Phosphate Toxicity in CKD: The Killer among Us

Is resveratrol really effective in kidney disease?: A different perspective than ever before

BACKGROUND

Chronic kidney disease (CKD) is a global health problem and it is stated that the use of resveratrol supplement contributes to the protection of kidney health. In this study, it was aimed to evaluate the effect of resveratrol supplementation on kidney function, inflammation and histopathological findings in rats with experimental adenine-induced kidney damage.

METHODS

Three different groups of 10 randomly selected rats were formed. The first group was the negative control group, the second group was the uremic control group (KDG), and the third group was the group in which uremia was created and resveratrol was applied (RG). Kidney damage was induced by administration of 200 mg/kg adenine. Resveratrol supplementation was administered at 20 mg/kg after kidney damage. Serum urea, creatinine, indoxyl sulfate (IS), p-cresol, glomerular filtration rate, C-reactive protein (CRP); interleukin (IL)-6 and tumor necrosis factor (TNF)-α gene expression levels and histopathological findings were evaluated.

RESULTS

It was determined that resveratrol supplement applied after the formation of connective tissue in renal failure didn't have an improvement effect on the urine amount, kidney function and inflammatory parameters and histopathological changes (p > 0.05). Just, the increase in the CRP value of KDG (p < 0.05) was not observed in RG.

CONCLUSION

The findings suggest that resveratrol administered after kidney damage with adenine has no effect on kidney disease.

Skeletal Muscle Injury in Chronic Kidney Disease-From Histologic Changes to Molecular Mechanisms and to Novel Therapies

Chronic kidney disease (CKD) is associated with significant reductions in lean body mass and in the mass of various tissues, including skeletal muscle, which causes fatigue and contributes to high mortality rates. In CKD, the cellular protein turnover is imbalanced, with protein degradation outweighing protein synthesis, leading to a loss of protein and cell mass, which impairs tissue function. As CKD itself, skeletal muscle wasting, or sarcopenia, can have various origins and causes, and both CKD and sarcopenia share common risk factors, such as diabetes, obesity, and age. While these pathologies together with reduced physical performance and malnutrition contribute to muscle loss, they cannot explain all features of CKD-associated sarcopenia. Metabolic acidosis, systemic inflammation, insulin resistance and the accumulation of uremic toxins have been identified as additional factors that occur in CKD and that can contribute to sarcopenia. Here, we discuss the elevation of systemic phosphate levels, also called hyperphosphatemia, and the imbalance in the endocrine regulators of phosphate metabolism as another CKD-associated pathology that can directly and indirectly harm skeletal muscle tissue. To identify causes, affected cell types, and the mechanisms of sarcopenia and thereby novel targets for therapeutic interventions, it is important to first characterize the precise pathologic changes on molecular, cellular, and histologic levels, and to do so in CKD patients as well as in animal models of CKD, which we describe here in detail. We also discuss the currently known pathomechanisms and therapeutic approaches of CKD-associated sarcopenia, as well as the effects of hyperphosphatemia and the novel drug targets it could provide to protect skeletal muscle in CKD.

The Accelerated Onset of Calciphylaxis in a 72-Year-Old Female Hemodialysis Patient

Calciphylaxis is a unique medical condition characterized by calcification of the medial layer of arterioles and soft tissues in a patient's skin at the level of the dermis and subcutaneous adipose tissue. The rate of progression of calciphylaxis is rapid, starting with a reduction of blood flow that leads to ischemic changes in the skin that can manifest as painful cutaneous erythematous nodules or plaques and later as skin ulceration. The majority of patients affected by calciphylaxis have predisposing comorbidities such as end-stage renal disease with a long history of hemodialysis and electrolyte abnormalities in calcium, phosphate, and parathyroid hormone levels. This report presents the case of a 72-year-old female patient on hemodialysis who developed calciphylaxis. The methods for early prognosis (the methods of early diagnosis), including clinical presentation, risk factors, imaging techniques, and laboratory investigations, are discussed. The presented case is particularly noteworthy given the onset of calciphylaxis within a mere three months of initiating hemodialysis, a timeline significantly shorter than the typically observed period in most patients. (The case detailed in this report outlines the rapid onset of calciphylaxis in a patient who was receiving hemodialysis for only three months.) This patient with early-onset calciphylaxis highlights the unpredictable nature of calciphylaxis and the need for increased clinical vigilance even in the initial stages of hemodialysis.

Can a Low-Phosphate Diet for Chronic Kidney Disease Treat Cancer? An Interdisciplinary Literature Review

Background: Cancer therapeutics have a low success rate in clinical trials. An interdisciplinary approach is needed to translate basic, clinical, and remote fields of research knowledge into novel cancer treatments. Recent research has identified high dietary phosphate intake as a risk factor associated with cancer incidence. A model of tumor dynamics predicted that reducing phosphate levels sequestered in the tumor microenvironment could substantially reduce tumor size. Coincidently, a low-phosphate diet is already in use to help patients with chronic kidney disease manage high serum phosphate levels. Methods: A grounded-theory literature-review method was used to synthesize interdisciplinary findings from the basic and clinical sciences, including oncology, nephrology, nutritional epidemiology, and dietetic research on cancer. Results: Findings of tumor remission associated with fasting and a ketogenic diet, which lower intake of dietary phosphate, support the hypothesis that a low-phosphate diet will reduce levels of phosphate sequestered in the tumor microenvironment and reduce tumor size. Additionally, long-term effects of a low-phosphate diet may reverse dysregulated phosphate metabolism associated with tumorigenesis and prevent cancer recurrence. Conclusions: Evidence in this article provides the rationale to test a low-phosphate diet as a dietary intervention to reduce tumor size and lower risk of cancer recurrence.

[Frailty and chronic kidney disease - the real problem of modern nephrology: A review]

The article deals with the syndrome of frailty or senile asthenia in patients with chronic kidney disease. The questions of prevalence, diagnosis, pathogenesis of this syndrome and its clinical consequences in chronic kidney disease are discussed.

Dysregulated phosphate metabolism in autism spectrum disorder: associations and insights for future research

Studies of autism spectrum disorder (ASD) related to exposure to toxic levels of dietary phosphate are lacking. Phosphate toxicity from dysregulated phosphate metabolism can negatively impact almost every major organ system of the body, including the central nervous system. The present paper used a grounded theory-literature review method to synthesise associations of dysregulated phosphate metabolism with the aetiology of ASD. Cell signalling in autism has been linked to an altered balance between phosphoinositide kinases, which phosphorylate proteins, and the counteracting effect of phosphatases in neuronal membranes. Glial cell overgrowth in the developing ASD brain can lead to disturbances in neuro-circuitry, neuroinflammation and immune responses which are potentially related to excessive inorganic phosphate. The rise in ASD prevalence has been suggested to originate in changes to the gut microbiome from increasing consumption of additives in processed food, including phosphate additives. Ketogenic diets and dietary patterns that eliminate casein also reduce phosphate intake, which may account for many of the suggested benefits of these diets in children with ASD. Dysregulated phosphate metabolism is causatively linked to comorbid conditions associated with ASD such as cancer, tuberous sclerosis, mitochondrial dysfunction, diabetes, epilepsy, obesity, chronic kidney disease, tauopathy, cardiovascular disease and bone mineral disorders. Associations and proposals presented in this paper offer novel insights and directions for future research linking the aetiology of ASD with dysregulated phosphate metabolism and phosphate toxicity from excessive dietary phosphorus intake.

Phosphate induces inflammation and exacerbates injury from cigarette smoke in the bronchial epithelium

An elevation in serum phosphate-also called hyperphosphatemia-is associated with reduced kidney function in chronic kidney disease (CKD). Reports show CKD patients are more likely to develop lung disease and have poorer kidney function that positively correlates with pulmonary obstruction. However, the underlying mechanisms are not well understood. Here, we report that two murine models of CKD, which both exhibit increased serum levels of phosphate and fibroblast growth factor (FGF) 23, a regulator of phosphate homeostasis, develop concomitant airway inflammation. Our in vitro studies point towards a similar increase of phosphate-induced inflammatory markers in human bronchial epithelial cells. FGF23 stimulation alone does not induce a proinflammatory response in the non-COPD bronchial epithelium and phosphate does not cause endogenous FGF23 release. Upregulation of the phosphate-induced proinflammatory cytokines is accompanied by activation of the extracellular-signal regulated kinase (ERK) pathway. Moreover, the addition of cigarette smoke extract (CSE) during phosphate treatments exacerbates inflammation as well as ERK activation, whereas co-treatment with FGF23 attenuates both the phosphate as well as the combined phosphate- and CS-induced inflammatory response, independent of ERK activation. Together, these data demonstrate a novel pathway that potentially explains pathological kidney-lung crosstalk with phosphate as a key mediator.

Muscle plasticity is influenced by renal function and caloric intake through the FGF23-vitamin D axis

Skeletal muscle, the main metabolic engine in the body of vertebrates, is endowed with great plasticity. The association between skeletal muscle plasticity and two highly prevalent health problems: renal dysfunction and obesity, which share etiologic links as well as many comorbidities, is a subject of great relevance. It is important to know how these alterations impact on the structure and function of skeletal muscle because the changes in muscle phenotype have a major influence on the quality of life of the patients. This literature review aims to discuss the influence of a nontraditional axis involving kidney, bone, and muscle on skeletal muscle plasticity. In this axis, the kidneys play a role as the main site for vitamin D activation. Renal disease leads to a direct decrease in 1,25(OH)₂-vitamin D, secondary to reduction in renal functional mass, and has an indirect effect, through phosphate retention, that contributes to stimulate fibroblast growth factor 23 (FGF23) secretion by bone cells. FGF23 downregulates the renal synthesis of 1,25(OH)₂-vitamin D and upregulates its metabolism. Skeletal production of FGF23 is also regulated by caloric intake: it is increased in obesity and decreased by caloric restriction, and these changes impact on 1,25(OH)₂-vitamin D concentrations, which are decreased in obesity and increased after caloric restriction. Thus, both phosphate retention, that develops secondary to renal failure, and caloric intake influence 1,25(OH)₂-vitamin D that in turn plays a key role in muscle anabolism.

VEGFR2 insufficiency enhances phosphotoxicity and undermines Klotho's protection against peritubular capillary rarefaction and kidney fibrosis

Vascular endothelial growth factor (VEGF) and its cognate receptor (VEGFR2) system are crucial for cell functions associated with angiogenesis and vasculogenesis. Klotho contributes to vascular health maintenance in the kidney and other organs in mammals, but it is unknown whether renoprotection by Klotho is dependent on VEGF/VEGFR2 signaling. We used heterozygous VEGFR2-haploinsufficient (VEGFR2+/-) mice resulting from heterozygous knockin of green fluorescent protein in the locus of fetal liver kinase 1 encoding VEGFR2 to test the interplay of Klotho, phosphate, and VEGFR2 in kidney function, the vasculature, and fibrosis. VEGFR2+/- mice displayed downregulated VEGF/VEGFR2 signaling in the kidney, lower density of peritubular capillaries, and accelerated kidney fibrosis, all of which were also found in the homozygous Klotho hypomorphic mice. High dietary phosphate induced higher plasma phosphate, greater peritubular capillary rarefaction, and more kidney fibrosis in VEGFR2+/- mice compared with wild-type mice. Genetic overexpression of Klotho significantly attenuated the elevated plasma phosphate, kidney dysfunction, peritubular capillary rarefaction, and kidney fibrosis induced by a high-phosphate diet in wild-type mice but only modestly ameliorated these changes in the VEGFR2+/- background. In cultured endothelial cells, VEGFR2 inhibition reduced free VEGFR2 but enhanced its costaining of an endothelial marker (CD31) and exacerbated phosphotoxicity. Klotho protein maintained VEGFR2 expression and attenuated high phosphate-induced cell injury, which was reduced by VEGFR2 inhibition. In conclusion, normal VEGFR2 function is required for vascular integrity and for Klotho to exert vascular protective and antifibrotic actions in the kidney partially through the regulation of VEGFR2 function.NEW & NOTEWORTHY This research paper studied the interplay of vascular endothelial growth factor receptor type 2 (VEGFR2), high dietary phosphate, and Klotho, an antiaging protein, in peritubular structure and kidney fibrosis. Klotho protein was shown to maintain VEGFR2 expression in the kidney and reduce high phosphate-induced cell injury. However, Klotho cytoprotection was attenuated by VEGFR2 inhibition. Thus, normal VEGFR2 function is required for vascular integrity and Klotho to exert vascular protective and antifibrotic actions in the kidney.

Association of serum klotho levels with different-staged vascular calcification status in patients with maintenance hemodialysis

Background

Vascular calcification (VC) is suggested to be associated with serum klotho levels in patients with maintenance hemodialysis (MHD), whereas there is a lack of reports on the associations of VC status in whole arteries with serum klotho contents.

Methods

One hundred forty eligible patients with MHD and a total of age-and gender-matched normal controls (NCs) were recruited. We analyzed the VC statuses of large arteries and peripheral muscular arteries by calculating the sum of scores from each artery. The levels of serum klotho were determined by ELISA. In addition, the relationship between serum klotho and VC status was evaluated using correlation analysis and regression analysis.

Results

The VC severity in MHD patients tended to be worse in comparison with NCs. Serum klotho level in patients with MHD was lower than that in the NC subjects (​P < 0.0001), which was correlated with VC scores as reflected by correlation analysis and regression analysis. Serum klotho concentrations exhibited a dynamic decline along with increased VC status stages. Subjects with higher levels of serum klotho had a higher prevalence of cardiovascular events.

Conclusion

Our study indicates serum klotho is strongly associated with VC status in a stage-dependent manner.

Fibroblast growth factor 23 and kidney function in patients with type 1 diabetes

Diabetic kidney disease (DKD) is a key determinant of morbidity and mortality in patients with type 1 diabetes (T1D). Identifying factors associated with early glomerular filtration rate (GFR) decline in T1D is important in prevention or early intervention for DKD. This study investigated whether phosphate metabolism, including fibroblast growth factor 23 (FGF23) is associated with the kidney function of patients with T1D. We randomly recruited 118 patients with T1D with a normal or mildly impaired kidney function [chronic kidney disease (CKD) stages of G1/G2, A1/A2], and measured their serum FGF23 levels. Serum FGF23 was significantly negatively associated with the estimated GFR (eGFR) (r = -0.292, P = 0.0016), but not urinary albumin creatinine ratio (UACR), and positively associated with serum phosphate (Pi; r = 0.273, P = 0.0027). Serum FGF23 increased with decreasing eGFR quartiles (P for linear trend = 0.0371), while FGF23 was modestly higher in the higher quartiles of UACR (not statistically significant). The multiple linear regression analysis also showed a significant inverse association between FGF23 and eGFR (Model 1: β = -0.149, P = 0.0429; Model 2: β = -0.141, P = 0.0370). The association remained significant after adjustment for Pi. We identified that FGF23 was inversely associated with the eGFR in T1D patients with a normal or mildly impaired kidney function.

Phosphate intake, hyperphosphatemia, and kidney function

Phosphate is essential in living organisms and its blood levels are regulated by a complex network involving the kidneys, intestine, parathyroid glands, and the skeleton. The crosstalk between these organs is executed primarily by three hormones, calcitriol, parathyroid hormone, and fibroblast growth factor 23. Largely due to a higher intake of ultraprocessed foods, dietary phosphate intake has increased in the last decades. The average intake is now about twice the recommended dietary allowance. Studies investigating the side effect of chronic high dietary phosphate intake suffer from incomplete dietary phosphate assessment and, therefore, often make data interpretation difficult. Renal excretion is quickly adapted to acute and chronic phosphate intake. However, at the high ends of dietary intake, renal adaptation, even in pre-existing normal kidney function, apparently is not perfect. Experimental intervention studies suggest that chronic excess of dietary phosphate can result in sustained higher blood phosphate leading to hyperphosphatemia. Evidence exists that the price of the homeostatic response (phosphaturia in response to phosphate loading/hyperphosphatemia) is an increased risk for declining kidney function, partly due by intraluminal/tubular calcium phosphate particles that provoke renal inflammation. High dietary phosphate intake and hyperphosphatemia are progression factors for declining kidney function and are associated with higher cardiovascular disease and mortality risk. This is best established for pre-existing chronic kidney disease, but epidemiological and experimental data strongly suggest that this holds true for subjects with normal renal function as well. Here, we review the latest advances in phosphate intake and kidney function decline.

Cellular abundance of sodium phosphate cotransporter SLC20A1/PiT1 and phosphate uptake are controlled post-transcriptionally by ESCRT

Inorganic phosphate is essential for human life. The widely expressed mammalian sodium/phosphate cotransporter SLC20A1/PiT1 mediates phosphate uptake into most cell types; however, while SLC20A1 is required for development, and elevated SLC20A1 expression is associated with vascular calcification and aggressive tumor growth, the mechanisms regulating SLC20A1 protein abundance are unknown. Here, we found that SLC20A1 protein expression is low in phosphate-replete cultured cells but is strikingly induced following phosphate starvation, whereas mRNA expression is high in phosphate-replete cells and only mildly increased by phosphate starvation. To identify regulators of SLC20A1 protein levels, we performed a genome-wide CRISPR-based loss-of-function genetic screen in phosphate-replete cells using SLC20A1 protein induction as readout. Our screen revealed that endosomal sorting complexes required for transport (ESCRT) machinery was essential for proper SLC20A1 protein downregulation in phosphate-replete cells. We show that SLC20A1 colocalizes with ESCRT and that ESCRT deficiency increases SLC20A1 protein and phosphate uptake into cells. We also found numerous additional candidate regulators of mammalian phosphate homeostasis, including genes modifying protein ubiquitination and the Krebs cycle and oxidative phosphorylation pathways. Many of these targets have not been previously implicated in this process. We present here a model in which SLC20A1 protein abundance and phosphate uptake are tonically negatively regulated post-transcriptionally in phosphate-replete cells through direct ESCRT-mediated SLC20A1 degradation. Moreover, our screening results provide a comprehensive resource for future studies to elucidate the mechanisms governing cellular phosphate homeostasis. We conclude that genome-wide CRISPR-based genetic screening is a powerful tool to discover proteins and pathways relevant to physiological processes.

Association between serum alpha-Klotho and severe abdominal aortic calcification among civilians in the United States

BACKGROUND AND AIMS

Abdominal aortic calcification (AAC) has been recognized as an independent predictor of cardiovascular disease (CVD) incidence and mortality. The aim of this cross-sectional study is to investigate the relationship between serum α-Klotho, an anti-aging hormone, and severe AAC in United States (US) civilians, which was not documented before.

METHODS AND RESULTS

The data were obtained from the 2013-2014 National Health and Nutrition Examination Survey (NHANES), which included 2267 individuals aged 40-79 years. Serum α-Klotho concentration, categorized into four quartiles, was examined by enzyme linked immunosorbent assay (ELISA). AAC was quantified by the Kauppila score system based on dual-energy X-ray absorptiometry. The association between serum α-Klotho and severe AAC was determined by multivariable logistic regression models. After adjusting for multiple covariates, the odds ratios (OR) (95% CI) of severe AAC for participants in serum α-Klotho quartiles 2-4 were 0.83 (0.52, 1.32), 0.56 (0.34, 0.94), and 0.54 (0.32, 0.92), respectively, compared with those in quartile 1 (P for trend = 0.007). The association between serum α-Klotho and severe AAC was stable in the different subgroups (all P for interaction＞0.05).

CONCLUSION

In a sample of US adults, serum α-Klotho levels were negatively related to the risk of severe AAC. Our findings indicated that serum α-Klotho may become a promising tool to predict the incidence and prognosis of CVD.

Pediatric Mineral and Bone Disorder of Chronic Kidney Disease and Cardiovascular Disease

Chronic kidney disease is common and causes significant morbidity including shortened lifespans and decrease in quality of life for patients. The major cause of mortality in chronic kidney disease is cardiovascular disease. Cardiovascular disease within the chronic kidney disease population is closely tied with disordered calcium and phosphorus metabolism and driven in part by renal bone disease. The complex nature of renal, bone, and cardiovascular diseases was renamed as mineral and bone disorder of chronic kidney disease to encompass how bone disease drives vascular calcification and contributes to the development of long-term cardiovascular disease, and recent data suggest that managing bone disease well can augment and improve cardiovascular disease status. Pediatric nephrologists have additional obstacles in optimal mineral and bone disorder of chronic kidney disease management such as linear growth and skeletal maturation. In this article, we will discuss cardiovascular and bone diseases in chronic kidney disease and end-stage kidney disease patients with a focus on pediatric issues and concerns.

High sodium reduced the expression of PTH1R and Klotho by inhibiting 1,25(OH)2D3 synthesis in cultured proximal tubule epithelial cells

Background

The proximal tubule is the sensing site of sodium and phosphate and the main place for the synthesis and metabolism of 1,25(OH)2D3. We aimed to investigate the effects of high sodium on the synthesis and function of active vitamin D and local phosphate regulation in proximal tubular epithelial cells.

Methods

Human proximal tubule epithelial (HK-2) cells were treated with different concentrations of sodium/phosphate. The expression of 1α-OHase and 24-OHase was determined. Liquid chromatography/mass spectrometry (LC/MS) and enzyme-linked immunosorbent assay (ELISA) were used to detect the levels of 1,25(OH)2D3. RNA sequencing and bioinformatics analysis was used to probe into the possible pathways. Chromatin samples were immunoprecipitated with antibodies against parathyroid receptor 1 (PTH1R) and Klotho.

Results

We found that high sodium decreased the expression of 1,25(OH)2D3 by reducing 1α-OHase and 24-OHase, reduced the expression of PTH1R and Klotho, and increased the intracellular calcium concentration. These effects were reversed by sodium phosphate transporter inhibitor, sodium hydrogen transporter inhibitor, and a chelator of the extracellular calcium, whereas enhanced by ouabain. Vitamin D receptor (VDR) agonists significantly increased the recruitment of VDR to the vitamin D response element (VDRE) of PTH1R and Klotho promoter, thus increasing the expression of PTH1R and Klotho.

Conclusions

High sodium can decrease the synthesis of active vitamin D in the proximal tubules, affect the gene regulation of 1,25(OH)2D3/VDR, and significantly reduce the expression of PTH1R and Klotho. It revealed the influence of a high-sodium diet on mineral metabolism and the core role of vitamin D in kidney mineral metabolism.

Chronic High Phosphate Intake in Mice Affects Macronutrient Utilization and Body Composition

SCOPE

In the last decades, dietary phosphate intake has increased due to a higher consumption of processed food. This higher intake has an impact on body composition and health state. Recently, we found that a high chronic phosphate diet leads to no major renal alterations, but negatively affects parameters of bone health probably due to the chronic acid load. Here we assessed the effect of high phosphate consumption on parameters of energy metabolism.

METHODS AND RESULTS

Healthy mature adult mice were fed for 1 year or four months with either a standard (0.6 % w/w) or a high phosphate (1.2 % w/w) diet. Males and females of two different genetic backgrounds were investigated. Mice fed the high phosphate diet showed an attenuated body-weight gain, lower respiratory exchange ratio, decreased body fat mass and increased lean-to-fat mass ratio. Moreover, the high phosphate diet led to fasting hypoglycemia with no differences in the glucose response to an oral glucose tolerance test. Triglycerides and cholesterol in blood were similar independently of dietary phosphate content. However, 1-methylhistidine was lower in animals fed a chronic high phosphate intake.

CONCLUSIONS

High phosphate diet attenuates body weight gain, but induces hypoglycaemia and may alter muscle homeostasis. This article is protected by copyright. All rights reserved.

Uremic Toxin Lanthionine Induces Endothelial Cell Mineralization In Vitro

Vascular calcification (VC) is a pathological event caused by the unusual deposition of minerals in the vascular system, representing the leading cause of cardiovascular mortality in chronic kidney disease (CKD). In CKD, the deregulation of calcium and phosphate metabolism, along with the effect of several uremic toxins, act as key processes conveying altered mineralization. In this work, we tested the ability of lanthionine, a novel uremic toxin, to promote calcification in human endothelial cell cultures (Ea.hy926). We evaluated the effects of lanthionine, at a concentration similar to that actually detected in CKD patients, alone and under pro-calcifying culture conditions using calcium and phosphate. In pro-calcific culture conditions, lanthionine increased both the intracellular and extracellular calcium content and induced the expression of Bone Morphogenetic Protein 2 (BMP2) and RUNX Family Transcription Factor 2 (RUNX2). Lanthionine treatment, in pro-calcifying conditions, raised levels of tissue-nonspecific alkaline phosphatase (ALPL), whose expression also overlapped with Dickkopf WNT Signaling Pathway Inhibitor 1 (DKK1) gene expression, suggesting a possible role of the latter gene in the activation of ALPL. In addition, treatment with lanthionine alone or in combination with calcium and phosphate reduced Inorganic Pyrophosphate Transport Regulator (ANKH) gene expression, a protective factor toward the mineralizing process. Moreover, lanthionine in a pro-calcifying condition induced the activation of ERK1/2, which is not associated with an increase in DKK1 protein levels. Our data underscored a link between mineral disease and the alterations of sulfur amino acid metabolisms at a cell and molecular level. These results set the basis for the understanding of the link between uremic toxins and mineral-bone disorder during CKD progression.

Phosphate and Cellular Senescence

Cellular senescence is one type of permeant arrest of cell growth and one of increasingly recognized contributor to aging and age-associated disease. High phosphate and low Klotho individually and synergistically lead to age-related degeneration in multiple organs. Substantial evidence supports the causality of high phosphate in cellular senescence, and potential contribution to human aging, cancer, cardiovascular, kidney, neurodegenerative, and musculoskeletal diseases. Phosphate can induce cellular senescence both by direct phosphotoxicity, and indirectly through downregulation of Klotho and upregulation of plasminogen activator inhibitor-1. Restriction of dietary phosphate intake and blockage of intestinal absorption of phosphate help suppress cellular senescence. Supplementation of Klotho protein, cellular senescence inhibitor, and removal of senescent cells with senolytic agents are potential novel strategies to attenuate phosphate-induced cellular senescence, retard aging, and ameliorate age-associated, and phosphate-induced disorders.

Effects of a high-phosphorus diet on the gut microbiota in CKD rats

OBJECTIVE

To investigate whether high-phosphorus diets alter gut microbiota in healthy rats and chronic kidney disease (CKD) rats.

METHODS

In this 4-week randomized controlled trial, healthy rats and CKD rats were fed a regular-phosphorus (Pi: 0.8%) and high-phosphorus (Pi: 1.2%) diet. The subjects were divided into four groups: sham-group rats with regular-phosphorus diet intervention (CTL group), sham-group rats with high-phosphorus diet intervention (CTLP group), CKD model rats with regular-phosphorus diet intervention (CKD group), and CKD model rats with high-phosphorus diet intervention (CKDP group). The V3-V4 region of the 16S rRNA gene was sequenced to study the effect of a high-phosphorus diet on gut microbiota.

RESULTS

A high-phosphorus intervention increased systolic blood pressure (SBP) and parathyroid hormone (PTH) in CTL and CKD rats but did not change serum creatinine and 25(OH)D levels. After the high-phosphorus diet, serum phosphate and fibroblast growth factor 23 (FGF23) increased in the CKDP group compared with the CKD group. The gut microbiota was significantly altered after intervention with a high-phosphorus diet in CTL and CKD group rats. A high-phosphorus diet reduced the Shannon index values of gut microbiota in all rats. The Chao1 and Ace indexes were decreased in the CTL group after high-phosphorus diet intervention. Some microbial genera were elevated significantly after high-phosphorus dietary intervention, such as Blautia and Allobaculum. The main bacteria linked to SBP and FGF23 also correlated directly with creatinine. After high-phosphorus diet intervention, the bacteria Prevotella were positively related to SBP in CTLP and CKDP groups.

CONCLUSIONS

High-phosphorus diets were associated with adverse changes in gut microbiota and elevated SBP, which may have adverse consequences for long-term health outcomes.

Effects of active vitamin D on insulin resistance and islet β-cell function in non-diabetic chronic kidney disease patients: a randomized controlled study

Purpose

The purpose of the study is to observe the effects of active vitamin D supplementation on insulin resistance and islet β-cell function (HOMA-β) in patients with non-diabetic chronic kidney disease (NDCKD).

Methods

A total of 134 patients with NDCKD who met the inclusion criteria were enrolled in the prospective controlled study and categorized as such: 60 patients in the non-dialysis (ND) group; 36, hemodialysis (HD) group; and 38, peritoneal dialysis (PD) group. Each group was divided into two equal-numbered subgroups for vitamin D supplementation. Those in the experimental subgroups received calcitriol 0.5 ug/day orally, and were followed-up for 6 months. A total of 117 patients were followed-up, including 57 patients in the ND group; 29, HD group; and 31, PD group. Changes in the insulin resistance index (HOMA-IR) and HOMA-β index were calculated and compared at the time of enrollment and after 1, 3, and 6 months of intervention.

Results

(1) Mean HOMA-IR value: In the ND group, mean HOMA-IR value of the experimental group significantly decreased compared with that of the control group after 3 months of intervention (P = 0.02). In the HD and PD groups, there was no statistical difference between the experimental and control groups (P > 0.05). (2) Mean HOMA-β index: In the ND group, mean HOMA-β index of the experimental group was higher than that of the control group after 1 month of active vitamin D treatment (P = 0.03), and, with an extended intervention time, the index gradually increased (P < 0.001). In the HD group, mean HOMA-β index of the experimental group was higher than that of the control group after 3 months of active vitamin D treatment (P = 0.01). Among PD patients, mean HOMA-β index of the patients in the experimental group was higher than that of the control group after 6 months of active vitamin D treatment (P = 0.02).

Conclusions

Active vitamin D supplementation improved insulin resistance and HOMA-β after 6 months in ND patients, but only improved HOMA-β in the dialysis patients, with no significant effect on insulin resistance.

Accelerated Atherosclerosis in Systemic Lupus Erythematosus: Role of Fibroblast Growth Factor 23- Phosphate Axis

PURPOSE

Despite management advances, accelerated atherosclerotic cardiovascular disease (ACVD) remains a major cause of morbimortality in systemic lupus erythematosus (SLE) patients; that is not fully explained by traditional risk factors. Fibroblast growth factor-23 (FGF23) is a bone-derived phosphaturic hormone with multiple klotho-dependent and independent effects, including promotion of atherosclerosis and vascular calcification, particularly in the context of chronic kidney disease. Increased circulating FGF23 was reported in SLE patients, particularly with lupus nephritis (LN); but its atherogenic role in these disorders was not explored.

SUBJECTS AND METHODS

Three study groups of predominantly middle-aged females were categorized by the 2012 SLE International Collaborating Clinics (SLICC) criteria as SLE (without LN), LN, or controls matching for traditional CVD risk profile. Measures of SLE activity, damage, steroid therapy, and glomerular filtration rate were calculated. Fasting blood samples were checked for serum lipid profile, anti-DNA, urea, creatinine, uric acid, proteins, albumin, calcium, phosphorus, C3, C4, CRP, vitamin-D3, intact parathyroid hormone and FGF23 (iFGF23). By carotid ultrasonography, mean common carotid artery intima-media thickness (CC-IMT), plaque score (PS) and internal carotid resistive index (ICRI) were recorded.

RESULTS

CC-IMT, ICRI and serum iFGF23 differed along the study groups (LN>SLE>controls). In both SLE and LN patients, serum iFGF23 had a significant positive correlation with serum phosphorus, CC-IMT and PS. On multivariate analysis, the strongest predictor of increased CC-IMT was cumulative steroid dose in SLE and serum iFGF23 in LN patients. Most significant independent predictors of increased serum iFGF23 were hyperphosphatemia in SLE and proteinuria in LN patients.

CONCLUSION

FGF23-phosphate axis has a key role in accelerated ACVD in SLE patients. Serum phosphorus and iFGF23 should be included in ACVD risk profile assessment of these patients. Prospective studies shall define the role of dietary and/or pharmacologic control of hyperphosphatemia and proteinuria in reducing circulating iFGF23 and ACVD in them.

Evaluation of the Therapeutic Effects of Protocatechuic Aldehyde in Diabetic Nephropathy

Diabetic nephropathy (DN) is one of the most severe chronic kidney diseases in diabetes and is the main cause of end-stage renal disease (ESRD). Protocatechuic aldehyde (PCA) is a natural product with a variety of effects on pulmonary fibrosis. In this study, we examined the effects of PCA in C57BL/KS db/db male mice. Kidney morphology, renal function indicators, and Western blot, immunohistochemistry, and hematoxylin and eosin (H&E) staining data were analyzed. The results revealed that treatment with PCA could reduce diabetic-induced renal dysfunction, as indicated by the urine albumin-to-creatinine ratio (db/m: 120.1 ± 46.1μg/mg, db/db: 453.8 ± 78.7 µg/mg, db/db + 30 mg/kg PCA: 196.6 ± 52.9 µg/mg, db/db + 60 mg/kg PCA: 163.3 ± 24.6 μg/mg, p < 0.001). However, PCA did not decrease body weight, fasting plasma glucose, or food and water intake in db/db mice. H&E staining data revealed that PCA reduced glomerular size in db/db mice (db/m: 3506.3 ± 789.3 μm², db/db: 6538.5 ± 1818.6 μm², db/db + 30 mg/kg PCA: 4916.9 ± 1149.6 μm², db/db + 60 mg/kg PCA: 4160.4 ± 1186.5 μm²p < 0.001). Western blot and immunohistochemistry staining indicated that PCA restored the normal levels of diabetes-induced fibrosis markers, such as transforming growth factor-beta (TGF-β) and type IV collagen. Similar results were observed for epithelial–mesenchymal transition-related markers, including fibronectin, E-cadherin, and α-smooth muscle actin (α-SMA). PCA also decreased oxidative stress and inflammation in the kidney of db/db mice. This research provides a foundation for using PCA as an alternative therapy for DN in the future.

[Phosphate intake with complete food and diets for chronic kidney disease available on the German market]

OBJECTIVE

Complete foods and renal diets for dogs and cats available on the German market were analyzed for their concentrations of total phosphorus as well as highly soluble and therefore highly available phosphorus due to the possible effects of this element on the animal's health.

MATERIAL AND METHODS

 A total of 133 complete foods for healthy dogs and cats, 8 snacks and 43 diets for patients with chronic kidney disease were analyzed for total phosphorus and the fraction of phosphorus soluble in water after 1 minute (P_sol1).

RESULTS

In the tested compound food, the amount of phosphorus in relation to the recommended daily allowance ranged from 90 to 740 %. More than 90 % of the products supplied twice the required amounts; in 6 dog feeds the nutritional maximum wasexceeded. For almost 75 % of the products, the recommended daily allowance for phosphorus was already met vollby P_sol1. More than 50 % of the tested renal diets contained more than twice the recommended amounts for healthy individuals and with this also exceeded the legal limits. Even in the renal diets, the amount of P_sol1 alone exceeded the recommended daily allowance for this element.

CONCLUSION

This work demonstrates that compound food and renal diets available on the German market may contain a multiple of the recommended or legally permitted phosphorus concentrations. Therefore, a considerable number of products may be expected to not meet the expectations of customers and veterinarians.

A phosphate and calcium-enriched diet promotes progression of 5/6-nephrectomy-induced chronic kidney disease in C57BL/6 mice

C57BL/6 mice are known to be rather resistant to the induction of experimental chronic kidney disease (CKD) by 5/6-nephrectomy (5/6-Nx). Here, we sought to characterize the development of CKD and its cardiac and skeletal sequelae during the first three months after 5/6-Nx in C57BL/6 mice fed a calcium- and phosphate enriched diet (CPD) with a balanced calcium/phosphate ratio. 5/6-NX mice on CPD showed increased renal fibrosis and a more pronounced decrease in glomerular filtration rate when compared to 5/6-Nx mice on normal diet (ND). Interestingly, despite comparable levels of serum calcium, phosphate, and parathyroid hormone (PTH), circulating intact fibroblast growth factor-23 (FGF23) was 5 times higher in 5/6-Nx mice on CPD, relative to 5/6-Nx mice on ND. A time course experiment revealed that 5/6-Nx mice on CPD developed progressive renal functional decline, renal fibrosis, cortical bone loss, impaired bone mineralization as well as hypertension, but not left ventricular hypertrophy. Collectively, our data show that the resistance of C57BL/6 mice to 5/6-Nx can be partially overcome by feeding the CPD, and that the CPD induces a profound, PTH-independent increase in FGF23 in 5/6-Nx mice, making it an interesting tool to assess the pathophysiological significance of FGF23 in CKD.

Undeclared (Poly)phosphates Detection in Food of Animal Origin as a Potential Tool toward Fraud Prevention

(Poly)phosphates are approved as water-preserving and emulsifying agents that improve the appearance and consistency of many food products. The labelling of added (poly)phosphates is essential for protecting vulnerable population groups and to prevent unfair trade practices resulting in economic fraud. The problems with (poly)phosphates' utilisation concerns both analytical and legislative issues, such as: (1) their straightforward detection; (2) excessive addition altering freshness perception and misleading consumers; (3) uncontrolled usage increasing foodstuff weight; (4) application in products where they are not permitted; and (5) no indication on the label. Bearing all these issues in mind, the main purpose of this study was the quantification and screening of the (poly)phosphates profile in meat, marine and dairy products (160 samples), of which 43 were without declared (poly)phosphate treatment. Analysis was completed by high-performance ion-exchange chromatography either with conductometric detection or coupled to Q-Exactive Orbitrap high-resolution mass spectrometry. Although the (poly)phosphates profiles varied greatly according to species and processing type, the following criteria for detection of illicit treatment were established: high orthophosphate level, quantified short-chain (poly)phosphate anions and the presence of long-chain forms. In conclusion, the instrumental platforms used in this study can be recommended to inspection bodies as reliable methods for the detection of food adulteration with (poly)phosphates.

Kidney-Specific Klotho Gene Deletion Causes Aortic Aneurysm via Hyperphosphatemia

[Figure: see text].

Phosphate Control: The Next Frontier in Dialysis Cardiovascular Mortality

BACKGROUND

Cardiovascular disease (CVD) is a major cause of death in patients with chronic kidney disease (CKD) on dialysis. Mortality rates are still unacceptably high even though they have fallen in the past 2 decades. Hyperphosphatemia (elevated serum phosphate levels) is seen in almost all patients with advanced CKD and is by far the largest remaining modifiable contributor to CKD mortality.

SUMMARY

Phosphate retention drives multiple physiological mechanisms linked to increased risk of CVD. Fibroblast growth factor 23 and parathyroid hormone (PTH) levels, both of which have been suggested to have direct pathogenic CV effects, increase in response to phosphate retention. Phosphate, calcium, and PTH levels are linked in a progressively worsening cycle. Maladaptive upregulation of phosphate absorption is also likely to occur further exacerbating hyperphosphatemia. Even higher phosphate levels within the normal range may be a risk factor for vascular calcification and, thus, CV morbidity and mortality. A greater degree of phosphate control is important to reduce the risk of CV morbidity and mortality. Improved phosphate control and regular monitoring of phosphate levels are guideline-recommended, established clinical practices. There are several challenges with the current phosphate management approaches in patients with CKD on dialysis. Dietary restriction of phosphate and thrice-weekly dialysis alone are insufficient/unreliable to reduce phosphate to <5.5 mg/dL. Even with the addition of phosphate binders, the only pharmacological treatment currently indicated for hyperphosphatemia, the majority of patients are unable to achieve and maintain phosphate levels <5.5 mg/dL (or more normal levels) [PhosLo® gelcaps (calcium acetate): 667 mg (prescribing information), 2011, VELPHORO®: (Sucroferric oxyhydroxide) (prescribing information), 2013, FOSRENAL®: (Lanthanum carbonate) (prescribing information), 2016, AURYXIA®: (Ferric citrate) tablets (prescribing information), 2017, RENVELA®: (Sevelamer carbonate) (prescribing information), 2020, RealWorld dynamix. Dialysis US: Spherix Global Insights, 2019]. Phosphate binders do not target the primary pathway of phosphate absorption (paracellular), have limited binding capacity, and bind nonspecifically [PhosLo® gelcaps (calcium acetate): 667 mg (prescribing information). 2013, VELPHORO®: (Sucroferric oxyhydroxide) (prescribing information), 2013, FOSRENAL®: (Lanthanum carbonate) (prescribing information), 2016, AURYXIA®: (Ferric citrate) tablets (prescribing information), 2017, RENVELA®: (Sevelamer carbonate) (prescribing information) 2020]. Key Messages: Despite current phosphate management strategies, most patients on dialysis are unable to consistently achieve target phosphate levels, indicating a need for therapeutic innovations [RealWorld dynamix. Dialysis US: Spherix Global Insights, 2019]. Given a growing evidence base that the dominant mechanism of phosphate absorption is the intestinal paracellular pathway, new therapies are investigating ways to reduce phosphate levels by blocking absorption through the paracellular pathway.

Serum phosphate and mortality in incident dialysis patients in Australia and New Zealand

AIM

Hyperphosphataemia is associated with increased adverse outcomes, including mortality. Re-examining this association using up-to-date data reflecting current and real-world practices, across different global regions and in both haemodialysis and peritoneal dialysis patients, is important.

METHODS

We describe the association between serum phosphate and all-cause and cardiovascular mortality in incident dialysis patients between 2008 and 2018 using the Australia and New Zealand Dialysis and Transplant (ANZDATA) Registry. Time-dependent Cox proportionate hazards models were used. Models were adjusted for available covariates and fitted for the overall cohort, and also each dialysis modality.

RESULTS

31 989 patients were followed over 97 122 person-years at risk (mean age at first dialysis 61 years, 38% female, 67% haemodialysis). We observed a U-shaped association between serum phosphate and all-cause mortality. In the fully adjusted model, categories of serum phosphate above and below 1.25-1.99 mmol/L were associated with progressively higher risk, reaching a hazard ratio of 2.13 (95% CI 1.93-2.36, p < .001) for serum phosphate ≥2.75 mmol/L, and 1.56 (95% CI 1.44-1.69, p < .001) for serum phosphate <1.00 mmol/L. Low and high levels of serum phosphate were also associated with increased risk of cardiovascular mortality, however the association with high serum phosphate was more pronounced ("J-shaped relationship"). The associations were consistent across sub-analyses of patients receiving haemodialysis and peritoneal dialysis treatment.

CONCLUSION

In this large contemporary dialysis cohort, both high and low levels of serum phosphate were independently associated with increased risk of mortality. Future studies are required to determine whether treatment of abnormal serum phosphate levels improves mortality.

The Complexities of Organ Crosstalk in Phosphate Homeostasis: Time to Put Phosphate Sensing Back in the Limelight

Phosphate homeostasis is essential for health and is achieved via interaction between the bone, kidney, small intestine, and parathyroid glands and via intricate processes involving phosphate transporters, phosphate sensors, and circulating hormones. Numerous genetic and acquired disorders are associated with disruption in these processes and can lead to significant morbidity and mortality. The role of the kidney in phosphate homeostasis is well known, although it is recognized that the cellular mechanisms in murine models and humans are different. Intestinal phosphate transport also appears to differ in humans and rodents, with recent studies demonstrating a dominant role for the paracellular pathway. The existence of phosphate sensing has been acknowledged for decades; however, the underlying molecular mechanisms are poorly understood. At least three phosphate sensors have emerged. PiT2 and FGFR1c both act as phosphate sensors controlling Fibroblast Growth Factor 23 secretion in bone, whereas the calcium-sensing receptor controls parathyroid hormone secretion in response to extracellular phosphate. All three of the proposed sensors are expressed in the kidney and intestine but their exact function in these organs is unknown. Understanding organ interactions and the mechanisms involved in phosphate sensing requires significant research to develop novel approaches for the treatment of phosphate homeostasis disorders.

Safety assessment of condensed phosphate intake from fishery and processed marine food products in Korea with respect to gender, age, and region

Condensed phosphates are used as food additives, especially in marine products and meat, to improve food quality. The import and consumption of fishery and processed marine food products in Republic of Korea have reportedly increased by ~5 per cent annually. However, processed marine food products are often intentionally adulterated with excessive amounts of condensed phosphates to increase their weight. Excessive intake of condensed phosphates via consuming processed marine food products can lead to various adverse effects on human health due to anionic imbalance. Herein, we conducted a safety assessment of condensed phosphates in 14 types of fishery and processed marine food products in Korea for the first time. Subgroup analysis of various factors including gender, age, and region was also performed, and the risk level of exposure for each group was estimated. Safety assessments by age and gender indicated that infants were at the highest risk. In the regional safety assessment, Chungnam, the most inland region, showed the lowest risk. For both the general and the high-intake groups (95th percentile) in all classifications, the risk was lower (&lt;20 per cent) than the international standard, and the phosphorus content of the 14 types of processed marine products in Korea was confirmed to be safe for human consumption.

The emerging role of phosphorus in human health

Phosphorus, an essential nutrient, performs vital functions in skeletal and non-skeletal tissues and is pivotal for energy production. The last two decades of research on the physiological importance of phosphorus have provided several novel insights about its dynamic nature as a nutrient performing functions as a phosphate ion. Phosphorous also acts as a signaling molecule and induces complex physiological responses. It is recognized that phosphorus homeostasis is critical for health. The intake of phosphorus by the general population world-wide is almost double the amount required to maintain health. This increase is attributed to the incorporation of phosphate containing food additives in processed foods purchased by consumers. Research findings assessed the impact of excessive phosphorus intake on cells' and organs' responses, and highlighted the potential pathogenic consequences. Research also identified a new class of bioactive phosphates composed of polymers of phosphate molecules varying in chain length. These polymers are involved in metabolic responses including hemostasis, brain and bone health, via complex mechanism(s) with positive or negative health effects, depending on their chain length. It is amazing, that phosphorus, a simple element, is capable of exerting multiple and powerful effects. The role of phosphorus and its polymers in the renal and cardiovascular system as well as on brain health appear to be important and promising future research directions.

[Prolonged hemodialysis: Rationale, practical organization, results]

In France, long nocturnal dialyses, eight hours three-times a week, are sparsely proposed. However, numerous studies reported that this specific type of dialysis is associated to better blood pressure control, better cardiac remodeling, better mineral and nutritional balance as well as better life quality and survival rate. MATERIAL AND METHODS: In this study, we aimed at quantifying the benefits, risks and obstacles of developing night dialysis and at describing the results of a program that took place in Rennes from 2002 to 2019. Data were collected between 2008 and 2014 for eighteen case-patients and were compared to thirty-six controls that underwent conventional dialysis. Patients were paired according sex, age and year of dialysis start. RESULTS: The median age for dialysis start was 47.5 years [27-60] with a male prevalence (5/1). After six months, a significant difference was reported for postdialytic, systolic and diastolic pressure (respectively 126±15 vs 139±21 [P=0.04] and 72±9 vs 81±14 [P=0.02]) despite an antihypertensive reduction ranging from 2.4±1.4 to 1.3±0.9 per day at six months and 0.7±0.9 at one year (P=0.02). An increase of nPCR was evidenced at 6 and 9 months (P=0.02). At the end of the study, the phosphate level was maintained for both cohorts at the expense of an increased consumption of phosphate binder for the long nocturnal dialysis group (P=0.025). As a whole, 61% of the patients that pursued long night dialysis maintained a professional activity compared to only 30% for the controls (P=0.04). This highlights the advantages of night dialysis for maintaining employment but also the bias that represents the employment status in observational study on this specific topic.

High Dietary Phosphate Exacerbates and Acts Independently of Low Autophagy Activity in Pathological Cardiac Remodeling and Dysfunction

High phosphate contributes to uremic cardiomyopathy. Abnormal autophagy is associated with the development and progression of heart disease. What is unknown is the effects of phosphate on autophagy and whether the ill effects of phosphate on cardiomyocytes are mediated by low autophagy. High (2.0% w/w)-phosphate diet reduced LC3 puncta in cardiomyocytes and ratio of LC3 II/I and increased p62 protein, indicating that autophagy activity was suppressed. Mice with cardiomyocyte-specific deletion of autophagy-related protein 5 (H-atg5-/-) had reduced autophagy only in the heart, developed cardiac dysfunction with hypertrophy and fibrosis, and had a short lifespan. When H-atg5-/- mice were fed a high-phosphate diet, they developed more apoptosis in cardiomyocytes, more severe cardiac remodeling, and shorter lifespan than normal phosphate-fed H-atg5-/- mice, indicating that cardiac phosphotoxicity is imparted independently of atg5. In conclusion, although high phosphate suppresses autophagy, high phosphate and low autophagy independently trigger and additionally amplify cardiac remodeling and dysfunction.

Uraemic Cardiomyopathy: A Review of Current Literature

Uraemic Cardiomyopathy (UC) is recognised as an intricate and multifactorial disease which portends a significant burden in patients with End-Stage Renal Disease (ESRD). The cardiovascular morbidity and mortality associated with UC is significant and can be associated with the development of arrythmias, cardiac failure and sudden cardiac death (SCD). The pathophysiology of UC involves a complex interplay of traditional implicative factors such as haemodynamic overload and circulating uraemic toxins as well as our evolving understanding of the Chronic Kidney Disease-Mineral Bone Disease pathway. There is an instrumental role for multi-modality imaging in the diagnostic process; including transthoracic echocardiography and cardiac magnetic resonance imaging in identifying the hallmarks of left ventricular hypertrophy and myocardial fibrosis that characterise UC. The appropriate utilisation of the aforementioned diagnostics in the ESRD population may help guide therapeutic approaches, such as pharmacotherapy including beta-blockers and aldosterone-antagonists as well as haemodialysis and renal transplantation. Despite this, there remains limitations in effective therapeutic interventions for UC and ongoing research on a cellular level is vital in establishing further therapies.

A chronic high phosphate intake in mice is detrimental for bone health without major renal alterations

BACKGROUND

Phosphate intake has increased in the last decades due to a higher consumption of processed foods. This higher intake is detrimental for patients with chronic kidney disease, increasing mortality and cardiovascular disease risk and accelerating kidney dysfunction. Whether a chronic high phosphate diet is also detrimental for the healthy population is still under debate.

METHODS

We fed healthy mature adult mice over a period of one year with either a high (1.2% w/w) or a standard (0.6% w/w) phosphate diet, and investigated the impact of a high phosphate diet on mineral homeostasis, kidney function and bone health.

RESULTS

The high phosphate diet increased plasma phosphate, parathyroid hormone (PTH) and calcitriol levels, with no change in fibroblast growth factor 23 levels. Urinary phosphate, calcium and ammonium excretion were increased. Measured glomerular filtration rate was apparently unaffected, while blood urea was lower and urea clearance was higher in animals fed the high phosphate diet. No change was observed in plasma creatinine levels. Blood and urinary pH were more acidic paralleled by higher bone resorption observed in animals fed a high phosphate diet. Total and cortical bone mineral density was lower in animals fed a high phosphate diet and this effect is independent of the higher PTH levels observed.

CONCLUSIONS

A chronic high phosphate intake did not cause major renal alterations, but affected negatively bone health, increasing bone resorption and decreasing bone mineral density.

High-phosphorus diet controlled for sodium elevates blood pressure in healthy adults via volume expansion

Whether increasing exposure to dietary phosphorus can lead to adverse clinical outcomes in healthy people is not clear. In this open‐label prospective cross‐over study, we are to explore the impact of various dietary phosphorus intake on mineral, sodium metabolisms and blood pressure in young healthy adults. There were 3 separate study periods of 5 days, each with a 5 days washout period between different diets interventions. Six young healthy male volunteers with normal nutrition status were recruited in Phase I Clinical Research Center and sequentially exposed to the following diets: (a) normal‐phosphorus diet (NPD): 1500 mg/d, (b) low‐phosphorus diet (LPD): 500 mg/d, (c) high‐phosphorus diet (HPD): 2300 mg/d. HPD induced a significant rise in daily average serum phosphate (1.47 ± 0.02 mmol/L [4.56 ± 0.06 mg/dl]) compared to NPD (1.34 ± 0.02 mmol/L [4.15 ± 0.06 mg/dL]) and LPD (1.17 ± 0.02 mmol/L [3.63 ± 0.06 mg/dL]) (p < .05). Daily average levels of serum parathyroid hormone and fibroblast growth factor 23 in HPD were significantly higher, and serum 1,25(OH)₂D₃ was remarkably lower than those in LPD. HPD induced a significant decrease in daily average serum aldosterone and an increase in daily average atrial natriuretic peptide level compared to LPD. The 24‐hour urine volume in HPD subjects was less than that in LPD subjects. HPD significantly increased daily average systolic blood pressure by 6.02 ± 1.24 mm Hg compared to NPD and by 8.58 ± 1.24mm Hg compared to LPD (p < .05). Our study provides the first evidence that 5‐day high‐phosphorus diet can induce elevation in SBP in young healthy adults, which may due to volume expansion.

Efficacy and safety of sucroferric oxyhydroxide in the treatment of hyperphosphataemia in chronic kidney disease in Asturias. FOSFASTUR study

Alterations in bone and mineral metabolism are very common in chronic kidney disease (CKD). The increase in phosphate levels leads to bone disease, risk of calcification and greater mortality, so any strategy aimed at reducing them should be welcomed. The latest drug incorporated into the therapeutic arsenal to treat hyperphosphataemia in CKD is Sucroferric Oxyhydroxide (SFO).

OBJECTIVE

To analyse the efficacy and safety of OSF in three cohorts of patients, one with advanced chronic kidney disease not on dialysis (CKD-NoD), another on peritoneal dialysis (PD) and the last on haemodialysis (HD), followed for six months.

METHODS

A prospective, observational, multicentre study in clinical practice. Clinical and epidemiological variables were analysed. The evolution of parameters relating to alterations in bone and mineral metabolism and anaemia was analysed.

RESULTS

Eighty-five patients were included in the study (62 ± 12 years, 64% male, 34% diabetic), 25 with CKD-NoD, 25 on PD and lastly, 35 on HD. In 66 patients (78%), SFO was the first phosphate binder; in the other 19, SFO replaced a previous phosphate binder due to poor tolerance or efficacy. The initial dose of SFO was 964 ± 323 mg/day. Overall, serum phosphate levels saw a significant reduction at three months of treatment (19.6%, P < 0.001). There were no differences in the efficacy of the drug when the different populations analysed were compared. Over the course of the study, there were no changes to levels of calcium, PTHi, ferritin, or the transferrin and haemoglobin saturation indices, although there was a tendency for the last two to increase. Twelve patients (14%) withdrew from follow-up, ten due to gastrointestinal adverse effects (primarily diarrhoea) and two were lost to follow-up (kidney transplant). The mean dose of the drug that the patients received increased over time, up to 1147 ± 371 mg/day.

CONCLUSIONS

SFO is an effective option for the treatment of hyperphosphataemia in patients with CKD both in the advanced phases of the disease and on dialysis. We found similar efficacy across the three groups analysed. The higher their baseline phosphate level, the greater the reduction in the serum levels. A notable reduction in phosphate levels can be achieved with doses of around 1000 mg/day. Diarrhoea was the most common side effect, although it generally was not significant.

Effect of Phosphate-Specific Diet Therapy on Phosphate Levels in Adults Undergoing Maintenance Hemodialysis: A Systematic Review and Meta-Analysis

BACKGROUND AND OBJECTIVES

Hyperphosphatemia is a persistent problem in individuals undergoing maintenance hemodialysis, which may contribute to vascular and bone complications. In some dialysis centers, dietitians work with patients to help them manage serum phosphate. Given the regularity of hyperphosphatemia in this population and constraints on kidney dietitian time, the authors aimed to evaluate the evidence for this practice.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

There was a systematic review and meta-analysis of clinical trials. MEDLINE, Embase, CINAHL, Web of Science, Cochrane Central Register of Controlled Trials, and other databases were searched for controlled trials published from January 2000 until November 2019 in the English language. Included studies were required to examine the effect of phosphate-specific diet therapy provided by a dietitian on serum phosphate in individuals on hemodialysis. Risk of bias and certainty of evidence were assessed using the Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) method.

RESULTS

Of the 8054 titles/abstracts identified, 168 articles were reviewed, and 12 clinical trials (11 randomized, one nonrandomized) were included. Diet therapy reduced serum phosphate compared with controls in all studies, reaching statistical significance in eight studies, although overall certainty of evidence was low, primarily due to randomization issues and deviations from protocol. Monthly diet therapy (20-30 minutes) significantly lowered serum phosphate in patients with persistent hyperphosphatemia for 4-6 months, without compromising nutrition status (mean difference, -0.87 mg/dl; 95% confidence interval, -1.40 to -0.33 mg/dl), but appeared unlikely to maintain these effects if discontinued. Unfortunately, trials were too varied in design, setting, and approach to appropriately pool in meta-analysis, and were too limited in number to evaluate the timing, dose, and strategy of phosphate-specific diet therapy.

CONCLUSIONS

There is low-quality evidence that monthly diet therapy by a dietitian appears to be a safe and efficacious treatment for persistent hyperphosphatemia in patients on HD.

Measurement of serum phosphate levels using a mobile sensor

The measurement of serum phosphate concentration is crucial for patients with advanced chronic kidney disease (CKD) and those on maintenance dialysis, as abnormal phosphate levels may be associated with severe health risks. It is important to monitor serum phosphate levels on a regular basis in these patients; however, such measurements are generally limited to every 0.5-3 months, depending on the severity of CKD. This is due to the fact that serum phosphate measurements can only be performed at regular clinic visits, in addition to cost considerations. Here we present a portable and cost-effective point-of-care device capable of measuring serum phosphate levels using a single drop of blood (<60 μl). This is achieved by integrating a paper-based microfluidic platform with a custom-designed smartphone reader. This mobile sensor was tested on patients undergoing dialysis, where whole blood samples were acquired before starting the hemodialysis and during the three-hour treatment. This sampling during the hemodialysis, under patient consent, allowed us to test blood samples with a wide range of phosphate concentrations, and our results showed a strong correlation with the ground truth laboratory tests performed on the same patient samples (Pearson coefficient r = 0.95 and p < 0.001). Our 3D-printed smartphone attachment weighs about 400 g and costs less than 80 USD, whereas the material cost for the disposable test is <3.5 USD (under low volume manufacturing). This low-cost and easy-to-operate system can be used to measure serum phosphate levels at the point-of-care in about 45 min and can potentially be used on a daily basis by patients at home.

Efficacy and safety of sucroferric oxyhydroxide in the treatment of hyperphosphataemia in chronic kidney disease. FOSFASTUR study

INTRODUCTION

Alterations in bone and mineral metabolism are very common in chronic kidney disease (CKD). The increase in phosphate levels leads to bone disease, risk of calcification and greater mortality, so any strategy aimed at reducing them should be welcomed. The latest drug incorporated into the therapeutic arsenal to treat hyperphosphataemia in CKD is sucroferric oxyhydroxide (SFO).

OBJECTIVE

To analyse the efficacy and safety of SFO in 3 cohorts of patients, one with advanced CKD not on dialysis, another on peritoneal dialysis and the last on haemodialysis, followed for 6 months.

METHODS

A prospective, observational, multicentre study in clinical practice. Clinical and epidemiological variables were analysed. The evolution of parameters relating to alterations in bone and mineral metabolism and anaemia was analysed.

RESULTS

Eighty-five patients were included in the study (62±12 years, 64% male, 34% diabetic), 25 with advanced CKD not on dialysis, 25 on peritoneal dialysis and lastly, 35 on haemodialysis. In 66 patients (78%), SFO was the first phosphate binder; in the other 19, SFO replaced a previous phosphate binder due to poor tolerance or efficacy. The initial dose of SFO was 964±323mg/day. Overall, serum phosphate levels saw a significant reduction at 3 months of treatment (19.6%; P<.001). There were no differences in the efficacy of the drug when the different populations analysed were compared. Over the course of the study, there were no changes to levels of calcium, PTHi, ferritin, transferrin saturation index or haemoglobin, although there was a tendency for the last 2 to increase. Twelve patients (14%) withdrew from follow-up, 10 due to gastrointestinal adverse effects (primarily diarrhoea) and 2 were lost to follow-up (kidney transplant). The mean dose of the drug that the patients received increased over time, up to 1,147±371mg/day.

CONCLUSIONS

SFO is an effective option for the treatment of hyperphosphataemia in patients with CKD both in the advanced phases of the disease and on dialysis. We found similar efficacy across the 3 groups analysed. The higher their baseline phosphate level, the greater the reduction in the serum levels. A notable reduction in phosphate levels can be achieved with doses of around 1,000mg/day. Diarrhoea was the most common side effect, although it generally was not significant.

Pilot Randomized Controlled Trial of a Standard Versus a Modified Low-Phosphorus Diet in Hemodialysis Patients

INTRODUCTION

The standard low-phosphorus diet restricts pulses, nuts, and whole grains and other high phosphorus foods to control hyperphosphatemia. We conducted a randomized controlled trial to evaluate the effectiveness, safety, and tolerability of the modified diet, which introduced some pulses and nuts, increased the use of whole grains, increased focus on the avoidance of phosphate additives, and introduced the prescription of low-biological-value protein such as bread.

METHODS

We conducted a multicenter, pragmatic, parallel-arm, open-label, randomized controlled trial of modified versus standard diet in 74 adults on hemodialysis with hyperphosphatemia over 1 month. Biochemistry was assessed using monthly laboratory tests. Dietary intake was assessed using a 2-day record of weighed intake of food, and tolerability was assessed using a patient questionnaire.

RESULTS

There was no significant difference in the change in serum phosphate between the standard and modified diets. Although total dietary phosphorus intake was similar, phytate-bound phosphorus, found in pulses, nuts, and whole grains, was significantly higher in the modified diet (P < 0.001). Dietary fiber intake was also significantly higher (P < 0.003), as was the percentage of patients reporting an increase in bowel movements while following the modified diet (P = 0.008). There was no significant difference in the change in serum potassium or in reported protein intake between the 2 diets. Both diets were similarly well tolerated.

CONCLUSION

The modified low phosphorus diet was well tolerated and was associated with similar phosphate and potassium control but with a wider food choice and greater fiber intake than the standard diet.

Brown tumor complicating end-stage kidney disease

Longstanding, severe hyperparathyroidism (HPT) can lead to the formation of “brown tumors”. A brown tumor is a radiolucent bone lesion that is locally destructive; it is not a neoplasm, but rather a stromal mass consisting of fibrous tissue, poorly mineralized woven bone, and supporting vasculature. These tumors are a rare complication of advanced primary or secondary HPT. We present a young female with chronic kidney disease (CKD) on hemodialysis with uncontrolled secondary HPT (SHPT). The patient presented with progressive lower extremity weakness and back pain. CT imaging showed multiple lytic bone lesions involving several ribs and the spine. Subsequent MRI imaging of the thoracic and lumbar spine confirmed expansile bone lesions consistent with brown tumors. One mass protruded into the spinal canal causing severe stenosis at T3 with underlying cord edema. The other lesion at T12 caused only moderate spinal canal stenosis. Our patient underwent urgent neurosurgical resection of the tumor at T3 followed by subtotal parathyroidectomy (PTX).

Phosphate and Kidney Healthy Aging

<b><i>Background:</i></b> The aging population is increasing rapidly, much faster than our understanding on how to promote healthy aging free of multimorbidities. The aging kidney shows a decline in its function. Whether this decline is preventable or physiological is still debated. Main risks factors for developing CKD are aging common comorbidites, such as hypertension, diabetes, and obesity. Phosphate is vital for our organism, but it is also present in a great variety of food products as food additive and preservative. Due to the higher consumption of processed food in the last century, concern has arisen if a chronic high consumption of phosphate may be toxic impacting on healthy aging. <b><i>Summary:</i></b> Several studies show an association between higher serum phosphate levels and a higher risk of overall mortality and cardiovascular disease. Moreover, higher phosphate levels also worsen CKD progression and may contribute to renal dysfunction in healthy individuals. Acute high phosphate intake is rare but can cause acute kidney injury. Yet, the question if controlling phosphate intake may modulate serum phosphate concentrations remains unanswered, as assessment of phosphate intake is still a difficult task. Phosphate consumption estimations by dietary recalls are largely underestimated, especially in populations groups consuming high amount of processed food. <b><i>Key Message:</i></b> A healthy diet with phosphate source from food may contribute to promote healthy aging and longevity.

High Phosphate Induces and Klotho Attenuates Kidney Epithelial Senescence and Fibrosis

Cellular senescence is an irreversible cell growth arrest and is associated with aging and age-related diseases. High plasma phosphate (Pi) and deficiency of Klotho contribute to aging and kidney fibrosis, a pathological feature in the aging kidney and chronic kidney disease. This study examined the interactive role of Pi and Klotho in kidney senescence and fibrosis. Homozygous Klotho hypomorphic mice had high plasma Pi, undetectable Klotho in plasma and kidney, high senescence with massive collagen accumulation in kidney tubules, and fibrin deposits in peritubular capillaries. To examine the Pi effect on kidney senescence, a high (2%) Pi diet was given to wild-type mice. One week of high dietary Pi mildly increased plasma Pi, and upregulated kidney p16/p21 expression, but did not significantly decrease Klotho. Two weeks of high Pi intake led to increase in plasminogen activator inhibitor (PAI)-1, and decrease in kidney Klotho, but still without detectable increase in kidney fibrosis. More prolonged dietary Pi for 12 weeks exacerbated kidney senescence and fibrosis; more so in heterozygous Klotho hypomorphic mice compared to wild-type mice, and in mice with chronic kidney disease (CKD) on high Pi diet compared to CKD mice fed a normal Pi diet. In cultured kidney tubular cells, high Pi directly induced cellular senescence, injury and epithelial-mesenchymal transition, and enhanced H₂O₂-induced cellular senescence and injury, which were abrogated by Klotho. Fucoidan, a bioactive molecule with multiple biologic functions including senescence inhibition, blunted Pi-induced cellular senescence, oxidation, injury, epithelial-mesenchymal transition, and senescence-associated secretary phenotype. In conclusion, high Pi activates senescence through distinct but interconnected mechanisms: upregulating p16/p21 (early), and elevating plasminogen activator inhibitor-1 and downregulating Klotho (late). Klotho may be a promising agent to attenuate senescence and ameliorate age-associated, and Pi-induced kidney degeneration such as kidney fibrosis.