Phosphate Intake Research Articles

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.

Association between the intake of plant and animal proteins and the serum fibroblast growth factor-23 level in patients with chronic kidney disease analyzed by the isocaloric substitution model.

Fibroblast growth factor-23 (FGF23) is a phosphaturic hormone secreted by the bone in response to dietary phosphate intake. Since the phosphate content in the diet correlates with the protein content, both plant- and animal-based protein intake can increase the serum FGF23 level. However, a higher percentage of energy from plant protein than from animal protein is associated with a lower serum FGF23 level in patients with chronic kidney disease (CKD) in the United States. Since dietary habits differ between Asian and Western populations, we performed a cross-sectional study to determine the association between the percentages of energy from plant and animal proteins and the serum FGF23 level in Japanese CKD patients. In 107 non-dialysis CKD patients (age: 66 ± 9 years; estimated glomerular filtration rate: 56 ± 21 mL/min/1.73 m2), the percentages of energy from plant and animal proteins were assessed using a food frequency questionnaire based on food groups. Venous blood samples were used to measure the serum FGF23, phosphate, 1,25-dihydroxyvitamin D, and intact parathyroid hormone levels. The percentages of energy from plant and animal proteins showed a negative and positive association, respectively, with the serum FGF23 level. Furthermore, isocaloric substitution modeling showed that replacing animal protein with plant protein was associated with a low serum FGF23 level. Our findings suggest that encouraging diets with high plant protein level may prevent an increase in the serum FGF23 level in Japanese CKD patients.

Intensive Nutritional Counseling and Education for Management of Hyperphosphatemia in Hemodialysis Patients at Al-Khor Hospital- Hamad Medical Corporation - State of Qatar

Objectives: To assess the dietary phosphate intake of hemodialysis patients with hyperphosphatemia and the effects of a dietetic intervention focused on limiting dietary phosphate load. Design: Cross-sectional dietary phosphate intake assessment and prospective intervention study. Setting: Hospital hemodialysis units of AL-Khor hospital – Hamad Medical Corporation, Qatar. Subjects: sixteen stable adult hemodialysis patients, who had phosphorus serum levels ≥1.6 mmol/L. Intervention: Analysis of dietary composition and of the effects of individual dietetic counseling to reduce phosphorus intake while preserving the same or improving protein intake. Main outcome measures: Differences in nutrient intake between pre and post-dietary intervention among hyperphosphatemia patients, and changes in phosphorus–protein ratio, and serum phosphate, after the dietetic intervention. Results: Significant differences in nutrient intake including energy, protein, and phosphorus were detected after the intervention. After dietetic intervention in the hyperphosphatemia patients, a decrease in the dietary phosphate–protein ratio (28.9 -13.4 mg/g, P <0.05) also occurred. Serum phosphate showed a trend of a significant decrease after the dietary intervention (2.2mmol/L-1.68mmol/L), P < 0.05). Conclusion: Individual intensive nutritional education and counseling may be useful in reducing phosphate load and improving serum phosphorus with a positive effect on nutrient intake. A phosphate-controlled diet has a role in an integrated therapeutic approach to hyperphosphatemia and positive calcium-phosphorus balance in hemodialysis patients.

Golgi damage caused by dysfunction of PiT-2 in primary familial brain calcification

The Golgi apparatus is vital for protein modification and molecular trafficking. It is essential for nerve development and activity, and damage thereof is implicated in many neurological diseases. Primary familial brain calcification (PFBC) is a rare inherited neurodegenerative disease characterized by multiple brain calcifications. SLC20A2, which encodes the inorganic phosphate transporter 2 (PiT-2) protein, is the main pathogenic gene in PFBC. The PiT-2 protein is a sodium-dependent phosphate type III transporter, and dysfunction leads to a deficit in the cellular intake of inorganic phosphate (Pi) and calcium deposits. Whether the impaired Golgi apparatus is involved in the PFBC procession requires elucidation. In this study, we constructed induced pluripotent stem cells (iPSCs) derived from two PFBC patients with different SLC20A2 gene mutations (c.613G > A or del exon10) and two healthy volunteers as dependable cell models for research on pathogenic mechanism. To study the mechanism, we differentiated iPSCs into neurons and astrocytes in vitro. Our study found disruptive Golgi structure and damaged autophagy in PFBC neurons with increased activity of mTOR. We also found damaged mitochondria and increased apoptosis in the PFBC dopaminergic neurons and astrocytes. In this study, we prove that dysfunctional PiT-2 leads to an imbalance of cellular Pi, which may disrupt the Golgi apparatus with impaired autophagy, mitochondria and apoptosis in PFBC. Our study provides a new avenue for understanding nerve damage and pathogenic mechanism in brain calcifications.

Cancer Cachexia and Dysregulated Phosphate Metabolism: Insights from Mutant p53 and Mutant Klotho Mouse Models.

The present perspective article proposes that cachexia, muscle wasting in cancer, is mediated by dysregulated phosphate metabolism and phosphate toxicity that can damage tissues in most major organ systems. A diet high in phosphorus fed to mice deficient in klotho, a cofactor that regulates phosphate metabolism, accelerates aging, sarcopenia, general organ atrophy, kyphosis, and osteoporosis. Similar effects are seen in phenotypes of mutant p53 mice that overexpress the p53 tumor suppressor gene. Although mutant p53 mice do not develop tumors compared to wild-type mice, mutant p53 mice have shorter mean lifespans. Furthermore, tumorigenesis is associated with the sequestration of excessive inorganic phosphate, and dangerous levels of phosphate are released into circulation during tumor lysis syndrome. In total, this evidence implies that tumorigenesis may be a compensatory mechanism that provides protective effects against systemic exposure to dysregulated phosphate metabolism and phosphate toxicity related to cachexia in cancer. Moreover, the hypothetical protection against phosphate toxicity afforded by tumorigenesis also provides an alternate explanation for putative tumor evasion of the immune system. Insights proposed in this perspective paper provide new directions for further research, with potential to develop novel interventions and clinical applications that modify dietary phosphate intake to reduce cachexia in cancer patients.

Sex Differences in Phosphate Homeostasis: Females Excrete More Phosphate and Calcium After an Oral Phosphate Challenge.

Dietary consumption of phosphate is increasing, and elevated serum phosphate is associated with increased cardiovascular disease (CVD) risk. Sex differences in phosphate homeostasis and response to changes in dietary phosphate intake, which are not captured by clinically measured analytes, may contribute to differences in CVD presentation and bone disease. To assess sex differences in acute phosphate homeostasis in response to a single oral phosphate challenge. Cross-sectional. General community. 78 participants (40-76 years) with measured glomerular filtration rate >60 mL/min/1.73 m2 and no clinically diagnosed CVD and 14 young healthy adults. To elucidate subtle alterations in phosphate homeostasis, we employ an acute challenge whereby the hormonal response, circulating mineral levels, and urinary excretion are assessed following an oral challenge of phosphate. Although both males and females had similar changes in circulating phosphate, calcium, and parathyroid hormone in response to the challenge, females excreted ∼1.9x more phosphate and ∼2.7x more calcium than males, despite not consuming calcium. These sex differences were recapitulated in healthy young adults. This excretion response did not correlate to age, serum phosphate, or estradiol levels. The females with greater excretion of phosphate had higher levels of bone resorption markers compared to formation markers. Taken together, these data identify sex differences in acute phosphate homeostasis, specifically that females may mobilize and excrete endogenous sources of calcium and phosphate in response to oral phosphate compared to males. While high levels of dietary phosphate negatively impact bone, our results suggest that females may incur more risk from these diets.

Long-Term Excessive Dietary Phosphate Intake Increases Arterial Blood Pressure, Activates the Renin-Angiotensin-Aldosterone System, and Stimulates Sympathetic Tone in Mice.

Increased dietary phosphate intake has been associated with severity of coronary artery disease, increased carotid intima–media thickness, left ventricular hypertrophy (LVH), and increased cardiovascular mortality and morbidity in individuals with normal renal function as well as in patients suffering from chronic kidney disease. However, the underlying mechanisms are still unclear. To further elucidate the cardiovascular sequelae of long-term elevated phosphate intake, we maintained male C57BL/6 mice on a calcium, phosphate, and lactose-enriched diet (CPD, 2% Ca, 1.25% P, 20% lactose) after weaning them for 14 months and compared them with age-matched male mice fed a normal mouse diet (ND, 1.0% Ca, 0.7% P). Notably, the CPD has a balanced calcium/phosphate ratio, allowing the effects of elevated dietary phosphate intake largely independent of changes in parathyroid hormone (PTH) to be investigated. In agreement with the rationale of this experiment, mice maintained on CPD for 14 months were characterized by unchanged serum PTH but showed elevated concentrations of circulating intact fibroblast growth factor-23 (FGF23) compared with mice on ND. Cardiovascular phenotyping did not provide evidence for LVH, as evidenced by unchanged LV chamber size, normal cardiomyocyte area, lack of fibrosis, and unchanged molecular markers of hypertrophy (Bnp) between the two groups. However, intra-arterial catheterization revealed increases in systolic pressure, mean arterial pressure, and pulse pressure in mice fed the CPD. Interestingly, chronically elevated dietary phosphate intake stimulated the renin–angiotensin–aldosterone system (RAAS) as evidenced by increased urinary aldosterone in animals fed the CPD, relative to the ND controls. Furthermore, the catecholamines epinephrine, norepinephrine, and dopamine as well as the catecholamine metabolites metanephrine. normetanephrine and methoxytyramine as measured by mass spectrometry were elevated in the urine of mice on CPD, relative to mice on the ND. These changes were partially reversed by switching 14-month-old mice on CPD back to ND for 2 weeks. In conclusion, our data suggest that excess dietary phosphate induces a rise in blood pressure independent of secondary hyperparathyroidism, and that this effect may be mediated through activation of the RAAS and stimulation of the sympathetic tone.

Obesity, Diabetes Mellitus, and Vascular Impediment as Consequences of Excess Processed Food Consumption

Regular intake of ready-to-eat meals is related to obesity and several noninfectious illnesses, such as cardiovascular diseases, hypertension, diabetes mellitus (DM), and tumors. Processed foods contain high calories and are often enhanced with excess refined sugar, saturated and trans fat, Na+ andphosphate-containing taste enhancers, and preservatives. Studies showed that monosodium glutamate (MSG) induces raised echelons of oxidative stress, and excessive hepatic lipogenesis is concomitant to obesity and type 2 diabetes mellitus (T2DM). Likewise, more than standard salt intake adversely affects the cardiovascular system, renal system, and central nervous system (CNS), especially the brain. Globally, excessive utilization of phosphate-containing preservatives and additives contributes unswervingly to excessive phosphate intake through food. In addition, communities and even health experts, including medical doctors, are not well-informed about the adverse effects of phosphate preservatives on human health. Dietary phosphate excess often leads to phosphate toxicity, ultimately potentiating kidney disease development. The mechanisms involved in phosphate-related adverse effects are not explainable. Study reports suggested that high blood level of phosphate causes vascular ossification through the deposition of Ca2+ and substantially alters fibroblast growth factor-23 (FGF23) and calcitriol.

39-Year-Old Woman With Severe Weakness

39-Year-Old Woman With Severe Weakness

Phosphate Frustration: Treatment Options to Complement Current Therapies.

Hyperphosphatemia eventually develops in almost all patients with advanced chronic kidney disease and is associated with negative clinical outcomes. Thus, guidelines recommend targeting treatment to normal phosphate levels in patients with chronic kidney disease. Despite low phosphorus diets, clearance by dialysis, and phosphate binder use, many patients with chronic kidney disease on dialysis are unable to consistently achieve and maintain serum phosphate concentrations <5.5 mg/dL. A chart audit of patients on dialysis receiving phosphate binders showed that 74 to 86% were unable to consistently achieve serum phosphate ≤5.5 mg/dL over 6 months. Furthermore, although there is evidence that serum phosphate concentrations <4.5 mg/dL are associated with improved survival and cardiovascular outcomes, real-world phosphate control data suggest achieving and maintaining this goal for most patients would be extremely challenging, if not near impossible, using current therapies. As phosphate binders can only remove approximately 300 mg of the 2,500 mg or more daily dietary phosphate intake, therapeutic innovations are necessary to improve phosphate management. We present treatment options to complement current therapies including tenapanor, a novel sodium/hydrogen exchanger isoform 3 inhibitor that blocks the dominant paracellular phosphate absorption pathway and has been shown to reduce phosphate levels in several clinical trials.

Nutrition Telemonitoring for CKD-HD Patients: A Qualitative Study on Patients, Patients’ Families, Medical Teams, and Hospital Management

BACKGROUND: CKD-HD patients require a nutritional monitoring system to control the amount of protein, fluid, sodium, potassium, and phosphate intake to reduce readmission rates and to improve their life quality. The Nutrition Telemonitoring Application (NTA) has a potential to resolve this problem. AIM: Therefore, this study aims to prepare NTA design materials conditioned to the needs of patients, families, medical teams, and hospital management. METHODS: A qualitative study with semi-structured interviews was conducted on 16 informants consisting of patients, families, medical teams, and hospital management teams. Furthermore, a purposive sampling technique was used to recruit participants, and the thematic analysis of the audio recording was conducted. RESULTS: Three main themes and seven sub-themes were identified. First, all participants in support of NTA will be beneficial. Second, NTA implementation requires family, medical team, hospital management, and BPJS (Health Social Security Agency). Third, all participants demand an easy Indonesian language interface equipped with pictures of food portions, additional alarm features, exercise, food recipes, educational videos, and free of charge. CONCLUSIONS: This study provides important insights considering the issues associated with the sustainability of NTA design and long-term benefits for CKD-HD patients.

Parkinson's Disease Etiology: Insights and Associations with Phosphate Toxicity.

The present paper investigated the association of Parkinson’s disease etiology with phosphate toxicity, a pathophysiological condition in which dysregulated phosphate metabolism causes excessive inorganic phosphate sequestration in body tissue that damages organ systems. Excessive phosphate is proposed to reduce Complex I function of the mitochondrial electron transport chain in Parkinson’s disease and is linked to opening of the mitochondrial permeability transition pore, resulting in increased reactive oxygen species, inflammation, DNA damage, mitochondrial membrane depolarization, and ATP depletion causing cell death. Parkinson’s disease is associated with α-synuclein and Lewy body dementia, a secondary tauopathy related to hyperphosphorylation of tau protein, and tauopathy is among several pathophysiological pathways shared between Parkinson’s disease and diabetes. Excessive phosphate is also associated with ectopic calcification, bone mineral disorders, and low levels of serum vitamin D in patients with Parkinson’s disease. Sarcopenia and cancer in Parkinson’s disease patients are also associated with phosphate toxicity. Additionally, Parkinson’s disease benefits are related to low dietary phosphate intake. More studies are needed to investigate the potential mediating role of phosphate toxicity in the etiology of Parkinson’s disease.

High phosphate-induced progressive proximal tubular injury is associated with the activation of Stat3/Kim-1 signaling pathway and macrophage recruitment.

Dietary phosphate intake in the Western population greatly exceeds the recommended dietary allowance and is linked to enhanced cardiovascular and all-cause mortality. It is unclear whether a chronic high phosphate diet (HPD) causes kidney injury in healthy individuals. Here, we show that feeding a 2% HPD in C57BL/6N mice for one up to six months resulted in hyperphosphatemia, hyperphosphaturia, increased plasma levels of fibroblast growth factor (FGF) 23, and parathyroid hormone (PTH) compared to mice on a 0.8% phosphate diet. Kidney injury was already noted after two months of HPD characterized by loss of proximal tubular (PT) cell polarity, flattened epithelia, disruption of brush border membranes, vacuolization, increased PT cell proliferation, marked interstitial mononuclear infiltration, and progressive accumulation of collagen fibers. HPD increased Stat3 activation and Kim-1 expression in PT epithelial cells and enhanced renal synthesis of chemokines recruiting monocytes and macrophages as well as macrophage related factors. Enhanced recruitment of F4/80+ macrophages around injured PT lesions was timely associated with increased Kim-1 synthesis, tubular MCP-1 expression, and degree of PT injury score. Likewise, tubulointerstitial fibrosis was associated with activation of Stat3/Kim-1 signaling pathway. The stimulation of human proximal tubular cells with high phosphate activated Stat3 signaling and induced HAVCR1 and CCL2 expression. We conclude that high phosphate results in progressive proximal tubular injury, indicating that high dietary phosphate intake may affect kidney health and therefore represents an underestimated health problem for the general population.

Inactivation of Osteoblast PKC Signaling Reduces Cortical Bone Mass and Density and Aggravates Renal Osteodystrophy in Mice with Chronic Kidney Disease on High Phosphate Diet.

Chronic kidney disease (CKD) frequently leads to hyperphosphatemia and hyperparathyroidism, mineral bone disorder (CKD-MBD), ectopic calcifications and cardiovascular mortality. PTH activates the osteoanabolic Gαs/PKA and the Gαq/11/PKC pathways in osteoblasts, the specific impact of the latter in CKD-MBD is unknown. We generated osteoblast specific Gαq/11 knockout (KO) mice and established CKD-MBD by subtotal nephrectomy and dietary phosphate load. Bone morphology was assessed by micro-CT, osteoblast function by bone planar scintigraphy at week 10 and 22 and by histomorphometry. Osteoblasts isolated from Gαq/11 KO mice increased cAMP but not IP3 in response to PTH 1-34, demonstrating the specific KO of the PKC signaling pathway. Osteoblast specific Gαq/11 KO mice exhibited increased serum calcium and reduced bone cortical thickness and mineral density at 24 weeks. CKD Gαq/11 KO mice had similar bone morphology compared to WT, while CKD Gαq/11-KO on high phosphate diet developed decreased metaphyseal and diaphyseal cortical thickness and area, as well as a reduction in trabecular number. Gαq/11-KO increased bone scintigraphic tracer uptake at week 10 and mitigated tracer uptake in CKD mice at week 22. Histological bone parameters indicated similar trends. Gαq/11-KO in osteoblast modulates calcium homeostasis, bone formation rate, bone morphometry, and bone mineral density. In CKD and high dietary phosphate intake, osteoblast Gαq/11/PKC KO further aggravates mineral bone disease.

Protein and Phosphate Intakes are Associated with Hyperphosphatemia in Hemodialysis Patients at Sanglah Hospital, Bali, Indonesia

Increased chronic kidney disease (CKD) mortality rate is significantly associated with increased blood phosphate levels. Hyperphosphatemia control is one of the main focuses in the management of hemodialysis (HD) patients. A high protein diet has been suggested to prevent malnutrition in hemodialysis patients. However, a high protein and phosphorus diet has the risk of increasing the phosphate level in the blood circulation, leading to a higher mortality rate of hemodialysis patients. This study aimed to prove that the level of protein and phosphate intake is associated with hyperphosphatemia in CKD patients with routine HD. This was cross-sectional analytical study conducted from September to October 2020 on 66 CKD patients who underwent hemodialysis. Subject characteristics and phosphorus and protein intake data were obtained from a questionnaire food recall adapted from the Food and Agriculture Organization of the United Nations. Data consumption patterns were processed using the nutritional survey software to obtain the nutritional values. Data were analyzed using the Chi-Square test to identify the relationship and risk between hyperphosphatemia and diet protein, phosphorus, and protein-phosphorus ratio. The confidence level in this study was 95%. There was a significant relationship between protein and phosphorus intake in hyperphosphatemia in CKD patients. The risk factors for hyperphosphatemia were high phosphorus intake (p=0.018; OR=3.886;95% CI: 1.212–12.460) and adequate protein intake (p=0.035; OR=3.674; 95% CI: 1.049-12.865). This study showed no significant relationship between phosphorus-protein ratio, protein-phosphorus ratio, and hyperphosphatemia incidence. In conclusion, high protein intake and excessive phosphorus intake provide a significant relationship to the incidence of hyperphosphatemia in CKD patients undergoing routine hemodialysis.

Comparison on the photogranules formation and microbial community shift between the batch and continuous-flow mode for the high saline wastewater treatment

The application of biological process for the high saline mariculture wastewater treatment was hindered primarily by salinity and settleability. Photogranule is an effective wastewater treatment technology with excellent settleability and resistance to environmental changes. In this study, internal circulating photogranular membrane bioreactor (IC-PMBR) and internal circulating photogranular sequencing batch bioreactor (IC-PSBR) were constructed to cultivated photogranules. The result showed that mature photogranules quickly formed within one month for both photobioreactors. IC-PMBR exhibited more excellent pollutants removal performance than IC-PSBR. The removal efficiencies of TN, PO43- and TOC in IC-PMBR were 95 ± 3%, 78 ± 6% and 85 ± 3%, respectively. The excellent nitrogen removal in both bioreactors was ascribed to the enrichment of Proteobacteria and Cyanobacteria. Interestingly, the increasing abundance of Leucothrix could enhance the denitrification in the IC-PMBR. The removal of phosphate was achieved by phosphate accumulating organisms (PAOs) (mainly Thiothrix) and cyanobacteria in the IC-PMBR, while only p-accumulation microalgae dominated the phosphate intake in the IC-PSBR. Moreover, the synergy of heterotrophic bacterial and microalgae improved the removal efficiency of organics in both bioreactors. Morphology observation and community analysis revealed that the key players in photogranules from IC-PMBR was Phormidium sp. acting as backbones and interweaving a mat on the surface of granules. In contrast, an integrated Leptolyngbya sp. with false branching was observed in photogranules from the IC-PSBR acting as an interior core and mat-like structure was absent. Noticeably, an anaerobic region was detected in photogranules from both bioreactors with different proportion, primary Rhodobacteraceae and Thiotrichaceae. Therefore, this study demonstrated that cultivating photogranules in continuous-flow membrane photobioreactor provided an alternative option for high saline wastewater treatment.

High phosphate intake induces bone loss in nephrectomized thalassemic mice.

Although patients with either β-thalassemia or chronic kidney disease (CKD) clinically correlate with severe osteoporosis, the mechanism by which CKD exposed to high phosphate affects bone turnover has not been characterized in β-thalassemia. We aimed to determine the effects of renal insufficiency on high phosphate intake induced changes in bone metabolism after 5/6th nephrectomy in hemizygous β-globin knockout (BKO) mice. Male BKO mice manifested severe anemia and osteopenia. Nephrectomy induced renal fibrosis and reduced renal function as assessed by increased serum urea nitrogen levels. Moreover, nephrectomy increased bone turnover leading to bone loss in wild type (WT) but not BKO mice. In nephrectomized BKO, PBS in drinking water induced hyperphosphatemia, and hypercalcemia along with osteopenia in both cancellous and cortical bone. Histomorphometric analysis confirmed reduced cancellous bone volume due to decreased bone formation rate, osteoblast number and osteoclast number. The mRNA levels for Alpl, Sp7, Kl, Tnfsf11, and Tnfsf11/Tnfrsf11b were decreased in nephrectomized BKO mice drinking PBS. Interestingly, Fgf23, a bone-derived hormone produced by osteocytes and osteoblasts in response to hyperphosphatemia, were remarkably increased in nephrectomized BKO mice following PBS intake. Serum FGF23 and erythropoietin levels were markedly elevated in BKO mice. Nephrectomy decreased serum erythropoietin but not FGF23 levels. Hyperphosphatemia in BKO mice increased serum erythropoietin, FGF23, and PTH levels, nominating these factors as candidate mediators of bone loss in thalassemic mice with CKD during phosphate retention.

MO813: The Validity of Combined Urea and Phosphate Kinetic Modelling in Estimation of Daily Protein and Phosphate Intake in Haemodialysis Patients

Abstract BACKGROUND AND AIMS The interpretation of patient dietary records, laboratory results in haemodialysis units to manage their phosphate and nutritional status is time and effort consuming and needs strictly compliant patients. This justifies the need of estimates of these parameters with accepted validity and applicability. METHOD In 100 haemodialysis patients [50 with residual kidney function (RKF) and 50 anuric patients], Daugirdas [1, 2] supposed urea and phosphate kinetic models’ estimates were extracted and correlated with the actual dietary records, phosphate binder dosage and dialysis prescription parameters. The estimates of interest were, daily ingested phosphorus (DIP), estimated phosphorus removed, intradialytic time averaged phosphate level, normalized protein catabolic ratio (nPCR) and dialysis estimated kt/v. RESULTS Modeled DIP is significantly correlated to calculated phosphate intake from average 3-day dietary records in both anuric and RKF patients (r = 0.89 and r = 91, respectively; P &amp;lt; .001). Also, the nPCR is significantly correlated with daily protein intake/kg in both study groups (r = 0.85 in anuric, r = 0.78 in RKF; P &amp;lt; .001). Estimated phosphorus removed is positively correlated to dialysis kt/v in both study groups (r = 0.51 in anuric, r = 0.52 in RKF; P &amp;lt; .001). Patients with RKF had significantly lower pre-dialysis serum phosphate (5.78 ± 1.05 versus 4.39 ± 0.78; P &amp;lt; .001), calcium-based phosphate binders’ dosage (2616.28 ± 390.93 mg/day versus 1937.5 ± 395.29 mg/day; P &amp;lt; .001), estimated phosphate removed in haemodialysis (1271.86 ± 274.5 mg/day versus 1016.82 ± 198.42 mg/day; P &amp;lt; .001) and intradialytic average phosphate levels (4.052 ± 0.87 mg/dL versus 3.26 ± 0.61 mg/dL; P &amp;lt; 0.001) than the anuric group. CONCLUSION Modeled DIP and nPCR can be used as estimates for phosphate and protein intake in haemodialysis patients with or without RKF. RKF has a positive impact on the phosphate measures and decreases the need for phosphate binders. For each patient is shown the mean result after CC treatment and after SO treatment. The red bold line represents mean values. (A) Bone turnover estimated from whole-body 18F-NaF PET/CT as Ki at lumbar vertebrae 1–5 in 20 participants. (B) Bone volume estimated as CT-derived HU at lumbar vertebrae 1–5 in 21 participants. * Significance level &amp;lt; 0.05.

MO448: Progressive Tubular Injury Caused by High Phosphate Intake is Associated With Activation of STAT3/KIM-1 Signalling and Macrophage Recruitment in Mice

Abstract BACKGROUND AND AIMS Dietary phosphate intake greatly exceeds the recommended daily allowance in the Western population. Elevated phosphate levels are linked to increased cardiovascular and all-cause mortality, impaired bone health and premature ageing. The renal effects of chronic high dietary phosphate intake for healthy individuals are still not clear. METHOD Male C57BL/6 mice received a 2% high phosphate diet (HPD) or a 0.8% normal phosphate diet (NPD) for 1 to 6 months. We collected blood, urine and kidneys to investigate phosphate metabolism and progression of kidney injury. In vitro analysis for the toxic effects of phosphate or the phosphaturic hormones parathyroid hormone (PTH) and fibroblast growth factor (FGF) 23 was done in HK-2 humane proximal tubule (PT) cells. RESULTS HPD in mice caused hyperphosphataemia despite increased phosphaturia. Both intact FGF23 and PTH plasma levels were significantly increased in mice on HPD at 1 month onward. Mice on HPD showed significantly increased creatinine levels and albuminuria. Histopathological analysis of the kidneys revealed increased PT injury in mice receiving HPD compared to NPD controls from 2 months onward followed by a rapid progression of organ damage from month 5 to 6. Picrosirius red staining of kidney sections showed a progressively increased accumulation of collagen fibers in renal cortex of mice on HPD, which was significant from 4 months onward and accompanied by enhanced expression of transforming growth factor-β1, collagen 1 and fibronectin. The significant induction of the tubular injury marker Havcr1, encodes for Kim-1, started already after 1 month of feeding HPD, progressed over time and was strongest after 6 months. Immunofluorescence staining revealed Kim-1 localization to damaged PT, which was most prominent after 3 and 6 months of HPD. Renal Kim-1 protein levels were positively associated with tubular injury score and tubulointerstitial fibrosis. Histological staining and quantification revealed significantly increased number of pStat3+ cells in PTs of HPD-fed mice at months 1, 2, 5 and 6, indicating activated Stat3 signaling. The number of pStat3+ cells was positively associated with Kim-1 synthesis. Inflammation cytokine array with kidney tissue lysates showed, among others, enhanced expression of monocyte chemoattractant protein (MCP)-1 and macrophage colony-stimulating factor (MCSF) in HPD-fed mice. The mRNA expression of Csf1 (encodes for MCSF) was upregulated in HPD-fed mice and most pronounced after 6 months. Ccl2 mRNA expression (encodes for MCP-1) was significantly enhanced after 3, 5 and 6 months of HPD compared to NPD. Immunofluorescence staining showed a strong and specific induction of MCP-1 in PT epithelial cells due to HPD. The HPD-induced Ccl2 expression was positively associated with Kim-1 expression indicating an interaction between pStat3/Kim-1 signalling pathway and MCP-1. Immunohistochemical staining and flow cytometry analysis revealed a significantly increased recruitment of F4/80+ macrophages in renal tissue of HPD-fed mice after 3 and 6 months. The enhanced renal macrophage recruitment in the entire HPD cohort was associated with increased MCP-1 protein synthesis and increased tubular injury score. In vitro experiments using HK-2 cells showed that stimulation with FGF23 or high phosphate, but not PTH, induced the phosphorylation of STAT3. Interestingly, only treatment with high phosphate significantly upregulated HAVCR1 and CCL2 expression. CONCLUSION Chronic oral phosphate load in mice induced progressive inflammatory kidney injury dominated by macrophages. The direct toxic effects of phosphate are mediated by Stat3/Kim-1 signalling activation in PT cells. Our data support the hypothesis that kidney injury induced by widespread high dietary phosphate intake may cause a global health problem and underline the urgent need for clinical studies on this issue.

FC026: Chronic High Phosphate Level Impairs Cardiac Health

Abstract BACKGROUND AND AIMS Patients with chronic kidney disease (CKD) suffer from disturbed mineral metabolism in which the chronic phosphate load leads to the elevation of the phosphaturic hormones parathyroid hormone (PTH) and fibroblast growth factor 23 (FGF23). Persistent hyperphosphatemia predisposes to cardiovascular events and increased morbidity and mortality rates. It is discussed that even in the general population, consumption of highly processed food increases phosphate level, which in turn may increase cardiovascular risk. Here, we aim to elucidate the pathological mechanisms of how chronic high phosphate intake mediates cardiac remodeling and dysfunction, respectively. METHOD Male C57BL/6 wild type mice received a high phosphate diet containing 2% inorganic phosphate (HPD) or a 0.8% normal phosphate diet (NPD) for 6 months. Echocardiographic analysis and ex-vivo measurements in cardiomyocytes using IonOptix system were assessed to evaluated cardiac function and contractility. Bulk RNA sequencing of whole heart tissue followed by pathway analysis was done to identify affected relevant signaling pathways, which were verified by in vitro studies using neonatal rat ventricular myocytes (NRVM). RESULTS Chronic phosphate overload resulted in increased level of serum and urinary phosphate and high plasma PTH and FGF23 concentrations. HPD caused impaired heart function as shown by reduced ejection fraction, increased end-systolic volumes and enlarged systolic left ventricular internal diameter accompanied by impaired left ventricular relaxation as seen in Doppler echocardiography. Histological analysis showed increased cardiomyocyte area and length in HPD-fed mice compared with NPD demonstrating cellular hypertrophy. RNA sequencing revealed differentially expressed genes of calcium signaling pathways in the HPD group. Besides, immunoblot analysis of whole heart tissue showed altered Phospholamban activity after 6 months of HPD compared with NPD, indicating altered calcium pump in cardiomyocytes. Preliminary analysis of sarcomere movements and changes of intracellular calcium levels in single cardiomyocytes isolated from NPD and HPD mice after 6 months suggested impaired contractility. Detailed results will be presented here. In vitro stimulation of isolated NRVM with high phosphate induced a hypertrophic growth response, verifying a direct effect of high phosphate on the heart. CONCLUSION HPD in mice causes a dilated cardiac phenotype including cellular hypertrophy, altered contractility and differentially expressed genes involved in calcium signaling pathways, indicating that a chronic high phosphate load is harmful for the heart also in the general population.