see commentary on page 2051
Long-term effects of spironolactone on proteinuria
and kidney function in patients with chronic kidney
disease
S Bianchi
1, R Bigazzi
1and VM Campese
21Unita` Operativa Nefrologia, Spedali Riuniti, Livorno, Italy and2Division of Nephrology, Keck School of Medicine, USC, Los Angeles, California, USA
Experimental evidence suggests that aldosterone contributes to progressive kidney disease. Angiotensin-converting enzyme inhibitors and angiotensin type 1 receptor antagonists suppress the renin–angiotensin system but they do not effectively reduce plasma aldosterone. Hence, administration of aldosterone receptor antagonists may provide additional renal protection. In the present prospective randomized open-label study, we evaluated the effects of spironolactone (25 mg/day for 1 year) on proteinuria and estimated glomerular filtration rate in 83 patients with chronic kidney disease already treated with angiotensin-converting enzyme inhibitors and/or angiotensin type 1 receptor antagonists. Eighty-two patients were treated with angiotensin-converting enzyme inhibitors and/or angiotensin type 1 receptor antagonists alone and served as controls. After 1 year of therapy, proteinuria decreased from 2.170.08 to 0.8970.06 g/g creatinine (Po0.001) in patients treated with spironolactone, but it did not change in control patients. Baseline aldosterone levels were significantly correlated with proteinuria (r¼0.76, Po0.0001), and predicted the degree of reduction in proteinuria with spironolactone (r¼0.42,Po0.0002). Baseline estimated glomerular filtration rate was similar in patients treated with spironolactone and controls (62.472.4 and 62.272.1 ml/min/1.73 m2, respectively). After 1 month of therapy with spironolactone, estimated glomerular filtration rate decreased more in patients treated with spironolactone than in controls. However, by the end of 1 year the monthly rate of decrease in estimated glomerular filtration rate from baseline was lower in patients treated with spironolactone than in controls (0.32370.044 vs 0.47470.037 ml/min/ 1.73 m2,Po0.01). Spironolactone caused a significant rise in serum potassium levels (from 4.270.04 at baseline to 5.070.05 mEq/l after 12 months of treatment,Po0.001). In conclusion, this study has shown that spironolactone may reduce proteinuria and retard renal progression in chronic kidney disease patients.
Kidney International(2006)70,2116–2123. doi:10.1038/sj.ki.5001854; published online 11 October 2006
KEYWORDS: aldosterone; spironolactone; proteinuria; glomerular filtration rate; chronic kidney disease; hyperkalemia
Background
The prevalence of chronic kidney disease (CKD) is increasing alarmingly mainly as a result of an ongoing epidemic of obesity, metabolic syndrome, and diabetes mellitus.1
Several factors may contribute to the progression of CKD including derangements of renal hemodynamics, vasoactive hormones such as angiotensin II and norepinephrine, cytokines, growth factors, oxidative stress, and inflamma-tion.2–4 Numerous studies have demonstrated that the renin–angiotensin–aldosterone system (RAAS) plays an im-portant role in the progression of CKD,5,6 and inhibition of the RAAS with angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin type 1 receptor antagonists (ARBs) may retard CKD progression.7–10These renoprotective effects are attributed to reduction of systemic arterial and glomerular pressures and to inhibition of angiotensin-II-related effects on mesangial cell proliferation and fibrosis.11 However, neither ACEIs nor ARBs abrogate the progression of kidney disease. This suggests that ACEIs and ARBs, at the doses currently approved, do not predictably suppress aldosterone in all patients, a phenomenon known as ‘aldosterone synthesis escape,’ leaving potentially detrimental effects of aldosterone unabated.12
Studies in experimental rat models have shown that aldosterone participates to the progression of kidney disease through hemodynamic and direct cellular actions13 and antagonists of aldosterone retard the progression or cause regression of existing glomerulosclerosis independently of effects on blood pressure (BP).14–16
The clinical evidence for a role of aldosterone in CKD progression is scanty.17–20In a pilot short-term uncontrolled study, we observed that spironolactone effectively reduced proteinuria in non-diabetic CKD patients already treated with ACEIs and/or ARBs.21
This is a prospective, randomized open-label study to evaluate the effects of spironolactone, an aldosterone receptor
Received 1 June 2006; revised 21 July 2006; accepted 1 August 2006; published online 11 October 2006
Correspondence:VM Campese, Keck School of Medicine, USC, 1200 North State Street, Los Angeles, California 90033, USA. E-mail: campese@usc.edu
antagonist, on proteinuria and estimated glomerular filtra-tion rate (eGFR) in a cohort of 165 CKD patients treated for 1 year.
RESULTS
The baseline and follow-up clinical characteristics of all patients included in the study are shown in Tables 1 and 2. The baseline clinical characteristics of patients treated with spironolactone did not differ from those of patients treated with conventional therapy. Baseline proteinuria was 2.170.08 g/g creatinine in patients treated with spirono-lactone and 2.070.07 g/g creatinine in patients treated with conventional therapy. After 1 year of follow-up, proteinuria decreased to 0.8970.06 g/g creatinine among patients treated with spironolactone, but it did not change among patients treated with conventional therapy (Table 3). In 23 out of 78 patients treated with spironolactone for 1 year, proteinuria decreased too500 mg/g creatinine. Baseline proteinuria was greater among patients with eGFRo60 ml/min/1.73 m2than among those with eGFR460 ml/min/1.73 m2 (2.1770.08 vs 1.8270.07 g/g creatinine in the conventional therapy group and 2.3370.09 vs 1.8470.08 g/g creatinine in the group of patients treated with spironolactone) (Table 3). After 1 year of treatment with spironolactone, the percent decline in proteinuria was significantly greater among patients with estimated GFRo60 than among patients with estimate GFR460 ml/min/1.732(62.2 vs42.9%,Po0.01) (Table 3, Figure 1).
After 1 year of treatment with spironolactone, the percent reduction in proteinuria was greater among patients treated
with ACEIs (60.974.8%) or ARBs alone (67.973.6%) than among patients treated with a combination of ACEIs and ARBs (42.875.5%,Po0.01) (Table 5).
After 4 weeks of treatment with spironolactone, eGFR decreased from 62.472.4 to 57.372.7 ml/min/1.732 (Po0.001) (Table 4). Thereafter, eGFR remained stable and at the end of 12 months treatment was 58.672.6 ml/min/ 1.732. By contrast, during 1 year of follow-up, eGFR declined slowly but progressively in subjects treated with conventional therapy (from 62.272.1 to 56.472.3 ml/min/1.732,Po0.01) (Table 4, Figure 2). At the end of 1 year of treatment, eGFR was not statistically different between the two groups. However, the percent decline in eGFR was lower in patients treated with spironolactone than in controls (Figure 2). Also, the monthly rate of decrease in eGFR from baseline was lower in patients treated with spironolactone than in controls (0.32370.044 vs 0.47470.037 ml/min,Po0.01). The reduc-tion in eGFR observed during treatment with spironolactone was more pronounced among patients with estimated GFRo60 ml/min than among patients with GFR460 ml/ min/1.73 m2(Table 4). After 1 year of treatment, we observed a weak but statistically significant correlation between the percent changes in proteinuria and changes in eGFR in the entire group of patients studied (r¼0.307 Po0.0001). This relationship was significant only for patients treated with spironolactone (r¼0.350, Po0.0001) and not for patients treated with conventional therapy. The relationship between the percent change in proteinuria and change in eGFR was already present after the first month of treatment with spironolactone (r¼0.436,Po0.0001).
Table 1 | Clinical characteristics at baseline of patients treated with conventional therapy and those receiving conventional therapy plus spironolactone 25 mg/day
All Conventional therapy Conventional therapy plus spironolactone
No. of patients 165 82 83 Age (years) 54.770.8 54.471.2 55.071.2 Sex (M/F) 106/59 50/32 56/27 BMI 24.970.2 24.870.2 24.970.2 Smokers (Y/N) 41/124 21/61 19/64 Basal SBP (mmHg) 132.370.5 131.670.6 132.970.8 Basal DBP (mmHg) 78.370.3 78.170.4 78.570.5 eGFR (ml/min/1.73 m2) 62.371.6 62.272.1 62.472.4 Uprotein (g/g creatinine) 2.170.05 2.070.07 2.170.08 Serum K+(mEq/l) 4.370.03 4.270.03 4.270.04 Basal aldosterone (pg/ml) 132.174.7 130.476.5 134.776.9 Antihypertensive drugs ACEIs 50 21 29 ARBs 35 18 17
Both ACEIs and ARBs 80 43 37
Other antihypertensive drugs
Number (O/1/2/3) 20/69/60/16 8/36/34/4 12/33/26/12
Diuretics (Y/N) 116/49 56/26 60/23
Statins (Y/N) 146/19 72/10 74/9
ACEIs, angiotensin-converting enzyme inhibitors; ARBs, angiotensin type 1 receptor antagonists; BMI, body mass index; SBP, systolic blood pressure; DBP, diastolic blood pressure; F, female; M, male; K+, potassium; N, no; Y, yes; eGFR; estimated glomerular filtration rate.
Baseline BP in patients randomized to conventional therapy was 131.670.6/78.170.4 mmHg and in patients randomized to spironolactone was 132.970.8/78.57 0.5 mmHg. After 9 and 12 months of therapy with spiro-nolactone, BP decreased (Po0.05) in patients treated with spironolactone (128.370.8/76.370.5 and 126.970.8/75.670.5, respectively) but not in the control group (130.570.6/77.570.5 and 130.270.6/78.170.7, respectively) (Table 2). No effect of spironolactone on BP was evident during the first 6 months of treatment.
Baseline serum potassium was not different between patients treated with conventional therapy and those rando-mized to spironolactone (4.270.03 and 4.270.04 mEq/l, respectively) (Table 2). However, during treatment with spironolactone, serum potassium increased progressively
from 4.270.04 at baseline to 5.070.05 mEq/l (Po0.001) at the end of 1 year of treatment. By contrast, serum potassium did not change in patients treated with conventional therapy. Four patients in the spironolactone arm and two in the conventional therapy arm of the study, all with estimated GFRo60 ml/min, reached a serum potassium level45.5 but o6.0 mEq/l and had to discontinue the study. Baseline serum potassium levels were higher (Po0.005) in patients treated with a combination of ACEIs and ARBs (4.470.07 mEq/l) than in those treated with ARBs alone (4.270.08 mEq/l). Baseline serum potassium levels were not different in patients treated with a combination of ACEIs and ARBs (4.47 0.07 mEq/l) than in those treated with ACEIs alone (4.37 0.08 mEq/l) (Table 5). The effects of spironolactone treat-ment on serum Kþ were not different in patients treated with a combination of ACEIs and ARBs than in those treated with ACEIs or ARBs alone (Table 5).
Baseline plasma aldosterone levels were not different between patients treated with conventional therapy and those randomized to spironolactone (130.476.5 and 134.77 6.9 pg/ml, respectively). Aldosterone levels were lower (Po0.001) among the 35 patients receiving ACEIs and ARBs combined (89.674.9 pg/ml) than the 27 patients receiving ACEIs alone (165.777 pg/ml) and the 16 patients receiving ARBs alone (18179.7 pg/ml) (Table 5).
Baseline levels of aldosterone were significantly correlated with levels of proteinuria (r¼0.766, Po0.0001) (Figure 3)
Table 2 | Blood pressure, estimated GFR and serum potassium levels at baseline and during follow-up in patients treated with conventional therapy and those treated with
conventional therapy plus spironolactone Conventional therapy Conventional therapy plus spironolactone Blood pressure (mmHg) Basal SBP 131.670.6 132.970.8 Basal DBP 78.170.4 78.570.5 1 month SBP 130.870.6 131.470.8 DBP 77.370.7 77.870.5 3 months SBP 130.770.6 131.370.9 DBP 76.570.9 78.370.6 6 months SBP 130.370.6 129.570.9 DBP 76.570.9 76.970.6 9 months SBP 130.570.6 128.570.9* DBP 77.570.5 76.570.5** 12 months SBP 130.270.6 126.970.8**,# DBP 77.370.5 75.670.5**,@ Estimated GFR (ml/min/1.73 m2) Basal 62.272.1 62.472.4 1 month 61.172.2 57.372.7* 3 months 59.772.3 56.672.7* 6 months 58.672.2* 57.872.7* 9 months 57.472.3* 58.072.6* 12 months 56.472.3** 58.672.6*
Serum potassium (mEq/l)
Basal 4.270.03 4.270.04 1 month 4.370.03 4.570.05**,# 3 months 4.370.04 4.770.05**,# 6 months 4.370.05 4.770.07**,# 9 months 4.370.05 4.870.05**,# 12 months 4.370.05 5.070.05**,#
DBP, diastolic blood pressure; GFR, glomerular filtration rate; SBP, systolic blood pressure.
Data are expressed as mean7s.e.m. *Po0.05 vs basal. **Po0.001 vs basal. # Po0.001 vs conventional therapy. @ Po0.03 vs conventional therapy.
Table 3 | Effect of spironolactone on proteinuria in patients with eGFRoor460 ml/min/1.73 m2
Conventional therapy Conventional therapy plus spironolactone Basal all 2.070.07 2.170.08 eGFRo60 ml/min 2.1770.08 2.3370.09 eGFR460 ml/min 1.8270.07** 1.8470.08** 1 month all 2.070.07 1.4970.06 (26.9%)* eGFRo60 ml/min 2.1670.08 1.6270.09 (29.8%) eGFR460 ml/min 1.8970.07 1.3170.07 (22.8%) 3 months all 1.9770.07 1.2670.06 (37.9%)* eGFRo60 ml/min 2.0170.08 1.3470.09 (42.3%) eGFR460 ml/min 1.8970.07 1.1570.07 (31.5)** 6 months all 1.9770.07 1.1370.06 (43.9%)* eGFRo60 ml/min 2.1470.08 1.1970.09 (48.5%) eGFR460 ml/min 1.8670.07 1.0570.08 (37.2%)# 9 months all 2.070.07 0.9970.06 (49.9%)* eGFRo60 ml/min 2.170.08 1.070.08 (56.4%) eGFR460 ml/min 1.9470.07 0.9870.08 (40.%)** 12 months all 2.1170.08 0.8970.06 (54.2%)* eGFRo60 ml/min 2.1970.09 0.8870.09 (62.2%) eGFR460 ml/min 1.9970.08 0.9370.09 (42.9%)**
eGFR, estimated glomerular filtration rate.
In parentheses are the % changes vs basal proteinuria. *Po0.001 vs basal proteinuria.
#
Po0.05 vs patients with eGFRo60 ml/min. **Po0.01 vs patients with eGFRo60 ml/min.
and with the percent reduction in proteinuria following treatment with spironolactone (r¼0.42,Po0.0002).
Single regression analyses showed that the level of urine protein excretion at 12 months was significantly correlated with systolic (r¼0.272, Po0.001) and diastolic BP (r¼
0.242,Po0.002), and with the change in eGFR after 1 month of treatment with spironolactone (r¼0.459,Po0.0001).
Table 4 | Effect of spironolactone 25 mg/day on renal function in patients with eGFRoor460 ml/min/1.73 m2
Conventional therapy Conventional therapy plus spironolactone Basal eGFR 62.272.1 62.472.4 eGFRo60 ml/min 49.571.7 46.571.3 eGFR460 ml/min 80.172.2 85.372.3 1 month 61.172.2 57.372.7# % Reduction vs basal All patients 1.67/0.2 8.270.8# eGFRo60 ml/min 2.370.3 13.670.8# eGFR460 ml/min 0.770.3 4.170.9* 3 months eGFR 59.772.3 56.672.7# % Reduction vs basal All patients 3.670.4 9.170.8# eGFRo60 ml/min 5.670.5 15.170.9# eGFR460 ml/min 1.870.4 4.670.9* 6 months eGFR 58.672.2# 57.8 72.7 % Reduction vs basal All patients 5.570.4# 7.570.8# eGFRo60 ml/min 8.270.5# 12.870.9# eGFR460 ml/min 3.170.5* 3.470.7* 9 months eGFR 57.472.3# 58.072.6# % Reduction vs basal All patient 7.470.6# 7.270.7# eGFRo60 ml/min 11.470.6# 10.070.9# eGFR460 ml/min 4.370.7* 4.270.7* 12 months eGFR 56.472.3# 58.672.6# % Reduction vs basal All patient 9.070.6#,# 6.270.7# eGFRo60 ml/min 13.570.7# 8.170.9# eGFR460 ml/min 5.770.7* 3.970.7*
eGFR, estimated glomerular filtration rate (ml/min/1.73 m2
) by Modification of Diet in Renal Disease formula.
*Po0.01 vs patients with eGFRo60 ml/min;#
Po0.001 vs baseline eGFR. 0 1 3 6 9 12 − 20 − 40 − 60 − 80 All patients
Patients with GFR<60 ml/min Patients with GFR>60 ml/min Months of treatment % reduction of protein ur ia vs basal v alue * * * * * * * * * * * * * * * # @ @
Figure 1|This slide shows the percent reduction of proteinuria from baseline in patients treated with spironolactone (25 mg/ day) in addition to conventional therapy divided on the basis of their eGFR (oor460 ml/min/1.73 m2).*Po0.001 vs basal proteinuria;#Po0.05 vs patients with eGFRo60 ml/min;@Po0.01 vs patients with eGFRo60 ml/min.
Table 5 | Clinical characteristics at baseline and end of the study in patients treated with spironolactone in addition to ACEIs alone, ARBs alone, or a combination of ACEIs and ARBs
ACEIs ARBs ACEIs+ARBs
No. of patients 27 16 35
Age 57.672.1 53.372.9 53.771.7
Sex (M/F) 17/10 11/5 25/10
BMI 24.970.5 24.870.6 24.970.3
Other antihypertensive drugs
(O/1/2/3) 2/16/6/3 3/8/3/2 6/7/16/6 Diuretics (Y/N) 19/8 10/6 22/13 Statins (Y/N) 25/2 14/2 32/3 Basal aldosterone (pg/ml) 165.777 18179.7 89.674.9* Basal SBP (mmHg) 132.871.9 136.571.7 131.371.3 Basal DBP (mmHg) 78.470.8 80.370.9 77.770.9
Basal serum potassium (mEq/l) 4.370.08 4.270.08 4.470.07**
% Increase at 12 months 5.070.08 4.870.07 5.170.09**
Basal proteinuria (g/g creatinine) 2.3870.1 2.7970.1 1.5970.09#
% Reduction at 12 months 60.974.8 67.973.6 42.875.5*
Basal eGFR (ml/min/1.73 m2) 55.573.6 58.474.9 69.774*
% Reduction at 12 months 6.771.3 8.171.4 6.771.5
ACEIs, angiotensin-converting enzyme inhibitors; ARBs, angiotensin type 1 receptor antagonists; BMI, body mass index; DBP, diastolic blood pressure; F, female; M, male; N, no; SBP, systolic blood pressure; Y, yes.
*Po0.01 vs patients treated with ACEIs or ARBs alone. #
Po0.05 vs patients treated with ACEIs and ARBs. **Po0.005 vs patients treated with ARBs.
Five of the original patients randomized to spironolactone did not complete the study owing to adverse events. These patients are not included in this analysis.
− 2 1 3 6 9 12 − 4 − 6 − 8 − 10 − 12 Conventional therapy Conventional therapy+Spironolactone ∗ ∗ ∗ ∗ ∗ ∗ ∗∗ ∗ Months of treatment
% reduction of eGFR vs basal v
alue
Figure 2|This slide shows the percent decline in eGFR in patients treated with spironolactone and those treated with conventional therapy.Patients were followed for 1 year. *Po0.001 vs basal eGFR, **Po0.0001 vs basal eGFR.
Step-wise multiple linear regression analyses using 12 months percentage reduction of proteinuria as a dependent variable and systolic and diastolic BP, plasma aldosterone, eGFR, and baseline proteinuria as independent explanatory variables showed that systolic BP at 12 months (P¼0.02), basal aldosterone (P¼0.017), and the percent change in eGFR at 1 month (P¼0.004), but not eGFR at 12 months (P¼0.06) and basal proteinuria (P¼0.56) predicted the reduction in proteinuria with spironolactone treatment.
Adverse events and dropouts
Nine patients did not complete the study, five in the spironolactone group and four in the control group. In the spironolactone group, four patients discontinued treatment after 3 months because of persistent serum Kþ45.5 mEq/l despite diuretic therapy and low Kþ diet. All these subjects had eGFRo60 ml/min/1.73 m2 and three out of four were taking a combination of ACEIs and ARBs; the fourth patient was taking an ACEI. One patient developed significant gynecomastia and discontinued treatment after 3 months. Five additional patients treated with spironolactone devel-oped mild gynecomastia that did not necessitate disconti-nuation of the drug. In the control group, four patients discontinued therapy during the first 3 months, two for hyperkalemia, and two were lost to follow-up. All patients with hyperkalemia had baseline eGFRo60 ml/min/1.732.
DISCUSSION
In this long-term study, we have confirmed that spirono-lactone can substantially reduce urine protein excretion in patients with CKD. This effect occurred in patients with the RAAS inhibited by ACEIs and/or ARBs for at least 1 year before the initiation of treatment with spironolactone and it was sustained throughout the period of observation.
In a previous study, we showed that treatment with 25 mg of spironolactone for 8 weeks reduced proteinuria from 2.0970.16 to 1.0570.08 g/24 h. The reduction in proteinuria was apparent as early as 2 weeks after initiation of treatment
and reverted to baseline 4 weeks after discontinuation of the drug.21
The observed early reduction in proteinuria was not related to changes in BP since it was evident after 1 month of treatment with spironolactone, at a time when there was no significant change in BP. Significant effects of spironolactone on BP became evident only after 9 and 12 months of treatment. After 12 months, multiple regression analyses showed a contribution of BP to proteinuria reduction. Chrysostomouet al.22observed a 50% decrease in proteinur-ia in CKD patients without significant changes in BP.
The baseline levels of proteinuria were lower among patients treated with a combination of ACEIs and ARBs than among those treated with any of these drugs alone. This is in line with the study of Nakao et al.23 who showed greater reduction of proteinuria with a combination of trandolapril and losartan than with any of these drugs alone23 and suggests that ACEIs and ARBs when given alone even at the highest approved doses may provide incomplete RAAS block-ade. The beneficial effects of spironolactone on proteinuria in patients with already suppressed RAAS by ACEIs or ARBs can be best explained by inadequate suppression of aldosterone secretion.24The percent decline in proteinuria with spirono-lactone was less pronounced among patients who received a combination of ACEIs and ARBs than among patients who received ACEIs or ARBs alone. It is noteworthy that the baseline levels of aldosterone were lower among patients treated with a combination of ACEI and ARBs than among patients treated with any of these classes of drugs alone. This is in keeping with the notion that levels of aldosterone are an important determinant of the degree of proteinuria and of the pharmacological response to spironolactone in CKD patients. In support of this hypothesis is also the strong correlation we observed between baseline levels of aldoster-one and levels of proteinuria.
Before this study, there was limited evidence that antagonists of aldosterone reduce proteinuria in CKD patients. In an uncontrolled trial of eight patients with various renal diseases and proteinuria 41 g per day, spiro-nolactone consistently reduced proteinuria.25In 13 patients with early diabetic nephropathy and ‘aldosterone escape’ from ACEIs, Sato et al.20 observed a significant reduction in urinary albumin excretion after 24 week of treatment with spironolactone. Of note, the decrease in urine albumin excretion was more pronounced among patients with aldo-sterone escape. Rachmani et al.19 compared the antiprotei-nuric effects of spironolactone with that of cilazapril in 60 female with diabetic nephropathy. Spironolactone reduced proteinuria more effectively than ACEIs and the combined administration of the ACEIs and spironolactone was more effective than either drug alone. Epsteinet al.26observed that eplerenone reduced proteinuria more effectively than an ACEI in patients with type II diabetes mellitus and the combi-nation of eplerenone and ACEI was more effective than either drug given alone in reducing proteinuria. Spironolactone treatment in addition to recommended antihypertensive 4 3.5 2.5 1.5 0.5 1 2 3 0 50 100 150 200 250 300 Basal aldosterone, pg /ml Basal protein ur ia, g/g creatinine
Figure 3|This slide shows the regression line between baseline plasma aldosterone levels and proteinuria in the 165 patients included in the study (r¼0.766,Po0.0001).
drugs reduced BP and proteinuria in type I and type II diabetic patients with nephropathy.27,28
This study is also the first to suggest that spironolactone may reduce the rate of decline in kidney function in CKD patients. Baseline eGFR was not different in the two groups of patients studied. However, in patients treated with spirono-lactone we observed an initial rapid (after 1 month) decline in eGFR, followed by stabilization. By contrast, in patients treated with conventional therapy, eGFR declined slowly but progressively. By the end of 1-year treatment, the percent decline in eGFR was significantly greater in patients treated with conventional therapy than in those treated with spironolactone.
The mechanisms responsible for the initial acute reduc-tion in eGFR are unclear. However, this phenomenon is reminiscent of the initial fall in eGFR seen in CKD patients treated with ACEIs, whereby an initial rapid decrease in GFR is usually followed by stabilization of kidney function.7
Schmidtet al.29have shown that aldosterone exerts rapid nongenomic effects on the renal vasculature resulting in increased renal vascular resistance and increased filtration fraction. These effect of aldosterone on the renal vasculature occurred only when endothelial NO synthase was inhibited by simultaneous administration of NG monomethyl-L -arginine. In an editorial accompanying the article by Schmidt
et al.,29 Chun and Pratt30 suggest that under conditions of endothelial dysfunction, as it might occur in patients with essential hypertension, metabolic syndrome, or CKD, these nongenomic effects of aldosterone might result in reduced renal blood flow and GFR. Using isolated afferent and efferent arterioles from rabbit kidneys, Arima et al.31 have shown that aldosterone exerts a vasoconstrictive action on both the afferent and efferent arterioles, but the sensitivity of the efferent arterioles to aldosterone was greater than that of the afferent arterioles. Interestingly, the vasoconstrictor effects of aldosterone were not blocked by spironolactone suggesting that the vasoconstrictor action is non-genomic. Endothelial denudation and pharmacological blockade of eNOS increased the sensitivity of the afferent arterioles to aldosterone suggesting that nitric oxide modulates the vasoconstrictor action of aldosterone.32 In a dog model of obesity-induced hypertension, both BP and GFR decreased after treatment with eplerenone.33In all, these studies suggest that antagonists of aldosterone may exert intrarenal hemo-dynamic changes resulting in an acute decrease in GFR.
After this initial rapid fall, eGFR remained stable throughout the rest of the year of treatment with spirono-lactone and the average percent decline in eGFR was signi-ficantly lower in patients treated with spironolactone than in those treated with conventional therapy. These findings are consistent with the wealth of experimental evidence showing aldosterone may contribute to renal injury34,35 and antago-nists of this hormone may result in renal protection. In 5/6 nephrectomized rats with subtotal nephrectomy and adrenal-ectomy, proteinuria hypertension and structural renal injury were less pronounced than in rats with intact adrenal
glands.36Aldosterone infusion abrogated the beneficial effects of ACEIs in stroke-prone spontaneously hypertensive rats, whereas spironolactone reduced vascular injury and protein-uria in these animals.14,15
The mechanisms responsible for the adverse effects of aldosterone on the kidney are complex. As a result of differential effects on the afferent and efferent glomerular arterioles, aldosterone could increase intraglomerular pres-sure, an action reminiscent of that of angiotensin II. Experi-mental evidence has shown that aldosterone may damage non-epithelial tissues, in the heart, brain, kidneys, and blood vessels.37–42 Aldosterone stimulates type IV collagen accu-mulation in rat mesangial cells and this may result in progressive renal fibrosis.43Aldosterone stimulates plasmino-gen activator inhibitor-1, which is centrally involved in the pathogenesis of fibrinolysis and it may contribute to glomerulosclerosis and tubulo-interstitial nephritis.44,45 Aldosterone stimulates transforming growth factor-b1, a cytokine that promotes fibroblast differentiation and pro-liferation,46and aldosterone antagonists improve experimen-tal chronic cyclosporine nephrotoxicity.47Eplerenone inhibits lectine-like oxidized low-density lipoprotein receptor-1-mediated adhesion molecules and results in improved endo-thelial function.48 In 4-week-old Dahl’s salt-sensitive rats fed high-salt diet, Nagase et al.49 observed proteinuria and glomerulosclerosis associated with a decrease in nephrin and an increase in markers of podocyte damage, such as B7-1 and desmin. Treatment with eplerenone dramatically improved podocyte damage and retarded progression of proteinuria and glomerulosclerosis.
Although 25 mg spironolactone appeared to be well tolerated in this population at increased risk for hyper-kalemia, owing to stage 3–4 CKD and co-administration of ACEIs and ARBs, caution should be exercised when using this drug in patients with eGFR below 60 ml/min. The low incidence of hyperkalemia in our study might be due to close clinical observation, adjustment of dietary intake of potas-sium and dose of diuretics and should not be taken as an indication for liberalized use of this drug in CKD patients.
Our study has several limitations. Although we observed lower degree of progression of CKD in patients treated with spironolactone, the number of patients included and the duration of the study were not adequate to clearly establish a long-term beneficial effect of spironolactone on progression of kidney disease. Prospective randomized trials on larger groups of patients and longer duration than 1 year are necessary to more adequately address this issue.
The study was open label and not placebo controlled. Therefore, potential bias in the evaluation of data cannot be completely excluded. Finally, the limitations of using eGFR instead of measured GFR are well known and have been the object of extensive reviews.50,51
In conclusion, this study has demonstrated that antago-nists of aldosterone reduce proteinuria in patients with CKD. This effect occurs in addition to that obtained with the administration of inhibitors of the RAS. The study also
suggests that spironolactone may reduce the rate of progression of CKD. However, larger prospective randomized studies of longer duration are needed to conclusively demonstrate beneficial effects of aldosterone antagonists on the progression of CKD. Concerns remain in regards to the risk of hyperkalemia particularly in patients with more advanced kidney disease.
MATERIALS AND METHODS
This is a prospective, open-label randomized study to evaluate the effects of spironolactone on proteinuria and eGFR and the safety of this drug in CKD patients. The Human Research Committee of the Spedali Riuniti di Livorno, Italy, approved the study and all subjects gave their informed consent. The randomization was performed using a computed generated system.
The clinical characteristics of patients included in the study are illustrated in Tables 1 and 2. We enrolled 165 CKD patients (106 males and 59 females) with eGFR ranging from 34 to 116 ml/min/ 1.73 m2and proteinuria ranging from 1.0 to 3.9 g/g creatinine. These subjects were screened among more than 400 patients with CKD followed in our outpatient clinic. To be included, all patients had to have a clinical diagnosis of idiopathic chronic glomerulonephritis based on the presence of proteinuria greater than 1.0 g/g creatinine, and no evidence of systemic diseases. In 62 of these patients, the diagnosis of chronic glomerulonephritis was confirmed by a renal biopsy: 33 patients had IgA nephropathy, five membrano-prolifera-tive glomerulonephritis, 14 focal and segmental glomerulosclerosis, eight membranous glomerulonephritis, and two had micro-scopic vasculitis. In patients who were not biopsied, we cannot exclude the possibility of renal diseases other than glomerulone-phritis.
One hundred and twenty-two patients were hypertensive (office systolic BPX140 mmHg and diastolic BPX90 mmHg). We excluded
patients with diabetes mellitus, renovascular or malignant hyper-tension, secondary glomerular disease, malignancies, myocardial infarction, or cerebrovascular accident within the 6 months prece-ding the study, congestive heart failure, hepatic dysfunction, serum potassium 45 mEq/l, eGFRo30 ml/min/1.73 m2, and a history of allergy to ACEIs or ARBs. We also excluded patients treated with steroids, nonsteroidal anti-inflammatory drugs, or immuno-suppressive agents.
Before inclusion in this trial, all patients had been followed in the outpatient clinic for at least 1 year and treated with ACEIs and/or ARBs. In the control group, 21 subjects were treated with ACEIs, 18 with ARBs, and 43 with a combination of these two classes of drugs. In the spironolactone group, 28 patients were treated with ACEIs, 17 with ARBs and 38 with a combination of ACEIs and ARBs. Fifty-six patients in the conventional therapy group and 60 in the spironolactone group received hydrochlorothiazide or furose-mide. Other antihypertensive drugs were used as needed to achieve a target BP ofo125/75 mmHg, and 74 patients achieved this target. The doses of ACEIs and ARBs were not changed after randomization and inclusion in the study. The dose of diuretics was increased in patients who developed hyperkalemia in an attempt to control serum potassium before deciding to withdraw patients from the study. Seventy-two patients in the conventional therapy group and 74 in the spironolactone group received atorvastatin (20–40 mg/day) for at least 1 year before the initiation of this study. Patients were advised to ingest a diet with approximately 2–3 g sodium per day, and if eGFR was lower than 60 ml/min/1.73 m2, they were counseled
to ingest a protein intake of 0.8 g/kg/day. We did not measure urinary sodium and urea excretion to assess compliance with these dietary restrictions.
The baseline evaluation included measurements of BP, heart rate, urine protein excretion, eGFR, and plasma aldosterone levels. After the baseline evaluation, 83 patients were randomized to receive spironolactone 25 mg/day and 82 continued conventional therapy. Thereafter, patients were seen in the clinic after 1, 3, 6, 9, and 12 months. At each clinic visit, BP and heart rate were measured at least three times after sitting for 30 min and a blood sample was drawn. At each clinic visit, including the baseline evaluation, each subject was asked to bring three spot morning urine samples obtained on 3 consecutive days for the measurement of urine protein/creatinine ratio. The average of these three samples was recorded.
Analytic procedures
BP was measured by mercury sphygmomanometer. Body mass index (BMI) was calculated as weight (kg) divided by height (m) squared. Urinary protein, serum creatinine, and potassium were measured by standard methods. Glomerular filtration rate was estimated using the Modification of Diet in Renal Disease formula.52 Plasma aldosterone was measured by a commercially available kit (Nichols Advantage Aldosterone, Nichols Institute Diagnostics, San Clem-ente, CA, USA).
For statistical analysis, we used the Student’st-test for parametric parameters and the Kolmogorov–Smirnov test for comparison of non-parametric parameters. We used univariate analyses to assess correlations between baseline urinary protein excretion and eGFR, age, gender, systolic and diastolic BP, percent change in urinary protein excretion, and plasma aldosterone levels. Any covariates that were significant in univariate analyses were assessed by step-wise multiple linear regression analyses. Changes in urine protein excretion, office BP, and eGFR were analyzed by repeated-measures analysis of variance.
ACKNOWLEDGMENTS
This study was supported with private funding. No support was received by pharmaceutical companies. Drs Bianchi and Bigazzi have participated in the planning, performance of the study and preparation of this paper. Dr Campese has only participated in the planning of the study, evaluation of data, and preparation of this paper.
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