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1.
Phosphate Binders and Nonphosphate Effects in the Gastrointestinal Tract.
Biruete, A, Hill Gallant, KM, Lindemann, SR, Wiese, GN, Chen, NX, Moe, SM
Journal of renal nutrition : the official journal of the Council on Renal Nutrition of the National Kidney Foundation. 2020;(1):4-10
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Abstract
Phosphate binders are commonly prescribed in patients with end-stage kidney disease to prevent and treat hyperphosphatemia. These binders are usually associated with gastrointestinal distress, may bind molecules other than phosphate, and may alter the gut microbiota, altogether having systemic effects unrelated to phosphate control. Sevelamer is the most studied of the available binders for nonphosphate-related effects including binding to bile acids, endotoxins, gut microbiota-derived metabolites, and advanced glycation end products. Other binders (calcium- and noncalcium-based binders) may bind vitamins, such as vitamin K and folic acid. Moreover, the relatively new iron-based phosphate binders may alter the gut microbiota, as some of the iron or organic ligands may be used by the gastrointestinal bacteria. The objective of this narrative review is to provide the current evidence for the nonphosphate effects of phosphate binders on gastrointestinal function, nutrient and molecule binding, and the gut microbiome.
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2.
Effect of Phosphate-Specific Diet Therapy on Phosphate Levels in Adults Undergoing Maintenance Hemodialysis: A Systematic Review and Meta-Analysis.
St-Jules, DE, Rozga, MR, Handu, D, Carrero, JJ
Clinical journal of the American Society of Nephrology : CJASN. 2020;(1):107-120
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Abstract
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.
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Drug-Induced Hypophosphatemia: Current Insights.
Megapanou, E, Florentin, M, Milionis, H, Elisaf, M, Liamis, G
Drug safety. 2020;(3):197-210
Abstract
Phosphate is actively involved in many important biochemical pathways, such as energy and nucleic acid metabolism, cellular signaling, and bone formation. Hypophosphatemia, defined as serum phosphate levels below 2.5 mg/dL (0.81 mmol/L), is frequently observed in the course of treatment with commonly used drugs, such as diuretics, bisphosphonates, antibiotics, insulin, and antacids. Furthermore, this undesired effect may complicate the use of several novel medications, including teriparatide, denosumab, parenteral iron, and antiviral and antineoplastic agents. This review addresses drug-associated hypophosphatemia, focusing on underlying mechanisms and the most recent knowledge on this topic, in order to increase the insight of clinicians, with reference to early diagnosis and appropriate management.
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Phosphate clearance in peritoneal dialysis.
Debowska, M, Gomez, R, Pinto, J, Waniewski, J, Lindholm, B
Scientific reports. 2020;(1):17504
Abstract
In renal failure, hyperphosphatemia is common and correlates with increased mortality making phosphate removal a key priority for dialysis therapy. We investigated phosphate clearance, removal and serum level, and factors associated with phosphate control in patients undergoing continuous ambulatory (CAPD), continuous cyclic (CCPD) and automated (APD) peritoneal dialysis (PD). In 154 prevalent PD patients (mean age 53.2 ± 17.6 year, 59% men, 47% anuric), 196 daily collections of urine and 368 collections of dialysate were evaluated in terms of renal, peritoneal and total (renal plus peritoneal) phosphorus removal (g/week), phosphate and creatinine clearances (L/week) and urea KT/V. Dialytic removal of phosphorus was lower in APD (1.34 ± 0.62 g/week) than in CAPD (1.89 ± 0.73 g/week) and CCPD (1.91 ± 0.63 g/week) patients; concomitantly, serum phosphorus was higher in APD than in CAPD (5.55 ± 1.61 vs. 4.84 ± 1.23 mg/dL; p < 0.05). Peritoneal and total phosphate clearances correlated with peritoneal (rho = 0.93) and total (rho = 0.85) creatinine clearances (p < 0.001) but less with peritoneal and total urea KT/V (rho = 0.60 and rho = 0.65, respectively, p < 0.001). Phosphate removal, clearance and serum levels differed between PD modalities. CAPD was associated with higher peritoneal removal and lower serum level of phosphate than APD.
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In Yarrowia lipolytica erythritol catabolism ends with erythrose phosphate.
Niang, PM, Arguelles-Arias, A, Steels, S, Denies, O, Nicaud, JM, Fickers, P
Cell biology international. 2020;(2):651-660
Abstract
In response to osmotic stress, the yeast Yarrowia lipolytica produces erythritol, a four-carbon sugar alcohol, from erythrose-P, an intermediate of the pentose phosphate pathway. Under non-stressing conditions (isotonic environment), the produced erythritol is subsequently recycled into erythrose-P that can feed the pentose phosphate pathway. Herein, gene YALI0F01584g was characterized as involved in the erythritol catabolic pathway. Several experimental evidences suggested that it encodes an erythrulose-1P isomerase that converts erythrulose-1P into erythrulose-4P. On the basis of our previous reports and results gathered in this study with genetically modified strains, including ΔYALI0F01584g and ΔYALI0F01628g disrupted mutants, the entire erythritol catabolic pathway has been characterized.
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Influence of phosphate dosing on biofilms development on lead in chlorinated drinking water bioreactors.
Del Olmo, G, Ahmad, A, Jensen, H, Karunakaran, E, Rosales, E, Calero Preciado, C, Gaskin, P, Douterelo, I
NPJ biofilms and microbiomes. 2020;(1):43
Abstract
Phosphate dosing is used by water utilities to prevent plumbosolvency in water supply networks. However, there is a lack of knowledge regarding biofilm formation on lead and plastic materials when phosphate concentrations are modified in drinking water systems. In this study, biofilms were grown over lead coupons and PVC tubes in bioreactors supplied with local drinking water treated to provide different phosphate doses (below 1, 1 and 2 mg/L) over a period of 28 days. A range of commercial iron pellets (GEH104 and WARP) were tested aiming to maintain phosphate levels below the average 1 mg/L found in drinking water. Changes in biofilm community structure in response to three different phosphate treatments were characterised by Illumina sequencing of the 16S rRNA gene for bacteria and the ITS2 gene for fungi. Scanning electron microscopy was used to visualise physical differences in biofilm development in two types of materials, lead and PVC. The experimental results from the kinetics of phosphate absorption showed that the GEH104 pellets were the best option to, in the long term, reduce phosphate levels while preventing undesirable turbidity increases in drinking water. Phosphate-enrichment promoted a reduction of bacterial diversity but increased that of fungi in biofilms. Overall, higher phosphate levels selected for microorganisms with enhanced capabilities related to phosphorus metabolism and heavy metal resistance. This research brings new insights regarding the influence of different phosphate concentrations on mixed-species biofilms formation and drinking water quality, which are relevant to inform best management practices in drinking water treatment.
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Serum phosphate levels modify the impact of parathyroid hormone levels on renal outcomes in kidney transplant recipients.
Doi, Y, Hamano, T, Ichimaru, N, Tomida, K, Obi, Y, Fujii, N, Yamaguchi, S, Oka, T, Sakaguchi, Y, Matsui, I, et al
Scientific reports. 2020;(1):13766
Abstract
Separate assessment of mineral bone disorder (MBD) parameters including calcium, phosphate, parathyroid hormone (PTH), fibroblast growth factor 23 (FGF23), 25-hydroxyvitamin D, and 1,25-dihydroxyvitamin D (1,25D) predict renal outcomes in kidney transplant recipients (KTRs), with conflicting results. To date, data simultaneously evaluating these parameters and interwoven relations on renal outcomes are scarce. We conducted a prospective long-term follow-up cohort study included 263 KTRs with grafts functioning at least 1 year after transplantation. The outcome was a composite of estimated GFR halving and graft loss. Cox regression analyses were employed to evaluate associations between a panel of six MBD parameters and renal outcomes. The outcome occurred in 98 KTRs during a median follow-up of 10.7 years. In a multivariate Cox analysis, intact PTH (iPTH), phosphate, and 1,25D levels were associated with the outcome (hazard ratio, 1.60 per log scale; 95% confidence interval, 1.19-2.14, 1.60 per mg/dL; 1.14-2.23 and 0.82 per 10 pg/mL; 0.68-0.99, respectively). Competing risk analysis with death as a competing event yielded a similar result. After stratification into four groups by iPTH and phosphate medians, high risks associated with high iPTH was not observed in KTRs with low phosphate levels (P-interaction < 0.1). Only KTRs not receiving active vitamin D, poor 1,25D status predicted the worse outcome (P-interaction < 0.1). High iPTH, phosphate, and low 1,25D, but not FGF23, levels predicted poor renal outcomes. Simultaneous evaluation of PTH and phosphate levels may provide additional information regarding renal allograft prognosis.
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A carbonate-rich lake solution to the phosphate problem of the origin of life.
Toner, JD, Catling, DC
Proceedings of the National Academy of Sciences of the United States of America. 2020;(2):883-888
Abstract
Phosphate is central to the origin of life because it is a key component of nucleotides in genetic molecules, phospholipid cell membranes, and energy transfer molecules such as adenosine triphosphate. To incorporate phosphate into biomolecules, prebiotic experiments commonly use molar phosphate concentrations to overcome phosphate's poor reactivity with organics in water. However, phosphate is generally limited to micromolar levels in the environment because it precipitates with calcium as low-solubility apatite minerals. This disparity between laboratory conditions and environmental constraints is an enigma known as "the phosphate problem." Here we show that carbonate-rich lakes are a marked exception to phosphate-poor natural waters. In principle, modern carbonate-rich lakes could accumulate up to ∼0.1 molal phosphate under steady-state conditions of evaporation and stream inflow because calcium is sequestered into carbonate minerals. This prevents the loss of dissolved phosphate to apatite precipitation. Even higher phosphate concentrations (>1 molal) can form during evaporation in the absence of inflows. On the prebiotic Earth, carbonate-rich lakes were likely abundant and phosphate-rich relative to the present day because of the lack of microbial phosphate sinks and enhanced chemical weathering of phosphate minerals under relatively CO2-rich atmospheres. Furthermore, the prevailing CO2 conditions would have buffered phosphate-rich brines to moderate pH (pH 6.5 to 9). The accumulation of phosphate and other prebiotic reagents at concentration and pH levels relevant to experimental prebiotic syntheses of key biomolecules is a compelling reason to consider carbonate-rich lakes as plausible settings for the origin of life.
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Integration of molecular tools in microbial phosphate solubilization research in agriculture perspective.
Alaylar, B, Egamberdieva, D, Gulluce, M, Karadayi, M, Arora, NK
World journal of microbiology & biotechnology. 2020;(7):93
Abstract
Phosphorus (P) is the second most crucial nutrient for plant growth after nitrogen. However, its highly reactive nature causes formation of insoluble derivatives and limits uptake by the plant roots. The wide spread applications of P based chemical fertilizers cause detrimental effects on soil fertility, agricultural product quality and environment. In this regard, phosphate-solubilizing microorganisms (PSMs) stand out as the most remarkable and promising tools for the development of safer and sustainable technologies. As a result of this, many bacterial and fungal species with significant phosphate-solubilizing activity have been discovered by using the conventional screening methods. However, the growing need for the discovery of new strains of PSMs necessitates the replacement or support to the time-consuming conventional methods with techniques that are more sensitive, reliable, reproducible and less time consuming. In this context, molecular tools and techniques provide novel approaches for microbial phosphate solubilization research. Hence, in this review information on the molecular approaches for the PSMs research is provided and its importance explained. The review also discusses the genes related to phosphate solubilizing mechanisms and molecular tools for screening these genes.
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10.
Effect of Ferric Citrate versus Ferrous Sulfate on Iron and Phosphate Parameters in Patients with Iron Deficiency and CKD: A Randomized Trial.
Womack, R, Berru, F, Panwar, B, Gutiérrez, OM
Clinical journal of the American Society of Nephrology : CJASN. 2020;(9):1251-1258
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Abstract
BACKGROUND AND OBJECTIVES Ferric citrate is an oral medication approved for treatment of iron deficiency anemia in patients with CKD not requiring dialysis. The relative efficacy of ferric citrate versus ferrous sulfate in treating iron deficiency in patients with CKD is unclear. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS We randomized 60 adults with moderate to severe CKD (eGFR 15-45 ml/min per 1.73 m2) and iron deficiency (transferrin saturation [TSAT] ≤30% and ferritin ≤300 ng/ml) to ferric citrate (2 g three times a day with meals, n=30) or ferrous sulfate (325 mg three times a day, n=30) for 12 weeks. Primary outcomes were change in TSAT and ferritin from baseline to 12 weeks. Secondary outcomes were change in hemoglobin, fibroblast growth factor 23 (FGF23), and hepcidin. RESULTS Baseline characteristics were well balanced between study arms. There was a greater increase in TSAT (between-group difference in mean change, 8%; 95% confidence interval [95% CI], 1 to 15; P=0.02) and ferritin (between-group difference in mean change, 37 ng/ml; 95% CI, 10 to 64; P=0.009) from baseline to 12 weeks in participants randomized to ferric citrate as compared with ferrous sulfate. Similarly, as compared with ferrous sulfate, treatment with ferric citrate resulted in a greater increase in hepcidin from baseline to 12 weeks (between-group difference, 69 pg/ml; 95% CI, 8 to 130). There were no between-group differences in mean change for hemoglobin (0.3 g/dl; 95% CI, -0.2 to 0.8), intact FGF23 (-29 pg/ml; 95% CI, -59 to 0.1), or C-terminal FGF23 (61 RU/ml; 95% CI, -181 to 58). The incidence of adverse events did not differ between treatment arms. CONCLUSIONS As compared with ferrous sulfate, treatment with ferric citrate for 12 weeks resulted in a greater mean increase in TSAT and ferritin concentrations in individuals with moderate to severe CKD and iron deficiency. CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER Impact of Ferric Citrate vs Ferrous Sulfate on Iron Parameters and Hemoglobin in Individuals With Moderate to Severe Chronic Kidney Disease (CKD) With Iron Deficiency, NCT02888171.