Efficacy and Safety of Burosumab in X-linked Hypophosphatemia

CONTEXT

Burosumab is approved for the treatment of X-linked hypophosphatemia (XLH).

OBJECTIVE

To assess the efficacy and safety of burosumab in XLH patients, we conducted a systematic review and meta-analysis.

METHODS

We searched PubMed, the Cochrane Library, Embase, ClinicalTrials.gov, and Web of Science for studies on the use of burosumab in patients with XLH. Meta-analysis of randomized controlled trials (RCTs) and single-arm trials (SATs) was done to explore burosumab treatment on the efficacy and safety of XLH.

RESULTS

Of the 8 eligible articles, 5 were from RCTs and 3 were from SATs. Compared with the control group in RCTs, serum phosphorus level was significantly increased in the burosumab group (0.52 mg/dL, 95% CI 0.24-0.80 mg/dL). A meta-analysis of the burosumab arms in all trials revealed significant increase in serum phosphorus levels (0.78 mg/dL, 95% CI 0.61-0.96 mg/dL), TmP/GFR (0.86 mg/dL, 95% CI 0.60-1.12 mg/dL), and 1,25-dihydroxyvitamin D level (13.23 pg/mL, 95% CI 4.82-21.64 pg/mL) as well. Changes in secondary events also validated the effects of burosumab treatment. Compared with the control group, in RCTs, the safety profile of burosumab is not much different from the control group. Data of the single-arm combined group demonstrated the incidence of any treatment emergency adverse event (TEAE) and the related TEAE rate were high, but the severity of most adverse events is mild to moderate, and the rate of serious TEAE is low.

CONCLUSION

This study suggests that burosumab can be an option for patients with XLH and did not significantly increase the incidence of adverse events.

Effect of low-calcium and standard-calcium dialysate on serum calcium, phosphorus and full-segment parathyroid hormone in patients on peritoneal dialysis: A retrospective observational study

OBJECTIVE

To investigate the effects of low-calcium and standard-calcium dialysate in patients with chronic kidney disease on peritoneal dialysis, and find out which dialysate has less vascular calcification effect.

METHODS

A total of 141 patients who had undergone peritoneal dialysis (PD) for 2 years in the PD centre from January 2012 to December 2017 were included and divided into two groups according to the calcium concentration of the PD fluid used. There were 79 cases in the low-calcium group, with a dialysate calcium concentration of 1.25 mmol/L and 62 cases in the standard-calcium group, with a dialysate calcium concentration of 1.75 mmol/L. The demographic characteristics and clinical information before initiation of PD were collected and compared between the two groups. Information on the serum calcium, phosphorus and PTH, systolic and diastolic blood pressures and the use of antihypertensive and phosphate-lowering drugs in the second year of dialysis was also collected and compared between the two groups. Vascular calcification was assessed in patients on PD treatment.

RESULTS

The mean serum calcium concentrations before initiation of PD in the low- and standard-calcium groups were 1.94 ± 0.27 and 1.89 ± 0.28 mmol/L, respectively. The serum calcium concentrations after PD were 2.30 ± 0.21 and 2.41 ± 0.23 mmol/L, respectively. After PD, the serum calcium concentration in both groups was significantly increased (p < 0.05). The serum calcium concentration in the low-calcium group after PD treatment was lower than that in the standard-calcium group, and the difference was statistically significant (p < 0.05). Compared with the standard-calcium group, patients in the low-calcium group had significantly higher parathyroid hormone concentrations (p < 0.05). More types of phosphate-lowering drugs were used (59.49%) in the low-calcium group than that in the standard-calcium group (35.48%; p < 0.05). The number of antihypertensive drug usage were also higher in the low-calcium group, and the difference was statistically significant (p < 0.05). As for the vascular calcification effect, the two groups have shown no statistical difference in abdominal aortic calcification rate, carotid arteriosclerosis rate and aortic arch calcification rate (p < 0.05).

CONCLUSION

We found that low-calcium PD fluid may increase the PTH level and the proportion of CKD patients using antihypertensive drug and phosphorus-lowering drug, but the vascular calcification effect of the low and standard calcium PD fluid needs further exploration. This paper provides new evidence for the choice of dialysate for PD, low-calcium dialysate has no outstanding advantages for long term dialysis.

Serum Phosphorus, Serum Bicarbonate, and Renal Function in Relation to Liver CYP1A2 Activity

The liver plays an important role in normal metabolism and physiological functions such as acid-base balance; however, limited epidemiologic studies have investigated how the liver contributes toward acid-base balance using non-invasive biomarkers. We determined associations between serum biomarkers related to acid-base balance and renal function with liver CYP1A2 activity. We used data from 1381 participants of the 2009-2010 National Health and Nutrition Examination Survey (NHANES) with measurements of serum phosphorus, serum bicarbonate, caffeine intake, caffeine metabolites, and estimated glomerular filtration rate (eGFR). Liver CYP1A2 activity was estimated using urine caffeine metabolite indices, which were calculated as the ratio of one of the urine caffeine metabolites (i.e., paraxanthine and 1-methyluric acid) to caffeine intake. We analyzed associations in the whole data set and in different strata of hepatic steatosis index (HSI) based on different cut-points. We found that serum bicarbonate was positively associated with CYP1A2 activity in the whole data set when comparing persons with bicarbonate at Q4 to Q1 (β = 0.18, p = 0.10 for paraxanthine; β = 0.20, p = 0.02 for 1-methyluric acid). Furthermore, serum phosphorus was positively associated with CYP1A2 activity only in the stratum of 30 ≤ HSI < 36. Lastly, low eGFR was significantly associated with lower CYP1A2 activity measured with paraxanthine in the whole dataset and in all the strata with HSI < 42; when comparing eGFR < 60 to eGFR > 90, β estimates ranged from -0.41 to -1.38, p-values ranged from 0.0018 to 0.004. We observed an opposite trend in the highest stratum (HSI ≥ 42). Non-invasive measurements of serum bicarbonate, serum phosphorus, and eGFR have dynamic associations with CYP1A2 activity. These associations depend on the extent of liver damage and the caffeine metabolite used to assess CYP1A2 activity.

The Association between Admission Serum Phosphorus and Preoperative Deep Venous Thrombosis in Geriatric Hip Fracture: A Retrospective Study

OBJECTIVE

This study aimed to evaluate the association between serum phosphorus level and preoperative deep vein thrombosis (DVT) in geriatric hip fractures.

METHODS

Older adults with hip fractures were screened between January 2015 and September 2019. Demographic and clinical characteristics of the patients were collected. Multivariate binary logistic regression and generalized additive models were used to identify the linear and nonlinear associations between serum phosphorus levels and preoperative DVT. Analyses were performed using Empower Stats and R software.

RESULTS

In this study, 1818 patients were included, with an average age of 79.39 ± 6.87. Of these, 30.25% were males, and 580 patients had DVT. The study found that when serum phosphorus was used as a continuous variable, there was a statistically significant difference in the relationship between blood phosphorus and the occurrence of DVT (p < 0.05). Furthermore, we also found curvilinear relationships. Serum phosphorus = 0.71 mmol/L was the inflection point in the curve. When serum phosphorus was <0.71 mmol/L, the serum phosphorus was associated with DVT (OR = 1.64; 95% CI: 1.04-2.59; p = 0.0333). With a 0.1 mmol/L increase, the DVT increased 0.64 times. When phosphorus was >0.71 mmol/L, there was no significant difference in the correlation between serum phosphorus levels and DVT (OR = 1.03; 95% CI: 0.98-1.09; p = 0.186).

CONCLUSION

Serum phosphorus was nonlinearly associated with preoperative DVT in geriatric patients with hip fractures, and serum phosphorus level could be considered a predictor of DVT risk.

Serum Phosphorus and Albumin in Patients Undergoing Peritoneal Dialysis: Interaction and Association With Mortality

Hyperphosphatemia and hypoalbuminemia confer worse clinical outcomes, whether these risk factors interact to predispose to mortality is unclear. In this prospective cohort study, 2,118 patients undergoing incident continuous ambulatory peritoneal dialysis (CAPD) were enrolled and categorized into four groups based on the changing point regarding mortality at 1.5 mmol/L for serum phosphorus and 35 g/L for serum albumin. Risks of all-cause and cardiovascular mortality were examined independently and interactively in overall and subgroups. There was no association between serum phosphorus with all-cause and cardiovascular mortality, but significant interactions (p = 0.02) between phosphorus and albumin existed in overall population. Patients in subgroup with high phosphorus and low albumin were at greater risk of all-cause (HR 1.95, 95%CI 1.27–2.98, p = 0.002) but not cardiovascular mortality (HR 0.37, 95%CI 0.10–1.33, p = 0.13), as compared to those with low phosphorus and high albumin. In contrast, patients with both low parameters had a higher risk of all-cause (HR 1.75, 95%CI 1.22–2.50, p = 0.002) and cardiovascular mortality (HR 1.92, 95%CI 1.07–3.45, p = 0.03). Notably, an elevated risk of both all-cause and cardiovascular mortality was observed in those with low serum albumin, irrespective of phosphorus levels, suggesting low albumin may be useful to identify a higher-risk subgroup of patients undergoing CAPD with different serum phosphorus levels.

Chronic Kidney Disease and Dietary Supplementation: Effects on Inflammation and Oxidative Stress

Chronic kidney disease (CKD) causes an irreversible loss of kidney functioning in dogs. This double-blind case-control study evaluates the efficacy of a dietary supplement, which contains calcium carbonate, calcium lactate-gluconate, chitosan, sodium bicarbonate, Lactobacillus acidophilus D2/CSL, Olea europaea L. extract, and fructooligosaccharides, in dogs in advanced CKD stage. Thirty dogs were enrolled in the study; half were administered the new dietary supplementation for 90 days, while the others were used as controls. Hematologic, biochemical, and urinalysis were performed. This novel dietary supplement mainly reported a good control of uremia, phosphate, acid-base balance, blood pressure, inflammation, and oxidative stress in dogs with advanced stages of CKD.

Higher Serum Phosphorus Is Not an Independent Risk Factor of Mortality in Heart Failure with Reduced Ejection Fraction

Higher serum phosphorus has detrimental health effects. Even high-normal rage sP is associated with worse outcomes. The relationship of serum phosphorus with prognostic markers in heart failure remains unclear. We investigated the association of serum phosphorus with heart failure prognostic factors and risk of mortality related to serum phosphorus. In 1029 stable heart failure patients, we investigated the distribution of markers of more advanced heart failure stage across quintiles of serum phosphorus and estimated the relative risk of mortality in comparison to reference. Higher serum phosphorus levels sP were associated with markers of a worse outcome. The best survival was observed in low-normal serum levels. The unadjusted hazard ratio for mortality increased toward higher phosphorus quintiles but not to lower levels of sP. The correction for age, sex, BMI, percent weight loss, inflammation, kidney function, and LVEF did not modify the risk profile substantially. The adjustment for NYHA, natriuretic peptides, serum sodium, and treatment characteristics broke down the risk relationship completely. A higher serum phosphorus is associated with markers of a more risky profile of heart failure. Elevated serum levels of phosphorus sP does not provide independent prognostic information beyond the strongest markers of the severity of the syndrome. The potential involvement of higher serum phosphorus as a mediator in the pathophysiology of heart failure warrants further study.

Serum phosphorus and calcium levels, and kidney disease progression in immunoglobulin A nephropathy

BACKGROUND

Disorders of calcium and phosphorus metabolism have been reported to be associated with all-cause and cardiovascular mortality in patients requiring long-term dialysis therapy. However, its role in disease progression is not well established in patients without dialysis, especially in immunoglobulin A (IgA) nephropathy. We aim to evaluate the association of serum phosphorus and calcium and progression of IgA nephropathy.

METHODS

We assessed 2567 patients with IgA nephropathy at the First Affiliated Hospital, College of Medicine, Zhejiang University. Serum phosphorus and calcium were collected at the time of kidney biopsy and at each visit. The associations of serum phosphorus and serum calcium with composite kidney disease progression events, defined as 50% estimated glomerular filtration rate (eGFR) decline and kidney failure, were examined using Cox models and restricted cubic splines.

RESULTS

During a median follow-up of 31.9 months, 248 (10%) patients reached composite kidney disease progression events. A linear relationship was observed between serum phosphorus and composite kidney disease progression events. With higher levels of phosphorus, the risk of kidney disease progression events increased {hazard ratio [HR] 3.54 [95% confidence interval (CI) 1.37-9.12]; P = 0.009}. Compared with the first quartile group, the HR of kidney disease progression events was 1.66 (95% CI 0.91-301) for the second quartile, 1.67 (95% CI 0.91-3.08) for the third and 2.62 (95% CI 1.44-4.77) for the fourth (P for trend = 0.002). The association between serum phosphorus and kidney disease progression was detectable [HR 8.94 (95% CI 2.33-34.21); P = 0.001] within the subgroup with eGFR <60 mL/min/1.73 m2 but not among patients with eGFR ≥60 mL/min/1.73 m2 [HR 0.87 (95% CI 0.17-4.44); P = 0.87]. After adjustment for traditional risk factors, a higher level of serum calcium was not associated with kidney disease progression events [HR 0.33 (95% CI 0.10-1.09)].

CONCLUSIONS

Higher serum phosphorus rather than serum calcium was independently associated with kidney disease progression in IgA nephropathy.

Population Pharmacokinetics and Pharmacodynamics of Burosumab in Adult and Pediatric Patients With X-linked Hypophosphatemia

Burosumab is a fully human monoclonal antibody against fibroblast growth factor 23, which has been approved to treat X‐linked hypophosphatemia (XLH) in adult and pediatric patients. The present work describes the pharmacokinetics (PK) of burosumab and the pharmacokinetic‐pharmacodynamic (PK‐PD) relationship between burosumab and serum phosphorus in adult and pediatric patients with XLH. A total of 2844 measurable serum concentrations of burosumab and 6047 measurable serum concentrations of phosphorus in 277 subjects from 9 clinical studies were included in the population PK and PK‐PD modeling. The serum concentration of burosumab following a subcutaneous administration was well described by a population PK model comprising a first‐order absorption, 1‐compartmental distribution, and a linear elimination. The relationship between serum burosumab and serum phosphorus was adequately described by a sigmoid maximal efficacy model. Body weight was the only covariate associated with PK and PK‐PD parameters. No other intrinsic factors affected PK or PK‐PD relationship in adult and pediatric patients with XLH. Further simulations helped to guide the dosing regimen of burosumab in adult and pediatric patients with XLH including age groups with no clinical data.

European hemodialysis patient satisfaction with phosphate binders is associated with serum phosphorus levels: the Dialysis Outcomes and Practice Patterns Study

Background

Hemodialysis (HD) patients are commonly prescribed phosphate binders (PBs) to manage serum phosphorus levels, as hyperphosphatemia is strongly associated with poorer survival. Nonadherence with the PB prescription is associated with elevated serum phosphorus levels. We studied associations between patient satisfaction with their PB and serum phosphorus levels and mortality rates.

Methods

Adult HD patients in Germany, Italy, Spain and the UK in the Dialysis Outcomes and Practice Patterns Study were administered a survey instrument in late 2017. Patients were asked about their satisfaction with their PBs, as measured through three questions (difficulty, inconvenience and dissatisfaction) on a 5-point Likert scale, with each dichotomized into average worst versus good responses. These were used as predictors in linear regression models of continuous serum phosphorus levels and in Cox proportional hazards models of mortality, with adjustments for demographics, comorbidities and laboratory values.

Results

Patients having greater difficulty, inconvenience and dissatisfaction with their PB had higher serum phosphorus levels in adjusted models {+0.21 mg/dL [95% confidence interval (CI) ±0.23], +0.30 (±0.21) and 0.36 (±0.22), respectively}, and higher odds of having serum phosphorus levels ≥6.0 mg/dL. Measures of dissatisfaction were also associated with an elevated risk of mortality, with adjusted hazard ratios of 2.2 (95% CI 1.3–3.6), 1.6 (1.0–2.6) and 1.7 (1.1–2.7), respectively; this association was not strongly affected by adjustment for baseline serum phosphorous level.

Conclusions

Self-reported difficulty, inconvenience and dissatisfaction in taking one’s prescribed PBs were associated with elevated serum phosphorus levels and serum phosphorus levels above clinically meaningful thresholds. While the mechanism for the association with mortality is unclear, patient-reported satisfaction should be considered when attempting to manage patient serum phosphorus levels.

Parathyroid Changes After RAI in Patients With Differentiated Thyroid Carcinoma

OBJECTIVE

The purpose of this study was to investigate parathyroid hormone (PTH), serum calcium, phosphorus, and 25-hydroxyvitamin D (25-OH-VD) changes before and after radioactive iodine (RAI) in differentiated thyroid carcinoma (DTC) patients at different time points.

METHODS

A total of 259 DTC patients who received RAI were prospectively enrolled. We evaluated PTH, serum calcium, phosphorus, and 25-OH-VD levels at baseline pre-RAI, five days, six weeks, and six months post-RAI, respectively. We analyzed the risk factors of hypocalcemia at five days post-RAI.

RESULTS

The mean PTH, serum calcium and phosphorus values decreased five days post-RAI compared with pre-RAI (PTH 4.18 ± 1.23 pmol/L vs. 3.95 ± 1.41 pmol/L; calcium 2.27 ± 0.09 mmol/L vs. 2.20 ± 0.11 mmol/L; phosphorus 1.25 ± 0.17 vs. 0.98 ± 0.20 mmol/L, P < 0.05), and the differences were statistically significant. The mean 25-OH-VD levels did not significantly decrease at five days post-RAI. 21.2% (55/259) of patients had hypocalcemia at five days post-RAI, and all of them were given oral calcium supplements. At six weeks post-RAI, all of the above parameters were higher than those at five days post-RAI. Multivariate regression analysis showed that baseline pre-RAI serum calcium < 2.27 mmol/L, PTH < 4.18 pmol/L and negative ^99mTcO₄^- thyroid imaging were risk factors for hypocalcemia at five days post-RAI.

CONCLUSION

For DTC patients with normal PTH and serum calcium levels at pre-RAI, their PTH, serum calcium, and phosphorus levels decreased at five days post-RAI. About one-fifth of patients could have hypocalcemia at five days post-RAI. Lower baseline pre-RAI serum calcium and PTH levels and negative ^99mTcO₄^- thyroid imaging were risk factors for hypocalcemia five days post-RAI.

Refeeding syndrome in a 12-year-old girl with distal renal tubular acidosis

Distal renal tubular acidosis is a risk factor for refeeding syndrome. Frequent measurement of serum phosphorus levels at the initiation of nutrition and rapid administration of phosphate preparations are required to prevent organ failure.

Blood Metabolic and Estradiol Level of Repeat Breeder and Fertile in Friesian Holstein Cross Breed Cows in the Tropic

BACKGROUND AND OBJECTIVE

The repeat breeding becomes the major reproduction problem in tropic area especially in Indonesia. It relates to blood metabolic and hormonal level. This research was conducted to investigate the level of blood metabolic and estradiol between the repeat breeder Friesian Holstein Cross Breed Cows (FHCB) and the fertile FHCB cows.

MATERIALS AND METHODS

Twenty FHCB cows in luteal phase on 2nd to 3rd lactation were used in this research. Group I consist of 10 repeat breeder FHCB cows and group II consist of 10 fertile FHCB cows. Blood samples were collected through jugular vein prior to feeding. The level of total protein, phosphorus, glucose, cholesterol and estradiol in serum were calculated. The data were analyzed by using the independent samples t-test for comparing the blood metabolic and estradiol between the repeat breeder FHCB cows and the fertile FHCB cows.

RESULTS

The results showed that repeat breeder FHCB cows were found to have lower level of all of the parameters of blood metabolic and estradiol descriptively, however, only the serum cholesterol and serum phosphorus had the significant difference (p<0.05) between the repeat breeder FHCB cows and the fertile FHCB cows.

CONCLUSION

It could be concluded that level of serum cholesterol and serum phosphorus played a role in repeat breeding.

Preliminary analysis of serum electrolytes and body mass index in patients with and without urolithiasis

OBJECTIVES

To compare body mass index (BMI); serum parameters; and urine parameters between patients with and without urolithiasis.

METHODS

Data from 1164 patients admitted to our Department of Urology from January 2011 to July 2013 were retrospectively reviewed; 714 patients (age, 5-87 years; male:female ratio, 1.8:1) exhibited urolithiasis, and 450 patients (age, 12-94 years; male:female ratio, 3.8:1) did not. Blood and urine were collected from patients the morning after hospital admission. Serum and urine parameters were checked by an automatic biochemistry analyzer. Statistical analysis included the Mann-Whitney U test and binary logistic regression.

RESULTS

Serum sodium, potassium, chloride, calcium, phosphorus, and carbon dioxide combining power significantly differed between groups. In male patients, serum sodium, calcium, and phosphorus levels were higher in the urolithiasis group, whereas serum potassium and urine pH levels were lower. In female patients, serum sodium was higher in the urolithiasis group. BMI was higher in the urolithiasis group in all patients, male and female. Respective β-values of serum sodium and BMI in male patients were 0.077 and 0.084; in female patients, these values were 0.119 and 0.102.

CONCLUSIONS

Changes in serum sodium and BMI may be involved in the pathogenesis and treatment of urolithiasis.

Sucroferric Oxyhydroxide in Maintenance Hemodialysis: A Retrospective, Comparative Cohort Study

Rationale & Objective

High pill burden associates with reduced phosphate-binder adherence among dialysis patients, contributing to elevated serum phosphorus levels. We compared the real-world effectiveness of sucroferric oxyhydroxide (SO) versus other phosphate binders in hemodialysis patients over 2 years.

Study Design

Retrospective cohort study.

Setting & Participants

Adult in-center hemodialysis patients prescribed 2 years of uninterrupted SO therapy (maintenance SO; n = 222) compared with patients who discontinued SO therapy (discontinued SO; n = 596) within 90 days of first prescription and switched to other phosphate binder(s) for 2 years.

Exposures

Phosphate binders.

Outcomes

Achievement of serum phosphorus levels ≤ 5.5 mg/dL, pill burden, and hospitalizations.

Analytical Approach

Comparisons were made quarterly (Q1-Q8) between maintenance SO and discontinued SO using Poisson and mixed-effects linear regression.

Results

Patients achieving serum phosphorus levels ≤ 5.5 mg/dL increased from baseline in maintenance SO (46 [20.7%] to a maximum of 104 [46.8%; P < 0.001]) and discontinued SO (96 [16.1%] to a maximum of 201 [33.7%]; P < 0.001). 100 (45%) maintenance SO patients achieved target serum phosphorus levels at Q8 with 3.1 fewer pills per day from baseline (7.5 to 4.4 pills per day; P < 0.001), and 190 (31.9%) discontinued SO patients achieved serum phosphorus levels ≤ 5.5 mg/dL at Q8 with pill burden unchanged (9.1 to 9.3 pills per day; P = 0.3). Among all patients during 2 years, mean serum phosphorus levels decreased by -0.66 mg/dL and -0.45 mg/dL (maintenance SO vs discontinued SO; P = 0.014), and mean pill burden decreased in maintenance SO (8.5 to 5.1 pills per day; P < 0.001), but not in discontinued SO (11.6 to 10.9 pills per day; P = 0.2). The serum phosphorus level decrease with SO was confirmed in a sensitivity analysis including patients with SO therapy for 2 or fewer years. Compared with discontinued SO, maintenance SO patients had 35.6 fewer hospitalizations per 100 patient-years (incidence rate ratio, 0.75 [95% CI, 0.58-0.96]).

Limitations

No data for treatment indication, tolerance, or adherence.

Conclusions

Patients maintained on SO therapy were more likely to achieve target serum phosphorus levels, use 50% fewer phosphate-binder pills per day, and have fewer hospital admissions than patients switched to treatment with other binders.

Education and Protein Supplementation Improve Nutritional Biomarkers among Hypoalbuminemic Peritoneal Dialysis Patients: A Quasi-Experimental Design

Protein-energy wasting is prevalent in peritoneal dialysis patients, which causes a heavy burden for individuals and healthcare systems. We aimed to investigate the effect of nutritional education, and/or protein supplementation on nutritional biomarkers in hypoalbuminemic peritoneal dialysis patients. A quasi-experimental study was conducted in two dialysis centers at Taipei Tzu Chi Hospital and Shin Kong Wu Ho-Su Memorial Hospital. Patients were allocated in three groups including control (n = 12), milk protein (n = 21) and soy protein (n = 20). All patients received dietary guidelines from dietitians and completed 3-day dietary records during monthly visits for consecutive three months. Nutrients were analyzed using Nutritionist Professional software. Blood urea nitrogen (BUN), creatinine, albumin, total protein, hemoglobin, serum calcium, phosphorus, sodium, and potassium were assessed monthly. Total cholesterol and triglycerides were measured every three months. After three-month intervention, protein intake (percent of total calories), and serum albumin were significantly increased in three groups. Protein, phosphorus intake, and BUN were increased in two intervention groups. Total serum protein increased in control and milk protein groups, and creatinine increased the control group. Serum phosphorus was not significantly changed. Nutritional education alone, or combined with protein supplementation, significantly improve protein intake, and nutritional status by increasing serum albumin, but not serum phosphorus in hypoalbuminemic peritoneal dialysis patients.

Serum Phosphorus as a Risk Factor of Metabolic Syndrome in the Elderly in Taiwan: A Large-Population Cohort Study

Background: The impact of serum phosphorus concentration on metabolic syndrome were limited. Therefore, this study aimed to explore the association between the serum phosphorus and incident metabolic syndrome in the elderly in Taiwan. Methods: We included 1491 participants who had health check-ups in the Tri-Service General Hospital for the period 2007 to 2015 and divided them based on age to assess the incidence of metabolic syndrome. We performed the COX regression model to explore the impact of serum phosphorus for metabolic syndrome, diabetes mellitus, and hypertension by an age-specific group. Results: Our result showed that higher serum phosphorus concentration was noted in the elderly in the baseline characteristics. In the group older than 60 years, serum phosphorus concentration was correlated with the incidence of metabolic syndrome (hazard ratios (HR) = 1.39, 95% CI 1.11–1.74) and diabetes mellitus (HR = 1.49, 95% CI 1.15–1.92) after adjustment. We further found the relationship between serum phosphorus and incidence of the components of metabolic syndrome, including higher waist circumference, high-density lipoprotein (HDL), serum triglyceride, and fast glucose. Conclusions: Our study might provide an epidemiological evidence that serum phosphorus was related with the incidence of metabolic syndrome in the elderly in Taiwan.

Urine albumin and serum uric acid are important determinants of serum 25 hydroxyvitamin D level in pre-dialysis chronic kidney disease patients

Low serum 25 hydroxyvitamin D (25 OH D) is common among chronic kidney disease (CKD) patients. This cross-sectional study is looking for the different factors associated with serum 25 OH D among pre-dialysis CKD. 1624 adult stage 3–5 CKD patients were studied beside 200 normal control subjects. All candidates were tested for body mass index (BMI), estimated glomerular filtration rate (eGFR), calcium (Ca), phosphorus (P), parathormone (PTH), 25 OH D, albumin, and uric acid (UA), and urine albumin/creatinine ratio (ACR). Multivariate linear regression analysis was done to determine predictors of 25 OH D. 98.6% of CKD patients have inadequate level of 25 OH D vs 48% of normal subjects. Serum 25 OH D was significantly lower in CKD patients (mean ± S.D = 16.54 ± 5.8 vs 37.79 ± 3.58 ng/mL for CKD vs control group respectively, p < .001). Serum level of 25 OH D has significant positive correlation with Ca (r = 0.337, p < .001), and significant negative correlation with P, PTH, UA, and ACR (r = −0.440, −0. 679, −0.724, and −0.781respectively, p < .001 in all). The independent predictors of 25 OH D were Ca, P, UA, PTH, and ACR (R square = 0.7, β = −0.087, −0.226, −0.313, −0.253, and −0.33 respectively, p < .001 in all). In conclusion, pre-dialysis CKD patients frequently suffer low 25 OH D. Among the different abnormalities related to CKD, urine albumin excretion rate and UA are the most important predictors of 25 OH D in these patients.

Nicotinic Acid as a Phosphate-lowering Agent in Patients with End-stage Renal Disease on Maintenance Hemodialysis: A Single-center Prospective Study

Background

Hyperphosphatemia increases the risk of mortality and morbidity in patients with end-stage renal disease (ESRD). In addition to dietary restriction and renal replacement therapy, phosphorus-binding agents are the mainstay of treatment. While the use of calcium-containing binders has certain limitations, non-calcium-based binders are expensive and not readily available in developing countries. Previous studies on nicotinic acid as a phosphorus-lowering agent have limited data. In this study, we evaluated the efficacy of nicotinic acid in patients with ESRD on hemodialysis (HD) in Pakistan.

Methods

Forty-five patients with ESRD on maintenance HD having serum phosphorus levels >5.5 mg/dL were recruited. Nicotinic acid 250 mg was administered with food for four weeks. All patients with serum phosphorus levels <8 mg/dL were placed on a twice-daily regimen while the rest received it three times a day with meals. Patients were assessed at the beginning and end of the study with serum phosphorus levels.

Results

Mean age of the sample population was 44.6 ± 13.9 years and 57.8% of participants were male. Serum phosphorus level before treatment ranged from 5.6 to 10.8 mg/dL (mean, 6.91 ± 1.33). After nicotinic acid therapy, it ranged from 2.60 to 8.70 mg/dL (mean, 5.82 ± 1.40). Mean decrease in serum phosphorus levels with nicotinic acid after one month of treatment was 1.08 ± 1.16 mg/dL (p-value <0.001).

Conclusion

Nicotinic acid is effective in lowering serum phosphorus levels in patients with ESRD who are under renal replacement therapy with maintenance HD.

Relationship of Estimated GFR and Albuminuria to Concurrent Laboratory Abnormalities: An Individual Participant Data Meta-analysis in a Global Consortium

RATIONALE & OBJECTIVE

Chronic kidney disease (CKD) is complicated by abnormalities that reflect disruption in filtration, tubular, and endocrine functions of the kidney. Our aim was to explore the relationship of specific laboratory result abnormalities and hypertension with the estimated glomerular filtration rate (eGFR) and albuminuria CKD staging framework.

STUDY DESIGN

Cross-sectional individual participant-level analyses in a global consortium.

SETTING & STUDY POPULATIONS

17 CKD and 38 general population and high-risk cohorts.

SELECTION CRITERIA FOR STUDIES

Cohorts in the CKD Prognosis Consortium with data for eGFR and albuminuria, as well as a measurement of hemoglobin, bicarbonate, phosphorus, parathyroid hormone, potassium, or calcium, or hypertension.

DATA EXTRACTION

Data were obtained and analyzed between July 2015 and January 2018.

ANALYTICAL APPROACH

We modeled the association of eGFR and albuminuria with hemoglobin, bicarbonate, phosphorus, parathyroid hormone, potassium, and calcium values using linear regression and with hypertension and categorical definitions of each abnormality using logistic regression. Results were pooled using random-effects meta-analyses.

RESULTS

The CKD cohorts (n=254,666 participants) were 27% women and 10% black, with a mean age of 69 (SD, 12) years. The general population/high-risk cohorts (n=1,758,334) were 50% women and 2% black, with a mean age of 50 (16) years. There was a strong graded association between lower eGFR and all laboratory result abnormalities (ORs ranging from 3.27 [95% CI, 2.68-3.97] to 8.91 [95% CI, 7.22-10.99] comparing eGFRs of 15 to 29 with eGFRs of 45 to 59mL/min/1.73m2), whereas albuminuria had equivocal or weak associations with abnormalities (ORs ranging from 0.77 [95% CI, 0.60-0.99] to 1.92 [95% CI, 1.65-2.24] comparing urinary albumin-creatinine ratio > 300 vs < 30mg/g).

LIMITATIONS

Variations in study era, health care delivery system, typical diet, and laboratory assays.

CONCLUSIONS

Lower eGFR was strongly associated with higher odds of multiple laboratory result abnormalities. Knowledge of risk associations might help guide management in the heterogeneous group of patients with CKD.

Dietary Phosphate and the Forgotten Kidney Patient: A Critical Need for FDA Regulatory Action

Careful dietary management that reduces high phosphate intake is recommended to slow the progression of chronic kidney disease (CKD) and prevent complications of CKD and may help reduce chronic disease risks such as incident CKD associated with high phosphate intake in the healthy general population. For patients treated with maintenance dialysis, control of serum phosphorus levels is considered a marker of good care and requires a coordinated plan that limits dietary phosphate intake, uses oral phosphate binders, and provides an adequate dialysis prescription. Even with traditional thrice-weekly hemodialysis or peritoneal dialysis, use of phosphate binders, and a concerted effort to limit dietary phosphate intake, adequately controlled serum phosphorus levels are not possible in all dialysis patients. Efforts to limit phosphate intake are thwarted by the underestimated and unquantified phosphate content of processed foods and some medications due to the hidden presence of phosphate additives or excipients added during processing or drug formulation. Effectively limiting phosphate intake could potentially be achieved through simple US Food and Drug Administration regulatory actions. Mandatory labeling of phosphate content on all packaged foods and drugs would enable identification of healthy low-phosphate foods and medications and permit critically important control of total phosphate intake. Simple changes in regulatory policy and labeling are warranted and would enable better management of dietary intake of phosphate at all stages of kidney disease, as well as potentially reduced health risks in the general population.

Changes With Lanthanum Carbonate, Calcium Acetate, and Phosphorus Restriction in CKD: A Randomized Controlled Trial

INTRODUCTION

Abnormal phosphorus homeostasis develops early in chronic kidney disease (CKD). It is unclear if its correction results in improved clinical outcomes in non-dialysis dependent CKD.

METHODS

We conducted a randomized controlled, parallel design clinical trial in 120 patients with estimated glomerular filtration rate 15 to 59 ml/min per 1.73 m2 and abnormal phosphorus homeostasis (serum phosphorus >4.6 mg/dl, parathyroid hormone [PTH] >70 pg/ml or tubular reabsorption of phosphorus [TRP] <80%). Patients were randomized to open-label lanthanum carbonate versus calcium acetate versus dietary intervention over 1 year. The co-primary outcomes were month 12 (vs. baseline) biochemical (serum phosphorus, TRP, PTH, calcium, bone-specific alkaline phosphatase [bALP], and fibroblast growth factor 23 [FGF23]) and vascular parameters (coronary artery calcium score, pulse wave velocity, and endothelial dysfunction) in all patients. Secondary outcomes were between-treatment differences in change for each parameter between month 12 and baseline. All analyses were intention to treat.

RESULTS

Baseline characteristics were similar in the 3 groups. A total of 107 patients (89%) completed 12 months of follow-up. Differences were not significant at month 12 (vs. baseline) for any of the outcomes except bALP (median [25th, 75th] percentile at month 12 versus baseline: 13.8 [10.6, 17.6] vs. 15.8 [12.1, 21.1], P < .001) and FGF23 (132 [99, 216] vs. 133 [86, 189], P = .002). Changes for all outcomes were similar in the 3 arms except for PTH, which was suppressed more effectively by calcium acetate (P < .001).

CONCLUSION

A 1-year intervention to limit phosphorus absorption using dietary restriction or 2 different phosphorus binders resulted in decreased bALP suggesting improved bone turnover, but no other significant changes in biochemical or vascular parameters in patients with CKD stage 3/4. (ClinicalTrials.gov: NCT01357317).

A novel variant of osteogenesis imperfecta type IV and low serum phosphorus level caused by a Val94Asp mutation in COL1A1

Osteogenesis imperfecta (OI) is a rare congenital disorder characterized by bone fragility and fractures, and associated with bone deformity, short stature, dentin, ligament and blue-gray eye sclera. OI is caused by a heterozygous mutation in collagen α-1(I) chain (COL1A1) or collagen α-2(I) chain (COL1A2) genes that encode α chains of type I collagen. Collagen α chain peptide contains an N-propeptide, which has a role in assembly and processing of collagen. Point mutations in the N-propeptide domain appear to trigger OI. In the present study, a novel heterozygous missense mutation, c.281T>A (p.Val94Asp), was identified in the von Willebrand C domain of N-terminal of type I collagen in an individual with type IV OI. The majority of N-terminal mutations are associated with OI/Ehlers-Danlos syndrome (EDS); however, in the present study, the affected individual did not suffer from EDS and the level of serum phosphorus of the patient was low (0.67 mmol/l). A number of clinical phenotypes were observed at the same variation site or in the same region on the polypeptide chain of COL1A, which suggests that additional genetic and environmental factors may influence the severity of OI. The present study may provide insight into the phenotype-genotype association in collagen-associated diseases and improve clinical diagnosis of OI.

Sevelamer hydrochloride suppresses proliferation of parathyroid cells during the early phase of chronic renal failure in rats

AIM

We examined the effects of sevelamer on parathyroid cell proliferation and secondary hyperparathyroidism in rats following induction of early-phase of chronic renal failure (CRF) by unilateral ureteral obstruction (UUO).

METHODS

For 5 days, rats in the control group received normal food, rats in the sevelamer group (SH) received control food plus 5% sevelamer, and rats in the low protein group (LP) received low protein food. Five rats of each group were killed at baseline (day 0). All other rats were given UUO, and five rats per group were killed on days 3, 7, 14, and 28 after UUO. Changes in body weight, serum phosphorus, calcium, intact-parathyroid hormone (i-PTH), creatinine (SCr), creatinine clearance rate (CCR), blood urea nitrogen (BUN), and 24-h urinary phosphorus were determined. Parathyroid tissues were removed for histological examination of proliferating cell nuclear antigen-positive (PCNA+) cells.

RESULTS

Measurement of body weight, BUN, and SCr in the controls indicated successful establishment of this model of early-phase CRF. The controls also had remarkable proliferation of PCNA+ cells beginning on day 3, but this did not occur in the SH or LP groups. After 28 days, serum phosphorus had decreased more in the SH and LP groups than in the control group, and phosphorus excretion was much greater in the control group than in the SH and LP groups. The three groups had similar increases in serum i-PTH.

CONCLUSION

Sevelamer rapidly lowered the serum phosphorus and inhibited the proliferation of PCNA+ cells in this experimental model of early-phase CRF.

Dietary Food-Additive Phosphate and Human Health Outcomes

Dietary intake of phosphorus is required for human health, and dietary reference intakes for phosphorus have been established. Food-grade phosphates are used as additives to provide a wide range of technical functions in food production. Phosphates are often the most efficient ingredients to provide the required functionality in many applications, and in some cases, there are not effective and approved alternatives. However, many investigators have expressed concern about the quantities of phosphorus and food-additive phosphate present in the diets of many populations. This paper presents the outcome of an extensive review of 110 primary research articles focused on identifying evidence that substantiates or refutes associations of total dietary phosphorus and food-additive phosphate intake with health and disease in humans. The lack of conclusive evidence prevented the drawing of firm conclusions about the safety and possible risks of food-additive phosphate in the general population, which is consonant with the overall assessments of authoritative institutions who have concluded that available data are insufficient to make the required determinations. Despite the inadequacy of the evidence currently available, many of the authors of the publications reviewed for this paper expressed concerns about the quantities of phosphorus and food-additive phosphate in the diets of the populations and subpopulations they studied. At the same time, most of these authors offered only qualified conclusions and expressed themselves tentatively. In addition, authors of primary research publications, authors of review articles, and authoritative institutions have called for the conduct of further research.

Serum Phosphorus and Risk of Cardiovascular Disease, All-Cause Mortality, or Graft Failure in Kidney Transplant Recipients: An Ancillary Study of the FAVORIT Trial Cohort

BACKGROUND

Mild hyperphosphatemia is a putative risk factor for cardiovascular disease [CVD], loss of kidney function, and mortality. Very limited data are available from sizable multicenter kidney transplant recipient (KTR) cohorts assessing the potential relationships between serum phosphorus levels and the development of CVD outcomes, transplant failure, or all-cause mortality.

STUDY DESIGN

Cohort study.

SETTING & PARTICIPANTS

The Folic Acid for Vascular Outcome Reduction in Transplantation (FAVORIT) Trial, a large, multicenter, multiethnic, controlled clinical trial that provided definitive evidence that high-dose vitamin B-based lowering of plasma homocysteine levels did not reduce CVD events, transplant failure, or total mortality in stable KTRs.

PREDICTOR

Serum phosphorus levels were determined in 3,138 FAVORIT trial participants at randomization.

RESULTS

During a median follow-up of 4.0 years, the cohort had 436 CVD events, 238 transplant failures, and 348 deaths. Proportional hazards modeling revealed that each 1-mg/dL higher serum phosphorus level was not associated with a significant increase in CVD risk (HR, 1.06; 95% CI, 0.92-1.22), but increased transplant failure (HR, 1.36; 95% CI, 1.15-1.62) and total mortality risk associations (HR, 1.21; 95% CI, 1.04-1.40) when adjusted for treatment allocation, traditional CVD risk factors, kidney measures, type of kidney transplant, transplant vintage, and use of calcineurin inhibitors, steroids, or lipid-lowering drugs. These associations were strengthened in models without kidney measures: CVD (HR, 1.14; 95% CI, 1.00-1.31), transplant failure (HR, 1.72; 95% CI, 1.46-2.01), and mortality (HR, 1.34; 95% CI, 1.15-1.54).

LIMITATIONS

We lacked data for concentrations of parathyroid hormone, fibroblast growth factor 23, or vitamin D metabolites.

CONCLUSIONS

Serum phosphorus level is marginally associated with CVD and more strongly associated with transplant failure and total mortality in long-term KTRs. A randomized controlled clinical trial in KTRs that assesses the potential impact of phosphorus-lowering therapy on these hard outcomes may be warranted.

Phosphorus Regulation in Chronic Kidney Disease

Serum phosphorus levels stay relatively constant through the influence of multiple factors-such as parathyroid hormone, fibroblast growth factor 23, and vitamin D-on the kidney, bone, and digestive system. Whereas normal serum phosphorus ranges between 3 mg/dL to 4.5 mg/dL, large cross-sectional studies have shown that even people with normal kidney function are sometimes found to have levels ranging between 1.6 mg/dL and 6.2 mg/dL. While this may partially be due to diet and the factors mentioned above, total understanding of these atypical ranges of serum phosphorus remains uncertain. Risks for bone disease are high in people aged 50 and older, and this group comprises a large proportion of people who also have chronic kidney disease. Consuming diets low in calcium and high in phosphorus, especially foods with phosphate additives, further exacerbates bone turnover. Existing bone disease increases the risk for high serum phosphorus, and higher serum phosphorus has been associated with increased adverse events and cardiovascular-related mortality both in people with chronic kidney disease and in those with no evidence of disease. Once kidney function has deteriorated to end-stage disease (Stage 5), maintaining normal serum phosphorus requires dietary restrictions, phosphate-binding medications, and dialysis. Even so, normal serum phosphorus remains elusive in many patients with Stage 5 kidney disease, and researchers are testing novel targets that may inhibit intestinal transport of phosphorus to achieve better phosphate control. Protecting and monitoring bone health should also aid in controlling serum phosphorus as kidney disease advances.

Pharmacokinetics and pharmacodynamics of a human monoclonal anti-FGF23 antibody (KRN23) in the first multiple ascending-dose trial treating adults with X-linked hypophosphatemia

In X-linked hypophosphatemia (XLH), serum fibroblast growth factor 23 (FGF23) is increased and results in reduced renal maximum threshold for phosphate reabsorption (TmP), reduced serum inorganic phosphorus (Pi), and inappropriately low normal serum 1,25 dihydroxyvitamin D (1,25[OH]2 D) concentration, with subsequent development of rickets or osteomalacia. KRN23 is a recombinant human IgG1 monoclonal antibody that binds to FGF23 and blocks its activity. Up to 4 doses of KRN23 were administered subcutaneously every 28 days to 28 adults with XLH. Mean ± standard deviation KRN23 doses administered were 0.05, 0.10 ± 0.01, 0.28 ± 0.06, and 0.48 ± 0.16 mg/kg. The mean time to reach maximum serum KRN23 levels was 7.0 to 8.5 days. The mean KRN23 half-life was 16.4 days. The mean area under the concentration-time curve (AUCn ) for each dosing interval increased proportionally with increases in KRN23 dose. The mean intersubject variability in AUCn ranged from 30% to 37%. The area under the effect concentration-time curve (AUECn ) for change from baseline in TmP per glomerular filtration rate, serum Pi, 1,25(OH)2 D, and bone markers for each dosing interval increased linearly with increases in KRN23 AUCn . Linear correlation between serum KRN23 concentrations and increase in serum Pi support KRN23 dose adjustments based on predose serum Pi concentration.

Serum phosphorus and association with anemia among a large diverse population with and without chronic kidney disease

BACKGROUND

We hypothesized that phosphorus has an effect on anemia in both normal kidney function and early chronic kidney disease (CKD). We sought to determine whether higher phosphorus levels are associated with anemia in a large diverse population without CKD and early CKD.

METHODS

This study is a historical population-based study within the Kaiser Permanente Southern California health system (1 January 1998 to 31 December 2013) among individuals aged 18 years and older with estimated glomerular filtration rate >30 mL/min/1.73 m(2) and measurements of serum phosphorus, creatinine and hemoglobin. Individuals were excluded if they had secondary causes of anemia. Odds ratio (OR) estimated for moderate anemia defined as hemoglobin <11 g/dL for both sexes. Mild anemia was defined as <12 g/dL (females) and <13 g/dL (males).

RESULTS

Among 155 974 individuals, 4.1% had moderate anemia and 12.9% had mild anemia. Serum phosphorus levels ≥3.5 mg/dL were associated with both mild and moderate anemia. Moderate anemia OR (95% confidence interval) was 1.16 (1.04-1.29) for every 0.5 mg/dL phosphorus increase and 1.26 (1.07-1.48) in the highest versus middle phosphorus tertile. Additional independent anemia risk factors, including female sex, Asian race, diabetes, low albumin and low iron saturation, were observed, but did not alter the anemia-phosphorus association.

CONCLUSIONS

Higher phosphorus levels were associated with a greater likelihood for anemia in a population with early CKD and normal kidney function. Phosphorus may be a biomarker for anemia and may affect aspects of hematopoiesis.

Joint Effect of Hypertension and Elevated Serum Phosphorus on the Risk of Mortality in National Health and Nutrition Examination Survey-III

Background

Elevated serum phosphorus might aggravate the effect of hypertension on mortality. The objective of this study was to examine the joint effect of hypertension and serum phosphorus on the risk of mortality.

Methods and Results

A large prospective (n=15 833), population-based cohort of participants from the National Health and Nutritional Examination Survey III was examined to test potential synergism between hypertension, elevated serum phosphorus, and the risk of mortality. Interaction on additive scale and multiplicative scale was estimated. After a median follow-up of 14.3 years, 1691 cases of cardiovascular mortality and 3875 cases of all-cause mortality were identified. Interaction was observed between hypertension and elevated serum phosphorus on the additive scale for cardiovascular mortality (relative excess risk due to interaction, 0.99, 95% CI: 0.06; 1.92, adjusted for age, gender, race, and estimated glomerular filtration rate). No statistically significant interaction was found between hypertension and serum phosphorus for all-cause mortality on the additive scale. No significant interaction was detected on the multiplicative scale. In sensitivity analysis, excluding participants who died in first 2 years and adjustment for additional confounders resulted in essentially similar findings.

Conclusions

The joint effect of hypertension and elevated serum phosphorus was larger than the sum of the independent effects on cardiovascular mortality but not on all-cause mortality. Future studies should investigate whether controlling elevated serum phosphorus in hypertensive individuals helps in prevention of extra risk of cardiovascular mortality.

Association between serum calcium and phosphorus concentrations with non-alcoholic fatty liver disease in Korean population

BACKGROUND AND AIM

Growing evidence suggests that non-alcoholic fatty liver disease (NAFLD) is interrelated with renal dysfunction and disturbed bone metabolism, both of which play a key role in calcium and phosphorus homeostasis. We investigated the association between NAFLD and serum calcium and phosphorus levels in Korean subjects.

METHODS

We performed a cross-sectional analysis of 16,592 subjects undergoing a general health checkup. NAFLD was assessed based on ultrasonographically detected fatty liver in the absence of excessive alcohol consumption and other causes of liver disease.

RESULTS

The proportion of the population with fatty liver detected by ultrasonography was 43.2% for males and 17.6% for females. We observed that a higher serum albumin-corrected calcium (Ca(c)) level was associated with smoking, hypertension, and unfavorable metabolic parameters in both genders, but the serum phosphorus levels showed an inconsistent correlation with metabolic abnormalities. After adjusting for age, gender, waist circumference, body mass index, smoking status, exercise, diabetes, hypertension, lipid profiles, and renal function, serum Cac , phosphorus, and Cac -phosphorus products were independent risk factors for fatty liver (odds ratio [OR]: 1.71, 95% confidence interval [CI]: 1.49-1.95, P < 0.001; OR: 1.34, 95% CI: 1.22-1.48, P < 0.001; and OR: 1.20, 95% CI: 1.14-1.26, P < 0.001, respectively), and the risk of fatty liver increased in a graded manner over the quartiles.

CONCLUSION

Serum calcium and phosphorus levels are significantly associated with NAFLD. Further investigation is needed to verify whether calcium and phosphorus levels indicate a higher risk of NAFLD.

A randomized, double-blind, placebo-controlled, dose-ranging study using Genz-644470 and sevelamer carbonate in hyperphosphatemic chronic kidney disease patients on hemodialysis

Background

Genz-644470 is a new, nonabsorbed phosphate binding polymer. In an in vitro competitive phosphate binding assay, Genz-644470 bound significantly more phosphate per gram than sevelamer. As a consequence, this clinical study evaluated the ability of Genz-644470 to lower serum phosphorus in patients on hemodialysis and compared serum phosphorus lowering of Genz-644470 with sevelamer carbonate and placebo. Because three different fixed doses of Genz-644470 and sevelamer carbonate were used, phosphate-lowering dose-responses of each agent were also analyzed.

Methods

A randomized, double-blind, dose-ranging study was conducted. After a 2-week phosphate binder washout, 349 hyperphosphatemic (serum phosphorus >5.5 mg/dL) hemodialysis patients were randomized to one of seven fixed-dose groups: placebo, Genz-644470 2.4 g/day, Genz-644470 4.8 g/day, Genz-644470 7.2 g/day, sevelamer carbonate 2.4 g/day, sevelamer carbonate 4.8 g/day, or sevelamer carbonate 7.2 g/day. Indicated total daily doses were administered in fixed divided doses three times a day with meals for 3 weeks. The change in serum phosphorus during the treatment period and its dose-response patterns were assessed.

Results

Dose-dependent reductions in serum phosphorus were observed with both Genz-644470 and sevelamer carbonate. Serum phosphorus-lowering responses to fixed doses of sevelamer carbonate and Genz-644470 were enhanced in a roughly linear fashion with increasing doses over a threefold range after 3 weeks of treatment. Genz-644470 did not show any advantage in phosphorus lowering per gram of binder compared with sevelamer carbonate. Overall toler-ability was similar between active treatment groups. The tolerability of sevelamer carbonate was consistent with prior studies and with the established safety profile of sevelamer.

Conclusion

Both Genz-644470 and sevelamer carbonate effectively lowered serum phosphate levels in a dose-dependent fashion in patients with chronic kidney disease on hemodialysis. However, Genz-644470 did not provide any advantage over sevelamer carbonate in phosphate lowering in vivo, as had been demonstrated in vitro.

Magnesium deficiency increases serum fibroblast growth factor-23 levels in rats

A magnesium (Mg)-deficient diet results in decreased serum phosphorus (P) levels and increased urinary P excretion; however, the mechanisms responsible for these effects are unclear. Fibroblast growth factor-23 (FGF-23) is a potent regulator of P homeostasis. To determine the mechanisms responsible for the change in serum levels and urinary excretion of P with Mg deficiency, the present study examined the effects of Mg deficiency on serum FGF-23 levels. Male rats were randomized by weight into two groups and fed a control diet (Mg concentration: 0.05%) or a Mg-deficient diet (Mg concentration: Mg-free) for 21 days. Serum P levels in rats fed the Mg-deficient diet were significantly lower than in rats fed the control diet. Furthermore, urinary P excretion was significantly higher in rats fed the Mg-deficient diet compared to rats fed the control diet. Conversely, the tubular reabsorption rate of P was significantly lower in rats fed the Mg-deficient diet than in the controls. Serum FGF-23 levels in rats fed the Mg-deficient diet were significantly higher than those in animals fed the control diet. The results from the present study indicate that 1) Mg deficiency increases serum FGF-23 levels; and 2) Mg deficiency causes increased urinary P excretion via inhibition of renal P reabsorption, resulting in a lowering of serum P levels. Moreover, we suggest that the high serum FGF-23 levels induced by Mg deficiency contribute to the decrease in renal P reabsorption.

Serum phosphorus reduction in dialysis patients treated with cinacalcet for secondary hyperparathyroidism results mainly from parathyroid hormone reduction

Background

The calcimimetic cinacalcet lowers parathyroid hormone (PTH), calcium (Ca) and phosphorus (P) in dialysis patients with secondary hyperparathyroidism (SHPT). We explored serum P changes in dialysis patients treated with cinacalcet, while controlling for vitamin D sterol and phosphate binder (PB) changes, based on data from the pan-European observational study ECHO.

Methods

Patients were categorized by serum P change (decreased/unchanged/increased) at 12 months after starting cinacalcet and subcategorized by vitamin D sterol and PB dose changes (decreased/unchanged/increased). The impact of PTH, Ca and P, and vitamin D sterol, PB and cinacalcet doses (absolute values and/or change) was evaluated. Predictors of P change were explored using univariate and multivariate general linear models (GLM) and logistic regression analysis.

Results

At Month 12, 661 (41%) of 1607 patients had decreased, 61 (4%) unchanged and 400 (25%) increased serum P, while 485 patients had missing data. In 45% of the patients with serum P reduction, vitamin D was either increased or unchanged and P binders decreased or unchanged. PTH was a key predictor of serum P reduction, with an estimated 3% decrease in P per 10% reduction in PTH. Changes in vitamin D sterol and PB doses were not generally significant factors in GLM and regression analyses.

Conclusions

The serum P reduction observed in a significant proportion of dialysis patients after adding cinacalcet to an existing therapeutic regimen for SHPT appears to result mainly from PTH reduction, rather than from changes in vitamin D sterol or PB doses. Financial support for the ECHO study was provided by Amgen.