The rationale for intermittent administration of PTH in the management of mineral and bone disorder of chronic kidney disease

A major complication of chronic kidney disease is the derangement of mineral metabolism, leading to increased risk of fractures and cardiovascular mortality. Current therapeutic regimens are focused on reducing parathyroid hormone levels caused by secondary hyperparathyroidism, and the active vitamin D metabolite l,25(OH)2D, with limited success. It may be a more effective approach, however, if we could target the delayed response of parathyroid hormone in the early retention of phosphate following loss of renal function.We propose intermittent administration (even in stage 2 chronic kidney disease) of parathyroid hormone, known for its bone anabolic effects compared to the catabolic effects of the continuously elevated parathyroid hormone associated with the hyperparathyroid state, to mitigate the retention of phosphate. This approach may prevent the compensatory responses of the other two major calcium- and phosphate-regulating hormones (FGF-23 and l,25(OH)2D) that lead to further worsening of the derangement of mineral metabolism.In addition to its strong theoretical basis, there are data supporting the need for further research focused on the use of intermittent parathyroid hormone in the management of chronic kidney disease-mineral bone disorder.

Association between serum phosphate levels and anemia in non-dialysis patients with chronic kidney disease: a retrospective cross-sectional study from the Fuji City CKD Network

BACKGROUND

Patients with chronic kidney disease (CKD) present high mortality and morbidity rates despite the availability of various therapies. Although CKD-mineral and bone disorder (MBD) and renal anemia are important factors in patients with CKD, only few studies have analyzed the relationship between them. Therefore, this study aimed to evaluate the relationship between CKD-MBD and anemia in patients with CKD who did not receive erythropoiesis-stimulating agent or iron therapies.

METHODS

This retrospective cross-sectional study included patients with CKD aged ≥ 20 years with estimated glomerular filtration rate (eGFR) categories G2a to G5 who were referred to the Fuji City General Hospital between April 2018 and July 2019. The exclusion criterion was ongoing treatment for CKD-MBD and/or anemia.

RESULTS

The data of 300 patients with CKD were analyzed in this study. The median age of patients was 71 (range, 56.5-79) years. The median eGFR was 34 (range, 20-48) mL/min/1.73 m2, and the mean hemoglobin (Hb) level was 12.7 g/dL (standard deviation, 2.3), which decreased as the CKD stage increased. In a multivariate linear regression analysis of anemia-related factors, including age, renal function (eGFR), nutritional status, inflammation, and iron dynamics (serum iron level, total iron-binding capacity, ferritin levels), the serum phosphate levels were significantly associated with the Hb levels (coefficient [95% confidence interval], -0.73 [-1.1, -0.35]; P < 0.001). Subgroup analysis revealed a robust association between serum phosphate levels and Hb levels in the low-ferritin (coefficient [95% confidence interval], -0.94 [-1.53, -0.35]; P = 0.002) and advanced CKD groups (coefficient [95% confidence interval], -0.89 [-1.37, -0.41]; P < 0.001).

CONCLUSIONS

We found an association between high serum phosphate levels and low Hb levels in patients with CKD not receiving treatment for anemia. These results underscore the possibility of a mechanistic overlap between CKD-MBD and anemia.

Sustained Efficacy and Safety of Burosumab, a Monoclonal Antibody to FGF23, in Children With X-Linked Hypophosphatemia

PURPOSE

In X-linked hypophosphatemia (XLH), excess fibroblast growth factor-23 causes hypophosphatemia and low calcitriol, leading to musculoskeletal disease with clinical consequences. XLH treatment options include conventional oral phosphate with active vitamin D, or monotherapy with burosumab, a monoclonal antibody approved to treat children and adults with XLH. We have previously reported outcomes up to 64 weeks, and here we report safety and efficacy follow-up results up to 160 weeks from an open-label, multicenter, randomized, dose-finding trial of burosumab for 5- to 12-year-old children with XLH.

METHODS

After 1 week of conventional therapy washout, patients were randomized 1:1 to burosumab every 2 weeks (Q2W) or every 4 weeks (Q4W) for 64 weeks, with dosing titrated based on fasting serum phosphorus levels between baseline and week 16. From week 66 to week 160, all patients received Q2W burosumab.

RESULTS

Twenty-six children were randomized initially into each Q2W and Q4W group and all completed treatment to week 160. In 41 children with open distal femoral and proximal tibial growth plates (from both treatment groups), total Rickets Severity Score significantly decreased by 0.9 ± 0.1 (least squares mean ± SE; P < 0.0001) from baseline to week 160. Fasting serum phosphorus increases were sustained by burosumab therapy throughout the study, with an overall population mean (SD) of 3.35 (0.39) mg/dL, within the pediatric normal range (3.2-6.1 mg/dL) at week 160 (mean change from baseline P < 0.0001). Most adverse events were mild to moderate in severity.

MAIN CONCLUSIONS

In children with XLH, burosumab administration for 160 weeks improved phosphate homeostasis and rickets and was well-tolerated. Long-term safety was consistent with the reported safety profile of burosumab.

CLINICALTRIALS.GOV

NCT02163577.

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.

Serum Phosphate: A Neglected Test in the Clinical Management of Primary Hyperparathyroidism

BACKGROUND

Although the inverse correlation between serum PTH and phosphate (P) levels in patients with primary hyperparathyroidism (PHPT) is well known, the relationship between P levels and the clinical picture of the disease has not been well investigated. This was thus the aim of this paper.

PATIENTS

A total of 472 consecutive patients with PHPT attending our center were retrospectively evaluated at diagnosis.

RESULTS

P levels lower than 2.5 mg/dL (HypoP) were found in 198/472 patients (41.9%). HypoP was mild (2-2.5 mg/dL), moderate (1-1.9 mg/dL), and severe (<1 mg/dL) in 168 (84.9%), 30 (15.1%), and 0 cases, respectively. P levels were lower in males than females. Patients with more severe bone density impairment at the radial (but not the vertebral or femoral) site had P levels significantly lower than other patients. PHPT severity was worse in HypoP patients, both clinically (higher prevalence of renal stones, but not of osteoporosis) and biochemically (higher serum calcium and PTH levels). All patients in the moderate HypoP group were either symptomatic or asymptomatic reaching surgical indication according to the latest guidelines.

CONCLUSIONS

We observed a relationship between P levels and biochemical and clinical features of PHPT severity. In asymptomatic PHPT patients, even moderate HypoP is predictive of surgical indication, regardless of age and hypercalcemia severity.

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.

Phosphaturic mesenchymal tumor: An underdiagnosed rare entity

Tumor-induced osteomalacia is a paraneoplastic syndrome resulting in renal phosphate wasting and decreased bone mineralization. Phosphaturic mesenchymal tumors represent a rare etiology of tumor-induced osteomalacia. They are exceptionally rare, probably accounting for < 0.01% of all soft tissue tumors. Most PMTs present as small inapparent lesions that require very careful clinical examination and radionucleotide scan for localization. Here we describe a case in a 65 years old woman with recurrent multiple bone fractures and subsequent detection of a tumor involving right femur and adjacent soft tissue, low phosphate level and elevated serum Fibroblast growth factor-23 (FGF-23).

A Reference Range for Plasma Levels of Inorganic Pyrophosphate in Children Using the ATP Sulfurylase Method

PURPOSE

Generalized arterial calcification of infancy, pseudoxanthoma elasticum, autosomal recessive hypophosphatemic rickets type 2, and hypophosphatasia are rare inherited disorders associated with altered plasma levels of inorganic pyrophosphate (PPi). In this study, we aimed to establish a reference range for plasma PPi in the pediatric population, which would be essential to support its use as a biomarker in children with mineralization disorders.

METHODS

Plasma samples were collected from 200 children aged 1 day to 18 years who underwent blood testing for medical conditions not affecting plasma PPi levels. PPi was measured in proband plasma utilizing a validated adenosine triphosphate (ATP) sulfurylase method.

RESULTS

The analytical sensitivity of the ATP sulfurylase assay consisted of 0.15 to 10 µM PPi. Inter- and intra-assay coefficients of variability on identical samples were below 10%. The standard range of PPi in the blood plasma of children and adolescents aged 0 to 18 years was calculated as 2.36 to 4.44 µM, with a median of 3.17 µM, with no difference between male and female probands. PPi plasma levels did not differ significantly in different pediatric age groups.

MAIN CONCLUSIONS

Our results yielded no noteworthy discrepancy to the reported standard range of plasma PPi in adults (2-5 µM). We propose the described ATP sulfurylase method as a diagnostic tool to measure PPi levels in plasma as a biomarker in the pediatric population.

Hypophosphatemia in acute liver failure of a broad range of etiologies is associated with phosphaturia without kidney damage or phosphatonin elevation

Hypophosphatemia is a common and dangerous complication of acute liver failure (ALF) of various etiologies. While various mechanisms for ALF-associated hypophosphatemia have been proposed including high phosphate uptake into regenerating hepatocytes, acetaminophen (APAP)-associated hypophosphatemia was linked to renal phosphate wasting, and APAP-induced renal tubular injury was proposed as underlying mechanism. We studied 30 normophosphatemic and 46 hypophosphatemic (serum phosphate < 2.5 mg/dL) patients from the Acute Liver Failure Study Group registry with APAP- or non-APAP-induced ALF. Since kidney injury affects phosphate excretion, patients with elevated serum creatinine (>1.2 mg/dL) were excluded. Maximal amount of renal tubular phosphate reabsorption per filtered volume (TmP/GFR) was calculated from simultaneous serum and urine phosphate and creatinine levels to assess renal phosphate handling. Instead of enhanced renal phosphate reabsorption as would be expected during hypophosphatemia of non-renal causes, serum phosphate was positively correlated with TmP/GFR in both APAP- and non-APAP-induced ALF patients (R2 = 0.66 and 0.46, respectively; both P < 0.0001), indicating renal phosphate wasting. Surprisingly, there was no evidence of kidney damage based on urinary markers including neutrophil gelatinase-associated lipocalin and cystatin C even in the APAP group. Additionally, there was no evidence that the known serum phosphatonins parathyroid hormone, fibroblast growth factor 23, and α-Klotho contribute to the observed hypophosphatemia. We conclude that the observed hypophosphatemia with renal phosphate wasting in both APAP- and non-APAP-mediated ALF is likely the result of renal tubular phosphate leak from yet-to-be identified factor(s) with no evidence for proximal tubular damage or contribution of known phosphatonins.

Phosphate Metabolism and Pathophysiology in Parathyroid Disorders and Endocrine Tumors

The advent of new insights into phosphate metabolism must urge the endocrinologist to rethink the pathophysiology of widespread disorders, such as primary hyperparathyroidism, and also of rarer endocrine metabolic bone diseases, such as hypoparathyroidism and tumor-induced hypophosphatemia. These rare diseases of mineral metabolism have been and will be a precious source of new information about phosphate and other minerals in the coming years. The parathyroid glands, the kidneys, and the intestine are the main organs affecting phosphate levels in the blood and urine. Parathyroid disorders, renal tubule defects, or phosphatonin-producing tumors might be unveiled from alterations of such a simple and inexpensive mineral as serum phosphate. This review will present all these disorders from a ‘phosphate perspective’.

Favorable effects of burosumab on tumor-induced osteomalacia caused by an undetectable tumor: A case report

RATIONALE

Tumor-induced osteomalacia (TIO) is curable by tumor resection, but detection of the tumor can be challenging. Overproduction of fibroblast growth factor 23 (FGF23) by the tumor causes hypophosphatemia and consequently induces inappropriate bone turnover. Conventionally oral phosphate supplementation was the only treatment for TIO, but had risks of hypercalciuria and nephrocalcinosis. Burosumab, a human monoclonal anti-FGF23 antibody, was recently post-marketed in Japan against for FGF23-related hypophosphatemia. Herein, we present a case of TIO with undetectable tumor that was successfully treated with burosumab.

PATIENT CONCERNS

A 47-year-old woman was forced to use a wheelchair because of pain in both feet.

DIAGNOSIS

Laboratory findings showed hypophosphatemia, elevated bone markers, and high serum FGF23 without renal tubular defects. Imaging studies revealed bone atrophy in the feet, decreased bone density, and multiple pseudofractures in the talar, sacral, and L5 vertebral regions. After excluding drug-induced and hereditary osteomalacia, we diagnosed her as TIO.

INTERVENTIONS

Comprehensive imaging studies and stepwise venous sampling failed to localize the tumor, and we started to administer subcutaneous burosumab.

OUTCOMES

After administration of burosumab, her serum phosphate was normalized without phosphate supplementation within 2 months. Improvement of pseudofractures, relief of pain evaluated by a visual analog scale, and normalization of bone biomarkers were observed. The patient was able to stand by herself after 6 months administration of burosumab.

LESSONS

This is the first report in clinical practice to demonstrate favorable effects of burosumab, including not only normalization of serum phosphate but also improvements of pseudofractures and subjective pain, in a patient with TIO and undetectable tumor.

Calciprotein Particles Link Disturbed Mineral Homeostasis with Cardiovascular Disease by Causing Endothelial Dysfunction and Vascular Inflammation

An association between high serum calcium/phosphate and cardiovascular events or death is well-established. However, a mechanistic explanation of this correlation is lacking. Here, we examined the role of calciprotein particles (CPPs), nanoscale bodies forming in the human blood upon its supersaturation with calcium and phosphate, in cardiovascular disease. The serum of patients with coronary artery disease or cerebrovascular disease displayed an increased propensity to form CPPs in combination with elevated ionised calcium as well as reduced albumin levels, altogether indicative of reduced Ca²⁺-binding capacity. Intravenous administration of CPPs to normolipidemic and normotensive Wistar rats provoked intimal hyperplasia and adventitial/perivascular inflammation in both balloon-injured and intact aortas in the absence of other cardiovascular risk factors. Upon the addition to primary human arterial endothelial cells, CPPs induced lysosome-dependent cell death, promoted the release of pro-inflammatory cytokines, stimulated leukocyte adhesion, and triggered endothelial-to-mesenchymal transition. We concluded that CPPs, which are formed in the blood as a result of altered mineral homeostasis, cause endothelial dysfunction and vascular inflammation, thereby contributing to the development of cardiovascular disease.

Association of Serum Phosphate with Low Handgrip Strength in Patients with Advanced Chronic Kidney Disease

Muscle wasting and hyperphosphatemia are becoming increasingly prevalent in patients who exhibit a progressive decline in kidney function. However, the association between serum phosphate (Pi) level and sarcopenia in advanced chronic kidney disease (CKD) patients remains unclear. We compared the serum Pi levels between advanced CKD patients with (n = 51) and those without sarcopenia indicators (n = 83). Low appendicular skeletal muscle mass index (ASMI), low handgrip strength, and low gait speed were defined per the standards of the Asian Working Group for Sarcopenia. Mean serum Pi level was significantly higher in advanced CKD patients with sarcopenia indicators than those without sarcopenia indicators (3.88 ± 0.86 vs. 3.54 ± 0.73 mg/dL; p = 0.016). Univariate analysis indicated that serum Pi was negatively correlated with ASMI, handgrip strength, and gait speed. Multivariable analysis revealed that serum Pi was significantly associated with handgrip strength (standardized β = -0.168; p = 0.022) and this association persisted even after adjustments for potential confounders. The optimal serum Pi cutoff for predicting low handgrip strength was 3.65 mg/dL, with a sensitivity of 82.1% and specificity of 56.6%. In summary, low handgrip strength is common in advanced CKD patients and serum Pi level is negatively associated with handgrip strength.

Phosphate Concentrations and Modifying Factors in Healthy Children From 12 to 24 Months of Age

CONTEXT

Phosphate homeostasis and its modifiers in early childhood are inadequately characterized.

OBJECTIVE

To determine physiological plasma phosphate concentration and modifying factors in healthy infants at 12 to 24 months of age.

DESIGN

This study included 525 healthy infants (53% girls), who participated in a randomized vitamin D intervention trial and received daily vitamin D3 supplementation of either 10 or 30 μg from age 2 weeks to 24 months. Biochemical parameters were measured at 12 and 24 months. Dietary phosphate intake was determined at 12 months.

MAIN OUTCOME MEASURES

Plasma phosphate concentrations at 12 and 24 months of age.

RESULTS

Mean (SD) phosphate concentration decreased from 12 months (1.9 ± 0.15 mmol/L) to 24 months (1.6 ± 0.17 mmol/L) of age (P < 0.001 for repeated measurements). When adjusted by covariates, such as body size, creatinine, serum 25-hydroxyvitamin D, intact and C-terminal fibroblast growth factor 23, mean plasma phosphate was higher in boys than girls during follow-up (P = 0.019). Phosphate concentrations were similar in the vitamin D intervention groups (P > 0.472 for all). Plasma iron was associated positively with plasma phosphate at both time points (B, 0.006 and 0.005; 95% CI, 0.004-0.009 and 0.002-0.008; P < 0.001 at both time points, respectively). At 24 months of age, the main modifier of phosphate concentration was plasma creatinine (B, 0.007; 95% CI 0.003-0.011, P < 0.001).

CONCLUSION

Plasma phosphate concentration decreased from age 12 to 24 months. In infants and toddlers, the strongest plasma phosphate modifiers were sex, iron, and creatinine, whereas vitamin D supplementation did not modify phosphate concentrations.

Prevalence and Factors Associated with Sarcopenia in Patients on Maintenance Dialysis in Australia-A Single Centre, Cross-Sectional Study

Background: Sarcopenia is associated with significant morbidity and mortality in patients with chronic kidney disease. The prevalence of sarcopenia in the dialysis population varies from 4% to 63%. However, the prevalence and risk factors of sarcopenia in the Australian dialysis population remain uncertain. Aim: To study the prevalence of sarcopenia in patients on maintenance dialysis by using the European Working Group on Sarcopenia in Older People (EWGSOP) diagnostic criteria of sarcopenia and to identify associated risk factors. Methods: We evaluated adult patients on maintenance haemodialysis and peritoneal dialysis in this single-centre cross-sectional study in Australia. Patient’s clinical (age, gender, dialysis modality and diabetic status) and laboratory parameters (serum albumin, calcium, phosphate, 25-hydroxy-vitamin D and parathyroid hormone levels) were investigated. We employed bioimpedance spectroscopy, hand grip dynamometer and the timed up and go test (TUG) to evaluate muscle mass, strength and function, respectively. Results: We evaluated 39 dialysis patients with a median age of 69 years old. The prevalence of sarcopenia was 18%. Sarcopenia was associated with low serum albumin (p = 0.02) and low serum phosphate level (p = 0.04). Increasing age and female sex were potential risk factors for sarcopenia (p = 0.05 and 0.08, respectively). Low lean muscle mass, reduced hand grip strength and prolonged TUG were present in 23.1%, 41% and 40.5%, respectively, of the cohort. The hand grip test had good correlation with lean muscle evaluation and the TUG. Conclusions: Sarcopenia was prevalent in 18% of maintenance haemodialysis patients from an Australian single-centre cohort, with low serum albumin and phosphate as significant risk factors.

Association between the initial serum phosphate level and 30-day mortality in blunt trauma patients

BACKGROUND

Studies on patients with cardiac arrest or sepsis have reported that high initial phosphate levels are associated with poor outcomes. However, no previous study has investigated the association between initial phosphate levels and outcomes in blunt trauma patients.

METHODS

This study was a retrospective observational study conducted on blunt trauma patients who had been treated at the single regional trauma center between January 2016 and December 2017. Patients' demographic data, initial vital signs, trauma scores, and laboratory parameters including phosphate levels were collected from the trauma registry. The primary outcome was set to 30-day mortality. The secondary outcomes were the total volume of blood transfused, 30-day hospital-free days, and 30-day intensive care unit-free days.

RESULTS

Of the 1,907 included patients, 1,836 were in the survival group, and 71 were in the nonsurvival group. The nonsurvival group had a significantly higher phosphate level than the survival group. Patients in the hyperphosphatemia group had a higher 30-day mortality, fewer 30-day intensive care unit-free days, and higher transfusion volume than those in the other groups. In multivariable logistic regression analysis, hyperphosphatemia was independently associated with 30-day mortality. The receiver operating characteristic curve analysis showed that the area under the curve with the inclusion of phosphate in addition to Injury Severity Score, Revised Trauma Score, and age was 0.911. Area under the curve was also increased when phosphate was simply added to Injury Severity Score and Revised Trauma Score.

CONCLUSION

In blunt trauma patients, hyperphosphatemia was associated with an increased 30-day mortality.

LEVEL OF EVIDENCE

Prognostic, level III.

Ferric Citrate Dosing in Iron Deficiency Anemia in Nondialysis-Dependent Chronic Kidney Disease

INTRODUCTION

Ferric citrate (FC) is indicated as an oral iron replacement for iron deficiency anemia in adult patients with chronic kidney disease (CKD) not on dialysis. The recommended starting dose is one 1-g tablet three times daily (TID). This study investigated long-term efficacy and safety of different FC dosing regimens for treating anemia in nondialysis-dependent CKD (NDD-CKD).

METHODS

In this phase 4, randomized, open-label, multicenter study, patients with anemia with NDD-CKD (estimated glomerular filtration rate, ≥20 mL/min and <60 mL/min) were randomized 1:1 to one FC tablet (1-g equivalent to 210 mg ferric iron) TID (3 g/day) or 2 tablets twice daily (BID; 4 g/day). At week 12, dosage was increased to 2 tablets TID (6 g/day) or 3 tablets BID (6 g/day) in patients whose hemoglobin (Hb) levels increased <0.5 g/dL or were <10 g/dL. Primary endpoint was mean change in Hb from baseline to week 24.

RESULTS

Of 484 patients screened, 206 were randomized and 205 received FC. Mean (standard deviation) changes from baseline in Hb at week 24 were 0.77 (0.84) g/dL with FC TID 3 g/day and 0.70 (0.98) g/dL with FC BID 4 g/day.

DISCUSSION/CONCLUSIONS

FC administered BID and TID for 48 weeks was safe and effective for treating anemia in this population, supporting potentially increased dosing flexibility.

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

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

Alfacalcidol vs Calcitriol in the Management of Patient With Hypoparathyroidism: A Randomized Controlled Trial

CONTEXT

Alfacalcidol and calcitriol are commonly used for managing hypoparathyroidism. Their relative merits have not been systematically assessed.

OBJECTIVE

We compared the effect of alfacalcidol and calcitriol on phosphatemic control, hypercalciuria, and associated factors in idiopathic-hypoparathyroidism (IH).

DESIGN AND SETTING

Open-label randomized controlled trial, tertiary care center.

SUBJECTS AND METHODS

IH patients with optimal calcemic control on alfacalcidol were continued on the same (n = 20) or switched to calcitriol (n = 25) at half of the ongoing alfacalcidol dose. The dose was adjusted during follow-up to maintain serum total calcium between 8.0 and 9.5 mg/dL. Serum calcium, phosphorus, 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, 24-h urine calcium-to-creatinine ratio, and fractional excretion of phosphorus (FEPh) were measured at baseline and 6 months. Plasma intact-FGF23 was measured at final follow-up.

RESULT

Patients receiving alfacalcidol and calcitriol had comparable serum calcium at 6 months (8.7 ± 0.4 vs 8.9 ± 0.4 mg/dL, P = 0.13). Their median [interquartile range (IQR)] dose at 6 months was 2.0 (1.0-2.5) and 0.75 (0.5-1.0) µg/d, respectively. Serum 1,25(OH)2D levels were physiological in both (35.3 ± 11.6 and 32.3 ± 16.9 pg/mL). Serum phosphate and calcium excretion were comparable in 2 arms. A majority had hyperphosphatemia (75% vs 76%), hypercalciuria (75% vs 72%), and elevated FGF23 (116 ± 68 and 113 ± 57 pg/mL). Age showed significant independent association with plasma FGF23 (β = 1.9, P = 0.001). Average FEPh was low despite high FGF23.

CONCLUSION

At optimal calcium control, both alfacalcidol and calcitriol lead to comparable but high serum phosphate levels, hypercalciuria, physiological circulating 1,25(OH)2D, and elevated FGF23. Further studies are required to systematically investigate other treatment options.

Novel Small Molecule Fibroblast Growth Factor 23 Inhibitors Increase Serum Phosphate and Improve Skeletal Abnormalities in Hyp Mice

Excess fibroblast growth factor (FGF) 23 causes hereditary hypophosphatemic rickets, such as X-linked hypophosphatemia (XLH) and tumor-induced osteomalacia (TIO). A small molecule that specifically binds to FGF23 to prevent activation of the fibroblast growth factor receptor/α-Klotho complex has potential advantages over the currently approved systemically administered FGF23 blocking antibody. Using structure-based drug design, we previously identified ZINC13407541 (N-[[2-(2-phenylethenyl)cyclopenten-1-yl]methylidene]hydroxylamine) as a small molecule antagonist for FGF23. Additional structure-activity studies developed a series of ZINC13407541 analogs with enhanced drug-like properties. In this study, we tested in a preclinical Hyp mouse homolog of XLH a direct connect analog [(E)-2-(4-(tert-butyl)phenyl)cyclopent-1-ene-1-carbaldehyde oxime] (8n), which exhibited the greatest stability in microsomal assays, and [(E)-2-((E)-4-methylstyryl)benzaldehyde oxime] (13a), which exhibited increased in vitro potency. Using cryo-electron microscopy structure and computational docking, we identified a key binding residue (Q156) of the FGF23 antagonists, ZINC13407541, and its analogs (8n and 13a) in the N-terminal domain of FGF23 protein. Site-directed mutagenesis and bimolecular fluorescence complementation-fluorescence resonance energy transfer assay confirmed the binding site of these three antagonists. We found that pharmacological inhibition of FGF23 with either of these compounds blocked FGF23 signaling and increased serum phosphate and 1,25-dihydroxyvitamin D [1,25(OH)2D] concentrations in Hyp mice. Long-term parenteral treatment with 8n or 13a also enhanced linear bone growth, increased mineralization of bone, and narrowed the growth plate in Hyp mice. The more potent 13a compound had greater therapeutic effects in Hyp mice. Further optimization of these FGF23 inhibitors may lead to versatile drugs to treat excess FGF23-mediated disorders. SIGNIFICANCE STATEMENT: This study used structure-based drug design and medicinal chemistry approaches to identify and optimize small molecules with different stability and potency, which antagonize excessive actions of fibroblast growth factor 23 (FGF23) in hereditary hypophosphatemic rickets. The findings confirmed that these antagonists bind to the N-terminus of FGF23 to inhibit its binding to and activation of the fibroblast growth factor receptors/α-Klotho signaling complex. Administration of these lead compounds improved phosphate homeostasis and abnormal skeletal phenotypes in a preclinical Hyp mouse model.

Calciprotein Particles: Balancing Mineral Homeostasis and Vascular Pathology

[Figure: see text].

Etelcalcetide decreases the PTH-calcium setpoint without changing maximum and minimum PTH secretion in mice with primary hyperparathyroidism

INTRODUCTION

Etelcalcetide binds to the extracellular domain of the calcium-sensing receptor (CaSR), while cinacalcet binds to the 7-transmembrane domain of the CaSR; however, it is unknown, whether etelcalcetide has similar effects to cinacalcet on parathyroid hormone (PTH) secretion.

MATERIALS AND METHODS

The PTH-calcium setpoint and maximum and minimum PTH secretion were determined using an 'in vivo setpoint analyses.' The PTH-calcium setpoint was obtained in a mouse model of primary hyperparathyroidism (PC) and wild-type (WT) mice, with PC mice divided into two groups. The setpoint was obtained after 7 days of etelcalcetide (3.0 mg/kg BW/day) or vehicle administration via anosmotic pump. After 7 days of crossover administration, the setpoint was obtained again. Parathyroid glands were obtained after crossover administration, and CaSR expression was analyzed by immunohistochemistry.

RESULTS

Etelcalcetide administration significantly decreased the setpoint from 9.03 ± 0.56 mg/dL to 6.80 ± 0.28 mg/dL, which was restored to 8.81 ± 0.38 mg/dL after vehicle administration. In the second group of mice, vehicle administration did not alter the setpoint (8.84 ± 0.69 mg/dL to 8.98 ± 0.63 mg/dL), but subsequent etelcalcetide administration significantly decreased it to 7.10 ± 0.72 mg/dL. There was no significant change in maximum and minimum PTH secretion. Expression levels of parathyroid CaSR were lower in PC mice than in WT mice; however, no significant differences were observed between the two mouse groups.

CONCLUSION

Etelcalcetide decreased the PTH-calcium setpoint without changing maximum and minimum PTH secretion in PC mice, suggesting that like cinacalcet, etelcalcetide has calcimimetic potency.

Constitutive depletion of Slc34a2/NaPi-IIb in rats causes perinatal mortality

Absorption of dietary phosphate (Pi) across intestinal epithelia is a regulated process mediated by transcellular and paracellular pathways. Although hyperphosphatemia is a risk factor for the development of cardiovascular disease, the amount of ingested Pi in a typical Western diet is above physiological needs. While blocking intestinal absorption has been suggested as a therapeutic approach to prevent hyperphosphatemia, a complete picture regarding the identity and regulation of the mechanism(s) responsible for intestinal absorption of Pi is missing. The Na+/Pi cotransporter NaPi-IIb is a secondary active transporter encoded by the Slc34a2 gene. This transporter has a wide tissue distribution and within the intestinal tract is located at the apical membrane of epithelial cells. Based on mouse models deficient in NaPi-IIb, this cotransporter is assumed to mediate the bulk of active intestinal absorption of Pi. However, whether or not this is also applicable to humans is unknown, since human patients with inactivating mutations in SLC34A2 have not been reported to suffer from Pi depletion. Thus, mice may not be the most appropriate experimental model for the translation of intestinal Pi handling to humans. Here, we describe the generation of a rat model with Crispr/Cas-driven constitutive depletion of Slc34a2. Slc34a2 heterozygous rats were indistinguishable from wild type animals under standard dietary conditions as well as upon 3 days feeding on low Pi. However, unlike in humans, homozygosity resulted in perinatal lethality.

Predictors of Survival in Chronic Hemodialysis Patients: A 10-Year Longitudinal Follow-Up Analysis

BACKGROUND

Risk factors of mortality in chronic hemodialysis patients have not yet been sufficiently evaluated. In particular, chronological transits and interactions of the impact of risk factors have rarely been described.

METHODS

This study is a post hoc analysis of the participants in the Olme-sartan Clinical Trial in Okinawan Patients under OKIDS (OCTOPUS) study conducted between June 2006 and June 2011. We additionally followed up on the prognosis of the participants until July 31, 2018. Standardized univariable and multivariable Cox regression analyses were used to evaluate the influences of the participants' baseline characteristics on all-cause mortality. We also evaluated chronological changes in the impacts of risk factors, interactions among predictors, and the influence of missing values using sensitivity analyses.

RESULTS

Of the 469 original trial participants, 461 participants were evaluated. The median time of follow-up was 10.2 years. A total of 211 (45.8%) participants were deceased. The leading causes of death were infection (n = 72, 34.1%) and cardiovascular disease (n = 66, 31.3%). Univariate and multivariate Cox regression analyses revealed that the impact of diabetes mellitus, history of coronary intervention, and hypoalbuminemia were significant risk factors for mortality during the whole follow-up period. During the early follow-up period (≤3 years), standardized univariate Cox regression analyses revealed that history of amputation (hazard ratio [HR] = 4.61, p < 0.001), lower dry weight, higher cardiothoracic ratio, and lower potassium levels were statistically significant risks. In those who survived for longer than 3 years, a history of stroke (HR = 1.73, p = 0.006), higher systolic blood pressure, lower serum sodium levels, and higher levels of hemoglobin, and serum phosphate were significant risks. We also observed a stable interaction between the impacts of serum phosphate and albumin on all-cause mortality.

CONCLUSION

In chronic hemodialysis patients, targets to improve the short-term prognosis and long-term prognosis are not equivalent. Hyperphosphatemia was a significant risk factor for the all-cause mortality among patients with normal serum albumin levels but not among patients with compromised albumin levels.

Optimal Phosphate Control Related to Coronary Artery Calcification in Dialysis Patients

BACKGROUND

In patients on maintenance dialysis, cardiovascular mortality risk is remarkably high, which can be partly explained by severe coronary artery calcification (CAC). Hyperphosphatemia has been reported to be associated with the severity of CAC. However, the optimal phosphate range in patients on dialysis remains unknown. This study was planned to compare the effects on CAC progression of two types of noncalcium-based phosphate binders and of two different phosphate target ranges.

METHODS

We conducted a randomized, open-label, multicenter, interventional trial with a two by two factorial design. A total of 160 adults on dialysis were enrolled and randomized to the sucroferric oxyhydroxide or lanthanum carbonate group, with the aim of reducing serum phosphate to two target levels (3.5-4.5 mg/dl in the strict group and 5.0-6.0 mg/dl in the standard group). The primary end point was percentage change in CAC scores during the 12-month treatment.

RESULTS

The full analysis set included 115 patients. We observed no significant difference in percentage change in CAC scores between the lanthanum carbonate group and the sucroferric oxyhydroxide group. On the other hand, percentage change in CAC scores in the strict group (median of 8.52; interquartile range, -1.0-23.9) was significantly lower than that in the standard group (median of 21.8; interquartile range, 10.0-36.1; P=0.006). This effect was pronounced in older (aged 65-74 years) versus younger (aged 20-64 years) participants (P value for interaction =0.003). We observed a similar finding for the absolute change in CAC scores.

CONCLUSIONS

Further study with a larger sample size is needed, but strict phosphate control shows promise for delaying progression of CAC in patients undergoing maintenance hemodialysis.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

Evaluate the New Phosphate Iron-Based Binder Sucroferric Oxyhydroxide in Dialysis Patients with the Goal of Advancing the Practice of EBM (EPISODE), jRCTs051180048.

FGF23 signalling and physiology

Fibroblast growth factor 23 (FGF23) is a phosphotropic hormone that belongs to a subfamily of endocrine FGFs with evolutionarily conserved functions in worms and fruit flies. FAM20C phosphorylates FGF23 post-translationally, targeting it to proteolysis through subtilisin-like proprotein convertase FURIN, resulting in secretion of FGF23 fragments. O-glycosylation of FGF23 through GALNT3 appears to prevent proteolysis, resulting in secretion of biologically active intact FGF23. In the circulation, FGF23 may undergo further processing by plasminogen activators. Crystal structures show that the ectodomain of the cognate FGF23 receptor FGFR1c binds with the ectodomain of the co-receptor alpha-KLOTHO. The KLOTHO-FGFR1c double heterodimer creates a high-affinity binding site for the FGF23 C-terminus. The topology of FGF23 deviates from that of paracrine FGFs, resulting in poor affinity for heparan sulphate, which may explain why FGF23 diffuses freely in the bone matrix to enter the bloodstream following its secretion by cells of osteoblastic lineage. Intact FGF23 signalling by this canonical pathway activates FRS2/RAS/RAF/MEK/ERK1/2. It reduces serum phosphate by inhibiting 1,25-dihydroxyvitamin D synthesis, suppressing intestinal phosphate absorption, and by downregulating the transporters NPT2a and NPT2c, suppressing phosphate reabsorption in the proximal tubules. The physiological role of FGF23 fragments, which may be inhibitory, remains unclear. Pharmacological and genetic activation of canonical FGF23 signalling causes hypophosphatemic disorders, while its inhibition results in hyperphosphatemic disorders. Non-canonical FGF23 signalling through binding and activation of FGFR3/FGFR4/calcineurin/NFAT in an alpha-KLOTHO-independent fashion mainly occurs at extremely elevated circulating FGF23 levels and may contribute to mortality due to cardiovascular disease and left ventricular hypertrophy in chronic kidney disease.

Prolonged Hypophosphatemia and Intensive Care After Curative Surgery of Tumor Induced Osteomalacia: A Case Report

INTRODUCTION

Rare FGF23-producing mesenchymal tumors lead to paraneoplastic tumor-induced osteomalacia (TIO) presenting with phosphate wasting, hypophosphatemia, chronic hypomineralization of the bone, fragility fractures and muscle weakness. Diagnosis of TIO requires exclusion of other etiologies and careful search for a mesenchymal tumor that often is very small and can appear anywhere in the body. Surgical removal of the tumor is the only definitive treatment of TIO. Surgical complications due to chronic hypophosphatemia are not well recognized.

CASE DESCRIPTION

The current case describes severe fragility fractures in a 58-year-old woman, who lost her ability to walk and was bedridden for two years. First, the initial diagnostic laboratory work-up did not include serum phosphorus measurements, second, the suspicion of adverse effects of pioglitazone as an underlying cause delayed correct diagnosis for at least two years. After biochemical discovery of hyperphosphaturic hypophosphatemia at a tertiary referral centre, a FGF23-producing tumor of the mandible was discovered on physical examination, and then surgically removed. Postoperatively, severe hypophosphatemia and muscle weakness prolonged the need for ventilation support, intensive care and phosphate supplementation. After two years of rehabilitation, the patient was able to walk short distances. The tumor has not recurred, and serum phosphate concentration has remained within normal limits during 3.5 years of follow-up.

CONCLUSIONS

The case report illustrates knowledge gaps in the diagnostic work-up of rare causes of low bone mass and fragility fractures. Compared to other low phosphate conditions, surgical recovery from TIO-induced hypophosphatemia warrants special attention. Increased alkaline phosphatase concentration may indicate impaired postsurgical recovery due to prolonged hypophosphatemia, underlining the need for proactive perioperative correction of hypophosphatemia.

Cortisol and Phosphate Homeostasis: Cushing's Syndrome Is Associated With Reversible Hypophosphatemia

OBJECTIVES

The influence of hypercortisolism on phosphate homeostasis is relatively unknown. A few previous studies have reported on patients with Cushing's syndrome (CS) with hypophosphatemia in whom serum phosphate normalized after initiation of treatment for CS. We aimed to investigate the prevalence of hypophosphatemia in CS, the association between the degree of hypercortisolism and serum phosphate and the change in serum phosphate after remission of CS. We compared the prevalence of hypophosphatemia in CS with the prevalence in the population-based Rotterdam Study (RS).

METHODS

Patients diagnosed with CS and treated at the Department of Endocrinology of Erasmus MC in the period of 2002-2020 were included and data was collected on age at diagnosis, sex, serum phosphate, calcium and potassium levels, kidney function and BMI. Using multivariate linear regression, we analyzed the association between 24h urinary free cortisol excretion (UFC) and serum phosphate. Changes in serum phosphate and covariates were tested with a repeated measurement ANOVA, using mean levels of laboratory values for the periods before remission, and 0-14 days and 15-180 days after remission.

RESULTS

Hypophosphatemia before treatment was present in 16% of the 99 CS patients with data on serum phosphate, 24h UFC and covariates. In comparison, the prevalence of hypophosphatemia in RS was 2.0-4.2%. Linear regression showed a negative association between the level of UFC and serum phosphate at diagnosis, which remained significant after adjusting for covariates [β -0.002 (95%CI -0.004; -0.0004), p=0.021]. A subset of 24 patients had additional phosphate measurements at 0-14 days and 15-180 days after remission. In this subgroup, serum phosphate significantly increased from 1.03 ± 0.17 mmol/L prior to remission to 1.22 ± 0.25 mmol/L 15-180 days after remission (p = 0.008). BMI decreased after remission [-1.1 kg/m², (95%CI -2.09 to -0.07), p=0.037]. Other covariates did not show an equivalent change over time.

CONCLUSION

In this retrospective study, we found that 16% of patients with CS had hypophosphatemia. Moreover, serum phosphate was related to the level of cortisoluria and increased after remission of CS. Potential underlying mechanisms related to urinary phosphate excretion and possibly involving FGF23, BMI and parathyroid hormone levels should be further explored.

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

BACKGROUND AND OBJECTIVES

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

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

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

RESULTS

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

CONCLUSIONS

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

Metabolic Bone Disease of Prematurity: Risk Factors and Associated Short-Term Outcomes

Despite the importance of early recognition of metabolic bone disease (MBD) of prematurity, there is still significant variability in screening practices across institutions. We conducted an observational study of infants born at ≤32 weeks of gestation with a birth weight of ≤1500 g (n = 218) to identify clinical factors associated with biochemical indicators of MBD. Bone mineral status was assessed by measuring alkaline phosphatase and phosphate levels between weeks 3 and 5 of life. Two comparisons were performed after classifying infants as either MBD (cases) or non-MBD (controls), and as either high or low risk for MBD, as determined based on the results of MBD screening. In total, 27 infants (12.3%) were classified as cases and 96 (44%) as high-risk. Compared with controls, MBD infants had a significantly lower gestational age and birth weight, and a longer duration of parenteral nutrition and hospital stay. Respiratory outcomes were significantly poorer in high- versus low-risk infants. Multivariate logistic regression showed that birth weight was the only independent risk factor for MBD (odds ratio [OR]/100 g, 0.811; confidence interval [CI95%], 0.656-0.992; p = 0.045) and that birth weight (OR/100 g, 0.853; CI95%, 0.731-0.991; p = 0.039) and red blood cell transfusion (OR, 2.661; CI95%, 1.308-5.467; p = 0.007) were independent risk factors for high risk of MBD. Our findings provide evidence of risk factors for MBD that could help clinicians to individualize perinatal management. The association of red blood cell transfusion with MBD is a novel finding that may be related to iron overload and that merits further study.

Examination of potential novel biochemical factors in relation to prostate cancer incidence and mortality in UK Biobank

BACKGROUND

Although prostate cancer is a leading cause of cancer death, its aetiology is not well understood. We aimed to identify novel biochemical factors for prostate cancer incidence and mortality in UK Biobank.

METHODS

A range of cardiovascular, bone, joint, diabetes, renal and liver-related biomarkers were measured in baseline blood samples collected from up to 211,754 men at recruitment and in a subsample 5 years later. Participants were followed-up via linkage to health administrative datasets to identify prostate cancer cases. Hazard ratios (HRs) and 95% confidence intervals were calculated using multivariable-adjusted Cox regression corrected for regression dilution bias. Multiple testing was accounted for by using a false discovery rate controlling procedure.

RESULTS

After an average follow-up of 6.9 years, 5763 prostate cancer cases and 331 prostate cancer deaths were ascertained. Prostate cancer incidence was positively associated with circulating vitamin D, urea and phosphate concentrations and inversely associated with glucose, total protein and aspartate aminotransferase. Phosphate and cystatin-C were the only biomarkers positively and inversely, respectively, associated with risk in analyses excluding the first 4 years of follow-up. There was little evidence of associations with prostate cancer death.

CONCLUSION

We found novel associations of several biomarkers with prostate cancer incidence. Future research will examine associations by tumour characteristics.

Trends in Mineral Metabolism Treatment Strategies in Patients Receiving Hemodialysis in the United States

BACKGROUND AND OBJECTIVES

With multiple medications indicated for mineral metabolism, dialysis providers can apply various strategies to achieve target phosphate and parathyroid hormone (PTH) levels. We describe common prescribing patterns and practice variation in mineral metabolism treatment strategies over the last decade.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In a cohort of adults initiating hemodialysis at Dialysis Clinic, Inc. facilities, we assessed prescriptions of vitamin D sterols, phosphate binders, and cinacalcet longitudinally. To identify the influence of secular trends in clinical practice, we stratified the cohort by dialysis initiation year (2006-2008, 2009-2011, and 2012-2015). To measure practice variation, we estimated the median odds ratio for prescribing different mineral metabolism treatment strategies at 12 months post-dialysis initiation across facilities using mixed effects multinomial logistic regression. Sensitivity analyses evaluated strategies used after detection of first elevated PTH.

RESULTS

Among 23,549 incident patients on hemodialysis, there was a decline in vitamin D sterol-based strategies and a corresponding increase in strategies without PTH-modifying agents (i.e., phosphate binders alone or no mineral metabolism medications) and cinacalcet-containing treatment strategies between 2006 and 2015. The proportion with active vitamin D sterol-based strategies at dialysis initiation decreased across cohorts: 15% (2006-2008) to 5% (2012-2015). The proportion with active vitamin D sterol-based strategies after 18 months of dialysis decreased across cohorts: 52% (2006-2008) to 34% (2012-2015). The odds of using individual strategies compared with reference (active vitamin D sterol with phosphate binder) varied from 1.5- to two-fold across facilities in 2006-2008 and 2009-2011 cohorts, and increased to two- to three-fold in the 2012-2015 cohort. Findings were similar in sensitivity analyses starting from first elevated PTH measurement.

CONCLUSIONS

Over time, mineral metabolism management involved less use of vitamin D sterol-based strategies, greater use of both more conservative and cinacalcet-containing strategies, and increased practice variation, suggesting growing equipoise.

A Randomized Trial on the Effect of Phosphate Reduction on Vascular End Points in CKD (IMPROVE-CKD)

BACKGROUND

Hyperphosphatemia is associated with increased fibroblast growth factor 23 (FGF23), arterial calcification, and cardiovascular mortality. Effects of phosphate-lowering medication on vascular calcification and arterial stiffness in CKD remain uncertain.

METHODS

To assess the effects of non-calcium-based phosphate binders on intermediate cardiovascular markers, we conducted a multicenter, double-blind trial, randomizing 278 participants with stage 3b or 4 CKD and serum phosphate >1.00 mmol/L (3.10 mg/dl) to 500 mg lanthanum carbonate or matched placebo thrice daily for 96 weeks. We analyzed the primary outcome, carotid-femoral pulse wave velocity, using a linear mixed effects model for repeated measures. Secondary outcomes included abdominal aortic calcification and serum and urine markers of mineral metabolism.

RESULTS

A total of 138 participants received lanthanum and 140 received placebo (mean age 63.1 years; 69% male, 64% White). Mean eGFR was 26.6 ml/min per 1.73 m2; 45% of participants had diabetes and 32% had cardiovascular disease. Mean serum phosphate was 1.25 mmol/L (3.87 mg/dl), mean pulse wave velocity was 10.8 m/s, and 81.3% had abdominal aortic calcification at baseline. At 96 weeks, pulse wave velocity did not differ significantly between groups, nor did abdominal aortic calcification, serum phosphate, parathyroid hormone, FGF23, and 24-hour urinary phosphate. Serious adverse events occurred in 63 (46%) participants prescribed lanthanum and 66 (47%) prescribed placebo. Although recruitment to target was not achieved, additional analysis suggested this was unlikely to have significantly affected the principle findings.

CONCLUSIONS

In patients with stage 3b/4 CKD, treatment with lanthanum over 96 weeks did not affect arterial stiffness or aortic calcification compared with placebo. These findings do not support the role of intestinal phosphate binders to reduce cardiovascular risk in patients with CKD who have normophosphatemia.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

Australian Clinical Trials Registry, ACTRN12610000650099.

Development of experimental chronic kidney disease and vascular calcification alters diurnal variation of phosphate and its hormonal regulators

The mineral-bone axis is tightly regulated and dependent on renal function. In chronic kidney disease (CKD) progressive loss of renal capacity disrupts this axis over-time, with marked changes in circulating calcium, phosphate, PTH, and fibroblast growth factor-23 (FGF-23). These changes contribute to the development of cardiovascular disease, like vascular calcification (VC), which worsens morbidity and mortality in CKD. Although the chronic changes in these circulating factors and their relationships are well known, no experimental studies have examined how the progressive development of CKD and VC alter the circadian rhythms of these factors. An adenine-induced experimental model of CKD in rats was used to establish (i) general circulating trends, (ii) if renal dysfunction affects these observed trends, and (iii) identify potential changes in these trends caused by VC. This study clearly discerned patterns of daily variations in circulating minerals and hormones, finding that both phosphate and PTH follow modelable diurnal variations whereas calcium and FGF-23 maintain relative stability over 24-hr. Surprisingly, the development of CKD was not sufficient to disrupt these patterns of diurnal variation and only altered the magnitude of change; however, it was found that the diurnal rhythms of circulating phosphate and daily stability of calcium were only significantly altered in the setting of CKD with established VC.

Real World Use and Effects of Calcimimetics in Treating Mineral and Bone Disorder in Hemodialysis Patients

BACKGROUND

Calcimimetics are used to treat mineral and bone disorder by reducing parathyroid hormone (PTH), calcium (Ca), and phosphorus (Phos). The study objectives were to assess the control of PTH, Ca, and Phos over time in patients receiving cinacalcet or etelcalcetide as well as dosing and time to discontinuation for etelcalcetide.

METHODS

This was a retrospective cohort study using electronic medical records from small and independent dialysis centers. Adults ≥18 years of age were identified as cinacalcet or etelcalcetide users based on the first calcimimetic received in 2018 (index date). Patients were followed from the index date until parathyroidectomy, kidney transplant, death, or end of data (December 31, 2018). Analyses of mean PTH, Ca, and Phos, as well as target achievement of PTH, Ca, and Phos were conducted over a 9-month period. Discontinuation with etelcalcetide was measured with the Kaplan-Meier estimator.

RESULTS

There were 1,346 cinacalcet patients (mean age 60.5 years, 43.5% female, and 47.1% Black) and 1,255 etelcalcetide patients (mean age 63.4 years, 46.6% female, and 38.5% Black). At baseline, the proportions in target were similar for etelcalcetide versus cinacalcet: 36 versus 38% for PTH, 79 versus 80% for Ca, and 43 versus 44% for Phos. Overall, 40-47% of cinacalcet users and 48-62% of etelcalcetide users were observed to be in target for PTH over 9 months. The proportion in target for Phos ranged from 41 to 46% for cinacalcet and 46-51% for etelcalcetide. The proportion in target for Ca ranged from 74 to 78% for cinacalcet and 60-73% for etelcalcetide. Etelcalcetide 12-month discontinuation was 37.4%.

CONCLUSION

Both calcimimetics were effective in keeping PTH, Ca, and Phos levels within target. Patients receiving etelcalcetide tended to have lower laboratory values for PTH, Ca, and Phos over time, while patients receiving cinacalcet tended to be more likely to be in target for Ca over time.

Effect of Ferric Citrate versus Ferrous Sulfate on Iron and Phosphate Parameters in Patients with Iron Deficiency and CKD: A Randomized Trial

BACKGROUND AND OBJECTIVES

Ferric citrate is an oral medication approved for treatment of iron deficiency anemia in patients with CKD not requiring dialysis. The relative efficacy of ferric citrate versus ferrous sulfate in treating iron deficiency in patients with CKD is unclear.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We randomized 60 adults with moderate to severe CKD (eGFR 15-45 ml/min per 1.73 m2) and iron deficiency (transferrin saturation [TSAT] ≤30% and ferritin ≤300 ng/ml) to ferric citrate (2 g three times a day with meals, n=30) or ferrous sulfate (325 mg three times a day, n=30) for 12 weeks. Primary outcomes were change in TSAT and ferritin from baseline to 12 weeks. Secondary outcomes were change in hemoglobin, fibroblast growth factor 23 (FGF23), and hepcidin.

RESULTS

Baseline characteristics were well balanced between study arms. There was a greater increase in TSAT (between-group difference in mean change, 8%; 95% confidence interval [95% CI], 1 to 15; P=0.02) and ferritin (between-group difference in mean change, 37 ng/ml; 95% CI, 10 to 64; P=0.009) from baseline to 12 weeks in participants randomized to ferric citrate as compared with ferrous sulfate. Similarly, as compared with ferrous sulfate, treatment with ferric citrate resulted in a greater increase in hepcidin from baseline to 12 weeks (between-group difference, 69 pg/ml; 95% CI, 8 to 130). There were no between-group differences in mean change for hemoglobin (0.3 g/dl; 95% CI, -0.2 to 0.8), intact FGF23 (-29 pg/ml; 95% CI, -59 to 0.1), or C-terminal FGF23 (61 RU/ml; 95% CI, -181 to 58). The incidence of adverse events did not differ between treatment arms.

CONCLUSIONS

As compared with ferrous sulfate, treatment with ferric citrate for 12 weeks resulted in a greater mean increase in TSAT and ferritin concentrations in individuals with moderate to severe CKD and iron deficiency.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

Impact of Ferric Citrate vs Ferrous Sulfate on Iron Parameters and Hemoglobin in Individuals With Moderate to Severe Chronic Kidney Disease (CKD) With Iron Deficiency, NCT02888171.

Evocalcet in patients with primary hyperparathyroidism: an open-label, single-arm, multicenter, 52-week, dose-titration phase III study

INTRODUCTION

Primary hyperparathyroidism (PHPT) is caused by parathyroid adenoma, primary parathyroid hyperplasia, or parathyroid carcinoma. For some patients with PHPT controlling serum calcium levels is critical.

MATERIALS AND METHODS

We conducted an open-label, single-arm, 52-week, phase III study in Japanese patients with hypercalcemia due to PHPT to demonstrate efficacy and safety of evocalcet, a new calcimimetic. Patients with intractable PHPT (n = 13), postsurgical recurrence (n = 2), and parathyroid carcinoma (n = 3) were enrolled. Evocalcet administration started at a dose of 2 mg once or twice daily and was titrated to achieve the target serum corrected calcium (cCa) concentration (≤ 10.3 mg/dL) for two consecutive weeks (maximal dose 24 mg/day).

RESULTS

Fourteen patients achieved the target (77.8%; 95% confidence interval [CI] 52.4-93.6). The lower limit of 95% CI exceeded the predetermined reference limit (11%), and thus, efficacy was confirmed. Of 18 patients, 12 (66.7%; 95% CI 41.0-86.7) showed decreased serum cCa of ≥ 1.0 mg/dL from the baseline for two consecutive weeks during the titration phase. Sixteen patients entered the maintenance phase, and 15 patients completed the study. Treatment-emergent adverse events (TEAEs) were recorded in 18/18 patients (100%) and drug-related TEAEs in 8/18 (44.4%). The most commonly observed drug-related TEAE was nausea (2/18 patients). No unexpected drug-related TEAEs were observed. All drug-related TEAEs were mild in severity. No patient discontinued the study because of drug-related TEAEs.

CONCLUSION

Evocalcet demonstrated long-term effectiveness in reducing serum cCa concentrations and safety without any unexpected drug-related TEAEs in PHPT patients.

Effects of Potassium or Sodium Supplementation on Mineral Homeostasis: A Controlled Dietary Intervention Study

CONTEXT

Although dietary potassium and sodium intake may influence calcium-phosphate metabolism and bone health, the effects on bone mineral parameters, including fibroblast growth factor 23 (FGF23), are unclear.

OBJECTIVE

Here, we investigated the effects of potassium or sodium supplementation on bone mineral parameters.

DESIGN, SETTING, PARTICIPANTS

We performed a post hoc analysis of a dietary controlled randomized, blinded, placebo-controlled crossover trial. Prehypertensive individuals not using antihypertensive medication (n = 36) received capsules containing potassium chloride (3 g/d), sodium chloride (3 g/d), or placebo. Linear mixed-effect models were used to estimate treatment effects.

RESULTS

Potassium supplementation increased plasma phosphate (from 1.10 ± 0.19 to 1.15 ± 0.19 mmol/L, P = 0.004), in line with an increase in tubular maximum of phosphate reabsorption (from 0.93 ± 0.21 to 1.01 ± 0.20 mmol/L, P < 0.001). FGF23 decreased (114.3 [96.8-135.0] to 108.5 [93.5-125.9] RU/mL, P = 0.01), without change in parathyroid hormone and 25-hydroxy vitamin D3. Fractional calcium excretion decreased (from 1.25 ± 0.50 to 1.11 ± 0.46 %, P = 0.03) without change in plasma calcium. Sodium supplementation decreased both plasma phosphate (from 1.10 ± 0.19 to 1.06 ± 0.21 mmol/L, P = 0.03) and FGF23 (from 114.3 [96.8-135.0] to 108.7 [92.3-128.1] RU/mL, P = 0.02). Urinary and fractional calcium excretion increased (from 4.28 ± 1.91 to 5.45 ± 2.51 mmol/24 hours, P < 0.001, and from 1.25 ± 0.50 to 1.44 ± 0.54 %, P = 0.004, respectively).

CONCLUSIONS

Potassium supplementation led to a decrease in FGF23, which was accompanied by increase in plasma phosphate and decreased calcium excretion. Sodium supplementation reduced FGF23, but this was accompanied by decrease in phosphate and increase in fractional calcium excretion. Our results indicate distinct effects of potassium and sodium intake on bone mineral parameters, including FGF23.

CLINICAL TRIAL REGISTRATION NUMBER

NCT01575041.

Association of Serum Calcium and Phosphate Concentrations with Glucose Metabolism Markers: The Furukawa Nutrition and Health Study

Calcium and phosphate may play an important role in cardio-metabolic abnormalities, including type 2 diabetes; however, epidemiological evidence of the association of calcium and phosphate status with glucose metabolism among Asians is limited. In the current study, we performed a cross-sectional analysis of the association of serum calcium, phosphate, and calcium–phosphate product concentrations with glucose metabolism markers among Japanese individuals. Overall, 1701 workers (aged 18–78 years) who participated in a health survey were enrolled in this study. Multivariable linear regression models were used to estimate means of homeostatic model assessment of insulin resistance (HOMA-IR), homeostatic model assessment of β-cell function (HOMA-β), and glycated hemoglobin (HbA1c). Serum calcium concentration was positively associated with HOMA-IR and HbA1c (p for trend < 0.01). Multivariable-adjusted means (95% confidence interval (CI)) of HOMA-IR for the lowest and highest quartiles of serum calcium were 0.78 (0.75–0.82) and 1.01 (0.96–1.07), respectively. The corresponding values for HbA1c were 5.24 (5.22–5.27) and 5.29 (5.26–5.32), respectively. Serum phosphate and calcium–phosphate product concentrations were inversely associated with HOMA-IR (p for trend < 0.01). Multivariable-adjusted means (95% CI) of HOMA-IR for the lowest and highest quartiles of serum phosphate were 1.04 (0.99–1.09) and 0.72 (0.69–0.76), respectively. The corresponding values for calcium–phosphate product were 1.04 (0.99–1.09) and 0.73 (0.69–0.77), respectively. The current findings suggest that higher serum calcium and lower serum phosphate concentrations are associated with IR among apparently healthy adults.

Early effects of androgen deprivation on bone and mineral homeostasis in adult men: a prospective cohort study

OBJECTIVE

Long-term androgen deprivation therapy (ADT) negatively influences bone. The short-term effects on bone and mineral homeostasis are less known. Therefore, we aimed to investigate the early effects of ADT on calcium/phosphate homeostasis and bone turnover.

DESIGN

Prospective cohort study.

METHODS

Eugonadal adult, male sex offenders, who were referred for ADT to the endocrine outpatient clinic, received cyproterone acetate. Changes in blood markers of calcium/phosphate homeostasis and bone turnover between baseline and first follow-up visit were studied.

RESULTS

Of 26 screened patients, 17 were included. The median age was 44 (range 20-75) years. The median time interval between baseline and first follow-up was 13 (6-27) weeks. Compared to baseline, an 81% decrease was observed for median total testosterone (to 3.4 nmol/L (0.4-12.2); P < 0.0001) and free testosterone (to 0.06 nmol/L (0.01-0.18); P < 0.0001). Median total estradiol decreased by 71% (to 17.6 pmol/L (4.7-35.6); P < 0.0001). Increased serum calcium (P < 0.0001) and phosphate (P = 0.0016) was observed, paralleled by decreased PTH (P = 0.0156) and 1,25-dihydroxyvitamin D3 (P = 0.0134). The stable calcium isotope ratio (δ44/42Ca) decreased (P = 0.0458), indicating net calcium loss from bone. Bone-specific alkaline phosphatase and osteocalcin decreased (P < 0.0001 and P = 0.0056, respectively), periostin tended to decrease (P = 0.0500), whereas sclerostin increased (P < 0.0001), indicating suppressed bone formation. Serum bone resorption markers (TRAP, CTX) were unaltered.

CONCLUSIONS

In adult men, calcium release from the skeleton occurs early following sex steroid deprivation, reflecting early bone resorption. The increase of sclerostin and reduction of bone formation markers, without changes in resorption markers, suggests a dominant negative effect on bone formation in the acute phase.

Stimulatory effects of short-term calcitonin administration on plasma calcium, magnesium, phosphate, and glucose in juvenile Siberian sturgeon Acipenser baerii

Calcitonin (CT) has a potential function in calcium (Ca) regulation, but there are conflicting observations in fishes. Because of the lack of calcified endoskeleton, sturgeons have low Ca circulating compared with teleost fish and the function of CT on Ca in sturgeon is very less understood. The purpose of this study was to investigate the impact of injection of salmon CT on plasma Ca, magnesium (Mg), phosphate (PHO), and glucose levels of juvenile Siberian sturgeon Acipenser baerii. Sixteen-month-old fish (429.6 ± 12.1 g) were intraperitoneally injected with a single dose of CT (5 μg kg^-1 BW) and saline solution as a control group. Thereafter, blood sampling was performed at 0, 1, 2, 4, 6, 12, 24, and 48 h after injection. CT produced marked increases in all variables measured. The highest levels of Ca (6.77 ± 0.53 mg dL^-1), Mg (9.79 ± 0.16 mg dL^-1) and PHO (1.74 ± 0.05 mg dL^-1) were recorded at 2 h after CT injection and showed significant difference compared with control treatment (Ca 4.75 ± 0.12 mg dL^-1; Mg 5.47 ± 0.16 mg dL^-1 and PHO 1.23 ± 0.06 mg dL^-1). It also likely produced hyperglycemia. However, the differences with the controls were not statistically significant, possibly due to interference with the hyperglycemia induced by the stress of injection. Our results showed that the injection of 5 μg kg^-1 BW CT to Siberian sturgeon has an incremental effect on plasma Ca, Mg, and PHO. The increase in plasma Ca level indicated that CT has a potent hypercalcemic effect in sturgeon under laboratory condition, in contrast to the hypocalcemic effects reported for teleosts.

Hypophosphatemic Hypovitaminosis D Induces Osteomalacia in the Adult Female Rat

Osteomalacia is a bone-demineralizing disease of adulthood, often caused by hypovitaminosis D. Current animal models of the disease mimic osteomalacia as a consequence of gastric bypass or toxic exposure to metals, but a relevant model of diet-induced osteomalacia is lacking. For that purpose, 7-month-old female Sprague Dawley rats were randomly assigned into 2 weight-stratified groups and maintained for 4 months on synthetic diets containing negligible or normal levels of vitamin D. The dietary regimen resulted in vitamin D deficiency as measured by 25-hydroxyvitamin D serum levels; however, hypovitaminosis D per se did not affect biomarkers of calcium metabolism and bone turnover, nor did it result in increased osteoid. Thus, vitamin D depletion through the diet was found to be insufficient to induce an osteomalacia-like phenotype in the adult rat. After 4 months, the phosphate content of the vitamin D-depleted diet had decreased to 0.16% (calcium:phosphorus ratio of 5.85), resulting in an osteomalacic-like condition (trabecular osteoid surface/bone surface constituted 33%; CI, 26-40). The diet change also affected both metabolic and bone turnover biomarkers, including significantly suppressing serum fibroblast growth factor 23. Furthermore, decreased dietary phosphate in a vitamin D-depleted diet led to microarchitectural changes of trabecular and cortical bone, lower bone mass density, lower bone mass content and decreased bone strength, all indicating reduced bone quality. Taken together, our results show that osteomalacia can be induced in the adult female rat by depleting vitamin D and lowering phosphate content in the diet.

Serum minerals (Ca, P, Co, Mn, Ni, Cd) and growth hormone (IGF-1 and IGF-2) levels in postmenopausal Saudi women with osteoporosis

Osteoporosis is reported to be common among Saudi women. Several minerals appear to be important determinants of insulin-like growth factor (IGF), the bioactivity of which regulates bone and mineral metabolism. Here we proposed that mineral status may alter the IGF system among individuals with osteoporosis. This study aims to evaluate the relationships between essential elements and IGF levels among postmenopausal Saudi women with osteoporosis. A total of 128 postmenopausal Saudi women aged ≥50 years old were recruited in this study. Diagnosis of osteoporosis was done by using dual-energy x-ray absorptiometry to determine the bone minerals density (BMD). Serum calcium and phosphate were determined using routine chemical analyzer. Serum Co, Mn, Ni, Cd were measured using inductively coupled plasma mass spectrometry. Serum IGF-1 and IGF-2 were determined using Luminex xMAP. Using stepwise linear regression analysis, only Cd was identified to be significantly associated with IGF1 in osteoporosis, explaining 3% (confidence interval 0.01-0.05; P = 0001) of the variance perceived. Our results suggest that Cd exposure indirectly affects BMD which may increase the risk of osteoporosis in postmenopausal women. Further longitudinal study using a larger sample size is recommended to determine causality of Cd levels and IGF-1.

Relationship between serum calcium or phosphate levels and mortality stratified by parathyroid hormone level: an analysis from the MBD-5D study

INTRODUCTION

There is limited evidence about the association between calcium and phosphate levels and mortality stratified by intact parathyroid hormone (iPTH) level.

METHODS

We investigated whether differences in iPTH level affect the relationship between calcium and phosphate levels and all-cause mortality in hemodialysis patients with secondary hyperparathyroidism (SHPT). Calcium and phosphate levels were categorized as low (< 8.5 mg/dL, < 4.0 mg/dL), medium (≥ 8.5-< 9.5 mg/dL, ≥ 4.0-< 7.0 mg/dL), and high (≥ 9.5 mg/dL, ≥ 7.0 mg/dL), respectively. iPTH levels were grouped into < 300 or ≥ 300 pg/mL. Adjusted incidence rate ratios (aIRRs) were analyzed by weighted Poisson regression.

RESULTS

For calcium, patients with higher iPTH (≥ 300 pg/mL) had significantly higher all-cause mortality rates in the high than in the medium category (aIRR 1.99, 95% confidence interval [CI] 1.16-3.42), and tended to have a higher mortality rate in the low category (aIRR 2.04, 95% CI 0.94-4.42). Patients with lower iPTH (< 300 pg/mL) had higher mortality rates in the high than in the medium category (aIRR 1.65, 95% CI 1.39-1.96). For phosphate, the mortality rate was significantly higher in the high than in the medium category in patients with higher and lower iPTH (aIRR 3.23, 95% CI 1.63-6.39 for iPTH ≥ 300 pg/mL; aIRR 1.58, 95% CI 1.06-2.36 for iPTH < 300 pg/mL).

CONCLUSION

High calcium and phosphate levels were associated with increased risk of mortality irrespective of iPTH level.

Gustatory Function and the Uremic Toxin, Phosphate, Are Modulators of the Risk of Vascular Calcification among Patients with Chronic Kidney Disease: A Pilot Study

Patients with chronic kidney disease (CKD) have an increased risk of vascular calcification (VC), including aortic arch calcification (AAC). Few investigated the influence of gustatory function on the probability of having VC. We examined whether gustatory function results modulated the probability of having VC in patients with CKD. We prospectively enrolled adults with CKD (estimated glomerular filtration rate <60 mL/min/1.73 m²), with their AAC rated semi-quantitatively and gustatory function assessed by objective and subjective approaches. Multiple logistic regression was used to analyze the relationship between gustatory function results and AAC. Those with AAC had significantly better objective gustatory function in aggregate scores (p = 0.039) and categories (p = 0.022) and less defective bitter taste (p = 0.045) and scores (p = 0.037) than those without. Multiple regression analyses showed that higher aggregate scores (odds ratio (OR) 1.288, p = 0.032), or better gustatory function, and higher bitter taste scores (OR 2.558, p = 0.019) were each associated with a higher probability of having AAC among CKD patients; such an association was modulated by serum phosphate levels. In conclusion, better gustatory function was independently correlated with having AAC among CKD patients. A follow-up of VC severity may be an underrecognized component of care for CKD patients with a preserved gustatory function.

Mediation of the relationship between proteinuria and serum phosphate: Insight from the KNOW-CKD study

Proteinuria and hyperphosphatemia are risk factors for cardiovascular disease in patients with chronic kidney disease (CKD). Although the interaction between proteinuria and the serum phosphate level is well established, the mechanistic link between the two, particularly the extent to which this interaction is mediated by phosphate-regulating factors, remains poorly understood. In this study, we examined the association between proteinuria and the serum phosphate level, as well as potential mediators, including circulating fibroblast growth factor (FGF23)/klotho, the 24-h urinary phosphate excretion rate to glomerular filtration rate ratio (EP/GFR), and the 24-h tubular phosphate reabsorption rate to GFR ratio (TRP/GFR). The analyses were performed with data from 1793 patients in whom 24-h urine protein and phosphate, serum phosphate, FGF23, and klotho levels were measured simultaneously, obtained from the KoreaN cohort study for Outcome in patients With Chronic Kidney Disease (KNOW-CKD). Multivariable linear regression and mediation analyses were performed. Total, direct, and indirect effects were also estimated. Patients with high serum phosphate levels were found to be more likely to exhibit greater proteinuria, higher FGF23 levels, and lower klotho levels. The 24-h EP/GFR increased and the 24-h TRP/GFR decreased with increasing proteinuria and CKD progression. Simple mediation analyses showed that 15.4% and 67.9% of the relationship between proteinuria and the serum phosphate level were mediated by the FGF23/klotho ratio and 24-h EP/GFR, respectively. Together, these two factors accounted for 73.1% of the relationship between serum markers. These findings suggest that proteinuria increases the 24-h EP/GFR via the FGF23/klotho axis as a compensatory mechanism for the increased phosphate burden well before the reduction in renal function is first seen.

Prevalence and association of depression with uremia in dialysis population: a retrospective cohort analysis

Depression may hamper the immune system and nutritional status, which leads to poor outcomes of treatment. It is very common in dialysis patients. There are the numbers of parameters affected by the depression of patients and available studies are not enough to define the association between biological parameters and depression in the dialysis population. The purposes of the study were to find the prevalence of depression and association of it with the biochemical abnormalities in the dialysis patients.The selected battery of tests (clinician-administered questionnaires) were applied to dialysis patients (test cohort, n = 298) and caregivers (control cohort, n = 202) for establishing depression. The demographic and clinical conditions of participants were also collected. Univariate analysis followed by multiple regression analysis was performed for demographical parameters, clinical conditions, and laboratory results for the detection of association of them with depression. The abnormal test considered as more than 2 SD of mean below the normal value. Out of all tests, at least 2 abnormal tests were considered as mild depression. More than half of abnormal parameters among all tests were considered as moderate depression and all abnormal parameters were considered as severe depression.There was a significant difference for all the test between dialysis patients and the caregivers (P < .0001 for all). The half (153 out of 298) of dialysis patients were depressive and clinically asymptomatic. 70 (23%) dialysis patients were mild depressive, 45 (15%) dialysis patients were moderate depressive, and 38 (13%) dialysis patients were severely depressive. Serum phosphate (P = .023), level of parathyroid hormone (P = .021), and urea reduction rate (P = .048) were directly associated with depression.Biochemical abnormalities (serum phosphate level, parathyroid hormone, and urea reduction rate) were independent predictors of depression in the dialysis population.Level of evidence: III.

Associations of Bariatric Interventions With Micronutrient and Endocrine Disturbances

IMPORTANCE

Few studies have described the longitudinal trajectories of serum levels of micronutrients whose deficiencies are associated with serious sequelae following bariatric procedures, such as anemia, osteoporotic fractures, and neuropathies. Furthermore, previous studies comparing laparoscopic sleeve gastrectomy (LSG) vs Roux-en-Y gastric bypass (LRYGB) or one-anastomosis gastric bypass (OAGB) procedures may have been limited by selection and confounding biases.

OBJECTIVE

To appraise the spectrum and temporal course of micronutrient deficiencies associated with bone metabolism and erythropoiesis after LSG vs OAGB or LRYGB procedures, using the propensity score as a balancing score.

DESIGN, SETTING, AND PARTICIPANTS

This prospective, longitudinal comparative effectiveness study was conducted at a high-volume bariatric unit in Singapore from September 1, 2008, to November 30, 2017, with a cutoff date for analysis of September 2018. Patients who underwent adjustable gastric banding, biliopancreatic diversion procedures, and intragastric balloon procedures were excluded. All other patients who underwent bariatric procedures were included. Data were analyzed from September 23 to 30, 2018.

MAIN OUTCOMES AND MEASURES

Serial assessment of 13 biochemical parameters at 12 time points for up to 5 years after bariatric procedure. Inverse probability-of-treatment weights were used to obtain estimates of the mean associations of variables assessed with the bariatric surgical interventions. Longitudinal trajectories were analyzed using mixed-effects generalized linear models to apportion the temporal variation of serum micronutrients into fixed-effects and random-effects components.

RESULTS

A total of 688 patients were included in this study, of whom 499 underwent LSG (mean [SD] age, 41.5 [11.3] years; 318 [63.7%] women) and 189 underwent OAGB or LRYGB (mean [SD] age, 48.6 [9.4] years; 112 [59.3%] women). There were no differences during follow-up among patients who underwent LSG vs those who underwent OAGB or LRYGB in intact parathyroid hormone levels (mean difference, 7.05 [95% CI, -28.67 to 42.77] pg/mL; P = .70), serum 25-hydroxyvitamin D levels (mean difference, -0.72 [95% CI, -1.56 to 0.12] ng/mL; P = .09), or phosphate levels (mean difference, 0.006 [95% CI, -0.052 to 0.064] mg/dL; P = .83). Hemoglobin levels were a mean 0.63 (95% CI, 0.41 to 0.85) g/dL higher among patients who underwent LSG compared with those who underwent OAGB or LRYGB (P < .001), despite no differences in iron concentration levels (mean difference, 1.50 [95% CI, -1.39 to 4.39] µg/dL; P = .31), total iron-binding capacity (mean difference, 4.36 [95% CI, -5.25 to 13.98] µg/dL; P = .37), or ferritin levels (mean difference, 3.0 [95% CI, -13.0 to 18.9] ng/mL; P = .71). Compared with patients who underwent LSG procedures, patients who underwent OAGB or LRYGB had higher folate levels (mean difference, 2.376 [95% CI, 1.716 to 3.036] ng/mL; P < .001) but lower serum magnesium levels (mean difference, -0.25 [95% CI, -0.35 to -0.16] mg/dL; P < .001) and zinc levels (mean difference, -7.58 [95% CI, -9.92 to -5.24] µg/dL; P < .001).

CONCLUSIONS AND RELEVANCE

These findings suggest that LSG vs OAGB or LRYGB procedures have differential associations with various micronutrient and metabolic parameters. These differences should be recognized in guidelines for postbariatric nutritional surveillance and prevention.

Pharmacokinetics of Oral Cholecalciferol in Healthy Subjects with Vitamin D Deficiency: A Randomized Open-Label Study

BACKGROUND

the aim of this study was to investigate the pharmacokinetic (PK) and safety profile of high-dose vitamin D supplementation, comparing different schedules (daily, weekly, or bi-weekly) in an otherwise healthy vitamin D-deficient population. Methods: single-center, open-label study on healthy subjects deficient in vitamin D (25 (OH)D < 20 ng/mL), randomized to receive cholecalciferol (DIBASE^®, Abiogen Pharma, Italy) using three different schedules: Group A: 10,000 IU/day for eight weeks followed by 1000 IU/day for four weeks; Group B: 50,000 IU/week for 12 weeks, Group C: 100,000 IU/every other week for 12 weeks. Total cumulative doses were: 588,000 IU, 600,000 IU, 600,000 IU. The treatment regimens corresponded to the highest doses allowed for cholecalciferol for the correction of vitamin D deficiency in adults in Italy.

RESULTS

mean 25 (OH)D plasma levels significantly increased from baseline 13.5 ± 3.7 ng/mL to peak values of 81.0 ± 15.0 ng/mL in Group A, 63.6 ± 7.9 ng/mL in Group B and 59.4 ± 12 ng/mL in Group C. On day 28, all subjects showed 25 (OH)D levels ≥ 20 ng/mL and 93.1% had 25 (OH)D levels ≥ 30 ng/mL. On day 56 and 84, all subjects had 25 (OH)D levels ≥ 30 ng/mL. No serious adverse events occurred during the study.

CONCLUSIONS

normalization of 25 (OH)D serum levels was quickly attained with all the studied regimens. A more refracted schedule provided a higher systemic 25 (OH)D exposure.