloproteinases)-2 and 9—were determined both during a single online HDF session (high-flux polysulfone membrane HF80, postdilution) and during a single HD session (low-flux polysulfone membrane F6, F7) at time 0 (start), 15 min, 120 min, and 240 min (end) of the session. Results. PAPP-A, elevated at baseline in dialysis patients, changes significantly both during HDF and HD without significant differences between these two procedures (mean levels during HDF were 24.3, 53.9, 24.3, and 27.3 mIU/L). It increases more than two-fold from 0 to 15 min of the session (p < 0.001) and then decreases until the end of the session (p < 0.001). MMP-2 decreased slightly during both sessions (p < 0.001), and changes of other molecules were only minimal. Conclusion. A single HDF session compared to HD has no advantage in the decrease of PAPP-A and other tested molecules, all of them related to cardiovascular risk. Studies aimed at a long-term effect of both procedures on these parameters would be needed to further evaluate these therapeutical strategies.