Long-Term Effect of Denosumab on Bone Disease in Patients with CKD

BACKGROUND

The effect of long-term denosumab therapy and of denosumab discontinuation on the cortical bone of the hip regions in dialysis patients has not been studied.

METHODS

This retrospective study investigated the cortical and trabecular compartments and estimated strength indices of the hip region, obtained using 3D-SHAPER software, after a maximum of 5 years of denosumab therapy in 124 dialysis patients. A Wilcoxon signed-rank test was used to identify the differences in each parameter before and after denosumab initiation. Similarly, we investigated the changes in these parameters after denosumab discontinuation in 11 dialysis patients.

RESULTS

Integral and trabecular volumetric bone mineral densities (BMD) were significantly lower at the start of denosumab therapy than those in 1 year before denosumab initiation. After starting denosumab, areal BMD (median change +7.7% [interquartile range (IQR), +4.6 to +10.6]), cortical volumetric BMD (median change +3.4% [IQR, +1.0 to +4.7]), cortical surface BMD (median change +7.1% [IQR, +3.4 to +9.4]), and cortical thickness (median change +3.2% [IQR, +1.8 to +4.9]) showed a significantly higher trend for 3.5 years, which then stabilized at a higher value compared with baseline. A similar trend in the trabecular volumetric BMD (median change +9.8% [IQR, +3.8 to +15.7]) was observed over 2.5 years, with a higher value maintained thereafter. The whole area of the hip region improved after denosumab therapy. Similar trajectories were also found in the estimated strength indices. Conversely, at 1 year after denosumab discontinuation, these 3D parameters and estimated strength indices tended to largely worsen. The lateral aspect of the greater trochanter was the most pronounced location showing volumetric BMD loss.

CONCLUSIONS

The BMD of both cortical and trabecular components in the hip region was significantly higher after starting denosumab therapy. However, these measurements exhibited a trend of declining substantially after the discontinuation of denosumab.

Effects of evocalcet on parathyroid calcium-sensing receptor and vitamin D receptor expression in uremic rats

Little is known about the effect of the recently developed calcimimetic evocalcet (Evo) on parathyroid calcium-sensing receptor (CaSR) and vitamin D receptor (VDR) expression. We examined the effects of Evo and cinacalcet (Cina) on CaSR and VDR expression in 5/6 nephrectomized Sprague-Dawley rats fed a high-phosphorus diet for 4 weeks to develop secondary hyperparathyroidism (SHPT). These uremic rats were divided into 4 groups-baseline control (Nx4W) and groups with additional treatment with either the Vehicle, Evo, or Cina for 2 weeks; normal rats were used as normal controls (NC). Blood parameters and parathyroid tissue were analyzed. CaSR and VDR expression levels were determined using immunohistochemistry. The degree of kidney injury and hyperphosphatemia was similar in the uremic groups (Nx4W, Vehicle, Cina, and Evo). Serum parathyroid hormone levels were significantly higher in the Nx4W and Vehicle groups than in the NC group. This increase was significantly suppressed in the Cina and Evo groups compared with that in the Vehicle group. Serum calcium levels were significantly and equally lower in the Cina and Evo groups relative to those in the Vehicle group. CaSR expression was significantly lower in the Nx4W and Vehicle groups than in the NC group. This downregulation was of an equally lesser magnitude in the Cina and Evo groups. A similar trend was observed for VDR expression. These results indicate that Evo and Cina treatment can increase parathyroid CaSR and VDR expression in uremic rats with SHPT, which could provide better control of mineral and bone disorder markers.

Fibroblast Growth Factor 23 Exacerbates Cardiac Fibrosis in Deoxycorticosterone Acetate-Salt Mice With Hypertension

Fibroblast growth factor 23 (FGF23) is associated with cardiovascular disease in patients with chronic kidney disease; however, the mechanisms underlying the effect of FGF23 on cardiac function remain to be investigated. Herein, we studied the effect of continuous intravenous (CIV) FGF23 loading in a deoxycorticosterone acetate (DOCA)-salt mouse model with mild chronic kidney disease and hypertension as well as heart failure with a preserved ejection fraction. Wild-type male mice were randomly allocated to 4 groups: normal control, vehicle-treated DOCA-salt mice, FGF23-treated DOCA-salt mice, and FGF23- and calcitriol-treated DOCA-salt mice. The DOCA-salt mice received the agents via the CIV route for 10 days using an infusion minipump. DOCA-salt mice that received FGF23 showed a marked increase in the serum FGF23 level, and echocardiography in these mice revealed heart failure with a preserved ejection fraction. These mice also showed exacerbation of myocardial fibrosis, concomitant with an inverse and significant correlation with Cyp27b1 expression. Calcitriol treatment attenuated FGF23-induced cardiac fibrosis and improved diastolic function via inhibition of transforming growth factor-β signaling. This effect was independent of the systemic and local levels of FGF23. These results suggest that CIV FGF23 loading exacerbates cardiac fibrosis and that locally abnormal vitamin D metabolism is involved in this mechanism. Calcitriol attenuates this exacerbation by mediating transforming growth factor-β signaling independently of the FGF23 levels.

One-Year Romosozumab Treatment Followed by One-Year Denosumab Treatment for Osteoporosis in Patients on Hemodialysis: An Observational Study

There is limited evidence on the use of romosozumab (ROMO) in the treatment of osteoporosis in patients on hemodialysis (HD); thus, we aimed to investigate this topic. This prospective, observational, single-center cohort study included 13 prior osteoporosis treatment-naïve patients on HD with osteoporosis. They first received ROMO once monthly for 12 months (210 mg; subcutaneously once every month). Thereafter, they received denosumab (DENO) for an additional 12 months (60 mg; subcutaneously once every 6 months). We examined the incidence of new fractures; treatment safety; and temporal changes in the bone mineral density (BMD), bone metabolism markers, and vascular calcification. No new cases of fractures were noted. The median one-year percentage changes (from the baseline) in the BMDs at the lumbar spine (LS), total hip (TH), and femoral neck (FN) were + 9.0%, + 2.5%, and + 4.7%, respectively. These changes were maintained for 24 months. The corresponding relative changes from the baseline to 24 months thereafter were + 14.9%, + 5.4%, and + 6.5%, respectively. The percentage changes in TH BMD and FN BMD were negatively correlated with baseline BMD. Coronary artery and thoracic aorta calcification scores increased slightly from baseline to 12 months thereafter. However, fatal events (cardiovascular disease-associated and all-cause deaths) did not occur during ROMO treatment. Effectiveness of ROMO was better in patients who had severe osteoporosis with low TH BMD, low FN BMD, and high tartrate-resistant acid phosphatase 5b level at ROMO initiation.

Romosozumab successfully regulated progressive osteoporosis in a patient with autosomal dominant polycystic kidney disease undergoing hemodialysis

Osteoporosis is a crucial complication in patients with chronic kidney disease (CKD), similar to that in the general population. Although romosozumab, a monoclonal antibody targeting sclerostin, has been administered for patients with CKD, its clinical effectiveness in these patients, especially in patients on hemodialysis (HD), remains to be studied. Herein, we report the case of a 42-year-old man on HD who developed severe osteoporosis. Serum calcium levels were extremely high, bone metabolic markers were abnormal, and the patient had pathological fractures. The bone biopsy indicated a bone metabolism disorder and high bone turnover. We administered romosozumab once a month as an intervention for bone alteration. Through the 10-month usage, bone metabolic markers improved, and the decrease in bone mineral density was ameliorated. We hypothesized that romosozumab could be a therapeutic option for osteoporosis in patients undergoing HD, especially in those with bone mineralization disorders.

Impact of radial compression protocols on the compression time and radial artery occlusion

Background

Trans-radial access (TRA) has been established as a safe and established approach for invasive coronary catheter procedures. However, protocols for post-procedural hemostasis varies depending on institutes and an evidence-based protocol is lacking.

Purpose

The objective of this study was to investigate the clinical implications of procedural hemostasis.

Methods

Consecutive patients who were referred to outpatient catheter examination before and after April 2018 were treated with an old and a new protocol, respectively. In both protocols, we used the same commercially available hemostasis band with injecting an air of 16 ml for hemostasis. In the old protocol, the amount and timing of deflation were fixed, whereas the air was removed as much as possible for every 30 minutes in the new protocol. Time to complete hemostasis, the rate of major bleeding, and the rate of radial artery occlusion (RAO) at 6 months after the catheter examination were compared between the protocols.

Results

Total of 1,843 (71±10 years old, 77% male) patients was included in the study. Between patients in the old and the new protocol group (n=1,000 and 843, respectively), there was no significant difference in age, gender, body size, or systolic blood pressure. The new group had significantly higher prevalence of diabetes (47% vs 39%, p=0.002), slightly larger sheath size (4.1±0.3 vs 4.0±0.2 Fr, p<0.001), and lower rate of dual antiplatelet therapy (DAPT: 24% vs. 35%, p<0.001). Time for complete hemostasis was about one-third with the new protocol compared with the old protocol (65±32 vs. 190±16 min, p<0.001) and there was no major bleeding in either group. The rate of radial artery occlusion was 0.7% and 9.8% in the old and the new group (p<0.001). Multivariate analysis showed that the significant predictor of prolonged hemostasis time were the old protocol (odds ratio: OR 80.5, p<0.001) and the prescription of DAPT (OR 2.9, p<0.001), while the factors associated with higher risk of radial occlusion were the old protocol (OR 13.9, p<0.001), the number of previous TRA (OR 1.1, p<0.001), and smaller body size (OR 0.127 per 1 m2 increase p=0.005).

Conclusions

Our new protocol for hemostasis after TRA was strongly associated with shorter hemostasis time and a lower rate of radial artery occlusion. This approach will decrease the post-procedural hospital time with even fewer complication rates.

Study outline

Funding Acknowledgement

Type of funding source: None

Lower soluble Klotho levels in the pretransplant period are associated with an increased risk of renal function decline in renal transplant patients

Serum soluble Klotho levels are associated with renal function in predialysis patients with chronic kidney disease. However, few reports exist regarding the association between soluble Klotho levels and renal function in kidney transplant (KTx) recipients. This was a retrospective observational study of 41 living KTx recipients. The serum soluble Klotho levels were classed as "high" (>456 pg/mL [i.e., high-Klotho group]) or "low" (≤456 pg/mL [i.e., low-Klotho group]). Renal function decline was defined as a decrease in the estimated glomerular filtration rate (eGFR) of 30% or more from the baseline value within 3 months after KTx. A multivariable time-to-event analysis between the groups was conducted. Among the KTx recipients, the incidence of a 30% decrease in the eGFR was significantly higher in the low-Klotho group than in the high-Klotho group (P = .036). After adjusting for donor age, donor sex, the presence of rejection, and the number of cytomegalovirus infections, multivariable Cox models revealed that low soluble Klotho levels remained associated with a higher risk of a 30% decrease in the eGFR (hazard ratio, 2.38; 95% confidence interval, 1.02-6.41). These findings suggested that lower soluble Klotho levels in the pre-KTx period are associated with an increased risk of renal function decline in KTx recipients.

Anti-MDA-5 antibody-positive clinically amyopathic dermatomyositis with rapidly progressive interstitial lung disease treated with therapeutic plasma exchange: A case series

We present six cases of antimelanoma differentiation-associated gene 5 antibody (anti-MDA5-Ab)-positive clinically amyopathic dermatomyositis (CADM) with rapidly progressive interstitial lung disease (RP-ILD), which is known to have a poor prognosis. The outcomes of these cases are described after treatment with therapeutic plasma exchange (TPE). Clinical and therapeutic data for patients with CADM with RP-ILD were collected retrospectively from medical records. All six patients received early intensive care including high-dose corticosteroids, intravenous cyclophosphamide, and a calcineurin inhibitor, but lung disease and hypoxia became more severe. TPE was performed over a median of 9.5 sessions (range 3-14) per patient, and the median duration from admission to TPE was 23 days. Three patients received combined direct hemoperfusion using a polymyxin B-immobilized fiber column (PMX-DHP) therapy on successive days to manage acute respiratory failure. Four patients survived and two died due to respiratory failure. In the survival cases, ferritin decreased, and ferritin and KL-6 were lower at diagnosis. The patients who died had a higher alveolar-arterial oxygen difference and more severe lung lesions at the time of initiation of TPE. These findings indicate that a combination of conventional therapy and TPE may be useful for improvement of the prognosis of CADM with RP-ILD at the early stage of onset.

Osteoblastic differentiation of bone marrow mesenchymal stem cells in uremic rats

Severe secondary hyperparathyroidism (SHPT) represents a high turnover bone disease, osteitis fibrosa, but the pathogenesis of osteitis fibrosa remains to be fully elucidated. We examined the characteristics of the differentiation of bone marrow mesenchymal stem cells (BMSCs) into osteoblasts in uremic rats. We bred 5/6 nephrectomized (Nx) rats with a high phosphorus (P) diet to induce SHPT (Nx + HP), or Nx (Nx + ND) and normal rats (Nc + ND) fed a standard diet (ND). After 8 weeks, BMSCs were isolated from the femur and serum were analyzed. BMSCs underwent flow cytometric examination for the expression patterns of cell surface markers (CD90⁺, CD29⁺, CD45^-, and CD31^-). Serum creatinine (Cre) levels were significantly elevated in the Nx + NP rats compared with the Nc + NP rats. Cre levels in the Nx + HP rats were levels to those in the Nx + ND rats. Serum P and PTH levels were significantly elevated in the Nx + HP rats compared with the Nx + ND rats. Bone morphometrical analysis showed increases in both osteoid volume and eroded surfaces in the Nx + HP but not in the Nx + ND rats. The populations of harvested BMSCs were similar between all three groups. Alp, Runx2, Pth1r and Cyclin D1 mRNA expression in the BMSCs from the Nx + ND rats were significantly suppressed compared with those isolated from the Nc + ND groups. Alizarin red staining tended to be similar to the expression of these mRNA. These results suggest that the BMSCs differentiation into osteoblasts was disturbed in the uremic rats.

Early response of the parathyroid gland to withdrawal of a calcimimetic compound in uremic rats

Little is known about changes in parathyroid cells when calcimimetics are withdrawn. We examined the response of parathyroid glands to cinacalcet (Cina) withdrawal in uremic Sprague-Dawley rats fed a high-phosphate diet to develop secondary hyperparathyroidism and divided into groups treated with vehicle (UC), Cina, and Cina and maxacalcitol (Maxa), a vitamin D receptor activator (CiNa + Maxa). After 2 wk of treatment, vehicle and Cina were withdrawn and Maxa was continued. Rats were analyzed immediately (day 0) and 7 days (day 7) after withdrawal. The Cina and CiNa + Maxa groups had significantly lower parathyroid hormone (PTH) than the UC group on day 0, although PTH in the Cina group reached UC levels on day 7. On day 0, there were significantly more proliferating cell nuclear antigen-positive cells in the UC group compared with normal controls, and this increase was significantly suppressed in the Cina and CiNa + Maxa groups. On day 7, the Cina group, but not the CiNa + Maxa group, showed a significant increase in proliferating cell nuclear antigen-positive cells compared with the UC group. This increase was related to parathyroid cell diameter regression to UC levels, whereas combination treatment maintained diameter suppression. These results indicate that parathyroid growth activity is stimulated by Cina withdrawal, although the PTH level was not further increased. Continuous administration of Cina may be required for optimal control of secondary hyperparathyroidism, and simultaneous use of a vitamin D receptor activator may be advisable during Cina withdrawal.

Multidisciplinary management of calciphylaxis: a series of 5 patients at a single facility

Calciphylaxis is a rare and severe disease that manifests with painful skin ulceration and necrosis. Herein, we report five patients of hemodialysis patients with skin biopsy-proven calciphylaxis at a single facility. One patient had undergone parathyroidectomy (PTx) due to severe secondary hyperparathyroidism, four had been treated with vitamin D receptor activators, and two were on warfarin therapy. All patients had hyperphosphatemia, and one had hypercalcemia. The intact parathyroid hormone level at diagnosis was 2 pg/ml in the patient after PTx, while three patients were within the target range. The average period after diagnosis of calciphylaxis was 2 months. Skin lesions were present on the thighs and lower legs in two patients, and on the dorsum of the foot in one patient. In skin biopsy, calcification was found in the arteriolar media in four patients, and calcium (Ca) was deposited in the dermal lesion in one patient. All patients received local cures, surgical debridement, antibiotics to control infectious diseases, and strict control of serum Ca and phosphate. Calcimimetics were used in all patients except one who had undergone PTx one month before, sodium thiosulfate was used in 4 patients, and low Ca dialysate was used in three patients. The average follow-up period was 7.4 months. Four patients were cured, and one died due to infection. We suggest that multidisciplinary management for infectious diseases, surgical debridement, strict control of mineral and bone markers from the early stage, and elimination of risk factors may improve the course of calciphylaxis, which is a life-threatening disease.

Secondary Hyperparathyroidism: Pathogenesis and Latest Treatment

The classic pathogenesis of secondary hyperparathyroidism (SHPT) began with the trade-off hypothesis based on parathyroid hormone hypersecretion brought about by renal failure resulting from a physiological response to correct metabolic disorder of calcium, phosphorus, and vitamin D. In dialysis patients with failed renal function, physiological mineral balance control by parathyroid hormone through the kidney fails and hyperparathyroidism progresses. In this process, many significant genetic findings have been established. Abnormalities of Ca-sensing receptor and vitamin D receptor are associated with the pathogenesis of SHPT, and fibroblast growth factor 23 has also been shown to be involved in the pathogenesis. Vitamin D receptor activators (VDRAs) are widely used for treatment of SHPT. However, VDRAs have calcemic and phosphatemic effects that limit their use to a subset of patients, and calcimimetics have been developed as alternative drugs for SHPT. Hyperphosphatemia also affects progression of SHPT, and control of hyperphosphatemia is, therefore, thought to be fundamental for control of SHPT. Currently, a combination of a VDRA and a calcimimetic is recognized as the optimal strategy for SHPT, and for other outcomes such as reduced cardiovascular disease and improved survival. The latest findings on the pathogenesis and treatment of SHPT are summarized in this review.

Effect of Continuous Intravenous Calcium Loading on Fibroblast Growth Factor 23 in Normal and Uremic Rats

Fibroblast growth factor 23 (FGF23) is associated with mortality in patients with CKD. However, the mechanisms underlying stimulation of FGF23 remain to be investigated. We examined whether hypercalcemia induced by continuous intravenous (CIV) calcium (Ca) infusion regulates FGF23 levels in normal rats (Normal) and 5/6 nephrectomized uremic rats (Nx). Microinfusion pumps were implanted in the Normal and Nx rats for CIV Ca infusion, and blood, urine, kidney, and tibia were collected. The results showed an increase in serum Ca-stimulated FGF23 independently of serum phosphate (P) and creatinine levels in Normal and Nx rats. FGF23 mRNA from the tibia was also increased by the Ca infusion. Despite high FGF23 levels after Ca infusion, urinary P excretion was decreased. Renal α-Klotho expression was significantly reduced by Ca infusion. These results suggest that intravenous Ca loading might stimulate FGF23 production from bone in normal and uremic rats. Reduction of renal P excretion suggests that the bioactivity of FGF23 is inhibited, and the decrease in renal α-Klotho expression might have a role in this pathological process. In conclusion, CIV Ca loading increased FGF23 in normal and uremic rats, and renal α-Klotho is necessary to maintain the bioactivity of FGF23 as a phosphaturic factor.

RAS Inhibitor Is Not Associated With Cardiovascular Benefits in Patients Undergoing Hemodialysis in Japan

Definitive evidence of whether renin angiotensin system (RAS) inhibition is beneficial on cardiovascular events (CVE) among patients undergoing hemodialysis (HD) is lacking. The objective of this study was to investigate the association of RAS inhibitor usage with CVEs in patients enrolled in the Dialysis Outcomes Practice Pattern Study in Japan (J-DOPPS). Association of RAS inhibitor prescription with outcomes including all-cause death, death caused by CVE, and hospitalization due to cardiac failure was investigated by using a multivariable Cox proportional hazards model. Of the 3848 patients enrolled, 1784 (45%) patients were treated by RAS inhibitors. After adjusting for potential cofounders by Cox proportional hazards models, we found a statistically insignificant but positive association of RAS inhibitor usage with death caused by CVE (HR: 1.46, 95%CI: 0.96-2.23, P = 0.08). Similar results were observed in the association of RAS inhibitor with all-cause death, hospitalization due to cardiac failure, and hospitalization due to CV disease (HR for all-cause death: 1.24, 95%CI: 0.84-1.48, P = 0.28, HR for hospitalization due to cardiac failure: 1.24, 95%CI: 0.84-1.81, P = 0.28, and HR for hospitalization due to CV disease: 1.20, 95%CI: 0.95-1.51, P = 0.13). Sensitivity analyses using propensity scores gave similar results. RAS inhibition did not show favorable association with CVEs suggesting that RAS inhibition alone was insufficient to reduce the risk of CV complications in patients undergoing HD. Some strategies in addition to RAS inhibition may be needed to protect against CVEs in this population.

The cardiothoracic ratio and all-cause and cardiovascular disease mortality in patients undergoing maintenance hemodialysis: results of the MBD-5D study

BACKGROUND

The cardiothoracic ratio (CTR) is a non-invasive left ventricular hypertrophy index. However, whether CTR associates with cardiovascular disease (CVD) and mortality in hemodialysis (HD) populations is unclear.

METHODS

Using a Mineral and Bone disorder Outcomes Study for Japanese CKD Stage 5D Patients (MBD-5D Study) subcohort, 2266 prevalent HD patients (age 62.8 years, female 38.0%, HD duration 9.4 years) with secondary hyperparathyroidism (SHPT) whose baseline CTR had been recorded were selected. We evaluated associations between CTR and all-cause death, CVD death, or composite events in HD patients.

RESULTS

CTR was associated significantly with various background and laboratory characteristics. All-cause death, CVD-related death, and composite events increased across the CTR quartiles (Q). Adjusted hazard risk (HR) for all-cause death was 1.4 (95% confidential interval, 0.9-2.1) in Q2, 1.9 (1.3-2.9) in Q3, and 2.6 (1.7-4.0) in Q4, respectively (Q1 as a reference). The corresponding adjusted HR for CVD-related death was 1.8 (0.8-4.2), 3.1 (1.4-6.8), and 3.5 (1.6-7.9), and that for composite outcome was 1.2 (1.0-1.6), 1.7 (1.3-2.2), and 1.8 (1.5-2.3), respectively. Exploratory analysis revealed that there were relationships between CTR and age, sex, body mass index, comorbidity of CVD, dialysis duration and intact parathyroid hormone, phosphorus, hemoglobin, and usage of phosphate binder [corrected].

CONCLUSION

CTR correlated with all-cause death, CVD death, and composite events in HD patients with SHPT.

Cardiac effect of vitamin D receptor modulators in uremic rats

Vitamin D receptor (VDR) modulators (VDRMs) are commonly used to control secondary hyperparathyroidism (SHPT) associated with chronic kidney disease, and are associated with beneficial outcomes in cardiovascular disease. In this study, we compared the cardiac effect of VS-105, a novel VDRM, with that of paricalcitol in 5/6 nephrectomized uremic rats. Male Sprague-Dawley rats were 5/6 nephrectomized, fed a standard diet for 4 weeks to establish uremia, and then treated (intraperitoneally, 3 times/week) with vehicle (propylene glycol), paricalcitol (0.025 and 0.15μg/kg), or VS-105 (0.05 and 0.3μg/kg) for 4 weeks. In uremic rats, neither VDRM (low and high doses) altered serum creatinine and phosphorus levels. Serum calcium was significantly higher with high dose paricalcitol compared to sham rats. PTH levels were significantly decreased with low dose paricalcitol and VS-105, and were further reduced in the high dose groups. Interestingly, serum FGF23 was significantly higher with high dose paricalcitol compared to sham rats, whereas VS-105 had no significant effect on FGF23 levels. Left ventricle (LV) weight and LV mass index determined by echocardiography were significantly suppressed in both high dose VDRM groups. This suppression was more evident with VS-105. Western blotting showed significant decreases in a fibrosis marker TGF-β1 in both high dose VDRM groups (vs. vehicle) and Masson trichrome staining showed significant decreases in cardiac fibrosis in these groups. These results suggest that VS-105 is less hypercalcemic than paricalcitol and has favorable effects on SHPT and cardiac parameters that are similar to those of paricalcitol in uremic rats. The cardioprotective effect is a noteworthy characteristic of VS-105.

PTH-dependence of the effectiveness of cinacalcet in hemodialysis patients with secondary hyperparathyroidism

Cinacalcet lowers parathyroid hormone levels. Whether it can prolong survival of people with chronic kidney disease (CKD) complicated by secondary hyperparathyroidism (SHPT) remains controversial, in part because a recent randomized trial excluded patients with iPTH <300 pg/ml. We examined cinacalcet’s effects at different iPTH levels. This was a prospective case-cohort and cohort study involving 8229 patients with CKD stage 5D requiring maintenance hemodialysis who had SHPT. We studied relationships between cinacalcet initiation and important clinical outcomes. To avoid confounding by treatment selection, we used marginal structural models, adjusting for time-dependent confounders. Over a mean of 33 months, cinacalcet was more effective in patients with more severe SHPT. In patients with iPTH ≥500 pg/ml, the reduction in the risk of death from any cause was about 50% (Incidence Rate Ratio [IRR] = 0.49; 95% Confidence Interval [95% CI]: 0.29–0.82). For a composite of cardiovascular hospitalization and mortality, the association was not statistically significant, but the IRR was 0.67 (95% CI: 0.43–1.06). These findings indicate that decisions about using cinacalcet should take into account the severity of SHPT.

Clinical significance of parathyroid intervention on CKD-MBD management

Recently published ‘Guidelines for the management of secondary hyperparathyroidism in chronic dialysis patients’ by the Japanese Society for Dialysis Therapy advocate that percutaneous ethanol injection into enlarged glands, which has been considered as the only alternative to parathyroidectomy (PTx), should be indicated in patients with a single enlarged parathyroid gland (estimated volume >500 mm³, or estimated major axis >10 mm), and that PTx should be recommended in patients with multiple enlarged glands. Cinacalcet cannot achieve optimal control of chronic kidney disease–mineral bone disorder in all patients, and parathyroid intervention will be required in a considerable number of patients with refractory secondary hyperparathyroidism.

Clinical uses of 22-oxacalcitriol

22-oxacalcitriol (OCT) is a vitamin D3 analog and a vitamin D receptor activator (VDRA) that is used as a drug for secondary hyperparathyroidism (SHPT) and has been available clinically in Japan since 2000. The pharmacological characteristics of OCT include rapid clearance from the systemic circulation compared to that of calcitriol, good tissue distribution, and relatively long retention in the nucleus in parathyroid cells. In clinical studies, OCT has been shown to decrease the parathyroid hormone (PTH) level with an effect equivalent to that of calcitriol. Other reports show that OCT produces superior improvement of bone metabolism compared to calcitriol. Treatment with ultrasound-guided direct injection of OCT into the parathyroid has also been attempted. In animal studies, OCT does not influence the blood Ca or P level and is less likely to promote progression of calcification in cardiovascular tissue. The influence of VDRAs including OCT on the progression of cardiovascular lesions and survival in SHPT patients requires further studies.

[New Developments in CKD-MBD. Future perspective of calcimimetics]

Calcimimetics have beneficial effects on not only secondary hyperparathyroidism, but also control of serum calcium and phosphate levels. Development of novel calcimimetics is progressing. Basic studies have demonstrated the direct effect of calcimimetics on the vascular tissues, which may contribute to the improvement of vascular calcification. Further studies are required to evaluate the usefulness of calcimimetics for mortality.

Is there a need for new phosphate binders to treat phosphate imbalance associated with chronic kidney disease?

INTRODUCTION

Mineral and bone disorder (MBD) begins early in the course of chronic kidney disease (CKD). Phosphate imbalance in CKD-MBD can lead to various pathologies of clinical importance such as further deterioration of kidney function, cardiovascular complications, renal osteodystrophy and increased mortality.

AREAS COVERED

The authors conducted a systematic review of the biomedical literature to evaluate currently available drugs and new phosphate binder therapeutics in development.

EXPERT OPINION

There is a need to continue searching for novel phosphate binders that better match an 'ideal' product profile. This profile should have: i) a product that is highly efficient in binding phosphate; ii) low patient compliance issues; iii) minimal interaction with other drugs; and iv) reduced side effects and safety concerns. Targeting alternative mechanisms, such as developing inhibitors for intestinal type II sodium-dependent phosphate co-transporter, may also improve the limitations of phosphate binder therapeutics. Current medical practice focuses on using serum phosphorus levels as the only marker for detecting, monitoring and treating phosphate imbalance in CKD. However, the consequences of phosphate imbalance are evident in non-dialysis patients before serum phosphate levels rise above the normal range. There is a need to search for other markers to guide detection and treatment of clinically significant alterations in phosphate metabolism of non-dialysis CKD.

Intravenous phosphate loading increases fibroblast growth factor 23 in uremic rats

Oral phosphate loading and calcitriol stimulate Fibroblast growth factor 23 (FGF23) secretion, but the mechanisms underlying the stimulation of FGF23 remain to be studied. We compared the effect of intravenous phosphate loading with that of oral loading on FGF23 levels in normal and 5/6 nephrectomized uremic rats. Uremic rats (Nx) and sham-operated rats were fed a normal phosphate diet for 2 weeks and then divided into 3 groups: 1) with the same phosphate diet (NP), 2) with a high phosphate diet (HP), and 3) NP rats with intravenous phosphate infusion using a microinfusion pump (IV). Blood and urine were obtained 1 day (early phase) and 7 days (late phase) after the interventions. In the early and late phases, serum phosphate levels and fractional excretion of phosphate (FEP) were comparable in the HP and IV groups in both Sham and Nx rats. Serum phosphate levels in the HP and IV groups were equally and significantly higher than those in the NP group only in the late phase in Nx rats. In the early phase, FGF23 levels were comparable in the NP, HP, and IV groups, but were significantly higher in the HP and IV groups compared to the NP group in the late phase in Nx rats. 1α-hydroxylase and sodium dependent phosphate co-transporter 2a expression levels in the kidney in Nx rats were equally and significantly decreased in the HP and IV groups compared with the NP group, while 24-hydroxylase expression was equally and significantly increased. These results show that chronic intravenous phosphate loading increases bioactive FGF23, indicating that an alternative pathway for FGF23 regulation, in addition to the dietary route, may be present. This pathway is clearer under conditions produced by a kidney injury in which phosphate is easily overloaded.

Mechanistic analysis for time-dependent effects of cinacalcet on serum calcium, phosphorus, and parathyroid hormone levels in 5/6 nephrectomized rats

This study investigates the time-dependent effects of cinacalcet on serum calcium, phosphorus, and parathyroid hormone (PTH) levels in 5/6 nephrectomized (NX) rats with experimental chronic renal insufficiency. In this study, 5/6 NX male, Sprague-Dawley rats were treated with vehicle or cinacalcet (10 mg/kg, oral, 1× daily). On Day 0 (before treatment), Day 12 and 13 after treatment (to approximate the clinical practice), and also at 0, 1, 4, 8, 16, and 24 hours after the last dosing, blood was collected for analysis. After 12 or 13 days of cinacalcet treatment, modest changes were observed in serum Ca and phosphorus (Pi), while PTH decreased by >45% to Sham levels (152 ± 15 pg/mL). Detailed mapping found that cinacalcet caused a significant time-dependent decrease in serum Ca following dosing, reaching a lowest point at 8 hours (decrease by 20% to 8.43 ± 0.37 mg/dL), and then returning to normal at 24 hours. Cinacalcet also caused a significant increase in serum Pi levels (by 18%). To investigate the potential mechanism of action, a broad approach was taken by testing cinacalcet in a panel of 77 protein-binding assays. Cinacalcet interacted with several channels, transporters, and neurotransmitter receptors, some of which are involved in brain and heart, and may impact Ca homeostasis. Cinacalcet dose-dependently increased brain natriuretic peptide (BNP) mRNA expression by 48% in cardiomyocytes, but had no significant effects on left ventricular hypertrophy and cardiac function. The results suggest that cinacalcet's hypocalcemic effect may be due to its nonspecific interaction with other receptors in brain and heart.

Correction of hyperphosphatemia suppresses cardiac remodeling in uremic rats

BACKGROUND

Hyperphosphatemia is associated with cardiovascular disease in patients with chronic kidney disease. To examine the effects of correction of hyperphosphatemia, we investigated the association between phosphate metabolism and cardiac remodeling in uremic rats.

METHODS

Four groups were studied for 8 weeks: (1) control (sham), (2) 5/6 nephrectomized (Nx) rats fed a normal phosphate regular diet (Nx + NP), (3) Nx rats fed a high phosphate (1.2 %) diet (Nx + HP), and (4) Nx rats fed a high phosphate diet containing 2 % lanthanum carbonate (Nx + HP + La). The relationship between phosphate metabolism and cardiac remodeling was analyzed.

RESULTS

Nx + HP rats showed a significant increase in serum phosphate and PTH compared with Nx + NP rats, while Nx + HP + La rats showed slight decreases in these levels. Both Nx + HP and Nx + HP + La rats showed a significant increase in fibroblast growth factor-23 (FGF23) compared with Nx + NP rats. Urinary phosphate excretion showed a similar trend to that of FGF23. Nx + HP rats showed a significant increase in LV weight and matrix deposition compared with Nx + NP rats, and this increase was also significantly suppressed in Nx + HP + La rats. Serum phosphate levels and PTH were significantly correlated with LV weight and matrix deposition, but FGF23 levels did not show the correlation. FGF23 had a high correlation with urinary phosphate excretion.

CONCLUSIONS

These results suggest that correction of hyperphosphatemia by lanthanum carbonate could suppress cardiac remodeling independently of changes in FGF23.

[Phosphate sensing and parathyroid gland]

In the latter 1990s, phosphate, as well as calcium, has been shown to have a direct action on parathyroid function. Since then although many researchers have tried to detect the phosphate sensor in parathyroid gland, none has found it yet. In 2000s, the importance of FGF23 was revealed in patients with autosomal dominant hypophosphatemic rickets and then investigating the role of FGF23 in mineral metabolism has spread. FGF23 target organs comprise those that express coreceptor Klotho, such as kidney and parathyroid glands. While associations of calcium sensing receptor or vitamin D receptor with parathyroid function have been mainly investigated for parathyroid dysfunction, many efforts recently have made to study the effects of FGF23 on parathyroid glands.

Vitamin D receptor activators inhibit vascular smooth muscle cell mineralization induced by phosphate and TNF-α

BACKGROUND

Vascular calcification is a highly regulated process. Tumor necrosis factor-α (TNF-α) has been shown to accelerate the highly regulated osteogenic process in vascular smooth muscle cells (VSMCs). Vitamin D receptor activators (VDRAs) have been associated with beneficial cardiovascular outcomes in patients with chronic kidney disease. We examined whether maxacalcitol, a vitamin D(3) analog, exhibits a suppressive effect on VSMC mineralization induced by phosphate and TNF-α.

METHODS

Human VSMCs were treated with either vehicle, maxacalcitol (10(-9) to 10(-7) M), or calcitriol (10(-9) to 10(-7) M) in 2.5 mM of phosphate media with TNF-α (1 ng/mL) for 9 days. VSMC mineralization was determined and expression of genes associated with the osteogenic process was examined by real-time reverse transcription-polymerase chain reaction. Expression of matrix metalloproteinase-2 (MMP-2) messenger RNA (mRNA) in VSMCs and MMP-2 protein in media was also analyzed.

RESULTS

Vehicle-treated VSMCs exhibited massive mineralization, which was inhibited by maxacalcitol in a concentration-dependent manner. Calcitriol also inhibited the mineralization. While vehicle-treated VSMCs exhibited increased mRNA expression of genes associated with the osteogenic process (Cbfa1/Runx2 and osteocalcin) compared with VSMCs grown in normal media without TNF-α (control), maxacalcitol and calcitriol suppressed the increase in mRNA species. Furthermore, vehicle-treated VSMCs exhibited increased MMP-2 mRNA and protein in the media that were suppressed notably by maxacalcitol.

CONCLUSIONS

Both the VDRAs abrogated the acceleration of the osteogenic process induced by phosphate and TNF-α in VSMCs, which was linked to inhibition of mineralization in VSMCs. MMP-2 blockade by VDRAs may contribute to an inhibitory effect on vascular calcification.

[Bone and calcium update; diagnosis and therapy of metabolic bone disease update. Advances in treatment of CKD-MBD]

Secondary hyperparathyroidism and vascular calcification are major clinical states in CKD-MBD (chronic kidney disease-mineral and bone disorder) . Recently fibroblast growth factor 23-klotho axis has been shown to be implicated in the pathogenesis of secondary hyperparathyroidism. Vascular calcification has been identified to be a highly regulated process. Novel therapeutic agents for CKD-MBD have been developed. The guidelines of CKD-MBD have been announced from many countries including Japan from the point of view of patient's survival, and it is expected that the development of practice for CKD-MBD will contribute to better survival.

Effects of calcimimetic combined with an angiotensin-converting enzyme inhibitor on uremic cardiomyopathy progression

BACKGROUND/AIMS

Angiotensin-converting enzyme (ACE) inhibitors have cardioprotective properties and functional calcium-sensing receptors express in cardiac myocytes.

METHODS

Rats were made uremic by 5/6 nephrectomy and treated as follows: uremic rats were fed on a regular diet (UC), uremic + enalapril (E), uremic + calcimimetic agent R-568 (R-568), and uremic + enalapril + R-568 (E+R-568). A group of normal rats served as controls (NC).

RESULTS

Blood pressure (BP) and left ventricle mass were elevated significantly in the UC and R-568 groups compared with those in the NC group, but were indistinguishable from normal controls in the E and E+R-568 groups. Cardiac fibrosis was significantly increased in the UC group compared with that in the NC group. This increase was significantly attenuated in the R-568 and E groups, and the attenuation was further enhanced in the E+R-568 group. Factors associated with cardiac hypertrophy such as proliferating cell nuclear antigen, cyclin D1, and cyclin D2, as well as factors associated with cardiac fibrosis such as type I collagen, fibronectin, and transforming growth factor-β1 were significantly increased in the UC group compared with those in the NC group. Monotherapy with R-568 or E attenuated this increase and the combination further attenuated these measures.

CONCLUSIONS

Calcimimetics can suppress the progression of uremic cardiomyopathy and this effect is amplified when BP is controlled via renin-angiotensin system blockade.

Detection of peripheral artery disease by duplex ultrasonography among hemodialysis patients

BACKGROUND AND OBJECTIVES

Peripheral arterial disease (PAD) is a known predictor of cardiovascular morbidity and mortality among hemodialysis patients. Although ankle-brachial BP index (ABI) is a simple and reliable test for PAD screening, its sensitivity has been suggested to decrease among dialysis patients.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We performed a cross-sectional outpatient cohort study to examine prevalence of PAD among hemodialysis patients using duplex ultrasonography of the lower extremity artery. We also evaluate the influence of increased arterial stiffness on impaired accuracy of ABI for PAD screening.

RESULTS

Of 315 total patients, 23.8% had PAD. PAD was associated with younger age, diabetes, current smoking, atherosclerotic comorbidities, increased total cholesterol levels, increased triglyceride levels, and lower Kt/V. The receiver operating characteristic analysis (area under the receiver operating characteristic curve = 0.846) showed that sensitivity and specificity of ABI values for PAD were 49.0 and 94.8%, respectively. An ABI cut-off value of 1.05 resulted in the best sensitivity (74.5%) and specificity (84.4%). There was a significant difference in sensitivity of ABI levels <0.9 for detecting PAD among patients in different brachial-ankle pulse wave velocity quartiles. In patients with the highest brachial-ankle pulse wave velocity quartile, PAD was most prevalent (46.5%), and ABI had the highest accuracy in detecting PAD (area under the curve, 0.933).

CONCLUSIONS

These results suggest that duplex ultrasonography was a useful tool for screening asymptomatic PAD among hemodialysis patients and that the diagnostic value of ABI for PAD was affected by various factors.

Myocardial effects of VDR activators in renal failure

Cardiovascular complications are the leading cause of death in patients with chronic kidney disease (CKD). Traditional causes such as diabetes, smoking, aging and hypertension do not fully explain the high rate of morbidity from cardiovascular disease seen in these patients. The renin-angiotensin-aldosterone system (RAAS) regulates extracellular volume homeostasis, which contributes to blood pressure stability. Overactivity of this system is involved in the pathophysiology of cardio-renal disease. New evidence suggests that vitamin D receptor activators (VDRAs) have a suppressive effect on the RAAS; however, VDRAs also have anti-inflammatory and anti-fibrotic effects. We have demonstrated that paricalcitol, a VDRA, ameliorates left ventricular hypertrophy (LVH) in uremic rats by up-regulating the VDR, decreasing myocardial PCNA and also decreasing myocardial oxidative stress. Thus, paricalcitol can suppress the progression of LVH, myocardial and perivascular fibrosis and myocardial arterial vessel thickness presumably by up-regulating the VDR. Paricalcitol may prove to have a substantial beneficial effect on cardiac disease and its outcome in patients with CKD. Prospective randomized studies in CKD patients are necessary to confirm these results.

[CKD-MBD (chronic kidney disease-mineral and bone disorder). CKD-MBD: chronic kidney disease-mineral and bone disorder]

Disturbances in bone and mineral metabolism in patients with chronic kidney disease (CKD) affect not only the bone diseases but also other organ disorders in the whole body and deteriorate the survival of these patients. The term CKD-Mineral and Bone Disorder (CKD-MBD) has been established describing a broader clinical syndrome that develops as a systemic disorder of mineral and bone metabolism due to CKD. Vascular calcification and secondary hyperparathyroidism are major diseases in CKD-MBD.

Novel markers of left ventricular hypertrophy in uremia

AIMS

Left ventricular hypertrophy (LVH) is the most frequent cardiac complication in chronic renal disease. Previous studies implicate elevated serum phosphorus as a risk factor for LVH.

METHODS

We treated 5/6 nephrectomized rats with enalapril or enalapril + sevelamer carbonate for 4 months to determine if sevelamer carbonate had an additional beneficial effect on the development of LVH and uremia-induced left ventricle (LV) remodeling.

RESULTS

Uremia increased LV weight and cardiomyocyte size. Enalapril and enalapril + sevelamer blunted the increase in left ventricular weight. Only enalapril + sevelamer diminished the increase in cardiomyocyte size. Uremia increased cyclin D2 and PCNA and decreased p27 protein expression in the heart. Enalapril + sevelamer diminished the decrease in p27 expression caused by uremia. Uremia increased Ki67-positive and phosphohistone H(3)-positive interstitial cells. This was not seen in cardiomyocytes. Multivariable regression analysis showed that increased phosphorus was an independent risk factor for both increased LV weight and cardiomyocyte size.

CONCLUSIONS

These data suggest left ventricular remodeling consists of cardiomyocyte hypertrophy and interstitial cell proliferation, but not cardiomyocyte proliferation. p27 and cyclin D2 may play important roles in the development of LVH. In addition, phosphorus can be an independent risk factor for the development of LVH.

Involvement of alpha-klotho and fibroblast growth factor receptor in the development of secondary hyperparathyroidism

BACKGROUND/AIMS

Fibroblast growth factor 23 (FGF23) has been shown to suppress parathyroid hormone (PTH) secretion. alpha-Klotho has been demonstrated to function as a fibroblast growth factor receptor (FGFR) cofactor for FGF23. Thus, both alpha-Klotho and FGFR may play roles in PTH synthesis and/or secretion. Functions of alpha-Klotho and FGFR in secondary hyperparathyroidism (SHPT) remain to be studied. The present studies explore the role of alpha-Klotho and FGFR in SHPT.

METHODS

Hyperplastic parathyroid glands (n = 44) were obtained from patients with SHPT.

RESULTS

Immunohistochemical study showed that both alpha-Klotho and FGFR1c expression in hyperplastic glands was significantly decreased compared with that in normal glands (Klotho p < 0.01, and FGFR1c p < 0.05). A significant positive correlation was observed between alpha-Klotho and FGFR1c (r(2) = 0.375, p < 0.01) indicating a cooperative system. Both alpha-Klotho (r(2) = 0.235, p < 0.05) and FGFR1c (r(2) = 0.181, p < 0.05) correlated positively with the calcium-sensing receptor (CaR), which plays an important role in the development of SHPT. In addition, expression of alpha-Klotho correlated negatively with parathyroid cell proliferation, as confirmed by Ki67 staining (r(2) = 0.148, p < 0.05).

CONCLUSION

Decreased expression of alpha-Klotho and FGFR1c in parallel with CaR expression and parathyroid cell growth may be involved in the pathogenesis of SHPT.

Elastin degradation accelerates phosphate-induced mineralization of vascular smooth muscle cells

Medial layer vascular calcification is common in patients with end-stage kidney disease. Inorganic phosphate has been shown to accelerate the transformation of vascular smooth muscle cells (VSMCs) into osteoblast-like cells, which is thought to be a major process of medial layer calcification. Although elastin degradation is associated with medial layer calcification, the linkage between elastin degradation and the transformation of VSMCs remains to be clarified. We investigated the involvement of elastin degradation in the transformation of VSMCs. Rat VSMCs were isolated and cultured with a normal- (NP, 1.0 mM) or high- (HP, 2.5 mM) phosphate medium. An elastin-derived peptide, alpha-elastin (500 microg/ml), was also added to the normal- (NP + E) or high- (HP + E) phosphate medium. After a culture period of 2 weeks, von Kossa staining revealed mineralization in the HP group, which was accelerated by alpha-elastin, whereas alpha-elastin did not affect the mineralization at a normal phosphate concentration. The gene expression of osteoblastic differentiation factors, i.e., Runx2 or osteocalcin (OC), in VSMCs was significantly increased in the HP (Runx2 P < 0.05, OC P < 0.05) and HP + E (OC P < 0.05) groups compared with the NP and NP + E groups. Both gene and protein expressions of tissue-nonspecific alkaline phosphatase (TNAP) were significantly increased in the HP group compared with the NP and NP + E groups (P < 0.01, respectively). This increment was augmented in the HP + E group (P < 0.01). These results suggest that elastin degradation would accelerate or stabilize the process of VSMC transformation, which is induced by high phosphate through the upregulation of TNAP.

Vitamin D and vascular calcification in chronic kidney disease

Vascular calcification is frequently observed and is closely associated with cardiovascular mortality in patients with chronic kidney disease (CKD). Vascular calcification is largely divided into two types. One is atherosclerotic intimal layer calcification and the other is medial layer calcification (Monckeberg's calcification). The latter is more common in patients with CKD than in general population. Evidence is growing that vascular calcification is a regulated active process as well as a passive process resulting from elevated serum phosphate (P) and an increase in the calcium phosphate (Ca x P) product leading to oversaturated plasma. Proving the active process, in vitro studies have demonstrated that the transformation of vascular smooth muscle cells (VSMCs) into osteoblast-like cells is a crucial mechanism in the progression of vascular calcification. Reduction of the activity of systemic and local inhibitors has also been recognized to be important. The link between vitamin D and vascular calcification is complex. Experimental and clinical researches have revealed that both vitamin D excess and vitamin D deficiency have been shown to be associated with vascular calcification in uremic milieu. On the other hand, although there are some biases, recent large observational studies have demonstrated that vitamin D has beneficial effects on the mortality of patients with CKD independent of serum Ca, P, and parathyroid hormone levels, likely due to its activation of the vitamin D receptor in vasculature and cardiac myocytes. Further prospective studies are necessary to evaluate the direct effect of vitamin D on vascular calcification in order to improve the cardiovascular health of patients with CKD.

Vascular calcification: the killer of patients with chronic kidney disease

Cardiovascular complications are the leading cause of death in patients with chronic kidney disease (CKD). Vascular calcification is a common complication in CKD, and investigators have demonstrated that the extent and histoanatomic type of vascular calcification are predictors of subsequent vascular mortality. Although research efforts in the past decade have greatly improved our knowledge of the multiple factors and mechanisms involved in vascular calcification in patients with kidney disease, many questions remain unanswered. No longer can we accept the concept that vascular calcification in CKD is a passive process resulting from an elevated calcium-phosphate product. Rather, as a result of the metabolic insults of diabetes, dyslipidemia, oxidative stress, uremia, and hyperphosphatemia, "osteoblast-like" cells form in the vessel wall. These mineralizing cells as well as the recruitment of undifferentiated progenitors to the osteochondrocyte lineage play a critical role in the calcification process. Important transcription factors such as Msx 2, osterix, and RUNX2 are crucial in the programming of osteogenesis. Thus, the simultaneous increase in arterial osteochondrocytic programs and reduction in active cellular defense mechanisms creates the "perfect storm" of vascular calcification seen in ESRD. Innovative clinical studies addressing the combined use of inhibitors that work on vascular calcification through distinct molecular mechanisms, such as fetuin-A, osteopontin, and bone morphogenic protein 7, among others, will be necessary to reduce significantly the accrual of vascular calcifications and cardiovascular mortality in kidney disease. In addition, the roles of oxidative stress and inflammation on the fate of smooth muscle vascular cells and their function deserve further translational investigation.

[Novel phosphate binders under development]

Controlling serum phosphorus levels in patients with chronic kidney disease is crucial. Since hyperphosphatemia is an established risk factor for not only secondary hyperparathyroidism, but also cardiovascular mortality in these patients, the adequate control of serum phosphorus is necessary. The target levels of serum phosphorus, however, are not consistently being met. To achieve better control of serum phosphorus levels, some novel phosphate binders, which do not contain calcium or metal, have been developed. In this manuscript we discuss some novel phosphate binders, which are now in clinical trials.

Blockage of the renin-angiotensin system attenuates mortality but not vascular calcification in uremic rats: sevelamer carbonate prevents vascular calcification

BACKGROUND/AIMS

Hyperphosphatemia is associated with vascular calcification and increased cardiovascular morbidity and mortality. Angiotensin-converting enzyme inhibitors are beneficial in suppressing the progression of kidney and cardiovascular disease. The present studies explore the influence of enalapril and sevelamer carbonate on renal function, vascular calcification and mortality in long-term experimental uremia.

METHODS

Normal and 5/6 nephrectomized rats were fed a high-phosphorus diet for 4 months and treated with enalapril or the combination of both enalapril and sevelamer carbonate.

RESULTS

The rats treated with enalapril alone or both enalapril and sevelamer had less deterioration in renal function compared to uremic control as seen by lower serum creatinine (1.6, 1.6 vs. 2.1 mg/dl, respectively, p < 0.05) and higher creatinine clearance. They also exhibited attenuated mortality (23.5, 12.5 vs. 75%, respectively, p < 0.01) and inhibition of myocardial hypertrophy. Enalapril alone did not suppress secondary hyperparathyroidism or vascular calcification. Combination therapy with both enalapril and sevelamer carbonate ameliorated secondary hyperparathyroidism and vascular calcification (calcium content: 854 +/- 40 vs. 1,735 +/- 479 microg/g wet tissue) compared to uremic controls.

CONCLUSION

In these experiments, animal mortality and myocardial hypertrophy were significantly reduced by both enalapril alone and enalapril in combination with sevelamer. In addition, sevelamer carbonate induced beneficial effects on renal dysfunction, secondary hyperparathyroidism and vascular calcification.