Antiproteinuric effect of ACE inhibitors

Effect of Mineralocorticoid Receptor Antagonism and ACE Inhibition on Angiotensin Profiles in Diabetic Kidney Disease: An Exploratory Study

BACKGROUND

Renin-angiotensin-aldosterone system (RAAS) blockade with angiotensin-converting enzyme inhibitors (ACEi) or angiotensin receptor blockers (ARB) is the cornerstone of antihypertensive treatment in patients with chronic kidney disease (CKD) and diabetes mellitus. Mineralocorticoid receptor antagonists (MRA) on top of conventional RAAS blockade confer cardio- and renoprotective effects. Yet, the detailed effects of this therapeutic approach on key RAAS effectors have not been elucidated to date.

METHODS

In this exploratory placebo-controlled study, 15 patients with CKD stages 2-3 and albuminuria due to diabetic kidney disease (DKD) were randomized to receive the MRA eplerenone or placebo in addition to ACEi therapy. Employing mass-spectrometry, we quantified plasma angiotensin levels [Ang I, Ang II, Ang-(1-7), Ang-(1-5), Ang III, Ang IV], renin and aldosterone in patients before and after 8 weeks of MRA treatment.

RESULTS

While blood pressure and kidney function were similar in the placebo and eplerenone treatment group during the study period, distinct differences in RAAS regulation occurred: eplerenone treatment resulted in an increase in plasma renin activity, Ang I and aldosterone concentrations, indicating global RAAS activation. In addition, eplerenone on top of ACEi profoundly upregulated the alternative RAAS effector Ang-(1-7).

CONCLUSIONS

Combined eplerenone and ACEi therapy increases Ang-(1-7) levels in patients with CKD indicating a unique nephroprotective RAAS pattern with considerable therapeutic implications.

Effects of direct renin inhibition versus angiotensin II receptor blockade on angiotensin profiles in non-diabetic chronic kidney disease

BACKGROUND

Direct renin inhibition (DRI) is clinically inferior to other blockers of the renin-angiotensin system (RAS). Thus far, the underlying molecular causes of this finding remain unknown.

METHODS

Twenty four patients with non-diabetic chronic kidney disease (CKD) stages III-IV and albuminuria were randomized to DRI or angiotensin receptor blocker (ARB). Employing a novel mass-spectrometry method, the concentrations of renin, aldosterone and plasma angiotensin peptides [Ang I, Ang II, Ang-(1-7), Ang-(1-5), Ang-(2-8), Ang-(3-8)] were quantified before and after an 8-week treatment.

RESULTS

While blood pressure, renal function and albuminuria decreased comparably in both groups, profound RAS component differences were observed: DRI led to a massive renin increase, while suppressing both vasoconstrictive (Ang I and Ang II) and vasodilatory RAS metabolites (Ang-(1-7) and Ang-(1-5)). In contrast, ARB led to a four-fold increase of Ang I and Ang II, while Ang-(1-7) and Ang-(1-5) increased moderately but significantly. With ARB treatment, a decreased aldosterone-to-Ang II ratio suggested efficacy in blocking AT1 receptor.

CONCLUSIONS

DRI therapy abolishes all RAS effector peptides. ARB increases both vasoconstrictive and vasodilative angiotensins, while this is accompanied by efficient blockade of vasoconstrictive effects. These differential molecular regulations should be considered when selecting optimal antihypertensive and disease-modifying therapy in CKD patients. Key messages Direct renin inhibition leads to a complete and lasting abolition of both classical and alternative RAS components. Angiotensin receptor blockade leads to effective receptor blockade and up-regulation of alternative RAS components. Differential molecular regulations of the RAS should be considered when selecting optimal antihypertensive and disease-modifying therapy in CKD patients.

Reduction of albuminuria after angiotensin converting enzyme inhibition in various renal disorders

The urinary albumin excretion measured by the albumin creatinine clearance ratio (Calb/Ccreat) and the mean supine arterial blood pressure (MAP) were studied before the start of ACE inhibition, at the start and during up to 1 year of ACE inhibition with Captopril or Enalapril in 35 patients with various chronic proteinuric renal disorders with or without renal failure, arterial hypertension and nephrotic syndrome. Before the start of ACE inhibition mean Calb/Ccreat, MAP, s-albumin and s-creatinine did not change. During ACE inhibition the Calb/Ccreat was reduced from 75% (p less than 0.05) in patients with minimal albuminuria to 41% (p less than 0.005) in patients with extensive albuminuria. Average reduction of albuminuria was 44% at one year's observation time. Serum albumin increased 9% (p less than 0.05), serum creatinine did not change significantly and MAP showed a slight, not uniformly significant decrease. The reduction of Calb/Ccreat was of the same order in the different renal disorders studied and was independent of the renal function, presence or absence of nephrotic syndrome and treatment with antihypertensive or immunosuppressive drugs. The decrease in Calb/Ccreat during ACE inhibition was related to the reduction in MAP at most time intervals, but Calb/Ccreat decreased also when MAP was unchanged or increased. Thus the decrease in Calb/Ccreat during ACE inhibition does not only seem to be a consequence of a decrease in the systemic arterial blood pressure but reasonably also due to changes in the intra-renal hemodynamics and most probably a decrease in the glomerular capillary pressure.