Serum Calcification Propensity and the Risk of Cardiovascular and All-Cause Mortality in the General Population:The PREVEND Study

Objective: Vascular calcification contributes to the cause of cardiovascular disease. The calciprotein particle maturation time (T50) in serum, a measure of calcification propensity, has been linked with adverse outcomes in patients with chronic kidney disease, but its role in the general population is unclear. We investigated whether serum T50 is associated with cardiovascular mortality in a large general population-based cohort. Approach and Results: The relationship between serum T50 and cardiovascular mortality was studied in 6231 participants of the PREVEND (Prevention of Renal and Vascular End-Stage Disease) cohort. All-cause mortality was the secondary outcome. Mean (±SD) age was 53±12 years, 50% were male, and mean serum T50 was 329±58 minutes. A shorter serum T50 is indicative of a higher calcification propensity. Serum T50 was inversely associated with circulating phosphate, age, estimated glomerular filtration rate, and alcohol consumption, whereas plasma magnesium was positively associated with serum T50 (P&lt;0.001, total multivariable model R2=0.281). During median (interquartile range) follow-up for 8.3 (7.8-8.9) years, 364 patients died (5.8%), of whom 95 (26.1%) died from a cardiovascular cause. In multivariable Cox proportional hazard models, each 60 minutes decrease in serum T50 was independently associated with a higher risk of cardiovascular mortality (fully adjusted hazard ratio [95% CI], 1.22 [1.04-1.36], P=0.021). This association was modified by diabetes mellitus; stratified analysis indicated a more pronounced association in individuals with diabetes mellitus. Conclusions: Serum T50 is independently associated with an increased risk of cardiovascular mortality in the general population and thus may be an early and potentially modifiable risk marker for cardiovascular mortality.</p

Elevated serum magnesium lowers calcification propensity in Memo1-deficient mice.

MEdiator of cell MOtility1 (MEMO1) is a ubiquitously expressed redox protein involved in extracellular ligand-induced cell signaling. We previously reported that inducible whole-body Memo1 KO (cKO) mice displayed a syndrome of premature aging and disturbed mineral metabolism partially recapitulating the phenotype observed in Klotho or Fgf23-deficient mouse models. Here, we aimed at delineating the contribution of systemic mineral load on the Memo1 cKO mouse phenotype. We attempted to rescue the Memo1 cKO phenotype by depleting phosphate or vitamin D from the diet, but did not observe any effect on survival. However, we noticed that, by contrast to Klotho or Fgf23-deficient mouse models, Memo1 cKO mice did not present any soft-tissue calcifications and displayed even a decreased serum calcification propensity. We identified higher serum magnesium levels as the main cause of protection against calcifications. Expression of genes encoding intestinal and renal magnesium channels and the regulator epidermal growth factor were increased in Memo1 cKO. In order to check whether magnesium reabsorption in the kidney alone was driving the higher magnesemia, we generated a kidney-specific Memo1 KO (kKO) mouse model. Memo1 kKO mice also displayed higher magnesemia and increased renal magnesium channel gene expression. Collectively, these data identify MEMO1 as a novel regulator of magnesium homeostasis and systemic calcification propensity, by regulating expression of the main magnesium channels

Sodium thiosulfate ameliorates oxidative stress and preserves renal function in hyperoxaluric rats

BACKGROUND: Hyperoxaluria causes crystal deposition in the kidney, which leads to oxidative stress and to injury and damage of the renal epithelium. Sodium thiosulfate (STS, Na2S2O3) is an anti-oxidant, which has been used in human medicine for decades. The effect of STS on hyperoxaluria-induced renal damage is not known. METHODS: Hyperoxaluria and renal injury were induced in healthy male Wistar rats by chronic exposure to ethylene glycol (EG, 0.75%) in the drinking water for 4 weeks. The treatment effects of STS, NaCl or Na2SO4 were compared. Furthermore, the effects of STS on oxalate-induced oxidative stress were investigated in vitro in renal LLC-PK1 cells. RESULTS: Chronic EG exposure led to hyperoxaluria, oxidative stress, calcium oxalate crystalluria and crystal deposition in the kidneys. Whereas all tested compounds significantly reduced crystal load, only STS-treatment maintained tissue superoxide dismutase activity and urine 8-isoprostaglandin levels in vivo and preserved renal function. In in vitro studies, STS showed the ability to scavenge oxalate-induced ROS accumulation dose dependently, reduced cell-released hydrogen peroxide and preserved superoxide dismutase activity. As a mechanism explaining this finding, STS was able to directly inactivate hydrogen peroxide in cell-free experiments. CONCLUSIONS: STS is an antioxidant, which preserves renal function in a chronic EG rat model. Its therapeutic use in oxidative-stress induced renal-failure should be considered

High-Flux Hemodialysis and High-Volume Hemodiafiltration Improve Serum Calcification Propensity

BACKGROUND:Calciprotein particles (CPPs) may play an important role in the calcification process. The calcification propensity of serum (T50) is highly predictive of all-cause mortality in chronic kidney disease patients. Whether T50 is therapeutically improvable, by high-flux hemodialysis (HD) or hemodiafiltration (HDF), has not been studied yet. METHODS:We designed a cross-sectional single center study, and included stable prevalent in-center dialysis patients on HD or HDF. Patients were divided into two groups based on dialysis modality, were on a thrice-weekly schedule, had a dialysis vintage of > 3 months and vascular access providing a blood flow rate > 300 ml/min. Calcification propensity of serum was measured by the time of transformation from primary to secondary CPP (T50 test), by time-resolved nephelometry. RESULTS:We included 64 patients, mean convective volume was 21.7L (SD 3.3L). In the pooled analysis, T50 levels increased in both the HD and HDF group with pre- and post-dialysis (mean (SD)) of 244(64) - 301(57) and 253(55) - 304(61) min respectively (P = 0.43(HD vs. HDF)). The mean increase in T50 was 26.29% for HD and 21.97% for HDF patients (P = 0.61 (HD vs. HDF)). The delta values (Δ) of calcium, phosphate and serum albumin were equal in both groups. Baseline T50 was negatively correlated with phosphate, and positively correlated with serum magnesium and fetuin-A. The ΔT50 was mostly influenced by Δ phosphate (r = -0.342; P = 0.002 HD and r = -0.396; P<0.001 HDF) in both groups. CONCLUSIONS:HD and HDF patients present with same baseline T50 calcification propensity values pre-dialysis. Calcification propensity is significantly improved during both HD and HDF sessions without significant differences between both modalities

Treatment effects on body weight, kidney weight and renal function.

<p>(A) Initial body weight and weight gain were similar in all animal groups irrespective of the treatment modality. (B) Kidney weight was increased in the EG group, but near-to-normal in the EG+STS, EG+SC and EG+SS groups. (C) Creatinine clearance derived from 24-hour urine samples collected after 4 weeks shows preserved renal function in STS-treated animals. The significance levels are with reference to the EG group. Data are presented as means ± SD from 7–8 animals per group *p< 0.05, **p < 0.01, ***p < 0.001.</p

L'Indépendant franc-comtois : journal politique de la région de l'Est

09 mars 19021902/03/09 (N67).Appartient à l’ensemble documentaire : FrancComt

Intra- and extracellular quenching of H₂O₂ by STS.

<p>(A) SOD activity was rescued by STS treatment upon 24 hours of oxalate-exposure to LLC-PK1 cells. (B) Oxalate-exposure of LLC-PK1 cells leads to the intracellular generation and accumulation of H₂O₂. While STS-treatment reduced the amount of H₂O₂ released from the cells after 72 hours, SC- and SS-treatment did not. (C) 72 hours of oxalate-exposure of LLC-PK1 cells leads to a significant decrease in cell viability (measured by sulforhodamine), which was maintained by STS in a dose dependent manner. (D) STS directly quenches H₂O₂ in aqueous solution, providing evidence for a direct interaction between STS and the non-radical oxidant H₂O₂. SC and SS in contrast did not lead to the consumption of H₂O₂. The changes and significance levels are with reference to the Ox group. The data are means ± SD from 8 values per group. *p< 0.05, **p < 0.01, ***p < 0.001.</p

STS reduces intracellular oxidative stress.

<p>Oxidative stress was induced by exposure of proximal tubular LLC-PK1 cells towards 1 mM oxalate, and detected using the fluorescence dye H₂DFFDA. (A) Fluorescence changes in untreated LLC-PK1 cells (Control), oxalate (Ox)-exposed LLC-PK1 cells (1 mM), and Ox+STS, Ox+SC and Ox+SS-exposed LLC-PK1 cells. STS largely protects LLC-PK1 cells against oxalate-induced oxidative stress. (B) Dose-dependent protection by STS against oxalate-induced ROS in LLC-PK1 cells. Data were analyzed by one-way analysis of variance (ANOVA) with Bonferroni’s multiple comparison. Asterisks (*) indicate statistically significant differences (<i>p <</i> 0.05) with respect to oxalate-exposed cells. (C) H₂DFFDA- and DAPI-fluorescence imaging of LLC-PK1 cells. The absence of green fluorescence in oxalate-exposed, STS-treated LLC-PK1 cells indicates the quenching of intracellular oxidative stress by STS. Control = 100% in (A) and (B). Significance levels are with reference to oxalate (Ox) group. The data are means ± SD from 8 values per group. *p< 0.05, **p < 0.01, ***p < 0.001.</p