Kontinuierliche veno-venöse Hämodialyse mit regionaler Citratantikoagulation bei kritisch kranken Patienten mit Hyperlaktatämie

Eine akute Nierenschädigung zeigt sich bei bis zu 60% der kritisch kranken Patienten auf Intensivstationen. Davon entwickeln 5-6% ein akutes schweres dialysepflichtiges Nierenversagen. Das Mittel der Wahl ist bei kritisch kranken Patienten das kontinuierliche Nierenersatzverfahren. Wenn keine Kontraindikation besteht, sollte die regionale Antikoagulation mit Citrat (RCA-CRRT) der systemischen Antikoagulation mit Heparin vorgezogen werden. Als Kontraindikationen für die Citratantikoagulation gelten Leberversagen und Schock mit muskulärer Hypoperfusion, da die Gefahr einer Citratakkumulation besteht. Die Citratakkumulation ist ein Zeichen für sehr schwere metabolische Störungen, insbesondere bei Multiorganversagen. Als gängiger Parameter für Schock mit muskulärer Hypoperfusion gilt das Laktat. Hintergrund der Studie ist die Frage, ob eine Hyperlaktatämie zu Beginn der Dialyse eine Citratakkumulation vorhersagen kann und ob der Laktatverlauf einen Einfluss auf das Auftreten einer Citratakkumulation hat. Es wurde eine retrospektive Studie durchgeführt, die alle Patienten einschließt, die innerhalb von 3 Jahren auf sechs Intensivstationen der Charité – Universitätsmedizin Berlin, Campus Mitte, mit RCA-CRRT behandelt wurden. Es wurden 1062 Verfahren in die Studie eingeschlossen. Sie wurden je nachdem ob eine Citratakkumulation auftrat oder nicht auftrat und ferner nach initialem Laktatwert aufgeteilt (normwertige Laktatkonzentration: < 19,8 mg/dl; moderat erhöhte Laktatkonzentration: ≥ 19,8 mg/dl und < 36,04 mg/dl; deutlich erhöhte Laktatkonzentration: ≥ 36,04 mg/dl). Bei insgesamt 2,26% der Verfahren ist eine Citratakkumulation innerhalb von 48 Stunden aufgetreten. Bei Verfahren mit normwertiger Blutlaktatkonzentration zu Beginn der RCA-CRRT liegt die Inzidenz bei 0,77%, bei moderat erhöhter Laktatkonzentration bei 2,69% und bei ausgeprägter Hyperlaktatämie bei 6,33%. Bei Patienten mit initial schwerer Hyperlaktatämie ohne Akkumulation ist ein Abfall der Laktatkonzentration über 24 Stunden zu verzeichnen, bei Patienten mit Akkumulation bleibt die Laktatkonzentration auf einem hohen Niveau. Die ROC-Kurven-Analyse ergab, dass 12 Stunden nach Beginn der Dialyse ein Laktatwert < 35,5 mg/dl einen negativen Prädiktionswert von 99,6% hat. Die Laktat-Clearance nach 12 Stunden sollte über 24,3% liegen, um eine Laktat-Akkumulation zu 99,98% auszuschließen. Die Ergebnisse lassen darauf schließen, dass eine initiale Hyperlaktatämie ein schwacher Prädiktor für eine Citratakkumulation ist und deshalb keine Kontraindikation per se für eine RCA-CRRT ist. Entscheidend ist der Laktatverlauf während der Behandlung. Ist die nach 12 Stunden gemessene Laktatkonzentration kleiner als 35,5 mg/dl und 25% niedriger als der initiale Wert, kann eine Citratakkumulation innerhalb der weiteren 36 Stunden zu 99% ausgeschlossen werden. Diese Ergebnisse können dazu führen, dass auch Patienten mit initialer Hyperlaktatämie mittels RCA-CRRT behandelt werden.An acute kidney injury occurs in 60% of critically ill patients in ICU. 5-6% of them develop a severe renal insufficiency which requires dialysis. First therapeutic choice is a continuous renal replacement therapy (CRRT). Regional citrate anticoagulation (RCA) should rather be used than systemic anticoagulation with heparin. According to KDGIO guidelines, major contraindications for RCA are severely impaired liver function or shock with muscle hypoperfusion, because of risk of citrate accumulation. In case of metabolic disorder patients develop citrate accumulation especially when having multi-organ failure. Lactate is one of the current parameters of muscle hypoperfusion or shock. A retrospective follow-up analysis was designed to answer the question whether hyperlactatemia or lactate kinetics can predict citrate accumulation. 1062 patients of 6 ICUs at Charité - Universitätsmedizin Berlin were included in the study. They were being treated with RCA-CRRT during a 3-year period. Patients were subdivided into 3 groups depending on their lactate level at the beginning of RCA-CRRT. The frequency of citrate accumulation during the first 48 hours of therapy was 2.26%. The incidence of citrate accumulation in patients with normal lactate concentration ( 36.04 mg/dl) was 0.77%, 2.69% and 6.33% respectively. Lactate concentration decreases in patients with hyperlactatemia who do not accumulate citrate. In those who accumulate citrate, lactate concentration remains on a high level. 12 hours after the beginning of RCA-CRRT, Receiver Operating Characteristics analysis showed that a lactate level < 35.5 mg/dl marks strong negative prediction for citrate accumulation (99.6%). If lactate-clearance 12 hours after the beginning of RCA-CRRT is higher than 24.3%, negative prediction for citrate accumulation is 99.98%. The results indicate that initial hyperlactatemia in patients undergoing RCA-CRRT is a weak predictor for citrate accumulation. Initial hyperlactatemia should not be a contraindication for RCA-CRRT per se, instead lactate kinetics is essential for the incidence of citrate accumulation. Our results can help treat more patients with RCA-CRRT since having initial hyperlactatemia means being excluded from this therapy by the current KDIGO-guidelines

Oxygen-sensitive 3He-MRI in bronchiolitis obliterans after lung transplantation

Oxygen-sensitive 3He-MRI was studied for the detection of differences in intrapulmonary oxygen partial pressure (pO2) between patients with normal lung transplants and those with bronchiolitis obliterans syndrome (BOS). Using software developed in-house, oxygen-sensitive 3He-MRI datasets from patients with normal lung grafts (n = 8) and with BOS (n = 6) were evaluated quantitatively. Datasets were acqiured on a 1.5-T system using a spoiled gradient echo pulse sequence. Underlying diseases were pulmonary emphysema (n = 10 datasets) and fibrosis (n = 4). BOS status was verified by pulmonary function tests. Additionally, 3He-MRI was assessed blindedly for ventilation defects. Median intrapulmonary pO2 in patients with normal lung grafts was 146 mbar compared with 108 mbar in patients with BOS. Homogeneity of pO2 distribution was greater in normal grafts (standard deviation pO2 34 versus 43 mbar). Median oxygen decrease rate during breath hold was higher in unaffected patients (−1.75 mbar/s versus −0.38 mbar/s). Normal grafts showed fewer ventilation defects (5% versus 28%, medians). Oxygen-sensitive 3He-MRI appears capable of demonstrating differences of intrapulmonary pO2 between normal lung grafts and grafts affected by BOS. Oxygen-sensitive 3He-MRI may add helpful regional information to other diagnostic techniques for the assessment and follow-up of lung transplant recipients

Genetic Determinants of Circulating Sphingolipid Concentrations in European Populations

Sphingolipids have essential roles as structural components of cell membranes and in cell signalling, and disruption of their metabolism causes several diseases, with diverse neurological, psychiatric, and metabolic consequences. Increasingly, variants within a few of the genes that encode enzymes involved in sphingolipid metabolism are being associated with complex disease phenotypes. Direct experimental evidence supports a role of specific sphingolipid species in several common complex chronic disease processes including atherosclerotic plaque formation, myocardial infarction (MI), cardiomyopathy, pancreatic beta-cell failure, insulin resistance, and type 2 diabetes mellitus. Therefore, sphingolipids represent novel and important intermediate phenotypes for genetic analysis, yet little is known about the major genetic variants that influence their circulating levels in the general population. We performed a genome-wide association study (GWAS) between 318,237 single-nucleotide polymorphisms (SNPs) and levels of circulating sphingomyelin (SM), dihydrosphingomyelin (Dih-SM), ceramide (Cer), and glucosylceramide (GluCer) single lipid species (33 traits); and 43 matched metabolite ratios measured in 4,400 subjects from five diverse European populations. Associated variants (32) in five genomic regions were identified with genome-wide significant corrected p-values ranging down to 9.08 x 10(-66). The strongest associations were observed in or near 7 genes functionally involved in ceramide biosynthesis and trafficking: SPTLC3, LASS4, SGPP1, ATP10D, and FADS1-3. Variants in 3 loci (ATP10D, FADS3, and SPTLC3) associate with MI in a series of three German MI studies. An additional 70 variants across 23 candidate genes involved in sphingolipid-metabolizing pathways also demonstrate association (p = 10(-4) or less). Circulating concentrations of several key components in sphingolipid metabolism are thus under strong genetic control, and variants in these loci can be tested for a role in the development of common cardiovascular, metabolic, neurological, and psychiatric diseases

PH wave-front propagation in the urea-urease reaction

The urease-catalyzed hydrolysis of urea displays feedback that results in a switch from acid (pH ∼3) to base (pH ∼9) after a controllable period of time (from 10 to \u3e5000 s). Here we show that the spatially distributed reaction can support pH wave fronts propagating with a speed of the order of 0.1-1 mm min-1. The experimental results were reproduced qualitatively in reaction-diffusion simulations including a Michaelis-Menten expression for the urease reaction with a bell-shaped rate-pH dependence. However, this model fails to predict that at lower enzyme concentrations, the unstirred reaction does not always support fronts when the well-stirred reaction still rapidly switches to high pH. © 2012 by the Biophysical Society

Establishment of Histone Modifications after Chromatin Assembly

Every cell has to duplicate its entire genome during S-phase of the cell cycle. After replication, the newly synthesized DNA is rapidly assembled into chromatin. The newly assembled chromatin ‘matures’ and adopts a variety of different conformations. This differential packaging of DNA plays an important role for the maintenance of gene expression patterns and has to be reliably copied in each cell division. Posttranslational histone modifications are prime candidates for the regulation of the chromatin structure. In order to understand the maintenance of chromatin structures, it is crucial to understand the replication of histone modification patterns. To study the kinetics of histone modifications in vivo, we have pulse-labeled synchronized cells with an isotopically labeled arginine (15N4) that is 4 Da heavier than the naturally occurring 14N4 isoform. As most of the histone synthesis is coupled with replication, the cells were arrested at the G1/S boundary, released into S-phase and simultaneously incubated in the medium containing heavy arginine, thus labeling all newly synthesized proteins. This method allows a comparison of modification patterns on parental versus newly deposited histones. Experiments using various pulse/chase times show that particular modifications have considerably different kinetics until they have acquired a modification pattern indistinguishable from the parental histones

Loss of ASAP1 in mice impairs adipogenic and osteogenic differentiation of mesenchymal progenitor cells through dysregulation of FAK/Src and AKT signaling

ASAP1 is a multi-domain adaptor protein that regulates cytoskeletal dynamics, receptor recycling and intracellular vesicle trafficking. Its expression is associated with poor prognosis for a variety of cancers, and promotes cell migration, invasion and metastasis. Little is known about its physiological role. In this study, we used mice with a gene-trap inactivated ASAP1 locus to study the functional role of ASAP1 in vivo, and found defects in tissues derived from mesenchymal progenitor cells. Loss of ASAP1 led to growth retardation and delayed ossification typified by enlarged hypertrophic zones in growth plates and disorganized chondro-osseous junctions. Furthermore, loss of ASAP1 led to delayed adipocyte development and reduced fat depot formation. Consistently, deletion of ASAP1 resulted in accelerated chondrogenic differentiation of mesenchymal cells in vitro, but suppressed osteo- and adipogenic differentiation. Mechanistically, we found that FAK/Src and PI3K/AKT signaling is compromised in Asap1GT/GT MEFs, leading to impaired adipogenic differentiation. Dysregulated FAK/Src and PI3K/AKT signaling is also associated with attenuated osteogenic differentiation. Together these observations suggest that ASAP1 plays a decisive role during the differentiation of mesenchymal progenitor cells

Genetic risk and a primary role for cell-mediated immune mechanisms in multiple sclerosis.

Multiple sclerosis is a common disease of the central nervous system in which the interplay between inflammatory and neurodegenerative processes typically results in intermittent neurological disturbance followed by progressive accumulation of disability. Epidemiological studies have shown that genetic factors are primarily responsible for the substantially increased frequency of the disease seen in the relatives of affected individuals, and systematic attempts to identify linkage in multiplex families have confirmed that variation within the major histocompatibility complex (MHC) exerts the greatest individual effect on risk. Modestly powered genome-wide association studies (GWAS) have enabled more than 20 additional risk loci to be identified and have shown that multiple variants exerting modest individual effects have a key role in disease susceptibility. Most of the genetic architecture underlying susceptibility to the disease remains to be defined and is anticipated to require the analysis of sample sizes that are beyond the numbers currently available to individual research groups. In a collaborative GWAS involving 9,772 cases of European descent collected by 23 research groups working in 15 different countries, we have replicated almost all of the previously suggested associations and identified at least a further 29 novel susceptibility loci. Within the MHC we have refined the identity of the HLA-DRB1 risk alleles and confirmed that variation in the HLA-A gene underlies the independent protective effect attributable to the class I region. Immunologically relevant genes are significantly overrepresented among those mapping close to the identified loci and particularly implicate T-helper-cell differentiation in the pathogenesis of multiple sclerosis