Plasma protein binding in uremia: Extraction and characterization of an inhibitor

Plasma protein binding in uremia: Extraction and characterization of an inhibitor. The impairment of binding of drugs and other substances to serum albumin in patients with uremia can be restored to normal or near normal levels by adsorption with charcoal or synthetic polymers at pH 3. We used a nonionic poly-styrene-divinylbenzene copolymer to treat uremic plasma at pH 3. We observed a marked improvement of binding. Subsequent elution of this resin with ethanol produced a substance that, when dried and recombined with normal plasma, caused dose-dependent impairment of phenytoin and tryptophan binding. Restoration of normal binding affinity occurred after retreatment of this abnormalized plasma with resin at pH 3. Plasma and pleural fluid exudate from patients with uremia yielded, after extraction by the above technique, an inhibitor(s) of phenytoin binding in amounts averaging five times that extracted from equal volumes of normal plasma. This inhibitor (Ix) is water soluble, heat stable, and dialyzable across cellophane membranes. Unlike fatty acids, which can also interfere with binding, Ix partitions primarily in the water phase in solvent partition studies but undergoes a sharp transition in the pH 4 to 5 range, suggesting the presence of a carboxyl group. These findings lend further support to the hypothesis that a retained ligand(s) is responsible for impaired plasma binding associated with uremia and suggests a role for organic acids known to accumulate in renal failure.Liaison aux protéines plasmatiques dans l'urémie: Extraction et caractérisation d'un inhibiteur. L'altération de la liaison de drogues et d'autres substances à l'albumine sérique au cours de l'urémie peut être complètement ou presque complètement supprimée par l'adsorption sur du charbon ou des polymères synthétiques à pH 3. Nous avons utilisé un co-polymère non ionique polystyrènedivinylbenzène pour traiter le plasma urémique à pH 3 et observé une amélioration importante de la liaison. L'élution ultérieure de cette résine par l'éthanol produit une substance qui, lorsqu'elle est séchée et recombinée avec du plasma normal, détermine une altération dose dépendante de la liaison de la diphényl-hydantoïne et du tryptophane. La récupération d'une affinité de liaison normale a été obtenue après un nouveau traitement du plasma par la résine à pH 3. Le plasma et le liquide pleural de malades urémiques a donné, après extraction par la technique ci-dessus, un inhibiteur(s) de la liaison de la phénylhydantoïne en quantité cinq fois plus grande que celle extraite devolumes identiques de plasma normal. Cet inhibiteur (Ix) est soluble dans l'eau, thermostable et dialysable à travers des membranes de cellophane. A la différence des acides gras, qui peuvent aussi interférer avec la liaison, Ix passe dans la phase aqueuse au cours des études de partition dans des solvants, mais subit une transition brusque dans la gamme de pH 4 à 5, ce qui suggère la présence d'un groupe carboxyle. Ces constatations apportent des arguments supplémentaires à l'hypothèse selon laquelle un ligand (ou des ligands) retenus au cours de l'urémie est responsable de l'altération de la liaison plasmatique et suggère un rôle des acides organiques dont l'accumulation est connue dans l'insuffisance rénale

Effect of frequent hemodialysis on residual kidney function.

Frequent hemodialysis can alter volume status, blood pressure, and the concentration of osmotically active solutes, each of which might affect residual kidney function (RKF). In the Frequent Hemodialysis Network Daily and Nocturnal Trials, we examined the effects of assignment to six compared with three-times-per-week hemodialysis on follow-up RKF. In both trials, baseline RKF was inversely correlated with number of years since onset of ESRD. In the Nocturnal Trial, 63 participants had non-zero RKF at baseline (mean urine volume 0.76 liter/day, urea clearance 2.3 ml/min, and creatinine clearance 4.7 ml/min). In those assigned to frequent nocturnal dialysis, these indices were all significantly lower at month 4 and were mostly so at month 12 compared with controls. In the frequent dialysis group, urine volume had declined to zero in 52% and 67% of patients at months 4 and 12, respectively, compared with 18% and 36% in controls. In the Daily Trial, 83 patients had non-zero RKF at baseline (mean urine volume 0.43 liter/day, urea clearance 1.2 ml/min, and creatinine clearance 2.7 ml/min). Here, treatment assignment did not significantly influence follow-up levels of the measured indices, although the range in baseline RKF was narrower, potentially limiting power to detect differences. Thus, frequent nocturnal hemodialysis appears to promote a more rapid loss of RKF, the mechanism of which remains to be determined. Whether RKF also declines with frequent daily treatment could not be determined

Comparison of methods to predict equilibrated Kt/V in the HEMO Pilot Study

Comparison of methods to predict equilibrated Kt/V in the HEMO Pilot Study. The ongoing HEMO Study, a National Institutes of Health (NIH) sponsored multicenter trial to test the effects of dialysis dosage and membrane flux on morbidity and mortality, was preceded by a Pilot Study (called the MMHD Pilot Study) designed to test the reliability of methods for quantifying hemodialysis. Dialysis dose was defined by the fractional urea clearance per dialysis determined by the predialysis BUN and the equilibrated postdialysis BUN after urea rebound is completed (eKt/V). In the Pilot Study the blood side standard for eKt/V was calculated from the predialysis, postdialysis, and 30-minute postdialysis BUN. Four techniques of approximating eKt/V that eliminated the requirement for the 30-minute postdialysis sample were also evaluated. The first adjusted the single compartment Kt/V using a linear equation with slope based on the relative rate of solute removal (K/V) to predict eKt/V (rate method). The second and third techniques used equations or mathematical curve fitting algorithms to fit data that included one or more samples drawn during dialysis (intradialysis methods). The fourth technique (dialysate-side) predicted eKt/V from an analysis of the time-dependent profile of dialysate urea nitrogen concentrations (BioStat method; Baxter Healthcare, Inc., Round Lake, IL, USA). The Pilot Study demonstrated the feasibility of conventional and high dose targets of about 1.0 and 1.4 for eKt/V. Based on the blood side standard method, the mean ± SD eKt/V for patients randomized to these targets was 1.14 ± 0.11 and 1.52 ± 0.15 (N = 19 and 16 patients, respectively). Single-pool Kt/Vs were about 0.2 Kt/V units higher. Results were similar when eKt/V was based on dialysate side measurements: 1.10 ± 0.11 and 1.50 ± 0.11. The approximations of eKt/V by the three blood side methods that eliminated the delayed 30-minute post-dialysis sample correlated well with eKt/V from the standard blood side method: r = 0.78 and 0.76 for the single-sample (Smye) and multiple-sample intradialysis methods (N = 295 and 229 sessions, respectively) and 0.85 for the rate method (N = 295). The median absolute difference between eKt/V computed using the standard blood side method and eKt/V from the four other methods ranged from 0.064 to 0.097, with the smallest difference (and hence best accuracy) for the rate method. The results suggest that, in a dialysis patient population selected for ability to achieve an equilibrated Kt/V of about 1.45 in less than a 4.5 hour period, use of the pre and postdialysis samples and a kinetically derived rate equation gives reasonably good prediction of equilibrated Kt/V. Addition of one or more intradialytic samples does not appear to increase accuracy of predicting the equilibrated Kt/V in the majority of patients. A method based on dialysate urea analysis and curve-fitting yields results for equilibrated Kt/V that are similar to those obtained using exclusively blood-based techniques of kinetic modeling

CX3CR1 Polymorphisms are associated with atopy but not asthma in German children

Chemokines and their receptors are involved in many aspects of immunity. Chemokine CX3CL1, acting via its receptor CX3CR1, regulates monocyte migration and macrophage differentiation as well as T cell-dependent inflammation. Two common, nonsynonymous polymorphisms in CX3CR1 have previously been shown to alter the function of the CX3CL1/CX3CR1 pathway and were suggested to modify the risk for asthma. Using matrix-assisted laser desorption/ionization time-of-flight technology, we genotyped polymorphisms Val249Ile and Thr280Met in a cross-sectional population of German children from Munich (n = 1,159) and Dresden ( n = 1,940). For 249Ile an odds ratio of 0.77 (95% confidence interval 0.63-0.96; p = 0.017) and for 280Met an odds ratio of 0.71 ( 95% confidence interval 0.56-0.89; p = 0.004) were found with atopy in Dresden but not in Munich. Neither polymorphism was associated with asthma. Thus, amino acid changes in CX3CR1 may influence the development of atopy but not asthma in German children. Potentially, other factors such as environmental effects may modify the role of CX3CR1 polymorphisms. Copyright (c) 2007 S. Karger AG, Basel

Genetic variants regulating ORMDL3 expression contribute to the risk of childhood asthma

Asthma is caused by a combination of poorly understood genetic and environmental factors(1,2). We have systematically mapped the effects of single nucleotide polymorphisms ( SNPs) on the presence of childhood onset asthma by genome-wide association. We characterized more than 317,000 SNPs in DNA from 994 patients with childhood onset asthma and 1,243 non-asthmatics, using family and case-referent panels. Here we show multiple markers on chromosome 17q21 to be strongly and reproducibly associated with childhood onset asthma in family and case-referent panels with a combined P value of P < 10(-12). In independent replication studies the 17q21 locus showed strong association with diagnosis of childhood asthma in 2,320 subjects from a cohort of German children (P=0.0003) and in 3,301 subjects from the British 1958 Birth Cohort (P=0.0005). We systematically evaluated the relationships between markers of the 17q21 locus and transcript levels of genes in Epstein - Barr virus (EBV)-transformed lymphoblastoid cell lines from children in the asthma family panel used in our association study. The SNPs associated with childhood asthma were consistently and strongly associated (P < 10(-22)) in cis with transcript levels of ORMDL3, a member of a gene family that encodes transmembrane proteins anchored in the endoplasmic reticulum(3). The results indicate that genetic variants regulating ORMDL3 expression are determinants of susceptibility to childhood asthma.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62682/1/nature06014.pd

Genome-Wide Scan on Total Serum IgE Levels Identifies FCER1A as Novel Susceptibility Locus

High levels of serum IgE are considered markers of parasite and helminth exposure. In addition, they are associated with allergic disorders, play a key role in anti-tumoral defence, and are crucial mediators of autoimmune diseases. Total IgE is a strongly heritable trait. In a genome-wide association study (GWAS), we tested 353,569 SNPs for association with serum IgE levels in 1,530 individuals from the population-based KORA S3/F3 study. Replication was performed in four independent population-based study samples (total n = 9,769 individuals). Functional variants in the gene encoding the alpha chain of the high affinity receptor for IgE (FCER1A) on chromosome 1q23 (rs2251746 and rs2427837) were strongly associated with total IgE levels in all cohorts with P values of 1.85×10−20 and 7.08×10−19 in a combined analysis, and in a post-hoc analysis showed additional associations with allergic sensitization (P = 7.78×10−4 and P = 1.95×10−3). The “top” SNP significantly influenced the cell surface expression of FCER1A on basophils, and genome-wide expression profiles indicated an interesting novel regulatory mechanism of FCER1A expression via GATA-2. Polymorphisms within the RAD50 gene on chromosome 5q31 were consistently associated with IgE levels (P values 6.28×10−7−4.46×10−8) and increased the risk for atopic eczema and asthma. Furthermore, STAT6 was confirmed as susceptibility locus modulating IgE levels. In this first GWAS on total IgE FCER1A was identified and replicated as new susceptibility locus at which common genetic variation influences serum IgE levels. In addition, variants within the RAD50 gene might represent additional factors within cytokine gene cluster on chromosome 5q31, emphasizing the need for further investigations in this intriguing region. Our data furthermore confirm association of STAT6 variation with serum IgE levels

Mechanisms of hypoalbuminemia in hemodialysis patients

Mechanisms of hypoalbuminemia in hemodialysis patients. Hypoalbuminemia is the most powerful predictor of mortality in end-stage renal disease. Since protein-calorie malnutrition can decrease albumin synthesis it is assumed that hypoalbuminemia results principally from malnutrition in these patients, but albumin synthesis may also be decreased as part of the acute-phase response, and hypoalbuminemia can also result from redistribution of albumin pools or from albumin losses. We measured albumin synthesis, fractional catabolic rate, and distribution from the turnover of [125I] human albumin in six hemodialysis patients with plasma albumin less than 35 mg/ml and in six patients with plasma albumin greater than 40 mg/ml. Patients with liver disease, HIV, or other infection were excluded. Both groups were maintained with high-flux polysulfone dialyzers for more than three months. Kt/Vurea and PCR were measured during each dialysis (N = 12 to 18/patient). A four-day calorie and protein intake was determined by dietary history and long-term nutritional status was determined anthropometrically. Measured variables included serum urea, creatinine, transferrin, and the positive acute-phase proteins α2-macroglobulin, C-reactive protein, ferritin, and IGF-1. Albumin synthesis was significantly reduced in the low albumin group. There were no differences in dietary intake, body composition, PCR, BUN, creatinine, or Kt/Vurea. Plasma albumin concentration correlated negatively with ferritin, C-reactive protein and α2-macroglobulin. Albumin synthesis rate correlated negatively with both α2-macroglobulin and Kt/Vurea. Both plasma albumin concentration and synthesis rate correlated positively with IGF-1, and both were independent of PCR and all other nutrition-related variables. Hypoalbuminemia was due to decreased albumin synthesis. The data suggest that albumin concentration and synthesis were primarily determined by non-nutritional factors in this well-dialyzed population, and that both were reduced partially as part of the acute-phase response