lncRNA FAS-AS1 served as a diagnostic biomarker of end-stage renal disease and mediated vascular calcification via regulating oxidative stress and inflammation.

PURPOSE: Vascular calcification is a frequently occurring complication of end-stage renal disease (ESRD). This study focused on the significance of long non-coding RNA Fas cell surface death receptor-antisense 1(lncRNA FAS-AS1) in ESRD-related vascular calcification aiming to explore a potential biomarker for the detection. METHODS: The study enrolled 65 healthy individuals, 79 ESRD patients (48 patients with vascular calcification), and 93 early-stage (I-IV) chronic kidney disease (CKD) patients. The expression of FAS-AS1 in serum was evaluated by real-time quantitative polymerase chain reaction (PCR). The diagnostic potential of FAS-AS1 was assessed in discriminating ESRD patients, vascular calcification, and the severity of vascular calcification. In vitro, the vascular smooth muscle cells (VSMCs) were treated with a hyperphosphatemia medium to evaluate the effect of FAS-AS1 on VSMCs calcification. RESULTS: Elevated serum FAS-AS1 was observed in ESRD patients, which could discriminate from healthy individuals and early-stage CKD patients. FAS-AS1 was associated with the development of ESRD and the occurrence of vascular calcification. FAS-AS1 was also upregulated in vascular calcification patients, especially the patients with severe calcification, which showed diagnostic significance in evaluating vascular calcification degrees. Calcified VSMCs showed significantly increased levels of Ca2+, reactive oxygen species (ROS), tumor necrosis factor-α (TNF-α), and interleukin 6 (IL-6), which was attenuated by silencing FAS-AS1. CONCLUSIONS: FAS-AS1 discriminated ERSD patients and was associated with the occurrence of vascular calcification. The knockdown of FAS-AS1 suppressed hyperphosphatemia-induced vascular calcification via alleviating oxidative stress and inflammation.

Exploring molecular profiles of calcification in aortic vascular smooth muscle cells and aortic valvular interstitial cells.

Cardiovascular calcification can occur in vascular and valvular structures and is commonly associated with calcium deposition and tissue mineralization leading to stiffness and dysfunction. Patients with chronic kidney disease and associated hyperphosphatemia have an elevated risk for coronary artery calcification (CAC) and calcific aortic valve disease (CAVD). However, there is mounting evidence to suggest that the susceptibility and pathobiology of calcification in these two cardiovascular structures may be different, yet clinically they are similarly treated. To better understand diversity in molecular and cellular processes that underlie hyperphosphatemia-induced calcification in vascular and valvular structures, we exposed aortic vascular smooth muscle cells (AVSMCs) and aortic valve interstitial cells (AVICs) to high (2.5 mM) phosphate (Ph) conditions in vitro, and examined cell-specific responses. To further identify hyperphosphatemic-specific responses, parallel studies were performed using osteogenic media (OM) as an alternative calcific stimulus. Consistent with clinical observations made by others, we show that AVSMCs are more susceptible to calcification than AVICs. In addition, bulk RNA-sequencing reveals that AVSMCs and AVICs activate robust ossification-programs in response to high phosphate or OM treatments, however, the signaling pathways, cellular processes and osteogenic-associated markers involved are cell- and treatment-specific. For example, compared to VSMCs, VIC-mediated calcification involves biological processes related to osteo-chondro differentiation and down regulation of 'actin cytoskeleton'-related genes, that are not observed in VSMCs. Furthermore, hyperphosphatemic-induced calcification in AVICs and AVSMCs is independent of P13K signaling, which plays a role in OM-treated cells. Together, this study provides a wealth of information suggesting that the pathogenesis of cardiovascular calcifications is significantly more diverse than previously appreciated.

Inhibition of mitochondrial phosphate carrier prevents high phosphate-induced superoxide generation and vascular calcification.

Vascular calcification is a serious complication of hyperphosphatemia that causes cardiovascular morbidity and mortality. Previous studies have reported that plasmalemmal phosphate (Pi) transporters, such as PiT-1/2, mediate depolarization, Ca2+ influx, oxidative stress, and calcific changes in vascular smooth muscle cells (VSMCs). However, the pathogenic mechanism of mitochondrial Pi uptake in vascular calcification associated with hyperphosphatemia has not been elucidated. We demonstrated that the phosphate carrier (PiC) is the dominant mitochondrial Pi transporter responsible for high Pi-induced superoxide generation, osteogenic gene upregulation, and calcific changes in primary VSMCs isolated from rat aortas. Notably, acute incubation with high Pi markedly increased the protein abundance of PiC via ERK1/2- and mTOR-dependent translational upregulation. Genetic suppression of PiC prevented Pi-induced ERK1/2 activation, superoxide production, osteogenic differentiation, and vascular calcification of VSMCs in vitro and aortic rings ex vivo. Pharmacological inhibition of mitochondrial Pi transport using butyl malonate (BMA) or mersalyl abolished all pathologic changes involved in high Pi-induced vascular calcification. BMA or mersalyl also effectively prevented osteogenic gene upregulation and calcification of aortas from 5/6 subtotal nephrectomized mice fed a high-Pi diet. Our results suggest that mitochondrial Pi uptake via PiC is a critical molecular mechanism mediating mitochondrial superoxide generation and pathogenic calcific changes, which could be a novel therapeutic target for treating vascular calcification associated with hyperphosphatemia.

A novel FGF23 mutation in hyperphosphatemic familial tumoral calcinosis and its deleterious effect on protein O-glycosylation.

Background: Hyperphosphatemic familial tumoral calcinosis (HFTC) is a rare disease characterized by hyperphosphatemia and ectopic calcification, predominantly at periarticular locations. This study was performed to characterize the clinical profile of tumoral calcinosis and to identify gene mutations associated with HFTC and elucidated its pathogenic role. Methods: The three subjects (two male and one female) were aged 30, 25 and 15 years, respectively. The clinical features, histopathological findings, and outcomes of three subjects with HFTC were retrospectively reviewed. The three subjects were analyzed for FGF23, GALNT3 and KL mutations. Function of mutant gene was analyzed by western blotting and wheat germ agglutinin affinity chromatography. Results: All subjects had hyperphosphatemia and elevated calcium-phosphorus product. Calcinosis positions included the left shoulder, left index finger, and right hip. Bone and joint damage were present in two cases and multiple foci influenced body growth in one case. The histopathological features were firm, rubbery masses comprising multiple nodules of calcified material bordered by the proliferation of mononuclear or multinuclear macrophages, osteoclastic-like giant cells, fibroblasts, and chronic inflammatory cells. The novel mutation c.484A>G (p.N162D) in exon 3 of FGF23 was identified in one subject and his family members. Measurement of circulating FGF23 in the subject confirmed low intact FGF23 and increased C-terminal fragment. In vitro experiments showed that the mutant FGF23 proteins had defective O-glycosylation and impaired protein proteolysis protection. Conclusion: We identified a novel FGF23 missense mutation, and confirmed its damaging role in FGF23 protein O-glycosylation. Our findings expand the current spectrum of FGF23 variations that influence phosphorus metabolism.

EOS789, pan-phosphate transporter inhibitor, ameliorates the progression of kidney injury in anti-GBM-induced glomerulonephritis rats.

Hyperphosphatemia associated with chronic kidney disease (CKD) not only dysregulates mineral metabolism and bone diseases, but also strongly contributes to the progression of kidney disease itself. We have identified a novel drug for hyperphosphatemia, EOS789, that interacts with several sodium-dependent phosphate transporters (NaPi-IIb, PiT-1, and PiT-2) known to contribute to intestinal phosphate absorption. In this study, we investigated whether EOS789 could ameliorate kidney disease progression in glomerulonephritis rats. Anti-glomerular basement membrane (GBM) nephritis was induced in rats by intravenously administering two types of anti-rat GBM antibodies. We evaluated the effect of EOS789 administered in food admixture on hyperphosphatemia and kidney disease progression. In an anti-GBM nephritis rats, which exhibit a significant increase in serum phosphate and a decline in renal function, EOS789 dose-dependently improved hyperphosphatemia and EOS789 at 0.3% food admixture significantly ameliorated kidney dysfunction as shown in the decline of serum creatinine and BUN. Renal histopathology analysis showed that EOS789 significantly decreased crescent formation in glomeruli. To elucidate the mechanism underlying glomerular disease progression, human mesangial cells were used. High phosphate concentration in media significantly increased the expression of Collagen 1A1, 3A1, and αSMA mRNA in human mesangial cells and EOS789 dose-dependently suppressed these fibrotic markers. These results indicate that EOS789 prevented glomerular crescent formation caused by mesangial fibrosis by ameliorating hyperphosphatemia. In conclusion, EOS789 would not only be useful against hyperphosphatemia but may also have the potential to relieve mesangial proliferative glomerulonephritis with crescent formation.

Familial hyperphosphatemic tumoral calcinosis in an unusual and usual sites and dramatic improvement with the treatment of acetazolamide, sevelamer and topical sodium thiosulfate.

OBJECTIVES: Familial hyperphosphatemic tumoral calcinosis is a rare disorder characterized by hyperphosphatemia with recurrent ectopic periarticular calcifications, in addition to other visceral and vascular manifestations, without any inflammatory or neoplastic disorder. The available treatment strategies are limited. Here we report an eight year old female patient with recurrent lesions under the chin, and bilateral hips which are painful and improving of the size of the lesions and hyperphosphatemia. CASE PRESENTATION: The patient was started to the treatment with peroral acetazolamide however the lesion did not regress but a new lesion appeared then we added sevelamer and topical sodium thiosulfate treatment for three months. After the three months of the combination treatment the lesions, there were no pain, no hyperphospahtemia regression/disappearance of the lesions. CONCLUSIONS: This combination treatment or topical sodium thiosulfate use only may be a novel treatment strategy for the patients prospective controlled trials are needed.

The impact of type III sodium-dependent phosphate transporters (Pit 1 and Pit 2) on podocyte and kidney function.

The sodium-dependent phosphate transporters Pit 1 and Pit 2 belong to the solute carrier 20 (SLC20) family of membrane proteins. They are ubiquitously distributed in the human body. Their crucial function is the intracellular transport of inorganic phosphate (Pi) in the form of H2 PO4- . They are one of the main elements in maintaining physiological phosphate homeostasis. Recent data have emerged that indicate novel roles of Pit 1 and Pit 2 proteins besides the well-known function of Pi transporters. These membrane proteins are believed to be precise phosphate sensors that mediate Pi-dependent intracellular signaling. They are also involved in insulin signaling and influence cellular insulin sensitivity. In diseases that are associated with hyperphosphatemia, such as diabetes and chronic kidney disease (CKD), disturbances in the function of Pit 1 and Pit 2 are observed. Phosphate transporters from the SLC20 family participate in the calcification of soft tissues, mainly blood vessels, during the course of CKD. The glomerulus and podocytes therein can also be a target of pathological calcification that damages these structures. A few studies have demonstrated the development of Pi-dependent podocyte injury that is mediated by Pit 1 and Pit 2. This paper discusses the role of Pit 1 and Pit 2 proteins in podocyte function, mainly in the context of the development of pathological calcification that disrupts permeability of the renal filtration barrier. We also describe the mechanisms that may contribute to podocyte damage by Pit 1 and Pit 2.

Adsorptivity of cationic cellulose nanocrystals for phosphate and its application in hyperphosphatemia therapy.

Nanocellulose has gained much attention because of its excellent properties. Cationic cellulose nanocrystals (cCNC) shows good adsorptivity toward negative ions and molecules. Phosphate binders are most used to treat hyperphosphatemia and it is significant to develop its alternatives with high specific and low cost in the clinic. Herein, we prepared cCNC and characterized it by FTIR, TEM, dynamic light scattering, and viscosity method. We simulated the binding process of cationic cellulose for phosphate and used it as phosphate binder for hyperphosphatemia therapy to study the phosphate binding effect and evaluate the oral toxicity. Cationic cellulose improved the conditions of mice models and efficiently decreased the level of phosphate in the serum. cCNC had a better binding effect than cationic microcrystalline cellulose both in vitro and in vivo. cCNC could be used as alternatives to phosphate binder for therapy of chronic renal failure and hyperphosphatemia.

Investigation of the transforming growth factor-beta 1 signalling pathway as a possible link between hyperphosphataemia and renal fibrosis in feline chronic kidney disease.

Chronic kidney disease (CKD) is common in geriatric cats, and is characterised in the majority of cases by tubulointerstitial inflammation and fibrosis. Hyperphosphataemia is a frequent complication of CKD and is independently associated with severity of renal fibrosis and disease progression. Transforming growth factor-beta 1 (TGF-ß1) signalling is thought to be a convergent pathway which mediates the progression of renal fibrosis in CKD. The aims of this study were to explore the interaction between increased extracellular phosphate and the TGF-ß1 signalling pathway by investigating: (a) the effect of a commercially available, phosphate-restricted, diet on urinary TGF-ß1 excretion in cats with CKD; and (b) the role of increased extracellular phosphate in regulating proliferation, apoptosis, and expression of genes related to TGF-ß1 signalling and extracellular matrix (ECM) production in feline proximal tubular epithelial cells (FPTEC) and cortical fibroblasts from cats with azotaemic CKD (CKD-FCF). The dietary intervention study revealed no effect of dietary phosphate restriction on urinary active TGF-ß1 excretion after 4-8 weeks (P=0.98), despite significantly decreasing serum phosphate (P<0.001). There was no effect of increased growth media phosphate concentration (from 0.95mM to 2mM and 3.5mM) on proliferation (P=0.99) and apoptotic activity in FPTEC (P=0.22), or expression of genes related to ECM production and the TGF-ß1 signalling pathway in FPTEC and CKD-FCF (P>0.05). These findings suggest the beneficial effects of dietary phosphate restriction on progression of feline CKD may not occur through modulation of renal TGF-ß1 production, and do not support a direct pro-fibrotic effect of increased extracellular phosphate on feline renal cells.

Oxidative stress by Ca2+ overload is critical for phosphate-induced vascular calcification.

Hyperphosphatemia is the primary risk factor for vascular calcification, which is closely associated with cardiovascular morbidity and mortality. Recent evidence showed that oxidative stress by high inorganic phosphate (Pi) mediates calcific changes in vascular smooth muscle cells (VSMCs). However, intracellular signaling responsible for Pi-induced oxidative stress remains unclear. Here, we investigated molecular mechanisms of Pi-induced oxidative stress related with intracellular Ca2+ ([Ca2+]i) disturbance, which is critical for calcification of VSMCs. VSMCs isolated from rat thoracic aorta or A7r5 cells were incubated with high Pi-containing medium. Extracellular signal-regulated kinase (ERK) and mammalian target of rapamycin were activated by high Pi that was required for vascular calcification. High Pi upregulated expressions of type III sodium-phosphate cotransporters PiT-1 and -2 and stimulated their trafficking to the plasma membrane. Interestingly, high Pi increased [Ca2+]i exclusively dependent on extracellular Na+ and Ca2+ as well as PiT-1/2 abundance. Furthermore, high-Pi induced plasma membrane depolarization mediated by PiT-1/2. Pretreatment with verapamil, as a voltage-gated Ca2+ channel (VGCC) blocker, inhibited Pi-induced [Ca2+]i elevation, oxidative stress, ERK activation, and osteogenic differentiation. These protective effects were reiterated by extracellular Ca2+-free condition, intracellular Ca2+ chelation, or suppression of oxidative stress. Mitochondrial superoxide scavenger also effectively abrogated ERK activation and osteogenic differentiation of VSMCs by high Pi. Taking all these together, we suggest that high Pi activates depolarization-triggered Ca2+ influx via VGCC, and subsequent [Ca2+]i increase elicits oxidative stress and osteogenic differentiation. PiT-1/2 mediates Pi-induced [Ca2+]i overload and oxidative stress but in turn, PiT-1/2 is upregulated by consequences of these alterations.NEW & NOTEWORTHY The novel findings of this study are type III sodium-phosphate cotransporters PiT-1 and -2-dependent depolarization by high Pi, leading to Ca2+ entry via voltage-gated Ca2+ channels in vascular smooth muscle cells. Cytosolic Ca2+ increase and subsequent oxidative stress are indispensable for osteogenic differentiation and calcification. In addition, plasmalemmal abundance of PiT-1/2 relies on Ca2+ overload and oxidative stress, establishing a positive feedback loop. Identification of mechanistic components of a vicious cycle could provide novel therapeutic strategies against vascular calcification in hyperphosphatemic patients.

Inorganic Phosphate (Pi) Signaling in Endothelial Cells: A Molecular Basis for Generation of Endothelial Microvesicles in Uraemic Cardiovascular Disease.

Hyperphosphataemia increases cardiovascular mortality in patients with kidney disease. Direct effects of high inorganic phosphate (Pi) concentrations have previously been demonstrated on endothelial cells (ECs), including generation of procoagulant endothelial microvesicles (MVs). However, no mechanism directly sensing elevated intracellular Pi has ever been described in mammalian cells. Here, we investigated the hypothesis that direct inhibition by Pi of the phosphoprotein phosphatase PP2A fulfils this sensing role in ECs, culminating in cytoskeleton disruption and MV generation. ECs were treated with control (1 mM [Pi]) vs. high (2.5 mM [Pi]), a condition that drives actin stress fibre depletion and MV generation demonstrated by confocal microscopy of F-actin and NanoSight Nanoparticle tracking, respectively. Immuno-blotting demonstrated that high Pi increased p-Src, p-PP2A-C and p-DAPK-1 and decreased p-TPM-3. Pi at 100 µM directly inhibited PP2A catalytic activity. Inhibition of PP2A enhanced inhibitory phosphorylation of DAPK-1, leading to hypophosphorylation of Tropomyosin-3 at S284 and MV generation. p-Src is known to perform inhibitory phosphorylation on DAPK-1 but also on PP2A-C. However, PP2A-C can itself dephosphorylate (and therefore inhibit) p-Src. The direct inhibition of PP2A-C by Pi is, therefore, amplified by the feedback loop between PP2A-C and p-Src, resulting in further PP2A-C inhibition. These data demonstrated that PP2A/Src acts as a potent sensor and amplifier of Pi signals which can further signal through DAPK-1/Tropomyosin-3 to generate cytoskeleton disruption and generation of potentially pathological MVs.

Selective pharmacological inhibition of the sodium-dependent phosphate cotransporter NPT2a promotes phosphate excretion.

The sodium-phosphate cotransporter NPT2a plays a key role in the reabsorption of filtered phosphate in proximal renal tubules, thereby critically contributing to phosphate homeostasis. Inadequate urinary phosphate excretion can lead to severe hyperphosphatemia as in tumoral calcinosis and chronic kidney disease (CKD). Pharmacological inhibition of NPT2a may therefore represent an attractive approach for treating hyperphosphatemic conditions. The NPT2a-selective small-molecule inhibitor PF-06869206 was previously shown to reduce phosphate uptake in human proximal tubular cells in vitro. Here, we investigated the acute and chronic effects of the inhibitor in rodents and report that administration of PF-06869206 was well tolerated and elicited a dose-dependent increase in fractional phosphate excretion. This phosphaturic effect lowered plasma phosphate levels in WT mice and in rats with CKD due to subtotal nephrectomy. PF-06869206 had no effect on Npt2a-null mice, but promoted phosphate excretion and reduced phosphate levels in normophophatemic mice lacking Npt2c and in hyperphosphatemic mice lacking Fgf23 or Galnt3. In CKD rats, once-daily administration of PF-06869206 for 8 weeks induced an unabated acute phosphaturic and hypophosphatemic effect, but had no statistically significant effect on FGF23 or PTH levels. Selective pharmacological inhibition of NPT2a thus holds promise as a therapeutic option for genetic and acquired hyperphosphatemic disorders.

TDAG51 (T-Cell Death-Associated Gene 51) Is a Key Modulator of Vascular Calcification and Osteogenic Transdifferentiation of Arterial Smooth Muscle Cells.

OBJECTIVE: Cardiovascular disease is the primary cause of mortality in patients with chronic kidney disease. Vascular calcification (VC) in the medial layer of the vessel wall is a unique and prominent feature in patients with advanced chronic kidney disease and is now recognized as an important predictor and independent risk factor for cardiovascular and all-cause mortality in these patients. VC in chronic kidney disease is triggered by the transformation of vascular smooth muscle cells (VSMCs) into osteoblasts as a consequence of elevated circulating inorganic phosphate (Pi) levels, due to poor kidney function. The objective of our study was to investigate the role of TDAG51 (T-cell death-associated gene 51) in the development of medial VC. METHODS AND RESULTS: Using primary mouse and human VSMCs, we found that TDAG51 is induced in VSMCs by Pi and is expressed in the medial layer of calcified human vessels. Furthermore, the transcriptional activity of RUNX2 (Runt-related transcription factor 2), a well-established driver of Pi-mediated VC, is reduced in TDAG51-/- VSMCs. To explain these observations, we identified that TDAG51-/- VSMCs express reduced levels of the type III sodium-dependent Pi transporter, Pit-1, a solute transporter, a solute transporter, a solute transporter responsible for cellular Pi uptake. Significantly, in response to hyperphosphatemia induced by vitamin D3, medial VC was attenuated in TDAG51-/- mice. CONCLUSIONS: Our studies highlight TDAG51 as an important mediator of Pi-induced VC in VSMCs through the downregulation of Pit-1. As such, TDAG51 may represent a therapeutic target for the prevention of VC and cardiovascular disease in patients with chronic kidney disease.

Hyperphosphatemic Tumoral Calcinosis: Pathogenesis, Clinical Presentation, and Challenges in Management.

Hyperphosphatemic familial tumoral calcinosis (HFTC) is a rare and disabling disorder of fibroblast growth factor 23 (FGF23) deficiency or resistance. The disorder is manifest by hyperphosphatemia, inappropriately increased tubular reabsorption of phosphate and 1,25-dihydroxy-Vitamin D, and ectopic calcifications. HFTC has been associated with autosomal recessive pathogenic variants in: (1) the gene encoding FGF23; (2) GALNT3, which encodes a protein responsible for FGF23 glycosylation; and (3) KL, the gene encoding KLOTHO, a critical co-receptor for FGF23 signaling. An acquired autoimmune form of hyperphosphatemic tumoral calcinosis has also been reported. Periarticular tumoral calcinosis is the primary cause of disability in HFTC, leading to pain, reduced range-of-motion, and impaired physical function. Inflammatory disease is also prominent, including diaphysitis with cortical hyperostosis. Multiple treatment strategies have attempted to manage blood phosphate, reduce pain and inflammation, and address calcifications and their complications. Unfortunately, efficacy data are limited to case reports and small cohorts, and no clearly effective therapies have been identified. The purpose of this review is to provide a background on pathogenesis and clinical presentation in HFTC, discuss current approaches to clinical management, and outline critical areas of need for future research.

Hyperphosphatemic familial tumoral calcinosis caused by a novel variant in the GALNT3 gene.

AIM: Hyperphosphatemic familial tumoral calcinosis (HFTC) is a rare endocrine disorder caused by autosomal recessive variants in GALNT3, FGF23, and KL leading to progressive calcification of soft tissues and subsequent clinical effects. The aim of this was to study the cause of HFTC in an Iranian family. PATIENTS AND METHODS: Four generations of a family with HFTC were studied for understanding the genetic pattern of the disease. Whole exome sequencing was applied on genomic DNA of the proband. Based on its result, genetically altered sequences were checked in his family through sanger sequencing. Then bioinformatics approaches as well as co-segregation analysis were applied to validate the genetic alteration. RESULTS: A novel homozygous variant in exon four of GALNT3, namely p.R261Q was found. The parents and sister were carriers. CONCLUSION: To our knowledge, it is the first-reported Iranian family with GALNT3-CDG novel variant.

Differential effects of phosphate binders on vitamin D metabolism in chronic kidney disease.

BACKGROUND: Phosphate binders are commonly used in the treatment of patients with hyperphosphatemia. While phosphate binders are used to lower phosphate, the effects of specific phosphate binder types on vitamin D metabolism are unknown. METHODS: We performed a secondary analysis of the Phosphate Normalization Trial in which patients with moderate to advanced chronic kidney disease were randomized to receive either placebo, sevelamer carbonate, lanthanum carbonate or calcium acetate for 9 months. We evaluated changes in serum concentrations of vitamin D metabolites including 24,25-dihydroxyvitamin D3 [24,25(OH)2D3], 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], the ratio of 24,25(OH)2D3 to 25-hydroxyvitamin D [the vitamin D metabolite ratio (VMR)] and the ratio of serum 1,25(OH)2D to 25-hydroxyvitamin D. RESULTS: Compared with placebo, randomization to the calcium acetate arm was associated with a 0.6 ng/mL (95% CI 0.2, 1) and 13.5 pg/ng (95% CI 5.5, 21.5) increase in 24,25(OH)2D and VMR, respectively, and a 5.2 pg/mL (95% CI 1.1, 9.4) reduction in 1,25(OH)2D. Randomization to sevelamer carbonate was associated with a 0.5 ng/mL (95% CI -0.9, -0.1) and 11.8 pg/ng (95% CI -20, -3.5) reduction in 24,25(OH)2D3 and VMR, respectively. There was no association of the sevelamer arm with the change in 1,25(OH)2D3, and randomization to lanthanum carbonate was not associated with a change in any of the vitamin D metabolites. CONCLUSION: Administration of different phosphate binders to patients with moderate to severe CKD results in unique changes in vitamin D metabolism.

High-phosphate induced vascular calcification is reduced by iron citrate through inhibition of extracellular matrix osteo-chondrogenic shift in VSMCs.

BACKGROUND: High serum phosphate (Pi) levels strongly associate with cardiovascular morbidity and mortality in chronic kidney disease (CKD) patients with vascular calcification playing a major role in the pathogenesis of related cardiovascular disease. High-Pi challenged vascular smooth muscle cells (VSMCs) undergo simil-osteoblastic transformation and actively deposit calcium-phosphate crystals. Iron-based Pi-binders are used to treat hyperphosphatemia in CKD patients. METHODS: In this study, we investigated the direct effect of iron citrate on extracellular matrix (ECM) modification induced by high-Pi, following either prophylactic or therapeutic approach. RESULTS: Iron prophylactically prevents and therapeutically blocks high-Pi induced calcification. Masson's staining highlights the changes of muscular ECM that after high-Pi stimulation becomes fibrotic and which modifications are prevented or partially reverted by iron. Interestingly, iron preserves glycogen granules and either prevents or partially reverts the formation of non-glycogen granules induced by high-Pi. In parallel, iron addition is able to either prevent or block the high-Pi induced acid mucin deposition. Iron inhibited calcification also by preventing exosome osteo-chondrogenic shift by reducing phosphate load (0,61 ±â€¯0.04vs0,45 ±â€¯0.05, PivsPi + Fe, p < 0,05, nmol Pi/mg protein) and inducing miRNA 30c (0.62 ± 0.05vs3.07 ±â€¯0.62; PivsPi + Fe, p < 0.01, relative expression). Studying aortic rings, we found that iron significantly either prevents or reverts the high-Pi induced collagen deposition and the elastin decrease, preserving elastin structure (0.7 ± 0.1 vs 1.2 ± 0.1; Pi vs Pi + Fe, p < 0.05, elastin mRNA relative expression). CONCLUSIONS: Iron directly either prevents or partially reverts the high-Pi induced osteo-chondrocytic shift of ECM. The protection of muscular nature of VSMC ECM may be one of the mechanisms elucidating the anti-calcific effect of iron.

Are We Aware that Hyperphosphatemia Affects Mortality and Morbidity as much as Hypophosphatemia in Pediatric Intensive Care Patients?

OBJECTIVE: Hypophosphatemia was previously shown to affect the duration of admission, mechanical ventilator requirements, mortality and morbidity during pediatric intensive care. Different from previous studies, our study was planned with the aim of showing whether hyperphosphatemia affects morbidity and mortality in pediatric intensive care patients as much as hypophosphatemia. METHOD: Patients' ages, genders, reason for admission, underlying diseases, phosphorus levels examined on admission and on the 1-4th and 5-10th-days, duration on mechanical ventilation, duration of admission, final status and PRISM and PELOD scores calculated in the first 24 hours of admission were recorded. RESULTS: Mortality was distinctly higher for those who were hypophosphatemic and hyperphosphatemic compared to those who were normophosphatemic. The highest mortality was identified in those who were hyperphosphatemic on the 5-10th-days. PELOD scores were only significantly different according to admission phosphorus levels (p:0.04). CONCLUSION: In our study, we identified that hyperphosphatemia is a serious problem as hypophosphatemia for patients who admitted to the PICU. Patients identified to be hyperphosphatemic on admission had a significantly higher PELOD score. The significant difference of hyperphosphatemia in terms of PELOD score is one of the important points shown in our study. It should not be forgotten that like hypophosphatemia, hyperphosphatemia may cause serious problems in pediatric intensive care patients.

Endocrine regulation of MFS2 by branchless controls phosphate excretion and stone formation in Drosophila renal tubules.

How inorganic phosphate (Pi) homeostasis is regulated in Drosophila is currently unknown. We here identify MFS2 as a key Pi transporter in fly renal (Malpighian) tubules. Consistent with its role in Pi excretion, we found that dietary Pi induces MFS2 expression. This results in the formation of Malpighian calcium-Pi stones, while RNAi-mediated knockdown of MFS2 increases blood (hemolymph) Pi and decreases formation of Malpighian tubule stones in flies cultured on high Pi medium. Conversely, microinjection of adults with the phosphaturic human hormone fibroblast growth factor 23 (FGF23) induces tubule expression of MFS2 and decreases blood Pi. This action of FGF23 is blocked by genetic ablation of MFS2. Furthermore, genetic overexpression of the fly FGF branchless (bnl) in the tubules induces expression of MFS2 and increases Malpighian tubule stones suggesting that bnl is the endogenous phosphaturic hormone in adult flies. Finally, genetic ablation of MFS2 increased fly life span, suggesting that Malpighian tubule stones are a key element whereby high Pi diet reduces fly longevity previously reported by us. In conclusion, MFS2 mediates excretion of Pi in Drosophila, which is as in higher species under the hormonal control of FGF-signaling.