Combination ACE inhibitor and angiotensin II receptor antagonist therapy in diabetic nephropathy

Mechanism & inhibition kinetics of bioassay-guided fractions of Indian medicinal plants and foods as ACE inhibitors

Hypertension is a becoming a major threat to the world. Angiotensin converting enzyme (ACE) is a key part in the renin angiotensin aldosterone system (RAAS) which control blood pressure. Over expression of RAAS is related with vascular hypertension, ACE inhibition has turned into a noteworthy target for controlling hypertension. In the search of lead molecules from plant origin as a substitute for toxic synthetic drugs, 25 Indian medicinal plants and foods were screened for their ACE inhibitory activity. IC₅₀ (50% inhibition of ACE) values of hydroalcoholic crude extracts and fraction were determined by a colorimetric method. Active fractions were further screened to determine the enzyme kinetics, mode, specificity and mechanism of inhibition. Standardization was done by determining total phenolics and flavonoids as gallic acid and quercetin equivalents/mg of extract respectively. Among 25 crude extracts, Cynara scolymus extract showed the best activity, IC₅₀ value 356.62 μg/mL. ACE inhibition resulting from protein precipitation was highest in Coscinium fenestratum. Lineweaver-Burk plots revealed a competitive mode of inhibition for Punica granatum ethyl acetate fraction. Fractions of Cassia occidentalis, Cynara scolymus and Embelia ribes were found to be non-specific inhibitors of ACE. Embelia ribes, Cassia occidentalis and Coscinium fenestratum fractions inhibited the ACE by Zn²⁺ ion chelation. Research revealed the potential of tested plants fractions as ACE inhibitors along with their inhibition kinetics and mechanism of inhibition. These active plant fractions might find importance in the development of potential antihypertensive agents after further investigations using preclinical and clinical trials.

Combined Treatment With Angiotensin-Converting Enzyme Inhibitors and Angiotensin II Receptor Blockers: A Review of the Current Evidence

Several studies have shown that angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers are useful in the treatment of hypertension, cardiovascular disease, chronic heart failure, and some types of nephropathy. In this context, dual renin-angiotensin system blockade with both angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers may be more effective than treatment with each agent alone. Many clinical trials have demonstrated the beneficial effect of this combined treatment on proteinuria, hypertension, heart failure, and cardiovascular events. Moreover, these studies demonstrated that dual renin-angiotensin system blockade is generally safe and well tolerated. Long-term studies are under way to confirm these effects and also investigate the effectiveness of dual reninangiotensin system blockade on cerebrovascular disease and prevention of type 2 diabetes mellitus. These studies are expected to define the optimal use of combination treatment in everyday clinical practice. This review considers the most important clinical trials that evaluated the effect of dual renin-angiotensin system blockade on blood pressure, heart failure, and renal function.

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.

Clinical challenges in diagnosis and management of diabetic kidney disease

Diabetic kidney disease (DKD) is a major and increasing worldwide public health issue. There is a great need for implementing treatments that either prevent or significantly slow the progression of DKD. Although there have been significant improvements in management, the increasing numbers of patients with DKD illustrate that current management is not wholly adequate. The reasons for suboptimal management include the lack of early diagnosis, lack of aggressive interventions, and lack of understanding about which interventions are most successful. There are a number of challenges and controversies regarding the current management of patients with DKD. Understanding of these issues is needed in order to provide the best care to patients with DKD. This article describes some of the clinically important challenges associated with DKD: the current epidemiology and cost burden and the role of biopsy in the diagnosis of DKD. Treatment controversies regarding current pharmacologic and nonpharmacologic approaches are reviewed and recommendations based on the published literature are made.

Combination use of angiotensin converting enzyme inhibitors and angiotensin receptor blockers in diabetic kidney disease

Angiotensin converting enzyme inhibitors (ACE-I) and angiotensin receptor blockers (ARB) have played a major role in slowing the progression of diabetic kidney disease, since they lower urine protein levels, lower blood pressure, and slow progression. Studies have suggested that the combination of ACE-I and ARB offered greater benefits for patients with diabetic kidney disease. In 2008, the large ONTARGET study reported no benefit with combination therapy, as compared with monotherapy. This study has changed practice patterns, but few patients in this study had diabetic kidney disease. In this review, the data in favor of the combination use of these agents in patients with diabetic kidney disease and data against the combination are reviewed. At this time, there is little support for using the combination in diabetic patients with no kidney disease or early stage diabetic kidney disease. But there are patients who may benefit from combination use.

Therapeutic approaches to slowing the progression of diabetic nephropathy - is less best?

OBJECTIVE

Angiotensin II receptor blockers (ARBs) and angiotensin-converting enzyme (ACE) inhibitors are known to reduce proteinuria and have been the first-line agents in the management of diabetic nephropathy for the past 20 years. This review covers recent studies that compare the benefit of additional blockage of the renin-angiotensin-aldosterone system through combination therapy with an ACE inhibitor and ARB, or a direct renin inhibitor (DRI), to monotherapy.

DESIGN

Primary and review articles that addressed the pathophysiology, diagnosis, and therapeutic options for attenuating the progression of diabetic nephropathy were retrieved through a MEDLINE search (January 1990 to December 2012) and the bibliographies of identified articles were reviewed. English language sources were searched using the following search terms: diabetes mellitus, nephropathy, proteinuria, ACE inhibitors, ARBs, and DRIs.

SETTING

Randomized, placebo-controlled, short- and long-term studies published in peer-reviewed journals that were determined to be methodologically sound, with appropriate statistical analysis of the results, were selected for inclusion in this review.

PARTICIPANTS

Adult (≥18 years) patients with diabetic nephropathy.

MEASUREMENTS

Serum creatinine level was used to estimate glomerular filtration rate (GFR). GFR was calculated using the four-variable Modification of Diet in Renal Disease formula. The urine albumin-to-creatinine ratio was measured at baseline and at the conclusion of each study. A value between 3.4 mg/mmol and below 33.9 mg/mmol was defined as microalbuminuria. A value of 33.9 mg/mmol or more (approximately 300 mg/g creatinine) was defined as macroalbuminuria.

RESULTS

ACE inhibitors and ARBs are now the mainstay of treatment for diabetic nephropathy. However, combination therapy with an ACE inhibitor and an ARB, or DRI, has not been found to be more effective than monotherapy with an ACE inhibitor or ARB, and may increase the risk of hyperkalemia or acute kidney injury.

CONCLUSION

Both ACE inhibitors and ARBs remain the first-line agents in attenuating the progression of diabetic nephropathy; however, recent studies suggest that combining an ACE inhibitor with an ARB, or combining a DRI with an ACE inhibitor or ARB, may increase adverse events without clinical benefits to offset them.

Potential antifibrotic effects of AT1 receptor antagonist, losartan, and/or praziquantel on acute and chronic experimental liver fibrosis induced by Schistosoma mansoni

1. This study investigates the potential antifibrotic effect of losartan, AT-1 receptor antagonist, and/or praziquantel (PZQ) on acute and chronic hepatic fibrosis induced by Schistosoma mansoni (S. mansoni). 2. Schistosoma mansoni-infected mice were in two batches (I & II), each in four groups: (i) Infected untreated; (ii) treated with losartan, starting from the 4th or 12th weeks post-infection (PI); (iii) treated with PZQ in the 7th week PI; and (iv) treated with losartan, as group (ii) plus PZQ as group (iii). Comparable groups of uninfected mice were run in parallel with infected groups. Mice of batches I and II were killed 10 and 18 weeks PI, respectively. Hepatic content of hydroxyproline (HYP), serum levels and tissue expression of matrix metalloproteinase-2 (MMP-2), and transforming growth factor-β1 (TGF-β1) were determined. Parasitological, biochemical and histological parameters, which reflect disease severity and morbidity, were examined. 3. Losartan alone caused a considerable decrease in worm burden, hepatic tissue egg load with an increase in percentage of dead eggs, modulation of granuloma size and regression of inflammatory reactions, which was less obvious in the chronic stage. The best results were obtained when losartan was co-administered with PZQ, especially in the acute stage. This was revealed by a remarkable reduction in serum levels and tissue expression of MMP-2, TGF-β1 and HYP content, accompanied by conservation of hepatic reduced glutathione (GSH) versus the PZQ-treated group. 4. In conclusion, losartan has a promising antifibrotic action and could be introduced as a therapeutic tool with PZQ especially in acute schistosomal hepatic fibrosis.

Pharmacologic inhibition of the renin-angiotensin system did not attenuate hepatic toxicity induced by carbon tetrachloride in rats

The renin-angiotensin system (RAS) subserves vital physiological functions and also implicated in certain pathological states. Modulation of this system has been proposed in recent studies to be a promising strategy in treating liver fibrosis. We investigated the effect of the pharmacologic inhibition of RAS with angiotensin-converting enzyme inhibitor or angiotensin receptor blocker in CCl4-induced liver injury with a view to ascertaining the chemopreventive benefit. Fifty-six Wistar albino rats were divided into eight experimental groups of seven rats/group. Groups 1–4 received normal saline (10 ml/kg), enalapril (0.6 mg/kg), losartan (1.4 mg/kg) and CCl4 (80 mg/kg), respectively. Groups 5–8 were pretreated with enalapril (0.3 mg/kg), enalapril (0.6 mg/kg), losartan (0.7 mg/kg) and losartan (1.4 mg/kg) 1 hour before CCl4 administration. Experiment lasted 11 days and dosing was via oral route. Rats were killed 24 hours after the last treatment. Serum activities of alkaline phosphatase, aspartate and alanine aminotransferases increased significantly ( p < 0.05) by 46.0%, 90.6% and 122.3%, respectively, with severe hepatic centrilobular necrosis, fatty infiltration and increase in liver weight ( p < 0.05) in the CCl4-treated rats. Enalapril (0.6 mg/kg) and losartan (1.4 mg/kg) significantly ( p < 0.05) increased aspartate aminotransferase activity by 37.0% and 94.7% and produced mild centrilobular and periportal hepatic necrosis, respectively, with enalapril significantly ( p < 0.05) increasing liver weight. Serum total cholesterol, triglyceride, albumin and total protein did not change significantly in these rats. Also, glutathione, malondialdehyde and uric acid levels were not significantly altered. Enalapril and losartan failed to attenuate liver injury associated with CCl4 treatment. Although both drugs did not significantly alter serum biochemistry in the CCl4-treated rats, they however produced slight elevations in biomarkers of liver function and appear to worsen liver histopathology. Overall, the chemopreventive benefits of RAS inhibitors in liver disease remain doubtful and should be used with caution during hepatic dysfunction.

Keeping pace with ACE: are ACE inhibitors and angiotensin II type 1 receptor antagonists potential doping agents?

In the decade since the angiotensin-converting enzyme (ACE) gene was first proposed to be a 'human gene for physical performance', there have been numerous studies examining the effects of ACE genotype on physical performance phenotypes such as aerobic capacity, muscle function, trainability, and athletic status. While the results are variable and sometimes inconsistent, and corroborating phenotypic data limited, carriers of the ACE 'insertion' allele (the presence of an alu repeat element in intron 16 of the gene) have been reported to have higher maximum oxygen uptake (VO2max), greater response to training, and increased muscle efficiency when compared with individuals carrying the 'deletion' allele (absence of the alu repeat). Furthermore, the insertion allele has been reported to be over-represented in elite athletes from a variety of populations representing a number of endurance sports. The mechanism by which the ACE insertion genotype could potentiate physical performance is unknown. The presence of the ACE insertion allele has been associated with lower ACE activity (ACEplasma) in number of studies, suggesting that individuals with an innate tendency to have lower ACE levels respond better to training and are at an advantage in endurance sporting events. This could be due to lower levels of angiotensin II (the vasoconstrictor converted to active form by ACE), higher levels of bradykinin (a vasodilator degraded by ACE) or some combination of the two phenotypes. Observations that individuals carrying the ACE insertion allele (and presumably lower ACEplasma) have an enhanced response to training or are over-represented amongst elite athletes raises the intriguing question: would individuals with artificially lowered ACEplasma have similar training or performance potential? As there are a number of drugs (i.e. ACE inhibitors and angiotensin II type 1 receptor antagonists [angiotensin receptor blockers--ARBs]) that have the ability to either reduce ACEplasma activity or block the action of angiotensin II, the question is relevant to the study of ergogenic agents and to the efforts to rid sports of 'doping'. This article discusses the possibility that ACE inhibitors and ARBs, by virtue of their effects on ACE or angiotensin II function, respectively, have performance-enhancing capabilities; it also reviews the data on the effects of these medications on VO2max, muscle composition and endurance capacity in patient and non-patient populations. We conclude that, while the direct evidence supporting the hypothesis that ACE-related medications are potential doping agents is not compelling, there are insufficient data on young, athletic populations to exclude the possibility, and there is ample, albeit indirect, support from genetic studies to suggest that they should be. Unfortunately, given the history of drug experimentation in athletes and the rapid appropriation of therapeutic agents into the doping arsenal, this indirect evidence, coupled with the availability of ACE-inhibiting and ACE-receptor blocking medications may be sufficiently tempting to unscrupulous competitors looking for a shortcut to the finish line.

Renal effects of dual renin-angiotensin-aldosterone system blockade in patients with diabetic nephropathy

Evidence from recent studies indicates that in patients with diabetic nephropathy combined therapy with ACE inhibitors (ACEI) and AT1-receptor antagonists (ARB) results in more complete blockade of the renin-angiotensin-aldosterone system (RAS) than monotherapy, and reduces proteinuria. Most of these trials, however, had short follow-up, included a small number of patients, and were heterogeneous, so the opportunity to start this treatment in these patients remains unclear. This review summarizes the results of these studies, describing the renal effects of dual RAS blockade in both type 1 and type 2 diabetic patients.

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.

Inhibition of the renin-angiotensin system attenuates the development of liver fibrosis and oxidative stress in rats

1. The present study was designed to investigate the potential antifibrotic and anti-oxidant effects of lisinopril, fosinopril and losartan in an experimental rat model of liver injury using carbon tetrachloride (CCl(4)). 2. First, the potential hepatoprotective dose of each drug was screened against CCl(4)-induced acute hepatotoxicity. Then, we chose the minimum hepatoprotective dose of each drug to further investigate the mechanisms involved in the hepatoprotection using a chronic model of hepatotoxicity induced by CCl(4). 3. Liver function was assessed in addition to histopathological examination. Furthermore, oxidative stress markers (reduced glutathione (GSH) and lipid peroxides levels) and markers of fibrosis (hydroxyproline content and liver fibrosis area) were assessed. 4. It was found that treatment of animals with different drugs concomitantly with CCl(4) significantly counteracted the changes in liver function induced by CCl(4) (except fosinopril). In addition, the drugs ameliorated the histopathological changes induced by CCl(4). All drugs significantly counteracted lipid peroxidation and GSH depletion (except fosinopril) compared with the CCl(4)-intoxicated group. Moreover, the drugs studied significantly reduced liver hydroxyproline levels and the area of fibrosis compared with the CCl(4)-intoxicated group. 5. In conclusion, the present study provides evidence for the hepatoprotective effect of lisinopril, fosinopril and losartan. Both lisinopril and losartan was found to have better hepatoprotective potential than fosinopril against CCl(4)-induced hepatotoxicity. These hepatoprotective effects can be explained on the basis of anti-oxidant and antifibrotic mechanisms, mainly enhancement of GSH and reduction of lipid peroxidation and fibrosis.

Combination Angiotensin-Converting Enzyme Inhibitor and Angiotensin Receptor Blocker Therapy: Its Role in Clinical Practice

Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers are commonly prescribed for the management of hypertension. In addition, each of these drug classes has been shown to be effective in the treatment of congestive heart failure, proteinuric chronic kidney disease, and most recently the high-cardiac-risk profile patient. The individual success of each of these drug classes has fueled the theory that given together, the overall biologic effect of both would surpass that of either given alone. The foundation of this premise, although biologically plausible, has yet to be proven in a compelling enough fashion to support the everyday use of these two drug classes in combination. Additional clarifying studies are required to establish whether specific patient subsets exist that might benefit from such combination therapy.

Combination therapy with an ACE inhibitor and an angiotensin receptor blocker for diabetic nephropathy: a meta-analysis

AIMS

Angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) prevent the progression of diabetic nephropathy (DN). Studies suggest that combination renin-angiotensin-aldosterone system (RAAS)-inhibiting therapy provides additive benefit in DN. However, these studies are small in size. We performed a meta-analysis of studies investigating combination therapy for DN.

METHODS

Studies were identified through a search of medline, embase, cinahl and the Cochrane Database. All trials involving combined ACEI and ARB for slowing progression of DN were included. The primary end point was 24-h urinary protein excretion. Blood pressure, serum potassium and glomerular filtration rate (GFR) were secondary end points.

RESULTS

In the 10 included trials, 156 patients received ACEI + ARB and 159 received ACEI only. Most studies were 8-12 weeks in duration. Proteinuria was reduced with ACEI + ARB (P = 0.01). This was associated with significant statistical heterogeneity (P = 0.005). ACEI + ARB was associated with a reduction in GFR [3.87 ml/min (7.32-0.42); P = 0.03] and a trend towards an increase in serum creatinine (6.86 micromol/l 95% CI -0.76-13.73; P = 0.09). Potassium was increased by 0.2 (0.08-0.32) mmol/l (P < 0.01) with ACEI + ARB. Systolic and diastolic blood pressure were reduced by 5.2 (2.1-8.4) mmHg (P < 0.01) and 5.3 (2.2-8.4) mmHg (P < 0.01), respectively.

CONCLUSIONS

This meta-analysis suggests that ACEI + ARB reduces 24-h proteinuria to a greater extent than ACEI alone. This benefit is associated with small effects on GFR, serum creatinine, potassium and blood pressure. These results should be interpreted cautiously as most of the included studies were of short duration and the few long-term studies (12 months) have not demonstrated benefit.

Olmesartan reducing incidence of endstage renal disease in diabetic nephropathy trial (ORIENT): rationale and study design

Diabetic nephropathy (DN) is a leading cause of endstage renal disease (ESRD) in Japan and Hong Kong. Asian patients are known to be more predisposed to DN and ESRD than Caucasians. Strict blood glucose and blood pressure control are key factors in prevention and treatment of DN. In the last decade, inhibition of the renin-angiotensin-aldosterone (RAA) system has been confirmed to reduce the incidence of cardiovascular complications in Caucasian patients with diabetes. Although the RENAAL study has demonstrated the beneficial effects of inhibition of the RAA system on prevention of ESRD and death in type 2 diabetic patients with overt proteinuria, only 17% of patients in this multicenter study were of Asian ethnicity. Given the predilection of Asian diabetic patients for renal complications and the rising burden of ESRD, there is a need to confirm these findings in a homogenous group of Asian patients. The ORIENT (Omesartan Reducing Incidence of Endstage Renal Disease in Diabetic Nephropathy Trial) is a randomized, double-blind, placebo-controlled study in Japan and Hong Kong to evaluate the renal protective benefits of olmesartan medoxomil in type 2 diabetic patients with overt proteinuria (urinary albumin to creatinine ratio > or =300 mg/g creatinine) and renal insufficiency (serum creatinine: 1.0-2.5 mg/dl). The study has a targeted enrollment of 400 Japanese and Hong Kong Chinese patients. The primary outcome is the composite endpoint of time to the first occurrence of doubling of serum creatinine, ESRD (serum creatinine more than 5.0 mg/dl, the need for chronic dialysis, or renal transplantation) or death. The average follow-up period is 4 years and the study ends in 2009.

Combination ACE Inhibitor and Angiotensin Receptor Blocker Therapy-Future Considerations

Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers are regularly prescribed for the management of hypertension. Each of these drug classes has also been shown to provide survival benefits for patients with heart failure, proteinuric chronic kidney disease, and/or a high cardiac risk profile. The individual gains seen with each of these drug classes have led to speculation that their combination might offer additive if not synergistic outcome benefits. The foundation of this hypothesis, although biologically possible, has thus far not been sufficiently well proven to support the everyday use of these 2 drug classes in combination. Additional outcomes trials, which are currently proceeding to their conclusion, may provide the necessary proof to support an expanded use of these 2 drug classes in combination.

New clinical investigations with selective angiotensin II receptor blocker therapy in diabetes and renal disease

Halting the reduction in glomerular filtration rate (GFR) is the primary aim of any treatment of patients presenting with progressive chronic renal failure, a very common corollary to diabetes. To improve GFR, the high blood pressure (BP) and proteinuria often seen in these patients must both be controlled. These symptoms lead not only to progressive loss of renal function, but also to an increase in cardiovascular risk. Use of angiotensin-converting enzyme (ACE) inhibitors in these patients has been reported to control BP and reduce protein excretion and cardiovascular risk. Complete blockade of angiotensin II (Ang II) action with the highly selective Ang II receptor blocker (ARB) valsartan, both as monotherapy and in combination with ACE inhibitors, is well-tolerated and efficacious in patients with renal failure. Unlike ACE inhibition, ARB treatment leads to no initial reduction in GFR, thus valsartan may be a better agent for the control of BP, with greater renal protection.

Mechanisms of progression of chronic kidney disease

Chronic kidney disease (CKD) occurs in all age groups, including children. Regardless of the underlying cause, CKD is characterized by progressive scarring that ultimately affects all structures of the kidney. The relentless progression of CKD is postulated to result from a self-perpetuating vicious cycle of fibrosis activated after initial injury. We will review possible mechanisms of progressive renal damage, including systemic and glomerular hypertension, various cytokines and growth factors, with special emphasis on the renin-angiotensin-aldosterone system (RAAS), podocyte loss, dyslipidemia and proteinuria. We will also discuss possible specific mechanisms of tubulointerstitial fibrosis that are not dependent on glomerulosclerosis, and possible underlying predispositions for CKD, such as genetic factors and low nephron number.

Optimizationvia experimental design of an SPE-HPLC-UV-fluorescence method for the determination of valsartan and its metabolite in human plasma samples

A chemometric approach was applied for the optimization of the extraction and separation of the antihypertensive drug valsartan and its metabolite valeryl-4-hydroxy-valsartan from human plasma samples. Due to the high number of experimental and response variables to be studied, fractional factorial design (FFD) and central composite design (CCD) were used to optimize the HPLC-UV-fluorescence method. First, the significant variables were chosen with the help of FFD; then, a CCD was run to obtain the optimal values for the significant variables. The measured responses were the corrected areas of the two analytes and the resolution between the chromatographic peaks. Separation of valsartan, its metabolite valeryl-4-hydroxy-valsartan and candesartan M1, used as internal standard, was made using an Atlantis dC18 100 mm x 3.9 mm id, 100 angstroms, 3 microm chromatographic column. The mobile phase was run in gradient elution mode and consisted of ACN with 0.025% TFA and a 5 mM phosphate buffer with 0.025% TFA at pH 2.5. The initial percentage of ACN was 32% with a stepness of 4.5%/min to reach the 50%. A flow rate of 1.30 mL/min was applied throughout the chromatographic run, and the column temperature was kept to 40+/-0.2 degrees C. In the SPE procedure, experimental design was also used in order at achieve a maximum recovery percentage and extracts free from plasma interferences. The extraction procedure for spiked human plasma samples was carried out using C8 cartridges, phosphate buffer (pH 2, 60 mM) as conditioning agent, a washing step with methanol-phosphate buffer (40:60 v/v), a drying step of 8 min, and diethyl ether as eluent. The SPE-HPLC-UV-fluorescence method developed allowed the separation and quantitation of valsartan and its metabolite from human plasma samples with an adequate resolution and a total analysis time of 1 h.

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.

Effects of angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers, and their combination on microalbuminuria in normotensive patients with type 2 diabetes

The goal of this study was to compare the effects of lisinopril, losartan, and their combination on microalbuminuria in normotensive patients with type 2 diabetes mellitus. Patients were randomly assigned to 3 groups: group 1 (n=9), group 2 (n=9), and group 3 (n=8) received 10 mg lisinopril, 50 mg losartan, and 10 mg lisinopril plus 50 mg losartan, respectively, each day. For 12 mo, the 24-h urine albumin excretion rate was assessed at 3-mo intervals. At study completion, the urine albumin excretion rate had been reduced significantly in each group (P=.001); however, no significant differences were noted among groups (P=.587). Investigators in the present study have concluded that lisinopril, losartan, and their combination have similar effects on microalbuminuria in normotensive patients with type 2 diabetes mellitus, and that combination therapy does not provide additional benefit.

Angiotensin-converting enzyme (ACE) inhibition in type 2, diabetic patients – interaction with ACE insertion/deletion polymorphism

Angiotensin-converting enzyme (ACE) insertion(I)/deletion (D) polymorphism may modify the effect of inhibition of the renin-angiotensin-aldosterone system (RAAS) on survival and cardiorenal outcomes in type 2, diabetes. A consecutive cohort of 2089 Chinese type 2 diabetic patients with mean (+/- standard deviation) age of 59.7 +/- 13.1 years were genotyped for this polymorphism by polymerase chain reaction method and were followed prospectively for a median period of 44.6 (interquartile range: 23.7, 57.5) months. Clinical outcomes, including all-cause mortality, cardiovascular and renal end points, were examined. The frequency for I allele was 67.1 and 32.9% for D allele, with observed genotype frequencies of 45.8, 42.6, and 11.6% for 3, DI and DD, respectively. ACE DD polymorphism was an independent predictor for renal end point with hazard ratio (HR) (95% confidence interval) of 1.72 (1.16, 2.56), but not for cardiovascular end point or mortality. After controlling for confounding factors, including ACE I/D genotype, the usage of RAAS inhibitors was associated with reduced risk of mortality (HR 0.34 (0.23, 0.50)) and renal end point (HR 0.55 (0.40, 0.75)). On subgroup analysis, the beneficial effects on survival (II vs DI vs DD: HR 0.29 (0.16, 0.51) vs 0.25 (0.14, 0.46) vs 1.33 (0.41, 4.31)) and renoprotection (II vs DI vs DD: 0.52 (0.30, 0.90) vs 0.43 (0.25, 0.72) vs 0.95 (0.43, 2.12)) were most evident in II and DI carriers. In conclusion, inhibition of RAAS was associated with reduced risk of mortality and occurrence of renal end point in Chinese type 2 diabetic patients. These benefits were most evident among II and DI carriers.

Transforming growth factor beta1 and additional renoprotective effect of combination ACE inhibitor and angiotensin II receptor blocker in hypertensive subjects with minor renal abnormalities: a 24-week randomized controlled trial

OBJECTIVE

To verify the benefit of renin-angiotensin system blockade in hypertension, the effects of 24 weeks' losartan and ramipril treatment, both alone and in combination, on urinary albumin excretion (UAE) and circulating transforming growth factor beta1 (TGF beta1) have been evaluated in hypertensive subjects with minor renal abnormalities.

DESIGN AND METHODS

Fifty-one patients with stage 1 and 2 essential hypertension and with UAE > or = 20 mg/24 h but with maintained renal function have been included. After a 4-week run-in with placebo administration, a randomized double-blind, three-arm double-dummy trial was used. All the hypertensives (HT) were allocated randomly to three treatment arms (17 patients for each group) and they were single-matched for age, gender, body mass index (BMI), systolic and diastolic blood pressure. Active treatment consisted of losartan (50 mg/day), ramipril (5 mg/day) and combined (losartan 50 mg/day plus ramipril 5 mg/day) for 24 weeks. Hydrochlorothiazide 12.5 mg/day was added in HT patients with uncontrolled blood pressure (> or = 140/90 mmHg) during the active treatment period. In all patients UAE, by immunonephelometric assay; circulating TGF beta1 by a solid-phase specific sandwich enzyme-linked immunosorbent assay (ELISA); and blood urea nitrogen (BUN), creatinine and creatinine clearance and potassium, by routine laboratory methods, were determined after placebo treatment and 24 weeks follow-up.

RESULTS

The three treatment groups were comparable for gender, age, BMI, blood pressure, UAE and renal function measurements. During the active treatment period it was necessary to add hydrochlorothiazide in five patients--two each of the losartan and ramipril groups and one of the combined group. At the end of treatment, significant (P < 0.05) reductions in systolic, diastolic and mean blood pressure, UAE and TGF beta1 levels were observed in all the groups. No change in renal function measurements were observed. The absolute and percentage reduction in UAE and TGF beta1 were significantly higher in the combined group than in the losartan or ramipril groups. No significant changes in absolute and percentage reduction of systolic, diastolic and mean blood pressure were found. All treatment regimens were well tolerated with few and transient side-effects.

CONCLUSION

These data indicate an additional renoprotective effect of dual blockade of the renin-angiotensin system (RAS) in hypertensive patients with minor renal abnormalities. In addition, the contemporaneus and marked decrease in TGF beta1 and UAE levels in hypertensives treated with combined therapy might indicate the presence of a subset of subjects who may benefit from complete RAS blockade.

Emerging drugs for renal failure

Renal failure involves a significant impairment of the essential functions of the kidney, which can be either acute with sudden and rapid onset (acute renal failure [ARF]) or chronic with gradual onset (chronic renal failure [CRF]). ARF, if detected early, may be halted or reversed, whereas CRF is generally irreversible. Without treatment or intervention, both forms of renal failure lead to end stage renal failure (ESRF) or end stage renal disease (ESRD), requiring renal replacement therapy (RRT) in the form of dialysis or renal transplantation for survival. However, provision of RRT requires expert teams working in specialised units, making therapy of patients with renal failure expensive; furthermore, RRT is complex, with its own complications. Although pharmacological interventions have shown promise in experimental models, these have not been as successful in the clinical setting (e.g., administration of atrial natriuretic peptide, low-dose dopamine). At present, drugs are administered during CRF to either reduce one of the many risk factors of CRF (e.g., angiotensin-converting enzyme inhibitors, statins) or to deal with the consequences of CRF (e.g., erythropoietin, calcitriol). Recent evidence suggests that some of these interventions may provide further direct beneficial effects via reduction of renal inflammation. Although these interventions have greatly improved the prospects for patients suffering ESRF, the development of novel drugs and therapies with which to reduce the consequences of renal failure and ESRD remain topics of great interest. This article reviews the therapies available for the prevention and management of renal failure in adults and describes, in detail, emerging drugs and novel interventions that may soon become available for the treatment or prevention of ESRF.

Combined blockade of AT1-receptors and ACE synergistically potentiates antihypertensive effects in SHR

OBJECTIVES AND DESIGN

To check whether antihypertensive effects are additive or synergistic upon blockade of both angiotensin (AT1)-receptors and angiotensin-converting enzyme (ACE), spontaneously hypertensive rats (SHR) were treated with candesartan-cilexetil (0.1-30 mg/kg per day), ramipril (0.03-10 mg/kg per day), the calcium-antagonist mibefradil (1-150 mg/kg per day) or combinations thereof. Systolic blood pressure (SBP), left ventricular weight (LVW) and the cardiac activity/mRNA levels of ACE were determined.

RESULTS

SBP was decreased by candesartan-cilexetil [inhibitory concentration (IC50) (mg/kg): 2.47], ramipril (1.97), mibefradil (4.41), candesartan-cilexetil/ramipril (0.68), and candesartan-cilexetil/mibefradil (5.68). Combining candesartan-cilexetil with ramipril increased SBP reduction synergistically rather than additively, since the dose-response curve was shifted 6.6-fold leftwards compared to a hypothetically generated additive curve, calculated by summing up the doses and corresponding effects of the ramipril and candesartan-cilexetil monotreatment regimes. A total threshold dose < 5.14 mg/kg (derived from dose-response curves) was found to exert synergistic effects when candesartan-cilexetil was combined with ramipril. Antihypertensive effects of mibefradil can not be increased when combined with candesartan-cilexetil. When LVW was correlated with SBP reduction, regression lines of candesartan-cilexetil, ramipril and their combination were congruent, while that for mibefradil was significantly flatter and became steeper under candesartan-cilexetil co-administration. Cardiac ACE activity was greatly reduced by ramipril independently of SBP reduction and dosage. With SBP-ineffective doses of ramipril, cardiac ACE mRNA levels were doubled, indicating a positive feedback mechanism. The increase in ACE mRNA was renormalized when SPB-effective ramipril doses were applied, suggesting a blood pressure-dependent regulation of cardiac ACE expression.

CONCLUSIONS

Since synergy was observed only after combining low doses of ramipril and candesartan-cilexetil, prospective clinical trials should be performed on a low-dose combination, revealing the antihypertensive/antiproliferative benefits.

Dual blockade of the renin angiotensin system in diabetic and nondiabetic kidney disease

Dual blockade of the renin angiotensin system is based on a principle of obtaining the broadest and most efficient blockade of the effects of angiotensin II, by using the combination of an angiotensin-converting enzyme (ACE) inhibitor and an angiotensin II-receptor blocker (ARB). By combining two, different pharmacologic principles and inhibiting both the ACE and the angiotensin II type 1 receptor, it seems possible to block both the production and the action of angiotensin II, which would serve as efficient antihypertensive therapy. Exploring the beneficial effects of dual-blockade therapy is a work in rapid progress, in both diabetic and non-diabetic nephropathy. But evidence is also emerging in cardiovascular medicine, an overview of which is provided in this article.

Anti-proteinuric effects of combination therapy with enalapril and losartan in patients with nephropathy due to type 2 diabetes

The benefits of angiotensin-converting enzyme inhibitors and angiotensin II (ATII) receptor antagonist therapy of diabetic nephropathy (DNP) are thought to be largely the result of attenuation of ATII effects on proteinuria. The aim of the study was to ascertain whether there is the additive anti-proteinuric effect of enalapril plus losartan in DNP. Twenty-two patients with DNP were studied. Patients were randomly assigned to enalapril 10 mg/day (11 patients) or losartan 50 mg/day (11 patients) administered in a single oral dose in the morning for 12 weeks. and then, in 10 patients (five patients from enalapril group and five patients from losartan group), combination therapy (10 mg/day enalapril and 50 mg/day losartan) was started and continued for 12 weeks. In 12 patients, initial drugs dosages were doubled (six patients 20 mg/day enalapril and six patients 100 mg/day losartan), and monotherapy was continued for 12 weeks. Blood pressure and proteinuria were measured before and after therapy. Adverse effects were recorded at every visit. Proteinuria decreased by 33% with enalapril and losartan administered alone (p < 0.05). Co-administration of enalapril and losartan decreased proteinuria by a greater extent compared with enalapril and losartan administered alone (51%, p<0.05). This proteinuria level was significantly lower than the proteinuria level of 12 weeks therapy with enalapril and losartan alone. The decrease of proteinuria was 37% in double-dose monotherapy group (p < 0.05). Reduction of mean arterial blood pressure (MAP) in co-administration of enalapril and losartan was higher than enalapril and losartan administered alone (p < 0.05). Combination of enalapril and losartan decreased proteinuria and MAP by a greater extent compared with enalapril and losartan administered alone. We have found that proteinuria reduction induced by combined therapy is maintained throughout short-term follow-up; a greater anti-proteinuric response was observed in the patients with DNP.

Cost-effective strategies in the prevention of diabetic nephropathy

A significant subgroup of patients with diabetes mellitus are predisposed to developing diabetic nephropathy and it is in this subgroup that other diabetes- related complications, and in particular greatly increased cardiovascular disease risk, are concentrated. The high personal, social and financial costs of managing end-stage renal failure and the other complications associated with diabetic nephropathy make a powerful case for screening and effective intervention programmes to prevent the condition or retard its progression. As major breakthroughs in finding genetic susceptibility factors remain elusive, screening efforts continue to be based on microalbuminuria testing, despite increasing recognition of its limitations as a positive predictor of nephropathy. Interventions have been extensively studied, but results remain conflicting. Economic evaluations of such screening and intervention programmes are essential for health planners, yet models of the cost/benefit ratio of such interventions often rely on a rather slim evidence base. Where economic models are developed, they are frequently based on those papers that propound the greatest clinical benefits of a given intervention, leading to a possible over-estimation of the advantages of the chosen approach. Furthermore, the benefits of even such generally accepted interventions as ACE inhibitor treatment are less firmly established than generally appreciated. Lifestyle interventions are instinctively attractive, but are by no means a low-cost option (as is often assumed by both medical professionals and politicians). This review critically assesses the evidence for clinical efficacy and economic benefit of microalbuminuria screening and interventions such as intensive glycaemic control, antihypertensive treatment, ACE inhibition and angiotensin receptor blockade, dietary protein restriction and lipid-modifying therapy. The various costs associated with diabetic nephropathy are so great that even expensive interventions may have a favourable cost/benefit ratio, provided they are truly effective.

Combined Treatment with an AT1 Receptor Blocker and Angiotensin Converting Enzyme Inhibitor Has an Additive Effect on Inhibiting Neointima Formation via Improvement of Nitric Oxide Production and Suppression of Oxidative Stress

Accumulating evidence shows that inhibition of the vascular renin-angiotensin system results in suppression of injury-elicited neointima formation. We attempted to determine whether or not combined treatment with an angiotensin II type 1 receptor blocker (ARB) and angiotensin converting enzyme inhibitor (ACEI) has an additive inhibitory effect on balloon-injury-elicited neointima formation in the carotid artery. Male Sprague-Dawley rats were treated with an ARB (valsartan: 3 mg/kg/day) and/or an ACEI (benazepril: 0.3 mg/kg/day) from 1 week before until 2 weeks after balloon injury. Experiments were also conducted with one-third of the dose combination used in the original experiments. Both ARB and ACEI inhibited neointima formation without any blood pressure changes. The full-dose combination lowered blood pressure and suppressed neointima formation significantly compared with the levels in the groups treated with either ACEI or ARB alone. The low-dose combination without blood pressure reduction also inhibited neointima formation to a similar extent as the full-dose combination. We measured 8-iso-prostaglandin F2alpha (8-iso-PGF2alpha), a marker of oxidative stress, and nitrite and nitrate (NOx), an index of nitric monoxide production, in media conditioned by the injured artery. NOx production was lower and 8-iso-PGF2alpha was higher in the media of the injured artery, compared with those in the normal artery. ACEI restored NOx production more dramatically than ARB, and ARB suppressed 8-iso-PGF2alpha markedly compared with ACEI. These results suggest that the combination of an ARB and an ACEI exerts an additive inhibitory effect, presumably through an increase in production and bioavailability of NO from the endothelium.

Management of Glomerular Proteinuria: A Commentary

ABSTRACT. It is widely accepted that proteinuria reduction is an appropriate therapeutic goal in chronic proteinuric kidney disease. Based on large randomized controlled clinical trials (RCT), ACE inhibitor (ACEI) and angiotensin receptor blocker (ARB) therapy have emerged as the most important antiproteinuric and renal protective interventions. However, there are numerous other interventions that have been shown to be antiproteinuric and, therefore, likely to be renoprotective. Unfortunately testing each of these antiproteinuric therapies in RCT is not feasible. The nephrologist has two choices: restrict antiproteinuric therapies to those shown to be effective in RCT or expand the use of antiproteinuric therapies to include those that, although unproven, are plausibly effective and prudent to use. The goal of this work is to provide the documentation needed for the nephrologist to choose between these strategies. This work describes 25 separate interventions that are either antiproteinuric or may block injurious mechanisms of proteinuria. Each intervention is assigned a level of recommendation (Level 1 is the highest; Level 3 is the lowest) according to the strength of the evidence supporting its antiproteinuric and renoprotective efficacy. Pathophysiologic mechanisms possibly involved are also discussed. The number of interventions at each level of recommendation are: Level 1, n = 7; Level 2, n = 9; Level 3, n = 9. Our experience indicates that we can achieve in most patients the majority of Level 1 and many of the Level 2 and 3 recommendations. We suggest that, until better information becomes available, a broad-based, multiple-risk factor intervention to reduce proteinuria can be justified in those with progressive nephropathies. This work is intended primarily for clinical nephrologists; therefore, each antiproteinuria intervention is described in practical detail.

Inhibition of angiotensin converting enzyme by lithospermic acid B isolated from Radix Salviae miltiorrhiza Bunge

The roots of Salviae miltiorrhiza (RSM) have been traditionally used for treatment of hypertensive disease in China, Korea, and Japan. Bioassay guided fractionation and purification as assayed by angiotensin converting enzyme (ACE) inhibitory assay resulted in the isolation of lithospermic acid B (LSB) as an active principle. The ACE plasma activities were significantly inhibited by the addition of LSB in a dose-dependent manner of which IC50 value was 86 microg/ml (120 microM). Moreover, angiotensin I-induced contraction was markedly attenuated by prior exposure of endothelium-intact aortic rings to LSB. These results suggest that RSM-induced antihypertensive effect may be, at least in part, due to ACE inhibitory effect of LSB.

Effects of berberine on angiotensin-converting enzyme and NO/cGMP system in vessels

The present study was designed to examine the relaxant and anticonstrictive effects of berberine in the isolated thoracic aorta in rats. Intravenous injection of berberine lowered the mean arterial pressure (MAP) of anesthesized rats in a dose-dependent manner. The angiotensin-converting enzyme (ACE) activities were inhibited significantly by the addition of berberine in a dose-dependent manner of which the IC50 value of berberine for ACE was 42 micrograms/ml (125 microM). In the endothelium-intact rings, angiotensin I-induced contraction was markedly attenuated by prior exposure of aortic rings to berberine. Treatment of the intact aortic rings with berberine (10 micrograms/ml) increased the NOx and cGMP productions relative to the vehicle-treated group. Berberine induced a dose-dependent relaxation in phenylephrine-precontracted aortic rings, but NG-nitro-L-arginine methyl ester (L-NAME)-pretreated intact aortic rings or functional removal of the endothelium attenuated the berberine-induced relaxation without an effect on maximum response. These results suggest that berberine has a hypotensive effect, at least in part, via the inhibition of ACE and direct release of NO/cGMP in the vascular tissues.

Angiotensin converting enzyme inhibitory phenylpropanoid glycosides from Clerodendron trichotomum

The stems of Clerodendron trichotomum have been traditionally used for treatment of hypertension in far East Asia including China, Korea, and Japan. Bioassay-guided fractionation and purification of the EtOAc-soluble extract of Clerodendron trichotomum afforded acteoside (1), leucosceptoside A (2), martynoside (3), acteoside isomer (4), and isomartynoside (5). The angiotensin converting enzyme (ACE) activities were significantly inhibited by the addition of these phenylpropanoid glycosides (1-5) in a dose-dependent manner of which IC(50) values were 373+/-9.3 microg/ml, 423+/-18.8 microg/ml, 524+/-28.1 microg/ml, 376+/-15.6 microg/ml, 505+/-26.7 microg/ml, respectively. These results suggest that the antihypertensive effect of Clerodendron trichotomum may be, at least in part, due to ACE inhibitory effect of phenylpropanoid glycosides.

Hypotensive effect of butein via the inhibition of angiotensin converting enzyme

Butein (3,4,2',4'-tetrahydroxychalcone), a plant polyphenol, has been known to elucidate endothelium-dependent vasodilation. In the present study, the hypotensive effect of butein and its possible mechanism, especially an angiotensin converting enzyme (ACE) inhibitory effect, were investigated. Intravenous injection of butein lowered the arterial blood pressure of anesthetized rats in a dose-dependent manner. The plasma ACE activities were significantly inhibited by the addition of butein in a dose-dependent manner, the IC(50) value of which was 198 microg/ml (730 microM). Moreover, angiotensin I-induced contraction was markedly attenuated by prior exposure of endothelium-intact aortic rings to butein, but angiotensin II-induced contraction was not altered. These results suggest that butein has a hypotensive effect, at least in part, via the inhibition of angiotensin converting enzyme.

The renin-angiotensin system and the long-term complications of diabetes: pathophysiological and therapeutic considerations

The relationship between the renin-angiotensin system (RAS) and the progression of diabetic renal disease has been a major focus of investigation over the past 20 years. More recently, experimental and clinical studies have also suggested that the RAS may have a pathogenetic role at other sites of micro- and macrovascular injury in diabetes. Complementing major advances into the understanding of the local, as distinct from the systemic RAS, a number of large clinical trials have examined whether blockade of the RAS might provide protection from the long-term complications of diabetes, beyond that due to blood pressure reduction alone. While some controversy remains, these studies have, in general, suggested that angiotensin converting enzyme (ACE) inhibition and more recently, angiotensin receptor blockade reduce the development and progression of diabetic nephropathy, cardiovascular disease and possibly retinopathy. This review will focus on recent developments in our understanding of the tissue-based RAS and its role in end-organ injury in diabetes, the results of recent clinical trials and newer strategies for the pharmacological manipulation of the RAS.

Chymase is upregulated in diabetic nephropathy: implications for an alternative pathway of angiotensin II-mediated diabetic renal and vascular disease

Angiotensin II (AngII) has been shown to play a critical role in diabetic nephropathy and vasculopathy. Although it is well recognized that an angiotensin-converting enzyme (ACE)-dependent AngII-generating system is a major source of intrarenal AngII production, it is here reported that the chymase-dependent AngII-generating system is upregulated in the human diabetic kidney. This becomes particularly strong in those with hypertension. In the normal kidney, while ACE was constitutively expressed by most kidney cells, chymase was weakly expressed by mesangial cells (MC) and vascular smooth muscle cells (VSMC) only. In the diabetic kidney, while ACE expression was significantly upregulated (1 to 3-fold) by tubular epithelial cells (TEC) and infiltrating mononuclear cells, there was also markedly increased chymase expression (10 to 15-fold) by both MC and VSMC, with strong deposition in the collagen-rich extracellular matrix including both diffuse and nodular glomerulosclerosis, tubulointerstitial fibrosis, and vascular sclerosis. Interestingly, while ACE expression showed no difference in patients with or without hypertension, upregulation of chymase in hypertensive patients was much stronger than that seen in those without hypertension (4 to 7-fold, P < 0.001). Correlation analysis showed that, in contrast to the ACE expression, upregulation of chymase correlated significantly with the increase in BP and the severity of collagen matrix deposition within the glomerulus, tubulointerstitium, and arterial walls (all with P < 0.001). In conclusion, the present study demonstrates that chymase, as an alternative AngII-generating enzyme, is markedly upregulated in the diabetic kidney and may be associated with the development of diabetic/hypertensive nephropathy. In addition, differential expression of ACE and chymase in the diabetic kidney indicates that both ACE and chymase may be of equal importance for AngII-mediated diabetic nephropathy and vascular disease. Results from this study suggest that blockade of both AngII-generating pathways may provide additional beneficial effect on diabetic nephropathy.

Dual blockade with candesartan cilexetil and lisinopril in hypertensive patients with diabetes mellitus: rationale and design

BACKGROUND

Blood pressure (BP) reduction is the key to risk reduction of cardiovascular disease or renal failure in hypertensive patients with diabetes mellitus. Inhibition of the renin-angiotensin system by an angiotensin-converting enzyme (ACE) inhibitor or an angiotensin II receptor blocker (ARB) provides efficient BP reduction and renal protection in hypertensive diabetes patients. But, despite this, the recommended BP levels can be difficult to achieve and dual blockade therapy might be a possible way of obtaining efficient BP reduction in hypertensive patients with diabetes. Dual blockade treatment is based on a principle of obtaining the broadest and most efficient blockade of angiotensin II, by using the combination of an ACE-inhibitor and an ARB.

METHODS

The Candesartan And Lisinopril Microalbuminuria (CALM II) study is a one centre, one observer, double-blind, randomised, active-controlled, parallel-group study, investigating the efficacy and tolerability of candesartan cilexetil in combination with lisinopril, compared with the maximum recommended dose of lisinopril in hypertensive patients with diabetes mellitus. The study design consists of two treatment arms with either 16 mg candesartan cilexetil or 20 mg lisinopril added to concomitant treatment with 20 mg lisinopril. It comprises 80 patients with a minimum of 35 patients in each group and statistical power of 90% to detect a difference in systolic BP reduction of 6.5 mmHg.

CONCLUSION

The CALM II study aims to investigate the effects of dual blockade on systolic BP, albuminuria, left ventricular mass and function, and retinopathy in hypertensive patients with diabetes mellitus.

The evolution of treatment guidelines for diabetic nephropathy. Strategies integrate JNC VI, more recent protocols

In recent years, new drug development and late-breaking research data have put treatment guidelines for diabetic nephropathy in a state of flux. In particular, trials of angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs), coupled with enhanced understanding of the renin-angiotensin pathway, have influenced recommendations for patient care. Here, Dr Bakris highlights both the steadfast features and the recent refinements of treatment guidelines for diabetic nephropathy. He describes their backing in research findings and outlines practical antihypertensive and renoprotective therapies to curtail risks of nephropathy and cardiovascular disease in patients with diabetes.

Outcome studies in diabetic nephropathy

Outcome studies in diabetic nephropathy have focused on strategies to prevent progression of diabetic nephropathy, the leading cause of ESRD in the United States. Once diabetics develop overt nephropathy, prognosis is poor. Risk factors for diabetic nephropathy are discussed, and include hyperglycemia, hypertension, angiotensin II, proteinuria, dyslipidemia, smoking, and anemia. Major outcomes as well as outcome studies in diabetic nephropathy for patients with microalbuminuria and macroalbuminuria are reviewed. Furthermore, the role of therapy with angiotensin converting enzyme inhibitors, angiotensin II receptor blockers, calcium channel blockers, and mineralocorticoid receptor antagonists as well as selected combination therapy are discussed. Recommendations for therapy with ace inhibitors and angiotensin II receptor blockers are made based on this evidence.

Angiotensin II receptor blockers in heart failure

Heart failure remains a significant cause of morbidity and mortality, despite major advances in therapy. Angiotensin II, the principal mediator of the renin-angiotensin system, exerts both short-term (e.g., hemodynamic, renal) and long-term (e.g., inflammation, cardiac remodeling) effects in the pathophysiology of cardiovascular disease. The effects of angiotensin II appear to be more completely inhibited by angiotensin II receptor blockers (ARBs), which act at the subtype 1 receptor level, than by angiotensin-converting enzyme (ACE) inhibitors because pathways other than that of ACE contribute to the generation of angiotensin II. Evidence demonstrates that ARBs, when added to conventional treatment for patients with heart failure, are associated with a reduction in morbidity and mortality as well as an improvement in quality of life. Clinical trials of ARB therapy indicate that these agents are generally well tolerated, both alone and in combination with other neurohormonal inhibitors. The current role of ARBs in heart failure is as an alternative for patients who cannot tolerate therapy with an ACE inhibitor. A number of ongoing clinical studies are likely to further define or expand the role of ARBs in the treatment of cardiovascular disease.

Combination treatment of angiotensin-II receptor blocker and angiotensin-converting-enzyme inhibitor in non-diabetic renal disease (COOPERATE): a randomised controlled trial

BACKGROUND

Present angiotensin-converting-enzyme inhibitor treatment fails to prevent progression of non-diabetic renal disease. We aimed to assess the efficacy and safety of combined treatment of angiotensin-converting-enzyme inhibitor and angiotensin-II receptor blocker, and monotherapy of each drug at its maximum dose, in patients with non-diabetic renal disease.

METHODS

336 patients with non-diabetic renal disease were enrolled from one renal outpatient department in Japan. After screening and an 18-week run-in period, 263 patients were randomly assigned angiotensin-II receptor blocker (losartan, 100 mg daily), angiotensin-converting-enzyme inhibitor (trandolapril, 3 mg daily), or a combination of both drugs at equivalent doses. Survival analysis was done to compare the effects of each regimen on the combined primary endpoint of time to doubling of serum creatinine concentration or end-stage renal disease. Analysis was by intention to treat.

FINDINGS

Seven patients discontinued or were otherwise lost to follow-up. Ten (11%) of 85 patients on combination treatment reached the combined primary endpoint compared with 20 (23%) of 85 on trandolapril alone (hazard ratio 0.38, 95% CI 0.18-0.63, p=0.018) and 20 (23%) of 86 on losartan alone (0.40, 0.17-0.69, p=0.016). Covariates affecting renal survival were combination treatment (hazard ratio 0.38, 95% CI 0.18-0.63, p=0.011), age (1.30, 1.03-2.29, p=0.009), baseline renal function (1.80, 1.02-2.99, p=0.021), change in daily urinary protein excretion rate (0.58, 0.24-0.88, p=0.022), use of diuretics (0.80, 0.30-0.94, p=0.043), and antiproteinuric response to trandolapril (0.81, 0.21-0.91, p=0.039). Frequency of side-effects with combination treatment was the same as with trandolapril alone.

INTERPRETATION

Combination treatment safely retards progression of non-diabetic renal disease compared with monotherapy. However, since some patients reached the combined primary endpoint on combined treatment, further strategies for complete management of progressive non-diabetic renal disease need to be researched.

Angiotensin II receptor blockade: is there truly a benefit of adding an ACE inhibitor?

We assessed the blockade of the renin-angiotensin system (RAS) achieved with 2 angiotensin (Ang) antagonists given either alone at different doses or with an ACE inhibitor. First, 20 normotensive subjects were randomly assigned to 100 mg OD losartan (LOS) or 80 mg OD telmisartan (TEL) for 1 week; during another week, the same doses of LOS and TEL were combined with 20 mg OD lisinopril. Then, 10 subjects were randomly assigned to 200 mg OD LOS and 160 mg OD TEL for 1 week and 100 mg BID LOS and 80 mg BID TEL during the second week. Blockade of the RAS was evaluated with the inhibition of the pressor effect of exogenous Ang I, an ex vivo receptor assay, and the changes in plasma Ang II. Trough blood pressure response to Ang I was blocked by 35+/-16% (mean+/-SD) with 100 mg OD LOS and by 36+/-13% with 80 mg OD TEL. When combined with lisinopril, blockade was 76+/-7% with LOS and 79+/-9% with TEL. With 200 mg OD LOS, trough blockade was 54+/-14%, but with 100 mg BID it increased to 77+/-8% (P<0.01). Telmisartan (160 mg OD and 80 mg BID) produced a comparable effect. Thus, at their maximal recommended doses, neither LOS nor TEL blocks the RAS for 24 hours; hence, the addition of an ACE inhibitor provides an additional blockade. A 24-hour blockade can be achieved with an angiotensin antagonist alone, provided higher doses or a BID regimen is used.

Pharmacologic management of diabetic nephropathy

BACKGROUND

Diabetes mellitus and hypertension are leading causes of end stage renal disease in the United States. Drug therapy that focuses on tight glycemic control and blood pressure control reduces the progression of nephropathy and cardiovascular complications. Angiotensin-converting enzyme (ACE) inhibitors have been shown to reduce the progression of renal disease in patients with diabetes. The angiotensin II receptor blockers (ARBs) losartan and irbesartan have also been shown to reduce microalbuminuria compared with placebo. The nondihydropyridine calcium channel blockers (CCBs) verapamil and diltiazem have been shown to be as effective as an ACE inhibitor in reducing urinary albumin excretion.

OBJECTIVE

This paper reviews the pathophysiology and diagnosis of diabetic nephropathy and recent clinical trials assessing the most appropriate therapeutic options for delaying the progression of nephropathy in patients with diabetes.

METHODS

Primary and review articles that addressed the pathophysiology, diagnosis, and therapeutic options for attenuating the progression of diabetic nephropathy were retrieved through a MEDLINE search (January 1990 to August 2002) and the bibliographies of identified articles were reviewed. English-language sources were searched using the following search terms: diabetes mellitus, nephropathy, proteinuria, ACE inhibitors, and ARBs. Studies published in peer-reviewed journals that were determined to be methodologically sound, with appropriate statistical analysis of the results, were selected for inclusion in this review.

RESULTS

Patients with type 1 diabetes mellitus and evidence of nephropathy should be started on an ACE inhibitor unless contraindicated. The ARBs and ACE inhibitors are viable choices for patients with type 2 diabetes mellitus and evidence of proteinuria. Patients who experience adverse events such as dry cough with ACE inhibitors can be switched to ARBs. Clinical literature suggests that if monotherapy with an ACE inhibitor or ARB does not provide an adequate response, a nondihydropyridine CCB should be added to the regimen. Nondihydropyridine CCBs should also be considered when ACE inhibitors and ARBs are contraindicated.

CONCLUSIONS

ACE inhibitors and ARBs should be considered first-line therapy for patients with type 2 diabetes mellitus and nephropathy. The ACE inhibitors are still the drug of choice for patients with type 1 diabetes mellitus and evidence of incipient or overt nephropathy. If therapeutic goals are not achieved with an ACE inhibitor or ARB, then the addition of a nondihydropyridine CCB should be considered.