Dual blockade of the renin-angiotensin system versus maximal recommended dose of ACE inhibition in diabetic nephropathy

Transcription

1 Kidney International, Vol. 63 (2003), pp Dual blockade of the renin-angiotensin system versus maximal recommended dose of ACE inhibition in diabetic nephropathy PETER JACOBSEN, STEEN ANDERSEN, KASPER ROSSING, BERIT R. JENSEN, and HANS-HENRIK PARVING Steno Diabetes Center, Gentofte, Denmark; and Faculty of Health Science, University of Aarhus, Denmark Dual blockade of the renin-angiotensin system versus maximal tensin-converting enzyme (ACE) inhibition, has been recommended dose of ACE inhibition in diabetic nephropathy. shown to reduce albuminuria, to diminish loss of kidney Background. Albuminuria and hypertension are predictors function, and to improve survival in type 1 patients with of poor renal and cardiovascular outcome in diabetic patients. We tested whether dual blockade of the renin-angiotensin system diabetic nephropathy (DN) [1 4]. Studies of diabetic and (RAS) with both an angiotensin-converting enzyme (ACE) inhibitor and an angiotensin II receptor blocker (ARB) is supe- reduction in albuminuria after blockade of the renin- nondiabetic kidney disease suggest the initial degree of rior to maximal recommended dose of ACE inhibitor in type 1 angiotensin system (RAS) system predicts an attenuated diabetic patients with diabetic nephropathy (DN). rate of decline in glomerular filtration rate (GFR), as Methods. We performed a randomized, double-blind, crossreviewed by Rossing [1]. As a consequence, albuminuria over trial with 8 weeks treatment with placebo and irbesartan 300 mg (once daily), added on top of enalapril 40 mg (once may serve as a surrogate endpoint for monitoring treatdaily). We included 24 type 1 patients with DN. At the end of ment efficacy and prognosis in DN [5]. each treatment period, albuminuria, 24-hour blood pressure, Dual blockade of the RAS with both ACE inibition and glomerular filtration rate (GFR) were measured. Results. Values on ACE inhibitors placebo were: albusuggested as superior to monotherapy in diabetic pa- and angiotensin II receptor blocker (ARB) has been minuria [mean (95% CI)], 519 (342 to 789) mg/24 hours; blood pressure [mean (SEM)], 131 (3)/74 (1) mm Hg, and GFR [mean tients with microalbuminuria [6] and in DN [7, 8] and (SEM)], 65 (5) ml/min/1.73 m 2. Dual blockade of the RAS nondiabetic nephropathy [9]. However, until now, all induced a reduction in albuminuria [mean (95% CI)] of 25% studies have compared dual blockade of the RAS with (15, 34) (P 0.001), a reduction in systolic blood pressure of 8 mm Hg (4, 12) (P 0.002), and a reduction of 4 mm Hg submaximal doses of monotherapy and, as a conse- (2, 7) (P 0.003) in diastolic blood pressure. GFR and plasma quence, beneficial effects may have been overestimated. potassium remained unchanged during both treatment regimes. Therefore, we tested if the addition of the maximal Dual blockade was safe and well tolerated. recommended dose ARB offers more complete block- Conclusion. Dual blockade of the RAS is superior to maxiade of the RAS in type 1 diabetic patients with DN mal recommended dose of ACE inhibitors with regard to lowreceiving maximal recommended dose of ACE inhibitors. ering of albuminuria and blood pressure in type 1 patients with DN. Long-term trials are needed to further establish the role of dual blockade of the RAS in renal and cardiovascular protection. METHODS Subjects From Steno Diabetes Center, we included 24 type 1 Albuminuria and hypertension are predictors of poor diabetic patients with DN. DN was diagnosed clinically renal and cardiovascular outcome in patients with diabe- if the following criteria were fulfilled: persistent albumintes [1, 2]. Antihypertensive treatment, especially angio- uria 300 mg/24 hours in two out of three consecutive determinations, presence of diabetic retinopathy, and no other kidney or renal tract disease [10, 11]. All patients Key words: ACE inhibition, albuminuria, angiotensin II receptor blockhad been dependent on insulin treatment from the time ade, blood pressure, cholesterol, diabetic nephropathy, dual blockade of the RAS, glomerular filtration rate, renin-angiotensin system, type I of diagnosis and received at least two daily injections of diabetes. insulin. Patients were on a diabetic diet (45% to 55% carbohydrates, 30% to 35% fat, and 15% to 20% pro- Received for publication October 24, 2002 and in revised form December 12, 2002 tein) without restriction in sodium or protein intake. Accepted for publication January 14, 2003 Exclusion criteria at start of the study were plasma 2003 by the International Society of Nephrology potassium 4.8 mmol/l, pregnancy, no use of contra- 1874

2 Jacobsen et al: Dual blockade of renin-angiotensin system 1875 ceptives, age 18 years, alcohol or medicine abuse, in- 30 minutes during nighttime (from p.m. to 7.00 a.m.). ability to understand the patient information, contraindication Values were averaged for each hour before calculating to treatment with ACE inhibitors or ARBs, systolic the mean 24-hour day and night arterial blood pressures. blood pressure 100 mm Hg, GFR 30 ml/min, heart GFR was measured after a single intravenous injection failure, myocardial infarction, or coronary by-pass within of 3.7 MBq 51 Cr-ethylenediaminetetraacetic acid (EDTA) the last 6 months. Twenty-four patients were included at 8.30 a.m. by following the plasma clearance of the in the study. tracer for 4 hours [12, 13]. Extra renal loss was corrected for by subtracting 3.7 ml/min [14]. The small underesti- Design mation (10%) of 51 Cr-EDTA renal clearance versus renal We performed a randomized, double-blind, placebocontrolled, clearance of inulin was corrected for by multiplying the crossover trial. Each patient received 8 weeks EDTA clearance by 1.10 [14]. The results were standard- treatment with irbesartan 300 mg once daily and 8 weeks ized for 1.73 m 2 body surface area. The mean day-to-day of placebo in random order. The study medication was coefficient of variation in GFR is 4% in our laboratory. added on top of the patient s usual antihypertensive From venous samples, hemoglobin, plasma potassium, treatment, including enalapril 40 mg once daily. This sodium, creatinine, and fasting cholesterol concentrations was left unchanged throughout the study except in two were determined. Plasma potassium was measured patients, who had the dose of diuretics increased (see by an indirect ion-selective method, normal range 3.2 to Results section). All patients had received 40 mg of enalapril 4.7 mmol/l (BM/HITACHI system, Boehringer Mannrandomization for more than 3 months prior to the study. The heim GmbH, Roche Lab Systems, Mannheim, Germany). was done by the manufacturing company s Our hemoglobin method has a normal range in females local office (Sanofi-Synthelabo, Copenhagen, Den- of 7 to 10 mmol/l and 8 to 11 in males (Sysmex SF mark). The code was kept in a concealed envelope and 3000, Sysmex Corp., Kobe, Japan). Hemoglobin A 1c was not broken until all data were entered in a database after measured by high-performance liquid chromatography the last patient visit. Patients visited the clinic 2 and 8 (HPLC) (normal range 4.1% to 6.1%) (Variant, Biorad weeks after start of each treatment period. Blood pres- Laboratories, Hercules, CA, USA). Blood samples for sure, plasma potassium, and plasma creatinine were measured renin concentration were taken after 30 minutes supine 2 weeks after the beginning of each treatment rest and plasma concentration was determined using the period for safety reasons. At the end of each treatment principle of antibody trapping [15] as modified by Millar period, we assessed clinical end points, including the et al [16]. primary end point of albuminuria and the secondary end points of 24-hour arterial blood pressure and GFR. Statistics Drug compliance was assessed by tablet counts. The Before carrying out the study, we calculated the standard study protocol was in accordance with the Declaration deviation (SD) (log scale, ) of the mean difstudy of Helsinki and was approved by the local ethical com- ference in urinary albumin excretion rate in three consecutive mittee. All patients gave their informed consent to participate 24-hour urine samples collected twice within in the study. 3 months in 36 type 1 patients with DN. On the basis of these data, a sample-size calculation revealed a necessary Methods minimum of 16 patients to detect a 25% difference in Albuminuria was determined by three consecutive change in urinary albumin excretion rate ( 0.05 and 24-hour urine collections, completed immediately before 0.80). each visit at the end of each treatment period (Turbidimetry, Normally distributed variables are expressed as mean Cobas Mira Plus, Roche, Montclair, NJ, USA). To (SEM). Values for albuminuria and renin were logarith- correct the reduction in 24-hour albuminuria for changes mically transformed and expressed as geometric mean in GFR and plasma albumin, we constructed the follow- (95% CI) because of their positively skewed distribution. ing fractional clearance index: [24-hour albuminuria]/ Changes in these variables between different treatments ([plasma albumin concentration] [GFR]). In addition, are expressed in percent. sodium, urea, creatinine, and carbamid excretion in the Test for time and carryover effects was performed as urine were determined (Cobas Mira Plus, Roche, Mont- described by Altman et al [17]. Data were analyzed using clair, NJ, USA). linear mixed models [18]. The software used was R ( Arterial blood pressure after each treatment period and SPSS 11.0 (SPSS, Inc., Chicago, was assessed by 24-hour ambulatory blood pressure measurements IL, USA). The adapted model was one with fixed effects with the Takeda TM2420 device; models 6 and of treatments and visit and a random effect for person 7 (A&D, Medical, Inc., Tokyo, Japan). A measurement included to account for the person-dependencies in data. of the blood pressure was performed every 15 minutes For the simplest models the P value and effects correspond during daytime (from 7.00 a.m. to p.m.) and every to results obtained from paired t test and two-

3 1876 Jacobsen et al: Dual blockade of renin-angiotensin system Table 1. Baseline clinical data in 24 type 1 patients with diabetic to the addition of irbesartan was not related to placebo nephropathy (DN) level of blood pressure. Age years 42 (9) Linear regression analysis showed a correlation be- Gender male/female 17/7 tween the change in diastolic blood pressure and the Duration of diabetes years 31 (9) Duration of DN years 13 (5) change in albuminuria when comparing dual blockade Retinopathy background/proliferative 5/19 with placebo (R 0.63, P 0.001, Fig. 1). A similar Total number of antihypertensive drugs (1/2/3/4) 5/12/6/1 correlation between change in albuminuria and change No. of patients receiving diuretics thiazide/furosemide a 8/11 No. of patients receiving calcium channel blockers b 6 in mean arterial blood pressure was seen (R 0.54, P No. of patients receiving statins ). No correlation between change in systolic blood Values presented are mean (SD). pressure and the change in albuminuria was seen (R a Dose, median (range): 120 (20 to 500) mg daily; b in addition to angiotensin- 0.30, P 0.17). We also found a correlation between converting enzyme (ACE) inhibitors and diuretics the change in plasma renin concentration and the change in albuminuria (R 0.52, P 0.011, Fig. 2) and change in diastolic blood pressure (R 0.64, P 0.001, Fig. 3). way analysis of variance, but these models allow for more Multivariate analysis revealed that decline in diastolic elaborate exploration of the material. Tests for presence blood pressure were associated with decline in albumin- of effects were performed as likelihood ratio tests, and uria (P 0.001), whereas treatment type and visit were final estimates were reported as restricted maximum likeli- not (R 2 (adjusted) 0.36, P 0.001). hood (REML) estimates [18]. Linear regression analyses We observed no changes in GFR or plasma creatinine were made between the changes in arterial blood pressure, during treatment with dual blockade of the RAS com- changes in albuminuria, and changes in renin concentraparameters are shown in Table 2. Dual blockade of the pared to placebo (Table 2). Changes in other laboratory tion. A multiple regression model with albuminuria as a dependent variable and blood pressure, treatments, RAS induced a significant decline in hemoglobin and an increase in hemoglobin A 1c. Triglyceride and plasma very and visit as independent variables were performed. A P low-density lipoprotein (VLDL) were unchanged throughvalue 0.05 was considered significant (two-tailed). out the study. Urinary sodium excretions were 152 and 148 mmol/24 hours during placebo and irbesartan treatment, RESULTS respectively (NS). No correlation between changes in albuminuria and changes in plasma cholesterol or Twenty four patients were randomized in the trial of plasma low-density lipoprotein (LDL) were demonstrated. which all completed the study. Baseline characteristics No carryover effect was seen. Statistical evidence of a are shown in Table 1. The median (range) duration of minor decline in albuminuria and 24-hour blood pressure both treatment periods was 58 days (45 to 76 days) and through the study period was demonstrated (time effect). compliance as assessed by tablet count was median (range) Our statistical model for evaluation of treatment effects 100% (71% to 100%) (no difference between irbesartan included and corrected for the observed time effect. Estiand placebo). mates of all treatment effects were the same with and Albuminuria and 24-hour blood pressure were signifi- without correction for time effect; however, all calculacantly reduced by the addition of irbesartan 300 mg com- tions were performed with the model including visit (time pared to placebo (Table 2). effect). Dual blockade of the RAS induced an additional reduction in albuminuria (mean, 95% CI) of 25% (15, Adverse effects 34) compared to placebo. When looking at fractional Six patients experienced signs of transient hypotension clearance index, dual blockade induced an additional (N 4) or described general tiredness (N 2) after start reduction in albuminuria of (mean, 95% CI) 22% (11, 31) of dual blockade treatment. Plasma potassium increased compared to placebo. The decline in albuminuria was to 5.2 mmol/l in two patients (one after start of placebo independent of the placebo level of albumin excretion. treatment and one after the start of irbesartan treat- An additional reduction in 24-hour systolic blood preswere treated with an increase of 50% in furosemide dose. ment). Both patients had GFR 40 ml/min/year and sure on dual blockade of 8 mm Hg (4, 12) (P 0.002) and a reduction of 4 mm Hg (2, 7) (P 0.003) diastolic Hemoglobin decreased (Table 2); however, none of the patients needed treatment for anemia during the study. compared to placebo was demonstrated. The decline of No other adverse effects were reported. mean arterial blood pressure when adding irbesartan was 5 mm Hg (3, 8) (P 0.001). No significant changes were found in the 24-hour mean heart rate. The reduction DISCUSSION in blood pressure was sustained both during daytime Our study is the first to demonstrate an effect of dual and nighttime (Table 2). The antihypertensive response blockade of the RAS on albuminuria and 24-hour blood

4 Jacobsen et al: Dual blockade of renin-angiotensin system 1877 Table 2. Dual blockade of the renin-angiotensin system (RAS) with irbesartan 300 mg once daily in 24 type 1 patients with diabetic nephropathy (DN) treated with enalapril 40 mg once daily Enalapril 40 mg Enalapril 40 mg placebo irbesartan 300 mg Mean difference (95% CI) P value Albuminuria mg/24 hour a 519 (342,789) 373 (224,622) 25% ( 34, 15) hour blood pressure mm Hg 131 (3)/74 (1) 123 (3)/70 (2) 8 ( 12, 4)/ 4 ( 7, 2) 0.002/0.003 Day (7-23) 135 (3)/76 (1) 128 (4)/73 (2) 7 ( 12, 2)/ 4 ( 6, 1) 0.012/0.018 Night (23-7) 118 (3)/70 (2) 110 (3)/63 (2) 9 ( 14, 3)/ 6 ( 9, 3) 0.007/0.001 Glomerular filtration rate ml/min/1.73 m 2 65 (5) 63 (5) 3 ( 1, 7) Plasma renin concentration mu/l a 177 (86, 364) 283 (133, 602) 64% (8, 150) Plasma creatinine lmol/l 134 (7) 139 (7) 4 ( 4, 13) Plasma potassium mmol/l 4.2 (0.1) 4.3 (0.1) 0.1 ( 0.1, 0.3) Hemoglobin mmol/l 8.0 (0.2) 7.6 (0.2) 0.4 ( 0.6, 0.1) Hemoglobin A 1C % 9.1 (0.3) 9.3 (0.2) 0.3 (0.1, 0.5) Plasma cholesterol mmol/l 5.0 (0.2) 4.7 (0.2) 0.3 ( 0.6, 0.0) Plasma low-density lipoprotein mmol/l 2.6 (0.2) 2.4 (0.2) 0.3 ( 0.6, 0.0) Plasma high-density lipoprotein mmol/l 1.7 (0.1) 1.7 (0.1) 0.0 ( 0.1, 0.1) Values represented are mean (SEM). a Mean (95% CI). Fig. 1. Linear regression analysis between the change in diastolic blood pressure and the change in albuminuria (LN) in type 1 patients with diabetic nephropathy (DN) treated with dual blockade of the renin- angiotensin system (RAS). Fig. 2. Linear regression analysis between the change in plasma renin concentration (LN) and the change in albuminuria (LN) in type 1 patients with diabetic nephropathy (DN) treated with dual blockade of the renin-angiotensin system (RAS). tion, ACE inhibitors decreased the degradation of brady- kinin, a powerful vasodilator [19]. However, an insuffi- cient response to ACE inhibitor might be explained by incomplete blockade of the ACE enzyme or by the gen- eration of angiotensin II by ACE-independent pathways such as chymase [20]. The incomplete blockade possibly explains the observation that plasma angiotensin II levels return to normal after chronic ACE inhibitor treatment, a phenomenon called ACE escape [21]. Treatment with ARB may result in more complete blockade of the unfavorable actions of angiotensin II mediated through the angiotensin II type 1 receptor. However, new data from animal studies indicate that some of the deleterious effects of angiotensin II on glomerular cell migration, tubular cell proliferation, and development of urinary pressure beyond what is obtainable with maximal recommended doses of ACE inhibitors alone in diabetic patients with DN. Dual blockade of the RAS with high doses of ACE inhibitors and ARB was safe and well tolerated. Six patients (25%) experienced transient symptoms of hypotension or tiredness. In all patients except one, symptoms disappeared within the 8 weeks treatment period. These side effects were related to the degree of drop in diastolic blood pressure, but not to placebo blood pressure level or the number of antihypertensive agents taken. The rationale for dual blockade of the RAS is based on the different mechanisms of actions of the two drug classes. In addition to decreased angiotensin II forma-

5 1878 Jacobsen et al: Dual blockade of renin-angiotensin system Fig. 3. Linear regression analysis between the change in diastolic blood pressure and the change in plasma renin concentration (LN) in type 1 African Americans with advanced renal failure. Surprisingly, this study showed a lowered plasma renin activity and enhanced GFR during losartan on top of ACE inhibitor treatment. Limitations of this study include underdosing with losartan, since 100 mg is more effective than 50 mg on both albuminuria and blood pressure in patients with DN [29]. Furthermore, the findings of Agarwal et al cannot be extrapolated to other ethnic groups due to differences in RAS activity and response to RAS blockade [30, 31]. In another nonrandomized openlabeled study of nine patients with nondiabetic renal disease, seven patients received both monotherapies in different doses followed by 40 mg of lisinopril losartan (50 to 150 mg) [32]. Dual blockade reduced proteinuria 85% from placebo, whereas 40 mg of lisinopril had significantly less antiproteinuric effect of 75% from pla- protein excretion may be mediated through the angiotensin II type 2 receptor [22 24]. Standard ARBs do not antagonize the type 2 receptor. Therefore, treatment with both ACE inhibitors and ARBs may offer synergistic blockade of the RAS, not obtainable with either drug alone. In accordance, in an animal model Komine et al [25] demonstrated that dual RAS blockade with captopril (1.7 mg/day) losartan (0.7 mg/day) treatment further reduces renal tissue angiotensin II level compared to treatment with captopril (2.4 mg/d) or losartan (1.7 mg/d) alone. Furthermore, tripling the dose of captopril (7.5 mg/day) or losartan (6.0 mg/day) did not reduce the intrarenal angiotensin II to the level observed with low-dose dual blockade therapy [25]. The mechanism underlying the lower renal tissue angiotensin II during ARB is not completely understood, but may involve decreased binding to the receptor and internalization of angiotensin II in the presence of a receptor blocker and/or increased degradation of angiotensin II. The authors concluded that the superior reduction in renal tissue angiotensin II with ACE inhibitors plus ARB provides a mechanism to understand the synergism of this combination in reducing proteinuria and blood pressure. On the other hand, conflicting results from studies of dual blockade of the RAS on blood pressure and urinary protein excretion in subtotally nephrectomized rats have been reported [26, 27]. Very limited information exists on the impact of dual blockade of the RAS compared to maximal recommended doses of ACE inhibitors in humans. Agarwal [28] reported that adding 50 mg of losartan daily to 40 mg of lisinopril daily had no effect on blood pressure and proteinuria in a small heterogeneous group of predominantly severely obese, hypertensive, proteinuric diabetic cebo. Dual blockade had similar antihypertensive effects patients with diabetic nephropathy (DN) treated with dual blockade compared to lisinopril 40 mg [32]. of the renin-angiotensin system (RAS). Several papers have reported on the effect of combining submaximal doses ACE inhibition and ARB, but carry the risk of underestimating the effect of monotherapy with ACE inhibition. The CALM-study [6] of type 2 diabetic patients with microalbuminuria and hypertension found an enhanced reduction in blood pressure and a tendency toward a more pronounced drop in urinary albumin excretion by dual blockade (16 mg candesartan cilexetil and 20 mg lisinopril) compared to therapy with either agent alone. Once DN has developed, we have recently demonstrated a beneficial short-term effect of dual blockade of the RAS in the subset of diabetic pa- tients with DN and albuminuria 1 g/24 hours blood pressure 135/85 mm Hg, despite treatment with ACE inhibitors (20 mg enalapril/lisinopril or equivalents) and diuretics [7, 8]. In nondiabetic renal disease, a superior effect of dual blockade compared to single blockade was reported in several short-term open-label studies [33 36]. The COOPERATE trial [9] is the first longterm trial addressing the effect of dual blockade on pri- mary renal end points. This double-blind, randomized study of 263 patients with nondiabetic renal disease dem- onstrated that 11% of patients on 100 mg losartan 3 mg of trandolapril developed doubling of serum creati- nine or reached end-stage renal disease during a median of 3 years of follow-up, whereas 23% reached the pri- mary end points during treatment with either monotherapies (P 0.02) [9]. In this study, we demonstrate an additional effect of dual blockade on albuminuria and blood pressure using maximal recommended doses that is comparable to what was obtained in our previous study using lower dose of ACE inhibitor and the same dose of irbesartan [7]. Furthermore, we saw an increase in plasma renin concentration of 64% in the present study equal to the 69% seen in our first study [7], indicating the same degree of incom- plete blockade of the RAS on 20 mg and 40 mg of enal-

6 Jacobsen et al: Dual blockade of renin-angiotensin system 1879 april/lisinopril (or equivalent) alone. This adds further with ACE inhibition alone in type 1 patients with DN. evidence to the idea of synergistic effect of using both Long-term trials are needed to further establish the role ACE inhibitors and ARB to interrupt the RAS. of dual blockade of the RAS. Even though using maximal recommended doses of enalapril and irbesartan, we cannot exclude the possibil- ACKNOWLEDGMENTS ity of underdosing with both agents. Unfortunately, there This study was supported by P. Carl Petersens Foundation, Copenhagen, The Danish Diabetes Association, and a grant from Sanofiis no dose-escalation studies of the antiproteinuric and antihypertensive effect of enalapril/lisinopril 20 mg or Synthelabo. The authors wish to express appreciation to Tina R. Juhl, Birgitte V. Hansen, Ulla M. Smidt, and Inge-Lise Rossing for technical irbesartan 300 mg daily in humans with DN. From assistance. studies in patients with moderate to severe essential hypertension, their is no evidence of an additional antihy- Reprint requests to Peter Jacobsen, M.D., Steno Diabetes Center, Niels Steensens Vej 2, 2820 Gentofte, Denmark. pertensive effect of doses of captopril up to 600 mg or pkjacobsen@dadlnet.dk enalapril/benazepril up to 80 mg [37 40] or irbesartan up to 900 mg [41]. REFERENCES Our study is not able to ascertain whether the benefi- 1. Rossing P: Promotion, prediction and prevention of progression cial effects of dual blockade are due to its blood pres- of nephropathy in type 1 diabetes mellitus. Diabet Med 15: , sure lowering action, per se, or the extra step in blocking 1998 the RAS. In order to do so a head-to-head comparison 2. Parving H-H, Østerby R, Ritz E: Diabetic nephropathy, in The Kidney, 6th ed, edited by Brenner BM, Philadelphia, WB Saunbetween dual blockade and mono blockade of the RAS ders, 2000, pp in combination with other antihypertensive drugs aiming 3. Bjorck S, Mulec H, Johnsen SA, et al: Renal protective effect at identical blood pressure levels is needed. However, of enalapril in diabetic nephropathy. Br Med J 304: , Lewis EJ, Hunsicker LG, Bain RP, et al: The effect of angiotensinthe observed relation between changes in blood pressure converting-enzyme inhibition on diabetic nephropathy. The Coland changes in albuminuria in addition to the multivari- laborative Study Group. N Engl J Med 329: , 1993 ate analysis suggests that blood pressure lowering is the 5. de Jong PE, Navis G, de Zeeuw D: Renoprotective therapy: Ti- tration against urinary protein excretion. Lancet 354: , 1999 major cause underlying the observed drop in albumin- 6. Mogensen CE, Neldam S, Tikkanen I, et al: Randomised conuria. On the other hand, a reduction in albuminuria inde- trolled trial of dual blockade of renin-angiotensin system in patients pendent of blood pressure reduction when starting lodiabetes: The candesartan and lisinopril microalbuminuria (CALM) with hypertension, microalbuminuria, and non-insulin dependent sartan treatment has been suggested in 62 patients study. Br Med J 321: , 2000 predominantly suffering from diabetic renal disease (ab- 7. Jacobsen P, Andersen S, Rossing K, et al: Dual blockade of the stract; Laverman GD et al, J Am Soc Nephrol 13:265A, renin-angiotensin system in type 1 patients with diabetic nephropa- 2002). This issue does not diminish the importance of thy. Nephrol Dial Transplant 17: , Rossing K, Christensen PK, Jensen BR, Parving H-H: Dual our observations since both reductions in blood pressure blockade of the renin-angiotensin system in diabetic nephropathy: and albuminuria are essential treatment goals in diabetic A randomized double-blind crossover study. Diabetes Care 25:95 patients with kidney disease. 100, Nakao N, Yoshimura A, Morita H, et al: Combination treatment In accordance with our previous study [7], the present of angiotensin-ii receptor blocker and angiotensin-converting enzyme inhibitor in non-diabetic renal disease (COOPERATE): A study demonstrated a decline in hemoglobin on dual blockrandomized controlled trial. Lancet 361: , 2003 ade of the RAS. The synthesis of erythropoietin (EPO) 10. Parving H-H, Andersen AR, Smidt UM, Svendsen PA: Early is stimulated by angiotensin II [42, 43]. The reduction aggressive antihypertensive treatment reduces rate of decline in in EPO level and consequently the drop in hemoglobin kidney function in diabetic nephropathy. Lancet 1: , 1983 level might therefore be expected to correspond to the 11. Mogensen CE, Chachati A, Christensen CK, et al: Microalbu- minuria: An early marker of renal involvement in diabetes. Uremia extent of intrarenal blockade of the RAS. We also found Invest 9:85 95, 1985 a tendency of increasing hemoglobin A 1c with dual blockglomerular filtration rate. Scand J Clin Lab Invest 30: , Brochner-Mortensen J: A simple method for the determination of ade treatment. When EPO level falls, the production of 13. Brochner-Mortensen J, Rodbro P: Selection of routine method new red blood cells will also decline, as a consequence for determination of glomerular filtration rate in adult patients. the mean age of the total population of red blood cells Scand J Clin Lab Invest 36:35 43, 1976 will transiently increase. As the hemoglobin A 14. Brochner-Mortensen J, Rodbro P: Comparison between total 1c increases and renal plasma clearance of [51Cr] EDTA. Scand J Clin Lab with time exposed to elevated blood glucose, this could Invest 36: , 1976 explain the apparent negative short-term effect of blockof renin activity, concentration and substrate in human and animal 15. Poulsen K, Jorgensen J: An easy radioimmunological microassay ade of the RAS on metabolic control. plasma and tissues based on angiotensin I trapping by antibody. J Clin Endocrinol Metab 39: , Millar JA, Leckie BJ, Morton JJ, et al: A microassay for active CONCLUSION and total renin concentration in human plasma based on antibody Our short-term study supports the concept that treat- trapping. Clin Chim Acta 101:5 15, Altman D: Clinical trials, in Practical Statistics for Medical Rement with both ACE inhibitors and ARB offer syner- search, edited by Altman G, London, Chapman & Hall/CRC, 1991, gistic renal and cardiovascular protection not obtainable pp

7 1880 Jacobsen et al: Dual blockade of renin-angiotensin system 18. Pinhero JC, Bates DM: Mixed-effects Models in S and S-PLUS compared with white patients with left ventricular dysfunction. J, New York, Springer, 2000 N Engl J Med 344: , Vanhoutte PM: Endothelium and control of vascular function. 32. Laverman GD, Navis G, Henning RH, et al: Dual renin-angiotensin State of the Art lecture. Hypertension 13: , 1989 system blockade at optimal doses for proteinuria. Kidney Int 20. Hollenberg NK, Fisher ND, Price DA: Pathways for angiotensin 62: , 2002 II generation in intact human tissue: Evidence from comparative 33. Ruilope LM, Aldigier JC, Ponticelli C, et al: Safety of the combipharmacological interruption of the renin system. Hypertension nation of valsartan and benazepril in patients with chronic renal 32: , 1998 disease. European Group for the Investigation of Valsartan in 21. Nussberger J, Brunner DB, Waeber B, Brunner HR: Plasma Chronic Renal Disease. J Hypertens 18:89 95, 2000 angiotensins under sustained converting enzyme inhibition with enalapril 34. Russo D, Minutolo R, Pisani A, et al: Coadministration of losar- in normal humans. J Hypertens 3(Suppl 3):S269 S270, 1985 tan and enalapril exerts additive antiproteinuric effect in IgA ne- 22. Wolf G, Ziyadeh FN, Thaiss F, et al: Angiotensin II stimulates phropathy. Am J Kidney Dis 38:18 25, 2001 expression of the chemokine RANTES in rat glomerular endothe- 35. Ferrari P, Marti HP, Pfister M, Frey FJ: Additive antiproteinuric lial cells. Role of the angiotensin type 2 receptor. J Clin Invest effect of combined ACE inhibition and angiotensin II receptor 100: , 1997 blockade. J Hypertens 20: , Cao Z, Kelly DJ, Cox A, et al: Angiotensin type 2 receptor is 36. Kincaid-Smith P, Fairley K, Packham D: Randomized controlled expressed in the adult rat kidney and promotes cellular prolifera- crossover study of the effect on proteinuria and blood pressure of tion and apoptosis. Kidney Int 58: , 2000 adding an angiotensin II receptor antagonist to an angiotensin con- 24. Cao Z, Bonnet F, Candido R, et al: Angiotensin type 2 receptor verting enzyme inhibitor in normotensive patients with chronic antagonism confers renal protection in a rat model of progressive renal disease and proteinuria. Nephrol Dial Transplant 17: , renal injury. J Am Soc Nephrol 13: , Komine N, Khang S, Wead LM, et al: Effect of combining an 37. Lijnen P, Fagard R, Staessen J, et al: Dose response in captopril ACE inhibitor and an angiotensin II receptor blocker on plasma therapy of hypertension. Clin Pharmacol Ther 28: , 1980 and kidney tissue angiotensin II levels. Am J Kidney Dis 39: Gomez HJ, Cirillo VJ, Sromovsky JA, et al: Lisinopril dose- 164, 2002 response relationship in essential hypertension. Br J Clin Pharmacol 26. Ots M, Mackenzie HS, Troy JL, et al: Effects of combination 28: , 1989 therapy with enalapril and losartan on the rate of progression of 39. Whalen JJ: Definition of the effective dose of the convertingenzyme renal injury in rats with 5/6 renal mass ablation. J Am Soc Nephrol inhibitor benazepril. Am Heart J 117: , : , Eber B, Brussee H, Rotman B, et al: Evaluation of the antihypertensive 27. Cao Z, Cooper ME, Wu LL, et al: Blockade of the renin-angiotensin effect of lisinopril compared with nifedipine in patients and endothelin systems on progressive renal injury. Hyperten- with mild to severe essential hypertension. Angiology 43: , sion 36: , Agarwal R: Add-on angiotensin receptor blockade with max- 41. Reeves RA, Lin CS, Kassler-Taub K, Pouleur H: Dose-related imized ACE inhibition. Kidney Int 59: , 2001 efficacy of irbesartan for hypertension: An integrated analysis. 29. Andersen S, Rossing P, Juhl TR, et al: Optimal dose of losartan Hypertension 31: , 1998 for renoprotection in diabetic nephropathy. Nephrol Dial Transplant 42. Freudenthaler SM, Schreeb K, Korner T, Gleiter CH: Angio- 17: , 2002 tensin II increases erythropoietin production in healthy human 30. Gibbs CR, Beevers DG, Lip GY: The management of hypertensive volunteers. Eur J Clin Invest 29: , 1999 disease in black patients. QJM 92: , Freudenthaler SM, Schenck T, Lucht I, Gleiter CH: Fenoterol 31. Exner DV, Dries DL, Domanski MJ, Cohn JN: Lesser response stimulates human erythropoietin production via activation of the to angiotensin-converting-enzyme inhibitor therapy in black as renin angiotensin system. Br J Clin Pharmacol 48: , 1999