Plasma Indoxyl Sulfate Research Articles

Integrated metagenomic and metabolomic analysis reveals distinctive stage-specific gut-microbiome-derived metabolites in intracranial aneurysms

ObjectiveOur study aimed to explore the influence of gut microbiota and their metabolites on intracranial aneurysms (IA) progression and pinpoint-related metabolic biomarkers derived from the gut microbiome.DesignWe recruited 358 patients...

#3023 Dietary protein intake modulates the tubular handling of the uremic retention solute indoxyl sulfate

Abstract Background and Aims Nutritional intervention constitutes a key part of the clinical management of individuals with chronic kidney disease (CKD). The gut emerged as an important source of uremic retention solutes, including indoxyl sulfate, p-cresyl sulfate and TMAO among the others. Indoxyl sulfate (IS) is produced through the gut microbial fermentation of tryptophan into indole and its conversion into indoxyl sulfate in the liver. Previous authors hypothesised that higher amounts of gut microbial metabolites can be sensed by kidney's proximal tubule cells through the use of receptors and signaling pathways. Particular evidence points to the involvement of kidney Organic Anion Transporters’(OATs') in controlling the gut-kidney communication. According to the so-called remote sensing hypothesis, kidney tubular cells respond to uremic toxins plasma fluctuations altering the activity of OAT1. Few studies have investigated whether in CKD the protein content in the diet affects gut generation, plasma retention and excretion mechanisms of indolic uremic toxins including kidney cells OAT1 expression. Method Eighteen male Sprague-Dawley rats (Janvier, France) aged 7-8 weeks and weighing between 270 and 388 g were randomly assigned to a low protein (LP) diet (n = 10) or a high protein (HP) diet (n = 8) after undergoing a 5/6 nephrectomy to develop CKD. For each diet, a sham-operated control group (n = 7 and n = 8 correspondingly) was used. After 7 weeks, urine was collected, and 8 weeks after the disease was induced, euthanasia was performed. Samples of kidney and blood were taken. mRNA and protein expression of OAT1 were sought via qPCR and Western blot. Forty patients with CKD were recruited in a cross-sectional study investigating eating habits and uremic toxins levels. Eating habits were searched via a food diary. Protein and energy intake were therefore calculated. Blood and 48 h-urine were collected. Blood creatinine and urea were determined with standard laboratory techniques. Total plasmatic and urinary IS concentrations were measured using LC-MS/MS. The fractional excretion (FE) i.e. the percentage of IS excreted relatively to the kidney filtered load, was calculated to assess IS remote sensing. Results Rats with chronic kidney disease (CKD) had considerably higher plasmatic levels of IS (p < .001) than sham rats. Rats with CKD on an HP diet, however, did not differ in plasma IS from rats fed an LP diet (p = .63). On the other hand, CKD rats fed an HP diet showed a substantial rise in 24-hour urinary IS (p < .001). The FE of IS was significantly higher (p = .005) in CKD rats on a HP diet and correlated with 24 h-urinary IS (Spearman r = .51, p value=.03) and with protein intake (Spearman r = .52, p value=.03) in CKD rats. OAT1 mRNA and protein expression was significantly higher in CKD rats given a HP diet (p = .025 and p = .009, respectively). By dividing the CKD patients into two groups by the median of protein intake, the FE of IS was significantly higher (p = .018) in the patients consuming a larger portion of proteins. Conclusion A diet higher in protein content in 5/6 nephrectomized CKD rats as well as in CKD patients likely leads to an increased production of indole in the colon. This results in increased IS fractional excretion but unchanged IS plasma retention. These findings offer more evidence for the mechanisms behind the remote sensing and signaling of uremic toxins derived from indole. In summary, a low-protein diet is still advised for people with chronic kidney disease.

Animal Models for Studying Protein-Bound Uremic Toxin Removal-A Systematic Review.

Protein-bound uremic toxins (PBUTs) are associated with the progression of chronic kidney disease (CKD) and its associated morbidity and mortality. The conventional dialysis techniques are unable to efficiently remove PBUTs due to their plasma protein binding. Therefore, novel approaches are being developed, but these require validation in animals before clinical trials can begin. We conducted a systematic review to document PBUT concentrations in various models and species. The search strategy returned 1163 results for which abstracts were screened, resulting in 65 full-text papers for data extraction (rats (n = 41), mice (n = 17), dogs (n = 3), cats (n = 4), goats (n = 1), and pigs (n = 1)). We performed descriptive and comparative analyses on indoxyl sulfate (IS) concentrations in rats and mice. The data on large animals and on other PBUTs were too heterogeneous for pooled analysis. Most rodent studies reported mean uremic concentrations of plasma IS close to or within the range of those during kidney failure in humans, with the highest in tubular injury models in rats. Compared to nephron loss models in rats, a greater rise in plasma IS compared to creatinine was found in tubular injury models, suggesting tubular secretion was more affected than glomerular filtration. In summary, tubular injury rat models may be most relevant for the in vivo validation of novel PBUT-lowering strategies for kidney failure in humans.

Evaluation of effects of indoxyl sulfate and parathyroid hormone on CYP3A activity considering the influence of CYP3A5 gene polymorphisms.

Indoxyl sulfate and parathyroid hormone (PTH), which accumulate in chronic kidney disease (CKD), have been reported to reduce cytochrome P450(CYP)3A activity. Homozygotes of the CYP3A5*3 allele have reduced CYP3A5 activity compared to carriers of at least one CYP3A5*1 allele. 4β-Hydroxycholesterol (4β-OHC) has been established as an endogenous substrate reflecting CYP3A activity. 4β-OHC is produced through hydroxylation by CYP3A4 and CYP3A5 and by autoxidation of cholesterol, whereas 4α-hydroxycholesterol (4α-OHC) is produced solely by autoxidation of cholesterol. This study focused on CKD patients and evaluated the effects of plasma indoxyl sulfate and intact-PTH concentrations on plasma 4β-OHC concentration, 4β-OHC/total cholesterol ratio and 4β-OHC-4α-OHC, with consideration of the influence of CYP3A5 polymorphism. Sixty-three CKD patients were analysed and divided into CYP3A5 carrier group (n = 26) and non-carrier group (n = 37). Plasma indoxyl sulfate significantly correlated inversely with 4β-OHC concentration and with 4β-OHC-4α-OHC in both the CYP3A5*1 carrier group (r = -0.42, P = .034; r = -0.39, P = .050, respectively) and the non-carrier group (r = -0.45, P = .0054; r = -0.39, P = .019, respectively). However, multiple regression analysis did not identify plasma indoxyl sulfate concentration as a significant independent factor associated with any of the CYP3A activity indices. There was no significant correlation between plasma intact-PTH concentration and any of the CYP3A activity indices. The present results suggest that plasma indoxyl sulfate and intact-PTH concentrations do not have clinically significant effects on CYP3A activity in patients with CKD.

Protective effect of Rhein against vancomycin-induced nephrotoxicity through regulating renal transporters and Nrf2 pathway.

Vancomycin (VCM)'s nephrotoxicity limits its application and therapeutic efficiency. The aim of this study was to determine the protective effect of rhein against VCM-induced nephrotoxicity (VIN). VIN models were established in rats and NRK-52E cells. Rhein up-regulated the expressions of renal organic anion transporter (Oat) 1, Oat3, organic cation transporter 2 (Oct2), multidrug resistance-associated protein 2 (Mrp2), mammal multidrug and toxin extrusion proteins 1 (Mate 1) and P-glycoprotein (P-gp) to facilitate the efflux of plasma creatinine, blood urea nitrogen (BUN), and plasma indoxyl sulfate. Rhein increased the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) to regulate the expression of Mrp2, P-gp, and Mate 1. The increased level of superoxide dismutase (SOD), decreased level of malondialdehyde (MDA) and reduced number of apoptosis cells were observed after treatment of rhein. Rhein decreased the number of apoptosis cells as well as increased the expression of B-cell lymphoma-2 (Bcl-2) and decreased expressions of Bcl-2-like protein 4 (Bax). ML385, as a typical inhibitor of Nrf2, reversed the protective effects of rhein in cells. Rhein oriented itself in the site of Keap1, inhibiting the Keap1-Nrf2 interaction. Rhein ameliorated VIN mainly through regulating the expressions of renal transporters and acting on Nrf2 pathway.

MO436: The Effect of Protein-Restriction on the Tubular Handling of the Uraemic Retention Solute Indoxyl Sulfate

Abstract BACKGROUND AND AIMS Chronic kidney disease (CKD) patients present an increased plasma level of protein-bound solutes known as uraemic toxins. Their accumulation is associated with, amongst others, cardiovascular events. The gut microbiome plays an important role in the generation of part of the uraemic toxins. It has been postulated that proximal tubule cells in kidneys are able to sense augmented levels of gut microbial metabolites via receptors and signalling pathways [1]. According to the so-called remote sensing hypothesis, kidney tubular cells respond to uraemic toxins plasma variations modulating the activity of membrane transporters involved in their excretion. Indoxyl sulfate (IS) originates from the microbial fermentation of tryptophan, a diet-derived amino acid. Nonetheless, few studies have investigated whether gut generation, absorption and plasma retention of indolic uraemic toxins and kidney cells’ secretory mechanisms are affected by the protein content in the diet. METHOD A total of 18 Sprague–Dawley male rats (Janvier, Le Genest- St Isle, France) 7–8 weeks old (weighing 270–388 g) were induced with CKD utilizing 5/6 nephrectomy and were randomly assigned to a low protein (LP) (n = 10) or a high protein (HP) (n = 8) diet. A sham-operated control group for each diet was used (n = 7 and n = 8 respectively). 24 h-urine was collected after 7 weeks, and euthanasia was carried out after 8 weeks from the induction of the disease (Figure 1). Blood and colon samples were collected. Diffusion chambers were used to assess colon permeability to indole over time (t = 0, 60, 90, 120 min). Indole concentration was quantified by Kovacs assay. Blood creatinine and urea were determined with standard laboratory techniques. Total plasmatic and urinary IS concentrations were measured using LC-MS/MS. The fractional excretion (FE) i.e. the percentage of IS excreted relatively to the kidney filtered load, was calculated to assess IS remote sensing. RESULTS Plasmatic levels of IS were significantly higher (P <0.001) in CKD rats compared to sham rats. However, CKD rats on an HP diet showed no difference in plasma IS (P = 0.63) compared to rats on an LP diet. Conversely, 24-h urinary IS was significantly increased in CKD rats on a HP diet (P <0.001). The FE of IS was significantly higher (P = 0.005) in CKD rats on an HP diet (Figure 2) and correlated with 24 h-urinary IS (Spearman r = 0.51, P -value = 0.03) and with protein intake (Spearman r = 0.52, P-value = 0.03) in CKD rats. Therefore, CKD rodent models’ results suggest higher absorption and/or production of indole at the intestinal level when an HP is administered to CKD rats. Plus, they provide additional proof of the remote sensing theory of indole metabolites. The permeability of colon to indole evaluated ex vivo with the diffusion chamber technique, showed an increased apparent apical-to-basolateral transport of indole (P = 0.049) in CKD rats on an HP diet compared to that of sham rats on the same diet, again suggesting modulatory mechanisms affecting indole metabolites transporters uptake. CONCLUSION An HP diet in 5/6 nephrectomized CKD rats leads to increased production of indole in the colon and increased fractional excretion of IS. These results provide an additional proof of mechanisms of remote sensing and signalling of indole-derived uraemic toxins. To conclude, the adoption of a low protein diet remains recommended in chronic kidney disease.

Highly sensitive simultaneous quantification of indoxyl sulfate and 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid in human plasma using ultra-high-performance liquid chromatography coupled with tandem mass spectrometry.

Indoxyl sulfate and 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid are uremic toxins that accumulate in renal failure and have been reported to decrease the activities of the drug-metabolizing enzyme cytochrome P450 3A and the drug transporter organic anion transporting polypeptides 1B, respectively. In this study, we established and validated an assay for simultaneous quantification of indoxyl sulfate and 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid in human plasma. The samples were pretreated by solid-phase extraction, and measured by ultra-high-performance liquid chromatography-tandem mass spectrometry. The validation results for this assay were within the acceptable limits recommended by the US Food and Drug Administration, with a lower limit of quantitation of 0.05μg/mL for both indoxyl sulfate and 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid. Recovery rates of indoxyl sulfate and 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid corrected by internal standard were 100.7-101.9 and 100.2-101.3%, respectively. Matrix effects of indoxyl sulfate and 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid corrected by internal standard were 101.1-105.5 and 97.0-103.8%, respectively. The validated assay was used to analyze indoxyl sulfate and 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid concentrations in the plasma samples of healthy volunteers and patients with chronic kidney disease. All the measured plasma indoxyl sulfate and 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid concentrations were within the calibration ranges. This novel method may contribute to predicting the activities of drug-metabolizing enzymes and drug transporters in individual patients.

Effect of cranberry supplementation on toxins produced by the gut microbiota in chronic kidney disease patients: A pilot randomized placebo-controlled trial.

Patients with Chronic Kidney Disease (CKD) have an imbalance in the gut microbiota that can lead to increase levels of lipopolysaccharides (LPS) and uremic toxins such as indoxyl sulfate (IS), p-cresyl sulfate (p-CS), and indole-3 acetic acid (IAA). Among the therapeutic options for modulating gut microbiota are the bioactive compounds such as polyphenols present in cranberry, fruit with potential antioxidant and anti-inflammatory effects. This clinical trial focuses on evaluating the effects of supplementation with a dry extract of cranberry on plasma levels of LPS and uremic toxins in non-dialysis CKD patients. It was a randomized, double-blind, placebo-controlled study. Patients were randomized into two groups: the cranberry group received 500mg of dry cranberry extract (2 times daily), and the placebo group received 500mg of corn starch (2 times daily) for two months. LPS plasma levels were evaluated by enzyme-linked immunosorbent assay (ELISA) and uremic toxins (IS, p-CS, and IAA) by high-performance liquid chromatography-fluorescence detection. Anthropometric measurements and food intake using the 24-h food recall technique were also evaluated before and after the intervention. Twenty-five participants completed two months of supplementation: 12 patients in the cranberry group (8 women, 56.7±7.5 years, estimated glomerular filtration rate (eGFR) of 39.2±21.9mL/min); 13 patients in the placebo group (9 women, 58.8±5.1 years, eGFR of 39.7±12.9mL/min). As expected, there was a negative association between glomerular filtration rate and p-CS and IS plasma levels at the baseline. No change was observed in the uremic toxins and LPS levels. Cranberry dry extract supplementation for two months did not reduce the LPS and uremic toxins plasma levels produced by the gut microbiota in non-dialysis CKD patients.

Effect of hyperphosphatemia on impairment of vascular function in adenine-induced renal injury in rats

We reported that vascular function in adenine-induced renal injury rats was impaired mediated by increase in plasma indoxyl sulfate concentration. It is known that hyperphosphatemia leads to calcification and atherosclerosis. In the present study, we examined effect of hyperphosphatemia on vascular dysfunction in adenine-induced renal injury in anesthetized rats. Renal injury was induced by feeding 0.75% adenine diet for 4 weeks. Lanthanum carbonate was treated with gavage after 2 weeks induced adenine. Treatment with lanthanum carbonate significantly decreased in plasma phosphorus concentration in adenine rats. N-nitro-L-arginine (L-NA) potentiated the ACh-induced depressor response in normal-diet. However, L-NA failed to potentiate the response in adenine rats or lanthanum-treated rats. Sodium nitroprusside (SNP)-induced depressor response in adenine rats was significantly smaller than that in normal rats. Lanthanum carbonate tended to recover impairment of SNP-induced depressor responses in adenine rats. These findings suggest that hyperphosphatemia is partially related to impairment of smooth muscle function rather than that of endothelial function in adenine rats.

(+)-Sesamin, a sesame lignan, is a potent inhibitor of gut bacterial tryptophan indole-lyase that is a key enzyme in chronic kidney disease pathogenesis

The progression of chronic kidney disease (CKD) increases the risks of cardiovascular morbidity and end-stage kidney disease. Indoxyl sulfate (IS), which is derived from dietary l-tryptophan by the action of bacterial l-tryptophan indole-lyase (TIL) in the gut, serves as a uremic toxin that exacerbates CKD-related kidney disorder. A mouse model previously showed that inhibition of TIL by 2-aza-l-tyrosine effectively reduced the plasma IS level, causing the recovery of renal damage. In this study, we found that (+)-sesamin and related lignans, which occur abundantly in sesame seeds, inhibit intestinal bacteria TILs. Kinetic studies revealed that (+)-sesamin and sesamol competitively inhibited Escherichia coli TIL (EcTIL) with Ki values of 7 μM and 14 μM, respectively. These Ki values were smaller than that of 2-aza-l-tyrosine (143 μM). Molecular docking simulation of (+)-sesamin- (or sesamol-)binding to EcTIL predicted that these inhibitors potentially bind near the active site of EcTIL, where the cofactor pyridoxal 5′-phosphate is bound, consistent with the kinetic results. (+)-Sesamin is a phytochemical with a long history of consumption and is generally regarded as safe. Hence, dietary supplementation of (+)-sesamin encapsulated in enteric capsules could be a promising mechanism-based strategy to prevent CKD progression. Moreover, the present findings would provide a new structural basis for designing more potent TIL inhibitors for the development of mechanism-based therapeutic drugs to treat CKD.

Effect of Dietary Inulin Supplementation on the Gut Microbiota Composition and Derived Metabolites of Individuals Undergoing Hemodialysis: A Pilot Study

The prebiotic fiber inulin has been studied in individuals undergoing hemodialysis (HD) due to its ability to reduce gut microbiota-derived uremic toxins. However, studies examining the effects of inulin on the gut microbiota and derived metabolites are limited in these patients. We aimed to assess the impact of a 4-week supplementation of inulin on the gut microbiota composition and microbial metabolites of patients on HD. In a randomized, double-blind, placebo-controlled, crossover study, twelve HD patients (55±10y, 50% male, 58% Black American, BMI 31.6±8.9kg/m2, 33% diabetes mellitus) were randomized to consume inulin [10g/d for females; 15g/d for males] or maltodextrin [6g/d for females; 9g/d for males] for 4weeks, with a 4-week washout period. We assessed the fecal microbiota composition, fecal metabolites (short-chain fatty acids (SCFA), phenols, and indoles), and plasma indoxyl sulfate and p-cresyl sulfate. At baseline, factors that explained the gut microbiota variability included BMI category and type of phosphate binder prescribed. Inulin increased the relative abundance of the phylum Verrucomicrobia and its genus Akkermansia (P interaction=0.045). Inulin and maltodextrin resulted in an increased relative abundance of the phylum Bacteroidetes and its genus Bacteroides (Ptime=0.04 and 0.03, respectively). Both treatments increased the fecal acetate and propionate (P time=0.032 and 0.027, respectively), and there was a trend toward increased fecal butyrate (P time=0.06). Inulin did not reduce fecal p-cresol or indoles, or plasma concentrations ofp-cresylsulfate or indoxyl sulfate. A 4-week supplementation of inulin did not lead to major shifts in the fecal microbiota and gut microbiota-derived metabolites. This may be due to high variability among participants and an unexpected increase in fecal excretion of SCFA with maltodextrin. Larger studies are needed to determine the effects of prebiotic fibers on the gut microbiota and clinical outcomes to justify their use in patients on HD.

Hypouricemic agents reduce indoxyl sulfate excretion by inhibiting the renal transporters OAT1/3 and ABCG2

Indoxyl sulfate (IS) accumulates in the body in chronic kidney disease (CKD). In the renal proximal tubules, IS excretion is mediated by OAT1/3 and ABCG2. These transporters are inhibited by some hypouricemic agents; OATs by probenecid and benzbromarone, ABCG2 by febuxostat and benzbromarone. Thus, we evaluated whether hypouricemic agents including dotinurad, a novel selective urate reabsorption inhibitor with minimal effect on OATs or ABCG2, affect IS clearance in rats. Intact and adenine-induced acute renal failure rats were orally administered hypouricemic agents, and both endogenous IS and exogenously administered stable isotope-labeled d4-IS in the plasma and kidney were measured. Our results demonstrated that OATs inhibitors, such as probenecid, suppress IS uptake into the kidney, leading to increased plasma IS concentration, whereas ABCG2 inhibitors, such as febuxostat, cause renal IS accumulation remarkably by suppressing its excretion in intact rats. The effects of these agents were reduced in adenine-induced acute renal failure rats, presumably due to substantial decrease in renal OAT1/3 and ABCG2 expression. Dotinurad did not significantly affected the clearance of IS under both conditions. Therefore, we suggest that hypouricemic agents that do not affect OATs and ABCG2 are effective therapeutic options for the treatment of hyperuricemia complicated by CKD.

Plasma indoxyl sulfate levels predict cardiovascular events in patients with mild chronic heart failure

Indoxyl sulfate (IS) is associated with either chronic kidney disease or renal failure, which may predict cardiovascular events via cardiorenal syndrome. The present study aimed to elucidate whether the plasma levels of IS can predict the occurrence of cardiovascular events in patients with chronic heart failure (CHF) and investigate which causes of CHF leading to cardiovascular events are highly influenced by plasma IS levels. We measured the plasma IS levels in 165 patients with CHF [valvular disease: 78, dilated cardiomyopathy: 29, hypertrophic cardiomyopathy (HCM): 25 and others: 33] admitted to our hospital in 2012, and we followed up these patients for more than 5 years (the median follow-up period: 5.3 years). We measured the plasma IS level in 165 patients with CHF, and Kaplan–Meier analyses showed that high plasma IS levels (≥ 0.79 µg/mL, the median value) could predict the occurrence of cardiovascular events, i.e., cardiovascular death or rehospitalization due to the worsening of CHF. The sub-analyses showed that the high IS level could predict cardiovascular events in patients with CHF due to HCM and that the plasma IS levels were closely associated with left ventricular (LV) dimension, LV systolic dysfunction, and plasma B-type natriuretic peptide levels, rather than LV diastolic dysfunction. Plasma IS level predicts cardiovascular events in patients with CHF, especially those with HCM along with cardiac dysfunction. Besides, IS may become a proper biomarker to predict cardiovascular events in patients with CHF.

Efficacy of Divinylbenzenic Resin in Removing Indoxyl Sulfate and P-Cresol Sulfate in Hemodialysis Patients: Results From an In Vitro Study and An In Vivo Pilot Trial (xuanro4-Nature 3.2).

High serum levels of microbiota-derived uremic toxins, indoxyl sulfate (IS) and p-cresyl sulfate (PCS), are associated with chronic kidney disease (CKD) progression and cardiovascular complications. IS and PCS cannot be efficiently removed by conventional hemodialysis (HD), due to their high binding affinity for albumin. This study evaluates the efficacy of a divinylbenzene-polyvinylpyrrolidone (DVB-PVP) cartridge and a synbiotic to reduce uremic toxins in HD patients. First, the in vitro efficacy of DVB-PVP in adsorbing IS and PCS was evaluated. Second, a randomized, placebo-controlled pilot study in HD patients was carried out to establish whether the administration of a synbiotic, either individually and in association with DVB-PVP-HD, could reduce the production of uremic toxins. In vitro data showed that DVB-PVP resin removed a mean of 56% PCS and around 54% IS, after 6 h of perfusion. While, in the in vivo study, the DVB-PVP cartridge showed its adsorbing efficacy only for IS plasma levels. The combination of synbiotic treatment with DVB-PVP HD decreased IS and PCS both at pre- and post-dialysis levels. In conclusion, this study provides the first line of evidence on the synergistic action of gut microbiota modulation and an innovative absorption-based approach in HD patients, aimed at reducing plasma levels of IS and PCS.

The Difference in the Changes of Indoxyl Sulfate after Catheter Ablation among Atrial Fibrillation Patients with and without Kidney Dysfunction

Indoxyl sulfate (IS), a protein-bound uremic toxin, induces chronic kidney disease (CKD) and atrial fibrillation (AF). Catheter ablation (CA) of AF improves the renal function. However, the transition of uremic toxins is unclear. This study aimed to investigate the transition of the serum IS level in AF patients with and without CKD after CA. A total of 138 consecutive AF patients who underwent CA and maintained sinus rhythm were prospectively enrolled (paroxysmal AF 67.4%). The patients were divided into 4 groups (non-CKD/low-IS:68, non-CKD/high-IS:28, CKD/low-IS:13, and CKD/high-IS:29). The plasma IS levels and estimated glomerular filtration rate (eGFR) were determined before and 1-year after CA. CKD was defined as CKD stage III and a high-IS according to the mean IS (IS ≥ 1.1 μg/ml). CA significantly improved the eGFR in CKD patients (p < 0.001). The serum IS level in the non-CKD/high-IS group was significantly decreased (from 1.7 ± 0.7 to 1.1 ± 0.6 μg/ml, p < 0.001). However, the serum IS level in the CKD/high-IS group did not improve (from 1.9 ± 0.9 to 1.7 ± 0.7 μg/ml, p = 0.22). The change in the IS in the CKD patients significantly differed from that in those without CKD. In the CKD patients, CA did not significantly decrease the IS, a risk factor of CKD, regardless of an improved eGFR.

AST-120, an Adsorbent of Uremic Toxins, Improves the Pathophysiology of Heart Failure in Conscious Dogs.

Several lines of evidence suggest that renal dysfunction is associated with cardiovascular toxicity through the action of uremic toxins. The levels of those uremic toxins can be reportedly reduced by the spherical carbon adsorbent AST-120. Because heart failure (HF) causes renal dysfunction by low cardiac output and renal edema, the removal of uremic toxins could be cardioprotective. To determine whether blood levels of the uremic toxin indoxyl sulfate (IS) increase in HF and whether AST-120 can reduce those levels and improve HF. We induced HF in 12 beagle dogs by 6weeks of rapid right ventricular pacing at 230 beats per min. We treated six dogs with a 1-g/kg/day oral dosage of AST-120 for 14days from week 4 after the start of rapid ventricular pacing. The other six dogs did not receive any treatment (control group). In the untreated dogs, IS levels increased as cardiac function deteriorated. In contrast, plasma IS levels in the treated dogs decreased to baseline levels, with both left ventricular fractional shortening and pulmonary capillary wedge pressure also improving when compared with untreated dogs. Finally, AST-120 treatment was shown to reduce both myocardial apoptosis and fibrosis along with decreases in extracellular signal-regulated kinase phosphorylation, the Bax/Bcl-2 ratio, and TGF-β1 expression and increases in AKT phosphorylation. IS levels are increased in HF. AST-120 treatment reduces the levels of IS and improves the pathophysiology of HF in a canine model. AST-120 could be a novel candidate for the treatment of HF.

The association of indoxyl sulfate with fibroblast growth factor-23 in cats with chronic kidney disease.

BackgroundIndoxyl sulfate (IS) has been reported not only to increase with the severity of impaired renal function, but also possibly to be a factor associated with bone abnormalities linked to fibroblast growth factor‐23 (FGF‐23) in humans with chronic kidney disease (CKD). It is not yet known whether this correlation between IS and FGF‐23 holds true for cats with CKD.HypothesisAccumulation of IS is related to FGF‐23 secretion in cats with CKD.AnimalsTwenty clinically healthy cats and 73 cats with CKD cases were evaluated retrospectively.MethodsThe concentrations of IS and FGF‐23 in plasma were determined by high‐performance liquid chromatography and ELISA, respectively. Progression was defined as an increment of 0.5 mg/dL of serum creatinine concentration within 3 months.ResultsPlasma IS and FGF‐23 concentrations were significantly increased concurrently with decreasing renal function. Higher concentration of FGF‐23 was significantly associated with higher concentration of IS after adjusting for various confounding factors including creatinine and phosphate. Furthermore, the correlation between IS and phosphate was higher than that between FGF‐23 and phosphate. When the renal progression group was compared with the non‐progression group, both IS and FGF‐23 were found to be significantly increased (P < .05). In addition, the area under receiver operator curve of the combination of IS and FGF‐23 predicted renal progression at a level >0.9.Conclusions and Clinical ImportanceBoth FGF‐23 and IS are associated with phosphate metabolism and CKD progression.

Zhenwu Decoction delays ventricular hypertrophy in rats with uremic cardiomyopathy

To investigate the inhibitory effect of Zhenwu Decoction on ventricular hypertrophy in rats with uremic cardiomyopathy and explore the mechanism. Cardiocytes isolated from suckling rats were divided into control group and indoxyl sulfate (IS) group, and the protein synthesis was assayed with [3H]- leucine incorporation and cellular protein expressions were detected using Western blotting. Fifty SD rats were randomly divided into sham operation group, model group, and low- and high-dose Zhenwu Decoction treatment groups, and except for those in the sham operation group, all the rats underwent 5/6 nephrectomy. Four weeks after the operation, the rats in low- and high-dose treatment groups were given Zhenwu Decoction via gavage at the dose of 4.5 g/kg and 13.5 g/kg, respectively; the rats in the sham-operated and model groups were given an equal volume of distilled water. After 4 weeks of treatment, serum levels of IS were determined, and cardiac and ventricular mass indexes were measured in the rats; cardiac ultrasound was performed and Western blotting was used to measure the expressions of BNP, p-ERK1/2, p-p38 and p-JNK in the myocardium. Rat cardiomyocytes treated with IS showed significantly enhanced protein synthesis and increased expression levels of BNP, p-erk1/2, and p-p38 as compared with the control cells (P &lt; 0.01), but the expression of p-jnk was comparable between the two groups. In the animal experiment, the rats in the model group showed significantly increased serum creatinine (SCr) and urea nitrogen (BUN) levels, 24-h urine protein (24 hUpro), plasma IS level, left ventricular mass index (LVMI) and whole heart mass index (HMI) compared with those in the sham group (P &lt; 0.01); Both LVESD and LVEDD were significantly reduced and LVAWS, LVAWD, LVPWS and LVPWD were significantly increased in the model rat, which also presented with obvious cardiomyocyte hypertrophy and increased myocardial expressions of BNP, p-ERK1/2, p-p38 and p-jnk (P &lt; 0.01). Compared with the rats in the model group, the rats treated with low-dose and high-dose Zhenwu Decoction had significantly lowered levels of SCr, BUN, 24 hUpro and IS (P &lt; 0.05) and decreased LVMI and HMI; LVESD, LVEDD, LVPWS, LVAWS, and LVAWD were improved more obviously in the high-dose group, and the myocardial expressions of BNP, p-ERK1/2, p-p38 and p-JNK was significantly downregulated after the treatment. Zhenwu Decoctin can reduce plasma IS levels and inhibit ventricular hypertrophy to delay ventricular remodeling in rats with uremic cardiomyopathy.

Factors involved in phenoconversion of CYP3A using 4β-hydroxycholesterol in stable kidney transplant recipients.

Phenoconversion is a phenomenon whereby some genotypic extensive metabolizers transiently exhibit drug metabolizing enzyme activity at similar level as that of poor metabolizers. Renal failure is known to decrease CYP3A activity in humans. Indoxyl sulfate, parathyroid hormone (PTH), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α) have been reported to cause CYP3A downregulation in renal failure. We measured plasma concentrations of the above compounds in stable kidney transplant recipients, and evaluated their relations with phenoconversion of CYP3A evaluated by plasma concentration of 4β-hydroxycholesterol, a biomarker of CYP3A activity. Phenoconversion was defined as a genotypic extensive/intermediate metabolizer exhibiting CYP3A activity below the cutoff value that discriminates extensive/intermediate from poor metabolizers. Sixty-three Japanese kidney transplant recipients who underwent transplantation more than 180 days prior to the study were included. Morning blood samples were collected, and CYP3A5 polymorphism as well as plasma concentrations of 4β-hydroxycholesterol, indoxyl sulfate, intact-PTH, IL-6 and TNF-α were determined. Significantly higher plasma 4β-hydroxycholesterol concentration was observed in recipients with CYP3A5*1 allele (n = 23) compared to those without the allele (n = 40), and the cut-off value was 40.0 ng/mL. Ten recipients with CYP3A5*1 allele exhibited CYP3A activity below 40.0 ng/mL (phenoconversion). Only plasma indoxyl sulfate concentration was significantly higher in recipients with CYP3A phenoconversion compared to those without phenoconversion. These findings suggest that higher plasma indoxyl sulfate concentration may be involved in CYP3A phenoconversion. Dose adjustment of drugs metabolized by CYP3A may be needed in patients with CYP3A5*1 allele and high blood indoxyl sulfate.

The relationship between serum indoxyl sulfate and the renal function after catheter ablation of atrial fibrillation in patients with mild renal dysfunction.

Indoxyl sulfate (IS), a protein-bound uremic toxin, induces renal disorders and atrial fibrillation (AF). It is well known that renal dysfunction is a risk factor for AF and radiofrequency catheter ablation (RFCA) improves the renal function. However, the improvement in the renal function after RFCA in patients with early stage chronic kidney disease (CKD) and the serial changes in the IS level have not been fully elucidated. This study aimed to investigate whether IS affects the improvement in the renal function. A total of 91 consecutive patients with mild kidney dysfunction (CKD stage I-II) who underwent RFCA and maintained sinus rhythm were prospectively enrolled. The plasma IS level and estimated glomerular filtration rate (eGFR) were determined before, 3months, and 1year after RFCA. The patients were divided according to the IS quartiles (Q1-4; < 0.4, 0.4-0.7, 0.7-1.2, and > 1.2μg/ml). There was no significant difference in the eGFR among the IS quartiles. A significantly higher eGFR improvement rate was obtained for IS-Q4 than the other quartiles (p = 0.039). The IS-Q4 IS level significantly decreased at 1year after RFCA (1.8 ± 0.8 to 1.2 ± 0.7μg/ml, p < 0.01). The multivariable logistic model revealed that a high-IS level (IS-Q4) was an independent predictor of an eGFR improvement (OR 3.33; 95% CI 1.16-9.59; p = 0.026). A high-IS level reduction after RFCA improved the renal function in AF patients with mild kidney dysfunction.