Reduction and residual proteinuria are therapeutic targets in type 2 diabetes with overt nephropathy: a post hoc analysis (ORIENT-proteinuria)

Angiotensin-converting-enzyme inhibitors and angiotensin receptor blockers for preventing the progression of diabetic kidney disease

BACKGROUND

Guidelines suggest that adults with diabetes and kidney disease receive treatment with angiotensin-converting-enzyme inhibitors (ACEi) or angiotensin receptor blockers (ARB). This is an update of a Cochrane review published in 2006.

OBJECTIVES

We compared the efficacy and safety of ACEi and ARB therapy (either as monotherapy or in combination) on cardiovascular and kidney outcomes in adults with diabetes and kidney disease.

SEARCH METHODS

We searched the Cochrane Kidney and Transplants Register of Studies to 17 March 2024 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Registry Platform (ICTRP) Search Portal, and ClinicalTrials.gov.

SELECTION CRITERIA

We included studies evaluating ACEi or ARB alone or in combination, compared to each other, placebo or no treatment in people with diabetes and kidney disease.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed the risk of bias and extracted data. Summary estimates of effect were obtained using a random-effects model, and results were expressed as risk ratios (RR) and their 95% confidence intervals (CI) for dichotomous outcomes and mean difference (MD) or standardised mean difference (SMD) and 95% CI for continuous outcomes. Confidence in the evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

MAIN RESULTS

One hundred and nine studies (28,341 randomised participants) were eligible for inclusion. Overall, the risk of bias was high. Compared to placebo or no treatment, ACEi may make little or no difference to all-cause death (24 studies, 7413 participants: RR 0.91, 95% CI 0.73 to 1.15; I2 = 23%; low certainty) and with similar withdrawals from treatment (7 studies, 5306 participants: RR 1.03, 95% CI 0.90 to 1.19; I2 = 0%; low certainty). ACEi may prevent kidney failure (8 studies, 6643 participants: RR 0.61, 95% CI 0.39 to 0.94; I2 = 0%; low certainty). Compared to placebo or no treatment, ARB may make little or no difference to all-cause death (11 studies, 4260 participants: RR 0.99, 95% CI 0.85 to 1.16; I2 = 0%; low certainty). ARB have uncertain effects on withdrawal from treatment (3 studies, 721 participants: RR 0.85, 95% CI 0.58 to 1.26; I2 = 2%; low certainty) and cardiovascular death (6 studies, 878 participants: RR 3.36, 95% CI 0.93 to 12.07; low certainty). ARB may prevent kidney failure (3 studies, 3227 participants: RR 0.82, 95% CI 0.72 to 0.94; I2 = 0%; low certainty), doubling of serum creatinine (SCr) (4 studies, 3280 participants: RR 0.84, 95% CI 0.72 to 0.97; I2 = 32%; low certainty), and the progression from microalbuminuria to macroalbuminuria (5 studies, 815 participants: RR 0.44, 95% CI 0.23 to 0.85; I2 = 74%; low certainty). Compared to ACEi, ARB had uncertain effects on all-cause death (15 studies, 1739 participants: RR 1.13, 95% CI 0.68 to 1.88; I2 = 0%; low certainty), withdrawal from treatment (6 studies, 612 participants: RR 0.91, 95% CI 0.65 to 1.28; I2 = 0%; low certainty), cardiovascular death (13 studies, 1606 participants: RR 1.15, 95% CI 0.45 to 2.98; I2 = 0%; low certainty), kidney failure (3 studies, 837 participants: RR 0.56, 95% CI 0.29 to 1.07; I2 = 0%; low certainty), and doubling of SCr (2 studies, 767 participants: RR 0.88, 95% CI 0.52 to 1.48; I2 = 0%; low certainty). Compared to ACEi plus ARB, ACEi alone has uncertain effects on all-cause death (6 studies, 1166 participants: RR 1.08, 95% CI 0.49 to 2.40; I2 = 20%; low certainty), withdrawal from treatment (2 studies, 172 participants: RR 0.78, 95% CI 0.33 to 1.86; I2 = 0%; low certainty), cardiovascular death (4 studies, 994 participants: RR 3.02, 95% CI 0.61 to 14.85; low certainty), kidney failure (3 studies, 880 participants: RR 1.36, 95% CI 0.79 to 2.32; I2 = 0%; low certainty), and doubling of SCr (2 studies, 813 participants: RR 1.14, 95% CI 0.70 to 1.85; I2 = 0%; low certainty). Compared to ACEi plus ARB, ARB alone has uncertain effects on all-cause death (7 studies, 2607 participants: RR 1.02, 95% CI 0.76 to 1.37; I2 = 0%; low certainty), withdrawn from treatment (3 studies, 1615 participants: RR 0.81, 95% CI 0.53 to 1.24; I2 = 0%; low certainty), cardiovascular death (4 studies, 992 participants: RR 3.03, 95% CI 0.62 to 14.93; low certainty), kidney failure (4 studies, 2321 participants: RR 1.15, 95% CI 0.67 to 1.95; I2 = 29%; low certainty), and doubling of SCr (3 studies, 2252 participants: RR 1.18, 95% CI 0.85 to 1.64; I2 = 0%; low certainty). Comparative effects of different ACEi or ARB and low-dose versus high-dose ARB were rarely evaluated. No study compared different doses of ACEi. Adverse events of ACEi and ARB were rarely reported.

AUTHORS' CONCLUSIONS

ACEi or ARB may make little or no difference to all-cause and cardiovascular death compared to placebo or no treatment in people with diabetes and kidney disease but may prevent kidney failure. ARB may prevent the doubling of SCr and the progression from microalbuminuria to macroalbuminuria compared with a placebo or no treatment. Despite the international guidelines suggesting not combining ACEi and ARB treatment, the effects of ACEi or ARB monotherapy compared to dual therapy have not been adequately assessed. The limited data availability and the low quality of the included studies prevented the assessment of the benefits and harms of ACEi or ARB in people with diabetes and kidney disease. Low and very low certainty evidence indicates that it is possible that further studies might provide different results.

[Treatment strategies in diabetic nephropathy - Update 2022]

TREATMENT GOALS IN DIABETIC NEPHROPATHY

A new classification of patients with diabetes mellitus into so-called clusters can be used to assess the risk of developing diabetic nephropathy. Up to date treatment of patients with diabetic nephropathy includes not only glycemic control, but focuses on a holistic approach with prevention of (progression of) secondary diabetic complications and reduction of the patient's cardiovascular mortality.

COMPONENTS OF TREATMENT OF DIABETIC NEPHROPATHY

To achieve this treatment goals, it requires comprehensive management of the patient to implement lifestyle interventions (regarding diet, physical activity, weight loss, smoking cessation) and selection of the medication with the greatest individual benefit.

DIETARY RECOMMENDATIONS IN DIABETIC NEPHROPATHY

Part of lifestyle intervention is adherence to a dietary regimen that has again been shown in recent studies to be relevant in inhibiting progression of chronic kidney disease and reducing cardiovascular risk. In particular, this includes protein restriction with preference for plant sources of protein, and salt restriction.

USE OF MEDICATION CLASSES WITH PROVEN CARDIORENAL BENEFITS

Adjustment of drug therapy is no longer based on antihyperglycemic effects alone, but takes into account inhibition of progression of nephropathy and cardiac risk, as well as support of body weight control. For this purpose, in addition to RAAS inhibitors from the field of antihypertensives, the antidiabetic classes of SGLT2 inhibitors and GLP-1 receptor agonists as well as the non-steroidal aldosterone antagonist finerenone are now available.

Use of sodium-glucose co-transporter-2 inhibitors in Asian patients with type 2 diabetes and kidney disease: An Asian perspective and expert recommendations

Early onset of type 2 diabetes and a high prevalence of co-morbidities predispose the Asian population to a high risk for, and rapid progression of, diabetic kidney disease (DKD). Apart from renin-angiotensin system inhibitors, sodium-glucose co-transporter-2 (SGLT-2) inhibitors have been shown to delay renal disease progression in patients with DKD. In this review article, we consolidate the existing literature on SGLT-2 inhibitor use in Asian patients with DKD to establish contemporary guidance for clinicians. We extensively reviewed recommendations from international and regional guidelines, data from studies on Asian patients with DKD, global trials (DAPA-CKD, CREDENCE and DELIGHT) and cardiovascular outcomes trials. In patients with DKD, SGLT-2 inhibitor therapy significantly reduced albuminuria and the risk of hard renal outcomes (defined as the onset of end-stage kidney disease, substantial decline in renal function from baseline and renal death), cardiovascular outcomes and hospitalization for heart failure. In all the cardiovascular and renal outcomes trials, there was an initial decline in the estimated glomerular filtration rate (eGFR), which was followed by a slowing in the decline of renal function compared with that seen with placebo. Despite an attenuation in glucose-lowering efficacy in patients with low eGFR, there were sustained reductions in body weight and blood pressure, and an increase in haematocrit. Based on the available evidence, we conclude that SGLT-2 inhibitors represent an evidence-based therapeutic option for delaying the progression of renal disease in Asian patients with DKD and preserving renal function in patients at high risk of kidney disease.

The short-term effects of angiotensin II receptor blockers on albuminuria and renal function in Korean patients

Each angiotensin II receptor blocker (ARB) asserts independent molecular effects. No study has compared the renoprotective potency of different types of ARBs in Korea. This study evaluated the differences among medications for treating albuminuria. Data were obtained from electronic medical records of adult patients who underwent albuminuria test and received treatment with either angiotensin-converting enzyme inhibitors (ACEIs) or ARBs between January 2009 and June 2016. Patients' albuminuria and renal function data were observed for three months after treatment initiation. In total, 1475 patients were included. Patients treated with ACEIs had no significant changes in albuminuria (from 127.7 ± 55.1 mg/g to 46.7 ± 18.7 mg/g, P = .127), but those treated with ARBs showed significant improvement (from 491.2 ± 33.2 mg/g to 372.0 ± 28.0 mg/g, P < .001). The ARB group had significantly more patients with normal albuminuria after treatment (from 55.8% to 59.3% for normal albuminuria, from 16.7% to 18.5% for moderately increased albuminuria and from 27.5% to 22.2% for severely increased albuminuria, P = .005), but renal function did not change significantly. Subgroup analysis of ARB types showed that candesartan (from 712.5 ± 71.1 to 489.8 ± 57.8 mg/g, P < .001) and irbesartan (from 522.6 ± 65.7 to 352.6 ± 54.3 mg/g, P < .001) had significant effects. Candesartan improved albuminuria in patients older than 60 years (from 506.9 ± 84.2 to 371.9 ± 70.6 mg/g, P = .004) and irbesartan improved albuminuria in patients with glomerular filtration rate <60 (from 551.6 ± 100.0 to 392.4 ± 76.2, P = .007). Only irbesartan and candesartan could reduce albuminuria, suggesting that all ARBs do not have the same outcome. This indicates the importance of optimizing ARB selection, considering both patient condition and organ-specific characteristics of medications.

Expression of Urokinase-type Plasminogen Activator Receptor and its Soluble Form in Type 2 Diabetic Kidney Disease

BACKGROUND

Urokinase-type plasminogen activator receptor (uPAR) and its soluble form (suPAR) are new injury biomarkers that have been recently suggested to play a vital role in renal diseases.

AIM AND METHODS

We evaluated the expression of uPAR and the serum concentration of suPAR in type 2 diabetes (T₂DM) patients with diabetic kidney disease (DKD) to determine the role of this molecule as a biomarker in DKD. The uPAR immunohistochemical staining was performed in biopsy-confirmed DKD renal tissues. Meanwhile, the serum suPAR, Interleukin-18 (IL-18) and C-reactive protein (CRP) levels of 70 diabetic patients with or without DKD and 15 healthy controls were measured.

RESULTS

The uPAR expression in DKD patients was significantly increased compared to that in healthy controls and was widely colocalized with the podocyte marker WT1. Meanwhile, serum suPAR and IL-18 levels gradually increased as DKD progressed to the advanced stage. Moreover, serum suPAR and IL-18 levels were negatively correlated with eGFR (ρ = ‒0.734, ρ = ‒0.462, p <0.01) and positively correlated with the urine protein to creatinine ratio (UP/CR) (ρ = 0.730, ρ = 0.440, p <0.01). The suPAR AUC performed better than the IL-18 AUC for the diagnosis of proteinuria (0.845 vs. 0.753, p <0.01) and the decline of renal function (0.895 vs. 0.796, p <0.01).

CONCLUSIONS

The uPAR expressed in the renal tissues of DKD patients. The soluble form of uPAR, suPAR, can be detected in the serum of DKD patients and has a better diagnostic efficiency in the diagnosis of proteinuria and renal dysfunction in patients with T₂DM than that of IL-18.

Effectiveness of renoprotective approaches for persistent proteinuria in lupus nephritis: more than just immunosuppression

OBJECTIVE

The objective of this study is to evaluate the efficacy of a tightly controlled renoprotective protocol in systemic lupus erythematosus (SLE) patients with persistent proteinuria.

METHODS

Thirteen SLE patients with nephritis and persistent proteinuria (>1 g/24 hours) were included. The protocol consisted of regular clinical evaluations every two weeks to assess blood pressure (BP, target <130/80 mmHg), adherence to therapy, diet and smoking. No change in immunosuppressive drugs was allowed but reduction of glucocorticoid dose was permitted if indicated. Clinical, laboratory and treatment evaluations were performed at baseline and at the end of the study (after three months).

RESULTS

SLE patients had a mean age of 37.85 ± 7.68 years and disease duration of 9.85 ± 7.29 years. At baseline, patients had a mean duration of maintenance therapy of 10.38 ± 7.56 months, 12 with mycophenolate mofetil (92.3%) and one with azathioprine (7.7%). At least one dose optimization of antihypertensive regimen was required in all patients during the study. Seven patients (53.8%) had BP>130/80mmHg at baseline. At the end, 11 patients (84.6%) achieved stable BP target; 92.3% were using an angiotensin-converting enzyme inhibitor, 53.9% an angiotensin receptor blocker, and 46.2% were using combined therapy. All patients had a significant reduction in proteinuria levels (2.26 ± 1.09 vs 0.88 ± 0.54 g/24 hours, p < 0.001) and 61.5% achieved proteinuria <1 g/24 hours. A significant decrease in mean prednisone dose was observed (10.96 ± 6.73 vs 5.38 ± 3.36 mg/day, p = 0.013) as well as mean Systemic Lupus Erythematosus Disease Activity Index score (4.38 ± 0.72 vs 3.08 ± 1.86, p = 0.043). No significant changes were identified in serum creatinine, albumin, potassium, complement 3 and complement 4 levels ( p > 0.05).

CONCLUSION

This study provides evidence that a tightly controlled renoprotective protocol is effective in reducing persistent proteinuria in lupus nephritis. The concomitant reduction of prednisone without any change in immunosuppression reinforces the importance of strategies beyond the treatment of nephritis activity.

Albuminuria during treatment with angiotensin type II receptor blocker is a predictor for GFR decline among non-diabetic hypertensive CKD patients

BACKGROUND

Albuminuria is a predictor of disease progression in patients with chronic kidney disease (CKD). However, the ability of proteinuria parameters measured at various time periods to predict renal outcomes is unclear.

METHOD

This observational cohort study included 165 non-diabetic hypertensive CKD patients who took olmesartan medoxomil. We measured the albuminuria at five different time points (0, 2, 4, 26, and 38 months) and the mean levels. The mean albuminuria levels were calculated during 0-4 months, 0-26 months, and 0-38 months. The renal outcome was defined as a decline in eGFR ≥ 40% during the entire study period.

RESULT

The albuminuria at five different time points and the mean albuminuria levels were independent risk factors for a worse renal outcome after adjusting for age, sex, and estimated glomerular filtration rate (eGFR) at enrollment and were able to predict the renal outcome, although the performance of the estimation tended to be more effective using the mean albuminuria level at the 38-month follow-up time point. The risk of a decline in eGFR ≥ 40% was increased by 1.690-folds [95% CI 1.110-2.572, P = 0.014] per 500 mg/day increase in the mean albuminuria at 38 months. With a cut-off value of 897 mg/day for mean albuminuria at 38 months after treatment, a decline in eGFR ≥ 40% was predicted with a sensitivity of 88.9% and specificity of 81.3%. The ability of albuminuria to predict a renal event at different measurement points does not differ in CKD patients.

CONCLUSION

The time-averaged albuminuria cut-off of 900 mg/day during the 3-year follow-up period showed high sensitivity and specificity for predicting a decline in eGFR ≥ 40% in CKD patients, although the albuminuria at different measurement points did not predict a worse renal outcome.

Changes in Albuminuria and the Risk of Major Clinical Outcomes in Diabetes: Results From ADVANCE-ON

OBJECTIVE

To assess the association between 2-year changes in urine albumin-to-creatinine ratio (UACR) and the risk of clinical outcomes in type 2 diabetes.

RESEARCH DESIGN AND METHODS

We analyzed data from 8,766 participants in the Action in Diabetes and Vascular Disease: Preterax and Diamicron MR Controlled Evaluation Post-Trial Observational Study (ADVANCE-ON). Change in UACR was calculated from UACR measurements 2 years apart, classified into three groups: decrease in UACR of ≥30%, minor change, and increase in UACR of ≥30%. By analyzing changes from baseline UACR groups, categorized into thirds, we repeated these analyses accounting for regression to the mean (RtM). The primary outcome was the composite of major macrovascular events, renal events, and all-cause mortality; secondary outcomes were these components. Cox regression models were used to estimate hazard ratios (HRs).

RESULTS

Over a median follow-up of 7.7 years, 2,191 primary outcomes were observed. Increases in UACR over 2 years independently predicted a greater risk of the primary outcome (HR for ≥30% UACR increase vs. minor change: 1.26; 95% CI 1.13-1.41), whereas a decrease in UACR was not significantly associated with lower risk (HR 0.93; 95% CI 0.83-1.04). However, after allowing for RtM, the effect of "real" decrease in UACR on the primary outcome was found to be significant (HR 0.84; 95% CI 0.75-0.94), whereas the estimated effect on an increase was unchanged.

CONCLUSIONS

Changes in UACR predicted changes in the risk of major clinical outcomes and mortality in type 2 diabetes, supporting the prognostic utility of monitoring albuminuria change over time.

Changes in Proteinuria on the Risk of All-Cause Mortality in People with Diabetes or Prediabetes: A Prospective Cohort Study

BACKGROUND

Proteinuria has been related to all-cause mortality, showing regression or progression. However, few studies have focused on the relationship between proteinuria changes and all-cause mortality. The main purpose of this paper is to examine the associations between proteinuria changes and all-cause mortality in people with diabetes or prediabetes.

METHODS

Dipstick proteinuria at baseline and a 2-year follow-up were determined in the participants attending the Kailuan prospective cohort study. Participants were then divided into three categories: elevated proteinuria, stable proteinuria, and reduced proteinuria. Four Cox proportional hazard models were built to access the relations of proteinuria changes to all-cause mortality, adjusting for other confounding covariates.

RESULTS

A total of 17,878 participants were finally included in this study. There were 1193 deaths after a median follow-up of 6.69 years. After adjusting for major covariates and proteinuria at baseline, mortality risk was significantly associated with elevated proteinuria (hazard ratio (HR): 1.54, 95% confidence interval (CI): 1.33-1.79) and reduced proteinuria (HR: 0.70, 95% CI: 0.55-0.89), compared to those with stable proteinuria.

CONCLUSION

Proteinuria changes were independently associated with mortality risk in either diabetic or prediabetic population.

Soluble urokinase receptor (suPAR) predicts microalbuminuria in patients at risk for type 2 diabetes mellitus

Early identification of patients at risk of developing diabetic nephropathy is essential. Elevated serum concentrations of soluble urokinase receptor (suPAR) associate with diabetes mellitus and predict onset and loss of renal function in chronic kidney disease. We hypothesize, that suPAR may be an early risk indicator for diabetic nephropathy, preceding microalbuminuria. The relationship of baseline suPAR and incident microalbuminuria was assessed in a prospective long-term cohort of subjects at increased risk for type 2 diabetes (TULIP, n = 258). Association with albuminuria at later stages of disease was studied in a cross-sectional cohort with manifest type 2 diabetes (ICEPHA, n = 266). A higher baseline suPAR was associated with an increased risk of new-onset microalbuminuria in subjects at risk for type 2 diabetes (hazard ratio 5.3 (95% CI 1.1-25.2, p = 0.03) for the highest vs. lowest suPAR quartile). The proportion of subjects with prediabetes at the end of observation was higher in subjects with new-onset microalbuminuria. suPAR consistently correlated with albuminuria in a separate cohort with manifest type 2 diabetes. Elevated baseline suPAR concentrations independently associate with new-onset microalbuminuria in subjects at increased risk of developing type 2 diabetes. suPAR may hence allow for earlier risk stratification than microalbuminuria.

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.

Is a reduction in albuminuria associated with renal and cardiovascular protection? A post hoc analysis of the ALTITUDE trial

AIMS

To investigate whether the degree of albuminuria reduction observed in the ALTITUDE trial is associated with renal and cardiovascular protection, and secondly, whether the reduction in albuminuria was too small to afford clinical benefit.

METHODS

In a post hoc analysis of the ALTITUDE trial in 8561 patients with type 2 diabetes and chronic kidney disease or cardiovascular disease we examined the effect of albuminuria changes at 6 months on renal and cardiovascular outcomes using Cox proportional hazard regression.

RESULTS

The median change in albuminuria in the first 6 months in the aliskiren arm of the trial was -12% (25th to 75th percentile: -48.7_to_ +41.9%) and 0.0% (25th to 75th percentile: -40.2_to_55%) in the placebo arm. Changes in albuminuria in the first 6 months were linearly associated with renal and cardiovascular endpoints: a >30% reduction in albuminuria in the first 6 months was associated with a 62% reduction in renal risk and a 25% reduction in cardiovascular risk compared with an increase in albuminuria. The association between changes at 6 months in albuminuria and renal or cardiovascular endpoints was similar in the two treatment groups (p for interaction >0.1 for both endpoints).

CONCLUSIONS

The addition of aliskiren to angiotensin-converting enzyme inhibitor/angiotensin receptor blocker therapy resulted in albuminuria changes that were associated with renal and cardiovascular risk changes. This did not translate into renal or cardiovascular protection because the overall reduction in albuminuria in the aliskiren arm was too small and nearly similar to that in the placebo arm.

The glycocalyx--linking albuminuria with renal and cardiovascular disease

Albuminuria is commonly used as a marker of kidney disease progression, but some evidence suggests that albuminuria also contributes to disease progression by inducing renal injury in specific disease conditions. Studies have confirmed that in patients with cardiovascular risk factors, such as diabetes and hypertension, endothelial damage drives progression of kidney disease and cardiovascular disease. A key mechanism that contributes to this process is the loss of the glycocalyx--a polysaccharide gel that lines the luminal endothelial surface and that normally acts as a barrier against albumin filtration. Degradation of the glycocalyx in response to endothelial activation can lead to albuminuria and subsequent renal and vascular inflammation, thus providing a pathophysiological framework for the clinical association of albuminuria with renal and cardiovascular disease progression. In this Review, we examine the likely mechanisms by which glycocalyx dysfunction contributes to kidney injury and explains the link between cardiovascular disease and albuminuria. Evidence suggests that glycocalyx dysfunction is reversible, suggesting that these mechanisms could be considered as therapeutic targets to prevent the progression of renal and cardiovascular disease. This possibility enables the use of existing drugs in new ways, provides an opportunity to develop novel therapies, and indicates that albuminuria should be reconsidered as an end point in clinical trials.

Predictors of Atrasentan-Associated Fluid Retention and Change in Albuminuria in Patients with Diabetic Nephropathy

BACKGROUND AND OBJECTIVES

Endothelin A receptor antagonists (ERAs) decrease residual albuminuria in patients with diabetic kidney disease; however, their clinical utility may be limited by fluid retention. Consequently, the primary objective of this study was to identify predictors for ERA-induced fluid retention among patients with type 2 diabetes and CKD. A secondary objective was to determine if the degree of fluid retention necessarily correlated with the magnitude of albuminuria reduction in those patients receiving ERAs.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A post hoc analysis was conducted of the phase IIb atrasentan trials assessing albuminuria reduction in 211 patients with type 2 diabetes, urine albumin/creatinine ratios of 300-3500 mg/g, and eGFRs of 30-75 ml/min per 1.73 m(2) who were randomly assigned to receive placebo (n=50) or atrasentan 0.75 mg/d (n=78) or 1.25 mg/d (n=83) for 12 weeks. Changes in body weight and hemoglobin (Hb) after 2 weeks of treatment were used as surrogate markers of fluid retention.

RESULTS

Baseline predictors of weight gain after 2 weeks of atrasentan treatment were higher atrasentan dose, lower eGFR, higher glycated hemoglobin, higher systolic BP, and lower homeostatic metabolic assessment product. Higher atrasentan dose and lower eGFR also predicted decreases in Hb. There were no changes in B-type natriuretic peptide. There was no correlation between reduction in albuminuria after 2 weeks of atrasentan treatment and changes in body weight or Hb.

CONCLUSIONS

In the Reducing Residual Albuminuria in Subjects With Diabetes and Nephropathy With Atrasentan/JAPAN trials, atrasentan-associated fluid retention was more likely in patients with diabetes and nephropathy who had lower eGFR or received a higher dose of atrasentan. Finding that albuminuria reduction was not associated with changes in body weight and Hb suggests that the albuminuria-reducing efficacy of atrasentan is not impaired by fluid retention.

Inhibition of RAS in diabetic nephropathy

Diabetic kidney disease (DKD) is a progressive proteinuric renal disorder in patients with type 1 or type 2 diabetes mellitus. It is a common cause of end-stage kidney disease worldwide, particularly in developed countries. Therapeutic targeting of the renin-angiotensin system (RAS) is the most validated clinical strategy for slowing disease progression. DKD is paradoxically a low systematic renin state with an increased intrarenal RAS activity implicated in its pathogenesis. Angiotensin II (AngII), the main peptide of RAS, is not only a vasoactive peptide but functions as a growth factor, activating interstitial fibroblasts and mesangial and tubular cells, while promoting the synthesis of extracellular matrix proteins. AngII also promotes podocyte injury through increased calcium influx and the generation of reactive oxygen species. Blockade of the RAS using either angiotensin converting enzyme inhibitors, or angiotensin receptor blockers can attenuate progressive glomerulosclerosis in animal models, and slows disease progression in humans with DKD. In this review, we summarize the role of intrarenal RAS activation in the pathogenesis and progression of DKD and the rationale for RAS inhibition in this population.

Drug-Induced Reduction in Albuminuria Is Associated with Subsequent Renoprotection: A Meta-Analysis

Albuminuria has been proposed as a surrogate end point in randomized clinical trials of renal disease progression. Most evidence comes from observational analyses showing that treatment-induced short-term changes in albuminuria correlate with risk change for ESRD. However, such studies are prone to selection bias and residual confounding. To minimize this bias, we performed a meta-analysis of clinical trials to correlate the placebo-corrected drug effect on albuminuria and ESRD to more reliably delineate the association between changes in albuminuria and ESRD. MEDLINE and EMBASE were searched for clinical trials reported between 1950 and April 2014. Included trials had a mean follow-up of ≥1000 patient-years, reported ESRD outcomes, and measured albuminuria at baseline and during follow-up. Twenty-one clinical trials involving 78,342 patients and 4183 ESRD events were included. Median time to first albuminuria measurement was 6 months. Fourteen trials tested the effect of renin-angiotensin-aldosterone-system inhibitors and seven trials tested other interventions. We observed variability across trials in the treatment effect on albuminuria (range, -1.3% to -32.1%) and ESRD (range, -55% to +35% risk change). Meta-regression analysis revealed that the placebo-adjusted treatment effect on albuminuria significantly correlated with the treatment effect on ESRD: for each 30% reduction in albuminuria, the risk of ESRD decreased by 23.7% (95% confidence interval, 11.4% to 34.2%; P=0.001). The association was consistent regardless of drug class (P=0.73) or other patient or trial characteristics. These findings suggest albuminuria may be a valid substitute for ESRD in many circumstances, even taking into account possible other drug-specific effects that may alter renal outcomes.