Combination Therapy with Angiotensin-Converting Enzyme Inhibitor and Oral Adsorbent of Uremic Toxins Can Delay the Appearance of Glomerular Sclerosis and Interstitial Fibrosis in Established Renal Failure

Effects and Safety of an Oral Adsorbent on Chronic Kidney Disease Progression: A Systematic Review and Meta-Analysis

Background: AST-120 (Kremezin), which is an oral spherical carbon adsorbent, has been reported to have the potential for retarding disease progression in patients with chronic kidney disease. We aimed to evaluate its efficacy and safety in this study. Methods: We systematically searched for randomized controlled trials published in PubMed, Embase, and Cochrane databases. The primary outcomes were the renal outcome and all-cause mortality, and the change in serum indoxyl sulfate (IS) levels. The safety outcome was also evaluated in terms of reported major adverse events. A random-effects model was used when heterogeneity was expected. Results: Eight studies providing data for 3349 patients were included in the meta-analysis. The risk ratio of renal outcome and all-cause mortality were 0.97 (95% CI: 0.88–1.07; 6 trials) and 0.94 (0.73–1.20; 5 trials), respectively. Furthermore, the weighted mean change in IS levels from baseline to the end of the study was −0.28 mg/dL (95% CI: −0.46 to −0.11; 4 trials). Conclusions: This study provides evidence that AST-120 can effectively lower IS levels but still controversial in terms of slowing disease progression and all-cause mortality. Except for dermatological events, the incidence of adverse events did not differ significantly between the AST-120 and placebo groups.

Oral adsorbents for preventing or delaying the progression of chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) is a worldwide public health problem which is at high increased risk of cardiovascular disease (CVD) and renal failure. Deterioration of kidney function causes an increase in circulating toxins, which, in turn promotes the progression of CKD. Oral adsorbents with capacity to adsorb and remove substances including uraemic toxins from the intestine could be effective in minimising kidney injury.

OBJECTIVES

To investigate the benefits and harms of oral adsorbents for preventing or delaying the progression of CKD.

SEARCH METHODS

We searched the Cochrane Renal Group's Specialised Register (to 22 September 2014) through contact with the Trials' Search Co-ordinator using search terms relevant to this review. The following four Chinese medical databases were also searched: China Biological Medicine Database (1979 to May 2012); Chinese Science and Technique Journals Database (to May 2012); China National Infrastructure (to May 2012); Wan Fang database (to May 2012).

SELECTION CRITERIA

Randomised controlled trials (RCTs) and quasi-RCTs comparing any oral adsorbents for preventing or delaying the progression of CKD.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed and extracted information. Information was collected on methods, participants, interventions and outcomes (incidence of end-stage kidney disease (ESKD), mortality, quality of life and adverse events). Results were expressed as risk ratios (RR) for dichotomous outcomes or as mean differences (MD) for continuous data with 95% confidence intervals (CI). Adverse events were expressed as risk differences (RD).

MAIN RESULTS

Fifteen studies (1590 patients) conducted in Japan, China, and the USA were identified. The risk of bias of the included studies was moderate or high and the sample sizes were small.Three studies compared oral AST-120 plus routine treatment with placebo plus routine treatment; however data on our outcome measures of interest were not reported in two studies. These studies did not assess or did not provide data for our primary outcomes of interest (incidence of ESKD; time to ESKD; all-cause mortality). There was no significant difference in the changes of serum creatinine (SCr), slope of 1/SCr over time and creatinine clearance (CrCl) between AST-120 and placebo for patients with CKD.Eight studies compared oral AST-120 plus routine treatment with routine treatment alone; data on our outcome measures of interest were not reported in one study. There was no significant difference in incidence of ESKD, all-cause mortality and the change in health-related quality of life between AST-120 and routine treatment for patients with CKD. AST-120 showed beneficial effects on delaying the decline of kidney function measured by using the slope of change in estimated CrCl (SMD 0.39, 95% CI 0.21 to 0.5) and the mean changes of glomerular filtration rate (GFR) (MD -0.76 mL/min/mo, 95% CI -0.82 to -0.70) for patients with CKD; AST-120 was not superior to routine treatment in retarding the decline of kidney function measured by using the 1/SCr slope over time, occurrence of increase in SCr concentration, doubling of SCr concentration, changes in GFR from baseline (mL/min/1.73 m²) and slope of the eGFR curve (mL/min/mo) for patients with CKD.Three studies compared oral Ai Xi Te plus routine treatment with routine treatment alone. These studies did not assess our primary outcomes of interest. Compared with routine treatment, Ai Xi Te had positive effects on reducing SCr (MD -113.40 (µmol/L), 95% CI -188.69 to -38.10) and retarding the decline of CrCl (MD 9.74 (mL/min), 95% CI 4.28 to 15.21) for patients with CKD.One study compared oral Niaoduqing granules plus routine treatment with routine treatment alone, but did not assess our primary outcomes of interest. Compared with routine treatment, Niaoduqing granules had positive effects on reducing SCr (MD -135.60 (µmol/L), 95% CI -198.03 to -73.17) and CrCl (MD 13.30 (mL/min), 95% CI 5.69 to 20.91).The most commonly reported adverse events associated with AST-120 and Ai Xi Te were gastrointestinal symptoms however no serious adverse events were reported.

AUTHORS' CONCLUSIONS

Few studies reported our primary outcomes of interest. For our secondary outcomes, there is evidence of limited quality that AST-120, Ai Xi Te and Niaoduqing granules may have positive effects on delaying the decline of kidney function. There were no serious adverse events for any of the interventions in patients with CKD. Given the lack of information for our primary outcomes, the low methodological quality of most studies, and the small sample sizes, there is no strong evidence on the effectiveness of these oral adsorbents.

CREB, NF-κB, and NADPH oxidase coordinately upregulate indoxyl sulfate-induced angiotensinogen expression in proximal tubular cells

In chronic kidney disease (CKD), indoxyl sulfate, a uremic toxin, accumulates in serum, and the expression of angiotensinogen (AGT) is upregulated in renal proximal tubular cells. The present study aimed to determine the relationship between indoxyl sulfate and the upregulation of AGT expression in proximal tubular cells. Indoxyl sulfate induced expression of AGT in rat renal cortex and in cultured human proximal tubular cells (HK-2). In proximal tubular cells, indoxyl sulfate induced phosphorylation of cAMP response element-binding protein (CREB) on Ser-133, and small interfering RNA (siRNA) specific to CREB inhibited indoxyl sulfate-induced AGT expression. Our previous study demonstrated that indoxyl sulfate activated nuclear factor-κB (NF-κB) through reactive oxygen species (ROS) production. NF-κB inhibitors (pyrrolidine dithiocarbamate and isohelenin), NF-κB p65 siRNA, an antioxidant [ N-acetylcysteine (NAC)], and a nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor [diphenyleneiodonium (DPI)] suppressed indoxyl sulfate-induced AGT expression. Both NAC and DPI suppressed indoxyl sulfate-induced expression of NF-κB p65 and CREB. CREB siRNA suppressed indoxyl sulfate-induced NF-κB p65 expression, whereas both NF-κB inhibitors and NF-κB p65 siRNA prevented indoxyl sulfate-induced CREB expression. Furthermore, we focused on the expression of NADPH oxidase 4 (NOX4), because indoxyl sulfate induced NOX4 expression in vascular smooth muscle cells and vascular endothelial cells. Indoxyl sulfate induced the expression of NOX4 in proximal tubular cells, which was suppressed by NAC, DPI, NF-κB inhibitors, NF-κB p65 siRNA, and CREB siRNA. Taken together, CREB, NF-κB, and NOX4 coordinately upregulate indoxyl sulfate-induced AGT expression in proximal tubular cells.

Mineralocorticoid Receptor Blocker Protects against Podocyte-Dependent Glomerulosclerosis

Background

We previously showed that angiotensin type 1 receptor (AT1) blocker (ARB) attenuates glomerular injury in Nphs1-hCD25 (NEP25) transgenic mice, a model of selective podocyte injury. However, subsequent studies in NEP25 mice with podocyte-specific deficiency of AT1 revealed that the protective effects of ARB are not through the podocyte AT1, thereby raising the possibility that the protective effects of ARB involve mineralocorticoids.

Methods

NEP25 mice were treated with the mineralocorticoid receptor blocker (MRB) spironolactone (25 mg/kg/day, n = 10), the ARB losartan (250 mg/kg/day, n = 11), both (ARB+MRB, n = 8) or vehicle (Vehicle, n = 9) from day −7 to day 9 of induction of podocyte injury.

Results

Although MRB did not reduce systolic blood pressure or proteinuria, addition of MRB to ARB significantly attenuated glomerulosclerosis (glomerulosclerosis index: ARB+MRB 1.67 ± 0.19 vs. MRB 2.01 ± 0.29, ARB 2.35 ± 0.19, and Vehicle 2.25 ± 0.26, p < 0.05) and preserved the number of WT1-positive podocytes (ARB+MRB 152.5 ± 9.7 vs. MRB 117.2 ± 9.0 or ARB 113.6 ± 7.4, and ARB+MRB vs. Vehicle 97.5 ± 4.0 per glomerulus; p < 0.05).

Conclusion

These data suggest that, while MRB does not attenuate proteinuria caused by podocyte-specific injury, it provides protective effects against glomerulosclerosis that is independent of systemic blood pressure.

Effect of a carbonaceous oral adsorbent on the progression of CKD: a multicenter, randomized, controlled trial

BACKGROUND

The carbonaceous oral adsorbent AST-120 slows the deterioration of kidney function in patients with advanced chronic kidney disease (CKD). However, information about AST-120 in patients with less severe stages of CKD is lacking.

STUDY DESIGN

Randomized controlled trial.

SETTING & PARTICIPANTS

75 medical facilities, 460 patients with CKD with serum creatinine (sCr) concentrations less than 5.0 mg/dL (not undergoing dialysis).

INTERVENTION

Random assignment to either a low-protein diet and antihypertensive medication in the control group or that treatment combined with AST-120 (6 g/d).

OUTCOMES & MEASUREMENTS

Composite primary end point: doubling of sCr level, increase in sCr level to 6.0 mg/dL or more, need for dialysis or transplantation, or death.

SECONDARY OUTCOMES

adverse events and changes in estimated creatinine clearance (CCr) rate, proteinuria (protein in milligrams per day), and quality of life.

RESULTS

Mean sCr level was 2.66 mg/dL and estimated CCr was 22.4 mL/min in both groups. During 56 weeks, numbers of primary end-point events (43 for control versus 42 for AST-120) and event-free survival (P = 0.9) did not differ between groups. Gastrointestinal adverse events were less common in the control group than the AST-120 group (2 versus 32 events). Estimated CCr decreased more in the control group than in the AST-120 group (-15% per year versus -12% per year, relative to the baseline value; [corrected] P = 0.001). Median proteinuria changed from protein of 1,162 to 1,167 mg/d in the control group versus 1,102 to 906 mg/d in the AST-120 group (P = 0.2).

LIMITATION

Infrequent primary end-point events.

CONCLUSION

AST-120 did not substantially slow the progression of kidney disease in patients with moderate to severe CKD during 1 year.

SGK1-dependent upregulation of connective tissue growth factor by angiotensin II

Angiotensin II has previously been shown to trigger fibrosis, an effect involving connective tissue growth factor (CTGF). The signaling pathways linking angiotensin II to CTGF formation are, however, incompletely understood. A gene highly expressed in fibrosing tissue is the serum- and glucocorticoid-inducible kinase SGK1. The present study explored whether SGK1 is transcriptionally regulated by angiotensin II and participates in the angiotensin II-dependent regulation of CTGF expression. To this end, experiments have been performed in human kidney fibroblasts and mouse lung fibroblasts from gene-targeted mice lacking SGK1 (sgk1-/-) and their wild-type littermates (sgk1+/+). In human renal fibroblasts, SGK1 and CTGF protein expression were enhanced by angiotensin II (10 nM) within 4 h. In sgk1+/+ mouse fibroblasts, SGK1 transcript levels were significantly increased after 4 h of angiotensin II treatment. Angiotensin II stimulated both transcript and protein abundance of CTGF in fibroblasts from sgk1+/+ mice, effects significantly blunted in fibroblasts of sgk1-/- mice. In conclusion, angiotensin II stimulates the expression of SGK1, which is in turn required for the stimulating effect of angiotensin II on the expression of CTGF. Thus, SGK1 presumably contributes to the profibrotic effect of angiotensin II.

NO-independent activation of soluble guanylate cyclase prevents disease progression in rats with 5/6 nephrectomy

1. Chronic renal disease is associated with oxidative stress, reduced nitric oxide (NO) availability and soluble guanylate cyclase (sGC) dysfunction. Recently, we discovered BAY 58-2667, a compound activating heme-deficient or oxidized sGC in a NO-independent manner. 2. We assessed potential of BAY 58-2667 in preventing cardiac and renal target organ damage in rats with 5/6 nephrectomy. 3. Male Wistar rats were allocated to three groups: 5/6 nephrectomy, 5/6 nephrectomy treated with BAY 58-2667 and sham operation. Study period was 18 weeks: blood pressure and creatinine clearance were assessed repeatedly. At study end blood samples were taken and hearts and kidneys harvested for histological studies. 4. BAY 58-2667 markedly lowered blood pressure in animals with 5/6 nephrectomy (untreated versus treated animals: 189+/-14 versus 146+/-11 mmHg, P<0.001). Left ventricular weight, cardiac myocyte diameter as well as cardiac arterial wall thickness significantly decreased in comparison to untreated animals with 5/6 nephrectomy. Natriuretic peptide plasma levels were also improved by BAY 58-2667. Kidney function and morphology as assessed by creatinine clearance, glomerulosclerosis, interstitial and perivascular fibrosis of intrarenal arteries were likewise significantly improved by BAY 58-2667. 5. This is the first study showing that BAY 58-2667 effectively lowers blood pressure, reduces left ventricular hypertrophy and slows renal disease progression in rats with 5/6 nephrectomy by targeting mainly oxidized sGC. Therefore, BAY 58-2667 represents a novel pharmacological principle with potential clinical value in treatment of chronic renal disease.

A multicenter, randomized, double-blind, placebo-controlled, dose-ranging study of AST-120 (Kremezin) in patients with moderate to severe CKD

BACKGROUND

AST-120 (Kremezin; Kureha Chemical Industry Co Ltd, Tokyo, Japan) is an orally administered adsorbent showing adsorption ability superior to activated charcoal for certain organic compounds known to be precursors of substances that accumulate in patients with chronic kidney disease (CKD) and that are believed to accelerate the decline in kidney function. AST-120 is approved in Japan for prolonging time to hemodialysis therapy and improving uremic symptoms in patients with CKD.

METHODS

A multicenter, randomized, double-blind, placebo-controlled, dose-ranging study was designed to examine the nephroprotective effects of 3 doses of AST-120 versus placebo in adult patients with moderate to severe CKD and elevated serum indoxyl sulfate levels while following an adequate protein-intake diet. Eligible patients were randomly assigned to 1 of 3 doses of AST-120 (0.9, 2.1, or 3.0 g) or placebo 3 times daily for 12 weeks.

RESULTS

AST-120 decreased serum indoxyl sulfate levels in a dose-dependent fashion. During the 12-week treatment period, AST-120 did not affect serum creatinine levels or 24-hour urine creatinine appearance. Significant improvements in malaise were observed in a dose-dependent fashion. All doses of AST-120 were well tolerated and did not adversely affect the general health status of patients.

CONCLUSION

Results suggest that the dose of 3 g 3 times daily is an optimal dose for the US population, and it may be useful in the treatment of patients with CKD. Because AST-120 did not directly affect serum creatinine levels or 24-hour urine creatinine appearance, the composite end point of doubling of serum creatinine level, transplantation, and dialysis therapy would be appropriate for a confirmatory phase III therapeutic outcome study.