Identifikation von Biomarkern bei renalen und vaskulären Erkrankungen

Der akute Nierenschaden (AKI, acute kidney injury) ist eine plötzlich auftretende Verschlechterung der glomerulären Filtrationsrate (GFR). Viele unterschiedliche Ursachen sind bekannt. Klassischerweise werden sie in prärenal, renal und postrenal eingeteilt. Seit vielen Jahren ist die Biomarker Forschung beim AKI von großem Interesse. Themen mit besonders hoher Beachtung sind die frühzeitige Diagnosestellung des AKI, die Identifkation von Ursachen des Nierenschadens und die Prognoseabschätzung. In meinen Arbeiten haben wir uns mit der Identifikation solcher Biomarker beschäftigt und dazu unter anderem difference gel electrophoresis (DIGE) als analytische Methode eingesetzt. Wir haben mit DIGE differentiell regulierte Proteine nach herzchirurgischen Operationen im Urin identifiziert, welche auf die Ursache eines Nierenschadens hinweisen. Ausserdem haben wir Marker für die Prognose des AKIs gesucht und insulin-like growth factor binding protein 7 (IGFBP-7) als neuen Biomarker für die renale Prognose identifiziert. In einer weiteren Studie zeigte sich die Kynurenin-Säure als potentieller Marker für die renale Prognose beim AKI. In einer klinischen Studie haben wir die GFR vor und nach perkutanem Aortenklappenersatz beobachtet. Dabei konnten wir feststellen, dass sich bei mehr als 50 % der Patienten die GFR nach Behebung der Aortenstenose verbesserte. Wir konnten mehrere Risikofaktoren für das Auftreten eines AKIs bei diesen Patienten identifizieren, wie den transapikale Zugang, das Auftreten einer Inflammation mit erhöhtem CRP oder erniedrigter Thrombozytenzahl sowie die Transfusion von Erythrozyten. Bei Patienten mit Aortenaneurysma aufgrund eines Marfan Syndroms haben wir mit DIGE eine erhöhte Fragmentierung von Filamin-A festgestellt. Ursache dieser Fragmentierung war eine erhöhte Aktivität der Protease Calpain-2. Zusammengefasst haben wir durch unterschiedliche Methoden Biomarker bei renalen und vaskulären Erkrankungen identifiziert

Molecular Diagnosis of Analbuminemia: A New Case Caused by a Nonsense Mutation in the Albumin Gene

Analbuminemia is a rare autosomal recessive disorder manifested by the absence, or severe reduction, of circulating serum albumin (ALB). We report here a new case diagnosed in a 45 years old man of Southwestern Asian origin, living in Switzerland, on the basis of his low ALB concentration (0.9 g/L) in the absence of renal or gastrointestinal protein loss, or liver dysfunction. The clinical diagnosis was confirmed by a mutational analysis of the albumin (ALB) gene, carried out by single-strand conformational polymorphism (SSCP), heteroduplex analysis (HA), and DNA sequencing. This screening of the ALB gene revealed that the proband is homozygous for two mutations: the insertion of a T in a stretch of eight Ts spanning positions c.1289 + 23–c.1289 + 30 of intron 10 and a c.802 G > T transversion in exon 7. Whereas the presence of an additional T in the poly-T tract has no direct deleterious effect, the latter nonsense mutation changes the codon GAA for Glu244 to the stop codon TAA, resulting in a premature termination of the polypeptide chain. The putative protein product would have a length of only 243 amino acid residues instead of the normal 585 found in the mature serum albumin, but no evidence for the presence in serum of such a truncated polypeptide chain could be obtained by two dimensional electrophoresis and western blotting analysis

Qualität in der Shuntchirurgie

Um die Qualität von Dialysezugängen zu verbessern, müssen Daten von Operationen und deren Langzeitergebnisse systematisch und vollständig dokumentiert werden. In der Schweiz verfügt das Swissvasc-Register 2.0 [1] seit 2019 über einen speziellen Datensatz zur Shuntchirurgie. Nun wurden erstmals diese Daten für ein Tertiärspital ausgewertet

Use of the pentasaccharide fondaparinux as an anticoagulant during haemodialysis

No data about the use of the pentasaccharide fondaparinux, a highly selective indirect inhibitor of factor Xa, in patients treated with haemodialysis are available. Therefore, we investigated the pharmacokinetics and -dynamics of fondaparinux in 12 patients during haemodialysis. The anti-Xa activity (expressed as fondaparinux equivalent) was monitored, a semiquantitative clotting scale (SQCS) ranging from 0 (no visible traces of coagula) to 3 (complete clotting of the dialysis circuit) was applied, and the digital compression time necessary to achieve haemostasis at the puncture site was determined. After an initial period, when the regular heparin dose was replaced once weekly by fondaparinux, 0.05 mg/kg, the pentasaccharide was administered for nine consecutive haemodialysis sessions. Peak anti-Xa activity increased from 0.61 +/- 0.14 microg/l after the first dose to 0.89 +/- 0.24 microg/l after dose 9 (P < 0.001), whereas predialysis anti-Xa activity steadily rose to 0.32 +/- 0.09 microg/l (P < 0.001). A sufficient but slightly less effective anticoagulation with a mean SQCS of 1.19 +/- 0.71 (n = 121) was obtained by fondaparinux as compared with 0.65 +/- 0.58 (n = 60, P < 0.005) by 4,825 +/- 1,703 U of unfractionated heparin. Mean digital compression time rose slightly during fondaparinux from 23.7 +/- 7.4 minutes to 24.8 +/- 7.5 minutes (P < 0.05) and, more important, six of the 12 patients reported minor bleeding problems during the interdialytic interval. Thus, fondaparinux can be used to prevent circuit clotting during haemodialysis; however, accumulation results in an interdialytic increase of anti-Xa activity. Therefore, fondaparinux should be reserved for patients requiring systemic anticoagulation on the days off dialysis

Increased urinary excretion of kynurenic acid is associated with non-recovery from acute kidney injury in critically ill patients.

BACKGROUND Acute kidney injury (AKI) is often observed in critically ill patients and is associated with high morbidity and mortality. Non-recovery from AKI has a negative impact on the prognosis of affected patients and early risk stratification seems key to improve clinical outcomes. We analyzed metabolites of a conserved key inflammatory pathway (i.e. tryptophan degradation pathway) in serial urine samples of patients with AKI. METHODS One hundred twelve ICU patients with AKI were included in a prospective observational analysis. After exclusion criteria, 92 patients were eligible for analysis. Serial urine samples were collected and tryptophan levels including key tryptophan metabolites were measured using tandem mass spectrometry. RESULTS Sixty-seven patients recovered in the first 7 days of AKI (early recovery, ER) whereas n = 25 had late-/non-recovery (LNR). Urinary concentrations of tryptophan, kynurenine, 3-OH anthranillic acid, serotonine, and kynurenine/tryptophan were significantly lower in LNR patients. In contrast, creatinine normalized excretion of kynurenic acid (KynA) was substantially increased in LNR patients (7.59 ± 6.81 vs. 3.19 ± 3.44 (ER) μmol/mmol, p <  0.005). High urinary KynA excretion was associated with higher RIFLE class, longer AKI duration, increased need for RRT, and 30-day mortality. Logistic regression revealed KynA as the single most important predictor of renal recovery on days 1 and 2 of AKI. CONCLUSIONS Increased urinary levels of kynurenic acid, a key inflammatory metabolite of the tryprophan degradation pathway, are associated with adverse renal and clinical outcomes in critically ill patients with AKI. Urinary KynA may serve as an early risk stratificator in respective patients with AKI

Nocturnal dipping behaviour in normotensive white children and young adults in response to changes in salt intake

Nocturnal nondipping is a feature of salt-sensitive, hypertensive individuals. In normotensive children and adults, the impact of salt intake on circadian blood pressure (BP) rhythm is not well defined

Urinary proteomics before and after extracorporeal circulation in patients with and without acute kidney injury

OBJECTIVE: Acute kidney injury is a well-known complication with high morbidity and mortality after cardiopulmonary bypass. Cardiopulmonary bypass-associated acute kidney injury is still poorly understood. METHODS: Thirty-six patients undergoing elective cardiopulmonary bypass were enrolled. Spot urine samples before and after cardiopulmonary bypass were collected. Acute kidney injury was defined according to the RIFLE classification. To identify differentially regulated proteins after cardiopulmonary bypass, we first analyzed the urinary proteome before and after cardiopulmonary bypass. To identify differentially regulated proteins in acute kidney injury, we next compared the urinary proteome obtained on the first postoperative day between patients with and without acute kidney injury. Difference fluorescence gel electrophoresis was used to compare protein profiles and mass spectrometry to identify individual proteins. RESULTS: After cardiopulmonary bypass, inflammation-associated (zinc-alpha-2-glycoprotein, leucine-rich alpha-2-glycoprotein, mannan-binding lectin serine protease 2, basement membrane-specific heparan sulfate proteoglycan, and immunoglobulin kappa) or tubular dysfunction-associated (retinol-binding protein, adrenomedullin-binding protein, and uromodulin) proteins were differentially regulated. Acute kidney injury developed in 6 of 36 patients. A modified urinary albumin was increased, and zinc-alpha-2-glycoprotein and a fragment of adrenomedullin-binding protein were decreased in patients with acute kidney injury. Decreased excretion of zinc-alpha-2-glycoprotein in patients with acute kidney injury was confirmed by Western blot and enzyme-linked immunosorbent assay in an independent cohort of 22 patients with and 46 patients without acute kidney injury. CONCLUSION: Cardiopulmonary bypass leads to increased urinary excretion of inflammatory proteins and markers of tubular injury. Zinc-alpha-2-glycoprotein is a potentially useful predictive marker for acute kidney injury after cardiopulmonary bypass surgery

Identification of IGFBP-7 by urinary proteomics as a novel prognostic marker in early acute kidney injury

Early diagnosis of acute kidney injury (AKI) and accurate prognostic stratification is a prerequisite for optimal medical management. To identify novel prognostic markers of AKI, urine was collected on the first day of AKI in critically ill patients. Twelve patients with early recovery and 12 matching patients with late/non-recovery were selected and their proteome analyzed by gel electrophoresis and mass spectrometry. We identified eight prognostic candidates including α-1 microglobulin, α-1 antitrypsin, apolipoprotein D, calreticulin, cathepsin D, CD59, insulin-like growth factor-binding protein 7 (IGFBP-7), and neutrophil gelatinase-associated lipocalin (NGAL). Subsequent quantification by ELISA showed that IGFBP-7 was the most potent predictor of renal recovery. IGFBP-7 and NGAL were then chosen for further analyses in an independent verification group of 28 patients with and 12 control patients without AKI. IGFBP-7 and NGAL discriminated between early and late/non-recovery patients and patients with and without AKI. Significant upregulation of the urinary markers predicted mortality (IGFBP-7: AUC 0.68; NGAL: AUC 0.81), recovery (IGFBP-7: AUC 0.74; NGAL: AUC 0.70), and severity of AKI (IGFBP-7: AUC 0.77; NGAL: AUC 0.69), and were associated with the duration of AKI. IGFBP-7 was a more accurate predictor of renal outcome than NGAL. Thus, IGFBP-7 is a novel prognostic urinary marker that warrants further investigation.Kidney International advance online publication, 25 September 2013; doi:10.1038/ki.2013.363