Comparison of serum alkaline phosphatase levels between two measurement methods in chronic hemodialysis patients in Japan: involvement of ABO blood group system and relationship with mortality risk.

BACKGROUND: Elevated serum alkaline phosphatase (ALP) levels are a risk factor for all-cause mortality in hemodialysis patients. Traditionally in Japan, ALP measurements were conducted using the JSCC method, which yields higher ALP measurement values than the IFCC method, mainly due to its increased sensitivity to intestinal ALP. METHODS: Serum total ALP levels before and after switching the assay method from JSCC to IFCC were compared among different blood types in 521 hemodialysis patients (Study 1). The association between ALP levels measured by the JSCC method and 7-year mortality was analyzed, including blood types and liver function parameters as covariates, in 510 hemodialysis patients (Study 2). RESULTS: ALP levels measured by the JSCC method were approximately three times higher than those measured by the IFCC method, with significant elevation in patients with blood types B and O compared to those with blood types A and AB. Similarly, ALP levels measured by the IFCC method were significantly higher in patients with blood types B and O compared to those with blood types A and AB (Study 1). The highest tertile of ALP levels showed a significantly increased risk of all-cause mortality, even after adjusting for patient background. However, this significance disappeared when serum liver function-related or inflammatory markers were included as covariates (Study 2). CONCLUSION: ALP levels measured by the JSCC method are associated with life prognosis, but caution should be exercised due to their elevation in patients with blood types B and O and in those with hepatic dysfunction or inflammation.

Association between phosphate binder pill burden and mortality risk in patients on maintenance hemodialysis: a single-center cohort study with 7-year follow-up of 513 patients.

BACKGROUND: Dialysis patients often take multiple oral medications, leading to a high pill burden. Phosphate binders (PBs) account for a large proportion of this daily pill burden (DPB). The relationship between DPB and mortality risk remains unclear, and we hypothesized that this relationship might be influenced by the proportion of PBs to all medications. METHODS: We divided DPB into those derived from PBs and non-PB drugs and analyzed the association with mortality risk over a 7-year period in 513 chronic hemodialysis patients using a baseline model. RESULTS: The median (interquartile range) DPB from all drugs was 15.8 (11.2-21.0) pills/day/patient, and the median ratio of PB pills to all drug pills was 29.3 (13.7-45.9)% at baseline. During a median observation period of 5.2 years, 161 patients (31.4%) died. Kaplan-Meier analysis showed no significant difference in all-cause mortality between PB users and non-users. However, a significant survival advantage was observed in the highest tertile of DPB from PBs compared to the lowest tertile. Conversely, the highest tertile of DPB from non-PB drugs was associated with worse survival. Consequently, the highest tertile of the ratio of PBs to all pills was associated with better survival. This association remained significant even after adjusting for patient characteristics in the Cox proportional hazards model. However, when serum nutritional parameters were included as covariates, the significant association disappeared. CONCLUSIONS: Dialysis patients prescribed a higher rate of PB pills to all medications exhibited a lower mortality risk, possibly due to their better nutritional status.

[Pharmacological characteristics of drugs targeted on calcium-sensing receptor.-properties of cinacalcet hydrochloride as allosteric modulator].

Calcimimetics act as positive allosteric modulators of the calcium-sensing receptor (CaSR), thereby decreasing parathyroid hormone (PTH) secretion from the parathyroid glands. On the other hand, negative allosteric modulators of the CaSR with stimulatory effect on PTH secretion are termed calcilytics. The calcimimetic cinacalcet hydrochloride (cinacalcet) is the world's first allosteric modulator of G protein-coupled receptor to enter the clinical market. Cinacalcet just tunes the physiological effects of Ca(2+), an endogenous ligand, therefore, shows high selectivity and low side effects. Calcimimetics also increase cell surface CaSR expression by acting as pharmacological chaperones (pharmacoperones). It is considered that the cinacalcet-induced upper gastrointestinal problems are resulted from enhanced physiological responses to Ca(2+) and amino acids via increased sensitivity of digestive tract CaSR by cinacalcet. While clinical developments of calcilytics for osteoporosis were unfortunately halted or terminated due to paucity of efficacy, it is expected that calcilytics may be useful for the treatment of patients with activating CaSR mutations, asthma, and idiopathic pulmonary artery hypertension.

Fibroblast growth factor 23/klotho axis in chronic kidney disease.

Fibroblast growth factor-23 (FGF23) is a bone-derived hormone that regulates phosphate and 1,25-hydroxyvitamin D [1,25(OH)2D] metabolism. FGF23 binds to FGF receptor 1 with its coreceptor Klotho and maintains serum phosphate levels within the normal range by increasing renal phosphate excretion. In addition, FGF23 reduces the synthesis and accelerates the degradation of 1,25(OH)2D to reduce intestinal phosphate absorption. Moreover, FGF23 acts at the parathyroid gland to decrease parathyroid hormone synthesis and secretion. In chronic kidney disease (CKD), serum FGF23 levels rise exponentially as renal function declines long before a significant increase in serum phosphate concentration occurs. Although there is room for argument, FGF23 and Klotho are recently reported contributors to vascular calcification. Finally, prospective observational studies have shown that serum FGF23 concentrations predict mortality not only among dialysis patients but among predialysis CKD patients. In addition to being a coreceptor for FGF23, Klotho circulates as an endocrine substance and exerts a multitude of effects. This review describes recent advances in research on the FGF23-Klotho axis in CKD. © 2014 S. Karger AG, Basel.

Serum oxalate concentration is associated with coronary artery calcification and cardiovascular events in Japanese dialysis patients.

Coronary artery calcification (CAC) is associated with cardiovascular disease (CVD). CAC might contain calcium oxalate, and a high serum oxalate (SOx) concentration is associated with cardiovascular mortality in dialysis patients. We assessed the associations between SOx and CAC or CVD events in Japanese hemodialysis patients. This cross-sectional and retrospective cohort study was done in 2011. Seventy-seven hemodialysis patients' Agatston CAC score was measured, and serum samples were collected. SOx concentrations were measured in 2021 by using frozen samples. Also, new-onset CVD events in 2011-2021 were retrospectively recorded. The association between SOx concentration and CAC score ≥ 1000, and new-onset CVD events were examined. Median SOx concentration and CAC score were 266.9 (229.5-318.5) µmol/L and 912.5 (123.7-2944), respectively. CAC score ≥ 1000 was associated with SOx [adjusted odds ratio (OR) 1.01, 95% confidence interval (CI), 1.00-1.02]. The number of new-onset CVD events was significantly higher in patients with SOx ≥ median value [hazard ratio (HR) 2.71, 95% CI 1.26-6.16]. By Cox proportional hazard models, new-onset CVD events was associated with SOx ≥ median value (adjusted HR 2.10, 95% CI 0.90-4.91). SOx was associated with CAC score ≥ 1000 and new-onset CVD events in Japanese hemodialysis patients.

[Cinacalcet hydrochloride and phosphate metabolism].

The inhibitory effect of cinacalcet hydrochloride (cinacalcet) on blood phosphorus (P) levels is widely-accepted. However, this effect is only observed in patients on dialysis. Reduction in parathyroid hormone (PTH) induced by cinacalcet increases blood P levels with decreased urinary P excretion in pre-dialysis patients with chronic kidney disease (CKD). Similar results observed in normal and CKD rats provide a pharmacological validation of the trade-off hypothesis. The lowering effect of cinacalcet on blood P levels in dialysis patients is attributed to decreased P mobilization from the bone caused by the decreased PTH secretion. It is unlikely that this P-lowering effect of cinacalcet would bring any benefits on the enhanced parathyroid gland function and bone metabolism. On the other hand, the P-lowering effect of this drug is considered to contribute to its inhibitory effects on the development and progression of vascular calcification in dialysis patients. Further studies should examine this beneficial cinacalcet effect would lead to the reduction of the mortality risk.

Impact of phosphate binders on medication dosing frequency, timing, and number of prescribed pills in hemodialysis patients.

INTRODUCTION: Phosphate binders (PBs) account for a large proportion of the daily pill burden in hemodialysis patients. However, patients do not take them all at once but at several dosing timings. METHODS: We analyzed the dosing timings of all 322 types of oral drugs prescribed to 533 hemodialysis patients. RESULTS: The median daily dosing frequency for all drugs was 6 (4-7) times/day/patient. Patients prescribed PBs had a markedly higher daily dosing frequency than those not taking PBs (7 [5-8] times/day/patient vs. 4 [3-5] times/day/patient, respectively [p < 0.001]). In addition, the ratio of the number of PB pills to other drugs varied greatly at each dosing timing. Furthermore, it was simulated that the daily dosing frequency could be reduced by approximately two times/day/patient by combining the dosing timings of PBs. CONCLUSION: Changing PB dosing timings can reduce the daily dosing frequency, which may lead to improved medication adherence.

Cinacalcet HCl suppresses Cyclin D1 oncogene-derived parathyroid cell proliferation in a murine model for primary hyperparathyroidism.

Cinacalcet HCl (cinacalcet) is a calcimimetic compound, which suppresses parathyroid (PTH) hormone secretion from parathyroid glands in both primary hyperparathyroidism (PHPT) and secondary hyperparathyroidism (SHPT). We previously reported the suppressive effect of cinacalcet on PTH secretion in vivo in a PHPT model mouse, in which parathyroid-targeted overexpression of the cyclin D1 oncogene caused chronic biochemical hyperparathyroidism and parathyroid cell hyperplasia. Although cinacalcet suppressed parathyroid cell proliferation in SHPT in 5/6-nephrectomized uremic rats, its effect on PHPT has not yet been determined. In this study, the effect of cinacalcet on parathyroid cell proliferation was analyzed in PHPT mice. Cinacalcet (1 mg/g) was mixed into the rodent diet and orally administrated to 80-week-old PHPT mice for 10 days before death. 5-Bromo-2'-deoxyuridine (BrdU, 6 mg/day) was infused by an osmotic pump for 5 days before death, followed by immunostaining of the thyroid-parathyroid complex using an anti-BrdU antibody to estimate parathyroid cell proliferation. Compared to untreated PHPT mice, cinacalcet significantly suppressed both serum calcium and PTH. The proportion of BrdU-positive cells to the total cell number in the parathyroid glands increased considerably in untreated PHPT mice (9.5 ± 3.1%) compared to wild-type mice (0.7 ± 0.1%) and was significantly suppressed by cinacalcet (1.2 ± 0.2%). Cinacalcet did not affect apoptosis in the parathyroid cells of PHPT mice. These data suggest that cinacalcet suppressed both serum PTH levels and parathyroid cell proliferation in vivo in PHPT.

Direct evidence for a causative role of FGF23 in the abnormal renal phosphate handling and vitamin D metabolism in rats with early-stage chronic kidney disease.

Circulating levels of fibroblast growth factor 23 (FGF23) are elevated in patients with early chronic kidney disease (CKD) and are postulated to cause low blood levels of 1,25-dihydroxyvitamin D, as well as normal phosphate levels. In order to provide more direct evidence for the pathophysiological role of FGF23 in the settings of mineral ion homeostasis typically seen in early CKD, we studied rats with progressive CKD treated with anti-FGF23 neutralizing antibody. Without antibody treatment, rats with CKD exhibited high circulating levels of FGF23 and parathyroid hormone, low 1,25-dihydroxyvitamin D, and normal serum phosphate levels, accompanied by increased fractional excretion of phosphate. Antibody treatment, however, lessened fractional excretion of phosphate, thus increasing serum phosphate levels, and normalized serum 1,25-dihydroxyvitamin D by increased 1α-OHase and decreased 24-OHase expressions in the kidney. These antibody-induced changes were followed by increased serum calcium levels, leading to decreased serum parathyroid hormone. Hence, our study shows that FGF23 normalizes serum phosphate and decreases 1,25-dihydroxyvitamin D levels in early-stage CKD, and suggests a pathological sequence of events for the development of secondary hyperparathyroidism triggered by increased FGF23, followed by a reduction of 1,25-dihydroxyvitamin D and calcium levels, thereby increasing parathyroid hormone secretion.

Cinacalcet suppresses calcification of the aorta and heart in uremic rats.

High serum parathyroid hormone levels are associated with vascular calcification. Cinacalcet is a calcimimetic agent that inhibits parathyroid hormone secretion and is used to treat patients with secondary hyperparathyroidism. Here we measured the effects of oral cinacalcet on calcification of the aorta and heart in rats with a remnant kidney (5/6 nephrectomy) model of uremia that were fed a high-phosphate diet containing lactose to accelerate the process of aortic calcification. Alizarin red staining showed that the smooth muscle in the aortic arch of rats with a remnant kidney was calcified. The tissue levels of calcium and phosphorus in the aorta and hearts of these rats were significantly increased compared to sham-operated rats. Expression of the osteoblastic lineage genes osteocalcin, osteopontin and runt-related gene 2 were also increased in the aorta of these rats. Cinacalcet suppressed these calcification-related changes by reducing serum parathyroid hormone, calcium, phosphorus, and the calcium-phosphorus product. Parathyroidectomy also suppressed calcification in this model. We suggest that cinacalcet inhibits calcification of the aorta and heart in uremic patients with secondary hyperparathyroidism by decreasing serum parathyroid hormone levels.

[Basic and clinical aspects of calcimimetics. Discovery and development of calcimimetics].

Parathyroid cells can sense small fluctuations in plasma calcium ion (Ca(2 + )) levels by virtue of a cell surface calcium receptor (CaR) that belongs to superfamily of G-protein-coupled receptors. Dr. Nemeth and his colleagues discovered that certain phenylalkylamine compounds stereo-selectively increased intracellular Ca(2 + ) concentration and inhibited parathyroid hormone (PTH) secretion in cultured bovine parathyroid cells. Calcimimetics are positive allosteric modulators that activate the parathyroid CaR and thereby immediately suppress PTH secretion. Cinacalcet hydrochloride (cinacalcet) , which was approved by the FDA in 2004 as the first calcimimetics drug, has just been approved in Japan for the treatment of secondary hyperparathyroidism (SHPT) in patients with chronic kidney disease on dialysis. Clinical trials have shown that cinacalcet has considerable potential as an innovative medical approach to manage SHPT. Thus, the true value of this medicine will be finally evaluated by the Japanese dialysis medical scene.

Phosphate Binders Derived from Natural Ores Contain Many Kinds of Metallic Elements Besides Their Active Ingredient Metals.

Most patients undergoing dialysis are required to take many phosphate binder pills to control hyperphosphatemia. Phosphate binders prescribed in Japan are classified into two types: metal-based binders (Ca carbonate, lanthanum carbonate, ferric citrate hydrate, and sucroferric oxyhydroxide) and chemically synthesized polymers (sevelamer hydrochloride and bixalomer). The raw materials of metal-based phosphate binders are natural ores; thus, such binders may contain several other metallic elements. We measured the elemental contents in six metal-based phosphate binders using an inductively coupled plasma mass - spectrometry (ICP-MS) method. As a result, despite being in small amounts, ore-derived phosphate binders contained various elements besides their active ingredient metals: Na, Mg, P, Mn, Fe, Sr, Y, Ba, La, Nd, and Pb in three Ca-based products; Mg, P, Se, Ce, and Gd in one La-based product; and Na, Mg, Al, P, Ca, Ti, Cr, Mn, Co, Ni, Ge, Ba, and La in two Fe-based products. These elements are considered to have originated from pharmaceutical bulk and from pharmaceutical additives. It is unlikely these elements are immediately harmful to patients. However, it should be emphasized that patients undergoing dialysis do not have a urinary excretion route and are administered many phosphate binder pills every day over a long period of time. In the future, pharmaceutical companies may have to disclose standard amounts and/or analytical values regarding the type and quantity of metallic elements in the final formulation or pharmaceutical bulk derived from natural ores.

Fibroblast growth factor 23 is upregulated in the kidney in a chronic kidney disease rat model.

The hormone fibroblast growth factor 23 (FGF23) is secreted from bone and is involved in phosphorus (P) metabolism. FGF23 mainly binds the FGF receptor, which interacts with αKlotho in the kidney or parathyroid and regulates Na-dependent phosphate co-transporter type IIa (NaPi-IIa) and type IIc (NaPi-IIc) expression, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) activity, and parathyroid hormone (PTH) secretion. In this study, we utilized hemi-nephrectomized rats fed a high-P diet (HP Nx), rats subjected to a partial nephrectomy (PN) and rats with doxorubicin-induced renal failure (DXR) as chronic kidney disease (CKD) animal models and analyzed the P metabolism and FGF23 expression in the kidneys in each CKD model. We cultured HK2 cells with a high level of P, 1,25(OH)2D3 or transforming growth factor-ß1 (TGFß1) to investigate the FGF23 expression mechanism. In both the HP Nx and PN rats, the blood FGF23 and PTH levels were increased. However, the 1,25(OH)2D3 level was increased in the HP Nx rats and decreased in the PN rats. In all three animal models, the mRNA expression of αKlotho, NaPi-IIa and NaPi-IIc was decreased, and the mRNA expression of TGFß1, collagen1a1, osteopontin and FGF23 was elevated in the kidney. FGF23 protein and mRNA were expressed at high levels in the extended tubule epithelium, which was an osteopontin-positive region in the HP and PN rats. FGF23 and osteopontin mRNAs were expressed in HK2 cells incubated with TGFß1; however, these levels were not altered in HK2 cells incubated with 1,25(OH)2D3 and high P levels in vitro. Altogether, FGF23 is expressed in the kidneys in CKD model rats. Following stimulation with TGFß1, the injured renal tubular epithelial cells are strongly suspected to express both FGF23 and osteopontin. FGF23 produced in the kidney might contribute to P metabolism in subjects with CKD.

Pharmacological and clinical properties of calcimimetics: calcium receptor activators that afford an innovative approach to controlling hyperparathyroidism.

Circulating levels of calcium ion (Ca2+) are maintained within a narrow physiological range mainly by the action of parathyroid hormone (PTH) secreted from parathyroid gland (PTG) cells. PTG cells can sense small fluctuations in plasma Ca2+ levels by virtue of a cell surface Ca2+ receptor (CaR) that belongs to the superfamily of G protein-coupled receptors (GPCR). Compounds that activate the CaR and inhibit PTH secretion are termed 'calcimimetics' because they mimic or potentiate the effects of extracellular Ca2+ on PTG cell function. Preclinical studies with NPS R-568, a first generation calcimimetic compound that acts as a positive allosteric modulator of the CaR, have demonstrated that oral administration decreases serum levels of PTH and calcium, with a leftward shift in the set-point for calcium-regulated PTH secretion in normal rats. NPS R-568 also suppresses the elevation of serum PTH levels and PTG hyperplasia and can improve bone mineral density (BMD) and strength in rats with chronic renal insufficiency (CRI). Clinical trials with cinacalcet hydrochloride (cinacalcet), a compound with an improved metabolic profile, have shown that long-term treatment continues to suppress the elevation of serum levels of calcium and PTH in patients with primary hyperparathyroidism (1HPT). Furthermore, clinical trials in patients with uncontrolled secondary hyperparathyroidism (2HPT) have demonstrated that cinacalcet not only lowers serum PTH levels, but also the serum phosphorus and calcium x phosphorus product; these are a hallmark of an increased risk of cardiovascular disease and mortality in dialysis patients with end-stage renal disease. Indeed, cinacalcet has already been approved for marketing in several countries. Calcimimetic compounds like cinacalcet have great potential as an innovative medical approach to manage 1HPT and 2HPT.

Efficacy of darbepoetin in doxorubicin-induced cardiorenal injury in rats.

This study was intended to elucidate the efficacy of an erythropoietin analog in cardiorenal dysfunction syndrome using a rodent model. Cardiorenal dysfunction was induced using doxorubicin hydrochloride (DXR). Lower doses (3 microg/kg) and higher doses (30 microg/kg) of darbepoetin alfa (DA) were used for intervention. Blood examinations for creatinine, blood urea nitrogen, iron, and hemoglobin were performed until 11 weeks after starting DA administration. Urine collection was performed 10 weeks after starting DA, and protein, iron, and N-acetyl-beta-D-glucosaminidase levels and antioxidation capacity of DA were determined. The dry left ventricular heart weight was measured, when the animals were sacrificed 11 weeks after starting DA administration. Histological analyses were performed for interstitial fibrotic changes and iron deposition in the kidney. Administration of DA markedly improved anemia to the normal control level and significantly alleviated DXR-induced increases of creatinine, blood urea nitrogen, renal interstitial fibrosis, renal iron deposition, and dry left ventricular weight, but serum and urinary iron and urinary protein and N-acetyl-beta-D-glucosaminidase levels were unchanged. The urinary total radical-trapping antioxidant capacity was improved to the normal control level in DA-treated animals. DA reduced the DXR-induced cardiorenal injury. This improvement was achieved, when anemia was corrected to the normal control level.

Impact of the Visceral Fat Area Measured by Dual Impedance Method on the Diagnostic Components of Metabolic Diseases in a Middle-aged Japanese Population.

Objective The aim of this study was to examine the associations between the visceral fat area (VFA) and the subcutaneous fat area (SFA) as estimated by the dual impedance method with a body composition monitor (BCM) and the diagnostic components of metabolic syndrome in a middle-aged Japanese population. Methods The subjects included 303 men (average age 51.3±9.0 years old) and 345 women (average age 40.0±9.4 years old). The VFA and SFA were estimated by BCM, and the associations among the components of metabolic syndrome (waist circumference, blood pressure and related blood sample tests) were evaluated. Results VFA showed positive correlations with waist circumference, HbA1c, high-density lipoprotein (HDL)/low-density lipoprotein (LDL) cholesterol, triglyceride and uric acid level in men, while showing positive correlations with waist circumference, HDL cholesterol, triglyceride and HbA1c in women. The estimated SFA showed positive correlations with systolic blood pressure, HDL/LDL cholesterol and triglyceride in men, and HDL cholesterol and triglyceride in women. A receiver operating characteristic (ROC) analysis showed the estimated VFA to be as effective as WC to identify subject with metabolic syndrome. Conclusion By estimating the VFA using BCM, it may be possible to identify patients at risk of developing metabolic syndrome and hyperuricemia.

Relationship between parathyroid calcium-sensing receptor expression and potency of the calcimimetic, cinacalcet, in suppressing parathyroid hormone secretion in an in vivo murine model of primary hyperparathyroidism.

Cinacalcet HCl, an allosteric modulator of the calcium-sensing receptor (CaR), has recently been approved for the treatment of secondary hyperparathyroidism in patients with chronic kidney disease on dialysis, due to its suppressive effect on parathyroid hormone (PTH) secretion. Although cinacalcet's effects in patients with primary and secondary hyperparathyroidism have been reported, the crucial relationship between the effect of calcimimetics and CaR expression on the parathyroid glands requires better understanding. To investigate its suppressive effect on PTH secretion in primary hyperparathyroidism, in which hypercalcemia may already have stimulated considerable CaR activity, we investigated the effect of cinacalcet HCl on PTH-cyclin D1 transgenic mice (PC2 mice), a model of primary hyperparathyroidism with hypo-expression of CaR on their parathyroid glands. A single administration of 30 mg/kg body weight (BW) of cinacalcet HCl significantly suppressed serum calcium (Ca) levels 2 h after administration in 65- to 85-week-old PC2 mice with chronic biochemical hyperparathyroidism. The percentage reduction in serum PTH was significantly correlated with CaR hypo-expression in the parathyroid glands. In older PC2 mice (93-99 weeks old) with advanced hyperparathyroidism, serum Ca and PTH levels were not suppressed by 30 mg cinacalcet HCl/kg. However, serum Ca and PTH levels were significantly suppressed by 100 mg/kg of cinacalcet HCl, suggesting that higher doses of this compound could overcome severe hyperparathyroidism. To conclude, cinacalcet HCl demonstrated potency in a murine model of primary hyperparathyroidism in spite of any presumed endogenous CaR activation by hypercalcemia and hypo-expression of CaR in the parathyroid glands.