Emerging effects of sevelamer in chronic kidney disease

The Influence of Sevelamer Hydrochloride and Calcium Carbonate on Markers of Inflammation and Oxidative Stress in Hemodialysis at Six Months of Follow-Up

Patients with end-stage renal disease (ESRD) present alterations in mineral and bone metabolism. Hyperphosphatemia in ESRD is considered an independent risk factor for cardiovascular disease (CVD), increasing morbidity, and mortality. Sevelamer hydrochloride is a calcium-free, non-absorbable phosphate-chelating polymer. Calcium carbonate chelator is helpful in controlling serum phosphate levels. There is insufficient information on the influence of sevelamer hydrochloride and calcium carbonate on the behavior of oxidative stress (OS) markers and inflammation in patients on hemodialysis (HD). A randomized open clinical trial was carried out on patients to evaluate sevelamer hydrochloride and calcium carbonate influence at 6 months of study follow-up. Levels of oxidants (LPO, NO, and 8-isoprostanes), antioxidants (SOD and TAC), oxidative DNA damage (8-OHdG and hOGG1), pro-inflammatory cytokines (IL-6 and TNF-α), and inflammation markers (ferritin and C-reactive protein) were measured with colorimetric and ELISA methods. We found a significant increase in oxidants LPO and NO, and antioxidants SOD and TAC, and downregulation of IL-6 and TNF-α. Ferritin decrease at 6 months follow-up in the sevelamer hydrochloride group. Increase in C-reactive protein was found in the group of patients treated with calcium carbonate. In conclusion, we found an oxidative state imbalance with increase in LPO and NO oxidants. The activity of the antioxidant enzymes (SOD and TAC) was also found to increase, suggesting a compensatory effect in the face of increase in oxidants. The same phenomenon was observed with increase in the oxidative damage marker to DNA and the increase in the DNA repair enzyme, suggesting a compensatory effect. Pro-inflammatory cytokines were predominantly downregulated by TNF-α in the group that ingested sevelamer hydrochloride in the final determination at 6 months of follow-up. Serum ferritin levels decreased significantly at the end of follow-up in patients on HD in the sevelamer hydrochloride group. The management of hyperphosphatemia with sevelamer hydrochloride appears to have obvious anti-inflammatory and antioxidant benefits.

Systematic review and meta-analysis of potential pleiotropic effects of sevelamer in chronic kidney disease: Beyond phosphate control

Sevelamer, has been shown to have many pleiotropic actions on lipid panel, various inflammatory markers, and blood glucose levels in chronic kidney disease patients. We conducted a systematic review and meta-analysis to compare these pleiotropic effects of sevelamer to other phosphate binders used in chronic kidney disease patients. The relevant randomized controlled trials published from 1 January 2001 to 31 November 2019 on the following databases: Cochrane Central Register of Controlled Trials published in The Cochrane Library, PubMed, Scopus and Google Scholar were identified. All the included studies were independently assessed for eligibility and risk of bias. The modified data extraction form of Cochrane was used. This review included 44 studies for qualitative analysis and 28 reports for quantitative analysis. A meta-analysis of three studies (n = 180) showed that glycated haemoglobin had significantly decreased in sevelamer-treated patients (MD: 0.5%; p = <.001). Compared with calcium-based phosphate binders, sevelamer showed a significant reduction in low-density lipoprotein (MD: -19.43 mg/dL; p = <.001) and total cholesterol (MD: -19.98 mg/dL; p < .001). A significant increase in high-density lipoprotein (MD: 1.29 mg/dL; p = .05) was also prominent in sevelamer treated patients. However, we were not able to observe a significant change in other biochemical parameters such as TG, CRP, hs-CRP, FGF-23, IL-6 and albumin as, no statistically significant difference was observed.

Chronic Kidney Disease, Gut Dysbiosis, and Constipation: A Burdensome Triplet

Gut dysbiosis has been implicated in the progression of chronic kidney disease (CKD). Alterations in the gut environment induced by uremic toxins, the dietary restriction of fiber-rich foods, and multiple drugs may be involved in CKD-related gut dysbiosis. CKD-related gut dysbiosis is considered to be characterized by the expansion of bacterial species producing precursors of harmful uremic toxins, such as indoxyl sulfate and p-cresyl sulfate, and the contraction of species generating beneficial short-chain fatty acids, such as butyrate. Gut-derived uremic toxins cause oxidative stress and pro-inflammatory responses, whereas butyrate exerts anti-inflammatory effects and contributes to gut epithelial integrity. Gut dysbiosis is associated with the disruption of the gut epithelial barrier, which leads to the translocation of endotoxins. Research on CKD-related gut dysbiosis has mainly focused on chronic inflammation and consequent cardiovascular and renal damage. The pathogenic relationship between CKD-related gut dysbiosis and constipation has not yet been investigated in detail. Constipation is highly prevalent in CKD and affects the quality of life of these patients. Under the pathophysiological state of gut dysbiosis, altered bacterial fermentation products may play a prominent role in intestinal dysmotility. In this review, we outline the factors contributing to constipation, such as the gut microbiota and bacterial fermentation; introduce recent findings on the pathogenic link between CKD-related gut dysbiosis and constipation; and discuss potential interventions. This pathogenic link needs to be elucidated in more detail and may contribute to the development of novel treatment options not only for constipation, but also cardiovascular disease in CKD.

Factors associated with serum fetuin-A concentrations after long-term use of different phosphate binders in hemodialysis patients

Background

Fetuin-A is known as a circulating inhibitor of vascular calcification. Factors associated with serum fetuin-A concentrations after long-term use of different phosphate binders in hemodialysis patients is still uncertain.

Methods

In the post-hoc study, we analyzed serum fetuin-A and biochemical factors (Ca, P, i-PTH, hsCRP, TG, LDL-C) in 50 hemodialysis patients, who completed a 48-week, open-Label, controlled randomized parallel-group study. 23 patients received sevelamer and 27 patients received calcium carbonate.

Results

After the 48-week treatment, the sevelamer group had less serum calcium increment, less iPTH decrement, more ALK-P increment, more hsCRP decrement and more LDL-C decrement. There was no significant difference in the serum fetuin-A decrement between two groups. Decreased serum fetuin-A levels were found after 48-week treatment in both groups: from 210.61 (104.73) to 153.85 (38.64) ug/dl, P = 0.003 in sevelamer group, from 203.95 (107.87) to 170.90 (58.02) ug/mL, P =0.002 in calcium group. The decrement in serum fetuin-A (Δfetuin-A) levels was associated with ΔCa (ρ = - 0.230, P = 0.040), ΔiPTH (ρ = 0.306, P = 0.031) and Δalbumin (ρ = 0.408, P = 0.003), not associated with sevelamer use, ΔP and ΔhsCRP.

Conclusion

After long-term sevelamer or calcium carbonate treatment, both groups of maintenance HD patients had lower serum fetuin-A levels. Serum levels of increased calcium, decreased iPTH and decreased albumin were associated with the serum fetuin-A decrement.

Use of sevelamer in chronic kidney disease: beyond phosphorus control

Sevelamer is a non-calcium phosphate binder used in advanced chronic kidney disease (CKD) and in dialysis for hyperphosphataemia control. Several experimental, observational studies and clinical trials have shown that sevelamer has pleiotropic effects, beyond hyperphosphataemia control, including actions on inflammation, oxidative stress, lipid profile and atherogenesis, vascular calcification, endothelial dysfunction and the reduction of several uremic toxins. This is the biological basis for its global effect on cardiovascular morbidity and mortality in patients with chronic kidney disease. This review focuses on these pleiotropic actions of sevelamer and their impact on cardiovascular health, with the experience published after more than ten years of clinical expertise.

Sevelamer carbonate: a review in hyperphosphataemia in adults with chronic kidney disease

Sevelamer carbonate (Renvela(®)), a buffered form of sevelamer hydrochloride (Renagel(®)), is an orally administered non-absorbed phosphate-binding anion exchange resin used in the treatment of hyperphosphataemia in chronic kidney disease (CKD). In the EU, sevelamer carbonate is approved in adult CKD patients who require dialysis and in those who do not require dialysis with serum phosphate levels ≥ 1.78 mmol/L, whereas in the USA sevelamer carbonate is approved in adult CKD patients who require dialysis. Sevelamer carbonate and sevelamer hydrochloride achieved similar reductions in serum phosphate levels in randomized comparative trials in patients with CKD receiving haemodialysis; sevelamer carbonate also reduced serum phosphate levels in noncomparative studies in CKD patients not requiring dialysis. The most common adverse events with sevelamer carbonate are gastrointestinal in nature. Sevelamer has pleiotropic effects, such as improving the serum lipid profile and attenuating endothelial and cardiovascular risk factors in CKD. All formulations of sevelamer have markedly higher acquisition costs than calcium-based phosphate binders. Cost-effectiveness analyses focusing specifically on sevelamer carbonate have not been conducted, and those based on clinical trial data with sevelamer hydrochloride have provided both favourable and unfavourable results compared with calcium-based phosphate binders, reflecting heterogeneity between modelled analyses in terms of data sources, assumptions, comparators, geographical regions, type of costs included and other factors. Although well-designed studies evaluating the impact of phosphate binders on hard clinical endpoints appear to be warranted, sevelamer carbonate may be particularly useful for the treatment of patients at risk of metabolic acidosis (offering advantages over sevelamer hydrochloride in this regard) and for individuals requiring treatment with a phosphate binding agent that does not contain aluminium or calcium.

Cardiovascular mortality in chronic kidney disease patients: potential mechanisms and possibilities of inhibition by resin-based phosphate binders

Cardiovascular mortality has been considered as the most important risk associated with chronic kidney disease. The mechanisms underlying this include inflammation, poor control of serum phosphate, high serum calcium, increased calcification of the arteries and cardiac valves, hyperlipidemia, diabetes, severe anemia, uric acid accumulation and others. Elevated phosphate levels have been strongly associated with increased mortality, thus phosphate-binding drugs have long been used to control the increase serum phosphate levels. However, phosphate-binding drugs differ considerably and recently numerous publications suggest differences between agents in the effects on overall mortality. The resin-based phosphate binders, comprising sevelamer and colestilan, not only reduce serum phosphate but also do not raise serum calcium. In addition, they reduce serum LDL-C, inflammation, uric acid and high Hba1c values. These differences suggest that not all phosphate binders may be equal in the context of cardiovascular mortality in this patient population.

Impact of aldosterone on osteoinductive signaling and vascular calcification

Vascular calcification is frequently found already in early stages of chronic kidney disease (CKD) patients and is associated with high cardiovascular risk. The process of vascular calcification is not considered a passive phenomenon but involves, at least in part, phenotypical transformation of vascular smooth muscle cells (VSMCs). Following exposure to excessive extracellular phosphate concentrations, VSMCs undergo a reprogramming into osteo-/chondroblast-like cells. Such 'vascular osteoinduction' is characterized by expression of osteogenic transcription factors and triggered by increased phosphate concentrations. A key role in this process is assigned to cellular phosphate transporters, most notably the type III sodium-dependent phosphate transporter Pit1. Pit1 expression is stimulated by mineralocorticoid receptor activation. Therefore, aldosterone participates in the phenotypical transformation of VSMCs. In preclinical models, aldosterone antagonism reduces vascular osteoinduction. Patients with CKD suffer from hyperphosphatemia predisposing to vascular osteogenic transformation, potentially further fostered by concomitant hyperaldosteronism. Clearly, additional research is required to define the role of aldosterone in the regulation of osteogenic signaling and the consecutive vascular calcification in CKD, but more generally also other diseases associated with excessive vascular calcification and even in individuals without overt disease.

Glycosaminoglycan overproduction in the aorta increases aortic calcification in murine chronic kidney disease

Background

Vascular calcification accompanying chronic kidney disease increases the mortality and morbidity associated with cardiovascular disorders, but no effective therapy is available. We hypothesized that glycosaminoglycans may contribute to osteoblastic differentiation of vascular smooth muscle cells during vascular calcification.

Methods and Results

We used exostosin‐like glycosyltranferase 2–deficient (EXTL2 knockout) mice expressing high levels of glycosaminoglycans in several organs including the aorta. We performed 5/6 subtotal nephrectomy and fed the mice a high‐phosphate diet to induce chronic kidney disease. Overexpression of glycosaminoglycans in the aorta enhanced aortic calcification in chronic kidney disease in EXTL2 knockout mice. Ex vivo and in vitro, matrix mineralization in aortic rings and vascular smooth muscle cells of EXTL2 knockout mice was augmented. Furthermore, removal of glycosaminoglycans in EXTL2 knockout and wild‐type mice‐derived vascular smooth muscle cells effectively suppressed calcium deposition in a high‐phosphate environment.

Conclusions

These results illustrate an important role for glycosaminoglycans in the development of vascular calcification. Manipulation of glycosaminoglycan expression may have beneficial effects on the progression of vascular calcification in chronic kidney disease patients.