Understanding glomerular diseases through proteomics.

INTRODUCTION: Chronic kidney disease is avery common and complex chronic disease. Uncovering the pathological patterns of CKD on the molecular level of bio-fluids and tissue appears to be both vital and promising for a more favorable outcome. We reviewed recently discovered proteomics biomarkers for CKD to provide new insight into disease pathology. AREAS COVERED: We review the application of proteome analysis in the context of CKD with various etiologies within the last 5 years. Proteins and peptides associated with CKD as derived from multiple sources (urine, blood and tissue) are reported along with their various biological pathways. EXPERT OPINION: A systematic and theoretical comprehension of the CKD pathology is essential for its successful management. The underlying complexity of the disease further requires specific conditions for reliable and interpretable results. In this context, clinical proteomics has resulted in first encouraging findings in CKD. A more complete understanding of the biological pathways related to the disease, based on the scope of a holistic proteomic approach, could improve substantially the management of CKD, especially when in conjunction with the current trend of personalized medicine.

[Early detection by urinary proteome analysis : A new concept in patient management of diabetic nephropathy]. / Früherkennung mittels Urinproteomanalyse : Ein neues Konzept im Patientenmanagement der diabetischen Nephropathie.

BACKGROUND: The early detection and treatment of diabetic nephropathy (DN) is of crucial importance as patients with diabetes mellitus represent the largest proportion of patients on dialysis, with the highest morbidity and mortality. Currently, the first clinical sign of incipient DN is microalbuminuria, but its precision is not optimal. Many studies now report that proteins and peptides are new biomarkers in urine that primarily depict the pathophysiology of DN and thus allow for improved diagnosis of DN. OBJECTIVES: The presentation of new concepts for the early detection and treatment of DN for better patient management. MATERIAL AND METHODS: A systematic literature search was carried out. RESULTS: Many potential markers have been described in the search for new biomarkers to diagnose DN by urinary proteome analysis. However, many of these studies were not meaningful due to the small number of samples. This limitation led to inadequate validation of proteins that could not be confirmed as markers. However, the diagnostic benefit of CKD 273, a multimarker of 273 protein fragments, was sustainably demonstrated for the early diagnosis of DN. This multi-marker shows significant advantages in the precision of diagnosis and prognosis compared to albuminuria. Furthermore, many of its peptide markers map the molecular pathophysiology of DN. CONCLUSIONS: Clinical urinary proteome analysis shows great benefits and is already an appropriate tool for the early detection of incipient DN.

Characteristics of high- and low-risk individuals in the PRIORITY study: urinary proteomics and mineralocorticoid receptor antagonism for prevention of diabetic nephropathy in Type 2 diabetes.

AIM: To compare clinical baseline data in individuals with Type 2 diabetes and normoalbuminuria, who are at high or low risk of diabetic kidney disease based on the urinary proteomics classifier CKD273. METHODS: We conducted a prospective, randomized, double-blind, placebo-controlled international multicentre clinical trial and observational study in participants with Type 2 diabetes and normoalbuminuria, stratified into high- or low-risk groups based on CKD273 score. Clinical baseline data for the whole cohort and stratified by risk groups are reported. The associations between CKD273 and traditional risk factors for diabetic kidney disease were evaluated using univariate and logistic regression analysis. RESULTS: A total of 1777 participants from 15 centres were included, with 12.3% of these having a high-risk proteomic pattern. Participants in the high-risk group (n=218), were more likely to be men, were older, had longer diabetes duration, a lower estimated GFR and a higher urinary albumin:creatinine ratio than those in the low-risk group (n=1559, P<0.02). Numerical differences were small and univariate regression analyses showed weak associations (R2 < 0.04) of CKD273 with each baseline variable. In a logistic regression model including clinical variables known to be associated with diabetic kidney disease, estimated GFR, gender, log urinary albumin:creatinine ratio and use of renin-angiotensin system-blocking agents remained significant determinants of the CKD273 high-risk group: area under the curve 0.72 (95% CI 0.68-0.75; P<0.01). CONCLUSIONS: In this population of individuals with Type 2 diabetes and normoalbuminuria, traditional diabetic kidney disease risk factors differed slightly between participants at high risk and those at low risk of diabetic kidney disease, based on CKD273. These data suggest that CKD273 may provide additional prognostic information over and above the variables routinely available in the clinic. Testing the added value will be subject to our ongoing study. (European Union Clinical Trials Register: EudraCT 2012-000452-34 and Clinicaltrials.gov: NCT02040441).

Effect of UMOD genotype on long-term graft survival after kidney transplantation in patients treated with cyclosporine-based therapy.

The genetic rs12917707-G>T variant in uromodulin (UMOD) has been associated with renal function, chronic kidney disease and hypertension with the minor T-allele showing a protective effect. Hypertension and nephrotoxicity are adverse effects of chronic cyclosporine treatment. We tested whether UMOD rs12917707-T in donor kidneys associates with long-term graft survival in 393 Caucasian patients with stable graft function for more than 10 weeks after kidney transplantation treated with a cyclosporine-based maintenance therapy (mean graft survival 9 years). Presence of the donor T-allele had no effect on blood pressure, serum creatinine 1 year after transplantation, and on number of acute graft rejections during the first year. No significant effect on overall graft survival was observed in Kaplan-Meier analysis (P=0.65). In death-censored adjusted multivariate analysis, presence of donor T-allele associated with a significant lower hazard ratio of 0.67 (95% confidence interval: 0.46-0.97, P=0.05) for graft loss. This protective effect of the donor T-allele on graft loss observed in multivariate adjusted analysis justifies further investigations including patients treated with similar or other immunosuppressive regimens.

[Baroreceptor activation therapy for therapy-resistant hypertension: indications and patient selection : Recommendations of the BAT consensus group 2017]. / Barorezeptorakivierungstherapie bei therapierefraktärer Hypertonie: Indikation und Patientenselektion : Empfehlungen der BAT-Konsensusgruppe 2017.

Baroreceptor activation therapy (BAT) has been available for several years for treatment of therapy-refractory hypertension (trHTN). This procedure is currently being carried out in a limited number of centers in Germany, also with the aim of offering a high level of expertise through sufficient experience; however, a growing number of patients who are treated with BAT experience problems that treating physicians are confronted with in routine medical practice. In order to address these problems, a consensus conference was held with experts in the field of trHTN in November 2016, which summarizes the current evidence and experience as well as the problem areas in handling BAT patients.

Circulating adipocyte fatty acid binding protein is increased in chronic and acute renal dysfunction.

BACKGROUND AND AIMS: The adipokine adipocyte fatty acid binding protein (AFABP) is positively associated with the development of the metabolic syndrome, diabetes mellitus, and cardiovascular disease. We hypothesized that AFABP also increases with deteriorating renal function. METHODS AND RESULTS: Serum AFABP levels were quantified by enzyme linked immunosorbent assay in 532 patients with chronic kidney disease (CKD) covering the whole spectrum of estimated glomerular filtration rate (eGFR) categories from G1 to G5 (study population 1). Furthermore, AFABP was measured in 32 patients before and within 30 h after elective unilateral nephrectomy, a model of acute kidney dysfunction (AKD) (study population 2). Moreover, circulating AFABP was investigated in rats undergoing bilateral nephrectomy (BNE) as compared to sham-operated animals. Median serum AFABP levels adjusted for age, gender, and body mass index significantly increased with increasing eGFR category (G1: 22.0 µg/l; G2: 34.6 µg/l; G3: 56.7 µg/l; G4: 95.2 µg/l; and G5: 173.9 µg/l). Furthermore, renal dysfunction remained positively associated with AFABP in multivariate analysis in this cohort. In patients undergoing unilateral nephrectomy, AFABP increased significantly after surgery (42.1 µg/l) as compared to pre-surgical values (29.3 µg/l). Furthermore, relative changes of post-to-pre-surgical AFABP levels were independently associated with relative changes of post-to-pre-surgical creatinine concentrations. After BNE in rats, AFABP increased significantly as compared to sham-operated animals. CONCLUSIONS: We show that AFABP is significantly elevated in CKD and AKD patients. Furthermore, measures of renal function are associated with circulating AFABP. Moreover, animal experiments indicate that AFABP levels strongly depend on renal function.

Lack of evidence for systemic cytomegalovirus reactivation in maintenance hemodialysis patients.

The risk of cytomegalovirus (CMV) reactivation among hemodialysis (HD) patients is unknown. In 52 HD patients from a single center, CMV serology and quantitative PCR were performed. The detection limit of PCR was 20 copies/ml. Here, PCR ruled out CMV viremia, despite CMV-IgM seropositivity in 15.4% patients.

CYP3A5 genotype is associated with longer patient survival after kidney transplantation and long-term treatment with cyclosporine.

The CYP3A5*1 allele has been linked to high expression of CYP3A5 and metabolism of cyclosporine. We evaluated the role of CYP3A5*1 for long-term survival in renal transplant patients in a cohort of 399 patients who underwent cadaveric or living donor kidney allograft transplantation. All patients were treated with a similar cyclosporine-based immunosuppressive maintenance therapy protocol. The mean duration of follow-up was 8.6+/-3.7 years. In univariate survival analysis, the presence of the CYP3A5*1 allele in recipients significantly increased patient survival P=0.028 (log-rank), resulting in a hazard ratio (HR) of 0.52 (95% CI=0.29-0.94). When the presence of the CYP3A5*1 allele was included in multivariate Cox regression analyses accounting for major risk factors for patient death, CYP3A5*1 still conferred a protective effect. Further, haplotype analysis at the CYP3A5 locus confirmed that CYP3A5*1 might indeed be responsible for this survival benefit.

[Acute renal failure: pathophysiology and clinical management]. / Akutes Nierenversagen: Pathophysiologie und klinisches Management.

The main pathomechanism of acute renal failure (ARF) is acute tubular necrosis (ATN) due to reduced perfusion of renal cortex resulting in ischemic injury. ATN has the potential for complete restitution. However, acute renal failure is often complicated by pre-existing renal disease, ongoing toxic injury or non-recovery of systemic circulation. From a clinical point of view, the reason of tubular injury may be based on pre-renal causes, glomerular- and/or interstitial disorders or obstructive nephropathy. Therapy must be specifically targeted on the underlying causes to overcome ARF. If kidney function is not reconstituted in an appropriate time period, renal replacement therapy has to be initiated. Recent evidence for improved patient survival supports an augmented dialysis dose to achieve a maximum of metabolic, volume and electrolyte control. To reach these goals, daily intermittent or continuous forms of hemodialysis or hemofiltration are appropriate measures.

[Hyperparathyroidism--new aspects]. / Neue Aspekte bei Hyperparathyreoidismus.

Hyperparathyroidism is generally classified into a primary and secondary form. The primary form is caused by an autonomous adenomatous hypertrophy and/or hyperplasia of parythyroideal glands without known cause in most of the patients. Resulting elevated levels of parathyroid hormone cause elevation of serum calcium, subsequently followed by cerebral symptoms, fatigue and calcinosis of vessels and kidneys. The mainstay of secondary HPT is the initial vitamin D deficiency such as associated with kidney failure. Via an increased PTH secretion, calcium homeostasis will be maintained together with ongoing hyperplasia of the parathyroidea. Therapeutic approaches are related to pathophysiological mechanisms. While surgical removal of adenomatous glands is the mainstay of therapy in primary and late secondary forms, during the still regulated initial period of secondary HPT supplementation of vitamin D and/or sensitation of parathyroideal Calcium-sensing-receptors are therapy of choice.

[Polyuria]. / Polyurie--Pathogenese, Diagnostik und Therapie.

Beyond polyuria following psychogenic polydipsia, in a more narrow sense, this condition may be classified into impaired water re-absorption (i) due to tubular injury or (ii) relative or absolute loss of function of antidiuretic hormone (ADH). Tubular injury may be caused by different toxins affecting the ascending Henle loop as hypercalciuria, drugs and antibiotics as tubular necrosis. ADH deficiency, either absolute or relative, occurs with central or peripheral diabetes insipidus, which is based on synthesis failure or loss of peripheral efficacy of ADH due to receptor malfunction. Diagnosis of polyuria rests upon a thirst challenge in conjunction with laboratory studies of osmolality in serum and urine, which discloses the non-function of the hypothalamic-renal axis. Administration of ADH may differentiate between central and peripheral diabetes insipidus.

Tacrolimus in steroid-resistant and steroid-dependent nephrotic syndrome.

BACKGROUND: Steroid resistance and steroid dependence constitute a major problem in the treatment of minimal-change disease and focal segmental glomerulosclerosis (FSGS). Cyclophosphamide and cyclosporine are well-established alternative immunomodulating agents, whereas data on FK 506 (tacrolimus) are rare. METHODS: The present work provides data from 10 patients of an open, monocentric, non-randomized, prospective trial. Five patients with steroid-dependent minimal-change nephrotic syndrome, 1 patient with steroid-refractory minimal-change disease and 4 patients with steroid-refractory FSGS were started on tacrolimus at trough levels of 5 10 microg/l. In case of steroid-dependence, prednisolone was tapered off in presence oftacrolimus within one month. RESULTS: Within 6 months, complete remission was achieved in 5 patients (50%) and partial remission in 4 patients (40%), yielding a final response rate of 90%. One patient was primarily resistent to tacrolimus (steroid-refractory minimal-change), another patient became secondarily resistant to tacrolimus after an initial remission (steroid-refractory FSGS). Average proteinuria significantly decreased by 77% from 9.5 +/- 1.4 - 2.2 +/- 1.1 g/day (p < 0.01). Serum protein significantly raised from 55.0 +/- 1.9 - 64.6 +/- 1.9 g/l (p < 0.01). Tacrolimus induced non-significant increases of blood glucose (4.9 +/- 0.1 - 5.1 +/- 0.2 mmol/l), systolic blood pressure (131.4 +/- 7.1 - 139.0 +/- 7.6 mmHg) and creatinine (93.2 +/- 13.9 103.2 +/- 15.3 mmol/l). Five patients have been tapered off tacrolimus so far, nephrotic syndrome relapsed in 4 of them (80%). Relapse occurred at tacrolimus levels between 2.6 and 6.9 ng/ml. CONCLUSIONS: Our data suggest that tacrolimus may be a promising alternative to cyclosporine both in steroid-resistant and steroid-dependent nephrotic syndrome.

G-protein beta(3)-subunit C825T genotype and nephropathy in diabetes mellitus.

BACKGROUND: Recent studies have identified a novel polymorphism (C825T) of the gene encoding the beta(3) subunit of heterotrimeric G proteins (G:beta(3)) which is associated with enhanced activation of G-proteins and appears to be more common in hypertensive patients and possibly contributes to decreased kidney allograft survival. METHODS: In the present study we examined the relationship between this genetic variant, type 1 and type 2 diabetes and renal complications of diabetes in 1008 Caucasian patients recruited from an outpatient diabetes clinic and four dialysis centres. We also studied 1940 healthy controls. RESULTS: After multivariate adjustment and in univariate statistics, the G:beta(3) 825TT genotype was not associated with a significantly enhanced risk of diabetes or renal complications. CONCLUSIONS: These findings indicate that the G:beta(3) 825T allele apparently does not contribute to the development of diabetes or associated renal complications in patients with type 1 or type 2 diabetes mellitus.

Computational analysis of blood volume curves and risk of intradialytic morbid events in hemodialysis.

BACKGROUND: Blood volume (BV) curves have been used to prevent intradialytic morbid events (IMEs) caused by hypotensive episodes in hemodialysis treatment. However, no standardized parameter is available to describe BV dynamics and to enable online interference with ultrafiltration rates in unselected patients. Moreover, only time-dependent BV reduction and absolute hematocrit threshold, but not BV variability, have been suggested as markers of pending hypotension. The present study therefore deals with a computer-aided analysis of indices characterizing both BV reduction per time and BV variability in treatments of nonselected maintenance hemodialysis patients. METHODS: The methodology uses indices obtained by mathematical analysis of BV curves and was designed to potentially enable automatic interference with ultrafiltration. RESULTS: In 46 out of 380 treatments (12.1%), IMEs occurred. In these treatments, the indices for long- and short-term variability and slope of the curves were significantly lower than in treatments without IMEs. Moreover, the last 10 minutes before an IME were characterized by additionally decreased variability and slope. In a risk analysis of long-term variability and IMEs, we established an index below 16 to be associated with the highest risk of IMEs. CONCLUSIONS: Using these kind of index thresholds and online analysis of BV curves, automatic management of ultrafiltration by BV dynamics could be a promising concept to avoid intradialytic morbidity.

G-protein beta3 subunit 825T allele and response to dietary salt in normotensive men.

BACKGROUND AND AIMS: A functional single-nucleotide variant of the gene encoding the beta3 subunit of heterotrimeric G proteins (Gbeta3 C825T), associated with enhanced G-protein activation and increased activity of the sodium-proton exchanger (NHE1), has been implicated in the development of hypertension. Given the possible involvement of NHE1 in sodium homeostasis, we tested the hypothesis that the Gbeta3 825T allele determines the response of the renin-angiotensin system and blood pressure to dietary salt restriction. METHODS: Young normotensive men (20-30 years old, n = 193) were recruited within the framework of the Berlin Salt-Sensitivity Trial and studied on low- (20 mmol/day) and high-salt (220 mmol/day) dietary protocols. Subjects were characterized for parameters of the renin-angiotensin system and blood pressure response and genotyped for the Gbeta3 C825T polymorphism. RESULTS: The genotype distribution was in Hardy-Weinberg equilibrium (CC = 90, CT = 81 and TT = 22). The responses of the renin-angiotensin system and blood pressure to the dietary protocol were virtually identical between the genotypic groups. Furthermore, when subjects were classified as salt-resistant (n = 145) or salt-sensitive (n = 48), genotype distribution was comparable between the two groups (salt-resistant: TT = 17, CT = 60, CC = 68, qT = 0.32; salt-sensitive: TT = 5, CT = 21, CC = 22, qT = 0.32). CONCLUSION: These findings do not support the hypothesis that the Gbeta3 C825T polymorphism determines the response of the renin-angiotensin system to salt depletion or can serve as an early genetic marker of salt sensitivity in young normotensive men.

Aldosterone synthase gene (CYP11B2) C-344T polymorphism in Caucasians from the Berlin Salt-Sensitivity Trial (BeSST).

OBJECTIVE: Aldosterone synthase (CYP11B2) is a key enzyme in the biosynthesis of aldosterone. Recently, the T allele of a polymorphism in the 5'-flanking region of the CYP11B2 gene (C-344T) has been reported to be more frequent in hypertensives than in normotensives, and has also been associated with increased plasma aldosterone levels. We therefore hypothesized that this variant may be related to increased blood-pressure response to dietary salt intake. SUBJECTS AND METHODS: We genotyped 1 63 young normotensive men recruited within the framework of the Berlin Salt-Sensitivity Trial (BeSST) for the CYP11B2 C-344T polymorphism. Subjects were characterized for family history of hypertension, plasma parameters of the renin-angiotensin-aldosterone system and blood-pressure response to a high (220 mmol/day) and low (20 mmol/day) salt diet RESULTS: The frequency of the -344T allele (0.45) was similar to that reported previously and genotype distribution was in Hardy-Weinberg equilibrium (CC, n = 55; CT, n = 71; TT, n = 37). There was a trend towards a higher frequency of the T allele in subjects with a positive family history of hypertension (0.48 versus 0.42), but the C-344T genotype was not related to blood pressure under either diet Furthermore, when subjects were classified into salt-sensitive and salt-resistant groups, allelic distribution did not differ between the two groups (qT = 0.43 versus qT = 0.45). While renin activity and plasma aldosterone levels were not related to genotype, plasma angiotensinogen was significantly higher in T-allele carriers under both the high (P = 0.02) and low (P = 0.008) salt diet. CONCLUSION: Our findings do not support the hypothesis that the C-344T polymorphism of the CYP11B2 gene is associated with salt sensitivity or increased activity of the renin-angiotensin system in young normotensive subjects. It is, therefore, unlikely that the C-344T polymorphism is a genetic marker for salt sensitivity in young normotensive Caucasian men.

Donor G protein beta3 subunit 825TT genotype is associated with reduced kidney allograft survival.

Recent studies have identified a novel polymorphism (C825T) of the gene encoding the beta3 subunit of heterotrimeric G proteins (Gbeta3), associated with enhanced activation of G proteins, which appears to be more common in hypertensive patients. In the present study, the relationship between this genetic variant and kidney allograft survival was examined over the first 3 yr after transplantation, in 320 consecutive Caucasian patients recruited from the Berlin-Steglitz transplantation center between 1988 and 1993. Clinical parameters, transplantation data, and details of graft survival were retrieved from clinical records. After multivariate adjustment for covariates (Cox hazard regression), the Gbeta3 825TT donor-genotype was associated with a significantly decreased graft survival representing a relative risk of graft loss of 2.2 (95% confidence interval, 1.1 to 4.8) compared to TC and CC grafts within the observation period. This association between donor TT genotype and graft survival remained stable even after stepwise exclusion of covariates from the multivariate model. In contrast, there was no significant relationship between recipient genotype and allograft function. These findings indicate that individuals receiving renal allografts from donors homozygous for the Gbeta3-825T allele may have an increased risk of developing allograft failure. Additional studies on the role of this genetic marker as well as the role of pertussis toxin-sensitive G proteins in the development of chronic rejection appear warranted.

Angiotensinogen M235T variant and salt sensitivity in young normotensive Caucasians.

BACKGROUND AND AIMS: A single-nucleotide variant of the angiotensinogen gene (AGT 235T) has been associated with essential hypertension and increased plasma levels of angiotensinogen. This variant may also serve as a genetic marker for the increased blood pressure response to dietary salt intake, but the relationship between AGT genotype and salt sensitivity has not been studied until now. We therefore examined the relationship between the AGT 235T genotype and the blood pressure response to short-term dietary salt restriction in young normotensive men. SUBJECTS AND METHODS: A total of 187 young normotensive men were characterized for family history of hypertension, salt sensitivity, plasma parameters of the renin-angiotensin system under high- and low-salt diets, and the AGT 235T genotype. RESULTS: While the T allele was significantly associated with a positive family history of hypertension (chi2 = 7.0; P< 0.03) and higher plasma angiotensinogen levels (P< 0.015) and renin activity (P < 0.037), blood pressure under both diets was not significantly affected by the AGT genotype. When the subjects were classified into salt-resistant and salt-sensitive groups, genotypic distribution was nearly identical between both groups (frequency of T allele: 0.45 versus 0.46). CONCLUSION: Our findings demonstrate that the AGT 235T allele is significantly associated with a positive family history of hypertension, but is not an important determinant of the blood pressure response to dietary salt intake in young normotensive subjects. It is therefore unlikely that the AGT 235T genotype can serve as an early genetic marker of salt sensitivity.