Effect of low-dose dual blockade of renin-angiotensin system on urinary TGF-beta in type 2 diabetic patients with advanced kidney disease

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.

Combination Therapy Use and Associated Events in Clinical Practice Following Dissemination of Trial Findings: A De-Implementation Study Using Interrupted Time Series Analysis

PURPOSE

It takes 17 years, on average, for trial results to be implemented into practice. Using data from the Department of Veterans Affairs (VA), this study assessed the potential impact on clinical practice of the dissemination of findings from a randomized, controlled trial reporting harm with the use of combination therapy. Communication between research and VA Pharmacy Benefits Management Services (PBM)  provided the impetus for communication from the PBM about the findings of the trial in accordance with policy.

METHODS

In this de-implementation study, interrupted time series analysis was used for assessing prescribing patterns and adverse clinical events before and after the dissemination of the trial findings. The de-implementation strategy was multicomponent and multilevel. Strategies were aligned with categories outlined in the Expert Recommendations for Implementing Change: train and educate stakeholders, use evaluative and iterative strategies, develop stakeholder inter-relationships, change infrastructure, provide interactive assistance, and engage consumers. VA patients with type 2 diabetes mellitus, chronic kidney disease stages 1 to 3, and a moderate or severe albuminuria who received care between July 2008 and November 2017 were included. Patients were subgrouped according to treatment with an angiotensin-converting enzyme inhibitor + angiotensin receptor blocker. The primary end point was the prevalence of combination therapy use. Secondary end points were the incidences of acute kidney injury and hyperkalemia.

FINDINGS

This study followed 712,245 patients, 9297 of whom used combination therapy. Data were available from 428,535 and 283,710 patients pre- and post-intervention, respectively; among these, 8324 and 973 patients used combination therapy, the median ages were 66 and 68 years, and 96.92% and 98.82% were men. One month following communication from the PBM, the reductions in combination therapy users, acute kidney injury events, and hyperkalemia were 331.94 (95% CI, 500.27-163.32), 36.58% (95% CI, 31.90%-41.95%), and 25.49% (95% CI, 14.17%-36.07%) per 100,000 patients per month, respectively (all, P < 0.001), whereas before the communication, these changes were +14.84 (95% CI, 10.27-19.42), -3.46% (95% CI, 3.18-3.74), and -3.27% (95% CI, 2.66%-3.87%) (all, P < 0.001).

IMPLICATIONS

The apparent speed and impact of the implementation of changes resulting from the dissemination of trial findings into VA clinical practice are encouraging. The speed of implementation was much faster than average for health care providers in the United States. Established communications between research and clinical practice, as well as established policy and communications between PBM and clinical practice, may be a model for other health care organizations.

Angiotensin-converting enzyme inhibitor induced cough compared with placebo, and other antihypertensives: A systematic review, and network meta-analysis

Studies have shown that angiotensin converting enzyme inhibitors (ACEIs) are superior in primary and secondary prevention for cardiac mortality and morbidity to angiotensin receptor blocker (ARBs). One of the common side effects from ACEI is dry cough. The aims of this systematic review, and network meta-analysis are to rank the risk of cough induced by different ACEIs and between ACEI and placebo, ARB or calcium channel blockers (CCB). We performed a systematic review, and network meta-analysis of randomized controlled trials to rank the risk of cough induced by each ACEI and between ACEI and placebo, ARB or CCB. A total of 135 RCTs with 45,420 patients treated with eleven ACEIs were included in the analyses. The pooled estimated relative risk (RR) between ACEI and placebo was 2.21 (95% CI: 2.05-2.39). ACEI had more incidences of cough than ARB (RR 3.2; 95% CI: 2.91, 3.51), and pooled estimated of RR between ACEI and CCB was 5.30 (95% CI: 4.32-6.50) Moexipril ranked as number one for inducing cough (SUCRA 80.4%) and spirapril ranked the least (SUCRA 12.3%). The order for the rest of the ACEIs are as follows: ramipril (SUCRA 76.4%), fosinopril (SUCRA 72.5%), lisinopril (SUCRA 64.7%), benazepril (SUCRA 58.6%), quinapril (SUCRA 56.5%), perindopril (SUCRA 54.1%), enalapril (SUCRA 49.7%), trandolapril (SUCRA 44.6%) and, captopril (SUCRA 13.7%). All ACEI has the similar risk of developing a cough. ACEI should be avoided in patients who have risk of developing cough, and an ARB or CCB is an alternative based on the patient's comorbidity.

Efficacy and safety of dual vs single renin-angiotensin-aldosterone system blockade in chronic kidney disease: An updated meta-analysis of randomized controlled trials

BACKGROUND

To lower albuminuria and to achieve blood pressure (BP) goals, dual renin-angiotensin-aldosterone system (RAAS) inhibitors are sometimes used in clinical practice for the treatment of CKD. However, the efficacy and safety of dual RAAS blockade therapy remains controversial.

METHODS

PubMed, EMBASE, and Cochrane Library were searched, and random effects model was used to calculate the effect sizes of eligible studies. Potential sources of heterogeneity were detected by meta-regression and subgroup analysis.

RESULTS

The present meta-analysis of 72 randomized controlled trials with 10,296 patients demonstrated that dual RAAS blockade therapy was superior to monotherapy in reducing the urine albumin excretion, urine protein excretion, and BP. These beneficial effects were related to the decrease of glomerular filtration rate, the increase of serum potassium level, and higher rates of hyperkalemia and hypotension. Meanwhile, these effects did not lead to improvements in short-term or long-term outcomes, including doubling of serum creatinine, acute kidney injury, end-stage renal disease, mortality, and hospitalization. Compared with the single therapy, angiotensin-converting enzyme inhibitor (ACEI) in combination with angiotensin-receptor blocker (ARB) was a better dual therapy than ACEI or ARB in combination with renin inhibitor or aldosterone receptor antagonist in decreasing urine albumin excretion, urine protein excretion and BP, and the combination was not associated with a lower glomerular filtration rate.

CONCLUSION

Compared with the single therapy, ACEI in combination with ARB was a better dual therapy than ACEI or ARB in combination with renin inhibitor or aldosterone receptor antagonist. Although ACEI in combination with ARB was associated with higher incidences of hyperkalemia and hypotension, careful individualized management and potassium binders may further expand its application (PROSPERO number CRD42020179398).

Efficacy and Safety of Angiotensin-Converting Enzyme Inhibitor in Combination with Angiotensin-Receptor Blocker in Chronic Kidney Disease Based on Dose: A Systematic Review and Meta-Analysis

Background: The purpose of this meta-analysis was to evaluate the controversy of angiotensin-converting enzyme inhibitor (ACEI) in combination with angiotensin-receptor blocker (ARB) in the treatment of chronic kidney disease (CKD) based on dose.

Methods: PubMed, EMBASE, and Cochrane Library were searched to identify randomized controlled trials (RCTs) from inception to March 2020. The random effects model was used to calculate the effect sizes. Potential sources of heterogeneity were detected using sensitivity analysis and meta-regression.

Results: This meta-analysis of 53 RCTs with 6,375 patients demonstrated that in patients with CKD, ACEI in combination with ARB was superior to low-dose ACEI or ARB in reducing urine albumin excretion (SMD, −0.43; 95% CI, −0.67 to −0.19; p = 0.001), urine protein excretion (SMD, −0.22; 95% CI, −0.33 to −0.11; p < 0.001), and blood pressure (BP), including systolic BP (WMD, −2.89; 95% CI, −3.88 to −1.89; p < 0.001) and diastolic BP (WMD, −3.02; 95% CI, −4.46 to −1.58; p < 0.001). However, it was associated with decreased glomerular filtration rate (GFR) (SMD, −0.13; 95% CI, −0.24 to −0.02; p = 0.02) and increased rates of hyperkalemia (RR, 2.07; 95% CI, 1.55 to 2.76; p < 0.001) and hypotension (RR, 2.19; 95% CI, 1.35 to 3.54; p = 0.001). ACEI in combination with ARB was more effective than high-dose ACEI or ARB in reducing urine albumin excretion (SMD, −0.84; 95% CI, −1.26 to −0.43; p < 0.001) and urine protein excretion (SMD, −0.24; 95% CI, −0.39 to −0.09; p = 0.002), without decrease in GFR (SMD, 0.02; 95% CI, −0.12 to 0.15; p = 0.78) and increase in rate of hyperkalemia (RR, 0.94; 95% CI, 0.65 to 1.37; p = 0.76). Nonetheless, the combination did not decrease the BP and increased the rate of hypotension (RR, 3.95; 95% CI, 1.13 to 13.84; p = 0.03) compared with high-dose ACEI or ARB.

Conclusion: ACEI in combination with ARB is superior in reducing urine albumin excretion and urine protein excretion. The combination is more effective than high-dose ACEI or ARB without decreasing GFR and increasing the incidence of hyperkalemia. Despite the risk of hypotension, ACEI in combination with ARB is a better choice for CKD patients who need to increase the dose of ACEI or ARB (PROSPERO CRD42020179398).

Efficacy of telmisartan for the treatment of persistent renal proteinuria in dogs: A double-masked, randomized clinical trial

BACKGROUND

Information regarding efficacy of the angiotensin II receptor blocker, telmisartan, for treatment of proteinuria in dogs is limited.

OBJECTIVE

To evaluate the antiproteinuric efficacy of telmisartan, as compared to enalapril, in dogs with chronic kidney disease and persistent, renal proteinuria.

ANIMALS

Thirty-nine client-owned dogs with chronic kidney disease and urinary protein-to-creatinine ratio (UPC) > 0.5 (if azotemic) or ≥ 1.0 (if nonazotemic).

METHODS

In this prospective, randomized, double-masked clinical trial, dogs were block randomized, according to presence or absence of azotemia and systemic arterial hypertension, to receive telmisartan (1.0 mg/kg PO q24h), or enalapril (0.5 mg/kg PO q12h), and followed for 120 days. Up-titration of study drug dosage on days 30 and 60, and addition of the other study drug at day 90, were performed if UPC > 0.5 was noted at these visits. Percentage change in UPC relative to baseline was calculated for all time points. Data are presented as median (range).

RESULTS

Thirty-nine (20 telmisartan-treated, 19 enalapril-treated) dogs were included. At day 30, percentage change in UPC was greater for telmisartan-treated (-65% [-95% to 104%]) vs enalapril-treated (-35% [-74% to 87%]) dogs (P = .002). Among dogs persistently proteinuric at earlier visits, telmisartan remained superior to enalapril at days 60 (P = .02) and 90 (P = .02). No difference in percentage change in UPC between study groups was observed at day 120, when combination therapy was allowed. Combination therapy resulted in relevant azotemia in 4/13 (31%) dogs.

CONCLUSIONS AND CLINICAL IMPORTANCE

Telmisartan might be a suitable first-line therapy for dogs with renal proteinuria.

Sodium Bicarbonate Supplementation and Urinary TGF-β1 in Nonacidotic Diabetic Kidney Disease: A Randomized, Controlled Trial

BACKGROUND AND OBJECTIVES

In early-phase studies of individuals with hypertensive CKD and normal serum total CO₂, sodium bicarbonate reduced urinary TGF-β1 levels and preserved kidney function. The effect of sodium bicarbonate on kidney fibrosis and injury markers in individuals with diabetic kidney disease and normal serum total CO₂ is unknown.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We conducted a randomized, double-blinded, placebo-controlled study in 74 United States veterans with type 1 or 2 diabetes mellitus, eGFR of 15-89 ml/min per 1.73 m², urinary albumin-to-creatinine ratio (UACR) ≥30 mg/g, and serum total CO₂ of 22-28 meq/L. Participants received oral sodium bicarbonate (0.5 meq/kg lean body wt per day; n=35) or placebo (n=39) for 6 months. The primary outcome was change in urinary TGF-β1-to-creatinine from baseline to months 3 and 6. Secondary outcomes included changes in urinary kidney injury molecule-1 (KIM-1)-to-creatinine, fibronectin-to-creatinine, neutrophil gelatinase-associated lipocalin (NGAL)-to-creatinine, and UACR from baseline to months 3 and 6.

RESULTS

Key baseline characteristics were age 72±8 years, eGFR of 51±18 ml/min per 1.73 m², and serum total CO₂ of 24±2 meq/L. Sodium bicarbonate treatment increased mean total CO₂ by 1.2 (95% confidence interval [95% CI], 0.3 to 2.1) meq/L, increased urinary pH by 0.6 (95% CI, 0.5 to 0.8), and decreased urinary ammonium excretion by 5 (95% CI, 0 to 11) meq/d and urinary titratable acid excretion by 11 (95% CI, 5 to 18) meq/d. Sodium bicarbonate did not significantly change urinary TGF-β1/creatinine (difference in change, 13%, 95% CI, -10% to 40%; change within the sodium bicarbonate group, 8%, 95% CI, -10% to 28%; change within the placebo group, -4%, 95% CI, -19% to 13%). Similarly, no significant effect on KIM-1-to-creatinine (difference in change, -10%, 95% CI, -38% to 31%), fibronectin-to-creatinine (8%, 95% CI, -15% to 37%), NGAL-to-creatinine (-33%, 95% CI, -56% to 4%), or UACR (1%, 95% CI, -25% to 36%) was observed.

CONCLUSIONS

In nonacidotic diabetic kidney disease, sodium bicarbonate did not significantly reduce urinary TGF-β1, KIM-1, fibronectin, NGAL, or UACR over 6 months.

Fixed combinations in modern hypertension treatment algorithms

Modern appropriate treatment of hypertension involves the use of combination antihypertensive therapy. According to updated version of European Society of Cardiology 2018 guidelines, renin-angiotensin-aldosterone system blockers must be used as first-line drugs, including in combination with hydrochlorothiazide. This article presents the algorithms for the management of patients with uncomplicated and asymptomatic (with target lesions) arterial hypertension. It also described the management of patients with concomitant cardiovascular, cerebrovascular, renal pathology and diabetes mellitus, and use of fixed combination of candesartan and hydrochlorothiazide. The article presents research data that confirmed not only the high antihypertensive efficacy of this combination, but also demonstrated its neutral metabolic profile, organ-protective effects, the ability to use in patients with chronic kidney disease, chronic heart failure, prior stroke, as well as high tolerability and treatment adherence.

From Renal Biomarkers to Therapeutic Targets: The Use of Monocyte Chemoattractant Protein 1, Transforming Growth Factor-Beta, and Connective Tissue Growth Factor in Diabetic Nephropathy and Antineutrophil Cytoplasmic Antibody-Associated Vasculitis

In an ideal world, every condition would have a sensitive and specific marker that could be measured in a noninvasive or minimally invasive way. Instead, the medical community depends on invasive biomarkers, which carry inherent risks, to make a diagnosis and plan treatment. In this review article, the current state of research into biomarkers for a range of kidney diseases is discussed, beginning with those biomarkers that are already in clinical use and then moving to conditions for which no validated biomarker yet exists. This review focusses on diabetic nephropathy at the proteinuric end of the spectrum and antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis at the nephritic end. An interesting feature is that the same biomarker, monocyte chemoattractant protein-1 (MCP-1, also known as CCL2), has been identified as a potential target in both conditions, which suggests a shared pathogenic process that results in two very distinct clinical presentations. One of the major limiting features of research into this area, particularly for ANCA-associated vasculitis, is the recruitment of a sufficient number of patients to generate strong enough evidence to justify the biomarker’s routine use; this overlap in biomarkers may enable research in one condition to be applied more generally. In addition to their role as biomarkers, these molecules are also therapeutic targets, and some early research has been carried out to investigate this. Overall, this review brings together research from diverse fields to focus attention on the outstanding areas and the future areas that warrant further investigation.

Genistein attenuates renal fibrosis in streptozotocin‑induced diabetic rats

The present study aimed to investigate the antifibrogenic effects of genistein (GEN) on the kidney in streptozotocin (STZ)-induced diabetic rats and to determine the associated mechanisms. Rats were randomized into four groups: Normal control (N), STZ (S), L (STZ + low-dose GEN) and H (STZ + high-dose GEN). After 8 weeks, the fasting blood glucose (FBG) level, the ratio of kidney weight to body weight (renal index), 24-h urine protein, blood urea nitrogen (BUN), serum creatinine (SCr), renal total antioxidant capacity (T-AOC), superoxide dismutase (SOD), lipid peroxidation (LPO), malondialdehyde (MDA) and hydroxyproline (Hyp) contents were measured. The histomorphology and ultrastructure of the kidney were also assessed. In addition, mRNA expression levels of transforming growth factor-β1 (TGF-β1) and protein expression levels of nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), NAD(P)H:quinone oxidoreductase 1 (NQO1), TGF-β1, mothers against decapentaplegic homolog 3 (Smad3), phosphorylated (p)-Smad3 and collagen IV were estimated. Compared with group N, the levels of FBG, renal index, 24-h urine protein, BUN, SCr, LPO, MDA and Hyp were increased, whereas the levels of T-AOC and SOD were decreased in group S. The structure of renal tissue was damaged, and the expression of Nrf2, HO-1 and NQO1 were reduced, whereas the expression of TGF-β1, Smad3, p-Smad3 and collagen IV were increased in group S. Compared with group S, the aforementioned indices were improved in groups L and H. In conclusion, GEN exhibited reno-protective effects in diabetic rats and its mechanisms may be associated with the inhibition of oxidative stress by activating the Nrf2-HO-1/NQO1 pathway, and the alleviation of renal fibrosis by suppressing the TGF-β1/Smad3 pathway.

Improvements in the Management of Diabetic Nephropathy

The burden of diabetes mellitus is relentlessly increasing. Diabetic nephropathy is the most common cause of end-stage renal disease (ESRD) worldwide and a major cause of morbidity and mortality in patients with diabetes. The current standard therapy of diabetic nephropathy involves intensive treatment of hyperglycemia and strict blood pressure control, mainly via blockade of the renin-angiotensin system (RAS). Attention has been drawn to additional beneficial effects of oral hypoglycemic drugs and fibrates on other aspects of diabetic nephropathy. On the other hand, antiproteinuric effects of RAS combination therapy do not seem to enhance the prevention of renal disease progression, and it has been associated with an increased rate of serious adverse events. Novel agents, such as bardoxolone methyl, pentoxifylline, inhibitors of protein kinase C (PKC), sulodexide, pirfenidone, endothelin receptor antagonists, vitamin D supplements, and phosphate binders have been associated with controversial outcomes or significant side effects. Although new insights into the pathogenetic mechanisms have opened new horizons towards novel interventions, there is still a long way to go in the field of DN research. The aim of this review is to highlight the recent progress made in the field of diabetes management based on the existing evidence. The article also discusses novel targets of therapy, with a special focus on the major pathophysiologic mechanisms implicated in the initiation and progression of diabetic nephropathy.

Beta-casomorphin-7 prevents epithelial-mesenchymal transdifferentiation of NRK-52E cells at high glucose level: Involvement of AngII-TGF-β1 pathway

BACKGROUND

Hyperglycemia is the most important risk factor in the progression of renal fibrosis in diabetic kidney. Based on previous studies, β-casomorphin-7 may exert anti-fibrotic activities in diabetic rats. However, the role of β-casomorphin-7 in the pathogenesis of renal tubulointerstitial fibrosis remains unclear. Thus, this study was designed to investigate the protective effect of β-casomorphin-7 on epithelial-mesenchymal transition (EMT) of NRK-52E cells treated under hyperglycemic condition and to explore the possible mechanism.

RESEARCH DESIGN AND METHODS

NRK-52E cells were cultured in high glucose (30 mM) for 3 days. Different concentrations of β-casomorphin-7, naloxone (antagonist of opioid receptor) and losartan (antagonist of angiotensin II type I receptor) were added in the culture. Expression of α-smooth muscle actin (α-SMA), E-cadherin, vimentin and cytokeratin19 mRNA were determined by real-time PCR. Protein levels of E-cadherin and α-SMA were analyzed by Western blotting. The concentrations of angiotensin (Ang) II and transforming growth factor β1 (TGF-β1) in the culture medium were determined.

RESULTS

High glucose-induced up-regulation of vimentin mRNA and α-SMA mRNA and protein were significantly inhibited by β-casomorphin-7. On the contrary, high glucose-induced down-regulation of cytokeratin19 mRNA and E-cad mRNA and protein was significantly reversed by β-casomorphin-7. β-casomorphin-7 significantly alleviate high glucose induced increase of AngII and TGF-β1 in the culture. Moreover, losartan significantly attenuated the expression of TGF-β1 and EMT of NRK-52E cells treated under hyperglycemic condition. But naloxone did not affect the EMT of NRK-52E cells treated by high glucose and β-casomorphin-7.

CONCLUSION

We demonstrate that β-casomorphin-7 has the potential to inhibit high glucose-induced renal proximal tubular EMT partly by modulating AngII-TGF-β1 pathway, but not by opioid receptor.

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.

Meta-analysis: the efficacy and safety of combined treatment with ARB and ACEI on diabetic nephropathy

OBJECTIVE

Angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) reduce proteinuria in diabetic nephropathy (DN). Some studies have suggested that dual blockade of the renin-angiotensin system provides additive benefits in DN but others showed increased adverse events. We performed a meta-analysis to evaluate the efficacy and safety of combination therapy for DN.

METHODS

Studies were identified by searching MEDLINE, EMBASE, PubMed, and CNKI. All trials involved ACEI + ARB (combination therapy), and ACEI or ARB alone (monotherapy) for DN. The outcomes measured were urinary total proteinuria (UTP), urinary albumin excretion rate (UAER), serum creatinine, glomerular filtration rate (GFR), end-stage renal disease (ESRD), hyperkalemia, hypotension, and acute kidney injury (AKI).

RESULTS

In the 32 included trials, 2596 patients received combination therapy and 3947 received monotherapy. UTP and UAER were significantly reduced by combined treatment compared with monotherapy. It was notable that low doses of combination therapy reduced UTP more than high doses. Serum creatinine, GFR, and ESRD were not significantly different between the two groups. In severe DN, the occurrence of hyperkalemia and AKI were higher with combination therapy. However, in mild DN, the prevalence of hyperkalemia and AKI were the same in both the groups. In mild DN, the occurrence of hypotension was higher with combination therapy; however, in severe DN, it was not different between the two groups.

CONCLUSION

Our meta-analysis suggests that combination therapy can be used on DN with proteinuria, but should be used with caution in those with decreased renal function, especially with severe renal failure.

Diabetic nephropathy - complications and treatment

Diabetic nephropathy is a significant cause of chronic kidney disease and end-stage renal failure globally. Much research has been conducted in both basic science and clinical therapeutics, which has enhanced understanding of the pathophysiology of diabetic nephropathy and expanded the potential therapies available. This review will examine the current concepts of diabetic nephropathy management in the context of some of the basic science and pathophysiology aspects relevant to the approaches taken in novel, investigative treatment strategies.

Angiotensin-converting enzyme inhibitors versus angiotensin receptor blockers for end-stage renal disease/mortality in type 2 diabetes

AIMS

To compare angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) for end-stage renal disease (ESRD) development and all-cause mortality in veterans with macroalbuminuria and with newly documented type 2 diabetes.

METHODS

A retrospective cohort study utilizing data from the national Department of Veterans Affairs (VA) databases. The study followed 5166 subjects without a history of use of ACEIs or ARBs. To control for differences in baseline characteristics between groups, comparisons of subjects ACEIs and ARBs were made by incorporating propensity scores analysis into multivariate logistic regression. This resulted in adjusted odds ratios and 95% confidence intervals for ESRD development and all-cause mortality.

RESULTS

The sample was followed up to five years with a mean follow-up of three years. Subjects taking ACEIs has lower odds of ESRD development (OR, 0.33 [95% CI, 0.13-0.82]) and all-cause mortality (OR, 0.10 [95% CI, 0.04-0.21]) than ARBs.

CONCLUSIONS

This study shows that ACEIs are associated with lower ESRD development and all-cause mortality than ARBs. This may have implications for guidelines which currently suggest that these two therapeutic classes provide similar benefits in people with newly diagnosed type 2 diabetes and macroalbuminuria.

The effect of aliskiren on urinary cytokine/chemokine responses to clamped hyperglycaemia in type 1 diabetes

AIMS/HYPOTHESIS

Acute clamped hyperglycaemia activates the renin-angiotensin-aldosterone system (RAAS) and increases the urinary excretion of inflammatory cytokines/chemokines in patients with uncomplicated type 1 diabetes mellitus. Our objective was to determine whether blockade of the RAAS would blunt the effect of acute hyperglycaemia on urinary cytokine/chemokine excretion, thereby giving insights into potentially protective effects of these agents prior to the onset of clinical nephropathy.

METHODS

Blood pressure, renal haemodynamic function (inulin and para-aminohippurate clearances) and urinary cytokines/chemokines were measured after 6 h of clamped euglycaemia (4-6 mmol/l) and hyperglycaemia (9-11 mmol/l) on two consecutive days in patients with type 1 diabetes mellitus (n = 27) without overt nephropathy. Measurements were repeated after treatment with aliskiren (300 mg daily) for 30 days.

RESULTS

Before aliskiren, clamped hyperglycaemia increased filtration fraction (from 0.188 ± 0.007 to 0.206 ± 0.007, p = 0.003) and urinary fibroblast growth factor-2 (FGF2), IFN-α2 and macrophage-derived chemokine (MDC) (p < 0.005). After aliskiren, the filtration fraction response to hyperglycaemia was abolished, resulting in a lower filtration fraction after aliskiren under clamped hyperglycaemic conditions (p = 0.004), and none of the biomarkers increased in response to hyperglycaemia. Aliskiren therapy also reduced levels of urinary eotaxin, FGF2, IFN-α2, IL-2 and MDC during clamped hyperglycaemia (p < 0.005).

CONCLUSIONS/INTERPRETATION

The increased urinary excretion of inflammatory cytokines/chemokines in response to acute hyperglycaemia is blunted by RAAS blockade in humans with uncomplicated type 1 diabetes mellitus.

Suramin: a potential therapy for diabetic nephropathy

Objective

To determine whether delayed administration of a single dose of suramin, a drug that has been used extensively in humans to treat trypanosomiasis, attenuates renal injury in a leptin receptor deficient C57BLKS/J db/db type 2 diabetic nephropathy (T2DN) mouse model.

Research Design and Methods

Groups of female non-diabetic (control) db/m and diabetic db/db mice of 8 and 16 weeks of age, respectively, were treated with suramin (10 mg/kg) or saline i.v. All animals were euthanized one week later. Measurements in mice 1 week following treatment included the following: body weight; blood glucose; urinary protein excretion; pathological lesions in glomeruli and proximal tubules; changes in protein expression of pro-inflammatory transcription factor nuclear factor κB (NF-κB) and intracellular adhesion molecule-1 (ICAM-1), profibrotic transforming growth factor-β1 (TGF-β1), phospho-SMAD-3 and alpha-smooth muscle actin (α-SMA); and immunohistochemical analysis of leukocyte infiltration and collagen 1A2 (COL1A2) deposition.

Results

Immunoblot analysis revealed increased NF-κB, ICAM-1, TGF-β1, phospho-SMAD-3, and α-SMA proteins in both 9 and 17 week db/db mice as compared to db/m control mice. Immunohistochemical analysis revealed moderate leukocyte infiltration and collagen 1A2 (COL1A2) deposition in 9 week db/db mice that was increased in the 17 week db/db mice. Importantly, suramin significantly decreased expression of all these markers in 9 week db/db mice and partially decreased in 17 week db/db mice without altering body weight, blood glucose or urinary protein excretion. There was no difference in creatinine clearance between 9 week db/m and db/db mice ± suramin. Importantly, in the 17 week db/db mice suramin intervention reversed the impaired creatinine clearance and overt histological damage.

Conclusions

Delayed administration of a single dose of suramin in a model of T2DN attenuated inflammation and fibrosis as well as improved renal function, supporting the use of suramin in T2DN.

Efficacy and safety of combined vs. single renin-angiotensin-aldosterone system blockade in chronic kidney disease: a meta-analysis

BACKGROUND

Although dual blockade of the renin-angiotensin-aldosterone system (RAAS) has gained popularity for the treatment of kidney disease, its benefits and potential risks have not been fully elucidated. We conducted a meta-analysis of all randomized controlled trials comparing the efficacy and safety of combined vs. single RAAS blockade therapy in chronic kidney disease (CKD).

METHODS

We performed a literature search using MEDLINE, the Cochrane Central Register of Controlled Trials, ClinicalTrials.gov, scientific abstracts from meetings, and bibliographies of retrieved articles. We used random-effects models to compute net changes and rate differences in variables.

RESULTS

Fifty-nine (25 crossover and 34 parallel-arm) randomized controlled trials (RCTs) comparing the efficacy and safety of combined vs. single RAAS blockade therapy in CKD were identified (4,975 patients). Combined RAAS blockade therapy was associated with a significant net decrease in glomerular filtration rate (GFR) (-1.8ml/min or ml/min/1.73 m(2); P = 0.005), albuminuria (-90mg/g of creatinine; P = 0.001 or -32mg/day; P = 0.03), and proteinuria (-291mg/g; P = 0.003 or -363mg/day; P < 0.001). Combined RAAS blockade therapy was associated with a 9.4% higher rate of regression to normoalbuminuria and a 5% higher rate of achieving the blood pressure (BP) goal (as defined in individual trials). However, combined RAAS blockade therapy was associated with a significant net increase in serum potassium level, a 3.4% higher rate of hyperkalemia, and a 4.6% higher rate of hypotension. There was no effect on doubling of the serum creatinine level, hospitalization, or mortality.

CONCLUSIONS

Although combined RAAS blockade therapy in CKD is associated with a decrease in albuminuria and proteinuria, it is associated with a decrease in GFR and a higher incidence of hyperkalemia and hypotension relative to monotherapy. The potential long-term kidney benefits of combined RAAS blockade therapy require further study.

Urinary MCP-1 and RBP: independent predictors of renal outcome in macroalbuminuric diabetic nephropathy

BACKGROUND

Albuminuria has been considered a sine qua non condition for the diagnosis of diabetic nephropathy (DN) and has been widely used as a surrogate outcome of chronic kidney disease (CKD). However, recent data suggest that albuminuria may fail as a biomarker in a subset of patients, and the search for novel markers is intense.

METHODS

We analyzed the role of urinary RBP and of serum and urinary cytokines (TGF-beta, MCP-1 and VEGF) as predictors of the risk of dialysis, doubling of serum creatinine or death (primary outcome, PO) in 56 type 2 diabetic patients with macroalbuminuric DN.

RESULTS

Mean follow-up time was 30.7±10 months. Urinary RBP and MCP-1 were significantly higher in patients presenting the PO, whereas no difference was shown for TGF-β or VEGF. In the Cox regression, urinary RBP, MCP-1 and VEGF were positively associated and serum VEGF was inversely related to the risk of the PO. However, after adjustments for creatinine clearance, proteinuria, and blood pressure only urinary RBP (OR 11.6; 95% CI 2.7-49.2, p=0.001 for log RBP) and urinary MCP-1 (OR 11.0; 95% CI 1.6-76.4, p=0.02 for log MCP-1) remained as significant independent predictors of the PO.

CONCLUSION

Urinary RBP and MCP-1 are independently related to the risk of CKD progression in patients with macroalbuminuric DN. Whether these biomarkers have a role in the setting of normoalbuminuria and microalbuminuria in DN should be further investigated.

Diabetes-induced renal injury in rats is attenuated by suramin

Progression of hyperglycemia-induced renal injury is a contributing factor for diabetic nephropathy (DN)-induced end-stage renal disease (ESRD), and development of novel therapeutic strategies that act early to prevent progression of DN and ESRD are important. We examined the efficacy and mechanism(s) of suramin on hyperglycemia-induced renal injury before development of overt histological damage. Two groups of male Sprague-Dawley rats received streptozotocin (STZ) and one group received saline. Three weeks later, one STZ group received suramin (10 mg/kg). All animals were euthanized 1 week later (4 weeks). Although there was a decrease in creatinine clearance between control and STZ ± suramin rats, there was no difference in creatinine clearance between STZ rats ± suramin intervention. Liquid chromatography-tandem mass spectroscopy-based analysis revealed increases in urinary proteins that are early indicators of DN (e.g., cystatin C, clusterin, cathepsin B, retinol binding protein 4, and peroxiredoxin-1) in the STZ group, which were blocked by suramin. Endothelial intracellular adhesion molecule-1 (ICAM-1) activation, leukocyte infiltration, and inflammation; transforming growth factor-β1 (TGF-β1) signaling; TGF-β1/SMAD-3-activated fibrogenic markers fibronectin-1, α-smooth muscle actin, and collagen 1A2; activation of proinflammatory and profibrotic transcription factors nuclear factor-κB (NF-κB) and signal transducer and activator of transcription factor-3 (STAT-3), respectively, were all increased in STZ rats and suramin blocked these changes. In conclusion, delayed administration of suramin attenuated 1) urinary markers of DN, 2) inflammation by blocking NF-κB activation and ICAM-1-mediated leukocyte infiltration, and 3) fibrosis by blocking STAT-3 and TGF-β1/SMAD-3 signaling. These results support the potential use of suramin in DN.

Smad3 mediates ANG II-induced hypertensive kidney disease in mice

Although Smad3 is a key mediator for fibrosis, its functional role and mechanisms in hypertensive nephropathy remain largely unclear. This was examined in the present study in a mouse model of hypertension induced in Smad3 knockout (KO) and wild-type (WT) mice by subcutaneous angiotensin II infusion and in vitro in mesangial cells lacking Smad3. After angiotensin II infusion, both Smad3 KO and WT mice developed equally high levels of blood pressure. However, disruption of Smad3 prevented angiotensin II-induced kidney injury by lowering albuminuria and serum creatinine ( P < 0.01), inhibiting renal fibrosis such as collagen type I and IV, fibronectin, and α-SMA expression (all P < 0.01), and blocking renal inflammation including macrophage and T cell infiltration and upregulation of IL-1β, TNF-α, and monocyte chemoattractant protein-1 in vivo and in vitro (all P < 0.001). Further studies revealed that blockade of angiotensin II-induced renal transforming growth factor (TGF)-β1 expression and inhibition of Smurf2-mediated degradation of renal Smad7 are mechanisms by which Smad3 KO mice were protected from angiotensin II-induced renal fibrosis and NF-κB-driven renal inflammation in vivo and in vitro. In conclusion, Smad3 is a key mediator of hypertensive nephropathy. Smad3 promotes Smurf2-dependent ubiquitin degradation of renal Smad7, thereby enhancing angiotensin II-induced TGF-β/Smad3-mediated renal fibrosis and NF-κB-driven renal inflammation. Results from this study suggest that inhibition of Smad3 or overexpression of Smad7 may be a novel therapeutic strategy for hypertensive nephropathy.

Urinary protein as a marker for systolic blood pressure reduction in patients with type 2 diabetes mellitus participating in an in-hospital diabetes education program

Increased blood pressure (BP) and urinary protein (UP)/microalbuminuria are risk factors for cardiovascular disease in patients with diabetes. Although the management of BP in patients with diabetes should involve a multidisciplinary therapy, there are no reports in which modulators have been identified in an in-hospital diabetes education program. The aim of the present study was to investigate the change in BP levels in patients with type 2 diabetes mellitus (T2DM) during a short-term (2-week) in-hospital education program on lifestyle modifications. A total of 167 patients with T2DM (101 men, 66 women; mean age, 61.1 years; glycated hemoglobin, 9.2%) were divided into 2 groups on the basis of their urinary albumin levels: 1 group without UP (urinary albumin level < 30 mg/day) and 1 group with UP (urinary albumin level ≥ 30 mg/day). We defined efficacy in reducing BP as a 20-mm Hg reduction in systolic BP (SBP) and a 10-mm Hg reduction in diastolic BP, and compared the changes between the 2 groups. Although the group with UP had higher SBP levels than the group without UP at baseline, this difference disappeared at the end of the program. Adjusted multivariate logistic regression analysis showed that UP at baseline was associated with a reduction in SBP (odds ratio, 3.361; 95% confidence interval, 1.29-8.79; P = 0.013). The data suggest that UP may be a marker related to the management of SBP through lifestyle modifications in patients with T2DM.

A glimpse of various pathogenetic mechanisms of diabetic nephropathy

Diabetic nephropathy is a well-known complication of diabetes and is a leading cause of chronic renal failure in the Western world. It is characterized by the accumulation of extracellular matrix in the glomerular and tubulointerstitial compartments and by the thickening and hyalinization of intrarenal vasculature. The various cellular events and signaling pathways activated during diabetic nephropathy may be similar in different cell types. Such cellular events include excessive channeling of glucose intermediaries into various metabolic pathways with generation of advanced glycation products, activation of protein kinase C, increased expression of transforming growth factor β and GTP-binding proteins, and generation of reactive oxygen species. In addition to these metabolic and biochemical derangements, changes in the intraglomerular hemodynamics, modulated in part by local activation of the renin-angiotensin system, compound the hyperglycemia-induced injury. Events involving various intersecting pathways occur in most cell types of the kidney.

Mesangial cells stimulated by immunoglobin A1 from IgA nephropathy upregulates transforming growth factor-beta1 synthesis in podocytes via renin-angiotensin system activation

BACKGROUND AND AIMS

We undertook this study to investigate the effect of mesangial cells stimulated by immunoglobin A1 from IgAN on transforming growth factor-beta1 synthesis in podocytes.

METHODS

Jacalin affinity chromatography and Sephacryl S-200 molecular sieve chromatography were used to isolate IgA1 from blood of IgAN patients, which was then used as aggregated IgA1 (aIgA1). Podocytes were incubated with special mesangial medium. Real-time polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA) were used, respectively, to measure TGF-beta1 mRNA expression and its protein concentration in medium.

RESULTS

TGF-beta1 mRNA and its protein concentration in the medium of podocytes increased when exposed to the medium of mesangial cells, which were stimulated by IgA1 from IgAN patients. Angiotensinogen and angiotensin-converting enzyme (ACE) mRNAs, as well as angiotensin II, were also increased by the medium (p <0.05). Enalaprilat and valsartan partly lowered overproduction of TGF-beta1 mRNA and excreted protein of podocytes, whereas enalaprilat plus valsartan completely restored them to the level as control.

CONCLUSIONS

These data suggest that mesangial cells stimulated by IgA1 from IgAN patients may excrete some material to facilitate TGF-beta1 synthesis in podocytes through activating renin-angiotensin system by cross-talk.

Feasibility of combined treatment with enalapril and candesartan in advanced chronic kidney disease

BACKGROUND

Dual blockade of the renin-angiotensin system (RAS) has been claimed to have a specific renal protective effect in chronic kidney disease (CKD). The present short-term study reports on the feasibility of dual blockade in a consecutive group of patients with CKD stage 3-5.

METHODS

Forty-seven CKD patients, mean age 59 years, with mean estimated glomerular filtration rate (GFR) 26 ml/min/1.73 m(2) (range 13-49) and blood pressure (BP) 133/78 mmHg, were block randomized in an open study to 16 weeks of monotherapy with increasing doses of RAS blockade aiming at enalapril 20 mg o.d. or candesartan 16 mg o.d. Thereafter, the complementary drug was added in incremental doses over a period of 5 weeks aiming at combined enalapril 20 mg and candesartan 16 mg for 3 weeks. Seventy-five percent of the patients were known to be RAS blockade tolerant. Blood samples and BP were measured every 2-3 weeks. Doses of study medication were reduced in case of hyperkalemia >5.5 mmol/l, a sustained rise in p-creatinine >30% or symptomatic hypotension.

RESULTS

Twenty-one patients (45%) did not tolerate dual blockade in aimed dosages due to unacceptable p-creatinine increase (n = 12, including two study withdrawals), hypotension (n = 6), general discomfort (n = 2) or unmanageable hyperkalemia (n = 1). Hyperkalemia >5.5 mmol/l was seen in seven patients (15%). The reduced-dose group had baseline lower eGFR and diastolic BP.

CONCLUSIONS

Forty-five percent of CKD stage 3-5 patients did not tolerate dual RAS blockade with 20 mg enalapril and 16 mg candesartan daily, primarily due to loss of renal function or hypotension. Hyperkalemia could be managed in most patients. Caution is recommended when giving this treatment to patients with advanced CKD.

ACE inhibitors, angiotensin receptor blockers and direct renin inhibitors in combination: a review of their role after the ONTARGET trial

BACKGROUND

Clinical trials have shown organ-protective effects of angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs); however, cardiovascular mortality and morbidity rates, and decline in renal function remain high. In the ONTARGET trial in patients with hypertension at high cardiovascular risk, ACE inhibitor/ARB combination therapy provided no significant clinical outcome benefits over monotherapy, and was associated with a worse safety and tolerability profile. These results raise the question of whether ACE inhibitor/ARB, direct renin inhibitor (DRI)/ACE inhibitor and DRI/ARB combinations are of clinical value.

SCOPE

Using PubMed and EMBASE databases, we conducted a systematic review of clinical trials published before June 2008 evaluating dual intervention with ACE inhibitors and ARBs, and compared these with trials of DRI/ACE inhibitor or DRI/ARB combinations.

FINDINGS

A total of 70 studies met the inclusion criteria for this analysis. In patients with hypertension, ACE inhibitor/ARB combinations provided limited additional reductions in blood pressure (BP) over monotherapy. Outcomes benefits were unclear: VALIANT and ONTARGET demonstrated no enhanced outcome benefit of combination therapy over monotherapy; Val-HeFT and CHARM-Added showed reduced morbidity/mortality in patients with heart failure, but at the expense of poorer tolerability. Combination therapy with the DRI aliskiren and an ACE inhibitor or ARB provided significant additional BP reductions over monotherapy in patients with mild-to-moderate hypertension, and reduced surrogate markers of organ damage in patients with heart failure or diabetic nephropathy, with generally similar safety and tolerability to the component monotherapies. No morbidity and mortality data for DRI/ACE inhibitor or DRI/ARB combinations are currently available.

CONCLUSIONS

ACE inhibitor/ARB combinations showed equivocal effects on clinical outcomes. DRI/ACE inhibitor and DRI/ARB combinations reduced markers of organ damage, but longer-term trials are required to establish whether more complete renin--angiotensin--aldosterone system control with aliskiren-based therapy translates into improved outcome benefits.

Fibrosis in diabetes complications: pathogenic mechanisms and circulating and urinary markers

Diabetes mellitus is characterized by a lack of insulin causing elevated blood glucose, often with associated insulin resistance. Over time, especially in genetically susceptible individuals, such chronic hyperglycemia can cause tissue injury. One pathological response to tissue injury is the development of fibrosis, which involves predominant extracellular matrix (ECM) accumulation. The main factors that regulate ECM in diabetes are thought to be pro-sclerotic cytokines and protease/anti-protease systems. This review will examine the key markers and regulators of tissue fibrosis in diabetes and whether their levels in biological fluids may have clinical utility.

Pulse pressure lowering effect of dual blockade with candesartan and lisinopril vs. high-dose ACE inhibition in hypertensive type 2 diabetic subjects: a CALM II study post-hoc analysis

BACKGROUND

Elevated pulse pressure (PP) is strongly associated with micro- and macrovascular complications in type 2 diabetic patients. We examined the effect of 12 months of dual blockade with candesartan and lisinopril vs. high-dose lisinopril monotherapy on ambulatory PP in hypertensive type 2 diabetic patients from the CALM (Candesartan and Lisinopril Microalbuminuria Trial) II study.

METHODS

The CALM II study was a 12-month prospective, randomized, parallel-group, double-masked study that included 75 type 1 and type 2 diabetic subjects with hypertension. Participants were randomized for treatment with either high-dose lisinopril (40 mg once daily (o.d.)) or for dual blockade treatment with candesartan (16 mg o.d.) and lisinopril (20 mg o.d.). In this article, we present data from the post-hoc subgroup of 51 type 2 diabetic subjects who completed the full 12-month study period with successful ambulatory blood pressure (BP) measurements at both baseline and follow-up visits.

RESULTS

Baseline 24-h BP values were similar in the two groups (24-h systolic BP (SBP) 130 +/- 12 vs. 127 +/- 9, 24-h diastolic BP (DBP) 77 +/- 8 vs. 74 +/- 7, and 24-h PP 53 +/- 8 vs. 53 +/- 7 mm Hg, for the lisinopril and dual blockade groups, respectively, P > 0.2 for all). Compared with lisinopril monotherapy, dual blockade treatment caused a highly significant reduction in 24-h PP levels (-5 +/- 5 mm Hg, P = 0.003), albeit the difference in the BP lowering effect between the treatment groups did not differ significantly for 24-h systolic (P = 0.21) or diastolic (P = 0.49) BP. Dual blockade treatment significantly lowered 24-h SBP (-5 +/- 11 mm Hg, P = 0.03), but not 24-h DBP (-2 +/- 7 mm Hg, P = 0.29), whereas in the lisinopril group, the opposite effect was observed (24-h SBP -1 +/- 9 mm Hg, P = 0.45, 24-h SBP -3 +/- 7 mm Hg, P = 0.03).

CONCLUSIONS

Twelve months of dual blockade with candesartan and lisinopril significantly reduced PP when compared with high-dose monotherapy with lisinopril. Larger studies are needed to confirm this observation, and to evaluate whether this effect translates into a greater degree of end-organ protection from dual blockade treatment than from conventional angiotensin-converting enzyme (ACE) inhibition.

Rationale for combination angiotensin receptor blocker and angiotensin-converting enzyme inhibitor treatment and end-organ protection in patients with chronic kidney disease

Chronic kidney disease (CKD) is a major public health problem that has received increasing attention because of the high rate of associated cardiovascular morbidity and mortality. Mounting evidence indicates that angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs), drugs that inhibit the renin-angiotensin-aldosterone system (RAAS) safely slow down progression of CKD. There is also growing evidence supporting combination treatment of nephropathies with an ACE inhibitor plus an ARB to more completely block the RAAS and provide greater renoprotection than either an ACE inhibitor-based or ARB-based regimen. The National Kidney Foundation suggests that ACE inhibitors and ARBs may be used in combination to reduce proteinuria in patients with kidney disease; however, larger outcomes trials are needed.

Polarity of Response to Transforming Growth Factor-β1 in Proximal Tubular Epithelial Cells Is Regulated by β-Catenin

Transforming growth factor-beta1 (TGF-beta1)-mediated loss of proximal tubular epithelial cell-cell interaction is regulated in a polarized fashion. The aim of this study was to further explore the polarity of the TGF-beta1 response and to determine the significance of R-Smad-beta-catenin association previously demonstrated to accompany adherens junction disassembly. Smad3 signaling response to TGF-beta1 was assessed by activity of the Smad3-responsive reporter gene construct (SBE)(4)-Lux and by immunoblotting for phospho-Smad proteins. Similar results were obtained with both methods. Apical application of TGF-beta1 led to increased Smad3 signaling compared with basolateral stimulation. Association of Smad proteins with beta-catenin was greater following basolateral TGFbeta-1 stimulation, as was the expression of cytoplasmic Triton-soluble beta-catenin. Inhibition of beta-catenin expression by small interfering RNA augmented Smad3 signaling. Lithium chloride, a GSK-3 inhibitor, increased expression of beta-catenin and attenuated TGF-beta1-dependent Smad3 signaling. Lithium chloride did not influence degradation of Smad3 but resulted in decreased nuclear translocation. Smad2 activation as assessed by Western blot analysis and activity of the Smad2-responsive reporter constructs ARE/MF1 was also greater following apical as compared with basolateral TGFbeta-1 stimulation, suggesting that this is a generally applicable mechanism for the regulation of TGF-beta1-dependent R-Smads. Caco-2 cells are a colonic carcinoma cell line, with known resistance to the anti-proliferative effects of TGF-beta1 and increased expression of beta-catenin. We used this cell line to address the general applicability of our observations. Inhibition of beta-catenin in this cell line by small interfering RNA resulted in increased TGF-beta1-dependent Smad3 phosphorylation and restoration of TGF-beta1 anti-proliferative effects.

Angiotensin receptor antagonist vs. angiotensin-converting enzyme inhibitor in Asian subjects with type 2 diabetes and albuminuria - a randomized crossover study

BACKGROUND

Subjects with type 2 diabetes mellitus (T2DM) and albuminuria are at risk for progressive diabetic nephropathy. The relative blood pressure lowering and antialbuminuric efficacy of angiotensin receptor antagonist (ARB) vs. angiotensin-converting enzyme (ACE) inhibitor has not been well studied.

METHODS

Forty-one ARB- and ACE inhibitor-naive T2DM subjects with albuminuria (>30 mg/g creatinine) were given either 50 mg of losartan (ARB) or 20 mg of quinapril (ACE inhibitor) (50% maximum dose) for 4 weeks, with a 4-week wash-out period in-between interventions in a crossover fashion. The order of intervention was randomized. The primary endpoint was the reduction of blood pressure and albuminuria. Secondary endpoint was changes in plasma transforming growth factor beta (TGF-beta).

RESULTS

Among the 41 subjects, 66% were male. The mean age (s.d.) was 52 (10) years, and duration of diabetes was 8 (14) years. Blood pressure reduction (though not statistically significant) was similar on both interventions [systolic: losartan 3 (15) vs. quinapril 2 (13) mmHg, p = 0.52; diastolic: losartan 1 (9) vs. quinapril 2 (8) mmHg, p = 0.55]. However, amelioration of albuminuria [mean (s.e.)] was significantly greater with losartan [losartan vs. quinapril: -93 (82) vs. -49 (65) mg/g, p = 0.02]. There was no change in plasma TGF-beta levels [mean (s.d.)] on either treatment, losartan [before 12.1 (8.9) vs. after 11.9 (9.6) ng/ml, p = 0.68] and quinapril [11.1 (7.9) vs. 11.1 (7.8) ng/ml, p = 0.87).

CONCLUSION

In Asian subjects with T2DM and albuminuria, 4 weeks of losartan therapy at 50 mg daily appeared to have greater antialbuminuric effect than 20 mg of quinapril.

Enhanced TGF-beta/Smad signaling in the early stage of diabetic nephropathy is independent of the AT1a receptor

BACKGROUND

Angiotensin II (AII) and transforming growth factor-beta (TGF-beta) are closely involved in the pathogenesis of diabetic nephropathy (DN). AII is known to induce TGF-beta production in resident renal cells, including glomerular mesangial cells and tubular epithelial cells. TGF-beta receptor types I and II (TGF-betaRI, II) are up-regulated in the diabetic kidney. The aim of this study was to clarify the role of AII in the regulation of the TGF-beta system in the early stage of DN using AII type1a receptor-deficient(AT1a(-/-)) mice.

METHODS

We investigated the expression of TGF-beta1, TGF-betaRI, II, and Smad signaling in AT1a(-/-) mice with streptozotocin (STZ)-induced DN. Mice were killed 10 and 20 days after the induction of hyperglycemia. The expression of TGF-beta receptors was analyzed by immunohistochemical staining and reverse transcriptase-polymerase chain reaction (RT-PCR). TGF-beta-specific Smad signaling was analyzed by electrophoretic mobility shift assay and Western blotting.

RESULTS

The expression of both TGF-betaRI and RII was up-regulated in the glomerular tufts and vasculature in diabetic AT1a(+/+) mice kidney by immunohistochemistry. RT-PCR revealed that mRNAs for TGF-betaRI and RII were also up-regulated. Smad2 and 4 protein levels were reduced in the renal cortex after the induction of diabetes, with an increase of Smad 3/4 complex in the nucleus. The expression of TGF-beta receptors increased in both diabetic AT1a(-/-) and AT1a(+/+) mice. Smad signaling in AT1a(-/-) mice was also enhanced.

CONCLUSIONS

Our results suggest that the complete blockade of the AT1a-mediated pathway has a minimal effect on the enhanced TGF-beta/Smad signaling in the early stage of DN, at least in the AT1a(-/-) model.

Urinary albumin excretion and the renin-angiotensin system in cardiovascular risk management

Microalbuminuria has been shown to be a strong predictor of cardiovascular morbidity and mortality in diabetic and hypertensive patients, but also in the general population. Moreover, several reports suggest that reduction of urinary albumin excretion (UAE) is associated with improvement of cardiovascular prognosis. Reduction of UAE can be achieved by lowering arterial blood pressure, but blockers of the renin-angiotensin system (RAS) with their specific renal actions have demonstrated to be able to reduce UAE more than might be expected from reduction of blood pressure alone. Consequently, angiotensin-converting enzyme inhibitors and angiotensin receptor blockers may also provide superior cardiovascular protection, especially in subjects with higher levels of albuminuria, but evidence is still scarce. The ability of both angiotensin-converting enzyme inhibitors and angiotensin receptor blockers to reduce UAE and provide cardiovascular protection suggests that the RAS may play a central role. New developments in this area include the use of aldosterone antagonists in albuminuric/proteinuric subjects, and the development of oral renin inhibitors. Combinations of the aforementioned drugs may have the ability to fully block the RAS, potentially avoiding all detrimental effects of this hormonal cascade. However, combination therapy is expected to also increase the incidence of side effects, such as hyperkalaemia and acute renal insufficiency. The current knowledge of microalbuminuria represents the proverbial tip of the iceberg, and future studies should focus on the underlying pathophysiological mechanism of urinary albumin excretion in relation to cardiovascular protection. Only then can a better understanding of the problem be achieved and the optimal pharmacological approach be ascertained.

Renal injury due to renin-angiotensin-aldosterone system activation of the transforming growth factor-beta pathway

Glomerulosclerosis, interstitial fibrosis, and tubular atrophy occur with end-stage kidney failure, irrespective of the primary etiology. The transforming growth factor-beta (TGF-beta) is a key factor in these alterations either directly, by stimulating synthesis of extracellular matrix components and reducing collagenase production, or indirectly through other profibrogenic factors such as connective tissue growth factor (CTGF). TGF-beta is important for the proliferation of intrarenal fibroblasts and the epithelial-mesenchymal transition through which tubular cells become fibroblasts. Although several factors induce TGF-beta expression in the kidney, one very interesting aspect is the link between the renin-angiotensin-aldosterone (Aldo) system (RAAS) and TGF-beta. Angiotensin II (ANG II) stimulates TGF-beta expression in the kidney by various mechanisms and upregulates receptors for TGF-beta. ANG II can directly phosphorylate Smads without inducing TGF-beta. Recent data provide compelling evidence that other components of the RAAS including ANG III, renin, and Aldo also activate the TGF-beta system. As direct modulation of the TGF-beta system is not yet feasible in humans, angiotensin-converting enzyme (ACE) inhibitors and angiotensin type 1 (AT1)-receptor blockers are currently the most potential drugs to interfere with this ANG II-mediated TGF-beta expression. This review highlights some current aspects of the interaction between the RAAS and the TGF-beta axis.

Combination Therapy With an Angiotensin Receptor Blocker and an ACE Inhibitor in Proteinuric Renal Disease: A Systematic Review of the Efficacy and Safety Data

Blockade of the renin-angiotensin system with either an angiotensin-converting enzyme (ACE) inhibitor or an angiotensin receptor blocker (ARB) was shown to decrease urinary protein excretion and slow the progression of both diabetic and nondiabetic proteinuric renal disease. The safety and efficacy of combined ACE-inhibitor and ARB therapy is not well established. We conducted a systematic review and meta-analysis of randomized trials evaluating the combination of an ACE inhibitor and an ARB in patients with chronic proteinuric renal disease. Twenty-one randomized controlled studies (n = 654 patients) were identified using MEDLINE, EMBASE, and Cochrane Central databases. Five trials had a parallel-group design and 16 trials used a crossover design. Combination therapy with an ACE inhibitor and an ARB resulted in a small, but significant, increase in serum potassium levels (weighted mean difference, 0.11 mEq/L [0.11 mmol/L]; 95% confidence interval [CI], 0.05 to 0.17) and a nonsignificant decrease in glomerular filtration rate (weighted mean difference, 1.4 mL/min [0.02 mL/s]; 95% CI, -2.6 to 0.2). Addition of an ARB resulted in a further decrease in proteinuria (weighted mean difference, 440 mg/d; 95% CI, 289 to 591) compared with an ACE inhibitor alone. This effect was observed in patients with diabetic (210 mg/d; 95% CI, 84 to 336) and nondiabetic (582 mg/d; 95% CI, 371 to 793) renal disease. In conclusion, the combination of ACE-inhibitor and ARB therapy in patients with chronic proteinuric renal disease is safe, without clinically meaningful changes in serum potassium levels or glomerular filtration rates. Combination therapy also was associated with a significant decrease in proteinuria, at least in the short term. Additional trials with longer follow-up are needed to determine whether the decrease in proteinuria will result in significant preservation of renal function.