The Effect of Extended Release Niacin on Markers of Mineral Metabolism in CKD

U-shaped association between dietary niacin intake and chronic kidney disease among US elderly: a nationwide cross-sectional study

Background

In addition to hypertension or diabetes, elderly people are also considered one of the high-risk groups for chronic kidney disease (CKD). Although niacin is recognized for its renal protective properties, the link between dietary niacin intake and CKD remains uncertain. This study investigated this relationship in the elderly.

Methods

We included participants aged 60 and older from the National Health and Nutrition Examination Survey (NHANES) for the years 2003-2018. Dietary niacin intake was assessed through two non-consecutive 24-hour dietary recalls. CKD was diagnosed in individuals with a urine albumin-to-creatinine ratio exceeding 30 mg/g or an estimated glomerular filtration rate below 60 mL/min per 1.73 m^2. The study cohort comprised 4,649 participants, 1,632 of whom had CKD. Propensity score matching (PSM) was utilized to adjust for baseline differences between the groups.

Results

Our analysis, using smooth curve fitting and generalized additive models both before and after PSM, found a U-shaped curve depicting the relationship between dietary niacin intake and CKD risk, confirmed by a log-likelihood ratio test (P < 0.05). Threshold effect analysis (after PSM) indicated a reduced risk of CKD in older adults with a niacin intake below 38.83 mg per day [odds ratio (OR) = 0.99, 95% confidence interval (CI) 0.97-1.00]. In contrast, higher intake levels significantly increased the risk (OR = 1.03, 95% CI 1.00-1.06). Subgroup analysis indicated that these associations were consistent across different stratification variables (P for interaction > 0.05).

Conclusion

Our findings suggested a U-shaped association between dietary niacin intake and CKD risk among older Americans. However, further prospective cohort studies are needed to confirm this finding.

Association of dietary niacin intake with all-cause and cardiovascular mortality of adult patients with chronic kidney disease in the United States: results from NHANES 1999-2018

Objective

The relationship between dietary niacin intake (DNI) and mortality rates among patients afflicted with chronic kidney disease (CKD) is a subject of debate. Utilizing data derived from the National Health and Nutrition Examination Survey (NHANES), this study adopts a retrospective cohort design with an aim to investigate the association in the American adult patients with CKD.

Methods

A cohort study was conducted in the National Health and Nutrition Examination Survey (NHANES) between 2009 and 2018 that enrolled 6,191 CKD patients aged 20 years and above. We collected data on mortality through 31 December 2018. DNI was measured using a 24-h recall method. The relationship between DNI levels and mortality from all causes and cardiovascular causes was analyzed using weighted Cox proportional hazards models. The Kaplan-Meier (K-M) survival curve was plotted to illustrate these associations.

Results

Following a median monitoring period of 85 months, it was observed that 2,419 individuals (33.08%) succumbed to all causes, whereas cardiovascular-related deaths were recorded for 746 participants (10.45%). When controlling for confounders, an inverse relationship was established between DNI and mortality rates. Specifically, a marginal increase of 1 mg/day in DNI corresponded to a reduced Hazard Ratios (HRs) of 0.993 (0.987, 0.999; p = 0.027) for all-cause mortality and 0.980 (0.969, 0.991; p < 0.001) for cardiovascular mortality. A further stratified analysis by quartiles of DNI, with the lowest quartile serving as the reference, revealed that the highest quartile was associated with HRs of 0.820 (0.697, 0.966) for all-cause mortality and 0.663 (0.465, 0.944) for cardiovascular mortality, both displaying a significant trend (p < 0.001). However, a subdivision of CKD patients by age showed that the protective effects of higher DNI were only confined to individuals aged 60 years and above but not to those under 60 years of age.

Conclusion

A negative correlation between DNI and mortality due to all causes and cardiovascular issues among CKD patients aged 60 and above was revealed based on the datasets; however, this association was not observed in younger individuals under 60. Consequently, enhancing DNI might serve as a beneficial therapeutic strategy specifically for the older CKD demographic.

Effect of Egg-White Protein Alone or Combined With Niacin on Nutritional Status, and Phosphorus Control in Maintenance Hemodialysis Patients: A Randomized Controlled Trial

OBJECTIVE

Niacin is reported to decrease phosphorus concentration in maintenance hemodialysis (MHD) patients. Egg white is one of the main substitutable proteins in MHD patients due to its low phosphorus content. Therefore, we aimed to evaluate the effects of combined egg white and niacin supplementation on dialysis patients' serum phosphorus and nutritional biomarkers.

DESIGN AND METHODS

In this randomized controlled clinical trial, 98 patients on MHD were randomly allocated to four groups for 8 weeks: 24 g egg white (n = 25), 600 g niacin daily (n = 24), egg white combined with niacin (n = 24), and control (n = 24). Calcium, phosphorus, fibroblast growth factor-23, and other nutritional markers were assessed.

RESULTS

There was a significant difference among the groups only in phosphorus at the end of the trial, which was significantly lower in the niacin group (4.38 + 0.812 mg/dL) than in both the egg white (5.07 + 0.49 mg/dL) and egg white with niacin supplementation (5.41 + 0.662 mg/dL) groups. In this regard, albumin increased in egg white and egg white with niacin supplementation, while albumin did not change significantly in the niacin group. Urea reduction ratio and Kt/V rose only in the egg-white group, while aspartate aminotransferase increased only in the niacin and control groups.

CONCLUSION

Niacin decreases serum phosphorus concentration more than egg-white protein or a combined intervention. Egg white protein supplementation has beneficial effects on some nutritional statuses other than phosphorus control without the side effects of niacin.

Hyperphosphatemia in Chronic Kidney Disease: The Search for New Treatment Paradigms and the Role of Tenapanor

Hyperphosphataemia represents a significant challenge in the management of chronic kidney disease, exerting a pronounced influence on the pathogenesis of cardiovascular complications and mineral bone disorders. Traditional approaches to address hyperphosphataemia involve implementing dietary phosphate restrictions, administering phosphate binders, and, in cases of end-stage renal disease, resorting to dialysis. Unfortunately, these interventions frequently prove inadequate in maintaining phosphate levels within recommended ranges. Additionally, commonly employed pharmacological agents are not immune to eliciting adverse events, thereby limiting their prescription and therapeutic adherence. There is a growing focus on exploring novel therapeutic strategies in this context. The current discussion centres on tenapanor, a pharmacological agent predominantly acting as a selective inhibitor of sodium/hydrogen exchanger isoform 3 (NHE3). Its mechanism of action involves modulating tight junctions, resulting in reduced sodium absorption and intestinal paracellular permeability to phosphate. Furthermore, tenapanor downregulates sodium-dependent phosphate 2b transport protein (NaPi2b) expression, thereby impeding active transcellular phosphate transport. Clinical trials have elucidated the efficacy and safety profile of tenapanor. This evidence hints at a potential paradigm shift in the management of hyperphosphataemia. However, the burgeoning optimism surrounding tenapanor warrants tempered enthusiasm, as further research remains indispensable. The imperative lies in meticulously delineating its efficacy and safety contours within the crucible of clinical practice. In this review, we synthesize the intricate interplay between hyperphosphataemia and Chronic Kidney Disease-Mineral Bone Disorder, and we discuss the existing pharmacological interventions for hyperphosphataemia and explore emerging treatment paradigms that offer novel perspectives in managing elevated phosphate levels in CKD patients.

Vitamin Supplement Use in Patients With CKD: Worth the Pill Burden?

All vitamins play essential roles in various aspects of body function and systems. Patients with chronic kidney disease (CKD), including those receiving dialysis, may be at increased risk of developing vitamin deficiencies due to anorexia, poor dietary intake, protein energy wasting, restricted diet, dialysis loss, or inadequate sun exposure for vitamin D. However, clinical manifestations of most vitamin deficiencies are usually subtle or undetected in this population. Testing for circulating levels is not undertaken for most vitamins except folate, B12, and 25-hydroxyvitamin D because assays may not be available or may be costly to perform and do not always correlate with body stores. The last systematic review through 2016 was performed for the Kidney Disease Outcome Quality Initiative (KDOQI) 2020 Nutrition Guideline update, so this article summarizes the more recent evidence. We review the use of vitamins supplementation in the CKD population. To date there have been no randomized trials to support the benefits of any vitamin supplementation for kidney, cardiovascular, or patient-centered outcomes. The decision to supplement water-soluble vitamins should be individualized, taking account the patient's dietary intake, nutritional status, risk of vitamins deficiency/insufficiency, CKD stage, comorbid status, and dialysis loss. Nutritional vitamin D deficiency should be corrected, but the supplementation dose and formulation need to be personalized, taking into consideration the degree of 25-hydroxyvitamin D deficiency, parathyroid hormone levels, CKD stage, and local formulation. Routine supplementation of vitamins A and E is not supported due to potential toxicity. Although more trial data are required to elucidate the roles of vitamin supplementation, all patients with CKD should undergo periodic assessment of dietary intake and aim to receive various vitamins through natural food sources and a healthy eating pattern that includes vitamin-dense foods.

Pharmacology of Mammalian Na+-Dependent Transporters of Inorganic Phosphate

Inorganic phosphate (Pi) is an essential component of many biologically important molecules such as DNA, RNA, ATP, phospholipids, or apatite. It is required for intracellular phosphorylation signaling events and acts as pH buffer in intra- and extracellular compartments. Intestinal absorption, uptake into cells, and renal reabsorption depend on a set of different phosphate transporters from the SLC20 (PiT transporters) and SLC34 (NaPi transporters) gene families. The physiological relevance of these transporters is evident from rare monogenic disorders in humans affecting SLC20A2 (Fahr's disease, basal ganglia calcification), SLC34A1 (idiopathic infantile hypercalcemia), SLC34A2 (pulmonary alveolar microlithiasis), and SLC34A3 (hereditary hypophosphatemic rickets with hypercalciuria). SLC34 transporters are inhibited by millimolar concentrations of phosphonoformic acid or arsenate while SLC20 are relatively resistant to these compounds. More recently, a series of more specific and potent drugs have been developed to target SLC34A2 to reduce intestinal Pi absorption and to inhibit SLC34A1 and/or SLC34A3 to increase renal Pi excretion in patients with renal disease and incipient hyperphosphatemia. Also, SLC20 inhibitors have been developed with the same intention. Some of these substances are currently undergoing preclinical and clinical testing. Tenapanor, a non-absorbable Na+/H+-exchanger isoform 3 inhibitor, reduces intestinal Pi absorption likely by indirectly acting on the paracellular pathway for Pi and has been tested in several phase III trials for reducing Pi overload in patients with renal insufficiency and dialysis.

NAD+ Metabolism and Interventions in Premature Renal Aging and Chronic Kidney Disease

Premature aging causes morphological and functional changes in the kidney, leading to chronic kidney disease (CKD). CKD is a global public health issue with far-reaching consequences, including cardio-vascular complications, increased frailty, shortened lifespan and a heightened risk of kidney failure. Dialysis or transplantation are lifesaving therapies, but they can also be debilitating. Currently, no cure is available for CKD, despite ongoing efforts to identify clinical biomarkers of premature renal aging and molecular pathways of disease progression. Kidney proximal tubular epithelial cells (PTECs) have high energy demand, and disruption of their energy homeostasis has been linked to the progression of kidney disease. Consequently, metabolic reprogramming of PTECs is gaining interest as a therapeutic tool. Preclinical and clinical evidence is emerging that NAD⁺ homeostasis, crucial for PTECs' oxidative metabolism, is impaired in CKD, and administration of dietary NAD⁺ precursors could have a prophylactic role against age-related kidney disease. This review describes the biology of NAD⁺ in the kidney, including its precursors and cellular roles, and discusses the importance of NAD⁺ homeostasis for renal health. Furthermore, we provide a comprehensive summary of preclinical and clinical studies aimed at increasing NAD⁺ levels in premature renal aging and CKD.

SIRT6 overexpression retards renal interstitial fibrosis through targeting HIPK2 in chronic kidney disease

Introduction: Renal interstitial fibrosis is a common pathophysiological change in the chronic kidney disease (CKD). Nicotinamide adenine dinucleotide (NAD)-dependent deacetylase sirtuin 6 (SIRT6) is demonstrated to protect against kidney injury. Vitamin B3 is the mostly used form of NAD precursors. However, the role of SIRT6 overexpression in renal interstitial fibrosis of CKD and the association between dietary vitamin B3 intake and renal function remain to be elucidated.

Methods: Wild-type (WT) and SIRT6-transgene (SIRT6-Tg) mice were given with high-adenine diets to establish CKD model. HK2 cells were exposed to transforming growth factor β1 (TGF-β1) in vitro to explore related mechanism. Population data from Multi-Ethnic Study of Atherosclerosis (MESA) was used to examine the association between dietary vitamin B3 intake and renal function decline.

Results: Compared to WT mice, SIRT6-Tg mice exhibited alleviated renal interstitial fibrosis as evidenced by reduced collagen deposit, collagen I and α-smooth muscle actin expression. Renal function was also improved in SIRT6-Tg mice. Homeodomain interacting protein kinase 2 (HIPK2) was induced during the fibrogenesis in CKD, while HIPK2 was downregulated after SIRT6 overexpression. Further assay in vitro confirmed that SIRT6 depletion exacerbated epithelial-to-mesenchymal transition of HK2 cells, which might be linked with HIPK2 upregulation. HIPK2 was inhibited by SIRT6 in the post-transcriptional level. Population study indicated that higher dietary vitamin B3 intake was independently correlated with a lower risk of estimate glomerular filtration rate decline in those ≥65 years old during follow-up.

Conclusion: SIRT6/HIPK2 axis serves as a promising target of renal interstitial fibrosis in CKD. Dietary vitamin B3 intake is beneficial for renal function in the old people.

Sodium phosphate cotransporter 2a inhibitors: potential therapeutic uses

PURPOSE OF REVIEW

Targeting sodium phosphate cotransporter 2a (Npt2a) offers a novel strategy for treating hyperphosphatemia in chronic kidney disease (CKD). Here we review recent studies on the efficacy of Npt2a inhibition, its plasma phosphate (Pi)-lowering effects, as well as potential "off-target" beneficial effects on cardiovascular consequences.

RECENT FINDINGS

Two novel Npt2a-selective inhibitors (PF-06869206 and BAY-767) have been developed. Pharmacological Npt2a inhibition shows a significant phosphaturic effect and consequently lowers plasma Pi and parathyroid hormone (PTH) levels regardless of CKD. However, plasma fibroblast growth factor 23 (FGF23), a master regulator of Pi homeostasis, shows inconsistent responses between these two inhibitors (no effect by PF-06869206 vs. reduction by BAY-767). In addition to the effects on Pi homeostasis, Npt2a inhibition also enhances urinary excretions of Na+, Cl-, and Ca2+, which is recapitulated in animal models with reduced kidney function. The effect of Npt2a inhibition by BAY-767 on vascular calcification has been studied, with positive results showing that oral treatment with BAY-767 (10 mg kg-1) attenuated the increases in plasma Pi and Ca2+ content in the aorta under the setting of vascular calcification induced by a pan-FGF receptor inhibitor. Together, Npt2a inhibition offers a promising therapeutic approach for treating hyperphosphatemia and reducing cardiovascular complications in CKD.

SUMMARY

Npt2a inhibition significantly increases urinary Pi excretion and lowers plasma Pi and PTH levels; moreover, it exerts pleiotropic "off-target" effects, providing a novel treatment for hyperphosphatemia and exhibiting beneficial potential for cardiovascular complications in CKD.

The efficacy and safety of niacin on hyperphosphatemia in ESRD patients undergoing hemodialysis: randomized controlled trial

Background

Hyperphosphatemia is a common complication of end-stage renal disease (ESRD) and particularly affects hemodialysis (HD) patients. Elevated serum phosphorus contributes to the development of secondary hyperparathyroidism, chronic kidney disease–mineral bone disorder (CKD-MBD), metastatic calcifications and calcific uremic arteriolopathy. There is a significant association between hyperphosphatemia and increased morbidity and mortality in ESRD patients including cardiovascular morbidity and mortality, and it is also associated with prolonged hospitalization of HD patients. This study aim to evaluate the serum phosphorus lowering effect of niacin in HD patients.

Results

There was a decrease in phosphate values during the first 3 months of the study in the niacin group, with a significant change in phosphate level at the third month (5.90 ± 0.52 vs. 6.42 ± 0.65 (mEq/l); P <  0.001) and at the sixth month (5.12 ± 0.41 vs. 5.76 ± 0.47 (mEq/l); P <  0.001) compared to the control group. It was noted that both groups had an insignificant difference regarding baseline parathormone (PTH), though the PTH showed a significantly lower level at the third month (192.39 ± 78.85 vs. 388.27 ± 263.10 pg/ml; P <  0.001) and at the sixth month (127.56 ± 90.87 vs. 249.85 ± 97.69 pg/ml; P <  0.001) in the niacin group.

Conclusion

Niacin caused a statistically significant decrease in levels of phosphate and PTH in dialysis patients.

Trial registration

Registered at ClinicalTrials.gov NCT03163576. Trial registration date: 22 May 2017. Date of first patient’s enrolment: 1 October 2018. Date of the ethical committee approval: 29 March 2017. Number of the ethical committee approval: 17100040.

Nicotinamide and acute kidney injury

In a recent issue of ckj, Piedrafita et al. reported that urine tryptophan and kynurenine are reduced in cardiac bypass surgery patients that develop acute kidney injury (AKI), suggesting reduced activity of the kynurenine pathway of nicotinamide (NAM) adenine dinucleotide (NAD+) synthesis from tryptophan. However, NAM supplementation aiming at repleting NAD+ did not replete kidney NAD+ and did not improve glomerular filtration or reduce histological injury in ischaemic-reperfusion kidney injury in mice. The lack of improvement of kidney injury is partially at odds with prior reports that did not study kidney NAD+, glomerular filtration or histology in NAM-treated wild-type mice with AKI. We now present an overview of research on therapy with vitamin B3 vitamers and derivate molecules {niacin, Nicotinamide [NAM; niacinamide], NAM riboside [Nicotinamide riboside (NR)], Reduced nicotinamide riboside [NRH] and NAM mononucleotide} in kidney injury, including an overview of ongoing clinical trials, and discuss the potential explanations for diverging reports on the impact of these therapeutic approaches on pre-clinical acute and chronic kidney disease.

Concepts and Controversies: Lipid Management in Patients with Chronic Kidney Disease

Atherosclerotic cardiovascular disease (ASCVD) remains an important contributor of morbidity and mortality in patients with chronic kidney disease (CKD). CKD is recognized as an important risk enhancer that identifies patients as candidates for more intensive low-density lipoprotein (LDL) cholesterol lowering. However, there is controversy regarding the efficacy of lipid-lowering therapy, especially in patients on dialysis. Among patients with CKD, not yet on dialysis, there is clinical trial evidence for the use of statins with or without ezetimibe to reduce ASCVD events. Newer cholesterol lowering agents have been introduced for the management of hyperlipidemia to reduce ASCVD, but these therapies have not been tested in the CKD population except in secondary analyses of patients with primarily CKD stage 3. This review summarizes the role of hyperlipidemia in ASCVD and treatment strategies for hyperlipidemia in the CKD population.

NaPi-IIb Inhibition for Hyperphosphatemia in CKD Hemodialysis Patients

Introduction

Chronic kidney disease (CKD) has a prevalence of 9.1% globally, and frequently results in elevated serum phosphate, increasing cardiovascular morbidity and mortality risk in hemodialysis (HD) patients. DS-2330b, an oral NaPi-IIb inhibitor, reduced intestinal phosphate absorption in preclinical studies, but its effect in patients with CKD is unknown. This 2-part, randomized, placebo- and active-controlled, single- and repeated-dose, phase 1b study evaluated safety and efficacy of DS-2330b in patients with CKD on HD.

Methods

Part A, a 2-period, 2-way study, evaluated safety and pharmacokinetics of DS-2330b 250 mg in solution and tablet formulations. Part B assessed the safety of DS-2330b in solution (chosen based on results of part A) and its effect on serum phosphate. Patients were randomized to placebo 3 times daily (TID), DS-2330b 400 mg TID, DS-2330b 400 mg with sevelamer 1.6 g TID, and sevelamer 1.6 g with placebo TID for 14 days. Safety endpoints included adverse event (AE) monitoring.

Results

Six patients completed part A. Two patients experienced serious AEs considered unrelated to DS-2330b treatment. Thirty-two patients enrolled and completed part B. Serum phosphate mean change from baseline ± SD was −2.2±1.5 mg/dl versus −1.9 ± 1.1 mg/dl for DS-2330b monotherapy versus placebo. Patients receiving DS-2330b with sevelamer or sevelamer with placebo experienced the greatest serum phosphate decrease from baseline. Nine patients (28.1%) experienced ≥1 treatment-emergent AE (TEAE); 7 patients experienced drug-related TEAEs. The TEAE incidence was comparable between DS-2330b and control groups.

Conclusions

DS-2330b, alone or in combination with sevelamer, was safe and well tolerated but did not demonstrate clinically meaningful efficacy in HD patients.

Pelacarsen for lowering lipoprotein(a): implications for patients with chronic kidney disease

Chronic kidney disease (CKD) patients are at an increased risk of cardiovascular disease (CVD) and statins may not be protective in advanced CKD. The reasons for the limited efficacy of statins in advanced CKD are unclear, but statins may increase plasma levels of the highly atherogenic molecule lipoprotein(a), also termed Lp(a), as well as PCSK9 (protein convertase subtilisin/kexin type 9) levels. Lp(a) has also been linked to calcific aortic stenosis, which is common in CKD. Moreover, circulating Lp(a) levels increase in nephrotic syndrome with declining renal function and are highest in patients on peritoneal dialysis. Thus, the recent publication of the Phase 2 randomized controlled trial of pelacarsen [also termed AKCEA-APO(a)-LRx and TQJ230], a hepatocyte-directed antisense oligonucleotide targeting the LPA gene messenger RNA, in persons with CVD should be good news for nephrologists. Pelacarsen safely and dose-dependently decreased Lp(a) levels by 35-80% and a Phase 3 trial [Lp(a)HORIZON, NCT04023552] is planned to run from 2020 to 2024. Unfortunately, patients with estimated glomerular filtration rate <60 mL/min or urinary albumin:creatinine ratio >100 mg/g were excluded from Phase 2 trials and those with 'significant kidney disease' will be excluded from the Phase 3 trial. Optimized exclusion criteria for Lp(a)HORIZON would provide insights into the role of Lp(a) in CVD in CKD patients.

Magnesium but not nicotinamide prevents vascular calcification in experimental uraemia

BACKGROUND

Optimal phosphate control is an unmet need in chronic kidney disease (CKD). High serum phosphate increases calcification burden and is associated with mortality and cardiovascular disease in CKD. Nicotinamide (NA) alone or in combination with calcium-free phosphate binders might be a strategy to reduce phosphate levels and calcification and thus impact cardiovascular disease in CKD.

METHODS

We studied the effect of NA alone and in combination with magnesium carbonate (MgCO3) as a potential novel treatment strategy. CKD was induced in dilute brown non-agouti/2 mice by subtotal nephrectomy followed by a high-phosphate diet (HP) and 7 weeks of treatment with NA, MgCO3 or their combination. Control mice underwent subtotal nephrectomy and received an HP or underwent sham surgery and received standard chow plus NA.

RESULTS

CKD mice showed increased serum fibroblast growth factor 23 and calcium-phosphate product that was normalized by all treatment regimes. NA alone increased soft tissue and vascular calcification, whereas any treatment with MgCO3 significantly reduced calcification severity in CKD. While MgCO3 supplementation alone resulted in decreased calcification severity, it resulted in increased intestinal expression of the phosphate transporters type II sodium-dependent phosphate transporter 1 (Pit-1). Combined therapy of MgCO3 and NA reduced tissue calcification and normalized expression levels of intestinal phosphate transporter proteins.

CONCLUSIONS

In conclusion, the data indicate that NA increases while MgCO3 reduces ectopic calcification severity. Augmented expression of intestinal phosphate transporters by MgCO3 treatment was abolished by the addition of NA. However, the clinical relevance of the latter remains to be explored. Importantly, the data suggest no benefit of NA regarding treatment of calcification in addition to MgCO3.

An expert update on novel therapeutic targets for hyperphosphatemia in chronic kidney disease: preclinical and clinical innovations

Introduction: The management of hyperphosphatemia in patients with chronic kidney disease (CKD) is complicated, requiring a multidisciplinary approach that includes dietary phosphate restriction, dialysis, and phosphate binders.Areas covered: We describe key players involved in regulating inorganic phosphate homeostasis and their differential role in healthy people and different stages of CKD. The contribution of paracellular and transcellular intestinal absorptive mechanisms are also examined. Finally, we illuminate recent therapeutic approaches for hyperphosphatemia in CKD. We searched PubMed/Medline (up to November 2019) using the following terms: chronic kidney disease, dialysis, diet, hyperphosphatemia, NaPi2b, nicotinamide, phosphate binder, secondary hyperparathyroidism, tenapanor and vascular calcification.Expert opinion: The precise mechanisms regulating intestinal phosphate absorption in humans is not completely understood. However, it is now established that this process involves two independent pathways: a) active transport (i.e. transcellular route, via specific ion transporters) and inactive transport (i.e. paracellular route across tight junctions). Dietary phosphate restriction and phosphate-binder use can lead to an undesirable maladaptive increase in phosphate uptake and promote active phosphate transport by increased expression of the gastrointestinal sodium-dependent phosphate transporter, NaPi2b. Nicotinamide may overcome these limitations through the inhibition of NaPi2b, by improved efficacy and reduced phosphate binder use and better compliance.

Pharmacological interventions for heart failure in people with chronic kidney disease

BACKGROUND

Approximately half of people with heart failure have chronic kidney disease (CKD). Pharmacological interventions for heart failure in people with CKD have the potential to reduce death (any cause) or hospitalisations for decompensated heart failure. However, these interventions are of uncertain benefit and may increase the risk of harm, such as hypotension and electrolyte abnormalities, in those with CKD.

OBJECTIVES

This review aims to look at the benefits and harms of pharmacological interventions for HF (i.e., antihypertensive agents, inotropes, and agents that may improve the heart performance indirectly) in people with HF and CKD.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies through 12 September 2019 in consultation with an Information Specialist and using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal and ClinicalTrials.gov.

SELECTION CRITERIA

We included randomised controlled trials of any pharmacological intervention for acute or chronic heart failure, among people of any age with chronic kidney disease of at least three months duration.

DATA COLLECTION AND ANALYSIS

Two authors independently screened the records to identify eligible studies and extracted data on the following dichotomous outcomes: death, hospitalisations, worsening heart failure, worsening kidney function, hyperkalaemia, and hypotension. We used random effects meta-analysis to estimate treatment effects, which we expressed as a risk ratio (RR) with 95% confidence intervals (CI). We assessed the risk of bias using the Cochrane tool. We applied the GRADE methodology to rate the certainty of evidence.

MAIN RESULTS

One hundred and twelve studies met our selection criteria: 15 were studies of adults with CKD; 16 studies were conducted in the general population but provided subgroup data for people with CKD; and 81 studies included individuals with CKD, however, data for this subgroup were not provided. The risk of bias in all 112 studies was frequently high or unclear. Of the 31 studies (23,762 participants) with data on CKD patients, follow-up ranged from three months to five years, and study size ranged from 16 to 2916 participants. In total, 26 studies (19,612 participants) reported disaggregated and extractable data on at least one outcome of interest for our review and were included in our meta-analyses. In acute heart failure, the effects of adenosine A1-receptor antagonists, dopamine, nesiritide, or serelaxin on death, hospitalisations, worsening heart failure or kidney function, hyperkalaemia, hypotension or quality of life were uncertain due to sparse data or were not reported. In chronic heart failure, the effects of angiotensin-converting enzyme inhibitors (ACEi) or angiotensin receptor blockers (ARB) (4 studies, 5003 participants: RR 0.85, 95% CI 0.70 to 1.02; I2 = 78%; low certainty evidence), aldosterone antagonists (2 studies, 34 participants: RR 0.61 95% CI 0.06 to 6.59; very low certainty evidence), and vasopressin receptor antagonists (RR 1.26, 95% CI 0.55 to 2.89; 2 studies, 1840 participants; low certainty evidence) on death (any cause) were uncertain. Treatment with beta-blockers may reduce the risk of death (any cause) (4 studies, 3136 participants: RR 0.69, 95% CI 0.60 to 0.79; I2 = 0%; moderate certainty evidence). Treatment with ACEi or ARB (2 studies, 1368 participants: RR 0.90, 95% CI 0.43 to 1.90; I2 = 97%; very low certainty evidence) had uncertain effects on hospitalisation for heart failure, as treatment estimates were consistent with either benefit or harm. Treatment with beta-blockers may decrease hospitalisation for heart failure (3 studies, 2287 participants: RR 0.67, 95% CI 0.43 to 1.05; I2 = 87%; low certainty evidence). Aldosterone antagonists may increase the risk of hyperkalaemia compared to placebo or no treatment (3 studies, 826 participants: RR 2.91, 95% CI 2.03 to 4.17; I2 = 0%; low certainty evidence). Renin inhibitors had uncertain risks of hyperkalaemia (2 studies, 142 participants: RR 0.86, 95% CI 0.49 to 1.49; I2 = 0%; very low certainty). We were unable to estimate whether treatment with sinus node inhibitors affects the risk of hyperkalaemia, as there were few studies and meta-analysis was not possible. Hyperkalaemia was not reported for the CKD subgroup in studies investigating other therapies. The effects of ACEi or ARB, or aldosterone antagonists on worsening heart failure or kidney function, hypotension, or quality of life were uncertain due to sparse data or were not reported. Effects of anti-arrhythmic agents, digoxin, phosphodiesterase inhibitors, renin inhibitors, sinus node inhibitors, vasodilators, and vasopressin receptor antagonists were very uncertain due to the paucity of studies.

AUTHORS' CONCLUSIONS

The effects of pharmacological interventions for heart failure in people with CKD are uncertain and there is insufficient evidence to inform clinical practice. Study data for treatment outcomes in patients with heart failure and CKD are sparse despite the potential impact of kidney impairment on the benefits and harms of treatment. Future research aimed at analysing existing data in general population HF studies to explore the effect in subgroups of patients with CKD, considering stage of disease, may yield valuable insights for the management of people with HF and CKD.

Molecular Control of Phosphorus Homeostasis and Precision Treatment of Hypophosphatemic Disorders

Purpose of Review

Serum phosphorus is maintained in a narrow range by balancing dietary phosphate absorption, influx and efflux of phosphorus from bone and intracellular stores, and renal reabsorption of filtered phosphate. Acute hypophosphatemia, typically caused by transient increases in cellular uptake, can lead to severe complications such as cardiopulmonary dysfunction and rhabdomyolysis that can warrant parenteral phosphate repletion. Chronic hypophosphatemia, however, generally represents true phosphate deficiency and may result in long-term metabolic and skeletal complications, particularly in children due to the critical importance of phosphorus to skeletal mineralization and longitudinal growth.

Recent Findings

In addition to the well characterized roles of vitamin D and parathyroid hormone (PTH), a new bone-kidney axis has been discovered that regulates phosphate homeostasis through the bone-derived hormone Fibroblast Growth Factor 23 (FGF23) and its phosphaturic actions that are mediated by activation of fibroblast growth factor receptors (FGFRs) complexed with α-Klotho in renal tubules. Chronic hypophosphatemia can now be classified as FGF23 dependent or independent.

Summary

In cases of FGF23 dependent hypophosphatemia, traditional non-specific treatments with elemental phosphorus and 1,25(OH)₂ vitamin D (calcitriol) can now be replaced with a targeted approach by using an FGF-23 blocking antibody (Burosumab).

Update on Chronic Kidney Disease Mineral and Bone Disorder in Cardiovascular Disease

Chronic kidney disease mineral and bone disorder (MBD) encompasses changes in mineral ion and vitamin D metabolism that are widespread in the setting of chronic kidney disease and end-stage renal disease. MBD components associate with cardiovascular disease in many epidemiologic studies. Through impacts on hypertension, activation of the renin-angiotensin-aldosterone system, vascular calcification, endothelial function, and cardiac remodeling and conduction, MBD may be a direct and targetable cause of cardiovascular disease. However, assessment and treatment of MBD is rife with challenges owing to biological tensions between its many components, such as calcium and phosphorus with their regulatory hormones fibroblast growth factor 23 and parathyroid hormone; fibroblast growth factor 23 with its co-receptor klotho; and vitamin D with control of calcium and phosphorus. These complex interactions between MBD components hinder the simple translation to clinical trials, which ultimately are needed to prove the benefits of treating MBD. Deeper investigation using precision medicine tools and principles, including genomics and individualized risk assessment and therapy, may help move the field closer toward clinical applications. This review provides a high-level overview of conventional and precision epidemiology in MBD, potential mechanisms of cardiovascular disease pathogenesis, and guiding therapeutic principles for established and emerging treatments.

Targeting Gastrointestinal Transport Proteins to Control Hyperphosphatemia in Chronic Kidney Disease

Management of hyperphosphatemia in patients with dialysis-dependent chronic kidney disease remains a major challenge, requiring a multifaceted approach that includes dietary phosphate restriction, dialysis, and phosphate binders. However, these treatments fail to meet serum phosphate targets in many patients, potentially further exacerbating the significant morbidity and mortality burden associated with the disease. Recent advances in our understanding of the mechanisms underlying phosphate homeostasis have shed new light on the issue and suggest that gastrointestinal transport proteins may be promising targets for new hyperphosphatemia treatments. Drugs that inhibit or downregulate these transport proteins, and thus reduce phosphate uptake from the gut, may overcome some of the limitations of existing phosphate-lowering strategies, such as interdialytic rises in serum phosphate levels, poor adherence to dietary and phosphate-binder regimens, and maladaptive responses that can increase gastrointestinal phosphate absorption. Here, we review the latest preclinical and clinical data for two candidates in this novel drug class: tenapanor, a small-molecule inhibitor of the sodium/hydrogen ion-exchanger isoform 3, and nicotinamide, an inhibitor of sodium-phosphate-2b cotransporters. We also discuss how potential synergies in their mechanisms of action suggest that coadministering phosphate binders with sodium-phosphate-2b cotransporter inhibitors may yield additive benefits over traditional phosphate-binder therapy.

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.