Integral pharmacological management of bone mineral disorders in chronic kidney disease (part II): from treatment of phosphate imbalance to control of PTH and prevention of progression of cardiovascular calcification

Recommendations of the Spanish Society of Nephrology for the management of mineral and bone metabolism disorders in patients with chronic kidney disease: 2021 (SEN-MM)

As in 2011, when the Spanish Society of Nephrology (SEN) published the Spanish adaptation to the Kidney Disease: Improving Global Outcomes (KDIGO) universal Guideline on Chronic Kidney Disease-Mineral and Bone Disorder (CKD-MBD), this document contains an update and an adaptation of the 2017 KDIGO guidelines to our setting. In this field, as in many other areas of nephrology, it has been impossible to irrefutably answer many questions, which remain pending. However, there is no doubt that the close relationship between the CKD-MBD/cardiovascular disease/morbidity and mortality complex and new randomised clinical trials in some areas and the development of new drugs have yielded significant advances in this field and created the need for this update. We would therefore highlight the slight divergences that we propose in the ideal objectives for biochemical abnormalities in the CKD-MBD complex compared to the KDIGO suggestions (for example, in relation to parathyroid hormone or phosphate), the role of native vitamin D and analogues in the control of secondary hyperparathyroidism and the contribution of new phosphate binders and calcimimetics. Attention should also be drawn to the adoption of important new developments in the diagnosis of bone abnormalities in patients with kidney disease and to the need to be more proactive in treating them. In any event, the current speed at which innovations are taking place, while perhaps slower than we might like, globally drives the need for more frequent updates (for example, through Nefrología al día).

Effectiveness and Safety of Ultrasound-Guided Local Paricalcitol Injection in Treating Secondary Hyperparathyroidism in ESRD: A Retrospective Study

PURPOSE

To compare the safety and efficacy of percutaneous paricalcitol injection with intravenously administered paricalcitol in treating parathyroid hyperplasia in patients with secondary hyperparathyroidism (SHPT).

METHODS

This study was approved by the Ethics Committee of our institution. We retrospectively collected data on patients who received percutaneous paricalcitol injection (24 patients) and intravenously administered paricalcitol (22 patients) based on their intact parathyroid hormone (iPTH) level. Serum iPTH, calcium, phosphorus, and the volume of the parathyroid gland were measured at several indicated time points after treatment, and adverse events associated with the two treatments were evaluated.

RESULTS

After 6 months of follow-up, we found that patients from the percutaneous injection group had significantly decreased levels of iPTH (from 1887.81 ± 726.81 pg/mL to 631.06 ± 393.06 pg/mL), phosphate (from 1.94 ± 0.36 mmol/L to 1.71 ± 0.34 mmol/L), and volume of the parathyroid gland (from 0.87 ± 0.50 cm³ to 0.60 ± 0.36 cm³), with relief from ostealgia within 48-72 h. In the intravenously administered group, the levels of iPTH decreased from 686.87 ± 260.44 pg/mL to 388.47 ± 167.36 pg/mL; while there was no significant change in phosphate levels, the volume of the parathyroid gland and ostealgia relief were observed at the end of follow-up. The serum calcium level did not significantly change, and no severe complications were observed in both groups. In vitro fluorescence-activated single cell sorting (FACS) analysis indicated that paricalcitol induced parathyroid cell apoptosis in a dose-dependent manner.

CONCLUSIONS

Percutaneous paricalcitol injection is a selective treatment for SHPT in ESRD.

Information and consensus document for the detection and management of chronic kidney disease

Chronic kidney disease (CKD) is a major public health problem worldwide that affects more than 10% of the Spanish population. CKD is associated with high comorbidity rates, poor prognosis and major consumption of health system resources. Since the publication of the last consensus document on CKD seven years ago, little evidence has emerged and few clinical trials on new diagnostic and treatment strategies in CKD have been conducted, apart from new trials in diabetic kidney disease. Therefore, CKD international guidelines have not been recently updated. The rigidity and conservative attitude of the guidelines should not prevent the publication of updates in knowledge about certain matters that may be key in detecting CKD and managing patients with this disease. This document, also prepared by 10 scientific associations, provides an update on concepts, clarifications, diagnostic criteria, remission strategies and new treatment options. The evidence and the main studies published on these aspects of CKD have been reviewed. This should be considered more as an information document on CKD. It includes an update on CKD detection, risk factors and screening; a definition of renal progression; an update of remission criteria with new suggestions in the older population; CKD monitoring and prevention strategies; management of associated comorbidities, particularly in diabetes mellitus; roles of the Primary Care physician in CKD management; and what not to do in Nephrology. The aim of the document is to serve as an aid in the multidisciplinary management of the patient with CKD based on current recommendations and knowledge.

Inhibitory effect of Astragalus Membranaceus on osteoporosis in SAMP6 mice by regulating vitaminD/FGF23/Klotho signaling pathway

Spontaneous senile osteoporosis severely threatens the health of the senior population which has emerged as a severe issue for society. A SAMP6 mouse model was utilized to estimate the impact of intragastrically administered Astragalus Membranaceus (AR) on spontaneous senile osteoporosis. Bone mineral density (BMD) and bone microstructure were measured using Micro-CT; contents of calcium and phosphorus were determined with the colorimetric method; and gene and protein expressions of fibroblast growth factor 23 (FGF23), Klotho, Vitamin D receptor (VDR), CYP27B1 and CYP24A1 were detected using qPCR, Western blot and ELISA assays, respectively. The findings indicated that AR could improve the femoral BMD and bone microstructure, elevate the contents of calcium and phosphorus, and increase the expression of Klotho, VDR, and CYP27B1 whereas decreasing the expression of FGF23 and CYP24A1 in SAMP6 mice in a dose independent manner. The present study has demonstrated that AR can promote osteogenesis and alleviate osteoporosis. It is also expected to provide a new insight for the treatment of spontaneous senile osteoporosis and to serve as a research basis for AR application.

Evidence in chronic kidney disease-mineral and bone disorder guidelines: is it time to treat or time to wait?

Chronic kidney disease-mineral and bone disorder (CKD-MBD) is one of the many important complications associated with CKD and may at least partially explain the extremely high morbidity and mortality among CKD patients. The 2009 Kidney Disease: Improving Global Outcomes (KDIGO) Clinical Practice Guideline document was based on the best information available at that time and was designed not only to provide information but also to assist in decision-making. In addition to the international KDIGO Work Group, which included worldwide experts, an independent Evidence Review Team was assembled to ensure rigorous review and grading of the existing evidence. Based on the evidence from new clinical trials, an updated Clinical Practice Guideline was published in 2017. In this review, we focus on the conceptual and practical evolution of clinical guidelines (from eMinence-based medicine to eVidence-based medicine and 'living' guidelines), highlight some of the current important CKD-MBD-related changes, and underline the poor or extremely poor level of evidence present in those guidelines (as well as in other areas of nephrology). Finally, we emphasize the importance of individualization of treatments and shared decision-making (based on important ethical considerations and the 'best available evidence'), which may prove useful in the face of the uncertainty over the decision whether 'to treat' or 'to wait'.

Alkaline Phosphatases in the Complex Chronic Kidney Disease-Mineral and Bone Disorders

Alkaline phosphatases (APs) remove the phosphate (dephosphorylation) needed in multiple metabolic processes (from many molecules such as proteins, nucleotides, or pyrophosphate). Therefore, APs are important for bone mineralization but paradoxically they can also be deleterious for other processes, such as vascular calcification and the increasingly known cross-talk between bone and vessels. A proper balance between beneficial and harmful activities is further complicated in the context of chronic kidney disease (CKD). In this narrative review, we will briefly update the complexity of the enzyme, including its different isoforms such as the bone-specific alkaline phosphatase or the most recently discovered B1x. We will also analyze the correlations and potential discrepancies with parathyroid hormone and bone turnover and, most importantly, the valuable recent associations of AP's with cardiovascular disease and/or vascular calcification, and survival. Finally, a basic knowledge of the synthetic and degradation pathways of APs promises to open new therapeutic strategies for the treatment of the CKD-Mineral and Bone Disorder (CKD-MBD) in the near future, as well as for other processes such as sepsis, acute kidney injury, inflammation, endothelial dysfunction, metabolic syndrome or, in diabetes, cardiovascular complications. However, no studies have been done using APs as a primary therapeutic target for clinical outcomes, and therefore, AP's levels cannot yet be used alone as an isolated primary target in the treatment of CKD-MBD. Nonetheless, its diagnostic and prognostic potential should be underlined.

Current and potential treatment options for hyperphosphatemia

INTRODUCTION

Hyperphosphatemia is common in late stages of chronic kidney disease and is often associated with elevated parathormone levels, abnormal bone mineralization, extra-osseous calcification, and increased risk of cardiovascular events and death. Several classes of oral phosphate binders are available to help control plasma phosphorus levels. Although effective at lowering serum phosphorus, they all have safety, tolerability, and compliance issues that need to be considered when selecting which one to use.

AREAS COVERED

This paper reviews the most established treatment options for hyperphosphatemia, in patients with chronic kidney disease, focusing on the new inhibitors of active phosphate absorption.

EXPERT OPINION

The prevention and the treatment of hyperphosphatemia is today far to be satisfactory. Nonetheless, an extending range of phosphate binders are now available. Aluminum has potentially serious toxic risks. Calcium-based binders are very effective but can lead to hypercalcemia and/or positive calcium balance and progression of cardiovascular calcification. No long-term data are available for the new calcium acetate/magnesium combination product. Lanthanum is an effective phosphate binder, and long-term effects of tissue deposition seem clinically irrelevant. Sevelamer, appear to have profiles that would lead to pleiotropic effects and reduced progression of vascular calcification, and the main adverse events seen with these agents are gastrointestinal. Iron has a powerful capability of binding phosphate, thus numerous preparations are available, both with and without significant systemic absorption of the iron component. The inhibitors of active intestinal phosphate transport, with their very selective mechanism of action and low pill burden seem the most interesting approach; however, do not seem at present to be effective alone, in reducing serum phosphorus levels.

Management of Osteoporosis in Chronic Kidney Disease

Chronic kidney disease (CKD) patients with coexisting osteoporosis are becoming common. Many of the therapeutic agents used to treat osteoporosis are known to be affected by the renal function. It is generally thought that osteoporosis in G1 to G3 CKD patients can be treated as in non-CKD patients with osteoporosis. In stage 4 or more advanced CKD patients and CKD patients on dialysis with osteoporosis, however, bisphosphonates must be used with caution, bearing in mind the potential development of such disorders as adynamic bone disease. The use of vitamin D preparations in low doses is relatively safe. In postmenopausal women, raloxifene must be administered with caution. When using denosumab, the serum calcium concentrations should be monitored carefully to prevent the development of hypocalcemia, and active vitamin D preparations should be administered concomitantly. The present article provides an overview of the management of osteoporosis in CKD patients.

Treatment of secondary hyperparathyroidism: the clinical utility of etelcalcetide

Secondary hyperparathyroidism (SHPT), a very frequent, severe, and worsening complication of chronic kidney disease, is characterized by high serum parathyroid hormone (PTH), parathyroid gland hyperplasia, and disturbances in mineral metabolism. Clinically, SHPT shows renal osteodystrophy, vascular calcification, cardiovascular damage, and fatal outcome. Calcium-sensing receptor (CaSR) is the main physiological regulator of PTH secretion; its activation by calcium rapidly inhibits PTH. Another important player in regulating mineral metabolism is vitamin D receptor (VDR), which is under the influence of vitamin D and influences the intestinal absorption of calcium and phosphate, PTH gene expression, and bone calcium mobilization. Serum phosphate levels influence fibroblast growth factor 23 (FGF-23) production, a phosphatonin that modulates serum phosphate reabsorption, PTH synthesis, and vitamin D production. Current therapeutic approaches consist of 1) phosphate intake control by diet or phosphate binders, 2) vitamin D by VDR activation, and 3) calcimimetic agents that activate CaSR. Recently, a new long-acting peptide (etelcalcetide) belonging to the calcimimetics class was approved for intravenous use in hemodialysis patients with SHPT. Etelcalcetide binds directly to CaSR, by a sulfide bond, inhibiting the production and secretion of PTH by parathyroid glands. After intravenous administration in rats, etelcalcetide is quickly distributed to the tissues and eliminated by kidneys, while in uremic animals the nonrenal excretion is only 1.2%. In hemodialysis patients, the treatment itself is the main route of elimination. Etelcalcetide in hemodialysis patients with SHPT was more effective than placebo and cinacalcet, with a PTH reduction of >30% in 76% of patients with etelcalcetide versus 10% with placebo. Particular attention was paid to the safety of the drug; the most common adverse event was asymptomatic blood calcium reduction, similar to cinacalcet, while gastrointestinal symptoms were less frequent. This promising new drug available for better control of SHPT will, together with drugs already in use, optimize the treatment to normalize the biochemical parameters.

Cardiovascular calcifications in chronic kidney disease: Potential therapeutic implications

Cardiovascular (CV) calcification is a highly prevalent condition at all stages of chronic kidney disease (CKD) and is directly associated with increased CV and global morbidity and mortality. In the first part of this review, we have shown that CV calcifications represent an important part of the CKD-MBD complex and are a superior predictor of clinical outcomes in our patients. However, it is also necessary to demonstrate that CV calcification is a modifiable risk factor including the possibility of decreasing (or at least not aggravating) its progression with iatrogenic manoeuvres. Although, strictly speaking, only circumstantial evidence is available, it is known that certain drugs may modify the progression of CV calcifications, even though a direct causal link with improved survival has not been demonstrated. For example, non-calcium-based phosphate binders demonstrated the ability to attenuate the progression of CV calcification compared with the liberal use of calcium-based phosphate binders in several randomised clinical trials. Moreover, although only in experimental conditions, selective activators of the vitamin D receptor seem to have a wider therapeutic margin against CV calcification. Finally, calcimimetics seem to attenuate the progression of CV calcification in dialysis patients. While new therapeutic strategies are being developed (i.e. vitamin K, SNF472, etc.), we suggest that the evaluation of CV calcifications could be a diagnostic tool used by nephrologists to personalise their therapeutic decisions.