Effects of calcium-containing phosphate binders on cardiovascular events and mortality in predialysis CKD stage 5 patients

Understanding Vascular Calcification in Chronic Kidney Disease: Pathogenesis and Therapeutic Implications

Vascular calcification (VC) is a biological phenomenon characterized by an accumulation of calcium and phosphate deposits within the walls of blood vessels causing the loss of elasticity of the arterial walls. VC plays a crucial role in the incidence and progression of chronic kidney disease (CKD), leading to a significant increase in cardiovascular mortality in these patients. Different conditions such as age, sex, dyslipidemia, diabetes, and hypertension are the main risk factors in patients affected by chronic kidney disease. However, VC may occur earlier and faster in these patients if it is associated with new or non-traditional risk factors such as oxidative stress, anemia, and inflammation. In chronic kidney disease, several pathophysiological processes contribute to vascular calcifications, including osteochondrogenic differentiation of vascular cells, hyperphosphatemia and hypercalcemia, and the loss of specific vascular calcification inhibitors including pyrophosphate, fetuin-A, osteoprotegerin, and matrix GLA protein. In this review we discuss the main traditional and non-traditional risk factors that can promote VC in patients with kidney disease. In addition, we provide an overview of the main pathogenetic mechanisms responsible for VC that may be crucial to identify new prevention strategies and possible new therapeutic approaches to reduce cardiovascular risk in patients with kidney disease.

Unraveling the Mechanisms of Magnesium Supplementation in Alleviating Chronic Kidney Disease Complications and Progression: Balancing Risks and Benefits

Chronic kidney disease (CKD) is a major cause of death and disability worldwide. It is usually diagnosed at early levels because of its slow progression. Treatment should consider CKD complications (such as electrolyte level imbalance, vascular calcification, and bone mineral disorders), as well as the development of CKD itself. Large-scale studies have shown that current treatment guidelines are nearly ineffective and fail to achieve treatment goals. Guidelines have not paid as much attention to magnesium (Mg) as the other electrolytes, while Mg has a significant role in the treatment goals of CKD. Hypomagnesemia is the only electrolyte imbalance that is equally prevalent in all stages of CKD. A lower plasma Mg level in each stage of CKD is associated with a higher risk of CKD progression and cardiac events. Magnesium exerts its effects both directly and via other ions. Mg supplementation increases insulin sensitivity while reducing proteinuria and inflammation. It lowers blood pressure and inhibits vascular calcification primarily because of its effects on calcium and phosphate, respectively. Vitamin D supplementation for low-active vitamin D in CKD patients increases vascular calcification and cardiac events, but magnesium supplementation enhances vitamin D levels and activity without increasing the risk of cardiac events. However, careful attention is required due to the potential threats of hypermagnesemia, particularly in advanced CKD stages. Starting magnesium supplementation early in patients' treatment plans will result in fewer side effects and more advantages. More original research is needed to determine its optimal dose and serum levels.

The efficacy and safety of cuttlebone for lowering serum phosphate in patients with end-stage renal disease: a meta-analysis of randomized controlled trials

Background: The efficacy of cuttlebone for treating hyperphosphatemia in patients with end-stage renal disease and its safety remained unclear. Methods: Randomized controlled trials comparing the efficacy of cuttlebone with conventional interventions were retrieved from MEDLINE, EMBASE, Cochrane Library, Airiti Library, and other major Chinese databases until 1 February 2023. The primary outcome was circulating phosphate concentration, while secondary outcomes included circulating calcium and intact parathyroid hormone levels, calcium-phosphorus product, and treatment-related side-effects. Results: Analysis of nine studies published between 2000 and 2019 including 726 participants showed a lower circulating phosphate concentration in the cuttlebone group than in controls [mean difference (MD) = -0.23, 95% CI: -0.39 to -0.06, p = 0.006, I2 = 94%, 726 patients] and a dose-dependent effect of cuttlebone against hyperphosphatemia. Therapeutic benefits were noted after both short-term (1-2 months) and long-term (3-6 months) treatments. Besides, patients receiving hemodialysis showed a better response to cuttlebone than those receiving peritoneal dialysis. There was no difference in circulating calcium level (mean difference = 0.03, 95% CI: -0.01 to 0.07, p = 0.17, I2 = 34%, 654 patients), while patients receiving cuttlebone showed lower circulating iPTH level and calcium-phosphorus product (MD = -43.63, 95% CI: -74.1 to -13.16, p = 0.005, I2 = 76%, 654 patients), (MD = -0.38, 95% CI: -0.38 to -0.01, p = 0.04, I2 = 83%, 520 patients). No difference in the risks of constipation, gastrointestinal discomfort, and elevated blood calcium was noted between the two groups. Conclusion: Compared with conventional phosphate-binding agents, cuttlebone more efficiently suppressed hyperphosphatemia with a dose-dependent effect. The limited number of included studies warrants further clinical investigations to verify our findings. Systematic Review Registration: https://www.crd.york.ac.uk/prospero/, identifier CRD42023396300.

Arterial calcifications and osteoprotegerin in chronic hemodialysis patients: impact on 6-year survival

AIM

The association between end-stage renal disease and cardiovascular mortality may be influenced through vascular alterations, in particular atherosclerosis and vascular calcification. The study goal was to assess the impact of each type of arterial intimal calcifications (AIC) and arterial medial calcifications (AMC), of osteoprotegerin (OPG), mineral metabolism markers and other features on all-cause and cardiovascular mortality in chronic hemodialysis patients.

METHODS

Ultrasound was performed in 87 patients on the carotid and femoral arteries, and the severity of AIC and AMC was assessed calculating a score according to the extension of calcification. We analyzed the link between AIC, AMC, OPG, mineral markers and mortality after 6 years of follow-up.

RESULTS

The cutoff value for OPG determined using ROC was 4.9 pmol/l for all-cause and cardiovascular mortality. Patients with higher serum OPG levels presented higher mortality rates. Our study revealed that AIC, high OPG, low ankle-arm index, presence of diabetes, smoking status, and lack of arteriovenous fistula are associated with all-cause and cardiovascular mortality in univariate regression analysis. Multivariate analysis identified AIC scoring based on the segmentation method as an independent predictor of all-cause and cardiovascular mortality, along with increased OPG levels. AMC scoring was not a predictor of mortality.

CONCLUSIONS

Identifying and scoring AIC on ultrasound and measuring OPG levels, as a basis of the HD patient assessment may become valuable tools in clinical work, as these have an impact on death toll.

Uremic Vascular Calcification: The Pathogenic Roles and Gastrointestinal Decontamination of Uremic Toxins

Uremic vascular calcification (VC) commonly occurs during advanced chronic kidney disease (CKD) and significantly increases cardiovascular morbidity and mortality. Uremic toxins are integral within VC pathogenesis, as they exhibit adverse vascular influences ranging from atherosclerosis, vascular inflammation, to VC. Experimental removal of these toxins, including small molecular (phosphate, trimethylamine-N-oxide), large molecular (fibroblast growth factor-23, cytokines), and protein-bound ones (indoxyl sulfate, p-cresyl sulfate), ameliorates VC. As most uremic toxins share a gut origin, interventions through gastrointestinal tract are expected to demonstrate particular efficacy. The “gastrointestinal decontamination” through the removal of toxin in situ or impediment of toxin absorption within the gastrointestinal tract is a practical and potential strategy to reduce uremic toxins. First and foremost, the modulation of gut microbiota through optimizing dietary composition, the use of prebiotics or probiotics, can be implemented. Other promising strategies such as reducing calcium load, minimizing intestinal phosphate absorption through the optimization of phosphate binders and the inhibition of gut luminal phosphate transporters, the administration of magnesium, and the use of oral toxin adsorbent for protein-bound uremic toxins may potentially counteract uremic VC. Novel agents such as tenapanor have been actively tested in clinical trials for their potential vascular benefits. Further advanced studies are still warranted to validate the beneficial effects of gastrointestinal decontamination in the retardation and treatment of uremic VC.