Captopril acutely lowers albuminuria in normotensive patients with diabetic nephropathy

Diabetic Proteinuria Revisited: Updated Physiologic Perspectives

Albuminuria, a hallmark of diabetic nephropathy, reflects not only injury and dysfunction of the filtration apparatus, but is also affected by altered glomerular hemodynamics and hyperfiltration, as well as by the inability of renal tubular cells to fully retrieve filtered albumin. Albuminuria further plays a role in the progression of diabetic nephropathy, and the suppression of glomerular albumin leak is a key factor in its prevention. Although microalbuminuria is a classic manifestation of diabetic nephropathy, often progressing to macroalbuminuria or overt proteinuria over time, it does not always precede renal function loss in diabetes. The various components leading to diabetic albuminuria and their associations are herein reviewed, and the physiologic rationale and efficacy of therapeutic interventions that reduce glomerular hyperfiltration and proteinuria are discussed. With these perspectives, we propose that these measures should be initiated early, before microalbuminuria develops, as substantial renal injury may already be present in the absence of proteinuria. We further advocate that the inhibition of the renin-angiotensin axis or of sodium-glucose co-transport likely permits the administration of a normal recommended or even high-protein diet, highly desirable for sarcopenic diabetic patients.

Urinary Albumin Excretion Reflects Cardiovascular Risk in Postmenopausal Women without Diabetes: The 2011 to 2013 Korean National Health and Nutrition Examination Survey

BACKGROUND

The objective of the current study was to determine whether there was an association between urinary albumin excretion and cardiovascular disease (CVD) risk by estimating the Framingham Risk Score (FRS) in postmenopausal women without diabetes.

METHODS

This study was based on data from the Korea National Health and Nutrition Examination Survey, which was conducted by the Korean Ministry of Health and Welfare in 2011 to 2013. Data on 2,316 postmenopausal women from a total of 24,594 participants was included in the analysis.

RESULTS

The mean FRS was significantly different in each of the urinary albumin to creatinine ratio (UACR) subgroups, and it increased with UACR. The FRS was 12.69±0.12 in the optimal group, 14.30±0.19 in the intermediate normal group, 14.62±0.26 in the high normal group, and 15.86±0.36 in the microalbuminuria group. After fully adjusting for potential confounding factors, high normal levels and microalbuminuria were significantly associated with the highest tertile of FRS ([odds ratio (OR), 1.642; 95% confidence interval (CI), 1.124 to 2.400] and [OR, 3.385; 95% CI, 2.088 to 5.488], respectively) compared with the optimal subgroup. High normal levels and microalbuminuria were also significantly associated with a ≥10% 10-year risk of CVD ([OR, 1.853; 95% CI, 1.122 to 3.060] and [OR, 2.831; 95% CI, 1.327 to 6.037], respectively) after adjusting for potential confounding covariates.

CONCLUSION

Urinary albumin excretion reflects CVD risk in postmenopausal women without diabetes, and high normal levels and microalbuminuria were independently associated with a higher risk of CVD.

Reduced tubular proteinuria in hypertensive rats treated with losartan is associated with higher renal cortical megalin expression

BACKGROUND

Several clinical studies have demonstrated that angiotensin II antagonists exert renoprotective effects beyond blood pressure control in hypertensive patients. The present work aimed to test the hypothesis that the antiproteinuric effects of losartan are associated with upregulation of the multi-ligand endocytic receptors megalin and cubilin in the proximal tubule of spontaneously hypertensive rats (SHR).

MATERIALS AND METHODS

Fourteen-week-old SHRs were orally treated for 7 weeks with losartan (50 mg/kg, SHR-L), hydralazine (30 mg/kg, SHR-H), or vehicle (SHR-V). Blood pressure and renal function were determined prior to and following drug treatment. Expression of renal cortical proteins was determined by immunoblotting.

RESULTS

Losartan and hydralazine reduced systolic blood pressure from pretreatment levels in SHRs to a similar extent. However, SHR-L displayed a much greater reduction in proteinuria than SHR-H (44±3% vs. 15±1%, p<0.01) relative to pretreatment urinary protein excretion levels. In SHRs treated with vehicle, proteinuria increased from 87±5 to 153±15 mg/(day kg BW). Reduced tubular proteinuria in SHRs treated with losartan was accompanied by a higher expression of megalin (125±28%) relative to either SHR-V or SHR-H. Neither losartan nor hydralazine significantly altered the renal cortical expression of cubilin in SHRs.

CONCLUSION

Collectively, our data demonstrate that the additional renoprotective effects of angiotensin II blockade by losartan are associated with upregulation of megalin in the renal proximal tubule of SHRs. Moreover, it strengthens the view that tubular dysfunction may represent an important contributing mechanism underlying proteinuria in hypertension.

Association between an increment of 30-minute postchallenge plasma glucose and urine albumin excretion exists in postmenopausal women but not in premenopausal women

OBJECTIVE

Usually, the increment of 30-minute postchallenge plasma glucose (ΔG30-0) represents the highest glucose spike in the population with normal glucose regulation (NGR). The aim of this study was to explore the differences in ΔG30-0 and urinary albumin excretion, a marker for widespread vascular damage, between premenopausal and postmenopausal women, and the relationship between ΔG30-0 and urinary albumin excretion.

METHODS

A population-based cross-sectional study, consisting of 5,289 participants aged 20 to 75 years from six different communities, was conducted in Shanghai between 2007 and 2008. We assessed postchallenge blood glucose and insulin at 0-, 30-, and 120-minute urinary albumin and creatinine. ΔG30-0 was calculated as 30-minute postchallenge glucose minus fasting plasma glucose, and the albumin-to-creatinine ratio (ACR) was used to reflect urinary albumin excretion. Among these, the data of 2,240 women with NGR were analyzed.

RESULTS

(1) Postmenopausal women had higher ΔG30-0 and ACR than did premenopausal women (3.55 ± 1.52 mmol/L vs 3.21 ± 1.49 mmol/L and 6.92 [4.91-10.99] mg/g vs 6.18 [4.17-10.07] mg/g, respectively; all P < 0.001). (2) Multivariable logistic regression showed that ΔG30-0 was independently associated with increased ACR in postmenopausal women with NGR (odds ratio, 1.10; P = 0.048) but not in premenopausal women. (3) The main factor associated with ΔG30-0 was the early-phase glucose disposition index drawn from the multivariable linear regression, which explained approximately 19% and 28% of the variation of ΔG30-0 in premenopausal and postmenopausal women, respectively (both P < 0.001).

CONCLUSIONS

In the NGR population, postmenopausal women have higher ΔG30-0 and ACR compared with premenopausal women. The relationship between ΔG30-0 and increased urine albumin excretion existed in postmenopausal women.

Post-menopausal hormone use and albuminuria

BACKGROUND

Higher levels of urinary albumin excretion predict future hypertension and chronic kidney disease. Post-menopausal hormone use may influence the renin-angiotensin system and renal endothelial function, impacting albumin excretion. The association between post-menopausal hormone use and albuminuria is not well defined.

METHODS

We explored the cross-sectional association between duration of PMH use and albuminuria in 2445 post-menopausal, non-diabetic women from the Nurses' Health Study. Women were categorized as hormone non-users, past users or current users grouped by 3-year intervals of duration of use, from < or =3 years to >15 years. The outcome was the top decile of urine albumin/creatinine ratio (ACR). Multivariate logistic regression was used to assess the association between duration of PMH use and risk of being in the top decile.

RESULTS

The mean age was 66.8 years, and 57% were currently using PMH. The median ACR was 2.9 mg/g, and the 90th percentile was 9.2 mg/g. Compared with women with no history of PMH use, the odds ratio for being in the top ACR decile was lower for women with use of >6-9 years, >9-12 years, >12-15 years and >15 years, but there was no dose-response. The overall odds ratio was 0.55 (95% CI: 0.39-0.77) among women with >6 years of current PMH use compared with non-users. Current hormone use of shorter duration and past hormone use were not associated with albumin excretion.

CONCLUSIONS

Current PMH use of >6 years is associated with a lower urinary ACR in non-diabetic women.

WITHDRAWN: Angiotensin converting enzyme inhibitors in normotensive diabetic patients with microalbuminuria

BACKGROUND

Renal disease is a serious complication of diabetes mellitus.

OBJECTIVES

To examine whether the progression of early diabetic renal disease to end-stage renal failure may be slowed by the use of angiotensin converting enzyme inhibitors for reasons other than their antihypertensive properties, so that they have value in the treatment of normotensive diabetics with microalbuminuria.

SEARCH STRATEGY

Medline was searched for English language reviews and randomised controlled trials. Personal reference lists, and reference lists of retrieved studies were also used.

SELECTION CRITERIA

Randomised controlled trials with separate identifiable results for initially normotensive diabetic patients, who received angiotensin converting enzyme inhibitors for at least one year and were compared with controls.

DATA COLLECTION AND ANALYSIS

Meta-analyses were performed on the results of 12 randomised controlled trials with a variety of patient inclusion and exclusion criteria. One further study met all conditions for inclusion but did not provide data in useable form for meta-analyses.

MAIN RESULTS

Albumin excretion rate fell for patients on angiotensin converting enzyme inhibition in 12 of the 13 studies but did so for only two of the 13 groups on placebo. Treatment provided a significant reduction in albumin excretion rate in both insulin dependent diabetes mellitus and non insulin dependent diabetes mellitus. Treatment with either captopril, enalapril or lisinopril reduced albumin excretion rate in comparison with control patients.A significantly greater lowering of blood pressure was experienced by initially normotensive patients in the angiotensin converting enzyme inhibitor than in the placebo group. Average glycosylated haemoglobin fell a little in the treated patients and rose in the controls, the difference being just significant. The difference in changes in glomerular filtration rate did not reach statistical significance.

AUTHORS' CONCLUSIONS

Inhibition of angiotensin converting enzyme can arrest or reduce the albumin excretion rate in microalbuminuric normotensive diabetics, as well as reduce or prevent an increase in blood pressure. But, given the drop in blood pressure in patients on angiotensin converting enzyme inhibitors, it is not certain that the reduction of albumin excretion rate is due to a separate renal effect. A direct link with postponement of end-stage renal failure has not been demonstrated. There appear to be no substantial side effects.

ACE inhibitor intervention in Type 1 diabetes with low grade microalbuminuria

Several clinical trials have consistently shown that antihypertensive treatment, particularly with angiotensin-converting enzyme inhibitors (ACE-I) reduces albuminuria in Type 1 diabetic patients. More recently, data on the beneficial effects of ACE-I on the preservation of glomerular filtration rate and renal ultrastructure have emerged. However, in general, these trials have recruited a wide spectrum of diabetics, including some patients with severe albuminuria. Thus, the question of the ideal stage at which to instigate what is likely to be lifelong therapy in young people still remains unanswered. Exercise is known to significantly increase both blood pressure (BP) and urinary albumin excretion (UAE), both of which are important determinants of progression of nephropathy in diabetes. Thus, it is possible that exercise may have an adverse effect on diabetic renal disease. The effects of ACE-I on exercise-BP and exercise-UAE in microalbuminuric Type 1 diabetic patients has not been examined in long-term placebo-controlled studies. In the second part of this two-part review, we examine the effects of the ACE-I, lisinopril, 20 mg o.d. for two years, in comparison with placebo, on UAE, 24-hour ambulatory BP, exercise-BP, exercise-UAE and renal haemodynamics in 22 patients with Type 1 diabetes and low-grade microalbuminuria. We further discuss the effects of ACE-I on nephropathy and other complications of diabetes.

Angiotensin converting enzyme inhibitors in normotensive diabetic patients with microalbuminuria

OBJECTIVES

To examine whether the progression of early diabetic renal disease to end-stage renal failure may be slowed by the use of angiotensin converting enzyme inhibitors for reasons other than their antihypertensive properties, so that they have value in the treatment of normotensive diabetics with microalbuminuria.

SEARCH STRATEGY

Medline was searched for English language reviews and randomised controlled trials. Personal reference lists, and reference lists of retrieved studies were also used.

SELECTION CRITERIA

Randomised controlled trials with separate identifiable results for initially normotensive diabetic patients, who received angiotensin converting enzyme inhibitors for at least one year and were compared with controls.

DATA COLLECTION AND ANALYSIS

Meta-analyses were performed on the results of 12 randomised controlled trials with a variety of patient inclusion and exclusion criteria. One further study met all conditions for inclusion but did not provide data in useable form for meta-analyses.

MAIN RESULTS

Albumin excretion rate fell for patients on angiotensin converting enzyme inhibition in 12 of the 13 studies but did so for only two of the 13 groups on placebo. Treatment provided a significant reduction in albumin excretion rate in both insulin dependent diabetes mellitus and non insulin dependent diabetes mellitus. Treatment with either captopril, enalapril or lisinopril reduced albumin excretion rate in comparison with control patients. A significantly greater lowering of blood pressure was experienced by initially normotensive patients in the angiotensin converting enzyme inhibitor than in the placebo group. Average glycosylated haemoglobin fell a little in the treated patients and rose in the controls, the difference being just significant. The difference in changes in glomerular filtration rate did not reach statistical significance.

REVIEWER'S CONCLUSIONS

Inhibition of angiotensin converting enzyme can arrest or reduce the albumin excretion rate in microalbuminuric normotensive diabetics, as well as reduce or prevent an increase in blood pressure. But, given the drop in blood pressure in patients on angiotensin converting enzyme inhibitors, it is not certain that the reduction of albumin excretion rate is due to a separate renal effect. A direct link with postponement of end-stage renal failure has not been demonstrated. There appear to be no substantial side effects.

Influence of angiotensin converting enzyme inhibition and angiotensin II type 1 receptor antagonism on renal sodium and water handling and albuminuria during infusion of atrial natriuretic factor into healthy volunteers

BACKGROUND

Atrial natriuretic factor increases urinary sodium and water excretion. It also causes an increase in albuminuria. Angiotensin converting enzyme inhibition attenuates the effects of atrial natriuretic factor on renal sodium and water handling; however, it is not known whether this effect is mediated by the accompanied decrease in blood pressure or by suppression of the renin-angiotensin system.

OBJECTIVE

To test the hypothesis that atrial natriuretic factor mediates natriuresis and diuresis by inhibiting angiotensin II, by studying the effects of the angiotensin converting enzyme inhibitor enalapril and the angiotensin II type 1 receptor antagonist losartan. In addition, the effects of these drugs on atrial natriuretic factor-induced albuminuria were examined.

DESIGN AND METHODS

We investigated the effects of enalapril and losartan on atrial natriuretic factor-induced changes in urinary excretion of sodium, water and albumin from eight healthy volunteers. Measurements of systemic and renal haemodynamics in these subjects were performed before and during a 2 h infusion of atrial natriuretic factor [0.01 microg/kg per min (low dose) for the first 60 min and 0.02 microg/kg per min (high dose) for the second 60 min]. Measurements were performed after 5 days of pretreatment with placebo, 50 mg losartan or 20 mg enalapril daily.

RESULTS

Mean arterial pressures during the clearance study were 84.6 +/- 1.7 mmHg after placebo, 84.0 +/- 2.2 mmHg after losartan treatment and 80.0 +/- 2.5 mmHg after enalapril treatment (P < 0.05). Plasma renin activity was significantly increased both by losartan and by enalapril treatments. Neither enalapril nor losartan treatment attenuated atrial natriuretic factor-induced changes in renal haemodynamics. After placebo pretreatment, fractional urinary excretion of sodium increased significantly during infusion of atrial natriuretic factor. Losartan treatment did not influence the increase in urinary excretion of sodium during infusion of atrial natriuretic factor, whereas enalapril treatment significantly attenuated this increase (P < 0.01). Atrial natriuretic factor significantly increased albuminuria. Neither losartan nor enalapril treatment reduced atrial natriuretic factor-induced albuminuria.

CONCLUSIONS

Enalapril treatment lowered blood pressure and attenuated the atrial natriuretic factor-induced increase in urinary excretion of sodium. In contrast, the angiotensin II type 1 receptor antagonist losartan, at a dosage that did not lower blood pressure, did not attenuate the increase in urinary excretion of sodium. These data indicate that atrial natriuretic factor increases natriuresis and diuresis independently of angiotensin II. The increase in albuminuria during infusion of atrial natriuretic factor was not influenced by enalapril and losartan treatments.

Blood pressure reduction initiates the antiproteinuric effect of ACE inhibition

Several observations question the role of blood pressure and renal hemodynamic changes in the long-term antiproteinuric effect of ACE inhibition. To differentiate blood pressure and renal effects in the initial antiproteinuric response, the placebo-controlled acute effects of the ACE inhibitor enalaprilat (10 mg i.v.) on blood pressure, renal hemodynamics, and proteinuria were compared with those of nitroprusside in nine patient with non-diabetic proteinuria. In addition, we studied whether an exogenous angiotensin II infusion reverse the initial enalaprilat-induced antiproteinuric response. Enalaprilat and nitroprusside reduced MAP by -11.3 +/- 2.4% and -14.1 +/- 2.3%, respectively, whereas only enalaprilat showed renal hemodynamic effects, reflected by an increase in ERPF of 18.4 +/- 5.4% and a decrease in FF of -17.1 +/- 2.6%. Despite the contrasting renal hemodynamic profiles, enalaprilat (-10.6 +/- 4.8%) and nitroprusside (-12.8 +/- 5.1% equally decreased proteinuria. Exogenous infusion of angiotensin II completely reversed the blood pressure reduction and renal efferent vasodilatation induced by enalaprilat. proteinuria also increased by 13.1 +/- 7.8% to placebo level, albeit statistically non-significant. We conclude that the initial antiproteinuric effect of ACE inhibition appears to be mediated by blood pressure reduction and does not require its specific renal hemodynamic effect. Further studies should clarify whether the renal efferent vasodilatation during ACE inhibition is required to gradually induce renal structural changes that prevent the abundant passage of proteins.

Captopril and atenolol are equally effective in retarding progression of diabetic nephropathy. Results of a 2-year prospective, randomized study

The progression of diabetic nephropathy can be positively influenced by maintaining a low blood pressure level. This has been shown in studies with conventional antihypertensive treatment as well as with ACE inhibitors. Whether the latter group of drugs is more effective remains to be proven and was the aim of our study. In a prospective randomized study we compared the effects of ACE inhibition and beta-blockade on retarding progression of renal function in IDDM patients with an early stage of overt diabetic nephropathy. Twenty-nine patients were studied for 2 years, 15 were randomized for treatment with captopril and 14 for atenolol. Every 6 weeks blood pressure and urinary albumin and total protein excretion were measured. GFR was measured every 6 months as 51Cr-EDTA clearance. Baseline values for blood pressure, renal function and albuminuria were identical in the two groups. The effect of both drugs on blood pressure was not significantly different. In the captopril-treated patients MAP before and after 2 years was 110 +/- 3 (SEM) and 100 +/- 2 mm Hg, respectively and in the atenolol-treated patients 105 +/- 2 vs 101 +/- 2 mm Hg. Both drugs reduced albuminuria and total proteinuria to the same extent. With captopril albuminuria decreased from 1549 (989-2399) to 851 (537-1380) mg/24 h and proteinuria from 2.5 (1.6-3.8) to 1.2 (0.8-1.8) g/24 h. With atenolol albuminuria decreased from 933 (603-1445) to 676 (437-1047) mg/24 h and proteinuria from 1.5 (1.0-2.4) to 0.9 (0.6-1.5) g/24 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Dissociation between the course of the hemodynamic and antiproteinuric effects of angiotensin I converting enzyme inhibition

Angiotensin I converting enzyme inhibition (ACEi) has been shown to lower urinary protein excretion in human renal disease. The mechanism of this antiproteinuric effect is hypothesized to be mediated by changes in renal hemodynamics. However, clinical studies suggest that the effect on renal hemodynamics is fully established immediately after the start of treatment, whereas others show the antiproteinuric effect to reach maximum only after several weeks. To clarify this issue we studied the course of renal hemodynamics, blood pressure and proteinuria during 28 days of ACEi (enalapril 10 mg oid) in nine patients with proteinuria due to non-diabetic renal disease. The effect of ACEi on blood pressure and renal hemodynamics was already maximal within few hours after start of treatment, and remained stable thereafter: MAP was lowered with 8.6 +/- 1.9%, 10.6 +/- 2.1%, 12.8 +/- 2.3% and 12.9 +/- 2.5%, while FF fell 23.0 +/- 2.0%, 17.0 +/- 2.6%, 16.8 +/- 2.8% and 15.9 +/- 4.0% on days 1, 7, 14 and 28 of ACEi, respectively. However, the antiproteinuric effect only gradually reached its maximum on day 28. Urinary protein excretion decreased with 10.9 +/- 6.1%, 32.7 +/- 6.2%, 46.3 +/- 2.5% and 54.0 +/- 2.5% on days 1, 7, 14 and 28 of ACEi, respectively. After drug withdrawal all parameters returned towards baseline. We conclude that a dissociation occurs in the course of the ACEi induced effects on hemodynamics and urinary protein excretion.(ABSTRACT TRUNCATED AT 250 WORDS)