The management of hyperphosphatemia by lanthanum carbonate in chronic kidney disease patients

Effects of cerium oxide nanoparticles on adenine-induced chronic kidney disease model rats

AIM

Cerium oxide, particularly in nanoparticle form (nanoceria), has been investigated for biomedical applications as a promising new agent for treating several pathologies. The aim of the present study was to characterize the pharmacologic effects of nanoceria in an animal model of chronic kidney disease.

METHODS

We created the chronic kidney disease animal model by feeding rats a 0.25% adenine diet. Male Wistar rats were divided into five groups: normal diet, 0.25% adenine diet, or adenine diet containing three different doses or durations of nanoceria treatment. Blood was collected weekly from the tail veins of each rat and analyzed for renal function markers. After 5 weeks, various biochemical markers in serum, plasma, and urine were also analyzed.

RESULTS

In the adenine-treated group, body weight was significantly decreased, and the kidneys lost much of their healthy reddish color and became lumpy and white in appearance. In addition, levels of serum creatinine, blood urea nitrogen, and plasma uremic toxins were significantly increased in adenine-treated rats compared with controls. Renal functional and structural damage in adenine diet model rats tended to be ameliorated by nanoceria ingestion. The high-dose cerium-treated group maintained reddish areas in the kidneys, and the increases in biomarker levels of creatinine, blood urea nitrogen, and inorganic phosphorus were markedly reduced, regardless of treatment duration.

CONCLUSIONS

Ingestion of nanoceria may be effective for improving or preventing renal damage caused by adenine. Geriatr Gerontol Int 2024; 24: 88-95.

Magnesium inhibits peritoneal calcification as a late-stage characteristic of encapsulating peritoneal sclerosis

Peritoneal calcification is a prominent feature of the later stage of encapsulating peritoneal sclerosis (EPS) in patients undergoing long-term peritoneal dialysis (PD). However, the pathogenesis and preventive strategy for peritoneal calcification remain unclear. Peritoneum samples from EPS patients were examined histologically. Peritoneal calcification was induced in mice by feeding with an adenine-containing diet combined with intraperitoneal administration of lipopolysaccharide and a calcifying solution containing high calcium and phosphate. Excised mouse peritoneum, human mesothelial cells (MeT5A), and mouse embryonic fibroblasts (MEFs) were cultured in calcifying medium. Immunohistochemistry confirmed the appearance of osteoblastic differentiation-marker-positive cells in the visceral peritoneum from EPS patients. Intraperitoneal administration of magnesium suppressed peritoneal fibrosis and calcification in mice. Calcifying medium increased the calcification of cultured mouse peritoneum, which was prevented by magnesium. Calcification of the extracellular matrix was accelerated in Met5A cells and MEFs treated with calcification medium. Calcifying medium also upregulated osteoblastic differentiation markers in MeT5A cells and induced apoptosis in MEFs. Conversely, magnesium supplementation mitigated extracellular matrix calcification and phenotypic transdifferentiation and apoptosis caused by calcifying conditions in cultured MeT5A cells and MEFs. Phosphate loading contributes to the progression of EPS through peritoneal calcification and fibrosis, which can be prevented by magnesium supplementation.

Evaluation of cerium oxide as a phosphate binder using 5/6 nephrectomy model rat

BACKGROUND

The number of chronic kidney disease (CKD) patients continues to increase worldwide. CKD patients need to take phosphate binders to manage serum phosphorus concentrations. Currently, several types of phosphate binder, including lanthanum carbonate, are used. However, they each have disadvantages.

METHODS

In this study, we evaluated cerium oxide as a new phosphate binder in vitro and in vivo. First, cerium oxide was mixed with phosphoric acid at pH 2.5 or 7.0, and residual phosphoric acid was measured by absorption photometry using colorimetric reagent. Second, cerium oxide was fed to 5/6 nephrectomy model rats (5/6Nx), a well-known renal damage model. All rats were measured food intake, water intake, feces volume, and urine volume, and collected serum and urine were analyzed for biochemical markers.

RESULTS

Cerium oxide can adsorb phosphate at acidic and neutral pH, while lanthanum carbonate, which is a one of popular phosphate binder, does not dissolve at neutral pH. Cerium oxide-treatment reduced serum phosphate concentrations of 5/6Nx rats without an increase in serum alanine transaminase levels that would indicate hepatotoxicity, and cerium oxide-treatment maintained serum creatinine and blood urea nitrogen levels, while those of normal 5/6Nx rats increased slightly.

CONCLUSIONS

These results suggest that cerium oxide can be a potential phosphate binder. Decreased body weight gain and increased water intake and urine volume in 5/6Nx rats were thought to be an effect of nephrectomy because these changes did not occur in sham operation rats. Additional investigations are needed to evaluate the longer-term safety and possible accumulation of cerium oxide in the body.

Pharmacotherapy in chronic kidney disease hyperphosphatemia – effects on vascular calcification and bone health

Hyperphosphatemia (HP) in patients with chronic kidney disease (CKD) leads to complications such as renal osteodistrophy, cardiovascular calcification and hemodynamic abnormalities, all of them having a serious impact on the survival rate and quality of life. Also, HP is a key pathogenic factor in the development of secondary hyperparathyroidism (SHPT) in CKD. Having in regard the significance of controlling serum phosphorus levels (Pi), in this paper, the needs and obstacles to successful pharmacological management of HP in CKD are presented, with an overview of major classes of phosphate binders (PBs) and other drugs affecting Pi level, such as active vitamin D sterols and calcimimetics (CMs). In addition, their effects on progression of cardiovascular calcification and bone health are elaborated. In this regard, a PubMed search was carried out to capture all abstracts and articles relevant to the topic of CKD, HP and mineral metabolism, bone disorders and vascular/valvular calcification (VC), published from January 2007 to August 2017. The search was limited to English language, with the search terms including drug name AND hyperphosphatemia or cardiovascular calcification or bone disorder. Comparative studies, clinical studies/trials and meta-analyses related to different classes/representatives of PBs, vitamin D analogues and CMs were reviewed and research data related to their efficacy and safety compared. Keywords: chronic kidney disease, hyperphosphatemia, phosphate binders, active vitamin D sterols, calcimimetics, bone disorders, cardiovascular calcification

The feasibility of in vivo detection of lanthanum using a 241Am K x-ray fluorescence system

OBJECTIVE

Lanthanum (La) is commonly used in phosphate binders in the form of lanthanum carbonate in patients with end-stage kidney disease undergoing hemodialysis treatments. With this administration, there is the potential for La storage in the body with bone being the main site of concern. However, the long-term effects of residual La in the body on bone health are not yet known. In this work, we investigate the feasibility of using a K x-ray fluorescence (K-XRF) spectroscopy system to measure bone La in vivo.

APPROACH

A series of hydroxyapatite (HAp) bone mineral phantoms were created to represent human bone. A 1.09 GBq ²⁴¹Am source was used to excite the HAp phantoms doped with various known concentrations of La placed in a 90° geometry relative to the photon source and high-purity germanium (HPGe) detector.

MAIN RESULTS

For a detector live time of 2000 s, the minimum detection limit was calculated to be 1.7 µg La g^-1 Ca or 0.7 µg La g^-1 HAp and is comparable to previously reported in vivo bone La concentrations.

SIGNIFICANCE

The technique developed in this study shows promising results and provides an alternative method to invasive biopsy sampling techniques to monitor the accumulation of bone La. To the best of our knowledge, this is the first reported work that seeks to non-invasively measure bone La via in vivo XRF.

Lanthanum deposition in the gastrointestinal mucosa and regional lymph nodes in dialysis patients: Analysis of surgically excised specimens and review of the literature

Lanthanum carbonate (LC) is one of the most potent phosphate binders currently used to reduce serum phosphate levels in dialysis patients with end-stage renal disease (ESRD). LC forms insoluble complexes with dietary phosphate that pass through the gastrointestinal (GI) tract with little absorption. GI lesions due to lanthanum deposition in biopsy specimens or those in endoscopic submucosal dissection (ESD) in dialysis patients have been recently identified. Here, we describe more detailed histopathological findings in the gastroduodenal mucosa and regional lymph nodes in three patients with gastric cancer. Three patients with ESRD, two elderly women and one man, underwent dialysis and were treated with LC for 3-36 months. The patients underwent laparoscopic distal gastrectomy and lymph node dissection due to gastric cancer. Many subepithelial histiocyte aggregates or small foreign body granulomas, which contained gray or brown pigments or crystal-like structures, were mostly present in non-neoplastic areas of the upper GI. Lanthanum accumulation was noted in the duodenal mucosa and the antral and body mucosae of the gastric lesser curvature. Lanthanum was also deposited in the regional lymph nodes of the three patients. Electron microscopy with energy dispersive X-ray spectroscopy confirmed lanthanum and phosphorus deposits in histiocytes. Long-term prognosis of patients and the excretion or the metabolic pathway of accumulated lanthanum remain unclear.

Effects of three blood purification methods on serum fibroblast growth factor-23 clearance in patients with hyperphosphatemia undergoing maintenance hemodialysis

The aim of the present study was to investigate the effects of three blood purification methods on fibroblast growth factor-23 (FGF-23) clearance in patients with hyperphosphatemia undergoing maintenance hemodialysis (MHD). In addition, the correlation between serum FGF-23 and phosphorus (Pi) levels and the clinical implications were identified. Sixty-five MHD patients with hyperphosphatemia were randomly divided into three groups: Hemodialysis, HD (n=23); hemodiafiltration, HDF (n=21); and hemodialysis+hemoperfusion, HD+HP (n=21) groups. Serum Pi, FGF-23, blood urea nitrogen, serum creatinine and associated bio-marker levels were measured prior to and following treatment. The expression level of serum FGF-23 was observed to be positively correlated with Pi (r=0.45, P<0.01). The three blood purification methods that were adopted for the present study exhibited significant and effective clearance of serum Pi (P<0.05). The post-treatment serum FGF-23 levels were significantly decreased in the HDF and HD+HP groups (P<0.05). Therefore, HDF may be an effective method for clearing serum FGF-23 in MHD patients exhibiting hyperphosphatemia.