Urinary protein excretion rate is the best independent predictor of ESRF in non-diabetic proteinuric chronic nephropathies. "Gruppo Italiano di Studi Epidemiologici in Nefrologia" (GISEN)

Reaccumulation of globotriaosylceramide in podocytes after agalsidase dose reduction in young Fabry patients

Background

Agalsidase-α 0.2 mg/kg every other week (eow) and agalsidase-β 1.0 mg/kg/eow are licensed in Europe as equipotent treatment of the α-galactosidase deficiency in Fabry disease. This case series describes the effects of agalsidase dose adjustments in serial kidney biopsies in switch patients.

Methods

All treatment-naïve patients with classical Fabry disease in our centre started on agalsidase-β 1.0 mg/kg/eow and subsequently switched to agalsidase-α 0.2 mg/kg/eow were included ( n = 3). The median age at enzyme replacement therapy start was 11 (range 7-18) years. Kidney biopsies were performed at baseline, after 5 years of agalsidase-β 1.0 mg/kg/eow and after 3 subsequent years of agalsidase-α 0.2 mg/kg/eow. One patient was re-biopsied 2 years after reswitch to agalsidase-β 1.0 mg/kg/eow. The scoring system of the International Scoring Group of Fabry Nephropathy was used.

Results

The patients completely cleared globotriaosylceramide (GL3) from mesangial and endothelial cells and partly cleared podocytes on agalsidase-β 1.0 mg/kg/eow. Reaccumulation of GL3 in podocytes, but not in the mesangium or endothelium, occurred after 3 years of agalsidase-α 0.2 mg/kg/eow. Subsequent reduction of podocyte GL3 was observed in the single patient rebiopsied 2 years after reswitch to agalsidase-β 1.0 mg/kg/eow.

Conclusion

Partial clearance, reaccumulation and renewed partial clearance of podocyte GL3 deposits in serial kidney biopsies over 8-10 years were seen in parallel with agalsidase dose adjustments. Repeated kidney biopsies may impact therapeutic choices in Fabry disease.

Changes in Albuminuria and Subsequent Risk of Incident Kidney Disease

BACKGROUND AND OBJECTIVES

Albuminuria is a robust predictor of CKD progression. However, little is known about the associations of changes in albuminuria with the risk of kidney events outside the settings of clinical trials.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In a nationwide cohort of 56,946 United States veterans with an eGFR≥60 ml/min per 1.73 m2, we examined the associations of 1-year fold changes in albuminuria with subsequent incident CKD (>25% decrease in eGFR reaching <60 ml/min per 1.73 m2) and rapid eGFR decline (eGFR slope <-5 ml/min per 1.73 m2 per year) assessed using Cox models and logistic regression, respectively, with adjustment for confounders.

RESULTS

The mean age was 64 (SD, 10) years old; 97% were men, and 91% were diabetic. There was a nearly linear association between 1-year fold changes in albuminuria and incident CKD. The multivariable-adjusted hazard ratios (95% confidence intervals) of incident CKD associated with more than twofold decrease, 1.25- to twofold decrease, 1.25- to twofold increase, and more than twofold increase (versus <1.25-fold decrease to <1.25-fold increase) in albuminuria were 0.82 (95% confidence interval, 0.77 to 0.89), 0.93 (95% confidence interval, 0.86 to 1.00), 1.12 (95% confidence interval, 1.05 to 1.20), and 1.29 (95% confidence interval, 1.21 to 1.38), respectively. Qualitatively similar associations were present for rapid eGFR decline (adjusted odds ratios; 95% confidence intervals for corresponding albuminuria changes: adjusted odds ratio, 0.86; 95% confidence interval, 0.78 to 0.94; adjusted odds ratio, 0.98; 95% confidence interval, 0.89 to 1.07; adjusted odds ratio, 1.18; 95% confidence interval, 1.08 to 1.29; and adjusted odds ratio, 1.67; 95% confidence interval, 1.54 and 1.81, respectively).

CONCLUSIONS

Relative changes in albuminuria over a 1-year interval were linearly associated with subsequent risk of kidney outcomes. Additional studies are warranted to elucidate the underlying mechanisms of the observed associations and test whether active interventions to lower elevated albuminuria can improve kidney outcomes.

Rare Renal Diseases Can Be Used as Tools to Investigate Common Kidney Disorders

BACKGROUND

The prevention and slowing of chronic kidney disease still represent major challenges in nephrology. To this end, a major contribution may come from the extensive knowledge on the molecular pathways involved in the pathogenesis of rare kidney diseases, since it is now possible to shed light on several aspects of these pathologies thanks to the introduction of new technologies, including next-generation sequencing.

SUMMARY

In steroid-resistant nephrotic patients, a genetic background has been demonstrated in both children and adults; individualized mutations have been correlated with glomerular filtration barrier alterations. In addition, studies on genetic tubulopathies expressing hypertensive phenotypes can provide useful information for a correct diagnostic and therapeutic approach in patients with essential hypertension and a poor responsiveness to therapy.

KEY MESSAGE

This review deals with the pathogenesis of rare glomerular diseases and tubulopathies associated with hypertension, highlighting the importance of the study of rare diseases to better understand the molecular basis of more common and complex disorders leading to end-stage renal disease.

Case Report of Spontaneous Remission of Biopsy-Proven Idiopathic Immune Complex-Mediated Membranoproliferative Glomerulonephritis

Membranoproliferative glomerulonephritis (MPGN) is a histopathologic diagnosis causing microscopic hematuria, nephrotic range proteinuria, and chronic renal failure. Current understanding divides pathogenesis into two broad categories: immune complex mediated and complement mediated (now termed C3 glomerulopathy). The term idiopathic immune complex-mediated MPGN would apply to a patient without an identifiable source of immune complex production and no evidence of C3 glomerulopathy. Presented is a patient with idiopathic immune complex mediated MPGN and her clinical course. The patient opted for conservative therapy with losartan, carvedilol, chlorthalidone, and atorvastatin. Nephrotic range proteinuria of 8.7 g per day resolved over 5 months, with improvement of serum from 3.3 to 1.2 mg/dL. Remission continues at follow-up 21 months after biopsy. For idiopathic immune complex-mediated MPGN, resorting to empiric immunosuppression therapy may not be the best option. As this patient demonstrates, a conservative approach of blood pressure control with anti-renin-angiotensin agents, control of lipids, and watchful follow-up can be successful.

Endoplasmic reticulum stress inhibition attenuates hypertensive chronic kidney disease through reduction in proteinuria

Endoplasmic reticulum (ER) stress is implicated in chronic kidney disease (CKD) development in patients and in animal models. Here we show that ER stress inhibition through 4-phenylbutyric acid (4-PBA) administration decreases blood pressure, albuminuria, and tubular casts in an angiotensin II/deoxycorticosterone acetate/salt murine model of CKD. Lower albuminuria in 4-PBA-treated mice was associated with higher levels of cubilin protein in renal tissue membrane fractions. 4-PBA decreased renal interstitial fibrosis, renal CD3⁺ T-cell and macrophage infiltration, mRNA expression of TGFβ1, Wnt signaling molecules, and ER stress-induced pro-inflammatory genes. CHOP deficient mice that underwent this model of CKD developed hypertension comparable to wild type mice, but had less albuminuria and tubular casts. CHOP deficiency resulted in higher nephrin levels and decreased glomerulosclerosis compared to wild type mice; this effect was accompanied by lower macrophage infiltration and fibrosis. Our findings portray ER stress inhibition as a means to alleviate hypertensive CKD by preserving glomerular barrier integrity and tubular function. These results demonstrate ER stress modulation as a novel target for preserving renal function in hypertensive CKD.

Life expectancy with chronic kidney disease: an educational review

Can renal prognosis and life expectancy be accurately predicted? Increasingly, the answer is yes. The natural history of different forms of renal disease is becoming clearer; the degree of reduction in glomerular filtration rate (GFR) and the magnitude of proteinuria are strong predictors of renal outcome. Actuarial data on life expectancy from the start of renal replacement therapy are available from renal registries such as the U.S. Renal Data System (USRDS), and the UK Renal Registry. Recently, similar data have become available for patients with chronic kidney disease. Data collected from a large population-based registry in Alberta, Canada and stratified for different levels of estimated GFR (eGFR) have shown that the reduction in life expectancy with kidney failure is not a uremic event associated with starting dialysis but a continuous process that is evident from an eGFR of ≤60 ml/min. Nevertheless, despite the poor prognosis of the last stages of renal failure, progress in the treatment and management of these patients and, in particular, of their cardiovascular risk factors continues to improve long-term outcome.

The Association of Vitamin D With Estimated Glomerular Filtration Rate and Albuminuria: 5th Korean National Health and Nutritional Examination Survey 2011-2012

OBJECTIVES

The kidney plays a key role in the metabolism of vitamin D. However, the relationship between GFR and 25(OH)D is not well understood. Moreover, few studies have investigated the effect of albuminuria, a known mediator of kidney function, on vitamin D levels. Our aim was to investigate the associations among estimated GFR (eGFR), albumin-creatinine ratio (ACR), and 25(OH)D.

METHODS

We investigated the relationship of 25-hydroxyvitamin D (25[OH]D) with eGFR and albuminuria in 11,336 adults who participated in the 5th Korea National Health and Nutrition Examination Survey (KNHANES) 2011-2012. The eGFR, ACR, and serum 25(OH)D were measured in participants who met the detailed inclusion criteria.

RESULTS

We found that after adjusting for covariates and log-ACR values, the mean (95% CI) eGFR decreased significantly with increasing 25(OH)D levels (Q1: 93.4 [92.7-94.0]; Q2: 91.9 [91.2-92.5]; Q3: 90.9 [90.3-91.6]; and Q4: 90.2 [89.5-90.8] mL/min/1.73m²; P < .001). However, the mean 25(OH)D value was highest at eGFR 61-90 mL/min per 1.73 m² and decreased significantly with decreasing eGFR levels (>90: 17.3 [17.1-17.5]; 61-90: 17.6 [17.4-17.8]; 46-60: 17.1 [16.2-18.0]; 31-45: 16.2 [14.2-18.2]; ≤30: 13.8 [17.0-10.7] ng/mL; P = .008). After adjusting for covariates and log-eGFR, the mean ACR decreased significantly with increasing 25(OH)D quartiles (Q1: 22.0 [18.1-25.9]; Q2: 20.4 [16.6-24.2]; Q3: 16.3 [12.5-20.0]; Q4: 15.0 [11.2-18.8] μg/mg; P = .043).

CONCLUSIONS

The mean eGFR values were negatively associated with 25(OH)D levels independently of ACR. However, the mean 25(OH)D values were decreased significantly with decreasing eGFR levels in moderate and severe chronic kidney disease stages. Also, the mean ACR values were negatively associated with 25(OH)D levels independently of eGFR in an Korean adult population.

Proteinuria as a Therapeutic Target in Advanced Chronic Kidney Disease: a Retrospective Multicenter Cohort Study

Current evidence of proteinuria reduction as a surrogate target in advanced chronic kidney disease (CKD) is incomplete due to lack of patient-pooled database. We retrospectively studied a multicenter cohort of 1891 patients who were enrolled in the nationwide multidisciplinary pre-end stage renal disease care program with a baseline glomerular filtration rate (GFR) <45 mL/min/1.73 m(2) and followed longitudinally to investigate the effect of the change in proteinuria on renal death (defined as composite of dialysis and death occurring before initiation of dialysis). The group with a change in proteinuria ≤0.30 g/g (n = 1261) had lower cumulative probabilities of renal death (p < 0.001). In a linear regression model, a higher baseline proteinuria and a greater increase in proteinuria were associated with faster annual GFR decline. Cox's analysis showed that every 1 unit increase in natural log(baseline proteinuria, 10 g/g) and every 0.1 g/g increase in the change in proteinuria resulted in 67% (HR = 1.67, 95% CI: 1.46-1.91) and 1% (HR = 1.01, 95% CI: 1.01-1.01) greater risk of renal death respectively after adjusting for the effects of the other covariates. Our study provided a patient-based evidence to support proteinuria as a therapeutic target in advanced CKD.

Stop chronic kidney disease progression: Time is approaching

Progression of chronic kidney disease (CKD) is inevitable. However, the last decade has witnessed tremendous achievements in this field. Today we are optimistic; the dream of withholding this progression is about to be realistic. The recent discoveries in the field of CKD management involved most of the individual diseases leading the patients to end-stage renal disease. Most of these advances involved patients suffering diabetic kidney disease, chronic glomerulonephritis, polycystic kidney disease, renal amyloidosis and chronic tubulointerstitial disease. The chronic systemic inflammatory status and increased oxidative stress were also investigated. This inflammatory status influences the anti-senescence Klotho gene expression. The role of Klotho in CKD progression together with its therapeutic value are explored. The role of gut as a major source of inflammation, the pathogenesis of intestinal mucosal barrier damage, the role of intestinal alkaline phosphatase and the dietary and therapeutic implications add a novel therapeutic tool to delay CKD progression.

Safety of Eplerenone for Kidney-Transplant Recipients with Impaired Renal Function and Receiving Cyclosporine A

Background

Animal studies have highlighted the role of vascular mineralocorticoid receptor during Cyclosporine A-induced nephrotoxicity. Mineralocorticoid receptor antagonists could improve kidney survival but are not commonly used during renal impairment and in association with several immunosuppressive drugs due to a supposed higher risk of adverse events. We tested the tolerance of eplerenone according to its expected adverse events: hyperkalemia, metabolic acidosis, hypotension, acute kidney failure, or any other adverse event.

Methods

We conducted a single-center, prospective, open-label study in 31 kidney-transplant recipients with impaired renal function (30 and 50 mL/min/1.73m²) and receiving cyclosporine A. All patients received eplerenone 25 mg/d for 8 weeks. Serum potassium, renal function and expected adverse events were closely monitored.

Results

Eight patients experienced mild hyperkalemia (>5 mmol/L), one moderate hyperkalemia (>5.5 mmol/L) and had to receive potassium-exchange resin. No severe hyperkalemia (>6 mmol/L) occurred. One acute kidney failure was observed, secondary to diarrhea. Basal serum potassium and bicarbonate were independently associated with a higher risk of developing mild hyperkalemia (>5 mmol/L) under treatment (OR 6.5, p = 0.003 and 0.7, p = 0.007, respectively). A cut-off value of 4.35 mmol/L for basal serum potassium was the best factor to predict the risk of developing mild hyperkalemia (>5 mmol/L).

Conclusions

Until eGFR falls to 30 mL/min/1.73m², eplerenone could be safely given to kidney-transplant recipients receiving cyclosporine A, if kalemia is closely monitored. When renal function is impaired and if basal kalemia is >4.35 mmol/L, then clinicians should properly balance risk and benefit of eplerenone use and offer dietary advice. An adequately powered prospective randomized study is now needed to test its efficiency (and safety) in this population.

Trial Registration

ClinicalTrials.gov NCT01834768

Inhibiting angiotensin-converting enzyme promotes renal repair by modulating progenitor cell activation

Independently of the initial insult, activation and accumulation of parietal progenitor cells within the Bowman's space is a peculiar feature of proliferative chronic kidney diseases. Clinical and experimental studies demonstrated that, in the presence of extensive renal damage, progenitor cells proliferate excessively in the failed attempt to replace the injured podocytes, contributing to the development of crescentic lesions. Inhibiting angiotensin-converting enzyme (ACE) halts crescent formation and promotes the restoration of normal glomerular architecture by limiting progenitor cell proliferation and migration towards the glomerular tuft. Among the mediators involved in the dysregulated response of renal precursors, the angiotensin II (ang II)/ang II type-1 (AT₁) receptor/CXCR4 pathway have been demonstrated to be crucial in proliferative diseases. Understanding the mechanisms underlying the formation of crescentic lesions could be instrumental to developing new therapies, which can be more effective and more targeted to molecular mediators than the currently used cytotoxic agents.

Risk Factors for Development and Progression of Chronic Kidney Disease: A Systematic Review and Exploratory Meta-Analysis

The risk factors influencing the natural course of chronic kidney disease (CKD) are complex and heterogeneous, and few systematic reviews to date have focused on this issue. The aim of the study is to identify the risk factors for disease development and progression in each stage of CKD. We conducted electronic literature searches of PubMed, MEDLINE, Scopus, and the Cochrane Library up to October 15, 2012, for observational studies evaluating the risk factors on the development or progression of CKD. Eligible studies should have collected repeated information that could evaluate changes in renal function. Extracted information from all the included studies was synthesized narratively. Quality assessments were performed using the Newcastle-Ottawa Scale. An exploratory random-effects meta-analysis was performed where feasible to pool effect sizes across studies for a specific risk factor in a specific outcome. We identified 38 cohort studies and 2 case-control studies from 40 articles, with a total of 318,898 participants from 14 countries. The follow-up duration ranged from 1.5 to 16 years. The majority of the included studies were of high quality. The baseline CKD stages of the included studies ranged from normal to later stages, and only 19 studies could be classified into a specific range of CKD stages during follow-up. Three risk factors from studies of the same baseline and follow-up CKD stages were eligible for the exploratory meta-analysis, including male sex, substantial proteinuria, and diabetes. The hazard ratios for the progression from CKD stages 3-5 to end-stage renal disease (ESRD) were 1.37 (95% confidence interval 1.17-1.62), 1.64 (1.01-2.66), and 1.16 (0.98-1.38) for male sex, substantial proteinuria, and diabetes, respectively. In conclusion, our analyses comprehensively summarize the initiating and perpetuating factors for CKD. Male sex and substantial proteinuria are significant perpetuating factors for the progression from late stage CKD to ESRD, and diabetes may play a minor role for the outcome of ESRD among patients with later stages of CKD.

Distinct Requirements for Vacuolar Protein Sorting 34 Downstream Effector Phosphatidylinositol 3-Phosphate 5-Kinase in Podocytes Versus Proximal Tubular Cells

The mechanisms by which the glomerular filtration barrier prevents the loss of large macromolecules and simultaneously, maintains the filter remain poorly understood. Recent studies proposed that podocytes have an active role in both the endocytosis of filtered macromolecules and the maintenance of the filtration barrier. Deletion of a key endosomal trafficking regulator, the class 3 phosphatidylinositol (PtdIns) 3-kinase vacuolar protein sorting 34 (Vps34), in podocytes results in aberrant endosomal membrane morphology and podocyte dysfunction. We recently showed that the vacuolation phenotype in cultured Vps34-deficient podocytes is caused by the absence of a substrate for the Vps34 downstream effector PtdIns 3-phosphate 5-kinase (PIKfyve), which phosphorylates Vps34-generated PtdIns(3)P to produce PtdIns (3,5)P2. PIKfyve perturbation and PtdIns(3,5)P2 reduction result in massive membrane vacuolation along the endosomal system, but the cell-specific functions of PIKfyve in vivo remain unclear. We show here that the genetic deletion of PIKfyve in endocytically active proximal tubular cells resulted in the development of large cytoplasmic vacuoles caused by arrested endocytic traffic progression at a late-endosome stage. In contrast, deletion of PIKfyve in glomerular podocytes did not significantly alter the endosomal morphology, even in age 18-month-old mice. However, on culturing, the PIKfyve-deleted podocytes developed massive cytoplasmic vacuoles. In summary, these data suggest that glomerular podocytes and proximal tubules have different requirements for PIKfyve function, likely related to distinct in vivo needs for endocytic flux.

How to improve duration and efficiency of the antiproteinuric response to Ramipril: RamiPROT-a prospective cohort study

BACKGROUND

The antiproteinuric pharmacokinetics of Ramipril in response to different doses and modalities of administration has been poorly investigated so far.

STUDY DESIGN

Prospective, open-label and not placebo controlled study.

SETTING AND PARTICIPANTS

40 Caucasian adult patients having GFR ≥ 50 mL/min, proteinuria 1-3 g/day; SBP/DBP ≤ 150/90 mmHg were recruited between June 2014 and November 2014.

FACTOR AND OUTCOME

Impact on 24 h proteinuria and fractioned proteinuria of Ramipril given at different dosages (2.5 mg/day or Ramipril 5 mg/day or Ramipril 10 mg/day) and with different daily administration modalities (single or two divided doses) for cycles of 10 days.

MEASUREMENTS

At the end of each cycle, 24 h and fractioned proteinuria on three timed urinary collections (morning, afternoon and night) were measured.

RESULTS

Compared to baseline, Ramipril significantly reduced 24 h proteinuria at each dose and modality of administration. In particular, the greatest effects were evident with the higher and divided dose of the drug. The analysis of the fractioned proteinuria showed that the greatest reduction was obtained in the night urinary collection by administering Ramipril 10 mg/day in two divided doses.

LIMITATIONS

Small sample size.

CONCLUSIONS

Ramipril reduces proteinuria at any of the tested doses. Although the using of high and divided doses seems to maximize the antiproteinuric effect of the drug, possibly due to a better pharmacological coverage of the nocturnal period.

Prognostic significance of urinary NGAL in chronic kidney disease

Background

Chronic kidney disease (CKD) is a worldwide public health problem. Recently urinary NGAL (uNGAL) has been proven to be a useful (potentially ideal) biomarker for early detection of CKD. The aim of the present study was to examine the correlation of uNGAL with severity of renal impairment in CKD and to evaluate its prognostic value in these subjects.

Methods

This was a prospective study carried out over a period of 24 months in subjects with CKD due to primary chronic glomerulonephritis. New cases of CKD stage II, III, IV aged between 18 and 65 years were enrolled as per KDIGO (Kidney Disease: Improving Global Outcomes) guidelines 2012. A total of 90 subjects completed the study up to the end-point. The primary follow-up end-point was 18 months, or decreased glomerular filtration rate of less than 15 mL/min. Secondary follow-up end-point was the number of subjects who expired during this period.

Results

Multiple regression model of estimated glomerular filtration rate showed significant associations with log uNGAL (β=0.38, P<0.001), Ca×PO4 (β=0.60, P<0.001), hemoglobin (β=0.37, P<0.001), urine protein (β=0.34, P<0.001), serum albumin (β=0.48, P<0.001), and systolic blood pressure (β=0.76, P<0.001). Receiver operator curve for uNGAL considering the progression of CKD showed area under the curve for uNGAL was 0.878 (95% confidence interval: 0.68–0.96). Cut-off value for uNGAL was log 3.5 unit with a sensitivity of 93.08% and specificity of 71.43% for predicting the progression of CKD. Kaplan–Meier survival curve showed that patients with log uNGAL levels <3.51 unit had a survival rate of 71.4% while patients with NGAL level >3.51 unit had a renal survival rate of 14.7%.

Conclusion

Our study result showed that uNGAL has a positive correlation with disease severity which signifies the prognostic importance of uNGAL in CKD.

Association of Relapse with Renal Outcomes under the Current Therapy Regimen for IgA Nephropathy: A Multi-Center Study

Background and Objectives

Renal relapse is a very common manifestation of IgA nephropathy (IgAN). The clinical characteristics and long-term outcomes of this condition have not yet been carefully explored.

Design and Patients

Patients with biopsy-proven IgAN between January 2005 and December 2010 from three medical centers in China was a primary cohort of patients. From January 2010 to April 2012, data of an independent cohort of IgAN patients from Ren Ji Hospital, Shanghai, China was collected using the same inclusion and exclusion criteria. These patients formed the validation cohort of this study.

Results

Of the patients with biopsy-proven IgAN from three medical centers, 489 patients achieved remission within 6 months following the therapy. Additionally, 76 (15.5%) of these patients experienced a relapse after achieving remission. During the median follow-up period of 66 months, 6 patients (1.4%) in the non-relapse group experienced renal deterioration, compared with 22 patients (29.6%) in the relapse group. Our study indicated that each 1-mmHg increase in the baseline diastolic blood pressure (DBP) was associated with a 4.5% increase in the risk of renal relapse; additionally, the male patients had a 3.324-fold greater risk of relapse compared with the female patients according to the adjusted multivariate Cox analysis. The nomogram was based on 489 patients achieved remission. The predictive accuracy and discriminative ability of the nomogram were determined by concordance index (C-index) and calibration curve. The results were validated using bootstrap resampling on the validation cohort.

Conclusions

This study demonstrated that renal relapse is a potential predictor of prognostic outcomes in patients under the current therapeutic regimens for IgAN. And male patients with higher diastolic blood pressure had a greater risk of experiencing relapse.

Resting heart rate is associated with renal disease outcomes in patients with vascular disease: results of the ONTARGET and TRANSCEND studies

BACKGROUND

Resting heart rate (RHR) is associated with cardiovascular disease outcomes in high-risk patients. It is not known whether RHR is predictive of renal outcomes such as albuminuria, end-stage renal disease (ESRD) or doubling of creatinine. We evaluated whether RHR could predict renal endpoints in patients at a high risk of cardiovascular disease. We also tested the effects of RHR at different levels of systolic blood pressure (SBP).

METHODS

We analysed data from 28 757 patients in the ONTARGET and TRANSCEND trials. RHR and SBP were available for a mean of 4.9 ± 0.4 visits (range 3-5) within the first 2 years of the studies. Albuminuria was determined at baseline, at 2 years and at study end.

RESULTS

Mean RHR was predictive of incident micro-albuminuria [hazard ratio (HR) for RHR ≥80 vs. <60 beats min(-1) 1.49, 95% confidence interval (CI) 1.29-1.71, P < 0.0001], incident macro-albuminuria (HR 1.84, 95% CI 1.39-2.42, P < 0.0001), doubling of creatinine (HR 1.47, 95% CI 1.00-2.17, P = 0.050) and ESRD (HR 1.78, 95% CI 1.00-3.16, P = 0.050), and the combined renal end-point (HR 1.51, 95% CI 1.32-1.74, P < 0.0001). Associations were robust at SBPs from <120 to ≥150 mmHg, with the lowest risk at a SBP of 130-140 mmHg.

CONCLUSION

Resting heart rate is a potent predictor of these renal outcomes, as well as their combination, in patients with cardiovascular disease. RHR at all SBP levels should be considered as a possible renal disease risk predictor and should be investigated as a treatment target with RHR-reducing agents.

Crosstalk between the unfolded protein response and NF-κB-mediated inflammation in the progression of chronic kidney disease

The chronic inflammatory response is emerging as an important therapeutic target in progressive chronic kidney disease. A key transcription factor in the induction of chronic inflammation is NF-κB. Recent studies have demonstrated that sustained activation of the unfolded protein response (UPR) can initiate this NF-κB signaling phenomenon and thereby induce chronic kidney disease progression. A key factor influencing chronic kidney disease progression is proteinuria and this condition has now been demonstrated to induce sustained UPR activation. This review details the crosstalk between the UPR and NF-κB pathways as pertinent to chronic kidney disease. We present potential tools to study this phenomenon as well as potential therapeutics that are emerging to regulate the UPR. These therapeutics may prevent inflammation specifically induced in the kidney due to proteinuria-induced sustained UPR activation.

Albumin overload down-regulates integrin-β1 through reactive oxygen species-endoplasmic reticulum stress pathway in podocytes

Proteinuria is a major hallmark of glomerular nephropathy and endoplasmic reticulum (ER) stress plays an important role in glomerular nephropathy. The protein levels of integrin-β1 in podocytes are found to be negative correlation with amount of proteinuria. This study investigated whether urinary protein, particularly albumin, induced ER stress that consequently reduced integrin-β1 expression. All experiments were performed using primary cultured rat podocyte. Protein and mRNA expression were measured by western blotting and semiquantified reverse transcriptase polymerase chain reaction. Albumin uptake was found at 1 h after albumin addition. Albumin reduced precursor and mature forms of integrin-β1, but did not change mRNA levels of integrin-β1. Albumin induced reactive oxygen species (ROS) generation and ER stress. Antioxidant (N-acetylcysteine) suppressed albumin-induced ER stress and decrements in precursor and mature forms of integrin-β1. Then, ER stress inhibitors (4-phenylbutyrate and salubrinal) also inhibited albumin-induced decrements in precursor and mature forms of integrin-β1. The potent ER stress inducers (thapsigargin and tunicamycin) directly decreased precursor and mature forms of integrin-β1 and led appearance of unglycosylated core protein of integrin-β1. Our results show that in proteinuric disease, albumin decreases precursor and mature forms of integrin-β1 through ROS-ER stress pathway in podocytes.

Nutritional treatment in chronic kidney disease: the concept of nephroprotection

Low-protein diets have been advocated for many decades as the cornerstone in the treatment of chronic kidney disease. Initially, the low intake of protein was used to reduce uremic symptoms; thereafter, albeit controversial, evidences suggested that dietary protein restriction can also slow the rate of progression of renal failure and the time until end-stage renal disease. This reviews focuses on the dietary factors and their influence on the loss of renal function and on the evidences in the literature supporting a nephroprotective role of the low-protein diet.

Effect of obstructive respiratory events on blood pressure and renal perfusion in a pig model for sleep apnea

BACKGROUND

Obstructive sleep apnea (OSA) is associated with hypertension and the progression of chronic kidney disease (CKD). Renal sympathetic innervation contributes to either condition.

METHODS

We investigated the effect of renal sympathetic denervation (RDN) on blood pressure (BP), renal perfusion, and neurohumoral responses during and after repetitive obstructive apneas in a pig model for OSA. BP, femoral artery, and renal artery flow were measured in 29 spontaneously breathing urethane-chloralose-anesthetized pigs. The effect of RDN (n = 14) and irbesartan (n = 3) was investigated. Repetitive tracheal occlusions for 2 minutes with applied negative tracheal pressure at -80 mbar were performed over 4 hours.

RESULTS

Spontaneous breathing attempts during tracheal occlusion caused an intra-apneic breathing synchronous oscillating pattern of renal flow. Renal flow oscillations were > 2-fold higher compared with femoral flow that almost showed changes proportional to the BP alterations (2.9%/mm Hg vs. 1.3%/mm Hg; P < 0.0001). A marked postapneic BP rise from 102 ± 3 to 172 ± 8 mm Hg (P < 0.00001) was associated with renal hypoperfusion (from 190 ± 24 to 70 ± 20 ml/min; P < 0.00001) occurring after application of obstructive respiratory events. RDN, but not irbesartan, inhibited postapneic BP rises and renal hypoperfusion and attenuated increased plasma renin activity and aldosterone concentration induced by repetitive tracheal occlusions. Additionally, increased urinary protein/creatinine ratio was significantly reduced by RDN, whereas intra-apneic hemodynamic changes or blood gases were not modified by RDN.

CONCLUSIONS

Repetitive obstructive respiratory events result in postapneic BP rises and renal hypoperfusion, as well as neurohumoral responses and increased protein/creatinine ratio. These changes are mainly sympathetically driven because they could be attenuated by RDN.

Stress in the kidney is the road to pERdition: is endoplasmic reticulum stress a pathogenic mediator of diabetic nephropathy?

The endoplasmic reticulum (ER) is an organelle that primarily functions to synthesise new proteins and degrade old proteins. Owing to the continual and variable nature of protein turnover, protein synthesis is inherently an error-prone process and is therefore tightly regulated. Fortunately, if this balance between synthesis and degradation is perturbed, an intrinsic response, the unfolded protein response (UPR) is activated to restore ER homoeostasis through the action of inositol-requiring protein 1, activating transcription factor 6 and PKR-like ER kinase transmembrane sensors. However, if the UPR is oversaturated and misfolded proteins accumulate, the ER can shift into a cytotoxic response, a physiological phenomenon known as ER stress. The mechanistic pathways of the UPR have been extensively explored; however, the role of this process in such a synthetic organ as the kidney requires further clarification. This review will focus on these aspects and will discuss the role of ER stress in specific resident kidney cells and how this may be integral in the pathogenesis and progression of diabetic nephropathy (DN). Given that diabetes is a perturbed state of protein turnover in most tissues, it is important to understand if ER stress is a secondary or tertiary response to other changes within the diabetic milieu or if it is an independent accelerator of kidney disease. Modulators of ER stress could provide a valuable tool for the treatment of DN and are under active investigation in other contexts.

Early change in proteinuria as a surrogate end point for kidney disease progression: an individual patient meta-analysis

BACKGROUND

It is controversial whether proteinuria is a valid surrogate end point for randomized trials in chronic kidney disease.

STUDY DESIGN

Meta-analysis of individual patient-level data.

SETTING & POPULATION

Individual patient data for 9,008 patients from 32 randomized trials evaluating 5 intervention types.

SELECTION CRITERIA FOR STUDIES

Randomized controlled trials of kidney disease progression until 2007 with measurements of proteinuria both at baseline and during the first year of follow-up, with at least 1 further year of follow-up for the clinical outcome.

PREDICTOR

Early change in proteinuria.

OUTCOMES

Doubling of serum creatinine level, end-stage renal disease, or death.

RESULTS

Early decline in proteinuria was associated with lower risk of the clinical outcome (pooled HR, 0.74 per 50% reduction in proteinuria); this association was stronger at higher levels of baseline proteinuria. Pooled estimates for the proportion of treatment effect on the clinical outcome explained by early decline in proteinuria ranged from -7.0% (95%CI, -40.6% to 26.7%) to 43.9% (95%CI, 25.3% to 62.6%) across 5 intervention types. The direction of the pooled treatment effects on early change in proteinuria agreed with the direction of the treatment effect on the clinical outcome for all 5 intervention types, with the magnitudes of the pooled treatment effects on the 2 end points agreeing for 4 of the 5 intervention types. The pooled treatment effects on both end points were simultaneously stronger at higher levels of proteinuria. However, statistical power was insufficient to determine whether differences in treatment effects on the clinical outcome corresponded to differences in treatment effects on proteinuria between individual studies.

LIMITATIONS

Limited variety of interventions tested and low statistical power for many chronic kidney disease clinical trials.

CONCLUSIONS

These results provide new evidence supporting the use of an early reduction in proteinuria as a surrogate end point, but do not provide sufficient evidence to establish its validity in all settings.

Non-linear association of serum 25-hydroxyvitamin D with urinary albumin excretion rate in normoalbuminuric subjects

Background

Vitamin D deficiencies and increases in urinary albumin excretion (UAE) are both important and potentially related health problems; however, the nature of their relationship has not been established in normoalbuminuric subjects.

Methods

We obtained data from 14,594 normoalbuminuric Korean adults who underwent voluntary health screenings. We used a generalized additive model to examine the threshold level for relationship between serum 25-hydroxyvitamin D [25(OH)D] and urinary-albumin creatinine ratio (UACR) levels. We conducted multivariate logistic regression for high-normal UAE (UACR, 10–29 mg/g), according to various categories of vitamin D status.

Results

The generalized additive model confirmed a non-linear relationship between serum 25(OH)D and UACR levels, and the threshold concentration of 25(OH)D was 8.0 ng/mL after multivariate adjustment. Comparing subjects who fell into the lowest category of serum 25(OH)D levels with subjects who were in the reference range (the highest category), we observed that the multivariate adjusted odds ratio (OR) for high-normal UAE was significantly increased, regardless of the criteria used to categorize vitamin D levels: OR of the 1^st quartile over the 4^th quartile, 1.20 (95% CI, 1.04-1.39); OR of the 1.0-4.9^th percentile over the 50-100^th percentile, 1.56 (95% CI, 1.25-1.93); and OR of vitamin D deficiency group over vitamin D sufficiency group, 1.28 (95% CI, 1.08-1.52).

Conclusions

We demonstrated that there was an inverse relationship between serum 25(OH)D less than 8.0 ng/mL and UACR in normoalbuminuric subjects, suggesting that severe vitamin D deficiency could cause an increase in UAE in subjects with normoalbuminuria.

Podocytes degrade endocytosed albumin primarily in lysosomes

Albuminuria is a strong, independent predictor of chronic kidney disease progression. We hypothesize that podocyte processing of albumin via the lysosome may be an important determinant of podocyte injury and loss. A human urine derived podocyte-like epithelial cell (HUPEC) line was used for in vitro experiments. Albumin uptake was quantified by Western blot after loading HUPECs with fluorescein-labeled (FITC) albumin. Co-localization of albumin with lysosomes was determined by confocal microscopy. Albumin degradation was measured by quantifying FITC-albumin abundance in HUPEC lysates by Western blot. Degradation experiments were repeated using HUPECs treated with chloroquine, a lysosome inhibitor, or MG-132, a proteasome inhibitor. Lysosome activity was measured by fluorescence recovery after photo bleaching (FRAP). Cytokine production was measured by ELISA. Cell death was determined by trypan blue staining. In vivo, staining with lysosome-associated membrane protein-1 (LAMP-1) was performed on tissue from a Denys-Drash trangenic mouse model of nephrotic syndrome. HUPECs endocytosed albumin, which co-localized with lysosomes. Choloroquine, but not MG-132, inhibited albumin degradation, indicating that degradation occurs in lysosomes. Cathepsin B activity, measured by FRAP, significantly decreased in HUPECs exposed to albumin (12.5% of activity in controls) and chloroquine (12.8%), and declined further with exposure to albumin plus chloroquine (8.2%, p<0.05). Cytokine production and cell death were significantly increased in HUPECs exposed to albumin and chloroquine alone, and these effects were potentiated by exposure to albumin plus chloroquine. Compared to wild-type mice, glomerular staining of LAMP-1 was significantly increased in Denys-Drash mice and appeared to be most prominent in podocytes. These data suggest lysosomes are involved in the processing of endocytosed albumin in podocytes, and lysosomal dysfunction may contribute to podocyte injury and glomerulosclerosis in albuminuric diseases. Modifiers of lysosomal activity may have therapeutic potential in slowing the progression of glomerulosclerosis by enhancing the ability of podocytes to process and degrade albumin.

Differences in susceptibility to develop parameters of diabetic nephropathy in four mouse strains with type 1 diabetes

One-third of diabetes mellitus patients develop diabetic nephropathy, and with underlying mechanisms unknown it is imperative that diabetic animal models resemble human disease. The present study investigated the susceptibility to develop diabetic nephropathy in four commonly used and commercially available mouse strains with type 1 diabetes to determine the suitability of each strain. Type 1 diabetes was induced in C57Bl/6, NMRI, BALB/c, and 129Sv mice by alloxan, and conscious glomerular filtration rate, proteinuria, and oxidative stress levels were measured in control and diabetic animals at baseline and after 5 and 10 wk. Histological alterations were analyzed using periodic acid-Schiff staining. Diabetic C57Bl/6 displayed increased glomerular filtration rate, i.e., hyperfiltration, whereas all other parameters remained unchanged. Diabetic NMRI developed the most pronounced hyperfiltration as well as increased oxidative stress and proteinuria but without glomerular damage. Diabetic BALB/c did not develop hyperfiltration but presented with pronounced proteinuria, increased oxidative stress, and glomerular damage. Diabetic 129Sv displayed proteinuria and increased oxidative stress without glomerular hyperfiltration or damage. However, all strains displayed intrastrain correlation between oxidative stress and proteinuria. In conclusion, diabetic C57Bl/6 and NMRI both developed glomerular hyperfiltration but neither presented with histological damage, although NMRI developed low-degree proteinuria. Thus these strains may be suitable when investigating the mechanism causing hyperfiltration. Neither BALB/c nor 129Sv developed hyperfiltration although both developed pronounced proteinuria. However, only BALB/c developed detectable histological damage. Thus BALB/c may be suitable when studying the roles of proteinuria and histological alterations for the progression of diabetic nephropathy.

Phosphotriesterase-related protein sensed albuminuria and conferred renal tubular cell activation in membranous nephropathy

BACKGROUND

Membranous nephropathy (MN) is a common cause of nephrotic syndrome that may progress to end-stage renal disease (ESRD). The formation of MN involves the in situ formation of subepithelial immune deposits and leads to albuminuria; however, the underlying mechanism of how MN leads to ESRD remains unclear. The aim of this study was to investigate the expression and biological functions of phosphotriesterase-related protein (PTER) in MN.

RESULTS

In the progression of MN, the expression of PTER increased significantly and was mainly expressed in the renal tubular cells. Both mRNA and protein expression levels of PTER were increased in a concentration- and time-dependent manner in the in vitro albuminuria tubular cell model. Silencing the expression of PTER by RNA interference diminished albuminuria-induced inflammatory and pro-fibrotic cytokines production.

CONCLUSIONS

Our findings reveal that PTER may sense albuminuria in the progression of MN, induce tubular cell activation and lead to ESRD.

Mesenchymal stem cells modulate albumin-induced renal tubular inflammation and fibrosis

Bone marrow-derived mesenchymal stem cells (BM-MSCs) have recently shown promise as a therapeutic tool in various types of chronic kidney disease (CKD) models. However, the mechanism of action is incompletely understood. As renal prognosis in CKD is largely determined by the degree of renal tubular injury that correlates with residual proteinuria, we hypothesized that BM-MSCs may exert modulatory effects on renal tubular inflammation and epithelial-to-mesenchymal transition (EMT) under a protein-overloaded milieu. Using a co-culture model of human proximal tubular epithelial cells (PTECs) and BM-MSCs, we showed that concomitant stimulation of BM-MSCs by albumin excess was a prerequisite for them to attenuate albumin-induced IL-6, IL-8, TNF-α, CCL-2, CCL-5 overexpression in PTECs, which was partly mediated via deactivation of tubular NF-κB signaling. In addition, albumin induced tubular EMT, as shown by E-cadherin loss and α-SMA, FN and collagen IV overexpression, was also prevented by BM-MSC co-culture. Albumin-overloaded BM-MSCs per se retained their tri-lineage differentiation capacity and overexpressed hepatocyte growth factor (HGF) and TNFα-stimulating gene (TSG)-6 via P38 and NF-κB signaling. Albumin-induced tubular CCL-2, CCL-5 and TNF-α overexpression were suppressed by recombinant HGF treatment, while the upregulation of α-SMA, FN and collagen IV was attenuated by recombinant TSG-6. Neutralizing HGF and TSG-6 abolished the anti-inflammatory and anti-EMT effects of BM-MSC co-culture in albumin-induced PTECs, respectively. In vivo, albumin-overloaded mice treated with mouse BM-MSCs had markedly reduced BUN, tubular CCL-2 and CCL-5 expression, α-SMA and collagen IV accumulation independent of changes in proteinuria. These data suggest anti-inflammatory and anti-fibrotic roles of BM-MSCs on renal tubular cells under a protein overloaded condition, probably mediated via the paracrine action of HGF and TSG-6.

Independent or synergistic relationship of proteinuria and glomerular filtration rate on patient and renal survival in patients with glomerulonephritis?

BACKGROUND

Glomerular filtration rate (GFR) in patients with chronic kidney disease (CKD) identifies patients at risk for death or end-stage renal disease (ESRD). CKD staging by GFR should incorporate proteinuria to augment risk stratification. We therefore tested the predictive power of the combination of GFR with proteinuria in patients with different histologically-diagnosed types of glomerulonephritis (GN).

METHODS

In a retrospective analysis, 2,687 patients with different forms of GN from 123 Austrian centres were investigated. Full data sets were available from 1,892 subjects. Classes of CKD on the basis of estimated GFR (eGFR) and of proteinuria grouped as <1, 1-3.5, and >3.5 g/24 h were tested for their association with all-cause mortality and ESRD.

RESULTS

During a median follow-up of 130 months [interquartile range (IQR) 90; 178] 478 patients (25.3 %) died. Median eGFR was 49 ml/min/1.73 m(2) (IQR 24; 81) and proteinuria 3.8 g/24 h (IQR 1.7; 8.0). Adjusted multivariate Cox regression indicated that renal survival but not overall survival is related to proteinuria >3.5 g/24 h [as opposed to <1 g/24 h; hazard ratio (HR) 1.91] and shows progression to ESRD. However, subgroup analyses revealed that this risk with proteinuria >3.5 g/24 h exists only in patients with immunoglobulin (Ig)A GN (HR 4.93), miscellaneous GN (HR 1.74), and CKD stage 5 (HR 2.50). Additionally, proteinuria is a risk factor for renal survival in males more than in females with GN and proteinuria >3.5 g/24 h (HR 1.91).

CONCLUSION

Proteinuria is a strong risk factor for renal survival particularly in patients with proteinuria >3.5 g/24 but not for all types of GN, nor for all CKD stages. Proteinuria is not a risk factor for overall survival in patients with GN.

Accuracy of spot urine protein creatinine ratio in measuring proteinuria in chronic kidney disease stage 3 and 4

We studied the accuracy of spot urine protein creatinine ratio (SpUr-PCR) to assess 24 h urine protein excretion (24 h-UP) in patients with chronic kidney disease (CKD). A total of 100 proteinuric CKD patients of stages 3 and 4 were studied. 24 h urine was collected to measure 24 h-UP and creatinine. A random day time urine sample was analyzed to measure the PCR. A formula to estimate 24 h creatinine excretion was derived from linear regression analysis and a correction factor was introduced to assess whether this improves the accuracy of the SpUr PCR in predicting 24 h-UP. Accuracy of the SpUr-PCR was assessed by Pearson's correlation, regression analysis, and Bland Altman analysis. Mean age was 51.85 ± 12 years and 81% of the patients were male. SpUr-PCR predicted 24 h-UP with good accuracy (r = 0.86 on a data transformed to a logarithmic scale, P < 0.001) and there was a good agreement between these two measures of proteinuria. However, SpUr-PCR was inaccurate in the subgroup with nephrotic range proteinuria (r = 0.35, P = 0.062), but when a correction factor for 24-h urine creatinine (24 h-UCr) was introduced, the accuracy of SpUr-PCR improved significantly in this group (r = 0.45, P = 0.013). Introduction of the correction factor improved the degree of agreement between these two measures in women, but not the correlation. Overall, SpUr-PCR accurately predicted 24 h-UP. Adding a correction factor for 24 h-UCr improved correlation in the subgroup of patients with the nephrotic range proteinuria and the degree of agreement in female patients, and hence may be used in expressing proteinuria measured by SpUr-PCR to improve its accuracy in them.

Increased number of Th22 cells and correlation with Th17 cells in peripheral blood of patients with IgA nephropathy

T-helper (Th) 22 and Th17 cells are involved in the pathogenesis of autoimmune diseases. However, the role of Th22 and correlation with Th17 cells in the pathophysiology of IgA nephropathy (IgAN) remain unknown. In our study, Th22 and Th17 cells in peripheral blood of IgAN patients, non-IgA mesangial proliferative glomerulonephritis (non-IgA MsPGN) patients, and healthy controls were measured by flow cytometry. The concentration of plasma interleukin-22 (IL-22) was examined by enzyme linked immunosorbent assay (ELISA). The results showed that Th22 cells, Th17 cells, and plasma IL-22 were significantly elevated in IgAN patients compared with non-IgA MsPGN patients and healthy controls. Th22 cells showed a positive correlation with the levels of plasma IL-22 in IgAN patients. Moreover, a significantly positive correlation between Th22 cells and Th17 in IgAN patients was observed. Furthermore, IgAN patients with proteinuria showed a higher percentage of Th22 cells than IgAN patients without proteinuria. Our data demonstrated that IgAN had increased frequencies of peripheral Th22, Th17 cells and plasma IL-22, indicating that Th22 along with Th17 cells are involved in the immune responses of IgAN.

Kidney hypoxia, attributable to increased oxygen consumption, induces nephropathy independently of hyperglycemia and oxidative stress

Diabetic nephropathy is strongly associated with both increased oxidative stress and kidney tissue hypoxia. The increased oxidative stress causes increased kidney oxygen consumption resulting in kidney tissue hypoxia. To date, it has been difficult to determine the role of kidney hypoxia, per se, for the development of nephropathy. We tested the hypothesis that kidney hypoxia, without confounding factors such as hyperglycemia or elevated oxidative stress, results in nephropathy. To induce kidney hypoxia, dinitrophenol (30 mg per day per kg bodyweight by gavage), a mitochondrial uncoupler that increases oxygen consumption and causes kidney hypoxia, was administered for 30 consecutive days to rats. Thereafter, glomerular filtration rate, renal blood flow, kidney oxygen consumption, kidney oxygen tension, kidney concentrations of glucose and glycogen, markers of oxidative stress, urinary protein excretion, and histological findings were determined and compared with vehicle-treated controls. Dinitrophenol did not affect arterial blood pressure, renal blood flow, glomerular filtration rate, blood glucose, or markers of oxidative stress but increased kidney oxygen consumption, and reduced cortical and medullary concentrations of glucose and glycogen, and resulted in intrarenal tissue hypoxia. Furthermore, dinitrophenol treatment increased urinary protein excretion, kidney vimentin expression, and infiltration of inflammatory cells. In conclusion, increased mitochondrial oxygen consumption results in kidney hypoxia and subsequent nephropathy. Importantly, these results demonstrate that kidney tissue hypoxia, per se, without confounding hyperglycemia or oxidative stress, may be sufficient to initiate the development of nephropathy and therefore demonstrate a new interventional target for treating kidney disease.

Hypertension in pregnancy is a risk factor for microalbuminuria later in life

The authors aimed to compare renal function by estimated glomerular filtration rate and albuminuria in 3 groups of women: nulliparous women, women with a history of normotensive pregnancies, and women with a history of at least one hypertensive pregnancy. Women who participated in the second Family Blood Pressure Program Study visit (2000-2004) and had serum creatinine and urine albumin measurements (n=3015) were categorized as having had no pregnancy lasting >6 months (n=341), having had only normotensive pregnancies (n=2199), or having had at least 1 pregnancy with hypertension (n=475) based on a standardized questionnaire. Women who reported having had at least one pregnancy with hypertension were significantly more likely to be hypertensive (75.6% vs 59.4%, P<.001), diabetic (34.2% vs 27.3%, P≤.001), and have higher body mass index (32.8 vs 30.5, P<.001) than those who reported normotensive pregnancies. There was a significantly greater risk of microalbuminuria (urine albumin-creatinine ratio >25 mg/g) in those who reported at least one pregnancy with hypertension (odds ratio, 1.37; confidence interval, 1.02-1.85; P=.04) than in those with normotensive pregnancies, after adjusting for risk factors for chronic kidney and cardiovascular disease. Hypertension in pregnancy is associated with an increased risk of future microalbuminuria.

Blood pressure, proteinuria, and phosphate as risk factors for progressive kidney disease: a hypothesis

Chronic kidney disease (CKD) affects approximately 500 million people worldwide and is increasingly common in both industrialized and emerging countries. Although the mechanisms underlying the inexorable progression of CKD are incompletely defined, recent discoveries may pave the way to a more comprehensive understanding of the pathophysiology of CKD progression and the development of new therapeutic strategies. In particular, there is accumulating evidence indicating a key role for the complex and yet incompletely understood system of divalent cation regulation, which includes phosphate metabolism and the recently discovered fibroblast growth factor 23 (FGF-23)/klotho system, which seems inextricably associated with vitamin D deficiency. The aim of this review is to discuss the links between high blood pressure, proteinuria, phosphate levels, and CKD progression and explore new therapeutic strategies to win the fight against CKD.

Additive antiproteinuric effect of enalapril and losartan in children with hemolytic uremic syndrome

BACKGROUND

Angiotensin-converting enzyme inhibitors or angiotensin II type 1 receptor blockers decrease postdiarrheal hemolytic uremic syndrome (D + HUS) sequelar proteinuria. However, proteinuria may persist in some patients. In nephropathies other than D + HUS, an additive antiproteinuric effect with coadministration of both drugs has been observed.

METHODS

To assess such an effect in D + HUS, 17 proteinuric children were retrospectively studied. After a median period of 1 year post-acute stage (range 0.5-1.9) patients received enalapril alone for a median of 2.6 years (range 0.33-12.0) at a median dose of 0.4 mg/kg/day (range 0.2-0.56). As proteinuria persisted, losartan was added at a median dose of 1.0 mg/kg/day (range 0.5-1.5) during 2.1 years (range 0.5-5.0).

RESULTS

The decrease in proteinuria with enalapril was 58.0 %, which was further reduced to 83.8 % from the initial value after losartan introduction. The percentage of reduction was significantly greater with the association of both drugs (p = 0.0006) compared with the effect of enalapril exclusively (p = 0.023). Serum potassium, glomerular filtration rate, and blood pressure remained unchanged.

CONCLUSIONS

Our results suggest that adding losartan to persisting proteinuric D + HUS children already on enalapril is safe and reduces proteinuria more effectively. Whereas this effect is associated with long-term kidney protection, it should be determined by prospective controlled studies.

Limited capacity of proximal tubular proteolysis in mice with proteinuria

Albuminuria is associated with the additional loss in the urine of small molecular weight proteins normally degraded by the proximal convoluted tubule (PCT), and competition for binding to the megalin/cubilin reuptake system has been considered the likely cause. We have previously reported that deficiency of the intrinsic lysosomal protein Limp-2 causes tubular proteinuria due to reduced fusion of endosomes with lysosomes in the PCT leading to inadequate proteolysis. To determine whether this mechanism also contributes to the tubular proteinuria induced by albumin overload in normal mice, wild-type (WT) mice received daily BSA injections intraperitoneally for 10 days, using untreated Limp-2(-/-) mice as positive controls for inadequate proteolysis. BSA overload induced significant urinary loss of megalin and cubilin ligands in WT mice. Tubular uptake of Alexa-conjugated BSA, administered by intravenous injection, was not reduced in the PCT of mice receiving intraperitoneal BSA. Expression of the tubular protein receptor megalin was also unchanged. There was a delay in proteolysis of reabsorbed proteins in WT mice receiving BSA, evidenced by an increased quantity of retinol-binding protein (RBP) in the kidney cortex, increased basal distribution of endocytosed RBP in cells of the PCT, and persistence of exogenous Alexa-conjugated BSA and RBP after injection. Upregulation of cathepsin L and normal fusion of lysosomes with endosomes were apparently not sufficient to maintain normal clearance of endocytosed proteins. The data suggest that in the presence of competition from albumin overload, reabsorption of filtered proteins is limited by the capacity of lysosomal degradation rather than receptor-mediated endocytosis.

Endocytosis of albumin by podocytes elicits an inflammatory response and induces apoptotic cell death

The presence of albuminuria is strongly associated with progression of chronic kidney disease. While albuminuria has been shown to injure renal proximal tubular cells, the effects of albumin on podocytes have been less well studied. We have addressed the hypothesis that exposure of podocytes to albumin initiates an injury response. We studied transformed human-urine derived podocytes-like epithelial cells (HUPECS, or podocytes). Upon differentiation, these cells retain certain characteristics of differentiated podocytes, including expression of synaptopodin, CD2AP, and nestin. We exposed podocytes to recombinant human albumin, which lacks lipids and proteins that bind serum albumin; this reagent allowed a direct examination of the effects of albumin. Podocytes endocytosed fluoresceinated albumin and this process was inhibited at 4°C, suggesting an energy-dependent process. Exposure to albumin at concentrations of 5 and 10 mg/ml was associated with increased cell death in a dose-dependent manner. The mechanism of cell death may involve apoptosis, as caspase 3/7 were activated and the pan-caspase inhibitor z-VAD reduced cell death. Albumin exposure also increased nuclear factor (NF)-κB activation and increased transcription and release of interleukin (IL-) 1β, tumor necrosis factor (TNF), and IL-6. We extended these findings to an in vivo model. Glomeruli isolated from mice with nephrotic syndrome also had increased expression of IL-1β and TNF RNA. These data suggest that while podocyte injury begets albuminuria, albumin in the glomerular ultrafiltrate may also beget podocyte injury. Thus, an additional mechanism by which anti-proteinuric therapies are beneficial in the treatment of glomerular diseases may be a reduction in injury to the podocyte by albumin.

Urinary neutrophil gelatinase-associated lipocalin may aid prediction of renal decline in patients with non-proteinuric Stages 3 and 4 chronic kidney disease (CKD)

BACKGROUND

Chronic kidney disease (CKD) is an increasing public health issue. It is therefore potentially highly advantageous to identify patients at risk of accelerated renal progression and death. Neutrophil gelatinase-associated lipocalin (NGAL) is an established urinary biomarker for acute kidney injury, but it is not known whether adding urinary NGAL (uNGAL) measurements to conventional risk factors will improve risk assessment in the setting of chronic disease.

METHODS

This is a prospective observational cohort study of 158 patients with Stage 3 or 4 CKD. The ability of baseline uNGAL to improve prediction of outcome was assessed by multivariate modelling and a number of metrics including net reclassification analysis. A primary composite endpoint of all-cause mortality or progression to end-stage renal disease (ESRD) requiring renal replacement therapy (RRT) at 2 years and a secondary endpoint of ≥5 mL/min/1.73 m(2) decline in the estimated glomerular filtration rate (eGFR) after 1 year were considered.

RESULTS

Forty patients (25%) reached the primary composite endpoint, 20 of whom died. Twenty-seven patients (19%) reached the secondary endpoint of a ≥5 mL/min/1.73 m(2) decline in the eGFR. The baseline uNGAL-to-creatinine ratio (uNCR) was associated with the combined endpoint of death or initiation of RRT (HR per 5 µg/mmol increase 1.27, 95% CI: 1.01-1.60, P = 0.036) independent of conventional cardiovascular and renal risk factors, including proteinuria. In separate analysis of these two competing endpoints, however, uNCR only remained associated with increased risk of progression to ESRD requiring RRT. Higher baseline uNCR was also independently predictive of rapid renal decline over 1 year (HR per 5 µg/mmol increase 1.47, 95% CI: 1.06-2.06, P = 0.022). Addition of uNCR to the base model resulted in a significant increase in discrimination for the secondary (C-statistic 0.76-0.85, P = 0.001) but not the primary endpoint (P = 0.276). Reclassification analysis on the other hand, demonstrated an improvement in risk predication of both primary and secondary endpoints by incorporating uNCR into the base model, but only in those with low-level urine protein excretion (<28 mg/mmol), with category-free net reclassification improvement (NRI) scores of 64% (95% CI: 8-70; P = 0.019) and 79% (95% CI: 12-83; P = 0.009), respectively.

CONCLUSION

The utilization of uNCR in addition to conventional established cardiovascular and renal risk factors may improve the prediction of disease progression in elderly Caucasian pre-dialysis CKD patients with low-grade proteinuria.

Combined renin angiotensin blockade in childhood steroid-resistant nephrotic syndrome

BACKGROUND

Reduced proteinuria results in delayed deterioration of renal function and remission of proteinuria predicts a good long-term prognosis in steroid-resistant nephrotic syndrome (SRNS). The aim of this study was to analyze the effects of the combined angiotensin-converting enzyme inhibitor and angiotensin II receptor blocker in reducing proteinuria in SRNS.

METHODS

A prospective study of eight patients with SRNS was conducted at the Department of Pediatrics, Faculty of Medicine Siriraj Hospital, Mahidol University from September 2003 to December 2007. Enalapril was given at 0.1 mg/kg/day and was increased by 0.1 mg/kg/day every 4 weeks up to 0.6 mg/kg/day (maximum 40 mg/day) and 1 mg/kg/day of losartan was added for 4 weeks and stepped up to 2 mg/kg/day (maximum 100 mg/day) for another 4 weeks.

RESULTS

There were five boys (62.5%) and three girls (37.5%). The mean age at diagnosis was 8.3 ± 4.1 years (range 2.05-13 years) and age at enrollment was 11.7 ± 3.8 years (range 6-16 years). Renal histology revealed seven focal segmental glomerulosclerosis and one immunoglobulin M nephropathy. The results showed significant reduction on mean spot urine protein : creatinine ratio from 9.6 ± 2.3 to 3.6 ± 1.6 (P < 0.05) and 24-h urine protein from 182.8 ± 59.6 to 28.7 ± 8.2 mg/m(2) /h (P < 0.05). Urine protein reduction ratio at the end of the study was 50% (P= 0.08). Serum cholesterol, albumin, potassium, blood pressure and renal function had no significant change. No clinical and laboratory side-effects were reported.

CONCLUSION

Combined high-dose angiotensin II receptor blocker to high-dose angiotensin-converting enzyme inhibitor therapy is safe and effective in reducing proteinuria in childhood SRNS. However a large-scale study should be conducted to validate this result.

Characteristics of urinary and serum soluble Klotho protein in patients with different degrees of chronic kidney disease

Background

Klotho is a single-pass transmembrane protein, which appears to be implicated in aging. The purpose of the present study was to characterize the relationship between the soluble Klotho level and renal function in patients with various degrees of chronic kidney disease (CKD).

Methods

The levels of soluble Klotho in the serum and urine obtained from one hundred thirty-one CKD patients were determined by a sandwich enzyme-linked immunosorbent assay system.

Results

The amount of urinary excreted Klotho during the 24 hr period ranged from 1.6 to 5178 ng/day (median 427 ng/day; interquartile range [IR] 56.8-1293.1), and the serum Klotho concentration ranged from 163.9 to 2123.7 pg/ml (median 759.7 pg/ml; IR 579.5-1069.1). The estimated glomerular filtration rate (eGFR) was significantly correlated with the log-transformed values of the amount of 24 hr urinary excreted Klotho (r = 0.407, p < 0.01) and the serum Klotho levels (r = 0.232, p < 0.01). However, a stepwise multiple regression analysis identified eGFR to be a variable independently associated only with the log-transformed value of the amount of 24-hr urinary excreted Klotho but not with the log-transformed serum Klotho concentration. Despite the strong correlation between random urine protein-to-creatinine ratio and the 24 hr urinary protein excretion (r = 0.834, p < 0.01), a moderate linear association was observed between the log-transformed value of the amount of 24 hr urinary excreted Klotho and that of the urinary Klotho-to-creatinine ratio (Klotho/Cr) in random urine specimens (r = 0.726, p < 0.01).

Conclusions

The amount of urinary Klotho, rather than the serum Klotho levels, should be linked to the magnitude of the functioning nephrons in CKD patients. The use of random urine Klotho/Cr as a surrogate for the amount of 24-hr urinary excreted Klotho needs to be evaluated more carefully.