Cardiovascular effects of systemic nitric oxide synthase inhibition with asymmetrical dimethylarginine in humans

BACKGROUND

Increased blood concentrations of the endogenous nitric oxide synthase (NOS) inhibitor asymmetrical dimethylarginine (ADMA) have been linked to excess cardiovascular morbidity and mortality and to progression of renal disease. We evaluated systemic cardiovascular effects of ADMA infusion in healthy subjects using invasive techniques, ie, right heart catheter and inulin/para-aminohippurate clearance.

METHODS AND RESULTS

Plasma ADMA concentrations encountered in patients with cardiovascular diseases, ie, between 2 and 10 micromol/L, caused a significant (P<0.05) decrease in concentrations of plasma cGMP, the main second messenger of NO. In addition, cardiac output was significantly lower (5.3+/-0.4 versus 5.8+/-0.6 L/min; P<0.05 versus baseline), and systemic vascular resistance was significantly higher (1403+/-123 versus 1221+/-100 dyn x s x cm(-5); P<0.05 versus baseline). The infusion of 0.25 mg ADMA x kg(-1) x min(-1) or 3 microg N(G)-nitro-L-arginine methyl ester x kg(-1) x min(-1), a potent synthetic NOS inhibitor with long action, resulted in a comparable decrease in effective renal plasma flow (from 670+/-40 to 596+/-29 mL x min(-1); P<0.05) and an increase in renovascular resistance (from 79+/-5 to 90+/-7 mm Hg x mL(-1) x min(-1); P<0.05). Moreover, administration of ADMA caused significant sodium retention and blood pressure increase (both P<0.05). The observed effects of ADMA in the systemic circulation were sustained corresponding to a mean plasma half-life of 23.5+/-6.8 minutes, calculated from plasma ADMA decay curves in healthy subjects.

CONCLUSIONS

Systemic ADMA infusion is responsible for a short-term, modest decrease in cardiac output with comparable decrease in effective renal plasma flow while increasing systemic vascular resistance and blood pressure in a dose-related manner.

Marked increase of asymmetric dimethylarginine in patients with incipient primary chronic renal disease

In patients with uremia, increased blood concentrations of the endogenous nitric oxide synthase inhibitor asymmetric dimethylarginine (ADMA) have been linked to the severity of atherosclerosis and to excess cardiovascular mortality. The ADMA levels and several traditional cardiovascular risk factors were assessed in 44 untreated nonsmoking patients with confirmed primary chronic renal disease at different stages of renal disease. True GFR was assessed by means of the inulin-clearance technique. For comparison, nonsmoking subjects matched with respect to age, gender, and body-mass index were examined. Mean plasma ADMA concentration was markedly higher (P < 0.0001) in all patients combined (4.2 +/- 0.9 micromol/L) than in control subjects (n = 16; age 45 +/- 10 yr; serum creatinine 1.0 +/- 0.1 mg/dl; ADMA 1.4 +/- 0.7 micromol/L). However, mean ADMA levels were similar in patients with normal renal function (n = 16; age 41 +/- 9 yr; serum creatinine 1.1 +/- 0.1 mg/dl; GFR 120 +/- 14 ml x min(-1) x 1.73 m2; ADMA 4.0 +/- 0.7 micromol/L), in patients with moderate renal failure (n = 15; 47 +/- 7 yr; 1.8 +/- 0.3 mg/dl; 65 +/- 10 ml x min(-1) x 1.73 m2; 3.8 +/- 0.6 micromol/L) and in patients with advanced renal failure (n = 13; 46 +/- 9 yr; 4.2 +/- 0.9 mg/dl; 25 +/- 4 ml x min(-1) x 1.73 m2; 4.7 +/- 1.2 micromol/L). Furthermore, ADMA levels were increased to the same extent in normotensive (n = 17; 4.0 +/- 0.8 micromol/L) and in hypertensive (n = 27; 4.2 +/- 0.9 micromol/L) patients. In contrast to ADMA, mean total plasma homocysteine concentration were similar in control subjects (10.6 +/- 2.9 micromol/L) and in patients with normal GFR (11.0 +/- 2.9 micromol/L), but were significantly higher in patients with moderate renal failure (17.7 +/- 4.1 micromol/L) and particularly in patients with advanced renal failure (28.2 +/- 10.6 micromol/L). Finally, mean total serum cholesterol concentrations were comparable in the control group and in the three groups of patients with renal disease. In contrast to several traditional cardiovascular risk factors, markedly increased blood concentrations of ADMA, a putative biochemical marker of atherosclerosis, are present even in nonsmoking patients without diabetes with incipient primary renal disease. Thus, the early increase of ADMA levels may be of relevance for the excess cardiovascular morbidity and mortality due to arterio- and atherosclerotic complications in patients with renal disease.

Symmetric dimethylarginine (SDMA) as endogenous marker of renal function--a meta-analysis

BACKGROUND

Dosing of most drugs must be adapted in renal insufficiency, making accurate assessment of renal function essential in clinical medicine. Furthermore, even modest impairment of renal function has been recognized as a cardiovascular risk factor. The purpose of this analysis was to identify the role of symmetric dimethylarginine (SDMA), the structural isomer of the cardiovascular risk marker asymmetric dimethylarginine, as an endogenous marker of renal function.

METHODS

Comprehensive searches of Medline and the Cochrane Library from 1970 to February 2006 were performed to identify studies that evaluated the correlation between SDMA and renal function. The search was augmented by scanning references of identified articles and reviews. The correlation coefficients (R) were recorded from each study for the values of 1/SDMA and clearance estimates and for SDMA and creatinine levels. The summary correlation coefficients with 95% confidence intervals (CIs) were pooled using the random-effects method.

RESULTS

In 18 studies involving 2136 patients systemic SDMA concentrations correlated highly with inulin clearance [R = 0.85 (CI 0.76-0.91, P < 0.0001)], as well as with various clearance estimates combined [R = 0.77 (CI 0.65-0.85, P < 0.0001)] and serum creatinine [R = 0.75 (CI 0.46-089, P < 0.0001)].

CONCLUSIONS

SDMA exhibits some properties of a reliable marker of renal function. Future studies have to clarify whether SDMA is indeed suited to improve diagnosis and eventually optimize care of patients.

Asymmetric dimethylarginine and progression of chronic kidney disease: the mild to moderate kidney disease study

Reduced bioavailability of nitric oxide (NO) is thought to play an important role in progression of renal damage. The hypothesis that the endogenous NO synthase inhibitor asymmetric dimethylarginine (ADMA) is involved in progression of kidney disease was tested. Plasma ADMA concentrations and other putative progression factors were assessed in 227 relatively young patients (45.7 +/- 12.6 yr) with nondiabetic kidney diseases and mild to moderate renal failure. Progression assessed as doubling of serum creatinine and/or renal replacement therapy was evaluated prospectively. Baseline plasma ADMA concentrations in renal patients correlated significantly with serum creatinine (r = 0.595), GFR (r = -0.591), age (r = 0.281), and proteinuria (r = 0.184; all P < 0.01). Patients who reached an end point during follow-up were significantly older (P < 0.05) and had significantly higher creatinine, ADMA, and parathyroid hormone blood concentrations and protein excretion rates at baseline, whereas GFR and hemoglobin were significantly lower (all P < 0.01). Cox regression analysis revealed baseline serum creatinine (odds ratio 2.00; 95% confidence interval [CI] 1.61 to 2.49; P < 0.001) and ADMA (odds ratio 1.47; 95% CI 1.12 to 1.93 for an increment of 0.1 mumol/L; P < 0.006) as independent predictors of disease progression. In patients with ADMA levels above median, progression was significantly faster (P < 0.0001), and their mean follow-up time to a progression end point was 52.8 mo (95% CI 46.9 to 58.8) as compared with 71.6 mo (95% CI 66.2 to 76.9) in patients with ADMA levels below the median. The endogenous NO synthase inhibitor ADMA is significantly associated with progression of nondiabetic kidney diseases. Lowering plasma ADMA concentrations may be a novel therapeutic target to prevent progressive renal impairment.

Asymmetric dimethylarginine plasma concentrations differ in patients with end-stage renal disease: relationship to treatment method and atherosclerotic disease

Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of endothelial nitric oxide (NO) synthase. Its concentration is elevated in patients with end-stage renal disease (ESRD), in part because it is excreted via the kidneys. In this study, the plasma concentrations of ADMA, symmetric dimethylarginine, and L-arginine were determined in relation to plasma nitrate levels (as an index of NO formation) for a group of 80 patients with ESRD. The effects of two treatment methods, i.e., hemodialysis (HD) and peritoneal dialysis (PD), and the role of the presence of atherosclerotic disease were evaluated. Forty-three patients receiving HD and 37 patients receiving PD were compared with healthy control subjects. Plasma L-arginine and dimethylarginine levels were determined by HPLC, using precolumn derivatization with o-phthaldialdehyde. Plasma nitrate levels were determined by gas chromatography-mass spectrometry. Predialysis ADMA concentrations in HD-treated patients were approximately sixfold higher than those in the control group (6.0+/-0.5 versus 1.0+/-0.1 micromol/L; P < 0.05). Plasma nitrate concentrations were significantly lower in HD-treated patients, which suggests that ADMA may inhibit NO synthase. In contrast, plasma ADMA levels and nitrate concentrations in PD-treated patients were similar to those in control subjects. Plasma L-arginine concentrations were not significantly decreased in patients with ESRD. ADMA concentrations were significantly decreased 5 h after HD, compared with baseline values. ADMA levels were significantly higher in HD-treated patients with manifest atherosclerotic disease than in HD-treated patients without atherosclerotic disease (7.31+/-0.70 versus 3.95+/-0.52 micromol/L; P < 0.05). This study confirms that ADMA is accumulated in ESRD. PD-treated patients exhibit significantly lower ADMA levels than do HD-treated patients. Accumulation of ADMA may be a risk factor for the development of endothelial dysfunction and cardiovascular disease in patients with ESRD.

Renal Insulin Resistance Syndrome, Adiponectin and Cardiovascular Events in Patients with Kidney Disease: The Mild and Moderate Kidney Disease Study

The relationship among insulin resistance, adiponectin, and cardiovascular (CV) morbidity in patients with mild and moderate kidney disease was investigated. Insulin sensitivity (Homeostasis Model Assessment of Insulin Resistance [HOMA-IR]) and adiponectin plasma levels were assessed in 227 nondiabetic renal patients at different degrees of renal dysfunction and in 76 healthy subjects of similar age and gender distribution and body mass index. In renal patients, association with prevalent CV events was evaluated, and incident CV events were evaluated in a prospective study. HOMA-IR was markedly higher in patients than in healthy subjects (3.59 +/- 3.55 versus 1.39 +/- 0.51; P < 0.01). In renal patients, HOMA-IR was significantly correlated with body mass index (r = 0.477; P < 0.01), triglycerides (r = 0.384; P < 0.01), adiponectin plasma levels (r = -0.253; P < 0.01), and age (r = 0.164; P < 0.05), but not with renal function (GFR by iod-thalamate clearance). Patients with previous CV events were significantly older, had higher HOMA-IR and serum triglycerides, and had lower adiponectin plasma levels (all P < 0.05). Logistic regression analysis revealed age (P < 0.001) and adiponectin (P < 0.002) as independent variables related to prevalent CV events. In the prospective study, median follow-up was 54 mo. Patients who experienced CV events had significantly higher serum glucose and lower adiponectin plasma levels (both P < 0.05). In patients with chronic kidney diseases, a syndrome of insulin resistance is present even in the earliest stage of renal dysfunction, and several components of this syndrome are associated with CV events. Moreover, hypoadiponectinemia is a novel putative CV risk factor in patients with mild and moderate renal failure.

Symmetrical dimethylarginine: a new combined parameter for renal function and extent of coronary artery disease

Symmetrical dimethylarginine (SDMA) is the structural isomer of the endogenous nitric oxide synthase (NOS) inhibitor asymmetric dimethylarginine. Whereas the major route of asymmetric dimethylarginine elimination is the hydrolytic degradation by dimethylarginine dimethylaminohydrolase, SDMA is eliminated by renal excretion. SDMA does not directly inhibit NOS but is a competitor of arginine transport. This study showed for the first time that measurement of SDMA can be a marker of estimated GFR and extent of coronary artery disease (CAD). In 97 patients with CAD, SDMA was a marker of estimated GFR. On multiple regression analysis of the CAD parameter stenosis score, SDMA was the only parameter retained. In addition, endothelial cells from the third passage were cultured in medium that contained 70 micromol/L arginine and was incubated for 24 h in the presence of various concentration of SDMA (0, 2, 5, 10, and 100 micromol/L). The levels of nitrate and nitrite in conditioned media, the protein expression of NOS, and the content of reactive oxygen species in endothelial cells were determined. SDMA inhibited dose dependently the NO synthesis in intact endothelial cells, whereas it had no effect on protein expression of NOS. This effect was associated with an increase in reactive oxygen species. Co-incubation with L-arginine but not D-arginine reversed the effect of SDMA on NOS pathway. Our data suggest that SDMA reduced the endothelial NO synthesis, probably by limiting L-arginine supply to NOS. It is concluded that SDMA might be a useful parameter for detecting patients in very early stages of chronic kidney disease and for determining their risk for developing cardiovascular disease.

Validation of treatment strategies for enterohaemorrhagic Escherichia coli O104:H4 induced haemolytic uraemic syndrome: case-control study

OBJECTIVE

To evaluate the effect of different treatment strategies on enterohaemorrhagic Escherichia coli O104:H4 induced haemolytic uraemic syndrome.

DESIGN

Multicentre retrospective case-control study.

SETTING

23 hospitals in northern Germany.

PARTICIPANTS

298 adults with enterohaemorrhagic E coli induced haemolytic uraemic syndrome.

MAIN OUTCOME MEASURES

Dialysis, seizures, mechanical ventilation, abdominal surgery owing to perforation of the bowel or bowel necrosis, and death.

RESULTS

160 of the 298 patients (54%) temporarily required dialysis, with only three needing treatment long term. 37 patients (12%) had seizures, 54 (18%) required mechanical ventilation, and 12 (4%) died. No clear benefit was found from use of plasmapheresis or plasmapheresis with glucocorticoids. 67 of the patients were treated with eculizumab, a monoclonal antibody directed against the complement cascade. No short term benefit was detected that could be attributed to this treatment. 52 patients in one centre that used a strategy of aggressive treatment with combined antibiotics had fewer seizures (2% v 15%, P = 0.03), fewer deaths (0% v 5%, p = 0.029), required no abdominal surgery, and excreted E coli for a shorter duration.

CONCLUSIONS

Enterohaemorrhagic E coli induced haemolytic uraemic syndrome is a severe self limiting acute condition. Our findings question the benefit of eculizumab and of plasmapheresis with or without glucocorticoids. Patients with established haemolytic uraemic syndrome seemed to benefit from antibiotic treatment and this should be investigated in a controlled trial.

Hyperuricaemia and gout in cardiovascular, metabolic and kidney disease

During the last century, there has been an increasing prevalence of hyperuricaemia noted in many populations. While uric acid is usually discussed in the context of gout, hyperuricaemia is also associated with hypertension, chronic kidney disease, hypertriglyceridaemia, obesity, atherosclerotic heart disease, metabolic syndrome, and type 2 diabetes. Here we review the connection between hyperuricaemia and cardiovascular, kidney and metabolic diseases. Contrary to the popular view that uric acid is an inert metabolite of purine metabolism, recent studies suggest serum uric acid may have a variety of pro-inflammatory, pro-oxidative and vasoconstrictive actions that may contribute to cardiometabolic diseases. Hyperuricaemia is a predictive factor for the development of hypertension, metabolic syndrome, type 2 diabetes, coronary artery disease, left ventricular hypertrophy, atrial fibrillation, myocardial infarction, stroke, heart failure and chronic kidney disease. Treatment with uric acid-lowering therapies has also been found to improve outcomes in patients with hypertension and kidney disease, in some but not all studies. In conclusion, uric acid is emerging as a potentially treatable risk factor for cardiometabolic diseases, and more clinical trials investigating the potential benefit of lowering serum uric acid are recommended in individuals with hyperuricaemia with and without deposition and concomitant hypertension, metabolic syndrome or chronic kidney disease.

ADMA increases arterial stiffness and decreases cerebral blood flow in humans

BACKGROUND AND PURPOSE

Preclinical studies have revealed that the endogenous nitric oxide synthase inhibitor, asymmetric dimethylarginine (ADMA), increases vascular tone in cerebral blood vessels. Marked elevations of ADMA blood levels were found in patients with diseases characterized by decreased cerebral perfusion, such as ischemic stroke. Arterial stiffness is an independent predictor of stroke and other adverse cardiovascular events. The aim of this study was to investigate the influence of a systemic subpressor dose of ADMA on arterial stiffness and cerebral perfusion in humans.

METHODS

Using a double-blind, vehicle-controlled study design, we allocated 20 healthy men in random order to infusion of either ADMA (0.10 mg ADMA/kg per min) or vehicle over a period of 40 minutes. Arterial stiffness was assessed noninvasively by pulse wave analysis. All volunteers underwent measurement of cerebral perfusion by dynamic contrast-enhanced perfusion magnetic resonance imaging of the brain.

RESULTS

Infusion of ADMA significantly decreased total cerebral perfusion by 15.1+/-4.5% (P=0.007), whereas blood flow in the vehicle group increased by 7.7+/-2.8% (P=0.02). ADMA also increased arterial stiffness as assessed by measurement of the augmentation index (-12.6+/-1.9 to -9.6+/-1.5, P=0.007).

CONCLUSIONS

Our results document for the first time that subpressor doses of ADMA increase vascular stiffness and decrease cerebral perfusion in healthy subjects. Thus, ADMA is an important endogenous modulator of cerebral vascular tone and may be involved in the pathogenesis of cerebrovascular disease.

Circulating miR-210 predicts survival in critically ill patients with acute kidney injury

BACKGROUND AND OBJECTIVES

MicroRNAs (miRNAs) are small ribonucleotides regulating gene expression. MicroRNAs are present in the blood in a remarkably stable form. We tested whether circulating miRNAs in the plasma of critically ill patients with acute kidney injury (AKI) at the inception of renal replacement therapy are deregulated and may predict survival.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We profiled miRNAs using RNA isolated from the plasma of patients with AKI and healthy controls. The results were validated in 77 patients with acute kidney injury, 30 age-matched healthy controls, and 18 critically ill patients with acute myocardial infarction by quantitative real-time PCR.

RESULTS

Circulating levels of miR-16 and miR-320 were downregulated in the plasma of kidney injury AKI patients, whereas miR-210 was upregulated compared with healthy controls (all P < 0.0001) and disease controls (miR-210 and miR-16: P < 0.0001; miR-320: P = 0.03). Cox regression (P < 0.05) and Kaplan-Meier curve analysis (P = 0.03) revealed miR-210 as an independent and powerful predictor of 28-day survival.

CONCLUSIONS

Circulating miRNAs are altered in patients with kidney injury AKI. MiR-210 predicts mortality in this patient cohort and may serve as a novel biomarker AKI reflecting pathophysiological changes on a cellular level.

Efficacy and cardiovascular tolerability of extended dialysis in critically ill patients: a randomized controlled study

BACKGROUND

Extended dialysis is an increasingly used modality of renal replacement therapy that theoretically offers advantages of both intermittent and continuous therapies in the intensive care unit (ICU).

METHODS

We randomly treated 39 ventilated critically ill patients with oliguric acute renal failure with either continuous venovenous hemofiltration (CVVH; n = 19; age, 50.1 +/- 3.2 years; Acute Physiology and Chronic Health Assessment II [APACHE II] score, 32.3 +/- 1.2; 79% sepsis) and a substitution fluid rate of at least 30 mL/kg/h for 24 hours or with extended dialysis for 12 hours (n = 20; age, 50.8 +/- 3.6 years; APACHE II score, 33.6 +/- 1.0; 85% sepsis). The latter was performed using an easy-to-handle, single-pass, batch dialysis system. All hemodynamic parameters were monitored invasively by means of an indwelling arterial catheter.

RESULTS

Average mean arterial blood pressure, heart rate, cardiac output, systemic vascular resistance, and catecholamine dose were not significantly different in both therapies. Urea reduction rate was similar with extended dialysis compared with CVVH therapy (53% +/- 2% versus 52% +/- 3%; P = not significant) despite an average rate of substitution fluid with the latter of 3.2 +/- 0.1 L/h. This was corroborated by the finding of similar amounts of urea eliminated in the collected spent total hemofiltration and dialysis fluid. Correction of acidosis was accomplished faster with extended dialysis than CVVH, and the amount of heparin used was significantly lower with extended dialysis (P < 0.01).

CONCLUSION

Extended dialysis combines excellent detoxification with cardiovascular tolerability, even in severely ill patients in the ICU. The technically simple dialysis system used offers flexibility of treatment time.

Asymmetrical dimethylarginine in idiopathic pulmonary arterial hypertension

OBJECTIVE

We explored the potential role of the endogenous NO synthase inhibitor asymmetrical dimethylarginine (ADMA) in patients with idiopathic pulmonary arterial hypertension (IPAH). Method and Results- We correlated plasma ADMA levels and cardiovascular indices from right heart catheterization in 57 patients with IPAH. Predictors of survival in patients with IPAH were studied. Furthermore, the effect of systemic ADMA infusion on pulmonary ventricular resistance and stroke volume was investigated in healthy volunteers using right heart catheterization. Mean plasma ADMA concentrations were significantly higher in patients with IPAH than in control subjects (0.53+/-0.15 versus 0.36+/-0.05 micromol/L; P<0.001). ADMA plasma concentrations correlated significantly with indices of right ventricular function, such as mixed-venous oxygen saturation (r=-0.49; P<0.0001), right atrial pressure (r=0.39; P<0.003), cardiac index (r=-0.35; P<0.008), as well as survival (r=-0.47; P<0.0001). Multiple regression analysis revealed that right atrial pressure (r=0.31; P<0.026) and ADMA (r=0.29; P<0.039) were independent predictors of mortality. Moreover, patients with supra-median plasma ADMA levels had significantly (P<0.021) worse survival than patients with infra-median ADMA values. ADMA infusion in healthy volunteers increased pulmonary vascular resistance (68.9+/-7.6 versus 95.6+/-6.3 dyne x s x cm(-5); P<0.05) and decreased stroke volume (101.1+/-6.7 mL versus 95.6+/-6.3 mL; P<0.05).

CONCLUSIONS

Increased ADMA plasma levels are associated with unfavorable pulmonary hemodynamics and worse outcome in patients with IPAH.

Management of patients at risk of acute kidney injury

Acute kidney injury (AKI) is a multifaceted syndrome that occurs in different settings. The course of AKI can be variable, from single hit and complete recovery, to multiple hits resulting in end-stage renal disease. No interventions to improve outcomes of established AKI have yet been developed, so prevention and early diagnosis are key. Awareness campaigns and education for health-care professionals on diagnosis and management of AKI-with attention to avoidance of volume depletion, hypotension, and nephrotoxic interventions-coupled with electronic early warning systems where available can improve outcomes. Biomarker-based strategies have not shown improvements in outcome. Fluid management should aim for early, rapid restoration of circulatory volume, but should be more limited after the first 24-48 h to avoid volume overload. Use of balanced crystalloid solutions versus normal saline remains controversial. Renal replacement therapy should only be started on the basis of hard criteria, but should not be delayed when criteria are met. On the basis of recent evidence, the risk of contrast-induced AKI might be overestimated for many conditions.

Best supportive care and therapeutic plasma exchange with or without eculizumab in Shiga-toxin-producing E. coli O104:H4 induced haemolytic-uraemic syndrome: an analysis of the German STEC-HUS registry

BACKGROUND

May 22nd marks the beginning of a Shiga-toxin-producing Escherichia coli (STEC) O104:H4 outbreak in Northern Germany. By its end on 27 July, it had claimed 53 deaths among 2987 STEC and 855 confirmed haemolytic-uraemic syndrome (HUS) cases.

METHODS

To describe short-term effectiveness of best supportive care (BSC), therapeutic plasma exchange (TPE) and TPE with eculizumab (TPE-Ecu) in 631 patients with suspected HUS treated in 84 hospitals in Germany, Sweden and the Netherlands using the web-based registry of the DGfN (online since 27 May).

RESULTS

Of 631 entries, 491 fulfilled the definition of HUS (median age 46 years; 71% females). The median (inter-quartile range) hospital stay was 22 (14-31) days. Two hundred and eighty-one (57%) patients underwent dialysis and 114 (23%) mechanical ventilation. Fifty-seven patients received BSC, 241 TPE and 193 TPE-Ecu. Treatment strategy was dependent on disease severity (laboratory signs of haemolysis, thrombocytopenia, peak creatinine level, need for dialysis, neurological symptoms, frequency of seizures) which was lower in BSC than in TPE and TPE-Ecu patients. At study endpoint (hospital discharge or death), the median creatinine was lower in BSC [1.1 mg/dL (0.9-1.3)] than in TPE [1.2 mg/dL (1.0-1.5), P < 0.05] and TPE-Ecu [1.4 mg/dL (1.0-2.2), P < 0.001], while need for dialysis was not different between BSC (0.0%, n = 0), TPE (3.7%; n = 9) and TPE-Ecu (4.7%, n = 9). Seizures were absent in BSC and rare in TPE (0.4%; n = 1) and TPE-Ecu (2.6%; n = 5) patients. Total hospital mortality in HUS patients was 4.1% (n = 20) and did not differ significantly between the TPE and TPE-Ecu groups.

CONCLUSIONS

Despite frequent renal impairment, advanced neurological disorders and severe respiratory failure, short-term outcome was better than expected when compared with previous reports. Within the limitations of a retrospective registry analysis, our data do not support the notion of a short-term benefit of Ecu in comparison to TPE alone in the treatment of STEC-HUS. A randomized trial comparing BSC, TPE and Ecu seems to be prudent and necessary prior to establishing new treatment guidelines for STEC-HUS.

Asymmetric dimethylarginine, blood pressure, and renal perfusion in elderly subjects

BACKGROUND

Reduced availability of nitric oxide (NO) is thought to contribute to the age-associated increase of renovascular tone and blood pressure. We assessed blood concentrations of the endogenous NO synthase inhibitor asymmetric dimethylarginine (ADMA) as well as renal hemodynamics, comparing young (n=24, 13 men, 25+/-1 years) and elderly (n=24, 13 men, 69+/-2 years) healthy subjects and elderly subjects with essential hypertension (n=24, 13 men, 70+/-2 years).

METHODS AND RESULTS

Plasma ADMA concentration and renovascular resistance (RVR) were significantly higher (P<0.05) and effective renal plasma flow (ERPF) significantly lower (P<0.05) in elderly (2.77+/-0.20 micromol/L, 125+/-10 mm Hg/mL per minute, 487+/-26 mL/min per 1.73 m2) than in young healthy subjects (1.30+/-0.11, 77+/-3, 654+/-18). Both ADMA levels and RVR were higher and ERPF lower in the hypertensive elderly subjects (3.53+/-0.23, 163+/-11, 427+/-19; P<0.05 versus both groups). In contrast, plasma concentrations of the biologically inactive stereoisomer symmetric dimethylarginine, l-arginine, and homocysteine were similar in the 3 groups studied. In the logistic regression analysis only ADMA was an independent determinant of both ERPF (P<0.001; r2=0.80) and RVR (P<0.002; r2=0.86). In addition, ADMA (P<0.002) and serum glucose (P<0.036) were independently related (r2=0.67) to the level of blood pressure.

CONCLUSIONS

These results are compatible with the notion that accumulation of the endogenous NO synthase inhibitor ADMA in senescent individuals is involved in the decrease of renal perfusion and increase of blood pressure.

Excess circulating angiopoietin-2 is a strong predictor of mortality in critically ill medical patients

Introduction

The endothelial specific angiopoietin (Ang)-Tie2 ligand-receptor system has been identified as a non-redundant mediator of endothelial activation in experimental sepsis. Binding of circulating Ang-1 to the Tie2 receptor protects the vasculature from inflammation and leakage, whereas binding of Ang-2 antagonises Tie2 signalling and disrupts endothelial barrier function. Here, we examine whether circulating Ang-1 and/or Ang-2 independently predict mortality in a cohort of critically ill medical patients.

Methods

Circulating vascular endothelial growth factor (VEGF), Ang-1 and Ang-2 were prospectively measured in sera from 29 healthy controls and 43 medical ICU patients by immunoradiometric assay (IRMA) and ELISA, respectively. Survival after 30 days was the primary outcome studied.

Results

Median serum Ang-2 concentrations were increasingly higher across the following groups: healthy controls, patients without sepsis, patients with sepsis and patients with septic shock. In contrast, Ang-1 and VEGF concentrations were significantly lower in all patient groups compared with healthy controls. Ang-2 correlated with partial pressure of oxygen in arterial blood (PaO₂)/fraction of inspired oxygen (FiO₂), tissue hypoxia, Sequential Organ Failure Assessment (SOFA) and Physiology and Chronic Health Evaluation II (APACHE II) score. Multivariate Cox regression analyses confirmed a strong independent prognostic impact of high Ang-2 as a novel marker of 30-day survival.

Conclusions

A marked imbalance of the Ang-Tie system in favour of Ang-2 is present in critically ill medical patients. Our findings highlight the independent prognostic impact of circulating Ang-2 in critical illness. Ang-2 may be used as a readily available powerful predictor of outcome and may open new perspectives to individualise treatment in the ICU.

The German Chronic Kidney Disease (GCKD) study: design and methods

BACKGROUND

Chronic kidney disease (CKD) is increasingly recognized as a global health problem. The conditions leading to CKD, the health impact of CKD and the prognosis differ markedly between affected individuals. In particular, renal failure and cardiovascular mortality are competing risks for CKD patients. Opportunities for targeted intervention are very limited so far and require an improved understanding of the natural course of CKD, of the risk factors associated with various clinical end points and co-morbidities as well as of the underlying pathogenic mechanisms.

METHODS

The German Chronic Kidney Disease (GCKD) study is a prospective observational national cohort study. It aims to enrol a total of 5000 patients with CKD of various aetiologies, who are under nephrological care, and to follow them for up to 10 years. At the time of enrolment, male and female patients have an estimated glomerular filtration rate (eGFR) of 30-60 mL/min×1.73 m2 or overt proteinuria in the presence of an eGFR>60 mL/min×1.73 m2. Standardized collection of biomaterials, including DNA, serum, plasma and urine will allow identification and validation of biomarkers associated with CKD, CKD progression and related complications using hypothesis-driven and hypothesis-free approaches. Patient recruitment and follow-up is organized through a network of academic nephrology centres collaborating with practising nephrologists throughout the country.

CONCLUSIONS

The GCKD study will establish one of the largest cohorts to date of CKD patients not requiring renal replacement therapy. Similarities in its design with other observational CKD studies, including cohorts that have already been established in the USA and Japan, will allow comparative and joint analyses to identify important ethnic and geographic differences and to enhance opportunities for identification of relevant risk factors and markers.

Renal function and survival in 200 patients undergoing ECMO therapy

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) is increasingly used in the intensive care unit (ICU) setting to improve gas exchange in patients with acute respiratory distress syndrome as well as in patients pre- and post-heart and lung transplantation. In this clinical setting, acute kidney injury (AKI) is frequently observed. So far, it is unknown how AKI affects the survival of critically ill patients receiving ECMO support and whether veno-veno and veno-arterial ECMO have different effects on kidney function.

METHODS

This is a retrospective analysis of patients undergoing ECMO treatment in medical and surgical ICUs in a tertiary care centre. We evaluated all patients undergoing ECMO treatment at our centre between 1 January 2005 and 31 December 2010. Data from all 200 patients (83F/117M), median age 45 (17-83) years, were obtained by chart review. Follow-up data were obtained for up to 3 months.

RESULTS

Three-month survival of all patients was 31%. Of the 200 patients undergoing ECMO treatment, 60% (120/200) required renal replacement therapy (RRT) for AKI. While patients without RRT showed a 3-month survival of 53%, the survival of patients with AKI requiring RRT was 17% (P = 0.001). Longer duration of RRT was associated with a higher mortality.

CONCLUSIONS

AKI requiring RRT therapy in patients undergoing ECMO treatment increases mortality in ICU patients. Future studies have to clarify whether it is possible to identify patients who benefit from the combination of ECMO and RRT.

Osteopontin is indispensible for AP1-mediated angiotensin II-related miR-21 transcription during cardiac fibrosis

Aims

Osteopontin (OPN) is a multifunctional cytokine critically involved in cardiac fibrosis. However, the underlying mechanisms are unresolved. Non-coding RNAs are powerful regulators of gene expression and thus might mediate this process.

Methods and results

OPN and miR-21 were significantly increased in cardiac biopsies of patients with myocardial fibrosis. Ang II infusion via osmotic minipumps led to specific miRNA regulations with miR-21 being strongly induced in wild-type (WT) but not OPN knockout (KO) mice. This was associated with enhanced cardiac collagen content, myofibroblast activation, ERK-MAP kinase as well as AKT signalling pathway activation and a reduced expression of Phosphatase and Tensin Homologue (PTEN) as well as SMAD7 in WT but not OPN KO mice. In contrast, cardiotropic AAV9-mediated overexpression of OPN in vivo further enhanced cardiac fibrosis. In vitro, Ang II induced expression of miR-21 in WT cardiac fibroblasts, while miR-21 levels were unchanged in OPN KO fibroblasts. As pri-miR-21 was also increased by Ang II, we studied potential involved upstream regulators; Electrophoretic Mobility Shift and Chromatin Immunoprecipitation analyses confirmed activation of the miR-21 upstream-transcription factor AP-1 by Ang II. Recombinant OPN directly activated miR-21, enhanced fibrosis, and activated the phosphoinositide 3-kinase pathway. Locked nucleic acid-mediated miR-21 silencing ameliorated cardiac fibrosis development in vivo.

Conclusion

In cardiac fibrosis related to Ang II, miR-21 is transcriptionally activated and targets PTEN/SMAD7 resulting in increased fibroblast survival. OPN KO animals are protected from miR-21 increase and fibrosis development due to impaired AP-1 activation and fibroblast activation.

Osteopontin (OPN) is a pleiotropic cytokine, which has been shown to be a pivotal factor in myofibroblast activation in cardiac fibrosis, thereby acting as a strong driver of heart failure development in humans. MicroRNAs (miRNAs) are under intense investigation as powerful regulators of various diseases. First phase I and II clinical trials using miRNA inhibitors have been initiated. We here show, that OPN is essential in the activation of AP-1 and subsequent transcription of miR-21 in cardiac fibrosis related to Ang II. OPN null mice are protected from miR-21 increase and fibrosis development due to impaired AP-1 activation and fibroblast activation. In the future, these findings may result in miRNA therapeutic approaches to treat patients with cardiac remodelling, in which levels of OPN and miR-21 are increased.

Asymmetric dimethylarginine: a cardiovascular risk factor and a uremic toxin coming of age?

The idea that asymmetric dimethylarginine (ADMA) accumulation may be a cardiovascular risk factor in patients with end-stage renal disease was advanced by Vallance in 1992. During the last decade, the relationship between ADMA and adverse cardiovascular events, including death, in dialysis patients has been investigated thoroughly. Several studies have shown that, independently of other risk factors, ADMA is strongly associated with intima-media thickness of the carotid artery and left ventricular mass, particularly concentric left ventricular hypertrophy. Furthermore, cohort studies in both the general population and the dialysis population showed a strong and independent link between ADMA, all-cause mortality, and cardiovascular events. Circumstantial evidence indicates that norepinephrine and ADMA may be in the same causal pathway leading to cardiovascular complications in patients with end-stage renal disease. Several lines of evidence show that high ADMA levels may exert toxic effects in various cell types. High ADMA levels have been associated with alterations in the regulation of cerebral blood flow and neural function, with insulin resistance, thyroid dysfunction, and alterations in bone homeostasis, fertility, and erectile function. The clinical significance of decreasing plasma ADMA concentrations, if any, is unknown. Well-designed and carefully conducted studies are needed to further clarify the role of ADMA in the pathophysiological states of renal disease and explore possible treatment options to improve the prognosis of patients with elevated ADMA levels. ADMA may enable us to predict risk and follow up the course of renal diseases.

Increased resistin blood levels are not associated with insulin resistance in patients with renal disease

BACKGROUND

Resistin is a newly discovered insulin inhibitor secreted by adipocytes. We explored the potential role of resistin in the pathophysiological process of insulin resistance encountered in patients with renal disease.

METHODS

Resistin blood concentrations, insulin sensitivity index (by intravenous glucose tolerance test), and glomerular filtration rate (GFR; by inulin clearance) were assessed in 30 male patients with immunoglobulin A glomerulonephritis in different stages of renal disease.

RESULTS

Patients with increased resistin blood concentrations had more advanced renal failure and were significantly older. Plasma resistin levels correlated significantly with GFR (r = -0.82; P < 0.0001), plasma homocysteine concentration (r = 0.68; P < 0.001), and age (r = 0.42; P = 0.05), but not with fasted plasma insulin (r = -0.34; P = 0.12), glucose (r = 0.25; P = 0.19), and leptin (r = -0.24; P = 0.21) concentrations; body mass index (r = -0.06; P = 0.75), waist-hip ratio (r = 0.09; P = 0.63), or insulin sensitivity (r = -0.05; P = 0.79). In multiple regression analysis, GFR was the only independent predictor of plasma resistin concentrations in renal patients (r = -0.812; P < 0.0001).

CONCLUSION

Resistin blood concentrations increase with progressive impairment of renal function. Thus, the kidney seems to be an important site of resistin elimination. However, the greater than 5-fold increase in resistin blood levels apparently is not associated with deterioration in insulin sensitivity in patients with renal disease.

Early therapeutic plasma exchange in septic shock: a prospective open-label nonrandomized pilot study focusing on safety, hemodynamics, vascular barrier function, and biologic markers

Background

Given the pathophysiological key role of the host response to an infection rather than the infection per se, an ideal therapeutic strategy would also target this response. This study was designed to demonstrate safety and feasibility of early therapeutic plasma exchange (TPE) in severely ill individuals with septic shock.

Methods

This was a prospective single center, open-label, nonrandomized pilot study enrolling 20 patients with early septic shock (onset < 12 h) requiring high doses of norepinephrine (NE; > 0.4 μg/kg/min) out of 231 screened septic patients. Clinical and biochemical data were obtained before and after TPE. Plasma samples were taken for ex-vivo stimulation of human umbilical vein endothelial cells (HUVECs) to analyze barrier function (immunocytochemistry and transendothelial electrical resistance (TER)). Cytokines were measured by cytometric bead array (CBA) and enzyme-linked immunosorbent assays (ELISAs). An immediate response was defined as > 20% NE reduction from baseline to the end of TPE.

Results

TPE was well tolerated without the occurrence of any adverse events and was associated with a rapid reduction in NE (0.82 (0.61–1.17) vs. 0.56 (0.41–0.78) μg/kg/min, p = 0.002) to maintain mean arterial pressure (MAP) above 65 mmHg. The observed 28-day mortality was 65%. Key proinflammatory cytokines and permeability factors (e.g., interleukin (IL)-6, IL-1b, and angiopoietin-2) were significantly reduced after TPE, while the protective antipermeability factor angiopoietin-1 was not changed. Ex-vivo stimulation of HUVECs with plasma obtained before TPE induced substantial cellular hyperpermeability, which was completely abolished with plasma obtained after TPE.

Conclusions

Inclusion of early septic shock patients with high doses of vasopressors was feasible and TPE was safe. Rapid hemodynamic improvement and favorable changes in the cytokine profile in patients with septic shock were observed. It has yet to be determined whether early TPE also improves outcomes in this patient cohort. An appropriately powered multicenter randomized controlled trial is desirable.

Trial registration

Clinicaltrials.gov, NCT03065751. Retrospectively registered on 28 February 2017.

Electronic supplementary material

The online version of this article (10.1186/s13054-018-2220-9) contains supplementary material, which is available to authorized users.

Circulating long noncoding RNATapSaki is a predictor of mortality in critically ill patients with acute kidney injury

BACKGROUND

Long noncoding RNAs (lncRNAs) are novel intracellular noncoding ribonucleotides regulating gene expression. Intriguingly, these RNA transcripts are detectable and stable in the blood of patients with cancer and cardiovascular disease. We tested whether circulating lncRNAs in plasma of critically ill patients with acute kidney injury (AKI) at inception of renal replacement therapy were deregulated and might predict survival.

METHODS

We performed a global lncRNA expression analysis using RNA isolated from plasma of patients with AKI, healthy controls, and ischemic disease controls. This global screen revealed several deregulated lncRNAs in plasma samples of patients with AKI. lncRNA-array-based alterations were confirmed in kidney biopsies of patients as well as in plasma of 109 patients with AKI, 30 age-matched healthy controls, and 30 disease controls by quantitative real-time PCR.

RESULTS

Circulating concentrations of the novel intronic antisense lncRNA TrAnscript Predicting Survival in AKI (TapSAKI) (P < 0.0001) were detectable in kidney biopsies and upregulated in plasma of patients with AKI. Cox regression and Kaplan-Meier curve analysis revealed TapSAKI as an independent predictor of 28-day survival (P < 0.01). TapSAKI was enriched in tubular epithelial cells subjected to ATP depletion (P = 0.03).

CONCLUSIONS

The alteration of circulating concentrations of lncRNAs in patients with AKI supports TapSAKI as a predictor of mortality in this patient cohort.

The Hannover Dialysis Outcome study: comparison of standard versus intensified extended dialysis for treatment of patients with acute kidney injury in the intensive care unit

BACKGROUND

Increasing the dose of renal replacement therapy has been shown to improve survival in critically ill patients with acute kidney injury (AKI) in several smaller European trials. However, a very recent large multicentre trial in the USA could not detect an effect of dose of renal replacement therapy on mortality. Based on those studies, it is not known whether a further increase in dialysis dose above and beyond the currently employed doses would improve survival in patients with AKI. We therefore aimed to assess mortality and renal recovery of patients with AKI receiving either standard (SED) or intensified extended dialysis (IED) therapy in the intensive care unit.

METHODS

A prospective randomized parallel group study was conducted in seven intensive care units of a tertiary university hospital. Pre-existing chronic kidney disease was an exclusion criterion. A total of 156 patients (570 screened) with AKI requiring renal replacement therapy were randomly assigned to receive standard dialysis [dosed to maintain plasma urea levels between 120 and 150 mg/dL (20-25 mmol/L)] or intensified dialysis [dosed to maintain plasma urea levels <90 mg/dL (<15 mmol/L)]. Outcome measures were survival at Day 14 (primary) and survival and renal recovery at Day 28 (secondary) after initiation of renal replacement therapy.

RESULTS

Treatment intensity differed significantly (P < 0.01 for plasma urea and administered dose). No differences between intensified and standard treatment were seen for survival by Day 14 (70.4% versus 70.7%) or Day 28 (55.6% versus 61.3%), or for renal recovery amongst the survivors by Day 28 (60.0% versus 63.0%).

CONCLUSIONS

Although this study cannot deliver a definitive answer, it suggests that increasing the dose of extended dialysis above the currently recommended dose might neither reduce mortality nor improve renal recovery in critically ill patients, mainly septic patients, with AKI.