Continuous conversion of CO2/H2 with Clostridium aceticum in biofilm reactors.

A lab-scale stirred-tank bioreactor was reversibly retrofitted to a packed-bed and a trickle-bed biofilm reactor to study and compare the conversion of CO2/H2 with immobilised Clostridiumaceticum. The biofilm reactors were characterised and their functionality confirmed. Up to 8.6 g of C. aceticum were immobilised onto 300 g sintered ceramic carrier material, proving biofilm formation to be a robust means for cell retention of C. aceticum. Continuous CO2/H2-fermentation studies were performed with both biofilm reactor configurations as function of dilution rates, partial gas pressures and gas flow rates. The experiments showed that in the packed-bed biofilm reactor, the acetate space-time yield was independent of the dilution rate, because of low H2 gas-liquid mass transfer rates (≤17 mmol H2 L-1 h-1). The continuous operation of the trickle-bed biofilm reactor increased the gas-liquid mass transfer rates to up to 56 mmol H2 L-1 h-1. Consequently, the acetate space-time yield of up to 14 mmol acetate L-1 h-1 was improved 3-fold at hydrogen conversions of up to 96%.

Bacterial Anaerobic Synthesis Gas (Syngas) and CO2+H2 Fermentation.

Anaerobic bacterial gas fermentation gains broad interest in various scientific, social, and industrial fields. This microbial process is carried out by a specific group of bacterial strains called acetogens. All these strains employ the Wood-Ljungdahl pathway but they belong to different taxonomic groups. Here we provide an overview of the metabolism of acetogens and naturally occurring products. Characteristics of 61 strains were summarized and selected acetogens described in detail. Acetobacterium woodii, Clostridium ljungdahlii, and Moorella thermoacetica serve as model organisms. Results of approaches such as genome-scale modeling, proteomics, and transcriptomics are discussed. Metabolic engineering of acetogens can be used to expand the product portfolio to platform chemicals and to study different aspects of cell physiology. Moreover, the fermentation of gases requires specific reactor configurations and the development of the respective technology, which can be used for an industrial application. Even though the overall process will have a positive effect on climate, since waste and greenhouse gases could be converted into commodity chemicals, some legislative barriers exist, which hamper successful exploitation of this technology.

Estimating the glomerular filtration rate in the general population using different equations: effects on classification and association.

BACKGROUND/AIMS: Several formulas for glomerular filtration rate (GFR) estimation, based on serum creatinine or cystatin C, have been proposed. We assessed the impact of some of these equations on estimated GFR (eGFR) and chronic kidney disease (CKD) prevalence, and on the association with cardiovascular risk factors, in a general population sample characterized by a young mean age. METHODS: We studied 1,199 individuals from three Alpine villages enrolled into the MICROS study. eGFR was obtained with the 4- and 6-parameter MDRD study equations, the Virga equation, and with the three CKD-EPI formulas for creatinine, cystatin C, and the combination of creatinine and cystatin C. We assessed the concordance between quantitative eGFR levels, CKD prevalence, and in terms of association with total, LDL, and HDL cholesterol. RESULTS: The highest and lowest eGFR levels corresponded to the cystatin C-based and MDRD-4 equations, respectively. CKD prevalence varied from 1.8% (Virga) to 5.8% (MDRD-4). The CKD-EPI based on creatinine showed the highest agreement with all other equations. Agreement between methods was higher at lower eGFR levels, older age, and in the presence of diabetes and hypertension. Creatinine-based estimates of eGFR were associated with total and low-density lipoprotein but not high-density lipoprotein cholesterol. The opposite was observed for the cystatin C-based GFR. CONCLUSION: GFR estimation is strongly affected by the chosen equation. Differences are more pronounced in healthy and younger individuals. To identify CKD risk factors, the choice of the equation is of secondary importance to the choice of the biomarker used in the formula. If eGFR is not calibrated to a gold standard GFR in the general population, reports about CKD prevalence should be considered with caution.

Characteristics of intracranial aneurysms in the else kröner-fresenius registry of autosomal dominant polycystic kidney disease.

BACKGROUND: Patients who harbor intracranial aneurysms (IAs) run a risk for aneurysm rupture and subsequent subarachnoid hemorrhage which frequently results in permanent deficits or death. Prophylactic treatment of unruptured aneurysms is possible and recommended depending on the size and location of the aneurysm as well as patient age and condition. IAs are major manifestations of autosomal dominant polycystic kidney disease (ADPKD). Current guidelines do not suggest surveillance of IAs in ADPKD except in the setting of family history if IA was known in any relative with ADPKD. Management of IAs in ADPKD is problematic because limited data exist from large studies. METHODS: We established the Else Kröner-Fresenius Registry for ADPKD in Germany. Clinical data were assessed for age at diagnosis of IAs, stage of renal insufficiency, and number, location and size of IAs as well as family history of cerebral events. Patients with symptomatic or asymptomatic IAs were included. All patients with ADPKD-related IAs were offered mutation scanning of the susceptibility genes for ADPKD, the PKD1 and PKD2 genes. RESULTS: Of 463 eligible ADPKD patients from the population base of Germany, 32 (7%) were found to have IAs, diagnosed at the age of 2-71 years, 19 females and 13 males. Twenty (63%) of these 32 patients were symptomatic, whereas IAs were detected in an asymptomatic stage in 12 patients. IAs were multifocal in 12 and unifocal in 20 patients. In 26 patients (81%), IAs were diagnosed before end-stage renal failure. Twenty-five out of 27 unrelated index cases (93%) had no IAs or cerebral events documented in their relatives with ADPKD. In 16 unrelated index patients and 3 relatives, we detected germline mutations. The mutations were randomly distributed across the PKD1 gene in 14 and the PKD2 gene in 2 index cases. Questionnaires answered for 320/441 ADPKD patients without IAs revealed that only 45/320 (14%) had MR angiography. CONCLUSION: In ADPKD, rupture of IAs occurs frequently before the start of dialysis, is only infrequently associated with a family history of IAs or subarachnoid hemorrhage, and is associated with mutations either of the PKD1 or the PKD2 gene of any type. Screening for IAs is widely insufficiently performed, should not be restricted to families with a history of cerebral events and should be started before end-stage renal failure.

Adult patients with sporadic polycystic kidney disease: the importance of screening for mutations in the PKD1 and PKD2 genes.

BACKGROUND: ADPKD is one of the most common inherited disorders, with high risk for end-stage renal disease. Numerous patients, however, have no relatives in whom this disorder is known and are unsure whether they may transmit the disease to their offsprings. The aim of this study was to evaluate whether germline mutation analysis adds substantial information to clinical symptoms for diagnosis of ADPKD in these patients. METHODS: Clinical data included renal function and presence of liver or pancreas cysts, heart valve insufficiency, intracranial aneurysms, colonic diverticles, and abdominal hernias. Family history was evaluated regarding ADPKD. Germline mutation screening of the PKD1 and PKD2 genes was performed for intragenic mutations and for large deletions. RESULTS: A total of 324 adult patients with ADPKD including 30 patients without a family history of ADPKD (sporadic cases) were included. PKD1 mutations were found in 24/30 and PKD2 mutations in 6 patients. Liver cysts were present in 14 patients and intracranial aneurysms in 2 patients. Fourteen patients (45%) had no extrarenal involvement. Compared to the 294 patients with familial ADPKD, the clinical characteristics and the age at the start of dialysis were similar in those with sporadic ADPKD. CONCLUSION: The clinical characteristics of patients with sporadic and familial ADPKD are similar, but sporadic ADPKD is often overlooked because of the absence of a family history. Molecular genetic screening for germline mutations in both PKD1 and PKD2 genes is essential for the definitive diagnosis of ADPKD.

A meta-analysis of genome-wide data from five European isolates reveals an association of COL22A1, SYT1, and GABRR2 with serum creatinine level.

BACKGROUND: Serum creatinine (S CR) is the most important biomarker for a quick and non-invasive assessment of kidney function in population-based surveys. A substantial proportion of the inter-individual variability in S CR level is explicable by genetic factors. METHODS: We performed a meta-analysis of genome-wide association studies of S CR undertaken in five population isolates ('discovery cohorts'), all of which are part of the European Special Population Network (EUROSPAN) project. Genes showing the strongest evidence for an association with SCR (candidate loci) were replicated in two additional population-based samples ('replication cohorts'). RESULTS: After the discovery meta-analysis, 29 loci were selected for replication. Association between SCR level and polymorphisms in the collagen type XXII alpha 1 (COL22A1) gene, on chromosome 8, and in the synaptotagmin-1 (SYT1) gene, on chromosome 12, were successfully replicated in the replication cohorts (p value = 1.0 x 10(-6) and 1.7 x 10(-4), respectively). Evidence of association was also found for polymorphisms in a locus including the gamma-aminobutyric acid receptor rho-2 (GABRR2) gene and the ubiquitin-conjugating enzyme E2-J1 (UBE2J1) gene (replication p value = 3.6 x 10(-3)). Previously reported findings, associating glomerular filtration rate with SNPs in the uromodulin (UMOD) gene and in the schroom family member 3 (SCHROOM3) gene were also replicated. CONCLUSIONS: While confirming earlier results, our study provides new insights in the understanding of the genetic basis of serum creatinine regulatory processes. In particular, the association with the genes SYT1 and GABRR2 corroborate previous findings that highlighted a possible role of the neurotransmitters GABAA receptors in the regulation of the glomerular basement membrane and a possible interaction between GABAA receptors and synaptotagmin-I at the podocyte level.

Genome-wide linkage analysis of serum creatinine in three isolated European populations.

There is increasing evidence for a role of genetic predisposition in the etiology of kidney disease, but linkage scans have been poorly replicated. Here we performed a genome-wide linkage analysis of serum creatinine on 2859 individuals from isolated villages in South Tyrol (Italy), Rucphen (The Netherlands) and Vis Island (Croatia), populations that have been stable and permanently resident in their region. Linkage of serum creatinine levels to loci on chromosomes 7p14, 9p21, 11p15, 15q15-21, 16p13, and 18p11 was successfully replicated in at least one discovery population or in the pooled analysis. A novel locus was found on chromosome 10p11. Linkage to chromosome 22q13, independent of diabetes and hypertension, was detected over a region containing the non-muscle myosin heavy chain type II isoform A (MYH9) gene (LOD score=3.52). In non-diabetic individuals, serum creatinine was associated with this gene in two of the three populations and in meta-analysis (SNP rs11089788, P-value=0.0089). In populations sharing a homogeneous environment and genetic background, heritability of serum creatinine was higher than in outbred populations, with consequent detection of a larger number of loci than reported before. Our finding of a replicated association of serum creatinine with the MYH9 gene, recently linked to pathological renal conditions in African Americans, suggests that this gene may also influence kidney function in healthy Europeans.

Fenestration of the Gerota's fascia as symptomatic treatment of floating kidneys.

A 16-year-old man presented with severe nephrotic syndrome complicated by massive perirenal fluid. Percutaneous drainage of fluid was performed 3 times, followed by improvement in renal function and hypertension, but perirenal fluid recurred within days. Nephrotic syndrome was unresponsive to steroid therapy. A laparoscopic bilateral fenestration of Gerota's fascia and peritoneum allowed permanent drainage of fluid into the peritoneal cavity. During the same procedure, a renal wedge biopsy was performed. Histological examination showed advanced focal glomerular sclerosis of the tip lesion variant. The glomerular disease was refractory to further treatment with cyclophosphamide, mycophenolate, and rituximab. However, perirenal fluid did not recur despite persistent nephrotic syndrome, showing that fenestration of Gerota's fascia is a successful treatment of floating kidneys in such patients.

Fibroblast growth factor 23 (FGF23) predicts progression of chronic kidney disease: the Mild to Moderate Kidney Disease (MMKD) Study.

It has not been firmly established whether disturbed calcium-phosphate metabolism affects progression of chronic kidney disease (CKD) in humans. In this cohort study of 227 nondiabetic patients with CKD, we assessed fibroblast growth factor 23 (FGF23) plasma concentrations in addition to other variables involved in calcium-phosphate metabolism, and we followed 177 of the patients prospectively for a median of 53 months to assess progression of renal disease. In the baseline cohort, we found a significant inverse correlation between glomerular filtration rate and both c-terminal and intact FGF23 levels (both P < 0.001). The 65 patients who experienced a doubling of serum creatinine and/or terminal renal failure were significantly older, had a significantly lower glomerular filtration rate at baseline, and significantly higher levels of intact parathormone, c-terminal and intact FGF23, and serum phosphate (all P < 0.001). Cox regression analysis revealed that both c-terminal and intact FGF23 independently predict progression of CKD after adjustment for age, gender, GFR, proteinuria, and serum levels of calcium, phosphate, and parathyroid hormone. The mean follow-up time to a progression end point was 46.9 (95% CI 40.2 to 53.6) months versus 72.5 (95% CI 67.7 to 77.3) months for patients with c-terminal FGF23 levels above or below the optimal cut-off level of 104 rU/mL (derived by receiver operator curve analysis), respectively. In conclusion, FGF23 is a novel independent predictor of progression of renal disease in patients with nondiabetic CKD. Its pathophysiological significance remains to be elucidated.

Apolipoprotein A-IV predicts progression of chronic kidney disease: the mild to moderate kidney disease study.

It has not been established firmly whether dyslipidemia contributes independently to the progression of kidney disease. Lipid and lipoprotein parameters, including levels of total, HDL, and LDL cholesterol; triglycerides; lipoprotein(a); apolipoprotein A-IV; and the apolipoprotein E and A-IV polymorphisms, were assessed in 177 patients who had mostly mild to moderate renal insufficiency and were followed prospectively for up to 7 yr. Progression of kidney disease was defined as doubling of baseline serum creatinine and/or terminal renal failure necessitating renal replacement therapy. In univariate analysis, patients who reached a progression end point (n = 65) were significantly older and had higher serum creatinine and proteinuria as well as lower GFR and hemoglobin levels. In addition, baseline apolipoprotein A-IV and triglyceride concentrations were higher and HDL cholesterol levels were lower. Multivariate Cox regression analysis revealed that baseline GFR (hazard ratio 0.714; 95% confidence interval [CI] 0.627 to 0.814 for an increment of 10 ml/min per 1.73 m(2); P < 0.0001) and serum apolipoprotein A-IV concentrations (hazard ratio 1.062; 95% CI 1.018 to 1.108 for an increment of 1 mg/dl; P = 0.006) were significant predictors of disease progression. Patients with apolipoprotein A-IV levels above the median had a significantly faster progression (P < 0.0001), and their mean follow-up time to a progression end point was 53.7 mo (95% CI 47.6 to 59.8) as compared with 70.0 mo (95% CI 64.6 to 75.4) in patients with apolipoprotein A-IV levels below the median. For the apolipoprotein E polymorphism, only the genotype epsilon2/epsilon4 was associated with an increased risk for progression. In summary, this prospective study in patients with nondiabetic primary kidney disease demonstrated that apolipoprotein A-IV concentration is a novel independent predictor of progression.

Oxidative stress in kidney transplant patients with calcineurin inhibitor-induced hypertension: effect of ramipril.

In patients with cyclosporine-induced hypertension, upregulation of the nitric oxide system and oxidative stress were shown, which could induce hypertension, remodeling, and chronic rejection by increasing nitric oxide catabolism. However, it is still debated whether cyclosporine and tacrolimus exert a different action. The aim of the current study was to compare the effects of cyclosporine and tacrolimus on markers of oxidative stress and endothelial dysfunction in kidney transplant patients with posttransplant hypertension. Monocyte p22, a NADH/NADPH system subunit, transforming growth factor-beta (TGF-beta), heme oxygenase-1 (HO-1), and endothelial NOS gene expression were measured in 16 patients. Angiotensin II is a potent stimulator of oxidative stress and angiotensin-converting enzyme inhibition may blunt this effect. Therefore, the same parameters were measured before and after 2 months of treatment with ramipril (5 mg/d). At baseline, in cyclosporine-and tacrolimus-treated patients, p22 and TGF-beta mRNA were similarly increased in comparison with normotensive healthy controls (0.90 +/- 0.05 d.u. and 0.83 +/- 0.05 in cyclosporine, 0.89 +/- 0.07 and 0.84 +/- 0.05 in tacrolimus; 0.53 +/- 0.07 and 0.75 +/- 0.03 in controls, respectively; p < 0.001). Endothelial NOS mRNA was increased in cyclosporine-and tacrolimus-treated patients in comparison with controls (0.92 +/- 0.09, 0.96 +/- 0.04, and 0.37 +/- 0.05 respectively; p < 0.001), whereas no difference was found between patients and controls in HO-1 mRNA. Ramipril reduced blood pressure (from 140 +/- 11/91 +/- 7 mm Hg to 129 +/- 6/85 +/- 5 mm Hg in cyclosporine and from 138 +/- 7/92 +/- 7 mm Hg to 127 +/- 10/82 +/- 6 mm Hg in tacrolimus group; p < 0.02 with no difference between groups). Ramipril also reduced p22 (to 0.83 +/- 0.05 in cyclosporine, p < 0.03 and to 0.81 +/- 0.08 in tacrolimus; p < 0.01) and TGF-beta mRNA (to 0.72 +/- 01 in cyclosporine, p < 0.02, and to 0.73 +/- 0.05 in tacrolimus; p < 0.01) with no difference between groups, but it did not change HO-1 and ecNOS mRNA. Cyclosporine and tacrolimus induce a comparable oxidative stress in kidney transplant patients with posttransplant hypertension. The association of ramipril normalizes blood pressure and reduces the oxidative stress induced by both drugs.

Apolipoprotein A-IV serum concentrations are elevated in patients with mild and moderate renal failure.

Cell culture studies and investigations in mice that overexpress either human or mouse apolipoprotein A-IV (apoA-IV) revealed anti-atherogenic properties of apoA-IV. An association between low apoA-IV concentrations and coronary artery disease in humans was demonstrated; therefore, apoA-IV may also play an antiatherogenic role in humans. Because apoA-IV is markedly elevated in dialysis patients, patients with the earliest and modest stages of renal impairment were studied to assess the association of apoA-IV with GFR and atherosclerotic complications. GFR was measured by the use of iohexol in 227 non-nephrotic patients with different degrees of renal impairment. ApoA-IV increased significantly with decreasing GFR and was already elevated in earliest stages of renal disease (GFR > 90 ml/min per 1.73 m2). Multiple linear regression analysis identified renal function parameters (GFR, creatinine, and urea) as the most important determinants of apoA-IV levels in serum of these patients. Twenty-six patients had already experienced 36 atherosclerotic events. Logistic regression analysis identified three variables associated with atherosclerotic complications: age, apoA-IV, and gender. Each 1 mg/dl increase of apoA-IV decreased the odds ratio for an atherosclerotic complication by 8% (P = 0.011). The data clearly show that the anti-atherogenic apoA-IV starts to increase during the earliest phases of renal insufficiency, which makes apoA-IV an early marker of renal impairment.

Lipoprotein(a) serum concentrations and apolipoprotein(a) phenotypes in mild and moderate renal failure.

High lipoprotein(a) (Lp(a)) serum concentrations and the underlying apolipoprotein(a) (apo(a)) phenotypes are risk factors for cardiovascular disease in the general population as well as in patients with renal disease. Lp(a) concentrations are markedly elevated in patients with end-stage renal disease. However, nothing is known about the changes of Lp(a) depending on apo(a) size polymorphism in the earliest stages of renal impairment. In this study, GFR was measured by iohexol technique in 227 non-nephrotic patients with different degrees of renal impairment and was then correlated with Lp(a) serum concentrations stratified according to low (LMW) and high (HMW) molecular weight apo(a) phenotypes. Lp(a) increased significantly with decreasing GFR. Such an increase was dependent on apo(a) phenotype. Only renal patients with HMW apo(a) phenotypes expressed higher median Lp(a) concentrations, i.e., 6.2 mg/dl at GFR >90 ml/min per 1.73 m2, 14.2 at GFR 45 to 90 ml/min per 1.73 m2, and 18.0 mg/dl at GFR <45 ml/min per 1.73 m2. These values were markedly different when compared with apo(a) phenotype-matched control subjects who had a median level of 4.4 mg/dl (ANOVA, linear relationship, P < 0.001). In contrast, no significant differences were observed at different stages of renal function in patients with LMW apo(a) phenotypes when compared with phenotype-matched control subjects. The elevation of Lp(a) was independent of the type of primary renal disease and was not related to the concentration of C-reactive protein. Multiple linear regression analysis found that the apo(a) phenotype and GFR were significantly associated with Lp(a) levels. Non-nephrotic-range proteinuria modified the association between GFR and Lp(a) levels. In summary, an increase of Lp(a) concentrations, compared with apo(a) phenotype-matched control subjects, is seen in non-nephrotic patients with primary renal disease even in the earliest stage when GFR is not yet subnormal. This change is found only in subjects with HMW apo(a) phenotypes, however.