Updates for Cardio‐Kidney Protective Effects by Angiotensin Receptor‐Neprilysin Inhibitor: Requirement for Additional Evidence of Kidney Protection

The incidence of heart failure and chronic kidney disease is increasing, and many patients develop both diseases. Angiotensin receptor‐neprilysin inhibitor (ARNI) is a promising therapeutic candidate for both diseases. ARNI has demonstrated superior cardioprotective effects compared with renin–angiotensin system inhibitors (RAS‐Is) in large clinical trials such as the PARADIGM‐HF (Prospective Comparison of ARNI With ACEI [Angiotensin‐Converting Enzyme Inhibitor] to Determine Impact on Global Mortality and Morbidity in Heart Failure) trial. It has also been suggested that ARNI can provide renoprotective effects beyond those of RAS‐Is in patients with HF. ARNI might have beneficial effects on the kidneys because of its ability to improve cardiac function in patients with heart failure and affect renal hemodynamics by enhancing the effects of hormones such as natriuretic peptide. In contrast, in the PARADIGM‐HF trial, ARNI was associated with more albuminuria compared with RAS‐I; thus, it is unclear whether long‐term ARNI therapy has renoprotective effects. Additionally, ARNI did not provide renoprotective effects beyond RAS‐I in patients with chronic kidney disease in the UK HARP‐III (United Kingdom Heart and Renal Protection‐III) trial. In other words, the patient population in which ARNI is more renoprotective than RAS‐I might be limited. Collectively, ARNI may have renoprotective effects in addition to cardioprotective effects, but the evidence to date is applicable only to heart failure. Theoretically, given the molecular mechanism of ARNI, it could also be renoprotective in conditions such as nephrosclerosis, which has low risks of albuminuria and reduced kidney perfusion, but the evidence for such effects is lacking. Further research is needed to clarify whether ARNI therapy is an acceptable treatment strategy for renal protection

Blood Pressure Elevation of Tubular Specific (P)RR Transgenic Mice and Lethal Tubular Degeneration due to Possible Intracellular Interactions between (P)RR and Alternative Renin Products

The prorenin/renin receptor ((P)RR) is a multifunctional protein that is widely distributed in various organs. Despite intensive research for more than 20 years, this receptor has not been fully characterized. In this study, we generated mice overexpressing the tubular epithelial (P)RR gene ((P)RR-TG mice) to test the previously reported functional role of (P)RR by Ramkumar et al. in 2015 using tubular specific (P)RR KO mice. (P)RR-TG mice were maintained and analyzed in individual metabolic cages and were administered angiotensin II blocker (ARB), direct renin inhibitor (DRI), and bafilomycin, that is, vacuolar ATPase (V-ATPase) antagonist. (P)RR-TG mice were hypertensive and had alkalized urine with lower osmolality and Na+ excretion. ARB and DRI, but not bafilomycin, concurrently decreased blood pressure. Bafilomycin acidized urine of (P)RR-TG mice, or equivalently this phenomenon restored the effect of overexpressed transgene, suggesting that (P)RR functioned as a V-ATPase in renal tubules. Afterall, (P)RR-TG mice were mated with alternative renin transgenic mice (ARen2-TG), which we identified as intracellular renin previously, to generate double transgenic mice (DT-TG). Lethal renal tubular damage was observed in DT-TG mice, suggesting that intracellular renin may be a ligand for (P)RR in tubules. In summary, (P)RR did not substantially affect the tissue renin-angiotensin system (RAS) in our model of tubular specific (P)RR gene over-expression, but alternative intracellular renin may be involved in (P)RR signaling in addition to conventional V-ATPase function. Further investigations are warranted

An Isoform of Nedd4-2 Plays a Pivotal Role in Electrophysiological Cardiac Abnormalities

We have previously shown that neural precursor cell-expressed developmentally downregulated gene 4-2 (Nedd4-2) isoforms with a C2 domain are closely related to ubiquitination of epithelial sodium channel (ENaC), resulting in salt-sensitive hypertension by Nedd4-2 C2 targeting in mice. The sodium voltage-gated channel alpha subunit 5 (SCN5A) gene encodes the α subunit of the human cardiac voltage-gated sodium channel (I Na), and the potassium voltage-gated channel subfamily H member 2 (KCNH2) gene encodes rapidly activating delayed rectifier K channels (I Kr). Both ion channels have also been shown to bind to Nedd4-2 via a conserved Proline-Tyrosine (PY) motif in C-terminal with subsequent ubiquitination and degradation by proteasome. Therefore, loss of Nedd4-2 C2 isoform might be involved in electrophysiological impairment under various conditions. We demonstrate here that Nedd4-2 C2 isoform causes cardiac conduction change in resting condition as well as proarrhythmic change after acute myocardial infarction (MI). The Nedd4-2 C2 knockout (KO) mice showed bradycardia, prolonged QRS, QT intervals, and suppressed PR interval in resting condition. In addition, enhancement of T peak/T end interval was found in mice with surgical ligation of the distal left coronary artery. Morphological analyses based on both ultrasonography of the living heart, as well as histopathological findings revealed that Nedd4-2 C2 KO mice show no significant structural changes from wild-type littermates under resting conditions. These results suggested that Nedd4-2 with C2 domain might play an important role in cardio-renal syndrome through post-transcriptional modification of both ENaC and cardiac ion channels, which are critical for kidney and heart functions

Eplerenone-Resistant Salt-Sensitive Hypertension in Nedd4-2 C2 KO Mice

The epithelial sodium channel (ENaC) plays critical roles in maintaining fluid and electrolyte homeostasis and is located in the aldosterone-sensitive distal nephron (ASDN). We previously found that Nedd4-2 C2 knockout (KO) mice showed salt-sensitive hypertension with paradoxically enhanced ENaC gene expression in ASDN under high oral salt intake. Eplerenone (EPL), a selective aldosterone blocker, is a promising therapeutic option for resistant or/and salt-sensitive hypertension. We examined the effect of EPL on Nedd4-2 C2 KO mice with respect to blood pressure, metabolic parameters, and molecular level changes in ASDN under high oral salt intake. We found that EPL failed to reduce blood pressure in KO mice with high oral salt intake and upregulated ENaC expression in ASDN. Thus, salt-sensitive hypertension in Nedd4-2 C2 KO was EPL-resistant. Gene expression analyses of laser-captured specimens in ASDN suggested the presence of non-aldosterone-dependent activation of ENaC transcription in ASDN of Nedd4-2 C2 KO mice, which was abolished by amiloride treatment. Our results from Nedd4-2 C2 KO mice suggest that enhanced ENaC gene expression is critically involved in salt-sensitive hypertension under certain conditions of specific enzyme isoforms for their ubiquitination

Comparison of the effects of weekly and biweekly intravenous CERA administration on erythropoiesis: A randomized controlled trial

Abstract Although continuous erythropoietin receptor activators (CERAs) are widely used erythropoiesis‐stimulating agents for correcting renal anemia in patients undergoing hemodialysis (HD), few reports have examined weekly CERA administration. In this randomized controlled trial, we compared the efficacy and changes in the parameters of iron metabolism and erythropoiesis between weekly and biweekly CERA administration. In total, 120 patients undergoing maintenance HD were randomized to the weekly or biweekly group. The primary end point was the total CERA dose needed to maintain the target hemoglobin (Hb) levels during a 12‐week evaluation period. There was no significant difference in the total dose between the weekly and biweekly groups (median 175.0 [interquartile range (IQR) 93.8–337.5] µg/12 weeks vs. 300.0 [IQR 125.0–375.0] µg/12 weeks, P = .18). The mean Hb levels during the evaluation period were 10.9 ± 0.8 g/dL in the weekly group and 10.7 ± 0.8 g/dL in the biweekly group (P = .25). Weekly CERA administration was well tolerated. Weekly CERA administration similarly managed anemia as biweekly administration in patients undergoing HD

Within-visit blood pressure variability and cardiovascular risk factors in hypertensive patients with non-dialysis chronic kidney disease

As there may be an association between within-visit blood pressure (BP) variability and cardiovascular disease (CVD), we investigated the clinical significance of this BP variability in non-dialysis chronic kidney disease (CKD) patients. Materials and methods: According to the median of coefficient of variation (CV) of three systolic BP (SBP) readings within a single visit, we divided hypertensive patients with stage G1-4 CKD already treated with antihypertensive therapy into the high SBP-CV group and the low SBP-CV group. Univariate and multivariate linear regression analyses were also performed to explore the contributing factors to within-visit BP variability. Results: In the high SBP-CV group, the clinic BP, total cholesterol level, dyslipidemia, and past history of CVD were significantly greater, while α1-blockers and renin-angiotensin system (RAS) inhibitors usage were significantly reduced compared with the lower SBP-CV group. Within-visit BP variability was significantly and positively correlated with total cholesterol (R = 0.392, P < 0.001) and low-density lipoprotein cholesterol (R = 0.284, P = 0.013). Total cholesterol (β = 0.269, P = 0.024), α1-blockers usage (β = −0.260, P = 0.015), and RAS inhibitors usage (β = −0.266, P = 0.017) were shown to independently contribute to the within-visit BP variability after adjustment for age, sex, presence of diabetes, CVD history, statins usage, and clinic SBP. Conclusions: We show that within-visit BP variability may be a clinically relevant factor of CVD risk, and lipid lowering and/or anti-hypertensive therapies using RAS inhibitors and α1-blockers may be associated with the improved within-visit BP variability observed in non-dialysis CKD patients

Addition of Aliskiren to Angiotensin Receptor Blocker Improves Ambulatory Blood Pressure Profile and Cardiorenal Function Better than Addition of Benazepril in Chronic Kidney Disease

to chronic kidney disease (CKD) and cardiorenal syndrome. In this study, we examined the effects of aliskiren, when added to angiotensin II type 1 receptor blockers, on ambulatory BP and cardiorenal function in CKD. Thirty-six hypertensive CKD patients were randomly assigned to the aliskiren add-on group (n = 18) or the benazepril add-on group (n = 18). Ambulatory BP and cardiorenal function parameters were measured at baseline and 24 weeks after treatment. Compared with the benazepril group, nighttime systolic BP variability in the aliskiren group was lower after treatment. Albuminuria was decreased in the aliskiren group, but not in the benazepril group. In addition, left ventricular mass index (LVMI) was significantly lower in the aliskiren group than in the benazepril group after treatment. In the aliskiren group, multivariate linear regression analysis showed an association between changes in albuminuria and changes in nighttime systolic BP

L/N-Type Calcium Channel Blocker Cilnidipine Added to Renin-Angiotensin Inhibition Improves Ambulatory Blood Pressure Profile and Suppresses Cardiac Hypertrophy in Hypertension with Chronic Kidney Disease

Abstract: Ambulatory blood pressure (BP) and heart rate (HR) profile are proposed to be related to renal deterioration and cardiovascular complication in hypertension and chronic kidney disease (CKD). In this study, we examined the beneficial effects cilnidipine, a unique L/N-type calcium channel blocker (CCB), in addition to renin-angiotensin system inhibitors, on ambulatory BP and HR profile, as well as cardiorenal function in hypertensive CKD patients. Forty-five patients were randomly assigned to the cilnidipine replacement group (n = 21) or the control CCBs group (n = 24) during a 24-week active treatment period. Although clinical BP values were similar in the cilnidipine and control CCBs groups after the treatment period, the results of ambulatory BP monitoring showed that the 24-h and daytime systolic BP levels in the cilnidipine group were significantly lower compared with the control group after the study. Furthermore, the left ventricularInt. J. Mol. Sci. 2013, 14 1686

Effects of a High-Protein Diet on Kidney Injury under Conditions of Non-CKD or CKD in Mice

Considering the prevalence of obesity and global aging, the consumption of a high-protein diet (HPD) may be advantageous. However, an HPD aggravates kidney dysfunction in patients with chronic kidney disease (CKD). Moreover, the effects of an HPD on kidney function in healthy individuals are controversial. In this study, we employed a remnant kidney mouse model as a CKD model and aimed to evaluate the effects of an HPD on kidney injury under conditions of non-CKD and CKD. Mice were divided into four groups: a sham surgery (sham) + normal diet (ND) group, a sham + HPD group, a 5/6 nephrectomy (Nx) + ND group and a 5/6 Nx + HPD group. Blood pressure, kidney function and kidney tissue injury were compared after 12 weeks of diet loading among the four groups. The 5/6 Nx groups displayed blood pressure elevation, kidney function decline, glomerular injury and tubular injury compared with the sham groups. Furthermore, an HPD exacerbated glomerular injury only in the 5/6 Nx group; however, an HPD did not cause kidney injury in the sham group. Clinical application of these results suggests that patients with CKD should follow a protein-restricted diet to prevent the exacerbation of kidney injury, while healthy individuals can maintain an HPD without worrying about the adverse effects