Independent Effects of Kidney Function and Cholesterol Efflux on Cardiovascular Mortality.

BACKGROUND: Impaired renal function is associated with cardiovascular and all-cause mortality. In the general population, HDL-cholesterol is associated with cardiovascular events, which is not true in patients with chronic kidney disease (CKD). This has been attributed to abnormal HDL function in CKD. METHODS: In this study, we analyzed the association of genetic markers for kidney function with cholesterol efflux capacity as one of the major HDL functions, as well as with cardiovascular mortality, in 2469 patients of the Ludwigshafen Risk and Cardiovascular Health Study who all underwent coronary angiography. RESULTS: A genetic score of 53 SNPs associated with GRF and the uromodulin SNP rs12917707 were inversely correlated with cholesterol efflux capacity. This was in line with the observed association between cholesterol efflux capacity and kidney function in these patients. Adjustment for eGFR and uromodulin as markers of kidney function did not affect the relationship between cholesterol efflux and cardiovascular mortality. CONCLUSIONS: Our data propose the view that cholesterol efflux and kidney function are exerting their effects on cardiovascular mortality via different and independent pathways. Decreased cholesterol efflux may therefore not mediate the effects of impaired kidney function on cardiovascular mortality.

Genome-wide studies reveal factors associated with circulating uromodulin and its relationships to complex diseases.

Uromodulin (UMOD) is a major risk gene for monogenic and complex forms of kidney disease. The encoded kidney-specific protein uromodulin is highly abundant in urine and related to chronic kidney disease, hypertension, and pathogen defense. To gain insights into potential systemic roles, we performed genome-wide screens of circulating uromodulin using complementary antibody-based and aptamer-based assays. We detected 3 and 10 distinct significant loci, respectively. Integration of antibody-based results at the UMOD locus with functional genomics data (RNA-Seq, ATAC-Seq, Hi-C) of primary human kidney tissue highlighted an upstream variant with differential accessibility and transcription in uromodulin-synthesizing kidney cells as underlying the observed cis effect. Shared association patterns with complex traits, including chronic kidney disease and blood pressure, placed the PRKAG2 locus in the same pathway as UMOD. Experimental validation of the third antibody-based locus, B4GALNT2, showed that the p.Cys466Arg variant of the encoded N-acetylgalactosaminyltransferase had a loss-of-function effect leading to higher serum uromodulin levels. Aptamer-based results pointed to enzymes writing glycan marks present on uromodulin and to their receptors in the circulation, suggesting that this assay permits investigating uromodulin's complex glycosylation rather than its quantitative levels. Overall, our study provides insights into circulating uromodulin and its emerging functions.

Combined Use of Serum Uromodulin and eGFR to Estimate Mortality Risk.

Serum uromodulin (sUmod) shows a strong direct correlation with eGFR in patients with impaired kidney function and an inverse association with mortality. However, there are patients in whom only one of both markers is decreased. Therefore, we aimed to investigate the effect of marker discordance on mortality risk. sUmod and eGFR were available in 3,057 participants of the Ludwigshafen Risk and Cardiovascular Health study and 529 participants of the VIVIT study. Both studies are monocentric prospective studies of patients that had been referred for coronary angiography. Participants were categorized into four groups according to the median values of sUmod (LURIC: 146 ng/ml, VIVIT: 156) and eGFR (LURIC: 84 ml/min/1.73 m2, VIVIT: 87). In 945 LURIC participants both markers were high (UHGH), in 935 both were low (ULGL), in 589 only eGFR (UHGL), and in 582 only sUmod (ULGH) was low. After balancing the groups for cardiovascular risk factors, hazard ratios (95%CI) for all-cause mortality as compared to UHGH were 2.03 (1.63-2.52), 1.43 (1.13-1.81), and 1.32 (1.03-1.69) for ULGL, UHGL, and ULGH, respectively. In VIVIT, HRs were 3.12 (1.38-7.08), 2.38 (1.01-5.61), and 2.06 (0.81-5.22). Adding uromodulin to risk prediction models that already included eGFR as a covariate slightly increased the Harrell's C and significantly improved the AUC in LURIC. In UHGL patients, hypertension, heart failure and upregulation of the renin-angiotensin-aldosterone-system seem to be the driving forces of disease development, whereas in ULGH patients metabolic disturbances might be key drivers of increased mortality. In conclusion, SUmod/eGFR subgroups mirror distinct metabolic and clinical patterns. Assessing sUmod additionally to creatinine or cystatin C has the potential to allow a more precise risk modeling and might improve risk stratification.

Urinary tract infections in patients with renal insufficiency and dialysis - epidemiology, pathogenesis, clinical symptoms, diagnosis and treatment.

Epidemiological studies show an increasing number of patients worldwide suffering from chronic kidney diseases (CKD), which are associated with a risk for progression to end-stage kidney disease (ESKD). CKD patients stage 2-5, patients with regular chronic dialysis treatment (hemo- or peritoneal dialysis), and patients suffering from kidney allograft dysfunction are at high risk to develop infections, e.g. urinary tract infections (UTI) and/or sepsis (urosepsis). These groups show metabolic disturbance, chronic inflammation, and impaired immunocompetence. Escherichia coli is still the most common pathogen in UTI. A wide variety of other pathogens may be involved in UTI. Urological interventions, catheterization, as well as repeated courses of antibiotics contribute to an increased challenge of antimicrobial resistance. The diagnosis of UTI in CKD is based on standard clinical and laboratory criteria. Pyuria (≥10 leucocytes/µl) is more often observed in patients with oligoanuria and low bacterial colony counts. The treatment strategies for this population are based on the same principles as in patients with normal renal function. However, drugs cleared by the kidney or by dialysis membranes need dose adjustment. Antimicrobials with potential systemic toxicity and nephrotoxicity should be administered with caution.

Individual uromodulin serum concentration is independent of glomerular filtration rate in healthy kidney donors.

OBJECTIVES: The mucoprotein uromodulin is considered to correlate with glomerular filtration rates (GFR) in patients with chronic kidney disease (CKD). Here we investigated how serum uromodulin is associated with measured GFR using inulin-clearance and GFR estimated by CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equation in healthy subjects. METHODS: We assessed possible correlations between uromodulin serum concentrations, inulin-GFR and CKD-EPI-GFR in a well characterized study cohort of 112 healthy living kidney donors with two kidneys before and 64 with one kidney after kidney donation. A subgroup of 32 individuals, which presented data before and after nephrectomy, was assessed separately. RESULTS: All 112 healthy living kidney donors with two kidneys revealed individual serum uromodulin concentrations between 60.1 and 450.5 µg/L. Sixty-four healthy kidney donors after nephrectomy had significantly lower median (interquartile range) serum uromodulin concentrations (124 [101-166] vs. 185 [152-238] µg/L), inulin-GFR (67.3 [60.6-74.6] vs. 93.5 [82.1-104.4] mL/min/1.73 m2), and CKD-EPI-GFR (61.2 [53.1-69.7] vs. 88.6 [80.0-97.1] mL/min/1.73 m2) as compared to the 112 donors before donation (p<0.001). The subgroup of 32 subjects, which presented data before and after nephrectomy, showed almost the same pattern of kidney function. No statistically relevant associations were found between serum uromodulin and inulin-GFR or CKD-EPI-GFR regarding this healthy population. CONCLUSIONS: These novel findings indicate that - in contrast to patients with CKD - serum uromodulin concentrations are not correlated with measured and estimated GFR in healthy individuals.

Serum uromodulin is inversely associated with arterial hypertension and the vasoconstrictive prohormone CT-proET-1 in the population-based KORA F4 study.

OBJECTIVES: Uromodulin has been associated with arterial hypertension in genome-wide association studies, but data from clinical and preclinical studies are inconsistent. We here analyzed the association of serum uromodulin (sUmod) with arterial hypertension and vasoactive hormones in a population-based study. METHODS: In 1108 participants of the KORA F4 study aged 62-81 years, sUmod was measured and the association of sUmod with arterial hypertension was assessed using logistic regression models. The associations of sUmod with renin and aldosterone and with the vasoconstrictive prohormone C-terminal pro-endothelin-1 (CT-proET-1) were analyzed in 1079 participants and in 618 participants, respectively, using linear regression models. RESULTS: After multivariable adjustment including sex, age, eGFR, BMI, fasting glucose, current smoking, previous stroke and myocardial infarction, sUmod was inversely associated with arterial hypertension (OR 0.78; 95% CI 0.68-0.91; p = 0.001). SUmod was not significantly associated with renin and aldosterone after adjustment for sex, age and eGFR. However, sUmod was inversely associated with CT-proET-1 (ß -0.19 ± 0.04; p < 0.001) after adjustment for sex, age, eGFR, BMI, arterial hypertension, fasting glucose, current smoking, previous stroke and myocardial infarction. The association with CT-proET-1 was stronger in participants with hypertension (ß -0.22 ± 0.04) than in normotensive participants (ß -0.13 ± 0.06; p for interaction hypertension = 0.003 in the model adjusted for hypertension). CONCLUSIONS: SUmod was inversely associated with arterial hypertension and the vasoconstrictive prohormone CT-proET-1, suggesting direct or indirect effects of sUmod on blood pressure regulation.

Association of Serum Uromodulin with Death, Cardiovascular Events, and Kidney Failure in CKD.

BACKGROUND AND OBJECTIVES: Uromodulin is exclusively produced by tubular epithelial cells and released into urine and serum. Higher serum uromodulin has been associated with lower risk for kidney failure in Chinese patients with CKD and with lower risk for mortality in the elderly and in patients undergoing coronary angiography. We hypothesized that lower serum uromodulin is associated with mortality, cardiovascular events, and kidney failure in white patients with CKD. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: We measured serum uromodulin in 5143 participants enrolled in the German CKD (GCKD) study. The associations of baseline serum uromodulin with all-cause mortality, major adverse cardiovascular events (MACE; a composite of cardiovascular mortality, nonfatal myocardial infarction or stroke, or incident peripheral vascular disease), and kidney failure (dialysis or transplantation) were evaluated using multivariable Cox proportional hazard regression analyses in a cohort study design, adjusting for demographics, eGFR, albuminuria, cardiovascular risk factors, and medication. RESULTS: The mean age of participants was 60±12 years, 60% were male. Mean serum uromodulin concentration was 98±60 ng/ml, eGFR was 49±18 ml/min per 1.73 m2, and 78% had eGFR <60 ml/min per 1.73 m2. Participants in lower serum uromodulin quartiles had lower eGFR and higher albuminuria, prevalence of diabetes, hypertension, coronary artery disease, and more frequent history of stroke at baseline. During a follow-up of 4 years, 335 participants died, 417 developed MACE, and 229 developed kidney failure. In multivariable analysis, the highest serum uromodulin quartile was associated with lower hazard for mortality (hazard ratio [HR], 0.57; 95% CI, 0.38 to 0.87), MACE (HR, 0.63; 95% CI, 0.45 to 0.90), and kidney failure (HR, 0.24; 95% CI, 0.10 to 0.55) compared with the lowest quartile. CONCLUSIONS: Higher serum uromodulin is independently associated with lower risk for mortality, cardiovascular events, and kidney failure in white patients with CKD. CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER: Deutsches Register für Klinische Studien (DRKS; German national database of clinical studies), DRKS00003971.

Serum uromodulin and Roux-en-Y gastric bypass: improvement of a marker reflecting nephron mass.

BACKGROUND: Early diagnosis of kidney disease in obese patients and in such patients with type 2 diabetes (T2D) can significantly improve treatment outcome. Serum uromodulin (sUMOD) may be a sensitive parameter for early detection of nephropathy. OBJECTIVES: To analyze sUMOD and traditional markers of kidney function in a cohort study of patients with and without obesity or T2D undergoing metabolic surgery compared with blood donors. SETTING: University of Heidelberg, Germany. METHODS: Patients with obesity (body mass index >35 kg/m2) without T2D (n = 10) and T2D (n = 10) and patients with nonsevere obesity (body mass index, 25-35 kg/m2) and insulin-dependent T2D (n = 16) undergoing Roux-en-Y gastric bypass (RYGB) were enrolled. The control group consisted of 190 blood donors. sUMOD was compared with established renal markers. RESULTS: Using sUMOD, impaired kidney function at baseline was present in both groups with T2D and in none of the patients with obesity without T2D. This impairment was not detectable through traditional markers. Significant improvement of sUMOD was shown in patients with obesity and T2D 12 months postoperatively (from 130.0 ± 77.5 to 239.5 ± 179.0 ng/mL; P = .004) and in patients with nonsevere obesity and T2D 6 months after RYGB (from 140.6 ± 78.0 to 298.7 ± 154.0 ng/mL; P = .017). In patients with obesity without T2D, sUMOD remained stable (P = .375). CONCLUSIONS: sUMOD may serve as a tissue-specific biomarker in incipient diabetic nephropathy. Improvement of sUMOD after RYGB seems to profoundly restore the structural integrity of nephrons in these patients at risk for diabetic nephropathy.

Serum uromodulin-a marker of kidney function and renal parenchymal integrity.

Background: An ELISA to analyse uromodulin in human serum (sUmod) was developed, validated and tested for clinical applications. Methods: We assessed sUmod, a very stable antigen, in controls, patients with chronic kidney disease (CKD) stages 1-5, persons with autoimmune kidney diseases and recipients of a renal allograft by ELISA. Results: Median sUmod in 190 blood donors was 207 ng/mL (women: men, median 230 versus 188 ng/mL, P = 0.006). sUmod levels in 443 children were 193 ng/mL (median). sUmod was correlated with cystatin C (rs = -0.862), creatinine (rs = -0.802), blood urea nitrogen (BUN) (rs = -0.645) and estimated glomerular filtration rate (eGFR)-cystatin C (rs = 0.862). sUmod was lower in systemic lupus erythematosus-nephritis (median 101 ng/mL), phospholipase-A2 receptor- positive glomerulonephritis (median 83 ng/mL) and anti-glomerular basement membrane positive pulmorenal syndromes (median 37 ng/mL). Declining sUmod concentrations paralleled the loss of kidney function in 165 patients with CKD stages 1-5 with prominent changes in sUmod within the 'creatinine blind range' (71-106 µmol/L). Receiver-operating characteristic analysis between non-CKD and CKD-1 was superior for sUmod (AUC 0.90) compared with eGFR (AUC 0.39), cystatin C (AUC 0.39) and creatinine (AUC 0.27). sUmod rapidly recovered from 0 to 62 ng/mL (median) after renal transplantation in cases with immediate graft function and remained low in delayed graft function (21 ng/mL, median; day 5-9: relative risk 1.5-2.9, odds ratio 1.5-6.4). Immunogold labelling disclosed that Umod is transferred within cytoplasmic vesicles to both the apical and basolateral plasma membrane. Umod revealed a disturbed intracellular location in kidney injury. Conclusions: We conclude that sUmod is a novel sensitive kidney-specific biomarker linked to the structural integrity of the distal nephron and to renal function.

Serum Uromodulin and Mortality Risk in Patients Undergoing Coronary Angiography.

The mucoprotein uromodulin is the most abundant protein in mammalian urine and has important roles in ion transport, maintenance of water and electrolyte balance, and clearance of bacteria from the urinary tract. Low urinary uromodulin concentrations have been associated with increased mortality risk. However, measuring uromodulin in urine has several preanalytic drawbacks, and sensitive assays for the detection of uromodulin in blood have become available. In this study, we investigated the association of serum uromodulin concentration with cardiovascular biomarkers and mortality risk in a large cohort of patients referred for coronary angiography. Uromodulin concentrations were available in 3057 of 3316 participants of the Ludwigshafen Risk and Cardiovascular Health Study. Higher serum uromodulin concentration associated with a favorable metabolic profile, lower prevalence rates of comorbidities (arterial hypertension, diabetes mellitus, and heart failure), and a lower risk for 10-year mortality, with hazard ratios (95% confidence intervals) of 0.65 (0.54 to 0.78), 0.71 (0.58 to 0.88), and 0.57 (0.45 to 0.73) in the second, third, and fourth quartiles, respectively, compared with the first quartile. The association with reduced mortality was independent of other cardiovascular risk factors, including eGFR, and stronger after adjustment for the genotype of the rs12917707 polymorphism at the UMOD locus. Adding serum uromodulin concentration to established cardiovascular risk prediction scores improved risk prediction. Uromodulin may, therefore, be a useful marker for cardiovascular and renal health.

Borrelia and nephropathy: cryoglobulinaemic membranoproliferative glomerulonephritis responsive to doxycyclin in active Lyme disease.

The association of membranoproliferative glomerulonephritis (MPGN) with Lyme borreliosis has only been reported for the C1q-negative subtype. A 64-year-old male presenting with rising creatinine, nephrotic syndrome and monoarthritis few months after a tick bite was noted to have mixed cryoglobulinaemia, a positive borrelia western blot and 'full-house' pattern MPGN with interstitial granuloma. Findings resolved with prednisolone and doxycyclin therapy. The histology is consistent with MPGN secondary to cryoglobulinaemia, which has most likely been caused by borrelia infection. 'Full-house' pattern MPGN may result from Lyme borreliosis through cryoglobulinaemia and may be treated successfully with the appropriate antibiotic therapy.

Diagnostic pathways for exclusion and diagnosis of kidney diseases.

In 2006, the German Society for Clinical Chemistry and Laboratory Medicine together with the Society of Nephrology founded a working group with the aim to develop diagnostic pathways for the detection and differentiation of renal diseases. Based on existing recommendations, these pathways may be structured to be a basis for implementation into hospital and laboratory information systems. The present paper describes the contents of these pathways regarding glomerular filtration rate, hematuria, leukocyturia and proteinuria.

Hepatic expression of gamma-glutamyltranspeptidase in the human liver of patients with alcoholic liver disease.

BACKGROUND: Gamma-glutamyltranspeptidase (GGT) has been recognized as an enzyme that converts glutathione into cysteine, and it is localized predominantly within the liver. Serum GGT is clinically recognized as the most useful marker for diagnosis of alcoholic liver disease (ALD). METHODS: GGT localization within the liver was examined immunohistochemically using an anti-GGT antibody and was visualized by confocal laser scanning microscopy in ALD and normal livers. Double immunostaining for GGT and dipeptidylpeptidase-IV (DPP-IV) was carried out to evaluate GGT localization in greater detail. RESULTS: Expression of GGT protein and mRNA was studied with immunoblot analysis and in situ hybridization, respectively. Immunohistochemically, the expression of GGT in the normal liver was faintly demonstrated in the bile canaliculi of hepatocytes and in biliary epithelial cells. In ALD livers, GGT was clearly demonstrated at the same sites. Double immunostaining demonstrated that GGT and DPP-IV were colocalized in hepatocytes in the ALD liver. In situ hybridization clearly demonstrated GGT-mRNA within the cytoplasm of hepatocytes and biliary epithelial cells. Immunoblot analysis revealed that GGT protein expression was increased in the ALD livers compared with that seen in the normal livers. CONCLUSION: These findings indicate that GGT in control and alcoholic livers is synthesized in hepatocytes and biliary epithelial cells, and is localized within the bile canalicular membrane and the luminal membrane in those cells, respectively. In conclusion, GGT synthesis and protein expression are increased in ALD livers, leading to the elevation of serum levels of GGT that are commonly noted in patients with the disease.

Influence of low molecular weight heparin compared to conventional heparin for anticoagulation during haemodialysis on low density lipoprotein subclasses.

BACKGROUND: In haemodialysis (HD) patients, low density lipoprotein (LDL) particle distribution is characterized by a higher proportion of more atherogenic dense LDL. Though clinical studies showed favourable effects of low molecular weight (LMW) heparin compared to standard heparin on triglycerides (TG) and cholesterol (CH) in HD patients with hypertriglyceridaemia, it is not known if LMW heparin influences LDL subfraction pattern. Thus, the aim of this pilot study was to investigate if a switch to LMW heparin influences LDL subfractions and apolipoproteins. METHODS: Ten outpatients with fasting TG >230 mg/dl in the chronic HD programme on heparin for anticoagulation (AC) were switched to dalteparin (80 IU/kg body weight as a bolus). Blood samples were drawn for CH, TG, LDL-CH, HDL-CH, apolipoproteins (apo), very low density lipoproteins (VLDL), intermediate density lipoproteins (IDL), and LDL subclasses at the beginning and after 12 months of therapy. Lipoproteins were isolated by preparative ultracentrifugation. Total LDL were fractionated into six density classes by equilibrium density gradient ultracentrifugation [(density in kg/l): LDL-1 1.019-1.031, LDL-2 1.031-1.034, LDL-3 1.034-1.037, LDL-4 1.037-1.040, LDL-5 1.040-1.044, LDL-6 1.045-1.063]. CH and TG were determined enzymatically, apolipoproteins by turbidimetry. RESULTS: In eight patients suitable for evaluation cholesterol decreased from 241 to 202 (P<0.05) and TG from 557 to 278 mg/dl (P<0.01), whereas LDL-CH and HDL-CH did not change significantly. A 28.2% decrease of VLDL (P<0.01) and a 19.3% decrease of IDL (P<0.05) paralleled by a significant drop of apoB were observed. Buoyant LDL subclasses increased (LDL-2, +34.3% and LDL-3, +20.3%) whereas dense LDL (LDL-5, -13.4% and LDL-6, -33.1%) decreased (P<0.05 for LDL-6). The ratio of buoyant LDL to dense LDL increased from 0.46+/-0.28 to 0.72+/-0.33 (P<0.05). CONCLUSION: In hypertriglyceridaemic HD patients, dalteparin improved metabolism of TG-rich lipoproteins, increased buoyant LDL and decreased potentially atherogenic dense LDL. Preservation of lipoprotein lipase by LMW heparin may be a possible mechanism to explain our findings.

A shift in the Th(1)/Th(2) ratio accompanies the clinical remission of systemic lupus erythematosus in patients with end-stage renal disease.

BACKGROUND: Patients suffering from systemic lupus erythematosus (SLE) with renal involvement often show remission of systemic clinical activity after progression to end-stage renal disease (ESRD). SLE is characterized by predominantly humoral, T-helper (Th)(2)-mediated autoimmune responses. Since ESRD induces a state of immunodeficiency that affects the balance of Th cell subsets, we hypothesized that a Th(1) shift induced by ESRD leads to clinical remission of SLE. METHODS: Using single-cell measurement of intracellular cytokines by flow cytometry after polyclonal stimulation with PMA/ionomycin, helper cell profiles were analysed in SLE patients with preserved renal function and in SLE patients with ESRD, from both isolated peripheral blood mononuclear cells (PBMC) and whole blood. RESULTS: Using the whole-blood assay, patients with SLE and preserved renal function showed a predominance of Th(2) cells compared to healthy controls (patients, Th(1)/Th(2) ratio 6.0+/-1.0 vs controls, 9.0+/-1.0; P<0.05). In contrast, SLE patients with ESRD have significantly more Th(1) cells (36.8+/-5.0%) than those without ESRD (23.4+/-3.6%; P<0.05). This results in an enhancement of the Th(1)/Th(2) ratio to 12.1+/-2.6, which is not significantly different from healthy controls. These data were confirmed using a PBMC-based assay. CONCLUSIONS: SLE patients with preserved renal function show a bias in the differentiation of Th cells towards Th(2). Once ESRD occurs, the Th(1)/Th(2) ratio normalizes. This may contribute to the remission of Th(2)-mediated autoimmune diseases such as SLE.