Evaluation of a Novel Enteral Phosphorus Therapy with Enteral Nutrition during a National Intravenous Sodium Phosphate Shortage.

The purpose of this study was to evaluate the efficacy and safety of intragastric administration of small volumes of sodium enema solution containing phosphorus as phosphorus replacement therapy in critically ill patients with traumatic injuries who required continuous enteral nutrition. Adult patients (>17 years of age) who had a serum phosphorus concentration <3 mg/dL (0.97 mmol/L) were evaluated. Patients with a serum creatinine concentration >1.4 mg/dL (124 µmol/L) were excluded. Patients were given 20 mL of saline enema solution intragastrically, containing 34 mmol of phosphorus and mixed in 240 mL water. A total of 55% and 73% of patients who received one (n = 22) or two doses (n = 11) had an improvement in the serum phosphorus concentration, respectively. The serum phosphorus concentration increased from 2.5 [2.1, 2.8] mg/dL (0.81 [0.69, 0.90] mmol/L) to 2.9 [2.2, 3.0] mg/dL (0.94 [0.71, 0.97 mmol/L) for those who received two doses (p = 0.222). Excluding two patients with a marked decline in serum phosphorus by 1.3 mg/dL (0.32 mmol/L) resulted in an increase in the serum phosphorus concentration from 2.3 [2.0, 2.8] mg/dL (0.74 [0.65, 0.90] mmol/L) to 2.9 [2.5, 3.2] mg/dL (0.94 [0.81, 1.03] mmol/L; n = 9; p = 0.012). No significant adverse effects were noted. Our data indicated that intragastric phosphate administration using a small volume of saline enema solution improved the serum phosphorus concentrations in most patients.

Trichostrongylus colubriformis infection damages intestine brush board cells and could negatively impact postabsorptive parameters of Santa Ines lambs.

This study aimed to evaluate histological, digestive and postabsorptive physiological parameters in Santa Ines lambs infected with Trichostrongylus colubriformis and fed different levels of phosphorus. Therefore, eighteen Santa Ines, castrated male, six-month old, healthy lambs (initial body weight 22.4 ± 2.7 kg) were distributed in one of four treatments arranged in a 2 × 2 split-plot arrangement: Sufficient dietary P level and uninfected (SPui; n = 4), Sufficient dietary P level and infected (SPi; n = 5), Deficient dietary P level and uninfected (DPui; n = 4), Deficient dietary P level and infected (DPi; n = 5). Infected lambs received, orally, a single pulse dose of 40.000 T. colubriformis infective larval stage (L3). Animals were fed Tifton 85 hay (Cynodon ssp.; 60%), and cassava meal and maize gluten meal (40%). Measurement of nutrient apparent digestibility and nitrogen metabolism were performed in individual metabolic stalls. To achieve the trial results, it was measured methane emissions in respiratory chambers, urine purine derivatives, ruminal short-chain fatty acids (SCFA), histological cuts of duodenal mucosal tissues and passage rates fluxes, analyzed by external (Yb, Cr, and Co) and internal (iNDF) markers. Statistical procedures were performed in R studio. The fixed main effects of treatment and the interactions were tested by ANOVA, and means compared by Duncan's test at 5% significance. Apparent digestibility was not affected by treatments, however, nitrogen retained decreased (P < 0.01) and urinary nitrogen losses increased (P < 0.01) in infected animals. Small intestine digesta content, empty segment weight, and length were higher in infected animals (P < 0.05). Passage rate was not majorly affected by infection or dietary P levels. Methane emissions, SCFA concentrations, and purine derivative excretion were also not affected by treatments. Regarding the histology, the vilosity weight (P < 0.05), and crypt depth (P < 0.01) decreased in infected animals. In conclusion, T. colubriformis infection can damage intestinal mucosa and affect nitrogen metabolism, but did not affect the digesta transit, and nutrient digestibility. The P dietary levels did not promote any modification in GIT physiological parameters tested in this study.

Effects of Short-Term Phosphate Loading on Aerobic Capacity under Acute Hypoxia in Cyclists: A Randomized, Placebo-Controlled, Crossover Study.

The aim of this study was to evaluate the effects of sodium phosphate (SP) supplementation on aerobic capacity in hypoxia. Twenty-four trained male cyclists received SP (50 mg·kg-1 of FFM/day) or placebo for six days in a randomized, crossover study, with a three-week washout period between supplementation phases. Before and after each supplementation phase, the subjects performed an incremental exercise test to exhaustion in hypoxia (FiO2 = 16%). Additionally, the levels of 2,3-diphosphoglycerate (2,3-DPG), hypoxia-inducible factor 1 alpha (HIF-1α), inorganic phosphate (Pi), calcium (Ca), parathyroid hormone (PTH) and acid-base balance were determined. The results showed that phosphate loading significantly increased the Pi level by 9.0%, whereas 2,3-DPG levels, hemoglobin oxygen affinity, buffering capacity and myocardial efficiency remained unchanged. The aerobic capacity in hypoxia was not improved following SP. Additionally, our data revealed high inter-individual variability in response to SP. Therefore, the participants were grouped as Responders and Non-Responders. In the Responders, a significant increase in aerobic performance in the range of 3-5% was observed. In conclusion, SP supplementation is not an ergogenic aid for aerobic capacity in hypoxia. However, in certain individuals, some benefits can be expected, but mainly in athletes with less training-induced central and/or peripheral adaptation.

Acute Effects of an Inorganic Phosphorus Additive on Mineral Metabolism and Cardiometabolic Risk Factors in Healthy Subjects.

CONTEXT: Hyperphosphatemia and high levels of fibroblast growth factor 23 (FGF23) are risk factors for cardiovascular events in patients with chronic kidney diseases. However, the impact of an inorganic phosphorus additive in healthy people is largely unknown. OBJECTIVE: We aimed to investigate the acute effect of excessive dietary phosphorus administered as sodium dihydrogen phosphate on the postprandial levels of Pi and FGF23 and the response to food. METHODS: This study was a double-blind placebo-controlled crossover study with 29 healthy male and female participants from the general community who were administered a single dose of either 700 mg phosphorus (NaH2PO4) or a sodium-adjusted placebo in combination with a test meal. Postprandial plasma levels of Pi and FGF23 were measured. RESULTS: Compared with placebo, oral phosphorus increased the plasma Pi level, which remained elevated during the ensuing 8 hours (at 480 minutes: 1.31 vs 1.16 mmol/l; P < 0.001), increased urinary Pi (iAUC0-480 789 vs 95 mmol/mmol; P < 0.001), reduced tubular Pi reabsorption (iAUC0-480 -31.5 vs -6.2; P < 0.001), decreased urinary calcium (iAUC0-240 30.6 vs 53.0 mmol/mmol; P = 0.009), and stimulated the release of parathyroid hormone (iAUC0-480 2212 vs 768 ng/l; P < 0.001). However, the FGF23 levels did not change. Postprandial levels of glucose, insulin, and lipids were not substantially affected by phosphorus vs placebo. CONCLUSION: An oral phosphorus load can induce elevated postprandial levels of circulating Pi for hours in healthy subjects, despite rapid homeostatic counterreactions. FGF23 levels and the postprandial response to food were not affected.

An Evaluation of Phosphate Buffer Saline as an Alternative Liquid-Based Medium for HPV DNA Detection.

OBJECTIVE: HPV detection has been proposed as part of the co-testing which improves the sensitivity of cervical screening. However, the commercially liquid-based medium adds cost in low-resource areas. This study aimed to evaluate the performance of ice-cold phosphate buffer saline (PBS) for HPV detection. METHODS: HPV DNA from SiHa cells (with 1-2 copies of HPV16 per cell) preserved in ice-cold PBS or PreserveCyt solution at different time points (24, 36, 48, 72, 120 and 168 h) was tested in triplicate using Cobas 4800. The threshold cycle (Ct) values of both solutions were compared. An estimated false negative rate of PBS was also assessed by using the difference in Ct values between both solutions (∆Ct) and Ct values of HPV16-positive PreserveCyt clinical samples (Ctsample) at corresponding time points. Samples with a (Ctsample+∆Ct) value > 40.5 (the cutoff of HPV16 DNA by Cobas 4800) were considered as false negativity. RESULTS: The Ct values of HPV16 DNA of SiHa cells collected in PBS were higher than PreserveCyt ranging from 0.43 to 2.36 cycles depending on incubation times. There was no significant difference at 24, 72, 120, and 168 h.  However, the Ct values were statistically significantly higher for PBS than PreserveCyt at 36 h (31.00 vs 29.26), and 48 h (31.06 vs 28.70). A retrospective analysis in 47 clinical PreserveCyt collected samples that were positive for HPV16 DNA found that 1 case (2%) would become negative if collected in ice-cold PBS. CONCLUSIONS: The PBS might be an alternative collecting medium for HPV detection in the low-resource areas. Further evaluations are warranted.

Phosphorothioate-DNA bacterial diet reduces the ROS levels in C. elegans while improving locomotion and longevity.

DNA phosphorothioation (PT) is widely distributed in the human gut microbiome. In this work, PT-diet effect on nematodes was studied with PT-bioengineering bacteria. We found that the ROS level decreased by about 20-50% and the age-related lipofuscin accumulation was reduced by 15-25%. Moreover, the PT-feeding worms were more active at all life periods, and more resistant to acute stressors. Intriguingly, their lifespans were prolonged by ~21.7%. Comparative RNA-seq analysis indicated that many gene expressions were dramatically regulated by PT-diet, such as cysteine-rich protein (scl-11/12/13), sulfur-related enzyme (cpr-2), longevity gene (jnk-1) and stress response (sod-3/5, gps-5/6, gst-18/20, hsp-12.8). Both the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis suggested that neuroactivity pathways were upregulated, while phosphoryl transfer and DNA-repair pathways were down-regulated in good-appetite young worms. The findings pave the way for pro-longevity of multicellular organisms by PT-bacterial interference.

Association between phosphate and long-term outcome in CAD patients underwent coronary intervention.

Phosphate has been linked to higher cardiovascular (CV) risk. However, whether phosphate is associated with poor outcomes for patients with coronary artery disease (CAD) after percutaneous coronary interventions (PCIs) remained undetermined. 2,894 CAD patients (2,220 male, aged 71.6 ± 12.2), who received PCI at TVGH from 2006 to 2015, with phosphate measurement, were enrolled. The primary outcome was the composite of major adverse CV events [MACE, comprising of CV death, nonfatal MI, and nonfatal stroke] and heart failure hospitalization (HHF). The key secondary outcome was MACE. There was a J-curve association between phosphate and CV events after adjusted for comorbidities and renal function. Phosphate around 3.2 ± 0.1 mg/dL was associated with the lowest CV risk. In Cox analysis, each 1 mg/dL increases in phosphate was associated with a higher risk of MACE + HHF (HR: 1.12, 95% CI: 1.05-1.21): CV death (HR: 1.37, 95% CI: 1.22-1.55) and HHF (HR: 1.12, 95% CI: 1.02-1.23). Subgroup analyses showed more prominent association between phosphate and MACE + HHF in male, age > 65, bare-metal stents (BMSs), LVEF < 50%, eGFR < 60, LDL > 70 mg/dL, and emergent PCI. Phosphate has a significant association with the risk of CV events in CAD patients undergoing PCI that was independent of comorbidities and renal function.

Ionic homeostasis, acid-base balance and the risk of citrate accumulation in patients after cardiovascular surgery treated with continuous veno-venous haemofiltration with post-dilution regional citrate anticoagulation - An observational case-control study.

BACKGROUND: Patients after cardiovascular surgery, requiring renal replacement therapy, can benefit from adequate non-heparin circuit anticoagulation. Simplified regional citrate anticoagulation (RCA) protocol proposes the use of citric acid dextrose formula A (ACD-A) during post-dilutional continuous veno-venous hemofiltration (CVVH) with standard bicarbonate buffered calcium containing replacement solution. Citrate accumulation diagnosed upon total to ionized calcium ratio (tCa/iCa) and low ionized calcium (iCa) are considered as the biggest risks related to regional citrate accumulation. METHODS: This prospective observational case-control study evaluated electrolyte and acid-base homeostasis in cardiovascular surgery patients treated with post-dilution CVVH with a simplified RCA protocol with ACD-A. In total, 50 consecutive cardiovascular surgery patients were evaluated. Base excess, pH, bicarbonate, lactate, Na+, Cl-, Mg++, and inorganic phosphate concentrations, the total to ionized calcium ratio (tCa/iCa), and high anion gap metabolic acidosis were assessed during haemofiltration treatment in survivors and non-survivors. RESULTS: Thirty-three (66%) patients died. The therapies were very well balanced in sodium and chloride homeostasis. The lactate concentration and anion gap decreased during CVVH sessions lasting longer than 72 hours, but no inter-group difference was observed. The tCa/iCa ratio exceeded 4.5% and was significantly higher in non-survivors (p=0.037). Initial lactate concentration did not correlate with tCa/iCa ratio during haemofiltration. Magnesium and phosphate concentrations decreased and additional supplementation with magnesium was necessary. The magnesium concentration was lower in the non-survivors. CONCLUSIONS: The incidence of citrate accumulation exceeded 4% and was significantly higher in non-survivors. Supplementation with magnesium and phosphate ions is needed in CVVH with RCA.

Genome accessibility dynamics in response to phosphate limitation is controlled by the PHR1 family of transcription factors in Arabidopsis.

As phosphorus is one of the most limiting nutrients in many natural and agricultural ecosystems, plants have evolved strategies that cope with its scarcity. Genetic approaches have facilitated the identification of several molecular elements that regulate the phosphate (Pi) starvation response (PSR) of plants, including the master regulator of the transcriptional response to phosphate starvation PHOSPHATE STARVATION RESPONSE1 (PHR1). However, the chromatin modifications underlying the plant transcriptional response to phosphate scarcity remain largely unknown. Here, we present a detailed analysis of changes in chromatin accessibility during phosphate starvation in Arabidopsis thaliana root cells. Root cells undergo a genome-wide remodeling of chromatin accessibility in response to Pi starvation that is often associated with changes in the transcription of neighboring genes. Analysis of chromatin accessibility in the phr1 phl2 double mutant revealed that the transcription factors PHR1 and PHL2 play a key role in remodeling chromatin accessibility in response to Pi limitation. We also discovered that PHR1 and PHL2 play an important role in determining chromatin accessibility and the associated transcription of many genes under optimal Pi conditions, including genes involved in the PSR. We propose that a set of transcription factors directly activated by PHR1 in Pi-starved root cells trigger a second wave of epigenetic changes required for the transcriptional activation of the complete set of low-Pi-responsive genes.

Asymmetric physiological response of a reef-building coral to pulsed versus continuous addition of inorganic nutrients.

Coral reefs, especially those located near-shore, are increasingly exposed to anthropogenic, eutrophic conditions that are often chronic. Yet, corals under unperturbed conditions may frequently receive natural and usually temporary nutrient supplementation through biological sources such as fishes. We compared physiological parameters indicative of long- and short-term coral health (day and night calcification, fragment surface area, productivity, energy reserves, and tissue stoichiometry) under continuous and temporary nutrient enrichment. The symbiotic coral Acropora intermedia was grown for 7 weeks under continuously elevated (press) levels of ammonium (14 µmol L-1) and phosphate (10 µmol L-1) as separate and combined treatments, to discern the individual and interactive nutrient effects. Another treatment exposed A. intermedia twice-daily to an ammonium and phosphate pulse of the same concentrations as the press treatments to simulate natural biotic supplementation. Press exposure to elevated ammonium or phosphate produced mixed effects on physiological responses, with little interaction between the nutrients in the combined treatment. Overall, corals under press exposure transitioned resources away from calcification. However, exposure to nutrient pulses often enhanced physiological responses. Our findings indicate that while continuous nutrient enrichment may pose a threat to coral health, episodic nutrient pulses that resemble natural nutrient supplementation may significantly benefit coral health and physiology.

Calcium phosphate microcrystals in the renal tubular fluid accelerate chronic kidney disease progression.

The Western pattern diet is rich not only in fat and calories but also in phosphate. The negative effects of excessive fat and calorie intake on health are widely known, but the potential harms of excessive phosphate intake are poorly recognized. Here, we show the mechanism by which dietary phosphate damages the kidney. When phosphate intake was excessive relative to the number of functioning nephrons, circulating levels of FGF23, a hormone that increases the excretion of phosphate per nephron, were increased to maintain phosphate homeostasis. FGF23 suppressed phosphate reabsorption in renal tubules and thus raised the phosphate concentration in the tubule fluid. Once it exceeded a threshold, microscopic particles containing calcium phosphate crystals appeared in the tubule lumen, which damaged tubule cells through binding to the TLR4 expressed on them. Persistent tubule damage induced interstitial fibrosis, reduced the number of nephrons, and further boosted FGF23 to trigger a deterioration spiral leading to progressive nephron loss. In humans, the progression of chronic kidney disease (CKD) ensued when serum FGF23 levels exceeded 53 pg/mL. The present study identified calcium phosphate particles in the renal tubular fluid as an effective therapeutic target to decelerate nephron loss during the course of aging and CKD progression.

Water-soluble derivatives of evodiamine: Discovery of evodiamine-10-phosphate as an orally active antitumor lead compound.

10-Hydroxyevodiamine is a multitargeting antitumor lead compound with excellent in vitro activity. However, its in vivo antitumor potency is rather limited, which has hampered its further clinical development. To overcome this obstacle, a series of novel water-soluble derivatives of 10-hydroxyevodiamine were designed and synthesized. Most of them exhibited good to excellent antitumor activities against several cancer cell lines. In particular, phosphate derivative 9 was orally active and showed improved in vivo antitumor efficacy in HCT116 xenograft models. Further antitumor mechanism studies indicated that compound 9 acted by triple Top1/Top2/tubulin inhibition and induced apoptosis with G2/M cell cycle arrest. Taken together, this study extended the structure-activity relationship of evodiamine and identified phosphate derivative 9 as a promising antitumor lead compound.

The Role of Phosphate in Alcohol-Induced Experimental Pancreatitis.

BACKGROUND & AIMS: Heavy alcohol consumption is a common cause of acute pancreatitis; however, alcohol abuse does not always result in clinical pancreatitis. As a consequence, the factors responsible for alcohol-induced pancreatitis are not well understood. In experimental animals, it has been difficult to produce pancreatitis with alcohol. Clinically, alcohol use predisposes to hypophosphatemia, and hypophosphatemia has been observed in some patients with acute pancreatitis. Because of abundant protein synthesis, the pancreas has high metabolic demands, and reduced mitochondrial function leads to organelle dysfunction and pancreatitis. We proposed, therefore, that phosphate deficiency might limit adenosine triphosphate synthesis and thereby contribute to alcohol-induced pancreatitis. METHODS: Mice were fed a low-phosphate diet (LPD) before orogastric administration of ethanol. Direct effects of phosphate and ethanol were evaluated in vitro in isolated mouse pancreatic acini. RESULTS: LPD reduced serum phosphate levels. Intragastric administration of ethanol to animals maintained on an LPD caused severe pancreatitis that was ameliorated by phosphate repletion. In pancreatic acinar cells, low-phosphate conditions increased susceptibility to ethanol-induced cellular dysfunction through decreased bioenergetic stores, specifically affecting total cellular adenosine triphosphate and mitochondrial function. Phosphate supplementation prevented ethanol-associated cellular injury. CONCLUSIONS: Phosphate status plays a critical role in predisposition to and protection from alcohol-induced acinar cell dysfunction and the development of acute alcohol-induced pancreatitis. This finding may explain why pancreatitis develops in only some individuals with heavy alcohol use and suggests a potential novel therapeutic approach to pancreatitis. Finally, an LPD plus ethanol provides a new model for studying alcohol-associated pancreatic injury.

Acylation of non-specific phospholipase C4 determines its function in plant response to phosphate deficiency.

Non-specific phospholipase C (NPC) is involved in plant growth, development and stress responses. To elucidate the mechanism by which NPCs mediate cellular functions, here we show that NPC4 is S-acylated at the C terminus and that acylation determines its plasma membrane (PM) association and function. The acylation of NPC4 was detected using NPC4 isolated from Arabidopsis and reconstituted in vitro. The C-terminal Cys-533 was identified as the S-acylation residue, and the mutation of Cys-533 to Ala-533 in NPC4 (NPC4C533A ) led to the loss of S-acylation and membrane association of NPC4. The knockout of NPC4 impeded the phosphate deficiency-induced decrease of the phosphosphingolipid glycosyl inositol phosphoryl ceramide (GIPC), but introducing NPC4C533A to npc4-1 failed to complement this defect, thereby supporting the hypothesis that the non-acylated NPC4C533A fails to hydrolyze GIPC during phosphate deprivation. Moreover, NPC4C533A failed to complement the primary root growth in npc4-1 under stress. In addition, NPC4 in Brassica napus was S-acylated and mutation of the S-acylating cysteine residue of BnaC01.NPC4 led to the loss of S-acylation and its membrane association. Together, our results reveal that S-acylation of NPC4 in the C terminus is conserved and required for its membrane association, phosphosphingolipid hydrolysis and function in plant stress responses.

A Reduced Dose Whole Virion Aluminum Adjuvanted Seasonal Influenza Vaccine Is Immunogenic, Safe, and Well Tolerated in Pediatric Patients.

BACKGROUND: Data suggest that pediatric patients might react differently to influenza vaccination, both in terms of immunity and side effects. We have recently shown that using a whole virion vaccine with aluminum phosphate adjuvants, reduced dose vaccines containing 6 µg of viral hemagglutinin (HA) per strain are immunogenic, and well tolerated in adult and elderly patients. Here we show the results of a multicenter clinical trial of pediatric patients, using reduced doses of a new, whole virion, aluminum phosphate adjuvanted vaccine (FluArt, Budapest, Hungary). METHODS: A total of 120 healthy volunteers were included in two age groups (3-11 years, receiving 3 µg of HA per strain, and 12-18 years, receiving 6 µg of HA per strain). We used hemagglutination inhibition testing to assess immunogenicity, based on EMA and FDA licensing criteria, including post/pre-vaccination geometric mean titer ratios, seroconversion and seropositivity rates. Safety and tolerability were assessed using CHMP guidelines. RESULTS: All subjects entered the study and were vaccinated (ITT population). All 120 subjects attended the control visit on Day 21 (PP population). All immunogenicity licensing criteria were met in both age groups for all three vaccine virus strains. No serious adverse events were detected and the vaccine was well tolerated by both age groups. DISCUSSION: Using a whole virion vaccine and aluminum phosphate adjuvants, a reduction in the amount of the viral hemmaglutinin is possible while maintaining immunogenicity, safety and tolerability in pediatric and adolescent patients.

Refractory hypophosphatemia following ferric carboxymaltose administration.

Hypophosphatemia is a rare side effect of intravenous iron replacement. Urinary phosphate wasting due to increased FGF23 is the most likely mechanism. Here, we present a case of intractable hypophosphatemia in a 32-year-old female patient with history of ulcerative colitis (UC), who was primarily hospitalized due to UC flare-up. Her urinary fractional excretion of phosphate was inappropriately elevated at 70%. A careful history revealed that she had been treated with ferric carboxymaltose 2 weeks prior to hospitalization, leading to a diagnosis of iron-induced hypophosphatemia. She was treated with 5 weeks of intravenous sodium phosphate since she did not tolerate oral supplementation. In conclusion, clinicians should be aware of iron-induced hypophosphatemia and be cautious when prescribing intravenous iron.

Assessment of Inorganic Phosphate Intake by the Measurement of the Phosphate/Urea Nitrogen Ratio in Urine.

In chronic kidney disease (CKD) patients, it would be desirable to reduce the intake of inorganic phosphate (P) rather than limit the intake of P contained in proteins. Urinary excretion of P should reflect intestinal absorption of P(inorganic plus protein-derived). The aim of the present study is to determine whether the ratio of urinary P to urinary urea nitrogen (P/UUN ratio) helps identify patients with a high intake of inorganic P.A cross-sectional study was performed in 71 patients affected by metabolic syndrome with CKD (stages 2-3) with normal serum P concentration. A 3-day dietary survey was performed to estimate the average daily amount and the source of P ingested. The daily intake ofPwas1086.5 ± 361.3mg/day; 64% contained in animal proteins, 22% in vegetable proteins, and 14% as inorganic P. The total amount of P ingested did not correlate with daily phosphaturia, but it did correlate with the P/UUN ratio (p < 0.018). Patients with the highest tertile of the P/UUN ratio >71.1 mg/g presented more abundant inorganic P intake (p < 0.038).The P/UUN ratio is suggested to be a marker of inorganic P intake. This finding might be useful in clinical practices to identify the source of dietary P and to make personalized dietary recommendations directed to reduce inorganic P intake.

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

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