Renin-angiotensin system inhibition in advanced chronic kidney disease: how low can the kidney function go?

Potential of soluble (pro)renin receptor in kidney disease: can it go beyond a biomarker?

(Pro)renin receptor (PRR), also termed ATPase H+-transporting accessory protein 2 (ATP6AP2), is a type I transmembrane receptor and is capable of binding and activating prorenin and renin. Apart from its association with the renin-angiotensin system, PRR has been implicated in diverse developmental, physiological, and pathophysiological processes. Within the kidney, PRR is predominantly expressed in the distal nephron, particularly the intercalated cells, and activation of renal PRR contributes to renal injury in various rodent models of chronic kidney disease. Moreover, recent evidence demonstrates that PRR is primarily cleaved by site-1 protease to produce 28-kDa soluble PRR (sPRR). sPRR seems to mediate most of the known pathophysiological functions of renal PRR through modulating the activity of the intrarenal renin-angiotensin system and provoking proinflammatory and profibrotic responses. Not only does sPRR activate renin, but it also directly binds and activates the angiotensin II type 1 receptor. This review summarizes recent advances in understanding the roles and mechanisms of sPRR in the context of renal pathophysiology.

Renin-angiotensin system blocker discontinuation and adverse outcomes in chronic kidney disease

BACKGROUND

Treatment with renin-angiotensin system inhibitors (RASIs), angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin II receptor blockers (ARBs) is the standard of care for those with chronic kidney disease (CKD) and albuminuria. However, ACEI/ARB treatment is often discontinued for various reasons. We investigated the association of ACEI/ARB discontinuation with outcomes among US veterans with non-dialysis-dependent CKD.

METHODS

We performed a retrospective cohort study of patients in the Veterans Affairs healthcare system with non-dialysis-dependent CKD who subsequently were started on ACEI/ARB therapy (new user design). Discontinuation events were defined as a gap in ACEI/ARB therapy of ≥14 days and were classified further based on duration (14-30, 31-60, 61-90, 91-180 and >180 days). This was treated as a time-varying risk factor in adjusted Cox proportional hazards models for the outcomes of death and incident end-stage kidney disease (ESKD), which also adjusted for relevant confounders.

RESULTS

We identified 141 252 people with CKD and incident ACEI/ARB use who met the inclusion criteria; these were followed for a mean 4.87 years. There were 135 356 discontinuation events, 68 699 deaths and 6152 incident ESKD events. Discontinuation of ACEI/ARB was associated with a higher risk of death [hazard ratio (HR) 2.3, 2.0, 1.99, 1.92 and 1.74 for those discontinued for 14-30, 31-60, 61-90, 91-180 and >180 days, respectively]. Similar associations were noted between ACEI and ARB discontinuation and ESKD (HR 1.64, 1.47, 1.54, 1.65 and 1.59 for those discontinued for 14-30, 31-60, 61-90, 91-180 and >180 days, respectively).

CONCLUSIONS

In a cohort of predominantly male veterans with CKD Stages 3 and 4, ACEI/ARB discontinuation was independently associated with an increased risk of subsequent death and ESKD. This may be due to the severity of illness factors that drive the decision to discontinue therapy. Further investigations to determine the causes of discontinuations and to provide an evidence base for discontinuation decisions are needed.

Effects of angiotensin-converting enzyme inhibitors or angiotensin receptor blockers on all-cause mortality, cardiovascular death, and cardiovascular events among peritoneal dialysis patients: A protocol for systematic review

BACKGROUND

Based on the International Society for peritoneal dialysis (PD) recommendations, blockade of renin-angiotensin systems with an angiotensin-converting enzyme inhibitors (ACEI) and angiotensin receptor blockers (ARB) improves residual kidney function in PD patients. However, the long-term effectiveness of ACEI/ARB use in PD patients has not been fully elucidated. We, therefore, intend to perform a systematic review and meta-analysis to summarize the effects of ACEI/ARB use on long-term mortality, cardiovascular outcomes, and adverse events among PD patients.

METHODS

This systematic review will include both randomized controlled trials and non-randomized studies in adult PD patients. We also plan to incorporate data from our cohort study in Thai PD population into this review. We will search PubMed, Medline, EMBASE, Cochrane Library, Web of Science, Scopus, CINAHL, and grey literature from inception to February 29, 2019, with no language restrictions. The process of study screening, selection, data extraction, risk of bias assessment, and grading the strength of evidence will be performed independently by a pair of reviewers. Any discrepancy will be resolved through a team discussion and/or consultation with the third reviewer. The pooled effects estimate and 95% confidence intervals will be estimated using DerSimonian-Laird random-effects models. Heterogeneity will be assessed by the Cochran Q test, I index and tau-squared statistics. The funnel plots along with the Begg and Egger test and trim and fill method will be performed to investigate any evidence of publication bias. Preplanned subgroup analyses and random-effects univariate meta-regressions will be performed to quantify the potential sources of heterogeneity based on studies- and patient-characteristics.

RESULTS

This will be the first systematic review and meta-analysis to summarize the long-term effectiveness of renin-angiotensin system inhibitors in PD populations.

CONCLUSION

In summary, this systematic review and meta-analysis will summarize the effectiveness of ACEI/ARB on long-term mortality, cardiovascular outcomes, and adverse events among adult PD patients by integrated all available evidences.

ETHICS AND DISSEMINATION

Based on the existing published data, an ethical approval is not required. The findings will be disseminated through scientific meetings and publications in peer-reviewed journals.PROSPERO registration number: CRD42019129492.