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Hypertension is the leading risk factor for global mortality and morbidity and those with hypertension are more likely to develop severe symptoms in cardiovascular and cerebrovascular system, which is closely related to abnormal renin-angiotensin system and elabela/apelin-apelin receptor (APJ) axis. The elabela/apelin-APJ axis exerts essential roles in regulating blood pressure levels, vascular tone, and cardiovascular dysfunction in hypertension by counterbalancing the action of the angiotensin II/angiotensin II type 1 receptor axis and enhancing the endothelial nitric oxide (NO) synthase/NO signaling. Furthermore, the elabela/apelin-APJ axis demonstrates beneficial effects in cardiovascular physiology and pathophysiology, including angiogenesis, cellular proliferation, fibrosis, apoptosis, oxidative stress, and cardiovascular remodeling and dysfunction during hypertension. More importantly, effects of the elabela/apelin-APJ axis on vascular tone may depend upon blood vessel type or various pathological conditions. Intriguingly, the broad distribution of elabela/apelin and alternative isoforms implicates its distinct functions in diverse cardiac and vascular cells and tissue types. Finally, both loss-of-function and gain-of-function approaches have defined critical roles of the elabela/apelin-APJ axis in reducing the development and severity of hypertensive diseases. Thus, targeting the elabela/apelin-APJ axis has emerged as a pre-warning biomarker and a novel therapeutic approach against progression of hypertension, and an increased understanding of cardiovascular actions of the elabela/apelin-APJ axis will help to develop effective interventions for hypertension. In this review, we focus on the physiology and biochemistry, diverse actions, and underlying mechanisms of the elabela/apelin-APJ axis, highlighting its role in hypertension and hypertensive cardiovascular injury and dysfunction, with a view to provide a prospective strategy for hypertensive disease therapy.

Hypertension is increasingly recognized as a contributor to intestinal barrier disruption and gut microbiota dysbiosis, thereby promoting systemic inflammation and end-organ damage. Sirtuin 7 (SIRT7), a nicotinamide adenine dinucleotide (NAD + )-dependent deacetylase, has been identified as a crucial regulator in the progression of cardiovascular diseases through multiple mechanistic pathways. However, the roles and underlying mechanisms of SIRT7 in the development of hypertensive intestinal injury remains unclear, and further investigation is required to determine whether SIRT7 can alleviate intestinal damage through modulation of the gut microbiota. In this study, SIRT7 expression and intestinal pathology were assessed in spontaneously hypertensive rats (SHRs). An intestinal SIRT7 overexpression model was subsequently established in SHRs to evaluate its effects on intestinal dysfunction and microbial composition. Histological and immunofluorescence staining were performed to examine the small intestine, and 16S rRNA amplicon sequencing was conducted to analyze the gut microbiota. There was a marked deficiency of SIRT7 in the intestinal tract of hypertensive animals, which was closely associated with reduced expression of tight junction proteins, including Occludin and zonula occludens-1, as well as intestinal pathological damage in SHRs. SIRT7 overexpression strikingly alleviated intestinal fibrosis, structural damage, and increased intestinal permeability. More importantly, restoration of SIRT7 partially reversed hypertension-associated gut microbiota dysbiosis. In summary, our findings provide novel mechanistic insights into the role of SIRT7 as a critical protector of intestinal barrier integrity and microenvironmental homeostasis under hypertensive stress, and highlight the intricate interplay between SIRT7 and the gut microbiota during hypertension.

Background The gut microbiota provides health benefits in humans by producing short-chain fatty acids (SCFAs), whose deficiency causes multiple disorders and inflammatory diseases. However, gut bacteria producing SCFAs in patients with atrial fibrillation (AF), an arrhythmia with increasing prevalence, have not been reported. To investigate major gut microbial organisms related to SCFA synthesis, SCFAs-associated KEGG orthologues (KOs), enzymatic genes, and potential producers were examined according to metagenomic data-mining in a northern Chinese cohort comprising 50 non-AF control and 50 AF patients. Results Compared with non-AF controls, individuals with AF had marked differences in microbial genes involved in SCFA-related synthesis, including 125 KOs and 5 SCFAs-related enzymatic genes. Furthermore, there were 10 species that harbored SCFA-synthesis related enzymatic genes, and were markedly decreased in the gut of AF patients. Notably, discriminative features about SCFA-synthesis related function, including 8 KOs (K01752, K01738, K00175, K03737, K01006, K01653, K01647 and K15023), 4 genes ( menI , tesB , yciA and CO dehydrogenase acetyl-CoA synthase complex ) and 2 species ( Coprococcus catus and Firmicutes bacterium CAG:103 ), were selected as key factors based on LASSO analysis. Furthermore, PLS-SEM analysis showed that 72.8 and 91.14 % of the overall effects on gut microbiota diversity and key species on AF, respectively, were mediated by the key KOs. Meanwhile, 46.31 % of the total effects of SCFA-synthesis related function on left atrial enlargement was mediated by hsCRP. Upon incorporation of clinical properties in AF, the KO score was still significantly associated with AF incidence (OR = 0.004, P = 0.001). Conclusions The current study revealed that dysbiotic gut microbiota in AF is coupled with disrupted SCFA-synthesis related genes, characterized by decreased abundances of KEGG orthologues, synthesis enzymatic genes and harboring species.

Background Post-infarction cardiovascular remodeling and heart failure are the leading cause of myocardial infarction (MI)-driven death during the past decades. Experimental observations have involved intestinal microbiota in the susceptibility to MI in mice; however, in humans, identifying whether translocation of gut bacteria to systemic circulation contributes to cardiovascular events post-MI remains a major challenge. Results Here, we carried out a metagenomic analysis to characterize the systemic bacteria in a cohort of 49 healthy control individuals, 50 stable coronary heart disease (CHD) subjects, and 100 ST-segment elevation myocardial infarction (STEMI) patients. We report for the first time higher microbial richness and diversity in the systemic microbiome of STEMI patients. More than 12% of post-STEMI blood bacteria were dominated by intestinal microbiota ( Lactobacillus , Bacteroides , and Streptococcus ). The significantly increased product of gut bacterial translocation (LPS and d -lactate) was correlated with systemic inflammation and predicted adverse cardiovascular events. Following experimental MI, compromised left ventricle (LV) function and intestinal hypoperfusion drove gut permeability elevation through tight junction protein suppression and intestinal mucosal injury. Upon abrogation of gut bacterial translocation by antibiotic treatment, both systemic inflammation and cardiomyocyte injury in MI mice were alleviated. Conclusions Our results provide the first evidence that cardiovascular outcomes post-MI are driven by intestinal microbiota translocation into systemic circulation. New therapeutic strategies targeting to protect the gut barrier and eliminate gut bacteria translocation may reduce or even prevent cardiovascular events post-MI.

Phenylacetylglutamine (PAGln), a gut microbiota (GM)-derived metabolite, is associated with cardiovascular disease. Studies have shown that disordered GM participated in the progression of atrial fibrillation (AF), but the relationship between PAGln and AF is unclear. This study investigated the characteristics of PAGln in AF patients and its impact on atrial myocytes. Based on our previous metagenomic data, the relative abundance of porA, a critical bacterial enzyme for PAGln synthesis, exhibited an increased tendency in AF. In an independent cohort consisting of 42 controls without AF and 92 AF patients, plasma PAGln levels were higher in AF patients than in controls (p < 0.001) by immunoassay. Notably, PAGln exerted a predictive potential of AF with an AUC of 0.774 (p < 0.001), and a predictive model constructed based on the PAGln and Taiwan AF score further improved the predictive potential. Furthermore, a positive correlation was determined between PAGln and LA diameter. Subsequently, the effect of PAGln intervention was examined on HL-1 cells in vitro, revealing that PAGln increased apoptosis, reactive oxygen species (ROS) production, CaMKII and RyR2 activation and decreased cell viability. In conclusion, increased PAGln was associated with AF, and PAGln might contribute to the AF pathogenesis by promoting oxidative stress and apoptosis in atrial myocytes.

Recently, the contribution of both insufficient sleep duration and gut microbiome dysbiosis to hypertension (HTN) have been revealed, yet the profile of gut flora in hypertensive patients with insufficient sleep duration remains unknown. To examine this condition, the specific shifts in the fecal microbiome of 53 participants with or without HTN were investigated. The patients were divided into those who slept short (≤6 h) or optimal (6–9 h) duration per day. Comprehensive metagenomic sequencing analysis of fecal specimens was performed in healthy controls with sufficient sleep (s-CTR, n = 10), healthy controls with insufficient sleep (ins-CTR, n = 6), hypertensive patients with sufficient sleep (s-HTN, n = 25), and HTNs complicated by short sleep duration (ins-HTN, n = 12). We found that the α-diversity and β-diversity were quite similar between s-HTN and ins-HTN. Similarities were also observed in the enterotype distribution between s-HTN and ins-HTN subjects. In addition, the enrichment of gut bacteria was evident, such as Fusobacterium mortiferum and Roseburia inulinivorans in ins-HTN subjects. Several functional modules that were distinct between s-HTN and ins-HTN subjects were identified, which were unique to hypertensive patients with insufficient sleep duration. Overall, the data demonstrated that the gut microbial features were largely maintained in hypertensive participants with insufficient sleep duration.

Human Recombinant ACE2 Reduces the Progression of Diabetic Nephropathy Gavin Y. Oudit 1 , 2 , George C. Liu 3 , JiuChang Zhong 1 , 2 , Ratnadeep Basu 1 , 2 , Fung L. Chow 1 , 2 , Joyce Zhou 3 , Hans Loibner 4 , Evelyne Janzek 4 , Manfred Schuster 4 , Josef M. Penninger 5 , Andrew M. Herzenberg 6 , Zamaneh Kassiri 2 , 7 and James W. Scholey 3 1 Division of Cardiology, Department of Medicine, University of Alberta, Edmonton, Alberta, Canada; 2 Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Alberta, Canada; 3 Division of Nephrology, Department of Medicine, University of Toronto, Toronto, Ontario, Canada; 4 Apeiron Biologics, Vienna, Austria; 5 Institute for Molecular Biotechnology of the Austrian Academy of Sciences, Vienna, Austria; 6 Department of Laboratory Medicine and Pathology, University of Toronto, Toronto, Ontario, Canada; 7 Department of Physiology, University of Alberta, Edmonton, Alberta, Canada. Corresponding author: Gavin Y. Oudit, gavin.oudit{at}ualberta.ca . Abstract OBJECTIVE Diabetic nephropathy is one of the most common causes of end-stage renal failure. Inhibition of ACE2 function accelerates diabetic kidney injury, whereas renal ACE2 is downregulated in diabetic nephropathy. We examined the ability of human recombinant ACE2 (hrACE2) to slow the progression of diabetic kidney injury. RESEARCH DESIGN AND METHODS Male 12-week-old diabetic Akita mice ( Ins2 WT/C96Y ) and control C57BL/6J mice ( Ins2 WT/WT ) were injected daily with placebo or with rhACE2 (2 mg/kg, i.p.) for 4 weeks. Albumin excretion, gene expression, histomorphometry, NADPH oxidase activity, and peptide levels were examined. The effect of hrACE2 on high glucose and angiotensin II (ANG II)–induced changes was also examined in cultured mesangial cells. RESULTS Treatment with hrACE2 increased plasma ACE2 activity, normalized blood pressure, and reduced the urinary albumin excretion in Akita Ins2 WT/C96Y mice in association with a decreased glomerular mesangial matrix expansion and normalization of increased α-smooth muscle actin and collagen III expression. Human recombinant ACE2 increased ANG 1–7 levels, lowered ANG II levels, and reduced NADPH oxidase activity. mRNA levels for p47 phox and NOX2 and protein levels for protein kinase Cα (PKCα) and PKCβ1 were also normalized by treatment with hrACE2. In vitro, hrACE2 attenuated both high glucose and ANG II–induced oxidative stress and NADPH oxidase activity. CONCLUSIONS Treatment with hrACE2 attenuates diabetic kidney injury in the Akita mouse in association with a reduction in blood pressure and a decrease in NADPH oxidase activity. In vitro studies show that the protective effect of hrACE2 is due to reduction in ANG II and an increase in ANG 1–7 signaling. Footnotes The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. Received August 17, 2009. Accepted October 31, 2009. © 2010 by the American Diabetes Association.

Sepsis-induced myocardial dysfunction represents a major cause of death in intensive care units. Dysregulated microRNAs (miR)-155 has been implicated in multiple cardiovascular diseases and miR-155 can be induced by lipopolysaccharide (LPS). However, the role of miR-155 in LPS-induced cardiac dysfunction is unclear. Septic cardiac dysfunction in mice was induced by intraperitoneal injection of LPS (5 mg/kg) and miR-155 was found to be significantly increased in heart challenged with LPS. Pharmacological inhibition of miR-155 using antagomiR improved cardiac function and suppressed cardiac apoptosis induced by LPS in mice as determined by echocardiography, terminal deoxynucleotidyl transferase nick-end labeling (TUNEL) assay, and Western blot for Bax and Bcl-2, while overexpression of miR-155 using agomiR had inverse effects. Pea15a was identified as a target gene of miR-155, mediating its effects in controlling apoptosis of cardiomyocytes as evidenced by luciferase reporter assays, quantitative real time-polymerase chain reaction, Western blot, and TUNEL staining. Noteworthy, miR-155 was also found to be upregulated in the plasma of patients with septic cardiac dysfunction compared to sepsis patients without cardiac dysfunction, indicating a potential clinical relevance of miR-155. The receiver-operator characteristic curve indicated that plasma miR-155 might be a biomarker for sepsis patients developing cardiac dysfunction. Therefore, inhibition of miR-155 represents a novel therapy for septic myocardial dysfunction.

The present study was performed to screen for potential molecular biomarkers and to assess the underlying mechanisms of chronic thromboembolic pulmonary hypertension (CTEPH) by using sequencing data analysis of microRNAs (miRNAs) and circular RNAs (circRNAs). Total RNA was isolated from peripheral-blood samples from five CTEPH patients and from five normal individuals. Based upon the identification of differentially expressed miRNAs (Affymetrix miRNA chip) and circRNAs (Agilent circRNA chip), target predictions for these differentially expressed miRNAs and functional enrichment analyses of the miRNAs and circRNAs were performed. Subsequently, the miRNA partner predictions of these differentially expressed circRNAs and co-expression analyses of differentially expressed circRNAs and miRNAs were conducted. Based on the results of these analyses, a competing endogenous RNA (ceRNA) network was constructed. Finally, the expression of circRNAs was detected by quantitative real-time PCR (qRT-PCR). Within the miRNA–circRNA regulatory network, hsa_circ_0026480 and hsa_circ_0046159 were predicted to interact with miR-27a-3p and miR-1226-3p, respectively with greater degree. Specially, ATP2A2—that had a ceRNA relationship with hsa_circ_0046159—was predicted as a target of miR-1226-3p. The results of RT-PCR also revealed a significantly increased expression of hsa_circ_0046159 in CTEPH samples than that in normal samples.

Background We aimed to establish the relationships between the expression of microRNAs (miRNAs) and echocardiographic right ventricular (RV) function parameters, and to explore the effectiveness and clinical value of miRNA expression in predicting RV injury and dysfunction in patients with chronic thromboembolic pulmonary hypertension (CTEPH). Methods In this retrospective study, clinical data were collected from eight CTEPH patients and eight healthy individuals. RV parameters on echocardiography were analyzed, and the expression levels of specific miRNAs were measured by quantitative real-time PCR. Correlation analysis was performed on structural and functional RV parameters and five candidate miRNAs (miR-20a-5p, miR-17-5p, miR-93-5p, miR-3202 and miR-665). The diagnostic value of RV functional parameters and miRNAs expression was assessed by receiver operating characteristic (ROC) curve analysis and C statistic. Results Among the tested miRNAs, miR-20a-5p expression showed the best correlation with echocardiographic RV functional parameters ( P  < 0.05), although the expression levels of miR-93-5p, miR-17-5p and miR-3202 showed positive associations with some RV parameters. ROC curve analysis demonstrated the ability of miR-20a-5p expression to predict RV dysfunction, with a maximum area under the curve of 0.952 ( P  = 0.003) when the predicted RV longitudinal strain was less than –20%. The C index for RV dysfunction prediction by the combination of miRNAs (miR-20a-5p, miR-93-5p and miR-17-5p) was 1.0, which was significantly larger than the values for miR-93-5p and miR-17-5p individually ( P  = 0.0337 and 0.0453, respectively). Conclusion Among the tested miRNAs, miR -20a-5p, miR -93-5p and miR -17-5p have potential value in the diagnosis of CTEPH based on the correlation between the abnormal expression of these miRNAs and echocardiographic parameters in CTEPH patients. miR-20a-5p showed the strongest correlation with echocardiographic RV functional parameters. Moreover, expression of a combination of miRNAs seemed to show excellent predictive power for RV dysfunction.