Aliskiren effect on plaque progression in established atherosclerosis using high resolution 3D MRI (ALPINE): a double-blind placebo-controlled trial

Dipeptidyl Peptidase 4/Midline-1 Axis Promotes T Lymphocyte Motility in Atherosclerosis

T cells play a crucial role in atherosclerosis, with its infiltration preceding the formation of atheroma. However, how T-cell infiltration is regulated in atherosclerosis remains largely unknown. Here, this work demonstrates that dipeptidyl peptidase-4 (DPP4) is a novel regulator of T-cell motility in atherosclerosis. Single-cell ribonucleic acid (RNA) sequencing and flow cytometry show that CD4+ T cells in atherosclerotic patients display a marked increase of DPP4. Lack of DPP4 in hematopoietic cells or T cells reduces T-cell infiltration and atherosclerotic plaque volume in atherosclerosis mouse models. Mechanistically, DPP4 deficiency reduces T-cell motility by suppressing the expression of microtubule associated protein midline-1 (Mid1) in T cells. Deletion of either DPP4 or Mid1 inhibits chemokine-induced shape change and motility, while restitution of Mid1 in Dpp4-/- T cell largely restores its migratory ability. Thus, DPP4/Mid1, as a novel regulator of T-cell motility, may be a potential inflammatory target in atherosclerosis.

Renin-Angiotensin System in Pathogenesis of Atherosclerosis and Treatment of CVD

Atherosclerosis has complex pathogenesis, which involves at least three serious aspects: inflammation, lipid metabolism alterations, and endothelial injury. There are no effective treatment options, as well as preventive measures for atherosclerosis. However, this disease has various severe complications, the most severe of which is cardiovascular disease (CVD). It is important to note, that CVD is among the leading causes of death worldwide. The renin–angiotensin–aldosterone system (RAAS) is an important part of inflammatory response regulation. This system contributes to the recruitment of inflammatory cells to the injured site and stimulates the production of various cytokines, such as IL-6, TNF-a, and COX-2. There is also an association between RAAS and oxidative stress, which is also an important player in atherogenesis. Angiotensin-II induces plaque formation at early stages, and this is one of the most crucial impacts on atherogenesis from the RAAS. Importantly, while stimulating the production of ROS, Angiotensin-II at the same time decreases the generation of NO. The endothelium is known as a major contributor to vascular function. Oxidative stress is the main trigger of endothelial dysfunction, and, once again, links RAAS to the pathogenesis of atherosclerosis. All these implications of RAAS in atherogenesis lead to an explicable conclusion that elements of RAAS can be promising targets for atherosclerosis treatment. In this review, we also summarize the data on treatment approaches involving cytokine targeting in CVD, which can contribute to a better understanding of atherogenesis and even its prevention.

Oxidized LDL upregulates macrophage DPP4 expression via TLR4/TRIF/CD36 pathways

Background

We and others have shown that dipeptidyl peptidase-IV (DPP4) expression is increased in obesity/atherosclerosis and is positively correlated with atherosclerotic burden. However, the mechanism by which DPP4 expression is regulated in obesity remains unclear. In this study, we investigated the pathways regulating the expression of DPP4 on macrophages.

Methods

Flowsight® Imaging Flow Cytometry was employed for the detection of DPP4 and immunophenotyping. DPP4 enzymatic activity was measured by a DPPIV-Glo™ Protease Assay kit.

Findings

Human monocytes expressed a moderate level of membrane-bound DPP4. Obese patients with body mass index (BMI) ≥ 30 had a higher level of monocyte DPP4 expression, in parallel with higher levels of HOMA-IR, blood glucose, triglycerides, and non-HDL cholesterol, compared to those in the non-obese (BMI < 30) patients. Oxidized low-density lipoprotein (oxLDL), but not native LDL, up-regulated DPP4 expression on macrophages with a preferential increase in CD36⁺ cells. OxLDL mediated DPP4 up-regulation was considerably diminished by Toll-like receptor-4 (TLR4) knockdown and CD36 deficiency. TRIF deficiency, but not MyD88 deficiency, attenuated oxLDL-induced DPP4 increase.

Interpretation

Our study suggests a key role for oxLDL and downstream CD36/TLR4/TRIF in regulating DPP4 expression. Increased DPP4 in response to oxidized lipids may represent an integrated mechanism linking post-prandial glucose metabolism to lipoprotein abnormality-potentiated atherosclerosis.

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.

Design of the Magnetic Resonance Imaging Evaluation of Mineralocorticoid Receptor Antagonism in Diabetic Atherosclerosis (MAGMA) Trial

Mineralocorticoid receptor (MR) activation plays an essential role in promoting inflammation, fibrosis, and target organ damage. Currently, no studies are investigating MR antagonism in patients with type 2 diabetes mellitus (T2DM) with chronic kidney disease, at high risk for cardiovascular complications, who are otherwise not candidates for MR antagonism by virtue of heart failure. Further, there is limited information on candidate therapies that may demonstrate differential benefit from this therapy. We hypothesized that MR antagonism may provide additional protection from atherosclerosis progression in higher-risk patients who otherwise may not be candidates for such a therapeutic approach. In this double-blind, randomized, placebo-controlled trial, subjects with T2DM with chronic kidney disease (≥ stage 3) will be randomized in a 1:1 manner to placebo or spironolactone (12.5 mg with eventual escalation to 25 mg daily over a 4-week period). The co-primary efficacy endpoint will be percentage change in total atheroma volume in thoracic aorta and left ventricular mass at 52 weeks in patients treated with spironolactone vs placebo. Secondary outcomes include 24-hour mean systolic blood pressure, central aortic blood pressure, and insulin resistance (HOMA-IR) at 6 weeks. A novel measure in the study will be changes in candidate miRNAs that regulate expression of NR3C2 (MR gene) as well as measuring monocyte/macrophage polarization in response to therapy with spironolactone. We envision that our strategy of simultaneously probing the effects of a drug combined with analysis of mechanisms of action and predictive response will likely provide key information with which to design event-based trials.

Blood pressure lowering efficacy of renin inhibitors for primary hypertension

BACKGROUND

Hypertension is a chronic condition associated with an increased risk of mortality and morbidity. Renin is the enzyme responsible for converting angiotensinogen to angiotensin I, which is then converted to angiotensin II. Renin inhibitors are a new class of drugs that decrease blood pressure (BP) by preventing the formation of both angiotensin I and angiotensin II.

OBJECTIVES

To quantify the dose-related BP lowering efficacy of renin inhibitors compared to placebo in the treatment of primary hypertension.To determine the change in BP variability, pulse pressure, and heart rate and to evaluate adverse events (mortality, non-fatal serious adverse events, total adverse events, withdrawal due to adverse effects and specific adverse events such as dry cough, diarrhoea and angioedema).

SEARCH METHODS

The Cochrane Hypertension Information Specialist searched the following databases for randomized controlled trials (RCTs) up to February 2017: the Cochrane Hypertension Specialized Register, the Cochrane Central Register of Controlled Trials (CENTRAL) (2017, Issue 2), MEDLINE (from 1946), Embase (from 1974), the World Health Organization International Clinical Trials Registry Platform, and ClinicalTrials.gov. There was no restriction by language or publication status. We also searched the European Medicines Agency (EMA) for clinical study reports, the Novartis Clinical Study Results Database, bibliographic citations from retrieved references, and contacted authors of relevant papers regarding further published and unpublished work.

SELECTION CRITERIA

We included randomized, double-blinded, placebo-controlled studies evaluating BP lowering efficacy of fixed-dose monotherapy with renin inhibitor compared with placebo for a minimum duration of three to 12 weeks in adult patients with primary hypertension.

DATA COLLECTION AND ANALYSIS

This systematic review is a comprehensive update which includes four additional studies and extensive detail from nine clinical study reports (CSRs) of previously included studies obtained from EMA. The remaining three CSRs are not available.Two review authors independently assessed study eligibility and extracted data. In all cases where there was a difference between the CSR and the published report, data from the CSR was used. Dichotomous outcomes were reported as risk ratio (RR) with 95% confidence intervals (CIs) and continuous outcomes as mean difference (MD) with 95% CIs.

MAIN RESULTS

12 studies (mean duration of eight weeks) in 7439 mostly Caucasian patients (mean age 54 years) with mild-to-moderate uncomplicated hypertension were eligible for inclusion in the review. Aliskiren was the only renin inhibitor evaluated. All included studies were assessed to have high likelihood of attrition, reporting and funding bias.Aliskiren has a dose-related systolic/diastolic blood pressure (SBP/DBP) lowering effect as compared with placebo MD with 95% CI: aliskiren 75 mg (MD -2.97, 95% CI -4.76 to -1.18)/(MD -2.05, 95% CI -3.13 to -0.96) mm Hg (moderate-quality evidence), aliskiren 150 mg (MD -5.95, 95% CI -6.85 to -5.06)/ (MD -3.16, 95% CI -3.74 to -2.58) mm Hg (moderate-quality evidence), aliskiren 300 mg (MD -7.88, 95% CI -8.94 to -6.82)/ (MD -4.49, 95% CI -5.17 to -3.82) mm Hg (moderate-quality evidence), aliskiren 600 mg (MD -11.35, 95% CI -14.43 to -8.27)/ (MD -5.86, 95% CI -7.73 to -3.99) mm Hg (low-quality evidence). There was a dose-dependent decrease in blood pressure for aliskiren 75 mg, 150 mg and 300 mg. The blood pressure lowering effect of aliskiren 600 mg was not different from 300 mg (MD -0.61, 95% CI -2.78 to 1.56)/(MD -0.68, 95% CI -2.03 to 0.67). Aliskiren had no effect on blood pressure variability. Due to very limited information available regarding change in heart rate and pulse pressure, it was not possible to meta-analyze these outcomes.Mortality and non-fatal serious adverse events were not increased. This review found that in studies of eight week duration aliskiren may not increase withdrawal due to adverse events (low-quality evidence). Diarrhoea was increased in a dose-dependent manner (RR 7.00, 95% CI 2.48 to 19.72) with aliskiren 600 mg (low-quality evidence). The most frequent adverse events reported were headache, nasopharyngitis, diarrhoea, dizziness and fatigue.

AUTHORS' CONCLUSIONS

Compared to placebo, aliskiren lowered BP and this effect is dose-dependent. This magnitude of BP lowering effect is similar to that for angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs). There is no difference in mortality, nonfatal serious adverse events or withdrawal due to adverse effects with short term aliskiren monotherapy. Diarrhoea was considerably increased with aliskiren 600 mg.

Direct Renin Inhibition with Aliskiren Improves Ischemia-Induced Neovasculogenesis in Diabetic Animals via the SDF-1 Related Mechanism

Objective

Aliskiren is a direct renin inhibitor which is suggested to modify proangiogenic cells in addition to lower blood pressure. Given that angiogenesis is impaired in the presence of diabetes mellitus, we would like to investigate whether and how aliskiren enhances endothelial progenitor cells (EPCs) and improves ischemic-induced neovasculogenesis by an effect independent of blood pressure reduction in diabetic animals.

Methods

Streptozotocin-induced diabetic mice were administered with either aliskiren (5 or 25 mg/kg/day) using an osmotic pump or hydralazine (2 or 10 mg/kg/day) given in drinking water for two weeks prior to a hind-limb ischemia surgery. Laser Doppler imaging and flow cytometry were used to evaluate the degree of neovasculogenesis and the circulating levels of EPCs, respectively.

Results

In streptozotocin-induced diabetic mice, aliskiren enhanced the recovery of limb perfusion and capillary density, increased the number of circulating Sca-1⁺/Flk-1⁺ EPC-like cells, and elevated the levels of the plasma vascular endothelial growth factor (VEGF) and stromal cell-derived factor (SDF)-1α in a dose-dependent manner, whereas there were no such effects in hydralazine-treated mice. Intraperitoneal administration of anti-SDF-1 neutralizing monoclonal antibodies abolished the effects of aliskiren.

Conclusions

Independent of the reduction of blood pressure, aliskiren enhanced ischemia-induced neovasculogenesis in a dose-dependent manner via VEGF/SDF-1α related mechanisms in diabetic mice.

Non-invasive volumetric assessment of aortic atheroma: a core laboratory validation using computed tomography angiography

Aortic atherosclerosis has been linked with worse peri- and post-procedural outcomes following a range of aortic procedures. Yet, there are currently no standardized methods for non-invasive volumetric pan-aortic plaque assessment. We propose a novel means of more accurately assessing plaque volume across whole aortic segments using computed tomography angiography (CTA) imaging. Sixty patients who underwent CTA prior to trans-catheter aortic valve implantation were included in this analysis. Specialized software analysis (3mensio Vascular™, Pie Medical, Maastricht, Netherlands) was used to reconstruct images using a centerline approach, thus creating true cross-sectional aortic images, akin to those images produced with intravascular ultrasonography. Following aortic segmentation (from the aortic valve to the renal artery origin), atheroma areas were measured across multiple contiguous evenly spaced (10 mm) cross-sections. Percent atheroma volume (PAV), total atheroma volume (TAV) and calcium score were calculated. In our populations (age 79.9 ± 8.5 years, male 52 %, diabetes 27 %, CAD 84 %, PVD 20 %), mean ± SD number of cross sections measured for each patient was 35.1 ± 3.5 sections. Mean aortic PAV and TAV were 33.2 ± 2.51 % and 83,509 ± 17,078 mm(3), respectively. Median (IQR) calcium score was 1.5 (0.7-2.5). Mean (SD) inter-observer coefficient of variation and agreement for plaque area among 4 different analysts was 14.1 (5.4), and the mean (95 % CI) Lin's concordance correlation coefficient was 0.79 (0.62-0.89), effectively simulating a Core Laboratory scenario. We provide an initial validation of cross-sectional volumetric aortic atheroma assessment using CTA. This proposed methodology highlights the potential for utilizing non-invasive aortic plaque imaging for risk prediction across a range of clinical scenarios.

Renin-sensitive microRNAs correlate with atherosclerosis plaque progression

Recent trials with inhibition of the renin-angiotensin-aldosterone system (RAAS) in patients with established atherosclerosis have been equivocal. MicroRNAs (miRs) are known to affect multiple pathways relevant to atherosclerosis, including RAAS. We postulated that the use of a direct renin antagonist would result in differential regulation of miRs. We examined monocyte miR expression before and after treatment with renin antagonist, Aliskiren, in patients with established cardiovascular disease as part of a prospective, single-center, randomized, double-blind and placebo-controlled clinical trial (NCT01417104). After screening, patients (mean age 62±3 years) were randomized to placebo or Aliskiren. Three-dimensional dark-blood magnetic resonance imaging assessment of atherosclerosis in the thoracic and abdominal aorta was conducted at baseline and at study completion (19-36 weeks). MiR expression arrays were performed on RNA from peripheral blood mononuclear cells collected at baseline and 12 weeks following randomization to placebo or Aliskiren and showed that hsa-miR-106b-5p, 27a-3p and 18b-5p were significantly downregulated with Aliskiren. Baseline expression of these miRs positively correlated with normalized total wall volume in subjects taking Aliskiren (miR-106b, R=0.62; miR-27a, R=0.63; miR-18b, R=0.77; P<0.05). Hsa-miR-106b-5p, 27a-3p and 18b-5p may represent pathway-specific adaptations to renin inhibition relevant to atherosclerosis.